Science.gov

Sample records for abundant surface hydroxyl

  1. Preparation of hydroxylated polyethylene surfaces.

    PubMed

    Zand, A; Walter, N; Bahu, M; Ketterer, S; Sanders, M; Sikorski, Y; Cunningham, R; Beholz, L

    2008-01-01

    The surfaces of high-density or ultra-high-molecular-weight polyethylenes were hydroxylated using a two-step process. The wetting and wear properties of the untreated (virgin) and surface hydroxylated polyethylenes were compared. The introduction of hydroxyl groups provided an increase in surface hydrophilicity resulting in reduced wear. Hydrophilicity was analyzed by optical analysis of water contact angle. Wear was determined by weight loss under conditions of a reciprocating pin-on-plate apparatus with the panels immersed in water or calf serum. These results suggest that hydroxylation of polyethylene friction-bearing orthopedic surfaces may lead to a longer joint life. PMID:18318959

  2. Column abundance measurements of atmospheric hydroxyl at 45 deg S

    NASA Technical Reports Server (NTRS)

    Wood, S. W.; Keep, D. J.; Burnett, C. R.; Burnett, E. B.

    1994-01-01

    The first Southern Hemisphere measurements of the vertical column abundance of atmospheric hydroxyl (OH) have been obtained at Lauder, New Zealand (45 deg S) with a PEPSIOS instrument measuring the absorption of sunlight at 308 nm. The variation of column OH with solar zenith angle is similar to that measured at other sites. However average annual abundances of OH are about 20% higher than those found by similar measurements at 40 deg N. Minimum OH abundances about 10% less than average levels at 40 deg N, are observed during austral spring. The OH abundance abruptly increases by 30% in early summer and remains at the elevated level until late the following winter.

  3. Production of Abundant Hydroxyl Radicals from Oxygenation of Subsurface Sediments.

    PubMed

    Tong, Man; Yuan, Songhu; Ma, Sicong; Jin, Menggui; Liu, Deng; Cheng, Dong; Liu, Xixiang; Gan, Yiqun; Wang, Yanxin

    2016-01-01

    Hydroxyl radicals (•OH) play a crucial role in the fate of redox-active substances in the environment. Studies of the •OH production in nature has been constrained to surface environments exposed to light irradiation, but is overlooked in the subsurface under dark. Results of this study demonstrate that abundant •OH is produced when subsurface sediments are oxygenated under fluctuating redox conditions at neutral pH values. The cumulative concentrations of •OH produced within 24 h upon oxygenation of 33 sediments sampled from different redox conditions are 2-670 μmol •OH per kg dry sediment or 6.7-2521 μM •OH in sediment pore water. Fe(II)-containing minerals, particularly phyllosilicates, are the predominant contributor to •OH production. This production could be sustainable when sediment Fe(II) is regenerated by the biological reduction of Fe(III) during redox cycles. Production of •OH is further evident in a field injection-extraction test through injecting oxygenated water into a 23-m depth aquifer. The •OH produced can oxidize pollutants such as arsenic and tetracycline and contribute to CO2 emissions at levels that are comparable with soil respiration. These findings indicate that oxygenation of subsurface sediments is an important source of •OH in nature that has not been previously identified, and •OH-mediated oxidation represents an overlooked process for substance transformations at the oxic/anoxic interface. PMID:26641489

  4. Interaction of Gold Clusters with a Hydroxylated Surface

    SciTech Connect

    Jiang, Deen; Overbury, Steven {Steve} H; Dai, Sheng

    2011-01-01

    We explore the interaction between gold nanoclusters and a fully hydroxylated surface, Mg(OH){sub 2}'s basal plane, by using a density functional theory-enabled local basin-hopping technique for global-minimum search. We find strong interaction of gold nanoclusters with the surface hydroxyls via a short bond between edge Au atoms and O atoms of the -OH groups. We expect that this strong interaction is ubiquitous on hydroxylated support surfaces and helps the gold nanoclusters against sintering, thereby contributing to their CO-oxidation activity at low temperatures.

  5. Surface abundances of OC supergiants

    NASA Astrophysics Data System (ADS)

    Martins, F.; Foschino, S.; Bouret, J.-C.; Barbá, R.; Howarth, I.

    2016-04-01

    Context. Some O and B stars show unusually strong or weak lines of carbon and/or nitrogen. These objects are classified as OBN or OBC stars. It has recently been shown that nitrogen enrichment and carbon depletion are the most likely explanations for the existence of the ON class. Aims: We investigate OC stars (all being supergiants) to check that surface abundances are responsible for the observed anomalous line strengths. Methods: We perform a spectroscopic analysis of three OC supergiants using atmosphere models. A fourth star was previously studied by us. Our sample thus comprises all OC stars known to date in the Galaxy. We determine the stellar parameters and He, C, N, and O surface abundances. Results: We show that all stars have effective temperatures and surface gravities fully consistent with morphologically normal O supergiants. However, OC stars show little, if any, nitrogen enrichment and carbon surface abundances consistent with the initial composition. OC supergiants are thus barely chemically evolved, unlike morphologically normal O supergiants. Based on observations obtained at the ESO/La Silla Observatory under programs 081.D-2008, 083.D-0589, 089.D-0975.

  6. A characterization study of a hydroxylated polycrystalline tin oxide surface

    NASA Technical Reports Server (NTRS)

    Hoflund, Gar B.; Grogan, Austin L., Jr.; Asbury, Douglas A.; Schryer, David R.

    1989-01-01

    In this study Auger electron spectroscopy, electron spectroscopy for chemical analysis (ESCA) and electron-stimulated desorption (ESD) have been used to examine a polycrystalline tin oxide surface before and after annealing in vacuum at 500 C. Features due to surface hydroxyl groups are present in both the ESCA and ESD spectra, and ESD shows that several chemical states of hydrogen are present. Annealing at 500 C causes a large reduction in the surface hydrogen concentration but not complete removal.

  7. Surface studies of hydroxylated multi-wall carbon nanotubes

    SciTech Connect

    Bradley, Robert; Cassity, Kelby; Andrews, Rodney; Meier, Mark; Osbeck, Susan; Andreu, Aurik; Johnston, Colin; Crossley, Alison

    2012-01-01

    CVD grown MWCNTs, of typical diameter 5 to 50 nm and with approximately 15-20 concentric graphene layers in the multi-walls, have been surface functionalised using the Fenton hydroxylation reaction. HRTEM reveals little physical difference between the treated and untreated materials; images from both exhibit similar multi-wall structure and contain evidence for some low-level disruption of the very outermost layers. Raman spectra from the two types of nanotubes are almost identical displaying the disorder (D) peaks at approximately 1350 cm{sup -1} and graphite (G) peaks at approximately 1580 cm{sup -1}, characteristic of graphene-based carbon materials, in approximately equal intensity ratios. Equilibrium adsorption data for nitrogen at 77 K leads to BET surface areas of 60.4 m{sup 2} g{sup -1} for the untreated and 71.8 m{sup 2} g{sup -1} for the hydroxylated samples; the increase in area being due to separation of the tube-bundles during functionalization. This is accompanied by a decrease in measured porosity, mostly at high relative pressures of nitrogen, i.e. where larger (meso 2-5 nm and macro >5 nm) pores are being filled, which is consistent with an attendant loss of inter-tube capillarity. X-ray photoelectron spectroscopy (XPS) shows that hydroxylation increases the nanotube surface oxygen level from 4.3 at.% to 22.3 at.%; chemical shift data indicate that approximately 75% of that oxygen is present as hydroxyl (-OH) groups. Water vapour adsorption by the hydroxylated surfaces leads to Type II isotherms which are characteristic of relatively high numbers of hydrogen bonding interactions compared to the untreated materials which exhibit Type III curves. This difference in polar surface energy is confirmed by calorimetric enthalpies of immersion in water which are -54 mJ m{sup -2} for the untreated and -192 mJ m{sup -2} for the hydroxylated materials. The treated materials therefore have significantly increased water wettability/dispersivity and a greater

  8. Periodic behaviors in the observed vertical column abundances of atmospheric hydroxyl

    NASA Technical Reports Server (NTRS)

    Burnett, Elizabeth Beaver; Burnett, Clyde R.; Minschwaner, Kenneth R.

    1989-01-01

    The data base for the vertical column abundance of atmospheric hydroxyl (OH) for Fritz Peak Observatory, Colorado (40 N, 105 W), now extends from 1976 through 1988 and is composed of 8849 independent data sets, averaging about 15 percent uncertainty and 20-minute time resolution each. The dominant solar zenith angle (chi) dependence of the OH abundance is characterized by an empirical curve, N(88), which has been updated from N(82) to include all valid data from 1980 through 1988. The chi-dependence of the OH abundance has been, to a first order, removed from the data base by a normalization procedure in which each data point is divided by the N(88,AM) value for the corresponding solar zenith angle. The resulting normalized OH values may then be examined for other systematic effects, particularly for periodic variations. Observations have also been made at Boca Raton, Florida (26 N, 80 W) and at Truk, Federated States of Micronesia (7 N, 152 E). These data bases are much less extensive and, as such, are less amenable to analysis for periodic behaviors. Some comparisons with the Colorado data may be made, however.

  9. Surface abundances of ON stars

    NASA Astrophysics Data System (ADS)

    Martins, F.; Simón-Díaz, S.; Palacios, A.; Howarth, I.; Georgy, C.; Walborn, N. R.; Bouret, J.-C.; Barbá, R.

    2015-06-01

    Context. Massive stars burn hydrogen through the CNO cycle during most of their evolution. When mixing is efficient or when mass transfer in binary systems occurs, chemically processed material is observed at the surface of O and B stars. Aims: ON stars show stronger lines of nitrogen than morphologically normal counterparts. Whether this corresponds to the presence of material processed through the CNO cycle is not known. Our goal is to answer this question. Methods: We performed a spectroscopic analysis of a sample of ON stars with atmosphere models. We determined the fundamental parameters as well as the He, C, N, and O surface abundances. We also measured the projected rotational velocities. We compared the properties of the ON stars to those of normal O stars. Results: We show that ON stars are usually rich in helium. Their CNO surface abundances are fully consistent with predictions of nucleosynthesis. ON stars are more chemically evolved and rotate - on average - faster than normal O stars. Evolutionary models including rotation cannot account for the extreme enrichment observed among ON main sequence stars. Some ON stars are members of binary systems, but others are single stars as indicated by stable radial velocities. Mass transfer is therefore not a simple explanation for the observed chemical properties. Conclusions: We conclude that ON stars show extreme chemical enrichment at their surface, consistent with nucleosynthesis through the CNO cycle. Its origin is not clear at present. Based on observations obtained 1) at the Anglo-Australian Telescope; 2) at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Science de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii; 3) at the ESO/La Silla Observatory under programs 081.D-2008, 083.D-0589, 086.D-0997; 4) the Nordic Optical Telescope, operated on the island of La

  10. Hydroxylation of organic polymer surface: method and application.

    PubMed

    Yang, Peng; Yang, Wantai

    2014-03-26

    It may be hardly believable that inert C-H bonds on a polymeric material surface could be quickly and efficiently transformed into C-OH by a simple and mild way. Thanks to the approaches developed recently, it is now possible to transform surface H atoms of a polymeric substrate into monolayer OH groups by a simple/mild photochemical reaction. Herein the method and application of this small-molecular interfacial chemistry is highlighted. The existence of hydroxyl groups on material surfaces not only determines the physical and chemical properties of materials but also provides effective reaction sites for postsynthetic sequential modification to fulfill the requirements of various applications. However, organic synthetic materials based on petroleum, especially polyolefins comprise mainly C and H atoms and thus present serious surface problems due to low surface energy and inertness in reactivity. These limitations make it challenging to perform postsynthetic surface sequential chemical derivatization toward enhanced functionalities and properties and also cause serious interfacial problems when bonding or integrating polymer substrates with natural or inorganic materials. Polymer surface hydroxylation based on direct conversion of C-H bonds on polymer surfaces is thus of significant importance for academic and practical industrial applications. Although highly active research results have reported on small-molecular C-H bond activation in solution (thus homogeneous), most of them, featuring the use of a variety of transition metals as catalysts, present a slow reaction rate, a low atom economy and an obvious environmental pollution. In sharp contrast to these conventional C-H activation strategies, the present Spotlight describes a universal confined photocatalytic oxidation (CPO) system that is able to directly convert polymer surface C-H bonds to C-OSO3(-) and, subsequently, to C-OH through a simple hydrolysis. Generally speaking, these newly implanted hydroxyl

  11. Determination of surface-accessible acidic hydroxyls and surface area of lignin by cationic dye adsorption.

    PubMed

    Sipponen, Mika Henrikki; Pihlajaniemi, Ville; Littunen, Kuisma; Pastinen, Ossi; Laakso, Simo

    2014-10-01

    A new colorimetric method for determining the surface-accessible acidic lignin hydroxyl groups in lignocellulose solid fractions was developed. The method is based on selective adsorption of Azure B, a basic dye, onto acidic hydroxyl groups of lignin. Selectivity of adsorption of Azure B on lignin was demonstrated using lignin and cellulose materials as adsorbents. Adsorption isotherms of Azure B on wheat straw (WS), sugarcane bagasse (SGB), oat husk, and isolated lignin materials were determined. The maximum adsorption capacities predicted by the Langmuir isotherms were used to calculate the amounts of surface-accessible acidic hydroxyl groups. WS contained 1.7-times more acidic hydroxyls (0.21 mmol/g) and higher surface area of lignin (84 m(2)/g) than SGB or oat husk materials. Equations for determining the amount of surface-accessible acidic hydroxyls in solid fractions of the three plant materials by a single point measurement were developed. A method for high-throughput characterization of lignocellulosic materials is now available. PMID:25033327

  12. Reassigning the most stable surface of hydroxyapatite to the water resistant hydroxyl terminated (010) surface

    NASA Astrophysics Data System (ADS)

    Zeglinski, Jacek; Nolan, Michael; Thompson, Damien; Tofail, Syed A. M.

    2014-05-01

    Understanding the surface stability and crystal growth morphology of hydroxyapatite is important to comprehend bone growth and repair processes and to engineer protein adsorption, cellular adhesion and biomineralization on calcium phosphate based bone grafts and implant coatings. It has generally been assumed from electronic structure calculations that the most stable hydroxyapatite surface is the (001) surface, terminated just above hydroxyl ions perpendicular to the {001} crystal plane. However, this is inconsistent with the known preferential growth direction of hydroxyapatite crystals and previous experimental work which indicates that, contrary to currently accepted theoretical predictions, it is actually the (010) surface that is preferentially exposed. The surface structure of the (010) face is still debated and needs reconciliation. In this work, we use a large set of density functional theory calculations to model the interaction of water with hydroxyapatite surfaces and probe the surface stability and resistance to hydrolytic remodeling of a range of surface faces including the (001) surface and the phosphate-exposed, calcium-exposed, and hydroxyl-exposed terminations of the (010) surface. For the (001) surface and the phosphate-exposed (010) surface, dissociative water adsorption is favorable. In contrast, the hydroxyl-terminated (010) surface will not split water and only molecular adsorption of water is possible. Our calculations show, overall, that the hydroxyl-terminated (010) surface is the most stable and thus should be the predominant form of the hydroxyapatite surface exposed in experiments. This finding reconciles discrepancies between the currently proposed surface terminations of hydroxyapatite and the experimentally observed crystal growth direction and surface stability, which may aid efforts to accelerate biomineralization and better control bone-repair processes on hydroxyapatite surfaces.

  13. Formation and Retention of Hydroxyl and Water on the Lunar Surface

    NASA Astrophysics Data System (ADS)

    Kramer, G. Y.; Clark, R. N.; Combe, J.; Noble, S. K.

    2012-12-01

    Spectral reflectance observations by the Moon Mineralogy Mapper (M3) showed that both hydroxyl and (molecular) water (hereafter referred to collectively as H/OH) vary spatially as a function of solar illumination geometry. At low solar incidence angles, the observed strengths of the H/OH spectral features are stronger than at higher angles, suggesting that the abundance varies with the diurnal cycle. This is also demonstrated in the increasing abundances with increasing latitude, such that above ~60 degrees there is little reduction in the depth of the water-related spectral absorption bands. It was immediately recognized that the wide-spread occurrence of H/OH across the lunar surface was the result of solar wind-induced hydroxylation, a phenomenon that was predicted almost 50 years ago. The lunar soil has a finite capacity to retain implanted hydrogen, and over time, the surface reaches a steady state, or background H/OH abundance, which is manifested in spectra of the mature soil. In addition to maturity, the retention of H/OH is a function of composition and texture (i.e., crystallinity and surface/volume). There are two hypotheses for how solar wind-implanted H/OH is retained in the soil: 1) H/OH adsorbs onto active surface sites on fresh soil particles. 2) H/OH is trapped in vesicles in agglutinates and amorphous coatings on soil grains created by space weathering. Undoubtedly both of these mechanisms occur, but one process is ultimately responsible for the observed steady state mature soil abundance, and this can be studied by measuring the strength of the H/OH spectral feature from soils as a function of variable composition, texture, and maturity. Space weathering is capable of both activating and neutralizing grain surfaces. Micrometeorite and larger impacts can activate mineral surfaces through mechanical forces, such as crushing and shattering of minerals, which creates fresh surfaces with partially unsatisfied chemical bonds. The freshly fractured

  14. Density functional study of the adsorption of aspirin on the hydroxylated (0 0 1) α-quartz surface

    NASA Astrophysics Data System (ADS)

    Abbasi, A.; Nadimi, E.; Plänitz, P.; Radehaus, C.

    2009-08-01

    In this study the adsorption geometry of aspirin molecule on a hydroxylated (0 0 1) α-quartz surface has been investigated using DFT calculations. The optimized adsorption geometry indicates that both, adsorbed molecule and substrate are strongly deformed. Strong hydrogen bonding between aspirin and surface hydroxyls, leads to the breaking of the original hydroxyl-hydroxyl hydrogen bonds (Hydrogenbridges) on the surface. In this case new hydrogen bonds on the hydroxylated (0 0 1) α-quartz surface appear which significantly differ from those at the clean surface. The 1.11 eV adsorption energy reveals that the interaction of aspirin with α-quartz is an exothermic chemical interaction.

  15. Surface hydroxylation of styrene-butadiene-styrene block copolymers for biomaterials.

    PubMed

    Sefton, M V; Merrill, E W

    1976-01-01

    This work pertains to the development of high strength elastomers potentially useful as nonthrombogenic cardiovascular prostheses. Triblock copolymers of the styrene-butadiene-styrene type have been subjected to surface hydroxylation which provide reactive sites at the surface for the subsequent coupling of heparin while retaining the unique mechanical properties of the SBS copolymers. Curves of hydroxyl content versus the copolymer film thickness demonstrate the effect of swelling in the surface region on the product distribution and on the time dependence of the hydroxylation process. In addition, the effect of time, temperature, and the composition of the reaction bath on the diffusion/reaction process is shown. Finally, the general applicability of this surface modification scheme to the development of biomaterials is discussed. PMID:1249089

  16. Role of hydroxyl groups on the stability and catalytic activity of Au clusters on rutile surface

    SciTech Connect

    Kent, Paul R

    2011-01-01

    Hydroxyls are present as surface terminations of transition metal oxides under ambient conditions and may modify the properties of supported catalysts. We perform first-principles density functional theory calculations to investigate the role of hydroxyls on the catalytic activity of supported gold clusters on TiO{sub 2} (rutile). We find that they have a long-range effect increasing the adhesion of gold clusters on rutile. While hydroxyls make one gold atom more electronegative, a more complex charge-transfer scenario is observed on larger clusters which are important for catalytic applications. This enhances the molecular adsorption and coadsorption energies of CO and O{sub 2}, thereby increasing the catalytic activity of gold clusters for CO oxidation, consistent with reported experiments. Hydroxyls at the interface between gold and rutile surface are most important to this process, even when not directly bound to gold. As such, accurate models of catalytic processes on gold and other catalysts should include the effect of surface hydroxyls.

  17. High physisorption affinity of water molecules to the hydroxylated aluminum oxide (001) surface.

    PubMed

    Kittaka, Shigeharu; Yamaguchi, Keisuke; Takahara, Shuichi

    2012-02-15

    The adsorption mechanism of water on the hydroxylated (001) plane of α-Al(2)O(3) was studied by measuring adsorption isotherms and GCMC simulations. The experimental adsorption isotherms for three α-Al(2)O(3) samples from different sources are typical type II, in which adsorption starts sharply at low pressures, suggesting a high affinity of water to the Al(2)O(3) surface. Water molecules are adsorbed in two registered forms (bilayer structure). In the first form, water is registered at the center of three surface hydroxyl groups by directing a proton of the water. In the second form, a water molecule is adsorbed by bridging two of the first-layer water molecules through hydrogen bonding, by which a hexagonal ring network is constructed over the hydroxylated surface. The network domains are spread over the surface, and their size decreases as the temperature increases. The simulated adsorption isotherms present a characteristic two-dimensional (2D) phase diagram including a 2D critical point at 365K, which is higher than that on the hydroxylated Cr(2)O(3) surface (319 K). This fact substantiates the high affinity of water molecules to the α-Al(2)O(3) surfaces, which enhances the adsorbability originating from higher heat of adsorption. The higher affinity of water molecules to the α-Al(2)O(3) (001) plane is ascribed to the high compatibility of the crystal plane to form a hexagonal ring network of (001) plane of ice Ih. PMID:22178567

  18. Effects of polycyclic aromatic hydrocarbons on microbial community structure and PAH ring hydroxylating dioxygenase gene abundance in soil.

    PubMed

    Sawulski, Przemyslaw; Clipson, Nicholas; Doyle, Evelyn

    2014-11-01

    Development of successful bioremediation strategies for environments contaminated with recalcitrant pollutants requires in-depth knowledge of the microorganisms and microbial processes involved in degradation. The response of soil microbial communities to three polycyclic aromatic hydrocarbons, phenanthrene (3-ring), fluoranthene (4-ring) and benzo(a)pyrene (5-ring), was examined. Profiles of bacterial, archaeal and fungal communities were generated using molecular fingerprinting techniques (TRFLP, ARISA) and multivariate statistical tools were employed to interpret the effect of PAHs on community dynamics and composition. The extent and rate of PAH removal was directly related to the chemical structure, with the 5-ring PAH benzo(a)pyrene degraded more slowly than phenathrene or fluoranthene. Bacterial, archaeal and fungal communities were all significantly affected by PAH amendment, time and their interaction. Based on analysis of clone libraries, Actinobacteria appeared to dominate in fluoranthene amended soil, although they also represented a significant portion of the diversity in phenanthrene amended and unamended soils. In addition there appeared to be more γ-Proteobacteria and less Bacteroidetes in soil amended with either PAH compared to the control. The soil bacterial community clearly possessed the potential to degrade PAHs as evidenced by the abundance of PAH ring hydroxylating (PAH-RHDα) genes from both gram negative (GN) and gram positive (GP) bacteria in PAH-amended and control soils. Although the dioxygenase gene from GP bacteria was less abundant in soil than the gene associated with GN bacteria, significant (p < 0.001) increases in the abundance of the GP PAH-RHDα gene were observed during phenanthrene and fluoranthene degradation, whereas there was no significant difference in the abundance of the GN PAH-RHDα gene during the course of the experiment. Few studies to-date have examined the effect of pollutants on more than one microbial

  19. A theoretical study of O2 activation by the Au7-cluster on Mg(OH)2: roles of surface hydroxyls and hydroxyl defects.

    PubMed

    Jia, Chuanyi; Fan, Weiliu

    2015-11-11

    Using density functional theory (DFT) calculations, we investigated O2 activation by the Au7-cluster supported on the perfect and hydroxyl defective Mg(OH)2(0001) surface. It is revealed that hydroxyl groups on the perfect Mg(OH)2(0001) surface can not only enhance the stability of the Au7-cluster, but also help the adsorption of the O2 molecule through hydrogen-bonding interactions with the 2nd-layered interfacial Au sites. Density of states (DOS) analysis shows that the d-band centers of the 2nd-layered interfacial Au atoms are very close to the Fermi level, which thereby reduce the Pauli repulsion and promote the O2 adsorption. These two responses make the 2nd-layered interfacial Au atoms favor O2 activation. Interestingly, the surface hydrogen atoms activated by the 1st-layered Au atoms can facilitate the O2 dissociation process as well. Such a process is dynamically favorable and more inclined to occur at low temperatures compared to the direct dissociation process. Meanwhile, the hydroxyl defects of Mg(OH)2(0001) located right under the Au7-cluster can also up-shift the d-band centers of the surrounding Au atoms toward the Fermi level, enhancing its catalytic activity for O2 dissociation. In contrast, the d-band center of Au atoms surrounding the hydroxyl defect near the Au7-cluster exhibits an effective down-shift to lower energies, and therefore holds low activity. These results unveiled the roles of surface hydroxyls and hydroxyl defects on the Au/Mg(OH)2 catalyst in O2 activation and could provide a theoretical guidance for chemists to efficiently synthesize Au/hydroxide catalysts. PMID:26529519

  20. Morphologies of fibroblast cells cultured on surfaces of PHB films implanted by hydroxyl ions.

    PubMed

    Hou, T; Zhang, J Z; Kong, L J; Zhang, X E; Hu, P; Zhang, D M; Li, N

    2006-01-01

    Polyhydroxybutyrate (PHB) films were implanted with 40 keV hydroxyl ions with fluences ranging from 1 x 10(12) to 1 x 10(15) ions/cm2, respectively. The as-implanted PHB films were characterized by scanning electron microscopy (SEM), electron spectroscopy for chemical analysis (ESCA) and water contact angle measurements. The surface structures and properties of the as-implanted PHB films were closely related with hydroxyl ion fluence. They were further investigated by inoculating 3T6 fibroblasts cells on their surfaces. Morphologies of the 3T6 fibroblast cells cultured on surfaces of the as-implanted PHB films were observed by SEM. Characterization of the cultural 3T6 cells was analyzed qualitatively. The preliminary experimental results reveal that the bioactivity of the PHB films modified by hydroxyl ion implantation was improved at different levels, and the fluence of 1 x 10(13) ions/cm2 is optimal for PHB film. PMID:16909942

  1. Detection analysis of surface hydroxyl active sites and simulation calculation of the surface dissociation constants of aqueous diatomite suspensions

    NASA Astrophysics Data System (ADS)

    Ma, Shu-Cui; Wang, Zhi-Gang; Zhang, Ji-Lin; Sun, De-Hui; Liu, Gui-Xia

    2015-02-01

    The surface properties of the diatomite were investigated using nitrogen adsorption/deadsorption isotherms, TG-DSC, FTIR, and XPS, and surface protonation-deprotonation behavior was determined by continuous acid-base potentiometric titration technique. The diatomite sample with porous honeycomb structure has a BET specific surface area of 10.21 m2/g and large numbers of surface hydroxyl functional groups (i.e. tbnd Si-OH, tbnd Fe-OH, and tbnd Al-OH). These surface hydroxyls can be protonated or deprotonated depending on the pH of the suspension. The experimental potentiometric data in two different ionic strength solutions (0.1 and 0.05 mol/L NaCl) were fitted using ProtoFit GUI V2.1 program by applying diffuse double layer model (DLM) with three amphoteric sites and minimizing the sum of squares between a dataset derivative function and a model derivative function. The optimized surface parameters (i.e. surface dissociation constants (log K1, log K2) and surface site concentrations (log C)) of the sample were obtained. Based on the optimized surface parameters, the surface species distribution was calculated using Program-free PHREEQC 3.1.2. Thus, this work reveals considerable new information about surface protonation-deprotonation processes and surface adsorptive behaviors of the diatomite, which helps us to effectively use the cheap and cheerful diatomite clay adsorbent.

  2. A simplified process design for P450 driven hydroxylation based on surface displayed enzymes.

    PubMed

    Ströhle, Frank W; Kranen, Eva; Schrader, Jens; Maas, Ruth; Holtmann, Dirk

    2016-06-01

    New production routes for fine and bulk chemicals are important to establish further sustainable processes in industry. Besides the identification of new biocatalysts and new production routes the optimization of existing processes in regard to an improved utilization of the catalysts are needed. In this paper we describe the successful expression of P450BM3 on the surface of E. coli cells with the Autodisplay system. The successful hydroxylation of palmitic acid by using surface-displayed P450BM3 was shown. Besides optimization of surface protein expression, several cofactor regeneration systems were compared and evaluated. Afterwards, the development of a suitable process for the biocatalytic hydroxylation of fatty acids based on the re-use of the catalysts after a simple centrifugation was investigated. It was shown that the catalyst can be used for several times without any loss in activity. By using surface-displayed P450s in combination with an enzymatic cofactor regeneration system a total turnover number of up to 54,700 could be reached, to the knowledge of the authors the highest value reported for a P450 monooxygenase to date. Further optimizations of the described reaction system can have an enormous impact on the process design for more sustainable bioprocesses. Biotechnol. Bioeng. 2016;113: 1225-1233. © 2015 Wiley Periodicals, Inc. PMID:26574191

  3. Oxidation of Au by surface OH: nucleation and electronic structure of gold on hydroxylated MgO(001).

    PubMed

    Brown, Matthew A; Fujimori, Yuichi; Ringleb, Franziska; Shao, Xiang; Stavale, Fernando; Nilius, Niklas; Sterrer, Martin; Freund, Hans-Joachim

    2011-07-13

    The nucleation and electronic structure of vapor-deposited Au on hydroxylated MgO(001) surfaces has been investigated under ultrahigh vacuum conditions. Hydroxylated MgO(001) surfaces with two different hydroxyl coverages, 0.4 and 1 monolayer, respectively, were prepared by exposure to water (D(2)O) at room temperature. Scanning tunneling microscopy experiments show significantly higher gold particle densities and smaller particle sizes on the hydroxylated MgO surface as compared to gold deposited on clean MgO(001). Infrared spectroscopy and X-ray photoelectron spectroscopy experiments were performed to reveal details about the initial nucleation of gold. Gold atoms are found to chemically interact with a specific type of hydroxyl groups on the MgO surface, leading to the formation of oxidized gold particles. The enhanced adhesion of Au particles, which is due to the formation of strong Au-O interfacial bonds, is responsible for the observed higher stability of small Au clusters toward thermal sintering on hydroxylated MgO surfaces. The results are compared to similar studies on Au/TiO(2)(110) model systems and powder samples prepared by the deposition-precipitation route. PMID:21634792

  4. Synthesis and surface activities of a novel di-hydroxyl-sulfate-betaine-type zwitterionic gemini surfactants

    NASA Astrophysics Data System (ADS)

    Geng, Xiang F.; Hu, Xing Q.; Xia, Ji J.; Jia, Xue C.

    2013-04-01

    A series of novel di-hydroxyl-sulfate-betaine-type zwitterionic gemini surfactants of 1,2-bis[N-ethyl-N-(2-hydroxyl-3-sulfopropyl)-alkylammonium] alkyl betaines (DBAs-n, where s and n represent the spacer length of 2, 4 and 6 and the hydrocarbon chain length of 8, 12, 14, 16 and 18, respectively) were synthesized by reacting alkylamine with sodium 3-chloro-2-hydroxypropanesulfonate (the alternative sulphonated agent), followed by the reactions with а,ω-dibromoalkyl and then ethyl bromide. Their adsorption and aggregation properties were investigated by means of equilibrium surface tension, dynamic light-scattering (DLS) and transmission electron microscopy (TEM). DBAs-n gemini surfactants showed excellent surface activities and packed tightly at the interface. For example, the minimum CMC value for DBAs-n series was of the order of 10-5 M and the surface tension of water can be decreased as low as 22.2 mN/m. It was also found that the aggregates of DBAs-n solutions were significantly dependent on their hydrocarbon chain lengths. The aggregates changed from vesicles to entangled fiber-like micelles as the chain length increased from dodecyl to tetradecyl.

  5. Autocatalytic Surface Hydroxylation of MgO(100) Terrace Sites Observed Under Ambient Conditions

    SciTech Connect

    Newberg, J.T.; Starr, D.; Yamamoto, S.; Kaya, S.; Kendelewicz, T.; Mysak E.R.; Porsgaard, S.; Salmeron, M.B.; Brown, Jr., G.E.; Nilsson, A.; Bluhm, H.

    2011-06-01

    We have investigated the reaction of water vapor with the MgO(100) surface using ambient pressure X-ray photoelectron spectroscopy (AP-XPS), which permits the study of the chemical composition of the MgO/water vapor interface at p(H{sub 2}O) in the Torr range. Water dissociation on thin MgO(100) films of 4-5.5 monolayers (ML) grown on Ag(100) was studied under isobaric conditions at p(H{sub 2}O) ranging from 0.005 to 0.5 Torr and temperatures from 380 to -10 C, up to a maximum relative humidity (RH) of 20%. At RH < 0.01% dissociative adsorption occurs only at defect sites (0.08 ML), while terrace sites remain unreactive toward water dissociation. In the range 0.01 < RH < 0.1% there is an abrupt onset of dissociative adsorption at terrace sites which saturates at 1 ML at 0.1% RH, and is accompanied by an increase in molecular water adsorption. At 20% RH there is 1 ML of molecularly adsorbed water interacting with a fully hydroxylated interface on MgO(100). The observed onset of hydroxylation near 0.01% RH is suggested to be due to water molecules aggregating at the surface, leading to an autocatalytic dissociation of water at MgO(100) terrace sites.

  6. Surface reactivity of V2O5(001): Effects of vacancies, protonation, hydroxylation, and chlorination

    NASA Astrophysics Data System (ADS)

    Negreira, Ana Suarez; Aboud, Shela; Wilcox, Jennifer

    2011-01-01

    Using density-functional theory we analyze the thermodynamic stability of partially reduced, protonated, hydroxylated, and chlorinated V2O5(001) surfaces under flue gas conditions. These surfaces are characterized geometrically through surface relaxation calculations and electronically through charge distribution and density-of-states analysis to understand the change in surface reactivity under different pressure and temperature conditions, with a primary focus on coal-fired flue gas conditions. The stoichiometric surface is found to be the most favorable termination under flue gas conditions, but at low oxygen partial pressures (i.e., ultra-high-vacuum conditions) and elevated temperatures, the partially reduced V2O5(001) surfaces with one or two vanadyl oxygen vacancies are found to be stable. A surface semiconductor-to-metal transformation takes place with the addition of oxygen vacancies indicated by a decrease in the band gap. The protonation of the V2O5(001) surface only takes place at low oxygen partial pressures where the main source or sink of hydrogen atoms comes from H2. The study of the thermodynamic stability of protonated surfaces and surfaces with dissociated water with both H- and OH- groups indicated that these surfaces are not stable under flue gas conditions. Chlorinated surfaces were not stable under the flue gas and the coverage conditions tested. Larger HCl concentrations or smaller coverages may lead to stable chlorinated structures; however, the small coverages required to accurately represent the chlorine flue gas concentrations would require much larger unit-cell sizes that would be too computationally expensive. From this work it is evident that the stoichiometric surface of V2O5 is the most stable under flue gas conditions, and likely reactivity corresponding to NOx reduction, surface chlorination, and mercury oxidation stems from support effects on the vanadia catalyst, which influences the vanadium oxidation state and subsequent

  7. Water Contact Angle Dependence with Hydroxyl Functional Groups on Silica Surfaces under CO2 Sequestration Conditions.

    PubMed

    Chen, Cong; Zhang, Ning; Li, Weizhong; Song, Yongchen

    2015-12-15

    Functional groups on silica surfaces under CO2 sequestration conditions are complex due to reactions among supercritical CO2, brine and silica. Molecular dynamics simulations have been performed to investigate the effects of hydroxyl functional groups on wettability. It has been found that wettability shows a strong dependence on functional groups on silica surfaces: silanol number density, space distribution, and deprotonation/protonation degree. For neutral silica surfaces with crystalline structure (Q(3), Q(3)/Q(4), Q(4)), as silanol number density decreases, contact angle increases from 33.5° to 146.7° at 10.5 MPa and 318 K. When Q(3) surface changes to an amorphous structure, water contact angle increases 20°. Water contact angle decreases about 12° when 9% of silanol groups on Q(3) surface are deprotonated. When the deprotonation degree increases to 50%, water contact angle decreases to 0. The dependence of wettability on silica surface functional groups was used to analyze contact angle measurement ambiguity in literature. The composition of silica surfaces is complicated under CO2 sequestration conditions, the results found in this study may help to better understand wettability of CO2/brine/silica system. PMID:26509282

  8. Hydrogen Reactivity on Highly-hydroxylated TiO2(110) Surfaces Prepared via Carboxylic Acid Adsorption and Photolysis

    SciTech Connect

    Du, Yingge; Petrik, Nikolay G.; Deskins, N. Aaron; Wang, Zhitao; Henderson, Michael A.; Kimmel, Gregory A.; Lyubinetsky, Igor

    2012-02-27

    Combined scanning tunneling microscopy, temperature-programmed desorption, photo stimulated desorption, and density functional theory studies have probed the formation and reactivity of highly-hydroxylated rutile TiO2(110) surfaces, which were prepared via a novel, photochemical route using trimethyl acetic acid (TMAA) dissociative adsorption and subsequent photolysis at 300 K. Deprotonation of TMAA molecules upon adsorption produces both surface bridging hydroxyls (OHb) and bidentate trimethyl acetate (TMA) species with a saturation coverage of near 0.5 monolayer (ML). Ultra-violet light irradiation selectively removes TMA species, producing a highly-hydroxylated surface with up to ~0.5 ML OHb coverage. At high coverages, the OHb species typically occupy second-nearest neighbor sites along the bridging oxygen row locally forming linear (2×1) structures of different lengths, although the surface is less ordered on a long scale. The annealing of the highly-hydroxylated surface leads to hydroxyl recombination and H2O desorption with ~100% yield, thus ruling out the diffusion of H into the bulk that has been suggested in the literature. In agreement with experimental data, theoretical results show that the recombinative H2O desorption is preferred over both H bulk diffusion and H2 desorption processes.

  9. Natural abundance 17O DNP two-dimensional and surface-enhanced NMR spectroscopy

    DOE PAGESBeta

    Perras, Frédéric A.; Kobayashi, Takeshi; Pruski, Marek

    2015-06-22

    Due to its extremely low natural abundance and quadrupolar nature, the 17O nuclide is very rarely used for spectroscopic investigation of solids by NMR without isotope enrichment. Additionally, the applicability of dynamic nuclear polarization (DNP), which leads to sensitivity enhancements of 2 orders of magnitude, to 17O is wrought with challenges due to the lack of spin diffusion and low polarization transfer efficiency from 1H. Here, we demonstrate new DNP-based measurements that extend 17O solid-state NMR beyond its current capabilities. The use of the PRESTO technique instead of conventional 1H–17O cross-polarization greatly improves the sensitivity and enables the facile measurementmore » of undistorted line shapes and two-dimensional 1H–17O HETCOR NMR spectra as well as accurate internuclear distance measurements at natural abundance. This was applied for distinguishing hydrogen-bonded and lone 17O sites on the surface of silica gel; the one-dimensional spectrum of which could not be used to extract such detail. As a result, this greatly enhanced sensitivity has enabled, for the first time, the detection of surface hydroxyl sites on mesoporous silica at natural abundance, thereby extending the concept of DNP surface-enhanced NMR spectroscopy to the 17O nuclide.« less

  10. Aluminum Nitride Hydrolysis Enabled by Hydroxyl-Mediated Surface Proton Hopping.

    PubMed

    Bartel, Christopher J; Muhich, Christopher L; Weimer, Alan W; Musgrave, Charles B

    2016-07-20

    Aluminum nitride (AlN) is used extensively in the semiconductor industry as a high-thermal-conductivity insulator, but its manufacture is encumbered by a tendency to degrade in the presence of water. The propensity for AlN to hydrolyze has led to its consideration as a redox material for solar thermochemical ammonia (NH3) synthesis applications where AlN would be intentionally hydrolyzed to produce NH3 and aluminum oxide (Al2O3), which could be subsequently reduced in nitrogen (N2) to reform AlN and reinitiate the NH3 synthesis cycle. No quantitative, atomistic mechanism by which AlN, and more generally, metal nitrides react with water to become oxidized and generate NH3 yet exists. In this work, we used density-functional theory (DFT) to examine the reaction mechanisms of the initial stages of AlN hydrolysis, which include: water adsorption, hydroxyl-mediated proton diffusion to form NH3, and NH3 desorption. We found activation barriers (Ea) for hydrolysis of 330 and 359 kJ/mol for the cases of minimal adsorbed water and additional adsorbed water, respectively, corroborating the high observed temperatures for the onset of steam AlN hydrolysis. We predict AlN hydrolysis to be kinetically limited by the dissociation of strong Al-N bonds required to accumulate protons on surface N atoms to form NH3. The hydrolysis mechanism we elucidate is enabled by the diffusion of protons across the AlN surface by a hydroxyl-mediated Grotthuss mechanism. A comparison between intrinsic (Ea = 331 kJ/mol) and mediated proton diffusion (Ea = 89 kJ/mol) shows that hydroxyl-mediated proton diffusion is the predominant mechanism in AlN hydrolysis. The large activation barrier for NH3 generation from AlN (Ea = 330 or 359 kJ/mol, depending on water coverage) suggests that in the design of materials for solar thermochemical ammonia synthesis, emphasis should be placed on metal nitrides with less covalent metal-nitrogen bonds and, thus, more-facile NH3 liberation. PMID:27341277

  11. Spectroscopic Character and Spatial Distribution of Hydroxyl and Water Absorption Features Measured on the Lunar Surface by the Moon Mineralogy Mapper Imaging Spectrometer on Chandrayaan-1

    NASA Astrophysics Data System (ADS)

    Green, R. O.; Pieters, C. M.; Goswami, J.; Clark, R. N.; Annadurai, M.; Boardman, J. W.; Buratti, B. J.; Combe, J.; Dyar, M. D.; Head, J. W.; Hibbitts, C.; Hicks, M.; Isaacson, P.; Klima, R. L.; Kramer, G. Y.; Kumar, S.; Livo, K. E.; Lundeen, S.; Malaret, E.; McCord, T. B.; Mustard, J. F.; Nettles, J. W.; Petro, N. E.; Runyon, C. J.; Staid, M.; Sunshine, J. M.; Taylor, L. A.; Tompkins, S.; Varanasi, P.

    2009-12-01

    The Moon Mineralogy Mapper imaging spectrometer on Chandrayaan-1 has a broad spectral range from 430 to 3000 nm. By design, the range was specified to extend to 3000 nm to allow for possible detection of trace volatile compounds that possess absorption bands near 3000 nm. Soon after acquisition and calibration of a large fraction of the lunar surface in early February 2009, absorption features in the 2700 to 3000 nm region were detected over unexpectedly large regional areas. This extraordinary discovery has withstood extensive re-analysis and falsification efforts. We have concluded these absorption features are fundamentally present in the M3 measurements and are indicators of extensive hydroxyl and water-bearing materials occurring on the surface of the Moon. Based on current analyses, these absorption features appear strongest at high latitudes, but also occur in association with several fresh feldspathic craters. Interestingly, the distribution of these absorption features are not directly correlated with existing neutron spectrometer hydrogen abundance data for the sunlight surface. This may indicate that the formation and retention of hydroxyl and water is an active process largely restricted to the upper most surface. We present the detailed spectroscopic character of these absorption features in the 2700 to 3000 nm spectral region, including selected examples through all levels of measurement processing from raw data to calibrated apparent surface reflectance. In summary we show the measured strength and latitudinal distribution of the absorptions as well as selected localized occurrences in association with fresh feldspathic craters. The presence of hydroxyl and water bearing material over extensive regions of the lunar surface provides a new and unexpected source of volatiles. Options for harvesting these elements directly from the regolith may provide an alternate supply of volatiles for long term human exploration objectives.

  12. Microbial abundance in surface ice on the Greenland Ice Sheet

    PubMed Central

    Stibal, Marek; Gözdereliler, Erkin; Cameron, Karen A.; Box, Jason E.; Stevens, Ian T.; Gokul, Jarishma K.; Schostag, Morten; Zarsky, Jakub D.; Edwards, Arwyn; Irvine-Fynn, Tristram D. L.; Jacobsen, Carsten S.

    2015-01-01

    Measuring microbial abundance in glacier ice and identifying its controls is essential for a better understanding and quantification of biogeochemical processes in glacial ecosystems. However, cell enumeration of glacier ice samples is challenging due to typically low cell numbers and the presence of interfering mineral particles. We quantified for the first time the abundance of microbial cells in surface ice from geographically distinct sites on the Greenland Ice Sheet (GrIS), using three enumeration methods: epifluorescence microscopy (EFM), flow cytometry (FCM), and quantitative polymerase chain reaction (qPCR). In addition, we reviewed published data on microbial abundance in glacier ice and tested the three methods on artificial ice samples of realistic cell (102–107 cells ml−1) and mineral particle (0.1–100 mg ml−1) concentrations, simulating a range of glacial ice types, from clean subsurface ice to surface ice to sediment-laden basal ice. We then used multivariate statistical analysis to identify factors responsible for the variation in microbial abundance on the ice sheet. EFM gave the most accurate and reproducible results of the tested methodologies, and was therefore selected as the most suitable technique for cell enumeration of ice containing dust. Cell numbers in surface ice samples, determined by EFM, ranged from ~ 2 × 103 to ~ 2 × 106 cells ml−1 while dust concentrations ranged from 0.01 to 2 mg ml−1. The lowest abundances were found in ice sampled from the accumulation area of the ice sheet and in samples affected by fresh snow; these samples may be considered as a reference point of the cell abundance of precipitants that are deposited on the ice sheet surface. Dust content was the most significant variable to explain the variation in the abundance data, which suggests a direct association between deposited dust particles and cells and/or by their provision of limited nutrients to microbial communities on the GrIS. PMID:25852678

  13. Promotional effect of surface hydroxyls on electrochemical reduction of CO2 over SnOx/Sn electrode

    DOE PAGESBeta

    Cui, Chaonan; Han, Jinyu; Zhu, Xinli; Liu, Xiao; Wang, Hua; Mei, Donghai; Ge, Qingfeng

    2016-01-16

    In this study, tin oxide (SnOx) formation on tin-based electrode surfaces during CO2 electrochemical reduction can have a significant impact on the activity and selectivity of the reaction. In the present study, density functional theory (DFT) calculations have been performed to understand the role of SnOx in CO2 reduction using a SnO monolayer on the Sn(112) surface as a model for SnOx. Water molecules have been treated explicitly and considered actively participating in the reaction. The results showed that H2O dissociates on the perfect SnO monolayer into two hydroxyl groups symmetrically on the surface. CO2 energetically prefers to react withmore » the hydroxyl, forming a bicarbonate (HCO3(t)*) intermediate, which can then be reduced to either formate (HCOO*) by hydrogenating the carbon atom or carboxyl (COOH*) by protonating the oxygen atom. Both steps involve a simultaneous Csingle bondO bond breaking. Further reduction of HCOO* species leads to the formation of formic acid in the acidic solution at pH < 4, while the COOH* will decompose to CO and H2O via protonation. Whereas the oxygen vacancy (VO) in the oxide monolayer maybe formed by the reduction, it can be recovered by H2O dissociation, resulting in two embedded hydroxyl groups. The results show that the hydroxylated surface with two symmetric hydroxyls is energetically more favorable for CO2 reduction than the hydroxylated VO surface with two embedded hydroxyls. The reduction potential for the former has a limiting-potential of –0.20 V (RHE), lower than that for the latter (–0.74 V (RHE)). Compared to the pure Sn electrode, the formation of SnOx monolayer on the electrode under the operating conditions promotes CO2 reduction more effectively by forming surface hydroxyls, thereby providing a new channel via COOH* to the CO formation, although formic acid is still the major reduction product.« less

  14. Ability of TiO2(110) Surface to Be Fully Hydroxylated and Fully Reduced

    SciTech Connect

    Wang, Zhitao; Garcia, Juan C.; Deskins, N. A.; Lyubinetsky, Igor

    2015-08-06

    Many TiO2 applications (e.g., in heterogeneous catalysis) involve contact with ambient atmosphere and/or water. The resulting hydroxylation can significantly alter its surface properties. While behavior of single, isolated OH species on the model metal oxide surface of rutile TiO2(110) is relatively well understood, much less is known regarding highly-hydroxylated surfaces and/or whether TiO2(110) could be fully-hydroxylated under ultra-high vacuum conditions. Here we report in situ formation of a well-ordered, fully-hydroxylated TiO2(110)-(1 x 1) surface using an enhanced photochemical approach, key parts of which are pre-dosing of water and multi-step dissociative adsorption and subsequent photolysis of the carboxylic (trimethyl acetic) acid. Combining scanning tunneling microscopy, ultra-violet photoelectron spectroscopy and density functional theory results, we show that the attained “super OH” surface is also fully-reduced, as a result of the photochemical trapping of electrons at the OH groups.

  15. Dealkylated and hydroxylated metabolites of atrazine in surface and ground water

    SciTech Connect

    Cai, Zongwei; Spalding, R.F.

    1995-12-01

    Atrazine is one of the most extensively used herbicides in the central United States. The herbicide and its metabolites are known to persist in surface and ground waters. The dealkylated metabolites of atrazine were determined in ground water taken from Pleistocene age sand and gravel aquifer located southeast of Grand Island, Nebraska by using gas chromatography/high resolution mass spectrometry, while hydroxyatrazine by fast atom bombartment-high resolution mass spectrometry at ultra-trace level. A high performance liquid chromatography method was developed to analyze run-off surface water for both dealkylated and hydroxylated metabolites. The analytical results were compared to validate the methods. The agreement is within a few percent. The levels of ATR and its metabolites in the ground water samples range from low parts-per-trillion (ppt) to parts-per-billion (ppb). The data indicate that a decrease in concentration levels with depth, and this is in record with the hypothesis that the deeper water is older. The results provide valuable information for the study of environmental kinetics of the degradation of atrazine.

  16. Photoluminescence of oxygen vacancies and hydroxyl group surface functionalized SnO2 nanoparticles.

    PubMed

    Bonu, Venkataramana; Das, Arindam; Amirthapandian, S; Dhara, Sandip; Tyagi, Ashok Kumar

    2015-04-21

    We report, for the first time, the luminescence property of the hydroxyl group surface functionalized quantum dots (QDs) and nanoparticles (NPs) of SnO2 using low energy excitations of 2.54 eV (488 nm) and 2.42 eV (514.5 nm). This luminescence is in addition to generally observed luminescence from 'O' defects. The as-prepared SnO2 QDs are annealed at different temperatures under ambient conditions to create NPs with varying sizes. Subsequently, the average size of the NPs is calculated from the acoustic vibrations observed at low frequencies in the Raman spectra and by the transmission electron microscopy measurements. Detailed photoluminescence studies with 3.815 eV (325 nm) excitation reveal the nature of in-plane and bridging 'O' vacancies as well as adsorption and desorption occurring at different annealing temperatures. X-ray photoelectron spectroscopy studies also support this observation. The defect level related to the surface -OH functional groups shows a broad luminescence peak at around 1.96 eV in SnO2 NPs which is elaborated using temperature dependent studies. PMID:25774472

  17. M3 spectral analysis of lunar swirls and the link between optical maturation and surface hydroxyl formation at magnetic anomalies

    USGS Publications Warehouse

    Kramer, G.Y.; Besse, S.; Dhingra, D.; Nettles, J.; Klima, R.; Garrick-Bethell, I.; Clark, R.N.; Combe, J.-P.; Head, J. W., III; Taylor, L.A.; Pieters, C.M.; Boardman, J.; McCord, T.B.

    2011-01-01

    We examined the lunar swirls using data from the Moon Mineralogy Mapper (M3). The improved spectral and spatial resolution of M3 over previous spectral imaging data facilitates distinction of subtle spectral differences, and provides new information about the nature of these enigmatic features. We characterized spectral features of the swirls, interswirl regions (dark lanes), and surrounding terrain for each of three focus regions: Reiner Gamma, Gerasimovich, and Mare Ingenii. We used Principle Component Analysis to identify spectrally distinct surfaces at each focus region, and characterize the spectral features that distinguish them. We compared spectra from small, recent impact craters with the mature soils into which they penetrated to examine differences in maturation trends on- and off-swirl. Fresh, on-swirl crater spectra are higher albedo, exhibit a wider range in albedos and have well-preserved mafic absorption features compared with fresh off-swirl craters. Albedoand mafic absorptions are still evident in undisturbed, on-swirl surface soils, suggesting the maturation process is retarded. The spectral continuum is more concave compared with off-swirl spectra; a result of the limited spectral reddening being mostly constrained to wavelengths less than ???1500 nm. Off-swirl spectra show very little reddening or change in continuum shape across the entire M3 spectral range. Off-swirl spectra are dark, have attenuated absorption features, and the narrow range in off-swirl albedos suggests off-swirl regions mature rapidly. Spectral parameter maps depicting the relative OH surface abundance for each of our three swirl focus regions were created using the depth of the hydroxyl absorption feature at 2.82 ??m. For each of the studied regions, the 2.82 ??m absorption feature is significantly weaker on-swirl than off-swirl, indicating the swirls are depleted in OH relative to their surroundings. The spectral characteristics of the swirls and adjacent terrains from

  18. Oxygen abundances in low surface-brightness galaxies

    NASA Technical Reports Server (NTRS)

    Roennback, Jari

    1993-01-01

    Recent theories predict that some protogalaxies, in low-density environments of the field, are contracting and interacting so slowly that global star formation can be delayed until today. These systems should be gas rich and have low surface-brightness. Blue compact galaxies (BCG's) and other compact HII region galaxies currently experiencing a burst of star formation are good candidates of truly young galaxies (in the sense that global star formation recently has been initiated). If they really are young, they ought to have a recent phase when their brightness was much lower than in the bursting phase. No claims of observations of such proto-BCG's exist. Observations of galaxies in their juvenile phases would undoubtedly be of great interest, e.g. the determination of the primordial helium abundance would improve. A proper place to search for young nearby galaxies could be among blue low surface-brightness galaxies (BLSBG's) in the local field. The study of low surface-brightness galaxies (LSBG's) as a group began relatively recently. They are galaxies with extraordinary properties both as individuals and as a group. A few years ago we started an optical study of a sample of BLSBG's selected from the ESO/Uppsala catalogue. Results of spectroscopic observations obtained on a subsample - 8 galaxies - of our selection are reported. The HII region oxygen chemical abundances and its relation to the blue absolute magnitude and surface-brightness is investigated.

  19. An efficient approach to derive hydroxyl groups on the surface of barium titanate nanoparticles to improve its chemical modification ability.

    PubMed

    Chang, Shinn-Jen; Liao, Wei-Sheng; Ciou, Ci-Jin; Lee, Jyh-Tsung; Li, Chia-Chen

    2009-01-15

    Highly hydroxylated barium titanate (BaTiO(3)) nanoparticles have been prepared via an easy and gentle approach which oxidizes BaTiO(3) nanoparticles using an aqueous solution of hydrogen peroxide (H(2)O(2)). The hydroxylated BaTiO(3) surface reacts with sodium oleate (SOA) to form oleophilic layers that greatly enhance the dispersion of BaTiO(3) nanoparticles in organic solvents such as tetrahydrofuran, toluene, and n-octane. The results of Fourier transform infrared spectroscopy confirmed that the major functional groups on the surface of H(2)O(2)-treated BaTiO(3) nanoparticles are hydroxyl groups which are chemically active, favoring chemical bonding with SOA. The results of transmission electron microscopy of SOA-modified BaTiO(3) nanoparticles suggested that the oleate molecules were bonded to the surfaces of nanoparticles and formed a homogeneous layer having a thickness of about 2 nm. Furthermore, the improved dispersion capability of the modified BaTiO(3) nanoparticles in organic solvents was verified through analytic results of its settling and rheological behaviors. PMID:18977001

  20. Optimization of hydroxyl radical scavenging activity of exo-polysaccharides from Inonotus obliquus in submerged fermentation using response surface methodology.

    PubMed

    Chen, Hui; Xu, Xiangqun; Zhu, Yang

    2010-04-01

    The objectives of this study were to investigate the effect of fermentation medium on the hydroxyl radical scavenging activity of exo-polysaccharides from Inonotus obliquus by response surface methodology. A two-level fractional factorial design was used to evaluate the effect of different components of medium. Corn flour, peptone, and KH2PO4 were important factors significantly affecting hydroxyl radical scavenging activity. These selected variables were subsequently optimized using path of steepest ascent (descent), a central composite design, and response surface analysis. The optimal medium composition was (% w/v): corn flour 5.30, peptone 0.32, KH2PO4 0.26, MgSO4 0.02, and CaCl2 0.01. Under the optimal condition, the hydroxyl radical scavenging rate (49.4%) was much higher than that using either basal fermentation medium (10.2%) and single variable optimization of fermentation medium (35.5%). The main monosaccharides components of the RSM optimized polysaccharides are rhamnose, arabinose, xylose, mannose, glucose and galactose with molar proportion at 1.45%, 3.63%, 2.17%, 15.94%, 50.00%, and 26.81%. PMID:20467262

  1. Ammonia formation from NO reaction with surface hydroxyls on rutile TiO2 (110) - 1×1

    SciTech Connect

    Kim, Boseong; Kay, Bruce D.; Dohnalek, Zdenek; Kim, Yu Kwon

    2015-01-15

    The reaction of NO with hydroxylated rutile TiO2(110)-1×1 surface (h-TiO2) was investigated as a function of NO coverage using temperature-programmed desorption. Our results show that NO reaction with h-TiO2 leads to formation of NH3 which is observed to desorb at ~ 400 K. Interestingly, the amount of NH3 produced depends nonlinearly on the coverage of NO. The yield increases up to a saturation value of ~1.3×1013 NH3/cm2 at a NO dose of 5×1013 NO/cm2, but subsequently decreases at higher NO doses. Preadsorbed H2O is found to have a negligible effect on the NH3 desorption yield. Additionally, no NH3 is formed in the absence of surface hydroxyls (HOb’s) upon coadsorption of NO and H2O on a stoichiometric TiO2(110) (s-TiO2(110)). Based on these observations, we conclude that nitrogen from NO has a strong preference to react with HOb’s on the bridge-bonded oxygen rows (but not with H2O) to form NH3. The absolute NH3 yield is limited by competing reactions of HOb species with titanium-bound oxygen adatoms to form H2O. Our results provide new mechanistic insight about the interactions of NO with hydroxyl groups on TiO2(110) .

  2. Density functional theory study of SO2-adsorbed Ni(1 1 1) and hydroxylated NiO(1 1 1) surface

    NASA Astrophysics Data System (ADS)

    Wei, Xin; Dong, Chaofang; Chen, Zhanghua; Xiao, Kui; Li, Xiaogang

    2015-11-01

    Spin polarized, DFT + U periodic calculation is used as an effective way to model the adsorption process of SO2 on hydroxylated NiO(1 1 1) surface. The adsorption of atomic O and O2 on the clean Ni(1 1 1) surface is calculated to investigate the forming process of passive film. The molecular and dissociated adsorptions of H2O on NiO(1 1 1) surface are evaluated to construct defect-free hydroxylated NiO(1 1 1) surface. The adsorption of SO2 and atomic O on clean Ni(1 1 1) surface is also investigated to compare with the adsorption capacity between passive film and substrate. With respect to the single adsorption process of SO2 on defect-free hydroxylated NiO(1 1 1) surface, the effects of O vacancy of surface and atomic O closed to the surface are investigated. The calculation results show that there is no chemical adsorption of SO2 on the defect-free hydroxylated NiO(1 1 1) surface with or without atomic O. Either single SO2 or SO2 with atomic O prefer adsorbing on the hydroxylated NiO(1 1 1) surface with O vacancies. The adsorption behavior is strengthened with the increase of percentage of surface O vacancy. The existence of atomic O leads to the production of SO3 on the hydroxylated NiO(1 1 1) surface and strengthens the adsorption capacity of SO2. Furthermore, the results also reveal the relationship between the charge transfer and the adsorption energy of SO2 and atomic O on the hydroxylated NiO(1 1 1) surface and clean Ni(1 1 1) surface. We inferred that broken passive film susceptibility to corrosion compare with substrate when surface O vacancies aggregate and its concentration large enough.

  3. Reliable Quantitative Mineral Abundances of the Martian Surface using THEMIS

    NASA Astrophysics Data System (ADS)

    Smith, R. J.; Huang, J.; Ryan, A. J.; Christensen, P. R.

    2013-12-01

    The following presents a proof of concept that given quality data, Thermal Emission Imaging System (THEMIS) data can be used to derive reliable quantitative mineral abundances of the Martian surface using a limited mineral library. The THEMIS instrument aboard the Mars Odyssey spacecraft is a multispectral thermal infrared imager with a spatial resolution of 100 m/pixel. The relatively high spatial resolution along with global coverage makes THEMIS datasets powerful tools for comprehensive fine scale petrologic analyses. However, the spectral resolution of THEMIS is limited to 8 surface sensitive bands between 6.8 and 14.0 μm with an average bandwidth of ~ 1 μm, which complicates atmosphere-surface separation and spectral analysis. This study utilizes the atmospheric correction methods of both Bandfield et al. [2004] and Ryan et al. [2013] joined with the iterative linear deconvolution technique pioneered by Huang et al. [in review] in order to derive fine-scale quantitative mineral abundances of the Martian surface. In general, it can be assumed that surface emissivity combines in a linear fashion in the thermal infrared (TIR) wavelengths such that the emitted energy is proportional to the areal percentage of the minerals present. TIR spectra are unmixed using a set of linear equations involving an endmember library of lab measured mineral spectra. The number of endmembers allowed in a spectral library are restricted to a quantity of n-1 (where n = the number of spectral bands of an instrument), preserving one band for blackbody. Spectral analysis of THEMIS data is thus allowed only seven endmembers. This study attempts to prove that this limitation does not prohibit the derivation of meaningful spectral analyses from THEMIS data. Our study selects THEMIS stamps from a region of Mars that is well characterized in the TIR by the higher spectral resolution, lower spatial resolution Thermal Emission Spectrometer (TES) instrument (143 bands at 10 cm-1 sampling and 3

  4. Modelling On Photogeneration Of Hydroxyl Radical In Surface Waters And Its Reactivity Towards Pharmaceutical Wastes

    SciTech Connect

    Das, Radha; Vione, Davide; Rubertelli, Francesca; Maurino, Valter; Minero, Claudio; Barbati, Stephane; Chiron, Serge

    2010-10-26

    This paper reports a simple model to describe the formation and reactivity of hydroxyl radicals in the whole column of freshwater lakes. It is based on empirical irradiation data and is a function of the water chemical composition (the photochemically significant parameters NPOC, nitrate, nitrite, carbonate and bicarbonate), the lake conformation best expressed as the average depth, and the water absorption spectrum in a simplified Lambert-Beer approach. The purpose is to derive the lifetime of dissolved molecules, due to reaction with OH, on the basis of their second-order rate constants with the hydroxyl radical. The model was applied to two compounds of pharmaceutical wastes ibuprofen and carbamazepine, for which the second-order rate constants for reaction with the hydroxyl radical were measured by means of the competition kinetics with 2-propanol. The measured values of the rate constants are 1.0x10{sup 10} and 1.6x10{sup 10} M{sup -1} s{sup -1} for ibuprofen and carbamazepine, respectively. The model suggests that the lifetime of a given compound can be very variable in different lakes, even more than the lifetime of different compounds in the same lake. It can be concluded that as far as the reaction with OH, is concerned the concepts of photolability and photostability, traditionally attached to definite compounds, are ecosystem-dependent at least as much as they depend on the molecule under consideration.

  5. Effect of alkyl chain length and hydroxyl group functionalization on the surface properties of imidazolium ionic liquids.

    PubMed

    Pensado, Alfonso S; Costa Gomes, Margarida F; Canongia Lopes, José N; Malfreyt, Patrice; Pádua, Agílio A H

    2011-08-14

    Properties of the surface of ionic liquids, such as surface tension, ordering, and charge and density profiles, were studied using molecular simulation. Two types of modification in the molecular structure of imidazolium cations were studied: the length of the alkyl side chain and the presence of a polar hydroxyl group at the end of the side chain. Four ionic liquids were considered: 1-ethyl-3-methylimidazolium tetrafluoroborate, [C(2)C(1)im][BF(4)]; 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate, [C(2)OHC(1)im][BF(4)]; 1-octyl-3-methylimidazolium tetrafluoroborate, [C(8)C(1)im][BF(4)] and 1-(8-hydroxyoctyl)-3-methylimidazolium tetrafluoroborate, [C(8)OHC(1)im][BF(4)]. The surface tension was calculated using both mechanical and thermodynamic definitions, with consistent treatment of the long-range corrections. The simulations reproduce the available experimental values of surface tension with a maximum deviation of ±10%. This energetic characterization of the interface is completed by microscopic structural analysis of orientational ordering at the interface and density profiles along the direction normal to the interface. The presence of the hydroxyl group modifies the local structure at the interface, leading to a less organized liquid phase. The results allow us to relate the surface tension to the structural ordering at the liquid-vacuum interface. PMID:21643581

  6. Local structural models of complex oxygen- and hydroxyl-rich GaP/InP(001) surfaces.

    PubMed

    Wood, Brandon C; Ogitsu, Tadashi; Schwegler, Eric

    2012-02-14

    We perform density-functional theory calculations on model surfaces to investigate the interplay between the morphology, electronic structure, and chemistry of oxygen- and hydroxyl-rich surfaces of InP(001) and GaP(001). Four dominant local oxygen topologies are identified based on the coordination environment: M-O-M and M-O-P bridges for the oxygen-decorated surface; and M-[OH]-M bridges and atop M-OH structures for the hydroxyl-decorated surface (M = In, Ga). Unique signatures in the electronic structure are linked to each of the bond topologies, defining a map to structural models that can be used to aid the interpretation of experimental probes of native oxide morphology. The M-O-M bridge can create a trap for hole carriers upon imposition of strain or chemical modification of the bonding environment of the M atoms, which may contribute to the observed photocorrosion of GaP/InP-based electrodes in photoelectrochemical cells. Our results suggest that a simplified model incorporating the dominant local bond topologies within an oxygen adlayer should reproduce the essential chemistry of complex oxygen-rich InP(001) or GaP(001) surfaces, representing a significant advantage from a modeling standpoint. PMID:22360213

  7. Hydroxyl radicals in indoor environments

    NASA Astrophysics Data System (ADS)

    Sarwar, Golam; Corsi, Richard; Kimura, Yosuke; Allen, David; Weschler, Charles J.

    Indoor hydroxyl radical concentrations were estimated using a new indoor air quality model which employs the SAPRC-99 atmospheric chemistry model to simulate indoor homogenous reactions. Model results indicate that typical indoor hydroxyl radical concentrations are lower than typical outdoor summertime urban hydroxyl radical levels of 5-10×10 6 molecules cm -3; however, indoor levels can be similar to or greater than typical nighttime outdoor hydroxyl radical levels of approximately 5×10 4 molecules cm -3. Effects of selected parameters on indoor hydroxyl radical concentrations are presented herein. Indoor hydroxyl radical concentrations are predicted to increase non-linearly with increasing outdoor ozone concentrations, indoor alkene emission rates, and air exchange rates. Indoor hydroxyl radical concentrations decrease with increasing outdoor nitric oxide concentrations. Indoor temperature and indoor light intensity have moderate impacts on indoor hydroxyl radical concentrations. Outdoor hydroxyl radical concentrations, outdoor nitrate (NO 3rad ) radical concentrations, outdoor hydroperoxy radical concentrations, and hydroxyl radical removal by indoor surfaces are predicted to have no appreciable impact on indoor hydroxyl radical concentrations. Production of hydroxyl radicals in indoor environments appears to be controlled primarily by reactions of alkenes with ozone, and nitric oxide with hydroperoxy radical. Estimated indoor hydroxyl radical levels may potentially affect indoor air quality. Two examples are presented in which reactions of d-limonene and α-pinene with indoor hydroxyl radicals produce aldehydes, which may be of greater concern than the original compounds.

  8. POPC Bilayers Supported on Nanoporous Substrates: Specific Effects of Silica-Type Surface Hydroxylation and Charge Density.

    PubMed

    Duro, Nalvi; Gjika, Marion; Siddiqui, Ahnaf; Scott, H Larry; Varma, Sameer

    2016-07-01

    Recent advances in nanotechnology bring to the forefront a new class of extrinsic constraints for remodeling lipid bilayers. In this next-generation technology, membranes are supported over nanoporous substrates. The nanometer-sized pores in the substrate are too small for bilayers to follow the substrate topology; consequently, the bilayers hang over the pores. Experiments demonstrate that nanoporous substrates remodel lipid bilayers differently from continuous substrates. The underlying molecular mechanisms, however, remain largely undetermined. Here we use molecular dynamics (MD) simulations to probe the effects of silica-type hydroxylation and charge densities on adsorbed palmitoyl-oleoylphosphatidylcholine (POPC) bilayers. We find that a 50% porous substrate decorated with a surface density of 4.6 hydroxyls/nm(2) adsorbs a POPC bilayer at a distance of 4.5 Å, a result consistent with neutron reflectivity experiments conducted on topologically similar silica constructs under highly acidic conditions. Although such an adsorption distance suggests that the interaction between the bilayer and the substrate will be buffered by water molecules, we find that the substrate does interact directly with the bilayer. The substrate modifies several properties of the bilayer-it dampens transverse lipid fluctuations, reduces lipid diffusion rates, and modifies transverse charge densities significantly. Additionally, it affects lipid properties differently in the two leaflets. Compared to substrates functionalized with sparser surface hydroxylation densities, this substrate adheres to bilayers at smaller distances and also remodels POPC more extensively, suggesting a direct correspondence between substrate hydrophilicity and membrane properties. A partial deprotonation of surface hydroxyls, as expected of a silica substrate under mildly acidic conditions, however, produces an inverse effect: it increases the substrate-bilayer distance, which we attribute to the formation of

  9. Theoretical study on the initial reaction mechanisms of ansa-metallocene zirconium precursor on hydroxylated Si(1 0 0) surface.

    PubMed

    Zhou, Guangfen; Ren, Jie; Zhang, Shaowen

    2016-05-01

    The initial reaction mechanisms for depositing ZrO2 thin films using ansa-metallocene zirconium (Cp2CMe2)ZrMe2 precursor were studied by density functional theory (DFT) calculations. The (Cp2CMe2)ZrMe2 precursor could be absorbed on the hydroxylated Si(1 0 0) surface via physisorption. Possible reaction pathways of (Cp2CMe2)ZrMe2 were proposed. For each reaction, the activation energies and reaction energies were compared, and stationary points along the reaction pathways were shown. In addition, the influence of dispersion effects on the reactions was evaluated by non-local dispersion corrected DFT calculations. PMID:27138945

  10. Oxidation Ability of Plasmon-Induced Charge Separation Evaluated on the Basis of Surface Hydroxylation of Gold Nanoparticles.

    PubMed

    Nishi, Hiroyasu; Tatsuma, Tetsu

    2016-08-26

    The oxidation ability of plasmonic photocatalysts, which has its origins in plasmon-induced charge separation and has not yet been studied quantitatively and systematically, is important for designing practical photocatalytic systems. Oxidation ability was investigated on the basis of surface hydroxylation of Au nanoparticles on TiO2 at various irradiation wavelengths and electrolyte pH values. The reaction proceeds only when the sum of the flat band potential of TiO2 and the irradiated photon energy is close to, or more positive than, the theoretical potential for the reaction. PMID:27505255

  11. Method of making a membrane having hydrophilic and hydrophobic surfaces for adhering cells or antibodies by using atomic oxygen or hydroxyl radicals

    NASA Technical Reports Server (NTRS)

    Koontz, Steven L. (Inventor); Spaulding, Glenn F. (Inventor)

    1994-01-01

    A portion of an organic polymer article such as a membrane is made hydrophilic by exposing a hydrophobic surface of the article to a depth of about 50 to about 5000 angstroms to atomic oxygen or hydroxyl radicals at a temperature below 100C., preferably below 40 C, to form a hydrophilic uniform surface layer of hydrophilic hydroxyl groups. The atomic oxygen and hydroxyl radicals are generated by a flowing afterglow microwave discharge, and the surface is outside of a plasma produced by the discharge. A membrane having both hydrophilic and hydrophobic surfaces can be used in an immunoassay by adhering antibodies to the hydrophobic surface. In another embodiment, the membrane is used in cell culturing where cells adhere to the hydrophilic surface. Prior to adhering cells, the hydrophilic surface may be grafted with a compatibilizing compound. A plurality of hydrophilic regions bounded by adjacent hydrophobic regions can be produced such that a maximum of one cell per each hydrophilic region adheres.

  12. Natural abundance 17O DNP two-dimensional and surface-enhanced NMR spectroscopy

    SciTech Connect

    Perras, Frédéric A.; Kobayashi, Takeshi; Pruski, Marek

    2015-06-22

    Due to its extremely low natural abundance and quadrupolar nature, the 17O nuclide is very rarely used for spectroscopic investigation of solids by NMR without isotope enrichment. Additionally, the applicability of dynamic nuclear polarization (DNP), which leads to sensitivity enhancements of 2 orders of magnitude, to 17O is wrought with challenges due to the lack of spin diffusion and low polarization transfer efficiency from 1H. Here, we demonstrate new DNP-based measurements that extend 17O solid-state NMR beyond its current capabilities. The use of the PRESTO technique instead of conventional 1H–17O cross-polarization greatly improves the sensitivity and enables the facile measurement of undistorted line shapes and two-dimensional 1H–17O HETCOR NMR spectra as well as accurate internuclear distance measurements at natural abundance. This was applied for distinguishing hydrogen-bonded and lone 17O sites on the surface of silica gel; the one-dimensional spectrum of which could not be used to extract such detail. As a result, this greatly enhanced sensitivity has enabled, for the first time, the detection of surface hydroxyl sites on mesoporous silica at natural abundance, thereby extending the concept of DNP surface-enhanced NMR spectroscopy to the 17O nuclide.

  13. ESSENTIAL ROLE OF SURFACE HYDROXYLS FOR THE STABILIZATION AND CATALYTIC ACTIVITY OF TiO2-SUPPORTED GOLD NANOPARTICLES

    SciTech Connect

    Veith, Gabriel M; Lupini, Andrew R; Dudney, Nancy J

    2009-01-01

    We report the investigation of titania supported gold catalysts prepared by magnetron sputtering. Catalysts grown on natural fumed titania were structurally unstable resulting in the rapid coarsening of 2.3 nm gold clusters into large ~20 nm gold clusters in a few days at room temperature under normal atmospheric conditions. However, treating the titania support powder to a mock-deposition-precipitation process, at pH 4 or pH 10, followed by the subsequent deposition of gold onto this treated powder produced a remarkable enhancement in gold particle stability and a 20-40 fold enhancement of catalytic activity respectively. This enhancement can not be attributed to the formation of oxygen vacancies on the TiO2 surface. Instead, it appears to be associated with the formation of strongly bound hydroxyl species on the TiO2 surface. The formation of surface hydroxyls during the deposition-precipitation method is coincidental and contributes significantly to the properties of Au/TiO2 catalysts.

  14. Observational Effects of Magnetism in O Stars: Surface Nitrogen Abundances

    NASA Technical Reports Server (NTRS)

    Martins, F.; Escolano, C.; Wade, G. A.; Donati, J. F.; Bouret, J. C.

    2011-01-01

    Aims. We investigate the surface nitrogen content of the six magnetic O stars known to date as well as of the early B-type star Tau Sco.. We compare these abundances to predictions of evolutionary models to isolate the effects of magnetic field on the transport of elements in stellar interiors. Methods. We conduct a quantitative spectroscopic analysis of the ample stars with state-of-the-art atmosphere models. We rely on high signal-to-noise ratio, high resolution optical spectra obtained with ESPADONS at CFHT and NARVAL at TBL. Atmosphere models and synthetic spectra are computed with the code CMFGEN. Values of N/H together with their uncertainties are determined and compared to predictions of evolutionary models. Results. We find that the magnetic stars can be divided into two groups: one with stars displaying no N enrichment (one object); and one with stars most likely showing extra N enrichment (5 objects). For one star (Ori C) no robust conclusion can be drawn due to its young age. The star with no N enrichment is the one with the weakest magnetic field, possibly of dynamo origin. It might be a star having experienced strong magnetic braking under the condition of solid body rotation, but its rotational velocity is still relatively large. The five stars with high N content were probably slow rotators on the zero age main sequence, but they have surface N/H typical of normal O stars, indicating that the presence of a (probably fossil) magnetic field leads to extra enrichment. These stars may have a strong differential rotation inducing shear mixing. Our results shOuld be viewed as a basis on which new theoretical simulations can rely to better understand the effect of magnetism on the evolution of massive stars.

  15. Ewald methods for polarizable surfaces with application to hydroxylation and hydrogen bonding on the (012) and (001) surfaces of α-Fe 2O 3

    NASA Astrophysics Data System (ADS)

    Wasserman, E.; Rustad, J. R.; Felmy, A. R.; Hay, B. P.; Halley, J. W.

    1997-08-01

    We present a clear and rigorous derivation of the Ewald-like method for calculation of the electrostatic energy of the systems infinitely periodic in two dimensions and of finite size in the third dimension (slabs). We have generalized this method originally developed by Rhee et al. (Phys. Rev. B 40 (1989) 36) to account for charge-dipole and dipole-dipole interactions and therefore made it suitable for treatment of polarizable systems. This method has the advantage over exact methods of being significantly faster and therefore appropriate for large-scale molecular dynamics simulations. However, it involves a Taylor expansion which has to be demonstrated to be of sufficient order. The method was extensively benchmarked against the exact methods by Leckner and Parry. We found it necessary to increase the order of the multipole expansion from 4 (as in the original work by Rhee et al.) to 6. In this case the method is adequate for aspect ratios (thickness/shortest side length of the unit cell) ≤ 0.5. Molecular dynamics simulations using the transferable/polarizable model by Rustad et al. were applied to study the surface relaxation of the nonhydroxylated, hydroxylated and solvated surfaces of α-Fe 2O 3 (hematite). We find that our nonhydroxylated structures and energies are in good agreement with previous LDA calculations on α-alumina by Manassidis et al. (Surf. Sci. 285 (1993) L517). Using the results of molecular dynamics simulations of solvated interfaces, we define end-member hydroxylated-hydrated states for the surfaces which are used in energy minimization calculations. We find that hydration has a small effect on the surface structure, but that hydroxylation has a significant effect. Our calculations, both for gas-phase and solution-phase adsorption, predict a greater amount of hydroxylation for the α-Fe 2O 3 (012) surface than for the (001) surface. Our simulations also indicate the presence of four-fold coordinated iron ions on the (001) surface.

  16. Analysis of rat plasma proteins desorbed from gold and methyl- and hydroxyl-terminated alkane thiols on gold surfaces.

    PubMed

    Källtorp, M; Carlén, A; Thomsen, P; Olsson, J; Tengvall, P

    2000-03-01

    It is believed that adsorbed blood or plasma components, such as water, peptides, carbohydrates and proteins, determine key events in the concomitant inflammatory tissue response close to implants. The aim of the present study was to develop a procedure for the collection and analysis of minor amounts of proteins bound to solid metal implant surfaces. The combination of a sodium dodecyl sulfate washing method coupled with a polyacylamide gel electrophoretic protein separation technique (SDS-PAGE), Western blot and image analysis enabled the desorption, identification and semiquantification of specific proteins. The analyzed proteins were albumin, immunoglobulin G, fibrinogen and fibronectin. Concentration procedures of proteins were not required with this method despite the small area of the test surfaces. The plasma proteins were adsorbed to pure gold and hydroxylated and methylated gold surfaces, which elicit different tissue responses in vivo and plasma protein adsorption patterns in vitro. The image analysis revealed that the pure gold surfaces adsorbed the largest amount of total and specific proteins. This is in accordance with previous ellipsometry/antibody experiments in vitro. Further, the principles described for the protein analysis can be applied on implant surfaces ex vivo. PMID:15348048

  17. The hydroxylated and reduced rutile TiO2(011)-2 × 1 surfaces: A first-principles study

    NASA Astrophysics Data System (ADS)

    Yuan, Feng; Zhang, Haifeng; Lu, Shixiang; Xu, Wenguo

    2014-10-01

    The hydroxylated and reduced rutile TiO2(011)-2 × 1 surfaces have been investigated by means of first-principles density functional theory calculations. For the H adsorption and O vacancy on the rutile TiO2(011)-2 × 1 surface, we investigated three different surface O sites. Based on the adsorption and formation energy calculations, we find that the top O is an energetically preferential site for the adsorption of H atom or the formation of O vacancy. The calculated electronic structures indicate that the energetically preferential O site cannot create a band gap state; only the O vacancy at the side O site gives rise to a Ti-3d like defect level at the edge of the conduction band. It is worth mentioning that all considered configurations of the H adsorption and O vacancy on the rutile TiO2(011)-2 × 1 surface obviously enhance the optical absorptions in the areas of infrared, not just the rutile TiO2(011)-2 × 1 surface only has a good absorption edge in the visible light region.

  18. Effect of surface hydroxyls on dimethyl ether synthesis over the γ-Al₂O₃ in liquid paraffin: a computational study.

    PubMed

    Zuo, Zhi-Jun; Wang, Le; Han, Pei-de; Huang, Wei

    2013-11-01

    In a recent paper (Zuo et al., Appl Catal A 408:130-136, 2011), the mechanism of dimethyl ether (DME) synthesis from methanol dehydration over γ-Al2O3 (110) was studied using density functional theory (DFT). Using the same method, the effect of surface hydroxyls on γ-Al2O3 in liquid paraffin during DME synthesis from methanol dehydration is investigated. It is found that DME is mainly formed from two adsorbed CH3O groups via methanol dehydrogenation on both dehydrated and hydrated γ-Al2O3 in liquid paraffin. No close correlation between catalytic activity and acid intensity was found. Before and after water adsorption at typical catalytic conditions (e.g., 553 K), the reaction rate is not obviously changed on γ-Al2O3(100) surface in liquid paraffin, but the reaction rate decreases by about 11 times on the (110) in liquid paraffin. Considering the area of the (110) and (100) surfaces under actual conditions, the catalytic activity decreased mainly because the Al3 sites on the (110) surface gradually become inactive. Catalytic activity decreased mainly due to surface hydrophilicity. The calculated results were consistent with the experiment. PMID:24057976

  19. Boron-doped bismuth oxybromide microspheres with enhanced surface hydroxyl groups: Synthesis, characterization and dramatic photocatalytic activity.

    PubMed

    Liu, ZhangSheng; Liu, JinLong; Wang, HaiYang; Cao, Gang; Niu, JiNan

    2016-02-01

    B-doped BiOBr photocatalysts were successfully synthesized via a facile solvothermal method with boric acid used as boron source. As-obtained products consist of novel hierarchical microspheres, whose nanosheet building units were formed by nanoparticles splicing. They showed dramatic photocatalytic efficiency toward the degradation of Rhodamine B (RhB) and phenol under the visible-light irradiation and the highest activity was achieved by 0.075B-BiOBr. The enhanced photocatalytic activity could be attributed to the enriched surface hydroxyl groups on B-doped BiOBr samples, which not only improved the adsorption of pollutant on the photocatalyst but also promoted the separation of photogenerated electron-hole pairs. In addition, it was found that the main reactive species responsible for the degradation of organic pollutant were h(+) and O2(-) radicals, instead of OH radicals. PMID:26590875

  20. Quantitative abundance estimates from bidirectional reflectance measurements. [for planetary surfaces

    NASA Technical Reports Server (NTRS)

    Mustard, John F.; Pieters, Carle M.

    1987-01-01

    A simplified approach for estimating mineral abundances in mineral mixtures from bidirectional reflectance measurements is presented. Fundamental to this approach is a priori information concerning reflectance spectra of the individual minerals and an estimate of the particle sizes of the components. Simplified equations for bidirectional reflectance are used to linearize the systematics of spectral mixing. The method was used to determine the relative proportions of olivine, magnetite, enstatite, and anorthite in a mixture; the mass fractions of mixture components were calculated on the basis of known particle diameters. The results indicate that for materials without strongly adsorbing components, the accuracy of abundance determinations is better than 5 percent.

  1. DFT study of interactions between calcium hydroxyl ions and pyrite, marcasite, pyrrhotite surfaces

    NASA Astrophysics Data System (ADS)

    Zhao, Cuihua; Chen, Jianhua; Li, Yuqiong; Huang, De wei; Li, Weizhou

    2015-11-01

    The interaction between CaOH+ ions and pyrite, marcasite and pyrrhotite surfaces was studied using density functional theory (DFT) calculations. The calculated results show that the adsorption energy of CaOH+ on the marcasite surface is the largest, -384.65 kJ/mol; then pyrrhotite, -346.61 kJ/mol; pyrite, -276.62 kJ/mol. After CaOH+ adsorption, oxygen atom is bonded to one iron atom, calcium atom is bonded to two sulfur atoms of pyrite surface. And there exists a Casbnd Fe2 anti-bonding on the pyrite surface. For marcasite, oxygen atom is bonded to one iron atom, calcium atom is bonded to two sulfur atoms of marcasite surface. As for pyrrhotite, calcium atom is only attached to three sulfur atoms of pyrrhotite surface. The charge transfers occur from CaOH+ to sulfides surfaces. The value of charge transfer from CaOH+ to marcasite surface is the largest, then pyrite, pyrrhotite in order. However, formation of Casbnd Fe2 anti-bonding on the pyrite surface weakens the reaction of CaOH+ with pyrite.

  2. Density functional theory based-study of 5-fluorouracil adsorption on β-cristobalite (1 1 1) hydroxylated surface: The importance of H-bonding interactions

    NASA Astrophysics Data System (ADS)

    Simonetti, S.; Compañy, A. Díaz; Pronsato, E.; Juan, A.; Brizuela, G.; Lam, A.

    2015-12-01

    Silica-based mesoporous materials have been recently proposed as an efficient support for the controlled release of a popular anticancer drug, 5-fluorouracil (5-FU). Although the relevance of this topic, the atomistic details about the specific surface-drug interactions and the energy of adsorption are almost unknown. In this work, theoretical calculations using the Vienna Ab-initio Simulation Package (VASP) applying Grimme's-D2 correction were performed to elucidate the drug-silica interactions and the host properties that control 5-FU drug adsorption on β-cristobalite (1 1 1) hydroxylated surface. This study shows that hydrogen bonding, electron exchange, and dispersion forces are mainly involved to perform the 5-FU adsorption onto silica. This phenomenon, revealed by favorable energies, results in optimum four adsorption geometries that can be adopted for 5-FU on the hydroxylated silica surface. Silanols are weakening in response to the molecule approach and establish H-bonds with polar groups of 5-FU drug. The final geometry of 5-FU adopted on hydroxylated silica surface is the results of H-bonding interactions which stabilize and fix the molecule to the surface and dispersion forces which approach it toward silica (1 1 1) plane. The level of hydroxylation of the SiO2 (1 1 1) surface is reflected by the elevated number of hydrogen bonds that play a significant role in the adsorption mechanisms.

  3. The role of hydroxylation in the step stability and in the interaction between steps: a first-principles study of vicinal MgO surfaces.

    PubMed

    Finocchi, Fabio; Geysermans, Pascale; Bourgeois, Antonin

    2012-10-21

    Atomic structure and thermodynamic stability of vicinal MgO surfaces showing monoatomic steps are studied using density functional theory. We extend the general definition of step energy to the case of ledges that are covered by adsorbates. Using this definition, we consider the effect of hydroxylation on the thermodynamic stability of steps, either polar or non-polar, on (001) or (011) terraces. Clean non-polar steps along [100] on MgO(001) are the most stable ones. Upon water adsorption, the free energy of all hydroxylated ledges, almost independently of their orientation, is significantly reduced and approaches thermal energies for increasing water pressure, favoring the formation of hydroxylated steps on MgO surfaces. Furthermore, we show that interaction between polar steps can be either repulsive or attractive. This quite unusual behavior is described in terms of electrostatic interactions between ledges. PMID:22968346

  4. Non-contact atomic force microscopy study of hydroxyl groups on the spinel MgAl2O4(100) surface.

    PubMed

    Federici Canova, F; Foster, A S; Rasmussen, M K; Meinander, K; Besenbacher, F; Lauritsen, J V

    2012-08-17

    Atom-resolved non-contact atomic force microscopy (NC-AFM) studies of the magnesium aluminate (MgAl(2)O(4)) surface have revealed that, contrary to expectations, the (100) surface is terminated by an aluminum and oxygen layer. Theoretical studies have suggested that hydrogen plays a strong role in stabilizing this surface through the formation of surface hydroxyl groups, but the previous studies did not discuss in depth the possible H configurations, the diffusion behaviour of hydrogen atoms and how the signature of adsorbed H is reflected in atom-resolved NC-AFM images. In this work, we combine first principles calculations with simulated and experimental NC-AFM images to investigate the role of hydrogen on the MgAl(2)O(4)(100) surface. By means of surface energy calculations based on density functional theory, we show that the presence of hydrogen adsorbed on the surface as hydroxyl groups is strongly predicted by surface stability considerations at all relevant partial pressures of H(2) and O(2). We then address the question of how such adsorbed hydrogen atoms are reflected in simulated NC-AFM images for the most stable surface hydroxyl groups, and compare with experimental atom-resolved NC-AFM data. In the appendices we provide details of the methods used to simulate NC-AFM using first principles methods and a virtual AFM. PMID:22827936

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

    PubMed Central

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

    2009-01-01

    Previously, we have developed and characterised a procedure for the deposition of thin silica films by a plasma enhanced chemical vapour deposition (PECVD) procedure using tetraethoxysilane (TEOS) as the main precursor. We have used the silica coatings for improving the corrosion resistance of metals and for enhancing the bioactivity of biomedical metallic implants. Recently, we have been fine-tuning the PECVD method for producing high quality and reproducible PECVD-silica (PECVD-Si) coatings on metals, primarily for biomaterial applications. In order to understand the interaction of the PECVD-Si coatings with biological species (such as proteins and cells), it is important to first analyse the properties of the silica films deposited using the optimised parameters. Therefore, this current investigation was carried out to analyse the characteristic features of PECVD-Si deposited on Ti substrates (PECVD-Si-Ti). We determined that the PECVD-Si coatings on Ti were conformal to the substrate surface, strongly adhered to the underlying substrate and were resistant to delamination. The PECVD-Si surface was composed of stoichiometric SiO2, showed a low carbon content (below 10 at.%) and was very hydrophilic (contact angle <10°). Finally, we also showed that the PECVD-Si coatings contain functional hydroxyl groups. PMID:19809536

  6. Enhanced visible-light photocatalytic activity of active Al₂O₃/g-C₃N₄ heterojunctions synthesized via surface hydroxyl modification.

    PubMed

    Li, Fa-Tang; Zhao, Ye; Wang, Qing; Wang, Xiao-Jing; Hao, Ying-Juan; Liu, Rui-Hong; Zhao, Dishun

    2015-01-01

    Novel Al2O3/g-C3N4 heterojunction photocatalysts were fabricated through ultrasonic dispersion method. Al2O3, obtained via solution combustion, contained amorphous ingredient with lots of defect sites and was used as active component for transferring photo-induced electrons of g-C3N4. G-C3N4 was grafted surface hydroxyl groups in the presence of ammonia aqueous solution to combine with Al2O3 possessing positive charges via hydrogen bond. The XRD, SEM, element map, TEM, HRTEM, FT-IR, and XPS results indicate that these synthesized materials are two-phase hybrids of Al2O3 and g-C3N4 with interaction. The photocatalytic results for the degradation of rhodamine B (RhB) indicate that the most active heterojunction proportion is 60wt.% g-C3N4:40wt.% Al2O3, the visible light photocatalytic activity of which is 3.8 times that of a mechanical mixture. The enhanced performance is attributed to the high separation efficiency of photo-induced electrons from the LUMO of g-C3N4 injected into the defect sites of Al2O3, which is verified by photoluminescence spectroscopy (PL) and surface photovoltage (SPV) measurements. The electron paramagnetic resonance (EPR) signals and radical scavengers trapping experiments reveal holes (h(+)) and superoxide anion radical (O2(-)) are the main active species responsible for the degradation of RhB. PMID:25306536

  7. Heterogeneity of hydroxyl and deuteroxyl groups on the surface of TiO{sub 2} polymorphs

    SciTech Connect

    Contescu, C.; Popa, V.T.; Schwarz, J.A.

    1996-06-01

    Potentiometric titration data from pure rutile, anatase, and a commercial fumed titania (Degussa P25) were analyzed in terms of proton binding isotherms from which proton affinity distributions (PADs) of surface sites were obtained. As-received samples, whose thermal and storage history were not systematically controlled, as well as samples subjected to controlled calcination-rehydration-drying treatments were studied. The results indicated the occurrence of a limited number of surface groups on the two polymorphs. The behavior of pure rutile and anatase could be admixed to simulate the acid-base behavior of the commercial sample; on this basis the surface of fumed titania consists largely of anatase-like structures with a small contribution (7%) of rutile-like groups. The region of {nu}{sub OD} stretching vibrations of isolated -OD groups on extensively dehydroxylated samples was found to correlate with the pK`s determined from PADs. A qualitative assignment of measured pK values based on either the original MUSIC model (Hiemstra, T., de Wit, J.C.M., and Van Riemsdijk, W.H., J. Colloid Interface Sci. 133, 105 (1989)) or a refined version of it is presented.

  8. The High Plains Groundwater Availability Study: Abundant Groundwater Doesn't Necessarily Mean Abundant Surface Water

    NASA Astrophysics Data System (ADS)

    Peterson, S. M.; Stanton, J. S.; Flynn, A. T.

    2013-12-01

    The U.S. Geological Survey's Groundwater Resources Program is conducting an assessment of groundwater availability to gain a clearer understanding of the status of the Nation's groundwater resources and the natural and human factors that can affect those resources. Additional goals are to better estimate availability and suitability of those resources in the future for various uses. The High Plains aquifer is a nationally important water resource that underlies about 174,000 square miles in parts of eight western states. The aquifer serves as a primary source of drinking water for approximately 2.3 million people and also sustains more than one quarter of the Nation's agricultural production. In 2000, total water withdrawals of 17.5 billion gallons per day from the aquifer accounted for 20 percent of all groundwater withdrawn in the United States, making it the most intensively pumped aquifer in the Nation. In the Central and Southern High Plains, the aquifer historically had less saturated thickness, and current resource management issues are focused on the availability of water, and reduced ability to irrigate as water levels and well productivity have declined. In contrast, the Northern High Plains aquifer includes the thickest part of the aquifer and a larger saturated thickness than the other parts of the aquifer, and current water resource management issues are related to the interaction of groundwater with surface water and resource management triggered primarily by the availability of surface water. The presentation will cover major components of the High Plains Groundwater Availability Study, including estimating water budget components for the entire High Plains aquifer, building a refined groundwater model for the Northern High Plains aquifer, and using that model to better understand surface- and groundwater interaction and characterize water availability.

  9. Chitin based polyurethanes using hydroxyl terminated polybutadiene, part III: surface characteristics.

    PubMed

    Zia, Khalid Mahmood; Zuber, Mohammad; Saif, Muhammad Jawwad; Jawaid, Mohammad; Mahmood, Kashif; Shahid, Muhammad; Anjum, Muhammad Naveed; Ahmad, Mirza Nadeem

    2013-11-01

    Hydroxy terminated polybutadiene (HTPB)-chitin based polyurethanes (PUs) with controlled hydrophobicity were synthesized using HTPB and toluene diisocyanate (TDI). The prepolymer was extended with different mass ratios of chitin and 1,4-butane diol (BDO). The effect of chitin contents in chain extender (CE) proportions on surface properties was studied and investigated. Incorporation of chitin contents into the final PU showed decrease in contact angle value of water drop, water absorption (%) and swelling behavior. The antibacterial activity of the prepared samples was affected by varying the chitin contents in the chemical composition of the final PU. The results demonstrated that the use of prepared material can be suggested as non-absorbable suture. PMID:24120963

  10. Gold Nanoparticles Supported on Carbon Nitride: Influence of Surface Hydroxyls on Low Temperature Carbon Monoxide Oxidation

    SciTech Connect

    Singh, Joseph A; Dudney, Nancy J; Li, Meijun; Overbury, Steven {Steve} H; Veith, Gabriel M

    2012-01-01

    This paper reports the synthesis of 2.5 nm gold clusters on the oxygen free and chemically labile support carbon nitride (C3N4). Despite having small particle sizes and high enough water partial pressure these Au/C3N4 catalysts are inactive for the gas phase and liquid phase oxidation of carbon monoxide. The reason for the lack of activity is attributed to the lack of surface OH groups on the C3N4. These OH groups are argued to be responsible for the activation of CO in the oxidation of CO. The importance of basic OH groups explains the well document dependence of support isoelectric point versus catalytic activity.

  11. Evaluation of a relationship between polymer bulk hydroxyl and surface oxygen content and in vitro serum - material interaction

    SciTech Connect

    Sawada, Koji; Shimoyama, Takashi ); Malchesky, P.S.; Goldcamp, J.B.; Omokawa, Susumu )

    1993-04-01

    To evaluate serum-material interaction for six types of minimodule and to assess the relationship between the interaction and chemical composition, notably bulk polymer hydroxyl ([minus]OH) percent of polymer, or surface oxygen (SO) percent, polymeric membranes with varying [minus]OH and SO percents were evaluated with normal human serum. The membrane materials ([minus]OH percent and SO percent) evaluated included polypropylene (PP; 0% and 1.9%), polyvinyl alcohol (PVA; 23.7% and 27.3%), ethylene vinyl alcohol (EVAL 4A and D; 30.4% and 25.3%), Cuprophan (CP; 31.5% and 37.4%), and Hemophan (HP; 30.9% and 23.6%), respectively. Data from serum perfusions expressed as percent changes to sham perfusion showed that solute percent decreases were less than 10% in all materials except PVA (10-22%). PVA and CP had higher C3a, C4a, and C5a, and C3a concentration increases, and had larger suppressive effects for all three mitogen-induced mononuclear cell transformation functions (MNCTF) and concanavalin A-induced MNCTF, respectively. PVA had higher SO percent than EVAL and CP was higher than HP, despite PVA and CP having lower or comparable bulk [minus]OH percent to EVAL or HP.

  12. Band profile of hydroxyl groups in the infrared spectrum of hydrogen-bonded surface complexes: Ammonia on silicon dioxide

    SciTech Connect

    Pavlov, A.Y.; Tsyganenko, A.A.

    1994-07-01

    Dependences of the band maximum and band half-width of the stretching modes of surface OH and OD groups perturbed by ammonia adsorption on Aerosil were studied as functions of sample temperature, amount of adsorbed ammonia, and thermal treatment in vacuum. The appearance of a low-frequency wing was explained by the formation of polymer chains of OH groups coupled via adsorbed molecules. The latter tend to form a second bond with an oxygen atom of the neighboring OH group in addition to a hydrogen bond with a hydroxyl proton via nitrogen. The wide band at 3250 cm{sup -1} was assigned to NH groups of adsorbed molecules perturbed by H-bonding with oxygen. This band is observed as a shoulder of the coupled-OH group band. The large width of the latter as well as its temperature behavior was explained by differences in the arrangement of OH groups and by anharmonic coupling with the low-frequency vibrational modes of the complex. 14 refs., 4 figs., 4 tabs.

  13. Dependence of Mercurian Atmospheric Column Abundance Estimations on Surface-Reflectance Modeling

    NASA Technical Reports Server (NTRS)

    Domingue, Deborah L.; Sprague, Ann L.; Hunten, Donald M.

    1997-01-01

    Column abundance estimates of sodium, and analogously, potassium, in Mercury's exosphere are strongly correlated to the surface reflection model used to calibrate the spectral data and the surface reflection model incorporated into the atmospheric radiative transfer solution. Depending on the surface reflection model parameters used, there can be differences in calibration factors of up to +/- 30% and differences in estimated column abundance of up to +/- 35%. Although the surface reflectance may not be used in the calibration of spacecraft measurements, the interaction between the reflected surface light and the atmospheric brightness remains important.

  14. Passivation of the La2NiMnO6 double perovskite to hydroxylation by excess nickel, and the fate of the hydroxylated surface upon heating

    NASA Astrophysics Data System (ADS)

    Fulmer, Adam T.; Dondlinger, Jasmine; Langell, Marjorie A.

    2014-06-01

    The double perovskites with a total elemental content of LaNi0.5Mn0.5O3 and LaNi0.75Mn0.25O3 were synthesized by solid state methods, although the LaNi0.75Mn0.25O3 material underwent phase separation into NiO, LaNiO3 and LaNi0.5Mn0.5O3. Auger Electron Spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) indicated substantial lanthanum surface segregation for the LaNi0.5Mn0.5O3 material, which formed an altered La(OH)3 layer 50-100 monolayers in thickness. The La(OH)3 could be removed by Ar+ sputtering to achieve a surface of approximately stoichiometric concentration. Heating the La(OH)3-covered LaNi0.5Mn0.5O3 did not regenerate the double perovskite but rather produced an overlayer of La2O3. While the LaNi0.75Mn0.25O3 material displayed extensive phase separation, the excess nickel appeared to prevent substantial lanthanum surface segregation.

  15. Layer by layer H-bonded assembly of P4VP with various hydroxylated PPFS: impact of the donor strength on growth mechanism and surface features.

    PubMed

    Chen, Jing; Duchet, Jannick; Portinha, Daniel; Charlot, Aurélia

    2014-09-01

    Hydrogen bond mediated films made by step by step deposition of poly(4-vinylpyridine) (P4VP) and hydroxylated poly(2,3,4,5,6-pentafluorostyrene) (PPFS) copolymers prepared by thiol para-fluoro coupling, bearing either one (PPFSME) or two (PPFSMPD) hydrogenated hydroxyl groups or a (poly)fluorinated hydroxyl (PPFSOH), respectively, were successfully constructed. The influence of the structural parameters, such as the hydroxyl environment (which dictates the H-bond strength) was in-depth investigated in terms of their impact on (i) growth mechanism, (ii) internal organization, and (iii) surface features. The use of the weaker H-bond donor partner (PPFSME) leads to low quality films composed of irregularly distributed aggregates. While [PPFSMPD/P4VP] multilayer films are comparatively thick and composed of stratified layers with smooth topology, the use of PPFSOH with P4VP yields thin films made of mixed and interpenetrated polymer layers. Playing on the interaction strength appears as a powerful tool to elaborate tailored multilayer films with molecularly tunable properties. PMID:25081421

  16. The abundance properties of nearby late-type galaxies. II. The relation between abundance distributions and surface brightness profiles

    SciTech Connect

    Pilyugin, L. S.; Grebel, E. K.; Zinchenko, I. A.; Kniazev, A. Y. E-mail: grebel@ari.uni-heidelberg.de E-mail: akniazev@saao.ac.za

    2014-12-01

    The relations between oxygen abundance and disk surface brightness (OH–SB relation) in the infrared W1 band are examined for nearby late-type galaxies. The oxygen abundances were presented in Paper I. The photometric characteristics of the disks are inferred here using photometric maps from the literature through bulge-disk decomposition. We find evidence that the OH–SB relation is not unique but depends on the galactocentric distance r (taken as a fraction of the optical radius R{sub 25}) and on the properties of a galaxy: the disk scale length h and the morphological T-type. We suggest a general, four-dimensional OH–SB relation with the values r, h, and T as parameters. The parametric OH–SB relation reproduces the observed data better than a simple, one-parameter relation; the deviations resulting when using our parametric relation are smaller by a factor of ∼1.4 than that of the simple relation. The influence of the parameters on the OH–SB relation varies with galactocentric distance. The influence of the T-type on the OH–SB relation is negligible at the centers of galaxies and increases with galactocentric distance. In contrast, the influence of the disk scale length on the OH–SB relation is at a maximum at the centers of galaxies and decreases with galactocentric distance, disappearing at the optical edges of galaxies. Two-dimensional relations can be used to reproduce the observed data at the optical edges of the disks and at the centers of the disks. The disk scale length should be used as a second parameter in the OH–SB relation at the center of the disk while the morphological T-type should be used as a second parameter in the relation at optical edge of the disk. The relations between oxygen abundance and disk surface brightness in the optical B and infrared K bands at the center of the disk and at optical edge of the disk are also considered. The general properties of the abundance–surface brightness relations are similar for the

  17. Trifluoroethanol and 19F magic angle spinning nuclear magnetic resonance as a basic surface hydroxyl reactivity probe for zirconium(IV) hydroxide structures.

    PubMed

    DeCoste, Jared B; Glover, T Grant; Mogilevsky, Gregory; Peterson, Gregory W; Wagner, George W

    2011-08-01

    A novel technique for determining the relative accessibility and reactivity of basic surface hydroxyl sites by reacting various zirconium(IV) hydroxide materials with 2,2,2-trifluoroethanol (TFE) and characterizing the resulting material using (19)F magic angle spinning (MAS) nuclear magnetic resonance (NMR) is presented here. Studied here are three zirconium hydroxide samples, two unperturbed commercial materials, and one commercial material that is crushed by a pellet press. Factors, such as the ratio of bridging/terminal hydroxyls, surface area, and pore size distribution, are examined and found to affect the ability of the zirconium(IV) hydroxide to react with TFE. X-ray diffraction, nitrogen isotherms, and (1)H MAS NMR were used to characterize the unperturbed materials, while thermogravitric analysis with gas chromatography and mass spectrometry along with the (19)F MAS NMR were used to characterize the materials that were reacted with TFE. Zirconium hydroxide materials with a high surface area and a low bridging/terminal hydroxyl ratio were found to react TFE in the greatest amounts. PMID:21699226

  18. Soil Type-Dependent Responses to Phenanthrene as Revealed by Determining the Diversity and Abundance of Polycyclic Aromatic Hydrocarbon Ring-Hydroxylating Dioxygenase Genes by Using a Novel PCR Detection System▿ †

    PubMed Central

    Ding, Guo-Chun; Heuer, Holger; Zühlke, Sebastian; Spiteller, Michael; Pronk, Geertje Johanna; Heister, Katja; Kögel-Knabner, Ingrid; Smalla, Kornelia

    2010-01-01

    A novel PCR primer system that targets a wide range of polycyclic aromatic hydrocarbon ring-hydroxylating dioxygenase (PAH-RHDα) genes of both Gram-positive and Gram-negative bacteria was developed and used to study their abundance and diversity in two different soils in response to phenanthrene spiking. The specificities and target ranges of the primers predicted in silico were confirmed experimentally by cloning and sequencing of PAH-RHDα gene amplicons from soil DNA. Cloning and sequencing showed the dominance of phnAc genes in the contaminated Luvisol. In contrast, high diversity of PAH-RHDα genes of Gram-positive and Gram-negative bacteria was observed in the phenanthrene-spiked Cambisol. Quantitative real-time PCR based on the same primers revealed that 63 days after phenanthrene spiking, PAH-RHDα genes were 1 order of magnitude more abundant in the Luvisol than in the Cambisol, while they were not detected in both control soils. In conclusion, sequence analysis of the amplicons obtained confirmed the specificity of the novel primer system and revealed a soil type-dependent response of PAH-RHDα gene-carrying soil bacteria to phenanthrene spiking. PMID:20495045

  19. Abundance distributions over the surfaces of magnetic ApBp stars: theoretical predictions

    NASA Astrophysics Data System (ADS)

    Alecian, G.

    2015-12-01

    Recently published empirical abundance maps, obtained through (Zeeman) Doppler mapping, do not currently agree with the abundance structures predicted by means of numerical models of atomic diffusion in magnetic atmospheres of ApBp stars. In a first step towards the resolution of these discrepancies, we present a state of the art grid of equilibrium abundance stratifications in the atmosphere of a magnetic Ap star with Teff = 10 000 K and log g = 4.0. A description of the behaviour of 16 chemical elements including predictions concerning the over- and/or underabundances over the stellar surface is followed by a discussion of the possible influence of presently neglected physical processes.

  20. Correlation of the Abundance of Betaproteobacteria on Mineral Surfaces with Mineral Weathering in Forest Soils

    PubMed Central

    Lepleux, C.; Turpault, M. P.; Oger, P.; Frey-Klett, P.

    2012-01-01

    Pyrosequencing-based analysis of 16S rRNA gene sequences revealed a significant correlation between apatite dissolution and the abundance of betaproteobacteria on apatite surfaces, suggesting a role for the bacteria belonging to this phylum in mineral weathering. Notably, the cultivation-dependent approach demonstrated that the most efficient mineral-weathering bacteria belonged to the betaproteobacterial genus Burhkolderia. PMID:22798365

  1. Synthesis of MOF having hydroxyl functional side groups and optimization of activation process for the maximization of its BET surface area

    SciTech Connect

    Kim, Jongsik; Kim, Dong Ok; Kim, Dong Wook; Sagong, Kil

    2013-01-15

    To accomplish the postsynthetic modification of MOF with organic-metal precursors (OMPs) described in our previous researches more efficiently, synthesis of MOF (HCC-2) possessing relatively larger pore size as well as higher number of hydroxyl functional side groups per its base unit than those of HCC-1 has been successfully conducted via adopting 1,4-di-(4-carboxy-2,6-dihydroxyphenyl)benzene as an organic ligand and Zn(NO{sub 3}){sub 2}{center_dot}6H{sub 2}O as a metal source, respectively. Also, optimization about the Activation process of HCC-2 was performed to maximize its BET (Brunauer-Emmett-Teller) surface area which was proved to be proportional to the number of exposed active sites on which its postsynthetic modification occurred. However, Activation process having been validated to be so effective with the acquirement of highly-purified HCC-1 (CO{sub 2} supercritical drying step followed by vacuum drying step) was less satisfactory with the case of HCC-2. This might be attributed to relatively higher hydrophilicity and bulkier molecular structure of organic ligand of HCC-2. However, it was readily settled by simple modification of above Activation process. Moreover, indispensable residues composed of both DMF and its thermally degraded derivatives which were chemically attached via coordination bond with hydroxyl functionalities even after Activation process III might enable their H{sub 2} adsorption properties to be seriously debased compared to that of IRMOF-16 having no hydroxyl functionalities. - Graphical abstract: Synthesis of new-structured MOF (HCC-2) simultaneously possessing relatively larger pore size as well as higher number of hydroxyl functional side groups per its base unit at the same time than those of HCC-1 has been performed via adopting 1,4-di-(4-carboxy-2,6-dihydroxyphenyl)benzene as an organic ligand and Zn(NO{sub 3}){sub 2}{center_dot}6H{sub 2}O as a metal source, respectively. Also, the optimization of activation process for HCC-2

  2. Photo and Chemical Reduction of Copper onto Anatase-Type TiO2 Nanoparticles with Enhanced Surface Hydroxyl Groups as Efficient Visible Light Photocatalysts.

    PubMed

    Eskandarloo, Hamed; Badiei, Alireza; Behnajady, Mohammad A; Mohammadi Ziarani, Ghodsi

    2015-01-01

    In this study, the photocatalytic efficiency of anatase-type TiO2 nanoparticles synthesized using the sol-gel low-temperature method, were enhanced by a combined process of copper reduction and surface hydroxyl groups enhancement. UV-light-assisted photo and NaBH4 -assisted chemical reduction methods were used for deposition of copper onto TiO2. The surface hydroxyl groups of TiO2 were enhanced with the assistance of NaOH modification. The prepared catalysts were immobilized on glass plates and used as the fixed-bed systems for the removal of phenazopyridine as a model drug contaminant under visible light irradiation. NaOH-modified Cu/TiO2 nanoparticles demonstrated higher photocatalytic efficiency than that of pure TiO2 due to the extending of the charge carriers lifetime and enhancement of the adsorption capacity of TiO2 toward phenazopyridine. The relationship of structure and performance of prepared nanoparticles has been established by using various techniques, such as XRD, XPS, TEM, EDX, XRF, TGA, DRS and PL. The effects of preparation variables, including copper content, reducing agents rate (NaBH4 concentration and UV light intensity) and NaOH concentration were investigated on the photocatalytic efficiency of NaOH-modified Cu/TiO2 nanoparticles. PMID:25809844

  3. Hydroxyl Fatty Acids and Hydroxyl Oils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soybean oil is produced domestically in large supply, averaging over 20 billion pounds per year with an annual carryover of more than one billion pounds. It is important to find new uses for this surplus soybean oil. Hydroxyl fatty acids and hydroxyl oils are platform materials for specialty chemi...

  4. Surface characterization and catalytic evaluation of copper-promoted Al-MCM-41 toward hydroxylation of phenol.

    PubMed

    Parida, K M; Rath, Dharitri

    2009-12-15

    The Mobil Composition of Matter No. 41 (MCM-41) containing Cu and Al with Si/Al ratios varying from 100 to 10 and 1 to 6wt.% of Cu was synthesized under hydrothermal and impregnation conditions, respectively. The samples were characterized by nitrogen adsorption-desorption measurements, X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), temperature-programmed reduction (TPR), temperature-programmed desorption (TPD), and (29)Si and (27)Al magic-angle spinning-nuclear magnetic resonance (MAS-NMR) spectra. X-ray diffraction patterns indicate that the modified materials retain the standard MCM-41 structure. TPR patterns show the two-step reduction of Cu species. TPD study shows that Cu-impregnated Al-MCM-41 samples are more acidic than Al-MCM-41. From the MAS-NMR it was confirmed that most of the Al atoms are present tetrahedrally within the framework and some are present octahedrally in extraframework position. Impregnation of Cu shifted Al to the extraframework position. The catalytic activity of the samples toward hydroxylation of phenol in aqueous medium was evaluated using H(2)O(2) as the oxidant at 80 degrees C. The effects of reaction parameters such as temperature, catalyst amount, amount of H(2)O(2), and solvent were also investigated. Sample containing 4wt.% copper-loaded Al-MCM-41-100 showed high phenol conversion (78%) with 68% catechol and 32% hydroquinone selectivity. PMID:19782994

  5. Abundance and Distribution Characteristics of Microplastics in Surface Seawaters of the Incheon/Kyeonggi Coastal Region.

    PubMed

    Chae, Doo-Hyeon; Kim, In-Sung; Kim, Seung-Kyu; Song, Young Kyoung; Shim, Won Joon

    2015-10-01

    Microplastics in marine environments are of emerging concern due to their widespread distribution, their ingestion by various marine organisms, and their roles as a source and transfer vector of toxic chemicals. However, our understanding of their abundance and distribution characteristics in surface seawater (SSW) remains limited. We investigated microplastics in the surface microlayer (SML) and the SSW at 12 stations near-shore and offshore of the Korean west coast, Incheon/Kyeonggi region. Variation between stations, sampling media, and sampling methods were compared based on abundances, size distribution, and composition profiles of microsized synthetic polymer particles. The abundance of microplastics was greater in the SML (152,688 ± 92,384 particles/m(3)) than in SSW and showed a significant difference based on the sampling method for SSWs collected using a hand net (1602 ± 1274 particles/m(3)) and a zooplankton trawl net (0.19 ± 0.14 particles/m(3)). Ship paint particles (mostly alkyd resin polymer) accounted for the majority of microplastics detected in both SML and SSWs, and increased levels were observed around the voyage routes of large vessels. This indicates that polymers with marine-based origins become an important contributor to microplastics in coastal SSWs of this coastal region. PMID:26135299

  6. Mapping impervious surface type and sub-pixel abundance using hyperion hyperspectral imagery

    USGS Publications Warehouse

    Falcone, J.A.; Gomez, R.

    2005-01-01

    Impervious surfaces have been identified as an important and quantifiable indicator of environmental degradation in urban settings. A number of research efforts have been directed at mapping impervious surface type using multispectral imagery. To date, however, no studies have compared equivalent techniques using multispectral and hyperspectral imagery to that end. In this study, data from NASA's 220-channel Hyperion instrument were used to: a) delineate three types of impervious surface, and b) map sub-pixel percent abundance for a study site near Washington, D.C., USA. The results were compared with the results of similar methods using same-spatial-resolution Landsat ETM+ data for mapping impervious surface type, and with the results of the U.S. Geological Survey's National Land Cover Data (NLCD) 2001 impervious surface data layer, which is derived from Landsat and high-resolution Ikonos data. The accuracy of discriminating impervious surface type using Hyperion data was assessed at 88% versus Landsat at 59%. The sub-pixel percent impervious map corresponded well with the NLCD 2001; impervious surface in the study area was calculated at 29.3% for NLCD 2001 and 28.4% for the Hyperion-derived layer. The results suggest that fairly simple techniques using hyperspectral data are effective for quantifying impervious surface type, and that high-spectral- resolution imagery may be a good alternative to high-spatial-resolution data.

  7. Molecular mechanics of the cooperative adsorption of a Pro-Hyp-Gly tripeptide on a hydroxylated rutile TiO2(110) surface mediated by calcium ions.

    PubMed

    Zheng, Ting; Wu, Chunya; Chen, Mingjun; Zhang, Yu; Cummings, Peter T

    2016-07-20

    The interaction of amino acids with inorganic materials at interfaces plays an important role in enhancing the biocompatibility of titanium-based alloys. The adsorption of a tripeptide, i.e. Pro-Hyp-Gly, on the hydroxylated rutile TiO2(110) surface was investigated by the MD simulations. The changes in free energy during the adsorption of both the tripeptide and calcium ions were calculated by using the PMF method in order to obtain the adsorption strength. The results suggested that the adsorption of the tripeptide on the TiO2 surface through the carboxyl groups in glycine residues can be more stable compared with other binding conformations. Special attention was focused on the cooperative adsorption of the tripeptide with the assistance of calcium ions. Calcium ions preferred to absorb at the tetradentate or monodentate sites on the negatively charged TiO2 surface. As a result of the strong attraction between the carboxyl group and calcium ions, the tripeptide can be pulled down to the surface by following the trajectory of the calcium ions, forming an indirect interaction with a sandwich structure of peptide-cation-TiO2. However, this indirect interaction could eventually transform to the direct adsorption of the tripeptide on the TiO2 surface with higher binding energy. The results may help to interpret the adsorption of peptides on inorganic materials in aqueous solution with ions. PMID:27383367

  8. Quantum Tunneling in Testosterone 6β-Hydroxylation by Cytochrome P450: Reaction Dynamics Calculations Employing Multiconfiguration Molecular-Mechanical Potential Energy Surfaces

    NASA Astrophysics Data System (ADS)

    Zhang, Yan; Lin, Hai

    2009-05-01

    Testosterone hydroxylation is a prototypical reaction of human cytochrome P450 3A4, which metabolizes about 50% of oral drugs on the market. Reaction dynamics calculations were carried out for the testosterone 6β-hydrogen abstraction and the 6β-d1-testosterone 6β-duterium abstraction employing a model that consists of the substrate and the active oxidant compound I. The calculations were performed at the level of canonical variational transition state theory with multidimensional tunneling and were based on a semiglobal full-dimensional potential energy surface generated by the multiconfiguration molecular mechanics technique. The tunneling coefficients were found to be around 3, indicating substantial contributions by quantum tunneling. However, the tunneling made only modest contributions to the kinetic isotope effects. The kinetic isotope effects were computed to be about 2 in the doublet spin state and about 5 in the quartet spin state.

  9. Quantum tunneling in testosterone 6beta-hydroxylation by cytochrome P450: reaction dynamics calculations employing multiconfiguration molecular-mechanical potential energy surfaces.

    PubMed

    Zhang, Yan; Lin, Hai

    2009-10-29

    Testosterone hydroxylation is a prototypical reaction of human cytochrome P450 3A4, which metabolizes about 50% of oral drugs on the market. Reaction dynamics calculations were carried out for the testosterone 6beta-hydrogen abstraction and the 6beta-d(1)-testosterone 6beta-duterium abstraction employing a model that consists of the substrate and the active oxidant compound I. The calculations were performed at the level of canonical variational transition state theory with multidimensional tunneling and were based on a semiglobal full-dimensional potential energy surface generated by the multiconfiguration molecular mechanics technique. The tunneling coefficients were found to be around 3, indicating substantial contributions by quantum tunneling. However, the tunneling made only modest contributions to the kinetic isotope effects. The kinetic isotope effects were computed to be about 2 in the doublet spin state and about 5 in the quartet spin state. PMID:19480428

  10. Probing surface hydrogen bonding and dynamics by natural abundance, multidimensional, 17O DNP-NMR spectroscopy

    DOE PAGESBeta

    Perras, Frederic A.; Chaudhary, Umesh; Slowing, Igor I.; Pruski, Marek

    2016-05-06

    Dynamic nuclear polarization (DNP)-enhanced solid-state nuclear magnetic resonance (SSNMR) spectroscopy is increasingly being used as a tool for the atomic-level characterization of surface sites. DNP surface-enhanced SSNMR spectroscopy of materials has, however, been limited to studying relatively receptive nuclei, and the particularly rare 17O nuclide, which is of great interest for materials science, has not been utilized. We demonstrate that advanced 17O SSNMR experiments can be performed on surface species at natural isotopic abundance using DNP. We use 17O DNP surface-enhanced 2D SSNMR to measure 17O{1H} HETCOR spectra as well as dipolar oscillations on a series of thermally treatedmore » mesoporous silica nanoparticle samples having different pore diameters. These experiments allow for a nonintrusive and unambiguous characterization of hydrogen bonding and dynamics at the surface of the material; no other single experiment can give such details about the interactions at the surface. Lastly, our data show that, upon drying, strongly hydrogen-bonded surface silanols, whose motions are greatly restricted by the interaction when compared to lone silanols, are selectively dehydroxylated.« less

  11. Variations in the abundance of iron on Mercury's surface from MESSENGER X-Ray Spectrometer observations

    NASA Astrophysics Data System (ADS)

    Weider, Shoshana Z.; Nittler, Larry R.; Starr, Richard D.; McCoy, Timothy J.; Solomon, Sean C.

    2014-06-01

    We present measurements of Mercury's surface composition from the analysis of MESSENGER X-Ray Spectrometer data acquired during 55 large solar flares, which each provide a statistically significant detection of Fe X-ray fluorescence. The Fe/Si data display a clear dependence on phase angle, for which the results are empirically corrected. Mercury's surface has a low total abundance of Fe, with a mean Fe/Si ratio of ˜0.06 (equivalent to ˜1.5 wt% Fe). The absolute Fe/Si values are subject to a number of systematic uncertainties, including the phase-angle correction and possible mineral mixing effects. Individual Fe/Si measurements have an intrinsic error of ˜10%. Observed Fe/Si values display small variations (significant at two standard deviations) from the planetary average value across large regions in Mercury's southern hemisphere. Larger differences are observed between measured Fe/Si values from more spatially resolved footprints on volcanic smooth plains deposits in the northern hemisphere and from those in surrounding terrains. Fe is most likely contained as a minor component in sulfide phases (e.g., troilite, niningerite, daubréelite) and as Fe metal, rather than within mafic silicates. Variations in surface reflectance (i.e., differences in overall reflectance and spectral slope) across Mercury are unlikely to be caused by variations in the abundance of Fe.

  12. The Water Vapor Abundance Near the Surface of Venus from Venus Express / VIRTIS Observations

    NASA Astrophysics Data System (ADS)

    Bezard, Bruno; Tsang, C. C. C.; Carlson, R. W.; Piccioni, G.; Marcq, E.; Drossart, P.; VIRTIS/Venus Express Team

    2008-09-01

    We present an analysis of Venus Express/VIRTIS observations of the 1.18-μm window on Venus' night side. We used the infrared M-channel of the VIRTIS instrument, an imaging spectrometer for the range 1-5 μm with a resolution of about 17 nm. The 1.18-μm window probes down to the surface and allows us to map and monitor the water abundance in the lowest scale height of the atmosphere. Besides CO2 and H2O molecular bands, an additional "continuum" source of absorption exists in the window, likely due to CO2 collision-induced bands and extreme far wings of strong CO2 bands. From the variation of the emission with surface elevation, we determined this absorption to be 1.1 ± 0.2 × 10-9 cm-1 amagat-2. From the best fit of the 1.18-micron window in various areas of Venus' southern hemisphere, we derived a H2O mole fraction of 32 ± 7 ppm in the altitude range 0-15 km. This result agrees with previous ground-based and Galileo/NIMS determinations (Taylor et al. 1997, in Venus II, pp. 325-351) but has significantly lower error bars. The derived mole fraction is similar to that inferred at higher altitudes from the 2.3- and 1.74-μm windows, suggesting a constant-with-height water profile from the surface up to 40 km. We also searched for spatial variations of the H2O near-surface abundance using various VIRTIS-M observational sequences and did not detect any latitudinal variations to within 1.5% (i.e. ± 0.5 ppm) in the range 60°S - 20°N.

  13. Effect of Polar Environments on the Aluminum Oxide Shell Surrounding Aluminum Particles: Simulations of Surface Hydroxyl Bonding and Charge.

    PubMed

    Padhye, Richa; Aquino, Adelia J A; Tunega, Daniel; Pantoya, Michelle L

    2016-06-01

    Density functional theory (DFT) calculations were performed to understand molecular variations on an alumina surface due to exposure to a polar environment. The analysis has strong implications for the reactivity of aluminum (Al) particles passivated by an alumina shell. Recent studies have shown a link between the carrier fluid used for Al powder intermixing and the reactivity of Al with fluorine containing reactive mixtures. Specifically, flame speeds show a threefold increase when polar liquids are used to intermix aluminum and fluoropolymer powder mixtures. It was hypothesized that the alumina lattice structure could be transformed due to hydrogen bonding forces exerted by the environment that induce modified bond distances and charges and influence reactivity. In this study, the alumina surface was analyzed using DFT calculations and model clusters as isolated systems embedded in polar environments (acetone and water). The conductor-like screening model (COSMO) was used to mimic environmental effects on the alumina surface. Five defect models for specific active -OH sites were investigated in terms of structures and vibrational -OH stretching frequencies. The observed changes of the surface OH sites invoked by the polar environment were compared to the bare surface. The calculations revealed a strong connection between the impact of carrier fluid polarity on the hydrogen bonding forces between the surface OH sites and surrounding species. Changes were observed in the OH characteristic properties such as OH distances (increase), atomic charges (increase), and OH stretching frequencies (decrease); these consequently improve OH surface reactivity. The difference between medium (acetone) and strong (water) polar environments was minimal in the COSMO approximation. PMID:27175545

  14. Abundance of Iron on Mercury's Surface from MESSENGER X-Ray Spectrometer Data

    NASA Astrophysics Data System (ADS)

    Weider, S. Z.; Nittler, L. R.; Starr, R. D.; Evans, L. G.; McCoy, T. J.; Solomon, S. C.

    2012-12-01

    Early orbital results from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) X-Ray Spectrometer (XRS) revealed that Mercury's surface has a low Fe content. The reported Fe/Si ratios (~0.03 to 0.15) gave an upper limit of ~4 wt% Fe. This limit is consistent with the bulk estimate provided by the Gamma-Ray Spectrometer (Fe/Si: ~0.12) and the upper limit of ~6 wt % FeO in silicate minerals that is constrained by reflectance spectroscopy. Reliable Fe abundance estimates are difficult to obtain from XRS data for several reasons, including: (i) strong solar flares are required to excite Fe X-ray fluorescence, and such flares occur rarely; and (ii) energetic particle events often accompany the strongest solar flares, causing fluorescence of the instrument's Cu collimators and spectral contamination close to the Fe K lines at 6.4-7 keV. Forward modeling of XRS data from more than 30 flares during the first year of MESSENGER's orbit reveal that Fe is ubiquitously lower on Mercury (Fe/Si ranging from 0.02 to 0.18, with a peak in the distribution at ~0.06, or ~1.5 wt% Fe) than on other terrestrial planets. Although the abundance of Mg across the surface of Mercury is known to vary according to geological terrain, our data indicate that this variation is not a result of Fe substitution for Mg in mafic silicates. A correlation between Ca and S (and to a lesser extent between Mg and S) has previously been reported from the XRS data. Mercury's high S contents likely reflect the presence of abundant sulfide minerals, such as oldhamite (Ca,Mg,Fe)S. Our data reveal further correlations between Fe and Ca, and between Fe and Mg, suggesting that sulfides (most likely troilite, FeS, and/or oldhamite) are a major carrier of Fe on Mercury's surface. The low Fe content of Mercury's surface supports the very low FeO contents that are predicted from both melting experiments on enstatite chondrites and from thermodynamic modeling. However, even the few wt% Fe on

  15. Implications of the MESSENGER Discovery of High Sulfur Abundance on the Surface of Mercury

    NASA Astrophysics Data System (ADS)

    Zolotov, M. Y.; Sprague, A. L.; Nittler, L. R.; Weider, S. Z.; Starr, R. D.; Evans, L. G.; Boynton, W. V.; Goldsten, J. O.; Hauck, S. A.; Solomon, S. C.

    2011-12-01

    The unusually high S content detected in Mercury's surface materials with the MESSENGER X-ray Spectrometer (XRS) constrains surface mineralogy, petrology, and the redox state of magmas and rocks. This discovery along with the low FeO content in surface silicates indicates a low oxygen fugacity (fO2) in corresponding melts and the occurrence of S in sulfides, which could be abundant in surface rocks. The detected high S content could reflect anomalously high (up to 8-10 wt%) solubility of sulfide S in extremely reduced magmas. The high bulk S/Fe ratio also suggests the presence of S in sulfides of Mg, Ca, Mn, and Cr, which occur in enstatite chondrites. Although the presence of some troilite (FeS) is possible, niningerite, (Mg, Fe, Mn)S, could be the most abundant sulfide. Niningerite could be partially responsible for Mercury's low surface albedo, its unusual reflectance spectrum at visible and near-infrared wavelengths, and the relatively high neutron absorption, because Mn is a strong neutron absorber. The presence of abundant niningerite would also imply a lower Mg/Si ratio in silicates than in bulk surface materials. It follows that Mg-rich mafic lavas could be present instead of, or in addition to, ultramafic lavas (komatiites). The occurrence of Mg-silicates (enstatite and forsterite) in Mercury's regolith as inferred from mid-infrared spectroscopy, together with the postulated presence of niningerite, helps characterize fO2 and fS2 in corresponding melts. If fS2 is controlled by the Fe-metal-Fe-sulfide equilibrium, the silicate-sulfide equilibria set fO2 values. For temperature less than 1700 K the evaluated values are less than 5.5 log fO2 units below the iron-wüstite buffer (IW-5.5). Lower temperatures and analogous considerations for Ca and Mn silicate-sulfide equilibria lead to lower fO2 values. For Fe-metal-saturated melts at 1700 K the fO2 value is IW-5.5 and corresponds to ~0.1 mol % FeO, which could be considered as an upper limit in magmas and

  16. Spectroscopic Variation of Water Ice Abundance Across Mimas and Tethys' Surface

    NASA Astrophysics Data System (ADS)

    Scipioni, Francesca; Schenk, Paul

    2014-11-01

    We present results from our ongoing work mapping the variation of the main water ice absorption bands across Mimas and Tethys’ surfaces using Cassini-VIMS cubes acquired in the IR range (0.8-5.1 μm). Mimas and Tethys are Enceladus’ orbital neighbours, lying inside and outside Enceladus’ orbit respectively. It is therefore likely that Mimas and Tethys surfaces interact with icy particles from the E-ring, resulting in a spectral, color modification. For all pixels in the selected VIMS cubes, we measured the band depths for water-ice absorptions at 1.25, 1.5 and 2.02 μm and the height of the 3.6 μm reflection peak, whose value relates to grain size. To characterize the global variation of water-ice band depths across Mimas and Tethys, we divided the surface into a 1°x1° grid and then averaged the band depths and peak values inside each square cell. The most prominent feature on Mimas surface is the crater Herschel with a diameter of 130 km, one-third of the satellite's one. Mimas has the most uniform surface among Saturn's principal satellites, with its trailing side just 10% brighter and redder than the leading one. The uniformity of Mimas extends on spectral appearance too. The 1.52 and 2.02 μm H2O-ice absorption bands are ˜10% deeper on trailing hemisphere.On Tethys' leading hemisphere a 400 km in diameter crater, Odysseus, is present. Its dimension represents ˜40% of Tethys diameter.For both moons we find that large geologic features, such as the Odysseus and Herschel impact basin, do not correlate with water ice’s abundance variation.For Tethys, we found a quite uniform surface on both hemispheres. The only deviation from this pattern shows up on the trailing hemisphere, where we notice two north-oriented, dark areas around 225° and 315°. For Mimas the selected dataset covers just the leading hemisphere and a portion of the trailing side. From the analysis, the two hemispheres appear to be quite similar in water ice abundance, the trailing

  17. Modeling Anisothermality in LRO Diviner Observations to Assess Surface Roughness and Rock Abundance

    NASA Astrophysics Data System (ADS)

    Williams, J.; Paige, D. A.; Hayne, P. O.; Vasavada, A. R.; Bandfield, J. L.

    2013-12-01

    The Diviner Lunar Radiometer Experiment on NASA's Lunar Reconnaissance Orbiter (LRO) observes radiance in 7 infrared spectral channels from which brightness temperatures of the lunar surface are derived [1]. Multiple temperatures in the instrument's field of view result in variations in brightness temperature in the individual channels, anisothermality, due to the non-linear nature of Planck radiance with respect to wavelength; the warmer temperatures have an increased proportional influence on brightness temperatures at shorter wavelengths. In general, Diviner's surface footprint contains small scale variations in temperature due to surface roughness and rocks. Anisothermality in Diviner nighttime brightness temperatures has been successfully exploited to map rock abundances on the Moon as rocks cool more slowly than the regolith, and therefore are generally warmer at night [2]. A three-dimensional thermal diffusion model that balances incident solar radiation with infrared emission and conduction into the subsurface is employed to model Diviner observations resulting from surface roughness and rocks at multiple length-scales and illumination conditions. The model includes ray tracing of illumination so that slope effects and shadowing at different solar incidence angles can be explored for arbitrary surface geometries. We find that surface roughness and rocks with length scales as small as 5 cm can generate anisothermality in the Diviner thermal channels in both daytime and nighttime observations. At smaller scales, lateral conduction should become important. The length-scale dependence of anisothermality will be explored further in this study. [1] Paige et al. (2010) Space Sci. Rev., 150: 125-160. [2] Bandfield et al. (2011), JGR, 116.

  18. Continuous enrichment of low-abundance cell samples using standing surface acoustic waves (SSAW).

    PubMed

    Chen, Yuchao; Li, Sixing; Gu, Yeyi; Li, Peng; Ding, Xiaoyun; Wang, Lin; McCoy, J Philip; Levine, Stewart J; Huang, Tony Jun

    2014-03-01

    Cell enrichment is a powerful tool in a variety of cellular studies, especially in applications with low-abundance cell types. In this work, we developed a standing surface acoustic wave (SSAW) based microfluidic device for non-contact, continuous cell enrichment. With a pair of parallel interdigital transducers (IDT) deposited on a piezoelectric substrate, a one-dimensional SSAW field was established along disposable micro-tubing channels, generating numerous pressure nodes (and thus numerous cell-enrichment regions). Our method is able to concentrate highly diluted blood cells by more than 100 fold with a recovery efficiency of up to 99%. Such highly effective cell enrichment was achieved without using sheath flow. The SSAW-based technique presented here is simple, bio-compatible, label-free, and sheath-flow-free. With these advantages, it could be valuable for many biomedical applications. PMID:24413889

  19. Infrared study of the interaction between Lewis bases and surface hydroxyl groups of {Pt}/{Cab-O-Sil}

    NASA Astrophysics Data System (ADS)

    Sárkány, János

    1997-06-01

    Transmission IR spectroscopic study at 298 K has revealed strong H-bonds between Lewis bases (LBs) containing one, [1-O], or two, [2-O], sp 3 hybridized O atoms and the surface OH groups of Cab-O-Sil. LB [1-O] (10 torr = 1.333 kPa) caused a greater | Δν(OH)| (470-520 cm -1) than did LB [2-O] (385-470 cm -1). In contrast with expectations, the intensity of the OH band at 3660 cm -1 decreased to a greater extent for LB [2-O] than for LB [1-O]. The results were interpreted on the basis of chargetransfer theory. The estimated sequence of electron-donating ability (EDA) was: oxepane > oxane > oxolane > diethyl ether ≥ 1,4-dioxane > 1,3-dioxepane > 1,3-dioxane > 1,3-dioxolane.

  20. Photochemical Formation of Hydroxyl Radical, Hydrogen Peroxide and Fe(II) in the Sea Surface Microlayer (SML) Collected in Okinawa, Japan

    NASA Astrophysics Data System (ADS)

    Higaonna, Y.; Tachibana, C.; Kasaba, T.; Ishikawa, R.; Arakaki, T.

    2014-12-01

    The sea surface microlayer (SML) covers upper 1 to 1000 μm deep boundary layer of the ocean, where important biogeochemical processes take place. Photo-chemical reactions are activated by sunlight, so it is assumed that more photo-chemical reactions occur in SML than underlying bulk seawater (bulk). We initiated a study to understand chemical changes occurring in the SML by studying photochemical formation of oxidants such as hydrogen peroxide and hydroxyl radical (OH), both of which react with various organic substances and determine their lifetimes. Since OH can be formed by reaction between hydrogen peroxide and Fe(II), Fe(II) photoformation was also studied. We collected SML samples using a widely-used glass plate method and bulk samples by using a polyethylene bottles near the coast of Okinawa Island, Japan. Results showed that dissolved organic carbon (DOC) concentrations in the SML were about twice those of bulk seawater samples. Hydrogen peroxide formation in the SML samples was ca. 2.8 times faster than the bulk seawater samples. On the other hand, Fe(II) and OH photoformation kinetics was similar for both SML and bulk samples. Although it was predicted that more OH could be formed from reaction between hydrogen peroxide and Fe(II), OH formation kinetics was similar in both SML and bulk, suggesting that either Fe(II) did not react with hydrogen peroxide or reaction is very slow, possibly by forming a complex with organic compounds in the SML and bulk.

  1. Chemical abundances in low surface brightness galaxies: Implications for their evolution

    NASA Technical Reports Server (NTRS)

    Mcgaugh, S. S.; Bothun, G. D.

    1993-01-01

    Low Surface Brightness (LSB) galaxies are an important but often neglected part of the galaxy content of the universe. Their importance stems both from the selection effects which cause them to be under-represented in galaxy catalogs, and from what they can tell us about the physical processes of galaxy evolution that has resulted in something other than the traditional Hubble sequence of spirals. An important constraint for any evolutionary model is the present day chemical abundances of LSB disks. Towards this end, spectra for a sample of 75 H 2 regions distributed in 20 LSB disks galaxies were obtained. Structurally, this sample is defined as having B(0) fainter than 23.0 mag arcsec(sup -2) and scale lengths that cluster either around 3 kpc or 10 kpc. In fact, structurally, these galaxies are very similar to the high surface brightness spirals which define the Hubble sequence. Thus, our sample galaxies are not dwarf galaxies but instead have masses comparable to or in excess of the Milky Way. The basic results from these observations are summarized.

  2. Barium Surface Abundances of Blue Stragglers in the Open Cluster NGC 6819

    NASA Astrophysics Data System (ADS)

    Milliman, Katelyn E.; Mathieu, Robert D.; Schuler, Simon C.

    2015-09-01

    We present a barium surface abundance of 12 blue stragglers (BSs) and 18 main-sequence (MS) stars in the intermediate-age open cluster NGC 6819 (2.5 Gyr) based on spectra obtained from the Hydra Multi-object Spectrograph on the WIYN 3.5 m telescope. For the MS stars we find [Fe/H] = +0.05 ± 0.04 and [Ba/Fe] = -0.01 ± 0.10. The majority of the BS stars are consistent with these values. We identify five BSs with significant barium enhancement. These stars most likely formed through mass transfer from an asymptotic giant branch star that polluted the surface of the BS with the nucleosynthesis products generated during thermal pulsations. This conclusion aligns with the results from the substantial work done on the BSs in old open cluster NGC 188 that identifies mass transfer as the dominant mechanism for BS formation in that open cluster. However, four of the BSs with enhanced barium show no radial-velocity evidence for a companion. The one star that is in a binary is a double-lined system, meaning the companion is not a white dwarf and not the remnant of a prior AGB star. In this paper we attempt to develop a consistent scenario to explain the origin of these five BSs.

  3. Theoretical Near-IR Spectra for Surface Abundance Studies of Massive Stars

    NASA Technical Reports Server (NTRS)

    Sonneborn, George; Bouret, J.

    2011-01-01

    We present initial results of a study of abundance and mass loss properties of O-type stars based on theoretical near-IR spectra computed with state-of-the-art stellar atmosphere models. The James Webb Space Telescope (JWST) will be a powerful tool to obtain high signal-to-noise ratio near-IR (1-5 micron) spectra of massive stars in different environments of local galaxies. Our goal is to analyze model near-IR spectra corresponding to those expected from NIRspec on JWST in order to map the wind properties and surface composition across the parameter range of 0 stars and to determine projected rotational velocities. As a massive star evolves, internal coupling, related mixing, and mass loss impact its intrinsic rotation rate. These three parameters form an intricate loop, where enhanced rotation leads to more mixing which in turn changes the mass loss rate, the latter thus affecting the rotation rate. Since the effects of rotation are expected to be much more pronounced at low metallicity, we pay special attention to models for massive stars in the the Small Magellanic Cloud. This galaxy provides a unique opportunity to probe stellar evolution, and the feedback of massive stars on galactic evol.ution in conditions similar to the epoch of maximal star formation. Plain-Language Abstract: We present initial results of a study of abundance and mass loss properties of massive stars based on theoretical near-infrared (1-5 micron) spectra computed with state-of-the-art stellar atmosphere models. This study is to prepare for observations by the James Webb Space Telescope.

  4. The radiocarbon hydroxyl technique

    NASA Technical Reports Server (NTRS)

    Campbell, Malcolm J.; Sheppard, John C.

    1994-01-01

    The Radiocarbon Technique depends upon measuring the rate of oxidation of CO in an essentially unperturbed sample of air. The airborne technique is slightly different. Hydroxyl concentrations can be calculated directly; peroxyl concentrations can be obtained by NO doping.

  5. Critical evaluation of 13C natural abundance techniques to partition soil-surface CO2 efflux

    NASA Astrophysics Data System (ADS)

    Snell, H.; Midwood, A. J.; Robinson, D.

    2013-12-01

    Soil is the largest terrestrial store of carbon and the flux of CO2 from soils to the atmosphere is estimated at around 98 Pg (98 billion tonnes) of carbon per year. The CO2 efflux from the soil surface is derived from plant root and rhizosphere respiration (autotrophically fuelled) and microbial degradation of soil organic matter (heterotrophic respiration). Heterotrophic respiration is a key determinant of an ecosystem's long-term C balance, but one that is difficult to measure in the field. One approach involves partitioning the total soil-surface CO2 efflux between heterotrophic and autotrophic components; this can be done using differences in the natural abundance stable isotope ratios (δ13C) of autotrophic and heterotrophic CO2 as the end-members of a simple mixing model. In most natural, temperate ecosystems, current and historical vegetation cover (and therefore also plant-derived soil organic matter) is produced from C3 photosynthesis so the difference in δ13C between the autotrophic and heterotrophic CO2 sources is small. Successful partitioning therefore requires accurate and precise measurements of the δ13CO2 of the autotrophic and heterotrophic end-members (obtained by measuring the δ13CO2 of soil-free roots and root-free soil) and of total soil CO2 efflux. There is currently little consensus on the optimum measurement protocols. Here we systematically tested some of the most commonly used techniques to identify and minimise methodological errors. Using soil-surface chambers to sample total CO2 efflux and a cavity ring-down spectrometer to measure δ13CO2 in a partitioning study on a Scottish moorland, we found that: using soil-penetrating collars leads to a more depleted chamber measurement of total soil δ13CO2 as a result of severing roots and fungal hyphae or equilibrating with δ13CO2 at depth or both; root incubations provide an accurate estimate of in-situ root respired δ13CO2 provided they are sampled within one hour; the δ13CO2 from root

  6. Hydroxyl radical mediated DNA base modification by manmade mineral fibres.

    PubMed Central

    Leanderson, P; Söderkvist, P; Tagesson, C

    1989-01-01

    Manmade mineral fibres (MMMFs) were examined for their ability to hydroxylate 2-deoxyguanosine (dG) to 8-hydroxydeoxyguanosine (8-OH-dG), a reaction that is mediated by hydroxyl radicals. It appeared that (1) catalase and the hydroxyl radical scavengers, dimethylsulphoxide and sodium benzoate, inhibited the hydroxylation, whereas Fe2+ and H2O2 potentiated it; (2) pretreatment of MMMFs with the iron chelator, deferoxamine, or with extensive heat (200-400 degrees C), attenuated the hydroxylation; (3) the hydroxylation obtained by various MMMFs varied considerably; (4) there was no apparent correlation between the hydroxylation and the surface area of different MMMFs, although increasing the surface area of a fibre by crushing it increased its hydroxylating capacity; and (5) there was good correlation between the hydroxylation of dG residues in DNA and the hydroxylation of pure dG in solution for the 16 different MMMFs investigated. These findings indicate that MMMFs cause a hydroxyl radical mediated DNA base modification in vitro and that there is considerable variation in the reactivity of different fibre species. The DNA modifying ability seems to depend on physical or chemical characteristics, or both, of the fibre. PMID:2765416

  7. Beryllium in the Galactic halo - Surface abundances from standard, diffusive, and rotational stellar evolution, and implications

    NASA Technical Reports Server (NTRS)

    Deliyannis, Constantine P.; Pinsonneault, Marc H.

    1990-01-01

    The recently observed upper limits to the beryllium abundances in population II stars are much lower than population I detections. This difference reflects an intrinsic difference in the initial abundances and is not caused by different degrees of depletion driven by stellar evolution processes from similar initial abundances. Evolutionary sequences of models from the early premain sequence to beyond the turnoff that correspond to halo dwarfs with Fe/H abundances of -1.3, -2.3, and -3.3 are constructed, and standard, diffusive, and rotational mechanisms are used to estimate a maximal possible beryllium depletion. Halo star models in the T(eff) range 6000 to 5000 K might be rotationally depleted by a factor of 1.5-2, and the total depletion should be no more than (conservatively) a factor of 3. Implications for cosmology, cosmic-ray theory, and Galactic chemical evolution are discussed.

  8. Hydroxyl speciation in felsic magmas

    NASA Astrophysics Data System (ADS)

    Malfait, Wim J.; Xue, Xianyu

    2014-09-01

    The hydroxyl speciation of hydrous, metaluminous potassium and calcium aluminosilicate glasses was investigated by 27Al-1H cross polarization and quantitative 1H MAS NMR spectroscopy. Al-OH is present in both the potassium and the calcium aluminosilicate glasses and its 1H NMR partial spectrum was derived from the 27Al-1H cross polarization data. For the calcium aluminosilicate glasses, the abundance of Al-OH could not be determined because of the low spectral resolution. For the potassium aluminosilicate glasses, the fraction of Al-OH was quantified by fitting its partial spectrum to the quantitative 1H NMR spectra. The degree of aluminum avoidance and the relative tendency for Si-O-Si, Si-O-Al and Al-O-Al bonds to hydrolyze were derived from the measured species abundances. Compared to the sodium, lithium and calcium systems, potassium aluminosilicate glasses display a much stronger degree of aluminum avoidance and a stronger tendency for the Al-O-Al linkages to hydrolyze. Combining our results with those for sodium aluminosilicate glasses (Malfait and Xue, 2010a), we predict that the hydroxyl groups in rhyolitic and phonolitic magmas are predominantly present as Si-OH (84-89% and 68-78%, respectively), but with a significant fraction of Al-OH (11-16% and 22-32%, respectively). For both rhyolitic and phonolitic melts, the AlOH/(AlOH + SiOH) ratio is likely smaller than the Al/(Al + Si) ratio for the lower end of the natural temperature range but may approach the Al/(Al + Si) ratio at higher temperatures.

  9. Unraveling the role of support surface hydroxyls and its effect on the selectivity of C2 species over Rh/γ-Al2O3 catalyst in syngas conversion: A theoretical study

    NASA Astrophysics Data System (ADS)

    Zhang, Riguang; Duan, Tian; Wang, Baojun; Ling, Lixia

    2016-08-01

    The supported Rh-based catalysts exhibit the excellent catalytic performances for syngas conversion to C2 species. In this study, all possible elementary steps leading to C2 species from syngas have been explored to identify the role of support and its surface hydroxyls over Rh/γ-Al2O3 catalyst; Here, the results are obtained using density functional theory (DFT) method. Two models: Rh4 cluster supported on the dry γ-Al2O3(110) surface, D(Rh4), and on the hydroxylated γ-Al2O3(110) surface, H(Rh4), have been used to model Rh/γ-Al2O3 catalyst. Our results show that CO prefers to be hydrogenated to CHO, subsequently, starting from CHO species, CH and CH2 species are the dominate monomers among CHx(x = 1-3) species rather than CH3 and CH3OH on D(Rh4) and H(Rh4) surfaces, suggesting that γ-Al2O3-supported Rh catalyst exhibits the high selectivity towards CHx formation compared to the pure Rh catalyst. On the other hand, D(Rh4) is more favorable for C2 hydrocarbon (C2H2) formation, whereas H(Rh4) surface easily produces C2 hydrocarbon (C2H2) and C2 oxygenates (CHCO,CH2CHO), indicating that the surface hydroxyls of support can affect the selectivity of C2 species over Rh/γ-Al2O3 catalyst in syngas conversion. Moreover, compared to the pure Rh(111) surface, Rh/γ-Al2O3 catalyst can achieve the excellent catalytic performances for syngas conversion to C2 species.

  10. Massive stars at low metallicity. Evolution and surface abundances of O dwarfs in the SMC

    NASA Astrophysics Data System (ADS)

    Bouret, J.-C.; Lanz, T.; Martins, F.; Marcolino, W. L. F.; Hillier, D. J.; Depagne, E.; Hubeny, I.

    2013-07-01

    Aims: We aim to study the properties of massive stars at low metallicity, with an emphasis on their evolution, rotation, and surface abundances. We focus on O-type dwarfs in the Small Magellanic Cloud. These stars are expected to have weak winds that do not remove significant amounts of their initial angular momentum. Methods: We analyzed the UV and optical spectra of twenty-three objects using the NLTE stellar atmosphere code cmfgen and derived photospheric and wind properties. Results: The observed binary fraction of the sample is ≈26%, which is consistent with more systematic studies if one considers that the actual binary fraction is potentially larger owing to low-luminosity companions and that the sample was biased because it excluded obvious spectroscopic binaries. The location of the fastest rotators in the Hertzsprung-Russell (H-R) diagram built with fast-rotating evolutionary models and isochrones indicates that these could be several Myr old. The offset in the position of these fast rotators compared with the other stars confirms the predictions of evolutionary models that fast-rotating stars tend to evolve more vertically in the H-R diagram. Only one star of luminosity class Vz, expected to best characterize extreme youth, is located on the zero-age main sequence, the other two stars are more evolved. We found that the distribution of O and B stars in the ɛ(N) - vsin i diagram is the same, which suggests that the mechanisms responsible for the chemical enrichment of slowly rotating massive stars depend only weakly on the star's mass. We furthermore confirm that the group of slowly rotating N-rich stars is not reproduced by the evolutionary tracks. Even for more massive stars and faster rotators, our results call for stronger mixing in the models to explain the range of observed N abundances. All stars have an N/C ratio as a function of stellar luminosity that match the predictions of the stellar evolution models well. More massive stars have a higher

  11. Mineralogical analyses of surface sediments in the Antarctic Dry Valleys: coordinated analyses of Raman spectra, reflectance spectra and elemental abundances.

    PubMed

    Bishop, Janice L; Englert, Peter A J; Patel, Shital; Tirsch, Daniela; Roy, Alex J; Koeberl, Christian; Böttger, Ute; Hanke, Franziska; Jaumann, Ralf

    2014-12-13

    Surface sediments at Lakes Fryxell, Vanda and Brownworth in the Antarctic Dry Valleys (ADV) were investigated as analogues for the cold, dry environment on Mars. Sediments were sampled from regions surrounding the lakes and from the ice cover on top of the lakes. The ADV sediments were studied using Raman spectra of individual grains and reflectance spectra of bulk particulate samples and compared with previous analyses of subsurface and lakebottom sediments. Elemental abundances were coordinated with the spectral data in order to assess trends in sediment alteration. The surface sediments in this study were compared with lakebottom sediments (Bishop JL et al. 2003 Int. J. Astrobiol. 2, 273-287 (doi:10.1017/S1473550403001654)) and samples from soil pits (Englert P et al. 2013 In European Planetary Science Congress, abstract no. 96; Englert P et al. 2014 In 45th Lunar and Planetary Science Conf., abstract no. 1707). Feldspar, quartz and pyroxene are common minerals found in all the sediments. Minor abundances of carbonate, chlorite, actinolite and allophane are also found in the surface sediments, and are similar to minerals found in greater abundance in the lakebottom sediments. Surface sediment formation is dominated by physical processes; a few centimetres below the surface chemical alteration sets in, whereas lakebottom sediments experience biomineralization. Characterizing the mineralogical variations in these samples provides insights into the alteration processes occurring in the ADV and supports understanding alteration in the cold and dry environment on Mars. PMID:25368345

  12. The impact of surface dynamo magnetic fields on the chemical abundance determination

    NASA Astrophysics Data System (ADS)

    Shchukina, Nataliya G.; Sukhorukov, Andrii V.; Bueno, Javier Trujillo

    2015-10-01

    The solar abundances of Fe and of the CNO elements play an important role in addressing a number of important issues such as the formation, structure, and evolution of the Sun and the solar system, the origin of the chemical elements, and the evolution of stars and galaxies. Despite the large number of papers published on this issue, debates about the solar abundances of these elements continue. The aim of the present investigation is to quantify the impact of photospheric magnetic fields on the determination of the solar chemical abundances. To this end, we used two 3D snapshot models of the quiet solar photosphere with a different magnetization taken from recent magneto-convection simulations with small-scale dynamo action. Using such 3D models we have carried out spectral synthesis for a large set of Fei, Ci, Ni, and Oi lines, in order to derive abundance corrections caused by the magnetic, Zeeman broadening of the intensity profiles and the magnetically induced changes of the photospheric temperature structure. We find that if the magnetism of the quiet solar photosphere is mainly produced by a small-scale dynamo, then its impact on the determination of the abundances of iron, carbon, nitrogen and oxygen is negligible.

  13. The impact of surface dynamo magnetic fields on the solar iron abundance

    NASA Astrophysics Data System (ADS)

    Shchukina, N.; Trujillo Bueno, J.

    2015-07-01

    Most chemical abundance determinations ignore that the solar photosphere is significantly magnetized by the ubiquitous presence of a small-scale magnetic field. A recent investigation has suggested that there should be a significant impact on the derived iron abundance, owing to the magnetically induced changes on the photospheric temperature and density structure (indirect effect). The three-dimensional (3D) photospheric models used in that investigation have non-zero net magnetic flux values and stem from magneto-convection simulations without small-scale dynamo action. Here we address the same problem by instead using 3D models of the quiet solar photosphere that result from a state-of-the-art magneto-convection simulation with small-scale dynamo action, where the net magnetic flux is zero. One of these 3D models has negligible magnetization, while the other is characterized by a mean field strength of 160 Gauss in the low photosphere. With such 3D models we carried out spectral synthesis for a large set of Fe i lines to derive abundance corrections, taking the above-mentioned indirect effect and the Zeeman broadening of the intensity profiles (direct effect) into account. We conclude that if the magnetism of the quiet solar photosphere is mainly produced by a small-scale dynamo, then its impact on the determination of the solar iron abundance is negligible. Table 1 is available in electronic form at http://www.aanda.org

  14. The surface nitrogen abundance of a massive star in relation to its oscillations, rotation, and magnetic field

    SciTech Connect

    Aerts, C.; Molenberghs, G.; Kenward, M. G.; Neiner, C.

    2014-02-01

    We have composed a sample of 68 massive stars in our galaxy whose projected rotational velocity, effective temperature, and gravity are available from high-precision spectroscopic measurements. The additional seven observed variables considered here are their surface nitrogen abundance, rotational frequency, magnetic field strength, and the amplitude and frequency of their dominant acoustic and gravity modes of oscillation. A multiple linear regression to estimate the nitrogen abundance combined with principal component analysis, after addressing the incomplete and truncated nature of the data, reveals that the effective temperature and the frequency of the dominant acoustic oscillation mode are the only two significant predictors for the nitrogen abundance, while the projected rotational velocity and the rotational frequency have no predictive power. The dominant gravity mode and the magnetic field strength are correlated with the effective temperature but have no predictive power for the nitrogen abundance. Our findings are completely based on observations and their proper statistical treatment and call for a new strategy in evaluating the outcome of stellar evolution computations.

  15. Spatial and Seasonal Dynamic of Abundance and Distribution of Guanaco and Livestock: Insights from Using Density Surface and Null Models

    PubMed Central

    Schroeder, Natalia M.; Matteucci, Silvia D.; Moreno, Pablo G.; Gregorio, Pablo; Ovejero, Ramiro; Taraborelli, Paula; Carmanchahi, Pablo D.

    2014-01-01

    Monitoring species abundance and distribution is a prerequisite when assessing species status and population viability, a difficult task to achieve for large herbivores at ecologically meaningful scales. Co-occurrence patterns can be used to infer mechanisms of community organization (such as biotic interactions), although it has been traditionally applied to binary presence/absence data. Here, we combine density surface and null models of abundance data as a novel approach to analyze the spatial and seasonal dynamics of abundance and distribution of guanacos (Lama guanicoe) and domestic herbivores in northern Patagonia, in order to visually and analytically compare the dispersion and co-occurrence pattern of ungulates. We found a marked seasonal pattern in abundance and spatial distribution of L. guanicoe. The guanaco population reached its maximum annual size and spatial dispersion in spring-summer, decreasing up to 6.5 times in size and occupying few sites of the study area in fall-winter. These results are evidence of the seasonal migration process of guanaco populations, an increasingly rare event for terrestrial mammals worldwide. The maximum number of guanacos estimated for spring (25951) is higher than the total population size (10000) 20 years ago, probably due to both counting methodology and population growth. Livestock were mostly distributed near human settlements, as expected by the sedentary management practiced by local people. Herbivore distribution was non-random; i.e., guanaco and livestock abundances co-varied negatively in all seasons, more than expected by chance. Segregation degree of guanaco and small-livestock (goats and sheep) was comparatively stronger than that of guanaco and large-livestock, suggesting a competition mechanism between ecologically similar herbivores, although various environmental factors could also contribute to habitat segregation. The new and compelling combination of methods used here is highly useful for researchers

  16. Measurement of clay surface areas by polyvinylpyrrolidone (PVP) sorption and its use for quantifying illite and smectite abundance

    USGS Publications Warehouse

    Blum, A.E.; Eberl, D.D.

    2004-01-01

    A new method has been developed for quantifying smectite abundance by sorbing polyvinylpyrrolidone (PVP) on smectite particles dispersed in aqueous solution. The sorption density of PVP-55K on a wide range of smectites, illites and kaolinites is ???0.99 mg/m2, which corresponds to ???0.72 g of PVP-55K per gram of montmorillonite. Polyvinylpyrrolidone sorption on smectites is independent of layer charge and solution pH. PVP sorption on Si02, Fe 2O3 and ZnO normalized to the BET surface area is similar to the sorption densities on smectites. ??-Al 2O3, amorphous Al(OH)3 and gibbsite have no PVP sorption over a wide range of pH, and sorption of PVP by organics is minimal. The insensitivity of PVP sorption densities to mineral layer charge, solution pH and mineral surface charge indicates that PVP sorption is not localized at charged sites, but is controlled by more broadly distributed sorption mechanisms such as Van der Waals' interactions and/or hydrogen bonding. Smectites have very large surface areas when dispersed as single unit-cell-thick particles (???725 m2/g) and usually dominate the total surface areas of natural samples in which smectites are present. In this case, smectite abundance is directly proportional to PVP sorption. In some cases, however, the accurate quantification of smectite abundance by PVP sorption may require minor corrections for PVP uptake by other phases, principally illite and kaolinite. Quantitative XRD can be combined with PVP uptake measurements to uniquely determine the smectite concentration in such sample. ?? 2004, The Clay Minerals Society.

  17. The surface abundance and stratigraphy of lunar rocks from data about their albedo

    NASA Technical Reports Server (NTRS)

    Shevchenko, V. V.

    1977-01-01

    The data pf ground-based studies and surveys of the lunar surface by the Zond and Apollo spacecraft have been used to construct an albedo map covering 80 percent of the lunar sphere. Statistical analysis of the distribution of areas with various albedos shows several types of lunar surface. Comparison of albedo data for maria and continental areas with the results of geochemical orbital surveys allows the identification of the types of surface with known types of lunar rock. The aluminum/silcon and magnesium/silicon ratios as measured by the geochemical experiments on the Apollo 15 and Apollo 16 spacecraft were used as an indication of the chemical composition of the rock. The relationship of the relative aluminum content to the age of crystalline rocks allows a direct dependence to be constructed between the mean albedo of areas and the age of the rocks of which they are composed.

  18. The MiMeS survey of magnetism in massive stars: CNO surface abundances of Galactic O stars

    NASA Astrophysics Data System (ADS)

    Martins, F.; Hervé, A.; Bouret, J.-C.; Marcolino, W.; Wade, G. A.; Neiner, C.; Alecian, E.; Grunhut, J.; Petit, V.

    2015-03-01

    Context. The evolution of massive stars is still partly unconstrained. Mass, metallicity, mass loss, and rotation are the main drivers of stellar evolution. Binarity and the magnetic field may also significantly affect the fate of massive stars. Aims: Our goal is to investigate the evolution of single O stars in the Galaxy. Methods: For that, we used a sample of 74 objects comprising all luminosity classes and spectral types from O4 to O9.7. We relied on optical spectroscopy obtained in the context of the MiMeS survey of massive stars. We performed spectral modelling with the code CMFGEN. We determined the surface properties of the sample stars, with special emphasis on abundances of carbon, nitrogen, and oxygen. Results: Most of our sample stars have initial masses in the range of 20 to 50 M⊙. We show that nitrogen is more enriched and carbon and oxygen are more depleted in supergiants than in dwarfs, with giants showing intermediate degrees of mixing. CNO abundances are observed in the range of values predicted by nucleosynthesis through the CNO cycle. More massive stars, within a given luminosity class, appear to be more chemically enriched than lower mass stars. We compare our results with predictions of three types of evolutionary models and show that for two sets of models, 80% of our sample can be explained by stellar evolution including rotation. The effect of magnetism on surface abundances is unconstrained. Conclusions: Our study indicates that in the 20-50 M⊙ mass range, the surface chemical abundances of most single O stars in the Galaxy are fairly well accounted for by stellar evolution of rotating stars. Based on observations obtained at 1) the Telescope Bernard Lyot (USR5026) operated by the Observatoire Midi-Pyrénées, Université de Toulouse (Paul Sabatier), Centre National de la Recherche Scientifique of France; 2) at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut

  19. Solar wind H-3 and C-14 abundances and solar surface processes. [in lunar soil

    NASA Technical Reports Server (NTRS)

    Fireman, E. L.; Defelice, J.; Damico, J.

    1976-01-01

    Tritium is measured as a function of depth in a Surveyor 3 sample. The upper limit for solar-wind-implanted tritium gives an H-3/H-1 limit for the solar wind of 10 to the -11th power. The temperature-release patterns of C-14 from lunar soils are measured. The C-14 release pattern from surface soils differs from a trench-bottom soil and gives positive evidence for the presence of C-14 in the solar wind with a C-14/H-1 ratio of approximately 6 by 10 to the -11th power. This C-14 content fixes a minimal magnitude for nuclear processes on the solar surface averaged over the past 10,000 yr. The H-3 and C-14 contents combine to require that either the mixing rate above the photosphere be rapid or that the H-3 produced by nuclear reactions be destroyed by secondary nuclear reactions before escaping in the solar wind.

  20. Nitrogen line spectroscopy of O-stars. II. Surface nitrogen abundances for O-stars in the Large Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Rivero González, J. G.; Puls, J.; Najarro, F.; Brott, I.

    2012-01-01

    Context. Nitrogen is a key element for testing the impact of rotational mixing on evolutionary models of massive stars. Recent studies of the nitrogen surface abundance in B-type stars within the VLT-FLAMES survey of massive stars have challenged part of the corresponding predictions. To obtain a more complete picture of massive star evolution, and to allow for additional constraints, these studies need to be extended to O-stars. Aims: This is the second paper in a series aiming at the analysis of nitrogen abundances in O-type stars, to establish tighter constraints on the early evolution of massive stars. In this paper, we investigate the N ivλ4058 emission line formation, provide nitrogen abundances for a substantial O-star sample in the Large Magellanic Cloud, and compare our (preliminary) findings with recent predictions from stellar evolutionary models. Methods: Stellar and wind parameters of our sample stars were determined by line profile fitting of hydrogen, helium and nitrogen lines, exploiting the corresponding ionization equilibria. Synthetic spectra were calculated by means of the NLTE atmosphere/spectrum synthesis code fastwind, using a new nitrogen model atom. We derived nitrogen abundances for 20 O- and 5 B-stars by analyzing all nitrogen lines (from different ionization stages) present in the available optical spectra. Results: The dominating process responsible for emission at N ivλ4058 in O-stars is the strong depopulation of the lower level of the transition, which increases as a function of Ṁ. Unlike the N iii triplet emission, resonance lines do not play a role for typical mass-loss rates and below. We find (almost) no problem in fitting the nitrogen lines, in particular the "f" features. Only for some objects, where lines from N iii/N iv/N v are visible in parallel, we need to opt for a compromise solution. For five objects in the early B-/late O-star domain that have been previously analyzed by different methods and model atmospheres, we

  1. Apoptotic epithelial cells control the abundance of Treg cells at barrier surfaces.

    PubMed

    Nakahashi-Oda, Chigusa; Udayanga, Kankanam Gamage Sanath; Nakamura, Yoshiyuki; Nakazawa, Yuta; Totsuka, Naoya; Miki, Haruka; Iino, Shuichi; Tahara-Hanaoka, Satoko; Honda, Shin-ichiro; Shibuya, Kazuko; Shibuya, Akira

    2016-04-01

    Epithelial tissues continually undergo apoptosis. Commensal organisms that inhabit the epithelium influence tissue homeostasis, in which regulatory T cells (Treg cells) have a central role. However, the physiological importance of epithelial cell apoptosis and how the number of Treg cells is regulated are both incompletely understood. Here we found that apoptotic epithelial cells negatively regulated the commensal-stimulated proliferation of Treg cells. Gut commensals stimulated CX3CR1(+)CD103(-)CD11b(+) dendritic cells (DCs) to produce interferon-β (IFN-β), which augmented the proliferation of Treg cells in the intestine. Conversely, phosphatidylserine exposed on apoptotic epithelial cells suppressed IFN-β production by the DCs via inhibitory signaling mediated by the cell-surface glycoprotein CD300a and thus suppressed Treg cell proliferation. Our findings reveal a regulatory role for apoptotic epithelial cells in maintaining the number of Treg cell and tissue homeostasis. PMID:26855029

  2. Activity, distribution, and abundance of methane-oxidizing bacteria in the near surface soils of onshore oil and gas fields.

    PubMed

    Xu, Kewei; Tang, Yuping; Ren, Chun; Zhao, Kebin; Wang, Wanmeng; Sun, Yongge

    2013-09-01

    Methane-oxidizing bacteria (MOB) have long been used as an important biological indicator for oil and gas prospecting, but the ecological characteristics of MOB in hydrocarbon microseep systems are still poorly understood. In this study, the activity, distribution, and abundance of aerobic methanotrophic communities in the surface soils underlying an oil and gas field were investigated using biogeochemical and molecular ecological techniques. Measurements of potential methane oxidation rates and pmoA gene copy numbers showed that soils inside an oil and gas field are hot spots of methane oxidation and MOB abundance. Correspondingly, terminal restriction fragment length polymorphism analyses in combination with cloning and sequencing of pmoA genes also revealed considerable differences in the methanotrophic community composition between oil and gas fields and the surrounding soils. Principal component analysis ordination furthermore indicated a coincidence between elevated CH4 oxidation activity and the methanotrophic community structure with type I methanotrophic Methylococcus and Methylobacter, in particular, as indicator species of oil and gas fields. Collectively, our results show that trace methane migrated from oil and gas reservoirs can considerably influence not only the quantity but also the structure of the methanotrophic community. PMID:23090054

  3. Molecular structures of (3-aminopropyl)trialkoxysilane on hydroxylated barium titanate nanoparticle surfaces induced by different solvents and their effect on electrical properties of barium titanate based polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Fan, Yanyan; Wang, Guanyao; Huang, Xingyi; Bu, Jing; Sun, Xiaojin; Jiang, Pingkai

    2016-02-01

    Surface modification of nanoparticles by grafting silane coupling agents has proven to be a significant approach to improve the interfacial compatibility between inorganic filler and polymer matrix. However, the impact of grafted silane molecular structure after the nanoparticle surface modification, induced by the utilized solvents and the silane alkoxy groups, on the electrical properties of the corresponding nanocomposites, has been seldom investigated. Herein, the silanization on the surface of hydroxylated barium titanate (BT-OH) nanoparticles was introduced by using two kinds of trialkoxysilane, 3-aminopropyltriethoxysilane (AMEO) and 3-aminopropyltrimethoxysilane (AMMO), with different solvents (toluene and ethanol), respectively. Solid-state 13C, 29Si nuclear magnetic resonance (NMR) spectroscopy and high-resolution X-ray photoelectron spectroscopy (XPS) were employed to validate the structure differences of alkoxysilane attachment to the nanoparticles. The effect of alkoxysilane structure attached to the nanoparticle surface on the dielectric properties of the BT based poly(vinylidene fluoride) (PVDF) nanocomposites were investigated. The results reveal that the solvents used for BT nanoparticle surface modification exhibit a significant effect on the breakdown strength of the nanocomposites. Nevertheless, the alkoxy groups of silane show a marginal influence on the dielectric properties of the nanocomposites. These research results provide important insights into the fabrication of advanced polymer nanocomposites for dielectric applications.

  4. The surface magnetic field and chemical abundance distributions of the B2V helium-strong star HD 184927

    NASA Astrophysics Data System (ADS)

    Yakunin, I.; Wade, G.; Bohlender, D.; Kochukhov, O.; Marcolino, W.; Shultz, M.; Monin, D.; Grunhut, J.; Sitnova, T.; Tsymbal, V.; MiMeS Collaboration

    2015-02-01

    A new time series of high-resolution Stokes I and V spectra of the magnetic B2V star HD 184927 has been obtained in the context of the Magnetism in Massive Stars Large Program with an Echelle SpectroPolarimetric Device for the Observation of Stars (ESPaDOnS) spectropolarimeter at the Canada-France-Hawaii Telescope and dimaPol liquid crystal spectropolarimeter at 1.8-m telescope of Dominion Astrophysical Observatory. We model the optical and UV spectrum obtained from the International Ultraviolet Explorer (IUE) archive to infer the stellar physical parameters. Using magnetic field measurements, we derive an improved rotational period of 9.531 02 ± 0.0007 d. We infer the longitudinal magnetic field from lines of H, He, and various metals, revealing large differences between the apparent field strength variations determined from different elements. Magnetic Doppler Imaging using He and O lines yields strongly non-uniform surface distributions of these elements. We demonstrate that the diversity of longitudinal field variations can be understood as due to the combination of element-specific surface abundance distributions in combination with a surface magnetic field that is comprised of dipolar and quadrupolar components. We have reanalysed IUE high-resolution spectra, confirming strong modulation of wind-sensitive C IV and S IV resonance lines. However, we are unable to detect any modulation of the Hα profile attributable to a stellar magnetosphere. We conclude that HD 184927 hosts a centrifugal magnetosphere (η _*˜ 2.4^{+22}_{-1.1}× 104), albeit one that is undetectable at optical wavelengths. The magnetic braking time-scale of HD 184927 is computed to be τJ = 0.96 or 5.8 Myr. These values are consistent with the slow rotation and estimated age of the star.

  5. Hydroxyl Radical Generation and DNA Nuclease Activity: A Mechanistic Study Based on a Surface-Immobilized Copper Thioether Clip-Phen Derivative.

    PubMed

    Romo, Adolfo I B; Abreu, Dieric S; de F Paulo, Tércio; Carepo, Marta S P; Sousa, Eduardo H S; Lemus, Luis; Aliaga, Carolina; Batista, Alzir A; Nascimento, Otaciro R; Abruña, Héctor D; Diógenes, Izaura C N

    2016-07-11

    Coordination compounds of copper have been invoked as major actors in processes involving the reduction of molecular oxygen, mostly with the generation of radical species the assignment for which has, so far, not been fully addressed. In the present work, we have carried out studies in solution and on surfaces to gain insights into the nature of the radical oxygen species (ROS) generated by a copper(II) coordination compound containing a thioether clip-phen derivative, 1,3-bis(1,10-phenanthrolin-2-yloxy)-N-(4-(methylthio)benzylidene)propan-2-amine (2CP-Bz-SMe), enabling its adsorption/immobilization to gold surfaces. Whereas surface plasmon resonance (SPR) and electrochemistry of the adsorbed complex indicated the formation of a dimeric Cu(I) intermediate containing molecular oxygen as a bridging ligand, scanning electrochemical microscopy (SECM) and nuclease assays pointed to the generation of a ROS species. Electron paramagnetic resonance (EPR) data reinforced such conclusions, indicating that radical production was dependent on the amount of oxygen and H2 O2 , thus pointing to a mechanism involving a Fenton-like reaction that results in the production of OH(.) . PMID:27310653

  6. Heterologous expression of rab4 reduces glucose transport and GLUT4 abundance at the cell surface in oocytes.

    PubMed Central

    Mora, S; Monden, I; Zorzano, A; Keller, K

    1997-01-01

    To evaluate the role of the small rab GTP-binding proteins in glucose transporter trafficking, we have heterologously co-expressed rab4 or rab5 and GLUT4 or GLUT1 glucose transporters in Xenopus oocytes. Co-injection of rab4 and GLUT4 cRNAs resulted in a dose-dependent decrease in glucose transport; this effect was specific for rab4, since co-injection of an inactive rab4 mutant or rab5 cRNA did not have any effect on glucose transport. The effect of rab4 was selective for GLUT4, since no effect was detected in GLUT1-expressing oocytes. The inhibitory effect of rab4 on GLUT4-induced glucose transport was not the result of a change in overall cellular levels of GLUT4 glucose transporters. However, rab4 expression caused a marked decrease in the abundance of GLUT4 transporters present at the cell surface. Finally, rab4 and inhibitors of PtdIns 3-kinase showed additive effects in decreasing glucose transport in GLUT4-expressing oocytes. We conclude that rab4 plays an important role in the regulation of the intracellular GLUT4 trafficking pathway, by contributing to the intracellular retention of GLUT4 through a PtdIns 3-kinase-independent mechanism. PMID:9182703

  7. Expression of CD36 by Olfactory Receptor Cells and Its Abundance on the Epithelial Surface in Mice

    PubMed Central

    Tsuzuki, Satoshi; Matsumura, Shigenobu; Inoue, Kazuo; Iwanaga, Toshihiko; Masuda, Daisaku; Yamashita, Shizuya; Fushiki, Tohru

    2015-01-01

    CD36 is a transmembrane protein that is involved in the recognition of certain amphiphilic molecules such as polar lipids in various tissues and body fluids. So far, CD36 homologues in insects have been demonstrated to be present on the surface of olfactory dendrites and to participate in the perception of exogenous compounds. However, little is known about the relationship between CD36 and mammalian olfaction. Indeed, the detection of only CD36 mRNA in the mouse olfactory epithelium has been reported to date. In the present study, to provide potential pieces of evidence for the involvement of CD36 in mammalian olfactory perception, we extensively investigated the localisation of this protein in the mouse olfactory mucosa. In situ hybridisation analysis using antisense oligonucleotides to CD36 mRNA detected aggregated signals within the deeper epithelial layer of olfactory mucosa. The mRNA signals were also detected consistently in the superficial layer of the olfactory epithelium, which is occupied by supporting cells. Immunostaining with an anti-CD36 polyclonal antibody revealed that CD36 localises in the somata and dendrites of distinct olfactory receptor cells and that it occurs abundantly on the olfactory epithelial surface. However, immunoreactive CD36 was rarely detectable in the nerve bundles running in the lamina propria of olfactory mucosa, the axons forming the olfactory nerve layer in the outermost layer of the bulb and axon terminals in the glomeruli. We also obtained electron microscopic evidence for the association of CD36 protein with olfactory cilia. Altogether, we suggest that CD36 plays a role in the mammalian olfaction. In addition, signals for CD36 protein were also detected on or around the microvilli of olfactory supporting cells and the cilia of nasal respiratory epithelium, suggesting a role for this protein other than olfaction in the nasal cavity. PMID:26186589

  8. Photocatalytic degradation of 1,10-dichlorodecane in aqueous suspensions of TiO{sub 2}: A reaction of adsorbed chlorinated alkane with surface hydroxyl radicals

    SciTech Connect

    El-Morsi, T.M.; Bubakowski, W.R.; Abd-El-Aziz, A.S.; Friesen, K.J.

    2000-03-15

    1,10-Dichlorodecane (D{sub 2}C{sub 10}) is shown to be effectively photodegraded in aqueous suspensions of TiO{sub 2} using a photoreactor equipped with 300 nm lamps. Solutions exposed to UV light intensities of 3.6 x 10{sup {minus}5} Ein L{sup {minus}1} min{sup {minus}1}, established by ferrioxalate actinometry, showed negligible direct photolysis in the absence of TiO{sub 2} and a D{sub 2}C{sub 10} concentration approaching its solubility limit. Kinetics of photodegradation followed a Langmuir-Hinshelwood model suggesting that the reaction occurred on the surface of the photocatalyst. The presence of h{sup +}{sub vb} and OH{sm_bullet} radical scavengers, including methanol and iodide, inhibited the degradation supporting a photooxidation reaction. Electron scavengers (Ag{sup +}, Cu{sup 2+}, and Fe{sup 3+}) had small effects on the degradation rate. The lack of transformation of D{sub 2}C{sub 10} in acetonitrile as solvent indicated that the major oxidants were OH{sm_bullet} radicals. The presence of tetranitromethane, effectively eliminating the formation of free OH{sm_bullet} radicals, did not affect the degradation rates significantly. This result, combined with observed increases in photolysis rates with the degree of adsorption of D{sub 2}C{sub 10} onto the surface of the photocatalyst, confirmed that the reaction involved adsorbed 1,10-dichlorodecane and surface bound OH{sm_bullet} radicals.

  9. Biotechnological production of plant-specific hydroxylated phenylpropanoids.

    PubMed

    Lin, Yuheng; Yan, Yajun

    2014-09-01

    Hydroxylated phenylpropanoid compounds (e.g., esculetin, piceatannol, and eriodictyol) have been proved to possess important biological activities and pharmacological properties. These compounds exist at low abundance in nature, which hampers their cost-effective isolation, and broad application. Meanwhile, regiospecific hydroxylation of complex aromatic compounds is still quite challenging for chemical synthesis. In past decades, biocatalytic hydroxylation of plant phenylpropanoids was achieved due to the identification and engineering of some cytochrome P450 hydroxylases; however, the conversion efficiency was still too low for scale-up production use. In this work, we identify a non-P450 monooxygenase (HpaBC) from Escherichia coli, which is able to catalyze the efficient ortho-hydroxylation towards plant phenylpropanoids umbelliferone and resveratrol; meanwhile it also exhibits activity towards naringenin. On this basis, whole-cell biocatalysis enables the production of esculetin and piceatannol at high titers (2.7 and 1.2 g/L, respectively, in shake flasks) and high yields (close to 100%). To our knowledge, this work reports the highest titers and yields for biotechnological production of esculetin and piceatannol, representing a promising hydroxylation platform. PMID:24752627

  10. DNA Binding Hydroxyl Radical Probes

    PubMed Central

    Tang, Vicky J; Konigsfeld, Katie M; Aguilera, Joe A; Milligan, Jamie R

    2011-01-01

    The hydroxyl radical is the primary mediator of DNA damage by the indirect effect of ionizing radiation. It is a powerful oxidizing agent produced by the radiolysis of water and is responsible for a significant fraction of the DNA damage associated with ionizing radiation. There is therefore an interest in the development of sensitive assays for its detection. The hydroxylation of aromatic groups to produce fluorescent products has been used for this purpose. We have examined four different chromophores which produce fluorescent products when hydroxylated. Of these, the coumarin system suffers from the fewest disadvantages. We have therefore examined its behavior when linked to a cationic peptide ligand designed to bind strongly to DNA. PMID:22125376

  11. [Effects of Corbicula fluminea bioturbation on the community composition and abundance of ammonia-oxidizing archaea and bacteria in surface sediments].

    PubMed

    Wang, Xue; Zhao, Da-Yong; Zeng, Jin; Yu, Duo-Wei; Wu, Qing-Long

    2014-06-01

    To better understand the effects of Corbicula fluminea bioturbation on the ammonia-oxidizing microorganisms in the surface sediment, sediment-water microcosms with different densities of Corbicula fluminea were constructed. Clone libraries and real-time qPCR were applied to analyze the community composition and abundance of ammonia-oxidizing archaea (AOA) and bacteria (AOB) in the surface sediments. The results obtained indicated that the bioturbation of Corbicula fluminea accelerated the release of nitrogen from the surface sediment. In the amoA gene clone libraries, the identified AOA amoA gene sequences affiliated with the two known clusters (marine and soil clusters). The identified AOB amoA gene sequences mostly belonged to the Nitrosomonas of beta-Proteobacteria. The abundance of the bacterial amoA gene was higher than that of the archaeal amoA gene in all treatments. With increasing density of Corbicula fluminea, decreased abundances of the bacterial amoA gene were observed. At the same time, the diversity of AOA and AOB reduced in the Corbicula fluminea containing microcosms. In conclusion, the bioturbation of Corbicula fluminea could affected the community composition and abundance of ammonia-oxidizing microorganisms in surface sediments. PMID:25158512

  12. Helium-abundance and other composition effects on the properties of stellar surface convection in solar-like main-sequence stars

    SciTech Connect

    Tanner, Joel D.; Basu, Sarbani; Demarque, Pierre

    2013-12-01

    We investigate the effect of helium abundance and α-element enhancement on the properties of convection in envelopes of solar-like main-sequence stars using a grid of three-dimensional radiation hydrodynamic simulations. Helium abundance increases the mean molecular weight of the gas and alters opacity by displacing hydrogen. Since the scale of the effect of helium may depend on the metallicity, the grid consists of simulations with three helium abundances (Y = 0.1, 0.2, 0.3), each with two metallicities (Z = 0.001, 0.020). We find that changing the helium mass fraction generally affects structure and convective dynamics in a way opposite to that of metallicity. Furthermore, the effect is considerably smaller than that of metallicity. The signature of helium differs from that of metallicity in the manner in which the photospheric velocity distribution is affected. We also find that helium abundance and surface gravity behave largely in similar ways, but differ in the way they affect the mean molecular weight. A simple model for spectral line formation suggests that the bisectors and absolute Doppler shifts of spectral lines depend on the helium abundance. We look at the effect of α-element enhancement and find that it has a considerably smaller effect on the convective dynamics in the superadiabatic layer compared to that of helium abundance.

  13. Observational evidence for interhemispheric hydroxyl-radical parity.

    PubMed

    Patra, P K; Krol, M C; Montzka, S A; Arnold, T; Atlas, E L; Lintner, B R; Stephens, B B; Xiang, B; Elkins, J W; Fraser, P J; Ghosh, A; Hintsa, E J; Hurst, D F; Ishijima, K; Krummel, P B; Miller, B R; Miyazaki, K; Moore, F L; Mühle, J; O'Doherty, S; Prinn, R G; Steele, L P; Takigawa, M; Wang, H J; Weiss, R F; Wofsy, S C; Young, D

    2014-09-11

    The hydroxyl radical (OH) is a key oxidant involved in the removal of air pollutants and greenhouse gases from the atmosphere. The ratio of Northern Hemispheric to Southern Hemispheric (NH/SH) OH concentration is important for our understanding of emission estimates of atmospheric species such as nitrogen oxides and methane. It remains poorly constrained, however, with a range of estimates from 0.85 to 1.4 (refs 4, 7-10). Here we determine the NH/SH ratio of OH with the help of methyl chloroform data (a proxy for OH concentrations) and an atmospheric transport model that accurately describes interhemispheric transport and modelled emissions. We find that for the years 2004-2011 the model predicts an annual mean NH-SH gradient of methyl chloroform that is a tight linear function of the modelled NH/SH ratio in annual mean OH. We estimate a NH/SH OH ratio of 0.97 ± 0.12 during this time period by optimizing global total emissions and mean OH abundance to fit methyl chloroform data from two surface-measurement networks and aircraft campaigns. Our findings suggest that top-down emission estimates of reactive species such as nitrogen oxides in key emitting countries in the NH that are based on a NH/SH OH ratio larger than 1 may be overestimated. PMID:25209800

  14. Hydroxyl radical detection in vivo

    SciTech Connect

    Chevion, M.; Floyd, R.A.

    1986-05-01

    Hydroxyl radicals have been implicated as the actual species responsible for the deleterious effects of active oxygen in biology. However, in most cases, its presence has only been inferred by circumstantial evidence. Using electrochemical detection coupled to HPLC separation technique the authors can identify and quantitate (at sub-picomole level) the hydroxylated products of 3 aromatic compounds (phenol, salicylate, and 2-deoxy-guanosine) as a direct measure of hydroxyl radical formation. Firstly, the authors showed that mixing ascorbate with copper ions (in the absence of presence of a protein) yields catechols, dihydroxybenzoic acids and 8-OH-deoxy-guanosine (8-OHdG). This approach has been used to study the formation of OH in vivo. Human granulocytes stimulated with TPA showed that 8-OHdG was formed in the cellular DNA at high levels (one 8-OHdG/800 DNA bases). Unstimulated granulocytes contained 8-OHdG below detection level. Formation of 8-OHdG in the TPA-stimulated granulocytes DNA was decreased by the addition of SOD and catalase. Using salicylate as an in vivo scavenger of hydroxyl radicals the authors showed that the level of trapped-dihydroxybenzoic acids is increased approx.8 and approx.3 fold in the lungs and liver of paraquat-poisoned mice, respectively, as compared to normal animals. Similarly, the detected level of dihydroxybenzoic acids in the hearts of adriamycin-treated rats was increased over 100-fold as compared to the hearts of control animals.

  15. Effective inhibition of hydroxyl radicals by hydroxylated biphenyl compounds.

    PubMed

    Taira, J; Ikemoto, T; Mimura, K; Hagi, A; Murakami, A; Makino, K

    1993-01-01

    In aqueous media, approximate rate constants for the reactions between hydroxyl radicals (.OH) and biphenyl compounds such as dehydrodieugenol, magnolol, honokiol, dehydrodidihydroeugenol, dehydrodivanillyl alcohol, and dehydrodicreosol were estimated by competition reactions for .OH between these biphenyls and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). By measuring the decrease in the height of the EPR signals of the .OH spin adduct, rate constants in the order of 10(9) to 10(10) M were measured. PMID:8282234

  16. Rapid changes in diatom silica surface charge density, silanol abundance, and oxygen isotope values elucidate silica maturation processes in biogenic silica

    NASA Astrophysics Data System (ADS)

    Wiedenheft, W.; Dodd, J. P.; Sunderlin, L.

    2014-12-01

    Oxygen isotope values of biogenic silica are increasingly used as proxies of paleoenvironmental conditions. Numerous studies have demonstrated a strong relationship between the diatom silica and the temperature/oxygen isotope value of the formation water; however, some studies have indicated that early diagenesis of biogenic silica may alter the oxygen isotope values by several permil. Quantification of the maturation process has proven difficult since the mechanisms that drive post-mortem changes in the silica oxygen isotope values have not been well characterized. New silica maturation data from marine diatoms, Stephanopyxis turris, cultured in a controlled laboratory experiment demonstrate rapid post-mortem decline in silica reactivity. A decrease in relative abundance of surface silanol groups coincides with a decrease in the surface charge density (excess proton concentration) of freshly harvested frustules. Over a maturation period of 20 days at 85ºC, S. turris samples in a 0.7 M NaCl solution at a pH of 8.0 demonstrate a rapid decrease in the surface charge density from -380 μmoles/g to -16 μmoles/g (Figure 1). FTIR analyses reveal a decrease in the abundance of silanol groups (Si-OH) in the diatom frustules occurs over the same time period. It is important to note that the surface charge density and silanol relative abundance appear to have an asymptotic change through time, indicating that further alteration/reactivity is greatly reduced. Preliminary data indicate that post-mortem increases in the oxygen isotope values of diatom silica observed here and in other studies are coincident with a reduction in the surface charge density and silanol abundance. These experiments demonstrate that rapid post-mortem alteration of biogenic silica is occurring and provide a possible mechanism for alteration of oxygen isotope values in biogenic silica.

  17. Hydroxylation of a metal-supported hexagonal boron nitride monolayer by oxygen induced water dissociation.

    PubMed

    Guo, Yufeng; Guo, Wanlin

    2015-07-01

    Hydroxylated hexagonal boron nitride (h-BN) nanosheets exhibit potential application in nanocomposites and functional surface coating. Our first-principles calculations reveal possible hydroxylation of a h-BN monolayer on a Ni substrate by surface O adatom induced spontaneous dissociation of water molecules. Here one H atom is split from a water molecule by bonding with the O adatom on the B atom and the resulting O-H radical then bonds with an adjacent B atom, which leads to two hydroxyl groups formed on h-BN/Ni. Hydroxylation slightly influences the electronic properties of a Ni-supported h-BN layer. Similar water dissociation and hydroxylation can occur on the surface of O functionalized h-BN/Cu depending on the O adsorption configuration. Metal substrates play an important catalytic role in enhancing the chemical reactivity of O adatoms on h-BN with water molecules through transferring additional charges to them. PMID:26051363

  18. Detection of adsorbed water and hydroxyl on the moon

    USGS Publications Warehouse

    Clark, R.N.

    2009-01-01

    Data from the Visual and Infrared Mapping Spectrometer (VIAAS) on Cassini during its flyby of the AAoon in 1999 show a broad absorption at 3 micrometers due to adsorbed water and near 2.8 micrometers attributed to hydroxyl in the sunlit surface on the AAoon. The amounts of water indicated in the spectra depend on the type of mixing and the grain sizes in the rocks and soils but could be 10 to 1000 parts per million and locally higher. Water in the polar regions may be water that has migrated to the colder environments there. Trace hydroxyl is observed in the anorthositic highlands at lower latitudes.

  19. Determinants of regioselective hydroxylation in the fungal polysaccharide monooxygenases.

    PubMed

    Vu, Van V; Beeson, William T; Phillips, Christopher M; Cate, Jamie H D; Marletta, Michael A

    2014-01-15

    The ubiquitous fungal polysaccharide monooxygenases (PMOs) (also known as GH61 proteins, LPMOs, and AA9 proteins) are structurally related but have significant variation in sequence. A heterologous expression method in Neurospora crassa was developed as a step toward connecting regioselectivity of the chemistry to PMO phylogeny. Activity assays, as well as sequence and phylogenetic analyses, showed that the majority of fungal PMOs fall into three major groups with distinctive active site surface features. PMO1s and PMO2s hydroxylate glycosidic positions C1 and C4, respectively. PMO3s hydroxylate both C1 and C4. A subgroup of PMO3s (PMO3*) hydroxylate C1. Mutagenesis studies showed that an extra subdomain of about 12 amino acids contribute to C4 oxidation in the PMO3 family. PMID:24350607

  20. Sulfur Dioxide Capture by Heterogeneous Oxidation on Hydroxylated Manganese Dioxide.

    PubMed

    Wu, Haodong; Cai, Weimin; Long, Mingce; Wang, Hairui; Wang, Zhiping; Chen, Chen; Hu, Xiaofang; Yu, Xiaojuan

    2016-06-01

    Here we demonstrate that sulfur dioxide (SO2) is efficiently captured via heterogeneous oxidation into sulfate on the surface of hydroxylated manganese dioxide (MnO2). Lab-scale activity tests in a fluidized bed reactor showed that the removal efficiency for a simulated flue gas containing 5000 mg·Nm(-3) SO2 could reach nearly 100% with a GHSV (gas hourly space velocity) of 10000 h(-1). The mechanism was investigated using a combination of experimental characterizations and theoretical calculations. It was found that formation of surface bound sulfate proceeds via association of SO2 with terminal hydroxyls. Both H2O and O2 are essential for the generation of reactive terminal hydroxyls, and the indirect role of O2 in heterogeneous SO2 oxidation at low temperature was also revealed. We propose that the high reactivity of terminal hydroxyls is attributed to the proper surface configuration of MnO2 to adsorb water with degenerate energies for associative and dissociative states, and maintain rapid proton dynamics. Viability analyses suggest that the desulfurization method that is based on such a direct oxidation reaction at the gas/solid interface represents a promising approach for SO2 capture. PMID:27123922

  1. Diversity and abundance of n-alkane-degrading bacteria in the near-surface soils of a Chinese onshore oil and gas field

    NASA Astrophysics Data System (ADS)

    Xu, K.; Tang, Y.; Ren, C.; Zhao, K.; Sun, Y.

    2013-03-01

    Alkane-degrading bacteria have long been used as an important biological indicator for oil and gas prospecting, but their ecological characteristics in hydrocarbon microseep habitats are still poorly understood. In this study, the diversity and abundance of n-alkane-degrading bacterial community in the near-surface soils of a Chinese onshore oil and gas field were investigated using molecular techniques. Terminal restriction fragment length polymorphism (T-RFLP) analyses in combination with cloning and sequencing of alkB genes revealed that Gram-negative genotypes (Alcanivorax and Acinetobacter) dominated n-alkane-degrading bacterial communities in the near-surface soils of oil and gas reservoirs, while the dominant microbial communities were Gram-positive bacteria (Mycobacterium and Rhodococcus) in background soil. Real-time quantitative polymerase chain reaction (PCR) results furthermore showed that the abundance of alkB genes increased substantially in the surface soils above oil and gas reservoirs even though only low or undetectable concentrations of hydrocarbons were measured in these soils. The results of this study implicate that trace amounts of volatile hydrocarbons migrate from oil and gas reservoirs, and likely result in the changes of microbial communities in the near-surface soil.

  2. Driving factors behind the distribution of dinocyst composition and abundance in surface sediments in a western Mediterranean coastal lagoon: report from a high resolution mapping study.

    PubMed

    Fertouna-Bellakhal, Mouna; Dhib, Amel; Béjaoui, Béchir; Turki, Souad; Aleya, Lotfi

    2014-07-15

    Species composition and abundance of dinocysts in relation to environmental factors were studied at 123 stations of surface sediment in Bizerte Lagoon. Forty-eight dinocyst types were identified, mainly dominated by Brigantidinium simplex, Votadinum spinosum, Alexandrium pseudogonyaulax, Alexandrium catenella, and Lingulodinum machaerophorum along with many round brown cysts and spiny round brown cysts. Cysts ranged from 1276 to 20126 cysts g(-1)dry weight sediment. Significant differences in cyst distribution pattern were recorded among the zones, with a higher cyst abundance occurring in the lagoon's inner areas. Redundancy analyses showed two distinct associations of dinocysts according to location and environmental variables. Ballast water discharges are potential introducers of non-indigenous species, especially harmful ones such as A. catenella and Polysphaeridium zoharyi, with currents playing a pivotal role in cyst distribution. Findings concerning harmful cyst species indicate potential seedbeds for initiation of future blooms and outbreaks of potentially toxic species in the lagoon. PMID:24841716

  3. Climate Impacts on Tropospheric Ozone and Hydroxyl

    NASA Technical Reports Server (NTRS)

    Shindell, Drew T.; Bell, N.; Faluvegi, G.

    2003-01-01

    Climate change may influence tropospheric ozone and OH via several main pathways: (1) altering chemistry via temperature and humidity changes, (2) changing ozone and precursor sources via surface emissions, stratosphere-troposphere exchange, and light- ning, and (3) affecting trace gas sinks via the hydrological cycle and dry deposition. We report results from a set of coupled chemistry-climate model simulations designed to systematically study these effects. We compare the various effects with one another and with past and projected future changes in anthropogenic and natural emissions of ozone precursors. We find that white the overall impact of climate on ozone is probably small compared to emission changes, some significant seasonal and regional effects are apparent. The global effect on hydroxyl is quite large, however, similar in size to the effect of emission changes. Additionally, we show that many of the chemistry-climate links that are not yet adequately modeled are potentially important.

  4. Soybean extracts increase cell surface ZIP4 abundance and cellular zinc levels: a potential novel strategy to enhance zinc absorption by ZIP4 targeting.

    PubMed

    Hashimoto, Ayako; Ohkura, Katsuma; Takahashi, Masakazu; Kizu, Kumiko; Narita, Hiroshi; Enomoto, Shuichi; Miyamae, Yusaku; Masuda, Seiji; Nagao, Masaya; Irie, Kazuhiro; Ohigashi, Hajime; Andrews, Glen K; Kambe, Taiho

    2015-12-01

    Dietary zinc deficiency puts human health at risk, so we explored strategies for enhancing zinc absorption. In the small intestine, the zinc transporter ZIP4 functions as an essential component of zinc absorption. Overexpression of ZIP4 protein increases zinc uptake and thereby cellular zinc levels, suggesting that food components with the ability to increase ZIP4 could potentially enhance zinc absorption via the intestine. In the present study, we used mouse Hepa cells, which regulate mouse Zip4 (mZip4) in a manner indistinguishable from that in intestinal enterocytes, to screen for suitable food components that can increase the abundance of ZIP4. Using this ZIP4-targeting strategy, two such soybean extracts were identified that were specifically able to decrease mZip4 endocytosis in response to zinc. These soybean extracts also effectively increased the abundance of apically localized mZip4 in transfected polarized Caco2 and Madin-Darby canine kidney cells and, moreover, two apically localized mZip4 acrodermatitis enteropathica mutants. Soybean components were purified from one extract and soyasaponin Bb was identified as an active component that increased both mZip4 protein abundance and zinc levels in Hepa cells. Finally, we confirmed that soyasaponin Bb is capable of enhancing cell surface endogenous human ZIP4 in human cells. Our results suggest that ZIP4 targeting may represent a new strategy to improve zinc absorption in humans. PMID:26385990

  5. Seed banks in a degraded desert shrubland: Influence of soil surface condition and harvester ant activity on seed abundance

    USGS Publications Warehouse

    DeFalco, L.A.; Esque, T.C.; Kane, J.M.; Nicklas, M.B.

    2009-01-01

    We compared seed banks between two contrasting anthropogenic surface disturbances (compacted, trenched) and adjacent undisturbed controls to determine whether site condition influences viable seed densities of perennial and annual Mojave Desert species. Viable seeds of perennials were rare in undisturbed areas (3-4 seeds/m2) and declined to <1 seed/m2 within disturbed sites. Annual seed densities were an order of magnitude greater than those of perennials, were one-third the undisturbed seed densities on compacted sites, but doubled on trenched sites relative to controls. On trenched sites, greater litter cover comprising the infructescences of the dominant spring annuals, and low gravel content, enhanced seed densities of both annuals and perennials. Litter cover and surface ruggedness were the best explanations for viable perennial seed densities on compacted sites, but litter cover and the presence of a common harvester ant explained annual seed densities better than any other surface characteristics that were examined. Surface disturbances can have a varied impact on the condition of the soil surface in arid lands. Nevertheless, the consistently positive relationship between ground cover of litter and viable seed density emphasizes the importance of litter as an indicator of site degradation and recovery potential in arid lands.

  6. Pumping the stellar hydroxyl maser

    NASA Technical Reports Server (NTRS)

    Dickinson, Dale F.

    1987-01-01

    IRAS far-IR flux data for 163 OH maser stars were analyzed to quantify the contributions 35 and 53 microns inversions make to pumping of the hydroxyl maser. The 35 microns transition is from the 3,3 ground state to the 1,5 rotationally excited level and subsequent decay; the 53 microns transition is a change from the ground state to the 1,3 excited level and relaxation. The stars examined included Mira, short period semi-regular and long-period semi-regular variables. Both transition lines had rough parity in contributing to the approximately 8 percent pumping efficiency at 1612 MHz. However, the individual contributions of the lines could not be determined for the stellar population studied.

  7. Pt-M (M = Cu, Fe, Zn, etc.) bimetallic nanomaterials with abundant surface defects and robust catalytic properties.

    PubMed

    Mao, Junjie; Chen, Yuanjun; Pei, Jiajing; Wang, Dingsheng; Li, Yadong

    2016-05-21

    Herein, we exploit two typical crystal growth modes, namely, "stacking" and "carving" routes, to synthesize Pt-based bimetallic nanomaterials with defect-rich surface structures, which exhibit enhanced electrocatalytic properties toward both methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) compared with commercial Pt/C. PMID:27063415

  8. A Clue to the Extent of Convective Mixing Inside Massive Stars: The Surface Hydrogen Abundances of Luminous Blue Variables and Hydrogen-Poor Wolf-Rayet Stars

    NASA Technical Reports Server (NTRS)

    Stothers, Richard B.; Chin, Chao-wen

    1999-01-01

    Interior layers of stars that have been exposed by surface mass loss reveal aspects of their chemical and convective histories that are otherwise inaccessible to observation. It must be significant that the surface hydrogen abundances of luminous blue variables (LBVs) show a remarkable uniformity, specifically X(sub surf) = 0.3 - 0.4, while those of hydrogen-poor Wolf-Rayet (WN) stars fall, almost without exception, below these values, ranging down to X(sub surf) = 0. According to our stellar model calculations, most LBVs are post-red-supergiant objects in a late blue phase of dynamical instability, and most hydrogen-poor WN stars are their immediate descendants. If this is so, stellar models constructed with the Schwarzschild (temperature-gradient) criterion for convection account well for the observed hydrogen abundances, whereas models built with the Ledoux (density-gradient) criterion fail. At the brightest luminosities, the observed hydrogen abundances of LBVs are too large to be explained by any of our highly evolved stellar models, but these LBVs may occupy transient blue loops that exist during an earlier phase of dynamical instability when the star first becomes a yellow supergiant. Independent evidence concerning the criterion for convection, which is based mostly on traditional color distributions of less massive supergiants on the Hertzsprung-Russell diagram, tends to favor the Ledoux criterion. It is quite possible that the true criterion for convection changes over from something like the Ledoux criterion to something like the Schwarzschild criterion as the stellar mass increases.

  9. Diversity and abundance of n-alkane degrading bacteria in the near surface soils of a Chinese onshore oil and gas field

    NASA Astrophysics Data System (ADS)

    Xu, K.; Tang, Y.; Ren, C.; Zhao, K.; Sun, Y.

    2012-10-01

    Alkane degrading bacteria have long been used as an important biological indicator for oil and gas prospecting, but their ecological characteristics in hydrocarbon microseep habitats are still poorly understood. In this study, the diversity and abundance of n-alkane degrading bacterial community in the near surface soils of a Chinese onshore oil and gas field were investigated using molecular techniques. Terminal restriction fragment length polymorphism (T-RFLP) analyses in combination with cloning and sequencing of alkB genes revealed that trace amount of volatile hydrocarbons migrated from oil and gas reservoirs caused a shift of the n-alkane degrading bacterial community from Gram-positive bacteria (Mycobacterium and Rhodococcus) to Gram-negative genotypes (Alcanivorax and Acinetobacter). Real-time PCR results furthermore showed that the abundance of alkB genes increased substantially in the surface soils underlying oil and gas reservoirs even though only low or undetectable concentrations of hydrocarbons were measured in these soils due to efficient microbial degradation. Our findings broadened the knowledge on the ecological characteristics of alkane degrading community in hydrocarbon microseeps and may provide a new approach for microbial prospecting for oil and gas (MPOG).

  10. Generation of hydroxyl radicals from metal-loaded humic acids

    SciTech Connect

    Paciolla, M.D.; Jansen, S.A.; Davies, G.

    1999-06-01

    Humic acids (HAs) are naturally occurring biopolymers that are ubiquitous in the environment. They are most commonly found in the soil, drinking water, and a variety of plants. Pharmacological and therapeutic studies involving humic acids have been reported to some extent. However, when certain transition metals are bound to humic acids, e.g., iron and copper, they can be harmful to biological organisms. For this study, humic acids were extracted from German, Irish, and New Hampshire soils that were selectively chosen because of their reich abundance in humic material. Each sample was treated at room temperature with 0.1 M ferric and cupric solutions for 48 h. The amount of iron and copper adsorbed by humic acid was accurately quantitated using atomic absorption spectroscopy. The authors further demonstrate that these metal-loaded humic acids can produce deleterious oxidizing species such as the hydroxyl radical (HO*) through the metal-driven Fenton reaction. Electron paramagnetic resonance (EPR) employing spin trapping techniques with 5,5-dimethylpyrroline N-oxide (DMPO) is used to confirm the generation of hydroxyl radicals. The DMPO-OH adduct with hyperfine splitting constants A{sub N} = A{sub H} = 14.9 G is observed upon the addition of exogenous hydrogen peroxide. The concentration of hydroxyl radical was determined using 4-hydroxytempo (TEMPO-OH) as a spin standard. The presence of another oxidizing species, Fe{double_bond}O{sup 2+}, is also proposed in the absence of hydrogen peroxide.

  11. An abundantly expressed mucin-like protein from Toxocara canis infective larvae: the precursor of the larval surface coat glycoproteins.

    PubMed Central

    Gems, D; Maizels, R M

    1996-01-01

    Evasion of host immunity by Toxocara canis infective larvae is mediated by the nematode surface coat, which is shed in response to binding by host antibody molecules or effector cells. The major constituent of the coat is the TES-120 glycoprotein series. We have isolated a 730-bp cDNA from the gene encoding the apoprotein precursor of TES-120. The mRNA is absent from T. canis adults but hyperabundant in larvae, making up approximately 10% of total mRNA, and is trans-spliced with the nematode 5' leader sequence SL1. It encodes a 15.8-kDa protein (after signal peptide removal) containing a typical mucin domain: 86 amino acid residues, 72.1% of which are Ser or Thr, organized into an array of heptameric repeats, interspersed with proline residues. At the C-terminal end of the putative protein are two 36-amino acid repeats containing six Cys residues, in a motif that can also be identified in several genes in Caenorhabditis elegans. Although TES-120 displays size and charge heterogeneity, there is a single copy gene and a homogeneous size of mRNA. The association of overexpression of some membrane-associated mucins with immunosuppression and tumor metastasis suggests a possible model for the role of the surface coat in immune evasion by parasitic nematodes. Images Fig. 1 Fig. 4 PMID:8643687

  12. Abundance, stock origin, and length of marked and unmarked juvenile Chinook salmon in the surface waters of greater Puget Sound

    USGS Publications Warehouse

    Rice, C.A.; Greene, C.M.; Moran, P.; Teel, D.J.; Kuligowski, D.R.; Reisenbichler, R.R.; Beamer, E.M.; Karr, J.R.; Fresh, K.L.

    2011-01-01

    This study focuses on the use by juvenile Chinook salmon Oncorhynchus tshawytscha of the rarely studied neritic environment (surface waters overlaying the sublittoral zone) in greater Puget Sound. Juvenile Chinook salmon inhabit the sound from their late estuarine residence and early marine transition to their first year at sea. We measured the density, origin, and size of marked (known hatchery) and unmarked (majority naturally spawned) juveniles by means of monthly surface trawls at six river mouth estuaries in Puget Sound and the areas in between. Juvenile Chinook salmon were present in all months sampled (April-November). Unmarked fish in the northern portion of the study area showed broader seasonal distributions of density than did either marked fish in all areas or unmarked fish in the central and southern portions of the sound. Despite these temporal differences, the densities of marked fish appeared to drive most of the total density estimates across space and time. Genetic analysis and coded wire tag data provided us with documented individuals from at least 16 source populations and indicated that movement patterns and apparent residence time were, in part, a function of natal location and time passed since the release of these fish from hatcheries. Unmarked fish tended to be smaller than marked fish and had broader length frequency distributions. The lengths of unmarked fish were negatively related to the density of both marked and unmarked Chinook salmon, but those of marked fish were not. These results indicate more extensive use of estuarine environments by wild than by hatchery juvenile Chinook salmon as well as differential use (e.g., rearing and migration) of various geographic regions of greater Puget Sound by juvenile Chinook salmon in general. In addition, the results for hatchery-generated timing, density, and length differences have implications for the biological interactions between hatchery and wild fish throughout Puget Sound. ?? American

  13. Microbial communities on glacier surfaces in Svalbard: impact of physical and chemical properties on abundance and structure of cyanobacteria and algae.

    PubMed

    Stibal, Marek; Sabacká, Marie; Kastovská, Klára

    2006-11-01

    Microbial communities occurring in three types of supraglacial habitats--cryoconite holes, medial moraines, and supraglacial kames--at several glaciers in the Arctic archipelago of Svalbard were investigated. Abundance, biovolume, and community structure were evaluated by using epifluorescence microscopy and culturing methods. Particular emphasis was laid on distinctions in the chemical and physical properties of the supraglacial habitats and their relation to the microbial communities, and quantitative multivariate analyses were used to assess potential relationships. Varying pH (4.8 in cryoconite; 8.5 in a moraine) and texture (the proportion of coarse fraction 2% of dry weight in cryoconite; 99% dw in a kame) were found, and rather low concentrations of organic matter (0.3% of dry weight in a kame; 22% dw in cryoconite) and nutrients (nitrogen up to 0.4% dw, phosphorus up to 0.8% dw) were determined in the samples. In cryoconite sediment, the highest numbers of bacteria, cyanobacteria, and algae were found, whereas relatively low microbial abundances were recorded in moraines and kames. Cyanobacterial cells were significantly more abundant than microalgal ones in cryoconite and supraglacial kames. Different species of the cyanobacterial genus Leptolyngbya were by far the most represented in all samples, and cyanobacteria of the genera Phormidium and Nostoc prevailed in cultures isolated from cryoconite samples. These species are considered opportunistic organisms with wide ecological valency and strong colonizing potential rather than glacial specialists. Statistical analyses suggest that fine sediment with higher water content is the most suitable condition for bacteria, cyanobacteria, and algae. Also, a positive impact of lower pH on microbial growth was found. The fate of a microbial cell deposited on the glacier surface seems therefore predetermined by the physical and chemical factors such as texture of sediment and water content rather than spatial factors

  14. Bacterial metabolism of hydroxylated biphenyls.

    PubMed Central

    Higson, F K; Focht, D D

    1989-01-01

    Isolates able to grow on 3- or 4-hydroxybiphenyl (HB) as the sole carbon source were obtained by enrichment culture. The 3-HB degrader Pseudomonas sp. strain FH12 used an NADPH-dependent monooxygenase restricted to 3- and 3,3'-HBs to introduce an ortho-hydroxyl. The 4-HB degrader Pseudomonas sp. strain FH23 used either a mono- or dioxygenase to generate a 2,3-diphenolic substitution pattern which allowed meta-fission of the aromatic ring. By using 3-chlorocatechol to inhibit catechol dioxygenase activity, it was found that 2- and 3-HBs were converted by FH23 to 2,3-HB, whereas biphenyl and 4-HB were attacked by dioxygenation. 4-HB was metabolized to 2,3,4'-trihydroxybiphenyl. Neither organism attacked chlorinated HBs. The degradation of 3- and 4-HBs by these strains is therefore analogous to the metabolism of biphenyl, 2-HB, and naphthalene in the requirement for 2,3-catechol formation. PMID:2729993

  15. Structure, electronic properties, and aggregation behavior of hydroxylated carbon nanotubes

    SciTech Connect

    López-Oyama, A. B.; Silva-Molina, R. A.; Ruíz-García, J.; Guirado-López, R. A.; Gámez-Corrales, R.

    2014-11-07

    We present a combined experimental and theoretical study to analyze the structure, electronic properties, and aggregation behavior of hydroxylated multiwalled carbon nanotubes (OH–MWCNT). Our MWCNTs have average diameters of ∼2 nm, lengths of approximately 100–300 nm, and a hydroxyl surface coverage θ∼0.1. When deposited on the air/water interface the OH–MWCNTs are partially soluble and the floating units interact and link with each other forming extended foam-like carbon networks. Surface pressure-area isotherms of the nanotube films are performed using the Langmuir balance method at different equilibration times. The films are transferred into a mica substrate and atomic force microscopy images show that the foam like structure is preserved and reveals fine details of their microstructure. Density functional theory calculations performed on model hydroxylated carbon nanotubes show that low energy atomic configurations are found when the OH groups form molecular islands on the nanotube's surface. This patchy behavior for the OH species is expected to produce nanotubes having reduced wettabilities, in line with experimental observations. OH doping yields nanotubes having small HOMO–LUMO energy gaps and generates a nanotube → OH direction for the charge transfer leading to the existence of more hole carriers in the structures. Our synthesized OH–MWCNTs might have promising applications.

  16. Structure, electronic properties, and aggregation behavior of hydroxylated carbon nanotubes

    NASA Astrophysics Data System (ADS)

    López-Oyama, A. B.; Silva-Molina, R. A.; Ruíz-García, J.; Gámez-Corrales, R.; Guirado-López, R. A.

    2014-11-01

    We present a combined experimental and theoretical study to analyze the structure, electronic properties, and aggregation behavior of hydroxylated multiwalled carbon nanotubes (OH-MWCNT). Our MWCNTs have average diameters of ˜2 nm, lengths of approximately 100-300 nm, and a hydroxyl surface coverage θ˜0.1. When deposited on the air/water interface the OH-MWCNTs are partially soluble and the floating units interact and link with each other forming extended foam-like carbon networks. Surface pressure-area isotherms of the nanotube films are performed using the Langmuir balance method at different equilibration times. The films are transferred into a mica substrate and atomic force microscopy images show that the foam like structure is preserved and reveals fine details of their microstructure. Density functional theory calculations performed on model hydroxylated carbon nanotubes show that low energy atomic configurations are found when the OH groups form molecular islands on the nanotube's surface. This patchy behavior for the OH species is expected to produce nanotubes having reduced wettabilities, in line with experimental observations. OH doping yields nanotubes having small HOMO-LUMO energy gaps and generates a nanotube → OH direction for the charge transfer leading to the existence of more hole carriers in the structures. Our synthesized OH-MWCNTs might have promising applications.

  17. Structure, electronic properties, and aggregation behavior of hydroxylated carbon nanotubes.

    PubMed

    López-Oyama, A B; Silva-Molina, R A; Ruíz-García, J; Gámez-Corrales, R; Guirado-López, R A

    2014-11-01

    We present a combined experimental and theoretical study to analyze the structure, electronic properties, and aggregation behavior of hydroxylated multiwalled carbon nanotubes (OH-MWCNT). Our MWCNTs have average diameters of ~2 nm, lengths of approximately 100-300 nm, and a hydroxyl surface coverage θ~0.1. When deposited on the air/water interface the OH-MWCNTs are partially soluble and the floating units interact and link with each other forming extended foam-like carbon networks. Surface pressure-area isotherms of the nanotube films are performed using the Langmuir balance method at different equilibration times. The films are transferred into a mica substrate and atomic force microscopy images show that the foam like structure is preserved and reveals fine details of their microstructure. Density functional theory calculations performed on model hydroxylated carbon nanotubes show that low energy atomic configurations are found when the OH groups form molecular islands on the nanotube's surface. This patchy behavior for the OH species is expected to produce nanotubes having reduced wettabilities, in line with experimental observations. OH doping yields nanotubes having small HOMO-LUMO energy gaps and generates a nanotube → OH direction for the charge transfer leading to the existence of more hole carriers in the structures. Our synthesized OH-MWCNTs might have promising applications. PMID:25381534

  18. Oxygen availability and distance to surface environments determine community composition and abundance of ammonia-oxidizing prokaroytes in two superimposed pristine limestone aquifers in the Hainich region, Germany.

    PubMed

    Opitz, Sebastian; Küsel, Kirsten; Spott, Oliver; Totsche, Kai Uwe; Herrmann, Martina

    2014-10-01

    We followed the abundance and compared the diversity of ammonia-oxidizing archaea (AOA) and bacteria (AOB) in the groundwater of two superimposed pristine limestone aquifers located in the Hainich region (Thuringia, Germany) over 22 months. Groundwater obtained from the upper aquifer (12 m depth) was characterized by low oxygen saturation (0-20%) and low nitrate concentrations (0-20 μM), contrasting with 50-80% oxygen saturation and 40-200 μM nitrate in the lower aquifer (48 m and 88 m depth). Quantitative PCR targeting bacterial and archaeal amoA and 16S rRNA genes suggested a much higher ammonia oxidizer fraction in the lower aquifer (0.4-7.8%) compared with the upper aquifer (0.01-0.29%). In both aquifers, AOB communities were dominated by one phylotype related to Nitrosomonas ureae, while AOA communities were more diverse. Multivariate analysis of amoA DGGE profiles revealed a stronger temporal variation of AOA and AOB community composition in the upper aquifer, pointing to a stronger influence of surface environments. Parallel fluctuations of AOA, AOB, and total microbial abundance suggested that hydrological factors (heavy rain falls, snow melt) rather than specific physicochemical parameters were responsible for the observed community dynamics. PMID:24953994

  19. On the Crimea-Texas project "Surface abundances of light elements for a large sample of early B-type stars".

    NASA Astrophysics Data System (ADS)

    Lyubimkov, L. S.

    2002-12-01

    A significant part of the project is already implemented. Actually, high-resolution spectra of more than 100 early B stars were obtained. A number of basic parameters was determined including the effective temperatures Teff , surface gravities log g, masses M, ages t etc. A detailed non-LTE analysis of HeI lines was effected to find the helium abundance He/H, microturbulent parameter Vt and rotational velocity v sin i . Relations between He/H and Vt , from the one hand, and M, t/tms and v sin i , from the other hand, were constructed. It was confirmed that there is the helium enrichment during the MS phase, which correlates with the masses M and rotational velocities v sin i . It is necessary to note that from the outset we tried to get a highest accuracy on each stage of this work. At present we are implementing a last stage of the project, i.e. an analysis of CII, NII and OII lines on the basis of non-LTE computations. Our goal is an accurate determination of the C, N and O abundances and a search for correlations with M, t/tms and v sin i.

  20. The relative abundance and seasonal distribution correspond with the sources of polycyclic aromatic hydrocarbons (PAHs) in the surface sediments of Chenab River, Pakistan.

    PubMed

    Hussain, Imran; Syed, Jabir Hussain; Kamal, Atif; Iqbal, Mehreen; Eqani, Syed-Ali-Mustjab-Akbar-Shah; Bong, Chui Wei; Taqi, Malik Mumtaz; Reichenauer, Thomas G; Zhang, Gan; Malik, Riffat Naseem

    2016-06-01

    Chenab River is one of the most important rivers of Punjab Province (Pakistan) that receives huge input of industrial effluents and municipal sewage from major cities in the Central Punjab, Pakistan. The current study was designed to evaluate the concentration levels and associated ecological risks of USEPA priority polycyclic aromatic hydrocarbons (PAHs) in the surface sediments of Chenab River. Sampling was performed from eight (n = 24) sampling stations of Chenab River and its tributaries. We observed a relatively high abundance of ∑16PAHs during the summer season (i.e. 554 ng g(-1)) versus that in the winter season (i.e. 361 ng g(-1)), with an overall abundance of two-, five- and six-ring PAH congeners. Results also revealed that the nitrate and phosphate contents in the sediments were closely associated with low molecular weight (LMW) and high molecular weight (HMW) PAHs, respectively. Source apportionment results showed that the combustion of fossil fuels appears to be the key source of PAHs in the study area. The risk quotient (RQ) values indicated that seven PAH congeners (i.e. phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)pyrene, chrysene and benzo(a)anthracene) could pose serious threats to the aquatic life of the riverine ecosystem in Pakistan. PMID:27234513

  1. A 3D general circulation model for Pluto and Triton with fixed volatile abundance and simplified surface forcing

    NASA Astrophysics Data System (ADS)

    Zalucha, Angela M.; Michaels, Timothy I.

    2013-04-01

    We present a 3D general circulation model of Pluto and Triton's atmospheres, which uses radiative-conductive-convective forcing. In both the Pluto and Triton models, an easterly (prograde) jet is present at the equator with a maximum magnitude of 10-12 m s-1 and 4 m s-1, respectively. Neither atmosphere shows any significant overturning circulation in the meridional and vertical directions. Rather, it is horizontal motions (mean circulation and transient waves) that transport heat meridionally at a magnitude of 1 and 3 × 107 W at Pluto's autumn equinox and winter solstice, respectively (seasons referenced to the Northern Hemisphere). The meridional and dayside-nightside temperature contrast is small (⩽5 K). We find that the lack of vertical motion can be explained on Pluto by the strong temperature inversion in the lower atmosphere. The height of the Voyager 2 plumes on Triton can be explained by the dynamical properties of the lower atmosphere alone (i.e., strong wind shear) and does not require a thermally defined troposphere (i.e., temperature decreasing with height at the surface underlying a region of temperature increasing with height). The model results are compared with Pluto stellar occultation light curve data from 1988, 2002, 2006, and 2007 and Triton light curve data from 1997.

  2. Hydroxyl functionalized thermosensitive microgels with quadratic crosslinking density distribution.

    PubMed

    Elmas, Begum; Tuncel, Murvet; Senel, Serap; Patir, S; Tuncel, Ali

    2007-09-01

    N-isopropylacrylamide (NIPA) based uniform thermosensitive microgels were synthesized by dispersion polymerization by using relatively hydrophilic crosslinking agents with hydroxyl functionality. Glycerol dimethacrylate (GDMA), pentaerythritol triacrylate (PETA) and pentaerythritol propoxylate triacrylate (PEPTA) were used as crosslinking agents with different hydrophilicities. A protocol was first proposed to determine the crosslinking density distribution in the thermosensitive microgel particles by confocal laser scanning microscopy (CLSM). The microgels were fluorescently labeled by using hydroxyl group of the crosslinking agent. The CLSM observations performed with the microgels synthesized by three different crosslinking agents showed that the crosslinking density exhibited a quadratic decrease with the increasing radial distance in the spherical microgel particles. This structure led to the formation of more loose gel structure on the particle surface with respect to the center. Then the use of hydrophilic crosslinking agents in the dispersion polymerization of NIPA made possible the synthesis of thermosensitive microgels carrying long, flexible and chemically derivatizable (i.e., hydroxyl functionalized) fringes on the surface by a single-stage dispersion polymerization. The microgels with all crosslinking agents exhibited volume phase transition with the increasing temperature. The microgel obtained by the most hydrophilic crosslinking agent, GDMA exhibited higher hydrodynamic diameters in the fully swollen form at low temperatures than those obtained by PETA and PEPTA. Higher hydrodynamic size decrease from fully swollen form to the fully shrunken form was also observed with the same microgel. PMID:17532327

  3. HETEROGENOUS PHOTOREACTION OF FORMALDEHYDE WITH HYDROXYL RADICALS

    EPA Science Inventory

    Atmospheric heterogeneous photoreactions occur between formaldehyde and hydroxyl radicals to produce formic acid. hese photoreactions not only occur in clouds, but also in other tropospheric hydrometeors such as precipitation and dew droplets. xperiments were performed by irradia...

  4. Steroid and sterol 7-hydroxylation: ancient pathways.

    PubMed

    Lathe, Richard

    2002-11-01

    B-ring hydroxylation is a major metabolic pathway for cholesterols and some steroids. In liver, 7 alpha-hydroxylation of cholesterols, mediated by CYP7A and CYP39A1, is the rate-limiting step of bile acid synthesis and metabolic elimination. In brain and other tissues, both sterols and some steroids including dehydroepiandrosterone (DHEA) are prominently 7 alpha-hydroxylated by CYP7B. The function of extra-hepatic steroid and sterol 7-hydroxylation is unknown. Nevertheless, 7-oxygenated cholesterols are potent regulators of cell proliferation and apoptosis; 7-oxygenated derivatives of DHEA, pregnenolone, and androstenediol can have major effects in the brain and in the immune system. The receptor targets involved remain obscure. It is argued that B-ring modification predated steroid evolution: non-enzymatic oxidation of membrane sterols primarily results in 7-oxygenation. Such molecules may have provided early growth and stress signals; a relic may be found in hydroxylation at the symmetrical 11-position of glucocorticoids. Early receptor targets probably included intracellular sterol sites, some modern steroids may continue to act at these targets. 7-Hydroxylation of DHEA may reflect conservation of an early signaling pathway. PMID:12398993

  5. Molecular Investigation of the Short-term Sequestration of Natural Abundance 13C -labelled Cow Dung in the Surface Horizons of a Temperate Grassland Soil

    NASA Astrophysics Data System (ADS)

    Dungait, J.; Bol, R.; Evershed, R. P.

    2004-12-01

    An adequate understanding of the carbon (C) sequestration potential of grasslands requires that the quantity and residence times of C inputs be measured. Herbivore dung is largely comprised of plant cell wall material, a significant source of stable C in intensively grazed temperate grassland ecosystems that contributes to the soil carbon budget. Our work uses compound-specific isotope analysis to identify the pattern of input of dung-derived compounds from natural abundance 13C/-labelled cow dung into the surface horizons of a temperate grassland soil over one year. C4 dung (δ 13C \\-12.6 ‰ ) from maize fed cows was applied to a temperate grassland surface (δ 13C \\-29.95 ‰ ) at IGER-North Wyke (Devon, UK), and dung remains and soil cores beneath the treatments collected at ŧ = 7, 14, 28, 56, 112, 224 and 372 days. Bulk dung carbon present in the 0\\-1 cm and 1\\-5 cm surface horizons of a grassland soil over one year was estimated using Δ 13C between C4 dung and C3 dung, after Bol {\\et al.} (2000). The major biochemical components of dung were quantified using proximate forage fibre analyses, after Goering and Van Soest (1970) and identified using `wet' chemical and GC-MS methods. Plant cell wall polysaccharides and lignin were found to account for up to 67 {%} of dung dry matter. Hydrolysed polysaccharides were prepared as alditol acetates for analyses (after Docherty {\\et al.}, 2001), and a novel application of an off-line pyrolysis method applied to measure lignin-derived phenolic compounds (after Poole & van Bergen, 2002). This paper focuses on major events in the incorporation of dung carbon, estimated using natural abundance 13C&-slash;labelling technique. This revealed a major bulk input of dung carbon after a period of significant rainfall with a consequent decline in bulk soil δ 13C values until the end of the experiment (Dungait {\\et al.}, submitted). Findings will be presented revealing contribution of plant cell wall polysaccharides and

  6. Hydroxyl Radical Generation from Environmentally Persistent Free Radicals (EPFRs) in PM2.5

    PubMed Central

    Gehling, William; Khachatryan, Lavrent; Dellinger, Barry

    2015-01-01

    Hydroxyl radicals were generated from an aqueous suspension of ambient PM2.5 and detected utilizing 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin trap coupled with electron paramagnetic resonance (EPR) spectroscopy. Results from this study suggested the importance of environmentally persistent free radicals (EPFRs) in PM2.5 to generate significant levels of ·OH without the addition of H2O2. Particles for which the EPFRs were allowed to decay over time induced less hydroxyl radical. Additionally, higher particle concentrations produced more hydroxyl radical. Some samples did not alter hydroxyl radical generation when the solution was purged by air. This is ascribed to internal, rather than external surface associated EPFRs. PMID:24004313

  7. Hydroxyl radical oxidation of feruloylated arabinoxylan.

    PubMed

    Bagdi, Attila; Tömösközi, Sándor; Nyström, Laura

    2016-11-01

    Feruloylated arabinoxylan (AX) has a unique capacity to form covalent gels in the presence of certain oxidizing agents. The present study demonstrates that hydroxyl radical oxidation does not provoke ferulic acid dimerization and thus oxidative gelation. We studied the hydroxyl radical mediated oxidation of an alkali-extracted AX preparation (purity: 92g/100g dry matter) that showed gel-forming capability upon peroxidase/hydrogen peroxide treatment. Hydroxyl radicals were produced with ascorbate-driven Fenton reaction and the radical formation was monitored with electron paramagnetic resonance, using a POBN/EtOH spin trapping system. Oxidation was carried out at different catalytic concentrations of iron (50 and 100μM) and at different temperatures (20°C, 50°C, and 80°C). It was demonstrated that hydroxyl radical oxidation does not provoke gel formation, but viscosity decrease in AX solution, which suggests polymer degradation. Furthermore, it was demonstrated that hydroxyl radical formation in AX solution can be initiated merely by increasing temperature. PMID:27516272

  8. Stage-specific binding of Leishmania donovani to the sand fly vector midgut is regulated by conformational changes in the abundant surface lipophosphoglycan.

    PubMed

    Sacks, D L; Pimenta, P F; McConville, M J; Schneider, P; Turco, S J

    1995-02-01

    The life cycle of Leishmania parasites within the sand fly vector includes the development of extracellular promastigotes from a noninfective, procyclic stage into an infective, metacyclic stage that is uniquely adapted for transmission by the fly and survival in the vertebrate host. These adaptations were explored in the context of the structure and function of the abundant surface lipophosphoglycan (LPG) on Leishmania donovani promastigotes. During metacyclogenesis, the salient structural feature of L. donovani LPG is conserved, involving expression of a phosphoglycan chain made up of unsubstituted disaccharide-phosphate repeats. Two important developmental modifications were also observed. First, the size of the molecule is substantially increased because of a twofold increase in the number of phosphorylated disaccharide repeat units expressed. Second, there is a concomitant decrease in the presentation of terminally exposed sugars. This later property was indicated by the reduced accessibility of terminal galactose residues to galactose oxidase and the loss of binding by the lectins, peanut agglutinin, and concanavalin A, to metacyclic LPG in vivo and in vitro. The loss of lectin binding was not due to downregulation of the capping oligosaccharides as the same beta-linked galactose or alpha-linked mannose-terminating oligosaccharides were present in both procyclic and metacyclic promastigotes. The capping sugars on procyclic LPG were found to mediate procyclic attachment to the sand fly midgut, whereas these same sugars on metacyclic LPG failed to mediate metacyclic binding. And whereas intact metacyclic LPG did not inhibit procyclic attachment, depolymerized LPG inhibited as well as procyclic LPG, demonstrating that the ligands are normally buried. The masking of the terminal sugars is attributed to folding and clustering of the extended phosphoglycan chains, which form densely distributed particulate structures visible on fracture-flip preparations of the

  9. Horseradish peroxidase catalyzed hydroxylations: mechanistic studies.

    PubMed

    Dordick, J S; Klibanov, A M; Marletta, M A

    1986-05-20

    The hydroxylation of phenol to hydroquinone and catechol in the presence of dihydroxyfumaric acid and oxygen catalyzed by horseradish peroxidase was studied under conditions where the product yield was high and the side reactions were minimal. The reaction is partially uncoupled with a molar ratio of dihydroxyfumaric acid consumed to hydroxylated products of 12:1. Hydrogen peroxide does not participate in the reaction as evidenced by the lack of effect of catalase and by the direct addition of hydrogen peroxide. Conversely, superoxide and hydroxyl radicals are involved as their scavengers are potent inhibitors. Experiments were all consistent with the involvement of compound III (oxygenated ferrous complex) of peroxidase in the reaction. Compound III is stable in the presence of phenol alone but decomposes rapidly in the presence of both phenol and dihydroxyfumaric acid with the concomitant formation of product. Therefore, phenol and dihydroxyfumaric acid must be present with compound III in order for the hydroxylation reaction to occur. A mechanism consistent with the experimental results is proposed. PMID:3718931

  10. Hydroxylated PBDEs induce developmental arrest in zebrafish

    SciTech Connect

    Usenko, Crystal Y. Hopkins, David C.; Trumble, Stephen J. Bruce, Erica D.

    2012-07-01

    The ubiquitous spread of polybrominated diphenyl ethers (PBDEs) has led to concerns regarding the metabolites of these congeners, in particular hydroxylated PBDEs. There are limited studies regarding the biological interactions of these chemicals, yet there is some concern they may be more toxic than their parent compounds. In this study three hydroxylated PBDEs were assessed for toxicity in embryonic zebrafish: 3-OH-BDE 47, 5-OH-BDE 47, and 6-OH-BDE 47. All three congeners induced developmental arrest in a concentration-dependent manner; however, 6-OH-BDE 47 induced adverse effects at lower concentrations than the other congeners. Furthermore, all three induced cell death; however apoptosis was not observed. In short-term exposures (24–28 hours post fertilization), all hydroxylated PBDEs generated oxidative stress in the region corresponding to the cell death at 5 and 10 ppm. To further investigate the short-term effects that may be responsible for the developmental arrest observed in this study, gene regulation was assessed for embryos exposed to 0.625 ppm 6-OH-BDE 47 from 24 to 28 hpf. Genes involved in stress response, thyroid hormone regulation, and neurodevelopment were significantly upregulated compared to controls; however, genes related to oxidative stress were either unaffected or downregulated. This study suggests that hydroxylated PBDEs disrupt development, and may induce oxidative stress and potentially disrupt the cholinergic system and thyroid hormone homeostasis. -- Highlights: ► OH-PBDEs induce developmental arrest in a concentration-dependent manner. ► Hydroxyl group location influences biological interaction. ► OH-PBDEs induce oxidative stress. ► Thyroid hormone gene regulation was disrupted following exposure. ► To our knowledge, this is the first whole organism study of OH-PBDE toxicity.

  11. Preparation of ZrO2/Al2O3-montmorillonite composite as catalyst for phenol hydroxylation

    PubMed Central

    Fatimah, Is

    2013-01-01

    Zirconium dispersed in aluminum-pillared montmorillonite was prepared as a catalyst for phenol hydroxylation. The effects of varying the Zr content on the catalyst’s physicochemical character and activity were studied with XRD, BET surface area analysis, surface acidity measurements and scanning electron microscopy before investigating the performance for phenol conversion. The zirconia dispersion significantly affects the specific surface area, the total surface acidity and surface acidity distribution related to the formation of porous zirconia particles on the surface. The prepared samples exhibited excellent catalytic activity during phenol hydroxylation. PMID:25685535

  12. Palaeoceanographic implications of abundance and mean proloculus diameter of benthic foraminiferal species Epistominella exigua in sub-surface sediments from distal Bay of Bengal fan

    NASA Astrophysics Data System (ADS)

    Saraswat, R.; Nigam, R.; Barreto, Lea

    2005-10-01

    Temporal variation in abundance and mean proloculus diameter of the benthic foraminiferal species Epistominella exigua has been reconstructed over the last ˜ 50,000 yr BP, from a core collected from the distal Bay of Bengal fan, to assess its potential application in palaeoceanographic reconstruction studies. The down-core variation shows significant change in abundance of E. exigua during the last ˜ 50,000 yr BP. In view of the present day abundance of this species from areas with strong seasonal organic matter supply, we conclude that at ˜ 7, ˜ 22, ˜ 33 and ˜ 46kyr BP, strong seasonality prevailed in the distal Bay of Bengal fan, probably indicating either strong or prolonged north-east monsoon or weakened south-west monsoon. For the first time, a strong correlation is observed in abundance and mean proloculus diameter of E. exigua. Based on coherent variation in mean proloculus diameter and abundance, it is postulated that mean proloculus diameter can also be used to infer increased seasonality in organic matter production, thus variation in strength or duration of monsoon. Thus, this study establishes that the down-core variation in the abundance and mean proloculus diameter of Epistominella exigua can be used to infer past climatic variations from the distal Bay of Bengal fan.

  13. Aromatic-Hydroxyl Interaction of a Lignin Model Compound on SBA-15, Present at Pyrolysis Temperatures

    DOE PAGESBeta

    Kandziolka, III, Michael V.; Kidder, Michelle; Gill, Lance W.; Wu, Zili; Savara, Aditya Ashi

    2014-07-14

    An aromatic alpha-aryl ether compound (a benzyl phenyl ether analogue) was covalently grafted to mesoporous silica SBA-15, to create BPEa-SBA-15. The BPEa-SBA-15 was subjected to successive heating cycles up to 600 °C, with in situ monitoring by DRIFTS. It was found that the toluene moiety coordinates to SBA-15 surface silanol hydroxyl groups via an aromatic–hydroxyl interaction. This interaction is evidenced by a red-shift of the aromatic C–H stretches, as well as a red-shift and broadening of the surface hydroxyl O–H stretches, which are features characteristic of a hydrogen bond. These features remain present during heating until ~400 °C whereupon themore » ether linkage of BPEa-SBA-15 is cleaved, accompanied by loss of the toluene moiety.« less

  14. Aromatic-Hydroxyl Interaction of a Lignin Model Compound on SBA-15, Present at Pyrolysis Temperatures

    SciTech Connect

    Kandziolka, III, Michael V.; Kidder, Michelle; Gill, Lance W.; Wu, Zili; Savara, Aditya Ashi

    2014-07-14

    An aromatic alpha-aryl ether compound (a benzyl phenyl ether analogue) was covalently grafted to mesoporous silica SBA-15, to create BPEa-SBA-15. The BPEa-SBA-15 was subjected to successive heating cycles up to 600 °C, with in situ monitoring by DRIFTS. It was found that the toluene moiety coordinates to SBA-15 surface silanol hydroxyl groups via an aromatic–hydroxyl interaction. This interaction is evidenced by a red-shift of the aromatic C–H stretches, as well as a red-shift and broadening of the surface hydroxyl O–H stretches, which are features characteristic of a hydrogen bond. These features remain present during heating until ~400 °C whereupon the ether linkage of BPEa-SBA-15 is cleaved, accompanied by loss of the toluene moiety.

  15. Clustering of Oxygen Vacancies at CeO2(111): Critical Role of Hydroxyls.

    PubMed

    Wu, Xin-Ping; Gong, Xue-Qing

    2016-02-26

    By performing density functional theory calculations corrected by an on site Coulomb interaction, we find that the defects at the CeO_{2}(111) surface observed by the scanning tunneling microscopy (STM) measurements of Esch et al. [Science 309, 752 (2005)] are not mere oxygen vacancies or fluorine impurities as suggested by Kullgren et al. [Phys. Rev. Lett. 112, 156102 (2014)], but actually the hydroxyl-vacancy combined species. Specifically, we show that hydroxyls play a critical role in the formation and propagation of oxygen vacancy clusters (VCs). In the presence of neighboring hydroxyls, the thermodynamically unstable VCs can be significantly stabilized, and the behaviors of oxygen vacancies become largely consistent with the STM observations. In addition to the clarification of the long term controversy on the surface defect structures of CeO_{2}(111), the "hydroxyl-vacancy model" proposed in this work emphasizes the coexistence of hydroxyls and oxygen vacancies, especially VCs, which is important for understanding the catalytic and other physicochemical properties of reducible metal oxides. PMID:26967428

  16. Clustering of Oxygen Vacancies at CeO2(111 ) : Critical Role of Hydroxyls

    NASA Astrophysics Data System (ADS)

    Wu, Xin-Ping; Gong, Xue-Qing

    2016-02-01

    By performing density functional theory calculations corrected by an on site Coulomb interaction, we find that the defects at the CeO2(111 ) surface observed by the scanning tunneling microscopy (STM) measurements of Esch et al. [Science 309, 752 (2005)] are not mere oxygen vacancies or fluorine impurities as suggested by Kullgren et al. [Phys. Rev. Lett. 112, 156102 (2014)], but actually the hydroxyl-vacancy combined species. Specifically, we show that hydroxyls play a critical role in the formation and propagation of oxygen vacancy clusters (VCs). In the presence of neighboring hydroxyls, the thermodynamically unstable VCs can be significantly stabilized, and the behaviors of oxygen vacancies become largely consistent with the STM observations. In addition to the clarification of the long term controversy on the surface defect structures of CeO2(111 ) , the "hydroxyl-vacancy model" proposed in this work emphasizes the coexistence of hydroxyls and oxygen vacancies, especially VCs, which is important for understanding the catalytic and other physicochemical properties of reducible metal oxides.

  17. Future Directions of Structural Mass Spectrometry using Hydroxyl Radical Footprinting

    SciTech Connect

    J Kiselar; M Chance

    2011-12-31

    Hydroxyl radical protein footprinting coupled to mass spectrometry has been developed over the last decade and has matured to a powerful method for analyzing protein structure and dynamics. It has been successfully applied in the analysis of protein structure, protein folding, protein dynamics, and protein-protein and protein-DNA interactions. Using synchrotron radiolysis, exposure of proteins to a 'white' X-ray beam for milliseconds provides sufficient oxidative modification to surface amino acid side chains, which can be easily detected and quantified by mass spectrometry. Thus, conformational changes in proteins or protein complexes can be examined using a time-resolved approach, which would be a valuable method for the study of macromolecular dynamics. In this review, we describe a new application of hydroxyl radical protein footprinting to probe the time evolution of the calcium-dependent conformational changes of gelsolin on the millisecond timescale. The data suggest a cooperative transition as multiple sites in different molecular subdomains have similar rates of conformational change. These findings demonstrate that time-resolved protein footprinting is suitable for studies of protein dynamics that occur over periods ranging from milliseconds to seconds. In this review, we also show how the structural resolution and sensitivity of the technology can be improved as well. The hydroxyl radical varies in its reactivity to different side chains by over two orders of magnitude, thus oxidation of amino acid side chains of lower reactivity are more rarely observed in such experiments. Here we demonstrate that the selected reaction monitoring (SRM)-based method can be utilized for quantification of oxidized species, improving the signal-to-noise ratio. This expansion of the set of oxidized residues of lower reactivity will improve the overall structural resolution of the technique. This approach is also suggested as a basis for developing hypothesis

  18. Hydroxyl Motion in Mg(OH)2

    NASA Astrophysics Data System (ADS)

    Itoh, Yutaka; Isobe, Masahiko

    2015-11-01

    We report on pulsed 1H NMR studies of the hydroxyl OH groups in magnesium hydroxide Mg(OH)2 at 77-355 K at 42.5772 MHz. The Fourier-transformed NMR spectra show the superposition of broad and narrow components. The broad NMR spectrum is assigned to dipole-coupled protons on a rigid lattice in the bulk Mg(OH)2, while the narrow NMR spectrum is assigned to extrinsic protons, e.g., conduction protons facilitated by lattice defects. We found a monotonically decreasing linewidth of the broad NMR spectrum on heating. The monotonic decrease in the linewidth is associated with hopping protons around a threefold axis (rotational hydroxyl protons).

  19. Aromatic hydroxylations in peroxidations by haemoglobin systems.

    PubMed

    Esclade, L; Guillochon, D; Thomas, D

    1986-07-01

    The catalytic activity of haemoglobin on aromatic substrates was studied in three systems: NADH-methylene blue-haemoglobin, ascorbic acid-haemoglobin, and red blood cells. Aniline and phenol but not acetanilide or p-toluidine are hydroxylated by haemoglobin. Dealkylations are not observed. Hydroxylations are postulated to be intermediate reactions in peroxidations catalysed by haemoglobin. The lifetime of the products depends on the presence of electron donors, such as NADH or ascorbic acid, in the medium. In the red blood cells where endogenous electron donors are recycled, levels of the products are higher and their lifetime is longer. This could have implications on drug metabolism by haemoglobin, as haemoglobin is present in large quantities in the organism. PMID:3751116

  20. Integration of the Ultraviolet-Visible Spectral Clementine Data and the Gamma-Ray Lunar Prospector Data: Preliminary Results Concerning FeO, TiO2, and Th Abundances of the Lunar Surface at Global Scale

    NASA Astrophysics Data System (ADS)

    Chevrel, S. D.; Pinet, P. C.; Barreau, G.; Daydou, Y.; Richard, G.; Maurice, S.; Feldman, W. C.

    1999-01-01

    The Clementine mission (CLM) produced global multispectral data that resulted in a map of FeO and Ti02 concentrations of the lunar surface. The recent Lunar Prospector (LP) mission returned the first global data for the distribution of surface abundances of key elements in lunar rocks, using a gamma-ray spectrometer (GRS) and neutron spectrometer(NS). Integrating CLM mineralogical spectral reflectance and LP chemical data is important to enhance our view of lunar crust origin and evolution, lunar volcanism, and surface processes. Iron, Ti, and Th having relatively large compositional variation over the lunar surface, as well as strong isolated peaks in the GRS spectra, information concerning the distribution and concentration of these elements has been derived from maps of corrected (cosmic ray, nonsymmetric response of the instrument) counting rates only, without converting them into absolute abundances. Maps produced contain count rates in equal-area projection averaged into 5 x 5 degrees latitude/longitude bins, from -90 to +90 degrees latitude and -180 to +180 degrees longitude. In this work, we have used the CLM global FeO and Ti02 abundances (wt%) maps converted at the LP spatial resolution (about 150 km/pixel) to produce FeO and TiO2 GRS abundance maps, through a linear regression based on the analysis of the scatter distribution of both datasets. The regression coefficients have been determined from the data taken between -60 and +60 degrees latitude to avoid uncertainties in the CLM spectral data due to nonnominal conditions of observation at high latitudes. After a critical assessment of the validity of these coefficients for every class of absolute abundance, the LP data have been transformed into absolute abundances for the whole Moon. The Th LP data have been converted into abundances (ppm) using Th concentrations in average soils from the Apollo and Luna sites given. Values of Th abundances for these samples range between 0.5 and 13 ppm. A nonlinear

  1. Green organocatalytic α-hydroxylation of ketones.

    PubMed

    Voutyritsa, Errika; Theodorou, Alexis; Kokotos, Christoforos G

    2016-06-28

    An efficient and green method for the α-hydroxylation of substituted ketones has been developed. This method includes the in situ conversion of various ketones into the corresponding silyl enol ethers and their oxidation to the corresponding α-hydroxy ketones. Two protocols have been established leading either to protected α-hydroxy carbonyls or free α-hydroxy ketones. Both procedures are easy to follow and lead to good to high yields for a variety of ketones. PMID:26867154

  2. Palladium-catalysed hydroxylation and alkoxylation.

    PubMed

    Enthaler, Stephan; Company, Anna

    2011-10-01

    The formation of oxygen-carbon bonds is one of the fundamental transformations in organic synthesis. In this regard the application of palladium-based catalysts has been extensively studied during recent years. Nowadays it is an established methodology and the success has been proven in manifold synthetic procedures. This tutorial review summarizes the advances on palladium-catalysed C-O bond formation, means hydroxylation and alkoxylation reactions. PMID:21643619

  3. Spectroscopy and reaction dynamics of collision complexes containing hydroxyl radicals

    SciTech Connect

    Lester, M.I.

    1993-12-01

    The DOE supported work in this laboratory has focused on the spectroscopic characterization of the interaction potential between an argon atom and a hydroxyl radical in the ground X{sup 2}II and excited A {sup 2}{summation}{sup +} electronic states. The OH-Ar system has proven to be a test case for examining the interaction potential in an open-shell system since it is amenable to experimental investigation and theoretically tractable from first principles. Experimental identification of the bound states supported by the Ar + OH (X {sup 2}II) and Ar + OH(A {sup 2}{summation}{sup +}) potentials makes it feasible to derive realistic potential energy surfaces for these systems. The experimentally derived intermolecular potentials provide a rigorous test of ab initio theory and a basis for understanding the dramatically different collision dynamics taking place on the ground and excited electronic state surfaces.

  4. Ultraviolet irradiation-induced substitution of fluorine with hydroxyl radical for mass spectrometric analysis of perfluorooctane sulfonyl fluoride.

    PubMed

    Wang, Peng; Tang, Xuemei; Huang, Lulu; Kang, Jie; Zhong, Hongying

    2016-01-28

    A rapid and solvent free substitution reaction of a fluorine atom in perfluorooctane sulfonyl fluoride (PFOSF) with a hydroxyl radical is reported. Under irradiation of ultraviolet laser on semiconductor nanoparticles or metal surfaces, hydroxyl radicals can be generated through hole oxidization. Among all fluorine atoms of PFOSF, highly active hydroxyl radicals specifically substitute the fluorine of sulfonyl fluoride functional group. Resultant perfluorooctane sulfonic acid is further ionized through capture of photo-generated electrons that switch the neutral molecules to negatively charged odd electron hypervalent ions. The unpaired electron subsequently initiates α O-H bond cleavage and produces perfluorooctane sulfonate negative ions. Hydroxyl radical substitution and molecular dissociation of PFOSF have been confirmed by masses with high accuracy and resolution. It has been applied to direct mass spectrometric imaging of PFOSF adsorbed on surfaces of plant leaves. PMID:26755143

  5. Investigating Hydroxyl at Asteroid 951 Gaspra

    NASA Astrophysics Data System (ADS)

    Granahan, James C.

    2015-11-01

    Recent investigations [Granahan, 2011; 2014] of Galileo Near Infrared Mapping Spectrometer (NIMS) observations of asteroid 951 Gaspra have detected an infrared absorption feature near 2.8 micrometers. These were detected in NIMS data acquired by the Galileo spacecraft on October 29, 1991 at wavelengths ranging from 0.7 - 5.2 micrometers [Carlson et al., 1992]. This abstract presents a summary of the investigation to identify the material creating the 2.8 micrometer spectral absorption feature. The current best match for the observed 951 Gaspra feature is the phyllosilicate bound hydroxyl signature present in a thermally desiccated QUE 99038 carbonaceous chondrite as measured by Takir et al. [2013].The 951 Gaspra absorption feature has been compared to a variety of hydroxyl bearing signatures. Many phyllosilicates, hydroxyl bearing minerals, have absorption minima at different positions (2.7 or 2.85 micrometers). It also differs from similar absorptions in a potential R chondrite analog, LAP 04840. The spectra LAP 04840 has a 2.7 micrometer feature due to biotite and a 2.9 micrometer feature due to adsorbed water [Klima et al., 2007]. 2.8 micrometer absorption minima have been found for adsorbed hydroxyl on the Moon [McCord et al., 2011] and various carbonaceous chondrites [Calvin and King, 1997; Takir et al., 2013]. The best match, with a minimum Euclidean distance difference to the 951 Gaspra feature, is found in the spectrum of QUE 99038 [Takir et al., 2013]. This spectrum is the product of an infrared measurement of a sample that had its adsorbed water baked off and removed in a vacuum chamber. The remaining hydroxyl in the sample belongs to a mixture of phyllosilicates dominated by the presence of cronstedtite.References: Calvin, W. M., and T. V. King (1997), Met. Planet. Sci., 32, 693-702. Carlson, R. W., et al. (1992), Bull. American Astro. Soc., 24, 932. Granahan, J. C. (2011), Icarus, 213, 265-272. Granahan, J. C. (2014), 45th LPSC, #1092. Klima, R., C. et

  6. Seasonal abundance of soil-surface arthropods in relation to some meteorological and edaphic variables of the grassland and tree-planted areas in a tropical semi-arid savanna

    NASA Astrophysics Data System (ADS)

    Vikram Reddy, M.; Venkataiah, B.

    1990-03-01

    Seasonality of relative population abundance in different groups of soil-surface arthropods was investigated monthly by pit-fall traps during a 2-year period in the grassland and tree-planted areas of a tropical semi-arid savanna at Warangal (south India). Densities of most groups were lowest during summer and highest during the rainy season. They were less abundant during winter. Arthropods were recorded in higher numbers in tree-planted compared to grassland areas. Certain arthropods that were found only during part of the year were recorded for a longer period in the tree-planted area. Formicidae, Monomorium indicum Forel, Crematogaster sp. and Pachycondyla? tesserinoda (Emery), and Coleoptera, Pachycera sp. reached maximum densities in the rainy season and minimum numbers during winter and summer in the grassland area. However, these species had lower densities during the rainy season and reached maximum densities during winter and summer in the tree-planted area. The seasonal abundance of arthropods showed significant linear correlations with different abiotic environmental variables such as rainfall, soil moisture, organic matter, soil and air temperatures, soil pH, relative humidity at the soil surface, and potassium and phosphorus of surface soil. Soil moisture and rainfall were generally the strongest correlates with densities, particularly in the grassland area.

  7. Abundance of field galaxies

    NASA Astrophysics Data System (ADS)

    Klypin, Anatoly; Karachentsev, Igor; Makarov, Dmitry; Nasonova, Olga

    2015-12-01

    We present new measurements of the abundance of galaxies with a given circular velocity in the Local Volume: a region centred on the Milky Way Galaxy and extending to distance ˜10 Mpc. The sample of ˜750 mostly dwarf galaxies provides a unique opportunity to study the abundance and properties of galaxies down to absolute magnitudes MB ≈ -10 and virial masses M_vir= 109{ M_{⊙}}. We find that the standard Λ cold dark matter (ΛCDM) model gives remarkably accurate estimates for the velocity function of galaxies with circular velocities V ≳ 70 kms-1 and corresponding virial masses M_vir≳ 5× 10^{10}{ M_{⊙}}, but it badly fails by overpredicting ˜5 times the abundance of large dwarfs with velocities V = 30-40 kms-1. The warm dark matter (WDM) models cannot explain the data either, regardless of mass of WDM particle. Just as in previous observational studies, we find a shallow asymptotic slope dN/dlog V ∝ Vα, α ≈ -1 of the velocity function, which is inconsistent with the standard ΛCDM model that predicts the slope α = -3. Though reminiscent to the known overabundance of satellite problem, the overabundance of field galaxies is a much more difficult problem. For the standard ΛCDM model to survive, in the 10 Mpc radius of the Milky Way there should be 1000 not yet detected galaxies with virial mass M_vir≈ 10^{10}{ M_{⊙}}, extremely low surface brightness and no detectable H I gas. So far none of this type of galaxies have been discovered.

  8. Character and spatial distribution of OH/H2O on the surface of the Moon seen by M3 on Chandrayaan-1.

    PubMed

    Pieters, C M; Goswami, J N; Clark, R N; Annadurai, M; Boardman, J; Buratti, B; Combe, J-P; Dyar, M D; Green, R; Head, J W; Hibbitts, C; Hicks, M; Isaacson, P; Klima, R; Kramer, G; Kumar, S; Livo, E; Lundeen, S; Malaret, E; McCord, T; Mustard, J; Nettles, J; Petro, N; Runyon, C; Staid, M; Sunshine, J; Taylor, L A; Tompkins, S; Varanasi, P

    2009-10-23

    The search for water on the surface of the anhydrous Moon had remained an unfulfilled quest for 40 years. However, the Moon Mineralogy Mapper (M3) on Chandrayaan-1 has recently detected absorption features near 2.8 to 3.0 micrometers on the surface of the Moon. For silicate bodies, such features are typically attributed to hydroxyl- and/or water-bearing materials. On the Moon, the feature is seen as a widely distributed absorption that appears strongest at cooler high latitudes and at several fresh feldspathic craters. The general lack of correlation of this feature in sunlit M3 data with neutron spectrometer hydrogen abundance data suggests that the formation and retention of hydroxyl and water are ongoing surficial processes. Hydroxyl/water production processes may feed polar cold traps and make the lunar regolith a candidate source of volatiles for human exploration. PMID:19779151

  9. Character and spatial distribution of OH/H2O on the surface of the moon seen by M3 on chandrayaan-1

    USGS Publications Warehouse

    Pieters, C.M.; Goswami, J.N.; Clark, R.N.; Annadurai, M.; Boardman, J.; Buratti, B.; Combe, J.-P.; Dyar, M.D.; Green, R.; Head, J.W.; Hibbitts, C.; Hicks, M.; Isaacson, P.; Klima, R.; Kramer, G.; Kumar, S.; Livo, E.; Lundeen, S.; Malaret, E.; McCord, T.; Mustard, J.; Nettles, J.; Petro, N.; Runyon, C.; Staid, M.; Sunshine, J.; Taylor, L.A.; Tompkins, S.; Varanasi, P.

    2009-01-01

    The search for water on the surface of the anhydrous Moon had remained an unfulfilled quest for 40 years. However, the Moon Mineralogy Mapper (M 3) on Chandrayaan-1 has recently detected absorption features near 2.8 to 3.0 micrometers on the surface of the Moon. For silicate bodies, such features are typically attributed to hydroxyl- and/or water-bearing materials. On the Moon, the feature is seen as a widely distributed absorption that appears strongest at cooler high latitudes and at several fresh feldspathic craters. The general lack of correlation of this feature in sunlit M3 data with neutron spectrometer hydrogen abundance data suggests that the formation and retention of hydroxyl and water are ongoing surficial processes. Hydroxyl/water production processes may feed polar cold traps and make the lunar regolith a candidate source of volatiles for human exploration.

  10. Role of hydroxyl radical during electrolytic degradation of contaminants.

    PubMed

    Li, Liang; Goel, Ramesh K

    2010-09-15

    The role of hydroxyl radical is investigated in electrochemical oxidation of organic contaminants with naphthalene as a model compound. The strategy employed was competitive kinetic for hydroxyl radical between naphthalene and other hydroxyl scavengers if the hydroxyl radical is produced in situ at the anode by the electrolysis of water. Methanol, d3-methanol, acetone and d6-acetone were used as competitors for hydroxyl radical and their molar concentrations were calculated based on their reaction constants with hydroxyl radical. The hydroxyl radical was not responsible for naphthalene loss in these experiments. The first order reaction rate constants in the batch experiments containing only naphthalene, 2 mM of each of acetone and d6-acetone were 0.093, 0.094 and 0.118 h(-1), respectively. Higher concentrations (4 mM) acetone and d6-acetone did not affect naphthalene degradation. Rate constants using methanol and d6-methanol as competitors for hydroxyl radical in batch degradations test were 0.128 and 0.099 h(-1), respectively. Based on the naphthalene degradation trends and reaction rate constants, it was concluded that, under the given set of conditions, hydroxyl radical was not responsible for naphthalene degradation during electrolytic degradation tests. This research suggests that the role of hydroxyl radical should be considered very carefully in modeling such indirect electrolytic oxidation processes. PMID:20580488

  11. Enhancement of microsomal aniline and acetanilide hydroxylation by haemoglobin.

    PubMed

    Jonen, H G; Kahl, R; Kahl, G F

    1976-05-01

    1. Haemogloblin and myoglobin enhance rat liver microsomal p-hydroxylation of aniline and acetanilide. Microsomal N-demethylation of ethylmorphine and aminopyrine is not increased by haemoproteins. 2. The enhancement of microsomal p-hydroxylation is maximal at high substrate concentration and high haeme compound concentration. 3. Detergent-purified NADPH-cytochrome c reductase, free flavins and manganese ions considerably increase the haemoglobin-mediated, tissue-free hydroxylation of aniline. Microsomal aniline hydroxylation is not enhanced by haeme, ferric ion or albumin. 4 Catalase and cyanide ions are powerful inhibitors of haemoglobin-mediated aniline hydroxylation both in the presence and absence of tissue. Carbon monoxide inhibits the hydroxylase activity of the tissue-free system to a smaller extent than that of a system containing microsomes plus haemoglobin whereas p-chloromercuribenzoate inhibits only the flavoprotein-dependent hydroxylation of aniline mediated by haemoglobin. 5. Several possibilities of interactions between substrate, microsomes and haeme compounds are proposed. PMID:820088

  12. Chlorine Abundances in Martian Meteorites

    NASA Technical Reports Server (NTRS)

    Bogard, D.D.; Garrison, D.H.; Park, J.

    2009-01-01

    Chlorine measurements made in martian surface rocks by robotic spacecraft typically give Chlorine (Cl) abundances of approximately 0.1-0.8%. In contrast, Cl abundances in martian meteorites appear lower, although data is limited, and martian nakhlites were also subjected to Cl contamination by Mars surface brines. Chlorine abundances reported by one lab for whole rock (WR) samples of Shergotty, ALH77005, and EET79001 range 108-14 ppm, whereas Cl in nakhlites range 73-1900 ppm. Measurements of Cl in various martian weathering phases of nakhlites varied 0.04-4.7% and reveal significant concentration of Cl by martian brines Martian meteorites contain much lower Chlorine than those measured in martian surface rocks and give further confirmation that Cl in these surface rocks was introduced by brines and weathering. It has been argued that Cl is twice as effective as water in lowering the melting point and promoting melting at shallower martian depths, and that significant Cl in the shergottite source region would negate any need for significant water. However, this conclusion was based on experiments that utilized Cl concentrations more analogous to martian surface rocks than to shergottite meteorites, and may not be applicable to shergottites.

  13. Surface abundances of light elements for a large sample of early B-type stars - III. An analysis of helium lines in spectra of 102 stars

    NASA Astrophysics Data System (ADS)

    Lyubimkov, L. S.; Rostopchin, S. I.; Lambert, D. L.

    2004-06-01

    Non-local thermodynamic equilibrium analysis of He I lines in spectra of 102 B stars is implemented in order to derive the helium abundance He/H, the microturbulent parameter Vt and the projected rotation velocity v sini. A simultaneous determination of He/H and Vt for the stars is effected by analysing equivalent widths of the 4471- and 4922-Å lines primarily as indicators of He/H and the 4713-, 5016-, 5876- and 6678-Å lines primarily as indicators of Vt. The rotation velocities v sini are found from profiles of the same lines. It is shown that, when Vt > 7 km s-1, the Vt(He I) values determined from He I lines are systematically overestimated as compared with the Vt(OII, NII) values derived from OII and NII lines. This discrepancy is especially appreciable for hot evolved B giants with Vt(He I) = 16-23 km s-1 and may indicate a failure of classical model atmospheres to represent the strong He I lines for these stars. Two programme stars, HR 1512 and 7651, are found to be helium-weak stars. The remaining 100 stars are divided into three groups according to their masses M. The microturbulent parameter Vt(He I) is low for all stars of group A (M= 4.1-6.9 Msolar) and for all stars with the relative ages t/tMS < 0.8 of group B (M= 7.0-11.2 Msolar). Their Vt(He I) values are within the 0 to 5 km s-1 range, as a rule; the mean value is Vt= 1.7 km s-1. Only evolved giants of group B, which are close to the termination of the main-sequence (MS) evolutionary phase (t/tMS > 0.8), show Vt(He I) up to 11 km s-1. The helium abundance He/H is correlated with the relative age t/tMS in both groups; the averaged He/H enhancement during the MS phase is 26 per cent. For group C, containing the most massive stars (M= 12.4-18.8 Msolar), the Vt(He I) values display a correlation with t/tMS, varying from 4 to 23 km s-1. The He/H determination for hot evolved B giants of the group with Vt(He I) > 15 km s-1 depends on a choice between the Vt(He I) and Vt(OII, NII) scales. The mean He

  14. Water, Hydroxyl, and the Search for Alteration and Oxidation on the Moon (Invited)

    NASA Astrophysics Data System (ADS)

    Clark, R. N.; Pieters, C. M.; Green, R. O.; Boardman, J. W.; Buratti, B. J.; Head, J. W.; Isaacson, P.; Livo, K. E.; McCord, T. B.; Mustard, J. F.; Nettles, J. W.; Petro, N. E.; Sunshine, J. M.; Taylor, L. A.

    2009-12-01

    Recent reports using imaging spectroscopy data from three spacecraft show absorption due to water and hydroxyl on the moon (Pieters et al, 2009; Clark, 2009; Sunshine, 2009). The Moon Mineralogy Mapper (M3) on Chandrayaan-1 provides high spatial resolution data showing extensive water and hydroxyl-bearing minerals in both polar regions and in some fresh lunar craters and mountains. A broad 3-micron bsorption is observed in many locations on the moon, with extensive deposits toward the lunar poles and small localized outcrops at all latitudes, often associated with fresh craters. Narrower absorptions attributed to hydroxyl are also observed regionally and in local outcrops, often associated with fresh craters. Hydroxyl absorption at ~2.85 microns is commonly found in association with anorthositic highlands rocks and soils, whereas an absorption near 2.73 microns is found in association with basaltic mare materials. Current M3 data do not yet allow us to assign specific mineralogy, but additional higher resolution targeted mode data might supply the needed spectral resolution to make identifications. Many OH-bearing minerals can be rejected, as their band positions do not match those observed in the lunar data. Hydroxyl absorptions in minerals cover a wide range of wavelength positions ranging from about 2.7 to beyond 3 microns. Several minerals, including altered anorthite and pyroxenes, have hydroxyl fundamentals in the 2.8-micron region and show spectral structure consistent with the lunar spectra. We find varying water, 2.73- and 2.85-micron absorption strengths with spatial location, and the three seem to vary independently, implying that multiple processes are responsible for the observed signatures. The existence of hydroxyl-bearing minerals in the lunar surface indicates probable alteration on the moon. This leads to the question: Could there be additional indications of alteration and oxidation on the moon? We are currently searching the M3 data for

  15. Analysis of Hydroxyl Radical Reactivity in the Sierra Nevada Mountains

    NASA Astrophysics Data System (ADS)

    Carlstad, J. M.; Schroeder, J.; Beyersdorf, A. J.; Blake, D. R.

    2015-12-01

    Using the UC Irvine Whole Air Sampler, volatile organic compounds (VOCs) were measured onboard the NASA DC-8 during the Student Airborne Research Program. High levels of ozone were observed near the surface over the Sierra Nevada mountains, and VOC data was used to investigate factors that contributed to ozone production. This was done by calculating the hydroxyl radical reactivity, which can, in proper conditions, be used to predict ozone formation potential. The region was divided into three boxes from east to west, based on wind direction, and the reactivity was analyzed over each region with respect to methane, non-methane alkanes, alkenes, aromatics, and biogenic compounds. In the westernmost box the reactivity was 1.7 ± 0.5 s-1 (1σ), in the middle section it was 1.4 ± 1 s-1, and in the easternmost region it was 0.8 ± 0.3 s-1. The data were compared with a region known to be heavily polluted, the Los Angeles (LA) basin, and it was observed that the reactivity was 1.1 ± 0.6 s-1, lower than in two of the mountainous regions. In the Sierra Nevada mountains a major percentage of the hydroxyl radical reactivity was the result of biogenic influence, at 24% for the western box, 39% for the middle box, and 31% for the easternmost box, in contrast to only 2% biogenic contribution in LA. This indicates that biogenic factors greatly contributed to overall ozone formation in the Sierra Nevada mountains. These mountains are strategically protected, and high pollution levels could lead to health impacts for visitors, vegetation, and wildlife.

  16. Scavenging of hydroxyl radical by catecholamines.

    PubMed

    Kładna, Aleksandra; Berczyński, Paweł; Kruk, Irena; Michalska, Teresa; Aboul-Enein, Hassan Y

    2012-01-01

    The direct effects of the four catecholamines (CATs), adrenaline (A), noradrenaline (NA), dopamine (D) and isoproterenol (I), on free radicals were investigated using the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH(•)) and hydroxyl radial (HO(•)). The CATs examined were found to inhibit the ESR signal intensity of DPPH(•) in a dose-dependent manner over the range 0.1-2.5 mmol/L in the following order: NA > A > I > D, with IC50= 0.30 ± 0.03 for noradrenaline and IC50= 0.86 ± 0.02 for dopamine. Hydroxyl radicals were produced using a Fenton reaction in the presence of the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO), and ESR technique was applied to detect the CATs reactivity toward the radicals. The reaction rates constant (k(r)) of CATs with HO(•) were found to be in the order of 10(9)  L/mol/s, and the k(r) value for noradrenaline was the highest (k(r)= 8.4 × 10(9)  L/mol/s). The CATs examined exhibited also a strong decrease in the light emission (62-73% at 1 mmol/L concentration and 79-89% at 2 mmol/L concentration) from a Fenton-like reaction. These reactions may be relevant to the biological action of these important polyphenolic compounds. PMID:22238226

  17. Hydrated goethite (alpha-FeOOH) (100) interface structure: Ordered water and surface functional groups.

    SciTech Connect

    Ghose, S.K.; Waychunas, G.A.; Trainor, T.P.; Eng, P.J.

    2009-12-15

    Goethite({alpha}-FeOOH), an abundant and highly reactive iron oxyhydroxide mineral, has been the subject of numerous stud-ies of environmental interface reactivity. However, such studies have been hampered by the lack of experimental constraints on aqueous interface structure, and especially of the surface water molecular arrangements. Structural information of this type is crucial because reactivity is dictated by the nature of the surface functional groups and the structure or distribution of water and electrolyte at the solid-solution interface. In this study we have investigated the goethite(100) surface using surface diffraction techniques, and have determined the relaxed surface structure, the surface functional groups, and the three dimensional nature of two distinct sorbed water layers. The crystal truncation rod (CTR) results show that the interface structure consists of a double hydroxyl, double water terminated interface with significant atom relaxations. Further, the double hydroxyl terminated surface dominates with an 89% contribution having a chiral subdomain structure on the(100) cleavage faces. The proposed interface stoichiometry is ((H{sub 2}O)-(H{sub 2}O)-OH{sub 2}-OH-Fe-O-O-Fe-R) with two types of terminal hydroxyls; a bidentate (B-type) hydroxo group and a monodentate (A-type) aquo group. Using the bond-valence approach the protonation states of the terminal hydroxyls are predicted to be OH type (bidentate hydroxyl with oxygen coupled to two Fe{sup 3+} ions) and OH{sub 2} type (monodentate hydroxyl with oxygen tied to only one Fe{sup 3+}). A double layer three dimensional ordered water structure at the interface was determined from refinement of fits to the experimental data. Application of bond-valence constraints to the terminal hydroxyls with appropriate rotation of the water dipole moments allowed a plausible dipole orientation model as predicted. The structural results are discussed in terms of protonation and H-bonding at the interface

  18. Adsorption of uranyl on hydroxylated α-SiO₂(001): a first-principle study.

    PubMed

    Wang, Hui; Chai, Zhifang; Wang, Dongqi

    2015-01-28

    The adsorption of [UO2(H2O)5](2+) on a hydroxylated α-SiO2(001) surface was studied by periodic density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulation. The effects of pH, CO2, aqua solution and anionic ligands (OH(-), NO3(-) and Cl(-)) on the adsorption geometry and stability were investigated. The results show that the adsorption of uranyl on a hydroxylated α-SiO2(001) surface leads to the formation of inner-sphere complexes, in which the bidentate complex at the double deprotonated site is most favored. The binding strengths of bidentate and monodentate complexes at the same site are similar, and they become weaker as the number of protons increases at the adsorption site, indicating an enhancement of the adsorption strength at higher pH values within a certain range. Strong chemical interaction plays an important role in all inner-sphere complexes. The hydrogen bonds are formed between uranyl and the hydroxylated surface in all inner- and outer-sphere complexes. The presence of CO2 weakens the adsorption of uranyl on the surface by forming uranyl carbonate (CO3(2-), HCO3(-)) complexes. The effect of the anion ligands depends on their charged state and their concentration in solutions. The explicit treatment of water environment in the models has a slight effect on the adsorption configuration. These results are consistent with the experimental observations. PMID:25437449

  19. Solar abundance of osmium

    PubMed Central

    Jacoby, George; Aller, Lawrence H.

    1976-01-01

    The abundance parameter, log gfA, where g is the statistical weight of the lower level, f is the oscillator strength, and A is the abundance (by numbers of atoms with respect to hydrogen), has been derived for three lines of osmium by a method of spectrum synthesis. An apparent discordance of the derived abundance with that found from the carbonaceous chondrites is probably to be attributed primarily to errors in the f-values, and blending with unknown contributors. PMID:16592314

  20. Effect of replacing a hydroxyl group with a methyl group on arsenic (V) species adsorption on goethite (alpha-FeOOH).

    PubMed

    Zhang, J S; Stanforth, R S; Pehkonen, S O

    2007-02-01

    Arsenate and methylated arsenicals, such as dimethylarsinate (DMA) and monomethylarsonate (MMA), are being found with increasing frequency in natural water systems. The mobility and bioavailability of these arsenic species in the environment are strongly influenced by their interactions with mineral surface, especially iron and aluminum oxides. Goethite (alpha-FeOOH), one of the most abundant ferric (hydr)oxides in natural systems, has a high retention capacity for arsenic species. Unfortunately, the sorption mechanism for the species is not completely understood, which limits our ability to model their behavior in natural systems. The purpose of this study is to investigate the effect of replacing a hydroxyl group with a methyl group on the adsorption behaviors of arsenic (V) species using adsorption edges, the influence of the background electrolyte on arsenic adsorption, and their effect on the zeta potential of goethite. The affinity of the three species to the goethite surface decreases in the order of AsO4=MMA>DMA. The uptake of DMA and MMA is independent of the concentration of background electrolyte, indicating that both species form inner-sphere complexes on the goethite surface and the most charge of adsorbed DMA and MMA locates at the surface plane. Arsenate uptake increases with increasing concentrations of background electrolyte at pH above 4, possibly due to that the charge of adsorbed arsenate is distributed between the surface plane and another electrostatic plane. DMA and lower concentrations of MMA have small effect on the zeta potential, whereas the zeta potential of goethite decreases in the presence of arsenate. The small effect on zeta potential of DMA or MMA adsorption suggests that the sorption sites for the anions is not important in controlling the surface charge. This observation is inconsistent with most adsorption models that postulate a singly coordinated hydroxyls contributing to both the adsorption and the surface charge, but

  1. Protein Hydroxylation Catalyzed by 2-Oxoglutarate-dependent Oxygenases*

    PubMed Central

    Markolovic, Suzana; Wilkins, Sarah E.; Schofield, Christopher J.

    2015-01-01

    The post-translational hydroxylation of prolyl and lysyl residues, as catalyzed by 2-oxoglutarate (2OG)-dependent oxygenases, was first identified in collagen biosynthesis. 2OG oxygenases also catalyze prolyl and asparaginyl hydroxylation of the hypoxia-inducible factors that play important roles in the adaptive response to hypoxia. Subsequently, they have been shown to catalyze N-demethylation (via hydroxylation) of Nϵ-methylated histone lysyl residues, as well as hydroxylation of multiple other residues. Recent work has identified roles for 2OG oxygenases in the modification of translation-associated proteins, which in some cases appears to be conserved from microorganisms through to humans. Here we give an overview of protein hydroxylation catalyzed by 2OG oxygenases, focusing on recent discoveries. PMID:26152730

  2. HYDROXYL CATION IN TRANSLUCENT INTERSTELLAR CLOUDS

    SciTech Connect

    Krelowski, J.; Beletsky, Y.; Galazutdinov, G. A. E-mail: ybialets@eso.or

    2010-08-10

    High-quality spectra acquired at the European Southern Observatory enabled us to discover a very weak spectral feature of the OH{sup +} molecule, near 3584 A. The species likely shares environments with another molecular ion, CH{sup +}. Its abundance is by a factor of 30 lower than that of neutral OH.

  3. Adsorption of uranyl species on hydroxylated titanium carbide nanosheet: A first-principles study.

    PubMed

    Zhang, Yu-Juan; Lan, Jian-Hui; Wang, Lin; Wu, Qun-Yan; Wang, Cong-Zhi; Bo, Tao; Chai, Zhi-Fang; Shi, Wei-Qun

    2016-05-01

    In this work, hydroxylated titanium carbide Ti3C2(OH)2, a representative of the two-dimensional transition metal carbides, has been predicted to be an effective adsorbent for uranyl ions in aqueous environments for the first time using density functional theory simulations. The calculations revealed that the uranyl ion can strongly bind with Ti3C2(OH)2 nanosheet in aqueous solution regardless of the presence of anionic ligands such as OH(-), Cl(-) and NO3(-). The bidentate coordination of uranyl to the surface is energetically more favorable than other adsorption configurations, and the uranyl ion prefers to bind with the deprotonated O adsorption site rather than the protonated one on the hydroxylated surface. During the adsorption process, the chemical adsorption as well as the formation of hydrogen bonds is the dominant factor. PMID:26859616

  4. Hydroxyl radical substitution in halogenated carbonyls: oxalic acid formation.

    PubMed

    Christiansen, Carrie J; Dalal, Shakeel S; Francisco, Joseph S; Mebel, Alexander M; Gaffney, Jeffrey S

    2010-03-01

    An ab initio study of OH radical substitution reactions in halogenated carbonyls is conducted. Hydroxyl radical substitution into oxalyl dichloride [ClC(O)C(O)Cl] and oxalyl dibromide [BrC(O)C(O)Br], resulting in the formation of oxalic acid, is presented. Analogous substitution reactions in formyl chloride [ClCH(O)], acetyl chloride [ClC(O)CH(3)], formyl bromide [BrCH(O)], and acetyl bromide [BrC(O)CH(3)] are considered. Energetics of competing hydrogen abstraction reactions for all applicable species are computed for comparison. Geometry optimizations and frequency computations are performed using the second-order Møller-Plesset perturbation theory (MP2) and the 6-31G(d) basis set for all minimum species and transition states. Single point energy computations are performed using fourth-order Møller-Plesset perturbation theory (MP4) and coupled cluster theory [CCSD(T)]. Potential energy surfaces, including activation energies and enthalpies, are determined from the computations. These potential energy surfaces show that OH substitution into ClC(O)C(O)Cl and BrC(O)C(O)Br, resulting in the formation of oxalic acid and other minor products, is energetically favorable. Energetics of analogous reactions with ClCH(O), BrCH(O), ClC(O)CH(3), and BrC(O)CH(3) are also computed. PMID:20131850

  5. Searching for a One-Step Bioprocess for the Production of Hydroxyl Fatty Acids and Hydroxyl Oils from Soybean Oil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soybean oil is produced domestically in large supply, averaging over 20 billion pounds per year with an annual carryover of more than one billion pounds. It is important to find new uses for this surplus soybean oil. Hydroxyl fatty acids and hydroxyl oils are platform materials for specialty chemi...

  6. Evaporative cooling of the dipolar hydroxyl radical.

    PubMed

    Stuhl, Benjamin K; Hummon, Matthew T; Yeo, Mark; Quéméner, Goulven; Bohn, John L; Ye, Jun

    2012-12-20

    Atomic physics was revolutionized by the development of forced evaporative cooling, which led directly to the observation of Bose-Einstein condensation, quantum-degenerate Fermi gases and ultracold optical lattice simulations of condensed-matter phenomena. More recently, substantial progress has been made in the production of cold molecular gases. Their permanent electric dipole moment is expected to generate systems with varied and controllable phases, dynamics and chemistry. However, although advances have been made in both direct cooling and cold-association techniques, evaporative cooling has not been achieved so far. This is due to unfavourable ratios of elastic to inelastic scattering and impractically slow thermalization rates in the available trapped species. Here we report the observation of microwave-forced evaporative cooling of neutral hydroxyl (OH(•)) molecules loaded from a Stark-decelerated beam into an extremely high-gradient magnetic quadrupole trap. We demonstrate cooling by at least one order of magnitude in temperature, and a corresponding increase in phase-space density by three orders of magnitude, limited only by the low-temperature sensitivity of our spectroscopic thermometry technique. With evaporative cooling and a sufficiently large initial population, much colder temperatures are possible; even a quantum-degenerate gas of this dipolar radical (or anything else it can sympathetically cool) may be within reach. PMID:23257881

  7. Vertical Distribution of Vibrationally Excited Hydroxyl

    NASA Astrophysics Data System (ADS)

    Grygalashvyly, Mykhaylo; Becker, Erich; Sonnemann, Gerd

    2016-04-01

    Knowledge about the vertical distribution of the vibrationally excited states of hydroxyl (OH*) is important for the interpretation of airglow measurements with respect to dynamical processes in the mesopause region. We derive an approximate analytical expression for the distribution of OH* that highlights the dependence on atomic oxygen and temperature. In addition, we use an advanced numerical model for the formation and relaxation of OH* and investigate the distributions of the different vibrationally exited states of OH*. For the production of OH*, the model includes the reaction of atomic hydrogen with ozone, as well as the reaction of atomic oxygen with hydroperoxy radicals. As loss processes we include 1) deactivation by atomic oxygen, molecular oxygen, and molecular nitrogen, 2) spontaneous emission, and 3) loss due to chemical reaction with atomic oxygen. All these processes take the dependence on the vibrational number into account. The quenching by molecular and atomic oxygen is parameterized by a multi-quantum relaxation scheme. This diagnostic model for OH* has been implemented as part of a chemistry-transport model that is driven by the dynamics simulated with the KMCM (Kühlungsborn Mechanistic general Circulation Model). Numerical results confirm that emission from excited states with higher vibrational number is weaker and emanates from higher altitudes. In addition we find that the OH*-peak altitudes depend significantly on season and latitude. This behavior is mainly controlled by the corresponding variations of atomic oxygen and temperature, as is also confirmed by the aforementioned approximate theory.

  8. Hydroxyl Emission in the Westbrook Nebula

    NASA Astrophysics Data System (ADS)

    Strack, Angelica; Araya, Esteban; Ghosh, Tapasi; Arce, Hector G.; Lebron, Mayra E.; Salter, Christopher J.; Minchin, Robert F.; Pihlstrom, Ylva; Kurtz, Stan; Hofner, Peter; Olmi, Luca

    2016-06-01

    CRL 618, also known as the Westbrook Nebula, is a carbon-rich pre-planetary nebula. Hydroxyl (OH) transitions are typically not detected in carbon-rich late-type stellar objects, however observations conducted with the 305m Arecibo Telescope in 2008 resulted in the detection of 4765 MHz OH emission in CRL 618. We present results of observations carried out a few months after the original detection that confirm the line. This is the first detection of 4765 MHz OH emission (most likely a maser) in a pre-planetary nebula. Follow up observations conducted in 2015 resulted in non-detection of the 4765 MHz OH transition. This behavior is consistent with the high level of variability of excited OH lines that have been detected toward a handful of other pre-planetary nebulae. Our work supports that excited OH masers are short-lived during the pre-planetary nebula phase. We also conducted a search for other OH transitions from 1612 MHz to 8611 MHz with the Arecibo Telescope; we report no other detections at rms levels of ~5 mJy.This work has made use of the computational facilities donated by Frank Rodeffer to the WIU Astrophysics Research Laboratory. We also acknowledge support from M. & C. Wong RISE scholarships and a grant from the WIU College of Arts and Sciences.

  9. Impact of sedimentary degradation and deep water column production on GDGT abundance and distribution in surface sediments in the Arabian Sea: Implications for the TEX86 paleothermometer

    NASA Astrophysics Data System (ADS)

    Lengger, Sabine K.; Hopmans, Ellen C.; Sinninghe Damsté, Jaap S.; Schouten, Stefan

    2014-10-01

    The TEX86 is a widely used paleotemperature proxy based on isoprenoid glycerol dibiphytanyl glycerol tetraethers (GDGTs) produced by Thaumarchaeota. Archaeal membranes are composed of GDGTs with polar head groups (IPL-GDGTs), most of which are expected to be degraded completely or transformed into more recalcitrant core lipid (CL)-GDGTs upon cell lysis. Here, we examined the differences in concentration and distribution of core lipid (CL)- and intact polar lipid (IPL)-GDGTs in surface sediments at different deposition depths, and different oxygen bottom water concentrations (<3-83 μmol L-1). Surface sediments were sampled from 900 to 3000 m depth on a seamount (Murray Ridge), whose summit protrudes into the oxygen minimum zone of the Arabian Sea. Concentrations of organic carbon, IPL- and CL-GDGTs decreased linearly with increasing maximum residence time in the oxic zone of the sediment (tOZ), suggesting increasing sedimentary degradation of organic matter and GDGTs. IPL-GDGT-0 was the only exception and increased with tOZ, indicating that this GDGT was probably produced in situ in the surface sediment. Concentrations of crenarchaeol with glycosidic headgroups decreased with increasing tOZ, while crenarchaeol with a hexose, phosphohexose head (HPH) group, in contrast, showed an increase with increasing tOZ, indicating that the concentration of HPH crenarchaeol was primarily determined by in situ production in surficial sediments. TEX86 values of both IPL-derived GDGTs and CL-GDGTs decreased by ∼0.08 units with increasing water depth, in spite of the sea surface temperatures being identical for the restricted area studied. In situ production in sediments could be excluded as the main cause, due to the slow production rates of GDGTs in sediments, and previous observations of the same trends in TEX86 in sediment trap material. Instead, the incorporation of GDGTs produced in the oxygen minimum zone (with high TEX86 values) and their preferential degradation during

  10. Low-temperature chemistry between water and hydroxyl radicals: H/D isotopic effects

    NASA Astrophysics Data System (ADS)

    Lamberts, T.; Fedoseev, G.; Puletti, F.; Ioppolo, S.; Cuppen, H. M.; Linnartz, H.

    2016-01-01

    Sets of systematic laboratory experiments are presented - combining Ultra High Vacuum cryogenic and plasma-line deposition techniques - that allow us to compare H/D isotopic effects in the reaction of H2O (D2O) ice with the hydroxyl radical OD (OH). The latter is known to play a key role as intermediate species in the solid-state formation of water on icy grains in space. The main finding of our work is that the reaction H2O + OD → OH + HDO occurs and that this may affect the HDO/H2O abundances in space. The opposite reaction D2O + OH → OD + HDO is much less effective, and also given the lower D2O abundances in space not expected to be of astronomical relevance. The experimental results are extended to the other four possible reactions between hydroxyl and water isotopes and are subsequently used as input for Kinetic Monte Carlo simulations. This way we interpret our findings in an astronomical context, qualitatively testing the influence of the reaction rates.

  11. A Combined FTIR and TPD Study on the Bulk and Surface Dehydroxylation and Decarbonation of Synthetic Goethite

    SciTech Connect

    Boily, Jean F; Szanyi, Janos; Felmy, Andrew R

    2006-08-01

    The thermal dehydroxylation of a goethite–carbonate solid solution was studied with combined Fourier-transform infrared (FTIR) – Temperature programmed desorption (TPD) experiments. The TPD data revealed dehydroxylation peaks involving the intrinsic dehydroxylation of goethite at 560 K and a low temperature peak at 485 K which was shown to be associated to the release of non-stoichiometric water from the goethite bulk and surface. The FTIR and the TPD data of goethite in the absence of adsorbed carbonate species revealed the presence of adventitious carbonate mostly sequestered in the goethite bulk. The release of carbonate was however not only related to the dehydration of goethite but also from the crystallization of hematite at temperatures exceeding 600 K. The relative abundance of surface hydroxyls was shown to change systematically upon goethite dehydroxylation with a preferential stripping of singlycoordinated AOH sites followed by a dramatic change in the dominance of the different surface hydroxyls upon the formation of hematite.

  12. Determining the geochemical structure of the mantle from surface isotope distribution patterns? Insights from Ne and He isotopes and abundance ratios

    NASA Astrophysics Data System (ADS)

    Stroncik, N.; Niedermann, S.; Schnabel, E.; Erzinger, J.

    2011-12-01

    It is a common procedure among geochemists to use surface distribution patterns of e.g. Sr, Nd, Pb or He isotopes of lavas erupted at oceanic islands to map the geochemical structure of the Earth's mantle. Advances in noble gas mass spectrometry within the last decade resulting in an increasing availability of Ne isotope data sets allow us to test the strength of this approach. 4He and 21Ne are coupled through the same parent nuclides and therefore should show analogous isotope distribution patterns. Here we present He and Ne fusion data of fresh olivines derived from Big Island, Hawaii, together with He and Ne fusion data of fresh glasses from the Easter Seamount Chain (ESC), indicating that the observed isotope distribution patterns are mainly controlled by melting and shallow mixing processes. He isotopic ratios of the investigated olivines vary from MORB-like (8 ± 1 RA) to ratios more typical for a primitive mantle source (up to 20 and 26 RA for Hawaii and the ESC, respectively; RA = atmospheric 3He/4He ratio of 1.39 x 10-6). In contrast, all Ne isotope data plot within error limits along the Loihi-Kilauea line in a Ne three-isotope diagram. The Loihi-Kilauea line is regarded to be typical for a primitive mantle source. Thus, the Ne isotope data are inconsistent with any kind of zoned plume model or even a heterogeneous mantle source. The combined He and Ne data show that these He and Ne isotope systematics are produced by a pre-degassing fractionation process and subsequent melt mixing. Basically, this process causes a He deficit in melts generated by the plume, as shown by 3He/22NeS below current estimates of solar or planetary composition and 4He/21Ne* lower than the production ratio, making the He isotopic composition more susceptible to changes than the Ne isotopic composition. This can best be explained by a model in which He is fractionated from Ne during formation of melts from a plume (or enriched parts of a plume) at low melting degrees, which

  13. Mechanism of hydroxylation of biphenyl by Cunninghamella echinulata.

    PubMed Central

    Smith, R V; Davis, P J; Clark, A M; Prasatik, S K

    1981-01-01

    The hydroxylation of [U-2H]biphenyl and [2,2',3,3',5,5',6,6'-2H]biphenyl by Cunninghamella echinulata A.T.C.C. 9244 has been studied. G.l.c.-mass-spectrometry analyses indicate the lack of an isotope effect during the hydroxylation of the perdeuterated substrate. Both g.l.c.-mass spectrometry and 1H n.m.r. were used to definitively demonstrate the presence of a 1,2-hydride-shift during the microbiological hydroxylation of [2,2',3,3',5,5',6,6'-2H]biphenyl. PMID:7306077

  14. Regioselective alkane hydroxylation with a mutant AlkB enzyme

    DOEpatents

    Koch, Daniel J.; Arnold, Frances H.

    2012-11-13

    AlkB from Pseudomonas putida was engineered using in-vivo directed evolution to hydroxylate small chain alkanes. Mutant AlkB-BMO1 hydroxylates propane and butane at the terminal carbon at a rate greater than the wild-type to form 1-propanol and 1-butanol, respectively. Mutant AlkB-BMO2 similarly hydroxylates propane and butane at the terminal carbon at a rate greater than the wild-type to form 1-propanol and 1-butanol, respectively. These biocatalysts are highly active for small chain alkane substrates and their regioselectivity is retained in whole-cell biotransformations.

  15. Earth Abundant Iron-Rich N-Doped Graphene Based Spacer and Cavity Materials for Surface Plasmon-Coupled Emission Enhancements.

    PubMed

    Srinivasan, Venkatesh; Vernekar, Dnyanesh; Jaiswal, Garima; Jagadeesan, Dinesh; Ramamurthy, Sai Sathish

    2016-05-18

    We demonstrate for the first time the use of Fe-based nanoparticles on N-doped graphene as spacer and cavity materials and study their plasmonic effect on the spontaneous emission of a radiating dipole. Fe-C-MF was produced by pyrolizing FeOOH and melamine formaldehyde precursor on graphene, while Fe-C-PH was produced by pyrolizing the Fe-phenanthroline complex on graphene. The use of the Fe-C-MF composite consisting of Fe-rich crystalline phases supported on N-doped graphene presented a spacer material with 116-fold fluorescence enhancements. On the other hand, the Fe-C-PH/Ag based cavity resulted in an 82-fold enhancement in Surface Plasmon-Coupled Emission (SPCE), with high directionality and polarization of Rhodamine 6G (Rh6G) emission owing to Casimir and Purcell effects. The use of a mobile phone as a cost-effective fluorescence detection device in the present work opens up a flexible perspective for the study of different nanomaterials as tunable substrates in cavity mode and spacer applications. PMID:27128348

  16. Sugars as hydroxyl radical scavengers: proof-of-concept by studying the fate of sucralose in Arabidopsis.

    PubMed

    Matros, Andrea; Peshev, Darin; Peukert, Manuela; Mock, Hans-Peter; Van den Ende, Wim

    2015-06-01

    Substantial formation of reactive oxygen species (ROS) is inevitable in aerobic life forms. Due to their extremely high reactivity and short lifetime, hydroxyl radicals are a special case, because cells have not developed enzymes to detoxify these most dangerous ROS. Thus, scavenging of hydroxyl radicals may only occur by accumulation of higher levels of simple organic compounds. Previous studies have demonstrated that plant-derived sugars show hydroxyl radical scavenging capabilities during Fenton reactions with Fe(2+) and hydrogen peroxide in vitro, leading to formation of less detrimental sugar radicals that may be subject of regeneration to non-radical carbohydrates in vivo. Here, we provide further evidence for the occurrence of such radical reactions with sugars in planta, by following the fate of sucralose, an artificial analog of sucrose, in Arabidopsis tissues. The expected sucralose recombination and degradation products were detected in both normal and stressed plant tissues. Oxidation products of endogenous sugars were also assessed in planta for Arabidopsis and barley, and were shown to increase in abundance relative to the non-oxidized precursor during oxidative stress conditions. We concluded that such non-enzymatic reactions with hydroxyl radicals form an integral part of plant antioxidant mechanisms contributing to cellular ROS homeostasis, and may be more important than generally assumed. This is discussed in relation to the recently proposed roles for Fe(2+) and hydrogen peroxide in processes leading to the origin of metabolism and the origin of life. PMID:25891826

  17. Silicon abundances in population I giants

    NASA Technical Reports Server (NTRS)

    Boehm-Vitense, Erika

    1992-01-01

    Silicon to carbon abundance ratios for population I giants were determined from emission lines originating in the transition layers between stellar chromospheres and coronae. For effective temperatures larger than 6200 K we find a group of stars with increased silicon to carbon but normal nitrogen to carbon abundance ratios. These stars are presumably descendents from Ap stars with increased surface silicon to carbon abundance ratios. For G stars this anomaly disappears as is to be expected due to the increased depth of the convection zone and therefore deeper mixing which dilutes the surface overabundances. The disappearance of the abundance anomalies proves that the anomalous abundances observed for the F giants are indeed only a surface phenomenon. It also proves that the same holds for their progenitors, the Ap and Am stars, as has been generally believed. Unexplained is the increased silicon to carbon abundance ratio observed for several stars cooler than 5100 L. RS CVn and related stars do not show this increased abundance ratio. There are also some giants which appear to be enriched in carbon, perhaps due to a helium flash with some mixing if the star is a clump star.

  18. Water growth on metals and oxides: binding, dissociation and role of hydroxyl groups

    SciTech Connect

    Salmeron, M.; Bluhm, H.; Tatarkhanov, M.; Ketteler, G.; Shimizu, T.K.; Mugarza, A.; Deng, Xingyi; Herranz, T.; Yamamoto, S.; Nilsson, A.

    2008-09-01

    The authors discuss the role of the presence of dangling H bonds from water or from surface hydroxyl species on the wetting behavior of surfaces. Using Scanning Tunneling and Atomic Force Microscopies, and Photoelectron Spectroscopy, they have examined a variety of surfaces, including mica, oxides, and pure metals. They find that in all cases, the availability of free, dangling H-bonds at the surface is crucial for the subsequent growth of wetting water films. In the case of mica electrostatic forces and H-bonding to surface O atoms determine the water orientation in the first layer and also in subsequent layers with a strong influence in its wetting characteristics. In the case of oxides like TiO{sub 2}, Cu{sub 2}O, SiO{sub 2} and Al{sub 2}O{sub 3}, surface hydroxyls form readily on defects upon exposure to water vapor and help nucleate the subsequent growth of molecular water films. On pure metals, such as Pt, Pd, and Ru, the structure of the first water layer and whether or not it exhibits dangling H bonds is again crucial. Dangling H-bonds are provided by molecules with their plane oriented vertically, or by OH groups formed by the partial dissociation of water. By tying the two II atoms of the water molecules into strong H-bonds with pre-adsorbed O on Ru can also quench the wettability of the surface.

  19. New insights into the aquatic photochemistry of fluoroquinolone antibiotics: Direct photodegradation, hydroxyl-radical oxidation, and antibacterial activity changes.

    PubMed

    Ge, Linke; Na, Guangshui; Zhang, Siyu; Li, Kai; Zhang, Peng; Ren, Honglei; Yao, Ziwei

    2015-09-15

    The ubiquity and photoreactivity of fluoroquinolone antibiotics (FQs) in surface waters urge new insights into their aqueous photochemical behavior. This study concerns the photochemistry of 6 FQs: ciprofloxacin, danofloxacin, levofloxacin, sarafloxacin, difloxacin and enrofloxacin. Methods were developed to calculate their solar direct photodegradation half-lives (td,E) and hydroxyl-radical oxidation half-lives (tOH,E) in sunlit surface waters. The td,E values range from 0.56 min to 28.8 min at 45° N latitude, whereas tOH,E ranges from 3.24h to 33.6h, suggesting that most FQs tend to undergo fast direct photolysis rather than hydroxyl-radical oxidation in surface waters. However, a case study for levofloxacin and sarafloxacin indicated that the hydroxyl-radical oxidation induced risky photochlorination and resulted in multi-degradation pathways, such as piperazinyl hydroxylation and clearage. Changes in the antibacterial activity of FQs caused by photodegradation in various waters were further examined using Escherichia coli, and it was found that the activity evolution depended on primary photodegradation pathways and products. Primary intermediates with intact FQ nuclei retained significant antibacterial activity. These results are important for assessing the fate and risk of FQs in surface waters. PMID:25956144

  20. Role of hydroxylation modification on the structure and property of reduced graphene oxide/TiO2 hybrids

    NASA Astrophysics Data System (ADS)

    Cao, Shiyi; Liu, Tiangui; Tsang, Yuenhong; Chen, Chuansheng

    2016-09-01

    To extend the spectra response of TiO2 and enhance its photocatalytic activity, surface modification and catalyst supporter have attracted great attention. In this report, a simple and versatile approach has been developed to hydroxylate the reduced graphene oxide/TiO2 hybrids (OH-rGO/TiO2) by UV-microwave method, and the enhanced mechanisms of hydroxylation were analyzed in details. Experimental results show that TiO2 nanocrystals@OH-TiO2 heterojunctions formed on rGO sheets in situ by UV/H2O2 process. Hydroxylation not only can induce many surface defects (Ti3+, O vacancy and Ti-OH) on the surface of TiO2, but also change the color into yellow and strengthen the interaction between rGO and TiO2. OH-rGO/TiO2 hybrids showed excellent durability for high-concentration dyes, and exhibited strong adsorbability and photocatalytic activity. These enhancements are attributed to the excellent property of rGO and surface defects of TiO2 induced by hydroxylation, which expand the light absorption up to 600 nm, benefit to the self-dispersion of hybrids, and improve the adsorption dynamic and charge transfer with lower carrier's recombination.

  1. Catalytic hydroxylation of benzoic acid by hydrogen peroxide

    SciTech Connect

    Pulippurasseril, C.R.; Filippova, T.Yu.; Dedov, A.G.

    1992-12-31

    An effective catalytic system based on Fe(III) and surfactants is proposed for the hydroxylation of benozic acid by hydrogen peroxide in an aqueous medium at a temperature of 30-80{degrees}C. 8 refs., 1 tab.

  2. Hydroxyl radical production in plasma electrolysis with KOH electrolyte solution

    NASA Astrophysics Data System (ADS)

    Saksono, Nelson; Febiyanti, Irine Ayu; Utami, Nissa; Ibrahim

    2015-12-01

    Plasma electrolysis is an effective technology for producing hydroxyl radical (•OH). This method can be used for waste degradation process. This study was conducted to obtain the influence of applied voltage, electrolyte concentration, and anode depth in the plasma electrolysis system for producing hydroxyl radical. The materials of anode and cathode, respectively, were made from tungsten and stainless steel. KOH solution was used as the solution. Determination of hydroxyl radical production was done by measuring H2O2 amount formed in plasma system using an iodometric titration method, while the electrical energy consumed was obtained by measuring the electrical current throughout the process. The highest hydroxyl radical production was 3.51 mmol reached with 237 kJ energy consumption in the power supply voltage 600 V, 0.02 M KOH, and 0.5 cm depth of anode.

  3. Hydroxyl radical production in plasma electrolysis with KOH electrolyte solution

    SciTech Connect

    Saksono, Nelson; Febiyanti, Irine Ayu Utami, Nissa; Ibrahim

    2015-12-29

    Plasma electrolysis is an effective technology for producing hydroxyl radical (•OH). This method can be used for waste degradation process. This study was conducted to obtain the influence of applied voltage, electrolyte concentration, and anode depth in the plasma electrolysis system for producing hydroxyl radical. The materials of anode and cathode, respectively, were made from tungsten and stainless steel. KOH solution was used as the solution. Determination of hydroxyl radical production was done by measuring H{sub 2}O{sub 2} amount formed in plasma system using an iodometric titration method, while the electrical energy consumed was obtained by measuring the electrical current throughout the process. The highest hydroxyl radical production was 3.51 mmol reached with 237 kJ energy consumption in the power supply voltage 600 V, 0.02 M KOH, and 0.5 cm depth of anode.

  4. Reactivity of perovskites with water: Role of hydroxylation in wetting and implications for oxygen electrocatalysis

    DOE PAGESBeta

    Stoerzinger, Kelsey A.; Hong, Wesley T.; Azimi, Gisele; Crumlin, Ethan J.; Biegalski, Michael D.; Bluhm, Hendrik; Varanasi, Kripa K.; Shao-Horn, Yang; Giordano, Livia; Lee, Yueh -Lin

    2015-07-15

    Oxide materials play an important role in technical applications such as gas sensing and catalysis, where they can react notably with water in vapor or liquid form. We find that the coverage of (*OH) measured at fixed relative humidity trends with the electron donor (basic) character of wetted perovskite oxide surfaces, corresponding to low contact angles when removing a droplet of water. We report for the first time that the affinity toward hydroxylation, coincident with strong adsorption energies calculated for dissociative and molecular adsorption of water, leads to strong H-bonding detrimental to catalysis of the oxygen reduction reaction (ORR). Furthermore,more » this suggests that hydrophobic oxides with low tendency to hydroxylate may demonstrate improved catalytic activity for the ORR.« less

  5. OXYGEN ABUNDANCES IN CEPHEIDS

    SciTech Connect

    Luck, R. E.; Andrievsky, S. M.; Korotin, S. N.; Kovtyukh, V. V. E-mail: serkor@skyline.od.ua E-mail: scan@deneb1.odessa.ua

    2013-07-01

    Oxygen abundances in later-type stars, and intermediate-mass stars in particular, are usually determined from the [O I] line at 630.0 nm, and to a lesser extent, from the O I triplet at 615.7 nm. The near-IR triplets at 777.4 nm and 844.6 nm are strong in these stars and generally do not suffer from severe blending with other species. However, these latter two triplets suffer from strong non-local thermodynamic equilibrium (NLTE) effects and thus see limited use in abundance analyses. In this paper, we derive oxygen abundances in a large sample of Cepheids using the near-IR triplets from an NLTE analysis, and compare those abundances to values derived from a local thermodynamic equilibrium (LTE) analysis of the [O I] 630.0 nm line and the O I 615.7 nm triplet as well as LTE abundances for the 777.4 nm triplet. All of these lines suffer from line strength problems making them sensitive to either measurement complications (weak lines) or to line saturation difficulties (strong lines). Upon this realization, the LTE results for the [O I] lines and the O I 615.7 nm triplet are in adequate agreement with the abundance from the NLTE analysis of the near-IR triplets.

  6. Selective hydroxylation of alkanes by an extracellular fungal peroxygenase.

    PubMed

    Peter, Sebastian; Kinne, Matthias; Wang, Xiaoshi; Ullrich, René; Kayser, Gernot; Groves, John T; Hofrichter, Martin

    2011-10-01

    Fungal peroxygenases are novel extracellular heme-thiolate biocatalysts that are capable of catalyzing the selective monooxygenation of diverse organic compounds, using only H(2)O(2) as a cosubstrate. Little is known about the physiological role or the catalytic mechanism of these enzymes. We have found that the peroxygenase secreted by Agrocybe aegerita catalyzes the H(2)O(2)-dependent hydroxylation of linear alkanes at the 2-position and 3-position with high efficiency, as well as the regioselective monooxygenation of branched and cyclic alkanes. Experiments with n-heptane and n-octane showed that the hydroxylation proceeded with complete stereoselectivity for the (R)-enantiomer of the corresponding 3-alcohol. Investigations with a number of model substrates provided information about the route of alkane hydroxylation: (a) the hydroxylation of cyclohexane mediated by H(2)(18)(2) resulted in complete incorporation of (18)O into the hydroxyl group of the product cyclohexanol; (b) the hydroxylation of n-hexane-1,1,1,2,2,3,3-D(7) showed a large intramolecular deuterium isotope effect [(k(H)/k(D))(obs)] of 16.0 ± 1.0 for 2-hexanol and 8.9 ± 0.9 for 3-hexanol; and (c) the hydroxylation of the radical clock norcarane led to an estimated radical lifetime of 9.4 ps and an oxygen rebound rate of 1.06 × 10(11) s(-1). These results point to a hydrogen abstraction and oxygen rebound mechanism for alkane hydroxylation. The peroxygenase appeared to lack activity on long-chain alkanes (> C(16)) and highly branched alkanes (e.g. tetramethylpentane), but otherwise exhibited a broad substrate range. It may accordingly have a role in the bioconversion of natural and anthropogenic alkane-containing structures (including alkyl chains of complex biomaterials) in soils, plant litter, and wood. PMID:21812933

  7. Observations and Analysis of Atmospheric Hydroxyl

    NASA Technical Reports Server (NTRS)

    Minschwaner, Ken R.

    1996-01-01

    Ground-based measurements of sunlight absorption at the OH P(sub 1)(l) resonance line at 308 nm have been made on a continuous basis at Fritz Peak, Colorado. The derived OH vertical column abundances show the persistence of a new seasonal regime which began in 1991. The fall minimum has been consistently depressed about 10-15% below the 1980-1990 average fall values. While the initial onset of depressed fall abundances occurred a few months after the Pinatubo eruption, there has been no fall OH recovery correlating with decreased amounts of volcanic aerosol found since spring 1993. The Colorado data also continues to exhibit an AM-PM asymmetry which varies seasonally, approximately in phase with local total ozone. These observations were presented at the Front Range AGU meeting in February 1996 and were published in Geophysical Research Letters in July 1996 (preprint enclosed). An update through the fall of 1996, when morning abundances were found to be extremely low, was presented at the Fall 1996 AGU meeting (abstract attached). A PEPSIOS instrument of identical design is currently operational and has been used since April 1996 for OH column measurements at New Mexico Tech, Socorro, NM. Title for both instruments was transferred from Florida Atlantic University to New Mexico Tech in February of 1996. Comparative measurements from the two instruments for April-July 1996 indicate small differences in OH column abundances, with New Mexico (34 deg N) abundances about 10% above Colorado (40 deg N) values for comparable solar zenith angles. A more detailed comparison will require at least one full year of data from both locations. New Mexico measurements were obtained on June 10, 1996, concurrently with a balloon launch of the NASA STRAT mission from Fort Sumner, New Mexico. We hope to make use of STRAT measurements H2O, CH4, and O3 which are particularly relevant to OH photochemistry. Additional work at New Mexico Tech involves a comparison of P(sub 1)(1) and Q(sub 1

  8. Solution behavior and solid phase transitions of quaternary ammonium surfactants with head groups decorated by hydroxyl groups.

    PubMed

    Song, Binglei; Shang, Shibin; Song, Zhanqian

    2012-09-15

    Hydrogen bonds are strong intermolecular interactions, which are very important in molecular aggregation and new phase formation. Three long-chain quaternary ammonium surfactants, N,N-diethyl-N-(2-hydroxyethyl)-N-octadecylammonium bromide with one hydroxyl group, N-ethyl-N,N-bis (2-hydroxyethyl)-N-octadecylammonium bromide with two hydroxyl groups and N,N,N-tris (2-hydroxyethyl)-N-octadecylammonium bromide with three hydroxyl groups, abbreviated as SHQ, DHQ, and THQ, respectively, were synthesized in this work. Their solution behavior and solid phase transitions were investigated by surface tension, differential scanning calorimetry (DSC), X-ray diffraction (XRD), polarizing optical microscopy (POM), and Infrared (IR) spectroscopy. The hydrogen bonds introduced by the substituted hydroxyl groups promoted surfactant adsorption at the air/water interface and aggregation in solution. In the crystal state, an increased number of hydroxyl groups caused a larger tilt angle of the long axis of surfactant molecules with the layer normal. Above certain temperatures, SHQ and DHQ formed highly ordered smectic T and smectic A phases while THQ only formed less ordered smectic A phase. The weakened electrostatic attractions between opposite ions and the thicker polar sublayers of mesophases caused by the enhanced number of hydrogen bonds are responsible for the mesophase formation and transition of these surfactants. PMID:22762982

  9. 7-alpha-hydroxylation of cholestanol by rat liver microsomes.

    PubMed

    Shefer, S; Hauser, S; Mosbach, E H

    1968-05-01

    In a study of the mechanism whereby 5alpha-bile acids are formed from cholestanol, the 7alpha-hydroxylation of cholestanol was investigated in rat liver preparations in vitro. It was found that in the presence of NADPH and oxygen, rat liver microsomes catalyzed the 7alpha-hydroxylation of cholestanol to the same extent as that of cholesterol. The rate of the hydroxylation was enhanced by prior treatment of the experimental rats with cholestyramine (a bile acid sequestrant) or by establishment of bile fistulas-i.e., by partial or complete removal of bile acids from the enterohepatic circulation. The 7-hydroxylation reaction was further stimulated by pretreatment of the animals with phenobarbital, a drug known to produce increased biosynthesis of hepatic endoplasmic membranes. The 7alpha-hydroxylase was inhibited by the reaction product, by sterols with 7-keto or 7beta-hydroxyl groups, and also by mono- and dihydroxy bile acids of the 5beta-series, although cholic acid or taurocholate produced no inhibition unless added in high concentrations. The results of these studies are in accord with the concept that the presence of a Delta(5)-double bond is not required for the enzymatic formation of the 7alpha-hydroxy derivative. The rate of this hydroxylation reaction in vitro appears to depend on the concentration of bile salts in the enterohepatic circulation of the experimental animals from whom the microsomes were obtained. PMID:5650927

  10. Oxidation processes of aromatic sulfides by hydroxyl radicals in colloidal solution of TiO 2 during pulse radiolysis

    NASA Astrophysics Data System (ADS)

    Tojo, Sachiko; Tachikawa, Takashi; Fujitsuka, Mamoru; Majima, Tetsuro

    2004-01-01

    The pulse radiolysis technique has been used to elucidate the oxidation reaction of aromatic sulfides by hydroxyl radicals on the TiO 2 nanoparticles in pH 2 aqueous solution. The hydroxyl radicals generated during the pulse radiolysis of the colloidal TiO 2 aqueous solution were strongly adsorbed on the TiO 2 particles with an apparent association constant ( Kapp) of ˜10 6 M -1. The hydroxyl radicals trapped on the TiO 2 surface exhibit the absorption spectrum with a maximum peak at 370 nm. In order to clear the oxidative ability of this species, the oxidation processes of 4-methylthiophenylmethanol (MTPM) and 2-phenylthioethanol (PTE) in the colloidal TiO 2 aqueous solution have been examined based on the kinetic analysis of the transient absorption.

  11. Effect of active hydroxyl groups on the interfacial bond strength of titanium with segmented polyurethane through gamma-mercapto propyl trimethoxysilane.

    PubMed

    Sakamoto, Harumi; Hirohashi, Yohei; Saito, Haruka; Doi, Hisashi; Tsutsumi, Yusuke; Suzuki, Yoshiaki; Noda, Kazuhiko; Hanawa, Takao

    2008-01-01

    The objective of this study was to investigate the effect of active hydroxyl groups on a titanium (Ti) surface on the bond strength between Ti and segmented polyurethane (SPU) composite through gamma-mercapto propyl trimethoxysilane (gamma-MPS). Active hydroxyl groups on Ti surface oxide were controlled by immersion in hydrogen peroxide (H2O2) with different lengths of immersion time, and the resulting concentrations of active hydroxyl groups were evaluated using a zinc-complex substitution technique. For the H2O2-treated Ti, it was characterized using X-ray photoelectron spectroscopy and scanning electron spectroscopy. For the bond strength of Ti/ gamma-MPS/SPU interface, it was determined using a shear bond test. Results showed that the bond strength increased with increase in the concentration of active hydroxyl groups. In terms of durability after immersion in water at 310 K for 30 days, it was found that bond strength was improved with increase in active hydroxyl groups. Based on the results obtained, active hydroxyl groups on the surface oxide film were clearly one of the causes governing the interfacial bond strength. PMID:18309616

  12. Hydroxyl radical measurements and oxidation capacity in a boreal forest environment

    NASA Astrophysics Data System (ADS)

    Hens, K.; Tatum Ernest, C.; Novelli, A.; Paasonen, P.; Sipilä, M.; Petäjä, T.; Nölscher, A.; Taraborrelli, D.; Keronen, P.; Trawny, K.; Kubistin, D.; Oswald, R.; Axinte, R.; Hosaynali Beygi, Z.; Auld, J.; Klüpfel, T.; Mesarchaki, E.; Song, W.; Valverde Canossa, J.; González Orozco, D.; Königstedt, R.; Bohn, B.; Rudolf, M.; Fischer, H.; Williams, J.; Crowley, J.; Martinez, M.; Harder, H. D.; Lelieveld, J.

    2012-12-01

    Forests cover about one third of the earth's total land surface and are known to be an important global source of biogenic volatile organic compounds (BVOCs) that are partly very reactive towards OH. Different types of forests are known to emit various characteristic BVOCs significantly influencing atmospheric oxidation chemistry. Measurements of OH and HO2 radicals in forest environments, however, reveal a serious lack of understanding of the underlying processes. The HUMPPA-COPEC intensive field campaign took place in summer 2010 at the SMEAR II station, located in Hyytiälä, Southern Finland, as collaboration between the Max Planck Institute for Chemistry and the University of Helsinki. The main goal of the campaign was to investigate the summertime emissions and photochemistry in a boreal forest. Comprehensive measurements including observations of many VOCs, HOx, and total OH reactivity were conducted to increase our understanding of atmospheric self-cleaning processes based on detailed analysis of production and loss mechanisms of the hydroxyl radical. Also the HOx budget in a coniferous forest was examined by using direct calculations from measured species as well as an observationally constrained chemical box model in steady state. For HUMPPA-COPEC chemical reaction schemes considering isoprene as the predominant primary BVOC lead to an over prediction of the measured OH concentration by a factor of up to 4. However, only a minor fraction of the measured total OH reactivity can be explained by measured isoprene. A preliminary terpene mechanism, taking the most abundant terpenes measured during HUMPPA-COPEC-2010 and their oxidation products into account, improves the agreement between simulated and measured OH, but is not sufficient to explain the missing OH reactivity in all cases. HO2 is described reasonably well by the model for conditions where the modeled and measured total OH reactivity agree. For lower than measured reactivity, the HO2 mixing ratios

  13. Bacterial adhesion to hydroxyl- and methyl-terminated alkanethiol self-assembled monolayers.

    PubMed Central

    Wiencek, K M; Fletcher, M

    1995-01-01

    The attachment of bacteria to solid surfaces is influenced by substratum chemistry, but to determine the mechanistic basis of this relationship, homogeneous, well-defined substrata are required. Self-assembled monolayers (SAMs) were constructed from alkanethiols to produce a range of substrata with different exposed functional groups, i.e., methyl and hydroxyl groups and a series of mixtures of the two. Percentages of hydroxyl groups in the SAMs and substratum wettability were measured by X-ray photoelectron spectroscopy and contact angles of water and hexadecane, respectively. SAMs exhibited various substratum compositions and wettabilities, ranging from hydrophilic, hydroxyl-terminated monolayers to hydrophobic, methyl-terminated monolayers. The kinetics of attachment of an estuarine bacterium to these surfaces in a laminar flow chamber were measured over periods of 120 min. The initial rate of net adhesion, the number of cells attached after 120 min, the percentage of attached cells that adsorbed or desorbed between successive measurements, and the residence times of attached cells were quantified by phase-contrast microscopy and digital image processing. The greatest numbers of attached cells occurred on hydrophobic surfaces, because (i) the initial rates of adhesion and the mean numbers of cells that attached after 120 min increased with the methyl content of the SAM and the contact angle of water and (ii) the percentage of cells that desorbed between successive measurements (ca. 2 min) decreased with increasing substratum hydrophobicity. With all surfaces, 60 to 80% of the cells that desorbed during the 120-min exposure period had residence times of less than 10 min, suggesting that establishment of firm adhesion occurred quickly on all of the test surfaces. PMID:7721687

  14. Regioselective hydroxylation of steroid hormones by human cytochromes P450.

    PubMed

    Niwa, Toshiro; Murayama, Norie; Imagawa, Yurie; Yamazaki, Hiroshi

    2015-05-01

    This article reviews in vitro metabolic activities [including Michaelis constants (Km), maximal velocities (Vmax) and Vmax/Km] and drug-steroid interactions [such as induction and cooperativity (activation)] of cytochromes P450 (P450 or CYP) in human tissues, including liver and adrenal gland, for 14 kinds of endogenous steroid compounds, including allopregnanolone, cholesterol, cortisol, cortisone, dehydroepiandrosterone, estradiol, estrone, pregnenolone, progesterone, testosterone and bile acids (cholic acid). First, we considered the drug-metabolizing P450s. 6β-Hydroxylation of many steroids, including cortisol, cortisone, progesterone and testosterone, was catalyzed primarily by CYP3A4. CYP1A2 and CYP3A4, respectively, are likely the major hepatic enzymes responsible for 2-/4-hydroxylation and 16α-hydroxylation of estradiol and estrone, steroids that can contribute to breast cancer risk. In contrast, CYP1A1 and CYP1B1 predominantly metabolized estrone and estradiol to 2- and 4-catechol estrogens, which are endogenous ultimate carcinogens if formed in the breast. Some metabolic activities of CYP3A4, including dehydroepiandrosterone 7β-/16α-hydroxylation, estrone 2-hydroxylation and testosterone 6β-hydroxylation, were higher than those for polymorphically expressed CYP3A5. Next, we considered typical steroidogenic P450s. CYP17A1, CYP19A1 and CYP27A1 catalyzed steroid synthesis, including hydroxylation at 17α, 19 and 27 positions, respectively. However, it was difficult to predict which hepatic drug-metabolizing P450 or steroidogenic P450 will be mainly responsible for metabolizing each steroid hormone in vivo based on these results. Further research is required on the metabolism of steroid hormones by various P450s and on prediction of their relative contributions to in vivo metabolism. The findings collected here provide fundamental and useful information on the metabolism of steroid compounds. PMID:25678418

  15. Evolving P450pyr Monooxygenase for Regio- and Stereoselective Hydroxylations.

    PubMed

    Yang, Yi; Li, Zhi

    2015-01-01

    P450pyr monooxygenase from Sphingomonas sp. HXN-200 catalysed the regio- and stereoselective hydroxylation at a non-activated carbon atom, a useful but challenging reaction in classic chemistry, with unique substrate specificity for a number of alicyclic compounds. New P450pyr mutants were developed by directed evolution with improved catalytic performance, thus significantly extending the application of the P450pyr monooxygenase family in biohydroxylation to prepare useful and valuable chiral alcohols. Directed evolution of P450pyr created new enzymes with improved S-enantioselectivity or R-enantioselectivity for the hydroxylation of N-benzyl pyrrolidine, enhanced regioselectivity for the hydroxylation of N-benzyl pyrrolidinone, and increased enantioselectivity for the hydroxylation of N-benzyl piperidinone, respectively. Directed evolution of P450pyr generated also mutants with fully altered regioselectivity (from terminal to subterminal) and newly created excellent S-enantioselectivity for the biohydroxylation of n-octane and propylbenzene, respectively, providing new opportunities for the regio- and enantioselective alkane functionalization. New P450pyr mutants were engineered as the first catalyst for highly selective terminal hydroxylation of n-butanol to 1,4-butanediol. Several novel, accurate, sensitive, simple, and HTS assays based on colorimetric or MS detection for measuring the enantio- and/or regioselectivity of hydroxylation were developed and proven to be practical in directed evolution. The P450pyr X-ray structure was obtained and used to guide the evolution. In silico modelling and substrate docking provided some insight into the influence of several important amino acid mutations of the engineered P450pyr mutants on the altered or enhanced regio- and enantioselectivity as well as new substrate acceptance. The obtained information and knowledge is useful for further engineering of P450pyr for other hydroxylations and oxidations. PMID:26507217

  16. Estradiol-15 alpha-hydroxylation: a new avenue of estrogen metabolism in peri-implantation pig blastocysts.

    PubMed

    Chakraborty, C; Davis, D L; Dey, S K

    1990-02-01

    Pig blastocysts have the capacity to convert estradiol into catechol estrogens. Our present study shows that they also have the capacity to hydroxylate estradiol in cycloaliphatic C-atom 15, and this aliphatic hydroxylation reaction is more predominate than the aromatic hydroxylations. The conversion of [4-14C]estradiol to [4-14C]15 alpha-hydroxyestradiol by mitochondrial-rich/microsomal fractions was examined by isolation of this product using reversed phase high-performance liquid chromatography (HPLC) attached to a radiometric flow detector, and its identification by gas chromatography-mass spectrometry. The enzyme kinetics for estrogen 15 alpha-hydroxylase were performed in the pig blastocyst obtained on Day 13 of pregnancy (Day 0 = first acceptance of the male). The enzyme follows classical Michaelis-Menten kinetics. The apparent Kms for estradiol were 2.47 and 1.85 microM, and the apparent Vmaxs were 0.25 and 0.197 nmol/mg/min in the mitochondrial-rich and microsomal fractions, respectively. The enzyme activity was inhibited by different steroidal compounds and non-steroidal estrogens, as well as by CO, SKF-525A, piperonyl butoxide and antibody to cytochrome P450 reductase. Ontogenesis of the blastocyst's estrogen 15 alpha-hydroxylase follows a similar pattern to that of estrogen-2/4-hydroxylase. Thus, highest activity was observed on Days 12 and 13 and lowest was on Day 15 of pregnancy. Furthermore, the enzyme is abundant primarily in the extraembryonic tissues rather than in the embryo proper. The abundance of the enzyme in the extraembryonic tissues, and its surge at a critical time of pregnancy recognition and just prior to implantation suggest that 15 alpha-hydroxylated estradiol could be involved in these processes. PMID:2155354

  17. Solar abundance of platinum

    PubMed Central

    Burger, Harry; Aller, Lawrence H.

    1975-01-01

    Three lines of neutral platinum, located at λ 2997.98 Å, λ 3064.71 Å, and λ 3301.86 Å have been used to determine the solar platinum abundance by the method of spectral synthesis. On the scale, log A(H) = 12.00, the thus-derived solar platinum abundance is 1.75 ± 0.10, in fair accord with Cameron's value of log A(Pt) = 1.69 derived by Mason from carbonaceous chondrites and calculated on the assumption that log A(Si) = 7.55 in the sun. PMID:16592278

  18. Pulsed Electron Beam Water Radiolysis for Sub-Microsecond Hydroxyl Radical Protein Footprinting

    PubMed Central

    Watson, Caroline; Janik, Ireneusz; Zhuang, Tiandi; Charvátová, Olga; Woods, Robert J.; Sharp, Joshua S.

    2009-01-01

    Hydroxyl radical footprinting is a valuable technique for studying protein structure, but care must be taken to ensure that the protein does not unfold during the labeling process due to oxidative damage. Footprinting methods based on sub-microsecond laser photolysis of peroxide that complete the labeling process faster than the protein can unfold have been recently described; however, the mere presence of large amounts of hydrogen peroxide can also cause uncontrolled oxidation and minor conformational changes. We have developed a novel method for sub-microsecond hydroxyl radical protein footprinting using a pulsed electron beam from a 2 MeV Van de Graaff electron accelerator to generate a high concentration of hydroxyl radicals by radiolysis of water. The amount of oxidation can be controlled by buffer composition, pulsewidth, dose, and dissolved nitrous oxide gas in the sample. Our results with ubiquitin and β-lactoglobulin A demonstrate that one sub-microsecond electron beam pulse produces extensive protein surface modifications. Highly reactive residues that are buried within the protein structure are not oxidized, indicating that the protein retains its folded structure during the labeling process. Time-resolved spectroscopy indicates that the major part of protein oxidation is complete in a timescale shorter than that of large scale protein motions. PMID:19265387

  19. In Vitro Toxicity Assessment of Three Hydroxylated Fullerenes in Human Skin Cells

    PubMed Central

    Saathoff, J.G.; Inman, A.O.; Xia, X.R.; Riviere, J.E.; Monteiro-Riviere, N.A.

    2011-01-01

    Carbon fullerenes possess unique properties and their interactions with biomolecules have widespread applications. Functionalization of fullerenes with hydroxyl groups (fullerenols) can increase the solubility and potential for cellular interaction, but the health and safety effects of varying degrees of fullerene hydroxylation in biological systems is poorly understood. Existing reports regarding the toxicity and inflammatory potential of fullerenols give conflicting conclusions. To further elucidate the potential for toxicity of fullerenols, human epidermal keratinocytes (HEK) were exposed to fullerenols (low (C60(OH)20), medium (C60(OH)24), and high (C60(OH)32)) at concentrations ranging from 0.000544–42.5μg/ml for 24 and 48h. A statistically significant (p < 0.05) decrease in viability with alamar Blue (aB) was noted only with C60(OH)32 at 42.5μg/ml after 24h. Nanoparticle (NP) controls showed minimal NP/assay interference of the three fullerenols with the aB viability assay. Normalized IL-8 concentration for C60(OH)20 was not significantly different from control, while C60(OH)24 and C60(OH)32 showed a significant decrease at 24 and 48h. These results suggest that different hydroxylation of fullerenes caused no cytotoxicity or inflammation up to 8.55μg/ml. These findings suggest that extrapolation across similar NP will be dependent upon surface chemistry and concentration which may affect the degree of agglomeration and thus biological effects. PMID:21964474

  20. Environmentally Persistent Free Radicals (EPFRs). 3. Free versus Bound Hydroxyl Radicals in EPFR Aqueous Solutions

    PubMed Central

    2015-01-01

    Additional experimental evidence is presented for in vitro generation of hydroxyl radicals because of redox cycling of environmentally persistent free radicals (EPFRs) produced after adsorption of 2-monochlorophenol at 230 °C (2-MCP-230) on copper oxide supported by silica, 5% Cu(II)O/silica (3.9% Cu). A chemical spin trapping agent, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), in conjunction with electron paramagnetic resonance (EPR) spectroscopy was employed. Experiments in spiked O17 water have shown that ∼15% of hydroxyl radicals formed as a result of redox cycling. This amount of hydroxyl radicals arises from an exogenous Fenton reaction and may stay either partially trapped on the surface of particulate matter (physisorbed or chemisorbed) or transferred into solution as free OH. Computational work confirms the highly stable nature of the DMPO–OH adduct, as an intermediate produced by interaction of DMPO with physisorbed/chemisorbed OH (at the interface of solid catalyst/solution). All reaction pathways have been supported by ab initio calculations. PMID:25036238

  1. Stellar Oxygen Abundances

    NASA Astrophysics Data System (ADS)

    King, Jeremy

    1994-04-01

    This dissertation addresses several issues concerning stellar oxygen abundances. The 7774 {\\AA} O I triplet equivalent widths of Abia & Rebolo [1989, AJ, 347, 186] for metal-poor dwarfs are found to be systematically too high. I also argue that current effective temperatures used in halo star abundance studies may be ~150 K too low. New color-Teff relations are derived for metal-poor stars. Using the revised Teff values and improved equivalent widths for the 7774A O I triplet, the mean [O/Fe] ratio for a handful of halo stars is found to be +0.52 with no dependence on Teff or [Fe/H]. Possible cosmological implications of the hotter Teff scale are discussed along with additional evidence supporting the need for a higher temperature scale for metal-poor stars. Our Teff scale leads to a Spite Li plateau value of N(Li)=2.28 +/- 0.09. A conservative minimal primordial value of N(Li)=2.35 is inferred. If errors in the observations and models are considered, consistency with standard models of Big Bang nucleosynthesis is still achieved with this larger Li abundance. The revised Teff scale raises the observed B/Be ratio of HD 140283 from 10 to 12, making its value more comfortably consistent with the production of the observed B and Be by ordinary spallation. Our Teff values are found to be in good agreement with values predicted from both the Victoria and Yale isochrone color-Teff relations. Thus, it appears likely that no changes in globular cluster ages would result. Next, we examine the location of the break in the [O/Fe] versus [Fe/H] plane in a quantitative fashion. Analysis of a relatively homogeneous data set does not favor any unique break point in the range -1.7 /= -3), in agreement with the new results for halo dwarfs. We find that the gap in the observed [O/H] distribution, noted by Wheeler et al

  2. Abundances of light elements.

    PubMed Central

    Pagel, B E

    1993-01-01

    Recent developments in the study of abundances of light elements and their relevance to cosmological nucleosynthesis are briefly reviewed. The simplest model, based on standard cosmology and particle physics and assuming homogeneous baryon density at the relevant times, continues to stand up well. PMID:11607388

  3. Ab initio dynamics of the cytochrome P450 hydroxylation reaction

    PubMed Central

    Elenewski, Justin E.; Hackett, John C

    2015-01-01

    The iron(IV)-oxo porphyrin π-cation radical known as Compound I is the primary oxidant within the cytochromes P450, allowing these enzymes to affect the substrate hydroxylation. In the course of this reaction, a hydrogen atom is abstracted from the substrate to generate hydroxyiron(IV) porphyrin and a substrate-centered radical. The hydroxy radical then rebounds from the iron to the substrate, yielding the hydroxylated product. While Compound I has succumbed to theoretical and spectroscopic characterization, the associated hydroxyiron species is elusive as a consequence of its very short lifetime, for which there are no quantitative estimates. To ascertain the physical mechanism underlying substrate hydroxylation and probe this timescale, ab initio molecular dynamics simulations and free energy calculations are performed for a model of Compound I catalysis. Semiclassical estimates based on these calculations reveal the hydrogen atom abstraction step to be extremely fast, kinetically comparable to enzymes such as carbonic anhydrase. Using an ensemble of ab initio simulations, the resultant hydroxyiron species is found to have a similarly short lifetime, ranging between 300 fs and 3600 fs, putatively depending on the enzyme active site architecture. The addition of tunneling corrections to these rates suggests a strong contribution from nuclear quantum effects, which should accelerate every step of substrate hydroxylation by an order of magnitude. These observations have strong implications for the detection of individual hydroxylation intermediates during P450 catalysis. PMID:25681906

  4. Ab initio dynamics of the cytochrome P450 hydroxylation reaction

    NASA Astrophysics Data System (ADS)

    Elenewski, Justin E.; Hackett, John C.

    2015-02-01

    The iron(IV)-oxo porphyrin π-cation radical known as Compound I is the primary oxidant within the cytochromes P450, allowing these enzymes to affect the substrate hydroxylation. In the course of this reaction, a hydrogen atom is abstracted from the substrate to generate hydroxyiron(IV) porphyrin and a substrate-centered radical. The hydroxy radical then rebounds from the iron to the substrate, yielding the hydroxylated product. While Compound I has succumbed to theoretical and spectroscopic characterization, the associated hydroxyiron species is elusive as a consequence of its very short lifetime, for which there are no quantitative estimates. To ascertain the physical mechanism underlying substrate hydroxylation and probe this timescale, ab initio molecular dynamics simulations and free energy calculations are performed for a model of Compound I catalysis. Semiclassical estimates based on these calculations reveal the hydrogen atom abstraction step to be extremely fast, kinetically comparable to enzymes such as carbonic anhydrase. Using an ensemble of ab initio simulations, the resultant hydroxyiron species is found to have a similarly short lifetime, ranging between 300 fs and 3600 fs, putatively depending on the enzyme active site architecture. The addition of tunneling corrections to these rates suggests a strong contribution from nuclear quantum effects, which should accelerate every step of substrate hydroxylation by an order of magnitude. These observations have strong implications for the detection of individual hydroxylation intermediates during P450 catalysis.

  5. Ab initio dynamics of the cytochrome P450 hydroxylation reaction

    SciTech Connect

    Elenewski, Justin E.; Hackett, John C

    2015-02-14

    The iron(IV)-oxo porphyrin π-cation radical known as Compound I is the primary oxidant within the cytochromes P450, allowing these enzymes to affect the substrate hydroxylation. In the course of this reaction, a hydrogen atom is abstracted from the substrate to generate hydroxyiron(IV) porphyrin and a substrate-centered radical. The hydroxy radical then rebounds from the iron to the substrate, yielding the hydroxylated product. While Compound I has succumbed to theoretical and spectroscopic characterization, the associated hydroxyiron species is elusive as a consequence of its very short lifetime, for which there are no quantitative estimates. To ascertain the physical mechanism underlying substrate hydroxylation and probe this timescale, ab initio molecular dynamics simulations and free energy calculations are performed for a model of Compound I catalysis. Semiclassical estimates based on these calculations reveal the hydrogen atom abstraction step to be extremely fast, kinetically comparable to enzymes such as carbonic anhydrase. Using an ensemble of ab initio simulations, the resultant hydroxyiron species is found to have a similarly short lifetime, ranging between 300 fs and 3600 fs, putatively depending on the enzyme active site architecture. The addition of tunneling corrections to these rates suggests a strong contribution from nuclear quantum effects, which should accelerate every step of substrate hydroxylation by an order of magnitude. These observations have strong implications for the detection of individual hydroxylation intermediates during P450 catalysis.

  6. Hydroxyl radicals do not crosslink a DNA-lysozyme complex

    SciTech Connect

    Werbin, H.; Cheng, C.J.

    1985-12-01

    The ionic complex between lysozyme and either Escherichia coli DNA or pBR322 DNA was not crosslinked by two systems capable of producing nanomolar amounts of hydroxyl radicals, the oxidation of xanthine by xanthine oxidase and the iron catalyzed oxidation of ascorbic acid. Nor did effective crosslinking occur with micromolar quantities of hydroxyl radicals raised by the addition of adenosine nucleotides to ferrous iron and hydrogen peroxide. In this case, radical content was estimated by colorimetric analysis of formaldehyde following hydroxyl radical oxidation of dimethyl sulfoxide. Similar amounts of radicals generated by pulse radiolysis in a nitrous oxide atmosphere failed also to induce crosslinking. These findings do not support a role for hydroxy radicals in the N-acetoxy-2-acetylaminofluorene induced crosslinking of DNA to lysozyme proposed earlier.

  7. Solar Models with New Low Metal Abundances

    NASA Astrophysics Data System (ADS)

    Yang, Wuming

    2016-04-01

    In the past decade, the photospheric abundances of the Sun had been revised several times by many observers. The standard solar models constructed with the new low-metal abundances disagree with helioseismic results and detected neutrino fluxes. The solar model problem has puzzled some stellar physicists for more than 10 years. Rotation, enhanced diffusion, convection overshoot, and magnetic fields are used to reconcile the new abundances with helioseismology. The too low helium subsurface abundance in enhanced diffusion models can be improved by the mixing caused by rotation and magnetic fields. The problem of the depth of the convective zone in rotating models can be resolved by convection overshoot. Consequently, the Asplund–Grevesse–Sauval rotation model including overshooting (AGSR) reproduces the seismically inferred sound-speed and density profiles and the convection zone depth as well as the Grevesse & Sauval model computed before. But this model fails to reproduce the surface helium abundance, which is 0.2393 (2.6σ away from the seismic value), and neutrino fluxes. The magnetic model called AGSM keeps the agreement of the AGSR and improves the prediction of the surface helium abundance. The observed separation ratios r02 and r13 are reasonably reproduced by AGSM. Moreover, neutrino fluxes calculated by this model are not far from the detected neutrino fluxes and the predictions of previous works.

  8. Hydroxyl Radical Dosimetry for High Flux Hydroxyl Radical Protein Footprinting Applications Using a Simple Optical Detection Method.

    PubMed

    Xie, Boer; Sharp, Joshua S

    2015-11-01

    Hydroxyl radical protein footprinting (HRPF) by fast photochemical oxidation of proteins (FPOP) is a powerful benchtop tool used to probe protein structure, interactions, and conformational changes in solution. However, the reproducibility of all HRPF techniques is limited by the ability to deliver a defined concentration of hydroxyl radicals to the protein. This ability is impacted by both the amount of radical generated and the presence of radical scavengers in solution. In order to compare HRPF data from sample to sample, a hydroxyl radical dosimeter is needed that can measure the effective concentration of radical that is delivered to the protein, after accounting for both differences in hydroxyl radical generation and nonanalyte radical consumption. Here, we test three radical dosimeters (Alexa Fluor 488, terepthalic acid, and adenine) for their ability to quantitatively measure the effective radical dose under the high radical concentration conditions of FPOP. Adenine has a quantitative relationship between UV spectrophotometric response, effective hydroxyl radical dose delivered, and peptide and protein oxidation levels over the range of radical concentrations typically encountered in FPOP. The simplicity of an adenine-based dosimeter allows for convenient and flexible incorporation into FPOP applications, and the ability to accurately measure the delivered radical dose will enable reproducible and reliable FPOP across a variety of platforms and applications. PMID:26455423

  9. GALA: Stellar atmospheric parameters and chemical abundances

    NASA Astrophysics Data System (ADS)

    Mucciarelli, A.; Pancino, E.; Lovisi, L.; Ferraro, F. R.; Lapenna, E.

    2013-02-01

    GALA is a freely distributed Fortran code to derive the atmospheric parameters (temperature, gravity, microturbulent velocity and overall metallicity) and abundances for individual species of stellar spectra using the classical method based on the equivalent widths of metallic lines. The abundances of individual spectral lines are derived by using the WIDTH9 code developed by R. L. Kurucz. GALA is designed to obtain the best model atmosphere, by optimizing temperature, surface gravity, microturbulent velocity and metallicity, after rejecting the discrepant lines. Finally, it computes accurate internal errors for each atmospheric parameter and abundance. The code obtains chemical abundances and atmospheric parameters for large stellar samples quickly, thus making GALA an useful tool in the epoch of the multi-object spectrographs and large surveys.

  10. Hydroxyl radical induced degradation of salicylates in aerated aqueous solution

    NASA Astrophysics Data System (ADS)

    Szabó, László; Tóth, Tünde; Homlok, Renáta; Rácz, Gergely; Takács, Erzsébet; Wojnárovits, László

    2014-04-01

    Ionizing radiation induced degradation of acetylsalicylic acid, its hydrolysis product salicylic acid and a salicylic acid derivative 5-sulpho-salicylic acid, was investigated in dilute aqueous solutions by UV-vis spectrophotometry, HPLC separation and diode-array or MS/MS detection, chemical oxygen demand, total organic carbon content and by Vibrio fischeri toxicity measurements. Hydroxyl radicals were shown to degrade these molecules readily, and first degradation products were hydroxylated derivatives in all cases. Due to the by-products, among them hydrogen peroxide, the toxicity first increased and then decreased with the absorbed dose. With prolonged irradiation complete mineralization was achieved.

  11. Radiocarbon tracer measurements of atmospheric hydroxyl radical concentrations

    NASA Technical Reports Server (NTRS)

    Campbell, M. J.; Farmer, J. C.; Fitzner, C. A.; Henry, M. N.; Sheppard, J. C.

    1986-01-01

    The usefulness of the C-14 tracer in measurements of atmospheric hydroxyl radical concentration is discussed. The apparatus and the experimental conditions of three variations of a radiochemical method of atmosphere analysis are described and analyzed: the Teflon bag static reactor, the flow reactor (used in the Wallops Island tests), and the aircraft OH titration reactor. The procedure for reduction of the aircraft reactor instrument data is outlined. The problems connected with the measurement of hydroxyl radicals are discussed. It is suggested that the gas-phase radioisotope methods have considerable potential in measuring tropospheric impurities present in very low concentrations.

  12. Regioselective ortho-Hydroxylations of Flavonoids by Yeast.

    PubMed

    Sordon, Sandra; Madej, Anna; Popłoński, Jarosław; Bartmańska, Agnieszka; Tronina, Tomasz; Brzezowska, Ewa; Juszczyk, Piotr; Huszcza, Ewa

    2016-07-13

    Natural flavonoids, such as naringenin, hesperetin, chrysin, apigenin, luteolin, quercetin, epicatechin, and biochanin A, were subjected to microbiological transformations by Rhodotorula glutinis. Yeast was able to regioselectively C-8 hydroxylate hesperetin, luteolin, and chrysin. Naringenin was transformed to 8- and 6-hydroxyderivatives. Quercetin, epicatechin, and biochanin A did not undergo biotransformation. A metabolic pathway for the degradation of chrysin has been elucidated. The metabolism of chrysin proceeds via an initial C-8 hydroxylation to norwogonin, followed by A-ring cleavage to 4-hydroxy-6-phenyl-2H-pyran-2-one. PMID:27324975

  13. Accelerated crystallization of zeolites via hydroxyl free radicals.

    PubMed

    Feng, Guodong; Cheng, Peng; Yan, Wenfu; Boronat, Mercedes; Li, Xu; Su, Ji-Hu; Wang, Jianyu; Li, Yi; Corma, Avelino; Xu, Ruren; Yu, Jihong

    2016-03-11

    In the hydrothermal crystallization of zeolites from basic media, hydroxide ions (OH(-)) catalyze the depolymerization of the aluminosilicate gel by breaking the Si,Al-O-Si,Al bonds and catalyze the polymerization of the aluminosilicate anions around the hydrated cation species by remaking the Si,Al-O-Si,Al bonds. We report that hydroxyl free radicals (•OH) are involved in the zeolite crystallization under hydrothermal conditions. The crystallization processes of zeolites-such as Na-A, Na-X, NaZ-21, and silicalite-1-can be accelerated with hydroxyl free radicals generated by ultraviolet irradiation or Fenton's reagent. PMID:26965626

  14. Mephenytoin hydroxylation in the Cuna Amerindians of Panama.

    PubMed Central

    Inaba, T; Jorge, L F; Arias, T D

    1988-01-01

    1 Mephenytoin p(4')-hydroxylation, which is deficient in 3-5% of Caucasians, was examined in 96 Cuna Amerindians of Panama. 2 Attempts were made to exclude poor compliance with urine collection and ingestion of the drug dose since the assignment of phenotype was based upon urinary recovery of the metabolite. These involved the measurement of the urinary recovery of sparteine, added to the ingested capsule, and of the renal excretion of creatinine. 3 Of the 90 Cunas deemed to be reasonably complaint, none of them appeared to be deficient in p(4')-hydroxylation of mephenytoin. PMID:3370193

  15. Solar abundance of iridium

    PubMed Central

    Drake, Stephen; Aller, Lawrence H.

    1976-01-01

    By a method of spectrum synthesis, which yields log gfA, where g is the statistical weight of the lower level, f is the oscillator strength, and A is the abundance, an attempt is made to deduce the solar iridium abundance from one relatively unblended, but fairly weak IrI line, λ 3220.78 Å. If the Corliss-Bozman f-value for this line is adopted, we find log A(Ir) = 0.82 on the scale log A(H) = 12.00. The discordance with the value found from carbonaceous chondrites may arise from faulty f-values or from difficulties arising from line blending in this far ultraviolet domain of the solar spectrum. PMID:16578735

  16. I. Airglow on Mars: Model predictions for the oxygen IR atmospheric band at 1.27 micrometers, the hydroxyl radical Meinel bands and the hydroxyl radical A-X band system. II. Physical and chemical aeronomy of HD 209458b

    NASA Astrophysics Data System (ADS)

    Garcia Munoz, Antonio

    The first part of this dissertation is concerned with model predictions of airglow from the O2 IR atmospheric band at 1.27 mum, the OH Meinel bands and the OH A-X band system in the low-latitude neutral atmosphere of Mars. As an observable feature, airglow provides a means to remotely probe the composition, dynamics and energetics of the Martian atmosphere. The daytime emission from the O2 IR atmospheric band, a direct result of ozone photodissociation, has long been known to be a prominent emission of the Martian airglow. The motivation for pursuing the modelling of the nighttime components of the O2 IR atmospheric band and the OH Meinel bands is the potential of these two processes for characterizing the atomic oxygen profile in the 50-80 km region of the atmosphere. Likewise, the OH A-X band system may be useful to constrain the abundance of the hydroxyl radical on the illuminated side of the planet below 60 km. Both, O and OH are indicators of the photochemical state of the atmosphere. The results reported herein are expected to serve as guidelines for prospective observations of the atmosphere of Mars. The second part of the dissertation investigates the physical and chemical aeronomy of HD 209458b. The discovery of this extrasolar planet by radial velocity measurements was announced in 2000. Shortly afterwards, the inference of the mean planetary density from transit observations indicated the plausible gaseous nature of the planet. Later in-transit spectrally-resolved photometric observations revealed a cloud of hydrogen, carbon and oxygen atoms extending to a few planetary radii above the surface of the planet, which has been interpreted as evidence for an escaping atmosphere around HD 209458b. At an orbital distance of 0.05 AU, intense EUV stellar irradiation may lead to the massive escape of the atmosphere. In this work, the composition, escape and energy balance of the atmosphere are consistently modelled. Escape rates and abundances of the main hydrogen

  17. Radiolysis of the polyethylene/water system: Studies on the role of hydroxyl radical

    NASA Astrophysics Data System (ADS)

    Billamboz, Nicolas; Grivet, Manuel; Foley, Sarah; Baldacchino, Gérard; Hubinois, Jean-Charles

    2010-01-01

    The role of hydroxyl radical on polyethylene degradation under aqueous conditions has been studied. The reactivity of HO· towards PE is highlighted by pulse radiolysis experiments on a PE powder suspension in water using the thiocyanate competition technique. Infrared analysis of PE films irradiated in the presence of water is performed. Solutions have been either degassed with Ar, in order to remove O 2 which would react with the PE, or N 2O which enhances the production of HO· radicals. Oxygenated groups and double bond groups created at the surface of PE are characterized using IR analysis, and the results for both saturated solution systems are compared.

  18. Concentration-dependent photodegradation kinetics and hydroxyl-radical oxidation of phenicol antibiotics.

    PubMed

    Li, Kai; Zhang, Peng; Ge, Linke; Ren, Honglei; Yu, Chunyan; Chen, Xiaoyang; Zhao, Yuanfeng

    2014-09-01

    Thiamphenicol and florfenicol are two phenicol antibiotics widely used in aquaculture and are ubiquitous as micropollutants in surface waters. The present study investigated their photodegradation kinetics, hydroxyl-radical (OH) oxidation reactivities and products. Firstly, the photolytic kinetics of the phenicols in pure water was studied as a function of initial concentrations (C0) under UV-vis irradiation (λ>200nm). It was found that the kinetics was influenced by C0. A linear plot of the pseudo-first-order rate constant vs C0 was observed with a negative slope. Secondly, the reaction between the phenicol antibiotics and OH was examined with a competition kinetic method under simulated solar irradiation (λ>290nm), which quantified their bimolecular reaction rate constants of (2.13±0.02)×10(9)M(-1)s(-1) and (1.82±0.10)×10(9)M(-1)s(-1) for thiamphenicol and florfenicol, respectively. Then the corresponding OH oxidated half-lives in sunlit surface waters were calculated to be 90.5-106.1h. Some main intermediates were formed from the reaction, which suggested that the two phenicols underwent hydroxylation, oxygenation and dehydrogenation when OH existed. These results are of importance to assess the phenicol persistence in wastewater treatment and sunlit surface waters. PMID:24997929

  19. One-step microwave synthesis of N-doped hydroxyl-functionalized carbon dots with ultra-high fluorescence quantum yields.

    PubMed

    Zhang, Yongqiang; Liu, Xingyuan; Fan, Yi; Guo, Xiaoyang; Zhou, Lei; Lv, Ying; Lin, Jie

    2016-08-18

    A one-step microwave synthesis of N-doped hydroxyl-functionalized carbon dots (CDs) with ultra-high fluorescence quantum yields (QYs) of 99% is reported. These ultra-high QY CDs were synthesized using citric acid and amino compound-containing hydroxyls like ethanolamine and tris(hydroxylmethyl)aminomethane. Amino and carboxyl moieties can form amides through dehydration condensation reactions, and these amides act as bridges between carboxyl and hydroxyl groups, and modify hydroxyl groups on the surface of the CDs. The entire reaction can be carried out within 5 min. When the molar ratio of reactants is 1 : 1, the hydroxyl and graphitic nitrogen content is the highest, and the synergy leads to a high ratio between the radiative transition rate and nonradiative transition rate as well as a high QY. The developed pathway to N-doped hydroxyl-functionalized CDs can provide unambiguous and remarkable insights into the design of highly luminescent functionalized carbon dots, and expedite the applications of CDs. PMID:27500530

  20. Lysine hydroxylation of collagen in a fibroblast cell culture system

    NASA Technical Reports Server (NTRS)

    Uzawa, Katsuhiro; Yeowell, Heather N.; Yamamoto, Kazushi; Mochida, Yoshiyuki; Tanzawa, Hideki; Yamauchi, Mitsuo

    2003-01-01

    The lysine (Lys) hydroxylation pattern of type I collagen produced by human fibroblasts in culture was analyzed and compared. Fibroblasts were cultured from normal human skin (NSF), keloid (KDF), fetal skin (FDF), and skin tissues of Ehlers-Danlos syndrome type VIA and VIB patients (EDS-VIA and -VIB). The type I collagen alpha chains with or without non-helical telopeptides were purified from the insoluble matrix and analyzed. In comparison with NSFs, KDF and FDF showed significantly higher Lys hydroxylation, particularly in the telopeptide domains of both alpha chains. Both EDS-VIA and -VIB showed markedly lower Lys hydroxylation in the helical domains of both alpha chains whereas that in the telopeptides was comparable with those of NSFs. A similar profile was observed in the tissue sample of the EDS-VIB patient. These results demonstrate that the Lys hydroxylation pattern is domain-specific within the collagen molecule and that this method is useful to characterize the cell phenotypes in normal/pathological connective tissues.

  1. Production of hydroxylated fatty acids in genetically modified plants

    DOEpatents

    Somerville, Chris; Broun, Pierre; van de Loo, Frank

    2001-01-01

    This invention relates to plant fatty acyl hydroxylases. Methods to use conserved amino acid or nucleotide sequences to obtain plant fatty acyl hydroxylases are described. Also described is the use of cDNA clones encoding a plant hydroxylase to produce a family of hydroxylated fatty acids in transgenic plants.

  2. Unique Phase Behaviors in the Gemini Surfactant/EAN Binary System: The Role of the Hydroxyl Group.

    PubMed

    Li, Qintang; Wang, Xudong; Yue, Xiu; Chen, Xiao

    2015-12-22

    The hydroxyl group in the spacer of a cationic Gemini surfactant (12-3OH-12) caused dramatic changes of the phase behaviors in a protic ionic liquid (EAN). Here, the effects of the hydroxyl group on micellization and lyotropic liquid crystal formation were investigated through the surface tension, small-angle X-ray scattering, polarized optical microscopy, and rheological measurements. With the hydroxyl group in the spacer, the critical micellization concentration of 12-3OH-12 was found to be lower than that of the homologue without hydroxyl (12-3-12) and the 12-3OH-12 molecules packed more densely at the air/EAN interface. It was then interesting to observe a coexistence of two separated phases at wide concentration and temperature ranges in this 12-3OH-12/EAN system. Such a micellar phase separation was rarely observed in the ionic surfactant binary system. With the increase of surfactant concentration, the reverse hexagonal and bicontinuous cubic phases appeared in sequence, whereas only a reverse hexagonal phase was found in 12-3-12/EAN system. But, the hexagonal phases formed with 12-3OH-12 exhibited lower viscoelasticity and thermostability than those observed in 12-3-12/EAN system. Such unique changes in phase behaviors of 12-3OH-12 were ascribed to their enhanced solvophilic interactions of 12-3OH-12 and relatively weak solvophobic interactions in EAN. PMID:26634877

  3. Late embryogenesis abundant proteins

    PubMed Central

    Olvera-Carrillo, Yadira; Reyes, José Luis

    2011-01-01

    Late Embryogenesis Abundant (LEA) proteins accumulate at the onset of seed desiccation and in response to water deficit in vegetative plant tissues. The typical LEA proteins are highly hydrophilic and intrinsically unstructured. They have been classified in different families, each one showing distinctive conserved motifs. In this manuscript we present and discuss some of the recent findings regarding their role in plant adaptation to water deficit, as well as those concerning to their possible function, and how it can be related to their intrinsic structural flexibility. PMID:21447997

  4. Hydroxylation of the eukaryotic ribosomal decoding center affects translational accuracy

    PubMed Central

    Loenarz, Christoph; Sekirnik, Rok; Thalhammer, Armin; Ge, Wei; Spivakovsky, Ekaterina; Mackeen, Mukram M.; McDonough, Michael A.; Cockman, Matthew E.; Kessler, Benedikt M.; Ratcliffe, Peter J.; Wolf, Alexander; Schofield, Christopher J.

    2014-01-01

    The mechanisms by which gene expression is regulated by oxygen are of considerable interest from basic science and therapeutic perspectives. Using mass spectrometric analyses of Saccharomyces cerevisiae ribosomes, we found that the amino acid residue in closest proximity to the decoding center, Pro-64 of the 40S subunit ribosomal protein Rps23p (RPS23 Pro-62 in humans) undergoes posttranslational hydroxylation. We identify RPS23 hydroxylases as a highly conserved eukaryotic subfamily of Fe(II) and 2-oxoglutarate dependent oxygenases; their catalytic domain is closely related to transcription factor prolyl trans-4-hydroxylases that act as oxygen sensors in the hypoxic response in animals. The RPS23 hydroxylases in S. cerevisiae (Tpa1p), Schizosaccharomyces pombe and green algae catalyze an unprecedented dihydroxylation modification. This observation contrasts with higher eukaryotes, where RPS23 is monohydroxylated; the human Tpa1p homolog OGFOD1 catalyzes prolyl trans-3-hydroxylation. TPA1 deletion modulates termination efficiency up to ∼10-fold, including of pathophysiologically relevant sequences; we reveal Rps23p hydroxylation as its molecular basis. In contrast to most previously characterized accuracy modulators, including antibiotics and the prion state of the S. cerevisiae translation termination factor eRF3, Rps23p hydroxylation can either increase or decrease translational accuracy in a stop codon context-dependent manner. We identify conditions where Rps23p hydroxylation status determines viability as a consequence of nonsense codon suppression. The results reveal a direct link between oxygenase catalysis and the regulation of gene expression at the translational level. They will also aid in the development of small molecules altering translational accuracy for the treatment of genetic diseases linked to nonsense mutations. PMID:24550462

  5. Report on carbon and nitrogen abundance studies

    NASA Technical Reports Server (NTRS)

    Boehm-Vitense, Erika

    1991-01-01

    The aim of the proposal was to determine the nitrogen to carbon abundance ratios from transition layer lines in stars with different T(sub eff) and luminosities. The equations which give the surface emission line fluxes and the measured ratio of the NV to CIV emission line fluxes are presented and explained. The abundance results are compared with those of photospheric abundance studies for stars in common with the photospheric investigations. The results show that the analyses are at least as accurate as the photospheric determinations. These studies can be extended to F and early G stars for which photospheric abundance determinations for giants are hard to do because molecular bands become too weak. The abundance determination in the context of stellar evolution is addressed. The N/C abundance ratio increases steeply at the point of evolution for which the convection zone reaches deepest. Looking at the evolution of the rotation velocities v sin i, a steep decrease in v sin i is related to the increasing depth of the convection zone. It is concluded that the decrease in v sin i for T(sub eff) less than or approximately = 5800 K is most probably due to the rearrangement of the angular momentum in the stars due to deep convective mixing. It appears that the convection zone is rotating with nearly depth independent angular momentum. Other research results and ongoing projects are discussed.

  6. Hydroxyl in diopside in diamond-free UHP dolomitic marble from the Kokchetav Massif

    NASA Astrophysics Data System (ADS)

    Kikuchi, M.; Ogasawara, Y.

    2004-12-01

    by Skogby (1990). In order to estimate the amount of hydroxyl in diopside, we chose areas in 30 diopside grains where amphibole band did not appear or was weak. Non-polarized spectra of 30 analyzed spots were averaged. Applying the procedures described by Katayama & Nakashima (2003), we obtained that diopside contained 1020 ppm H2O by weight. The source of OH in submicroscopic amphibole could be derived from precursor diopside, not a fluid infiltration origin during retrogression. Microscopic observations and isotopic studies on diamond-free dolomitic marble have shown no evidence for retrograde fluid effect (Ogasawara et al., 2000; Ohta et al., 2003). Therefore, the precursor diopside might contain much higher hydroxyl than 1000 ppm. Diopside in diamond-free dolomitic marble from the Kokchetav could contain at least 1000 ppm OH under UHP conditions. Large part of hydroxyl survived in diopside during the journey to the surface. These results are new evidence for UHP metamorphism in diamond-free carbonate rocks.

  7. EXPERIMENTAL STUDY OF CO{sub 2} FORMATION BY SURFACE REACTIONS OF NON-ENERGETIC OH RADICALS WITH CO MOLECULES

    SciTech Connect

    Oba, Yasuhiro; Watanabe, Naoki; Kouchi, Akira; Hama, Tetsuya; Pirronello, Valerio

    2010-04-01

    Surface reactions between carbon monoxide and non-energetic hydroxyl radicals were carried out at 10 K and 20 K in order to investigate possible reaction pathways to yield carbon dioxide in dense molecular clouds. Hydroxyl radicals, produced by dissociating water molecules in microwave-induced plasma, were cooled down to 100 K prior to the introduction of CO. The abundances of species were monitored in situ using a Fourier transform infrared spectrometer. Formation of CO{sub 2} was clearly observed, even at 10 K, suggesting that reactions of CO with OH proceed with little or no activation barrier. The present results indicate that CO{sub 2} formation, due to reactions between CO and OH, occurs in tandem with H{sub 2}O formation, and this may lead to the formation of CO{sub 2} ice in polar environments, as typically observed in molecular clouds.

  8. Flare Plasma Iron Abundance

    NASA Technical Reports Server (NTRS)

    Dennis, Brian R.; Dan, Chau; Jain, Rajmal; Schwartz, Richard A.; Tolbert, Anne K.

    2008-01-01

    The equivalent width of the iron-line complex at 6.7 keV seen in flare X-ray spectra suggests that the iron abundance of the hottest plasma at temperatures >approx.10 MK may sometimes be significantly lower than the nominal coronal abundance of four times the photospheric value that is commonly assumed. This conclusion is based on X-ray spectral observations of several flares seen in common with the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and the Solar X-ray Spectrometer (SOXS) on the second Indian geostationary satellite, GSAT-2. The implications of this will be discussed as it relates to the origin of the hot flare plasma - either plasma already in the corona that is directly heated during the flare energy release process or chromospheric plasma that is heated by flare-accelerated particles and driven up into the corona. Other possible explanations of lower-than-expected equivalent widths of the iron-line complex will also be discussed.

  9. Use of molecular dynamics to assess the biophysiological role of hydroxyl groups in glycerol dyalkyl glycerol teraethers

    NASA Astrophysics Data System (ADS)

    Huguet, Carme; Costenaro, Lionel; Fietz, Susanne; Daura, Xavier

    2015-04-01

    The cell membrane of some Archaea is constituted by lipids that span the whole membrane width and contain two alkyl chains bound by two glycerol groups (glycerol dyalkyl glycerol teraethers or GDGTs). These lipids confer stability to the membrane in mesophile to extremophile environments. Besides the more frequently studied isoprenoid archaeal lipids, both mono- and dihydroxy-GDGTs (OH-GDGT) have been recently reported to occur in marine sediments (1). OH-GDGTs contain up to two cyclopentane moieties and have been identified in both core and intact forms. In 2013, a correlation between OH-GDGTs and temperature was reported, with higher relative OH-GDGT abundances at high latitudes (2,3). The physiological function of the hydroxyl group in a GDGT is not yet known, but given the field results, it could be linked to an adaptation of the membrane to changes in temperature. For hydroxydiether lipid cores in methanogenic bacteria, it has been postulated that the hydroxyl group may alter the cell membrane properties: either extending the polar head group region or creating a hydrophilic pocket (4). It has also been suggested that the hydroxylation of the biphytany (l) moiety may result in enhanced membrane rigidity (1). To improve our understanding of the effect of the hydroxylation on physical properties of membranes, we performed molecular-dynamics simulations of GDGT membranes presenting and lacking these additional OH groups. This is an approach with a great development potential in the archaea lipid field, especially in relation to proxy validation. Our results indicate that the addition of an OH increases the membrane fluidity, thus providing an advantage in cold environments. We also observe a widening of the polar head group area, which could enhance transport. 1. Liu et al. 2012, GCA 2. Huguet et al. 2013, Org. Geochem 3. Fietz et al. 2013 4. Sprott et al. 1990. J. Biol. Chem. 265, 13735-13740.

  10. Differential effects of collagen prolyl 3-hydroxylation on skeletal tissues.

    PubMed

    Homan, Erica P; Lietman, Caressa; Grafe, Ingo; Lennington, Jennifer; Morello, Roy; Napierala, Dobrawa; Jiang, Ming-Ming; Munivez, Elda M; Dawson, Brian; Bertin, Terry K; Chen, Yuqing; Lua, Rhonald; Lichtarge, Olivier; Hicks, John; Weis, Mary Ann; Eyre, David; Lee, Brendan H L

    2014-01-01

    Mutations in the genes encoding cartilage associated protein (CRTAP) and prolyl 3-hydroxylase 1 (P3H1 encoded by LEPRE1) were the first identified causes of recessive Osteogenesis Imperfecta (OI). These proteins, together with cyclophilin B (encoded by PPIB), form a complex that 3-hydroxylates a single proline residue on the α1(I) chain (Pro986) and has cis/trans isomerase (PPIase) activity essential for proper collagen folding. Recent data suggest that prolyl 3-hydroxylation of Pro986 is not required for the structural stability of collagen; however, the absence of this post-translational modification may disrupt protein-protein interactions integral for proper collagen folding and lead to collagen over-modification. P3H1 and CRTAP stabilize each other and absence of one results in degradation of the other. Hence, hypomorphic or loss of function mutations of either gene cause loss of the whole complex and its associated functions. The relative contribution of losing this complex's 3-hydroxylation versus PPIase and collagen chaperone activities to the phenotype of recessive OI is unknown. To distinguish between these functions, we generated knock-in mice carrying a single amino acid substitution in the catalytic site of P3h1 (Lepre1(H662A) ). This substitution abolished P3h1 activity but retained ability to form a complex with Crtap and thus the collagen chaperone function. Knock-in mice showed absence of prolyl 3-hydroxylation at Pro986 of the α1(I) and α1(II) collagen chains but no significant over-modification at other collagen residues. They were normal in appearance, had no growth defects and normal cartilage growth plate histology but showed decreased trabecular bone mass. This new mouse model recapitulates elements of the bone phenotype of OI but not the cartilage and growth phenotypes caused by loss of the prolyl 3-hydroxylation complex. Our observations suggest differential tissue consequences due to selective inactivation of P3H1 hydroxylase activity

  11. Differential Effects of Collagen Prolyl 3-Hydroxylation on Skeletal Tissues

    PubMed Central

    Homan, Erica P.; Lietman, Caressa; Grafe, Ingo; Lennington, Jennifer; Morello, Roy; Napierala, Dobrawa; Jiang, Ming-Ming; Munivez, Elda M.; Dawson, Brian; Bertin, Terry K.; Chen, Yuqing; Lua, Rhonald; Lichtarge, Olivier; Hicks, John; Weis, Mary Ann; Eyre, David; Lee, Brendan H. L.

    2014-01-01

    Mutations in the genes encoding cartilage associated protein (CRTAP) and prolyl 3-hydroxylase 1 (P3H1 encoded by LEPRE1) were the first identified causes of recessive Osteogenesis Imperfecta (OI). These proteins, together with cyclophilin B (encoded by PPIB), form a complex that 3-hydroxylates a single proline residue on the α1(I) chain (Pro986) and has cis/trans isomerase (PPIase) activity essential for proper collagen folding. Recent data suggest that prolyl 3-hydroxylation of Pro986 is not required for the structural stability of collagen; however, the absence of this post-translational modification may disrupt protein-protein interactions integral for proper collagen folding and lead to collagen over-modification. P3H1 and CRTAP stabilize each other and absence of one results in degradation of the other. Hence, hypomorphic or loss of function mutations of either gene cause loss of the whole complex and its associated functions. The relative contribution of losing this complex's 3-hydroxylation versus PPIase and collagen chaperone activities to the phenotype of recessive OI is unknown. To distinguish between these functions, we generated knock-in mice carrying a single amino acid substitution in the catalytic site of P3h1 (Lepre1H662A). This substitution abolished P3h1 activity but retained ability to form a complex with Crtap and thus the collagen chaperone function. Knock-in mice showed absence of prolyl 3-hydroxylation at Pro986 of the α1(I) and α1(II) collagen chains but no significant over-modification at other collagen residues. They were normal in appearance, had no growth defects and normal cartilage growth plate histology but showed decreased trabecular bone mass. This new mouse model recapitulates elements of the bone phenotype of OI but not the cartilage and growth phenotypes caused by loss of the prolyl 3-hydroxylation complex. Our observations suggest differential tissue consequences due to selective inactivation of P3H1 hydroxylase activity

  12. Oxygen abundance and convection

    NASA Astrophysics Data System (ADS)

    Van't Veer, C.; Cayrel, R.

    The triplet IR lines of O I near 777 nm are computed with the Kurucz's code, modified to accept several convection models. The program has been run with the MLT algorithm, with l/H = 1.25 and 0.5, and with the Canuto-Mazzitelli and Canuto-Goldman-Mazzitelli approaches, on a metal-poor turnoff-star model atmosphere with Teff=6200 K, log g = 4.3, [Fe/H]= -1.5. The results show that the differences in equivalent widths for the 4 cases do not exceed 2 per cent (0.3 mA). The convection treatment is therefore not an issue for the oxygen abundance derived from the permitted lines.

  13. On the radial abundance gradients in discs of irregular galaxies

    NASA Astrophysics Data System (ADS)

    Pilyugin, L. S.; Grebel, E. K.; Zinchenko, I. A.

    2015-07-01

    We determine the radial abundance distributions across the discs of 14 irregular galaxies of the types Sm and Im (morphological T types 9 and 10) as traced by their H II regions. The oxygen and nitrogen abundances in H II regions are estimated through the Te method or/and with the counterpart method (C method). Moreover, we examine the correspondence between the radial abundance gradient and the surface brightness profile. We find that irregular galaxies with a flat inner profile (flat or outwardly increasing surface brightness in the central region) show shallow (if any) radial abundance gradients. On the other hand, irregular galaxies with a steep inner profile (with or without a bulge or central star cluster) usually show rather steep radial abundance gradients. This is in contrast to the widely held belief that irregular galaxies do not usually show a radial abundance gradient.

  14. Influence of hydroxyl substitution on flavanone antioxidants properties.

    PubMed

    Masek, Anna; Chrzescijanska, Ewa; Latos, Malgorzata; Zaborski, Marian

    2017-01-15

    The aim of our study was to determine the effect of the position of the hydroxyl group on the antioxidant properties of flavonoid derivatives. For this purpose, we performed electrochemical analysis and quantum-mechanical calculations to describe the mechanisms of electrochemical oxidation, and we selected the two methods of ABTS (2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) and DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate), which allowed us to determine the ability to scavenge free radicals. On the basis of the research, we found that the derivatives of flavonoids, which have a hydroxyl group substituted at the R-3 position on the C ring, have outstanding antioxidant activity. Flavone, which had an OH group substituted at the R-6 and R-7 position on the ring A, showed similar antioxidant activity to flavone without -OH groups in the structure and slightly higher activity than the di-substituted flavone on the ring A. PMID:27542504

  15. A ribozyme that triphosphorylates RNA 5′-hydroxyl groups

    PubMed Central

    Moretti, Janina E.; Müller, Ulrich F.

    2014-01-01

    The RNA world hypothesis describes a stage in the early evolution of life in which RNA served as genome and as the only genome-encoded catalyst. To test whether RNA world organisms could have used cyclic trimetaphosphate as an energy source, we developed an in vitro selection strategy for isolating ribozymes that catalyze the triphosphorylation of RNA 5′-hydroxyl groups with trimetaphosphate. Several active sequences were isolated, and one ribozyme was analyzed in more detail. The ribozyme was truncated to 96 nt, while retaining full activity. It was converted to a trans-format and reacted with rates of 0.16 min−1 under optimal conditions. The secondary structure appears to contain a four-helical junction motif. This study showed that ribozymes can use trimetaphosphate to triphosphorylate RNA 5′-hydroxyl groups and suggested that RNA world organisms could have used trimetaphosphate as their energy source. PMID:24452796

  16. Treating ballast water with hydroxyl radical on introduced organisms

    NASA Astrophysics Data System (ADS)

    Zhang, Zhitao; Bai, Mindi; Xiao, Yu; Bai, Mindong; Yang, Bo; Bai, Xiyao

    2006-06-01

    With physical method of micro-gap gas discharge, a large amount of hydroxyl radical can be produced in 20t/h pilot-scale system using the ionization of O2 and H2O. In this paper, the effect of biochemistry of hydroxyl radicals on introduced organisms in ballast water was experimentally investigated. The results indicate that the contents of chlorophyl- a, chlorophyl- b, chlorophyl- c and carotenoid are decreased by 35% 64% within 8.0s and further to the lowest limit of test 5 minutes. In addition, the main reasons of cell death are the lipid peroxidation, the strong destruction to the monose, amylose, protein, DNA and RNA of cell, and damage in CAT, POD and SOD of antioxidant enzyme system.

  17. Glow Discharge Induced Hydroxyl Radical Degradation of 2-Naphthylamine

    NASA Astrophysics Data System (ADS)

    Lu, Quanfang; Yu, Jie; Gao, Jinzhang; Yang, Wu

    2005-06-01

    In an aqueous solution, normal electrolysis at high voltages switches over spontaneously to glow discharge electrolysis and gives rise to hydroxyl radical, hydrogen peroxide, and aqueous electron, as well as several other active species. Hydroxyl radical directly attacks organic contaminants to make them oxidized. In the present paper, 2-naphthylamine is eventually degraded into hydrogen carbonate and carbon dioxide. The degradation process is analyzed by using an Ultraviolet (UV) absorption spectrum, high-performance liquid chromatography (HPLC) and chemical oxygen demand (COD). It is demonstrated that 2-naphthylamine (c0 =30 mg·l-1) is completely converted within 2h at 30°C and 600 V by glow discharge electrolysis, and the degradation is strongly dependent upon the presence of ferrous ions. COD is ascended in the absence of ferrous ions and descended in the presence of them.

  18. Development of a bioconversion process for hydroxylation of aromatic hydrocarbons

    SciTech Connect

    Sanchez-Riera, F.; Grund, A.D.

    1995-12-01

    The hydroxylation of aromatics is a usual step in the microbial degradation pathway of these type of compounds. This ability can be exploited for the preparation of biocatalysts capable of hydroxylating a wide range of substrates. We have specifically applied it to the production of the monomer 4-hydroxy-benzocyclobutene. Various environmental isolates were screened and found to oxidize benzocyclobutene in two distinct manners. One of them included formation of a diol intermediate which could be dehydrated exclusively to the desired phenol. A fermentation process for organism growth and substrate bioconversion was developed. one phase systems with controlled substrate feed and two phase systems with an insoluble organic phase were used, and the process was applied at a 14 liters scale. Concentrations of products up to 9 g/l were obtained in around 20 hours. Details of the process development are discussed.

  19. Twilight Intensity Variation of the Infrared Hydroxyl Airglow

    NASA Technical Reports Server (NTRS)

    Lowe, R. P.; Gilbert, K. L.; Niciejewski, R. J.

    1984-01-01

    The vibration rotation bands of the hydroxyl radical are the strongest features in the night airglow and are exceeded in intensity in the dayglow only by the infrared atmospheric bands of oxygen. The variation of intensity during evening twilight is discussed. Using a ground-based Fourier Transform Spectrometer (FTS), hydroxyl intensity measurements as early as 3 deg solar depression were made. Models of the twilight behavior show that this should be sufficient to provide measurement of the main portion of the twilight intensity change. The instrument was equipped with a liquid nitrogen-cooled germanium detector whose high sensitivity combined with the efficiency of the FTS technique permits spectra of the region 1.1 to 1.6 microns at high signal-to-noise to be obtained in two minutes. The use of a polarizer at the entrance aperture of the instrument reduces the intensity of scattered sunlight by a factor of at least ten for zenith observations.

  20. 6-hydroxylation: effect on the psychotropic potency of tryptamines.

    PubMed

    Taborsky, R G; Delvigs, P; Page, I H

    1966-08-26

    6-Hydroxy-5-methoxy-N,N dimethyltryptamine and 5-methoxy-N, N-dimnethyltryptamine were synthesized and their psychotropic effects compared on trained rats in a Skinner box. The nonhydroxylated form was the more po tent. The metabolism of 5-methoxytryp tophol acetate ester was also studied to determine whether hydroxylation might occur in other than the six position with exogenous indoles. One metabolite was formed, with properties of a hydroxy-5-methoxyindole-3-acetic acid, which proved on chromatography not to be the 6-hydroxy structural isomer. Phar macologic and metabolic studies suggest that psychotropic activity of trypt amines may result from metabolites other than the 6-hydroxylated forms. PMID:5917552

  1. Photocatalytic activity of Pt-TiO2 films supported on hydroxylated fly ash cenospheres under visible light

    NASA Astrophysics Data System (ADS)

    Wang, Bing; Yang, Zewei; An, Hao; Zhai, Jianping; Li, Qin; Cui, Hao

    2015-01-01

    TiO2 was coated on the surface of hydroxylated fly ash cenospheres (FACs) by the sol-gel method. Platinum (Pt) was then deposited on these TiO2/FAC particles by a photoreduction method to form PTF photocatalyst. The photocatalytic activity of PTF for the degradation of methylene blue (MB) under visible-light irradiation was determined. The PTF sample that was calcined at 450 °C and had a Pt/TiO2 mass ratio of 1.5% exhibited the optimal photocatalytic activity for degradation of MB with a catalyst concentration of 3 g L-1. MB was photodecomposed by PTF in aqueous solution more effectively at alkali pH than at acidic pH, because more MB molecules were adsorbed on the surface of PTF under alkaline conditions than that under acidic. The effect of various inorganic anions (HCO3-, F-, SO42-, NO3-, and Cl-) on the photodegradation of MB by PTF was also investigated. Addition of anions with a concentration of 5 mM enhanced the photocatalytic efficiency of PTF because of the improved adsorption of MB. This effect weakened as the anion concentration was increased, which was attributed to the ability of the anions to scavenge hydroxyl radicals and holes. Our results indicated that the photodegradation of MB took place mainly on the catalyst surface. The generation of hydroxyl radicals in the photocatalytic reaction was measured by the fluorescence method. KI was used to determine the participation of holes in the photocatalytic reaction. Both hydroxyl radicals and valence-band holes were detected in the PTF system. Recycling tests revealed that calcination of the used PTF helped to regain its photocatalytic activity.

  2. Generation of hydroxyl radicals during ascites experimentally induced in broilers.

    PubMed

    Arab, H A; Jamshidi, R; Rassouli, A; Shams, G; Hassanzadeh, M H

    2006-04-01

    Increased metabolic rates, pulmonary hypertension and cardiac dysfunction are the most important features of the ascites syndrome in broiler chickens. However, the mechanism of cell injury causing the pathogenesis of the syndrome is not clearly understood. Our study aimed to examine the generation of hydroxyl radicals (OH*) in broiler chickens experiencing ascites. The hundred and fifty 1-d-old chickens were purchased from a local hatchery and reared in an open poultry house for 46 d. They were divided at random into three groups and ascites was induced in two groups by exposing them to low temperature or administration of triiodothyronine (T(3)). The third group served as control and was reared normally. Haematological, biochemical and pathological tests were used to determine the incidence of ascites: including total red blood cell (RBC), packed cell volume (PCV), release of alanine transaminase (ALT) and aspartate transaminase (AST) and ratio of right ventricular weight to total ventricular weight (RV/TV). A salicylate hydroxylation method was used to examine the generation of hydroxyl radicals (OH*) in treated groups. TWo hydroxylated salicylic acid metabolites, 2,3- and 2,5-dihydroxy benzoic acid (2,3- and 2,5-DHBA), were measured by HPLC to detect the generation of OH*. An ascites syndrome was observed in T(3) and low-temperature treated groups, as shown by necropsy changes and increases in f RBC, PCV, ALT, AST and the ratio of RV/TV. Concentrations of 2,3- and 2,5-DHBA were increased in groups experiencing ascites compared to control group. It is suggested that reactive oxygen species that is OH* ions, may be involved in the pathogenesis of the ascites syndrome in broiler chickens. PMID:16641033

  3. Production of hydroxylated fatty acids in genetically modified plants

    DOEpatents

    Somerville, Chris; Broun, Pierre; van de Loo, Frank; Boddupalli, Sekhar S.

    2005-08-30

    This invention relates to plant fatty acyl hydroxylases. Methods to use conserved amino acid or nucleotide sequences to obtain plant fatty acyl hydroxylases are described. Also described is the use of cDNA clones encoding a plant hydroxylase to produce a family of hydroxylated fatty acids in transgenic plants. In addition, the use of genes encoding fatty acid hydroxylases or desaturases to alter the level of lipid fatty acid unsaturation in transgenic plants is described.

  4. Production of hydroxylated fatty acids in genetically modified plants

    DOEpatents

    Somerville, Chris; Broun, Pierre; van de Loo, Frank; Boddupalli, Sekhar S.

    2011-08-23

    This invention relates to plant fatty acyl hydroxylases. Methods to use conserved amino acid or nucleotide sequences to obtain plant fatty acyl hydroxylases are described. Also described is the use of cDNA clones encoding a plant hydroxylase to produce a family of hydroxylated fatty acids in transgenic plants. In addition, the use of genes encoding fatty acid hydroxylases or desaturases to alter the level of lipid fatty acid unsaturation in transgenic plants is described.

  5. Actinide abundances in ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Hagee, B.; Bernatowicz, T. J.; Podosek, F. A.; Johnson, M. L.; Burnett, D. S.

    1990-01-01

    Measurements of actinide and light REE (LREE) abundances and of phosphate abundances in equilibrated ordinary chondrites were obtained and were used to define the Pu abundance in the solar system and to determine the degree of variation of actinide and LREE abundances. The results were also used to compare directly the Pu/U ratio with the earlier obtained ratio determined indirectly, as (Pu/Nd)x(Nd/U), assuming that Pu behaves chemically as a LREE. The data, combined with high-accuracy isotope-dilution data from the literature, show that the degree of gram-scale variability of the Th, U, and LREE abundances for equilibrated ordinary chondrites is a factor of 2-3 for absolute abundances and up to 50 percent for relative abundances. The observed variations are interpreted as reflecting the differences in the compositions and/or proportions of solar nebula components accreted to ordinary chondrite parent bodies.

  6. Method of dehydroxylating a hydroxylated material and method of making a mesoporous film

    DOEpatents

    Domansky, Karel [Richland, WA; Fryxell, Glen E [Kennewick, WA; Liu, Jun [West Richland, WA; Kohler, Nathan J [Richland, WA; Baskaran, Suresh [Kennewick, WA

    2002-05-07

    The present invention is a method of dehydroxylating a silica surface that is hydroxylated having the steps of exposing the silica surface separately to a silicon organic compound and a dehydroxylating gas. Exposure to the silicon organic compound can be in liquid, gas or solution phase, and exposure to a dehydroxylating gas is typically at elevated temperatures. In one embodiment, the improvement of the dehydroxylation procedure is the repetition of the soaking and dehydroxylating gas exposure. In another embodiment, the improvement is the use of an inert gas that is substantially free of hydrogen. In yet another embodiment, the present invention is the combination of the two-step dehydroxylation method with a surfactant templating method of making a mesoporous film.

  7. Supercharging by m-NBA Improves ETD-Based Quantification of Hydroxyl Radical Protein Footprinting

    NASA Astrophysics Data System (ADS)

    Li, Xiaoyan; Li, Zixuan; Xie, Boer; Sharp, Joshua S.

    2015-08-01

    Hydroxyl radical protein footprinting (HRPF) is an MS-based technique for analyzing protein structure based on measuring the oxidation of amino acid side chains by hydroxyl radicals diffusing in solution. Spatial resolution of HRPF is limited by the smallest portion of the protein for which oxidation amounts can be accurately quantitated. Previous work has shown electron transfer dissociation (ETD) to be the most reliable method for quantifying the amount of oxidation of each amino acid side chain in a mixture of peptide oxidation isomers, but efficient ETD requires high peptide charge states, which limits its applicability for HRPF. Supercharging reagents have been used to enhance peptide charge state for ETD analysis, but previous work has shown supercharging reagents to enhance charge state differently for different peptides sequences; it is currently unknown if different oxidation isomers will experience different charge enhancement effects. Here, we report the effect of m-nitrobenzyl alcohol ( m-NBA) on the ETD-based quantification of peptide oxidation. The addition of m-NBA to both a defined mixture of synthetic isomeric oxidized peptides and Robo-1 protein subjected to HRPF increased the abundance of higher charge state ions, improving our ability to perform efficient ETD of the mixture. No differences in the reported quantitation by ETD were noted in the presence or absence of m-NBA, indicating that all oxidation isomers were charge-enhanced to a similar extent. These results indicate the utility of m-NBA for residue-level quantification of peptide oxidation in HRPF and other applications.

  8. A sensitive technique for measuring hydroxyl radicals, atmospheric cleansing molecules

    SciTech Connect

    Kleoppel, J.E.

    1993-06-01

    Despite its diminutive size, the hydroxyl radical (OH) is probably the single most important cleansing agent in the earth's atmosphere. These molecules continually purge the atmosphere of a wide variety of pollutants, including carbon monoxide, methane, and nitrogen dioxide. As more and more compounds are released into the atmosphere, an accurate understanding of the role played by OH becomes increasingly important. Accurately measuring the hydroxyl radical has been a problem because it lasts only a few seconds before reacting with some other chemical species, thus concentrations are extremely low at any given place and time. A researcher at Georgia Tech Research Institute has successfully demonstrated a powerful new OH measurement technique which uses extremely sensitive mass spectrometry, a radical concept that could revolutionize OH measurement methodology. The technique relies on the inherent sensitivity of atmospheric pressure chemical ionization/mass spectrometry by converting the hydroxyl into an ion that can be detected. By reacting with sulfur dioxide, the OH is converted to isotopically labelled sulfuric acid which can be measured to obtain the ambient OH concentration. The new system is fast, accurate, reliable, and highly portable. This article describes the development and initial field testing of the methodology.

  9. Capella: Structure and Abundances

    NASA Technical Reports Server (NTRS)

    Brickhouse, Nancy S.

    1999-01-01

    This grant covers the analysis of EUVE spectra of the cool star binary system Capella. This project has also required the analysis of simultaneous Advanced Satellite for Cosmology and Astrophysics (ASCA) data. The ASCA spectrum of Capella could not be fit with standard models; by imposing models based on strong lines observed with EUVE, a problem wavelength region was identified. Correcting the problem required calculations of atomic collision strengths of higher principal quantum number than had ever been calculated. With these new models applied to the ASCA spectrum, better fits were obtained. Findings are that: (1) ASCA and EUVE spectra are both dominated by a region at 6 x 10(exp 6) K. (2) The high energy cut-off of the ASCA spectrum is consistent with emission from the highest ionization stages of EUVE, namely Fe XXIV. (3) EUVE requires a continuous emission measure distribution with more than two temperatures. (4) The ASCA spectra are of such high statistical significance that systematic uncertainties dominate, including atomic physics issues and calibration issues. (5) While the ASCA spectral fits achieve lower Chi(exp 2 with two-temperature fits, the EUVE-derived emission measure distribution models are also consistent with the spectra. (6) The Fe/H ratio obtained from the ASCA fit is within 20 % of the Fe/H abundance obtained from the summed spectra of Capella over 5 EUVE pointings, as well as the 1996 EUVE data. This result confirms our claims that quasi-continua composed of weak emission lines in the short wavelength spectrometer of EUVE are not major contributors to the measured Capella continuum. Other abundance ratios are also determined from the ASCA data, using models derived with EUVE. Si, Si, and Mg appear to be close to solar photospheric values, while the ratio of Ne/Fe is three to four times lower than solar photospheric values. Whether there is a general First Ionization Potential (FIP) effect or a specific neon anomaly cannot be determined

  10. An aromatic hydroxylation assay for hydroxyl radicals utilizing high-performance liquid chromatography (HPLC). Use to investigate the effect of EDTA on the Fenton reaction.

    PubMed

    Grootveld, M; Halliwell, B

    1986-01-01

    A highly sensitive HPLC method for the separation of hydroxylation products derived from the attack of hydroxyl radical upon phenol is described. Catechol and hydroquinone are the major hydroxylation products formed, with little resorcinol. The effect of EDTA upon hydroxyl radical generation from an iron (II)-H2O2 system is shown to depend upon the order of addition of chelator and metal ion to the reaction mixture, the ratio [iron salt]/[chelator] and the presence or absence of a phosphate buffer. Reasons for these different effects are discussed. PMID:2849582

  11. Why is Trichodesmium abundant in the Kuroshio?

    NASA Astrophysics Data System (ADS)

    Shiozaki, T.; Takeda, S.; Itoh, S.; Kodama, T.; Liu, X.; Hashihama, F.; Furuya, K.

    2015-12-01

    The genus Trichodesmium is recognized as an abundant and major diazotroph in the Kuroshio, but the reason for this remains unclear. The present study investigated the abundance of Trichodesmium spp. and nitrogen fixation together with concentrations of dissolved iron and phosphate in the Kuroshio and its marginal seas. We performed the observations near the Miyako Islands, which form part of the Ryukyu Islands, situated along the Kuroshio, since our satellite analysis suggested that material transport could occur from the islands to the Kuroshio. Trichodesmium spp. bloomed (> 20 000 filaments L-1) near the Miyako Islands, abundance was high in the Kuroshio and the Kuroshio bifurcation region of the East China Sea, but was low in the Philippine Sea. The abundance of Trichodesmium spp. was significantly correlated with the total nitrogen fixation activity. The surface concentrations of dissolved iron (0.19-0.89 nM) and phosphate (< 3-36 nM) were similar for all of the study areas, indicating that the nutrient distribution could not explain the spatial differences in Trichodesmium spp. abundance and nitrogen fixation. Numerical particle-tracking experiments simulated the transportation of water around the Ryukyu Islands to the Kuroshio. Our results indicate that Trichodesmium growing around the Ryukyu Islands could be advected into the Kuroshio.

  12. Aromatic hydroxylation by Fenton reagents (reactive intermediate [Lx+FeIIOOH(BH+)], not free hydroxyl radical (HO.)).

    PubMed

    Hage, J P; Llobet, A; Sawyer, D T

    1995-10-01

    Several iron complexes [FeII(bpy)2(2+), FeII(OPPh3)4(2+), and FeII(PA)2] in combination with hydrogen peroxide (HOOH) catalytically hydroxylate aromatic substrates (ArH). The base-induced nucleophilic addition of HOOH to the electrophilic iron center yields the reactive intermediate of Fenton reagents [FeIILx2+ + HOOH<-->Lx+FeIIOOH(BH+)(1)]. The latter includes a 'stabilized' hydroxyl radical that is able to replace an aromatic hydrogen (H) with a hydroxyl group (HO) via an initial addition reaction. With PhCH3 and PhCH2CH3 as substrates free HO. (from the radiolysis of H2O) reacts via aryl addition (97 and 85%, respectively) to give Ar-Ar as the predominant product, whereas 1 favors H-atom abstraction from the alkyl group (50 and 80%, respectively) and the only detectable products from aryl addition are the respective substituted phenols (o:p-ArOH). Other substituted benzenes (PhX) undergo addition by free HO at the ortho and para aryl carbons (o:p ratio, 2), followed by dimerization and elimination of two H2O molecules to yield substituted biphenyls. In contrast, 1 reacts with PhX to yield substituted phenol (ArOH; o:p ratio, 0.5-1.1). With phenol (PhOH) as the substrate, reaction with 1 yields mainly catechol (o-Ar(OH)2; o:p ratio, 20). In a solvent matrix of MeCN:H2O (3:1 mol:mol ratio) the reaction efficiencies with FeII(bpy)2(2+) and FeII(OPPh3)4(2+) for the hydroxylation of benzene to phenol are 36 and 42%, respectively (product per HOOH). PMID:8564405

  13. Structure-activity relationship of Au-ZrO2 catalyst on formation of hydroxyl groups and its influence on CO oxidation

    SciTech Connect

    Karwacki, Christopher J; Ganesh, Panchapakesan; Kent, P. R. C.; Gordon, Wesley O; Peterson, Gregory W; Niu, Jun Jie; Gogotsi, Yury G.

    2013-01-01

    The effect of changes in morphology and surface hydroxyl species upon thermal treatment of zirconia on the oxidation activity of Au/ZrO2 catalyst was studied. We observed using transmission Fourier transform infrared (FTIR) spectroscopy progressive changes in the presence of monodentate (type I), bidentate (type II) and hydrogen bridged species (type III) for each of the thermally treated (85 to 500 C) supports consisting of bare zirconia and Au/ZrO2 catalysts. Furthermore, structural changes in zirconia were accompanied by an increase in crystal size (7 to 58 nm) and contraction of the supports porosity (SSA 532 to 7 m2 g 1) with increasing thermal treatment. Deposition of gold nanoparticles under similar preparation conditions on different thermally treated zirconia resulted in changes in the mean gold cluster size, ranging from 3.7 to 5.6 nm. Changes in the surface hydroxyl species, support structure and size of the gold centers are important parameters responsible for the observed decrease (>90%) in CO conversion activity for the Au/ZrO2 catalysts. Density functional theory calculations provide evidence of increased CO binding to Au nanoclusters in the presence of surface hydroxyls on zirconia, which increases charge transfer at the perimeter of the gold nanocluster on zirconia support. This further helps in reducing a model CO-oxidation reaction barrier in the presence of surface hydroxyls. This work demonstrates the need to understand the structure activity relationship of both the support and active particles for the design of catalytic materials.

  14. Structure–activity relationship of Au/ZrO2 catalyst on formation of hydroxyl groups and its influence on CO oxidation

    SciTech Connect

    Karwacki, Christopher J.; Ganesh, P.; Kent, Paul R. C.; Gordon, Wesley O.; Peterson, Gregory W.; Niu, Jun Jie; Gogotsi, Yury

    2013-01-01

    The effect of changes in morphology and surface hydroxyl species upon thermal treatment of zirconia on the oxidation activity of Au/ZrO2 catalyst was studied. We observed using transmission fourier transform infrared (FTIR) spectroscopy progressive changes in the presence of monodentate (type I), bidentate (type II) and hydrogen bridged species (type III) for each of the thermally treated (85 to 500 C) supports consisting of bare zirconia and Au/ZrO2 catalysts. Furthermore, structural changes in zirconia were accompanied by an increase in crystal size (7 to 58 nm) and contraction of the supports porosity (SSA 532 to 7 m2/g) with increasing thermal treatment. Deposition of gold nanoparticles under similar preparation conditions on different thermally treated zirconia resulted in changes in the mean gold cluster size, ranging from 3.7 to 5.6 nm. Changes in the surface hydroxyl species, support structure and size of the gold centers are important parameters responsible for the observed decrease (> 90 %) in CO conversion activity for the Au/ZrO2 catalysts. Density functional theory calculations provide evidence of increased CO binding to Au nanoclusters in the presence of surface hydroxyls on zirconia, which increases charge transfer at the perimeter of the gold nanocluster on zirconia support. This further helps in reducing a model CO-oxidation reaction barrier in the presence of surface hydroxyls. This work demonstrates the need to understand the structure-activity relationship of both the support and active particles for the design of catalytic materials.

  15. A first report of hydroxylated apatite as structural biomineral in Loasaceae - plants' teeth against herbivores.

    PubMed

    Ensikat, Hans-Jürgen; Geisler, Thorsten; Weigend, Maximilian

    2016-01-01

    Biomineralization provides living organisms with various materials for the formation of resilient structures. Calcium phosphate is the main component of teeth and bones in vertebrates, whereas especially silica serves for the protection against herbivores on many plant surfaces. Functional calcium phosphate structures are well-known from the animal kingdom, but had not so far been reported from higher plants. Here, we document the occurrence of calcium phosphate biomineralization in the South-American plant group Loasaceae (rock nettle family), which have stinging trichomes similar to those of the well-known stinging nettles (Urtica). Stinging hairs and the smaller, glochidiate trichomes contained nanocrystalline hydroxylated apatite, especially in their distal portions, replacing the silica found in analogous structures of other flowering plants. This could be demonstrated by chemical, spectroscopic, and diffraction analyses. Some species of Loasaceae contained both calcium phosphate and silica in addition to calcium carbonate. The intriguing discovery of structural hydroxylated apatite in plants invites further studies, e.g., on its systematic distribution across the family, the genetic and cellular control of plant biomineralization, the properties and ultrastructure of calcium phosphate. It may prove the starting point for the development of biomimetic calcium phosphate composites based on a cellulose matrix. PMID:27194462

  16. A first report of hydroxylated apatite as structural biomineral in Loasaceae – plants’ teeth against herbivores

    PubMed Central

    Ensikat, Hans-Jürgen; Geisler, Thorsten; Weigend, Maximilian

    2016-01-01

    Biomineralization provides living organisms with various materials for the formation of resilient structures. Calcium phosphate is the main component of teeth and bones in vertebrates, whereas especially silica serves for the protection against herbivores on many plant surfaces. Functional calcium phosphate structures are well-known from the animal kingdom, but had not so far been reported from higher plants. Here, we document the occurrence of calcium phosphate biomineralization in the South-American plant group Loasaceae (rock nettle family), which have stinging trichomes similar to those of the well-known stinging nettles (Urtica). Stinging hairs and the smaller, glochidiate trichomes contained nanocrystalline hydroxylated apatite, especially in their distal portions, replacing the silica found in analogous structures of other flowering plants. This could be demonstrated by chemical, spectroscopic, and diffraction analyses. Some species of Loasaceae contained both calcium phosphate and silica in addition to calcium carbonate. The intriguing discovery of structural hydroxylated apatite in plants invites further studies, e.g., on its systematic distribution across the family, the genetic and cellular control of plant biomineralization, the properties and ultrastructure of calcium phosphate. It may prove the starting point for the development of biomimetic calcium phosphate composites based on a cellulose matrix. PMID:27194462

  17. Dual-emissive fluorescence measurements of hydroxyl radicals using a coumarin-activated silica nanohybrid probe.

    PubMed

    Liu, Saisai; Zhao, Jun; Zhang, Kui; Yang, Lei; Sun, Mingtai; Yu, Huan; Yan, Yehan; Zhang, Yajun; Wu, Lijun; Wang, Suhua

    2016-04-01

    This work reports a novel dual-emissive fluorescent probe based on dye hybrid silica nanoparticles for ratiometric measurement of the hydroxyl radical (˙OH). In the probe sensing system, the blue emission of coumarin dye (coumarin-3-carboxylic acid, CCA) immobilized on the nanoparticle surface is selectively enhanced by ˙OH due to the formation of a coumarin hydroxylation product with strong fluorescence, whereas the emission of red fluorescent dye encapsulated in the silica nanoparticle is insensitive to ˙OH as a self-referencing signal, and so the probe provides a good quantitative analysis based on ratiometric fluorescence measurement with a detection limit of 1.65 μM. Moreover, the probe also shows high selectivity for ˙OH determination against metal ions, other reactive oxygen species and biological species. More importantly, it exhibits low cytotoxicity and high biocompatibility in living cells, and has been successfully used for cellular imaging of ˙OH, showing its promising application for monitoring of intracellular ˙OH signaling events. PMID:26958658

  18. The influence of distribution of hydroxyl groups on vibrational spectra of fullerenol C60(OH)24 isomers: DFT study.

    PubMed

    Dawid, A; Górny, K; Gburski, Z

    2015-02-01

    The infrared and Raman spectra of C60(OH)24 molecule with uniform and non-uniform distribution of hydroxyl groups have been investigated using first principle DFT calculations at the B3LYP/6-31G(d,p) level of theory. The important features of the obtained geometries have been measured and compared to experimental results. The reference calculations of C60 molecule geometry and vibrational spectra have been made and compared to available experimental data. The striking differences of infrared spectra between C60(OH)24 molecule with uniform and non-uniform distribution of hydroxyl groups have been shown and discussed. The OH modes have been identified as the most sensitive to C60(OH)24 isomer configuration. The C-C stretching modes in the Raman spectra of the C60(OH)24 molecule have been found as a potential sensor of OH groups distribution over fullerene C60 surface. PMID:25223813

  19. Capella: Structure and Abundances

    NASA Technical Reports Server (NTRS)

    Brickhouse, Nancy S.

    1999-01-01

    This grant covers the analysis of ASCA spectra of the cool star binary system Capella. This project has also required the analysis of simultaneous EUVE data. The ASCA spectrum of Capella could not be fit with standard models; by imposing models based on strong lines observed with EUVE, a problem wavelength region was identified. Correcting the problem required calculations of atomic collision strengths of higher principal quantum number than had ever been calculated, resulting in a paper in process by Liedahl and Brickhouse. With these new models applied to the ASCA spectrum, better fits were obtained. While solar abundance ratios are generally consistent with the ASCA data, the ratio of Ne/Fe is three to four times lower than solar photospheric values. Whether there is a general First Ionization Potential (FIP) effect or a specific neon anomaly cannot be determined from these data. Detailed discussion has been provided to NASA in the most recent annual report (1997). Two poster presentations have been made regarding modeling requirements. A substantial paper is in the final revision form, following review by six co-authors. The results of this work have wide implications, since the newly calculated emission lines almost certainly contribute to other problems in fitting not only other stellar spectra, but also composite supernova remnants, galaxies, and cooling flow clusters of galaxies. Furthermore, Liedahl and Brickhouse have identified other species for which lines of a similar nature (high principal quantum number) will contribute significant flux. For moderate resolution X-ray spectra, lines left out of the models in relatively isolated bands, will be attributed to continuum flux by spectral fitting engines, causing errors in line-to-continuum ratios. Thus addressing the general theoretical problem is of crucial importance.

  20. Abundances in dwarf irregular galaxies

    NASA Technical Reports Server (NTRS)

    Dufour, Reginald J.

    1986-01-01

    The results of abundance studies of dwarf irregular galaxies and similar objects are reviewed with special attention to variations in the CNO element group. Observations of the forbidden N II and semiforbidden C III lines in the most metal-poor galaxy known, IZw 18, are presented for the first time and CNO abundances are derived via a photoionization model and discussed in the context of the abundances found in other metal-poor H II regions and galaxies.

  1. Aqueous photochemical degradation of hydroxylated PAHs: Kinetics, pathways, and multivariate effects of main water constituents.

    PubMed

    Ge, Linke; Na, Guangshui; Chen, Chang-Er; Li, Jun; Ju, Maowei; Wang, Ying; Li, Kai; Zhang, Peng; Yao, Ziwei

    2016-03-15

    Hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) are contaminants of emerging concern in the aquatic environment, so it is of great significance to understand their environmental transformation and toxicity. This study investigated the aqueous photochemical behavior of four OH-PAHs, 9-Hydroxyfluorene (9-OHFL), 2-Hydroxyfluorene, 9-Hydroxyphenanthrene and 1-Hydroxypyrene, under simulated sunlight irradiation (λ>290nm). It was observed that their photodegradation followed the pseudo-first-order kinetics. Based on the determined quantum yields, their calculated solar apparent photodegradation half-lives in surface waters at 45° N latitude ranged from 0.4min for 9-Hydroxyphenanthrene to 7.5×10(3)min for 9-OHFL, indicating that the OH-PAHs would intrinsically photodegrade fast in sunlit surface waters. Furthermore, 9-OHFL as an example was found to undergo direct photolysis, and self-sensitized photooxidation via OH rather than (1)O2 in pure water. The potential photoreactions involved photoinduced hydroxylation, dehydrogenation and isomerization based on product identification by GC-MS/MS. 9-OHFL photodegraded slower in natural waters than in pure water, which was attributed to the integrative effects of the most photoreactive species, such as Fe(III), NO3(-), Cl(-) and humic acid. The photomodified toxicity was further examined using Vibrio fischeri, and it was found that the toxicity of photolyzed 9-OHFL did not decrease significantly (p>0.05) either in pure water or in seawater, implying the comparable or higher toxicity of some intermediates. These results are important for assessing the fate and risks of OH-PAHs in surface waters. PMID:26780142

  2. Abundance coefficients, a new method for measuring microorganism relative abundance

    USGS Publications Warehouse

    Forester, R.M.

    1977-01-01

    A new method of measuring the relative abundance of microorganisms by using a set of interrelated coefficients, termed 'abundance coefficients' or 'AC', is proposed. These coefficients provide a means of recording abundance for geometric density categories, and each density measurement represents an approximation of the Poisson parameter ??t. The AC is the natural logarithm of a 'characteristic value,' which is a particular number for each geometric density category. The 'characteristic values' are based upon a probabilistic error statement derived from the Poisson formula, and they present evidence for separation of the geometric category boundaries by e = 2.71828. The proposed AC provide a means for recording species abundance in a manner suitable for arithmetic manipulation, for population structure studies, and for the determination of practical limits for defining the presence or absence of a species. Further, these coefficients provide for both intrasample and intersample abundance comparisons. ?? 1977 Plenum Publishing Corporation.

  3. Beryllium Abundances in Solar Mass Stars

    NASA Astrophysics Data System (ADS)

    Krugler, J. A.; Boesgaard, A. M.

    2008-08-01

    Light element abundance analysis allows for a deeper understanding of the chemical composition of a star beneath its surface. Beryllium provides a probe down to 3.5×106 K, where it fuses with protons. In this study, Be abundances were determined for 52 F and G dwarfs selected from a sample of local thin disc stars. These stars were selected by mass to range from 0.9 to 1.1 M⊙. They have effective temperatures from 5600 to 6400 K, and their metallicities [Fe/H]=-0.65 to +0.11. The data were taken with the Keck HIRES instrument and the Gecko spectrograph on the Canada France Hawaii Telescope. The abundances were calculated via spectral synthesis and were analyzed to investigate the Be abundance as a function of age, temperature, metallicity, and its relation to the lithium abundance for this narrow mass range. Be is found to decrease linearly with metallicity down to [Fe/H]˜-4.0 with slope 0.86 ± 0.02. The relation of the Be abundance to effective temperature is dependent upon metallicity, but when metallicity effects are taken into account, there is a spread ˜1.2 dex. We find a 1.5 dex spread in A(Be) when plotted against age, with the largest spread occurring from 6-8 Gyr. The relation with Li is found to be linear with slope 0.36 ± 0.06 for the temperature regime of 5900-6300 K.

  4. Beryllium Abundances in Solar Mass Stars

    NASA Astrophysics Data System (ADS)

    Krugler, Julie A.; Boesgaard, A. M.

    2007-12-01

    Light element abundance analysis allows for a deeper understanding of the chemical composition of a star beneath its surface. Beryllium provides a probe down to 3.5x106 K, where it fuses with protons. In this study, Be abundances were determined for 52 F and G dwarfs selected from a sample of local thin disc stars. These stars were selected by their mass to be in a mass range of 0.9 to 1.1 solar masses as determined by Lambert & Reddy (2004). They have effective temperatures from 5600 to 6400 K, and their metallicities [Fe/H] -0.65 to +0.11. The data were taken over several nights, with forty-six spectra taken with the Keck HIRES instrument and six spectra on the Canada France Hawaii Telescope (CFHT) using the Gecko spectrograph. The abundances were calculated via spectral synthesis, fitting a 4Å region around the resonance lines of Be II. The data were then analyzed to investigate the Be abundance as a function of age, temperature, and metallicity and its relation to the lithium abundance for this narrow mass range. Be is found to increase with metallicity and the linear relationship evident when extended to metallicities down to -4.0 dex with slope 0.86 ± 0.02. The relation of the Be abundance to effective temperature is dependent upon metallicity, but when metallicity effects are taken into account, there is a spread 1.2 dex. We find a 1.5 dex spread in A(Be) when plotted against age, with the largest spread occurring from 6-8 Gyr. The relation with Li is found to be linear with slope 0.36 ± 0.06 for the temperature regime of 5900-6300 K. This research was conducted through the Research Experiences for Undergraduate (REU) program at the University of Hawaii's Institute for Astronomy and was funded by the NSF.

  5. Direct Hydroxylation and Amination of Arenes via Deprotonative Cupration.

    PubMed

    Tezuka, Noriyuki; Shimojo, Kohei; Hirano, Keiichi; Komagawa, Shinsuke; Yoshida, Kengo; Wang, Chao; Miyamoto, Kazunori; Saito, Tatsuo; Takita, Ryo; Uchiyama, Masanobu

    2016-07-27

    Deprotonative directed ortho cupration of aromatic/heteroaromatic C-H bond and subsequent oxidation with t-BuOOH furnished functionalized phenols in high yields with high regio- and chemoselectivity. DFT calculations revealed that this hydroxylation reaction proceeds via a copper (I → III → I) redox mechanism. Application of this reaction to aromatic C-H amination using BnONH2 efficiently afforded the corresponding primary anilines. These reactions show broad scope and good functional group compatibility. Catalytic versions of these transformations are also demonstrated. PMID:27348154

  6. Tunable photoluminescence and spectrum split from fluorinated to hydroxylated graphene

    NASA Astrophysics Data System (ADS)

    Gong, Peiwei; Wang, Jinqing; Sun, Weiming; Wu, Di; Wang, Zhaofeng; Fan, Zengjie; Wang, Honggang; Han, Xiuxun; Yang, Shengrong

    2014-02-01

    Tunable control over the functionalization of graphene is significantly important to manipulate its structure and optoelectronic properties. Yet the chemical inertness of this noble carbon material poses a particular challenge for its decoration without forcing reaction conditions. Here, a mild, operationally simple and controllable protocol is developed to synthesize hydroxylated graphene (HOG) from fluorinated graphene (FG). We successfully demonstrate that under designed alkali environment, fluorine atoms on graphene framework are programmably replaced by hydroxyl groups via a straightforward substitution reaction pathway. Element constituent analyses confirm that homogeneous C-O bonds are successfully grafted on graphene. Rather different from graphene oxide, the photoluminescence (PL) emission spectrum of the obtained HOG becomes split when excited with UV radiation. More interestingly, such transformation from FG facilitates highly tunable PL emission ranging from greenish white (0.343, 0.392) to deep blue (0.156, 0.094). Additionally, both experimental data and density function theory calculation indicate that the chemical functionalization induced structural rearrangement is more important than the chemical decoration itself in tuning the PL emission band tail and splitting energy gaps. This work not only presents a new way to effectively fabricate graphene derivatives with tunable PL performance, but also provides an enlightening insight into the PL origin of graphene related materials.Tunable control over the functionalization of graphene is significantly important to manipulate its structure and optoelectronic properties. Yet the chemical inertness of this noble carbon material poses a particular challenge for its decoration without forcing reaction conditions. Here, a mild, operationally simple and controllable protocol is developed to synthesize hydroxylated graphene (HOG) from fluorinated graphene (FG). We successfully demonstrate that under designed

  7. Erratum: Interstellar Abundance Standards Revisited

    NASA Astrophysics Data System (ADS)

    Sofia, U. J.; Meyer, D. M.

    2001-09-01

    In the Letter ``Interstellar Abundance Standards Revisited'' by U. J. Sofia and D. M. Meyer (ApJ, 554, L221 [2001]), Table 2 and its footnotes contain several typographical errors. The corrected table is shown below. We note that the solar reference standard now implies a positive abundance of nitrogen in halo dust.

  8. The role of chemisorbed hydroxyl species in alkaline electrocatalysis of glycerol on gold.

    PubMed

    Shi, X; Simpson, D E; Roy, D

    2015-05-01

    The mechanism of energy conversion in a direct glycerol fuel cell (DGFC) is governed by the anode supported heterogeneous steps of glycerol electro-oxidation. In aerated alkaline electrolytes, glycerol also participates in a base catalyzed process, which can release certain species mixing with the anode catalyzed surface products. As a result, selective probing of the surface catalytic reactions involving such systems can be difficult. The present work addresses this issue for a gold anode by using the analytical capability of cyclic voltammetry (CV). In addition, surface plasmon resonance measurements are used to optically probe the adsorption characteristics of the electrolyte species. The net exchange current of the oxidation process and the transfer coefficient of the rate determining step are evaluated by analyzing the CV data. The interfacial reactions and their products on Au are identified by measuring the number of electrons released during the electro-oxidation of glycerol. The results indicate that these reactions are facilitated by the surface bound hydroxyl species on Au (chemisorbed OH(-) and faradaically formed Au-OH). By comparing the findings for stationary and rotating electrodes, it is shown that, convective mass transport is critical to maintaining efficient progression of the consecutive oxidation steps of glycerol. In the absence of hydrodynamic support, the main surface products of glycerol oxidation appear to be glyceraldehyde, glycerate and malonate, formed through a net six-electron route. In the presence of controlled convection, a ten-electron process is activated, where mesaxolate is the likely additional product. PMID:25855265

  9. Laser smoothing of sub-micron grooves in hydroxyl-rich fused silica

    SciTech Connect

    Shen, N; Matthews, M J; Fair, J E; Britten, J A; Nguyen, H T; Cooke, D; Elhadj, S; Yang, S T

    2009-10-30

    Nano- to micrometer-sized surface defects on UV-grade fused silica surfaces are known to be effectively smoothed through the use of high-temperature localized CO{sub 2} laser heating, thereby enhancing optical properties. However, the details of the mass transport and the effect of hydroxyl content on the laser smoothing of defective silica at submicron length scales is still not completely understood. In this study, we examine the morphological evolution of sub-micron, dry-etched periodic surface structures on type II and type III SiO{sub 2} substrates under 10.6 {micro}m CO{sub 2} laser irradiation using atomic force microscopy (AFM). In-situ thermal imaging was used to map the transient temperature field across the heated region, allowing assessment of the T-dependent mass transport mechanisms under different laser-heating conditions. Computational fluid dynamics simulations correlated well with experimental results, and showed that for large effective capillary numbers (N{sub c} > 2), surface diffusion is negligible and smoothing is dictated by capillary action, despite the relatively small spatial scales studied here. Extracted viscosity values over 1700-2000K were higher than the predicted bulk values, but were consistent with the surface depletion of OH groups, which was confirmed using confocal Raman microscopy.

  10. Pulsed corona discharge: the role of ozone and hydroxyl radical in aqueous pollutants oxidation.

    PubMed

    Preis, S; Panorel, I C; Kornev, I; Hatakka, H; Kallas, J

    2013-01-01

    Ozone and hydroxyl radical are the most active oxidizing species in water treated with gas-phase pulsed corona discharge (PCD). The ratio of the species dependent on the gas phase composition and treated water contact surface was the objective for the experimental research undertaken for aqueous phenol (fast reaction) and oxalic acid (slow reaction) solutions. The experiments were carried out in the reactor, where aqueous solutions showered between electrodes were treated with 100-ns pulses of 20 kV voltage and 400 A current amplitude. The role of ozone increased with increasing oxygen concentration and the oxidation reaction rate. The PCD treatment showed energy efficiency surpassing that of conventional ozonation. PMID:24135102

  11. A Consideration for Design of Ammonium Perchlorate/Hydroxyl Terminated Polybutadiene Composite Propellant

    NASA Astrophysics Data System (ADS)

    Kohga, Makoto

    Specific impulse and burning rate characteristics are the important properties for the propellant design. Because of the requirements for the preparation of ammonium perchlorate (AP)/hydroxyl-terminated polybutadiene (HTPB) composite propellant, there is an upper limit content, φ of AP contained propellant. Specific impulse and burning rate increase with increasing the AP content. The specific impulse, Ispφ and the burning rate, rφ of the propellant prepared at φ, rφ are the highest values of the propellant prepared with AP used as an oxidizer. It is necessary for the propellant design to estimate φ, Ispφ and rφ. The φ, Ispφ and rφ are closely associated with the specific surface area, Swp measured by air-permeability method. Therefore, these values are estimated with Swp. A process for the design of AP/HTPB composite propellant would be proposed in this study.

  12. Adsorption of an azo dye in an aqueous solution using hydroxyl-terminated polybutadiene (HTPB).

    PubMed

    Olya, Mohammad Ebrahim; Pirkarami, Azam; Mirzaie, Mohammad

    2013-05-01

    This paper reports an investigation into the effect of a number of operating factors on the removal of Acid Blue 92 (AB92) from an aqueous solution using hydroxyl-terminated polybutadiene (HTPB) as an adsorbent. The optimum values of adsorbent dose and pH were found to be 35mgL(-1) and 6, respectively. Temperature showed a significant effect, with maximum dye removal being observed at 45°C. Stirring the solution during the treatment process resulted in significant removal improvement. The Langmuir adsorption model was used to quantify the amount of AB92 adsorbed on the surface of HTPB. FT-IR spectrometry results for HTPB, AB92, and HTPB-AB92 verified the efficiency of the treatment. Further, the adsorbent was characterized using SEM and H NMR techniques. PMID:23484459

  13. Probing the solution structure of Factor H using hydroxyl radical protein footprinting and cross-linking.

    PubMed

    Baud, Anna; Gonnet, Florence; Salard, Isabelle; Le Mignon, Maxime; Giuliani, Alexandre; Mercère, Pascal; Sclavi, Bianca; Daniel, Régis

    2016-06-15

    The control protein Factor H (FH) is a crucial regulator of the innate immune complement system, where it is active on host cell membranes and in the fluid phase. Mutations impairing the binding capacity of FH lead to severe autoimmune diseases. Here, we studied the solution structure of full-length FH, in its free state and bound to the C3b complement protein. To do so, we used two powerful techniques, hydroxyl radical protein footprinting (HRPF) and chemical cross-linking coupled with mass spectrometry (MS), to probe the structural rearrangements and to identify protein interfaces. The footprint of C3b on the FH surface matches existing crystal structures of C3b complexed with the N- and C-terminal fragments of FH. In addition, we revealed the position of the central portion of FH in the protein complex. Moreover, cross-linking studies confirmed the involvement of the C-terminus in the dimerization of FH. PMID:27099340

  14. Solvothermal synthesis of Fe-MOF-74 and its catalytic properties in phenol hydroxylation.

    PubMed

    Bhattacharjee, Samiran; Choi, Jung-Sik; Yang, Seung-Tae; Choi, Sang Beom; Kim, Jaheon; Ahn, Wha-Seung

    2010-01-01

    A Fe-containing metal-organic framework, Fe-MOF-74, was solvothermally synthesized using FeCl2.4H2O and 2,5-di-hydroxy-1,4-benzenedicarboxylic acid. Characterization was conducted by XRD, BET surface area measurement, FT-IR spectroscopy, TGA, and elemental analysis, which confirmed successful preparation of Fe-MOF-74 having an identical framework structure to that reported for MOF-74. Fe-MOF-74 was found to be an effective heterogeneous catalyst for the hydroxylation of phenol using H2O2 as an oxidant; 60% phenol conversion was achieved at 20 degrees C in water with 68 and 32% selectivity to catechol and hydroquinone, respectively. The effect of temperature, phenol/H2O2 mole ratio, catalyst quantity, and solvent on catalytic performance was discussed, and a reaction mechanism is proposed based upon the experimental results. PMID:20352823

  15. Triclosan and Hydroxylated Polybrominated Diphenyl Ethers in Lake and Esturaine Sediments

    NASA Astrophysics Data System (ADS)

    Arnold, W. A.; Kerrigan, J. F.; McNeill, K.; Erickson, P. R.; Grandbois, M.

    2014-12-01

    Halogenated diphenyl ethers are a class of emerging contaminants that includes the antibacterial compound triclosan and the flame retardant polybrominated diphenyl ethers (PBDEs). Both triclosan and hydroxylated polybrominated diphenyl ethers (OH-BDEs) are known to form dioxins when exposed to sunlight in aqueous solution. Thus, it is important to understand the sources and presence of these compounds in the environment, especially because OH-BDEs are breakdown products of PBDEs and also naturally produced compounds. In this work, the levels of OH-BDEs were determined in lake sediments from Minnesota and esturaine sediments from San Francisco Bay. Both surface sediments over a broad spatial area and sediment cores were collected and analyzed. Triclosan was used as a marker of wastewater as a source of the targeted emerging contaminants. The relationship between triclosan and OH-BDE levels provides insight into the importance of natural and anthropogenic influences on the levels of OH-BDEs.

  16. Presence of hydroxyl in the Fra Mauro region

    NASA Astrophysics Data System (ADS)

    Berezhnoy, Alexey; Wöhler, Christian; Sinitsyn, Mikhail; Grumpe, Arne; Feoktistova, Ekaterina; Shevchenko, Vladislav

    Lunar pyroclastic deposits (LPDs) are known to consist of volcanic material (basalt and glass) ejected by eruptions [1]. In the southern part of the crater Fra Mauro, a localised LPD is associated with Rima Parry V [2]. In [3], a suppressed neutron flux is described for the Fra Mauro region based on measurements of the Lunar Exploration Neutron Detector (LEND) [4], interpreted as an indicator of hydroxyl (OH). In this study we compare these measurements with NIR hyperspectral data acquired by the Moon Mineralogy Mapper (M(3) ) [5] instrument. The suppression factor of the neutron flux is defined according to delta = (N_ref-N_ex)/N_ref [6,7] with N_ex as the average count rate of the omnidirectional sensor (SETN) [8] of LEND for the region under study (here: the Fra Mauro region) and N_ref as the average count rate for a reference area (here: immediately west of Fra Mauro). For Fra Mauro crater, a suppression factor of 2.4% with a standard error of 0.41% was found. The epithermal neutron flux can be assumed to be inversely proportional to the hydrogen content. Hence, the measured positive suppression factor indicates a positive anomaly of the hydrogen content at up to 1 m depth. Under the approximative assumption of a proportional relation between the suppression factor delta and the hydrogen content, the observation in [7] of a suppression factor of 18% in the crater Cabeus associated with a homogeneous hydrogen content of about 500 ppm implies an enrichment in hydrogen by about 70 ppm for the Fra Mauro region. However, these values do not specifically refer to the small Fra Mauro LPD but to a larger area of about 150 km diameter. To identify the LPD-specific suppression factor, it would be necessary to acquire collimated neutron flux measurements. We have complemented the LEND-based measurements by the analysis of spectral reflectance data acquired by the M(3) instrument. The presence of OH in the surface material leads to an absorption band beyond 2700 nm

  17. High structural resolution hydroxyl radical protein footprinting reveals an extended Robo1-heparin binding interface.

    PubMed

    Li, Zixuan; Moniz, Heather; Wang, Shuo; Ramiah, Annapoorani; Zhang, Fuming; Moremen, Kelley W; Linhardt, Robert J; Sharp, Joshua S

    2015-04-24

    Interaction of transmembrane receptors of the Robo family and the secreted protein Slit provides important signals in the development of the central nervous system and regulation of axonal midline crossing. Heparan sulfate, a sulfated linear polysaccharide modified in a complex variety of ways, serves as an essential co-receptor in Slit-Robo signaling. Previous studies have shown that closely related heparin octasaccharides bind to Drosophila Robo directly, and surface plasmon resonance analysis revealed that Robo1 binds more tightly to full-length unfractionated heparin. For the first time, we utilized electron transfer dissociation-based high spatial resolution hydroxyl radical protein footprinting to identify two separate binding sites for heparin interaction with Robo1: one binding site at the previously identified site for heparin dp8 and a second binding site at the N terminus of Robo1 that is disordered in the x-ray crystal structure. Mutagenesis of the identified N-terminal binding site exhibited a decrease in binding affinity as measured by surface plasmon resonance and heparin affinity chromatography. Footprinting also indicated that heparin binding induces a minor change in the conformation and/or dynamics of the Ig2 domain, but no major conformational changes were detected. These results indicate a second low affinity binding site in the Robo-Slit complex as well as suggesting the role of the Ig2 domain of Robo1 in heparin-mediated signal transduction. This study also marks the first use of electron transfer dissociation-based high spatial resolution hydroxyl radical protein footprinting, which shows great utility for the characterization of protein-carbohydrate complexes. PMID:25752613

  18. High Structural Resolution Hydroxyl Radical Protein Footprinting Reveals an Extended Robo1-Heparin Binding Interface*

    PubMed Central

    Li, Zixuan; Moniz, Heather; Wang, Shuo; Ramiah, Annapoorani; Zhang, Fuming; Moremen, Kelley W.; Linhardt, Robert J.; Sharp, Joshua S.

    2015-01-01

    Interaction of transmembrane receptors of the Robo family and the secreted protein Slit provides important signals in the development of the central nervous system and regulation of axonal midline crossing. Heparan sulfate, a sulfated linear polysaccharide modified in a complex variety of ways, serves as an essential co-receptor in Slit-Robo signaling. Previous studies have shown that closely related heparin octasaccharides bind to Drosophila Robo directly, and surface plasmon resonance analysis revealed that Robo1 binds more tightly to full-length unfractionated heparin. For the first time, we utilized electron transfer dissociation-based high spatial resolution hydroxyl radical protein footprinting to identify two separate binding sites for heparin interaction with Robo1: one binding site at the previously identified site for heparin dp8 and a second binding site at the N terminus of Robo1 that is disordered in the x-ray crystal structure. Mutagenesis of the identified N-terminal binding site exhibited a decrease in binding affinity as measured by surface plasmon resonance and heparin affinity chromatography. Footprinting also indicated that heparin binding induces a minor change in the conformation and/or dynamics of the Ig2 domain, but no major conformational changes were detected. These results indicate a second low affinity binding site in the Robo-Slit complex as well as suggesting the role of the Ig2 domain of Robo1 in heparin-mediated signal transduction. This study also marks the first use of electron transfer dissociation-based high spatial resolution hydroxyl radical protein footprinting, which shows great utility for the characterization of protein-carbohydrate complexes. PMID:25752613

  19. Synthesis, photocatalytic activity, and photogenerated hydroxyl radicals of monodisperse colloidal ZnO nanospheres

    NASA Astrophysics Data System (ADS)

    Yang, Chong; Li, Qingsong; Tang, Limei; Xin, Kun; Bai, Ailing; Yu, Yingmin

    2015-12-01

    In the present study, monodisperse colloidal zinc oxide (ZnO) nanospheres were successfully synthesized via a newly developed two-stage solution method followed by facile calcination at various temperatures. The effects of calcination temperature on the structure, morphology, and optical properties as well as the photocatalytic activity of the as-made ZnO samples were investigated systematically by Fourier transform infrared spectrometry, X-ray diffraction, field emission scanning electron microscopy, nitrogen adsorption/desorption isotherms, diffuse reflectance UV-visible spectroscopy (DRS), photoluminescence, and related photocatalytic activity tests. The thermal decomposition was analyzed by thermogravimetric analysis. The crystallinity was found to gradually increase with increasing calcination temperature, whereas the decrease in the Brunauer-Emmett-Teller specific surface area of the samples with calcination may be ascribed to the increased particle size. The DRS results provided clear evidence for the decrease in band gap energy of ZnO samples with an increase in calcination temperature. The photoluminescence spectra demonstrated the calcination-dependent emission features, especially the UV emission intensity. In particular, the ZnO product calcined at 400 °C exhibited the highest photocatalytic activity, degrading methylene blue by almost 99.1% in 70 min, which is ascribed to the large specific surface area and pore volume, high electron-hole pair separation efficient, and great redox potential of the obtained ZnO nanoparticles. In addition, the production of photogenerated hydroxyl radicals (•OH) was consistent with the methylene blue degradation efficiency over the as-made ZnO nanoparticles. Using isopropanol as a hydroxyl radical scavenger, •OH was determined to be the main active oxygen species in the photocatalytic process. A possible mechanism of photodegradation under UV light irradiation also is proposed.

  20. Hydroxylated Polychlorinated Biphenyls in the Environment: Sources, Fate, and Toxicities

    PubMed Central

    Tehrani, Rouzbeh; Van Aken, Benoit

    2013-01-01

    Hydroxylated polychlorinated biphenyls (OH-PCBs) are produced in the environment by the oxidation of PCBs through a variety of mechanisms, including metabolic transformation in living organisms and abiotic reactions with hydroxyl radicals. As a consequence, OH-PCBs have been detected in a wide range of environmental samples, including animal tissues, water, and sediments. OH-PCBs have recently raised serious environmental concerns because they exert a variety of toxic effects at lower doses than the parent PCBs and they are disruptors of the endocrine system. Although evidence has accumulated about the widespread dispersion of OH-PCBs in various compartments of the ecosystem, little is currently known about their biodegradation and behavior in the environment. OH-PCBs are today increasingly considered as a new class of environmental contaminants that possess specific chemical, physical, and biological properties not shared with the parent PCBs. This article reviews recent findings regarding the sources, fate, and toxicities of OH-PCBs in the environment. PMID:23636595

  1. Structural Characterization of Hydroxyl Radical Adducts in Aqueous Media

    NASA Astrophysics Data System (ADS)

    Janik, Ireneusz; Tripathi, G. N. R.

    2015-06-01

    The oxidation by the hydroxyl (OH) radical is one of the most widely studied reactions because of its central role in chemistry, biology, organic synthesis, and photocatalysis in aqueous environments, wastewater treatment, and numerous other chemical processes. Although the redox potential of OH is very high, direct electron transfer (ET) is rarely observed. If it happens, it mostly proceeds through the formation of elusive OH adduct intermediate which facilitates ET and formation of hydroxide anion. Using time resolved resonance Raman technique we structurally characterized variety of OH adducts to sulfur containing organic compounds, halide ions as well as some metal cations. The bond between oxygen of OH radical and the atom of oxidized molecule differs depending on the nature of solute that OH radical reacts with. For most of sulfur containing organics, as well as halide and pseudo-halide ions, our observation suggested that this bond has two-center three-electron character. For several metal aqua ions studied, the nature of the bond depends on type of the cation being oxidized. Discussion on spectral parameters of all studied hydroxyl radical adducts as well as the role solvent plays in their stabilization will be presented.

  2. Hydroxylated collagen peptide in urine as biomarker for detecting colorectal liver metastases

    PubMed Central

    Lalmahomed, Zarina S; Bröker, Mirelle EE; van Huizen, Nick A; van den Braak, Robert RJ Coebergh; Dekker, Lennard JM; Rizopoulos, Dimitris; Verhoef, Cornelis; Steyerberg, Ewout W; Luider, Theo M; IJzermans, Jan NM

    2016-01-01

    The clinical efficacy of carcinoembryonic antigen (CEA) as a marker of colorectal liver metastasis is limited, motivating a search for new biomarkers. Recently, urine proteomic analysis revealed AGPP(-OH)GEAGKP(-OH)GEQGVP(-OH)GDLGAP(-OH)GP (AGP), a promising peptide for this application. This study aimed to determine whether combining urine AGP testing with serum CEA analyses improves the sensitivity of detecting colorectal liver metastases. Urine samples from 100 patients with CRLM were collected prospectively and compared to three control groups: healthy kidney donors, patients who were relapse-free for 24 months after curative CRLM surgery, and primary colorectal cancer patients. A stable isotope labeled peptide standard was used to quantify the abundance of AGP in urine samples by selective reaction monitoring. Combined testing of urine AGP levels and serum CEA levels revealed a significantly increased sensitivity compared to CEA alone (85% vs. 68%, P<0.001; specificity 84% and 91%, respectively). No correlation was found between CEA and AGP-positive test results within individual patients (r2 = 0.08). Urine AGP testing was negative in the three control groups. These results indicate that collagen-derived urine AGP peptide with a specific hydroxylation pattern combined with serum CEA levels may significantly improve the detection of colorectal liver metastases in patients at risk. PMID:27186406

  3. A new perspective on the molecular oxygen and hydroxyl airglow emissions

    NASA Astrophysics Data System (ADS)

    Mlynczak, Martin G.

    The mesospheric molecular oxygen and hydroxyl airglow emissions have traditionally been measured in order to derive minor species abundances or to diagnose dynamical phenomena. We present a new interpretation of these airglow emissions and show them to be fundamental measures of energy deposition from which rates of atmospheric heating are readily derived. The heating rate due to absorption of ultraviolet radiation in the Hartley band of ozone may be derived from simultaneous measurements of the oxygen atmospheric band and infrared atmospheric band volume emission rates independent of knowledge of the ozone density, the solar irradiance, and the ozone absorption cross sections. The heating rates due to key exothermic reactions may be derived directly from appropriate airglow observations independent of the reactant concentrations and the temperature-dependent reaction rates. The accuracy of heating rates derived directly from airglow measurements is also inherently higher than that obtained in standard approaches. We suggest that heating rates derived in this manner be treated as data products and that they be compared with numerical model computations to enhance understanding of atmospheric thermodynamics. An initial comparison of airglow-derived energy deposition rates with deposition rates traditionally computed from numerical models shows agreement to within 20% for the Hartley band of ozone in the lower and upper mesosphere.

  4. New strategy for expression of recombinant hydroxylated human collagen α1(III) chains in Pichia pastoris GS115.

    PubMed

    He, Jing; Ma, Xiaoxuan; Zhang, Fenglong; Li, Linbo; Deng, Jianjun; Xue, Wenjiao; Zhu, Chenhui; Fan, Daidi

    2015-01-01

    Type III collagen is one of the most abundant proteins in the human body, which forms collagen fibrils and provides the stiff, resilient characteristics of many tissues. In this paper, a new method for secretory expression of recombinant hydroxylated human collagen α1(III) chain in Pichia pastoris GS115 was applied. The gene encoding for full-length human collagen α1(III) chain (COL3A1) without N-terminal propeptide and C-terminal propeptide was cloned in the pPIC9K expression vector. The prolyl 4-hydroxylase (P4H, EC 1.14.11.2) α-subunit (P4Hα) and β-subunit (P4Hβ) genes were cloned in the same expression vector, pPICZB. Fluorogenic quantitative PCR indicates that COL3A1 and P4H genes have been expressed in mRNA level. SDS-PAGE shows that secretory expression of recombinant human collagen α1(III) chain was successfully achieved in P. pastoris GS115. In addition, the result of amino acids composition analysis shows that the recombinant human collagen α1(III) chain contains hydroxyproline by coexpression with the P4H. Furthermore, liquid chromatography coupled with tandem mass spectrometry analysis demonstrates that proline residues of the recombinant human collagen α1(III) chain were hydroxylated in the X or Y positions of Gly-X-Y triplets. PMID:24953863

  5. Evaluation of alcoholic hydroxyl derivatives for chemically amplified extreme ultraviolet resist

    NASA Astrophysics Data System (ADS)

    Furukawa, Kikuo; Kozawa, Takahiro; Tagawa, Seiichi

    2009-03-01

    Extreme ultraviolet (EUV) lithography is the most favorable process as next-generation lithography. For the development of EUV resists, phenolic materials such as poly (4-hydroxystyrene) have been investigated. Phenolic hydroxyl groups of polymers play an important role in acid diffusion, dissolution kinetics, and adhesion to substrates. Besides these important roles, phenolic hydroxyl groups are also an effective proton source in acid generation in EUV resists. However, the roles of alcohol hydroxyl groups have not been well-studied. To clarify the difference between phenolic and alcoholic hydroxyl groups upon exposure to EUV radiation, we synthesized acrylic terpolymers containing alcoholic hydroxyl groups as model photopolymers and exposed the resist samples based on these polymers to EUV radiation. On the basis of the lithographic performances of these resist samples, we evaluated the characteristics of alcoholic hydroxyl groups upon exposure to EUV radiation. We discuss the relationship between the chemical structures of these derivatives and lithographic performance.

  6. Hydroxyl radical scavenging-based method for evaluation of TiO₂ photocatalytic activity.

    PubMed

    Mencigar, Danijela Pucko; Strlič, Matija; Štangar, Urška Lavrenčič; Korošec, Romana Cerc

    2013-01-01

    A novel hydroxyl radical scavenging method was developed to establish the photocatalytic activity of TiO₂ thin films. Transparent TiO₂ thin films were prepared on soda-lime glass substrates using the sol-gel method and characterized using X-ray diffraction. During photoirradiation in aqueous buffered solutions, activity of the films was followed using the substituted nitrobenzene N,N'-(5-nitro-1,3-phenylene)bisglutaramide as a hydroxyl radical scavenger and its hydroxylated products were quantified using HPLC. The yield of hydroxyl radicals was evaluated at various pH of the reaction media, and reflected the dependence of the rate of the hydroxylation reaction on the experimental conditions and on the different qualities of the TiO₂ thin films. The proposed method allows for direct assessment of hydroxyl radical production, it is straightforward and is proposed for routine use. PMID:24362997

  7. Theory of vibrationally assisted tunneling for hydroxyl monomer flipping on Cu(110)

    NASA Astrophysics Data System (ADS)

    Gustafsson, Alexander; Ueba, Hiromu; Paulsson, Magnus

    2014-10-01

    To describe vibrationally mediated configuration changes of adsorbates on surfaces we have developed a theory to calculate both reaction rates and pathways. The method uses the T-matrix to describe excitations of vibrational states by the electrons of the substrate, adsorbate, and tunneling electrons from a scanning tunneling probe. In addition to reaction rates, the theory also provides the reaction pathways by going beyond the harmonic approximation and using the full potential energy surface of the adsorbate which contains local minima corresponding to the adsorbates different configurations. To describe the theory, we reproduce the experimental results in [T. Kumagai et al., Phys. Rev. B 79, 035423 (2009), 10.1103/PhysRevB.79.035423], where the hydrogen/deuterium atom of an adsorbed hydroxyl (OH/OD) exhibits back and forth flipping between two equivalent configurations on a Cu(110) surface at T =6 K. We estimate the potential energy surface and the reaction barrier, ˜160 meV, from DFT calculations. The calculated flipping processes arise from (i) at low bias, tunneling of the hydrogen through the barrier, (ii) intermediate bias, tunneling electrons excite the vibrations increasing the reaction rate although over the barrier processes are rare, and (iii) higher bias, overtone excitations increase the reaction rate further.

  8. Recombination Line vs. Forbidden Line Abundances in Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    Robertson-Tessi, M.; Garnett, D. R.

    2004-05-01

    Recombination lines (RLs) of C II, N II, and O II in planetary nebulae (PNe) have been found to give abundances that are much larger in some cases than abundances from collisionally-excited forbidden lines (CELs). The origins of this abundance discrepancy are highly debated. We present new spectroscopic observations of O II and C II recombination lines for six planetary nebulae. With these data we compare the abundances derived from the optical recombination lines with those determined from collisionally-excited lines. Combining our new data with published results on RLs in other PNe, we examine the discrepancy in abundances derived from RLs and CELs. We find that there is a wide range in the measured abundance discrepancy Δ (O+2) = log O+2(RL) - log O+2(CEL), ranging from approximately 0.1 dex (within the 1σ measurement errors) up to 1.3 dex. This tends to rule out errors in the recombination coefficients as a source of the discrepancy. Most RLs yield similar abundances, with the notable exception of O II multiplet V15, known to arise primarily from dielectronic recombination, which gives abundances averaging 0.6 dex higher than other O II RLs. We compare Δ (O+2) against a variety of physical properties of the PNe to look for clues as to the mechanism responsible for the abundance discrepancy. The strongest correlation is found with Balmer surface brightness; high surface brightness, compact PNe show small values of Δ (O+2), while large low surface brightness PNe show the largest discrepancies. Rougher correlations of Δ (O+2) are found with He+2/He+ and with the expansion velocity. No correlations are seen with electron temperature, electron density, central star effective temperature and luminosity, stellar mass loss rate, or nebular morphology. Similar results are found for carbon, comparing C II RL abundances with ultraviolet measurements of C III]. This work is supported by NSF grant AST-0203905.

  9. Chemical abundances and kinematics of barium stars

    NASA Astrophysics Data System (ADS)

    de Castro, D. B.; Pereira, C. B.; Roig, F.; Jilinski, E.; Drake, N. A.; Chavero, C.; Silva, J. V. Sales

    2016-04-01

    In this paper we present an homogeneous analysis of photospheric abundances based on high-resolution spectroscopy of a sample of 182 barium stars and candidates. We determined atmospheric parameters, spectroscopic distances, stellar masses, ages, luminosities and scale height, radial velocities, abundances of the Na, Al, alpha-elements, iron-peak elements, and s-process elements Y, Zr, La, Ce, and Nd. We employed the local-thermodynamic-equilibrium model atmospheres of Kurucz and the spectral analysis code MOOG. We found that the metallicities, the temperatures and the surface gravities for barium stars can not be represented by a single gaussian distribution. The abundances of alpha-elements and iron peak elements are similar to those of field giants with the same metallicity. Sodium presents some degree of enrichment in more evolved stars that could be attributed to the NeNa cycle. As expected, the barium stars show overabundance of the elements created by the s-process. By measuring the mean heavy-element abundance pattern as given by the ratio [s/Fe], we found that the barium stars present several degrees of enrichment. We also obtained the [hs/ls] ratio by measuring the photospheric abundances of the Ba-peak and the Zr-peak elements. Our results indicated that the [s/Fe] and the [hs/ls] ratios are strongly anti-correlated with the metallicity. Our kinematical analysis showed that 90% of the barium stars belong to the thin disk population. Based on their luminosities, none of the barium stars are luminous enough to be an AGB star, nor to become self-enriched in the s-process elements. Finally, we determined that the barium stars also follow an age-metallicity relation.

  10. Chemical abundances and kinematics of barium stars

    NASA Astrophysics Data System (ADS)

    de Castro, D. B.; Pereira, C. B.; Roig, F.; Jilinski, E.; Drake, N. A.; Chavero, C.; Sales Silva, J. V.

    2016-07-01

    In this paper, we present an homogeneous analysis of photospheric abundances based on high-resolution spectroscopy of a sample of 182 barium stars and candidates. We determined atmospheric parameters, spectroscopic distances, stellar masses, ages, luminosities and scaleheight, radial velocities, abundances of the Na, Al, α-elements, iron-peak elements, and s-process elements Y, Zr, La, Ce, and Nd. We employed the local thermodynamic equilibrium model atmospheres of Kurucz and the spectral analysis code MOOG. We found that the metallicities, the temperatures and the surface gravities for barium stars cannot be represented by a single Gaussian distribution. The abundances of α-elements and iron peak elements are similar to those of field giants with the same metallicity. Sodium presents some degree of enrichment in more evolved stars that could be attributed to the NeNa cycle. As expected, the barium stars show overabundance of the elements created by the s-process. By measuring the mean heavy-element abundance pattern as given by the ratio [s/Fe], we found that the barium stars present several degrees of enrichment. We also obtained the [hs/ls] ratio by measuring the photospheric abundances of the Ba-peak and the Zr-peak elements. Our results indicated that the [s/Fe] and the [hs/ls] ratios are strongly anticorrelated with the metallicity. Our kinematical analysis showed that 90 per cent of the barium stars belong to the thin disc population. Based on their luminosities, none of the barium stars are luminous enough to be an asymptotic giant branch star, nor to become self-enriched in the s-process elements. Finally, we determined that the barium stars also follow an age-metallicity relation.

  11. On-going laboratory efforts to quantitatively address clay abundance on Mars

    NASA Astrophysics Data System (ADS)

    Roush, T. L.; Bishop, J. L.; Brown, A. J.; Blake, D. F.; Bristow, T. F.

    2012-12-01

    Data obtained at visible and near-infrared wavelengths by OMEGA on MarsExpress and CRISM on MRO provide definitive evidence for the presence of phyllosilicates and other hydrated phases on Mars. A diverse range of both Fe/Mg-OH and Al-OH-bearing phyllosilicates were identified including the smectites, nontronite, saponite, and montmorillonite. In order to constrain the abundances of these phyllosilicates spectral analyses of mixtures are needed. We report on our on-going effort to enable the quantitative evaluation of the abundance of hydrated-hydroxylated silicates when they are contained in mixtures. We include two component mixtures of hydrated/hydroxylated silicates with each other and with two analogs for other martian materials; pyroxene (enstatite) and palagonitic soil (an alteration product of basaltic glass). For the hydrated-hydroxylated silicates we include saponite and montmorillonite (Mg- and Al- rich smectites). We prepared three size separates of each end-member for study: 20-45, 63-90, and 125-150 μm. As the second phase of our effort we used scanning electron microscopy imaging and x-ray diffraction to characterize the grain size distribution, and structural nature, respectively, of the mixtures. Visible and near-infrared reflectance spectra of the 63-90 μm grain size of the mixture samples are shown in Figure 1. We discuss the results of our measurements of these mixtures.

  12. On-Going Laboratory Efforts to Quantitatively Address Clay Abundance on Mars

    NASA Technical Reports Server (NTRS)

    Roush, Ted L.; Bishop, Janice L.; Brown, Adrian J.; Blake, David F.; Bristow, Thomas F.

    2012-01-01

    Data obtained at visible and near-infrared wavelengths by OMEGA on MarsExpress and CRISM on MRO provide definitive evidence for the presence of phyllosilicates and other hydrated phases on Mars. A diverse range of both Fe/Mg-OH and Al-OH-bearing phyllosilicates were identified including the smectites, nontronite, saponite, and montmorillonite. In order to constrain the abundances of these phyllosilicates spectral analyses of mixtures are needed. We report on our on-going effort to enable the quantitative evaluation of the abundance of hydrated-hydroxylated silicates when they are contained in mixtures. We include two component mixtures of hydrated/hydroxylated silicates with each other and with two analogs for other martian materials; pyroxene (enstatite) and palagonitic soil (an alteration product of basaltic glass). For the hydrated-hydroxylated silicates we include saponite and montmorillonite (Mg- and Al- rich smectites). We prepared three size separates of each end-member for study: 20-45, 63-90, and 125-150 µm. As the second phase of our effort we used scanning electron microscopy imaging and x-ray diffraction to characterize the grain size distribution, and structural nature, respectively, of the mixtures. Visible and near-infrared reflectance spectra of the 63-90 micrometers grain size of the mixture samples are shown in Figure 1. We discuss the results of our measurements of these mixtures.

  13. The boron abundance of Procyon

    NASA Technical Reports Server (NTRS)

    Lemke, Michael; Lambert, David L.; Edvardsson, Bengt

    1993-01-01

    The B I 2496.8 A resonance line and HST/GHRS echelle spectra are used with model atmospheres and synthetic spectra to derive the B abundance of the F dwarfs Procyon (Alpha Canis Minoris), Theta Ursae Majoris, and Iota Pegasi. The B abundance of Theta UMa and Iota Peg is similar to that derived by Boesgaard and Heacox (1978) from the B II resonance line in spectra of A- and B-type stars. These two dwarfs show normal abundances of Li, Be, and B. Procyon, which is highly depleted in Li and Be, is depleted in B by a factor of at least 3. Comparison of the spectra of Procyon and the halo dwarf HD 140283 shows that the B abundance assigned by Duncan et al. (1992) to three halo dwarfs is not greatly overestimated as a result of contamination of the B I line by an unidentified line.

  14. Revised Thorium Abundances for Lunar Red Spots

    NASA Technical Reports Server (NTRS)

    Hagerty, J. J.; Lawrence, D. J.; Elphic, R. C.; Feldman, W. C.; Vaniman, D. T.; Hawke, B. R.

    2005-01-01

    Lunar red spots are features on the nearside of the Moon that are characterized by high albedo and by a strong absorption in the ultraviolet. These red spots include the Gruithuisen domes, the Mairan domes, Hansteen Alpha, the southern portion of Montes Riphaeus, Darney Chi and Tau, Helmet, and an area near the Lassell crater. It has been suggested that many of the red spots are extrusive, nonmare, volcanic features that could be composed of an evolved lithlogy enriched in thorium. In fact, Hawke et al. used morphological characteristics to show that Hansteen Alpha is a nonmare volcanic construct. However, because the apparent Th abundances (6 - 7 ppm) were lower than that expected for evolved rock types, Hawke et al. concluded that Hansteen Alpha was composed of an unknown rock type. Subsequent studies by Lawrence et al. used improved knowledge of the Th spatial distribution for small area features on the lunar surface to revisit the interpretation of Th abundances at the Hansteen Alpha red spot. As part of their study, Lawrence et al. used a forward modeling technique to show that the Th abundance at Hansteen Alpha is not 6 ppm, but is more likely closer to 25 ppm, a value consistent with evolved lithologies. This positive correlation between the morphology and composition of Hansteen Alpha provides support for the presence of evolved lithologies on the lunar surface. It is possible, however, that Hansteen Alpha represents an isolated occurrence of non-mare volcanism. That is why we have chosen to use the forward modeling technique of Lawrence et al. to investigate the Th abundances at other lunar red spots, starting with the Gruithuisen domes. Additional information is included in the original extended abstract.

  15. An Iminium Salt Organocatalyst for Selective Aliphatic C-H Hydroxylation.

    PubMed

    Wang, Daoyong; Shuler, William G; Pierce, Conor J; Hilinski, Michael K

    2016-08-01

    The first examples of catalysis of aliphatic C-H hydroxylation by an iminium salt are presented. The method allows the selective organocatalytic hydroxylation of unactivated 3° C-H bonds at room temperature using hydrogen peroxide as the terminal oxidant. Hydroxylation of an unactivated 2° C-H bond is also demonstrated. Furthermore, improved functional group compatibility over other catalytic methods is reported in the form of selectivity for aliphatic C-H hydroxylation over alcohol oxidation. On the basis of initial mechanistic studies, an oxaziridinium species is proposed as the active oxidant. PMID:27391543

  16. New hydroxylated metabolites of 4-monochlorobiphenyl in whole poplar plants

    PubMed Central

    2011-01-01

    Two new monohydroxy metabolites of 4-monochlorobiphenyl (CB3) were positively identified using three newly synthesized monohydroxy compounds of CB3: 2-hydroxy-4-chlorobiphenyl (2OH-CB3), 3-hydroxy-4-chlorobiphenyl (3OH-CB3) and 4-hydroxy-3-chlorobiphenyl (4OH-CB2). New metabolites of CB3, including 2OH-CB3 and 3OH-CB3, were confirmed in whole poplars (Populus deltoides × nigra, DN34), a model plant in the application of phytoremediation. Furthermore, the concentrations and masses of 2OH-CB3 and 3OH-CB3 formed in various tissues of whole poplar plants and controls were measured. Results showed that 2OH-CB3 was the major product in these two OH-CB3s with chlorine and hydroxyl moieties in the same phenyl ring of CB3. Masses of 2OH-CB3 and 3OH-CB3 in tissues of whole poplar plants were much higher than those in the hydroponic solution, strongly indicating that the poplar plant itself metabolizes CB3 to both 2OH-CB3 and 3OH-CB3. The total yield of 2OH-CB3 and 3OH-CB3, with chlorine and hydroxyl in the same phenyl ring of CB3, was less than that of three previously found OH-CB3s with chlorine and hydroxyl in the opposite phenyl rings of CB3 (2'OH-CB3, 3'OH-CB3, and 4'OH-CB3). Finally, these two newly detected OH-CB3s from CB3 in this work also suggests that the metabolic pathway was via epoxide intermediates. These five OH-CB3s clearly showed the complete metabolism profile from CB3 to monohydroxylated CB3. More importantly, it's the first report and confirmation of 2OH-CB3 and 3OH-CB3 (new metabolites of CB3) in a living organism. PMID:22185578

  17. Hydroxyl radical in/on illuminated polar snow: formation rates, lifetimes, and steady-state concentrations

    NASA Astrophysics Data System (ADS)

    Chen, Zeyuan; Chu, Liang; Galbavy, Edward S.; Ram, Keren; Anastasio, Cort

    2016-08-01

    While the hydroxyl radical (OH) in the snowpack is likely a dominant oxidant for organic species and bromide, little is known about the kinetics or steady-state concentrations of OH on/in snow and ice. Here we measure the formation rate, lifetime, and concentration of OH for illuminated polar snow samples studied in the laboratory and in the field. Laboratory studies show that OH kinetics and steady-state concentrations are essentially the same for a given sample studied as ice and liquid; this is in contrast to other photooxidants, which show a concentration enhancement in ice relative to solution as a result of kinetic differences in the two phases. The average production rate of OH in samples studied at Summit, Greenland, is 5 times lower than the average measured in the laboratory, while the average OH lifetime determined in the field is 5 times higher than in the laboratory. These differences indicate that the polar snows we studied in the laboratory are affected by contamination, despite significant efforts to prevent this; our results suggest similar contamination may be a widespread problem in laboratory studies of ice chemistry. Steady-state concentrations of OH in clean snow studied in the field at Summit, Greenland, range from (0.8 to 3) × 10-15 M, comparable to values reported for midlatitude cloud and fog drops, rain, and deliquesced marine particles, even though impurity concentrations in the snow samples are much lower. Partitioning of firn air OH to the snow grains will approximately double the steady-state concentration of snow-grain hydroxyl radical, leading to an average [OH] in near-surface, summer Summit snow of approximately 4 × 10-15 M. At this concentration, the OH-mediated lifetimes of organics and bromide in Summit snow grains are approximately 3 days and 7 h, respectively, suggesting that hydroxyl radical is a major

  18. Sum frequency spectroscopy of the hydrophobic nanodroplet/water interface: Absence of hydroxyl ion and dangling OH bond signatures

    NASA Astrophysics Data System (ADS)

    Samson, Jean-Sebastién; Scheu, Rüdiger; Smolentsev, Nikolay; Rick, Steven W.; Roke, Sylvie

    2014-11-01

    Vibrational sum frequency scattering measurements were performed on deuterated hexadecane oil nanodroplets dispersed in aqueous pH neutral and basic solutions. The predominant symmetry of the observed vibrational signatures was derived using nonlinear light scattering theory. The probed spectral region contains information about two distinct phenomena: The surface structure of water, and the spectral signature of surface OD- ions. The spectral data differ from that of the planar alkane/water interface, but can be interpreted consistently by considering differences in chain orientation and molecular surface corrugation. In terms of the second phenomenon, we find that although the electrokinetic mobility increases with pH, the SF spectra do not change with increasing pH, and do not contain any evidence for the presence of interfacial hydroxyl ions. Based on expected surface charge densities, signal strength and recent literature, we conclude that a charge transfer scenario is most in accord with the present data.

  19. Kinetics of the reaction of hydroxyl radicals with nitric acid

    NASA Technical Reports Server (NTRS)

    Margitan, J. J.; Watson, R. T.

    1982-01-01

    An extensive study was made of the reaction of hydroxyl radicals with nitric acid in a laser photolysis-resonance fluorescence system. A 266 nm laser was used to photolyze HNO3 in the temperature range 225-415 K at pressures of 20-300 torr. A temperature dependence was detected below room temperature, with a leveling off at 298 K and a wide spread in the rate constants. A pressure dependence was observed over the entire range and was more pronounced at lower temperatures. The results are noted to be in agreement with those of previous investigations. However, the wide range of rate constants are suggested to be a problem for stratospheric HO(x) modeling for anthropogenic effects. No explanation could be given of the varying results obtained by other investigators regarding the kinetics of the reactions.

  20. Kinetics of hydrogen peroxide decomposition by catalase: hydroxylic solvent effects.

    PubMed

    Raducan, Adina; Cantemir, Anca Ruxandra; Puiu, Mihaela; Oancea, Dumitru

    2012-11-01

    The effect of water-alcohol (methanol, ethanol, propan-1-ol, propan-2-ol, ethane-1,2-diol and propane-1,2,3-triol) binary mixtures on the kinetics of hydrogen peroxide decomposition in the presence of bovine liver catalase is investigated. In all solvents, the activity of catalase is smaller than in water. The results are discussed on the basis of a simple kinetic model. The kinetic constants for product formation through enzyme-substrate complex decomposition and for inactivation of catalase are estimated. The organic solvents are characterized by several physical properties: dielectric constant (D), hydrophobicity (log P), concentration of hydroxyl groups ([OH]), polarizability (α), Kamlet-Taft parameter (β) and Kosower parameter (Z). The relationships between the initial rate, kinetic constants and medium properties are analyzed by linear and multiple linear regression. PMID:22565543

  1. [Angiotensin-converting enzyme inhibitors as neutralizers of hydroxyl radical].

    PubMed

    Mira, M L; Silva, M M; Queirós, M J; Manso, C

    1992-05-01

    Angiotensin converting enzyme inhibitors are utilized in the treatment of essential hypertension and of chronic cardiac failure. They are also employed in the treatment of the myocardial lesion of ischemia-reperfusion, which involves oxygen free radicals. In the present study we investigated the possibility of three angiotensin converting enzyme inhibitors (captopril, enalapril, lisinopril) to act as hydroxyl radical scavengers. The rate constants for reactions of those compounds with .OH were determined using the deoxyribose method. All there compounds proved to be good scavengers of .OH with rate constants of about 10(10)M-1s-1 and are iron chelators specially enalapril. The fact that captopril possesses a thiol group does not confer an higher antioxidative capacity. These results suggest that scavenging of oxygen free radicals may be a possible mechanism contributing to the therapeutic effect of angiotensin converting enzyme inhibitors. PMID:1325814

  2. Crystal structure of tris-(hydroxyl-ammonium) orthophosphate.

    PubMed

    Leinemann, Malte; Jess, Inke; Boeckmann, Jan; Näther, Christian

    2015-11-01

    The crystal structure of the title salt, ([H3NOH](+))3·[PO4](3-), consists of discrete hydroxyl-ammonium cations and ortho-phos-phate anions. The atoms of the cation occupy general positions, whereas the anion is located on a threefold rotation axis that runs through the phospho-rus atom and one of the phosphate O atoms. In the crystal structure, cations and anions are linked by inter-molecular O-H⋯O and N-H⋯O hydrogen bonds into a three-dimensional network. Altogether, one very strong O-H⋯O, two N-H⋯O hydrogen bonds of medium strength and two weaker bifurcated N-H⋯O inter-actions are observed. PMID:26594525

  3. SPLASH: A Southern Parkes Large Area Survey in Hydroxyl

    NASA Astrophysics Data System (ADS)

    Dawson, Joanne; Caswell, James; Gomez, Jose F.; Mcclure-Griffiths, Naomi; Lo, Nadia; Jones, Paul; Dickey, John; Cunningham, Maria; Green, James; Carretti, Ettore; Ellingsen, Simon; Walsh, Andrew; Purcell, Cormac; Breen, Shari; Hennebelle, Patrick; Imai, Hiroshi; Lowe, Vicki; Gibson, Steven; Brown, Courtney; Krishnan, Vasaant

    2014-04-01

    The OH 18 cm lines are powerful and versatile probes of diffuse molecular gas, that trace a largely unstudied component of the Galactic ISM. SPLASH (the Southern Parkes Large Area Survey in Hydroxyl) is a large, unbiased and fully-sampled survey of OH emission, absorption and masers in the Galactic Plane that will achieve sensitivities an order of magnitude better than previous work. The survey is answering critical questions on the global distribution of diffuse OH, the degree to which it traces ‘hidden’ material caught between the regimes probed by traditional tracers of the neutral ISM, and its role as a probe of molecular cloud formation. As a blind survey for all four ground-state transitions, SPLASH is also detecting many new OH masers, facilitating a broad range of astrophysical studies. This proposal requests 250 hours to complete Phase 1 of the SPLASH project, which is mapping 152 square degrees in the inner Galactic Plane, including the Galactic Centre.

  4. Spectroscopic study of combustion diagnostics on hydroxyl radicals

    NASA Technical Reports Server (NTRS)

    Hung, R. J.

    1990-01-01

    Experimental observations of propane-air flames were performed. Measurements of hydroxyl (OH) radical concentration were made using resonance line absorption techniques. A microwave-pumped low pressure discharge in argon and water vapor is employed to produce strong OH radical band radiation in the 308 nm region. This radiation is transmitted through the plume and absorption data are taken at various radical positions using an optical multichannel analyzer. This absorption data is used to compute OH number density using a model for the absorption band characteristics as a function of temperature based on an atlas of line strengths. A numerical computation of flow fields, temperature profile and OH number density is carried out by using a technique of computational fluid dynamics (CFD). The results of CFD computation are good compared with experimental observation with a good agreement.

  5. Electrocatalytic hydrocarbon hydroxylation by ethylbenzene dehydrogenase from Aromatoleum aromaticum.

    PubMed

    Kalimuthu, Palraj; Heider, Johann; Knack, Daniel; Bernhardt, Paul V

    2015-02-26

    We report the electrocatalytic activity of ethylbenzene dehydrogenase (EBDH) from the β-proteobacterium Aromatoleum aromaticum. EBDH is a complex 155 kDa heterotrimeric molybdenum/iron-sulfur/heme protein which catalyzes the enantioselective hydroxylation of nonactivated ethylbenzene to (S)-1-phenylethanol without molecular oxygen as cosubstrate. Furthermore, it oxidizes a wide range of other alkyl-substituted aromatic and heterocyclic compounds to their secondary alcohols. Hydroxymethylferrocenium (FM) is used as an artificial electron acceptor for EBDH in an electrochemically driven catalytic system. Electrocatalytic activity of EBDH is demonstrated with both its native substrate ethylbenzene and the related substrate p-ethylphenol. The catalytic system has been modeled by electrochemical simulation across a range of sweep rates and concentrations of each substrate, which provides new insights into the kinetics of the EBDH catalytic mechanism. PMID:25635950

  6. Crystal structure of tris­(hydroxyl­ammonium) orthophosphate

    PubMed Central

    Leinemann, Malte; Jess, Inke; Boeckmann, Jan; Näther, Christian

    2015-01-01

    The crystal structure of the title salt, ([H3NOH]+)3·[PO4]3−, consists of discrete hydroxyl­ammonium cations and ortho­phos­phate anions. The atoms of the cation occupy general positions, whereas the anion is located on a threefold rotation axis that runs through the phospho­rus atom and one of the phosphate O atoms. In the crystal structure, cations and anions are linked by inter­molecular O—H⋯O and N—H⋯O hydrogen bonds into a three-dimensional network. Altogether, one very strong O—H⋯O, two N—H⋯O hydrogen bonds of medium strength and two weaker bifurcated N—H⋯O inter­actions are observed. PMID:26594525

  7. Carbon and nitrogen abundances determined from transition layer lines

    NASA Technical Reports Server (NTRS)

    Boehm-Vitense, Erika; Mena-Werth, Jose

    1992-01-01

    The possibility of determining relative carbon, nitrogen, and silicon abundances from the emission-line fluxes in the lower transition layers between stellar chromospheres and coronae is explored. Observations for main-sequence and luminosity class IV stars with presumably solar element abundances show that for the lower transition layers Em = BT sup -gamma. For a given carbon abundance the constants gamma and B in this relation can be determined from the C II and C IV emission-line fluxes. From the N V and S IV lines, the abundances of these elements relative to carbon can be determined from their surface emission-line fluxes. Ratios of N/C abundances determined in this way for some giants and supergiants agree within the limits of errors with those determined from molecular bands. For giants, an increase in the ratio of N/C at B-V of about 0.8 is found, as expected theoretically.

  8. An "Andesitic" Component in Shergottites with Restored LREE Abundances?

    NASA Technical Reports Server (NTRS)

    Nyquist, L. E.; Shih, C.-Y.; Wiesmann, H.; Barrat, J. A.

    2002-01-01

    The shergottite Martian meteorites present a variety of oft-confusing petrologic features. In particular, represented among this subgroup are basalts with very depleted LREE abundances, as well as those with nearly chondritic overall REE abundances. The LREE-depleted basalts appear to more closely record the REE and isotopic features of their mantle source legions. Those basalts with more nearly chondritic REE abundances appear to contain an extra component often referred to as a "crustal" component. The addition of the crustal component tends to restore the overall REE abundance pattern towards chondritic relative abundances. Here we suggest that the crustal component could derive from andesitic rocks observed remotely to occur on the Martian surface, and which were analysed at the Pathfinder site.

  9. An "Andestic" Component in Shergottites with Restored LREE Abundances?

    NASA Technical Reports Server (NTRS)

    Nyquist, L. E.; Shih, C.-Y.; Wiesmann, H.; Barrat, J. A.

    2002-01-01

    The shergottite Martian meteorites present a variety of oft-confusing petrologic features. In particular, represented among this subgroup are basalts with very depleted LREE abundances, as well as those with nearly chondritic overall REE abundances. The LREE-depleted basalts appear to more closely record the REE and isotopic features of their mantle source regions. Those basalts with more nearly chondritic REE abundances appear to contain an extra component often referred to as a "crustal" component. The addition of the crustal component tends to restore the overall REE abundance pattern towards chondritic relative abundances. Here we suggest that the crustal component could derive from "andesitic" rocks observed remotely to occur on the Martian surface, and which were analysed at the Pathfinder site.

  10. Profound Effect of Substrate Hydroxylation and Hydration on Electronic and Optical Properties of Monolayer MoS2.

    PubMed

    Zheng, Changxi; Xu, Zai-Quan; Zhang, Qianhui; Edmonds, Mark T; Watanabe, Kenji; Taniguchi, Takashi; Bao, Qiaoliang; Fuhrer, Michael S

    2015-05-13

    Atomic force microscopy, Kelvin probe force microscopy, and scanning photoluminescence spectroscopy image the progressive postgrowth hydroxylation and hydration of atomically flat Al2O3(0001) under monolayer MoS2, manifested in large work function shifts (100 mV) due to charge transfer (>10(13) cm(-2)) from the substrate and changes in PL intensity, energy, and peak width. In contrast, trapped water between exfoliated graphene and Al2O3(0001) causes surface potential and doping changes one and two orders of magnitude smaller, respectively, and MoS2 grown on hydrophobic hexagonal boron nitride is unaffected by water exposure. PMID:25897823

  11. Formation of hydroxyl radical from the photolysis of frozen hydrogen peroxide.

    PubMed

    Chu, Liang; Anastasio, Cort

    2005-07-21

    Hydrogen peroxide (HOOH) in ice and snow is an important chemical tracer for the oxidative capacities of past atmospheres. However, photolysis in ice and snow will destroy HOOH and form the hydroxyl radical (*OH), which can react with snowpack trace species. Reactions of *OH in snow and ice will affect the composition of both the overlying atmosphere (e.g., by the release of volatile species such as formaldehyde to the boundary layer) and the snow and ice (e.g., by the *OH-mediated destruction of trace organics). To help understand these impacts, we have measured the quantum yield of *OH from the photolysis of HOOH on ice. Our measured quantum yields (Phi(HOOH --> *OH)) are independent of ionic strength, pH, and wavelength, but are dependent upon temperature. This temperature dependence for both solution and ice data is best described by the relationship ln(Phi(HOOH --> *OH)) = -(684 +/- 17)(1/T) + (2.27 +/- 0.064) (where errors represent 1 standard error). The corresponding activation energy (Ea) for HOOH (5.7 kJ mol(-1)) is much smaller than that for nitrate photolysis, indicating that the photochemistry of HOOH is less affected by changes in temperature. Using our measured quantum yields, we calculate that the photolytic lifetimes of HOOH in surface snow grains under midday, summer solstice sunlight are approximately 140 h at representative sites on the Greenland and Antarctic ice sheets. In addition, our calculations reveal that the majority of *OH radicals formed on polar snow grains are from HOOH photolysis, while nitrate photolysis is only a minor contributor. Similarly, HOOH appears to be much more important than nitrate as a photochemical source of *OH on cirrus ice clouds, where reactions of the photochemically formed hydroxyl radical could lead to the release of oxygenated volatile organic compounds to the upper troposphere. PMID:16833967

  12. Terpene hydroxylation with microbial cytochrome P450 monooxygenases.

    PubMed

    Janocha, Simon; Schmitz, Daniela; Bernhardt, Rita

    2015-01-01

    Terpenoids comprise a highly diverse group of natural products. In addition to their basic carbon skeleton, they differ from one another in their functional groups. Functional groups attached to the carbon skeleton are the basis of the terpenoids' diverse properties. Further modifications of terpene olefins include the introduction of acyl-, aryl-, or sugar moieties and usually start with oxidations catalyzed by cytochrome P450 monooxygenases (P450s, CYPs). P450s are ubiquitously distributed throughout nature, involved in essential biological pathways such as terpenoid biosynthesis as well as the tailoring of terpenoids and other natural products. Their ability to introduce oxygen into nonactivated C-H bonds is unique and makes P450s very attractive for applications in biotechnology. Especially in the field of terpene oxidation, biotransformation methods emerge as an attractive alternative to classical chemical synthesis. For this reason, microbial P450s depict a highly interesting target for protein engineering approaches in order to increase selectivity and activity, respectively. Microbial P450s have been described to convert industrial and pharmaceutically interesting terpenoids such as ionones, limone, valencene, resin acids, and triterpenes (including steroids) as well as vitamin D3. Highly selective and active mutants have been evolved by applying classical site-directed mutagenesis as well as directed evolution of proteins. As P450s usually depend on electron transfer proteins, mutagenesis has also been applied to improve the interactions between P450s and their respective redox partners. This chapter provides an overview of terpenoid hydroxylation reactions catalyzed by bacterial P450s and highlights the achievements made by protein engineering to establish productive hydroxylation processes. PMID:25682070

  13. Quantitative Mass Spectrometry Reveals Dynamics of Factor-inhibiting Hypoxia-inducible Factor-catalyzed Hydroxylation*

    PubMed Central

    Singleton, Rachelle S.; Trudgian, David C.; Fischer, Roman; Kessler, Benedikt M.; Ratcliffe, Peter J.; Cockman, Matthew E.

    2011-01-01

    The asparaginyl hydroxylase, factor-inhibiting hypoxia-inducible factor (HIF), is central to the oxygen-sensing pathway that controls the activity of HIF. Factor-inhibiting HIF (FIH) also catalyzes the hydroxylation of a large set of proteins that share a structural motif termed the ankyrin repeat domain (ARD). In vitro studies have defined kinetic properties of FIH with respect to different substrates and have suggested FIH binds more tightly to certain ARD proteins than HIF and that ARD hydroxylation may have a lower Km value for oxygen than HIF hydroxylation. However, regulation of asparaginyl hydroxylation on ARD substrates has not been systematically studied in cells. To address these questions, we employed isotopic labeling and mass spectrometry to monitor the accrual, inhibition, and decay of hydroxylation under defined conditions. Under the conditions examined, hydroxylation was not reversed but increased as the protein aged. The extent of hydroxylation on ARD proteins was increased by addition of ascorbate, whereas iron and 2-oxoglutarate supplementation had no significant effect. Despite preferential binding of FIH to ARD substrates in vitro, when expressed as fusion proteins in cells, hydroxylation was found to be more complete on HIF polypeptides compared with sites within the ARD. Furthermore, comparative studies of hydroxylation in graded hypoxia revealed ARD hydroxylation was suppressed in a site-specific manner and was as sensitive as HIF to hypoxic inhibition. These findings suggest that asparaginyl hydroxylation of HIF-1 and ARD proteins is regulated by oxygen over a similar range, potentially tuning the HIF transcriptional response through competition between the two types of substrate. PMID:21808058

  14. Poly(amidoamine)-mediated self-assembly of hydroxyl-modified anatase TiO2 nanocrystals on cotton fabric

    NASA Astrophysics Data System (ADS)

    Xu, Sijun; Zhang, Feng; Jiao, Chenlu; Chen, Siyu; Morikawa, Hedeaki; Chen, Yuyue; Lin, Hong

    2016-06-01

    Here, water-soluble hydroxyl-terminated hyperbranched poly(amino ester) (HBPAE)-capped titanium dioxide nanocrystals (TiO2 NCs) were synthesized for coating a cotton fabric via an amino-terminated hyperbranched poly(amidoamine) (HBPAA)-mediated self-assembly strategy in order to produce a controllable and uniform TiO2 coating on the cotton surface. As-prepared TiO2 NCs were characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and X-ray diffraction (XRD). It was demonstrated that hydroxyl-modified TiO2 NCs were egg-shaped and had a narrow size distribution. A TiO2 NC-coated cotton fabric was prepared by sequential impregnation with solutions of HBPAAs and TiO2 NCs. The attachment of HBPAAs to TiO2 NCs was evaluated by FTIR. It was shown that HBPAAs were chemically bound to the cotton surface. FESEM and XRD characterizations demonstrated that TiO2 NCs could self-assemble on a cotton fabric efficiently and were distributed uniformly on the cotton surface.

  15. Efficient Production of Hydroxylated Human-Like Collagen Via the Co-Expression of Three Key Genes in Escherichia coli Origami (DE3).

    PubMed

    Tang, Yunping; Yang, Xiuliang; Hang, Baojian; Li, Jiangtao; Huang, Lei; Huang, Feng; Xu, Zhinan

    2016-04-01

    Mature collagen is abundant in human bodies and very valuable for a range of industrial and medical applications. The biosynthesis of mature collagen requires post-translational modifications to increase the stability of collagen triple helix structure. By co-expressing the human-like collagen (HLC) gene with human prolyl 4-hydroxylase (P4H) and D-arabinono-1, 4-lactone oxidase (ALO) in Escherichia coli, we have constructed a prokaryotic expression system to produce the hydroxylated HLC. Then, five different media, as well as the induction conditions were investigated with regard to the soluble expression of such protein. The results indicated that the highest soluble expression level of target HLC obtained in shaking flasks was 49.55 ± 0.36 mg/L, when recombinant cells were grew in MBL medium and induced by 0.1 mM IPTG at the middle stage of exponential growth phase. By adopting the glucose feeding strategy, the expression level of target HLC can be improved up to 260 mg/L in a 10 L bench-top fermentor. Further, HPLC analyses revealed that more than 10 % of proline residues in purified HLC were successfully hydroxylated. The present work has provided a solid base for the large-scale production of hydroxylated HLC in E. coli. PMID:26712247

  16. THE CORONAL ABUNDANCE ANOMALIES OF M DWARFS

    SciTech Connect

    Wood, Brian E.; Laming, J. Martin; Karovska, Margarita

    2012-07-01

    We analyze Chandra X-ray spectra of the M0 V+M0 V binary GJ 338. As quantified by X-ray surface flux, these are the most inactive M dwarfs ever observed with X-ray grating spectroscopy. We focus on measuring coronal abundances, in particular searching for evidence of abundance anomalies related to first ionization potential (FIP). In the solar corona and wind, low-FIP elements are overabundant, which is the so-called FIP effect. For other stars, particularly very active ones, an 'inverse FIP effect' is often observed, with low-FIP elements being underabundant. For both members of the GJ 338 binary, we find evidence for a modest inverse FIP effect, consistent with expectations from a previously reported correlation between spectral type and FIP bias. This amounts to strong evidence that all M dwarfs should exhibit the inverse FIP effect phenomenon, not just the active ones. We take the first step toward modeling the inverse FIP phenomenon in M dwarfs, building on past work that has demonstrated that MHD waves coursing through coronal loops can lead to a ponderomotive force that fractionates elements in a manner consistent with the FIP effect. We demonstrate that in certain circumstances this model can also lead to an inverse FIP effect, pointing the way to more detailed modeling of M dwarf coronal abundances in the future.

  17. The Coronal Abundance Anomalies of M Dwarfs

    NASA Astrophysics Data System (ADS)

    Wood, Brian E.; Laming, J. Martin; Karovska, Margarita

    2012-07-01

    We analyze Chandra X-ray spectra of the M0 V+M0 V binary GJ 338. As quantified by X-ray surface flux, these are the most inactive M dwarfs ever observed with X-ray grating spectroscopy. We focus on measuring coronal abundances, in particular searching for evidence of abundance anomalies related to first ionization potential (FIP). In the solar corona and wind, low-FIP elements are overabundant, which is the so-called FIP effect. For other stars, particularly very active ones, an "inverse FIP effect" is often observed, with low-FIP elements being underabundant. For both members of the GJ 338 binary, we find evidence for a modest inverse FIP effect, consistent with expectations from a previously reported correlation between spectral type and FIP bias. This amounts to strong evidence that all M dwarfs should exhibit the inverse FIP effect phenomenon, not just the active ones. We take the first step toward modeling the inverse FIP phenomenon in M dwarfs, building on past work that has demonstrated that MHD waves coursing through coronal loops can lead to a ponderomotive force that fractionates elements in a manner consistent with the FIP effect. We demonstrate that in certain circumstances this model can also lead to an inverse FIP effect, pointing the way to more detailed modeling of M dwarf coronal abundances in the future.

  18. Chemical abundance analysis of 19 barium stars

    NASA Astrophysics Data System (ADS)

    Yang, Guo-Chao; Liang, Yan-Chun; Spite, Monique; Chen, Yu-Qin; Zhao, Gang; Zhang, Bo; Liu, Guo-Qing; Liu, Yu-Juan; Liu, Nian; Deng, Li-Cai; Spite, Francois; Hill, Vanessa; Zhang, Cai-Xia

    2016-01-01

    We aim at deriving accurate atmospheric parameters and chemical abundances of 19 barium (Ba) stars, including both strong and mild Ba stars, based on the high signal-to-noise ratio and high resolution Echelle spectra obtained from the 2.16 m telescope at Xinglong station of National Astronomical Observatories, Chinese Academy of Sciences. The chemical abundances of the sample stars were obtained from an LTE, plane-parallel and line-blanketed atmospheric model by inputting the atmospheric parameters (effective temperatures Teff, surface gravities log g, metallicity [Fe/H] and microturbulence velocity ξt) and equivalent widths of stellar absorption lines. These samples of Ba stars are giants as indicated by atmospheric parameters, metallicities and kinematic analysis about UVW velocity. Chemical abundances of 17 elements were obtained for these Ba stars. Their Na, Al, α- and iron-peak elements (O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Ni) are similar to the solar abundances. Our samples of Ba stars show obvious overabundances of neutron-capture (n-capture) process elements relative to the Sun. Their median abundances of [Ba/Fe], [La/Fe] and [Eu/Fe] are 0.54, 0.65 and 0.40, respectively. The Y I and Zr I abundances are lower than Ba, La and Eu, but higher than the α- and iron-peak elements for the strong Ba stars and similar to the iron-peak elements for the mild stars. There exists a positive correlation between Ba intensity and [Ba/Fe]. For the n-capture elements (Y, Zr, Ba, La), there is an anti-correlation between their [X/Fe] and [Fe/H]. We identify nine of our sample stars as strong Ba stars with [Ba/Fe] >0.6 where seven of them have Ba intensity Ba=2-5, one has Ba=1.5 and another one has Ba=1.0. The remaining ten stars are classified as mild Ba stars with 0.17<[Ba/Fe] <0.54.

  19. Substrate specificity for the 12beta-hydroxylation of bufadienolides by Alternaria alternata.

    PubMed

    Ye, Min; Guo, Dean

    2005-05-25

    Hydroxylation is an important route to synthesize more hydrophilic compounds of pharmaceutical significance. Microbial hydroxylation offers advantages over chemical means for its high specificity. In this study, a fungal strain Alternaria alternata AS 3.4578 was found to be able to catalyze the specific 12beta-hydroxylation of a variety of cytotoxic bufadienolides. Cinobufagin and resibufogenin could be completely metabolized by A. alternata to generate their 12beta-hydroxylated products in high yields (>90%) within 8 h of incubation. A. alternata could also convert 3-epi-desacetylcinobufagin into 3-epi-12beta-hydroxyl desacetylcinobufagin as the major product (70% yield). C-3 dehydrogenated products were detected in these reactions in fair yields, while their accumulation was relatively slow. The 12beta-hydroxylation of bufadienolides could be significantly inhibited by the substitution of 1beta-, 5-, or 16alpha-hydroxyl groups, and the 14beta,15beta-epoxy ring appeared to be a necessary structural requirement for the specificity. For the biotransformation of bufalin, a 14beta-OH bufadienolide, this reaction was not specific, and accompanied by 7beta-hydroxylation as a parallel and competing metabolic route. The biotransformation products were identified by comparison with authentic samples or tentatively characterized by high-performance liquid chromatography-diode array detection-atmospheric pressure chemical ionization-mass spectrometry analyses. PMID:15862355

  20. Comparison of fluorescence-based techniques for the quantification of particle-induced hydroxyl radicals

    PubMed Central

    Cohn, Corey A; Simon, Sanford R; Schoonen, Martin AA

    2008-01-01

    Background Reactive oxygen species including hydroxyl radicals can cause oxidative stress and mutations. Inhaled particulate matter can trigger formation of hydroxyl radicals, which have been implicated as one of the causes of particulate-induced lung disease. The extreme reactivity of hydroxyl radicals presents challenges to their detection and quantification. Here, three fluorescein derivatives [aminophenyl fluorescamine (APF), amplex ultrared, and dichlorofluorescein (DCFH)] and two radical species, proxyl fluorescamine and tempo-9-ac have been compared for their usefulness to measure hydroxyl radicals generated in two different systems: a solution containing ferrous iron and a suspension of pyrite particles. Results APF, amplex ultrared, and DCFH react similarly to the presence of hydroxyl radicals. Proxyl fluorescamine and tempo-9-ac do not react with hydroxyl radicals directly, which reduces their sensitivity. Since both DCFH and amplex ultrared will react with reactive oxygen species other than hydroxyl radicals and another highly reactive species, peroxynitite, they lack specificity. Conclusion The most useful probe evaluated here for hydroxyl radicals formed from cell-free particle suspensions is APF due to its sensitivity and selectivity. PMID:18307787

  1. RF-Hydroxysite: a random forest based predictor for hydroxylation sites.

    PubMed

    Ismail, Hamid D; Newman, Robert H; Kc, Dukka B

    2016-07-19

    Protein hydroxylation is an emerging posttranslational modification involved in both normal cellular processes and a growing number of pathological states, including several cancers. Protein hydroxylation is mediated by members of the hydroxylase family of enzymes, which catalyze the conversion of an alkyne group at select lysine or proline residues on their target substrates to a hydroxyl. Traditionally, hydroxylation has been identified using expensive and time-consuming experimental methods, such as tandem mass spectrometry. Therefore, to facilitate identification of putative hydroxylation sites and to complement existing experimental approaches, computational methods designed to predict the hydroxylation sites in protein sequences have recently been developed. Building on these efforts, we have developed a new method, termed RF-hydroxysite, that uses random forest to identify putative hydroxylysine and hydroxyproline residues in proteins using only the primary amino acid sequence as input. RF-Hydroxysite integrates features previously shown to contribute to hydroxylation site prediction with several new features that we found to augment the performance remarkably. These include features that capture physicochemical, structural, sequence-order and evolutionary information from the protein sequences. The features used in the final model were selected based on their contribution to the prediction. Physicochemical information was found to contribute the most to the model. The present study also sheds light on the contribution of evolutionary, sequence order, and protein disordered region information to hydroxylation site prediction. The web server for RF-hydroxysite is available online at . PMID:27292874

  2. Fluorescent and Luminescent Probes for Monitoring Hydroxyl Radical under Biological Conditions.

    PubMed

    Żamojć, Krzysztof; Zdrowowicz, Magdalena; Jacewicz, Dagmara; Wyrzykowski, Dariusz; Chmurzyński, Lech

    2016-01-01

    Detection and quantitative determination in biological media of the hydroxyl radical are of great importance due to the role this radical plays in many physiological and pathological processes. This review focuses on the progress that has been made in recent years in the development of fluorescent and luminescent probes employed to monitor hydroxyl radical concentrations under biological conditions. PMID:26042844

  3. Solar and stellar photospheric abundances

    NASA Astrophysics Data System (ADS)

    Allende Prieto, Carlos

    2016-07-01

    The determination of photospheric abundances in late-type stars from spectroscopic observations is a well-established field, built on solid theoretical foundations. Improving those foundations to refine the accuracy of the inferred abundances has proven challenging, but progress has been made. In parallel, developments on instrumentation, chiefly regarding multi-object spectroscopy, have been spectacular, and a number of projects are collecting large numbers of observations for stars across the Milky Way and nearby galaxies, promising important advances in our understanding of galaxy formation and evolution. After providing a brief description of the basic physics and input data involved in the analysis of stellar spectra, a review is made of the analysis steps, and the available tools to cope with large observational efforts. The paper closes with a quick overview of relevant ongoing and planned spectroscopic surveys, and highlights of recent research on photospheric abundances.

  4. Robust Abundance Estimation in Animal Abundance Surveys with Imperfect Detection

    EPA Science Inventory

    Surveys of animal abundance are central to the conservation and management of living natural resources. However, detection uncertainty complicates the sampling process of many species. One sampling method employed to deal with this problem is depletion (or removal) surveys in whi...

  5. Coronal abundances and their variation

    NASA Technical Reports Server (NTRS)

    Saba, Julia L. R.

    1995-01-01

    This contract supports the investigation of elemental abundances in the solar corona, principally through analysis of high-resolution soft X-ray spectra from the Flat Crystal Spectrometer on the Solar Maximum Mission. The goals of the study are a characterization of the mean values of relative abundances of elements accessible in the FCS data, and information on the extent and circumstances of their variability. This report is a summation of the data analysis and reporting activities which occurred during the period of 15 April 1994 to 15 April 1995.

  6. The solar abundance of beryllium

    NASA Technical Reports Server (NTRS)

    Ross, J. E.; Aller, L. H.

    1974-01-01

    The solar abundance of beryllium is deduced from high-resolution Kitt Peak observations of the 3130.43- and 3131.08-A lines of Be II interpreted by the method of spectrum synthesis. The results are in good agreement with those previously obtained by Grevesse (1968) and by Hauge and Engvold (1968) and indicate that in the photospheric layers, beryllium is depleted below the chondritic value by a factor of about two. It is found that the beryllium abundance is equal to logN(Be)/N(H) + 12 = 1.08 plus or minus 0.05.

  7. Chemical Abundances of Symbiotic Giants

    NASA Astrophysics Data System (ADS)

    Gałan, C.; Mikołajewska, J.; Hinkle, K. H.; Joyce, R. R.

    2015-12-01

    High resolution (R ˜ 50000), near-IR spectra were used to measure photospheric abundances of CNO and elements around the iron peak for 24 symbiotic giants. Spectrum synthesis was employed using local thermal equilibrium and hydrostatic model atmospheres. The metallicities are distributed in a wide range with maximum around [Fe/H] ˜-0.4 - - 0.3 dex. Enrichment in 14N indicates that all the sample giants have experienced the first dredge-up. The relative abundance of [Ti/Fe] is generally large in red symbiotic systems.

  8. Coronal Abundances and Their Variation

    NASA Technical Reports Server (NTRS)

    Saba, Julia L. R.

    1996-01-01

    This contract supported the investigation of elemental abundances in the solar corona, principally through analysis of high-resolution soft X-ray spectra from the Flat Crystal Spectrometer on NASA's Solar Maximum Mission. The goals of the study were a characterization of the mean values of relative abundances of elements accessible in the FCS data, and information on the extent and circumstances of their variability. This is the Final Report, summarizing the data analysis and reporting activities which occurred during the period of performance, June 1993 - December 1996.

  9. SOLAR MODELS WITH REVISED ABUNDANCE

    SciTech Connect

    Bi, S. L.; Li, T. D.; Yang, W. M.; Li, L. H.

    2011-04-20

    We present new solar models in which we use the latest low abundances and further include the effects of rotation, magnetic fields, and extra-mixing processes. We assume that the extra-element mixing can be treated as a diffusion process, with the diffusion coefficient depending mainly on the solar internal configuration of rotation and magnetic fields. We find that such models can well reproduce the observed solar rotation profile in the radiative region. Furthermore, the proposed models can match the seismic constraints better than the standard solar models, also when these include the latest abundances, but neglect the effects of rotation and magnetic fields.

  10. Effect of liquefaction temperature on hydroxyl groups of bio-oil from loblolly pine (Pinus taeda).

    PubMed

    Celikbag, Yusuf; Via, Brian K; Adhikari, Sushil; Wu, Yonnie

    2014-10-01

    Loblolly pine was liquefied with ethylene glycol at 100, 150, 200 and 250 °C in order to analyze the effect of liquefaction temperature on hydroxyl groups of bio-oil, and to determine the source and variation of hydroxyl groups. The optimum temperature was found to be 150-200 °C. Hydroxyl number (OHN) of the bio-oil was ranged from 632 to 1430 mg KOH/g. GC-MS analysis showed that 70-90% of OHN was generated from unreacted EG. (31)P NMR analysis showed that the majority of hydroxyl groups were aliphatic, and none of the bio-oil exhibited any detectable hydroxyl groups from phenolic sources. Finally, it was found that all bio-oils were stable in terms of OHN for 2 months when stored at -10 °C. PMID:25113882

  11. Regulation of Hydroxylation and Nitroreduction Pathways during Metabolism of the Neonicotinoid Insecticide Imidacloprid by Pseudomonas putida.

    PubMed

    Lu, Tian-Qi; Mao, Shi-Yun; Sun, Shi-Lei; Yang, Wen-Long; Ge, Feng; Dai, Yi-Jun

    2016-06-22

    Imidacloprid (IMI) is mainly metabolized via nitroreduction and hydroxylation pathways, which produce different metabolites that are toxic to mammals and insects. However, regulation of IMI metabolic flux between nitroreduction and hydroxylation pathways is still unclear. In this study, Pseudomonas putida was found to metabolize IMI to 5-hydroxy and nitroso IMI and was therefore used for investigating the regulation of IMI metabolic flux. The cell growth time, cosubstrate, dissolved oxygen concentration, and pH showed significant effect on IMI degradation and nitroso and 5-hydroxy IMI formation. Gene cloning and overexpression in Escherichia coli proved that P. putida KT2440 aldehyde oxidase mediated IMI nitroreduction to nitroso IMI, while cytochrome P450 monooxygenase (CYP) failed to improve IMI hydroxylation. Moreover, E. coli cells without CYP could hydroxylate IMI, demonstrating the role of a non-CYP enzyme in IMI hydroxylation. Thus, the present study helps to further understand the environmental fate of IMI and its underlying mechanism. PMID:27230024

  12. Elucidation of the beta-carotene hydroxylation pathway in Arabidopsis thaliana.

    PubMed

    Fiore, Alessia; Dall'osto, Luca; Fraser, Paul D; Bassi, Roberto; Giuliano, Giovanni

    2006-08-21

    The first dedicated step in plant xanthophyll biosynthesis is carotenoid hydroxylation. In Arabidopsis thaliana, this reaction is performed by both heme (LUT1 and LUT5) and non-heme (CHY1 and CHY2) hydroxylases. No mutant completely abolishing alpha- or beta-carotene hydroxylation has been described to date. We constructed double and triple mutant combinations in CHY1, CHY2, LUT1, LUT5 and LUT2 (lycopene epsilon-cyclase). In chy1chy2lut2, 80% of leaf carotenoids is represented by beta-carotene. In chy1chy2lut5, beta-carotene hydroxylation is completely abolished, while hydroxylation of the beta-ring of alpha-carotene is still observed. The data are consistent with a role of LUT5 in beta-ring hydroxylation, and with the existence of an additional hydroxylase, acting on the beta-ring of alpha-, but not beta-carotene. PMID:16890225

  13. Hepatic drug hydroxylation and lipid peroxidation in riboflavin-deficient rats*

    PubMed Central

    Patel, J. M.; Galdhar, N. R.; Pawar, S. S.

    1974-01-01

    The effect of riboflavin deficiency and phenobarbital pretreatment on drug hydroxylation and lipid peroxidation was investigated. A significant decrease in aniline and acetanilide hydroxylation as well as NADPH-linked and ascorbate-induced lipid peroxidation was observed during 4- and 7-week riboflavin deficiency in both adult male and adult female rats. The drug-hydroxylation and lipid-peroxidation activities were further lowered with the increase in riboflavin deficiency. The phenobarbital pretreatment induced aniline and acetanilide hydroxylase activity even in riboflavin-deficient animals. Drug hydroxylation inhibits lipid peroxidation in both deficient and normal rats. The administration of riboflavin was followed by a significant increase in drug hydroxylation and lipid peroxidation. PMID:4374935

  14. Hepatic drug hydroxylation and lipid peroxidation in riboflavin-deficient rats.

    PubMed

    Patel, J M; Galdhar, N R; Pawar, S S

    1974-06-01

    The effect of riboflavin deficiency and phenobarbital pretreatment on drug hydroxylation and lipid peroxidation was investigated. A significant decrease in aniline and acetanilide hydroxylation as well as NADPH-linked and ascorbate-induced lipid peroxidation was observed during 4- and 7-week riboflavin deficiency in both adult male and adult female rats. The drug-hydroxylation and lipid-peroxidation activities were further lowered with the increase in riboflavin deficiency. The phenobarbital pretreatment induced aniline and acetanilide hydroxylase activity even in riboflavin-deficient animals. Drug hydroxylation inhibits lipid peroxidation in both deficient and normal rats. The administration of riboflavin was followed by a significant increase in drug hydroxylation and lipid peroxidation. PMID:4374935

  15. Trimethylaluminum and Oxygen Atomic Layer Deposition on Hydroxyl-Free Cu(111)

    PubMed Central

    2015-01-01

    Atomic layer deposition (ALD) of alumina using trimethylaluminum (TMA) has technological importance in microelectronics. This process has demonstrated a high potential in applications of protective coatings on Cu surfaces for control of diffusion of Cu in Cu2S films in photovoltaic devices and sintering of Cu-based nanoparticles in liquid phase hydrogenation reactions. With this motivation in mind, the reaction between TMA and oxygen was investigated on Cu(111) and Cu2O/Cu(111) surfaces. TMA did not adsorb on the Cu(111) surface, a result consistent with density functional theory (DFT) calculations predicting that TMA adsorption and decomposition are thermodynamically unfavorable on pure Cu(111). On the other hand, TMA readily adsorbed on the Cu2O/Cu(111) surface at 473 K resulting in the reduction of some surface Cu1+ to metallic copper (Cu0) and the formation of a copper aluminate, most likely CuAlO2. The reaction is limited by the amount of surface oxygen. After the first TMA half-cycle on Cu2O/Cu(111), two-dimensional (2D) islands of the aluminate were observed on the surface by scanning tunneling microscopy (STM). According to DFT calculations, TMA decomposed completely on Cu2O/Cu(111). High-resolution electron energy loss spectroscopy (HREELS) was used to distinguish between tetrahedrally (Altet) and octahedrally (Aloct) coordinated Al3+ in surface adlayers. TMA dosing produced an aluminum oxide film, which contained more octahedrally coordinated Al3+ (Altet/Aloct HREELS peak area ratio ≈ 0.3) than did dosing O2 (Altet/Aloct HREELS peak area ratio ≈ 0.5). After the first ALD cycle, TMA reacted with both Cu2O and aluminum oxide surfaces in the absence of hydroxyl groups until film closure by the fourth ALD cycle. Then, TMA continued to react with surface Al–O, forming stoichiometric Al2O3. O2 half-cycles at 623 K were more effective for carbon removal than O2 half-cycles at 473 K or water half-cycles at 623 K. The growth rate was approximately 3–4

  16. Interactive enhancements of ascorbic acid and iron in hydroxyl radical generation in quinone redox cycling.

    PubMed

    Li, Yi; Zhu, Tong; Zhao, Jincai; Xu, Bingye

    2012-09-18

    Quinones are toxicological substances in inhalable particulate matter (PM). The mechanisms by which quinones cause hazardous effects can be complex. Quinones are highly active redox molecules that can go through a redox cycle with their semiquinone radicals, leading to formation of reactive oxygen species. Electron spin resonance spectra have been reported for semiquinone radicals in PM, indicating the importance of ascorbic acid and iron in quinone redox cycling. However, these findings are insufficient for understanding the toxicity associated with quinone exposure. Herein, we investigated the interactions among anthraquinone (AQ), ascorbic acid, and iron in hydroxyl radical (·OH) generation through the AQ redox cycling process in a physiological buffer. We measured ·OH concentration and analyzed the free radical process. Our results showed that AQ, ascorbic acid, and iron have synergistic effects on ·OH generation in quinone redox cycling; i.e., ascorbyl radical oxidized AQ to semiquinone radical and started the redox cycling, iron accelerated this oxidation and enhanced ·OH generation through Fenton reactions, while ascorbic acid and AQ could help iron to release from quartz surface and enhance its bioavailability. Our findings provide direct evidence for the redox cycling hypothesis about airborne particle surface quinone in lung fluid. PMID:22891791

  17. Hydroxyl radical and thermal annealing on amorphous InGaZnO4 films for DNA immobilizations.

    PubMed

    Sun, Dali; Yamahara, Hiroyasu; Nakane, Ryosho; Matsui, Hiroaki; Tabata, Hitoshi

    2015-06-01

    The effect of hydroxyl radicals (OH) and thermal annealing on an amorphous InGaZnO4 (aIGZO) film surface was investigated for manipulation of DNA immobilization. X-ray photoemission and fluorescence measurements were conducted to reveal the status of surface OH coverage and DNA immobilization, respectively. Systematic examinations concerning OH termination on the film surface suggested that the surface coverage of OH leveling DNA immobilization was related to the local surface potential. Furthermore, OH affinity on the aIGZO film surface was sensitive to thermal annealing. A remarkable change in surface OH coverage was observed for the film surface annealed at high temperature. This behavior was framed by a structural change from amorphous to crystalline state, which regulated DNA immobilization. These results indicate that the OH affinity on aIGZO films is dependent on structural properties such as defects. This study suggests that an amorphous structure is critical for obtaining a high OH surface coverage governing DNA immobilization, and is hence more suitable for biosensing. PMID:25935561

  18. THE SOLAR FLARE IRON ABUNDANCE

    SciTech Connect

    Phillips, K. J. H.; Dennis, B. R. E-mail: Brian.R.Dennis@nasa.gov

    2012-03-20

    The abundance of iron is measured from emission line complexes at 6.65 keV (Fe line) and 8 keV (Fe/Ni line) in RHESSI X-ray spectra during solar flares. Spectra during long-duration flares with steady declines were selected, with an isothermal assumption and improved data analysis methods over previous work. Two spectral fitting models give comparable results, viz., an iron abundance that is lower than previous coronal values but higher than photospheric values. In the preferred method, the estimated Fe abundance is A(Fe) = 7.91 {+-} 0.10 (on a logarithmic scale, with A(H) = 12) or 2.6 {+-} 0.6 times the photospheric Fe abundance. Our estimate is based on a detailed analysis of 1898 spectra taken during 20 flares. No variation from flare to flare is indicated. This argues for a fractionation mechanism similar to quiet-Sun plasma. The new value of A(Fe) has important implications for radiation loss curves, which are estimated.

  19. Origin of Coverage Dependence in Photoreactivity of Carboxylate on TiO2(110): Hindering by Charged Coadsorbed Hydroxyls

    SciTech Connect

    Wang, Zhitao; Henderson, Michael A.; Lyubinetsky, Igor

    2015-09-30

    The influence of reactant coverage on photochemical activity was explored using scanning tunneling microscopy (STM) and ultraviolet photoelectron spectroscopy (UPS). We observed diminished reactivity of carboxylate species (trimethyl acetate, TMA) on TiO2(110) as a function of increasing coverage. This effect was not linked to intermolecular interactions of TMA but to the accumulation of the coadsorbed bridging hydroxyls (HOb) deposited during (thermal) dissociative adsorption of the parent, trimethylacetic acid (TMAA). Confirmation of the hindering influence of HOb groups was obtained by the observation that HOb species originated from H2O dissociation at O-vacancy sites have a similar hindering effect on TMA photochemistry. Though HOb’s are photoinactive on TiO2(110) under ultrahigh vacuum conditions, UPS results show that these sites trap photoexcited electrons, which in turn likely (electrostatically) attract and neutralize photoexcited holes, thus suppressing the hole-mediated photoreactivity of TMA. This negative influence of surface hydroxyls on hole-mediated photochemistry is likely a major factor in other anaerobic photochemical processes on reducible oxide surfaces.

  20. Actinide abundances in ordinary chondrites

    USGS Publications Warehouse

    Hagee, B.; Bernatowicz, T.J.; Podosek, F.A.; Johnson, M.L.; Burnett, D.S.; Tatsumoto, M.

    1990-01-01

    Measurements of 244Pu fission Xe, U, Th, and light REE (LREE) abundances, along with modal petrographic determinations of phosphate abundances, were carried out on equilibrated ordinary chondrites in order to define better the solar system Pu abundance and to determine the degree of variation of actinide and LREE abundances. Our data permit comparison of the directly measured Pu/ U ratio with that determined indirectly as (Pu/Nd) ?? (Nd/U) assuming that Pu behaves chemically as a LREE. Except for Guaren??a, and perhaps H chondrites in general, Pu concentrations are similar to that determined previously for St. Se??verin, although less precise because of higher trapped Xe contents. Trapped 130Xe 136Xe ratios appear to vary from meteorite to meteorite, but, relative to AVCC, all are similar in the sense of having less of the interstellar heavy Xe found in carbonaceous chondrite acid residues. The Pu/U and Pu/Nd ratios are consistent with previous data for St. Se??verin, but both tend to be slightly higher than those inferred from previous data on Angra dos Reis. Although significant variations exist, the distribution of our Th/U ratios, along with other precise isotope dilution data for ordinary chondrites, is rather symmetric about the CI chondrite value; however, actinide/(LREE) ratios are systematically lower than the CI value. Variations in actinide or LREE absolute and relative abundances are interpreted as reflecting differences in the proportions and/or compositions of more primitive components (chondrules and CAI materials?) incorporated into different regions of the ordinary chondrite parent bodies. The observed variations of Th/U, Nd/U, or Ce/U suggest that measurements of Pu/U on any single equilibrated ordinary chondrite specimen, such as St. Se??verin, should statistically be within ??20-30% of the average solar system value, although it is also clear that anomalous samples exist. ?? 1990.

  1. PBDEs, hydroxylated PBDEs and methoxylated PBDEs in bivalves from Beijing markets.

    PubMed

    Liu, Xitao; Jiao, Ying; Lin, Chunye; Sun, Ke; Zhao, Ye

    2014-09-01

    The structural analogues of polybrominated diphenyl ethers (PBDEs), hydroxylated PBDEs (OH-PBDEs) and methoxylated PBDEs (MeO-PBDEs) have been attracting increasing concern in recent years. Five bivalve species (blue mussel, short-necked clam, surf clam, ark shell and razor clam) were collected from Beijing markets, and the concentrations of seven PBDEs, four OH-PBDEs and fourteen MeO-PBDEs in the bivalves were measured. The seasonal variations of these three types of polybrominated compound in blue mussels were also monitored. The results indicate that the levels of ΣPBDEs in this study were comparable to those in short-necked clams from Liaodong Bay, China, with BDE47 as the dominant congener. For the ortho-MeO-PBDEs, 6-MeO-BDE47 was found at higher concentrations than the others, while for the meta- and para-MeO-PBDEs, 4'-MeO-BDE17 was found at higher concentrations. 6-OH-BDE-47 was the most abundant congener among the 4 measured OH-PBDEs, followed by 6-OH-BDE-137 and 6-OH-BDE-85. The levels of OH-PBDEs and MeO-PBDEs in bivalves from Beijing markets were much lower than the corresponding compounds in blue mussels from the Baltic Sea. In the blue mussels collected in April, June and September of 2012, apparent seasonal variations were observed for these three types of polybrominated compounds, but the acidic components displayed different trends from the neutral components, with PBDEs and MeO-PBDEs showing the highest concentrations in June, while OH-PBDEs had the lowest concentrations in June. This difference in seasonal variations between the neutral components and the acidic components may be explained by their different sources and transformation/elimination mechanisms. PMID:24636323

  2. Formation of hydroxylated polybrominated diphenyl ethers from laccase-catalyzed oxidation of bromophenols.

    PubMed

    Lin, Kunde; Zhou, Shiyang; Chen, Xi; Ding, Jiafeng; Kong, Xiaoyan; Gan, Jay

    2015-11-01

    Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) have been frequently found in the marine biosphere as emerging organic contaminants. Studies to date have suggested that OH-PBDEs in marine biota are natural products. However, the mechanisms leading to the biogenesis of OH-PBDEs are still far from clear. In this study, using a laccase isolated from Trametes versicolor as the model enzyme, we explored the formation of OH-PBDEs from the laccase-catalyzed oxidation of simple bromophenols (e.g., 2,4-DBP and 2,4,6-TBP). Experiments under ambient conditions clearly showed that OH-PBDEs were produced from 2,4-DBP and 2,4,6-TBP in presence of laccase. Polybrominated compounds 2'-OH-BDE68, 2,2'-diOH-BB80, and 1,3,8-TrBDD were identified as the products from 2,4-DBP, and 2'-OH-BDE121 and 4'-OH-BDE121 from 2,4,6-TBP. The production of OH-PBDEs was likely a result of the coupling of bromophenoxy radicals, generated from the laccase-catalyzed oxidation of 2,4-DBP or 2,4,6-TBP. The transformation of bromophenols by laccase was pH-dependant, and was also influenced by enzymatic activity. In view of the abundance of 2,4-DBP and 2,4,6-TBP and the phylogenetic distribution of laccases in the environment, laccase-catalyzed conversion of bromophenols may be potentially an important route for the natural biosynthesis of OH-PBDEs. PMID:26295539

  3. Kinetic of benzotriazole oxidation by ozone and hydroxyl radical.

    PubMed

    Vel Leitner, Nathalie Karpel; Roshani, Babak

    2010-03-01

    Ozonation experiments were performed in batch reactors in order to determine the rate constants for the reaction of molecular ozone and OH radicals with benzotriazole (BT) at different pHs. The first group of ozonation experiments was carried out for the determination of the rate constant for the direct reactions between ozone and BT. Two different kinetic models were used for the determination of kinetic rate constants: (i) the log-reduction of BT with ozone in excess, (ii) the competition kinetic model. The second-order rate constants for BT with molecular ozone were determined to be 36.4+/-3.8M(-1) s(-1) and 18.4+/-0.8M(-1) s(-1) at pH 2 from the two methods respectively. With the competition method, the value at pH 5 was found to be 22.0+/-2.0M(-1) s(-1). In a following stage, the reaction of BT with OH radicals was investigated at pH values ranging from 2 to 10.2. Using a method involving two probe compounds during the ozonation, the second-order rate constants of the BT reaction with hydroxyl radicals were determined. The rate constants were found to vary from 6.2x10(9)M(-1) s(-1) at pH 10.2 to 1.7x10(10)M(-1) s(-1) at pH 2. PMID:20097402

  4. Hydroxylated Polybrominated Diphenyl Ethers in Paired Maternal and Cord Sera

    PubMed Central

    Chen, Aimin; Park, June-Soo; Linderholm, Linda; Rhee, Alexandra; Petreas, Myrto; DeFranco, Emily A.; Dietrich, Kim N.; Ho, Shuk-mei

    2015-01-01

    Polybrominated diphenyl ethers (PBDEs) were widely used as flame retardants in the past three decades. These compounds are lipophilic and easily cross the placenta from pregnant woman to fetus. It is not clear whether hydroxylated PBDEs (OH-PBDEs), with greater hydrophilicity, have different concentrations in maternal and cord serum samples. We analyzed PBDEs (BDE-28, -47, -99, -100, -153, -154, -209) and OH-PBDEs (6-OH-BDE-47, 5-OH-BDE-47, 4′-OH-BDE-49, 5′-OH-BDE-99) in 20 pairs of maternal and cord serum samples collected in Cincinnati, OH in 2011. The geometric mean concentration of ΣOH-BDEs (the sum of four OH-PBDEs) was 49.76 pg/ml in cord sera, higher than 32.84 pg/ml in maternal sera. Similarly, cord serum total BDEs had a higher geometric mean than maternal serum (45.51 vs. 32.07 ng/g lipid). Equal or higher levels of total OH-BDEs and total BDEs in cord serum were observed in 85% and 80% of the mother-neonate pairs, respectively. The study suggests fetuses might receive higher OH-PBDE and PBDE exposure than their mothers. PMID:23506475

  5. Hydroxyl radical formation in phagocytic cells of the rat.

    PubMed

    Drath, D B; Karnovsky, M L; Huber, G L

    1979-01-01

    Polymorphonuclear leukocytes (PMN) and macrophages, harvested from the peritoneum and lung, release superoxide (O-.2) and hydrogen peroxide (H2O2) during phagocytosis. These two agents are thought to react with each other to produce a highly active oxidative substance known as hydroxyl radical (OH.). We present evidence suggesting that these radicals are generated by phagocytic cells of the rat. Our findings are based upon an assay where ethylene gas is generated from methional by the action of this radical. Ethylene generation was shown to be inhibited by superoxide dismutase, catalase, and scavengers of OH.. Of the cells examined, PMN generated the most ethylene from methional, exhibiting a fourfold increase during phagocytosis. Pulmonary and peritoneal macrophages caused smaller amounts of this gas to be formed. Regardless of cell type, an intact cell was required for ethylene generation. Zymosan appeared to be the most effective particle for all cells in ethylene formation from methional, although opsonization was critical only for PMN. Ethylene generation was dependent on cell concentration to an extent and increased with time. PMID:222719

  6. Two supramolecular microporous frameworks stabilized by hydroxyl anionic water cluster

    NASA Astrophysics Data System (ADS)

    Jian, Fang Fang; Wang, Jing; Huang, Li Hua; Wang, Xian; Xiao, Hai Lian

    2010-06-01

    Two stable supramolecular microporous framework complexes, from the same [MCl(phen) 2] + (M = Cu, Ni), containing chiral hydroxyl anionic water cluster polymer, were synthesized, and their crystal structures were described. These supramolecular frameworks showed very high stability even if they were heated to 300 °C. Thermal analysis and powder X-ray diffraction results indicated that the water molecules were removed when heated from 150 °C to 300 °C without losing the main crystal framework. Water molecules can be reassembled by exposing the dehydrated form to an atmosphere saturated with water vapor. It indicated that the dehydrated form may be utilized as a potential absorbing agent for water and water vapor. The stable dehydrated form, [MCl(phen) 2][(OH)(H 2O)], suggested the stronger anionic H-bonding and intracluster proton transfer process OH -·H 2O → H 2O·OH -. The "anion- π interaction" was found in the crystal lattice of [MCl(phen) 2][(OH)(H 2O)]. This paper reported an example of supramolecular polymer with open channels that could be formed/collapse reversibly upon hydration/dehydration.

  7. SPLASH: A Southern Parkes Large Area Survey in Hydroxyl

    NASA Astrophysics Data System (ADS)

    Dawson, Joanne; Caswell, James; Gomez, Jose F.; Mcclure-Griffiths, Naomi; Lo, Nadia; Jones, Paul; Dickey, John; Cunningham, Maria; Green, James; Carretti, Ettore; Ellingsen, Simon; Walsh, Andrew; Purcell, Cormac; Breen, Shari; Hennebelle, Patrick; Imai, Hiroshi; Lowe, Vicki; Gibson, Steven; Jones, Courtney; Krishnan, Vasaant

    2013-10-01

    The OH 18 cm lines are powerful and versatile probes of diffuse molecular gas, that may trace a largely unstudied component of the Galactic ISM. SPLASH (the Southern Parkes Large Area Survey in Hydroxyl) is a large, unbiased and fully-sampled survey of OH emission, absorption and masers in the Galactic Plane that will achieve sensitivities an order of magnitude better than previous work. The survey will answer critical questions on the global distribution of diffuse OH, the degree to which it traces ‘hidden’ material caught between the regimes probed by traditional tracers of the neutral ISM, and its role as a probe of molecular cloud formation. As a blind survey for all four ground-state transitions, SPLASH will also detect many new OH masers, facilitating a broad range of astrophysical studies. This proposal requests 670 hours spread over two semesters to complete Phase 1 of the SPLASH project, which will map 152 square degrees in the inner Galactic Plane, including the Galactic Centre. Following the ongoing success of the project, we request that its pre-graded status be renewed for a final two semesters.

  8. Production of hydroxyl radical by redox active flavonoids

    SciTech Connect

    Kalyanaraman, B.; Hodnick, W.F.; Pardini, R.S.

    1986-05-01

    The authors have previously shown that flavonoids autoxidize and generate superoxide (O/sub 2//sup -/) and hydrogen peroxide (H/sub 2/O/sub 2/), suggesting that hydroxyl radical (OH) could be formed via the metal-ion catalyzed Haber-Weiss reaction. In the presence of ethylenediamine tetraacetic acid (EDTA) and 5,5-dimethyl-1-pyrroline-1-oxide (DMPO), myricetin, quercetagetin and quercetin gave an ESR signal for the DMPO-OH spin adduct, and the DMPO-Eto adduct in the presence of excess ethanol, indicating the production of free OH. The addition of FeCl/sub 3/ to the reaction mixture resulted in a dramatic increase in the DMPO-OH signal. Without chelator (EDTA) there was no signal and the presence of diethylenetriamine-pentaacetic acid (DETAPAC) greatly diminished the signal. The presence of superoxide dismutase (SOD) had no effect on the signal while catalase completely abrogated the signal. The addition of Fe (III)-EDTA to flavonoid solutions under anaerobic conditions produced time dependent auxochromic shifts in their absorption spectra and resulted in the reduction of Fe (III) to Fe (II). These data suggest that the flavonoids autoxidize to produce O/sub 2//sup -/ and H/sub 2/O/sub 2/ by dismutation and in the presence of Fe (III)-EDTA the flavonoid can directly reduce the Fe (III) to Fe (II) resulting in the production of OH through Fenton chemistry.

  9. Hydroxylation of methane through component interactions in soluble methane monooxygenases.

    PubMed

    Lee, Seung Jae

    2016-04-01

    Methane hydroxylation through methane monooxygenases (MMOs) is a key aspect due to their control of the carbon cycle in the ecology system and recent applications of methane gas in the field of bioenergy and bioremediation. Methanotropic bacteria perform a specific microbial conversion from methane, one of the most stable carbon compounds, to methanol through elaborate mechanisms. MMOs express particulate methane monooxygenase (pMMO) in most strains and soluble methane monooxygenase (sMMO) under copper-limited conditions. The mechanisms of MMO have been widely studied from sMMO belonging to the bacterial multicomponent monooxygenase (BMM) superfamily. This enzyme has diiron active sites where different types of hydrocarbons are oxidized through orchestrated hydroxylase, regulatory and reductase components for precise control of hydrocarbons, oxygen, protons, and electrons. Recent advances in biophysical studies, including structural and enzymatic achievements for sMMO, have explained component interactions, substrate pathways, and intermediates of sMMO. In this account, oxidation of methane in sMMO is discussed with recent progress that is critical for understanding the microbial applications of C-H activation in one-carbon substrates. PMID:27033202

  10. Cellulose based hybrid hydroxylated adducts for polyurethane foams

    NASA Astrophysics Data System (ADS)

    De Pisapia, Laura; Verdolotti, Letizia; Di Mauro, Eduardo; Di Maio, Ernesto; Lavorgna, Marino; Iannace, Salvatore

    2012-07-01

    Hybrid flexible polyurethane foams (HPU) were synthesized by using a hybrid hydroxilated adduct (HHA) based on renewable resources. In particular the HHA was obtained by dispersing cellulose wastes in colloidal silica at room temperature, pressure and humidity. The colloidal silica was selected for its ability of modifying the cellulose structure, by inducing a certain "destructurization" of the crystalline phase, in order to allow cellulose to react with di-isocyanate for the final synthesis of the polyurethane foam. In fact, cellulose-polysilicate complexes are engaged in the reaction with the isocyanate groups. This study provides evidence of the effects of the colloidal silica on the cellulose structure, namely, a reduction of the microfiber cellulose diameter and the formation of hydrogen bonds between the polysilicate functional groups and the hydroxyl groups of the cellulose, as assessed by IR spectroscopy and solid state NMR. The HHA was added to a conventional polyol in different percentages (between 5 and 20%) to synthesize HPU in presence of catalysts, silicone surfactant and diphenylmethane diisocyanate (MDI). The mixture was expanded in a mold and cured for two hours at room temperature. Thermal analysis, optical microscopy and mechanical tests were performed on the foams. The results highlighted an improvement of thermal stability and a decrease of the cell size with respect neat polyurethane foam. Mechanical tests showed an improvement of the elastic modulus and of the damping properties with increasing HHA amount.

  11. Single vs multi-level quenching of the hydroxyl airglow

    NASA Astrophysics Data System (ADS)

    Franzen, Christoph; Espy, Patrick J.; Hibbins, Robert; Djupvik, Anlaug Amanda

    2016-04-01

    The reaction in the upper mesosphere between atomic hydrogen and ozone results in hydroxyl (OH) that is produced in excited vibrational levels 6 through 9. The vibrationally excited OH radiates in a thin (~8 km thick) layer near 87 km, giving rise to the strong near infrared airglow emission that has been used for remote sensing of the mesopause region. The interpretation of the emission relies on accurate knowledge of the population and quenching of the upper states, and open questions remain as to whether the quenching takes place through single- or multi-quantum deactivation. Here we will demonstrate how high quality spectral observations of OH (9,7) and (8,6) airglow emissions are available as background measurements during standard K-band astronomical observations from the Nordic Optical Telescope (18°W, 29°N). These emissions have been analysed to ascertain the quenching of the upper vibrational populations. Together with a steady-state model of these emissions, an estimate of the ratio of single to multi-quantum quenching efficiency and the impact on the populations of the lower vibrational levels will be presented.

  12. Eosinophil peroxidase-dependent hydroxyl radical generation by human eosinophils.

    PubMed

    McCormick, M L; Roeder, T L; Railsback, M A; Britigan, B E

    1994-11-11

    Eosinophil production of superoxide (O2-.) and hydrogen peroxide (H2O2) is important in host defense. The present study assessed the potential of eosinophils to generate another potent cytotoxic species, the hydroxyl radical (.OH). .OH formation by phorbol myristate acetate (PMA)-stimulated eosinophils was demonstrated using an alpha-(4-pyridyl-1-oxide)-N-tert-butyl nitrone/ethanol spin trapping system. Additionally, .OH was spin trapped following the addition of purified eosinophil peroxidase (EPO) to a cell-free O2-./H2O2 generating systems. Effects of superoxide dismutase, catalase, azide, aminotriazole, chloride-depleted buffer, and extensive metal chelation were consistent with .OH formation via the reaction of O2-. and EPO-generated hypohalous acid. Under chloride-depleted conditions, physiologic concentrations of Br- increased .OH formation by both PMA-stimulated eosinophils and the cell-free EPO system. Physiologic concentrations of SCN-, however, did not increase .OH formation, and in the presence of both Br- and SCN-, .OH formation was similar to SCN- only. Eosinophils appear to form .OH via an EPO-dependent mechanism, the magnitude of which varies with the availability of various EPO substrates. Given the highly reactive nature of this radical and the ability of EPO to adhere to cell membranes, even small amounts of .OH formed at such sites could contribute to eosinophil-mediated cytotoxicity. PMID:7961724

  13. Hydroxylated poly(N-isopropylacrylamide) as functional thermoresponsive materials.

    PubMed

    Maeda, Tomohiro; Kanda, Tomohide; Yonekura, Yuuki; Yamamoto, Kazuya; Aoyagi, Takao

    2006-02-01

    In this study, we developed a poly(N-isopropylacrylamide)-based thermoresponsive polymeric material with a high content of hydroxyl groups. We newly designed the functional monomer, N-(2-hydroxyisopropyl)acrylamide (HIPAAm), considering maintaining the continuous and repeated structure of the isopropylamide group after copolymerization and the monomer reactivity ratios. The thermoresponsive polymer was derived by conventional radical copolymerization of HIPAAm with N-isopropylacrylamide (NIPAAm) in high yield. Estimation of monomer reactivity ratios, r(1) and r(2), supported the almost random sequence of the comonomers. The obtained copolymers showed a very sensitive phase transition and/or separation in response to temperature in aqueous media although they have many hydrophilic parts, and their thermoresponsive behavior was not affected by the pH. Furthermore, the cloud points of these copolymers closely depended on the HIPAAm content and could be easily controlled by adding salts. HIPAAm is expected to regulate the phase transition and/or separation temperature of the NIPAAm-based copolymers while maintaining their desirable sensitive thermoresponse. Differential scanning calorimetric analysis showed that dehydration of the polymer chains occurring in phase transition became incomplete with increasing HIPAAm content. Moreover, it was found that poly(NIPAAm-co-HIPAAm) having a high content of the HIPAAm unit showed liquid-liquid phase separation involving coacervation. The sizes of the coacervate droplets were relatively monodisperse and very minimal. Poly(NIPAAm-co-HIPAAm) is valuable for use in biomedical fields such as bioseparation. PMID:16471928

  14. Hydroxyl PAMAM dendrimer-based gene vectors for transgene delivery to human retinal pigment epithelial cells

    NASA Astrophysics Data System (ADS)

    Mastorakos, Panagiotis; Kambhampati, Siva P.; Mishra, Manoj K.; Wu, Tony; Song, Eric; Hanes, Justin; Kannan, Rangaramanujam M.

    2015-02-01

    Ocular gene therapy holds promise for the treatment of numerous blinding disorders. Despite the significant progress in the field of viral and non-viral gene delivery to the eye, significant obstacles remain in the way of achieving high-level transgene expression without adverse effects. The retinal pigment epithelium (RPE) is involved in the pathogenesis of retinal diseases and is a key target for a number of gene-based therapeutics. In this study, we addressed the inherent drawbacks of non-viral gene vectors and combined different approaches to design an efficient and safe dendrimer-based gene-delivery platform for delivery to human RPE cells. We used hydroxyl-terminated polyamidoamine (PAMAM) dendrimers functionalized with various amounts of amine groups to achieve effective plasmid compaction. We further used triamcinolone acetonide (TA) as a nuclear localization enhancer for the dendrimer-gene complex and achieved significant improvement in cell uptake and transfection of hard-to-transfect human RPE cells. To improve colloidal stability, we further shielded the gene vector surface through incorporation of PEGylated dendrimer along with dendrimer-TA for DNA complexation. The resultant complexes showed improved stability while minimally affecting transgene delivery, thus improving the translational relevance of this platform.Ocular gene therapy holds promise for the treatment of numerous blinding disorders. Despite the significant progress in the field of viral and non-viral gene delivery to the eye, significant obstacles remain in the way of achieving high-level transgene expression without adverse effects. The retinal pigment epithelium (RPE) is involved in the pathogenesis of retinal diseases and is a key target for a number of gene-based therapeutics. In this study, we addressed the inherent drawbacks of non-viral gene vectors and combined different approaches to design an efficient and safe dendrimer-based gene-delivery platform for delivery to human RPE

  15. Diffusion of hydroxyl groups in silica glass through the binding interface

    NASA Astrophysics Data System (ADS)

    Sato, Naoya; Yamamoto, Takaki; Kuzuu, Nobu; Horikoshi, Hideharu; Niwa, Shohei

    2016-02-01

    Diffusion of hydroxyl groups in silica glass through an interface formed by binding between high-hydroxyl (ca. 1200 wt.ppm) and low-hydroxyl (ca. 130 wt.ppm)-containing silica glasses in the temperature range of 900-1150 °C was investigated. Although the theoretical curve with a hydroxyl-concentration-independent diffusion coefficient deviates from the experimental curve, the diffusion coefficients obtained by fitting to the experimental results by the least squares method coincided with the “effective diffusion coefficients” in the literature, which were obtained from the total absorption change in the IR absorption peak for the hydroxyl group using thin samples. By the analysis considering the hydroxyl concentration dependence of the diffusion coefficient, we showed that the diffusion coefficient is proportional to hydroxyl concentration at each temperature, which is consistent with the model of the diffusion: SiOSi + H2O = 2SiOH. On the basis of this scheme, we tried to evaluate the diffusion coefficients of molecular water using equilibrium constant in the literature.

  16. Spin trapping evidence for myeloperoxidase-dependent hydroxyl radical formation by human neutrophils and monocytes

    SciTech Connect

    Ramos, C.L.; Pou, S.; Britigan, B.E.; Cohen, M.S.; Rosen, G.M. )

    1992-04-25

    Using the electron spin resonance/spin trapping system, 4-pyridyl 1-oxide N-tert-butylnitrone (4-POBN)/ethanol, hydroxyl radical was detected as the alpha-hydroxyethyl spin trapped adduct of 4-POBN, 4-POBN-CH(CH3)OH, from phorbol 12-myristate 13-acetate-stimulated human neutrophils and monocytes without the addition of supplemental iron. 4-POBN-CH(CH3)OH was stable in the presence of a neutrophil-derived superoxide flux. Hydroxyl radical formation was inhibited by treatment with superoxide dismutase, catalase, and azide. Treatment with a series of transition metal chelators did not appreciably alter 4-POBN-CH(CH3)OH, which suggested that hydroxyl radical generation was mediated by a mechanism independent of the transition metal-catalyzed Haber-Weiss reaction. Kinetic differences between transition metal-dependent and -independent mechanisms of hydroxyl radical generation by stimulated neutrophils were demonstrated by a greater rate of 4-POBN-CH(CH3)-OH accumulation in the presence of supplemental iron. Detection of hydroxyl radical from stimulated monocyte-derived macrophages, which lack myeloperoxidase, required the addition of supplemental iron. The addition of purified myeloperoxidase to an enzymatic superoxide generating system resulted in the detection of hydroxyl radical that was dependent upon the presence of chloride and was inhibited by superoxide dismutase, catalase, and azide. These findings implicated the reaction of hypochlorous acid and superoxide to produce hydroxyl radical. 4-POBN-CH(CH3)OH was not observed upon stimulation of myeloperoxidase-deficient neutrophils, whereas addition of myeloperoxidase to the reaction mixture resulted in the detection of hydroxyl radical. These results support the ability of human neutrophils and monocytes to generate hydroxyl radical through a myeloperoxidase-dependent mechanism.

  17. Li-7 abundances in halo stars: Testing stellar evolution models and the primordial Li-7 abundance

    NASA Technical Reports Server (NTRS)

    Chaboyer, Brian; Demarque, P.

    1994-01-01

    A large number of stellar evolution models with (Fe/H) = -2.3 and -3.3 have been calculated in order to determine the primordial Li-7 abundance and to test current stellar evolution models by a comparison to the extensive database of accurate Li abundances in extremely metal-poor halo stars observed by Thorburn (1994). Standard models with gray atmospheres do a very good job of fitting the observed Li abundances in stars hotter than approximately 5600 K. They predict a primordial. Li-7 abundance of log N(Li) = 2.24 +/- 0.03. Models which include microscopic diffusion predict a downward curvature in the Li-7 destruction isochrones at hot temperatures which is not present in the observations. Thus, the observations clearly rule out models which include uninhibited microscopic diffusion of Li-7 from the surface of the star. Rotational mixing inhibits the microscopic diffusion and the (Fe/H) = -2.28 stellar models which include both diffusion and rotational mixing provide an excellent match to the mean trend in T(sub eff) which is present in the observations. Both the plateau stars and the heavily depleted cool stars are well fit by these models. The rotational mixing leads to considerable Li-7 depletion in these models and the primordial Li-7 abundance inferred from these models is log N(Li) = 3.08 +/- 0.1. However, the (Fe/H) = -3.28 isochrones reveal problems with the combined models. These isochrones predict a trend of decreasing log N(Li) with increasing T(sub eff) which is not present in the observations. Possible causes for this discrepancy are discussed.

  18. Li-7 abundances in halo stars: Testing stellar evolution models and the primordial Li-7 abundance

    NASA Astrophysics Data System (ADS)

    Chaboyer, Brian; Demarque, P.

    1994-10-01

    A large number of stellar evolution models with (Fe/H) = -2.3 and -3.3 have been calculated in order to determine the primordial Li-7 abundance and to test current stellar evolution models by a comparison to the extensive database of accurate Li abundances in extremely metal-poor halo stars observed by Thorburn (1994). Standard models with gray atmospheres do a very good job of fitting the observed Li abundances in stars hotter than approximately 5600 K. They predict a primordial. Li-7 abundance of log N(Li) = 2.24 +/- 0.03. Models which include microscopic diffusion predict a downward curvature in the Li-7 destruction isochrones at hot temperatures which is not present in the observations. Thus, the observations clearly rule out models which include uninhibited microscopic diffusion of Li-7 from the surface of the star. Rotational mixing inhibits the microscopic diffusion and the (Fe/H) = -2.28 stellar models which include both diffusion and rotational mixing provide an excellent match to the mean trend in Teff which is present in the observations. Both the plateau stars and the heavily depleted cool stars are well fit by these models. The rotational mixing leads to considerable Li-7 depletion in these models and the primordial Li-7 abundance inferred from these models is log N(Li) = 3.08 +/- 0.1. However, the (Fe/H) = -3.28 isochrones reveal problems with the combined models. These isochrones predict a trend of decreasing log N(Li) with increasing Teff which is not present in the observations. Possible causes for this discrepancy are discussed.

  19. Coronal abundances and their variation

    NASA Technical Reports Server (NTRS)

    Saba, Julia L. R.

    1994-01-01

    This contract supports the investigation of elemental abundances in the solar corona, principally through analysis of high-resolution software X-ray spectra from the Flat Crystal Spectrometer on NASA's Solar Maximum Mission. The goals of the study are a characterization of the mean values of relative abundances of elements accessible in the FCS data, and information on the extent and circumstances of their variability. This report is a summation of the data analysis and reporting activities which occurred since the last report, submitted two months early, in April 1994, to facilitate evaluation of the first year's progress for contract renewal. Hence this report covers the period 15 April 1994 - 15 December 1994. A list of publications resulting from this research is included.

  20. Curable liquid hydrocarbon prepolymers containing hydroxyl groups and process for producing same

    NASA Technical Reports Server (NTRS)

    Rhein, R. A.; Ingham, J. D. (Inventor)

    1978-01-01

    Production of hydroxyl containing curable liquid hydrocarbon prepolymers by ozonizing a high molecular weight saturated hydrocarbon polymer such as polyisobutylene or ethylene propylene rubber is discussed. The ozonized material is reduced using reducing agents, preferably diisobutyl aluminum hydride, to form the hydroxyl containing liquid prepolymers having a substantially lower molecular weight than the parent polymer. The resulting curable liquid hydroxyl containing prepolymers can be poured into a mold and readily cured, with reactants such as toluene diisocyanate, to produce highly stable elastomers having a variety of uses such as binders for solid propellants.

  1. The solar abundance of thulium

    NASA Technical Reports Server (NTRS)

    Ross, J. E.; Aller, L. H.

    1974-01-01

    Consideration of one relatively unblended line of the solar spectrum, namely, the 3131.258-A line of Tm II, which yields a thulium abundance of 0.80 plus or minus 0.10 with the Corliss and Bozman (1962) f-value. The uncertainty of this figure is discussed in conjunction with the contradictory findings of some other investigators. The need for further detailed study of the lanthanides by the method of spectrum synthesis is pointed out.

  2. Endogenous 3, 4- Dihydroxyphenylalanine and Dopaquinone Modifications on Protein Tyrosine: links to mitochondrially derived oxidative stress via hydroxyl radical

    SciTech Connect

    Zhang, Xu; Monroe, Matthew E.; Chen, Baowei; Chin, Mark H.; Heibeck, Tyler H.; Schepmoes, Athena A.; Yang, Feng; Petritis, Brianne O.; Camp, David G.; Pounds, Joel G.; Jacobs, Jon M.; Smith, Desmond J.; Bigelow, Diana J.; Smith, Richard D.; Qian, Weijun

    2010-06-02

    Oxidative modifications of protein tyrosines have been implicated in multiple human diseases. Among these modifications, elevations in levels of 3, 4-dihydroxyphenylalanine (DOPA), a major product of hydroxyl radical addition to tyrosine, has been observed in a number of pathologies. Here we report the first global proteome survey of endogenous site-specific modifications, i.e, DOPA and its further oxidation product dopaquinone (DQ) in mouse brain and heart tissues. Results from LC-MS/MS analyses included 203 and 71 DOPA-modified tyrosine sites identified from brain and heart, respectively, with a false discovery rate of ~1%; while only a few nitrotyrosine containing peptides, a more commonly studied marker of oxidative stress, were detectable, suggesting the much higher abundance for DOPA modification as compared with tyrosine nitration. Moreover, 57 and 29 DQ modified peptides were observed from brain and heart, respectively; nearly half of these peptides were also observed with DOPA modification on the same sites. For both tissues, these modifications are preferentially found in mitochondrial proteins with metal-binding properties, consistent with metal catalyzed hydroxyl radical formation from mitochondrial superoxide and hydrogen peroxide. These modifications also link to a number of mitochondria-associated and other signaling pathways. Furthermore, many of the modification sites were common sites of previously reported tyrosine phosphorylation suggesting potential disruption of signaling pathways. Structural aspects of DOPA-modified tyrosine sequences are distinct from those of nitrotyrosines suggesting that each type of modifications provides a marker for different in vivo reactive chemistries and can be used to predict sensitive protein targets. Collectively, the results suggest that these modifications are linked with mitochondrially-derived oxidative stress, and may serve as sensitive markers for disease pathologies.

  3. Kinetic studies of the hydroxyl radical reaction with PAHs

    NASA Astrophysics Data System (ADS)

    Ananthula, Rajeshwar

    An existing quartz optical reactor heating system was designed to permit higher temperature kinetic measurements more closely associated with post-combuston conditions (up to 1200 K). A pulsed laser photolysis/pulsed laser-induced fluorescence (PLP/PLIF) technique was then applied with this modified reactor to study the OH radical kinetics with polycyclic aromatic hydrocarbons (PAHs). The kinetics of the reaction of a surrogate three-ring PAH, anthracene (and its deuterated form) with hydroxyl (OH) radicals was investigated over the temperature range of 373 to 1200 K. This study represents the first examination of the OH kinetics for this class of reactions at elevated temperatures (>470 K). The results indicate a complex temperature dependence similar to that observed for simpler aromatic compounds, e.g., benzene. At low temperatures (373-498 K), the rate measurements exhibited Arrhenius behavior (1.82 x 10-11 exp(542.35/T) in units of cm3 molecule -1 s-1) and kinetic isotope effect (KIE) measurements were consistent with an OH addition mechanism. The low temperature results are extrapolated to atmospheric temperatures and compared with previous measurements. Rate measurements between 673 and 923 K exhibited a sharp decrease in the magnitude of the rate coefficients (a factor of 9). KIE measurements under these conditions were still consistent with an OH addition mechanism. The following modified Arrhenius equation is the best fit to our anthracene measurements between 373 and 923 K, 8.17 x 1014 T-8.3 exp(-3171.71/T) (in units of cm3 molecule-1 s-1). For a limited temperature range between 1000 and 1200 K, the rate measurements exhibited an apparent positive temperature dependence with the following Arrhenius equation the best fit to the data, 2.18 x 10-11*exp(-1734.11/T) (in units of cm3molecule-1s -1). KIE measurements above 999 K were slightly larger than unity, but inclusive regarding the mechanism of the reaction. Theoretical calculations of the KIE indicate

  4. Unexpectedly high indoor hydroxyl radical concentrations associated with nitrous acid.

    PubMed

    Gómez Alvarez, Elena; Amedro, Damien; Afif, Charbel; Gligorovski, Sasho; Schoemaecker, Coralie; Schoemacker, Coralie; Fittschen, Christa; Doussin, Jean-Francois; Wortham, Henri

    2013-08-13

    The hydroxyl (OH) radical is the most important oxidant in the atmosphere since it controls its self-oxidizing capacity. The main sources of OH radicals are the photolysis of ozone and the photolysis of nitrous acid (HONO). Due to the attenuation of solar radiation in the indoor environment, the possibility of OH formation through photolytic pathways indoors has been ignored up to now. In the indoor air, the ozonolysis of alkenes has been suggested as an alternative route of OH formation. Models and indirect measurements performed up to now according to this hypothesis suggest concentrations of OH radicals on the order of 10(4)-10(5) molecules per cubic centimeter. Here, we present direct measurements of significant amounts of OH radicals of up to 1.8⋅10(6) molecules per cubic centimeter during an experimental campaign carried out in a school classroom in Marseille. This concentration is on the same order of magnitude of outdoor OH levels in the urban scenario. We also show that photolysis of HONO is an important source of OH radicals indoors under certain conditions (i.e., direct solar irradiation inside the room). Additionally, the OH concentrations were found to follow a linear dependence with the product J(HONO)⋅[HONO]. This was also supported by using a simple quasiphotostationary state model on the OH radical budget. These findings force a change in our understanding of indoor air quality because the reactivity linked to OH would involve formation of secondary species through chemical reactions that are potentially more hazardous than the primary pollutants in the indoor air. PMID:23898188

  5. Hydroxyl layer: Mean state and trends at midlatitudes

    NASA Astrophysics Data System (ADS)

    Grygalashvyly, M.; Sonnemann, G. R.; Lübken, F.-J.; Hartogh, P.; Berger, U.

    2014-11-01

    Based on an advanced model of excited hydroxyl relaxation we calculate trends of number densities and altitudes of the OH*-layer during the period 1961-2009. The OH*-model takes into account all major chemical processes such as the production by H + O3, deactivation by O, O2, and N2, spontaneous emission, and removal by chemical reactions. The OH*-model is coupled with a chemistry-transport model (CTM). The dynamical part (Leibniz Institute Model of the Atmosphere, LIMA) adapts ECMWF/ERA-40 data in the troposphere-stratosphere. The change of greenhouse gases (GHGs) such as CH4, CO2, O3, and N2O is parameterized in LIMA/CTM. The downward shift of the OH*-layer in geometrical altitudes occurs entirely due to shrinking (mainly in the mesosphere) as a result of cooling by increasing CO2 concentrations. In order to identify the direct chemical effect of GHG changes on OH*-trends under variable solar cycle conditions, we consider three cases: (a) variable GHG and Lyman-α fluxes, (b) variable GHG and constant Lyman-α fluxes, and (c) constant GHG and Lyman-α. At midlatitudes, shrinking of the middle atmosphere descends the OH*-layer by ~ -300 m/decade in all seasons. The direct chemical impact of GHG emission lifts up the OH*-layer by ~15-25 m/decade depending on season. Trends of the thermal and dynamical state within the layer lead to a trend of OH* height by ~ ±100 m/decade, depending on latitude and season. Trends in layer altitudes lead to differences between temperature trends within the layer, at constant pressure, and at constant altitude, respectively, of typically 0.5 to 1 K/decade.

  6. Development of Hydroxyl Tagging Velocimetry for Low Velocity Flows

    NASA Technical Reports Server (NTRS)

    Andre, Matthieu A.; Bardet, Philippe M.; Burns, Ross A.; Danehy, Paul M.

    2016-01-01

    Hydroxyl tagging velocimetry (HTV) is a molecular tagging technique that relies on the photo-dissociation of water vapor into OH radicals and their subsequent tracking using laser induced fluorescence. Velocities are then obtained from time-of-flight calculations. At ambient temperature in air, the OH species lifetime is relatively short (<50 µs), making it suited for high speed flows. Lifetime and radicals formation increases with temperature, which allows HTV to also probe low-velocity, high-temperature flows or reacting flows such as flames. The present work aims at extending the domain of applicability of HTV, particularly towards low-speed (<10 m/s) and moderate (<500 K) temperature flows. Results are compared to particle image velocimetry (PIV) measurements recorded in identical conditions. Single shot and averaged velocity profiles are obtained in an air jet at room temperature. By modestly raising the temperature (100-200 degC) the OH production increases, resulting in an improvement of the signal-to-noise ratio (SNR). Use of nitrogen - a non-reactive gas with minimal collisional quenching - extends the OH species lifetime (to over 500 µs), which allows probing of slower flows or, alternately, increases the measurement precision at the expense of spatial resolution. Instantaneous velocity profiles are resolved in a 100degC nitrogen jet (maximum jet-center velocity of 6.5 m/s) with an uncertainty down to 0.10 m/s (1.5%) at 68% confidence level. MTV measurements are compared with particle image velocimetry and show agreement within 2%.

  7. Unexpectedly high indoor hydroxyl radical concentrations associated with nitrous acid

    PubMed Central

    Gómez Alvarez, Elena; Amedro, Damien; Afif, Charbel; Gligorovski, Sasho; Schoemaecker, Coralie; Fittschen, Christa; Doussin, Jean-Francois; Wortham, Henri

    2013-01-01

    The hydroxyl (OH) radical is the most important oxidant in the atmosphere since it controls its self-oxidizing capacity. The main sources of OH radicals are the photolysis of ozone and the photolysis of nitrous acid (HONO). Due to the attenuation of solar radiation in the indoor environment, the possibility of OH formation through photolytic pathways indoors has been ignored up to now. In the indoor air, the ozonolysis of alkenes has been suggested as an alternative route of OH formation. Models and indirect measurements performed up to now according to this hypothesis suggest concentrations of OH radicals on the order of 104–105 molecules per cubic centimeter. Here, we present direct measurements of significant amounts of OH radicals of up to 1.8⋅106 molecules per cubic centimeter during an experimental campaign carried out in a school classroom in Marseille. This concentration is on the same order of magnitude of outdoor OH levels in the urban scenario. We also show that photolysis of HONO is an important source of OH radicals indoors under certain conditions (i.e., direct solar irradiation inside the room). Additionally, the OH concentrations were found to follow a linear dependence with the product J(HONO)⋅[HONO]. This was also supported by using a simple quasiphotostationary state model on the OH radical budget. These findings force a change in our understanding of indoor air quality because the reactivity linked to OH would involve formation of secondary species through chemical reactions that are potentially more hazardous than the primary pollutants in the indoor air. PMID:23898188

  8. Ocular biocompatibility evaluation of hydroxyl-functionalized graphene.

    PubMed

    Lin, Mimi; Zou, Ruitao; Shi, Haiyan; Yu, Shanshan; Li, Xiaojian; Guo, Rui; Yan, Lu; Li, Guoxing; Liu, Yong; Dai, Liming

    2015-05-01

    We have presented our recent efforts on genotoxicity and intraocular biocompatibility of hydroxylated graphene (G-OH) prepared by ball milling. We have previously demonstrated that the as-synthesized G-OH could be considered as an excellent alternative for graphene oxide which had been applied widely. Following our last report on G-OH, we carried out detailed studies on genotoxicity and in vivo biocompatibility of G-OH in this work. Less than 5% enhanced caspase-3 level was observed for cells exposed to more than 50 μg/mL G-OH over 72 h, suggesting G-OH caused cell apoptosis was slight. The G-OH induced DNA damage was also found to be mild since expression of p53 and ROS regeneration level was quite low even at high concentration of G-OH over a long time. Cell viability was found to be higher than 90% with 50 μg/mL G-OH and 80% with 100 μg/mL G-OH using flow cytometry. Comet results suggested that less than 5% tail could be found with 100 μg/mL G-OH. TEM results confirmed that G-OH could penetrate into and out of the cytoplasm by means of endocytosis and exocytosis without causing damage on cell membranes. In vivo biocompatibility of G-OH was studied by intravitreal injection of G-OH into rabbits. The ocular fundus photography results showed that G-OH could be diffused in the vitreous body gradually without any damage caused. Injection of G-OH had caused few damages on eyesight related functions such as intraocular pressure, electroretinogram and histological structures of the retina. PMID:25746274

  9. Atmospheric sulfur and hydroxyl radical measurements at Palmer Station

    SciTech Connect

    Berresheim, H.; Eisele, F.L.; Tanner, D.J.

    1994-12-31

    The emission of dimethylsulfide (DMS) by marine algae represents the dominant natural contribution to reactive sulfur in the lower atmosphere. On a global scale, antarctic coastal waters are among the most productive oceanic regions and show extremely high DMS emission rates during austral summer. Following its release into the atmosphere, DMS is rapidly oxidized by the hydroxyl radical (OH), which itself is produced via photolysis of ozone and subsequent reaction of excited singlet oxygen [O({sup 1}D)] with water vapor. The most important stable products of the DMS+OH reaction are believed to be sulfur dioxide (SO{sub 2}), sulfuric acid (H{sub 2}SO{sub 4}), methanesulfonic acid (MSA), dimethylsulfoxide (DMSO), and dimethylsulfone (DMSO{sub 2}). Under atmospheric conditions, both H{sub 2}SO{sub 4} and MSA, due to their low vapor pressures, rapidly condense onto existing aerosol particles, thus contributing to the growth of these particles and their potential activation as cloud condensation nuclei. In addition, gas phase H{sub 2}SO{sub 4} (and, to a lesser extent, MSA) may also be responsible for new particle production via the poorly understood gas-to-particle conversion process. This potential for new particle formation is maximized (and can be most easily studied) in remote regions such as Antarctica where background levels of existing particles and rates of H{sub 2}SO{sub 4} loss onto particles are very low. In January and Bebruary 1994, project SCATE (Sulfur chemistry in the antarctic trophosphere experiment) was conducted at Palmer Station with the goal of obtaining a comprehensive database for modeling atmopsheric sulfur chemistry in high latitudes. 12 refs., 3 figs., 1 tab.

  10. The Abundance of Interstellar Fluorine

    NASA Technical Reports Server (NTRS)

    Lauroesch, James T.

    2005-01-01

    The primary objective of this program was to obtain FUSE observations of the interstellar absorption lines of F I at 951 and 954 Angstroms to derive the abundance of fluorine toward the star HD 164816. The nucleosynthetic source(s) of fluorine are still a matter of debate - the present day abundance of fluorine can potentially constrain models for pulsationally driven dredge-up in asymptotic giant branch stars. An accurate measure for the depletion behavior of fluorine will determine whether it may be detectable in QSO absorption line systems - an unambiguous detection of fluorine at suitably high redshifts would provide the best evidence to date for the neutrino process in massive stars. Furthermore, due to its extreme reactivity, measurement of the gas-phase interstellar fluorine abundance is important for models of grain chemistry. Despite the importance of measuring the interstellar fluorine abundance, at the time of our proposal only one previous detection has been made due to the low relative abundance of fluorine, the lack of lines outside the far-UV, and the blending of the available F I transitions with lines of Hz. The star HD 164816 is associated with the Lagoon nebula (M8), and at a distance of approximately 1.5 kpc probes both distant and local gas. Beginning April 8th, 2004 FUSE FP-Split observations of the star HD 164816 were obtained for this program. This data became available in the FUSE data archive May 21, 2004, and these observations were then downloaded and we began our analysis. Our analysis procedure has involved (1) fitting stellar models to the FUSE spectra, (2) using the multiple lines of Hz and N I at other wavelengths in the FUSE bandpass to derive column densities for the lines of H2 and N I which are blended with the F I features at 951 and 954 angstroms (3) the measurement of the column densities of F I and the species O I and C1 I which are important species for the dis-entangling of dust and nucleosynthetic effects. As discussed in

  11. Carbon and nitrogen abundance variations in globular cluster red giants

    NASA Astrophysics Data System (ADS)

    Martell, Sarah L.

    2008-06-01

    This dissertation describes investigations into two of the persistent questions of elemental abundances in Galactic globular clusters: the phenomenon of deep mixing, observed through the progressive depletion of surface carbon abundance as stars evolve along the red giant branch, and abundance bimodality, a phenomenon observed only in globular clusters, in which a subset of stars in a given globular cluster have a distinctive pattern of elemental enhancements and depletions relative to the Solar pattern. The first chapter gives an introduction to the history of globular cluster abundance studies, with particular focus on low-resolution spectroscopy. For both deep mixing and abundance bimodality, the leading theoretical models and the data which support and challenge them are laid out. Each section ends with a description of presently-unanswered questions; these are the motivation for the various projects contained in this dissertation. The second chapter describes the use of molecular handstrengths for determining elemental abundances from low-resolution spectra, and introduces a new CH bandstrength index that is designed to be sensitive to carbon abundance and insensitive to nitrogen abundance in Pop. II red giants over a wide range of metallicity. Various CH indices defined elsewhere in the literature are also discussed, and are shown to have comparable accuracy to the new index only over a limited range of stellar properties. Carbon abundances determined using the new CH index are compared to literature abundances for a few stars, and general concordance with published abundances is found. The third chapter contains a large-scale application of the new CH index: a survey of present-day carbon abundances and calculated carbon depletion rates in bright red giants belonging to eleven Galactic globular clusters spanning the full metallicity range of halo globular clusters. Targets were selected with similar evolutionary states, were observed with one instrument on

  12. A combined FTIR and TPD study on the bulk and surface dehydroxylation and decarbonation of synthetic goethite

    NASA Astrophysics Data System (ADS)

    Boily, Jean-François; Szanyi, János; Felmy, Andrew R.

    2006-07-01

    The thermal dehydroxylation of a goethite-carbonate solid solution was studied with combined Fourier-transform infrared (FTIR)-Temperature programmed desorption (TPD) experiments. The TPD data revealed dehydroxylation peaks involving the intrinsic dehydroxylation of goethite at 560 K and a low temperature peak at 485 K which was shown to be associated to the release of non-stoichiometric water from the goethite bulk and surface. The FTIR and the TPD data of goethite in the absence of adsorbed carbonate species revealed the presence of adventitious carbonate mostly sequestered in the goethite bulk. The release of carbonate was however not only related to the dehydration of goethite but also from the crystallization of hematite at temperatures exceeding 600 K. The relative abundance of surface hydroxyls was shown to change systematically upon goethite dehydroxylation with a preferential stripping of singly-coordinated sbnd OH sites followed by a dramatic change in the dominance of the different surface hydroxyls upon the formation of hematite.

  13. On the role of hydroxyl radicals in the self-cleansing capacity of the troposphere

    NASA Astrophysics Data System (ADS)

    Lelieveld, J.; Dentener, F. J.; Peters, W.; Krol, M. C.

    2004-11-01

    Thousands of megatons natural and anthropogenic gases are released and subsequently removed from the troposphere each year. Photochemical reactions, initiated by hydroxyl (OH) radicals, oxidise most gases to products which are more easily removed by precipitation and dry deposition at the earth's surface. Since human-induced pollution emissions strongly affect OH formation and loss, large global changes in OH concentrations are possible. Global models and observations of trace gas distributions from global networks have been used to study geographical and temporal changes in tropospheric OH. Here we present a synopsis of recent studies, indicating that global mean OH has changed remarkably little in the past century, even though regional changes have probably been substantial. Globally, depletion of OH by reactive carbon gases has been compensated by increased OH formation by nitrogen oxides, an act of "inadvertent geo-engineering". However, OH analyses for the past 1-2 decades, partly based on methyl chloroform measurements, are inconclusive. Some work, assuming that methyl chloroform emissions have largely ceased, suggests a very strong downward global OH trend in the 1990s, inconsistent with modelling studies. The discrepancy could be much reduced by assuming continued small emissions of methyl chloroform. We recommend the continuation of high precision monitoring of this compound and improved analyses based on detailed meteorological-chemical models.

  14. Effects of the Hydroxyl Group on Phenyl Based Ligand/ERRγ Protein Binding

    PubMed Central

    2015-01-01

    Bisphenol-A (4,4′-dihydroxy-2,2-diphenylpropane, BPA, or BPA-A) and its derivatives, when exposed to humans, may affect functions of multiple organs by specific binding to the human estrogen-related receptor γ (ERRγ). We carried out atomistic molecular dynamics (MD) simulations of three ligand compounds including BPA-A, 4-α-cumylphenol (BPA-C), and 2,2-diphenylpropane (BPA-D) binding to the ligand binding domain (LBD) of a human ERRγ to study the structures and energies associated with the binding. We used the implicit Molecular Mechanics/Poisson–Boltzmann Surface Area (MM/PBSA) method to estimate the free energies of binding for the phenyl based compound/ERRγ systems. The addition of hydroxyl groups to the aromatic ring had only a minor effect on binding structures and a significant effect on ligand/protein binding energy in an aqueous solution. Free binding energies of BPA-D to the ERRγ were found to be considerably less than those of BPA-A and BPA-C to the ERRγ. These results are well correlated with those from experiments where no binding affinities were determined in the BPA-D/ERRγ complex. No conformational change was observed for the helix 12 (H-12) of ERRγ upon binding of these compounds preserving an active transcriptional conformation state. PMID:25098505

  15. The effect of hydroxylated fatty acid-containing phospholipids in the remodeling of lipid membranes.

    PubMed

    Piotto, Stefano; Trapani, Alfonso; Bianchino, Erminia; Ibarguren, Maitane; López, David J; Busquets, Xavier; Concilio, Simona

    2014-06-01

    The synthetic fatty acid 2-hydroxyoleic acid (2OHOA) is an antitumor drug that regulates membrane lipid composition and structure. An important effect of this drug is the restoration of sphingomyelin (SM) levels in cancer cell membranes, where the SM concentration is lower than in non-tumor cells. It is well known that free fatty acid concentration in cell membranes is lower than 5%, and that fatty acid excess is rapidly incorporated into phospholipids. In a recent work, we have considered the effect of free 2OHOA in model membranes in liquid ordered (Lo) and liquid disordered (Ld) phases, by using all-atom molecular dynamics. This study concerns membranes that are modified upon incorporation of 2OHOA into different phospholipids. 2OHOA-containing phospholipids have a permanent effect on lipid membranes, making a Ld membrane surface more compact and less hydrated, whereas the opposite effect is observed in Lo domains. Moreover, the hydroxyl group of fatty acid chains increases the propensity of Ld model membranes to form hexagonal or other non-lamellar structures. This article is part of a Special Issue entitled: Membrane Structure and Function: Relevance in the Cell's Physiology, Pathology and Therapy. PMID:24463068

  16. Hydroxyl PAMAM dendrimer-based gene vectors for transgene delivery to human retinal pigment epithelial cells†

    PubMed Central

    Mastorakos, Panagiotis; Kambhampati, Siva P.; Mishra, Manoj K.; Wu, Tony; Song, Eric; Hanes, Justin

    2016-01-01

    Ocular gene therapy holds promise for the treatment of numerous blinding disorders. Despite the significant progress in the field of viral and non-viral gene delivery to the eye, significant obstacles remain in the way of achieving high-level transgene expression without adverse effects. The retinal pigment epithelium (RPE) is involved in the pathogenesis of retinal diseases and is a key target for a number of gene-based therapeutics. In this study, we addressed the inherent drawbacks of non-viral gene vectors and combined different approaches to design an efficient and safe dendrimer-based gene-delivery platform for delivery to human RPE cells. We used hydroxyl-terminated polyamidoamine (PAMAM) dendrimers functionalized with various amounts of amine groups to achieve effective plasmid compaction. We further used triamcinolone acetonide (TA) as a nuclear localization enhancer for the dendrimer-gene complex and achieved significant improvement in cell uptake and transfection of hard-to-transfect human RPE cells. To improve colloidal stability, we further shielded the gene vector surface through incorporation of PEGylated dendrimer along with dendrimer-TA for DNA complexation. The resultant complexes showed improved stability while minimally affecting transgene delivery, thus improving the translational relevance of this platform. PMID:25213606

  17. Influence of hydroxylation on fabrication of PVC/CaSO4 composite

    NASA Astrophysics Data System (ADS)

    Chen, H. Y.; Wang, J.; Ma, P. Y.; Liang, J.; Xiang, L.

    2015-12-01

    The influences of hydroxylation on grafting of aminopropyltrimethoxysilane ((CH3O)3sbnd Sisbnd CH2sbnd CH2sbnd CH2sbnd NH2, abbreviated as APS) and fabrication of CaSO4/PVC composite were investigated in this paper. The experimental results indicated that the pre-treatment of CaSO4 particles by NaOH promoted the formation of OH-, which enhanced the grafting of APS on CaSO4 surface and improved the interfacial adhesion between CaSO4 and PVC matrix. Compared with the use of CaSO4 with sole APS modification, the use of the CaSO4 with NaOH and APS modification led to the increase of the impact strength of the CaSO4/PVC composite from 36.5 kJ m-2 to 50.2 kJ m-2 and the flexural strength from 48.7 MPa to 62.1 MPa.

  18. Monolayer Nickel Cobalt Hydroxyl Carbonate for High Performance All-Solid-State Asymmetric Supercapacitors.

    PubMed

    Zhao, Yufeng; Ma, Hongnan; Huang, Shifei; Zhang, Xuejiao; Xia, Meirong; Tang, Yongfu; Ma, Zi-Feng

    2016-09-01

    The emergence of atomically thick nanolayer materials, which feature a short ion diffusion channel and provide more exposed atoms in the electrochemical reactions, offers a promising occasion to optimize the performance of supercapacitors on the atomic level. In this work, a novel monolayer Ni-Co hydroxyl carbonate with an average thickness of 1.07 nm is synthesized via an ordinary one-pot hydrothermal route for the first time. This unique monolayer structure can efficiently rise up the exposed electroactive sites and facilitate the surface dependent electrochemical reaction processes, and thus results in outstanding specific capacitance of 2266 F g(-1). Based on this material, an all-solid-state asymmetric supercapacitor is developed adopting alkaline PVA (poly(vinyl alcohol)) gel (PVA/KOH) as electrolyte, which performs remarkable cycling stability (no capacitance fade after 19 000 cycles) together with promising energy density of 50 Wh kg(-1) (202 μWh cm(-2)) and high power density of 8.69 kW kg(-1) (35.1 mW cm(-2)). This as-assembled all-solid-state asymmetric supercapacitor (AASC) holds great potential in the field of portable energy storage devices. PMID:27525445

  19. Characterizing Water and Hydroxyl on Airless Bodies from Vacuum UV and IR Measurements

    NASA Astrophysics Data System (ADS)

    Hibbitts, Charles A.

    2015-11-01

    Water exists in the surfaces of airless bodies as ice and potentially as adsorbed species [1], either as molecular water or dissociated into hydroxyl when bulk water (ice) is not stable [2]. All physical states of water have a strong spectral signatures in the infrared from 2.7 to 3-um because of a fundamental OH-cation or H-O-H stretch vibration. But the IR is not always definitive of physical state. Although a band at 3.07 um is associated with water ice, an almost identical band exists in some hydrated minerals. Brucite, an alteration product of olivine, possesses this band [6] as does goethite, another alteration mineral of basalts [7]. In fact, the 3.05-um band on Ceres, which was initially attributed to water ice, has more recently been attributed to brucite [6]. Spectral observations in the UV can potentially resolve this degeneracy. In the UV, water ice possesses a very strong band near 180 nm [8], but adsorbed molecular water does not induce a band. Because of this, a combination of UV measurements at wavelengths from ~ 150 nm to ~200 nm and IR measurements near 3 um can discriminate ice from adsorbed water. The UV region, however, is also sensitive to silicate composition, with iron bearing minerals having a strong OMCT absorption feature near 300 nm and again shortward of 200 nm, that can potentially be a source of confusion between the identification of iron-poor minerals and water ice. In conclusion, the IR can sense all three forms of water (ice, adsorbed molecular water, and hydroxyl) and the UV, being sensitive to ice, may potentially be used either alone or with the IR to identify water ice separately from other phases of hydration.References: [1] Hibbitts et al., Icarus, 213, 64-72, 2011. [2] Schorghofer, N and G.J. Taylor, JGR, 112, E02010,doi:10.1029, 2007; [3] Poston et al., JGR, 118, 105-115, 2013; [4] Dyar et al., Icarus, 208,425-437, 2010; [5] Zeller et al., JGR, 71, 4855-4860, 1966;[6] Milliken, R.E. and A.S. Rivkin, Nature Geosci, DOI: 10

  20. Recombination Line versus Forbidden Line Abundances in Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    Robertson-Tessi, Mark; Garnett, Donald R.

    2005-04-01

    Recombination lines (RLs) of C II, N II, and O II in planetary nebulae (PNs) have been found to give abundances that are much larger in some cases than abundances from collisionally excited forbidden lines (CELs). The origins of this abundance discrepancy are highly debated. We present new spectroscopic observations of O II and C II recombination lines for six planetary nebulae. With these data we compare the abundances derived from the optical recombination lines with those determined from collisionally excited lines. Combining our new data with published results on RLs in other PNs, we examine the discrepancy in abundances derived from RLs and CELs. We find that there is a wide range in the measured abundance discrepancy Δ(O+2)=logO+2(RL)-logO+2(CEL), ranging from approximately 0.1 dex (within the 1 σ measurement errors) up to 1.4 dex. This tends to rule out errors in the recombination coefficients as a source of the discrepancy. Most RLs yield similar abundances, with the notable exception of O II multiplet V15, known to arise primarily from dielectronic recombination, which gives abundances averaging 0.6 dex higher than other O II RLs. We compare Δ(O+2) against a variety of physical properties of the PNs to look for clues as to the mechanism responsible for the abundance discrepancy. The strongest correlations are found with the nebula diameter and the Balmer surface brightness; high surface brightness, compact PNs show small values of Δ(O+2), while large low surface brightness PNs show the largest discrepancies. An inverse correlation of Δ(O+2) with nebular density is also seen. A marginal correlation of Δ(O+2) is found with expansion velocity. No correlations are seen with electron temperature, He+2/He+, central star effective temperature and luminosity, stellar mass-loss rate, or nebular morphology. Similar results are found for carbon in comparing C II RL abundances with ultraviolet measurements of C III].

  1. Elemental Abundances of Mercury-Manganese Stars

    NASA Astrophysics Data System (ADS)

    Adelman, Saul J.

    We propose to obtain a carefully planned set of multiple high dispersion exposures of three MercuryManganese stars in both the SWP and LWP cameras. These observations will be coadded to increase the S/N ratio so that accurate elemental abundances can be derived for these examples of HgMn stars, each of which represents some extreme class aspect. This will increase of sample of HgMn stars from four to seven. Of particular interest are the abundances of N and Co in which some HgMn stars have shown remarkable underabundances. Comparison of the UV and optical spectra features due to light elements such as N (and C and 0) provide an observational framework to test NLTE models such as those of Takada (1993). This work has already shed some light on some of earlier findings for normal stars. The ability to accurately determine the surface chemical composition of the late B stars through such studies will lead to better tests for theories purporting to explain the origin of the chemical peculiarities seen in this temperature domain.

  2. Investigation of water and hydroxyl groups associated with coal fly ash by thermal desorption and fourier transform infrared photoacoustic spectroscopies

    SciTech Connect

    Seaverson, L.M.; McClelland, J.F.; Burnet, G.; Anderegg, J.W.; Iles, M.K.

    1985-01-01

    Thermal desorption spectrometry (TDS) and Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) have been used in combination to analyze the water and hydroxyl groups associated with four coal fly ashes. Measurements using the former technique on these ashes resulted in identification of three water desorption regions in the temperature range from 25/sup 0/ to 1100/sup 0/C. The regions consisted of a small desorption peak at 50/sup 0/, a broad band from 180/sup 0/ to 400/sup 0/, and an intense peak from 400/sup 0/ to 590/sup 0/. No additional water desorption was observed up to 1100/sup 0/. A fourth ash gave a similar spectrum except that it lacked the intense last peak. The TDS spectra together with FT-IR/PAS spectra taken on samples exposed to pre- and post-desorption peak temperatures allowed the first TDS peak to be assigned to the desorption of physically adsorbed water, the broad band to desorption of hydrogenbonded surface hydroxyls, and the intense last peak to the decomposition of Ca(OH)/sub 2/.

  3. Imaging Consecutive Steps of O2 Reaction with Hydroxylated TiO₂(110): Identification of HO₂ and Terminal OH Intermediates

    SciTech Connect

    Du, Yingge; Deskins, N. Aaron; Zhang, Zhenrong; Dohnalek, Zdenek; Dupuis, Michel; Lyubinetsky, Igor

    2009-01-15

    We report results of the combined experimental and theoretical investigation of the molecular oxygen reaction with a partially hydroxylated TiO₂(110) surface. The consecutive steps of both primary and secondary site-specific reactions have been tracked with high-resolution scanning tunneling microscopy (STM). For the first time, we have directly imaged stable, adsorbed hydroperoxyl (HO₂) species, which is believed to be a key intermediate in many heterogeneous photochemical processes but generally metastable and “elusive” until now. We also found terminal hydroxyl groups, another critical but never directly observed intermediates. A conclusive evidence that O₂ reacts spontaneously with a single bridging OH group as an initial reaction step is provided. The experimental results are supported by density functional theory (DFT) calculations that have determined species energies and configurations. Reported observations provide a basis for a consistent description of the elementary reaction steps and offer molecular-level insight into the underlying reaction mechanisms. In a broader perspective, the results are expected to have far reaching implications for various catalytic systems involving the interconversion of O₂ and H₂O.

  4. Creation of localized spins in graphene by ring-opening of epoxy derived hydroxyl

    PubMed Central

    Chen, Jie; Zhang, Weili; Sun, Yuanyuan; Zheng, Yongping; Tang, Nujiang; Du, Youwei

    2016-01-01

    Creation of high-density localized spins in the basal plane of graphene sheet by introduction of sp3-type defects is considered to be a potential route for the realization of high-magnetization graphene. Theoretical and experimental studies confirmed that hydroxyl can be an effective sp3-type candidate for inducing robust magnetic moment. However, the artificial generation of hydroxyl groups for creating high-density spins on the basal plane of graphene sheet is very scarce. Here we demonstrate that high-content hydroxyl groups can be generated on the basal plane of graphene oxide (GO) sheet by ring opening of epoxy groups. We show that by introduction of 10.74 at.% hydroxyl groups, the density of localized spins of GO can be significantly increased from 0.4 to 5.17 μB/1000 C. Thus, this study provided an effective method to obtain graphene with high-density localized spins. PMID:27225991

  5. Observation of temperature dependence of the IR hydroxyl absorption bands in silica optical fiber

    NASA Astrophysics Data System (ADS)

    Yu, Li; Bonnell, Elizabeth; Homa, Daniel; Pickrell, Gary; Wang, Anbo; Ohodnicki, P. R.; Woodruff, Steven; Chorpening, Benjamin; Buric, Michael

    2016-07-01

    This study reports on the temperature dependent behavior of silica based optical fibers upon exposure to high temperatures in hydrogen and ambient air. The hydroxyl absorption bands in the wavelength range of 1000-2500 nm of commercially available multimode fibers with pure silica and germanium doped cores were examined in the temperature range of 20-800 °C. Two hydroxyl-related infrared absorption bands were observed: ∼2200 nm assigned to the combination of the vibration mode of Si-OH bending and the fundamental hydroxyl stretching mode, and ∼1390 nm assigned to the first overtone of the hydroxyl stretching. The absorption in the 2200 nm band decreased in intensity, while the 1390 nm absorption band shifted to longer wavelengths with an increase in temperature. The observed phenomena were reversible with temperature and suspected to be due, in part, to the conversion of the OH spectral components into each other and structural relaxation.

  6. Tuning magnetic splitting of zigzag graphene nanoribbons by edge functionalization with hydroxyl groups

    SciTech Connect

    Zhang, Huizhen; Yang, Haifang; Li, Lin; Fu, Huixia; Ma, Wei; Niu, Chunyao; Sun, Jiatao; Meng, Sheng; Gu, Changzhi

    2015-03-21

    The electronic properties and relative stability of zigzag graphene nanoribbons are studied by varying the percentage of hydroxyl radicals for edge saturation using first principle calculations. The passivated structures of zigzag graphene nanoribbon have spin-polarized ground state with antiferromagnetic exchange coupling across the edge and ferromagnetic coupling along the edges. When the edges are specially passivated by hydroxyl, the potentials of spin exchange interaction across the two edges shift accordingly, resulting into a spin-semiconductor. Varying the concentration of hydroxyl groups can alter the maximum magnetization splitting. When the percentage of asymmetrically adsorbed hydroxyl reaches 50%, the magnetization splitting can reach a value as high as 275 meV due to the asymmetrical potential across the nanoribbon edges. These results would favor spintronic device applications based on zigzag graphene nanoribbons.

  7. Atmospheric hydroxyl radical production from electronically excited NO2 and H2O.

    PubMed

    Li, Shuping; Matthews, Jamie; Sinha, Amitabha

    2008-03-21

    Hydroxyl radicals are often called the "detergent" of the atmosphere because they control the atmosphere's capacity to cleanse itself of pollutants. Here, we show that the reaction of electronically excited nitrogen dioxide with water can be an important source of tropospheric hydroxyl radicals. Using measured rate data, along with available solar flux and atmospheric mixing ratios, we demonstrate that the tropospheric hydroxyl contribution from this source can be a substantial fraction (50%) of that from the traditional O(1D) + H2O reaction in the boundary-layer region for high solar zenith angles. Inclusion of this chemistry is expected to affect modeling of urban air quality, where the interactions of sunlight with emitted NOx species, volatile organic compounds, and hydroxyl radicals are central in determining the rate of ozone formation. PMID:18356524

  8. Influence of hydroxyl content on selected properties of 45S5 bioactive glass.

    PubMed

    Hall, Matthew M

    2007-12-01

    Numerous material properties may be influenced by the concentration of chemically dissolved hydroxyl species within a glass. A tube furnace connected to a steam generator was used to create hydroxyl-saturated 45S5 glass under 1 atm of water at 1100 degrees C. Selected properties of as-melted and hydroxyl-saturated samples were compared to assess the sensitivity of 45S5 to excess hydroxylation. The glass transition temperature and the peak crystallization temperature of the treated 45S5 glass were reduced in comparison to the as-melted 45S5 glass. In addition, the treated glass exhibited a broad endothermic signal that may be indicative of enhanced viscous flow. A simple dissolution experiment indicated that the treated 45S5 glass was also less durable than the as-melted 45S5 glass. PMID:17559121

  9. Stratospheric ozone and hydroxyl radical measurements by balloon-borne lidar

    NASA Technical Reports Server (NTRS)

    Heaps, W. S.; Mcgee, T. J.; Hudson, R. D.; Caudill, L. O.

    1982-01-01

    An experiment is reported in which a balloon-borne lidar system was used to measure ozone and the hydroxyl radical in the stratosphere by two lidar techniques. Ozone was measured in the 20-37 km altitude range using differential absorption lidar, and the hydroxyl radical was measured in the 34-37 km range using remote laser-induced fluorescence. Ozone concentrations were determined with a vertical resolution of 0.5 km, and in addition, horizontally resolved ozone measurements with 0.15-km resolution were obtained over a 2-km range. The temporal variation of the hydroxyl radical concentration ranged from 40 parts/trillion shortly after noon to about 5 parts/trillion two hours after sunset. Possible modifications to the system are discussed which can yield an improvement in the sensitivity of between one and two orders of magnitude, thus permitting measurements of the hydroxyl radical in the 20-30-km altitude range.

  10. Creation of localized spins in graphene by ring-opening of epoxy derived hydroxyl

    NASA Astrophysics Data System (ADS)

    Chen, Jie; Zhang, Weili; Sun, Yuanyuan; Zheng, Yongping; Tang, Nujiang; Du, Youwei

    2016-05-01

    Creation of high-density localized spins in the basal plane of graphene sheet by introduction of sp3-type defects is considered to be a potential route for the realization of high-magnetization graphene. Theoretical and experimental studies confirmed that hydroxyl can be an effective sp3-type candidate for inducing robust magnetic moment. However, the artificial generation of hydroxyl groups for creating high-density spins on the basal plane of graphene sheet is very scarce. Here we demonstrate that high-content hydroxyl groups can be generated on the basal plane of graphene oxide (GO) sheet by ring opening of epoxy groups. We show that by introduction of 10.74 at.% hydroxyl groups, the density of localized spins of GO can be significantly increased from 0.4 to 5.17 μB/1000 C. Thus, this study provided an effective method to obtain graphene with high-density localized spins.

  11. Creation of localized spins in graphene by ring-opening of epoxy derived hydroxyl.

    PubMed

    Chen, Jie; Zhang, Weili; Sun, Yuanyuan; Zheng, Yongping; Tang, Nujiang; Du, Youwei

    2016-01-01

    Creation of high-density localized spins in the basal plane of graphene sheet by introduction of sp(3)-type defects is considered to be a potential route for the realization of high-magnetization graphene. Theoretical and experimental studies confirmed that hydroxyl can be an effective sp(3)-type candidate for inducing robust magnetic moment. However, the artificial generation of hydroxyl groups for creating high-density spins on the basal plane of graphene sheet is very scarce. Here we demonstrate that high-content hydroxyl groups can be generated on the basal plane of graphene oxide (GO) sheet by ring opening of epoxy groups. We show that by introduction of 10.74 at.% hydroxyl groups, the density of localized spins of GO can be significantly increased from 0.4 to 5.17 μB/1000 C. Thus, this study provided an effective method to obtain graphene with high-density localized spins. PMID:27225991

  12. Selective Aromatic C–H Hydroxylation Enabled by η6-Coordination to Iridium(III)

    PubMed Central

    D'Amato, Erica M.; Neumann, Constanze N.; Ritter, Tobias

    2016-01-01

    We report an aromatic C–H hydroxylation protocol in which the arene is activated through η6-coordination to an iridium(III) complex. η6-Coordination of the arene increases its electrophilicity and allows for high positional selectivity of hydroxylation at the site of least electron density. Through investigation of intermediate η5-cyclohexadienyl adducts and arene exchange reactions, we evaluate incorporation of arene π-activation into a catalytic cycle for C–H functionalization. PMID:26877574

  13. Mechanisms of hydroxyl radical production from abiotic oxidation of pyrite under acidic conditions

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Yuan, Songhu; Liao, Peng

    2016-01-01

    Hydroxyl radicals (radOH) produced from pyrite oxidation by O2 have been recognized, but mechanisms regarding the production under anoxic and oxic conditions are not well understood. In this study, the mechanisms of radOH production from pyrite oxidation under anoxic and oxic conditions were explored using benzoic acid (BA) as an radOH probe. Batch experiments were conducted at pH 2.6 to explore radOH production under anoxic and oxic conditions. The cumulative radOH concentrations produced under anoxic and oxic conditions increased linearly to 7.5 and 52.2 μM, respectively within 10 h at 10 g/L pyrite. Under anoxic conditions, radOH was produced from the oxidation of H2O on the sulfur-deficient sites on pyrite surface, showing an increased production with the increase of pyrite surface exposure due to oxidation. Under oxic conditions, the formation of radOH proceeds predominantly via the two-electron reduction of O2 on pyrite surface along with a minor contribution from the oxidation of H2O on surface sulfur-defects and the reactions of Fe2+/sulfur intermediates with O2. For both O2 reduction and H2O oxidation on the surface sulfur-defects, H2O2 was the predominant intermediate, which subsequently transformed to radOH through Fenton mechanism. The radOH produced had a significant impact on the transformation of contaminants in the environment. Anoxic pyrite suspensions oxidized 13.9% As(III) (C0 = 6.67 μM) and 17.6% sulfanilamide (C0 = 2.91 μM) within 10 h at pH 2.6 and 10 g/L pyrite, while oxic pyrite suspensions improved the oxidation percentages to 55.4% for As(III) and 51.9% for sulfanilamide. The ratios of anoxic to oxic oxidation are consistent with the relative contribution of surface sulfur-defects to radOH production. However, Fe2+ produced from pyrite oxidation competed with the contaminants for radOH, which is of particular significance with the increase of time in a static environment. We conclude that radOH can be produced from abiotic oxidation of

  14. Origin of cosmic chemical abundances

    NASA Astrophysics Data System (ADS)

    Maio, Umberto; Tescari, Edoardo

    2015-11-01

    Cosmological N-body hydrodynamic computations following atomic and molecular chemistry (e-, H, H+, H-, He, He+, He++, D, D+, H2, H_2^+, HD, HeH+), gas cooling, star formation and production of heavy elements (C, N, O, Ne, Mg, Si, S, Ca, Fe, etc.) from stars covering a range of mass and metallicity are used to explore the origin of several chemical abundance patterns and to study both the metal and molecular content during simulated galaxy assembly. The resulting trends show a remarkable similarity to up-to-date observations of the most metal-poor damped Lyman α absorbers at redshift z ≳ 2. These exhibit a transient nature and represent collapsing gaseous structures captured while cooling is becoming effective in lowering the temperature below ˜ 104 K, before they are disrupted by episodes of star formation or tidal effects. Our theoretical results agree with the available data for typical elemental ratios, such as [C/O], [Si/Fe], [O/Fe], [Si/O], [Fe/H], [O/H] at redshifts z ˜ 2-7. Correlations between H I and H2 abundances show temporal and local variations and large spreads as a result of the increasing cosmic star formation activity from z ˜ 6 to 3. The scatter we find in the abundance ratios is compatible with the observational data and is explained by simultaneous enrichment by sources from different stellar phases or belonging to different stellar populations. Simulated synthetic spectra support the existence of metal-poor cold clumps with large optical depth at z ˜ 6 that could be potential Population III sites at low or intermediate redshift. The expected dust content is in line with recent determinations.

  15. Element abundances of classical novae

    NASA Astrophysics Data System (ADS)

    Andrea, J.; Drechsel, H.; Starrfield, S.

    1994-11-01

    Physical conditions and element abundances in the optically thin shells of 11 classical novae with outbursts between 1978 and 1989 were determined from an analysis of UV and optical spectra obtained during the nebular stage. Eight novae were studied on the basis of new optical and UV spectra. The accuracy of the element abundances depends on whether or not simultaneous UV spectra were available to determine individual ionization stage dependent gas temperatures. Generally, slightly higher than solar abundances of helium and pronounced overabundances of the heavier elements were found. QU Vul turned out to be an ONeMg nova, while the other objects belong to the class of CO novae. The nature of V2214 Oph could not be completely clarified. The novae V1668 Cyg (1978), V693 CrA (1981), and V1370 Aql (1982), for which published element abundances exist, were reanalyzed to check the consistency of our spectral analysis approach. Satisfactory agreement of the results was found. Photoionization calculations were carried out for PW Vul using the code of Aldrovandi, Pequignot, and Stasinska. A synthetic spectrum was generated for the parameters derived from the analysis of the UV and optical spectra, which is in very good agreement with the observations. The spectral analysis technique was then applied to the model spectrum and reproduced the model parameters well. Electron temperatures for the C(2+) and C(3+) ions between 7 500 and 12,000 K and for N(4+) betwen 12,000 and 16,000 K were derived. For PW Vul these temperatures remained relatively constant over several months. The decline in density of the ejected shells with time could be investigated for V842 Cen, QV Vul, V977 Sco, and V443 Sct, and was found to deviate from the relation Ne proportional to t-2 for free expansion of a shell in a different way for each object. A possible explanation may be the complex density structure of the shells. This suspicion is supported by high resolution spectra (ESO 3.6m telescope

  16. Abundance measurements in stellar environments

    NASA Astrophysics Data System (ADS)

    Leone, F.

    2014-05-01

    Most of what we know about stars, and systems of stars, is derived from the analysis of their electromagnetic radiation. This lesson is an attempt to describe to Physicists, without any Astrophysical background, the framework to understand the present status of abundance determination in stellar environments and its limit. These notes are dedicated to the recently passed, November 21, 2013, Prof. Dimitri Mihalas who spent his life confuting the 19th century positivist philosopher Auguste Comte who stated that we shall not at all be able to determine the chemical composition of stars.

  17. Abundance measurements in stellar environments

    SciTech Connect

    Leone, F.

    2014-05-09

    Most of what we know about stars, and systems of stars, is derived from the analysis of their electromagnetic radiation. This lesson is an attempt to describe to Physicists, without any Astrophysical background, the framework to understand the present status of abundance determination in stellar environments and its limit. These notes are dedicated to the recently passed, November 21, 2013, Prof. Dimitri Mihalas who spent his life confuting the 19th century positivist philosopher Auguste Comte who stated that we shall not at all be able to determine the chemical composition of stars.

  18. The solar abundance of Oxygen

    NASA Astrophysics Data System (ADS)

    Grevesse, N.

    2009-07-01

    With Martin Asplund (Max Planck Institute of Astrophysics, Garching) and Jacques Sauval (Observatoire Royal de Belgique, Brussels) I recently published detailed reviews on the solar chemical composition ({Asplund et al. 2005}, {Grevesse et al. 2007}). A new one, with Pat Scott (Stockholm University) as additional co-author, will appear in Annual Review of Astronomy and Astrophysics ({Asplund et al. 2009}). Here we briefly analyze recent works on the solar abundance of Oxygen and recommend a value of 8.70 in the usual astronomical scale.

  19. Surface Composition, Work Function, and Electrochemical Characteristics of Gallium-Doped Zinc Oxide

    SciTech Connect

    Ratcliff, E. L.; Sigdel, A. K.; Macech, M. R.; Nebesny, K.; Lee, P. A.; Ginley, D. S.; Armstrong, N. R.; Berry, J. J.

    2012-06-30

    Gallium-doped zinc oxide (GZO) possesses the electric conductivity, thermal stability, and earth abundance to be a promising transparent conductive oxide replacement for indium tin oxide electrodes in a number of molecular electronic devices, including organic solar cells and organic light emitting diodes. The surface chemistry of GZO is complex and dominated by the hydrolysis chemistry of ZnO, which influences the work function via charge transfer and band bending caused by adsorbates. A comprehensive characterization of the surface chemical composition and electrochemical properties of GZO electrodes is presented, using both solution and surface adsorbed redox probe molecules. The GZO surface is characterized using monochromatic X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy after the following pretreatments: (i) hydriodic acid etch, (ii) potassium hydroxide etch, (iii) RF oxygen plasma etching, and (iv) high-vacuum argon-ion sputtering. The O 1s spectra for the GZO electrodes have contributions from the stoichiometric oxide lattice, defects within the lattice, hydroxylated species, and carbonaceous impurities, with relative near-surface compositions varying with pretreatment. Solution etching procedures result in an increase of the work function and ionization potential of the GZO electrode, but yield different near surface Zn:Ga atomic ratios, which significantly influence charge transfer rates for a chemisorbed probe molecule. The near surface chemical composition is shown to be the dominant factor in controlling surface work function and significantly influences the rate of electron transfer to both solution and tethered probe molecules.

  20. 3D QSAR studies of hydroxylated polychlorinated biphenyls as potential xenoestrogens.

    PubMed

    Ruiz, Patricia; Ingale, Kundan; Wheeler, John S; Mumtaz, Moiz

    2016-02-01

    Mono-hydroxylated polychlorinated biphenyls (OH-PCBs) are found in human biological samples and lack of data on their potential estrogenic activity has been a source of concern. We have extended our previous in silico 2D QSAR study through the application of advance techniques such as docking and 3D QSAR to gain insights into their estrogen receptor (ERα) binding. The results support our earlier findings that the hydroxyl group is the most important feature on the compounds; its position, orientation and surroundings in the structure are influential for the binding of OH-PCBs to ERα. This study has also revealed the following additional interactions that influence estrogenicity of these chemicals (a) the aromatic interactions of the biphenyl moieties with the receptor, (b) hydrogen bonding interactions of the p-hydroxyl group with key amino acids ARG394 and GLU353, (c) low or no electronegative substitution at para-positions of the p-hydroxyl group, (d) enhanced electrostatic interactions at the meta position on the B ring, and (e) co-planarity of the hydroxyl group on the A ring. In combination the 2D and 3D QSAR approaches have led us to the support conclusion that the hydroxyl group is the most important feature on the OH-PCB influencing the binding to estrogen receptors, and have enhanced our understanding of the mechanistic details of estrogenicity of this class of chemicals. Such in silico computational methods could serve as useful tools in risk assessment of chemicals. PMID:26598992

  1. Production and contribution of hydroxyl radicals between the DSA anode and water interface.

    PubMed

    Li, Guoting; Zhu, Meiya; Chen, Jing; Li, Yunxia; Zhang, Xiwang

    2011-01-01

    Hydroxyl radicals play the key role during electrochemical oxidation and photoelectrochemical oxidation. The production and effect of hydroxyl radicals on the interface between DSA anode and water was investigated by examining the quenching effect of iso-propanol on Orange II decolorization. We observed that with an increase in electrode potential from 4 to 12 V across electrodes at pH 7.0, the contribution percentage of hydroxyl radicals increased dramatically. More OH radicals were produced in acidic and alkaline conditions than at neutral conditions. At electrode potential of 4 V, the contribution percentage of hydroxyl radicals was obviously higher at near neutral pH conditions, while removal efficiency of Orange II achieved was the lowest concurrently. Finally, for photocatalytic oxidation, electrochemical oxidation, and photoelectrochemical oxidation using the same DSA electrode, the effect of hydroxyl radicals proved to be dominant in photocatalytic oxidation but the contribution of hydroxyl radicals was not dominant in electrochemical oxidation, which implies the necessity of UV irradiation for electrochemical oxidation during water treatment. PMID:21790045

  2. Lysyl 5-Hydroxylation, a Novel Histone Modification, by Jumonji Domain Containing 6 (JMJD6)*

    PubMed Central

    Unoki, Motoko; Masuda, Akiko; Dohmae, Naoshi; Arita, Kyohei; Yoshimatsu, Masanori; Iwai, Yukiko; Fukui, Yoshinori; Ueda, Koji; Hamamoto, Ryuji; Shirakawa, Masahiro; Sasaki, Hiroyuki; Nakamura, Yusuke

    2013-01-01

    JMJD6 is reported to hydroxylate lysyl residues of a splicing factor, U2AF65. In this study, we found that JMJD6 hydroxylates histone lysyl residues. In vitro experiments showed that JMJD6 has a binding affinity to histone proteins and hydroxylates multiple lysyl residues of histone H3 and H4 tails. Using JMJD6 knock-out mouse embryos, we revealed that JMJD6 hydroxylates lysyl residues of histones H2A/H2B and H3/H4 in vivo by amino acid composition analysis. 5-Hydroxylysine was detected at the highest level in histones purified from murine testis, which expressed JMJD6 at a significantly high level among various tissues examined, and JMJD6 overexpression increased the amount of 5-hydroxylysine in histones in human embryonic kidney 293 cells. These results indicate that histones are additional substrates of JMJD6 in vivo. Because 5-hydroxylation of lysyl residues inhibited N-acetylation and N-methylation by an acetyltransferase and a methyltransferase, respectively, in vitro, histone 5-hydroxylation may have important roles in epigenetic regulation of gene transcription or chromosomal rearrangement. PMID:23303181

  3. Elemental Abundances in NGC 3516

    NASA Technical Reports Server (NTRS)

    Turner, T. J.; Kraemer, S. B.; Mushotzky, R. F.; George, I. M.; Gabel, J. R.

    2003-01-01

    We present Reflection Grating Spectrometer data from an XMM-Newton observation of the Seyfert 1 galaxy NGC 3516, taken while the continuum source was in an extremely low flux state. This observation offers a rare opportunity for a detailed study of emission from a Seyfert 1 galaxy as these are usually dominated by high nuclear continuum levels and heavy absorption. The spectrum shows numerous narrow emission lines (FWHM approximately less than 1300 kilometers per second) in the 0.3 - 2 keV range, including the H-like lines of C, N, and O and the He-like lines of N, O and Ne. The emission-line ratios and the narrow width of the radiative recombination continuum of CVI indicate that the gas is photoionized and of fairly low temperature (kT approximately less than 0.01 keV). The availability of emission lines from different elements for two iso-electronic sequences allows us to constrain the element abundances. These data show that the N lines are far stronger than would be expected from gas of solar abundances. Based on our photoionization models we find that nitrogen is overabundant in the central regions of the galaxy, compared to carbon, oxygen and neon by at least a factor of 2.5. We suggest that this is the result of secondary production of nitrogen in intermediate mass stars, and indicative of the history of star formation in NGC 3516.

  4. Reactions of hydroxyl radical with humic substances: bleaching, mineralization, and production of bioavailable carbon substrates.

    PubMed

    Goldstone, J V; Pullin, M J; Bertilsson, S; Voelker, B M

    2002-02-01

    In this study, we examine the role of the hydroxyl (OH*) radical as a mechanism for the photodecomposition of chromophoric dissolved organic matter (CDOM) in sunlit surface waters. Using gamma-radiolysis of water, OH* was generated in solutions of standard humic substances in quantities comparable to those produced on time scales of days in sunlit surface waters. The second-order rate coefficients of OH* reaction with Suwannee River fulvic (SRFA; 2.7 x 10(4) s(-1) (mg of C/L)(-1)) and humic acids (SRHA; 1.9 x 10(4) s(-1) (mg of C/L)(-1)) are comparable to those observed for DOM in natural water samples and DOM isolates from other sources but decrease slightly with increasing OH* doses. OH* reactions with humic substances produced dissolved inorganic carbon (DIC) with a high efficiency of approximately 0.3 mol of CO2/mol of OH*. This efficiency stayed approximately constant from early phases of oxidation until complete mineralization of the DOM. Production rates of low molecular weight (LMW) acids including acetic, formic, malonic, and oxalic acids by reaction of SRFA and SRHA with OH* were measured using HPLC. Ratios of production rates of these acids to rates of DIC production for SRHA and for SRFA were similar to those observed upon photolysis of natural water samples. Bioassays indicated that OH* reactions with humic substances do not result in measurable formation of bioavailable carbon substrates other than the LMW acids. Bleaching of humic chromophores by OH* was relatively slow. Our results indicate that OH* reactions with humic substances are not likely to contribute significantly to observed rates of DOM photomineralization and LMW acid production in sunlit waters. They are also not likely to be a significant mechanism of photobleaching except in waters with very high OH* photoformation rates. PMID:11871550

  5. Chemical abundances of solar-type dwarfs in open clusters

    NASA Astrophysics Data System (ADS)

    Schuler, Simon C.

    Open clusters have proven continuously to be invaluable tools to the studies of stellar physics and Galactic evolution. Until recently, however, the chemical abundances of the populous and astrophysically important late-F, G, and K open cluster dwarfs have gone largely unanalyzed. In this thesis I report on the study of the chemical abundances derived from high-resolution, moderate-to-high signal-to-noise echelle spectra obtained with the 10-m Keck I, 9.2-m Hobby- Eberly, 8.2-m VLT, 4.0-m KPNO, 2.7-m Harlan J. Smith, and the 2.1-m Otto Struve telescopes of cool dwarfs in the Pleiades, Hyades, and M34 open clusters. The main result of the study is the identification of excitation-related abundance trends found among cool open cluster dwarfs ( T eff <= 5500 K), as well as an overionization of Fe- abundances derived from singly ionized lines are greater than those derived from neutral lines- among the cool Hyades dwarfs; the trends are such that abundances derived from high-excitation (h >= 4.0 eV) spectral lines and using atmospheric models assuming local thermodynamic equilibrium (LTE) increase with decreasing T eff . Particular attention is given to the high-excitation (h = 9.15 eV) near-IR ll7774 O I triplet, a line used often in the derivation of stellar O abundances and known to be susceptible to non-LTE (NLTE) effects. The O I triplet-based abundances show a dramatic increase with decreasing T eff in all three clusters, behavior that is in stark contrast to expectations from canonical NLTE calculations. Other elements with lines of various excitation potentials are also analyzed and are found to exhibit abundance trends that are qualitatively similar to those of the O I triplet. Possible explanations for the observed cool open cluster dwarf abundance anomalies are investigated, and photospheric surface temperature inhomogeneities possibly due to spots, faculae, and/or plages are found to be a plausible culprit. Indeed, multi-component LTE model atmospheres are

  6. Inhibition of hydroxyl radical reaction with aromatics by dissolved natural organic matter

    USGS Publications Warehouse

    Lindsey, M.E.; Tarr, M.A.

    2000-01-01

    Reaction of aromatic compounds with hydroxyl radical is inhibited by dissolved natural organic matter (NOM). The degree of inhibition is significantly greater than that expected based on a simple model in which aromatic compound molecules bound to NOM are considered to be unreactive. In this study, hydroxyl radical was produced at steady-state concentrations using Fenton chemistry (H2O2 + Fe2+ ??? Fe3+ + HO- + HO??). Suwannee River fulvic acid and humic acid were used as NOM. The most likely mechanism for the observed inhibition is that hydroxyl radical formation occurs in microenvironmental sites remote from the aromatic compounds. In addition to changes in kinetics, pyrene hydroxyl radical reaction also exhibited a mechanistic change in the presence of fulvic acid. The mechanism changed from a reaction that was apparently firstorder in pyrene to one that was apparently secondorder in pyrene, indicating that pyrene self-reaction may have become the dominant mechanism in the presence of fulvic acid. Dissolved NOM causes significant changes in the rate and mechanism of hydroxyl radical degradation of aromatic compounds. Consequently, literature rate constants measured in pure water will not be useful for predicting the degradation of pollutants in environmental systems. The kinetic and mechanistic information in this study will be useful for developing improved degradation methods involving Fenton chemistry.Reaction of aromatic compounds with hydroxyl radical is inhibited by dissolved natural organic matter (NOM). The degree of inhibition is significantly greater than that expected based on a simple model in which aromatic compounds molecules bounds to NOM are considered to be unreactive. In this study, hydroxyl radical was produced at steady-state concentrations using Fenton chemistry (H2O2 + Fe2+ ??? Fe3+ + HO- + HO??). Suwannee River fulvic acid and humic acid were used as NOM. The most likely mechanisms for the observed inhibition is that hydroxyl radical

  7. The Surface Polarized Graphene Oxide Quantum Dot Films for Flexible Nanogenerators

    PubMed Central

    Liu, Liangbin; Cheng, Yafei; Zhu, Lili; Lee, Shuit-Tong; Liao, Fan; Shao, Mingwang

    2016-01-01

    Abundant disorderly-distributed surface functional groups, such as hydroxyl, carboxyl, ether and amino groups, endow an isolated graphene oxide quantum dot (GOQD) the polar property due to the symmetry breaking, although the aggregated counterparts present no polarization owing to the random orientation. Here, flexible polarized films were fabricated using aggregated GOQDs with the assistance of external electric fields and their polarization was confirmed with the electrostatic force microscopy and polarization-electric field hysteresis loop. Such polarized GOQD films may induce charges under externally applied deformation. Here, we fabricated nanogenerators based on the films, which gave out an average current value of 0.12 μA and an average voltage value of 12 V under a mechanical force of 60 N. This work has proposed a convenient electric-field-assisted method to give the nanomaterials new functions, which can be generalized to other materials and found applications in various fields. PMID:27596991

  8. The Surface Polarized Graphene Oxide Quantum Dot Films for Flexible Nanogenerators.

    PubMed

    Liu, Liangbin; Cheng, Yafei; Zhu, Lili; Lee, Shuit-Tong; Liao, Fan; Shao, Mingwang

    2016-01-01

    Abundant disorderly-distributed surface functional groups, such as hydroxyl, carboxyl, ether and amino groups, endow an isolated graphene oxide quantum dot (GOQD) the polar property due to the symmetry breaking, although the aggregated counterparts present no polarization owing to the random orientation. Here, flexible polarized films were fabricated using aggregated GOQDs with the assistance of external electric fields and their polarization was confirmed with the electrostatic force microscopy and polarization-electric field hysteresis loop. Such polarized GOQD films may induce charges under externally applied deformation. Here, we fabricated nanogenerators based on the films, which gave out an average current value of 0.12 μA and an average voltage value of 12 V under a mechanical force of 60 N. This work has proposed a convenient electric-field-assisted method to give the nanomaterials new functions, which can be generalized to other materials and found applications in various fields. PMID:27596991

  9. Martian surface

    SciTech Connect

    Carr, M.H.

    1987-03-01

    The surface of Mars is characterized on the basis of reformatted Viking remote-sensing data, summarizing results published during the period 1983-1986. Topics examined include impact craters, ridges and faults, volcanic studies (modeling of surface effects on volcanic activity, description and interpretation of volcanic features, and calculations on lava-ice interactions), the role of liquid water on Mars, evidence for abundant ground ice at high latitudes, water-cycle modeling, and the composition and dynamics of Martian dust.

  10. Fabrication and characterization of a novel hydrophobic CaCO3 grafted by hydroxylated poly(vinyl chloride) chains

    NASA Astrophysics Data System (ADS)

    Bao, Lixia; Yang, Simei; Luo, Xin; Lei, Jingxin; Cao, Qiue; Wang, Jiliang

    2015-12-01

    The hydroxylated PVC (PVC-OH) was successfully synthesized by a suspension polymerization of vinyl chloride (VC), butyl acrylate (BA) and hydroxyethyl acrylate (HEA). Novel hydrophobic CaCO3 was then prepared by a urethane formation reaction between methylene diphenyl diisocyanate (MDI) and the sbnd OH groups both in the PVC-OH chains and on the surface of pristine CaCO3 particles. The effect of the PVC-OH content on the grafting ratio of treated CaCO3 particles was extensively investigated. Combining the result of Fourier transform infrared (FTIR) with that of water contact angle, it can be concluded that the hydrophobicity of CaCO3 had been efficiently improved by the PVC-OH segments grafted on the surface of CaCO3 particles. X-ray diffraction (XRD), thermal gravity analysis (TGA), scanning electron microscope (SEM) and transmission electron microscope (TEM) were also used to study crystalline behaviors, thermal stability and surface morphology of the modified CaCO3 particles, respectively. The change of specific surface area implying surface modification was investigated as well.

  11. Estimates of Cl atom concentrations and hydrocarbon kinetic reactivity in surface air at Appledore Island, Maine (USA), during International Consortium for Atmospheric Research on Transport and Transformation/Chemistry of Halogens at the Isles of Shoals

    NASA Astrophysics Data System (ADS)

    Pszenny, Alexander A. P.; Fischer, Emily V.; Russo, Rachel S.; Sive, Barkley C.; Varner, Ruth K.

    2007-05-01

    Average hydroxyl radical (OH) to chlorine atom (Cl·) ratios ranging from 45 to 119 were determined from variability-lifetime relationships for selected nonmethane hydrocarbons (NMHC) in surface air from six different transport sectors arriving at Appledore Island, Maine, during July 2004. Multiplying these ratios by an assumed average OH concentration of 2.5 × 106 cm-3 yielded estimates of Cl· concentrations of 2.2 to 5.6 × 104 cm-3. Summed reaction rates of methane and more than 30 abundant NMHCs with OH and Cl· suggest that Cl· reactions increased the kinetic reactivity of hydrocarbons by 16% to 30% over that due to OH alone in air associated with the various transport sectors. Isoprene and other abundant biogenic alkenes were the most important hydrocarbon contributors after methane to overall kinetic reactivity.

  12. Hydroxyl radical regeneration in isoprene oxidation: upgraded mechanism LIM1

    NASA Astrophysics Data System (ADS)

    Peeters, Jozef; Son Nguyen, Vinh; Nguyen, Thanh Lam; Stravrakou, Trissevgeni; Muller, Jean-Francois

    2013-04-01

    The OH regeneration known to occur in isoprene oxidation at low/moderate NO is attributed in the Leuven Isoprene Mechanism to novel, theoretically characterized chemical pathways (LIM0: Peeters et al. 2009; Peeters and Muller 2010). Its key new features are (i) quasi-equilibration of the thermally labile beta-OH- and delta-OH-isoprenylperoxy isomers; (ii) 1,6-H shift isomerisation of the Z-delta-OH-peroxy isomers to yield hydroperoxy-methyl-butenals (HPALDs); (iii) fast photolysis of the HPALDs resulting overall in several OH radicals per HPALD. The OH-regeneration through photolabile HPALDs has recently found experimental support, but the peroxy isomerisation rate, HPALD yield and extent of OH recycling are still uncertain (Crounse et al. 2011; Wolfe et al. 2012). In this work, the upgraded LIM1 mechanism is presented. Based on much higher levels of theory that fully account for dispersion effects, the crucial equilibrium ratio of the isomerising Z-delta-OH-peroxys over the majority beta-OH-isoprenylperoxys is reduced by a factor ≈5 and the isomerisation rate of the Z-delta-OH-peroxys by a factor ≈1.5 compared to LIM0. The chemistry following the 1,6-H shift of the Z-delta-OH-peroxys is also much expanded and extended. Firstly, LIM1 introduces other pathways beside HPALD formation following the Z-delta-OH-peroxy isomerisation, but resulting likewise in OH recycling. This, together with the revised Z-delta-OH- equilibrium and isomerisation data above, affords a fair model-reproduction of the HPALD and other product yields observed by Crounse et al. (2011). Secondly, LIM1 proposes new fast reactions of HO2 with the alpha-oxoketene products from the peroxy isomerisation routes; these reactions are shown to efficiently convert HO2 into OH and are prime candidates for the unknown X + HO2 → OH + ... hydroxyl-recycling routes invoked in recent studies (Hofzumahaus et al.2009; Whalley et al. 2011). Modeling results using the IMAGES global CTM will be presented on

  13. Abundance patterns in planetary nebulae

    NASA Astrophysics Data System (ADS)

    Henry, Richard B. C.

    1990-06-01

    Abundances of He, N, O, and Ne have been uniformly calculated for 192 planetary nebulas residing in the Galactic disk and halo, the LMC, the SMC, and M31. Direct correlations appear to exist for type I as well as non-type I objects for the following pairs of parameters: N/O-He/H, N/O-N/H, and Ne/H-O/H. Separately, type I planetaries show a weak anticorrelation between N/O and O/H, while non-type I's exhibit direct correlations between N/H and O/H and between N/O and O/H. From these patterns, it is inferred that non-type I's synthesize N via the CN cycle. Type I planetaries, on the other hand, manufacture N at least partially via the ON cycle, destroying O in the process. Neither type appears to synthesize O or Ne.

  14. A model study of atmospheric temperatures and the concentrations of ozone, hydroxyl, and some other photochemically active gases during the glacial, the pre-industrial holocene and the present

    SciTech Connect

    Crutzen, P.J.; Bruehl, C. )

    1993-06-07

    This paper presents a one and one half D calculation of the atmospheric content of CO[sub 2], CH[sub 4], and N[sub 2]O, along with temperature changes, from the glacial, pre-industrial holocene, to the industrial era. The question is what the changes in these gases have done to the atmospheric abundance of ozone and hydroxyl radical. There have been large increases in the first three gases over this time span, and yet the column abundance of ozone has remained relatively constant. Todays heterogeneous reactions with halogen compounds are decreasing ozone abundance, particularly in certain seasons and regions. The atmospheric loss rates of CH[sub 4] have varied considerably over this period.

  15. Pseudomonas and neutrophil products modify transferrin and lactoferrin to create conditions that favor hydroxyl radical formation.

    PubMed Central

    Britigan, B E; Edeker, B L

    1991-01-01

    In vivo most extracellular iron is bound to transferrin or lactoferrin in such a way as to be unable to catalyze the formation of hydroxyl radical from superoxide (.O2-) and hydrogen peroxide (H2O2). At sites of Pseudomonas aeruginosa infection bacterial and neutrophil products could possibly modify transferrin and/or lactoferrin forming catalytic iron complexes. To examine this possibility, diferrictransferrin and diferriclactoferrin which had been incubated with pseudomonas elastase, pseudomonas alkaline protease, human neutrophil elastase, trypsin, or the myeloperoxidase product HOCl were added to a hypoxanthine/xanthine oxidase .O2-/H2O2 generating system. Hydroxyl radical formation was only detected with pseudomonas elastase treated diferrictransferrin and, to a much lesser extent, diferriclactoferrin. This effect was enhanced by the combination of pseudomonas elastase with other proteases, most prominently neutrophil elastase. Addition of pseudomonas elastase-treated diferrictransferrin to stimulated neutrophils also resulted in hydroxyl radical generation. Incubation of pseudomonas elastase with transferrin which had been selectively iron loaded at either the NH2- or COOH-terminal binding site yielded iron chelates with similar efficacy for hydroxyl radical catalysis. Pseudomonas elastase and HOCl treatment also decreased the ability of apotransferrin to inhibit hydroxyl radical formation by a Fe-NTA supplemented hypoxanthine/xanthine oxidase system. However, apotransferrin could be protected from the effects of HOCl if bicarbonate anion was present during the incubation. Apolactoferrin inhibition of hydroxyl radical generation was unaffected by any of the four proteases or HOCl. Alteration of transferrin by enzymes and oxidants present at sites of pseudomonas and other bacterial infections may increase the potential for local hydroxyl radical generation thereby contributing to tissue injury. Images PMID:1655825

  16. Synthesis, characterization of bimetallic V-Fe-SBA-15 and its catalytic performance in the hydroxylation of phenol.

    PubMed

    Gao, Fei; Zhang, Yanhua; Wang, Chunling; Wu, Cheng; Kong, Yan; Zhao, Bin; Dong, Lin; Chen, Yi

    2007-12-01

    A series of V-Fe incorporated-SBA-15 has been synthesized by adjustment of the pH value of the gel mixtures and characterized by using XRD, N2-adsorption, ICP, FT-IR, Raman, and UV-vis techniques. Results indicated that all samples exhibited typical hexagonal arrangement of mesoporous structure with high surface areas and the heteroatoms were probably incorporated into the framework of SBA-15. Catalytic performances of the obtained materials were evaluated in the hydroxylation of phenol with H2O2, and the catalytic results revealed that the selectivity for catechol (CAT) and hydroquinone (HQ) could be controlled by adjusting the contents of V and Fe in the samples, and an appropriate n(V)/n(Fe) mol ratio in SBA-15 could approach the optimal catalytic performance. PMID:18283835

  17. Ab initio and experimental study of the interaction of nitrous oxide with the isolated hydroxyl of silica

    NASA Astrophysics Data System (ADS)

    Garrone, E.; Ugliengo, P.; Ghiotti, G.; Borello, E.; Saunders, V. R.

    1993-08-01

    High-quality ab initio computational results for the interaction of N 2O with the silanol molecule H 3SiOH, taken as representative of the isolated hydroxyl at the silica surface, are compared with IR data concerning the real system measured at 195 K. Besides a non-specific interaction, features typical of hydrogen bonding are observed: two types of complexes are formed simultaneously, differing in their 2 v1 mode, probably one nitrogen-bonded, the other oxygen-bonded. Ab initio results are in excellent agreement as far as binding energies are concerned: the two complexes show comparable stabilities, once electron correlation has been taken into account; however, SCF-calculated IR features do not allow a definite vibrational assignment of the two complexes.

  18. Increased iron abundances in slope avalanches of certain lunar craters

    NASA Astrophysics Data System (ADS)

    Lu, Ya.; Shevchenko, V. V.

    2012-07-01

    On the basis of the first images of certain areas of Lunar surface obtained by the Chang'e-2 spacecraft and materials of large-scale image acquisition from the LRO (Lunar Reconnaissance Orbiter) spacecraft, supplemented with remote spectral measurements performed from the Clementine spacecraft, the slope movements of material have been studied in lunar craters Daniell, Burg and Mauri A. It is established that despite a significantly different age of formation of these craters, the slope formations are of similar structure and differ by increased iron abundance in the soil surface layer. All objects are characterized with by increase in FeO abundance to 20 wt % at depths of several hundred meters from the surface. The material of the slope structures is distinguished by a low maturity rate. According to preliminary assessments using the optical maturity index and spectropolarimetric maturity index, the fresher slope formations can have an exposure age from several tens of years to several years.

  19. Synergistic photocatalysis of Cr(VI) reduction and 4-Chlorophenol degradation over hydroxylated α-Fe2O3 under visible light irradiation.

    PubMed

    Wang, Ji-Chao; Ren, Juan; Yao, Hong-Chang; Zhang, Lin; Wang, Jian-She; Zang, Shuang-Quan; Han, Li-Feng; Li, Zhong-Jun

    2016-07-01

    A series of Fe2O3 materials with hydroxyl are synthesized in different monohydric alcohol (C2-C5) solvents by solvothermal method and characterized by XRD, BET, XPS, TG and EA. The amount of hydroxyl is demonstrated to be emerged on the surface of the as-synthesized Fe2O3 particles and their contents are determined to be from 7.99 to 3.74 wt%. The Cr(VI) reduction experiments show that the hydroxyl content of Fe2O3 samples exacts great influence on the photocatalytic activity under visible light irradiation (λ>400 nm) and that the Fe2O3 sample synthesized in n-butyl alcohol exhibits the optimal photocatalytic activity. The synergistic photocatalysis for 4-Chlorophenol (4-CP) degradation and Cr(VI) reduction over above Fe2O3 sample is further investigated. The photocatalytic ratio of Cr(VI) reduction are enhanced from 24.8% to 70.2% while that of 4-CP oxidation are increased from 13.5% to 47.8% after 1 h visible light irradiation. The Fe2O3 sample keeps good degradation rates of mixed pollutants after 9 runs. The active oxygen intermediates O2(-)˙, ˙OH and H2O2 formed in the photoreaction process are discovered by ESR measurement and UV-vis test. The photocatalytic degradation mechanism is proposed accordingly. PMID:26954471

  20. In vitro effects of coal fly ashes: hydroxyl radical generation, iron release, and DNA damage and toxicity in rat lung epithelial cells

    SciTech Connect

    van Maanen, J.M.; Borm, P.J.; Knaapen, A; van Herwijnen, M.; Schilderman, P.A.; Smith, K.R.; Aust, A.E.; Tomatis, M.; Fubini, B.

    1999-12-15

    The authors measured iron release, acellular generation of hydroxyl radicals, and oxidative DNA damage and cytotoxicity in rat lung epithelial (RLE) cells by different coal fly ashes (CFA) that contain both quartz and iron. Seven samples of CFA with different particle size and quartz content (up to 14.1%) were tested along with silica (alpha-quartz), ground coal, and coal mine dust (respirable) as positive control particles, and fine TiO{sub 2} (anatase) as a negative control. Five test samples were pulverized fuel ashes (PFA), two samples were coal gasification (SCG) ashes (quartz content {lt} 0.1%), and one sample was a ground coal. No marked differences between SCG and PFA fly ashes were observed, and toxicity did not correlate with physicochemical characteristics or effect parameters. Stable surface radicals were only detected in the reference particles silica and coal mine dust, but not in CFA. On the other hand, hydroxyl radical generation by all fly ashes was observed in the presence of hydrogen peroxide. Also a relationship between acellular hydroxyl radical generation and oxidative DNA damage in RLE cells by CFA was observed. The respirable ashes (MAT023, 38, and 41) showed an extensive level of hydroxyl radical generation in comparison to nonrespirable fly ashes and respirable references. This was related to the iron mobilization from these particles. Themechanisms by which CFA and the positive references (silica, coal mine dust) affect rat lung epithelial cells seem to be different, and the data suggest that quartz in CFA does not act the same as quartz in silica or coal mine dust. However, the results indicate an important role for size and iron release in generation and subsequent effects of reactive oxygen species caused by CFA.

  1. The chemical abundances of the Ap star HD94660

    SciTech Connect

    Giarrusso, M.

    2014-05-09

    In this work I present the determination of chemical abundances of the Ap star HD94660, a possible rapid oscillating star. As all the magnetic chemically peculiar objects, it presents CNO underabundance and overabundance of iron peak elements of ∼100 times and of rare earths up to 4 dex with respect to the Sun. The determination was based on the conversion of the observed equivalent widths into abundances simultaneously to the determination of effective temperature and gravity. Since the Balmer lines of early type stars are very sensitive to the surface gravity while the flux distribution is sensitive to the effective temperature, I have adopted an iterative procedure to match the H{sub α} line profile and the observed UV-Vis-NIR magnitudes of HD94660 looking for a consistency between the metallicity of the atmosphere model and the derived abundances. From my spectroscopic analysis, this star belongs to the no-rapid oscillating class.

  2. Carbon abundances of sdO stars from SPY

    NASA Astrophysics Data System (ADS)

    Hirsch, Heiko; Heber, Uli

    2009-06-01

    Ströer et al. (2007) recently suggested a classification of sdOs according to supersolar and subsolar helium abundances, with only the helium-enriched stars showing signes of carbon and/or nitrogen in their optical spectra. We aim to derive reliable carbon and nitrogen abundances by fitting synthetic spectra to data obtained with the UVES spectrograph at ESO. Here we present our first results of the analysis of carbon abundances in hot subdwarf O stars. By constructing a grid of model atmospheres consisting of hydrogen, helium and carbon we were able to derive atmospheric parameters of nine carbon rich sdOs. We find log(NC/Ntotal) up to ten times higher than the solar value, while the mean value for the effective temperature and the surface gravity is slightly lower than derived by helium-hydrogen models only. Surprisingly, we also find three fast rotators among our program stars.

  3. Identification of Putative Genes Involved in Bisphenol A Degradation Using Differential Protein Abundance Analysis of Sphingobium sp. BiD32.

    PubMed

    Zhou, Nicolette A; Kjeldal, Henrik; Gough, Heidi L; Nielsen, Jeppe L

    2015-10-20

    Discharge of the endocrine disrupting compound bisphenol A (BPA) with wastewater treatment plant (WWTP) effluents into surface waters results in deleterious effects on aquatic life. Sphingobium sp. BiD32 was previously isolated from activated sludge based on its ability to degrade BPA. This study investigated BPA metabolism by Sphingobium sp. BiD32 using label-free quantitative proteomics. The genome of Sphingobium sp. BiD32 was sequenced to provide a species-specific platform for optimal protein identification. The bacterial proteomes of Sphingobium sp. BiD32 in the presence and absence of BPA were identified and quantified. A total of 2155 proteins were identified; 1174 of these proteins were quantified, and 184 of these proteins had a statistically significant change in abundance in response to the presence/absence of BPA (p ≤ 0.05). Proteins encoded by genes previously identified to be responsible for protocatechuate degradation were upregulated in the presence of BPA. The analysis of the metabolites from BPA degradation by Sphingobium sp. BiD32 detected a hydroxylated metabolite. A novel p-hydroxybenzoate hydroxylase enzyme detected by proteomics was implicated in the metabolic pathway associated with the detected metabolite. This enzyme is hypothesized to be involved in BPA degradation by Sphingobium sp. BiD32, and may serve as a future genetic marker for BPA degradation. PMID:26390302

  4. On the weighting of SABER temperature profiles for comparison with ground based hydroxyl rotational temperatures.

    NASA Astrophysics Data System (ADS)

    French, William; Mulligan, Frank

    2010-05-01

    Kinetic temperature profiles are retrieved from limb-emission radiance measurements of CO2 at 15 and 4.3 um by the SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) instrument on the TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics) satellite. Profiles extend from about 20-120km and measurements are available since the spacecraft launch in Dec-2001. Hydroxyl (6-2) band rotational temperatures are measured using a ground-based scanning spectrometer at Davis station, Antarctica (68°S, 78°E). Measurements are available each year since 1995 on nights between early February and late October, when the sun is more than 6° below the horizon. In order to compare temperatures from these two instruments we must derive hydroxyl layer equivalent temperatures for the SABER profiles using a weighting function which represents the hydroxyl layer profile. In this study, we examine a number of different weighting profiles to determine the best equivalent to hydroxyl nightly average temperatures at Davis. These profiles include (1) the customary Gaussian peaked at 87km and width 8km [Baker and Stair, 1988 :Physica Scripta. 37 611-622], (2) the layer profile derived from WINDIIUARS hydroxyl height profiles [She and Lowe, 1998 :JASTP 60, 1573-1583], (3) layer profiles derived from the hydroxyl volume emission rate (VER) from the SABER OH-B channel at 1.6um, which contains the Meinel OH(4-2) and OH(5-3) bands and (4) a Gaussian fitted to the SABER hydroxyl VER peak. The comparison is made with approximately 2500 SABER retrievals from overpasses within 500km of Davis station, and with solar zenith angle >97°, which have coincident hydroxyl temperature measurements over the 8 winters between 2002 and 2009. Due to the satellite 60 day yaw cycle the sampling over Davis has occurred in approximately the same three time intervals each year; between days 75-140, 196-262 and 323-014, however the latter interval is entirely rejected on the solar zenith

  5. Detection of methoxylated and hydroxylated polychlorinated biphenyls in sewage sludge in China with evidence for their microbial transformation

    PubMed Central

    Sun, Jianteng; Zhu, Lizhong; Pan, Lili; Wei, Zi; Song, Yao; Zhang, Yuduo; Qu, Liping; Zhan, Yu

    2016-01-01

    The concentrations of methoxylated polychlorinated biphenyls (MeO-PCBs) and hydroxylated polychlorinated biphenyls (OH-PCBs) were measured in the sewage sludge samples collected from twelve wastewater treatment plants in China. Two MeO-PCB congeners, including 3′-MeO-CB-65 and 4′-MeO-CB-101, were detected in three sludge with mean concentrations of 0.58 and 0.52 ng/g dry weight, respectively. OH-PCBs were detected in eight sludge samples, with an average total concentration of 4.2 ng/g dry weight. Furthermore, laboratory exposure was conducted to determine the possible source of OH-PCBs and MeO-PCBs in the sewage sludge, and their metabolism by the microbes. Both 4′-OH-CB-101 and 4′-MeO-CB-101 were detected as metabolites of CB-101 at a limited conversion rate after 5 days. Importantly, microbial interconversion between OH-PCBs and MeO-PCBs was observed in sewage sludge. Demethylation of MeO-PCBs was favored over methylation of OH-PCBs. The abundant and diverse microbes in sludge play a key role in the transformation processes of the PCB analogues. To our knowledge, this is the first report on MeO-PCBs in environmental matrices and on OH-PCBs in sewage sludge. The findings are important to understand the environmental fate of PCBs. PMID:27417462

  6. Detection of methoxylated and hydroxylated polychlorinated biphenyls in sewage sludge in China with evidence for their microbial transformation.

    PubMed

    Sun, Jianteng; Zhu, Lizhong; Pan, Lili; Wei, Zi; Song, Yao; Zhang, Yuduo; Qu, Liping; Zhan, Yu

    2016-01-01

    The concentrations of methoxylated polychlorinated biphenyls (MeO-PCBs) and hydroxylated polychlorinated biphenyls (OH-PCBs) were measured in the sewage sludge samples collected from twelve wastewater treatment plants in China. Two MeO-PCB congeners, including 3'-MeO-CB-65 and 4'-MeO-CB-101, were detected in three sludge with mean concentrations of 0.58 and 0.52 ng/g dry weight, respectively. OH-PCBs were detected in eight sludge samples, with an average total concentration of 4.2 ng/g dry weight. Furthermore, laboratory exposure was conducted to determine the possible source of OH-PCBs and MeO-PCBs in the sewage sludge, and their metabolism by the microbes. Both 4'-OH-CB-101 and 4'-MeO-CB-101 were detected as metabolites of CB-101 at a limited conversion rate after 5 days. Importantly, microbial interconversion between OH-PCBs and MeO-PCBs was observed in sewage sludge. Demethylation of MeO-PCBs was favored over methylation of OH-PCBs. The abundant and diverse microbes in sludge play a key role in the transformation processes of the PCB analogues. To our knowledge, this is the first report on MeO-PCBs in environmental matrices and on OH-PCBs in sewage sludge. The findings are important to understand the environmental fate of PCBs. PMID:27417462

  7. Detection of methoxylated and hydroxylated polychlorinated biphenyls in sewage sludge in China with evidence for their microbial transformation

    NASA Astrophysics Data System (ADS)

    Sun, Jianteng; Zhu, Lizhong; Pan, Lili; Wei, Zi; Song, Yao; Zhang, Yuduo; Qu, Liping; Zhan, Yu

    2016-07-01

    The concentrations of methoxylated polychlorinated biphenyls (MeO-PCBs) and hydroxylated polychlorinated biphenyls (OH-PCBs) were measured in the sewage sludge samples collected from twelve wastewater treatment plants in China. Two MeO-PCB congeners, including 3‧-MeO-CB-65 and 4‧-MeO-CB-101, were detected in three sludge with mean concentrations of 0.58 and 0.52 ng/g dry weight, respectively. OH-PCBs were detected in eight sludge samples, with an average total concentration of 4.2 ng/g dry weight. Furthermore, laboratory exposure was conducted to determine the possible source of OH-PCBs and MeO-PCBs in the sewage sludge, and their metabolism by the microbes. Both 4‧-OH-CB-101 and 4‧-MeO-CB-101 were detected as metabolites of CB-101 at a limited conversion rate after 5 days. Importantly, microbial interconversion between OH-PCBs and MeO-PCBs was observed in sewage sludge. Demethylation of MeO-PCBs was favored over methylation of OH-PCBs. The abundant and diverse microbes in sludge play a key role in the transformation processes of the PCB analogues. To our knowledge, this is the first report on MeO-PCBs in environmental matrices and on OH-PCBs in sewage sludge. The findings are important to understand the environmental fate of PCBs.

  8. Lithium Abundance in Planet Search Stars

    NASA Astrophysics Data System (ADS)

    Myles, Justin; Yale Exoplanets

    2016-01-01

    Since most lithium in the universe is primordial and is destroyed in stars, lithium abundance can be used as a stellar age indicator. Some research seems to show that planet formation may also affect lithium abundance in exoplanet host stars (EHS). However, small and heterogenous samples have made both of these phenomena unclear. Further study of lithium abundance in EHS is needed to better understand possible physical roles of lithium in planet formation theory. We use a large homogenous sample with accurate stellar parameters on which we will use equivalent width analysis to determine precise lithium abundances. From these abundance values we determine an age vs. abundance relation. Additionally, we aim to explore correlation between lithium abundance and planet formation.

  9. A comparison of fenuron degradation by hydroxyl and carbonate radicals in aqueous solution.

    PubMed

    Mazellier, Patrick; Busset, Cécile; Delmont, Anne; De Laat, Joseph

    2007-12-01

    A comparative study of the transformation of the herbicide fenuron (1,1-dimethyl-3-phenylurea) by hydroxyl radicals and carbonate radicals in aqueous solution (pH 7.2-phosphate buffer) has been undertaken. Hydroxyl radical was generated by the well-known photolysis of hydrogen peroxide at 254 nm and carbonate radical was formed by photolysis of Co(NH(3))(5)CO(3)(+) at 254 nm. Competitive kinetic experiments were performed with atrazine used as the main competitor for both processes. Accordingly, the second-order rate constant of reaction between fenuron and carbonate radical was found to be (7-12+/-3)x10(6)M(-1)s(-1) [(7+/-1)x10(9)M(-1)s(-1) for hydroxyl radical]. The formation of degradation products was studied by LC-MS in the two cases and a comparison has been performed. The reaction with carbonate radical leads to the formation of a quinone-imine derivative which appears as the major primary product together with ortho and para hydroxylated compounds. These two compounds represent the major products in the reaction with hydroxyl radicals. The reaction of both radicals also leads to the transformation of the dimethylurea moiety. PMID:17675205

  10. Hydroxyl-decorated Graphene Systems: Organic metal-free Ferroelectrics, Multiferroics, and Proton battery Cathode Materials

    NASA Astrophysics Data System (ADS)

    Wu, Menghao; Burton, J. D.; Tsymbal, Evgeny; Zeng, Xiao; Jena, Puru; Jena's Group Team, Prof.; Burton's Group Team, Prof.; Tsymbal's Group Team, Prof.; Zeng's Group Team, Prof.

    2013-03-01

    Through density-functional-theory calculations we show that hydroxylized graphene systems are ideal candidates for light-weight organic ferroelectric materials with giant polarizations. For example, the polarization of semi-hydroxylized graphane and graphone as well as fully hydroxylized graphane are, respectively, 41.1, 43.7, 67.7 μC/cm2, much higher than any organic ferroelectric materials known to date. In addition, hydroxylized graphone is multiferroic due to the coexistence of ferroeletricity and ferromagnetism. Zigzag graphene nanoribbons decorated by hydroxyl groups also exhibit ferroelectric properties with a large polarization of 27.0 μC/cm2. Moreover, proton vacancies at the end of ribbons can induce large dipole moments that can be reversed by both hopping of protons and rotation of O-H bonds under an electric field. These materials have the potential as high-capacity cathode materials with specific capacity six times larger than lead-acid batteries and five times that of lithium-ion batteries.

  11. Isotopically labeled chlorobenzenes as probes for the mechanism of cytochrome P-450 catalyzed aromatic hydroxylation

    SciTech Connect

    Korzekwa, K.R.; Swinney, D.C.; Trager, W.F. )

    1989-11-14

    Noncompetitive and competitive intermolecular deuterium isotope effects were measured for the cytochrome P-450 catalyzed hydroxylation of a series of selectively deuterated chlorobenzenes. An isotope effect of 1.27 accompanied the meta hydroxylation of chlorobenzene-2H5 as determined by two totally independent methods (EC-LC and GC-MS assays). All isotope effects associated with the meta hydroxylation of chlorobenzenes-3,5-2H2 and -2,4,6-2H3 were approximately 1.1. In contrast, competitive isotope studies on the ortho and para hydroxylation of chlorobenzenes-4-2H1, -3,5-2H2, and -2,4,6-2H3 resulted in significant inverse isotope effects (approximately 0.95) when deuterium was substituted at the site of oxidation whereas no isotope effect was observed for the oxidation of protio sites. These results eliminate initial epoxide formation and initial electron abstraction (charge transfer) as viable mechanisms for the cytochrome P-450 catalyzed hydroxylation of chlorobenzene. The results, however, can be explained by a mechanism in which an active triplet-like oxygen atom adds to the pi system in a manner analogous to that for olefin oxidation. The resulting tetrahedral intermediate can then rearrange to phenol directly or via epoxide or ketone intermediates.

  12. Developmental Stage-dependent Regulation of Prolyl 3-Hydroxylation in Tendon Type I Collagen.

    PubMed

    Taga, Yuki; Kusubata, Masashi; Ogawa-Goto, Kiyoko; Hattori, Shunji

    2016-01-01

    3-Hydroxyproline (3-Hyp), which is unique to collagen, is a fairly rare post-translational modification. Recent studies have suggested a function of prolyl 3-hydroxylation in fibril assembly and its relationships with certain disorders, including recessive osteogenesis imperfecta and high myopia. However, no direct evidence for the physiological and pathological roles of 3-Hyp has been presented. In this study, we first estimated the overall alterations in prolyl hydroxylation in collagens purified from skin, bone, and tail tendon of 0.5-18-month-old rats by LC-MS analysis with stable isotope-labeled collagen, which was recently developed as an internal standard for highly accurate collagen analyses. 3-Hyp was found to significantly increase in tendon collagen until 3 months after birth and then remain constant, whereas increased prolyl 3-hydroxylation was not observed in skin and bone collagen. Site-specific analysis further revealed that 3-Hyp was increased in tendon type I collagen in a specific sequence region, including a previously known modification site at Pro(707) and newly identified sites at Pro(716) and Pro(719), at the early ages. The site-specific alterations in prolyl 3-hydroxylation with aging were also observed in bovine Achilles tendon. We postulate that significant increases in 3-Hyp at the consecutive modification sites are correlated with tissue development in tendon. The present findings suggest that prolyl 3-hydroxylation incrementally regulates collagen fibril diameter in tendon. PMID:26567337

  13. Hydroxylation of quinocetone and carbadox is mediated by CYP1As in the chicken (Gallus gallus).

    PubMed

    Yang, Jiannan; Liu, Zhaoying; Li, Mei; Qiu, Xinghui

    2013-08-01

    Quinoxaline derivatives (quinoxalines) comprise a class of drugs that have been widely used as animal antimicrobial agents and feed additives. Although the metabolism of quinoxaline drugs has been mostly studied using chicken liver microsomes, the biochemical mechanism of biotransformation of these chemicals in the chicken has yet to be characterized. In this study, using bacteria produced enzymes, we demonstrated that both CYP1A4 and CYP1A5 participate in the oxidative metabolism of quinoxalines. For CYP1A5, three hydroxylated metabolites of quinocetone were generated. In addition, CYP1A5 is able to hydroxylate carbadox. For CYP1A4, only one hydroxylated product of quinocetone on the phenyl ring was identified. Neither CYP1A5 nor CYP1A4 showed hydroxylation activity towards mequindox and cyadox. Our results suggest that CYP1A4 and CYP1A5 have different and somewhat overlapping substrate specificity in quinoxaline metabolism, and CYP1A5 represents a crucial enzyme in hydroxylation of both quinocetone and carbadox. PMID:23726999

  14. Effect of apotransferrin, lactoferrin and ovotransferrin on the hydroxyl radical mediated degradation of beta-glucan.

    PubMed

    Faure, Audrey M; Nyström, Laura

    2016-08-01

    Beta-glucan is a polysaccharide widely accepted and used as a functional ingredient due to its positive effects on human health. However, beta-glucan is readily degraded in aqueous systems in presence of a hydroxyl radical generating system such as ascorbic/iron(II). In the present study, we tested whether iron binding proteins; apotransferrin, lactoferrin and ovotransferrin; could prevent the hydroxyl radical mediated degradation of beta-glucan. The radical formation was investigated by ESR spectroscopy and the polysaccharide degradation was monitored by the viscosity loss of the solutions. Apo-transferrin increased the formation of hydroxyl radicals and this related with a faster degradation of beta-glucan. Lactoferrin did not have any effect on the ascorbate induced degradation of beta-glucan, whereas ovotransferrin completely inhibited the hydroxyl radical generation by a system containing ascorbic acid and iron(II). However, the presence of ovotransferrin in beta-glucan decreased the viscosity of the solution, which was accompanied by the apparition of a precipitate, indicating a potential interaction between the protein and beta-glucan. FT-IR analyses indicate the presence of beta-glucan and ovotransferrin in both precipitate and supernatant, as well as the occurrence of interactions between the two compounds. This study reveals that ovotransferrin is a promising candidate for inhibiting the formation of ascorbate/iron(II) induced hydroxyl radicals in beta-glucan solutions. PMID:26988468

  15. Human Insulin Resistance Is Associated With Increased Plasma Levels of 12α-Hydroxylated Bile Acids

    PubMed Central

    Haeusler, Rebecca A.; Astiarraga, Brenno; Camastra, Stefania; Accili, Domenico; Ferrannini, Ele

    2013-01-01

    Bile acids (BAs) exert pleiotropic metabolic effects, and physicochemical properties of different BAs affect their function. In rodents, insulin regulates BA composition, in part by regulating the BA 12α-hydroxylase CYP8B1. However, it is unclear whether a similar effect occurs in humans. To address this question, we examined the relationship between clamp-measured insulin sensitivity and plasma BA composition in a cohort of 200 healthy subjects and 35 type 2 diabetic (T2D) patients. In healthy subjects, insulin resistance (IR) was associated with increased 12α-hydroxylated BAs (cholic acid, deoxycholic acid, and their conjugated forms). Furthermore, ratios of 12α-hydroxylated/non–12α-hydroxylated BAs were associated with key features of IR, including higher insulin, proinsulin, glucose, glucagon, and triglyceride (TG) levels and lower HDL cholesterol. In T2D patients, BAs were nearly twofold elevated, and more hydrophobic, compared with healthy subjects, although we did not observe disproportionate increases in 12α-hydroxylated BAs. In multivariate analysis of the whole dataset, controlling for sex, age, BMI, and glucose tolerance status, higher 12α-hydroxy/non–12α-hydroxy BA ratios were associated with lower insulin sensitivity and higher plasma TGs. These findings suggest a role for 12α-hydroxylated BAs in metabolic abnormalities in the natural history of T2D and raise the possibility of developing insulin-sensitizing therapeutics based on manipulations of BA composition. PMID:23884887

  16. Chemical Abundances of Solar-Type Dwarfs in Open Clusters

    NASA Astrophysics Data System (ADS)

    Schuler, S. C.

    2005-12-01

    Open clusters present homogeneous samples of stars that are of the same age, distance, and initial chemical composition, making open clusters valuable observational targets for studies of stellar evolution, stellar structure, exoplanetary systems, and Galactic chemical evolution. I present an overview of my graduate dissertation research on LTE abundances of solar-type dwarfs (4200 ≲ T eff ≲ 6400 ; {K}) in the open clusters Pleiades, M34, and Hyades, as well as in the Ursa Major moving group. For the dwarfs of intermediate T eff (5500 ≲ T eff ≲ 6100 ; {K}), intracluster metal abundances are in good agreement. Conversely, we have identified excitation/ionization-related abundance anomalies among the cool dwarfs (T eff ≤ 5500 ; {K}) of all three clusters and UMa; for example, O abundances derived from the high-excitation, near-IR \\ion{O}{1} triplet show a dramatic increase with decreasing T eff, a behavior that is not predicted by current non-LTE calculations. Intercluster comparisons are suggestive of an age-related diminution of the \\ion{O}{1} triplet abundance trend, and possible causes of these observed abundance anomalies, i.e., chromospheric activity, surface inhomogeneities, etc., are explored. Using multi-component ``toy model'' stellar atmospheres, we demonstrate that the \\ion{O}{1} triplet abundance trend may be due to inhomogeneous temperature structure, possibly resulting from spots or plages, in the photospheres of cool open cluster dwarfs. I gratefully acknowledge the following agencies that have provided support during this research: NSF (through grants AST 00-86576 and AST 02-39518 to Prof. J.R. King), South Carolina Space Grant Consortium (through the Graduate Student Research Fellowship program), and the Charles Curry Foundation (through a generous grant to Clemson University).

  17. Synthesis of mesoporous iron-incorporated silica-pillared clay and catalytic performance for phenol hydroxylation

    NASA Astrophysics Data System (ADS)

    Yang, Shengjun; Liang, Guozheng; Gu, Aijuan; Mao, Huihui

    2013-11-01

    Fe-incorporated silica-pillared clays (Fe-SPCs) with ordered interlayer mesoporous structure have been synthesized through a new two-step procedure including the modification of the silica nano-pillars with potassium ferricyanide (K3Fe(CN)6) and successive calcination. X-ray diffraction, nitrogen adsorption-desorption, Fourier transform infrared spectra, X-ray fluorescence analyses, diffuse reflectance UV-vis spectra and X-ray absorption near-edge structure spectra were used to characterize the structures and the synthesizing mechanism of Fe-SPCs. Results show that all iron species were tetrahedrally coordinated with the interlayer silica nano-pillars, and the cationic surfactant molecule plays an important role in the intercalation of tetraethoxysilane and the introduction of iron into the intragallery silica framework. Moreover, the structural parameters of Fe-SPC can be adjusted by controlling the concentration of K3Fe(CN)6, as the concentration of K3Fe(CN)6 increases from 1 M to 2 M, the gallery height of Fe-SPC increases from 2.51 to 2.66 nm, while the Brunauer-Emmett-Teller (BET) surface area, pore volume and Barrett-Joyner-Halenda (BJH) pore size decrease from 856 to 794 m2/g, 0.75 to 0.69 cm3/g, and 2.2 to 2.0 nm, respectively. The Fe-SPCs show good catalytic activity in phenol hydroxylation using H2O2 as oxidant (phenol:H2O2 = 1:1, water), specifically, the phenol conversion is 46.2%, and the selectivity of dihydroxybenzenes is 70.6% at 343 K.

  18. Different photolysis kinetics and photooxidation reactivities of neutral and anionic hydroxylated polybrominated diphenyl ethers.

    PubMed

    Xie, Qing; Chen, Jingwen; Zhao, Hongxia; Qiao, Xianliang; Cai, Xiyun; Li, Xuehua

    2013-01-01

    Hydroxylated polybrominated diphenyl ethers (HO-PBDEs) pose potential ecological risks due to their endocrine disrupting effects and extensive sources. It is of great importance to know their environmental transformation for the purpose of ecological risk assessment. Photodegradation is an important transformation pathway of HO-PBDEs. As HO-PBDEs ionize in natural waters, the photochemical reactivities of both neutral and anionic HO-PBDEs need to be unveiled. In this study, six HO-PBDEs were selected as model compounds. Their direct photolysis rate constants (k(d)), quantum yields (Φ), light absorptions (A), second-order reaction rate constants with (1)O(2) (k(1O2)) and (·)OH (k(OH)) at different pH were determined, as well as these parameters for the neutral and anionic HO-PBDEs. The k(d), Φ, A, k(1O2) and k(OH) for the anions are much higher than those for the neutral molecules and vary with the bromination degree. Molecular parameters computed with the density functional theory (DFT) were employed to construct structure-reactivity equations. The ether bond strength, the frontier molecular orbital energy and the charge distribution were found to be the intrinsic structural characters governing the photochemical reactivities. The half-lives range from 0.7 to 60.1h for the photodegradation including the direct photolysis and the reactions with (1)O(2) and ()OH in surface waters at 45°N latitude under the continuous solar irradiation of sunny noon on 15 July. Direct photolysis is the dominant pathway. The photochemical reactivities of other HO-PBDEs at a given pH can also be estimated based on the structure-reactivity equations, which is important for the ecological risk assessment of HO-PBDEs. PMID:22832336

  19. HONO fluxes from soil surfaces: an overview

    NASA Astrophysics Data System (ADS)

    Wu, Dianming; Sörgel, Matthias; Tamm, Alexandra; Ruckteschler, Nina; Rodriguez-Caballero, Emilio; Cheng, Yafang; Pöschl, Ulrich; Weber, Bettina

    2016-04-01

    Gaseous nitrous acid (HONO) contributes up to 80% of atmospheric hydroxyl (OH) radicals and is also linked to health risks through reactions with tobacco smoke forming carcinogens. Field and modeling results suggested a large unknown HONO source in the troposphere during daytime. By measuring near ground HONO mixing ratio, up to 30% of HONO can be released from forest, rural and urban ground as well as snow surfaces. This source has been proposed to heterogeneous reactions of nitrogen dioxide (NO2) on humic acid surfaces or nitric acid photolysis. Laboratory studies showed that HONO emissions from bulk soil samples can reach 258 ng m‑2 s‑1 (in term of nitrogen), which corresponding to 1.1 × 1012 molecules cm‑2 s‑1and ˜ 100 times higher than most of the field studies, as measured by a dynamic chamber system. The potential mechanisms for soil HONO emissions include chemical equilibrium of acid-base reaction and gas-liquid partitioning between soil nitrite and HONO, but the positive correlation of HONO fluxes with pH (largest at neutral and slightly alkaline) points to the dominance of the formation process by ammonia-oxidizing bacteria (AOB). In general soil surface acidity, nitrite concentration and abundance of ammonia-oxidizing bacteria mainly regulate the HONO release from soil. A recent study showed that biological soil crusts in drylands can also emit large quantities of HONO and NO, corresponding to ˜20% of global nitrogen oxide emissions from soils under natural vegetation. Due to large concentrations of microorganisms in biological soil crusts, particularly high HONO and NO emissions were measured after wetting events. Considering large areas of arid and arable lands as well as peatlands, up to 70% of global soils are able to emitting HONO. However, the discrepancy between large soil HONO emissions measured in lab and low contributions of HONO flux from ground surfaces in field as well as the role of microorganisms should be further investigated.

  20. Molecular simulation of the effects of humidity and of interfacial Si- and B-hydroxyls on the adhesion energy between glass plates.

    PubMed

    Savoy, Elizabeth S; Escobedo, Fernando A

    2016-03-01

    Adhesion energies for sub-micron particles cannot be accurately calculated with macro-scale theories, in part because heterogeneities in surface morphology and chemistry play a significant role. Atomistic models have been used previously to quantify adhesion energies in wet environments for pure silica surfaces. To extend such modeling to more complex glass materials, we adopt a more comprehensive amorphous glass potential, and use a simplified approach to define the interaction between the hydroxylated surface and SPC/E water. We compute adhesion energies for pure SiO2, and 90mol% SiO2+10mol% B2O3, in dry and humid conditions. We find that the addition of B2O3 reduces adhesion, due to multiple effects which result in reduced hydrogen bonding. At high RH, the water between the plates forms a clear liquid bridge, whereas at the lowest RH, the water connects in chains of hydrogen bonded molecules that form and break during the adhesion process, so that capillary forces do not come into play. We also find that for under-hydroxylated pure SiO2 surfaces, a transitional state which may be found after heating or during glass formation, adhesion energies are the highest. PMID:26674240

  1. Significant biases affecting abundance determinations

    NASA Astrophysics Data System (ADS)

    Wesson, Roger

    2015-08-01

    I have developed two highly efficient codes to automate analyses of emission line nebulae. The tools place particular emphasis on the propagation of uncertainties. The first tool, ALFA, uses a genetic algorithm to rapidly optimise the parameters of gaussian fits to line profiles. It can fit emission line spectra of arbitrary resolution, wavelength range and depth, with no user input at all. It is well suited to highly multiplexed spectroscopy such as that now being carried out with instruments such as MUSE at the VLT. The second tool, NEAT, carries out a full analysis of emission line fluxes, robustly propagating uncertainties using a Monte Carlo technique.Using these tools, I have found that considerable biases can be introduced into abundance determinations if the uncertainty distribution of emission lines is not well characterised. For weak lines, normally distributed uncertainties are generally assumed, though it is incorrect to do so, and significant biases can result. I discuss observational evidence of these biases. The two new codes contain routines to correctly characterise the probability distributions, giving more reliable results in analyses of emission line nebulae.

  2. Hydroxyl radical (OH) scavenging in young and mature landfill leachates.

    PubMed

    Ghazi, Niloufar M; Lastra, Andres A; Watts, Michael J

    2014-06-01

    The final discharge point for collected landfill leachates is frequently the local municipal wastewater treatment facility. The salinity, color, nutrient, and anthropogenic organics contamination of leachates often necessitate some form of pre-treatment. When advanced oxidation processes (AOPs) are considered for pre-treatment, the unique composition of dissolved organic matter (DOM) and the relatively high concentrations of some inorganic solutes in leachate will inhibit treatment efficiency. The most important benchmark for design of AOPs is the expected steady-state production of free radical (OH). Without a quantitative assessment of total OH consumption in high-strength waste water, like a landfill leachate, efficient AOP treatment is uncertain. For this reason, two landfill leachates, distinct in color, DOM, and age of landfill, were characterized for OH-scavenging using an established competition kinetics method. After stripping the samples of inorganic carbon, the DOM in leachate from mature (stabilized) landfill was found to react with OH at a rate of 9.76 × 10(8) M(-1)s(-1). However, DOM in leachate from newer landfill was observed to scavenge available OH at a faster rate (8.28 × 10(9) M(-1)s(-1)). The combination of fast rate of reaction with OH and abundance of DOM in the sampled leachate severely limited the contribution of OH to degradation of an O3- and OH-labile organic probe compound (bisphenol-a) in oxidized mature leachate (fOH = 0.03). Substantial dosing of both O3 and H2O2 (>70 mg/L and >24 mg/L, respectively) may be required to see at least 1-log-removal (>90%) of an OH-selective leachate contaminant (i.e., parachlorobenzoic acid) in a mature landfill leachate. PMID:24675270

  3. Geminate recombination of hydroxyl radicals generated in 200 nm photodissociation of aqueous hydrogen peroxide.

    SciTech Connect

    Crowell, R. A.; Lian, R.; Oulianov, D. A.; Shkrob, I. A.; Chemistry

    2004-01-15

    The picosecond dynamics of hydroxyl radicals generated in 200 nm photoinduced dissociation of aqueous hydrogen peroxide have been observed through their transient absorbance at 266 nm. It is shown that these kinetics are nearly exponential, with a decay time of ca. 30 ps. The prompt quantum yield for the decomposition of H2O2 is 0.56, and the fraction of hydroxyl radicals escaping from the solvent cage to the water bulk is 64-68%. These recombination kinetics suggest strong caging of the geminate hydroxyl radicals by water. Phenomenologically, these kinetics may be rationalized in terms of the diffusion of hydroxide radicals out of a shallow potential well (a solvent cage) with an Onsager radius of 0.24 nm.

  4. Hydroxylation and hydrolysis: two main metabolic ways of spiramycin I in anaerobic digestion.

    PubMed

    Zhu, Pei; Chen, Daijie; Liu, Wenbin; Zhang, Jianbin; Shao, Lei; Li, Ji-an; Chu, Ju

    2014-02-01

    The anaerobic degradation behaviors of five macrolides including spiramycin I, II, III, midecamycin and josamycin by sludge were investigated. Within 32days, 95% of spiramycin I, II or III was degraded, while the remove rate of midecamycin or josamycin was 75%. SPM I degradation was much higher in nutrition supplementation than that just in sludge. The degradation products and processes of spiramycin I were further characterized. Three molecules, designated P-1, P-2 and P-3 according to their order of occurrence, were obtained and purified. Structural determination was then performed by nuclear magnetic resonance and MS/MS spectra, and data indicated that hydroxylation and hydrolysis were main reactions during the anaerobic digestion of spiramycin I. P-1 is the intermediate of hydroxylation, and P-2 is the intermediate of hydrolysis. P-3 is the final product of the both reaction. This study revealed a hydroxylation and hydrolysis mechanism of macrolide in anaerobic digestion. PMID:24345568

  5. Quantitative hydroxyl concentration time-series measurements in turbulent nonpremixed flames.

    PubMed

    Renfro, M W; King, G B; Laurendeau, N M

    1999-07-20

    Quantitative hydroxyl concentration time-series measurements have been obtained by picosecond time-resolved laser-induced fluorescence in a series of methane-air and hydrogen-argon-air nonpremixed flames. The recovery of a quantitative time series is complicated by the need to account for fluctuations in the fluorescence lifetime. We have recently developed instrumentation that enables the simultaneous measurement of fluorescence signal and lifetime. The present research represents the first application of this technique to turbulent flames. The correction for hydroxyl lifetime fluctuations is shown to be significant for mean concentrations and thus probability density functions but negligible for power spectral densities (PSD's). The hydroxyl PSD's were found to vary slightly with radial and axial location in the flames and to vary significantly with Reynolds number. However, the PSD's in the H(2)-Ar-air flames are nearly identical to those in the CH(4)-air flames. PMID:18323947

  6. Entropy Loss of Hydroxyl Groups of Balanol upon Binding to Protein Kinase A

    NASA Astrophysics Data System (ADS)

    Gidofalvi, Gergely; Wong, Chung F.; McCammon, J. Andrew

    2002-09-01

    This article describes a short project for an undergraduate to learn several techniques for computer-aided drug design. The project involves estimating the loss of the rotational entropy of the hydroxyl groups of balanol upon its binding to the enzyme protein kinase A (PKA), as the entropy loss can significantly influence PKA balanol binding affinity. This work employs semiempirical quantum mechanical techniques for estimating the potential energy curves for the rotation of the hydroxyl groups of balanol in vacuum and in PKA, and solves the Poisson equation to correct the potential energy curves for hydration effects. Statistical mechanical principles are then applied to estimate the desired entropy loss from the potential energy curves. The analysis examines the influence of hydration effects on the rotational preference of the hydroxyl groups and the significance of the rotational entropy in determining binding affinity.

  7. Influence of hydroxylation and glycosylation in ring A of soybean isoflavones on interaction with BSA

    NASA Astrophysics Data System (ADS)

    Zhao, Jinyao; Ren, Fenglian

    2009-04-01

    In this paper, the influence of hydroxylation and glycosylation of soybean isoflavones in ring A on the interaction with BSA was investigated. Two soybean isoflavone aglycones (daidzein and genistein) and their glycosides (daidzin and genistin) were used to study their ability to bind BSA by quenching the BSA intrinsic fluorescence in solution. The hydroxylation and glycosylation of soybean isoflavones in ring A significantly affected the binding/quenching process; in general, the hydroxylation increases the binding affinity and the glycosylation decreased the binding affinity. For daidzein and daidzin, the binding constants for BSA were 5.2 × 10 4 and 5.58 × 10 3 L mol -1, respectively. For genistein and genistin, the binding constants were 8.40 × 10 5 and 1.44 × 10 5 L mol -1, respectively.

  8. Catalytic activity of unsaturated coordinated Cu-MOF to the hydroxylation of phenol

    NASA Astrophysics Data System (ADS)

    Jian, Lijuan; Chen, Chao; Lan, Fan; Deng, Shengjun; Xiao, Weiming; Zhang, Ning

    2011-05-01

    A 2D metal-organic framework [Cu 2 (BPTC) (Im) 4(H 2O) (DMF)] n ( 1) with unsaturated coordinated Cu(II) sites has been prepared under solvothermal condition, and applied to the hydroxylation of phenol after activating. The catalytic results indicate that 1a (the activated 1) exhibits an obvious activity for phenol hydroxylation at 40 °C for 4 h. Compared to the control experiments where the free Cu(II) (from Cu(OAc) 2 salt) has been utilized as the catalysts, 1a shows the higher selectivity to diphenols. This suggests that the coordinated environment of unsaturated coordinated Cu(II) sites in the 2D layer play the key role in the phenol hydroxylation.

  9. Mechanism of the N-hydroxylation of primary and secondary amines by cytochrome P450.

    PubMed

    Seger, Signe T; Rydberg, Patrik; Olsen, Lars

    2015-04-20

    Cytochrome P450 enzymes (CYPs) metabolize alkyl- and arylamines, generating several different products. For the primary and secondary amines, some of these reactions result in hydroxylated amines, which may be toxic. Thus, when designing new drugs containing amine groups, it is important to be able to predict if a given compound will be a substrate for CYPs, in order to avoid toxic metabolites, and hence to understand the mechanism that is utilized by CYPs. Two possible mechanisms, for the N-hydroxylation of primary and secondary amines mediated by CYPs, are studied by density functional theory (DFT) for four different amines (aniline, N-methylaniline, propan-2-amine, and dimethylamine). The hydrogen abstraction and rebound mechanism is found to be preferred over a direct oxygen transfer mechanism for all four amines. However, in contrast to the same mechanism for the hydroxylation of aliphatic carbon atoms, the rebound step is shown to be rate-limiting in most cases. PMID:25651340

  10. Soy intake is associated with increased 2-hydroxylation and decreased 16α-hydroxylation of estrogens in Asian-American women

    PubMed Central

    Fuhrman, Barbara J.; Pfeiffer, Ruth; Xu, Xia; Wu, Anna H.; Korde, Larissa; Gail, Mitchell H.; Keefer, Larry K.; Veenstra, Timothy D.; Hoover, Robert N.; Ziegler, Regina G.

    2009-01-01

    Introduction In Asian women, soy consumption is associated with reduced breast cancer risk, perhaps due to effects on estrogen production or metabolism. In a sample of Asian-American women, we investigated associations of usual adult soy intake with urinary concentrations of 15 estrogens and estrogen metabolites (EM) measured using liquid chromatography-tandem mass spectrometry. Methods Participants included 430 Chinese-, Japanese-, and Filipino-American women, aged 20–55 years, and living in San Francisco-Oakland (CA), Los Angeles (CA) or Oahu (HI). They were postmenopausal (n=167) or premenopausal in luteal phase (n=263) when they collected 12-hour urines. Robust linear regression was used to assess soy tertiles as predictors of log-transformed EM measures. Individual and grouped EM were considered as concentrations (pmol/mg creatinine) and as percentages of total EM (%EM). Results Factor analysis confirmed that EM groups defined by metabolic pathways appropriately captured covariation in EM profiles. Total EM concentrations (pmol/mg creatinine) were not significantly associated with soy in pre- or postmenopausal women. Among all women, %2-hydroxylated EM and %4-hydroxylated EM were 16.3% higher (ptrend= 0.02) and 18.6% higher (ptrend= 0.03) in highest vs. lowest soy tertiles. In contrast, %16-hydroxylated EM were 10.6% lower (ptrend< 0.01). Results were consistent across ethnic and menopausal groups and after adjustment for Westernization measured by birthplace (Asia or U.S.). Discussion Findings suggest that regular soy intake is associated with increased ratios of 2:16-pathway EM and with higher relative levels of 4-hydroxylated EM. Observed variations in estrogen metabolism may modify breast cancer risk. PMID:19789363

  11. Influence of self-assembled monolayer surface chemistry on Candida antarctica lipase B adsorption and specific activity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Immobilization of Candida antarctica B lipase was examined on gold surfaces modified with either methyl- or hydroxyl-terminated self-assembled alkylthiol monolayers (SAMs), representing hydrophobic and hydrophilic surfaces, respectively. Lipase adsorption was monitored gravimetrically using a quart...

  12. Coordination Changes And Auto-Hydroxylation of FIH-1: Uncoupled O(2)-Activa in a Human Hypoxia Sensor

    SciTech Connect

    Chen, Y.-H.; Comeaux, L.M.; Herbst, R.W.; Saban, E.; Kennedy, D.C.; Maroney, M.J.; Knapp, M.J.

    2009-05-12

    Hypoxia sensing is the generic term for pO2-sensing in humans and other higher organisms. These cellular responses to pO2 are largely controlled by enzymes that belong to the Fe(II) alpha-ketoglutarate (alphaKG) dependent dioxygenase superfamily, including the human enzyme called the factor inhibiting HIF (FIH-1), which couples O2-activation to the hydroxylation of the hypoxia inducible factor alpha (HIFalpha). Uncoupled O2-activation by human FIH-1 was studied by exposing the resting form of FIH-1 (alphaKG + Fe)FIH-1, to air in the absence of HIFalpha. Uncoupling lead to two distinct enzyme oxidations, one a purple chromophore (lambda(max) = 583 nm) arising from enzyme auto-hydroxylation of Trp296, forming an Fe(III)-O-Trp296 chromophore [Y.-H. Chen, L.M. Comeaux, S.J. Eyles, M.J. Knapp, Chem. Commun. (2008), doi:10.1039/B809099H]; the other a yellow chromophore due to Fe(III) in the active site, which under some conditions also contained variable levels of an oxygenated surface residue (oxo)Met275. The kinetics of purple FIH-1 formation were independent of Fe(II) and alphaKG concentrations, however, product yield was saturable with increasing [alphaKG] and required excess Fe(II). Yellow FIH-1 was formed from (succinate+Fe)FIH-1, or by glycerol addition to (alphaKG+Fe)FIH-1, suggesting that glycerol could intercept the active oxidant from the FIH-1 active site and prevent hydroxylation. Both purple and yellow FIH-1 contained high-spin, rhombic Fe(III) centers, as shown by low temperature EPR. XAS indicated distorted octahedral Fe(III) geometries, with subtle differences in inner-shell ligands for yellow and purple FIH-1. EPR of Co(II)-substituted FIH-1 (alphaKG + Co)FIH-1, indicated a mixture of 5-coordinate and 6-coordinate enzyme forms, suggesting that resting FIH-1 can readily undergo uncoupled O2-activation by loss of an H2O ligand from the metal center.

  13. Coordination changes and auto-hydroxylation of FIH-1: uncoupled O2-activation in a human hypoxia sensor

    PubMed Central

    Chen, Yuan-Han; Comeaux, Lindsay M.; Herbst, Robert W.; Saban, Evren; Kennedy, David C.; Maroney, Michael J.; Knapp, Michael J.

    2008-01-01

    Hypoxia sensing is the generic term for pO2-sensing in humans and other higher organisms. These cellular responses to pO2 are largely controlled by enzymes that belong to the Fe(II) α-ketoglutarate (αKG) dependent dioxygenase superfamily, including the human enzyme called the Factor Inhibiting HIF (FIH-1), which couples O2-activation to the hydroxylation of the Hypoxia Inducible Factor α (HIFα). Uncoupled O2-activation by human FIH-1 was studied by exposing the resting form of FIH-1, (αKG+Fe)FIH-1, to air in the absence of HIFα. Uncoupling lead to two distinct enzyme oxidations, one a purple chromophore (λmax = 583 nm) arising from enzyme auto-hydroxylation of Trp296, forming an Fe(III)–O–Trp296 chromophore (Y.-H. Chen, L. M. Comeaux, S. J. Eyles, M. J. Knapp, Chem. Commun. (2008) DOI:10.1039/B809099H); the other a yellow chromophore due to Fe(III) in the active site, which under some conditions also contained variable levels of an oxygenated surface residue, (oxo)Met275. The kinetics of purple FIH-1 formation were independent of Fe(II) and αKG concentrations, however product yield was saturable with increasing [αKG] and required excess Fe(II). Yellow FIH-1 was formed from (succinate+Fe)FIH-1, or by glycerol addition to (αKG+Fe)FIH-1, suggesting that glycerol could intercept the active oxidant from the FIH-1 active site and prevent hydroxylation. Both purple and yellow FIH-1 contained high-spin, rhombic Fe(III) centers, as shown by low temperature EPR. XAS indicated distorted octahedral Fe(III) geometries, with subtle differences in inner-shell ligands for yellow and purple FIH-1. EPR of Co(II)-substituted FIH-1, (αKG+Co)FIH-1, indicated a mixture of 5-coordinate and 6-coordinate enzyme forms, suggesting that resting FIH-1 can readily undergo uncoupled O2-activation by loss of an H2O ligand from the metal center. PMID:18805587

  14. Effect of ethanol on tyrosine hydroxylation in brain regions of long and short sleep mice.

    PubMed

    French, T A; Weiner, N

    1984-01-01

    The effect of ethanol on the in vivo rate of tyrosine hydroxylation in 6 brain regions was examined in two lines of mice selectively bred for a differential sensitivity to ethanol. The mice are designated long-sleep (LS) and short-sleep (SS) and lose their righting reflex for a duration of 100 minutes (LS) and 13 minutes (SS) following an intraperitoneal dose of ethanol of 4.0 g/kg. DOPA accumulation after NSD-1015 administration was measured in the absence and presence of ethanol (4.0 g/kg, IP) in the periods 5-35 minutes and 85-115 minutes after saline or ethanol. There were no differences between the lines in either basal catecholamine levels or basal tyrosine hydroxylation rates (as measured by DOPA accumulation) in any brain region except the cerebellum, where the norepinephrine content in the SS mice is 33% greater and the tyrosine hydroxylation rate is 25% higher than that in the LS mice. In the presence of ethanol, there was a differential effect on the in vivo tyrosine hydroxylation rate. In the cerebellum of both LS and SS mice there was a decreased rate of tyrosine hydroxylation in the early period after ethanol, but the rate in the cerebellum of SS mice returned to the control value at 85-115 min. At that time, the rate in LS mice is still decreased. In the locus ceruleus, hypothalamus and frontal cortex, ethanol has no effect on the rate of tyrosine hydroxylation in either LS or SS mice during the early period, but ethanol decreases the rate during the later period in the LS mice only.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:6443068

  15. Evidence suggesting a role for hydroxyl radical in gentamicin-induced acute renal failure in rats.

    PubMed Central

    Walker, P D; Shah, S V

    1988-01-01

    The protective effect of hydroxyl radical scavengers and iron chelators has strongly implicated the hydroxyl radical in several models of tissue injury. Based on in vitro studies showing gentamicin-enhanced generation of reactive oxygen metabolites in renal cortical mitochondria, we examined the effect of hydroxyl radical scavengers and iron chelators in gentamicin-induced acute renal failure. Rats treated with gentamicin (G) alone (100 mg/kg, s.c. x 8 d) developed advanced renal failure (BUN 215 +/- 30 mg/dl) compared to saline-treated controls (BUN 16 +/- 1 mg/dl, P less than 0.001). In contrast, rats treated with gentamicin and either dimethylthiourea (DMTU, an hydroxyl radical scavenger, 125 mg/kg, i.p. twice a day) or deferoxamine (DFO, an iron chelator, 20 mg/day by osmotic pump) had significantly lower BUN (G + DMTU 48.8 +/- 8 mg/dl, P less than 0.001, n = 8; G + DFO 30 +/- 7 mg/dl, P less than 0.001, n = 8). In separate experiments, treatment with two other hydroxyl radical scavengers (dimethyl sulfoxide or sodium benzoate) and a second iron chelator (2,3,dihydroxybenzoic acid) had a similar protective effect on renal function (as measured by both BUN and creatinine). In addition, histological evidence of damage was markedly reduced by the interventional agents. Finally, concurrent treatment with DMTU prevented the gentamicin induced increase in renal cortical malondialdehyde content (G: 4.4 +/- 0.2 nmol/mg; G + DMTU: 3.1 +/- 0.2 nmol/mg, P less than 0.0001, n = 8) suggesting that the protective effect of DMTU was related to free radical mechanisms rather than to some other effect. Taken together, these data strongly support a role for hydroxyl radical or a similar oxidant in gentamicin-induced acute renal failure. Images PMID:3123518

  16. Hydroxylation-Dependent Interaction of Substrates to the Von Hippel-Lindau Tumor Suppressor Protein (VHL).

    PubMed

    Heir, Pardeep; Ohh, Michael

    2016-01-01

    Oxygen-dependent hydroxylation of critical proline residues, catalyzed by prolyl hydroxylase (PHD1-3) enzymes, is a crucial posttranslational modification (PTM) within the canonical hypoxia-inducible factor (HIF)-centric cellular oxygen-sensing pathway. Alteration of substrates in this way often leads to proteasomal degradation mediated by the von Hippel-Lindau Tumor Suppressor protein (VHL) containing E3-ubiquitin ligase complex known as ECV (Elongins B/C, CUL2, VHL). Here, we outline in vitro protocols to demonstrate the ability of VHL to bind to a prolyl-hydroxylated substrate. PMID:27581016

  17. Regioselective alkane hydroxylation with a mutant CYP153A6 enzyme

    DOEpatents

    Koch, Daniel J.; Arnold, Frances H.

    2013-01-29

    Cytochrome P450 CYP153A6 from Myobacterium sp. strain HXN1500 was engineered using in-vivo directed evolution to hydroxylate small-chain alkanes regioselectively. Mutant CYP153A6-BMO1 selectively hydroxylates butane and pentane at the terminal carbon to form 1-butanol and 1-pentanol, respectively, at rates greater than wild-type CYP153A6 enzymes. This biocatalyst is highly active for small-chain alkane substrates and the regioselectivity is retained in whole-cell biotransformations.

  18. Whole-Cell Mediated 11β-Hydroxylation on the Basic Limonoid Skeleton by Cunninghamella echinulata.

    PubMed

    Haldar, Saikat; Mulani, Fayaj A; Aarthy, Thiagarayaselvam; Thulasiram, Hirekodathakallu V

    2015-06-19

    Regio- and stereoselective 11β-hydroxylation was achieved on the basic limonoid skeleton through microbial transformation. Whole cells of Cunninghamella echinulata efficiently converted basic limonoids such as epoxyazadiradione, azadiradione, and gedunin to their 11β-hydroxy analogues as the sole metabolite. Fermentation conditions affecting the efficiency (96%) of biotransformation including substrate concentration, incubation period, pH, and temperature were optimized. The position and stereochemistry of hydroxyl functionality on the isolated metabolites were established through extensive spectroscopic and spectrometric studies (1D, 2D NMR, ESI-MS, and MS/MS). PMID:25985231

  19. Black Hydroxylated Titanium Dioxide Prepared via Ultrasonication with Enhanced Photocatalytic Activity

    PubMed Central

    Fan, Chenyao; Chen, Chao; Wang, Jia; Fu, Xinxin; Ren, Zhimin; Qian, Guodong; Wang, Zhiyu

    2015-01-01

    The amorphous TiO2 derived from hydroxylation has become an effective approach for the enhancement of photocatalytic activity of TiO2 since a kind of special black TiO2 was prepared by engineering disordered layers on TiO2 nanocrystals via hydrogenation. In this contribution, we prepared totally amorphous TiO2 with various degrees of blackness by introducing hydroxyls via ultrasonic irradiation, through which can we remarkably enhance the photocatalytic activity of TiO2 with improved light harvesting and narrowed band gap. PMID:26133789

  20. Development of a Concise Synthesis of Ouabagenin and Hydroxylated Corticosteroid Analogues

    PubMed Central

    2016-01-01

    The natural product ouabagenin is a complex cardiotonic steroid with a highly oxygenated skeleton. This full account describes the development of a concise synthesis of ouabagenin, including the evolution of synthetic strategy to access hydroxylation at the C19 position of a steroid skeleton. In addition, approaches to install the requisite butenolide moiety at the C17 position are discussed. Lastly, methodology developed in this synthesis has been applied in the generation of novel analogues of corticosteroid drugs bearing a hydroxyl group at the C19 position. PMID:25594682