Photodegradation of the antineoplastic cyclophosphamide: a comparative study of the efficiencies of UV/H2O2, UV/Fe2+/H2O2 and UV/TiO2 processes.

PubMed

Lutterbeck, Carlos Alexandre; Machado, Ênio Leandro; Kümmerer, Klaus

2015-02-01

Anticancer drugs are harmful substances that can have carcinogenic, mutagenic, teratogenic, genotoxic, and cytotoxic effects even at low concentrations. More than 50 years after its introduction, the alkylating agent cyclophosphamide (CP) is still one of the most consumed anticancer drug worldwide. CP has been detected in water bodies in several studies and is known as being persistent in the aquatic environment. As the traditional water and wastewater treatment technologies are not able to remove CP from the water, different treatment options such as advanced oxidation processes (AOPs) are under discussion to eliminate these compounds. The present study investigated the degradation of CP by three different AOPs: UV/H2O2, UV/Fe(2+)/H2O2 and UV/TiO2. The light source was a Hg medium-pressure lamp. Prescreening tests were carried out and afterwards experiments based on the optimized conditions were performed. The primary elimination of the parent compounds and the detection of transformation products (TPs) were monitored with LC-UV-MS/MS analysis, whereas the degree of mineralization was monitored by measuring the dissolved organic carbon (DOC). Ecotoxicological assays were carried out with the luminescent bacteria Vibrio fischeri. CP was completely degraded in all treatments and UV/Fe(2+)/H2O2 was the fastest process, followed by UV/H2O2 and UV/TiO2. All the reactions obeyed pseudo-first order kinetics. Considering the mineralization UV/Fe(2+)/H2O2 and UV/TiO2 were the most efficient process with mineralization degrees higher than 85%, whereas UV/H2O2 achieved 72.5% of DOC removal. Five transformation products were formed during the reactions and identified. None of them showed significant toxicity against V. fischeri. Copyright © 2014 Elsevier Ltd. All rights reserved.

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.

Peroxisomal fatty acid oxidation as detected by H2O2 production in intact perfused rat liver.

PubMed Central

Foerster, E C; Fährenkemper, T; Rabe, U; Graf, P; Sies, H

1981-01-01

1. H2O2 formation associated with the metabolism of added fatty acids was quantitatively determined in isolated haemoglobin-free perfused rat liver (non-recirculating system) by two different methods. 2. Organ spectrophotometry of catalase Compound I [Sies & Chance (1970) FEBS Lett. 11, 172-176] was used to detect H2O2 formation (a) by steady-state titration with added hydrogen donor, methanol or (b) by comparison of fatty-acid responses with those of the calibration compound, urate. 3. In the use of the peroxidatic reaction of catalase, [14C]methanol was added as hydrogen donor at an optimal concentration of 1 mM in the presence of 0.2 mM-L-methionine, and 14CO2 production rates were determined. 4. Results obtained by the different methods were similar. 5. The yield of H2O2 formation, expressed as the rate of H2O2 formation in relation to the rate of fatty-acid supply, was less than 1.0 in all cases, indicating that, regardless of chain length, less than one acetyl unit was formed per mol of added fatty acid by the peroxisomal system. In particular, the standard substrate used with isolated peroxisomal preparations (C16:0 fatty acid) gave low yield (close to zero). Long-chain monounsaturated fatty acids exhibit a relatively high yield of H2O2 formation. 6. The hypolipidaemic agent bezafibrate led to slightly increased yields for most of the acids tested, but the yield with oleate was decreased to one-half the original yield. 7. It is concluded that in the intact isolated perfused rat liver the assayable capacity for peroxisomal beta-oxidation is used to only a minor degree. However, the observed rates of H2O2 production with fatty acids can account for a considerable share of the endogenous H2O2 production found in the intact animal. PMID:7317011

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.

[Mechanism and performance of styrene oxidation by O3/H2O2].

PubMed

He, Jue-Cong; Huang, Qian-Ru; Ye, Qi-Hong; Luo, Yu-Wei; Zhang, Zai-Li; Fan, Qing-Juan; Wei, Zai-Shan

2013-10-01

It can produce a large number of free radicals in O3/H2O2, system, ozone and free radical coupling oxidation can improve the styrene removal efficiency. Styrene oxidation by O3/H2O2 was investigated. Ozone dosage, residence time, H2o2 volume fraction, spray density and molar ratio of O3/C8H8 on styrene removal were evaluated. The experimental results showed that styrene removal efficiency achieved 85.7%. The optimal residence time, H2O2, volume fraction, spray density and O3/C8H8 molar ratio were 20. 6 s, 10% , 1.72 m3.(m2.h)-1 and 0.46, respectively. The gas-phase degradation intermediate products were benzaldehyde(C6H5CHO) and benzoic acid (C6H5 COOH) , which were identified by means of gas chromatography-mass spectrometry(GC-MS). The degradation mechanism of styrene is presented.

Age-related differences in cigarette smoke extract-induced H2O2 production by lung endothelial cells.

PubMed

Downs, Charles A; Montgomery, David W; Merkle, Carrie J

2011-11-01

Cigarette smoke causes oxidative stress in the lung resulting in injury and disease. The purpose of this study was to determine if there were age-related differences in cigarette smoke extract (CSE)-induced production of reactive species in single and co-cultures of alveolar epithelial type I (AT I) cells and microvascular endothelial cells harvested from the lungs (MVECLs) of neonatal, young and old male Fischer 344 rats. Cultures of AT I cells and MVECLs grown separately (single culture) and together (co-culture) were exposed to CSE (1, 10, 50, 100%). Cultures were assayed for the production of intracellular reactive oxygen species (ROS), hydroxyl radical (OH), peroxynitrite (ONOO(-)), nitric oxide (NO) and extracellular hydrogen peroxide (H(2)O(2)). Single and co-cultures of AT I cells and MVECLs from all three ages produced minimal intracellular ROS in response to CSE. All ages of MVECLs produced H(2)O(2) in response to CSE, but young MVECLs produced significantly less H(2)O(2) compared to neonatal and old MVECLs. Interestingly, when grown as a co-culture with age-matched AT I cells, neonatal and old MVECLs demonstrated ~50% reduction in H(2)O(2) production in response to CSE. However, H(2)O(2) production in young MVECLs grown as a co-culture with young AT I cells did not change with CSE exposure. To begin investigating for a potential mechanism to explain the reduction in H(2)O(2) production in the co-cultures, we evaluated single and co-cultures for extracellular total antioxidant capacity. We also performed gene expression profiling specific to oxidant and anti-oxidant pathways. The total antioxidant capacity of the AT I cell supernatant was ~5 times greater than that of the MVECLs, and when grown as a co-culture and exposed to CSE (≥ 10%), the total antioxidant capacity of the supernatant was reduced by ~50%. There were no age-related differences in total antioxidant capacity of the cell supernatants. Gene expression profiling found eight genes to be

Direct Z-scheme TiO2/CdS hierarchical photocatalyst for enhanced photocatalytic H2-production activity

NASA Astrophysics Data System (ADS)

Meng, Aiyun; Zhu, Bicheng; Zhong, Bo; Zhang, Liuyang; Cheng, Bei

2017-11-01

Photocatalytic H2 evolution, which utilizes solar energy via water splitting, is a promising route to deal with concerns about energy and environment. Herein, a direct Z-scheme TiO2/CdS binary hierarchical photocatalyst was fabricated via a successive ionic layer adsorption and reaction (SILAR) technique, and photocatalytic H2 production was measured afterwards. The as-prepared TiO2/CdS hybrid photocatalyst exhibited noticeably promoted photocatalytic H2-production activity of 51.4 μmol h-1. The enhancement of photocatalytic activity was ascribed to the hierarchical structure, as well as the efficient charge separation and migration from TiO2 nanosheets to CdS nanoparticles (NPs) at their tight contact interfaces. Moreover, the direct Z-scheme photocatalytic reaction mechanism was demonstrated to elucidate the improved photocatalytic performance of TiO2/CdS composite photocatalyst. The photoluminescence (PL) analysis of hydroxyl radicals were conducted to provide clues for the direct Z-scheme mechanism. This work provides a facile route for the construction of redox mediator-free Z-scheme photocatalytic system for photocatalytic water splitting.

A Tale of Two Gases: Isotope Effects Associated with the Enzymatic Production of H2 and N2O

NASA Astrophysics Data System (ADS)

Yang, H.; Gandhi, H.; Kreuzer, H. W.; Moran, J.; Hill, E. A.; McQuarters, A.; Lehnert, N.; Ostrom, N. E.; Hegg, E. L.

2014-12-01

Stable isotopes can provide considerable insight into enzymatic mechanisms and fluxes in various biological processes. In our studies, we used stable isotopes to characterize both enzyme-catalyzed H2 and N2O production. H2 is a potential alternative clean energy source and also a key metabolite in many microbial communities. Biological H2 production is generally catalyzed by hydrogenases, enzymes that combine protons and electrons to produce H2 under anaerobic conditions. In our study, H isotopes and fractionation factors (α) were used to characterize two types of hydrogenases: [FeFe]- and [NiFe]-hydrogenases. Due to differences in the active site, the α associated with H2 production for [FeFe]- and [NiFe]-hydrogenases separated into two distinct clusters (αFeFe > αNiFe). The calculated kinetic isotope effects indicate that hydrogenase-catalyzed H2 production has a preference for light isotopes, consistent with the relative bond strengths of O-H and H-H bonds. Interestingly, the isotope effects associated with H2 consumption and H2-H2O exchange reactions were also characterized, but in this case no specific difference was observed between the different enzymes. N2O is a potent greenhouse gas with a global warming potential 300 times that of CO2, and the concentration of N2O is currently increasing at a rate of ~0.25% per year. Thus far, bacterial and fungal denitrification processes have been identified as two of the major sources of biologically generated N2O. In this study, we measured the δ15N, δ18O, δ15Nα (central N atom in N2O), and δ15Nβ (terminal N atom in N2O) of N2O generated by purified fungal P450 nitric oxide reductase (P450nor) from Histoplasma capsulatum. We observed normal isotope effects for δ18O and δ15Nα, and inverse isotope effects for bulk δ15N (the average of Nα and Nβ) and δ15Nβ. The observed isotope effects have been used in conjunction with DFT calculations to provide important insight into the mechanism of P450nor. Similar

The vibration-rotation-tunneling levels of N2-H2O and N2-D2O.

PubMed

Wang, Xiao-Gang; Carrington, Tucker

2015-07-14

In this paper, we report vibration-rotation-tunneling levels of the van der Waals clusters N2-H2O and N2-D2O computed from an ab initio potential energy surface. The only dynamical approximation is that the monomers are rigid. We use a symmetry adapted Lanczos algorithm and an uncoupled product basis set. The pattern of the cluster's levels is complicated by splittings caused by H-H exchange tunneling (larger splitting) and N-N exchange tunneling (smaller splitting). An interesting result that emerges from our calculation is that whereas in N2-H2O, the symmetric H-H tunnelling state is below the anti-symmetric H-H tunnelling state for both K = 0 and K = 1, the order is reversed in N2-D2O for K = 1. The only experimental splitting measurements are the D-D exchange tunneling splittings reported by Zhu et al. [J. Chem. Phys. 139, 214309 (2013)] for N2-D2O in the v2 = 1 region of D2O. Due to the inverted order of the split levels, they measure the sum of the K = 0 and K = 1 tunneling splittings, which is in excellent agreement with our calculated result. Other splittings we predict, in particular those of N2-H2O, may guide future experiments.

The vibration-rotation-tunneling levels of N2-H2O and N2-D2O

NASA Astrophysics Data System (ADS)

Wang, Xiao-Gang; Carrington, Tucker

2015-07-01

In this paper, we report vibration-rotation-tunneling levels of the van der Waals clusters N2-H2O and N2-D2O computed from an ab initio potential energy surface. The only dynamical approximation is that the monomers are rigid. We use a symmetry adapted Lanczos algorithm and an uncoupled product basis set. The pattern of the cluster's levels is complicated by splittings caused by H-H exchange tunneling (larger splitting) and N-N exchange tunneling (smaller splitting). An interesting result that emerges from our calculation is that whereas in N2-H2O, the symmetric H-H tunnelling state is below the anti-symmetric H-H tunnelling state for both K = 0 and K = 1, the order is reversed in N2-D2O for K = 1. The only experimental splitting measurements are the D-D exchange tunneling splittings reported by Zhu et al. [J. Chem. Phys. 139, 214309 (2013)] for N2-D2O in the v2 = 1 region of D2O. Due to the inverted order of the split levels, they measure the sum of the K = 0 and K = 1 tunneling splittings, which is in excellent agreement with our calculated result. Other splittings we predict, in particular those of N2-H2O, may guide future experiments.

Photodegradation of pharmaceuticals and personal care products during UV and UV/H2O2 treatments.

PubMed

Kim, Ilho; Yamashita, Naoyuki; Tanaka, Hiroaki

2009-10-01

Photodegradation characteristics of pharmaceuticals and personal care products (PPCPs) and the effectiveness of H(2)O(2) addition for PPCPs photodegradation during UV treatment were examined in this study. Average k (1st order rate constant) value for all the PPCPs investigated increased by a factor of 1.3 by H(2)O(2) addition during UV treatment using biologically treated water (TW) spiked with the 30 PPCPs. Therefore, the effectiveness of H(2)O(2) addition for PPCPs removal during UV treatment in real wastewater treatment process was expected. It could be also known that H(2)O(2) addition would improve photodegradation rates of PPCPs highly resistant for UV treatment such as DEET, ethenzamide and theophylline. UV dose required for 90% degradation of each PPCP was calculated from k values obtained in UV and UV/H(2)O(2) treatment experiments using TW spiked with 30 PPCPs. For UV treatment, UV dose required for degrading each PPCP by 90% of initial concentration ranged from 38 mJ cm(-2) to 5644 mJ cm(-2), indicating that most of PPCPs will not be removed sufficiently in UV disinfection process in wastewater treatment plant. For UV/H(2)O(2) treatment, all the PPCPs except seven PPCPs including cyclophosphamide and 2-QCA were degraded by more than 90% by UV irradiation for 30 min (UV dose: 691 mJ cm(-2)), indicating that H(2)O(2) addition during UV treatment will be highly effective for improving the degradation of PPCPs by UV, even though much higher UV dose is still necessary comparing to for UV disinfection.

Tracking the energy flow in the hydrogen exchange reaction OH + H2O → H2O + OH.

PubMed

Zhu, Yongfa; Ping, Leilei; Bai, Mengna; Liu, Yang; Song, Hongwei; Li, Jun; Yang, Minghui

2018-05-09

The prototypical hydrogen exchange reaction OH + H2O → H2O + OH has attracted considerable interest due to its importance in a wide range of chemically active environments. In this work, an accurate global potential energy surface (PES) for the ground electronic state was developed based on ∼44 000 ab initio points at the level of UCCSD(T)-F12a/aug-cc-pVTZ. The PES was fitted using the fundamental invariant-neural network method with a root mean squared error of 4.37 meV. The mode specific dynamics was then studied by the quasi-classical trajectory method on the PES. Furthermore, the normal mode analysis approach was employed to calculate the final vibrational state distribution of the product H2O, in which a new scheme to acquire the Cartesian coordinates and momenta of each atom in the product molecule from the trajectories was proposed. It was found that, on one hand, excitation of either the symmetric stretching mode or the asymmetric stretching mode of the reactant H2O promotes the reaction more than the translational energy, which can be rationalized by the sudden vector projection model. On the other hand, the relatively higher efficacy of exciting the symmetric stretching mode than that of the asymmetric stretching mode is caused by the prevalence of the indirect mechanism at low collision energies and the stripping mechanism at high collision energies. In addition, the initial collision energy turns ineffectively into the vibrational energy of the products H2O and OH while a fraction of the energy transforms into the rotational energy of the product H2O. Fundamental excitation of the stretching modes of H2O results in the product H2O having the highest population in the fundamental state of the asymmetric stretching mode, followed by the ground state and the fundamental state of the symmetric stretching mode.

Influence of Background H2O on the Collision-Induced Dissociation Products Generated from [UO2NO3]+

NASA Astrophysics Data System (ADS)

Van Stipdonk, Michael J.; Iacovino, Anna; Tatosian, Irena

2018-04-01

Developing a comprehensive understanding of the reactivity of uranium-containing species remains an important goal in areas ranging from the development of nuclear fuel processing methods to studies of the migration and fate of the element in the environment. Electrospray ionization (ESI) is an effective way to generate gas-phase complexes containing uranium for subsequent studies of intrinsic structure and reactivity. Recent experiments by our group have demonstrated that the relatively low levels of residual H2O in a 2-D, linear ion trap (LIT) make it possible to examine fragmentation pathways and reactions not observed in earlier studies conducted with 3-D ion traps (Van Stipdonk et al. J. Am. Soc. Mass Spectrom. 14, 1205-1214, 2003). In the present study, we revisited the dissociation of complexes composed of uranyl nitrate cation [UVIO2(NO3)]+ coordinated by alcohol ligands (methanol and ethanol) using the 2-D LIT. With relatively low levels of background H2O, collision-induced dissociation (CID) of [UVIO2(NO3)]+ primarily creates [UO2(O2)]+ by the ejection of NO. However, CID (using He as collision gas) of [UVIO2(NO3)]+ creates [UO2(H2O)]+ and UO2 + when the 2-D LIT is used with higher levels of background H2O. Based on the results presented here, we propose that product ion spectrum in the previous experiments was the result of a two-step process: initial formation of [UVIO2(O2)]+ followed by rapid exchange of O2 for H2O by ion-molecule reaction. Our experiments illustrate the impact of residual H2O in ion trap instruments on the product ions generated by CID and provide a more accurate description of the intrinsic dissociation pathway for [UVIO2(NO3)]+. [Figure not available: see fulltext.

Influence of experimental parameters on sonochemistry dosimetries: KI oxidation, Fricke reaction and H2O2 production.

PubMed

Merouani, Slimane; Hamdaoui, Oualid; Saoudi, Fethi; Chiha, Mahdi

2010-06-15

Central events of the ultrasonic action are the cavitation bubbles that can be considered as microreactors. Adiabatic collapse of cavitation bubbles leads to the formation of reactive species such as hydroxyl radicals (*OH), hydrogen peroxide (H(2)O(2)) and hydroperoxyl radicals (HOO*). Several chemical methods were used to detect the production of these reactive moieties in sonochemistry. In this work, the influence of several operational parameters on the sonochemistry dosimetries namely KI oxidation, Fricke reaction and H(2)O(2) production using 300 kHz ultrasound was investigated. The main experimental parameters showing significant effect in KI oxidation dosimetry were initial KI concentration, acoustic power and pH. The solution temperature showed restricted influence on KI oxidation. The acoustic power and liquid temperature highly affected Fricke reaction dosimetry. Operational conditions having important influence on H(2)O(2) formation were acoustic power, solution temperature and pH. For the three tested dosimetries, the sonochemical efficiency was independent of liquid volume. Copyright 2010 Elsevier B.V. All rights reserved.

New metal-organic frameworks of [M(C6H5O7)(C6H6O7)(C6H7O7)(H2O)] . H2O (M=La, Ce) and [Ce2(C2O4)(C6H6O7)2] . 4H2O

NASA Astrophysics Data System (ADS)

Weng, Sheng-Feng; Wang, Yun-Hsin; Lee, Chi-Shen

2012-04-01

Two novel materials, [M(C6H5O7)(C6H6O7)(C6H7O7)(H2O)] . H2O (M=La(1a), Ce(1b)) and [Ce2(C2O4)(C6H6O7)2] . 4H2O (2), with a metal-organic framework (MOF) were prepared with hydrothermal reactions and characterized with photoluminescence, magnetic susceptibility, thermogravimetric analysis and X-ray powder diffraction in situ. The crystal structures were determined by single-crystal X-ray diffraction. Compound 1 crystallized in triclinic space group P1¯ (No. 2); compound 2 crystallized in monoclinic space group P21/c (No. 14). The structure of 1 is built from a 1D MOF, composed of deprotonated citric ligands of three kinds. Compound 2 contains a 2D MOF structure consisting of citrate and oxalate ligands; the oxalate ligand arose from the decomposition in situ of citric acid in the presence of CuII ions. Photoluminescence spectra of compounds 1b and 2 revealed transitions between the 5d1 excited state and two levels of the 4f1 ground state (2F5/2 and 2F7/2). Compounds 1b and 2 containing CeIII ion exhibit a paramagnetic property with weak antiferromagnetic interactions between the two adjacent magnetic centers.

Exploration of H2O-CO2 Solubility in Alkali Basalt at low-H2O

NASA Astrophysics Data System (ADS)

Roggensack, K.; Allison, C. M.; Clarke, A. B.

2017-12-01

A number of recent experimental studies have found conflicting evidence for and against the influence of H2O on CO2 solubility in basalt and alkali-rich mafic magma (e.g. Behrens et al., 2009; Shishkina et al., 2010;2014; Iacono-Marziano et al., 2012). Some of the uncertainty is due to the error with spectroscopic determination (FTIR) of carbon and the challenge of controlling H2O abundance in experiments. It's been widely observed that even experimental capsules without added H2O may produce hydrous glasses containing several wt.% H2O. We conducted fluid-saturated, mixed-fluid (H2O-CO2) experiments to determine the solubility in alkali basalt with particular emphasis on conditions at low-H2O. To limit possible H2O contamination, materials were dried prior to loading and experimental capsules were sealed under vacuum. Experiments were run using a piston-cylinder, in Pt (pre-soaked in Fe) or AuPd capsules and operating at pressures from 400 to 600 MPa. Post-run the capsules were punctured under vacuum and fluids were condensed, separated, and measured by mercury manometry. A comparison between two experiments run at the same temperature and pressure conditions but with different fluid compositions illustrates the correlation between carbonate and H2O solubility. Uncertainties associated with using concentrations calculated from FTIR data can be reduced by directly comparing analyses on wafers of similar thickness. We observe that the experiment with greater H2O absorbance also has a higher carbonate absorbance than the experiment with lower H2O absorbance. Since the experiments were run at the same pressure, the experiment with more water-rich fluid, and higher dissolved H2O, has lower CO2 fugacity, but surprisingly has higher dissolved CO2 content. Overall, the results show two distinct trends. Experiments conducted at low-H2O (0.5 to 0.8 wt.%) show lower dissolved CO2 than those conducted at moderate-H2O (2 to 3 wt.%) at similar CO2 fugacity. These data show that

The denitrification paradox: The role of O2 in sediment N2O production

NASA Astrophysics Data System (ADS)

Barnes, Jonathan; Upstill-Goddard, Robert C.

2018-01-01

We designed a novel laboratory sediment flux chamber in which we maintained the headspace O2 partial pressure at preselected values, allowing us to experimentally regulate "in-situ" O2 to evaluate its role in net N2O production by an intertidal estuarine sediment (Tyne, UK). In short-term (30 h) incubations with 10 L of overlying estuarine water (∼3 cm depth) and headspace O2 regulation (headspace: sediment/water ratio ∼9:1), net N2O production was highest at 1.2% O2 (sub-oxic; 32.3 nmol N2O m-2 d-1), an order of magnitude higher than at either 0.0% (anoxic; 2.5 N2O nmol m-2 d-1) or 20.85% (ambient; 2.3 nmol N2O m-2 d-1) O2. In a longer-term sealed incubation (∼490 h) without O2 control, time-dependent behaviour of N2O in the tank headspace was highly non-linear with time, showing distinct phases: (i) an initial period of no or little change in O2 or N2O up to ∼ 100 h; (ii) a quasi-linear, inverse correlation between O2 and N2O to ∼360 h, in which O2 declined to ∼2.1% and N2O rose to ∼7800 natm; (iii) over the following 50 h a slower O2 decline, to ∼1.1%, and a more rapid N2O increase, to ∼12000 natm; (iv) over the next 24 h a slowed O2 decline towards undetectable levels and a sharp fall in N2O to ∼4600 natm; (iv) a continued N2O decrease at zero O2, to ∼3000 natm by ∼ 490 h. These results show clearly that rapid N2O consumption (∼115 nmol m-2 d-1), presumably via heterotrophic denitrification (HD), occurs under fully anoxic conditions and therefore that N2O production, which was optimal for sub-oxic O2, results from other nitrogen transformation processes. In experiments in which we amended sediment overlying water to either 1 mM NH4+ or 1 mM NO3-, N2O production rates were 2-134 nmol N2O m-2 d-1 (NH4+ addition) and 0.4-2.2 nmol N2O m-2 d-1 (NO3- addition). We conclude that processes involving NH4+ oxidation (nitrifier nitrification; nitrifier denitrification; nitrification-coupled denitrification) are principally responsible for N2O

The effect of ZnO addition on H2O activation over Co/ZrO2 catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davidson, Stephen D.; Sun, Junming; Wang, Yong

The effect of ZnO addition on the dissociation of H2O and subsequent effects on cobalt oxidation state and ethanol reaction pathway were investigated over Co/ZrO2 catalyst during ethanol steam reforming (ESR). Catalyst physical properties were characterized by BET, XRD, and TEM. To characterize the catalysts ability to dissociate H2O, Raman spectroscopy, H2O-TPO, and pulsed H2O oxidation coupled with H2-TPR were used. It was found that the addition of ZnO to cobalt supported on ZrO2 decreased the activity for H2O dissociation, leading to a lower degree of cobalt oxidation. The decreased H2O dissociation was also found to affect the reaction pathway,more » evidenced by a shift in liquid product selectivity away from acetone and towards acetaldehyde.« less

Solar kerosene from H2O and CO2

NASA Astrophysics Data System (ADS)

Furler, P.; Marxer, D.; Scheffe, J.; Reinalda, D.; Geerlings, H.; Falter, C.; Batteiger, V.; Sizmann, A.; Steinfeld, A.

2017-06-01

The entire production chain for renewable kerosene obtained directly from sunlight, H2O, and CO2 is experimentally demonstrated. The key component of the production process is a high-temperature solar reactor containing a reticulated porous ceramic (RPC) structure made of ceria, which enables the splitting of H2O and CO2 via a 2-step thermochemical redox cycle. In the 1st reduction step, ceria is endo-thermally reduced using concentrated solar radiation as the energy source of process heat. In the 2nd oxidation step, nonstoichiometric ceria reacts with H2O and CO2 to form H2 and CO - syngas - which is finally converted into kerosene by the Fischer-Tropsch process. The RPC featured dual-scale porosity for enhanced heat and mass transfer: mm-size pores for volumetric radiation absorption during the reduction step and μm-size pores within its struts for fast kinetics during the oxidation step. We report on the engineering design of the solar reactor and the experimental demonstration of over 290 consecutive redox cycles for producing high-quality syngas suitable for the processing of liquid hydrocarbon fuels.

Nanostructured N-doped TiO2 marigold flowers for an efficient solar hydrogen production from H2S

NASA Astrophysics Data System (ADS)

Chaudhari, Nilima S.; Warule, Sambhaji S.; Dhanmane, Sushil A.; Kulkarni, Milind V.; Valant, Matjaz; Kale, Bharat B.

2013-09-01

Nitrogen-doped TiO2 nanostructures in the form of marigold flowers have been synthesized for the first time using a facile solvothermal method. The structural analysis has shown that such an N-doped TiO2 system crystallizes in the anatase structure. The optical absorption spectra have clearly shown the shift in the absorption edge towards the visible-light range, which indicates successful nitrogen doping. The nitrogen doping has been further confirmed by photoluminescence and photoemission spectroscopy. Microscopy studies have shown the thin nanosheets (petals) of N-TiO2 with a thickness of ~2-3 nm, assembled in the form of the marigold flower with a high surface area (224 m2 g-1). The N-TiO2 nanostructure with marigold flowers is an efficient photocatalyst for the decomposition of H2S and production of hydrogen under solar light. The maximum hydrogen evolution obtained is higher than other known N-TiO2 systems. It is noteworthy that photohydrogen production using the unique marigold flowers of N-TiO2 from abundant H2S under solar light is hitherto unattempted. The proposed synthesis method can also be utilized to design other hierarchical nanostructured N-doped metal oxides.Nitrogen-doped TiO2 nanostructures in the form of marigold flowers have been synthesized for the first time using a facile solvothermal method. The structural analysis has shown that such an N-doped TiO2 system crystallizes in the anatase structure. The optical absorption spectra have clearly shown the shift in the absorption edge towards the visible-light range, which indicates successful nitrogen doping. The nitrogen doping has been further confirmed by photoluminescence and photoemission spectroscopy. Microscopy studies have shown the thin nanosheets (petals) of N-TiO2 with a thickness of ~2-3 nm, assembled in the form of the marigold flower with a high surface area (224 m2 g-1). The N-TiO2 nanostructure with marigold flowers is an efficient photocatalyst for the decomposition of H2S and

Decreased N2O reduction by low soil pH causes high N2O emissions in a riparian ecosystem.

PubMed

Van den Heuvel, R N; Bakker, S E; Jetten, M S M; Hefting, M M

2011-05-01

Quantification of harmful nitrous oxide (N(2)O) emissions from soils is essential for mitigation measures. An important N(2)O producing and reducing process in soils is denitrification, which shows deceased rates at low pH. No clear relationship between N(2)O emissions and soil pH has yet been established because also the relative contribution of N(2)O as the denitrification end product decreases with pH. Our aim was to show the net effect of soil pH on N(2)O production and emission. Therefore, experiments were designed to investigate the effects of pH on NO(3)(-) reduction, N(2)O production and reduction and N(2) production in incubations with pH values set between 4 and 7. Furthermore, field measurements of soil pH and N(2)O emissions were carried out. In incubations, NO(3)(-) reduction and N(2) production rates increased with pH and net N(2)O production rate was highest at pH 5. N(2)O reduction to N(2) was halted until NO(3)(-) was depleted at low pH values, resulting in a built up of N(2)O. As a consequence, N(2)O:N(2) production ratio decreased exponentially with pH. N(2)O reduction appeared therefore more important than N(2)O production in explaining net N(2)O production rates. In the field, a negative exponential relationship for soil pH against N(2)O emissions was observed. Soil pH could therefore be used as a predictive tool for average N(2)O emissions in the studied ecosystem. The occurrence of low pH spots may explain N(2)O emission hotspot occurrence. Future studies should focus on the mechanism behind small scale soil pH variability and the effect of manipulating the pH of soils. © 2011 Blackwell Publishing Ltd.

Reactions of CH3SH and CH3SSCH3 with gas-phase hydrated radical anions (H2O)n(•-), CO2(•-)(H2O)n, and O2(•-)(H2O)n.

PubMed

Höckendorf, Robert F; Hao, Qiang; Sun, Zheng; Fox-Beyer, Brigitte S; Cao, Yali; Balaj, O Petru; Bondybey, Vladimir E; Siu, Chi-Kit; Beyer, Martin K

2012-04-19

The chemistry of (H(2)O)(n)(•-), CO(2)(•-)(H(2)O)(n), and O(2)(•-)(H(2)O)(n) with small sulfur-containing molecules was studied in the gas phase by Fourier transform ion cyclotron resonance mass spectrometry. With hydrated electrons and hydrated carbon dioxide radical anions, two reactions with relevance for biological radiation damage were observed, cleavage of the disulfide bond of CH(3)SSCH(3) and activation of the thiol group of CH(3)SH. No reactions were observed with CH(3)SCH(3). The hydrated superoxide radical anion, usually viewed as major source of oxidative stress, did not react with any of the compounds. Nanocalorimetry and quantum chemical calculations give a consistent picture of the reaction mechanism. The results indicate that the conversion of e(-) and CO(2)(•-) to O(2)(•-) deactivates highly reactive species and may actually reduce oxidative stress. For reactions of (H(2)O)(n)(•-) with CH(3)SH as well as CO(2)(•-)(H(2)O)(n) with CH(3)SSCH(3), the reaction products in the gas phase are different from those reported in the literature from pulse radiolysis studies. This observation is rationalized with the reduced cage effect in reactions of gas-phase clusters. © 2012 American Chemical Society

Cross section data sets for electron collisions with H2, O2, CO, CO2, N2O and H2O

NASA Astrophysics Data System (ADS)

Anzai, K.; Kato, H.; Hoshino, M.; Tanaka, H.; Itikawa, Y.; Campbell, L.; Brunger, M. J.; Buckman, S. J.; Cho, H.; Blanco, F.; Garcia, G.; Limão-Vieira, P.; Ingólfsson, O.

2012-02-01

We review earlier cross section data sets for electron-collisions with H2, O2, CO, CO2, H2O and N2O, updated here by experimental results for their electronic states. Based on our recent measurements of differential cross sections for the electronic states of those molecules, integral cross sections (ICSs) are derived by applying a generalized oscillator strength analysis and then assessed against theory (BE f-scaling [Y.-K. Kim, J. Chem. Phys. 126, 064305 (2007)]). As they now represent benchmark electronic state cross sections, those ICSs for the above molecules are added into the original cross section sets taken from the data reviews for H2, O2, CO2 and H2O (the Itikawa group), and for CO and N2O (the Zecca group).

Expansion of antimonato polyoxovanadates with transition metal complexes: (Co(N3C5H15)2)2[{Co(N3C5H15)2}V15Sb6O42(H2O)]·5H2O and (Ni(N3C5H15)2)2[{Ni(N3C5H15)2}V15Sb6O42(H2O)]·8H2O.

PubMed

Antonova, Elena; Näther, Christian; Kögerler, Paul; Bensch, Wolfgang

2012-02-20

Two new polyoxovanadates (Co(N(3)C(5)H(15))(2))(2)[{Co(N(3)C(5)H(15))(2)}V(15)Sb(6)O(42)(H(2)O)]·5H(2)O (1) and (Ni(N(3)C(5)H(15))(2))(2)[{Ni(N(3)C(5)H(15))(2)}V(15)Sb(6)O(42)(H(2)O)]·8H(2)O (2) (N(3)C(5)H(15) = N-(2-aminoethyl)-1,3-propanediamine) were synthesized under solvothermal conditions and structurally characterized. In both structures the [V(15)Sb(6)O(42)(H(2)O)](6-) shell displays the main structural motif, which is strongly related to the {V(18)O(42)} archetype cluster. Both compounds crystallize in the triclinic space group P1 with a = 14.3438(4), b = 16.6471(6), c = 18.9186(6) Å, α = 87.291(3)°, β = 83.340(3)°, γ = 78.890(3)°, and V = 4401.4(2) Å(3) (1) and a = 14.5697(13), b = 15.8523(16), c = 20.2411(18) Å, α = 86.702(11)°, β = 84.957(11)°, γ = 76.941(11)°, and V = 4533.0(7) Å(3) (2). In the structure of 1 the [V(15)Sb(6)O(42)(H(2)O)](6-) cluster anion is bound to a [Co(N(3)C(5)H(15))(2)](2+) complex via a terminal oxygen atom. In the Co(2+)-centered complex, one of the amine ligands coordinates in tridentate mode and the second one in bidentate mode to form a strongly distorted CoN(5)O octahedron. Similarly, in compound 2 an analogous NiN(5)O complex is joined to the [V(15)Sb(6)O(42)(H(2)O)](6-) anion via the same attachment mode. A remarkable difference between the two compounds is the orientation of the noncoordinated propylamine group leading to intermolecular Sb···O contacts in 1 and to Sb···N interactions in 2. In the solid-state lattices of 1 and 2, two additional [M(N(3)C(5)H(15))(2)](2+) complexes act as countercations and are located between the [{M(N(3)C(5)H(15))(2)}V(15)Sb(6)O(42)(H(2)O)](4-) anions. Between the anions and cations strong N-H···O hydrogen bonds are observed. In both compounds the clusters are stacked along the b axis in an ABAB fashion with cations and water molecules occupying the space between the clusters. Magnetic characterization demonstrates that the Ni(2+) and Co(2+) cations do not

The pH dependency of N-converting enzymatic processes, pathways and microbes: effect on net N2 O production.

PubMed

Blum, Jan-Michael; Su, Qingxian; Ma, Yunjie; Valverde-Pérez, Borja; Domingo-Félez, Carlos; Jensen, Marlene Mark; Smets, Barth F

2018-05-01

Nitrous oxide (N 2 O) is emitted during microbiological nitrogen (N) conversion processes, when N 2 O production exceeds N 2 O consumption. The magnitude of N 2 O production vs. consumption varies with pH and controlling net N 2 O production might be feasible by choice of system pH. This article reviews how pH affects enzymes, pathways and microorganisms that are involved in N-conversions in water engineering applications. At a molecular level, pH affects activity of cofactors and structural elements of relevant enzymes by protonation or deprotonation of amino acid residues or solvent ligands, thus causing steric changes in catalytic sites or proton/electron transfer routes that alter the enzymes' overall activity. Augmenting molecular information with, e.g., nitritation or denitrification rates yields explanations of changes in net N 2 O production with pH. Ammonia oxidizing bacteria are of highest relevance for N 2 O production, while heterotrophic denitrifiers are relevant for N 2 O consumption at pH > 7.5. Net N 2 O production in N-cycling water engineering systems is predicted to display a 'bell-shaped' curve in the range of pH 6.0-9.0 with a maximum at pH 7.0-7.5. Net N 2 O production at acidic pH is dominated by N 2 O production, whereas N 2 O consumption can outweigh production at alkaline pH. Thus, pH 8.0 may be a favourable pH set-point for water treatment applications regarding net N 2 O production. © 2018 Society for Applied Microbiology and John Wiley & Sons Ltd.

Preparation and characterization of magnetic CsH{sub 2}PW{sub 12}O{sub 40}/Fe–SiO{sub 2} nanocatalysts for biodiesel production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feyzi, Mostafa, E-mail: Dalahoo2011@yahoo.com; Nanoscience and Nanotechnology Research Center; Nourozi, Leila

Graphical abstract: In this study, a series of magnetic CsH{sub 2}PW{sub 12}O{sub 40}/Fe–SiO{sub 2} nanocatalysts were prepared and tested for biodiesel production. The best operational conditions were CH3OH/oil = 12/1 at 60 °C with mechanical stirring, the biodiesel yield reaches to 81% in 4 h. Also notably, recovery of the catalyst can be achieved easily with the help of an external magnet with no need for expensive ultracentrifugation. - Highlights: • Effects of preparation conditions for biodiesel production were studied. • The CsH{sub 2}PW{sub 12}O{sub 40}/Fe–SiO{sub 2} catalyst is efficient catalyst for biodiesel production. • The reaction conditions were foundmore » methanol/oil = 12/1, T = 60 °C. - Abstract: The magnetic CsH{sub 2}PW{sub 12}O{sub 40}/Fe–SiO{sub 2} nanocatalysts were prepared via combination of sol–gel and impregnation methods. The effects of different H{sub 3}PW{sub 12}O{sub 40}/(Fe–SiO{sub 2}) weight percentage, loading of Cs as a promotor and calcination conditions on the catalytic performance has been studied. It was found that the catalyst with H{sub 3}PW{sub 12}O{sub 40}/Fe–SiO{sub 2} = 4 wt.% and Cs = 2 wt.% is an optimal catalyst for biodiesel production. The activity of optimal catalyst was studied in different operational conditions. The best operational conditions were CH{sub 3}OH/oil = 12/1 at 60 °C with mechanical stirring rate of 500 rpm and the biodiesel yield reaches to 81% in 4 h. Characterization of catalysts was carried out by using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), vibrating sample magnetometry (VSM), N{sub 2} adsorption–desorption measurements methods, Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC)« less

CO2 splitting by H2O to CO and O2 under UV light in TiMCM-41silicate sieve

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Wenyong; Han, Hongxian; Frei, Heinz

2004-04-06

The 266 nm light-induced reaction of CO{sub 2} and H{sub 2}O gas mixtures (including isotopic modifications {sup 13}CO{sub 2}, C{sup 18}O{sub 2}, and D{sub 2}O) in framework TiMCM-41 silicate sieve was monitored by in-situ FT-IR spectroscopy at room temperature. Carbon monoxide gas was observed as the sole product by infrared, and the growth was found to depend linearly on the photolysis laser power. H{sub 2}O was confirmed as stoichiometric electron donor. The work establishes CO as the single photon, 2-electron transfer product of CO{sub 2} photoreduction by H{sub 2}O at framework Ti centers for the first time. O{sub 2} wasmore » detected as co-product by mass spectrometric analysis of the photolysis gas mixture. These results are explained by single UV photon-induced splitting of CO{sub 2} by H{sub 2}O to CO and surface OH radical.« less

Odin observations of H2O and O2 in comets and interstellar clouds

NASA Astrophysics Data System (ADS)

Hjalmarson, Åke; Odin Team

2002-11-01

We here report on results from single-position observations, and in some cases also mapping, of the 557 GHz ortho-H2O line in several comets and in many interstellar molecular clouds by the Odin sub-millimetre wave spectroscopy satellite. The H2O production rates have been accurately determined in four comets, C/2001 A2 (LINEAR), 19P/Borrelly, C/2000 WM1 (LINEAR), and 153P/2002 C1 (Ikeya-Zhang). In comet Ikeya-Zhang our detection at a low level of the corresponding H218O emission line verifies the H2O production rate (which depends upon the assumed radiative and collisional excitation and also upon radiative transfer modelling) and is consistent with a nearly terrestrial 16O/18O-isotope ratio. In an astrobiological context, the cometary H2O production rates are especially important as reference levels for comparison with abundances of other molecules simultaneously observed with ground-based telescopes. In interstellar clouds the observed gas-phase H2O abundances (vs H2) range from 5×10-4 in the Orion KL outflow/shock region (where essentially all oxygen is locked up in H2O) to circa 10-8 in quiescent cloud regions (where H2O) is just one of many trace molecules). From an astrobiological point of view, the molecular abundances in star forming clouds are important in terms of initial conditions for the chemistry in proto-planetary disks ("proto-solar nebulae"), the formation sites of new planetary systems. In simultaneous observations, Odin has also detected the 572 GHz ortho-NH3 line in cold and warm clouds as well as in the Orion outflow and Bar/PDR regions (an area of increased ionisation caused by the intense UV flux from newly born massive stars). In other simultaneous observations, we have performed sensitive searches for O2 at 119 GHz. Although no detection can be reported as yet, the resulting very low abundance limits (<10-7) are very intriguing when they are compared with current "standard" model expectations, which fall in the range 10-5-10-4.

Fluoresence cross section of the H2O(+) A 2A1(0,7,0) produced through photoionization of H2O

NASA Technical Reports Server (NTRS)

Wu, C. Y. Robert; Hwang, M. Y.

1988-01-01

The cross section for the production of the H2O(+) A 2A1(0,7,0) - X 2B1(0,0,0) fluorescence through photoionization of H2O was measured in the 14.5-20.5 eV region. The maximum quantum yield is 1.4 x 10 to the -3rd at 16.5 eV.

High light harvesting efficiency CuInS2 quantum dots/TiO2/MoS2 photocatalysts for enhanced visible light photocatalytic H2 production.

PubMed

Yuan, Yong-Jun; Fang, Gaoliang; Chen, Daqin; Huang, Yanwei; Yang, Ling-Xia; Cao, Da-Peng; Wang, Jingjing; Yu, Zhen-Tao; Zou, Zhi-Gang

2018-04-24

Expanding the photoresponse range of TiO2-based photocatalysts is of great interest for photocatalytic H2 production. Herein, noble-metal-free CuInS2 quantum dots were employed as a novel inorganic dye to expand the visible light absorption of TiO2/MoS2 for solar H2 generation. The as-prepared CuInS2/TiO2/MoS2 photocatalysts exhibit broad absorption from the ultraviolet to near-infrared region. Under visible light irradiation (λ > 420 nm), the CuInS2/TiO2/MoS2 photocatalyst with 0.6 mmol g-1 CuInS2 and 0.5 wt% MoS2 showed the highest H2 evolution rate with a value of 1034 μmol h-1 g-1. Moreover, a considerable H2 evolution rate of 141 μmol h-1 g-1 was obtained under the irradiation of the optimized CuInS2/TiO2/MoS2 photocatalyst with >500 nm light. The reaction mechanism of the CuInS2/TiO2/MoS2 photocatalyst for photocatalytic H2 evolution was investigated in detail by photoluminescence decay study, and the results showed that the photoexcited electrons of CuInS2 can be transferred efficiently through TiO2 to MoS2 and then react with the absorbed protons to generate H2. The reported sensitization strategy tremendously improves the visible light absorption capacity and the photocatalytic performance of TiO2-based photocatalysts.

Crystal structures of ZnCl2·2.5H2O, ZnCl2·3H2O and ZnCl2·4.5H2O

PubMed Central

Hennings, Erik; Schmidt, Horst; Voigt, Wolfgang

2014-01-01

The formation of different complexes in aqueous solutions is an important step in understanding the behavior of zinc chloride in water. The structure of concentrated ZnCl2 solutions is governed by coordination competition of Cl− and H2O around Zn2+. According to the solid–liquid phase diagram, the title compounds were crystallized below room temperature. The structure of ZnCl2·2.5H2O contains Zn2+ both in a tetra­hedral coordination with Cl− and in an octa­hedral environment defined by five water mol­ecules and one Cl− shared with the [ZnCl4]2− unit. Thus, these two different types of Zn2+ cations form isolated units with composition [Zn2Cl4(H2O)5] (penta­aqua-μ-chlorido-tri­chlorido­di­zinc). The trihydrate {hexa­aqua­zinc tetra­chlorido­zinc, [Zn(H2O)6][ZnCl4]}, consists of three different Zn2+ cations, one of which is tetra­hedrally coordinated by four Cl− anions. The two other Zn2+ cations are each located on an inversion centre and are octa­hedrally surrounded by water mol­ecules. The [ZnCl4] tetra­hedra and [Zn(H2O)6] octa­hedra are arranged in alternating rows parallel to [001]. The structure of the 4.5-hydrate {hexa­aqua­zinc tetra­chlorido­zinc trihydrate, [Zn(H2O)6][ZnCl4]·3H2O}, consists of isolated octa­hedral [Zn(H2O)6] and tetra­hedral [ZnCl4] units, as well as additional lattice water mol­ecules. O—H⋯O hydrogen bonds between the water mol­ecules as donor and ZnCl4 tetra­hedra and water mol­ecules as acceptor groups leads to the formation of a three-dimensional network in each of the three structures. PMID:25552980

H2O Paradox and its Implications on H2O in Moon

NASA Astrophysics Data System (ADS)

Zhang, Youxue

2017-04-01

The concentration of H2O in the mantle of a planetary body plays a significant role in the viscosity and partial melting and hence the convection and evolution of the planetary body. Even though the composition of the primitive terrestrial mantle (PTM) is thought to be well known [1-2], the concentration of H2O in PTM remains paradoxial because different methods of estimation give different results [3]: Using H2O/Ce ratio in MORB and OIB and Ce concentration in PTM, the H2O concentration in PTM would be (300÷×1.5) ppm; using mass balance by adding surface water to the mantle [3-4], H2O concentration in PTM would be (900÷×1.3) ppm [2-3]. The inconsistency based on these two seemingly reliable methods is referred to as the H2O paradox [3]. For Moon, H2O contents in the primitive lunar mantle (PLM) estimated from H2O in plagioclase in lunar anorthosite and that from H2O/Ce ratio in melt inclusions are roughly consistent at ˜110 ppm [5-6] even though there is still debate about the volatile depletion trend [7]. One possible solution to the H2O paradox in PTM is to assume that early Earth experienced whole mantle degassing, which lowered the H2O/Ce ratio in the whole mantle but without depleting Ce in the mantle. The second possible solution is that some deep Earth reservoirs with high H2O/Ce ratios have not been sampled by MORB and OIB. Candidates include the transition zone [8] and the D" layer. The third possible solution is that ocean water only partially originated from mantle degassing, but partially from extraterrestrial sources such as comets [9-10]. At present, there is not enough information to determine which scenario is the answer to the H2O paradox. On the other hand, each scenario would have its own implications to H2O in PLM. If the first scenario applies to Moon, because degassed H2O or H2 would have escaped from the lunar surface, the very early lunar mantle could have much higher H2O [11] than that obtained using the H2O/Ce ratio method. The

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.

Crystal and molecular structure of Sr{sub 2}(Edta) . 5H{sub 2}O, Sr{sub 2}(H{sub 2}Edta)(HCO{sub 3}){sub 2} . 4H{sub 2}O, and Sr{sub 2}(H{sub 2}Edta)Cl{sub 2} . 5H{sub 2}O strontium ethylenediaminetetraacetates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Polyakova, I. N., E-mail: polyakova@igic.ras.ru; Poznyak, A. L.; Sergienko, V. S.

2009-03-15

Three Sr{sup 2+} compounds with the Edta{sup 4-} and H{sub 2}Edta{sup 2-} ligands-Sr{sub 2}(Edta) . 5H{sub 2}O (I), Sr{sub 2}(H{sub 2}Edta)(HCO{sub 3}){sub 2} . 4H{sub 2}O (II), and Sr{sub 2}(H{sub 2}Edta)Cl{sub 2} . 5H{sub 2}O (III)-are synthesized, and their crystal structures are studied. In I, the Sr(1) atom is coordinated by the hexadentate Edta{sup 4-} ligand following the 2N + 4O pattern and by two O atoms of the neighboring ligands, which affords the formation of zigzag chains. The Sr(2) atom forms bonds with O atoms of five water molecules and attaches itself to a chain via bonds with threemore » O atoms of the Edta{sup 4-} ligands. The Sr(1)-O and Sr(2)-O bond lengths fall in the ranges 2.520(2)-2.656(3) and 2.527(3)-2.683(2) A, respectively. The Sr(1)-N bonds are 2.702(3) and 2.743(3) A long. In II and III, the H{sub 2}Edta{sup 2-} anions have a centrosymmetric structure with the trans configuration of the planar ethylenediamine fragment. The N atoms are blocked by acid protons. In II, the environment of the Sr atom is formed by six O atoms of three H{sub 2}Edta ligands, two O atoms of water molecules, and an O atom of the bicarbonate ion, which is disordered over two positions. In III, the environment of the Sr atom includes six O atoms of four H{sub 2}Edta{sup 2-} ligands and three O atoms of water molecules. The coordination number of the Sr atoms is equal to 8 + 1. In II and III, the main bonds fall in the ranges 2.534(3)-2.732(2) and 2.482(2)-2.746(3) A, whereas the ninth bond is elongated to 2.937(3) and 3.055(3) A, respectively. In II, all the structural elements are linked into wavy layers. The O-H-O interactions contribute to the stabilization of the layer and link neighboring layers. In III, hydrated Sr{sup 2+} cations and H{sub 2}Edta{sup -} anions form a three-dimensional [Sr{sub 2}(H{sub 2}Edta)(H{sub 2}O){sub 3}]{sub n}{sup 2n+} framework. The Cl{sup -} anions are fixed in channels of the framework by hydrogen bonds with four water

Studies of CW lasing action in CO2-CO, N2O-CO, CO2-H2O, and N2O-H2O mixtures pumped by blackbody radiation

NASA Technical Reports Server (NTRS)

Abel, Robert W.; Christiansen, Walter H.; Li, Jian-Guo

1988-01-01

A proof of principle experiment to evaluate the efficacy of CO and H2O in increasing the power output for N2O and CO2 lasing mixtures has been conducted and theoretically analyzed for a blackbody radiation-pumped laser. The results for N2O-CO, CO2-CO, N2O-H2O and CO2-H2O mixtures are presented. Additions of CO to the N2O lasant increased power up to 28 percent for N2O laser mixtures, whereas additions of CO to the CO2 lasant, and the addition of H2O to both the CO2 and N2O lasants, resulted in decreased output power.

Preparation and enhanced visible-light photocatalytic H2-production activity of CdS-sensitized Pt/TiO2 nanosheets with exposed (001) facets.

PubMed

Qi, Lifang; Yu, Jiaguo; Jaroniec, Mietek

2011-05-21

CdS-sensitized Pt/TiO(2) nanosheets with exposed (001) facets were prepared by hydrothermal treatment of a Ti(OC(4)H(9))(4)-HF-H(2)O mixed solution followed by photochemical reduction deposition of Pt nanoparticles (NPs) on TiO(2) nanosheets (TiO(2) NSs) and chemical bath deposition of CdS NPs on Pt/TiO(2) NSs, successively. The UV and visible-light driven photocatalytic activity of the as-prepared samples was evaluated by photocatalytic H(2) production from lactic acid aqueous solution under UV and visible-light (λ ≥ 420 nm) irradiation. It was shown that no photocatalytic H(2)-production activity was observed on the pure TiO(2) NSs under UV and/or visible-light irradiation. Deposition of CdS NPs on Pt/TiO(2) NSs caused significant enhancement of the UV and visible-light photocatalytic H(2)-production rates. The morphology of TiO(2) particles had also significant influence on the visible-light H(2)-production activity. Among TiO(2) NSs, P25 and the NPs studied, the CdS-sensitized Pt/TiO(2) NSs show the highest photocatalytic activity (13.9% apparent quantum efficiency obtained at 420 nm), exceeding that of CdS-sensitized Pt/P25 by 10.3% and that of Pt/NPs by 1.21%, which can be attributed to the combined effect of several factors including the presence of exposed (001) facets, surface fluorination and high specific surface area. After many replication experiments of the photocatalytic hydrogen production in the presence of lactic acid, the CdS-sensitized Pt/TiO(2) NSs did not show great loss in the photocatalytic activity, confirming that the CdS/Pt/TiO(2) NSs system is stable and not photocorroded. © The Owner Societies 2011

On the role of the termolecular reactions 2O2 + H2 → 2HO2 and 2O2 + H2 → H + HO2 + O2 in formation of the first radicals in hydrogen combustion: ab initio predictions of energy barriers.

PubMed

Monge-Palacios, M; Rafatijo, Homayoon

2017-01-18

We have investigated the role of termolecular reactions in the early chemistry of hydrogen combustion. We performed molecular chemical dynamics simulations using ReaxFF in LAMMPS to identify potential initial reactions for a 1 : 4 mixture of H 2  : O 2 in the NVT ensemble at density 276.3 kg m -3 and ∼3000 K (∼4000 atm) and ∼4000 K (∼5000 atm), and then characterized the saddle points for those reactions using ab initio methods: CCSD(T) = FC/cc-pVTZ//MP2/6-31G, CCSD(T) = FULL/aug-cc-pVTZ//CCSD = FC/cc-pVTZ and CASSCF MP2/6-31G//MP2/6-31G. The main initial reaction is H 2 + O 2 → H + HO 2 , frequently occurring in the presence of a second O 2 as a third body; that is, 2O 2 + H 2 → H + HO 2 + O 2 . The second most frequent reaction is 2O 2 + H 2 → 2HO 2 . We found three saddle points on the triplet PES of these termolecular reactions: one for 2O 2 + H 2 → H + HO 2 + O 2 and two for 2O 2 + H 2 → 2HO 2 . In the latter case, one has a symmetric structure consistent with simultaneous formation of two HO 2 and the other corresponds to a bimolecular reaction between O 2 and H 2 that is "interrupted" by a second O 2 before going to completion. The classical barrier height of the symmetric saddle point for 2O 2 + H 2 → 2HO 2 is 49.8 kcal mol -1 . The barrier to H 2 + O 2 → H + HO 2 is 58.9 kcal mol -1 . The termolecular reaction will be competitive with H 2 + O 2 → H + HO 2 only at sufficiently high pressures.

Reactions of electronically excited molecular nitrogen with H2 and H2O molecules: theoretical study

NASA Astrophysics Data System (ADS)

Pelevkin, Alexey V.; Sharipov, Alexander S.

2018-05-01

Comprehensive quantum chemical analysis with the usage of the second-order perturbation multireference XMCQDPT2 approach was carried out to study the processes in the   +  H2 and   +  H2O systems. The energetically favorable reaction pathways have been revealed based on the exploration of potential energy surfaces. It has been shown that the reactions   +  H2 and   +  H2O occur with small activation barriers and, primarily, lead to the formation of N2H  +  H and N2H  +  OH products, respectively. Further, the interaction of these species could give rise to the ground state and H2 (or H2O) products, however, the estimations, based on RRKM theory and dynamic reaction coordinate calculations, exhibited that the   +  H2 and   +  H2O reactions lead to the dissociative quenching predominately. Appropriate rate constants for revealed reaction channels have been estimated by using a canonical variational theory and capture approximation. Corresponding three-parameter Arrhenius expressions for the temperature range T  =  300  ‑  3000 K were reported.

Synthesis, DFT calculations of structure, vibrational and thermal decomposition studies of the metal complex Pb[Mn(C3H2O4)2(H2O)2].

PubMed

Gil, Diego M; Carbonio, Raúl E; Gómez, María Inés

2015-04-15

The metallo-organic complex Pb[Mn(C3H2O4)2(H2O)2] was synthesized and characterized by IR and Raman spectroscopy and powder X-ray diffraction methods. The cell parameters for the complex were determined from powder X-ray diffraction using the autoindexing program TREOR, and refined by the Le Bail method with the Fullprof program. A hexagonal unit cell was determined with a=b=13.8366(7)Å, c=9.1454(1)Å, γ=120°. The DFT calculated geometry of the complex anion [Mn(C3H2O4)2(H2O)2](2-) is very close to the experimental data reported for similar systems. The IR and Raman spectra and the thermal analysis of the complex indicate that only one type of water molecules is present in the structure. The thermal decomposition of Pb[Mn(C3H2O4)2(H2O)2] at 700 °C in air produces PbO and Pb2MnO4 as final products. The crystal structure of the mixed oxide is very similar to that reported for Pb3O4. Copyright © 2015 Elsevier B.V. All rights reserved.

H2O2 Production in Species of the Lactobacillus acidophilus Group: a Central Role for a Novel NADH-Dependent Flavin Reductase

PubMed Central

Hertzberger, Rosanne; Arents, Jos; Dekker, Henk L.; Pridmore, R. David; Gysler, Christof; Kleerebezem, Michiel

2014-01-01

Hydrogen peroxide production is a well-known trait of many bacterial species associated with the human body. In the presence of oxygen, the probiotic lactic acid bacterium Lactobacillus johnsonii NCC 533 excretes up to 1 mM H2O2, inducing growth stagnation and cell death. Disruption of genes commonly assumed to be involved in H2O2 production (e.g., pyruvate oxidase, NADH oxidase, and lactate oxidase) did not affect this. Here we describe the purification of a novel NADH-dependent flavin reductase encoded by two highly similar genes (LJ_0548 and LJ_0549) that are conserved in lactobacilli belonging to the Lactobacillus acidophilus group. The genes are predicted to encode two 20-kDa proteins containing flavin mononucleotide (FMN) reductase conserved domains. Reductase activity requires FMN, flavin adenine dinucleotide (FAD), or riboflavin and is specific for NADH and not NADPH. The Km for FMN is 30 ± 8 μM, in accordance with its proposed in vivo role in H2O2 production. Deletion of the encoding genes in L. johnsonii led to a 40-fold reduction of hydrogen peroxide formation. H2O2 production in this mutant could only be restored by in trans complementation of both genes. Our work identifies a novel, conserved NADH-dependent flavin reductase that is prominently involved in H2O2 production in L. johnsonii. PMID:24487531

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miliordos, Evangelos; Xantheas, Sotiris S.

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 theymore » 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

Synthesis, structure and reactivity of rare-earth metallacarborane alkyls [η(1):η(5)-O(CH2)2C2B9H9]Ln(σ:η(1)-CH2C6H4-o-NMe2)(THF)2.

PubMed

Yang, Jingying; Xie, Zuowei

2015-04-14

Rare-earth metallacarborane alkyls can be stabilized by the incorporation of a functional sidearm into both π and σ ligands. Reaction of [Me3NH][7,8-O(CH2)2-7,8-C2B9H10] with one equiv. of Ln(CH2C6H4-o-NMe2)3 gave metallacarborane alkyls [η(1):η(5)-O(CH2)2C2B9H9]Ln(σ:η(1)-CH2C6H4-o-NMe2)(THF)2 (Ln = Y (), Gd (), Er ()) via alkane elimination. They represent the first examples of rare-earth metallacarborane alkyls. Treatment of with RN[double bond, length as m-dash]C[double bond, length as m-dash]NR (R = Cy, (i)Pr) or 2-benzoylpyridine afforded the corresponding mono-insertion products [η(1):η(5)-O(CH2)2C2B9H9]Y[η(2)-(RN)2C(CH2C6H4-o-NMe2)](DME) (R = Cy (), (i)Pr ()) or [η(1):η(5)-O(CH2)2C2B9H9]Y[C5H4NC(Ph)(CH2C6H4-o-NMe2)O](THF)2 (), respectively. Complex also reacted with ArNCO or ArNC (Ar = 2,6-diisopropylphenyl, 2,6-dimethylphenyl) to give di-insertion products [η(1):η(5)-O(CH2)2C2B9H9]Y[OC([double bond, length as m-dash]NC6H3Me2)N(C6H3Me2)C(CH2C6H4-o-NMe2)O](THF)2 () or [η(1):η(5)-O(CH2)2C2B9H9]Y[C([double bond, length as m-dash]NC6H3(i)Pr2)C([double bond, length as m-dash]NC6H3(i)Pr2)(CH2C6H4-o-NMe2)](DME) (). These results showed that the reactivity pattern of the Ln-C σ bond in rare-earth metallacarborane alkyls was dependent on the nature of the unsaturated organic molecules. New complexes were characterized by various spectroscopic techniques and elemental analysis. Some were further confirmed by single-crystal X-ray analysis.

Novel Process of Simultaneous Removal of Nitric Oxide and Sulfur Dioxide Using a Vacuum Ultraviolet (VUV)-Activated O2/H2O/H2O2 System in A Wet VUV-Spraying Reactor.

PubMed

Liu, Yangxian; Wang, Qian; Pan, Jianfeng

2016-12-06

A novel process for NO and SO 2 simultaneous removal using a vacuum ultraviolet (VUV, with 185 nm wavelength)-activated O 2 /H 2 O/H 2 O 2 system in a wet VUV-spraying reactor was developed. The influence of different process variables on NO and SO 2 removal was evaluated. Active species (O 3 and ·OH) and liquid products (SO 3 2- , NO 2 - , SO 4 2- , and NO 3 - ) were analyzed. The chemistry and routes of NO and SO 2 removal were investigated. The oxidation removal system exhibits excellent simultaneous removal capacity for NO and SO 2 , and a maximum removal of 96.8% for NO and complete SO 2 removal were obtained under optimized conditions. SO 2 reaches 100% removal efficiency under most of test conditions. NO removal is obviously affected by several process variables. Increasing VUV power, H 2 O 2 concentration, solution pH, liquid-to-gas ratio, and O 2 concentration greatly enhances NO removal. Increasing NO and SO 2 concentration obviously reduces NO removal. Temperature has a dual impact on NO removal, which has an optimal temperature of 318 K. Sulfuric acid and nitric acid are the main removal products of NO and SO 2 . NO removals by oxidation of O 3 , O·, and ·OH are the primary routes. NO removals by H 2 O 2 oxidation and VUV photolysis are the complementary routes. A potential scaled-up removal process was also proposed initially.

Molecular Cobalt Catalysts for O 2 Reduction: Low-Overpotential Production of H 2 O 2 and Comparison with Iron-Based Catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yu-Heng; Pegis, Michael L.; Mayer, James M.

A series of mononuclear pseudo-macrocyclic cobalt complexes have been investigated as catalysts for O2 reduction. Each of these complexes, with CoIII/II reduction potentials that span nearly 400 mV, mediate highly selective two- electron reduction of O2 to H2O2 (93–99%) using decamethylferrocene (Fc*) as the reductant and acetic acid as the proton source. Kinetic studies reveal that the rate exhibits a first- order dependence on [Co] and [AcOH], but no dependence on [O2] or [Fc*]. A linear correlation is observed between log(TOF) vs. E1/2(CoIII/II) for the different cobalt complexes (TOF = turnover frequency). The thermodynamic potential for+ O2 reduction to H2O2more » was estimated by measuring the H /H2 open-circuit potential under the reaction conditions. This value provides the basis for direct assessment of the thermodynamic efficiency of the different catalysts and shows that H2O2 is formed with overpotentials as low as 90 mV. These results are compared with a recently reported series of Fe-porphyrin complexes, which catalyze four-electron reduction of O2 to H2O. The data show that the TOFs of the Co complexes exhibit a shallower dependence on E1/2(MIII/II) than the Fe complexes. This behavior, which underlies the low overpotential, is rationalized on the basis of the catalytic rate law.« less

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).

The effect of pH on N2O production under aerobic conditions in a partial nitritation system.

PubMed

Law, Yingyu; Lant, Paul; Yuan, Zhiguo

2011-11-15

Ammonia-oxidising bacteria (AOB) are a major contributor to nitrous oxide (N(2)O) emissions during nitrogen transformation. N(2)O production was observed under both anoxic and aerobic conditions in a lab-scale partial nitritation system operated as a sequencing batch reactor (SBR). The system achieved 55 ± 5% conversion of the 1g NH(4)(+)-N/L contained in a synthetic anaerobic digester liquor to nitrite. The N(2)O emission factor was 1.0 ± 0.1% of the ammonium converted. pH was shown to have a major impact on the N(2)O production rate of the AOB enriched culture. In the investigated pH range of 6.0-8.5, the specific N(2)O production was the lowest between pH 6.0 and 7.0 at a rate of 0.15 ± 0.01 mg N(2)O-N/h/g VSS, but increased with pH to a maximum of 0.53 ± 0.04 mg N(2)O-N/h/g VSS at pH 8.0. The same trend was also observed for the specific ammonium oxidation rate (AOR) with the maximum AOR reached at pH 8.0. A linear relationship between the N(2)O production rate and AOR was observed suggesting that increased ammonium oxidation activity may have promoted N(2)O production. The N(2)O production rate was constant across free ammonia (FA) and free nitrous acid (FNA) concentrations of 5-78 mg NH(3)-N/L and 0.15-4.6 mg HNO(2)-N/L, respectively, indicating that the observed pH effect was not due to changes in FA or FNA concentrations. Copyright © 2011 Elsevier Ltd. All rights reserved.

Crystal structures of Sr(ClO4)2·3H2O, Sr(ClO4)2·4H2O and Sr(ClO4)2·9H2O

PubMed Central

Hennings, Erik; Schmidt, Horst; Voigt, Wolfgang

2014-01-01

The title compounds, strontium perchlorate trihydrate {di-μ-aqua-aquadi-μ-perchlorato-strontium, [Sr(ClO4)2(H2O)3]n}, strontium perchlorate tetra­hydrate {di-μ-aqua-bis­(tri­aqua­diperchloratostrontium), [Sr2(ClO4)4(H2O)8]} and strontium perchlorate nona­hydrate {hepta­aqua­diperchloratostrontium dihydrate, [Sr(ClO4)2(H2O)7]·2H2O}, were crystallized at low temperatures according to the solid–liquid phase diagram. The structures of the tri- and tetra­hydrate consist of Sr2+ cations coordinated by five water mol­ecules and four O atoms of four perchlorate tetra­hedra in a distorted tricapped trigonal–prismatic coordination mode. The asymmetric unit of the trihydrate contains two formula units. Two [SrO9] polyhedra in the trihydrate are connected by sharing water mol­ecules and thus forming chains parallel to [100]. In the tetra­hydrate, dimers of two [SrO9] polyhedra connected by two sharing water mol­ecules are formed. The structure of the nona­hydrate contains one Sr2+ cation coordinated by seven water mol­ecules and by two O atoms of two perchlorate tetra­hedra (point group symmetry ..m), forming a tricapped trigonal prism (point group symmetry m2m). The structure contains additional non-coordinating water mol­ecules, which are located on twofold rotation axes. O—H⋯O hydrogen bonds between the water mol­ecules as donor and ClO4 tetra­hedra and water mol­ecules as acceptor groups lead to the formation of a three-dimensional network in each of the three structures. PMID:25552979

Kinetic removal of haloacetonitrile precursors by photo-based advanced oxidation processes (UV/H2O2, UV/O3, and UV/H2O2/O3).

PubMed

Srithep, Sirinthip; Phattarapattamawong, Songkeart

2017-06-01

The objective of the study is to evaluate the performance of conventional treatment process (i.e., coagulation, flocculation, sedimentation and sand filtration) on the removals of haloacetonitrile (HAN) precursors. In addition, the removals of HAN precursors by photo-based advanced oxidation processes (Photo-AOPs) (i.e., UV/H 2 O 2 , UV/O 3 , and UV/H 2 O 2 /O 3 ) are investigated. The conventional treatment process was ineffective to remove HAN precursors. Among Photo-AOPs, the UV/H 2 O 2 /O 3 was the most effective process for removing HAN precursors, followed by UV/H 2 O 2 , and UV/O 3 , respectively. For 20min contact time, the UV/H 2 O 2 /O 3 , UV/H 2 O 2 , and UV/O 3 suppressed the HAN formations by 54, 42, and 27% reduction. Increasing ozone doses from 1 to 5 mgL -1 in UV/O 3 systems slightly improved the removals of HAN precursors. Changes in pH (6-8) were unaffected most of processes (i.e., UV, UV/H 2 O 2 , and UV/H 2 O 2 /O 3 ), except for the UV/O 3 system that its efficiency was low in the weak acid condition. The pseudo first-order kinetic constant for removals of dichloroacetonitrile precursors (k' DCANFP ) by the UV/H 2 O 2 /O 3 , UV/H 2 O 2 and standalone UV systems were 1.4-2.8 orders magnitude higher than the UV/O 3 process. The kinetic degradation of dissolved organic nitrogen (DON) tended to be higher than the k' DCANFP value. This study firstly differentiates the kinetic degradation between DON and HAN precursors. Copyright © 2017 Elsevier Ltd. All rights reserved.

Active sites and mechanisms for H2O2 decomposition over Pd catalysts

PubMed Central

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

2016-01-01

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

Lactobacillus Species Identification, H2O2 Production, and Antibiotic Resistance and Correlation with Human Clinical Status

PubMed Central

Felten, Annie; Barreau, Claude; Bizet, Chantal; Lagrange, Philippe Henri; Philippon, Alain

1999-01-01

Lactobacilli recovered from the blood, cerebrospinal fluid, respiratory tract, and gut of 20 hospitalized immunocompromised septic patients were analyzed. Biochemical carbohydrate fermentation and total soluble cell protein profiles were used to identify the species. Hydrogen peroxide production was measured. Susceptibility to 19 antibiotics was tested by a diffusion method, and the MICs of benzylpenicillin, amoxicillin, imipenem, erythromycin, vancomycin, gentamicin, and levofloxacin were determined. A small number of species produced H2O2, and antibiotic susceptibilities were species related. Eighteen (90%) of the isolates were L. rhamnosus, one was L. paracasei subsp. paracasei, and one was L. crispatus. L. rhamnosus, L. paracasei subsp. paracasei isolates, and the type strains were neither H2O2 producers nor vancomycin susceptible (MICs, ≥256 μg/ml). L. crispatus, as well as most of the type strains of lactobacilli which belong to the L. acidophilus group, was an H2O2 producer and vancomycin susceptible (MICs, <4 μg/ml). PMID:9986841

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.

Vibrational energy transfer and relaxation in O2 and H2O.

PubMed

Huestis, David L

2006-06-01

Near-resonant vibrational energy exchange between oxygen and water molecules is an important process in the Earth's atmosphere, combustion chemistry, and the chemical oxygen iodine laser (COIL). The reactions in question are (1) O2(1) + O2(0) --> O2(0) + O2(0); (2) O2(1) + H2O(000) --> O2(0) + H2O(000); (3) O2(1) + H2O(000) <--> O2(0) + H2O(010); (4) H2O(010) + H2O(000) --> H2O(000) + H2O(000); and (5) H2O(010) + O2(0) --> H2O(000) + O2(0). Reanalysis of the data available in the chemical kinetics literature provides reliable values for rate coefficients for reactions 1 and 4 and strong evidence that reactions 2 and 5 are slow in comparison with reaction 3. Analytical solution of the chemical rate equations shows that previous attempts to measure the rate of reaction 3 are unreliable unless the water mole fraction is higher than 1%. Reanalysis of data from the only experiment satisfying this constraint provides a rate coefficient of (5.5 +/- 0.4) x 10(-13) cm3/s at room temperature, between the values favored by the atmospheric and laser modeling communities.

Water Ice Radiolytic O2, H2, and H2O2 Yields for Any Projectile Species, Energy, or Temperature: A Model for Icy Astrophysical Bodies

NASA Astrophysics Data System (ADS)

Teolis, B. D.; Plainaki, C.; Cassidy, T. A.; Raut, U.

2017-10-01

O2, H2, and H2O2 radiolysis from water ice is pervasive on icy astrophysical bodies, but the lack of a self-consistent, quantitative model of the yields of these water products versus irradiation projectile species and energy has been an obstacle to estimating the radiolytic oxidant sources to the surfaces and exospheres of these objects. A major challenge is the wide variation of O2 radiolysis yields between laboratory experiments, ranging over 4 orders of magnitude from 5 × 10-7 to 5 × 10-3 molecules/eV for different particles and energies. We revisit decades of laboratory data to solve this long-standing puzzle, finding an inverse projectile range dependence in the O2 yields, due to preferential O2 formation from an 30 Å thick oxygenated surface layer. Highly penetrating projectile ions and electrons with ranges ≳30 Å are therefore less efficient at producing O2 than slow/heavy ions and low-energy electrons (≲ 400 eV) which deposit most energy near the surface. Unlike O2, the H2O2 yields from penetrating projectiles fall within a comparatively narrow range of (0.1-6) × 10-3 molecules/eV and do not depend on range, suggesting that H2O2 forms deep in the ice uniformly along the projectile track, e.g., by reactions of OH radicals. We develop an analytical model for O2, H2, and H2O2 yields from pure water ice for electrons and singly charged ions of any mass and energy and apply the model to estimate possible O2 source rates on several icy satellites. The yields are upper limits for icy bodies on which surface impurities may be present.

Co-modification of amorphous-Ti(IV) hole cocatalyst and Ni(OH)2 electron cocatalyst for enhanced photocatalytic H2-production performance of TiO2

NASA Astrophysics Data System (ADS)

Wang, Ping; Lu, Yanggang; Wang, Xuefei; Yu, Huogen

2017-01-01

Highly efficient TiO2 photocatalysts co-modified by amorphous-Ti(IV) hole cocatalyst and Ni(OH)2 electron cocatalyst (referred to as Ni(OH)2-Ti(IV)/TiO2) were prepared by facile two-step process which was the initial formation of amorphous Ti(IV) on the TiO2 surface via hydrolysis method and the following formation of Ni(OH)2 via precipitation reaction. It was found that the Ni(OH)2-Ti(IV)/TiO2 showed obviously high hydrogen-production performance. When the amount of Ni(OH)2 and Ti(IV) was 1 wt% and 0.1 wt%, respectively, the hydrogen-production rate of the resultant Ni(OH)2-Ti(IV)/TiO2 reached 7280.04 μmol h-1 g-1, which was significantly higher than that of TiO2, Ti(IV)/TiO2 and Ni(OH)2/TiO2 by a factor of 215, 63 and 1.8, respectively. Moreover, it was found that Ni(OH)2-Ti(IV)/TiO2 photocatalyst preserved a steady and highly efficient H2-production performance during repeated tests and also exhibited a high transient photocurrent density. The enhanced hydrogen-production performance of Ni(OH)2-Ti(IV)/TiO2 can be attributed to the synergistic effect of Ti(IV) hole cocatalyst and Ni(OH)2 electron cocatalyst to simultaneously accelerate the interfacial transfer of photogenerated holes and electrons. The present surface modification of dual cocatalysts can be regarded as one of the ideal strategies for the preparation of highly efficient hydrogen-production materials in view of their abundance, low cost and facile method.

Reactions of hydrated electrons (H2O)n- with carbon dioxide and molecular oxygen: hydration of the CO2- and O2- ions.

PubMed

Balaj, O Petru; Siu, Chi-Kit; Balteanu, Iulia; Beyer, Martin K; Bondybey, Vladimir E

2004-10-04

The gas-phase reactions of hydrated electrons with carbon dioxide and molecular oxygen were studied by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Both CO2 and O2 react efficiently with (H2O)n- because they possess low-lying empty pi* orbitals. The molecular CO2- and O2- anions are concurrently solvated and stabilized by the water ligands to form CO2(-)(H2O)n and O2(-)(H2O)n. Core exchange reactions are also observed, in which CO2(-)(H2O)n is transformed into O2(-)(H2O)n upon collision with O2. This is in agreement with the prediction based on density functional theory calculations that O2(-)(H2O)n clusters are thermodynamically favored with respect to CO2(-)(H2O)n. Electron detachment from the product species is only observed for CO2(-)(H2O)2, in agreement with the calculated electron affinities and solvation energies.

Full-dimensional, high-level ab initio potential energy surfaces for H{sub 2}(H{sub 2}O) and H{sub 2}(H{sub 2}O){sub 2} with application to hydrogen clathrate hydrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Homayoon, Zahra; Conte, Riccardo; Qu, Chen

2015-08-28

New, full-dimensional potential energy surfaces (PESs), obtained using precise least-squares fitting of high-level electronic energy databases, are reported for intrinsic H{sub 2}(H{sub 2}O) two-body and H{sub 2}(H{sub 2}O){sub 2} three-body potentials. The database for H{sub 2}(H{sub 2}O) consists of approximately 44 000 energies at the coupled cluster singles and doubles plus perturbative triples (CCSD(T))-F12a/haQZ (aug-cc-pVQZ for O and cc-pVQZ for H) level of theory, while the database for the three-body interaction consists of more than 36 000 energies at the CCSD(T)-F12a/haTZ (aug-cc-pVTZ for O, cc-pVTZ for H) level of theory. Two precise potentials are based on the invariant-polynomial technique and are comparedmore » to computationally faster ones obtained via “purified” symmetrization. All fits use reduced permutational symmetry appropriate for these non-covalent interactions. These intrinsic potentials are employed together with existing ones for H{sub 2}, H{sub 2}O, and (H{sub 2}O){sub 2}, to obtain full PESs for H{sub 2}(H{sub 2}O) and H{sub 2}(H{sub 2}O){sub 2}. Properties of these full PESs are presented, including a diffusion Monte Carlo calculation of the zero-point energy and wavefunction, and dissociation energy of the H{sub 2}(H{sub 2}O) dimer. These PESs together with an existing one for water clusters are used in a many-body representation of the PES of hydrogen clathrate hydrates, illustrated for H{sub 2}@(H{sub 2}O){sub 20}. An analysis of this hydrate is presented, including the electronic dissociation energy to remove H{sub 2} from the calculated equilibrium structure.« less

Chlorogenic acid analogues from Gynura nepalensis protect H9c2 cardiomyoblasts against H2O2-induced apoptosis

PubMed Central

Yu, Bang-wei; Li, Jin-long; Guo, Bin-bin; Fan, Hui-min; Zhao, Wei-min; Wang, He-yao

2016-01-01

Aim: Chlorogenic acid has shown protective effect on cardiomyocytes against oxidative stress-induced damage. Herein, we evaluated nine caffeoylquinic acid analogues (1–9) isolated from the leaves of Gynura nepalensis for their protective effect against H2O2-induced H9c2 cardiomyoblast damage and explored the underlying mechanisms. Methods: H9c2 cardiomyoblasts were exposed to H2O2 (0.3 mmol/L) for 3 h, and cell viability was detected with MTT assay. Hoechst 33342 staining was performed to evaluate cell apoptosis. MMPs (mitochondrial membrane potentials) were measured using a JC-1 assay kit, and ROS (reactive oxygen species) generation was measured using CM-H2 DCFDA. The expression levels of relevant proteins were detected using Western blot analysis. Results: Exposure to H2O2 markedly decreased the viability of H9c2 cells and catalase activity, and increased LDH release and intracellular ROS production; accompanied by a loss of MMP and increased apoptotic rate. Among the 9 chlorogenic acid analogues as well as the positive control drug epigallocatechin gallate (EGCG) tested, compound 6 (3,5-dicaffeoylquinic acid ethyl ester) was the most effective in protecting H9c2 cells from H2O2-induced cell death. Pretreatment with compound 6 (1.56–100 μmol/L) dose-dependently alleviated all the H2O2-induced detrimental effects. Moreover, exposure to H2O2 significantly increased the levels of Bax, p53, cleaved caspase-8, and cleaved caspase-9, and decreased the level of Bcl-2, resulting in cell apoptosis. Exposure to H2O2 also significantly increased the phosphorylation of p38, JNK and ERK in the H9c2 cells. Pretreatment with compound 6 (12.5 and 25 μmol/L) dose-dependently inhibited the H2O2-induced increase in the level of cleaved caspase-9 but not of cleaved caspase-8. It also dose-dependently suppressed the H2O2-induced phosphorylation of JNK and ERK but not that of p38. Conclusion: Compound 6 isolated from the leaves of Gynura nepalensis potently protects H9c2

Can perchlorates be transformed to hydrogen peroxide (H2O2) products by cosmic rays on the Martian surface?

NASA Astrophysics Data System (ADS)

Crandall, Parker B.; Góbi, Sándor; Gillis-Davis, Jeffrey; Kaiser, Ralf I.

2017-09-01

Due to their oxidizing properties, perchlorates (ClO4-) are suggested by the planetary science community to play a vital role in the scarcity of organics on the Martian surface. However, alternative oxidation agents such as hydrogen peroxide (H2O2) have received surprisingly little attention. In this study, samples of magnesium perchlorate hexahydrate (Mg(ClO4)2 · 6H2O) were exposed to monoenergetic electrons and D2+ ions separately, sequentially, and simultaneously to probe the effects of galactic cosmic ray exposure of perchlorates and the potential incorporation of hydrogen (deuterium) into these minerals. The experiments were carried out under ultrahigh-vacuum conditions at 50 K, after which the samples were slowly heated to 300 K while the subliming products were monitored by a quadrupole mass spectrometer. In all cases, molecular oxygen (O2) was detected upon the onset of irradiation and also during the warmup phase. In case of a simultaneous D2+-electron exposure, deuterated water (D2O) and deuterium peroxide (D2O2) were also detected in the warmup phase, whereas only small amounts of D2O2 were found after an exclusive D2+ irradiation. These experiments yield the first data identifying hydrogen peroxide as a potential product in the interaction of cosmic rays with perchlorates in the Martian regolith revealing that perchlorates are capable of producing multiple oxidizing agents (O2 and D2O2) that may account for the destruction of organics on the Martian surface.

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

PubMed

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

2010-10-14

The hydrated nucleoside anions, uridine(-)(H(2)O)(n=0-2), cytidine(-)(H(2)O)(n=0-2), and thymidine(-)(H(2)O)(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(-)(H(2)O)(1) and its calculated value in the companion article by S. Kim and H. F. Schaefer III.

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.

Kinetics of Al + H2O reaction: theoretical study.

PubMed

Sharipov, Alexander; Titova, Nataliya; Starik, Alexander

2011-05-05

Quantum chemical calculations were carried out to study the reaction of Al atom in the ground electronic state with H(2)O molecule. Examination of the potential energy surface revealed that the Al + H(2)O → AlO + H(2) reaction must be treated as a complex process involving two steps: Al + H(2)O → AlOH + H and AlOH + H → AlO + H(2). Activation barriers for these elementary reaction channels were calculated at B3LYP/6-311+G(3df,2p), CBS-QB3, and G3 levels of theory, and appropriate rate constants were estimated by using a canonical variational theory. Theoretical analysis exhibited that the rate constant for the Al + H(2)O → products reaction measured by McClean et al. must be associated with the Al + H(2)O → AlOH + H reaction path only. The process of direct HAlOH formation was found to be negligible at a pressure smaller than 100 atm.

Comparative study of the degradation of real textile effluents by photocatalytic reactions involving UV/TiO2/H2O2 and UV/Fe2+/H2O2 systems.

PubMed

Garcia, J C; Oliveira, J L; Silva, A E C; Oliveira, C C; Nozaki, J; de Souza, N E

2007-08-17

This work investigated the treatability of real textile effluents using several systems involving advanced oxidation processes (AOPs) such as UV/H2O2, UV/TiO2, UV/TiO2/H2O2, and UV/Fe2+/H2O2. The efficiency of each technique was evaluated according to the reduction levels observed in the UV absorbance of the effluents, COD, and organic nitrogen reduction, as well as mineralization as indicated by the formation of ammonium, nitrate, and sulfate ions. The results indicate the association of TiO2 and H2O2 as the most efficient treatment for removing organic pollutants from textile effluents. In spite of their efficiency, Fenton reactions based treatment proved to be slower and exhibited more complicated kinetics than the ones using TiO2, which are pseudo-first-order reactions. Decolorization was fast and effective in all the experiments despite the fact that only H2O2 was used.

Physical and chemical effects on crystalline H2O2 induced by 20 keV protons.

PubMed

Loeffler, M J; Baragiola, R A

2009-03-21

We present laboratory studies on radiation chemistry, sputtering, and amorphization of crystalline H(2)O(2) induced by 20 keV protons at 80 K. We used infrared spectroscopy to identify H(2)O, O(3), and possibly HO(3), measure the fluence dependence of the fraction of crystalline and amorphous H(2)O(2) and of the production of H(2)O and destruction of H(2)O(2). Furthermore, using complementary techniques, we observe that the sputtering yield depends on fluence due to the buildup of O(2) radiation products in the sample. In addition, we find that the effective cross sections for the destruction of hydrogen peroxide and the production of water are very high compared to radiation chemical processes in water even though the fluence dependence of amorphization is nearly the same for the two materials. This result is consistent with a model of fast cooling of a liquid track produced by each projectile ion rather than with the disorder produced by the formation of radiolytic products.

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

Effect of pH on H2O2 production in the radiolysis of water.

PubMed

Roth, Olivia; LaVerne, Jay A

2011-02-10

The yields of hydrogen peroxide have been measured in the radiolysis of aqueous solutions of acrylamide, bromide, nitrate, and air in the pH range of 1-13. Hydrogen peroxide is the main stable oxidizing species formed in the radiolysis of water, and its long-term yield is found to be very sensitive to the system used in the measurements. Experiments with γ-irradiation combined with model calculations show that the primary yields of hydrogen peroxide are nearly independent of pH in the range of 2-12. Slightly higher primary yields are suggested at very low pH in particular when O(2) is present, while the yields seem to decrease at very high pH. Irradiations were performed with 5 MeV H ions, 5 MeV He ions, and 10 MeV C ions to evaluate the intratrack and homogeneous kinetic contributions to H(2)O(2) formation with different ions. Many of the trends in hydrogen peroxide yields with pH observed with γ-irradiations are observed with irradiation by the heavy ions. The lower yields of radicals in the homogeneous phase with the heavier ions tend to minimize the effects of radicals on the hydrogen peroxide yields at long times.

Role of chemical interaction between MgH2 and TiO2 additive on the hydrogen storage behavior of MgH2

NASA Astrophysics Data System (ADS)

Pukazhselvan, D.; Nasani, Narendar; Sandhya, K. S.; Singh, Budhendra; Bdikin, Igor; Koga, Nobuaki; Fagg, Duncan Paul

2017-10-01

The present study explores how the additive titania chemically reacts with magnesium hydride and influences the dehydrogenation of MgH2. Quantitative X - ray diffraction study of ball milled MgH2 + xTiO2 (x = 0.25, 0.33, 0.5 and 1) suggests that Ti substituted MgO is the main reaction product in all the product powders. Convincing evidence is obtained to conclude that Ti dissolution in MgO makes a dramatic behavioral change to MgO; passive MgO turns as an active in-built catalyst. The analysis correlating the dehydrogenation kinetics, composition of in-situ catalyst and sample durability suggests that effectiveness of Ti substituted MgO (MgxTiyOx+y) as a catalyst for MgH2 depends on the concentration of Ti in MgxTiyOx+y rock salt. These observations are immensely helpful for understanding the hydrogen desorption mechanism of metal oxide additives loaded MgH2 system.

Optimization of NO oxidation by H2O2 thermal decomposition at moderate temperatures.

PubMed

Zhao, Hai-Qian; Wang, Zhong-Hua; Gao, Xing-Cun; Liu, Cheng-Hao; Qi, Han-Bing

2018-01-01

H2O2 was adopted to oxidize NO in simulated flue gas at 100-500°C. The effects of the H2O2 evaporation conditions, gas temperature, initial NO concentration, H2O2 concentration, and H2O2:NO molar ratio on the oxidation efficiency of NO were investigated. The reason for the narrow NO oxidation temperature range near 500°C was determined. The NO oxidation products were analyzed. The removal of NOx using NaOH solution at a moderate oxidation ratio was studied. It was proven that rapid evaporation of the H2O2 solution was critical to increase the NO oxidation efficiency and broaden the oxidation temperature range. the NO oxidation efficiency was above 50% at 300-500°C by contacting the outlet of the syringe needle and the stainless-steel gas pipe together to spread H2O2 solution into a thin film on the surface of the stainless-steel gas pipe, which greatly accelerated the evaporation of H2O2. The NO oxidation efficiency and the NO oxidation rate increased with increasing initial NO concentration. This method was more effective for the oxidation of NO at high concentrations. H2O2 solution with a concentration higher than 15% was more efficient in oxidizing NO. High temperatures decreased the influence of the H2O2 concentration on the NO oxidation efficiency. The oxidation efficiency of NO increased with an increase in the H2O2:NO molar ratio, but the ratio of H2O2 to oxidized NO decreased. Over 80% of the NO oxidation product was NO2, which indicated that the oxidation ratio of NO did not need to be very high. An 86.7% NO removal efficiency was obtained at an oxidation ratio of only 53.8% when combined with alkali absorption.

Optimization of NO oxidation by H2O2 thermal decomposition at moderate temperatures

PubMed Central

Wang, Zhong-hua; Gao, Xing-cun; Liu, Cheng-hao; Qi, Han-bing

2018-01-01

H2O2 was adopted to oxidize NO in simulated flue gas at 100–500°C. The effects of the H2O2 evaporation conditions, gas temperature, initial NO concentration, H2O2 concentration, and H2O2:NO molar ratio on the oxidation efficiency of NO were investigated. The reason for the narrow NO oxidation temperature range near 500°C was determined. The NO oxidation products were analyzed. The removal of NOx using NaOH solution at a moderate oxidation ratio was studied. It was proven that rapid evaporation of the H2O2 solution was critical to increase the NO oxidation efficiency and broaden the oxidation temperature range. the NO oxidation efficiency was above 50% at 300–500°C by contacting the outlet of the syringe needle and the stainless-steel gas pipe together to spread H2O2 solution into a thin film on the surface of the stainless-steel gas pipe, which greatly accelerated the evaporation of H2O2. The NO oxidation efficiency and the NO oxidation rate increased with increasing initial NO concentration. This method was more effective for the oxidation of NO at high concentrations. H2O2 solution with a concentration higher than 15% was more efficient in oxidizing NO. High temperatures decreased the influence of the H2O2 concentration on the NO oxidation efficiency. The oxidation efficiency of NO increased with an increase in the H2O2:NO molar ratio, but the ratio of H2O2 to oxidized NO decreased. Over 80% of the NO oxidation product was NO2, which indicated that the oxidation ratio of NO did not need to be very high. An 86.7% NO removal efficiency was obtained at an oxidation ratio of only 53.8% when combined with alkali absorption. PMID:29668672

Low levels of iron enhance UV/H2O2 efficiency at neutral pH.

PubMed

Ulliman, Sydney L; McKay, Garrett; Rosario-Ortiz, Fernando L; Linden, Karl G

2018-03-01

While the presence of iron is generally not seen as favorable for UV-based treatment systems due to lamp fouling and decreased UV transmittance, we show that low levels of iron can lead to improvements in the abatement of chemicals in the UV-hydrogen peroxide advanced oxidation process. The oxidation potential of an iron-assisted UV/H 2 O 2 (UV 254  + H 2 O 2  + iron) process was evaluated at neutral pH using iron levels below USEPA secondary drinking water standards (<0.3 mg/L). Para-chlorobenzoic acid (pCBA) was used as a hydroxyl radical (HO) probe to quantify HO steady state concentrations. Compounds degraded by different mechanisms including, carbamazepine (CBZ, HO oxidation) and N-nitrosodimethylamine (NDMA, direct photolysis), were used to investigate the effect of iron on compound degradation for UV/H 2 O 2 systems. The effects of iron species (Fe 2+ and Fe 3+ ), iron concentration (0-0.3 mg/L), H 2 O 2 concentration (0-10 mg/L) and background water matrix (low-carbon tap (LCT) and well water) on HO production and compound removal were examined. Iron-assisted UV/H 2 O 2 efficiency was most influenced by the target chemical and the water matrix. Added iron to UV/H 2 O 2 was shown to increase the steady-state HO concentration by approximately 25% in all well water scenarios. While CBZ removal was unchanged by iron addition, 0.3 mg/L iron improved NDMA removal rates in both LCT and well water matrices by 15.1% and 4.6% respectively. Furthermore, the combination of UV/Fe without H 2 O 2 was also shown to enhance NDMA removal when compared to UV photolysis alone indicating the presence of degradation pathways other than HO oxidation. Copyright © 2017 Elsevier Ltd. All rights reserved.

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

2015-09-09

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.

Decomposition of 3,5-dinitrobenzamide in aqueous solution during UV/H2O2 and UV/TiO2 oxidation processes.

PubMed

Yan, Yingjie; Liao, Qi-Nan; Ji, Feng; Wang, Wei; Yuan, Shoujun; Hu, Zhen-Hu

2017-02-01

3,5-Dinitrobenzamide has been widely used as a feed additive to control coccidiosis in poultry, and part of the added 3,5-dinitrobenzamide is excreted into wastewater and surface water. The removal of 3,5-dinitrobenzamide from wastewater and surface water has not been reported in previous studies. Highly reactive hydroxyl radicals from UV/hydrogen peroxide (H 2 O 2 ) and UV/titanium dioxide (TiO 2 ) advanced oxidation processes (AOPs) can decompose organic contaminants efficiently. In this study, the decomposition of 3,5-dinitrobenzamide in aqueous solution during UV/H 2 O 2 and UV/TiO 2 oxidation processes was investigated. The decomposition of 3,5-dinitrobenzamide fits well with a fluence-based pseudo-first-order kinetics model. The decomposition in both two oxidation processes was affected by solution pH, and was inhibited under alkaline conditions. Inorganic anions such as NO 3 - , Cl - , SO 4 2- , HCO 3 - , and CO 3 2- inhibited the degradation of 3,5-dinitrobenzamide during the UV/H 2 O 2 and UV/TiO 2 oxidation processes. After complete decomposition in both oxidation processes, approximately 50% of 3,5-dinitrobenzamide was decomposed into organic intermediates, and the rest was mineralized to CO 2 , H 2 O, and other inorganic anions. Ions such as NH 4 + , NO 3 - , and NO 2 - were released into aqueous solution during the degradation. The primary decomposition products of 3,5-dinitrobenzamide were identified using time-of-flight mass spectrometry (LCMS-IT-TOF). Based on these products and ions release, a possible decomposition pathway of 3,5-dinitrobenzamide in both UV/H 2 O 2 and UV/TiO 2 processes was proposed.

Plant Aquaporin AtPIP1;4 Links Apoplastic H2O2 Induction to Disease Immunity Pathways.

PubMed

Tian, Shan; Wang, Xiaobing; Li, Ping; Wang, Hao; Ji, Hongtao; Xie, Junyi; Qiu, Qinglei; Shen, Dan; Dong, Hansong

2016-07-01

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. © 2016 American Society of Plant Biologists. All Rights Reserved.

Enhanced photocatalytic H2-production activity of graphene-modified titania nanosheets

NASA Astrophysics Data System (ADS)

Xiang, Quanjun; Yu, Jiaguo; Jaroniec, Mietek

2011-09-01

Graphene-modified TiO2 nanosheets with exposed (001) facets (graphene/TiO2) were prepared by microwave-hydrothermal treatment of graphene oxide (GO) and hydrothermally synthesized TiO2 nanosheets with exposed (001) facets in an ethanol-water solvent. These nanocomposite samples showed high photocatalytic H2-production activity in aqueous solutions containing methanol, as sacrificial reagent, even without Pt co-catalyst. The optimal graphene content was found to be ~1.0 wt%, giving a H2-production rate of 736 μmol h-1 g-1 with a quantum efficiency (QE) of 3.1%, which exceeded the rate observed on pure TiO2 nanosheets by more than 41 times. This high photocatalytic H2-production activity is due to the deposition of TiO2 nanosheets on graphene sheets, which act as an electron acceptor to efficiently separate the photogenerated charge carriers. The observed enhancement in the photocatalytic activity is due to the lower absolute potential of graphene/graphene z.rad- (-0.08 V vs. SHE, pH = 0) in comparison to the conduction band (-0.24 V) of anatase TiO2, meanwhile the aforementioned absolute value is higher than the reduction potential of H+ (0 V), which favors the electron transfer from the conduction band (CB) of TiO2 to graphene sheets and the reduction of H+, thus enhancing photocatalytic H2-production activity. The proposed mechanism for the observed photocatalytic performance of TiO2 nanosheets, modified with a small amount of graphene, was further confirmed by photoluminescence spectroscopy and transient photocurrent response. This work not only shows a possibility for the utilization of low cost graphene sheets as a substitute for noble metals (such as Pt) in the photocatalytic H2-production but also for the first time shows a significant enhancement in the H2-production activity by using metal-free carbon material as an effective co-catalyst.

In-vivo electrochemical monitoring of H2O2 production induced by root-inoculated endophytic bacteria in Agave tequilana leaves.

PubMed

Lima, Alex S; Prieto, Kátia R; Santos, Carla S; Paula Valerio, Hellen; Garcia-Ochoa, Evelyn Y; Huerta-Robles, Aurora; Beltran-Garcia, Miguel J; Di Mascio, Paolo; Bertotti, Mauro

2018-01-15

A dual-function platinum disc microelectrode sensor was used for in-situ monitoring of H 2 O 2 produced in A. tequilana leaves after inoculation of their endophytic bacteria (Enterobacter cloacae). Voltammetric experiments were carried out from 0.0 to -1.0V, a potential range where H 2 O 2 is electrochemically reduced. A needle was used to create a small cavity in the upper epidermis of A. tequilana leaves, where the fabricated electrochemical sensor was inserted by using a manual three-dimensional micropositioner. Control experiments were performed with untreated plants and the obtained electrochemical results clearly proved the formation of H 2 O 2 in the leaves of plants 3h after the E. cloacae inoculation, according to a mechanism involving endogenous signaling pathways. In order to compare the sensitivity of the microelectrode sensor, the presence of H 2 O 2 was detected in the root hairs by 3,3-diaminobenzidine (DAB) stain 72h after bacterial inoculation. In-situ pH measurements were also carried out with a gold disc microelectrode modified with a film of iridium oxide and lower pH values were found in A. tequilana leaves treated with bacteria, which may indicate the plant produces acidic substances by biosynthesis of secondary metabolites. This microsensor could be an advantageous tool for further studies on the understanding of the mechanism of H 2 O 2 production during the plant-endophyte interaction. Copyright © 2017 Elsevier B.V. All rights reserved.

Electron transport chain dysfunction by H(2)O (2) is linked to increased reactive oxygen species production and iron mobilization by lipoperoxidation: studies using Saccharomyces cerevisiae mitochondria.

PubMed

Cortés-Rojo, Christian; Estrada-Villagómez, Mirella; Calderón-Cortés, Elizabeth; Clemente-Guerrero, Mónica; Mejía-Zepeda, Ricardo; Boldogh, Istvan; Saavedra-Molina, Alfredo

2011-04-01

The mitochondrial electron transport chain (ETC) contains thiol groups (-SH) which are reversibly oxidized to modulate ETC function during H(2)O(2) overproduction. Since deleterious effects of H(2)O(2) are not limited to -SH oxidation, due to the formation of other H(2)O(2)-derived species, some processes like lipoperoxidation could enhance the effects of H(2)O(2) over ETC enzymes, disrupt their modulation by -SH oxidation and increase superoxide production. To verify this hypothesis, we tested the effects of H(2)O(2) on ETC activities, superoxide production and iron mobilization in mitochondria from lipoperoxidation-resistant native yeast and lipoperoxidation-sensitized yeast. Only complex III activity from lipoperoxidation-sensitive mitochondria exhibited a higher susceptibility to H(2)O(2) and increased superoxide production. The recovery of ETC activity by the thiol reductanct β-mercaptoethanol (BME) was also altered at complex III, and a role was attributed to lipoperoxidation, the latter being also responsible for iron release. A hypothetical model linking lipoperoxidation, increased complex III damage, superoxide production and iron release is given.

Effect of Soil pH Increase by Biochar on NO, N2O and N2 Production during Denitrification in Acid Soils

PubMed Central

Obia, Alfred; Cornelissen, Gerard; Mulder, Jan; Dörsch, Peter

2015-01-01

Biochar (BC) application to soil suppresses emission of nitrous- (N2O) and nitric oxide (NO), but the mechanisms are unclear. One of the most prominent features of BC is its alkalizing effect in soils, which may affect denitrification and its product stoichiometry directly or indirectly. We conducted laboratory experiments with anoxic slurries of acid Acrisols from Indonesia and Zambia and two contrasting BCs produced locally from rice husk and cacao shell. Dose-dependent responses of denitrification and gaseous products (NO, N2O and N2) were assessed by high-resolution gas kinetics and related to the alkalizing effect of the BCs. To delineate the pH effect from other BC effects, we removed part of the alkalinity by leaching the BCs with water and acid prior to incubation. Uncharred cacao shell and sodium hydroxide (NaOH) were also included in the study. The untreated BCs suppressed N2O and NO and increased N2 production during denitrification, irrespective of the effect on denitrification rate. The extent of N2O and NO suppression was dose-dependent and increased with the alkalizing effect of the two BC types, which was strongest for cacao shell BC. Acid leaching of BC, which decreased its alkalizing effect, reduced or eliminated the ability of BC to suppress N2O and NO net production. Just like untreated BCs, NaOH reduced net production of N2O and NO while increasing that of N2. This confirms the importance of altered soil pH for denitrification product stoichiometry. Addition of uncharred cacao shell stimulated denitrification strongly due to availability of labile carbon but only minor effects on the product stoichiometry of denitrification were found, in accordance with its modest effect on soil pH. Our study indicates that stimulation of denitrification was mainly due to increases in labile carbon whereas change in product stoichiometry was mainly due to a change in soil pH. PMID:26397367

Effect of Soil pH Increase by Biochar on NO, N2O and N2 Production during Denitrification in Acid Soils.

PubMed

Obia, Alfred; Cornelissen, Gerard; Mulder, Jan; Dörsch, Peter

2015-01-01

Biochar (BC) application to soil suppresses emission of nitrous- (N2O) and nitric oxide (NO), but the mechanisms are unclear. One of the most prominent features of BC is its alkalizing effect in soils, which may affect denitrification and its product stoichiometry directly or indirectly. We conducted laboratory experiments with anoxic slurries of acid Acrisols from Indonesia and Zambia and two contrasting BCs produced locally from rice husk and cacao shell. Dose-dependent responses of denitrification and gaseous products (NO, N2O and N2) were assessed by high-resolution gas kinetics and related to the alkalizing effect of the BCs. To delineate the pH effect from other BC effects, we removed part of the alkalinity by leaching the BCs with water and acid prior to incubation. Uncharred cacao shell and sodium hydroxide (NaOH) were also included in the study. The untreated BCs suppressed N2O and NO and increased N2 production during denitrification, irrespective of the effect on denitrification rate. The extent of N2O and NO suppression was dose-dependent and increased with the alkalizing effect of the two BC types, which was strongest for cacao shell BC. Acid leaching of BC, which decreased its alkalizing effect, reduced or eliminated the ability of BC to suppress N2O and NO net production. Just like untreated BCs, NaOH reduced net production of N2O and NO while increasing that of N2. This confirms the importance of altered soil pH for denitrification product stoichiometry. Addition of uncharred cacao shell stimulated denitrification strongly due to availability of labile carbon but only minor effects on the product stoichiometry of denitrification were found, in accordance with its modest effect on soil pH. Our study indicates that stimulation of denitrification was mainly due to increases in labile carbon whereas change in product stoichiometry was mainly due to a change in soil pH.

The Relationship of HCN, C2H6, & H2O in Comets: A Key Clue to Origins?

NASA Astrophysics Data System (ADS)

Mumma, Michael J.; Charnley, Steven B.; Cordiner, Martin; Paganini, Lucas; Villanueva, Geronimo Luis

2017-10-01

Background: HCN, C2H6, and H2O are three of the best characterized volatiles in comets. It is often assumed that all three are primary volatiles, native to the nucleus. Here, we compare their properties in 26 comets (9 JFC and 17 Oort-cloud), making 6 points:1. Both HCN and C2H6 are poor proxies for water production. The production rate ratio (Q-ratio) of each trace gas relative to water varies by a factor of six among these comets.2. All 26 comets have Q-ratios HCN/C2H6 > 0.1. In 18 comets the Q-ratios HCN/H2O and C2H6/H2O are correlated, with a mean ratio of 0.33. In 6 comets undergoing complete disruption, this Q-ratio exceeds 0.5.3. Q-ratios HCN/C2H6 are not correlated with Q(H2O), nor are they correlated with dynamical class (Oort cloud vs. JFC).4. The nucleus-centered rotational temperatures measured for H2O and other primary species (C2H6, CH3OH) usually agree within error, but those for HCN are often slightly cooler. Could this mean that HCN is not fully developed in the warm near-nucleus region, and instead is at least in part a product species?5. With its strong dipole moment and H-bonding character, HCN should be linked more strongly in the nuclear ice to other molecules with similar properties (H2O, CH3OH), but instead its spatial release in some comets seems strongly coupled to volatiles that lack a dipole moment and thus do not form H-bonds (methane, ethane). Is HCN produced in part from an apolar precursor?6. ALMA maps of HCN and the dust continuum show a slight displacement in their centroids. Is this the signature of extended production of HCN?HCN as a product species: Points 4-6 suggest that HCN may have a significant distributed source. The astrochemical species ammonium cyanide is a strong candidate for this HCN precursor; at moderately low temperatures (< 200K) NH4CN is a stable solid, but it dissociates into HCN and NH3 when warmed. Disruption could eject macroscopic solid NH4CN into the coma where subsequent warming and release could augment

Organic Contaminant Abatement in Reclaimed Water by UV/H2O2 and a Combined Process Consisting of O3/H2O2 Followed by UV/H2O2: Prediction of Abatement Efficiency, Energy Consumption, and Byproduct Formation.

PubMed

Lee, Yunho; Gerrity, Daniel; Lee, Minju; Gamage, Sujanie; Pisarenko, Aleksey; Trenholm, Rebecca A; Canonica, Silvio; Snyder, Shane A; von Gunten, Urs

2016-04-05

UV/H2O2 processes can be applied to improve the quality of effluents from municipal wastewater treatment plants by attenuating trace organic contaminants (micropollutants). This study presents a kinetic model based on UV photolysis parameters, including UV absorption rate and quantum yield, and hydroxyl radical (·OH) oxidation parameters, including second-order rate constants for ·OH reactions and steady-state ·OH concentrations, that can be used to predict micropollutant abatement in wastewater. The UV/H2O2 kinetic model successfully predicted the abatement efficiencies of 16 target micropollutants in bench-scale UV and UV/H2O2 experiments in 10 secondary wastewater effluents. The model was then used to calculate the electric energies required to achieve specific levels of micropollutant abatement in several advanced wastewater treatment scenarios using various combinations of ozone, UV, and H2O2. UV/H2O2 is more energy-intensive than ozonation for abatement of most micropollutants. Nevertheless, UV/H2O2 is not limited by the formation of N-nitrosodimethylamine (NDMA) and bromate whereas ozonation may produce significant concentrations of these oxidation byproducts, as observed in some of the tested wastewater effluents. The combined process of O3/H2O2 followed by UV/H2O2, which may be warranted in some potable reuse applications, can achieve superior micropollutant abatement with reduced energy consumption compared to UV/H2O2 and reduced oxidation byproduct formation (i.e., NDMA and/or bromate) compared to conventional ozonation.

Short belt-like Ca 2 B 2 O 5 ·H 2 O nanostructures: Hydrothermal formation, FT-IR, thermal decomposition, and optical properties

NASA Astrophysics Data System (ADS)

Zhu, Wancheng; Zhang, Xiao; Wang, Xiaoli; Zhang, Heng; Zhang, Qiang; Xiang, Lan

2011-10-01

Uniform high crystallinity short belt-like Ca 2B 2O 5·H 2O nanostructures (nanobelts) were facilely synthesized through a room temperature coprecipitation of CaCl 2, H 3BO 3, and NaOH solutions, followed by a mild hydrothermal treatment (180 °C, 12.0 h). By a preferential growth parallel to the (1 0 0) planes, Ca 2B 2O 5·H 2O nanobelts with a length of 1-5 μm, a width of 100-400 nm, and a thickness of 55-90 nm were obtained. The calcination of the nanobelts at 500 °C for 2.0 h led to short Ca 2B 2O 5 nanobelts with well preserved 1D morphology. Calcination at 800 °C led to a mixture of Ca 2B 2O 5 and Ca 3B 2O 6. The products were with belt-like and quasi-polyhedron morphology, while they turned into pore-free micro-rod like and polyhedron morphology when the calcination was taken in the presence of NaCl. NaCl assisted high temperature calcination at 900 °C promoted the formation of Ca 3B 2O 6 in the products. When dispersed in deionized water or absolute ethanol, the Ca 2B 2O 5·H 2O nanobelts and Ca 2B 2O 5 nanobelts showed good transparency from the ultraviolet to the visible region. The as-synthesized Ca 2B 2O 5·H 2O and Ca 2B 2O 5 nanobelts can be employed as novel metal borate nanomaterials for further potential applications in the area of glass fibers, antiwear additive, ceramic coatings, and so on.

A Computational Investigation of the Oxidative Deboronation of BoroGlycine, H2N–CH2–B(OH)2, Using H2O and H2O2

PubMed Central

Larkin, Joseph D.; Markham, George D.; Milkevitch, Matt; Brooks, Bernard R.; Bock, Charles W.

2014-01-01

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, 111, 6489–6500, 2007). 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 a 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 multi-step 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 anti-cancer drug Bortezomib (Velcade™, PS-341) where it was found to be the principle deactivation pathway. (Labutti et al. Chem. Res. Toxicol., 19, 539–546

Facile synthesis of core-shell Cu2O@ ZnO structure with enhanced photocatalytic H2 production

NASA Astrophysics Data System (ADS)

Zhang, Yong-Hui; Jiu, Bei-Bei; Gong, Fei-Long; Lu, Kuan; Jiang, Nan; Zhang, Hao-Li; Chen, Jun-Li

2018-05-01

Core-shell Cu2O@ZnO composites were synthesized successfully based on a one-pot hydrothermal method in the presence of dioctyl sulfosuccinate sodium salt (AOT) surfactant. The Cu2O can be converted to rough core-shell Cu2O@ZnO structure by adjusting the amount of zinc powder added. The as-synthesized Cu2O@ZnO composites exhibited excellent photocatalytic activity and the amount of H2 generated using these composites was 4.5-fold more than that produced with Cu2O cubes. A possible photocatalytic mechanism for the Cu2O@ZnO composites with enhanced photocatalytic activity could be the separation by ZnO of the effective charge carriers.

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

Salt at concentrations relevant to meat processing enhances Shiga toxin 2 production in Escherichia coli O157:H7.

PubMed

Harris, Shaun M; Yue, Wan-Fu; Olsen, Sarena A; Hu, Jia; Means, Warrie J; McCormick, Richard J; Du, Min; Zhu, Mei-Jun

2012-10-15

Escherichia coli (E. coli) O157:H7 remains a major food safety concern associated with meat, especially beef products. Shiga toxins (Stx) are key virulence factors produced by E. coli O157:H7 that are responsible for hemorrhagic colitis and Hemolytic Uremic Syndrome. Stx are heat stable and can be absorbed after oral ingestion. Despite the extensive study of E. coli O157:H7 survival during meat processing, little attention is paid to the production of Stx during meat processing. The objective of this study was to elucidate the effect of salt, an essential additive to processed meat, at concentrations relevant to meat processing (0%, 1%, 2%, 3%, W/V) on Stx2 production and Stx2 prophage induction by E. coli O157:H7 strains. For both E. coli O157:H7 86-24 and EDL933 strains, including 2% salt in LB broth decreased (P<0.05) E. coli O157:H7 population, but increased (P<0.05) Stx2 production (as measured relative to Log(10)CFU) compared to that of the control (1% salt). Supplementing 3% salt decreased (P<0.05) both E. coli O157:H7 number and Stx2 production. Quantitative RT-PCR indicated that stx2 mRNA expression in culture media containing 2% salt was greatly increased (P<0.05) compared to other salt concentrations. Consistent with enhanced Stx2 production and stx2 expression, the 2% salt group had highest lambdoid phage titer and stx2 prophage induction among all salt treatments. RecA is a key mediator of bacterial response to stress, which mediates prophage activation. Quantitative RT-PCR further indicated that recA mRNA expression was higher in both 2% and 3% salt than that of 0% and 1% salt treatments, indicating that stress was involved in enhanced Stx2 production. In conclusion, salt at the concentration used for meat processing enhances Stx production, a process linked to bacterial stress response and lambdoid prophage induction. Published by Elsevier B.V.

Enhancement of sludge anaerobic biodegradability by combined microwave-H2O2 pretreatment in acidic conditions.

PubMed

Eswari, Parvathy; Kavitha, S; Kaliappan, S; Yeom, Ick-Tae; Banu, J Rajesh

2016-07-01

The aim of this study was to increase the sludge disintegration and reduce the cost of microwave (MW) pretreatment. Thermodynamic analysis of MW hydrolysis revealed the best fit with a first-order kinetic model at a specific energy of 18,600 kJ/kg total solids (TS). Combining H2O2 with MW resulted in a significant increment in solubilization from 30 to 50 % at 18,600 kJ/kg TS. The pH of H2O2-assisted MW-pretreated sludge (MW + H2O2) was in the alkaline range (pH 9-10), and it made the sludge unfavorable for subsequent anaerobic digestion and inhibits methane production. In order to nullify the alkaline effect caused by the MW + H2O2 combination, the addition of acid was considered for pH adjustment. H2O2-assisted MW-pretreated sludge in acidic conditions (MW + H2O2 + acid) showed a maximum methane production of 323 mL/g volatile solids (VS) than others during anaerobic biodegradability. A cost analysis of this study reveals that MW + H2O2 + acid was the most economical method with a net profit of 59.90 €/t of sludge.

The catalytic effects of H2CO3, CH3COOH, HCOOH and H2O on the addition reaction of CH2OO + H2O → CH2(OH)OOH

NASA Astrophysics Data System (ADS)

Zhang, Tianlei; Lan, Xinguang; Wang, Rui; Roy, Soumendra; Qiao, Zhangyu; Lu, Yousong; Wang, Zhuqing

2018-07-01

The addition reaction of CH2OO + H2O → CH2(OH)OOH without and with X (X = H2CO3, CH3COOH and HCOOH) and H2O was studied at CCSD(T)/6-311+ G(3df,2dp)//B3LYP/6-311+G(2d,2p) level of theory. Our results show that X can catalyse CH2OO + H2O → CH2(OH)OOH reaction both by increasing the number of rings, and by adding the size of the ring in which ring enlargement by COOH moiety of X inserting into CH2OO...H2O is favourable one. Water-assisted CH2OO + H2O → CH2(OH)OOH can occur by H2O moiety of (H2O)2 or the whole (H2O)2 forming cyclic structure with CH2OO, where the latter form is more favourable. Because the concentration of H2CO3 is unknown, the influence of CH3COOH, HCOOH and H2O were calculated within 0-30 km altitude of the Earth's atmosphere. The results calculated within 0-5 km altitude show that H2O and HCOOH have obvious effect on enhancing the rate with the enhancement factors are, respectively, 62.47%-77.26% and 0.04%-1.76%. Within 5-30 km altitude, HCOOH has obvious effect on enhancing the title rate with the enhancement factor of 2.69%-98.28%. However, compared with the reaction of CH2OO + HCOOH, the rate of CH2OO...H2O + HCOOH is much slower.

FLYING-WATER Renewables-H2-H2O TERRAFORMING: PERMANENT Drought(s)-Elimination FOREVER!!!

NASA Astrophysics Data System (ADS)

Ertl, G.; Alefeld, G.; Youdelis, W.; Radd, H.; Oertle, G.; Siegel, Edward

2011-03-01

"H2O H2O everywhere; ne'er a drop to drink"[Coleridge(1798)]; now: "H2 H2 everywhere; STILL ne'er a drop to drink": ONLY H2 (or methane CH4) can be FLYING-WATER(F-W) chemical-rain-in-pipelines Hindenberg-effect (H2-UP;H2O-DOWN): {O/H2O}=[16]/[18] 90 % ; O already in air uphill; NO H2O pumping need! In global-warming driven H2O-starved glacial-melting world, rescue is possible ONLY by Siegel [{3rd Intl. Conf. Alt.-Energy }(1980)-vol.5/p.459!!!] Renewables-H2-H2O purposely flexible versatile agile customizable scaleable retrofitable integrated operating-system. Rosenfeld[Science 315,1396(3/9/2007)]-Biello [Sci.Am.(3/9/2007)] crucial geomorph-ology which ONLY maximal-buoyancy H2 can exploit, to again make "Mountains into Fountains", ``upthrust rocks trapping the clouds to precipitate their rain/snow/H2O'': "terraforming"(and ocean-rebasificaton!!!) Siegel proprietary magnetic-hydrogen-valve (MHV) permits H2 flow in already in-ground dense BCC/ferritic-steels pipelines-network (NO new infrastructure) counters Tromp[Science 300,1740(2003)] dire warning of global-pandemics (cancers/ blindness/famine) Hydrogen-economy CATASTROPHIC H2 ozone-layer destruction sobering cavat to dangerous H2-automotion-economy panacea hype!!!

Melting and subsolidus reactions in the system K2O-CaO-Al2O3-SiO2-H2O

NASA Astrophysics Data System (ADS)

Johannes, Wilhelm

1980-09-01

Beginning of melting and subsolidus relationships in the system K2O-CaO-Al2O3-SiO2-H2O have been experimentally investigated at pressures up to 20 kbars. The equilibria discussed involve the phases anorthite, sanidine, zoisite, muscovite, quartz, kyanite, gas, and melt and two invariant points: Point [Ky] with the phases An, Or, Zo, Ms, Qz, Vapor, and Melt; point [Or] with An, Zo, Ms, Ky, Qz, Vapor, and Melt. The invariant point [Ky] at 675° C and 8.7 kbars marks the lowest solidus temperature of the system investigated. At pressures above this point the hydrated phases zoisite and muscovite are liquidus phases and the solidus temperatures increase with increasing pressure. At 20 kbars beginning of melting occurs at 740 °C. The solidus temperatures of the quinary system K2O-CaO-Al2O3-SiO2-H2O are almost 60° C (at 20 kbars) and 170° C (at 2kbars) below those of the limiting quaternary system CaO-Al2O3-SiO2-H2O. The maximum water pressure at which anorthite is stable is lowered from 14 to 8.7 kbars in the presence of sanidine. The stability limits of anorthite+ vapor and anorthite+sanidine+vapor at temperatures below 700° C are almost parallel and do not intersect. In the wide temperature — pressure range at pressures above the reaction An+Or+Vapor = Zo+Ms+Qz and temperatures below the melting curve of Zo+Ms+Ky+Qz+Vapor, the feldspar assemblage anorthite+sanidine is replaced by the hydrated phases zoisite and muscovite plus quartz. CaO-Al2O3-SiO2-H2O. Knowledge of the melting relationships involving the minerals zoisite and muscovite contributes to our understanding of the melting processes occuring in the deeper parts of the crust. Beginning of melting in granites and granodiorites depends on the composition of plagioclase. The solidus temperatures of all granites and granodiorites containing plagioclases of intermediate composition are higher than those of the Ca-free alkali feldspar granite system and below those of the Na-free system discussed in this

Porous microspheres of MgO-patched TiO2 for CO2 photoreduction with H2O vapor: temperature-dependent activity and stability.

PubMed

Liu, Lianjun; Zhao, Cunyu; Zhao, Huilei; Pitts, Daniel; Li, Ying

2013-05-07

A novel MgO-patched TiO2 microsphere photocatalyst demonstrated 10 times higher activity toward CO production from CO2 photoreduction with H2O vapor, when the reaction temperature increased from 50 to 150 °C. The catalytic performance of hybrid MgO-TiO2 was much more stable than TiO2, particularly at a higher temperature, likely due to easier desorption of reaction intermediates and the enhanced CO2 adsorption by MgO.

Suppressors of Superoxide-H2O2 Production at Site IQ of Mitochondrial Complex I Protect against Stem Cell Hyperplasia and Ischemia-Reperfusion Injury.

PubMed

Brand, Martin D; Goncalves, Renata L S; Orr, Adam L; Vargas, Leonardo; Gerencser, Akos A; Borch Jensen, Martin; Wang, Yves T; Melov, Simon; Turk, Carolina N; Matzen, Jason T; Dardov, Victoria J; Petrassi, H Michael; Meeusen, Shelly L; Perevoshchikova, Irina V; Jasper, Heinrich; Brookes, Paul S; Ainscow, Edward K

2016-10-11

Using high-throughput screening we identified small molecules that suppress superoxide and/or H 2 O 2 production during reverse electron transport through mitochondrial respiratory complex I (site I Q ) without affecting oxidative phosphorylation (suppressors of site I Q electron leak, "S1QELs"). S1QELs diminished endogenous oxidative damage in primary astrocytes cultured at ambient or low oxygen tension, showing that site I Q is a normal contributor to mitochondrial superoxide-H 2 O 2 production in cells. They diminished stem cell hyperplasia in Drosophila intestine in vivo and caspase activation in a cardiomyocyte cell model driven by endoplasmic reticulum stress, showing that superoxide-H 2 O 2 production by site I Q  is involved in cellular stress signaling. They protected against ischemia-reperfusion injury in perfused mouse heart, showing directly that superoxide-H 2 O 2 production by site I Q is a major contributor to this pathology. S1QELs are tools for assessing the contribution of site I Q to cell physiology and pathology and have great potential as therapeutic leads. Copyright © 2016 Elsevier Inc. All rights reserved.

Two mixed-ligand lanthanide–hydrazone complexes: [Pr(NCS)3(pbh)2]·H2O and [Nd(NCS)(NO3)(pbh)2(H2O)]NO3·2.33H2O [pbh is N′-(pyridin-2-ylmethylidene)benzo­hydrazide, C13H11N3O

PubMed Central

Paschalidis, Damianos G.; Harrison, William T. A.

2016-01-01

The gel-mediated syntheses and crystal structures of [N′-(pyridin-2-ylmethylidene-κN)benzohydrazide-κ2 N′,O]tris(thiocyanato-κN)praseodymium(III) mono­hydrate, [Pr(NCS)3(C13H11N3O)2]·H2O, (I), and aqua(nitrato-κ2 O,O′)[N′-(pyri­din-2-ylmethylidene-κN)benzohydrazide-κ2 N′,O](thiocyanato-κN)neo­dym­ium(III) nitrate 2.33-hydrate, [Nd(NCS)(NO3)(C13H11N3O)2(H2O)]NO3·2.33H2O, (II), are reported. The Pr3+ ion in (I) is coordinated by two N,N,O-tridentate N′-(pyridin-2-ylmethylidene)benzohydrazide (pbh) ligands and three N-bonded thio­cyanate ions to generate an irregular PrN7O2 coordination polyhedron. The Nd3+ ion in (II) is coordinated by two N,N,O-tridentate pbh ligands, an N-bonded thio­cyanate ion, a bidentate nitrate ion and a water mol­ecule to generate a distorted NdN5O5 bicapped square anti­prism. The crystal structures of (I) and (II) feature numerous hydrogen bonds, which lead to the formation of three-dimensional networks in each case. PMID:26958385

Photogeneration of H2O2 in Water-Swollen SPEEK/PVA Polymer Films.

PubMed

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

2016-06-09

Efficient reduction of O2 took place via illumination with 350 nm photons of cross-linked films containing a blend of sulfonated poly(ether etherketone) and poly(vinyl alcohol) in contact with air-saturated aqueous solutions. Swelling of the solid macromolecular matrices in H2O enabled O2 diffusion into the films and also continuous extraction of the photogenerated H2O2, which was the basis for a method that allowed quantification of the product. Peroxide formed with similar efficiencies in films containing sulfonated polyketones prepared from different precursors and the initial photochemical process was found to be the rate-determining step. Generation of H2O2 was most proficient in the range of 4.9 ≤ pH ≤ 8 with a quantum yield of 0.2, which was 10 times higher than the efficiencies determined for solutions of the polymer blend. Increases in temperature as well as [O2] in solution were factors that enhanced the H2O2 generation. H2O2 quantum yields as high as 0.6 were achieved in H2O/CH3CN mixtures with low water concentrations, but peroxide no longer formed when film swelling was suppressed. A mechanism involving reduction of O2 by photogenerated α-hydroxy radicals from the polyketone in competition with second-order radical decay processes explains the kinetic features. Higher yields result from the films because cross-links present in them hinder diffusion of the radicals, limiting their decay and enhancing the oxygen reduction pathway.

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.

Stoichiometry and possible mechanism of SiH/sub 4/-O/sub 2/ explosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hartman, J.R.; Famil-Ghiriha, J.; Ring, M.A.

1987-04-01

The products of silane-O/sub 2/ mixture explosions vary with mixture composition. For O/sub 2/-rich mixtures (>70% O/sub 2/), the products are H/sub 2/O and SiO/sub 2/. As the mixtures become richer in silane, H/sub 2/ replaces H/sub 2/O as a final product. For very SiH/sub 4/-rich mixtures (>70% SiH/sub 4/), the products are H/sub 2/, SiO/sub x/, and Si. The fact that silane is totally consumed in silane-rich mixtures (70-90% silane) demonstrates that solid particle formation (SiO/sub 2/, SiO, and Si) occurs very rapidly and that the accompanying heat release is essential to drive the reactions to completion. It ismore » also clear that the explosion of a silane-rich mixture is primarily a thermal explosion of silane. Effects due to problems associated with upper pressure limit measurements and mechanistic aspects of the SiH/sub 4/-O/sub 2/ explosion reaction are discussed.« less

TES/Aura L2 Water Vapor (H2O) Limb V6 (TL2H2OL)

Atmospheric Science Data Center

2018-03-01

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 ...

A Key Role for Apoplastic H2O2 in Norway Spruce Phenolic Metabolism.

PubMed

Laitinen, Teresa; Morreel, Kris; Delhomme, Nicolas; Gauthier, Adrien; Schiffthaler, Bastian; Nickolov, Kaloian; Brader, Günter; Lim, Kean-Jin; Teeri, Teemu H; Street, Nathaniel R; Boerjan, Wout; Kärkönen, Anna

2017-07-01

Apoplastic events such as monolignol oxidation and lignin polymerization are difficult to study in intact trees. To investigate the role of apoplastic hydrogen peroxide (H 2 O 2 ) in gymnosperm phenolic metabolism, an extracellular lignin-forming cell culture of Norway spruce ( Picea abies ) was used as a research model. Scavenging of apoplastic H 2 O 2 by potassium iodide repressed lignin formation, in line with peroxidases activating monolignols for lignin polymerization. Time-course analyses coupled to candidate substrate-product pair network propagation revealed differential accumulation of low-molecular-weight phenolics, including (glycosylated) oligolignols, (glycosylated) flavonoids, and proanthocyanidins, in lignin-forming and H 2 O 2 -scavenging cultures and supported that monolignols are oxidatively coupled not only in the cell wall but also in the cytoplasm, where they are coupled to other monolignols and proanthocyanidins. Dilignol glycoconjugates with reduced structures were found in the culture medium, suggesting that cells are able to transport glycosylated dilignols to the apoplast. Transcriptomic analyses revealed that scavenging of apoplastic H 2 O 2 resulted in remodulation of the transcriptome, with reduced carbon flux into the shikimate pathway propagating down to monolignol biosynthesis. Aggregated coexpression network analysis identified candidate enzymes and transcription factors for monolignol oxidation and apoplastic H 2 O 2 production in addition to potential H 2 O 2 receptors. The results presented indicate that the redox state of the apoplast has a profound influence on cellular metabolism. © 2017 American Society of Plant Biologists. All Rights Reserved.

Stable solid and aqueous H2CO3 from CO2 and H2O at high pressure and high temperature

NASA Astrophysics Data System (ADS)

Wang, Hongbo; Zeuschner, Janek; Eremets, Mikhail; Troyan, Ivan; Willams, Jonathan

2016-01-01

Carbonic acid (H2CO3) forms in small amounts when CO2 dissolves in H2O, yet decomposes rapidly under ambient conditions of temperature and pressure. Despite its fleeting existence, H2CO3 plays an important role in the global carbon cycle and in biological carbonate-containing systems. The short lifetime in water and presumed low concentration under all terrestrial conditions has stifled study of this fundamental species. Here, we have examined CO2/H2O mixtures under conditions of high pressure and high temperature to explore the potential for reaction to H2CO3 inside celestial bodies. We present a novel method to prepare solid H2CO3 by heating CO2/H2O mixtures at high pressure with a CO2 laser. Furthermore, we found that, contrary to present understanding, neutral H2CO3 is a significant component in aqueous CO2 solutions above 2.4 GPa and 110 °C as identified by IR-absorption and Raman spectroscopy. This is highly significant for speciation of deep C-O-H fluids with potential consequences for fluid-carbonate-bearing rock interactions. As conditions inside subduction zones on Earth appear to be most favorable for production of aqueous H2CO3, a role in subduction related phenomena is inferred.

Stable solid and aqueous H2CO3 from CO2 and H2O at high pressure and high temperature.

PubMed

Wang, Hongbo; Zeuschner, Janek; Eremets, Mikhail; Troyan, Ivan; Willams, Jonathan

2016-01-27

Carbonic acid (H2CO3) forms in small amounts when CO2 dissolves in H2O, yet decomposes rapidly under ambient conditions of temperature and pressure. Despite its fleeting existence, H2CO3 plays an important role in the global carbon cycle and in biological carbonate-containing systems. The short lifetime in water and presumed low concentration under all terrestrial conditions has stifled study of this fundamental species. Here, we have examined CO2/H2O mixtures under conditions of high pressure and high temperature to explore the potential for reaction to H2CO3 inside celestial bodies. We present a novel method to prepare solid H2CO3 by heating CO2/H2O mixtures at high pressure with a CO2 laser. Furthermore, we found that, contrary to present understanding, neutral H2CO3 is a significant component in aqueous CO2 solutions above 2.4 GPa and 110 °C as identified by IR-absorption and Raman spectroscopy. This is highly significant for speciation of deep C-O-H fluids with potential consequences for fluid-carbonate-bearing rock interactions. As conditions inside subduction zones on Earth appear to be most favorable for production of aqueous H2CO3, a role in subduction related phenomena is inferred.

Candidate Water Vapor Lines to Locate the H2O Snowline through High-dispersion Spectroscopic Observations. III. Submillimeter H2 16O and H2 18O Lines

NASA Astrophysics Data System (ADS)

Notsu, Shota; Nomura, Hideko; Walsh, Catherine; Honda, Mitsuhiko; Hirota, Tomoya; Akiyama, Eiji; Millar, T. J.

2018-03-01

In this paper, we extend the results presented in our former papers on using ortho-{{{H}}}2{}16{{O}} line profiles to constrain the location of the H2O snowline in T Tauri and Herbig Ae disks, to include submillimeter para-{{{H}}}2{}16{{O}} and ortho- and para-{{{H}}}2{}18{{O}} lines. Since the number densities of the ortho- and para-{{{H}}}2{}18{{O}} molecules are about 560 times smaller than their 16O analogs, they trace deeper into the disk than the ortho-{{{H}}}2{}16{{O}} lines (down to z = 0, i.e., the midplane). Thus these {{{H}}}2{}18{{O}} lines are potentially better probes of the position of the H2O snowline at the disk midplane, depending on the dust optical depth. The values of the Einstein A coefficients of submillimeter candidate water lines tend to be lower (typically <10‑4 s‑1) than infrared candidate water lines. Thus in the submillimeter candidate water line cases, the local intensity from the outer optically thin region in the disk is around 104 times smaller than that in the infrared candidate water line cases. Therefore, in the submillimeter lines, especially {{{H}}}2{}18{{O}} and para-{{{H}}}2{}16{{O}} lines with relatively lower upper state energies (∼a few 100 K) can also locate the position of the H2O snowline. We also investigate the possibility of future observations with ALMA to identify the position of the water snowline. There are several candidate water lines that trace the hot water gas inside the H2O snowline in ALMA Bands 5–10.

TES/Aura L2 Water Vapor (H2O) Limb V6 (TL2H2OLS)

Atmospheric Science Data Center

2018-03-01

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 ...

Submillimeter H2O and H2O+emission in lensed ultra- and hyper-luminous infrared galaxies at z 2-4

NASA Astrophysics Data System (ADS)

Yang, C.; Omont, A.; Beelen, A.; González-Alfonso, E.; Neri, R.; Gao, Y.; van der Werf, P.; Weiß, A.; Gavazzi, R.; Falstad, N.; Baker, A. J.; Bussmann, R. S.; Cooray, A.; Cox, P.; Dannerbauer, H.; Dye, S.; Guélin, M.; Ivison, R.; Krips, M.; Lehnert, M.; Michałowski, M. J.; Riechers, D. A.; Spaans, M.; Valiante, E.

2016-11-01

We report rest-frame submillimeter H2O emission line observations of 11 ultra- or hyper-luminous infrared galaxies (ULIRGs or HyLIRGs) at z 2-4 selected among the brightest lensed galaxies discovered in the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS). Using the IRAM NOrthern Extended Millimeter Array (NOEMA), we have detected 14 new H2O emission lines. These include five 321-312ortho-H2O lines (Eup/k = 305 K) and nine J = 2 para-H2O lines, either 202-111(Eup/k = 101 K) or 211-202(Eup/k = 137 K). The apparent luminosities of the H2O emission lines are μLH2O 6-21 × 108 L⊙ (3 <μ< 15, where μ is the lens magnification factor), with velocity-integrated line fluxes ranging from 4-15 Jy km s-1. We have also observed CO emission lines using EMIR on the IRAM 30 m telescope in seven sources (most of those have not yet had their CO emission lines observed). The velocity widths for CO and H2O lines are found to be similar, generally within 1σ errors in the same source. With almost comparable integrated flux densities to those of the high-J CO line (ratios range from 0.4 to 1.1), H2O is found to be among the strongest molecular emitters in high-redshift Hy/ULIRGs. We also confirm our previously found correlation between luminosity of H2O (LH2O) and infrared (LIR) that LH2O LIR1.1-1.2, with ournew detections. This correlation could be explained by a dominant role of far-infrared pumping in the H2O excitation. Modelling reveals that the far-infrared radiation fields have warm dust temperature Twarm 45-75 K, H2O column density per unit velocity interval NH2O /ΔV ≳ 0.3 × 1015 cm-2 km-1 s and 100 μm continuum opacity τ100> 1 (optically thick), indicating that H2O is likely to trace highly obscured warm dense gas. However, further observations of J ≥ 4 H2O lines are needed to better constrain the continuum optical depth and other physical conditions of the molecular gas and dust. We have also detected H2O+ emission in three sources. A tight correlation

Protective effect of Dendrobium officinale polysaccharides on H2O2-induced injury in H9c2 cardiomyocytes.

PubMed

Zhao, Xiaoyan; Dou, Mengmeng; Zhang, Zhihao; Zhang, Duoduo; Huang, Chengzhi

2017-10-01

The preliminary studies have shown that Dendrobium officinale possessed therapeutic effects on hypertension and atherosclerosis. Studies also reported that Dendrobium officinale polysaccharides showed antioxidant capabilities. However, little is known about its effects on myocardial cells under oxidative stress. The present study was designed to study the protective effect of Dendrobium officinale polysaccharides against H 2 O 2 -induced oxidative stress in H9c2 cells. MTT assay was carried out to determine the cell viability of H9c2 cells when pretreated with Dendrobium officinale polysaccharides. Fluorescent microscopy measurements were performed for evaluating the apoptosis in H9c2 cells. Furthermore, effects of Dendrobium officinale polysaccharides on the activities of antioxidative indicators (malondialdehyde, superoxide dismutase), reactive oxygen species (ROS) production and mitochondrial membrane potential (MMP) levels were analyzed. Dendrobium officinale polysaccharides attenuated H 2 O 2 -induced cell death, as determined by the MTT assay. Dendrobium officinale polysaccharides decreased malondialdehyde levels, increased superoxide dismutase activities, and inhibited the generation of intracellular ROS. Moreover, pretreatment with Dendrobium officinale polysaccharides also inhibited apoptosis and increased the MMP levels in H9c2 cells. These results suggested the protective effects of Dendrobium officinale polysaccharides against H 2 O 2 -induced injury in H9c2 cells. The results also indicated the anti-oxidative capability of Dendrobium officinale polysaccharides. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Studies of proton irradiated H2O + CO2 and H2O + CO ices and analysis of synthesized molecules

NASA Technical Reports Server (NTRS)

Moore, M. H.; Khanna, R.; Donn, B.

1991-01-01

Infrared spectra of H2O + CO2 and H2O + CO ices before and after proton irradiation showed that a major reaction in both mixtures was the interconversion of CO2 yields CO. Radiation synthesized organic compounds such as carbonic acid were identified in the H2O + CO2 ice. Different chemical pathways dominate in the H2O + CO ice in which formaldehyde, methanol, ethanol, and methane were identified. Sublimed material was also analyzed using a mass spectrometer. Implications of these results are discussed in reference to comets.

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

FoxO proteins restrain osteoclastogenesis and bone resorption by attenuating H2O2 accumulation

PubMed Central

Bartell, Shoshana M.; Kim, Ha-Neui; Ambrogini, Elena; Han, Li; Iyer, Srividhya; Serra Ucer, S.; Rabinovitch, Peter; Jilka, Robert L.; Weinstein, Robert S.; Zhao, Haibo; O’Brien, Charles A.; Manolagas, Stavros C.; Almeida, Maria

2014-01-01

Besides their cell-damaging effects in the setting of oxidative stress, reactive oxygen species (ROS) play an important role in physiological intracellular signalling by triggering proliferation and survival. FoxO transcription factors counteract ROS generation by upregulating antioxidant enzymes. Here we show that intracellular H2O2 accumulation is a critical and purposeful adaptation for the differentiation and survival of osteoclasts, the bone cells responsible for the resorption of mineralized bone matrix. Using mice with conditional loss or gain of FoxO transcription factor function, or mitochondria-targeted catalase in osteoclasts, we demonstrate this is achieved, at least in part, by downregulating the H2O2-inactivating enzyme catalase. Catalase downregulation results from the repression of the transcriptional activity of FoxO1, 3 and 4 by RANKL, the indispensable signal for the generation of osteoclasts, via an Akt-mediated mechanism. Notably, mitochondria-targeted catalase prevented the loss of bone caused by loss of oestrogens, suggesting that decreasing H2O2 production in mitochondria may represent a rational pharmacotherapeutic approach to diseases with increased bone resorption. PMID:24781012

Outbursts of H2O in Comet P/Halley

NASA Astrophysics Data System (ADS)

Larson, H. P.; Hu, H.-Y.; Mumma, M. J.; Weaver, H. A.

1990-07-01

Comet Halley gas-production monitoring efforts in March 1986 with the NASA Kuiper Airborne Observatory's Fourier transform spectrometer have indicated rapid temporal variations in H2O emissions; a continuous record of an H2O outburst was thus obtained. The event, in which H2O brightness increased by a factor of 2.2 in less than 10 min, is ascribable to an energetic process in the nucleus whose character may have been that of amorphous H2O ice crystallization, chemical explosion, thermal stress, or a compressed gas pocket. The timing and energy of the event appear to require an internal energy source; amorphous ice crystallization is held to be most consistent with compositional and thermal models of cometary nuclei as well as the observations.

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.;

Catalase activity is stimulated by H2O2 in rich culture medium and is required for H2O2 resistance and adaptation in yeast☆

PubMed Central

Martins, Dorival; English, Ann M.

2014-01-01

Catalases are efficient scavengers of H2O2 and protect cells against H2O2 stress. Examination of the H2O2 stimulon in Saccharomyces cerevisiae revealed that the cytosolic catalase T (Ctt1) protein level increases 15-fold on H2O2 challenge in synthetic complete media although previous work revealed that deletion of the CCT1 or CTA1 genes (encoding peroxisomal/mitochondrial catalase A) does not increase the H2O2 sensitivity of yeast challenged in phosphate buffer (pH 7.4). This we attributed to our observation that catalase activity is depressed when yeast are challenged with H2O2 in nutrient-poor media. Hence, we performed a systematic comparison of catalase activity and cell viability of wild-type yeast and of the single catalase knockouts, ctt1∆ and cta1∆, following H2O2 challenge in nutrient-rich medium (YPD) and in phosphate buffer (pH 7.4). Ctt1 but not Cta1 activity is strongly induced by H2O2 when cells are challenged in YPD but suppressed when cells are challenged in buffer. Consistent with the activity results, exponentially growing ctt1∆ cells in YPD are more sensitive to H2O2 than wild-type or cta1∆ cells, whereas in buffer all three strains exhibit comparable H2O2 hypersensitivity. Furthermore, catalase activity is increased during adaptation to sublethal H2O2 concentrations in YPD but not in buffer. We conclude that induction of cytosolic Ctt1 activity is vital in protecting yeast against exogenous H2O2 but this activity is inhibited by H2O2 when cells are challenged in nutrient-free media. PMID:24563848

The roles of two O-donor ligands in the Fe2+-binding and H2O2-sensing by the Fe2+-dependent H2O2 sensor PerR.

PubMed

Ji, Chang-Jun; Yang, Yoon-Mo; Kim, Jung-Hoon; Ryu, Su-Hyun; Youn, Hwan; Lee, Jin-Won

2018-05-10

PerR is a metal-dependent peroxide sensing transcription factor which controls the expression of genes involved in peroxide resistance. The function of Bacillus subtilis PerR is mainly dictated by the regulatory metal ion (Fe 2+ or Mn 2+ ) coordinated by three N-donor ligands (His37, His91, and His93) and two O-donor ligands (Asp85 and Asp104). While H 2 O 2 sensing by PerR is mediated by Fe 2+ -dependent oxidation of N-donor ligand (either His37 or His91), one of the O-donor ligands (Asp104), but not Asp85, has been proposed as the key residue that regulates the sensitivity of PerR to H 2 O 2 . Here we systematically investigated the relative roles of two O-donor ligands of PerR in metal-binding affinity and H 2 O 2 sensitivity in vivo and in vitro. Consistent with the previous report, in vitro the D104E-PerR could not sense low levels of H 2 O 2 in the presence of excess Fe 2+ sufficient for the formation of the Fe 2+ -bound D104E-PerR. However, the expression of PerR-regulated reporter fusion was not repressed by D104E-PerR in the presence of Fe 2+ , suggesting that Fe 2+ is not an effective corepressor for this mutant protein in vivo. Furthermore, in vitro metal titration assays indicate that D104E-PerR has a significantly reduced affinity for Fe 2+ , but not for Mn 2+ , when compared to wild type PerR. These data indicate that the type of O-donor ligand (Asp vs. Glu) at position 104 is an important determinant in providing high Fe 2+ -binding affinity required for the sensing of the physiologically relevant Fe 2+ -levels, in addition to its role in rendering PerR highly sensitive to physiological levels of H 2 O 2 . In comparison, the D85E-PerR did not show a perturbed change in Fe 2+ -binding affinity, however, it displayed a slightly decreased sensitivity to H 2 O 2 both in vivo and in vitro, suggesting that the type of O-donor ligand (Asp vs. Glu) at position 85 may be important for the fine-tuning of H 2 O 2 sensitivity. Copyright © 2018 Elsevier

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. Copyright © 2015 Elsevier Ltd. All rights reserved.

Electrochemical Quantification of Extracellular Local H2O2 Kinetics Originating from Single Cells.

PubMed

Bozem, Monika; Knapp, Phillip; Mirčeski, Valentin; Slowik, Ewa J; Bogeski, Ivan; Kappl, Reinhard; Heinemann, Christian; Hoth, Markus

2017-05-15

H 2 O 2 is produced by all eukaryotic cells under physiological and pathological conditions. Due to its enormous relevance for cell signaling at low concentrations and antipathogenic function at high concentrations, precise quantification of extracellular local H 2 O 2 concentrations ([H 2 O 2 ]) originating from single cells is required. Using a scanning electrochemical microscope and bare platinum disk ultramicroelectrodes, we established sensitive long-term measurements of extracellular [H 2 O 2 ] kinetics originating from single primary human monocytes (MCs) ex vivo. For the electrochemical techniques square wave voltammetry, cyclic and linear scan voltammetry, and chronoamperometry, detection limits for [H 2 O 2 ] were determined to be 5, 50, and 500 nM, respectively. Following phorbol ester stimulation, local [H 2 O 2 ] 5-8 μm above a single MC increased by 3.4 nM/s within the first 10 min before reaching a plateau. After extracellular addition of H 2 O 2 to an unstimulated MC, the local [H 2 O 2 ] decreased on average by 4.2 nM/s due to degradation processes of the cell. Using the scanning mode of the setup, we found that H 2 O 2 is evenly distributed around the producing cell and can still be detected up to 30 μm away from the cell. The electrochemical single-cell measurements were validated in MC populations using electron spin resonance spectroscopy and the Amplex ® UltraRed assay. Innovation and Conclusion: We demonstrate a highly sensitive, spatially, and temporally resolved electrochemical approach to monitor dynamics of production and degradation processes for H 2 O 2 separately. Local extracellular [H 2 O 2 ] kinetics originating from single cells is quantified in real time. Antioxid. Redox Signal. 00, 000-000.

Photoproduction of One-Electron Reducing Intermediates by Chromophoric Dissolved Organic Matter (CDOM): Relation to O2- and H2O2 Photoproduction and CDOM Photooxidation.

PubMed

Zhang, Yi; Blough, Neil V

2016-10-06

A molecular probe, 3-amino-2,2,5,5,-tetramethy-1-pyrrolydinyloxy (3ap), was employed to determine the formation rates of one-electron reducing intermediates generated photochemically from both untreated and borohydride-reduced Suwanee River fulvic and humic acids (SRFA and SRHA, respectively). This stable nitroxyl radical reacts rapidly with reducing radicals and other one-electron reductants to produce a relatively stable product, the hydroxylamine, which can be derivatized with fluorescamine, separated by HPLC and quantified fluorimetrically. We provide evidence that O 2 and 3ap compete for the same pool(s) of photoproduced reducing intermediates, and that under appropriate experimental conditions, the initial rate of hydroxylamine formation (R H ) can provide an estimate of the initial rate of superoxide (O 2 - ) formation. However, comparison of the initial rates of H 2 O 2 formation (R H2O2 ) to that of R H show far larger ratios of R H /R H2O2 (∼6-13) than be accounted for by simple O 2 - dismutation (R H /R H2O2 = 2), implying a significant oxidative sink of O 2 - (∼67-85%). Because of their high reactivity with O 2 - and their likely importance in the photochemistry of CDOM, we suggest that coproduced phenoxy radicals could represent a viable oxidative sink. Because O 2 - /phenoxy radical reactions can lead to more highly oxidized products, O 2 - could be playing a far more significant role in the photooxidation of CDOM than has been previously recognized.

ESR investigation of ROS generated by H2O2 bleaching with TiO2 coated HAp.

PubMed

Saita, Makiko; Kobayashi, Kyo; Kobatashi, Kyou; Yoshino, Fumihiko; Hase, Hiriko; Nonami, Toru; Kimoto, Katsuhiko; Lee, Masaichi-Chang-il

2012-01-01

It is well known that clinical bleaching can be achieved with a solution of 30% hydrogen peroxide (H2O2) or H2O2/titanium dioxide (TiO2) combination. This study examined the hypothesis that TiO2 coated with hydroxyapatite (HAp-TiO2) can generate reactive oxygen species (ROS). ROS are generated via photocatalysis using electron spin resonance (ESR). The bleaching properties of HAp-TiO2 in the presence of H2O2 can be measured using hematoporphyrin litmus paper and extracted teeth. We demonstrate that superoxides (O2(•-)) and hydroxyl radicals (HO(•)) can be generated through excitation of anatase TiO2, rutile TiO2, anatase HAp-TiO2, and rutile HAp-TiO2 in the presence of H2O2. The combination of R HAp-TiO2 with H2O2 produced the highest level of HO(•) generation and the most marked bleaching effects of all the samples. The superior bleaching effects exhibited by R HAp-TiO2 with H2O2 suggest that this combination may lead to novel methods for the clinical application of bleaching treatments.

Infrared photodissociation spectroscopy of H(+)(H2O)6·M(m) (M = Ne, Ar, Kr, Xe, H2, N2, and CH4): messenger-dependent balance between H3O(+) and H5O2(+) core isomers.

PubMed

Mizuse, Kenta; Fujii, Asuka

2011-04-21

Although messenger mediated spectroscopy is a widely-used technique to study gas phase ionic species, effects of messengers themselves are not necessarily clear. In this study, we report infrared photodissociation spectroscopy of H(+)(H(2)O)(6)·M(m) (M = Ne, Ar, Kr, Xe, H(2), N(2), and CH(4)) in the OH stretch region to investigate messenger(M)-dependent cluster structures of the H(+)(H(2)O)(6) moiety. The H(+)(H(2)O)(6), the protonated water hexamer, is the smallest system in which both the H(3)O(+) (Eigen) and H(5)O(2)(+) (Zundel) hydrated proton motifs coexist. All the spectra show narrower band widths reflecting reduced internal energy (lower vibrational temperature) in comparison with bare H(+)(H(2)O)(6). The Xe-, CH(4)-, and N(2)-mediated spectra show additional band features due to the relatively strong perturbation of the messenger. The observed band patterns in the Ar-, Kr-, Xe-, N(2)-, and CH(4)-mediated spectra are attributed mainly to the "Zundel" type isomer, which is more stable. On the other hand, the Ne- and H(2)-mediated spectra are accounted for by a mixture of the "Eigen" and "Zundel" types, like that of bare H(+)(H(2)O)(6). These results suggest that a messenger sometimes imposes unexpected isomer-selectivity even though it has been thought to be inert. Plausible origins of the isomer-selectivity are also discussed.

Ab initio studies on Al(+)(H(2)O)(n), HAlOH(+)(H(2)O)(n-1), and the size-dependent H(2) elimination reaction.

PubMed

Siu, Chi-Kit; Liu, Zhi-Feng; Tse, John S

2002-09-11

We report computational studies on Al(+)(H(2)O)(n), and HAlOH(+)(H(2)O)(n-1), n = 6-14, by the density functional theory based ab initio molecular dynamics method, employing a planewave basis set with pseudopotentials, and also by conventional methods with Gaussian basis sets. The mechanism for the intracluster H(2) elimination reaction is explored. First, a new size-dependent insertion reaction for the transformation of Al(+)(H(2)O)(n), into HAlOH(+)(H(2)O)(n-1) is discovered for n > or = 8. This is because of the presence of a fairly stable six-water-ring structure in Al(+)(H(2)O)(n) with 12 members, including the Al(+). This structure promotes acidic dissociation and, for n > or = 8, leads to the insertion reaction. Gaussian based BPW91 and MP2 calculations with 6-31G* and 6-31G** basis sets confirmed the existence of such structures and located the transition structures for the insertion reaction. The calculated transition barrier is 10.0 kcal/mol for n = 9 and 7.1 kcal/mol for n = 8 at the MP2/6-31G** level, with zero-point energy corrections. Second, the experimentally observed size-dependent H(2) elimination reaction is related to the conformation of HAlOH(+)(H(2)O)(n-1), instead of Al(+)(H(2)O)(n). As n increases from 6 to 14, the structure of the HAlOH(+)(H(2)O)(n-1) cluster changes into a caged structure, with the Al-H bond buried inside, and protons produced in acidic dissociation could then travel through the H(2)O network to the vicinity of the Al-H bond and react with the hydride H to produce H(2). The structural transformation is completed at n = 13, coincident approximately with the onset of the H(2) elimination reaction. From constrained ab initio MD simulations, we estimated the free energy barrier for the H(2) elimination reaction to be 0.7 eV (16 kcal/mol) at n = 13, 1.5 eV (35 kcal/mol) at n = 12, and 4.5 eV (100 kcal/mol) at n = 8. The existence of transition structures for the H(2) elimination has also been verified by ab initio calculations

Enhanced visible-light-driven photocatalytic H2-production activity of CdS-loaded TiO2 microspheres with exposed (001) facets

NASA Astrophysics Data System (ADS)

Gao, Bifen; Yuan, Xia; Lu, Penghui; Lin, Bizhou; Chen, Yilin

2015-12-01

CdS-loaded TiO2 microspheres with highly exposed (001) facets were prepared by hydrothermal treatment of a TiF4-HCl-H2O mixed solution followed by a chemical bath deposition of CdS onto TiO2 microspheres. The crystal structure, surficial micro-structure and photo-absorption property of the samples were characterized by XRD, FE-SEM, TEM and UV-vis diffuse reflectance spectroscopy, etc. The as-prepared samples exhibited superior visible-light-driven photocatalytic H2-production activity from lactic acid aqueous solution in comparison with CdS-sensitized TiO2 nanoparticles, whose surface was dominated by (101) facets. Photoelectrochemical measurement confirmed that (001) facet is beneficial for the transfer of photo-generated electron from CdS to TiO2 microsphere, which led to the unexpected high photocatalytic activity of CdS-loaded TiO2 microspheres.

An Investigation of Armenite, BaCa2Al6Si9O302H2O.H2O Molecules and H Bonding in Microporous Silicates

NASA Astrophysics Data System (ADS)

Geiger, C. A.; Gatta, G.; Xue, X.; McIntyre, G.

2012-12-01

The crystal chemistry of armenite, ideally BaCa2Al6Si9O30.2H2O, a double-ring structure belonging to the milarite group, was studied to better understand the nature of extra-framework "Ca-oxygen-anion-H2O-molecule quasi-clusters" and H bonding behavior in microporous silicates. Neutron and X-ray single-crystal diffraction and IR powder and 1H NMR spectroscopic measurements were made. Four crystallographically independent Ca and H2O molecule sites were refined from the diffraction data, whereby both sites appear to have partial occupancies such that locally a Ca atom can have only a single H2O molecule bonded to it through an ion-dipole interaction. The Ca cation is further bonded to six O atoms of the framework forming a quasi cluster around it. The neutron results give the first static description of the protons in armenite, allowing bond distances and angles relating to the H2O molecules and H bonds to be determined. The IR spectrum of armenite is characterized in the OH-stretching region at RT by two broad bands at roughly 3470 and 3410 cm-1 and by a single H2O bending mode at 1654 cm-1. At 10 K four intense OH bands are located at 3479, 3454, 3401 and 3384 cm-1 and two H2O bending modes at 1650 and 1606 cm-1. The 1H MAS NMR spectrum shows a single strong resonance near 5.3 ppm and a smaller one near 2.7 ppm. The former can be assigned to H2O molecules bonded to Ca and the latter to weakly bonded H2O located at a site at the center of the structural double ring and it is partially occupied. The nature of H bonding in the microporous Ca-bearing zeolites scolecite, wairakite and epistilbite are also analyzed. The average OH stretching wavenumber shown by the IR spectra of armenite (~3435 cm-1) and scolecite (~3430 cm-1) are similar, while the average OH wavenumbers for wairakite (~3475 cm-1) and epistilbite (~3500 cm-1) are greater. In all cases the average OH stretching wavenumber is more similar to that of liquid water (~3400 cm-1) than of ice (~3220 cm-1). The

Degradation mechanisms of Microcystin-LR during UV-B photolysis and UV/H2O2 processes: Byproducts and pathways.

PubMed

Moon, Bo-Ram; Kim, Tae-Kyoung; Kim, Moon-Kyung; Choi, Jaewon; Zoh, Kyung-Duk

2017-10-01

The removal and degradation pathways of microcystin-LR (MC-LR, [M+H] +  = 995.6) in UV-B photolysis and UV-B/H 2 O 2 processes were examined using liquid chromatography-tandem mass spectrometry. The UV/H 2 O 2 process was more efficient than UV-B photolysis for MC-LR removal. Eight by-products were newly identified in the UV-B photolysis ([M+H] +  = 414.3, 417.3, 709.6, 428.9, 608.6, 847.5, 807.4, and 823.6), and eleven by-products were identified in the UV-B/H 2 O 2 process ([M+H] +  = 707.4, 414.7, 429.3, 445.3, 608.6, 1052.0, 313.4, 823.6, 357.3, 245.2, and 805.7). Most of the MC-LR by-products had lower [M+H] + values than the MC-LR itself during both processes, except for the [M+H] + value of 1052.0 during UV-B photolysis. Based on identified by-products and peak area patterns, we proposed potential degradation pathways during the two processes. Bond cleavage and intramolecular electron rearrangement by electron pair in the nitrogen atom were the major reactions during UV-B photolysis and UV-B/H 2 O 2 processes, and hydroxylation by OH radical and the adduct formation reaction between the produced by-products were identified as additional pathways during the UV-B/H 2 O 2 process. Meanwhile, the degradation by-products identified from MC-LR during UV-B/H 2 O 2 process can be further degraded by increasing H 2 O 2 dose. Copyright © 2017 Elsevier Ltd. All rights reserved.

Comparative investigation of X-ray contrast medium degradation by UV/chlorine and UV/H2O2.

PubMed

Kong, Xiujuan; Jiang, Jin; Ma, Jun; Yang, Yi; Pang, Suyan

2018-02-01

The degradation of iopamidol and diatrizoate sodium (DTZ) by UV/chlorine was carried out according to efficiency, mechanism, and oxidation products, and compared to that by UV/H 2 O 2 . The pseudo-first order rate (k') of iopamidol and DTZ was accelerated by UV/chlorine compared to that by UV and chlorine alone. k' of iopamidol and DTZ by UV/chlorine increased with increasing chlorine dosage. Both of iopamidol and DTZ could not be effectively removed by UV/H 2 O 2 compared to that by UV/chlorine. Secondary radicals (Cl 2 - and ClO) rather than primary radicals (HO and Cl) were demonstrated to be mainly responsible for the enhanced removal of iopamidol and DTZ by UV/chlorine. The oxidation products of iopamidol and DTZ resulting from UV/chlorine and UV/H 2 O 2 process were identified, and differences existed in the two systems. IO 3 - (the desired sink of I - ) was the major inorganic product in the UV/chlorine process whereas I - was the predominant inorganic product in the UV/H 2 O 2 process. The formation of chlorine-containing products during the degradation of iopamidol and DTZ by UV/chlorine was also observed. H-abstraction, additions, de-iodination were shared during the degradation of iopamidol by UV/chlorine and UV/H 2 O 2 . Neutral pH condition was preferred for the removal of iopamidol and DTZ by UV/chlorine. UV/chlorine could also be applied in real waters for the removal of iopamidol and DTZ. Copyright © 2017 Elsevier Ltd. All rights reserved.

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

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

2016-03-03

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.

Heterojunction CuO-TiO2 nanocomposite synthesis for significant photocatalytic hydrogen production

NASA Astrophysics Data System (ADS)

Manjunath, K.; Souza, V. S.; Ramakrishnappa, T.; Nagaraju, G.; Scholten, J. D.; Dupont, J.

2016-11-01

Effective and low-cost photocatalysts have been synthesized by a simple hydrothermal process. In this process, the two CuO and TiO2 bound one over the other and formed a heterojunction CuO-TiO2 nanocomposite. CuO serves as electron reservoir by receiving electrons from TiO2, which suppresses the recombination of e-/h+ and transfers the received electron to split water, which results in enhanced H2 production. Heterojunction CuO-TiO2 nanocomposite material recorded a maximum of 9284 μmolg-1 H2 production for 2.5 h. The recorded result is 15 times higher than bare TiO2 and 16 times higher than bare CuO. The synthesized materials were characterized and analyzed using various analytical techniques such as XRD, FTIR, UV-vis spectra and the morphology was studied using SEM, TEM, and HRTEM images.

Adsorption, Desorption, and Displacement Kinetics of H2O and CO2 on TiO2(110)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, R. Scott; Li, Zhenjun; Chen, Long

The adsorption, desorption, and displacement kinetics of H2O and CO2 on TiO2(110) are investigated using temperature programmed desorption (TPD) and molecular beam techniques. The TPD spectra for both H2O and CO2 have well-resolved peaks corresponding to desorption from bridge-bonded oxygen (BBO), Ti, and oxygen vacancies (VO) sites in order of increasing peak temperature. Analysis of the saturated monolayer peak for both species reveals that the corresponding adsorption energies on all sites are greater for H2O and for CO2. Sequential dosing of H2O and CO2 reveals that, independent of the dose order, H2O molecules will displace CO2 in order to occupymore » the highest energy binding sites available. Isothermal experiments show that the displacement of CO2 by H2O occurs between 75 and 80 K. Further analysis shows that a ratio of 4 H2O to 3 CO2 molecules is needed to displace CO2 from the TiO2(110) surface.« less

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

Influence of Ar/O2/H2O Feed Gas and N2/O2/H2O Environment on the Interaction of Time Modulated MHz Atmospheric Pressure Plasma Jet (APPJ) with Model Polymers

NASA Astrophysics Data System (ADS)

Oehrlein, Gottlieb; Luan, Pingshan; Knoll, Andrew; Kondeti, Santosh; Bruggeman, Peter

2016-09-01

An Ar/O2/H2O fed time modulated MHz atmospheric pressure plasma jet (APPJ) in a sealed chamber was used to study plasma interaction with model polymers (polystyrene, poly-methyl methacrylate, etc.). The amount of H2O in the feed gas and/or present in the N2, O2, or N2/O2 environment was controlled. Short lived species such as O atoms and OH radicals play a crucial role in polymer etching and surface modifications (obtained from X-ray photoelectron spectroscopy of treated polymers without additional atmospheric exposure). Polymer etching depth for Ar/air fed APPJ mirrors the decay of gas phase O atoms with distance from the APPJ nozzle in air and is consistent with the estimated O atom flux at the polymer surface. Furthermore, whereas separate O2 or H2O admixture to Ar enhances polymer etching, simultaneous addition of O2 and H2O to Ar quenches polymer etching. This can be explained by the mutual quenching of O with OH, H and HO2 in the gas phase. Results where O2 and/or H2O in the environment were varied are consistent with these mechanisms. All results will be compared with measured and simulated species densities reported in the literature. We gratefully acknowledge funding from US Department of Energy (DE-SC0001939) and National Science Foundation (PHY-1415353).

Degradation of sulfamethoxazole by UV, UV/H2O2 and UV/persulfate (PDS): Formation of oxidation products and effect of bicarbonate.

PubMed

Yang, Yi; Lu, Xinglin; Jiang, Jin; Ma, Jun; Liu, Guanqi; Cao, Ying; Liu, Weili; Li, Juan; Pang, Suyan; Kong, Xiujuan; Luo, Congwei

2017-07-01

The frequent detection of sulfamethoxazole (SMX) in wastewater and surface waters gives rise of concerns about their ecotoxicological effects and potential risks to induce antibacterial resistant genes. UV/hydrogen peroxide (UV/H 2 O 2 ) and UV/persulfate (UV/PDS) advanced oxidation processes have been demonstrated to be effective for the elimination of SMX, but there is still a need for a deeper understanding of product formations. In this study, we identified and compared the transformation products of SMX in UV, UV/H 2 O 2 and UV/PDS processes. Because of the electrophilic nature of SO 4 - , the second-order rate constant for the reaction of sulfate radical (SO 4 - ) with the anionic form of SMX was higher than that with the neutral form, while hydroxyl radical (OH) exhibited comparable reactivity to both forms. The direct photolysis of SMX predominately occurred through cleavage of the NS bond, rearrangement of the isoxazole ring, and hydroxylation mechanisms. Hydroxylation was the dominant pathway for the reaction of OH with SMX. SO 4 - favored attack on NH 2 group of SMX to generate a nitro derivative and dimeric products. The presence of bicarbonate in UV/H 2 O 2 inhibited the formation of hydroxylated products, but promoted the formation of the nitro derivative and the dimeric products. In UV/PDS, bicarbonate increased the formation of the nitro derivative and the dimeric products, but decreased the formation of the hydroxylated dimeric products. The different effect of bicarbonate on transformation products in UV/H 2 O 2 vs. UV/PDS suggested that carbonate radical (CO 3 - ) oxidized SMX through the electron transfer mechanism similar to SO 4 - but with less oxidation capacity. Additionally, SO 4 - and CO 3 - exhibited higher reactivity to the oxazole ring than the isoxazole ring of SMX. Ecotoxicity of transformation products was estimated by ECOSAR program based on the quantitative structure-activity relationship analysis as well as by experiments using

Heterogeneous Ag-TiO2-SiO2 composite materials as novel catalytic systems for selective epoxidation of cyclohexene by H2O2

PubMed Central

Wang, Xin; Xue, Jianyue; Wang, Xinyun; Liu, Xiaoheng

2017-01-01

TiO2-SiO2 composites were synthesized using cetyl trimethyl ammonium bromide (CTAB) as the structure directing template. Self-assembly hexadecyltrimethyl- ammonium bromide TiO2-SiO2/(CTAB) were soaked into silver nitrate (AgNO3) aqueous solution. The Ag-TiO2-SiO2(Ag-TS) composite were prepared via a precipitation of AgBr in soaking process and its decomposition at calcination stage. Structural characterization of the materials was carried out by various techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption and ultraviolet visible spectroscopy (UV-Vis). Characterization results revealed that Ag particles were incorporated into hierarchical TiO2-SiO2 without significantly affecting the structures of the supports. Further heating-treatment at 723 K was more favorable for enhancing the stability of the Ag-TS composite. The cyclohexene oxide was the major product in the epoxidation using H2O2 as the oxidant over the Ag-TS catalysts. Besides, the optimum catalytic activity and stability of Ag-TS catalysts were obtained under operational conditions of calcined at 723 K for 2 h, reaction time of 120 min, reaction temperature of 353 K, catalyst amount of 80 mg, aqueous H2O2 (30 wt.%) as oxidant and chloroform as solvent. High catalytic activity with conversion rate up to 99.2% of cyclohexene oxide could be obtainable in water-bathing. The catalyst was found to be stable and could be reused three times without significant loss of catalytic activity under the optimized reaction conditions. PMID:28493879

A Chebyshev method for state-to-state reactive scattering using reactant-product decoupling: OH + H2 → H2O + H.

PubMed

Cvitaš, Marko T; Althorpe, Stuart C

2013-08-14

We extend a recently developed wave packet method for computing the state-to-state quantum dynamics of AB + CD → ABC + D reactions [M. T. Cvitaš and S. C. Althorpe, J. Phys. Chem. A 113, 4557 (2009)] to include the Chebyshev propagator. The method uses the further partitioned approach to reactant-product decoupling, which uses artificial decoupling potentials to partition the coordinate space of the reaction into separate reactant, product, and transition-state regions. Separate coordinates and basis sets can then be used that are best adapted to each region. We derive improved Chebyshev partitioning formulas which include Mandelshtam-and-Taylor-type decoupling potentials, and which are essential for the non-unitary discrete variable representations that must be used in 4-atom reactive scattering calculations. Numerical tests on the fully dimensional OH + H2 → H2O + H reaction for J = 0 show that the new version of the method is as efficient as the previously developed split-operator version. The advantages of the Chebyshev propagator (most notably the ease of parallelization for J > 0) can now be fully exploited in state-to-state reactive scattering calculations on 4-atom reactions.

Stable solid and aqueous H2CO3 from CO2 and H2O at high pressure and high temperature

PubMed Central

Wang, Hongbo; Zeuschner, Janek; Eremets, Mikhail; Troyan, Ivan; Willams, Jonathan

2016-01-01

Carbonic acid (H2CO3) forms in small amounts when CO2 dissolves in H2O, yet decomposes rapidly under ambient conditions of temperature and pressure. Despite its fleeting existence, H2CO3 plays an important role in the global carbon cycle and in biological carbonate-containing systems. The short lifetime in water and presumed low concentration under all terrestrial conditions has stifled study of this fundamental species. Here, we have examined CO2/H2O mixtures under conditions of high pressure and high temperature to explore the potential for reaction to H2CO3 inside celestial bodies. We present a novel method to prepare solid H2CO3 by heating CO2/H2O mixtures at high pressure with a CO2 laser. Furthermore, we found that, contrary to present understanding, neutral H2CO3 is a significant component in aqueous CO2 solutions above 2.4 GPa and 110 °C as identified by IR-absorption and Raman spectroscopy. This is highly significant for speciation of deep C–O–H fluids with potential consequences for fluid-carbonate-bearing rock interactions. As conditions inside subduction zones on Earth appear to be most favorable for production of aqueous H2CO3, a role in subduction related phenomena is inferred. PMID:26813580

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.

Synthesis and characterization of polymer eight-coordinate (enH 2)[Y III(pdta)(H 2O)] 2·10H 2O as well as the interaction of [Y III(pdta)(H 2O)] 22- with BSA

NASA Astrophysics Data System (ADS)

Liu, Bin; Wang, Jun; Wang, Xin; Liu, Bing-Mi; He, Ling-Ling; Xu, Shu-Kun

2010-12-01

The eight-coordinate (enH 2)[Y III(pdta)(H 2O)] 2·10H 2O (en = ethylenediamine and H 4pdta = 1,3-propylenediamine- N, N, N', N'-tetraacetic acid) was synthesized, meanwhile its molecular and crystal structures were determined by single-crystal X-ray diffraction technology. The interaction between [Y III(pdta)(H 2O)] 22- and bovine serum albumin (BSA) was investigated by UV-vis and fluorescence spectra. The results indicate that [Y III(pdta)(H 2O)] 22- quenched effectively the intrinsic fluorescence of BSA via a static quenching process with the binding constant ( Ka) of the order of 10 4. Meanwhile, the binding and damaging sites to BSA molecules were also estimated by synchronous fluorescence. Results indicate that the hydrophobic environments around Trp and Tyr residues were all slightly changed. The thermodynamic parameters (Δ G = -25.20 kJ mol -1, Δ H = -26.57 kJ mol -1 and Δ S = -4.58 J mol -1 K -1) showed that the reaction was spontaneous and exothermic. What is more, both Δ H and Δ S were negative values indicated that hydrogen bond and Van der Waals forces were the predominant intermolecular forces between [Y III(pdta)(H 2O)] 22- and BSA.

The reaction of O(1 D) with H2O and the reaction of OH with C3H6

NASA Technical Reports Server (NTRS)

Simonaitis, R.; Heicklen, J.

1972-01-01

The N2O was photolyzed at 2139 A to produce O(1 D) atoms in the presence of H2O and CO. The O(1 D) atoms react with H2O to produce HO radicals, as measured by CO2 production from the reaction of OH with CO. The relative rate constant for O(1 D) removal by H2O compared to that by N2O is 2.1. In the presence of C3H6, the OH can be removed by reaction with either CO or C3H6.

Highly stable CuO incorporated TiO(2) catalyst for photo-catalytic hydrogen production from H(2)O.

PubMed

Bandara, J; Udawatta, C P K; Rajapakse, C S K

2005-11-01

A CuO incorporated TiO(2) catalyst was found to be an active photo-catalyst for the reduction of H(2)O under sacrificial conditions. The catalytic activity originates from the photogeneration of excited electrons in the conduction bands of both TiO(2) and CuO resulting in a build-up of excess electrons in the conduction band of CuO. Consequently, the accumulation of excess electrons in CuO causes a negative shift in the Fermi level of CuO. The efficient inter-particle charge transfer leads to a higher catalytic activity and the formation of highly reduced states of TiO(2)/CuO, which are stable even under oxygen saturated condition. Negative shift in the Fermi level of CuO of the catalyst TiO(2)/CuO gains the required over-voltage necessary for efficient water reduction reaction. The function of CuO is to help the charge separation and to act as a water reduction site. The amount of CuO and crystalline structure were found to be crucial for the catalytic activity and the optimum CuO loading was ca. approximately 5-10%(w/w).

FLYING-WATER Renewables-H2-H2O TERRAFORMING: PERMANENT ETERNAL Drought(s)-Elimination FOREVER!!!

NASA Astrophysics Data System (ADS)

Wignall, J.; Lyons, Marv; Ertl, G.; Alefeld, Georg; Youdelis, W.; Radd, H.; Oertle, G.; Siegel, Edward

2013-03-01

''H2O H2O everywhere; ne'er a drop to drink''[Coleridge(1798)] now: ''H2 H2 everywhere; STILL ne'er a drop to drink'': ONLY H2 (or methane CH4) can be FLYING-WATER(F-W) chemical-rain-in-pipelines Hindenberg-effect (H2-UP;H2O-DOWN): { ∖{}O/H2O{ ∖}} =[16]/[18] ∖sim 90{ ∖%} O already in air uphill; NO H2O pumping need! In global-warming driven H2O-starved glacial-melting world, rescue is possible ONLY by Siegel [ ∖underline {3rd Intl. Conf. Alt.-Energy }(1980)-vol.5/p.459!!!] Renewables-H2-H2O purposely flexible versatile agile customizable scaleable retrofitable integrated operating-system. Rosenfeld[Science 315,1396(3/9/2007)]-Biello [Sci.Am.(3/9 /2007)] crucial geomorphology which ONLY maximal-buoyancy H2 can exploit, to again make ''Mountains into Fountains'', ``upthrust rocks trapping the clouds to precipitate their rain/snow/H2O'': ''terraforming''(and ocean-rebasificaton!!!) ONLY VIA Siegel[APS March MTGS.:1960s-2000ss) DIFFUSIVE-MAGNETORESISTANCE (DMR) proprietary MAGNETIC-HYDROGEN-VALVE(MHV) ALL-IMPORTANT PRECLUDED RADIAL-diffusion, permitting ONLY AXIAL-H2-BALLISTIC-flow (``G.A''.''/DoE''/''Terrapower''/''Intellectual-Ventures''/ ''Gileland''/ ''Myhrvold''/''Gates'' ``ARCHIMEDES'') in ALREADY IN-ground dense BCC/ferritic-steels pipelines-network (NO new infrastructure) counters Tromp[Science 300,1740(2003)] dire warning of global-pandemics (cancers/ blindness/ famine)

Three-dimensional ruthenium-doped TiO 2 sea urchins for enhanced visible-light-responsive H 2 production

DOE PAGES

Nguyen-Phan, Thuy -Duong; Luo, Si; Vovchok, Dimitriy; ...

2016-05-23

Here, three-dimensional (3D) monodispersed sea urchin-like Ru-doped rutile TiO 2 hierarchical architectures composed of radially aligned, densely-packed TiO 2 nanorods have been successfully synthesized via an acid-hydrothermal method at low temperature without the assistance of any structure-directing agent and post annealing treatment. The addition of a minuscule concentration of ruthenium dopants remarkably catalyzes the formation of the 3D urchin structure and drives the enhanced photocatalytic H 2 production under visible light irradiation, not possible on undoped and bulk rutile TiO 2. Increasing ruthenium doping dosage not only increases the surface area up to 166 m 2 g –1 but alsomore » induces enhanced photoresponse in the regime of visible and near infrared light. The doping introduces defect impurity levels, i.e. oxygen vacancy and under-coordinated Ti 3+, significantly below the conduction band of TiO 2, and ruthenium species act as electron donors/acceptors that accelerate the photogenerated hole and electron transfer and efficiently suppress the rapid charge recombination, therefore improving the visible-light-driven activity.« less

FLYING-WATER Renewables-H2-H2O TERRAFORMING: PERMANENT Drought(s)-Elimination FOREVER!!!

NASA Astrophysics Data System (ADS)

Lyons, M.; Siegel, E.

2010-03-01

``Water water everywhere; ne'er a drop to drink''[Coleridg(1798)]; now:``Hydrogen hydrogen everywhere;STILL ne'er a drop to drink'': ONLY H2 can be ``FLYING-WATER''/``chemical-rain-in-pipelines''/ ``Hindenberg-effect (H2-UP;H2O-DOWN): atomic-weights ratio: O/H2O=[16]/[18]˜90%; O already in air uphill; NO H2O pumping need! In water-starved glacial-melting world, rescue ONLY by Siegel[3rd Intl.Conf.Alt.Energy,Hemisphere/Springer(1980)- vol.5/ p.459]Renewables-H2-H2O purposely flexible versatile agile customizable scaleable retrofitable integrated operating- system. Rosenfeld[Sci.315,1396(3/9/2007)]-Biello[Sci.Am.(3/9/ 2007)]crucial geomorphology which ONLY maximal-buoyancy light- est-element H2 can exploit, to again make ``Mountains into Fount- ains": Siegel ``terra-forming''(and ocean-rebasificaton!!!) long pre-``Holdren''-``Ciccerine" ``geo-enginering'', only via Siegel proprietary magnetic-hydrogen-valve permits H2 flow in already in-ground dense BCC/ferritic-steels pipelines-network (NO new infrastructure) counters Tromp[Sci.300,1740(03)]global-pandemics (cancers/blindness/famine)dire-warning about H2-(ALONE)economy CATASTROPHIC H2 ozone-layer destruction sobering cavat to dangerous H2-automotion-economy panacea hype!

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.