Science.gov

Sample records for open channel h2o

  1. Epigallocatechin-3-gallate induces mesothelioma cell death via H2 O2 -dependent T-type Ca2+ channel opening.

    PubMed

    Ranzato, Elia; Martinotti, Simona; Magnelli, Valeria; Murer, Bruno; Biffo, Stefano; Mutti, Luciano; Burlando, Bruno

    2012-11-01

    Malignant mesothelioma (MMe) is a highly aggressive, lethal tumour requiring the development of more effective therapies. The green tea polyphenol epigallocathechin-3-gallate (EGCG) inhibits the growth of many types of cancer cells. We found that EGCG is selectively cytotoxic to MMe cells with respect to normal mesothelial cells. MMe cell viability was inhibited by predominant induction of apoptosis at lower doses and necrosis at higher doses. EGCG elicited H(2) O(2) release in cell cultures, and exogenous catalase (CAT) abrogated EGCG-induced cytotoxicity, apoptosis and necrosis. Confocal imaging of fluo 3-loaded, EGCG-exposed MMe cells showed significant [Ca(2+) ](i) rise, prevented by CAT, dithiothreitol or the T-type Ca(2+) channel blockers mibefradil and NiCl(2) . Cell loading with dihydrorhodamine 123 revealed EGCG-induced ROS production, prevented by CAT, mibefradil or the Ca(2+) chelator BAPTA-AM. Direct exposure of cells to H(2) O(2) produced similar effects on Ca(2+) and ROS, and these effects were prevented by the same inhibitors. Sensitivity of REN cells to EGCG was correlated with higher expression of Ca(v) 3.2 T-type Ca(2+) channels in these cells, compared to normal mesothelium. Also, Ca(v) 3.2 siRNA on MMe cells reduced in vitro EGCG cytotoxicity and abated apoptosis and necrosis. Intriguingly, Ca(v) 3.2 expression was observed in malignant pleural mesothelioma biopsies from patients, but not in normal pleura. In conclusion, data showed the expression of T-type Ca(2+) channels in MMe tissue and their role in EGCG selective cytotoxicity to MMe cells, suggesting the possible use of these channels as a novel MMe pharmacological target. PMID:22564432

  2. Epigallocatechin-3-gallate induces mesothelioma cell death via H2O2—dependent T-type Ca2+ channel opening

    PubMed Central

    Ranzato, Elia; Martinotti, Simona; Magnelli, Valeria; Murer, Bruno; Biffo, Stefano; Mutti, Luciano; Burlando, Bruno

    2012-01-01

    Malignant mesothelioma (MMe) is a highly aggressive, lethal tumour requiring the development of more effective therapies. The green tea polyphenol epigallocathechin-3-gallate (EGCG) inhibits the growth of many types of cancer cells. We found that EGCG is selectively cytotoxic to MMe cells with respect to normal mesothelial cells. MMe cell viability was inhibited by predominant induction of apoptosis at lower doses and necrosis at higher doses. EGCG elicited H2O2 release in cell cultures, and exogenous catalase (CAT) abrogated EGCG-induced cytotoxicity, apoptosis and necrosis. Confocal imaging of fluo 3-loaded, EGCG-exposed MMe cells showed significant [Ca2+]i rise, prevented by CAT, dithiothreitol or the T-type Ca2+ channel blockers mibefradil and NiCl2. Cell loading with dihydrorhodamine 123 revealed EGCG-induced ROS production, prevented by CAT, mibefradil or the Ca2+ chelator BAPTA-AM. Direct exposure of cells to H2O2 produced similar effects on Ca2+ and ROS, and these effects were prevented by the same inhibitors. Sensitivity of REN cells to EGCG was correlated with higher expression of Cav3.2 T-type Ca2+ channels in these cells, compared to normal mesothelium. Also, Cav3.2 siRNA on MMe cells reduced in vitro EGCG cytotoxicity and abated apoptosis and necrosis. Intriguingly, Cav3.2 expression was observed in malignant pleural mesothelioma biopsies from patients, but not in normal pleura. In conclusion, data showed the expression of T-type Ca2+ channels in MMe tissue and their role in EGCG selective cytotoxicity to MMe cells, suggesting the possible use of these channels as a novel MMe pharmacological target. PMID:22564432

  3. X-ray irradiation activates K+ channels via H2O2 signaling.

    PubMed

    Gibhardt, Christine S; Roth, Bastian; Schroeder, Indra; Fuck, Sebastian; Becker, Patrick; Jakob, Burkhard; Fournier, Claudia; Moroni, Anna; Thiel, Gerhard

    2015-01-01

    Ionizing radiation is a universal tool in tumor therapy but may also cause secondary cancers or cell invasiveness. These negative side effects could be causally related to the human-intermediate-conductance Ca2+-activated-K+-channel (hIK), which is activated by X-ray irradiation and affects cell proliferation and migration. To analyze the signaling cascade downstream of ionizing radiation we use genetically encoded reporters for H2O2 (HyPer) and for the dominant redox-buffer glutathione (Grx1-roGFP2) to monitor with high spatial and temporal resolution, radiation-triggered excursions of H2O2 in A549 and HEK293 cells. The data show that challenging cells with ≥1 Gy X-rays or with UV-A laser micro-irradiation causes a rapid rise of H2O2 in the nucleus and in the cytosol. This rise, which is determined by the rate of H2O2 production and glutathione-buffering, is sufficient for triggering a signaling cascade that involves an elevation of cytosolic Ca2+ and eventually an activation of hIK channels. PMID:26350345

  4. X-ray irradiation activates K+ channels via H2O2 signaling

    PubMed Central

    Gibhardt, Christine S.; Roth, Bastian; Schroeder, Indra; Fuck, Sebastian; Becker, Patrick; Jakob, Burkhard; Fournier, Claudia; Moroni, Anna; Thiel, Gerhard

    2015-01-01

    Ionizing radiation is a universal tool in tumor therapy but may also cause secondary cancers or cell invasiveness. These negative side effects could be causally related to the human-intermediate-conductance Ca2+-activated-K+-channel (hIK), which is activated by X-ray irradiation and affects cell proliferation and migration. To analyze the signaling cascade downstream of ionizing radiation we use genetically encoded reporters for H2O2 (HyPer) and for the dominant redox-buffer glutathione (Grx1-roGFP2) to monitor with high spatial and temporal resolution, radiation-triggered excursions of H2O2 in A549 and HEK293 cells. The data show that challenging cells with ≥1 Gy X-rays or with UV-A laser micro-irradiation causes a rapid rise of H2O2 in the nucleus and in the cytosol. This rise, which is determined by the rate of H2O2 production and glutathione-buffering, is sufficient for triggering a signaling cascade that involves an elevation of cytosolic Ca2+ and eventually an activation of hIK channels. PMID:26350345

  5. A Minimal Cysteine Motif Required to Activate the SKOR K+ Channel of Arabidopsis by the Reactive Oxygen Species H2O2*

    PubMed Central

    Garcia-Mata, Carlos; Wang, Jianwen; Gajdanowicz, Pawel; Gonzalez, Wendy; Hills, Adrian; Donald, Naomi; Riedelsberger, Janin; Amtmann, Anna; Dreyer, Ingo; Blatt, Michael R.

    2010-01-01

    Reactive oxygen species (ROS) are essential for development and stress signaling in plants. They contribute to plant defense against pathogens, regulate stomatal transpiration, and influence nutrient uptake and partitioning. Although both Ca2+ and K+ channels of plants are known to be affected, virtually nothing is known of the targets for ROS at a molecular level. Here we report that a single cysteine (Cys) residue within the Kv-like SKOR K+ channel of Arabidopsis thaliana is essential for channel sensitivity to the ROS H2O2. We show that H2O2 rapidly enhanced current amplitude and activation kinetics of heterologously expressed SKOR, and the effects were reversed by the reducing agent dithiothreitol (DTT). Both H2O2 and DTT were active at the outer face of the membrane and current enhancement was strongly dependent on membrane depolarization, consistent with a H2O2-sensitive site on the SKOR protein that is exposed to the outside when the channel is in the open conformation. Cys substitutions identified a single residue, Cys168 located within the S3 α-helix of the voltage sensor complex, to be essential for sensitivity to H2O2. The same Cys residue was a primary determinant for current block by covalent Cys S-methioylation with aqueous methanethiosulfonates. These, and additional data identify Cys168 as a critical target for H2O2, and implicate ROS-mediated control of the K+ channel in regulating mineral nutrient partitioning within the plant. PMID:20605786

  6. ROLE OF H2O2-ACTIVATED TRPM2 CALCIUM CHANNEL IN OXIDANT-INDUCED ENDOTHELIAL INJURY

    PubMed Central

    Hecquet, Claudie M.; Malik, Asrar B.

    2013-01-01

    The transient receptor potential (melastatin) 2 (TRPM2), is an oxidant-activated nonselective cation channel, that is widely expressed in mammalian tissues including the vascular endothelium. Oxidative stress, through the generation of oxygen metabolites including H2O2, stimulates intracellular ADP-ribose formation which, in turn, opens TRPM2 channels. These channels act as an endogenous redox sensor for mediating oxidative stress/ROS-induced Ca2+ entry and the subsequent specific Ca2+-dependent cellular reactions such as endothelial hyper-permeability and apoptosis. This review summarizes recent findings on the mechanism by which oxidants induce TRPM2 activation, the role of these channels in the signaling vascular endothelial dysfunctions, and the modulation of oxidant-induced TRPM2 activation by PKCα and phospho-tyrosine phosphates L1. PMID:19350103

  7. Synthesis and structure of [C 6H 14N 2][(UO 2) 4(HPO 4) 2(PO 4) 2(H 2O)]·H 2O: An expanded open-framework amine-bearing uranyl phosphate

    NASA Astrophysics Data System (ADS)

    Bray, Travis H.; Gorden, John D.; Albrecht-Schmitt, Thomas E.

    2008-09-01

    A new open-framework compound, [C 6H 14N 2][(UO 2) 4(HPO 4) 2(PO 4) 2(H 2O)]·H 2O, ( DUP-1) has been synthesized under mild hydrothermal conditions. The resulting structure consists of diprotonated DABCOH 22+ (C 6H 14N 22+) cations and occluded water molecules occupying the channels of a complex uranyl phosphate three-dimensional framework. The anionic lattice contains uranophane-like sheets connected by hydrated pentagonal bipyramidal UO 7 units. [C 6H 14N 2][(UO 2) 4(HPO 4) 2(PO 4) 2(H 2O)]·H 2O possesses five crystallographically unique U centers. U(VI) is present here in both six- and seven-coordinate environments. The DABCOH 22+ cations are held within the channels by hydrogen bonds to both two uranyl oxygen atoms and a μ2-O atom. Crystallographic data (193 K, Mo Kα, λ=0.71073 Å): DUP-1, monoclinic, P2 1/ n, a=7.017(1) Å, b=21.966(4) Å, c=17.619(3) Å, β=90.198(3)°, Z=4, R(F)=4.76% for 382 parameters with 6615 reflections with I>2 σ( I).

  8. Differential regulation of TRPV1 channels by H2O2: implications for diabetic microvascular dysfunction

    PubMed Central

    DelloStritto, Daniel J.; Connell, Patrick J.; Dick, Gregory M.; Fancher, Ibra S.; Klarich, Brittany; Fahmy, Joseph N.; Kang, Patrick T.; Chen, Yeong-Renn; Damron, Derek S.; Thodeti, Charles K.

    2016-01-01

    We demonstrated previously that TRPV1-dependent coupling of coronary blood flow (CBF) to metabolism is disrupted in diabetes. A critical amount of H2O2 contributes to CBF regulation; however, excessive H2O2 impairs responses. We sought to determine the extent to which differential regulation of TRPV1 by H2O2 modulates CBF and vascular reactivity in diabetes. We used contrast echocardiography to study TRPV1 knockout (V1KO), db/db diabetic, and wild type C57BKS/J (WT) mice. H2O2 dose-dependently increased CBF in WT mice, a response blocked by the TRPV1 antagonist SB366791. H2O2-induced vasodilation was significantly inhibited in db/db and V1KO mice. H2O2 caused robust SB366791-sensitive dilation in WT coronary microvessels; however, this response was attenuated in vessels from db/db and V1KO mice, suggesting H2O2-induced vasodilation occurs, in part, via TRPV1. Acute H2O2 exposure potentiated capsaicin-induced CBF responses and capsaicin-mediated vasodilation in WT mice, whereas prolonged luminal H2O2 exposure blunted capsaicin-induced vasodilation. Electrophysiology studies re-confirms acute H2O2 exposure activated TRPV1 in HEK293A and bovine aortic endothelial cells while establishing that H2O2 potentiate capsaicin-activated TRPV1 currents, whereas prolonged H2O2 exposure attenuated TRPV1 currents. Verification of H2O2-mediated activation of intrinsic TRPV1 specific currents were found in isolated mouse coronary endothelial cells from WT mice and decreased in endothelial cells from V1KO mice. These data suggest prolonged H2O2 exposure impairs TRPV1-dependent coronary vascular signaling. This may contribute to microvascular dysfunction and tissue perfusion deficits characteristic of diabetes. PMID:26907473

  9. SK channel activation modulates mitochondrial respiration and attenuates neuronal HT-22 cell damage induced by H2O2.

    PubMed

    Richter, Maren; Nickel, Catharina; Apel, Lisa; Kaas, Alexander; Dodel, Richard; Culmsee, Carsten; Dolga, Amalia M

    2015-02-01

    Previous studies established an essential role for small conductance calcium-activated potassium (SK) channels in neuronal cell death pathways induced by glutamate excitotoxicity in cortical neurons in vitro and after cerebral ischemia in vivo. In addition to the intracellular calcium deregulation, glutamate-induced cell death also involves mechanisms of oxidative stress and mitochondrial dysfunction. Therefore, we sought to investigate whether SK channel activation might also affect mechanisms of intrinsic death pathways induced by reactive oxygen species (ROS) such as hydrogen peroxide (H2O2). Exposure of immortalized hippocampal HT-22 cells to H2O2 imposed activation of a cascade of intracellular toxic events resulting in intracellular ROS production, mitochondrial loss of function, and ultimately cell death. Using a pharmacological approach to activate SK channels with CyPPA, we demonstrated a reduction of H2O2-mediated intracellular ROS production and cell death. Interestingly, CyPPA mediated neuroprotection in conditions of extracellular calcium and/or pyruvate depletion, pointing to a neuroprotective role of mitochondrial SK channels. Moreover, CyPPA partially inhibited H2O2-induced mitochondrial superoxide production, but did not prevent mitochondrial membrane depolarization. CyPPA treatment resulted in slight ATP depletion and a reduction of mitochondrial respiration/oxygen consumption. These findings postulate that SK channels mediate a protective effect by preventing neuronal death from subsequent oxidative stress through an adaptive metabolic response at the level of mitochondria. Therefore, SK channel activation may serve as a therapeutic target, where mitochondrial dysfunction and related mechanisms of oxidative stress contribute to progressive degeneration and death of neurons. PMID:25576183

  10. Role of H2O2 dynamics in brassinosteroid-induced stomatal closure and opening in Solanum lycopersicum.

    PubMed

    Xia, Xiao-Jian; Gao, Chun-Juan; Song, Liu-Xia; Zhou, Yan-Hong; Shi, Kai; Yu, Jing-Quan

    2014-09-01

    Brassinosteroids (BRs) are essential for plant growth and development; however, their roles in the regulation of stomatal opening or closure remain obscure. Here, the mechanism underlying BR-induced stomatal movements is studied. The effects of 24-epibrassinolide (EBR) on the stomatal apertures of tomato (Solanum lycopersicum) were measured by light microscopy using epidermal strips of wild type (WT), the abscisic acid (ABA)-deficient notabilis (not) mutant, and plants silenced for SlBRI1, SlRBOH1 and SlGSH1. EBR induced stomatal opening within an appropriate range of concentrations, whereas high concentrations of EBR induced stomatal closure. EBR-induced stomatal movements were closely related to dynamic changes in H(2)O(2) and redox status in guard cells. The stomata of SlRBOH1-silenced plants showed a significant loss of sensitivity to EBR. However, ABA deficiency abolished EBR-induced stomatal closure but did not affect EBR-induced stomatal opening. Silencing of SlGSH1, the critical gene involved in glutathione biosynthesis, disrupted glutathione redox homeostasis and abolished EBR-induced stomatal opening. The results suggest that transient H(2)O(2) production is essential for poising the cellular redox status of glutathione, which plays an important role in BR-induced stomatal opening. However, a prolonged increase in H(2)O(2) facilitated ABA signalling and stomatal closure. PMID:24428600

  11. H2O2 generated by NADPH oxidase 4 contributes to transient receptor potential vanilloid 1 channel-mediated mechanosensation in the rat kidney.

    PubMed

    Lin, Chian-Shiung; Lee, Shang-Hsing; Huang, Ho-Shiang; Chen, Yih-Sharng; Ma, Ming-Chieh

    2015-08-15

    The presence of NADPH oxidase (Nox) in the kidney, especially Nox4, results in H2O2 production, which regulates Na(+) excretion and urine formation. Redox-sensitive transient receptor potential vanilloid 1 channels (TRPV1s) are distributed in mechanosensory fibers of the renal pelvis and monitor changes in intrapelvic pressure (IPP) during urine formation. The present study tested whether H2O2 derived from Nox4 affects TRPV1 function in renal sensory responses. Perfusion of H2O2 into the renal pelvis dose dependently increased afferent renal nerve activity and substance P (SP) release. These responses were attenuated by cotreatment with catalase or TRPV1 blockers. In single unit recordings, H2O2 activated afferent renal nerve activity in response to rising IPP but not high salt. Western blots revealed that Nox2 (gp91(phox)) and Nox4 are both present in the rat kidney, but Nox4 is abundant in the renal pelvis and originates from dorsal root ganglia. This distribution was associated with expression of the Nox4 regulators p22(phox) and polymerase δ-interacting protein 2. Coimmunoprecipitation experiments showed that IPP increases polymerase δ-interacting protein 2 association with Nox4 or p22(phox) in the renal pelvis. Interestingly, immunofluorescence labeling demonstrated that Nox4 colocalizes with TRPV1 in sensory fibers of the renal pelvis, indicating that H2O2 generated from Nox4 may affect TRPV1 activity. Stepwise increases in IPP and saline loading resulted in H2O2 and SP release, sensory activation, diuresis, and natriuresis. These effects, however, were remarkably attenuated by Nox inhibition. Overall, these results suggest that Nox4-positive fibers liberate H2O2 after mechanostimulation, thereby contributing to a renal sensory nerve-mediated diuretic/natriuretic response. PMID:26136558

  12. Structure and thermal behaviour of ScK(C 2O 4) 2(H 2O) 2 and InRb 1- x(H 3O) x(C 2O 4) 2(H 2O) 2ṡ0.5(H 2O): Two members of a family of open-framework oxalates with isotypic helical structures and zeolite-like properties

    NASA Astrophysics Data System (ADS)

    Mahé, Nathalie; Audebrand, Nathalie

    2006-08-01

    Two new mixed oxalates with an open architecture, ScK(C 2O 4) 2(H 2O) 2 ( I) and InRb 0.77(H 3O) 0.23(C 2O 4) 2(H 2O) 2ṡ0.5(H 2O) ( II), have been synthesised from precipitation methods at ambient temperature. They crystallize in hexagonal system, space group P622 (No. 180), Z=3, with the following unit-cell parameters for I: a=8.8667(2) Å, c=11.4908(4) Å, V=782.36(4) Å, for II: a=9.0148(3) Å, c=11.4645(3) Å, V=806.86(4) Å. The two structures belong to a family of isotypic helical anionic open-frameworks built from square antiprismatic coordinated metals and bischelating oxalates. The counter-cations K + and Rb +/H 3O + are located in the tunnels of the framework. The thermal decomposition process has demonstrated zeolite-like properties associated with weakly-bonded water molecules located in the voids of the framework.

  13. H2O2: a dynamic neuromodulator.

    PubMed

    Rice, Margaret E

    2011-08-01

    Increasing evidence implicates hydrogen peroxide (H(2)O(2)) as an intracellular and intercellular signaling molecule that can influence processes from embryonic development to cell death. Most research has focused on relatively slow signaling, on the order of minutes to days, via second messenger cascades. However, H(2)O(2) can also mediate subsecond signaling via ion channel activation. This rapid signaling has been examined most thoroughly in the nigrostriatal dopamine (DA) pathway, which plays a key role in facilitating movement mediated by the basal ganglia. In DA neurons of the substantia nigra, endogenously generated H(2)O(2) activates ATP-sensitive K(+) (K-ATP) channels that inhibit DA neuron firing. In the striatum, H(2)O(2) generated downstream from glutamatergic AMPA receptor activation in medium spiny neurons acts as a diffusible messenger that inhibits axonal DA release, also via K-ATP channels. The source of dynamically generated H(2)O(2) is mitochondrial respiration; thus, H(2)O(2) provides a novel link between activity and metabolism via K-ATP channels. Additional targets of H(2)O(2) include transient receptor potential (TRP) channels. In contrast to the inhibitory effect of H(2)O(2) acting via K-ATP channels, TRP channel activation is excitatory. This review describes emerging roles of H(2)O(2) as a signaling agent in the nigrostriatal pathway and basal ganglia neurons. PMID:21666063

  14. Ring-opening polymerization of epoxidized soybean oil catalyzed by the superacid, Fluroantimonic acid hexahydrate (HSbF6-6H2O)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ring-opening polymerization of epoxidized soybean oil (ESO) catalyzed by the super acid, fluroantimonic acid hexahydrate (HSbF6-6H2O), in ethyl acetate was conducted. The resulting polymers, SA-RPESO, were characterized using infrared spectroscopy, differential scanning calorimetry, thermogravimetri...

  15. Synthesis of Open-Framework Iron Phosphates, [C 6N 2H 14][Fe III2F 2(HPO 4) 2(H 2PO 4) 2]·2H 2O and [C 6N 2H 14] 2[Fe III3(OH)F 3(PO 4)(HPO 4) 2] 2·H 2O, with One- and Three-Dimensional Structures

    NASA Astrophysics Data System (ADS)

    Mahesh, S.; Green, Mark A.; Natarajan, Srinivasan

    2002-05-01

    The hydrothermal syntheses and structures of two new open-framework iron phosphates, I, [C6N2H14][FeIII2F2(HPO4)2 (H2PO4)2].2H2O, II, and [C6N2H14]2[FeIII3(OH)F3(PO4) (HPO4)2]2. H2O, are presented. The structures of both I and II consist of FeO4F2 octahedra and PO4 terahedra linked to form one- and three-dimensional structures. Both the compounds possess infinite one-dimensional chains of Fe-O/F-Fe formed by the FeO4F2 octahedra. The di-protonated DABCO cations are located in between the chains in I and within the channels in II. Whilst I possess the tancoite structure with a new chain composition, II has a three-dimensional structure similar to the gallophosphate, ULM-1. Crystal data for I: M=685.84, monoclinic, space group=C2/c (no. 15), a=7.232(2), b=20.520(7), c=13.933(4) Å, β=97.68(3)°, ν=2049.1(1) Å3, Z=4, ρcalc.=2.223 g cm-3, μ(MoKα)=1.841 mm-1, R1=0.06, wR2=0.12, S=1.17 for 163 parameters; II, M=1303.33, monoclinic, space group =C2/c (no. 15), a=18.1836(2), b=10.0126(7), c=20.0589(4) Å, β=106.08(3)°, ν=3509.0(2) Å3, Z=4, ρcalc=2.467 g cm-3, μ(MoKα)=2.830 mm-1, R1=0.034, wR2=0.081, S=1.06 for 284 parameters.

  16. Results of first field tests of the improved open-path and enclosed models of CO2 and H2O flux measurements systems

    NASA Astrophysics Data System (ADS)

    Begashaw, Israel; Fratini, Gerardo; Griessbaum, Frank; Kathilankal, James; Xu, Liukang; Franz, Daniela; Joseph, Everett; Larmanou, Eric; Miller, Scott; Papale, Dario; Sabbatini, Simone; Sachs, Torsten; Sakai, Ricardo; McDermitt, Dayle; Burba, George

    2016-04-01

    In 2014-2015, improved open-path and enclosed-path flux measurement systems were developed, based on established LI-7500A and LI-7200 gas analyzer models, with the focus on improving stability in the presence of contamination, refining temperature control and compensation, and providing more accurate gas concentration measurements. In addition to optical and electronic redesign, both systems incorporate automated on-site flux calculations using EddyPro® software run by a weatherized remotely-accessible microcomputer, SmartFlux 2, with fully digital inputs. The ultimate goal of such development was to reduce errors in CO2 and H2O hourly fluxes and in long-term carbon and water budgets. Field tests of both systems were conducted over six periods, each 5-14 months long, at 6 sites with diverse environments, setups, and types of contamination, using 26 gas analyzers. The open-path LI-7500RS system performed significantly better than the original LI-7500A model in terms of contamination-related drifts in mean concentrations. Improvements in CO2 drifts were strong, with RS models often drifting few-to-tens of times less than the original. Improvements in H2O contamination-related drifts were particularly significant, with modified models often drifting many tens of times less than the original. The enclosed-path LI-7200RS system performed substantially better than the original LI-7200 in terms of the drifts in H2O, sometimes drifting few-to-tens of times less than the original. Improvements in CO2 contamination-related drifts were modest, being similar or just a bit better than the original. Results from field tests suggest that both RS systems can help improve flux data coverage and potentially reduce site maintenance: (i) Frequency of cleaning and site visits for service and maintenance should decrease, especially for the open-path design (ii) Amount of highest quality data with smallest error bars on fluxes is expected to increase for both open-path and enclosed

  17. COMBINING THE STRENGTHS OF OPEN-PATH AND CLOSED-PATH DESIGNS INTO A SINGLE CO2/H2O GAS ANALYZER

    NASA Astrophysics Data System (ADS)

    Burba, G. G.; Furtaw, M.; McDermitt, D. K.; Eckles, R.

    2009-12-01

    Open-path and closed-path designs of the fast CO2/H2O gas analyzers are widely used to measure concentrations and fluxes. Both designs have their advantages and deficiencies. Open-path analyzers have excellent frequency response, long-term stability, and low sensitivity to window contamination. They are pump-free and require infrequent calibrations. Yet they are susceptible to data loss during precipitation and icing, and may need instrument surface heat flux correction when used in cold conditions. Closed-path analyzers can collect data during precipitation, can be climate-controlled, and are not susceptible to surface heating issues. Yet they experience significant frequency loss in long intake tubes, especially problematic when computing water vapor flux. They may require frequent calibrations and need powerful pump. Here we present preliminary data from third kind of a design: a compact enclosed CO2/H2O analyzer, the LI-7200, enabled for operation with short intake tube, intended to maximize strengths and to minimize weaknesses of both traditional open-path and closed-path designs. Four prototypes were extensively field-tested in three experiments over contrasting ecosystems in 2006-2009. Instantaneous temperature fluctuations were attenuated, on average, by about 85-90% with 0.5 m intake tube, and by about 90-95% with 1 m intake tube, minimizing sensible heat flux portion of Webb-Pearman-Leuning term. The remainder was measured directly eliminating open-path heating or any other temperature issues. Fast temperature and pressure measured inside the cell of LI-7200, and low sensitivity to window contamination allowed for the use of short intake tube (0.5-1.0 m or less), leading to a low power demand for the pump and entire system. The power demand of the tested blower with flow control was about 15 W, which is considerably less than that of traditional closed-path systems (about 50-100 W). Frequency losses for CO2 and H2O fluxes from LI-7200 were small, yet

  18. Measurements of CO2 and H2O Fluxes with New Enclosed Design and with Modified Open-path Design of Fast Gas Analyzers

    NASA Astrophysics Data System (ADS)

    Burba, George; McDermitt, Dayle K.; Velgersdyk, Michael; Eckles, Robert; Anderson, Dan

    2010-05-01

    In this presentation two novel approaches to designing fast CO2/H2O gas analyzers (e.g., new enclosed short tube enabled design and modified open-path low temperature controlled design) are discussed in comparison with two conventional approaches (e.g., traditional closed-path and open-path designs) in terms of their field performance for Eddy Covariance flux measurements. Closed- and open-path designs of the fast gas analyzers are two well-established sampling cell configurations widely utilized for measurements of CO2 and H2O fluxes and concentrations. Each configuration has advantages and deficiencies. Open-path analyzers have excellent frequency response, long-term stability, and low sensitivity to window contamination. They are pump-free and require infrequent calibrations. Yet they are susceptible to data loss during precipitation and icing, and may need instrument surface heat flux correction when used in extremely cold conditions. Closed-path analyzers can collect data during precipitation, can be climate-controlled, and are not susceptible to surface heating issues. Yet they experience significant frequency loss in long intake tubes, especially problematic when computing water vapor flux. They may require frequent calibrations and need powerful pump. The study presents field data from an alternative new design: a compact enclosed CO2/H2O analyzer, the LI-7200, enabled for operation with short intake tube, intended to maximize strengths and to minimize weaknesses of both traditional open-path and closed-path designs. Also presented are data from a new open-path CO2/H2O gas analyzer, LI-7500A, based on the LI-7500 model modified to produce substantially less heat during extremely cold conditions. Four prototypes of LI-7200, were extensively field-tested in three experiments over contrasting ecosystems in 2006-2009. Instantaneous temperature fluctuations were attenuated, on average, by about 85-90% with 0.5 m intake tube, and by about 90-95% with 1 m intake

  19. Plant Aquaporin AtPIP1;4 Links Apoplastic H2O2 Induction to Disease Immunity Pathways1[OPEN

    PubMed Central

    Tian, Shan; Wang, Xiaobing; Li, Ping; Wang, Hao; Ji, Hongtao; Xie, Junyi; Qiu, Qinglei

    2016-01-01

    Hydrogen peroxide (H2O2) is a stable component of reactive oxygen species, and its production in plants represents the successful recognition of pathogen infection and pathogen-associated molecular patterns (PAMPs). This production of H2O2 is typically apoplastic but is subsequently associated with intracellular immunity pathways that regulate disease resistance, such as systemic acquired resistance and PAMP-triggered immunity. Here, we elucidate that an Arabidopsis (Arabidopsis thaliana) aquaporin (i.e. the plasma membrane intrinsic protein AtPIP1;4) acts to close the cytological distance between H2O2 production and functional performance. Expression of the AtPIP1;4 gene in plant leaves is inducible by a bacterial pathogen, and the expression accompanies H2O2 accumulation in the cytoplasm. Under de novo expression conditions, AtPIP1;4 is able to mediate the translocation of externally applied H2O2 into the cytoplasm of yeast (Saccharomyces cerevisiae) cells. In plant cells treated with H2O2, AtPIP1;4 functions as an effective facilitator of H2O2 transport across plasma membranes and mediates the translocation of externally applied H2O2 from the apoplast to the cytoplasm. The H2O2-transport role of AtPIP1;4 is essentially required for the cytoplasmic import of apoplastic H2O2 induced by the bacterial pathogen and two typical PAMPs in the absence of induced production of intracellular H2O2. As a consequence, cytoplasmic H2O2 quantities increase substantially while systemic acquired resistance and PAMP-triggered immunity are activated to repress the bacterial pathogenicity. By contrast, loss-of-function mutation at the AtPIP1;4 gene locus not only nullifies the cytoplasmic import of pathogen- and PAMP-induced apoplastic H2O2 but also cancels the subsequent immune responses, suggesting a pivotal role of AtPIP1;4 in apocytoplastic signal transduction in immunity pathways. PMID:26945050

  20. Open-path TDL-Spectrometry for a Tomographic Reconstruction of 2D H2O-Concentration Fields in the Soil-Air-Boundary-Layer of Permafrost

    NASA Astrophysics Data System (ADS)

    Seidel, Anne; Wagner, Steven; Dreizler, Andreas; Ebert, Volker

    2013-04-01

    The melting of permafrost soils in arctic regions is one of the effects of climate change. It is recognized that climatically relevant gases are emitted during the thawing process, and that they may lead to a positive atmospheric feedback [1]. For a better understanding of these developments, a quantification of the gases emitted from the soil would be required. Extractive sensors with local point-wise gas sampling are currently used for this task, but are hampered due to the complex spatial structure of the soil surface, which complicates the situation due to the essential need for finding a representative gas sampling point. For this situation it would be much preferred if a sensor for detecting 2D-concentration fields of e.g. water vapor, (and in the mid-term also for methane or carbon dioxide) directly in the soil-atmosphere-boundary layer of permafrost soils would be available. However, it also has to be kept in mind that field measurements over long time periods in such a harsh environment require very sturdy instrumentation preferably without the need for sensor calibration. Therefore we are currently developing a new, robust TDLAS (tuneable diode laser absorption spectroscopy)-spectrometer based on cheap reflective foils [2]. The spectrometer is easily transportable, requires hardly any alignment and consists of industrially available, very stable components (e.g. diode lasers and glass fibers). Our measurement technique, open path TDLAS, allows for calibration-free measurements of absolute H2O concentrations. The static instrument for sampling open-path H2O concentrations consists of a joint sending and receiving optics at one side of the measurement path and a reflective element at the other side. The latter is very easy to align, since it is a foil usually applied for traffic purposes that retro-reflects the light to its origin even for large angles of misalignment (up to 60°). With this instrument, we achieved normalized detection limits of up to 0

  1. HAI: A novel airborne multi-channel hygrometer for fast multi-phase H2O quantification: Performance of the HAI instrument during the first flights on the German HALO aircraft

    NASA Astrophysics Data System (ADS)

    Buchholz, B.; Ebert, V.; Kraemer, M.; Afchine, A.

    2014-12-01

    Common gas phase H2O measurements on fast airborne platforms e.g. using backward facing or "Rosemount"-inlets can lead to a high risk of ice and droplets contamination. In addition, currently no single hygrometer exists that allows a simultaneous, high-speed measurement of all phases (gas, liquid, ice) with the same detection principle. In the rare occasions multi-phase measurements are realized, gas-and condensed-phase observations rely on different methods, instruments and calibration strategies so that precision and accuracy levels are quite difficult to quantify. This is effectively avoided by the novel TDLAS instrument, HAI, Hygrometer for Atmospheric Investigation, which allows a simultaneous, high speed, multi-phase detection without any sensor calibration in a unique "2+2" channel concept. Hai combines two independent wavelength channels, at 1.4 µm and at 2.6 µm, for a wide dynamic range from 1 to 30 000 ppmv, with a simultaneous closed path (extractive) and open path detection. Thus, "Total", i.e. gas-phase plus condensed-phase water is measured by sampling via a forward facing inlet into "closed-path" extractive cells. A selective, sampling-free, high speed gas phase detection is realized via a dual-wavelength "open-path" cell placed outside of the aircraft fuselage. All channels can be sampled with 120 Hz (measurement cycle time Dt=1.6 ms) allowing an unprecedented spatial resolution of 30 cm at 900 km/h. The evaluation of the individual multi-channel raw-data is done post flight, without any channel interdependencies, in calibration-free mode, thus allowing fast, accurate and precise multi-phase water detection in flight. The performance could be shown in more than 200 net flights hours in three scientific flight campaigns (TACTS, ESMVal, ML-CIRRUS) on the new German HALO aircraft. In addition the level of the accuracy of the calibration free evaluation was evaluated at the German national primary water vapor standard.

  2. Theoretical characterization of the reaction CH3 +OH yields CH3OH yeilds products: The (1)CH2 + H2O, H2 + HCOH, and H2 + H2CO channels

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.

    1993-01-01

    The potential energy surface (PES) for the CH3OH system has been characterized for the (1)CH2 + H2O, H2 + HCOH, and H2 + H2CO product channels using complete-active-space self-consistent-field (CASSCF) gradient calculations to determine the stationary point geometries and frequencies followed by CASSCF/internally contracted configuration-interaction (CCI) calculations to refine the energetics. The (1)CH2 + H2O channel is found to have no barrier. The long range interaction is dominated by the dipole-dipole term, which orients the respective dipole moments parallel to each other but pointing in opposite directions. At shorter separations there is a dative bond structure in which a water lone pair donates into the empty a" orbital of CH2. Subsequent insertion of CH2 into an OH bond of water have barriers located at -5.2 kcal/mol and 1.7 kcal/mol, respectively, with respect to CH3 + OH. From comparison of the computed energetics of the reactants and products to known thermochemical data it is estimated that the computed PES is accurate to plus or minus 2 kcal/mol.

  3. Channel formation in Pb-Sn, Pb-Sb, and Pb-Sn-Sb alloy ingots and comparison with the system NH4Cl-H2O

    NASA Technical Reports Server (NTRS)

    Hellawell, A.; Sarazin, J. R.

    1988-01-01

    The formation of segregation channels during the unidirectional solidification of base chilled ingots has been studied as a function of composition in binary Pb-Sn and Pb-Sb and ternary Pb-Sn-Sb alloys. The patterns of channel distribution were characterized in the binary and ternary systems and are described as functions of temperature gradients, growth rates, dendrite spacings, and interdendritic permeabilities. Channels appear to nucleate at random across a dendritic front and subsequently to interact as they propagate, decreasing in density across the front. Assuming that the interdendritic spacing is the characteristic distance for a liquid perturbation, yields critical effective Rayleigh numbers which lie within a factor of x 40 for both metallic and aqueous systems. This correlation is close, considering the sensitivity to any assumed dimension and the range of material properties involved, and is taken to support a model for channel nucleation occurring close to the dendritic growth front.

  4. Photolysis of H2O-H2O2 Mixtures: The Destruction of H2O2

    NASA Technical Reports Server (NTRS)

    Loeffler, M. J.; Fama, M.; Baragiola, R. A.; Carlson, R. W.

    2013-01-01

    We present laboratory results on the loss of H2O2 in solid H2O + H2O2 mixtures at temperatures between 21 and 145 K initiated by UV photolysis (193 nm). Using infrared spectroscopy and microbalance gravimetry, we measured the decrease of the 3.5 micrometer infrared absorption band during UV irradiation and obtained a photodestruction cross section that varies with temperature, being lowest at 70 K. We use our results, along with our previously measured H2O2 production rates via ionizing radiation and ion energy fluxes from the spacecraft to compare H2O2 creation and destruction at icy satellites by ions from their planetary magnetosphere and from solar UV photons. We conclude that, in many cases, H2O2 is not observed on icy satellite surfaces because the H2O2 photodestruction rate is much higher than the production rate via energetic particles, effectively keeping the H2O2 infrared signature at or below the noise level.

  5. Transit of H2O2 across the endoplasmic reticulum membrane is not sluggish.

    PubMed

    Appenzeller-Herzog, Christian; Bánhegyi, Gabor; Bogeski, Ivan; Davies, Kelvin J A; Delaunay-Moisan, Agnès; Forman, Henry Jay; Görlach, Agnes; Kietzmann, Thomas; Laurindo, Francisco; Margittai, Eva; Meyer, Andreas J; Riemer, Jan; Rützler, Michael; Simmen, Thomas; Sitia, Roberto; Toledano, Michel B; Touw, Ivo P

    2016-05-01

    Cellular metabolism provides various sources of hydrogen peroxide (H2O2) in different organelles and compartments. The suitability of H2O2 as an intracellular signaling molecule therefore also depends on its ability to pass cellular membranes. The propensity of the membranous boundary of the endoplasmic reticulum (ER) to let pass H2O2 has been discussed controversially. In this essay, we challenge the recent proposal that the ER membrane constitutes a simple barrier for H2O2 diffusion and support earlier data showing that (i) ample H2O2 permeability of the ER membrane is a prerequisite for signal transduction, (ii) aquaporin channels are crucially involved in the facilitation of H2O2 permeation, and (iii) a proper experimental framework not prone to artifacts is necessary to further unravel the role of H2O2 permeation in signal transduction and organelle biology. PMID:26928585

  6. On the Stark effect in open shell complexes exhibiting partially quenched electronic angular momentum: Infrared laser Stark spectroscopy of OH-C2H2, OH-C2H4, and OH-H2O

    NASA Astrophysics Data System (ADS)

    Moradi, Christopher P.; Douberly, Gary E.

    2015-08-01

    The Stark effect is considered for polyatomic open shell complexes that exhibit partially quenched electronic angular momentum. Matrix elements of the Stark Hamiltonian represented in a parity conserving Hund's case (a) basis are derived for the most general case, in which the permanent dipole moment has projections on all three inertial axes of the system. Transition intensities are derived, again for the most general case, in which the laser polarization has projections onto axes parallel and perpendicular to the Stark electric field, and the transition dipole moment vector is projected onto all three inertial axes in the molecular frame. Simulations derived from this model are compared to experimental rovibrational Stark spectra of OH-C2H2, OH-C2H4, and OH-H2O complexes formed in helium nanodroplets.

  7. Speciation and diffusion profiles of H2O in water-poor beryl: comparison with cordierite

    NASA Astrophysics Data System (ADS)

    Della Ventura, G.; Radica, F.; Bellatreccia, F.; Freda, C.; Cestelli Guidi, M.

    2015-10-01

    This paper reports on water speciation and diffusion in synthetic beryl samples treated in CO2-rich atmosphere, at 700 MPa and 700 and 800 °C, respectively. The study has been conducted by means of polarized FTIR (Fourier transform infrared) integrated with FPA (focal plane array) imaging. As expected, the infrared spectra show the presence of CO2 but also of minor H2O interpreted as resulting from moisture present in the starting materials used for the experiments. FPA-FTIR images show that H2O diffuses into the beryl matrix along the structural channels oriented parallel to [001]. Spectra collected along profiles parallel to the c-axis show subtle changes as a function of the distance from the crystal edge; these changes can be correlated to a progressive change in the H2O coordination environment in the channel, as a response to the varying H2O/alkali ratio. In particular, the data show that when 2H2O > Na+ apfu (atoms per formula unit), H2O can assume both type I and type II orientation; in the latter case, each Na cation coordinates two H2O[II] molecules (doubly coordinated H2O). If 2H2O < Na+ apfu, then H2O[II] molecules are singly coordinated to each Na cation. The same type of feature is observed and commented for the structurally related cordierite. Diffusion coefficients and activation energies have been also determined for both types of water molecules.

  8. Nonadiabatic dissociation dynamics in H2O: Competition between rotationally and nonrotationally mediated pathways

    PubMed Central

    Yuan, Kaijun; Cheng, Yuan; Cheng, Lina; Guo, Qing; Dai, Dongxu; Wang, Xiuyan; Yang, Xueming; Dixon, Richard N.

    2008-01-01

    The photochemistry of H2O in the VUV region is important in interstellar chemistry. Whereas previous studies of the photodissociation used excitation via unbound states, we have used a tunable VUV photolysis source to excite individual levels of the rotationally structured C̃ state near 124 nm. The ensuing OH product state distributions were recorded by using the H-atom Rydberg tagging technique. Experimental results indicate a dramatic variation in the OH product state distributions and its stereodynamics for different resonant states. Photodissociation of H2O(C̃) in rotational states with k′a = 0 occurs exclusively through a newly discovered homogeneous coupling to the à state, leading to OH products that are vibrationally hot (up to v = 13), but rotationally cold. In contrast, for H2O in rotationally excited states with k′a > 0, an additional pathway opens through Coriolis-type coupling to the B̃ state surface. This yields extremely rotationally hot and vibrationally cold ground state OH(X) and electronically excited OH(A) products, through 2 different mechanisms. In the case of excitation via the 110 ← 000 transition the H atoms for these 2 product channels are ejected in completely different directions. Quantum dynamical models for the C̃-state photodissociation clearly support this remarkable dynamical picture, providing a uniquely detailed illustration of nonadiabatic dynamics involving at least 4 electronic surfaces. PMID:19047628

  9. The Successive H2O Binding Energies for Fe(H2O)n(+)

    NASA Technical Reports Server (NTRS)

    Ricca, Alessandra; Bauschlicher, Charles W., Jr.; Langhoff, Stephen R. (Technical Monitor)

    1994-01-01

    The binding energy, computed using density functional theory (DFT), are in good agreement with experiment. The bonding is electrostatic (charge-dipole) in origin for all systems. The structures are therefore determined mostly by metal-ligand and ligand-ligand repulsion. The computed structure for FeH2O(+) is C(2v) where sp hybridization is important in reducing the Fe-H2O repulsion. Fe(H2O)2(+) has D2d symmetry where sdo hybridization is the primary factor leading to the linear O-Fe-O geometry. The bonding in Fe(H2O)3(+) and Fe(H2O)4(+) are very complex because ligand-ligand and metal-ligand repulsion, both for the in-plane and out-of-plane water lone-pair orbitals, are important.

  10. EPA H2O User Manual

    EPA Science Inventory

    EPA H2O is a software tool designed to support research being conducted in the Tampa Bay watershed to provide information, data, and approaches and guidance that communities can use to examine alternatives when making strategic decisions to support a prosperous and environmentall...

  11. EPA H2O Software Tool

    EPA Science Inventory

    EPA H2O allows user to: Understand the significance of EGS in Tampa Bay watershed; visually analyze spatial distribution of the EGS in Tampa Bay watershed; obtain map and summary statistics of EGS values in Tampa Bay watershed; analyze and compare potential impacts of development...

  12. Crystal structure of K0.75[FeII 3.75FeIII 1.25(HPO3)6]·0.5H2O, an open-framework iron phosphite with mixed-valent FeII/FeIII ions

    PubMed Central

    Larrea, Edurne S.; Mesa, José Luis; Legarra, Estibaliz; Aguayo, Andrés Tomás; Arriortua, Maria Isabel

    2016-01-01

    Single crystals of the title compound, potassium hexa­phosphito­penta­ferrate(II,III) hemihydrate, K0.75[FeII 3.75FeIII 1.25(HPO3)6]·0.5H2O, were grown under mild hydro­thermal conditions. The crystal structure is isotypic with Li1.43[FeII 4.43FeIII 0.57(HPO3)6]·1.5H2O and (NH4)2[FeII 5(HPO3)6] and exhibits a [FeII 3.75FeIII 1.25(HPO3)6]0.75− open framework with disordered K+ (occupancy 3/4) as counter-cations. The anionic framework is based on (001) sheets of two [FeO6] octa­hedra (one with point group symmetry 3.. and one with point group symmetry .2.) linked along [001] through [HPO3]2− oxoanions. Each sheet is constructed from 12-membered rings of edge-sharing [FeO6] octa­hedra, giving rise to channels with a radius of ca 3.1 Å where the K+ cations and likewise disordered water mol­ecules (occupancy 1/4) are located. O⋯O contacts between the water mol­ecule and framework O atoms of 2.864 (5) Å indicate hydrogen-bonding inter­actions of medium strength. The infrared spectrum of the compound shows vibrational bands typical for phosphite and water groups. The Mössbauer spectrum is in accordance with the presence of FeII and FeIII ions. PMID:26870587

  13. Large cavities with nanosized channels in a three-dimensional neutral framework: structure and properties of a novel oxovanadium arsenate: As 2V IVV VO 26(OH)]·8H 2O

    NASA Astrophysics Data System (ADS)

    Zhao, Yongnan; Li, Yafeng; Liu, Qingsheng; Chen, Xiangming; Wang, Yong; Li, Xiuhong; Li, Ming; Mai, Zhenhong

    2002-12-01

    A novel open-framework oxovanadium arsenate has been hydrothermally synthesized. It crystallizes in space group I 4¯3 m with cell parameters of a=16.708(2) Å, V=4664.4(9) Å 3 and Z=4. Its structure is composed of a new type of decavandium cluster, which is constructed by two pentamers. Linking this decavanadate by AsO 4 tetrahedral, a three-dimensional open-framework structure forms, which possesses large cavities. These high symmetric cavities interconnected through 12-membered ring windows forming a three-dimensional channel system. Catalytic measurements indicate that this compound is active for phenol hydroxylation using hydrogen peroxide as the oxidant. Catechol, hydroquinone and benzoquinone are the main products with 15.8% conversion of phenol (taking no account of the secondary product of tar) and 59.6% selectivity for hydroquinone, when the reaction was performed in water at 60°C for 6 h.

  14. The H2O2-H2O Hypothesis: Extremophiles Adapted to Conditions on Mars?

    NASA Astrophysics Data System (ADS)

    Houtkooper, Joop M.; Schulze-Makuch, Dirk

    2007-08-01

    The discovery of extremophiles on Earth is a sequence of discoveries of life in environments where it had been deemed impossible a few decades ago. The next frontier may be the Martian surface environment: could life have adapted to this harsh environment? What we learned from terrestrial extremophiles is that life adapts to every available niche where energy, liquid water and organic materials are available so that in principle metabolism and propagation are possible. A feasible adaptation mechanism to the Martian surface environment would be the incorporation of a high concentration of hydrogen peroxide in the intracellular fluid of organisms. The H2O2-H2O hypothesis suggests the existence of Martian organisms that have a mixture of H2O2 and H2O instead of salty water as their intracellular liquid (Houtkooper and Schulze-Makuch, 2007). The advantages are that the freezing point is low (the eutectic freezes at 56.5°C) and that the mixture is hygroscopic. This would enable the organisms to scavenge water from the atmosphere or from the adsorbed layers of water molecules on mineral grains, with H2O2 being also a source of oxygen. Moreover, below its freezing point the H2O2-H2O mixture has the tendency to supercool. Hydrogen peroxide is not unknown to biochemistry on Earth. There are organisms for which H2O2 plays a significant role: the bombardier beetle, Brachinus crepitans, produces a 25% H2O2 solution and, when attacked by a predator, mixes it with a fluid containing hydroquinone and a catalyst, which produces an audible steam explosion and noxious fumes. Another example is Acetobacter peroxidans, which uses H2O2 in its metabolism. H2O2 plays various other roles, such as the mediation of physiological responses such as cell proliferation, differentiation, and migration. Moreover, most eukaryotic cells contain an organelle, the peroxisome, which mediates the reactions involving H2O2. Therefore it is feasible that in the course of evolution, water-based organisms

  15. Theoretical studies of photoexcitation and ionization in H2O

    NASA Technical Reports Server (NTRS)

    Diercksen, G. H. F.; Kraemer, W. P.; Rescigno, T. N.; Bender, C. F.; Mckoy, B. V.; Langhoff, S. R.; Langhoff, P. W.

    1982-01-01

    Theoretical studies using Franck-Condon and static-exchange approximations are reported for the complete dipole excitation and ionization spectrum in H2O, where (1) large Cartesian Gaussian basis sets are used to represent the required discrete and continuum electronic eigenfunctions at the ground state equilibrium geometry, and (2) previously devised moment-theory techniques are employed in constructing the continuum oscillator-strength densities from the calculated spectra. Comparisons are made of the calculated excitation and ionization profiles with recent experimental photoabsorption studies and corresponding spectral assignments, electron impact-excitation cross sections, and dipole and synchrotron-radiation studies of partial-channel photoionization cross sections. The calculated partial-channel cross sections are found to be atomic-like, and dominated by 2p-kd components. It is suggested that the latter transition couples with the underlying 1b(1)-kb(1) channel, accounting for a prominent feature in recent synchrotron-radiation measurements.

  16. Influences of H2O mass fraction and chemical kinetics mechanism on the turbulent diffusion combustion of H2-O2 in supersonic flows

    NASA Astrophysics Data System (ADS)

    Huang, Wei; Wang, Zhen-guo; Li, Shi-bin; Liu, Wei-dong

    2012-07-01

    Hydrogen is one of the most promising fuels for the airbreathing hypersonic propulsion system, and it attracts an increasing attention of the researchers worldwide. In this study, a typical hydrogen-fueled supersonic combustor was investigated numerically, and the predicted results were compared with the available experimental data in the open literature. Two different chemical reaction mechanisms were employed to evaluate their effects on the combustion of H2-O2, namely the two-step and the seven-step mechanisms, and the vitiation effect was analyzed by varying the H2O mass fraction. The obtained results show that the predicted mole fraction profiles for different components show very good agreement with the available experimental data under the supersonic mixing and combustion conditions, and the chemical reaction mechanism has only a slight impact on the overall performance of the turbulent diffusion combustion. The simple mechanism of H2-O2 can be employed to evaluate the performance of the combustor in order to reduce the computational cost. The H2O flow vitiation makes a great difference to the combustion of H2-O2, and there is an optimal H2O mass fraction existing to enhance the intensity of the turbulent combustion. In the range considered in this paper, its optimal value is 0.15. The initiated location of the reaction appears far away from the bottom wall with the increase of the H2O mass fraction, and the H2O flow vitiation quickens the transition from subsonic to supersonic mode at the exit of the combustor.

  17. Phase transitions in natural zeolites and the importance of P H2O

    NASA Astrophysics Data System (ADS)

    Bish, David L.; Wang, Hsiu-Wen

    2010-06-01

    Zeolites are low-density silicates with structures consisting of a negatively charged aluminosilicate framework that creates a system of uniform linked channels and cavities. Variable amounts of extraframework cations and H2O molecules occupy the channel system, and the H2O molecules are very responsive to changes in temperature, pressure and partial pressure of water (i.e. P H2O or relative humidity, RH). As the H2O molecules occupy much of the volume of the extraframework sites, a gain or loss of H2O molecules has a direct effect on the extraframework cations and an indirect effect on the framework. Temperature or RH-induced changes can result in both first- and second-order phase transitions, the latter resulting from continuous, minor changes in hydration state and cation position, and the former resulting from discrete changes in hydration state, which can cause similar shifts in cation position. Second-order transitions are typically reversible with no hysteresis, but first-order transitions exhibit considerable hysteresis. As H2O molecules are crucial in determining zeolite behavior, it is important that any study of thermal behavior involve control of not only temperature but also of relative humidity. Stabilization of a zeolite's hydrated phase to higher temperatures under higher RH conditions can cause some phase transitions to be missed, as is the case with natrolite.

  18. H2O2 space shuttle APU

    NASA Technical Reports Server (NTRS)

    1975-01-01

    A cryogenic H2-O2 auxiliary power unit (APU) was developed and successfully demonstrated. It has potential application as a minimum weight alternate to the space shuttle baseline APU because of its (1) low specific propellant consumption and (2) heat sink capabilities that reduce the amount of expendable evaporants. A reference system was designed with the necessary heat exchangers, combustor, turbine-gearbox, valves, and electronic controls to provide 400 shp to two aircraft hydraulic pumps. Development testing was carried out first on the combustor and control valves. This was followed by development of the control subsystem including the controller, the hydrogen and oxygen control valves, the combustor, and a turbine simulator. The complete APU system was hot tested for 10 hr with ambient and cryogenic propellants. Demonstrated at 95 percent of design power was 2.25 lb/hp-hr. At 10 percent design power, specific propellant consumption was 4 lb/hp-hr with space simulated exhaust and 5.2 lb/hp-hr with ambient exhaust. A 10 percent specific propellant consumption improvement is possible with some seal modifications. It was demonstrated that APU power levels could be changed by several hundred horsepower in less than 100 msec without exceeding allowable turbine inlet temperatures or turbine speed.

  19. Simultaneous in situ measurements and diurnal variations of NO, NO2, O3, jNO2, CH4, H2O, and CO2 in the 40- to 26-km region using an open path tunable diode laser spectrometer

    NASA Technical Reports Server (NTRS)

    Webster, Christopher R.; May, Randy D.

    1987-01-01

    Simultaneous in situ measurements of temperature, pressure, and the NO, NO2, O3, jNO2, CH4, H2O, and CO2 concentrations were conducted in the 40- to 26-km region of the stratosphere using the JPL Balloon-borne Laser In Situ Sensor, a tunable diode laser absorption spectrometer. The NO, NO2, CH4, H2O, and CO2 concentration measurements generally show good agreement with previous observations, with a tendency for somewhat lower NO2 amounts. Measured O3 concentrations at 38 km agree well with comparable measurements from in situ UV photometers, but at 28 km they are lower by about 10 percent and agree more closely with the solar backscattered UV data. A decline was found in NO2 during the night over a 5-km altitude range, which implies either lower NO2 postsunset profiles, or an NO2 decay rate that is significantly higher than current model predictions that use N2O5 chemistry.

  20. Arabidopsis CALCIUM-DEPENDENT PROTEIN KINASE8 and CATALASE3 Function in Abscisic Acid-Mediated Signaling and H2O2 Homeostasis in Stomatal Guard Cells under Drought Stress[OPEN

    PubMed Central

    Wang, Cun; Zhang, Wen-Zheng

    2015-01-01

    Drought is a major threat to plant growth and crop productivity. Calcium-dependent protein kinases (CDPKs, CPKs) are believed to play important roles in plant responses to drought stress. Here, we report that Arabidopsis thaliana CPK8 functions in abscisic acid (ABA)- and Ca2+-mediated plant responses to drought stress. The cpk8 mutant was more sensitive to drought stress than wild-type plants, while the transgenic plants overexpressing CPK8 showed enhanced tolerance to drought stress compared with wild-type plants. ABA-, H2O2-, and Ca2+-induced stomatal closing were impaired in cpk8 mutants. Arabidopsis CATALASE3 (CAT3) was identified as a CPK8-interacting protein, confirmed by yeast two-hybrid, coimmunoprecipitation, and bimolecular fluorescence complementation assays. CPK8 can phosphorylate CAT3 at Ser-261 and regulate its activity. Both cpk8 and cat3 plants showed lower catalase activity and higher accumulation of H2O2 compared with wild-type plants. The cat3 mutant displayed a similar drought stress-sensitive phenotype as cpk8 mutant. Moreover, ABA and Ca2+ inhibition of inward K+ currents were diminished in guard cells of cpk8 and cat3 mutants. Together, these results demonstrated that CPK8 functions in ABA-mediated stomatal regulation in responses to drought stress through regulation of CAT3 activity. PMID:25966761

  1. Polynuclear complexes with bridging pyrophosphate ligands: synthesis and characterisation of {[(bipy)Cu(H2O)(mu-P2O7)Na2(H2O)6] x 4H2O}, {[(bipy)Zn-(H2O)(mu-P2O7)Zn(bipy)]2 x 14H2O} and {[(bipy)(VO)2]2(mu-P2O7)] x 5H2O}.

    PubMed

    Doyle, Robert P; Nieuwenhuyzen, Mark; Kruger, Paul E

    2005-12-01

    The reaction in water of M(II) ions (M = Cu, 1; Zn, 2; VO, 3) with 2,2'-bipyridine (bipy) followed by Na4P2O7 leads to the formation of three new complexes which feature the pyrophosphate anion, P2O7(4-), as a bridging ligand. Single crystal X-ray diffraction revealed 1 to be {[(bipy)Cu(H2O)(micro-P2O7)Na2(H2O)6] x 4H2O}, and 2 as a tetranuclear Zn(II) complex, {[(bipy)Zn(H2O)(micro-P2O7)Zn(bipy)]2 x 14H2O}. The structure of 1 consists of a mononuclear [(bipy)Cu(H2O)(P2O7)]2- unit that links via a pyrophosphate bridge to two Na atoms. The hydrated six-coordinate Na atoms themselves join together through bridging water molecules to generate a 2D Na-water sheet. The structure of 2 consists of a tetranuclear Zn(II) cluster (dimer-of-dimers) with two pyrophosphate ligands bridging between four metal centres. Adjacent clusters interact through face-to-face pi-pi interactions via the bipy ligands to yield a 2D sheet. Adjacent sheets pack in register to create channels, which are filled by the water molecules of crystallisation. An intricate 2D H-bonded water network separates adjacent sheets and encapsulates the tetranuclear clusters. Aspects of the pyrophosphate coordination modes in 1 and 2 are of structural relevance to those found within the inorganic pyrophosphatases. Compound 3, {[(bipy)(VO)2]2(micro-P2O7)] x 5H2O}, was isolated as an insoluble lime-green powder. Its dinuclear structure was elucidated from elemental and thermal analysis, magnetic susceptibility measurement and IR spectroscopy. The latter displayed characteristic bridging pyrophosphate and signature V=O stretches, which were corroborated by contrast to the IR spectra of 1 and 2 and through comparison with those found in the structurally characterised dinuclear complex, {[(bipy)Cu(H2O)]2(micro-P2O7) x 7H2O}, 4. PMID:16471055

  2. Electron swarm coefficients for H2O and H2O-N2

    NASA Astrophysics Data System (ADS)

    Juarez, A. M.; Basurto, E.; Hernandez-Avila, J. L.; de Urquijo, J.

    2008-10-01

    We have used a pulsed Townsend technique to measure the electron drift velocity ve, the density normalized longitudinal diffusion coefficient NDL, and effective ionization coefficient (α-η)/N, in water vapour and water vapour-nitrogen mixtures over the density-reduced electric field range E/N, 16-650 x 10-17V cm^2. The ve values are in good agreement with previous ones, while those for NDL agree well with a previous calculation. The limiting value for E/N was found to be E/Nlim=137 x 10-17 V cm^2. For E/N<70x10-17 V cm^2, the ve curves lie below that for pure N2; however, the 10% H2O-N2 curve for ve shows the trend for negative differential conductivity. The (α-η)/N curve for H2O shows a shallow, negative minimum, in disagreement with a recent measurement using the steady-state Townsend technique. The H2O-N2 curves for (α-η)/N show a progressively smaller minima, together with a trend to lower values of (α-η)/N as the N2 content in the mixture increases. This research aims to provide a complete set of self-consistent electron swarm parameters for the simulation of flue-gas discharges.

  3. Experiments on H2-O2 MHD power generation

    NASA Astrophysics Data System (ADS)

    Smith, J. M.

    1980-06-01

    MHD power generation experiments utilizing a cesium-seeded H2-O2 working fluid have been carried out using a diverging area Hall duct having an entrance Mach number of 2. The experiments are conducted in a high-field strength cryomagnet facility at field strengths up to 5 tesla. The effects of power takeoff location, axial duct location within the magnetic field, generator loading, B-field strength, and electrode breakdown voltage were investigated. For the operating conditions of these experiments it is found that the power output increases with the square of the B-field and can be limited by choking of the channel or interelectrode voltage breakdown which occurs at Hall fields greater than 50 volts/insulator.

  4. Experiments on H2-O2MHD power generation

    NASA Technical Reports Server (NTRS)

    Smith, J. M.

    1980-01-01

    Magnetohydrodynamic power generation experiments utilizing a cesium-seeded H2-O2 working fluid were carried out using a diverging area Hall duct having an entrance Mach number of 2. The experiments were conducted in a high-field strength cryomagnet facility at field strengths up to 5 tesla. The effects of power takeoff location, axial duct location within the magnetic field, generator loading, B-field strength, and electrode breakdown voltage were investigated. For the operating conditions of these experiments, it is found that the power output increases with the square of the B-field and can be limited by choking of the channel or interelectrode voltage breakdown which occurs at Hall fields greater than 50 volts/insulator. Peak power densities of greater than 100 MW/cu M were achieved.

  5. Drosophila TRPA1 isoforms detect UV light via photochemical production of H2O2

    PubMed Central

    Guntur, Ananya R.; Gu, Pengyu; Takle, Kendra; Chen, Jingyi; Xiang, Yang; Yang, Chung-Hui

    2015-01-01

    The transient receptor potential A1 (TRPA1) channel is an evolutionarily conserved detector of temperature and irritant chemicals. Here, we show that two specific isoforms of TRPA1 in Drosophila are H2O2 sensitive and that they can detect strong UV light via sensing light-induced production of H2O2. We found that ectopic expression of these H2O2-sensitive Drosophila TRPA1 (dTRPA1) isoforms conferred UV sensitivity to light-insensitive HEK293 cells and Drosophila neurons, whereas expressing the H2O2-insensitive isoform did not. Curiously, when expressed in one specific group of motor neurons in adult flies, the H2O2-sensitive dTRPA1 isoforms were as competent as the blue light-gated channelrhodopsin-2 in triggering motor output in response to light. We found that the corpus cardiacum (CC) cells, a group of neuroendocrine cells that produce the adipokinetic hormone (AKH) in the larval ring gland endogenously express these H2O2-sensitive dTRPA1 isoforms and that they are UV sensitive. Sensitivity of CC cells required dTRPA1 and H2O2 production but not conventional phototransduction molecules. Our results suggest that specific isoforms of dTRPA1 can sense UV light via photochemical production of H2O2. We speculate that UV sensitivity conferred by these isoforms in CC cells may allow young larvae to activate stress response—a function of CC cells—when they encounter strong UV, an aversive stimulus for young larvae. PMID:26443856

  6. [Relationships between H2O2 metabolism and Ca2+ transport in dormancy-breaking process of nectarine floral buds].

    PubMed

    Tan, Yue; Gao, Dong-sheng; Li, Ling; Wei, Hai-rong; Wang, Jia-wei; Liu, Qing-zhong

    2015-02-01

    In order to explore regulatory function of H2O2 in bud dormancy release, main effects of three dormancy-breaking treatments (high temperature, hydrogen cyanamide and TDZ) on H2O2 metabolism were determined, and impacts of H2O2 on Ca2+ transport were tested using non-invasive micro-test technique. The results showed that both high temperature and hydrogen cyanamide induced H2O2 accumulation and CAT inhibition were efficient in breaking dormancy during deep dormancy period. However, TDZ showed little impacts on H2O2 metabolism and was much less effective in breaking dormancy. Dormant floral primordium was absorbing state to exogenous Ca2+ due to active calcium channels. The Ca2+ transport could be changed by exogenous H2O2. H2O2 of low concentration reduced the absorption rate of Ca2+, and at high concentration, it changed the Ca2+ transport direction from absorption to release. The results indicated that H2O2 signals were related with Ca2+ signals in dormant buds. Ca2+ signal regulated by H2O2 accumulation might be important in the dormancy-breaking signal transduction process induced by high temperature and hydrogen cyanamide. PMID:26094456

  7. Microscopic shifts of size-assigned p-cresol/H2O-cluster spectra

    NASA Astrophysics Data System (ADS)

    Pohl, M.; Schmitt, M.; Kleinermanns, K.

    1991-02-01

    p-cresol and its complexes with H2O and CH3OH were cooled in a pulsed supersonic free jet and studied by resonant multiphoton ionization with time-of-flight mass analysis. Detailed mass and concentration analysis allowed an unambiguous assignment of cluster size. The electronic origins of p-cresol (H2O)1,2,3 show irregular red- and blueshifts with change of cluster size, which is referred to the bivalent role of p-cresol as proton donor and acceptor. Ab initio and semiempirical quantum chemical calculations support this interpretation and show the spectral shifts to be essentially due to the inductive effect of the solvent molecules Y exerted on X in X-H...Y. While the vibronic bands of p-cresol (H2O)2 are quite broad, those of p-cresol (H2O)3 are sharp again. The ab initio calculations show that this may be attributed to the quite rigid ``open cyclic'' structure of p-cresol (H2O)3. Our experimental and theoretical investigations show a completely analogous behavior of phenol (H2O)1,2,3 clusters

  8. Synthesis, X-ray crystal structure, and EPR study of [Na(H 2O) 2] 2[VO(H 2O) 5][SiW 12O 40]·4H 2O

    NASA Astrophysics Data System (ADS)

    Tézé, André; Marchal-Roch, Catherine; So, Hyunsoo; Fournier, Michel; Hervé, Gilbert

    2001-03-01

    The vanadyl salt [Na(H 2O) 2] 2[VO(H 2O) 5][SiW 12O 40]·4H 2O has been synthesized in mild conditions by cationic exchanges from dodecasilicotungstic acid. Structural determination and EPR study have been achieved on single crystals. They are tetragonal, space group P4/ n with a=14.7759(1), c=10.4709(2) Å, V=2286(1) Å 3 and Z=2. A three-dimensional framework built from Keggin anions [SiW 12O 40] 4- linked by sodium cations in (110) and ( 1 1¯0 ) planes generates channels along the c axis in which are localized aquo vanadyl complexes [VO(H 2O) 5] 2+ and water molecules. Single crystal EPR spectra show eight hyperfine lines of the vanadium atom ( I=7/2) which are split into 1:2:1 pattern when the magnetic field is parallel to the c axis. The triplet pattern may be attributed to weak dipolar interactions between the nearest-neighbor vanadium atoms which are 10.47 Å apart in the infinite chain. A ring model was used to simulate the spectrum, and a very small antiferromagnetic exchange interaction was determined accurately . The EPR parameters determined are gx= gy=1.980, gz=1.9336, Ax= Ay=0.0072 cm -1, and Az=0.01805 cm -1, J=-0.00025 cm -1.

  9. Production of vibrationally excited H(2)O from charge exchange of H(3)O(+) with cesium.

    PubMed

    Mann, Jennifer E; Xie, Zhen; Savee, John D; Bowman, Joel M; Continetti, Robert E

    2009-01-28

    The center-of-mass kinetic energy release for the dissociation of H(3)O following charge exchange of H(3)O(+) with cesium has been studied experimentally and modeled using quasiclassical trajectory calculations based on an ab initio potential energy surface for H(3)O(+) and "direct dynamics" for H(3)O. Branching fractions for the H(2)O+H and OH+H(2) dissociation channels have been measured and compared to the calculations. The dominant channel is found to be H(2)O+H and the experimental kinetic energy release spectrum reveals that H(2)O is formed with a vibrational inversion in stretching vibrations, coupled with low bending and rotational excitation. PMID:19191369

  10. Tuning the conductance of H2O@C60 by position of the encapsulated H2O.

    PubMed

    Zhu, Chengbo; Wang, Xiaolin

    2015-01-01

    The change of conductance of single-molecule junction in response to various external stimuli is the fundamental mechanism for the single-molecule electronic devices with multiple functionalities. We propose the concept that the conductance of molecular systems can be tuned from inside. The conductance is varied in C60 with encapsulated H2O, H2O@C60. The transport properties of the H2O@C60-based nanostructure sandwiched between electrodes are studied using first-principles calculations combined with the non-equilibrium Green's function formalism. Our results show that the conductance of the H2O@C60 is sensitive to the position of the H2O and its dipole direction inside the cage with changes in conductance up to 20%. Our study paves a way for the H2O@C60 molecule to be a new platform for novel molecule-based electronics and sensors. PMID:26643873

  11. Tuning the conductance of H2O@C60 by position of the encapsulated H2O

    PubMed Central

    Zhu, Chengbo; Wang, Xiaolin

    2015-01-01

    The change of conductance of single-molecule junction in response to various external stimuli is the fundamental mechanism for the single-molecule electronic devices with multiple functionalities. We propose the concept that the conductance of molecular systems can be tuned from inside. The conductance is varied in C60 with encapsulated H2O, H2O@C60. The transport properties of the H2O@C60-based nanostructure sandwiched between electrodes are studied using first-principles calculations combined with the non-equilibrium Green’s function formalism. Our results show that the conductance of the H2O@C60 is sensitive to the position of the H2O and its dipole direction inside the cage with changes in conductance up to 20%. Our study paves a way for the H2O@C60 molecule to be a new platform for novel molecule-based electronics and sensors. PMID:26643873

  12. Tuning the conductance of H2O@C60 by position of the encapsulated H2O

    NASA Astrophysics Data System (ADS)

    Zhu, Chengbo; Wang, Xiaolin

    2015-12-01

    The change of conductance of single-molecule junction in response to various external stimuli is the fundamental mechanism for the single-molecule electronic devices with multiple functionalities. We propose the concept that the conductance of molecular systems can be tuned from inside. The conductance is varied in C60 with encapsulated H2O, H2O@C60. The transport properties of the H2O@C60-based nanostructure sandwiched between electrodes are studied using first-principles calculations combined with the non-equilibrium Green’s function formalism. Our results show that the conductance of the H2O@C60 is sensitive to the position of the H2O and its dipole direction inside the cage with changes in conductance up to 20%. Our study paves a way for the H2O@C60 molecule to be a new platform for novel molecule-based electronics and sensors.

  13. Effect of H2O, and combined effects of H2O + F, H2O + CO2, and H2O + F + CO2 on the viscosity of a natural basalt from Fuego volcano, Guatemala

    NASA Astrophysics Data System (ADS)

    Robert, G.; Whittington, A. G.; Knipping, J.; Scherbarth, S.; Stechern, A.; Behrens, H.

    2012-12-01

    We measured the viscosity of 5 series of remelted natural basalt from Fuego volcano, Guatemala. These series include single and multiple volatile species: H2O, F, H2O-F, H2O-CO2, and H2O-CO2-F. The hydrous glasses were synthesized at 3 kbar and 1250°C in Internally Heated Pressure Vessels. The multiple volatile series were synthesized at 5 kbar and 1250°C. CO2 was added as Ag2C2O4, F as AlF3, and H2O as distilled water. The anhydrous, F-bearing series was synthesized at 1 atm by simply remelting the Fuego basalt and adding F as CaF2.The natural, dry, remelted Fuego basalt has an NBO/T of 0.64. The following comparisons are based on parallel-plate viscosity measurements in the range ~108 to 1012 Pa s. The temperature at which the viscosity is 1012 Pa s (T12) is taken to be the viscosimetric glass transition temperature (Tg). The addition of 2 wt.% H2O results in a decrease of T12 of ~150°C for basalt. Fluorine on its own has a measurable, but much smaller effect, than the equivalent amount of water. Indeed, ~2 wt.% F results in a T12 depression of only ~30°C. When H2O and F are both present, their effects are approximately additive. For example, the viscosity of a basalt with 1.44 wt.% H2O is very similar to the viscosity of a basalt with ~1 wt.% H2O and ~1.25 wt.% F, and the viscosities of a basalt with 2.29 wt.% H2O and a basalt with ~1.65 wt.% H2O and ~1.3 wt.% F are also very similar. The effect of CO2 is somewhat ambiguous. The viscosity of a basalt with ~1.7 wt.% H2O, ~1.3 wt.% F and ~0.2 wt.% CO2 is essentially the same as the viscosity of a basalt with 2.29 wt.% H2O, so CO2 seems to have a negligible or even viscosity-increasing effect when F and H2O are also present. However, a basalt with ~0.84 wt.% H2O and ~0.09 wt.% CO2 has about the same viscosity as a basalt with 1.34 wt.% H2O, which could suggest a strong (viscosity-decreasing) effect of very small amounts of CO2. These results suggest that the effects on viscosity of F in basaltic systems are

  14. K(NpO(2))(3)(H(2)O)Cl(4): A channel structure assembled two- and three-center cation-cation interactions of neptunyl cations

    SciTech Connect

    Wang, Shuao; Alekseev, Evgeny V.; Depmeier, Wulf; Albrecht-Schmitt, Thomas E.

    2011-06-06

    A Np(V) compound containing three-center cation–cation interations, K(NpO₂)₃(H₂O)Cl₄, has been prepared by reacting Np(V) with KCl in molten boric acid. This compound forms a three-dimensional channel structure that is constructed from both two- and three-center cation–cation interactions. Three new bonding modes for cation–cation interactions are added to the summary of all known Np(V) compounds.

  15. Hormetic Effect of H2O2 in Saccharomyces cerevisiae

    PubMed Central

    Valishkevych, Bohdana V.

    2016-01-01

    In this study, we investigated the relationship between target of rapamycin (TOR) and H2O2-induced hormetic response in the budding yeast Saccharomyces cerevisiae grown on glucose or fructose. In general, our data suggest that: (1) hydrogen peroxide (H2O2) induces hormesis in a TOR-dependent manner; (2) the H2O2-induced hormetic dose–response in yeast depends on the type of carbohydrate in growth medium; (3) the concentration-dependent effect of H2O2 on yeast colony growth positively correlates with the activity of glutathione reductase that suggests the enzyme involvement in the H2O2-induced hormetic response; and (4) both TOR1 and TOR2 are involved in the reciprocal regulation of the activity of glucose-6-phosphate dehydrogenase and glyoxalase 1. PMID:27099601

  16. CO Diffusion into Amorphous H2O Ices

    NASA Astrophysics Data System (ADS)

    Lauck, Trish; Karssemeijer, Leendertjan; Shulenberger, Katherine; Rajappan, Mahesh; Öberg, Karin I.; Cuppen, Herma M.

    2015-03-01

    The mobility of atoms, molecules, and radicals in icy grain mantles regulates ice restructuring, desorption, and chemistry in astrophysical environments. Interstellar ices are dominated by H2O, and diffusion on external and internal (pore) surfaces of H2O-rich ices is therefore a key process to constrain. This study aims to quantify the diffusion kinetics and barrier of the abundant ice constituent CO into H2O-dominated ices at low temperatures (15-23 K), by measuring the mixing rate of initially layered H2O(:CO2)/CO ices. The mixed fraction of CO as a function of time is determined by monitoring the shape of the infrared CO stretching band. Mixing is observed at all investigated temperatures on minute timescales and can be ascribed to CO diffusion in H2O ice pores. The diffusion coefficient and final mixed fraction depend on ice temperature, porosity, thickness, and composition. The experiments are analyzed by applying Fick’s diffusion equation under the assumption that mixing is due to CO diffusion into an immobile H2O ice. The extracted energy barrier for CO diffusion into amorphous H2O ice is ˜160 K. This is effectively a surface diffusion barrier. The derived barrier is low compared to current surface diffusion barriers in use in astrochemical models. Its adoption may significantly change the expected timescales for different ice processes in interstellar environments.

  17. Surface and bulk uptake of H2O2 to snow: Insights from laboratory studies

    NASA Astrophysics Data System (ADS)

    Bartels-Rausch, Thorsten; Ulrich, Thomas; Ammann, Markus

    2014-05-01

    crystals, the bulk uptake is thought to occur into grain boundaries. Characterizing the uptake of trace gases to ice on different time-scales and identifying the compartment to which trace gases are taken up in snow are essential, but open questions. In this study the H2O2 uptake to thin ice films was investigated over long time-scales of hours, thus combining features of previous experiments. A long-lasting uptake of H2O2 to thin ice films is observed for the first time. The initial component of the overall uptake agrees perfectly with the parameterisation of surface adsorption derived in the previous study on thin ice films. The total uptake that was observed in this study agrees with the pioneering study on H2O2 uptake to backed snow samples. The total amount of H2O2 taken up by the ice film via this slow process might easily exceed the adsorbed H2O2 under environmental time scales.

  18. Pyruvate Protects Pathogenic Spirochetes from H2O2 Killing

    PubMed Central

    Troxell, Bryan; Zhang, Jun-Jie; Bourret, Travis J.; Zeng, Melody Yue; Blum, Janice; Gherardini, Frank; Hassan, Hosni M.; Yang, X. Frank

    2014-01-01

    Pathogenic spirochetes cause clinically relevant diseases in humans and animals, such as Lyme disease and leptospirosis. The causative agent of Lyme disease, Borrelia burgdorferi, and the causative agent of leptospirosis, Leptospria interrogans, encounter reactive oxygen species (ROS) during their enzootic cycles. This report demonstrated that physiologically relevant concentrations of pyruvate, a potent H2O2 scavenger, and provided passive protection to B. burgdorferi and L. interrogans against H2O2. When extracellular pyruvate was absent, both spirochetes were sensitive to a low dose of H2O2 (≈0.6 µM per h) generated by glucose oxidase (GOX). Despite encoding a functional catalase, L. interrogans was more sensitive than B. burgdorferi to H2O2 generated by GOX, which may be due to the inherent resistance of B. burgdorferi because of the virtual absence of intracellular iron. In B. burgdorferi, the nucleotide excision repair (NER) and the DNA mismatch repair (MMR) pathways were important for survival during H2O2 challenge since deletion of the uvrB or the mutS genes enhanced its sensitivity to H2O2 killing; however, the presence of pyruvate fully protected ΔuvrB and ΔmutS from H2O2 killing further demonstrating the importance of pyruvate in protection. These findings demonstrated that pyruvate, in addition to its classical role in central carbon metabolism, serves as an important H2O2 scavenger for pathogenic spirochetes. Furthermore, pyruvate reduced ROS generated by human neutrophils in response to the Toll-like receptor 2 (TLR2) agonist zymosan. In addition, pyruvate reduced neutrophil-derived ROS in response to B. burgdorferi, which also activates host expression through TLR2 signaling. Thus, pathogenic spirochetes may exploit the metabolite pyruvate, present in blood and tissues, to survive H2O2 generated by the host antibacterial response generated during infection. PMID:24392147

  19. Microchannel Reactor System Design & Demonstration For On-Site H2O2 Production by Controlled H2/O2 Reaction

    SciTech Connect

    Adeniyi Lawal

    2008-12-09

    We successfully demonstrated an innovative hydrogen peroxide (H2O2) production concept which involved the development of flame- and explosion-resistant microchannel reactor system for energy efficient, cost-saving, on-site H2O2 production. We designed, fabricated, evaluated, and optimized a laboratory-scale microchannel reactor system for controlled direct combination of H2 and O2 in all proportions including explosive regime, at a low pressure and a low temperature to produce about 1.5 wt% H2O2 as proposed. In the second phase of the program, as a prelude to full-scale commercialization, we demonstrated our H2O2 production approach by ‘numbering up’ the channels in a multi-channel microreactor-based pilot plant to produce 1 kg/h of H2O2 at 1.5 wt% as demanded by end-users of the developed technology. To our knowledge, we are the first group to accomplish this significant milestone. We identified the reaction pathways that comprise the process, and implemented rigorous mechanistic kinetic studies to obtain the kinetics of the three main dominant reactions. We are not aware of any such comprehensive kinetic studies for the direct combination process, either in a microreactor or any other reactor system. We showed that the mass transfer parameter in our microreactor system is several orders of magnitude higher than what obtains in the macroreactor, attesting to the superior performance of microreactor. A one-dimensional reactor model incorporating the kinetics information enabled us to clarify certain important aspects of the chemistry of the direct combination process as detailed in section 5 of this report. Also, through mathematical modeling and simulation using sophisticated and robust commercial software packages, we were able to elucidate the hydrodynamics of the complex multiphase flows that take place in the microchannel. In conjunction with the kinetics information, we were able to validate the experimental data. If fully implemented across the whole

  20. A comparison of ice VII formed in the H2O, NaCl-H2O, and CH3OH-H2O systems: Implications for H2O-rich planets

    NASA Astrophysics Data System (ADS)

    Frank, Mark R.; Aarestad, Elizabeth; Scott, Henry P.; Prakapenka, Vitali B.

    2013-02-01

    High-pressure H2O polymorphs, namely ice VI, ice VII, and ice X, are hypothesized to make up a considerable portion of the interiors of large icy satellites and select extra-solar planets. The incorporation of foreign ions or molecules into these high-pressure phases is possible through ocean-ice interaction, rock-ice interaction at depth, or processes that occurred during accretion. Recent research concerning the effects charged ions have on ice VII has shown that these ions notably affect the structure of ice VII (Frank et al., 2006; Klotz et al., 2009). This study was designed to determine the effects of a molecular impurity on ice VII and compare those effects to both pure H2O ice and ice with an ionic impurity. Ice samples were formed in this study via compression in a diamond anvil cell from either H2O, a 1.60 mol% NaCl aqueous solution, a 1.60 mol% CH3OH aqueous solution, or a 5.00 mol% CH3OH aqueous solution and were compressed up to 71 GPa at room temperature. Ice formed from pure H2O had no impurities whereas ices formed in the NaCl-H2O and CH3OH-H2O systems contained the impurities Na+ and Cl- and CH3OH, respectively. Pressure-volume relations were observed in situ by using synchrotron based X-ray diffraction and were used to determine the equations of state for ices formed in the H2O, NaCl-H2O and CH3OH-H2O systems. The data illustrate that ice VII formed from a NaCl-bearing aqueous solution exhibited a depressed volume when compared to that of H2O-only ice VII at any given pressure, whereas ice VII formed from CH3OH-bearing aqueous solutions showed an opposite trend, with an increase in volume relative to that of pure ice VII. The ices within planetary bodies will most likely have both ionic and molecular impurities and the trends outlined in this study can be used to improve density profiles of H2O-rich planetary bodies.

  1. Self-encapsulation of [MII(phen)2(H2O)2]2+ (M=Co, Zn) in one-dimensional nanochannels of [MII(H2O)6(BTC)2]4- (M=Co, Cu, Mn): a high HQ/CAT ratio catalyst for hydroxylation of phenols.

    PubMed

    Bi, Jianhong; Kong, Lingtao; Huang, Zixiang; Liu, Jinhuai

    2008-06-01

    Four novel three-dimensional (3D) microporous supramolecular compounds containing nanosized channels, namely, [Co(phen)2(H2O)2]2[Co(H2O)6].2BTC.21.5H2O (1), [Co(phen)2(H2O)2]2[Cu(H2O)6].2BTC.21.5H2O (2), [Co(phen)2(H2O)2]2[Mn(H2O)6].2BTC.18H2O (3), and [Zn(phen)2(H2O)2]2[Mn(H2O)6].2BTC.22.5H2O (4), were synthesized from 1,3,5-benzenetricarboxylate (BTC), 1,10-phenanthroline (phen), and the transition-metal salt(s) by self-assembly. Single-crystal X-ray structural analysis showed that the resulting 3D microporous supramolecular frameworks consist of a two-dimensional (2D) hydrogen-bonded host framework of [MII(H2O)6(BTC)2]4- (M=Co for 1, Cu for 2, Mn for 3, 4) with rectangular-shaped cavities containing [MII(phen)2(H2O)2]2+ (M=Co for 1-3, Zn for 4) guests. The guest complex is encapsulated in the 2D hydrogen-bonded host framework by hydrogen bonding and aromatic pi-pi stacking interactions, forming the 3D hydrogen-bonded framework. The catalytic activities of 1, 2, 3, and 4 were studied using hydroxylation of phenols with 30% aqueous H2O2 as a test reaction. The compounds displayed a good phenol conversion ratio and excellent channel selectivity in the hydroxylation reaction, with a maximum hydroquinone (HQ)/catechol (CAT) ratio of 3.9. PMID:18439004

  2. Destruction and Sequestration of H2O on Mars

    NASA Astrophysics Data System (ADS)

    Clark, Benton

    2016-07-01

    The availability of water in biologically useable form on any planet is a quintessential resource, even if the planet is in a zone habitable with temperature regimes required for growth of organisms (above -18 °C). Mars and most other planetary objects in the solar system do not have sufficient liquid water at their surfaces that photosynthesis or chemolithoautotrophic metabolism could occur. Given clear evidence of hydrous mineral alteration and geomorphological constructs requiring abundant supplies of liquid water in the past, the question arises whether this H2O only became trapped physically as ice, or whether there could be other, more or less accessible reservoirs that it has evolved into. Salts containing S or Cl appear to be ubiquitous on Mars, having been measured in soils by all six Mars landed missions, and detected in additional areas by orbital investigations. Volcanoes emit gaseous H2S, S, SO2, HCl and Cl2. A variety of evidence indicates the geochemical fate of these gases is to be transformed into sulfates, chlorides, chlorates and perchlorates. Depending on the gas, the net reaction causes the destruction of between one and up to eight molecules of H2O per atom of S or Cl (although hydrogen atoms are also released, they are lost relatively rapidly to atmospheric escape). Furthermore, the salt minerals formed often incorporate H2O into their crystalline structures, and can result in the sequestration of up to yet another six (sometimes, more) molecules of H2O. In addition, if the salts are microcrystalline or amorphous, they are potent adsorbents for H2O. In certain cases, they are even deliquescent under martian conditions. Finally, the high solubility of the vast majority of these salts (with notable exception of CaSO4) can result in dense brines with low water activity, aH, as well as cations which can be inimical to microbial metabolism, effectively "poisoning the well." The original geologic materials on Mars, igneous rocks, also provide some

  3. Interaction between sulphide and H 2O in silicate melts

    NASA Astrophysics Data System (ADS)

    Stelling, Jan; Behrens, Harald; Wilke, Max; Göttlicher, Jörg; Chalmin-Aljanabi, Emilie

    2011-06-01

    Reaction between dissolved water and sulphide was experimentally investigated in soda-lime-silicate (NCS) and sodium trisilicate (NS3) melts at temperatures from 1000 to 1200 °C and pressures of 100 or 200 MPa in internally heated gas pressure vessels. Diffusion couple experiments were conducted at water-undersaturated conditions with one half of the couple being doped with sulphide (added as FeS or Na 2S; 1500-2000 ppm S by weight) and the other with H 2O (˜3.0 wt.%). Additionally, two experiments were performed using a dry NCS glass cylinder and a free H 2O fluid. Here, the melt was water-saturated at least at the melt/fluid interface. Profiling by electron microprobe (sulphur) and infrared microscopy (H 2O) demonstrate that H 2O diffusion in the melts is faster by 1.5-2.3 orders of magnitude than sulphur diffusion and, hence, H 2O can be considered as a rapidly diffusing oxidant while sulphur is quasi immobile in these experiments. In Raman spectra a band at 2576 cm -1 appears in the sulphide - H 2O transition zone which is attributed to fundamental S-H stretching vibrations. Formation of new IR absorption bands at 5025 cm -1 (on expense of the combination band of molecular H 2O at 5225 cm -1) and at 3400 cm -1 was observed at the front of the in-diffusing water in the sulphide bearing melt. The appearance and intensity of these two IR bands is correlated with systematic changes in S K-edge XANES spectra. A pre-edge excitation at 2466.5 eV grows with increasing H 2O concentration while the sulphide peak at 2474.0 eV decreases in intensity relative to the peak at 2477.0 eV and the feature at 2472.3 eV becomes more pronounced (all energies are relative to the sulphate excitation, calibrated to 2482.5 eV). The observations by Raman, IR and XANES spectroscopy indicate a well coordinated S 2- - H 2O complex which was probably formed in the glasses during cooling at the glass transition. No oxidation of sulphide was observed in any of the diffusion couple

  4. Electrochemical, H2O2-Boosted Catalytic Oxidation System

    NASA Technical Reports Server (NTRS)

    Akse, James R.; Thompson, John O.; Schussel, Leonard J.

    2004-01-01

    An improved water-sterilizing aqueous-phase catalytic oxidation system (APCOS) is based partly on the electrochemical generation of hydrogen peroxide (H2O2). This H2O2-boosted system offers significant improvements over prior dissolved-oxygen water-sterilizing systems in the way in which it increases oxidation capabilities, supplies H2O2 when needed, reduces the total organic carbon (TOC) content of treated water to a low level, consumes less energy than prior systems do, reduces the risk of contamination, and costs less to operate. This system was developed as a variant of part of an improved waste-management subsystem of the life-support system of a spacecraft. Going beyond its original intended purpose, it offers the advantage of being able to produce H2O2 on demand for surface sterilization and/or decontamination: this is a major advantage inasmuch as the benign byproducts of this H2O2 system, unlike those of systems that utilize other chemical sterilants, place no additional burden of containment control on other spacecraft air- or water-reclamation systems.

  5. Role of Metabolic H2O2 Generation

    PubMed Central

    Sies, Helmut

    2014-01-01

    Hydrogen peroxide, the nonradical 2-electron reduction product of oxygen, is a normal aerobic metabolite occurring at about 10 nm intracellular concentration. In liver, it is produced at 50 nmol/min/g of tissue, which is about 2% of total oxygen uptake at steady state. Metabolically generated H2O2 emerged from recent research as a central hub in redox signaling and oxidative stress. Upon generation by major sources, the NADPH oxidases or Complex III of the mitochondrial respiratory chain, H2O2 is under sophisticated fine control of peroxiredoxins and glutathione peroxidases with their backup systems as well as by catalase. Of note, H2O2 is a second messenger in insulin signaling and in several growth factor-induced signaling cascades. H2O2 transport across membranes is facilitated by aquaporins, denoted as peroxiporins. Specialized protein cysteines operate as redox switches using H2O2 as thiol oxidant, making this reactive oxygen species essential for poising the set point of the redox proteome. Major processes including proliferation, differentiation, tissue repair, inflammation, circadian rhythm, and aging use this low molecular weight oxygen metabolite as signaling compound. PMID:24515117

  6. [Functional characteristics of yeast cells in nutrient aqueous solution enriched with ortho-H2O isomers].

    PubMed

    Pershin, S M; Ismailov, E Sh; Suleimanova, Z G; Abdulmagomedova, Z N; Zagirova, D Z

    2014-01-01

    It has been experimentally established that cultivation of yeast cells in depleted, dietary or normal nutrient aqueous solutions enriched with ortho-H2O spin isomers is accompanied by an increase in the amount of carbon dioxide produced by the cells and an increase in their biomass. It has been revealed that the rate of metabolic processes and biological activity depends on the quality of nutrition and enhances in time in both nutrient solutions. In contrast, the reproductive function and the rate of cell division are insusceptible to the components of nutrition, but intensified in a solution enriched with ortho-H2O similar to retardation of aging. The observed effects are discussed in assumption that an increase of a portion of ortho-H2O molecules occurs in the neighborhood of water channels in the cell membrane that let through only monomers of H2O and determine the rate of metabolic processes. PMID:25702495

  7. Amorphous and Crystalline H2O-Ice

    NASA Astrophysics Data System (ADS)

    Mastrapa, Rachel M. E.; Grundy, William M.; Gudipati, Murthy S.

    On the surfaces of Solar System objects, H2O-ice can form in several different phases, including amorphous and crystalline. The stability of these phases as a function of thermal and radiation history is an active area of laboratory research. Meanwhile, remote detection of H2O-ice depends on the interpretation of infrared absorptions that are also dependent on phase and temperature. Surface processes, such as surface chemistry, micrometeorite gardening, and cryovolcanic resurfacing, on the surfaces of objects are linked to H2O-ice phase. We review the current state of laboratory measurements in the context of observations of Solar System objects and list the areas where new measurements are needed.

  8. Explosive origin of silicic lava: Textural and δD-H2O evidence for pyroclastic degassing during rhyolite effusion

    NASA Astrophysics Data System (ADS)

    Castro, Jonathan M.; Bindeman, Ilya N.; Tuffen, Hugh; Ian Schipper, C.

    2014-11-01

    A long-standing challenge in volcanology is to explain why explosive eruptions of silicic magma give way to lava. A widely cited idea is that the explosive-to-effusive transition manifests a two-stage degassing history whereby lava is the product of non-explosive, open-system gas release following initial explosive, closed-system degassing. Direct observations of rhyolite eruptions indicate that effusive rhyolites are in fact highly explosive, as they erupt simultaneously with violent volcanic blasts and pyroclastic fountains for months from a common vent. This explosive and effusive overlap suggests that pyroclastic processes play a key role in rendering silicic magma sufficiently degassed to generate lava. Here we use precise H-isotope and magmatic H2O measurements and textural evidence to demonstrate that effusion results from explosion(s)-lavas are the direct product of brittle deformation that fosters batched degassing into transient pyroclastic channels (tuffisites) that repetitively and explosively vent from effusing lava. Our measurements show, specifically that D/H ratios and H2O contents of a broad suite of explosive and effusive samples from Chaitén volcano (hydrous bombs, Plinian pyroclasts, tuffisite veins, and lava) define a single and continuous degassing trend that links wet explosive pyroclasts (∼1.6 wt.% H2O, δD=-76.4‰) to dry obsidian lavas (∼0.13 wt.% H2O, δD=-145.7‰). This geochemical pattern is best fit with batched degassing model that comprises small repeated closed-system degassing steps followed by pulses of vapour extraction. This degassing mechanism is made possible by the action of tuffisite veins, which, by tapping already vesicular or brecciated magma, allow batches of exsolved gas to rapidly and explosively escape from relatively isolated closed-system domains and large tracts of conduit magma by giving them long-range connectivity. Even though tuffisite veins render magma degassed and capable of effusing, they are

  9. NASA Lewis H2-O2 MHD program

    NASA Technical Reports Server (NTRS)

    Smith, M.; Nichols, L. D.; Seikel, G. R.

    1974-01-01

    Performance and power costs of H2-O2 combustion powered steam-MHD central power systems are estimated. Hydrogen gas is assumed to be transmitted by pipe from a remote coal gasifier into the city and converted to electricity in a steam MHD plant having an integral gaseous oxygen plant. These steam MHD systems appear to offer an attractive alternative to both in-city clean fueled conventional steam power plants and to remote coal fired power plants with underground electric transmission into the city. Status and plans are outlined for an experimental evaluation of H2-O2 combustion-driven MHD power generators at NASA Lewis Research Center.

  10. Maps of [HDO]/[H2O] near Mars’ Aphelion

    NASA Astrophysics Data System (ADS)

    Novak, Robert E.; Mumma, M. J.; Villanueva, G. L.

    2013-10-01

    We report maps of HDO and H2O taken at three seasonal points before and near Mars’ aphelion (Ls = 71°). These observations were taken at Ls = 357° (15 January 2006), Ls = 50° (26 March 2008) and Ls = 72° (2/3 April 2010) using CSHELL at the NASA Infrared Telescope Facility. For these three seasonal dates, the entrance slit of the spectrometer was positioned N-S on Mars centered at the sub-Earth point; on 3 April 2010, the slit was positioned E-W. Data were extracted at 0.6 arc-second intervals from the spectral-spatial images. Individual spectral lines were measured near 3.67 μm (HDO) and 3.29 μm (H2O). The column densities were obtained by comparing the observed lines to those of a multi-layered, radiative transfer model. The model includes solar Fraunhofer lines, two-way transmission through Mars’ atmosphere, thermal emission from Mars’ surface and atmosphere, and a one-way transmission through the Earth’s atmosphere. Latitudinal maps of HDO, H2O, and their ratios were then constructed. The [HDO]/[H2O] ratios have been found to be larger than those on Earth and they vary with both latitude and season. For the Ls = 357° and 50° observations, the ratio peaks near the sub-solar latitude ([HDO]/[H2O] ~ 6.9 VSMOW) and decreases towards both the North and South polar-regions. At Ls = 72°, column densities of both HDO and H2O and their ratios increase from the Southern hemisphere to the North polar-region. Observations from 3 April 2013 show diurnal variations of both the column densities and their ratio. Specific points on Mars’ surface were tracked for four hours. It is believed that this variation is caused by the vaporization of ground frost and water ice clouds that are formed during the night and disappear during daytime. Our results for H2O column densities will be compared to TES results. The results for HDO and the [HDO]/[H2O] ratios will be compared to model results.This work was partially funded by grants from NASA's Planetary Astronomy

  11. Sensitization of H2O2-induced TRPM2 activation and subsequent interleukin-8 (CXCL8) production by intracellular Fe(2+) in human monocytic U937 cells.

    PubMed

    Shimizu, Shunichi; Yonezawa, Ryo; Negoro, Takaharu; Yamamoto, Shinichiro; Numata, Tomohiro; Ishii, Masakazu; Mori, Yasuo; Toda, Takahiro

    2015-11-01

    Transient receptor potential melastatin 2 (TRPM2) is an oxidative stress-sensitive Ca(2+)-permeable channel. In monocytes/macrophages, H2O2-induced TRPM2 activation causes cell death and/or production of chemokines that aggravate inflammatory diseases. However, relatively high concentrations of H2O2 are required for activation of TRPM2 channels in vitro. Thus, in the present study, factors that sensitize TRPM2 channels to H2O2 were identified and subsequent physiological responses were examined in U937 human monocytes. Temperature increase from 30°C to 37°C enhanced H2O2-induced TRPM2-mediated increase in intracellular free Ca(2+) ([Ca(2+)]i) in TRPM2-expressing HEK 293 cells (TRPM2/HEK cells). The H2O2-induced TRPM2 activation enhanced by the higher temperature was dramatically sensitized by intracellular Fe(2+)-accumulation following pretreatment with FeSO4. Thus intracellular Fe(2+)-accumulation sensitizes H2O2-induced TRPM2 activation at around body temperature. Moreover, intracellular Fe(2+)-accumulation increased poly(ADP-ribose) levels in nuclei by H2O2 treatment, and the sensitization of H2O2-induced TRPM2 activation were almost completely blocked by poly(ADP-ribose) polymerase inhibitors, suggesting that intracellular Fe(2+)-accumulation enhances H2O2-induced TRPM2 activation by increase of ADP-ribose production through poly(ADP-ribose) polymerase pathway. Similarly, pretreatment with FeSO4 stimulated H2O2-induced TRPM2 activation at 37°C in U937 cells and enhanced H2O2-induced ERK phosphorylation and interleukin-8 (CXCL8) production. Although the addition of H2O2 to cells under conditions of intracellular Fe(2+)-accumulation caused cell death, concentration of H2O2 required for CXCL8 production was lower than that resulting in cell death. These results indicate that intracellular Fe(2+)-accumulation sensitizes TRPM2 channels to H2O2 and subsequently produces CXCL8 at around body temperature. It is possible that sensitization of H2O2-induced TRPM2

  12. Global Flux Balance in the Terrestrial H2O Cycle: Reconsidering the Post-Arc Subducted H2O Flux

    NASA Astrophysics Data System (ADS)

    Parai, R.; Mukhopadhyay, S.

    2010-12-01

    Quantitative estimates of H2O fluxes between the mantle and the exosphere (i.e., the atmosphere, oceans and crust) are critical to our understanding of the chemistry and dynamics of the solid Earth: the abundance and distribution of water in the mantle has dramatic impacts upon mantle melting, degassing history, structure and style of convection. Water is outgassed from the mantle is association with volcanism at mid-ocean ridges, ocean islands and convergent margins. H2O is removed from the exosphere at subduction zones, and some fraction of the subducted flux may be recycled past the arc into the Earth’s deep interior. Estimates of the post-arc subducted H2O flux are primarily based on the stability of hydrous phases at subduction zone pressures and temperatures (e.g. Schmidt and Poli, 1998; Rüpke et al., 2004; Hacker, 2008). However, the post-arc H2O flux remains poorly quantified, in part due to large uncertainties in the water content of the subducting slab. Here we evaluate estimated post-arc subducted fluxes in the context of mantle-exosphere water cycling, using a Monte Carlo simulation of the global H2O cycle. Literature estimates of primary magmatic H2O abundances and magmatic production rates at different tectonic settings are used with estimates of the total subducted H2O flux to establish the parameter space under consideration. Random sampling of the allowed parameter space affords insight into which input and output fluxes satisfy basic constraints on global flux balance, such as a limit on sea-level change over time. The net flux of H2O between mantle and exosphere is determined by the total mantle output flux (via ridges and ocean islands, with a small contribution from mantle-derived arc output) and the input flux subducted beyond the arc. Arc and back-arc output is derived mainly from the slab, and therefore cancels out a fraction of the trench intake in an H2O subcycle. Limits on sea-level change since the end of the Archaean place

  13. H2O-mediated isatin spiro-epoxide ring opening with NaCN: Synthesis of novel 3-tetrazolylmethyl-3-hydroxy-oxindole hybrids and their anticancer evaluation.

    PubMed

    Sharma, Pankaj; Senwar, Kishna Ram; Jeengar, Manish Kumar; Reddy, T Srinivasa; Naidu, V G M; Kamal, Ahmed; Shankaraiah, Nagula

    2015-11-01

    A simple method for isatin spiro-epoxide ring-opening by sodium cyanide in water to obtain a variety of isatin hydroxy nitriles has been developed. Further, these intermediates have been converted into new 3-tetrazolylmethyl-3-hydroxy-oxindole hybrids via azide-nitrile cycloaddition reaction in a sealed tube. These compounds were evaluated for their in vitro anticancer activity on five human cancer cell lines i.e. breast (BT549 and MDA MB-231), prostate (PC-3 and DU-145) and ovarian (PA-1). The compounds 6d and 6r showed potent anticancer activity against DU-145 cell line with IC50 values in the range of 7.01 ± 0.91 and 4.26 ± 0.09 μM respectively. The compounds 6d, 6g, 6q and 6r were also tested on human normal prostate epithelial (RWPE-1) cells and found to be safer with lesser cytotoxicity. The morphology and long term clonogenic survival of DU-145 cells were severely affected by compound 6r. Cell cycle analysis revealed that the compounds arrest the cells in G2/M phase. Acridine orange/ethidium bromide (AO/EB) staining, DAPI staining, annexin-V binding assay and DNA fragmentation analysis showed that cell proliferation was inhibited through induction of apoptosis. Moreover, one of the compounds 6r treatment led to collapse of the mitochondrial membrane potential (DΨm) and increased levels of reactive oxygen species (ROS) in DU-145 cells. PMID:26413726

  14. New Optical Constants for Amorphous and Crystalline H2O-ice and H2O-mixtures.

    NASA Technical Reports Server (NTRS)

    Mastrapa, Rachel; Bernstein, Max; Sandford, Scott

    2006-01-01

    We will present the products of new laboratory measurements of ices relevant to Trans-Neptunian Objects. We have calculated the real and imaginary indices of refraction for amorphous and crystalline H2O-ice and also H2O-rich ices containing other molecular species. We create ice samples by condensing gases onto a cold substrate. We measure the thickness of the sample by reflecting a He-Ne laser off of the sample and counting interference fringes as it grows. We then collect transmission spectra of the samples in the wavelength range from 0.7-22 micrometers. Using the thickness and the transmission spectra of the ice we calculate the imaginary part of the index of refraction. We then use a Kramers-Kronig calculation to calculate the real part of the index of refraction (Berland et al. 1994; Hudgins et al. 1993). These optical constants can then be used to create model spectra for comparison to spectra from Solar System objects, including TNOs. We will summarize the difference between the amorphous and crystalline H2O-ice spectra. These changes include weakening of features and shifting of features to shorter wavelength. One important result is that the 2 pm feature is stronger in amorphous H2O ice than it is in crystalline H2O-ice. We will also discuss the changes seen when H2O is mixed with other components, including CO2, CH4, HCN, and NH3 (Bernstein et al. 2005; Bernstein et al. 2006).

  15. Ground and excited states of the [Fe(H2O)6]2+ and [Fe(H2O)6]3+ clusters: Insight into the electronic structure of the [Fe(H2O)6]2+ – [Fe(H2O)6]3+ complex

    SciTech Connect

    Miliordos, Evangelos; Xantheas, Sotiris S.

    2015-04-14

    We report the ground and low lying electronically excited states of the [Fe(H2O)6]2+ and [Fe(H2O)6]3+ clusters using multi-configuration electronic structure theory. In particular, we have constructed the Potential Energy Curves (PECs) with respect to the iron-oxygen distance when removing all water ligands at the same time from the cluster minima and established their correlation to the long range dissociation channels. Due to the fact that both the second and third ionization potentials of iron are larger than the one for water, the ground state products asymptotically correlate with dissociation channels that are repulsive in nature at large separations as they contain at least one H2O+ fragment and a positive metal center. The most stable equilibrium structures emanate – via intersections and/or avoided crossings – from the channels consisting of the lowest electronic states of Fe2+(5D; 3d6) or Fe3+(6S; 3d5) and six neutral water molecules. Upon hydration, the ground state of Fe2+(H2O)6 is a triply (5Tg) degenerate one with the doubly (5Eg) degenerate state lying slightly higher in energy. Similarly, Fe3+(H2O)6 has a ground state of 6Ag symmetry under Th symmetry. We furthermore examine a multitude of electronically excited states of many possible spin multiplicities, and report the optimized geometries for several selected states. The PECs for those cases are characterized by a high density of states. Focusing on the ground and the first few excited states of the [Fe(H2O)6]2+ and [Fe(H2O)6]3+ clusters, we studied their mutual interaction in the gas phase. We obtained the optimal geometries of the Fe2+(H2O)6 – Fe3+(H2O)6 gas phase complex for different Fe–Fe distances. For distances shorter than 6.0 Å, the water molecules in the respective first solvation shells located between the two metal centers were found to interact via weak hydrogen bonds. We examined a total of ten electronic states for this complex, including those corresponding to the

  16. A laser flash photolysis kinetics study of the reaction OH + H2O2 yields HO2 + H2O

    NASA Technical Reports Server (NTRS)

    Wine, P. H.; Semmes, D. H.; Ravishankara, A. R.

    1981-01-01

    Absolute rate constants for the reaction are reported as a function of temperature over the range 273-410 K. OH radicals are produced by 266 nm laser photolysis of H2O2 and detected by resonance fluorescence. H2O2 concentrations are determined in situ in the slow flow system by UV photometry. The results confirm the findings of two recent discharge flow-resonance fluorescence studies that the title reaction is considerably faster, particularly at temperatures below 300 K, than all earlier studies had indicated. A table giving kinetic data from the reaction is included.

  17. Preformance Analysis of NH3-H2O Absorption Cycle

    NASA Astrophysics Data System (ADS)

    Tsujimori, Atsushi; Ozaki, Eiichi

    Different from H2O-LiBr absorption cycle, it is necessary to have rectifier between generator and condenser in NH3-H2O absorption cycle, because there mixes some steam in refrigerant vapor in the process of regenerating refrigerant from the ammonia strong aqueous solution. And in some case ex. partial load or heating, the efficiency of rectifier might decrease, if the flow rate of refrigerant vapor and ammonia aqueous solution decrease. As a result, steam flow into condenser with ammonia refrigerant vapor, which reduces cycle COPs of cooling and heating. Accordingly in order to evaluate the effect of ammonia concentration in refrigerant for the performance of NH3-H2O absorption heat pump, the simple design approach of modeling condenser and evaporator is introduced in this paper. In the model, the calculation of heat rate in condenser and evaporator was simplified considering the characteristic of NH3-H2O liquid-vapor equilibrium. Then the simulation for cycle perforance based on GAX absorption cycle was made using the efficiency of rectifier that established the ammonia concentration in refrigerant and it was derived that 3 [%] decrease of ammonia concentration in refrigerant induced 15 [%] decrcase of cooling COP and 7 [%] decrease of heating COP and that there existed the most suitable circulation ratio for each ammonia concentration in refrigerant.

  18. Multidimentional Normal Mode Calculations for the OH Vibrational Spectra of (H_2O)_3^+, (H_2O)_3^+Ar, H^+(H_2O)_3, and H^+(H_2O)_3Ar

    NASA Astrophysics Data System (ADS)

    Li, Ying-Cheng; Chuang, Hsiao-Han; Tan, Jake Acedera; Takahashi, Kaito; Kuo, Jer-Lai

    2014-06-01

    Recent experimental observations of (H_2O)_3^+, (H_2O)_3^+Ar, H^+(H_2O)_3, and H^+(H_2O)_3Ar clusters in the region 1400-3800 wn show that the OH stretching vibration has distinct characteristics. Multidimensional normal mode calculations were carried out for OH stretching vibrations in the 1200-4000 wn photon energy range. The potential energy and dipole surfaces were evaluated by using first-principles methods. By comparing the calculated frequencies and intensities of OH stretching vibration with experimental spectra, we found that the assignment of OH strecthing of H_3O^+ moiety and free OH strectching vibration have resonable agreement with experimental data. Jeffrey M. Headrick, Eric G. Diken, Richard S. Walters, Nathan I. Hammer, Richard A. Christie, Jun Cui, Evgeniy M. Myshakin, Michael A. Duncan, Mark A. Johnson, Kenneth D. Jordan, Science, 2005, 17, 1765. Kenta Mizuse, Jer-Lai Kuo and Asuka Fujii, Chem. Sci., 2011, 2, 868 Kenta Mizuse and Asuka Fujii, J. Phys. Chem. A, 2013, 117, 929.

  19. Cyclosis-mediated transfer of H2O 2 elicited by localized illumination of Chara cells and its relevance to the formation of pH bands.

    PubMed

    Eremin, Alexey; Bulychev, Alexander; Hauser, Marcus J B

    2013-12-01

    Cytoplasmic streaming occurs in most plant cells and is vitally important for large cells as a means of long-distance intracellular transport of metabolites and messengers. In internodal cells of characean algae, cyclosis participates in formation of light-dependent patterns of surface pH and photosynthetic activity, but lateral transport of regulatory metabolites has not been visualized yet. Hydrogen peroxide, being a signaling molecule and a stress factor, is known to accumulate under excessive irradiance. This study was aimed to examine whether H2O2 produced in chloroplasts under high light conditions is released into streaming fluid and transported downstream by cytoplasmic flow. To this end, internodes of Chara corallina were loaded with the fluorogenic probe dihydrodichlorofluorescein diacetate and illuminated locally by a narrow light beam through a thin optic fiber. Fluorescence of dihydrodichlorofluorescein (DCF), produced upon oxidation of the probe by H2O2, was measured within and around the illuminated cell region. In cells exhibiting active streaming, H2O2 first accumulated in the illuminated region and then entered into the streaming cytoplasm, giving rise to the expansion of DCF fluorescence downstream of the illuminated area. Inhibition of cyclosis by cytochalasin B prevented the spreading of DCF fluorescence along the internode. The results suggest that H2O2 released from chloroplasts under high light is transported along the cell with the cytoplasmic flow. It is proposed that the shift of cytoplasmic redox poise and light-induced elevation of cytoplasmic pH facilitate the opening of H(+)/OH(-)-permeable channels in the plasma membrane. PMID:23760663

  20. Oxidative degradation of endotoxin by advanced oxidation process (O3/H2O2 & UV/H2O2).

    PubMed

    Oh, Byung-Taek; Seo, Young-Suk; Sudhakar, Dega; Choe, Ji-Hyun; Lee, Sang-Myeong; Park, Youn-Jong; Cho, Min

    2014-08-30

    The presence of endotoxin in water environments may pose a serious public health hazard. We investigated the effectiveness of advanced oxidative processes (AOP: O3/H2O2 and UV/H2O2) in the oxidative degradation of endotoxin. In addition, we measured the release of endotoxin from Escherichia coli following typical disinfection methods, such as chlorine, ozone alone and UV, and compared it with the use of AOPs. Finally, we tested the AOP-treated samples in their ability to induce tumor necrosis factor alpha (TNF-α) in mouse peritoneal macrophages. The production of hydroxyl radical in AOPs showed superior ability to degrade endotoxin in buffered solution, as well as water samples from Korean water treatment facilities, with the ozone/H2O2 being more efficient compared to UV/H2O2. In addition, the AOPs proved effective not only in eliminating E. coli in the samples, but also in endotoxin degradation, while the standard disinfection methods lead to the release of endotoxin following the bacteria destruction. Furthermore, in the experiments with macrophages, the AOPs-deactivated endotoxin lead to the smallest induction of TNF-α, which shows the loss of inflammation activity, compared to ozone treatment alone. In conclusion, these results suggest that AOPs offer an effective and mild method for endotoxin degradation in the water systems. PMID:25038578

  1. Silicate-H2O Systems at High Pressure Conditions

    NASA Astrophysics Data System (ADS)

    Tailby, N.; Mavrogenes, J. A.; Hermann, J.; O'Neill, H. S.

    2008-12-01

    Since the discovery of the second critical endpoint (CP2) in the albite-water system, numerous attempts have been made to determine the pressure and temperature of this CP2 and the mutual solubilities within more complex systems. The P-T position of the CP2 has been estimated for many systems: SiO2 (<10 kb/900 °C, Newton and Manning, 2008); NaAlSi3O8 (15 kb/800 °C, Burnham and Davis, 1974; Shen and Keppler, 1997); Pelite (50 kb/1,000 °C, Schmidt et al., 2004), basalt (50 kb/ 1000 °C, Kessel et al., 2004), Peridotite (38 kb/1000 °C, Mibe et al., 2007). A number of experimental techniques have been used to determine phase relations and H2O solubility in experiments. These include in-situ experimental techniques (e.g., HYDAC; Shen and Keppler, 1997), fluid trap techniques (e.g., diamond traps; Stalder et al., 2000), and single crystal weight-loss techniques (e.g., SiO2-H2O techniques employed by Newton and Manning, 2008). None of these techniques is without difficulties, as H2O rich experiments need to overcome huge retrograde fluid solubilities upon quench in order to determine mutual solubilities at experimental conditions. We have developed a new technique to determine "rock"-H2O relationships at high-P conditions, with particular focus on the shape and locus of solvi in pressure temperature space. In this series of experiments, an oxygen fugacity buffer (Re-ReO2) and a sliding H-fugacity sensor (NiO-Ni-Pd mixture) are combined to monitor H2O activity over the entire range of pressure and temperature. Unlike other techniques, the use of sensor capsules does not require textural interpretation of experiments. H2O activity is related to oxygen and hydrogen fugacity by the reaction: H2O = H2 + ½O2 NiO-Ni-Pd mixtures were placed within a ZrO2 jacket and sealed within a welded 2.3 mm Pt capsule. This 2.3 mm Pt sensor capsule was then encased within a larger, thick walled 6 mm diameter Ag capsule. Pelite-H2O mixtures and oxygen buffers were held within this larger

  2. Vibrational investigations of CO2-H2O, CO2-(H2O)2, and (CO2)2-H2O complexes isolated in solid neon.

    PubMed

    Soulard, P; Tremblay, B

    2015-12-14

    The van der Waals complex of H2O with CO2 has attracted considerable theoretical interest as a typical example of a weak binding complex with a dissociation energy less than 3 kcal/mol. Up to now, experimental vibrational data are sparse. We have studied by FTIR the complexes involving CO2 and water molecules in solid neon. Many new absorption bands close to the well known monomers fundamentals give evidence for at least three (CO2)n-(H2O)m complexes, noted n:m. Concentration effects combined with a detailed vibrational analysis allow for the identification of sixteen, twelve, and five transitions for the 1:1, 1:2, and 2:1 complexes, respectively. Careful examination of the far infrared spectral region allows the assignment of several 1:1 and 1:2 intermolecular modes, confirmed by the observation of combinations of intra + intermolecular transitions, and anharmonic coupling constants have been derived. Our results demonstrate the high sensibility of the solid neon isolation to investigate the hydrogen-bonded complexes in contrast with the gas phase experiments for which two quanta transitions cannot be easily observed. PMID:26671379

  3. Vibrational investigations of CO2-H2O, CO2-(H2O)2, and (CO2)2-H2O complexes isolated in solid neon

    NASA Astrophysics Data System (ADS)

    Soulard, P.; Tremblay, B.

    2015-12-01

    The van der Waals complex of H2O with CO2 has attracted considerable theoretical interest as a typical example of a weak binding complex with a dissociation energy less than 3 kcal/mol. Up to now, experimental vibrational data are sparse. We have studied by FTIR the complexes involving CO2 and water molecules in solid neon. Many new absorption bands close to the well known monomers fundamentals give evidence for at least three (CO2)n-(H2O)m complexes, noted n:m. Concentration effects combined with a detailed vibrational analysis allow for the identification of sixteen, twelve, and five transitions for the 1:1, 1:2, and 2:1 complexes, respectively. Careful examination of the far infrared spectral region allows the assignment of several 1:1 and 1:2 intermolecular modes, confirmed by the observation of combinations of intra + intermolecular transitions, and anharmonic coupling constants have been derived. Our results demonstrate the high sensibility of the solid neon isolation to investigate the hydrogen-bonded complexes in contrast with the gas phase experiments for which two quanta transitions cannot be easily observed.

  4. Crystalline and amorphous H2O on Charon

    NASA Astrophysics Data System (ADS)

    Dalle Ore, Cristina M.; Cruikshank, Dale P.; Grundy, Will M.; Ennico, Kimberly; Olkin, Catherine B.; Stern, S. Alan; Young, Leslie A.; Weaver, Harold A.

    2015-11-01

    Charon, the largest satellite of Pluto, is a gray-colored icy world covered mostly in H2O ice, with spectral evidence for NH3, as previously reported (Cook et al. 2007, Astrophys. J. 663, 1406-1419 Merlin, et al. 2010, Icarus, 210, 930; Cook, et al. 2014, AAS/Division for Planetary Sciences Meeting Abstracts, 46, #401.04). Images from the New Horizons spacecraft reveal a surface with terrains of widely different ages and a moderate degree of localized coloration. The presence of H2O ice in its crystalline form (Brown & Calvin 2000 Science 287, 107-109; Buie & Grundy 2000 Icarus 148, 324-339; Merlin et al, 2010) along with NH3 is consistent with a fresh surface.The phase of H2O ice is a key tracer of variations in temperature and physical conditions on the surface of outer Solar System objects. At Charon’s surface temperature H2O is expected to be amorphous, but ground-based observations (e.g., Merlin et al. 2010) show a clearly crystalline signature. From laboratory experiments it is known that amorphous H2O ice becomes crystalline at temperatures of ~130 K. Other mechanisms that can change the phase of the ice from amorphous to crystalline include micro-meteoritic bombardment (Porter et al. 2010, Icarus, 208, 492) or resurfacing processes such as cryovolcanism.New Horizons observed Charon with the LEISA imaging spectrometer, part of the Ralph instrument (Reuter, D.C., Stern, S.A., Scherrer, J., et al. 2008, Space Science Reviews, 140, 129). Making use of high spatial resolution (better than 10 km/px) and spectral resolving power of 240 in the wavelength range 1.25-2.5 µm, and 560 in the range 2.1-2.25 µm, we report on an analysis of the phase of H2O ice on parts of Charon’s surface with a view to investigate the recent history and evolution of this small but intriguing object.This work was supported by NASA’s New Horizons project.

  5. The Structures of Fluorene-(H2O)(1,2) Determined by Rotational Coherence Spectroscopy

    SciTech Connect

    Laman, David M.; Joly, Alan G.; Ray, Douglas

    2003-07-22

    Rotational coherence spectroscopy (RCS), via time-correlated single photon counting, and two-color resonant two-photon ionization (R2PI) time-of-flight mass spectrometry, have been used to characterize fluorene-(water)1,2 (FL-(water)1,2) van der Waals clusters generated in supersonic jets. Rotational coherence traces have been obtained at excitation energies corresponding to several resonant features in the S1S0 R2PI spectra of FL-(H2O)1,2. RCS simulations and diagonalization of the moment of inertia tensor have been used to obtain the S1 excited state rotational constants and structures of FL-(H2O)1,2 that are consistent with the experimental rotational coherence traces. The RCS results indicate that: (i) the water molecule in FL-H2O bridges the central five-membered ring of fluorene and hydrogen bonds to both aromatic sites; (ii) the water molecules in FL-(H2O)2 form a water dimer that is oriented along the long axis of fluorene and is hydrogen-bonded to both aromatic sites. The S1S0 R2PI spectra of FL-(D2O)1,2 and FL-HDO have also been obtained. The transition is a doublet in the R2PI spectra of FL-H2O, FL-D2O, and a singlet in the R2PI spectrum of FL-HDO. The presence of this doublet in the FL-H2O/D2O spectra, and the absence of such a splitting in the FL-HDO spectrum, is an indication of nearly free internal rotation of the water molecule on a potential energy surface that changes upon electronic excitation. Lastly, the use of RCS and psec time-resolved fluorescence as a tool for assigning features in R2PI spectra that are of ambiguous origin due to fragmentation of higher mass clusters into lower mass channels is demonstrated.

  6. H2-O2 auxiliary power unit for Space Shuttle vehicles - A progress report.

    NASA Technical Reports Server (NTRS)

    Joyce, J. P.; Beremand, D. G.; Cameron, H. M.; Jefferies, K. S.

    1973-01-01

    Description of a program to establish technology readiness of hydrogen-oxygen (H2-O2) auxiliary power units for use on board the Space Shuttle orbiter vehicle. Fundamental objectives include experimentally establishing an acceptable propellant flow control method, verification of combustor stability, and adequate thermal management. An initial auxiliary power unit (APU) configuration with recycled hydrogen flow has been studied and revised toward greater simplicity and scaling ease. The selected APU is a recuperated open-cycle, turbine-driven unit. Series flow of cryogenic hydrogen removes internally-generated heat and heat from the hydraulic system. The revised configuration schematic and its calculated performance are reviewed. A weight comparison is made between the shuttle baseline hydrazine and H2-O2 APU systems, showing that hydrogen-oxygen APUs have the potential of increasing the payload of the Space Shuttle.

  7. The target: H2O on the Moon

    NASA Astrophysics Data System (ADS)

    Green, J.; Wys, J. Negusde; Zuppero, A.

    1992-09-01

    The importance of H2O on the lunar surface has long been identified as a high priority for the existence of a human colony for mining activities and, more recently, for space fuel. Using the Earth as an analog, volcanic activity would suggest the generation of water during lunar history. Evidence of volcanism is found not only in present lunar morphology, but in over 400 locations of lunar transient events cataloged by Middlehurst and Kuiper in the 1960's. These events consisted of sightings since early history of vapor emissions and bright spots or flares. Later infrared scanning by Saari and Shorthill showed 'hot spots', many of which coincided with transient event sites. Many of the locations of Middlehurst and Kuiper were the sites of repeat events, leading to the conclusion that these were possibly volcanic in nature. The detection and use of H2O from the lunar surface is discussed.

  8. Antiferromagnetism of UO2⋅2H2O

    USGS Publications Warehouse

    Pankey, T.; Senftle, F.E.; Cuttitta, F.

    1963-01-01

    Magnetic susceptibility measurements have been made on UO2⋅xH2O for x=1.78 to x=2.13, and from 77° to 375°K. As the value of x decreased the susceptibility increased. Both these data and structural arguments imply that the formula of this compound is U(OH)4 rather than the dihydrate form. Based on this concept the data have been corrected for diamagnetism and also small amounts of UO2 and H2O which were present. The molar susceptibility of U4+ in U(OH)4 is nearly an order of magnitude less than in other uranium compounds, and it is suggested that this is probably due to superexchange between adjacent uranium atoms through intervening oxygen atoms.

  9. The Target: H2O on the Moon

    NASA Technical Reports Server (NTRS)

    Green, J.; Wys, J. Negusde; Zuppero, A.

    1992-01-01

    The importance of H2O on the lunar surface has long been identified as a high priority for the existence of a human colony for mining activities and, more recently, for space fuel. Using the Earth as an analog, volcanic activity would suggest the generation of water during lunar history. Evidence of volcanism is found not only in present lunar morphology, but in over 400 locations of lunar transient events cataloged by Middlehurst and Kuiper in the 1960's. These events consisted of sightings since early history of vapor emissions and bright spots or flares. Later infrared scanning by Saari and Shorthill showed 'hot spots', many of which coincided with transient event sites. Many of the locations of Middlehurst and Kuiper were the sites of repeat events, leading to the conclusion that these were possibly volcanic in nature. The detection and use of H2O from the lunar surface is discussed.

  10. Detection Of OH+ And H2O+ Towards Orion KL

    NASA Astrophysics Data System (ADS)

    Gupta, Harshal; Rimmer, P.; Pearson, J. C.; Herbst, E.; Yu, S.; Bergin, E. A.; Key Program, HEXOS

    2011-01-01

    The reactive molecular ions, OH+, H2O+, and H3O+, key probes of the oxygen chemistry of the interstellar gas, have been observed toward Orion KL with the Heterodyne Instrument for Far Infrared on board the Herschel Space Observatory. All three N = 1 - 0 fine-structure transitions of OH+ at 909, 971, and 1033 GHz and both fine-structure components of the doublet ortho-H2O+ 111 - 000 transition at 1115 and 1139 GHz were detected, and an upper limit was obtained for H3O+. OH+ and H2O+ are observed purely in absorption, showing a narrow component at the source velocity of 9 km s-1, and a broad blue shifted absorption similar to that reported recently for HF and para-H218O, and attributed to the low velocity outflow of Orion KL. We estimate column densities of OH+ and H2O+ for the 9 km s-1 component of 9 ± 3 x 1012 cm-2 and 7 ± 2 x 1012 cm-2, and those in the outflow of 1.9 ± 0.7 x 1013 cm-2 and 1.0 ± 0.3 x 1013 cm-2. Upper limits of 2.4 x 1012 cm-2 and 8.7 ± 1012 cm-2 were derived for the column densities of ortho and para-H3O+ from transitions near 985 and 1657 GHz. The column densities of the three ions are up to an order of magnitude lower than those obtained from recent observations of W31C and W49N. A higher gas density, despite the assumption of a large ionization rate, may explain the comparatively low column densities of the ions. A part of this work was performed at the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration. Copyright 2010© California Institute of Technology. All rights reserved.

  11. Near Infrared Spectra of H2O/HCN Mixtures

    NASA Technical Reports Server (NTRS)

    Mastrapa, R. M.; Bernstein, M. P.; Sanford, S. A.

    2006-01-01

    Cassini's VIMS has already returned exciting results interpreting spectra of Saturn's icy satellites. The discovery of unidentified features possibly due to CN compounds inspired the work reported here. We wanted to test HCN as a possibility for explaining these features, and also explore how the features of HCN change when mixed with H2O. We have previously noted that mixing H20 and CO2 produces new spectral features and that those features change with temperature and mixing ratio.

  12. The Effect of H2O on Ice Photochemistry

    NASA Astrophysics Data System (ADS)

    Öberg, Karin I.; van Dishoeck, Ewine F.; Linnartz, Harold; Andersson, Stefan

    2010-08-01

    UV irradiation of simple ices is proposed to efficiently produce complex organic species during star formation and planet formation. Through a series of laboratory experiments, we investigate the effects of the H2O concentration, the dominant ice constituent in space, on the photochemistry of more volatile species, especially CH4, in ice mixtures. In the experiments, thin (~40 ML) ice mixtures, kept at 20-60 K, are irradiated under ultra-high vacuum conditions with a broadband UV hydrogen discharge lamp. Photodestruction cross sections of volatile species (CH4 and NH3) and production efficiencies of new species (C2H6, C2H4, CO, H2CO, CH3OH, CH3CHO, and CH3CH2OH) in water-containing ice mixtures are determined using reflection-absorption infrared spectroscopy during irradiation and during a subsequent slow warm-up. The four major effects of increasing the H2O concentration are: (1) an increase of the destruction efficiency of the volatile mixture constituent by up to an order of magnitude due to a reduction of back reactions following photodissociation, (2) a shift to products rich in oxygen, e.g., CH3OH and H2CO, (3) trapping of up to a factor of 5 more of the formed radicals in the ice, and (4) a disproportional increase in the diffusion barrier for the OH radical compared with the CH3 and HCO radicals. The radical diffusion temperature dependencies are consistent with calculated H2O-radical bond strengths. All the listed effects are potentially important for the production of complex organics in H2O-rich icy grain mantles around protostars and should thus be taken into account when modeling ice chemistry.

  13. Third-generation synchrotron x-ray diffraction of 6-μm crystal of raite, ≈Na3Mn3Ti0.25Si8O20(OH)2⋅10H2O, opens up new chemistry and physics of low-temperature minerals

    PubMed Central

    Pluth, Joseph J.; Smith, Joseph V.; Pushcharovsky, Dmitry Y.; Semenov, Eugenii I.; Bram, Andreas; Riekel, Christian; Weber, Hans-Peter; Broach, Robert W.

    1997-01-01

    The crystal structure of raite was solved and refined from data collected at Beamline Insertion Device 13 at the European Synchrotron Radiation Facility, using a 3 × 3 × 65 μm single crystal. The refined lattice constants of the monoclinic unit cell are a = 15.1(1) Å; b = 17.6(1) Å; c = 5.290(4) Å; β = 100.5(2)°; space group C2/m. The structure, including all reflections, refined to a final R = 0.07. Raite occurs in hyperalkaline rocks from the Kola peninsula, Russia. The structure consists of alternating layers of a hexagonal chicken-wire pattern of 6-membered SiO4 rings. Tetrahedral apices of a chain of Si six-rings, parallel to the c-axis, alternate in pointing up and down. Two six-ring Si layers are connected by edge-sharing octahedral bands of Na+ and Mn3+ also parallel to c. The band consists of the alternation of finite Mn–Mn and Na–Mn–Na chains. As a consequence of the misfit between octahedral and tetrahedral elements, regions of the Si–O layers are arched and form one-dimensional channels bounded by 12 Si tetrahedra and 2 Na octahedra. The channels along the short c-axis in raite are filled by isolated Na(OH,H2O)6 octahedra. The distorted octahedrally coordinated Ti4+ also resides in the channel and provides the weak linkage of these isolated Na octahedra and the mixed octahedral tetrahedral framework. Raite is structurally related to intersilite, palygorskite, sepiolite, and amphibole. PMID:11038590

  14. H2O Adsorption on Smectites: Application to the Diurnal Variation of H2O in the Martian Atmosphere

    NASA Technical Reports Server (NTRS)

    Zent, Aaron P.; Howard, J.; Quinn, R. C.

    2000-01-01

    Observations of the Martian planetary boundary layer lead to interpretations that are baffling and contradictory. In this paper, we specifically address the question of whether or not water vapor finds a substantial diurnal reservoir in the Martian regolith. To address this issue, we have measured H2O adsorption kinetics on SWy-1, a Na-rich montmorillonite from Wyoming. The highest-temperature (273 K) data equilibrates rapidly. Data gathered at realistic H2O partial pressures and temperatures appropriate to early morning show two phenomena that preclude a significant role for smectites in diurnally exchanging a large column abundance. First, the equilibration timescale is longer than a sol. Second, the equilibrium abundances are a small fraction of that predicted by earlier adsorption isotherms. The explanation for this phenomenon is that smectite clay actually increases its surface area as a function of adsorptive coverage. At Mars-like conditions, we show that the interlayer sites of smectites are likely to be unavailable.

  15. Mesospheric H2O and H2O2 densities inferred from in situ positive ion composition measurement

    NASA Technical Reports Server (NTRS)

    Kopp, E.

    1984-01-01

    A model for production and loss of oxonium ions in the high-latitude D-region is developed, based on the observed excess of 34(+) which has been interpreted as H2O2(+). The loss mechanism suggested in the study is the attachment of N2 and/or CO2 in three-body reactions. Furthermore, mesospheric water vapor and H2O2 densities are inferred from measurements of four high-latitude ion compositions, based on the oxonium model. Mixing ratios of hydrogen peroxide of up to two orders of magnitude higher than previous values were obtained. A number of reactions, reaction constants, and a block diagram of the oxonium ion chemistry in the D-region are given.

  16. Effects of H2O and H2O2 on Thermal Desorption of Tritium from Stainless Steel

    SciTech Connect

    Quinlan, M.J.; Shmayda, W.T.; Lim, S.; Salnikov, S.; Chambers, Z.; Pollock, E.; Schroder, W.U.

    2010-03-12

    Tritiated stainless steel was subjected to thermal desorption at various temperatures, different temperature profiles, and in the presence of different helium carrier gas additives. In all cases the identities of the desorbing tritiated species were characterized as either water-soluble or insoluble. The samples were found to contain 1.1 mCi±0.4 mCi. Approximately ninety-five percent of this activity was released in molecular water-soluble form. Additives of H2O or H2O2 to dry helium carrier gas increase the desorption rate and lower the maximum temperature to which the sample must be heated, in order to remove the bulk of the tritium. The measurements validate a method of decontamination of tritiated steel and suggest a technique that can be used to further explore the mechanisms of desorption from tritiated metals.

  17. Increasing extracellular H2O2 produces a bi-phasic response in intracellular H2O2, with peroxiredoxin hyperoxidation only triggered once the cellular H2O2-buffering capacity is overwhelmed.

    PubMed

    Tomalin, Lewis Elwood; Day, Alison Michelle; Underwood, Zoe Elizabeth; Smith, Graham Robert; Dalle Pezze, Piero; Rallis, Charalampos; Patel, Waseema; Dickinson, Bryan Craig; Bähler, Jürg; Brewer, Thomas Francis; Chang, Christopher Joh-Leung; Shanley, Daryl Pierson; Veal, Elizabeth Ann

    2016-06-01

    Reactive oxygen species, such as H2O2, can damage cells but also promote fundamental processes, including growth, differentiation and migration. The mechanisms allowing cells to differentially respond to toxic or signaling H2O2 levels are poorly defined. Here we reveal that increasing external H2O2 produces a bi-phasic response in intracellular H2O2. Peroxiredoxins (Prx) are abundant peroxidases which protect against genome instability, ageing and cancer. We have developed a dynamic model simulating in vivo changes in Prx oxidation. Remarkably, we show that the thioredoxin peroxidase activity of Prx does not provide any significant protection against external rises in H2O2. Instead, our model and experimental data are consistent with low levels of extracellular H2O2 being efficiently buffered by other thioredoxin-dependent activities, including H2O2-reactive cysteines in the thiol-proteome. We show that when extracellular H2O2 levels overwhelm this buffering capacity, the consequent rise in intracellular H2O2 triggers hyperoxidation of Prx to thioredoxin-resistant, peroxidase-inactive form/s. Accordingly, Prx hyperoxidation signals that H2O2 defenses are breached, diverting thioredoxin to repair damage. PMID:26944189

  18. H2O masers from low and intermediate luminosity young stellar objects: H2O masers and YSOs

    NASA Astrophysics Data System (ADS)

    Persi, P.; Palagi, F.; Felli, M.

    1994-11-01

    We have used the Medicina 32-m radiotelescope to search for H2O 22.2 GHz maser emission from a sample of 68 red peculiar nebulosities associated with low luminosity (LIR less than 103 solar luminosity)) and intermediate luminosity (LIR approximately 104 solar luminosity) Young Stellar Objects (YSOs). H2O maser emission was detected in 9 sources, with a new detection in IRAS 18265+0028. Comparison with other samples indicates that YSOs have a higher probability of hosting an H2O maser, when they are associated with red peculiar nebulosities. Seven of the detected sources are associated with molecular outflows, which confirms that these two phenomena are strictly correlated. The maser sources associated with the Class I YSOs (IRAS 03225+3034, and IRAS 03245+3002, in the dark clouds L1448 and L1455 respectively) appear overluminous with respect to their IR luminosity. The maser emission shows a remarkable variability on time scales of months and years, which tends to be larger for lower luminosity sources. This is indicative of unsaturated emission in low luminosity sources.

  19. The effects of small amounts of H2O on partial melting of model spinel lherzolite in the system CMAS

    NASA Astrophysics Data System (ADS)

    Liu, X.; St. C. Oneill, H.

    2003-04-01

    quantify the amounts of H_2O. This is necessary, as Pt capsules are to some extent open to H_2 diffusion. All melts were found to contain CO_2 (<0.7 wt%), which appears to come mainly from the hydroxide starting materials but also by C diffusion through the Pt capsule. Since CO_2 is experimentally correlated with H_2O, its presence significantly effects the interpretation of the results. Ignoring this complication, we find that 1 wt% H_2O decreases the solidus by ˜40 K; melt compositions do not change greatly, the main effect being a small decrease in MgO.

  20. Reconstructing Final H2O Contents of Hydrated Rhyolitic Glasses: Insights into H2O Degassing and Eruptive Style of Silicic Submarine Volcanoes

    NASA Astrophysics Data System (ADS)

    McIntosh, I. M.; Nichols, A. R.; Tani, K.; Llewellin, E. W.

    2015-12-01

    H2O degassing influences the evolution of magma viscosity and vesicularity during ascent through the crust, and ultimately the eruptive style. Investigating H2O degassing requires data on both initial and final H2O contents. Initial H2O contents are revealed by melt inclusion data, while final H2O contents are found from dissolved H2O contents of volcanic glass. However volcanic glasses, particularly of silicic composition, are susceptible to secondary hydration i.e. the addition of H2O from the surrounding environment at ambient temperature during the time following pyroclast deposition. Obtaining meaningful final H2O data therefore requires distinguishing between the original final dissolved H2O content and the H2O added subsequently during hydration. Since H2O added during hydration is added as molecular H2O (H2Om), and the species interconversion between H2Om and hydroxyl (OH) species is negligible at ambient temperature, the final OH content of the glass remains unaltered during hydration. By using H2O speciation models to find the original H2Om content that would correspond to the measured OH content of the glass, the original total H2O (H2Ot) content of the glass prior to hydration can be reconstructed. These H2O speciation data are obtained using FTIR spectroscopy. In many cases, particularly where vesicular glasses necessitate thin wafers, OH cannot be measured directly and instead is calculated indirectly as OH = H2Ot - H2Om. Here we demonstrate the importance of using a speciation-dependent H2Ot molar absorptivity coefficient to obtain accurate H2Ot and H2O speciation data and outline a methodology for calculating such a coefficient for rhyolite glasses, with application to hydrated silicic pumice from submarine volcanoes in the Japanese Izu-Bonin Arc. Although hydrated pumice from Kurose Nishi and Oomurodashi now contain ~1.0 - 2.5 wt% H2Ot, their pre-hydration final H2O contents were typically ~0.3 - 0.4 wt% H2Ot. Furthermore, we show that pre

  1. H2O2 assisted room temperature oxidation of Ti2C MXene for Li-ion battery anodes

    NASA Astrophysics Data System (ADS)

    Ahmed, Bilal; Anjum, Dalaver H.; Hedhili, Mohamed N.; Gogotsi, Yury; Alshareef, Husam N.

    2016-03-01

    Herein we demonstrate that a prominent member of the MXene family, Ti2C, undergoes surface oxidation at room temperature when treated with hydrogen peroxide (H2O2). The H2O2 treatment results in opening up of MXene sheets and formation of TiO2 nanocrystals on their surface, which is evidenced by the high surface area of H2O2 treated MXene and X-ray diffraction (XRD) analysis. We show that the reaction time and the amount of hydrogen peroxide used are the limiting factors, which determine the morphology and composition of the final product. Furthermore, it is shown that the performance of H2O2 treated MXene as an anode material in Li ion batteries (LIBs) was significantly improved as compared to as-prepared MXenes. For instance, after 50 charge/discharge cycles, specific discharge capacities of 389 mA h g-1, 337 mA h g-1 and 297 mA h g-1 were obtained for H2O2 treated MXene at current densities of 100 mA g-1, 500 mA g-1 and 1000 mA g-1, respectively. In addition, when tested at a very high current density, such as 5000 mA g-1, the H2O2 treated MXene showed a specific capacity of 150 mA h g-1 and excellent rate capability. These results clearly demonstrate that H2O2 treatment of Ti2C MXene improves MXene properties in energy storage applications, such as Li ion batteries or capacitors.Herein we demonstrate that a prominent member of the MXene family, Ti2C, undergoes surface oxidation at room temperature when treated with hydrogen peroxide (H2O2). The H2O2 treatment results in opening up of MXene sheets and formation of TiO2 nanocrystals on their surface, which is evidenced by the high surface area of H2O2 treated MXene and X-ray diffraction (XRD) analysis. We show that the reaction time and the amount of hydrogen peroxide used are the limiting factors, which determine the morphology and composition of the final product. Furthermore, it is shown that the performance of H2O2 treated MXene as an anode material in Li ion batteries (LIBs) was significantly improved as

  2. Ionization yield and absorption spectra reveal superexcited Rydberg state relaxation processes in H2O and D2O

    NASA Astrophysics Data System (ADS)

    Fillion, J.-H.; Dulieu, F.; Baouche, S.; Lemaire, J.-L.; Jochims, H. W.; Leach, S.

    2003-07-01

    The absorption cross section and the ionization quantum yield of H2O have been measured using a synchrotron radiation source between 9 and 22 eV. Comparison between the two curves highlights competition between relaxation processes for Rydberg states converging to the first tilde A 2A 1 and to the second tilde B 2B 2 excited states of H2O+. Comparison with D2O absorption and ionization yields, derived from Katayama et al (1973 J. Chem. Phys. 59 4309), reveals specific energy-dependent deuteration effects on competitive predissociation and autoionization relaxation channels. Direct ionization was found to be only slightly affected by deuteration.

  3. H2O2 assisted room temperature oxidation of Ti2C MXene for Li-ion battery anodes.

    PubMed

    Ahmed, Bilal; Anjum, Dalaver H; Hedhili, Mohamed N; Gogotsi, Yury; Alshareef, Husam N

    2016-04-14

    Herein we demonstrate that a prominent member of the MXene family, Ti2C, undergoes surface oxidation at room temperature when treated with hydrogen peroxide (H2O2). The H2O2 treatment results in opening up of MXene sheets and formation of TiO2 nanocrystals on their surface, which is evidenced by the high surface area of H2O2 treated MXene and X-ray diffraction (XRD) analysis. We show that the reaction time and the amount of hydrogen peroxide used are the limiting factors, which determine the morphology and composition of the final product. Furthermore, it is shown that the performance of H2O2 treated MXene as an anode material in Li ion batteries (LIBs) was significantly improved as compared to as-prepared MXenes. For instance, after 50 charge/discharge cycles, specific discharge capacities of 389 mA h g(-1), 337 mA h g(-1) and 297 mA h g(-1) were obtained for H2O2 treated MXene at current densities of 100 mA g(-1), 500 mA g(-1) and 1000 mA g(-1), respectively. In addition, when tested at a very high current density, such as 5000 mA g(-1), the H2O2 treated MXene showed a specific capacity of 150 mA h g(-1) and excellent rate capability. These results clearly demonstrate that H2O2 treatment of Ti2C MXene improves MXene properties in energy storage applications, such as Li ion batteries or capacitors. PMID:26984324

  4. Crystal structures, UV spectra of solid iodide anionic water clusters I(-)(H2O)(1-4), and electrochemical reaction of I(-)(H2O)(1-4) → I· + e(-)(H2O)(1-4).

    PubMed

    Qiu, Yanxuan; Yang, Meng; Chen, Wenbin; Su, Yuzhi; Ouyang, Zhenjie; Yan, Hua; Gao, Feixian; Dong, Wen

    2013-05-16

    Four iodide anionic water clusters of I(-)(H2O)1-4 in two supramolecular complexes of [Fe(phen)3][I2(H2O)3] (1) and [Zn(phen)3][I2(H2O)4.5] (2) have been determined by single-crystal X-ray diffraction analysis. The diffuse reflectance spectra for the solid iodide anionic water clusters of I(-)(H2O)1-4 were investigated, and their absorption bands were demonstrated by denisty functional theory calculation. The electrochemical reaction of I(-)(H2O)1-4 → I· + e(-)(H2O)1-4 with the oxidation potential of Ep = 0.61 eV was first found and reported in two aqueous solutions (1 mmol·dm(-3)) of 1 and 2. PMID:23614806

  5. Timescales of magma ascent recorded by H2O zonation in clinopyroxene

    NASA Astrophysics Data System (ADS)

    Lloyd, A. S.; Plank, T. A.; Ruprecht, P.; Hauri, E. H.; Rose, W. I.

    2013-12-01

    Magma ascent prior to explosive eruptions occurs on timescales of minutes to hours, and so requires exceptionally fast chronometers to quantify. One promising approach involves the diffusion of water in clinopyroxene (cpx), given laboratory measurements of diffusivities on the order of 10-9.5 to 10-11.5 at temperatures appropriate for mafic magmas [1]. Previous studies have observed H2O zonation in cpx grains but this was accompanied by major element zonation, leaving open the possibility for crystal growth zonation instead of diffusive loss of water [2]. We report SIMS and EMP analyses for three cpx phenocrysts from ash samples collected in situ during the Oct 17, 1974 sub-plinian eruption of Volcán de Fuego. Concentration profiles were assessed by 5-6 measurements along ~350-450 μm transects measured perpendicular to glassy rims. The maximum H2O measured in the cores of the cpx ranges from 230-320 ppm; whereas, the measurements closest to the rim range from 80-170 ppm. Importantly, we chose grains with limited major element zonation (i.e., Mg# and Al2O3 remain relatively constant or do not co-vary with H2O concentrations). Based on a temperature-dependent parameterization for the partition coefficient of H2O between cpx and melt that accounts for tetrahedrally coordinated Al3+ [3], cores and rims of these cpx are in equilibrium with a melt containing 2.0-2.7 wt% (core) and 0.7-1.6 wt% (rim). The maximum H2O concentration measured in olivine-hosted melt inclusions (~4.2 wt% H2O) erupted on the same day as the cpx phenocrysts [4] suggests that the cpx are not in equilibrium with the melt inclusions. The Mg# of the cpxs (73-77) fall within the range of that for the olivines (72-78) indicating that cpx and olivine were co-crystalizing and that H+ loss by diffusion has potentially occurred. Utilizing the same melt inclusion data to constrain the degassing path for the ascending magma under Fuego, we used forward models to estimate the decompression rate needed to

  6. H2O Isotopologues in Extreme OH/IR Stars

    NASA Astrophysics Data System (ADS)

    Justtanont, K.; Barlow, M. J.; Blommaert, J. A. D. L.; Decin, L.; Kerschbaum, F.; Matsuura, M.; Olofsson, H.; Swinyard, B.; Teyssier, D.; Waters, L. B. F. M.; Yates, J.

    2015-08-01

    Using Herschel Space Observatory, we observed isotopologues of H2O in extreme OH/IR stars. We detected strong H216O and H217O while the H218O lines are missing, contrary to the overall galactic oxygen abundance in the interstellar medium and the Sun, where 18O is more abundant than 17O. Theoretical stellar evolution suggests that 18O is being destroyed during the hot-bottom burning. This implies that these OH/IR stars come from a population of intermediate-mass stars which have an initial mass ≥ 5 M⊙.

  7. Advanced H2/O2 space engine parametrics

    NASA Technical Reports Server (NTRS)

    Schneider, J. A.

    1989-01-01

    Engine cycle analyses conducted on a 3000-lbf component testing model of an H2/O2-fueled advanced orbit-transfer vehicle engine employing a dual-expander cycle have yielded pressure and temperature trend predictions. On the basis of the results obtained, the dual-expander cycle is projected to be scalable to thrust levels of as much as 50,000 lbf, with chamber pressures of 2000 psi. The high chamber pressure, in conjunction with the use of a gas-gas injector element, facilitates 10:1-range continuously variable throttling. The preferred thrust level for supporting mission studies would be of the order of 20,000 lbf.

  8. Radiative Lifetime for Nuclear Spin Conversion of Water-Ion H_2O^+

    NASA Astrophysics Data System (ADS)

    Tanaka, Keiichi; Harada, Kensuke; Oka, Takeshi

    2013-06-01

    Nuclear spin conversion interaction of the water ion, H_2O^+, has been studied to derive the spontaneous emission lifetime between the ortho- and para-levels. The H_2O^+ ion is a radical with ^2 B _1 electronic ground state and the off-diagonal electron spin-nuclear spin interaction term, T_{ab} (S_aΔ I_b + S_bΔ I_a), connects para and ortho levels, because Δ {I} = {I}_1 - {I}_2 has nonvanishing matrix elements between I = 0 and 1. The T_{ab} coupling constant, derived by an ab initio calculation in MRD-CI/Bk level to be 72 MHz, is larger than that of H_2O by 4 orders of magnitude, makes the ortho to para conversion of H_2O^+ faster than that of H_2O by 8 orders of magnitude and possibly competitive with other astrophysical processes. Last year we reported ortho and para coupling channels below 900 cm^{-1} caused by accidental near degeneracy of rotational levels. For example, hyperfine components of the 4_{2,2}(o) and 3_{3,0}(p) levels mix each other by 1.2 x 10^{-3} due to the near degeneracy (Δ E = 0.417 cm^{-1}), but the lower lying 1_{0,1}(p) and 1_{1,1}(o) levels mix only by 8.9 x 10^{-5} because of their large separation (Δ E = 16.27 cm^{-1}). In the present study, we solved the radiative rate equations including all the rotational levels below 900 cm^{-1} to give the o-p conversion lifetime to be 0.451, 3.27, 398 and 910 years for the equilibrium o/p ratio of 3.00, 3.00, 4.52, and 406 when the radiation temperature T_r is 100, 60, 20 and 5 K. These results qualitatively help to understand the observed high o/p ratio of 4.8 ± 0.5 (corresponding to the nuclear spin temperature of 21 K) toward Sgr B2, but they are too slow to compete with the reaction by collision unless the number of density of H_2 in the region is very low (n˜1 cm^{-3}) or the radiative temperature is very high (T_r > 50K). K. Tanaka, K. Harada, and T. Oka, the 67th OSU Symposium MG06, 2012. P. Schilke, et al., A&A 521, L11 (2010). K. Tanaka, K. Harada, and T. Oka, J. Phys. Chem. A

  9. VOLATILECALC: A silicate melt-H2O-CO2 solution model written in Visual Basic for excel

    USGS Publications Warehouse

    Newman, S.; Lowenstern, J. B.

    2002-01-01

    We present solution models for the rhyolite-H2O-CO2 and basalt-H2O-CO2 systems at magmatic temperatures and pressures below ~ 5000 bar. The models are coded as macros written in Visual Basic for Applications, for use within MicrosoftR Excel (Office'98 and 2000). The series of macros, entitled VOLATILECALC, can calculate the following: (1) Saturation pressures for silicate melt of known dissolved H2O and CO2 concentrations and the corresponding equilibrium vapor composition; (2) open- and closed-system degassing paths (melt and vapor composition) for depressurizing rhyolitic and basaltic melts; (3) isobaric solubility curves for rhyolitic and basaltic melts; (4) isoplethic solubility curves (constant vapor composition) for rhyolitic and basaltic melts; (5) polybaric solubility curves for the two end members and (6) end member fugacities of H2O and CO2 vapors at magmatic temperatures. The basalt-H2O-CO2 macros in VOLATILECALC are capable of calculating melt-vapor solubility over a range of silicate-melt compositions by using the relationships provided by Dixon (American Mineralogist 82 (1997) 368). The output agrees well with the published solution models and experimental data for silicate melt-vapor systems for pressures below 5000 bar. ?? 2002 Elsevier Science Ltd. All rights reserved.

  10. Molecular complex morpholine-CO 2-H 2O

    NASA Astrophysics Data System (ADS)

    Jiang, Huiming; Zhang, Shufen; Xu, Yingmei

    2009-02-01

    Morpholine absorbs CO 2 and H 2O in air to form a molecular complex: morpholinium-1-morpholinecarboxylate-H 2O. The structure of the complex was characterized by X-ray single crystal diffraction, 1H NMR and FT-IR. The crystal structure was determined to be triclinic, space group P1¯ with a = 6.494(2) Å, b = 8.098(4) Å, c = 13.533(4) Å, α = 96.99(3)°, β = 102.57(2)°, γ = 104.15(3)°, Z = 2. The complex is stabilized via three hydrogen bonds between the three components, N…O electrostatic attraction and O…O interaction (electron transfer). Due to electron transfer of the carbamate ion, the oxygen atom in water molecule is strongly negatively charged and the O sbnd H bond is considerably shorter than that of free water molecules. The formation of the molecular complex is a reversible process and will decompose upon heating. The mechanism of formation and stabilization is further investigated herein.

  11. Competition between H2O and (H2O)2 reactions with CH2OO/CH3CHOO.

    PubMed

    Lin, Liang-Chun; Chang, Hung-Tzu; Chang, Chien-Hsun; Chao, Wen; Smith, Mica C; Chang, Chun-Hung; Jr-Min Lin, Jim; Takahashi, Kaito

    2016-02-14

    In this study, we performed ab initio calculations and obtained the bimolecular rate coefficients for the CH2OO/CH3CHOO reactions with H2O/(H2O)2. The energies were calculated with QCISD(T)/CBS//B3LYP/6-311+G(2d,2p) and the partition functions were estimated with anharmonic vibrational corrections by using the second order perturbation theory. Furthermore, we directly measured the rate of the CH2OO reaction with water vapor at high temperatures (348 and 358 K) to reveal the contribution of the water monomer in the CH2OO decay kinetics. We found that the theoretical rate coefficients reproduce the experimental results of CH2OO for a wide range of temperatures. For anti- (syn-) CH3CHOO, we obtained theoretical rate coefficients of 1.60 × 10(-11) (2.56 × 10(-14)) and 3.40 × 10(-14) (1.98 × 10(-19)) cm(3) s(-1) for water dimer and monomer reactions at room temperature. From the detailed analysis of the quantum chemistry and approximations for the thermochemistry calculations, we conclude that our calculated values would be within a factor of 3 of the correct values. Furthermore, at [H2O] = 1 × 10(17) to 5 × 10(17) cm(-3), we estimate that the effective first-order rate coefficients for CH2OO, anti- and syn-CH3CHOO reactions with water vapor will be ∼10(3), ∼10(4), and ∼10(1) s(-1), respectively. Thereby, for Criegee intermediates with a hydrogen atom on the same side as the terminal oxygen atom, the reaction with water vapor will likely dominate the removal processes of these CIs in the atmosphere. PMID:26797528

  12. H2-O2 auxiliary power unit for space shuttle vehicles

    NASA Technical Reports Server (NTRS)

    Joyce, J. P.; Beremand, D. G.; Cameron, H. M.; Jefferies, K. S.

    1973-01-01

    A program to establish technology readiness of hydrogen-oxygen (H2-O2) auxiliary power units for use on board the space shuttle orbiter vehicle is discussed. Fundamental objectives include experimentally establishing an acceptable propellant flow control method, verification of combustor stability, and adequate thermal management. An initial APU configuration with recycled hydrogen flow has been studied and revised towards greater simplicity and scaling ease. The selected APU is a recuperated open-cycle, turbine-driven unit. Series flow of cryogenic hydrogen removes internally-generated heat and from the hydraulic system. Steady-state test of the combustor has been successful.

  13. LiOH - H2O2 - H2O trinary system study for the selection of optimal conditions of lithium peroxide synthesis

    NASA Astrophysics Data System (ADS)

    Nefedov, R. A.; Ferapontov, Yu A.; Kozlova, N. P.

    2016-01-01

    Using solubility method the decay kinetics of peroxide products contained in liquid phase of LiOH - H2O2 - H2O trinary system with 2 to 6% by wt hydrogen peroxide content in liquid phase in 21 to 33 °C temperature range has been studied. Conducted studies have allowed to determine temperature and concentration limits of solid phase existence of Li2O2·H2O content, distinctness of which has been confirmed using chemical and qualitative X- ray phase analysis. Stabilizing effect of solid phase of Li2O2·H2O content on hydrogen peroxide decay contained in liquid phase of LiOH - H2O2 - H2O trinary system under conditions of experiments conducted has been shown.

  14. ALA Inhibits ABA-induced Stomatal Closure via Reducing H2O2 and Ca(2+) Levels in Guard Cells.

    PubMed

    An, Yuyan; Liu, Longbo; Chen, Linghui; Wang, Liangju

    2016-01-01

    5-Aminolevulinic acid (ALA), a newly proved natural plant growth regulator, is well known to improve plant photosynthesis under both normal and stressful conditions. However, its underlying mechanism remains largely unknown. Stomatal closure is one of the major limiting factors for photosynthesis and abscisic acid (ABA) is the most important hormone in provoking stomatal closing. Here, we showed that ALA significantly inhibited ABA-induced stomatal closure using wild-type and ALA-overproducing transgenic Arabidopsis (YHem1). We found that ALA decreased ABA-induced H2O2 and cytosolic Ca(2+) accumulation in guard cells with stomatal bioassay, laser-scanning confocal microscopy and pharmacological methods. The inhibitory effect of ALA on ABA-induced stomatal closure was similar to that of AsA (an important reducing substrate for H2O2 removal), CAT (a H2O2-scavenging enzyme), DPI (an inhibitor of the H2O2-generating NADPH oxidase), EGTA (a Ca-chelating agent), and AlCl3 (an inhibitor of calcium channel). Furthermore, ALA inhibited exogenous H2O2- or Ca(2+)-induced stomatal closure. Taken together, we conclude that ALA inhibits ABA-induced stomatal closure via reducing H2O2, probably by scavenging, and Ca(2+) levels in guard cells. Moreover, the inhibitive effect of ALA on ABA-induced stomatal closure was further confirmed in the whole plant. Finally, we demonstrated that ALA inhibits stomatal closing, but significantly improves plant drought tolerance. Our results provide valuable information for the promotion of plant production and development of a sustainable low-carbon society. PMID:27148309

  15. ALA Inhibits ABA-induced Stomatal Closure via Reducing H2O2 and Ca2+ Levels in Guard Cells

    PubMed Central

    An, Yuyan; Liu, Longbo; Chen, Linghui; Wang, Liangju

    2016-01-01

    5-Aminolevulinic acid (ALA), a newly proved natural plant growth regulator, is well known to improve plant photosynthesis under both normal and stressful conditions. However, its underlying mechanism remains largely unknown. Stomatal closure is one of the major limiting factors for photosynthesis and abscisic acid (ABA) is the most important hormone in provoking stomatal closing. Here, we showed that ALA significantly inhibited ABA-induced stomatal closure using wild-type and ALA-overproducing transgenic Arabidopsis (YHem1). We found that ALA decreased ABA-induced H2O2 and cytosolic Ca2+ accumulation in guard cells with stomatal bioassay, laser-scanning confocal microscopy and pharmacological methods. The inhibitory effect of ALA on ABA-induced stomatal closure was similar to that of AsA (an important reducing substrate for H2O2 removal), CAT (a H2O2-scavenging enzyme), DPI (an inhibitor of the H2O2-generating NADPH oxidase), EGTA (a Ca-chelating agent), and AlCl3 (an inhibitor of calcium channel). Furthermore, ALA inhibited exogenous H2O2- or Ca2+-induced stomatal closure. Taken together, we conclude that ALA inhibits ABA-induced stomatal closure via reducing H2O2, probably by scavenging, and Ca2+ levels in guard cells. Moreover, the inhibitive effect of ALA on ABA-induced stomatal closure was further confirmed in the whole plant. Finally, we demonstrated that ALA inhibits stomatal closing, but significantly improves plant drought tolerance. Our results provide valuable information for the promotion of plant production and development of a sustainable low-carbon society. PMID:27148309

  16. Relationship between NaCl- and H2O2-Induced Cytosolic Ca2+ Increases in Response to Stress in Arabidopsis

    PubMed Central

    Ye, Rui; Xue, Yan; Chen, Amelia; An, Lizhe; Pei, Zhen-Ming

    2013-01-01

    Salinity is among the environmental factors that affect plant growth and development and constrain agricultural productivity. Salinity stress triggers increases in cytosolic free Ca2+ concentration ([Ca2+]i) via Ca2+ influx across the plasma membrane. Salinity stress, as well as other stresses, induces the production of reactive oxygen species (ROS). It is well established that ROS also triggers increases in [Ca2+]i. However, the relationship and interaction between salinity stress-induced [Ca2+]i increases and ROS-induced [Ca2+]i increases remain poorly understood. Using an aequorin-based Ca2+ imaging assay we have analyzed [Ca2+]i changes in response to NaCl and H2O2 treatments in Arabidopsis thaliana. We found that NaCl and H2O2 together induced larger increases in [Ca2+]i in Arabidopsis seedlings than either NaCl or H2O2 alone, suggesting an additive effect on [Ca2+]i increases. Following a pre-treatment with either NaCl or H2O2, the subsequent elevation of [Ca2+]i in response to a second treatment with either NaCl or H2O2 was significantly reduced. Furthermore, the NaCl pre-treatment suppressed the elevation of [Ca2+]i seen with a second NaCl treatment more than that seen with a second treatment of H2O2. A similar response was seen when the initial treatment was with H2O2; subsequent addition of H2O2 led to less of an increase in [Ca2+]i than did addition of NaCl. These results imply that NaCl-gated Ca2+ channels and H2O2-gated Ca2+ channels may differ, and also suggest that NaCl- and H2O2-evoked [Ca2+]i may reduce the potency of both NaCl and H2O2 in triggering [Ca2+]i increases, highlighting a feedback mechanism. Alternatively, NaCl and H2O2 may activate the same Ca2+ permeable channel, which is expressed in different types of cells and/or activated via different signaling pathways. PMID:24124535

  17. Utilization of membranes for H2O recycle system

    NASA Technical Reports Server (NTRS)

    Ohya, H.; Oguchi, M.

    1986-01-01

    Conceptual studies of closed ecological life support systems (CELSS) carried out at NAL in Japan for a water recycle system using membranes are reviewed. The system will treat water from shower room, urine, impure condensation from gas recycle system, and so on. The H2O recycle system is composed of prefilter, ultrafiltration membrane, reverse osmosis membrane, and distillator. Some results are shown for a bullet train of toilet-flushing water recycle equipment with an ultraviltration membrane module. The constant value of the permeation rate with a 4.7 square meters of module is about 70 1/h after 500th of operation. Thermovaporization with porous polytetrafluorocarbon membrane is also proposed to replce the distillator.

  18. Intermolecular potential for thermal H2O-He collisions

    NASA Technical Reports Server (NTRS)

    Palma, Amedeo; Green, Sheldon; Defrees, D. J.; Mclean, A. D.

    1988-01-01

    Theoretical potentials for rotational excitation of H2O by He were constructed via several methods, all of which start with a large basis set SCF interaction. The semiempirical Hartree-Fock with damped dispersion model adds a damped long-range attraction with parameters adjusted to fit experimental total differential cross sections. Purely ab initio potentials add correlation energies obtained via perturbation theory (MP2 and MP4) or a variational method (ICF1). Scattering calculations were performed on all surfaces to compare wih available beam scattering and pressure broadening data and to assess sensitivity of state-to-state rates to uncertainties in the potential. From comparison with the limited experimental data, the ICF1 surface appears to be marginally better than the MP4 surface. Thermal rates calculated from this surface should be accurate to better than 50 percent, at least for the larger, more important rates.

  19. H2O at the Phoenix landing site.

    PubMed

    Smith, P H; Tamppari, L K; Arvidson, R E; Bass, D; Blaney, D; Boynton, W V; Carswell, A; Catling, D C; Clark, B C; Duck, T; Dejong, E; Fisher, D; Goetz, W; Gunnlaugsson, H P; Hecht, M H; Hipkin, V; Hoffman, J; Hviid, S F; Keller, H U; Kounaves, S P; Lange, C F; Lemmon, M T; Madsen, M B; Markiewicz, W J; Marshall, J; McKay, C P; Mellon, M T; Ming, D W; Morris, R V; Pike, W T; Renno, N; Staufer, U; Stoker, C; Taylor, P; Whiteway, J A; Zent, A P

    2009-07-01

    The Phoenix mission investigated patterned ground and weather in the northern arctic region of Mars for 5 months starting 25 May 2008 (solar longitude between 76.5 degrees and 148 degrees ). A shallow ice table was uncovered by the robotic arm in the center and edge of a nearby polygon at depths of 5 to 18 centimeters. In late summer, snowfall and frost blanketed the surface at night; H(2)O ice and vapor constantly interacted with the soil. The soil was alkaline (pH = 7.7) and contained CaCO(3), aqueous minerals, and salts up to several weight percent in the indurated surface soil. Their formation likely required the presence of water. PMID:19574383

  20. First Principle Predictions of Isotopic Shifts in H2O

    NASA Technical Reports Server (NTRS)

    Schwenke, David W.; Kwak, Dochan (Technical Monitor)

    2002-01-01

    We compute isotope independent first and second order corrections to the Born-Oppenheimer approximation for water and use them to predict isotopic shifts. For the diagonal correction, we use icMRCI wavefunctions and derivatives with respect to mass dependent, internal coordinates to generate the mass independent correction functions. For the non-adiabatic correction, we use scaled SCF/CIS wave functions and a generalization of the Handy method to obtain mass independent correction functions. We find that including the non-adiabatic correction gives significantly improved results compared to just including the diagonal correction when the Born-Oppenheimer potential energy surface is optimized for H2O-16. The agreement with experimental results for deuterium and tritium containing isotopes is nearly as good as our best empirical correction, however, the present correction is expected to be more reliable for higher, uncharacterized levels.

  1. Infrared spectrum and predissociation dynamics of H2O+ -Ar.

    PubMed

    Dopfer, O; Engel, V

    2004-12-22

    The infrared (IR) spectrum and vibrational predissociation of the proton-bound H(2)O(+)-Ar ionic complex are investigated within an ab initio and quantum dynamical study. For this purpose, a two-dimensional potential energy surface (2D PES) is determined as a function of the HO-H and OH-Ar coordinates. This PES is then employed in a wave-packet calculation to determine spectral properties of the system and to calculate the IR absorption spectrum. The vibrational energy levels and relative IR intensities agree well with the experimental spectrum reported earlier. On the other hand, the predissociation lifetimes in the nanosecond regime derived from the 2D PES are in disagreement with the experimental observations, indicating the importance of the neglected degrees of freedom for a correct description of the dynamics of the complex. PMID:15606253

  2. Ferroelectricity in high-density H2O ice.

    PubMed

    Caracas, Razvan; Hemley, Russell J

    2015-04-01

    The origin of longstanding anomalies in experimental studies of the dense solid phases of H2O ices VII, VIII, and X is examined using a combination of first-principles theoretical methods. We find that a ferroelectric variant of ice VIII is energetically competitive with the established antiferroelectric form under pressure. The existence of domains of the ferroelectric form within anti-ferroelectric ice can explain previously observed splittings in x-ray diffraction data. The ferroelectric form is stabilized by density and is accompanied by the onset of spontaneous polarization. The presence of local electric fields triggers the preferential parallel orientation of the water molecules in the structure, which could be stabilized in bulk using new high-pressure techniques. PMID:25854247

  3. Observations of H2O in Titan's atmosphere with Herschel

    NASA Astrophysics Data System (ADS)

    Moreno, R.; Lellouch, E.; Lara, L. M.; Courtin, R.; Hartogh, P.; Rengel, M.

    2012-04-01

    Disk averaged observations of several H2O far infrared lines in Titan’s atmosphere were performed with the Herschel Space Observatory, as part of the guaranteed time key program "Water and related chemistry in the Solar System" (HssO, see Hartogh et al 2011). Two instruments were used: (i) HIFI, a heterodyne instrument (R~ 106 ) in the sub-millimeter, which measured the H2O(110-101) rotational transition at 557 GHz on June 10 and Dec. 31, 2010 (ii) PACS, a photoconductor spectrometer (R~103) which measured three water lines at 108.1, 75.4 and 66.4 microns on June 22, 2010. Additional PACS measurements at 66.4 microns on Dec. 15 and 22, 2010 and on July 09, 2011, do not show any significant line intensity variation with time, nor between the leading/trailing sides (i.e. longitude). Spectra were analyzed with a line-by-line radiative transfer code accounting for spherical geometry (Moreno et al. 2011). This model considers the H2O molecular opacity from JPL catalog (Pickett et al. 1998) and also includes collision-induced opacities N2-N2, N2-CH4 and CH4-CH4 (Borysow and Frommhold 1986, 1987, Borysow and Tang 1993). Far infrared aerosol opacities derived by CIRS were included, following Anderson and Samuelson (2011) for their vertical distribution and spectral dependencies. Analysis of the 557 GHz narrow line (FWHM ~ 2 MHz) indicates that it originates at altitudes above 300 km, while lines measured with PACS probe mainly deeper levels (80-150 km). The HIFI and PACS observations are fitted simultaneously, considering a vertical distribution of H2O mixing ratio which follows a power law dependency q=q0(P/P0)n, where q0 is the mixing ratio at some reference pressure level P0, taken near the expected condensation level. Model fits will be presented, and compared with previously proposed H2O vertical distributions. We show in particular that both the steep profile proposed by Lara et al. (1996) (and adopted by Coustenis et al. (1998) to model the first detection of H2O

  4. Opening the shaker K+ channel with hanatoxin.

    PubMed

    Milescu, Mirela; Lee, Hwa C; Bae, Chan Hyung; Kim, Jae Il; Swartz, Kenton J

    2013-02-01

    Voltage-activated ion channels open and close in response to changes in membrane voltage, a property that is fundamental to the roles of these channels in electrical signaling. Protein toxins from venomous organisms commonly target the S1-S4 voltage-sensing domains in these channels and modify their gating properties. Studies on the interaction of hanatoxin with the Kv2.1 channel show that this tarantula toxin interacts with the S1-S4 domain and inhibits opening by stabilizing a closed state. Here we investigated the interaction of hanatoxin with the Shaker Kv channel, a voltage-activated channel that has been extensively studied with biophysical approaches. In contrast to what is observed in the Kv2.1 channel, we find that hanatoxin shifts the conductance-voltage relation to negative voltages, making it easier to open the channel with membrane depolarization. Although these actions of the toxin are subtle in the wild-type channel, strengthening the toxin-channel interaction with mutations in the S3b helix of the S1-S4 domain enhances toxin affinity and causes large shifts in the conductance-voltage relationship. Using a range of previously characterized mutants of the Shaker Kv channel, we find that hanatoxin stabilizes an activated conformation of the voltage sensors, in addition to promoting opening through an effect on the final opening transition. Chimeras in which S3b-S4 paddle motifs are transferred between Kv2.1 and Shaker Kv channels, as well as experiments with the related tarantula toxin GxTx-1E, lead us to conclude that the actions of tarantula toxins are not simply a product of where they bind to the channel, but that fine structural details of the toxin-channel interface determine whether a toxin is an inhibitor or opener. PMID:23359283

  5. Melatonin reverses H2 O2 -induced premature senescence in mesenchymal stem cells via the SIRT1-dependent pathway.

    PubMed

    Zhou, Long; Chen, Xi; Liu, Tao; Gong, Yihong; Chen, Sijin; Pan, Guoqing; Cui, Wenguo; Luo, Zong-Ping; Pei, Ming; Yang, Huilin; He, Fan

    2015-09-01

    Mesenchymal stem cells (MSCs) represent an attractive source for stem cell-based regenerative therapy, but they are vulnerable to oxidative stress-induced premature senescence in pathological conditions. We previously reported antioxidant and antiarthritic effects of melatonin on MSCs against proinflammatory cytokines. In this study, we hypothesized that melatonin could protect MSCs from premature senescence induced by hydrogen peroxide (H2 O2 ) via the silent information regulator type 1 (SIRT1)-dependent pathway. In response to H2 O2 at a sublethal concentration of 200 μm, human bone marrow-derived MSCs (BM-MSCs) underwent growth arrest and cellular senescence. Treatment with melatonin before H2 O2 exposure cannot significantly prevent premature senescence; however, treatment with melatonin subsequent to H2 O2 exposure successfully reversed the senescent phenotypes of BM-MSCs in a dose-dependent manner. This result was made evident by improved cell proliferation, decreased senescence-associated β-galactosidase activity, and the improved entry of proliferating cells into the S phase. In addition, treatment with 100 μm melatonin restored the osteogenic differentiation potential of BM-MSCs that was inhibited by H2 O2 -induced premature senescence. We also found that melatonin attenuated the H2 O2 -stimulated phosphorylation of p38 mitogen-activated protein kinase, decreased expression of the senescence-associated protein p16(INK) (4α) , and increased SIRT1. Further molecular experiments revealed that luzindole, a nonselective antagonist of melatonin receptors, blocked melatonin-mediated antisenescence effects. Inhibition of SIRT1 by sirtinol counteracted the protective effects of melatonin, suggesting that melatonin reversed the senescence in cells through the SIRT1-dependent pathway. Together, these findings lay new ground for understanding oxidative stress-induced premature senescence and open perspectives for therapeutic applications of melatonin in stem cell

  6. A HIFI view on circumstellar H2O in M-type AGB stars: radiative transfer, velocity profiles, and H2O line cooling

    NASA Astrophysics Data System (ADS)

    Maercker, M.; Danilovich, T.; Olofsson, H.; De Beck, E.; Justtanont, K.; Lombaert, R.; Royer, P.

    2016-06-01

    Aims: We aim to constrain the temperature and velocity structures, and H2O abundances in the winds of a sample of M-type asymptotic giant branch (AGB) stars. We further aim to determine the effect of H2O line cooling on the energy balance in the inner circumstellar envelope. Methods: We use two radiative-transfer codes to model molecular emission lines of CO and H2O towards four M-type AGB stars. We focus on spectrally resolved observations of CO and H2O from HIFI aboard the Herschel Space Observatory. The observations are complemented by ground-based CO observations, and spectrally unresolved CO and H2O observations with PACS aboard Herschel. The observed line profiles constrain the velocity structure throughout the circumstellar envelopes (CSEs), while the CO intensities constrain the temperature structure in the CSEs. The H2O observations constrain the o-H2O and p-H2O abundances relative to H2. Finally, the radiative-transfer modelling allows to solve the energy balance in the CSE, in principle including also H2O line cooling. Results: The fits to the line profiles only set moderate constraints on the velocity profile, indicating shallower acceleration profiles in the winds of M-type AGB stars than predicted by dynamical models, while the CO observations effectively constrain the temperature structure. Including H2O line cooling in the energy balance was only possible for the low-mass-loss-rate objects in the sample, and required an ad hoc adjustment of the dust velocity profile in order to counteract extreme cooling in the inner CSE. H2O line cooling was therefore excluded from the models. The constraints set on the temperature profile by the CO lines nevertheless allowed us to derive H2O abundances. The derived H2O abundances confirm previous estimates and are consistent with chemical models. However, the uncertainties in the derived abundances are relatively large, in particular for p-H2O, and consequently the derived o/p-H2O ratios are not well constrained.

  7. I + (H2O)2 → HI + (H2O)OH Forward and Reverse Reactions. CCSD(T) Studies Including Spin-Orbit Coupling.

    PubMed

    Wang, Hui; Li, Guoliang; Li, Qian-Shu; Xie, Yaoming; Schaefer, Henry F

    2016-03-01

    The potential energy profile for the atomic iodine plus water dimer reaction I + (H2O)2 → HI + (H2O)OH has been explored using the "Gold Standard" CCSD(T) method with quadruple-ζ correlation-consistent basis sets. The corresponding information for the reverse reaction HI + (H2O)OH → I + (H2O)2 is also derived. Both zero-point vibrational energies (ZPVEs) and spin-orbit (SO) coupling are considered, and these notably alter the classical energetics. On the basis of the CCSD(T)/cc-pVQZ-PP results, including ZPVE and SO coupling, the forward reaction is found to be endothermic by 47.4 kcal/mol, implying a significant exothermicity for the reverse reaction. The entrance complex I···(H2O)2 is bound by 1.8 kcal/mol, and this dissociation energy is significantly affected by SO coupling. The reaction barrier lies 45.1 kcal/mol higher than the reactants. The exit complex HI···(H2O)OH is bound by 3.0 kcal/mol relative to the asymptotic limit. At every level of theory, the reverse reaction HI + (H2O)OH → I + (H2O)2 proceeds without a barrier. Compared with the analogous water monomer reaction I + H2O → HI + OH, the additional water molecule reduces the relative energies of the entrance stationary point, transition state, and exit complex by 3-5 kcal/mol. The I + (H2O)2 reaction is related to the valence isoelectronic bromine and chlorine reactions but is distinctly different from the F + (H2O)2 system. PMID:26562487

  8. Simultaneous mapping of H 2O and H 2O 2 on Mars from infrared high-resolution imaging spectroscopy

    NASA Astrophysics Data System (ADS)

    Encrenaz, T.; Greathouse, T. K.; Richter, M. J.; Bézard, B.; Fouchet, T.; Lefèvre, F.; Montmessin, F.; Forget, F.; Lebonnois, S.; Atreya, S. K.

    2008-06-01

    New maps of martian water vapor and hydrogen peroxide have been obtained in November-December 2005, using the Texas Echelon Cross Echelle Spectrograph (TEXES) at the NASA Infra Red Telescope facility (IRTF) at Mauna Kea Observatory. The solar longitude L was 332° (end of southern summer). Data have been obtained at 1235-1243 cm -1, with a spectral resolution of 0.016 cm -1 ( R=8×10). The mean water vapor mixing ratio in the region [0°-55° S; 345°-45° W], at the evening limb, is 150±50 ppm (corresponding to a column density of 8.3±2.8 pr-μm). The mean water vapor abundance derived from our measurements is in global overall agreement with the TES and Mars Express results, as well as the GCM models, however its spatial distribution looks different from the GCM predictions, with evidence for an enhancement at low latitudes toward the evening side. The inferred mean H 2O 2 abundance is 15±10 ppb, which is significantly lower than the June 2003 result [Encrenaz, T., Bézard, B., Greathouse, T.K., Richter, M.J., Lacy, J.H., Atreya, S.K., Wong, A.S., Lebonnois, S., Lefèvre, F., Forget, F., 2004. Icarus 170, 424-429] and lower than expected from the photochemical models, taking in account the change in season. Its spatial distribution shows some similarities with the map predicted by the GCM but the discrepancy in the H 2O 2 abundance remains to be understood and modeled.

  9. Self-sufficing H2O2-responsive nanocarriers through tumor-specific H2O2 production for synergistic oxidation-chemotherapy.

    PubMed

    Li, Junjie; Ke, Wendong; Wang, Lei; Huang, Mingming; Yin, Wei; Zhang, Ping; Chen, Qixian; Ge, Zhishen

    2016-03-10

    One of distinct features in tumor tissues is the elevated concentration of reactive oxygen species (ROS) during tumor immortality, proliferation and metastasis. However, ROS-responsive materials are rarely utilized in the field of in vivo tumoral ROS-responsive applications due to the fact that the intrinsic ROS level in the tumors could not escalate to an adequate level that the developed materials can possibly respond. Herein, palmitoyl ascorbate (PA) as a prooxidant for hydrogen peroxide (H2O2) production in tumor tissue is strategically compiled into a H2O2-responsive camptothecin (CPT) polymer prodrug micelle, which endowed the nanocarriers with self-sufficing H2O2 stimuli in tumor tissues. Molecular oncology manifests the hallmarks of tumoral physiology with deteriorating propensity in eliminating hazardous ROS. H2O2 production was demonstrated to specifically sustain in tumors, which not only induced tumor cell apoptosis by elevated oxidation stress but also served as autochthonous H2O2 resource to trigger CPT release for chemotherapy. Excess H2O2 and released CPT could penetrate into cells efficiently, which showed synergistic cytotoxicity toward cancer cells. Systemic therapeutic trial revealed potent tumor suppression of the proposed formulation via synergistic oxidation-chemotherapy. This report represents a novel nanomedicine platform combining up-regulation of tumoral H2O2 level and self-sufficing H2O2-responsive drug release to achieve novel synergistic oxidation-chemotherapy. PMID:26806789

  10. Partial mitochondrial inhibition causes striatal dopamine release suppression and medium spiny neuron depolarization via H2O2 elevation, not ATP depletion.

    PubMed

    Bao, Li; Avshalumov, Marat V; Rice, Margaret E

    2005-10-26

    Mitochondrial dysfunction is a potential causal factor in Parkinson's disease. We show here that acute exposure to the mitochondrial complex I inhibitor rotenone (30-100 nM; 30 min) causes concentration-dependent suppression of single-pulse evoked dopamine (DA) release monitored in real time with carbon-fiber microelectrodes in guinea pig striatal slices, with no effect on DA content. Suppression of DA release was prevented by the sulfonylurea glibenclamide, implicating ATP-sensitive K+ (KATP) channels; however, tissue ATP was unaltered. Because KATP channels can be activated by hydrogen peroxide (H2O2), as well as by low ATP, we examined the involvement of rotenone-enhanced H2O2 generation. Confirming an essential role for H2O2, the inhibition of DA release by rotenone was prevented by catalase, a peroxide-scavenging enzyme. Striatal H2O2 generation during rotenone exposure was examined in individual medium spiny neurons using fluorescence imaging with dichlorofluorescein (DCF). An increase in intracellular H2O2 levels followed a similar time course to that of DA release suppression and was accompanied by cell membrane depolarization, decreased input resistance, and increased excitability. Extracellular catalase markedly attenuated the increase in DCF fluorescence and prevented rotenone-induced effects on membrane properties; membrane changes were also largely prevented by flufenamic acid, a blocker of transient receptor potential (TRP) channels. Thus, partial mitochondrial inhibition can cause functional DA denervation via H2O2 and KATP channels, without DA or ATP depletion. Furthermore, amplified H2O2 levels and TRP channel activation in striatal spiny neurons indicate potential sources of damage in these cells. Overall, these novel factors could contribute to parkinsonian motor deficits and neuronal degeneration caused by mitochondrial dysfunction. PMID:16251452

  11. A portable microfluidic-based biophotonic sensor for extracellular H2O2 measurements

    NASA Astrophysics Data System (ADS)

    Koman, V.; Suárez, G.; Santschi, Ch.; Cadarso, V. J.; Brugger, J.; von Moos, N.; Slaveykova, V. I.; Martin, O. J. F.

    2013-03-01

    In this work a portable analytical biosensor for real-time extracellular monitoring of released hydrogen peroxide (H2O2 ) is presented. The biosensor is based on the optical detection of the cytochrome c (cyt c) oxidation state. The setup consists of an integrated microscope combined with a compact spectrometer. The light being absorbed by cyt c is enhanced via multiscattering produced by random aggregates of polystyrene beads in a cross-linked cyt c matrix. Using ink-jet printing technique, the sensing elements, namely cyt c loaded polystyrene aggregates, are fabricated with high reliability in terms of repeatability of size and sensitivity. Additionally, the sensing elements are enclosed in a microfluidic channel assuring a fast and efficient analytes delivery. As an example, the effect of trace concentrations of functionalized cadmium selenide/zinc sulfide (CdSe/ZnS) core shell quantum dots on the green algae Chlamydomonas reinhardtii is investigated, showing extracellular H2O2 release with different production rates over a period of 1 hour. In conclusion, the presented portable biosensor enables the highly sensitive and non-invasive real-time monitoring of the cell metabolism of C. reinhardtii.

  12. H2O2 levels in rainwater collected in south Florida and the Bahama Islands

    NASA Technical Reports Server (NTRS)

    Zika, R.; Saltzman, E.; Chameides, W. L.; Davis, D. D.

    1982-01-01

    Measurements of H2O2 in rainwater collected in Miami, Florida, and the Bahama Islands area indicate the presence of H2O2 concentration levels ranging from 100,000 to 700,000 M. No systematic trends in H2O2 concentration were observed during an individual storm, in marked contrast to the behavior of other anions for example, NO3(-), SO4(-2), and Cl(-). The data suggest that a substantial fraction of the H2O2 found in precipitation is generated by aqueous-phase reactions within the cloudwater rather than via rainout and washout of gaseous H2O2.

  13. An Accurate Potential Energy Surface for H2O

    NASA Technical Reports Server (NTRS)

    Schwenke, David W.; Partridge, Harry; Langhoff, Stephen R. (Technical Monitor)

    1997-01-01

    We have carried out extensive high quality ab initio electronic structure calculations of the ground state potential energy surface (PES) and dipole moment function (DMF) for H2O. A small adjustment is made to the PES to improve the agreement of line positions from theory and experiment. The theoretical line positions are obtained from variational ro-vibrational calculations using the exact kinetic energy operator. For the lines being fitted, the root-mean-square error was reduced from 6.9 to 0.08 /cm. We were then able to match 30,092 of the 30,117 lines from the HITRAN 96 data base to theoretical lines, and 80% of the line positions differed less than 0.1 /cm. About 3% of the line positions in the experimental data base appear to be incorrect. Theory predicts the existence of many additional weak lines with intensities above the cutoff used in the data base. To obtain results of similar accuracy for HDO, a mass dependent correction to the PH is introduced and is parameterized by simultaneously fitting line positions for HDO and D2O. The mass dependent PH has good predictive value for T2O and HTO. Nonadiabatic effects are not explicitly included. Line strengths for vibrational bands summed over rotational levels usually agree well between theory and experiment, but individual line strengths can differ greatly. A high temperature line list containing about 380 million lines has been generated using the present PES and DMF

  14. Determination of the ortho to para ratio of H2Cl+ and H2O+ from submillimeter observations.

    PubMed

    Gerin, Maryvonne; de Luca, Massimo; Lis, Dariusz C; Kramer, Carsten; Navarro, Santiago; Neufeld, David; Indriolo, Nick; Godard, Benjamin; Le Petit, Franck; Peng, Ruisheng; Phillips, Thomas G; Roueff, Evelyne

    2013-10-01

    The opening of the submillimeter sky with the Herschel Space Observatory has led to the detection of new interstellar molecular ions, H2O(+), H2Cl(+), and HCl(+), which are important intermediates in the synthesis of water vapor and hydrogen chloride. In this paper, we report new observations of H2O(+) and H2Cl(+) performed with both Herschel and ground-based telescopes, to determine the abundances of their ortho and para forms separately and derive the ortho-to-para ratio. At the achieved signal-to-noise ratio, the observations are consistent with an ortho-to-para ratios of 3 for both H2O(+) and H2Cl(+), in all velocity components detected along the lines-of-sight to the massive star-forming regions W31C and W49N. We discuss the mechanisms that contribute to establishing the observed ortho-to-para ratio and point to the need for a better understanding of chemical reactions, which are important for establishing the H2O(+) and H2Cl(+) ortho-to-para ratios. PMID:23869910

  15. Novel design of an enclosed CO2/H2O gas analyser for eddy covariance flux measurements

    NASA Astrophysics Data System (ADS)

    Burba, G. G.; McDermitt, D. K.; Anderson, D. J.; Furtaw, M. D.; Eckles, R. D.

    2010-11-01

    ABSTRACT This study describes design and field performance of a new enclosed CO2/H2O gas analyser, LI-7200. Unlike present closed-path analysers, this new instrument is designed for operation with short intake tubes, with the intention to maximize strengths and to minimize weaknesses of both traditional open-path and closed-path approaches. The study provides description of the instrument, shows the principles of its operation, and explains advantages of a new design. Field results are provided from three field experiments with the prototypes, and cover such parameters as high frequency air temperature and pressure fluctuations inside the sampling cell versus ambient conditions, instantaneous concentrations and cospectra for CO2 and H2O in comparison with open-path instrument, and eddy covariance hourly CO2 and H2O fluxes in comparison with both open-path and closed-path instruments. Field data loss inventory is also provided in comparison with open-path and closed-path gas analysers. The new enclosed design results in little data loss during precipitation and icing, similar to the closed-path design, but with a low power consumption and high field stability comparable to open-path instruments.

  16. Seasonal variation of HDO/H2O ratio in the atmosphere of Mars observed by SUBARU/IRCS and MEX/PFS

    NASA Astrophysics Data System (ADS)

    Aoki, S.; Giuranna, M.; Sindoni, G.; Nakagawa, H.; Sagawa, H.; Aronica, A.; Kasaba, Y.

    2014-04-01

    We present the seasonal variation of HDO/H2O ratio caused by sublimation-condensation process in a global view of the Martian water cycle. It is well-known that water on Mars exists as vapor (in the atmosphere) and ice (ice clouds, surface ice, and possibly subsurface ice), and its phase change occurs via sublimationcondensation process. Mapping of HDO/H2O ratio could provide the information to discriminate these physical processes. The key theory here is that the condensation process induces an isotopic fractionation on water vapor due to the difference in their vapor pressures, i.e., the heavier HDO vapor preferentially condensates compared to the lighter H2O vapor [1], whereas there is no isotope fractionation during sublimation due to very slow molecular diffusion within ice. Indeed, general Circulation Model (GCM) predicted that HDO/H2O ratio changes by a factor of 2 due to condensationinduced fractionation in the polar region [2]. So far, distribution of HDO/H2O ratio has been investigated by only a few ground-based observations. They found that HDO/H2O ratio was not constant but varied in the range between 2 and 10 wrt VSMOW [3,4]. In addition, latitudinal gradients of HDO/H2O ratio probably due to condensation of HDO vapor over high latitude at the middle of the northern spring was suggested [4]. However, it is still open question that what causes the un-uniform distribution of the HDO/H2O ratio due to lack of its seasonal behavior. In order to answer the question, we investigated the HDO/H2O ratio at two different seasons, the northern spring (Ls=52°) and summer (Ls=96°), and revealed the seasonal variation. The HDO/H2O ratio was retrieved from groundbased observations by high-dispersion echelle spectroscopy of Infrared Camera and Spectrograph (IRCS) [5] onboard Subaru telescope and the coordinated joint observation by Planetary Fourier Spectrometer (PFS) [6] onboard Mars Express (MEX) spacecraft. The observations were performed at middle of the northern

  17. The open pore conformation of potassium channels

    NASA Astrophysics Data System (ADS)

    Jiang, Youxing; Lee, Alice; Chen, Jiayun; Cadene, Martine; Chait, Brian T.; MacKinnon, Roderick

    2002-05-01

    Living cells regulate the activity of their ion channels through a process known as gating. To open the pore, protein conformational changes must occur within a channel's membrane-spanning ion pathway. KcsA and MthK, closed and opened K+ channels, respectively, reveal how such gating transitions occur. Pore-lining `inner' helices contain a `gating hinge' that bends by approximately 30°. In a straight conformation four inner helices form a bundle, closing the pore near its intracellular surface. In a bent configuration the inner helices splay open creating a wide (12Å) entryway. Amino-acid sequence conservation suggests a common structural basis for gating in a wide range of K+ channels, both ligand- and voltage-gated. The open conformation favours high conduction by compressing the membrane field to the selectivity filter, and also permits large organic cations and inactivation peptides to enter the pore from the intracellular solution.

  18. Photoelectron spectroscopic study of the hydrated nucleoside anions: Uridine-(H2O)n=0-2, cytidine-(H2O)n=0-2, and thymidine-(H2O)n=0,1

    NASA Astrophysics Data System (ADS)

    Li, Xiang; Wang, Haopeng; Bowen, Kit H.

    2010-10-01

    The hydrated nucleoside anions, uridine-(H2O)n=0-2, cytidine-(H2O)n=0-2, and thymidine-(H2O)n=0,1, have been prepared in beams and studied by anion photoelectron spectroscopy in order to investigate the effects of a microhydrated environment on parent nucleoside anions. Vertical detachment energies (VDEs) were measured for all eight anions, and from these, estimates were made for five sequential anion hydration energies. Excellent agreement was found between our measured VDE value for thymidine-(H2O)1 and its calculated value in the companion article by S. Kim and H. F. Schaefer III.

  19. Visible spectrum photofragmentation of O3-(H2O)n, n ≤ 16

    NASA Astrophysics Data System (ADS)

    Lehman, Julia H.; Lineberger, W. Carl

    2014-10-01

    Photofragmentation of ozonide solvated in water clusters, O3-(H2O)n, n ≤ 16, has been studied as a function of photon energy as well as the degree of solvation. Using mass selection, the effect of the presence of the solvent molecule on the O3- photodissociation process is assessed one solvent molecule at a time. The O3- acts as a visible light chromophore within the water cluster, namely the O3-(H2O) total photodissociation cross-section exhibits generally the same photon energy dependence as isolated O3- throughout the visible wavelength range studied (430-620 nm). With the addition of a single solvent molecule, new photodissociation pathways are opened, including the production of recombined O3-. As the degree of solvation of the parent anion increases, recombination to O3--based products accounts for close to 40% of photoproducts by n = 16. The remainder of the photoproducts exist as O--based; no O2--based products are observed. Upper bounds on the O3- solvation energy (530 meV) and the O--OO bond dissociation energy in the cluster (1.06 eV) are derived.

  20. Comparison of the efficiency of *OH radical formation during ozonation and the advanced oxidation processes O3/H2O2 and UV/H2O2.

    PubMed

    Rosenfeldt, Erik J; Linden, Karl G; Canonica, Silvio; von Gunten, Urs

    2006-12-01

    Comparison of advanced oxidation processes (AOPs) can be difficult due to physical and chemical differences in the fundamental processes used to produce OH radicals. This study compares the ability of several AOPs, including ozone, ozone+H2O2, low pressure UV (LP)+H2O2, and medium pressure UV (MP)+H2O2 in terms of energy required to produce OH radicals. Bench scale OH radical formation data was generated for each AOP using para-chlorobenzoic acid (pCBA) as an OH radical probe compound in three waters, Lake Greifensee water, Lake Zurich water, and a simulated groundwater. Ozone-based AOPs were found to be more energy efficient than the UV/H2O2 process at all H2O2 levels, and the addition of H2O2 in equimolar concentration resulted in 35% greater energy consumption over the ozone only process. Interestingly, the relatively high UV/AOP operational costs were due almost exclusively to the cost of hydrogen peroxide while the UV portion of the UV/AOP process typically accounted for less than 10 percent of the UV/AOP cost and was always less than the ozone energy cost. As the *OH radical exposure increased, the energy gap between UV/H2O2 AOP and ozone processes decreased, becoming negligible in some water quality scenarios. PMID:17078993

  1. Ultrafast phosphate hydration dynamics in bulk H2O

    NASA Astrophysics Data System (ADS)

    Costard, Rene; Tyborski, Tobias; Fingerhut, Benjamin P.; Elsaesser, Thomas

    2015-06-01

    Phosphate vibrations serve as local probes of hydrogen bonding and structural fluctuations of hydration shells around ions. Interactions of H2PO4- ions and their aqueous environment are studied combining femtosecond 2D infrared spectroscopy, ab-initio calculations, and hybrid quantum-classical molecular dynamics (MD) simulations. Two-dimensional infrared spectra of the symmetric ( ν S ( PO2 - ) ) and asymmetric ( ν A S ( PO2 - ) ) PO 2- stretching vibrations display nearly homogeneous lineshapes and pronounced anharmonic couplings between the two modes and with the δ(P-(OH)2) bending modes. The frequency-time correlation function derived from the 2D spectra consists of a predominant 50 fs decay and a weak constant component accounting for a residual inhomogeneous broadening. MD simulations show that the fluctuating electric field of the aqueous environment induces strong fluctuations of the ν S ( PO2 - ) and ν A S ( PO2 - ) transition frequencies with larger frequency excursions for ν A S ( PO2 - ) . The calculated frequency-time correlation function is in good agreement with the experiment. The ν ( PO2 - ) frequencies are mainly determined by polarization contributions induced by electrostatic phosphate-water interactions. H2PO4-/H2O cluster calculations reveal substantial frequency shifts and mode mixing with increasing hydration. Predicted phosphate-water hydrogen bond (HB) lifetimes have values on the order of 10 ps, substantially longer than water-water HB lifetimes. The ultrafast phosphate-water interactions observed here are in marked contrast to hydration dynamics of phospholipids where a quasi-static inhomogeneous broadening of phosphate vibrations suggests minor structural fluctuations of interfacial water.

  2. Theoretical calculations of pressure broadening coefficients for H2O perturbed by hydrogen or helium gas

    NASA Technical Reports Server (NTRS)

    Gamache, Robert R.; Pollack, James B.

    1995-01-01

    Halfwidths were calculated for H2O with H2 as a broadening gas and were estimated for He as the broadening species. The calculations used the model of Robert and Bonamy with parabolic trajectories and all relevant terms in the interaction potential. The calculations investigated the dependence of the halfwidth on the order of the atom-atom expansion, the rotational states, and the temperature in the range 200 to 400K. Finally, calculations were performed for many transitions of interest in the 5 micrometer window region of the spectrum. The resulting data will be supplied to Dr. R. Freedman for extracting accurate water mixing ratios from the analysis of the thermal channels for the Net Flux experiment on the Galileo probe.

  3. Real-time monitoring of basal H2O2 levels with peroxiredoxin-based probes.

    PubMed

    Morgan, Bruce; Van Laer, Koen; Owusu, Theresa N E; Ezeriņa, Daria; Pastor-Flores, Daniel; Amponsah, Prince Saforo; Tursch, Anja; Dick, Tobias P

    2016-06-01

    Genetically encoded probes based on the H2O2-sensing proteins OxyR and Orp1 have greatly increased the ability to detect elevated H2O2 levels in stimulated or stressed cells. However, these proteins are not sensitive enough to monitor metabolic H2O2 baseline levels. Using yeast as a platform for probe development, we developed two peroxiredoxin-based H2O2 probes, roGFP2-Tsa2ΔCR and roGFP2-Tsa2ΔCPΔCR, that afford such sensitivity. These probes are ∼50% oxidized under 'normal' unstressed conditions and are equally responsive to increases and decreases in H2O2. Hence, they permit fully dynamic, real-time measurement of basal H2O2 levels, with subcellular resolution, in living cells. We demonstrate that expression of these probes does not alter endogenous H2O2 homeostasis. The roGFP2-Tsa2ΔCR probe revealed real-time interplay between basal H2O2 levels and partial oxygen pressure. Furthermore, it exposed asymmetry in H2O2 trafficking between the cytosol and mitochondrial matrix and a strong correlation between matrix H2O2 levels and cellular growth rate. PMID:27089028

  4. Thermal Reactions of H2O2 on Icy Satellites and Small Bodies: Descent with Modification?

    NASA Technical Reports Server (NTRS)

    Hudson, Reggie L.; Loeffler, Mark J.

    2012-01-01

    Magnetospheric radiation drives surface and near-surface chemistry on Europa, but below a few meters Europa's chemistry is hidden from direct observation . As an example, surface radiation chemistry converts H2O and SO2 into H2O2 and (SO4)(sup 2-), respectively, and these species will be transported downward for possible thermally-driven reactions. However, while the infrared spectra and radiation chemistry of H2O2-containing ices are well documented, this molecule's thermally-induced solid-phase chemistry has seldom been studied. Here we report new results on thermal reactions in H2O + H2O2 + SO2 ices at 50 - 130 K. As an example of our results, we find that warming H2O + H2O2 + SO2 ices promotes SO2 oxidation to (SO4)(sup 2-). These results have implications for the survival of H2O2 as it descends, with modification, towards a subsurface ocean on Europa. We suspect that such redox chemistry may explain some of the observations related to the presence and distribution of H2O2 across Europa's surface as well as the lack of H2O2 on Ganymede and Callisto.

  5. Hydrogen peroxide (H2O2) controls axon pathfinding during zebrafish development.

    PubMed

    Gauron, Carole; Meda, Francesca; Dupont, Edmond; Albadri, Shahad; Quenech'Du, Nicole; Ipendey, Eliane; Volovitch, Michel; Del Bene, Filippo; Joliot, Alain; Rampon, Christine; Vriz, Sophie

    2016-06-15

    It is now becoming evident that hydrogen peroxide (H2O2), which is constantly produced by nearly all cells, contributes to bona fide physiological processes. However, little is known regarding the distribution and functions of H2O2 during embryonic development. To address this question, we used a dedicated genetic sensor and revealed a highly dynamic spatio-temporal pattern of H2O2 levels during zebrafish morphogenesis. The highest H2O2 levels are observed during somitogenesis and organogenesis, and these levels gradually decrease in the mature tissues. Biochemical and pharmacological approaches revealed that H2O2 distribution is mainly controlled by its enzymatic degradation. Here we show that H2O2 is enriched in different regions of the developing brain and demonstrate that it participates to axonal guidance. Retinal ganglion cell axonal projections are impaired upon H2O2 depletion and this defect is rescued by H2O2 or ectopic activation of the Hedgehog pathway. We further show that ex vivo, H2O2 directly modifies Hedgehog secretion. We propose that physiological levels of H2O2 regulate RGCs axonal growth through the modulation of Hedgehog pathway. PMID:27158028

  6. Using H2O and trace element ratios to produce a spatial map of magmatic H2O contents throughout the Trans-Mexican Volcanic Belt

    NASA Astrophysics Data System (ADS)

    Johnson, E. R.; Wallace, P. J.; Manea, V. C.

    2007-12-01

    Along with fluids, trace elements are released during dehydration of subducting sediment and altered oceanic crust. Large ion lithophile elements are typically fluid mobile, and thus may be used as tracers for fluid fluxing. We used melt inclusion H2O and trace element data from nine cinder cones across the subduction-related Michoacan-Guanajuato Volcanic Field (MGVF) of central Mexico to assess the fluid mobility of trace element species. We found correlations between H2O and Sr/La, Ba/Nb, Ba/Y, Pb/Y, Sr/Ti, suggesting that Sr, Ba, and Pb are present in fluids released from the downgoing slab. Additionally, we used regression lines for these correlations to estimate magmatic H2O for cinder cones across Mexico. We have applied the Sr/La and Sr/Ti relationships to the extensive dataset of cinder cone lava and scoria analyses from the MGVF by Hasenaka and Carmichael (1985). In order to see 2-D spatial patterns in H2O across the MGVF, we plotted the localities and the calculated H2O contents on a digital elevation model of Mexico. Initial results from this modeling show that, like our melt inclusion data, magmatic H2O contents are generally high (>3 wt%) across a broad region from the volcanic front to ~100 km behind the front. High H2O concentrations (4-6 wt%) are most abundant along the volcanic front, whereas much lower values (1-2 wt%) occur in an extensional region far behind the front. The relationship between H2O and trace element ratios can also be extended to other regions of Mexico, as the correlation between H2O/La and Sr/La is consistent to the east in the Chichinautzin Volcanic Field (Cervantes and Wallace, 2003) and to the west in the Colima Graben. Using analyses from these and other regions, we have created a spatial map of H2O contents across the Trans- Mexican Volcanic Belt, enabling us to see trends both along and across the arc. We can then use these spatial maps to relate patterns in H2O content to subduction processes such as arc migration over

  7. Hydrocalcite (CaCO3 * H2O) and Nesquehonite (MgCO3 * 3H2O) in Carbonate Scales.

    PubMed

    Marschner, H

    1969-09-12

    Hydrocalcite (CaCO(3) * H(2)O) with exactly one molecule of hydrate water is the main component of carbonate scales deposited from cold water in contact with air. When the magnesium content of the water is high, the hydrocalcite occurs together with MgCO(3) * 3H(2)O (nesquehonite). From the conditions under which hydrocalcite is transformed into calcite and aragonite, it appears that in some cases aragonite in nature may be formed by way of an intermediary of CaCO(3) * H(2)O. PMID:17779803

  8. H 2O in basalt and basaltic andesite glass inclusions from four subduction-related volcanoes

    NASA Astrophysics Data System (ADS)

    Sisson, T. W.; Layne, G. D.

    1993-06-01

    Total dissolved H 2O and major element abundances were measured in basalt and basaltic andesite glass inclusions in olivine phenocrysts from Quaternary eruptions of four subduction-related volcanoes to test the hypothesis that low-MgO high-alumina basalts contain high H 2O at depth [1] and to reveal any petrogenetically significant correlations between arc basalt compositions and H 2O contents. Total dissolved H 2O (combined molecular H 2O and OH groups) measured by ion microprobe in mafic glass inclusions from the 1974 eruption of Fuego, Guatemala, reaches 6.2 wt.%. Dissolved H 2O contents decrease in more evolved Fuego glasses. Correlations of H 2O with MgO, Na 2O, K 2O, S and Cl indicate that aqueous fluid exsolution during magma ascent forced crystallization and differentiation of residual liquids. Low-K 2O magnesian high-alumina basalt glass inclusions from the 3 ka eruption of Black Crater (Medicine Lake volcano, California) have low H 2O contents, near 0.2 wt.%, which are consistent with the MORB-like character of these and other primitive lavas of the Medicine Lake region. Basalt and basaltic andesite glass inclusions from Copco Cone and Goosenest volcano on the Cascade volcanic front north of Mt. Shasta have H 2O contents of up to 3.3 wt.%. The range of H 2O contents in Cascade mafic magmas is too large to have resulted solely from enrichment by crystallization and indicates the participation of an H 2O-rich component in magma generation or crustal-level modification. Whereas fluid-absent melting of amphibole-bearing peridotite can account for the H 2O in most mafic arc liquids, the very high H 2O/alkali ratios of the 1974 Fuego eruptives suggest that an aqueous fluid was involved in the generation of Fuego basalts.

  9. Lithium diaqua­magnesium catena-borodiphosphate(V) monohydrate, LiMg(H2O)2[BP2O8]·H2O, at 173 K

    PubMed Central

    Lin, Jin-Ru; Huang, Ya-Xi; Wu, Yu-Huan; Zhou, Yan

    2008-01-01

    The crystal structure of LiMg(H2O)2[BP2O8]·H2O consists of tubular structural units, built from tetra­hedral ∞ 1{[BP2O8]3−} borophosphate ribbons and (LiO4)n helices running along [001], which are inter­connected by MgO4(H2O)2 octa­hedra, forming a three-dimensional network structure with one-dimensional channels along [001] in which the water mol­ecules are located. The water mol­ecule in the channel is significantly displaced by up to 0.3 Å from the special position 6b (..2) to a half-occupied general position. Mg, B and one Li atom all lie on twofold axes. Of the two Li positions, one is at a special position 6b (..2), while the other is at a general position; both are only half-occupied. PMID:21202441

  10. Association-Dissociation of Glycolate Oxidase with Catalase in Rice: A Potential Switch to Modulate Intracellular H2O2 Levels.

    PubMed

    Zhang, Zhisheng; Xu, Yuanyuan; Xie, Zongwang; Li, Xiangyang; He, Zheng-Hui; Peng, Xin-Xiang

    2016-05-01

    Rapid and dynamic change in hydrogen peroxide (H2O2) levels can serve as an important signal to regulate various biological processes in plants. The change is realized by tilting the balance between its production and scavenging rates, in which membrane-associated NADPH oxidases are known to play a crucial role. Functioning independently from NADPH oxidases, glycolate oxidase (GLO) was recently demonstrated as an alternative source for H2O2 production during both gene-for-gene and non-host resistance in plants. In this study, we show that GLO physically interacts with catalase (CAT) in rice leaves, and that the interaction can be deregulated by salicylic acid (SA). Furthermore, the GLO-mediated H2O2 accumulation is synergistically enhanced by SA. Based on the well-known mechanism of substrate channeling in enzyme complexes, SA-induced H2O2 accumulation likely results from SA-induced GLO-CAT dissociation. In the GLO-CAT complex, GLO-mediated H2O2 production during photorespiration is very high, whereas the affinity of CAT for H2O2 (measured Km ≈ 43 mM) is extraordinarily low. This unique combination can further potentiate the increase in H2O2 when GLO is dissociated from CAT. Taken together, we propose that the physical association-dissociation of GLO and CAT, in response to environmental stress or stimuli, seems to serve as a specific mechanism to modulate H2O2 levels in rice. PMID:26900141

  11. Crystal structures of hydrates of simple inorganic salts. II. Water-rich calcium bromide and iodide hydrates: CaBr2 · 9H2O, CaI2 · 8H2O, CaI2 · 7H2O and CaI2 · 6.5H2O.

    PubMed

    Hennings, Erik; Schmidt, Horst; Voigt, Wolfgang

    2014-09-01

    Single crystals of calcium bromide enneahydrate, CaBr(2) · 9H2O, calcium iodide octahydrate, CaI(2) · 8H2O, calcium iodide heptahydrate, CaI(2) · 7H2O, and calcium iodide 6.5-hydrate, CaI(2) · 6.5H2O, were grown from their aqueous solutions at and below room temperature according to the solid-liquid phase diagram. The crystal structure of CaI(2) · 6.5H2O was redetermined. All four structures are built up from distorted Ca(H2O)8 antiprisms. The antiprisms of the iodide hydrate structures are connected either via trigonal-plane-sharing or edge-sharing, forming dimeric units. The antiprisms in calcium bromide enneahydrate are monomeric. PMID:25186361

  12. The Paradox of a Wet (High H2O) and Dry (Low H2O/Ce) Mantle: High Water Concentrations in Mantle Garnet Pyroxenites from Hawaii

    NASA Technical Reports Server (NTRS)

    Peslier, Anne H.; Bizimis, Michael

    2013-01-01

    Water dissolved as trace amounts in anhydrous minerals has a large influence on the melting behavior and physical properties of the mantle. The water concentration of the oceanic mantle is inferred from the analyses of Mid-Ocean Ridge Basalt (MORB) and Oceanic Island Basalt (OIB). but there is little data from actual mantle samples. Moreover, enriched mineralogies (pyroxenites, eclogites) are thought as important sources of heterogeneity in the mantle, but their water concentrations and their effect on the water budget and cycling in the mantle are virtually unknown. Here, we analyzed by FTIR water in garnet clinopyroxenite xenoliths from Salt Lake Crater, Oahu, Hawaii. These pyroxenites are high-pressure (>20kb) crystal fractionates from alkalic melts. The clinopyroxenes (cpx) have 260 to 576 ppm wt H2O, with the least differentiated samples (Mg#>0.8) in the 400-500 ppm range. Orthopyroxene (opx) contain 117-265 ppm H2O, about half of that of cpx, consistent with other natural sample studies, but lower than cpx/opx equilibrium from experimental data. The pyroxenite cpx and opx H2O concentrations are at the high-end of on-and off-craton peridotite xenolith concentrations and those of Hawaiian spinel peridotites. In contrast, garnet has extremely low water contents (<5ppm H2O). There is no correlation between H2O in cpx and lithophile element concentrations. Phlogopite is present in some samples, and its modal abundance shows a positive correlation in Mg# with cpx, implying equilibrium. However, there is no correlation between H2O concentrations and or the presence of phlogopite. These data imply that cpx and opx may be at water saturation, far lower than experimental data suggest. Reconstructed bulk rock pyroxenite H2O ranges from 200-460 ppm (average 331 +/- 75 ppm), 2 to 8 times higher than H2O estimates for the MORB source (50-200 ppm), but in the range of E-MORB, OIB and the source of rejuvenated Hawaiian magmas. The average bulk rock pyroxenite H2O/Ce is 69

  13. Direct N2H4/H2O2 Fuel Cells Powered by Nanoporous Gold Leaves

    PubMed Central

    Yan, Xiuling; Meng, Fanhui; Xie, Yun; Liu, Jianguo; Ding, Yi

    2012-01-01

    Dealloyed nanoporous gold leaves (NPGLs) are found to exhibit high electrocatalytic properties toward both hydrazine (N2H4) oxidation and hydrogen peroxide (H2O2) reduction. This observation allows the implementation of a direct hydrazine-hydrogen peroxide fuel cell (DHHPFC) based on these novel porous membrane catalysts. The effects of fuel and oxidizer flow rate, concentration and cell temperature on the performance of DHHPFC are systematically investigated. With a loading of ~0.1 mg cm−2 Au on each side, an open circuit voltage (OCV) of 1.2 V is obtained at 80°C with a maximum power density 195 mW cm−2, which is 22 times higher than that of commercial Pt/C electrocatalyst at the same noble metal loading. NPGLs thus hold great potential as effective and stable electrocatalysts for DHHPFCs. PMID:23230507

  14. Characterization of a real time H2O2 monitor for use in studies on H2O2 production by antibodies and cells.

    PubMed

    Sharma, Harish A; Balcavage, Walter X; Waite, Lee R; Johnson, Mary T; Nindl, Gabi

    2003-01-01

    It was recently shown that antibodies catalyze a reaction between water and ultraviolet light (UV) creating singlet oxygen and ultimately H2O2. Although the in vivo relevance of these antibody reactions is unclear, it is interesting that among a wide variety of non-antibody proteins tested, the T cell receptor is the only protein with similar capabilities. In clinical settings UV is believed to exert therapeutic effects by eliminating inflammatory epidermal T cells and we hypothesized that UV-triggered H2O2 production is involved in this process. To test the hypothesis we developed tools to study production of H2O2 by T cell receptors with the long-term goal of understanding, and improving, UV phototherapy. Here, we report the development of an inexpensive, real time H2O2 monitoring system having broad applicability. The detector is a Clark oxygen electrode (Pt, Ag/AgCl) modified to detect UV-driven H2O2 production. Modifications include painting the electrode black to minimize UV effects on the Ag/AgCl electrode and the use of hydrophilic, large pore Gelnots electrode membranes. Electrode current was converted to voltage and then amplified and recorded using a digital multimeter coupled to a PC. A reaction vessel with a quartz window was developed to maintain constant temperature while permitting UV irradiation of the samples. The sensitivity and specificity of the system and its use in cell-free and cell-based assays will be presented. In a cellfree system, production of H2O2 by CD3 antibodies was confirmed using our real time H2O2 monitoring method. Additionally we report the finding that splenocytes and Jurkat T cells also produce H2O2 when exposed to UV light. PMID:12724951

  15. Absolute linestrengths in the H2O2 nu6 band

    NASA Technical Reports Server (NTRS)

    May, Randy D.

    1991-01-01

    Absolute linestrengths at 295 K have been measured for selected lines in the nu6 band of H2O2 using a tunable diode-laser spectrometer. H2O2 concentrations in a flowing gas mixture were determined by ultraviolet (uv) absorption at 254 nm using a collinear infrared (ir) and uv optical arrangement. The measured linestrengths are approx. 60 percent larger than previously reported values when absorption by hot bands in H2O2 is taken into account.

  16. Comparison of genes required for H2O2 resistance in Streptococcus gordonii and Streptococcus sanguinis

    PubMed Central

    Xu, Yifan; Itzek, Andreas

    2014-01-01

    Hydrogen peroxide (H2O2) is produced by several members of the genus Streptococcus mainly through the pyruvate oxidase SpxB under aerobic growth conditions. The acute toxic nature of H2O2 raises the interesting question of how streptococci cope with intrinsically produced H2O2, which subsequently accumulates in the microenvironment and threatens the closely surrounding population. Here, we investigate the H2O2 susceptibility of oral Streptococcus gordonii and Streptococcus sanguinis and elucidate potential mechanisms of how they protect themselves from the deleterious effect of H2O2. Both organisms are considered primary colonizers and occupy the same intraoral niche making them potential targets for H2O2 produced by other species. We demonstrate that S. gordonii produces relatively more H2O2 and has a greater ability for resistance to H2O2 stress. Functional studies show that, unlike in Streptococcus pneumoniae, H2O2 resistance is not dependent on a functional SpxB and confirms the important role of the ferritin-like DNA-binding protein Dps. However, the observed increased H2O2 resistance of S. gordonii over S. sanguinis is likely to be caused by an oxidative stress protection machinery present even under anaerobic conditions, while S. sanguinis requires a longer period of time for adaptation. The ability to produce more H2O2 and be more resistant to H2O2 might aid S. gordonii in the competitive oral biofilm environment, since it is lower in abundance yet manages to survive quite efficiently in the oral biofilm. PMID:25280752

  17. Elucidating the interaction of H2O2 with polar amino acids - Quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Karmakar, Tarak; Balasubramanian, Sundaram

    2014-10-01

    Quantum chemical calculations have been carried out to investigate the interaction motifs of H2O2 with polar amino acid residues. Binding energies obtained from gas phase and continuum solvent phase calculations range between 2 and 30 kcal/mol. H2O2 interacts with the side chain of polar amino acids chiefly through the formation of hydrogen bonds. The sbnd CH group in side chains of a few residues provides additional stabilization to H2O2.

  18. The thioredoxin and glutathione-dependent H2O2 consumption pathways in muscle mitochondria: Involvement in H2O2 metabolism and consequence to H2O2 efflux assays.

    PubMed

    Munro, Daniel; Banh, Sheena; Sotiri, Emianka; Tamanna, Nahid; Treberg, Jason R

    2016-07-01

    The most common methods of measuring mitochondrial hydrogen peroxide production are based on the extramitochondrial oxidation of a fluorescent probe such as amplex ultra red (AUR) by horseradish peroxidase (HRP). These traditional HRP-based assays only detect H2O2 that has escaped the matrix, raising the potential for substantial underestimation of production if H2O2 is consumed by matrix antioxidant pathways. To measure this underestimation, we characterized matrix consumers of H2O2 in rat skeletal muscle mitochondria, and developed specific means to inhibit these consumers. Mitochondria removed exogenously added H2O2 (2.5µM) at rates of 4.7 and 5.0nmol min(-1) mg protein(-1) when respiring on glutamate+malate and succinate+rotenone, respectively. In the absence of respiratory substrate, or after disrupting membranes by cycles of freeze-thaw, rates of H2O2 consumption were negligible. We concluded that matrix consumers are respiration-dependent (requiring respiratory substrates), suggesting the involvement of either the thioredoxin (Trx) and/or glutathione (GSH)-dependent enzymatic pathways. The Trx-reductase inhibitor auranofin (2µM), and a pre-treatment of mitochondria with 35µM of 1-chloro-2,4-dintrobenzene (CDNB) to deplete GSH specifically compromise these two consumption pathways. These inhibition approaches presented no undesirable "off-target" effects during extensive preliminary tests. These inhibition approaches independently and additively decreased the rate of consumption of H2O2 exogenously added to the medium (2.5µM). During traditional HRP-based H2O2 efflux assays, these inhibition approaches independently and additively increased apparent efflux rates. When used in combination (double inhibition), these inhibition approaches allowed accumulation of (endogenously produced) H2O2 in the medium at a comparable rate whether it was measured with an end point assay where 2.5µM H2O2 is initially added to the medium or with traditional HRP-based efflux

  19. High resolution pore water delta2H and delta18O measurements by H2O(liquid)-H2O(vapor) equilibration laser spectroscopy.

    PubMed

    Wassenaar, L I; Hendry, M J; Chostner, V L; Lis, G P

    2008-12-15

    A new H2O(liquid)-H2O(vapor) pore water equilibration and laser spectroscopy method provides a fast way to obtain accurate high resolution deltaD and delta18O profiles from single core samples from saturated and unsaturated geologic media. The precision and accuracy of the H2O(liquid)-H2O(vapor) equilibration method was comparable to or better than conventional IRMS-based methods, and it can be conducted on geologic cores that contain volumetric water contents as low as 5%. Significant advantages of the H2O(liquid)-H2O(vapor) pore water equilibration method and laser isotopic analysis method include dual hydrogen- and oxygen-isotope assays on single small core samples, low consumable and instrumentation costs, and the potential for field-based hydrogeologic profiling. A single core is sufficient to obtain detailed vertical isotopic depth profiles in geologic, soil, and lacustrine pore water, dramatically reducing the cost of obtaining pore water by conventional wells or physical water extraction methods. In addition, other inherent problems like contamination of wells by leakage and drilling fluids can be eliminated. PMID:19174902

  20. Heterogeneous degradation of precipitated hexamine from wastewater by catalytic function of silicotungstic acid in the presence of H2O2 and H2O2/Fe2+.

    PubMed

    Taghdiri, Mehdi; Saadatjou, Naghi; Zamani, Navid; Farrokhi, Reyhaneh

    2013-02-15

    The industrial wastewater produced by hexamine plants is considered as a major environmental polluting factor due to resistance to biodegradation. So the treatment of such wastewater is required. In this work, the removal of hexamine from wastewater and its degradation have been studied. Hexamine was precipitated through formation of an insoluble and stable compound with silicotungstic acid. The oxidative heterogeneous degradation of precipitated hexamine was carried out with hydrogen peroxide (H(2)O(2)) aqueous solution and H(2)O(2)/Fe(2+) under the catalysis of silicotungstic acid. The operating conditions including amount of precipitate, hydrogen peroxide and ferrous ion dosage, temperature, time and pH were optimized by evaluating the removal of total organic carbon from system. A total organic carbon conversion higher than 70% was achieved in the presence of H(2)O(2)/Fe(2+). The experimental results showed that hexamine can be effectively degraded with H(2)O(2) and H(2)O(2)/Fe(2+) under the catalysis of silicotungstic acid. It was interesting that the solution of dissolved precipitate with H(2)O(2) can re-react with hexamine after the removal of excess hydrogen peroxide. This observation indicates the catalysis role of silicotungstic acid in the degradation of hexamine. A kinetic analysis based on total organic carbon reduction was carried out. The two steps mechanism was proposed for the degradation of hexamine. PMID:23313893

  1. Modelling of OH production in cold atmospheric-pressure He-H2O plasma jets

    NASA Astrophysics Data System (ADS)

    Naidis, G. V.

    2013-06-01

    Results of the modelling of OH production in the plasma bullet mode of cold atmospheric-pressure He-H2O plasma jets are presented. It is shown that the dominant source of OH molecules is related to the Penning and charge transfer reactions of H2O molecules with excited and charged helium species produced by guided streamers (plasma bullets), in contrast to the case of He-H2O glow discharges where OH production is mainly due to the dissociation of H2O molecules by electron impact.

  2. H2O2-triggered bubble generating antioxidant polymeric nanoparticles as ischemia/reperfusion targeted nanotheranostics.

    PubMed

    Kang, Changsun; Cho, Wooram; Park, Minhyung; Kim, Jinsub; Park, Sanghoon; Shin, Dongho; Song, Chulgyu; Lee, Dongwon

    2016-04-01

    Overproduction of reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) leads to oxidative stress, causing inflammation and cellular damages and death. H2O2 is one of the most stable and abundant ROS and H2O2-mediated oxidative stress is considered as a key mediator of cellular and tissue damages during ischemia/reperfusion (I/R) injury. Therefore, H2O2 could hold tremendous potential as a diagnostic biomarker and therapeutic target for oxidative stress-associated inflammatory conditions such as I/R injury. Here, we report a novel nanotheranostic agent that can express ultrasound imaging and simultaneous therapeutic effects for hepatic I/R treatment, which is based on H2O2-triggered CO2-generating antioxidant poly(vanillin oxalate) (PVO). PVO nanoparticles generate CO2 through H2O2-triggered oxidation of peroxalate esters and release vanillin, which exerts antioxidant and anti-inflammatory activities. PVO nanoparticles intravenously administrated remarkably enhanced the ultrasound signal in the site of hepatic I/R injury and also effectively suppressed the liver damages by inhibiting inflammation and apoptosis. To our best understanding, H2O2-responsive PVO is the first platform which generates bubbles to serve as ultrasound contrast agents and also exerts therapeutic activities. We therefore anticipate that H2O2-triggered bubble-generating antioxidant PVO nanoparticles have great potential for ultrasound imaging and therapy of H2O2-associated diseases. PMID:26874282

  3. Mesospheric H2O Concentrations Retrieved from SABER/TIMED Measurements

    NASA Technical Reports Server (NTRS)

    Feofilov, A. G.; Marshall, B. T.; Garcia-Comas, M.; Kutepov, A. A.; Lopez-Puertas, M.; Manuilova, R. O.; Yankovsky, V.A.; Goldberg, R. A.; Gordley, L. L.; Petelin, S.; Russell, J. M., III

    2008-01-01

    The SABER instrument on board the TIMED Satellite is a limb scanning infrared radiometer designed to measure temperature and minor constituent vertical profiles and energetics parameters in the mesosphere and lower thermosphere (MLT). The H2O concentrations are retrieved from 6.3 micron band radiances. The populations of H2O(v2) vibrational levels are in non-Local Thermodynamic Equilibrium (non-LTE) above approximately 55 km altitude and the interpretation of 6.3 micron radiance requires utilizing non-LTE H2O model that includes various energy exchange processes in the system of H2O vibrational levels coupled with O2, N2, and CO2 vibrational levels. We incorporated these processes including kinetics of O2/O3 photolysis products to our research non-LTE H2O model and applied it for the development and optimization of SABER operational model. The latter has been validated using simultaneous SCISAT1/ACE occultation measurements. This helped us to estimate CO2(020)-O2(X,v=I), O2(X,v=I)- H2O(010), and O2(X,v=1) O rates at mesopause temperatures that is critical for an adequate interpretation of non-LTE H2O radiances in the MLT. The first distributions of seasonal and meridional H2O concentrations retrieved from SABER 6.3 micron radiances applying an updated non-LTE H2O model are demonstrated and discussed.

  4. 22 GHz H2O maser survey towards 221 BGPS sources

    NASA Astrophysics Data System (ADS)

    Xi, Hongwei; Zhou, Jianjun; Esimbek, Jarken; Wu, Gang; He, Yuxin; Ji, Weiguang; Tang, Xiaoke

    2015-11-01

    We performed a 22 GHz H2O maser survey towards 221 Bolocam Galactic Plane Survey (BGPS) sources. We detected 107 H2O masers, of which 12 are new. The detection rate is 48.4 per cent for our sample. We obtained the positions of five new H2O masers via On The Fly (OTF) observations. The detection rate of H2O masers is correlated with continuum emission fluxes of BGPS sources at far-infrared, sub-millimetre and millimetre wavelengths. We employed the classification of Dunham et al. to classify the evolutionary stage of BGPS sources into Group 0, 1, 2, and 3. The detection rate and velocity range of H2O masers increases as the BGPS sources evolve from Group 1 to Group 3. The BGPS sources associated with both H2O and CH3OH masers are more compact than that associated with either only H2O or only CH3OH masers. This indicates that the sources associated with both H2O and CH3OH masers are in relative later evolutionary stage. The detection rate of H2O masers towards BGPS sources displaying evidence of the collapse phenomenon is 62.1 per cent, which suggests that most BGPS sources showing indications of collapse phenomena contain ongoing active star formation activities.

  5. The reaction of H2O2 with NO2 and NO

    NASA Technical Reports Server (NTRS)

    Gray, D.; Lissi, E.; Heicklen, J.

    1972-01-01

    The reactions of NO and NO2 with H2O2 have been examined at 25 C. Reaction mixtures were monitored by continuously bleeding through a pinhole into a monopole mass spectrometer. NO2 was also monitored by its optical absorption in the visible part of the spectrum. Reaction mixtures containing initially 1.5 - 2.5 torr of NO2 and 0.8 - 1.4 torr of H2O2 or 1 - 12 torr of NO and 0.5 - 1.5 torr of H2O2 were studied. The H2O2 - NO reaction was complex. There was an induction period followed by a marked acceleration in reactant removal. The final products of the reaction, NO2, probably H2O, and possibly HONO2 were produced mainly after all the H2O2 was removed. The HONO intermediate was shown to disproportionate to NO2 + NO + H2O in a relatively slow first order reaction. The acceleration in H2O2 removal after the NO - H2O2 reaction is started is caused by NO2 catalysis.

  6. Ionic fragmentation of CO and H2O under impact of 10 keV electrons: kinetic energy release distributions

    NASA Astrophysics Data System (ADS)

    Singh, Raj; Bhatt, Pragya; Yadav, Namita; Shanker, R.

    2014-04-01

    Dissociative ionization of COq+ (q=2-4) and H2Oq+ (q=2-3) molecular ions produced from the collisions of CO and H2O with 10 keV electrons is studied using time-of-flight mass spectrometer and position sensitive detector with multi-hit ability, respectively. The kinetic energy release distributions for these channels are obtained. We found that a pure Coulomb explosion model is insufficient to explain the observed kinetic release distributions for the Coulomb explosion channels. A detail of this study is given in references [3, 4].

  7. Heat-Storage Modules Containing LiNO3-3H2O and Graphite Foam

    NASA Technical Reports Server (NTRS)

    Bootle, John

    2008-01-01

    A heat-storage module based on a commercial open-cell graphite foam (Poco-Foam or equivalent) imbued with lithium nitrate trihydrate (LiNO3-3H2O) has been developed as a prototype of other such modules for use as short-term heat sources or heat sinks in the temperature range of approximately 28 to 30 C. In this module, the LiNO3-3H2O serves as a phase-change heat-storage material and the graphite foam as thermally conductive filler for transferring heat to or from the phase-change material. In comparison with typical prior heat-storage modules in which paraffins are the phase-change materials and aluminum fins are the thermally conductive fillers, this module has more than twice the heat-storage capacity per unit volume.

  8. Spontaneous openings of the acetylcholine receptor channel.

    PubMed Central

    Jackson, M B

    1984-01-01

    Patch clamp recordings from embryonic mouse muscle cells in culture revealed spontaneous openings of the acetylcholine receptor channel in the absence of exogenously applied cholinergic agent. The conductance of the spontaneous channel currents was, within experimental error, identical with the conductance of suberyldicholine-activated channel currents. The comparison of channel conductance was made with sodium and with cesium, each at two concentrations, with the same result. Treatment of the cells with alpha-bungarotoxin blocked the spontaneous channel currents. To determine whether the spontaneous openings were caused by an endogenous agent with cholinergic activity a reactive disulfide bond near the receptor binding site was reduced with dithiothreitol and alkylated with N-ethylmaleimide. This chemical modification reduced the effectiveness with which suberyldicholine and curare activated channel currents but did not reduce the frequency of spontaneous openings. These experiments indicate that the acetylcholine receptor briefly and infrequently fluctuates into an active state in the absence of agonist. Agonist activation of the receptor presumably accelerates this spontaneously occurring process. PMID:6328531

  9. Possibility of Detecting the H2O Snowline in Protoplanetary Disks Using Spectroscopic Observations

    NASA Astrophysics Data System (ADS)

    Notsu, Shota; Nomura, Hideko; Ishimoto, Daiki; Walsh, Catherine; Honda, Mitsuhiko; Millar, Thomas J.

    2015-08-01

    Inside the H2O snowline in protoplanetary disks, H2O evaporates from grain surfaces into the gas. On the other hand, it is frozen out on the grain surface in the cold region beyond the H2O snowline. The H2O snowline is thought to divide the regions of rocky planet and gas giant planet formation. Observationally measuring the position of the H2O snowline in protoplanetary disks in exoplanetary systems will constrain modern theories of planet formation. In disks around solar-mass T-tauri stars, the H2O snowline is thought to exist at a few AU from the central star. Therefore, it is difficult to detect the H2O snowline of exoplanetary systems by direct imaging, since the spatial resolution of existing telescopes is insufficient. In this work, we propose a method of detecting the H2O snowline directly by analyzing the velocity profiles of H2O line spectra which can be obtained by high dispersion spectroscopic observations in the near future.First, we use self-consistent physical models of protoplanetary disks (e.g., Nomura & Millar 2005, Nomura et al. 2007, Walsh et al. 2010, 2012) to investigate the abundance distribution of H2O gas and the position of the snowline. We confirm that the abundance of H2O gas is high not only inside the H2O snowline near the equatorial plane but also in the hot surface layer of the outer disk. Second, we calculate the emergent intensity of H2O emission lines from protoplanetary disks that are assumed to rotate with Keplerian velocity profiles. We can find information on the H2O snowline through investigating the profiles of emission lines that have small Einstein A coefficients and large excitation energies. The wavelengths of the useful H2O emission lines range from mid-infrared to sub-millimeter wavelengths. These lines will be observable with future high dispersion spectroscopic observations (e.g., ALMA, TMT).

  10. Solar-Driven H2 O2 Generation From H2 O and O2 Using Earth-Abundant Mixed-Metal Oxide@Carbon Nitride Photocatalysts.

    PubMed

    Wang, Ruirui; Pan, Kecheng; Han, Dandan; Jiang, Jingjing; Xiang, Chengxiang; Huang, Zhuangqun; Zhang, Lu; Xiang, Xu

    2016-09-01

    Light-driven generation of H2 O2 only from water and molecular oxygen could be an ideal pathway for clean production of solar fuels. In this work, a mixed metal oxide/graphitic-C3 N4 (MMO@C3 N4 ) composite was synthesized as a dual-functional photocatalyst for both water oxidation and oxygen reduction to generate H2 O2 . The MMO was derived from a NiFe-layered double hydroxide (LDH) precursor for obtaining a high dispersion of metal oxides on the surface of the C3 N4 matrix. The C3 N4 is in the graphitic phase and the main crystalline phase in MMO is cubic NiO. The XPS analyses revealed the doping of Fe(3+) in the dominant NiO phase and the existence of surface defects in the C3 N4 matrix. The formation and decomposition kinetics of H2 O2 on the MMO@C3 N4 and the control samples, including bare MMO, C3 N4 matrix, Ni- or Fe-loaded C3 N4 and a simple mixture of MMO and C3 N4 , were investigated. The MMO@C3 N4 composite produced 63 μmol L(-1) of H2 O2 in 90 min in acidic solution (pH 3) and exhibited a significantly higher rate of production for H2 O2 relative to the control samples. The positive shift of the valence band in the composite and the enhanced water oxidation catalysis by incorporating the MMO improved the light-induced hole collection relative to the bare C3 N4 and resulted in the enhanced H2 O2 formation. The positively shifted conduction band in the composite also improved the selectivity of the two-electron reduction of molecular oxygen to H2 O2 . PMID:27484581

  11. A Search for Submillimeter H2O Masers in Active Galaxies: The Detection of 321 GHZ H2O Maser Emission in NGC 4945

    NASA Astrophysics Data System (ADS)

    Hagiwara, Yoshiaki; Horiuchi, Shinji; Doi, Akihiro; Miyoshi, Makoto; Edwards, Philip G.

    2016-08-01

    We present further results of a search for extragalactic submillimeter H2O masers using the Atacama Large Millimeter/submillimeter Array (ALMA). The detection of a 321 GHz H2O maser in the nearby type 2 Seyfert galaxy, the Circinus galaxy, has previously been reported, and here the spectral analysis of four other galaxies is described. We have discovered H2O maser emission at 321 GHz toward the center of NGC 4945, a nearby type 2 Seyfert. The maser emission shows Doppler-shifted velocity features with velocity ranges similar to those of the previously reported 22 GHz H2O masers however, the non-contemporaneous observations also show differences in velocity offsets. The subparsec-scale distribution of the 22 GHz H2O masers revealed by earlier very long baseline interferometry observations suggests that the submillimeter masers could arise in an edge-on rotating disk. The maser features remain unresolved by the synthesized beam of ∼0.″54 (∼30 pc) and are located toward the 321 GHz continuum peak within errors. A marginally detected (3σ) high-velocity feature is redshifted by 579 km {{{s}}}-1 with respect to the systemic velocity of the galaxy. Assuming that this feature is real and arises from a Keplerian rotating disk in this galaxy, it is located at a radius of ∼0.020 pc (∼1.5 × 105 Schwarzschild radii), which would enable molecular material closer to the central engine to be probed than the 22 GHz H2O masers. This detection confirms that submillimeter H2O masers are a potential tracer of the circumnuclear regions of active galaxies, which will benefit from higher angular resolution studies with ALMA.

  12. A Search for Submillimeter H2O Masers in Active Galaxies: The Detection of 321 GHZ H2O Maser Emission in NGC 4945

    NASA Astrophysics Data System (ADS)

    Hagiwara, Yoshiaki; Horiuchi, Shinji; Doi, Akihiro; Miyoshi, Makoto; Edwards, Philip G.

    2016-08-01

    We present further results of a search for extragalactic submillimeter H2O masers using the Atacama Large Millimeter/submillimeter Array (ALMA). The detection of a 321 GHz H2O maser in the nearby type 2 Seyfert galaxy, the Circinus galaxy, has previously been reported, and here the spectral analysis of four other galaxies is described. We have discovered H2O maser emission at 321 GHz toward the center of NGC 4945, a nearby type 2 Seyfert. The maser emission shows Doppler-shifted velocity features with velocity ranges similar to those of the previously reported 22 GHz H2O masers however, the non-contemporaneous observations also show differences in velocity offsets. The subparsec-scale distribution of the 22 GHz H2O masers revealed by earlier very long baseline interferometry observations suggests that the submillimeter masers could arise in an edge-on rotating disk. The maser features remain unresolved by the synthesized beam of ˜0.″54 (˜30 pc) and are located toward the 321 GHz continuum peak within errors. A marginally detected (3σ) high-velocity feature is redshifted by 579 km {{{s}}}-1 with respect to the systemic velocity of the galaxy. Assuming that this feature is real and arises from a Keplerian rotating disk in this galaxy, it is located at a radius of ˜0.020 pc (˜1.5 × 105 Schwarzschild radii), which would enable molecular material closer to the central engine to be probed than the 22 GHz H2O masers. This detection confirms that submillimeter H2O masers are a potential tracer of the circumnuclear regions of active galaxies, which will benefit from higher angular resolution studies with ALMA.

  13. Crystal structures of hydrates of simple inorganic salts. III. Water-rich aluminium halide hydrates: AlCl3 · 15H2O, AlBr3 · 15H2O, AlI3 · 15H2O, AlI3 · 17H2O and AlBr3 · 9H2O.

    PubMed

    Schmidt, Horst; Hennings, Erik; Voigt, Wolfgang

    2014-09-01

    Water-rich aluminium halide hydrate structures are not known in the literature. The highest known water content per Al atom is nine for the perchlorate and fluoride. The nonahydrate of aluminium bromide, stable pentadecahydrates of aluminium chloride, bromide and iodide, and a metastable heptadecahydrate of the iodide have now been crystallized from low-temperature solutions. The structures of these hydrates were determined and are discussed in terms of the development of cation hydration spheres. The pentadecahydrate of the chloride and bromide are isostructural. In AlI(3) · 15H2O, half of the Al(3+) cations are surrounded by two complete hydration spheres, with six H2O in the primary and 12 in the secondary. For the heptadecahydrate of aluminium iodide, this hydration was found for every Al(3+). PMID:25186362

  14. TES/Aura L2 Water Vapor (H2O) Limb (TL2H2OL)

    Atmospheric Science Data Center

    2015-02-06

    TES/Aura L2 Water Vapor (H2O) Limb (TL2H2OL) News:  TES News ... Level:  L2 Platform:  TES/Aura L2 Water Vapor Spatial Coverage:  27 x 23 km Limb ... Access: OPeNDAP Parameters:  H2O Water Volume Mixing Radio Precision Vertical Resolution Order ...

  15. The discovery of five new H2O megamasers in active galaxies

    NASA Technical Reports Server (NTRS)

    Braatz, J. A.; Wilson, A. S.; Henkel, C.

    1994-01-01

    H2O megamasers with (isotropic) luminosities between 60 and 200 solar luminosity (H(sub 0) = 75 km/s/Mpc) have been detected in the Seyfert 2 galaxies Mrk 1, Mrk 1210, and NGC 5506 and in the LINERs NGC 1052 and NGC 2639. No megamasers have been found in Seyfert 1's. The galaxies have redshifts between 1500 and 4800 km/s and are the most distant H2O sources reported to date. NGC 1052 is also the first elliptical galaxy known to contain an H2O maser. The intensity distribution of an H2O five-point map obtained toward NGC 5506 shows that the H2O emission is pointlike compared to the 40 sec telescope beam. The lack of CO emission in NGC 1052 implies a conservative lower limit to the H2O brightness temperature of 1000 K, thus ruling out a thermal origin for the H2O emission. The success of this survey relative to other recent searches makes it evident that H2O megamasers are preferentially found in galaxies with active nuclei.

  16. Characterization and optimization of cathodic conditions for H2O2 synthesis in microbial electrochemical cells.

    PubMed

    Sim, Junyoung; An, Junyeong; Elbeshbishy, Elsayed; Ryu, Hodon; Lee, Hyung-Sool

    2015-11-01

    Cathode potential and O2 supply methods were investigated to improve H2O2 synthesis in an electrochemical cell, and optimal cathode conditions were applied for microbial electrochemical cells (MECs). Using aqueous O2 for the cathode significantly improved current density, but H2O2 conversion efficiency was negligible at 0.3-12%. Current density decreased for passive O2 diffusion to the cathode, but H2O2 conversion efficiency increased by 65%. An MEC equipped with a gas diffusion cathode was operated with acetate medium and domestic wastewater, which presented relatively high H2O2 conversion efficiency from 36% to 47%, although cathode overpotential was fluctuated. Due to different current densities, the maximum H2O2 production rate was 141 mg H2O2/L-h in the MEC fed with acetate medium, but it became low at 6 mg H2O2/L-h in the MEC fed with the wastewater. Our study clearly indicates that improving anodic current density and mitigating membrane fouling would be key parameters for large-scale H2O2-MECs. PMID:26141667

  17. 40 CFR 1065.370 - CLD CO2 and H2O quench verification.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 34 2013-07-01 2013-07-01 false CLD CO2 and H2O quench verification... POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Calibrations and Verifications Nox and N2o Measurements § 1065.370 CLD CO2 and H2O quench verification. (a) Scope and frequency. If you use a CLD analyzer to...

  18. NARSTO EPA SS HOUSTON TEXAQS2000 HCHO H2O2 DATA

    Atmospheric Science Data Center

    2014-04-25

    NARSTO EPA SS HOUSTON TEXAQS2000 HCHO H2O2 DATA Project Title:  NARSTO ... Instrument:  Fluorescence Location:  Houston, Texas Spatial Resolution:  Point Measurements ...   Order Data Guide Documents:  Houston TexAQS2000 HCHO H2O2Guide Houston Project Plan  (PDF) ...

  19. Transport properties of the H2O@C60-dimer-based junction.

    PubMed

    Zhu, Chengbo; Wang, Xiaolin

    2015-09-23

    Theoretical predictions play an important role in finding potential applications in molecular electronics. Fullerenes have a number of potential applications, and the charge flow from a single C60 molecule to another becomes more versatile and more interesting after doping. Here, we report the conductance of two H2O@C60 molecules in series order and how the number of encapsulated water molecules influences the transport properties of the junction. Encapsulating an H2O molecule into one of the C60 cages increases the conductance of the dimer. Negative differential resistance is found in the dimer systems, and its peak-to-valley current ratio depends on the number of encapsulated H2O molecules. The conductance of the C60 dimer and the H2O@C60 dimer is two orders of magnitude smaller than that of the C60 monomer. Furthermore, we demonstrate that the conductance of the molecular junctions based on the H2O@C60 dimer can be tuned by moving the encapsulated H2O molecules. The conductance is H2O-position dependent. Our findings indicate that H2O@C60 can be used as a building block in C60-based molecular electronic devices and sensors. PMID:26325223

  20. Transport properties of the H2O@C60-dimer-based junction

    NASA Astrophysics Data System (ADS)

    Zhu, Chengbo; Wang, Xiaolin

    2015-09-01

    Theoretical predictions play an important role in finding potential applications in molecular electronics. Fullerenes have a number of potential applications, and the charge flow from a single C60 molecule to another becomes more versatile and more interesting after doping. Here, we report the conductance of two H2O@C60 molecules in series order and how the number of encapsulated water molecules influences the transport properties of the junction. Encapsulating an H2O molecule into one of the C60 cages increases the conductance of the dimer. Negative differential resistance is found in the dimer systems, and its peak-to-valley current ratio depends on the number of encapsulated H2O molecules. The conductance of the C60 dimer and the H2O@C60 dimer is two orders of magnitude smaller than that of the C60 monomer. Furthermore, we demonstrate that the conductance of the molecular junctions based on the H2O@C60 dimer can be tuned by moving the encapsulated H2O molecules. The conductance is H2O-position dependent. Our findings indicate that H2O@C60 can be used as a building block in C60-based molecular electronic devices and sensors.

  1. 40 CFR 1065.350 - H2O interference verification for CO2 NDIR analyzers.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... through distilled water in a sealed vessel. If the sample is not passed through a dryer during emission... dryer during this verification test, measure the water mole fraction, x H2O, of the humidified test gas... pressure, p total, to calculate x H2O. Verify that the water content meets the requirement in paragraph...

  2. UV and VUV photolysis vs. UV/H2O2 and VUV/H2O2, treatment for removal of clofibric acid from aqueous solution.

    PubMed

    Li, Wenzhen; Lu, Shuguang; Qiu, Zhaofu; Lin, Kuangfei

    2011-07-01

    Clofibric acid (CA), a metabolite of lipid regulators, was investigated in ultra-pure water and sewage treatment plant (STP) effluent at 10 degrees C under UV, vacuum UV (VUV), UV/H2O2 and VUV/H2O2 processes. The influences of NO3-, HCO3- and humic acid (HA) on CA photolysis in all processes were examined. The results showed that all the experimental data well fitted the pseudo-first-order kinetic model, and the apparent rate constant (k(ap)) and half-life time (t(1/2)) were calculated accordingly. Direct photolysis of CA through UV irradiation was the main process, compared with the indirect oxidation of CA due to the slight generation of hydroxyl radicals dissociated from water molecules under UV irradiation below 200 nm monochromatic wavelength emission. In contrast, indirect oxidation was the main CA degradation mechanism in UV/H2O2 and VUV/H2O2, and VUV/H2O2 was the most effective process for CA degradation. The addition of 20 mg L(-1) HA could significantly inhibit CA degradation, whereas, except for UV irradiation, the inhibitive effects of NO3- and HCO3- (1.0 x 10(-3) and 0.1 mol L(-1), respectively) on CA degradation were observed in all processes, and their adverse effects were more significant in UV/H2O2 and VUV/H2O2 processes, particularly at the high NO3- and HCO3- concentrations. The degradation rate decreased 1.8-4.9-fold when these processes were applied to a real STP effluent owing to the presence of complex constituents. Of the four processes, VUV/H2O2 was the most effective, and the CA removal efficiency reached over 99% after 40 min in contrast to 80 min in both the UV/H2O2 and VUV processes and 240 min in the UV process. PMID:21882559

  3. Application of H2O and UV/H2O2 processes for enhancing the biodegradability of reactive black 5 dye.

    PubMed

    Kalpana, S Divya; Kalyanaraman, Chitra; Gandhi, N Nagendra

    2011-07-01

    Leather processing is a traditional activity in India during which many organic and inorganic chemicals are added while part of it is absorbed by the leather, the remaining chemicals are discharged along with the effluent. The effluent contains both easily biodegradable and not easily biodegradable synthetic organics like dyes, syntans. Easily biodegradable organics are removed in the existing biological treatment units whereas synthetic organics present in the wastewater are mostly adsorbed over the microbes. As the tannery effluent contains complex chemicals, it is difficult to ascertain the degradation of specific pollutants. To determine the increase in the biodegradability, one of the complex and synthetic organic chemical like dye used in the tanning operation was selected for Advanced Oxidation Process (AOPs) treatment for cleaving complex organics and its subsequent treatment in aerobic process. In the present study, Reactive Black 5 Dye used in the tanning operation was selected for Hydrogen Peroxide (H2O2) and UV/H2O2 pre-treatment for different operating conditions like pH, contact time and different volume of H2O2. A comparison was made between the untreated, Hydrogen Peroxide (H2O2) and UV/H2O2 treated effluent in order to ascertain the influence of AOP on the improvement of biodegradability of effluent. An increase in the BOD5/COD ratio from 0.21 to 0.435 was achieved in the UV/H2O2 pre-treatment process. This pre-treated effluent was further subjected to aerobic process. Biochemical Oxygen Demand (BOD5) and Chemical Oxygen Demand (COD) removal efficiency of the UV/H2O2 pre-treated dye solution in the aerobic process was found to be 86.39% and 77.82% when compared to 52.43% of BOD5 and 51.55% of COD removal efficiency without any pre-treatment. Hence from these results, to increase the biodegradability of Reactive Black 5 dye pre-treatment methods like H2O2 and UV/H2O2 can be used prior to biological treatment process. PMID:23029927

  4. UV and IR Spectroscopy of Cold H2O(+)-Benzo-Crown Ether Complexes.

    PubMed

    Inokuchi, Yoshiya; Ebata, Takayuki; Rizzo, Thomas R

    2015-11-12

    The H2O(+) radical ion, produced in an electrospray ion source via charge transfer from Eu(3+), is encapsulated in benzo-15-crown-5 (B15C5) or benzo-18-crown-6 (B18C6). We measure UV photodissociation (UVPD) spectra of the (H2O·B15C5)(+) and (H2O·B18C6)(+) complexes in a cold, 22-pole ion trap. These complexes show sharp vibronic bands in the 35 700-37 600 cm(-1) region, similar to the case of neutral B15C5 or B18C6. These results indicate that the positive charge in the complexes is localized on H2O, giving the forms H2O(+)·B15C5 and H2O(+)·B18C6, in spite of the fact that the ionization energy of B15C5 and B18C6 is lower than that of H2O. The formation of the H2O(+) complexes and the suppression of the H3O(+) production through the reaction of H2O(+) and H2O can be attributed to the encapsulation of hydrated Eu(3+) clusters by B15C5 and B18C6. On the contrary, the main fragment ions subsequent to the UV excitation of these complexes are B15C5(+) and B18C6(+) radical ions; the charge transfer occurs from H2O(+) to B15C5 and B18C6 after the UV excitation. The position of the band origin for the H2O(+)·B18C6 complex (36323 cm(-1)) is almost the same as that for Rb(+)·B18C6 (36315 cm(-1)); the strength of the intermolecular interaction of H2O(+) with B18C6 is similar to that of Rb(+). The spectral features of the H2O(+)·B15C5 complex also resemble those of the Rb(+)·B15C5 ion. We measure IR-UV spectra of these complexes in the CH and OH stretching region. Four conformers are found for the H2O(+)·B15C5 complex, but there is one dominant form for the H2O(+)·B18C6 ion. This study demonstrates the production of radical ions by charge transfer from multivalent metal ions, their encapsulation by host molecules, and separate detection of their conformers by cold UV spectroscopy in the gas phase. PMID:26491792

  5. Three-dimensional WS2 nanosheet networks for H2O2 produced for cell signaling

    NASA Astrophysics Data System (ADS)

    Tang, Jing; Quan, Yingzhou; Zhang, Yueyu; Jiang, Min; Al-Enizi, Abdullah M.; Kong, Biao; An, Tiance; Wang, Wenshuo; Xia, Limin; Gong, Xingao; Zheng, Gengfeng

    2016-03-01

    Hydrogen peroxide (H2O2) is an important molecular messenger for cellular signal transduction. The capability of direct probing of H2O2 in complex biological systems can offer potential for elucidating its manifold roles in living systems. Here we report the fabrication of three-dimensional (3D) WS2 nanosheet networks with flower-like morphologies on a variety of conducting substrates. The semiconducting WS2 nanosheets with largely exposed edge sites on flexible carbon fibers enable abundant catalytically active sites, excellent charge transfer, and high permeability to chemicals and biomaterials. Thus, the 3D WS2-based nano-bio-interface exhibits a wide detection range, high sensitivity and rapid response time for H2O2, and is capable of visualizing endogenous H2O2 produced in living RAW 264.7 macrophage cells and neurons. First-principles calculations further demonstrate that the enhanced sensitivity of probing H2O2 is attributed to the efficient and spontaneous H2O2 adsorption on WS2 nanosheet edge sites. The combined features of 3D WS2 nanosheet networks suggest attractive new opportunities for exploring the physiological roles of reactive oxygen species like H2O2 in living systems.Hydrogen peroxide (H2O2) is an important molecular messenger for cellular signal transduction. The capability of direct probing of H2O2 in complex biological systems can offer potential for elucidating its manifold roles in living systems. Here we report the fabrication of three-dimensional (3D) WS2 nanosheet networks with flower-like morphologies on a variety of conducting substrates. The semiconducting WS2 nanosheets with largely exposed edge sites on flexible carbon fibers enable abundant catalytically active sites, excellent charge transfer, and high permeability to chemicals and biomaterials. Thus, the 3D WS2-based nano-bio-interface exhibits a wide detection range, high sensitivity and rapid response time for H2O2, and is capable of visualizing endogenous H2O2 produced in

  6. Probing active galactic nuclei with H2O megamasers.

    PubMed Central

    Moran, J; Greenhill, L; Herrnstein, J; Diamond, P; Miyoshi, M; Nakai, N; Inque, M

    1995-01-01

    the disk must be <1000 K and the toroidal magnetic field component must be <250 mG. If the molecular mass density in the disk is 10(10) cm-3, then the disk mass is approximately 10(4) M[symbol: see text], and the disk is marginally stable as defined by the Toomre stability parameter Q (Q = 6 at the inner edge and 1 at the outer edge). The inward drift velocity is predicted to be <0.007 km.s-1, for a viscosity parameter of 0.1, and the accretion rate is <7 x 10(-5) M[symbol: see text].yr-1. At this value the accretion would be sufficient to power the nuclear x-ray source of 4 x 10(40) ergs-1 (1 erg = 0.1 microJ). The volume of individual maser components may be as large as 10(46) cm3, based on the velocity gradients, which is sufficient to supply the observed luminosity. The pump power undoubtedly comes from the nucleus, perhaps in the form of x-rays. The warp may allow the pump radiation to penetrate the disk obliquely [Neufeld, D. A. & Maloney, P. R. (1995) Astrophys. J. Lett. 447, L17-L19]. A total of 15 H2O megamasers have been identified out of >250 galaxies searched. Galaxy NGC4258 may be the only case where conditions are optimal to reveal a well-defined nuclear disk. Future measurement of proper motions and accelerations for NGC4258 will yield an accurate distance and a more precise definition of the dynamics of the disk Images Fig. 6 PMID:11607612

  7. Copernicus observational searches for OH and H2O in diffuse clouds

    NASA Technical Reports Server (NTRS)

    Smith, W. H.; Snow, T. P., Jr.

    1979-01-01

    An intensive search for OH and H2O in the directions of Sigma Sco, Alpha Cam, and Omicron Per was undertaken with the Copernicus satellite. Multiple scans were carried out over the wavelength region for the expected absorption features due to the OH D-X and H2O C-X transitions. The feature due to OH was possibly detected toward Sigma Sco, and only an upper limit can be given toward Alpha Cam. H2O was not detected in any of the stars at the signal level accumulated. The OH abundance toward Sigma Sco and the respective lower limits for the OH/H2O ratios are discussed with regard to the extant models for the steady-state abundances of OH and H2O, and shown not to be inconsistent with ion-molecule schemes.

  8. Copernicus observational searches for OH and H2O in diffuse clouds

    NASA Technical Reports Server (NTRS)

    Smith, W. H.; Snow, T. P., Jr.

    1983-01-01

    An intensive search for OH and H2O in the directions of sigma Sco, alpha Cam, and micron Per was undertaken with the Copernicus satellite. Multiple scans were carried out over the wavelength region for the expected absorption features due to the OH D-X and H2O C-X transitions. The feature due to OH was detected marginally towards sigma Sco, and only an upper limit can be given towards alpha Cam. H2O was not detected in any of the stars at the signal level accumulated. The OH abundance towards sigma Sco and the respective lower limits for the OH/H2O ratios are discussed with regard to the extant models for the steady state abundances of OH and H2O, and shown not to be inconsistent with ion-molecule schemes.

  9. CCD observations of comet Tuttle 1980 XIII - The H2O(+) ionosphere

    NASA Technical Reports Server (NTRS)

    Ip, W.-H.; Fink, U.; Johnson, J. R.

    1985-01-01

    A CCD spectrum of comet Tuttle 1980h has been analyzed with emphasis on the emission of H2O(+) ions. The fine angular resolution (1.5 arcsec) and the capability of absolute brightness calibration of the CCD instrument made it possible to determine the spatial concentration of the H2O(+) ions of this faint comet and the total number of these ions confined within a spherical region. Solar photoionization of the H2O atmosphere can account for the production of the H2O(+) ions observed in the confined region. The dimension of the H2O(+) ionosphere at the time of observation was found to be comparatively small, implying the possible existence of an ionopause sharply delineating the extension of the cometary ionosphere.

  10. Hydrogen-bond-directed assemblies of [La(18-crown-6)(H2O)4](BiCl6)·3H2O and [Nd(18-crown-6)(H2O)4](BiCl6)·3.5H2O regulated by different symmetries

    NASA Astrophysics Data System (ADS)

    Zhang, Shi-Yong; Li, Jian; Zeng, Ying; Wen, He-Rui; Du, Zi-Yi

    2016-12-01

    The reactions of La2O3 or Nd2O3 with BiCl3 and 18-crown-6 in the presence of excessive hydrochloric acid afforded two ion-pair compounds, namely [La(18-crown-6)(H2O)4](BiCl6)·3H2O (1) and [Nd(18-crown-6)(H2O)4](BiCl6)·3.5H2O (2). Although these two compounds contain similar building blocks, they exhibit two distinct hydrogen-bonded networks, which are mainly induced by the slightly different geometries of their large-sized cationic [Ln(18-crown-6)(H2O)4]3+ components.

  11. The effect of H2O and CO2 on planetary mantles

    NASA Technical Reports Server (NTRS)

    Wyllie, P. J.

    1978-01-01

    The peridotite-H2O-CO2 system is discussed, and it is shown that even traces of H2O and CO2, in minerals or vapor, lower mantle solidus temperatures through hundreds of degrees in comparison with the volatile-free solidus. The solidus for peridotite-H2O-CO2 is a divariant surface traversed by univariant lines that locate the intersections of subsolidus divariant surfaces for carbonation or hydration reactions occurring in the presence of H2O-CO2 mixtures. Vapor phase compositions are normally buffered to these lines, and near the buffered curve for the solidus of partly carbonated peridotite there is a temperature maximum on the peridotite-vapor solidus. Characteristics on the CO2 side of the maximum and on the H2O side of the maximum are described.

  12. Structures and rearrangement reactions of 4-aminophenol(H2O)1+ and 3-aminophenol(H2O)1+ clusters

    NASA Astrophysics Data System (ADS)

    Gerhards, M.; Jansen, A.; Unterberg, C.; Gerlach, A.

    2005-08-01

    In this paper the structures of 4-aminophenol(H2O)1+ and 3-aminophenol(H2O)1+ clusters are investigated in molecular beam experiments by different IR/UV-double resonance techniques as well as the mass analyzed threshold ionization spectroscopy yielding both inter- and intramolecular vibrations of the ionic and neutral species. Possible structures are extensively calculated at the level of density functional theory (DFT) or at the ab initio level of theory. From the experimental and theoretical investigations it can be concluded that in the case of 4-aminophenol(H2O)1 one O H⋯O hydrogen-bonded structure exists in the neutral cluster but two structures containing either an O H⋯O or a N H⋯O hydrogen-bonded arrangement are observed in the spectra of the ionic species. This observation is a result of an intramolecular rearrangement reaction within the ion which can only take place if high excess energies are used. A reaction path via the CH bonds is calculated and explains the experimental observations. In the case of 3-aminophenol(H2O)1+ only one O H⋯O bound structure is observed both in the neutral and ionic species. Ab initio and DFT calculations show that due to geometrical and energetical reasons a rearrangement cannot be observed in the 3-aminophenol(H2O)1+ cluster ion.

  13. Propofol Protects Against H2O2-Induced Oxidative Injury in Differentiated PC12 Cells via Inhibition of Ca(2+)-Dependent NADPH Oxidase.

    PubMed

    Chen, Xiao-Hui; Zhou, Xue; Yang, Xiao-Yu; Zhou, Zhi-Bin; Lu, Di-Han; Tang, Ying; Ling, Ze-Min; Zhou, Li-Hua; Feng, Xia

    2016-05-01

    Propofol (2,6-diisopropylphenol) is a widely used general anesthetic with anti-oxidant activities. This study aims to investigate protective capacity of propofol against hydrogen peroxide (H2O2)-induced oxidative injury in neural cells and whether the anti-oxidative effects of propofol occur through a mechanism involving the modulation of NADPH oxidase (NOX) in a manner of calcium-dependent. The rat differentiated PC12 cell was subjected to H2O2 exposure for 24 h to mimic a neuronal in vitro model of oxidative injury. Our data demonstrated that pretreatment of PC12 cells with propofol significantly reversed the H2O2-induced decrease in cell viability, prevented H2O2-induced morphological changes, and reduced the ratio of apoptotic cells. We further found that propofol attenuated the accumulation of malondialdehyde (biomarker of oxidative stress), counteracted the overexpression of NOX core subunit gp91(phox) (NOX2) as well as the NOX activity following H2O2 exposure in PC12 cells. In addition, blocking of L-type Ca(2+) channels with nimodipine reduced H2O2-induced overexpression of NOX2 and caspase-3 activation in PC12 cells. Moreover, NOX inhibitor apocynin alone or plus propofol neither induces a significant downregulation of NOX activity nor increases cell viability compared with propofol alone in the PC12 cells exposed to H2O2. These results demonstrate that the protective effects of propofol against oxidative injury in PC12 cells are mediated, at least in part, through inhibition of Ca(2+)-dependent NADPH oxidase. PMID:26162968

  14. An H2O Maser survey towards BGPS sources in the Outer Galaxy

    NASA Astrophysics Data System (ADS)

    Xi, Hong-Wei; Zhou, Jian-Jun; Esimbek, Jarken; Wu, Gang; He, Yu-Xin; Ji, Wei-Guang; Tang, Xiao-Ke; Yuan, Ye

    2016-06-01

    We performed an H2O maser survey towards 274 Bolocam Galactic Plane Survey (BGPS) sources with 85° < l < 193° using the Nanshan 25 m radio telescope. We detected 25 H2O masers, and five of them are new detections. The detection rate of H2O masers in our sample is 9% which is very low. The detection rate of H2O masers increases as the 1.1 mm flux density of BGPS sources increases, and both the peak flux density and luminosity of H2O masers increase as the sources evolve. The detection rate of H2O masers toward BGPS sources without HCO+ emission is low. The BGPS sources associated with both H2O and CH3OH masers seem to be more compact than those only associated with H2O masers. This indicates that the sources with both masers may be in a relatively later evolutionary stage. The strongest H2O maser source G133.715+01.217, also well known as W3 IRS 5 which has a flux density of 2.9×103 Jy, was detected at eight different nearby positions. By measuring the correlation between the flux densities of these H2O masers and their angular distance from the true source location, we get the influence radius r = \\frac{1}{{0.8}}log ≤ft({\\frac{{F_0}}{{3\\text{rms}}}}\\right). For our observations, strong sources can be detected anywhere within this radius. It is helpful to determine whether or not a weak maser nearby the strong maser is a true detection.

  15. In Vivo Monitoring of H2O2 with Polydopamine and Prussian Blue-coated Microelectrode.

    PubMed

    Li, Ruixin; Liu, Xiaomeng; Qiu, Wanling; Zhang, Meining

    2016-08-01

    In vivo monitoring of hydrogen peroxide (H2O2) in the brain is of importance for understanding the function of both reactive oxygen species (ROS) and signal transmission. Producing a robust microelectrode for in vivo measurement of H2O2 is challenging due to the complex brain environment and the instability of electrocatalysts employed for the reduction of H2O2. Here, we develop a new kind of microelectrode for in vivo monitoring of H2O2, which is prepared by, first, electrodeposition of Prussian blue (PB) onto carbon nanotube (CNT) assembled carbon fiber microelectrodes (CFEs) and then overcoating of the CFEs with a thin membrane of polydopamine (PDA) through self-polymerization. Scanning electron microscopic and X-ray proton spectroscopic results confirm the formation of PDA/PB/CNT/CFEs. The PDA membrane enables PB-based electrodes to show high stability in both in vitro and in vivo studies and to stably catalyze the electrochemical reduction of H2O2. The microelectrode is selective for in vivo measurements of H2O2, interference-free from O2 and other electroactive species coexisting in the brain. These properties, along with good linearity, high biocompatibility, and stability toward H2O2, substantially enable the microelectrode to track H2O2 changes in vivo during electrical stimulation and microinfusion of H2O2 and drug, which demonstrates that the microelectrode could be well suited for in vivo monitoring of dynamic changes of H2O2 in rat brain. PMID:27385361

  16. Low-potential sensitive H2O2 detection based on composite micro tubular Te adsorbed on platinum electrode.

    PubMed

    Guascito, M R; Chirizzi, D; Malitesta, C; Mazzotta, E; M Siciliano; Siciliano, T; Tepore, A; Turco, A

    2011-04-15

    In this work a new original amperometric sensor for H(2)O(2) detection based on a Pt electrode modified with Te-microtubes was developed. Te-microtubes, synthesized by the simple thermal evaporation of Te powder, have a tubular structure with a hexagonal cross-section and are open ended. Modified electrode was prepared by direct drop casting of the mixture of Te-microtubes dispersed in ethanol on Pt surface. The spectroscopic characterization of synthesized Te-microtubes and Pt/Te-microtubes modified electrodes was performed by scanning electron microscopy (SEM), energy-dispersive X-rays microanalysis (EDX), X-ray diffraction analysis (XRD) and X-ray photoelectron spectroscopy (XPS). Moreover a complete electrochemical characterization of the new composite material Pt/Te-microtubes was performed by cyclic voltammetry (CV) and cronoamperometry (CA) in phosphate buffer solution (PBS) at pH 7. Electrochemical experiments showed that the presence of Te-microtubes on modified electrode was responsible for an increment of both cathodic and anodic currents in presence of H(2)O(2) with respect to bare Pt. Specifically, data collected from amperometric experiments at -150 mV vs. SCE in batch and -200 mV vs. SCE in flow injection analysis (FIA) experiments show a remarkable increment of the cathodic current. The electrochemical performances of tested sensors make them suitable for the quantitative determination of H(2)O(2) substrate both in batch and in FIA. PMID:21377859

  17. Hydrogen constituents of the mesosphere inferred from positive ions - H2O, CH4, H2CO, H2O2, and HCN

    NASA Technical Reports Server (NTRS)

    Kopp, E.

    1990-01-01

    The concentrations in the mesosphere of H2O, CH4, H2CO, H2O2, and HCN were inferred from data on positive ion compositions, obtained from one mid-latitude and four high-latitude rocket flights. The inferred concentrations were found to agree only partially with the ground-based microwave measurements and/or model prediction by Garcia and Solomon (1985). The CH4 concentration was found to vary between 70 and 4 ppb in daytime and 900 and 100 ppbv at night, respectively. Unexpectedly high H2CO concentrations were obtained, with H2CO/H2O ratios between 0.0006 and 0.1, and a mean HCN volume mixing ratio of 6 x 10 to the -10th was inferred.

  18. Generation of H2, O2, and H2O2 from water by the use of intense femtosecond laser pulses and the possibility of laser sterilization

    NASA Astrophysics Data System (ADS)

    Chin, S. L.; Lagacé, S.

    1996-02-01

    An intense femtosecond Ti-sapphire laser pulse was focused into water, leading to self-focusing. Apart from generating a white light (supercontinuum), the intense laser field in the self-focusing regions of the laser pulse dissociated the water molecules, giving rise to hydrogen and oxygen gas as well as hydrogen peroxide. Our analysis shows that the formation of free radicals O, H, and OH preceded the formation of the stable products of H2, O2, and H2O2. Because O radicals and H2O2 are strong oxydizing agents, one can take advantage of this phenomenon to design a laser scheme for sterilization in medical and biological applications.

  19. Rutile Solubility in Supercritical Albite-H2O fluids: Implications for Element Mobility in Subduction Zones

    NASA Astrophysics Data System (ADS)

    Antignano, A.; Manning, C. E.

    2006-12-01

    in high- P veins. Low Ti solubility requires that these features result from channelized flow and/or high fluid fluxes. For example, at our experimental conditions, growth of a 1 mm3 crystal from a fluid produced by 2 wt% dehydration from metabasalt and containing 5 wt% ab would require 61 m3 of rock, assuming the fluid precipitates all dissolved Ti. If the supercritical ab-H2O system adequately approximates the possible range of natural fluids, it is evident that supercritical fluids may not have the ability to dissolve and mobilize significant concentrations of nominally insoluble trace elements.

  20. Hydrothermal synthesis and characteristics of 3-D hydrated bismuth oxalate coordination polymers with open-channel structure

    NASA Astrophysics Data System (ADS)

    Chen, Xinxiang; Cao, Yanning; Zhang, Hanhui; Chen, Yiping; Chen, Xuehuan; Chai, Xiaochuan

    2008-05-01

    Two new 3-D porous bismuth coordination polymers, (C 5NH 6) 2[Bi 2(H 2O) 2(C 2O 4) 4]·2H 2O 1 and (NH 4)[Bi(C 2O 4) 2]·3H 2O 2, have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic symmetry, P2 1/ c space group with a=10.378(2) Å, b=17.285(3) Å, c=16.563(5) Å, α=90°, β=119.66(2)°, γ=90°, V=2581.8(10) Å 3, Z=4, R1=0.0355 and w R2=0.0658 for unique 4713 reflections I >2 σ( I). Compound 2 crystallizes in the tetragonal symmetry, I4 1/ amd space group with a=11.7026(17) Å, b=11.7026(17) Å, c=9.2233(18) Å, α=90°, β=90°, γ=90°, V=1263.1(4) Å 3, Z=32, R1=0.0208 and w R2=0.0518 for unique 359 reflections I> 2 σ( I). Compounds 1 and 2 are 3-D open-framework structures with a 6 6 uniform net, which consist of honeycomb-like layers connected to each other by oxalate units. While different guest molecules fill in their cavities of honeycomb-like layers, study of ultrasonic treatment on 2 indicates the replacement of NH 4+ by K + on potassium ion exchange. Thermogravimetric analysis indicates that the open-channel frameworks are thermally stable up to 200 °C, and other characterizations are also described by elemental analysis, IR and ultraviolet-visible diffuse reflectionintegral spectrum (UV-Vis DRIS).

  1. Heterogeneous distribution of H2O in the Martian interior: Implications for the abundance of H2O in depleted and enriched mantle sources

    NASA Astrophysics Data System (ADS)

    McCubbin, Francis M.; Boyce, Jeremy W.; Srinivasan, Poorna; Santos, Alison R.; Elardo, Stephen M.; Filiberto, Justin; Steele, Andrew; Shearer, Charles K.

    2016-04-01

    We conducted a petrologic study of apatite within 12 Martian meteorites, including 11 shergottites and one basaltic regolith breccia. These data were combined with previously published data to gain a better understanding of the abundance and distribution of volatiles in the Martian interior. Apatites in individual Martian meteorites span a wide range of compositions, indicating they did not form by equilibrium crystallization. In fact, the intrasample variation in apatite is best described by either fractional crystallization or crustal contamination with a Cl-rich crustal component. We determined that most Martian meteorites investigated here have been affected by crustal contamination and hence cannot be used to estimate volatile abundances of the Martian mantle. Using the subset of samples that did not exhibit crustal contamination, we determined that the enriched shergottite source has 36-73 ppm H2O and the depleted source has 14-23 ppm H2O. This result is consistent with other observed geochemical differences between enriched and depleted shergottites and supports the idea that there are at least two geochemically distinct reservoirs in the Martian mantle. We also estimated the H2O, Cl, and F content of the Martian crust using known crust-mantle distributions for incompatible lithophile elements. We determined that the bulk Martian crust has ~1410 ppm H2O, 450 ppm Cl, and 106 ppm F, and Cl and H2O are preferentially distributed toward the Martian surface. The estimate of crustal H2O results in a global equivalent surface layer (GEL) of ~229 m, which can account for at least some of the surface features on Mars attributed to flowing water and may be sufficient to support the past presence of a shallow sea on Mars' surface.

  2. Vibrational and reorientational motions of H2O ligands, phase transition and thermal properties of [Sr(H2O)6]Cl2

    NASA Astrophysics Data System (ADS)

    Hetmańczyk, Joanna; Hetmańczyk, Łukasz; Migdał-Mikuli, Anna; Mikuli, Edward

    2013-11-01

    One phase transition (PT) at TCh = 252.9 K (on heating) and at TCc = 226.5 K (on cooling) was detected by DSC for [Sr(H2O)6]Cl2 in 123-295 K range. Thermal hysteresis of this PT equals to 26.4 K. Entropy change (ΔS) value at this first-order type phase transition equals to ca. 1.5 J mol-1 K-1. The temperature dependences of the full width at half maximum (FWHM) values of the infrared bands associated with ρt(H2O)E and δas(HOH)E modes (at ca. 417 and 1628 cm-1, respectively) suggest that the observed phase transition is associated with a sudden change of a speed of the H2O reorientational motions. The H2O ligands in the high temperature phase reorientate quickly (correlation times 10-11-10-13 s) with the activation energy of ca. 2 kJ mol-1. Below TCc probably a part of the H2O ligands stop their reorientation, while the remainders continue their fast reorientation but with the activation energy of ca. 8 kJ mol-1. Far and middle infrared spectra indicated characteristic changes at the vicinity of PT with decreasing of temperature, which suggested lowering of the crystal structure symmetry. Splitting of the band (at 3601 cm-1) connected with vas(OH) mode near the TCc suggests lowering of the crystal lattice symmetry. All these facts suggest that the discovered PT is connected both with a change of the reorientational dynamics of the H2O ligands and with the change of the crystal structure.

  3. Salidroside Stimulates Mitochondrial Biogenesis and Protects against H2O2-Induced Endothelial Dysfunction

    PubMed Central

    Xing, Shasha; Yang, Xiaoyan; Li, Wenjing; Bian, Fang; Wu, Dan; Chi, Jiangyang; Xu, Gao; Zhang, Yonghui; Jin, Si

    2014-01-01

    Salidroside (SAL) is an active component of Rhodiola rosea with documented antioxidative properties. The purpose of this study is to explore the mechanism of the protective effect of SAL on hydrogen peroxide- (H2O2-) induced endothelial dysfunction. Pretreatment of the human umbilical vein endothelial cells (HUVECs) with SAL significantly reduced the cytotoxicity brought by H2O2. Functional studies on the rat aortas found that SAL rescued the endothelium-dependent relaxation and reduced superoxide anion (O2∙−) production induced by H2O2. Meanwhile, SAL pretreatment inhibited H2O2-induced nitric oxide (NO) production. The underlying mechanisms involve the inhibition of H2O2-induced activation of endothelial nitric oxide synthase (eNOS), adenosine monophosphate-activated protein kinase (AMPK), and Akt, as well as the redox sensitive transcription factor, NF-kappa B (NF-κB). SAL also increased mitochondrial mass and upregulated the mitochondrial biogenesis factors, peroxisome proliferator-activated receptor gamma-coactivator-1alpha (PGC-1α), and mitochondrial transcription factor A (TFAM) in the endothelial cells. H2O2-induced mitochondrial dysfunction, as demonstrated by reduced mitochondrial membrane potential (Δψm) and ATP production, was rescued by SAL pretreatment. Taken together, these findings implicate that SAL could protect endothelium against H2O2-induced injury via promoting mitochondrial biogenesis and function, thus preventing the overactivation of oxidative stress-related downstream signaling pathways. PMID:24868319

  4. Optical Absorption and Photo-Thermal Conversion Properties of CuO/H2O Nanofluids.

    PubMed

    Wang, Liangang; Wu, Mingyan; Wu, Daxiong; Zhang, Canying; Zhu, Qunzhi; Zhu, Haitao

    2015-04-01

    Stable CuO/H2O nanofluids were synthesized in a wet chemical method. Optical absorption property of CuO/H2O nanofluids was investigated with hemispheric transmission spectrum in the wavelength range from 200 nm to 2500 nm. Photo-thermal conversion property of the CuO/H2O nanofluids was studied with an evaluation system equipped with an AUT-FSL semiconductor/solid state laser. The results indicate that CuO/H2O nanofluids have strong absorption in visible light region where water has little absorption. Under the irradiation of laser beam with a wavelength of 635 nm and a power of 0.015 W, the temperature of CuO/H2O nanofluids with 1.0% mass fraction increased by 5.6 °C within 40 seconds. Furthermore, the temperature elevation of CuO/H2O nanofluids was proved to increase with increasing mass fractions. On the contrast, water showed little temperature elevation under the identical conditions. The present work shows that the CuO/H2O nanofluids have high potential in the application as working fluids for solar utilization purpose. PMID:26353558

  5. Decoloration Kinetics of Waste Cooking Oil by 60Co γ-ray/H2O2

    NASA Astrophysics Data System (ADS)

    Xiang, Yulin; Xiang, Yuxiu; Wang, Lipeng

    2016-03-01

    In order to decolorize, waste cooking oil, a dark red close to black solution from homes and restaurants, was subjected to 60Co γ-ray/H2O2 treatment. By virtue of UV/Vis spectrophotometric method, the influence of Gamma irradiation to decoloration kinetics and rate constants of the waste cooking oil in the presence of H2O2 was researched. In addition, the influence of different factors such as H2O2 concentration and irradiation dose on the decoloration rate of waste cooking oil was investigated. Results indicated that the decoloration kinetics of waste cooking oil conformed to the first-order reaction. The decoloration rate increased with the increase of irradiation dose and H2O2 concentration. Saponification analysis and sensory evaluation showed that the sample by 60Co γ-ray/H2O2 treatment presented better saponification performance and sensory score. Furthermore, according to cost estimate, the cost of the 60Co γ-ray/H2O2 was lower and more feasible than the H2O2 alone for decoloration of waste cooking oil.

  6. Density functional study of H2O molecule adsorption on α-U(001) surface.

    PubMed

    Huang, Shanqisong; Zeng, Xiu-Lin; Zhao, Feng-Qi; Ju, Xuehai

    2016-04-01

    Periodic density functional theory (DFT) calculations were performed to investigate the adsorption of H2O on U(001) surface. The metallic nature of uranium atom and different adsorption sites of U(001) surface play key roles in the H2O molecular dissociate reaction. The long-bridge site is the most favorable site of H2O-U(001) adsorption configuration. The triangle-center site of the H atom is the most favorable site of HOH-U(001) adsorption configuration. The interaction between H2O and U surface is more evident on the first layer than that on any other two sub-layers. The dissociation energy of one hydrogen atom from H2O is -1.994 to -2.215 eV on U(001) surface, while the dissociating energy decreases to -3.351 to -3.394 eV with two hydrogen atoms dissociating from H2O. These phenomena also indicate that the Oads can promote the dehydrogenation of H2O. A significant charge transfer from the first layer of the uranium surface to the H and O atoms is also found to occur, making the bonding partly ionic. PMID:26994022

  7. Distribution and state of H2O in the high-latitude shallow subsurface of Mars

    NASA Technical Reports Server (NTRS)

    Zent, A. P.; Fanale, F. P.; Salvail, J. R.; Postawko, S. E.

    1986-01-01

    The state and distribution of H2O molecules at high latitudes are evaluated numerically with emphasis on the effects of seasonal temperatures on the kinetics of H2O transport. The investigation is carried out with a thermal model for the regolith regions from the surface through the ice interface and an atmospheric model for the H2O vapor density at the surface as a function of latitude. Few differences are found in the state and distribution of H2O whether the regolith is composed of Montmorillonite or basalt. During an obliquity cycle, the average exchanged H2O mass is determined to be in the range 1-20 gr/sq cm over the planetary surface, with a total maximum exchanged volume of 1500 cu km of H2O. The exchanged mass would arise mainly from ground ice in the case of a basalt regolith and from adsorbed H2O with Montmorillonite. Finally, seasonal ice stabilization is expected to occur at latitudes above 40 deg when obliquities exceed 25 deg.

  8. Tyrosine Kinase Signal Modulation: A Matter of H2O2 Membrane Permeability?

    PubMed Central

    Bertolotti, Milena; Bestetti, Stefano; García-Manteiga, Jose M.; Medraño-Fernandez, Iria; Dal Mas, Andrea; Malosio, Maria Luisa

    2013-01-01

    Abstract H2O2 produced by extracellular NADPH oxidases regulates tyrosine kinase signaling inhibiting phosphatases. How does it cross the membrane to reach its cytosolic targets? Silencing aquaporin-8 (AQP8), but not AQP3 or AQP4, inhibited H2O2 entry into HeLa cells. Re-expression of AQP8 with silencing-resistant vectors rescued H2O2 transport, whereas a C173A-AQP8 mutant failed to do so. Lowering AQP8 levels affected H2O2 entry into the endoplasmic reticulum, but not into mitochondria. AQP8 silencing also inhibited the H2O2 spikes and phosphorylation of downstream proteins induced by epidermal growth factor. These observations lead to the hypothesis that H2O2 does not freely diffuse across the plasma membrane and AQP8 and other H2O2 transporters are potential targets for manipulating key signaling pathways in cancer and degenerative diseases. Antioxid. Redox Signal. 19, 1447–1451. PMID:23541115

  9. Three-dimensional WS2 nanosheet networks for H2O2 produced for cell signaling.

    PubMed

    Tang, Jing; Quan, Yingzhou; Zhang, Yueyu; Jiang, Min; Al-Enizi, Abdullah M; Kong, Biao; An, Tiance; Wang, Wenshuo; Xia, Limin; Gong, Xingao; Zheng, Gengfeng

    2016-03-01

    Hydrogen peroxide (H2O2) is an important molecular messenger for cellular signal transduction. The capability of direct probing of H2O2 in complex biological systems can offer potential for elucidating its manifold roles in living systems. Here we report the fabrication of three-dimensional (3D) WS2 nanosheet networks with flower-like morphologies on a variety of conducting substrates. The semiconducting WS2 nanosheets with largely exposed edge sites on flexible carbon fibers enable abundant catalytically active sites, excellent charge transfer, and high permeability to chemicals and biomaterials. Thus, the 3D WS2-based nano-bio-interface exhibits a wide detection range, high sensitivity and rapid response time for H2O2, and is capable of visualizing endogenous H2O2 produced in living RAW 264.7 macrophage cells and neurons. First-principles calculations further demonstrate that the enhanced sensitivity of probing H2O2 is attributed to the efficient and spontaneous H2O2 adsorption on WS2 nanosheet edge sites. The combined features of 3D WS2 nanosheet networks suggest attractive new opportunities for exploring the physiological roles of reactive oxygen species like H2O2 in living systems. PMID:26909564

  10. Anionic ordering and thermal properties of FeF3·3H2O.

    PubMed

    Burbano, Mario; Duttine, Mathieu; Borkiewicz, Olaf; Wattiaux, Alain; Demourgues, Alain; Salanne, Mathieu; Groult, Henri; Dambournet, Damien

    2015-10-01

    Iron fluoride trihydrate can be used to prepare iron hydroxyfluoride with the hexagonal-tungsten-bronze (HTB) type structure, a potential cathode material for batteries. To understand this phase transformation, a structural description of β-FeF3·3H2O is first performed by means of DFT calculations and Mössbauer spectroscopy. The structure of this compound consists of infinite chains of [FeF6]n and [FeF2(H2O)4]n. The decomposition of FeF3·3H2O induces a collapse and condensation of these chains, which lead to the stabilization, under specific conditions, of a hydroxyfluoride network FeF3-x(OH)x with the HTB structure. The release of H2O and HF was monitored by thermal analysis and physical characterizations during the decomposition of FeF3·3H2O. An average distribution of FeF4(OH)2 distorted octahedra in HTB-FeF3-x(OH)x was obtained subsequent to the thermal hydrolysis/olation of equatorial anionic positions involving F(-) and H2O. This study provides a clear understanding of the structure and thermal properties of FeF3·3H2O, a material that can potentially bridge the recycling of pickling sludge from the steel industry by preparing battery electrodes. PMID:26378743

  11. Anionic ordering and thermal properties of FeF3·3H2O

    DOE PAGESBeta

    Burbano, Mario; Duttine, Mathieu; Borkiewicz, Olaf; Wattiaux, Alain; Demourgues, Alain; Salanne, Mathieu; Groult, Henri; Dambournet, Damien

    2015-09-17

    In this study, iron fluoride tri-hydrate can be used to prepare iron hydroxyfluoride with the Hexagonal-Tungsten-Bronze (HTB) type structure, a potential cathode material for batteries. To understand this phase transformation, a structural description of β-FeF3·3H2O is first performed by means of DFT calculations and Mössbauer spectroscopy. The structure of this compound consists of infinite chains of [FeF6]n and [FeF2(H2O)4]n. The decomposition of FeF3·3H2O induces a collapse and condensation of these chains, which lead to the stabilization, under specific conditions, of a hydroxyfluoride network FeF3-x(OH)x with the HTB structure. The release of H2O and HF was monitored by thermal analysis andmore » physical characterizations during the decomposition of FeF3·3H2O. An average distribution of FeF4(OH)2 distorted octahedra in HTB-FeF3-x(OH)x was obtained subsequent to the thermal hydrolysis/olation of equatorial anionic positions involving F- and H2O. This study provides a clear understanding of the structure and thermal properties of FeF3·3H2O, a material that can potentially bridge the recycling of pickling sludge from the steel industry by preparing battery electrodes.« less

  12. Ametryn degradation in the ultraviolet (UV) irradiation/hydrogen peroxide (H2O2) treatment.

    PubMed

    Gao, Nai-Yun; Deng, Yang; Zhao, Dandan

    2009-05-30

    Ultraviolet (UV) irradiation (253.7nm) in the presence of hydrogen peroxide (H(2)O(2)) was used to decompose aqueous ametryn. The concentrations of ametryn were measured with time under various experiment conditions. The investigated factors included H(2)O(2) dosages, initial pH, initial ametryn concentrations, and a variety of inorganic anions. Results showed that ametryn degradation in UV/H(2)O(2) process was a pseudo-first-order reaction. Removal rates of ametryn were greatly affected by H(2)O(2) dosage and initial concentrations of ametryn, but appeared to be slightly influenced by initial pH. Furthermore, we investigated the effects of four anions (SO(4)(2-), Cl(-), HCO(3)(-), and CO(3)(2-)) on ametryn degradation by UV/H(2)O(2). The impact of SO(4)(2-) seemed to be insignificant; however, Cl(-), HCO(3)(-), and CO(3)(2-) considerably slowed down the degradation rate because they could strongly scavenge hydroxyl radicals (OH) produced during the UV/H(2)O(2) process. Finally, a preliminary cost analysis revealed that UV/H(2)O(2) process was more cost-effective than the UV alone in removal of ametryn from water. PMID:18824296

  13. Sodium channel slow inactivation interferes with open channel block

    PubMed Central

    Hampl, Martin; Eberhardt, Esther; O’Reilly, Andrias O.; Lampert, Angelika

    2016-01-01

    Mutations in the voltage-gated sodium channel Nav1.7 are linked to inherited pain syndromes such as erythromelalgia (IEM) and paroxysmal extreme pain disorder (PEPD). PEPD mutations impair Nav1.7 fast inactivation and increase persistent currents. PEPD mutations also increase resurgent currents, which involve the voltage-dependent release of an open channel blocker. In contrast, IEM mutations, whenever tested, leave resurgent currents unchanged. Accordingly, the IEM deletion mutation L955 (ΔL955) fails to produce resurgent currents despite enhanced persistent currents, which have hitherto been considered a prerequisite for resurgent currents. Additionally, ΔL955 exhibits a prominent enhancement of slow inactivation (SI). We introduced mutations into Nav1.7 and Nav1.6 that either enhance or impair SI in order to investigate their effects on resurgent currents. Our results show that enhanced SI is accompanied by impaired resurgent currents, which suggests that SI may interfere with open-channel block. PMID:27174182

  14. H2O content of nominally anhydrous mineral inclusions in diamonds from the Udachnaya kimberlite

    NASA Astrophysics Data System (ADS)

    Novella, D.; Bolfan-Casanova, N.; Nestola, F.; Harris, J. W.

    2015-12-01

    Nominally anhydrous minerals (such as olivine, pyroxene and garnet) present in mantle xenoliths have been found to contain up to hundreds of ppm wt H2O, bonded as H to their mineral structure. However, it is not well understood whether these H2O contents are representative for the hydrous state of the deep mantle where they formed, or if they are the result of interactions between the xenoliths and metasomatic fluids or magmas during their travel to the surface. Given the fact that trace amounts of H2O can alter the physical and chemical properties of mantle materials and therefore affect Earth's dynamics, it is important to accurately determine the H2O content of deep mantle minerals. Natural diamonds can contain mineral inclusions that formed at high depths (>5 GPa) and are representative for the deep and inaccessible portions of the mantle where they originated. This is because the strong and inert diamond prevents the inclusions to react with any fluid or melt that get in contact with it. Therefore, valuable information regarding the H2O content of the deep mantle can be obtained by studying these minerals trapped in diamonds. In this study we measured the H2O contents of 10 olivine and garnet inclusions in diamonds from the Udachnaya kimberlite (Siberian craton) by Fourier Transform Infrared spectroscopy. Olivine crystals contain 1-5 ppm wt H2O while garnets do not show absorption bands indicating the presence of detectable H in their structure and are therefore considered dry. The H2O contents of olivine and garnet inclusions in diamonds presented here are considerably lower than those found in xenoliths or xenocrists from the same locality. Based on these new results, we discuss the presence of H2O in the cratonic mantle and its importance in stabilizing these areas during geological time, as well as the volatile signature of diamond forming melts in the Siberian craton.

  15. Stability and prospect of UV/H2O2 activated titania films for biomedical use

    NASA Astrophysics Data System (ADS)

    Unosson, Erik; Welch, Ken; Persson, Cecilia; Engqvist, Håkan

    2013-11-01

    Biomedical implants and devices that penetrate soft tissue are highly susceptible to infection, but also accessible for UV induced decontamination through photocatalysis if coated with suitable surfaces. As an on-demand antibacterial strategy, photocatalytic surfaces should be able to maintain their antibacterial properties over repeated activation. This study evaluates the surface properties and photocatalytic performance of titania films obtained by H2O2-oxidation and heat treatment of Ti and Ti-6Al-4V substrates, as well as the prospect of assisting photocatalytic reactions with H2O2 for improved efficiency. H2O2-oxidation generated a nanoporous coating, and subsequent heat treatment above 500 °C resulted in anatase formation. Tests using photo-assisted degradation of rhodamine B showed that prior to heat treatment, an initially high photocatalytic activity (PCA) of H2O2-oxidized substrates decayed significantly with repeated testing. Heat treating the samples at 600 °C resulted in stable yet lower PCA. Addition of 3% H2O2 during the photo-assisted reaction led to a substantial increase in PCA due to synergetic effects at the surface and H2O2 photolysis, the effect being most notable for non-heat treated samples. Both heat treated and non-heat treated samples showed stable PCA through repeated tests with H2O2-assisted photocatalysis, indicating that the combination of H2O2-oxidized titania films, UV light and added H2O2 can improve efficiency of these photocatalytic surfaces.

  16. Characteristics of natural organic matter degradation in water by UV/H2O2 treatment.

    PubMed

    Wang, G S; Liao, C H; Chen, H W; Yang, H C

    2006-03-01

    This study evaluated the UV/H2O2 system for degradation of natural organic matter in water. The photolysis experiments were conducted in a 10-l batch reactor using a 450-watt high-pressure mercury vapor lamp as the light source. The addition of H2O2 in water greatly improved the rate of humic acid degradation by UV light and 90% of the humic acid was removed within 30 min of photolysis. Kinetic data showed that the first-order reaction could be used to describe the kinetics of both humic acid oxidation and H2O2 decomposition, and the optimum H2O2 dose was 0.01%-0.05% for humic acid oxidation. It was also observed that the absorption of UVC (UV with wavelength between 200 and 280 nm) is responsible for the dissociation of H2O2 to generate the reactive hydroxyl radicals. Depending on the initial dosages, the H2O2 added to the system can be completely decomposed by UV within 50 to 90 minutes. Upon UV irradiation, the humic intermediates with smaller molecular sizes increase as a result of the degradation of larger humic substances. Photolysis of surface water also shows that the UV/H2O2 was effective in reducing trihalomethanes (THMs) formation in treating surface water with high contents of organic precursors. The distribution of THMs shifted from chlorine-THMs to bromine-THMs after UV/H2O2 treatments when bromide was present in water. However, higher H2O2 dosages would be necessary for the photolysis of surface water containing high concentrations of organic THM precursors. As observed from the Fourier transform infrared (FTIR) spectra, the functional groups of treated humic acids were destructed significantly, including -OH (from -COOH and -COH), aromatic -C=C, and -C=O conjugated with aromatic rings. PMID:16548208

  17. Role of Structural H2O in Intercalation Electrodes: The Case of Mg in Nanocrystalline Xerogel-V2O5.

    PubMed

    Sai Gautam, Gopalakrishnan; Canepa, Pieremanuele; Richards, William Davidson; Malik, Rahul; Ceder, Gerbrand

    2016-04-13

    Cointercalation is a potential approach to influence the voltage and mobility with which cations insert in electrodes for energy storage devices. Combining a robust thermodynamic model with first-principles calculations, we present a detailed investigation revealing the important role of H2O during ion intercalation in nanomaterials. We examine the scenario of Mg(2+) and H2O cointercalation in nanocrystalline Xerogel-V2O5, a potential cathode material to achieve energy density greater than Li-ion batteries. Water cointercalation in cathode materials could broadly impact an electrochemical system by influencing its voltages or causing passivation at the anode. The analysis of the stable phases of Mg-Xerogel V2O5 and voltages at different electrolytic conditions reveals a range of concentrations for Mg in the Xerogel and H2O in the electrolyte where there is no thermodynamic driving force for H2O to shuttle with Mg during electrochemical cycling. Also, we demonstrate that H2O shuttling with the Mg(2+) ions in wet electrolytes yields higher voltages than in dry electrolytes. The thermodynamic framework used to study water and Mg(2+) cointercalation in this work opens the door for studying the general phenomenon of solvent cointercalation observed in other complex solvent-electrode pairs used in the Li- and Na-ion chemical spaces. PMID:26982964

  18. Submillimeter H2O emission in infrared bright galaxies near and far

    NASA Astrophysics Data System (ADS)

    Yang, Chentao

    2015-08-01

    We conduct the first systematic study of the submillimeter H2O rotational emission lines in the infrared bright galaxies from local to high redshift universe observed by FTS/Herschel and PdBI. Among the 176 local galaxies, 45 have at least one H2O emission line detected. And H2O is found to be the strongest molecular emitter after CO in FTS spectra. For the five most detected H2O lines, the luminosity is near-linearly correlated with LIR no matter strong AGN signature is present or not. However, the luminosity of H2O (211-202) and H2O (220-211) appears to increase slightly faster than linear with LIR. Although the slope turns out to be slightly steeper when z˜2-4 ULIRGs (Ultra-Luminous InfraRed Galaxies) are included, the correlation is still not far from linear. We find that LH2O/LIR decreases with increasing infrared color f25/f60, but nearly no dependence on f60/f100, possibly indicating that very warm dust contributes little to the excitation of submillimeter H2O lines, and this is consistent with later modeling studies. The average spectral line energy distribution (SLED) of entire sample is consistent with individual SLEDs and the IR pumping plus collisional excitation model, showing that the strongest lines are H2O (202-111) and H2O (321-312). Moreover, we have detected J=2 and J=3 H2O lines in 17 high-z lensed ULIRGs that picked from H-ATLAS survey. Most of their line profiles are similar to those of the high-J CO lines, indicating the similar location. By comparing the map of H2O and dust continuum emission, the emission from H2O is more compact than dust. A slightly faster than linear correlation has been found in these high-z ULIRGs. However, high resolution study by the telescopes, e.g., NOEMA and ALMA, is still need for studying the spatial distribution of the water vapor.

  19. Do aerosols influence the diurnal variation of H2O2 in the atmosphere?

    NASA Astrophysics Data System (ADS)

    Liang, H.; Chen, Z.; Wu, Q.; Huang, D.; Zhao, Y.

    2013-12-01

    Hydrogen peroxide (H2O2) and organic peroxides are crucial reactive species that are involved in the cycling of HOx (OH and HO2) radicals and the formation of secondary inorganic and organic aerosols in the atmosphere. Despite the importance of peroxides, their formation and removal mechanisms with the coexistence of aerosols are as yet less well known. From June 10 to July 15 2013, summertime surface measurements for atmospheric peroxides were simultaneously obtained in urban Beijing (UB) and Gucheng (GC). The UB site is located in the northern downtown of Beijing city, while the GC site is a rural site located in the North China Plain and ~100 km southwest of Beijing. In both sites, the major peroxides were determined to be H2O2, methyl hydroperoxide (MHP), peroxyformic acid (PFA) and peroxyacetic acid (PAA). By comparing the concentrations of PFA and PAA in the gas phase and rainwater, for the first time, we estimated the Henry's law constant for PFA as ~210 M atm-1 at 298 K, a quarter of that for PAA. Interestingly, we observed different H2O2 profiles in the two sites as follows: (i) the average concentration of H2O2 in UB was 50% higher than that in GC; (ii) H2O2 in GC reached its peak concentration at around 15:30, whereas the peak concentration in UB appeared at as late as 21:00; and (iii) the daily variation of H2O2 in GC generally kept consistent with that of O3 and organic peroxides while it was not always the case in UB. These differences indicate a hitherto unrecognized storage-release mechanism for H2O2 in UB, that is, an extra sink in the noontime and an extra source in the early evening. The extra source of H2O2 would enhance the aerosol phase OH radical in the early evening by the Fenton reaction. A box model analysis shows that the impacts of aerosols were majorly responsible to this unrecognized mechanism, although NOx, regional transport and planet boundary layer height also contributed a minor part. Aerosols participated in the storage

  20. Hydrothermal synthesis and characterization of the lutetium borate-nitrate Lu2B2O5(NO3)2·2H2O

    NASA Astrophysics Data System (ADS)

    Ortner, Teresa S.; Wurst, Klaus; Hejny, Clivia; Huppertz, Hubert

    2016-01-01

    The lutetium diborate-dinitrate Lu2B2O5(NO3)2·2H2O was discovered through a hydrothermal synthesis from Lu(NO3)3·H2O and H3BO3. The compound crystallizes in the space group P 1 ̅ (no. 2) with the lattice parameters a=789.52(5), b=988.62(6), c=1460.33(8) pm, α=90.83(1), β=101.75(1), and γ=110.02(1)° (Z=4). Isolated [B2O5]4- units show coplanar alignment and the coordinating [NO3]- groups are stacked perpendicular to the borate plane. Thereby, a novel, open arrangement solely built up from diborate and nitrate groups at a 1:1 ratio is formed. Additionally, Lu2B2O5(NO3)2·2H2O is characterized by vibrational spectroscopy (IR/Raman).

  1. Calculating CO2 and H2O eddy covariance fluxes from an enclosed gas analyzer using an instantaneous mixing ratio 2159

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Eddy covariance flux research has relied on open- or closed-path gas analyzers for producing estimates of net ecosystem exchange of carbon dioxide (CO2) and water vapor (H2O). The two instruments have had different challenges that have led to development of an enclosed design that is intended to max...

  2. Measurements of CO2 and H2O fluxes of crop plants are essential to understand the impacts of environmental variables on crop productivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Measurements of CO2 and H2O fluxes of crop plants are essential to understand the impacts of environmental variables on crop productivity. A portable, CETA (Canopy Evapo-Transpiration and Assimilation) chamber system was built and evaluated at Big Spring, TX. This chamber system is an open or flow...

  3. A novel open-framework copper borophosphate containing 1-D borophosphate anion with 10-MR windows and 12-MR channels.

    PubMed

    Feng, Yuquan; Li, Min; Fan, Huitao; Huang, Qunzeng; Qiu, Dongfang; Shi, Hengzhen

    2015-01-21

    A novel open-framework copper borophosphate, Na5KCu3[B9P6O33(OH)3]·H2O (), has been synthesised by a boric acid flux method. Its structure can be viewed as a 3-D open framework constructed by the connection of Cu(II)O6 octahedra and 1-D (4,4)-connected borophosphate anionic structures composed of trigonal-planar BO2(OH) groups, tetrahedral BO4 and PO4 groups. The compound not only features a novel borophosphate anionic partial structure containing 1-D 12-MR channels, but also exhibits ferromagnetic interactions and high catalytic activity for the oxidative degradation of chitosan. PMID:25437261

  4. Absorption cross sections of surface-adsorbed H2O in the 295-370 nm region and heterogeneous nucleation of H2O on fused silica surfaces.

    PubMed

    Du, Juan; Huang, Li; Zhu, Lei

    2013-09-12

    We have determined absorption cross sections of a monolayer of H2O adsorbed on the fused silica surfaces in the 295-370 nm region at 293 ± 1 K by using Brewster angle cavity ring-down spectroscopy. Absorption cross sections of surface-adsorbed H2O vary between (4.66 ± 0.83) × 10(-20) and (1.73 ± 0.52) × 10(-21) cm(2)/molecule over this wavelength range, where errors quoted represent experimental scatter (1σ). Our experimental study provides direct evidence that surface-adsorbed H2O is an absorber of the near UV solar radiation. We also varied the H2O pressure in the surface study cell over the 0.01-17 Torr range and obtained probe laser absorptions at 295, 340, and 350 nm by multilayer of adsorbed H2O molecules until the heterogeneous nucleation of water occurred on fused silica surfaces. The average absorption cross sections of multilayer adsorbed H2O are (2.17 ± 0.53) × 10(-20), (2.48 ± 0.67) × 10(-21), and (2.34 ± 0.59) × 10(-21) cm(2)/molecule at 295, 340, and 350 nm. The average absorption cross sections of transitional H2O layer are (6.06 ± 2.73) × 10(-20), (6.48 ± 3.85) × 10(-21), and (8.04 ± 4.92) × 10(-21) cm(2)/molecule at 295, 340, and 350 nm. The average thin water film absorption cross sections are (2.39 ± 0.50) × 10(-19), (3.21 ± 0.81) × 10(-20), and (3.37 ± 0.94) × 10(-20) cm(2)/molecule at 295 nm, 340 nm, and 350 nm. Atmospheric implications of the results are discussed. PMID:23947798

  5. The evolution of the early Martian climate and the initial emplacement of crustal H2O

    NASA Technical Reports Server (NTRS)

    Clifford, S. M.

    1993-01-01

    Given the geomorphic evidence for the widespread occurrence of water and ice in the early Martian crust, and the difficulty involved in accounting for this distribution given the present climate, it has been suggested that the planet's early climate was originally more Earth-like, permitting the global emplacement of crustal H2O by direct precipitation as snow or rain. The resemblance of the Martian valley networks to terrestrial runoff channels and their almost exclusive occurrence in the planet's ancient (approximately 4-b.y.-old) heavily cratered terrain are often cited as evidence of just such a period. An alternative school of thought suggests that the early climate did not differ substantially from that of today. Advocates of this view find no compelling reason to invoke a warmer, wetter period to explain the origin of the valley networks. Rather, they cite evidence that the primary mechanism of valley formation was groundwater sapping, a process that does not require that surface water exists in equilibrium with the atmosphere. However, while sapping may successfully explain the origin of the small valleys, it fails to address how the crust was initially charged with ice as the climate evolved towards its present state. Therefore, given the uncertainty regarding the environmental conditions that prevailed on early Mars, the initial emplacement of ground ice is considered here from two perspectives: (1) the early climate started warm and wet, but gradually cooled with time, and (2) the early climate never differed substantially from that of today.

  6. Redetermination of kovdorskite, Mg2PO4(OH)·3H2O

    PubMed Central

    Morrison, Shaunna M.; Downs, Robert T.; Yang, Hexiong

    2012-01-01

    The crystal structure of kovdorskite, ideally Mg2PO4(OH)·3H2O (dimagnesium phosphate hydroxide trihydrate), was reported previously with isotropic displacement paramaters only and without H-atom positions [Ovchinnikov et al. (1980 ▶). Dokl. Akad. Nauk SSSR. 255, 351–354]. In this study, the kovdorskite structure is redetermined based on single-crystal X-ray diffraction data from a sample from the type locality, the Kovdor massif, Kola Peninsula, Russia, with anisotropic displacement parameters for all non-H atoms, with all H-atom located and with higher precision. Moreover, inconsistencies of the previously published structural data with respect to reported and calculated X-ray powder patterns are also discussed. The structure of kovdorskite contains a set of four edge-sharing MgO6 octa­hedra inter­connected by PO4 tetra­hedra and O—H⋯O hydrogen bonds, forming columns and channels parallel to [001]. The hydrogen-bonding system in kovdorskite is formed through the water mol­ecules, with the OH− ions contributing little, if any, to the system, as indicated by the long H⋯A distances (>2.50 Å) to the nearest O atoms. The hydrogen-bond lengths determined from the structure refinement agree well with Raman spectroscopic data. PMID:22346789

  7. Optimization of a gas sampling system for measuring eddy-covariance fluxes of H2O and CO2

    NASA Astrophysics Data System (ADS)

    Metzger, S.; Burba, G.; Burns, S. P.; Blanken, P. D.; Li, J.; Luo, H.; Zulueta, R. C.

    2015-10-01

    Several initiatives are currently emerging to observe the exchange of energy and matter between the earth's surface and atmosphere standardized over larger space and time domains. For example, the National Ecological Observatory Network (NEON) and the Integrated Carbon Observing System (ICOS) will provide the ability of unbiased ecological inference across eco-climatic zones and decades by deploying highly scalable and robust instruments and data processing. In the construction of these observatories, enclosed infrared gas analysers are widely employed for eddy-covariance applications. While these sensors represent a substantial improvement compared to their open- and closed-path predecessors, remaining high-frequency attenuation varies with site properties, and requires correction. Here, we show that the gas sampling system substantially contributes to high-frequency attenuation, which can be minimized by careful design. From laboratory tests we determine the frequency at which signal attenuation reaches 50 % for individual parts of the gas sampling system. For different models of rain caps and particulate filters, this frequency falls into ranges of 2.5-16.5 Hz for CO2, 2.4-14.3 Hz for H2O, and 8.3-21.8 Hz for CO2, 1.4-19.9 Hz for H2O, respectively. A short and thin stainless steel intake tube was found to not limit frequency response, with 50 % attenuation occurring at frequencies well above 10 Hz for both H2O and CO2. From field tests we found that heating the intake tube and particulate filter continuously with 4 W was effective, and reduced the occurrence of problematic relative humidity levels (RH > 60 %) by 50 % in the infrared gas analyser cell. No further improvement of H2O frequency response was found for heating in excess of 4 W. These laboratory and field tests were reconciled using resistor-capacitor theory, and NEON's final gas sampling system was developed on this basis. The design consists of the stainless steel intake tube, a pleated mesh

  8. Optimization of an enclosed gas analyzer sampling system for measuring eddy covariance fluxes of H2O and CO2

    NASA Astrophysics Data System (ADS)

    Metzger, Stefan; Burba, George; Burns, Sean P.; Blanken, Peter D.; Li, Jiahong; Luo, Hongyan; Zulueta, Rommel C.

    2016-03-01

    Several initiatives are currently emerging to observe the exchange of energy and matter between the earth's surface and atmosphere standardized over larger space and time domains. For example, the National Ecological Observatory Network (NEON) and the Integrated Carbon Observing System (ICOS) are set to provide the ability of unbiased ecological inference across ecoclimatic zones and decades by deploying highly scalable and robust instruments and data processing. In the construction of these observatories, enclosed infrared gas analyzers are widely employed for eddy covariance applications. While these sensors represent a substantial improvement compared to their open- and closed-path predecessors, remaining high-frequency attenuation varies with site properties and gas sampling systems, and requires correction. Here, we show that components of the gas sampling system can substantially contribute to such high-frequency attenuation, but their effects can be significantly reduced by careful system design. From laboratory tests we determine the frequency at which signal attenuation reaches 50 % for individual parts of the gas sampling system. For different models of rain caps and particulate filters, this frequency falls into ranges of 2.5-16.5 Hz for CO2, 2.4-14.3 Hz for H2O, and 8.3-21.8 Hz for CO2, 1.4-19.9 Hz for H2O, respectively. A short and thin stainless steel intake tube was found to not limit frequency response, with 50 % attenuation occurring at frequencies well above 10 Hz for both H2O and CO2. From field tests we found that heating the intake tube and particulate filter continuously with 4 W was effective, and reduced the occurrence of problematic relative humidity levels (RH > 60 %) by 50 % in the infrared gas analyzer cell. No further improvement of H2O frequency response was found for heating in excess of 4 W. These laboratory and field tests were reconciled using resistor-capacitor theory, and NEON's final gas sampling system was developed on this

  9. Chemical Reactions in Protoplanetary Disks and Possibility of Detecting H2O Snowline Using Spectroscopic Observations with ALMA

    NASA Astrophysics Data System (ADS)

    Notsu, S.; Nomura, H.; Ishimoto, D.; Walsh, C.; Honda, M.; Millar, T. J.

    2015-12-01

    We calculate chemical reactions and obtain abundance distribution of H2O gas. We confirm that the abundance of H2O is high not only in the region inside H2 O snowline near the equatorial plane but also in the hot surface layer of outer disk. We also calculate velocity profiles of H2O emission lines, and find that we can obtain the information of H2O snowline through investigating the profiles of some line transitions that have small Einstein A coefficient and large excitation energy. Some useful H2O emission lines exist at sub-millimeter wavelength and are observable with ALMA.

  10. The condensation and vaporization behavior of H2O:CO ices and implications for interstellar grains and cometary activity

    NASA Technical Reports Server (NTRS)

    Sandford, Scott A.; Allamandola, Louis J.

    1988-01-01

    IR spectroscopy has been used to ascertain several parameters associated with CO, H2O, and H2O:CO ices' physical behavior. Since CO is noted to be capable of condensing into H2O-rich ices at temperatures that are twice as high as those required for condensation in pure CO, CO is able to condense onto H2O-rich ice grains at temperatures of up to 50 K. CO's presence in H2O ice modestly enhances the effective volatility of the H2O. Attention is given to the implications of these results for cometary models generally and the question of cometary formation specifically.

  11. New H2O masers in Seyfert and FIR bright galaxies. III. The southern sample

    NASA Astrophysics Data System (ADS)

    Surcis, G.; Tarchi, A.; Henkel, C.; Ott, J.; Lovell, J.; Castangia, P.

    2009-08-01

    Context: A relationship between the water maser detection rate and far infrared (FIR) flux densities was established as a result of two 22 GHz maser surveys in a complete sample of galaxies ({Dec>-30°) with {100 μ m} flux densities of >50 Jy and >30 Jy. Aims: We attempted to discover new maser sources and investigate the galaxies hosting the maser spots by extending previous surveys to southern galaxies with particular emphasis on the study of their nuclear regions. Methods: A sample of 12 galaxies with {Dec<-30° and S100 μ m>50 Jy was observed with the 70-m telescope of the Canberra deep space communication complex (CDSCC) at Tidbinbilla (Australia) in a search for water maser emission. The average 3σ noise level of the survey was 15 mJy for a {0.42 km s-1} channel, corresponding to a detection threshold of ˜ 0.1 L⊙ for the isotropic maser luminosity at a distance of 25 Mpc. Results: Two new detections are reported: a kilomaser with an isotropic luminosity L{H2O}˜5 L⊙ in NGC 3620 and a maser with about twice this luminosity in the merger system NGC 3256. The detections have been followed-up by continuum and spectral line interferometric observations with the Australia Telescope Compact Array (ATCA). In NGC 3256, a fraction (about a third) of the maser emission originates in two hot spots associated with star formation activity, which are offset from the galactic nuclei of the system. The remaining emission may originate in weaker centres of maser activity distributed over the central 50''. For NGC 3620, the water maser is coincident with the nuclear region of the galaxy. Our continuum observations indicate that the nature of the nuclear emission is probably linked to particularly intense star formation. Including the historical detection in NGC 4945, the water maser detection rate in the southern sample is 15% (3/20), consistent with the northern sample. The high rate of maser detections in the complete all-sky FIR sample (23%, 15/65) confirms the

  12. Radiolytic corrosion of uranium dioxide induced by He2+ localized irradiation of water: Role of the produced H2O2 distance

    NASA Astrophysics Data System (ADS)

    Traboulsi, Ali; Vandenborre, Johan; Blain, Guillaume; Humbert, Bernard; Haddad, Ferid; Fattahi, Massoud

    2015-12-01

    The short-range (few μm in water) of the α-emitting from the spent fuel involves that the radiolytic corrosion of this kind of sample occurs at the solid/solution interface. In order to establish the role of localization of H2O2 species produced by the He2+ particle beam in water from the surface, we perform UO2 radiolytic corrosion experiment with different distance between H2O2 production area and UO2 surface. Then, in this work, the radiolytic corrosion of UO2 particles by oxidative species produced by 4He2+ radiolysis of water was investigated in open to air atmosphere. The dose rate, the localization of H2O2 produced by water radiolysis and the grain boundaries present on the surface of the particles were investigated. UO2 corrosion was investigated by in situ (during irradiation) characterization of the solid surface, analysis of H2O2 produced by water radiolysis and quantification of the uranium species released into the solution during irradiation. Characterization of the UO2 particles, surface and volume, was realized by Raman spectroscopy. UV-vis spectrophotometry was used to monitor H2O2 produced by water radiolysis and in parallel the soluble uranium species released into the solution were quantified by inductively coupled plasma mass spectrometry. During the He2+ irradiation of ultra-pure water in contact with the UO2 particles, metastudtite phase was formed on the solid surface indicating an oxidation process of the particles by the oxidative species produced by water radiolysis. This oxidation occurred essentially on the grain boundaries and was accompanied by migration of soluble uranium species (U(VI)) into the irradiated solution. Closer to the surface the localization of H2O2 formation, higher the UO2 oxidation process occurs, whereas the dose rate had no effect on it. Simultaneously, closer to the surface the localization of H2O2 formation lower the H2O2 concentration measured in solution. Moreover, the metastudtite was the only secondary

  13. 40 CFR 1065.370 - CLD CO2 and H2O quench verification.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... analyzer uses quench compensation algorithms that utilize H2O and/or CO2 measurement instruments, evaluate quench with these instruments active and evaluate quench with the compensation algorithms applied....

  14. New Optical Constants of Amorphous and Crystalline H2O-ice, 3-20_m

    NASA Technical Reports Server (NTRS)

    Mastrapa, Rachel Michelle Elizab

    2008-01-01

    We will present new optical constants forth amorphous and crystalline H2O-ice in the spectral range 3-20 _m. Our new measurements provide high temperature resolution for crystalline H2O-ice, 10 K intervals from 20-150 K, including temperatures relevant to Solar System ices. We have found that the shape of the 3 _m feature in amorphous H2O-ice is strongly dependant on deposition temperature and the high and low density phases of amorphous H2O-ice are not easily distinguishable. We will present methods of measuring the change in band shape with phase and temperature. We acknowledge financial support from the NASA Origins of the Solar System Program and the NASA Planetary Geology and Geophysics Program.

  15. Reactions of chlorine nitrate with HCl and H2O. [ozone controlling chemistry in stratosphere

    NASA Technical Reports Server (NTRS)

    Hatakeyama, Shiro; Leu, Ming-Taun

    1986-01-01

    The kinetics of the reactions of chlorine nitrate with HCl and H2O are characterized using a static photolysis/Fourier transform infrared spectrophotometer apparatus. For the homogeneous gas-phase reaction with HCl, an upper limit for the rate constant of less than 8.4 x 10 to the -21st, and for the reaction with H2O, a limit of less than 3.4 x 10 to the -21st cu cm/molecule per s, were obtained at 296 + or - 2 K. The yield of HNO3 is almost unity in both cases, and no synergistic effect is noted between HCl and H2O. The kinetic behavior of the reaction with H2O is well described by simple first-order kinetics, while the behavior of the reaction with HCl is described in terms of the Langmuir adsorption isotherm.

  16. [Cryogenic Raman spectroscopic characteristics of NaCl-H2O, CaCl2-H2O and NaCl-CaCl2-H2O: application to analysis of fluid inclusions].

    PubMed

    Mao, Cui; Chen, Yong; Zhou, Yao-Qi; Ge, Yun-Jin; Zhou, Zhen-Zhu; Wang, You-Zhi

    2010-12-01

    Accurately diagnosing the types of the salt and calculating the salinity quantitatively are the significant content of fluid inclusions. The traditional method of testing fluid inclusions salinity is cooling. To overcome the difficulty for observing freezing phase transition, the authors tested the spectrum of NaCl-H2O, CaCl2-H2O and NaCl-CaCl2-H2O systems at -180 degrees C by laser Raman spectroscopy. The result demonstrates that the ratio of peak values has linear relationship with salinity. Calibration curves were established by typical ratio of hydro-halite at 3 420 cm(-1) to the ice at 3 092 cm(-1), and the ratio of antarcticite at 3 432 cm(-1) to the ice at 3 092 cm(-1). The calibration curves have very high correlation coefficient. This method is verified by synthetic hydrocarbon-bearing aqueous fluid inclusions and quartz aqueous fluid inclusions of well Fengshen 6 in Dongying sag. The results of the authors' experiments show that cryogenic Raman spectroscopy can not only identify the types of the salts but also determine the salinity effectively in fluid inclusions. PMID:21322218

  17. Amphibole stability in primitive arc magmas: effects of temperature, H2O content, and oxygen fugacity

    NASA Astrophysics Data System (ADS)

    Krawczynski, Michael J.; Grove, Timothy L.; Behrens, Harald

    2012-08-01

    The water-saturated phase relations have been determined for a primitive magnesian andesite (57 wt% SiO2, 9 wt% MgO) from the Mt. Shasta, CA region over the pressure range 200-800 MPa, temperature range of 915-1,070 °C, and oxygen fugacities varying from the nickel-nickel oxide (NNO) buffer to three log units above NNO (NNO+3). The phase diagram of a primitive basaltic andesite (52 wt% SiO2, 10.5 wt% MgO) also from the Mt. Shasta region (Grove et al. in Contrib Miner Petrol 145:515-533; 2003) has been supplemented with additional experimental data at 500 MPa. Hydrous phase relations for these compositions allow a comparison of the dramatic effects of dissolved H2O on the crystallization sequence. Liquidus mineral phase stability and appearance temperatures vary sensitively in response to variation in pressure and H2O content, and this information is used to calibrate magmatic barometers-hygrometers for primitive arc magmas. H2O-saturated experiments on both compositions reveal the strong dependence of amphibole stability on the partial pressure of H2O. A narrow stability field is identified where olivine and amphibole are coexisting phases in the primitive andesite composition above 500 MPa and at least until 800 MPa, between 975-1,025 °C. With increasing H2O pressure ({P}_{{H}_2O}), the temperature difference between the liquidus and amphibole appearance decreases, causing a change in chemical composition of the first amphibole to crystallize. An empirical calibration is proposed for an amphibole first appearance barometer-hygrometer that uses Mg# of the amphibole and f_{{O}_2}: P_{{H}2O}(MPa)=[{Mg#/52.7}-0.014 * Updelta NNO]^{15.12} This barometer gives a minimum {P}_{{H}2O} recorded by the first appearance of amphibole in primitive arc basaltic andesite and andesite. We apply this barometer to amphibole antecrysts erupted in mixed andesite and dacite lavas from the Mt. Shasta, CA stratocone. Both high H2O pressures (500-900 MPa) and high pre-eruptive magmatic

  18. TES/Aura L2 Water Vapor (H2O) Limb (TL2H2OLS)

    Atmospheric Science Data Center

    2015-01-30

    TES/Aura L2 Water Vapor (H2O) Limb (TL2H2OLS) News:  TES News ... Level:  L2 Platform:  TES/Aura L2 Water Vapor Spatial Coverage:  27 x 23 km Limb ... Access:  OPeNDAP Parameters:  H2O Water Volume Mixing Radio Precision Vertical Resolution Order ...

  19. Decolorization of alkaline TNT hydrolysis effluents using UV/H(2)O(2).

    PubMed

    Hwang, Sangchul; Bouwer, Edward J; Larson, Steven L; Davis, Jeffrey L

    2004-04-30

    Effects of H(2)O(2) dosage (0, 10, 50, 100 and 300 mg/l), reaction pH (11.9, 6.5 and 2.5) and initial color intensity (85, 80 and 60 color unit) on decolorization of alkaline 2,4,6-trinitrotoluene (TNT) hydrolysis effluents were investigated at a fixed UV strength (40 W/m(2)). Results indicated that UV/H(2)O(2) oxidation could efficiently achieve decolorization and further mineralization. Pseudo first-order decolorization rate constants, k, ranged between 2.9 and 5.4 h(-1) with higher values for lower H(2)O(2) dosage (i.e., 10 mg/l H(2)O(2)) when the decolorization occurred at the reaction pH of 11.9, whereas a faster decolorization was achieved with increase in H(2)O(2) dosage at both pH 6.5 and 2.5, resulting in the values of k as fast as 15.4 and 26.6 h(-1) with 300 mg/l H(2)O(2) at pH 6.5 and 2.5, respectively. Difference in decolorization rates was attributed to the reaction pH rather than to the initial color intensity, resulting from the scavenging of hydroxyl radical by carbonate ion. About 40% of spontaneous mineralization was achieved with addition of 10 mg/l H(2)O(2) at pH 6.5. Efficient decolorization and extension of H(2)O(2) longevity were observed at pH 6.5 conditions. It is recommended that the colored effluents from alkaline TNT hydrolysis be neutralized prior to a decolorization step. PMID:15081163

  20. Titanium silicalite-1 zeolite microparticles for enzymeless H2O2 detection.

    PubMed

    Liu, Sen; Tian, Jingqi; Zhai, Junfeng; Wang, Lei; Lu, Wenbo; Sun, Xuping

    2011-05-21

    In this communication, we demonstrate for the first time that titanium silicalite-1 zeolite microparticles (TSZMs) can effectively catalyze the reduction of H(2)O(2), leading to an enzymeless H(2)O(2) sensor with a linear detection range from 100 μM to 40 mM (r = 0.994) and a detection limit of 0.5 μM at a signal-to-noise ratio of 3. PMID:21431231

  1. Removal of azo dye C.I. acid red 14 from contaminated water using Fenton, UV/H(2)O(2), UV/H(2)O(2)/Fe(II), UV/H(2)O(2)/Fe(III) and UV/H(2)O(2)/Fe(III)/oxalate processes: a comparative study.

    PubMed

    Daneshvar, N; Khataee, A R

    2006-01-01

    The decolorization of the solution containing a common textile and leather dye, C.I. Acid Red 14 (AR14), at pH 3 by hydrogen peroxide photolysis, Fenton, Fenton-like and photo-Fenton processes was studied. The dark and light reactions were carried out in stirred batch photoreactor equipped with an UV-C lamp (30 W) as UV light source. The experiments showed that the dye was resistant to the UV illumination, but was oxidized when one of Fe(II), Fe(III) and H(2)O(2) compounds was present. It was also found that UV light irradiation can accelerate significantly the rate of AR14 decolorization in the presence of Fe(III)/H(2)O(2) or Fe(II)/H(2)O(2), comparing to that in the dark. The effect of different system variables like initial concentration of the azo dye, effect of UV light irradiation, initial concentration of Fe(II) or Fe(III) and added oxalate ion has been investigated. The results showed that the decolorization efficiency of AR14 at the reaction time of 2 min follows the decreasing order: UV/H(2)O(2)/Fe(III)/oxalate > UV/H(2)O(2)/Fe(III) > UV/H(2)O(2)/Fe(II) > UV/H(2)O(2). Our results also showed that the UV/H(2)O(2)/Fe(III)/oxalate process was appropriate as the effective treatment method for decolorization of a real dyeing and finishing. The mechanism for each process is also discussed and linked together for understanding the observed differences in reactivity. PMID:16484066

  2. Radiolysis of H2O:CO2 ices by heavy energetic cosmic ray analogs

    NASA Astrophysics Data System (ADS)

    Pilling, S.; Seperuelo Duarte, E.; Domaracka, A.; Rothard, H.; Boduch, P.; da Silveira, E. F.

    2010-11-01

    An experimental study of the interaction of heavy, highly charged, and energetic ions (52 MeV 58Ni13+) with pure H2O, pure CO2 and mixed H2O:CO2 astrophysical ice analogs is presented. This analysis aims to simulate the chemical and the physicochemical interactions induced by heavy cosmic rays inside dense and cold astrophysical environments, such as molecular clouds or protostellar clouds. The measurements were performed at the heavy ion accelerator GANIL (Grand Accélérateur National d'Ions Lourds in Caen, France). The gas samples were deposited onto a CsI substrate at 13 K. In-situ analysis was performed by a Fourier transform infrared (FTIR) spectrometer at different fluences. Radiolysis yields of the produced species were quantified. The dissociation cross sections of pure H2O and CO2 ices are 1.1 and 1.9 × 10-13 cm2, respectively. For mixed H2O:CO2 (10:1), the dissociation cross sections of both species are about 1 × 10-13 cm2. The measured sputtering yield of pure CO2 ice is 2.2 × 104 molec ion-1. After a fluence of 2-3 × 1012 ions cm-2, the CO2/CO ratio becomes roughly constant (~0.1), independent of the initial CO2/H2O ratio. A similar behavior is observed for the H2O2/H2O ratio, which stabilizes at 0.01, independent of the initial H2O column density or relative abundance.

  3. Mechanisms underlying H(2)O(2)-mediated inhibition of synaptic transmission in rat hippocampal slices.

    PubMed

    Avshalumov, M V; Chen, B T; Rice, M E

    2000-11-01

    Hydrogen peroxide (H(2)O(2)) inhibits the population spike (PS) evoked by Schaffer collateral stimulation in hippocampal slices. Proposed mechanisms underlying this effect include generation of hydroxyl radicals (.OH) and inhibition of presynaptic Ca(2+) entry. We have examined these possible mechanisms in rat hippocampal slices. Inhibition of the evoked PS by H(2)O(2) was sharply concentration-dependent: 1.2 mM H(2)O(2) had no effect, whereas 1.5 and 2.0 mM H(2)O(2) reversibly depressed PS amplitude by roughly 80%. The iron chelator, deferoxamine (1 mM), and the endogenous.OH scavenger, ascorbate (400 microM), prevented PS inhibition, confirming.OH involvement. Isoascorbate (400 microM), which unlike ascorbate is not taken up by brain cells, also prevented PS inhibition, indicating an extracellular site of.OH generation or action. We then investigated whether H(2)O(2)-induced PS depression could be overcome by prolonged stimulation, which enhances Ca(2+) entry. During 5-s, 10-Hz trains under control conditions, PS amplitude increased to over 200% during the first three-four pulses, then stabilized. In the presence of H(2)O(2), PS amplitude was initially depressed, but began to recover after 2.5 s of stimulation, finally reaching 80% of the control maximum. In companion experiments, we assessed the effect of H(2)O(2) on presynaptic Ca(2+) entry by monitoring extracellular Ca(2+) concentration ([Ca(2+)](o)) during train stimulation in the presence of postsynaptic receptor blockers. Evoked [Ca(2+)](o) shifts were apparently unaltered by H(2)O(2), suggesting a lack of effect on Ca(2+) entry. Taken together, these findings suggest new ways in which reactive oxygen species (ROS) might act as signaling agents, specifically as modulators of synaptic transmission. PMID:11056187

  4. Photometric Measurements of H2O Ice Crystallinity on Trans-Neptunian Objects

    NASA Astrophysics Data System (ADS)

    Terai, Tsuyoshi; Itoh, Yoichi; Oasa, Yumiko; Furusho, Reiko; Watanabe, Junichi

    2016-08-01

    We present a measurement of H2O ice crystallinity on the surface of trans-neptunian objects with near-infrared narrow-band imaging. The newly developed photometric technique allows us to efficiently determine the strength of a 1.65 μm absorption feature in crystalline H2O ice. Our data for three large objects—Haumea, Quaoar, and Orcus—which are known to contain crystalline H2O ice on the surfaces, show a reasonable result with high fractions of the crystalline phase. It can also be pointed out that if the grain size of H2O ice is larger than ∼20 μm, the crystallinities of these objects are obviously below 1.0, which suggests the presence of the amorphous phase. In particular, Orcus exhibits a high abundance of amorphous H2O ice compared to Haumea and Quaoar, possibly indicating a correlation between the bulk density of the bodies and the degree of surface crystallization. We also found the presence of crystalline H2O ice on Typhon and 2008 AP129, both of which are smaller than the minimum size limit for inducing cryovolcanism as well as a transition from amorphous to crystalline phase through thermal evolution due to the decay of long-lived isotopes. Based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan (NAOJ).

  5. Effects of Convective Ice Lofting on H2O and HDO in the Tropical Tropopause Layer

    NASA Technical Reports Server (NTRS)

    Dessler, A. E.; Hanisco, T. F.; Fueglistaler, S.

    2007-01-01

    We have added convective ice lofting to a Lagrangian trajectory model of near-tropopause water vapor (H2O) and its isotopologue HDO. The ice lofting simulation is based on a parameterization derived from Aura Microwave Limb Sounder (MLS) icewater content measurements. In previous papers, the Lagrangian model has accurately interannual and seasonal H2O abundances; there was no need for convection to be included in the model. We show here that this model does a poor job of simulating near-tropopause HDO, but that the addition of convective ice lofting greatly improves the HDO simulation. Convective ice lofting has a small effect on lower stratospheric H2O. H2O there is set by the minimum temperature encountered at the cold-point tropopause, so H2O added by convection below this level does not make it through this cold point and into the lower stratosphere. Thus, adding convection to the model does not degrade the model's previously demonstrated accurate simulations of H2O. We conclude that the HDO data suggest an important role for convective mass flux into the so-called tropical tropopause layer.

  6. Fluorescent gold nanoclusters based photoelectrochemical sensors for detection of H2O2 and glucose.

    PubMed

    Zhang, Jianxiu; Tu, Liping; Zhao, Shuang; Liu, Guohua; Wang, Yangyun; Wang, Yong; Yue, Zhao

    2015-05-15

    In this work, low-toxicity fluorescent gold nanoclusters (AuNCs) based photoelectrochemical sensors were developed for H2O2 and glucose detection. Herein, the processes used to fabricate the sensors and the photoelectrochemical performances of the sensors under different conditions were presented. Based on the energy band levels of the AuNCs and electron tunneling processes, a detailed photoelectrochemical sensing model was given. The designed sensors were then used for H2O2 and glucose detection without any extra modification of the AuNCs or complex enzyme immobilization. The results demonstrate that the AuNCs allow for H2O2 sensing based on their capacity for both fluorescence and catalysis. Indeed, it was observed that H2O2 was catalyzed by the AuNCs and reduced by photoinduced electrons derived from excited AuNCs. Furthermore, an enhancement in photocurrent amplitude followed the increase in the concentrations of H2O2 and glucose. The effects of the types of ligands surrounding the AuNCs and the applied potential on the output photocurrent were well studied to optimize the measurement conditions. The sensitivity and LOD of MUA-AuNCs at -500 mV were 4.33 nA/mM and 35 μM, respectively. All experimental results indicated that AuNCs could not only serve as a promising photoelectrical material for building the photoelectrochemical biosensors but as catalysts for H2O2 sensing. PMID:25190086

  7. Catalase-like activity of horseradish peroxidase: relationship to enzyme inactivation by H2O2.

    PubMed Central

    Hernández-Ruiz, J; Arnao, M B; Hiner, A N; García-Cánovas, F; Acosta, M

    2001-01-01

    H2O2 is the usual oxidizing substrate of horseradish peroxidase C (HRP-C). In the absence in the reaction medium of a one-electron donor substrate, H2O2 is able to act as both oxidizing and reducing substrate. However, under these conditions the enzyme also undergoes a progressive loss of activity. There are several pathways that maintain the activity of the enzyme by recovering the ferric form, one of which is the decomposition of H2O2 to molecular oxygen in a similar way to the action of catalase. This production of oxygen has been kinetically characterized with a Clark-type electrode coupled to an oxygraph. HRP-C exhibits a weak catalase-like activity, the initial reaction rate of which is hyperbolically dependent on the H2O2 concentration, with values for K(2) (affinity of the first intermediate, compound I, for H2O2) and k(3) (apparent rate constant controlling catalase activity) of 4.0 +/- 0.6 mM and 1.78 +/- 0.12 s(-1) respectively. Oxygen production by HRP-C is favoured at pH values greater than approx. 6.5; under similar conditions HRP-C is also much less sensitive to inactivation during incubations with H2O2. We therefore suggest that this pathway is a major protective mechanism of HRP-C against such inactivation. PMID:11171085

  8. Application of the Hartmann-Tran profile to analysis of H2O spectra

    NASA Astrophysics Data System (ADS)

    Lisak, D.; Cygan, A.; Bermejo, D.; Domenech, J. L.; Hodges, J. T.; Tran, H.

    2015-10-01

    The Hartmann-Tran profile (HTP), which has been recently recommended as a new standard in spectroscopic databases, is used to analyze spectra of several lines of H2O diluted in N2, SF6, and in pure H2O. This profile accounts for various mechanisms affecting the line-shape and can be easily computed in terms of combinations of the complex Voigt profile. A multi-spectrum fitting procedure is implemented to simultaneously analyze spectra of H2O transitions acquired at different pressures. Multi-spectrum fitting of the HTP to a theoretical model confirms that this profile provides an accurate description of H2O line-shapes in terms of residuals and accuracy of fitted parameters. This profile and its limiting cases are also fit to measured spectra for three H2O lines in different vibrational bands. The results show that it is possible to obtain accurate HTP line-shape parameters when measured spectra have a sufficiently high signal-to-noise ratio and span a broad range of collisional-to-Doppler line widths. Systematic errors in the line area and differences in retrieved line-shape parameters caused by the overly simplistic line-shape models are quantified. Also limitations of the quadratic speed-dependence model used in the HTP are demonstrated in the case of an SF6 broadened H2O line, which leads to a strongly asymmetric line-shape.

  9. Optimization of intermolecular potential parameters for the CO2/H2O mixture.

    PubMed

    Orozco, Gustavo A; Economou, Ioannis G; Panagiotopoulos, Athanassios Z

    2014-10-01

    Monte Carlo simulations in the Gibbs ensemble were used to obtain optimized intermolecular potential parameters to describe the phase behavior of the mixture CO2/H2O, over a range of temperatures and pressures relevant for carbon capture and sequestration processes. Commonly used fixed-point-charge force fields that include Lennard-Jones 12-6 (LJ) or exponential-6 (Exp-6) terms were used to describe CO2 and H2O intermolecular interactions. For force fields based on the LJ functional form, changes of the unlike interactions produced higher variations in the H2O-rich phase than in the CO2-rich phase. A major finding of the present study is that for these potentials, no combination of unlike interaction parameters is able to adequately represent properties of both phases. Changes to the partial charges of H2O were found to produce significant variations in both phases and are able to fit experimental data in both phases, at the cost of inaccuracies for the pure H2O properties. By contrast, for the Exp-6 case, optimization of a single parameter, the oxygen-oxygen unlike-pair interaction, was found sufficient to give accurate predictions of the solubilities in both phases while preserving accuracy in the pure component properties. These models are thus recommended for future molecular simulation studies of CO2/H2O mixtures. PMID:25198539

  10. Addition of H2O and O-2 to Acetone and Dimethylsulfoxide Ligated Uranyl (V) Dioxocations

    SciTech Connect

    C. M. Leavitt; V. S. Bryantsev; W. A. deJong; M. S. Diallo; W. A. Goddard III; G. S. Groenewold; M. J. Van Stipdonk

    2009-03-01

    Gas-phase complexes of the formula [UO2(lig)]+ (lig = acetone (aco) or dimethylsulfoxide (dmso)) were generated by electrospray ionization (ESI) and studied by tandem ion-trap mass spectrometry to determine the general effect of ligand charge donation on the reactivity of UO2+ with respect to water and dioxygen. The original hypothesis that addition of O2 is enhanced by strong s-donor ligands bound to UO2+ is supported by results from competitive collision-induced dissociation (CID) experiments, which show near exclusive loss of H2O from [UO2(dmso)(H2O)(O2)]+, whereas both H2O and O2 are eliminated from the corresponding [UO2(aco)(H2O)(O2)]+ species. Ligand-addition reaction rates were investigated by monitoring precursor and product ion intensities as a function of ion storage time in the ion-trap mass spectrometer: these experiments suggest that the association of dioxygen to the UO2+ complex is enhanced when the more basic dmso ligand was coordinated to the metal complex. Conversely, addition of H2O is favored for the analogous complex ion that contains an aco ligand. Experimental rate measurements are supported by density function theory calculations of relative energies, which show stronger bonds between UO2+ and O2 when dmso is the coordinating ligand, whereas bonds to H2O are stronger for the aco complex.

  11. Cross Talk between H2O2 and Interacting Signal Molecules under Plant Stress Response.

    PubMed

    Saxena, Ina; Srikanth, Sandhya; Chen, Zhong

    2016-01-01

    It is well established that oxidative stress is an important cause of cellular damage. During stress conditions, plants have evolved regulatory mechanisms to adapt to various environmental stresses. One of the consequences of stress is an increase in the cellular concentration of reactive oxygen species, which is subsequently converted to H2O2. H2O2 is continuously produced as the byproduct of oxidative plant aerobic metabolism. Organelles with a high oxidizing metabolic activity or with an intense rate of electron flow, such as chloroplasts, mitochondria, or peroxisomes are major sources of H2O2 production. H2O2 acts as a versatile molecule because of its dual role in cells. Under normal conditions, H2O2 immerges as an important factor during many biological processes. It has been established that it acts as a secondary messenger in signal transduction networks. In this review, we discuss potential roles of H2O2 and other signaling molecules during various stress responses. PMID:27200043

  12. Photometric Measurements of H2O Ice Crystallinity on Trans-Neptunian Objects

    NASA Astrophysics Data System (ADS)

    Terai, Tsuyoshi; Itoh, Yoichi; Oasa, Yumiko; Furusho, Reiko; Watanabe, Junichi

    2016-08-01

    We present a measurement of H2O ice crystallinity on the surface of trans-neptunian objects with near-infrared narrow-band imaging. The newly developed photometric technique allows us to efficiently determine the strength of a 1.65 μm absorption feature in crystalline H2O ice. Our data for three large objects—Haumea, Quaoar, and Orcus—which are known to contain crystalline H2O ice on the surfaces, show a reasonable result with high fractions of the crystalline phase. It can also be pointed out that if the grain size of H2O ice is larger than ˜20 μm, the crystallinities of these objects are obviously below 1.0, which suggests the presence of the amorphous phase. In particular, Orcus exhibits a high abundance of amorphous H2O ice compared to Haumea and Quaoar, possibly indicating a correlation between the bulk density of the bodies and the degree of surface crystallization. We also found the presence of crystalline H2O ice on Typhon and 2008 AP129, both of which are smaller than the minimum size limit for inducing cryovolcanism as well as a transition from amorphous to crystalline phase through thermal evolution due to the decay of long-lived isotopes. Based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan (NAOJ).

  13. Quantification of the production of hydrogen peroxide H2O2 during accelerated wine oxidation.

    PubMed

    Héritier, Julien; Bach, Benoît; Schönenberger, Patrik; Gaillard, Vanessa; Ducruet, Julien; Segura, Jean-Manuel

    2016-11-15

    Understanding how wines react towards oxidation is of primary importance. Here, a novel approach was developed based on the quantitative determination of the key intermediate H2O2 produced during accelerated oxidation by ambient oxygen. The assay makes use of the conversion of the non-fluorescent Amplex Red substrate into a fluorescent product in presence of H2O2. The total production of H2O2 during 30min was quantified with low within-day and between-day variabilities. Polymerized pigments, but not total polyphenols, played a major role in the determination of H2O2 levels, which were lower in white wines than red wines. H2O2 amounts also increased with temperature and the addition of metal ions, but did not depend on the concentration of many other wine constituents such as SO2. H2O2 levels did not correlate with anti-oxidant properties. We believe that this novel methodology might be generically used to decipher the oxidation mechanisms in wines and food products. PMID:27283717

  14. Oxidative degradation of dimethyl phthalate (DMP) by UV/H(2)O(2) process.

    PubMed

    Xu, Bin; Gao, Nai-Yun; Cheng, Hefa; Xia, Sheng-Ji; Rui, Min; Zhao, Dan-Dan

    2009-03-15

    The photochemical degradation of dimethyl phthalate (DMP) in UV/H(2)O(2) advanced oxidation process was studied and a kinetic model based on the elementary reactions involved was developed in this paper. Relatively slow DMP degradation was observed during UV radiation, while DMP was not oxidized by H(2)O(2) alone. In contrast, the combined UV/H(2)O(2) process could effectively degraded DMP, which is attributed to the strong oxidation strength of hydroxyl radical produced. Results show that DMP degradation rate was affected by H(2)O(2) concentration, intensity of UV radiation, initial DMP concentration, and solution pH. A kinetic model without the pseudo-steady state assumption was established according to the generally accepted elementary reactions in UV/H(2)O(2) advanced oxidation process. The rate constant for the reaction between DMP and hydroxyl radical was found to be 4.0 x 10(9) M(-1)s(-1) through fitting the experimental data to this model. The kinetic model could adequately describe the influence of key factors on DMP degradation rate in UV/H(2)O(2) advanced oxidation process, and could serve as a guide in designing treatment systems for DMP removal. PMID:18639981

  15. Cross Talk between H2O2 and Interacting Signal Molecules under Plant Stress Response

    PubMed Central

    Saxena, Ina; Srikanth, Sandhya; Chen, Zhong

    2016-01-01

    It is well established that oxidative stress is an important cause of cellular damage. During stress conditions, plants have evolved regulatory mechanisms to adapt to various environmental stresses. One of the consequences of stress is an increase in the cellular concentration of reactive oxygen species, which is subsequently converted to H2O2. H2O2 is continuously produced as the byproduct of oxidative plant aerobic metabolism. Organelles with a high oxidizing metabolic activity or with an intense rate of electron flow, such as chloroplasts, mitochondria, or peroxisomes are major sources of H2O2 production. H2O2 acts as a versatile molecule because of its dual role in cells. Under normal conditions, H2O2 immerges as an important factor during many biological processes. It has been established that it acts as a secondary messenger in signal transduction networks. In this review, we discuss potential roles of H2O2 and other signaling molecules during various stress responses. PMID:27200043

  16. Close-coupling study of rotational energy transfer in H2O collisions with He atoms

    NASA Astrophysics Data System (ADS)

    Yang, Benhui; Stancil, Phillip

    2007-06-01

    Due to the astrophysical importance of water and helium, the H2O-He collisional system has been the subject of numerous experimental and theoretical studies. For numerical astrophysical models, quantitative determinations of state-to-state cross sections and rate coefficients for H2O-He collisions are crucial. In this work quantum close-coupling scattering calculations of rotational energy transfer (RET) of rotationally excited H2O due to collisions with He are presented for collision energies between 10-6 and 1000 cm-1 with para-H2O initially in levels 11,1, 20,2, 21,1, 22,0, and ortho-H2O in levels 11,0, 21,2, 22,1. Differential cross section, quenching cross sections and rate coefficients for state-to-state RET were computed on three new H2O-He potential energy surfaces (PESs). The inelastic and elastic differential cross sections are also compared with available experimental measurements.

  17. Vibrationally mediated photolysis dynamics of H2O in the vOH=3 manifold: Far off resonance photodissociation cross sections and OH product state distributions

    NASA Astrophysics Data System (ADS)

    Votava, Ondrej; Plusquellic, David F.; Nesbitt, David J.

    1999-05-01

    Vibrationally mediated photodissociation dynamics of water on the first excited electronic state surface (Ã) has been studied with slit jet-cooled H2O prepared in the complete polyad of vOH=3 overtone stretch levels (|03+>, |12+>, |12->, and |03->). (Notationally, |n1n2±> refers to symmetric/antisymmetric combinations of local mode OH stretch excitation, roughly corresponding to n1 and n2 quanta in the spectator and photolyzed OH bond, respectively.) At 248 nm photolysis wavelength the Condon point for bond cleavage occurs in the classically forbidden region, primarily sampling highly asymmetric H+OH exit valley geometries of the potential energy surface. Rotational, vibrational, spin orbit, and lambda doublet distributions resulting from this "far off resonance" photodissociation process are probed via laser induced fluorescence, exploiting the high efficiency laser excitation and light collection properties of the slit jet expansion geometry. Only vibrationally unexcited OH products are observed for both |12±> and |03±> initial excitation of H2O, despite different levels of vibration in the spectator OH bond. This is in contrast with "near-resonance" vibrationally mediated photolysis studies by Crim and co-workers in the |04-> and |13-> manifold, but entirely consistent with theoretical predictions from a simple two-dimensional quantum model. Photolysis out of the rotational ground H2O state (i.e., JKaKc=000) yields OH product state distributions that demonstrate remarkable insensitivity to the initial choice of H2O vibrational stretch state, in good agreement with rotational Franck-Condon models. However, this simple trend is not followed uniformly for rotationally excited H2O precursors, which indicates that these Franck-Condon models are insufficient and suggests that exit channel interactions do play a significant role in photodissociation dynamics of H2O at the fully state-to-state level.

  18. Stable chlorine isotope behavior during volcanic degassing of H2O and CO2 at Mono Craters, CA

    NASA Astrophysics Data System (ADS)

    Barnes, Jaime D.; Prather, Timothy J.; Cisneros, Miguel; Befus, Kenneth; Gardner, James E.; Larson, Toti E.

    2014-03-01

    Trends in CO2 and H2O concentrations and δD values of obsidian clasts from Mono Craters volcanic field, California demonstrate clear chemical and isotopic evidence for eruptive degassing. However, neither Cl concentrations nor stable isotopes (35Cl and 37Cl) track the degassing process, which is likely because of disequilibrium due to slow diffusion of Cl in the cooling melt. Obsidian pyroclasts ( n = 29) were collected from tuff layers representing a single eruptive sequence that occurred circa 1340 A.D., as well as, rhyolitic obsidian samples ( n = 12) were collected from three high-silica (>74 % SiO2) flows forming the domes and coulees in the region. The Cl, H2O, and CO2 concentrations recorded by the eruptive pyroclastic obsidians track the chemical evolution of the magmatic system during eruption, whereas the concentrations of the dome samples represent the final degassed product. The H2O and CO2 concentrations of the pyroclastic samples range from 0.49 to 2.13 wt% and 2 to 35 ppm, respectively; whereas concentrations in the dome glasses range from 0.17 to 0.33 wt% and 1 to 3 ppm, respectively. H2O and CO2 concentrations in the pyroclastic fall and dome samples are strongly correlated and reflect the degassing trend of the eruptive sequence. Chlorine concentrations of the pyroclastic fall samples and the domes range from 609 to 833 ppm and 681 to 872 ppm, respectively. Cl concentrations do not display a strong correlation with either H2O or CO2 concentrations. δD values of the pyroclastic fall obsidians vary between -84 ‰ and -55 ‰, whereas the δD values of the dome obsidians vary between -117 ‰ and -91 ‰. D/H ratios decrease with total water content following a distillation trend controlled by both closed and open system degassing. δ37Cl values of pyroclastic fall obsidians (-1.9 ‰ to -0.1 ‰) overlap with those of dome samples (-1.2 ‰ to 0.0 ‰). The similar Cl concentrations between the pyroclastic fall and dome obsidians argue for lack

  19. Efficiency and energy requirements for the transformation of organic micropollutants by ozone, O3/H2O2 and UV/H2O2.

    PubMed

    Katsoyiannis, Ioannis A; Canonica, Silvio; von Gunten, Urs

    2011-07-01

    The energy consumptions of conventional ozonation and the AOPs O(3)/H(2)O(2) and UV/H(2)O(2) for transformation of organic micropollutants, namely atrazine (ATR), sulfamethoxazole (SMX) and N-nitrosodimethylamine (NDMA) were compared. Three lake waters and a wastewater were assessed. With p-chlorobenzoic acid (pCBA) as a hydroxyl radical ((•)OH) probe compound, we experimentally determined the rate constants of organic matter of the selected waters for their reaction with (•)OH (k(OH,DOM)), which varied from 2.0 × 10(4) to 3.5 × 10(4) L mgC(-1) s(-1). Based on these data we calculated (•)OH scavenging rates of the various water matrices, which were in the range 6.1-20 × 10(4) s(-1). The varying scavenging rates influenced the required oxidant dose for the same degree of micropollutant transformation. In ozonation, for 90% pCBA transformation in the water with the lowest scavenging rate (lake Zürich water) the required O(3) dose was roughly 2.3 mg/L, and in the water with the highest scavenging rate (Dübendorf wastewater) it was 13.2 mg/L, corresponding to an energy consumption of 0.035 and 0.2 kWh/m(3), respectively. The use of O(3)/H(2)O(2) increased the rate of micropollutant transformation and reduced bromate formation by 70%, but the H(2)O(2) production increased the energy requirements by 20-25%. UV/H(2)O(2) efficiently oxidized all examined micropollutants but energy requirements were substantially higher (For 90% pCBA conversion in lake Zürich water, 0.17-0.75 kWh/m(3) were required, depending on the optical path length). Energy requirements between ozonation and UV/H(2)O(2) were similar only in the case of NDMA, a compound that reacts slowly with ozone and (•)OH but is transformed efficiently by direct photolysis. PMID:21645916

  20. Vibrational relaxation of H2O(|04> ) in collisions with H2O, Ar, H2, N2 and O2: dynamical and atmospheric implications

    NASA Astrophysics Data System (ADS)

    Barnes, P. W.; Sims, I. R.; Smith, I. W.

    2003-04-01

    It has been suggested that sequential two-photon dissociation of water might provide a mechanism for the atmospheric production of OH radical. ^1 This mechanism requires that photodissociation of vibrationally excited molecules must occur at a rate competitive with their relaxation by collisions with atmospheric gases. In this paper, we shall describe new experiments on the collisional relaxation of H_2O molecules from the highly excited mid04>± vibrational state in collisions with H_2O, Ar, H_2, N_2 and O_2. In our experiments, the mid04>^- state is populated by direct absorption of radiation from a pulsed dye laser tuned to ca. 719 nm. Evolution of the population in the (mid04>±) levels is observed using the combination of a frequency-quadrupled Nd:YAG laser, which selectively photolyses H_2O(mid04>±), and a frequency-doubled dye laser, which observes the OH(v = 0) produced via laser-induced fluorescence (LIF). The delay between the pulse from the pump laser and those from the photolysis and probe lasers was systematically varied to generate kinetic decays. The rate coefficients for relaxation obtained from these experiments, in units of cm^3 molecule-1 s-1, are: k(H_2O) = (4.1 ± 1.2) x 10-10, k(Ar) = (4.9 ± 1.1) x 10-12, k(H_2) = (6.8 ± 1.1) x 10-12, k(N_2) = (7.7 ± 1.5) x 10-12, k(O_2) = (6.7 ± 1.4) x 10-12. The results will be discussed in two contexts. First, we shall consider the implications of our new results for the interpretation of our previous experiments on the reactions of vibrationally excited H_2O with H atoms.^2 Second, we shall consider the proposal of Goss et al.1 in the light of our finding that the collisional relaxation of H_2O(mid04>±) by N_2 and O_2 is rather rapid. ^1 L. M Goss, V. Vaida, J. W. Brault and R. T. Skodje, J. Phys. Chem. A, 05, 70 (2001). ^2 (a) G. Hawthorne, P. Sharkey and I. W. M. Smith, J. Chem. Phys., 108, 4693(1998); (b) P. W. Barnes, P. Sharkey, I. R. Sims and I. W. M. Smith, Faraday Discuss. Chem. Soc., 13, 167

  1. Critical Velocity in Open Capillary Channel Flows

    NASA Technical Reports Server (NTRS)

    Rosendahl, Uwe; Dreyer, Michael E.; Rath, Hans J.; Motil, Brian; Singh, Bhim S. (Technical Monitor)

    2001-01-01

    We investigate forced liquid flows through open capillary channels with free surfaces experimentally. The experiments were performed under low gravity conditions in the Bremen Drop Tower and on board the sounding rocket TEXUS-37. Open capillary channels (vanes) are used in surface tension tanks to transport the propellant and to provide a flow path for the bubble-free liquid supply to the thrusters. Since the free surfaces can only withstand a certain pressure differential between the liquid and ambient, the flow rate in the channel is limited. The maximum flow rate is achieved when the surfaces collapse and gas is ingested into the outlet. Since experimental and theoretical data of this flow rate limitation is lacking, the safety factors for the application of vanes in surface tension tanks must be unnecessary high. The aim of the investigation is to determine the maximum liquid flow rate and the corresponding critical flow velocity. The characteristic nondimensional parameters, OHNESORGE number, and gap ratio, cover a wide range of usual vanes. For the theoretical approach a one-dimensional momentum balance was set up. The numerical solution yields the maximum volume flux and the position of the free surface in good agreement with the experiments.

  2. Experimental determination of the H2O-undersaturated peridotite solidus

    NASA Astrophysics Data System (ADS)

    Sarafian, E. K.; Gaetani, G. A.; Hauri, E. H.; Sarafian, A. R.

    2014-12-01

    Knowledge of the H2O-undersaturated lherzolite solidus places important constraints on the process of melt generation and mantle potential temperatures beneath oceanic spreading centers. The small concentration of H2O (~50-200 μg/g) dissolved in the oceanic mantle is thought to exert a strong influence on the peridotite solidus, but this effect has not been directly determined. The utility of existing experimental data is limited by a lack of information on the concentration of H2O dissolved in the peridotite and uncertainties involved with identifying small amounts of partial melt. We have developed an experimental approach for determining the peridotite solidus as a function of H2O content that overcomes these difficulties. Our initial results demonstrate that the solidus temperature for spinel lherzolite containing 150 μg/g H2O is higher than existing estimates for the anhydrous solidus. Our approach to determining the H2O-undersaturated lherzolite solidus is as follows. First, a small proportion (~5 %) of San Carlos olivine spheres, ~300 μm in diameter, are added to a peridotite synthesized from high-purity oxides and carbonates. Melting experiments are then conducted in pre-conditioned Au80Pd20 capsules over a range of temperatures at a single pressure using a piston-cylinder device. Water diffuses rapidly in olivine resulting in thorough equilibration between the olivine spheres and the surrounding fine-grained peridotite, and allowing the spheres to be used as hygrometers. After the experiment, the concentration of H2O dissolved in the olivine spheres is determined by secondary ion mass spectrometry. Melting experiments, spaced 20°C apart, were performed from 1250 to 1430°C at 1.5 GPa. The starting material has the composition of the depleted MORB mantle of Workman and Hart (2005) containing 0.13 wt% Na2O and 150 µg/g H2O. The concentration of H2O in the olivine spheres remains constant up to 1350°C, and then decreases systematically with increasing

  3. High pressure experimental study of eclogite with varying H2O contents

    NASA Astrophysics Data System (ADS)

    Rosenthal, A.; Frost, D. J.; Petitgirard, S.; Yaxley, G. M.; Berry, A.; Woodland, A. B.; Pinter, Z.; Vasilyev, P.; Ionov, D. A.; Jacob, D. E.; Pearson, G. D.; Kovacs, I.; Padron-Navarta, A.

    2014-12-01

    Given the strong influence of volatiles on mantle melting processes, it is critical to understand the behaviour of volatiles (such as H2O) in subducted oceanic crustal material (eclogite) during subduction and subsequent recycling and mantle melting processes, and their impacts on volcanism. As natural samples from subduction zones from the deep Earth's interior are largely inaccessible, the only way to determine the H2O content of eclogite is to simulate high pressure (P) and temperature (T) conditions equivalent to conditions of the Earth's interior using high-P experimental facilities. A particular interest is to determine the H2O content of eclogitic nominally anhydrous minerals (NAMs; such as garnet, clinopyroxene) at the conditions where hydrous phases (such as phengite) are breaking down to release H2O that would then leave the slab. As a starting material, we use average oceanic basalt (GA1, representative of recycled oceanic crust [1]) with varying bulk %H2O (≤7 wt.%). We conducted experiments using GA1 at different P's (6-10 GPa), T's (850-1500°C) and bulk %H2O (up to 7 wt.%) using multi anvil apparatuses. The run products at each P, T, and bulk H2O contents show well-equilibrated eclogitic phase assemblages of garnet ± clinopyroxene ± coesite/stishovite ± rutile ± phengite ± melt ± vapour. Runs (>0.5 wt.% H2O) at 6 GPa and up to ~950°C, and at 8-9 GPa and up to ~1050°C are subsolidus, while towards higher T small melt fractions appear. Similar to previous studies [e.g. 2-6], the stability of phengite varies as a function of P, T, buffering mineral paragenesis and bulk H2O concentration. Phengite breaks down >9 GPa. Eclogitic NAMs and phengite also break down at subsolidus conditions in the presence of excess of hydrous fluids. For instance, K2O in phengite and clinopyroxene decrease with increasing bulk H2O content at subsolidus conditions at given P, T, suggesting a leaching role of K2O by a vapour-rich fluid. [1] Yaxley, G. M. & Green, D. H

  4. Dual Oxidase 2 (Duox2) Regulates Pannexin 1-mediated ATP Release in Primary Human Airway Epithelial Cells via Changes in Intracellular pH and Not H2O2 Production.

    PubMed

    Krick, Stefanie; Wang, Junjie; St-Pierre, Melissa; Gonzalez, Carlos; Dahl, Gerhard; Salathe, Matthias

    2016-03-18

    Human airway epithelial cells express pannexin 1 (Panx1) channels to release ATP, which regulates mucociliary clearance. Airway inflammation causes mucociliary dysfunction. Exposure of primary human airway epithelial cell cultures to IFN-γ for 48 h did not alter Panx1 protein expression but significantly decreased ATP release in response to hypotonic stress. The IFN-γ-induced functional down-regulation of Panx1 was due to the up-regulation of dual oxidase 2 (Duox2). Duox2 suppression by siRNA led to an increase in ATP release in control cells and restoration of ATP release in cells treated with IFN-γ. Both effects were reduced by the pannexin inhibitor probenecid. Duox2 up-regulation stoichiometrically increases H2O2 and proton production. H2O2 inhibited Panx1 function temporarily by formation of disulfide bonds at the thiol group of its terminal cysteine. Long-term exposure to H2O2, however, had no inhibitory effect. To assess the role of cellular acidification upon IFN-γ treatment, fully differentiated airway epithelial cells were exposed to ammonium chloride to alkalinize the cytosol. This led to a 2-fold increase in ATP release in cells treated with IFN-γ that was also inhibited by probenecid. Duox2 knockdown also partially corrected IFN-γ-mediated acidification. The direct correlation between intracellular pH and Panx1 open probability was shown in oocytes. Therefore, airway epithelial cells release less ATP in response to hypotonic stress in an inflammatory environment (IFN-γ exposure). Decreased Panx1 function is a response to cell acidification mediated by IFN-γ-induced up-regulation of Duox2, representing a novel mechanism for mucociliary dysfunction in inflammatory airway diseases. PMID:26823467

  5. Variability of CO, OCS And H2O Below The Clouds of Venus From VIRTIS-HNight-side Spectra

    NASA Astrophysics Data System (ADS)

    Marcq, Emmanuel; Bezard, B.; Drossart, P.; Piccioni, G.; VIRTIS Team

    2007-10-01

    The VIRTIS imaging spectrometer has provided numerous spectra of Venus since the beginning of the Venus Express mission in April 2006. The high resolution of the H-channel (R 2000) enables the investigation of the composition below the clouds using the thermal emission from the night side of the planet, since several absorption of minor components (CO, OCS, H2O, HDO, SO2, HF) are located in the 2.3 µm transparency window of CO2. Using a radiative transfer computer model, we were able to derive constraints on the vertical profiles of CO, OCS and H2O in the 30-40 km altitude range up to areas unreacheable with Earth-based instruments (0° - 60°S). Our findings extend the latitudinal trends already noticed from both space (Collard et al., 1993, using Galileo/NIMS) and Earth (Marcq et al. 2005,2006, using IRTF/SpeX): an increase of CO towards high latitudes (30 ± 10 % between 60°S and 0°), a correlated decrease of OCS in the same region and a constant abundance of 28 ± 4 ppmv at 35 km for H2O. The latitudinal variations of CO are in good agreement with the VIRTIS-M observations from Tsang et al. (private communication). The quantitative interpretation of CO and OCS variations in terms of global-scale vertical circulation is in progress, using circulation models such as Yung et al's (private communication) in 2D and Lebonnois et al.'s (38th DPS meeting, #19.04) in 3D, thus helping in precising the understanding of both dynamics and chemistry in the deep atmopshere of Venus. This work has been funded by the CNES space agency.

  6. Low H2O/Ce in Icelandic basalts as evidence for crustal recycling

    NASA Astrophysics Data System (ADS)

    Neave, David; Shorttle, Oliver; Hartley, Margaret; Maclennan, John

    2016-04-01

    The generation of new crust at mid-ocean ridges is balanced by the subduction of partially hydrothermally altered basaltic material back into the mantle. This subducted material may then be recycled and returned via mantle plumes to the Earth's surface at hot spots. Long-identified isotopic and trace element signatures of oceanic crust recycling in ocean island basalts (OIBs) have been recently supplemented by evidence of major element, i.e. lithological, heterogeneity in the melting region. For example, combined major and trace element systematics from Iceland suggest that the mantle source contains at least 5% recycled basalt. Observations of high water (H2O) contents in subglacially quenched basalts from Iceland have previously been attributed to the incorporation of wet recycled material into the mantle source. However, when combined with trace element analyses, recent volatile analyses from the Laki-Grímsvötn and Bárðarbunga-Veiðivötn systems in the Eastern Volcanic Zone (EVZ) of Iceland suggest that the underlying mantle is comparatively depleted in H2O for its degree of major and trace element enrichment. Correlations between H2O and cerium (Ce) within individual mid-ocean ridge basalt (MORB) suites reveal that these elements partition similarly prior to H2O degassing at low pressures; H2O/Ce remains constant during melting and fractionation, and hence reflects the average H2O/Ce of the melting region. MORBs from the Mid-Atlantic Ridge south of Iceland have a mean H2O/Ce value of 304±48 at a mean La/Yb of 2.1±1.5. In contrast, basalts from the EVZ have a lower mean H2O/Ce of 180±20 at a higher mean La/Yb of 3.1±0.5. Thus, despite coming from an enriched section of the Mid-Atlantic ridge in terms of trace element content, basalts from the EVZ have the lowest H2O/Ce values known from the ridge, and are hence comparatively depleted in H2O. Given that H2O/Ce from un-degassed basalts is considered to represent mantle source values, we suggest that low H

  7. Influence of H2O Rich Fluid Inclusions on Quartz Deformation

    NASA Astrophysics Data System (ADS)

    Thust, Anja; Heilbronner, Renée.; Stünitz, Holger; Tarantola, Alexandre; Behrens, Harald

    2010-05-01

    The effect of H2O on the strength of quartz is well known and has been discussed many times in the literature (e.g. Griggs & Blacic 1965, Kronenberg 1994). In this project we study the H2O interactions between natural dry quartz and H2O rich fluid inclusions during deformation in the solid medium Griggs apparatus. High pressure and temperature experiments were carried out using a quartz single crystal containing a large number of H2O-rich fluid inclusions. Adjacent to the fluid inclusions the crystal is essentially dry (< 100 H/106Si, as determined by FTIR). Two sample orientations where used: (1) ⊥{m} orientation: normal to one of the prism planes, (2) O+ orientation: 45° to and 45° to [c]. Confining pressures were 700 MPa, 1000 MPa and 1500 MPa, with a constant displacement rate of 10-6 s-1 and a constant temperature of 900° C. Additionally, experiments where carried out at lower temperatures (800° C, 700° C) and faster strain rate ( 10-5 s-1). During increasing pressure and temperature we remained close to the fluid inclusion isochore and exceeded the α - β transition as late as possible. The strengths of the majority of the samples are between 150 and 250 MPa (the weakest is 84 MPa, the strongest 414 MPa). Low strength can be explained by dynamic recrystallization and deformation by dislocation creep, higher strength correlates with a lower H2O content and absence of dislocation creep. In the undeformed material, the H2O rich fluid inclusions contain different chlorides like antarticite (CaCl2×6H2O) and hydrohalite (NaCl×2H2O), as measured with micro thermometry. They show a large range in size from 50 μm to 700 μm and their spatial distribution is extremely heterogeneous. After deformation the inclusions are more homogeneously distributed throughout the sample and dramatically reduced in size (< 0.1μm). Regions with a high density of very small fluid inclusions are the regions with the highest concentration of deformation and yield an H2O content

  8. Ionization chemistry in the H2O-dominant atmospheres of the icy moons

    NASA Astrophysics Data System (ADS)

    Shematovich, V. I.; Johnson, R. E.

    2007-08-01

    The main pathways of the ionization chemistry for pure H2O- and mixed H2O+O2+CO2+NH3+CH4 atmospheres which are representative for neutral and ionized atmospheres of the icy bodies in the Jovian and Saturnian systems are discussed. The gaseous envelopes of the icy moons of the giant planets are formed usually due to the surface radiolysis by the solar UV radiation and energetic magnetospheric plasma (Johnson, 1990). The standard astrochemical UMIST2005 (UDFA05) network is used to infer the main chemical pathways of ionization chemistry in the pure or with admixtures of other volatile molecules water vapor atmospheres. In case of the H2O- dominant atmosphere the parent H2O molecules are easily dissociated and ionized by the solar UVradiation and the energetic magnetospheric electrons. These impact processes result in the formation of the secondary neutral and ionized products - chemically active radicals O and OH, and H+, H2+, O+, OH+, and H2O+ ions. Secondary ions have admixture abundances in the H2O-dominant atmospheres, because they are efficiently transformed to H3O+ hydroxonium ions in the fast ion-molecular reactions. The major H3O+ hydroxonium ion does not chemically interact with other neutrals, and is destroyed in the dissociative recombination with thermal electrons mainly reproducing the chemically simple H, H2, O, and OH species. In case of the mixed H2O+O2-dominant atmosphere corresponding to the near-surface atmospheres of icy moons (Shematovich et al., 2005), the ionization chemistry results in the formation of the second major ion O2+ - because ion of molecular oxygen has the lower ionization potential comparing with other parent species -H2, H2O, CO2. The H+, O+, OH+, and H2O+ ions can be easily converted to O2+ ions through the ion-molecular reactions. In case of significant admixture of molecular hydrogen it is possible to transfer the O2+ ions to the O2H+ ions through the fast reaction with H2 and further to the H3O+ ions through the ion

  9. Effect of chirality on domain wall dynamics in molecular ferrimagnet [MnII(HL-pn)(H2O)][MnIII(CN)6]·2H2O

    NASA Astrophysics Data System (ADS)

    Mushenok, F.; Koplak, O.; Morgunov, R.

    2011-11-01

    In this paper we distinguish the contributions of switching, slide, creep and Debye relaxation modes of the domain wall dynamics to the low-frequency magnetic properties of chiral and racemic [MnII(HL-pn)(H2O)][MnIII(CN)6]·2H2O molecular ferrimagnets. We demonstrate that crystal and spin chirality affects the characteristic transition temperatures between different modes. In chiral crystals, transitions to the creep and Debye relaxation modes were observed at T = 7 K and 5 K, whereas in racemic crystals the same transitions occurred at higher temperatures T = 13 K and 9 K, respectively. Difference of the Peierls relief in chiral and racemic crystals is a possible reason of the chirality effect on the domain walls dynamics.

  10. Base fluid and temperature effects on the heat transfer characteristics of SiC in ethylene glycol/H2O and H2O nanofluids

    NASA Astrophysics Data System (ADS)

    Timofeeva, Elena V.; Yu, Wenhua; France, David M.; Singh, Dileep; Routbort, Jules L.

    2011-01-01

    Experimental data are presented for the thermal conductivity, viscosity, and turbulent flow heat transfer coefficient of nanofluids with SiC particles suspended in ethylene glycol (EG)/water (H2O) mixture with a 50/50 volume ratio. The results are compared to the analogous suspensions in water for four sizes of SiC particles (16-90 nm). It is demonstrated that the heat transfer efficiency is a function of both the average particle size and the system temperature. The results show that adding SiC nanoparticles to an EG/H2O mixture can significantly improve the cooling efficiency while water-based nanofluids are typically less efficient than the base fluids. This is one of the few times that substantial nanofluid heat transfer enhancement has been reported in the literature based on a realistic comparison basis of constant velocity or pumping power. The trends important for engineering efficient heat transfer nanofluids are summarized.

  11. Oxidative damage to fibronectin. 2. The effect of H2O2 and the hydroxyl radical

    SciTech Connect

    Vissers, M.C.; Winterbourn, C.C. )

    1991-03-01

    The effect of H2O2 and the hydroxyl radical (.OH) on fibronectin was investigated. .OH was generated in three ways: (1) by radiolysis with 60Co under N2O, or by the Fenton system using either (2) equimolar Fe(2+)-EDTA and H2O2 or (3) H2O2 and catalytic amounts of Fe(2+)-EDTA recycled with ascorbate. Each system had a different effect. H2O2 alone caused no changes, even at an 800-fold molar excess. Radiolytic .OH caused a rapid loss of tryptophan fluorescence, an increase in bityrosine fluorescence, and extensive crosslinking. The Fenton system using Fe-EDTA, H2O2, and ascorbate caused a loss in tryptophan fluorescence, a smaller increase in bityrosine than was seen with radiolytic .OH, and a threefold increase in carbonyl groups. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis fragmentation of fibronectin was seen. In contrast, when .OH was generated with equimolar Fe-EDTA and H2O2, the only change was a small increase in bityrosine fluorescence at the highest dose of oxidant. None of the systems used affected cysteine. All the changes except the loss of tryptophan by radiolytic .OH were completely inhibited with mannitol. The differences seen with radiolytic .OH and the Fe-EDTA, H2O2, ascorbate system were not solely due to O2 in the latter system since similar results were obtained under N2. The differences between radiolytic .OH and the Fenton systems could be partly due to the components of the latter systems reacting with .OH and thus competing with fibronectin. The authors results demonstrate that the extent and type of fibronectin damage by .OH is dependent on the mode of radical generation.

  12. Crystal and molecular structure of the coordination compounds of Er3+ with 1-(methoxydiphenylphosphoryl)-2-diphenylphosphorylbenzene [Er L {2/1}(NO3)2]2[Er(NO3)2(H2O)5]0.333(NO3)2.333 · 2.833H2O and its ethyl substituted derivative [Er L {2/2}(NO3)2][Er(NO3)5]0.5 · 0.5H2O

    NASA Astrophysics Data System (ADS)

    Polyakova, I. N.; Baulin, V. E.; Ivanova, I. S.; Pyatova, E. N.; Sergienko, V. S.; Tsivadze, A. Yu.

    2015-01-01

    The coordination compounds of Er3+ with 1-(methoxydiphenylphosphoryl)-2-diphenylphosphorylbenzene [Er L {2/1}(NO3)2]2[Er(NO3)2(H2O)5]0.333(NO3)2.333 · 2.833H2O ( I) and its ethyl substituted derivative [Er L {2/2}(NO3)2][Er(NO3)5]0.5 · 0.5H2O ( II) are synthesized and their crystal structures are studied. I and II contain [Er L 2(NO3)2]+ complex cations of identical composition and close structure. The eight-vertex polyhedron of the Er atom in the shape of a distorted octahedron with two split trans vertices is formed by the O atoms of the phosphoryl groups of L ligands and nitrate anions. L ligands close nine-membered metallocycles. The structures contain spacious channels which are populated differently, namely, by disordered [Er(NO3)2(H2O)5]+ complex cations, NO{3/-} anions, and crystallization water molecules in I and disordered [Er(NO3)5]2- complex anions and crystallization water molecules in II. The IR spectra of I and II are studied.

  13. Investigating Disequilibrium Degassing of H2O and CO2 in Rhyolitic Melts: New Insights from Cold-Seal Decompression Experiments

    NASA Astrophysics Data System (ADS)

    Johnson, E. R.; Wallace, P. J.

    2012-12-01

    vapor bubbles. Analyses by SEM and electron microprobe will provide insight into both the textures and compositions of the resulting glasses. This research will provide further insight into the behavior of H2O, OH-, and in particular, CO2, during decompression and degassing. Numerous studies of the volatile contents of basaltic magmas have shown that the CO2 and H2O contents of melt inclusions often are not well matched by equilibrium closed- or open-system degassing. Gas-fluxing, or the flushing and re-equilibration of melts with a CO2-rich vapor from depth, has been increasingly cited to explain such deviations. However, another possibility is that the variability reported in mafic melt inclusion volatile contents is instead caused by disequilibrium degassing. The same data could be explained if, for example, rapid depressurization of the melt and slow diffusion of CO2 resulted in melts with higher levels of dissolved CO2 than expected under equilibrium conditions. Depending on the extent of disequilibrium degassing of CO2 under rapid decompression, this work has the potential to offer an alternative explanation to the gas-fluxing hypothesis for the variability in melt inclusion CO2 and H2O reported in the literature.

  14. V2O2F4(H2O)2·H2O: a new V(4+) layer structure related to VOF3.

    PubMed

    Black, Cameron; Lightfoot, Philip

    2016-01-01

    V(IV) oxyfluorides are of interest as frustrated magnets. The successful synthesis of two-dimensionally connected vanadium(IV) oxyfluoride structures generally requires the use of ionic liquids as solvents. During solvothermal synthesis experiments aimed at producing two- and three-dimensional vanadium(IV) selenites with triangular lattices, the title compound, diaquatetra-μ-fluorido-dioxidodivanadium(IV) monohydrate, V2O2F4(H2O)2·H2O, was discovered and features a new infinite V(4+)-containing two-dimensional layer comprised of fluorine-bridged corner- and edge-sharing VOF4(H2O) octahedral building units. The synthesis was carried out under solvothermal conditions. The V(4+) centre exhibits a typical off-centring, with a short V=O bond and an elongated trans-V-F bond. Hydrogen-bonded water molecules occur between the layers. The structure is related to previously reported vanadium oxyfluoride structures, in particular, the same layer topology is seen in VOF3. PMID:26742832

  15. One-dimensional decavanadate chains in the crystal structure of Rb4[Na(H2O)6][HV10O28]·4H2O.

    PubMed

    Yakubovich, Olga V; Steele, Ian M; Yakovleva, Ekaterina V; Dimitrova, Olga V

    2015-06-01

    New decavanadate minerals, the products of the leaching or metasomatic processes, are possible in nature via Na/Rb removal/inclusion reactions. As part of our search for novel vanadate phases with varying functionalities, a new phase, tetrarubidium hexaaquasodium hydrogen decavanadate tetrahydrate, Rb4[Na(H2O)6][HV10O28]·4H2O, has been synthesized by the hydrothermal technique at 553 K. Ten shared edges of V-centred octahedra form monoprotonated decavanadate cages, which are joined together via hydrogen bonds into one-dimensional chains parallel to the [101] direction. Within these chains, H atoms are sandwiched between neighbouring polyanions. Na and Rb atoms and H2O molecules occupy interstices flanked by the anionic chains providing additional crosslinking in the structure. This compound is the second decavanadate with P2/n symmetry. Structural relationships among protonated and deprotonated decavanadates with inorganic cations, including minerals of the pascoite group, are discussed. PMID:26044328

  16. H2O2 Synthesis Induced by Irradiation of H2O with Energetic H(+) and Ar(+) Ions at Various Temperatures

    NASA Technical Reports Server (NTRS)

    Baragiola, R. A.; Loeffler, M. J.; Raut, U.; Vidal, R. A.; Carlson, R. W.

    2004-01-01

    The detection of H2O2 on Jupiter's icy satellite Europa by the Galileo NIMS instrument presented a strong evidence for the importance of radiation effects on icy surfaces. A few experiments have investigated whether solar flux of protons incident on Europa ice could cause a significant if any H2O2 production. These published results differ as to whether H2O2 can be formed by ions impacting water at temperatures near 80 K, which are appropriate to Europa. This discrepancy may be a result of the use of different incident ion energies, different vacuum conditions, or different ways of processing the data. The latter possibility comes about from the difficulty of identifying the 3.5 m peroxide OH band on the long wavelength wing of the much stronger water 3.1 m band. The problem is aggravated by using straight line baselines to represent the water OH band with a curvature, in the region of the peroxide band, that increases with temperature. To overcome this problem, we use polynomial baselines that provide good fits to the water band and its derivative.

  17. Quantum chemical study of the reactions of Al, AlO and AlOH with H2O2

    NASA Astrophysics Data System (ADS)

    Sharipov, Alexander S.; Starik, Alexander M.

    2016-02-01

    Quantum chemical calculations with the use of hybrid density functional with perturbative second-order correlation and dispersion correction are carried out to study the reactions of Al, AlO and AlOH with the H2O2 molecule. The values of energy barriers are estimated by means of extrapolation to the basis set limit. The energetically favorable reaction pathways have been revealed during the examination of the potential energy surfaces. Complex character of the processes under study has been established. It has been found that the initial stages of the considered processes are barrierless. Appropriate rate constants for principal channels of the reactions under study have been estimated by using capture model and canonical variational theory. The Arrhenius approximations for these channels have been proposed for the temperature range T = 300-4000 K.

  18. H2O vapor excitation in dusty AGB envelopes. A PACS view of OH 127.8+0.0

    NASA Astrophysics Data System (ADS)

    Lombaert, R.; Decin, L.; de Koter, A.; Blommaert, J. A. D. L.; Royer, P.; De Beck, E.; de Vries, B. L.; Khouri, T.; Min, M.

    2013-06-01

    -4 M⊙ yr-1, depending on the temperature profile. In addition, a change in mass-loss rate is needed to explain the J = 1-0 and J = 2-1 CO lines formed in the outer wind, where the older mass-loss rate is estimated to be 1 × 10-7 M⊙ yr-1. The dust-to-gas ratio found with method 1) is 0.01, accurate to within a factor of three; method 2) yields a lower limit of 0.0005; and method 3) results in an upper limit of 0.005. The H2O ice fraction leads to a minimum required H2O vapor abundance with respect to H2 of (1.7 ± 0.2) × 10-4. Finally, we report detecting 1612 MHz OH maser pumping channels in the far-infrared at 79.1, 98.7, and 162.9 μm. Conclusions: Abundance predictions for a stellar atmosphere in local thermodynamic equilibrium yield a twice higher H2O vapor abundance (~3 × 10-4), suggesting a 50% freeze-out. This is considerably higher than current freeze-out predictions. Regarding the dust-to-gas ratio, methods 2) and 3) probe a deeper part of the envelope, while method 1) is sensitive to the outermost regions. The latter diagnostic yields a significantly higher dust-to-gas ratio than do the two other probes. We offer several potential explanations for this behavior: a clumpy outflow, a variable mass loss, or a continued dust growth. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. Appendix A is available in electronic form at http://www.aanda.org

  19. Infrared spectrum of NH4+(H2O): Evidence for mode specific fragmentation

    SciTech Connect

    Pankewitz, Tobias; Lagutschenkov, Anita; Niedner-schatteburg, Gereon; Xantheas, Sotiris S; Lee, Yuan-Tseh

    2007-02-21

    The gas phase infrared spectrum (3250 to 3810 cm1) of the singly hydrated ammonium ion, NH4+(H2O), has been recorded by consequence spectroscopy of mass selected and isolated ions. The obtained four bands are assigned to N-H stretching modes and O-H stretching modes, respectively. The observed N-H stretching modes are blueshifted with respect to the corresponding modes of the free NH4+ ion, whereas a redshift is observed with respect to the modes of the free NH3 molecule. The observed O-H stretching modes are redshifted when compared to the free H2O molecule. The asymmetric stretching modes give rise to rotationally resolved perpendicular transitions. The K-type equidistant rotational spacings of 11.1(2) cm1 (NH4+) and 29(3) cm1 (H2O) deviate systematically from the corresponding values of the free molecules, a fact which is rationalized in terms of a symmetric top analysis. The recorded relative band intensities compare favorably with predictions of high level ab initio calculations except for the 3(H2O) band for which the observed value is about 20 times weaker than the calculated one. This long standing puzzle motivated us to examine the a 3(H2O)/1(H2O) intensity ratios from other published action spectra in other cationic complexes. These suggest that the 3(H2O) intensities become smaller the stronger the complexes are bound. The recorded ratios vary, in particular among the data collected from action spectra that were recorded with and without rare gas tagging. The calculated anharmonic coupling constants in NH4+(H2O) further suggested that the coupling of the 3(H2O) and 1(H2O) modes to other cluster modes indeed varies by orders of magnitude. These findings altogether render the picture of a mode specific fragmentation dynamic that modulates band intensities in action spectra with respect to absorption spectra. Additional high-level electronic structure calculations at the coupled-cluster single and double with perturbative treatment of triple excitations

  20. Effects of a single water molecule on the OH + H2O2 reaction.

    PubMed

    Buszek, Robert J; Torrent-Sucarrat, Miquel; Anglada, Josep M; Francisco, Joseph S

    2012-06-21

    The effect of a single water molecule on the reaction between H(2)O(2) and HO has been investigated by employing MP2 and CCSD(T) theoretical approaches in connection with the aug-cc-PVDZ, aug-cc-PVTZ, and aug-cc-PVQZ basis sets and extrapolation to an ∞ basis set. The reaction without water has two elementary reaction paths that differ from each other in the orientation of the hydrogen atom of the hydroxyl radical moiety. Our computed rate constant, at 298 K, is 1.56 × 10(-12) cm(3) molecule(-1) s(-1), in excellent agreement with the suggested value by the NASA/JPL evaluation. The influence of water vapor has been investigated by considering either that H(2)O(2) first forms a complex with water that reacts with hydroxyl radical or that H(2)O(2) reacts with a previously formed H(2)O·OH complex. With the addition of water, the reaction mechanism becomes much more complex, yielding four different reaction paths. Two pathways do not undergo the oxidation reaction but an exchange reaction where there is an interchange between H(2)O(2)·H(2)O and H(2)O·OH complexes. The other two pathways oxidize H(2)O(2), with a computed total rate constant of 4.09 × 10(-12) cm(3) molecule(-1) s(-1) at 298 K, 2.6 times the value of the rate constant of the unassisted reaction. However, the true effect of water vapor requires taking into account the concentration of the prereactive bimolecular complex, namely, H(2)O(2)·H(2)O. With this consideration, water can actually slow down the oxidation of H(2)O(2) by OH between 1840 and 20.5 times in the 240-425 K temperature range. This is an example that demonstrates how water could be a catalyst in an atmospheric reaction in the laboratory but is slow under atmospheric conditions. PMID:22455374

  1. A coupled soil-atmosphere model of H2O2 on Mars.

    PubMed

    Bullock, M A; Stoker, C R; McKay, C P; Zent, A P

    1994-01-01

    The Viking Gas Chromatograph Mass Spectrometer failed to detect organic compounds on Mars, and both the Viking Labeled Release and the Viking Gas Exchange experiments indicated a reactive soil surface. These results have led to the widespread belief that there are oxidants in the martian soil. Since H2O2 is produced by photochemical processes in the atmosphere of Mars, and has been shown in the laboratory to reproduce closely the Viking LR results, it is a likely candidate for a martian soil oxidant. Here, we report on the results of a coupled soil/atmosphere transport model for H2O2 on Mars. Upon diffusing into the soil, its concentration is determined by the extent to which it is adsorbed and by the rate at which it is catalytically destroyed. An analytical model for calculating the distribution of H2O2 in the martian atmosphere and soil is developed. The concentration of H2O2 in the soil is shown to go to zero at a finite depth, a consequence of the nonlinear soil diffusion equation. The model is parameterized in terms of an unknown quantity, the lifetime of H2O2 against heterogeneous catalytic destruction in the soil. Calculated concentrations are compared with a H2O2 concentration of 30 nmoles/cm3, inferred from the Viking Labeled Release experiment. A significant result of this model is that for a wide range of H2O2 lifetimes (up to 10(5) years), the extinction depth was found to be less than 3 m. The maximum possible concentration in the top 4 cm is calculated to be approximately 240 nmoles/cm3, achieved with lifetimes of greater than 1000 years. Concentrations higher than 30 nmoles/cm3 require lifetimes of greater than 4.3 terrestrial years. For a wide range of H2O2 lifetimes, it was found that the atmospheric concentration is only weakly coupled with soil loss processes. Losses to the soil become significant only when lifetimes are less than a few hours. If there are depths below which H2O2 is not transported, it is plausible that organic compounds

  2. H2O2: A precursor for O2 on icy satellites? Laboratory studies

    NASA Astrophysics Data System (ADS)

    Loeffler, M. J.; Baragiola, R. A.

    2005-08-01

    Radiation processes affect the surface chemistry in planetary systems and in the ISM, and thus they need to be studied extensively. Recently, we have studied H2O2 production in water ice by 100 keV H+ irradiation at temperatures relevant to Europa and the ISM. Although hydrogen peroxide has only been detected so far in the infrared reflectance of Europa, this molecule is believed to be an important factor for the radiation-induced chemistry that occurs in water ice in other outer solar system objects. In particular, it has been proposed that this molecule may be a precursor for the production of O2 exospheres around icy satellites and Saturn's rings. Previously, we have irradiated crystalline H2O2 and identified the synthesis of H2O and O3. The saturation water concentration appeared to be high, but quantification of initial radiation yields (G values) was not possible because of the large change in the shape of the infrared absorption bands due to the concurrent amorphization. Further measurements could not be made, because we could only grow H2O2 at high temperatures by distillation, and thus growing amorphous H2O2 was not possible. Recently, we developed a method to grow amorphous H2O2 in the solid phase that allowed us to measure H2O2 destruction quantitatively. We have performed radiolysis with 50 keV H+ at 17 K to ensure that most radiolytic products stay in the ice and have detected H2O, O2 and O3 but not HO2; we have measured initial radiation yields for H2O and O2. Annealing the irradiated samples at 0.2 K/min to 200 K we found that most of the O2 produced stays trapped in the ice until 154 K, where it leaves immediately. Infrared absorption shows the production of dangling H bonds, which grow in importance during annealing and can even be observed at 150 K.

  3. Gas-Phase Condensation Reactions of SixOyHz- Oxyanions with H2O

    SciTech Connect

    Groenewold, Gary Steven; Scott, Jill Rennee; Gianotto, Anita Kay; Hodges, Brittany DM; Kessinger, Glen Frank; Benson, Michael Timothy; Wright, J. B.

    2001-09-01

    Water was reacted with gas-phase oxyanions having the general composition SixOyHz- that were formed and isolated in an ion trap-secondary ion mass spectrometer (IT-SIMS). The radical SiO2- reacted slowly with H2O to abstract HO, forming SiO3H-, at a rate of 8 × 10-13 cm3 molecule-1 s-1, corresponding to an efficiency of about 0.03% compared with the theoretical collision rate constant (average dipole orientation). The product ion SiO3H- underwent a consecutive condensation reaction with H2O to form SiO4H3- at a rate that was approximately 0.4-0.7% efficient. SiO4H3- did not undergo further reaction with water. The multiple reaction pathways by which radical SiO3- reacted with H2O were kinetically modeled using a stochastic approach. SiO3- reacted with water by three parallel reaction pathways: (1) abstraction of a radical H to form SiO3H-, which then reacted with a second H2O to form SiO4H3-; (2) abstraction of a radical OH to form SiO4H-, which further reacted by consecutive H abstractions to form SiO4H2- and then SiO4H3-; and (3) condensation with H2O to form SiO4H2-, which subsequently abstracted a radical H from a second H2O to form SiO4H3-. In all of these reactions, the rate constants were determined to be very slow, as determined by both direct measurement and stochastic modeling. For comparison, the even electron ion Si2O5H- was also investigated: it underwent condensation with H2O to form Si2O6H3-, with a rate constant corresponding to 50% efficiency. The reactions were also modeled using ab initio calculations at the UB3LYP/6-311+G(2d,p) level. Addition of H2O to SiO3-, SiO3H-, and Si2O5H- was calculated to be approximately 42, 45, and 55 kcal mol-1 exothermic, respectively, and encountered low activation barriers. Modeling of SiO2- and SiO3- reactions with H2O failed to produce radical abstraction reaction pathways observed in the IT-SIMS, possibly indicating that alternative reaction mechanisms are operative.

  4. Oxidation of nonionic surfactants by Fenton and H2O2/UV processes.

    PubMed

    Pagano, M; Lopez, A; Volpe, A; Mascolo, G; Ciannarella, R

    2008-04-01

    The oxidation of 10 nonionic surfactants (6 alcohol ethoxylates and 4 alkylphenol ethoxylates) by Fenton and H2O2/UV processes was investigated in synthetic (deionized water) and real aqueous matrices, i.e. secondary effluent from municipal wastewater treatment plant and groundwater. Batch tests were carried out to assess the optimal dosages of reagents leading to the total removal of surfactants. Regardless to the specific surfactant, both Fenton and H2O2/UV treatments of synthetic solutions containing one single surfactant (C0=14 mg l(-1)) always caused its rapid and quantitative removal (96-99%) with a corresponding very low (0-18%) TOC decrease. Only for the Fenton treatment, linear relationships were found between the amounts of H2O2 and Fe2+ necessary for surfactant removal and the ethoxy chain length of each surfactant. Conversely, in the case of H2O2/UV treatment the H2O2 dosage causing the quantitative oxidation of the treated surfactant depended on the length of both chains: the ethoxy and the hydrophobic one. Mixtures of the 10 surfactants (1.4 mg l(-1) each) were treated in both synthetic and real matrices. These latter were different in the case of Fenton (i.e. municipal secondary effluent) or H2O2/UV (i.e. real groundwater) treatments. Fenton treatment of municipal secondary effluent containing the surfactants mixture led to its total removal when a molar ratio [Total surfactants]/[H2O2]/[Fe2+] equal to 1/17/12 was used. As for H2O2/UV treatment of real groundwater samples, quantitative removal of surfactants mixture was achieved with a molar ratio [Total surfactants]/[H2O2] equal to 1/7.4. Surfactants mixture removals, if compared in deionized water and in real matrices, showed the same matrix effect during both treatments, i.e. less amounts of reagents were always required in synthetic solutions. PMID:18619147

  5. Partitioning of H2O in the mantle transition zone and lower mantle

    NASA Astrophysics Data System (ADS)

    Inoue, T.; Katsuda, M.; Yurimoto, H.

    2008-12-01

    Water is the most abundant volatile component in the Earth, and the presence of H2O into the mantle minerals affects the elastic and rheological properties. It is well known that wadsleyite and ringwoodite, which are the most abundant minerals in the mantle transition zone, can accommodate significant amount (~3 wt%) of H2O in the crystal structures (e.g. Inoue et al., 1995; Kohlstedt et al, 1996). On the other hand, majorite garnet is the second abundant mineral in the mantle transition zone, and the H2O content was reported to be ~0.2 wt% (Katayama et al., 2003). It is important to know the maximum H2O storage capacity in the minerals, and also to know the partitioning of H2O in the mantle minerals to evaluate the water content in the Earth with temperature and pressure dependence. We have conducted high pressure experiment to determine the partitioning of H2O between wadsleyite, ringwoodite, perovskite and garnet. High-pressure experiments were conducted by MA-8 type (Kawai-type) high-pressure apparatus in Ehime University. We used pyrolite composition which was approximated with respect to five major components, CaO, MgO, FeO, Al2O3 and SiO2. Three starting H2O contents, 2.9, 8.3 and 15.6 wt% were selected. The experimental P-T conditions were 14-23 GPa and 1200-1700°C. The recovered samples were polished and then the chemical compositions were determined by EPMA in Ehime University and the water contents of minerals were measured by SIMS in Hokkaido University. The H2O contents of wadsleyite and ringwoodite decreased with increasing temperature, which is consistent with Ohtani et al. (2000). However the H2O content of majorite did not change so much with increasing temperature. As the results, the partition coefficients between wadsleyite and majorite, and between ringwoodite and majorite decreased with increasing temperature. Further details will be presented.

  6. Competitive sorption of CO2 and H2O in 2:1 layer phyllosilicates

    NASA Astrophysics Data System (ADS)

    Schaef, Herbert T.; Loring, John S.; Glezakou, Vassiliki-Alexandra; Miller, Quin R. S.; Chen, Jeffrey; Owen, Antoinette T.; Lee, Mal-Soon; Ilton, Eugene S.; Felmy, Andrew R.; McGrail, B. Pete; Thompson, Christopher J.

    2015-07-01

    Expandable clays such as montmorillonite have interlayer exchange sites whose hydration state can be systematically varied from near anhydrous to almost bulk-like water conditions. This phenomenon has new significance with the simultaneous implementation of geological sequestration and secondary utilization of CO2 to both mitigate climate warming and enhance extraction of methane from hydrated clay-rich formations. In this study, the partitioning of CO2 and H2O between Na-, Ca-, and Mg-exchanged montmorillonite and variably hydrated supercritical CO2 (scCO2) was investigated using in situ X-ray diffraction (HXRD), infrared (IR) spectroscopic titrations, and quartz crystal microbalance (QCM) measurements. Density functional theory calculations provided mechanistic insights. Structural volumetric changes were correlated to quantified changes in sorbed H2O and CO2 concentrations as a function of percent H2O saturation in scCO2. Intercalation of CO2 is inhibited when the clay is fully collapsed (dehydrated interlayer), peaks sharply with the introduction of some H2O and partial expansion of the interlayer region, and then decreases systematically with further hydration of the clay. This behavior is discussed in the context of recent theoretical calculations of the montmorillonite H2O-CO2 system.

  7. Atmospheric H2O2 measurement: comparison of cold trap method with impinger bubbling method

    NASA Technical Reports Server (NTRS)

    Sakugawa, H.; Kaplan, I. R.

    1987-01-01

    Collection of atmospheric H2O2 was performed by a cold trap method using dry ice-acetone as the refrigerant. The air was drawn by a pump into a glass gas trap immersed in the dry ice-acetone slush in a dewar flask at a flow rate of 2.5 l min-1 for approximately 2 h. Collection efficiency was > 99% and negligible interferences by O3, SO2 or organic matter with the collected H2O2 in the trap were observed. This method was compared with the air impinger bubbling method which has been previously described (Kok et al., 1978a, b, Envir. Sci. Technol. 12, 1072-1080). The measured total peroxide (H2O2 + organic peroxide) values in a series of aim samples collected by the impinger bubbling method (0.06-3.7 ppb) were always higher than those obtained by the cold trap method (0.02-1.2 ppb). Laboratory experiments suggest that the difference in values between the two methods probably results from the aqueous phase generation of H2O2 and organic peroxide in the impinger solution by a reaction of atmospheric O3 with olefinic and aromatic compounds. If these O3-organic compound reactions which occur in the impinger also occur in aqueous droplets in the atmosphere, the process could be very important for aqueous phase generation of H2O2 in clouds and rainwater.

  8. The extracellular matrix modulates H2O2 degradation and redox signaling in endothelial cells

    PubMed Central

    Bagulho, Ana; Vilas-Boas, Filipe; Pena, Andreia; Peneda, Catarina; Santos, Filipa C.; Jerónimo, Ana; de Almeida, Rodrigo F.M.; Real, Carla

    2015-01-01

    The molecular processes that are crucial for cell function, such as proliferation, migration and survival, are regulated by hydrogen peroxide (H2O2). Although environmental cues, such as growth factors, regulate redox signaling, it was still unknown whether the ECM, a component of the cell microenvironment, had a function in this process. Here, we showed that the extracellular matrix (ECM) differently regulated H2O2 consumption by endothelial cells and that this effect was not general for all types of cells. The analysis of biophysical properties of the endothelial cell membrane suggested that this modification in H2O2 consumption rates was not due to altered membrane permeability. Instead, we found that the ECM regulated GPx activity, a known H2O2 scavenger. Finally, we showed that the extent of PTEN oxidation was dependent on the ECM, indicating that the ECM was able to modulate H2O2-dependent protein oxidation. Thus, our results unraveled a new mechanism by which the ECM regulates endothelial cell function by altering redox balance. These results pinpoint the ECM as an important component of redox-signaling. PMID:26409032

  9. Carboxylesterase converts Amplex red to resorufin: Implications for mitochondrial H2O2 release assays

    PubMed Central

    Miwa, Satomi; Treumann, Achim; Bell, Amy; Vistoli, Giulio; Nelson, Glyn; Hay, Sam; von Zglinicki, Thomas

    2016-01-01

    Amplex Red is a fluorescent probe that is widely used to detect hydrogen peroxide (H2O2) in a reaction where it is oxidised to resorufin by horseradish peroxidase (HRP) as a catalyst. This assay is highly rated amongst other similar probes thanks to its superior sensitivity and stability. However, we report here that Amplex Red is readily converted to resorufin by a carboxylesterase without requiring H2O2, horseradish peroxidase or oxygen: this reaction is seen in various tissue samples such as liver and kidney as well as in cultured cells, causing a serious distortion of H2O2 measurements. The reaction can be inhibited by Phenylmethyl sulfonyl fluoride (PMSF) at concentrations which do not disturb mitochondrial function nor the ability of the Amplex Red-HRP system to detect H2O2.In vitro experiments and in silico docking simulations indicate that carboxylesterases 1 and 2 recognise Amplex Red with the same kinetics as carboxylesterase-containing mitochondria. We propose two different approaches to correct for this problem and re-evaluate the commonly performed experimental procedure for the detection of H2O2 release from isolated liver mitochondria. Our results call for a serious re-examination of previous data. PMID:26577176

  10. Photogeneration of H2O2 in SPEEK/PVA aqueous polymer solutions.

    PubMed

    Little, Brian K; Lockhart, PaviElle; Slaten, B L; Mills, G

    2013-05-23

    Photolysis of air-saturated aqueous solutions containing sulphonated poly(ether etherketone) and poly(vinyl alcohol) results in the generation of hydrogen peroxide. Consumption of oxygen and H2O2 formation are initially concurrent processes with a quantum yield of peroxide generation of 0.02 in stirred or unstirred solutions within the range of 7 ≤ pH ≤ 9. The results are rationalized in terms of O2 reduction by photogenerated α-hydroxy radicals of the polymeric ketone in competition with radical-radical processes that consume the macromolecular reducing agents. Generation of H2O2 is controlled by the photochemical transformation that produces the polymer radicals, which is most efficient in neutral and slightly alkaline solutions. Quenching of the excited state of the polyketone by both H3O(+) and OH(-) affect the yields of the reducing macromolecular radicals and of H2O2. Deprotonation of the α-hydroxy polymeric radicals at pH > 9 accelerate their decay and contribute to suppressing the peroxide yields in basic solutions. Maxima in [H2O2] are observed when illuminations are performed with static systems, where O2 reduction is faster than diffusion of oxygen into the solutions. Under such conditions H2O2 can compete with O2 for the reducing radicals resulting in a consumption of the peroxide. PMID:23654204

  11. Use and abuse of exogenous H2O2 in studies of signal transduction

    PubMed Central

    Forman, Henry Jay

    2007-01-01

    The goal of this review is to present a rationale for use of exogenous H2O2, which has been demonstrated to have both toxicological and physiological signaling roles. Reasons for the use of exogenous application of non-toxic concentrations of H2O2 in model systems and caveats for interpretation of the data obtained will both be presented. Briefly, an argument for the cautious use of the addition of exogenous H2O2 is that, because of the permeability of cell membranes to this neutral small molecule, a concentration that is produced locally that is necessary for the physiological action can be mimicked. On the other hand, it must be recognized that the addition of an agent or its enzymatic generation in the media may produce reactions that may not normally occur because the total dose of H2O2 and the concentration of H2O2 in some cellular locations will exceed what is normally achieved even under a pathophysiological state. For this reason, this review will try to provide an unbiased balanced pros and cons analysis of this issue. PMID:17349920

  12. Selenoprotein X Gene Knockdown Aggravated H2O2-Induced Apoptosis in Liver LO2 Cells.

    PubMed

    Tang, Jiayong; Cao, Lei; Li, Qiang; Wang, Longqiong; Jia, Gang; Liu, Guangmang; Chen, Xiaoling; Cai, Jingyi; Shang, Haiying; Zhao, Hua

    2016-09-01

    To determine the roles of selenoprotein X gene (Selx) in protecting liver cells against oxidative damage, the influences of Selx knockdown on H2O2-induced apoptosis in human normal hepatocyte (LO2) cells were studied. pSilencer 3.1 was used to develop knockdown vector targeting the 3'-UTR of human Selx. The Selx knockdown and control cells were further exposed to H2O2, and cell viability, cell apoptosis rate, and the expression levels of mRNA and protein of apoptosis-related genes were detected. The results showed that vector targeting the 3'-UTR of Selx successfully silenced mRNA or protein expression of SelX in LO2 cells. Selx knockdown resulted in decreased cell viability, increased percentage of early apoptotic cells, decreased Bcl2A1 and Bcl-2 expression, and increased phosphorylation of P38 in LO2 cells. When Selx knockdown LO2 cells were exposed to H2O2, characteristics of H2O2-induced cell dysfunctions were further exacerbated. Taken together, our findings suggested that SelX played important roles in protecting LO2 cells against oxidative damage and reducing H2O2-induced apoptosis in liver cells. PMID:26899321

  13. Carboxylesterase converts Amplex red to resorufin: Implications for mitochondrial H2O2 release assays.

    PubMed

    Miwa, Satomi; Treumann, Achim; Bell, Amy; Vistoli, Giulio; Nelson, Glyn; Hay, Sam; von Zglinicki, Thomas

    2016-01-01

    Amplex Red is a fluorescent probe that is widely used to detect hydrogen peroxide (H2O2) in a reaction where it is oxidised to resorufin by horseradish peroxidase (HRP) as a catalyst. This assay is highly rated amongst other similar probes thanks to its superior sensitivity and stability. However, we report here that Amplex Red is readily converted to resorufin by a carboxylesterase without requiring H2O2, horseradish peroxidase or oxygen: this reaction is seen in various tissue samples such as liver and kidney as well as in cultured cells, causing a serious distortion of H2O2 measurements. The reaction can be inhibited by Phenylmethyl sulfonyl fluoride (PMSF) at concentrations which do not disturb mitochondrial function nor the ability of the Amplex Red-HRP system to detect H2O2.In vitro experiments and in silico docking simulations indicate that carboxylesterases 1 and 2 recognise Amplex Red with the same kinetics as carboxylesterase-containing mitochondria. We propose two different approaches to correct for this problem and re-evaluate the commonly performed experimental procedure for the detection of H2O2 release from isolated liver mitochondria. Our results call for a serious re-examination of previous data. PMID:26577176

  14. Degradation of 40 selected pharmaceuticals by UV/H2O2.

    PubMed

    Wols, B A; Hofman-Caris, C H M; Harmsen, D J H; Beerendonk, E F

    2013-10-01

    The occurrence of pharmaceuticals in source waters is increasing. Although UV advanced oxidation is known to be an effective barrier against micropollutants, degradation rates are only available for limited amounts of pharmaceuticals. Therefore, the degradation of a large group of pharmaceuticals has been studied in this research for the UV/H2O2 process under different conditions, including pharmaceuticals of which the degradation by UV/H2O2 was never reported before (e.g., metformin, paroxetine, pindolol, sotalol, venlafaxine, etc.). Monochromatic low pressure (LP) and polychromatic medium pressure (MP) lamps were used for three different water matrices. In order to have well defined hydraulic conditions, all experiments were conducted in a collimated beam apparatus. Degradation rates for the pharmaceuticals were determined. For those compounds used in this research that are also reported in literature, measured degradation results are in good agreement with literature data. Pharmaceutical degradation for only photolysis with LP lamps is small, which is increased by using a MP lamp. Most of the pharmaceuticals are well removed when applying both UV (either LP or MP) and H2O2. However, differences in degradation rates between pharmaceuticals can be large. For example, ketoprofen, prednisolone, pindolol are very well removed by UV/H2O2, whereas metformin, cyclophosphamide, ifosfamide are very little removed by UV/H2O2. PMID:23906776

  15. Hematocrit and oxygenation dependence of blood (1)H(2)O T(1) at 7 Tesla.

    PubMed

    Grgac, Ksenija; van Zijl, Peter C M; Qin, Qin

    2013-10-01

    Knowledge of blood (1)H2O T1 is critical for perfusion-based quantification experiments such as arterial spin labeling and cerebral blood volume-weighted MRI using vascular space occupancy. The dependence of blood (1)H2O T1 on hematocrit fraction (Hct) and oxygen saturation fraction (Y) was determined at 7 T using in vitro bovine blood in a circulating system under physiological conditions. Blood (1)H2O R1 values for different conditions could be readily fitted using a two-compartment (erythrocyte and plasma) model, which are described by a monoexponential longitudinal relaxation rate constant dependence. It was found that T1 = 2171 ± 39 ms for Y = 1 (arterial blood) and 2010 ± 41 ms for Y = 0.6 (venous blood), for a typical Hct of 0.42. The blood (1)H2O T1 values in the normal physiological range (Hct from 0.35 to 0.45, and Y from 0.6 to 1.0) were determined to range from 1900 to 2300 ms. The influence of oxygen partial pressure (pO2) and the effect of plasma osmolality for different anticoagulants were also investigated. It is discussed why blood (1)H2O T1 values measured in vivo for human blood may be about 10-20% larger than found in vitro for bovine blood at the same field strength. PMID:23169066

  16. Kinetics and mechanisms of reactions between H2O2 and copper and copper oxides.

    PubMed

    Björkbacka, Åsa; Yang, Miao; Gasparrini, Claudia; Leygraf, Christofer; Jonsson, Mats

    2015-09-28

    One of the main challenges for the nuclear power industry today is the disposal of spent nuclear fuel. One of the most developed methods for its long term storage is the Swedish KBS-3 concept where the spent fuel is sealed inside copper canisters and placed 500 meters down in the bedrock. Gamma radiation will penetrate the canisters and be absorbed by groundwater thereby creating oxidative radiolysis products such as hydrogen peroxide (H2O2) and hydroxyl radicals (HO˙). Both H2O2 and HO˙ are able to initiate corrosion of the copper canisters. In this work the kinetics and mechanism of reactions between the stable radiolysis product, H2O2, and copper and copper oxides were studied. Also the dissolution of copper into solution after reaction with H2O2 was monitored by ICP-OES. The experiments show that both H2O2 and HO˙ are present in the systems with copper and copper oxides. Nevertheless, these species do not appear to influence the dissolution of copper to the same extent as observed in recent studies in irradiated systems. This strongly suggests that aqueous radiolysis can only account for a very minor part of the observed radiation induced corrosion of copper. PMID:26287519

  17. H2O2-responsive molecularly engineered polymer nanoparticles as ischemia/reperfusion-targeted nanotherapeutic agents

    NASA Astrophysics Data System (ADS)

    Lee, Dongwon; Bae, Soochan; Hong, Donghyun; Lim, Hyungsuk; Yoon, Joo Heung; Hwang, On; Park, Seunggyu; Ke, Qingen; Khang, Gilson; Kang, Peter M.

    2013-07-01

    The main culprit in the pathogenesis of ischemia/reperfusion (I/R) injury is the overproduction of reactive oxygen species (ROS). Hydrogen peroxide (H2O2), the most abundant form of ROS produced during I/R, causes inflammation, apoptosis and subsequent tissue damages. Here, we report H2O2-responsive antioxidant nanoparticles formulated from copolyoxalate containing vanillyl alcohol (VA) (PVAX) as a novel I/R-targeted nanotherapeutic agent. PVAX was designed to incorporate VA and H2O2-responsive peroxalate ester linkages covalently in its backbone. PVAX nanoparticles therefore degrade and release VA, which is able to reduce the generation of ROS, and exert anti-inflammatory and anti-apoptotic activity. In hind-limb I/R and liver I/R models in mice, PVAX nanoparticles specifically reacted with overproduced H2O2 and exerted highly potent anti-inflammatory and anti-apoptotic activities that reduced cellular damages. Therefore, PVAX nanoparticles have tremendous potential as nanotherapeutic agents for I/R injury and H2O2-associated diseases.

  18. The interaction of H(2)O(2) with ice surfaces between 203 and 233 K.

    PubMed

    Pouvesle, N; Kippenberger, M; Schuster, G; Crowley, J N

    2010-12-21

    The interaction of H(2)O(2) with ice surfaces at temperatures between 203 and 233 K was investigated using a low pressure, coated-wall flow tube equipped with a chemical ionisation/electron impact mass spectrometer. Equilibrium surface coverages of H(2)O(2) on ice were measured at various concentrations and temperatures to derive Langmuir-type adsorption isotherms. H(2)O(2) was found to be strongly partitioned to the ice surface at low temperatures, with a partition coefficient, K(linC), equal to 2.1 × 10(-5) exp(3800/T) cm. At 228 K, this expression results in values of K(linC) which are orders of magnitude larger than the single previous determination and suggests that H(2)O(2) may be significantly partitioned to the ice phase in cirrus clouds. The partition coefficient for H(2)O(2) was compared to several other trace gases which hydrogen-bond to ice surfaces and a good correlation with the free energy of condensation found. For this class of trace gas a simple parameterisation for calculating K(linC)(T) from thermodynamic properties was established. PMID:20976362

  19. H2O2 Signalling Pathway: A Possible Bridge between Insulin Receptor and Mitochondria

    PubMed Central

    Pomytkin, Igor A

    2012-01-01

    This review is focused on the mechanistic aspects of the insulin-induced H2O2 signalling pathway in neurons and the molecules affecting it, which act as risk factors for developing central insulin resistance. Insulin-induced H2O2 promotes insulin receptor activation and the mitochondria act as the insulin-sensitive H2O2 source, providing a direct molecular link between mitochondrial dysfunction and irregular insulin receptor activation. In this view, the accumulation of dysfunctional mitochondria during chronological ageing and Alzheimer’s disease (AD) is a risk factor that may contribute to the development of dysfunctional cerebral insulin receptor signalling and insulin resistance. Due to the high significance of insulin-induced H2O2 for insulin receptor activation, oxidative stress-induced upregulation of antioxidant enzymes, e.g., in AD brains, may represent another risk factor contributing to the development of insulin resistance. As insulin-induced H2O2 signalling requires fully functional mitochondria, pharmacological strategies based on activating mitochondria biogenesis in the brain are central to the treatment of diseases associated with dysfunctional insulin receptor signalling in this organ. PMID:23730255

  20. Phase Separation Kinetics in Isopycnic Mixtures of H2O/CO2/Ethoxylated Alcohol Surfactants

    NASA Technical Reports Server (NTRS)

    Lesemann, Markus; Paulaitis, Michael E.; Kaler, Eric W.

    1999-01-01

    Ternary mixtures of H2O and CO2 with ethoxylated alcohol (C(sub i)E(sub j)) surfactants form three coexisting liquid phases at conditions where two of the phases have equal densities (isopycnic phases). Isopycnic phase behavior has been observed for mixtures containing C8E5, C10E6, and C12E6 surfactants, but not for those mixtures containing either C4E1 or C8E3 surfactants. Pressure-temperature (PT) projections for this three-phase equilibrium were determined for H2O/CO2/C8E5 and H2O/CO2/C10E6 mixtures at temperatures from approximately 25 to 33 C and pressures between 90 and 350 bar. Measurements of the microstructure in H2O/CO2/C12E6 mixtures as a function of temperature (25-31 C), pressure (63.1-90.7 bar), and CO2 composition (0-3.9 wt%) have also been carried out to show that while micellar structure remains essentially un-changed, critical concentration fluctuations increase as the phase boundary and plait point are approached. In this report, we present our first measurements of the kinetics of isopycnic phase separation for ternary mixtures of H2O/CO2/C8E5.

  1. Effect of H2O2 concentrations on copper removal using the modified hydrothermal biochar.

    PubMed

    Zuo, XiaoJun; Liu, Zhengang; Chen, MinDong

    2016-05-01

    This study investigated effect of H2O2 concentrations on copper removal using H2O2 modified hydrothermal carbonization Cymbopogon schoenanthus L. Spreng (HLG). Sorption behaviors of Cu (II) on the modified HLG by 20% H2O2 (mHLG2) could be the most desirable. Based on Langmuir isotherm, the maximum amount of Cu (II) uptake was in the sequence of mHLG2 (53.8mgg(-1))>mHLG1 (44.2mgg(-1))>mHLG3 (42.0mgg(-1))>mHLG0 (35.8mgg(-1)), which was higher than the results from majority of previous studies, suggesting that H2O2 modification advanced sorption capacity of hydrothermal biochars evidently. Effect mechanisms exploration indicated that the difference of Cu (II) removal by biochars before and after the modification was mainly related to functional groups. Carboxylic group was responsible for the best sorption property of Cu (II) by mHLG2, which was attributed to its significant relationships with H2O2 modification and Cu (II) removal. PMID:26894566

  2. Active sites and mechanisms for H2O2 decomposition over Pd catalysts.

    PubMed

    Plauck, Anthony; Stangland, Eric E; Dumesic, James A; Mavrikakis, Manos

    2016-04-01

    A combination of periodic, self-consistent density functional theory (DFT-GGA-PW91) calculations, reaction kinetics experiments on a SiO2-supported Pd catalyst, and mean-field microkinetic modeling are used to probe key aspects of H2O2 decomposition on Pd in the absence of cofeeding H2 We conclude that both Pd(111) and OH-partially covered Pd(100) surfaces represent the nature of the active site for H2O2 decomposition on the supported Pd catalyst reasonably well. Furthermore, all reaction flux in the closed catalytic cycle is predicted to flow through an O-O bond scission step in either H2O2 or OOH, followed by rapid H-transfer steps to produce the H2O and O2 products. The barrier for O-O bond scission is sensitive to Pd surface structure and is concluded to be the central parameter governing H2O2 decomposition activity. PMID:27006504

  3. Atmospheric H 2O 2 measurement: Comparison of cold trap method with impinger bubbling method

    NASA Astrophysics Data System (ADS)

    Sakugawa, Hiroshi; Kaplan, Isaac R.

    Collection of atmospheric H 2O 2 was performed by a cold trap method using dry ice-acetone as the refrigerant. The air was drawn by a pump into a glass gas trap immersed in the dry ice-acetone slush in a dewar flask at a flow rate of 2.5ℓ -1 for ~ 2 h. Collection efficiency was > 99% and negligible interferences by O 3, SO 2 or organic matter with the collected H 2O 2 in the trap were observed. This method was compared with the air impinger bubbling method which has been previously described (Kok et al., 1978a, b, Envir, Sci. Technol.12, 1072-1080). The measured total peroxide (H 2O 2 + organic peroxide) values in a series of air samples collected by the impinger bubbling method (0.06-3.7 ppb) were always higher than those obtained by the cold trap method (0.02-1.2 ppb). Laboratory experiments suggest that the difference in values between the two methods probably results from the aqueous phase generation of H 2O 2 and organic peroxide in the impinger solution by a reaction of atmospheric O 3 with olefinic and aromatic compounds. If these O 3-organic compound reactions which occur in the impinger also occur in aqueous droplets in the atmosphere, the process could be very important for aqueous phase generation of H 2O 2 in clouds and rainwater.

  4. Atmospheric H2O2 measurement: comparison of cold trap method with impinger bubbling method.

    PubMed

    Sakugawa, H; Kaplan, I R

    1987-01-01

    Collection of atmospheric H2O2 was performed by a cold trap method using dry ice-acetone as the refrigerant. The air was drawn by a pump into a glass gas trap immersed in the dry ice-acetone slush in a dewar flask at a flow rate of 2.5 l min-1 for approximately 2 h. Collection efficiency was > 99% and negligible interferences by O3, SO2 or organic matter with the collected H2O2 in the trap were observed. This method was compared with the air impinger bubbling method which has been previously described (Kok et al., 1978a, b, Envir. Sci. Technol. 12, 1072-1080). The measured total peroxide (H2O2 + organic peroxide) values in a series of aim samples collected by the impinger bubbling method (0.06-3.7 ppb) were always higher than those obtained by the cold trap method (0.02-1.2 ppb). Laboratory experiments suggest that the difference in values between the two methods probably results from the aqueous phase generation of H2O2 and organic peroxide in the impinger solution by a reaction of atmospheric O3 with olefinic and aromatic compounds. If these O3-organic compound reactions which occur in the impinger also occur in aqueous droplets in the atmosphere, the process could be very important for aqueous phase generation of H2O2 in clouds and rainwater. PMID:11542111

  5. Electrical conductivity of NaCl-H2O fluid in the crust

    NASA Astrophysics Data System (ADS)

    Sakuma, Hiroshi; Ichiki, Masahiro

    2016-02-01

    Ionic electrical conductivity of NaCl-H2O fluid as a function of pressure (0.2-2.0 GPa), temperature (673-2000 K), and NaCl concentration (0.6-9.6 wt %) was investigated using molecular dynamics (MD) simulations. Conductivity versus NaCl concentration has a nonlinear relationship due to the presence of electrically neutral ion pairs in concentrated solutions. The calculated conductivity at 0.6 wt % NaCl is consistent with the available experimental data, and the calculated conductivity at higher temperatures shows a greater degree of pressure dependence. The major factors controlling the conductivity are the density of the NaCl-H2O fluid and the permittivity of solvent H2O. A purely empirical equation for deriving the conductivity was proposed. Highly conductive zones below a depth of 35 km in the middle portion of the continental crust can be interpreted by the presence of NaCl-H2O fluid with the salinity ranging from 0.2 to 7.0 wt %. A highly conductive zone observed at a depth of 20 to 40 km above the subducting oceanic crust in Cascadia can be explained by the presence of low-salinity (0.5 wt %) NaCl-H2O fluid possibly generated by the dehydration of basalt.

  6. Interhemispheric differences in polar stratospheric HNO3, H2O, ClO, and O3

    NASA Technical Reports Server (NTRS)

    Santee, M. L.; Read, W. G.; Waters, J. W.; Froidevaux, L.; Manney, G. L.; Flower, D. A.; Jarnot, R. F.; Harwood, R. S.; Peckham, G. E.

    1995-01-01

    Simultaneous global measurements of nitric acid (HNO3), water (H2O), chlorine monoxide (ClO), and ozone (O3) in the stratosphere have been obtained over complete annual cycles in both hemispheres by the Microwave Limb Sounder on the Upper Atmosphere Research Satellite. A sizeable decrease in gas-phase HNO3 was evident in the lower stratospheric vortex over Antarctica by early June 1992, followed by a significant reduction in gas-phase H2O after mid-July. By mid-August, near the time of peak ClO, abundances of gas-phase HNO3 and H2O were extremely low. The concentrations of HNO3 and H2O over Antarctica remained depressed into November, well after temperatures in the lower stratosphere had risen above the evaporation threshold for polar stratospheric clouds, implying that denitrification and dehydration had occurred. No large decreases in either gas-phase HNO3 or H2O were observed in the 1992-1993 Arctic winter vortex. Although ClO was enhanced over the Arctic as it was over the Antarctic, Arctic O3 depletion was substantially smaller than that over Antarctica. A major factor currently limiting the formation of an Arctic ozone 'hole' is the lack of denitrification in the northern polar vortex, but future cooling of the lower stratosphere could lead to more intense denitrification and consequently larger losses of Arctic ozone.

  7. Accurate positions of H2 O masers in the Large Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Lazendic, J. S.; Whiteoak, J. B.; Klamer, I.; Harbison, P. D.; Kuiper, T. B. H.

    2002-04-01

    Positions with subarcsecond accuracy have been measured for seven 22-GHz H2 O masers associated with Hii regions in the Large Magellanic Cloud (LMC); two of the masers are new detections. Initial position measurements were obtained with the 70-m antenna of the Canberra NASA Deep Space Network during a period of more than two years in which the antenna was used to monitor the maser emission. The positions were further improved using 22-GHz observations involving three antennas of the Australia Telescope Compact Array. The positions have been compared with those of 1.6-GHz continuum emission and other LMC masers (of OH and CH3 OH). The H2 O maser positions range from within 1arcsec (270mpc) of the centre of a compact Hii component to beyond the boundary of significant continuum emission. Three of the four masers located near continuum peaks are close to OH masers. In two cases the positional agreement is better than 0.2arcsec (53mpc) in the third case the agreement is worse (0.9arcsec) but the positions of the individual H2 O features appear to be spread over more than 1arcsec. The velocities of the OH masers are within the spread of the H2 O velocities. The three H2 O masers offset from continuum centres are located 3-7arcsec from optical or infrared phenomena probably associated with very early stages of star formation; no other molecular masers are known in these directions.

  8. Interhemispheric differences in polar stratospheric HNO3, H2O, ClO, and O3

    SciTech Connect

    Santee, M.L.; Read, W.G.; Waters, J.W.; Froidevaux, L.; Manney, G.L.; Flower, D.A.; Jarnot, R.F.; Harwood, R.S.; Peckham, G.E.

    1995-02-01

    Simultaneous global measurements of nitric acid (HNO3), water (H2O), chlorine monoxide (ClO), and ozone (O3) in the stratosphere have been obtained over complete annual cycles in both hemispheres by the Microwave Limb Sounder on the Upper Atmosphere Research Satellite. A sizeable decrease in gas-phase HNO3 was evident in the lower stratospheric vortex over Antarctica by early June 1992, followed by a significant reduction in gas-phase H2O after mid-July. By mid-August, near the time of peak ClO, abundances of gas-phase HNO3 and H2O were extremely low. The concentrations of HNO3 and H2O over Antarctica remained depressed into November, well after temperatures in the lower stratosphere had risen above the evaporation threshold for polar stratospheric clouds, implying that denitrification and dehydration had occurred. No large decreases in either gas-phase HNO3 or H2O were observed in the 1992-1993 Arctic winter vortex. Although ClO was enhanced over the Arctic as it was over the Antarctic, Arctic O3 depletion was substantially smaller than that over Antarctica. A major factor currently limiting the formation of an Arctic ozone `hole` is the lack of denitrification in the northern polar vortex, but future cooling of the lower stratosphere could lead to more intense denitrification and consequently larger losses of Arctic ozone.

  9. Interhemispheric Differences in Polar Stratospheric HNO3, H2O, CIO, and O3.

    PubMed

    Santee, M L; Read, W G; Waters, J W; Froidevaux, L; Manney, G L; Flower, D A; Jarnot, R F; Harwood, R S; Peckham, G E

    1995-02-10

    Simultaneous global measurements of nitric acid (HNO(3)), water (H(2)O), chlorine monoxide (CIO), and ozone (O(3)) in the stratosphere have been obtained over complete annual cycles in both hemispheres by the Microwave Limb Sounder on the Upper Atmosphere Research Satellite. A sizeable decrease in gas-phase HNO(3) was evident in the lower stratospheric vortex over Antarctica by early June 1992, followed by a significant reduction in gas-phase H(2)O after mid-July. By mid-August, near the time of peak CIO, abundances of gas-phase HNO(3) and H(2)O were extremely low. The concentrations of HNO(3) and H(2)O over Antarctica remained depressed into November, well after temperatures in the lower stratosphere had risen above the evaporation threshold for polar stratospheric clouds, implying that denitrification and dehydration had occurred. No large decreases in either gas-phase HNO(3) or H(2)O were observed in the 1992-1993 Arctic winter vortex. Although CIO was enhanced over the Arctic as it was over the Antarctic, Arctic O(3) depletion was substantially smaller than that over Antarctica. A major factor currently limiting the formation of an Arctic ozone "hole" is the lack of denitrification in the northern polar vortex, but future cooling of the lower stratosphere could lead to more intense denitrification and consequently larger losses of Arctic ozone. PMID:17813911

  10. Mycobacterial growth and sensitivity to H2O2 killing in human monocytes in vitro.

    PubMed Central

    Laochumroonvorapong, P; Paul, S; Manca, C; Freedman, V H; Kaplan, G

    1997-01-01

    The intracellular growth and susceptibilities to killing by H2O2 in cultured human monocytes of a number of mycobacterial species including laboratory strains and clinical isolates of Mycobacterium tuberculosis, and Mycobacterium bovis bacillus Calmette-Guerin (BCG) and a clinical isolate of Mycobacterium avium-M. intracellulare were examined. The clinical isolate of M. avium-M. intracellulare did not replicate in freshly explanted monocytes (generation time of >400 h); BCG replicated with a generation time of 95 h, and M. tuberculosis strains CDC551, H37Rv, and H37Ra replicated with generation times of 24, 35, and 37 h, respectively, during the 4-day growth assay. When cultured in monocytes for 4 days, the mycobacteria were variably sensitive to H2O2-induced killing. A positive correlation between the generation time and percent killing of intracellular bacilli was observed. By comparison, mycobacterial strains were similarly sensitive to H2O2 treatment in cell-free culture media and in sonicated cell suspensions. Using a number of inhibitors of reactive oxygen intermediates we determined that other than catalase the inhibitors tested did not affect H2O2-induced killing of intracellular mycobacteria. Our studies suggest that the killing of mycobacteria growing in human monocytes in vitro by the addition of exogenous H2O2 is dependent on the susceptibility to a peroxide-induced killing pathway as well as on the intracellular growth rate of the mycobacteria. PMID:9353075

  11. Computational Investigation of the Oxidative Deboronation of Boroglycine, H2N-CH2-B(OH)2, Using H2O and H2O2

    NASA Astrophysics Data System (ADS)

    Larkin, Joseph D.; Markham, George D.; Milkevitch, Matt; Brooks, Bernard R.; Bock, Charles W.

    2009-09-01

    We report results from a computational investigation of the oxidative deboronation of boroglycine, H2N-CH2-B(OH)2, using H2O and H2O2 as the reactive oxygen species (ROS) to yield aminomethanol, H2N-CH2-OH; these results complement our study on the protodeboronation of boroglycine to produce methylamine, H2N-CH3 (Larkin et al. J. Phys. Chem. A 2007, 111, 6489-6500). Second-order Møller-Plesset (MP2) perturbation theory with Dunning-Woon correlation-consistent (cc) basis sets were used for the calculations with comparisons made to results from density functional theory (DFT) at the PBE1PBE/6-311++G(d,p)(cc-pVDZ) levels. The effects of a bulk aqueous environment were also incorporated into the calculations employing PCM and CPCM methodology. Using H2O as the ROS, the reaction H2O + H2N-CH2-B(OH)2 → H2N-CH2-OH + H-B(OH)2 was calculated to be endothermic; the value of ΔH2980 was +12.0 kcal/mol at the MP2(FC)/cc-pVTZ computational level in vacuo and +13.7 kcal/mol in PCM aqueous media; the corresponding value for the activation barrier, ΔH‡, was +94.3 kcal/mol relative to the separated reactants in vacuo and +89.9 kcal/mol in PCM aqueous media. In contrast, the reaction H2O2 + H2N-CH2-B(OH)2 → H2N-CH2-OH + B(OH)3 was calculated to be highly exothermic with an ΔH2980 value of -100.9 kcal/mol at the MP2(FC)/cc-pVTZ computational level in vacuo and -99.6 kcal/mol in CPCM aqueous media; the highest-energy transition state for the multistep process associated with this reaction involved the rearrangement of H2N-CH2-B(OH)(OOH) to H2N-CH2-O-B(OH)2 with a ΔH‡ value of +23.2 kcal/mol in vacuo relative to the separated reactants. These computational results for boroglycine are in accord with the experimental observations for the deboronation of the FDA approved anticancer drug bortezomib (Velcade, PS-341), where it was found to be the principle deactivation pathway (Labutti et al. Chem. Res. Toxicol. 2006, 19, 539-546).

  12. Reversible adsorption of a planar cyclic (H2O)6 cluster held in a 2D CuII-coordination framework

    NASA Astrophysics Data System (ADS)

    Zhao, Yang; Lu, Hui; Yang, Le; Luo, Geng-Geng

    2015-05-01

    Coordination polymeric solid, {[Cu(btec)0.5(bpe)(H2O)2]ṡ(H2O)4}n (1) (H4btec = 1,2,4,5-benzenetetracarboxylic acid, and bpe = 1,2-bis(4-pyridyl)ethane), has been obtained by the solution phase ultrasonic synthesis techniques. The structure established through X-ray structural analysis shows that a centrosymmetric water hexamer with planar conformation structurally similar to aromatic benzene is unambiguously crystallized within the hydrophilic channel of 1. Water escapes at 150 °C but is re-absorbed using water vapor. The reversible formation of this water cluster was supported from powder X-ray diffraction (PXRD), FTIR spectra and TGA/DTA. The reversible dehydration/rehydration behaviors enable analysis of the nature of the intermolecular interactions that occur between the planar hexameric water and the resulting host framework. When the auxiliary ligand bpe was removed from the synthetic conditions, another complex {[Cu(btec)0.5(H2O)3]ṡH2O}n (2) only encapsulating a water dimer was afforded, which suggests bpe plays an important role in the formation of the framework and water clusters.

  13. Convective dominated flows in open capillary channels

    NASA Astrophysics Data System (ADS)

    Rosendahl, Uwe; Grah, Aleksander; Dreyer, Michael E.

    2010-05-01

    This paper is concerned with convective dominated liquid flows in open capillary channels. The channels consist of two parallel plates bounded by free liquid surfaces along the open sides. In the case of steady flow the capillary pressure of the free surface balances the differential pressure between the liquid and the surrounding constant pressure gas phase. A maximum flow rate is achieved when the adjusted volumetric flow rate exceeds a certain limit leading to a collapse of the free surfaces. The convective dominated flow regime is a special case of open capillary flow, since the viscous forces are negligibly small compared with the convective forces. Flows of this type are of peculiar interest since the free surfaces possess a quasisymmetry in the flow direction. This quasisymmetry enables the application of a new effective method for evaluation of the flow limit. The flow limit is caused by a choking effect. This effect is indicated by the speed index, S, which is defined by the ratio of the flow velocity and the longitudinal capillary wave speed. The speed index is defined analogously to Mach number and tends toward unity in the case of flow limitation, i.e., when the maximum flow rate is reached. Utilizing the quasisymmetry, a new approach for a very precise determination of the speed index is presented. This approach uses a new approximation for the curvature of the surfaces by means of the empirical surface profiles. On the basis of empirical and theoretical data, the paper discusses the typical features of the stable flow. The experiments were performed under microgravity aboard the sounding rockets TEXUS 41 and TEXUS 42. The experiment setup enables the approach to the flow limit through either increase in flow rate or channel length. The theoretical data have been gained from numerical solutions of a one-dimensional flow model. The empirical and theoretical results are in good agreement and both confirm the choking effect as cause of the flow limitation

  14. FTIR imaging in diffusion studies: CO2 and H2O in a synthetic sector-zoned beryl

    NASA Astrophysics Data System (ADS)

    Della Ventura, Giancarlo; Radica, Francesco; Bellatreccia, Fabio; Cavallo, Andrea; Cinque, Gianfelice; Behrens, Harald

    2015-06-01

    In this work we investigate the strongly inhomogeneous distribution of CO2 and H2O in a synthetic beryl having a peculiar hourglass zoning of Cr due to the crystal growth. The sample was treated at 800°C, 500 MPa, in a CO2-rich atmosphere. High-resolution FESEM images revealed that the hourglass boundary is not correlated to physical discontinuities, at least at the scale of tens of nanometers. Polarized FPA-FTIR imaging, on the other side, revealed that the chemical zoning acts as a fast pathway for carbon dioxide diffusion, a feature never observed so far in minerals. The hourglass zone boundary may be thus considered as a structural defect possibly due to the mismatch induced by the different growth rates of each sector. High-resolution synchrotron-light FTIR imaging, in addition, also allows enhancement of CO2 diffusion along the hourglass boundary to be distinguished from diffusion along fractures in the grain. Therefore, FTIR imaging provides evidence that different diffusion mechanisms may locally combine, suggesting that the distribution of the target molecules needs to be be carefully characterized in experimental studies. This piece of information is mandatory when the study is aimed at extracting diffusion coefficients from analytical profiles. Combination of TOF-SIMS and FPA data shows a significant depletion of type II H2O along the hourglass boundary, indicating that water diffusion could be controlled by the distribution of alkali cations within channels, coupled to a plug effect of CO2.

  15. Infrared Spectra of the CO_2-H_2O, CO_2-(H_2O)2, and (CO_2)2-H_2O Complexes Isolated in Solid Neon Between 90 and 5300 wn

    NASA Astrophysics Data System (ADS)

    Tremblay, Benoît; Soulard, Pascale

    2015-06-01

    The van der Waals complex of H_2O with CO_2 has attracted considerable theoretical interest since it is a typical example of a weak binding complex (less than 3 kcal/mol), but a very few IR data are available in gas. For these reasons, we have studied in solid neon hydrogen bonded complexes involving carbon dioxide and water molecules. Evidence for the existence of at least three (CO_2)m(H_2O)n, or m:n, complexes has been obtained from the appearance of many new absorptions near the well-know monomers fundamental transitions. Concentration effects and detailed vibrational analysis allowed identification of fifteen, eleven and four transitions for the 1:1, 1:2, and 2:1 complexes, respectively. Careful examination of the far infrared allows the assignment of several 1:1 and 1:2 intermolecular modes, confirmed by the observation of combinations of intra+intermolecular transitions. All of these results significantly increase the number of one and, especially, two quanta vibrational transitions observed for these complexes, and anharmonic coupling constants have been derived. This study shows the high sensibility of the solid neon isolation for the spectroscopy of the hydrogen-bonded complexes since two quanta transitions can't be easily observed in gas phase.

  16. Water's Role in Reshaping a Macrocycle's Binding Pocket: Conformation-Specific Infrared and Ultraviolet Spectroscopy of BENZO-15-CROWN-5-(H_{2}O)_{n}-CLUSTERS (n = 1, 2)

    NASA Astrophysics Data System (ADS)

    Shubert, V. Alvin; Müller, Christian W.; James, William H. James, III; Zwier, Timothy S.

    2009-06-01

    Crown ethers are well-studied examples of flexible macrocycles with a high binding selectivity for substrates, especially cations. We investigated the conformational preferences of the singly and doubly complexed water clusters of the crown ethers benzo-15-crown-5 (B15C) and its amino-derivative 4'-aminobenzo-15-crown-5 (ABC) cooled in a supersonic jet expansion. The fluorescence excitation, resonance enhanced two-photon ionization (R2PI), UV-UV holeburning (UVHB), fluorescence-dip infrared (FDIR), resonant ion-dip infrared (RIDIR) and novel IR-IR-UV holeburning^{1} spectra allowed for the identification of two B15C-(H_{2}O)_{1} conformers and one ABC-(H_{2}O)_{1} conformer. These conformers are characterized by an all-planar arrangement of the atoms directly bound to the benzene ring in which the crown ether macrocycle opens up to a symmetric structure and accomodates a doubly and triply H-bonded H_{2}O molecule in two distinct ways, respectively. Two B15C-(H_{2}O)_{2} conformers and one ABC-(H_{2}O)_{2} conformer were identified. One of the B15C-(H_{2}O)_{2} conformers contains a macrocycle configuration identical to that found in the monohydrated clusters with an H-bonding topology in which the H_{2}O molecules occupy both available sites simultaneously. The second B15C-(H_{2}O)_{2} conformer is assigned to an H-bond pattern in which the two H_{2}O molecules are concatenated to form an H-bonded bridge involving only three of the four available O-H-bonds (see figure). (1) V. A. Shubert and T. S. Zwier, J. Phys. Chem. A, 2007, 111, 13283.

  17. Molecule survival in magnetized protostellar disk winds. II. Predicted H2O line profiles versus Herschel/HIFI observations

    NASA Astrophysics Data System (ADS)

    Yvart, W.; Cabrit, S.; Pineau des Forêts, G.; Ferreira, J.

    2016-01-01

    Context. The origin of molecular protostellar jets and their role in extracting angular momentum from the accreting system are important open questions in star formation research. In the first paper of this series we showed that a dusty magneto-hydrodynamic (MHD) disk wind appeared promising to explain the pattern of H2 temperature and collimation in the youngest jets. Aims: We wish to see whether the high-quality H2O emission profiles of low-mass protostars, observed for the first time by the HIFI spectrograph on board the Herschel satellite, remain consistent with the MHD disk wind hypothesis, and which constraints they would set on the underlying disk properties. Methods: We present synthetic H2O line profiles predictions for a typical MHD disk wind solution with various values of disk accretion rate, stellar mass, extension of the launching area, and view angle. We compare them in terms of line shapes and intensities with the HIFI profiles observed by the WISH key program towards a sample of 29 low-mass Class 0 and Class 1 protostars. Results: A dusty MHD disk wind launched from 0.2-0.6 AU AU to 3-25 AU can reproduce to a remarkable degree the observed shapes and intensities of the broad H2O component observed in low-mass protostars, both in the fundamental 557 GHz line and in more excited lines. Such a model also readily reproduces the observed correlation of 557 GHz line luminosity with envelope density, if the infall rate at 1000 AU is 1-3 times the disk accretion rate in the wind ejection region. It is also compatible with the typical disk size and bolometric luminosity in the observed targets. However, the narrower line profiles in Class 1 sources suggest that MHD disk winds in these sources, if present, would have to be slower and/or less water rich than in Class 0 sources. Conclusions: MHD disk winds appear as a valid (though not unique) option to consider for the origin of the broad H2O component in low-mass protostars. ALMA appears ideally suited to

  18. Magnesium Corrosion Triggered Spontaneous Generation of H2O2 on Oxidized Titanium for Promoting Angiogenesis.

    PubMed

    Park, Jimin; Du, Ping; Jeon, Jin-Kyung; Jang, Gun Hyuk; Hwang, Mintai Peter; Han, Hyung-Seop; Park, Kwideok; Lee, Kwan Hyi; Lee, Jee-Wook; Jeon, Hojeong; Kim, Yu-Chan; Park, Jong Woong; Seok, Hyun-Kwang; Ok, Myoung-Ryul

    2015-12-01

    Although the use of reactive oxygen species (ROS) has been extensively studied, current systems employ external stimuli such as light or electrical energy to produce ROS, which limits their practical usage. In this report, biocompatible metals were used to construct a novel electrochemical system that can spontaneously generate H2O2 without any external light or voltage. The corrosion of Mg transfers electrons to Au-decorated oxidized Ti in an energetically favorable process, and the spontaneous generation of H2O2 in an oxygen reduction reaction was revealed to occur at titanium by combined spectroscopic and electrochemical analyses. The controlled release of H2O2 noticeably enhanced in vitro angiogenesis even in the absence of growth factors. Finally, a new titanium implant prototype was developed by Mg incorporation, and its potential for promoting angiogenesis was demonstrated. PMID:26482466

  19. Palladium-tin catalysts for the direct synthesis of H2O2 with high selectivity

    DOE PAGESBeta

    Freakley, Simon J.; He, Qian; Harrhy, Jonathan H.; Lu, Li; Crole, David A.; Morgan, David J.; Ntainjua, Edwin N.; Edwards, Jennifer K.; Carley, Albert F.; Borisevich, Albina Y.; et al

    2016-02-25

    The direct synthesis of hydrogen peroxide (H2O2 ) from H2 and O2 represents a potentially atom-efficient alternative to the current industrial indirect process. We show that the addition of tin to palladium catalysts coupled with an appropriate heat treatment cycle switches off the sequential hydrogenation and decomposition reactions, enabling selectivities of >95% toward H2O2 . This effect arises from a tin oxide surface layer that encapsulates small Pd-rich particles while leaving larger Pd-Sn alloy particles exposed. In conclusion, we show that this effect is a general feature for oxide-supported Pd catalysts containing an appropriate second metal oxide component, and wemore » set out the design principles for producing high-selectivity Pd-based catalysts for direct H2O2 production that do not contain gold.« less

  20. The molecular environment of H_2_O masers: VLA ammonia observations.

    NASA Astrophysics Data System (ADS)

    Codella, C.; Testi, L.; Cesaroni, R.

    1997-09-01

    We present the results of single dish and interferometric observations of ammonia towards 5 sources selected from a sample of H_2_O and OH masers associated with star forming regions. The Medicina telescope was used to observe the NH_3_(1,1), (2,2), and (3,3) inversion transitions. High resolution maps in the NH_3_(2,2) and (3,3) lines and in the 1.3 cm continuum were then obtained with the Very Large Array. The main result of this research is to confirm the belief that H_2_O masers form in hot dense molecular cores which are sites of massive star formation. We also find evidence for the H_2_O maser phase to be prior to the appearance of an ultracompact HII region around the embedded high mass star(s).

  1. Concentrated solar energy for thermochemically producing liquid fuels from CO2 and H2O

    NASA Astrophysics Data System (ADS)

    Loutzenhiser, Peter G.; Stamatiou, Anastasia; Villasmil, Willy; Meier, Anton; Steinfeld, Aldo

    2011-01-01

    A two-step solar thermochemical cycle for producing syngas from H2O and CO2 via Zn/ZnO redox reactions is considered. The first, endothermic step is the thermolysis of ZnO to Zn and O2 using concentrated solar radiation as the source of process heat. The second, non-solar, exothermic step is the reaction of Zn with mixtures of H2O and CO2 yielding high-quality syngas (mainly H2 and CO) and ZnO; the latter is recycled to the first solar step, resulting in net reactions CO2 = CO+0.5O2 and H2O= H2 +0.5O2. Syngas is further processed to liquid fuels via Fischer-Tropsch or other catalytic reforming processes. State-of-the-art reactor technologies and experimental results are provided for both steps of the cycle.

  2. Influence of H2O2 on LPG fuel performance evaluation

    NASA Astrophysics Data System (ADS)

    Khan, Muhammad Saad; Ahmed, Iqbal; Mutalib, Mohammad Ibrahim bin Abdul; Nadeem, Saad; Ali, Shahid

    2014-10-01

    The objective of this mode of combustion is to insertion of hydrogen peroxide (H2O2) to the Liquefied Petroleum Gas (LPG) combustion on spark plug ignition engines. The addition of hydrogen peroxide may probably decrease the formation of NOx, COx and unburned hydrocarbons. Hypothetically, Studies have shown that addition of hydrogen peroxide to examine the performance of LPG/H2O2 mixture in numerous volumetric compositions starting from lean LPG until obtaining a better composition can reduce the LPG fuel consumption. The theory behind this idea is that, the addition of H2O2 can cover the lean operation limit, increase the lean burn ability, diminution the burn duration along with controlling the exhaust emission by significantly reducing the greenhouse gaseous.

  3. Correction of Doppler-broadened Rayleigh backscattering effects in H2O dial measurements

    NASA Technical Reports Server (NTRS)

    Ansmann, A.; Bosenberg, J.

    1986-01-01

    A general method of solutions for treating effects of Doppler-broadened Rayleigh backscattering in H2O Differential Absorption Lidar (DIAL) measurements are described and discussed. Errors in vertical DIAL measuremtns caused by this laser line broadening effect can be very large and, therfore, this effect has to be accounted for accurately. To analyze and correct effects of Doppler-broadened Rayleigh backscattering in DIAL experiments, a generalized DIAL approximation was derived starting from a lidar equation, which includes Doppler broadening. To evaluate the accuracy of H2O DIAL measurements, computer simulations were performed. It was concluded that correction of Doppler broadened Rayleigh backscattering is possible with good accuracy in most cases of tropospheric H2O DIAL measurements, but great care has to be taken when layers with steep gradients of Mie backscattering like clouds or inversion layers are present.

  4. Influence of Rayleigh-Doppler broadening on the selection of H2O dial system parameters

    NASA Technical Reports Server (NTRS)

    Ismail, S.; Browell, E. V.

    1986-01-01

    Computer simulations have enabled the performance of a H2O Differential Absorption Lidar (DIAL) system to be studied by spectrally analyzing the forward propagating and backscattered laser energy. The simulations were done for a high altitude (21 km) DIAL system operating in a nadir-viewing mode. The influence of Rayleigh Doppler broadening on DIAL measurement accuracies were evaluated and show that the Rayleigh broadening influence, which can be corrected to first order in regions free of large aerosol gradients, reduces the sensitivity of DIAL H2O measurement errors in the upper tropospheric region. The ability to correct the Rayleigh broadening and the selection of H2O DIAL parameters when all the systematic effects are combined, were discussed.

  5. Dissolved, Exsolved and Re-dissolved H2O in Volcanology: Rheology, Glass Transition, and Thermodynamics

    NASA Astrophysics Data System (ADS)

    Russell, K.; kennedy, B.; Giordano, D.; Friedlander, E. A.

    2012-12-01

    All natural magmas originate with dissolved H2O. All such magmas degas during transport and eruption. The presence, abundance, and state of H2O in magmas control phase relations and the transport properties of melts and magmas. For example, dissolved H2O lowers viscosity, lowers glass transition temperatures (Tg), and controls the temperature and nature of crystallization. The effects of exsolved water are also substantial in terms of modifying the bulk transport properties of the magma, facilitating egress of volatiles and, thus, promoting crystallization. Of great interest is the coupling this component (H2O) creates between the thermodynamic processes (i.e. cooling, crystallization, vesiculation) and the properties (i.e. density, viscosity) controlling the mechanical behaviour (i.e. flow and fracture) of magma during transport and eruption. The coupling allows for strong feedbacks between system variables. The component H2O also has a retrograde solubility in silicate melts wherein H2O solubility in the melt increases with decreasing T. Here, we explore some of the consequences of retrograde solubility of H2O for volcanic systems using a new preliminary experimental dataset. These data establish the 1-atmosphere solubility limits of H2O in silicic melt at volcanic temperatures and are complementary to the growing literature on the low pressure (<50 MPa) solubility of volatiles in silicate melts (e.g., Behrens et al. 2009; DiMatteo et al. 2004; Liu et al. 2005; Zhang 1999). We specifically look at the implications of these data, especially the retrograde solubility limits, for welding of pyroclastic deposits (e.g. ignimbrites, conduit fill, fall out). The cessation of welding and compaction processes in pyroclastic deposits is reached when deposits cool below Tg. However, the fact that H2O has a retrograde solubility means that inter- and intraclast water will be resorbed by vitric pyroclasts as the deposit cools (regardless of load). This has the immediate

  6. Photochemical modeling of H2O in Titan's atmosphere constrained by Herschel Observations

    NASA Astrophysics Data System (ADS)

    Lara, L. M.; Lellouch, E.; Moreno, R.; Courtin, R.; Hartogh, P.; Rengel, M.

    2012-04-01

    As a species subject to photolytic, chemical and condensation losses, H2O present in Titan's stratosphere must be of external origin. The discovery of CO2 by Voyager (Samuelson et al. 1981) pointed to an external supply of oxygen to Titan's atmosphere. Indeed, CO2, which also condenses, was recognized to be formed via CO+OH, where OH was likely produced by H2O photolysis. This view was supported by the ground-based discovery of CO (Lutz et al. 1983) and subsequent measurements confirming an abundance of ~50 ppm. The source of CO itself remained elusive, but inspired by the Cassini/CAPS discovery of a O+ influx rate (Hartle et al. 2006), Hörst et al. (2008) showed that an external source of O or O+ leads to the formation of CO, also pointing to the likely external origin of this compound. The most up-to-date model of Titan's oxygen chemistry by Hörst et al. (2008) adjusted the OH/H2O deposition rate as a function of the eddy diffusion coefficient below 200 km to match the observed CO2 mixing ratio (15 ppb, uniform over 100-200 km), and producing a H2O profile that was deemed consistent with ISO/SWS measurement of the H2O abundance at a nominal altitude of 400 km (Coustenis et al. 1998). Therefore, the Hörst et al. (2008) study provided an apparently self-consistent picture of the origin of oxygen compounds in Titan's atmosphere, with the three main species (CO, CO2 and H2O) being produced from a permanent external supply of oxygen in two distinct forms. However, recent measurements of several H2O lines by the HIFI and PACS instruments (Herschel Space Observatory) have shown that none of the H2O profiles calculated in Hörst et al. (2008) reproduces the observed lines (Moreno et al., this workshop), and neither does the Lara et al. (1996) H2O profile. Here we revisit the Lara et al. (1996) photochemical model by including (i) an updated eddy diffusion coefficient profile (K(z)), constrained by the C2H6 vertical distribution (ii) an adjustable O+/OH/H2O influx. Our

  7. Highly H2O2-sensitive electrospun quantum dots nanocomposite films for fluorescent biosensor.

    PubMed

    Tan, Longfei; He, Xiaolong; Chen, Dong; Wu, Xiaoli; Li, Hongbo; Ren, Xiangling; Meng, Xianwei; Tang, Fangqiong

    2013-01-01

    Bright CdSe quantum dots (QDs)/polycaprolactone (PCL) nanocomposite fluorescent films were fabricated by electronspinning. By using chloroform and N,N-dimethylformamide as electronspinning solvent, the oil-soluble CdSe QDs were uniformly distributed in PCL fibers, and were directly employed as optical probe without any modification processing. The fluorescences of CdSe QDs/PCL nanocomposite films were quickly quenched when the films were contacted with H2O2, solution. In the presence of glucose oxidase (GOD), the fluorescence intensities of these fluorescent films exhibit a liner change with the concentrations of glucose. The H2O2-sensitive electrospun QDs nanocomposite films are highly uniform and repeatable, demonstrating the potential to fabricate stable, sensitive and recyclable fluorescent biosensor for the detection different H2O2-generating oxidases and their substrates. PMID:23627067

  8. Possible sources of H2 to H2O enrichment at evaporation of parent chondritic material

    NASA Technical Reports Server (NTRS)

    Makalkin, A. B.; Dorofeyeva, V. A.; Vityazev, A. V.

    1993-01-01

    One of the results obtained from thermodynamic simulation of recondensation of the source chondritic material is that at 1500-1800 K it's possible to form iron-rich olivine by reaction between enstatite, metallic iron and water vapor in the case of (H2O)/(H2) approximately equal to 0.1. This could be reached if the gas depletion in hydrogen is 200-300 times relative to solar abundance. To get this range of depletion one needs some source material more rich in hydrogen than the carbonaceous CI material which is the richest in volatiles among chondrites. In the case of recondensation at impact heating and evaporation of colliding planetesimals composed of CI material, we obtain insufficiently high value of (H2)/(H2O) ratio. In the present paper we consider some possible source materials and physical conditions necessary to reach gas composition with (H2)/(H2O) approximately 10 at high temperature.

  9. Successive openings of the same acetylcholine receptor channel are correlated in open time.

    PubMed Central

    Jackson, M B; Wong, B S; Morris, C E; Lecar, H; Christian, C N

    1983-01-01

    Previous analysis of single-channel current records has shown that both the opening and closing transitions of chemically activated ion channels are operated by fast and slow kinetic processes. The fast component in the kinetics of channel opening has been interpreted as the reopening of a channel that has just closed. The fast component in the kinetics of channel closure has many possible explanations and is therefore more difficult to interpret. We can gain insight into the closing process by asking whether the lifetimes of successive openings of an acetylcholine receptor channel are correlated in open-state lifetime. Five kinetic models of channel closure are considered. Two of these models predict uncorrelated open-state lifetimes, one predicts correlated open-state lifetimes, and for two others a range of behavior is possible. Acetylcholine receptor channel data from cultured rat muscle are analyzed to show that open-state lifetimes are correlated, eliminating two models of channel gating. PMID:6301575

  10. No effect of H2O degassing on the oxidation state of magmatic liquids

    NASA Astrophysics Data System (ADS)

    Waters, Laura E.; Lange, Rebecca A.

    2016-08-01

    The underlying cause for why subduction-zone magmas are systematically more oxidized than those formed at mid-ocean spreading ridges is a topic of vigorous debate. It is either a primary feature inherited from the subduction of oxidized oceanic crust into the mantle or a secondary feature that develops because of H2O degassing and/or magma differentiation. Low total iron contents and high melt H2O contents render rhyolites sensitive to any effect of H2O degassing on ferric-ferrous ratios. Here, pre-eruptive magmatic Fe2+ concentrations, measured using Fe-Ti oxides that co-crystallized with silicate phenocrysts under hydrous conditions, are compared with Fe2+ post-eruptive concentrations in ten crystal-poor, fully-degassed obsidian samples; five are microlite free. No effect of H2O degassing on the ferric-ferrous ratio is found. In addition, Fe-Ti oxide data from this study and the literature show that arc magmas are systematically more oxidized than both basalts and hydrous silicic melts from Iceland and Yellowstone prior to extensive degassing. Nor is there any evidence that differentiation (i.e., crystal fractionation, crustal assimilation) is the cause of the higher redox state of arc magmas relative to those of Iceland/Yellowstone rhyolites. Instead, the evidence points to subduction of oxidized crust and the release of an H2O-rich fluid and/or melt with a high oxygen fugacity (fO2), which plays a role during H2O-flux melting of the mantle in creating basalts that are relatively oxidized.

  11. The thermodynamic properties of H2O in magnesium and iron cordierite

    NASA Astrophysics Data System (ADS)

    Skippen, G. B.; Gunter, Avril E.

    1996-06-01

    The equilibrium water content of cordierite has been measured for 31 samples synthesized at pressures of 1000 and 2000 bars and temperatures from 600 to 750° C using the cold-seal hydrothermal technique. Ten data points are presented for pure magnesian cordierite, 11 data points for intermediate iron/magnesium ratios from 0.25 to 0.65 and 10 data points for pure iron cordierite. By representing the contribution of H2O to the heat capacity of cordierite as steam at the same temperature and pressure, it is possible to calculate a standard enthalpy and entropy of reaction at 298.18° K and 1 bar for, (Mg,Fe)2Al4Si5O18+H2O ⇄ (Fe,Mg)2Al4Si5O18.H2O Combining the 31 new data points with 89 previously published experimental measurements gives: Δ H ° r = 37141±3520 J and Δ S ° r = 99.2±4 J/degree. This enthalpy of reaction is within experimental uncertainty of calorimetric data. The enthalpy and entropy of hydration derived separately for magnesian cordierite ( 34400±3016 J, 96.5±3.4 J/degree) and iron cordierite ( 39613±2475, 99.5±2.5 J/degree) cannot be distinguished within the present experimental uncertainty. The water content as a function of temperature, T(K), and water fugacity, f(bars), is given by n H2O=1/[1+1/( K ṡ f H2O)] where the equilibrium constant for the hydration reaction as written above is, ln K=4466.4/ T 11.906 with the standard state for H2O as the gas at 1 bar and T, and for cordierite components, the hydrous and anhydrous endmembers at P and T.

  12. H2O2 Production and Destruction in the Outer Solar System: Laboratory Studies

    NASA Astrophysics Data System (ADS)

    Loeffler, M. J.; Raut, U.; Vidal, R. A.; Baragiola, R. A.; Carlson, R. W.

    2004-11-01

    There has been a recent interest in the possible production mechanisms of H2O2 in water ice, since the Galileo NIMS instrument reported an absorption band (3.5 μm) on the surface of Europa (Carlson 1999). Here we present results from laboratory studies that show H2O2 creation and destruction by ion bombardment. We have found that 100 keV H+ irradiation can produce H2O2 from a water ice film at temperatures as high as 120 K and have measured the production rates at 20 K and 80 K. Furthermore, we have studied the temperature dependence and stability of the 3.5 μm band. To understand the nature of the peroxide produced by ion irradiation, we have grown solid hydrogen peroxide by distillation in an ultra high vacuum chamber and have used infrared spectroscopy to study the band shape and position as a function of temperature in various mixtures of water. Furthermore, we have measured the crystallization and sublimation of H2O2 at temperatures between 155 and 190 K. We have also irradiated a film of crystalline H2O2 with 20 keV H+ at 80 K and have observed what is most likely amorphization of the peroxide. Furthermore, infrared spectroscopy indicated that during irradiation, water and ozone are produced, while HO2 is not detected. The presence of ozone suggests that H2O2 is a likely precursor molecule for oxygen formation at 80 K. Work supported by NSF Astronomy, NASA Planetary Atmospheres and Origin programs.

  13. Competitive Sorption of CO2 and H2O in 2:1 Layer Phyllosilicates

    SciTech Connect

    Schaef, Herbert T.; Loring, John S.; Glezakou, Vassiliki Alexandra; Miller, Quin R.; Chen, Jeffrey; Owen, Antionette T.; Lee, Mal Soon; Ilton, Eugene S.; Felmy, Andrew R.; McGrail, B. Peter; Thompson, Christopher J.

    2015-07-01

    The salting out effect, where increasing the ionic strength of aqueous solutions decreases the solubility of dissolved gases is a well-known phenomenon. Less explored is the opposite process where an initially anhydrous system containing a volatile, relatively non-polar component and inorganic ions is systematically hydrated. Expandable clays such as montmorillonite are ideal systems for exploring this scenario as they have readily accessible exchange sites containing cations that can be systematically dehydrated or hydrated, from near anhydrous to almost bulk-like water conditions. This phenomenon has new significance with the simultaneous implementation of geological sequestration and secondary utilization of CO2 to both mitigate climate warming and enhance extraction of methane from hydrated clay-rich formations. Here, the partitioning of CO2 and H2O between Na-, Ca-, and Mg-exchanged montmorillonite and variably hydrated supercritical CO2 (scCO2) was investigated using in situ X-ray diffraction, infrared (IR)spectroscopic titrations, and quartz crystal microbalance (QCM) measurements. Density functional theory calculations provided mechanistic insights. Structural volumetric changes were correlated to quantified changes in sorbed H2O and CO2 concentrations as a function of %H2O saturated in scCO2. Intercalation of CO2 is favored at low H2O/CO2 ratios in the interlayer region, where CO2 can solvate the interlayer cation. As the clay becomes more hydrated and the H2O/CO2 ratio increases, H2O displaces CO2 from the solvation shell of the cation and CO2 tends to segregate. This transition decreases both the entropic and enthalpic driving force for CO2 intercalation, consistent with experimentally observed loss of intercalated CO2.

  14. Ortho-para mixing hyperfine interaction in the H2O+ ion and nuclear spin equilibration.

    PubMed

    Tanaka, Keiichi; Harada, Kensuke; Oka, Takeshi

    2013-10-01

    The ortho to para conversion of water ion, H2O(+), due to the interaction between the magnetic moments of the unpaired electron and protons has been theoretically studied to calculate the spontaneous emission lifetime between the ortho- and para-levels. The electron spin-nuclear spin interaction term, Tab(SaΔIb + SbΔIa) mixes ortho (I = 1) and para (I = 0) levels to cause the "forbidden" ortho to para |ΔI| = 1 transition. The mixing term with Tab = 72.0 MHz is 4 orders of magnitude higher for H2O(+) than for its neutral counterpart H2O where the magnetic field interacting with proton spins is by molecular rotation rather than the free electron. The resultant 10(8) increase of ortho to para conversion rate possibly makes the effect of conversion in H2O(+) measurable in laboratories and possibly explains the anomalous ortho to para ratio recently reported by Herschel heterodyne instrument for the far-infrared (HIFI) observation. Results of our calculations show that the ortho ↔ para mixings involving near-degenerate ortho and para levels are high (∼10(-3)), but they tend to occur at high energy levels, ∼300 K. Because of the rapid spontaneous emission, such high levels are not populated in diffuse clouds unless the radiative temperature of the environment is very high. The low-lying 101 (para) and 111 (ortho) levels of H2O(+) are mixed by ∼10(-4) making the spontaneous emission lifetime for the para 101 → ortho 000 transition 520 years and 5200 years depending on the F value of the hyperfine structure. Thus the ortho ↔ para conversion due to the unpaired electron is not likely to seriously affect thermalization of interstellar H2O(+) unless either the radiative temperature is very high or number density of the cloud is very low. PMID:23530629

  15. Partial phase diagram for the system NH3-H2O - The water-rich region

    NASA Technical Reports Server (NTRS)

    Johnson, M. L.; Schwake, A.; Nicol, M.

    1984-01-01

    Phase boundaries of the H2O-NH3 system for (NH3)/x/(H2O)/1-x/ have been determined with diamond-anvil cells for mixtures in two composition ranges: (1) for x in the range from 0 to 0.3, at pressures up to 4 GPa at 21 C, and (2) for x in the range from 0.46 to 0.50, at pressures up to 5 GPa from 150 to 400 K. Phases were identified visually with a microscope and polarized optics. The NH3.2(H2O) phase is strongly anisotropic with a much smaller refractive index than that of ice VII and cracks in two nonperpendicular networks. NH3.H2O has a refractive index closer to that of Ice VII and does not appear to form cracks. Both phases are colorless. Phase boundaries were determined on both increasing and decreasing pressures, and compositions of the ammonia ices were determined by estimating relative amounts of water and ammonia ices at known overall compositions. For low-ammonia compositions (x equal to or less than 0.15), the following assemblages succedd one another as pressure increases: liquid; liquid and Ice VI (at 1.0 + GPa); liquid and Ice VII (at 2.1 GPa); Ice VII and NH3.H2O (at 3.5 GPa). For x in the range from 0.15 to 0.30, the water ice and liquid fields are replaced by the NH3.2(H2O) and liquid field at pressures down to 1.0 GPa and lower.

  16. Studies on the formation of H 2O 2 in the ozonolysis of alkenes

    NASA Astrophysics Data System (ADS)

    Becker, K. H.; Bechara, J.; Brockmann, K. J.

    The formation of H 2O 2 in the reactions of ozone with alkenes, isoprene and some terpenes has been studied with tunable diode laser absorption spectroscopy. The measured yields of H 2O 2 were found to be considerably enhanced in the presence of water vapour. H 2O 2 is thought to be formed in the ozonolysis of the alkene with O 3 by direct reaction of an intermediate with water vapour. The yield of H 2O 2 relative to the reacted alkene in the ozonolysis of trans-2-butene in the presence of water vapour was also studied with long path FTIR spectroscopy. Irrespective of the analytical methods and reaction conditions applied, the H 2O 2 yields in the reaction of O 3 with the different alkenes in the presence of water vapour were found to be in the range of a few per cent or less. Under the assumption that the reactive species forming H 2O 2 in the ozonolysis is the Criegee biradical, the overall rate constants for the reactions of some biradicals with water vapour were measured relative to the rate constant of the biradical with SO 2. For the H 2COO biradical a rate constant of (5.8 ± 2.5) × 10 -17 cm 3 s -1 was determined and for the (CH 3) 2COO biradical (2.9 ± 1.5) × 10 -17 cm 3 s -1; in the latter case with the assumption that (CH 3) 2COO reacts with SO 2 as fast as CH 2COO.

  17. Use of Enzymatic Biosensors to Quantify Endogenous ATP or H2O2 in the Kidney.

    PubMed

    Palygin, Oleg; Levchenko, Vladislav; Evans, Louise C; Blass, Gregory; Cowley, Allen W; Staruschenko, Alexander

    2015-01-01

    Enzymatic microelectrode biosensors have been widely used to measure extracellular signaling in real-time. Most of their use has been limited to brain slices and neuronal cell cultures. Recently, this technology has been applied to the whole organs. Advances in sensor design have made possible the measuring of cell signaling in blood-perfused in vivo kidneys. The present protocols list the steps needed to measure ATP and H2O2 signaling in the rat kidney interstitium. Two separate sensor designs are used for the ex vivo and in vivo protocols. Both types of sensor are coated with a thin enzymatic biolayer on top of a permselectivity layer to give fast responding, sensitive and selective biosensors. The permselectivity layer protects the signal from the interferents in biological tissue, and the enzymatic layer utilizes the sequential catalytic reaction of glycerol kinase and glycerol-3-phosphate oxidase in the presence of ATP to produce H2O2. The set of sensors used for the ex vivo studies further detected analyte by oxidation of H2O2 on a platinum/iridium (Pt-Ir) wire electrode. The sensors for the in vivo studies are instead based on the reduction of H2O2 on a mediator coated gold electrode designed for blood-perfused tissue. Final concentration changes are detected by real-time amperometry followed by calibration to known concentrations of analyte. Additionally, the specificity of the amperometric signal can be confirmed by the addition of enzymes such as catalase and apyrase that break down H2O2 and ATP correspondingly. These sensors also rely heavily on accurate calibrations before and after each experiment. The following two protocols establish the study of real-time detection of ATP and H2O2 in kidney tissues, and can be further modified to extend the described method for use in other biological preparations or whole organs. PMID:26485400

  18. H2O2 Improves Quality of Radix scutellariae Through Anti-oxidant Effect

    PubMed Central

    Qi, Song; Wu-lin, Cao; Hua, Jiang; Ai-hua, Zhang; Xiang-cai, Meng

    2016-01-01

    Introduction: The correlation between the quality and geographical origin of herbal medicine was traced back to Tang Dynasty in China, more than 1200 years, and the effects of ecological environments on the secondary metabolites such as flavonoids have been confirmed. However, little is known about how the adversity impacts on the quality. Reactive oxygen species (ROS) may be medium between the ecological environment and the secondary metabolism. Materials and Methods: The fresh roots of Scutellaria baicalensis Georgi were treated with 0.002 μmol/L, 0.2 μmol/L, and 20 μmol/L H2O2, respectively. A stress model was established to elucidate the change of secondary metabolism, anti-oxidant enzyme system, and enzymes relating to flavonoids. Results: The activities of superoxide dismutase, catalase and peroxidase decreased. Too much H2O2, firstly, boosted transformation of flavonoids glycoside into aglucon with the most remarkable activities through UDP-glucuronate baicalein 7-O-glucuronosyltransferase (UBGAT), and β-glucuronidase (GUS), then regulated the gene expression of phenylalanine ammonialyase, GUS, and UBGAT, and increased the contents of flavones, motivated the flavonoid glycoside converting into aglucon. With this action, the flavones displaced the anti-oxidant enzymes. The higher the dosage, the more baicalein and wogonin increased, the later they took action. Conclusion: The plant secondary metabolites to keep ROS constant are identical to the effective materials in clinic. They are closely linked. H2O2 can improve flavones, especially the aglucon, and further increased the quality of herbal medicine, which possesses very important value in medical practice. SUMMARY H2O2 decreasing the activities of CAT and POD lead to accumulation of more H2O2. Excess of H2O2 up-regulated PAL, BUG, promote biosynthesis of flavones, and enhance the nonenzyme system. “↑” and “↓” represent activity or content “up” and “down” respectively. PMID:27019566

  19. 16. VIEW NORTH FROM SWINGSPAN DECK, CHANNEL OPEN, FENDER SYSTEM ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    16. VIEW NORTH FROM SWING-SPAN DECK, CHANNEL OPEN, FENDER SYSTEM AND ABUTMENT ON CHANNEL END OF NORTHERN FIXED SPAN; new bridge located on right - Tipers Bridge, Spanning Great Wicomico River at State Route 200, Kilmarnock, Lancaster County, VA

  20. Horizontal Distribution of CO, OCS and H2O Below the Clouds of Venus From Venus Express/VIRTIS Observations

    NASA Astrophysics Data System (ADS)

    Bezard, Bruno; Marcq, E.; Tsang, C. C.; Taylor, F. W.; Drossart, P.; Piccioni, G.; Encrenaz, T.; Vex/VIRTIS Team

    2006-09-01

    Nightside spectroscopy in the 2.3-μm window allows us to probe the composition of the lower atmosphere of Venus in the altitude range 28-42 km. Besides CO2, signatures from CO, OCS, H2O, HDO, HF and SO2 can be detected (e.g. Bézard et al. 1990, Nature 345, 508-511; Taylor et al. 1997, in Venus II, pp. 325-351, Univ. Arizona Press, Tucson). We report here on the first observations of this window on Venus' night side obtained with the VIRTIS instrument aboard Venus Express. It was observed at a resolving power (R) of about 2000 with the H-channel, a high-resolution spectrometer covering the range 1.9-5 μm, and at R 250 with the infrared M-channel, an imaging spectrometer for the range 1-5 μm. We present maps of CO in the southern hemisphere obtained with the M-channel and latitudinal variations of CO, OCS and H2O derived from a set of VIRTIS-H scans. CO clearly increases from equator to 60°S with a slight decrease polewards. Longitudinal structure is also present. The inferred gradient is consistent with the ground-based observations of Marcq et al. (2005, Icarus 179, 375-386; 2006, Planet. Space Sci., in press) below 40° latitude and mirrors the enhancement seen at high northern latitudes in the Galileo data (Collard et al. 1993, Planet. Space Sci. 41, 487-494). CO appears as a tracer of the atmospheric dynamics, giving evidence for upwelling in the equatorial region and subsidence at high latitudes.

  1. Water treatment by H2O2 and/or UV affects carbon nanotube (CNT) properties and fate in water and tannic acid solution.

    PubMed

    Czech, Bożena; Oleszczuk, Patryk; Wiącek, Agnieszka Ewa; Barczak, Mariusz

    2015-12-01

    The objective of the study was to estimate how water treatment (stimulation of real conditions) by H2O2 and/or UV affects carbon nanotube (CNT) properties and fate (stability/aggregation) in water and tannic acid solution. The processes studied had only a slight effect on SBET, porosity, and surface composition of CNTs. There was a change in the morphology of CNTs. After H2O2 and/or UV treatment, CNTs underwent shortening, opening up of their ends, and exfoliation. Treatment with H2O2 increased the content of oxygen in CNTs. A decrease was observed in the surface charge and in the mobility of CNTs, which caused an increase in their stability. UV irradiation of CNTs led to an increased incidence of defects that were manifested by both an increase of zeta potential and an increased mobility of CNT, whereas the presence of H2O2 during UV irradiation had only a slight effect on the parameters of the porous structure of nanotubes. PMID:26304806

  2. MgCO3·3H2O and MgO complex nanostructures: controllable biomimetic fabrication and physical chemical properties.

    PubMed

    Wu, Xiaoming; Cao, Huaqiang; Yin, Gui; Yin, Jiefu; Lu, Yuexiang; Li, Baojun

    2011-03-21

    In this paper, we report a method of biomimetic synthesis of MgCO(3)·3H(2)O and MgO Viburnum opulus-like complex nanostructures with superhydrophobicity and adsorption properties. The MgCO(3)·3H(2)O complex nanostructures can be obtained by changing experimental parameters, including concentrations of reactants (dextran and MgCl(2)), molar ratios of reactants, and reaction time. The phase structure of as-synthesized samples was characterized by X-ray diffraction (XRD). The morphology and structure are studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) spectroscopy. The MgCO(3)·3H(2)O complex nanostructures exhibited superhydrophobicity, due to their unique superstructures, and was proved by the contact angle (CA) measurement. We also show that a simple calcination of these unusually shaped MgCO(3)·3H(2)O results in spontaneous formation of MgO complex nanostructures while the unique shape can be maintained, and the as-synthesized MgO nanostructures show excellent adsorption property. These unique structures and properties will open up a wide range of potential applications in material and environmental protection. PMID:21170433

  3. Effect of plant extracts on H2O2-induced inflammatory gene expression in macrophages

    PubMed Central

    Pomari, Elena; Stefanon, Bruno; Colitti, Monica

    2014-01-01

    Background Arctium lappa (AL), Camellia sinensis (CS), Echinacea angustifolia, Eleutherococcus senticosus, Panax ginseng (PG), and Vaccinium myrtillus (VM) are plants traditionally used in many herbal formulations for the treatment of various conditions. Although they are well known and already studied for their anti-inflammatory properties, their effects on H2O2-stimulated macrophages are a novel area of study. Materials and methods Cell viability was tested after treatment with increasing doses of H2O2 and/or plant extracts at different times of incubation to identify the optimal experimental conditions. The messenger (m)RNA expression of TNFα, COX2, IL1β, NFκB1, NFκB2, NOS2, NFE2L2, and PPARγ was analyzed in macrophages under H2O2 stimulation. The same genes were also quantified after plant extract treatment on cells pre-stimulated with H2O2. Results A noncytotoxic dose (200 μM) of H2O2 induced active mRNA expression of COX2, IL1β, NFE2L2, NFκB1, NFκB2, NOS2, and TNFα, while PPARγ was depressed. The expression of all genes tested was significantly (P<0.001) regulated by plant extracts after pre-stimulation with H2O2. COX2 was downregulated by AL, PG, and VM. All extracts depressed IL1β expression, but upregulated NFE2L2. NFκB1, NFκB2, and TNFα were downregulated by AL, CS, PG, and VM. NOS2 was inhibited by CS, PG, and VM. PPARγ was decreased only after treatment with E. angustifolia and E. senticosus. Conclusion The results of the present study indicate that the stimulation of H2O2 on RAW267.4 cells induced the transcription of proinflammatory mediators, showing that this could be an applicable system by which to activate macrophages. Plant extracts from AL, CS, PG, and VM possess in vitro anti-inflammatory activity on H2O2-stimulated macrophages by modulating key inflammation mediators. Further in vitro and in vivo investigation into molecular mechanisms modulated by herbal extracts should be undertaken to shed light on the development of novel

  4. Visual Observations of the Amorphous-Amorphous Transition in H2O Under Pressure.

    PubMed

    Mishima, O; Takemura, K; Aoki, K

    1991-10-18

    The vapor-deposited low-density amorphous phase of H(2)O was directly compressed at 77 kelvin with a diamond-anvil cell, and the boundary between the low-density amorphous phase and the high-density amorphous phase was observed while the sample was warmed under compression. The transition from the low-density amorphous phase to the high-density amorphous phase was distinct and reversible in an apparently narrow pressure range at approximately 130 to approximately 150 kelvin, which provided experimental evidence for polymorphism in amorphous H(2)O. PMID:17742228

  5. H2O/Ni(100) and NH3/Ni(100) - A computational approach

    NASA Technical Reports Server (NTRS)

    Bauschlicher, C. W., Jr.

    1985-01-01

    The adsorption of NH3 and H2O on the Ni(100) is treated using a cluster model. The adsorption is found to have only a small effect on the HXH angle. Rotation about the principal ligand axis requires virtually no energy. Ligand tilts of 15 deg are found to require small amounts of energy, leading to the suggestion that the ESDIAD signal is a result of excited tilting modes, not a change in the HXH angle. For H2O additional bending modes are considered and all are found to be quite flat in energy.

  6. The influence of H2O line blanketing on the spectra of cool dwarf stars

    NASA Technical Reports Server (NTRS)

    Allard, F.; Hauschildt, P. H.; Miller, S.; Tennyson, J.

    1994-01-01

    We present our initial results of model atmosphere calculations for cool M dwarfs using an opacity sampling method and a new list of H2O lines. We obtain significantly improved fits to the infrared spectrum of the M dwarf VB10 when compared to earlier models. H2O is by far the dominant opacity source in cool stars. To illustrate this, we show the Rosseland mean of the total extinction under various assumptions. Our calculations demonstrate the importance of a good treatment of the water opacities in cool stars and the improvements possible by using up-to-date data for the water line absorption.

  7. Cardiovascular effects of resveratrol and atorvastatin treatments in an H2O2-induced stress model.

    PubMed

    Soner, Burak Cem; Sahin, Ayşe Saide

    2014-11-01

    Oxidative stress has been implicated in the pathophysiology of several types of cardiovascular disease (CVD). Statins are widely used to inhibit the progression of atherosclerosis and reduce the incidence of CVD. Certain over-the-counter products, including resveratrol, show similar effects to statins and may thus be used in conjunction with statins for the treatment of the majority of patients with CVD. The aim of the present study was to evaluate the effects of atorvastatin, resveratrol and resveratrol + atorvastatin (R+A) pretreatment on myocardial contractions and vascular endothelial functions in the presence of H2O2 as an experimental model of oxidative stress in rats. Four groups were established and referred to as the control, atorvastatin, resveratrol and R+A groups. Atorvastatin (40 mg/kg, per oral) and/or resveratrol (30 mg/kg, intraperitoneal) treatments were administered for 14 days. On the 15th day, the thoracic aortas and hearts of the rats were dissected and placed into isolated organ baths. Vascular responses to cumulative doses of H2O2 (1×10(-8)-1×10(-4) M H2O2) with and without N (G)-nitro-L-arginine methyl ester (L-NAME) incubation were measured. In addition, myocardial electrical stimulation (ES) responses to various H2O2 concentrations (1×10(-7)-1×10(-5) M H2O2) were evaluated. In the control and atorvastatin groups, H2O2 application caused a significant dose-dependent decrease in the ES-induced contractions in the myocardial tissue of rats. In the resveratrol and R+A groups, H2O2 application did not significantly affect myocardial contraction at any dose. In all groups, incubation with L-NAME caused a significant augmentation in the H2O2 response, revealing that this effect was mediated via the vascular endothelium. In conclusion, pretreatment with R+A for CVD appears to be superior to pretreatment with either agent alone. PMID:25289077

  8. Application of multiwalled carbon nanotubes-graphene hybrid nanocomposite for nonenzymatic H2O2 biosensor

    NASA Astrophysics Data System (ADS)

    Nayak, Pranati; Santhosh, P. N.; Ramaprabhu, S.

    2013-02-01

    In the present work, we report the fabrication of nonenzymatic hydrogen peroxide (H2O2) biosensor using multiwalled carbon nanotubes-solar exfoliated graphene hybrid nanocomposite (MWCNTs-sG) as a transducer candidate. The hybrid material has been synthesized by solar reduction technique from a mixture of MWCNTs and graphite oxide (GO). The fabricated MWCNTs-sG based biosensor shows a high catalytic response towards H2O2 reduction at a low potential of -0.4 V and good linearity over a wide range of concentration from 2 mM to 344 mM.

  9. Magic numbers in Al n+(H 2O) 1 cluster cations

    NASA Astrophysics Data System (ADS)

    Lippa, T. P.; Lyapustina, S. A.; Xu, S.-J.; Thomas, O. C.; Bowen, K. H.

    1999-05-01

    We report the observation of magic numbers in the mass spectrum of Al n+(H 2O) 1. These cluster cations were produced in a laser vaporization source in the presence of trace amounts of water. The most prominent magic number species observed was Al 13+(H 2O) 1. We attribute its pronounced intensity to its enhanced stability resulting from the formation of a coordinate bond between the Al 13+ moiety and the oxygen atom of water. The sharing of an oxygen lone electron pair with Al 13+ lends to it some of the character of the 40-valence electron, closed shell Al 13- magic cluster.

  10. Critical behavior of dilute NaCl in H2O

    USGS Publications Warehouse

    Pitzer, Kenneth S.; Bischoff, J.L.; Rosenbauer, R.J.

    1987-01-01

    The compositions of the saturated vapor and liquid phases are measured for the system NaCl-H2O at 380??C, which is close to the critical point of pure water. The shape of the phase equilibrium curve is classical, which confirms a conclusion reached earlier on the basis of less accurate data. This implies that the long-range forces introduced by the NaCl suppress the non-classical effects present in pure H2O. An empirical equation of a classical type fits these data. ?? 1987.

  11. Comet Halley O(1D) and H2O production rates

    NASA Technical Reports Server (NTRS)

    Magee-Sauer, K.; Scherb, F.; Roesler, F. L.; Harlander, J.

    1990-01-01

    Ground-based dual-etalon Fabry-Perot spectrometer observations have been made of Comet Halley's forbidden O I 6300 A emission. The 0.2 A resolution of the spectral scans was sufficient to resolve the O I forbidden line emissions from both nearby cometary NH2 and telluric emissions. On the basis of these measurements, the production rate Q of O(1D) was determined; it is then found, by taking into account the photodissociation of H2O and OH as sources of O(1D), that the ratio of H2O/O(1D) production rates is of the order of 6.

  12. Seasonal Mapping of HDO and H2O in the Martian Atmosphere

    NASA Technical Reports Server (NTRS)

    Mumma, M. J.; Novak, R. E.; DiSanti, M. A.; Bonev, B.; DelloRusso, N.; Magee-Sauer, K.

    2003-01-01

    We report investigations of HDO and H2O on Mars using CSHELL at the NASA IRTF, on dates that span an entire Mars year. Our objective is to understand whether deuterium is preferentially sequestered in the polar regions, and to determine whether the two polar caps are equivalent in that regard. The instrument slit is typically positioned N-S along the central meridian resulting in a one-dimensional map of HDO (1997- 2003) and/or H2O (2001-2003). Column burdens are extracted at one arc-second intervals along the slit, permitting a direct comparison of the D/H ratio at various latitudes and seasons.

  13. Role of weakly bound complexes in temperature-dependence and relative rates of MxOy- + H2O (M = Mo, W) reactions

    NASA Astrophysics Data System (ADS)

    Kafader, Jared O.; Ray, Manisha; Raghavachari, Krishnan; Jarrold, Caroline Chick

    2016-02-01

    Results of a systematic comparison of the MoxOy- + H2O and WxOy- + H2O reaction rate coefficients are reported and compared to previous experimental and computational studies on these reactions. WxOy- clusters undergo more direct oxidation by water to yield WxOy+1- + H2, while for MoxOy- clusters, production of MoxOyH2- (trapped intermediates in the oxidation reaction) is comparatively more prevalent. However, MoxOy- clusters generally have higher rate coefficients than analogous WxOy- clusters if MoxOy+1H2- formation is included. Results of calculations on the M2Oy- + H2O (M = Mo, W; y = 4, 5) reaction entrance channel are reported. They include charge-dipole complexes formed from long-range interactions, and the requisite conversion to a Lewis acid-base complex that leads to MxOy+1H2- formation. The results predict that the Lewis acid-base complex is more strongly bound for MoxOy- clusters than for WxOy- clusters. The calculated free energies along this portion of the reaction path are also consistent with the modest anti-Arrhenius temperature dependence measured for most MoxOy- + H2O reactions, and the WxOy- + H2O reaction rate coefficients generally being constant over the temperature range sampled in this study. For clusters that exhibit evidence of both water addition and oxidation reactions, increasing the temperature increases the branching ratio toward oxidation for both species. A more direct reaction path to H2 production may therefore become accessible at modest temperatures for certain cluster stoichiometries and structures.

  14. Reaction Pathways and Excited States in H2O2+OH → HO2+H2O : A New ab initio Investigation

    SciTech Connect

    Ginovska, Bojana; Camaioni, Donald M.; Dupuis, Michel

    2007-08-28

    The mechanism of the hydrogen abstraction reaction H2O2+OH→ HO2+H2O in gas phase was studied, using DFT (MPW1K) level of theory. We located 2 pathways for the reaction, both going through the same intermediate complex OH-H2O2, but via two distinct transition state structures that differ by the orientation of the hydroxyl hydrogen relative to the incipient hydroperoxy hydrogen. In one case, these hydrogens are on same side of the plane made by the 3 oxygen atoms and in the other these hydrogens are on opposite sides of the plane. The first two excited states were calculated for selected points of both pathways using time-dependent DFT, multiconfigurational quasi-degenerate-perturbation theory (MCQDPT2/ CASSCF) and equation of motion coupled cluster singles, doubles model (EOM-CCSD) EOMCCSD energies and completely renormalized EOM-CCSD(T)(IA) correction. An avoided crossing between the two excited states was found on both reaction pathways, on the product side of the barrier to H-transfer on the ground state surface, near the transition states. Further more, we report on the calculation of the rate of the reaction in the gas phase for temperatures in the range of 250-500 K, and suggest that the strong temperature dependence of the rate at high temperatures is due to reaction on the low-lying excited state surface over a barrier that is much larger than on the ground state surface. This work was supported in part by the Office of Basic Energy Sciences of the Department of Energy (DOE), Chemical Sciences program (BG and MD) and in part by the U.S. Department of Energy’s Office of Biological and Environmental Research, Environmental Management Science Program (BG and DMC). The Pacific Northwest National Laboratory is operated for DOE by Battelle Memorial Institute.

  15. Photodesorption of H2O, HDO, and D2O ice and its impact on fractionation

    NASA Astrophysics Data System (ADS)

    Arasa, Carina; Koning, Jesper; Kroes, Geert-Jan; Walsh, Catherine; van Dishoeck, Ewine F.

    2015-03-01

    The HDO/H2O ratio measured in interstellar gas is often used to draw conclusions on the formation and evolution of water in star-forming regions and, by comparison with cometary data, on the origin of water on Earth. In cold cores and in the outer regions of protoplanetary disks, an important source of gas-phase water comes from photodesorption of water ice. This research note presents fitting formulae for implementation in astrochemical models using previously computed photodesorption efficiencies for all water ice isotopologues obtained with classical molecular dynamics simulations. The results are used to investigate to what extent the gas-phase HDO/H2O ratio reflects that present in the ice or whether fractionation can occur during the photodesorption process. Probabilities for the top four monolayers are presented for photodesorption of X (X = H, D) atoms, OX radicals, and X2O and HDO molecules following photodissociation of H2O, D2O, and HDO in H2O amorphous ice at ice temperatures from 10-100 K. Significant isotope effects are found for all possible products: (1) H atom photodesorption probabilities from H2O ice are larger than those for D atom photodesorption from D2O ice by a factor of 1.1; the ratio of H and D photodesorbed upon HDO photodissociation is a factor of 2. This process will enrich the ice in deuterium atoms over time; (2) the OD/OH photodesorption ratio upon D2O and H2O photodissociation is on average a factor of 2, but the OD/OH photodesorption ratio upon HDO photodissociation is almost constant at unity for all ice temperatures; (3) D atoms are more effective in kicking out neighbouring water molecules than H atoms. However, the ratio of the photodesorbed HDO and H2O molecules is equal to the HDO/H2O ratio in the ice, therefore, there is no isotope fractionation when HDO and H2O photodesorb from the ice. Nevertheless, the enrichment of the ice in D atoms due to photodesorption can over time lead to an enhanced HDO/H2O ratio in the ice, and

  16. Descent without Modification? The Thermal Chemistry of H2O2 on Europa and Other Icy Worlds.

    PubMed

    Loeffler, Mark J; Hudson, Reggie L

    2015-06-01

    The strong oxidant H2O2 is known to exist in solid form on Europa and is suspected to exist on several other Solar System worlds at temperatures below 200 K. However, little is known of the thermal chemistry that H2O2 might induce under these conditions. Here, we report new laboratory results on the reactivity of solid H2O2 with eight different compounds in H2O-rich ices. Using infrared spectroscopy, we monitored compositional changes in ice mixtures during warming. The compounds CH4 (methane), C3H4 (propyne), CH3OH (methanol), and CH3CN (acetonitrile) were unaltered by the presence of H2O2 in ices, showing that exposure to either solid H2O2 or frozen H2O+H2O2 at cryogenic temperatures will not oxidize these organics, much less convert them to CO2. This contrasts strongly with the much greater reactivity of organics with H2O2 at higher temperatures, and particularly in the liquid and gas phases. Of the four inorganic compounds studied, CO, H2S, NH3, and SO2, only the last two reacted in ices containing H2O2, NH3 making NH4+ and SO2 making SO(4)2- by H+ and e- transfer, respectively. An important astrobiological conclusion is that formation of surface H2O2 on Europa and that molecule's downward movement with H2O-ice do not necessarily mean that all organics encountered in icy subsurface regions will be destroyed by H2O2 oxidation. PMID:26060983

  17. Descent Without Modification? The Thermal Chemistry of H2O2 on Europa and Other Icy Worlds

    NASA Technical Reports Server (NTRS)

    Loeffler, Mark Josiah; Hudson, Reggie Lester

    2015-01-01

    The strong oxidant H2O2 is known to exist in solid form on Europa and is suspected to exist on several other Solar System worlds at temperatures below 200 K. However, little is known of the thermal chemistry that H2O2 might induce under these conditions. Here, we report new laboratory results on the reactivity of solid H2O2 with eight different compounds in H2O-rich ices. Using infrared spectroscopy, we monitored compositional changes in ice mixtures during warming. The compounds CH4 (methane), C3H4 (propyne), CH3OH (methanol), and CH3CN (acetonitrile) were unaltered by the presence of H2O2 in ices, showing that exposure to either solid H2O2 or frozen H2O+H2O2 at cryogenic temperatures will not oxidize these organics, much less convert them to CO2. This contrasts strongly with the much greater reactivity of organics with H2O2 at higher temperatures, and particularly in the liquid and gas phases. Of the four inorganic compounds studied, CO, H2S, NH3, and SO2, only the last two reacted in ices containing H2O2, NH3 making NHþ 4 and SO2 making SO2 4 by H+ and e - transfer, respectively. An important astrobiological conclusion is that formation of surface H2O2 on Europa and that molecule's downward movement with H2O-ice do not necessarily mean that all organics encountered in icy subsurface regions will be destroyed by H2O2 oxidation.

  18. NO Removal in High Pressure Plasmas of N_2/H_2O/NO Mixtures

    NASA Astrophysics Data System (ADS)

    Fresnet, F.; Baravian, G.; Magne, L.; Pasquiers, S.; Postel, C.; Puech, V.; Rousseau, A.

    2001-10-01

    Influence of H_2O on NO removal has been studied using a homogeneous photo-triggered discharge with a time resolved LIF measurement of the NO density, in N_2/H_2O/NO mixtures at 460 mbar. The H_2O maximum concentration was 2.5 was between 70 and 160 J/l. Measurement of NO density has been performed up to 180 µs after the current pulse excitation of short duration, 50 ns. Kinetic analysis has been made using a self-consistent 0D-discharge model. NO is in great part dissociated, in N_2/NO, through collisions with the excited singlet states of N_2. We have previously shown that addition of ethene induces de-excitation of these states, leading to a decrease of the NO removal ( F. Fresnet, G. Baravian, L. Magne, S. Pasquiers, C. Postel, V. Puech, A. Rousseau, Appl. Phys. Lett., 77 (2000) 4118.). Similar processes take place when C_2H4 is replaced by H_2O. The value of the rate constant for collision of singlet states with water, 3.10-10 cm^3 s-1, is obtained from our study.

  19. Effective Reuse of Electroplating Rinse Wastewater by Combining PAC with H2O2/UV Process.

    PubMed

    Yen, Hsing Yuan; Kang, Shyh-Fang; Lin, Chen Pei

    2015-04-01

    This study evaluated the performance of treating electroplating rinse wastewater by powder activated carbon (PAC) adsorption, H2O2/UV oxidation, and their combination to remove organic compounds and heavy metals. The results showed that neither the process of PAC adsorption nor H2O2/UV oxidation could reduce COD to 100 mg/L, as enforced by the Taiwan Environmental Protection Agency. On the other hand, the water sample treated by the combined approach of using PAC (5 g/L) pre-adsorption and H2O2/UV post-oxidation (UV of 64 W, H2O2 of 100 mg/L, oxidation time of 90 min), COD and DOC were reduced to 8.2 mg/L and 3.8 mg/L, respectively. Also, the combined approach reduced heavy metals to meet the effluent standards and to satisfy the in-house water reuse criteria for the electroplating factory. The reaction constant analysis indicated that the reaction proceeded much more rapidly for the combined process. Hence, it is a more efficient, economic and environmentally friendly process. PMID:26462075

  20. H 2O 2 and radiation induced dissolution of UO 2 and SIMFUEL pellets

    NASA Astrophysics Data System (ADS)

    Nilsson, Sara; Jonsson, Mats

    2011-03-01

    Dissolution of the UO 2 matrix is of major importance in the safety assessment of a future deep repository for spent nuclear fuel. The aim of this work is to elucidate if the observed differences in dissolution rates between SIMFUEL and UO 2 can be attributed to differences in oxidant reactivity towards these two materials. To elucidate this, the oxidative dissolution of U(VI) and consumption of H 2O 2 have been studied for UO 2 and SIMFUEL pellets under N 2 and H 2 atmosphere. The H 2O 2 and U(VI) concentrations have been measured as a function of reaction time. In addition, γ-radiation induced dissolution UO 2 and SIMFUEL pellets have been studied. The experiments show that while the reactivity of the two types of pellets towards H 2O 2 is almost identical and in good agreement with the previously determined rate constant for the reaction, the dissolution rates differ considerably. The significantly lower rate of dissolution of the SIMFUEL pellet is attributed to an increased fraction of catalytic decomposition of H 2O 2. The radiation chemical experiments reveal a similar but less pronounced difference between the two types of pellets. This implies that the relative impact of the radiolytic oxidants in radiation induced UO 2 dissolution differs between a pure UO 2 pellet and SIMFUEL.

  1. Water in planetary and cometary atmospheres: H2O/HDO transmittance and fluorescence models

    NASA Astrophysics Data System (ADS)

    Villanueva, G. L.; Mumma, M. J.; Bonev, B. P.; Novak, R. E.; Barber, R. J.; Disanti, M. A.

    2012-02-01

    We developed a modern methodology to retrieve water (H2O) and deuterated water (HDO) in planetary and cometary atmospheres, and constructed an accurate spectral database that combines theoretical and empirical results. On the basis of a greatly expanded set of spectroscopic parameters, we built a full non-resonance cascade fluorescence model and computed fluorescence efficiencies for H2O (500 million lines) and HDO (700 million lines). The new line list was also integrated into an advanced terrestrial radiative transfer code (LBLRTM) and adapted to the CO2 rich atmosphere of Mars, for which we adopted the complex Robert-Bonamy formalism for line shapes. We retrieved water and D/H in the atmospheres of Mars, comet C/2007 W1 (Boattini), and Earth by applying the new formalism to spectra obtained with the high-resolution spectrograph NIRSPEC/Keck II atop Mauna Kea (Hawaii). The new model accurately describes the complex morphology of the water bands and greatly increases the accuracy of the retrieved abundances (and the D/H ratio in water) with respect to previously available models. The new model provides improved agreement of predicted and measured intensities for many H2O lines already identified in comets, and it identifies several unassigned cometary emission lines as new emission lines of H2O. The improved spectral accuracy permits retrieval of more accurate rotational temperatures and production rates for cometary water.

  2. TES/Aura L2 Water Vapor (H2O) Nadir (TL2H2ON)

    Atmospheric Science Data Center

    2015-01-30

    TES/Aura L2 Water Vapor (H2O) Nadir (TL2H2ON) News:  TES News ... Title:  TES Discipline:  Tropospheric Chemistry Level:  L2 Instrument:  TES/Aura L2 Water Vapor Spatial Coverage:  5.3 x 8.5 km nadir ...

  3. TES/Aura L2 Water Vapor (H2O) Nadir (TL2H2ONS)

    Atmospheric Science Data Center

    2015-01-30

    TES/Aura L2 Water Vapor (H2O) Nadir (TL2H2ONS) News:  TES News ... Title:  TES Discipline:  Tropospheric Chemistry Level:  L2 Platform:  TES/Aura L2 Water Vapor Spatial Coverage:  5.3 8.5 km nadir ...

  4. Pressure-dependent mobility of negative ions in mixtures of H2O with Ar

    NASA Astrophysics Data System (ADS)

    de Urquijo, J.; Ruiz-Vargas, G.

    2016-04-01

    The mobility of negative ions in H2O-Ar mixtures has been measured with a pulsed Townsend technique. It has been found that for a fixed value of the density-normalized electric field strength, E/N, the mobility of the H2O anions is strongly pressure dependent. We have also found that even for a single, total gas mixture pressure, even though at first sight the mobility of the anions seems to follow Blanc’s relation closely, a closer view indicates that the mobilities tend to shift to higher values as the water vapour concentration decreases. In spite of the lack of mass spectrometry to assess the mass and abundance of the drifting anions under specific conditions of E/N, water vapour concentration and gas pressure, the present measurements are strongly indicative of a complex ion transport and ion-molecule reaction scheme of daughter H2O anions in the H2O-Ar mixture.

  5. Conductivity measurements on H2O-bearing CO2-rich fluids

    DOE PAGESBeta

    Capobianco, Ryan M.; Miroslaw S. Gruszkiewicz; Bodnar, Robert J.; Rimstidt, J. Donald

    2014-09-10

    Recent studies report rapid corrosion of metals and carbonation of minerals in contact with carbon dioxide containing trace amounts of dissolved water. One explanation for this behavior is that addition of small amounts of H2O to CO2 leads to significant ionization within the fluid, thus promoting reactions at the fluid-solid interface analogous to corrosion associated with aqueous fluids. The extent of ionization in the bulk CO2 fluid was determined using a flow-through conductivity cell capable of detecting very low conductivities. Experiments were conducted from 298 to 473 K and 7.39 to 20 MPa with H2O concentrations up to ~1600 ppmwmore » (xH2O ≈ 3.9 x 10-3), corresponding to the H2O solubility limit in liquid CO2 at ambient temperature. All solutions showed conductivities <10 nS/cm, indicating that the solutions were essentially ion-free. Furthermore, this observation suggests that the observed corrosion and carbonation reactions are not the result of ionization in CO2-rich bulk phase, but does not preclude ionization in the fluid at the fluid-solid interface.« less

  6. H2O and CO emission towards IRAS point sources in regions of star formation.

    NASA Astrophysics Data System (ADS)

    Fiegle, K.; Wouterloot, J. G. A.; Brand, J.

    H2O masers are good indicators for the presence of star formation in molecular clouds. Wouterloot and Walmsley (1986) showed that all H2O maser sources in regions of star formation are associated with IRAS point sources with specific colours, so that the IRAS Point Source Catalog can be used to select maser candidates. The authors have searched for 22 GHz H2O maser emission using the 100-m radiotelescope in Effelsberg and the 32-m radiotelescope in Medicina, Italy. The total sample of sources consists of 1390 objects, selected according to their IRAS colour indices. Spectra and line parameters are given in Wouterloot et al. (1993). The H2O data are compared with results of observations of 12CO (1-0) (and of 12CO (2-1) and 12CO(3-2) in some cases) towards a large fraction of these sources, made with the 30-m IRAM, 15-m SEST, or 3-m KOSMA telescopes.

  7. Factors affecting UV/H2O2 inactivation of Bacillus atrophaeus spores in drinking water.

    PubMed

    Zhang, Yongji; Zhang, Yiqing; Zhou, Lingling; Tan, Chaoqun

    2014-05-01

    This study aims at estimating the performance of the Bacillus atrophaeus spores inactivation by the UV treatment with addition of H2O2. The effect of factors affecting the inactivation was investigated, including initial H2O2 dose, UV irradiance, initial cell density, initial solution pH and various inorganic anions. Under the experimental conditions, the B. atrophaeus spores inactivation followed both the modified Hom Model and the Chick's Model. The results revealed that the H2O2 played dual roles in the reactions, while the optimum reduction of 5.88lg was received at 0.5mM H2O2 for 10min. The inactivation effect was affected by the UV irradiance, while better inactivation effect was achieved at higher irradiance. An increase in the initial cell density slowed down the inactivation process. A slight acid condition at pH 5 was considered as the optimal pH value. The inactivation effect within 10min followed the order of pH 5>pH 7>pH 9>pH 3>pH 11. The effects of three added inorganic anions were investigated and compared, including sulfate (SO4(2)(-)), nitrate (NO3(-)) and carbonate (CO3(2)(-)). The sequence of inactivation effect within 10min followed the order of control group>SO4(2)(-)>NO3(-)>CO3(2)(-). PMID:24792469

  8. H2O-Rich Interstellar Grain Mantles: An Equilibrium Picture

    NASA Technical Reports Server (NTRS)

    Dissly, R. W.; Allen, M.; Anicich, V. G.

    1994-01-01

    Experiments simulating the codeposition of molecular hydrogen and water ice on interstellar grains demonstrate that amorphous water ice at 12 K can incorporate a substantial amount of H2, up to a molar ratio of H2/H2O=0.53.

  9. Degradation characteristic of monoazo, diazo and anthraquinone dye by UV / H2O2 process

    NASA Astrophysics Data System (ADS)

    Abidin, Che Zulzikrami Azner; Fahmi, Muhammad Ridwan; Fazara, Md Ali Umi; Nadhirah, Siti Nurfatin

    2014-10-01

    In this study, the degradation characteristic of monoazo, diazo and anthraquinone dye by UV / H2O2 process was evaluated based on the trend of color, chemical oxygen demand (COD) and total organic carbon (TOC) removal. Three types of dyes consist of monoazo, diazo and anthraquinone dyes were used to compare the degradation mechanism of the dyes. The UV / H2O2 experiments were conducted in a laboratory scale cylindrical glass reactor operated in semi-batch mode. The UV/Vis characterization of monoazo, diazo and anthraquinone dye indicated that the rapid degradation of the dyes by UV / H2O2 process is meaningful with respect to decolourization, as a result of the azo bonds and substitute antraquinone chromophore degradation. However, this process is not efficient for aromatic amines removal. The monoazo MO was difficult to be decolorized than diazo RR120 dye, which imply that number of sulphonic groups in the dye molecules determines the reactivity with hydroxyl radical. The increased in COD removal is the evidence for oxidation and decreased in carbon content of dye molecules. TOC removal analysis shows that low TOC removal of monoazo MO and diazo RR120, as compared to anthraquinone RB19 may indicate an accumulation of by-products that are resistant to the H2O2 photolysis.

  10. Linkages between CO2 and H2O fluxes over corn and soybean canopies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Measurements of CO2 and H2O vapor exchanges are becoming routine observations over many surfaces. These data are generally used to estimate the fluxes of these two critical gases as part of the energy exchanges between the plant and atmosphere. The value in these observations extends beyond that con...

  11. High Concentrations of H2O2 Make Aerobic Glycolysis Energetically More Favorable for Cellular Respiration.

    PubMed

    Molavian, Hamid R; Kohandel, Mohammad; Sivaloganathan, Sivabal

    2016-01-01

    Since the original observation of the Warburg Effect in cancer cells, over 8 decades ago, the major question of why aerobic glycolysis is favored over oxidative phosphorylation has remained unresolved. An understanding of this phenomenon may well be the key to the development of more effective cancer therapies. In this paper, we use a semi-empirical method to throw light on this puzzle. We show that aerobic glycolysis is in fact energetically more favorable than oxidative phosphorylation for concentrations of peroxide (H2O2) above some critical threshold value. The fundamental reason for this is the activation and high engagement of the pentose phosphate pathway (PPP) in response to the production of reactive oxygen species (ROS) H2O2 by mitochondria and the high concentration of H2O2 (produced by mitochondria and other sources). This makes oxidative phosphorylation an inefficient source of energy since it leads (despite high levels of ATP production) to a concomitant high energy consumption in order to respond to the hazardous waste products resulting from cellular processes associated with this metabolic pathway. We also demonstrate that the high concentration of H2O2 results in an increased glucose consumption, and also increases the lactate production in the case of glycolysis. PMID:27601999

  12. Pathway for H2O2 and O2 detoxification in Clostridium acetobutylicum

    PubMed Central

    Riebe, Oliver; Fischer, Ralf-Jörg; Wampler, David A.; Kurtz, Donald M.; Bahl, Hubert

    2009-01-01

    An unusual non-haem diiron protein, reverse rubrerythrin (revRbr), is known to be massively upregulated in response to oxidative stress in the strictly anaerobic bacterium Clostridium acetobutylicum. In the present study both in vivo and in vitro results demonstrate an H2O2 and O2 detoxification pathway in C. acetobutylicum involving revRbr, rubredoxin (Rd) and NADH: rubredoxin oxidoreductase (NROR). RevRbr exhibited both NADH peroxidase (NADH: H2O2 oxidoreductase) and NADH oxidase (NADH: O2 oxidoreductase) activities in in vitro assays using NROR as the electron-transfer intermediary from NADH to revRbr. Rd increased the NADH consumption rate by serving as an intermediary electron-transfer shuttle between NROR and revRbr. While H2O2 was found to be the preferred substrate for revRbr, its relative oxidase activity was found to be significantly higher than that reported for other Rbrs. A revRbr-overexpressing strain of C. acetobutylicum showed significantly increased tolerance to H2O2 and O2 exposure. RevRbr thus appears to protect C. acetobutylicum against oxidative stress by functioning as the terminal component of an NADH peroxidase and NADH oxidase. PMID:19118342

  13. Mixed protein-templated luminescent metal clusters (Au and Pt) for H2O2 sensing

    PubMed Central

    2013-01-01

    A simple and cost-effective method to synthesize the luminescent noble metal clusters (Au and Pt) in chicken egg white aqueous solution at room temperature is reported. The red-emitting Au cluster is used as fluorescent probe for sensitive detection of H2O2. PMID:23601828

  14. Crystal Structures and Thermal Properties of Two Transition-Metal Compounds {[Ni(DNI)2(H2O)3][Ni(DNI)2 (H2O)4]}·6H2O and Pb(DNI)2(H2O)4 (DNI = 2,4-Dinitroimidazolate)

    PubMed Central

    Zhang, Guo-Fang; Cai, Mei-Yu; Jing, Ping; He, Chong; Li, Ping; Zhao, Feng-Qi; Li, Ji-Zhen; Fan, Xue-Zhong; Ng, Seik Weng

    2010-01-01

    Two transition-metal compounds derived from 2,4-dinitroimidazole, {[Ni(DNI)2(H2O)3][Ni(DNI)2 (H2O)4]}·6H2O, 1, and Pb(DNI)2(H2O)4, 2, were characterized by elemental analysis, FT-IR, TG-DSC and X-ray single-crystal diffraction analysis. Crystal data for 1: monoclinic, space group C2/c, a = 26.826(3), b = 7.7199(10), c = 18.579(2) Å, β = 111.241(2)° and Z = 4; 2: monoclinic, space group C2/c, a = 6.5347(6), b = 17.1727(17), c = 14.1011(14) Å, β = 97.7248(10) and Z = 4. Compound 1 contains two isolated nickel centers in its structure, one being six-coordinate and another five-coordinate. The structure of 2 contains a lead (II) center surrounded by two chelating DNI ligands and four water molecules in distorted square-antiprism geometry. The abundant hydrogen bonds in two compounds link the molecules into three-dimensional network and stabilize the molecules. The TG-DSC analysis reveals that the first step is the loss of water molecules and the final residue is the corresponding metal oxides and carbon. PMID:20526419

  15. High Concentrations of H2O2 Make Aerobic Glycolysis Energetically More Favorable for Cellular Respiration

    PubMed Central

    Molavian, Hamid R.; Kohandel, Mohammad; Sivaloganathan, Sivabal

    2016-01-01

    Since the original observation of the Warburg Effect in cancer cells, over 8 decades ago, the major question of why aerobic glycolysis is favored over oxidative phosphorylation has remained unresolved. An understanding of this phenomenon may well be the key to the development of more effective cancer therapies. In this paper, we use a semi-empirical method to throw light on this puzzle. We show that aerobic glycolysis is in fact energetically more favorable than oxidative phosphorylation for concentrations of peroxide (H2O2) above some critical threshold value. The fundamental reason for this is the activation and high engagement of the pentose phosphate pathway (PPP) in response to the production of reactive oxygen species (ROS) H2O2 by mitochondria and the high concentration of H2O2 (produced by mitochondria and other sources). This makes oxidative phosphorylation an inefficient source of energy since it leads (despite high levels of ATP production) to a concomitant high energy consumption in order to respond to the hazardous waste products resulting from cellular processes associated with this metabolic pathway. We also demonstrate that the high concentration of H2O2 results in an increased glucose consumption, and also increases the lactate production in the case of glycolysis. PMID:27601999

  16. Reaction of N2O5 with H2O on carbonaceous surfaces

    NASA Technical Reports Server (NTRS)

    Brouwer, L.; Rossi, M. J.; Golden, D. M.

    1986-01-01

    The heterogeneous reaction of N2O5 with commercially available ground charcoal in the absence of H2O revealed a physisorption process (gamma = 0.003), together with a redox reaction generating mostly NO. Slow HNO3 formation was the result of the interaction of N2O5 with H2O that was still adsorbed after prolonged pumping at 0.0001 torr. In the presence of H2O, the same processes with gamma = 0.005 are observed. The redox reaction dominates in the early stages of the reaction, whereas the hydrolysis gains importance later at the expense of the redox reaction. The rate law for HNO3 generation was found to be d(HNO3)/dt = k(bi)(H2O)(N2O5) with k(bi), the effective bimolecular rate constants, for 10 mg of carbon being (1.6 + or - 0.3) x 10 to the -13th cu cm/s.

  17. Formation of low-temperature cirrus from H2SO4/H2O aerosol droplets.

    PubMed

    Bogdan, A; Molina, M J; Sassen, K; Kulmala, M

    2006-11-23

    We present experimental results obtained with a differential scanning calorimeter (DSC) that indicate the small ice particles in low-temperature cirrus clouds are not completely solid but rather coated with an unfrozen H2SO4/H2O overlayer. Our results provide a new look on the formation, development, and microphysical properties of low-temperature cirrus clouds. PMID:17107102

  18. New Optical Constants for Amorphous and Crystalline H2O-ice

    NASA Technical Reports Server (NTRS)

    Mastrapa, Rachel; Bernstein, Max; Sandford, Scott

    2006-01-01

    We have used the infrared spectra of laboratory ices to calculate the real and imaginary indices of refraction for amorphous and crystalline H2O-ice. We create H2O-ice samples in vacuum (approx. 10(exp ^-8)Torr). We measure the thickness of the sample by reflecting a He-Ne laser off of the sample and counting interference fringes as it grows and then collect transmission spectra of the samples in the wavelength range 1.25-22 micrometers. Using the ice thickness and transmission spectrum we calculate the imaginary part of the index of refraction. A Kramers-Kronig calculation is then used to calculate the real part of the index of refraction (Berland et al. 1994; Hudgins et al. 1993). These optical constants can be used to create model spectra for comparison to spectra from Solar System objects. We will summarize the differences between the amorphous and crystalline H2O-ice spectra. These include weakening of features and shifting of features to shorter wavelength in amorphous H,O-ice spectra. We will also discuss methods of using band area ratios to quickly estimate the fraction of amorphous to crystalline H2O-ice. We acknowledge financial support from the NASA Origins of the Solar System Program, the NASA Planetary Geology and Geophysics Program, and the NASA Postdoctoral Program.

  19. Comparison of sludge treatment by O3 and O3/H2O2.

    PubMed

    Yuxin, Zhao; Liang, Wang; Helong, Yu; Baojun, Jiang; Jinming, Jiang

    2014-01-01

    This work focuses on the comparison of sludge decomposition caused by ozone (O3) alone and by ozone/hydrogen peroxide (O3/H2O2). The content of carbonaceous organic materials, nitrogenous compounds and phosphoric substances in sludge supernatant were measured. The release of soluble chemical oxygen demand, total nitrogen (TN) and total phosphorus (TP) caused by O3/H2O2 treatment were more than by O3 alone. As a result, it can be concluded that the efficiency of sludge breakup in O3/H2O2 was better than that in O3 alone. However, a peak appeared in both systems for the biodegradable substances such as carbohydrate. Carbohydrate could be used as the carbon source for denitrification, and the releasing of TN and TP may become an additional burden for a subsequent biological system. So, it was of benefit for the enhancement of cryptic growth and cost reduction by raising and maintaining the content of biodegradable substance and reducing the concentrations of the nitrogenous and phosphoric substances as far as possible. Therefore, sludge treated by O3/H2O2 with lower O3 dose would be more suitable than O3 alone. PMID:25026588

  20. Polyoxometalates as peroxidase mimetics and their applications in H2O2 and glucose detection.

    PubMed

    Wang, Jingjing; Han, Dongxue; Wang, Xiaohong; Qi, Bin; Zhao, Meisheng

    2012-01-01

    Polyoxometalates (H(3)PW(12)O(40), H(4)SiW(12)O(40) and H(3)PMo(12)O(40)) have been proven to possess intrinsic peroxidase-like activity for the first time, which can catalyze oxidation of the peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) by H(2)O(2) to form a blue color in aqueous solution. Among them, H(3)PW(12)O(40) (PW(12)) exhibits higher catalytic activity to TMB than natural enzyme HRP and other two POMs. In addition, H(3)PW(12)O(40)/graphene exhibited higher activity than H(3)PW(12)O(40) in this catalytic oxidation reaction due to the effect of graphene in promoting the electron transfer between the substrate and catalyst. POMs/H(2)O(2)/TMB system provides a simple, accurate approach to colorimetric detection for H(2)O(2) or glucose. The colorimetric method based on POMs showed good response toward H(2)O(2) and glucose detection with a linear range from 1.34×10(-7) to 6.7×10(-5) mol/L and 1×10(-7) to 1×10(-4) mol/L, respectively. The results showed that it is a simple, cheap, more convenient, highly selective, sensitive, and easy handling colorimetric assay. PMID:22560441

  1. Influence of the H2O2 in the plasma gene transfection method

    NASA Astrophysics Data System (ADS)

    Kimura, Masanori; Tachibana, Hiroki; Ohno, Yuki; Ikeda, Yoshihisa; Motomura, Hideki; Kido, Yugo; Satoh, Susumu; Tachibana, Kunihide; Jinno, Masafumi

    2015-09-01

    Gene transfection is the process of deliberately introducing nucleic acids into cells. The authors have been developing a novel gene transfection method using microplasma irradiation (plasma gene transfection method). Our previous study shows that long life chemically reactive species contribute to gene transfection, which induce the transfection at least 60 s after plasma irradiation (after effect). In order to clarify the key reactive species which is effective on the after effect, the effect of H2O2 addition after plasma irradiation was investigated. Addition of H2O2 at 1/1000 -1 ppm after plasma irradiation did not largely affect or slightly decease the transfection ratio, whereas the H2O2 concentration induced by plasma irradiation is estimated as 2.7 ppb after dilution by the medium. It is found that the H2O2 is not main species for the after effect. This work was partly supported by JSPS KAKENHI Grant-in-Aid for Scientific Research on Innovative Areas (Number 25108509, 15H00896) and a grant from Ehime University.

  2. MUTAGENIC ACTIVITY OF IRRADIATED TOLUENE/NOX/H2O/AIR MIXTURES

    EPA Science Inventory

    Irradiated mixtures of toluene/NOx/H2O/air were brought to a steady-state distribution of reactants and products in a 22.7 cu. m. flow-mode smog chamber, and the effluent was tested for mutagenic activity by exposing Salmonella typhimurum strains TA100 and TA98 to it. Two differe...

  3. Linkages between CO2 and H2O fluxes over corn and soybean canopies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Measurements of CO2 and H2O vapor exchanges are becoming routine observations over many surfaces. These data are generally used to estimate the fluxes of two critical gases as part of the energy exchanges between a vegetated surface and lowest boundary-layer of the atmosphere. The value in these typ...

  4. Effect of H2O2 and nonionic surfactant in alkaline copper slurry

    NASA Astrophysics Data System (ADS)

    Haobo, Yuan; Yuling, Liu; Mengting, Jiang; Guodong, Chen; Weijuan, Liu; Shengli, Wang

    2015-01-01

    For improving the polishing performance, in this article, the roles of a nonionic surfactant (Fatty alcohol polyoxyethylene ether) and H2O2 were investigated in the chemical mechanical planarization process, respectively. Firstly, the effects of the nonionic surfactant on the within-wafer non-uniformity (WIWNU) and the surface roughness were mainly analyzed. In addition, the passivation ability of the slurry, which had no addition of BTA, was also discussed from the viewpoint of the static etch rate, electrochemical curve and residual step height under different concentrations of H2O2. The experimental results distinctly revealed that the nonionic surfactant introduced in the slurry improved the WIWNU and surface roughness, and that a 2 vol% was considered as an appropriate concentration relatively. When the concentration of H2O2 surpasses 3 vol%, the slurry will possess a relatively preferable passivation ability, which can effectively decrease the step height and contribute to acquiring a flat and smooth surface. Hence, based on the result of these experiments, the influences of the nonionic surfactant and H2O2 are further understood, which means the properties of slurry can be improved.

  5. Wogonin inhibits H2O2-induced vascular permeability through suppressing the phosphorylation of caveolin-1.

    PubMed

    Wang, Fei; Song, Xiuming; Zhou, Mi; Wei, Libin; Dai, Qinsheng; Li, Zhiyu; Lu, Na; Guo, Qinglong

    2013-03-01

    Wogonin, a naturally occurring monoflavonoid extracted from the root of Scutellaria baicalensis Georgi, has been reported for its anti-oxidant activity. However, it is still unclear whether wogonin can inhibit oxidant-induced vascular permeability. In this study, we evaluated the effects of wogonin on H2O2-induced vascular permeability in human umbilical vein endothelial cells (HUVECs). We found that wogonin can suppress the H2O2-stimulated actin remodeling and albumin uptake of HUVECs, as well as transendothelial cell migration of the human breast carcinoma cell MDA-MB-231. The mechanism revealed that wogonin inhibited H2O2-induced phosphorylation of caveolin-1 (cav-1) associating with the suppression of stabilization of VE-cadherin and β-catenin. Moreover, wogonin repressed anisomycin-induced phosphorylation of p38, cav-1 and vascular permeability. These results suggested that wogonin could inhibit H2O2-induced vascular permeability by downregulating the phosphorylation of cav-1, and that it might have a therapeutic potential for the diseases associated with the development of both oxidant and vascular permeability. PMID:23246481

  6. Advanced NaBH4/H2O2 Fuel Cell for Space Applications

    NASA Astrophysics Data System (ADS)

    Miley, George H.; Kim, Kyu-Jung; Luo, Nie; Shrestha, Prajakti Joshi

    2009-03-01

    Fuel cells have played an important role in NASA's space program starting with the Gemini space program. However, improved fuel cell performance will be needed to enable demanding future missions. An advanced fuel cell (FC) using liquid fuel and oxidizer is being developed by U of IL/NPL team to provide air independence and to achieve higher power densities than normal H2/O2 fuel cells (Lou et al., 2008; Miley, 2007). Hydrogen peroxide (H2O2) is used in this FC directly at the cathode (Lou and Miley, 2004). Either of two types of reactant, namely a gas-phase hydrogen or an aqueous NaBH4 solution, is utilized as fuel at the anode. Experiments with both 10-W single cells and 500-W stacks demonstrate that the direct utilization of H2O2 and NaBH4 at the electrodes result in >30% higher voltage output compared to the ordinary H2/O2 FC (Miley, 2007). Further, the use of this combination of all liquid fuels provides—from an operational point of view—significant advantages (ease of storage, reduced pumping requirements, simplified heat removal). This design is inherently compact compared to other fuel cells that use gas phase reactants. This results in a high overall system (including fuel tanks, pumps and piping, waste heat radiator) power density. Further, work is in progress on a regenerative version which uses an electrical input, e.g. from power lines or a solar panel to regenerate reactants.

  7. Responses of the rabbit tracheal epithelium in vitro to H(2)O(2)-induced oxidative stress.

    PubMed

    Baeza-Squiban, A; Delcher, L; Kukreti, R; Joly, A C; Guennou, C; Houcine, O; Marano, F

    2000-04-01

    A model of rabbit tracheal epithelial (RTE) cells in primary culture was used to characterize specific and repair responses of airway epithelial cells to oxidative stress. Two well-known reactive oxygen species (ROS) generating systems were used: H(2)O(2) alone or in combination with Fe(2+) to produce the hydroxyl radical. RTE cells exhibited lipid peroxidation when exposed to H(2)O(2) + Fe(2+). Moreover, catalase (CAT) activity decreased after a 1-hour treatment in 3-day-old cultures but increased in 7-day-old cultures which have higher antioxidant enzyme activities. Superoxide dismutase (SOD) activity was never affected. In addition, RTE cells displayed a repair response leading to squamous metaplasia. H(2)O(2) + Fe(2+) treatment resulted in a time-dependent increase in the steady-state level of c-myc mRNA while c-jun and c-fos were not activated. Moreover, a chronic exposure induced the expression of the squamous phenotype characterized by the expression of the cytokeratin 13 confirmed both at the message and protein levels. RTE cells in primary culture react early to H(2)O(2) + Fe(2+) exposure by an increase in c-myc expression and by modifications in CAT activity. Further, a lipid peroxidation occurs and the tracheal epithelium evolves to squamous metaplasia. PMID:10793294

  8. Particle-in-Cell Simulations of Atmospheric Pressure He/2%H2O Discharges

    NASA Astrophysics Data System (ADS)

    Kawamura, E.; Lieberman, M. A.; Lichtenberg, A. J.; Graves, D. B.; Gopalakrishnan, R.

    2015-09-01

    Atmospheric pressure micro-discharges in contact with liquid surfaces are of increasing interest, especially in the bio-medical field. We conduct 1D3v particle-in-cell (PIC) simulations of a voltage-driven 1 mm width atmospheric pressure He/2% H2O plasma discharge in series with an 0.5 mm width liquid H2O layer and a 1mm width quartz dielectric layer. A previously developed two-temperature hybrid global model of atmospheric pressure He/H2O discharges was used to determine the most important species and collisional reactions to use in the PIC simulations. We found that H13O6+, H5O3-, and electrons were the most prominent charged species, while most of the metastable helium He* was quenched via Penning ionization. The ion-induced secondary emission coefficient γi was assumed to be 0.15 at all surfaces. A series of simulations were conducted at 27.12 MHz with Jrf ~ 800-2200 A/m2. The H2O rotational and vibrational excitation losses were so high that electrons reached the walls at thermal temperatures. We also simulated a much lower frequency case of 50 kHz with Vrf = 10 kV. In this case, the discharge ran in a pure time-varying γ-mode. This work was supported by the Department of Energy Office of Fusion Energy Science Contract DE-SC0001939.

  9. Characterization and optimization of cathodic conditions for H2O2 synthesis in microbial electrochemical cells

    EPA Science Inventory

    Cathode potential and O2 supply methods were investigated to improve H2O2 synthesis in an electrochemical cell, and optimal cathode conditions were applied for microbial electrochemical cells (MECs). Using aqueous O2 for the cathode significantly improved current density, but H2...

  10. Water Planetary and Cometary Atmospheres: H2O/HDO Transmittance and Fluorescence Models

    NASA Technical Reports Server (NTRS)

    Villanueva, G. L.; Mumma, M. J.; Bonev, B. P.; Novak, R. E.; Barber, R. J.; DiSanti, M. A.

    2012-01-01

    We developed a modern methodology to retrieve water (H2O) and deuterated water (HDO) in planetary and cometary atmospheres, and constructed an accurate spectral database that combines theoretical and empirical results. Based on a greatly expanded set of spectroscopic parameters, we built a full non-resonance cascade fluorescence model and computed fluorescence efficiencies for H2O (500 million lines) and HDO (700 million lines). The new line list was also integrated into an advanced terrestrial radiative transfer code (LBLRTM) and adapted to the CO2 rich atmosphere of Mars, for which we adopted the complex Robert-Bonamy formalism for line shapes. We then retrieved water and D/H in the atmospheres of Mars, comet C/2007 WI, and Earth by applying the new formalism to spectra obtained with the high-resolution spectrograph NIRSPEC/Keck II atop Mauna Kea (Hawaii). The new model accurately describes the complex morphology of the water bands and greatly increases the accuracy of the retrieved abundances (and the D/H ratio in water) with respect to previously available models. The new model provides improved agreement of predicted and measured intensities for many H2O lines already identified in comets, and it identifies several unassigned cometary emission lines as new emission lines of H2O. The improved spectral accuracy permits retrieval of more accurate rotational temperatures and production rates for cometary water.

  11. Mars: Long Term Changes in the State and Distribution of H2O

    NASA Technical Reports Server (NTRS)

    Fanale, F. P.; Salvail, J. R.; Zent, A. P.; Postawko, S. E.

    1985-01-01

    A model for H2O distribution and migration on Mars was formulated which takes into account: (1) thermal variations at all depths in the regolith due to variations in obliquity, eccentricity and the solar constant; (2) variations in atmospheric PH2O caused by corresponding changes in polar surface insolation; and (3) the finite kinetics of H2O migration in both the regolith and atmosphere. Results suggest that regolith H2O transport rates are more strongly influenced by polar-controlled atmospheric PH2O variations than variations in pore gas PH2O brought about by thermal variations at the buried ice interface. The configuration of the ice interface as a function of assumed soil parameter and time is derived. Withdrawal of ice proceeds to various depths at latitudes less than 50 deg and is accompanied by filling of regolith pores at latitudes greater than 50 deg and transfer of H2O to the polar cap. The transfer has a somewhat oscillatory character, but only less than 1g/sq cm is shifted into and out the regolith during each obliquity cycle. It is concluded that this process combined with periodic thermal cycles played a major role in development of the fretted terrain, deflationary features in general, patterned ground, the north polar cap and the layered terrain.

  12. Drift and clustering of daughter negative ions of H2O in parent gas

    NASA Astrophysics Data System (ADS)

    de Urquijo, J.; Bekstein, A.; Ruiz-Vargas, G.; Gordillo-Vázquez, F. J.

    2013-01-01

    The mobility of daughter negative ions of H2O in parent gas has been measured with a pulsed Townsend technique over the density-reduced field strength, E/N, range 9-100 Td and a pressure range 2-16 Torr. It has been found that the mobility of the anions is dependent on the gas pressure. Using a transport theory considering the influence of the permanent dipole field of H2O, we have found that the pressure-dependent mobilities can be associated with a series of cluster ions of the type OH-(H2O)n (n = 1-3), with the mass of the cluster species increasing with the total gas pressure. Also, the mobility of H- and OH- could be estimated. Using a Townsend avalanche simulator we have been able to explain the measured ionic currents in terms of an ion-molecule reaction scheme with a single set of swarm and reaction coefficients for each value of the density-reduced field strength, E/N, at several pressures. Regarding the positive ions, the only drifting ion is H3O+, the mobility of which could be estimated. The rate constants relative to the formation of the OH-(H2O)n (n = 1-3) species were also derived from this study.

  13. Acid mine treatment with open limestone channels

    SciTech Connect

    Ziemkiewicz, P.F.; Brant, D.L.; Skousen, J.G.

    1996-12-31

    Acid mine drainage (AMD) is often associated with mining of pyritic coal and metal deposits. Typical AMD associated with coal mines in the eastern US can have acidity and iron concentrations ranging from the teens to the thousands of mg/l. Aluminum and manganese can be present in concentrations ranging from zero to the low hundreds of mg/l. Much attention has been devoted to developing inexpensive, limestone (LS)-based systems for treating AMID with little or no maintenance. However, LS tends to coat with metal hydroxides when exposed to AMID in an oxidized state, a process known as {open_quotes}armoring{close_quotes}. It is generally assumed that once armored, LS ceases to neutralize acid. Another problem is that the hydroxides tend to settle into plug the pore spaces in LS beds forcing water to move around rather than through the LS. While both are caused by the precipitation of metal hydroxides, armoring and plugging are two different problems. Plugging of LS pores can be avoided by maintaining a high flushing rate through the LS bed. Armoring, however, occurs regardless of water velocity. This study investigated the influence of armoring on LS solubility and the implications of armoring and plugging on the construction of open (oxidizing) LS channels for treating AMD. We evaluated the AMID treatment performance of armored and unarmored LS in oxidizing environments both in laboratory and field studies.

  14. First outer-sphere 1,3-diethyl-2-thiobarbituric compounds [M(H2O)6](1,3-diethyl-2-thiobarbiturate)2·2H2O (M = Co2+, Ni2+): Crystal structure, spectroscopic and thermal properties

    NASA Astrophysics Data System (ADS)

    Golovnev, Nicolay N.; Molokeev, Maxim S.; Lesnikov, Maxim K.; Atuchin, Victor V.

    2016-06-01

    Two new d-element compounds, [Co(H2O)6](Detba)2·2H2O (1) and [Ni(H2O)6](Detba)2·2H2O (2) (HDetba - 1,3-diethyl-2-thiobarbituric acid) were synthesized and characterized by single-crystal and powder X-ray diffraction analysis, TG-DSC and FT-IR. Structural analysis revealed that (1) and (2) are discrete structures, in which M2+ ion (M = Co, Ni) is six-coordinated by water molecules and it forms an octahedron. The outer-sphere Detba- ions and H2O molecules participate in Osbnd H⋯(O/S) intermolecular hydrogen bonds which form the 2D layer. Thermal decomposition includes the stage of dehydration and the following stage of oxidation of Detba- with a release of CO2, SO2, H2O, NH3 and isocyanate gases.

  15. Analysis of Ground-State Zero-Field Splitting for Mn2+ in ZnNbOF5·6(H2O) and CoNbOF5·6(H2O)

    NASA Astrophysics Data System (ADS)

    Li, Ju-Fen; Kuang, Xiao-Yu

    2011-06-01

    The electron paramagnetic resonance spectra of trigonal Mn2+ centers in ZnNbOF5·6(H2O) and CoNbOF5·6(H2O) crystals are studied on the basis of the complete energy matrices for a d5 configuration ion in a trigonal ligand field. It is demonstrated that the local lattice structure around a trigonal Mn2+ center has an elongation distortion along the crystalline c3 axis, and when Mn2+ is doped in the ZnNbOF5·6(H2O) and CoNbOF5·6(H2O) crystals, there is a similar local distortion. From the EPR calculation, the local lattice structure parameters for trigonal Mn2+ centers in ZnNbOF5·6(H2O) and CoNbOF5·6(H2O) are determined.

  16. SO-LAAO, a novel L-amino acid oxidase that enables Streptococcus oligofermentans to outcompete Streptococcus mutans by generating H2O2 from peptone.

    PubMed

    Tong, Huichun; Chen, Wei; Shi, Wenyuan; Qi, Fengxia; Dong, Xiuzhu

    2008-07-01

    We previously demonstrated that Streptococcus oligofermentans suppressed the growth of Streptococcus mutans, the primary cariogenic pathogen, by producing hydrogen peroxide (H(2)O(2)) through lactate oxidase activity. In this study, we found that the lox mutant of S. oligofermentans regained the inhibition while growing on peptone-rich plates. Further studies demonstrated that the H(2)O(2) produced on peptone by S. oligofermentans was mainly derived from seven L-amino acids, i.e., L-aspartic acid, L-tryptophan, L-lysine, L-isoleucine, L-arginine, L-asparagine, and L-glutamine, indicating the possible existence of L-amino acid oxidase (LAAO) that can produce H(2)O(2) from L-amino acids. Through searching the S. oligofermentans genome for open reading frames with a conserved flavin adenine dinucleotide binding motif that exists in the known LAAOs, including those of snake venom, fungi, and bacteria, a putative LAAO gene, assigned as aao(So), was cloned and overexpressed in Escherichia coli. The purified protein, SO-LAAO, showed a molecular mass of 43 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis and catalyzed H(2)O(2) formation from the seven L-amino acids determined above, thus confirming its LAAO activity. The SO-LAAO identified in S. oligofermentans differed evidently from the known LAAOs in both substrate profile and sequence, suggesting that it could represent a novel LAAO. An aao(So) mutant of S. oligofermentans did lose H(2)O(2) formation from the seven L-amino acids, further verifying its function as an LAAO. Furthermore, the inhibition by S. oligofermentans of S. mutans in a peptone-rich mixed-species biofilm was greatly reduced for the aao(So) mutant, indicating the gene's importance in interspecies competition. PMID:18469105

  17. Quantitative evaluation of the effect of H2O degassing on the oxidation state of magmas

    NASA Astrophysics Data System (ADS)

    Lange, R. A.; Waters, L.

    2014-12-01

    The extent to which degassing of the H2O component affects the oxidation state of hydrous magmas is widely debated. Several researchers have examined how degassing of mixed H-C-O-S-Cl fluids may change the Fe3+/FeT ratio of various magmas, whereas our focus is on the H2O component. There are two ways that degassing of H2O by itself may cause oxidation: (1) the reaction: H2O (melt) + 2FeO (melt) = H2 (fluid) + Fe2O3 (melt), and/or (2) if dissolved water preferentially enhances the activity of ferrous vs. ferric iron in magmatic liquids. In this study, a comparison is made between the pre-eruptive oxidation states of 14 crystal-poor, jet-black obsidian samples (obtained from two Fe-Ti oxides) and their post-eruptive values (analyzed with the Wilson 1960 titration method tested against USGS standards). The obsidians are from Medicine Lake (CA), Long Valley (CA), and the western Mexican arc; all have low FeOT (1.1-2.1 wt%), rendering their Fe2+/Fe3+ ratios highly sensitive to the possible effects of substantial H2O degassing. The Fe-Ti oxide thermometer/oxybarometer of Ghiorso and Evans, (2008) gave temperatures for the 14 samples that range for 720 to 940°C and ∆NNO values of -0.9 to +1.4. With temperature known, the plagioclase-liquid hygrometer was applied and show that ≤ 6.5 wt% H2O was dissolved in the melts prior to eruption. In addition, pre-eruptive Cl and S concentrations were constrained on the basis of apatite analyses (Webster et al., 2009) and sulfur concentrations needed for saturation with pyrrhotite (Clemente et al., 2004), respectively. Maximum pre-eruptive chlorine and sulfur contents are 6000 and 200 ppm, respectively. After eruption, the rhyolites lost nearly all of their volatiles. Our results indicate no detectable change between pre- and post-eruptive Fe2+ concentrations, with an average deviation of ± 0.1 wt % FeO. Although degassing of large concentrations of S and/or Cl may affect the oxidation state of magmas, at the pre-eruptive levels

  18. The Infrared Spectra of Nitriles and Related Compounds Frozen in Ar and H2O

    NASA Technical Reports Server (NTRS)

    Bernstain, Max P.; Sandford, Scott A.; Allamandola, Louis J.; Witteborn, Fred C. (Technical Monitor)

    1996-01-01

    We present the 2320-2050/cm (4.31-4.88 micron) infrared spectra of 16 solid state nitrites, isonitriles, and related compounds in order to facilitate the assignment of absorption features in a spectral region now becoming accessible to astronomers for the first time through the Infrared Space Observatory (ISO). This frequency range spans the positions of the strong C(is congruent to)N stretching vibration of these compounds and is inaccessible from the ground due to absorption by CO2 in the terrestrial atmosphere. Band positions, profiles, and intrinsic strengths (A values) were measured for compounds frozen in Ar and H2O matrices at 12 K. The molecular species examined included acetonitrile, benzonitrile phenylcyanide) 9-anthracenecarbonitrile, dimethylcyanamide, isopropy1nitrile (isobutyronitrile), methylacrylonitrile, crotononitrile, acrylonitrile (vinyl cyanide), 3-aminocrotononitrile, pyr-uvonitrile, dicyandiamide, cyanamide, n-butyfisocyanide, methylisocyanoacetate, dilsopropylcarbodiimide, and hydrogen cyanide. The C(is congruent to)N stretching bands of the majority of nitrites fall in the 2300-2200/cm (4.35-4.55 micron) range and have similar positions in both Ar and H2O matrices, although the bands are generally considerably broader in the H2O matrices. In contest, the isonitriles and a few exceptional nitrites and related species produce bands at lower frequencies spanning the 2200-2080/cm (4.55-4.81 micron) range. These features also have similar positions in both Am and H2O matrices and the bands are broader in the H2O matrices. Three of the compounds (pyruvonitrile, dicyandiamide, and cyanamide) show unusually large shifts of their C(is congruent to)N stretching frequencies when changing from Ar to H2O matrices. We attribute these shifts to the formation of H2O:nitrile complexes with these compounds. The implications of these results for the identification of the 2165/cm (4.62 micron) "XCN" interstellar feature and the 4550/cm (2.2 micron) feature of

  19. The infrared spectra of nitriles and related compounds frozen in Ar and H2O

    NASA Technical Reports Server (NTRS)

    Bernstein, M. P.; Sandford, S. A.; Allamandola, L. J.

    1997-01-01

    We present the 2320-2050 cm-1 (4.31-4.88 micrometers) infrared spectra of 16 solid-state nitriles, isonitriles, and related compounds in order to facilitate the assignment of absorption features in a spectral region now becoming accessible to astronomers for the first time through the Infrared Space Observatory (ISO). This frequency range spans the positions of the strong C triple bond N stretching vibration of these compounds and is inaccessible from the ground due to absorption by CO2 in the terrestrial atmosphere. Band positions, profiles, and intrinsic strengths (A values) were measured for compounds frozen in Ar and H2O matrices at 12 K. The molecular species examined included acetonitrile, benzonitrile (phenylcyanide), 9-anthracenecarbonitrile, dimethylcyanamide, isopropylnitrile (isobutyronitrile), methylacrylonitrile, crotononitrile, acrylonitrile (vinyl cyanide), 3-aminocrotononitrile, pyruvonitrile, dicyandiamide, cyanamide, n-butylisocyanide, methylisocyanoacetate, diisopropylcarbodiimide, and hydrogen cyanide. The C triple bond N stretching bands of the majority of nitriles fall in the 2300-2200 cm-1 (4.35-4.55 micrometers) range and have similar positions in both Ar and H2O matrices, although the bands are generally considerably broader in the H2O matrices. In contrast, the isonitriles and a few exceptional nitriles and related species produce bands at lower frequencies spanning the 2200-2080 cm-1 (4.55-4.81 micrometers) range. These features also have similar positions in both Ar and H2O matrices, and the bands are broader in the H2O matrices. Three of the compounds (pyruvonitrile, dicyandiamide, and cyanamide) show unusually large shifts of their C triple bond N stretching frequencies when changing from Ar to H2O matrices. We attribute these shifts to the formation of H2O:nitrile complexes with these compounds. The implications of these results for the identification of the 2165 cm-1 (4.62 micrometers) "XCN" interstellar feature and the 4550 cm-1 (2

  20. Uptaking of plagioclase xenocryst into H2O-rich rear-arc basaltic magma

    NASA Astrophysics Data System (ADS)

    Hamada, M.

    2015-12-01

    Kuritani et al. (2013, Mineral. Petrol.) and Kuritani et al. (2014, Contrib. Mineral. Petrol.) estimated genetic conditions of primary arc magmas beneath the Iwate volcano (a frontal arc volcano in the northeast Japan arc) and the Sannome-gata volcano (a rear-arc volcano in the northeast Japan arc) based on analyses of volcanic rocks and numerical simulation. They estimated that H2O concentrations of primary melts are 4-5 wt.% beneath the Iwate volcano and 6-7 wt.% beneath the Sannnome-gata volcano, respectively. Their arguments mean that primary melts beneath frontal-arc volcanoes and rear-arc volcanoes are both H2O-rich, yet there has been no direct evidence to support their arguments at the Sannnome-gata volcano because volcanic rocks are either almost aphyric and/or almost no melt inclusions were found. Hydrogen concentration in nominally anhydrous minerals serves as a hygrometer of arc basaltic melts (e.g., Hamada et al. 2013, Earth Planet. Sci. Lett.). In this study, hydrogen concentration of plagioclase as a crustal xenocryst was analyzed to estimate H2O concentration of basaltic melt coexisted with plagioclase before the eruption. Plagioclase xenocrists were separated from crushed scoria which erupted from the Sannome-gata volcano 20,000-24,000 years ago. Composition of the plagioclase core is homogeneous and ranges from An30 through An35. The rim is 150 to 200-μm-thick dusty zone whose composition is around An60, suggesting that the rim crystallized rapidly from degassed basaltic melt. The profiles of infrared absorption area per unit thickness across the plagioclase core were obtained using Fourier Transform InfraRed spectrometer (FTIR). The inner core contains hydrogen of about 60 wt. ppm H2O, and hydrogen concentration elevates at outer core. Hydrogen concentration at the outermost core of plagioclase is >200 wt. ppm H2O, suggesting that plagioclase xenocrists were taken by hydrous melt (H2O>5 wt.%; Hamada et al. 2014, Earth Planet. Sci. Lett.) and

  1. Degassing of H2O in a phonolitic melt: A closer look at decompression experiments

    NASA Astrophysics Data System (ADS)

    Marxer, Holger; Bellucci, Philipp; Nowak, Marcus

    2015-05-01

    Melt degassing during magma ascent is controlled by the decompression rate and can be simulated in decompression experiments. H2O-bearing phonolitic melts were decompressed at a super-liquidus T of 1323 K in an internally heated argon pressure vessel, applying continuous decompression (CD) as well as to date commonly used step-wise decompression (SD) techniques to investigate the effect of decompression method on melt degassing. The hydrous melts were decompressed from 200 MPa at nominal decompression rates of 0.0028-1.7 MPa·s- 1. At final pressure (Pfinal), the samples were quenched rapidly at isobaric conditions with ~ 150 K·s- 1. The bubbles in the quenched samples are often deformed and dented. Flow textures in the glass indicate melt transport at high viscosity. We suggest that this observation is due to bubble shrinkage during quench. This general problem was mostly overlooked in the interpretation of experimentally degassed samples to date. Bubble shrinkage due to decreasing molar volume (Vm) of the exsolved H2O in the bubbles occurs during isobaric rapid quench until the melt is too viscous too relax. The decrease of Vm(H2O) during cooling at Pfinal of the experiments results in a decrease of the bubble volume by a shrinking factor Bs: At nominal decompression rates > 0.17 MPa·s- 1 and a Pfinal of 75 MPa, the decompression method has only minor influence on melt degassing. SD and CD result in high bubble number densities of 104-105 mm- 3. Fast P drop leads to immediate supersaturation with H2O in the melt. At such high nominal decompression rates, the diffusional transport of H2O is limited and therefore bubble nucleation is the predominant degassing process. The residual H2O contents in the melts decompressed to 75 MPa increase with nominal decompression rate. After homogeneous nucleation is triggered, CD rates ≤ 0.024 MPa·s- 1 facilitate continuous reduction of the supersaturation by H2O diffusion into previously nucleated bubbles. Bubble number

  2. H2O2-Induced Oxidative Stress Affects SO4= Transport in Human Erythrocytes

    PubMed Central

    Morabito, Rossana; Romano, Orazio; La Spada, Giuseppa; Marino, Angela

    2016-01-01

    The aim of the present investigation was to verify the effect of H2O2-induced oxidative stress on SO4= uptake through Band 3 protein, responsible for Cl-/HCO3- as well as for cell membrane deformability, due to its cross link with cytoskeletal proteins. The role of cytoplasmic proteins binding to Band 3 protein has been also considered by assaying H2O2 effects on hemoglobin-free resealed ghosts of erythrocytes. Oxidative conditions were induced by 30 min exposure of human erythrocytes to different H2O2 concentrations (10 to 300 μM), with or without GSH (glutathione, 2 mM) or curcumin (10 μM), compounds with proved antioxidant properties. Since SO4= influx through Band 3 protein is slower and better controllable than Cl- or HCO3- exchange, the rate constant for SO4= uptake was measured to prove anion transport efficiency, while MDA (malondialdehyde) levels and –SH groups were estimated to quantify the effect of oxidative stress. H2O2 induced a significant decrease in rate constant for SO4= uptake at both 100 and 300 μM H2O2. This reduction, observed in erythrocytes but not in resealed ghosts and associated to increase in neither MDA levels nor in –SH groups, was impaired by both curcumin and GSH, whereas only curcumin effectively restored H2O2-induced changes in erythrocytes shape. Our results show that: i) 30 min exposure to 300 μM H2O2 reduced SO4= uptake in human erythrocytes; ii) oxidative damage was revealed by the reduction in rate constant for SO4= uptake, but not by MDA or –SH groups levels; iii) the damage was produced via cytoplasmic components which cross link with Band 3 protein; iv) the natural antioxidant curcumin may be useful in protecting erythrocytes from oxidative injury; v) SO4= uptake through Band 3 protein may be reasonably suggested as a tool to monitor erythrocytes function under oxidative conditions possibly deriving from alcohol consumption, use of drugs, radiographic contrast media administration, hyperglicemia or

  3. H2O2-Induced Oxidative Stress Affects SO4= Transport in Human Erythrocytes.

    PubMed

    Morabito, Rossana; Romano, Orazio; La Spada, Giuseppa; Marino, Angela

    2016-01-01

    The aim of the present investigation was to verify the effect of H2O2-induced oxidative stress on SO4= uptake through Band 3 protein, responsible for Cl-/HCO3- as well as for cell membrane deformability, due to its cross link with cytoskeletal proteins. The role of cytoplasmic proteins binding to Band 3 protein has been also considered by assaying H2O2 effects on hemoglobin-free resealed ghosts of erythrocytes. Oxidative conditions were induced by 30 min exposure of human erythrocytes to different H2O2 concentrations (10 to 300 μM), with or without GSH (glutathione, 2 mM) or curcumin (10 μM), compounds with proved antioxidant properties. Since SO4= influx through Band 3 protein is slower and better controllable than Cl- or HCO3- exchange, the rate constant for SO4= uptake was measured to prove anion transport efficiency, while MDA (malondialdehyde) levels and -SH groups were estimated to quantify the effect of oxidative stress. H2O2 induced a significant decrease in rate constant for SO4= uptake at both 100 and 300 μM H2O2. This reduction, observed in erythrocytes but not in resealed ghosts and associated to increase in neither MDA levels nor in -SH groups, was impaired by both curcumin and GSH, whereas only curcumin effectively restored H2O2-induced changes in erythrocytes shape. Our results show that: i) 30 min exposure to 300 μM H2O2 reduced SO4= uptake in human erythrocytes; ii) oxidative damage was revealed by the reduction in rate constant for SO4= uptake, but not by MDA or -SH groups levels; iii) the damage was produced via cytoplasmic components which cross link with Band 3 protein; iv) the natural antioxidant curcumin may be useful in protecting erythrocytes from oxidative injury; v) SO4= uptake through Band 3 protein may be reasonably suggested as a tool to monitor erythrocytes function under oxidative conditions possibly deriving from alcohol consumption, use of drugs, radiographic contrast media administration, hyperglicemia or neurodegenerative

  4. Step-by-step thermal transformations of a new porous coordination polymer [(H2O)5CuBa(Me2mal)2]n (Me2mal2-=dimethylmalonate): Thermal degradation to barium cuprate

    NASA Astrophysics Data System (ADS)

    Zauzolkova, Natalya; Dobrokhotova, Zhanna; Lermontov, Anatoly; Zorina, Ekaterina; Emelina, Anna; Bukov, Mikhail; Chernyshev, Vladimir; Sidorov, Aleksey; Kiskin, Mikhail; Bogomyakov, Artem; Lytvynenko, Anton; Kolotilov, Sergey; Velikodnyi, Yuriy; Kovba, Maksim; Novotortsev, Vladimir; Eremenko, Igor

    2013-01-01

    The reactions of CuSO4·5H2O, dimethylmalonic acid and Ba(OH)2·H2O (Cu: H2Me2mal: Ba=1: 2: 2) in aqueous and aqueous-ethanol solutions (H2O: EtOH=1: 1) resulted in formation of 3D-porous coordination polymers [(H2O)3(μ-H2O)2CuBa(μ3-Me2mal)(Me2mal)]n (1) and [(μ-H2O)CuBa(μ3-Me2mal)(μ4-Me2mal)]n (2), respectively. It has been shown that compound 2 was an intermediate in the thermal degradation of compound 1. Thorough studies of solid-state thermolysis of 1 and 2 allowed to detect formation of coordination polymer [CuBa(μ4-Me2mal)(μ5-Me2mal)]n (3), structure of which was determined by X-ray powder diffraction. It has been found that the channels in polymer 3 were accessible for guest molecules (MeOH). Theoretical estimation of methanol diffusion barrier was carried out. Complete solid-phase thermolysis of 1 and 2 leads to a mixture of BaCuO2, BaCO3, and CuO. Special conditions for obtaining of a crystalline phase of pure cubic BaCuO2 were determined.

  5. Mapping of [HDO]/[H2O] in the Martian Atmosphere

    NASA Astrophysics Data System (ADS)

    Novak, R. E.; Mumma, M. J.; Villanueva, G.; Bonev, B.; Disanti, M.

    Observations of the Martian atmosphere were taken for several seasonal dates at NASA's IRTF using CSHELL. Column densities of HDO and H2O were extracted from individual spectral lines near 3.67 ìm and 3.29 ìm. The slit was positioned N-S on Mars centered at the sub-earth point producing spectral/spatial images. Spectra were extracted at 0.6 arc-sec. intervals and analyzed with models created from GENLN2 atmospheric software; the models include solar Fraunhofer lines, a two-way transmission through Mars' atmosphere, thermal emission from Mars' surface and atmosphere, and a one way transmission through the Earth's atmosphere. From these, latitudinal maps of HDO/H2O were constructed across the observable planet. The HDO/H2O ratios have been found to be larger than those on Earth and they vary with both latitude and season. The higher global HDO/H2O value on Mars compared to that of the Earth is attributed to differential Jeans escape of D and H over geologic time. The ratio in the southern Martian hemisphere is found to be larger than that in the north. This difference could be the signature of Rayleigh distillation, a process in which the different mean temperatures of the polar caps causes a different degree of HDO sequestration resulting in different degrees of enrichment in the polar caps. Detailed results for Ls= 357o in 2006 will be presented when both the HDO and the H2O column densities were obtain from CSHELL data. These will be compared to results from other seasons.Observations of the Martian atmosphere were taken for several seasonal dates at NASA's IRTF using CSHELL. Column densities of HDO and H2O were extracted from individual spectral lines near 3.67 ìm and 3.29 ìm. The slit was positioned N-S on Mars centered at the sub-earth point producing spectral/spatial images. Spectra were extracted at 0.6 arc-sec. intervals and analyzed with models created from GENLN2 atmospheric software; the models include solar Fraunhofer lines, a two-way transmission

  6. Melting phase relations in the system H2O - NH3 at high pressure

    NASA Astrophysics Data System (ADS)

    Sugimura, E.; Hirose, K.; Komabayashi, T.; Ohishi, Y.; Hirao, N.; Dubrovinsky, L. S.

    2012-12-01

    The density models of Uranus and Neptune constrained by their gravitational moments from Voyager mission suggest that mantles of these planets may be predominantly comprised of water (H2O), methane (CH4), and ammonia (NH3). The impurities in pure water would greatly influence the phase relations in the water-rich system expected in the icy mantle, which must be known to construct a plausible planetary model. One of important effects of the impurity is on the liquidus temperature (Tliq), since it decides the actual presence of solid phase within the icy mantle. In order to determine Tliq in H2O-rich region of the H2O - CH4 - NH3 ternary system, the melting phase relations in the H2O - CH4 and H2O - NH3 systems must be accurately known. However, previous melting experiments on each binary system were limited to several gigapascals, thus need to be explored to higher P-T conditions for application in interiors of Uranus and Neptune. We have investigated high-pressure (P) and -temperature (T) melting phase relations in the H2O - NH3 system based on a combination of visual observation and angle-dispersive x-ray diffraction (XRD) measurements at BL10XU, SPring-8. High-P-T conditions were generated in an externally-resistive heated diamond anvil cell (DAC). Starting material was 20wt% NH3 aqueous solution whose composition was checked via Tliq of the solution measured in a DAC at near atmospheric pressure. The aqueous solution was loaded into a gold-lined hole in a preindented rhenium gasket in order to insulate the sample from rhenium. Pressure was determined from the unit-cell volume of gold liner. Melting and freezing of the sample were detected by monitoring disappearance/appearance of diffraction peaks of solid and diffuse scattering of liquids, as well as observing melting/crystallization of crystal grains under microscope. Up to 20 GPa at room temperature, in addition to ice VII, diffraction peaks of bcc-like phase, which is most likely to be the reported phase VI

  7. Crystal structures of Ca(ClO4)2·4H2O and Ca(ClO4)2·6H2O.

    PubMed

    Hennings, Erik; Schmidt, Horst; Voigt, Wolfgang

    2014-12-01

    The title compounds, calcium perchlorate tetra-hydrate and calcium perchlorate hexa-hydrate, were crystallized at low temperatures according to the solid-liquid phase diagram. The structure of the tetra-hydrate consists of one Ca(2+) cation eightfold coordinated in a square-anti-prismatic fashion by four water mol-ecules and four O atoms of four perchlorate tetra-hedra, forming chains parallel to [01-1] by sharing corners of the ClO4 tetra-hedra. The structure of the hexa-hydrate contains two different Ca(2+) cations, each coordinated by six water mol-ecules and two O atoms of two perchlorate tetra-hedra, forming [Ca(H2O)6(ClO4)]2 dimers by sharing two ClO4 tetra-hedra. The dimers are arranged in sheets parallel (001) and alternate with layers of non-coordinating ClO4 tetra-hedra. O-H⋯O hydrogen bonds between the water mol-ecules as donor and ClO4 tetra-hedra and water mol-ecules as acceptor groups lead to the formation of a three-dimensional network in the two structures. Ca(ClO4)2·6H2O was refined as a two-component inversion twin, with an approximate twin component ratio of 1:1 in each of the two structures. PMID:25552974

  8. Slow spin relaxation induced by magnetic field in [NdCo(bpdo)(H2O)4(CN)6]⋅3H2O.

    PubMed

    Vrábel, P; Orendáč, M; Orendáčová, A; Čižmár, E; Tarasenko, R; Zvyagin, S; Wosnitza, J; Prokleška, J; Sechovský, V; Pavlík, V; Gao, S

    2013-05-01

    We report on a comprehensive investigation of the magnetic properties of [NdCo(bpdo)(H2O)4(CN)6]⋅3H2O (bpdo=4, 4'-bipyridine-N,N'-dioxide) by use of electron paramagnetic resonance, magnetization, specific heat and susceptibility measurements. The studied material was identified as a magnet with an effective spin S = 1/2 and a weak exchange interaction J/kB = 25 mK. The ac susceptibility studies conducted at audio frequencies and at temperatures from 1.8 to 9 K revealed that the application of a static magnetic field induces a slow spin relaxation. It is suggested that the relaxation in the magnetic field appears due to an Orbach-like process between the two lowest doublet energy states of the magnetic Nd(3+) ion. The appearance of the slow relaxation in a magnetic field cannot be associated with a resonant phonon trapping. The obtained results suggest that the relaxation is influenced by nuclear spin driven quantum tunnelling which is suppressed by external magnetic field. PMID:23587762

  9. EPR, Endor and DFT Studies on X-Irradiated Single Crystals of L-Lysine HCl 2 H 2O and L-Arginine HCl H2O

    NASA Astrophysics Data System (ADS)

    Zhou, Yiying; Nelson, William H.

    2011-03-01

    When proteins and DNA interact, arginine and lysine are the two amino acids most often in close contact with the DNA. In order to understand the radiation damage to DNA in vivo, which is always associated with protein, it is important to learn the radiation chemistry of arginine and lysine independently, and then complexed to DNA. This work studied X-irradiated single crystals of L- lysine . HCl . 2 H2 O and L- arginine . HCl . H2 O with EPR, ENDOR techniques and DFT calculations. In both crystal types irradiated at 66K, the carboxyl anion radical and the decarboxylation radical were identified. Specifically, the calculations performed on the cluster models for the carboxyl anion radicals reproduced the proton transfers to the carboxyl group from the neighboring molecules through the hydrogen bonds. Moreover, computations supported the identification of one radical type within irradiated arginine as the guanidyl radical anion with an electron trapped by the guanidyl group. Based on the radicals detected in the crystal irradiated at 66K and at 298K, and the annealing experiments from the irradiation at 66K, the mechanisms of the irradiation damage on lysine and arginine were proposed, and the possible effects of irradiated arginine and lysine to the DNA within chromatin were analyzed.

  10. The Frequency Detuning Correction and the Asymmetry of Line Shapes: The Far Wings of H2O-H2O

    NASA Technical Reports Server (NTRS)

    Ma, Q.; Tipping, R. H.; Hansen, James E. (Technical Monitor)

    2002-01-01

    A far-wing line shape theory which satisfies the detailed balance principle is applied to the H2O-H2O system. Within this formalism, two line shapes are introduced, corresponding to band-averages over the positive and negative resonance lines, respectively. Using the coordinate representation, the two line shapes can be obtained by evaluating 11-dimensional integrations whose integrands are a product of two factors. One depends on the interaction between the two molecules and is easy to evaluate. The other contains the density matrix of the system and is expressed as a product of two 3-dimensional distributions associated with the density matrices of the absorber and the perturber molecule, respectively. If most of the populated states are included in the averaging process, to obtain these distributions requires extensive computer CPU time, but only have to be computed once for a given temperature. The 11-dimensional integrations are evaluated using the Monte Carlo method, and in order to reduce the variance, the integration variables are chosen such that the sensitivity of the integrands on them is clearly distinguished.

  11. Shocking H2O Ice: The Role of Phase Changes during Impact Crater Formation

    NASA Astrophysics Data System (ADS)

    Stewart, S. T.; Senft, L. E.; Seifter, A.; Obst, A. W.

    2008-12-01

    New experimental data and cratering calculations illustrate the complex response of H2O ice to shock compression. We present peak and post-shock temperature measurements from shocked H2O ice. In experiments with shock pressures between 8 and 14 GPa, initially ~150 K ice is compressed to a supercritical state. In the time frame of the experiment, the supercritical H2O releases to the saturation vapor curve and does not achieve full decompression. Further decompression requires a significant volume expansion. In general, the time scale of expansion will depend on the internal energy and the surrounding conditions (e.g., confined or unconfined). The temperature data validate a new 5-Phase hydrocode equation of state model for H2O, which includes ice Ih, VI, VII, liquid, and vapor. Using the 5-Phase EOS, we model impact cratering onto icy satellites. After passage of the impact-generated shock wave, material beneath the growing transient crater has a layered composition: vapor, liquid, high- pressure phases (ices VII and VI), and ice Ih. The high pressure phases cannot fully decompress without a large volume increase. Thus, these phases initially unload to the pressure along the phase boundary; this pressurized region affects the excavation flow field. The changes in crater excavation lead to differences in crater size and amount of ejecta compared to excavation in a homogeneous target. The differences are significant for large craters (e.g., complex craters on Ganymede and Callisto). The modified excavation flow field also concentrates highly shocked material in the crater floor. In cases where a large, hot plug is buried during crater collapse, explosions occur as the material cools by transforming to vapor, producing features similar to central pits observed on Ganymede, Callisto, and Mars. The behavior of shocked H2O ice during decompression should lead to a variety of features that depend on the ambient conditions specific to each icy planetary body.

  12. CO2 and H2O diluted oxy-fuel combustion for zero-emission power

    SciTech Connect

    G A Richards; K H Casleton; B T Chorpening

    2005-01-01

    Concerns about climate change have encouraged significant interest in concepts for zero-emission power generation systems. These systems are intended to produce power without releasing CO2 into the atmosphere. One method to achieve this goal is to produce hydrogen from the gasification of fossil or biomass fuels. Using various membrane and reforming technologies, the carbon in the parent fuel can be shifted to CO2 and removed from the fuel stream, followed by direct CO2 sequestration. The hydrogen fuel can be used directly in gas turbines fitted with low-NOx combustors. A second approach to producing zero-emission power is to replace the nitrogen diluent that accompanies conventional combustion in air with either CO2 or H2O. In this concept, CO2 or H2O is added to oxygen to control combustion temperatures in oxygen–fuel reactions. In the absence of nitrogen, the primary combustion products for any hydrocarbon under lean conditions are then simply CO2 and H2O. Thus, merely cooling the exhaust stream condenses the water and produces an exhaust of pure CO2, ready for sequestration. The dilute oxy-fuel combustion strategy can be incorporated in power cycles that are similar to Brayton or Rankine configurations, using CO2 or H2O as the primary diluent respectively. While the relativemerits of the various strategies to zero-emission power are the subject of various technical and economic studies, very little work has focused on defining the combustion issues associated with the dilute oxy-fuel option. In this paper, the expected combustion performance of CO2 and H2O diluted systems are compared. Experimental results from a high-pressure oxy-fuel combustor are also presented.

  13. Effect of ionic strength on ruthenium CMP in H2O2-based slurries

    NASA Astrophysics Data System (ADS)

    Jiang, Liang; He, Yongyong; Li, Yuzhuo; Luo, Jianbin

    2014-10-01

    With the development of ultra-large scale integrated circuits, ruthenium has been selected as one of the most promising barrier metals for copper interconnects to replace traditional Ta/TaN bilayer. This paper mainly investigated the effect of ionic strength on the chemical mechanical polishing performance of ruthenium in H2O2-based slurries. The results show that, the ruthenium removal rate (RR) increases with the increasing concentration of H2O2 due to the formation of ruthenium oxides like Ru(OH)3, RuO2·2H2O and even RuO42-; additionally, the ruthenium RR can be further enhanced with the increase of K+ ionic strength. It is revealed that the added K+ can intensify the electrochemical reactions between H2O2 and the ruthenium surface by increasing the conductivity, meanwhile can also result in the neutralization of the zeta potentials of both silica particles and the ruthenium surface, and thus can lead to the decrease of the electrostatic repulsive force and the increase of the mechanical abrasion intensity between silica particles and the ruthenium surface. Therefore, the ruthenium RR increases with the increase of K+ ionic strength. Furthermore, the effects of K+ ionic strength on the material removal rate (MRR) selectivity of Ru vs. Cu and the galvanic corrosion of Cu/Ru couple are studied. It is found that, in order to achieve higher MRR selectivity than 1.0, KNO3 is preferred for the K+ source; and with H2O2 as the oxidizer, copper galvanic corrosion problem can be effectively suppressed.

  14. Chemistry in glow discharges of H2 / O2 mixtures. Diagnostics and modelling

    PubMed Central

    Jiménez-Redondo, M; Carrasco, E; Herrero, V J; Tanarro, I

    2015-01-01

    The chemistry of low pressure H2 + O2 discharges with different mixture ratios has been studied in a hollow cathode DC reactor. Neutral and positive ion distributions have been measured by mass spectrometry, and Langmuir probes have been used to provide charge densities and electron temperatures. A simple zero order kinetic model including neutral species and positive and negative ions, which takes into account gas-phase and heterogeneous chemistry, has been used to reproduce the global composition of the plasmas over the whole range of mixtures experimentally studied, and allows for the identification of the main physicochemical mechanisms that may explain the experimental results. To our knowledge, no combined experimental and modelling studies of the heavy species kinetics of low pressure H2 + O2 plasmas including ions has been reported before. As expected, apart from the precursors, H2O is detected in considerable amounts. The model also predicts appreciable concentrations of H and O atoms and the OH radical. The relevance of the metastable species O(1D) and O2(a1Δg) is analysed. Concerning the charged species, positive ion distributions are dominated by H3O+ for a wide range of intermediate mixtures, while H3+ and O2+ are the major ions for the higher and lower H2/O2 ratios, respectively. The mixed ions OH+, H2O+ and HO2+ are also observed in small amounts. Negative ions are shown to have a limited relevance in the global chemistry; their main contribution is the reduction of the electron density available for electron impact processes. PMID:26702195

  15. Distillation of H2O from hard-frozen Martian permafrost

    NASA Technical Reports Server (NTRS)

    Zent, A. P.; Gwynne, O.

    1991-01-01

    The authors present a method for distillation of hard-frozen Martian permafrost. A cable-tool is drilled into hard frozem permafrost to a depth of 10 to 20 m. They calculate that a 10 m hole could be drilled in a few days. A 10 m shaft with a diameter equal to the bore is inserted into the hole, and a air tight tent-like structure is erected over the borehole. Photovoltaic cells mounted on the tent supply electrical energy that is dissipated in the shaft. Drilling power can be supplied by other sources. With 1000 watts, the shaft can be heated to near 350 K, producing relatively high temperatures in the vicinity of the borehole. Surrounding H2O is vaporized and diffuses up through the regolith. The authors calculate that a tent of a radius of no more than a few meters would intercept most of the H2O as it diffused to the surface. Calculations suggest that it would require perhaps 30 days to extract H2O from most of the volume drained by this technique. Assuming that the hard frozen regolith is no more than 10 percent ice, the author's calculate that that about 2890 kg of H2O could be extracted in 30 days. Since the nominal requirement for each crew member is about 5 kg/day, one such borehole might be expected to supply enough H2O to maintain a crew of 5 for perhaps 100 days. Additional engineering studies will be done to attempt to improve the capacity or efficiency of this method.

  16. Bacterial Ice Nucleation in Monodisperse D2O and H2O-in-Oil Emulsions.

    PubMed

    Weng, Lindong; Tessier, Shannon N; Smith, Kyle; Edd, Jon F; Stott, Shannon L; Toner, Mehmet

    2016-09-13

    Ice nucleation is of fundamental significance in many areas, including atmospheric science, food technology, and cryobiology. In this study, we investigated the ice-nucleation characteristics of picoliter-sized drops consisting of different D2O and H2O mixtures with and without the ice-nucleating bacteria Pseudomonas syringae. We also studied the effects of commonly used cryoprotectants such as ethylene glycol, propylene glycol, and trehalose on the nucleation characteristics of D2O and H2O mixtures. The results show that the median freezing temperature of the suspension containing 1 mg/mL of a lyophilized preparation of P. syringae is as high as -4.6 °C for 100% D2O, compared to -8.9 °C for 100% H2O. As the D2O concentration increases every 25% (v/v), the profile of the ice-nucleation kinetics of D2O + H2O mixtures containing 1 mg/mL Snomax shifts by about 1 °C, suggesting an ideal mixing behavior of D2O and H2O. Furthermore, all of the cryoprotectants investigated in this study are found to depress the freezing phenomenon. Both the homogeneous and heterogeneous freezing temperatures of these aqueous solutions depend on the water activity and are independent of the nature of the solute. These findings enrich our fundamental knowledge of D2O-related ice nucleation and suggest that the combination of D2O and ice-nucleating agents could be a potential self-ice-nucleating formulation. The implications of self-nucleation include a higher, precisely controlled ice seeding temperature for slow freezing that would significantly improve the viability of many ice-assisted cryopreservation protocols. PMID:27495973

  17. Reducing THMFP by H2O2/UV oxidation for humic acid of small molecular weight.

    PubMed

    Yen, Hsing Yuan; Yen, Li Shuang

    2015-01-01

    In this study, the merits of using H2O2/UV oxidation for reducing trihalomethane formation potential (THMFP), colour, and dissolved organic carbon (DOC) of smaller molecular humic acid were investigated, especially the energy consumption based on EEO. The results show that THMFP decreases by increasing oxidation time, H2O2 dose and UV intensity. The reaction constant in descending order is kColour>kDOC>kTHMFP. Furthermore, EEO shows three trends. First, it decreases as H2O2 dose increases. That is, by increasing the amount of H2O2 dose, the electrical energy efficiency becomes better. Second, EEO,9 W>EEO,13 W, implying that higher UV power would result in a higher electrical energy efficiency. Third, EEO,THMFP>EEO,DOC>EEO,colour. That is, the electric energy efficiency is the best for colour removal, second for DOC removal, and third for THMFP reduction. The operation costs for 90% removal of colour, DOC, and THMFP are from 0.31 to 0.69, from 0.78 to 1.72, and from 1.11 to 2.29 US$/m3, respectively. However, reducing THMs to Taiwan's drinking water standard of 80 µg/L needs only 0.25-0.60 US$/m3. Therefore, the condition with UV of 9 W, H2O2 of 50 mg/L, and oxidation time of 23 min can be applied for THMs reduction as the cost is the smallest of 0.25 US$/m3, even lower than current Taiwan's drinking water price of 0.3 US$/m3. PMID:25518984

  18. Distillation of H2O from hard-frozen Martian permafrost

    NASA Astrophysics Data System (ADS)

    Zent, A. P.; Gwynne, O.

    The authors present a method for distillation of hard-frozen Martian permafrost. A cable-tool is drilled into hard frozem permafrost to a depth of 10 to 20 m. They calculate that a 10 m hole could be drilled in a few days. A 10 m shaft with a diameter equal to the bore is inserted into the hole, and a air tight tent-like structure is erected over the borehole. Photovoltaic cells mounted on the tent supply electrical energy that is dissipated in the shaft. Drilling power can be supplied by other sources. With 1000 watts, the shaft can be heated to near 350 K, producing relatively high temperatures in the vicinity of the borehole. Surrounding H2O is vaporized and diffuses up through the regolith. The authors calculate that a tent of a radius of no more than a few meters would intercept most of the H2O as it diffused to the surface. Calculations suggest that it would require perhaps 30 days to extract H2O from most of the volume drained by this technique. Assuming that the hard frozen regolith is no more than 10 percent ice, the author's calculate that that about 2890 kg of H2O could be extracted in 30 days. Since the nominal requirement for each crew member is about 5 kg/day, one such borehole might be expected to supply enough H2O to maintain a crew of 5 for perhaps 100 days. Additional engineering studies will be done to attempt to improve the capacity or efficiency of this method.

  19. Promotion of CO oxidation on PdO(101) by adsorbed H2O

    NASA Astrophysics Data System (ADS)

    Choi, Juhee; Pan, Li; Mehar, Vikram; Zhang, Feng; Asthagiri, Aravind; Weaver, Jason F.

    2016-08-01

    We investigated the influence of adsorbed H2O on the oxidation of CO on PdO(101) using temperature programmed reaction spectroscopy (TPRS), reflection absorption infrared spectroscopy (RAIRS) and density functional theory (DFT) calculations. We find that water inhibits CO adsorption on PdO(101) by site blocking, but also provides a more facile pathway for CO oxidation compared with the bare oxide surface. In the presence of adsorbed H2O, the oxidation of CO on PdO(101) produces a CO2 TPRS peak that is centered at a temperature ~ 50 K lower than the main CO2 TPRS peak arising from CO oxidation on clean PdO(101) (~ 330 vs. 380 K). RAIRS shows that CO continues to adsorb on atop-Pd sites of PdO(101) when H2O is co-adsorbed, and provides no evidence of other reactive intermediates. DFT calculations predict that the CO oxidation mechanism follows the same steps for CO adsorbed on PdO(101) with and without co-adsorbed H2O, wherein an atop-CO species recombines with an oxygen atom from the oxide surface lattice. According to DFT, hydrogen bonding interactions with adsorbed H2O species stabilize the carboxyl-like transition structure and intermediate that result from the initial recombination of CO and O on the PdO(101) surface. This stabilization lowers the energy barrier for CO oxidation on PdO(101) by ~ 10 kJ/mol, in good agreement with our experimental estimate.

  20. Degradation of selected pharmaceuticals in aqueous solution with UV and UV/H(2)O(2).

    PubMed

    Yuan, Fang; Hu, Chun; Hu, Xuexiang; Qu, Jiuhui; Yang, Min

    2009-04-01

    The degradation of four pharmaceutical compounds (PhACs), ibuprofen (IBU), diphenhydramine (DP), phenazone (PZ), and phenytoin (PHT) was investigated via ultraviolet (UV) photolysis and UV/H(2)O(2) process with a low-pressure (LP) UV lamp. For each PhAC tested, direct photolysis quantum yields at 254 nm were found to be ranging from 6.32 x 10(-2) to 2.79 x 10(-1)molE(-1) at pH 7. The second-order rate constants of the reaction between the PhACs and OH were determined to be from 4.86 x 10(9) to 6.67 x 10(9)M(-1)s(-1) by using a competition kinetic model which utilized para-chlorobenzoic acid (pCBA) as a reference compound. The overall effect of OH radical scavenging from humic acid (HA) and anions HCO(3)(-), NO(3)(-) was measured utilizing R(OH,UV) method through examining the aqueous photodegradation of pCBA as a probe compound. Moreover, these fundamental direct and indirect photolysis parameters were applied in the model prediction for oxidation rate constants of the PhACs in UV/H(2)O(2) process. It was found that the predicted oxidation rate constants approximated the observed ones. The results indicated that the new R(OH,UV) probe compound method was applicable for measuring background OH radical scavenging effects in water treatment process of UV/H(2)O(2). Furthermore, by GC-MS analysis, most of the intermediates created during the photodegradation of the selected PhACs in UV/H(2)O(2) process were identified. For the photodegradation of PZ, a competition mechanism existed between the direct UV photolysis and the oxidation of OH. An appropriate dosage of H(2)O(2) could hinder the occurrence of the direct photolysis. PMID:19232423

  1. Vapor-liquid phase equilibria of potassium chloride-water mixtures: Equation-of-state representation for KCl-H2O and NaCl-H2O

    USGS Publications Warehouse

    Hovey, J.K.; Pitzer, Kenneth S.; Tanger, J.C., IV; Bischoff, J.L.; Rosenbauer, R.J.

    1990-01-01

    Measurements of isothermal vapor-liquid compositions for KCl-H2O as a function of pressure are reported. An equation of state, which was originally proposed by Pitzer and was improved and used by Tanger and Pitzer to fit the vapor-liquid coexistence surface for NaCl-H2O, has been used for representation of the KCl-H2O system from 300 to 410??C. Improved parameters are also reported for NaCl-H2O from 300 to 500??C. ?? 1990 American Chemical Society.

  2. Inventory of H2O in the ancient Martian regolith from Northwest Africa 7034: The important role of Fe oxides

    NASA Astrophysics Data System (ADS)

    Muttik, Nele; McCubbin, Francis M.; Keller, Lindsay P.; Santos, Alison R.; McCutcheon, Whitney A.; Provencio, Paula P.; Rahman, Zia; Shearer, Charles K.; Boyce, Jeremy W.; Agee, Carl B.

    2014-12-01

    Water-rich Martian regolith breccia Northwest Africa (NWA) 7034 was analyzed by Fourier transform infrared spectroscopy and transmission electron microscopy to determine the inventory and phase distribution of H2O (used herein to refer to both molecular H2O and OH- structural components in hydrous minerals). Hydrous Fe oxide phases (hydromaghemite and an unidentified nanocrystalline Fe-bearing oxide phase observed with hydromaghemite) and phyllosilicates (saponite) were identified as the primary mineralogic hosts for H2O with a minor contribution from Cl-rich apatite. Based on mass balance calculations and modal abundances of minerals constrained by powder X-ray diffraction and petrography, we can account for the entire 6000 ppm H2O measured in bulk rock analyses of NWA 7034. This H2O is distributed evenly between hydrous Fe-rich oxides and phyllosilicates, indicating that Fe oxides could be as important as phyllosilicates for H2O storage in Martian surface material.

  3. Adsorption of H2O2 at the surface of Ih ice, as seen from grand canonical Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Picaud, Sylvain; Jedlovszky, Pál

    2014-04-01

    Adsorption of H2O2 at the (0 0 0 1) surface of Ih ice is investigated by GCMC simulations under tropospheric conditions. The results are in qualitative agreement with experimental data and reveal that the main driving force of the adsorption is the formation of new H2O2-H2O2 rather than H2O2-water H-bonds. The isotherm belongs to class III and not even its low pressure part can be described by the Langmuir formalism. At low coverages H2O2 prefers perpendicular alignment to the surface, in which they can form three H-bonds with surface waters. At higher coverages parallel alignment, stabilized by H-bonds between neighbouring H2O2 molecules, becomes increasingly preferred.

  4. IDENTIFICATION OF RESONANCE WAVES IN OPEN WATER CHANNELS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This article presents a procedure to determine the characteristics of open water channels required for controller and filter design, with special focus on the resonance waves. Also, a new simplified model structure for open water channels is proposed. The procedure applies System Identification tool...

  5. OPEN SEGMENT OF INLET CHANNEL, KACHESS RESERVOIR TO REAR, FROM ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    OPEN SEGMENT OF INLET CHANNEL, KACHESS RESERVOIR TO REAR, FROM BERM OVER START OF BURIED CONDUIT SEGMENT OF INLET CHANNEL (6/96), LOOKING NORTHEAST - Kachess Dam, Inlet Channel, Kachess River, 1.5 miles north of Interstate 90, Easton, Kittitas County, WA

  6. Improved oxidative tolerance in suspension-cultured cells of C4-pepctransgenic rice by H2O2 and Ca(2+) under PEG-6000.

    PubMed

    Qian, Baoyun; Li, Xia; Liu, Xiaolong; Wang, Man

    2015-06-01

    To understand the molecular responses of PC (Overexpressing the maize C4-pepc gene, which encodes phosphoenolpyruvate carboxylase (PEPC)), to drought stress at cell level, we analyzed changes in the levels of signaling molecules (hydrogen peroxide (H2O2), calcium ion (Ca(2+)), and nitric oxide (NO)) in suspension-cultured PC and wild-type (WT) rice (Oryza sativa L.) cell under drought stress induced by 20% polyethylene glycol 6000 (PEG-6000). Results demonstrated that PC improved drought tolerance by enhancing antioxidant defense, retaining higher relative water content, survival percentages, and dry weight of cells. In addition, PEPC activity in PC under PEG treatment was strengthened by addition of H2O2 inhibitor, dimethylthiourea (DMTU) and NO synthesis inhibitor, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), respectively, while that in PC was weakened by addition of free calcium chelator, ethylene glycol-bis(b-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) + calcium channel outflow inhibitor, ruthenium red (RR) + plasma membrane channel blocker La(NO3)3, but EGTA + RR did not. Results also showed that NO and Ca(2+) was lying downstream of H2O2 in drought-induced signaling. Calcium ion was also involved in the expression of C4-pepc in PC. These results suggested that PC could improve oxidative tolerance in suspension-cultured cells and the acquisition of this tolerance required downregulation of H2O2 and the entry of extracellular Ca(2+) into cells across the plasma membrane for regulation of PEPC activity and C4-pepc expression. PMID:25231250

  7. Kinetics and mechanisms of degradation of chloroacetonitriles by the UV/H2O2 process.

    PubMed

    Ling, Li; Sun, Jianliang; Fang, Jingyun; Shang, Chii

    2016-08-01

    Haloacetonitriles (HANs) are emerging disinfection by-products (DBPs) that are more toxic than the regulated DBPs and widely found in the chlorinated/chloraminated water. This paper studied kinetics and mechanisms of the degradation of chloroacetonitriles (CANs) by the UV/H2O2 process at pH 6 and 7.5 and H2O2 concentrations of 1 × 10(-3) M, 5 × 10(-3) M and 1 × 10(-2) M. The degradation followed pseudo first-order degradation kinetics. The degradation rate of monochloroacetonitrile (MCAN) remained similar, while those of dichloroacetonitrile (DCAN) and trichloroacetonitrile (TCAN) increased with increasing pH and H2O2 concentrations. The different trends were attributed to the changing contributions of the two major mechanisms: the nucleophilic attack by hydroperoxide ions ( [Formula: see text] ) and the hydroxyl radical (•OH) oxidation. The second-order rate constants of [Formula: see text] towards MCAN, DCAN and TCAN were determined to be 11.8 (±0.62), 4.83 (±0.01) × 10(3), and 2.54 (±0.23) × 10(5) M(-1) s(-1), respectively, while that of •OH were 8.7 × 10(6), 4.4 × 10(6), and < 10(6) M(-1) s(-1), respectively. The degradation of TCAN was mainly attributed to the [Formula: see text] nucleophilic attack, while that of MCAN was dominated by the •OH oxidation. DCAN was degraded by both mechanisms. The nucleophilic attack increased linearly with increasing [Formula: see text] concentration as a result of increasing H2O2 concentration and/or pH, while the •OH oxidation was less dependent on H2O2 concentrations and/or pH. The nucleophilic attack mainly transformed HANs to haloacetamides, while the •OH oxidation dechlorinated HANs. This paper firstly illustrated the importance of the [Formula: see text] nucleophilic attack, in addition to the •OH oxidation, on the CAN degradation in the UV/H2O2 process. PMID:27161887

  8. The physical conditions in IRDC clumps from Herschel/HIFI observations of H2O

    NASA Astrophysics Data System (ADS)

    Shipman, R. F.; van der Tak, F. F. S.; Wyrowski, F.; Herpin, F.; Frieswijk, W.

    2014-10-01

    Context. The earliest phases of high-mass star formation are poorly understood. Aims: Our goal is to determine the physical conditions and kinematic structure of massive starforming cloud clumps. Methods: We analyse H2O 557 GHz line profiles observed with HIFI toward four positions in two infrared-dark cloud clumps. By comparison with ground-based C17O, N2H+, CH3OH, and NH3 line observations, we constrain the volume density and kinetic temperature of the gas and estimate the column density and abundance of H2O and N2H+. Results: The observed water lines are complex with emission and absorption components. The absorption is redshifted and consistent with a cold envelope, while the emission is interpreted as resulting from proto-stellar outflows. The gas density in the clumps is ~107 cm-3. The o-H2O outflow column density is 0.3-3.0 × 1014 cm-2. The o-H2O absorption column density is between 1.5 × 1014 and 2.6 × 1015 cm-2 with cold o-H2O abundances between 1.5 × 10-9 and 3.1 × 10-8. Conclusions: All clumps have high gas densities (~107 cm-3) and display infalling gas. Three of the four clumps have outflows. The clumps form an evolutionary sequence as probed by H2O N2H+, NH3, and CH3OH. We find that G28-MM is the most evolved, followed by G11-MM and then G28-NH3. The least evolved clump is G11-NH3 which shows no signposts of starformation; G11-NH3 is a high-mass pre-stellar core. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia with important participation of NASA.Tables 4, 6, 8, 10, 11, and Appendix A are available in electronic form at http://www.aanda.orgFinal Herschel and APEX data used in the paper (FITS files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/570/A51

  9. Solid organic residues produced by irradiation of hydrocarbon-containing H2O and H2O/NH3 ices - Infrared spectroscopy and astronomical implications

    NASA Technical Reports Server (NTRS)

    Khare, B. N.; Thompson, W. R.; Murray, B. G. J. P. T.; Chyba, C. F.; Sagan, C.

    1989-01-01

    Plasma-discharge irradiations were conducted for the methane clathrate expected in outer solar system satellites and cometary nuclei; also irradiated were ices prepared from other combinations of H2O with CH4, C2H6, or C2H2. Upon evaporation of the yellowish-to-tan irradiated ices, it is found that a colored solid film adheres to the walls of the reaction vessel at room temperature. These organic films are found to exhibit IR band identifiable with alkane, aldehide, alcohol, and perhaps alkene, as well as substituted aromatic functional groups. These spectra are compared with previous studies of UV- or photon-irradiated nonclathrated hydrocarbon-containing ices.

  10. A high temperature equation of state for the H 2O-CaCl 2 and H 2O-MgCl 2 systems

    NASA Astrophysics Data System (ADS)

    Duan, Zhenhao; Moller, Nancy; Weare, John H.

    2006-08-01

    An equation of state (EOS) is developed for salt-water systems in the high temperature range. As an example of the applications, this EOS is parameterized for the calculation of density, immiscibility, and the compositions of coexisting phases in the CaCl 2-H 2O and MgCl 2-H 2