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Sample records for activated chemical vapour

  1. Growth of ZnO Nanorods on Stainless Steel Wire Using Chemical Vapour Deposition and Their Photocatalytic Activity

    PubMed Central

    Abd Aziz, Siti Nor Qurratu Aini; Pung, Swee-Yong; Ramli, Nurul Najiah; Lockman, Zainovia

    2014-01-01

    The photodegradation efficiency of ZnO nanoparticles in removal of organic pollutants deteriorates over time as a high percentage of the nanoparticles can be drained away by water during the wastewater treatment. This problem can be solved by growing the ZnO nanorods on stainless steel wire. In this work, ZnO nanorods were successfully grown on stainless steel wire by chemical vapour deposition. The SAED analysis indicates that ZnO nanorod is a single crystal and is preferentially grown in [0001] direction. The deconvoluted O 1s peak at 531.5 eV in XPS analysis is associated with oxygen deficient, revealing that the ZnO nanorods contain many oxygen vacancies. This observation is further supported by the finding of the small Iuv/Ivis ratio, that is, ~1 in the photoluminescence analysis. The growth of ZnO nanorods on stainless steel wire was governed by vapour-solid mechanism as there were no Fe particles observed at the tips of the nanorods. The photodegradation of Rhodamine B solution by ZnO nanorods followed the first-order kinetics. PMID:24587716

  2. Infrared hyperspectral imaging for chemical vapour detection

    NASA Astrophysics Data System (ADS)

    Ruxton, K.; Robertson, G.; Miller, W.; Malcolm, G. P. A.; Maker, G. T.; Howle, C. R.

    2012-10-01

    Active hyperspectral imaging is a valuable tool in a wide range of applications. One such area is the detection and identification of chemicals, especially toxic chemical warfare agents, through analysis of the resulting absorption spectrum. This work presents a selection of results from a prototype midwave infrared (MWIR) hyperspectral imaging instrument that has successfully been used for compound detection at a range of standoff distances. Active hyperspectral imaging utilises a broadly tunable laser source to illuminate the scene with light at a range of wavelengths. While there are a number of illumination methods, the chosen configuration illuminates the scene by raster scanning the laser beam using a pair of galvanometric mirrors. The resulting backscattered light from the scene is collected by the same mirrors and focussed onto a suitable single-point detector, where the image is constructed pixel by pixel. The imaging instrument that was developed in this work is based around an IR optical parametric oscillator (OPO) source with broad tunability, operating in the 2.6 to 3.7 μm (MWIR) and 1.5 to 1.8 μm (shortwave IR, SWIR) spectral regions. The MWIR beam was primarily used as it addressed the fundamental absorption features of the target compounds compared to the overtone and combination bands in the SWIR region, which can be less intense by more than an order of magnitude. We show that a prototype NCI instrument was able to locate hydrocarbon materials at distances up to 15 metres.

  3. Chemical vapour transport of III-V semiconductor materials

    NASA Astrophysics Data System (ADS)

    Davis, Mervyn Howard

    Over the temperature range 770 to 1310 K, however, two bromides compete for prominence, dependent upon temperature. In both instances, it is shown that vapour transport becomes rate limited at low temperature. Further to the chemical vapour transport of indium phosphide, the dissociative sublimation of the compound has also been investigated. Raman spectroscopy has been used to identify high temperature molecular species involved in vapour transport of III-V semiconductor materials. Supplementary work has been performed on the thermochemistry of indium monobromide. The heat of formation of indium bromide crystals has been determined using a solution calormetric technique. Differential scanning calorimetry was used to measure the heat capacity and heat of fusion, of the salt. An entrainment study of the evaporation of liquid indium monobromide was undertaken to yield a value for its heat of vaporisation. Using a statistical thermodynamic approach, the heat capacity of the vapour was calculated. Collating the information, a value for the heat of formation of indium monobromide gas at 1000 K has been calculated for use in other thermodynamic calculations.

  4. Heat stress in chemical protective clothing: porosity and vapour resistance.

    PubMed

    Havenith, George; den Hartog, Emiel; Martini, Svein

    2011-05-01

    Heat strain in chemical protective clothing is an important factor in industrial and military practice. Various improvements to the clothing to alleviate strain while maintaining protection have been attempted. More recently, selectively permeable membranes have been introduced to improve protection, but questions are raised regarding their effect on heat strain. In this paper the use of selectively permeable membranes with low vapour resistance was compared to textile-based outer layers with similar ensemble vapour resistance. For textile-based outer layers, the effect of increasing air permeability was investigated. When comparing ensembles with a textile vs. a membrane outer layer that have similar heat and vapour resistances measured for the sum of fabric samples, a higher heat strain is observed in the membrane ensemble, as in actual wear, and the air permeability of the textile version improves ventilation and allows better cooling by sweat evaporation. For garments with identical thickness and static dry heat resistance, but differing levels of air permeability, a strong correlation of microclimate ventilation due to wind and movement with air permeability was observed. This was reflected in lower values of core and skin temperatures and heart rate for garments with higher air permeability. For heart rate and core temperature the two lowest and the two highest air permeabilities formed two distinct groups, but they did not differ within these groups. Based on protection requirements, it is concluded that air permeability increases can reduce heat strain levels allowing optimisation of chemical protective clothing. STATEMENT OF RELEVANCE: In this study on chemical, biological, radiological and nuclear (CBRN) protective clothing, heat strain is shown to be significantly higher with selectively permeable membranes compared to air permeable ensembles. Optimisation of CBRN personal protective equipment needs to balance sufficient protection with reduced heat

  5. Control and Characterization of Individual Grains and Grain Boundaries in Graphene Grown by Chemical Vapour Deposition

    DTIC Science & Technology

    2011-06-01

    active investigation, both experimentally25–28 and theoretically29–31. For example, exfoliated monolayer graphene flakes can show both zigzag and...crystalsmade of eithermultilayer or monolayer CVD graphene as well as transferred exfoliated graphene /graphite. Seeds made from multilayer CVD graphene ...synthesis of graphene by chemical vapour deposition and its application in hydrogen sensing. Sens. Actuat. B 150, 296–300 (2010). 21. Li, X. S., Cai, W. W

  6. Nano structured carbon nitrides prepared by chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Karuppannan, Ramesh; Prashantha, M.

    2010-08-01

    Nanostructured carbon nitride films were prepared by pyrolysis assisted chemical vapour deposition(CVD). A two zone furnace with a temperature profile having a uniform temperature over a length of 20 cm length has been designed and developed. The precursor Azabenzimidazole was taken in a quartz tube and evaporated at 400 0C. The dense vapours enter the pyrolysis zone kept at a desired temperature and deposit on the quartz substrates. The FTIR spectrum of the prepared samples shows peaks at 1272 cm-1 (C.N stretching) and 1600 cm-1 (C=N) confirms the bonding of nitrogen with carbon. Raman D and G peaks, are observed at 1360 cm-1 and 1576 cm-1 respectively. XPS core level spectra of C 1s and N 1s show the formation of π bonding between carbon and nitrogen atoms. The size of the nano crystals estimated from the SEM images and XRD is ~100 nm. In some regions of the sample a maximum of 57 atom % of nitrogen has been observed.

  7. Chemical vapour deposition synthetic diamond: materials, technology and applications

    NASA Astrophysics Data System (ADS)

    Balmer, R. S.; Brandon, J. R.; Clewes, S. L.; Dhillon, H. K.; Dodson, J. M.; Friel, I.; Inglis, P. N.; Madgwick, T. D.; Markham, M. L.; Mollart, T. P.; Perkins, N.; Scarsbrook, G. A.; Twitchen, D. J.; Whitehead, A. J.; Wilman, J. J.; Woollard, S. M.

    2009-09-01

    Substantial developments have been achieved in the synthesis of chemical vapour deposition (CVD) diamond in recent years, providing engineers and designers with access to a large range of new diamond materials. CVD diamond has a number of outstanding material properties that can enable exceptional performance in applications as diverse as medical diagnostics, water treatment, radiation detection, high power electronics, consumer audio, magnetometry and novel lasers. Often the material is synthesized in planar form; however, non-planar geometries are also possible and enable a number of key applications. This paper reviews the material properties and characteristics of single crystal and polycrystalline CVD diamond, and how these can be utilized, focusing particularly on optics, electronics and electrochemistry. It also summarizes how CVD diamond can be tailored for specific applications, on the basis of the ability to synthesize a consistent and engineered high performance product.

  8. Light-induced chemical vapour deposition painting with titanium dioxide

    NASA Astrophysics Data System (ADS)

    Halary-Wagner, E.; Bret, T.; Hoffmann, P.

    2003-03-01

    Light-induced chemical vapour deposits of titanium dioxide are obtained from titanium tetra-isopropoxide (TTIP) in an oxygen and nitrogen atmosphere with a long pulse (250 ns) 308 nm XeCl excimer laser using a mask projection set-up. The demonstrated advantages of this technique are: (i) selective area deposition, (ii) precise control of the deposited thickness and (iii) low temperature deposition, enabling to use a wide range of substrates. A revolving mask system enables, in a single reactor load, to deposit shapes of controlled heights, which overlap to build up a complex pattern. Interferential multi-coloured deposits are achieved, and the process limitations (available colours and resolution) are discussed.

  9. Chemical vapour deposition: Transition metal carbides go 2D

    DOE PAGES

    Gogotsi, Yury

    2015-08-17

    Here, the research community has been steadily expanding the family of few-atom-thick crystals beyond graphene, discovering new materials or producing known materials in a 2D state and demonstrating their unique properties1, 2. Recently, nanometre-thin 2D transition metal carbides have also joined this family3. Writing in Nature Materials, Chuan Xu and colleagues now report a significant advance in the field, showing the synthesis of large-area, high-quality, nanometre-thin crystals of molybdenum carbide that demonstrate low-temperature 2D superconductivity4. Moreover, they also show that other ultrathin carbide crystals, such as tungsten and tantalum carbides, can be grown by chemical vapour deposition with a highmore » crystallinity and very low defect concentration.« less

  10. Chemical vapour deposition: Transition metal carbides go 2D

    SciTech Connect

    Gogotsi, Yury

    2015-08-17

    Here, the research community has been steadily expanding the family of few-atom-thick crystals beyond graphene, discovering new materials or producing known materials in a 2D state and demonstrating their unique properties1, 2. Recently, nanometre-thin 2D transition metal carbides have also joined this family3. Writing in Nature Materials, Chuan Xu and colleagues now report a significant advance in the field, showing the synthesis of large-area, high-quality, nanometre-thin crystals of molybdenum carbide that demonstrate low-temperature 2D superconductivity4. Moreover, they also show that other ultrathin carbide crystals, such as tungsten and tantalum carbides, can be grown by chemical vapour deposition with a high crystallinity and very low defect concentration.

  11. Functionalization of Hydrogenated Chemical Vapour Deposition-Grown Graphene by On-Surface Chemical Reactions.

    PubMed

    Drogowska, Karolina; Kovaříček, Petr; Kalbáč, Martin

    2017-03-23

    The reactivity of hydrogenated graphene when treated with oxidising agents, KMnO4 and KIO4 , as well as alkylated with benzyl bromide (BnBr) was studied. The probed reactions are strictly limited to the partly hydrogenated form of graphene in which most of the hydrogen atoms are located in activated benzylic/allylic positions. This, in turn, clearly demonstrates the presence of hydrogen attached to the graphene lattice. Attachment of the benzyl group was also unequivocally demonstrated by characteristic vibrations recorded in the surface-enhanced Raman spectra, and all reactions were shown to proceed solely on hydrogenated graphene as evidenced by the comparison with pristine chemical vapour deposition-grown graphene.

  12. Photo Initiated Chemical Vapour Deposition To Increase Polymer Hydrophobicity

    NASA Astrophysics Data System (ADS)

    Bérard, Ariane; Patience, Gregory S.; Chouinard, Gérald; Tavares, Jason R.

    2016-08-01

    Apple growers face new challenges to produce organic apples and now many cover orchards with high-density polyethylene (HDPE) nets to exclude insects, rather than spraying insecticides. However, rainwater- associated wetness favours the development of apple scabs, Venturia inaequalis, whose lesions accumulate on the leaves and fruit causing unsightly spots. Treating the nets with a superhydrophobic coating should reduce the amount of water that passes through the net. Here we treat HDPE and polyethylene terephthalate using photo-initiated chemical vapour deposition (PICVD). We placed polymer samples in a quartz tube and passed a mixture of H2 and CO through it while a UVC lamp (254 nm) illuminated the surface. After the treatment, the contact angle between water droplets and the surface increased by an average of 20°. The contact angle of samples placed 70 cm from the entrance of the tube was higher than those at 45 cm and 20 cm. The PICVD-treated HDPE achieved a contact angle of 124°. Nets spray coated with a solvent-based commercial product achieved 180° but water ingress was, surprisingly, higher than that for nets with a lower contact angle.

  13. Reducing chemical vapour infiltration time for ceramic matrix composites.

    PubMed

    Timms, L. A.; Westby, W.; Prentice, C.; Jaglin, D.; Shatwell, R. A.; Binner, J. G. P.

    2001-02-01

    Conventional routes to producing ceramic matrix composites (CMCs) require the use of high temperatures to sinter the individual ceramic particles of the matrix together. Sintering temperatures are typically much higher than the upper temperature limits of the fibres. This paper details preliminary work carried out on producing a CMC via chemical vapour infiltration (CVI), a process that involves lower processing temperatures, thus avoiding fibre degradation. The CVI process has been modified and supplemented in an attempt to reduce the CVI process time and to lower the cost of this typically expensive process. To this end microwave-enhanced CVI (MECVI) has been chosen, along with two alternative pre-infiltration steps: electrophoretic infiltration and vacuum bagging. The system under investigation is based on silicon carbide fibres within a silicon carbide matrix (SiCf/SiC). The results demonstrate that both approaches result in an enhanced initial density and a consequent significant reduction in the time required for the MECVI processing step. Dual energy X-ray absorptiometry was used as a non-destructive, density evaluation technique. Initial results indicate that the presence of the SiC powder in the pre-form changes the deposition profile during the MECVI process.

  14. Photo Initiated Chemical Vapour Deposition To Increase Polymer Hydrophobicity

    PubMed Central

    Bérard, Ariane; Patience, Gregory S.; Chouinard, Gérald; Tavares, Jason R.

    2016-01-01

    Apple growers face new challenges to produce organic apples and now many cover orchards with high-density polyethylene (HDPE) nets to exclude insects, rather than spraying insecticides. However, rainwater- associated wetness favours the development of apple scabs, Venturia inaequalis, whose lesions accumulate on the leaves and fruit causing unsightly spots. Treating the nets with a superhydrophobic coating should reduce the amount of water that passes through the net. Here we treat HDPE and polyethylene terephthalate using photo-initiated chemical vapour deposition (PICVD). We placed polymer samples in a quartz tube and passed a mixture of H2 and CO through it while a UVC lamp (254 nm) illuminated the surface. After the treatment, the contact angle between water droplets and the surface increased by an average of 20°. The contact angle of samples placed 70 cm from the entrance of the tube was higher than those at 45 cm and 20 cm. The PICVD-treated HDPE achieved a contact angle of 124°. Nets spray coated with a solvent-based commercial product achieved 180° but water ingress was, surprisingly, higher than that for nets with a lower contact angle. PMID:27531048

  15. Tungsten Deposition on Graphite using Plasma Enhanced Chemical Vapour Deposition.

    NASA Astrophysics Data System (ADS)

    Sharma, Uttam; Chauhan, Sachin S.; Sharma, Jayshree; Sanyasi, A. K.; Ghosh, J.; Choudhary, K. K.; Ghosh, S. K.

    2016-10-01

    The tokamak concept is the frontrunner for achieving controlled thermonuclear reaction on earth, an environment friendly way to solve future energy crisis. Although much progress has been made in controlling the heated fusion plasmas (temperature ∼ 150 million degrees) in tokamaks, technological issues related to plasma wall interaction topic still need focused attention. In future, reactor grade tokamak operational scenarios, the reactor wall and target plates are expected to experience a heat load of 10 MW/m2 and even more during the unfortunate events of ELM's and disruptions. Tungsten remains a suitable choice for the wall and target plates. It can withstand high temperatures, its ductile to brittle temperature is fairly low and it has low sputtering yield and low fuel retention capabilities. However, it is difficult to machine tungsten and hence usages of tungsten coated surfaces are mostly desirable. To produce tungsten coated graphite tiles for the above-mentioned purpose, a coating reactor has been designed, developed and made operational at the SVITS, Indore. Tungsten coating on graphite has been attempted and successfully carried out by using radio frequency induced plasma enhanced chemical vapour deposition (rf -PECVD) for the first time in India. Tungsten hexa-fluoride has been used as a pre-cursor gas. Energy Dispersive X-ray spectroscopy (EDS) clearly showed the presence of tungsten coating on the graphite samples. This paper presents the details of successful operation and achievement of tungsten coating in the reactor at SVITS.

  16. Controlled oxidation of iron nanoparticles in chemical vapour synthesis

    NASA Astrophysics Data System (ADS)

    Ruusunen, Jarno; Ihalainen, Mika; Koponen, Tarmo; Torvela, Tiina; Tenho, Mikko; Salonen, Jarno; Sippula, Olli; Joutsensaari, Jorma; Jokiniemi, Jorma; Lähde, Anna

    2014-02-01

    In the present study, iron oxide nanoparticles (primary particle size of 80-90 nm) with controlled oxidation state were prepared via an atmospheric pressure chemical vapour synthesis (APCVS) method. Iron pentacarbonyl [Fe(CO)5], a precursor material, was thermally decomposed to iron in the APCVS reactor. Subsequently, the iron was oxidized with controlled amount of oxygen in the reactor to produce nearly pure magnetite or haematite particles depending on the oxygen concentration. Size, morphology and crystal structure of the synthesized nanoparticles were studied with scanning mobility particle sizer (SMPS), transmission electron microscopy (TEM) and X-ray diffraction (XRD). In addition, thermodynamic equilibrium calculations and computational fluid dynamics model were used to predict the oxidation state of the iron oxides and the reaction conditions during mixing. Aggregates of crystalline particles were formed, determined as magnetite at the oxygen volumetric fraction of 0.1 % and haematite at volumetric fraction of 0.5 %, according to the XRD. The geometric mean electrical mobility diameter of the aggregates increased from 110 to 155 nm when the volumetric fraction of oxygen increased from 0.1 to 0.5 %, determined using the SMPS. The aggregates were highly sintered based on TEM analyses. As a conclusion, APCVS method can be used to produce nearly pure crystalline magnetite or haematite nanoparticles with controlled oxidation in a continuous one-stage gas-phase process.

  17. Long distance spin communication in chemical vapour deposited graphene

    PubMed Central

    Kamalakar, M. Venkata; Groenveld, Christiaan; Dankert, André; Dash, Saroj P.

    2015-01-01

    Graphene is an ideal medium for long-distance spin communication in future spintronic technologies. So far, the prospect is limited by the smaller sizes of exfoliated graphene flakes and lower spin transport properties of large-area chemical vapour-deposited (CVD) graphene. Here we demonstrate a high spintronic performance in CVD graphene on SiO2/Si substrate at room temperature. We show pure spin transport and precession over long channel lengths extending up to 16 μm with a spin lifetime of 1.2 ns and a spin diffusion length ∼6 μm at room temperature. These spin parameters are up to six times higher than previous reports and highest at room temperature for any form of pristine graphene on industrial standard SiO2/Si substrates. Our detailed investigation reinforces the observed performance in CVD graphene over wafer scale and opens up new prospects for the development of lateral spin-based memory and logic applications. PMID:25857650

  18. On The Stability Of Model Flows For Chemical Vapour Deposition

    NASA Astrophysics Data System (ADS)

    Miller, Robert

    2016-11-01

    The flow in a chemical vapour deposition (CVD) reactor is assessed. The reactor is modelled as a flow over an infinite-radius rotating disk, where the mean flow and convective instability of the disk boundary layer are measured. Temperature-dependent viscosity and enforced axial flow are used to model the steep temperature gradients present in CVD reactors and the pumping of the gas towards the disk, respectively. Increasing the temperature-dependence parameter of the fluid viscosity (ɛ) results in an overall narrowing of the fluid boundary layer. Increasing the axial flow strength parameter (Ts) accelerates the fluid both radially and axially, while also narrowing the thermal boundary layer. It is seen that when both effects are imposed, the effects of axial flow generally dominate those of the viscosity temperature dependence. A local stability analysis is performed and the linearized stability equations are solved using a Galerkin projection in terms of Chebyshev polynomials. The neutral stability curves are then plotted for a range of ɛ and Ts values. Preliminary results suggest that increasing Ts has a stabilising effect on both type I and type II stationary instabilities, while small increases in ɛ results in a significant reduction to the critical Reynolds number.

  19. Carbon Nanotubes/Nanofibers by Plasma Enhanced Chemical Vapour Deposition

    NASA Technical Reports Server (NTRS)

    Teo, K. B. K.; Hash, D. B.; Bell, M. S.; Chhowalla, M.; Cruden, B. A.; Amaratunga, G. A. J.; Meyyappan, M.; Milne, W. I.

    2005-01-01

    Plasma enhanced chemical vapour deposition (PECVD) has been recently used for the production of vertically aligned carbon nanotubedfibers (CN) directly on substrates. These structures are potentially important technologically as electron field emitters (e.g. microguns, microwave amplifiers, displays), nanoelectrodes for sensors, filter media, superhydrophobic surfaces and thermal interface materials for microelectronics. A parametric study on the growth of CN grown by glow discharge dc-PECVD is presented. In this technique, a substrate containing thin film Ni catalyst is exposed to C2H2 and NH3 gases at 700 C. Without plasma, this process is essentially thermal CVD which produces curly spaghetti-like CN as seen in Fig. 1 (a). With the plasma generated by biasing the substrate at -6OOV, we observed that the CN align vertically during growth as shown in Fig. l(b), and that the magnitude of the applied substrate bias affects the degree of alignment. The thickness of the thin film Ni catalyst was found to determine the average diameter and inversely the length of the CN. The yield and density of the CN were controlled by the use of different diffusion barrier materials under the Ni catalyst. Patterned CN growth [Fig. l(c)], with la variation in CN diameter of 4.1% and 6.3% respectively, is achieved by lithographically defining the Ni thin film prior to growth. The shape of the structures could be varied from very straight nanotube-like to conical tip-like nanofibers by increasing the ratio of C2H2 in the gas flow. Due to the plasma decomposition of C2H2, amorphous carbon (a-C) is an undesirable byproduct which could coat the substrate during CN growth. Using a combination of depth profiled Auger electron spectroscopy to study the substrate and in-situ mass spectroscopy to examine gas phase neutrals and ions, the optimal conditions for a-C free growth of CN is determined.

  20. Spatial homogeneity criteria for active media of cataphoresis repetitively pulsed metal vapour lasers

    SciTech Connect

    Chebotarev, Gennady D; Prutsakov, Oleg O; Latush, Evgeny L

    2005-07-31

    The formation of the transverse distribution of the metal vapour concentration in repetitively pulsed lasers is analysed. The criterion for the homogeneity of this distribution is found. The optimal conditions for excitation of the active media of cataphoresis repetitively pulsed metal vapour lasers are determined under which a high degree of both longitudinal and transverse homogeneity is achieved. (active media)

  1. Chemical vapour deposition of thermochromic vanadium dioxide thin films for energy efficient glazing

    SciTech Connect

    Warwick, Michael E.A.; Binions, Russell

    2014-06-01

    Vanadium dioxide is a thermochromic material that undergoes a semiconductor to metal transitions at a critical temperature of 68 °C. This phase change from a low temperature monoclinic structure to a higher temperature rutile structure is accompanied by a marked change in infrared reflectivity and change in resistivity. This ability to have a temperature-modulated film that can limit solar heat gain makes vanadium dioxide an ideal candidate for thermochromic energy efficient glazing. In this review we detail the current challenges to such glazing becoming a commercial reality and describe the key chemical vapour deposition technologies being employed in the latest research. - Graphical abstract: Schematic demonstration of the effect of thermochromic glazing on solar radiation (red arrow represents IR radiation, black arrow represents all other solar radiation). - Highlights: • Vanadium dioxide thin films for energy efficient glazing. • Reviews chemical vapour deposition techniques. • Latest results for thin film deposition for vanadium dioxide.

  2. Electrical Conduction Mechanism in Chemical Vapour Deposition Grown Multi-Wall Carbon Nanotubes Film.

    PubMed

    Al-Hazmi, F S

    2015-07-01

    Multi-walled carbon nanotubes are interesting systems where different aspects of conduction are observed, mostly due to their low dimensionalities and small dimensions. Electrical conduction mechanism in multi wall carbon nanotubes film is studied. The studied multi-walled nanotubes are grown by a low pressure chemical vapour deposition system. To understand the conduction mechanism in these nanotubes, temperature dependence of conductivity of the multi wall nanotubes film over a temperature range of (400-200 K) is studied. On the basis of the results, one may suggest the thermally activated conduction mechanism for the temperature range (400-300 K). The low temperature data is fitted with the hopping conduction for the transport of charge carriers in the temperature range of 300-200 K. This hopping conduction mechanism is characterized by variable range hopping (VRH), which shows complete agreement with the Mott's type of VRH mechanism. Applying this model, a number of Mott's parameters such as density of states, hopping distance, hopping energy are calculated. The calculated values of all the studied parameters matches well the reported results on other multi-wall nanotubes film.

  3. Light induced chemical vapour deposition of titanium oxide thin films at room temperature

    NASA Astrophysics Data System (ADS)

    Halary, E.; Benvenuti, G.; Wagner, F.; Hoffmann, P.

    2000-02-01

    High resolution patterned deposition of titania is achieved by light induced chemical vapour deposition (LICVD), by imaging a mask onto a glass substrate. A long pulse XeCl Excimer laser (308 nm) provides, by perpendicular irradiation, the energy to convert titanium tetraisopropoxide (TTIP) vapour into titanium dioxide films, in an oxygen atmosphere, on unheated glass substrates. The amorphous titania deposits contain about 6% carbon contamination according to X-ray photoelectron spectroscopy (XPS) measurements. The deposition rate increases with increasing laser fluence until a maximum value is reached, then remains constant over a wide range, and finally decreases with further fluence increase due to titania ablation or thermal effects. The film thickness increases linearly with the number of pulses after a nucleation period. The strong influence of the laser pulse repetition rate on the growth rate and the thickness profile are reported.

  4. Chemical vapour deposition of zeolitic imidazolate framework thin films.

    PubMed

    Stassen, Ivo; Styles, Mark; Grenci, Gianluca; Gorp, Hans Van; Vanderlinden, Willem; Feyter, Steven De; Falcaro, Paolo; Vos, Dirk De; Vereecken, Philippe; Ameloot, Rob

    2016-03-01

    Integrating metal-organic frameworks (MOFs) in microelectronics has disruptive potential because of the unique properties of these microporous crystalline materials. Suitable film deposition methods are crucial to leverage MOFs in this field. Conventional solvent-based procedures, typically adapted from powder preparation routes, are incompatible with nanofabrication because of corrosion and contamination risks. We demonstrate a chemical vapour deposition process (MOF-CVD) that enables high-quality films of ZIF-8, a prototypical MOF material, with a uniform and controlled thickness, even on high-aspect-ratio features. Furthermore, we demonstrate how MOF-CVD enables previously inaccessible routes such as lift-off patterning and depositing MOF films on fragile features. The compatibility of MOF-CVD with existing infrastructure, both in research and production facilities, will greatly facilitate MOF integration in microelectronics. MOF-CVD is the first vapour-phase deposition method for any type of microporous crystalline network solid and marks a milestone in processing such materials.

  5. Gettering of interstitial iron in silicon by plasma-enhanced chemical vapour deposited silicon nitride films

    NASA Astrophysics Data System (ADS)

    Liu, A. Y.; Sun, C.; Markevich, V. P.; Peaker, A. R.; Murphy, J. D.; Macdonald, D.

    2016-11-01

    It is known that the interstitial iron concentration in silicon is reduced after annealing silicon wafers coated with plasma-enhanced chemical vapour deposited (PECVD) silicon nitride films. The underlying mechanism for the significant iron reduction has remained unclear and is investigated in this work. Secondary ion mass spectrometry (SIMS) depth profiling of iron is performed on annealed iron-contaminated single-crystalline silicon wafers passivated with PECVD silicon nitride films. SIMS measurements reveal a high concentration of iron uniformly distributed in the annealed silicon nitride films. This accumulation of iron in the silicon nitride film matches the interstitial iron loss in the silicon bulk. This finding conclusively shows that the interstitial iron is gettered by the silicon nitride films during annealing over a wide temperature range from 250 °C to 900 °C, via a segregation gettering effect. Further experimental evidence is presented to support this finding. Deep-level transient spectroscopy analysis shows that no new electrically active defects are formed in the silicon bulk after annealing iron-containing silicon with silicon nitride films, confirming that the interstitial iron loss is not due to a change in the chemical structure of iron related defects in the silicon bulk. In addition, once the annealed silicon nitride films are removed, subsequent high temperature processes do not result in any reappearance of iron. Finally, the experimentally measured iron decay kinetics are shown to agree with a model of iron diffusion to the surface gettering sites, indicating a diffusion-limited iron gettering process for temperatures below 700 °C. The gettering process is found to become reaction-limited at higher temperatures.

  6. Chemical vapour deposition of thermochromic vanadium dioxide thin films for energy efficient glazing

    NASA Astrophysics Data System (ADS)

    Warwick, Michael E. A.; Binions, Russell

    2014-06-01

    Vanadium dioxide is a thermochromic material that undergoes a semiconductor to metal transitions at a critical temperature of 68 °C. This phase change from a low temperature monoclinic structure to a higher temperature rutile structure is accompanied by a marked change in infrared reflectivity and change in resistivity. This ability to have a temperature-modulated film that can limit solar heat gain makes vanadium dioxide an ideal candidate for thermochromic energy efficient glazing. In this review we detail the current challenges to such glazing becoming a commercial reality and describe the key chemical vapour deposition technologies being employed in the latest research.

  7. Amorphous hollow carbon spheres synthesized using radio frequency plasma-enhanced chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Yang, G. M.; Xu, Q.; Tian, H. W.; Wang, X.; Zheng, W. T.

    2008-10-01

    We report a method to synthesize amorphous hollow carbon spheres, with diameters ranging from 100 to 800 nm, which are dispersed among bent graphitized carbon nanotubes using radio frequency plasma-enhanced chemical vapour deposition in mixed CH4/H2 gases. The products are characterized by techniques including scanning electron microscopy, energy-dispersive x-ray spectroscopy, Raman spectroscopy and transmission electron microscopy. It is found that MgO and Ni nanoparticles together with hydrogen play important roles in the formation of the spheres. A possible formation mechanism for the carbon composites has been proposed.

  8. Graphene growth by transfer-free chemical vapour deposition on a cobalt layer

    NASA Astrophysics Data System (ADS)

    Macháč, Petr; Hejna, Ondřej; Slepička, Petr

    2017-01-01

    The contribution deals with the preparation of graphene films by a transfer-free chemical vapour deposition process utilizing a thin cobalt layer. This method allows growing graphene directly on a dielectric substrate. The process was carried out in a cold-wall reactor with methane as carbon precursor. We managed to prepare bilayer graphene. The best results were obtained for a structure with a cobalt layer with a thickness of 50 nm. The quality of prepared graphene films and of the number of graphene layers were estimated using Raman spectroscopy. with a minimal dots diameter of 180 nm and spacing of 1000 nm were successfully developed.

  9. Laser-induced chemical vapour deposition of conductive and insulating thin films

    NASA Astrophysics Data System (ADS)

    Reisse, G.; Gaensicke, F.; Ebert, R.; Illmann, U.; Johansen, H.

    1992-01-01

    Investigations concerning the laser-induced chemical vapour deposition of Mo, W, Co and TiSi 2 conductive thin film structures from Mo(CO) 6, W(CO) 6, Co 2(CO) 8, TiCl 4 and SiH 4 using a direct writing method are presented. SiO 2 thin films were deposited from SiH 4 and N 2O in a large area deposition process stimulated by an excimer laser by using a parallel beam configuration.

  10. Single-source precursor for chemical vapour deposition of collapsed boron nitride nanotubes

    NASA Astrophysics Data System (ADS)

    Tang, Chengchun; Bando, Yoshio; Shen, Guozhen; Zhi, Chunyi; Golberg, Dmitri

    2006-12-01

    Ammonium tetrafluoroborate, a cheap and commonly used chemical, was successfully utilized in this study to synthesize BN-coated MgF2 nanowires and collapsed BN nanotubes, although previous investigations have indicated that the compound cannot be used as a chemical vapour deposition (CVD) reaction precursor of amorphous or crystalline BN. Our study reveals that when MgCl2 is used as a promoter a crystalline BN phase can be obtained on a large scale. The MgCl2 also controls the product morphology, resulting in collapsed BN-coated MgF2 nanowires at the first stage of CVD. The detailed morphology of the composite nanowires also depends on the reaction temperature. Increase in temperature stimulates the nanowire formation. The MgF2 inclusions can be fully removed via a simple high-temperature evaporation procedure, forming collapsed BN nanotubes of high purity and yield.

  11. Graphene growth from reduced graphene oxide by chemical vapour deposition: seeded growth accompanied by restoration

    NASA Astrophysics Data System (ADS)

    Chang, Sung-Jin; Hyun, Moon Seop; Myung, Sung; Kang, Min-A.; Yoo, Jung Ho; Lee, Kyoung G.; Choi, Bong Gill; Cho, Youngji; Lee, Gaehang; Park, Tae Jung

    2016-03-01

    Understanding the underlying mechanisms involved in graphene growth via chemical vapour deposition (CVD) is critical for precise control of the characteristics of graphene. Despite much effort, the actual processes behind graphene synthesis still remain to be elucidated in a large number of aspects. Herein, we report the evolution of graphene properties during in-plane growth of graphene from reduced graphene oxide (RGO) on copper (Cu) via methane CVD. While graphene is laterally grown from RGO flakes on Cu foils up to a few hundred nanometres during CVD process, it shows appreciable improvement in structural quality. The monotonous enhancement of the structural quality of the graphene with increasing length of the graphene growth from RGO suggests that seeded CVD growth of graphene from RGO on Cu surface is accompanied by the restoration of graphitic structure. The finding provides insight into graphene growth and defect reconstruction useful for the production of tailored carbon nanostructures with required properties.

  12. Hot-wire chemical vapour deposition at low substrate temperatures for optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Bakker, R.

    2010-09-01

    The need for large quantities of rapidly and cheaply produced electronic devices has increased rapidly over the past decades. The transistors and diodes that are used to build these devices are predominantly made of crystalline silicon. Since crystalline silicon is very expensive to produce on a large scale and cannot be directly deposited on plastic substrates, much research is being done on thin film amorphous or nanocrystalline semiconductors and insulators. Hot-wire chemical vapour deposition (HWCVD) is a novel, low cost, and convenient way to deposit these materials. The process can be controlled in such a way that specific chemical reactions take place and unwanted side reactions are minimized. It can easily be scaled up to produce large-area thin film electronics. Conventionally, plasma enhanced chemical vapour deposition (PECVD) is used to deposit semiconductors and inorganic dielectrics. Recently, HWCVD has been explored for fast deposition of such materials. An adaptation of HWCVD, initiated chemical vapour deposition (iCVD), offers the unique possibility of producing organic materials and polymers in a vacuum reactor, without the use of solvents. This technique was originally proposed at the Massachusetts institute of technology (MIT) by Prof. Karen Gleason. The iCVD process involves the creation of radicals by dissociation of a peroxide (a molecule with a ~O-O~ bond) by a heated wire in a vacuum reactor. This radical initiates a polymerization reaction of a vinyl (a molecule with a double carbon-carbon bond, ~C=C~) monomer at a substrate held at room temperature. This thesis describes a dedicated iCVD reactor for polymer deposition, installed at Utrecht University, along with a reactor with a cooled substrate holder in an existing HWCVD multi-chamber setup for low-temperature silicon nitride (SiNx) depositions. The most important features of these reactors are described and the characterization techniques are explained. This thesis contains four new

  13. Application of copper vapour lasers for controlling activity of uranium isotopes

    SciTech Connect

    Barmina, E V; Sukhov, I A; Lepekhin, N M; Priseko, Yu S; Filippov, V G; Simakin, Aleksandr V; Shafeev, Georgii A

    2013-06-30

    Beryllium nanoparticles are generated upon ablation of a beryllium target in water by a copper vapour laser. The average size of single crystalline nanoparticles is 12 nm. Ablation of a beryllium target in aqueous solutions of uranyl chloride leads to a significant (up to 50 %) decrease in the gamma activity of radionuclides of the uranium-238 and uranium-235 series. Data on the recovery of the gamma activity of these nuclides to new steady-state values after laser irradiation are obtained. The possibility of application of copper vapour lasers for radioactive waste deactivation is discussed. (laser applications and other topics in quantum electronics)

  14. Vapour and Liquid-Phase Artemisia annua Essential Oil Activities against Several Clinical Strains of Candida.

    PubMed

    Santomauro, Francesca; Donato, Rosa; Sacco, Cristiana; Pini, Gabriella; Flamini, Guido; Bilia, Anna Rita

    2016-07-01

    Candida spp. are often the cause of infection in immune-compromised individuals. They are characterized by a strong resistance to antimicrobial drugs and disinfectants. The activity of Artemisia annua essential oil against Candida spp. was determined by vapour contact and microdilution assay. The oil was characterized by the presence of oxygenated monoterpenes (more than 75 % of the constituents), mainly represented by the irregular monoterpene artemisia ketone (ca. 22 %), and the widespread monoterpenes 1,8 cineole (ca. 19 %) and camphor (ca. 17 %). Other representative constituents were artemisia alcohol (5.9 %), α-pinene (5.7 %), and pinocarvone (3.0 %). Thujone, a typical toxic constituent of the Artemisia species, was not detected. The results are reported as minimum inhibitory concentration, minimum fungicidal concentration, and diameter of inhibition zone obtained by the vapour diffusion assay. We tested 10 clinical Candida strains, coming from both clinical samples and international collections. The results show that the antifungal activity of A. annua is influenced by the type of method adopted. The inhibitory action of the essential oil was, in fact, higher in the vapour than in the liquid phase. Our results show an average minimum inhibitory concentration in the liquid phase of 11.88 µL/mL, while in the vapour phase, the growth of all Candida strains tested at a concentration of 2.13 µL/cm(3) was inhibited. A strain of Candida glabrata was found to be less susceptible to the liquid medium than the vapour assay (50 µL/mL vs. 0.64 µL/cm(3), respectively). Candida albicans and Candida dubliniensis were the most susceptible to the vapour test, while Candida parapsilosis was the most resistant.

  15. Methyldichloroborane evidenced as an intermediate in the chemical vapour deposition synthesis of boron carbide.

    PubMed

    Reinisch, G; Patel, S; Chollon, G; Leyssale, J-M; Alotta, D; Bertrand, N; Vignoles, G L

    2011-09-01

    The most recent ceramic-matrix composites (CMC) considered for long-life applications as thermostructural parts in aerospace propulsion contain, among others, boron-rich phases like boron carbide. This compound is prepared by thermal Chemical Vapour Infiltration (CVI), starting from precursors like boron halides and hydrocarbons. We present a study aiming at a precise knowledge of the gas-phase composition in a hot-zone LPCVD reactor fed with BCl3, CH4 and H2, which combines experimental and theoretical approaches. This work has brought strong evidences of the presence of Methydichloroborane (MDB, BCl2CH3) in the process. It is demonstrated that this intermediate, the presence of which had never been formally proved before, appears for processing temperatures slightly lower than the deposition temperature of boron carbide. The study features quantum chemical computations, which provide several pieces of information like thermochemical and kinetic data, as well as vibration and rotation frequencies, reaction kinetics computations, and experimental gas-phase characterization of several species by FTIR, for several processing parameter sets. The main results are presented, and the place of MDB in the reaction scheme is discussed.

  16. Fluorinated carboxylic membranes deposited by plasma enhanced chemical vapour deposition for fuel cell applications

    NASA Astrophysics Data System (ADS)

    Thery, J.; Martin, S.; Faucheux, V.; Le Van Jodin, L.; Truffier-Boutry, D.; Martinent, A.; Laurent, J.-Y.

    Among the fuel cell technologies, the polymer electrolyte membrane fuel cells (PEMFCs) are particularly promising because they are energy-efficient, clean, and fuel-flexible (i.e., can use hydrogen or methanol). The great majority of PEM fuel cells rely on a polymer electrolyte from the family of perfluorosulfonic acid membranes, nevertheless alternative materials are currently being developed, mainly to offer the alternative workout techniques which are required for the portable energy sources. Plasma polymerization represents a good solution, as it offers the possibility to deposit thin layer with an accurate and homogeneous thickness, even on 3D surfaces. In this paper, we present the results for the growth of proton conductive fluoro carboxylic membranes elaborated by plasma enhanced chemical vapour deposition. These membranes present conductivity values of the same order than the one of Nafion ®. The properties of the membrane, such as the chemical composition, the ionic conductivity, the swelling behaviour and the permeability were correlated to the plasma process parameters. The membranes were integrated in fuel cells on porous substrates and we present here the results regarding the barrier effect and the power output. Barrier effect similar to those of 40 μm Nafion ® layers was reached for 10 μm thick carboxylic membranes. Power outputs around 3 mW cm -2 were measured. We discuss the results regarding the gas barrier effect and the power outputs.

  17. Chemical vapour deposition of tungsten oxide thin films from single-source precursors

    NASA Astrophysics Data System (ADS)

    Cross, Warren Bradley

    This thesis describes the chemical vapour deposition (CVD) of tungsten oxide thin films on glass from a wide range of single-source precursors. Chapter 1 describes previous work that has motivated this research. Chapter 2 discusses the synthesis of conventional style candidates for single-source precursors. Reactions of WOCl4 with 3-methyl salicylic acid (MesaliH2) and 3,5-di-iso-propyl salicylic acid (di-i-PrsaliH2) yielded the ditungsten complexes [WO(Mesali)(MesaliH)2(mu-O)], 1, and [WO(di-i-Prsali)(di-i-PrsaliH)2(mu-O)], 2, and the monotungsten complex [WO(di-i-Pr sali)(di-i-PrsaliH)Cl], 3. Tungsten(VI) dioxo complexes were prepared by ligand exchange reactions of [WO2(acac)2], 4, yielding [WO2(catH)2], 5, and [WO2(malt)2], 6, (catH2 = 3,5-di-tert-butyl-catechol; maltH = maltol). Chapter 3 describes thermal analyses of the complexes 1 - 6 and tungsten hexaphenoxide, and consequently their suitability for CVD. The use of [W(OPh)6] and 2 - 6 in aerosol assisted CVD is reported in Chapter 4. Brown tungsten oxide was deposited from 2 and 3 at 600 °C; blue partially-reduced WO3-x thin films were deposited from [W(OPh)6] from 300 to 500 °C, from 4 at 600 °C and 6 at 620 °C. Sintering all of the coatings in air at 550 °C afforded yellow films of stoichiometric WO3. Raman spectroscopy and glancing angle XRD showed that coatings deposited from [W(OPh)6] at 300 °C were amorphous, whereas all the other films were the monoclinic phase gamma-tungsten oxide. Taking full advantage of the aerosol vaporisation technique led to the CVD of tungsten oxide films from polyoxometalate single-source precursors, as described in Chapter 5. The isopolyanion [nBu4N]2[W6O19], 7, afforded WO3 at 410 °C; the heteropolyanions [nBu4N]4H3[PW11O39], 8, and [nBu4N]4[PNbW11O40], 9, were used to deposit doped WO3 thin films in a highly-controlled manner at 480 °C. Thus, the unprecedented use of large, charged clusters for CVD was demonstrated. Chapter 6 describes investigations of the

  18. Preparation, characterisation and optimisation of lithium battery anodes consisting of silicon synthesised using Laser assisted Chemical Vapour Pyrolysis

    NASA Astrophysics Data System (ADS)

    Veliscek, Ziga; Perse, Lidija Slemenik; Dominko, Robert; Kelder, Erik; Gaberscek, Miran

    2015-01-01

    Suitability of silicon prepared using Laser assisted Chemical Vapour Pyrolysis (LaCVP) as a potential anode material in lithium batteries is systematically investigated. Its compositional, morphological, physical-chemical and electrochemical properties are compared to a current benchmark commercial silicon. Important differences in particle size and particle composition are found which, as shown, affect critically the rheological properties of the corresponding electrode slurries. In order to overcome the rheological problems of prepared nanosilicon, we introduce and optimise a spraying method instead of using the usual casting technique for slurry application. Interestingly, the optimised electrodes show similar electrochemical performance, regardless of the particle size or composition of nanosilicon. This unexpected result is explained by the unusually high resistance of electrochemical wiring in silicon-based electrodes (about 60 Ohm per 1 mg cm-2 of active material loading). Despite that, the optimised material still shows a capacity up to 1200 mA h g-1 at a relatively high loading of 1.6 mg cm-2 and after 20 cycles. On the other hand, by decreasing the loading to below ca. 0.9 mg cm-2 the wiring problems are effectively overcome and capacities close to theoretical values can be obtained.

  19. Some considerations of the thermodynamics and kinetics of the chemical vapour deposition of tungsten

    NASA Astrophysics Data System (ADS)

    Hitchman, Michael L.; Jobson, Andrew D.; Kwakman, Loek F. Tz.

    1989-09-01

    The possibility of the chemical vapour deposition of tungsten for metallisation for microelectronic applications has been considered and investigated for about twenty years, but the process still remains problematical and has serious limitations. Many of the difficulties arise from a lack of a good understanding of the chemistry of the processes and on the effect of that chemistry on layer properties and characteristics. In particular, the very limited information about the thermodynamics and kinetics of the processes allows little more than an empirical approach to the control of reaction parameters or reactor design. In this paper we review the two predominant reactions of silicon and hydrogen reduction of tungsten hexafluoride and we make some observations and comments on the thermodynamics and kinetics of the two reactions. We also review the chemistry of selective deposition of tungsten. However, in order to fully exploit the chemistry of the deposition processes it is pointed out that for both basic studies and applications it is necessary to make use of high vacuum technology in order to minimise the effect of atmospheric impurities, particularly water, and reaction by-products.

  20. Epitaxial chemical vapour deposition growth of monolayer hexagonal boron nitride on a Cu(111)/sapphire substrate.

    PubMed

    Uchida, Yuki; Iwaizako, Tasuku; Mizuno, Seigi; Tsuji, Masaharu; Ago, Hiroki

    2017-03-22

    Hexagonal boron nitride (h-BN), an atomically thin insulating material, shows a large band gap, mechanical flexibility, and optical transparency. It can be stacked with other two-dimensional (2D) materials through van der Waals interactions to form layered heterostructures. These properties promise its application as an insulating layer of novel 2D electronic devices due to its atomically smooth surface with a large band gap. Herein, we demonstrated the ambient-pressure chemical vapour deposition (CVD) growth of high-quality, large-area monolayer h-BN on a Cu(111) thin film deposited on a c-plane sapphire using ammonia borane (BH3NH3) as the feedstock. Highly oriented triangular h-BN grains grow on Cu(111), which finally coalescence to cover the entire Cu surface. Low-energy electron diffraction (LEED) measurements indicated that the hexagonal lattice of the monolayer h-BN is well-oriented along the underlying Cu(111) lattice, thus implying the epitaxial growth of h-BN, which can be applied in various 2D electronic devices.

  1. Assessment of conservative weighting scheme in simulating chemical vapour deposition with trace species

    NASA Astrophysics Data System (ADS)

    Wu, J.-S.; Hsiao, W.-J.; Lian, Y.-Y.; Tseng, K.-C.

    2003-09-01

    Low-pressure or ultra-high vacuum chemical vapour deposition often involves important trace species in both gas-phase and surface reactions. The conservative weighting scheme (J. Thermophys. Heat Transfer 1996; 10(4) : 579) has been used to deal with the trace species often involved in some non-reactive physical processes, which is otherwise considered computationally impossible using the conventional DSMC method. This conservative weighting scheme (CWS) improves greatly the statistical uncertainties by decreasing the weighting factors of trace-species particles and ensures the conservation of both momentum and energy between two colliding particles with large difference of weighting factors. This CWS is further extended to treat reactive processes for gas-phase and surface reactions with trace species, which is called extended conservative weighting scheme (ECWS). A single-cell equilibrium simulation is performed for verifying both the CWS and ECWS in treating trace species. The results of using CWS show that it is most efficient and accurate for weight ratio (trace to non-trace) equal to or less than 0.01 for flows with two and three species. The results of a single-cell simulation using ECWS for gas-phase reaction and surface reactions show that only ECWS can produce acceptable results with reasonable computational time.

  2. Chemical Vapour Deposition of Graphene with Re-useable Pt and Cu substrates for Flexible Electronics

    NASA Astrophysics Data System (ADS)

    Karamat, Shumaila; Sonusen, Selda; Celik, Umit; Uysalli, Yigit; Oral, Ahmet

    2015-03-01

    Graphene has gained the attention of scientific world due to its outstanding physical properties. The future demand of flexible electronics such as solar cells, light emitting diodes, photo-detectors and touch screen technology requires more exploration of graphene properties on flexible substrates. The most interesting application of graphene is in organic light emitting diodes (OLED) where efforts are in progress to replace brittle indium tin oxide (ITO) electrode with a flexible graphene electrode because ITO raw materials are becoming increasingly expensive, and its brittle nature makes it unsuitable for flexible devices. In this work, we grow graphene on Pt and Cu substrates using chemical vapour deposition (CVD) and transferred it to a polymer material (PVA) using lamination technique. We used hydrogen bubbling method for separating graphene from Pt and Cu catalyst to reuse the substrates many times. After successful transfer of graphene on polymer samples, we checked the resistivity values of the graphene sheet which varies with growth conditions. Furthermore, Raman, atomic force microscopy (AFM), I-V and Force-displacement measurements will be presented for these samples.

  3. Characterisation of TiO 2 deposited by photo-induced chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Kaliwoh, Never; Zhang, Jun-Ying; Boyd, Ian W.

    2002-01-01

    We report the deposition of thin TiO 2 films on crystalline Si and quartz by photo-induced chemical vapour deposition (CVD) using UV excimer lamps employing a dielectric barrier discharge in krypton chloride (KrCl ∗) to provide intense narrow band radiation at λ=222 nm. The precursor used was titanium isopropoxide (TTIP). Films from around 20-510 nm in thickness with refractive indices from 2.20 to 2.54 were grown at temperatures between 50 and 350 °C. The higher refractive index values compare favourably with the value of 2.58 recorded for the bulk material. The measured deposition rate was around 50 nm/min at 350 °C. Fourier transform infrared spectroscopy (FTIR) revealed the presence of TiO 2 through the observation of a Ti-O absorption peak and the absence of OH in films deposited at 250-350 °C indicated relatively good quality films. The phase of films deposited at 200-350 °C was anatase as determined by X-ray diffraction.

  4. The reaction-field effect on the chemical potentials of polar aprotic non-aromatic liquids 1. Vapour pressure

    NASA Astrophysics Data System (ADS)

    Rosseinsky, D. R.; Stead, K.; Mowforth, C. W.

    1998-10-01

    The reaction field for the interaction of a molecule with its identical neighbours is shown to be a major determinant of the chemical potential of many dipolar liquids. The electrostatic potential w, derived for immersion of the dipolar molecule in its own kind, and notably comprising solely static and hf permittivities, is equated with the difference between the polar-liquid chemical potential and that of an isostructural non-polar hydrocarbon. For all the 26 non-aromatic Onsager liquids for which the requisite data are available, acceptable conformity is established of the vapour pressure calculated from w with that observed, fluorocarbons excepted. If w turns out to be small, vapour pressures of (these 12) dipolars approximate quite closely to those of the isostructural non-polars, as expected. For ketones and nitroalkanes varied-temperature data are available and well reproduced via w: thus calculated vaporization enthalpies equal the observed.

  5. Effects of precursor concentration on the optical and electrical properties of SnXSY thin films prepared by plasma-enhanced chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Sanchez-Juarez, A.; Ortíz, A.

    2002-09-01

    We have carried out the electrical and optical characterization of thin films of compounds based on Sn-S bonds (SnS2, Sn2S3), prepared by plasma-enhanced chemical vapour deposition (PECVD), as a function of the relative concentration of the precursor vapours, SnCl4 and H2S, keeping all other deposition parameters constant. In all studied cases, the deposited films were formed by polycrystalline materials. The optical bandgap values of deposited materials were calculated from optical transmittance and reflectance measurements. The SnS2 compound produced under certain deposition conditions has a forbidden bandgap around 2.2 eV. This compound shows n-type electrical conductivity, whose dark value at room temperature is 2 × 10-2 (Ω cm)-1. Also, it shows the typical semiconductor dependence of its electrical conductivity on the temperature with an activation energy of about 0.15 eV. However, thin films of a mixture of SnS2 and Sn2S3 compounds were deposited with higher values of the relative concentration of source vapours than those used to obtain the SnS2 compound. The optical bandgap shows a decreasing trend as the relative concentration increases. A similar trend is observed for dark electrical conductivity. These results create the opportunity to use SnX SY compounds in thin films for building heterojunction solar cells prepared completely by PECVD.

  6. Vapour breakthrough behaviour of carbon tetrachloride - A simulant for chemical warfare agent on ASZMT carbon: A comparative study with whetlerite carbon

    NASA Astrophysics Data System (ADS)

    Srivastava, Avanish Kumar; Shah, Dilip K.; Mahato, T. H.; Roy, A.; Yadav, S. S.; Srivas, S. K.; Singh, Beer

    2013-06-01

    ASZMT and whetlerite carbon was prepared by impregnation of active carbon with ammonical salts of Cu (II), Ag (I), Zn (II), Mo (VI), TEDA and Cu (II), Ag (I), Cr (VI), NaOH, C5H5N respectively using incipient wetness technique. Thereafter, impregnated carbon systems were characterized using scanning electron microscopy, energy dispersive X-ray, atomic absorption spectroscopy, thermogravimetry and surface characterization techniques. Impregnated carbon systems were evaluated under dynamic conditions against carbon tetrachloride (CCl4) vapour that was used as a simulant for the persistent chemical warfare agents for testing breakthrough times of filter cartridges and canisters of gas masks in the national approval test of respirators. The protective potential of ASZMT carbon was compared with the whetlerite carbon which is presently used in NBC filtration system. The effect of CCl4 concentration, test flow rate, temperature and relative humidity on the breakthrough behaviour of the impregnated carbon systems has also been studied. The study clearly indicated that the whetlerite carbon possessed breakthrough time greater than ASZMT carbon. However, ASZMT carbon provided adequate protection against CCl4 vapours and can be used as an alternative to whetlerite carbon that contain Cr(VI), which is reported to be carcinogenic and having lesser shelf life. The study indicated the breakthrough time of impregnated carbon systems were found to decrease with the increase of the CCl4 concentration and flow rate. The variation in temperature and relative humidity did not significantly affect the breakthrough behaviour of impregnated carbon systems at high vapour concentration of CCl4 whereasbreak through time of impregnated carbon systems reduced by an increase of relative humidity at low CCl4 vapour concentration.

  7. Titanium oxide thin films obtained with physical and chemical vapour deposition methods for optical biosensing purposes.

    PubMed

    Dominik, M; Leśniewski, A; Janczuk, M; Niedziółka-Jönsson, J; Hołdyński, M; Wachnicki, Ł; Godlewski, M; Bock, W J; Śmietana, M

    2017-07-15

    This work discusses an application of titanium oxide (TiOx) thin films deposited using physical (reactive magnetron sputtering, RMS) and chemical (atomic layer deposition, ALD) vapour deposition methods as a functional coating for label-free optical biosensors. The films were applied as a coating for two types of sensors based on the localised surface plasmon resonance (LSPR) of gold nanoparticles deposited on a glass plate and on a long-period grating (LPG) induced in an optical fibre. Optical and structural properties of the TiOx thin films were investigated and discussed. It has been found that deposition method has a significant influence on optical properties and composition of the films, but negligible impact on TiOx surface silanization effectiveness. A higher content of oxygen with lower Ti content in the ALD films leads to the formation of layers with higher refractive index and slightly higher extinction coefficient than for the RMS TiOx. Moreover, application of the TiOx film independently on deposition method enables not only for tuning of the spectral response of the investigated biosensors, but also in case of LSPR for enhancing the ability for biofunctionalization, i.e., TiOx film mechanically protects the nanoparticles and induces change in the biofunctionalization procedure to the one typical for oxides. TiOx coated LSPR and LPG sensors with refractive index sensitivity of close to 30 and 3400nm/RIU, respectively, were investigated. The ability for molecular recognition was evaluated with the well-known complex formation between avidin and biotin as a model system. The shift in resonance wavelength reached 3 and 13.2nm in case of LSPR and LPG sensors, respectively. Any modification in TiOx properties resulting from the biofunctionalization process can be also clearly detected.

  8. The Role of Plasma in Plasma Enhanced Chemical Vapour Deposition of Nanostructure Growth

    NASA Technical Reports Server (NTRS)

    Hash, David B.; Meyyappan, M.; Teo, Kenneth B. K.; Lacerda, Rodrigo G.; Rupesinghe, Nalin L.

    2004-01-01

    Chemical vapour deposition (CVD) has become the preferred process for high yield growth of carbon nanotubes and nanofibres because of its ability to pattern growth through lithographic positioning of transition metal catalysts on substrates. Many potential applications of nanotubes such as field emitters [1] require not only patterned growth but also vertical alignment. Some degree of ali,ment in thermal CVD processes can be obtained when carbon nanotubes are grown closely together as a result of van der Waals interactions. The ali,onment however is marginal, and the van der Waals prerequisite makes growth of freestanding nanofibres with thermal CVD unrealizable. The application of electric fields as a means of ali,onment has been shown to overcome this limitation [2-5], and highly aligned nanostructures can be grown if electric fields on the order of 0.5 V/microns are employed. Plasma enhanced CVD in various configurations including dc, rf, microwave, inductive and electron cyclotron resonance has been pursued as a means of enabling alignment in the CVD process. However, the sheath fields for the non-dc sources are in general not sufficient for a high degree of ali,pment and an additional dc bias is usually applied to the growth substrate. This begs the question as to the actual role of the plasma. It is clear that the plasma itself is not required for aligned growth as references [3] and [4] employed fields through small applied voltages (3-20 V) across very small electrode spacings (10-100 microns) and thus avoided striking a discharge.

  9. Temperature-dependent Hall effect studies of ZnO thin films grown by metalorganic chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Roro, K. T.; Kassier, G. H.; Dangbegnon, J. K.; Sivaraya, S.; Westraadt, J. E.; Neethling, J. H.; Leitch, A. W. R.; Botha, J. R.

    2008-05-01

    The electrical properties of zinc oxide (ZnO) thin films of various thicknesses (0.3-4.4 µm) grown by metalorganic chemical vapour deposition on glass substrates have been studied by using temperature-dependent Hall-effect (TDH) measurements in the 18-300 K range. The high quality of the layers has been confirmed with x-ray diffraction, transmission electron microscopy, scanning electron microscopy and photoluminescence techniques. TDH measurements indicate the presence of a degenerate layer which significantly influences the low-temperature data. It is found that the measured mobility generally increases with increasing layer thickness, reaching a value of 120 cm2 V-1 s-1 at room temperature for the 4.4 µm thick sample. The lateral grain size of the layers is also found to increase with thickness indicating a clear correlation between the size of the surface grains and the electrical properties of corresponding films. Theoretical fits to the Hall data suggest that the bulk conduction of the layers is dominated by a weakly compensated donor with activation energy in the 33-41 meV range and concentration of the order of 1017 cm-3, as well as a total acceptor concentration of mid-1015 cm-3. Grain boundary scattering is found to be an important limiting factor of the mobility throughout the temperature range considered.

  10. Evaluation of freestanding boron-doped diamond grown by chemical vapour deposition as substrates for vertical power electronic devices

    SciTech Connect

    Issaoui, R.; Achard, J.; Tallaire, A.; Silva, F.; Gicquel, A.; Bisaro, R.; Servet, B.; Garry, G.; Barjon, J.

    2012-03-19

    In this study, 4 x 4 mm{sup 2} freestanding boron-doped diamond single crystals with thickness up to 260 {mu}m have been fabricated by plasma assisted chemical vapour deposition. The boron concentrations measured by secondary ion mass spectroscopy were 10{sup 18} to 10{sup 20} cm{sup -3} which is in a good agreement with the values calculated from Fourier transform infrared spectroscopy analysis, thus indicating that almost all incorporated boron is electrically active. The dependence of lattice parameters and crystal mosaicity on boron concentrations have also been extracted from high resolution x-ray diffraction experiments on (004) planes. The widths of x-ray rocking curves have globally shown the high quality of the material despite a substantial broadening of the peak, indicating a decrease of structural quality with increasing boron doping levels. Finally, the suitability of these crystals for the development of vertical power electronic devices has been confirmed by four-point probe measurements from which electrical resistivities as low as 0.26 {Omega} cm have been obtained.

  11. Temporal Stability of Metal-Chloride-Doped Chemical-Vapour-Deposited Graphene.

    PubMed

    Kang, Moon H; Milne, William I; Cole, Matthew T

    2016-08-18

    Graphene has proven to be a promising material for transparent flexible electronics. In this study, we report the development of a transfer and doping scheme of large-area chemical vapour deposited (CVD) graphene. A technique to transfer the as-grown material onto mechanically flexible and optically transparent polymeric substrates using an ultraviolet adhesive (UVA) is outlined, along with the temporal stability of the sheet resistance and optical transparency following chemical doping with various metal chlorides (Mx Cly The sheet resistance (RS ) and 550 nm optical transparency (%T550 ) of the transferred un-doped graphene was 3.5 kΩ sq(-1) (±0.2 kΩ sq(-1) ) and 84.1 % (±2.9 %), respectively. Doping with AuCl3 showed a notable reduction in RS by some 71.4 % (to 0.93 kΩ sq(-1) ) with a corresponding %T550 of 77.0 %. After 200 h exposure to air at standard temperature and pressure, the increase in RS was found to be negligible (ΔRS AuCl3 =0.06 kΩ sq(-1) ), indicating that, of the considered Mx Cly species, AuCl3 doping offered the highest degree of time stability under ambient conditions. There appears a tendency of increasing RS with time for the remaining metal chlorides studied. We attribute the observed temporal shift to desorption of molecular dopants. We find that desorption was most significant in RhCl3 -doped samples whereas, in contrast, after 200 h in ambient conditions, AuCl3 -doped graphene showed only marginal desorption. The results of this study demonstrate that chemical doping of UVA-transferred graphene is a promising means for enhancing large-area CVD graphene in order to realise a viable platform for next-generation optically transparent and mechanically flexible electronics.

  12. Aerosol assisted chemical vapour deposition of gas sensitive SnO2 and Au-functionalised SnO2 nanorods via a non-catalysed vapour solid (VS) mechanism

    PubMed Central

    Vallejos, Stella; Selina, Soultana; Annanouch, Fatima Ezahra; Gràcia, Isabel; Llobet, Eduard; Blackman, Chris

    2016-01-01

    Tin oxide nanorods (NRs) are vapour synthesised at relatively lower temperatures than previously reported and without the need for substrate pre-treatment, via a vapour-solid mechanism enabled using an aerosol-assisted chemical vapour deposition method. Results demonstrate that the growth of SnO2 NRs is promoted by a compression of the nucleation rate parallel to the substrate and a decrease of the energy barrier for growth perpendicular to the substrate, which are controlled via the deposition conditions. This method provides both single-step formation of the SnO2 NRs and their integration with silicon micromachined platforms, but also allows for in-situ functionalization of the NRs with gold nanoparticles via co-deposition with a gold precursor. The functional properties are demonstrated for gas sensing, with microsensors using functionalised NRs demonstrating enhanced sensing properties towards H2 compared to those based on non-functionalised NRs. PMID:27334232

  13. Vapour-liquid coexistence of an active Lennard-Jones fluid.

    PubMed

    Prymidis, Vasileios; Paliwal, Siddharth; Dijkstra, Marjolein; Filion, Laura

    2016-09-28

    We study a three-dimensional system of self-propelled Lennard-Jones particles using Brownian dynamics simulations. Using recent theoretical results for active matter, we calculate the pressure and report equations of state for the system. Additionally, we chart the vapour-liquid coexistence and show that the coexistence densities can be well described using simple power laws. Lastly, we demonstrate that our out-of-equilibrium system shows deviations from both the law of rectilinear diameters and the law of corresponding states.

  14. Vapour-liquid coexistence of an active Lennard-Jones fluid

    NASA Astrophysics Data System (ADS)

    Prymidis, Vasileios; Paliwal, Siddharth; Dijkstra, Marjolein; Filion, Laura

    2016-09-01

    We study a three-dimensional system of self-propelled Lennard-Jones particles using Brownian dynamics simulations. Using recent theoretical results for active matter, we calculate the pressure and report equations of state for the system. Additionally, we chart the vapour-liquid coexistence and show that the coexistence densities can be well described using simple power laws. Lastly, we demonstrate that our out-of-equilibrium system shows deviations from both the law of rectilinear diameters and the law of corresponding states.

  15. Hair analysis as a useful procedure for detection of vapour exposure to chemical warfare agents: simulation of sulphur mustard with methyl salicylate.

    PubMed

    Spiandore, Marie; Piram, Anne; Lacoste, Alexandre; Josse, Denis; Doumenq, Pierre

    2014-06-01

    Chemical warfare agents (CWA) are highly toxic compounds which have been produced to kill or hurt people during conflicts or terrorist attacks. Despite the fact that their use is strictly prohibited according to international convention, populations' exposure still recently occurred. Development of markers of exposure to CWA is necessary to distinguish exposed victims from unexposed ones. We present the first study of hair usage as passive sampler to assess contamination by chemicals in vapour form. This work presents more particularly the hair adsorption capacity for methyl salicylate used as a surrogate of the vesicant sulphur mustard. Chemical vapours toxicity through the respiratory route has historically been defined through Haber's law's concentration-time (Ct) product, and vapour exposure of hair to methyl salicylate was conducted with various times or doses of exposure in the range of incapacitating and lethal Ct products corresponding to sulphur mustard. Following exposure, extraction of methyl salicylate from hair was conducted by simple soaking in dichloromethane. Methyl salicylate could be detected on hair for vapour concentration corresponding to about one fifth of the sulphur mustard concentration that would kill 50% of exposed individuals (LCt50). The amount of methyl salicylate recovered from hair increased with time or dose of exposure. It showed a good correlation with the concentration-time product, suggesting that hair could be used like a passive sampler to assess vapour exposure to chemical compounds. It introduces great perspectives concerning the use of hair as a marker of exposure to CWA.

  16. Modelling of infrared optical constants for polycrystalline low pressure chemical vapour deposition ZnO:B films

    NASA Astrophysics Data System (ADS)

    Prunici, P.; Hamelmann, F. U.; Beyer, W.; Kurz, H.; Stiebig, H.

    2013-03-01

    Doped zinc oxide films are of high interest in thin film solar cell technology for application as transparent conducting oxide. Rapid and detailed characterisation of ZnO thin film properties is required for quality control and optimisation of the deposited films. In the present work, a new model of dielectric functions based on the effective medium approximation (EMA) is developed and is applied for characterisation of polycrystalline boron doped zinc oxide (ZnO:B) films, deposited by low pressure chemical vapour deposition (LPCVD) technique onto glass substrates. The model takes into account that polycrystalline ZnO is considered to consist of crystal grains surrounded by depletion layers. Using this model and Fourier Transform Infrared Spectroscopy (FTIR) performed in reflection configuration over a wide mid-infrared spectral region (from 2 μm up to 25 μm), the properties of depletion layer and the bulk of the grains in ZnO can be rapidly characterised in detail, and the volume fraction of the depletion layer can be extracted. The results are in good agreement with previously presented theories of electron transport in polycrystalline materials. Using electrical measurements like conductivity and Hall techniques in addition to the optically determined parameters, predominant electron scattering mechanisms in polycrystalline films for different doping levels are identified. The measurements show the impact of the doping level on depletion layer of the crystallites. It is shown, furthermore, that under a water vapour rich environment the volume fraction of the depletion layer may increase up to 5 times and more, while the mobility of the charge carriers in the depletion layer drops drastically from about 31 cm2V-1s-1 to about 8 cm2V-1s-1. This indicates that water vapour exposure causes an increase of the potential barrier in the grain boundary depletion layer, limiting the electron transport across the grain boundaries to a classical thermionic emission

  17. Sticking non-stick: Surface and Structure control of Diamond-like Carbon in Plasma Enhanced Chemical Vapour Deposition

    NASA Astrophysics Data System (ADS)

    Jones, B. J.; Nelson, N.

    2016-10-01

    This short review article explores the practical use of diamond-like carbon (DLC) produced by plasma enhanced chemical vapour deposition (PECVD). Using as an example issues relating to the DLC coating of a hand-held surgical device, we draw on previous works using atomic force microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, tensiometry and electron paramagnetic resonance. Utilising data from these techniques, we examine the surface structure, substrate-film interface and thin film microstructure, such as sp2/sp3 ratio (graphitic/diamond-like bonding ratio) and sp2 clustering. We explore the variations in parameters describing these characteristics, and relate these to the final device properties such as friction, wear resistance, and diffusion barrier integrity. The material and device characteristics are linked to the initial plasma and substrate conditions.

  18. Palm Oil as the Carbon Source for the Synthesis of Carbon Nanotubes using Floating Catalyst—Chemical Vapour Deposition Method

    NASA Astrophysics Data System (ADS)

    Zobir, S. A. M.; Suriani, A. B.; Khusaimi, Z.; Mamat, H.; Zainal, Z.; Sarijo, S. H.; Rusop, M.

    2011-03-01

    CNTs were synthesized using floating catalyst by dual-furnace thermal chemical vapour deposition method at 800-1000° C. Cooking oil made of palm oil was used as the carbon precursor. Ferrocene in the presence of 0.05 M zinc nitrate and a p-type silicon wafer was used as a catalyst precursor and a sample target, respectively. The deposition temperature was varied from 800-1000° C. Nitrogen gas was used as a gas carrier with a constant flow rate of 150 sccm/min. Field emission scanning electron micrographs show the formation of CNTs together with other carbons formed on the silicon substrate. Raman spectroscopy studies were also supported the formation of CNTs.

  19. Perfluorodecyltrichlorosilane-based seed-layer for improved chemical vapour deposition of ultrathin hafnium dioxide films on graphene

    PubMed Central

    Kitzmann, Julia; Göritz, Alexander; Fraschke, Mirko; Lukosius, Mindaugas; Wenger, Christian; Wolff, Andre; Lupina, Grzegorz

    2016-01-01

    We investigate the use of perfluorodecyltrichlorosilane-based self-assembled monolayer as seeding layer for chemical vapour deposition of HfO2 on large area CVD graphene. The deposition and evolution of the FDTS-based seed layer is investigated by X-ray photoelectron spectroscopy, Auger electron spectroscopy, and transmission electron microscopy. Crystalline quality of graphene transferred from Cu is monitored during formation of the seed layer as well as the HfO2 growth using Raman spectroscopy. We demonstrate that FDTS-based seed layer significantly improves nucleation of HfO2 layers so that graphene can be coated in a conformal way with HfO2 layers as thin as 10 nm. Proof-of-concept experiments on 200 mm wafers presented here validate applicability of the proposed approach to wafer scale graphene device fabrication. PMID:27381715

  20. Construction of conductive multilayer films of biogenic triangular gold nanoparticles and their application in chemical vapour sensing

    NASA Astrophysics Data System (ADS)

    Singh, Amit; Chaudhari, Minakshi; Sastry, Murali

    2006-05-01

    Metal nanoparticles are interesting building blocks for realizing films for a number of applications that include bio- and chemical sensing. To date, spherical metal nanoparticles have been used to generate functional electrical coatings. In this paper we demonstrate the synthesis of electrically conductive coatings using biologically prepared gold nanotriangles as the building blocks. The gold nanotriangles are prepared by the reduction of aqueous chloroaurate ions using an extract of the lemongrass plant (Cymbopogon flexuosus) which are thereafter assembled onto a variety of substrates by simple solution casting. The conductivity of the film shows a drastic fall upon mild heat treatment, leading to the formation of electrically conductive thin films of nanoparticles. We have also investigated the possibility of using the gold nanotriangle films in vapour sensing. A large fall in film resistance is observed upon exposure to polar molecules such as methanol, while little change occurs upon exposure to weakly polar molecules such as chloroform.

  1. Perfluorodecyltrichlorosilane-based seed-layer for improved chemical vapour deposition of ultrathin hafnium dioxide films on graphene

    NASA Astrophysics Data System (ADS)

    Kitzmann, Julia; Göritz, Alexander; Fraschke, Mirko; Lukosius, Mindaugas; Wenger, Christian; Wolff, Andre; Lupina, Grzegorz

    2016-07-01

    We investigate the use of perfluorodecyltrichlorosilane-based self-assembled monolayer as seeding layer for chemical vapour deposition of HfO2 on large area CVD graphene. The deposition and evolution of the FDTS-based seed layer is investigated by X-ray photoelectron spectroscopy, Auger electron spectroscopy, and transmission electron microscopy. Crystalline quality of graphene transferred from Cu is monitored during formation of the seed layer as well as the HfO2 growth using Raman spectroscopy. We demonstrate that FDTS-based seed layer significantly improves nucleation of HfO2 layers so that graphene can be coated in a conformal way with HfO2 layers as thin as 10 nm. Proof-of-concept experiments on 200 mm wafers presented here validate applicability of the proposed approach to wafer scale graphene device fabrication.

  2. Growth of large size diamond single crystals by plasma assisted chemical vapour deposition: Recent achievements and remaining challenges

    NASA Astrophysics Data System (ADS)

    Tallaire, Alexandre; Achard, Jocelyn; Silva, François; Brinza, Ovidiu; Gicquel, Alix

    2013-02-01

    Diamond is a material with outstanding properties making it particularly suited for high added-value applications such as optical windows, power electronics, radiation detection, quantum information, bio-sensing and many others. Tremendous progresses in its synthesis by microwave plasma assisted chemical vapour deposition have allowed obtaining single crystal optical-grade material with thicknesses of up to a few millimetres. However the requirements in terms of size, purity and crystalline quality are getting more and more difficult to achieve with respect to the forecasted applications, thus pushing the synthesis method to its scientific and technological limits. In this paper, after a short description of the operating principles of the growth technique, the challenges of increasing crystal dimensions both laterally and vertically, decreasing and controlling point and extended defects as well as modulating crystal conductivity by an efficient doping will be detailed before offering some insights into ways to overcome them.

  3. Electric, dielectric and optical properties of Ga2O3 grown by metal organic chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Paskaleva, A.; Spassov, D.; Terziyska, P.

    2017-01-01

    Thin film (15-130 nm) of gallium oxide were grown by the industry relevant metal organic chemical vapour deposition (MOCVD) technique on p-type Si to check the possibility for integration of newly rediscovered wide bandgap material with the Si technology. Electric, dielectric and optical properties were studied and analyzed. To perform electrical characterization, Ga2O3 films were integrated into Al/Ga2O3/p-Si metal–oxide–semiconductor (MOS) capacitors. Relative dielectric permittivity, flat-band voltage shift and effective oxide charge density were obtained from C-V measurements. Spectroscopic ellipsometry measurements reveal that Ga2O3 deposited by MOCVD is a direct bandgap material with a large optical bandgap of about 5.1 eV. Both ellipsometrical and electrical results show formation of a thick interfacial SiO2.

  4. A novel three-jet microreactor for localized metal-organic chemical vapour deposition of gallium arsenide: design and simulation

    NASA Astrophysics Data System (ADS)

    Konakov, S. A.; Krzhizhanovskaya, V. V.

    2016-08-01

    We present a novel three-jet microreactor design for localized deposition of gallium arsenide (GaAs) by low-pressure Metal-Organic Chemical Vapour Deposition (MOCVD) for semiconductor devices, microelectronics and solar cells. Our approach is advantageous compared to the standard lithography and etching technology, since it preserves the nanostructure of the deposited material, it is less time-consuming and less expensive. We designed two versions of reactor geometry with a 10-micron central microchannel for precursor supply and with two side jets of a dilutant to control the deposition area. To aid future experiments, we performed computational modeling of a simplified-geometry (twodimensional axisymmetric) microreactor, based on Navier-Stokes equations for a laminar flow of chemically reacting gas mixture of Ga(CH3)3-AsH3-H2. Simulation results show that we can achieve a high-rate deposition (over 0.3 μm/min) on a small area (less than 30 μm diameter). This technology can be used in material production for microelectronics, optoelectronics, photovoltaics, solar cells, etc.

  5. Effects of ball-milling on lithium insertion into multi-walled carbon nanotubes synthesized by thermal chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Eom, JiYong; Kim, DongYung; Kwon, HyukSang

    The effects of ball-milling on Li insertion into multi-walled carbon nanotubes (MWNTs) are presented. The MWNTs are synthesized on supported catalysts by thermal chemical vapour deposition, purified, and mechanically ball-milled by the high energy ball-milling. The purified MWNTs and the ball-milled MWNTs were electrochemically inserted with Li. Structural and chemical modifications in the ball-milled MWNTs change the insertion-extraction properties of Li ions into/from the ball-milled MWNTs. The reversible capacity (C rev) increases with increasing ball-milling time, namely, from 351 mAh g -1 (Li 0.9C 6) for the purified MWNTs to 641 mAh g -1 (Li 1.7C 6) for the ball-milled MWNTs. The undesirable irreversible capacity (C irr) decreases continuously with increase in the ball-milling time, namely, from 1012 mAh g -1 (Li 2.7C 6) for the purified MWNTs to 518 mAh g -1 (Li 1.4C 6) for the ball-milled MWNTs. The decrease in C irr of the ball-milled samples results in an increase in the coulombic efficiency from 25% for the purified samples to 50% for the ball-milled samples. In addition, the ball-milled samples maintain a more stable capacity than the purified samples during charge-discharge cycling.

  6. Well-controlled metal co-catalysts synthesised by chemical vapour impregnation for photocatalytic hydrogen production and water purification.

    PubMed

    Su, Ren; Forde, Michael M; He, Qian; Shen, Yanbin; Wang, Xueqin; Dimitratos, Nikolaos; Wendt, Stefan; Huang, Yudong; Iversen, Bo B; Kiely, Christopher J; Besenbacher, Flemming; Hutchings, Graham J

    2014-10-28

    As co-catalyst materials, metal nanoparticles (NPs) play crucial roles in heterogeneous photocatalysis. The photocatalytic performance strongly relies on the physical properties (i.e., composition, microstructure, and surface impurities) of the metal NPs. Here we report a convenient chemical vapour impregnation (CVI) approach for the deposition of monometallic-, alloyed, and core-shell structured metal co-catalysts onto the TiO2 photocatalyst. The as-synthesised metal NPs are highly dispersed on the support and show narrow size distributions, which suit photocatalysis applications. More importantly, the surfaces of the as-synthesised metal NPs are free of protecting ligands, enabling the photocatalysts to be ready to use without further treatment. The effect of the metal identity, the alloy chemical composition, and the microstructure on the photocatalytic performance has been investigated for hydrogen production and phenol decomposition. Whilst the photocatalytic H2 production performance can be greatly enhanced by using the core-shell structured co-catalyst (Pdshell-Aucore and Ptshell-Aucore), the Ptshell-Aucore modified TiO2 yields enhanced quantum efficiency but a reduced effective decomposition of phenol to CO2 compared to that of the monometallic counterparts. We consider the CVI approach provides a feasible and elegant process for the decoration of photocatalyst materials.

  7. Microstructural and conductivity changes induced by annealing of ZnO:B thin films deposited by chemical vapour deposition.

    PubMed

    David, C; Girardeau, T; Paumier, F; Eyidi, D; Lacroix, B; Papathanasiou, N; Tinkham, B P; Guérin, P; Marteau, M

    2011-08-24

    Zinc oxide (ZnO) thin films have attracted much attention in recent years due to progress in crystal growth for a large variety of technological applications including optoelectronics and transparent electrodes in solar cells. Boron (B)-doped ZnO thin films are deposited by low pressure chemical vapour deposition (LPCVD) on Si(100). These films exhibit a strong (002) texture with a pyramidal grain structure. The ZnO films were annealed after growth; the annealing temperature and the atmosphere appear to strongly impact the layer conductivity. This work will first present the modification of the physical properties (carrier concentration, mobility) extracted from the simulation of layer reflection in the infrared range. At low annealing temperatures the mobility increases slightly before decreasing drastically above a temperature close to 250 °C. The chemical and structural evolution (XPS, x-ray diffraction) of the films was also studied to identify the relationship between microstructural modifications and the variations observed in the film conductivity. An in situ XRD study during annealing has been performed under air and low pressure conditions. As observed for electrical properties, the microstructural modifications shift to higher temperatures for vacuum annealing.

  8. Anti-yeast activity of mentha oil and vapours through in vitro and in vivo (real fruit juices) assays.

    PubMed

    Tyagi, Amit Kumar; Gottardi, Davide; Malik, Anushree; Guerzoni, Maria Elisabetta

    2013-04-15

    The anti-yeast activity of mentha oil and vapours was evaluated against 8 food spoiling yeasts through disc diffusion, disc volatilisation and micro broth dilution method. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) varied from 0.28 to 2.25 and 1.13 to 4.5 mg/ml, respectively. Furthermore, the anti-yeast efficacy of mentha oil alone and in combination with thermal treatment was evaluated in a real food system i.e. mixed fruit juices. The samples treated with a combination of mentha oil at the MIC, ½ MIC and ¼ MIC levels and thermal treatment enhanced the reduction viability. Chemical characterisation of mentha oil by gas chromatography-mass spectrometry (GC-MS) revealed that the dominant compounds were cis-menthone (27.43%), menthol (24.3%), trans-menthone (9.23%), limonene (5.84%), menthofuran (4.44%) and isomenthol (3.21%). Present results established the superior performance of integrated treatment over individual exposure for fruit juice preservation.

  9. Detection of chemical substances in water using an oxide nanowire transistor covered with a hydrophobic nanoparticle thin film as a liquid-vapour separation filter

    NASA Astrophysics Data System (ADS)

    Lim, Taekyung; Lee, Jonghun; Ju, Sanghyun

    2016-08-01

    We have developed a method to detect the presence of small amounts of chemical substances in water, using a Al2O3 nanoparticle thin film covered with phosphonic acid (HDF-PA) self-assembled monolayer. The HDF-PA self-assembled Al2O3 nanoparticle thin film acts as a liquid-vapour separation filter, allowing the passage of chemical vapour while blocking liquids. Prevention of the liquid from contacting the SnO2 nanowire and source-drain electrodes is required in order to avoid abnormal operation. Using this characteristic, the concentration of chemical substances in water could be evaluated by measuring the current changes in the SnO2 nanowire transistor covered with the HDF-PA self-assembled Al2O3 nanoparticle thin film.

  10. Effects of boron addition on a-Si(90)Ge(10):H films obtained by low frequency plasma enhanced chemical vapour deposition.

    PubMed

    Pérez, Arllene M; Renero, Francisco J; Zúñiga, Carlos; Torres, Alfonso; Santiago, César

    2005-06-29

    Optical, structural and electric properties of (a-(Si(90)Ge(10))(1-y)B(y):H) thin film alloys, deposited by low frequency plasma enhanced chemical vapour deposition, are presented. The chemical bonding structure has been studied by IR spectroscopy, while the composition was investigated by Raman spectroscopy. A discussion about boron doping effects, in the composition and bonding of samples, is presented. Transport of carriers has been studied by measurement of the conductivity dependence on temperature, which increases from 10(-3) to 10(1) Ω(-1) cm(-1) when the boron content varies from 0 to 50%. Similarly, the activation energy is between 0.62 and 0.19 eV when the doping increases from 0 to 83%. The optical properties have been determined from the film's optical transmission, using Swanepoel's method. It is shown that the optical gap varies from 1.3 to 0.99 eV.

  11. Synthesis of ultrathin polymer insulating layers by initiated chemical vapour deposition for low-power soft electronics.

    PubMed

    Moon, Hanul; Seong, Hyejeong; Shin, Woo Cheol; Park, Won-Tae; Kim, Mincheol; Lee, Seungwon; Bong, Jae Hoon; Noh, Yong-Young; Cho, Byung Jin; Yoo, Seunghyup; Im, Sung Gap

    2015-06-01

    Insulating layers based on oxides and nitrides provide high capacitance, low leakage, high breakdown field and resistance to electrical stresses when used in electronic devices based on rigid substrates. However, their typically high process temperatures and brittleness make it difficult to achieve similar performance in flexible or organic electronics. Here, we show that poly(1,3,5-trimethyl-1,3,5-trivinyl cyclotrisiloxane) (pV3D3) prepared via a one-step, solvent-free technique called initiated chemical vapour deposition (iCVD) is a versatile polymeric insulating layer that meets a wide range of requirements for next-generation electronic devices. Highly uniform and pure ultrathin films of pV3D3 with excellent insulating properties, a large energy gap (>8 eV), tunnelling-limited leakage characteristics and resistance to a tensile strain of up to 4% are demonstrated. The low process temperature, surface-growth character, and solvent-free nature of the iCVD process enable pV3D3 to be grown conformally on plastic substrates to yield flexible field-effect transistors as well as on a variety of channel layers, including organics, oxides, and graphene.

  12. Optimization of parameters by Taguchi method for controlling purity of carbon nanotubes in chemical vapour deposition technique.

    PubMed

    Dasgupta, K; Sen, D; Mazumder, S; Basak, C B; Joshi, J B; Banerjee, S

    2010-06-01

    The process parameters (viz. temperature of synthesis, type of catalyst, concentration of catalyst and type of catalyst-support material) for controlling purity of carbon nanotubes synthesized by catalytic chemical vapour deposition of acetylene have been optimized by analyzing the experimental results using Taguchi method. It has been observed that the catalyst-support material has the maximum (59.4%) and the temperature of synthesis has the minimum effect (2.1%) on purity of the nanotubes. At optimum condition (15% ferrocene supported on carbon black at the synthesis temperature of 700 degrees C) the purity of nanotubes was found out to be 96.2% with yield of 1900%. Thermogravimetry has been used to assess purity of nanotubes. These nantubes have been further characterized by scanning electron microscopy, transmission electron microscopy and Raman Spectroscopy. Small angle neutron scattering has been used to find out their average inner and outer diameter using an appropriate model. The nanotubes are well crystallized but with wide range of diameter varying between 20-150 nm.

  13. Catalyst-free growth of ZnO nanowires by metal-organic chemical vapour deposition (MOCVD) and thermal evaporation

    SciTech Connect

    Lee, Woong; Jeong, Min-Chang; Myoung, Jae-Min

    2004-08-02

    ZnO nanowires were grown on GaAs(0 0 2) substrates using metal-organic chemical vapour deposition (MOCVD) and on Si(0 0 1) substrates using thermal evaporation of source powders, respectively. It was demonstrated that well-aligned single crystalline nanowires could be grown with controlled sizes using a typical thin film deposition technique without catalysts. Arsenic doping of the ZnO nanowires grown on GaAs substrate was possible using post-growth heat-treatment, proposing a possible way of producing p-type ZnO nanowires. It was also shown that simplified process of carrier-free thermal evaporation without catalyst could be employed to grow nanowires with high yield while maintaining good crystalline and optical properties. Application potential of the nanowires as probes of atomic force microscopes (AFMs) was discussed by predicting their structural compatibility with AFM cantilevers based on continuum elasticity. It was predicted that the nanowires fabricated herein are structurally compatible with typical AFM cantilevers suggesting that they are promising candidates for high aspect ratio probes.

  14. Direct synthesis of solid and hollow carbon nanospheres over NaCl crystals using acetylene by chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Chandra Kishore, S.; Anandhakumar, S.; Sasidharan, M.

    2017-04-01

    Carbon nanospheres (CNS) with hollow and solid morphologies have been synthesised by a simple chemical vapour deposition method using acetylene as a carbon precursor. Sodium chloride (NaCl) powder as a template was used for the direct growth of CNS via facile and low-cost approach. The effect of various temperatures (500 °C, 600 °C and 700 °C) and acetylene flow rates were investigated to study the structural evolution on the carbon products. The purified CNS thus obtained was characterized by various physicochemical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and cyclicvoltametry. The synthesised hollow nanospheres were investigated as anode materials for Li-ion batteries. After 25 cycles of repeated charge/discharge cycles, the discharge and charge capacities were found to be 574 mAh/g and 570 mAh/g, respectively which are significantly higher than the commercial graphite samples.

  15. Plasma enhanced chemical vapour deposition of silica onto Ti: Analysis of surface chemistry, morphology and functional hydroxyl groups.

    PubMed

    Szili, Endre J; Kumar, Sunil; Smart, Roger St C; Lowe, Rachel; Saiz, Eduardo; Voelcker, Nicolas H

    2008-07-15

    Previously, we have developed and characterised a procedure for the deposition of thin silica films by a plasma enhanced chemical vapour deposition (PECVD) procedure using tetraethoxysilane (TEOS) as the main precursor. We have used the silica coatings for improving the corrosion resistance of metals and for enhancing the bioactivity of biomedical metallic implants. Recently, we have been fine-tuning the PECVD method for producing high quality and reproducible PECVD-silica (PECVD-Si) coatings on metals, primarily for biomaterial applications. In order to understand the interaction of the PECVD-Si coatings with biological species (such as proteins and cells), it is important to first analyse the properties of the silica films deposited using the optimised parameters. Therefore, this current investigation was carried out to analyse the characteristic features of PECVD-Si deposited on Ti substrates (PECVD-Si-Ti). We determined that the PECVD-Si coatings on Ti were conformal to the substrate surface, strongly adhered to the underlying substrate and were resistant to delamination. The PECVD-Si surface was composed of stoichiometric SiO(2), showed a low carbon content (below 10 at.%) and was very hydrophilic (contact angle <10°). Finally, we also showed that the PECVD-Si coatings contain functional hydroxyl groups.

  16. Low temperature silicon nitride by hot wire chemical vapour deposition for the use in impermeable thin film encapsulation on flexible substrates.

    PubMed

    Spee, D A; van der Werf, C H M; Rath, J K; Schropp, R E I

    2011-09-01

    High quality non porous silicon nitride layers were deposited by hot wire chemical vapour deposition at substrate temperatures lower than 110 degrees C. The layer properties were investigated using FTIR, reflection/transmission measurements and 1:6 buffered HF etching rate. A Si-H peak position of 2180 cm(-1) in the Fourier transform infrared absorption spectrum indicates a N/Si ratio around 1.2. Together with a refractive index of 1.97 at a wavelength of 632 nm and an extinction coefficient of 0.002 at 400 nm, this suggests that a transparent high density silicon nitride material has been made below 110 degrees C, which is compatible with polymer films and is expected to have a high impermeability. To confirm the compatibility with polymer films a silicon nitride layer was deposited on poly(glycidyl methacrylate) made by initiated chemical vapour deposition, resulting in a highly transparent double layer.

  17. Titania Coated Mica via Chemical Vapour Deposition, Post N-doped by Liquid Ammonia Treatment

    NASA Astrophysics Data System (ADS)

    Powell, Michael J.; Parkin, Ivan P.

    TiO2 films were successfully grown on synthetic mica powders via Chemical Vapor Deposition (CVD). The CVD rig is a cold-walled design that allows surface coverage of a powder to be successfully achieved. The TiO2 was produced by the reaction between TiCl4 and Ethyl Acetate. The powder produced could be successfully N-doped using post liquid ammonia treatment. The TiO2 powder produced could have potential applications in self-cleaning surfaces or antimicrobial paints.

  18. Strain and structure heterogeneity in MoS2 atomic layers grown by chemical vapour deposition

    DOE PAGES

    Liu, Zheng; Amani, Matin; Najmaei, Sina; ...

    2014-11-18

    Monolayer molybdenum disulfide (MoS2) has attracted tremendous attention due to its promising applications in high-performance field-effect transistors, phototransistors, spintronic devices, and nonlinear optics. The enhanced photoluminescence effect in monolayer MoS2 was discovered and, as a strong tool, was employed for strain and defect analysis in MoS2. Recently, large-size monolayer MoS2 has been produced by chemical vapor deposition but has not yet been fully explored. Here we systematically characterize chemical vapor deposition grown MoS2 by PL spectroscopy and mapping, and demonstrate non-uniform strain in single-crystalline monolayer MoS2 and strain-induced band gap engineering. We also evaluate the effective strain transferred from polymermore » substrates to MoS2 by three-dimensional finite element analysis. In addition, our work demonstrates that PL mapping can be used as a non-contact approach for quick identification of grain boundaries in MoS2.« less

  19. Nanofabrication using home-made RF plasma coupled chemical vapour deposition system

    NASA Astrophysics Data System (ADS)

    Ong, Si Ci; Ilyas, Usman; Rawat, Rajdeep Singh

    2014-08-01

    Zinc oxide, ZnO, a popular semiconductor material with a wide band gap (3.37 eV) and high binding energy of the exciton (60 meV), has numerous applications such as in optoelectronics, chemical/biological sensors, and drug delivery. This project aims to (i) optimize the operating conditions for growth of ZnO nanostructures using the chemical vapor deposition (CVD) method, and (ii) investigate the effects of coupling radiofrequency (RF) plasma to the CVD method on the quality of ZnO nanostructures. First, ZnO nanowires were synthesized using a home-made reaction setup on gold-coated and non-coated Si (100) substrates at 950 °C. XRD, SEM, EDX, and PL measurements were used for characterizations and it was found that a deposition duration of 10 minutes produced the most well-defined ZnO nanowires. SEM analysis revealed that the nanowires had diameters ranging from 30-100 mm and lengths ranging from 1-4 µm. In addition, PL analysis showed strong UV emission at 380 nm, making it suitable for UV lasing. Next, RF plasma was introduced for 30 minutes. Both remote and in situ RF plasma produced less satisfactory ZnO nanostructures with poorer crystalline structure, surface morphology, and optical properties due to etching effect of energetic ions produced from plasma. However, a reduction in plasma discharge duration to 10 minutes produced thicker and shorter ZnO nanostructures. Based on experimentation conducted, it is insufficient to conclude that RF plasma cannot aid in producing well-defined ZnO nanostructures. It can be deduced that the etching effect of energetic ions outweighed the increased oxygen radical production in RF plasma nanofabrication.

  20. Biological properties of carbon powders synthesized using chemical vapour deposition and detonation methods.

    PubMed

    Batory, M; Batory, D; Grabarczyk, J; Kaczorowski, W; Kupcewicz, B; Mitura, K; Nasti, T H; Yusuf, N; Niedzielski, P

    2012-12-01

    Carbon powders can be synthesized using variety of CVD and detonation methods. Several interesting properties of carbon powder particles make them a very attractive material examined in many laboratories all over the world. However there is a lack of information discussing investigation of carbon powders directed to its application in pharmaceutical-cosmetic industry and medicine. Earlier investigation results proved that diamond powders present properties fighting free radicals. Presented work discusses the influence of carbon powder particles manufactured using MW/RF PACVD, RF PACVD and detonation methods onto hydro-lipid skin coat. Before the biological examinations physicochemical properties of carbon powders were determined. Grain size, shape and chemical composition of carbon powders were determined using the scanning electron microscopy. Surface functional groups were characterized by IR Fourier-transform spectroscopy and X-ray photoelectron spectroscopy. Structure and phase composition were investigated by means of the Raman spectroscopy. Results of allergy tests performed on laboratory mice proved that carbon powder particles synthesized using different methods do not cause allergy. In the following stage, the group of 20 patients applied the formula including carbon powder on their face skin. The influence of carbon powder onto hydro-lipid skin coat was determined by measurement of such parameters as: pH reaction, skin temperature, lipid fotometry and level of hydration. Additionally, macro pictures of places where the cream had been applied were registered. As the result of the investigation it was found that powders synthesized using various methods present different physicochemical properties which may individually affect the face skin parameters. The noticeable improvement of hydro-lipid skin coat kilter was observed.

  1. Plasma and ion beam enhanced chemical vapour deposition of diamond and diamond-like carbon

    NASA Astrophysics Data System (ADS)

    Tang, Yongji

    WC-Co cutting tools are widely used in the machining industry. The application of diamond coatings on the surfaces of the tools would prolong the cutting lifetime and improves the manufacturing efficiency. However, direct chemical vapor deposition (CVD) of diamond coatings on WC-Co suffer from severe premature adhesion failure due to interfacial graphitization induced by the binder phase Co. In this research, a combination of hydrochloric acid (HCl) and hydrogen (H2) plasma pretreatments and a novel double interlayer of carbide forming element (CFE)/Al were developed to enhance diamond nucleation and adhesion. The results showed that both the pretreatments and interlayers were effective in forming continuous and adhesive nanocrystalline diamond coatings. The method is a promising replacement of the hazardous Murakami's regent currently used in WC-Co pretreatment with a more environmental friendly approach. Apart from coatings, diamond can be fabricated into other forms of nanostructures, such as nanotips. In this work, it was demonstrated that oriented diamond nanotip arrays can be fabricated by ion beam etching of as-grown CVD diamond. The orientation of diamond nanotips can be controlled by adjusting the direction of incident ion beam. This method overcomes the limits of other techniques in producing nanotip arrays on large areas with controlled orientation. Oriented diamond nano-tip arrays have been used to produce anisotropic frictional surface, which is successfully used in ultra-precision positioning systems. Diamond-like carbon (DLC) has many properties comparable to diamond. In this thesis, the preparation of alpha-C:H thin films by end-Hall (EH) ion source and the effects of ion energy and nitrogen doping on the microstructure and mechanical properties of the as-deposited thin films were investigated. The results have demonstrated that smooth and uniform alpha-C:H and alpha-C:H:N films with large area and reasonably high hardness and Young's modulus can be

  2. Rapid thermal low-pressure chemical vapour deposition of tungsten films onto InP using WF6 and H2

    NASA Astrophysics Data System (ADS)

    Katz, A.; Feingold, A.; El-Roy, A.; Pearton, S. J.; Lane, E.; Nakahara, S.; Geva, M.

    1992-11-01

    Tungsten (W) films were deposited onto InP in a cold wall, rapid thermal low-pressure chemical vapour deposition (RT-LPCVD) reactor, from a tungsten hexafluoride (WF6) gas reduced by hydrogen (H2). W films of thickness 50-450 nm were deposited in the temperature range 350-550 degrees C, pressure range 0.5-4.5 Torr at deposition rates up to 4 nm s-1 with an apparent activation energy of about 1.12 eV. The film stress varied depending upon the deposition pressure, from low compressive for deposition at 0.5 Torr to moderate tensile for deposition at about 4.5 Torr. The films were aged at temperatures as high as 300 degrees C for about 800 h and exhibited an excellent mechanical stability. Post-deposition sintering of the W films at temperatures up to 600 degrees C led to reduction of the resistivity with a minimum value of about 55 mu Omega cm as a result of heating at 500 degrees C. Conditions for both selective and blanket deposition were defined, and a dry etching process for further geometrical definitions of the films was developed, providing etch rates of 40-50 nm min-1. This report reflects the first attempt to deposit W films onto III-V semiconductor at a very high rate by means of RT-LPCVD.

  3. Computational studies of elementary steps relating to boron doping during diamond chemical vapour deposition.

    PubMed

    Cheesman, Andrew; Harvey, Jeremy N; Ashfold, Michael N R

    2005-03-21

    Density functional theory-based electronic structure computations on small models of the diamond {100} surface have enabled prediction of the energetics and activation parameters of a number of plausible mechanistic steps for boron incorporation into, and boron loss from, the growing diamond surface. Initial proving calculations for the carbon-only case show, as in previous work, that the rate-limiting step for diamond growth involves opening of a five-membered ring species, and subsequent closure to form six-membered rings as in bulk diamond. The five-membered ring intermediate arises following 2 x 1 reconstruction of the {100} surface, or at steps on the {111} surface. Diamond growth arises as a result of successful competition between the ring-opening step and a two-carbon loss step, both of which involve significant activation barriers. In the boron case, we find that BH(x) (x = 0-3) species can all bind to radical sites on the diamond {100} surface to form stable adducts. Interconversion between the surface bound BH, species is facile at the H and H2 number densities and temperatures typical for diamond CVD conditions. B incorporation can occur by a ring expansion mechanism, as in the all-carbon case, and by direct insertion of surface bound BH (and B) species into the C-C bond on the diamond {100} surface. BH(x) loss processes identified include release of surface bound BH3 and/or CH2BH species into the gas phase. Both B incorporation into, and B loss from, the diamond {100} surface are deduced to be significantly less energy demanding than the corresponding carbon addition and loss processes.

  4. Study of barrier properties and chemical resistance of recycled PET coated with amorphous carbon through a plasma enhanced chemical vapour deposition (PECVD) process.

    PubMed

    Cruz, S A; Zanin, M; Nerin, C; De Moraes, M A B

    2006-01-01

    Many studies have been carried out in order to make bottle-to-bottle recycling feasible. The problem is that residual contaminants in recycled plastic intended for food packaging could be a risk to public health. One option is to use a layer of virgin material, named functional barrier, which prevents the contaminants migration process. This paper shows the feasibility of using polyethylene terephthalate (PET) recycled for food packaging employing a functional barrier made from hydrogen amorphous carbon film deposited by Plasma Enhanced Chemical Vapour Deposition (PECVD) process. PET samples were deliberately contaminated with a series of surrogates using a FDA protocol. After that, PET samples were coated with approximately 600 and 1200 Angstrons thickness of amorphous carbon film. Then, the migration tests using as food simulants: water, 10% ethanol, 3% acetic acid, and isooctane were applied to the sample in order to check the chemical resistance of the new coated material. After the tests, the liquid extracts were analysed using a solid-phase microextraction device (SPME) coupled to GC-MS.

  5. Atmospheric pressure chemical vapour deposition of BPSG films from TEOS, 03, TMB, TMPI: Determination of a chemical mechanism

    NASA Astrophysics Data System (ADS)

    Nieto, J.-P.; Caussat, B.; Couderc, J.-P.; Orain', I.; Jeannerot, L.

    2002-06-01

    APCVD of boro-phospho silicate glass from mixtures of TEOS, TMB and TMP, has been analysed then modelled in a continuous reactor. A reduced chemical mechanism has been developed and the corresponding rate constants have been identified. The first results obtained are encouraging and suggest that the very simple gas phase chemistry selected could be precise enough to represent the main trends of this very complex deposition procedure.

  6. N-type crystalline silicon films free of amorphous silicon deposited on glass by HCl addition using hot wire chemical vapour deposition.

    PubMed

    Chung, Yung-Bin; Park, Hyung-Ki; Lee, Sang-Hoon; Song, Jean-Ho; Hwang, Nong-Moon

    2011-09-01

    Since n-type crystalline silicon films have the electric property much better than those of hydrogenated amorphous and microcrystalline silicon films, they can enhance the performance of advanced electronic devices such as solar cells and thin film transistors (TFTs). Since the formation of amorphous silicon is unavoidable in the low temperature deposition of microcrystalline silicon on a glass substrate at temperatures less than 550 degrees C in the plasma-enhanced chemical vapour deposition and hot wire chemical vapour deposition (HWCVD), crystalline silicon films have not been deposited directly on a glass substrate but fabricated by the post treatment of amorphous silicon films. In this work, by adding the HCl gas, amorphous silicon-free n-type crystalline silicon films could be deposited directly on a glass substrate by HWCVD. The resistivity of the n-type crystalline silicon film for the flow rate ratio of [HCl]/[SiH4] = 7.5 and [PH3]/[SiH4] = 0.042 was 5.31 x 10(-4) ohms cm, which is comparable to the resistivity 1.23 x 10(-3) ohms cm of films prepared by thermal annealing of amorphous silicon films. The absence of amorphous silicon in the film could be confirmed by high resolution transmission electron microscopy.

  7. Thermocamera studies of gases and vapours.

    PubMed Central

    Carlsson, P; Ljungqvist, B; Neikter, K

    1982-01-01

    Most gases and vapours with a bipolar molecular structure absorb infrared energy. If such a gas is interposed between an object emitting infrared radiation and a thermocamera the gas will absorb some of the infrared radiation and thus cast a shadow on the thermocamera picture. In this assay it is possible to visualise the gas. This method had been used to study pollution with anaesthetic gases and vapours in operating theatres. The vapours of other chemicals used in hospitals and other places of work also have been studied. The method permits the study of dispersion and flow patterns of polluting gases and vapours during work. Images PMID:7093159

  8. A novel mission concept for upper air water vapour observations: active limb sounding with a constellation of retroreflectors

    NASA Astrophysics Data System (ADS)

    Clifford, D.; Hoffmann, A.; Weitnauer, C.; Topham, R.; Romano, P.; Lohrey, S.; Kox, S.; Krings, T.; Krejci, D.; Kern, K.; Huesing, J.; Esen, B.; Deconinck, F.; Carton, J. G.; Aulinas, J.

    2011-12-01

    The topic for the Alpbach summer school 2010 was "Missions for Understanding Climate Change''. Early career scientists and engineers from many countries formed working groups to devise new space missions to tackle this challenging subject. Following the summer school, one mission concept was chosen for further development at a subsequent workshop in Obergurgl, which is described in this paper. At the core of the mission chosen for further study was a novel active limb-sounding instrument, used as part of a multi-instrument measurement approach to observing upper air water vapour. The concept combines a LiDAR in nadir-viewing mode with a LiDAR in limb sounding by occultation geometry, designed to operate as a multiple discrete wavelength, very long path system for intergrated path differential absorption measurements. This is achieved using a monostatic transmitter-receiver spacecraft flown in formation with multiple spaceborne retroreflectors. Looking through the limb of the atmosphere, this system will sample the upper troposphere-lower stratosphere and above at high vertical resolution, with a long integration path allowing detection of the low concentrations of water vapour at this height. A secondary payload of a medium resolution multispectral radiometer allows wide-swath cloud and aerosol imaging. Active limb sounding has not yet been attempted in space, and this novel concept presents significant challenges, including the performance of the lasers in space, the tracking and locking procedure between the main spacecraft and the retroreflectors, and the design of the telescopes to achieve a high enough signal-to-noise ratio for the high precision measurements. These issues are addressed in this preliminary feasibility study, which shows promising results.

  9. An in situ vapour phase hydrothermal surface doping approach for fabrication of high performance Co3O4 electrocatalysts with an exceptionally high S-doped active surface.

    PubMed

    Tan, Zhijin; Liu, Porun; Zhang, Haimin; Wang, Yun; Al-Mamun, Mohammad; Yang, Hua Gui; Wang, Dan; Tang, Zhiyong; Zhao, Huijun

    2015-04-04

    A facile in situ vapour phase hydrothermal (VPH) surface doping approach has been developed for fabrication of high performance S-doped Co3O4 electrocatalysts with an unprecedentedly high surface S content (>47%). The demonstrated VPH doping approach could be useful for enrichment of surface active sites for other metal oxide electrocatalysts.

  10. A Comparative Study of the Dispersion of Multi-Wall Carbon Nanotubes Made by Arc-Discharge and Chemical Vapour Deposition.

    PubMed

    Frømyr, Tomas-Roll; Bourgeaux-Goget, Marie; Hansen, Finn Knut

    2015-05-01

    A method has been developed to characterize the dispersion of multi-wall carbon nanotubes in water using a disc centrifuge for the detection of individual carbon nanotubes, residual aggregates, and contaminants. Carbon nanotubes produced by arc-discharge have been measured and compared with carbon nanotubes produced by chemical vapour deposition. Studies performed on both pristine (see text) arc-discharge nanotubes is rather strong and that high ultra-sound intensity is required to achieve complete dispersion of carbon nanotube bundles. The logarithm of the mode of the particle size distribution of the arc-discharge carbon nanotubes was found to be a linear function of the logarithm of the total ultrasonic energy input in the dispersion process.

  11. Al2O3 thin films by plasma-enhanced chemical vapour deposition using trimethyl-amine alane (TMAA) as the Al precursor

    NASA Astrophysics Data System (ADS)

    Chryssou, C. E.; Pitt, C. W.

    We report the low temperature (200-300 °C) deposition of uniform, amorphous Al2O3 thin films by plasma-enhanced chemical vapour deposition (PECVD) using trimethyl-amine alane (TMAA) as the Al precursor. The thin films were deposited on both Si and quartz silica (SiO2) substrates. Deposition rates were typically 60 Åmin-1 keeping the TMAA temperature constant at 45 °C. The deposited Al2O3 thin films were stoichiometric alumina with low carbon contamination (0.7-1.3 At%). The refractive index ranged from 1.54 to 1.62 depending on the deposition conditions. The deposition rate was studied as a function of both the RF power and the substrate temperature. The structure and the surface of the deposited Al2O3 thin films were studied using X-ray diffraction, atomic force microscopy (AFM) and scanning electron microscopy (SEM).

  12. Excitation and relaxation of metastable atomic states in an active medium of a repetitively pulsed copper vapour laser

    SciTech Connect

    Bokhan, P A; Zakrevskii, D E; Lavrukhin, M A; Lyabin, N A; Chursin, A D

    2016-02-28

    The influence of a pre-pulse population of copper atom metastable states and their sub-population at a current pulse edge on the copper vapour laser pulse energy is studied under optimal temperature conditions. Experiments have been performed with active elements of a commercial laser having an internal diameter of a discharge channel of 14 and 20 mm. It is found that at a pulse repetition frequency of 12 – 14 kHz, corresponding to a maximal output power, the reduction of the energy due to a residual population of metastable states is by an order of magnitude less than due to their sub-population at a current pulse edge. The modelling based on the experimental results obtained has shown that in the case of an active element with an internal diameter of 14 mm, a decrease in the pulse leading edge from ∼25 ns to 0.6 ns does not reduce the laser pulse energy up to the repetition frequency of ∼50 kHz at an average output power of 70 W m{sup -1} and efficiency of ∼11%. (lasers)

  13. Evaluation of water vapour assimilation in the tropical upper troposphere and lower stratosphere by a chemical transport model

    NASA Astrophysics Data System (ADS)

    Payra, Swagata; Ricaud, Philippe; Abida, Rachid; El Amraoui, Laaziz; Attié, Jean-Luc; Rivière, Emmanuel; Carminati, Fabien; von Clarmann, Thomas

    2016-09-01

    The present analysis deals with one of the most debated aspects of the studies on the upper troposphere/lower stratosphere (UTLS), namely the budget of water vapour (H2O) at the tropical tropopause. Within the French project "Multiscale water budget in the upper troposphere and lower stratosphere in the TROpics" (TRO-pico), a global-scale analysis has been set up based on space-borne observations, models and assimilation techniques. The MOCAGE-VALENTINA assimilation tool has been used to assimilate the Aura Microwave Limb Sounder (MLS) version 3.3 H2O measurements within the 316-5 hPa range from August 2011 to March 2013 with an assimilation window of 1 h. Diagnostics based on observations minus analysis and forecast are developed to assess the quality of the assimilated H2O fields. Comparison with an independent source of H2O measurements in the UTLS based on the space-borne Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) observations and with meteorological ARPEGE analyses is also shown. Sensitivity studies of the analysed fields have been performed by (1) considering periods when no MLS measurements are available and (2) using H2O data from another MLS version (4.2). The studies have been performed within three different spaces in time and space coincidences with MLS (hereafter referred to as MLS space) and MIPAS (MIPAS space) observations and with the model (model space) outputs and at three different levels: 121 hPa (upper troposphere), 100 hPa (tropopause) and 68 hPa (lower stratosphere) in January and February 2012. In the MLS space, the analyses behave consistently with the MLS observations from the upper troposphere to the lower stratosphere. In the model space, the analyses are wetter than the reference atmosphere as represented by ARPEGE and MLS in the upper troposphere (121 hPa) and around the tropopause (100 hPa), but are consistent with MLS and MIPAS in the lower stratosphere (68 hPa). In the MIPAS space, the sensitivity and the

  14. Electrical activation of carbon δ-doped (Al,Ga)As grown by metalorganic vapour-phase epitaxy

    NASA Astrophysics Data System (ADS)

    Li, G.; Petravić, M.; Jagadish, C.

    1997-04-01

    Carbon δ-doped (Al,Ga)As was grown by metalorganic vapour-phase epitaxy using trimethylaluminium (TMAl) or trimethylgallium (TMGa) as a doping precursor. The best C δ-doped Al 0.3Ga 0.7As has a peak hole density of 1.6 × 10 19 (1.4 × 10 19 for GaAs) cm -3 with a full hole profile width at half maximum of 85 Å (84 Å for GaAs). For C δ-doped Al 0.3Ga 0.7 As grown at 630°C, the use of TMGa as a doping precursor leads to both the sheet C atom density and the free hole density increasing with an increase in the total TMGa moles introduced during a δ-doping step. As a result, the electrical activation remains almost constant with the change of TMGa moles supplied. The sheet C atom density always increases with increasing supply of TMAl, but approaches its maximum value at an amount of TMAl of 6.4 × 10 -7 mol. The electrical activation reduces from > 90% to < 10% when the supply of TMAl increases from 2.1 × 10 -7 to 8 × 10 -7 mol. Regardless of the doping precursors, the hole density weakly decreases and the C atom density significantly increases with increasing growth temperature. Low growth temperatures are required for high electrical activation. Using optimised growth conditions, C δ-doped pipi doping superlattices with different average hole densities are fabricated to obtain C bulk-doped-like layers.

  15. Substrate patterning with NiOx nanoparticles and hot-wire chemical vapour deposition of WO3x and carbon nanostructures

    NASA Astrophysics Data System (ADS)

    Houweling, Z. S.

    2011-10-01

    The first part of the thesis treats the formation of nickel catalyst nanoparticles. First, a patterning technique using colloids is employed to create ordered distributions of monodisperse nanoparticles. Second, nickel films are thermally dewetted, which produces mobile species that self-arrange in non-ordered distributions of polydisperse particles. Third, the mobility of the nickel species is successfully reduced by the addition of air during the dewetting and the use of a special anchoring layer. Thus, non-ordered distributions of self-arranged monodisperse nickel oxide nanoparticles (82±10 nm x 16±2 nm) are made. Studies on nickel thickness, dewetting time and dewetting temperature are conducted. With these particle templates, graphitic carbon nanotubes are synthesised using catalytic hot-wire chemical vapour deposition (HWCVD), demonstrating the high-temperature processability of the nanoparticles. The second part of this thesis treats the non-catalytic HWCVD of tungsten oxides (WO3-x). Resistively heated tungsten filaments exposed to an air flow at subatmospheric pressures, produce tungsten oxide vapour species, which are collected on substrates and are subsequently characterised. First, a complete study on the process conditions is conducted, whereby the effects of filament radiation, filament temperature, process gas pressure and substrate temperature, are investigated. The thus controlled growth of nanogranular smooth amorphous and crystalline WO3-x thin films is presented for the first time. Partially crystalline smooth hydrous WO3-x thin films consisting of 20 nm grains can be deposited at very high rates. The synthesis of ultrafine powders with particle sizes of about 7 nm and very high specific surface areas of 121.7±0.4 m2·g-1 at ultrahigh deposition rates of 36 µm·min-1, is presented. Using substrate heating to 600°C or more, while using air pressures of 3·10-5 mbar to 0.1 mbar, leads to pronounced crystal structures, from nanowires, to

  16. Breakthrough of toluene vapours in granular activated carbon filled packed bed reactor.

    PubMed

    Mohan, N; Kannan, G K; Upendra, S; Subha, R; Kumar, N S

    2009-09-15

    The objective of this research was to determine the toluene removal efficiency and breakthrough time using commercially available coconut shell-based granular activated carbon in packed bed reactor. To study the effect of toluene removal and break point time of the granular activated carbon (GAC), the parameters studied were bed lengths (2, 3, and 4 cm), concentrations (5, 10, and 15 mg l(-1)) and flow rates (20, 40, and 60 ml/min). The maximum percentage removal of 90% was achieved and the maximum carbon capacity for 5 mg l(-1) of toluene, 60 ml/min flow rate and 3 cm bed length shows 607.14 mg/g. The results of dynamic adsorption in a packed bed were consistent with those of equilibrium adsorption by gravimetric method. The breakthrough time and quantity shows that GAC with appropriate surface area can be utilized for air cleaning filters. The result shows that the physisorption plays main role in toluene removal.

  17. A water-vapour giga-maser in the active galaxy TXFS2226-184.

    PubMed

    Koekemoer, A M; Henkel, C; Greenhill, L J; Dey, A; van Breugel, W; Codella, C; Antonucci, R

    1995-12-14

    Active galactic nuclei are thought to be powered by gas falling into a massive black hole; the different types of active galaxy may arise because we view them through a thick torus of molecular gas at varying angles of inclination. One way to determine whether the black hole is surrounded by a torus, which would obscure the accretion disk around the black hole along certain lines of sight, is to search for water masers, as these exist only in regions with plentiful molecular gas. Since the first detection of an extra-galactic water maser in 1979, they have come to be associated primarily with active galaxies, and have even been used to probe the mass of the central engine. Here we report the detection of a water giga-maser in the radio galaxy TXFS2226-184. The strength of the emission supports a recently proposed theory of maser pumping that allows for even more powerful masers, which might be detectable at cosmological distances. Water masers may accordingly provide a way to determine distances to galaxies outside the usual distance ladder, providing an independent calibration of the Hubble constant.

  18. Surface engineering of artificial heart valve disks using nanostructured thin films deposited by chemical vapour deposition and sol-gel methods.

    PubMed

    Jackson, M J; Robinson, G M; Ali, N; Kousar, Y; Mei, S; Gracio, J; Taylor, H; Ahmed, W

    2006-01-01

    Pyrolytic carbon (PyC) is widely used in manufacturing commercial artificial heart valve disks (HVD). Although PyC is commonly used in HVD, it is not the best material for this application since its blood compatibility is not ideal for prolonged clinical use. As a result thrombosis often occurs and the patients are required to take anti-coagulation drugs on a regular basis in order to minimize the formation of thrombosis. However, anti-coagulation therapy gives rise to some detrimental side effects in patients. Therefore, it is extremely urgent that newer and more technically advanced materials with better surface and bulk properties are developed. In this paper, we report the mechanical properties of PyC-HVD, i.e. strength, wear resistance and coefficient of friction. The strength of the material was assessed using Brinell indentation tests. Furthermore, wear resistance and coefficient of friction values were obtained from pin-on-disk testing. The micro-structural properties of PyC were characterized using XRD, Raman spectroscopy and SEM analysis. Also in this paper we report the preparation of freestanding nanocrystalline diamond films (FSND) using the time-modulated chemical vapour deposition (TMCVD) process. Furthermore, the sol-gel technique was used to uniformly coat PyC-HVD with dense, nanocrystalline-titanium oxide (nc-TiO2) coatings. The as-grown nc-TiO2 coatings were characterized for microstructure using SEM and XRD analysis.

  19. Effect of organic additives in catalyst preparation on the growth of single-wall carbon nanotubes prepared by catalyst-assisted chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Shen, Lihua; Zhang, Xiaobin; Li, Yu; Yang, Xiaofang; Luo, Junhang; Xu, Guoliang

    2004-03-01

    The effect of organic additives, including citric acid, PEG (2000) and PEG (200), on the yield and quality of single-wall carbon nanotubes (SWNTs) synthesized by a Fe-Mo catalyst dispersed on an alumina matrix prepared by the sol-gel process in assisted chemical vapour deposition (CVD) has been investigated by transmission electron microscopy (TEM), thermo-gravimetric analysis (TGA) and Raman spectroscopy. Different morphologies of catalyst including big flakes, spherical particles and porous supporting materials were obtained using citric acid, PEG (2000) and PEG (200) as dispersant, respectively. SWNT yields of 10 wt%, 16 wt% and 33 wt% were obtained using citric acid, PEG (2000) and PEG (200) as the dispersants, respectively, which implies that the PEG (200) is the most effective at improving the yield of SWNTs due to the effect of additives on the specific surface area of the catalyst. The as-grown SWNTs are mostly in large bundles with diameters of 0.5-2 nm, but in some cases, isolated tubes with much larger diameters can also be found. Finally a preliminary explanation for the increased SWNT yield using PEG (200) is presented.

  20. Effect of gas flow rates on the anatase-rutile transformation temperature of nanocrystalline TiO2 synthesised by chemical vapour synthesis.

    PubMed

    Ahmad, Md Imteyaz; Bhattacharya, S S; Fasel, Claudia; Hahn, Horst

    2009-09-01

    Of the three crystallographic allotropes of nanocrystalline titania (rutile, anatase and brookite), anatase exhibits the greatest potential for a variety of applications, especially in the area of catalysis and sensors. However, with rutile being thermodynamically the most stable phase, anatase tends to transform into rutile on heating to temperatures in the range of 500 degrees C to 700 degrees C. Efforts made to stabilize the anatase phase at higher temperatures by doping with metal oxides suffer from the problems of having a large amorphous content on synthesis as well as the formation of secondary impurity phases on doping. Recent studies have suggested that the as-synthesised phase composition, crystallite size, initial surface area and processing conditions greatly influence the anatase to rutile transformation temperature. In this study nanocrystalline titania was synthesised in the anatase form bya chemical vapour synthesis (CVS) method using titanium tetra iso-propoxide (TTIP) as a precursor under varying flow rates of oxygen and helium. The anatase to rutile transformation was studied using high temperature X-ray diffraction (HTXRD) and simultaneous thermogravimetric analysis (STA), followed by transmission electron microscopy (TEM). It was demonstrated that the anatase-rutile transformation temperatures were dependent on the oxygen to helium flow rate ratio during CVS and the results are presented and discussed.

  1. Effect of oxygen plasma on field emission characteristics of single-wall carbon nanotubes grown by plasma enhanced chemical vapour deposition system

    SciTech Connect

    Kumar, Avshish; Parveen, Shama; Husain, Samina; Ali, Javid; Zulfequar, Mohammad; Harsh; Husain, Mushahid

    2014-02-28

    Field emission properties of single wall carbon nanotubes (SWCNTs) grown on iron catalyst film by plasma enhanced chemical vapour deposition system were studied in diode configuration. The results were analysed in the framework of Fowler-Nordheim theory. The grown SWCNTs were found to be excellent field emitters, having emission current density higher than 20 mA/cm{sup 2} at a turn-on field of 1.3 V/μm. The as grown SWCNTs were further treated with Oxygen (O{sub 2}) plasma for 5 min and again field emission characteristics were measured. The O{sub 2} plasma treated SWCNTs have shown dramatic improvement in their field emission properties with emission current density of 111 mA/cm{sup 2} at a much lower turn on field of 0.8 V/μm. The as grown as well as plasma treated SWCNTs were also characterized by various techniques, such as scanning electron microscopy, high resolution transmission electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy before and after O{sub 2} plasma treatment and the findings are being reported in this paper.

  2. Polyethylene Oxide Films Polymerized by Radio Frequency Plasma-Enhanced Chemical Vapour Phase Deposition and Its Adsorption Behaviour of Platelet-Rich Plasma

    NASA Astrophysics Data System (ADS)

    Hu, Wen-Juan; Xie, Fen-Yan; Chen, Qiang; Weng, Jing

    2008-10-01

    We present polyethylene oxide (PEO) functional films polymerized by rf plasma-enhanced vapour chemical deposition (rf-PECVD) on p-Si (100) surface with precursor ethylene glycol dimethyl ether (EGDME) and diluted Ar in pulsed plasma mode. The influences of discharge parameters on the film properties and compounds are investigated. The film structure is analysed by Fourier transform infrared (FTIR) spectroscopy. The water contact angle measurement and atomic force microscope (AFM) are employed to examine the surface polarity and to detect surface morphology, respectively. It is concluded that the smaller duty cycle in pulsed plasma mode contributes to the rich C-O-C (EO) group on the surfaces. As an application, the adsorption behaviour of platelet-rich plasma on plasma polymerization films performed in-vitro is explored. The shapes of attached cells are studied in detail by an optic invert microscope, which clarifies that high-density C-O-C groups on surfaces are responsible for non-fouling adsorption behaviour of the PEO films.

  3. Strain and structure heterogeneity in MoS2 atomic layers grown by chemical vapour deposition

    SciTech Connect

    Liu, Zheng; Amani, Matin; Najmaei, Sina; Xu, Quan; Zou, Xiaolong; Zhou, Wu; Yu, Ting; Qiu, Caiyu; Birdwell, A. Glen; Crowne, Frank J.; Vajtai, Robert; Yakobson, Boris I.; Xia, Zhenhai; Dubey, Madan; Ajayan, Pulickel M.; Lou, Jun

    2014-11-18

    Monolayer molybdenum disulfide (MoS2) has attracted tremendous attention due to its promising applications in high-performance field-effect transistors, phototransistors, spintronic devices, and nonlinear optics. The enhanced photoluminescence effect in monolayer MoS2 was discovered and, as a strong tool, was employed for strain and defect analysis in MoS2. Recently, large-size monolayer MoS2 has been produced by chemical vapor deposition but has not yet been fully explored. Here we systematically characterize chemical vapor deposition grown MoS2 by PL spectroscopy and mapping, and demonstrate non-uniform strain in single-crystalline monolayer MoS2 and strain-induced band gap engineering. We also evaluate the effective strain transferred from polymer substrates to MoS2 by three-dimensional finite element analysis. In addition, our work demonstrates that PL mapping can be used as a non-contact approach for quick identification of grain boundaries in MoS2.

  4. Effect of reaction parameters on the growth of MWCNTs using mesoporous Sb/MCM-41 by chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Atchudan, R.; Pandurangan, A.; Subramanian, K.

    2011-11-01

    Mesoporous Si-MCM-41 molecular sieve was synthesized hydrothermally and different wt.% of Sb (1.0, 2.0, 3.0, 5.0, 10.0, 15.0 and 20.0) was loaded on it by wet impregnation method. The Sb/MCM-41 materials were characterized by various physico-chemical techniques such as XRD, TGA and TEM. The TEM image showed a honeycomb structure of the host material. They were used as catalytic templates for the growth of MWCNTs by CVD method with different temperatures at 700, 800, 900 and 1000 °C using acetylene as a carbon precursor. The reaction temperature was optimized for the better formation of MWCNTs and they were purified and then characterized by XRD, SEM, HR-TEM and Raman spectroscopy techniques. The formation of MWCNTs with diameter in the range of 4-6 nm was observed from HR-TEM. The good thermal stability and high productivity of catalyst observed in this study revealed that the 2 wt.% Sb loaded MCM-41 could be a promising support for the catalytic synthesis of MWCNTs at 800 °C by CVD method.

  5. Direct observation of electron emission from the grain boundaries of chemical vapour deposition diamond films by tunneling atomic force microscopy

    SciTech Connect

    Chatterjee, Vijay; Harniman, Robert; May, Paul W.; Barhai, P. K.

    2014-04-28

    The emission of electrons from diamond in vacuum occurs readily as a result of the negative electron affinity of the hydrogenated surface due to features with nanoscale dimensions, which can concentrate electric fields high enough to induce electron emission from them. Electrons can be emitted as a result of an applied electric field (field emission) with possible uses in displays or cold-cathode devices. Alternatively, electrons can be emitted simply by heating the diamond in vacuum to temperatures as low as 350 °C (thermionic emission), and this may find applications in solar energy generation or energy harvesting devices. Electron emission studies usually use doped polycrystalline diamond films deposited onto Si or metallic substrates by chemical vapor deposition, and these films have a rough, faceted morphology on the micron or nanometer scale. Electron emission is often improved by patterning the diamond surface into sharp points or needles, the idea being that the field lines concentrate at the points lowering the barrier for electron emission. However, there is little direct evidence that electrons are emitted from these sharp tips. The few reports in the literature that have studied the emission sites suggested that emission came from the grain boundaries and not the protruding regions. We now present direct observation of the emission sites over a large area of polycrystalline diamond using tunneling atomic force microscopy. We confirm that the emission current comes mostly from the grain boundaries, which is consistent with a model for emission in which the non-diamond phase is the source of electrons with a threshold that is determined by the surrounding hydrogenated diamond surface.

  6. A dilute Cu(Ni) alloy for synthesis of large-area Bernal stacked bilayer graphene using atmospheric pressure chemical vapour deposition

    SciTech Connect

    Madito, M. J.; Bello, A.; Dangbegnon, J. K.; Momodu, D. Y.; Masikhwa, T. M.; Barzegar, F.; Manyala, N.; Oliphant, C. J.; Jordaan, W. A.; Fabiane, M.

    2016-01-07

    A bilayer graphene film obtained on copper (Cu) foil is known to have a significant fraction of non-Bernal (AB) stacking and on copper/nickel (Cu/Ni) thin films is known to grow over a large-area with AB stacking. In this study, annealed Cu foils for graphene growth were doped with small concentrations of Ni to obtain dilute Cu(Ni) alloys in which the hydrocarbon decomposition rate of Cu will be enhanced by Ni during synthesis of large-area AB-stacked bilayer graphene using atmospheric pressure chemical vapour deposition. The Ni doped concentration and the Ni homogeneous distribution in Cu foil were confirmed with inductively coupled plasma optical emission spectrometry and proton-induced X-ray emission. An electron backscatter diffraction map showed that Cu foils have a single (001) surface orientation which leads to a uniform growth rate on Cu surface in early stages of graphene growth and also leads to a uniform Ni surface concentration distribution through segregation kinetics. The increase in Ni surface concentration in foils was investigated with time-of-flight secondary ion mass spectrometry. The quality of graphene, the number of graphene layers, and the layers stacking order in synthesized bilayer graphene films were confirmed by Raman and electron diffraction measurements. A four point probe station was used to measure the sheet resistance of graphene films. As compared to Cu foil, the prepared dilute Cu(Ni) alloy demonstrated the good capability of growing large-area AB-stacked bilayer graphene film by increasing Ni content in Cu surface layer.

  7. Mechanical characteristics of ultra-long horizontal nanocantilevers grown by real-time feedback control on focused-ion-beam chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Guo, Dengji; Warisawa, Shin'ichi; Ishihara, Sunao; Kometani, Reo

    2015-12-01

    Focused-ion-beam chemical vapour deposition (FIB-CVD) has been repeatedly proved to be a useful tool for the growth of three-dimensional (3D) micro- and nano-structures. The strategy of real-time feedback control on FIB-CVD was previously proposed and experimentally demonstrated to be effective for growing ultra-long horizontal nanocantilevers. To fabricate various nanoelectromechanical systems that consist of such types of nanocantilever structures, the mechanical characteristics of ultra-long horizontal nanocantilevers should be investigated. In this study, nanocantilevers with an overhang length of up to 35 μm were grown by using a 30 kV Ga+ FIB, a beam current of 0.50 pA and phenanthrene (C14H10) as the gas source to deposit a diamond-like carbon structure. The Young’s modulus of each nanocantilever was measured by bending the nanocantilever with a nanopillar whose Young’s modulus was known. The average density of each nanocantilever was calculated from the Young’s modulus and the measured resonant frequency. We found that the mechanical characteristics of each nanocantilever depended on the length of the nanocantilever if the strategy of real-time feedback control was applied in fabrication. The Young’s moduli and the averaged densities of the nanocantilevers with a length of 11 to 34 μm were found to be 86 to 254 GPa and 1950 to 5750 kg m-3, respectively. With the increase of the overhang length, the Young’s modulus and the average density were found to gradually increase.

  8. A dilute Cu(Ni) alloy for synthesis of large-area Bernal stacked bilayer graphene using atmospheric pressure chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Madito, M. J.; Bello, A.; Dangbegnon, J. K.; Oliphant, C. J.; Jordaan, W. A.; Momodu, D. Y.; Masikhwa, T. M.; Barzegar, F.; Fabiane, M.; Manyala, N.

    2016-01-01

    A bilayer graphene film obtained on copper (Cu) foil is known to have a significant fraction of non-Bernal (AB) stacking and on copper/nickel (Cu/Ni) thin films is known to grow over a large-area with AB stacking. In this study, annealed Cu foils for graphene growth were doped with small concentrations of Ni to obtain dilute Cu(Ni) alloys in which the hydrocarbon decomposition rate of Cu will be enhanced by Ni during synthesis of large-area AB-stacked bilayer graphene using atmospheric pressure chemical vapour deposition. The Ni doped concentration and the Ni homogeneous distribution in Cu foil were confirmed with inductively coupled plasma optical emission spectrometry and proton-induced X-ray emission. An electron backscatter diffraction map showed that Cu foils have a single (001) surface orientation which leads to a uniform growth rate on Cu surface in early stages of graphene growth and also leads to a uniform Ni surface concentration distribution through segregation kinetics. The increase in Ni surface concentration in foils was investigated with time-of-flight secondary ion mass spectrometry. The quality of graphene, the number of graphene layers, and the layers stacking order in synthesized bilayer graphene films were confirmed by Raman and electron diffraction measurements. A four point probe station was used to measure the sheet resistance of graphene films. As compared to Cu foil, the prepared dilute Cu(Ni) alloy demonstrated the good capability of growing large-area AB-stacked bilayer graphene film by increasing Ni content in Cu surface layer.

  9. Perovskite tungsten bronze-type crystals of Li{sub x}WO{sub 3} grown by chemical vapour transport and their characterisation

    SciTech Connect

    Ruescher, Claus H. Dey, Kalpana R.; Debnath, Tapas; Horn, Ingo; Glaum, Robert; Hussain, Altaf

    2008-01-15

    Crystals of Li{sub x}WO{sub 3} with nominal compositions, x=0.1, 0.25, 0.3, 0.35, 0.4 and 0.45 were grown by chemical vapour transport method using HgCl{sub 2} as transporting agent. A complete transport was achieved with a temperature gradient T{sub 1}/T{sub 2}=800/700 deg. C revealing bluish-black crystals of sizes up to a few 10th of a millimeter. X-ray powder diffraction and infrared (IR) absorption spectra show Perovskite tungsten bronze of cubic symmetry (PTB{sub c}) for x=0.45 and 0.4, mixed phase of PTB{sub c} and Perovskite tungsten bronze of tetragonal symmetry (PTB{sub t}) for x=0.35, 0.3 and 0.25 and of PTB{sub t} and Perovskite tungsten bronze of orthorhombic symmetry (PTB{sub o}) for x=0.1. The structure of PTB{sub t} is explained by the off centring of the W-ions along c and tilting of the WO{sub 6} octahedra around c. Crystal slices of mixed phase (i.e. PTB{sub c} and PTB{sub t}) reveal bright and dark areas on a sub-millimeter scale which are separated by sharp interfaces. Laser ablation inductively coupled plasma optical emission (LA ICP OES) analysis on small spot sizes show the separation into Li contents of x=0.18 (bright areas) and x=0.38 (dark areas) as threshold compositions of PTB{sub t} and PTB{sub c}, respectively. Polarized reflectivity using a microscope technique in the bright area of the crystals indicates strong anisotropic absorption effects with maximum between 1000 and 6000 cm{sup -1}, which are related to optical excitations of polarons. Crystals of composition x=0.4 and 0.45 appear optically homogeneous and show an effective 'free carrier-type plasma frequency' (w{sub p}) of about 12,900 and 13,700 cm{sup -1}, respectively. - Graphical abstract: Optical microscope image (reflection mode) of Li{sub x}WO{sub 3} crystals of nominal composition x=0.35. The separation into PTB{sub cubic} (dark areas) and PTB{sub tetragonal} (bright areas) were used to determine the miscibility gap and optical properties.

  10. Current Chemical Risk Reduction Activities

    EPA Pesticide Factsheets

    EPA's existing chemicals programs address pollution prevention, risk assessment, hazard and exposure assessment and/or characterization, and risk management for chemicals substances in commercial use.

  11. A liquid crystalline chirality balance for vapours

    NASA Astrophysics Data System (ADS)

    Ohzono, Takuya; Yamamoto, Takahiro; Fukuda, Jun-Ichi

    2014-04-01

    Chiral discrimination of vapours plays an important role in olfactory perception of biological systems and its realization by artificial sensors has been an intriguing challenge. Here, we report a simple method that tangibly visualizes the chirality of a diverse variety of molecules dissolved from vapours with high sensitivity, by making use of a structural change in a periodic microstructure of a nematic liquid crystal confined in open microchannels. This microstructure is accompanied by a topological line defect of a zigzag form with equal lengths of ‘zig’ and ‘zag.’ We find that a tiny amount of vapour of chiral molecules injected onto the liquid crystal induces the imbalance of ‘zig’ and ‘zag’ depending on its enantiomeric excess within a few seconds. Our liquid-crystal-based ‘chirality balance’ offers a simple, quick and versatile chirality-sensing/-screening method for gas-phase analysis (for example, for odours, environmental chemicals or drugs).

  12. A liquid crystalline chirality balance for vapours.

    PubMed

    Ohzono, Takuya; Yamamoto, Takahiro; Fukuda, Jun-ichi

    2014-04-30

    Chiral discrimination of vapours plays an important role in olfactory perception of biological systems and its realization by artificial sensors has been an intriguing challenge. Here, we report a simple method that tangibly visualizes the chirality of a diverse variety of molecules dissolved from vapours with high sensitivity, by making use of a structural change in a periodic microstructure of a nematic liquid crystal confined in open microchannels. This microstructure is accompanied by a topological line defect of a zigzag form with equal lengths of 'zig' and 'zag.' We find that a tiny amount of vapour of chiral molecules injected onto the liquid crystal induces the imbalance of 'zig' and 'zag' depending on its enantiomeric excess within a few seconds. Our liquid-crystal-based 'chirality balance' offers a simple, quick and versatile chirality-sensing/-screening method for gas-phase analysis (for example, for odours, environmental chemicals or drugs).

  13. Inorganic chemically active adsorbents (ICAAs)

    SciTech Connect

    Ally, M.R.; Tavlarides, L.

    1997-10-01

    Oak Ridge National Laboratory (ORNL) researchers are developing a technology that combines metal chelation extraction technology and synthesis chemistry. They begin with a ceramic substrate such as alumina, titanium oxide or silica gel because they provide high surface area, high mechanical strength, and radiolytic stability. One preparation method involves silylation to hydrophobize the surface, followed by chemisorption of a suitable chelation agent using vapor deposition. Another route attaches newly designed chelating agents through covalent bonding by the use of coupling agents. These approaches provide stable and selective, inorganic chemically active adsorbents (ICAAs) tailored for removal of metals. The technology has the following advantages over ion exchange: (1) higher mechanical strength, (2) higher resistance to radiation fields, (3) higher selectivity for the desired metal ion, (4) no cation exchange, (5) reduced or no interference from accompanying anions, (6) faster kinetics, and (7) easy and selective regeneration. Target waste streams include metal-containing groundwater/process wastewater at ORNL`s Y-12 Plant (multiple metals), Savannah River Site (SRS), Rocky Flats (multiple metals), and Hanford; aqueous mixed wastes at Idaho National Engineering Laboratory (INEL); and scrubber water generated at SRS and INEL. Focus Areas that will benefit from this research include Mixed Waste, and Subsurface Contaminants.

  14. Water vapour variability and trends in the Arctic stratosphere

    NASA Astrophysics Data System (ADS)

    Thölix, Laura; Kivi, Rigel; Backman, Leif; Karpechko, Alexey

    2014-05-01

    Water vapour in the upper troposphere-lower stratosphere (UTLS) is a radiatively and chemically important trace gas. Stratospheric water vapour also affects ozone chemistry through odd-hydrogen chemistry and formation of polar stratospheric clouds (PSC). Both transport and chemistry contribute to the extratropical lower stratospheric water vapour distribution and trends. The main sources of stratospheric water vapour are intrusion through the tropical tropopause and production from oxidation of methane. Accurate observations of UTLS water vapour are difficult to obtain due to the strong gradient in the water vapour profile over the tropopause. However, modelling the stratospheric water vapour distribution is challenging and accurate measurements are needed for model validation. Trends in Arctic water vapour will be analysed and explained in terms of contribution from different processes (transport and chemistry), using observations and chemistry transport model (CTM) simulations. Accurate water vapour soundings from Sodankylä will be used to study water vapour within the Arctic polar vortex, including process studies on formation of PSCs and dehydration. Water vapour profiles measured during the LAPBIAT atmospheric sounding campaign in Sodankylä in January 2010 indicated formation of ice clouds and dehydration. Effects on ozone chemistry will also be studied. Global middle atmospheric simulations have been performed with the FinROSE-ctm using ERA-Interim winds and temperatures. The FinROSE-ctm is a global middle atmosphere model that produces the distribution of 30 long-lived species and tracers and 14 short-lived species. The chemistry describes around 110 gas phase reactions, 37 photodissociation processes and the main heterogeneous reactions related to aerosols and polar stratospheric clouds.

  15. From GNSS and meteorological data to NRT 4D water vapour distribution - GNSS meteorology activities at WUELS

    NASA Astrophysics Data System (ADS)

    Bosy, Jaroslaw; Kaplon, Jan; Rohm, Witold; Sierny, Jan; Wilgan, Karina; Hadas, Tomasz; Hordyniec, Pawel

    2014-05-01

    The GNSS and Meteo group at Wroclaw University of Environmental and Life Sciences (WUELS), Poland is continuously working on GNSS meteorology since 2010. Currently group maintain real-time (RT) service collecting GNSS and meteorological data and near real-time (NRT) services for estimation of Zenith Troposphere Delay (ZTD), Zenith Hydrostatic Delay (ZHD), Integrated Water Vapour (IWV) and GNSS tomography over the territory of Poland. Data are obtained with high resolution from EUREF Permanent Network (EPN) stations and Ground Base Augmentation System (GBAS) called ASG-EUPOS (www.asgeupos.pl). The GNSS data are available from 124 reference stations located in Poland and neighbour countries, with the average 70km distance between stations. The ground meteorological observations in the area of Poland and neighbour countries are available from: ASG-EUPOS stations included in EUREF Permanent Network (EPN), airport meteorological stations (METAR messages stations) and stations managed by national Institute of Meteorology and Water Management (SYNOP messages stations). The first part of the paper presents the methodology of ASG-EUPOS GNSS data processing for NRT ZTD and ZTD horizontal gradients estimation in double-differenced mode (under Bernese GNSS Software V5.0) as well as new results from PPP mode (under Bernese GNSS Software V5.2) and their validation with respect to Rapid and Final troposphere products. The second part is describing the quality assessment of meteorological parameters interpolation methods for determination of ZHD at GNSS sites performed on GNSS stations equipped with meteorological sensors. The third part concerns on the comparisons of ZTD from GNSS data and meteorological parameters from SYNOP stations with data from COAMPS numerical weather prediction system (NWP) and IWV calculation. The fourth part presents the development of GNSS tomography model TOMO2. The last part describes methods of above products validation and visualization over the

  16. On-line chemical vapour generation of cadmium in the presence of hexacyanochromate(III) for determination by inductively coupled plasma mass spectrometry (ICP-MS)

    PubMed Central

    Yilmaz, Vedat; Rose, LaKeysha; Little, Maria D.

    2012-01-01

    A vapour generation (VG) procedure has been described for determination of Cd by ICP-MS. Volatile species of Cd were generated on-line by interacting acidic sample solution containing potassium hexacyanochromate(III), K3Cr(CN)6, with sodium borohydride (NaBH4). The hexacyanochromate(III) complex was generated on-line by reacting 0.04 mol L−1 chromium(III) nitrate and 0.16 mol L−1 potassium cyanide (KCN) solutions in water. The resulting suspension of chromium(III) hydroxide, Cr(OH)3, was fed continuously to acidic stream of sample solution in the presence of excess KCN. The experimental conditions were optimized for effective generation of volatile species of Cd. Optimum signals were obtained from reaction of sample solutions in 4% v/v HCl with 2% m/v NaBH4 solution. Presence of K3Cr(CN)6 improved the efficiency of Cd vapour generation substantially affording 15-fold higher sensitivity. This phenomenon was thought to occur through formation of reactive intermediates evolved from interaction of [Cr(CN)6]3− with NaBH4 that react with Cd(II) to increase the yield volatile Cd species. Under the optimum conditions, no significant interferences were observed from the transition metals, including Cu and Ni, up to 1.0 μg mL−1 levels. Among the hydride forming elements, Bi, Pb, Sb and Sn depressed the signals above 0.1 μg mL−1. The detection limits (3s) were 6.2 and 5.2 ng L−1 for 110Cd and 111Cd isotopes, respectively. The method was successfully applied to determination of Cd by ICP-MS in several certified reference materials, including Nearshore seawater (CASS-4), Bone ash (SRM 1400), Dogfish liver (DOLT-4) and Mussel tissue (SRM 2976). PMID:23997384

  17. The interaction of an atmospheric pressure plasma jet using argon or argon plus hydrogen peroxide vapour addition with bacillus subtilis

    NASA Astrophysics Data System (ADS)

    Deng, San-Xi; Cheng, Cheng; Ni, Guo-Hua; Meng, Yue-Dong; Chen, Hua

    2010-10-01

    This paper reports that an atmospheric pressure dielectric barrier discharge plasma jet, which uses argon or argon + hydrogen peroxide vapour as the working gas, is designed to sterilize the bacillus subtilis. Compared with the pure argon plasma, the bacterial inactivation efficacy has a significant improvement when hydrogen peroxide vapour is added into the plasma jet. In order to determine which factors play the main role in inactivation, several methods are used, such as determination of optical emission spectra, high temperature dry air treatment, protein leakage quantification, and scanning electron microscope. These results indicate that the possible inactivation mechanisms are the synergistic actions of chemically active species and charged species.

  18. Annealing study of H2O and O3 grown Al2O3 deposited by atomic layer chemical vapour deposition on n-type 4H-SiC

    NASA Astrophysics Data System (ADS)

    Avice, Marc; Grossner, Ulrike; Nilsen, Ola; Christensen, Jens S.; Fjellvåg, Helmer; Svensson, Bengt G.

    2006-09-01

    Al2O3 has been grown by atomic layer chemical vapour deposition on HF cleaned n-type 4H-SiC using either H2O or O3 as an oxidant. After post-deposition annealing at high temperature (1000°C) in argon atmosphere for different durations (1, 2 and 3 h), bulk and interface properties of the films were studied by capacitance-voltage (CV), current-voltage (IV) and secondary ion mass spectrometry (SIMS) measurements. Electrical measurements show a decreasing shift of the flatband voltage indicating a diminution of the negative oxide charges with increasing annealing time. The SIMS measurements reveal accumulation of boron, sodium and potassium at the Al2O3/SiC interface but the accumulation decreases with annealing at 1000°C where also out diffusion of silicon into the Al2O3 film takes place.

  19. Science Activities in Energy: Chemical Energy.

    ERIC Educational Resources Information Center

    Oak Ridge Associated Universities, TN.

    Presented is a science activities in energy package which includes 15 activities relating to chemical energy. Activities are simple, concrete experiments for fourth, fifth and sixth grades which illustrate principles and problems relating to energy. Each activity is outlined on a single card which is introduced by a question. A teacher's…

  20. Chemical Potentials and Activities: An Electrochemical Introduction.

    ERIC Educational Resources Information Center

    Wetzel, T. L.; And Others

    1986-01-01

    Describes a laboratory experiment which explores the effects of adding inert salts to electrolytic cells and demonstrates the difference between concentration and chemical activity. Examines chemical potentials as the driving force of reactions. Provides five examples of cell potential and concentration change. (JM)

  1. Self-diffusiophoresis of chemically active colloids

    NASA Astrophysics Data System (ADS)

    Popescu, Mihail N.; Uspal, William E.; Dietrich, Siegfried

    2016-11-01

    Chemically active colloids locally change the chemical composition of their solvent via catalytic reactions which occur on parts of their surface. They achieve motility by converting the released chemical free energy into mechanical work through various mechanisms, such as phoresis. Here we discuss the theoretical aspects of self-diffusiophoresis, which - despite being one of the simplest motility mechanisms - captures many of the general features characterizing self-phoresis, such as self-generated and maintained hydrodynamic flows "driven" by surface activity induced inhomogeneities in solution. By studying simple examples, which provide physical insight, we highlight the complex phenomenology which can emerge from self-diffusiophoresis.

  2. Metabolic activation and inactivation of chemical carcinogens

    SciTech Connect

    Pelkonen, O.; Vaehaekangas, K.

    1980-09-01

    Chemical carcinogens are metabolized by numerous pathways catalyzed by enzymes in endoplasmic reticulum and other parts of the cell. Reactions in which functional groups are created are especially important in the activation of polycyclic hydrocarbon carcinogens to ultimate carcinogenic forms, although other enzymes may also participate in the activation of other chemical carcinogens. The reasons why carcinogens act on specific target tissues are incompletely understood, although differences in enzyme profiles between tissues certainly contribute to the target tissue variability. The concept of metabolic activation of carcinogens by body's own enzymes has led to the development of short-term assay systems, which essentially measure the production of biologically active metabolites from potential carcinogens.

  3. Vapour-induced solid-state C-H bond activation for the clean synthesis of an organopalladium biothiol sensor.

    PubMed

    Monas, Andrea; Užarević, Krunoslav; Halasz, Ivan; Kulcsár, Marina Juribašić; Ćurić, Manda

    2016-10-27

    Room-temperature accelerated aging in the solid state has been applied for atom- and energy-efficient activation of either one or two C-H bonds of azobenzene and methyl orange by palladium(ii) acetate. Organopalladium complexes are prepared in quantitative reactions without potentially harmful side products. Dicyclopalladated methyl orange is water-soluble and is a selective chromogenic biothiol sensor at physiologically-relevant micromolar concentrations in buffered aqueous media.

  4. Resonant and nonresonant vibrational excitation of ammonia molecules in the growth of gallium nitride using laser-assisted metal organic chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Golgir, Hossein Rabiee; Zhou, Yun Shen; Li, Dawei; Keramatnejad, Kamran; Xiong, Wei; Wang, Mengmeng; Jiang, Li Jia; Huang, Xi; Jiang, Lan; Silvain, Jean Francois; Lu, Yong Feng

    2016-09-01

    The influence of exciting ammonia (NH3) molecular vibration in the growth of gallium nitride (GaN) was investigated by using an infrared laser-assisted metal organic chemical vapor deposition method. A wavelength tunable CO2 laser was used to selectively excite the individual vibrational modes. Resonantly exciting the NH-wagging mode (v2) of NH3 molecules at 9.219 μm led to a GaN growth rate of 84 μm/h, which is much higher than the reported results. The difference between the resonantly excited and conventional thermally populated vibrational states was studied via resonant and nonresonant vibrational excitations of NH3 molecules. Resonant excitation of various vibrational modes was achieved at 9.219, 10.35, and 10.719 μm, respectively. Nonresonant excitation was conducted at 9.201 and 10.591 μm, similar to conventional thermal heating. Compared to nonresonant excitation, resonant excitation noticeably promotes the GaN growth rate and crystalline quality. The full width at half maximum value of the XRD rocking curves of the GaN (0002) and GaN (10-12) diffraction peaks decreased at resonant depositions and reached its minimum value of 45 and 53 arcmin, respectively, at the laser wavelength of 9.219 μm. According to the optical emission spectroscopic studies, resonantly exciting the NH3 v2 mode leads to NH3 decomposition at room temperature, reduces the formation of the TMGa:NH3 adduct, promotes the supply of active species in GaN formation, and, therefore, results in the increased GaN growth rate.

  5. [CO2-gas exchange of mosses following water vapour uptake].

    PubMed

    Lange, O L

    1969-03-01

    The CO2-gas exchange of dry mosses which were exposed to air of high water vapour content has been followed. Some moss species behave as do lichens and aerophilic green algae: they are able to take up enough water vapour to make a rather high photosynthetic activity possible. Other species lack this ability. They need liquid water for reactivation of photosynthesis, as do poikilohydric ferns and phanerogams. In this respect too the mosses are located between the real thallophytes and the cormophytes. From this point of view they are useful objects for studying the relationships between water vapour reactivation, morphological organisation and ecological capability.

  6. The Chemical Composition of the Active Stars

    NASA Astrophysics Data System (ADS)

    Glazunova, L. V.

    The comparison of the results of the studies of the active stars' chemical composition obtained by different authors has been performed. It was concluded that the difference between the abundances of some elements in active and inactive stars becomes significant (> 3σ) only for the active stars with high chromospheric activity (lgR'HK > -4). This is the case primarily for the light elements, namely Li, Na and Al, as well as heavy elements with Z > 30.

  7. Chemical activation of carbon mesophase pitches.

    PubMed

    Mora, E; Blanco, C; Pajares, J A; Santamaría, R; Menéndez, R

    2006-06-01

    This paper studies the chemical activation of mesophase pitches of different origins in order to obtain activated carbons suitable for use as electrodes in supercapacitors. The effect that the activating agent (NaOH, LiOH, and KOH), the alkaline hydroxide/pitch ratio, and the activation temperature had on the characteristics of the resultant activated carbons was studied. LiOH was found to be a noneffective activating agent, while activation with NaOH and KOH yielded activated carbons with high apparent surface areas and pore volumes. The increase of the KOH/pitch ratio caused an increase of the chemical attack on the carbon, producing higher burnoffs and development of porosity. Extremely high apparent surface areas were obtained when the petroleum pitch was activated with 5:1 KOH/carbon ratio. The increase of the activation temperature caused an increase of the burnoff, although the differences were not as significant as those derived from the use of different proportions of activating agent.

  8. Activated coconut shell charcoal carbon using chemical-physical activation

    NASA Astrophysics Data System (ADS)

    Budi, Esmar; Umiatin, Nasbey, Hadi; Bintoro, Ridho Akbar; Wulandari, Futri; Erlina

    2016-02-01

    The use of activated carbon from natural material such as coconut shell charcoal as metal absorbance of the wastewater is a new trend. The activation of coconut shell charcoal carbon by using chemical-physical activation has been investigated. Coconut shell was pyrolized in kiln at temperature about 75 - 150 °C for about 6 hours in producing charcoal. The charcoal as the sample was shieved into milimeter sized granule particle and chemically activated by immersing in various concentration of HCl, H3PO4, KOH and NaOH solutions. The samples then was physically activated using horizontal furnace at 400°C for 1 hours in argon gas environment with flow rate of 200 kg/m3. The surface morphology and carbon content of activated carbon were characterized by using SEM/EDS. The result shows that the pores of activated carbon are openned wider as the chemical activator concentration is increased due to an excessive chemical attack. However, the pores tend to be closed as further increasing in chemical activator concentration due to carbon collapsing.

  9. Annealing effects on capacitance-voltage characteristics of a-Si/SiN(x) multilayer prepared using hot-wire chemical vapour deposition.

    PubMed

    Panchal, A K; Rai, D K; Solanki, C S

    2011-04-01

    Post-deposition annealing of a-Si/SiN(x) multilayer films at different temperature shows varying shift in high frequency (1 MHz) capacitance-voltage (HFCV) characteristics. Various a-Si/SiN(x) multilayer films were deposited using hot wire chemical vapor deposition (HWCVD) and annealed in the temperature range of 800 to 900 degrees C to precipitate Si quantum dots (Si-QD) in a-Si layers. HFCV measurements of the as-deposited and annealed films in metal-insulator-semiconductor (MIS) structures show hysterisis in C-V curves. The hysteresis in the as-deposited films and annealed films is attributed to charge trapping in Si-dangling bonds in a-Si layer and in Si-QD respectively. The charge trapping density in Si-QD increases with temperature while the interface defects density (D(it)) remains constant.

  10. Antimicrobial activity of chemically modified dextran derivatives.

    PubMed

    Tuchilus, Cristina G; Nichifor, Marieta; Mocanu, Georgeta; Stanciu, Magdalena C

    2017-04-01

    Cationic amphiphilic dextran derivatives with a long alkyl group attached to the reductive end of the polysaccharide chain and quaternary ammonium groups attached as pendent groups to the main dextran backbone were synthesized and tested for their antimicrobial properties against several bacteria and fungi strains. Dependence of antimicrobial activity on both polymer chemical composition (dextran molar mass, length of end alkyl group and chemical structure of ammonium groups) and type of microbes was highlighted by disc-diffusion method (diameter of inhibition zone) and broth microdilution method (minimum inhibitory concentrations). Polymers had antimicrobial activity for all strains studied, except for Pseudomonas aeruginosa ATCC 27853. The best activity against Staphylococcus aureus (Minimun Inhibitory Concentration 60μg/mL) was provided by polymers obtained from dextran with lower molecular mass (Mn=4500), C12H25 or C18H37 end groups, and N,N-dimethyl-N-benzylammonium pendent groups.

  11. Insight into hydroxides-activated coals: chemical or physical activation?

    SciTech Connect

    Alcaniz-Monge, J.; Illan-Gomez, M.J.

    2008-02-15

    The objective of this paper is to get an insight into the chemical activation mechanism using KOH and NaOH as activated agents. Three coals have been selected as carbon precursors. It was found that KOH and NaOH develop a similar narrow microporosity, independently of the coal rank, whereas only KOH generates supermicroporosity. Temperature-programmed desorption experiments, carried out with impregnated anthracite, show differences on the gas evolved during the activated carbon preparation using the two activating agents. Thus, whereas hydrogen profiles are quite similar for both activated agents, the CO and H{sub 2}O profiles are different. It is remarkable the high amount of H{sub 2}O evolved at the maximum treatment temperature for both activating agents. The results obtained to allow conclusion that the chemical activation is due to a combination of different process driving the development of material porosity.

  12. Investigation of chemical vapour deposition MoS2 field effect transistors on SiO2 and ZrO2 substrates.

    PubMed

    Liu, Xi; Chai, Yang; Liu, Zhaojun

    2017-04-21

    With the development of portable electronics, higher performance transistors are required to reduce the form factor and improve the performance of the devices. The key issue relies on developing transistors with outstanding electrical properties and low energy consumption at small scale. Here we demonstrate chemical vapor deposition (CVD) grown MoS2 transistors with a high on/off ratio using ZrO2 as a gate dielectric. Using 10 nm thick ZrO2, the transistor has an on/off ratio of 10(8), a sub-threshold swing of 0.1 V/dec, and a mobility of 64.66 cm(2) V(-1) s(-1). Compared to the MoS2 devices grown on 300 nm SiO2, the electrical performance demonstrates an all round improvement, which indicates the high crystalline quality of MoS2/ZrO2. Owing to the high-k ZrO2 dielectrics, the MoS2 transistor has a high on/off ratio, a low operating voltage, and good channel modulation capability which ensures that MoS2 is a good candidate for low power electronics.

  13. Chemical vapour deposition of graphene on Nk(111) and Co(0001) and intercalation with Au to study Dirac Cone Formation and Rashba splitting

    SciTech Connect

    Sanchez-Barriga, J.; Vescovo, E.; Varykhalov, A.; Scholz, M.R.; Rader, O.; Marchenko, D.; Rybkin, A.

    2010-01-01

    We show in detail monitoring by photoelectron spectroscopy how graphene can be grown by chemical vapor deposition on the transition-metal surfaces Ni(111) and Co(0001) and intercalated by a monoatomic layer of Au. For both systems, a linear E(k) dispersion of massless Dirac fermions appears in the graphene {pi}-band in the vicinity of the Fermi energy. In order to study ferromagnetism and spin-orbit effects by spin- and angle-resolved photoelectron spectroscopy, the sample must be magnetized in remanence. To this end, a W(110) substrate is prepared, its cleanliness verified by photoemission from W(110) surface states and surface core levels, and epitaxial Ni(111) and Co(0001) thin films are grown on top. Spin-resolved photoemission from the {pi}-band shows that the ferromagnetic polarization of graphene/Ni(111) and graphene/Co(0001) is negligible and that graphene on Ni(111) is after intercalation of Au spin-orbit split by the Rashba effect.

  14. Investigation of chemical vapour deposition MoS2 field effect transistors on SiO2 and ZrO2 substrates

    NASA Astrophysics Data System (ADS)

    Liu, Xi; Chai, Yang; Liu, Zhaojun

    2017-04-01

    With the development of portable electronics, higher performance transistors are required to reduce the form factor and improve the performance of the devices. The key issue relies on developing transistors with outstanding electrical properties and low energy consumption at small scale. Here we demonstrate chemical vapor deposition (CVD) grown MoS2 transistors with a high on/off ratio using ZrO2 as a gate dielectric. Using 10 nm thick ZrO2, the transistor has an on/off ratio of 108, a sub-threshold swing of 0.1 V/dec, and a mobility of 64.66 cm2 V‑1 s‑1. Compared to the MoS2 devices grown on 300 nm SiO2, the electrical performance demonstrates an all round improvement, which indicates the high crystalline quality of MoS2/ZrO2. Owing to the high-k ZrO2 dielectrics, the MoS2 transistor has a high on/off ratio, a low operating voltage, and good channel modulation capability which ensures that MoS2 is a good candidate for low power electronics.

  15. Collective surfing of chemically active particles.

    PubMed

    Masoud, Hassan; Shelley, Michael J

    2014-03-28

    We study theoretically the collective dynamics of immotile particles bound to a 2D surface atop a 3D fluid layer. These particles are chemically active and produce a chemical concentration field that creates surface-tension gradients along the surface. The resultant Marangoni stresses create flows that carry the particles, possibly concentrating them. For a 3D diffusion-dominated concentration field and Stokesian fluid we show that the surface dynamics of active particle density can be determined using nonlocal 2D surface operators. Remarkably, we also show that for both deep or shallow fluid layers this surface dynamics reduces to the 2D Keller-Segel model for the collective chemotactic aggregation of slime mold colonies. Mathematical analysis has established that the Keller-Segel model can yield finite-time, finite-mass concentration singularities. We show that such singular behavior occurs in our finite-depth system, and study the associated 3D flow structures.

  16. A Photoacoustic Study of Chemically Active Systems.

    DTIC Science & Technology

    1983-09-01

    unless so designated by other documentation IS. KEY WORDS (Continue w reverse aide If neceeairy wd Identify by block nmber) Photoacoustic, Spectroscopy ...CwcAhnm i, pwo If w M Idntitty by block nin1b9) -,xThe method of gas-microphone photoacoustic spectroscopy and the related photothermal deflection... spectroscopy have been developed for application to chemically active systems. Fourier Transform Infrared Photoacoustic Spectros- copy has been used to study

  17. Chemically activated manganese dioxide for dry batteries

    NASA Astrophysics Data System (ADS)

    Askar, M.; Abbas, H.

    1994-10-01

    The present investigation has enabled us to convert inactive beta-manganese dioxide to high electrochemically active types by chemical processes. Natural and chemically prepared beta-manganese dioxides were roasted at 1050 C to form Mn3O4. This compound was subjected to activation treatment using hydrochloric and sulfuric acid under various reaction conditions. The manganese dioxide so obtained was examined by x-ray diffraction, thermogravimetric, differential thermal, and chemical analyses. The structure of the dioxide obtained was found to be greatly dependent on the origin of MnO2 and type of acid used. Treatment with hydrochloric acid yielded the so-called gamma-variety while sulfuric acid tended to produce gamma- or alpha-MnO2. In addition, waste manganese sulfate obtained as by-product from sulfuric acid digestion treatment was recycled and electrolytically oxidized to gamma-MnO2. The discharge performance of the above-mentioned MnO2 samples as battery cathodic active material was evaluated and compared with the ordinary battery grade.

  18. Experimental and theoretical rationalization of the growth mechanism of silicon quantum dots in non-stoichiometric SiN x : role of chlorine in plasma enhanced chemical vapour deposition.

    PubMed

    Mon-Pérez, E; Salazar, J; Ramos, E; Salazar, J Santoyo; Suárez, A López; Dutt, A; Santana, G; Monroy, B Marel

    2016-11-11

    Silicon quantum dots (Si-QDs) embedded in an insulator matrix are important from a technological and application point of view. Thus, being able to synthesize them in situ during the matrix growth process is technologically advantageous. The use of SiH2Cl2 as the silicon precursor in the plasma enhanced chemical vapour deposition (PECVD) process allows us to obtain Si-QDs without post-thermal annealing. Foremost in this work, is a theoretical rationalization of the mechanism responsible for Si-QD generation in a film including an analysis of the energy released by the extraction of HCl and the insertion of silylene species into the terminal surface bonds. From the results obtained using density functional theory (DFT), we propose an explanation of the mechanism responsible for the formation of Si-QDs in non-stoichiometric SiN x starting from chlorinated precursors in a PECVD system. Micrograph images obtained through transmission electron microscopy confirmed the presence of Si-QDs, even in nitrogen-rich (N-rich) samples. The film stoichiometry was controlled by varying the growth parameters, in particular the NH3/SiH2Cl2 ratio and hydrogen dilution. Experimental and theoretical results together show that using a PECVD system, along with chlorinated precursors it is possible to obtain Si-QDs at a low substrate temperature without annealing treatment. The optical property studies carried out in the present work highlight the prospects of these thin films for down shifting and as an antireflection coating in silicon solar cells.

  19. Experimental and theoretical rationalization of the growth mechanism of silicon quantum dots in non-stoichiometric SiN x : role of chlorine in plasma enhanced chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Mon-Pérez, E.; Salazar, J.; Ramos, E.; Santoyo Salazar, J.; López Suárez, A.; Dutt, A.; Santana, G.; Marel Monroy, B.

    2016-11-01

    Silicon quantum dots (Si-QDs) embedded in an insulator matrix are important from a technological and application point of view. Thus, being able to synthesize them in situ during the matrix growth process is technologically advantageous. The use of SiH2Cl2 as the silicon precursor in the plasma enhanced chemical vapour deposition (PECVD) process allows us to obtain Si-QDs without post-thermal annealing. Foremost in this work, is a theoretical rationalization of the mechanism responsible for Si-QD generation in a film including an analysis of the energy released by the extraction of HCl and the insertion of silylene species into the terminal surface bonds. From the results obtained using density functional theory (DFT), we propose an explanation of the mechanism responsible for the formation of Si-QDs in non-stoichiometric SiN x starting from chlorinated precursors in a PECVD system. Micrograph images obtained through transmission electron microscopy confirmed the presence of Si-QDs, even in nitrogen-rich (N-rich) samples. The film stoichiometry was controlled by varying the growth parameters, in particular the NH3/SiH2Cl2 ratio and hydrogen dilution. Experimental and theoretical results together show that using a PECVD system, along with chlorinated precursors it is possible to obtain Si-QDs at a low substrate temperature without annealing treatment. The optical property studies carried out in the present work highlight the prospects of these thin films for down shifting and as an antireflection coating in silicon solar cells.

  20. Chemical inhibition of nitrification in activated sludge.

    PubMed

    Kelly, R T; Henriques, I D S; Love, N G

    2004-03-20

    Conventional aerobic nitrification was adversely affected by single pulse inputs of six different classes of industrially relevant chemical toxins: an electrophilic solvent (1-chloro-2,4-dinitrobenzene, CDNB), a heavy metal (cadmium), a hydrophobic chemical (1-octanol), an uncoupling agent (2,4-dinitrophenol, DNP), alkaline pH, and cyanide in its weak metal complexed form. The concentrations of each chemical source that caused 1 5, 25, and 50% respiratory inhibition of a nitrifying mixed liquor during a short-term assay were used to shock sequencing batch reactors containing nitrifying conventional activated sludge. The reactors were monitored for recovery over a period of 30 days or less. All shock conditions inhibited nitrification, but to different degrees. The nitrate generation rate (NGR) of the shocked reactors recovered overtime to control reactor levels and showed that it was a more sensitive indicator of nitrification inhibition than both initial respirometric tests conducted on unexposed biomass and effluent nitrogen species analyses. CDNB had the most severe impact on nitrification, followed by alkaline pH 11, cadmium, cyanide, octanol, and DNP. Based on effluent data, cadmium and octanol primarily inhibited ammonia-oxidizing bacteria (AOB) while CDNB, pH 11,and cyanide inhibited both AOB and nitrite-oxidizing bacteria (NOB). DNP initially inhibited nitrification but quickly increased the NGR relative to the control and stimulated nitrification after several days in a manner reflective of oxidative uncoupling. The shocked mixed liquor showed trends toward recovery from inhibition for all chemicals tested, but in some cases this reversion was slow. These results contribute to our broader effort to identify relationships between chemical sources and the process effects they induce in activated sludge treatment systems.

  1. Chemical activation through super energy transfer collisions.

    PubMed

    Smith, Jonathan M; Nikow, Matthew; Ma, Jianqiang; Wilhelm, Michael J; Han, Yong-Chang; Sharma, Amit R; Bowman, Joel M; Dai, Hai-Lung

    2014-02-05

    Can a molecule be efficiently activated with a large amount of energy in a single collision with a fast atom? If so, this type of collision will greatly affect molecular reactivity and equilibrium in systems where abundant hot atoms exist. Conventional expectation of molecular energy transfer (ET) is that the probability decreases exponentially with the amount of energy transferred, hence the probability of what we label "super energy transfer" is negligible. We show, however, that in collisions between an atom and a molecule for which chemical reactions may occur, such as those between a translationally hot H atom and an ambient acetylene (HCCH) or sulfur dioxide, ET of chemically significant amounts of energy commences with surprisingly high efficiency through chemical complex formation. Time-resolved infrared emission observations are supported by quasi-classical trajectory calculations on a global ab initio potential energy surface. Results show that ∼10% of collisions between H atoms moving with ∼60 kcal/mol energy and HCCH result in transfer of up to 70% of this energy to activate internal degrees of freedom.

  2. Vapour Intrusion into Buildings - A Literature Review

    EPA Science Inventory

    This chapter provides a review of recent research on vapour intrusion of volatile organic compounds (VOCs) into buildings. The chapter builds on a report from Tillman and Weaver (2005) which reviewed the literature on vapour intrusion through 2005. Firstly, the term ‘vapour intru...

  3. Vapour growth and characterization of beta indium sesquitelluride crystals

    NASA Astrophysics Data System (ADS)

    Reshmi, P. M.; Kunjomana, A. G.; Chandrasekharan, K. A.; Teena, M.

    2014-05-01

    Physical Vapour Deposition (PVD) provides stoichiometric crystals of different morphology, depending upon the materials, geometry of ampoules, temperature profiles, growth parameters and kinetics of crystallization. The crystal forms such as needles, platelets and spherulites of beta indium sesquitelluride (β-In2Te3) were produced by controlling the temperature of source and growth zones. The X-Ray Diffraction (XRD) and chemical analysis of the spherulitic crystals confirmed zinc blende structure with beta phase. Their resistivity (135.16 Ω cm) at room temperature (300 K) was determined by van der Pauw method. The temperature dependence of DC conductivity was investigated using the conventional two-probe technique. The variation of dielectric constant (ε1) and dielectric loss (tan δ) with temperature has been studied for different frequencies (1 kHz-1 MHz). The AC conductivity, σac(ω) was found to vary with angular frequency as ωs, where s is the frequency exponent. The values of s lie very close to unity and show a slight decrease with increase in temperature, which indicate a Correlated Barrier Hopping (CBH) between centres forming Intimate Valence Alternation Pairs (IVAP). The activation energy for conduction ranges from 0.187 eV to 0.095 eV. The microhardness of β-In2Te3 spherulites is found to be 353.5 kg/mm2, which is higher than that of other semiconducting chalcogenides. The results thus obtained on crystals grown from vapour phase open up ample possibilities for radiation detector applications.

  4. The seasonal cycle of water vapour on Mars from assimilation of Thermal Emission Spectrometer data

    NASA Astrophysics Data System (ADS)

    Steele, Liam J.; Lewis, Stephen R.; Patel, Manish R.; Montmessin, Franck; Forget, François; Smith, Michael D.

    2014-07-01

    We present for the first time an assimilation of Thermal Emission Spectrometer (TES) water vapour column data into a Mars global climate model (MGCM). We discuss the seasonal cycle of water vapour, the processes responsible for the observed water vapour distribution, and the cross-hemispheric water transport. The assimilation scheme is shown to be robust in producing consistent reanalyses, and the global water vapour column error is reduced to around 2-4 pr μm depending on season. Wave activity is shown to play an important role in the water vapour distribution, with topographically steered flows around the Hellas and Argyre basins acting to increase transport in these regions in all seasons. At high northern latitudes, zonal wavenumber 1 and 2 stationary waves during northern summer are responsible for spreading the sublimed water vapour away from the pole. Transport by the zonal wavenumber 2 waves occurs primarily to the west of Tharsis and Arabia Terra and, combined with the effects of western boundary currents, this leads to peak water vapour column abundances here as observed by numerous spacecraft. A net transport of water to the northern hemisphere over the course of one Mars year is calculated, primarily because of the large northwards flux of water vapour which occurs during the local dust storm around LS=240-260°. Finally, outlying frost deposits that surround the north polar cap are shown to be important in creating the peak water vapour column abundances observed during northern summer.

  5. The Seasonal Cycle of Water Vapour on Mars from Assimilation of Thermal Emission Spectrometer Data

    NASA Technical Reports Server (NTRS)

    Steele, Liam J.; Lewis, Stephen R.; Patel, Manish R.; Montmessin, Franck; Forget, Francois; Smith, Michael D.

    2014-01-01

    We present for the first time an assimilation of Thermal Emission Spectrometer (TES) water vapour column data into a Mars global climate model (MGCM). We discuss the seasonal cycle of water vapour, the processes responsible for the observed water vapour distribution, and the cross-hemispheric water transport. The assimilation scheme is shown to be robust in producing consistent reanalyses, and the global water vapour column error is reduced to around 2-4 pr micron depending on season. Wave activity is shown to play an important role in the water vapour distribution, with topographically steered flows around the Hellas and Argyre basins acting to increase transport in these regions in all seasons. At high northern latitudes, zonal wavenumber 1 and 2 stationary waves during northern summer are responsible for spreading the sublimed water vapour away from the pole. Transport by the zonal wavenumber 2 waves occurs primarily to the west of Tharsis and Arabia Terra and, combined with the effects of western boundary currents, this leads to peak water vapour column abundances here as observed by numerous spacecraft. A net transport of water to the northern hemisphere over the course of one Mars year is calculated, primarily because of the large northwards flux of water vapour which occurs during the local dust storm around L(sub S) = 240-260deg. Finally, outlying frost deposits that surround the north polar cap are shown to be important in creating the peak water vapour column abundances observed during northern summer.

  6. Active Chemical Thermodynamics promoted by activity of cortical actin

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Bhaswati; Chaudhuri, Abhishek; Gowrishankar, Kripa; Rao, Madan

    2011-03-01

    The spatial distribution and dynamics of formation and breakup of the nanoclusters of cell surface proteins is controlled by the active remodeling dynamics of the underlying cortical actin. To explain these observations, we have proposed a novel mechanism of nanoclustering, involving the transient binding to and advection along constitutively occuring ``asters'' of cortical actin. We study the consequences of such active actin-based clustering, in the context of chemical reactions involving conformational changes of cell surface proteins. We find that the active remodeling of cortical actin, can give rise to a dramatic increase in efficiency and extent of conformational spread, even at low levels of expression at the cell surface. We define a activity temperature (τa) arising due to actin activities which can be used to describe chemical thermodynamics of the system. We plot TTT (time-temparature-transformation) curves and compute the Arrhenius factors which depend on τa . With this, the active asters can be treated as enzymes whose enzymatic reaction rate can be related to the activity.

  7. Electron Transport in Water Vapour

    NASA Astrophysics Data System (ADS)

    Kawaguchi, Satoru; Satoh, Kohki; Itoh, Hidenori

    2015-09-01

    Sets of electron collision cross sections for water vapour previously reported are examined by comparing calculated electron swarm parameters with measured parameters. Further, reliable cross section set of water vapour is estimated by the electron swarm method using Monte Carlo simulation to ensure the accuracy of the swarm parameter calculation. The values of an electron drift velocity, a longitudinal diffusion coefficient, and an effective ionisation coefficient calculated from Yousfi and Benabdessadok's set and those calculated from Itikawa and Mason's set do not necessarily agree with measured data. A new cross section set of water vapour, which consists of three kinds of rotational excitation, two kinds of vibrational excitation, three kinds of electron attachment, twenty-six kinds of electronic excitation, and six kinds of ionisation cross sections, and an elastic collision cross section, is estimated, and an anisotropic electron scattering for elastic and rotational excitation collision is considered. The swarm parameters calculated from the estimated cross section set is in good agreement with measured data in a wide range of reduced electric field.

  8. Antimicrobial action of essential oil vapours and negative air ions against Pseudomonas fluorescens.

    PubMed

    Tyagi, A K; Malik, A

    2010-10-15

    The aim of this study was to investigate the antibacterial activity of essential oil (in liquid as well as in vapour phase) and negative air ions (NAI) against Pseudomonas fluorescens. The combined effect of NAI with essential oil vapour was also investigated to determine kill time and morphological changes in bacterial cells. The MIC of Cymbopogon citratus (0.567 mg/ml), Mentha arvensis (0.567 mg/ml), Mentha piperita (1.125 mg/ml) and Eucalyptus globulus (2.25 mg/ml) was studied via the agar dilution method. To estimate the antibacterial activity of essential oils in the vapour phase, agar plates inoculated with P. fluorescens were incubated with various concentrations of each essential oil vapour and zone of inhibition was recorded. Further, in order to assess the kill time, P. fluorescens inoculated agar plates were exposed to selected bactericidal essential oil vapour and NAI, separately, in an air-tight chamber. A continuous decrease in bacterial count was observed over time. A significant enhancement in the bactericidal action was observed by exposure to the combination of essential oil vapour and NAI as compared to their individual action. Scanning electron microscopy was used to study the alteration in morphology of P. fluorescens cells after exposure to C. citratus oil vapour, NAI, and combination of C. citratus oil vapour and NAI. Maximum morphological deformation was found due to the combined effect of C. citratus oil vapour and NAI. This study demonstrates that the use of essential oils in the vapour phase is more advantageous than the liquid phase. Further the antibacterial effect of the essential oil vapours can be significantly enhanced by the addition of NAI. The work described here offers a novel and efficient approach for control of bacterial contamination that could be applied for food stabilization practices.

  9. Condensation of water vapour on moss-dominated biological soil crust, NW China

    NASA Astrophysics Data System (ADS)

    Wang, Xin-Ping; Pan, Yan-Xia; Hu, Rui; Zhang, Ya-Feng; Zhang, Hao

    2014-03-01

    Characteristics of water vapour condensation, including the onset, duration, and amount of water vapour condensation on moss-dominated biological soil crust (BSC) and dune sand were studied under simulated conditions with varying air temperature and relative humidity. The simulations were performed in a plant growth chamber using an electronic balance recording the weight of condensation. There was a positive linear correlation between the water vapour condensation and relative humidity while the mean temperature was negatively linearly related to amounts of water vapour condensation for both soil surfaces. The amount of water vapour condensation on BSC and dune sand can be described by the difference between air temperature and dew point with an exponential function, indicating that when the difference of air temperature and dew point exceeds a value of 35.3◦C, there will be zero water vapour condensed on BSC. In contrast, when the difference of air temperature and dew point exceeds a value of 20.4◦C, the water vapour condensation will be zero for dune sand. In general, when the air is fully saturated with water and the dew point is equal to the current air temperature, the water vapour condensed on BSC attained its maximum value of 0.398 mm, whereas it was 0.058 mm for dune sand. In comparison, water vapour condensed on BSC was at a relatively high temperature and low relative humidity, while we did not detect water vapour condensation on the dune sand under the similar conditions. Physical and chemical analyses of the samples pointed to a greater porosity, high content of fine particles, and high salinity for BSC compared to the dune sand. These results highlight that soil physicochemical properties are the likely factors influencing the mechanism of water vapour condensation under specific meteorological conditions, as onset was earlier and the duration was longer for water vapour condensation on BSC in comparison with that of dune sand. This contributed to

  10. Towards outperforming conventional sensor arrays with fabricated individual photonic vapour sensors inspired by Morpho butterflies

    PubMed Central

    Potyrailo, Radislav A.; Bonam, Ravi K.; Hartley, John G.; Starkey, Timothy A.; Vukusic, Peter; Vasudev, Milana; Bunning, Timothy; Naik, Rajesh R.; Tang, Zhexiong; Palacios, Manuel A.; Larsen, Michael; Le Tarte, Laurie A.; Grande, James C.; Zhong, Sheng; Deng, Tao

    2015-01-01

    Combining vapour sensors into arrays is an accepted compromise to mitigate poor selectivity of conventional sensors. Here we show individual nanofabricated sensors that not only selectively detect separate vapours in pristine conditions but also quantify these vapours in mixtures, and when blended with a variable moisture background. Our sensor design is inspired by the iridescent nanostructure and gradient surface chemistry of Morpho butterflies and involves physical and chemical design criteria. The physical design involves optical interference and diffraction on the fabricated periodic nanostructures and uses optical loss in the nanostructure to enhance the spectral diversity of reflectance. The chemical design uses spatially controlled nanostructure functionalization. Thus, while quantitation of analytes in the presence of variable backgrounds is challenging for most sensor arrays, we achieve this goal using individual multivariable sensors. These colorimetric sensors can be tuned for numerous vapour sensing scenarios in confined areas or as individual nodes for distributed monitoring. PMID:26324320

  11. Towards outperforming conventional sensor arrays with fabricated individual photonic vapour sensors inspired by Morpho butterflies

    NASA Astrophysics Data System (ADS)

    Potyrailo, Radislav A.; Bonam, Ravi K.; Hartley, John G.; Starkey, Timothy A.; Vukusic, Peter; Vasudev, Milana; Bunning, Timothy; Naik, Rajesh R.; Tang, Zhexiong; Palacios, Manuel A.; Larsen, Michael; Le Tarte, Laurie A.; Grande, James C.; Zhong, Sheng; Deng, Tao

    2015-09-01

    Combining vapour sensors into arrays is an accepted compromise to mitigate poor selectivity of conventional sensors. Here we show individual nanofabricated sensors that not only selectively detect separate vapours in pristine conditions but also quantify these vapours in mixtures, and when blended with a variable moisture background. Our sensor design is inspired by the iridescent nanostructure and gradient surface chemistry of Morpho butterflies and involves physical and chemical design criteria. The physical design involves optical interference and diffraction on the fabricated periodic nanostructures and uses optical loss in the nanostructure to enhance the spectral diversity of reflectance. The chemical design uses spatially controlled nanostructure functionalization. Thus, while quantitation of analytes in the presence of variable backgrounds is challenging for most sensor arrays, we achieve this goal using individual multivariable sensors. These colorimetric sensors can be tuned for numerous vapour sensing scenarios in confined areas or as individual nodes for distributed monitoring.

  12. Isothermal vapour flow in extremely dry soils

    NASA Astrophysics Data System (ADS)

    Todman, L. C.; Ireson, A. M.; Butler, A. P.; Templeton, M. R.

    2012-04-01

    In dry soils hydraulic connectivity within the liquid water phase decreases and vapour flow becomes a significant transport mechanism for water. The temperature or solute concentration of the liquid phase affects the vapour pressure of the surrounding air, thus temperature or solute gradients can drive vapour flows. However, in extremely dry soils where water is retained by adsorptive forces rather than capillarity, vapour flows can also occur. In such soils tiny changes in water content significantly affect the equilibrium vapour pressure in the soil, and hence small differences in water content can initiate vapour pressure gradients. In many field conditions this effect may be negligible compared to vapour flows driven by other factors. However, flows of this type are particularly significant in a new type of subsurface irrigation system which uses pervaporation, via a polymer tubing, as the mechanism for water supply. In this system, water enters the soil in vapour phase. Experiments were performed in laboratory conditions using marine sand that had previously been oven dried and cooled. This dry sand was used to represent the desert conditions in which this irrigation system is intended for use. Experimental results show that isothermal vapour flows can significantly affect the performance of such irrigation systems due to the rapid transport of water through the soil via the vapour phase. When the irrigation pipe was buried at a depth of 10cm a vapour flow from the soil surface was observed in less than 2 hours. These flows therefore affect the loss of mass into the atmosphere and thus must be considered when evaluating the availability of water for the irrigated crop. The experiments also provide a rare opportunity to observe isothermal vapour flows initiating from a subsurface source. Such experiments allow the significance of these flows to be quantified and potentially applied to other areas of arid zone hydrology.

  13. SOME CHEMICAL PROPERTIES UNDERLYING ARSENIC'S BIOLOGICAL ACTIVITY

    EPA Science Inventory

    ABSTRACT

    In this paper some of the chemical properties of arsenicals (atomic
    and molecular orbitals, electronegativity, valence state, changes between
    valence state, nucleophilicity, the hard/soft acid/base principle) that may
    account for some of the b...

  14. Dose Response Data for Hormonally Active Chemicals ...

    EPA Pesticide Factsheets

    The shape of the dose response curve in the low dose region has been debated since the late 1940s. The debate originally focused on linear no threshold (LNT) vs threshold responses in the low dose range for cancer and noncancer related effects. For noncancer effects the default assumption is that noncancer effects generally display threshold rather than LNT responses. More recently, claims have arisen that the chemicals, like endocrine disrupters (EDS), which act via high affinity, low capacity nuclear receptors, may display LNT or nonmonotonic low dose responses: responses that could be missed in multigenerational guideline toxicity testing. This presentation will discuss LNT, threshold and nonmonotonic dose response relationships from case studies of chemicals that disrupt reproductive development and function via the ER, AR and AhR pathways and will include in vitro and in vivo multigenerational data. The in vivo studies in this discussion include only robust, well designed, comprehensive studies that administered the chemical via a relevant route(s) of exposure over a broad dose response range, including low dose(s) in the microgram/kg/d range. The chemicals include ethinyl estradiol, estradiol, genistein, bisphenol a, trenbolone, finasteride, flutamide, phthalate esters and 2,3,7,8 TCDD. The objective is to critically evaluate the data from well done studies in this field to address concerns that current multigenerational reproductive test gui

  15. Water vapour in the UT/LS

    NASA Astrophysics Data System (ADS)

    Schiller, C.

    2003-04-01

    The water vapour abundance increased at all levels in the stratosphere during the last decades. Though the observed increase cannot be explained quantitatively, the water vapour distribution and underlying processes seem to be sufficiently understood in the overworld. In the lowermost stratosphere and in the tropical tropopause layer, however, the complex transport and temperature patterns on different scales result in a high variability and strong gradients of the water vapour distribution. The long-term increase of water vapour seems to be apparent also in the lowermost stratosphere, but its significance is decreasing towards the tropopause. In this presentation, measurements of water vapour in the extratropical UT/LS from several airborne campaigns are discussed and compared to distribution patterns obtained from satellite data sets. A mixing layer with H2O mixing ratios up to 100 ppmv is found above the tropopause, frequently resulting in saturation of these air masses. A seasonal cycle of the water content with a late spring and summer maximum is apparent in the LS. The role of jet streams moistening the lowermost stratosphere will be discussed. In a second part, water vapour distributions in the tropics as the stratospheric source region are presented. As an example, measurements over the Indian ocean are discussed where temperatures and water vapour mixing ratios as low as in the classical 'fountain' region over Micronesia occurred. Frequently, ongoing dehydration was observed in the TTL up to the tropopause, independent on deep convection cells.

  16. ILO activities in the area of chemical safety.

    PubMed

    Obadia, Isaac

    2003-08-21

    The ILO has been active in the area of safety in the use of chemicals at work since the year of its creation in 1919, including the development of international treaties and other technical instruments, the provision of technical assistance to its member States, and the development of chemical safety information systems. The two key ILO standards in this area are the Conventions on safety in the use of chemicals at work (No. 170, 1990), and the Prevention of Major Industrial Accidents (No. 174, 1993). The ILO Programme on occupational safety, health and environment (Safe Work) is currently responsible for ILO chemical safety activities. In the past two decades, most of ILO work in this area has been carried out within the context of inter-agency collaboration frameworks linking the ILO, WHO, UNEP, FAO, UNIDO, UNITAR, and the OECD, including the International Programme on Chemical Safety (IPCS), the Inter-Organisation Programme for the Sound Management of Chemicals (IOMC), and the Intergovernmental Forum on Chemical Safety (IFCS). Apart from the regular development, updating and dissemination of chemical safety information data bases such as the IPCS International Chemical Cards, the elaboration of a Globally harmonized system for the classification and labelling of Chemicals (GHS) has been the most outstanding achievement of this international collaboration on chemical safety.

  17. Physical properties of vapour grown indium monotelluride platelets

    NASA Astrophysics Data System (ADS)

    Kunjomana, A. G.; Chandrasekharan, K. A.; Teena, M.

    2015-02-01

    Indium monotelluride (InTe) crystals were grown from vapour phase under different temperature gradients by employing physical vapour deposition (PVD) method. The morphology of these crystals such as whiskers, needles, platelets etc., strongly depends on the temperature distribution in the horizontal dual zone furnace. InTe platelets were deposited by setting the temperature of the charge (TC) and growth (TS) zones at 1073 K and 773 K (ΔT=300 K), respectively, for different growth periods (24 h, 48 h, 72 h and 96 h). The surface growth features have been analyzed by scanning electron microscopes, which indicate layer growth mechanism for all the crystals. Various crystals grown under ΔT=200 K and 300 K (retaining TS invariant) were examined by X-ray diffraction and elemental analysis. InTe samples exhibited consistent lattice parameters, density and atomic percentage, establishing stoichiometry and chemical homogeneity. The results obtained for Seebeck coefficient, electrical conductivity, power factor, dislocation density and microhardness are found to be reproducible as well. The vapour deposited InTe platelets are mechanically stable and possess high value of TEP, which ensure their practical application in thermoelectric power generation.

  18. Activating secondary metabolism with stress and chemicals.

    PubMed

    Yoon, Vanessa; Nodwell, Justin R

    2014-02-01

    The available literature on the secondary or nonessential metabolites of the streptomycetes bacteria suggests that there may be poorly expressed or "cryptic" compounds that have yet to be identified and that may have significant medical utility. In addition, it is clear that there is a large and complex regulatory network that controls the production of these molecules in the laboratory and in nature. Two approaches that have been taken to manipulating the yields of secondary metabolites are the use of various stress responses and, more recently, the use of precision chemical probes. Here, we review the status of this work and outline the challenges and opportunities afforded by each of them.

  19. Influence of process parameters on the surface and chemical properties of activated carbon obtained from biochar by chemical activation.

    PubMed

    Angın, Dilek; Altintig, Esra; Köse, Tijen Ennil

    2013-11-01

    Activated carbons were produced from biochar obtained through pyrolysis of safflower seed press cake by chemical activation with zinc chloride. The influences of process variables such as the activation temperature and the impregnation ratio on textural and chemical-surface properties of the activated carbons were investigated. Also, the adsorptive properties of activated carbons were tested using methylene blue dye as the targeted adsorbate. The experimental data indicated that the adsorption isotherms are well described by the Langmuir equilibrium isotherm equation. The optimum conditions resulted in activated carbon with a monolayer adsorption capacity of 128.21 mg g(-1) and carbon content 76.29%, while the BET surface area and total pore volume corresponded to 801.5m(2)g(-1) and 0.393 cm(3)g(-1), respectively. This study demonstrated that high surface area activated carbons can be prepared from the chemical activation of biochar with zinc chloride as activating agents.

  20. TSCA Chemical Data Reporting Fact Sheet: Reporting Manufactured Chemical Substances from Metal Mining and Related Activities

    EPA Pesticide Factsheets

    This fact sheet provides guidance on the Chemical Data Reporting (CDR) rule requirements related to the reporting of mined metals, intermediates, and byproducts manufactured during metal mining and related activities.

  1. Chemically-related Groups of Active Ingredients

    EPA Pesticide Factsheets

    Many pesticide active ingredients affect pests in similar ways, and we re-evaluate them together as a group. Groups include carbamate insecticides, neonicotinoids, organochlorines, organophosphates, pyrethrins, and pyrethroids.

  2. Chemical Classification of Nearby Active Galaxies

    NASA Astrophysics Data System (ADS)

    Aladro, R.; Martín, S.; Kramer, C.

    2015-12-01

    We present an unbiased λ=3 mm survey done with the IRAM 30 telescope towards the central parts of eight galaxies considered as archetypes of nearby starbursts, galaxies with an active galactic nucleus (AGN) and ultra-luminous infrared galaxies (ULIRGs). The spatial resolution range from ˜200 pc to ˜1.6 kpc, depending on the galaxy. We compare the abundances of thirty-seven species among the sample, and highlight the molecules that characterise the gas in each of them. These results can be very useful to prepare future interferometric observations of active galaxies.

  3. Gas and Chemical Activation of Charcoal

    DTIC Science & Technology

    1945-06-29

    supplemented ’ by runs in the laboratory has shown that zinc chloride is by far the most suitable activating agent. 1. In the dehydration mixing of...istics with time of dehydration . 3. The physical appearance of the mixture during the impregnation pperation provides sufficient significant information...to enable the operator to predict .mechanical characteristics of the briquet. CONFIDENTIAL " • ’< i£: • CONFIDENTIAL -4- 4* In the dehydration

  4. 75 FR 69630 - Impact of Implementation of the Chemical Weapons Convention on Commercial Activities Involving...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-15

    ...-0543-02] Impact of Implementation of the Chemical Weapons Convention on Commercial Activities Involving... Chemical Weapons Convention (CWC), through the Chemical Weapons Convention Implementation Act (CWCIA) and the Chemical Weapons Convention Regulations (CWCR), has had on commercial activities...

  5. Vapour transport of rare earth elements (REE) in volcanic gas: Evidence from encrustations at Oldoinyo Lengai

    NASA Astrophysics Data System (ADS)

    Gilbert, C. D.; Williams-Jones, A. E.

    2008-10-01

    Fumarolic encrustations and natrocarbonatite lava from the active crater of Oldoinyo Lengai volcano, Tanzania, were sampled and analysed. Two types of encrustation were distinguished on the basis of their REE content, enriched (~ 2800-5600 × [REE chondrite]) and depleted (~ 100-200 × [REE chondrite]) relative to natrocarbonatite (1700-1900 × [REE chondrite]. REE-enriched encrustations line the walls of actively degassing fumaroles, whereas REE-depleted encrustations occur mainly along cracks in and as crusts on cooling natrocarbonatite lava flows; one of the low REE encrustation samples was a stalactite from the wall of a possible fumarole. The encrustations are interpreted to have different origins, the former precipitating from volcanic gas and the latter from meteoric/ground water converted to steam by the heat of the overlying lava flow(s). REE-profiles of encrustations and natrocarbonatite are parallel, suggesting that there was no preferential mobilization of specific REE by either volcanic vapour or meteoric water vapour. The elevated REE-content of the first group of encrustations suggests that direct REE-transport from natrocarbonatite to volcanic vapour is possible. The REE trends observed in samples precipitating directly from the volcanic vapour cannot be explained by dry volatility based on the available data as there is no evidence in the encrustation compositions of the greatly enhanced volatility predicted for Yb and Eu. The observed extreme REE-fractionation with steep La/Sm slopes parallel to those of the natrocarbonatite reflects solvation and complexation reactions in the vapour phase that did not discriminate amongst the different REE or similar transport of REE in both the natrocarbonatite magma and its exsolving vapour. The low concentrations of REE in the encrustations produced by meteoric vapour suggest that the temperature was too low or that this vapour did not contain the ligands necessary to permit significant mobilization of the REE.

  6. Tetrapleura tetraptera: molluscicidal activity and chemical constituents.

    PubMed

    Aladesanmi, Adetunji J

    2006-08-28

    Tetrapleura tetraptera (Schumach. And Thonn) Taub, Mimosaceae, commonly known as Aridan (fruit), A single stemmed, robust, perennial tree of about 30 m. It has a grey/brown, smooth/rough bark with glabrous yound branchlets. The flower is yellow/pink and racemes white the fruit has dark brown, four winged pods 12-25 x 3.5-6.5 cm. It is generally found in the lowland forest of tropical Africa. The fruit consists of a fleshy pulp with small, brownish-black seeds. The fruit possesses a fragrant, characteristically pungent aromatic odour, which is attributed to its insect repellent property. It is used as spices and aroma (exotic tropical scents) and fish poisoning. It is one of the molluscicidal medicinal plants of Nigeria, also useful in the management of convulsions, leprosy, inflammation and/or rheumatoid pains. The documented biological and-or pharmacological activities are found to be molluscicidal, cardio-vascular, neuromuscular, hypotensive, anti-convulsant, trypanocidal, hirudinicidal, schistosomiasis control, anti-ulcerative, ectoxicity, anti-inflammatory, hypoglycaemic, anti-microbial, emulsifying property, birth control, food value and the control of intestinal parasites. Activity-guided fractionation of the methanol extract of the fruits of T. tetraptera led to the isolation of a saponin glycoside with an oleanolic acid aglycone, a monodesmosidic diglycoside of the rare sapogenin 27-hydroxyolean-12 (13)-en-28-oic acid; echinocystic acid-3-0-sodium sulfate from the stembark, umbelliferone and ferulic acid from the leaves and branches respectively. Also isolated from the fruits were aridanin and three of its olean-12-en-28-oic acid derivatives. All the compounds isolated either from the fruits or other parts were found to exhibit strong molluscicidal properties against the schistosomiasis-transmitting snails Biomphalaria glabrata.

  7. Land cover change and water vapour flows: learning from Australia.

    PubMed Central

    Gordon, Line; Dunlop, Michael; Foran, Barney

    2003-01-01

    Australia is faced with large-scale dryland salinization problems, largely as a consequence of the clearing of native vegetation for cropland and grassland. We estimate the change in continental water vapour flow (evapotranspiration) of Australia during the past 200 years. During this period there has been a substantial decrease in woody vegetation and a corresponding increase in croplands and grasslands. The shift in land use has caused a ca. 10% decrease in water vapour flows from the continent. This reduction corresponds to an annual freshwater flow of almost 340 km(3). The society-induced alteration of freshwater flows is estimated at more than 15 times the volume of run-off freshwater that is diverted and actively managed in the Australian society. These substantial water vapour flow alterations were previously not addressed in water management but are now causing serious impacts on the Australian society and local economies. Global and continental freshwater assessments and policy often neglects the interplay between freshwater flows and landscape dynamics. Freshwater issues on both regional and global levels must be rethought and the interplay between terrestrial ecosystems and freshwater better incorporated in freshwater and ecosystem management. PMID:14728792

  8. Activated chemical defenses suppress herbivory on freshwater red algae.

    PubMed

    Goodman, Keri M; Hay, Mark E

    2013-04-01

    The rapid life cycles of freshwater algae are hypothesized to suppress selection for chemical defenses against herbivores, but this notion remains untested. Investigations of chemical defenses are rare for freshwater macrophytes and absent for freshwater red algae. We used crayfish to assess the palatability of five freshwater red algae relative to a palatable green alga and a chemically defended aquatic moss. We then assessed the roles of structural, nutritional, and chemical traits in reducing palatability. Both native and non-native crayfish preferred the green alga Cladophora glomerata to four of the five red algae. Batrachospermum helminthosum, Kumanoa holtonii, and Tuomeya americana employed activated chemical defenses that suppressed feeding by 30-60 % following damage to algal tissues. Paralemanea annulata was defended by its cartilaginous structure, while Boldia erythrosiphon was palatable. Activated defenses are thought to reduce ecological costs by expressing potent defenses only when actually needed; thus, activation might be favored in freshwater red algae whose short-lived gametophytes must grow and reproduce rapidly over a brief growing season. The frequency of activated chemical defenses found here (three of five species) is 3-20× higher than for surveys of marine algae or aquatic vascular plants. If typical for freshwater red algae, this suggests that (1) their chemical defenses may go undetected if chemical activation is not considered and (2) herbivory has been an important selective force in the evolution of freshwater Rhodophyta. Investigations of defenses in freshwater rhodophytes contribute to among-system comparisons and provide insights into the generality of plant-herbivore interactions and their evolution.

  9. Spontaneous and specific activation of chemical bonds in macromolecular fluids.

    PubMed

    Park, Insun; Shirvanyants, David; Nese, Alper; Matyjaszewski, Krzysztof; Rubinstein, Michael; Sheiko, Sergei S

    2010-09-08

    Mechanical activation of chemical bonds typically involves the application of external forces, which implies a broad distribution of bond tensions. We demonstrate that controlling the flow profile of a macromolecular fluid generates and delineates mechanical force concentration, enabling a hierarchical activation of chemical bonds on different length scales from the macroscopic to the molecular. Bond tension is spontaneously generated within brushlike macromolecules as they spread on a solid substrate. The molecular architecture creates an uneven distribution of tension in the covalent bonds, leading to spatially controlled bond scission. By controlling the flow rate and the gradient of the film pressure, one can sever the flowing macromolecules with high precision. Specific chemical bonds are activated within distinct macromolecules located in a defined area of a thin film. Furthermore, the flow-controlled loading rate enables quantitative analysis of the bond activation parameters.

  10. Formation and Yield of Multi-Walled Carbon Nanotubes Synthesized via Chemical Vapour Deposition Routes Using Different Metal-Based Catalysts of FeCoNiAl, CoNiAl and FeNiAl-LDH

    PubMed Central

    Hussein, Mohd Zobir; Mohamad Jaafar, Adila; Hj. Yahaya, Asmah; Masarudin, Mas Jaffri; Zainal, Zulkarnain

    2014-01-01

    Multi-walled carbon nanotubes (MWCNTs) were prepared via chemical vapor deposition (CVD) using a series of different catalysts, derived from FeCoNiAl, CoNiAl and FeNiAl layered double hydroxides (LDHs). Catalyst-active particles were obtained by calcination of LDHs at 800 °C for 5 h. Nitrogen and hexane were used as the carrier gas and carbon source respectively, for preparation of MWCNTs using CVD methods at 800 °C. MWCNTs were allowed to grow for 30 min on the catalyst spread on an alumina boat in a quartz tube. The materials were subsequently characterized through X-ray diffraction, Fourier transform infrared spectroscopy, surface area analysis, field emission scanning electron microscopy and transmission electron microscopy. It was determined that size and yield of MWCNTs varied depending on the type of LDH catalyst precursor that is used during synthesis. MWCNTs obtained using CoNiAl-LDH as the catalyst precursor showed smaller diameter and higher yield compared to FeCoNiAl and FeNiAl LDHs. PMID:25380526

  11. An Investigation of Tertiary Students' Understanding of Evaporation, Condensation and Vapour Pressure

    ERIC Educational Resources Information Center

    Gopal, Hemant; Kleinsmidt, Jacques; Case, Jennifer; Musonge, Paul

    2004-01-01

    Based on a purposive sample of 15 second-year chemical engineering students, this study investigates students' conceptions of evaporation, condensation and vapour pressure. During individual interviews the students were questioned on three tasks that had been designed around these topics. Qualitative analysis of student responses showed a range of…

  12. An Investigation of Tertiary Students' Understanding of Evaporation, Condensation and Vapour Pressure. Research Report

    ERIC Educational Resources Information Center

    Gopal, Hemant; Kleinsmidt, Jacques; Case, Jennifer; Musonge, Paul

    2004-01-01

    Based on a purposive sample of 15 second-year chemical engineering students, this study investigates students' conceptions of evaporation, condensation and vapour pressure. During individual interviews the students were questioned on three tasks that had been designed around these topics. Qualitative analysis of student responses showed a range of…

  13. Endocrine-active chemicals in mammary cancer causation and prevention.

    PubMed

    Jenkins, Sarah; Betancourt, Angela M; Wang, Jun; Lamartiniere, Coral A

    2012-04-01

    Endocrine-active chemicals alter or mimic physiological hormones. These compounds are reported to originate from a wide variety of sources, and recent studies have shown widespread human exposure to several of these compounds. Given the role of the sex steroid hormone, estradiol, in human breast cancer causation, endocrine-active chemicals which interfere with estrogen signaling constitute one potential factor contributing to the high incidence of breast cancer. Thus, the aim of this review is to examine several common endocrine-active chemicals and their respective roles in breast cancer causation or prevention. The plastic component, bisphenol A (BPA), the synthetic estrogen, diethylstilbestrol (DES), the by-product of organic combustion, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the soy component, genistein, and the red grape phytoalexin, resveratrol, have some degree of structural similarities to each other and estradiol. However, despite these structural similarities, the in vitro and in vivo properties of each of these chemicals vary greatly in terms of breast cancer causation and prevention. Early life exposure to BPA and DES increases rodent susceptibility to chemically induced mammary carcinogenesis, presumably through retardation of normal mammary gland maturation and/or disrupting the ratio of cell proliferation and apoptosis in the mammary gland. On the other hand, early exposures to genistein and resveratrol protect rodents against chemically induced and spontaneous mammary cancers. This is reported to occur through the ability of genistein and resveratrol to accelerate mammary gland maturation. Interestingly, TCDD, which is the most structurally dissimilar to the above chemicals and functions as an anti-estrogen, also increases chemically induced mammary carcinogenesis through retardation of mammary gland maturation. This article is part of a Special Issue entitled 'Endocrine disruptors'.

  14. Quantitative genetic activity graphical profiles for use in chemical evaluation

    SciTech Connect

    Waters, M.D.; Stack, H.F.; Garrett, N.E.; Jackson, M.A.

    1990-12-31

    A graphic approach, terms a Genetic Activity Profile (GAP), was developed to display a matrix of data on the genetic and related effects of selected chemical agents. The profiles provide a visual overview of the quantitative (doses) and qualitative (test results) data for each chemical. Either the lowest effective dose or highest ineffective dose is recorded for each agent and bioassay. Up to 200 different test systems are represented across the GAP. Bioassay systems are organized according to the phylogeny of the test organisms and the end points of genetic activity. The methodology for producing and evaluating genetic activity profile was developed in collaboration with the International Agency for Research on Cancer (IARC). Data on individual chemicals were compiles by IARC and by the US Environmental Protection Agency (EPA). Data are available on 343 compounds selected from volumes 1-53 of the IARC Monographs and on 115 compounds identified as Superfund Priority Substances. Software to display the GAPs on an IBM-compatible personal computer is available from the authors. Structurally similar compounds frequently display qualitatively and quantitatively similar profiles of genetic activity. Through examination of the patterns of GAPs of pairs and groups of chemicals, it is possible to make more informed decisions regarding the selection of test batteries to be used in evaluation of chemical analogs. GAPs provided useful data for development of weight-of-evidence hazard ranking schemes. Also, some knowledge of the potential genetic activity of complex environmental mixtures may be gained from an assessment of the genetic activity profiles of component chemicals. The fundamental techniques and computer programs devised for the GAP database may be used to develop similar databases in other disciplines. 36 refs., 2 figs.

  15. Modelling vapour transport in Surtseyan bombs

    NASA Astrophysics Data System (ADS)

    McGuinness, Mark J.; Greenbank, Emma; Schipper, C. Ian

    2016-05-01

    We address questions that arise if a slurry containing liquid water is enclosed in a ball of hot viscous vesicular magma ejected as a bomb in the context of a Surtseyan eruption. We derive a mathematical model for transient changes in temperature and pressure due to flashing of liquid water to vapour inside the bomb. The magnitude of the transient pressure changes that are typically generated are calculated together with their dependence on material properties. A single criterion to determine whether the bomb will fragment as a result of the pressure changes is derived. Timescales for ejection of water vapour from a bomb that remains intact are also revealed.

  16. Force-activated reactivity switch in a bimolecular chemical reaction.

    PubMed

    Garcia-Manyes, Sergi; Liang, Jian; Szoszkiewicz, Robert; Kuo, Tzu-Ling; Fernández, Julio M

    2009-06-01

    The effect of mechanical force on the free-energy surface that governs a chemical reaction is largely unknown. The combination of protein engineering with single-molecule force-clamp spectroscopy allows us to study the influence of mechanical force on the rate at which a protein disulfide bond is reduced by nucleophiles in a bimolecular substitution reaction (S(N)2). We found that cleavage of a protein disulfide bond by hydroxide anions exhibits an abrupt reactivity 'switch' at ∼500 pN, after which the accelerating effect of force on the rate of an S(N)2 chemical reaction greatly diminishes. We propose that an abrupt force-induced conformational change of the protein disulfide bond shifts its ground state, drastically changing its reactivity in S(N)2 chemical reactions. Our experiments directly demonstrate the action of a force-activated switch in the chemical reactivity of a single molecule.

  17. Simulation of Discharge Production in a Water Vapour Layer on an Electrode

    NASA Astrophysics Data System (ADS)

    Karim, Mohammad; Evans, Benjamin; Asimakoulas, Leonidas; Stalder, Kenneth; Field, Thomas; Graham, Bill; Murakami, Tomoyuki

    2016-09-01

    Electrical discharges in water are receiving increasing attention because of chemical, environmental and biomedical applications.The work to be presented focuses on plasmas created directly in high conductivity water, saline solution. Here the plasma is produced at low voltage ( 200V) and is clearly associated with an initial vapour layer on the electrode surface that isolates the electrode from the liquid. In a previous paper a finite element multi-physics program, incorporating all relevant electrical and thermal properties of the solution was shown to reproduce the experimentally observed pre-plasma vapour layer behaviour. The results of a simulation of the plasma production in vapour layers of the same size and shape as predicted in will be presented, At present inert gas fills the ``vapour layer''. However this produces spatial distributions of the electron parameters that are consistent with the electric fields predicted in the original simulations. The water plasma simulation recently developed by Murakami is currently being included. It is anticipated that results of the coupled codes, showing the temporal and 2-D spatial development of the vapour and plasma, will be presented.

  18. Active colloids in the context of chemical kinetics

    NASA Astrophysics Data System (ADS)

    Oshanin, G.; Popescu, M. N.; Dietrich, S.

    2017-03-01

    We study a mesoscopic model of a chemically active colloidal particle which on certain parts of its surface promotes chemical reactions in the surrounding solution. For reasons of simplicity and conceptual clarity, we focus on the case in which only electrically neutral species are present in the solution and on chemical reactions which are described by first order kinetics. Within a self-consistent approach we explicitly determine the steady state product and reactant number density fields around the colloid as functionals of the interaction potentials of the various molecular species in solution with the colloid. By using a reciprocal theorem, this allows us to compute and to interpret—in a transparent way in terms of the classical Smoluchowski theory of chemical kinetics—the external force needed to keep such a catalytically active colloid at rest (stall force) or, equivalently, the corresponding velocity of the colloid if it is free to move. We use the particular case of triangular-well interaction potentials as a benchmark example for applying the general theoretical framework developed here. For this latter case, we derive explicit expressions for the dependences of the quantities of interest on the diffusion coefficients of the chemical species, the reaction rate constant, the coverage by catalyst, the size of the colloid, as well as on the parameters of the interaction potentials. These expressions provide a detailed picture of the phenomenology associated with catalytically-active colloids and self-diffusiophoresis.

  19. Capillary microextraction: A new method for sampling methamphetamine vapour.

    PubMed

    Nair, M V; Miskelly, G M

    2016-11-01

    Clandestine laboratories pose a serious health risk to first responders, investigators, decontamination companies, and the public who may be inadvertently exposed to methamphetamine and other chemicals used in its manufacture. Therefore there is an urgent need for reliable methods to detect and measure methamphetamine at such sites. The most common method for determining methamphetamine contamination at former clandestine laboratory sites is selected surface wipe sampling, followed by analysis with gas chromatography-mass spectrometry (GC-MS). We are investigating the use of sampling for methamphetamine vapour to complement such wipe sampling. In this study, we report the use of capillary microextraction (CME) devices for sampling airborne methamphetamine, and compare their sampling efficiency with a previously reported dynamic SPME method. The CME devices consisted of PDMS-coated glass filter strips inside a glass tube. The devices were used to dynamically sample methamphetamine vapour in the range of 0.42-4.2μgm(-3), generated by a custom-built vapour dosing system, for 1-15min, and methamphetamine was analysed using a GC-MS fitted with a ChromatoProbe thermal desorption unit. The devices showed good reproducibility (RSD<15%), and a curvilinear pre-equilibrium relationship between sampling times and peak area, which can be utilised for calibration. Under identical sampling conditions, the CME devices were approximately 30 times more sensitive than the dynamic SPME method. The CME devices could be stored for up to 3days after sampling prior to analysis. Consecutive sampling of methamphetamine and its isotopic substitute, d-9 methamphetamine showed no competitive displacement. This suggests that CME devices, pre-loaded with an internal standard, could be a feasible method for sampling airborne methamphetamine at former clandestine laboratories.

  20. Grazing-activated chemical defence in a unicellular marine alga

    NASA Astrophysics Data System (ADS)

    Wolfe, Gordon V.; Steinke, Michael; Kirst, Gunter O.

    1997-06-01

    Marine plankton use a variety of defences against predators, some of which affect trophic structure and biogeochemistry. We have previously shown that, during grazing by the protozoan Oxyrrhis marina on the alga Emiliania huxleyi, dimethylsulphoniopropionate (DMSP) from the prey is converted to dimethyl sulphide (DMS) when lysis of ingested prey cells initiates mixing of algal DMSP and the enzyme DMSP lyase. Such a mechanism is similar to macrophyte defence reactions,. Here we show that this reaction deters protozoan herbivores, presumably through the production of highly concentrated acrylate, which has antimicrobial activity. Protozoan predators differ in their ability to ingest and survive on prey with high-activity DMSP lyase, but all grazers preferentially select strains with low enzyme activity when offered prey mixtures. This defence system involves investment in a chemical precursor, DMSP, which is not self-toxic and has other useful metabolic functions. We believe this is the first report of grazing-activated chemical defence in unicellular microorganisms.

  1. Chemical Components and Cardiovascular Activities of Valeriana spp.

    PubMed Central

    Chen, Heng-Wen; Wei, Ben-Jun; He, Xuan-Hui; Liu, Yan; Wang, Jie

    2015-01-01

    Valeriana spp. is a flowering plant that is well known for its essential oils, iridoid compounds such as monoterpenes and sesquiterpenes, flavonoids, alkaloids, amino acids, and lignanoids. Valeriana spp. exhibits a wide range of biological activities such as lowering blood pressure and heart rate, antimyocardial ischemia reperfusion injury, antiarrhythmia, and regulation of blood lipid levels. This review focuses on the chemical constituents and cardiovascular activities of Valeriana spp. PMID:26788113

  2. Saturated Vapour Pressure and Refrigeration - Part I

    ERIC Educational Resources Information Center

    Bunker, C. A.

    1973-01-01

    The first part of a two-part article describes an experimental approach that can be used in teaching the concept of saturated vapour pressure. This leads to a discussion of refrigeration cycles in the second part of the article. (JR)

  3. Sensitive detection of chemical agents and toxic industrial chemicals using active open-path FTIRs

    NASA Astrophysics Data System (ADS)

    Walter, William T.

    2004-03-01

    Active open-path FTIR sensors provide more sensitive detection of chemical agents than passive FTIRs, such as the M21 RSCAAL and JSLSCAD, and at the same time identify and quantify toxic industrial chemicals (TIC). Passive FTIRs are bistatic sensors relying on infrared sources of opportunity. Utilization of earth-based sources of opportunity limits the source temperatures available for passive chemical-agent FTIR sensors to 300° K. Active FTIR chemical-agent sensors utilize silicon carbide sources, which can be operated at 1500° K. The higher source temperature provides more than an 80-times increase in the infrared radiant flux emitted per unit area in the 7 to 14 micron spectral fingerprint region. Minimum detection limits are better than 5 μgm/m3 for GA, GB, GD, GF and VX. Active FTIR sensors can (1) assist first responders and emergency response teams in their assessment of and reaction to a terrorist threat, (2) provide information on the identification of the TIC present and their concentrations and (3) contribute to the understanding and prevention of debilitating disorders analogous to the Gulf War Syndrome for military and civilian personnel.

  4. Structure activity relationships to assess new chemicals under TSCA

    SciTech Connect

    Auletta, A.E.

    1990-12-31

    Under Section 5 of the Toxic Substances Control Act (TSCA), manufacturers must notify the US Environmental Protection Agency (EPA) 90 days before manufacturing, processing, or importing a new chemical substance. This is referred to as a premanufacture notice (PMN). The PMN must contain certain information including chemical identity, production volume, proposed uses, estimates of exposure and release, and any health or environmental test data that are available to the submitter. Because there is no explicit statutory authority that requires testing of new chemicals prior to their entry into the market, most PMNs are submitted with little or no data. As a result, EPA has developed special techniques for hazard assessment of PMN chemicals. These include (1) evaluation of available data on the chemical itself, (2) evaluation of data on analogues of the PMN, or evaluation of data on metabolites or analogues of metabolites of the PMN, (3) use of quantitative structure activity relationships (QSARs), and (4) knowledge and judgement of scientific assessors in the interpretation and integration of the information developed in the course of the assessment. This approach to evaluating potential hazards of new chemicals is used to identify those that are most in need of addition review of further testing. It should not be viewed as a replacement for testing. 4 tabs.

  5. Water Vapour Abundance and Distribution in the Lower Venusian Atmosphere

    NASA Astrophysics Data System (ADS)

    Chamberlain, S.; Bailey, J.

    2012-04-01

    We present ground-based observations and modelling studies of water vapour abundance and distribution in the Venusian lower atmosphere through analysis of absorption band depths within the 1.18 μm window. The lower atmosphere of Venus is difficult to study by both in situ and remote instruments. This is due to the planet wide cloud cover that obscures visual wavelengths and surface pressures approaching 100 times that of the Earth. In 1984 ground based observations resulted in the discovery of atmospheric windows on the Venusian nightside (Allen and Crawford, 1984). Here, near infrared radiation originating at the surface and lower atmosphere, pass relatively unimpeded through the Venus clouds. This discovery enabled remote studies of the Venusian subcloud region. Determining the abundance and distribution of water vapour is key to understanding the development, maintenance and links between major radiative and dynamical features of the Venus atmosphere. Water vapour in the lower atmosphere plays an important role in heat transfer and is pertinent to the runaway greenhouse effect and dynamical superrotation observed on Venus. Detailed studies of water vapour abundance and distribution throughout the lower atmosphere of Venus are therefore needed in order to develop accurate chemical, radiative and dynamical models. Ground-based spatially resolved near infrared spectroscopic observations of the Venusian nightside have been obtained from Siding Spring Observatory at each inferior conjunction since 2002. Observations have been made using the IRIS2 instrument on the Anglo-Australian Telescope and CASPIR on the 2.3m ANU telescope. The model VSTAR (Bailey and Kedziora-Chudczer 2012) is used to simulate the observed Venus spectra as seen through the Earth's atmosphere and best fit water vapour abundances are found for approximately 300 locations across the Venus nightside disk. Recent improvements in ground-based near-infrared instruments allow a substantial improvement

  6. Simulation of the isotopic composition of stratospheric water vapour - Part 2: Investigation of HDO / H2O variations

    NASA Astrophysics Data System (ADS)

    Eichinger, R.; Jöckel, P.; Lossow, S.

    2015-06-01

    Studying the isotopic composition of water vapour in the lower stratosphere can reveal the driving mechanisms of changes in the stratospheric water vapour budget and therefore help to explain the trends and variations of stratospheric water vapour during recent decades. We equipped a global chemistry climate model with a description of the water isotopologue HDO, comprising its physical and chemical fractionation effects throughout the hydrological cycle. We use this model to improve our understanding of the processes which determine the patterns in the stratospheric water isotope composition and in the water vapour budget itself. The link between the water vapour budget and its isotopic composition in the tropical stratosphere is presented through their correlation in a simulated 21-year time series. The two quantities depend on the same processes; however, they are influenced with different strengths. A sensitivity experiment shows that fractionation effects during the oxidation of methane have a damping effect on the stratospheric tape recorder signal in the water isotope ratio. Moreover, the chemically produced high water isotope ratios overshadow the tape recorder in the upper stratosphere. Investigating the origin of the boreal-summer signal of isotopically enriched water vapour reveals that in-mixing of old stratospheric air from the extratropics and the intrusion of tropospheric water vapour into the stratosphere complement each other in order to create the stratospheric isotope ratio tape recorder signal. For this, the effect of ice lofting in monsoon systems is shown to play a crucial role. Furthermore, we describe a possible pathway of isotopically enriched water vapour through the tropopause into the tropical stratosphere.

  7. Simulation of the isotopic composition of stratospheric water vapour - Part 2: Investigation of HDO/H2O variations

    NASA Astrophysics Data System (ADS)

    Eichinger, R.; Jöckel, P.; Lossow, S.

    2014-11-01

    Studying the isotopic composition of water vapour in the lower stratosphere can reveal the driving mechanisms of changes in the stratospheric water vapour budget and therefore help to explain the trends and variations of stratospheric water vapour during the recent decades. We equipped a global chemistry climate model with a description of the water isotopologue HDO, comprising its physical and chemical fractionation effects throughout the hydrological cycle. We use this model to improve our understanding of the processes, which determine the patterns in the stratospheric water isotope composition and in the water vapour budget, itself. The link between the water vapour budget and its isotopic composition in the tropical stratosphere is presented through their correlation in a simulated 21 year time series. The two quantities depend on the same processes, however, are influenced with different strengths. A sensitivity experiment shows that fractionation effects during the oxidation of methane has a damping effect on the stratospheric tape recorder signal in the water isotope ratio. Moreover, the chemically produced high water isotope ratios overshadow the tape recorder in the upper stratosphere. Investigating the origin of the boreal summer tape recorder signal in the lower stratosphere reveals isotopically enriched water vapour crossing the tropopause over the subtropical Western Pacific. A correlation analysis confirms this link, which identifies the Asian Summer Monsoon as the major contributor for the intrusion of isotopically enriched water vapour into the stratosphere during boreal summer. Furthermore, convective ice lofting is shown to have a substantial impact on the isotope ratios of water vapour in the upper troposphere and lower stratosphere.

  8. Propolis volatile compounds: chemical diversity and biological activity: a review

    PubMed Central

    2014-01-01

    Propolis is a sticky material collected by bees from plants, and used in the hive as building material and defensive substance. It has been popular as a remedy in Europe since ancient times. Nowadays, propolis use in over-the-counter preparations, “bio”-cosmetics and functional foods, etc., increases. Volatile compounds are found in low concentrations in propolis, but their aroma and significant biological activity make them important for propolis characterisation. Propolis is a plant-derived product: its chemical composition depends on the local flora at the site of collection, thus it offers a significant chemical diversity. The role of propolis volatiles in identification of its plant origin is discussed. The available data about chemical composition of propolis volatiles from different geographic regions are reviewed, demonstrating significant chemical variability. The contribution of volatiles and their constituents to the biological activities of propolis is considered. Future perspectives in research on propolis volatiles are outlined, especially in studying activities other than antimicrobial. PMID:24812573

  9. Chemical composition and antimicrobial activity of Polish herbhoneys.

    PubMed

    Isidorov, V A; Bagan, R; Bakier, S; Swiecicka, I

    2015-03-15

    The present study focuses on samples of Polish herbhoneys (HHs), their chemical composition and antimicrobial activity. A gas chromatography-mass spectrometry (GC-MS) method was used to analyse eight samples of herbal honeys and three samples of nectar honeys. Their antimicrobial activities were tested on selected Gram-positive (Bacillus cereus, Staphylococcus aureus, Staphylococcus schleiferi) and Gram-negative (Escherichia coli) bacteria, as well as on pathogenic fungi Candida albicans. Ether extracts of HHs showed significant differences in composition but the principal groups found in the extracts were phenolics and aliphatic hydroxy acids typical of royal jelly and unsaturated dicarboxylic acids. In spite of the differences in chemical composition, antimicrobial activity of the extracts of HHs against all the tested microorganisms except E. coli was observed.

  10. Chemical transformations that yield compounds with distinct activity profiles.

    PubMed

    Hu, Ye; Bajorath, Jürgen

    2011-07-14

    We have systematically searched for chemical changes that generate compounds with distinct biological activity profiles. For this purpose, activity profiles were generated for ∼42000 compounds active against human targets. Unique activity profiles involving multiple target proteins were determined, and all possible matched molecular pairs (MMPs) were identified for compounds representing these profiles. An MMP is defined as a pair of compounds that are distinguished from each other only at a single site such as an R group or ring system. For example, in an MMP, a hydroxyl group might be replaced by a halogen atom or a benzene ring by an amide group. From ∼37500 MMPs, more than 300 nonredundant chemical transformations were isolated that yielded compounds with distinct activity profiles. None of these transformations was found in pairs of compounds with overlapping activity profiles. These transformations were ranked according to the number of MMPs, the number of activity profiles, and the total number of targets that they covered. In many instances, prioritized transformations involved ring systems of varying complexity. All transformations that were found to switch activity profiles are provided to enable further analysis and aid in compound design efforts.

  11. Photocatalytic property of titanium dioxide thin films deposited by radio frequency magnetron sputtering in argon and water vapour plasma

    NASA Astrophysics Data System (ADS)

    Sirghi, L.; Hatanaka, Y.; Sakaguchi, K.

    2015-10-01

    The present work is investigating the photocatalytic activity of TiO2 thin films deposited by radiofrequency magnetron sputtering of a pure TiO2 target in Ar and Ar/H2O (pressure ratio 40/3) plasmas. Optical absorption, structure, surface morphology and chemical structure of the deposited films were comparatively studied. The films were amorphous and included a large amount of hydroxyl groups (about 5% of oxygen atoms were bounded to hydrogen) irrespective of the intentional content of water in the deposition chamber. Incorporation of hydroxyl groups in the film deposited in pure Ar plasma is explained as contamination of the working gas with water molecules desorbed by plasma from the deposition chamber walls. However, intentional input of water vapour into the discharge chamber decreased the deposition speed and roughness of the deposited films. The good photocatalytic activity of the deposited films could be attributed hydroxyl groups in their structures.

  12. Chemical peels in active acne and acne scars.

    PubMed

    Kontochristopoulos, Georgios; Platsidaki, Eftychia

    Chemical peeling is a widely used procedure in the management of acne and acne scars. It causes controlled destruction of a part of or the entire epidermis, with or without the dermis, leading to exfoliation and removal of superficial lesions, followed by regeneration of new epidermal and dermal tissues. The most frequently used peeling agents are salicylic acid, glycolic acid, pyruvic acid, lactic acid, mandelic acid, Jessner solution, trichloroacetic acid, and phenol. The appropriate peel is chosen based on the patient's skin type, acne activity, and type of acne scars. Combination peels minimize side effects. In acne scars, chemical peels may be combined with other procedures to achieve better clinical results. A series of chemical peels can lead to significant improvement over a short period, leading to patient satisfaction and maintenance of clinical results. © 2016 Elsevier Inc. All rights reserved.

  13. Contributions of Organic Vapours to Atmospheric Nanoparticle Growth

    NASA Astrophysics Data System (ADS)

    Wang, L.; Xu, W.; Khalizov, A. F.; Zhang, R.

    2010-12-01

    Atmospheric aerosol particles alter radiative balance of the earth-atmosphere system, impact the regional and global climate, and pose negative effects on human health. Aerosol nucleation events have been frequently observed under various tropospheric conditions and account for a major fraction of the total aerosol population. Although a number of studies suggest that organics are involved in both new particle formation and their subsequent growth, the fundamental chemical processes responsible for organic vapours’ contribution remain poorly understood. This work will focus on laboratory studies on the role of various organic vapours in sulphuric acid nanoparticles growth. Sulfuric acid nanoparticles of 4-20 nm diameter size are generated from homogeneous binary nucleation of H2SO4 and H2O vapors in a laminar flow reactor. The growth factor of H2SO4 nanoparticles exposed to organics including methyglyoxal, ethanol, 1-butanol, 1-heptanol, 1-decanol, and cis-pinonic acid is measured using a nano-tandem differential mobility analyzer (nano-TDMA). Also studied is the potential synergistic effect in the presence of two or more organic vapours to which sulphuric acid nanoparticles are exposed. The chemical compositions of H2SO4 particles exposed to the organics are analyzed by a thermal desorption-ion drift-chemical ionization mass spectrometer (TD-ID-CIMS), and the spectroscopic evolution of functional groups in H2SO4 particles of ~40 nm diameter size, deposited on ZnSe crystal and subsequently exposed to organics, is studied using attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FT-IR). The combined techniques are used to elucidate the key factors in controlling atmospheric nanoparticle growth.

  14. Dynamics of self-propelled nanomotors in chemically active media

    NASA Astrophysics Data System (ADS)

    Thakur, Snigdha; Kapral, Raymond

    2011-07-01

    Synthetic chemically powered nanomotors often rely on the environment for their fuel supply. The propulsion properties of such motors can be altered if the environment in which they move is chemically active. The dynamical properties of sphere dimer motors, composed of linked catalytic and noncatalytic monomers, are investigated in active media. Chemical reactions occur at the catalytic monomer and the reactant or product of this reaction is involved in cubic autocatalytic or linear reactions that take place in the bulk phase environment. For these reactions, as the bulk phase reaction rates increase, the motor propulsion velocity decreases. For the cubic autocatalytic reaction, this net effect arises from a competition between a reduction of the nonequilibrium concentration gradient that leads to smaller velocity and the generation of fuel in the environment that tends to increase the motor propulsion. The role played by detailed balance in determining the form of the concentration gradient in the motor vicinity in the active medium is studied. Simulations are carried out using reactive multiparticle collision dynamics and compared with theoretical models to obtain further insight into sphere dimer dynamics in active media.

  15. Guiding catalytically active particles with chemically patterned surfaces

    NASA Astrophysics Data System (ADS)

    Uspal, William; Popescu, Mihail; Dietrich, Siegfried; Tasinkevych, Mykola

    Catalytically active Janus particles in solution create gradients in the chemical composition of the solution along their surfaces, as well as along any nearby container walls. The former leads to self-phoresis, while the latter gives rise to chemi-osmosis, providing an additional contribution to self-motility. Chemi-osmosis strongly depends on the molecular interactions between the diffusing chemical species and the wall. We show analytically, using an approximate ``point-particle'' approach, that by chemically patterning a planar substrate (e.g., by adsorbing two different materials) one can direct the motion of Janus particles: the induced chemi-osmotic flows can cause particles to either ``dock'' at a chemical step between the two materials, or to follow a chemical stripe. These theoretical predictions are confirmed by full numerical calculations. Generically, docking occurs for particles which tend to move away from their catalytic caps, while stripe-following occurs in the opposite case. Our analysis reveals the physical mechanisms governing this behavior.

  16. EDITORIAL Metal vapour in atmospheric-pressure arcs Metal vapour in atmospheric-pressure arcs

    NASA Astrophysics Data System (ADS)

    Murphy, Anthony B.

    2010-11-01

    Metal vapour has a significant, and in some cases dominant, influence in many applications of atmospheric-pressure plasmas, including arc welding, circuit interruption and mineral processing. While the influence of metal vapour has long been recognized, it is only recently that diagnostic and computational tools have been sufficiently well-developed to allow this influence to be more thoroughly examined and understood. Some unexpected findings have resulted: for example, that the presence of metal vapour in gas-metal arc welding leads to local minima in the temperature and current density in the centre of the arc. It has become clear that the presence of metal vapour, as well as having intrinsic scientific interest, plays an important role in determining the values of critical parameters in industrial applications, such as the weld penetration in arc welding and the extinction time in circuit breakers. In gas-tungsten arc welding, metal vapour concentrations are formed by evaporation of the weld pool, and are relatively low, typically at most a few per cent. Moreover, the convective flow of the plasma near the weld pool tends to direct the metal vapour plume radially outwards. In gas-metal arc welding, in contrast, metal vapour concentrations can reach over 50%. In this case, the metal vapour is produced mainly by evaporation of the wire electrode, and the strong downwards convective flow below the electrode concentrates the metal vapour in the central region of the arc. The very different metal concentrations and distributions in the two welding processes mean that the metal vapour has markedly different influences on the arc. In gas-tungsten arc welding, the current density distribution is broadened near the weld pool by the influence of the metal vapour on the electrical conductivity of the plasma, and the arc voltage is decreased. In contrast, in gas-metal arc welding, the arc centre is cooled by increased radiative emission and the arc voltage is increased. In

  17. Mining Chemical Activity Status from High-Throughput Screening Assays.

    PubMed

    Soufan, Othman; Ba-alawi, Wail; Afeef, Moataz; Essack, Magbubah; Rodionov, Valentin; Kalnis, Panos; Bajic, Vladimir B

    2015-01-01

    High-throughput screening (HTS) experiments provide a valuable resource that reports biological activity of numerous chemical compounds relative to their molecular targets. Building computational models that accurately predict such activity status (active vs. inactive) in specific assays is a challenging task given the large volume of data and frequently small proportion of active compounds relative to the inactive ones. We developed a method, DRAMOTE, to predict activity status of chemical compounds in HTP activity assays. For a class of HTP assays, our method achieves considerably better results than the current state-of-the-art-solutions. We achieved this by modification of a minority oversampling technique. To demonstrate that DRAMOTE is performing better than the other methods, we performed a comprehensive comparison analysis with several other methods and evaluated them on data from 11 PubChem assays through 1,350 experiments that involved approximately 500,000 interactions between chemicals and their target proteins. As an example of potential use, we applied DRAMOTE to develop robust models for predicting FDA approved drugs that have high probability to interact with the thyroid stimulating hormone receptor (TSHR) in humans. Our findings are further partially and indirectly supported by 3D docking results and literature information. The results based on approximately 500,000 interactions suggest that DRAMOTE has performed the best and that it can be used for developing robust virtual screening models. The datasets and implementation of all solutions are available as a MATLAB toolbox online at www.cbrc.kaust.edu.sa/dramote and can be found on Figshare.

  18. Mining Chemical Activity Status from High-Throughput Screening Assays

    PubMed Central

    Soufan, Othman; Ba-alawi, Wail; Afeef, Moataz; Essack, Magbubah; Rodionov, Valentin; Kalnis, Panos; Bajic, Vladimir B.

    2015-01-01

    High-throughput screening (HTS) experiments provide a valuable resource that reports biological activity of numerous chemical compounds relative to their molecular targets. Building computational models that accurately predict such activity status (active vs. inactive) in specific assays is a challenging task given the large volume of data and frequently small proportion of active compounds relative to the inactive ones. We developed a method, DRAMOTE, to predict activity status of chemical compounds in HTP activity assays. For a class of HTP assays, our method achieves considerably better results than the current state-of-the-art-solutions. We achieved this by modification of a minority oversampling technique. To demonstrate that DRAMOTE is performing better than the other methods, we performed a comprehensive comparison analysis with several other methods and evaluated them on data from 11 PubChem assays through 1,350 experiments that involved approximately 500,000 interactions between chemicals and their target proteins. As an example of potential use, we applied DRAMOTE to develop robust models for predicting FDA approved drugs that have high probability to interact with the thyroid stimulating hormone receptor (TSHR) in humans. Our findings are further partially and indirectly supported by 3D docking results and literature information. The results based on approximately 500,000 interactions suggest that DRAMOTE has performed the best and that it can be used for developing robust virtual screening models. The datasets and implementation of all solutions are available as a MATLAB toolbox online at www.cbrc.kaust.edu.sa/dramote and can be found on Figshare. PMID:26658480

  19. Material design of plasma-enhanced chemical vapour deposition SiCH films for low-k cap layers in the further scaling of ultra-large-scale integrated devices-Cu interconnects.

    PubMed

    Shimizu, Hideharu; Nagano, Shuji; Uedono, Akira; Tajima, Nobuo; Momose, Takeshi; Shimogaki, Yukihiro

    2013-10-01

    Cap layers for Cu interconnects in ultra-large-scale integrated devices (ULSIs), with a low dielectric constant (k-value) and strong barrier properties against Cu and moisture diffusion, are required for the future further scaling of ULSIs. There is a trade-off, however, between reducing the k-value and maintaining strong barrier properties. Using quantum mechanical simulations and other theoretical computations, we have designed ideal dielectrics: SiCH films with Si-C2H4-Si networks. Such films were estimated to have low porosity and low k; thus they are the key to realizing a cap layer with a low k and strong barrier properties against diffusion. For fabricating these ideal SiCH films, we designed four novel precursors: isobutyl trimethylsilane, diisobutyl dimethylsilane, 1, 1-divinylsilacyclopentane and 5-silaspiro [4,4] noname, based on quantum chemical calculations, because such fabrication is difficult by controlling only the process conditions in plasma-enhanced chemical vapor deposition (PECVD) using conventional precursors. We demonstrated that SiCH films prepared using these newly designed precursors had large amounts of Si-C2H4-Si networks and strong barrier properties. The pore structure of these films was then analyzed by positron annihilation spectroscopy, revealing that these SiCH films actually had low porosity, as we designed. These results validate our material and precursor design concepts for developing a PECVD process capable of fabricating a low-k cap layer.

  20. Insect-gene-activity detection system for chemical and biological warfare agents and toxic industrial chemicals

    NASA Astrophysics Data System (ADS)

    Mackie, Ryan S.; Schilling, Amanda S.; Lopez, Arturo M.; Rayms-Keller, Alfredo

    2002-02-01

    Detection of multiple chemical and biological weapons (CBW) agents and/or complex mixtures of toxic industrial chemicals (TIC) is imperative for both the commercial and military sectors. In a military scenario, a multi-CBW attack would create confusion, thereby delaying decontamination and therapeutic efforts. In the commercial sector, polluted sites invariably contain a mixture of TIC. Novel detection systems capable of detecting CBW and TIC are sorely needed. While it may be impossible to build a detector capable of discriminating all the possible combinations of CBW, a detection system capable of statistically predicting the most likely composition of a given mixture is within the reach of current emerging technologies. Aquatic insect-gene activity may prove to be a sensitive, discriminating, and elegant paradigm for the detection of CBW and TIC. We propose to systematically establish the expression patterns of selected protein markers in insects exposed to specific mixtures of chemical and biological warfare agents to generate a library of biosignatures of exposure. The predicting capabilities of an operational library of biosignatures of exposures will allow the detection of emerging novel or genetically engineered agents, as well as complex mixtures of chemical and biological weapons agents. CBW and TIC are discussed in the context of war, terrorism, and pollution.

  1. Textile damage caused by vapour cloud explosions.

    PubMed

    Was-Gubala, J; Krauss, W

    2004-01-01

    The aim of the project was to investigate the damage to garments caused by particular vapour cloud explosions. The authors would like to be able to provide investigators with specific information on how to link clothes to a specific type of crime: a particular case study was the inspiration for the examinations. Experiments were carried out in the fire reconstruction chamber of the laboratory using a selection of 26 clothes and 15 household garments differing in colour, fibre composition and textile construction.

  2. Vapour-liquid equilibria measurements for carbon dioxide with normal and isobutane from 250 to 280 K

    NASA Astrophysics Data System (ADS)

    Weber, L. A.

    Vapour-liquid equilibria measurements were made on binary mixtures of carbon dioxide with normal and isobutane at 250, 260, 270 and 280 K. Both liquid and vapour compositions were measured. The data were correlated using the Peng-Robinson equation of state, and values are given for the activity coefficients and the excess Gibbs free energy, G E. The heat of mixing is estimated from the temperature dependence of G E.

  3. Tomographic retrieval of water vapour and temperature around polar mesospheric clouds using Odin-SMR

    NASA Astrophysics Data System (ADS)

    Christensen, O. M.; Eriksson, P.; Urban, J.; Murtagh, D.; Hultgren, K.; Gumbel, J.

    2015-05-01

    A special observation mode of the Odin satellite provides the first simultaneous measurements of water vapour, temperature and polar mesospheric cloud (PMC) brightness over a large geographical area while still resolving both horizontal and vertical structures in the clouds and background atmosphere. The observation mode was activated during June, July and August of 2010 and 2011, and for latitudes between 50 and 82° N. This paper focuses on the water vapour and temperature measurements carried out with Odin's sub-millimetre radiometer (SMR). The tomographic retrieval approach used provides water vapour and temperature between 75 and 90 km with a vertical resolution of about 2.5 km and a horizontal resolution of about 200 km. The precision of the measurements is estimated to 0.2 ppmv for water vapour and 2 K for temperature. Due to limited information about the pressure at the measured altitudes, the results have large uncertainties (> 3 ppmv) in the retrieved water vapour. These errors, however, influence mainly the mean atmosphere retrieved for each orbit, and variations around this mean are still reliably captured by the measurements. SMR measurements are performed using two different mixer chains, denoted as frequency mode 19 and 13. Systematic differences between the two frontends have been noted. A first comparison with the Solar Occultation For Ice Experiment instrument (SOFIE) on-board the Aeronomy of Ice in the Mesosphere (AIM) satellite and the Fourier Transform Spectrometer of the Atmospheric Chemistry Experiment (ACE-FTS) on-board SCISAT indicates that the measurements using the frequency mode 19 have a significant low bias in both temperature (> 15 K) and water vapour (> 0.5 ppmv), while the measurements using frequency mode 13 agree with the other instruments considering estimated errors. PMC brightness data is provided by OSIRIS, Odin's other sensor. Combined SMR and OSIRIS data for some example orbits is considered. For these orbits, effects of

  4. STRUCTURE-ACTIVITY RELATIONSHIP STUIDES AND THEIR ROLE IN PREDICTING AND INVESTIGATING CHEMICAL TOXICITY

    EPA Science Inventory

    Structure-Activity Relationship Studies and their Role in Predicting and Investigating Chemical Toxicity

    Structure-activity relationships (SAR) represent attempts to generalize chemical information relative to biological activity for the twin purposes of generating insigh...

  5. Chemical reactivity and antimicrobial activity of N-substituted maleimides.

    PubMed

    Salewska, Natalia; Boros-Majewska, Joanna; Lącka, Izabela; Chylińska, Katarzyna; Sabisz, Michał; Milewski, Sławomir; Milewska, Maria J

    2012-02-01

    Several N-substituted maleimides containing substituents of varying bulkiness and polarity were synthesised and tested for antimicrobial and cytostatic activity. Neutral maleimides displayed relatively strong antifungal effect minimum inhibitory concentrations (MICs in the 0.5-4 µg ml(-1) range); their antibacterial activity was structure dependent and all were highly cytostatic, with IC(50) values below 0.1 µg ml(-1). Low antimicrobial but high cytostatic activity was noted for basic maleimides containing tertiary aminoalkyl substituents. Chemical reactivity and lipophilicity influenced antibacterial activity of neutral maleimides but had little if any effect on their antifungal and cytostatic action. N-substituted maleimides affected biosynthesis of chitin and β(1,3)glucan, components of the fungal cell wall. The membrane enzyme, β(1,3)glucan synthase has been proposed as a putative primary target of N-ethylmaleimide and some of its analogues in Candida albicans cells.

  6. Active hydrothermal and non-active massive sulfide mound investigation using a new multiparameter chemical sensor

    NASA Astrophysics Data System (ADS)

    Han, C.; Wu, G.; Qin, H.; Wang, Z.

    2012-12-01

    Investigation of active hydrothermal mound as well as non-active massive sulfide mound are studied recently. However, there is still lack of in-situ detection method for the non-active massive sulfide mound. Even though Transient ElectroMagnetic (TEM) and Electric Self-potential (SP) methods are good, they both are labour, time and money cost work. We proposed a new multiparameter chemical sensor method to study the seafloor active hydrothermal mound as well as non-active massive sulfide mound. This sensor integrates Eh, S2- ions concentration and pH electrochemical electrodes together, and could found chemical change caused by the active hydrothermal vent, even weak chemical abnormalities by non-active massive sulfide hydrothermal mound which MARP and CTD sometimes cannot detect. In 2012, the 1st Leg of the Chinese 26th cruise, the multiparameter chemical sensor was carried out with the deepsea camera system over the Carlsberg Ridge in Indian Ocean by R/V DAYANGYIHAO. It was shown small Eh and S2- ions concentration abnormal around a site at Northwest Indian ridge. This site was also evidenced by the TV grab. In the 2nd Leg of the same cruise in June, this chemical sensor was carried out with TEM and SP survey system. The chemical abnormalities are matched very well with both TEM and SP survey results. The results show that the multiparameter chemical sensor method not only can detect active hydrothermal mound, but also can find the non-active massive sulfide hydrothermal mound.

  7. Metal Vapour Lasers: Physics, Engineering and Applications

    NASA Astrophysics Data System (ADS)

    Little, Christopher E.

    1999-03-01

    Metal Vapour Lasers Christopher E. Little University of St Andrews, St Andrews, Scotland Since the first successful demonstration of a metal vapour laser (MVL) in 1962, this class of laser has become widely used in a broad range of fields including precision materials processing, isotope separation and medicine. The MVLs that are used today have a range of impressive characteristics that are not readily available using other technologies. In particular, the combination of high average output powers, pulse recurrence frequencies and beam quality available from green/yellow Cu vapour lasers (CVLs) and Cu bromide lasers, coupled with the high-quality, multiwatt ultraviolet (265-289 nm) radiation that can be produced using simple nonlinear optical techniques, means that Cu lasers will continue to be important for many years. Metal Vapour Lasers covers all the most commercially important and scientifically interesting pulsed and continuous wave (CW) gas-discharge MVLs, and includes device histories, operating characteristics, engineering, kinetics, commercial exploitation and applications. Short descriptions of gas discharges and excitation techniques make this volume self-consistent. A comprehensive bibliography is also provided. The greater part of this book is devoted to CVLs and their variants, including new sealed-off, high-power 'kinetically enhanced' CVLs and Cu bromide lasers. However, many other self-terminating MVLs are also discussed, including the red AuVL, green/infrared MnVL and infrared BaVL. Pulsed, high-gain, high average power lasers in the UV/violet (373.7, 430.5 nm) spectral regions are represented by Sr¯+ and Ca¯+ discharge-afterglow recombination lasers. The most commercially successful of the MVLs - the CW, UV/blue cataphoretic He-Cd¯+ ion laser - is described. Hollow cathode lasers are represented in two guises: 'white light' (blue/green/red) He-Cd¯+ ion lasers and UV/infrared Ne/He-Cu¯+ ion lasers. This unique volume is an

  8. Variability of water vapour in the Arctic stratosphere

    NASA Astrophysics Data System (ADS)

    Thölix, L.; Backman, L.; Kivi, R.; Karpechko, A.

    2015-08-01

    This study evaluates the stratospheric water vapour distribution and variability in the Arctic. A FinROSE chemistry climate model simulation covering years 1990-2013 is compared to observations (satellite and frostpoint hygrometer soundings) and the sources of stratospheric water vapour are studied. According to observations and the simulations the water vapour concentration in the Arctic stratosphere started to increase after year 2006, but around 2011 the concentration started to decrease. Model calculations suggest that the increase in water vapour during 2006-2011 (at 56 hPa) is mostly explained by transport related processes, while the photochemically produced water vapour plays a relatively smaller role. The water vapour trend in the stratosphere may have contributed to increased ICE PSC occurrence. The increase of water vapour in the precense of the low winter temperatures in the Arctic stratosphere led to more frequent occurrence of ICE PSCs in the Arctic vortex. The polar vortex was unusually cold in early 2010 and allowed large scale formation of the polar stratospheric clouds. The cold pool in the stratosphere over the Northern polar latitudes was large and stable and a large scale persistent dehydration was observed. Polar stratospheric ice clouds and dehydration were observed at Sodankylä with accurate water vapour soundings in January and February 2010 during the LAPBIAT atmospheric sounding campaign. The observed changes in water vapour were reproduced by the model. Both the observed and simulated decrease of the water vapour in the dehydration layer was up to 1.5 ppm.

  9. [Qualitative Determination of Organic Vapour Using Violet and Visible Spectrum].

    PubMed

    Jiang, Bo; Hu, Wen-zhong; Liu, Chang-jian; Zheng, Wei; Qi, Xiao-hui; Jiang, Ai-li; Wang, Yan-ying

    2015-12-01

    Vapours of organic matters were determined qualitatively employed with ultraviolet-visible absorption spectroscopy. Vapours of organic matters were detected using ultraviolet-visible spectrophotometer employing polyethylene film as medium, the ultraviolet and visible absorption spectra of vegetable oil vapours of soybean oil, sunflower seed oil, peanut oil, rapeseed oil, sesame oil, cotton seed oil, tung tree seed oil, and organic compound vapours of acetone, ethyl acetate, 95% ethanol, glacial acetic acid were obtained. Experimental results showed that spectra of the vegetable oil vapour and the organic compound vapour could be obtained commendably, since ultra violet and visible spectrum of polyethylene film could be deducted by spectrograph zero setting. Different kinds of vegetable oils could been distinguished commendably in the spectra since the λ(max), λ(min), number of absorption peak, position, inflection point in the ultra violet and visible spectra obtained from the vapours of the vegetable oils were all inconsistent, and the vapours of organic compounds were also determined perfectly. The method had a good reproducibility, the ultraviolet and visible absorption spectra of the vapours of sunflower seed oil in 10 times determination were absolutely the same. The experimental result indicated that polyethylene film as a kind of medium could be used for qualitative analysis of ultraviolet and visible absorption spectroscopy. The method for determination of the vapours of the vegetable oils and organic compounds had the peculiarities of fast speed analysis, well reproducibility, accuracy and reliability and low cost, and so on. Ultraviolet and visible absorption spectrum of organic vapour could provide feature information of material vapour and structural information of organic compound, and provide a novel test method for identifying vapour of compound and organic matter.

  10. Pereskia aculeata Muller (Cactaceae) Leaves: Chemical Composition and Biological Activities.

    PubMed

    Souza, Lucèia Fàtima; Caputo, Lucia; Inchausti De Barros, Ingrid Bergman; Fratianni, Florinda; Nazzaro, Filomena; De Feo, Vincenzo

    2016-09-03

    The aims of this work were to study the chemical composition of the essential oil from the leaves of Pereskia aculeata and to evaluate some biological activities of three leaf extracts. The phenolic content, antioxidant activity, and in vitro antimicrobial and antifungal activities were determined. The methanol extract showed antioxidant activity (EC50 7.09 mg/mL) and high polyphenols content (15.04 ± 0.31 mg gallic acid equivalents (GAE)/g). The petroleum ether extract exhibited potent antibacterial activity against Escherichia coli, whereas the chloroform extract showed inhibitory activity against Bacillus cereus and Staphylococcus aureus. The petroleum ether and methanol extracts were more effective in inhibiting the growth of Aspergillus versicolor. The possible cytotoxicity of extracts on neuroblastoma SH-SY5Y cancer cell line and the influence on adenylate cyclase (ADCY) expression was also studied. P. aculeata chloroform extract showed antiproliferative activity with an IC50 value of 262.83 µg/mL. Treatments of SH-SY5Y neuroblastoma cells with 100 µg/mL of methanol extract significantly reduced ADCY1 expression.

  11. Pereskia aculeata Muller (Cactaceae) Leaves: Chemical Composition and Biological Activities

    PubMed Central

    Souza, Lucèia Fàtima; Caputo, Lucia; Inchausti De Barros, Ingrid Bergman; Fratianni, Florinda; Nazzaro, Filomena; De Feo, Vincenzo

    2016-01-01

    The aims of this work were to study the chemical composition of the essential oil from the leaves of Pereskia aculeata and to evaluate some biological activities of three leaf extracts. The phenolic content, antioxidant activity, and in vitro antimicrobial and antifungal activities were determined. The methanol extract showed antioxidant activity (EC50 7.09 mg/mL) and high polyphenols content (15.04 ± 0.31 mg gallic acid equivalents (GAE)/g). The petroleum ether extract exhibited potent antibacterial activity against Escherichia coli, whereas the chloroform extract showed inhibitory activity against Bacillus cereus and Staphylococcus aureus. The petroleum ether and methanol extracts were more effective in inhibiting the growth of Aspergillus versicolor. The possible cytotoxicity of extracts on neuroblastoma SH-SY5Y cancer cell line and the influence on adenylate cyclase (ADCY) expression was also studied. P. aculeata chloroform extract showed antiproliferative activity with an IC50 value of 262.83 µg/mL. Treatments of SH-SY5Y neuroblastoma cells with 100 µg/mL of methanol extract significantly reduced ADCY1 expression. PMID:27598154

  12. Understanding vapour plume structure in indoor environments for the detection of explosives

    NASA Astrophysics Data System (ADS)

    Foat, Tim

    2015-11-01

    Dogs remain the most effective method for the detection of explosives in many situations yet the spatially, temporally and chemically varying signature that they sense cannot easily be quantified. Vapour plumes can be highly unsteady and intermittent and the problem is further complicated in indoor spaces where turbulent, transitional and laminar regions may exist and where there may be no dominant flow direction. Intermittent plumes can have peak concentrations that are considerably higher than the time averaged values. As dogs can sample the air at 5 Hz it is possible that these unsteady fluctuations play a key part in their detection process. A low Reynolds number (Re less than 5000 at the inlet) benchmark test case for indoor airflow has been studied using large-eddy simulation computational fluid dynamics. Fixed concentration vapour sources have been included on the floor of the room and the resulting vapour dispersion has been modelled. Sources with different surface areas have been included and their instantaneous and mean concentration profiles compared. The results from this study will provide insight into canine detection of vapour in indoor environments.

  13. Chemical Signaling and Functional Activation in Colloidosome-Based Protocells.

    PubMed

    Sun, Shiyong; Li, Mei; Dong, Faqin; Wang, Shengjie; Tian, Liangfei; Mann, Stephen

    2016-04-13

    An aqueous-based microcompartmentalized model involving the integration of partially hydrophobic Fe(III)-rich montmorillonite (FeM) clay particles as structural and catalytic building blocks for colloidosome membrane assembly, self-directed membrane remodeling, and signal-induced protocell communication is described. The clay colloidosomes exhibit size- and charge-selective permeability, and show dual catalytic functions involving spatially confined enzyme-mediated dephosphorylation and peroxidase-like membrane activity. The latter is used for the colloidosome-mediated synthesis and assembly of a temperature-responsive poly(N-isopropylacrylamide)(PNIPAM)/clay-integrated hybrid membrane. In situ PNIPAM elaboration of the membrane is coupled to a glucose oxidase (GOx)-mediated signaling pathway to establish a primitive model of chemical communication and functional activation within a synthetic "protocell community" comprising a mixed population of GOx-containing silica colloidosomes and alkaline phosphatase (ALP)-containing FeM-clay colloidosomes. Triggering the enzyme reaction in the silica colloidosomes gives a hydrogen peroxide signal that induces polymer wall formation in a coexistent population of the FeM-clay colloidosomes, which in turn generates self-regulated membrane-gated ALP-activity within the clay microcompartments. The emergence of new functionalities in inorganic colloidosomes via chemical communication between different protocell populations provides a first step toward the realization of interacting communities of synthetic functional microcompartments.

  14. Atypical Hydrogen Uptake on Chemically Activated, Ultramicroporous Carbon

    SciTech Connect

    Bhat, Vinay V; Contescu, Cristian I; Gallego, Nidia C; Baker, Frederick S

    2010-01-01

    Hydrogen adsorption at near-ambient temperatures on ultramicroporous carbon (UMC), derived through secondary chemical activation from a wood-based activated carbon was studied using volumetric and gravimetric methods. The results showed that physisorption is accompanied by a process of different nature that causes slow uptake at high pressures and hysteresis on desorption. In combination, this results in unusually high levels of hydrogen uptake at near-ambient temperatures and pressures (e.g. up to 0.8 wt % at 25 oC and 2 MPa). The heat of adsorption corresponding to the slow process leading to high uptake (17 20 kJ/mol) is higher than usually reported for carbon materials, but the adsorption kinetics is slow, and the isotherms exhibit pronounced hysteresis. These unusual properties were attributed to contributions from polarization-enhanced physisorption caused by traces of alkali metals residual from chemical activation. The results support the hypothesis that polarization-induced physisorption in high surface area carbons modified with traces of alkali metal ions is an alternate route for increasing the hydrogen storage capacity of carbon adsorbents.

  15. Regular Wave Propagation Out of Noise in Chemical Active Media

    SciTech Connect

    Alonso, S.; Sendina-Nadal, I.; Perez-Munuzuri, V.; Sancho, J. M.; Sagues, F.

    2001-08-13

    A pacemaker, regularly emitting chemical waves, is created out of noise when an excitable photosensitive Belousov-Zhabotinsky medium, strictly unable to autonomously initiate autowaves, is forced with a spatiotemporal patterned random illumination. These experimental observations are also reproduced numerically by using a set of reaction-diffusion equations for an activator-inhibitor model, and further analytically interpreted in terms of genuine coupling effects arising from parametric fluctuations. Within the same framework we also address situations of noise-sustained propagation in subexcitable media.

  16. Regular wave propagation out of noise in chemical active media.

    PubMed

    Alonso, S; Sendiña-Nadal, I; Pérez-Muñuzuri, V; Sancho, J M; Sagués, F

    2001-08-13

    A pacemaker, regularly emitting chemical waves, is created out of noise when an excitable photosensitive Belousov-Zhabotinsky medium, strictly unable to autonomously initiate autowaves, is forced with a spatiotemporal patterned random illumination. These experimental observations are also reproduced numerically by using a set of reaction-diffusion equations for an activator-inhibitor model, and further analytically interpreted in terms of genuine coupling effects arising from parametric fluctuations. Within the same framework we also address situations of noise-sustained propagation in subexcitable media.

  17. Genotoxic activity of organic chemicals in drinking water.

    PubMed

    Meier, J R

    1988-11-01

    The information summarized in this review provides substantial evidence for the widespread presence of genotoxins in drinking water. In many, if not most cases, the genotoxic activity can be directly attributed to the chlorination stage of drinking water treatment. The genotoxic activity appears to originate primarily from reactions of chlorine with humic substances in the source waters. Genotoxic activity in drinking water concentrates has been most frequently demonstrated using bacterial mutagenicity tests but results with mammalian cell assay systems are generally consistent with the findings from the bacterial assays. There is currently no evidence for genotoxic damage following in vivo exposures to animals. In some locations genotoxic contaminants of probable industrial and/or agricultural origin occur in the source waters and contribute substantially to the genotoxic activity of finished drinking waters. The method used for sample concentration can have an important bearing on study results. In particular, organic acids account for most of the mutagenicity of chlorinated drinking water, and their recovery from water requires a sample acidification step prior to extraction or XAD resin adsorption. Considerable work has been done to determine the identity of the compounds responsible for the mutagenicity of organic concentrates of drinking water. Recently, one class of acidic compounds, the chlorinated hydroxyfuranones, has been shown to be responsible for a major part of the mutagenic activity. Strategies for drinking water treatment that have been evaluated with respect to reduction of genotoxins in drinking water include granular activated carbon (GAC) filtration, chemical destruction, and the use of alternative means of treatment (i.e., ozone, chlorine dioxide, and monochloramine). GAC treatment has been found to be effective for removal of mutagens from drinking water even after the GAC is beyond its normal use for organic carbon removal. All disinfectant

  18. Halloysite clay nanotubes for controlled delivery of chemically active agents

    NASA Astrophysics Data System (ADS)

    Abdullayev, Elshard

    In this work we explored the capabilities of halloysite nanotubes as capsules for encapsulation and controlled delivery of the chemically and biologically active substances. Halloysite is a two-layered aluminosilicate which has a predominantly hollow tubular structure in the submicron range and is chemically similar to kaolinite [1, 2]. In the first section of this work, we analyzed the structure of the halloysite nanotubes as well as its capability to encapsulate and deliver biologically and chemically active agents, similarities and differences between release characteristics of different agents and how these differences relate with their chemical structure. Models were used to describe the release characteristics of the active agents. Study of the interaction between loaded agents and halloysite nanotubes provides better understanding of the release characteristics of the loaded agents and how halloysite can be implemented for technological and medical applications. The second part of the work deals with self-healing coatings produced on the basis of halloysite nanotubes loaded with corrosion inhibitors. Self-healing coatings are one of the effective methods to protect metals from corrosion and deterioration. The difference between self-healing coatings and the usual coatings is the ability of the first to recover after the formation of the damages due to external or internal stresses. High efficiency of the self- healing coatings produced by halloysite nanotubes were demonstrated on 110 Copper alloys and 2024 aluminum alloys. Controlled delivery of the corrosion inhibitors with additional encapsulation of the halloysite nanotubes by synthesizing stoppers at tube endings was also demonstrated. Additional encapsulation of the halloysite nanotubes may be necessary when slow release of the loaded agents is required or rapid convection of the liquid in the surrounding environment takes place (since this may cause rapid release of the loaded agents without additional

  19. Variability of water vapour in the Arctic stratosphere

    NASA Astrophysics Data System (ADS)

    Thölix, Laura; Backman, Leif; Kivi, Rigel; Karpechko, Alexey Yu.

    2016-04-01

    This study evaluates the stratospheric water vapour distribution and variability in the Arctic. A FinROSE chemistry transport model simulation covering the years 1990-2014 is compared to observations (satellite and frost point hygrometer soundings), and the sources of stratospheric water vapour are studied. In the simulations, the Arctic water vapour shows decadal variability with a magnitude of 0.8 ppm. Both observations and the simulations show an increase in the water vapour concentration in the Arctic stratosphere after the year 2006, but around 2012 the concentration started to decrease. Model calculations suggest that this increase in water vapour is mostly explained by transport-related processes, while the photochemically produced water vapour plays a relatively smaller role. The increase in water vapour in the presence of the low winter temperatures in the Arctic stratosphere led to more frequent occurrence of ice polar stratospheric clouds (PSCs) in the Arctic vortex. We perform a case study of ice PSC formation focusing on January 2010 when the polar vortex was unusually cold and allowed large-scale formation of PSCs. At the same time a large-scale persistent dehydration was observed. Ice PSCs and dehydration observed at Sodankylä with accurate water vapour soundings in January and February 2010 during the LAPBIAT (Lapland Atmosphere-Biosphere facility) atmospheric measurement campaign were well reproduced by the model. In particular, both the observed and simulated decrease in water vapour in the dehydration layer was up to 1.5 ppm.

  20. Active membrane having uniform physico-chemically functionalized ion channels

    DOEpatents

    Gerald, II, Rex E; Ruscic, Katarina J; Sears, Devin N; Smith, Luis J; Klingler, Robert J; Rathke, Jerome W

    2012-09-24

    The present invention relates to a physicochemically-active porous membrane for electrochemical cells that purports dual functions: an electronic insulator (separator) and a unidirectional ion-transporter (electrolyte). The electrochemical cell membrane is activated for the transport of ions by contiguous ion coordination sites on the interior two-dimensional surfaces of the trans-membrane unidirectional pores. One dimension of the pore surface has a macroscopic length (1 nm-1000 .mu.m) and is directed parallel to the direction of an electric field, which is produced between the cathode and the anode electrodes of an electrochemical cell. The membrane material is designed to have physicochemical interaction with ions. Control of the extent of the interactions between the ions and the interior pore walls of the membrane and other materials, chemicals, or structures contained within the pores provides adjustability of the ionic conductivity of the membrane.

  1. Chemical composition and biological activity of Salvia verbenaca essential oil.

    PubMed

    Canzoneri, Marisa; Bruno, Maurizio; Rosselli, Sergio; Russo, Alessandra; Cardile, Venera; Formisano, Carmen; Rigano, Daniela; Senatore, Felice

    2011-07-01

    Salvia verbenaca L. (syn. S. minore) is a perennial herb known in the traditional medicine of Sicily as "spaccapetri" and is used to resolve cases of kidney stones, chewing the fresh leaves or in decoction. The chemical composition of the essential oil obtained from aerial parts of S. verbenaca collected in Piano Battaglia (Sicily) on July 2009, was analyzed by GC and GC-MS. The oil was strongly characterized by fatty acids (39.5%) and carbonylic compounds (21.2%), with hexadecanoic acid (23.1%), (Z)-9-octadecenoic acid (11.1%) and benzaldehyde (7.3%) as the main constituents. The in vitro activity of the essential oil against some microorganisms in comparison with chloramphenicol by the broth dilution method was determined. The oil exhibited a good activity as inhibitor of growth of Gram + bacteria.

  2. Convective self-propulsion of chemically active particles

    NASA Astrophysics Data System (ADS)

    Shklyaev, Oleg; Shum, Henry; Balazs, Anna

    2016-11-01

    A mechanism of particle self-propulsion activated by transduction of chemical energy into convective motion of fluid that drags microscale particles is proposed. The convection is generated by an active spherical particle located on the bottom of a microchannel and coated with a catalyst that decomposes reagent dissolved in the solution into less dense products and gives rise to a buoyancy force. The symmetry of the flow generated around the active particle can be broken if a passive spherical particle, which does not produce the flow, is present in the vicinity of the first one. The generated flow drags the passive particle toward the active one along the bottom wall until they form a dimer. The resulting asymmetric fluid flow, which is generated by only one of the particles, imposes a different drag on the different sides on the dimer. The net force causes the dimer to translate along the bottom wall. By varying numbers of active and passive particles, as well as their positions within a group, one can control the structure of the generated convective flow and, therefore, design clusters with different mobile properties. The proposed mechanism can be harnessed to transport cargo in microchannels.

  3. Kinetics of photoplasma of dense barium vapour

    SciTech Connect

    Kosarev, N I

    2015-03-31

    Barium vapour ionisation under laser photoexcitation of the resonance line at a wavelength of λ = 553.5 nm is studied numerically. Seed electrons, arising due to the associative ionisation of atoms, gain energy in superelastic collisions and lead to electron avalanche ionisation of the medium. The influence of radiative transfer in a cylindrical gas volume on the excitation kinetics of barium atoms, absorption dynamics of laser radiation and oscillation of ionisation-brightening wave under competition between ionising and quenching collisions of electrons with excited atoms is studied. (interaction of laser radiation with matter)

  4. A conservative vapour intrusion screening model of oxygen-limited hydrocarbon vapour biodegradation accounting for building footprint size

    NASA Astrophysics Data System (ADS)

    Knight, John H.; Davis, Gregory B.

    2013-12-01

    Petroleum hydrocarbon vapours pose a reduced risk to indoor air due to biodegradation processes where oxygen is available in the subsurface or below built structures. However, no previous assessment has been available to show the effects of a building footprint (slab size) on oxygen-limited hydrocarbon vapour biodegradation and the potential for oxygen to be present beneath the entire sub-slab region of a building. Here we provide a new, conservative and conceptually simple vapour screening model which links oxygen and hydrocarbon vapour transport and biodegradation in the vicinity and beneath an impervious slab. This defines when vapour risk is insignificant, or conversely when there is potential for vapour to contact the sub-slab of a building. The solution involves complex mathematics to determine the position of an unknown boundary interface between oxygen diffusing in from the ground surface and vapours diffusing upwards from a subsurface vapour source, but the mathematics reduces to a simple relationship between the vapour source concentration and the ratio of the half slab width and depth to the vapour source. Data from known field investigations are shown to be consistent with the model predictions. Examples of 'acceptable' slab sizes for vapour source depths and strengths are given. The predictions are conservative as an estimator of when petroleum hydrocarbon vapours might come in contact with a slab-on-ground building since additional sources of oxygen due to advective flow or diffusion through the slab are ignored. As such the model can be used for screening sites for further investigation.

  5. A conservative vapour intrusion screening model of oxygen-limited hydrocarbon vapour biodegradation accounting for building footprint size.

    PubMed

    Knight, John H; Davis, Gregory B

    2013-12-01

    Petroleum hydrocarbon vapours pose a reduced risk to indoor air due to biodegradation processes where oxygen is available in the subsurface or below built structures. However, no previous assessment has been available to show the effects of a building footprint (slab size) on oxygen-limited hydrocarbon vapour biodegradation and the potential for oxygen to be present beneath the entire sub-slab region of a building. Here we provide a new, conservative and conceptually simple vapour screening model which links oxygen and hydrocarbon vapour transport and biodegradation in the vicinity and beneath an impervious slab. This defines when vapour risk is insignificant, or conversely when there is potential for vapour to contact the sub-slab of a building. The solution involves complex mathematics to determine the position of an unknown boundary interface between oxygen diffusing in from the ground surface and vapours diffusing upwards from a subsurface vapour source, but the mathematics reduces to a simple relationship between the vapour source concentration and the ratio of the half slab width and depth to the vapour source. Data from known field investigations are shown to be consistent with the model predictions. Examples of 'acceptable' slab sizes for vapour source depths and strengths are given. The predictions are conservative as an estimator of when petroleum hydrocarbon vapours might come in contact with a slab-on-ground building since additional sources of oxygen due to advective flow or diffusion through the slab are ignored. As such the model can be used for screening sites for further investigation.

  6. Influences of chemical activators on incinerator bottom ash

    SciTech Connect

    Qiao, X.C. Cheeseman, C.R.; Poon, C.S.

    2009-02-15

    This research has applied different chemical activators to mechanically and thermally treated fine fraction (<14 mm) of incinerator bottom ash (IBA), in order to investigate the influences of chemical activators on this new pozzolanic material. IBA has been milled and thermally treated at 800 deg. C (TIBA). The TIBA produced was blended with Ca(OH){sub 2} and evaluated for setting time, reactivity and compressive strength after the addition of 0.0565 mole of Na{sub 2}SO{sub 4}, K{sub 2}SO{sub 4}, Na{sub 2}CO{sub 3}, K{sub 2}CO{sub 3}, NaOH, KOH and CaCl{sub 2} into 100 g of binder (TIBA+Ca(OH){sub 2}). The microstructures of activated IBA and hydrated samples have been characterized by X-ray diffraction (XRD) and thermogravimetry (TG) analysis. Thermal treatment is found to produce gehlenite (Ca{sub 2}Al{sub 2}SiO{sub 7}), wollastonite (CaSiO{sub 3}) and mayenite (Ca{sub 12}Al{sub 14}O{sub 33}) phases. The thermally treated IBA samples are significantly more reactive than the milled IBA. The addition of Na{sub 2}CO{sub 3} can increase the compressive strength and calcium hydroxide consumption at 28-day curing ages. However, the addition of Na{sub 2}SO{sub 4}, K{sub 2}SO{sub 4}, K{sub 2}CO{sub 3}, NaOH and KOH reduces the strength and hydration reaction. Moreover, these chemicals produce more porous samples due to increased generation of hydrogen gas. The addition of CaCl{sub 2} has a negative effect on the hydration of TIBA samples. Calcium aluminium oxide carbonate sulphide hydrate (Ca{sub 4}Al{sub 2}O{sub 6}(CO{sub 3}){sub 0.67}(SO{sub 3}){sub 0.33}(H{sub 2}O){sub 11}) is the main hydration product in the samples with activated IBA, except for the sample containing CaCl{sub 2}.

  7. Biological activities and chemical composition of lichens from Serbia

    PubMed Central

    Kosanic, Marijana; Rankovic, Branislav; Stanojkovic, Tatjana; Vasiljevic, Perica; Manojlovic, Nedeljko

    2014-01-01

    The aim of this study is to investigate chemical composition of acetone extracts of the lichens Parmelia arseneana and Acarospora fuscata and in vitro antioxidant, antimicrobial, and anticancer activities of these extracts and gyrophoric acid isolated from A. fuscata. The HPLC-UV method was used for the identification of secondary metabolites. Stictic acid, norstictic acid, gyrophoric acid, usnic acid, atranorin and chloroatranorin were identified in the A. fuscata. In P. arseneana, we detected stictic acid, norstictic acid, usnic acid and atranorin, while gyrophoric acid was not identified. Antioxidant activity was evaluated by measuring the scavenging capacity of tested samples on DPPH and superoxide anion radicals, reducing the power of samples and determination of total phenolic compounds in extracts. As a result of the study, gyrophoric acid was found to have the largest DPPH radical scavenging activity with an IC50 value of 105.75 µg/ml. Moreover, the tested samples had an effective superoxide anion radical scavenging and reducing power. The total content of phenol in extracts was determined as pyrocatechol equivalent. The antimicrobial activity was estimated by determination of the minimal inhibitory concentration by the broth microdilution method. The most active was also gyrophoric acid, with minimum inhibitory concentration values ranging from 0.019 to 1.25 mg/ml. Anticancer activity was tested against LS174 (human colon carcinoma cell line), A549 (human lung carcinoma cell line), Fem-x (malignant melanoma cell line), and a chronic myelogeneous leukaemia K562 cell line using the MTT method. Extract of P. arseneana expressed the strongest anticancer activity against all cell lines with IC50 values ranging from 11.61 to 47.06 µg/ml. PMID:26417336

  8. Preparation of fungal conidia impacts their susceptibility to inactivation by ethanol vapours.

    PubMed

    Dao, Thien; Dantigny, Philippe

    2009-11-15

    A common protocol employed for the preparation of conidia employs flooding a fungal colony grown on semi-solid media under optimum conditions with an aqueous solution. In contrast, conidia produced in a natural environment are usually not hydrated when disseminated in air and can be produced under water stress. In order to simulate the latter conditions, cultures were grown at different water activities and conidia were dry-harvested on the lid by turning the dishes upside-down then gently tapping the bottom of the box. This study aimed at assessing the effect of the preparation of fungal conidia on their inactivation by ethanol vapours. Firstly ethanol vapours (either 0.30 or 0.45 kPa) were applied to conidia obtained from the standardised protocol and to dry-harvested conidia for some species of Penicillium. While all dry-harvested conidia remained viable after 24 h of treatment, about 1.0, 3.5 and 2.5 log(10) reductions were observed for hydrated conidia of Penicillium chrysogenum, Penicillium digitatum and Penicillium italicum respectively. Secondly ethanol vapours (0.67 kPa) were applied to dry-harvested conidia obtained from cultures grown at 0.99 a(w) and at reduced water activities. For all species, the susceptibility to ethanol vapours of conidia obtained at 0.99 a(w) was significantly greater than that of conidia obtained at reduced water activities. Conidia produced in a natural environment under non-optimal conditions would be much more resistant to ethanol vapours than those produced in the laboratory. This phenomenon may be due to a reduced intracellular water activity of dry-harvested conidia.

  9. Properties of meso-Erythritol; phase state, accommodation coefficient and saturation vapour pressure

    NASA Astrophysics Data System (ADS)

    Emanuelsson, Eva; Tschiskale, Morten; Bilde, Merete

    2016-04-01

    Introduction Saturation vapour pressure and the associated temperature dependence (enthalpy ΔH), are key parameters for improving predictive atmospheric models. Generally, the atmospheric aerosol community lack experimentally determined values of these properties for relevant organic aerosol compounds (Bilde et al., 2015). In this work we have studied the organic aerosol component meso-Erythritol. Methods Sub-micron airborne particles of meso-Erythritol were generated by nebulization from aqueous solution, dried, and a mono disperse fraction of the aerosol was selected using a differential mobility analyser. The particles were then allowed to evaporate in the ARAGORN (AaRhus Atmospheric Gas phase OR Nano particle) flow tube. It is a temperature controlled 3.5 m long stainless steel tube with an internal diameter of 0.026 m (Bilde et al., 2003, Zardini et al., 2010). Changes in particle size as function of evaporation time were determined using a scanning mobility particle sizer system. Physical properties like air flow, temperature, humidity and pressure were controlled and monitored on several places in the setup. The saturation vapour pressures were then inferred from the experimental results in the MATLAB® program AU_VaPCaP (Aarhus University_Vapour Pressure Calculation Program). Results Following evaporation, meso-Erythriol under some conditions showed a bimodal particle size distribution indicating the formation of particles of two different phase states. The issue of physical phase state, along with critical assumptions e.g. the accommodation coefficient in the calculations of saturation vapour pressures of atmospheric relevant compounds, will be discussed. Saturation vapour pressures from the organic compound meso-Erythritol will be presented at temperatures between 278 and 308 K, and results will be discussed in the context of atmospheric chemistry. References Bilde, M. et al., (2015), Chemical Reviews, 115 (10), 4115-4156. Bilde, M. et. al., (2003

  10. Speciation and chemical activities in superheated sodium borate solutions

    SciTech Connect

    Weres, O. )

    1993-06-01

    The system H[sub 2]O-B[sub 2]O[sub 3]-Na[sub 2]O has been studied experimentally at 277[degrees] and 317[degrees]C. The activities of water and boric acid have been determined at mole ratios Na/B from 0 to 1.5, and total dissolved solids 3 to 80 weight percent. The activity of boric acid has been fitted to within experimental error using a speciation model with eight complex species. This model is consistent with the model previously published by Mesmer et al. The electrolyte properties of the liquid are modelled using the Pitzer-Simonson Model of very concentrated electrolyte solutions. The calculated values of water activity agree with experiment, and the activity of NaOH and pOH have also been calculated. These data will allow prediction of the composition and chemical behavior of sodium borate liquids that may accumulate in the superheated crevices within a steam generator. A modified form of the model is provided for use with MULTEQ. The potassium borate system also was briefly studied at 317[degrees]C, and is adequately described by a model with five complex species. The potassium borate liquid is more alkaline at K/B = 1 than a sodium borate liquid at the same mole ratio, but pOH in the two systems is the same at lower mole ratios.

  11. High performance vapour-cell frequency standards

    NASA Astrophysics Data System (ADS)

    Gharavipour, M.; Affolderbach, C.; Kang, S.; Bandi, T.; Gruet, F.; Pellaton, M.; Mileti, G.

    2016-06-01

    We report our investigations on a compact high-performance rubidium (Rb) vapour-cell clock based on microwave-optical double-resonance (DR). These studies are done in both DR continuous-wave (CW) and Ramsey schemes using the same Physics Package (PP), with the same Rb vapour cell and a magnetron-type cavity with only 45 cm3 external volume. In the CW-DR scheme, we demonstrate a DR signal with a contrast of 26% and a linewidth of 334 Hz; in Ramsey-DR mode Ramsey signals with higher contrast up to 35% and a linewidth of 160 Hz have been demonstrated. Short-term stabilities of 1.4×10-13 τ-1/2 and 2.4×10-13 τ-1/2 are measured for CW-DR and Ramsey-DR schemes, respectively. In the Ramsey-DR operation, thanks to the separation of light and microwave interactions in time, the light-shift effect has been suppressed which allows improving the long-term clock stability as compared to CW-DR operation. Implementations in miniature atomic clocks are considered.

  12. Is there a solar signal in lower stratospheric water vapour?

    NASA Astrophysics Data System (ADS)

    Schieferdecker, Tobias; Lossow, Stefan; Stiller, Gabriele; von Clarmann, Thomas

    2016-04-01

    A merged time series of stratospheric water vapour built from the Halogen Occultation Instrument (HALOE) and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) data between 60 deg S and 60 deg N and 15 to 30 km, and covering the years 1992 to 2012, was analysed by multivariate linear regression, including an 11-year solar cycle proxy. Lower stratospheric water vapour was found to reveal a phase-shifted anti-correlation with the solar cycle, with lowest water vapour after solar maximum. The phase shift is composed of an inherent constant time lag of about 2 years and a second component following the stratospheric age of air. The amplitudes of the water vapour response are largest close to the tropical tropopause (up to 0.35 ppmv) and decrease with altitude and latitude. Including the solar cycle proxy in the regression results in linear trends of water vapour being negative over the full altitude/latitude range, while without the solar proxy, positive water vapour trends in the lower stratosphere were found. We conclude from these results that a solar signal seems to be generated at the tropical tropopause which is most likely imprinted on the stratospheric water vapour abundances and transported to higher altitudes and latitudes via the Brewer-Dobson circulation. Hence it is concluded that the tropical tropopause temperature at the final dehydration point of air may also be governed to some degree by the solar cycle. The negative water vapour trends obtained when considering the solar cycle impact on water vapour abundances can possibly solve the "water vapour conundrum" of increasing stratospheric water vapour abundances despite constant or even decreasing tropopause temperatures.

  13. Is there a solar signal in lower stratospheric water vapour?

    NASA Astrophysics Data System (ADS)

    Schieferdecker, T.; Lossow, S.; Stiller, G. P.; von Clarmann, T.

    2015-09-01

    A merged time series of stratospheric water vapour built from the Halogen Occultation Instrument (HALOE) and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) data between 60° S and 60° N and 15 to 30 km and covering the years 1992 to 2012 was analysed by multivariate linear regression, including an 11-year solar cycle proxy. Lower stratospheric water vapour was found to reveal a phase-shifted anti-correlation with the solar cycle, with lowest water vapour after solar maximum. The phase shift is composed of an inherent constant time lag of about 2 years and a second component following the stratospheric age of air. The amplitudes of the water vapour response are largest close to the tropical tropopause (up to 0.35 ppmv) and decrease with altitude and latitude. Including the solar cycle proxy in the regression results in linear trends of water vapour being negative over the full altitude/latitude range, while without the solar proxy, positive water vapour trends in the lower stratosphere were found. We conclude from these results that a solar signal seems to be generated at the tropical tropopause which is most likely imprinted on the stratospheric water vapour abundances and transported to higher altitudes and latitudes via the Brewer-Dobson circulation. Hence it is concluded that the tropical tropopause temperature at the final dehydration point of air may also be governed to some degree by the solar cycle. The negative water vapour trends obtained when considering the solar cycle impact on water vapour abundances can possibly solve the "water vapour conundrum" of increasing stratospheric water vapour abundances despite constant or even decreasing tropopause temperatures.

  14. Wound Healing Activity and Chemical Standardization of Eugenia pruniformis Cambess

    PubMed Central

    de Albuquerque, Ricardo Diego Duarte Galhardo; Perini, Jamila Alessandra; Machado, Daniel Escorsim; Angeli-Gamba, Thaís; Esteves, Ricardo dos Santos; Santos, Marcelo Guerra; Oliveira, Adriana Passos; Rocha, Leandro

    2016-01-01

    Background: Eugenia pruniformis is an endemic species from Brazil. Eugenia genus has flavonoids as one of the remarkable chemical classes which are related to the improvement of the healing process. Aims: To evaluate of wound healing activity of E. pruniformis leaves and to identify and quantify its main flavonoids compounds. Materials And Methods: Wound excision model in rats was used to verify the hydroethanolic and ethyl acetate extracts potential. The animals were divided in four groups of six and the samples were evaluated until the 15° day of treatment. Hydroxyproline dosage and histological staining with hematoxilin-eosin and Sirius Red were used to observe the tissue organization and quantify the collagen deposition, respectively. Chemical compounds of the ethyl acetate extract were identified by chromatographic techniques and mass spectrometry analysis and total flavonoids content was determined by spectrophotometric method. The antioxidant activity was determined by oxygen radical absorbing capacity (ORAC) and 2,2-diphenyl-1-picrylhydrazylhydrate radical photometric (DPPH) assays. Results: The treated group with the ethyl acetate extract showed collagen deposition increase, higher levels of hidroxyproline, better tissue reorganization and complete remodeling of epidermis. Quercetin, kaempferol and hyperoside were identified as main compounds and flavonoids content value was 43% (w/w). The ORAC value of the ethyl acetate extract was 0.81± 0.05 mmol TE/g whereas the concentration to produce 50% reduction of the DPPH was 7.05± 0.09 μg/mL. Conclusion: The data indicate a wound healing and antioxidant activities of E. pruniformis. This study is the first report of flavonoids and wound healing activity of E. pruniformis. KEY MESSAGES Eugenia pruniformis extract accelerates wound healing in skin rat model, probably due to its involvement with the collagen deposition increase, higher levels of hidroxyproline, dermal remodelling and potent antioxidant activity

  15. Transport mechanisms through PE-CVD coatings: influence of temperature, coating properties and defects on permeation of water vapour

    NASA Astrophysics Data System (ADS)

    Kirchheim, Dennis; Jaritz, Montgomery; Mitschker, Felix; Gebhard, Maximilian; Brochhagen, Markus; Hopmann, Christian; Böke, Marc; Devi, Anjana; Awakowicz, Peter; Dahlmann, Rainer

    2017-03-01

    Gas transport mechanisms through plastics are usually described by the temperature-dependent Arrhenius-model and compositions of several plastic layers are represented by the CLT. When it comes to thin films such as plasma-enhanced chemical vapour deposition (PE-CVD) or plasma-enhanced atomic layer deposition (PE-ALD) coatings on substrates of polymeric material, a universal model is lacking. While existing models describe diffusion through defects, these models presume that permeation does not occur by other means of transport mechanisms. This paper correlates the existing transport models with data from water vapour transmission experiments.

  16. High activity redox catalysts synthesized by chemical vapor impregnation.

    PubMed

    Forde, Michael M; Kesavan, Lokesh; Bin Saiman, Mohd Izham; He, Qian; Dimitratos, Nikolaos; Lopez-Sanchez, Jose Antonio; Jenkins, Robert L; Taylor, Stuart H; Kiely, Christopher J; Hutchings, Graham J

    2014-01-28

    The use of precious metals in heterogeneous catalysis relies on the preparation of small nanoparticles that are stable under reaction conditions. To date, most conventional routes used to prepare noble metal nanoparticles have drawbacks related to surface contamination, particle agglomeration, and reproducibility restraints. We have prepared titania-supported palladium (Pd) and platinum (Pt) catalysts using a simplified vapor deposition technique termed chemical vapor impregnation (CVI) that can be performed in any standard chemical laboratory. These materials, composed of nanoparticles typically below 3 nm in size, show remarkable activity under mild conditions for oxidation and hydrogenation reactions of industrial importance. We demonstrate the preparation of bimetallic Pd-Pt homogeneous alloy nanoparticles by this new CVI method, which show synergistic effects in toluene oxidation. The versatility of our CVI methodology to be able to tailor the composition and morphology of supported nanoparticles in an easily accessible and scalable manner is further demonstrated by the synthesis of Pdshell-Aucore nanoparticles using CVI deposition of Pd onto preformed Au nanoparticles supported on titania (prepared by sol immobilization) in addition to the presence of monometallic Au and Pd nanoparticles.

  17. Generator of chemically active low-temperature plasma

    NASA Astrophysics Data System (ADS)

    Tyuftyaev, A. S.; Gadzhiev, M. Kh; Sargsyan, M. A.; Demirov, N. A.; Spector, N. O.

    2016-11-01

    A new generator of high enthalpy (H 0 > 40 kJ/g), chemically active nitrogen and air plasmas was designed and constructed. Main feature of the generator is an expanding channel of an output electrode; the generator belongs to the class of DC plasma torches with thermionic cathode with an efficiency of 80%. The generator ensures the formation of a slightly divergent plasma jet (2α = 12°) with a diameter of D = 10-12 mm, an electric arc maximum power of 20-50 kW, plasma forming gas flow rate 1.0-2.0 g/s, and the average plasma temperature at an outlet of 8000-11000 K.

  18. Thymus vulgaris essential oil: chemical composition and antimicrobial activity.

    PubMed

    Borugă, O; Jianu, C; Mişcă, C; Goleţ, I; Gruia, A T; Horhat, F G

    2014-01-01

    The study was designed to determine the chemical composition and antimicrobial properties of the essential oil of Thymus vulgaris cultivated in Romania. The essential oil was isolated in a yield of 1.25% by steam distillation from the aerial part of the plant and subsequently analyzed by GC-MS. The major components were p-cymene (8.41%), γ-terpinene (30.90%) and thymol (47.59%). Its antimicrobial activity was evaluated on 7 common food-related bacteria and fungus by using the disk diffusion method. The results demonstrate that the Thymus vulgaris essential oil tested possesses strong antimicrobial properties, and may in the future represent a new source of natural antiseptics with applications in the pharmaceutical and food industry.

  19. Atmospheric pressure chemical vapour deposition of vanadium oxides

    NASA Astrophysics Data System (ADS)

    Manning, Troy Darrell

    The APCVD of vanadium(IV) oxide thin films from halide precursors was investigated. It was found that the phase of vanadium oxide obtained could be controlled by the reactor temperature and precursor ratio. For vanadium(IV) chloride and water, reactor temperatures > 550 °C and an excess of water over VCI4 was required to produce VO2 thin films. For vanadium(V) oxytrichloride and water, reactor temperatures > 550 °C and an excess of water over VOCI3 also produced VO2 but required low total gas flow rates (< 1 L min 1) for complete coverage of the substrate. Vanadium(IV) oxide thin films doped with metal ions (W, Cr, Nb, Ti, Mo or Sn) were also prepared by the APCVD process in order to reduce the thermochromic transition temperature (TC) from 68 °C for the undoped material to < 30 °C. The most successful dopant was tungsten, introduced into the VOCl3, and water system as WCI6, which lowered T to 5 °C for a 3 atom% tungsten doped thin film. Tungsten (VI) ethoxide was introduced into the VCI4 and water system and reduced TC, of VO2, to 42 °C for a 1 atom% tungsten doped thin film. Chromium, introduced as CrCO2Cl2, formed a chromium vanadium oxide that did not display any thermochromic properties. Niobium, introduced as NbCl5 into the VOCl3 system, reduced TC of VO2, but the amount of niobium introduced could not be easily controlled. Molybdenum, introduced as MoCI5, also reduced TC of VO2, but the form of the molybdenum appeared to be different from that required for complete control of TC, Titanium, introduced as TiCl4, produced phase segregated films of VO2 and TiO2, with interesting multifunctional properties and a reduced TC. Tin, introduced as SnCl4, also formed a phase segregated material of VO2, and SnO2, with a slightly reduced TC.

  20. Enhancement of immunotoxin activity using chemical and biological reagents.

    PubMed Central

    Wu, M.

    1997-01-01

    One of the major discoveries of effective therapeutics is the use of targeted treatment, such as antibody-directed toxins, i.e. immunotoxins; however, this medicine delivery strategy is still at a developmental stage. A number of problems need to be resolved; one is their inefficacy when applied in vivo. Research has stimulated interest in this area through the use of chemical reagents and other moieties to increase the activity of immunotoxins. In this article, reagents that can potentiate the cytotoxicity of immunotoxins are reviewed and the mechanisms that increase activity of immunotoxins are discussed. Lysosomotropic amines, especially ammonium chloride and chloroquine, may raise the pH value of the lysosome in which the conjugates enter. Carboxylic ionophores, e.g. monensin, can influence Golgi vacuolation, which may facilitate the routing of conjugates, augmenting activity. Calcium channel antagonists may increase immunotoxin killing through morphological or other mechanisms that are not yet well understood. Viral particles and surface structure can enhance the cytotoxicity of conjugates, probably through the mechanism of disrupting endosomes. In addition, cytokines, beta-adrenergic blockers, immunosuppressive agents (cyclosporin A) and some antibiotics (daunorubicin) can be used to increase the effect of immunotoxins. PMID:9155057

  1. Antibacterial activity of silver bionanocomposites synthesized by chemical reduction route

    PubMed Central

    2012-01-01

    Background The aim of this study is to investigate the functions of polymers and size of nanoparticles on the antibacterial activity of silver bionanocomposites (Ag BNCs). In this research, silver nanoparticles (Ag NPs) were incorporated into biodegradable polymers that are chitosan, gelatin and both polymers via chemical reduction method in solvent in order to produce Ag BNCs. Silver nitrate and sodium borohydride were employed as a metal precursor and reducing agent respectively. On the other hand, chitosan and gelatin were added as a polymeric matrix and stabilizer. The antibacterial activity of different sizes of silver nanoparticles was investigated against Gram-positive and Gram-negative bacteria by the disk diffusion method using Mueller-Hinton Agar. Results The properties of Ag BNCs were studied as a function of the polymer weight ratio in relation to the use of chitosan and gelatin. The morphology of the Ag BNCs films and the distribution of the Ag NPs were also characterized. The diameters of the Ag NPs were measured and their size is less than 20 nm. The antibacterial trait of silver/chitosan/gelatin bionanocomposites was investigated. The silver ions released from the Ag BNCs and their antibacterial activities were scrutinized. The antibacterial activities of the Ag BNC films were examined against Gram-negative bacteria (E. coli and P. aeruginosa) and Gram-positive (S. aureus and M. luteus) by diffusion method using Muller-Hinton agar. Conclusions The antibacterial activity of Ag NPs with size less than 20 nm was demonstrated and showed positive results against Gram-negative and Gram-positive bacteria. The Ag NPs stabilized well in the polymers matrix. PMID:22967920

  2. Active sampling technique to enhance chemical signature of buried explosives

    NASA Astrophysics Data System (ADS)

    Lovell, John S.; French, Patrick D.

    2004-09-01

    Deminers and dismounted countermine engineers commonly use metal detectors, ground penetrating radar and probes to locate mines. Many modern landmines have a very low metal content, which severely limits the effectiveness of metal detectors. Canines have also been used for landmine detection for decades. Experiments have shown that canines smell the explosives which are known to leak from most types of landmines. The fact that dogs can detect landmines indicates that vapor sensing is a viable approach to landmine detection. Several groups are currently developing systems to detect landmines by "sniffing" for the ultra-trace explosive vapors above the soil. The amount of material that is available to passive vapor sensing systems is limited to no more than the vapor in equilibrium with the explosive related chemicals (ERCs) distributed in the surface soils over and near the landmine. The low equilibrium vapor pressure of TNT in the soil/atmosphere boundary layer and the limited volume of the boundary layer air imply that passive chemical vapor sensing systems require sensitivities in the picogram range, or lower. ADA is working to overcome many of the limitations of passive sampling methods, by the use of an active sampling method that employs a high-powered (1,200+ joules) strobe lamp to create a highly amplified plume of vapor and/or ERC-bearing fine particulates. Initial investigations have demonstrated that this approach can amplify the detectability of TNT by two or three orders of magnitude. This new active sampling technique could be used with any suitable explosive sensor.

  3. Dynamic model for selective metabolic activation in chemical carcinogenesis

    SciTech Connect

    Selkirk, J.K.; MacLeod, M.C.

    1980-01-01

    Theoretical calculations predict the relative ease of formation of carbonium ions from 7,8-dihydro-7,8-dihydroxybenzo(a)pyrene-9,10-oxide or from either of the 2 symmetrical bay regions of B(e)P, and suggest their attraction to cellular nucleophiles. When both isomers were metabolized by hamster embryo fibroblasts (HEF) and the products analyzed, the results showed that the probable reason for benzo(e)pyrene's lack of carcinogenicity was its metabolic preference to attack the molecule away from the bay-region area. Particularly striking was the absence of any evidence for the formation of a significant amount of B(e)P-9,10-dihydrodiol. This suggests a metabolic basis for the relative lack of carcinogenic and mutagenic activity of B(e)P. The reason for this is not clear but may be due to physical or chemical factors such as membrane solubility or stereochemical requirements of the active site of the enzyme. The bay-region theory of PAH carcinogenesis predicts that carbonium ion formation from 9,10-dihydro-9,10-dihydroxybenzo(e)pyrene-11, 12-oxide, if formed, would be energetically favorable. Thus, the inability of HEF and microcomes to form B(e)P-9,10-dihydrodiol, the precursor of its potentially highly reactive diol-epoxide, would explain the relative inertness of B(e)P in several biological systems. As the subtle biochemical interactions of the various carcinogen intermediates become clarified, it becomes apparent that susceptibility and resistance to malignant transformation are based on a complex set of both chemical and physical parameters. It is becoming clear that metabolism kinetics, membrane interaction, and the role of nuclear metabolism help dictate the passage of the carcinogen and its reactive intermediates into and through the metabolic machinery of the cell. (ERB)

  4. INCREASED ENDOCRINE ACTIVITY OF XENOBIOTIC CHEMICALS AS MEDIATED BY METABOLIC ACTIVATION

    EPA Science Inventory

    This research is part of an effort to develop in vitro assays and QSARs applicable to untested chemicals on EPA inventories through study of estrogen receptor (ER) binding and estrogen mediated gene expression in fish. The current effort investigates metabolic activation of chemi...

  5. Age and structure of a model vapour-deposited glass

    PubMed Central

    Reid, Daniel R.; Lyubimov, Ivan; Ediger, M. D.; de Pablo, Juan J.

    2016-01-01

    Glass films prepared by a process of physical vapour deposition have been shown to have thermodynamic and kinetic stability comparable to those of ordinary glasses aged for thousands of years. A central question in the study of vapour-deposited glasses, particularly in light of new knowledge regarding anisotropy in these materials, is whether the ultra-stable glassy films formed by vapour deposition are ever equivalent to those obtained by liquid cooling. Here we present a computational study of vapour deposition for a two-dimensional glass forming liquid using a methodology, which closely mimics experiment. We find that for the model considered here, structures that arise in vapour-deposited materials are statistically identical to those observed in ordinary glasses, provided the two are compared at the same inherent structure energy. We also find that newly deposited hot molecules produce cascades of hot particles that propagate far into the film, possibly influencing the relaxation of the material. PMID:27762262

  6. Introducing VESPA-22: a ground-based microwave spectrometer for measuring middle atmospheric water vapour at polar latitudes

    NASA Astrophysics Data System (ADS)

    Bertagnolio, P. P.; Muscari, G.; Fiorucci, I.; Mari, M.

    2012-04-01

    We present the latest updates on the project VESPA-22 (water Vapour Emission Spectrometer for Polar Atmospheres at 22 GHz), a ground-based microwave instrument developed for long-term observations of water vapour in the polar stratosphere and mesosphere (SMWV). The short- and long-term change in water vapour concentration from the lower stratosphere to the mesosphere is one of the main areas of interest for atmospheric composition studies in the current decade. In fact, SMWV influences the temperature of the stratosphere by radiative processes, the concentration of several chemical species (also through the production of OH) and the formation of aerosols. Recent studies showed that in the last 30 years mid-latitude SMWV has been changing for mechanisms not yet fully understood. Model studies indicate that these changes could have had a significant impact (25-30%) on the tropospheric radiative forcing and surface temperature trends observed since 1980. Moreover, at polar regions, changes in SMWV strongly affect the formation rate of polar stratospheric clouds, both directly (how much is available for uptake on PSC particles) and indirectly (impact on stratospheric temperature). This is especially critical in the Arctic stratosphere where temperatures are not as cold they are over Antarctica and, for the purpose of denitrification and ozone depletion processes, an increase in SMWV of 1 ppmv is modelled to be equivalent to a 1 K decrease in temperature. In the past decade, satellite-based instruments have provided accurate and global measurements of SMWV, but a similar coverage is not expected in this decade. Conversely, the ground-based microwave spectrometers currently active provide both the long-time series necessary for decadal scale monitoring and the high time resolution (a few hours) needed to understand fast dynamical processes. Today, none of these sustained SMWV measurements are being carried out at polar regions. Our observation technique is based on the

  7. Chemical activation by mechanochemical mixing, microwave, and ultrasonic irradiation

    EPA Science Inventory

    The use of emerging MW-assisted chemistry techniques in conjunction with benign reaction media is dramatically reducing chemical waste ad reaction times in several organic syntheses and chemical transformations. This editorial comments on the recent developments in mechanochemica...

  8. Stabilization of Leidenfrost vapour layer by textured superhydrophobic surfaces.

    PubMed

    Vakarelski, Ivan U; Patankar, Neelesh A; Marston, Jeremy O; Chan, Derek Y C; Thoroddsen, Sigurdur T

    2012-09-13

    In 1756, Leidenfrost observed that water drops skittered on a sufficiently hot skillet, owing to levitation by an evaporative vapour film. Such films are stable only when the hot surface is above a critical temperature, and are a central phenomenon in boiling. In this so-called Leidenfrost regime, the low thermal conductivity of the vapour layer inhibits heat transfer between the hot surface and the liquid. When the temperature of the cooling surface drops below the critical temperature, the vapour film collapses and the system enters a nucleate-boiling regime, which can result in vapour explosions that are particularly detrimental in certain contexts, such as in nuclear power plants. The presence of these vapour films can also reduce liquid-solid drag. Here we show how vapour film collapse can be completely suppressed at textured superhydrophobic surfaces. At a smooth hydrophobic surface, the vapour film still collapses on cooling, albeit at a reduced critical temperature, and the system switches explosively to nucleate boiling. In contrast, at textured, superhydrophobic surfaces, the vapour layer gradually relaxes until the surface is completely cooled, without exhibiting a nucleate-boiling phase. This result demonstrates that topological texture on superhydrophobic materials is critical in stabilizing the vapour layer and thus in controlling--by heat transfer--the liquid-gas phase transition at hot surfaces. This concept can potentially be applied to control other phase transitions, such as ice or frost formation, and to the design of low-drag surfaces at which the vapour phase is stabilized in the grooves of textures without heating.

  9. A solar signal in lower stratospheric water vapour?

    NASA Astrophysics Data System (ADS)

    Schieferdecker, T.; Lossow, S.; Stiller, G. P.; von Clarmann, T.

    2015-04-01

    A merged time series of stratospheric water vapour built from HALOE and MIPAS data between 60° S and 60° N and 15 to 30 km and covering the years 1992 to 2012 was analyzed by multivariate linear regression including an 11 year solar cycle proxy. Lower stratospheric water vapour was found to reveal a phase-shifted anti-correlation with the solar cycle, with lowest water vapour after solar maximum. The phase shift is composed of an inherent constant time lag of about 2 years and a second component following the stratospheric age of air. The amplitudes of the water vapour response are largest close to the tropical tropopause (up to 0.35 ppmv) and decrease with altitude and latitude. Including the solar cycle proxy in the regression results in linear trends of water vapour being negative over the full altitude/latitude range, while without the solar proxy positive water wapour trends in the lowermost stratosphere were found. We conclude from these results that a solar signal generated at the tropical tropopause is imprinted on the stratospheric water vapour abundances and transported to higher altitudes and latitudes via the Brewer-Dobson circulation. Hence it is concluded that the tropical tropopause temperature at the final dehydration point of air is also governed to some degree by the solar cycle. The negative water vapour trends obtained when considering the solar cycle impact on water vapour abundances can solve the water vapour conundrum of increasing stratospheric water vapour abundances at constant or even decreasing tropopause temperatures.

  10. Localisation of an Unknown Number of Land Mines Using a Network of Vapour Detectors

    PubMed Central

    Chhadé, Hiba Haj; Abdallah, Fahed; Mougharbel, Imad; Gning, Amadou; Julier, Simon; Mihaylova, Lyudmila

    2014-01-01

    We consider the problem of localising an unknown number of land mines using concentration information provided by a wireless sensor network. A number of vapour sensors/detectors, deployed in the region of interest, are able to detect the concentration of the explosive vapours, emanating from buried land mines. The collected data is communicated to a fusion centre. Using a model for the transport of the explosive chemicals in the air, we determine the unknown number of sources using a Principal Component Analysis (PCA)-based technique. We also formulate the inverse problem of determining the positions and emission rates of the land mines using concentration measurements provided by the wireless sensor network. We present a solution for this problem based on a probabilistic Bayesian technique using a Markov chain Monte Carlo sampling scheme, and we compare it to the least squares optimisation approach. Experiments conducted on simulated data show the effectiveness of the proposed approach. PMID:25384008

  11. THE USE OF STRUCTURE-ACTIVITY RELATIONSHIPS IN INTEGRATING THE CHEMISTRY AND TOXICOLOGY OF ENDOCRINE DISRUPTING CHEMICALS

    EPA Science Inventory

    Structure activity relationships (SARs) are based on the principle that structurally similar chemicals should have similar biological activity. SARs relate specifically-defined toxicological activity of chemicals to their molecular structure and physico-chemical properties. To de...

  12. Chemical Variability and Biological Activities of Eucalyptus spp. Essential Oils.

    PubMed

    Barbosa, Luiz Claudio Almeida; Filomeno, Claudinei Andrade; Teixeira, Robson Ricardo

    2016-12-07

    Many plant species produce mixtures of odorous and volatile compounds known as essential oils (EOs). These mixtures play important roles in Nature and have been utilized by mankind for different purposes, such as pharmaceuticals, agrochemicals, aromatherapy, and food flavorants. There are more than 3000 EOs reported in the literature, with approximately 300 in commercial use, including the EOs from Eucalyptus species. Most EOs from Eucalyptus species are rich in monoterpenes and many have found applications in pharmaceuticals, agrochemicals, food flavorants, and perfumes. Such applications are related to their diverse biological and organoleptic properties. In this study, we review the latest information concerning the chemical composition and biological activities of EOs from different species of Eucalyptus. Among the 900 species and subspecies of the Eucalyptus genus, we examined 68 species. The studies associated with these species were conducted in 27 countries. We have focused on the antimicrobial, acaricidal, insecticidal and herbicidal activities, hoping that such information will contribute to the development of research in this field. It is also intended that the information described in this study can be useful in the rationalization of the use of Eucalyptus EOs as components for pharmaceutical and agrochemical applications as well as food preservatives and flavorants.

  13. Chemically modified RNA activated matrices enhance bone regeneration.

    PubMed

    Elangovan, Satheesh; Khorsand, Behnoush; Do, Anh-Vu; Hong, Liu; Dewerth, Alexander; Kormann, Michael; Ross, Ryan D; Sumner, D Rick; Allamargot, Chantal; Salem, Aliasger K

    2015-11-28

    There exists a dire need for improved therapeutics to achieve predictable bone regeneration. Gene therapy using non-viral vectors that are safe and efficient at transfecting target cells is a promising approach to overcoming the drawbacks of protein delivery of growth factors. Here, we investigated the transfection efficiency, cytotoxicity, osteogenic potential and in vivo bone regenerative capacity of chemically modified ribonucleic acid (cmRNA) (encoding BMP-2) complexed with polyethylenimine (PEI) and made comparisons with PEI complexed with conventional plasmid DNA (encoding BMP-2). The polyplexes were fabricated at an amine (N) to phosphate (P) ratio of 10 and characterized for transfection efficiency using human bone marrow stromal cells (BMSCs). The osteogenic potential of BMSCs treated with these polyplexes was validated by determining the expression of bone-specific genes, osteocalcin and alkaline phosphatase as well as through the detection of bone matrix deposition. Using a calvarial bone defect model in rats, it was shown that PEI-cmRNA (encoding BMP-2)-activated matrices promoted significantly enhanced bone regeneration compared to PEI-plasmid DNA (BMP-2)-activated matrices. Our proof of concept study suggests that scaffolds loaded with non-viral vectors harboring cmRNA encoding osteogenic proteins may be a powerful tool for stimulating bone regeneration with significant potential for clinical translation.

  14. Removal of toxic chemicals from water with activated carbon

    USGS Publications Warehouse

    Dawson, V.K.; Marking, L.L.; Bills, T.D.

    1976-01-01

    Activated carbon was effective in removing fish toxicants and anesthetics from water solutions. Its capacity to adsorb 3-trifluoromethyl-4-nitrophenol (TFM), antimycin, NoxfishA? (5% rotenone), Dibrorms, juglone, MSa??222, and benzocaine ranged from 0.1 to 64 mg per gram of carbon. The adsorptive capacity (end point considered as a significant discharge) of activated carbon for removal of TFM was determined at column depths of 15, 30, and 60 cm; temperatures of 7, 12, 17, and 22 C; pH's of 6.5, 7.5, 8.5, and 9.5; and flow rates of 50, 78, 100, 200, and 940 ml/min. Adsorptive capacity increased when the contact time was increased by reducing the flow rate or increasing the column depth. The adsorptive capacity was not significantly influenced by temperature but was substantially higher at pH 6.5 than at the other pH's tested. A practical and efficient filter for purifying chemically treated water was developed.

  15. 15 CFR 712.2 - Restrictions on activities involving Schedule 1 chemicals.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Schedule 1 chemicals. 712.2 Section 712.2 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS ACTIVITIES INVOLVING SCHEDULE 1 CHEMICALS § 712.2 Restrictions on activities...

  16. 15 CFR 712.2 - Restrictions on activities involving Schedule 1 chemicals.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Schedule 1 chemicals. 712.2 Section 712.2 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS ACTIVITIES INVOLVING SCHEDULE 1 CHEMICALS § 712.2 Restrictions on activities...

  17. 15 CFR 712.2 - Restrictions on activities involving Schedule 1 chemicals.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Schedule 1 chemicals. 712.2 Section 712.2 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS ACTIVITIES INVOLVING SCHEDULE 1 CHEMICALS § 712.2 Restrictions on activities...

  18. Do Training Programs Work? An Assessment of Pharmacists Activities in the Field of Chemical Dependency.

    ERIC Educational Resources Information Center

    Brooks, Valerie G.; Brock, Tina Penick; Ahn, Jungeun

    2001-01-01

    Seeks to determine if pharmacists who attended a chemical dependency training program were performing more chemical dependency related activities. Results reveal that participants were more likely to perform the following activities: lecture to community groups about chemical dependency; participate in a pharmacists' recovery program; provide…

  19. 15 CFR 712.2 - Restrictions on activities involving Schedule 1 chemicals.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Schedule 1 chemicals. 712.2 Section 712.2 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS ACTIVITIES INVOLVING SCHEDULE 1 CHEMICALS § 712.2 Restrictions on activities...

  20. The ignitability of petrol vapours and potential for vapour phase explosion by use of TASER® law enforcement electronic control device.

    PubMed

    Clarke, C; Andrews, S P

    2014-12-01

    An experimental study was made of the potential of the TASER-X26™ law enforcement electronic control device to ignite petrol vapours if used by an officer to incapacitate a person soaked in petrol, or within a flammable atmosphere containing petrol vapour. Bench scale tests have shown that a wooden mannequin with pig skin covering the chest was a suitable representation of a human target. Full scale tests using the mannequin have shown that the arc from a TASER-X26™ is capable of igniting petrol/air vapours on a petrol-soaked person. Further tests in a 1/5 scale and a full scale compartment have shown that if a TASER is used within a compartment, a petrol vapour explosion (deflagration) may be achieved. It is evident from this research that if used in a flammable vapour rich environment, the device could prove fatal not only to the target but the TASER® operator as well.

  1. Chemical Composition and Antioxidant Activities of Broussonetia papyrifera Fruits

    PubMed Central

    Sun, Jie; Liu, Shao-fang; Zhang, Chu-shu; Yu, Li-na; Bi, Jie; Zhu, Feng; Yang, Qing-li

    2012-01-01

    Fruits of Broussonetia papyrifera from South China were analyzed for their total chemical composition, and antioxidant activities in ethanol and aqueous extracts. In the fruit of this plant, the crude protein, crude fat and carbohydrates was 7.08%, 3.72% and 64.73% of dry weight, respectively. The crude protein, crude fat and carbohydrates were 15.71%, 20.51% and 36.09% of dry weight, respectively. Fatty acid and amino acid composition of the fruit were analyzed. Unsaturated fatty acid concentration was 70.6% of the total fatty acids. The percentage of the essential amino acids (EAAs) was 40.60% of the total amino acids. Furthermore, B. papyrifera fruit are rich in many mineral elements and vitamins. Total phenolic content was assessed using the Folin-Ciocalteau assay, whereas antioxidant activities were assessed by measuring the ability of the two extracts to scavenge DPPH radicals, inhibit peroxidation, and chelate ferric ions. Their reducing power was also assessed. Results indicated that the aqueous extract of B. papyrifera was a more potent reducing agent and radical-scavenger than the ethanol extract. GC–MS analysis of the ethanol extract showed the presence of some acid-containing compounds. The changes in total phenolic content and antioxidant capacity in B. papyrifera from four different regions grown under normal conditions were assessed. The antioxidant activity of different extracts was positively associated with their total phenolic content. These results suggest that the fruit of B. papyrifera could be used in dietary supplement preparations, or as a food additive, for nutritional gain, or to prevent oxidation in food products. PMID:22389678

  2. PREDICTING TOXICOLOGICAL ENDPOINTS OF CHEMICALS USING QUANTITATIVE STRUCTURE-ACTIVITY RELATIONSHIPS (QSARS)

    EPA Science Inventory

    Quantitative structure-activity relationships (QSARs) are being developed to predict the toxicological endpoints for untested chemicals similar in structure to chemicals that have known experimental toxicological data. Based on a very large number of predetermined descriptors, a...

  3. Chemically activated carbon from lignocellulosic wastes for heavy metal wastewater remediation: Effect of activation conditions.

    PubMed

    Nayak, Arunima; Bhushan, Brij; Gupta, Vartika; Sharma, P

    2017-05-01

    Chemical activation is known to induce specific surface features of porosity and functionality which play a definite role in enhancing the adsorptive potential of the developed activated carbons. Different conditions of temperature, time, reagent type and impregnation ratio were applied on sawdust precursor and their effect on the physical, surface chemical features and finally on the adsorption potential of the developed activated carbons were analysed. Under activation conditions of 600°C, 1hr, 1:0.5 ratio, ZnCl2 impregnated carbon (CASD_ZnCl2) resulted in microporosity while KOH impregnation (CASD_KOH) yielded a carbon having a wider pore size distribution. The surface chemistry revealed similar functionalities. At same pH, temperature and adsorbate concentrations, CASD_KOH demonstrated better adsorption potential (1.06mmoles/g for Cd(2+) and 1.61mmoles/g for Ni(2+)) in comparison to CASD_ZnCl2 (0.23mmoles/g and 0.33mmoles/g for Cd(2+) and Ni(2+) respectively). Other features were a short equilibrium time of 60mins and an adsorbent dose of 0.2g/L for the CASD_KOH in comparison to CASD_ZnCl2 (equilibrium time of 150min and dosage of 0.5g/L). The nature of interactions was physical for both adsorbents and pore diffusion mechanisms were operative. The results reveal the potentiality of chemical activation so as to achieve the best physico-chemical properties suited for energy efficient, economical and eco-friendly water treatment.

  4. Discussion of the Separation of Chemical and Relaxational Kinetics of Chemically Activated Intermediates in Master Equation Simulations.

    PubMed

    Döntgen, Malte; Leonhard, Kai

    2017-03-02

    Chemical activation of intermediates, such as hydrogen abstraction products, is emerging as a basis for a fully new reaction type: hot β-scission. While for thermally equilibrated intermediates chemical kinetics are typically orders of magnitude slower than relaxational kinetics, chemically activated intermediates raise the issue of inseparable chemical and relaxational kinetics. Here, this separation problem is discussed in the framework of master equation simulations, proposing three cases often encountered in chemistry: insignificant chemical activation, predominant chemical activation, and the transition between these two limits. These three cases are illustrated via three example systems: methoxy (CH3Ȯ), diazenyl (ṄNH), and methyl formate radicals (CH3OĊO). For diazenyl, it is found that hot β-scission fully replaces the sequence of hydrogen abstraction and β-scission of thermally equilibrated diazenyl. Building on the example systems, a rule of thumb is proposed that can be used to intuitively judge the significance of hot β-scission: if the reverse hydrogen abstraction barrier height is comparable to or larger than the β-scission barrier height, hot β-scission should be considered in more detail.

  5. Two-phase flow in a chemically active porous medium

    SciTech Connect

    Darmon, Alexandre Dauchot, Olivier; Benzaquen, Michael; Salez, Thomas

    2014-12-28

    We study the problem of the transformation of a given reactant species into an immiscible product species, as they flow through a chemically active porous medium. We derive the equation governing the evolution of the volume fraction of the species, in a one-dimensional macroscopic description, identify the relevant dimensionless numbers, and provide simple models for capillary pressure and relative permeabilities, which are quantities of crucial importance when tackling multiphase flows in porous media. We set the domain of validity of our models and discuss the importance of viscous coupling terms in the extended Darcy’s law. We investigate numerically the steady regime and demonstrate that the spatial transformation rate of the species along the reactor is non-monotonous, as testified by the existence of an inflection point in the volume fraction profiles. We obtain the scaling of the location of this inflection point with the dimensionless lengths of the problem. Eventually, we provide key elements for optimization of the reactor.

  6. Thymus mastichina: chemical constituents and their anti-cancer activity.

    PubMed

    Gordo, Joana; Máximo, Patrícia; Cabrita, Eurico; Lourenço, Ana; Oliva, Abel; Almeida, Joana; Filipe, Mariana; Cruz, Pedro; Barcia, Rita; Santos, Miguel; Cruz, Helder

    2012-11-01

    The cytotoxicity-guided study of the dichloromethane and ethanol extracts of Thymus mastichina L. using the HCT colon cancer cell line allowed the identification of nine compounds, sakuranetin (1), sterubin (2), oleanolic acid (3), ursolic acid (4), lutein (5), beta-sitosterol (6), rosmarinic acid (7), 6-hydroxyluteolin-7-O-beta-glucopyranoside (8), and 6-hydroxyapigenin-7-O-beta-glucopyranoside (9). All compounds were tested for their cytotoxicity against the HCT colon cancer cell line. Compound 4 showed cytotoxicity with GI50 value of 6.8 microg/mL. A fraction composed of a mixture (1:1) of triterpenoid acids 3 and 4 displayed improved cytotoxicity with a GI50 of 2.8 microg/mL suggesting a synergistic behavior. This is the first report on the chemical constituents of Thymus mastichina L. based on structural assignments by spectroscopic analysis. The presence of these constituents identified by colon cancer cytotoxicity-guided activity indicates that extracts of T. mastichina L. may have a protective effect against colon cancers.

  7. Adsorption of copper cyanide on chemically active adsorbents

    SciTech Connect

    Lee, J.S.; Deorkar, N.V.; Tavlarides, L.L.

    1998-07-01

    An inorganic chemically active adsorbent (ICAA), SG(1)-TEPA (tetraethylenepentaamine)-propyl, is developed for removal, recovery, and recycling of copper cyanide from industrial waste streams. Equilibrium studies are executed to determine and model adsorption of the copper cyanide complex from aqueous solutions in a batch and packed column. It appears that adsorption is dependent on anionic copper cyanide species and the basicity of the ligand. Aqueous-phase equilibrium modeling shows that monovalent (Cu(CN){sub 2}{sup {minus}}), divalent (Cu(CN){sub 3}{sup 2{minus}}), and trivalent (Cu(CN){sub 4}{sup 3{minus}}) species of copper cyanide exist in the solution, depending on the pH and the concentration of total cyanide ions. Batch adsorption data are modeled using a modified multicomponent Langmuir isotherm which includes aqueous-phase speciation and basicity of the SG(1)-TEPA-propyl. This developed model is applied with a mass balance equation to describe the adsorption of copper cyanide complexes in a packed column.

  8. Chemical and thermal modulation of molecular motor activities

    NASA Astrophysics Data System (ADS)

    Hong, Weili

    Molecular motors of kinesin and dynein families are responsible for various intracellular activities, from long distance movement of organelles, vesicles, protein complexes, and mRNAs to powering mitotic processes. They can take nanometer steps using chemical energy from the hydrolysis of ATP (adenosine triphosphate), and their dysfunction is involved in many neurodegenerative diseases that require long distance transport of cargos. Here I report on the study of the properties of molecular motors at a single-molecule level using optical trappings. I first studied the inhibition properties of kinesin motors by marine natural compound adociasulfates. I showed that adociasulfates compete with microtubules for binding to kinesins and thus inhibit kinesins' activity. Although adociasulfates are a strong inhibitor for all kinesin members, they show a much higher inhibition effect for conventional kinesins than for mitotic kinesins. Thus adociasulfates can be used to specifically inhibit conventional kinesins. By comparing the inhibition of kinesins by two structurally similar adociasulfates, one can see that the negatively charged sulfate residue of adociasulfates can be replaced by other negative residues and thus make it possible for adociasulfate-derived compounds to be more cell permeable. Kinesins and dyneins move cargos towards opposite directions along a microtubule. Cargos with both kinesins and dyneins attached often move bidirectionally due to undergoing a tug-of-war between the oppositely moving kinesin and dynein motors. Here I studied the effect of temperature on microtubule-based kinesin and dynein motor transport. While kinesins' and dyneins' velocities are closely matched above 15 °C, below this temperature the dyneins' velocity decreases much faster than the kinesins'. The kinesins' and dyneins' forces do not measurably change with temperature. The results suggest that temperature has significant effects on bidirectional transport and can be used to

  9. Heat-activated Plasmonic Chemical Sensors for Harsh Environments

    SciTech Connect

    Carpenter, Michael; Oh, Sang-Hyun

    2015-12-01

    A passive plasmonics based chemical sensing system to be used in harsh operating environments was investigated and developed within this program. The initial proposed technology was based on combining technologies developed at the SUNY Polytechnic Institute Colleges of Nanoscale Science and Engineering (CNSE) and at the University of Minnesota (UM). Specifically, a passive wireless technique developed at UM was to utilize a heat-activated plasmonic design to passively harvest the thermal energy from within a combustion emission stream and convert this into a narrowly focused light source. This plasmonic device was based on a bullseye design patterned into a gold film using focused ion beam methods (FIB). Critical to the design was the use of thermal stabilizing under and overlayers surrounding the gold film. These stabilizing layers were based on both atomic layer deposited films as well as metal laminate layers developed by United Technologies Aerospace Systems (UTAS). While the bullseye design was never able to be thermally stabilized for operating temperatures of 500oC or higher, an alternative energy harvesting design was developed by CNSE within this program. With this new development, plasmonic sensing results are presented where thermal energy is harvested using lithographically patterned Au nanorods, replacing the need for an external incident light source. Gas sensing results using the harvested thermal energy are in good agreement with sensing experiments, which used an external incident light source. Principal Component Analysis (PCA) was used to reduce the wavelength parameter space from 665 variables down to 4 variables with similar levels of demonstrated selectivity. The method was further improved by patterning rods which harvested energy in the near infrared, which led to a factor of 10 decrease in data acquisition times as well as demonstrated selectivity with a reduced wavelength data set. The combination of a plasmonic-based energy harvesting

  10. The Influence of Chemical Chaperones on Enzymatic Activity under Thermal and Chemical Stresses: Common Features and Variation among Diverse Chemical Families

    PubMed Central

    Feibish, Nir; Sharon, Noa; Schnaider, Lee; Shmul, Guy; Amir, Yaniv; Buzhansky, Ludmila; Gazit, Ehud

    2014-01-01

    Molecular and chemical chaperones are key components of the two main mechanisms that ensure structural stability and activity under environmental stresses. Yet, chemical chaperones are often regarded only as osmolytes and their role beyond osmotic regulation is not fully understood. Here, we systematically studied a large group of chemical chaperones, representatives of diverse chemical families, for their protective influence under either thermal or chemical stresses. Consistent with previous studies, we observed that in spite of the structural similarity between sugars and sugar alcohols, they have an apparent difference in their protective potential. Our results support the notion that the protective activity is mediated by the solvent and the presence of water is essential. In the current work we revealed that i) polyols and sugars have a completely different profile of protective activity toward trifluoroethanol and thermal stress; ii) minor changes in solvent composition that do not affect enzyme activity, yet have a great effect on the ability of osmolytes to act as protectants and iii) increasing the number of active groups of carbohydrates makes them better protectants while increasing the number of active groups of methylamines does not, as revealed by attempts to synthesize de novo designed methylamines with multiple functional groups. PMID:24520396

  11. The influence of chemical chaperones on enzymatic activity under thermal and chemical stresses: common features and variation among diverse chemical families.

    PubMed

    Levy-Sakin, Michal; Berger, Or; Feibish, Nir; Sharon, Noa; Schnaider, Lee; Shmul, Guy; Amir, Yaniv; Buzhansky, Ludmila; Gazit, Ehud

    2014-01-01

    Molecular and chemical chaperones are key components of the two main mechanisms that ensure structural stability and activity under environmental stresses. Yet, chemical chaperones are often regarded only as osmolytes and their role beyond osmotic regulation is not fully understood. Here, we systematically studied a large group of chemical chaperones, representatives of diverse chemical families, for their protective influence under either thermal or chemical stresses. Consistent with previous studies, we observed that in spite of the structural similarity between sugars and sugar alcohols, they have an apparent difference in their protective potential. Our results support the notion that the protective activity is mediated by the solvent and the presence of water is essential. In the current work we revealed that i) polyols and sugars have a completely different profile of protective activity toward trifluoroethanol and thermal stress; ii) minor changes in solvent composition that do not affect enzyme activity, yet have a great effect on the ability of osmolytes to act as protectants and iii) increasing the number of active groups of carbohydrates makes them better protectants while increasing the number of active groups of methylamines does not, as revealed by attempts to synthesize de novo designed methylamines with multiple functional groups.

  12. Phthalides: Distribution in Nature, Chemical Reactivity, Synthesis, and Biological Activity.

    PubMed

    León, Alejandra; Del-Ángel, Mayela; Ávila, José Luis; Delgado, Guillermo

    2017-01-01

    oxidation, reduction, addition, elimination, and cycloaddition reactions, and treatments with Lewis acids of (Z)-ligustilide have afforded linear dimers. Some intramolecular condensations and differentiated cyclizations of the dimeric phthalides have been carried out, providing evidences for the particular chemical reactivity of these compounds.Several structural modifications of phthalides have been carried out subjecting them to microbial transformations by different species of bacteria, fungi and algae, and these included resolutions of racemic mixtures and oxidations, among others.The [π4s + π2s] and [π2s + π2s] cycloadditions of (Z)-ligustilide for the synthesis of dimeric phthalides have been reported, and different approaches involving cyclizations, Alder-Rickert reactions, Sharpless asymmetric hydroxylations, or Grignard additions have been used for the synthesis of monomeric phthalides. The use of phthalides as building blocks for divergent oriented synthesis has been proven.Many of the naturally occurring phthalides display different biological activities including antibacterial, antifungal, insecticidal, cytotoxic, and anti-inflammatory effects, among many others, with a considerable recent research on the topic. In the case of compounds isolated from the Apiaceae, the bioactivities correlate with the traditional medicinal uses of the natural sources. Some monomeric phthalides have shown their ability to attenuate certain neurological diseases, including stroke, Alzheimer's and Parkinson's diseases.The present contribution covers the distribution of phthalides in nature and the findings in the structural diversity, chemical reactivity, biotransformations, syntheses, and bioactivity of natural and semisynthetic phthalides.

  13. Synergistic activation of estrogen receptor with combinations of environmental chemicals

    SciTech Connect

    Arnold, S.F.; Klotz, D.M.; Collins, B.M.

    1996-06-07

    Certain chemicals in the environment are estrogenic. The low potencies of the compounds, when studied singly, suggest that they may have little effect on biological systems. The estrogenic potencies of combinations of such chemicals were screened in a simple yeast estrogen potencies of combination of such chemicals were screened in a simple yeast estrogen systems (YES) containing human estrogen receptor (hER). Combinations of two weak environmental estrogens, such as dieldrin, endosulfan, or toxaphene, were 100 times as potent in hER-mediated transactivation as any chemical alone. Hydroxylated polychlorinated biphenyls shown previously to synergistically alter sexual development in turtles also synergized in the YES. The synergistic interaction of chemical mixtures with the estrogen receptor may have profound environmental implications. These results may represent a previously uncharacterized level of regulation of estrogen-associated responses. 32 refs., 3 figs., 3 tabs.

  14. Use of hydrogen peroxide vapour & plasma irradiation in combination for quick decontamination of closed chambers

    PubMed Central

    Mourya, Devendra T.; Shahani, Hamish C.; Yadav, Pragya D.; Barde, Pradip V.

    2016-01-01

    Background & objectives: Various conventional methods such as gaseous, vapour and misting systems, fogging, manual spray and wipe techniques employing a number of chemical agents are used for decontamination of enclosed spaces. Among all these methods, use of aerosolized formaldehyde is the most preferred method due to cost-effectiveness and practical aspects. However, being extremely corrosive in nature generating very irritating fumes and difficulty in maintaining a high level of gas concentration, many laboratories prefer the vaporization of hydrogen peroxide (H2O2) as an alternative. We present here the results of using H2O2 vapour in combination with plasma irradiation for quick decontamination of closed chambers. Methods: The present study describes a decontamination method, using plasma irradiation in combination with H2O2 (5%). Effect of plasma irradiation and H2O2 on the viability of bacterial spores (Bacillus subtilis), Chikungunya and Kyasanur Forest Disease viruses was assessed. Results: Data suggest that with the combination of H2O2 vapour and plasma irradiation, within short time (three minutes), decontamination of surfaces and space volume could be achieved. Although it showed damage of spores present on the strips, it did not show any penetration power. Interpretation & conclusions: The results were encouraging, and this method was found to be efficient for achieving surface sterilization in a short time. This application may be useful in laboratories and industries particularly, those working on clean facility concept following good laboratory and manufacturing practices. PMID:27934804

  15. Advanced deposition model for thermal activated chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Cai, Dang

    Thermal Activated Chemical Vapor Deposition (TACVD) is defined as the formation of a stable solid product on a heated substrate surface from chemical reactions and/or dissociation of gaseous reactants in an activated environment. It has become an essential process for producing solid film, bulk material, coating, fibers, powders and monolithic components. Global market of CVD products has reached multi billions dollars for each year. In the recent years CVD process has been extensively used to manufacture semiconductors and other electronic components such as polysilicon, AlN and GaN. Extensive research effort has been directed to improve deposition quality and throughput. To obtain fast and high quality deposition, operational conditions such as temperature, pressure, fluid velocity and species concentration and geometry conditions such as source-substrate distance need to be well controlled in a CVD system. This thesis will focus on design of CVD processes through understanding the transport and reaction phenomena in the growth reactor. Since the in situ monitor is almost impossible for CVD reactor, many industrial resources have been expended to determine the optimum design by semi-empirical methods and trial-and-error procedures. This approach has allowed the achievement of improvements in the deposition sequence, but begins to show its limitations, as this method cannot always fulfill the more and more stringent specifications of the industry. To resolve this problem, numerical simulation is widely used in studying the growth techniques. The difficulty of numerical simulation of TACVD crystal growth process lies in the simulation of gas phase and surface reactions, especially the latter one, due to the fact that very limited kinetic information is available in the open literature. In this thesis, an advanced deposition model was developed to study the multi-component fluid flow, homogeneous gas phase reactions inside the reactor chamber, heterogeneous surface

  16. Combined Chemical Activation and Fenton Degradation to Convert Waste Polyethylene into High-Value Fine Chemicals.

    PubMed

    Chow, Cheuk-Fai; Wong, Wing-Leung; Ho, Keith Yat-Fung; Chan, Chung-Sum; Gong, Cheng-Bin

    2016-07-04

    Plastic waste is a valuable organic resource. However, proper technologies to recover usable materials from plastic are still very rare. Although the conversion/cracking/degradation of certain plastics into chemicals has drawn much attention, effective and selective cracking of the major waste plastic polyethylene is extremely difficult, with degradation of C-C/C-H bonds identified as the bottleneck. Pyrolysis, for example, is a nonselective degradation method used to crack plastics, but it requires a very high energy input. To solve the current plastic pollution crisis, more effective technologies are needed for converting plastic waste into useful substances that can be fed into the energy cycle or used to produce fine chemicals for industry. In this study, we demonstrate a new and effective chemical approach by using the Fenton reaction to convert polyethylene plastic waste into carboxylic acids under ambient conditions. Understanding the fundamentals of this new chemical process provides a possible protocol to solve global plastic-waste problems.

  17. Active targeting in a random porous medium by chemical swarm robots with secondary chemical signaling

    NASA Astrophysics Data System (ADS)

    Grančič, Peter; Štěpánek, František

    2011-08-01

    The multibody dynamics of a system of chemical swarm robots in a porous environment is investigated. The chemical swarm robots are modeled as Brownian particles capable of delivering an encapsulated chemical payload toward a given target location and releasing it in response to an external stimulus. The presence of chemical signals (chemo-attractant) in the system plays a crucial role in coordinating the collective movement of the particles via chemotaxis. For a number of applications, such as distributed chemical processing and targeted drug delivery, the understanding of factors that govern the collective behavior of the particles, especially their ability to localize a given target, is of immense importance. A hybrid modeling methodology based on the combination of the Brownian dynamics method and diffusion problem coupled through the chemotaxis phenomena is used to analyze the impact of a varying signaling threshold and the strength of chemotaxis on the ability of the chemical robots to fulfill their target localization mission. The results demonstrate that the selected performance criteria (the localization half time and the success rate) can be improved when an appropriate signaling process is chosen. Furthermore, for an optimum target localization strategy, the topological complexity of the porous environment needs to be reflected.

  18. Stand-off detection of alcohol vapours in moving cars

    NASA Astrophysics Data System (ADS)

    Kopczyński, Krzysztof; Kubicki, Jan; Młyńczak, Jaroslaw; Mierczyk, Jadwiga; Hackiewicz, Klaudia

    2016-12-01

    In this article we present the research on optoelectronic system for stand-off detection of alcohol vapours in moving cars. The idea of using commercially available cascade lasers was presented. Special attention was paid to the optical characteristics of the car windowpanes. It was shown that using 3.45 μm and 3.59 μm wavelengths the alcohol vapours inside a car can be successfully detected even for cars with different windows

  19. Chemical properties and toxicity of soils contaminated by mining activity.

    PubMed

    Agnieszka, Baran; Tomasz, Czech; Jerzy, Wieczorek

    2014-09-01

    This research is aimed at assessing the total content and soluble forms of metals (zinc, lead and cadmium) and toxicity of soils subjected to strong human pressure associated with mining of zinc and lead ores. The research area lay in the neighbourhood of the Bolesław Mine and Metallurgical Plant in Bukowno (Poland). The study obtained total cadmium concentration between 0.29 and 51.91 mg, zinc between 7.90 and 3,614 mg, and that of lead between 28.4 and 6844 mg kg(-1) of soil d.m. The solubility of the heavy metals in 1 mol dm(-3) NH4NO3 was 1-49% for zinc, 5-45% for cadmium, and <1-10% for lead. In 1 mol HCl dm(-3), the solubility of the studied metals was much higher and obtained values depending on the collection site, from 45 to 92% for zinc, from 74 to 99%, and from 79 to 99% for lead. The lower solubility of the heavy metals in 1 mol dm(-3) NH4NO3 than 1 mol HCl dm(-3) is connected with that, the ammonium nitrate has low extraction power, and it is used in determining the bioavailable (active) form of heavy metals. Toxicity assessment of the soil samples was performed using two tests, Phytotoxkit and Microtox(®). Germination index values were between 22 and 75% for Sinapis alba, between 28 and 100% for Lepidium sativum, and between 10 and 28% for Sorghum saccharatum. Depending on the studied soil sample, Vibrio fischeri luminescence inhibition was 20-96%. The sensitivity of the test organisms formed the following series: S. saccharatum > S. alba = V. fischeri > L. sativum. Significant positive correlations (p ≤ 0.05) of the total and soluble contents of the metals with luminescence inhibition in V. fischeri and root growth inhibition in S. saccharatum were found. The general trend observed was an increase in metal toxicity measured by the biotest with increasing available metal contents in soils. All the soil samples were classified into toxicity class III, which means that they are toxic and present severe danger. Biotest are a good complement to

  20. The screening of chemicals for juvenoid-related endocrine activity using the water flea Daphnia magna.

    PubMed

    Wang, Helen Ying; Olmstead, Allen W; Li, Hong; Leblanc, Gerald A

    2005-09-10

    U.S. Environmental Protection Agency is charged with developing a screening and testing paradigm for detecting endocrine toxicity of chemicals that are subject to regulation under the Food Quality Protection and the Safe Drinking Water Acts. In this study, we developed and evaluated a screening assay that could be employed to detect juvenoid-related endocrine-modulating activity in an invertebrate species. Juvenoid activity, anti-juvenoid activity, and juvenoid potentiator activity of chemicals was assessed using the water flea Daphnia magna. Male sex determination is under the regulatory control of juvenoid hormone, presumably methyl farnesoate, and this endpoint was used to detect juvenoid modulating activity of chemicals. Eighteen chemicals were evaluated for juvenoid agonist activity. Positive responses were detected with the juvenoid hormones methyl farnesoate and juvenile hormone III along with the insect growth regulating insecticides pyriproxyfen, fenoxycarb, and methoprene. Weak juvenoid activity also was detected with the cyclodiene insecticide dieldrin. Assays performed repetitively with compounds that gave either strong positive, weak positive, or negative response were 100% consistent indicating that the assay is not prone to false positive or negative responses. Five candidate chemicals were evaluated for anti-juvenoid activity and none registered positive. Four chemicals (all trans-retinoic acid, methoprene, kinoprene, bisphenol A) also were evaluated for their ability to potentiate the activity of methyl farnesoate. All registered positive. Results demonstrate that an in vivo assay with a crustacean species customarily employed in toxicity testing can be used to effectively screen chemicals for juvenoid-modulating activity.

  1. A new approach to the water vapour feedback

    NASA Astrophysics Data System (ADS)

    Ingram, W.

    2012-12-01

    Climate sensitivity is often said to be doubled by water vapour feedback. From simple physical arguments, confirmed by GCMs, and consistent with the limited observational evidence, we expect the distribution of RH to change little under climate change. This implies a substantial positive feedback on climate change - but why about a doubling? And why is this value so robust even to major modelling errors and approximations? And why do GCMs never give a run-away water vapour greenhouse effect, plausible though extrapolation can make it seem? Considering the "paradox" of Simpson (1928) leads to a simple model that explains all these. The "partly-Simpsonian" model for the water vapour feedback on climate change implies a very simple constraint - that the component of OLR radiated by water vapour does not change as climate changes, while that radiated by everything else (surface, clouds, CO2, etc.) increases following Planck's Law. This does not predict the actual non-cloud LW response λCSLW of GCMs quantitatively accurately, but gives the general size. It also explains why a run-away water vapour greenhouse effect is not possible in Earth-like conditions: the partly-Simpsonian water vapour feedback can do no more than cancel part of the basic Planck's-Law negative feedback - less than 100% as long as some OLR is not from water vapour. The robustness of the GCMs' water vapour feedbacks, even if they simulate the water vapour distribution very badly, also follows: the fraction of emission by water vapour is both innately computationally robust (even large errors in water vapour amounts can only affect those limited parts of the spectrum of intermediate optical depth: most of the spectrum will be effectively opaque or effectively transparent at any given location), and closely related to the surface downward LW flux, which is verifiable and tunable. In addition, the partly-Simpsonian model provides a physical explanation for the long-known fact that LW radiances or OLR

  2. LIMITED-USE CHEMICAL PROTECTIVE CLOTHING FOR EPA SUPERFUND ACTIVITIES

    EPA Science Inventory

    Because contractor field personnel complained about the poor durability and fit of limited-use chemical protective clothing (CPC) most commonly used at hazardous waste site operations, the U.S. Environmental Protection Agency (EPA) initiated a study to • characterize use of CPC...

  3. Adsorption studies of methylene blue and phenol onto vetiver roots activated carbon prepared by chemical activation.

    PubMed

    Altenor, Sandro; Carene, Betty; Emmanuel, Evens; Lambert, Jacques; Ehrhardt, Jean-Jacques; Gaspard, Sarra

    2009-06-15

    Vetiver roots have been utilized for the preparation of activated carbon (AC) by chemical activation with different impregnation ratios of phosphoric acid, X(P) (gH(3)PO(4)/g precursor): 0.5:1; 1:1 and 1.5:1. Textural characterization, determined by nitrogen adsorption at 77K shows that mixed microporous and mesoporous structures activated carbons (ACs) with high surface area (>1000 m(2)/g) and high pore volume (up to 1.19 cm(3)/g) can be obtained. The surface chemical properties of these ACs were investigated by X-ray photoelectron spectroscopy (XPS) and Boehm titration. Their textural and chemical characteristics were compared to those of an AC sample obtained by steam activation of vetiver roots. Classical molecules used for characterizing liquid phase adsorption, phenol and methylene blue (MB), were used. Adsorption kinetics of MB and phenol have been studied using commonly used kinetic models, i.e., the pseudo-first-order model, the pseudo-second-order model, the intraparticle diffusion model and as well the fractal, BWS (Brouers, Weron and Sotolongo) kinetic equation. The correlation coefficients (R(2)) and the normalized standard deviation Deltaq (%) were determined showing globally, that the recently derived fractal kinetic equation could best describe the adsorption kinetics for the adsorbates tested here, indicating a complex adsorption mechanism. The experimental adsorption isotherms of these molecules on the activated carbon were as well analysed using four isotherms: the classical Freundlich, Langmuir, Redlich-Peterson equations, but as well the newly published deformed Weibull Brouers-Sotolongo isotherm. The results obtained from the application of the equations show that the best fits were achieved with the Brouers-Sotolongo equation and with the Redlich-Peterson equation. Influence of surface functional groups towards MB adsorption is as well studied using various ACs prepared from vetiver roots and sugar cane bagasse. Opposite effects governing MB

  4. Explicit modelling of SOA formation from α-pinene photooxidation: sensitivity to vapour pressure estimation

    NASA Astrophysics Data System (ADS)

    Valorso, R.; Aumont, B.; Camredon, M.; Raventos-Duran, T.; Mouchel-Vallon, C.; Ng, N. L.; Seinfeld, J. H.; Lee-Taylor, J.; Madronich, S.

    2011-07-01

    The sensitivity of the formation of secondary organic aerosol (SOA) to the estimated vapour pressures of the condensable oxidation products is explored. A highly detailed reaction scheme was generated for α-pinene photooxidation using the Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A). Vapour pressures (Pvap) were estimated with three commonly used structure activity relationships. The values of Pvap were compared for the set of secondary species generated by GECKO-A to describe α-pinene oxidation. Discrepancies in the predicted vapour pressures were found to increase with the number of functional groups borne by the species. For semi-volatile organic compounds (i.e. organic species of interest for SOA formation), differences in the predicted Pvap range between a factor of 5 to 200 on average. The simulated SOA concentrations were compared to SOA observations in the Caltech chamber during three experiments performed under a range of NOx conditions. While the model captures the qualitative features of SOA formation for the chamber experiments, SOA concentrations are systematically overestimated. For the conditions simulated, the modelled SOA speciation appears to be rather insensitive to the Pvap estimation method.

  5. Explicit modelling of SOA formation from α-pinene photooxidation: sensitivity to vapour pressure estimation

    NASA Astrophysics Data System (ADS)

    Valorso, R.; Aumont, B.; Camredon, M.; Raventos-Duran, T.; Mouchel-Vallon, C.; Ng, N. L.; Seinfeld, J. H.; Lee-Taylor, J.; Madronich, S.

    2011-03-01

    The sensitivity of the formation of secondary organic aerosol (SOA) to the estimated vapour pressures of the condensable oxidation products is explored. A highly detailed reaction scheme was generated for α-pinene photooxidation using the Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A). Vapour pressures (Pvap) were estimated with three commonly used structure activity relationships. The values of Pvap were compared for the set of secondary species generated by GECKO-A to describe α-pinene oxidation. Discrepancies in the predicted vapour pressures were found to increase with the number of functional groups borne by the species. For semi-volatile organic compounds (i.e. organic species of interest for SOA formation), differences in the predicted Pvap range between a factor of 5 to 200 in average. The simulated SOA concentrations were compared to SOA observations in the Caltech chamber during three experiments performed under a range of NOx conditions. While the model captures the qualitative features of SOA formation for the chamber experiments, SOA concentrations are systematically overestimated. For the conditions simulated, the modelled SOA speciation appears to be rather insensitive to the Pvap estimation method.

  6. New H2SO4 and HSO3 vapour measurements in the stratosphere - Evidence for a volcanic influence

    NASA Astrophysics Data System (ADS)

    Arnold, F.; Buehrke, T.

    1983-01-01

    In situ measurements of stratospheric H2SO4 and HSO3 vapour concentrations using passive chemical ionization mass spectrometry were made in 1982 before and after the dramatic eruptions of the Mexican volcano El Chichon. Substantial increases of the total concentration of these gases over previously measured values were observed, particularly around 25 km altitude where most of the eruption cloud material was deposited. Implications for stratospheric SO2-oxidation and nucleation processes are discussed.

  7. RESEARCH NOTE WCA repulsive and attractive contributions to the thermodynamic properties at the vapour-liquid equilibrium

    NASA Astrophysics Data System (ADS)

    Cuadros, F.; Mulero, A.; Faundez, C. A.

    The Lennard-Jones attractive and repulsive contributions of intermolecular forces (as separated in the Weeks-Chandler-Andersen (WCA) theory) to the pressure and chemical potential of coexisting vapour and liquid phases are obtained by using an equation of state recently proposed by us. Some comments are given about the computer simulation results obtained by Plackov and Sadus (1997, Fluid Phase Equilib., 134, 77) using the McQuarrie-Katz separation of the intermolecular potential.

  8. Physico-chemical characterization of atmospheric aerosols in a rural area affected by the Aznalcollar toxic spill, south-west Spain during the soil reclamation activities.

    PubMed

    Querol, X; Alastuey, A; Lopez-Soler, A; Plana, F; Mesas, A; Ortiz, L; Alzaga, R; Bayona, J M; de la Rosa, J

    1999-12-06

    High levels of atmospheric contamination due to the re-suspension of pyrite particles from the mining waste slurry were recorded in the Guadiamar valley (the Guadiamar is a tributary of the Guadalquivir river) after the toxic spill of Aznalcóllar, north of the Doñana Natural Park (SW Spain). Major high-particulate events occurred during the extraction of the pyrite-rich mud layer, which covered an extensive area of the valley downstream of the confluence of the Agrio and Guadiamar rivers. This study deals with the monitoring of the ambient air quality at two stations near the village of Aznalcázar in the central part of the flooded area. Although the Spanish legal limit for atmospheric particles and lead in environmental air were not exceeded, high daily levels of total suspended particles (TSP) and of some elements with an environmental significance (As, Cd, Cu, Mn, Ni, Pb, Sn, Tl and Zn) were recorded at Aznalcázar and in the Guadiamar valley during soil reclamation (July-August 1998). Despite a progressive decrease in TSP levels through September-October 1998, background was higher than the levels for the May-June period. Evolution of levels for most of the elements studied showed a similar trend. The exceptions were copper, which was partially increased by other emission sources such as fumigation activities, and sodium, which remained at relatively constant levels during the study period because of its marine origin. The physico-chemical characterisation of the atmospheric particulates allowed us to determine the major grain size modes of the pyrite related elements and the solubility of the potentially toxic elements, and to identify the major particulate types present in the atmosphere in the area. Secondary and tertiary aromatic amines (i.e. alkyldiphenylamines and phenylcarbazoles, respectively) were identified in the suspended particles and in the vapour phase collected at the same station as the TSP samples. As some of these aromatic amines had been

  9. Nanofluidic transport governed by the liquid/vapour interface.

    PubMed

    Lee, Jongho; Laoui, Tahar; Karnik, Rohit

    2014-04-01

    Liquid/vapour interfaces govern the behaviour of a wide range of systems but remain poorly understood, leaving ample margin for the exploitation of intriguing functionalities for applications. Here, we systematically investigate the role of liquid/vapour interfaces in the transport of water across apposing liquid menisci in osmosis membranes comprising short hydrophobic nanopores that separate two fluid reservoirs. We show experimentally that mass transport is limited by molecular reflection from the liquid/vapour interface below a certain length scale, which depends on the transmission probability of water molecules across the nanopores and on the condensation probability of a water molecule incident on the liquid surface. This fundamental yet elusive condensation property of water is measured under near-equilibrium conditions and found to decrease from 0.36 ± 0.21 at 30 °C to 0.18 ± 0.09 at 60 °C. These findings define the regime in which liquid/vapour interfaces govern nanofluidic transport and have implications for understanding mass transport in nanofluidic devices, droplets and bubbles, biological components and porous media involving liquid/vapour interfaces.

  10. Oncogene activation in spontaneous and chemically induced rodent tumors: implications for risk analysis

    SciTech Connect

    Reynolds, S.H.; Stowers, S.J.; Patterson, R.M.; Maronpot, R.R.; Anderson, M.W.

    1988-06-01

    The validity of rodent tumor end points in assessing the potential hazards of chemical exposure to humans is a somewhat controversial but very important issue since most chemicals are classified as potentially hazardous to humans on the basis of long-term carcinogenesis studies in rodents. The ability to distinguish between genotoxic, cytotoxic, or receptor-mediated promotion effects of chemical treatment would aid in the interpretation of rodent carcinogenesis data. Activated oncogenes in spontaneously occurring and chemically induced rodent tumors were examined and compared as one approach to determine the mechanism by which chemical treatment caused an increased incidence of rodent tumors. Different patterns of activated oncogenes were found not only in spontaneous versus chemically induced mouse liver tumors but also in a variety of spontaneous rat tumors versus chemically induced rat lung tumors. In the absence of cytotoxic effects, it could be argued that the chemicals in question activated protooncogenes by a direct genotoxic mechanism. These results provided a basis for the analysis of activated oncogenes in spontaneous and chemically induced rodent tumors to provide information at a molecular level to aid in the extrapolation of rodent carcinogenesis data to human risk assessment.

  11. Chemical modification of capuramycins to enhance antibacterial activity

    PubMed Central

    Bogatcheva, Elena; Dubuisson, Tia; Protopopova, Marina; Einck, Leo; Nacy, Carol A.; Reddy, Venkata M.

    2011-01-01

    Objectives To extend capuramycin spectrum of activity beyond mycobacteria and improve intracellular drug activity. Methods Three capuramycin analogues (SQ997, SQ922 and SQ641) were conjugated with different natural and unnatural amino acids or decanoic acid (DEC) through an ester bond at one or more available hydroxyl groups. In vitro activity of the modified compounds was determined against Mycobacterium spp. and representative Gram-positive and Gram-negative bacteria. Intracellular activity was evaluated in J774A.1 mouse macrophages infected with Mycobacterium tuberculosis (H37Rv). Results Acylation of SQ997 and SQ641 with amino undecanoic acid (AUA) improved in vitro activity against most of the bacteria tested. Conjugation of SQ922 with DEC, but not AUA, improved its activity against Gram-positive bacteria. In the presence of efflux pump inhibitor phenylalanine arginine β-naphthyl amide, MICs of SQ997-AUA, SQ641-AUA and SQ922-DEC compounds improved even further against drug-susceptible and drug-resistant Staphylococcus aureus. In Gram-negative bacteria, EDTA-mediated permeabilization caused 4- to 16-fold enhancement of the activity of AUA-conjugated SQ997, SQ922 and SQ641. Conjugation of all three capuramycin analogues with AUA improved intracellular killing of H37Rv in murine macrophages. Conclusions Conjugation of capuramycin analogues with AUA or DEC enhanced in vitro activity, extended the spectrum of activity in Gram-positive bacteria and increased intracellular activity against H37Rv. PMID:21186194

  12. Chemical transformations on botryane skeleton. Effect on the cytotoxic activity.

    PubMed

    Reino, José L; Durán-Patrón, Rosa; Segura, Inmaculada; Hernández-Galán, Rosario; Riese, Hans H; Collado, Isidro G

    2003-03-01

    Eighteen compounds with a botryane skeleton have been obtained through chemical transformations of various toxins from the fungus Botrytis cinerea. During the course of these transformations, the C-10 carbon of the botryane skeleton was found to exhibit an interesting high regioselectivity to oxidizing and reducing agents. In addition, the cytotoxicity of 27 botryane derivatives was determined in vitro against Hs578T, MDA-MB-231, HT-1080, U87-MG, IMR-90, and HUVEC cell lines. The results of this study confirm that the cytotoxicity of botrydial (1) and its derivatives is related to the presence of a 1,5-dialdehyde functionality.

  13. Adsorption of n-alkane vapours at the water surface.

    PubMed

    Biscay, Frédéric; Ghoufi, Aziz; Malfreyt, Patrice

    2011-06-21

    Monte Carlo simulations are reported here to predict the surface tension of the liquid-vapour interface of water upon adsorption of alkane vapours (methane to hexane). A decrease of the surface tension has been established from n-pentane. A correlation has been evidenced between the decrease of the surface tension and the absence of specific arrangement at the water surface for n-pentane and n-hexane. The thermodynamic stability of the adsorption layer and the absence of film for longer alkanes have been checked through the calculation of a potential of mean force. This complements the work recently published [Ghoufi et al., Phys. Chem. Chem. Phys., 2010, 12, 5203] concerning the adsorption of methane at the water surface. The decrease of the surface tension has been interpreted in terms of the degree of hydrogen bonding of water molecules at the liquid-vapour interface upon adsorption.

  14. Vapour-liquid equilibrium in the krypton-xenon system

    NASA Astrophysics Data System (ADS)

    Calado, Jorge C. G.; Chang, Elaine; Streett, William B.

    1983-01-01

    Isothermal vapour-liquid data were measured for the krypton-xenon system at ten temperatures between 165 and 270 K and pressures to 6.7 MPa, using a vapour recirculating technique. The mixture critical line has been located in ( P, T, x) space. Barker's method of data reduction has been used to test the thermodynamic consistency of isotherms below the critical temperature of krypton (209.4 K) and the excess Gibbs energy was evaluated, at the same temperatures, as a function of composition. The results of the experiments have been compared with predictions of the Peng-Robinson equation of state. With interaction parameter calculated by fitting the isotherm of 200.64 K, this equation predicts the liquid and vapour phase compositions to within about a few mole per cent over most of the experimental range.

  15. CO2-fluxing collapses metal mobility in magmatic vapour

    DOE PAGES

    van Hinsberg, V. J.; Berlo, K.; Migdisov, A. A.; ...

    2016-05-18

    Magmatic systems host many types of ore deposits, including world-class deposits of copper and gold. Magmas are commonly an important source of metals and ore-forming fluids in these systems. In many magmatic-hydrothermal systems, low-density aqueous fluids, or vapours, are significant metal carriers. Such vapours are water-dominated shallowly, but fluxing of CO2-rich vapour exsolved from deeper magma is now recognised as ubiquitous during open-system magma degassing. Furthermore, we show that such CO2-fluxing leads to a sharp drop in element solubility, up to a factor of 10,000 for Cu, and thereby provides a highly efficient, but as yet unrecognised mechanism for metalmore » deposition.« less

  16. A Mechanical System for Dispensing Known Amounts of Insecticidal Vapours*

    PubMed Central

    Jensen, J. A.; Pearce, G. W.; Quarterman, K. D.

    1961-01-01

    The requirements for a self-contained semi-automatic insecticidal vapour dispenser for use in the disinsection of aircraft are presented. A prototype device meeting these requirements is described and data on its performance, using DDVP (O,O-dimethyl-2,2-dichlorovinyl phosphate) as the insecticide, are given. In this system a miniature air compressor forces air through a membrane impregnated with DDVP, and the vapour-laden air exits into the cabin through a tubular distribution system equipped with orifices. The vapour output is governed by the volume and the temperature of the air passing through the membrane, and the system is adaptable to all types of aircraft at present in use or projected for the near future. The system can also be adapted for use in the disinsection of other closed or semi-closed spaces. PMID:13789905

  17. Functional Imaging of Chemically Active Surfaces with Optical Reporter Microbeads

    PubMed Central

    Ahuja, Punkaj; Nair, Sumitha; Narayan, Sreenath; Gratzl, Miklós

    2015-01-01

    We have developed a novel approach to allow for continuous imaging of concentration fields that evolve at surfaces due to release, uptake, and mass transport of molecules, without significant interference of the concentration fields by the chemical imaging itself. The technique utilizes optical “reporter” microbeads immobilized in a thin layer of transparent and inert hydrogel on top of the surface. The hydrogel has minimal density and therefore diffusion in and across it is like in water. Imaging the immobilized microbeads over time provides quantitative concentration measurements at each location where an optical reporter resides. Using image analysis in post-processing these spatially discrete measurements can be transformed into contiguous maps of the dynamic concentration field across the entire surface. If the microbeads are small enough relative to the dimensions of the region of interest and sparsely applied then chemical imaging will not noticeably affect the evolution of concentration fields. In this work colorimetric optode microbeads a few micrometers in diameter were used to image surface concentration distributions on the millimeter scale. PMID:26332766

  18. Intercomparison of TCCON and MUSICA Water Vapour Products

    NASA Astrophysics Data System (ADS)

    Weaver, D.; Strong, K.; Deutscher, N. M.; Schneider, M.; Blumenstock, T.; Robinson, J.; Notholt, J.; Sherlock, V.; Griffith, D. W. T.; Barthlott, S.; García, O. E.; Smale, D.; Palm, M.; Jones, N. B.; Hase, F.; Kivi, R.; Ramos, Y. G.; Yoshimura, K.; Sepúlveda, E.; Gómez-Peláez, Á. J.; Gisi, M.; Kohlhepp, R.; Warneke, T.; Dohe, S.; Wiegele, A.; Christner, E.; Lejeune, B.; Demoulin, P.

    2014-12-01

    We present an intercomparison between the water vapour products from the Total Carbon Column Observing Network (TCCON) and the MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water (MUSICA), two datasets from ground-based Fourier Transform InfraRed (FTIR) spectrometers with good global representation. Where possible, comparisons to radiosondes are also included. The near-infrared TCCON measurements are optimized to provide precise monitoring of greenhouse gases for carbon cycle studies; however, TCCON's retrievals also produce water vapour products. The mid-infrared MUSICA products result from retrievals optimized to give precise and accurate information about H2O, HDO, and δD. The MUSICA water vapour products have been validated by extensive intercomparisons with H2O and δD in-situ measurements made from ground, radiosonde, and aircraft (Schneider et al. 2012, 2014), as well as by intercomparisons with satellite-based H2O and δD remote sensing measurements (Wiegele et al., 2014). This dataset provides a valuable reference point for other measurements of water vapour. This study is motivated by the limited intercomparisons performed for TCCON water vapour products and limited characterisation of their uncertainties. We compare MUSICA and TCCON products to assess the potential for TCCON measurements to contribute to studies of the water cycle, water vapour's role in climate and use as a tracer for atmospheric dynamics, and to evaluate the performance of climate models. The TCCON and MUSICA products result from measurements taken using the same FTIR instruments, enabling a comparison with constant instrumentation. The retrieval techniques differ, however, in their method and a priori information. We assess the impact of these differences and characterize the comparability of the TCCON and MUSICA datasets.

  19. Active Metamaterial Based Terahertz Polarimeter for Spectroscopic Detection of Chemical and Biological Hazards

    DTIC Science & Technology

    2014-04-01

    Active Metamaterial Based Terahertz Polarimeter for Spectroscopic Detection of Chemical and Biological Hazards by Grace D. Metcalfe ...for Spectroscopic Detection of Chemical and Biological Hazards Grace D. Metcalfe and Michael Wraback Sensors and Electron Devices Directorate, ARL...GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Grace D. Metcalfe , Michael Wraback, Richard D. Averitt, and Xin Zhang 5d. PROJECT NUMBER

  20. 15 CFR 712.2 - Restrictions on activities involving Schedule 1 chemicals.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 15 Commerce and Foreign Trade 2 2011-01-01 2011-01-01 false Restrictions on activities involving Schedule 1 chemicals. 712.2 Section 712.2 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL...

  1. HIGH-DIMENSIONAL PROFILING OF TRANSCRIPTION FACTOR ACTIVITY DIFFERENTIATES TOXCAST CHEMICAL GROUPS

    EPA Science Inventory

    The ToxCast™ project at the U.S. EPA uses a diverse battery of high throughput screening assays and informatics models to rapidly characterize the activity of chemicals. A central goal of the project is to provide empirical evidence to aid in the prioritization of chemicals for a...

  2. Hydrogeology, chemical and microbial activity measurement through deep permafrost

    SciTech Connect

    Stotler, R.L.; Frape, S.K.; Freifeld, B.M.; Holden, B.; Onstott, T.C.; Ruskeeniemi, T.; Chan, E.

    2010-04-01

    Little is known about hydrogeochemical conditions beneath thick permafrost, particularly in fractured crystalline rock, due to difficulty in accessing this environment. The purpose of this investigation was to develop methods to obtain physical, chemical, and microbial information about the subpermafrost environment from a surface-drilled borehole. Using a U-tube, gas and water samples were collected, along with temperature, pressure, and hydraulic conductivity measurements, 420 m below ground surface, within a 535 m long, angled borehole at High Lake, Nunavut, Canada, in an area with 460-m-thick permafrost. Piezometric head was well above the base of the permafrost, near land surface. Initial water samples were contaminated with drill fluid, with later samples <40% drill fluid. The salinity of the non-drill fluid component was <20,000 mg/L, had a Ca/Na ratio above 1, with {delta}{sup 18}O values {approx}5{per_thousand} lower than the local surface water. The fluid isotopic composition was affected by the permafrost-formation process. Nonbacteriogenic CH{sub 4} was present and the sample location was within methane hydrate stability field. Sampling lines froze before uncontaminated samples from the subpermafrost environment could be obtained, yet the available time to obtain water samples was extended compared to previous studies. Temperature measurements collected from a distributed temperature sensor indicated that this issue can be overcome easily in the future. The lack of methanogenic CH{sub 4} is consistent with the high sulfate concentrations observed in cores. The combined surface-drilled borehole/U-tube approach can provide a large amount of physical, chemical, and microbial data from the subpermafrost environment with few, controllable, sources of contamination.

  3. Hydrogeology, chemical and microbial activity measurement through deep permafrost.

    PubMed

    Stotler, Randy L; Frape, Shaun K; Freifeld, Barry M; Holden, Brian; Onstott, Tullis C; Ruskeeniemi, Timo; Chan, Eric

    2011-01-01

    Little is known about hydrogeochemical conditions beneath thick permafrost, particularly in fractured crystalline rock, due to difficulty in accessing this environment. The purpose of this investigation was to develop methods to obtain physical, chemical, and microbial information about the subpermafrost environment from a surface-drilled borehole. Using a U-tube, gas and water samples were collected, along with temperature, pressure, and hydraulic conductivity measurements, 420 m below ground surface, within a 535 m long, angled borehole at High Lake, Nunavut, Canada, in an area with 460-m-thick permafrost. Piezometric head was well above the base of the permafrost, near land surface. Initial water samples were contaminated with drill fluid, with later samples <40% drill fluid. The salinity of the non-drill fluid component was <20,000 mg/L, had a Ca/Na ratio above 1, with δ(18) O values ∼5‰ lower than the local surface water. The fluid isotopic composition was affected by the permafrost-formation process. Nonbacteriogenic CH(4) was present and the sample location was within methane hydrate stability field. Sampling lines froze before uncontaminated samples from the subpermafrost environment could be obtained, yet the available time to obtain water samples was extended compared to previous studies. Temperature measurements collected from a distributed temperature sensor indicated that this issue can be overcome easily in the future. The lack of methanogenic CH(4) is consistent with the high sulfate concentrations observed in cores. The combined surface-drilled borehole/U-tube approach can provide a large amount of physical, chemical, and microbial data from the subpermafrost environment with few, controllable, sources of contamination.

  4. Hydrogeology, Chemical and Microbial Activity Measurement Through Deep Permafrost

    USGS Publications Warehouse

    Stotler, R.L.; Frape, S.K.; Freifeld, B.M.; Holden, B.; Onstott, T.C.; Ruskeeniemi, T.; Chan, E.

    2011-01-01

    Little is known about hydrogeochemical conditions beneath thick permafrost, particularly in fractured crystalline rock, due to difficulty in accessing this environment. The purpose of this investigation was to develop methods to obtain physical, chemical, and microbial information about the subpermafrost environment from a surface-drilled borehole. Using a U-tube, gas and water samples were collected, along with temperature, pressure, and hydraulic conductivity measurements, 420 m below ground surface, within a 535 m long, angled borehole at High Lake, Nunavut, Canada, in an area with 460-m-thick permafrost. Piezometric head was well above the base of the permafrost, near land surface. Initial water samples were contaminated with drill fluid, with later samples <40% drill fluid. The salinity of the non-drill fluid component was <20,000 mg/L, had a Ca/Na ratio above 1, with ??18O values ???5??? lower than the local surface water. The fluid isotopic composition was affected by the permafrost-formation process. Nonbacteriogenic CH4 was present and the sample location was within methane hydrate stability field. Sampling lines froze before uncontaminated samples from the subpermafrost environment could be obtained, yet the available time to obtain water samples was extended compared to previous studies. Temperature measurements collected from a distributed temperature sensor indicated that this issue can be overcome easily in the future. The lack of methanogenic CH4 is consistent with the high sulfate concentrations observed in cores. The combined surface-drilled borehole/U-tube approach can provide a large amount of physical, chemical, and microbial data from the subpermafrost environment with few, controllable, sources of contamination. ?? 2010 The Author(s). Journal compilation ?? 2010 National Ground Water Association.

  5. Application of the Activity Framework for Assessing Aquatic Ecotoxicology Data for Organic Chemicals.

    PubMed

    Thomas, Paul; Dawick, James; Lampi, Mark; Lemaire, Philippe; Presow, Shaun; van Egmond, Roger; Arnot, Jon A; Mackay, Donald; Mayer, Philipp; Galay Burgos, Malyka

    2015-10-20

    Toxicological research in the 1930s gave the first indications of the link between narcotic toxicity and the chemical activity of organic chemicals. More recently, chemical activity has been proposed as a novel exposure parameter that describes the fraction of saturation and that quantifies the potential for partitioning and diffusive uptake. In the present study, more than 2000 acute and chronic algal, aquatic invertebrates and fish toxicity data, as well as water solubility and melting point values, were collected from a series of sources. The data were critically reviewed and grouped by mode of action (MoA). We considered 660 toxicity data to be of acceptable quality. The 328 data which applied to the 72 substances identified as MoA 1 were then evaluated within the activity-toxicity framework: EC50 and LC50 values for all three taxa correlated generally well with (subcooled) liquid solubilities. Acute toxicity was typically exerted within the chemical activity range of 0.01-0.1, whereas chronic toxicity was exerted in the range of 0.001-0.01. These results confirm that chemical activity has the potential to contribute to the determination, interpretation and prediction of toxicity to aquatic organisms. It also has the potential to enhance regulation of organic chemicals by linking results from laboratory tests, monitoring and modeling programs. The framework can provide an additional line of evidence for assessing aquatic toxicity, for improving the design of toxicity tests, reducing animal usage and addressing chemical mixtures.

  6. Quantum Chemical Studies on Stability and Chemical Activities in Calcium Ion Bound Calmodulin Loops.

    PubMed

    Sikdar, Samapan; Ghosh, Mahua; De Raychaudhury, Molly; Chakrabarti, J

    2015-11-19

    Quantum chemical (QC) calculations for macromolecules require truncation of the molecule, highlighting the portion of interest due to heavy computation cost. As a result, an estimation of the effects of truncation is important to interpret the energy spectrum of such calculations. We perform density functional theory based QC calculations on calcium ion bound EF-hand loops of Calmodulin isolated from the crystal structure in an implicit solvent. We find that the terminal contributions of neutral capping are negligible across the entire ground-state energy spectrum. The coordination energy range and the nature of hybridization of the coordination state molecular orbitals remain qualitatively similar across these loops. While the HOMO and LUMO of loops in the N-terminal domain are dominated by the acidic aspartates, and the polar/hydrophobic residues, respectively, these levels of the C-terminal domain loops show strong localized electron density on the phenyl rings of the tyrosines. The Fukui index calculation identifies the hydroxyl oxygen in the phenyl ring of Y99 as a potent nucleophile. Our analysis indicates a general way of interpreting the electronic energy spectra to understand stability and functions of large biomolecules where the truncation of the molecule and, hence, the terminal capping effects are inevitable.

  7. Chemical Constituents Antioxidant and Anticholinesterasic Activity of Tabernaemontana catharinensis

    PubMed Central

    Moura, Sidnei; Echeverrigaray, Sergio

    2013-01-01

    The present work aimed to analyze the alkaloid content of the ethanolic extract of Tabernaemontana catharinensis (Apocynaceae family) and its fractions as well as to evaluate their antioxidant and anticholinesterasic activities. The analyses of the ethanolic extract of T. catharinensis by mass spectrometry allowed identifying the presence of the alkaloids 16-epi-affinine, coronaridine-hydroxyindolenine, voachalotine, voacristine-hydroxyindolenine, and 12-methoxy-n-methyl-voachalotine, as well as an alkaloid with m/z 385.21 whose spectrum suggests a derivative of voacristine or voacangine. The extract and its alkaloid rich fractions showed antioxidant activity, especially those that contain the alkaloid m/z 385.21 or 16-epi-affinine with DPPH scavenging activity (IC50) between 37.18 and 74.69 μg/mL. Moreover, the extract and its fractions exhibited anticholinesterasic activity, particularly the fractions characterized by the presence of 12-methoxy-n-methyl-voachalotine, with IC50 = 2.1 to 2.5 μg/mL. Fractions with 16-epi-affinine combined good antioxidant (IC50 = 65.59 to 74.69 μg/mL) and anticholinesterasic (IC50 = 7.7 to 8.3 μg/mL) activities, representing an option for further studies aimed at treating neurodegenerative diseases. PMID:23983637

  8. Foeniculum vulgare essential oils: chemical composition, antioxidant and antimicrobial activities.

    PubMed

    Miguel, Maria Graça; Cruz, Cláudia; Faleiro, Leonor; Simões, Mariana T F; Figueiredo, Ana Cristina; Barroso, José G; Pedro, Luis G

    2010-02-01

    The essential oils from Foeniculum vulgare commercial aerial parts and fruits were isolated by hydrodistillation, with different distillation times (30 min, 1 h, 2 h and 3 h), and analyzed by GC and GC-MS. The antioxidant ability was estimated using four distinct methods. Antibacterial activity was determined by the agar diffusion method. Remarkable differences, and worrying from the quality and safety point of view, were detected in the essential oils. trans-Anethole (31-36%), alpha-pinene (14-20%) and limonene (11-13%) were the main components of the essentials oil isolated from F. vulgare dried aerial parts, whereas methyl chavicol (= estragole) (79-88%) was dominant in the fruit oils. With the DPPH method the plant oils showed better antioxidant activity than the fruits oils. With the TBARS method and at higher concentrations, fennel essential oils showed a pro-oxidant activity. None of the oils showed a hydroxyl radical scavenging capacity > 50%, but they showed an ability to inhibit 5-lipoxygenase. The essential oils showed a very low antimicrobial activity. In general, the essential oils isolated during 2 h were as effective, from the biological activity point of view, as those isolated during 3 h.

  9. Push for new materials, chemicals from biomass sparks active R and D

    SciTech Connect

    Borman, S. )

    1990-09-01

    This paper discusses how a resurgence of interest in the production of new materials, chemicals, and fuels from biomass resources such as wood, cellulose, lignin, starch, and chitin is sparking active R and D efforts in these areas. Biobased materials and chemicals currently under development include composites of conventional plastics with lignocellulosics (chemicals from wood and other plant sources); lignocellulosic nonwoven mates that can be pressed into rigid shapes to form doors, walls, and even auto body parts; phenolic chemicals produced from wood waste and bark; membranes made from chitosan (a substance derived from crustacean shells); and biodegradable plastics containing starch.

  10. Chemical Bond Activation Observed with an X-ray Laser.

    PubMed

    Beye, Martin; Öberg, Henrik; Xin, Hongliang; Dakovski, Georgi L; Dell'Angela, Martina; Föhlisch, Alexander; Gladh, Jörgen; Hantschmann, Markus; Hieke, Florian; Kaya, Sarp; Kühn, Danilo; LaRue, Jerry; Mercurio, Giuseppe; Minitti, Michael P; Mitra, Ankush; Moeller, Stefan P; Ng, May Ling; Nilsson, Anders; Nordlund, Dennis; Nørskov, Jens; Öström, Henrik; Ogasawara, Hirohito; Persson, Mats; Schlotter, William F; Sellberg, Jonas A; Wolf, Martin; Abild-Pedersen, Frank; Pettersson, Lars G M; Wurth, Wilfried

    2016-09-15

    The concept of bonding and antibonding orbitals is fundamental in chemistry. The population of those orbitals and the energetic difference between the two reflect the strength of the bonding interaction. Weakening the bond is expected to reduce this energetic splitting, but the transient character of bond-activation has so far prohibited direct experimental access. Here we apply time-resolved soft X-ray spectroscopy at a free-electron laser to directly observe the decreased bonding-antibonding splitting following bond-activation using an ultrashort optical laser pulse.

  11. Cooperative enhancement of deoxyribozyme activity by chemical modification and added cationic copolymer

    PubMed Central

    Saito, Ken; Shimada, Naohiko; Maruyama, Atushi

    2016-01-01

    Abstract Deoxyribozymes (DNAzymes) having RNA-cleaving activity have widely been explored as tools for therapeutic and diagnostic purposes. Both the chemical cleaving step and the turnover step should be improved for enhancing overall activity of DNAzymes. We have shown that cationic copolymer enhanced DNAzyme activity by increasing turnover efficacy. In this paper, effects of the copolymer on DNAzymes modified with locked nucleic acids (LNA) or 2′-O-methylated (2′-OMe) nucleic acids were studied. The copolymer increased activity of these chemically modified DNAzymes. More than 30-fold enhancement in multiple-turnover catalytic activity was observed with 2′-OMe-modified DNAzyme in the presence of the copolymer. DNAzyme catalytic activity was successfully enhanced by cooperation of the added copolymer and chemical modification of DNAzyme. PMID:27877894

  12. Chemical Modification of Papain and Subtilisin: An Active Site Comparison

    ERIC Educational Resources Information Center

    St-Vincent, Mireille; Dickman, Michael

    2004-01-01

    An experiment using methyle methanethiosulfonate (MMTS) and phenylmethylsulfonyl flouride (PMSF) to specifically modify the cysteine and serine residues in the active sites of papain and subtilism respectively is demonstrated. The covalent modification of these enzymes and subsequent rescue of papain shows the beginning biochemist that proteins…

  13. Incorporating Nondrug Social & Recreational Activities in Outpatient Chemical Dependency Treatment

    ERIC Educational Resources Information Center

    Siporin, Sheldon; Baron, Lisa

    2012-01-01

    "Contingency Management programs (CMP) and non-drug social and recreational activities (NDSRA) are interventions premised on behavior theory that rely on external sources of reinforcement alternative to drug-based forms to decrease drug use. CMP usually employs vouchers as reinforcement for negative toxicologies. Despite research support, CMP…

  14. Antifungal activities and chemical composition of some medicinal plants.

    PubMed

    Mohammadi, A; Nazari, H; Imani, S; Amrollahi, H

    2014-06-01

    The use of and search for drugs and dietary supplements derived from plants have accelerated in recent years. Ethnopharmacologists, botanists, microbiologists and natural-products scientists are combing the earth for phytochemicals and leads, which could be developed for treatment of infectious diseases. The aim of this study was to investigate the antifungal activities of the essential oils of some medicinal plants such as Stachys pubescens, Thymus kotschyanus, Thymus daenensis and Bupleurum falcatum against Fusarium oxysporum, Aspergillus flavus and Alternaria alternata. The essential oils were used to evaluate their MICs and MFCs compared to the amphotricin B as a standard drug. The essential oils were also analyzed by GC/MS. Essential oils isolated from the S. pubescens, T. kotschyanus and B. falcatum showed strong antifungal activities. The essential oil of T. daenensis exhibited a moderate activity against the selected fungi in comparison with the other plants' essential oils. In addition, the results showed that 26, 23, 22 and 15 components were identified from the essential oils of T. kotschyanus, S. pubescens, T. daenensis and B. falcatum, respectively. These oils exhibited a noticeable antifungal activity against the selected fungi. Regarding obtained results and that natural antimicrobial substances are inexpensive and have fewer side effects, they convey potential for implementation in fungal pathogenic systems.

  15. Essential oil from Artemisia phaeolepis: chemical composition and antimicrobial activities.

    PubMed

    Ben Hsouna, Anis; Ben Halima, Nihed; Abdelkafi, Slim; Hamdi, Naceur

    2013-01-01

    Artemisia phaeolepis, a perennial herb with a strong volatile odor, grows on the grasslands of Mediterranean region. Essential oil obtained from Artemisia phaeolepis was analyzed by gas chromatography-flame ionization detection and gas chromatography-mass spectrometry. A total of 79 components representing 98.19% of the total oil were identified, and the main compounds in the oil were found to be eucalyptol (11.30%), camphor (8.21%), terpine-4-ol (7.32%), germacrene D (6.39), caryophyllene oxide (6.34%), and caryophyllene (5.37%). The essential oil showed definite inhibitory activity against 10 strains of test microorganisms. Eucalyptol, camphor, terpine-4-ol, caryophyllene, germacrene D and caryophyllene oxide were also examined as the major components of the oil. Camphor showed the strongest antimicrobial activity; terpine-4-ol, eucalyptol, caryophyllene and germacrene D were moderately active and caryophyllene oxide was weakly active. The study revealed that the antimicrobial properties of the essential oil can be attributed to the synergistic effects of its diverse major and minor components.

  16. Passive dosing of soil invertebrates with polycyclic aromatic hydrocarbons: limited chemical activity explains toxicity cutoff.

    PubMed

    Mayer, Philipp; Holmstrup, Martin

    2008-10-01

    The partitioning of organic soil pollutants into soil organisms is driven by their chemical activity, which normally does not exceed that of the pure pollutant. Passive dosing with the silicone poly(dimethylsiloxane) (PDMS) was used to initiate and maintain the maximum chemical activity of 10 polycyclic aromatic hydrocarbons (PAHs) in toxicity tests with the springtail Folsomia candida. The test animals could move freely on the PDMS saturated with PAHs, resulting in direct contact and exposure to saturated air. After 7 days, springtail lethality correlated neither with the octanol-water partition coefficients of the PAHs nor with their molecular size, but with their melting point All low-melting PAHs (T(M) < or = 110 degrees C) caused 100% lethality, whereas all high-melting PAHs (TM > or = 180 degrees C) caused no significant lethality. The lethality was successfully fitted to one chemical activity response curve for all PAHs tested, with effective chemical activity causing 50% lethality (Ea-50) of 0.058. It was also fitted to the PAH concentration in the PDMS, resulting in an EC(PDMS)-50 of 8.7 mM. Finally, the combined exposure to anthracene and pyrene was described by the sum of chemical activities causing lethality, in good agreement with the chemical activity-response curve obtained.

  17. Global distributions of water vapour isotopologues retrieved from IMG/ADEOS data

    NASA Astrophysics Data System (ADS)

    Herbin, H.; Hurtmans, D.; Turquety, S.; Wespes, C.; Barret, B.; Hadji-Lazaro, J.; Clerbaux, C.; Coheur, P.-F.

    2007-07-01

    The isotopologic composition of water vapour in the atmosphere provides valuable information on many climate, chemical and dynamical processes. The accurate measurements of the water isotopologues by remote-sensing techniques remains a challenge, due to the large spatial and temporal variations. Simultaneous profile retrievals of the main water isotopologues (i.e. H216O, H218O and HDO) and their ratios are presented here for the first time, along their retrieved global distributions. The results are obtained by exploiting the high resolution infrared spectra recorded by the Interferometric Monitor for Greenhouse gases (IMG) instrument, which has operated in the nadir geometry onboard the ADEOS satellite between 1996 and 1997. The retrievals are performed on cloud-free radiances, measured during ten days of April 1997, considering two atmospheric windows (1205-1228 cm-1; 2004-2032 cm-1) and using a line-by-line radiative transfer model and an inversion procedure based on the Optimal Estimation Method (OEM). Characterizations in terms of vertical sensitivity and error budget are provided. We show that a relatively high vertical resolution is achieved for H216O (~4-5 km), and that the retrieved profiles are in fair agreement with local sonde measurements, at different latitudes. The retrieved global distributions of H216O, H218O, HDO and their ratios are presented and found to be consistent with previous experimental studies and models. The Ocean-Continent difference, the latitudinal and vertical dependence of the water vapour amount and the isotopologic depletion are notably well reproduced. Others trends, possibly related to small-scale variations in the vertical profiles are also discussed. Despite the difficulties encountered for computing accurately the isotopologic ratios, our results demonstrate the ability of infrared nadir sounding for monitoring atmospheric isotopologic water vapour distributions on a global scale.

  18. Hypoglycemic activity evaluation and chemical study on hollyhock flowers.

    PubMed

    Zhang, Yi; Jin, Lijun; Chen, Qiu; Wu, Zhizhen; Dong, Yongzhe; Han, Lifeng; Wang, Tao

    2015-04-01

    Hollyhock (Althaea rosea (Linn.) Cavan) belongs to Althaea genus, Malvaceae family, is a perennial garden plant distributed throughout the world in warm temperate and tropical regions, which was used as anti-diabetes ingredient in traditional Chinese medicine. In the process of our research, ethanolic extract of hollyhock flower (HFE) was found to decrease serum triglyceride and glucose levels significantly in KK-A(y) mice after oral administration for 8weeks. Meanwhile, gene expressions on AMPK, IRS2, PI3K, AKT and GLUT4 in liver were remarkably up-regulated. Three new dihydroflavonol glycosides, named as roseaflavanonolosides A (1), B (2), and C (3), together with two known ones were obtained from HFE. Their structures were elucidated by chemical and spectroscopic methods. Hepatic cell glucose uptake experiment was performed using 2-NBDG as a glucose uptake indicator. At the dosage of 20μg/mL for 1-5, the glucose uptake increasing level was nearly 30%-40% in HepG2 cells. We partly revealed the glucose metabolism regulation effect may relate to dihydroflavonols in hollyhock flower.

  19. The boiling liquid expanding vapour explosion (BLEVE): mechanism, consequence assessment, management.

    PubMed

    Abbasi, Tasneem; Abbasi, S A

    2007-03-22

    Among the most devastating of accidents likely in chemical process industry is the boiling liquid expanding vapour explosion (BLEVE). It is accompanied by highly destructive blast waves and missiles. In most situations there is also a fireball or a toxic gas cloud. The damaging effect of BLEVEs is reflected in the fact that the 80-odd major BLEVEs that have occurred between 1940 and 2005 have claimed over a 1000 lives and have injured over 10,000 persons besides harming property worth billions of dollars. Release of toxic chemicals like chlorine and phosgene from BLEVEs have damaged large chunks of areas surrounding the BLEVE site. This paper presents an overview of the mechanism, the causes, the consequences, and the preventive strategies associated with BLEVEs.

  20. Hangman Catalysis for Photo- and Photoelectro- Chemical Activation of Water

    SciTech Connect

    Nocera, Daniel

    2014-04-15

    The focus of this DOE program is solar fuels – specifically the chemistry for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) from water and the oxygen reduction reaction (ORR) to water These three reactions are at the heart of renewable energy conversion. The bond-making and bond-breaking chemistry that underpins these transformations is not well understood. We are developing insight into such chemistry by creating a series of ligand constructs that poise an acid-base functionality over a redox active metal platform. These “hangman” ligands utilize the acid-base functionality to form a secondary coordination sphere that can assist proton movement and facilitate substrate assembly and activation within the molecular cleft. The grant period funding cycle focused on synthesis and reactivity of hangman porphyrins and corroles for HER, OER and ORR.

  1. Chemical Composition, Antifungal and Insecticidal Activities of Hedychium Essential Oils

    DTIC Science & Technology

    2013-04-11

    composition of the essential oils for the majority of the genotypes as well as their antifungal and insecticidal activities against the fungi C...essential oils were ineffective against the fungi Colletotrichum gloeosporioides, C. fragariae, and C. acutatum in this study, but essential oils...extracts against mycotoxigenic fungi . J. Crop Improv. 2012, 26, 389–396. Sample Availability: Contact the authors. © 2013 by the authors; licensee

  2. Hematite Surface Activation by Chemical Addition of Tin Oxide Layer.

    PubMed

    Carvalho, Waldemir M; Souza, Flavio L

    2016-09-05

    In this study, the effect of tin (Sn(4+) ) modification on the surface of hematite electrodes synthesized by an aqueous solution route at different times (2, 5, 10, 18, and 24 h) is investigated. As confirmed from X-ray diffraction results, the as-synthesized electrode exhibits an oxyhydroxide phase, which is converted into a pure hematite phase after being subjected to additional thermal treatment at 750 °C for 30 min. The tin-modified hematite electrode is prepared by depositing a solution of Sn(4+) precursor on the as-synthesized electrode, followed by thermal treatment under the same abovementioned conditions. This modification results in an enhancement of the photocurrent response for all hematite electrodes investigated and attains the highest values of around 1.62 and 2.3 mA cm(-2) at 1.23 and 1.4 V versus RHE, respectively, for electrodes obtained in short synthesis times (2 h). Contact angle measurements suggest that the deposition of Sn(4+) on the hematite electrode provides a more hydrophilic surface, which favors a chemical reaction at the interface between the electrode and electrolyte. This result generates new perspectives for understanding the deposition of Sn(4+) on the hematite electrode surface, which is in contrast with several studies previously reported; these studies state that the enhancement in photocurrent density is related to either the induction of an increased donor charge density or shift in the flat-band potential, which favors charge separation.

  3. Turkish Undergraduates' Misconceptions of Evaporation, Evaporation Rate, and Vapour Pressure

    ERIC Educational Resources Information Center

    Canpolat, Nurtac

    2006-01-01

    This study focused on students' misconceptions related to evaporation, evaporation rate, and vapour pressure. Open-ended diagnostic questions were used with 107 undergraduates in the Primary Science Teacher Training Department in a state university in Turkey. In addition, 14 students from that sample were interviewed to clarify their written…

  4. Energy losses through entrance condensation in small vapour engines

    SciTech Connect

    Bom, G.J. )

    1993-03-01

    The effects of entrance condensation were studied in a small piston type vapour engine as could be used for low power thermodynamic solar waterpumping (50-1000 W output). Indicative relations have been established between the magnitude of energy losses caused by this phenomenon and engine design features. 2 refs., 5 figs.

  5. Distillation with Vapour Compression. An Undergraduate Experimental Facility.

    ERIC Educational Resources Information Center

    Pritchard, Colin

    1986-01-01

    Discusses the need to design distillation columns that are more energy efficient. Describes a "design and build" project completed by two college students aimed at demonstrating the principles of vapour compression distillation in a more energy efficient way. General design specifications are given, along with suggestions for teaching…

  6. No sodium in the vapour plumes of Enceladus.

    PubMed

    Schneider, Nicholas M; Burger, Matthew H; Schaller, Emily L; Brown, Michael E; Johnson, Robert E; Kargel, Jeffrey S; Dougherty, Michele K; Achilleos, Nicholas A

    2009-06-25

    The discovery of water vapour and ice particles erupting from Saturn's moon Enceladus fuelled speculation that an internal ocean was the source. Alternatively, the source might be ice warmed, melted or crushed by tectonic motions. Sodium chloride (that is, salt) is expected to be present in a long-lived ocean in contact with a rocky core. Here we report a ground-based spectroscopic search for atomic sodium near Enceladus that places an upper limit on the mixing ratio in the vapour plumes orders of magnitude below the expected ocean salinity. The low sodium content of escaping vapour, together with the small fraction of salt-bearing particles, argues against a situation in which a near-surface geyser is fuelled by a salty ocean through cracks in the crust. The lack of observable sodium in the vapour is consistent with a wide variety of alternative eruption sources, including a deep ocean, a freshwater reservoir, or ice. The existing data may be insufficient to distinguish between these hypotheses.

  7. No sodium in the vapour plumes of Enceladus

    NASA Astrophysics Data System (ADS)

    Schneider, Nicholas M.; Burger, Matthew H.; Schaller, Emily L.; Brown, Michael E.; Johnson, Robert E.; Kargel, Jeffrey S.; Dougherty, Michele K.; Achilleos, Nicholas A.

    2009-06-01

    The discovery of water vapour and ice particles erupting from Saturn's moon Enceladus fuelled speculation that an internal ocean was the source. Alternatively, the source might be ice warmed, melted or crushed by tectonic motions. Sodium chloride (that is, salt) is expected to be present in a long-lived ocean in contact with a rocky core. Here we report a ground-based spectroscopic search for atomic sodium near Enceladus that places an upper limit on the mixing ratio in the vapour plumes orders of magnitude below the expected ocean salinity. The low sodium content of escaping vapour, together with the small fraction of salt-bearing particles, argues against a situation in which a near-surface geyser is fuelled by a salty ocean through cracks in the crust. The lack of observable sodium in the vapour is consistent with a wide variety of alternative eruption sources, including a deep ocean, a freshwater reservoir, or ice. The existing data may be insufficient to distinguish between these hypotheses.

  8. THE INTERACTION OF VAPOUR PHASE ORGANIC COMPOUNDS WITH INDOOR SINKS

    EPA Science Inventory

    The interaction of indoor air pollutants with interior surfaces (i.e., sinks) is a well known, but poorly understood, phenomenon. Studies have shown that re-emissions of adsorbed organic vapours can contribute to elevated concentrations of organics in indoor environments. Researc...

  9. Impact of major volcanic eruptions on stratospheric water vapour

    NASA Astrophysics Data System (ADS)

    Löffler, M.; Brinkop, S.; Jöckel, P.

    2015-12-01

    Volcanic eruptions can have significant impact on the earth's weather and climate system. Besides the subsequent tropospheric changes also the stratosphere is influenced by large eruptions. Here changes in stratospheric water vapour after the two major volcanic eruptions of El Chichón in Mexico in 1982 and Mount Pinatubo on the Philippines in 1991 are investigated with chemistry-climate model simulations. This study is based on two simulations with specified dynamics of the EMAC model, performed within the Earth System Chemistry integrated Modelling (ESCiMo) project, of which only one includes the volcanic forcing through prescribed aerosol optical properties. The results show a significant increase in stratospheric water vapour after the eruptions, resulting from increased heating rates and the subsequent changes in stratospheric and tropopause temperatures in the tropics. The tropical vertical advection and the South Asian summer monsoon are identified as important sources for the additional water vapour in the stratosphere. Additionally, volcanic influences on the tropospheric water vapour and ENSO are evident.

  10. Impact of major volcanic eruptions on stratospheric water vapour

    NASA Astrophysics Data System (ADS)

    Löffler, Michael; Brinkop, Sabine; Jöckel, Patrick

    2016-05-01

    Volcanic eruptions can have a significant impact on the Earth's weather and climate system. Besides the subsequent tropospheric changes, the stratosphere is also influenced by large eruptions. Here changes in stratospheric water vapour after the two major volcanic eruptions of El Chichón in Mexico in 1982 and Mount Pinatubo on the Philippines in 1991 are investigated with chemistry-climate model simulations. This study is based on two simulations with specified dynamics of the European Centre for Medium-Range Weather Forecasts Hamburg - Modular Earth Submodel System (ECHAM/MESSy) Atmospheric Chemistry (EMAC) model, performed within the Earth System Chemistry integrated Modelling (ESCiMo) project, of which only one includes the long-wave volcanic forcing through prescribed aerosol optical properties. The results show a significant increase in stratospheric water vapour induced by the eruptions, resulting from increased heating rates and the subsequent changes in stratospheric and tropopause temperatures in the tropics. The tropical vertical advection and the South Asian summer monsoon are identified as sources for the additional water vapour in the stratosphere. Additionally, volcanic influences on tropospheric water vapour and El Niño-Southern Oscillation (ENSO) are evident, if the long-wave forcing is strong enough. Our results are corroborated by additional sensitivity simulations of the Mount Pinatubo period with reduced nudging and reduced volcanic aerosol extinction.

  11. Copper vapour laser with an efficient semiconductor pump generator having comparable pump pulse and output pulse durations

    SciTech Connect

    Yurkin, A A

    2016-03-31

    We report the results of experimental studies of a copper vapour laser with a semiconductor pump generator capable of forming virtually optimal pump pulses with a current rise steepness of about 40 A ns{sup -1} in a KULON LT-1.5CU active element. To maintain the operating temperature of the active element's channel, an additional heating pulsed oscillator is used. High efficiency of the pump generator is demonstrated. (lasers)

  12. X-ray imaging of chemically active valence electrons during a pericyclic reaction

    PubMed Central

    Bredtmann, Timm; Ivanov, Misha; Dixit, Gopal

    2014-01-01

    Time-resolved imaging of chemically active valence electron densities is a long-sought goal, as these electrons dictate the course of chemical reactions. However, X-ray scattering is always dominated by the core and inert valence electrons, making time-resolved X-ray imaging of chemically active valence electron densities extremely challenging. Here we demonstrate an effective and robust method, which emphasizes the information encoded in weakly scattered photons, to image chemically active valence electron densities. The degenerate Cope rearrangement of semibullvalene, a pericyclic reaction, is used as an example to visually illustrate our approach. Our work also provides experimental access to the long-standing problem of synchronous versus asynchronous bond formation and breaking during pericyclic reactions. PMID:25424639

  13. Collective dynamics of chemically active particles trapped at a fluid interface.

    PubMed

    Domínguez, Alvaro; Malgaretti, P; Popescu, M N; Dietrich, S

    2016-10-12

    Chemically active colloids generate changes in the chemical composition of their surrounding solution and thereby induce flows in the ambient fluid which affect their dynamical evolution. Here we study the many-body dynamics of a monolayer of spherically symmetric active particles trapped at a fluid-fluid interface. To this end we consider a model for the large-scale spatial distribution of particles which incorporates the direct pair interaction (including also the capillary interaction which is caused specifically by the interfacial trapping) as well as the effect of hydrodynamic interactions (including the Marangoni flow induced by the response of the interface to the chemical activity). The values of the relevant physical parameters for typical experimental realizations of such systems are estimated and various scenarios, which are predicted by our approach for the dynamics of the monolayer, are discussed. In particular, we show that the chemically-induced Marangoni flow can prevent the clustering instability driven by the capillary attraction.

  14. Immune activation affects chemical sexual ornaments of male Iberian wall lizards

    NASA Astrophysics Data System (ADS)

    López, Pilar; Gabirot, Marianne; Martín, José

    2009-01-01

    Many animals use chemical signals in sexual selection, but it is not clear how these sexual traits might have evolved to signal honestly male condition. It is possible that there is a trade-off between maintaining the immune system and the elaboration of ornaments. We experimentally challenged the immune system of male Iberian wall lizards, Podarcis hispanica, with a bacterial antigen (lipopolysaccharide), without pathogenic effects, to explore whether the immune activation affected chemical ornaments. Immune activation resulted in decreased proportions of a major chemical in femoral secretions (cholesta-5,7-dien-3-ol = provitamin D3) known to be selected in scent of males by females and which active form (vitamin D) has a variety of important effects on immune system function. This result suggests the existence of a potential trade-off between physiological regulation of the immune system and the allocation of essential nutrients (vitamins) to sexual chemical ornaments in male lizards.

  15. Prompt activation of telomerase by chemical carcinogens in rats detected with a modified TRAP assay.

    PubMed

    Miura, M; Karasaki, Y; Abe, T; Higashi, K; Ikemura, K; Gotoh, S

    1998-05-08

    The maintenance of telomere length is crucial for survival of cells. Telomerase is an RNA-containing reverse transcriptase, which is responsible for elongation of shortened telomeres. Telomerase reactivation has been suggested to be involved in malignant progressions. To study on the involvement of telomerase activation in in vivo carcinogenesis, we first modified the original TRAP assay by changing the primer designs and the labeling method of PCR products to an end-labeling method. Second, we investigated the activation of telomerase in different organs after treatments of rats with various chemical carcinogens. Very early after the beginning of the treatment, telomerase activity in the liver, kidney, and lung was increased. In most cases, telomerase activation occurred in the primary or favorite target organs. The present results suggest that telomerase activation occurs promptly when animals are exposed to chemical carcinogens, which may contribute to in vivo chemical carcinogenesis.

  16. Chemical composition and analgesic activity of Calophyllum brasiliense leaves.

    PubMed

    da Silva, K L; dos Santos, A R; Mattos, P E; Yunes, R A; Delle-Monache, F; Cechinel-Filho, V

    2001-01-01

    This paper describes a phytochemical and pharmacological study with Calophyllum brasiliense leaves, a medicinal plant employed in folk medicine for the treatment of several ailments. Based on spectroscopic evidence, five phenolic compounds were identified as hyperin (hyperoside), amentoflavone, quercetin, gallic acid, and protocatechuic acid. The fractions and some phenolic compounds exhibited significant analgesic activity against the writhing test and in relation to the second phase (inflammatory pain) of the formalin test in mice, suggesting that this plant can be useful for the treatment of dolorous processes.

  17. Chemical composition and antibacterial activity of Iranian Lavandula x hybrida.

    PubMed

    Bajalan, Iman; Rouzbahani, Razieh; Ghasemi Pirbalouti, Abdollah; Maggi, Filippo

    2017-03-17

    Lavandin (Lavandula x hybrida) is an evergreen shrub and cultivated worldwide for its essential oil which possesses various biological activities. In this study, the essential oils were isolated from the leaves of ten lavandin populations in western Iran. The hydrodistilled essential oils were analyzed by GC-FID/MS. Results indicated significant differences (p ≤0.05) among the various populations for the main essential oil constituents. The major components from different populations were 1,8-cineole (31.64 to 47.94%), borneol (17.11 to 26.14%), and camphor (8.41 to 12.68%). In vitro antibacterial activity was evaluated against S. agalactiae, S. aureus, E. coli and K. pneumoniae. The inhibition zones were in the range of 09.36 mm for S. aureus to 23.30 mm for E. coli. Results indicated that there was a significant correlation between essential oil composition and level of antibacterial efficacy expressed as inhibition zones. This article is protected by copyright. All rights reserved.

  18. Chemical constituents and biological activities of two Iranian Cystoseira species.

    PubMed

    Yegdaneh, Afsaneh; Ghannadi, Alireza; Dayani, Ladan

    2016-07-01

    The marine environment represents approximately half of the global biodiversity and could provide unlimited biological resources for the production of therapeutic drugs. Marine seaweeds comprise few thousands of species representing a considerable part of the littoral biomass. Extracts of the Cystoseira indica and Cystoseira merica were subjected to phytochemical and cytotoxicity evaluation. The amount of total phenol was determined with Folin-Ciocalteu reagent. Cytotoxicity was characterized by IC50 of human cancer cell lines including MCF-7 (human breast adenocarcinoma), HeLa (cervical carcinoma), and HT-29 (human colon adenocarcinoma) using Sulforhodamin assay. Antioxidant activities were evaluated using 2,2-diphenylpicrylhydrazyl (DPPH) method. The analysis revealed that tannins, saponins, sterols and triterpenes were the most abundant constituents in these Cystoseira species while cyanogenic and cardiac glycosides were the least ones. C. indica had the higher content of total phenolics and also showed higher antioxidant activity. Cytotoxic results showed that both species inhibited cell growth effectively, especially against MCF-7 cell line. The present findings suggest potential pharmacological applications of selected seaweeds but require further investigation and identification of their bioactive principles.

  19. [Chemical constituents of Jasminum giraldii and their antioxidant activity].

    PubMed

    Zhang, Xiu-Peng; Qin, Hui; Yang, Fang; Chai, Jiang; Wang, Xin; Song, Xiao-Mei; Mei, Qi-Bing; Feng, Feng; Yue, Zheng-Gang

    2014-06-01

    Ten compounds were isolated from the barks of Jasminum giraldii by means of various of chromatographic techniques such as silica gel, Sephadex LH-20 and Rp-HPLC. Their structures were identified by spectroscopic data analysis as (+)-medioresinol (1), (+) -syringaresinol (2), syringaresinol-4'-O-beta-D-glucopyranoside (3), oleanic acid (4), 3-methoxy-4-hydroxy-trans-cinnamaldehyde (5), trans-sinapaldehyde (6), syringaldehyde (7), 1-(4-methoxy -phenyl) -ethanol (8), trans-cinnamic acid (9), and 4-(1-methoxyethyl) -phenol (10). Among them, compounds 1-3, 5-8 and 10 were isolated from the J. genus for the first time and compounds 4 and 9 were obtained from J. giraldii for the first time. In the DPPH free radical scavenging assay, compound 1 exhibited significant activity (IC50 55.1 micromol x L(-1)), compared with vitamin C(IC50 59.9 micromol x L(-1)); and compound 2 showed moderate activity (IC50 79.0 micromol x L(-1)), compared with 2, 6-di-tert-butyl4-methylphenol (IC50 236 micromol x L(-1)).

  20. Chemical constituents and biological activities of two Iranian Cystoseira species

    PubMed Central

    Yegdaneh, Afsaneh; Ghannadi, Alireza; Dayani, Ladan

    2016-01-01

    The marine environment represents approximately half of the global biodiversity and could provide unlimited biological resources for the production of therapeutic drugs. Marine seaweeds comprise few thousands of species representing a considerable part of the littoral biomass. Extracts of the Cystoseira indica and Cystoseira merica were subjected to phytochemical and cytotoxicity evaluation. The amount of total phenol was determined with Folin-Ciocalteu reagent. Cytotoxicity was characterized by IC50 of human cancer cell lines including MCF-7 (human breast adenocarcinoma), HeLa (cervical carcinoma), and HT-29 (human colon adenocarcinoma) using Sulforhodamin assay. Antioxidant activities were evaluated using 2,2-diphenylpicrylhydrazyl (DPPH) method. The analysis revealed that tannins, saponins, sterols and triterpenes were the most abundant constituents in these Cystoseira species while cyanogenic and cardiac glycosides were the least ones. C. indica had the higher content of total phenolics and also showed higher antioxidant activity. Cytotoxic results showed that both species inhibited cell growth effectively, especially against MCF-7 cell line. The present findings suggest potential pharmacological applications of selected seaweeds but require further investigation and identification of their bioactive principles. PMID:27651811

  1. Legal requirements and guidelines for the control of harmful laser generated particles, vapours and gases

    NASA Astrophysics Data System (ADS)

    Horsey, John

    2015-07-01

    This paper is a review of the Health and Safety laws and guidelines relating to laser generated emissions into the workplace and outside environment with emphasis on the differences between legal requirements and guideline advice. The types and nature of contaminants released by various laser processes (i.e. cutting, coding, engraving, marking etc) are discussed, together with the best methods for controlling them to within legal exposure limits. A brief description of the main extract air filtration techniques, including the principles of particulate removal and the action of activated carbon for gas/vapour/odour filtration, is given.

  2. Extended Functional Groups (EFG): An Efficient Set for Chemical Characterization and Structure-Activity Relationship Studies of Chemical Compounds.

    PubMed

    Salmina, Elena S; Haider, Norbert; Tetko, Igor V

    2015-12-23

    The article describes a classification system termed "extended functional groups" (EFG), which are an extension of a set previously used by the CheckMol software, that covers in addition heterocyclic compound classes and periodic table groups. The functional groups are defined as SMARTS patterns and are available as part of the ToxAlerts tool (http://ochem.eu/alerts) of the On-line CHEmical database and Modeling (OCHEM) environment platform. The article describes the motivation and the main ideas behind this extension and demonstrates that EFG can be efficiently used to develop and interpret structure-activity relationship models.

  3. Water vapour is a pre-oviposition attractant for the malaria vector Anopheles gambiae sensu stricto

    PubMed Central

    2013-01-01

    Background To date no semiochemicals affecting the pre-oviposition behaviour of the malaria vector Anopheles gambiae sensu lato have been described. Water vapour must be the major chemical signal emanating from a potential larval habitat, and although one might expect that gravid An. gambiae s.l. detect and respond to water vapour in their search for an aquatic habitat, this has never been experimentally confirmed for this species. This study aimed to investigate the role of relative humidity or water vapour as a general cue for inducing gravid An. gambiae sensu stricto to make orientated movements towards the source. Methods Three experiments were carried out with insectary-reared An. gambiae s.s. One with unfed females and two with gravid females during their peak oviposition time in the early evening. First, unfed females and gravid females were tested separately in still air where a humidity difference was established between opposite ends of a WHO bioassay tube and mosquitoes released individually in the centre of the tube. Movement of mosquitoes to either low or high humidity was recorded. Additionally, gravid mosquitoes were released into a larger air-flow olfactometer and responses measured towards collection chambers that contained cups filled with water or empty cups. Results Unfed females equally dispersed in the small bioassay tubes to areas of high and low humidity (mean 50% (95% confidence interval (CI) 38-62%). In contrast, gravid females were 2.4 times (95% CI 1.3-4.7) more likely to move towards high humidity than unfed females. The results were even more pronounced in the airflow olfactometer. Gravid females were 10.6 times (95% CI 5.4-20.8) more likely to enter the chamber with water than a dry chamber. Conclusions Water vapour is a strong pre-oviposition attractant to gravid An. gambiae s.s. in still and moving air and is likely to be a general cue used by mosquitoes for locating aquatic habitats. PMID:24120083

  4. Fungal phytotoxins with potential herbicidal activity: chemical and biological characterization.

    PubMed

    Cimmino, Alessio; Masi, Marco; Evidente, Marco; Superchi, Stefano; Evidente, Antonio

    2015-12-19

    Covering: 2007 to 2015 Fungal phytotoxins are secondary metabolites playing an important role in the induction of disease symptoms interfering with host plant physiological processes. Although fungal pathogens represent a heavy constraint for agrarian production and for forest and environmental heritage, they can also represent an ecofriendly alternative to manage weeds. Indeed, the phytotoxins produced by weed pathogenic fungi are an efficient tool to design natural, safe bioherbicides. Their use could avoid that of synthetic pesticides causing resistance in the host plants and the long term impact of residues in agricultural products with a risk to human and animal health. The isolation and structural and biological characterization of phytotoxins produced by pathogenic fungi for weeds, including parasitic plants, are described. Structure activity relationships and mode of action studies for some phytotoxins are also reported to elucidate the herbicide potential of these promising fungal metabolites.

  5. Chemical constituents and antioxidant activity of Mallotus roxburghianus leaves.

    PubMed

    Rana, Virendra S; Rawat, Mohan S M; Pant, Geeta; Nagatsu, Akito

    2005-06-01

    Mallotus roxburghianus is used in the traditional medicine in North-Eastern India, but previously no work has been done on the identification of bioactive compounds. Two new compounds, 3-(1-C-beta-D-glucopyranosyl)-2,6-dihydroxy-5-methoxybenzoic acid (6) and 2,4,8,9,10-pentahydroxy-3,7-dimethoxyanthracene-6-O-beta-D-rhamnopyranoside (7) together with beta-sitosterol (1), stigmasterol (2), betulinic acid (3), 4-hydroxybenzoic acid (4), beta-sitosterol-beta-D-glucoside (5), and bergenin (8) were isolated and identified from the leaves of M. roxburghianus. The chloroform soluble portion of the alcoholic extract of leaf, and compounds 3, 6, 7, and 8 exhibited encouraging antioxidant activities.

  6. Estrogenic activity of chemical constituents from Tephrosia candida.

    PubMed

    Hegazy, Mohamed-Elamir F; El-Hamd H Mohamed, Abou; El-Halawany, Ali M; Djemgou, Pierre C; Shahat, Abdelaaty A; Paré, Paul W

    2011-05-27

    In a continued investigation of medicinal plants from the genus Tephrosia, phytochemical analysis of a methylene chloride-methanol (1:1) extract of the air-dried aerial parts of Tephrosia candida afforded two new 8-prenylated flavonoids, namely, tephrocandidins A (1) and B (2), a new prenylated chalcone, candidachalcone (3), a new sesquiterpene (4), and a previously reported pea flavonoid phytoalexin, pisatin (5). The structures of 1-4 were established by spectroscopic methods, including HREIMS, and 1H, 13C, DEPT, HMQC, and HMBC NMR experiments. The most potent estrogenic activity of these isolated natural products in an estrogen receptor (ERα) competitive-binding assay was for 3, which exhibited an IC50 value of 80 μM, compared with 18 nM for the natural steroid 17β-estradiol. Results were interpreted via virtual docking of isolated compounds to an ERα crystal structure.

  7. Accelerated degradation of methylammonium lead iodide perovskites induced by exposure to iodine vapour

    NASA Astrophysics Data System (ADS)

    Wang, Shenghao; Jiang, Yan; Juarez-Perez, Emilio J.; Ono, Luis K.; Qi, Yabing

    2017-01-01

    Efficiencies of organic-inorganic lead halide perovskite solar cells (PSCs) have significantly increased in recent years, but instability issues impede their further development and application. Previous studies reported that volatile species (for example, iodine, I2) were generated when perovskites were subjected to moisture, oxygen, light illumination, applied electric field, and thermal stress (all of which are relevant to the operation of PSCs in practical applications). Here we show that I2 vapour causes severe degradation of MAPbI3 (MA: CH3NH3+) perovskite, due to chemical chain reactions. Furthermore, I2 vapour could also induce degradation of other iodide-based perovskites, such as FAPbI3 (FA: HC(NH2)2+) and FA0.8Cs0.2PbI3. The results reveal a universal degradation factor for iodide-based perovskite by I2. As the release of I2 is nearly inevitable during practical applications, this work suggests that MAPbI3 may not be suitable for long-term stable solar cells and it is imperative to develop other types of perovskite material to achieve stable PSCs.

  8. Water Vapour, Ozone and Cirrus In The Tropical Lower Stratosphere Observed By Uars

    NASA Astrophysics Data System (ADS)

    Clark, H. L.; Harwood, R. S.; Pumphrey, H. C.

    The Upper Atmosphere Research Satellite (UARS) was launched on 19th September 1991 to make measurements of a variety of atmospheric constituents. The Microwave Limb Sounder (MLS), an instrument on UARS, is sensitive to water vapour and ozone in the lower stratosphere and made coincident, daily measurements of the two species in the tropical region until April 1993. The Cryogenic Limb Array Etalon Spectrom- eter (CLAES), another of the instruments on UARS has a similar spatial and tempo- ral coverage to that of MLS and can be used to indicate the presence of cirrus. We use measurements of water vapour and ozone and data from the European Centre for Medium Range Weather Forecasts to investigate the transport of air in the regions of cirrus formation and describe the chemical and physical environment in which they are found. Ozone mixing ratios have a tendency to be lower in such regions suggesting that the air has entered the stratosphere relatively recently. The importance of cirrus in dehydrating the lower stratosphere and the consequences of cirrus formation within the context of stratosphere-troposphere exchange are discussed.

  9. Polysaccharides from Arctium lappa L.: Chemical structure and biological activity.

    PubMed

    Carlotto, Juliane; de Souza, Lauro M; Baggio, Cristiane H; Werner, Maria Fernanda de P; Maria-Ferreira, Daniele; Sassaki, Guilherme L; Iacomini, Marcello; Cipriani, Thales R

    2016-10-01

    The plant Arctium lappa L. is popularly used to relieve symptoms of inflammatory disorders. A crude polysaccharide fraction (SAA) resulting of aqueous extraction of A. lappa leaves showed a dose dependent anti-edematogenic activity on carrageenan-induced paw edema, which persisted for up to 48h. Sequential fractionation by ultrafiltration at 50kDa and 30kDa cut-off membranes yielded three fractions, namely RF50, RF30, and EF30. All these maintained the anti-edematogenic effect, but RF30 showed a more potent action, inhibiting 57% of the paw edema at a dose of 4.9mg/kg. The polysaccharide RF30 contained galacturonic acid, galactose, arabinose, rhamnose, glucose, and mannose in a 7:4:2:1:2:1 ratio and had a Mw of 91,000g/mol. Methylation analysis and NMR spectroscopy indicated that RF30 is mainly constituted by a type I rhamnogalacturonan branched by side chains of types I and II arabinogalactans, and arabinan.

  10. CO2 adsorption on chemically modified activated carbon.

    PubMed

    Caglayan, Burcu Selen; Aksoylu, A Erhan

    2013-05-15

    CO2 adsorption capacity of a commercial activated carbon was improved by using HNO3 oxidation, air oxidation, alkali impregnation and heat treatment under helium gas atmosphere. The surface functional groups produced were investigated by diffuse reflectance infrared Fourier transform spectrometer (DRIFTS). CO2 adsorption capacities of the samples were determined by gravimetric analyses for 25-200°C temperature range. DRIFTS studies revealed the formation of carboxylic acid groups on the HNO3 oxidized adsorbents. Increased aromatization and uniform distribution of the Na particles were observed on the samples prepared by Na2CO3 impregnation onto HNO3 oxidized AC support. The adsorption capacities of the nonimpregnated samples were increased by high temperature helium treatments or by increasing the adsorption temperature; both leading to decomposition of surface oxygen groups, forming sites that can easily adsorb CO2. The adsorption capacity loss due to cyclic adsorption/desorption procedures was overcome with further surface stabilization of Na2CO3 modified samples with high temperature He treatments. With Na2CO3 impregnation the mass uptakes of the adsorbents at 20 bars and 25 °C were improved by 8 and 7 folds and at 1 bar were increased 15 and 16 folds, on the average, compared to their air oxidized and nitric acid oxidized supports, respectively.

  11. The effects of activation temperature on physico-chemical characteristics of activated carbons derived from biomass wastes

    NASA Astrophysics Data System (ADS)

    Sutrisno, Bachrun; Hidayat, Arif

    2015-12-01

    This research focused on investigating in the effect of activation temperature on the physico-chemical properties of palm empty fruit bunch (PEFB) based activated carbon prepared by physical activation with carbon dioxide. The activation temperature was studied in the range of 400-800°C by keeping the activation temperature at 800°C for 120 min. It was found that the porous properties of activated carbon decreased with an increase in carbonization temperature. The activated carbons prepared at the highest activation temperature at 800°C and activation time of 120 min gave the activated carbon with the highest of BET surface area and pore volume of 938 m2/g and 0.4502 cm3/g, respectively

  12. Using Laboratory Chemicals to Imitate Illicit Drugs in a Forensic Chemistry Activity

    ERIC Educational Resources Information Center

    Hasan, Shawn; Bromfield-Lee, Deborah; Oliver-Hoyo, Maria T.; Cintron-Maldonado, Jose A.

    2008-01-01

    This forensic chemistry activity utilizes presumptive forensic testing procedures and laboratory chemicals that produce screening results similar to controlled substances. For obvious reasons, obtaining heavily regulated controlled substances to create an undergraduate student activity is not practical for most educational institutions. We were…

  13. CHARACTERIZATION OF ACTIVATED CARBONS' PHYSICAL AND CHEMICAL PROPERTIES IN RELATION TO THEIR MERCURY ADSORPTION

    EPA Science Inventory

    The paper gives results of a characterization of the physical and chemical properties of the activated carbons used for elemental mercury (Hgo) adsorption, in order to understand the role of oxygen surface functional groups on the mechanism of Hgo adsorption by activated carbons....

  14. Chemical proteomic probes for profiling cytochrome P450 activities and drug interactions in vivo

    PubMed Central

    Wright, Aaron T.; Cravatt, Benjamin F.

    2007-01-01

    The cytochrome P450 (P450) superfamily metabolizes many endogenous signaling molecules and drugs. P450 enzymes are regulated by post-translational mechanisms in vivo, which hinders their functional characterization by conventional genomic or proteomic methods. Here, we describe a chemical proteomic strategy to profile P450 activities directly in living systems. Derivatization of a mechanism-based inhibitor with a “clickable” handle provided an activity-based probe that labels multiple P450s both in proteomic extracts and in vivo. This probe was used to record alterations in liver P450 activities triggered by chemical agents, including inducers of P450 expression and direct P450 inhibitors. The chemical proteomic strategy described herein thus offers a versatile method to monitor P450 activities and small molecule interactions in any biological system and, through doing so, should facilitate the functional characterization of this large and diverse enzyme class. PMID:17884636

  15. Cloud Condensation Nuclei Activity Associated with Chemical Composition and Precipitation Events

    NASA Astrophysics Data System (ADS)

    Corrigan, C.; Roberts, G. C.; Zauscher, M.; Suski, K.; Noblitts, S.; Sullivan, A. P.; Collett, J. L.

    2010-12-01

    Measurements of ambient cloud condensation nuclei (CCN) concentrations can be improved by simultaneously collecting information on the activation size of the CCN along with chemical composition of the ambient aerosol. A size scanning CCN instrument developed at Scripps Institution of Oceanography was deployed as part of the Calwater project in the Sierra Nevada foothills of California during February and March of 2010. The instrument was capable of determining the critical diameter of activation for the ambient aerosol during a 20 minute scan. During the study period, the CCN activation size increased after each rain event and the activity slowly returned over the next few days. The critical diameter of the overall aerosol was largest (least active) immediately following precipitation events. The average critical diameter would typically decrease by 20% in the time between major precipitation events. This regeneration of the CCN activity can be partially attributed to the transport of sulfate and nitrate pollution to replace the particles that were washed out by the rain, but it may also be due to chemical changes via aging and oxidation mechanisms. Since CCN activity is determined by the particles size and chemical composition, the changes in critical diameter indicate a change in the chemical composition of the available CCN particles. By comparing the critical diameters with aerosol chemical data from a semi-real time aerosol ion chromatograph, the CCN activity was generally correlated with the mass loading of sulfate and nitrate. Deviations from the expected activity of sulfate and nitrate indicate the existence of other compounds that contribute to activity through additional dissolution and by reducing the surface tension. The contribution to CCN activity from additional compounds, including organic surfactants, can be estimated by observing the deviation of the measured critical diameters from values calculated using only the measured nitrate+sulfate mass

  16. Structure-activity comparison of hydrazine to other Nasotoxic chemicals. Final report, August-October 1991

    SciTech Connect

    Godin, C.S.; Wall, H.G.

    1992-08-01

    The biotransformation of 19 chemicals that have caused nasal epithelial toxicity in-long-term carcinogenesis experiments in laboratory rodents was compared with the biotransformation of hydrazine, in order to determine if these chemicals share common metabolic pathways. Ten of the 19 chemicals were tumorigenic; four were epoxides or epoxide-formers; three were metabolized to reactive aldehydes; and one was metabolized to a lactone ring. The two remaining chemicals, p-cresidene and 2,6-xylidene, possess an amino group that can undergo biotransformation to reactive metabolites in a way similar to hydrazine, but there is no evidence to support this hypothesis. Therefore, none of the 19 chemicals are metabolized in a way similar to hydrazine.... Structure-activity, Hydrazine, Nasotoxicity, Carcinogenicity.

  17. Chemically active colloids near osmotic-responsive walls with surface-chemistry gradients

    NASA Astrophysics Data System (ADS)

    Popescu, M. N.; Uspal, W. E.; Dietrich, S.

    2017-04-01

    Chemically active colloids move by creating gradients in the composition of the surrounding solution and by exploiting the differences in their interactions with the various molecular species in solution. If such particles move near boundaries, e.g. the walls of the container confining the suspension, gradients in the composition of the solution are also created along the wall. This give rise to chemi-osmosis (via the interactions of the wall with the molecular species forming the solution), which drives flows coupling back to the colloid and thus influences its motility. Employing an approximate ‘point-particle’ analysis, we show analytically that—owing to this kind of induced active response (chemi-osmosis) of the wall—such chemically active colloids can align with, and follow, gradients in the surface chemistry of the wall. In this sense, these artificial ‘swimmers’ exhibit a primitive form of thigmotaxis with the meaning of sensing the proximity of a (not necessarily discontinuous) physical change in the environment. We show that the alignment with the surface-chemistry gradient is generic for chemically active colloids as long as they exhibit motility in an unbounded fluid, i.e. this phenomenon does not depend on the exact details of the propulsion mechanism. The results are discussed in the context of simple models of chemical activity, corresponding to Janus particles with ‘source’ chemical reactions on one half of the surface and either ‘inert’ or ‘sink’ reactions over the other half.

  18. Activity profiles of 309 ToxCast™ chemicals evaluated across 292 biochemical targets.

    PubMed

    Knudsen, Thomas B; Houck, Keith A; Sipes, Nisha S; Singh, Amar V; Judson, Richard S; Martin, Matthew T; Weissman, Arthur; Kleinstreuer, Nicole C; Mortensen, Holly M; Reif, David M; Rabinowitz, James R; Setzer, R Woodrow; Richard, Ann M; Dix, David J; Kavlock, Robert J

    2011-03-28

    Understanding the potential health risks posed by environmental chemicals is a significant challenge elevated by the large number of diverse chemicals with generally uncharacterized exposures, mechanisms, and toxicities. The present study is a performance evaluation and critical analysis of assay results for an array of 292 high-throughput cell-free assays aimed at preliminary toxicity evaluation of 320 environmental chemicals in EPA's ToxCast™ project (Phase I). The chemicals (309 unique, 11 replicates) were mainly precursors or the active agent of commercial pesticides, for which a wealth of in vivo toxicity data is available. Biochemical HTS (high-throughput screening) profiled cell and tissue extracts using semi-automated biochemical and pharmacological methodologies to evaluate a subset of G-protein coupled receptors (GPCRs), CYP450 enzymes (CYPs), kinases, phosphatases, proteases, HDACs, nuclear receptors, ion channels, and transporters. The primary screen tested all chemicals at a relatively high concentration 25 μM concentration (or 10 μM for CYP assays), and a secondary screen re-tested 9132 chemical-assay pairs in 8-point concentration series from 0.023 to 50 μM (or 0.009-20 μM for CYPs). Mapping relationships across 93,440 chemical-assay pairs based on half-maximal activity concentration (AC50) revealed both known and novel targets in signaling and metabolic pathways. The primary dataset, summary data and details on quality control checks are available for download at http://www.epa.gov/ncct/toxcast/.

  19. Structural features of endocrine active chemicals--A comparison of in vivo and in vitro data.

    PubMed

    Lewin, Geertje; Escher, Sylvia E; van der Burg, Bart; Simetska, Nelly; Mangelsdorf, Inge

    2015-08-01

    Studies on reproductive toxicity need high numbers of test animals. Therefore, we investigated whether chemical structural features (SF) in combination with in vitro data on specific adverse outcome pathways (AOPs) may be used for predicting reproductive toxicity of untested chemicals. Using the OECD Toolbox and expert judgment, we identified 89 structure groups for 275 chemicals for which the results of prenatal developmental toxicity or multigeneration studies were present in the Fraunhofer database on Fertility and Developmental Toxicity in experimental animals (FeDTex) database. Likewise, we evaluated 220 chemicals which had been tested in reporter gene assays on endocrine ((anti)estrogenic and (anti)androgenic) properties in the CALUX(®) test battery. There was a large spread of effect levels for substances within the chemical structure groups for both, in vivo and in vitro results. The groups of highest concern (diphenyl derivatives, planar conjugated systems with fused rings, phenols and organophosphates) correlated quite well, however, between the in vivo and in vitro data on estrogenic activity. For the 56 chemicals represented in both databases, lowest effect doses in vivo correlated well with the estrogenic activity in vitro. These results suggest that a panel of assays covering relevant AOPs and data on metabolism and toxicokinetics may allow prediction of relative reproductive or development toxicity potency within the identified chemical structure groups.

  20. Catalytic Functionalities of Nano Ruthenium/gamma-Al2O3 Catalysts for the Vapour Phase Hydrogenolysis of Glycerol.

    PubMed

    Kumar, Vanama Pavan; Priya, Samudrala Shanthi; Harikrishna, Yengaidas; Kumar, Ashish; Chary, Komandur V R

    2016-02-01

    A series of Ruthenium catalysts with different Ru contents supported on gamma-alumina were prepared by deposition-precipitation method. The catalysts were characterized by X-ray diffraction (XRD), trans- mission electron microscopy (TEM), temperature programmed reduction (TPR), CO-chemisorption, surface area and pore-size distribution (PSD) measurements. The catalytic activities were evaluated for the vapour phase hydrogenolysis of glycerol to propanediols. The pore size distribution (PSD) results suggest that Ru loadings considerably affect the pore volume, pore diameter and surface area. The particle size measured from CO-chemisorption and TEM analysis are well correlated to the activity results during the hydrogenolysis reaction. The catalytic properties of Ru/gamma-Al2O3 catalysts were evaluated for the first time over vapour phase hydrogenolysis of glycerol to propanediols.

  1. Fault Diagnosis Based on Chemical Sensor Data with an Active Deep Neural Network.

    PubMed

    Jiang, Peng; Hu, Zhixin; Liu, Jun; Yu, Shanen; Wu, Feng

    2016-10-13

    Big sensor data provide significant potential for chemical fault diagnosis, which involves the baseline values of security, stability and reliability in chemical processes. A deep neural network (DNN) with novel active learning for inducing chemical fault diagnosis is presented in this study. It is a method using large amount of chemical sensor data, which is a combination of deep learning and active learning criterion to target the difficulty of consecutive fault diagnosis. DNN with deep architectures, instead of shallow ones, could be developed through deep learning to learn a suitable feature representation from raw sensor data in an unsupervised manner using stacked denoising auto-encoder (SDAE) and work through a layer-by-layer successive learning process. The features are added to the top Softmax regression layer to construct the discriminative fault characteristics for diagnosis in a supervised manner. Considering the expensive and time consuming labeling of sensor data in chemical applications, in contrast to the available methods, we employ a novel active learning criterion for the particularity of chemical processes, which is a combination of Best vs. Second Best criterion (BvSB) and a Lowest False Positive criterion (LFP), for further fine-tuning of diagnosis model in an active manner rather than passive manner. That is, we allow models to rank the most informative sensor data to be labeled for updating the DNN parameters during the interaction phase. The effectiveness of the proposed method is validated in two well-known industrial datasets. Results indicate that the proposed method can obtain superior diagnosis accuracy and provide significant performance improvement in accuracy and false positive rate with less labeled chemical sensor data by further active learning compared with existing methods.

  2. Fault Diagnosis Based on Chemical Sensor Data with an Active Deep Neural Network

    PubMed Central

    Jiang, Peng; Hu, Zhixin; Liu, Jun; Yu, Shanen; Wu, Feng

    2016-01-01

    Big sensor data provide significant potential for chemical fault diagnosis, which involves the baseline values of security, stability and reliability in chemical processes. A deep neural network (DNN) with novel active learning for inducing chemical fault diagnosis is presented in this study. It is a method using large amount of chemical sensor data, which is a combination of deep learning and active learning criterion to target the difficulty of consecutive fault diagnosis. DNN with deep architectures, instead of shallow ones, could be developed through deep learning to learn a suitable feature representation from raw sensor data in an unsupervised manner using stacked denoising auto-encoder (SDAE) and work through a layer-by-layer successive learning process. The features are added to the top Softmax regression layer to construct the discriminative fault characteristics for diagnosis in a supervised manner. Considering the expensive and time consuming labeling of sensor data in chemical applications, in contrast to the available methods, we employ a novel active learning criterion for the particularity of chemical processes, which is a combination of Best vs. Second Best criterion (BvSB) and a Lowest False Positive criterion (LFP), for further fine-tuning of diagnosis model in an active manner rather than passive manner. That is, we allow models to rank the most informative sensor data to be labeled for updating the DNN parameters during the interaction phase. The effectiveness of the proposed method is validated in two well-known industrial datasets. Results indicate that the proposed method can obtain superior diagnosis accuracy and provide significant performance improvement in accuracy and false positive rate with less labeled chemical sensor data by further active learning compared with existing methods. PMID:27754386

  3. 15 CFR 712.1 - Round to zero rule that applies to activities involving Schedule 1 chemicals.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... activities involving Schedule 1 chemicals. 712.1 Section 712.1 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS ACTIVITIES INVOLVING SCHEDULE 1 CHEMICALS § 712.1 Round to...

  4. 15 CFR 712.1 - Round to zero rule that applies to activities involving Schedule 1 chemicals.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... activities involving Schedule 1 chemicals. 712.1 Section 712.1 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS ACTIVITIES INVOLVING SCHEDULE 1 CHEMICALS § 712.1 Round to...

  5. 15 CFR 712.1 - Round to zero rule that applies to activities involving Schedule 1 chemicals.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... activities involving Schedule 1 chemicals. 712.1 Section 712.1 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS ACTIVITIES INVOLVING SCHEDULE 1 CHEMICALS § 712.1 Round to...

  6. 15 CFR 712.1 - Round to zero rule that applies to activities involving Schedule 1 chemicals.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... activities involving Schedule 1 chemicals. 712.1 Section 712.1 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS ACTIVITIES INVOLVING SCHEDULE 1 CHEMICALS § 712.1 Round to...

  7. 15 CFR 712.1 - Round to zero rule that applies to activities involving Schedule 1 chemicals.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... activities involving Schedule 1 chemicals. 712.1 Section 712.1 Commerce and Foreign Trade Regulations Relating to Commerce and Foreign Trade (Continued) BUREAU OF INDUSTRY AND SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS ACTIVITIES INVOLVING SCHEDULE 1 CHEMICALS § 712.1 Round to...

  8. A new test method for measuring the water vapour permeability of fabrics

    NASA Astrophysics Data System (ADS)

    Huang, Jianhua; Qian, Xiaoming

    2007-09-01

    The water vapour permeability of textile fabrics is a critical determinant of wearer comfort. Existing test methods are either time consuming or require large amounts of material. A new test apparatus was developed for characterizing the water vapour permeability of fabrics. An aluminium cylinder covered with waterproof and vapour permeable PTFE laminate is used for generating water vapour source on one side of the sample. A dry nitrogen sweep gas stream is used to carry water vapour away. The calculation of the rate of water vapour transmission across the fabric is based on the measurement of the relative humidity of the outgoing nitrogen stream. This new measuring apparatus offers a short test time and calls for a small sample size. The comparison measurements show that the test results correlated well with those obtained from ISO 11092 and ASTM E96. Therefore, this test method provides a new technique to accurately and precisely characterize the water vapour transport properties of fabrics.

  9. Removal of vapour phase PCDD/Fs in electric arc furnace steelmaking emissions by sorption using plastics.

    PubMed

    Ooi, Tze Chean; Ewan, Bruce C R; Cliffe, Keith R; Anderson, David R; Fisher, Raymond; Thompson, Dennis

    2008-08-01

    Plastics are potentially suitable for the removal of vapour phase PCDD/Fs in emissions from the electric arc furnace (EAF) steelmaking process. Three different commercial plastics, i.e. polypropylene BE170MO (Borealis A/S, Denmark), polypropylene in the form of 5 mm spheres (The Precision Plastic Ball Co. Ltd., UK) and polyethylene LD605BA (ExxonMobil Chemical, Belgium), have been studied using a novel experimental apparatus for the removal of vapour phase PCDD/Fs. Polypropylene BE170MO was identified to be the most suitable product amongst the three plastics in terms of PCDD/F sorption and potential industrial application. The optimum temperature for PCDD/F sorption on polypropylene BE170MO was below 90 degrees C for a removal efficiency of >99% at an average vapour phase PCDD/F concentration of 3.5 ng I-TEQ/Nm(3). At 130 degrees C, 53% of the PCDD/Fs trapped on polypropylene BE170MO were desorbed.

  10. Analysis of essential oils from Voacanga africana seeds at different hydrodistillation extraction stages: chemical composition, antioxidant activity and antimicrobial activity.

    PubMed

    Liu, Xiong; Yang, Dongliang; Liu, Jiajia; Ren, Na

    2015-01-01

    In this study, essential oils from Voacanga africana seeds at different extraction stages were investigated. In the chemical composition analysis, 27 compounds representing 86.69-95.03% of the total essential oils were identified and quantified. The main constituents in essential oils were terpenoids, alcohols and fatty acids accounting for 15.03-24.36%, 21.57-34.43% and 33.06-57.37%, respectively. Moreover, the analysis also revealed that essential oils from different extraction stages possessed different chemical compositions. In the antioxidant evaluation, all analysed oils showed similar antioxidant behaviours, and the concentrations of essential oils providing 50% inhibition of DPPH-scavenging activity (IC50) were about 25 mg/mL. In the antimicrobial experiments, essential oils from different extraction stages exhibited different antimicrobial activities. The antimicrobial activity of oils was affected by extraction stages. By controlling extraction stages, it is promising to obtain essential oils with desired antimicrobial activities.

  11. Air sampling and determination of vapours and aerosols of bitumen and polycyclic aromatic hydrocarbons in the Human Bitumen Study.

    PubMed

    Breuer, Dietmar; Hahn, Jens-Uwe; Höber, Dieter; Emmel, Christoph; Musanke, Uwe; Rühl, Reinhold; Spickenheuer, Anne; Raulf-Heimsoth, Monika; Bramer, Rainer; Seidel, Albrecht; Schilling, Bernd; Heinze, Evelyn; Kendzia, Benjamin; Marczynski, Boleslaw; Welge, Peter; Angerer, Jürgen; Brüning, Thomas; Pesch, Beate

    2011-06-01

    The chemical complexity of emissions from bitumen applications is a challenge in the assessment of exposure. Personal sampling of vapours and aerosols of bitumen was organized in 320 bitumen-exposed workers and 69 non-exposed construction workers during 2001-2008. Area sampling was conducted at 44 construction sites. Area and personal sampling of vapours and aerosols of bitumen showed similar concentrations between 5 and 10 mg/m(3), while area sampling yielded higher concentrations above the former occupational exposure limit (OEL) of 10 mg/m(3). The median concentration of personal bitumen exposure was 3.46 mg/m(3) (inter-quartile range 1.80-5.90 mg/m(3)). Only few workers were exposed above the former OEL. The specificity of the method measuring C-H stretch vibration is limited. This accounts for a median background level of 0.20 mg/m³ in non-exposed workers which is likely due to ubiquitous aliphatic hydrocarbons. Further, area measurements of polycyclic aromatic hydrocarbons (PAHs) were taken at 25 construction sites. U.S. EPA PAHs were determined with GC/MS, with the result of a median concentration of 2.47 μg/m(3) at 15 mastic asphalt worksites associated with vapours and aerosols of bitumen, with a Spearman correlation coefficient of 0.45 (95% CI -0.13 to 0.78). PAH exposure at mastic-asphalt works was higher than at reference worksites (median 0.21 μg/m(3)), but about one order of magnitude lower compared to coke-oven works. For a comparison of concentrations of vapours and aerosols of bitumen and PAHs in asphalt works, differences in sampling and analytical methods must to be taken into account.

  12. Temperature distribution in a mixture surrounding a growing vapour bubble

    NASA Astrophysics Data System (ADS)

    Mohammadein, S. A.; Gouda, Sh. A.

    2006-03-01

    The paper presents temperature distribution of superheated liquid during the growth of spherical vapour bubble between two-phase temperatures. The heat equation is resolved by the modification of similarity parameter method of Screven [Chem Engng Sci 10:1-13(1959)] between two finite boundaries. Under these conditions, the growth of vapour bubble and temperature are obtained analytically in an implicit form which are different than that obtained before. The growth rate is obtained as a generalized formula compared with Plesset amd Zwick and Scriven et al. theories [J Appl Phys 25:493-500(1954);Chem Engng Sci 10:1-13(1959)]. The growth and temperature field affected by the initial superheating and thermal diffusivity.

  13. Anti-arthritic active fraction of Capparis spinosa L. fruits and its chemical constituents.

    PubMed

    Feng, Xiaolu; Lu, Jincai; Xin, Hailiang; Zhang, Lei; Wang, Yuliang; Tang, Kexuan

    2011-03-01

    The aim of this study was to ascertain the anti-arthritic active fraction of Capparis spinosa L. (Capparidaceae) fruits and its chemical constituents. The adjuvant arthritic rat model was developed to evaluate the anti-arthritic effects of different fractions of ethanol extraction from C. spinosa L. The fraction eluted by ethanol-water (50:50, v/v) had the most significant anti-arthritic activity. The chemical constituents of this fraction were therefore studied; seven known compounds were isolated and identified as: P-hydroxy benzoic acid; 5-(hydroxymethyl) furfural; bis(5-formylfurfuryl) ether; daucosterol; α-D-fructofuranosides methyl; uracil; and stachydrine.

  14. Numerical investigation of oscillatory multiphase flow in porous medium with chemically active skeleton

    NASA Astrophysics Data System (ADS)

    Konyukhov, A. V.; Zavialov, I. N.

    2016-11-01

    Self-oscillating mode of reaction front propagation in multiphase flow in the porous medium with chemically active skeleton is investigated numerically. The considered flow represents an immiscible displacement process, such that the displacing fluid and the skeleton of the porous medium have chemically active components which react with production of gaseous phase. The calculations have demonstrated strong influence of the reaction kinetics on stability of the reactive flow. The presence of a time delay between the change of concentration of the reactants and the change of the reaction rate is shown to stimulate transition of the reaction front propagation to the oscillatory mode.

  15. Inactivation of conidia of Penicillium chrysogenum, P. digitatum and P. italicum by ethanol solutions and vapours.

    PubMed

    Dao, Thien; Bensoussan, Maurice; Gervais, Patrick; Dantigny, Philippe

    2008-02-29

    A fractional factorial design, 2(5-1) experiments, was used for assessing the influence of 5 factors: water activity, aw [0.7, 0.9], temperature, T ( degrees C) [10, 30], mode of application, A [liquid, vapour], ethanol concentration, E (% w/w) [5, 10] and time, t (d) [1, 4] on the inactivation of spores of Penicillium chrysogenum, P. digitatum and P. italicum. Survival was determined by germination at optimal conditions within 3d. The experimental response was log (N 0/Nt), where N 0 and Nt (spore ml(-1)) the concentrations of viable spores at t=0 and t respectively. By a decreasing order of sensitivity to ethanol, moulds were ranked as followed: P. digitatum, P. italicum and P. chrysogenum. A greater inactivation for P. digitatum, P. italicum, that were the most sensitive moulds to ethanol, was obtained by applying vapour rather than ethanol solution. The order of significance of the main factors depended upon the mould. The key factor for explaining inactivation of P. chrysogenum was water activity. But, temperature was the main factor for explaining inactivation of P. digitatum and P. italicum. In the more drastic conditions, (i.e., 0.7 aw, 30 degrees C, 10% w/w ethanol), all spores were inactivated by applying liquid solution for 4d.

  16. A Global Genomic Screening Strategy Reveals Genetic and Chemical Activators ofPeroxisome Proliferator-Activated Receptor alpha (PPARalpha)

    EPA Science Inventory

    A comprehensive survey of chemical, diet and genetic perturbations that activate PPARalpha in the mouse liver has not been carried out but would be useful to identify the factors that may contribute to PPARalpha-dependent liver tumors. A gene signature dependent on PPARalpha ac...

  17. Troposphere-stratosphere exchange - constraints from water vapour

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Fueglistaler, S.; Haynes, P. H.

    2009-04-01

    Troposphere-to-stratosphere transport involves both cross-isentropic transport across the tropical tropopause to the stratospheric 'overworld' and quasi-horizontal transport into the lowermost stratosphere. The distribution of stratospheric water vapour is sensitively dependent on the detailed temperature history of air parcels entering the stratosphere, which can be used to constrain troposphere-stratosphere exchange pathways. We carry out trajectory calculations for the years 2001 and 2005-2008 with winds and diabatic heating rates from the ECMWF 40-year reanalysis project (ERA-40) and the new interim reanalysis project (ERA-Interim). Trajectories are either kinematic, where the vertical velocity is calculated from mass continuity, or diabatic, where diabatic heating rates are used to drive cross-isentropic motion. Water vapour is estimated using a simple dehydration model, and results are compared with measurements from HALOE and the Microwave Limb Sounder (MLS) on board the AURA satellite. In general diabatic trajectories yield spatial and temporal variations in water vapour that are in better agreement with observations, but for the ERA-Interim dataset the differences between kinematic and diabatic trajectories are small. Diabatic trajectories, which give the best estimate in seasonal variation of water vapour, show a consistent dry bias for the stratospheric overworld of 0.5 ppmv compared to previously published ERA-40 trajectory results and observations. The results suggest that trajectories calculated using ERA-40 winds show excessive vertical dispersion which overestimates troposphere-to-stratosphere exchange, an effect also seen in the lowermost stratosphere. The new results suggest that moistening processes in addition to the instantaneous dehydration to large-scale saturation mixing ratio could contribute up to 0.5 ppmv to stratospheric H2O.

  18. Transversely diode-pumped alkali metal vapour laser

    SciTech Connect

    Parkhomenko, A I; Shalagin, A M

    2015-09-30

    We have studied theoretically the operation of a transversely diode-pumped alkali metal vapour laser. For the case of high-intensity laser radiation, we have obtained an analytical solution to a complex system of differential equations describing the laser. This solution allows one to exhaustively determine all the energy characteristics of the laser and to find optimal parameters of the working medium and pump radiation (temperature, buffer gas pressure, and intensity and width of the pump spectrum). (lasers)

  19. Infrared Laser Optoacoustic Detection Of Gases And Vapours

    NASA Astrophysics Data System (ADS)

    Johnson, S. A.; Cummins, P. G.; Bone, S. A.; Davies, P. B.

    1988-10-01

    Mid-infrared laser optoacoustic spectroscopy has been used to detect a variety of gases and vapours. Performance was calibrated using the signal from a known concentration of ethene, and then the method applied to the perfume alcohol geraniol. Detection limits were found to be 1 ppb for ethene and 70 ppb for geraniol on their strongest absorption lines for a few seconds measurement time.

  20. Collisional thulium vapour gas-discharge laser

    SciTech Connect

    Gerasimov, V A; Pavlinskii, A V

    2004-01-31

    A collisional laser on a system of atomic levels based on the principle proposed by Gould is built for the first time. The population of the upper laser level and relaxation of the lower level occur upon inelastic collisions of excited thulium atoms with helium atoms. The lower-level relaxation occurs in a reaction with an energy defect of > 13000 cm{sup -1}. (active media. lasers)

  1. Nonequilibrium study of the intrinsic free-energy profile across a liquid-vapour interface

    SciTech Connect

    Braga, Carlos Muscatello, Jordan Lau, Gabriel Müller, Erich A. Jackson, George

    2016-01-28

    We calculate an atomistically detailed free-energy profile across a heterogeneous system using a nonequilibrium approach. The path-integral formulation of Crooks fluctuation theorem is used in conjunction with the intrinsic sampling method to calculate the free-energy profile for the liquid-vapour interface of the Lennard-Jones fluid. Free-energy barriers are found corresponding to the atomic layering in the liquid phase as well as a barrier associated with the presence of an adsorbed layer as revealed by the intrinsic density profile. Our findings are in agreement with profiles calculated using Widom’s potential distribution theorem applied to both the average and the intrinsic profiles as well as the literature values for the excess chemical potential.

  2. Nonequilibrium study of the intrinsic free-energy profile across a liquid-vapour interface

    NASA Astrophysics Data System (ADS)

    Braga, Carlos; Muscatello, Jordan; Lau, Gabriel; Müller, Erich A.; Jackson, George

    2016-01-01

    We calculate an atomistically detailed free-energy profile across a heterogeneous system using a nonequilibrium approach. The path-integral formulation of Crooks fluctuation theorem is used in conjunction with the intrinsic sampling method to calculate the free-energy profile for the liquid-vapour interface of the Lennard-Jones fluid. Free-energy barriers are found corresponding to the atomic layering in the liquid phase as well as a barrier associated with the presence of an adsorbed layer as revealed by the intrinsic density profile. Our findings are in agreement with profiles calculated using Widom's potential distribution theorem applied to both the average and the intrinsic profiles as well as the literature values for the excess chemical potential.

  3. Structure and properties of molecular and ionic clusters in vapour over caesium fluoride

    NASA Astrophysics Data System (ADS)

    Mwanga, Stanley F.; Pogrebnaya, Tatiana P.; Pogrebnoi, Alexander M.

    2015-06-01

    The properties of neutral molecules Cs2F2, Cs3F3, and Cs4F4, and positive and negative cluster ions Cs2F+, CsF2-, Cs3F2+, Cs2F3-, Cs4F3+, and Cs5F4+ were studied by several of quantum chemical methods implementing density function theory and Möller-Plesset perturbation theory of second and fourth orders. For all species, the equilibrium geometrical structure and vibrational spectra were determined. Different isomers have been revealed for the trimer neutral molecule Cs3F3; pentaatomic, both positive and negative, Cs3F2+, Cs2F3-; and heptaatomic Cs4F3+ ions. The most abundant isomers in the saturated vapour were determined. Enthalpies of dissociation reactions and enthalpies of formation of the species were obtained.

  4. Gamma irradiation effect on the chemical composition and the antioxidant activity of Ipomoea batatas L

    SciTech Connect

    Tahir, D. Halide, H. Kurniawan, D.; Wahab, A. W.

    2014-09-25

    The chemical composition and antioxidant activity of Ipomoea batatas L. (sweet potato) were studied by x-ray fluorescence (XRF) spectroscopy, Fourier transform infrared spectroscopy, and by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity. The irradiation treatment was performed by using Cs-137 as a gamma sources in experimental equipment. Treatment by irradiation emerges as a possible conservation technique that has been tested successfully in several food products. The amount of chemical composition was changed and resulting new chemical for absorbed dose 40 mSv. Interestingly, it was found that gamma irradiation significantly increased the antioxidant activity, as measured by DPPH radical scavenging capacity. The antioxidant activity of Ipomoea batatas L. extract was dramatically increased in the non-irradiated sample to the sample irradiated at 40 mSv. These results indicate that gamma irradiation of Ipomoea batatas L. extract can enhance its antioxidant activity through the formation of a new chemical compound. Based on these results, increased antioxidant activity of Ipomoea batatas L. extracts by gamma rays can be applied to various industries, especially cosmetics, foodstuffs, and pharmaceuticals.

  5. Gamma irradiation effect on the chemical composition and the antioxidant activity of Ipomoea batatas L.

    NASA Astrophysics Data System (ADS)

    Tahir, D.; Halide, H.; Wahab, A. W.; Kurniawan, D.

    2014-09-01

    The chemical composition and antioxidant activity of Ipomoea batatas L. (sweet potato) were studied by x-ray fluorescence (XRF) spectroscopy, Fourier transform infrared spectroscopy, and by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity. The irradiation treatment was performed by using Cs-137 as a gamma sources in experimental equipment. Treatment by irradiation emerges as a possible conservation technique that has been tested successfully in several food products. The amount of chemical composition was changed and resulting new chemical for absorbed dose 40 mSv. Interestingly, it was found that gamma irradiation significantly increased the antioxidant activity, as measured by DPPH radical scavenging capacity. The antioxidant activity of Ipomoea batatas L. extract was dramatically increased in the non-irradiated sample to the sample irradiated at 40 mSv. These results indicate that gamma irradiation of Ipomoea batatas L. extract can enhance its antioxidant activity through the formation of a new chemical compound. Based on these results, increased antioxidant activity of Ipomoea batatas L. extracts by gamma rays can be applied to various industries, especially cosmetics, foodstuffs, and pharmaceuticals.

  6. ADHESIVES WITH DIFFERENT PHS: EFFECT ON THE MTBS OF CHEMICALLY ACTIVATED AND LIGHT-ACTIVATED COMPOSITES TO HUMAN DENTIN

    PubMed Central

    Mallmann, André; de Melo, Renata Marques; Estrela, Verbênia; Pelogia, Fernanda; Campos, Laura; Bottino, Marco Antonio; Valandro, Luiz Felipe

    2007-01-01

    Purpose: To evaluate the bond strength between human dentin and composites, using two light-activated single-bottle total-etch adhesive systems with different pHs combined with chemically activated and light-activated-composites. The tested hypothesis was that the dentin bond strength is not influenced by an adhesive system of low pH, combined with chemically activated or light-activated composites. Material and Method: Flat dentin surfaces of twenty-eight human third molars were allocated in 4 groups (n=7), depending on the adhesive system: (One Step Plus-OS and Prime & Bond NT-PB) and composite (light-activated Filtek Z-100 [Z100] and chemically activated Bisfil 2B [B2B]). Each adhesive system was applied on acid-etched dentin and then one of the composites was added to form a 5 mm-high resin block. The specimens were stored in tap water (37°C/24 h) and sectioned into two axes, x and y. This was done with a diamond disk under coolant irrigation to obtain beams with a cross-section area of approximately 0.8 mm2. Each specimen was then attached to a custom-made device and submitted to the microtensile test (1 mm.min−1). Data were analyzed using two-way ANOVA and Tukey’s tests (p<0.05). Results: The anticipated hypothesis was not confirmed (p<0.0001). The bond strengths (MPa) were not statistically different between the two adhesive systems when light-activated composite was used (OS+Z100 = 24.7±7.1ª; PB+Z100 = 23.8±5.7ª). However, with use of the chemically activated composite (B2B), PB (7.8±3.6b MPa) showed significantly lower dentin bond strengths than OS (32.2±7.6ª). Conclusion: The low pH of the adhesive system can affect the bond of chemically activated composite to dentin. On the other hand, under the present conditions, the low pH did not seem to affect the bond of light-activated composites to dentin significantly. PMID:19089142

  7. Identification of chemical modulators of the constitutive activated receptor (CAR) in a gene expression compendium

    PubMed Central

    Oshida, Keiyu; Vasani, Naresh; Jones, Carlton; Moore, Tanya; Hester, Susan; Nesnow, Stephen; Auerbach, Scott; Geter, David R.; Aleksunes, Lauren M.; Thomas, Russell S.; Applegate, Dawn; Klaassen, Curtis D.; Corton, J. Christopher

    2015-01-01

    The nuclear receptor family member constitutive activated receptor (CAR) is activated by structurally diverse drugs and environmentally-relevant chemicals leading to transcriptional regulation of genes involved in xenobiotic metabolism and transport. Chronic activation of CAR increases liver cancer incidence in rodents, whereas suppression of CAR can lead to steatosis and insulin insensitivity. Here, analytical methods were developed to screen for chemical treatments in a gene expression compendium that lead to alteration of CAR activity. A gene expression biomarker signature of 83 CAR-dependent genes was identified using microarray profiles from the livers of wild-type and CAR-null mice after exposure to three structurally-diverse CAR activators (CITCO, phenobarbital, TCPOBOP). A rank-based algorithm (Running Fisher’s algorithm (p-value ≤ 10-4)) was used to evaluate the similarity between the CAR biomarker signature and a test set of 28 and 32 comparisons positive or negative, respectively, for CAR activation; the test resulted in a balanced accuracy of 97%. The biomarker signature was used to identify chemicals that activate or suppress CAR in an annotated mouse liver/primary hepatocyte gene expression database of ~1850 comparisons. CAR was activated by 1) activators of the aryl hydrocarbon receptor (AhR) in wild-type but not AhR-null mice, 2) pregnane X receptor (PXR) activators in wild-type and to lesser extents in PXR-null mice, and 3) activators of PPARα in wild-type and PPARα-null mice. CAR was consistently activated by five conazole fungicides and four perfluorinated compounds. Comparison of effects in wild-type and CAR-null mice showed that the fungicide propiconazole increased liver weight and hepatocyte proliferation in a CAR-dependent manner, whereas the perfluorinated compound perfluorooctanoic acid (PFOA) increased these endpoints in a CAR-independent manner. A number of compounds suppressed CAR coincident with increases in markers of

  8. Identification of chemical modulators of the constitutive activated receptor (CAR) in a gene expression compendium.

    PubMed

    Oshida, Keiyu; Vasani, Naresh; Jones, Carlton; Moore, Tanya; Hester, Susan; Nesnow, Stephen; Auerbach, Scott; Geter, David R; Aleksunes, Lauren M; Thomas, Russell S; Applegate, Dawn; Klaassen, Curtis D; Corton, J Christopher

    2015-01-01

    The nuclear receptor family member constitutive activated receptor (CAR) is activated by structurally diverse drugs and environmentally-relevant chemicals leading to transcriptional regulation of genes involved in xenobiotic metabolism and transport. Chronic activation of CAR increases liver cancer incidence in rodents, whereas suppression of CAR can lead to steatosis and insulin insensitivity. Here, analytical methods were developed to screen for chemical treatments in a gene expression compendium that lead to alteration of CAR activity. A gene expression biomarker signature of 83 CAR-dependent genes was identified using microarray profiles from the livers of wild-type and CAR-null mice after exposure to three structurally-diverse CAR activators (CITCO, phenobarbital, TCPOBOP). A rank-based algorithm (Running Fisher's algorithm (p-value ≤ 10(-4))) was used to evaluate the similarity between the CAR biomarker signature and a test set of 28 and 32 comparisons positive or negative, respectively, for CAR activation; the test resulted in a balanced accuracy of 97%. The biomarker signature was used to identify chemicals that activate or suppress CAR in an annotated mouse liver/primary hepatocyte gene expression database of ~1850 comparisons. CAR was activated by 1) activators of the aryl hydrocarbon receptor (AhR) in wild-type but not AhR-null mice, 2) pregnane X receptor (PXR) activators in wild-type and to lesser extents in PXR-null mice, and 3) activators of PPARα in wild-type and PPARα-null mice. CAR was consistently activated by five conazole fungicides and four perfluorinated compounds. Comparison of effects in wild-type and CAR-null mice showed that the fungicide propiconazole increased liver weight and hepatocyte proliferation in a CAR-dependent manner, whereas the perfluorinated compound perfluorooctanoic acid (PFOA) increased these endpoints in a CAR-independent manner. A number of compounds suppressed CAR coincident with increases in markers of

  9. Essential Oil Composition of Phagnalon sordidum (L.) from Corsica, Chemical Variability and Antimicrobial Activity.

    PubMed

    Brunel, Marion; Vitrac, Caroline; Costa, Jean; Mzali, Fatima; Vitrac, Xavier; Muselli, Alain

    2016-03-01

    The chemical composition of Phagnalon sordidum (L.) essential oil was investigated for the first time using gas chromatography and chromatography/mass spectrometry. Seventy-six compounds, which accounted for 87.9% of the total amount, were identified in a collective essential oil of P. sordidum from Corsica. The main essential oil components were (E)-β-caryophyllene (14.4%), β-pinene (11.0%), thymol (9.0%), and hexadecanoic acid (5.3%). The chemical compositions of essential oils from 19 Corsican locations were investigated. The study of the chemical variability using statistical analysis allowed identifying direct correlation between the three populations of P. sordidum widespread in Corsica and the essential oil compositions they produce. The in vitro antimicrobial activity of P. sordidum essential oil was evaluated and it exhibited a notable activity on a large panel of clinically significant microorganisms.

  10. Computer-assisted mechanistic structure-activity studies: application to diverse classes of chemical carcinogens.

    PubMed Central

    Loew, G H; Poulsen, M; Kirkjian, E; Ferrell, J; Sudhindra, B S; Rebagliati, M

    1985-01-01

    In the first part of this paper we have indicated how the techniques and capabilities of theoretical chemistry, together with experimental results, can be used in a mechanistic approach to structure-activity studies of toxicity. In the second part, we have illustrated how this computer-assisted approach has been used to identify and calculate causally related molecular indicators of relative carcinogenic activity in five classes of chemical carcinogens: polycyclic aromatic hydrocarbons and their methyl derivatives, aromatic amines, chloroethanes, chloroalkenes and dialkyl nitrosamines. In each class of chemicals studied, candidate molecular indicators have been identified that could be useful in predictive screening of unknown compounds. In addition, further insights into some mechanistic aspects of chemical carcinogenesis have been obtained. Finally, experiments have been suggested to both verify the usefulness of the indicators and test their mechanistic implications. PMID:3905382

  11. C15078. Essential oil composition of Phagnalon sordidum (L.) from Corsica, chemical variability and antimicrobial activity.

    PubMed

    Brunel, Marion; Vitrac, Caroline; Costa, Jean; Mzali, Fatima; Vitrac, Xavier; Muselli, Alain

    2016-02-10

    The chemical composition of Phagnalon sordidum (L.) essential oil was investigated for the first time using gas chromatography and chromatography-mass spectrometry. Seventy-six compounds, which accounted for 87.9% of the total amount, were identified in a collective essential oil of P. sordidum from Corsica. The main essential oil components were (E)-β-caryophyllene (14.4%), β-pinene (11.0%), thymol (9.0%), and hexadecanoic acid (5.3%). The chemical compositions of essential oils from 19 Corsican locations were investigated. The study of the chemical variability using statistical analysis allowed identifying direct correlation between the three populations of P. sordidum widespread in Corsica and the essential oil compositions they produce. The in vitro antimicrobial activity of P. sordidum essential oil was evaluated and exhibited a notable activity on a large panel of clinically significant microorganisms. This article is protected by copyright. All rights reserved.

  12. Chemical features of Ganoderma polysaccharides with antioxidant, antitumor and antimicrobial activities.

    PubMed

    Ferreira, Isabel C F R; Heleno, Sandrina A; Reis, Filipa S; Stojkovic, Dejan; Queiroz, Maria João R P; Vasconcelos, M Helena; Sokovic, Marina

    2015-06-01

    Ganoderma genus comprises one of the most commonly studied species worldwide, Ganoderma lucidum. However, other Ganoderma species have been also reported as important sources of bioactive compounds. Polysaccharides are important contributors to the medicinal properties reported for Ganoderma species, as demonstrated by the numerous publications, including reviews, on this matter. Yet, what are the chemical features of Ganoderma polysaccharides that have bioactivity? In the present manuscript, the chemical features of Ganoderma polysaccharides with reported antioxidant, antitumor and antimicrobial activities (the most studied worldwide) are analyzed in detail. The composition of sugars (homo- versus hetero-glucans and other polysaccharides), type of glycosidic linkages, branching patterns, and linkage to proteins are discussed. Methods for extraction, isolation and identification are evaluated and, finally, the bioactivity of polysaccharidic extracts and purified compounds are discussed. The integration of data allows deduction of structure-activity relationships and gives clues to the chemical aspects involved in Ganoderma bioactivity.

  13. Structure-activity relations between alkyl nucleophilic chemicals causing duodenal ulcer and adrenocortical necrosis

    SciTech Connect

    Szabo, S.; Reynolds, E.S.; Unger, S.H.

    1982-10-01

    Structure-activity relationships were qualitatively and quantitatively examined for 56 chemicals (e.g., derivatives of propionitrile, acrylonitrile and cysteamine) which caused duodenal ulcer and/or adrenocortical necrosis in rats. For the first time the duodenal ulcerogenic property of numerous chemicals has been studied in a rational and predictive manner. Ulcerogenic activity was most intense in the carbonitriles attached to two or three carbon backbones and diminished by shortening, lengthening, branching, unsaturating, halogenating or hydroxylating the carbon chains. Different modes of action are implied. Adrenocorticolytic potency was associated with unsaturation of the carbon chain and substitution of the nitrile by thiol or amine radicals. An action of these chemicals on the central nervous system has been suggested.

  14. Idaho Chemical Processing Plant low-activity waste grout stabilization development program FY-97 status report

    SciTech Connect

    Herbst, A.K.; Marshall, D.W.; McCray, J.A.

    1998-02-01

    The general purpose of the Grout Development Program is to solidify and stabilize the liquid low-activity wastes (LAW) generated at the Idaho Chemical Processing Plant (ICPP). It is anticipated that LAW will be produced from the following: (1) chemical separation of the tank farm high-activity sodium-bearing waste, (2) retrieval, dissolution, and chemical separation of the aluminum, zirconium, and sodium calcines, (3) facility decontamination processes, and (4) process equipment waste. Grout formulation studies for sodium-bearing LAW, including decontamination and process equipment waste, continued this fiscal year. A second task was to develop a grout formulation to solidify potential process residual heels in the tank farm vessels when the vessels are closed.

  15. Estimating Air Chemical Emissions from Research Activities Using Stack Measurement Data

    SciTech Connect

    Ballinger, Marcel Y.; Duchsherer, Cheryl J.; Woodruff, Rodger K.; Larson, Timothy V.

    2013-02-15

    Current methods of estimating air emissions from research and development (R&D) activities use a wide range of release fractions or emission factors with bases ranging from empirical to semi-empirical. Although considered conservative, the uncertainties and confidence levels of the existing methods have not been reported. Chemical emissions were estimated from sampling data taken from four research facilities over ten years. The approach was to use a Monte Carlo technique to create distributions of annual emission estimates for target compounds detected in source test samples. Distributions were created for each year and building sampled for compounds with sufficient detection frequency to qualify for the analysis. The results using the Monte Carlo technique without applying a filter to remove negative emission values showed almost all distributions spanning zero, and forty percent of the distributions having a negative mean. This indicates that emissions are so low as to be indistinguishable from building background. Application of a filter to allow only positive values in the distribution provided a more realistic value for emissions and increased the distribution mean by an average of sixteen percent. Release fractions were calculated by dividing the emission estimates by a building chemical inventory quantity. Two variations were used for this quantity: chemical usage, and chemical usage plus one-half standing inventory. Filters were applied so that only release fraction values from zero to one were included in the resulting distributions. Release fractions had a wide range among chemicals and among data sets for different buildings and/or years for a given chemical. Regressions of release fractions to molecular weight and vapor pressure showed weak correlations. Similarly, regressions of mean emissions to chemical usage, chemical inventory, molecular weight and vapor pressure also gave weak correlations. These results highlight the difficulties in estimating

  16. Modeling Chemical Detection Sensitivities of Active and Passive Remote Sensing Systems

    SciTech Connect

    Scharlemann, E T

    2003-07-28

    During nearly a decade of remote sensing programs under the auspices of the U. S. Department of Energy (DOE), LLNL has developed a set of performance modeling codes--called APRS--for both Active and Passive Remote Sensing systems. These codes emphasize chemical detection sensitivity in the form of minimum detectable quantities with and without background spectral clutter and in the possible presence of other interfering chemicals. The codes have been benchmarked against data acquired in both active and passive remote sensing programs at LLNL and Los Alamos National Laboratory (LANL). The codes include, as an integral part of the performance modeling, many of the data analysis techniques developed in the DOE's active and passive remote sensing programs (e.g., ''band normalization'' for an active system, principal component analysis for a passive system).

  17. Endocrine active chemicals and endocrine disruption in Minnesota streams and lakes: implications for aquatic resources, 1994-2008

    USGS Publications Warehouse

    Lee, Kathy E.; Schoenfuss, Heiko L.; Barber, Larry B.; Writer, Jeff H.; Blazer, Vicki; Keisling, Richard L.; Ferrey, Mark L.

    2010-01-01

    Although these studies indicate that wastewater-treatment plant effluent is a conduit for endocrine active chemicals to surface waters, endocrine active chemicals also were present in surface waters with no obvious wastewater-treatment plant effluent sources. Endocrine active chemicals were detected and indicators of endocrine disruption in fish were measured at numerous sites upstream from discharge of wastewater-treatment plant effluent. These observations indicate that other unidentified sources of endocrine active chemicals exist, such as runoff from land surfaces, atmospheric deposition, inputs from onsite septic systems, or other groundwater sources. Alternatively, some endocrine active chemicals may not yet have been identified or measured. The presence of biological indicators of endocrine disruption in male fish indicates that the fish are exposed to endocrine active chemicals. However indicators of endocrine disruption in male fish does not indicate an effect on fish reproduction or changes in fish populations.

  18. Functional, photochemically active, and chemically asymmetric membranes by interfacial polymerization of derivatized multifunctional prepolymers

    DOEpatents

    Lonsdale, Harold K.; Wamser, Carl C.

    1990-01-01

    The preparation of a novel class of thin film membranes by interfacial polymerization is disclosed, said membranes incorporating as part of their polymeric structure the functionality of monomeric or oligomeric precursors. Specific embodiments include porphyrin and phthalocyanine derivatives that are photochemically or electrochemically active, as well as chemically asymmetric membranes.

  19. Functional, photochemically active, and chemically asymmetric membranes by interfacial polymerization of derivatized multifunctional prepolymers

    DOEpatents

    Lonsdale, H.K.; Wamser, C.C.

    1990-04-17

    The preparation of a novel class of thin film membranes by interfacial polymerization is disclosed, said membranes incorporating as part of their polymeric structure the functionality of monomeric or oligomeric precursors. Specific embodiments include porphyrin and phthalocyanine derivatives that are photochemically or electrochemically active, as well as chemically asymmetric membranes.

  20. Functional, photochemically active, and chemically asymmetric membranes by interfacial polymerization of derivatized multifunctional prepolymers

    DOEpatents

    Lonsdale, Harold K.; Wamser, Carl C.

    1988-01-01

    The preparation of a novel class of thin film membranes by interfacial polymerization is disclosed, said membanes incorporating as part of their polymeric structure the functionality of monomeric or oligomeric precursors. Specific embodiments include porphyrin and phthalocyanime derivatives that are photochemically or electrochemically active, as well as chemically asymmetric membranes.

  1. Application of Protein Expression Profiling to Screen Chemicals for Androgenic Activity.

    EPA Science Inventory

    Protein expression changes can be used for detection of biomarkers that can be applied diagnostically to screen chemicals for endocrine modifying activity. In this study, Surface Enhanced Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (SELDI-TOF-MS) coupled with a s...

  2. Chemical composition and biological activity of the essential oil of rhizome of Zingiber zerumbet (L.) smith

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Technical Abstract: The aim was designed to study the biological activity and chemical composition of essential oil of Zingiber zerumbet (L.) Smith. The essential oil extracted from the rhizome of the plant was analysed by gas chromatography-mass spectroscopy and its major components amounting t...

  3. Phoenix dactylifera L. spathe essential oil: Chemical composition and repellent activity against the yellow fever mosquito

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Date palm, Phoenix dactylifera L. (Arecaceae), grows commonly in the Arabian Peninsula and is traditionally used to treat various diseases. The aim of the present study was to identify chemical composition of the essential oil and to investigate the repellent activity. The essential oil of P. dacty...

  4. Lantana montevidensis Essential Oil: Chemical Composition and Mosquito Repellent Activity against Aedes aegypti

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The essential oil (EO) of Lantana montevidensis (Spreng.) Briq. (L. sellowiana Link & Otto) was investigated for its chemical composition and mosquito repellent activity. The essential oil obtained by hydrodistillation of aerial plant parts was analyzed by GC-FID and GC-MS. The major constituents we...

  5. Fenton-Driven Chemical Regeneration of MTBE-Spent Granular Activated Carbon -- A Pilot Study

    EPA Science Inventory

    MTBE-spent granular activated carbon (GAC) underwent 3 adsorption/oxidation cycles. Pilot-scale columns were intermittently placed on-line at a ground water pump and treat facility, saturated with MTBE, and regenerated with H2O2 under different chemical, physical, and operational...

  6. Kinetic effect of Pd additions on the hydrogen uptake of chemically activated, ultramicroporous carbon

    SciTech Connect

    Bhat, Vinay V; Contescu, Cristian I; Gallego, Nidia C

    2010-01-01

    The effect of mixing chemically-activated ultramicroporous carbon (UMC) with Pd nanopowder is investigated. Results show that Pd addition doubles the rate of hydrogen uptake, but does not enhance the hydrogen capacity or improve desorption kinetics. The effect of Pd on the rate of hydrogen adsorption supports the occurrence of the hydrogen spillover mechanism in the Pd - UMC system.

  7. Evaluation of surface waters associated with animal feeding operations for estrogenic chemicals and activity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Estrogens and estrogenic activity (EA) were evaluated in surface waters associated with animal feeding operations. Water was sampled at 19 sites in 12 states using discrete (n=41) and POCIS (n=19) sampling methods. Estrogenic chemicals measured in unfiltered water by GC/MS2 included: estrone (E1),17...

  8. Combining phosphate and bacteria removal on chemically active filter membranes allows prolonged storage of drinking water.

    PubMed

    Rotzetter, A C C; Kellenberger, C R; Schumacher, C M; Mora, C; Grass, R N; Loepfe, M; Luechinger, N A; Stark, W J

    2013-11-13

    A chemically active filtration membrane with incorporated lanthanum oxide nanoparticles enables the removal of bacteria and phosphate at the same time and thus provides a simple device for preparation of drinking water and subsequent safe storage without using any kind of disinfectants.

  9. Estimating Toxicity Pathway Activating Doses for High Throughput Chemical Risk Assessments

    EPA Science Inventory

    Estimating a Toxicity Pathway Activating Dose (TPAD) from in vitro assays as an analog to a reference dose (RfD) derived from in vivo toxicity tests would facilitate high throughput risk assessments of thousands of data-poor environmental chemicals. Estimating a TPAD requires def...

  10. Chemical Genetics: receptor-ligand pairs for rapid manipulation of neuronal activity

    PubMed Central

    Wulff, Peer; Arenkiel, Benjamin R.

    2012-01-01

    Towards the functional dissection of neuronal circuits, a number of new genetic tools have been developed that enable rapid and reversible manipulation of genetically defined neuronal subtypes in intact mammalian brain circuits. Alongside the breakthrough technology of optogenetics, receptor-ligand pairs provide complementary approaches to modulate neuronal activity using chemical-genetics. PMID:22119143

  11. Influence of water and water vapour on the characteristics of KI treated HgI 2 detectors

    NASA Astrophysics Data System (ADS)

    Ponpon, J. P.; Amann, M.; Sieskind, M.

    After being cleaned using a potassium iodide solution in water followed by a water rinse, the surface of mercuric iodide is covered by a chemical complex identified as being KHgI 3·H 2O. This compound can adsorb large quantities of water and its electrical properties are strongly sensitive to water and water vapour. The consequences on the manufacturing and storing conditions (especially the relative humidity), of mercuric iodide-based devices are therefore of great concern. They are illustrated by the study of the electrical and spectrometric properties of HgI 2 nuclear radiation detectors.

  12. Physical and chemical properties and adsorption type of activated carbon prepared from plum kernels by NaOH activation.

    PubMed

    Tseng, Ru-Ling

    2007-08-25

    Activated carbon was prepared from plum kernels by NaOH activation at six different NaOH/char ratios. The physical properties including the BET surface area, the total pore volume, the micropore ratio, the pore diameter, the burn-off, and the scanning electron microscope (SEM) observation as well as the chemical properties, namely elemental analysis and temperature programmed desorption (TPD), were measured. The results revealed a two-stage activation process: stage 1 activated carbons were obtained at NaOH/char ratios of 0-1, surface pyrolysis being the main reaction; stage 2 activated carbons were obtained at NaOH/char ratios of 2-4, etching and swelling being the main reactions. The physical properties of stage 2 activated carbons were similar, and specific area was from 1478 to 1887m(2)g(-1). The results of reaction mechanism of NaOH activation revealed that it was apparently because of the loss ratio of elements C, H, and O in the activated carbon, and the variations in the surface functional groups and the physical properties. The adsorption of the above activated carbons on phenol and three kinds of dyes (MB, BB1, and AB74) were used for an isotherm equilibrium adsorption study. The data fitted the Langmuir isotherm equation. Various kinds of adsorbents showed different adsorption types; separation factor (R(L)) was used to determine the level of favorability of the adsorption type. In this work, activated carbons prepared by NaOH activation were evaluated in terms of their physical properties, chemical properties, and adsorption type; and activated carbon PKN2 was found to have most application potential.

  13. Force-activated reactivity switch in a bimolecular chemical reaction at the single molecule level

    NASA Astrophysics Data System (ADS)

    Szoszkiewicz, Robert; Garcia-Manyes, Sergi; Liang, Jian; Kuo, Tzu-Ling; Fernandez, Julio M.

    2009-10-01

    Mechanical force is a distinct and usually less explored way to activate chemical reaction because it can deform the reacting molecules along a well-defined direction of the reaction coordinate. However, the effect of mechanical force on the free- energy surface that governs a chemical reaction is still largely unknown. The combination of protein engineering with single-molecule force-clamp spectroscopy allows us to study the influence of mechanical force on the rate at which a protein disulfide bond is reduced by some reducing agents in a bimolecular substitution reaction (so-called SN2). We found that cleavage of a protein disulfide bond by hydroxide anions exhibits an abrupt reactivity ``switch'' at 500 pN, after which the accelerating effect of force on the rate of an SN2 chemical reaction greatly diminishes. We propose that an abrupt force- induced conformational change of the protein disulfide bond shifts its ground state, drastically changing its reactivity in SN2 chemical reactions. Our experiments directly demonstrate the action of a force-activated switch in the chemical reactivity of a single molecule. References: S. Garcia-Manyes, J. Liang, R. Szoszkiewicz, T-L. Kuo and J. M. Fernandez, Nature Chemistry, 1, 236-242, 2009.

  14. Active chlorine and nitric oxide formation from chemical rocket plume afterburning

    NASA Technical Reports Server (NTRS)

    Leone, D. M.; Turns, S. R.

    1994-01-01

    Chlorine and oxides of nitrogen (NO(x)) released into the atmosphere contribute to acid rain (ground level or low-altitude sources) and ozone depletion from the stratosphere (high-altitude sources). Rocket engines have the potential for forming or activating these pollutants in the rocket plume. For instance, H2/O2 rockets can produce thermal NO(x) in their plumes. Emphasis, in the past, has been placed on determining the impact of chlorine release on the stratosphere. To date, very little, if any, information is available to understand what contribution NO(x) emissions from ground-based engine testing and actual rocket launches have on the atmosphere. The goal of this work is to estimate the afterburning emissions from chemical rocket plumes and determine their local stratospheric impact. Our study focuses on the space shuttle rocket motors, which include both the solid rocket boosters (SRB's) and the liquid propellant main engines (SSME's). Rocket plume afterburning is modeled employing a one-dimensional model incorporating two chemical kinetic systems: chemical and thermal equilibria with overlayed nitric oxide chemical kinetics (semi equilibrium) and full finite-rate chemical kinetics. Additionally, the local atmospheric impact immediately following a launch is modeled as the emissions diffuse and chemically react in the stratosphere.

  15. Comparison on pore development of activated carbon produced by chemical and physical activation from palm empty fruit bunch

    NASA Astrophysics Data System (ADS)

    Hidayat, A.; Sutrisno, B.

    2016-11-01

    It is well-known that activated carbon is considered to be the general adsorbent due to the large range of applications. Numerous works are being continuously published concerning its use as adsorbent for: treatment of potable water; purification of air; retention of toxins by respirators; removal of organic and inorganic pollutants from flue gases and industrial waste gases and water; recuperation of solvents and hydrocarbons volatilized from petroleum derivatives; catalysis; separation of gas mixtures (molecularsieve activated carbons); storage of natural gas and hydrogen; energy storage in supercapacitors; recovery of gold, silver and othernoble metals; etc. This work presents producing activated carbons from palm empty fruit bunch using both physical activation with CO2 and chemical activation with KOH. The resultant activated carbons were characterized by measuring their porosities and pore size distributions. A comparison of the textural characteristics and surface chemistry of the activated carbon from palm empty fruit bunch by the CO2 and the KOH activation leads to the following findings: An activated carbon by the CO2 activation under the optimum conditions has a BET surface area of 717 m2/g, while that by the KOH activation has a BET surface area of 613 m2/g. The CO2 activation generated a highly microporous carbon (92%) with a Type-I isotherm, while the KOH activation generated a mesoporous one (70%) with a type-IV isotherm, the pore volumes are 0.2135 and 0.7426 cm3.g-1 respectively. The average pore size of the activated carbons is 2.72 and 2.56 nm for KOH activation and CO2 activation, respectively. The FT-IR spectra indicated significant variation in the surface functional groups are quite different for the KOH activated and CO2 activated carbons.

  16. GABA-A receptor antagonists increase firing, bursting and synchrony of spontaneous activity in neuronal networks grown on microelectrode arrays: a step towards chemical "fingerprinting"

    EPA Science Inventory

    Assessment of effects on spontaneous network activity in neurons grown on MEAs is a proposed method to screen chemicals for potential neurotoxicity. In addition, differential effects on network activity (chemical "fingerprints") could be used to classify chemical modes of action....

  17. Characteristics, chemical compositions and biological activities of propolis from Al-Bahah, Saudi Arabia

    PubMed Central

    Elnakady, Yasser A.; Rushdi, Ahmed I.; Franke, Raimo; Abutaha, Nael; Ebaid, Hossam; Baabbad, Mohannad; Omar, Mohamed O. M.; Al Ghamdi, Ahmad A.

    2017-01-01

    Propolis has been used to treat several diseases since ancient times, and is an important source of bioactive natural compounds and drug derivatives. These properties have kept the interest of investigators around the world, leading to the investigation of the chemical and biological properties and application of propolis. In this report, the chemical constituents that are responsible for the anticancer activities of propolis were analyzed. The propolis was sourced from Al-Baha in the southern part of the Kingdom of Saudi Arabia. Standard protocols for chemical fractionation and bioactivity-guided chemical analysis were used to identify the bio-active ethyl acetate fraction. The extraction was performed in methanol and then analyzed by gas chromatography-mass spectrometry (GC-MS). The major compounds are triterpenoids, with a relative concentration of 74.0%; steroids, with a relative concentration of 9.8%; and diterpenoids, with a relative concentration of 7.9%. The biological activity was characterized using different approaches and cell-based assays. Propolis was found to inhibit the proliferation of cancer cells in a concentration-dependent manner through apoptosis. Immunofluorescence staining with anti-α-tubulin antibodies and cell cycle analysis indicated that tubulin and/or microtubules are the cellular targets of the L-acetate fraction. This study demonstrates the importance of Saudi propolis as anti-cancer drug candidates. PMID:28165013

  18. Characteristics, chemical compositions and biological activities of propolis from Al-Bahah, Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Elnakady, Yasser A.; Rushdi, Ahmed I.; Franke, Raimo; Abutaha, Nael; Ebaid, Hossam; Baabbad, Mohannad; Omar, Mohamed O. M.; Al Ghamdi, Ahmad A.

    2017-02-01

    Propolis has been used to treat several diseases since ancient times, and is an important source of bioactive natural compounds and drug derivatives. These properties have kept the interest of investigators around the world, leading to the investigation of the chemical and biological properties and application of propolis. In this report, the chemical constituents that are responsible for the anticancer activities of propolis were analyzed. The propolis was sourced from Al-Baha in the southern part of the Kingdom of Saudi Arabia. Standard protocols for chemical fractionation and bioactivity-guided chemical analysis were used to identify the bio-active ethyl acetate fraction. The extraction was performed in methanol and then analyzed by gas chromatography-mass spectrometry (GC-MS). The major compounds are triterpenoids, with a relative concentration of 74.0%; steroids, with a relative concentration of 9.8%; and diterpenoids, with a relative concentration of 7.9%. The biological activity was characterized using different approaches and cell-based assays. Propolis was found to inhibit the proliferation of cancer cells in a concentration-dependent manner through apoptosis. Immunofluorescence staining with anti-α-tubulin antibodies and cell cycle analysis indicated that tubulin and/or microtubules are the cellular targets of the L-acetate fraction. This study demonstrates the importance of Saudi propolis as anti-cancer drug candidates.

  19. A Study of a QCM Sensor Based on TiO2 Nanostructures for the Detection of NO2 and Explosives Vapours in Air

    PubMed Central

    Procek, Marcin; Stolarczyk, Agnieszka; Pustelny, Tadeusz; Maciak, Erwin

    2015-01-01

    The paper deals with investigations concerning the construction of sensors based on a quartz crystal microbalance (QCM) containing a TiO2 nanostructures sensor layer. A chemical method of synthesizing these nanostructures is presented. The prepared prototype of the QCM sensing system, as well as the results of tests for detecting low NO2 concentrations in an atmosphere of synthetic air have been described. The constructed NO2 sensors operate at room temperature, which is a great advantage, because resistance sensors based on wide gap semiconductors often require much higher operation temperatures, sometimes as high as 500 °C. The sensors constructed by the authors can be used, among other applications, in medical and chemical diagnostics, and also for the purpose of detecting explosive vapours. Reactions of the sensor to nitroglycerine vapours are presented as an example of its application. The influence of humidity on the operation of the sensor was studied. PMID:25912352

  20. Eucalyptus (gracilis, oleosa, salubris, and salmonophloia) essential oils: their chemical composition and antioxidant and antimicrobial activities.

    PubMed

    Ben Marzoug, Hajer Naceur; Bouajila, Jalloul; Ennajar, Monia; Lebrihi, Ahmed; Mathieu, Florence; Couderc, François; Abderraba, Manef; Romdhane, Mehrez

    2010-08-01

    Essential oils of four different Eucalyptus species (Eucalyptus salubris, Eucalyptus salmonophloia, Eucalyptus oleosa, and Eucalyptus gracilis) grown in southern Tunisia were screened for their antioxidant and antimicrobial properties as well as their chemical compositions. According to gas chromatography-flame ionization detection and gas chromatography-mass spectrometry analysis, chemical compositions of the Eucalyptus species E. salubris (27 compounds; 99.2%), E. salmonophloia (31 compounds; 99.2%), E. oleosa (32 compounds; 97.6%), and E. gracilis (18 compounds; 97.7%) were identified. In the 1,1-diphenyl-2-picrylhydrazyl assay, the antioxidant activity was in the range of 12.0-52.8 mg/mL, whereas in the 2,2'-azinobis-3-ethylbenzothiazoline-6-sulfonate assay, E. oleosa (176.5 +/- 3.1 mg/L) gave the best inhibition result. To evaluate antimicrobial activity, all essential oils were tested against bacteria (two Gram-positive and two Gram-negative), two yeast, and two fungi. Essential oils exhibited an interesting antibacterial activity against all microorganisms tested (activity was better against Gram-positive bacteria) except for Staphylococcus aureus and Escherichia coli. Correlations between chemical composition and biological and antioxidant activities were studied.

  1. Enhanced catalytic activity in strained chemically exfoliated WS₂ nanosheets for hydrogen evolution.

    PubMed

    Voiry, Damien; Yamaguchi, Hisato; Li, Junwen; Silva, Rafael; Alves, Diego C B; Fujita, Takeshi; Chen, Mingwei; Asefa, Tewodros; Shenoy, Vivek B; Eda, Goki; Chhowalla, Manish

    2013-09-01

    Efficient evolution of hydrogen through electrocatalysis at low overpotentials holds tremendous promise for clean energy. Hydrogen evolution can be easily achieved by electrolysis at large potentials that can be lowered with expensive platinum-based catalysts. Replacement of Pt with inexpensive, earth-abundant electrocatalysts would be significantly beneficial for clean and efficient hydrogen evolution. To this end, promising results have been reported using 2H (trigonal prismatic) XS₂ (where X  =  Mo or W) nanoparticles with a high concentration of metallic edges. The key challenges for XS₂ are increasing the number and catalytic activity of active sites. Here we report monolayered nanosheets of chemically exfoliated WS₂ as efficient catalysts for hydrogen evolution with very low overpotentials. Analyses indicate that the enhanced electrocatalytic activity of WS₂ is associated with the high concentration of the strained metallic 1T (octahedral) phase in the as-exfoliated nanosheets. Our results suggest that chemically exfoliated WS₂ nanosheets are interesting catalysts for hydrogen evolution.

  2. Spatiotemporal regulation of chemical reaction kinetics of cell surface molecules by active remodeling of cortical actin

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, Bhaswati; Chaudhuri, Abhishek; Gowrishankar, Kripa; Mayor, Satyajit; Rao, Madan

    2010-03-01

    Cell surface proteins such as lipid tethered GPI-anchored proteins and Ras-proteins are distributed as monomers and nanoclusters on the surface of living cells. Recent work from our laboratory suggests that the spatial distribution and dynamics of formation and breakup of these nanoclusters is controlled by the active remodeling dynamics of the underlying cortical actin. To explain these observations, we propose a novel mechanism of nanoclustering, involving the transient binding to and advection along constitutively occuring ``asters'' of cortical actin. Here we study the consequences of such active actin based clustering, in the context of chemical reactions involving conformational changes of cell surface proteins. We find that active remodeling of cortical actin, can give rise to a dramatic increase in the reaction efficiency and output levels. In general, such actin driven clustering of membrane proteins could be a cellular mechanism to spatiotemporally regulate and amplify local chemical reaction rates, in the context of signalling and endocytosis.

  3. Chemical composition and antibacterial activity of Opuntia ficus-indica f. inermis (cactus pear) flowers.

    PubMed

    Ennouri, Monia; Ammar, Imene; Khemakhem, Bassem; Attia, Hamadi

    2014-08-01

    Opuntia ficus-indica f. inermis (cactus pear) flowers have wide application in folk medicine. However, there are few reports focusing on their biological activity and were no reports on their chemical composition. The nutrient composition and hexane extracts of Opuntia flowers at 4 flowering stages and their antibacterial and antifungal activities were investigated. The chemical composition showed considerable amounts of fiber, protein, and minerals. Potassium (K) was the predominant mineral followed by calcium (Ca), magnesium (Mg), sodium (Na), iron (Fe), and zinc (Zn). The main compounds in the various hexane extracts were 9.12-octadecadienoic acid (29-44%) and hexadecanoic acid (8.6-32%). The antibacterial activity tests showed that O. inermis hexane extracts have high effectiveness against Escherichia coli and Staphylococcus aureus, making this botanical source a potential contender as a food preservative or food control additive.

  4. Chemical composition and larvicidal activity of several essential oils from Hypericum species from Tunisia.

    PubMed

    Rouis, Zyed; Laamari, Ali; Abid, Nabil; Elaissi, Ameur; Cioni, Pier Luigi; Flamini, Guido; Aouni, Mahjoub

    2013-02-01

    The chemical composition of the essential oils extracted from some Tunisian Hypericum species and their larvicidal activity against Culex pipiens larvae were evaluated. The chemical compositions of the essential oils from the aerial plant parts were analyzed using gas chromatography-mass spectrometry. One hundred and thirty-four compounds were identified, ranging between 85.1 and 95.4 % of the oil's composition. The components were monoterpene hydrocarbons, oxygenated monoterpenes, sesquiterpene hydrocarbons, oxygenated sesquiterpenes, non-terpenic hydrocarbons, and others. The larvicidal activity of the essential oils was evaluated using a method recommended by WHO. Larvicidal tests revealed that essential oils from the Hypericum species have a significant larvicidal activity against C. pipiens, with LC(50) ranging between 102.82 and 194.70 ppm. The most powerful essential oils against these larvae were Hypericum tomentosum and Hypericum humifusum samples, followed by the essential oil of Hypericum perforatum.

  5. Seasonal Variation, Chemical Composition and Antioxidant activity of Brazilian Propolis Samples

    PubMed Central

    Teixeira, Érica Weinstein; Message, Dejair; Negri, Giuseppina; Stringheta, Paulo César

    2010-01-01

    Total phenolic contents, antioxidant activity and chemical composition of propolis samples from three localities of Minas Gerais state (southeast Brazil) were determined. Total phenolic contents were determined by the Folin–Ciocalteau method, antioxidant activity was evaluated by DPPH, using BHT as reference, and chemical composition was analyzed by GC/MS. Propolis from Itapecerica and Paula Cândido municipalities were found to have high phenolic contents and pronounced antioxidant activity. From these extracts, 40 substances were identified, among them were simple phenylpropanoids, prenylated phenylpropanoids, sesqui- and diterpenoids. Quantitatively, the main constituent of both samples was allyl-3-prenylcinnamic acid. A sample from Virginópolis municipality had no detectable phenolic substances and contained mainly triterpenoids, the main constituents being α- and β-amyrins. Methanolic extracts from Itapecerica and Paula Cândido exhibited pronounced scavenging activity towards DPPH, indistinguishable from BHT activity. However, extracts from Virginópolis sample exhibited no antioxidant activity. Total phenolic substances, GC/MS analyses and antioxidant activity of samples from Itapecerica collected monthly over a period of 1 year revealed considerable variation. No correlation was observed between antioxidant activity and either total phenolic contents or contents of artepillin C and other phenolic substances, as assayed by CG/MS analysis. PMID:18955317

  6. Seasonal variation, chemical composition and antioxidant activity of Brazilian propolis samples.

    PubMed

    Teixeira, Erica Weinstein; Message, Dejair; Negri, Giuseppina; Salatino, Antonio; Stringheta, Paulo César

    2010-09-01

    Total phenolic contents, antioxidant activity and chemical composition of propolis samples from three localities of Minas Gerais state (southeast Brazil) were determined. Total phenolic contents were determined by the Folin-Ciocalteau method, antioxidant activity was evaluated by DPPH, using BHT as reference, and chemical composition was analyzed by GC/MS. Propolis from Itapecerica and Paula Cândido municipalities were found to have high phenolic contents and pronounced antioxidant activity. From these extracts, 40 substances were identified, among them were simple phenylpropanoids, prenylated phenylpropanoids, sesqui- and diterpenoids. Quantitatively, the main constituent of both samples was allyl-3-prenylcinnamic acid. A sample from Virginópolis municipality had no detectable phenolic substances and contained mainly triterpenoids, the main constituents being α- and β-amyrins. Methanolic extracts from Itapecerica and Paula Cândido exhibited pronounced scavenging activity towards DPPH, indistinguishable from BHT activity. However, extracts from Virginópolis sample exhibited no antioxidant activity. Total phenolic substances, GC/MS analyses and antioxidant activity of samples from Itapecerica collected monthly over a period of 1 year revealed considerable variation. No correlation was observed between antioxidant activity and either total phenolic contents or contents of artepillin C and other phenolic substances, as assayed by CG/MS analysis.

  7. Evaluation of mycobactericidal activity of selected chemical disinfectants and antiseptics according to European standards

    PubMed Central

    Bocian, Ewa; Grzybowska, Wanda; Tyski, Stefan

    2014-01-01

    Background The history of the investigation of standardized mycobactericidal activity of disinfectants and antiseptics is not very long. There is growing interest among the manufacturers of disinfectants in carrying out research on the antimicrobial activities in accordance with European standards (EN). This research could facilitate the introduction of high-quality disinfectants to the market. The aim of this study was to evaluate the mycobactericidal activity of selected chemical disinfectants and antiseptics used in the medical and veterinary fields. Material/Methods This study included 19 products submitted to the National Medicines Institute in Poland for evaluation of mycobactericidal activity. These products contain in their composition active substances belonging to different chemical groups, including aldehydes, alcohols, amines, quaternary ammonium compounds, phenols, guanidine, and oxidizing compounds. This study, conducted according to the manufacturers’ description of the preparations, was carried out in accordance with European standards, which also met the Polish standards: PN-EN 14204: 2013, PN-EN 14348: 2006, and PN-EN 14563: 2012. Results Tested products for disinfection and antiseptics containing active substances from different chemical groups showed high mycobactericidal activity and met the requirements of the appropriate European standards in most cases. In the case of products containing guanidine and amine compounds, the concentration of active ingredients used in the test and the test conditions specified by the manufacturer did not provide the mycobactericidal activity required by the standards. Conclusions Prior to the launch of a new product on the market, it is important to establish the appropriate usage and testing conditions of the preparation, such as its practical concentration, contact time, and environment condition (clean or dirty). PMID:24755666

  8. Influence of Copper Nanoparticles on the Physical-Chemical Properties of Activated Sludge

    PubMed Central

    Chen, Hong; Zheng, Xiong; Chen, Yinguang; Li, Mu; Liu, Kun; Li, Xiang

    2014-01-01

    The physical-chemical properties of activated sludge, such as flocculating ability, hydrophobicity, surface charge, settleability, dewaterability and bacteria extracellular polymer substances (EPS), play vital roles in the normal operation of wastewater treatment plants (WWTPs). The nanoparticles released from commercial products will enter WWTPs and can induce potential adverse effects on activated sludge. This paper focused on the effects of copper nanoparticles (CuNPs) on these specific physical-chemical properties of activated sludge. It was found that most of these properties were unaffected by the exposure to lower CuNPs concentration (5 ppm), but different observation were made at higher CuNPs concentrations (30 and 50 ppm). At the higher CuNPs concentrations, the sludge surface charge increased and the hydrophobicity decreased, which were attributed to more Cu2+ ions released from the CuNPs. The carbohydrate content of EPS was enhanced to defense the toxicity of CuNPs. The flocculating ability was found to be deteriorated due to the increased cell surface charge, the decreased hydrophobicity, and the damaged cell membrane. The worsened flocculating ability made the sludge flocs more dispersed, which further increased the toxicity of the CuNPs by increasing the availability of the CuNPs to the bacteria present in the sludge. Further investigation indicated that the phosphorus removal efficiency decreased at higher CuNPs concentrations, which was consistent with the deteriorated physical-chemical properties of activated sludge. It seems that the physical-chemical properties can be used as an indicator for determining CuNPs toxicity to the bacteria in activated sludge. This work is important because bacteria toxicity effects to the activated sludge caused by nanoparticles may lead to the deteriorated treatment efficiency of wastewater treatment, and it is therefore necessary to find an easy way to indicate this toxicity. PMID:24663333

  9. Influence of copper nanoparticles on the physical-chemical properties of activated sludge.

    PubMed

    Chen, Hong; Zheng, Xiong; Chen, Yinguang; Li, Mu; Liu, Kun; Li, Xiang

    2014-01-01

    The physical-chemical properties of activated sludge, such as flocculating ability, hydrophobicity, surface charge, settleability, dewaterability and bacteria extracellular polymer substances (EPS), play vital roles in the normal operation of wastewater treatment plants (WWTPs). The nanoparticles released from commercial products will enter WWTPs and can induce potential adverse effects on activated sludge. This paper focused on the effects of copper nanoparticles (CuNPs) on these specific physical-chemical properties of activated sludge. It was found that most of these properties were unaffected by the exposure to lower CuNPs concentration (5 ppm), but different observation were made at higher CuNPs concentrations (30 and 50 ppm). At the higher CuNPs concentrations, the sludge surface charge increased and the hydrophobicity decreased, which were attributed to more Cu2+ ions released from the CuNPs. The carbohydrate content of EPS was enhanced to defense the toxicity of CuNPs. The flocculating ability was found to be deteriorated due to the increased cell surface charge, the decreased hydrophobicity, and the damaged cell membrane. The worsened flocculating ability made the sludge flocs more dispersed, which further increased the toxicity of the CuNPs by increasing the availability of the CuNPs to the bacteria present in the sludge. Further investigation indicated that the phosphorus removal efficiency decreased at higher CuNPs concentrations, which was consistent with the deteriorated physical-chemical properties of activated sludge. It seems that the physical-chemical properties can be used as an indicator for determining CuNPs toxicity to the bacteria in activated sludge. This work is important because bacteria toxicity effects to the activated sludge caused by nanoparticles may lead to the deteriorated treatment efficiency of wastewater treatment, and it is therefore necessary to find an easy way to indicate this toxicity.

  10. Chemical characteristic and anticoagulant activity of the sulfated polysaccharide isolated from Monostroma latissimum (Chlorophyta).

    PubMed

    Mao, Wenjun; Li, Hongyan; Li, Yi; Zhang, Huijuan; Qi, Xiaohui; Sun, Haihong; Chen, Yin; Guo, Shoudong

    2009-01-01

    A polysaccharide was isolated from marine green algae Monostroma latissimum, and its chemical characteristic and anticoagulant activity were investigated. The results demonstrated that the polysaccharide was high rhamnose-containing sulfated polysaccharide, and was mainly composed of 1,2-linked l-rhamnose residues with sulfate groups substituted at positions C-3 and/or C-4. The sulfated polysaccharide exhibited high anticoagulant activities by assays of the activated partial thromboplastin time (APTT) and thrombin time (TT). The anticoagulant property of the sulfated polysaccharide was mainly attributed to powerful potentiation thrombin by heparin cofactor II.

  11. Estimating the toxicities of organic chemicals to bioluminescent bacteria and activated sludge.

    PubMed

    Ren, Shijin; Frymier, Paul D

    2002-10-01

    Toxicity assays based on bioluminescent bacteria have several advantages including a quick response and an easily measured signal. The Shk1 assay is a procedure for wastewater toxicity testing based on the bioluminescent bacterium Shk1. Using the Shk1 assay, the toxicity of 98 organic chemicals were measured and EC50 values were obtained. Quantitative structure-activity relationship (QSAR) models based on the logarithm of the octanol-water partition coefficient (log(Kow)) were developed for individual groups of organic chemicals with different functional groups. The correlation coefficients for different groups of organic compounds varied between 0.69 and 0.99. An overall QSAR model without discriminating the functional groups, which can be used for a quick estimate of the toxicities of organic chemicals, was also developed and model predictions were compared to experimental data. The model accuracy was found to be one order of magnitude from the observed values.

  12. Effect of mechanical activation on structure changes and reactivity in further chemical modification of lignin.

    PubMed

    Zhao, Xiaohong; Zhang, Yanjuan; Hu, Huayu; Huang, Zuqiang; Yang, Mei; Chen, Dong; Huang, Kai; Huang, Aimin; Qin, Xingzhen; Feng, Zhenfei

    2016-10-01

    Lignin was treated by mechanical activation (MA) in a customized stirring ball mill, and the structure and reactivity in further esterification were studied. The chemical structure and morphology of MA-treated lignin and the esterified products were analyzed by chemical analysis combined with UV/vis spectrometer, FTIR,NMR, SEM and particle size analyzer. The results showed that MA contributed to the increase of aliphatic hydroxyl, phenolic hydroxyl, carbonyl and carboxyl groups but the decrease of methoxyl groups. Moreover, MA led to the decrease of particle size and the increase of specific surface area and roughness of surface in lignin. The reactivity of lignin was enhanced significantly for the increase of hydroxyl content and the improvement of mass transfer in chemical reaction caused by the changes of molecular structure and morphological structure. The process of MA is green and simple, and is an effective method for enhancing the reactivity of lignin.

  13. Chemical composition measurements of the low activity waste (LAW) EPA-Series glasses

    SciTech Connect

    Fox, K.; Edwards, T. B.

    2016-03-01

    In this report, the Savannah River National Laboratory provides chemical analysis results for a series of simulated low activity waste glasses provided by Pacific Northwest National Laboratory as part of an ongoing development task. The measured chemical composition data are reported and compared with the targeted values for each component for each glass. A detailed review showed no indications of errors in the preparation or measurement of the study glasses. All of the measured sums of oxides for the study glasses fell within the interval of 100.2 to 100.8 wt %, indicating recovery of all components. Comparisons of the targeted and measured chemical compositions showed that the measured values for the glasses met the targeted concentrations within 10% for those components present at more than 5 wt %.

  14. Removal efficiency of vapour/particulate phase PAHs by using alternative protective respirators in PAHs exposure workers.

    PubMed

    Chen, Hsiu-Ling; Yang, Chien-Hung; Lin, Ming-Hsiu

    2012-06-15

    Due to the high heat environment in foundry industries, it is difficult for foundry workers to wear masks during their workday. Thus, how to prevent inhaling vapour or the particulate phase of polycyclic aromatic hydrocarbons (PAHs) is important for occupational hazard management. The present study assesses the characteristics of PAHs emission in foundry and plastic industries to evaluate the removal efficiencies of PAHs while workers use alternative personal protective equipment. The highest 1-hydroxypyrene (1-OHP) level was found for workers who used a cotton-fabric face mask (1.19 μg/g creatinine) and activated-carbon face mask (1.16 μg/g creatinine), compared to a lower level in workers who wore a surgical face mask (0.27 μg/g creatinine) and a N95 respirator (0.51 μg/g creatinine). The urinary 1-OHP in end-of-shift samples correlated to the airborne vapour phase Bapeq, but not for the particulate phase Bapeq in the foundry industry. This is probably because workers wore personal protective equipment that only removed the particulate phase PAH. The current study suggests that future work focus on developing an appropriate and comfortable respirator with high removal efficiency for ultrafine particulates and vapour phase PAHs simultaneously in PAH work environments.

  15. Effect of operating temperature on transient behaviour of a biofilter treating waste-air containing n-butanol vapour during intermittent loading.

    PubMed

    Feizi, Farzaneh; Nasernejad, Bahram; Zamir, Seyed Morteza

    2016-01-01

    Transient-state removal of n-butanol vapour was investigated in a biofilter (BF) packed with compost and lava rock at different operating temperatures in the range of 30-45°C under intermittent loading (8 h per day). Adsorption on the inactive bed and biodegradation in the microbial-active bed were studied separately at an empty bed residence time (EBRT) of 1 min and inlet concentrations of 2.6-3.2 g m(-3), respectively. According to the transient experiments, the highest removal efficiency (RE) around 86% was obtained at 40°C due to a high microbial activity. Comparison of CO2 production and pure adsorption of n-butanol showed that adsorption was the major mechanism in the start-up of BF at each operating condition; although the impact of adsorption declined as temperature increased from 30°C to 45°C. The process was reaction limited at all operating conditions. Based on the determination of stoichiometric coefficients of n-butanol biodegradation, the CO2 production level was significantly lower than that of the chemical oxidation process which resulted in a decrease in environmental pollution.

  16. Chemical analysis of Greek pollen - Antioxidant, antimicrobial and proteasome activation properties

    PubMed Central

    2011-01-01

    Background Pollen is a bee-product known for its medical properties from ancient times. In our days is increasingly used as health food supplement and especially as a tonic primarily with appeal to the elderly to ameliorate the effects of ageing. In order to evaluate the chemical composition and the biological activity of Greek pollen which has never been studied before, one sample with identified botanical origin from sixteen different common plant taxa of Greece has been evaluated. Results Three different extracts of the studied sample of Greek pollen, have been tested, in whether could induce proteasome activities in human fibroblasts. The water extract was found to induce a highly proteasome activity, showing interesting antioxidant properties. Due to this activity the aqueous extract was further subjected to chemical analysis and seven flavonoids have been isolated and identified by modern spectral means. From the methanolic extract, sugars, lipid acids, phenolic acids and their esters have been also identified, which mainly participate to the biosynthetic pathway of pollen phenolics. The total phenolics were estimated with the Folin-Ciocalteau reagent and the total antioxidant activity was determined by the DPPH method while the extracts and the isolated compounds were also tested for their antimicrobial activity by the dilution technique. Conclusions The Greek pollen is rich in flavonoids and phenolic acids which indicate the observed free radical scavenging activity, the effects of pollen on human fibroblasts and the interesting antimicrobial profile. PMID:21699688

  17. Chemical stability of a cold-active cellulase with high tolerance toward surfactants and chaotropic agent.

    PubMed

    Souza, Thaís V; Araujo, Juscemácia N; da Silva, Viviam M; Liberato, Marcelo V; Pimentel, Agnes C; Alvarez, Thabata M; Squina, Fabio M; Garcia, Wanius

    2016-03-01

    CelE1 is a cold-active endo-acting glucanase with high activity at a broad temperature range and under alkaline conditions. Here, we examined the effects of pH on the secondary and tertiary structures, net charge, and activity of CelE1. Although variation in pH showed a small effect in the enzyme structure, the activity was highly influenced at acidic conditions, while reached the optimum activity at pH 8. Furthermore, to estimate whether CelE1 could be used as detergent additives, CelE1 activity was evaluated in the presence of surfactants. Ionic and nonionic surfactants were not able to reduce CelE1 activity significantly. Therefore, CelE1 was found to be promising candidate for use as detergent additives. Finally, we reported a thermodynamic analysis based on the structural stability and the chemical unfolding/refolding process of CelE1. The results indicated that the chemical unfolding proceeds as a reversible two-state process. These data can be useful for biotechnological applications.

  18. Sequential extraction study of stability of adsorbed mercury in chemically modified activated carbons.

    PubMed

    Tong, Shitang; Fan, Mingxia; Mao, Lei; Jia, Charles Q

    2011-09-01

    Activated carbons chemically modified with sulfur and bromine are known for their greater effectiveness in capturing vapor Hg from coal combustion and other industrial flue gases. The stability of captured Hg in spent activated carbons determines the final fate of Hg and is critical to devising Hg control strategy. However, it remains a subject that is largely unknown, particularly for Br-treated activated carbons. Using a six-step sequential extraction procedure, this work evaluated the leaching potential of Hg captured with four activated carbons, one lignite-derived activated carbon, and three chemically treated with Br(2), KClO(3), and SO(2). The results demonstrated clearly the positive effect of Br- and SO(2)-treatment on the stability of captured Hg. The Hg captured with brominated activated carbon was very stable and likely in the form of mercurous bromide complex. Sulfur added at high temperature with SO(2) was able to stabilize a majority of Hg by forming sulfide and possibly sulfonate chelate. The presence of sulfate however made a small fraction of captured Hg (<10%) labile under mild conditions. Treating activated carbon with KClO(3) lowered the overall stability of captured Hg. A positive dependence of Hg stability on Hg loading temperature was observed for the first time.

  19. Chemical composition and lipoxygenase activity in soybeans (Glycine max L. Merr.) submitted to gamma irradiation

    NASA Astrophysics Data System (ADS)

    Barros, Érica Amanda de; Broetto, Fernando; Bressan, Dayanne F.; Sartori, Maria M. P.; Costa, Vladimir E.

    2014-05-01

    Soybeans are an important food due to their functional and nutritional characteristics. However, consumption by western populations is limited by the astringent taste of soybeans and their derivatives which results from the action of lipoxygenase, an enzyme activated during product processing. The aim of this study was to evaluate the effect of gamma irradiation on the chemical composition and specific activity of lipoxygenase in different soybean cultivars. Soybeans were stored in plastic bags and irradiated with doses of 2.5, 5 and 10 kGy. The chemical composition (moisture, protein, lipids, ashes, crude fiber, and carbohydrates) and lipoxygenase specific activity were determined for each sample. Gamma irradiation induced a small increase of protein and lipid content in some soybean cultivars, which did not exceed the highest content of 5% and 26%, respectively, when compared to control. Lipoxygenase specific activity decreased in the three cultivars with increasing gamma irradiation dose. In conclusion, the gamma irradiation doses used are suitable to inactivate part of lipoxygenase while not causing expressive changes in the chemical composition of the cultivars studied.

  20. Chemical Structure-Biological Activity Models for Pharmacophores’ 3D-Interactions

    PubMed Central

    Putz, Mihai V.; Duda-Seiman, Corina; Duda-Seiman, Daniel; Putz, Ana-Maria; Alexandrescu, Iulia; Mernea, Maria; Avram, Speranta

    2016-01-01

    Within medicinal chemistry nowadays, the so-called pharmaco-dynamics seeks for qualitative (for understanding) and quantitative (for predicting) mechanisms/models by which given chemical structure or series of congeners actively act on biological sites either by focused interaction/therapy or by diffuse/hazardous influence. To this aim, the present review exposes three of the fertile directions in approaching the biological activity by chemical structural causes: the special computing trace of the algebraic structure-activity relationship (SPECTRAL-SAR) offering the full analytical counterpart for multi-variate computational regression, the minimal topological difference (MTD) as the revived precursor for comparative molecular field analyses (CoMFA) and comparative molecular similarity indices analysis (CoMSIA); all of these methods and algorithms were presented, discussed and exemplified on relevant chemical medicinal systems as proton pump inhibitors belonging to the 4-indolyl,2-guanidinothiazole class of derivatives blocking the acid secretion from parietal cells in the stomach, the 1-[(2-hydroxyethoxy)-methyl]-6-(phenylthio)thymine congeners’ (HEPT ligands) antiviral activity against Human Immunodeficiency Virus of first type (HIV-1) and new pharmacophores in treating severe genetic disorders (like depression and psychosis), respectively, all involving 3D pharmacophore interactions. PMID:27399692

  1. Quantitative structure-activity relationship models of chemical transformations from matched pairs analyses.

    PubMed

    Beck, Jeremy M; Springer, Clayton

    2014-04-28

    The concepts of activity cliffs and matched molecular pairs (MMP) are recent paradigms for analysis of data sets to identify structural changes that may be used to modify the potency of lead molecules in drug discovery projects. Analysis of MMPs was recently demonstrated as a feasible technique for quantitative structure-activity relationship (QSAR) modeling of prospective compounds. Although within a small data set, the lack of matched pairs, and the lack of knowledge about specific chemical transformations limit prospective applications. Here we present an alternative technique that determines pairwise descriptors for each matched pair and then uses a QSAR model to estimate the activity change associated with a chemical transformation. The descriptors effectively group similar transformations and incorporate information about the transformation and its local environment. Use of a transformation QSAR model allows one to estimate the activity change for novel transformations and therefore returns predictions for a larger fraction of test set compounds. Application of the proposed methodology to four public data sets results in increased model performance over a benchmark random forest and direct application of chemical transformations using QSAR-by-matched molecular pairs analysis (QSAR-by-MMPA).

  2. Chemical Structure-Biological Activity Models for Pharmacophores' 3D-Interactions.

    PubMed

    Putz, Mihai V; Duda-Seiman, Corina; Duda-Seiman, Daniel; Putz, Ana-Maria; Alexandrescu, Iulia; Mernea, Maria; Avram, Speranta

    2016-07-08

    Within medicinal chemistry nowadays, the so-called pharmaco-dynamics seeks for qualitative (for understanding) and quantitative (for predicting) mechanisms/models by which given chemical structure or series of congeners actively act on biological sites either by focused interaction/therapy or by diffuse/hazardous influence. To this aim, the present review exposes three of the fertile directions in approaching the biological activity by chemical structural causes: the special computing trace of the algebraic structure-activity relationship (SPECTRAL-SAR) offering the full analytical counterpart for multi-variate computational regression, the minimal topological difference (MTD) as the revived precursor for comparative molecular field analyses (CoMFA) and comparative molecular similarity indices analysis (CoMSIA); all of these methods and algorithms were presented, discussed and exemplified on relevant chemical medicinal systems as proton pump inhibitors belonging to the 4-indolyl,2-guanidinothiazole class of derivatives blocking the acid secretion from parietal cells in the stomach, the 1-[(2-hydroxyethoxy)-methyl]-6-(phenylthio)thymine congeners' (HEPT ligands) antiviral activity against Human Immunodeficiency Virus of first type (HIV-1) and new pharmacophores in treating severe genetic disorders (like depression and psychosis), respectively, all involving 3D pharmacophore interactions.

  3. Activity Enhancement Based on the Chemical Equilibrium of Multiple-Subunit Nitrile Hydratase from Bordetella petrii.

    PubMed

    Liu, Yi; Liu, Ping; Lin, Lu; Zhao, Yueqin; Zhong, Wenjuan; Wu, Lunjie; Zhou, Zhemin; Sun, Weifeng

    2016-09-01

    The maturation mechanism of nitrile hydratase (NHase) of Pseudomonas putida NRRL-18668 was discovered and named as "self-subunit swapping." Since the NHase of Bordetella petrii DSM 12804 is similar to that of P. putida, the NHase maturation of B. petrii is proposed to be the same as that of P. putida. However, there is no further information on the application of NHase according to these findings. We successfully rapidly purified NHase and its activator through affinity his tag, and found that the cell extracts of NHase possessed multiple types of protein ingredients including α, β, α2β2, and α(P14K)2 who were in a state of chemical equilibrium. Furthermore, the activity was significantly enhanced through adding extra α(P14K)2 to the cell extracts of NHase according to the chemical equilibrium. Our findings are useful for the activity enhancement of multiple-subunit enzyme and for the first time significantly increased the NHase activity according to the chemical equilibrium.

  4. Plasma formation in water vapour layers in high conductivity liquids

    NASA Astrophysics Data System (ADS)

    Kelsey, C. P.; Schaper, L.; Stalder, K. R.; Graham, W. G.

    2011-10-01

    The vapour layer development stage of relatively low voltage plasmas in conducting solutions has already been well explored. The nature of the discharges formed within the vapour layer however is still largely unexplored. Here we examine the nature of such discharges through a combination of fast imaging and spatially, temporally resolved spectroscopy and electrical characterisation. The experimental setup used is a pin-to-plate discharge configuration with a -350V, 200 μs pulse applied at a repetition rate of 2Hz. A lens, followed by beam splitter allows beams to one Andor ICCD camera to capture images of the plasma emission with a second camera at the exit of a high resolution spectrometer. Through synchronization of the camera images at specified times after plasma ignition (as determined from current-voltage characteristics) they can be correlated with the spectra features. Initial measurements reveal two apparently different plasma formations. Stark broadening of the hydrogen Balmer beta line indicate electron densities of 3 to 5 ×1020 m-3 for plasmas produced early in the voltage pulse and an order of magnitude less for the later plasmas. The vapour layer development stage of relatively low voltage plasmas in conducting solutions has already been well explored. The nature of the discharges formed within the vapour layer however is still largely unexplored. Here we examine the nature of such discharges through a combination of fast imaging and spatially, temporally resolved spectroscopy and electrical characterisation. The experimental setup used is a pin-to-plate discharge configuration with a -350V, 200 μs pulse applied at a repetition rate of 2Hz. A lens, followed by beam splitter allows beams to one Andor ICCD camera to capture images of the plasma emission with a second camera at the exit of a high resolution spectrometer. Through synchronization of the camera images at specified times after plasma ignition (as determined from current

  5. The uptake of elemental iodine vapour by bean leaves

    NASA Astrophysics Data System (ADS)

    Garland, J. A.; Cox, L. C.

    Deposition of iodine vapour to leaves of phaseolus vulgaris was measured over a range of conditions of humidity, temperature and illumination. Transpiration measurements were used to deduce stomatal opening. The results showed that stomatal resistance controlled iodine absorption at relative humidities below 40 per cent, but that the rate of absorption of iodine increased by an order of magnitude when the relative humidity was raised to 80 per cent, presumably due to cuticular absorption. After exposure to iodine at high humidity, a substantial fraction of the iodine could be washed from the leaves. In Britain, cuticular uptake would probably dominate stomatal uptake of iodine on most occasions.

  6. Combined Dial Sounding of Ozone, Water Vapour and Aerosol

    NASA Astrophysics Data System (ADS)

    Trickl, Thomas; Vogelmann, Hannes

    2016-06-01

    Routine high-quality lidar measurements of ozone, water vapour and aerosol at Garmisch-Partenkirchen since 2007 have made possible more comprehensive atmospheric studies and lead to a growing insight concerning the most frequently occurring long-range transport pathways. In this contribution we present as examples results on stratospheric layers travelling in the free troposphere for extended periods of time without eroding. In particular, we present a case of an intrusion layer that subsided over as many as fifteen days and survived the interference by strong Canadian fires. These results impose a challenge on atmospheric modelling that grossly overestimates free-tropospheric mixing.

  7. Metabolomic Assessment of Induced and Activated Chemical Defence in the Invasive Red Alga Gracilaria vermiculophylla

    PubMed Central

    Nylund, Göran M.; Weinberger, Florian; Rempt, Martin; Pohnert, Georg

    2011-01-01

    In comparison with terrestrial plants the mechanistic knowledge of chemical defences is poor for marine macroalgae. This restricts our understanding in the chemically mediated interactions that take place between algae and other organisms. Technical advances such as metabolomics, however, enable new approaches towards the characterisation of the chemically mediated interactions of organisms with their environment. We address defence responses in the red alga Gracilaria vermiculophylla using mass spectrometry based metabolomics in combination with bioassays. Being invasive in the north Atlantic this alga is likely to possess chemical defences according to the prediction that well-defended exotics are most likely to become successful invaders in systems dominated by generalist grazers, such as marine macroalgal communities. We investigated the effect of intense herbivore feeding and simulated herbivory by mechanical wounding of the algae. Both processes led to similar changes in the metabolic profile. Feeding experiments with the generalist isopod grazer Idotea baltica showed that mechanical wounding caused a significant increase in grazer resistance. Structure elucidation of the metabolites of which some were up-regulated more than 100 times in the wounded tissue, revealed known and novel eicosanoids as major components. Among these were prostaglandins, hydroxylated fatty acids and arachidonic acid derived conjugated lactones. Bioassays with pure metabolites showed that these eicosanoids are part of the innate defence system of macroalgae, similarly to animal systems. In accordance with an induced defence mechanism application of extracts from wounded tissue caused a significant increase in grazer resistance and the up-regulation of other pathways than in the activated defence. Thus, this study suggests that G. vermiculophylla chemically deters herbivory by two lines of defence, a rapid wound-activated process followed by a slower inducible defence. By unravelling

  8. Metabolomic assessment of induced and activated chemical defence in the invasive red alga Gracilaria vermiculophylla.

    PubMed

    Nylund, Göran M; Weinberger, Florian; Rempt, Martin; Pohnert, Georg

    2011-01-01

    In comparison with terrestrial plants the mechanistic knowledge of chemical defences is poor for marine macroalgae. This restricts our understanding in the chemically mediated interactions that take place between algae and other organisms. Technical advances such as metabolomics, however, enable new approaches towards the characterisation of the chemically mediated interactions of organisms with their environment. We address defence responses in the red alga Gracilaria vermiculophylla using mass spectrometry based metabolomics in combination with bioassays. Being invasive in the north Atlantic this alga is likely to possess chemical defences according to the prediction that well-defended exotics are most likely to become successful invaders in systems dominated by generalist grazers, such as marine macroalgal communities. We investigated the effect of intense herbivore feeding and simulated herbivory by mechanical wounding of the algae. Both processes led to similar changes in the metabolic profile. Feeding experiments with the generalist isopod grazer Idotea baltica showed that mechanical wounding caused a significant increase in grazer resistance. Structure elucidation of the metabolites of which some were up-regulated more than 100 times in the wounded tissue, revealed known and novel eicosanoids as major components. Among these were prostaglandins, hydroxylated fatty acids and arachidonic acid derived conjugated lactones. Bioassays with pure metabolites showed that these eicosanoids are part of the innate defence system of macroalgae, similarly to animal systems. In accordance with an induced defence mechanism application of extracts from wounded tissue caused a significant increase in grazer resistance and the up-regulation of other pathways than in the activated defence. Thus, this study suggests that G. vermiculophylla chemically deters herbivory by two lines of defence, a rapid wound-activated process followed by a slower inducible defence. By unravelling

  9. Computational reverse chemical ecology: Virtual screening and predicting behaviorally active semiochemicals for Bactrocera dorsalis

    PubMed Central

    2014-01-01

    Background Semiochemical is a generic term used for a chemical substance that influences the behaviour of an organism. It is a common term used in the field of chemical ecology to encompass pheromones, allomones, kairomones, attractants and repellents. Insects have mastered the art of using semiochemicals as communication signals and rely on them to find mates, host or habitat. This dependency of insects on semiochemicals has allowed chemical ecologists to develop environment friendly pest management strategies. However, discovering semiochemicals is a laborious process that involves a plethora of behavioural and analytical techniques, making it expansively time consuming. Recently, reverse chemical ecology approach using odorant binding proteins (OBPs) as target for elucidating behaviourally active compounds is gaining eminence. In this scenario, we describe a “computational reverse chemical ecology” approach for rapid screening of potential semiochemicals. Results We illustrate the high prediction accuracy of our computational method. We screened 25 semiochemicals for their binding potential to a GOBP of B. dorsalis using molecular docking (in silico) and molecular dynamics. Parallely, compounds were subjected to fluorescent quenching assays (Experimental). The correlation between in silico and experimental data were significant (r2 = 0.9408; P < 0.0001). Further, predicted compounds were subjected to behavioral bioassays and were found to be highly attractive to insects. Conclusions The present study provides a unique methodology for rapid screening and predicting behaviorally active semiochemicals. This methodology may be developed as a viable approach for prospecting active semiochemicals for pest control, which otherwise is a laborious process. PMID:24640964

  10. Activation of chemical promutagens by Selenastrum capricornutum in the plant cell/microbe coincubation assay

    SciTech Connect

    Gentile, J.M.; Lippert, M.; Johnson, P.; Shafer, T. )

    1990-05-01

    The critical balance of organisms living in aquatic environments is influenced by the presence and relationship of plants to those environments. However, even though plants occupy a fundamental trophic level within aquatic ecosystems, few studies have focused upon the effect of xenobiotics on aquatic plants, and even fewer studies have dealt with xenobiotic metabolism by aquatic plants. It is well established that plants can metabolize chemicals into mutagens. The impact of these unique plant-activated chemical mutagens on ecosystems, food chains and, ultimately, human health is an important question that will require intensive and integrative investigation. The plant cell/microbe coincubation assay is particularly advantageous for use with unicellular algae. The conditions of this assay are such that chemical metabolism and subsequent mutagen detection can be followed in intact algal cells under simulated field conditions. The purpose of this research was to demonstrate that a unicellular algal species could be used effectively in the plant cell/microbe coincubation assay to activate model chemical mutagens.

  11. [Advances in research of chemical constituents and pharmacological activities of common used spices].

    PubMed

    Sun, Chao-nan; Zhu, Yuan; Xu, Xi-ming; Yu, Jiang-nan

    2014-11-01

    Spices have enjoyed a long history and a worldwide application. Of particular interest is the pharmaceutical value of spices in addition to its basic seasoning function in cooking. Concretely, equipped with complex chemical compositions, spices are of significant importance in pharmacologic actions, like antioxidant, antibacterial, antitumor, as well as therapeutical effects in gastrointestinal disorders and cardiovascular disease. Although increasing evidences in support of its distinct role in the medical field has recently reported, little information is available for substantive, thorough and sophisticated researches on its chemical constituents and pharmacological activities, especially mechanism of these actions. Therefore, in popular wave of studies directed at a single spice, this review presents systematic studies on the chemical constituents and pharmacological activities associated with common used spices, together with current typical individual studies on functional mechanism, in order to pave the way for the exploitation and development of new medicines derived from the chemical compounds of spice (such as, piperine, curcumin, geniposide, cinnamaldehyde, cinnamic acid, linalool, estragole, perillaldehyde, syringic acid, crocin).

  12. Modeling the effect of water activity and storage temperature on chemical stability of coffee brews.

    PubMed

    Manzocco, Lara; Nicoli, Maria Cristina

    2007-08-08

    This work was addressed to study the chemical stability of coffee brew derivatives as a function of water activity (aw) and storage temperature. To this purpose, coffee brew was freeze-dried, equilibrated at increasing aw values, and stored for up to 10 months at different temperatures from -30 to 60 degrees C. The chemical stability of the samples was assessed by measuring H3O+ formation during storage. Independently of storage temperature, the rate of H3O+ formation was considerably low only when aw was reduced below 0.5 (94% w/w). Beyond this critical boundary, the rate increased, reaching a maximum value at ca. 0.8 aw (78% w/w). Further hydration up to the aw of the freshly prepared beverage significantly increased chemical stability. It was suggested that mechanisms other than lactones' hydrolysis, probably related to nonenzymatic browning pathways, could contribute to the observed increase in acidity during coffee staling. The temperature dependence of H3O+ formation was well-described by the Arrhenius equation in the entire aw range considered. However, aw affected the apparent activation energy and frequency factor. These effects were described by simple equations that were used to set up a modified Arrhenius equation. This model was validated by comparing experimental values, not used to generate the model, with those estimated by the model itself. The model allowed efficient prediction of the chemical stability of coffee derivatives on the basis of only the aw value and storage temperature.

  13. Chemical aspects of the trapping and recovery of uranium hexafluoride and fluorine during remediation activities

    SciTech Connect

    Del Cul, G.D.; Toth, L.M.

    1996-10-01

    Decontamination and decommission activities related to the Molten Salt Reactor Experiment (MSRE) involve the trapping and recovery of radiolitically generated uranium hexafluoride and fluorine. Although fission product radiolysis was known to generate F{sub 2}, the formation of UF{sub 6} and its transport from the fuel salt was unexpected. Some of these gaseous radiolysis products have been moving through the gas piping to a charcoal bed since the reactor was shut down in 1969. Current and planned remediation and clean-up activities involve the trapping of the gaseous products, deactivation and treatment of the activated charcoal bed, stabilization and reconditioning of the fuel salt, and recovery of the uranium. The chemical aspects of these processes, including radiolytic generation mechanisms, reactions between uranium hexafluoride and fluorine and trapping materials such as activated charcoal, activated alumina, and sodium fluoride, along with the analytical techniques used for the characterization of the materials and process control will be described.

  14. Redox activity and chemical interactions of metal oxide nano- and micro-particles with dithiothreitol (DTT).

    PubMed

    Nicolas, Johny; Jaafar, Malek; Sepetdjian, Elizabeth; Saad, Walid; Sioutas, Constantinos; Shihadeh, Alan; Saliba, Najat A

    2015-11-01

    The wide application and production of nanotechnology have increased the interest in studying the toxicity of nano- and micro-sized particles escaping into air from various aspects of the production process. Metal oxides (MOs) are one particular class of particles that exist abundantly in ambient PM. Studies show an emphasis on biological mechanisms by which inhalation exposure to MOs leads to disease. However, different biological assays provide different redox activity rankings making it difficult to assess the contributions of various MOs to measures of aggregate toxicity in multi-pollutant systems such as ambient PM. Therefore, research to evaluate the chemical interaction between these particles and molecules that are relevant to cellular redox activity can help in establishing indicators of reactivity. In particular, this study assesses the redox activity of six MOs mainly emitted from anthropogenic industrial activities using the dithiothreitol (DTT) assay. DTT is commonly used in acellular assays due to its analogous structure to cellular glutathione. The structural and chemical behaviors between active MOs and DTT were elucidated using FTIR, NMR, and BET methods. The results indicate that the health risk (redox activity) associated with MOs is mainly a function of their surface reactivity demonstrated by the ability of the oxidized (S-H) bond in DTT to form a stable bond with the MO surface.

  15. Chemical Constituents and Antimicrobial Activity of Indian Green Leafy Vegetable Cardiospermum halicacabum.

    PubMed

    Jeyadevi, R; Sivasudha, T; Ilavarasi, A; Thajuddin, N

    2013-06-01

    The present study was carried out to analyze chemical constituents and antibacterial activity of ethanolic leaf extract of Cardiospermum halicacabum (ECH). The FT-IR spectrum confirmed the presence of alcohols, phenols, alkanes, alkynes, aliphatic ester and flavonoids in ECH. The GC-MS analysis revealed that ECH contained about twenty four compounds. The major chemical compounds identified were cyclohexane-1, 4, 5-triol-3-one-1-carboxylic acid, benzene acetic acid, caryophyllene, phytol and neophytadiene. The ECH was screened for its antibacterial activity against different bacterial strains and anti fungal activity against Candida albicans by agar well diffusion and minimum inhibitory concentration (MIC) assay. ECH exhibited antibacterial and antifungal activity. All the tested bacterial strains showed MIC values ranging from 80 to 125 μg of extract/ml and C. albicans showed 190 μg of extract/ml as a MIC. The maximum activity ECH was observed against human pathogen Staphylococcus aureus followed by Escherichia coli and the fish pathogen Aeromonas hydrophila. ECH exhibited moderate activity against some of the tested multidrug resistant strains.

  16. Chemical composition and antimicrobial activity of the essential oils of Pistacia lentiscus var. chia.

    PubMed

    Magiatis, P; Melliou, E; Skaltsounis, A L; Chinou, I B; Mitaku, S

    1999-12-01

    The chemical composition of the three essential oils obtained by steam distillation of the mastic gum, leaves and twigs of Pistacia lentiscus var. chia, was studied by GC/MS. Sixty nine constituents were identified from the oils. alpha-Pinene, myrcene, trans-caryophyllene and germacrene D were found to be the major components. The in vitro antimicrobial activity of the three essential oils and of the resin (total, acid and neutral fraction) against six bacteria and three fungi is reported.

  17. Effect of chemical activation of 10% carbamide peroxide gel in tooth bleaching.

    PubMed

    Batista, Graziela Ribeiro; Arantes, Paula Tamiao; Attin, Thomas; Wiegand, Annette; Torres, Carlos Rocha

    2013-01-01

    This study aimed to evaluate the efficacy of chemical agents to increase the bleaching effectiveness of 10% carbamide peroxide. Two hundred and ninety enamel-dentin discs were prepared from bovine incisors. The color measurement was performed by a spectrophotometer using the CIE L*a*b*system. The groups were divided according to the bleaching treatment: negative control group (NC): without bleaching; positive control group (PC): bleached with 10% carbamide peroxide gel without any chemical activator; Manganese gluconate (MG); Manganese chloride (MC); Ferrous gluconate (FG); Ferric chloride (FC); and Ferrous sulphate (FS). Three different concentrations (MG, MC, FG, FC: 0.01, 0.02 and 0.03% w/w; FS: 0.001, 0.002 and 0.003% w/w) for each agent were tested. The bleaching gel was applied on the specimens for 8 h, after which they were immersed in artificial saliva for 16 h, during 14 days. Color assessments were made after 7 and 14 days. The data were analyzed by repeated measures analysis of variance and Tukey's test (5%). Generally, the test groups were unable to increase the bleaching effect (ΔE) significantly compared to the PC group. Only for ΔL, significant higher values compared to the PC group could be seen after 7 days in groups MG (0.02%), and FS (0.002 and 0.003%). The NC group showed significantly lower values than all tested groups. It was concluded that for home bleaching procedures, the addition of chemical activators did not produce a bleaching result significantly higher than the use of 10% carbamide peroxide without activation, and that the concentration of chemical activators used did not significantly influence the effectiveness of treatment.

  18. Modeling Joint Effects of Mixtures of Chemicals on Microorganisms Using Quantitative Structure Activity Relationships

    DTIC Science & Technology

    1993-08-22

    toxicity results from the 40 chemicals placed in the testing set were used to develop QSAR models. Molecular connectivity indexes were calculated for...Toxic Unit, Additivity Index , and Mixture Toxicity Index . The validity of these concepts was further verified using the results of the 8-component testing...standard deviation of 22.6. These variations are comparable to those reported by Blum (1989) for activated sludge cultures and Microtox , and may be

  19. Chemical Composition and Biological Activities of Fragrant Mexican Copal (Bursera spp.).

    PubMed

    Gigliarelli, Giulia; Becerra, Judith X; Curini, Massimo; Marcotullio, Maria Carla

    2015-12-12

    Copal is the Spanish word used to describe aromatic resins from several genera of plants. Mexican copal derives from several Bursera spp., Protium copal, some Pinus spp. (e.g., P. pseudostrobus) and a few Fabaceae spp. It has been used for centuries as incense for religious ceremonies, as a food preservative, and as a treatment for several illnesses. The aim of this review is to analyze the chemical composition and biological activity of commercial Mexican Bursera copal.

  20. Preparation of porous bio-char and activated carbon from rice husk by leaching ash and chemical activation.

    PubMed

    Ahiduzzaman, Md; Sadrul Islam, A K M

    2016-01-01

    Preparation porous bio-char and activated carbon from rice husk char study has been conducted in this study. Rice husk char contains high amount silica that retards the porousness of bio-char. Porousness of rice husk char could be enhanced by removing the silica from char and applying heat at high temperature. Furthermore, the char is activated by using chemical activation under high temperature. In this study no inert media is used. The study is conducted at low oxygen environment by applying biomass for consuming oxygen inside reactor and double crucible method (one crucible inside another) is applied to prevent intrusion of oxygen into the char. The study results shows that porous carbon is prepared successfully without using any inert media. The adsorption capacity of material increased due to removal of silica and due to the activation with zinc chloride compared to using raw rice husk char. The surface area of porous carbon and activated carbon are found to be 28, 331 and 645 m(2) g(-1) for raw rice husk char, silica removed rice husk char and zinc chloride activated rice husk char, respectively. It is concluded from this study that porous bio-char and activated carbon could be prepared in normal environmental conditions instead of inert media. This study shows a method and possibility of activated carbon from agro-waste, and it could be scaled up for commercial production.

  1. Retrieval of Temperature and Water Vapour from Multiple Channel Lidar Systems Using an Optimal Estimation Method

    NASA Astrophysics Data System (ADS)

    Sica, Robert; Haefele, Alexander

    2016-04-01

    While the application of optimal estimation methods (OEMs) is well-known for the retrieval of atmospheric parameters from passive instruments, active instruments have typically not employed the OEM. For instance, the measurement of temperature in the middle atmosphere with Rayleigh-scatter lidars is an important technique for assessing atmospheric change. Current retrieval schemes for these temperatures have several shortcomings which can be overcome using an OEM. Forward models have been constructed that fully characterize the measurement and allow the simultaneous retrieval of temperature, dead time and background. The OEM allows a full uncertainty budget to be obtained on a per profile basis that includes, in addition to the statistical uncertainties, the smoothing error and uncertainties due to Rayleigh extinction, ozone absorption, the lidar constant, nonlinearity in the counting system, variation of the Rayleigh-scatter cross section with altitude, pressure, acceleration due to gravity and the variation of mean molecular mass with altitude. The vertical resolution of the temperature profile is found at each height, and a quantitative determination is made of the maximum height to which the retrieval is valid. A single temperature profile can be retrieved from measurements with multiple channels that cover different height ranges, vertical resolutions and even different detection methods. The OEM employed is shown to give robust estimates of temperature consistent with previous methods, while requiring minimal computational time. Retrieval of water vapour mixing ratio from vibrational Raman scattering lidar measurements is another example where an OEM offers a considerable advantage over the standard analysis technique, with the same advantages as discussed above for Rayleigh-scatter temperatures but with an additional benefit. The conversion of the lidar measurement into mixing ratio requires a calibration constant to be employed. Using OEM the calibration

  2. Retrieval of Temperature and Water Vapour From Multiple Channel Lidar Systems Using an Optimal Estimation Method

    NASA Astrophysics Data System (ADS)

    Sica, Robert; Haefele, Alexander

    2015-04-01

    While the application of optimal estimation methods (OEMs) is well-known for the retrieval of atmospheric parameters from passive instruments, active instruments have typically not employed the OEM. For instance, the measurement of temperature in the middle atmosphere with Rayleigh-scatter lidars is an important technique for assessing atmospheric change. Current retrieval schemes for these temperatures have several shortcomings which can be overcome using an OEM. Forward models have been constructed that fully characterize the measurement and allow the simultaneous retrieval of temperature, dead time and background. The OEM allows a full uncertainty budget to be obtained on a per profile basis that includes, in addition to the statistical uncertainties, the smoothing error and uncertainties due to Rayleigh extinction, ozone absorption, the lidar constant, nonlinearity in the counting system, variation of the Rayleigh-scatter cross section with altitude, pressure, acceleration due to gravity and the variation of mean molecular mass with altitude. The vertical resolution of the temperature profile is found at each height, and a quantitative determination is made of the maximum height to which the retrieval is valid. A single temperature profile can be retrieved from measurements with multiple channels that cover different height ranges, vertical resolutions and even different detection methods. The OEM employed is shown to give robust estimates of temperature consistent with previous methods, while requiring minimal computational time. Retrieval of water vapour mixing ratio from vibrational Raman scattering lidar measurements is another example where an OEM offers a considerable advantage over the standard analysis technique, with the same advantages as discussed above for Rayleigh-scatter temperatures but with an additional benefit. The conversion of the lidar measurement into mixing ratio requires a calibration constant to be employed. Using OEM the calibration

  3. Chemical composition and biological activity of ripe pumpkin fruits (Cucurbita pepo L.) cultivated in Egyptian habitats.

    PubMed

    Badr, Sherif E A; Shaaban, Mohamed; Elkholy, Yehya M; Helal, Maher H; Hamza, Akila S; Masoud, Mohamed S; El Safty, Mounir M

    2011-09-01

    The chemical composition and biological activity of three parts (rind, flesh and seeds) of pumpkin fruits (Cucurbita pepo L.) cultivated in Egypt were studied. Chemical analysis of fibre, protein, β-carotene, carbohydrates, minerals and fatty acids present in the rind, flesh, seeds and defatted seeds meal was conducted. Chemical, GC-MS and biological assays of organic extracts of the main fruit parts, rind and flesh established their unique constituents. Chromatographic purification of the extracts afforded triglyceride fatty acid mixture (1), tetrahydro-thiophene (2), linoleic acid (3), calotropoleanly ester (4), cholesterol (5) and 13(18)-oleanen-3-ol (6). GC-MS analysis of the extract's unpolar fraction revealed the existence of dodecane and tetradecane. Structures of the isolated compounds (1-6) were confirmed by NMR and EI-MS spectrometry. Antimicrobial, antiviral and antitumour activities of the fruit parts were discussed. The promising combined extract of rind and flesh was biologically studied for microbial and cytotoxic activities in comparison with the whole isolated components.

  4. Synthesis of sulfonated porous carbon nanospheres solid acid by a facile chemical activation route

    SciTech Connect

    Chang, Binbin Guo, Yanzhen; Yin, Hang; Zhang, Shouren; Yang, Baocheng

    2015-01-15

    Generally, porous carbon nanospheres materials are usually prepared via a template method, which is a multi-steps and high-cost strategy. Here, we reported a porous carbon nanosphere solid acid with high surface area and superior porosity, as well as uniform nanospheical morphology, which prepared by a facile chemical activation with ZnCl{sub 2} using resorcinol-formaldehyde (RF) resins spheres as precursor. The activation of RF resins spheres by ZnCl{sub 2} at 400 °C brought high surface area and large volume, and simultaneously retained numerous oxygen-containing and hydrogen-containing groups due to the relatively low processing temperature. The presence of these functional groups is favorable for the modification of –SO{sub 3}H groups by a followed sulfonation treating with sulphuric acid and organic sulfonic acid. The results of N{sub 2} adsorption–desorption and electron microscopy clearly showed the preservation of porous structure and nanospherical morphology. Infrared spectra certified the variation of surface functional groups after activation and the successful modification of –SO{sub 3}H groups after sulfonation. The acidities of catalysts were estimated by an indirect titration method and the modified amount of –SO{sub 3}H groups were examined by energy dispersive spectra. The results suggested sulfonated porous carbon nanospheres catalysts possessed high acidities and –SO{sub 3}H densities, which endowed their significantly catalytic activities for biodiesel production. Furthermore, their excellent stability and recycling property were also demonstrated by five consecutive cycles. - Graphical abstract: Sulfonated porous carbon nanospheres with high surface area and superior catalytic performance were prepared by a facile chemical activation route. - Highlights: • Porous carbon spheres solid acid prepared by a facile chemical activation. • It owns high surface area, superior porosity and uniform spherical morphology. • It possesses

  5. Subpicotesla atomic magnetometry with a microfabricated vapour cell

    NASA Astrophysics Data System (ADS)

    Shah, Vishal; Knappe, Svenja; Schwindt, Peter D. D.; Kitching, John

    2007-11-01

    Highly sensitive magnetometers capable of measuring magnetic fields below 1 pT have an impact on areas as diverse as geophysical surveying, the detection of unexploded ordinance, space science, nuclear magnetic resonance, health care and perimeter and remote monitoring. Recently, it has been shown that laboratory optical magnetometers, based on the precession of the spins of alkali atoms in the vapour phase, could achieve sensitivities in the femtotesla range, comparable to, or even exceeding, those of superconducting quantum interference devices. We demonstrate here an atomic magnetometer based on a millimetre-scale microfabricated alkali vapour cell with sensitivity below 70 fT Hz-1/2. Additionally, we use a simplified optical configuration that requires only a single low-power laser. This result suggests that millimetre-scale, low-power femtotesla magnetometers are feasible, and we support this proposition with a simple sensitivity scaling analysis. Such an instrument would greatly expand the range of applications in which atomic magnetometers could be used.

  6. Detecting vapour bubbles in simulations of metastable water

    SciTech Connect

    González, Miguel A.; Abascal, Jose L. F.; Valeriani, Chantal E-mail: cvaleriani@quim.ucm.es; Menzl, Georg; Geiger, Philipp; Dellago, Christoph E-mail: cvaleriani@quim.ucm.es; Aragones, Juan L.; Caupin, Frederic

    2014-11-14

    The investigation of cavitation in metastable liquids with molecular simulations requires an appropriate definition of the volume of the vapour bubble forming within the metastable liquid phase. Commonly used approaches for bubble detection exhibit two significant flaws: first, when applied to water they often identify the voids within the hydrogen bond network as bubbles thus masking the signature of emerging bubbles and, second, they lack thermodynamic consistency. Here, we present two grid-based methods, the M-method and the V-method, to detect bubbles in metastable water specifically designed to address these shortcomings. The M-method incorporates information about neighbouring grid cells to distinguish between liquid- and vapour-like cells, which allows for a very sensitive detection of small bubbles and high spatial resolution of the detected bubbles. The V-method is calibrated such that its estimates for the bubble volume correspond to the average change in system volume and are thus thermodynamically consistent. Both methods are computationally inexpensive such that they can be used in molecular dynamics and Monte Carlo simulations of cavitation. We illustrate them by computing the free energy barrier and the size of the critical bubble for cavitation in water at negative pressure.

  7. Charge Transport in Polyaniline and Vapour Induced Structural Changes

    NASA Astrophysics Data System (ADS)

    Minto, C. D. G.; Vaughan, A. S.

    1996-03-01

    Camphor sulphonic acid protonation renders polyaniline soluble in both m-cresol and chloroform. Films cast from these solvents exhibit vastly differing transport properties. m-cresol cast films are metallic or lie on the metal/insulator transition, whereas those cast from chloroform are insulators. Similarly pellets of pressed doped polyaniline powder exhibit insulating characteristics. We present an investigation of such effects in polyaniline obtained from both insulating conditions (films and powders). We find that m-cresol -- vapour treatment of these materials causes a rapid increase both in the conductivity and the type of conduction, changing from an insulator to a material approaching the metal/insulator transition. Chloroform films actually take on characteristics of those cast from m-cresol, including a positive temperature coefficient of resistivity. Both starting materials exhibit similar X-ray scattering patterns, after exposure to vapour, the pattern becomes more similar to that which is found in m-cresol cast films. Conformational changes resulting from a strong polymer--interaction are discussed as the motivation for the improvements in transport properties.

  8. Detecting vapour bubbles in simulations of metastable water

    NASA Astrophysics Data System (ADS)

    González, Miguel A.; Menzl, Georg; Aragones, Juan L.; Geiger, Philipp; Caupin, Frederic; Abascal, Jose L. F.; Dellago, Christoph; Valeriani, Chantal

    2014-11-01

    The investigation of cavitation in metastable liquids with molecular simulations requires an appropriate definition of the volume of the vapour bubble forming within the metastable liquid phase. Commonly used approaches for bubble detection exhibit two significant flaws: first, when applied to water they often identify the voids within the hydrogen bond network as bubbles thus masking the signature of emerging bubbles and, second, they lack thermodynamic consistency. Here, we present two grid-based methods, the M-method and the V-method, to detect bubbles in metastable water specifically designed to address these shortcomings. The M-method incorporates information about neighbouring grid cells to distinguish between liquid- and vapour-like cells, which allows for a very sensitive detection of small bubbles and high spatial resolution of the detected bubbles. The V-method is calibrated such that its estimates for the bubble volume correspond to the average change in system volume and are thus thermodynamically consistent. Both methods are computationally inexpensive such that they can be used in molecular dynamics and Monte Carlo simulations of cavitation. We illustrate them by computing the free energy barrier and the size of the critical bubble for cavitation in water at negative pressure.

  9. Omani propolis: chemical profiling, antibacterial activity and new propolis plant sources

    PubMed Central

    2013-01-01

    Background Propolis (bee glue) is a resinous honeybee product having a long history of application in many countries as a traditional remedy for treating wounds, burns, soar throat, stomach disorders, etc. It has been proved to possess beneficial biological effects, including antimicrobial, antioxidant, anti-inflammatory, cytotoxic, antiulcer, and many others. Bees gather propolis from diverse resinous plant parts and in different phytogeographic regions its chemical composition might vary significantly. In this article we report the results of the first study on the chemical profiles of propolis from Oman, its plant origin and antibacterial activity. Results The chemical profiles of Omani propolis extracts were obtained by GC-MS analysis after silylation. Over 50 individual compounds were identified in the samples, belonging to different compound types: sugars, polyols, hydroxy acids, fatty acids, cardanols and cardols, anacardic acids, flavan derivatives, triterpenes, prenylated flavanones and chalcones. The profiles were dissimilar from other known propolis types. They demonstrate that although Oman is not a large country, the plant sources of propolis vary significantly, even in the same apiary and the same season. Based on chemical profiles, and isolation and identification of major marker compounds (new propolis constituents), new plant sources of propolis were found: Azadiracta indica (neem tree) and Acacia spp. (most probably A. nilotica). The ethanol extracts of the studied propolis samples demonstrated activity against S. aureus (MIC < 100 μg. mL-1) and E. coli (MIC < 380 μg. mL-1). Conclusion Omani propolis is different form the known propolis types and demonstrates significant chemical diversity. Its most important plant source is the resin of Azadirachta indica, and as a result its typical components are С5-prenyl flavanones. Other plant sources have been identified, too, playing some role in resin collection by bees in Oman: Acacia spp

  10. Chemical graphs, molecular matrices and topological indices in chemoinformatics and quantitative structure-activity relationships.

    PubMed

    Ivanciuc, Ovidiu

    2013-06-01

    Chemical and molecular graphs have fundamental applications in chemoinformatics, quantitative structureproperty relationships (QSPR), quantitative structure-activity relationships (QSAR), virtual screening of chemical libraries, and computational drug design. Chemoinformatics applications of graphs include chemical structure representation and coding, database search and retrieval, and physicochemical property prediction. QSPR, QSAR and virtual screening are based on the structure-property principle, which states that the physicochemical and biological properties of chemical compounds can be predicted from their chemical structure. Such structure-property correlations are usually developed from topological indices and fingerprints computed from the molecular graph and from molecular descriptors computed from the three-dimensional chemical structure. We present here a selection of the most important graph descriptors and topological indices, including molecular matrices, graph spectra, spectral moments, graph polynomials, and vertex topological indices. These graph descriptors are used to define several topological indices based on molecular connectivity, graph distance, reciprocal distance, distance-degree, distance-valency, spectra, polynomials, and information theory concepts. The molecular descriptors and topological indices can be developed with a more general approach, based on molecular graph operators, which define a family of graph indices related by a common formula. Graph descriptors and topological indices for molecules containing heteroatoms and multiple bonds are computed with weighting schemes based on atomic properties, such as the atomic number, covalent radius, or electronegativity. The correlation in QSPR and QSAR models can be improved by optimizing some parameters in the formula of topological indices, as demonstrated for structural descriptors based on atomic connectivity and graph distance.

  11. [Advances on investigation of chemical constituents, pharmacological activities and clinical applications of Capparis spinosa].

    PubMed

    Yang, Tao; Liu, Yu-Qing; Wang, Chang-Hong; Wang, Zheng-Tao

    2008-11-01

    In this paper, the chemical constituents, pharmacological activities and clinical applications of Capparis spinosa had been reviewed. The constituents of C. spinosa include the saccharides and glycosides, flavonoids, alkaloids, terpenoids and volatile oils, fatty acids and steroides and so on. C. spinosa had many extensive pharmacological effects such as anti-inflammatory, odynolysis, antifungus, hepatoprotective effect, hypoglycemic activity, antioxidation, anti-hyperlipemia, anticoagulated blood, smooth muscle stimulation, anti-stress reaction, improve memory. It was used to treat arthrolithiasis, rheumarthritis and dermatosis in clinic in domestic, and it would have a broad application prospects.

  12. Activation of chemicals into mutagens by green plants: a preliminary discussion.

    PubMed Central

    Plewa, M J

    1978-01-01

    This paper is a review of recent studies that demonstrate the activation of chemicals (especially pesticides into mutagens by green plants. Such activation of pesticides may be hazardous to the public health because of their widespread use in agriculture and the current lack of information that exists about such processes. The mutagenic properties of the s-triazine herbicides (atrazine, simazine, and cyanazine) as exhibited in various assay systems are discussed. In vivo, in vitro, and in situ plant assays are presented, and the maize wx locus assay is discussed. PMID:367774

  13. An Update on Oligosaccharides and Their Esters from Traditional Chinese Medicines: Chemical Structures and Biological Activities

    PubMed Central

    Chen, Xiang-Yang; Wang, Ru-Feng; Liu, Bin

    2015-01-01

    A great number of naturally occurring oligosaccharides and oligosaccharide esters have been isolated from traditional Chinese medicinal plants, which are used widely in Asia and show prominent curative effects in the prevention and treatment of kinds of diseases. Numerous in vitro and in vivo experiments have revealed that oligosaccharides and their esters exhibited various activities, including antioxidant, antidepressant, cytotoxic, antineoplastic, anti-inflammatory, neuroprotective, cerebral protective, antidiabetic, plant growth-regulatory, and immunopotentiating activities. This review summarizes the investigations on the distribution, chemical structures, and bioactivities of natural oligosaccharides and their esters from traditional Chinese medicines between 2003 and 2013. PMID:25861364

  14. High surface area activated carbon prepared from cassava peel by chemical activation.

    PubMed

    Sudaryanto, Y; Hartono, S B; Irawaty, W; Hindarso, H; Ismadji, S

    2006-03-01

    Cassava is one of the most important commodities in Indonesia, an agricultural country. Cassava is one of the primary foods in our country and usually used for traditional food, cake, etc. Cassava peel is an agricultural waste from the food and starch processing industries. In this study, this solid waste was used as the precursor for activated carbon preparation. The preparation process consisted of potassium hydroxide impregnation at different impregnation ratio followed by carbonization at 450-750 degrees C for 1-3 h. The results revealed that activation time gives no significant effect on the pore structure of activated carbon produced, however, the pore characteristic of carbon changes significantly with impregnation ratio and carbonization temperature. The maximum surface area and pore volume were obtained at impregnation ratio 5:2 and carbonization temperature 750 degrees C.

  15. Chemical composition and antibacterial activity of essential oils from the Tunisian Allium nigrum L.

    PubMed Central

    Rouis-Soussi, Lamia Sakka; Ayeb-Zakhama, Asma El; Mahjoub, Aouni; Flamini, Guido; Jannet, Hichem Ben; Harzallah-Skhiri, Fethia

    2014-01-01

    The chemical composition of the essential oils of different Allium nigrum L. organs and the antibacterial activity were evaluated. The study is particularly interesting because hitherto there are no reports on the antibacterial screening of this species with specific chemical composition. Therefore, essential oils from different organs (flowers, stems, leaves and bulbs) obtained separately by hydrodistillation were analyzed using gas chromatography–mass spectrometry (GC–MS). The antibacterial activity was evaluated using the disc and microdilution assays. In total, 39 compounds, representing 90.8-96.9 % of the total oil composition, were identified. The major component was hexadecanoic acid (synonym: palmitic acid) in all the A. nigrum organs oils (39.1-77.2 %). We also noted the presence of some sesquiterpenes, mainly germacrene D (12.8 %) in leaves oil) and some aliphatic compounds such as n-octadecane (30.5 %) in bulbs oil. Isopentyl isovalerate, 14-oxy-α-muurolene and germacrene D were identified for the first time in the genus Allium L. All the essential oils exhibited antimicrobial activity, especially against Enterococcus faecalis and Staphylococcus aureus. The oil obtained from the leaves exhibited an interesting antibacterial activity, with a Minimum Inhibitory Concentration (MIC) of 62.50 µg/mL against these two latter strains. The findings showed that the studied oils have antibacterial activity, and thus great potential for their application in food preservation and natural health products. PMID:26417280

  16. Chemical composition and antibacterial activity of essential oils from the Tunisian Allium nigrum L.

    PubMed

    Rouis-Soussi, Lamia Sakka; Ayeb-Zakhama, Asma El; Mahjoub, Aouni; Flamini, Guido; Jannet, Hichem Ben; Harzallah-Skhiri, Fethia

    2014-01-01

    The chemical composition of the essential oils of different Allium nigrum L. organs and the antibacterial activity were evaluated. The study is particularly interesting because hitherto there are no reports on the antibacterial screening of this species with specific chemical composition. Therefore, essential oils from different organs (flowers, stems, leaves and bulbs) obtained separately by hydrodistillation were analyzed using gas chromatography-mass spectrometry (GC-MS). The antibacterial activity was evaluated using the disc and microdilution assays. In total, 39 compounds, representing 90.8-96.9 % of the total oil composition, were identified. The major component was hexadecanoic acid (synonym: palmitic acid) in all the A. nigrum organs oils (39.1-77.2 %). We also noted the presence of some sesquiterpenes, mainly germacrene D (12.8 %) in leaves oil) and some aliphatic compounds such as n-octadecane (30.5 %) in bulbs oil. Isopentyl isovalerate, 14-oxy-α-muurolene and germacrene D were identified for the first time in the genus Allium L. All the essential oils exhibited antimicrobial activity, especially against Enterococcus faecalis and Staphylococcus aureus. The oil obtained from the leaves exhibited an interesting antibacterial activity, with a Minimum Inhibitory Concentration (MIC) of 62.50 µg/mL against these two latter strains. The findings showed that the studied oils have antibacterial activity, and thus great potential for their application in food preservation and natural health products.

  17. Design, in vitro stability, and ocular hypotensive activity of t-butalone chemical delivery systems.

    PubMed

    Reddy, I K; Vaithiyalingam, S R; Khan, M A; Bodor, N S

    2001-08-01

    The objective of this work was to synthesize two bioreversible diacyl derivatives of t-butalone (chemical delivery systems), determine their chemical and in vitro stability, and investigate their potential use as topical antiglaucoma agents. The stability of these compounds was determined in isotonic phosphate buffers (pH range 5-8) and in selected biological media, including human whole blood, rabbit and rat blood, and the anterior segment tissues of rabbit. The ocular hypotensive activity of these compounds in unrestrained, normotensive albino rabbits was determined with a pneumatonometer. The two compounds were stable at lower pH. The stability decreased as the pH increased, suggesting their lability to base-catalyzed hydrolysis. These compounds exhibited significant differences in the hydrolytic rates in the whole blood among species examined (rat > rabbit > human). The observed rates of disappearance in different ocular tissues were indicative of relative enzyme activity in these media (iris-ciliary body > cornea > aqueous humor). The two compounds exhibited a significant ocular hypotensive activity (P < 0.01) at 2% dose level. The peak activity was found between 2 and 4 h, and the activity was maintained for 4.5 to 7 h. The dipivalyl derivative of t-butalone exhibited more pronounced decrease in intraocular pressure than that of diisovaleryl derivative. The present study suggests the possible use of diacyl derivatives of t-butalone as ocular hypotensive agents.

  18. Chemically and biologically modified activated carbon sorbents for the removal of lead ions from aqueous media.

    PubMed

    Mahmoud, Mohamed E; Abdel-Fattah, Tarek M; Osman, Maher M; Ahmed, Somia B

    2012-01-01

    A method is described for hybridization of the adsorption and biosorption characteristics of chemically treated commercial activated carbon and baker's yeast, respectively, for the formation of environmental friendly multifunctional sorbents. Activated carbon was loaded with baker's yeast after acid-base treatment. Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) Spectroscopy were used to characterize these sorbents. Moreover, the sorption capabilities for lead (II) ions were evaluated. A value of 90 μmol g(-1) was identified as the maximum sorption capacity of activated carbon. Acid-base treatment of activated carbon was found to double the sorption capacity (140-180 μmol g(-1)). Immobilization of baker's yeast on the surface of activated carbon sorbents was found to further improve the sorption capacity efficiency of lead to 360, 510 and 560 μmol g(-1), respectively. Several important factors such as pH, contact time, sorbent dose, lead concentration and interfering ions were examined. Lead sorption process was studied and evaluated by several adsorption isotherms and found to follow the Langmuir and BET models. The potential applications of various chemically and biologically modified sorbents and biosorbents for removal of lead from real water matrices were also investigated via multistage micro-column technique and the results referred to excellent recovery values of lead (95.0-99.0 ± 3.0-5.0 %).

  19. Eupatorium capillifolium essential oil: chemical composition antifungal activity and insecticidal activity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Natural plant extracts often contain compounds that are useful in pest management applications. The essential oil of Eupatorium capillifolium (dog-fennel) was investigated for antifungal and insecticidal activities. Essential oil obtained by hydrodistillation of aerial parts was analyzed by gas chro...

  20. Chemical composition and genotoxic activity of petroleum derivatives collected in two working environments

    SciTech Connect

    Pasquini, R.; Taningher, M.; Monarca, S.; Pala, M.; Angeli, G.

    1989-01-01

    Pitch and bitumen, two complex petroleum derivative mixtures, were studied for both their chemical composition and their mutagenic/DNA damaging activity. While bitumen revealed no genotoxic effect and low polycyclic aromatic hydrocarbons (PAHs) concentration, petroleum pitch showed a high concentration of mutagenic/carcinogenic PAHs, and also an elevated mutagenic activity when assayed by the Ames test, in the presence of postmitochondrial rat liver fractions. The in vitro mutagenic activity was detectable as frameshift mutation by assaying the pitch both as an in toto mixture and after HPLC fractionation, the most polar fractions being the most active. In contrast, both derivatives showed no in vivo DNA damage in rat liver, using the DNA alkaline elution technique and the fluorometric assay of DNA unwinding.

  1. Chemical composition, antimicrobial and antioxidant activities of essential oils from organically cultivated fennel cultivars.

    PubMed

    Shahat, Abdelaaty A; Ibrahim, Abeer Y; Hendawy, Saber F; Omer, Elsayed A; Hammouda, Faiza M; Abdel-Rahman, Fawzia H; Saleh, Mahmoud A

    2011-02-01

    Essential oils of the fruits of three organically grown cultivars of Egyptian fennel (Foeniculum vulgare var. azoricum, Foeniculum vulgare var. dulce and Foeniculum vulgare var. vulgare) were examined for their chemical constituents, antimicrobial and antioxidant activities. Gas chromatography/mass spectrometry analysis of the essential oils revealed the presence of 18 major monoterpenoids in all three cultivars but their percentage in each oil were greatly different. trans-Anethole, estragole, fenchone and limonene were highly abundant in all of the examined oils. Antioxidant activities of the essential oils were evaluated using the DPPH radical scavenging, lipid peroxidation and metal chelating assays. Essential oils from the azoricum and dulce cultivars were more effective antioxidants than that from the vulgare cultivar. Antimicrobial activities of each oil were measured against two species of fungi, two species of Gram negative and two species of Gram positive bacteria. All three cultivars showed similar antimicrobial activity.

  2. Chemical acceleration of a neutral granulated blast-furnace slag activated by sodium carbonate

    SciTech Connect

    Kovtun, Maxim Kearsley, Elsabe P. Shekhovtsova, Julia

    2015-06-15

    This paper presents results of a study on chemical acceleration of a neutral granulated blast-furnace slag activated using sodium carbonate. As strength development of alkali-activated slag cements containing neutral GBFS and sodium carbonate as activator at room temperature is known to be slow, three accelerators were investigated: sodium hydroxide, ordinary Portland cement and a combination of silica fume and slaked lime. In all cements, the main hydration product is C–(A)–S–H, but its structure varies between tobermorite and riversideite depending on the accelerator used. Calcite and gaylussite are present in all systems and they were formed due to either cation exchange reaction between the slag and the activator, or carbonation. With accelerators, compressive strength up to 15 MPa can be achieved within 24 h in comparison to 2.5 MPa after 48 h for a mix without an accelerator.

  3. Ascaroside activity in Caenorhabditis elegans is highly dependent on chemical structure.

    PubMed

    Hollister, Kyle A; Conner, Elizabeth S; Zhang, Xinxing; Spell, Mark; Bernard, Gary M; Patel, Pratik; de Carvalho, Ana Carolina G V; Butcher, Rebecca A; Ragains, Justin R

    2013-09-15

    The nematode Caenorhabditis elegans secretes ascarosides, structurally diverse derivatives of the 3,6-dideoxysugar ascarylose, and uses them in chemical communication. At high population densities, specific ascarosides, which are together known as the dauer pheromone, trigger entry into the stress-resistant dauer larval stage. In order to study the structure-activity relationships for the ascarosides, we synthesized a panel of ascarosides and tested them for dauer-inducing activity. This panel includes a number of natural ascarosides that were detected in crude pheromone extract, but as yet have no assigned function, as well as many unnatural ascaroside derivatives. Most of these ascarosides, some of which have significant structural similarity to the natural dauer pheromone components, have very little dauer-inducing activity. Our results provide a primer to ascaroside structure-activity relationships and suggest that slight modifications to ascaroside structure dramatically influence binding to the relevant G protein-coupled receptors that control dauer formation.

  4. Ascaroside activity in Caenorhabditis elegans is highly dependent on chemical structure

    PubMed Central

    Hollister, Kyle A.; Conner, Elizabeth S.; Zhang, Xinxing; Spell, Mark; Bernard, Gary M.; Patel, Pratik; de Carvalho, Ana Carolina G.V.; Butcher, Rebecca A.; Ragains, Justin R.

    2015-01-01

    The nematode Caenorhabditis elegans secretes ascarosides, structurally diverse derivatives of the 3,6-dideoxysugar ascarylose, and uses them in chemical communication. At high population densities, specific ascarosides, which are together known as the dauer pheromone, trigger entry into the stress-resistant dauer larval stage. In order to study the structure-activity relationships for the ascarosides, we synthesized a panel of ascarosides and tested them for dauer-inducing activity. This panel includes a number of natural ascarosides that were detected in crude pheromone extract, but as yet have no assigned function, as well as many unnatural ascaroside derivatives. Most of these ascarosides, some of which have significant structural similarity to the natural dauer pheromone components, have very little dauer-inducing activity. Our results provide a primer to ascaroside structure-activity relationships and suggest that slight modifications to ascaroside structure dramatically influence binding to the relevant G protein-coupled receptors that control dauer formation. PMID:23920482

  5. Chemical composition and in vitro antitrypanosomal activity of fractions of essential oil from Cymbopogon nardus L.

    PubMed

    Muhd Haffiz, J; Norhayati, I; Getha, K; Nor Azah, M A; Mohd Ilham, A; Lili Sahira, H; Roshan Jahn, M S; Muhd Syamil, A

    2013-03-01

    Essential oil from Cymbopogon nardus was evaluated for activity against Trypanosoma brucei brucei BS221 (IC50 = 0.31 ± 0.03 μg/mL) and cytotoxic effect on normal kidney (Vero) cells (IC50 = >100 μg/mL). The crude essential oil was subjected to various chromatography techniques afforded active sub fractions with antitrypanosomal activity; F4 (IC50 = 0.61 ± 0.06 μg/mL), F6 (IC50= 0.73 ± 0.33 μg/mL), F7 (IC50 = 1.15 ± 0 μg/mL) and F8 (IC50 = 1.11 ± 0.01 μg/mL). These active fractions did not exhibit any toxic effects against Vero cell lines and the chemical profiles investigation indicated presence of α-and γ-eudesmol, elemol, α-cadinol and eugenol by GC/MS analysis.

  6. Chemical constituents from the rhizome of Polygonum paleaceum and their antifungal activity.

    PubMed

    Yang, Yi-Xi; An, Mao-Mao; Jin, Yong-Sheng; Chen, Hai-Sheng

    2017-01-01

    A new compounds neopaleaceolactoside (1), along with nine known compounds phyllocoumarin (2), quercetin (3), quercitrin (4), quercetin-3-methyl ether (5), vincetoxicoside B (6), isoquercitrin (7), kaempferol (8), (-)-epicatechin (9), and chlorogenic acid (10), was isolated from Polygonum paleaceum Wall. Their chemical structures were established based on one-dimensional and two-dimensional nuclear magnetic resonance techniques, mass spectrometry and by comparison with spectroscopic data reported. Some selected compounds were screened for their antifungal activity. Quercetin (3), vincetoxicoside B (6), kaempferol (8), and (-)-epicatechin (9) showed synergistic antifungal activities with the FICI values <0.5. A preliminary structure-activity relationship could be observed that free 3-OH in the structure of flavonoids was important for synergistic antifungal activity.

  7. Optimization of nickel adsorption from aqueous solution by using activated carbon prepared from waste apricot by chemical activation

    NASA Astrophysics Data System (ADS)

    Erdoğan, S.; Önal, Y.; Akmil-Başar, C.; Bilmez-Erdemoğlu, S.; Sarıcı-Özdemir, Ç.; Köseoğlu, E.; İçduygu, G.

    2005-12-01

    Waste apricot supplied by Malatya apricot plant (Turkey) was activated by using chemical activation method and K 2CO 3 was chosen for this purpose. Activation temperature was varied over the temperature range of 400-900 °C and N 2 atmosphere was used with 10 °C/min heat rate. The maximum surface area (1214 m 2/g) and micropore volume (0.355 cm 3/g) were obtained at 900 °C, but activated carbon was predominantly microporous at 700 °C. The resulting activated carbons were used for removal of Ni(II) ions from aqueous solution and adsorption properties have been investigated under various conditions such as pH, activation temperature, adsorbent dosage and nickel concentration. Adsorption parameters were determined by using Langmuir model. Optimal condition was determined as; pH 5, 0.7 g/10 ml adsorbent dosage, 10 mg/l Ni(II) concentration and 60 min contact time. The results indicate that the effective uptake of Ni(II) ions was obtained by activating the carbon at 900 °C.

  8. Chemical reactivity and biological activity of chalcones and other α,β-unsaturated carbonyl compounds.

    PubMed

    Maydt, Daniela; De Spirt, Silke; Muschelknautz, Christian; Stahl, Wilhelm; Müller, Thomas J J

    2013-08-01

    Abstract 1. Chalcones are structural analogues of benzalacetophenone (BAP). Several derivatives have been identified in plants and anticarcinogenic and anti-inflammatory properties were attributed to the compounds, probably related to their direct antioxidant activity or stimulatory effects on the expression of endogenous defence enzymes like hemeoxygenase-1 (HO-1). HO-1 expression is triggered by the Nrf2-Keap1 signalling pathway, initiated by the addition of chalcones to thiol groups of Keap1 via Michael-type reaction. 2. The present study used a model system estimating the reactivity of different synthetic chalcones and other α,β-unsaturated carbonyl compounds with thiols and compared the chemical reactivity with the biological activity, measured by HO-1 expression in human dermal fibroblasts. 3. Chemical reactivity with the thiol group of N-acetylcysteine was determined with 5,5'-dithiobis-(2-nitrobenzoic acid) and followed chemical principles of structure-reactivity relationship. Most reactive were sulforaphane, dimethylfumarate, chalcone 3 ((2E)-1-phenyl-3-pyrimidin-2-ylprop-2-en-1-one) and chalcone 7 (1,3-diphenylprop-2-yn-1-one). This result demonstrates that α,β-unsaturated carbonyl derivatives react with thiols differently. All compounds were also biologically active; however, expression of HO-1 was not only related to the chemical reactivity but also to the lipophilicity of the molecules which likely affected transmembrane uptake. Most efficient inducers of HO-1 expression were BAP, 4-hydroxynonenal and chalcone 1 (4-[(1E)-3-oxo-3-phenylprop-1-en-1-yl]benzonitrile), chalcone 5 ((2E)-1-phenyl-3-[4-(trifluoromethyl)-phenyl]prop-2-en-1-one) and chalcone 7.

  9. Chemical composition, nutritional value, and antioxidant activities of eight mulberry cultivars from China

    PubMed Central

    Liang, Linghong; Wu, Xiangyang; Zhu, Maomao; Zhao, Weiguo; Li, Fang; Zou, Ye; Yang, Liuqing

    2012-01-01

    Background: Mulberry (Morus, Moraceae) is widely distributed in the temperate, subtropical, or tropical regions of the world, while there are no conclusive reports on the chemical composition, nutritional value, and antioxidant properties of mulberry cultivars from China. Objective: To investigate chemical properties and to determine proximate nutritive compounds of the eight mulberry cultivars. Materials and Methods: Chemical properties (including moisture, ash, total dry matter, total soluble solids, pH, and total titratable acidity) of the eight mulberry cultivars were investigated. Proximate nutritive compounds (including crude protein, crude fat, mineral elements, total anthocyanins, total polyphenols, total flavonoids, and total sugars) were also determined. Results: The results indicated that the moisture contents were 70.0-87.4%, the crude protein contents 1.62-5.54%, and the crude fat contents from 1.23-2.23%. The major fatty acids in mulberry fruits were linoleic acid (C18:2) and palmitic acid (C16:0), 26.40-74.77% and 9.29-22.26%, respectively. Mulberry fruit is also a good source of minerals and the potassium content (521.37-1718.60 mg/100g DW) is especially higher than that of other elements. Compared with other species, the Morus atropurpurea Roxb. had relatively high total polyphenols content (189.67-246.00 mg GAE/100mg) and anthocyanins content (114.67-193.00 mg/100mg). There was a good linear correlation between antioxidant activity and total polyphenols content. Conclusion: Significant differences of the chemical composition, nutritional value, and antioxidant activities among the mulberry cultivars were observed, the Morus atropurpurea Roxb. showed considerable high nutritional value and antioxidant activity which could be developed for functional food that benefits human health. PMID:23060696

  10. The chemical precipitation of nickel on ion exchangers and active carbons

    NASA Astrophysics Data System (ADS)

    Khorol'Skaya, S. V.; Zolotukhina, E. V.; Polyanskii, L. N.; Peshkov, S. V.; Kravchenko, T. A.; Krysanov, V. A.

    2010-12-01

    The chemical precipitation of nickel in the form of poorly soluble precipitates in ion exchanger matrices and on active carbons from solutions of nickel chloride and chemical nickel plating electrolytes was studied. The sorption of nickel ions from a solution of nickel chloride occurs most effectively on Purolite D24002 macroporous chelate forming ion exchanger, KU-23-15/100 sulfo cation exchanger, and KU-2-8 gel sulfo cation exchanger. Nickel enters sulfo cation exchangers in the form of counterions, and is adsorbed on Purolite D24002 largely because of complex formation. The subsequent precipitation of nickel in the solid state in matrix pores liberates ionogenic centers, which allows repeated sorption cycles to be performed. After three chemical precipitation cycles under static conditions, the amount of nickel is higher by 170-250% than the ion exchange capacity of the sorbents. The electrolyte of chemical nickel plating contains nickel predominantly in the form of negatively charged and neutral complexes with glycine, which cannot form bonds with the matrices under study. It is therefore reasonable to perform sorption at decreased solution pH values.

  11. Force-activated reactivity switch in a bimolecular chemical reaction at the single molecule level

    NASA Astrophysics Data System (ADS)

    Szoszkiewicz, Robert; Garcia-Manyes, Sergi; Liang, Jian; Kuo, Tzu-Ling; Fernandez, Julio M.

    2010-03-01

    Mechanical force can deform the reacting molecules along a well-defined direction of the reaction coordinate. However, the effect of mechanical force on the free-energy surface that governs a chemical reaction is still largely unknown. The combination of protein engineering with single-molecule AFM force-clamp spectroscopy allows us to study the influence of mechanical force on the rate at which a protein disulfide bond is reduced by some reducing agents in a bimolecular substitution reaction (so-called SN2). We found that cleavage of a protein disulfide bond by hydroxide anions exhibits an abrupt reactivity ``switch'' at 500 pN, after which the accelerating effect of force on the rate of an SN2 chemical reaction greatly diminishes. We propose that an abrupt force-induced conformational change of the protein disulfide bond shifts its ground state, drastically changing its reactivity in SN2 chemical reactions. Our experiments directly demonstrate the action of a force-activated switch in the chemical reactivity of a single molecule. References: Sergi Garcia-Manyes, Jian Liang, Robert Szoszkiewicz, Tzu-Ling Kuo and Julio M. Fernandez, Nature Chemistry, 1, 236-242, 2009.

  12. Synthesis, characterization, biocompatible and anticancer activity of green and chemically synthesized silver nanoparticles - A comparative study.

    PubMed

    Kummara, Sivaiah; Patil, Mrityunjaya B; Uriah, Tiewlasubon

    2016-12-01

    Silver nanoparticles (AgNPs) are superior cluster of nanomaterials that are recently recognized for their different applications in various pharmaceutical and clinical settings. The objective of this work deals with novel method for biosynthesis of AgNPs using Azadirachta indica (neem) leaf extract as reducing agent. These bio and chemical synthesized nanoparticles were characterized with the help of UV-vis Spectroscopy, Nanotarc, Dynamic light scattering (DLS), Zeta Potential (ZP), Transmission Electron Microscopy and Fourier transform infrared spectroscopy (FTIR). The obtained results from Nanotrac and TEM revealed that the synthesized AgNPs possess spherical shape with a mean diameter at 94nm for green and 104nm for chemical method, the zeta potential values was -12.02mV for green AgNPs and -10.4mV for chemical AgNPs. In addition, FT-IR measurement analysis was conceded out to identify the Ag(+) ions reduced from the specific functional groups on the AgNPs, which increased the stability of the particles. Further, we compared the toxicities of green and chemical AgNPs against human skin dermal fibroblast (HDFa) and brine shrimp followed by anticancer activity in NCI-H460 cells. We observed green AgNPs cause dose-dependent decrease in cell viability and increase in reactive oxygen species (ROS) generation. Further, we proved to exhibit excellent cytotoxic effect and induction of cellular apoptosis in NCI-H460 cells. Furthermore, green AgNPs had no significant changes in cell viability, ROS production and apoptotic changes in HDFa cells. In contrary, we observed that the chemical AgNPs possess significant toxicities in HDFa cells. Hence, the green AgNPs were able to induce selective toxicity in cancer cells than the chemical AgNPs. Furthermore, green AgNPs exhibit less toxic effects against human red blood cells and brine shrimp (Artemia salina) nauplii than the chemical AgNPs. It was concluded, that apart from being superior over chemical AgNPs, the green Ag

  13. Effects of biologically-active chemical mixtures on fish in a wastewater-impacted urban stream

    USGS Publications Warehouse

    Barber, L.B.; Brown, G.K.; Nettesheim, T.G.; Murphy, E.W.; Bartell, S.E.; Schoenfuss, H.L.

    2011-01-01

    Stream flow in urban aquatic ecosystems often is maintained by water-reclamation plant (WRP) effluents that contain mixtures of natural and anthropogenic chemicals that persist through the treatment processes. In effluent-impacted streams, aquatic organisms such as fish are continuously exposed to biologically-active chemicals throughout their life cycles. The North Shore Channel of the Chicago River (Chicago, Illinois) is part of an urban ecosystem in which > 80% of the annual flow consists of effluent from the North Side WRP. In this study, multiple samplings of the effluent and stream water were conducted and fish (largemouth bass and carp) were collected on 2 occasions from the North Shore Channel. Fish also were collected once from the Outer Chicago Harbor in Lake Michigan, a reference site not impacted by WRP discharges. Over 100 organic chemicals with differing behaviors and biological effects were measured, and 23 compounds were detected in all of the water samples analyzed. The most frequently detected and highest concentration (> 100 ??g/L) compounds were ethylenediaminetetraacetic acid and 4-nonylphenolmono-to-tetraethoxycarboxylic acids. Other biologically-active chemicals including bisphenol A, 4-nonylphenol, 4-nonylphenolmono-to-tetraethoxylates, 4- tert-octylphenol, and 4- tert-octylphenolmono-to-tetraethoxylates were detected at lower concentrations (< 5 ??g/L). The biogenic steroidal hormones 17??-estradiol, estrone, testosterone, 4-androstene-3,17-dione, and cis-androsterone were detected at even lower concentrations (< 0.005 ??g/L). There were slight differences in concentrations between the North Side WRP effluent and the North Shore Channel, indicating minimal in-stream attenuation. Fish populations are continuously exposed to mixtures of biologically-active chemicals because of the relative persistency of the chemicals with respect to stream hydraulic residence time, and the lack of a fresh water source for dilution. The majority of male fish

  14. Effects of biologically-active chemical mixtures on fish in a wastewater-impacted urban stream.

    PubMed

    Barber, Larry B; Brown, Gregory K; Nettesheim, Todd G; Murphy, Elizabeth W; Bartell, Stephen E; Schoenfuss, Heiko L

    2011-10-15

    Stream flow in urban aquatic ecosystems often is maintained by water-reclamation plant (WRP) effluents that contain mixtures of natural and anthropogenic chemicals that persist through the treatment processes. In effluent-impacted streams, aquatic organisms such as fish are continuously exposed to biologically-active chemicals throughout their life cycles. The North Shore Channel of the Chicago River (Chicago, Illinois) is part of an urban ecosystem in which >80% of the annual flow consists of effluent from the North Side WRP. In this study, multiple samplings of the effluent and stream water were conducted and fish (largemouth bass and carp) were collected on 2 occasions from the North Shore Channel. Fish also were collected once from the Outer Chicago Harbor in Lake Michigan, a reference site not impacted by WRP discharges. Over 100 organic chemicals with differing behaviors and biological effects were measured, and 23 compounds were detected in all of the water samples analyzed. The most frequently detected and highest concentration (>100μg/L) compounds were ethylenediaminetetraacetic acid and 4-nonylphenolmono-to-tetraethoxycarboxylic acids. Other biologically-active chemicals including bisphenol A, 4-nonylphenol, 4-nonylphenolmono-to-tetraethoxylates, 4-tert-octylphenol, and 4-tert-octylphenolmono-to-tetraethoxylates were detected at lower concentrations (<5μg/L). The biogenic steroidal hormones 17β-estradiol, estrone, testosterone, 4-androstene-3,17-dione, and cis-androsterone were detected at even lower concentrations (<0.005μg/L). There were slight differences in concentrations between the North Side WRP effluent and the North Shore Channel, indicating minimal in-stream attenuation. Fish populations are continuously exposed to mixtures of biologically-active chemicals because of the relative persistency of the chemicals with respect to stream hydraulic residence time, and the lack of a fresh water source for dilution. The majority of male fish exhibited

  15. 76 FR 76935 - Impact of Implementing the Chemical Weapons Convention (CWC) on Commercial Activities Involving...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-09

    ... Bureau of Industry and Security Impact of Implementing the Chemical Weapons Convention (CWC) on... implementation of the Chemical Weapons Convention (CWC), through the Chemical Weapons Convention Implementation Act (CWCIA), and the Chemical Weapons Convention Regulations (CWCR), has had on commercial...

  16. The millennium water vapour drop in the stratosphere in chemistry-climate model simulations

    NASA Astrophysics Data System (ADS)

    Brinkop, Sabine; Dameris, Martin; Joeckel, Patrick; Garny, Hella; Lossow, Stefan; Stiller, Gabriele

    2015-04-01

    This study investigates the millennium water vapour drop, the abrupt and severe water vapour decline in the stratosphere beginning in year 2000, by means of various simulations using the Chemistry-Climate Model (CCM) EMAC. Since the beginning 1980s, balloon borne stratospheric water vapour measurements and corresponding satellite measurements starting in the early 1990s indicated a long-term steady increase of water vapour concentrations. However, the multi-year data sets also show significant fluctuations on different time scales. In the year 2000, an extraordinary sudden drop of stratospheric water vapour concentration has been observed followed by persistent low values for several years. Solomon et al. (2010) showed that this drop slowed down the rate of increase in global surface temperature over the following decade by about 25%. So far, the stratospheric water vapour variations observed by satellite from 1992 to 2012 are not reproduced by CCM simulations forced by observed changes in sea surface temperatures, greenhouse gases and ozone-depleting substances (Gettelman et al., 2010, Randel and Jensen, 2013). However, the CCM EMAC is able to reproduce the signature and pattern of the water vapour disturbances in agreement with those derived from observations. In this paper we present results of a hierarchy of simulations with the CCM EMAC, demonstrating that it is possible to retrace the observed water vapour fluctuations in the stratosphere (incl. the millennium drop), if suitable inner and outer boundary conditions are applied.

  17. Liquid-vapour equilibrium in the restricted primitive model for ionic liquids

    NASA Astrophysics Data System (ADS)

    Gillan, M. J.

    We study the thermodynamic equilibrium between liquid and vapour for the restricted primitive model (charged hard spheres of equal diameters) of a two component ionic liquid. We point out that physical clustering of ions will have a crucial effect on this equilibrium. The calculations presented are based on the representation of the vapour as a mixture of clusters of different types, the interactions between clusters being neglected. The relative proportions of the different types are governed by the law of mass action. We show that neglect of interactions yields a lower bound to the true vapour pressure. The internal free energies of the clusters in the vapour are obtained from a combination of analytic and Monte Carlo calculations and the thermodynamic properties of the liquid phase are derived from Larsen's published Monte Carlo results. We present numerical results for the densities of different cluster types in the vapour phase, for the overall liquid and vapour densities and for the vapour pressure. A comparison with the predictions of the mean spherical approximation and of Larsen's empirical equation show that these yield vapour pressures which are far below our lower bound and are therefore erroneous. We point out that Larsen's equation implies a weak subsidiary critical point on the liquid branch of the coexistence curve, an effect which we suggest is spurious. Finally, we discuss the relation between our work and that of Stell, Wu and Larsen.

  18. The recovery of VOC from vapours and condensates by membrane processes

    SciTech Connect

    Chmiel, H.; Mavrov, V.; Faehnrich, A.

    1995-12-31

    Membrane separation processes, applied individually or combined with other separation processes, have proven to be particularly suitable for integration into production processes. This paper provides examples which focus on the recovery of volatile organic components from exhaust air, vapours and condensates by membrane processes. The processes described are vapour permeation combined with adsorption, nanofiltration, and reverse osmosis.

  19. The injection of water into and extraction of vapour from bounded geothermal reservoirs

    SciTech Connect

    Fitzgerald, Shaun D.; Woods, Andrew W.

    1993-01-28

    When liquid is injected into a geothermal reservoir, a fraction of the liquid may vaporise if the reservoir is sufficiently hot. The vapour forms at an approximately planar liquid-vapour interface and diffuses towards the far boundary of the reservoir. If vapour is extracted from the far boundary, then once the new vapour has diffused across the reservoir, the rate of production of vapour at the liquid-vapour interface approximately balances the rate of extraction. We find that if the pressure at the injection pump and extraction well is fixed, then the fraction of the liquid which vaporises and the rate of extraction of vapour from the reservoir increase with time. However, the rate at which liquid is pumped into the reservoir inay initially decrease but subsequently increases with time, if a sufficient fraction of the liquid vaporises. If the mass flux of liquid injected into the reservoir is fixed, then again both the fraction of the liquid which vaporises and the mass flux of vapour which may be extracted increase with time. In this case, the pressure at the injection pump may increase but subsequently decreases with time, again if a sufficient fraction of the liquid vaporises.

  20. Eupatorium Capillifolium Essential Oil: Chemical Composition, Antifungal Activity, and Insecticidal Activity

    DTIC Science & Technology

    2010-01-01

    hydrodistillation of aerial parts was analyzed by gas chromatography (GC) and gas chromatography–mass spectrometry (GC/MS). The major components were determined...on the use of Eupatorium species in pest management. The potential molluscicidal activities of aqueous extracts of E. adenophorum were recently...cloth [23]. The result of this assay indicated that the oil was repellent, implicating that one or more components of the oil were producing this