Simulated effects of nitrogen saturation the global carbon budget using the IBIS model

USGS Publications Warehouse

Lu, Xuehe; Jiang, Hong; Liu, Jinxun; Zhang, Xiuying; Jin, Jiaxin; Zhu, Qiuan; Zhang, Zhen; Peng, Changhui

2016-01-01

Over the past 100 years, human activity has greatly changed the rate of atmospheric N (nitrogen) deposition in terrestrial ecosystems, resulting in N saturation in some regions of the world. The contribution of N saturation to the global carbon budget remains uncertain due to the complicated nature of C-N (carbon-nitrogen) interactions and diverse geography. Although N deposition is included in most terrestrial ecosystem models, the effect of N saturation is frequently overlooked. In this study, the IBIS (Integrated BIosphere Simulator) was used to simulate the global-scale effects of N saturation during the period 1961–2009. The results of this model indicate that N saturation reduced global NPP (Net Primary Productivity) and NEP (Net Ecosystem Productivity) by 0.26 and 0.03 Pg C yr−1, respectively. The negative effects of N saturation on carbon sequestration occurred primarily in temperate forests and grasslands. In response to elevated CO2 levels, global N turnover slowed due to increased biomass growth, resulting in a decline in soil mineral N. These changes in N cycling reduced the impact of N saturation on the global carbon budget. However, elevated N deposition in certain regions may further alter N saturation and C-N coupling.

Spruce-fir forest changes during a 30-year nitrogen saturation experiment

Treesearch

Steven G. McNulty; Johnny L. Boggs; John D. Aber; Lindsey E. Rustad

2017-01-01

A field experiment was established in a high elevation red spruce (Picea rubens Sarg.) – balsam fir (Abies balsamea) forest on Mount Ascutney Vermont, USA in 1988 to test the nitrogen (N) saturation hypothesis, and to better understand the mechanisms causing forest decline at the time. The study established replicate control, lowand high dose nitrogen addition plots (i...

Effects of ion doping at different sites on electrical properties of multiferroic BiFeO3 ceramics

NASA Astrophysics Data System (ADS)

Yu, Benfang; Li, Meiya; Liu, Jun; Guo, Dongyun; Pei, Ling; Zhao, Xingzhong

2008-03-01

Pure, La3+ doped at A site, V5+ doped at B site, and La3+ and V5+ co-doped multiferroic BiFeO3 ceramics: BiFeO3 (BFO), Bi0.85La0.15FeO3 (BLF), BiFe0.97V0.03O3 (BFV), Bi0.85La0.15Fe0.97V0.03O3 (BLFV), etc were successfully prepared by a rapid liquid sintering technique. X-ray diffraction indicated that these ceramics were of polycrystalline perovskite structures, accompanied with a tiny residual Bi2O3 phase. It was found that, among these ceramics, BLFV ceramic exhibited the best electrical properties. The leakage current density of BLFV ceramic was only 2.1 × 10-6 A cm-2 at 10 kV cm-1, two and one orders of magnitude lower than those of the BLF and BFV ceramics, respectively. In the measuring frequency of 4 KHz-1 MHz, the dielectric constants and losses of this sample exhibited slight variation and the lowest loss tangent was 0.08. The sample had a relatively saturated ferroelectric hysteresis loop. These suggested that the co-doped BiFeO3 ceramic by La3+ and V5+ at A and B sites showed advantages in application over the pure BFO, doped BLF and BFV ceramics, respectively.

Sensitivity analysis of tracer transport in variably saturated soils at USDA-ARS OPE3 field site

USDA-ARS?s Scientific Manuscript database

The objective of this study was to assess the effects of uncertainties in hydrologic and geochemical parameters on the results of simulations of the tracer transport in variably saturated soils at the USDA-ARS OPE3 field site. A tracer experiment with a pulse of KCL solution applied to an irrigatio...

Simulated effects of nitrogen saturation on the global carbon budget using the IBIS model

PubMed Central

Lu, Xuehe; Jiang, Hong; Liu, Jinxun; Zhang, Xiuying; Jin, Jiaxin; Zhu, Qiuan; Zhang, Zhen; Peng, Changhui

2016-01-01

Over the past 100 years, human activity has greatly changed the rate of atmospheric N (nitrogen) deposition in terrestrial ecosystems, resulting in N saturation in some regions of the world. The contribution of N saturation to the global carbon budget remains uncertain due to the complicated nature of C-N (carbon-nitrogen) interactions and diverse geography. Although N deposition is included in most terrestrial ecosystem models, the effect of N saturation is frequently overlooked. In this study, the IBIS (Integrated BIosphere Simulator) was used to simulate the global-scale effects of N saturation during the period 1961–2009. The results of this model indicate that N saturation reduced global NPP (Net Primary Productivity) and NEP (Net Ecosystem Productivity) by 0.26 and 0.03 Pg C yr−1, respectively. The negative effects of N saturation on carbon sequestration occurred primarily in temperate forests and grasslands. In response to elevated CO2 levels, global N turnover slowed due to increased biomass growth, resulting in a decline in soil mineral N. These changes in N cycling reduced the impact of N saturation on the global carbon budget. However, elevated N deposition in certain regions may further alter N saturation and C-N coupling. PMID:27966643

Coniferous coverage as well as catchment steepness influences local stream nitrate concentrations within a nitrogen-saturated forest in central Japan.

PubMed

Watanabe, Mirai; Miura, Shingo; Hasegawa, Shun; Koshikawa, Masami K; Takamatsu, Takejiro; Kohzu, Ayato; Imai, Akio; Hayashi, Seiji

2018-04-28

High concentrations of nitrate have been detected in streams flowing from nitrogen-saturated forests; however, the spatial variations of nitrate leaching within those forests and its causes remain poorly explored. The aim of this study is to evaluate the influences of catchment topography and coniferous coverage on stream nitrate concentrations in a nitrogen-saturated forest. We measured nitrate concentrations in the baseflow of headwater streams at 40 montane forest catchments on Mount Tsukuba in central Japan, at three-month intervals for 1 year, and investigated their relationship with catchment topography and with coniferous coverage. Although stream nitrate concentrations varied from 0.5 to 3.0 mgN L -1 , those in 31 catchments consistently exceeded 1 mgN L -1 , indicating that this forest had experienced nitrogen saturation. A classification and regression tree analysis with multiple environmental factors showed that the mean slope gradient and coniferous coverage were the best and second best, respectively, at explaining inter-catchment variance of stream nitrate concentrations. This analysis suggested that the catchments with steep topography and high coniferous coverage tend to have high nitrate concentrations. Moreover, in the three-year observation period for five adjacent catchments, the two catchments with relatively higher coniferous coverage consistently had higher stream nitrate concentrations. Thus, the spatial variations in stream nitrate concentrations were primarily regulated by catchment steepness and, to a lesser extent, coniferous coverage in this nitrogen-saturated forest. Our results suggest that a decrease in coniferous coverage could potentially contribute to a reduction in nitrate leaching from this nitrogen-saturated forest, and consequently reduce the risk of nitrogen overload for the downstream ecosystems. This information will allow land managers and researchers to develop improved management plans for this and similar

Flexible nitrogen-doped graphene/carbon nanotube/Co3O4 paper and its oxygen reduction activity

NASA Astrophysics Data System (ADS)

Li, Shan-Shan; Cong, Huai-Ping; Wang, Ping; Yu, Shu-Hong

2014-06-01

Due to the demand of an efficient, inexpensive and scalable synthesis of oxygen reduction reaction (ORR) catalyst for practical application in fuel cell, we demonstrate a facile strategy to fabricate the flexible nitrogen-doped graphene/carbon nanotube/Co3O4 (NG/CNT/Co3O4) paper catalyst. In the hydrothermal process, the in situ formation of Co3O4 nanoparticles, reduction of GO and doping of nitrogen species occur simultaneously in the assembled paper in ammonia solution. Because of the synergistic effects of three active components and the spacing effect of CNTs and Co3O4 nanoparticles on avoiding the re-aggregation of assembled graphene nanosheets, the free-standing NG/CNT/Co3O4 paper exhibits an enhanced ORR catalytic performance with stable durability and strong methanol-tolerant capability, indicating promising potential as ORR electrocatalyst in practical applications.Due to the demand of an efficient, inexpensive and scalable synthesis of oxygen reduction reaction (ORR) catalyst for practical application in fuel cell, we demonstrate a facile strategy to fabricate the flexible nitrogen-doped graphene/carbon nanotube/Co3O4 (NG/CNT/Co3O4) paper catalyst. In the hydrothermal process, the in situ formation of Co3O4 nanoparticles, reduction of GO and doping of nitrogen species occur simultaneously in the assembled paper in ammonia solution. Because of the synergistic effects of three active components and the spacing effect of CNTs and Co3O4 nanoparticles on avoiding the re-aggregation of assembled graphene nanosheets, the free-standing NG/CNT/Co3O4 paper exhibits an enhanced ORR catalytic performance with stable durability and strong methanol-tolerant capability, indicating promising potential as ORR electrocatalyst in practical applications. Electronic supplementary information (ESI) available: XRD patterns, elemental mapping images, DSC-TGA curves and XPS spectrum of NG/CNT/Co3O4 paper; SEM images and XPS spectra of NG/Co3O4 paper; RDE curves and corresponding

A case study of nitrogen saturation in western U.S. forests

Treesearch

Mark E. Fenn; Mark A. Poth

2001-01-01

Virtually complete nitrification of the available ammonium in soil and nitrification activity in the forest floor are important factors predisposing forests in the San Bernardino Mountains of southern California to nitrogen (N) saturation. As a result, inorganic N in the soil solution is dominated by nitrate. High nitrification rates also generate elevated nitric oxide...

Oxides of nitrogen at two sites in New Zealand

NASA Astrophysics Data System (ADS)

Stedman, D. H.; McEwan, M. J.

1983-02-01

Oxides of nitrogen, ozone and solar UV radiation were measured at two New Zealand sites, four months at Mt. John near Lake Tekapo, and one month at the New Zealand Department of scientific and Industrial Research, Physics and Engineering Laboratory Atmospheric Station (PELAS) near Lauder. The former site proved ideal for clean-air measurements. Ozone concentrations of ˜20-25 ppb, with little diurnal variation were accompanied by total nitrogen oxide (NOy) levels frequently less than 150 ppt (parts in 1012 by volume). The noon NO and NO2 data were well correlated with a slope comparable to model values. Gaseous HNO3 was observed to be significantly above the noise level (˜15 ppt) for only twenty-seven four-hour averages. For these a median of 43 ppt was obtained with a median ([NOy]-[HNO3])/[HNO3] ratio of 7.5, not comparable with model values of around 1.1. This low HNO3 may arise from the fact that the Mt. John site is downwind of a mountain range which experiences significant upwind precipitation. At the PELAS site, strong diurnal variation of ozone and much larger NOy concentrations were observed. The difference is apparently caused by local sources of nitrogen oxides and the local meteorology at the fertile valley PELAS site.

Nitrogen transport and transformations in a shallow aquifer receiving wastewater discharge: A mass balance approach

USGS Publications Warehouse

Desimone, Leslie A.; Howes, Brian L.

1998-01-01

Nitrogen transport and transformations were followed over the initial 3 years of development of a plume of wastewater-contaminated groundwater in Cape Cod, Massachusetts. Ammonification and nitrification in the unsaturated zone and ammonium sorption in the saturated zone were predominant, while loss of fixed nitrogen through denitrification was minor. The major effect of transport was the oxidation of discharged organic and inorganic forms to nitrate, which was the dominant nitrogen form in transit to receiving systems. Ammonification and nitrification in the unsaturated zone transformed 16–19% and 50–70%, respectively, of the total nitrogen mass discharged to the land surface during the study but did not attenuate the nitrogen loading. Nitrification in the unsaturated zone also contributed to pH decrease of 2 standard units and to an N2O increase (46–660 µg N/L in the plume). Other processes in the unsaturated zone had little net effect: Ammonium sorption removed <1% of the total discharged nitrogen mass; filtering of particulate organic nitrogen was less than 3%; ammonium and nitrate assimilation was less than 6%; and ammonia volatilization was less than 0.25%. In the saturated zone a central zone of anoxic groundwater (DO ≤ 0.05 mg/L) was first detected 17 months after effluent discharge to the aquifer began, which expanded at about the groundwater-flow velocity. Although nitrate was dominant at the water table, the low, carbon-limited rates of denitrification in the anoxic zone (3.0–9.6 (ng N/cm3)/d) reduced only about 2% of the recharged nitrogen mass to N2. In contrast, ammonium sorption in the saturated zone removed about 16% of the recharged nitrogen mass from the groundwater. Ammonium sorption was primarily limited to anoxic zone, where nitrification was prevented, and was best described by a Langmuir isotherm in which effluent ionic concentrations were simulated. The initial nitrogen load discharged from the groundwater system may depend

Assessing the extent of nitrogen saturation in northern West Virginia forested watersheds: a survey of stream nitrate concentrations

Treesearch

Karl W. J. Williard; David R. DeWalle; Pamela J. Edwards

2003-01-01

Twenty-seven forested watersheds in northern West Virginia were sampled for stream nitrate concentrations during summer 1997 and fall 1998 baseflow periods to determine if Fernow watershed 4, an often-cited and studied nitrogen saturated basin, was anomalous or regionally representative in terms of stream nitrate levels. Baseflow stream NO3-N...

Evaluation of ozone, nitrogen dioxide, and carbon monoxide at nine sites in Saudi Arabia during 2007.

PubMed

Butenhoff, Christopher L; Khalil, M Aslam K; Porter, William C; Al-Sahafi, Mohammed Saleh; Almazroui, Mansour; Al-Khalaf, Abdulrahman

2015-07-01

This paper presents a one-year record of in situ air-quality data from nine sites throughout Saudi Arabia. The data set is composed of hourly measurements of ozone (O3), nitrogen dioxide (NO2), and carbon monoxide (CO) at six of the largest cities in Saudi Arabia (Riyadh, Jeddah, Makkah, Yanbu, Dammam, Hafouf) and two remote locations in the mountainous southwestern region of Alsodah for the year 2007. The authors found that international O3 and CO standards were routinely exceeded throughout the year at many sites, and that exceedances increased during Ramadan (Sep. 12-Oct. 13), the Islamic month of fasting when much of normal daily activity is shifted to nighttime hours. In general NO2 and CO levels were higher in Saudi cities compared to U.S. cities of comparable population, while O3 levels were lower. There was a general trend for O3 and NO2 to be negatively correlated in Saudi cities in contrast to U.S. cities where the correlation is positive, suggesting that ozone chemistry in Saudi Arabia is limited by volatile organic compound emissions. This may be caused by low biogenic emissions from vegetation. Pollutant levels were lower at most Saudi sites during the four day Hajj period (Dec. 18-21) but higher in Makkah which receives millions of visitors during Hajj. The authors also found that ozone levels were elevated during the weekend (Thursday & Friday) relative to weekday levels despite lower NO2, a phenomenon known as the "weekend effect." As little air quality data is available from Saudi Arabia in the English-language literature, this data set fills a knowledge gap and improves understanding of air quality in an important but under-reported region of the world. Air quality measurements at nine sites in Saudi Arabia provide a detailed look at spatial and temporal patterns of ozone (O3), nitrogen dioxide (NO2), and carbon monoxide (CO). NO2 and CO levels increased in most cities during the fasting month of Ramadan, whereas O3 levels decreased. This led to

Effect of Iron Redox Equilibrium on the Foaming Behavior of MgO-Saturated Slags

NASA Astrophysics Data System (ADS)

Park, Youngjoo; Min, Dong Joon

2018-04-01

In this study, the foaming index of CaO-SiO2-FetO and CaO-SiO2-FetO-Al2O3 slags saturated with MgO was measured to understand the relationship between their foaming behavior and physical properties. The foaming index of MgO-saturated slags increases with the FetO content due to the redox equilibrium of FetO. Experimental results indicated that MgO-saturated slag has relatively high ferric ion concentration, and the foaming index increases due to the effect of ferric ion. Therefore, the foaming behavior of MgO-saturated slag is more reasonably explained by considering the effect of ferric ion on the estimation of slag properties such as viscosity, surface tension, and density. Specifically, the estimation of slag viscosity was additionally verified by NBO/T, and this is experimentally obtained through Raman spectroscopy.

Characteristics of surface ozone and nitrogen oxides at urban, suburban and rural sites in Ningbo, China

NASA Astrophysics Data System (ADS)

Tong, Lei; Zhang, Huiling; Yu, Jie; He, Mengmeng; Xu, Nengbin; Zhang, Jingjing; Qian, Feizhong; Feng, Jiayong; Xiao, Hang

2017-05-01

Surface ozone (O3) is a harmful air pollutant that has attracted growing concern in China. In this study, the mixing ratios of O3 and nitrogen oxides (NOx) at three different sites (urban, suburban and rural) of Ningbo were continuously measured to investigate the spatiotemporal characteristics of O3 and its relationships with environmental variables. The diurnal O3 variations were characterized by afternoon maxima (38.7-53.1 ppb on annual average) and early morning minima (11.7-26.2 ppb) at all the three sites. Two seasonal peaks of O3 were observed in spring (April or May) and autumn (October) with minima being observed in winter (December). NOx levels showed generally opposite variations to that of O3 with diurnal and seasonal maxima occurring in morning/evening rush-hours and in winter, respectively. As to the inter-annual variations of air pollutants, generally decreasing and increasing trends were observed in NO and O3 levels, respectively, from 2012 to 2015 at both urban and suburban sites. O3 levels were positively correlated with temperature but negatively correlated with relative humidity and NOx levels. Significant differences in O3 levels were observed for different wind speeds and wind directions (p < 0.001). O3 levels varied non-linearly with wind speed ranges with an increasing trend within 4 m/s. Higher mixing ratio of O3 was observed for wind blowing from the sea, which indicates that the coastal air mass might carry more O3. A decreasing trend in O3 levels was observed from weekdays to weekends at all the three sites. As to the spatial variation, higher levels of O3 were observed at the suburban and rural sites where less O3 was depleted by NO titration. In contrast, the urban site exhibited lower O3 but higher NOx levels due to the influence of traffic emissions. Larger amplitudes of diurnal and monthly O3 variations were observed at the suburban site than those at the urban and rural sites. In general, the O3 levels at the non-urban sites were

Effects of silvicultural practices on soil carbon and nitrogen in a nitrogen saturated central Appalachian (USA) hardwood forest ecosystem

Treesearch

Frank S. Gilliam; David A. Dick; Michelle L. Kerr; Mary Beth Adams

2004-01-01

Silvicultural treatments represent disturbances to forest ecosystems often resulting in transient increases in net nitrification and leaching of nitrate and base cations from the soil. Response of soil carbon (C) is more complex, decreasing from enhanced soil respiration and increasing from enhanced postharvest inputs of detritus. Because nitrogen (N) saturation can...

One pot synthesis of ilmenite-type NiMnO3-"nitrogen-doped" graphene nanocomposite as next generation supercapacitors.

PubMed

Giri, Soumen; Ghosh, Debasis; Das, Chapal Kumar

2013-10-28

NiMnO3-nitrogen doped graphene composite has been synthesized by a simple hydrothermal method and its supercapacitor performance investigated. The composite exhibits a specific capacitance of 750.2 F g(-1) in 1 M Na2SO4 at a scan rate of 1 mV s(-1). Nitrogen insertion inside the carbon lattice plays a crucial role in the enhancement of the overall specific capacitance and its long-term stability. This reproducible and superior performance of NiMnO3-nitrogen doped graphene composite make it attractive as a candidate for energy storage materials.

Eddy covariance fluxes of the NO-O3-NO2 triad above the forest canopy at the ATTO Site in the Amazon Basin

NASA Astrophysics Data System (ADS)

Tsokankunku, Anywhere; Wolff, Stefan; Sörgel, Matthias; Berger, Martina; Zelger, Michael; Dlugi, Ralf

2017-04-01

Nitrogen monoxide (NO) and nitrogen dioxide (NO2) (denoted together as NOx) determine the abundance of the tropospheric oxidants OH, O3 and NO3 that regulate atmospheric self-cleaning. The three reactive trace gases NO, NO2 and O3 undergo a series of interconnected photochemical reactions and are often referred to as the NO-O3-NO2 triad. Ozone deposition is mainly controlled by stomatal uptake, thus contributes to oxidative stress for the plants. Similarly, nitrogen dioxide from above or below the canopy is deposited to leaves through stomatal uptake. NO emissions from soils contribute to above canopy O3 formation and accelerate OH recycling. Therefore, quantification of the exchange fluxes of these species between the atmosphere and the biosphere are important for atmospheric chemistry and ecosystem research as well. The eddy covariance method is state of the art for direct measurements of ecosystem fluxes of trace gases. Eddy covariance measurements of NOx in pristine environments are rare because of lack of availability of instruments with the required precision to resolve concentrations characteristic of these environments. The Amazon Tall Tower Observatory (ATTO) is located in a pristine rainforest environment in the Amazon basin about 150 km northeast of the city of Manaus. It is the ideal site for studying the biosphere-atmosphere exchange of the NO-O3-NO2 triad, being largely undisturbed by anthropogenic sources. During an intensive measurement campaign in November 2015 at the ATTO site, measurements of NO, NO2 and O3 were carried out at 42 m above ground level on the 80 m walk-up tower with a fast (5 Hz) and sensitive (< 30 ppt) instrument (CLD790SR2, Eco Physics) for NO and NO2 and with 10 Hz for O3 (Enviscope). Additionally, measurements of turbulent and micrometeorological parameters were conducted with a profile of 3-dimensional sonic anemometers and meteorological sensors for temperature, humidity and radiation. Vertical concentration profile

Site energy distribution analysis and influence of Fe3O4 nanoparticles on sulfamethoxazole sorption in aqueous solution by magnetic pine sawdust biochar.

PubMed

Reguyal, Febelyn; Sarmah, Ajit K

2018-02-01

Magnetisation of carbonaceous adsorbents using iron oxides has been found to be one of the potential solutions for easy recovery of adsorbent after use. We evaluated the effects of Fe 3 O 4 nanoparticle addition on the physico-chemical properties of biochar and its sorption properties. Five adsorbents with varying amount of Fe 3 O 4 per mass of adsorbent (0%, 25%, 50%, 75% and 100%) were used to adsorb sulfamethoxazole (SMX), an emerging micropollutant. Five isotherm models were used to evaluate the sorption behaviour of SMX onto the adsorbents where Redlich-Peterson model was found to best describe the data. Based on this model, the approximate site energy distribution for each adsorbent was determined. Surface area and sorption capacity had strong negative linear relationship with the amount of Fe 3 O 4 per mass of adsorbent while the pore volume and saturation magnetisation of the adsorbent increased with increasing percentage of Fe 3 O 4 . The results of the approximate site energy distribution analysis showed that the addition of Fe 3 O 4 on biochar reduced the area under the frequency distribution curve of sorption site energies leading to the lowering of the sorption sites available for SMX. This could be attributed to the blockage of the hydrophobic surface of biochar reducing the hydrophobic interaction between SMX and biochar. Copyright © 2017 Elsevier Ltd. All rights reserved.

A-site cationic disorder induced significantly large magnetoresistance in polycrystalline La0.2Gd0.5Ba0.3MnO3 compound

NASA Astrophysics Data System (ADS)

Saha, Suvayan; Das, Kalipada; Bandyopadhyay, Sudipta; Das, I.

2017-11-01

The observation of significantly large magnetoresistance at the liquid nitrogen temperature range in the polycrystalline La0.2Gd0.5Ba0.3MnO3 (LGBMO) compound has been addressed in the present manuscript. The motivation of considering LGBMO sample is the average 'A' site ionic radius 〈rA 〉 and tolerance factor (t), almost same as that of La0.7Sr0.3MnO3 (LSMO), which is a well studied colossal magnetoresistive material. Magnetoresistance of the LGBMO compound has been compared with the LSMO as well as parent compound La0.7Ba0.3MnO3(LBMO) to show the enhancement of magnetoresistance in LGBMO compound. This observed nature has been elucidated considering the disorder induced short range magnetic interaction due to the enhance size disorder parameter (σ2). Our study revels that, size disorder parameter plays the crucial role for enhancing the colossal magnetoresistance.

Eddy Covariance Fluxes of the NO-O3-NO2 Triad above the Forest Canopy at the ATTO Site in the Amazon Basin

NASA Astrophysics Data System (ADS)

Tsokankunku, A.; Wolff, S.; Berger, M.; Zelger, M.; Dlugi, R. J. W.; Andreae, M. O.; Sörgel, M.

2017-12-01

Nitrogen monoxide (NO) and nitrogen dioxide (NO2) (denoted together as NOx) determine the abundance of the tropospheric oxidants OH, O3 and NO3 that regulate atmospheric self-cleaning. The three reactive trace gases NO, NO2 and O3 undergo a series of interconnected photochemical reactions and are therefore often referred to as the NO-O3-NO2 triad. Ozone deposition is mainly controlled by stomatal uptake, therefore resulting in oxidative stress for the plants. Similarly, nitrogen dioxide from above or below the canopy is deposited to leaves through stomatal uptake. NO emissions from soils contribute to above canopy O3 formation and accelerate OH recycling. Therefore, quantification of the biosphere-atmosphere exchange fluxes of these species is important for atmospheric chemistry and ecosystem research. The eddy covariance method is state of the art for direct measurements of ecosystem fluxes of trace gases. Eddy covariance measurements of NOx in pristine environments are rare because of lack of availability of instruments with the required precision to resolve concentrations characteristic of these environments with the required high time resolution. The Amazon Tall Tower Observatory (ATTO) is located in a pristine rainforest environment in the Amazon basin about 150 km northeast of the city of Manaus. It is the ideal site for studying the biosphere-atmosphere exchange of the NO-O3-NO2 triad, because of the absence of nearby anthropogenic sources. During an intensive measurement campaign in November 2015 at the ATTO site, measurements of NO, NO2 and O3 were carried out at 42 m above ground level on the 80 m walk-up tower with a fast (5 Hz) and sensitive (< 30 ppt) instrument (CLD790SR2, Eco Physics) for NO and NO2 and with 10 Hz for O3 (Enviscope GmbH). Additionally, a suite of micrometeorological instruments was installed, including a profile of 3-dimensional sonic anemometers and meteorological sensors. Vertical concentration profile measurements of NO, NO2 and O

Co@Co3O4 nanoparticle embedded nitrogen-doped carbon architectures as efficient bicatalysts for oxygen reduction and evolution reactions

NASA Astrophysics Data System (ADS)

Qi, Chunling; Zhang, Li; Xu, Guancheng; Sun, Zhipeng; Zhao, Aihua; Jia, Dianzeng

2018-01-01

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play crucial roles in efficient energy conversion and storage solutions. Here, Co@Co3O4 nanoparticle embedded nitrogen-doped carbon architectures (denoted as Co@Co3O4/NCs) are prepared via a simple two-step and in situ approach by carbonization and subsequent oxidation of Co-MOF containing high contents of carbon and nitrogen. When evaluated as electrocatalyst towards both ORR and OER in a KOH electrolyte solution, the as-fabricated Co@Co3O4/NC-2 exhibits similar ORR catalytic activity to the commercial Pt/C catalyst, but superior stability and good methanol tolerance. Furthermore, the as-fabricated catalysts also show promising catalytic activity for OER. The effective catalytic activities originate from the synergistic effects between well wrapped Co@Co3O4 nanoparticles and nitrogen doped carbon structures.

Biofilter design for effective nitrogen removal from stormwater - influence of plant species, inflow hydrology and use of a saturated zone.

PubMed

Payne, Emily G I; Pham, Tracey; Cook, Perran L M; Fletcher, Tim D; Hatt, Belinda E; Deletic, Ana

2014-01-01

The use of biofilters to remove nitrogen and other pollutants from urban stormwater runoff has demonstrated varied success across laboratory and field studies. Design variables including plant species and use of a saturated zone have large impacts upon performance. A laboratory column study of 22 plant species and designs with varied outlet configuration was conducted across a 1.5-year period to further investigate the mechanisms and influences driving biofilter nitrogen processing. This paper presents outflow concentrations of total nitrogen from two sampling events across both 'wet' and 'dry' frequency dosing, and from sampling across two points in the outflow hydrograph. All plant species were effective under conditions of frequent dosing, but extended drying increased variation between species and highlighted the importance of a saturated zone in maintaining biofilter function. The saturated zone also effectively treated the volume of stormwater stored between inflow events, but this extended detention provided no additional benefit alongside the rapid processing of the highest performing species. Hence, the saturated zone reduced performance differences between plant species, and potentially acts as an 'insurance policy' against poor sub-optimal plant selection. The study shows the importance of biodiversity and inclusion of a saturated zone in protecting against climate variability.

Modelling carbon and nitrogen turnover in variably saturated soils

NASA Astrophysics Data System (ADS)

Batlle-Aguilar, J.; Brovelli, A.; Porporato, A.; Barry, D. A.

2009-04-01

Natural ecosystems provide services such as ameliorating the impacts of deleterious human activities on both surface and groundwater. For example, several studies have shown that a healthy riparian ecosystem can reduce the nutrient loading of agricultural wastewater, thus protecting the receiving surface water body. As a result, in order to develop better protection strategies and/or restore natural conditions, there is a growing interest in understanding ecosystem functioning, including feedbacks and nonlinearities. Biogeochemical transformations in soils are heavily influenced by microbial decomposition of soil organic matter. Carbon and nutrient cycles are in turn strongly sensitive to environmental conditions, and primarily to soil moisture and temperature. These two physical variables affect the reaction rates of almost all soil biogeochemical transformations, including microbial and fungal activity, nutrient uptake and release from plants, etc. Soil water saturation and temperature are not constants, but vary both in space and time, thus further complicating the picture. In order to interpret field experiments and elucidate the different mechanisms taking place, numerical tools are beneficial. In this work we developed a 3D numerical reactive-transport model as an aid in the investigation the complex physical, chemical and biological interactions occurring in soils. The new code couples the USGS models (MODFLOW 2000-VSF, MT3DMS and PHREEQC) using an operator-splitting algorithm, and is a further development an existing reactive/density-dependent flow model PHWAT. The model was tested using simplified test cases. Following verification, a process-based biogeochemical reaction network describing the turnover of carbon and nitrogen in soils was implemented. Using this tool, we investigated the coupled effect of moisture content and temperature fluctuations on nitrogen and organic matter cycling in the riparian zone, in order to help understand the relative

Highly dispersed SiO x/Al 2O 3 catalysts illuminate the reactivity of isolated silanol sites

DOE PAGES

Mouat, Aidan R.; George, Cassandra; Kobayashi, Takeshi; ...

2015-09-23

The reaction of γ-alumina with tetraethylorthosilicate (TEOS) vapor at low temperatures selectively yields monomeric SiO x species on the alumina surface. These isolated (-AlO) 3Si(OH) sites are characterized by PXRD, XPS, DRIFTS of adsorbed NH 3, CO, and pyridine, and 29Si and 27Al DNP-enhanced solid-state NMR spectroscopy. The formation of isolated sites suggests that TEOS reacts preferentially at strong Lewis acid sites on the γ-Al 2O 3 surface, functionalizing the surface with “mild” Brønsted acid sites. As a result, for liquid-phase catalytic cyclohexanol dehydration, these SiO x sites exhibit up to 3.5-fold higher specific activity than the parent alumina withmore » identical selectivity.« less

Preparation of raspberry-like γ-Fe2O3/crackled nitrogen-doped carbon capsules and their application as supports to improve catalytic activity.

PubMed

Zhang, Junshuai; Yao, Tongjie; Zhang, Hui; Zhang, Xiao; Wu, Jie

2016-11-10

In this manuscript, we have introduced a novel method to improve the catalytic activity of metal nanoparticles via optimizing the support structure. To this end, raspberry-like γ-Fe 2 O 3 /crackled nitrogen-doped carbon (CNC) capsules were prepared by a two-step method. Compared with traditional magnetic capsules, in γ-Fe 2 O 3 /CNC capsules, the γ-Fe 2 O 3 nanoparticles were embedded in a CNC shell; therefore, they neither occupied the anchoring sites for metal nanoparticles nor came into contact with them, which was beneficial for increasing the metal nanoparticle loading. Numerous tiny cracks appeared on the porous CNC shell, which effectively improved the mass diffusion and transport in catalytic reactions. Additionally, the coordination interaction could be generated between the precursor metal ions and doped-nitrogen atoms in the capsule shell. With the help of these structural merits, γ-Fe 2 O 3 /CNC capsules were ideal supports for Pd nanoparticles, because they were beneficial for improving the Pd loading, reducing the nanoparticle size, increasing their dispersity and maximizing the catalytic performance of Pd nanoparticles anchored on the inner shell surface. As expected, γ-Fe 2 O 3 /CNC@Pd catalysts exhibited a dramatically enhanced catalytic activity towards hydrophilic 4-nitrophenol and hydrophobic nitrobenzene. The reaction rate constant k was compared with recent work and the corresponding reference samples. Moreover, they could be easily recycled by using a magnet and reused without an obvious loss of catalytic activity.

Experimental, in-situ carbon solution mechanisms and isotope fractionation in and between (C-O-H)-saturated silicate melt and silicate-saturated (C-O-H) fluid to upper mantle temperatures and pressures

NASA Astrophysics Data System (ADS)

Mysen, Bjorn

2017-02-01

Our understanding of materials transport processes in the Earth relies on characterizing the behavior of fluid and melt in silicate-(C-O-H) systems at high temperature and pressure. Here, Raman spectroscopy was employed to determine structure of and carbon isotope partitioning between melts and fluids in alkali aluminosilicate-C-O-H systems. The experimental data were recorded in-situ while the samples were at equilibrium in a hydrothermal diamond anvil cell at temperatures and pressures to 825 °C and >1300 MPa, respectively. The carbon solution equilibrium in both (C-O-H)-saturated melt and coexisting, silicate-saturated (C-O-H) fluid is 2CO3 + H2O + 2Qn + 1 = 2HCO3 + 2Qn. In the Qn-notation, the superscript, n, is the number of bridging oxygen in silicate structural units. At least one oxygen in CO3 and HCO3 groups likely is shared with silicate tetrahedra. The structural behavior of volatile components described with this equilibrium governs carbon isotope fractionation factors between melt and fluid. For example, the ΔH equals 3.2 ± 0.7 kJ/mol for the bulk 13C/12C exchange equilibrium between fluid and melt. From these experimental data, it is suggested that at deep crustal and upper mantle temperatures and pressures, the δ13C-differences between coexisting silicate-saturated (C-O-H) fluid and (C-O-H)-saturated silicate melts may change by more than 100‰ as a function of temperature in the range of magmatic processes. Absent information on temperature and pressure, the use of carbon isotopes of mantle-derived magma to derive isotopic composition of magma source regions in the Earth's interior, therefore, should be exercised with care.

Zn2+ in-situ substitution behavior during the formation of BaTiO3 coatings from plasma-sprayed powders collected in liquid nitrogen

NASA Astrophysics Data System (ADS)

Liu, Zhe; Xing, Zhiguo; Wang, Haidou; Xue, Zifan; Chen, Shuying; Cui, Xiufang; Jin, Guo

2018-04-01

The dielectric performance of BaTiO3 ceramic coatings is enhanced significantly by the addition of ZnO. In this study, the maximum relative permittivity value (εr ≈ 923) was measured in BaTiO3 coatings with ZnO added at 6 wt%. The Curie temperature (Tc) was in the range of 111 °C-121 °C for all of the ZnO-modified BaTiO3 coatings. Tc shifted to low temperatures as the ZnO content increased. Detailed analyses were performed to determine the phase composition and optical band gaps of powders collected in liquid nitrogen, which showed that the Zn2+ ions were incorporated into the BaTiO3 lattice where they substituted into the Ti4+ sites, and the composite powders (BaTiO3 + 6 wt% ZnO) tolerated high temperatures in the plasma beam. In addition, some residual Zn accumulated in the grain boundary in the form of ZnO. X-ray diffraction and Raman spectroscopy showed that the substitution led to changes in the compositional and structural properties. The red shift in the optical band gap of BaTiO3 indicated that the ZnTi'' defects caused by the dopants acted as carriers in the doped BaTiO3 coatings.

Two classes of binding sites for [3H]substance P in rat cerebral cortex.

PubMed

Geraghty, D P; Burcher, E

1993-01-22

The binding characteristics of [3H]substance P ([3H]SP) were investigated in membranes prepared from rat cerebral cortex. Binding of [3H]SP reached equilibrium after 50 min at 25 degrees C and was saturable at 8 nM. Saturation data could be resolved into high affinity (equilibrium dissociation constant, Kd, 0.22 nM) and low affinity sites (Kd, 2.65 nM). The low affinity sites were more numerous than the high affinity sites, with a ratio of 4:1. The non-hydrolyzable GTP analogue GppNHp had no effect on binding, indicating that the high and low affinity sites are not guanine nucleotide-regulated states of the same (NK-1) receptor. The low affinity sites are unlikely to represent NK-3 receptors since coincubation with the selective NK-3 receptor agonist senktide did not alter the biphasic nature of [3H]SP binding. The rank order of potency for inhibition of [3H]SP (2 nM) binding was SP > or = [Sar9, Met(O2)11]-SP > or = physalaemin > SP(3-11) > NP gamma = [Ala3]-SP > or = SP(4-11) > or = NPK > or = SP(5-11) > or = NKB approximately NKA > SP(1-9), compatible with binding to an NK-1 site. N-terminal fragments and non-amidated analogues were ineffective competitors for [3H]SP binding. However, competition data for several peptides including substance P (SP) and the NK-1 selective agonist [Sar9, Met(O2)11]-SP could be resolved into two components.(ABSTRACT TRUNCATED AT 250 WORDS)

Antiferromagnetic interaction between A'-site Mn spins in A-site-ordered perovskite YMn3Al4O12.

PubMed

Tohyama, Takenori; Saito, Takashi; Mizumaki, Masaichiro; Agui, Akane; Shimakawa, Yuichi

2010-03-01

The A-site-ordered perovskite YMn(3)Al(4)O(12) was prepared by high-pressure synthesis. Structural analysis with synchrotron powder X-ray diffraction data and the Mn L-edges X-ray absorption spectrum revealed that the compound has a chemical composition Y(3+)Mn(3+)(3)Al(3+)(4)O(2-)(12) with magnetic Mn(3+) at the A' site and non-magnetic Al(3+) at the B site. An antiferromagnetic interaction between the A'-site Mn(3+) spins is induced by the nearest neighboring Mn-Mn direct exchange interaction and causes an antiferromagnetic transition at 34.3 K.

Anchorage of γ-Al 2O 3 nanoparticles on nitrogen-doped multiwalled carbon nanotubes

DOE PAGES

Rodríguez-Pulido, A.; Martínez-Gutiérrez, H.; Calderon-Polania, G. A.; ...

2016-06-07

Nitrogen-doped multiwalled carbon nanotubes (CNx-MWNTs) have been decorated with γ-Al 2O 3 nanoparticles by a novel method. This process involved a wet chemical approach in conjunction with thermal treatment. During the particle anchoring process, individual CNx-MWNT nanotubes agglomerated into bundles, resulting in arrays of aligned CNx-MWNT coated with γ-Al 2O 3. Extensive characterization of the resulting γ-Al 2O 3/CNx-MWNT bundles was performed using a range of electron microscopy imaging and microanalytical techniques. In conclusion, a possible mechanism explaining the nanobundle alignment is described, and possible applications of these materials for the fabrication of ceramic composites using CNx-MWNTs are briefly discussed.

Effective nitrogen doping into TiO2 (N-TiO2) for visible light response photocatalysis.

PubMed

Yoshida, Tomoko; Niimi, Satoshi; Yamamoto, Muneaki; Nomoto, Toyokazu; Yagi, Shinya

2015-06-01

The thickness-controlled TiO2 thin films are fabricated by the pulsed laser deposition (PLD) method. These samples function as photocatalysts under UV light irradiation and the reaction rate depends on the TiO2 thickness, i.e., with an increase of thickness, it increases to the maximum, followed by decreasing to be constant. Such variation of the reaction rate is fundamentally explained by the competitive production and annihilation processes of photogenerated electrons and holes in TiO2 films, and the optimum TiO2 thickness is estimated to be ca. 10nm. We also tried to dope nitrogen into the effective depth region (ca. 10nm) of TiO2 by an ion implantation technique. The nitrogen doped TiO2 enhanced photocatalytic activity under visible-light irradiation. XANES and XPS analyses indicated two types of chemical state of nitrogen, one photo-catalytically active N substituting the O sites and the other inactive NOx (1⩽x⩽2) species. In the valence band XPS spectrum of the high active sample, the additional electronic states were observed just above the valence band edge of a TiO2. The electronic state would be originated from the substituting nitrogen and be responsible for the band gap narrowing, i.e., visible light response of TiO2 photocatalysts. Copyright © 2015 Elsevier Inc. All rights reserved.

Upper limit for the effect of elastic bending stress on the saturation magnetization of L a 0.8 S r 0.2 Mn O 3

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

Wang, Qiang; Chen, A. P.; Guo, Erjia J.

In this study, using polarized neutron reflectometry, we measured the influence of elastic bending stress on the magnetization depth profile of a La 0.8Sr 0.2MnO 3 (LSMO) epitaxial film grown on a SrTiO 3 substrate. The elastic bending strain of ±0.03% has no obvious effect on the magnetization depth profile at saturation. This result is in stark contrast to that of (La 1-xPr x)1-yCayMnO 3 (LPCMO) films for which strain of ±0.01% produced dramatic changes in the magnetization profile and Curie temperature. We attribute the difference between the influence of strain on the saturation magnetization in LSMO (weak or none)more » and LPCMO (strong) to a difference in the ability of LSMO (weak or none) and LPCMO (strong) to phase separate. Our observation provides an upper limit of tuning LSMO saturation magnetization via elastic strain effect.« less

Upper limit for the effect of elastic bending stress on the saturation magnetization of L a 0.8 S r 0.2 Mn O 3

DOE PAGES

Wang, Qiang; Chen, A. P.; Guo, Erjia J.; ...

2018-01-31

In this study, using polarized neutron reflectometry, we measured the influence of elastic bending stress on the magnetization depth profile of a La 0.8Sr 0.2MnO 3 (LSMO) epitaxial film grown on a SrTiO 3 substrate. The elastic bending strain of ±0.03% has no obvious effect on the magnetization depth profile at saturation. This result is in stark contrast to that of (La 1-xPr x)1-yCayMnO 3 (LPCMO) films for which strain of ±0.01% produced dramatic changes in the magnetization profile and Curie temperature. We attribute the difference between the influence of strain on the saturation magnetization in LSMO (weak or none)more » and LPCMO (strong) to a difference in the ability of LSMO (weak or none) and LPCMO (strong) to phase separate. Our observation provides an upper limit of tuning LSMO saturation magnetization via elastic strain effect.« less

Upper limit for the effect of elastic bending stress on the saturation magnetization of L a0.8S r0.2Mn O3

NASA Astrophysics Data System (ADS)

Wang, Q.; Chen, A. P.; Guo, E. J.; Roldan, M. A.; Jia, Q. X.; Fitzsimmons, M. R.

2018-01-01

Using polarized neutron reflectometry, we measured the influence of elastic bending stress on the magnetization depth profile of a L a0.8S r0.2Mn O3 (LSMO) epitaxial film grown on a SrTi O3 substrate. The elastic bending strain of ±0.03 % has no obvious effect on the magnetization depth profile at saturation. This result is in stark contrast to that of (L a1 -xP rx)1 -y C ayMn O3 (LPCMO) films for which strain of ±0.01 % produced dramatic changes in the magnetization profile and Curie temperature. We attribute the difference between the influence of strain on the saturation magnetization in LSMO (weak or none) and LPCMO (strong) to a difference in the ability of LSMO (weak or none) and LPCMO (strong) to phase separate. Our observation provides an upper limit of tuning LSMO saturation magnetization via elastic strain effect.

Comparison of N2O Emissions from Soils at Three Temperate Agricultural Sites

NASA Technical Reports Server (NTRS)

Frolking, S. E.; Moiser, A. R.; Ojima, D. S.; Li, C.; Parton, W. J.; Potter, C. S.; Priesack, E.; Stenger, R.; Haberbosch, C.; Dorsch, P.;

Electric-field control of magnetic properties for α-Fe2O3/Al2O3 films

NASA Astrophysics Data System (ADS)

Cheng, Bin; Qin, Hongwei; Liu, Liang; Xie, Jihao; Zhou, Guangjun; Chen, Lubin; Hu, Jifan

2018-06-01

α-Fe2O3/Al2O3 films can exhibit weak ferromagnetism at room temperature. The saturation magnetization of the thinner film is larger than that of the thick one deposited at the same temperature of 500 °C, which implies that the weak ferromagnetism at room temperature comes not only from the intrinsic canted magnetic structure, but also from the effects of interface between α-Fe2O3/Al2O3, such as the effect of Al diffusion into α-Fe2O3 film. Perpendicular electric field upon α-Fe2O3/Al2O3 film at room temperature could adjust the magnetic properties (saturation magnetization, magnetic remanence, coercivity and saturation magnetizing field). The positive electric field can enhance the magnetism of α-Fe2O3/Al2O3 thin film, while negative electric field can reduce it. The change induced by electric field may be connected with the migration effects of Al3+ ions. The steps of curve for saturation magnetization versus the electric field may reflect these complicated processes. The magnetization of the film deposited at a higher temperature can be changed by electric field more easily. This study may inspire more in-depth research and lead to an alternative approach to future magneto-electronic devices.

Adsorption of methyl orange on mesoporous γ-Fe2O3/SiO2 nanocomposites

NASA Astrophysics Data System (ADS)

Deligeer, W.; Gao, Y. W.; Asuha, S.

2011-02-01

Mesoporous γ-Fe2O3/SiO2 nanocomposite containing 30 mol% of γ-Fe2O3 was prepared by a template-free sol-gel method, and its removal ability for methyl orange (MO) was investigated. The nanocomposite was characterized using X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM), Fourier transform infrared (FTIR) absorption measurements, nitrogen adsorption-desorption measurements, and magnetic measurements. The synthesized γ-Fe2O3/SiO2 nanocomposite has a mesoporous structure with an average pore size of 3.5 nm and a specific surface area of 245 m2/g, and it exhibits ferrimagnetic characteristics with the maximum saturation magnetization of 20.9 emu/g. The adsorption of MO on the nanocomposite reaches the maximum adsorbed percentage of ca. 80% within a few minutes, showing that most of MO can be removed in a short time. The MO adsorption data fit well with both Langmuir and Freundlich adsorption isotherms. The maximum adsorption capacity of MO is estimated to be 476 mg/g.

High saturation magnetization of γ-Fe2O3 nano-particles by a facile one-step synthesis approach

PubMed Central

Cao, Derang; Li, Hao; Pan, Lining; Li, Jianan; Wang, Xicheng; Jing, Panpan; Cheng, Xiaohong; Wang, Wenjie; Wang, Jianbo; Liu, Qingfang

2016-01-01

We have demonstrated the synthesis of γ-Fe2O3 nano-particles through a facile and novel calcination process in the air. There is no pH regulation, gas atmosphere, additive, centrifugation or other complicated procedures during the preparing process. A detailed formation process of the nano-particles is proposed, and DMF as a polar solvent may slower the reaction process of calcination. The structures, morphologies, and magnetic properties of γ-Fe2O3 nano-particles were investigated systematically, and the pure γ-Fe2O3 nano-particles obtained at 200 °C display uniform morphology good magnetic property. The saturation magnetization of obtained pure γ-Fe2O3 is about 74 emu/g, which is comparable with bulk material (76 emu/g) and larger than other results. In addition, the photocatalytic activity for degradation of methylene blue is also studied, which shows proper photocatalytic activity. PMID:27581732

Site Occupancies, Luminescence, and Thermometric Properties of LiY9(SiO4)6O2:Ce3+ Phosphors.

PubMed

Zhou, Weijie; Pan, Fengjuan; Zhou, Lei; Hou, Dejian; Huang, Yan; Tao, Ye; Liang, Hongbin

2016-10-04

In this work, we report the tunable emission properties of Ce 3+ in an apatite-type LiY 9 (SiO 4 ) 6 O 2 compound via adjusting the doping concentration or temperature. The occupancies of Ce 3+ ions at two different sites (Wyckoff 6h and 4f sites) in LiY 9 (SiO 4 ) 6 O 2 have been determined by Rietveld refinements. Two kinds of Ce 3+ f-d transitions have been studied in detail and then assigned to certain sites. The effects of temperature and doping concentration on Ce 3+ luminescence properties have been systematically investigated. It is found that the Ce 3+ ions prefer occupying Wyckoff 6h sites and the energy transfer between Ce 3+ at two sites becomes more efficient with an increase in doping concentration. In addition, the charge-transfer vibronic exciton (CTVE) induced by the existence of free oxygen ion plays an important role in the thermal quenching of Ce 3+ at 6h sites. Because of the tunable emissions from cyan to blue with increasing temperature, the phosphors LiY 9 (SiO 4 ) 6 O 2 :Ce 3+ are endowed with possible thermometric applications.

Partial nitrogen loss in SrTaO2N and LaTiO2N oxynitride perovskites

NASA Astrophysics Data System (ADS)

Chen, Daixi; Habu, Daiki; Masubuchi, Yuji; Torii, Shuki; Kamiyama, Takashi; Kikkawa, Shinichi

2016-04-01

SrTaO2N heated in a helium atmosphere began to release nitrogen of approximately 30 at% at 950 °C while maintaining the perovskite structure and its color changed from orange to dark green. Then it decomposed above 1200 °C to a black mixture of Sr1.4Ta0.6O2.73, Ta2N, and Sr5Ta4O15. The second decomposition was not clearly observed when SrTaO2N was heated in a nitrogen atmosphere below 1550 °C. After heating at 1500 °C for 3 h under a 0.2 MPa nitrogen atmosphere, the perovskite product became dark green and conductive. Structure refinement results suggested that the product was a mixture of tetragonal and cubic perovskites with a decreased ordering of N3-/O2-. The sintered body was changed to an n-type semiconductor after a partial loss of nitrogen to be reduced from the originally insulating SrTaO2N perovskite lattice. LaTiO2N was confirmed to have a similar cis-configuration of the TiO4N2 octahedron as that of TaO4N2 in SrTaO2N. It also released some of its nitrogen at 800 °C changing its color from brown to black and then decomposed to a mixture of LaTiO3, La2O3, and TiN at 1100 °C. These temperatures are lower than those in SrTaO2N.

Relationship of peroxyacetyl nitrate to active and total odd nitrogen at northern high latitudes - Influence of reservoir species on NO(x) and O3

NASA Technical Reports Server (NTRS)

Singh, H. B.; Herlth, D.; O'Hara, D.; Zahnle, K.; Bradshaw, J. D.; Sandholm, S. T.; Talbot, R.; Crutzen, P. J.; Kanakidou, M. A.

1992-01-01

The partitioning of relative nitrogen in the Arctic and the sub-Arctic troposphere based on measurements conducted during the 1988 Arctic Boundary Layer Expedition (ABLE 3A) is described. The first set of comprehensive odd nitrogen and O3 measurements from the Arctic/sub-Arctic free troposphere shows that a highly aged air mass that has persisted under very cold conditions is present. A large fraction of the odd nitrogen appears to be present in the form of reservoir species such as PAN. Significant quantities of as yet unknown reactive nitrogen species, such as complex alkyl nitrates and pernitrates, are expected to be present. Together with PAN, these nitrate and pernitrate reservoir species could control the entire NO(x) availability of the high-latitude troposphere and in turn influence the O3 photochemistry of the region. The role of PAN in influencing the O3 reservoir is shown to be important and may be responsible for the increasing O3 temporal trend observed at high latitudes.

Soil variability along a nitrogen mineralization and nitrification gradient in a nitrogen-saturated hardwood forest

Treesearch

Frank S. Gilliam; Nikki L. Lyttle; Ashley Thomas; Mary Beth Adams

2005-01-01

Some N-saturated watersheds of the Fernow Experimental Forest (FEF), West Virginia, exhibit a high degree of spatial heterogeneity in soil N processing. We used soils from four sites at FEF representing a gradient in net N mineralization and nitrification to consider the causes and consequences of such spatial heterogeneity. We collected soils with extremely high vs....

Highly efficient saturated visible up-conversion photoluminescent Y 2 O 3 :Er 3+ microspheres pumped with a 1.55 μm laser diode

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

Zhao, Jinbo; Wu, Lili; Zhang, Chuanjiang

2017-01-01

Highly efficient saturation up-conversion (UC) luminescent Y2O3:Er3+ microspheres have been successfully prepared via a hydrothermal-homogeneous precipitation method. Bright visible luminescence can be clearly seen with a 1.55 mu m laser diode excitation power as low as similar to 0.03 W cm(-2). The up-conversion (UC) emission spectra indicate that the strongest red emission with a peak situated at similar to 660 nm originated from the I-4(9/2) -> I-4(15/2) transition of Er3+. The peaks situated at similar to 520 and 550 nm can be assigned to the transition from H-2(11/2)/S-4(3/2) state to the ground state of Er3+. The high efficient saturation up-conversionmore » emission is related to the highly crystalline structure. These results indicate a new way to enhance UC radiation in rare-earth ion-doped materials prepared using a hydrothermal-homogeneous precipitation method.« less

NO-assisted molecular-beam epitaxial growth of nitrogen substituted EuO

NASA Astrophysics Data System (ADS)

Wicks, R.; Altendorf, S. G.; Caspers, C.; Kierspel, H.; Sutarto, R.; Tjeng, L. H.; Damascelli, A.

2012-04-01

We have investigated a method for substituting oxygen with nitrogen in EuO thin films, which is based on molecular beam epitaxy distillation with NO gas as the oxidizer. By varying the NO gas pressure, we produce crystalline, epitaxial EuO1 -xNx films with good control over the films' nitrogen concentration. In situ x-ray photoemission spectroscopy reveals that nitrogen substitution is connected to the formation Eu3+4f6 and a corresponding decrease in the number of Eu2+4f7, indicating that nitrogen is being incorporated in its 3- oxidation state. While small amounts of Eu3+ in over-oxidized Eu1-δO thin films lead to a drastic suppression of the ferromagnetism, the formation of Eu3+ in EuO1-xNx still allows the ferromagnetic phase to exist with an unaffected Tc, thus providing an ideal model system to study the interplay between the magnetic f7 (J = 7/2) and the non-magnetic f6 (J = 0) states close to the Fermi level.

Interfacial magnetism in CaRuO3/CaMnO3 superlattices grown on (001) SrTiO3

NASA Astrophysics Data System (ADS)

He, C.; Zhai, X.; Mehta, V. V.; Wong, F. J.; Suzuki, Y.

2011-04-01

We have studied epitaxially grown superlattices of CaRuO3/CaMnO3 as well as an alloy film of CaMn0.5Ru0.5O3 on (001) SrTiO3 substrates. In contrast to previous experiments, we have studied CRO/CMO superlattices with a constant CRO thickness and variable CMO thickness. All superlattices exhibit Curie temperatures (TC) of 110 K. The saturated magnetization per interfacial Mn cation has been found to be 1.1 μB/Mn ion. The TC's of the superlattices are much lower than the TC of the alloy film while the saturated magnetization values are larger than that of the alloy film. These observations suggest that interdiffusion alone cannot account for ferromagnetism in the superlattices and that double exchange induced FM must play a role at the interfaces.

Denitrification constitutes an import N sink in subtropical N-saturated forests - a nitrate dual isotope study

NASA Astrophysics Data System (ADS)

Yu, Lonfei; Zhu, Jing; Mulder, Jan; Dörsch, Peter

2016-04-01

Forests in China receive variable but increasing amounts of nitrogen from the atmosphere causing N saturation and nitrate runoff. Surprisingly high N-retention has been reported from subtropical forests, suggesting active mechanisms of N removal. Here we report a multi-site study of 15N and 18O abundances in soil nitrate (NO3-) across seven forested catchments spanning from temperate to subtropical China. In each catchment, samples were taken on one date during one or two summer along the hydrological continuum comprising hillslope positions and riparian zones. We had found previously in an intensive multi-year study at one of the sites, that the spatial pattern of summertime 15N and 18O in soil nitrate was remarkably stable across climatically distinct years, suggesting persistent N removal by denitrification at the foot of hill slopes and in groundwater discharge zones (Yu et al., submitted). In the present study, we extended the scope to five subtropical Chinese catchments and compared them with two temperate forests. Our data confirm the general pattern of efficient nitrification on hillslopes and strong denitrification in riparian zones in the subtropical catchments but not in the temperate ones. This is likely because high summer rainfalls at the monsoonal sites connect N mineralization and oxidation in upland positions with NO3- reduction in ground water discharge zones via NO3- runoff, rendering subtropical forests an efficient sink for reactive N with implications for regional N budgets. The impact of N deposition level, hydrology and edaphic factors on the predictive power of nitrate isotope signatures for N removal processes will be discussed. Yu L, Zhu J, Mulder J, Dörsch P: Spatiotemporal patterns in dual nitrate isotopes reveal efficient N transformation and denitrification along a hydrological continuum in N-saturated, subtropical forest. Submitted

Raising the Corrosion Resistance of Low-Carbon Steels by Electrolytic-Plasma Saturation with Nitrogen and Carbon

NASA Astrophysics Data System (ADS)

Kusmanov, S. A.; Grishina, E. P.; Belkin, P. N.; Kusmanova, Yu. V.; Kudryakova, N. O.

2017-05-01

Structural features of the external oxide layer and internal nitrided, carbonitrided and carburized layers in steels 10, 20 and St3 produced by the method of electrolytic plasma treatment are studied. Specimens of the steels are tested for corrosion in a naturally aerated 1-N solution of sodium chloride. The condition of the metal/sodium chloride solution interface is studied by the method of electrochemical impedance spectroscopy. It is shown that the corrosion resistance of low-carbon steels can be raised by anode electrolytic-plasma saturation with nitrogen and carbon. Recommendations are given on the choice of carbonitriding modes for structural steels.

Gaseous nitrogen losses from a forest site in the North Tyrolean Limestone Alps.

PubMed

Härtel, Elisabeth; Zechmeister-Boltenstern, Sophie; Gerzabck, Martin

2002-01-01

Microorganisms are responsible for the mineralisation of organic nitrogen in soils. NH4+ can be further oxidised to NO3- during nitrification and NO3- can be reduced to gaseous nitrogen compounds during denitrification. During both processes, nitrous oxide (N2O), which is known as greenhouse gas, can be lost from the ecosystem. The aim of this study was to quantify N2O emissions and the internal microbial N cycle including net N mineralisation and net nitrification in a montane forest ecosystem in the North Tyrolean Limestone Alps during an 18-month measurement period and to estimate the importance of these fluxes in comparison with other components of the N cycle. Gas samples were taken every 2 weeks using the closed chamber method. Additionally, CO2 emission rates were measured to estimate soil respiration activity. Net mineralisation and net nitrification rates were determined by the buried bag method every month. Ion exchange resin bags were used to determine the N availability in the root zone. Mean N2O emission rate was 0.9 kg N ha(-1) a(-1), which corresponds to 5% of the N deposited in the forest ecosystem. The main influencing factors were air and soil temperature and NO3- accumulated on the ion exchange resin bags. In the course of net ammonification, 14 kg NH4+-N ha(-1) were produced per year. About the same amount of NO3--N was formed during nitrification, indicating a rather complete nitrification going on at the site. NO3- concentrations found on the ion exchange resin bags were about 3 times as high as NO3- produced during net nitrification, indicating substantial NO3- immobilisation. The results of this study indicate significant nitrification activities taking place at the Mühleggerköpfl.

Erbium and nitrogen co-doped SrTiO{sub 3} with highly visible light photocatalytic activity and stability by solvothermal synthesis

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

Xu, Jing; Wei, Yuelin, E-mail: ylwei@hqu.edu.cn; Huang, Yunfang

Highlights: • Er/N co-doped SrTiO{sub 3} was prepared by a solvothermal process at low temperature. • The co-doping induces the band gap narrowing and prominent absorbance in visible light region. • The samples show excellent catalytic activity and stability under visible light irradiation. - Abstract: Erbium–nitrogen co-doped SrTiO{sub 3} photocatalysts have been synthesized by a facile solvothermal method. The resulting samples were analyzed by FE-SEM, XRD, BET-surface area and UV–vis. The UV–vis absorption spectra of these powders indicated that erbium–nitrogen co-doped SrTiO{sub 3} possessed stronger absorption bands in the visible light region in comparison with that of pure SrTiO{sub 3}.more » The occurrence of the erbium–nitrogen co-doped cubic SrTiO{sub 3} induced the higher photocatalytic activities for the degradation of methyl orange (MO) under irradiation by ultraviolet light and visible light, respectively, being superior to that of pure SrTiO{sub 3} and commercial TiO{sub 2} (P-25) powders. In addition, the Er–N co-doped SrTiO{sub 3} (initial molar ratios of Sr/Er/N = 1:0.015:0.1, designated as S5) sample showed the best photocatalytic activity with the degradation rate as high as 98% after 30 min under the visible light irradiation. After five cycles, the photocatalytic activity of the S5 catalyst showed no significant decrease, which indicated that the photocatalysts were stable under visible light irradiation.« less

N2O and N2 emissions from contrasting soil environments - interactive effects of soil nitrogen, hydrology and microbial communities

NASA Astrophysics Data System (ADS)

Christiansen, Jesper; Elberling, Bo; Ribbons, Relena; Hedo, Javier; José Fernández Alonso, Maria; Krych, Lukasz; Sandris Nielsen, Dennis; Kitzler, Barbara

2016-04-01

Reactive nitrogen (N) in the environment has doubled relative to the natural global N cycle with consequences for biogeochemical cycling of soil N. Also, climate change is expected to alter precipitation patterns and increase soil temperatures which in Arctic environments may accelerate permafrost thawing. The combination of changes in the soil N cycle and hydrological regimes may alter microbial transformations of soil N with unknown impacts on N2O and N2 emissions from temperate and Arctic soils. We present the first results of soil N2O and N2 emissions, chemistry and microbial communities over soil hydrological gradients (upslope, intermediate and wet) across a global N deposition gradient. The global gradient covered an N-limited high Arctic tundra (Zackenberg-ZA), a pacific temperate rain forest (Vancouver Island-VI) and an N saturated forest in Austria (Klausenleopoldsdorf-KL). The N2O and N2 emissions were measured from intact cores at field moisture in a He-atmosphere system. Extractable NH4+ and NO3-, organic and microbial C and N and potential enzyme-activities were determined on soil samples. Soil genomic DNA was subjected to MiSeq-based tag-encoded 16S rRNA and ITS gene amplicon sequencing for the bacterial and fungal community structure. Similar soil moisture levels were observed for the upslope, intermediate and wet locations at ZA, VI and KL, respectively. Extractable NO3- was highest at the N rich KL and lowest at ZA and showed no trend with soil moisture similar to NH4+. At ZA and VI soil NH4+ was higher than NO3- indicating a tighter N cycling. N2O emissions increased with soil moisture at all sites. The N2O emissions for the wet locations ranked similarly to NO3- with the largest response to soil moisture at KL. N2 emissions were remarkably similar across the sites and increased with soil wetness. Microbial C and N also increased with soil moisture and were overall lowest at the N rich KL site. The potential activity of protease enzyme was site

Epitaxial phase diagrams of SrTiO3, CaTiO3, and SrHfO3: Computational investigation including the role of antiferrodistortive and A -site displacement modes

NASA Astrophysics Data System (ADS)

Angsten, Thomas; Asta, Mark

2018-04-01

Ground-state epitaxial phase diagrams are calculated by density functional theory (DFT) for SrTiO3, CaTiO3, and SrHfO3 perovskite-based compounds, accounting for the effects of antiferrodistortive and A -site displacement modes. Biaxial strain states corresponding to epitaxial growth of (001)-oriented films are considered, with misfit strains ranging between -4 % and 4%. Ground-state structures are determined using a computational procedure in which input structures for DFT optimizations are identified as local minima in expansions of the total energy with respect to strain and soft-mode degrees of freedom. Comparison to results of previous DFT studies demonstrates the effectiveness of the computational approach in predicting ground-state phases. The calculated results show that antiferrodistortive octahedral rotations and associated A -site displacement modes act to suppress polarization and reduce the epitaxial strain energy. A projection of calculated atomic displacements in the ground-state epitaxial structures onto soft-mode eigenvectors shows that three ferroelectric and six antiferrodistortive displacement modes are dominant at all misfit strains considered, with the relative contributions from each varying systematically with the strain. Additional A -site displacement modes contribute to the atomic displacements in CaTiO3 and SrHfO3, which serve to optimize the coordination of the undersized A -site cation.

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

Interfacial B-site atomic configuration in polar (111) and non-polar (001) SrIrO3/SrTiO3 heterostructures

NASA Astrophysics Data System (ADS)

Anderson, T. J.; Zhou, H.; Xie, L.; Podkaminer, J. P.; Patzner, J. J.; Ryu, S.; Pan, X. Q.; Eom, C. B.

2017-09-01

The precise control of interfacial atomic arrangement in ABO3 perovskite heterostructures is paramount, particularly in cases where the subsequent electronic properties of the material exhibit geometrical preferences along polar crystallographic directions that feature inevitably complex surface reconstructions. Here, we present the B-site interfacial structure in polar (111) and non-polar (001) SrIrO3/SrTiO3 interfaces. The heterostructures were examined using scanning transmission electron microscopy and synchrotron-based coherent Bragg rod analysis. Our results reveal the preference of B-site intermixing across the (111) interface due to the polarity-compensated SrTiO3 substrate surface prior to growth. By comparison, the intermixing at the non-polar (001) interface is negligible. This finding suggests that the intermixing may be necessary to mitigate epitaxy along heavily reconstructed and non-stoichiometric (111) perovskite surfaces. Furthermore, this preferential B-site configuration could allow the geometric design of the interfacial perovskite structure and chemistry to selectively engineer the correlated electronic states of the B-site d-orbital.

Passively Q-switched 1.6 µm Er:YAG laser with a γ-Ga2O3:Co-based glass-ceramics as a saturable absorber

NASA Astrophysics Data System (ADS)

Shi, Yang; Gao, Chunqing; Ye, Qing; Wang, Shuo; Wang, Qing; Gao, Mingwei; Loiko, Pavel; Skoptsov, Nikolai; Dymshits, Olga; Zhilin, Alexander; Zapalova, Svetlana; Tsenter, Marina; Vitkin, Vladimir; Mateos, Xavier; Yumashev, Konstantin

2018-04-01

A resonantly pumped passively Q-switched Er:YAG laser operating at 1.617 and 1.645 µm is reported with γ-Ga2O3:Co2+-based glass-ceramics (GCs) as a saturable absorber. The maximum average output power achieved from this laser was 273 mW; the highest pulse energy was 5.9 µJ, corresponding to a pulse duration of 3.0 µs at a repetition frequency of 31 kHz. To the best of our knowledge, this is the first time to use the γ-Ga2O3:Co2+-based GC as a passive Q-switcher for Er:YAG lasers and this is also the first time to obtain 1.617 µm and 1.645 µm pulses with a GC-based saturable absorber.

Effect of A-site deficiency in LaMn{sub 0.9}Co{sub 0.1}O{sub 3} perovskites on their catalytic performance for soot combustion

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

Dinamarca, Robinson; Garcia, Ximena; Jimenez, Romel

Highlights: • A-site defective perovskites increases the oxidation state of the B-cation. • Not always non-stoichiometric perovskites exhibit higher catalytic activity in soot combustion. • The highly symmetric cubic crystalline structure diminishes the redox properties of perovskites. - Abstract: The influence of lanthanum stoichiometry in Ag-doped (La{sub 1-x}Ag{sub x}Mn{sub 0.9}Co{sub 0.1}O{sub 3}) and A-site deficient (La{sub 1-x}Mn{sub 0.9}Co{sub 0.1}O{sub 3-δ}) perovskites with x equal to 10, 20 and 30 at.% has been investigated in catalysts for soot combustion. The catalysts were prepared by the amorphous citrate method and characterized by XRD, nitrogen adsorption, XPS, O{sub 2}-TPD and TPR. The formationmore » of a rhombohedral excess-oxygen perovskite for Ag-doped and a cubic perovskite structure for an A-site deficient series is confirmed. The efficient catalytic performance of the larger Ag-doped perovskite structure is attributed to the rhombohedral crystalline structure, Ag{sub 2}O segregated phases and the redox pair Mn{sup 4+}/Mn{sup 3+}. A poor catalytic activity for soot combustion was observed with A-site deficient perovskites, despite the increase in the redox pair Mn{sup 4+}/Mn{sup 3+}, which is attributed to the cubic crystalline structure.« less

Mn-Site Doped CaMnO 3: Creation of the CMR Effect

NASA Astrophysics Data System (ADS)

Raveau, B.; Zhao, Y. M.; Martin, C.; Hervieu, M.; Maignan, A.

2000-01-01

The doping of CaMnO3-δ at Mn sites with pentavalent and hexavalent d0 elements - Nb, Ta, W, Mo - modifies the resistivity behavior of this phase, extending the insulating domain and increasing significantly the resistivity at low temperature as the doping element content increases. The higher valency of the doping element introduces electrons; i.e., Mn3+ species are formed in the Mn4+ matrix. Double exchange phenomena then allow ferromagnetic interactions, by application of external magnetic fields which are similar to those observed for electron-doped manganites Ca1-xLnxMnO3 (x≤0.15), but with smaller magnetic moments. Consequently, this Mn site doping induces CMR properties with resistivity ratios considerably larger than those for CaMnO3-δ.

Reassessment of the NH4 NO3 thermal decomposition technique for calibration of the N2 O isotopic composition.

PubMed

Mohn, Joachim; Gutjahr, Wilhelm; Toyoda, Sakae; Harris, Eliza; Ibraim, Erkan; Geilmann, Heike; Schleppi, Patrick; Kuhn, Thomas; Lehmann, Moritz F; Decock, Charlotte; Werner, Roland A; Yoshida, Naohiro; Brand, Willi A

2016-09-08

In the last few years, the study of N 2 O site-specific nitrogen isotope composition has been established as a powerful technique to disentangle N 2 O emission pathways. This trend has been accelerated by significant analytical progress in the field of isotope-ratio mass-spectrometry (IRMS) and more recently quantum cascade laser absorption spectroscopy (QCLAS). Methods The ammonium nitrate (NH 4 NO 3 ) decomposition technique provides a strategy to scale the 15 N site-specific (SP ≡ δ 15 N α - δ 15 N β ) and bulk (δ 15 N bulk  = (δ 15 N α  + δ 15 N β )/2) isotopic composition of N 2 O against the international standard for the 15 N/ 14 N isotope ratio (AIR-N 2 ). Within the current project 15 N fractionation effects during thermal decomposition of NH 4 NO 3 on the N 2 O site preference were studied using static and dynamic decomposition techniques. The validity of the NH 4 NO 3 decomposition technique to link NH 4 + and NO 3 - moiety-specific δ 15 N analysis by IRMS to the site-specific nitrogen isotopic composition of N 2 O was confirmed. However, the accuracy of this approach for the calibration of δ 15 N α and δ 15 N β values was found to be limited by non-quantitative NH 4 NO 3 decomposition in combination with substantially different isotope enrichment factors for the conversion of the NO 3 - or NH 4 + nitrogen atom into the α or β position of the N 2 O molecule. The study reveals that the completeness and reproducibility of the NH 4 NO 3 decomposition reaction currently confine the anchoring of N 2 O site-specific isotopic composition to the international isotope ratio scale AIR-N 2 . The authors suggest establishing a set of N 2 O isotope reference materials with appropriate site-specific isotopic composition, as community standards, to improve inter-laboratory compatibility. This article is protected by copyright. All rights reserved.

Thermoelectric properties of p-type perovskite compounds LaCoO3 systems containing the A-site vacancy

NASA Astrophysics Data System (ADS)

Anzai, Mayuka; Kawakami, Hiroshi; Saito, Miwa; Yamamura, Hiroshi

2011-05-01

Thermoelectric properties of Sr-doped LaCoO3 system which includes both La1-xSrxCoO3 and La0.95-xSrxsquare0.05CoO3 containing the A-site vacancy were prepared by solid state reaction. The crystal phases of the samples were investigated by X-ray diffraction method. The electrical conductivity, Seebeck coefficient, and thermal conductivity were investigated, focusing the effect of A-site vacancy. Doping of Sr to LaCoO3 improved the electrical conductivity but decreased the seebeck coefficient and increased the thermal conductivity. A-site vacancy of La0.95-xSrxsquare0.05CoO3 system, in comparison with La1-xSrxCoO3 system, increased electrical conductivity, and decreased lattice thermal conductivity. As a result, it was found that the thermoelectric properties of La0.95-xSrxsquare0.05CoO3 containing the A-site vacancy showed the higher values than those of La1-xSrxCoO3. The introduction of A-site vacancy was effective on the improvement of thermoelectric property.

Reactive nitrogen oxides and ozone above a taiga woodland

NASA Technical Reports Server (NTRS)

Bakwin, Peter S.; Jacob, Daniel J.; Wofsy, Steven C.; Munger, J. William; Daube, Bruce C.; Bradshaw, John D.; Sandholm, Scott T.; Talbot, Robert W.; Singh, Hanwant B.; Gregory, Gerald L.

1994-01-01

Measurements of reactive nitrogen oxides (NO(x) and NO(y)) and ozone (O3) were made in the planetary boundary layer (PBL) above a taiga woodland in northern Quebec, Canada, during June-August, 1990, as part of NASA Artic Boundary Layer Expedition (ABLE) 3B. Levels of nitrogen oxides and O3 were strongly modulated by the synoptic scale meteorology that brought air from various source regions to the site. Industrial pollution from the Great Lakes region of the U.S. and Canada appears to be a major source for periodic elevation of NO(x), and NO(y) and O3. We find that NO/NO2 ratios at this site at midday were approximately 50% those expected from a simple photochemical steady state between NO(x) and O3, in contrast to our earlier results from the ABLE 3A tundra site. The difference between the taiga and tundra sites is likely due to much larger emissions of biogenic hydrocarbons (particularly isoprene) from the taiga vegetation. Hydrocarbon photooxidation leads to relatively rapid production of peroxy radicals, which convert NO to NO2, at the taiga site. Ratios of NO(x) to NO(y) were typically 2-3 times higher in the PBL during ABLE 3B than during ABLE 3A. This is probably the result of high PAN levels and suppressed formation of HNO3 from NO2 due to high levels of biogenic hydrocarbons at the ABLE 3B site.

Enhanced Removal of Arsenic and Antimony in the Mining Site by Calcined γ-Fe2O3/Layered Double Hydroxide Nanocomposite

NASA Astrophysics Data System (ADS)

Lee, Sang-Ho; Choi, Heechul; Kim, Kyoung-Woong

2016-04-01

chemical complexation between γ-Fe2O3 and LDH in the nanocomposite. The saturation magnetization of raw γ-Fe2O3 and calcined γ-Fe2O3/LDH nanocomposite were 63.2 and 14.3 emu/g, respectively. Although there was distinct decrease of saturation magnetization of calcined γ-Fe2O3/LDH nanocomposite, the particles were rapidly separated by external magnetic field. The kinetic study revealed that the removal of arsenic and antimony reached equilibrium quickly at about 120 min for initial concentration of 50 mg/L. The regeneration rate of arsenic may retain 70% for five regeneration cycles by 0.5M NaOH with 5M NaCl solution, whereas antimony showed lower regenerability than arsenic due to the higher irreversible fraction in calcined γ-Fe2O3/LDH nanocomposite. Consequently, the effective removal efficiency for arsenic and antimony with its easy magnetic separation makes γ-Fe2O3/LDH nanocomposite be a potential for the field application in the contaminated sites including several mining sites in Korea.

Nitrogen biogeochemistry in tropical peatlands: nitrogen gas emissions and metagenomic insights into related microbial groups

NASA Astrophysics Data System (ADS)

Kasak, Kuno; Espenberg, Mikk; Oopkaup, Kristjan; Ligi, Teele; Truu, Marika; Truu, Jaak; Maddison, Martin; Järveoja, Järvi; Teemusk, Alar; Mander, Ülo

2017-04-01

Tropical peatlands constitute considerable amount of global peatland areas and are one of the most important and vulnerable terrestrial ecosystems in terms of impact on the atmospheric greenhouse gas composition. Anthropogenic actions, especially drainage and agriculture, are transforming biochemical cycles in tropical peatlands substantially. It is well known that drainage of tropical peatlands will result in huge amount of carbon loss, however a comprehensive study of the nitrogen cycling genetic potential in tropical areas is still less known. In the current study, nitrogen gas (N2, N2O) emissions from tropical peatlands (French Guiana, South America) were measured and their relationships with the soil chemical parameters, water regime, and abundances and diversity of genes in nitrogen cycle was assessed. The measurements and soil sampling were carried out in October 2013 in two sites (undisturbed and drainage influenced) of the northern part of French Guiana. At both sampling sites, N2O emissions were measured in six sessions during three days using static closed chambers. N2 and N2O emission from the top soil samples were measured in the laboratory applying He-O (N2) method. Soil pHKCl, NO3-N, NH4-N, soluble P, K, Ca and Mg, totN and soil organic matter content were determined from the collected samples. The bacterial and archaeal 16S rRNA genes and functional genes involved in nitrogen cycle (nirS, nirK, nosZI, nosZII, bacterial and archaeal amoA, nifH, nrfA, ANAMMOX bacteria specific 16S rRNA genes) in soil were quantified by using quantitative PCR method. DNA extracted from soil samples was sequenced on Illumina NextSeq system. Metagenomes were used for microbial profiling, identifying functional genes and relating them to biogeochemical cycles and biological processes. N2O emissions were significantly lower and N2 emissions higher (p<0.05 in both cases) in natural site (mean values -0.3 and 9.9 μg m-2 h-1 for N2O, and 1477.3 and 637.2 μg m-2 h-1 for N2

Uncertainty quantification of CO₂ saturation estimated from electrical resistance tomography data at the Cranfield site

DOE PAGES

Yang, Xianjin; Chen, Xiao; Carrigan, Charles R.; ...

2014-06-03

A parametric bootstrap approach is presented for uncertainty quantification (UQ) of CO₂ saturation derived from electrical resistance tomography (ERT) data collected at the Cranfield, Mississippi (USA) carbon sequestration site. There are many sources of uncertainty in ERT-derived CO₂ saturation, but we focus on how the ERT observation errors propagate to the estimated CO₂ saturation in a nonlinear inversion process. Our UQ approach consists of three steps. We first estimated the observational errors from a large number of reciprocal ERT measurements. The second step was to invert the pre-injection baseline data and the resulting resistivity tomograph was used as the priormore » information for nonlinear inversion of time-lapse data. We assigned a 3% random noise to the baseline model. Finally, we used a parametric bootstrap method to obtain bootstrap CO₂ saturation samples by deterministically solving a nonlinear inverse problem many times with resampled data and resampled baseline models. Then the mean and standard deviation of CO₂ saturation were calculated from the bootstrap samples. We found that the maximum standard deviation of CO₂ saturation was around 6% with a corresponding maximum saturation of 30% for a data set collected 100 days after injection began. There was no apparent spatial correlation between the mean and standard deviation of CO₂ saturation but the standard deviation values increased with time as the saturation increased. The uncertainty in CO₂ saturation also depends on the ERT reciprocal error threshold used to identify and remove noisy data and inversion constraints such as temporal roughness. Five hundred realizations requiring 3.5 h on a single 12-core node were needed for the nonlinear Monte Carlo inversion to arrive at stationary variances while the Markov Chain Monte Carlo (MCMC) stochastic inverse approach may expend days for a global search. This indicates that UQ of 2D or 3D ERT inverse problems can be performed

Carbon and nitrogen speciation in nitrogen-rich C-O-H-N fluids at 5.5-7.8 GPa

NASA Astrophysics Data System (ADS)

Sokol, Alexander G.; Palyanov, Yury N.; Tomilenko, Anatoly A.; Bul'bak, Taras A.; Palyanova, Galina A.

2017-02-01

Carbon and nitrogen speciation has been studied in high-pressure experiments in the C-O-H-N and C-O-H-N-Fe3C systems at 5.5 to 7.8 GPa and 1100 to 1500 °C using a split-sphere multi-anvil apparatus. Oxygen fugacity in the samples was either buffered by the Mo-MoO2 (MMO) and Fe-FeO (IW) equilibria using a double-capsule technique or left unbuffered. fO2 varied from 2 log units below to +4 log units above the iron-wüstite oxygen buffer (IW) depending on water contents in the charges and buffering. Ultra-reduced fluids contained NH3 as the dominant species, but its concentration was slightly lower, while CH4 was higher at higher temperatures. As oxygen fugacity and temperature increased to fO2 0.7 log units above IW and T ≥ 1400 °C, N2 became the predominant nitrogen species; the dominance among carbon species changed from CH4 and C2-C5 alkanes to oxygenated hydrocarbons and higher alkanes. It has been found out for the first time that the N2-rich fluid lacks methane at fO2 4 log units above IW but may bear a few percent of C2H6, C3H8, and C15-C18 alkanes and within one percent of alcohols, aldehydes, ketones, carboxylic acids, and furans. Thus, the NH3 enrichment of fluids and the nitrogen storage capacity of silicates at depths ∼200 km are expected to be the greatest in cold (1100-1200 °C) and reduced continental lithospheric mantle. In a hotter lithosphere of ∼1400 °C, the concentrations of NH3 and N2 in fluids are similar, and the nitrogen storage capacity of silicates should be relatively low. The stability of some higher alkanes and oxygenated hydrocarbons in nitrogen-rich fluids near the enstatite-magnesite-olivine-diamond/graphite (EMOG/D) equilibrium suggest that these carbon species, together with N2, can survive at the redox barrier, where silicate or silicate-carbonate melts capture them and entrain to shallow mantle.

Characterization of La/Fe/TiO2 and Its Photocatalytic Performance in Ammonia Nitrogen Wastewater

PubMed Central

Luo, Xianping; Chen, Chunfei; Yang, Jing; Wang, Junyu; Yan, Qun; Shi, Huquan; Wang, Chunying

2015-01-01

La/Fe/TiO2 composite photocatalysts were synthesized by Sol-Gel method and well characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen-physical adsorption, and UV-Vis diffuse reflectance spectra (UV-Vis DRS). It is interesting that the doped catalysts were in anatase phase while the pure TiO2 was in rutile phase. In addition, the composites possessed better physical chemical properties in photocatalytic activity than pure TiO2: stronger visible-light-response ability, larger specific surface area, and more regular shape in morphology. The photodegradation results of ammonia nitrogen indicate that: the La/Fe/TiO2 had higher catalytic activity to ammonia nitrogen waste water compared pure TiO2 and the other single metal-doped TiO2. pH 10 and 2 mmol/L H2O2 were all beneficial to the removal of ammonia nitrogen by La/Fe/TiO2. However, the common inorganic ions of Cl−, NO3−, SO42−, HCO3−/CO32−, Na+, K+, Ca2+ and Mg2+ in water all inhibited the degradation of ammonia nitrogen. By balance calculation, at least 20% of ammonia nitrogen was converted to N2 during the 64.6% removal efficiency of ammonia nitrogen. PMID:26593929

Facile synthesis of a nitrogen-doped graphene flower-like MnO2 nanocomposite and its application in supercapacitors

NASA Astrophysics Data System (ADS)

Dong, Jinyang; Lu, Gang; Wu, Fan; Xu, Chenxi; Kang, Xiaohong; Cheng, Zhiming

2018-01-01

A flower-like MnO2 nanocomposite embedded in nitrogen-doped graphene (NG-MnO2) is fabricated by a hydrothermal method. It is a mesoporous nanomaterial with a pore size of approximately 0.765 cm3 g-1 and specific surface area of 201.8 m2 g-1. NG-MnO2 exhibits a superior average specific capacitance of 220 F g-1 at 0.5 A g-1 and a preferable capacitance of 189.1 F g-1, even at 10 A g-1. After 1000 cycles, over 98.3% of the original specific capacitance retention of the NG-MnO2 electrode is maintained, and it can even activate a red light emitting diode (LED) after being charged, which indicates that it has excellent cycling stability as an electrode material. This prominent electrochemical performance is primarily attributed to the nitrogen doping and mesoporous structures of NG-MnO2, which can be attributed to its numerous electroactive sites as well as faster ion and electron transfer for redox reactions than general graphene-MnO2 nanocomposites (G-MnO2).

Saturation curve of SiO{sub 2} component in rutile-type GeO{sub 2}: A recoverable high-temperature pressure standard from 3 GPa to 10 GPa

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

Leinenweber, Kurt, E-mail: kurtl@asu.edu; Gullikson, Amber L.; Stoyanov, Emil

2015-09-15

The accuracy and precision of pressure measurements and the pursuit of reliable and readily available pressure scales at simultaneous high temperatures and pressures are still topics in development in high pressure research despite many years of work. In situ pressure scales based on x-ray diffraction are widely used but require x-ray access, which is lacking outside of x-ray beam lines. Other methods such as fixed points require several experiments to bracket a pressure calibration point. In this study, a recoverable high-temperature pressure gauge for pressures ranging from 3 GPa to 10 GPa is presented. The gauge is based on themore » pressure-dependent solubility of an SiO{sub 2} component in the rutile-structured phase of GeO{sub 2} (argutite), and is valid when the argutite solid solution coexists with coesite. The solid solution varies strongly in composition, mainly in pressure but also somewhat in temperature, and the compositional variations are easily detected by x-ray diffraction of the recovered products because of significant changes in the lattice parameters. The solid solution is measured here on two isotherms, one at 1200 °C and the other at 1500 °C, and is developed as a pressure gauge by calibrating it against three fixed points for each temperature and against the lattice parameter of MgO measured in situ at a total of three additional points. A somewhat detailed thermodynamic analysis is then presented that allows the pressure gauge to be used at other temperatures. This provides a way to accurately and reproducibly evaluate the pressure in high pressure experiments and applications in this pressure-temperature range, and could potentially be used as a benchmark to compare various other pressure scales under high temperature conditions. - Graphical abstract: The saturation curve of SiO{sub 2} in TiO{sub 2} shows a strong pressure dependence and a strong dependence of unit cell volume on composition. This provides an opportunity to use this

Field evaluations of newly available "interference-free" monitors for nitrogen dioxide and ozone at near-road and conventional National Ambient Air Quality Standards compliance sites.

PubMed

Leston, Alan R; Ollison, Will M

2017-11-01

Long-standing measurement techniques for determining ground-level ozone (O 3 ) and nitrogen dioxide (NO 2 ) are known to be biased by interfering compounds that result in overestimates of high O 3 and NO 2 ambient concentrations under conducive conditions. An increasing near-ground O 3 gradient (NGOG) with increasing height above ground level is also known to exist. Both the interference bias and NGOG were investigated by comparing data from a conventional Federal Equivalent Method (FEM) O 3 photometer and an identical monitor upgraded with an "interference-free" nitric oxide O 3 scrubber that alternatively sampled at 2 m and 6.2 m inlet heights above ground level (AGL). Intercomparison was also made between a conventional nitrogen oxide (NO x ) chemiluminescence Federal Reference Method (FRM) monitor and a new "direct-measure" NO 2 NO x 405 nm photometer at a near-road air quality measurement site. Results indicate that the O 3 monitor with the upgraded scrubber recorded lower regulatory-oriented concentrations than the deployed conventional metal oxide-scrubbed monitor and that O 3 concentrations 6.2 m AGL were higher than concentrations 2.0 m AGL, the nominal nose height of outdoor populations. Also, a new direct-measure NO 2 photometer recorded generally lower NO 2 regulatory-oriented concentrations than the conventional FRM chemiluminescence monitor, reporting lower daily maximum hourly average concentrations than the conventional monitor about 3 of every 5 days. Employing bias-prone instruments for measurement of ambient ozone or nitrogen dioxide from inlets at inappropriate heights above ground level may result in collection of positively biased data. This paper discusses tests of new regulatory instruments, recent developments in bias-free ozone and nitrogen dioxide measurement technology, and the presence/extent of a near-ground O 3 gradient (NGOG). Collection of unbiased monitor inlet height-appropriate data is crucial for determining accurate design

Influence of nitrogen loading and plant nitrogen assimilation on nitrogen leaching and N₂O emission in forage rice paddy fields fertilized with liquid cattle waste.

PubMed

Riya, Shohei; Zhou, Sheng; Kobara, Yuso; Sagehashi, Masaki; Terada, Akihiko; Hosomi, Masaaki

2015-04-01

Livestock wastewater disposal onto rice paddy fields is a cost- and labor-effective way to treat wastewater and cultivate rice crops. We evaluated the influence of nitrogen loading rates on nitrogen assimilation by rice plants and on nitrogen losses (leaching and N2O emission) in forage rice fields receiving liquid cattle waste (LCW). Four forage rice fields were subjected to nitrogen loads of 107, 258, 522, and 786 kg N ha(-1) (N100, N250, N500, and N750, respectively) using basal fertilizer (chemical fertilizer) (50 kg N ha(-1)) and three LCW topdressings (each 57-284 kg N ha(-1)). Nitrogen assimilated by rice plants increased over time. However, after the third topdressing, the nitrogen content of the biomass did not increase in any treatment. Harvested aboveground biomass contained 93, 60, 33, and 31 % of applied nitrogen in N100, N250, N500, and N750, respectively. The NH4 (+) concentration in the pore water at a depth of 20 cm was less than 1 mg N L(-1) in N100, N250, and N500 throughout the cultivation period, while the NH4 (+) concentration in N750 increased to 3 mg N L(-1) after the third topdressing. Cumulative N2O emissions ranged from -0.042 to 2.39 kg N ha(-1); the highest value was observed in N750, followed by N500. In N750, N2O emitted during the final drainage accounted for 80 % of cumulative N2O emissions. This study suggested that 100-258 kg N ha(-1) is a recommended nitrogen loading rate for nitrogen recovery by rice plants without negative environmental impacts such as groundwater pollution and N2O emission.

Formation of Submicron Magnesite during Reaction of Natural Forsterite in H2O-Saturated Supercritical CO2

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

Qafoku, Odeta; Hu, Jian Z.; Hess, Nancy J.

Natural forsterite was reacted in a) liquid water saturated with supercritical CO2 (scCO2) and in b) H2O-saturated scCO2 at 35-80 °C and 90 atm. The solid reaction products were analyzed with nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), and confocal Raman spectroscopy. Two carbonate phases, nesquehonite (MgCO3.3H2O) and magnesite (MgCO3), were identified with the proportions of the two phases depending on experimental conditions. In water saturated with scCO2, nesquehonite was the dominant carbonate phase at 35-80 °C with only a limited number of large, micron size magnesite particles forming at the highest temperature, 80 °C. In contrast, in H2O-saturatedmore » scCO2 magnesite formation was identified at all three temperatures: 35 °, 50 °, and 80 °C. Magnesite was the dominant carbonation reaction product at 50 ° and 80 °C; but nesquehonite was dominant at 35 °C. The magnesite particles formed under H2O-saturated scCO2 conditions exhibited an extremely uniform submicron grain-size and nearly identical rhombohedral morphologies at all temperatures. The distribution and form of the particles were not consistent with epitaxial nucleation and growth on the forsterite surface.« less

Real structure of (Sb1/3Zn2/3)GaO3(ZnO)3, a member of the homologous series ARO3(ZnO)m with ordered site occupation

NASA Astrophysics Data System (ADS)

Garling, Jennifer; Assenmacher, Wilfried; Schmid, Herbert; Longo, Paolo; Mader, Werner

2018-02-01

The hitherto unknown compound (Sb1/3Zn2/3)GaO3(ZnO)3, a member of the homologous series with general formula ARO3(ZnO)m (A,R = trivalent metal cation), was prepared by solid state methods from the binary oxides in sealed Pt-tubes. The structure of (Sb1/3Zn2/3)GaO3(ZnO)3 has been determined by X-ray diffraction from flux-grown single crystals (R 3 ̅ m , Z = 3, aR = 3.2387(7) Å, cR = 41.78(1) Å. The analysis revealed that (Sb1/3Zn2/3)GaO3(ZnO)m is isostructural with InGaO3(ZnO)m, where In3+ on octahedral sites is replaced by Sb5+ and Zn2+ in a ratio of 1:2, preserving an average charge of 3+. (Sb1/3Zn2/3)GaO3(ZnO)3 was furthermore analyzed by electron diffraction, High Angle Annular Dark Field (HAADF) scanning TEM, and high precision EELS spectroscopic imaging, where a periodic ordering of SbO6 octahedra connected via edge sharing to six ZnO6 octahedra in the octahedral layers in a honeycomb motif is found. Due to the large lateral distance of ca. 1.4 nm between adjacent octahedral layers, electrostatic interaction might hardly dictate Sb and Zn positions in neighbouring layers, and hence is a characteristic of the real structure of (Sb1/3Zn2/3)GaO3(ZnO)3. A structure model of the compound in space group P3112 (Nr. 151) with strictly ordered and discrete Sb and Zn positions is derived by crystallographic transformations as closest approximant for the real structure of (Sb1/3Zn2/3)GaO3(ZnO)3. UV-vis measurements confirm this compound to be a transparent oxide with an optical band gap in the UV region with Eg = 3.15 eV.

Nitrogen removal pathway of anaerobic ammonium oxidation in on-site aged refuse bioreactor.

PubMed

Wang, Chao; Zhao, Youcai; Xie, Bing; Peng, Qing; Hassan, Muhammad; Wang, Xiaoyuan

2014-05-01

The nitrogen removal pathways and nitrogen-related functional genes in on-site three-stage aged refuse bioreactor (ARB) treating landfill leachate were investigated. It was found that on average 90.0% of CODCr, 97.6% of BOD5, 99.3% of NH4(+)-N, and 81.0% of TN were removed with initial CODCr, BOD5, NH4(+)-N, and TN concentrations ranging from 2323 to 2754, 277 to 362, 1237 to 1506, and 1251 to 1580 mg/L, respectively. Meanwhile, the functional genes amoA, nirS and anammox 16S rRNA gene were found to coexist in every bioreactor, and their relative proportions in each bioreactor were closely related to the pollutant removal performance of the corresponding bioreactor, which indicated the coexistence of multiple nitrogen removal pathways in the ARB. Detection of anammox expression proved the presence of the anammox nitrogen removal pathway during the process of recirculating mature leachate to the on-site ARB, which provides important information for nitrogen management in landfills. Copyright © 2014 Elsevier Ltd. All rights reserved.

Nitrogen deposition alters nitrogen cycling and reduces soil carbon content in low-productivity semiarid Mediterranean ecosystems

PubMed Central

Ochoa-Hueso, Raúl; Maestre, Fernando T.; Ríos, Asunción de los; Valea, Sergio; Theobald, Mark R.; Vivanco, Marta G.; Manrique, Esteban; Bowker, Mathew A.

2015-01-01

Nitrogen (N) deposition is a threat to European Mediterranean ecosystems, but the evidence of real ecological impacts is still scarce. We combined data from a real N deposition gradient (4.3-7.3 kg N ha−1 yr−1) from semiarid portions of Spain with data from a field experiment in central Spain to evaluate N deposition effects on soil fertility, function and cyanobacteria community structure. Soil organic N did not increase along the extant deposition gradient, whereas C:N ratios decreased in most locations. Nitrogen fixation decreased along existing and experimental N deposition gradients, a result possibly related to compositional shifts in soil cyanobacteria community. Nitrogen mineralization rates were reduced by N fertilization, suggesting ecosystem N saturation. Soil organic C content and the activity of β-glucosidase decreased along the extant gradient. Our results suggest that semiarid soils in low-productivity sites are unable to store additional N inputs, and that are also unable to mitigate increasing C emissions to the atmosphere when experiencing increased N deposition. PMID:23685631

Nitrogen Saturation in Temperate Forest Ecosystems

Treesearch

John Aber; William McDowell; Knute Nadelhoffer; Alison Magill; Glenn Berntson; Mark Kamakea; Steven McNulty; William Currie; Lindsey Rustad; Ivan Fernandez

1998-01-01

Nitrogen emissions to the atmosphere due to human activity remain elevated in industrialized regions of the world and are accelerating in many developing regions (Galloway 1995). Although the deposition of sulfur has been reduced over much of the United States and Europe by aggressive environmental protection policies, current nitrogen deposition reduction targets in...

Atmospheric Nitrogen Deposition at Two Sites in an Arid Environment of Central Asia.

PubMed

Li, Kaihui; Liu, Xuejun; Song, Wei; Chang, Yunhua; Hu, Yukun; Tian, Changyan

2013-01-01

Arid areas play a significant role in the global nitrogen cycle. Dry and wet deposition of inorganic nitrogen (N) species were monitored at one urban (SDS) and one suburban (TFS) site at Urumqi in a semi-arid region of central Asia. Atmospheric concentrations of NH3, NO2, HNO3, particulate ammonium and nitrate (pNH4 (+) and pNO3 (-)) concentrations and NH4-N and NO3-N concentrations in precipitation showed large monthly variations and averaged 7.1, 26.6, 2.4, 6.6, 2.7 µg N m(-3) and 1.3, 1.0 mg N L(-1) at both SDS and TFS. Nitrogen dry deposition fluxes were 40.7 and 36.0 kg N ha(-1) yr(-1) while wet deposition of N fluxes were 6.0 and 8.8 kg N ha(-1) yr(-1) at SDS and TFS, respectively. Total N deposition averaged 45.8 kg N ha(-1) yr(-1)at both sites. Our results indicate that N dry deposition has been a major part of total N deposition (83.8% on average) in an arid region of central Asia. Such high N deposition implies heavy environmental pollution and an important nutrient resource in arid regions.

Artificial O3 formation during fireworks

NASA Astrophysics Data System (ADS)

Fiedrich, M.; Kurtenbach, R.; Wiesen, P.; Kleffmann, J.

2017-09-01

In several previous studies emission of ozone (O3) during fireworks has been reported, which was attributed to either photolysis of molecular oxygen (O2) or nitrogen dioxide (NO2) by short/near UV radiation emitted during the high-temperature combustion of fireworks. In contrast, in the present study no O3 formation was observed using a selective O3-LOPAP instrument during the combustion of pyrotechnical material in the laboratory, while a standard O3 monitor using UV absorption showed extremely high O3 signals. The artificial O3 response of the standard O3 monitor was caused by known interferences associated with high levels of co-emitted VOCs and could also be confirmed in field measurements during New Year's Eve in the city of Wuppertal, Germany. The present results help to explain unreasonably high ozone levels documented during ambient fireworks, which are in contradiction to the fast titration of O3 by nitrogen monoxide (NO) in the night-time atmosphere.

Nitrogen-doped graphene aerogel-supported spinel CoMn2O4 nanoparticles as an efficient catalyst for oxygen reduction reaction

NASA Astrophysics Data System (ADS)

Liu, Yisi; Li, Jie; Li, Wenzhang; Li, Yaomin; Chen, Qiyuan; Zhan, Faqi

2015-12-01

Spinel CoMn2O4 (CMO) nanoparticles grown on three-dimensional (3D) nitrogen-doped graphene areogel (NGA) is prepared by a facile two-step hydrothermal method. The NGA not only possesses the intrinsic property of graphene, but also has abundant pore conformations for supporting spinel metal oxide nanoparticles, thus would be suitable as a good electrocatalysts' support for oxygen reduction reaction (ORR). The structure, morphology, porous properties, and chemical composition of CMO/NGA are investigated by X-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, nitrogen adsorption-desorption measurements, and X-ray photoelectron spectroscopy (XPS). The electrocatalytic activity of catalysts is discussed by cyclic voltammograms (CV), electrochemical impedance spectroscopy (EIS), and rotating disk electrode (RDE) measurements in O2-saturated 0.1 M KOH electrolyte. The CMO/NGA hybrid exhibits more positive onset potential and half-wave potential, faster charge transfer than that of CMO and NGA, and its electrocatalytic performance is comparable with the commercial 20 wt.% Pt/C. Furthermore, it mainly favors a direct 4e- reaction pathway, and has excellent ethanol tolerance and high durability, which is attributed to the unique 3D crumpled porous nanostructure of NGA with large specific area and fast electron transport, and the synergic covalent coupling between the CoMn2O4 nanoparticles and NGA.

A DFT+U study of A-site and B-site substitution in BaFeO3-δ.

PubMed

Baiyee, Zarah Medina; Chen, Chi; Ciucci, Francesco

2015-09-28

BaFeO3-δ (BFO)-based perovskites have emerged as cheap and effective oxygen electrocatalysts for oxygen reduction reaction at high temperatures. The BFO cubic phase facilitates a high oxygen deficiency and is commonly stabilised by partial substitution. Understanding the electronic mechanisms of substitution and oxygen deficiency is key to rational material design, and can be realised through DFT analysis. In this work an in-depth first principle DFT+U study is undertaken to determine site distinctive characteristics for 12.5%, Y, La and Ce substitutions in BFO. In particular, it is shown that B-site doped structures exhibit a lower energy cost for oxygen vacancy formation relative to A site doping and pristine BFO. This is attributed to the stabilisation of holes in the oxygen sub-lattice and increased covalency of the Fe-O bonds of the FeO6 octahedra in B-site-substituted BFO. Charge analysis shows that A-site substitution amounts to donor doping and consequently impedes the accommodation of other donors (i.e. oxygen vacancies). However, A-site substitution may also exhibit a higher electronic conductivity due to less lattice distortion for oxygen deficiency compared to B-site doped structures. Furthermore, analysis of the local structural effects provides physical insight into stoichiometric expansions observed for this material.

Reactive nitrogen oxides and ozone above a taiga woodland

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

Bakwin, P.S.; Jacob, D.J.; Wofsy, S.C.

1994-01-20

Measurements of reactive nitrogen oxides (NO{sub x} and NO{sub y}) and ozone (O{sub 3}) were made in the planetary boundary layer (PBL) above a taiga woodland in northern Quebec, Canada, during June-August, 1990, as part of NASA Arctic Boundary Layer Expedition (ABLE) 3B. Levels of nitrogen oxides and O{sub 3} were strongly modulated by the synoptic scale meteorology that brought air from various regions to the site. Industrial pollution from the Great Lakes region of the US and Canada appears to be a major source for periodic elevation of NO{sub x}, NO{sub y} and O{sub 3}. We find that NO/NO{submore » 2} ratios at this site at midday were approximately 50% those expected from a simple photochemical steady state between NO{sub x} and O{sub 3}, in contrast to our earlier results from the ABLE 3A tundra site. The difference between the taiga and tundra sites is likely due to much larger emissions of biogenic hydrocarbons (particularly isoprene) from the taiga vegetation. Hydrocarbon photooxidation leads to relatively rapid production of peroxy radicals, which convert NO to NO{sub 2}, at the taiga site. Ratios of NO{sub x} to NO{sub y} were typically 2-3 times higher in the PBL during ABLE 3B than during ABLE 3A. This is probably the result of high PAN levels and suppressed formation of HNO{sub 3} from NO{sub 2} due to high levels of biogenic hydrocarbons at the ABLE 3B site. 36 refs., 7 figs., 3 tabs.« less

Hydrodeoxygenation of p -Cresol over Pt/Al 2 O 3 Catalyst Promoted by ZrO 2 , CeO 2 , and CeO 2 –ZrO 2

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

Wang, Weiyan; Wu, Kui; Liu, Pengli

2016-07-20

ZrO 2-Al 2O 3 and CeO 2-Al 2O 3 were prepared by a co-precipitation method and selected as supports for Pt catalysts. The effects of CeO 2 and ZrO 2 on the surface area and Brønsted acidity of Pt/Al 2O 3 were studied. In the hydrodeoxygenation (HDO) of p-cresol, the addition of ZrO 2 promoted the direct deoxygenation activity on Pt/ZrOO 2-Al 2O 3 via Caromatic-O bond scission without benzene ring saturation. Pt/CeOO 2-Al 2O 3 exhibited higher deoxygenation extent than Pt/Al 2O 3 due to the fact that Brønsted acid sites on the catalyst surface favored the adsorption ofmore » p-cresol. With the advantages of CeO 2 and ZrO 2 taken into consideration, CeO 2-ZrOO 2-Al 2O 3 was prepared, leading to the highest HDO activity of Pt/CeO 2-ZrOO 2-Al 2O 3. The deoxygenation extent for Pt/CeO 2-ZrOO 2-Al 2O 3 was 48.4% and 14.5% higher than that for Pt/ZrO2O 2-Al 2O 3 and Pt/CeOO 2-Al 2O 3, respectively.« less

Evaluating the uncertainties of thermal catalytic conversion in measuring atmospheric nitrogen dioxide at four differently polluted sites in China

NASA Astrophysics Data System (ADS)

Xu, Zheng; Wang, Tao; Xue, L. K.; Louie, Peter K. K.; Luk, Connie W. Y.; Gao, J.; Wang, S. L.; Chai, F. H.; Wang, W. X.

2013-09-01

A widely used method for measuring nitrogen dioxide (NO2) in the atmosphere is the conversion of NO2 to nitric oxide (NO) on the hot surface of a molybdenum oxide (MoO) catalyst followed by the chemiluminescence detection of NO. Although it has long been recognized that this type of conversion may suffer from the positive interference of other oxidized nitrogen compounds, evaluations of such interference in the atmosphere are scarce, thus rendering it difficult to make use of a large portion of the NO2 or NOx data obtained via this method (often denoted as NO2* or NOx*). In the present study, we compared the MoO converter with a selective, more accurate photolytic approach at four differently polluted sites in China. The converter worked well at the urban site, which was greatly affected by fresh emissions, but, on average, overestimated NO2 by 30%-50% at the two suburban sites and by more than 130% at the mountain-top site during afternoon hours, with a much larger positive bias seen during the top 10% of ozone events. The degree of overestimation depended on both air-parcel age and the composition of the oxidation products/intermediates of NOx (NOz). We attempted to derive an empirical formula to correct for this overestimation using concurrently measured O3, NO, and NO2* at the two suburban sites. Although the formula worked well at each individual site, the different NOz partitions at the sites made it difficult to obtain a universal formula. In view of the difficulty of assessing the uncertainties of the conventional conversion method, thus limiting the usability of data obtained via this method in atmospheric research, we suggest that, in areas away from fresh NOx emission sources, either a more selective NO2 measurement method or a NOy (NOx and its reaction products and intermediates) instrument should be adopted.

Novel Co3O4 Nanoparticles/Nitrogen-Doped Carbon Composites with Extraordinary Catalytic Activity for Oxygen Evolution Reaction (OER)

NASA Astrophysics Data System (ADS)

Yang, Xiaobing; Chen, Juan; Chen, Yuqing; Feng, Pingjing; Lai, Huixian; Li, Jintang; Luo, Xuetao

2018-03-01

Herein, Co3O4 nanoparticles/nitrogen-doped carbon (Co3O4/NPC) composites with different structures were prepared via a facile method. Structure control was achieved by the rational morphology design of ZIF-67 precursors, which were then pyrolyzed in air to obtain Co3O4/NPC composites. When applied as catalysts for the oxygen evolution reaction (OER), the M-Co3O4/NPC composites derived from the flower-like ZIF-67 showed superior catalytic activities than those derived from the rhombic dodecahedron and hollow spherical ZIF-67. The former M-Co3O4/NPC composite displayed a small over-potential of 0.3 V, low onset potential of 1.41 V, small Tafel slope of 83 mV dec-1, and a desirable stability. (94.7% OER activity was retained after 10 h.) The excellent performance of the flower-like M-Co3O4/NPC composite in the OER was attributed to its favorable structure. [Figure not available: see fulltext.

Cottonwood Response to Nitrogen Related To Plantation Age and Site

Treesearch

B.G. Blackmon

1977-01-01

When applied at plantation age 4,336 kg N/ha increased diameter growth of cottonwood on Sharkey clay by 33 percent over unfertilized controls. Fertilizing at ages 2 and 3 resulted in no response, nor was there any benefit from applying nitrogen fertilizer to cottonwood on Commerce silt loam. On both sites, foliar N levels were increased by fertilization regardless of...

Using one filter stage of unsaturated/saturated vertical flow filters for nitrogen removal and footprint reduction of constructed wetlands.

PubMed

Morvannou, Ania; Troesch, Stéphane; Esser, Dirk; Forquet, Nicolas; Petitjean, Alain; Molle, Pascal

2017-07-01

French vertical flow constructed wetlands (VFCW) treating raw wastewater have been developed successfully over the last 30 years. Nevertheless, the two-stage VFCWs require a total filtration area of 2-2.5 m 2 /P.E. Therefore, implementing a one-stage system in which treatment performances reach standard requirements is of interest. Biho-Filter ® is one of the solutions developed in France by Epur Nature. Biho-Filter ® is a vertical flow system with an unsaturated layer at the top and a saturated layer at the bottom. The aim of this study was to assess this new configuration and to optimize its design and operating conditions. The hydraulic functioning and pollutant removal efficiency of three different Biho-Filter ® plants commissioned between 2011 and 2012 were studied. Outlet concentrations of the most efficient Biho-Filter ® configuration are 70 mg/L, 15 mg/L, 15 mg/L and 25 mg/L for chemical oxygen demand (COD), 5-day biological oxygen demand (BOD 5 ), total suspended solids (TSS) and total Kjeldahl nitrogen (TKN), respectively. Up to 60% of total nitrogen is removed. Nitrification efficiency is mainly influenced by the height of the unsaturated zone and the recirculation rate. The optimum recirculation rate was found to be 100%. Denitrification in the saturated zone works at best with an influent COD/NO 3 -N ratio at the inflet of this zone larger than 2 and a hydraulic retention time longer than 0.75 days.

Effects of ZnO nanoparticles on wastewater biological nitrogen and phosphorus removal.

PubMed

Zheng, Xiong; Wu, Rui; Chen, Yinguang

2011-04-01

With the increasing utilization of nanomaterials, zinc oxide nanoparticles (ZnO NPs) have been reported to induce adverse effects on human health and aquatic organisms. However, the potential impacts of ZnO NPs on wastewater nitrogen and phosphorus removal with an activated sludge process are unknown. In this paper, short-term exposure experiments were conducted to determine whether ZnO NPs caused adverse impacts on biological nitrogen and phosphorus removal in the unacclimated anaerobic-low dissolved oxygen sequencing batch reactor. Compared with the absence of ZnO NPs, the presence of 10 and 50 mg/L of ZnO NPs decreased total nitrogen removal efficiencies from 81.5% to 75.6% and 70.8%, respectively. The corresponding effluent phosphorus concentrations increased from nondetectable to 10.3 and 16.5 mg/L, respectively, which were higher than the influent phosphorus (9.8 mg/L), suggesting that higher concentration of ZnO NPs induced the loss of normal phosphorus removal. It was found that the inhibition of nitrogen and phosphorus removal induced by higher concentrations of ZnO NPs was due to the release of zinc ions from ZnO NPs dissolution and increase of reactive oxygen species (ROS) production, which caused inhibitory effect on polyphosphate-accumulating organisms and decreased nitrate reductase, exopolyphosphatase, and polyphosphate kinase activities.

Core-Shell Co/CoO Integrated on 3D Nitrogen Doped Reduced Graphene Oxide Aerogel as an Enhanced Electrocatalyst for the Oxygen Reduction Reaction

PubMed Central

Wang, Meng; Hou, Yuyang; Slade, Robert C. T.; Wang, Jiazhao; Shi, Dongqi; Wexler, David; Liu, Huakun; Chen, Jun

2016-01-01

Here, we demonstrate that Cobalt/cobalt oxide core-shell nanoparticles integrated on nitrogen-doped (N-doped) three-dimensional reduced graphene oxide aerogel-based architecture (Co/CoO-NGA) were synthesized through a facile hydrothermal method followed by annealing treatment. The unique endurable porous structure could provide sufficient mass transfer channels and ample active sites on Co/CoO-NGA to facilitate the catalytic reaction. The synthesized Co/CoO-NGA was explored as an electrocatalyst for the oxygen reduction reaction, showing comparable oxygen reduction performance with excellent methanol resistance and better durability compared with Pt/C. PMID:27597939

High stability of electro-transport and magnetism against the A-site cation disorder in SrRuO3

PubMed Central

Wang, Y. L.; Liu, M. F.; Liu, R.; Xie, Y. L.; Li, X.; Yan, Z. B.; Liu, J.-M.

2016-01-01

It is known that the electro-transport and magnetism of perovskite alkaline-earth ruthenate oxides are sensitive to the lattice distortion associated with the A-site cation size. Orthorhombic CaRuO3 and cubic BaRuO3 exhibit distinctly different electro-transport and magnetic properties from orthorhombic SrRuO3. It has been suggested that SrRuO3 can be robust against some intrinsic/external perturbations but fragile against some others in terms of electro-transport and magnetism, and it is our motivation to explore such stability against the local site cation disorder. In this work, we prepare a set of SrRuO3-based samples with identical averaged A-site size but different A-site cation disorder (size mismatch) by Ca and Ba co-substitution of Sr. It is revealed that the electro-transport and magnetism of SrRuO3 demonstrate relatively high stability against this A-site cation disorder, characterized by the relatively invariable electrical and magnetic properties in comparison with those of SrRuO3 itself. A simple electro-transport network model is proposed to explain quantitatively the measured behaviors. The present work suggests that SrRuO3 as an itinerant electron ferromagnetic metal possesses relatively high robustness against local lattice distortion and cation occupation disorder. PMID:27297396

A study of nitrogen incorporation in pyramidal site-controlled quantum dots

PubMed Central

2011-01-01

We present the results of a study of nitrogen incorporation in metalorganic-vapour-phase epitaxy-grown site-controlled quantum dots (QDs). We report for the first time on a significant incorporation (approximately 0.3%), producing a noteworthy red shift (at least 50 meV) in some of our samples. Depending on the level of nitrogen incorporation/exposure, strong modifications of the optical features are found (variable distribution of the emission homogeneity, fine-structure splitting, few-particle effects). We discuss our results, especially in relation to a specific reproducible sample which has noticeable features: the usual pattern of the excitonic transitions is altered and the fine-structure splitting is suppressed to vanishing values. Distinctively, nitrogen incorporation can be achieved without detriment to the optical quality, as confirmed by narrow linewidths and photon correlation spectroscopy. PMID:22029752

Multiple Site-Directed and Saturation Mutagenesis by the Patch Cloning Method.

PubMed

Taniguchi, Naohiro; Murakami, Hiroshi

2017-01-01

Constructing protein-coding genes with desired mutations is a basic step for protein engineering. Herein, we describe a multiple site-directed and saturation mutagenesis method, termed MUPAC. This method has been used to introduce multiple site-directed mutations in the green fluorescent protein gene and in the moloney murine leukemia virus reverse transcriptase gene. Moreover, this method was also successfully used to introduce randomized codons at five desired positions in the green fluorescent protein gene, and for simple DNA assembly for cloning.

A periodic DFT study of ammonia adsorption on the V2O5 (001), V2O5 (010) and V2O5 (100) surfaces: Lewis versus Brönsted acid sites

NASA Astrophysics Data System (ADS)

Yao, Huichao; Chen, Yu; Wei, Yuechang; Zhao, Zhen; Liu, Zhichang; Xu, Chunming

2012-11-01

The adsorption of ammonia at Brönsted and Lewis acid sites on three low-index (001), (010) and (100) surfaces of V2O5 catalyst was investigated using density functional theory (DFT) method. Three levels of surface relaxation periodic models including top single layer relaxation (S-model), moderately deeper relaxation (M-model) and full relaxation model (F-model) were applied to examine the effect of the surface relaxation on the binding structures and adsorption energies. The results of calculations showed that on the saturated basal plane V2O5 (001), ammonia adsorption at the Brönsted acid sites (VOH) is energetically more favorable. On unsaturated (010) and (100) surfaces, ammonia is adsorbed strongly on both Brönsted (VOH) and Lewis acid sites (V). Surface relaxations have no influence on ammonia adsorption on saturated (001) surface, while a strong dependence on the relaxation models is observed for NH3-adsorption energies on (010) and (100) surfaces, especially at the Lewis acid sites of both side planes. When complete relaxation considered (F-model), ammonia adsorption on the Lewis acid sites (V) dominates for side planes (010) and (100). In the presence of VOH as neighbor, the ammonia adsorption at V sites is however weakened significantly due to steric hindrance. Hydrogen bonds may play a role, although not determining one, in the respect of the adsorption of ammonia on (010) and (100) surfaces. Moderate relaxation and full relaxation are absolutely necessary for the description of both H and NH3 adsorption on unsaturated (100) and (010) surfaces, respectively.

Nitrogen Incorporation Effects On Site-Controlled Quantum Dots

NASA Astrophysics Data System (ADS)

Juska, G.; Dimastrodonato, V.; Mereni, L. O.; Pelucchi, E.

2011-12-01

We report here on the optical properties of site-controlled diluted nitride In0.25Ga0.75As1-xNx quantum dots grown by metalorganic vapour phase epitaxy (MOVPE). We show photoluminescence energy shift as a function of nitrogen precursor U-dimethylhydrazine, with a maximum value of 35 meV achieved. Optical features, substantially different from the counterpart nitrogen-free dots, are presented: an antibinding biexciton, a large distribution of lifetimes, significantly reduced fine structure splitting.

Nitrogen balance of a boreal Scots pine forest

NASA Astrophysics Data System (ADS)

Korhonen, J. F. J.; Pihlatie, M.; Pumpanen, J.; Aaltonen, H.; Hari, P.; Levula, J.; Kieloaho, A.-J.; Nikinmaa, E.; Vesala, T.; Ilvesniemi, H.

2013-02-01

The productivity of boreal forests is considered to be limited by low nitrogen (N) availability. Increased atmospheric N deposition has altered the functioning and N cycling of these N-sensitive ecosystems by increasing the availability of reactive nitrogen. The most important components of N pools and fluxes were measured in a boreal Scots pine stand in Hyytiälä, Southern Finland. The measurements at the site allowed direct estimations of nutrient pools in the soil and biomass, inputs from the atmosphere and outputs as drainage flow and gaseous losses from two micro-catchments. N was accumulating in the system, mainly in woody biomass, at a rate of 7 kg N ha-1 yr-1. Nitrogen input as atmospheric deposition was 7.4 kg N ha-1 yr-1. Dry deposition and organic N in wet deposition contributed over half of the inputs in deposition. Total outputs were 0.4 kg N ha-1 yr-1, the most important outputs being N2O emission to the atmosphere and organic N flux in drainage flow. Nitrogen uptake and retranslocation were equally important sources of N for plant growth. Most of the assimilated N originated from decomposition of organic matter, and the fraction of N that could originate directly from deposition was about 30%. In conclusion, atmospheric N deposition fertilizes the site considerably, but there are no signs of N saturation. Further research is needed to estimate soil N2 fluxes (emission and fixation), which may amount up to several kg N ha-1 yr-1.

Genetic selection for a highly functional cysteine-less membrane protein using site-saturation mutagenesis

PubMed Central

Arendt, Cassandra S.; Ri, Keirei; Yates, Phillip A.; Ullman, Buddy

2007-01-01

We describe an efficient method for generating highly functional membrane proteins with variant amino acids at defined positions that couples a modified site-saturation strategy with functional genetic selection. We applied this method to the production of a cysteine-less variant of the Crithidia fasciculata inosine-guanosine permease CfNT2, in order to facilitate biochemical studies using thiol-specific modifying reagents. Of ten endogenous cysteine residues in CfNT2, two cannot be replaced with serine or alanine without loss of function. High-quality single- and double-mutant libraries were produced by combining a previously reported site-saturation mutagenesis scheme based on the Quikchange method with a novel gel purification step that effectively eliminated template DNA from the products. Following selection for functional complementation in S. cerevisiae cells auxotrophic for purines, several highly functional non-cysteine substitutions were efficiently identified at each desired position, allowing the construction of cysteine-less variants of CfNT2 that retained wild-type affinity for inosine. This combination of an improved site-saturation mutagenesis technique and positive genetic selection provides a simple and efficient means to identify functional and perhaps unexpected amino acid variants at a desired position. PMID:17481563

Do Forest Age and Soil Depth Affect Carbon and Nitrogen Adsorption in Mineral Horizons?

NASA Astrophysics Data System (ADS)

Spina, P. G.; Lovett, G. M.; Fuss, C. B.; Goodale, C. L.; Lang, A.; Fahey, T.

2015-12-01

Mineral soils retain large amounts of organic matter through sorption on the surfaces of mineral soils, the largest pools of carbon (C) and nitrogen (N) in the forests of the northeastern U.S. In addition to determining organic matter storage, adsorption and desorption processes are important controllers of runoff chemistry. We are studying adsorption dynamics of mineral soils collected from a chronosequence of hardwood forest sites in the White Mountains, NH to determine how soils vary in their DOM adsorption capacities as a function of effective C and N saturation. We hypothesize that forest age determines proximity to saturation because young forests may need to mine soil organic matter (SOM) in mineral soils to obtain nitrogen to meet growth demands, while the soils of older forests have had time to reaccumulate SOM, eventually reaching C and N saturation. Consequently, we expect adsorption capacities to first increase with forest age in young forests, as the trees mine C and N from mineral surfaces. They will then decrease with forest age in older forests as mining slows and C and N begin to re-accumulate. Batch experiments were conducted with mineral soil samples and dilutions of forest floor leachate. However, preliminary results from a mature forest site (about 100 years old), which we predicted to be a low point of C and N saturation from decades of mining, contradict expectations. Dissolved organic carbon (DOC) adsorption in its shallow mineral soil layers (0-3 cm below E or A horizons) are lower than younger sites ranging from 20 to about 40 years old. In addition to forest age, soil depths also affect N retention dynamics in forest soils. We hypothesized that deeper mineral soils might have greater adsorption capacities due to the fact that they are exposed to less DOC and DON leaching from organic layers and therefore less saturated. Results from the same mature forest site confirm this. Soils from 3-10 cm depth have more potential to adsorb DOC and

Throughfall and fog deposition of nitrogen and sulfur at an N-limited and N-saturated site in the San Bernardino Mountains, southern California

Treesearch

Mark E. Fenn; Mark A. Poth; Susan L. Schilling; David B. Grainger

2000-01-01

Inorganic nitrogen (N) and sulfur (S) deposition in bulk throughfall and fog were determined at two sites located at opposite ends (42 km apart) of a pollution gradient in the San Bernardino Mountains. Plot-level averages for total annual N and S deposition in throughfall in 1996 were 18.8 and 2.9 kg·ha–1, respectively, at Camp Paivika (CP) and 2...

Dissolved organic nitrogen budgets for upland, forested ecosystems in New England

Treesearch

John L. Campbell; James W. Hornbeck; William H. McDowell; Donald C. Buso; James B. Shanley; Gene E. Likens

2000-01-01

Relatively high deposition of nitrogen (N) in the northeastern United States has caused concern because sites could become N saturated. In the past, mass-balance studies have been used to monitor the N status of sites and to investigate the impact of increased N deposition. Typically, these efforts have focused on dissolved inorganic forms of N (DIN = NH4-...

Passive Q-switching of ˜2.7 µm Er:Lu2O3 ceramic laser with a semiconductor saturable absorber mirror

NASA Astrophysics Data System (ADS)

Ren, Xiaojing; Shen, Deyuan; Zhang, Jian; Tang, Dingyuan

2018-02-01

We demonstrate the passively Q-switched operation of an Er:Lu2O3 ceramic laser at ˜2.7 µm for the first time, to the best of our knowledge. By using a semiconductor saturable absorber mirror (SESAM), stable pulse trains with a repetition rate of 20-33.3 kHz are produced in a compacted v-shaped resonator. The pulse duration (FWHM), pulse energy, and peak power are 660 ns, 1.8 µJ, and ˜2.73 W, respectively, at 33.3 kHz repetition rate. Prospects for further improvements in terms of laser performances are discussed.

An X-ray absorption spectroscopic study of the metal site preference in Al1-xGaxFeO3

NASA Astrophysics Data System (ADS)

Walker, James D. S.; Grosvenor, Andrew P.

2013-01-01

Magnetoelectric materials have potential for being introduced into next generation technologies, especially memory devices. The AFeO3 (Pna21; A=Al, Ga) system has received attention to better understand the origins of magnetoelectric coupling. The magnetoelectric properties this system exhibits depend on the amount of anti-site disorder present, which is affected by the composition and the method of synthesis. In this study, Al1-xGaxFeO3 was synthesized by the ceramic method and studied by X-ray absorption spectroscopy. Al L2,3-, Ga K-, and Fe K-edge spectra were collected to examine how the average metal coordination number changes with composition. Examination of XANES spectra from Al1-xGaxFeO3 indicate that with increasing Ga content, Al increasingly occupies octahedral sites while Ga displays a preference for occupying the tetrahedral site. The Fe K-edge spectra indicate that more Fe is present in the tetrahedral site in AlFeO3 than in GaFeO3, implying more anti-site disorder is present in AlFeO3.

Infrared spectroscopy and surface chemistry of beta-Ga(2)O(3) nanoribbons.

PubMed

Bermudez, V M; Prokes, S M

2007-12-04

The structure and surface chemistry of crystalline beta-Ga2O3 nanoribbons (NRs), deposited in a thin layer on various metallic and dielectric substrates (mainly on Au), have been characterized using vibrational spectroscopy. The results have been analyzed with the aid of a previous ab initio theoretical model for the beta-Ga2O3 surface structure. Raman spectra and normal-incidence infrared (IR) transmission data show little if any difference from corresponding results for bulk single crystals. For a layer formed on a metallic substrate, IR reflection-absorption spectroscopy (IRRAS) shows longitudinal-optic (LO) modes that are red-shifted by approximately 37 cm-1 relative to those of a bulk crystal. Evidence is also seen for a bonding interaction at the Ga2O3/Au interface following heating in room air. Polarization-modulated IRRAS has been used to study the adsorption of pyridine under steady-state conditions in ambient pressures as high as approximately 5 Torr. The characteristic nu19b and nu8a modes of adsorbed pyridine exhibit little or no shift from the corresponding gas-phase values. This indicates that the surface is only weakly acidic, consistent with the theoretical prediction that singly unsaturated octahedral Ga sites are the only reactive cation sites on the NR surface. However, evidence for adsorption at defect sites is seen in the form of more strongly shifted modes that saturate in intensity at low pyridine coverage. The effect of H atoms, formed by thermal cracking of H2, has also been studied. No Ga-H or O-H bonds are observed on the pristine NR surface. This suggests that the previously reported presence of such species on Ga2O3 powders heated in H2 is a result of a partial reduction of the oxide surface. The heat of adsorption of atomic H on the pristine beta-Ga2O3(100) surface at 0 K is computed to be -1.79 eV per H at saturation (average of Ga-H and O-H sites), whereas a value of +0.45 eV per H is found for the dissociative adsorption of H2. This

Analysis of High Frequency Site-Specific Nitrogen and Oxygen Isotopic Composition of Atmospheric Nitrous Oxide at Mace Head, Ireland

NASA Astrophysics Data System (ADS)

McClellan, M. J.; Harris, E. J.; Olszewski, W.; Ono, S.; Prinn, R. G.

2014-12-01

Atmospheric nitrous oxide (N2O) significantly impacts Earth's climate due to its dual role as an inert potent greenhouse gas in the troposphere and as a reactive source of ozone-destroying nitrogen oxides in the stratosphere. However, there remain significant uncertainties in the global budget of this gas. The marked spatial divide in its reactivity means that all stages in the N2O life cycle—emission, transport, and destruction—must be examined to understand the overall effect of N2O on climate. Source and sink processes of N2O lead to varying concentrations of N2O isotopologues (14N14N16O, 14N15N16O, 15N14N16O, and 14N14N18O being measured) due to preferential isotopic production and elimination in different environments. Estimation of source and sink fluxes can be improved by combining isotopically resolved N2O observations with simulations using a chemical transport model with reanalysis meteorology and treatments of isotopic signatures of specific surface sources and stratospheric intrusions. We present the first few months of site-specific nitrogen and oxygen isotopic composition data from the Stheno-TILDAS instrument (Harris et al, 2013) at Mace Head, Ireland and compare these to results from MOZART-4 (Model for Ozone and Related Chemical Tracers, version 4) chemical transport model runs including N2O isotopic fractionation processes and reanalysis meterological fields (NCEP/NCAR, MERRA, and GEOS-5). This study forms the basis for future inverse modeling experiments that will improve the accuracy of isotopically differentiated N2O emission and loss estimates. Ref: Harris, E., D. Nelson, W. Olszewski, M. Zahniser, K. Potter, B. McManus, A. Whitehill, R. Prinn, and S. Ono, Development of a spectroscopic technique for continuous online monitoring of oxygen and site-specific nitrogen isotopic composition of atmospheric nitrous oxide, Analytical Chemistry, 2013; DOI: 10.1021/ac403606u.

Nitrogen fluxes through unsaturated zones in five agricultural settings across the USA

NASA Astrophysics Data System (ADS)

Green, C. T.; Fisher, L. H.; Bekins, B. A.

2006-12-01

The main controls on nitrogen (N) fluxes between the root zone and the water table were determined for agricultural sites in California, Washington, Nebraska, Indiana, and Maryland in 2004 and 2005. Sites included irrigated and non-irrigated fields; soil textures ranging from clay to sand; crops including corn, soybeans, almonds, and pasture; and unsaturated zone thicknesses ranging from 0.5 to 20 m. Chemical analyses of water from lysimeters, shallow wells, and sediment cores indicate that advective transport of nitrate is the dominant process affecting the rate of N transport below the root zone. Vertical profiles of (1) N species, (2) stable N and O isotopes, and (3) oxygen gas in unsaturated zone air and shallow ground water, and correlations between N and other agricultural chemicals indicate that reactions do not greatly affect N concentrations between the root zone and the capillary fringe. Relatively stable concentrations at depths greater than a few meters allow calculation of nitrogen fluxes to the saturated zone. These fluxes are equivalent to 14 - 64% of the N application rates. At the same locations, median vertical fluxes of N in ground water are generally lower, ranging from 4 - 37% of N application rates. The lower nitrate fluxes in ground water reflect processes including lateral flow to tile drains and denitrification in the capillary fringe, as well as historical changes in N inputs.

Modification of YNbO4 and YNbTiO6 photoluminescence by nitrogen doping

NASA Astrophysics Data System (ADS)

Pei, H.; Su, L. M.; Cai, G. M.; Jin, Z. P.

2018-04-01

Niobates as multifunctional materials were of vital importance in the industry production and daily life. In present work, niobates YNbO4 and YNbTiO6 are investigated as luminescence materials. The compounds have self-activated luminescence, and it is discussed how nitrogen doping affects their electronic structure and optical properties. Various analytical techniques, including x-ray diffraction, nitrogen-content analysis, x-ray photoelectron spectroscopy, scanning electron microscopy, UV-vis absorption spectroscopy and vacuum ultraviolet emission spectroscopy at variable temperature, were used to characterize the structure, composition, crystallinity and optical performance of these niobates. By considering the luminescence mechanisms in YNbO4 and YNbTiO6, the enhanced luminescence obtained upon nitrogen doping is attributed to the presence of oxygen vacancies and nitrogen levels, which changes the band gaps of the materials. Present work demonstrates the use of nitrogen doping for improving the photoluminescence properties of self-activated niobates.

Dual-wavelength passively Q-switched ytterbium-doped fiber laser using Fe3O4-nanoparticle saturable absorber and intracavity polarization

NASA Astrophysics Data System (ADS)

Al-Hayali, S. K. M.; Al-Janabi, A. H.

2018-03-01

We have experimentally demonstrated the operation of a dual-wavelength passively Q-switched ytterbium-doped fiber laser by using a saturable absorber (SA) based on Fe3O4 nanoparticles in a magnetic fluid. The SA was fabricated by depositing magnetic fluid at the end of an optical fiber ferrule. By performing adjustments to the pump power and polarization controller state in the cavity, a stable dual-wavelength lasing operation was generated without intracavity spectral filters or modulation elements. The Q-switched laser output was achieved at a pump threshold of 80 mW with a maximum output pulse energy of 38.8 nJ, a repetition rate of 73.4 kHz and a minimum pulse width of 3.4 µs. To the best of the authors’ knowledge, this is the first demonstration of a dual-wavelength passively Q-switched fiber laser using Fe3O4 nanoparticles as the SA in the 1.0 µm operation region.

Ring-through-ring molecular shuttling in a saturated [3]rotaxane

NASA Astrophysics Data System (ADS)

Zhu, Kelong; Baggi, Giorgio; Loeb, Stephen J.

2018-06-01

Mechanically interlocked molecules such as rotaxanes and catenanes comprise two or more components whose motion relative to each other can be controlled. A [2]rotaxane molecular shuttle, for example, consists of an axle bearing two recognition sites and a single macrocyclic wheel that can undergo a to-and-fro motion along the axle—shuttling between the recognition sites. The ability of mechanically interlocked molecules to undergo this type of large-amplitude change is the core mechanism behind almost every interlocked molecular switch or machine, including sophisticated mechanical systems such as a molecular elevator and a peptide synthesizer. Here, as a way to expand the scope of dynamics possible at the molecular level, we have developed a molecular shuttling mechanism involving the exchange of rings between two recognition sites in a saturated [3]rotaxane (one with no empty recognition sites). This was accomplished by passing a smaller ring through a larger one, thus achieving ring-through-ring molecular shuttling.

Magnetic properties of mixed spinel BaTiO{sub 3}-NiFe{sub 2}O{sub 4} composites

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

Sarkar, Babusona; Dalal, Biswajit; Dev Ashok, Vishal

2014-03-28

Solid solution of nickel ferrite (NiFe{sub 2}O{sub 4}) and barium titanate (BaTiO{sub 3}), (100-x)BaTiO{sub 3}–(x) NiFe{sub 2}O{sub 4} has been prepared by solid state reaction. Compressive strain is developed in NiFe{sub 2}O{sub 4} due to mutual structural interaction across the interface of NiFe{sub 2}O{sub 4} and BaTiO{sub 3} phases. Quantitative analysis of X-ray diffraction and X-ray photo electron spectrum suggest mixed spinel structure of NiFe{sub 2}O{sub 4}. A systematic study of composition dependence of composite indicates BaTiO{sub 3} causes a random distribution of Fe and Ni cations among octahedral and tetrahedral sites during non-equilibrium growth of NiFe{sub 2}O{sub 4}. Themore » degree of inversion decreases monotonically from 0.97 to 0.75 with increase of BaTiO{sub 3} content. Temperature dependence of magnetization has been analyzed by four sublattice model to describe complex magnetic exchange interactions in mixed spinel phase. Curie temperature and saturation magnetization decrease with increase of BaTiO{sub 3} concentration. Enhancement of strain and larger occupancy of Ni{sup 2+} at tetrahedral site increase coercivity up to 200 Oe. Magnetostructual coupling induced by BaTiO{sub 3} improves coercivity in NiFe{sub 2}O{sub 4}. An increase in the demagnetization and homogeneity in magnetization process in NiFe{sub 2}O{sub 4} is observed due to the interaction with diamagnetic BaTiO{sub 3}.« less

DMPP-added nitrogen fertilizer affects soil N2O emission and microbial activity in Southern Italy

NASA Astrophysics Data System (ADS)

Vitale, Luca; De Marco, Anna; Maglione, Giuseppe; Polimeno, Franca; Di Tommasi, Paul; Magliulo, Vincenzo

2014-05-01

Arable sites contributes to global N2O emission due to massive utilization of nitrogen fertilizers. N2O derives from the biological processes such as nitrification and denitrification influenced by soil nitrogen availability. The use of nitrogen fertilizers added with nitrification inhibitors represents one among the proposed strategy to reduce soil N2O emission form arable sites. The aim of this work was to evaluate the effects of 3,4-dimethylphyrazole phosphate (DMPP), a nitrification inhibitor, on N2O emission and microbial activity of a soil cropped to potato in Southern Italy. The experiment was a randomized block design with two treatments applied and three replicates: control (C) and DMPP (Entec®, K+S Nitrogen) plots, both supplied with the same amount of ammonium nitrate. The nitrogen fertilizer was supplied in three events: at 0 Day After Sowing (DAS; 100 kg N ha-1), at 57 DAS (30 kg N ha-1), and at 71 DAS (30 kg N ha-1). Soil N2O emission was monitored by both dynamic and static chambers. Static chambers were located both on hills and furrows whereas dynamic chambers were located on furrows. Air samples were collected from chambers at different times and analysed by a gas chromatograph (SRI 8610C, Gas Chromatograph). Fluxes were estimated as a linear interpolation of N2O changes over a 30 min time. Microbial biomass and basal respiration were determined as CO2 evolution, analysed by means of an IRGA (Li6200, Licor), on 2 g of fresh soil over a 4h incubation time. Microbial biomass was determined by Substrate Induced Respiration method. Data show no statistical differences in N2O fluxes measured with either dynamic chambers between C and DMPP plots in studied period. However, after the first fertilization event, when the fertilizer was applied as 100 kg N ha-1, the average N2O fluxes measured with static chambers were higher in DMPP plots compared to C plots. In the same period, the microbial biomass significantly decreased in DMPP plots as compared to C

Manipulating vineyard nitrogen on a saline site: 1. Effect of nitrogen on growth, grape yield and nutrients of Vitis vinifera L. cv Shiraz.

PubMed

Bell, Sally-Jean; Francis, I Leigh

2013-08-15

With increased prevalence of saline irrigation water applied to vines worldwide, the issue of appropriate nitrogen management is of concern. Different rates of nitrogen per vine as urea were applied to Shiraz vines on own roots over four seasons in a low-rainfall, saline growing environment. Application of nitrogen in the vineyard early in the season not only altered the vine nitrogen status but also increased some other elements in the petioles, notably chloride and sodium but also manganese and magnesium. In contrast, nitrogen application decreased petiole phosphorus. In comparison with the majority of nitrogen studies on non-saline sites, nitrogen-induced growth responses were restricted under the saline conditions in this study. While some changes in canopy density in response to nitrogen were observed, this did not affect light interception in the fruit zone. Yield responses were varied and could be related to the nutritional conditions under which bud development and flowering took place. This study demonstrated that current best practice guidelines, in terms of rate of nitrogen applied, for correcting a nitrogen deficiency on a non-saline site may not be appropriate for saline sites and that application of nitrogen can increase the potential for salt toxicity in vines. © 2013 Society of Chemical Industry.

Effects of skin pigmentation on pulse oximeter accuracy at low saturation.

PubMed

Bickler, Philip E; Feiner, John R; Severinghaus, John W

2005-04-01

It is uncertain whether skin pigmentation affects pulse oximeter accuracy at low HbO2 saturation. The accuracy of finger pulse oximeters during stable, plateau levels of arterial oxygen saturation (Sao2) between 60 and 100% were evaluated in 11 subjects with darkly pigmented skin and in 10 with light skin pigmentation. Oximeters tested were the Nellcor N-595 with the OxiMax-A probe (Nellcor Inc., Pleasanton, CA), the Novametrix 513 (Novametrix Inc., Wallingford, CT), and the Nonin Onyx (Nonin Inc., Plymouth, MN). Semisupine subjects breathed air-nitrogen-carbon dioxide mixtures through a mouthpiece. A computer used end-tidal oxygen and carbon dioxide concentrations determined by mass spectrometry to estimate breath-by-breath Sao2, from which an operator adjusted inspired gas to rapidly achieve 2- to 3-min stable plateaus of desaturation. Comparisons of oxygen saturation measured by pulse oximetry (Spo2) with Sao2 (by Radiometer OSM3) were used in a multivariate model to determine the interrelation between saturation, skin pigmentation, and oximeter bias (Spo2 - Sao2). At 60-70% Sao2, Spo2 (mean of three oximeters) overestimated Sao2 (bias +/- SD) by 3.56 +/- 2.45% (n = 29) in darkly pigmented subjects, compared with 0.37 +/- 3.20% (n = 58) in lightly pigmented subjects (P < 0.0001). The SD of bias was not greater with dark than light skin. The dark-light skin differences at 60-70% Sao2 were 2.35% (Nonin), 3.38% (Novametrix), and 4.30% (Nellcor). Skin pigment-related differences were significant with Nonin below 70% Sao2, with Novametrix below 90%, and with Nellcor at all ranges. Pigment-related bias increased approximately in proportion to desaturation. The three tested pulse oximeters overestimated arterial oxygen saturation during hypoxia in dark-skinned individuals.

Relationship of peroxyacetyl nitrate to active and total odd nitrogen at northern high latitudes: influence of reservoir species on NOx and O3

NASA Technical Reports Server (NTRS)

Singh, H. B.; Herlth, D.; O'Hara, D.; Zahnle, K.; Bradshaw, J. D.; Sandholm, S. T.; Talbot, R.; Crutzen, P. J.; Kanakidou, M.

1992-01-01

Measurements of peroxyacetyl nitrate (PAN), NO, NO2, HNO3, NOy (total odd nitrogen), and O3 were made in the high-latitude troposphere over North America and Greenland (35 degrees to 82 degrees N) during the Arctic Boundary Layer Expedition (ABLE 3A) (July-August 1988) throughout 0-to 6-km altitudes. These data are analyzed to quantitatively describe the relationships between various odd nitrogen species and assess their significance to global tropospheric chemistry. In the free troposphere, PAN was as much as 25 times more abundant than NOx. PAN to NOx ratio increased with increasing altitude and latitude. PAN was found to be the single most abundant reactive nitrogen species in the free troposphere and constituted a major fraction of NOy, PAN to NOy ratios were about 0.1 in the boundary layer and increased to 0.4 in the free troposphere. A 2-D global photochemical model with C1-C3 hydrocarbon chemistry is used to compare model predictions with measured results. A sizable portion (approximately 50%) of the gaseous reactive nitrogen budget is unaccounted for, and unknown organic nitrates and pernitrates are expected to be present. Model calculations (August 1, 70 degrees N) show that a major fraction of the observed NOx (50 to 70% of median) may find its source in the available PAN reservoir. PAN and the unknown reservoir species may have the potential to control virtually the entire NOx availability of the high latitude troposphere. It is predicted that the summer NOx and O3 mixing ratios in the Arctic/sub-Arctic troposphere would be considerably lower in the absence of the ubiquitous PAN reservoir. Conversely, this PAN reservoir may be responsible for the observed temporal increase in tropospheric O3 at high latitudes.

Synthesis and characterization of Eu{sup 3+}-doped CaZrO{sub 3}-based perovskite-type phosphors. Part I: Determination of the Eu{sup 3+} occupied site using the ALCHEMI technique

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

Sakaida, Satoshi; Shimokawa, Yohei; Asaka, Toru

2015-07-15

Highlights: • Eu{sup 3+}-doped CaZrO{sub 3}-based compounds were synthesized by the solid state reaction. • PL emission intensity at 614 nm was changed by the second dopant cations. • The site substituted by Eu{sup 3+} cations was investigated by using XRD and ALCHEMI technique. • The dominant Eu{sup 3+} substitution site was found as the B site (Zr{sup 4+}) in the CaZrO{sub {sup 3}}. • The dominant Eu{sup 3+} substitution site could be strongly influenced by the co-dopants. - Abstract: Eu{sup 3+}-doped CaZrO{sub 3}, SrZrO{sub 3}, and Mg{sup 2+}- or Sr{sup 2+}-co-doped CaZrO{sub 3} were synthesized by conventional solid statemore » reaction and their photoluminescence (PL) properties were characterized. The Eu{sup 3+}-doped CaZrO{sub 3}-based compounds exhibited characteristic emissions of Eu{sup 3+} (f–f transition). The intensity of the main PL emission peak at 614 nm increased with Mg{sup 2+} co-doping, while it decreased with the amount of co-doped Sr{sup 2+}. The site substituted by Eu{sup 3+} cations in the CaZrO{sub 3}-based compounds was investigated by X-ray diffraction analysis and energy-dispersive X-ray analysis based on the electron channeling effects in transmission electron microscopy. The Eu{sup 3+} cations were determined to occupy mainly the B site (Zr{sup 4+}) in CaZrO{sub 3}. The dominant Eu{sup 3+} substitution site was also strongly influenced by the co-dopant, and the ionic radius of the co-dopant was identified as an important factor that determines the dominant Eu{sup 3+} substitution site.« less

Analysis of nitrogen saturation potential in Rocky Mountain tundra and forest: implications for aquatic systems

USGS Publications Warehouse

Baron, Jill S.; Ojima, Dennis S.; Holland, Elisabeth A.; Parton, William J.

1994-01-01

We employed grass and forest versions of the CENTURY model under a range of N deposition values (0.02–1.60 g N m−2 y−1) to explore the possibility that high observed lake and stream N was due to terrestrial N saturation of alpine tundra and subalpine forest in Loch Vale Watershed, Rocky Mountain National Park, Colorado. Model results suggest that N is limiting to subalpine forest productivity, but that excess leachate from alpine tundra is sufficient to account for the current observed stream N. Tundra leachate, combined with N leached from exposed rock surfaces, produce high N loads in aquatic ecosystems above treeline in the Colorado Front Range. A combination of terrestrial leaching, large N inputs from snowmelt, high watershed gradients, rapid hydrologic flushing and lake turnover times, and possibly other nutrient limitations of aquatic organisms constrain high elevation lakes and streams from assimilating even small increases in atmospheric N. CENTURY model simulations further suggest that, while increased N deposition will worsen the situation, nitrogen saturation is an ongoing phenomenon.

Biomonitors of atmospheric nitrogen deposition: potential uses and limitations.

PubMed

Díaz-Álvarez, Edison A; Lindig-Cisneros, Roberto; de la Barrera, Erick

2018-01-01

Atmospheric nitrogen deposition is the third largest cause of global biodiversity loss, with rates that have more than doubled over the past century. This is especially threatening for tropical regions where the deposition may soon exceed 25 kg of N ha -1 year -1 , well above the threshold for physiological damage of 12-20 kg of N ha -1 year -1 , depending on plant species and nitrogenous compound. It is thus urgent to monitor these regions where the most diverse biotas occur. However, most studies have been conducted in Europe, the USA and recently in China. This review presents the case for the potential use of biological organisms to monitor nitrogen deposition, with emphasis on tropical plants. We first present an overview of atmospheric chemistry and the nitrogen metabolism of potential biomonitors, followed by a framework for monitoring nitrogen deposition based on the simultaneous use of various functional groups. In particular, the tissue nitrogen content responds to the rate of deposition, especially for mosses, whose nitrogen content increases by 1‰ per kilogram of N ha -1 year -1 . The isotopic signature, δ 15 N, is a useful indicator of the nitrogen source, as the slightly negative values (e.g. 5‰) of plants from natural environments can become very negative (-11.2‰) in sites with agricultural and husbandry activities, but very positive (13.3‰) in urban environments with high vehicular activity. Mosses are good biomonitors for wet deposition and atmospheric epiphytes for dry deposition. In turn, the nitrogen saturation of ecosystems can be monitored with trees whose isotopic values increase with saturation. Although given ecophysiological limitations of different organisms, particular studies should be conducted in each area of interest to determine the most suitable biomonitors. Overall, biomonitors can provide an integrative approach for characterizing nitrogen deposition in regions where the deployment of automated instruments or passive

Biomonitors of atmospheric nitrogen deposition: potential uses and limitations

PubMed Central

Díaz-Álvarez, Edison A; Lindig-Cisneros, Roberto

2018-01-01

Abstract Atmospheric nitrogen deposition is the third largest cause of global biodiversity loss, with rates that have more than doubled over the past century. This is especially threatening for tropical regions where the deposition may soon exceed 25 kg of N ha−1 year−1, well above the threshold for physiological damage of 12–20 kg of N ha−1 year−1, depending on plant species and nitrogenous compound. It is thus urgent to monitor these regions where the most diverse biotas occur. However, most studies have been conducted in Europe, the USA and recently in China. This review presents the case for the potential use of biological organisms to monitor nitrogen deposition, with emphasis on tropical plants. We first present an overview of atmospheric chemistry and the nitrogen metabolism of potential biomonitors, followed by a framework for monitoring nitrogen deposition based on the simultaneous use of various functional groups. In particular, the tissue nitrogen content responds to the rate of deposition, especially for mosses, whose nitrogen content increases by 1‰ per kilogram of N ha−1 year−1. The isotopic signature, δ15N, is a useful indicator of the nitrogen source, as the slightly negative values (e.g. 5‰) of plants from natural environments can become very negative (−11.2‰) in sites with agricultural and husbandry activities, but very positive (13.3‰) in urban environments with high vehicular activity. Mosses are good biomonitors for wet deposition and atmospheric epiphytes for dry deposition. In turn, the nitrogen saturation of ecosystems can be monitored with trees whose isotopic values increase with saturation. Although given ecophysiological limitations of different organisms, particular studies should be conducted in each area of interest to determine the most suitable biomonitors. Overall, biomonitors can provide an integrative approach for characterizing nitrogen deposition in regions where the deployment of automated instruments

Enhancement in magnetocaloric properties of ErCrO3 via A-site Gd substitution

NASA Astrophysics Data System (ADS)

Shi, Jianhang; Yin, Shiqi; Seehra, Mohindar S.; Jain, Menka

2018-05-01

Rare earth chromites (RCrO3) continue to be of considerable interest due to their intriguing physical properties such as spin-reorientation, multiferroicity, and magnetocaloric effect. In this paper, we compare the structural, magnetic, and magnetocaloric properties of bulk ErCrO3 with those of bulk Er0.33Gd0.67CrO3, the latter obtained by Gd substitution at the A-site (Er-site) and report substantial enhancement in the magnetocaloric response by Gd substitution. The samples prepared by the citrate route were structurally characterized at room temperature using x-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy. The XRD measurements refined by Rietveld analysis indicate that both samples crystallized in the orthorhombically distorted perovskite structure with Pbnm space group. Magnetic measurements on both samples were carried out between 5 K and 300 K in magnetic fields up to 7 T and show that TNC r (where Cr3+ orders) for Er0.33Gd0.67CrO3 is enhanced to 155 K vs. 133 K for ErCrO3 with analogous changes in the other magnetic parameters. Isothermal magnetization M vs. H data at different temperatures were used to determine changes in the magnetic entropy ( -ΔS ) and relative cooling power (RCP) for the two samples showing considerable improvement with Gd substitution in bulk ErCrO3. The maximum value of -ΔS for Er0.33Gd0.67CrO3 is 27.6 J kg-1 K-1 at 5 K and 7 T with a RCP of 531.1 J kg-1, in comparison to maximum -ΔS = 10.7 J kg-1 K-1 at 15 K with an RCP of 416.4 J kg-1 for ErCrO3 at 7 T.

[Preparation, spectral analysis and photocatalytic activities of TiO2 films codoped with iron and nitrogen].

PubMed

Liu, Wan-bing; Deng, Jian; Zhao, Yu-bao; Xu, Jin-sheng; Zhou, Liang

2009-05-01

Using tetrabutyl titanate as the titanium source, and ammonia and ferric nitrate as the sources of nitrogen and ferrum respectively, iron and nitrogen-codoped nano-TiO2 gelatins were prepared by sol-gel method. The iron and nitrogen-codoped nano-TiO2 complex films were prepared with the obtained gelatins used to coat the surface of cleaned glass slides by several times of dipping-lifting procedure, followed by natural seasoning at room temperature and calcined at 450 degrees C for 3 hours, then the films were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectrum (XPS) and ultraviolet-visible diffuse reflectance spectrum (UV-Vis). The XRD spectra o f samples showed that the Fe-TiO(2-x)Nx, filmswere of anatase structure with a few of oxygen atoms in the lattice of anatase TiO2 substituted by nitrogen atoms, resulting in the distortion of crystal lattice. The SEM image showed that the nanoparticles of the films have a good dispersion characteristic and uniform orbicular shape with an average diameter of about 19 nm. The absorption edges of UV-Vis spectra exhibited a red shift up to 740 nm when the TiO2 films were codoped with iron and nitrogen. The XPS of the Fe-TiO(2-x)Nx film presented a lowering of Ti 2p(3/2) electron binding energy because of the codoping of iron and nitrogen, which then resulted in the widening of the absorption of visible light range. The photocatalytic properties were studied by photocatalytical degradation of sudan I as a model reaction in a self-assembled light-reactor. When the atomic ratio of Fe3+/Ti4+ reached 0.4%, the Fe-TiO(2-x)Nx film showed the highest catalytic performance in degradation of sudan I which was decomposed by up to 97% after 4 hours of photocatalytic reaction. Codoping of nitrogen and appropriate amount of iron in TiO2 enhances photoresponse and utilizing efficiency in visible light region, and then improves the performances of Fe-TiO(2-x)Nx photocatalyst. The complex

Nitrogen isotopes as indicators of streamflow generation processes in a headwater forested catchment: Focusing on atmospheric NO3- contribution using δ 18O signature

NASA Astrophysics Data System (ADS)

Ohte, N.; Sebestyen, S. D.; Doctor, D. H.; Wankel, S. D.; Shanley, J. B.; Kendall, C.; Boyer, E. W.

2003-12-01

To quantify the contributions of atmospheric nitrogen deposition and mechanisms of nitrate discharge to stream, nitrogen chemistry and isotopes (δ 15N and δ 18O of NO3-) of streamwater were studied as part of an ongoing study of nutrient dynamics at the Sleepers River Research Watershed in Vermont, USA. We employed novel analytical procedures for high throughput of NO3- isotopic measurements. The denitrifier method for measurement of δ 15N and δ 18O of NO3- requires a smaller volume of water samples than previously applied methods, thus it enables fine resolution analysis of isotopes for stream, well, and soil water samples. Samples were collected throughout the spring 2003 snowmelt. Snowmelt runoff was initiated in the middle of March and peaked at the end of the month. Then, the runoff rate decreased gradually through April and May, and responded to several storm events. The highest concentration of NO3- in the stream was observed at the beginning of snowmelt (the end of March), and thereafter it declined continuously. The temporal course of NO3- discharge process during snowmelt period was divided into four phases based on changes in the relationship between runoff rate and NO3- concentration. During the earliest phase (very low runoff rate and highest NO3- concentration) isotope signatures, especially δ 18O of NO3-, indicated higher contribution of the atmospherically derived NO3-, meaning that the direct discharge from snow pack was the dominant source of NO3- to the stream. This also suggested that streamwater consisted only of a small volume of groundwater discharge and melt water of the in-stream snow pack and/or stream-covering snow pack. The δ 15N and δ 18O isotope compositions of NO3- during the middle phase of snowmelt indicated that the contribution of the NO3- generated by nitrifiers in soil increased gradually accompanied with increase of groundwater level. These detailed descriptions in the changes of NO3- discharge during snowmelt events

Effect of anti-site disorder on magnetism in La2NiMnO6

NASA Astrophysics Data System (ADS)

Pal, Somnath; Sharada Govinda, Goyal, Manik; Mukherjee, Soham; Pal, Banabir; Saha, Rana; Sundaresan, A.; Jana, Somnath; Karis, Olof; Freeland, John W.; Sarma, D. D.

2018-04-01

La2NiMnO6 has been reported to exhibit a paramagnetic to ferromagnetic transition with a transition temperature of ˜260 K. However, most of its magnetic properties, such as the saturation magnetization and even the transition temperature, appear to vary considerably among different reports. This is possibly because the crystallographic structure as well as the extent of the anti-site disorder (ASD) at the Ni/Mn sites are strongly influenced by the choice of synthesis routes. There are diverse reports connecting the extent of ASD to the valencies of Ni and Mn ions, such as Ni2 +-Mn4 + and Ni3 +-Mn3 + , including suggestions of thermally induced valence transitions. Consequently, these reports arrive at very different conclusions on the mechanism behind the magnetic properties of La2NiMnO6 . To address the correlation between ASD and valency, we have carried out a comparative study of two monoclinic La2NiMnO6 polycrystals with different degrees of ASD. Using a combination of x-ray absorption spectroscopy, x-ray magnetic circular dichroism, and magnetometry, we conclude that the valency of the transition metal ions, and the transition temperature, are insensitive to the extent of ASD. However, we find the magnetic moment decreases strongly with an increasing ASD. We attribute this effect to the introduction of antiferromagnetic interactions in the anti-site disordered regions.

Modeling variably saturated multispecies reactive groundwater solute transport with MODFLOW-UZF and RT3D

USGS Publications Warehouse

Bailey, Ryan T.; Morway, Eric D.; Niswonger, Richard G.; Gates, Timothy K.

2013-01-01

A numerical model was developed that is capable of simulating multispecies reactive solute transport in variably saturated porous media. This model consists of a modified version of the reactive transport model RT3D (Reactive Transport in 3 Dimensions) that is linked to the Unsaturated-Zone Flow (UZF1) package and MODFLOW. Referred to as UZF-RT3D, the model is tested against published analytical benchmarks as well as other published contaminant transport models, including HYDRUS-1D, VS2DT, and SUTRA, and the coupled flow and transport modeling system of CATHY and TRAN3D. Comparisons in one-dimensional, two-dimensional, and three-dimensional variably saturated systems are explored. While several test cases are included to verify the correct implementation of variably saturated transport in UZF-RT3D, other cases are included to demonstrate the usefulness of the code in terms of model run-time and handling the reaction kinetics of multiple interacting species in variably saturated subsurface systems. As UZF1 relies on a kinematic-wave approximation for unsaturated flow that neglects the diffusive terms in Richards equation, UZF-RT3D can be used for large-scale aquifer systems for which the UZF1 formulation is reasonable, that is, capillary-pressure gradients can be neglected and soil parameters can be treated as homogeneous. Decreased model run-time and the ability to include site-specific chemical species and chemical reactions make UZF-RT3D an attractive model for efficient simulation of multispecies reactive transport in variably saturated large-scale subsurface systems.

Ab initio study of nitrogen and position-specific oxygen kinetic isotope effects in the NO + O3 reaction

NASA Astrophysics Data System (ADS)

Walters, Wendell W.; Michalski, Greg

2016-12-01

Ab initio calculations have been carried out to investigate nitrogen (k15/k14) and position-specific oxygen (k17/k16O & k18/k16) kinetic isotope effects (KIEs) for the reaction between NO and O3 using CCSD(T)/6-31G(d) and CCSD(T)/6-311G(d) derived frequencies in the complete Bigeleisen equations. Isotopic enrichment factors are calculated to be -6.7‰, -1.3‰, -44.7‰, -14.1‰, and -0.3‰ at 298 K for the reactions involving the 15N16O, 14N18O, 18O16O16O, 16O18O16O, and 16O16O18O isotopologues relative to the 14N16O and 16O3 isotopologues, respectively (CCSD(T)/6-311G(d)). Using our oxygen position-specific KIEs, a kinetic model was constructed using Kintecus, which estimates the overall isotopic enrichment factors associated with unreacted O3 and the oxygen transferred to NO2 to be -19.6‰ and -22.8‰, respectively, (CCSD(T)/6-311G(d)) which tends to be in agreement with previously reported experimental data. While this result may be fortuitous, this agreement suggests that our model is capturing the most important features of the underlying physics of the KIE associated with this reaction (i.e., shifts in zero-point energies). The calculated KIEs will useful in future NOx isotopic modeling studies aimed at understanding the processes responsible for the observed tropospheric isotopic variations of NOx as well as for tropospheric nitrate.

Gas hydrate saturations estimated from fractured reservoir at Site NGHP-01-10, Krishna-Godavari Basin, India

USGS Publications Warehouse

Lee, M.W.; Collett, T.S.

2009-01-01

During the Indian National Gas Hydrate Program Expedition 01 (NGHP-Ol), one of the richest marine gas hydrate accumulations was discovered at Site NGHP-01-10 in the Krishna-Godavari Basin. The occurrence of concentrated gas hydrate at this site is primarily controlled by the presence of fractures. Assuming the resistivity of gas hydratebearing sediments is isotropic, th?? conventional Archie analysis using the logging while drilling resistivity log yields gas hydrate saturations greater than 50% (as high as ???80%) of the pore space for the depth interval between ???25 and ???160 m below seafloor. On the other hand, gas hydrate saturations estimated from pressure cores from nearby wells were less than ???26% of the pore space. Although intrasite variability may contribute to the difference, the primary cause of the saturation difference is attributed to the anisotropic nature of the reservoir due to gas hydrate in high-angle fractures. Archie's law can be used to estimate gas hydrate saturations in anisotropic reservoir, with additional information such as elastic velocities to constrain Archie cementation parameters m and the saturation exponent n. Theory indicates that m and n depend on the direction of the measurement relative to fracture orientation, as well as depending on gas hydrate saturation. By using higher values of m and n in the resistivity analysis for fractured reservoirs, the difference between saturation estimates is significantly reduced, although a sizable difference remains. To better understand the nature of fractured reservoirs, wireline P and S wave velocities were also incorporated into the analysis.

Understanding cation ordering and oxygen vacancy site preference in Ba3CaNb2O9 from first-principles

NASA Astrophysics Data System (ADS)

Ding, Hepeng; Virkar, Anil; Liu, Feng

2014-03-01

We investigate the physical mechanism underlying the formation of the B-site cation ordering and the oxygen vacancy site selection in Ba3CaNb2O9 using density functional theory calculations. We found that either cation site exchange or oxygen vacancy formation induces negligible lattice strain. This implies that the ionic radius plays an insignificant role in governing these two processes. Furthermore, the electrostatic interactions are found dominant in the ordering of mixed valence species on one or more sites, the ionic bond strength is identified as the dominant force in governing both the 1:2 B-site cation ordering along the <111>direction and the oxygen vacancy site preference in Ba3CaNb2O9. Specifically, the cation ordering can be rationalized by the increased mixing bonding energy of the Ca-O-Nb bonds over the Ca-O-Ca and Nb-O-Nb bonds, i.e., 1/2(Ca-O-Ca + Nb-O-Nb) O-Nb while oxygen vacancy prefers a site to minimize the electrostatic energy and to break the weaker B-O-B bond. Funded by DOE EFRC Grant Number DE-SC0001061 as a flow through from the University of South Carolina.

Enhancements of magnetic properties and planar magnetoresistance by electric fields in γ-Fe{sub 2}O{sub 3}/MgO thin films

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

Cheng, Bin; Qin, Hongwei; Pei, Jinliang

2016-05-23

The treatment of perpendicular electric field upon γ-Fe{sub 2}O{sub 3}/MgO film at room temperature could adjust the magnetic properties (saturation magnetization, magnetic remanence, coercivity, and saturation magnetizing field) of the film. The enhancement of saturation magnetization after the treatment of electric field may be connected with the combined shift effects of Mg ions from MgO to γ-Fe{sub 2}O{sub 3} and O{sup 2−} ions from γ-Fe{sub 2}O{sub 3} to MgO. The negative magnetoresistance of the γ-Fe{sub 2}O{sub 3}/MgO film also enhances with the treatment of perpendicular electric field at room temperature, possibly due to the increasing of electron hopping rate betweenmore » Fe{sup 2+} and Fe{sup 3+}.« less

Gaseous Nitrogen Losses from Tropical Savanna Soils of Northern Australia: Dynamics, Controls and Magnitude of N2O, NO, and N2 emissions

NASA Astrophysics Data System (ADS)

Werner, C.; Hickler, T.; Hutley, L. B.; Butterbach-Bahl, K.

2014-12-01

Tropical savanna covers a large fraction of the global land area and thus may have a substantial effect on the global soil-atmosphere exchange of nitrogen. The pronounced seasonality of hygric conditions in this ecosystem affects strongly microbial process rates in the soil. As these microbial processes control the uptake, production, and release of nitrogen compounds, it is thought that this seasonality finally leads to strong temporal dynamics and varying magnitudes of gaseous losses to the atmosphere. However, given their areal extent and in contrast to other ecosystems, still few in-situ or laboratory studies exist that assess the soil-atmosphere exchange of nitrogen. We present laboratory incubation results from intact soil cores obtained from a natural savanna site in Northern Australia, where N2O, NO, and N2 emissions under controlled environmental conditions were investigated. Furthermore, in-situ measurements of high temporal resolution at this site recorded with automated static and dynamic chamber systems are discussed (N2O, NO). This data is then used to assess the performance of a process-based biogeochemical model (LandscapeDNDC), and the potential magnitude and dynamics of components of the site-scale nitrogen cycle where no measurements exist (biological nitrogen fixation and nitrate leaching). Our incubation results show that severe nutrient limitation of the soil only allows for very low N2O emissions (0.12 kg N ha-1 yr-1) and even a periodic N2O uptake. Annual NO emissions were estimated at 0.68 kg N ha-1 yr-1, while the release of inert nitrogen (N2) was estimated at 6.75 kg N ha-1 yr-1 (data excl. contribution by pulse emissions). We observed only minor N2O pulse emissions after watering the soil cores and initial rain events of the dry to wet season transition in-situ, but short-lived NO pulse emissions were substantial. Interestingly, some cores exhibited a very different N2O emission potential, indicating a substantial spatial variability of

Catalytic dehydrofluorination of 1,1,1,3,3-pentafluoropropane to 1,3,3,3-tetrafluoropropene over fluorinated NiO/Cr2O3 catalysts

NASA Astrophysics Data System (ADS)

Luo, Jian-Wei; Song, Jian-Dong; Jia, Wen-Zhi; Pu, Zhi-Ying; Lu, Ji-Qing; Luo, Meng-Fei

2018-03-01

Catalytic dehydrofluorination of 1,1,1,3,3-pentafluoropropane to 1,3,3,3-tetrafluoropropene was performed on a series of fluorinated NiO/Cr2O3 catalysts. The NiO/Cr2O3 catalysts were more active than the Cr2O3 because the new acid sites provided by NiF2 had higher turnover frequencies (9.43 × 10-3 - 12.08 × 10-3 s-1) than those on the Cr2O3 (4.55 × 10-3 s-1). Also, the NiO/Cr2O3 was more stable than the Cr2O3 due to its lower density of surface acid sites, which alleviated the coke deposition on the catalyst as evidenced by the Raman spectroscopic results. The kinetic results revealed that the15NiO/Cr2O3 had much lower activation energy (63.6 ± 4.5 kJ mol-1) than the Cr2O3 (127.6 ± 3.8 kJ mol-1). Accordingly, different reaction pathways on the two catalysts were proposed, which involved the cleavage of the Csbnd F and Csbnd H bonds on the surface acid and base sites, respectively.

Electronic refractive index changes and measurement of saturation intensity in Cr3+-doped YAG crystal

NASA Astrophysics Data System (ADS)

Kesavulu, C. R.; Moncorgé, R.; Fromager, M.; Ait-Ameur, K.; Catunda, T.

2018-04-01

The electronic refractive index variation is associated with the difference in the polarizabilities (Δαp) of the Cr3+ ion in its ground and excited states. In order to further address the physical origin of Δαp in a Cr3+-doped YAG crystal, time-resolved Z-scan measurements were performed and analyzed at λ = 457 nm by using a chopped Ar+ ion laser. It is found a nonlinear refractive index with the real and imaginary parts n2‧ = 2.2 × 10-8 cm2/W and n2‧‧ = 2.8 × 10-10 cm2/W, respectively. The real part is associated with a polarizability difference Δαp = 2.2 × 10-25 cm3. The imaginary part indicates that excited state absorption (ESA) occurs and that Cr:YAG behaves as a saturable absorber. The transient response of the Z-scan signal decreases with the laser intensity as τ-1 = τo-1(1+I/Is), where τo is the excited state lifetime and Is the saturation intensity. By measuring this transient response at different laser intensities, it was possible to confirm the τo value which can be derived from fluorescence measurements and to determine a Is value of 8.3 kW/cm2.

Thermodynamic model for uranium release from hanford site tank residual waste.

PubMed

Cantrell, Kirk J; Deutsch, William J; Lindberg, Mike J

2011-02-15

A thermodynamic model of U solid-phase solubility and paragenesis was developed for Hanford Site tank residual waste that will remain in place after tank closure. The model was developed using a combination of waste composition data, waste leach test data, and thermodynamic modeling of the leach test data. The testing and analyses were conducted using actual Hanford Site tank residual waste. Positive identification of U phases by X-ray diffraction was generally not possible either because solids in the waste were amorphous or their concentrations were not detectable by XRD for both as-received and leached residual waste. Three leachant solutions were used in the studies: deionized water, CaCO3 saturated solution, and Ca(OH)2 saturated solution. Analysis of calculated saturation indices indicate that NaUO2PO4·xH2O and Na2U2O7(am) are present in the residual wastes initially. Leaching of the residual wastes with deionized water or CaCO3 saturated solution results in preferential dissolution Na2U2O7(am) and formation of schoepite. Leaching of the residual wastes with Ca(OH)2 saturated solution appears to result in transformation of both NaUO2PO4·xH2O and Na2U2O7(am) to CaUO4. Upon the basis of these results, the paragenetic sequence of secondary phases expected to occur as leaching of residual waste progresses for two tank closure scenarios was identified.

The effect of oxygen vacancies on the binding interactions of NH3 with rutile TiO2(110) -1×1

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

Kim, Boseong; Li, Zhenjun; Kay, Bruce D.

2012-11-21

A series of NH3 temperature-programmed desorption (TPD) spectra was taken after the NH3 dose at 70 K on rutile TiO2(110)-1×1 surfaces with the oxygen vacancy (VO) concentrations of ~0% (p-TiO2) and 5% (r-TiO2), respectively, to study the effect of VO’s on the desorption energy of NH3 as a function of the coverage, θ. Our results show that at zero coverage limit, the desorption energy of NH3 on r-TiO2 is 115 kJ/mol, which is 10 kJ/mol less than that on p-TiO2. The desorption energy from the Ti4+ sites decreases with increasing θ due to the repulsive NH3 - NH3 interactions andmore » approaches ~ 55 kJ/mol upon the saturation of Ti4+ sites (θ = 1 monolayer, ML) on both p- and r-TiO2. The absolute saturation coverage is determined to be about 10% smaller on r-TiO2 than that on p-TiO2. Further, the trailing edges of the NH3 TPD spectra on the hydroxylated TiO2(110) (h-TiO2) appear to be the same as that on r-TiO2 while those on oxidized TiO2(110) (o-TiO2) shift to higher temperatures. We present the detailed analysis of the results and reconcile the observed differences based on the repulsive adsorbate-adsorbate interactions between neighboring NH3 molecules and the surface charge associated with the presence of VO’s. Besides NH3, no other reaction products are observed in the TPD spectra.« less

Biogeochemistry of a temperate forest nitrogen gradient

USGS Publications Warehouse

Perakis, Steven S.; Sinkhorn, Emily R.

2011-01-01

Wide natural gradients of soil nitrogen (N) can be used to examine fundamental relationships between plant–soil–microbial N cycling and hydrologic N loss, and to test N-saturation theory as a general framework for understanding ecosystem N dynamics. We characterized plant production, N uptake and return in litterfall, soil gross and net N mineralization rates, and hydrologic N losses of nine Douglas-fir (Pseudotsuga menziesii) forests across a wide soil N gradient in the Oregon Coast Range (USA). Surface mineral soil N (0–10 cm) ranged nearly three-fold from 0.29% to 0.78% N, and in contrast to predictions of N-saturation theory, was linearly related to 10-fold variation in net N mineralization, from 8 to 82 kg N·ha−1·yr−1. Net N mineralization was unrelated to soil C:N, soil texture, precipitation, and temperature differences among sites. Net nitrification was negatively related to soil pH, and accounted for −1·yr−1. Aboveground net primary production per unit net N mineralization varied inversely with soil N, suggesting progressive saturation of plant N demands at high soil N. Hydrologic N losses were dominated by dissolved organic N at low-N sites, with increased nitrate loss causing a shift to dominance by nitrate at high-N sites, particularly where net nitrification exceeded plant N demands. With the exception of N mineralization patterns, our results broadly support the application of the N-saturation model developed from studies of anthropogenic N deposition to understand N cycling and saturation of plant and microbial sinks along natural soil N gradients. This convergence of behavior in unpolluted and polluted forest N cycles suggests that where future reductions in deposition to polluted sites do occur, symptoms of N saturation are most likely to persist where soil N content remains elevated.

Reactive nitrogen oxides in the southeast United States national parks: source identification, origin, and process budget

NASA Astrophysics Data System (ADS)

Tong, Daniel Quansong; Kang, Daiwen; Aneja, Viney P.; Ray, John D.

2005-01-01

We present in this study both measurement-based and modeling analyses for elucidation of source attribution, influence areas, and process budget of reactive nitrogen oxides at two rural southeast United States sites (Great Smoky Mountains national park (GRSM) and Mammoth Cave national park (MACA)). Availability of nitrogen oxides is considered as the limiting factor to ozone production in these areas and the relative source contribution of reactive nitrogen oxides from point or mobile sources is important in understanding why these areas have high ozone. Using two independent observation-based techniques, multiple linear regression analysis and emission inventory analysis, we demonstrate that point sources contribute a minimum of 23% of total NOy at GRSM and 27% at MACA. The influence areas for these two sites, or origins of nitrogen oxides, are investigated using trajectory-cluster analysis. The result shows that air masses from the West and Southwest sweep over GRSM most frequently, while pollutants transported from the eastern half (i.e., East, Northeast, and Southeast) have limited influence (<10% out of all air masses) on air quality at GRSM. The processes responsible for formation and removal of reactive nitrogen oxides are investigated using a comprehensive 3-D air quality model (Multiscale Air Quality SImulation Platform (MAQSIP)). The NOy contribution associated with chemical transformations to NOz and O3, based on process budget analysis, is as follows: 32% and 84% for NOz, and 26% and 80% for O3 at GRSM and MACA, respectively. The similarity between NOz and O3 process budgets suggests a close association between nitrogen oxides and effective O3 production at these rural locations.

Magneto-optical properties of BaTiO3/La0.76Sr0.24MnO3/BaTiO3 heterostructures

NASA Astrophysics Data System (ADS)

Moog, M.; Singamaneni, S. R.; Prater, J. T.; Biegalski, M. D.; Tsui, F.

2018-05-01

The magnetic properties of epitaxial BaTiO3/La0.76Sr0.24MnO3/BaTiO3 (BTO/LSMO/BTO) heterostructures have been studied using magneto-optic Kerr effect (MOKE) technique. Both longitudinal and polar MOKE were probed as a function of magnetic field and temperature (in the range between 80 and 320 K) for epitaxial films of BTO/LSMO/BTO and LSMO grown on TiO2-terminated SrTiO3 (001) substrates by pulsed laser deposition technique. The LSMO film without the BTO layers exhibits nearly square field-dependent MOKE hysteresis loops with low saturation fields below a bulk-like Curie temperature (TC) of ˜ 350K. In contrast, the film with the BTO layers exhibits a significantly suppressed TC of 155 K, accompanied by significantly enhanced coercive fields and perpendicular magnetic anisotropy.

Orthorhombic YBaCo{sub 4}O{sub 8.4} crystals as a result of saturation of hexagonal YBaCo{sub 4}O{sub 7} crystals with oxygen

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

Podberezskaya, N. V., E-mail: podberez@niic.nsc.ru; Bolotina, N. B., E-mail: nb-bolotina@mail.ru; Komarov, V. Yu., E-mail: komarov-v-y@niic.nsc.ru

Hexagonal YBaCo{sub 4}O{sub 7} crystals (sp. gr. P6{sub 3}mc, a{sub h} = 6.3058(4) Å, c{sub h} = 10.2442(7) Å, Z = 2) are saturated with oxygen to the YBaCo{sub 4}O{sub 8.4} composition and studied by X-ray diffraction (XRD) analysis. The saturation is completed by a structural first-order phase transition to orthorhombic crystals (sp. gr. Pbc2{sub 1}, a{sub o} = 31.8419(2) Å, b{sub o} = 10.9239(5) Å, c{sub o} = 10.0960(5) Å, Z = 20). The connection of two lattices is expressed in terms of the action of matrix (500/120/001) on the hexagonal basis. Five structural fragments of the same typemore » but with different degrees of order alternate along the long axis of the oxygen-saturated orthorhombic structure. The XRD data on single crystals differ from the results obtained by other researchers on ceramic samples; possible causes of these differences are discussed.« less

CAIRPOL CAIRCLIP O3-NO2

EPA Science Inventory

The CairPol CairClip O₃-NO₂ is a lightweight, portable sensor for measuring ozone (O₃) and nitrogen dioxide (NO₂) in parts per billion (ppb) or micrograms per cubic meter (µg/m³) in applications such as personal exposure and ...

Exploration of sensing of nitrogen dioxide and ozone molecules using novel TiO2/Stanene heterostructures employing DFT calculations

NASA Astrophysics Data System (ADS)

Abbasi, Amirali; Sardroodi, Jaber Jahanbin

2018-06-01

Based on the density functional theory (DFT) calculations, we explored the sensing capabilities and electronic structures of TiO2/Stanene heterostructures as novel and highly efficient materials for detection of toxic NO2 and O3 molecules in the environment. Studied gas molecules were positioned at different sites and orientations towards the nanocomposite, and the adsorption process was examined based on the most stable structures. We found that both of these molecules are chemically adsorbed on the TiO2/Stanene heterostructures. The calculations of the adsorption energy indicate that the fivefold coordinated titanium sites of the TiO2/Stanene are the most stable sites for the adsorption of NO2 and O3 molecules. The side oxygen atoms of the gas molecules were found to be chemically bonded to these titanium atoms. The adsorption of gas molecules is an exothermic process, and the adsorption on the pristine nanocomposite is more favorable in energy than that on the nitrogen-doped nanocomposite. The effects of van der Waals interactions were taken into account, which indicate the adsorption energies were increased for the most sable configurations. The gas sensing response and charge transfers were analyzed in detail. The pristine nanocomposites have better sensing response than the doped ones. The spin density distribution plots indicate that the magnetization was mainly located over the adsorbed gas molecules. Mulliken charge analysis reveals that both NO2 and O3 molecules behave as charge acceptors, as evidenced by the accumulation of electronic charges on the adsorbed molecules predicted by charge density difference calculations. Our DFT results provide a theoretical basis for an innovative gas sensor system designed from a sensitive TiO2/Stanene heterostructures for efficient detection of harmful air pollutants such as NO2 and O3.

Stomata open at night in pole-sized and mature ponderosa pine: implications for O3 exposure metrics.

PubMed

Grulke, N E; Alonso, R; Nguyen, T; Cascio, C; Dobrowolski, W

2004-09-01

Ponderosa pine (Pinus ponderosa Dougl. ex Laws.) is widely distributed in the western USA. We report the lack of stomatal closure at night in early summer for ponderosa pine at two of three sites investigated. Trees at a third site with lower nitrogen dioxide and nitric acid exposure, but greater drought stress, had slightly open stomata at night in early summer but closed stomata at night for the rest of the summer. The three sites had similar background ozone exposure during the summer of measurement (2001). Nighttime stomatal conductance (gs) ranged from one tenth to one fifth that of maximum daytime values. In general, pole-sized trees (< 40 years old) had greater nighttime gs than mature trees (> 250 years old). In late summer, nighttime gs was low (< 3.0 mmol H2O m(-2) s(-1)) for both tree size classes at all sites. Measurable nighttime gs has also been reported in other conifers, but the values we observed were higher. In June, nighttime ozone (O3) uptake accounted for 9, 5 and 3% of the total daily O3 uptake of pole-sized trees from west to east across the San Bernardino Mountains. In late summer, O3 uptake at night was < 2% of diel uptake at all sites. Nocturnal O3 uptake may contribute to greater oxidant injury development, especially in pole-sized trees in early summer.

Effect of aging on ZnO and nitrogen doped P-Type ZnO

NASA Astrophysics Data System (ADS)

Majumdar, Sayanee; Bhunia, S.

2012-06-01

The withholding of p-type conductivity in as-prepared and 3% nitrogen (N) doped zinc oxide (ZnO) even after 2 months of preparation was systematically studied. The films were grown on glass substrates by pulsed laser deposition (PLD) at 350 °C under different conditions, viz. under vacuum and at oxygen (O) ambience using 2000 laser pulses. In O ambience for as-prepared ZnO the carrier concentration reduces and mobility increases with increasing number of laser shots. The resistivity of as-prepared and 3% N-doped ZnO is found to increase with reduction in hole concentration after 60 days of aging while maintaining its p-type conductivity irrespective of growth condition. AFM and electrical properties showed aging effect on the doped and undoped samples. For as-prepared ZnO, with time, O migration makes the film high resistive by reducing free electron concentrations. But for N-doped p-type ZnO, O-migration, metastable N and hydrogen atom present in the source induced instability in structure makes it less conducting p-type.

Synthesis and characterization of (1-x)Bi(Mg{sub 2/3}Sb{sub 1/3})O{sub 3}-xPbTiO{sub 3} piezoceramics

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

Upadhyay, Ashutosh; Dwivedi, Saurabh; Pandey, Rishikesh

2016-05-23

We present here the comprehensive x-ray diffraction and polarization-electric field hysteresis studies on (1-x)Bi(Mg{sub 2/3}Sb{sub 1/3})O{sub 3}-xPbTiO{sub 3} piezoceramics with x = 0.52, 0.56 and 0.60. The powder x-ray diffraction data reveals the presence of tetragonal phase for all the compositions. The saturation of hysteresis loop is observed for x ≤ 0.56.

Synthesis of raspberry-like monodisperse magnetic hollow hybrid nanospheres by coating polystyrene template with Fe(3)O(4)@SiO(2) particles.

PubMed

Wang, Chunlei; Yan, Juntao; Cui, Xuejun; Wang, Hongyan

2011-02-01

In this paper, we present a novel method for the preparation of raspberry-like monodisperse magnetic hollow hybrid nanospheres with γ-Fe(2)O(3)@SiO(2) particles as the outer shell. PS@Fe(3)O(4)@SiO(2) composite nanoparticles were successfully prepared on the principle of the electrostatic interaction between negatively charged silica and positively charged polystyrene, and then raspberry-like magnetic hollow hybrid nanospheres with large cavities were achieved by means of calcinations, simultaneously, the magnetite (Fe(3)O(4)) was transformed into maghemite (γ-Fe(2)O(3)). Transmission electron microscopy (TEM) demonstrated that the obtained magnetic hollow silica nanospheres with the perfect spherical profile were well monodisperse and uniform with the mean size of 253nm. The Fourier transform infrared (FTIR) spectrometry, energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) provided the sufficient evidences for the presence of Fe(3)O(4) in the silica shell. Moreover, the magnetic hollow silica nanospheres possessed a characteristic of superparamagnetic with saturation magnetization value of about 7.84emu/g by the magnetization curve measurement. In addition, the nitrogen adsorption-desorption measurement exhibited that the pore size, BET surface area, pore volume of magnetic hollow silica nanospheres were 3.5-5.5nm, 307m(2)g(-1) and 1.33cm(3)g(-1), respectively. Therefore, the magnetic hollow nanospheres possess a promising future in controlled drug delivery and targeted drug applications. Copyright © 2010 Elsevier Inc. All rights reserved.

Inside Story of Gas Processes within Stormwater Biofilters: Does Greenhouse Gas Production Tarnish the Benefits of Nitrogen Removal?

PubMed

Payne, Emily G I; Pham, Tracey; Cook, Perran L M; Deletic, Ana; Hatt, Belinda E; Fletcher, Tim D

2017-04-04

Stormwater biofilters are dynamic environments, supporting diverse processes that act to capture and transform incoming pollutants. However, beneficial water treatment processes can be accompanied by undesirable greenhouse gas production. This study investigated the potential for nitrous oxide (N 2 O) and methane (CH 4 ) generation in dissolved form at the base of laboratory-scale stormwater biofilter columns. The influence of plant presence, species, inflow frequency, and inclusion of a saturated zone and carbon source were studied. Free-draining biofilters remained aerobic with negligible greenhouse gas production during storm events. Designs with a saturated zone were oxygenated at their base by incoming stormwater before anaerobic conditions rapidly re-established, although extended dry periods allowed the reintroduction of oxygen by evapotranspiration. Production of CH 4 and N 2 O in the saturated zone varied significantly in response to plant presence, species, and wetting and drying. Concentrations of N 2 O typically peaked rapidly following stormwater inundation, associated with limited plant root systems and poorer nitrogen removal from biofilter effluent. Production of CH 4 also commenced quickly but continued throughout the anaerobic interevent period and lacked clear relationships with plant characteristics or nitrogen removal performance. Dissolved greenhouse gas concentrations were highly variable, but peak concentrations of N 2 O accounted for <1.5% of the incoming total nitrogen load. While further work is required to measure surface emissions, the potential for substantial release of N 2 O or CH 4 in biofilter effluent appears relatively low.

Mechanisms of spin-flipping and metal-insulator transition in nano-Fe3O4

NASA Astrophysics Data System (ADS)

Dito Fauzi, Angga; Aziz Majidi, Muhammad; Rusydi, Andrivo

2017-04-01

Fe3O4 is a half-metallic ferrimagnet with {{T}\\text{C}}˜ 860 K exhibiting metal-insulator transition (MIT) at  ˜120 K. In bulk form, the saturation magnetization is 0.6 Tesla (˜471 emu cm-3). A recent experimental study has shown that the saturation magnetization of nano-Fe3O4 thin films can achieve up to  ˜760 emu cm-3, attributed to spin-flipping of Fe ions at tetrahedral sites assisted by oxygen vacancies (V O). Such a system has shown to have higher MIT temperature (˜150 K). The spin-flipping is a new phenomenon in Fe3O4, while the MIT is a long-standing one. Here, we propose a model and calculations to investigate the mechanisms of both phenomena. Our results show that, for the system without V O, the ferrimagnetic configuration is energetically favorable. Remakably, upon inclusion of V O, the ground-state configuration switches into ferromagnetic. As for the MIT, by proposing temperature dependences of some hopping integrals in the model, we demonstrate that the system without and with V O undergo the MIT in slightly different ways, leading to higher MIT temperature for the system with V O, in agreement with the experimental data. Our results also show that the MIT in both systems occur concomitantly with the redistribution of electrons among the three Fe ions in each Fe3O4 formula unit. As such temperature dependences of hopping integrals may arise due to dynamic Jahn-Teller effects, our phenomenological theory may provide a way to reconcile existing theories relating the MIT to the structural transition and the charge ordering.

Crystal field excitations from Yb3 + ions at defective sites in highly stuffed Yb2Ti2O7

NASA Astrophysics Data System (ADS)

Sala, G.; Maharaj, D. D.; Stone, M. B.; Dabkowska, H. A.; Gaulin, B. D.

2018-06-01

The pyrochlore magnet Yb2Ti2O7 has been proposed as a quantum spin ice candidate, a spin liquid state expected to display emergent quantum electrodynamics with gauge photons among its elementary excitations. However, Yb2Ti2O7 's ground state is known to be very sensitive to its precise stoichiometry. Powder samples, produced by solid-state synthesis at relatively low temperatures, tend to be stoichiometric, while single crystals grown from the melt tend to display weak "stuffing" wherein ˜2 % of the Yb3 +, normally at the A site of the A2B2O7 pyrochlore structure, reside as well at the B site. In such samples Yb3 + ions should exist in defective environments at low levels and be subjected to crystalline electric fields very different from those at the stoichiometric A sites. Neutron scattering measurements of Yb3 + in four compositions of Yb2 +xTi2 -xO7 -y show the spectroscopic signatures for these defective Yb3 + ions and explicitly demonstrate that the spin anisotropy of the Yb3 + moment changes from X Y -like for stoichiometric Yb3 + to Ising-like for "stuffed" B site Yb3 + or for A site Yb3 + in the presence of oxygen vacancies.

Novel solid-state synthesis of α-Fe and Fe3O4 nanoparticles embedded in a MgO matrix

NASA Astrophysics Data System (ADS)

Schneeweiss, O.; Zboril, R.; Pizurova, N.; Mashlan, M.; Petrovsky, E.; Tucek, J.

2006-01-01

Thermally induced reduction of amorphous Fe2O3 nanopowder (2-3 nm) with nanocrystalline Mg (~20 nm) under a hydrogen atmosphere is presented as a novel route to obtain α-Fe and Fe3O4 magnetic nanoparticles dispersed in a MgO matrix. The phase composition, structural and magnetic properties, size and morphology of the nanoparticles were monitored by x-ray diffraction, 57Fe Mössbauer spectroscopy at temperatures of 24-300 K, transmission electron microscopy and magnetic measurements. Spherical magnetite nanoparticles prepared at a reaction temperature of 300 °C revealed a well-defined structure, with a ratio of tetrahedral to octahedral Fe sites of 1/2 being common for the bulk material. A narrow particle size distribution (20-30 nm) and high saturation magnetization (95 ± 5 A m2 kg-1) predispose the magnetite nanoparticles to various applications, including magnetic separation processes. The Verwey transition of Fe3O4 nanocrystals was found to be decreased to about 80 K. The deeper reduction of amorphous ferric oxide at 600 °C allows α-Fe (40-50 nm) nanoparticles to be synthesized with a coercive force of about 30 mT. They have a saturation magnetization 2.2 times higher than that of synthesized magnetite nanoparticles, which corresponds well with the ratio usually found for the pure bulk phases. The magnetic properties of α-Fe nanocrystals combined with the high chemical and thermal stability of the MgO matrix makes the prepared nanocomposite useful for various magnetic applications.

Investigation of site preference of Zn doped Ba{sub 3}Co{sub 2−x}Zn{sub x}Fe{sub 24}O{sub 41} by Mössbauer spectroscopy

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

Lim, Jung Tae; Kim, Chul Sung, E-mail: cskim@kookmin.ac.kr

2014-05-07

The polycrystalline Ba{sub 3}Co{sub 2−x}Zn{sub x}Fe{sub 24}O{sub 41} (x = 0.0, 0.5, 1.0) samples were prepared by using solid-state-reaction method. The crystal structures and magnetic properties of samples were investigated with x-ray diffractometer, vibrating sample magnetometer, and Mössbauer spectroscopy. The crystal structure of Ba{sub 3}Co{sub 2−x}Zn{sub x}Fe{sub 24}O{sub 41} (x = 0.0, 0.5, 1.0) samples was determined to be a hexagonal structure with P6{sub 3}/mmc space group at 295 K, and the saturation magnetization (M{sub s}) of Ba{sub 3}Co{sub 2−x}Zn{sub x}Fe{sub 24}O{sub 41} (x = 0.0, 0.5, 1.0) samples were found to be M{sub s} = 50.9, 53.1, 55.0 emu/g, respectively. From the temperature dependence of magnetizationmore » curves under 100 Oe between 4.2 and 740 K, we were able to observe the spin transition, and both spin transition temperature (T{sub s}) and Curie temperature (T{sub C}) decrease with increasing Zn concentration. Mössbauer spectra of all samples were obtained and analyzed at various temperatures ranging from 4.2 to 295 K. With ten-sextets for Fe sites corresponding to the Z-type hexagonal crystallographic sites, all spectra below T{sub C} were fitted by least-square method. In addition, from the site occupation numbers of Fe, calculated from the relative areas fitted to the Mössbauer spectra, we find that Zn ions preferentially occupy the tetrahedral sublattices of down sites.« less

The solubility and site preference of Fe3+ in Li7−3xFexLa3Zr2O12 garnets

PubMed Central

Rettenwander, D.; Geiger, C.A.; Tribus, M.; Tropper, P.; Wagner, R.; Tippelt, G.; Lottermoser, W.; Amthauer, G.

2015-01-01

A series of Fe3+-bearing Li7La3Zr2O12 (LLZO) garnets was synthesized using solid-state synthesis methods. The synthetic products were characterized compositionally using electron microprobe analysis and inductively coupled plasma optical emission spectroscopy (ICP-OES) and structurally using X-ray powder diffraction and 57Fe Mössbauer spectroscopy. A maximum of about 0.25 Fe3+ pfu could be incorporated in Li7−3xFexLa3Zr2O12 garnet solid solutions. At Fe3+ concentrations lower than about 0.16 pfu, both tetragonal and cubic garnets were obtained in the synthesis experiments. X-ray powder diffraction analysis showed only a garnet phase for syntheses with starting materials having intended Fe3+ contents lower than 0.52 Fe3+ pfu. Back-scattered electron images made with an electron microprobe also showed no phase other than garnet for these compositions. The lattice parameter, a0, for all solid-solution garnets is similar with a value of a0≈12.98 Å regardless of the amount of Fe3+. 57Fe Mössbauer spectroscopic measurements indicate the presence of poorly- or nano-crystalline FeLaO3 in syntheses with Fe3+ contents greater than 0.16 Fe3+ pfu. The composition of different phase pure Li7−3xFexLa3Zr2O12 garnets, as determined by electron microprobe (Fe, La, Zr) and ICP-OES (Li) measurements, give Li6.89Fe0.03La3.05Zr2.01O12, Li6.66Fe0.06La3.06Zr2.01O12, Li6.54Fe0.12La3.01Zr1.98O12, and Li6.19Fe0.19La3.02Zr2.04O12. The 57Fe Mössbauer spectrum of cubic Li6.54Fe0.12La3.01Zr1.98O12 garnet indicates that most Fe3+ occurs at the special crystallographic 24d position, which is the standard tetrahedrally coordinated site in garnet. Fe3+ in smaller amounts occurs at a general 96h site, which is only present for certain Li-oxide garnets, and in Li6.54Fe0.12La3.01Zr1.98O12 this Fe3+ has a distorted 4-fold coordination. PMID:26435549

Quality changes in sea urchin (Strongylocentrotus nudus) during storage in artificial seawater saturated with oxygen, nitrogen and air.

PubMed

Wang, Chao; Xue, Changhu; Xue, Yong; Li, Zhaojie; Lv, Yingchun; Zhang, Hao

2012-01-15

Sea urchin gonads are highly valued seafood that degenerates rapidly during the storage period. To study the influence of dissolved oxygen concentration on quality changes of sea urchin (Strongylocentrotus nudus) gonads, they were stored in artificial seawater saturated with oxygen, nitrogen or air at 5 ± 1 °C for 12 days. The sensory acceptability limit was 11-12, 6-7 and 7-8 days for gonads with oxygen, nitrogen or air packaging, respectively. Total volatile basic nitrogen (TVB-N) values reached 22.60 ± 1.32, 32.37 ± 1.37 and 24.91 ± 1.54 mg 100 g(-1) for gonads with oxygen, nitrogen or air packaging at the points of near to, exceeding and reaching the limit of sensory acceptability, indicating that TVB-N values of about 25 mg 100 g(-1) should be regarded as the limit of acceptability for sea urchin gonads. Relative ATP content values were 56.55%, 17.36% and 18.75% for gonads with oxygen, nitrogen or air packaging, respectively, on day 2. K-values were 19.37%, 25.05% and 29.02% for gonads with oxygen, nitrogen or air packaging, respectively, on day 2. Both pH and aerobic plate count values showed no significant difference (P > 0.05) for gonads with the three treatments. Gonads with oxygen packaging had lower sensory demerit point (P < 0.05) and TVB-N values (P < 0.05), and higher relative ATP content (P < 0.01) and K-values (P < 0.05), than that with nitrogen or air packaging, with an extended shelf life of 4-5 days during storage in artificial seawater at 5 ± 1 °C. Copyright © 2011 Society of Chemical Industry.

Unraveling the distinct luminescence thermal quenching behaviours of A/B-site Eu3+ ions in double perovskite Sr2CaMoO6:Eu3+

NASA Astrophysics Data System (ADS)

Wang, Chunhao; Ye, Shi; Zhang, Qinyuan

2018-01-01

Eu3+-doped Sr2CaMoO6 phosphors have a broad excitation band at around 350-425 nm, which meets the demand of Near-ultraviolet (NUV, 365-410 nm) absorption when applied in NUV-excitable phosphor-converted white light emitting diodes (WLEDs). The luminescence thermal quenching effects of Eu3+ ions at A/B sites (612 nm/593 nm) in Sr2CaMoO6 might be distinct with resultant emission colour variation, which is less studied but of significance for a scientific perspective. This research investigates on the temperature-dependent luminescence and decay curves of the nominal Sr1.9Li0.05Eu0.05CaMoO6 and Sr2Ca0.9Li0.05Eu0.05MoO6 phosphors. Results indicate that the luminescence of B-site Eu3+ ions is quenched more easily than that of A-site Eu3+ ions, directly evidenced by the fast and slow decay components in the decay curves. A distortion of B-site octahedron with elevating temperature and strong coupling with phonons may be partially responsible for the relatively poor thermal quenching behaviors of B-site Eu3+ ions. The research gives perspective on the thermal quenching of emissive lanthanide ions at different sites in phosphors.

In situ DRIFTS study of O3 adsorption on CaO, γ-Al2O3, CuO, α-Fe2O3 and ZnO at room temperature for the catalytic ozonation of cinnamaldehyde

NASA Astrophysics Data System (ADS)

Wu, Jianfeng; Su, Tongming; Jiang, Yuexiu; Xie, Xinling; Qin, Zuzeng; Ji, Hongbing

2017-08-01

In situ DRIFTS were conducted to identify adsorbed ozone and/or adsorbed oxygen species on CaO, ZnO, γ-Al2O3, CuO and α-Fe2O3 surfaces at room temperature. Samples were characterized by means of TG, XRD, N2 adsorption-desorption, pyridine-IR, nitrobenzene-IR, chloroform-IR, and CO2-TPD. Pyridine-DRIFTS measurements evidence two kinds of acid sites in all the samples. Nitrobenzene, chloroform-DRIFTS, and CO2-TPD reveal that there are large amounts of medium-strength base sites on all the metal oxides, and only CaO, ZnO, and γ-Al2O3 have strong base sites. And the benzaldehyde selectivity was increased in the same order of the alkalinity of the metal oxides. With weaker sites, ozone molecules form coordinative complexes bound via the terminal oxygen atom, observed by vibrational frequencies at 2095-2122 and 1026-1054 cm-1. The formation of ozonide O3- at 790 cm-1, atomic oxygen at 1317 cm-1, and superoxide O2- at 1124 cm-1 was detected; these species are believed to be intermediates of O3 decomposition on strong acid/base sites. The adsorption of ozone on metal oxides is a weak adsorption, and other gases, such as CO2, will compete with O3 adsorption. The mechanism of cinnamaldehyde ozonation at room temperature over CaO shows that cinnamaldehyde can not only be oxidized into cinnamic acid, but also be further oxidized into benzaldehyde, benzoic acid, maleic anhydride, and ultimately mineralized to CO2 in the presence of O3.

Nitrided SrTiO3 as charge-trapping layer for nonvolatile memory applications

NASA Astrophysics Data System (ADS)

Huang, X. D.; Lai, P. T.; Liu, L.; Xu, J. P.

2011-06-01

Charge-trapping characteristics of SrTiO3 with and without nitrogen incorporation were investigated based on Al/Al2O3/SrTiO3/SiO2/Si (MONOS) capacitors. A Ti-silicate interlayer at the SrTiO3/SiO2 interface was confirmed by x-ray photoelectron spectroscopy and transmission electron microscopy. Compared with the MONOS capacitor with SrTiO3 as charge-trapping layer (CTL), the one with nitrided SrTiO3 showed a larger memory window (8.4 V at ±10 V sweeping voltage), higher P/E speeds (1.8 V at 1 ms +8 V) and better retention properties (charge loss of 38% after 104 s), due to the nitrided SrTiO3 film exhibiting higher dielectric constant, higher deep-level traps induced by nitrogen incorporation, and suppressed formation of Ti silicate between the CTL and SiO2 by nitrogen passivation.

Air-snow exchange of nitrogen oxides and ozone at a polluted mid-latitude site

NASA Astrophysics Data System (ADS)

Murphy, Jennifer G.; Hong, Angela C.; Quinn, Patricia K.; Bates, Tim

2017-04-01

Vertical gradients of O3, NO, NO2 and NOywere measured within and above the snowpack between January 17 to February 14, 2014 as part of the Uintah Basin Winter Ozone Study. During the first half of the campaign, the snowpack was relatively aged and contained high levels of inorganic ions and dissolved and particulate organics. A snowfall on Jan 31 added 5 cm of fresh snow with lower solute concentrations to the top of the snowpack. Vertical gradients (ΔC = C(25cm) - C(125cm)) in the measured gas phase species were used to investigate the role of the snowpack as a source or sink. Small positive gradients were seen for NO, peaking in the middle of the day, which much larger negative gradients were seen for O3 and NOy. Comparing the fresh to the aged snowpacks, there was a noticeable decrease in the gradient for O3, but not for NOy over the fresh snow, implying a chemical control of O3 deposition to the snow. The ratio of the gradient of NOx to the gradient of NOy was used to determine a snowpack NOy recycling ratio (emission/deposition) of approximately 4 %, consistent with independent estimates of low nitrate photolysis rates inferred from nitrogen isotopes by Zatko et al., (2016). Reference Zatko et al., The magnitude of the snow-sourced reactive nitrogen flux to the boundary layer in the Uintah Basin, Utah, USA, Atmos. Chem. Phys., 16, 13837-13851, 2016.

Selective labeling of serotonin uptake sites in rat brain by (/sup 3/H)citalopram contrasted to labeling of multiple sites by (/sup 3/H)imipramine

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

D'Amato, R.J.; Largent, B.L.; Snowman, A.M.

1987-07-01

Citalopram is a potent and selective inhibitor of neuronal serotonin uptake. In rat brain membranes (/sup 3/H)citalopram demonstrates saturable and reversible binding with a KD of 0.8 nM and a maximal number of binding sites (Bmax) of 570 fmol/mg of protein. The drug specificity for (/sup 3/H)citalopram binding and synaptosomal serotonin uptake are closely correlated. Inhibition of (/sup 3/H)citalopram binding by both serotonin and imipramine is consistent with a competitive interaction in both equilibrium and kinetic analyses. The autoradiographic pattern of (/sup 3/H)citalopram binding sites closely resembles the distribution of serotonin. By contrast, detailed equilibrium-saturation analysis of (/sup 3/H)imipramine bindingmore » reveals two binding components, i.e., high affinity (KD = 9 nM, Bmax = 420 fmol/mg of protein) and low affinity (KD = 553 nM, Bmax = 8560 fmol/mg of protein) sites. Specific (/sup 3/H)imipramine binding, defined as the binding inhibited by 100 microM desipramine, is displaced only partially by serotonin. Various studies reveal that the serotonin-sensitive portion of binding corresponds to the high affinity sites of (/sup 3/H)imipramine binding whereas the serotonin-insensitive binding corresponds to the low affinity sites. Lesioning of serotonin neurons with p-chloroamphetamine causes a large decrease in (/sup 3/H)citalopram and serotonin-sensitive (/sup 3/H)imipramine binding with only a small effect on serotonin-insensitive (/sup 3/H)imipramine binding. The dissociation rate of (/sup 3/H)imipramine or (/sup 3/H)citalopram is not altered by citalopram, imipramine or serotonin up to concentrations of 10 microM. The regional distribution of serotonin sensitive (/sup 3/H)imipramine high affinity binding sites closely resembles that of (/sup 3/H)citalopram binding.« less

Retinal oxygen saturation in Chinese adolescents.

PubMed

Liu, Xue; Wang, Shuang; Liu, Yi; Liu, Li Juan; Lv, Yan Yun; Tang, Ping; Jonas, Jost B; Xu, Liang

2017-02-01

To study the retinal oxygen saturation in normal eyes of Chinese adolescents. Performing retinal oximetry with the Oxymap T1 Retinal Oximeter in healthy children and adolescents (aged 5-18 years old), we measured the arterial (SaO 2 ) and venular (SvO 2 ) oxygen saturation and the arteriovenous difference in oxygen saturation (Sa-vO 2 ). The study included 122 individuals with a mean age of 13.0 ± 2.9 years (range: 5-18 years) and a mean refractive error of -3.25 ± 2.49 dioptres (range:-8.88 to +3.13 dioptres). Mean SaO 2 , SvO 2 and Sa-vO 2 was 85.5 ± 7.1%, 48.2 ± 5.5% and 37.3 ± 6.5%, respectively. Mean SaO 2 was significantly (p < 0.001) the lowest in the inferotemporal quadrant (79.1 ± 9.0%), followed by the superotemporal quadrant (83.4 ± 9.7%), the inferonasal quadrant (90.4 ± 10.6%) and the superonasal quadrant (93.4 ± 10.8%). In a similar manner, the values of the SvO 2 were the lowest (p < 0.001) in the inferotemporal quadrant (42.1 ± 8.3%), followed by the superotemporal quadrant (47.8 ± 7.2%), the inferonasal quadrant (52.3 ± 8.4%) and the superonasal quadrant (55.1 ± 7.6%). Arteriovenous difference in oxygen saturation (Sa-vO 2 ) did not differ significantly (all p > 0.05) between the fundus quadrants. In multiple linear regression analysis, SaO 2 increased (regression coefficient r 2  = 0.28) with older age (standardized regression coefficient β: 0.23; p = 0.01) and more myopic refractive error (β: -0.39; p < 0.001). Higher SvO 2 was significantly correlated with more myopic refractive error (β: -0.46; p < 0.001; r 2  = 0.20), while Sa-vO 2 increased significantly only with older age in the multivariate analysis (β: 0.26; p = 0.01; r 2  = 0.07). Our study provides normative data for Chinese children and adolescents who showed lower values than adults for SaO 2 and SvO 2 . SaO 2 increased with older age and higher myopic refractive error, SvO 2 increased with higher myopic refractive

Reactivity of Hydrogen and Methanol on (001) Surfaces of WO3, ReO3, WO3/ReO3 and ReO3/WO3

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

Ling, Sanliang; Mei, Donghai; Gutowski, Maciej S.

2011-05-16

Bulk tungsten trioxide (WO3) and rhenium trioxide (ReO3) share very similar structures but display different electronic properties. WO3 is a wide bandgap semiconductor while ReO3 is an electronic conductor. With the advanced molecular beam epitaxy techniques, it is possible to make heterostructures comprised of layers of WO3 and ReO3. These heterostructures might display reactivity different than pure WO3 and ReO3. The interactions of two probe molecules (hydrogen and methanol) with the (001) surfaces of WO3, ReO3, and two heterostructures ReO3/WO3 and WO3/ReO3 were investigated at the density functional theory level. Atomic hydrogen prefers to adsorb at the terminal O1C sitesmore » forming a surface hydroxyl on four surfaces. Dissociative adsorption of a hydrogen molecule at the O1C site leads to formation of a water molecule adsorbed at the surface M5C site. This is thermodynamically the most stable state. A thermodynamically less stable dissociative state involves two surface hydroxyl groups O1CH and O2CH. The interaction of molecular hydrogen and methanol with pure ReO3 is stronger than with pure WO3 and the strength of the interaction substantially changes on the WO3/ReO3 and ReO3/WO3 heterostructures. The reaction barriers for decomposition and recombination reactions are sensitive to the nature of heterostructure. The calculated adsorption energy of methanol on WO3(001) of -65.6 kJ/mol is consistent with the previous experimental estimation of -67 kJ/mol. This material is based upon work supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences.« less

Synergistic effects of abiotic stresses in plants: a case study of nitrogen limitation and saturating light intensity in Arabidopsis thaliana.

PubMed

Cohen, Itay; Rapaport, Tal; Chalifa-Caspi, Vered; Rachmilevitch, Shimon

2018-05-22

Under natural conditions, plants are regularly exposed to combinations of stress factors. A common example is the conjunction between nitrogen (N) deficiency and excess light. The combined effect of stress factors is often ignored in studies using controlled conditions, possibly resulting in misleading conclusions. To address this issue, the current study examined the physiological behavior of Arabidopsis thaliana under the effect of varying nitrogen levels and light intensities. The joint influence of low N and excess light had an adverse effect on plant growth, chlorophyll and anthocyanin concentrations, photochemical capacity, and the abundance of proteins involved in carbon assimilation and anti-oxidative metabolism. In contrast, no adverse physiological responses were observed for plants under either nitrogen limitation or high light intensity conditions (i.e., single stress). The underline mechanisms for the increased growth in conditions of high light and sufficient nitrogen was due to a combination of chlorophyll accumulation and an increased number of proteins involved in C3 carbon assimilation, amino acids biosynthesis and chloroplast development. In contrast, combined stress conditions caused anthocyanin accumulation and increased number proteins involved in catabolism of lipids and amino acids as energy substrates. Ultimately switching plants from growth to survival. Our results suggest that an assessment of the physiological response to the combined effect of multiple stresses cannot be directly extrapolated from the physiological response to a single stress. Specifically, the synergistic interaction between N deficiency and saturating light in Arabidopsis plants could not have been modeled via only one of the stress factors. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Application of nitrogen-doped TiO2 nano-tubes in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Tran, Vy Anh; Truong, Trieu Thinh; Phan, Thu Anh Pham; Nguyen, Trang Ngoc; Huynh, Tuan Van; Agresti, Antonio; Pescetelli, Sara; Le, Tien Khoa; Di Carlo, Aldo; Lund, Torben; Le, So-Nhu; Nguyen, Phuong Tuyet

2017-03-01

Our research aimed to improve the overall energy conversion efficiency of DSCs by applying nitrogen-doped TiO2 nano-tubes (N-TNT) for the preparation of DSCs photo-anodes. The none-doped TiO2 nano-tubes (TNTs) were synthesized by alkaline hydrothermal treatment of Degussa P25 TiO2 particles in 10 M NaOH. The nano-tubes were N-doped by reflux in various concentrations of NH4NO3. The effects of nitrogen doping on the structure, morphology, and crystallography of N-TNT were analyzed by transmission electron microscopy (TEM), infrared spectroscopy (IR), Raman spectroscopy, and X-ray photoelectron spectra (XPS). DSCs fabricated with doped N-TNT and TNT was characterized by J-V measurements. Results showed that nitrogen doping significantly enhanced the efficiency of N-TNT cells, reaching the optimum value (η = 7.36%) with 2 M nitrogen dopant, compared to η = 4.75% of TNT cells. The high efficiency of the N-TNT cells was attributed to increased current density due to the reduction of dark current in the DSCs.

Using random forests to explore the effects of site attributes and soil properties on near-saturated and saturated hydraulic conductivity

NASA Astrophysics Data System (ADS)

Jorda, Helena; Koestel, John; Jarvis, Nicholas

2014-05-01

Knowledge of the near-saturated and saturated hydraulic conductivity of soil is fundamental for understanding important processes like groundwater contamination risks or runoff and soil erosion. Hydraulic conductivities are however difficult and time-consuming to determine by direct measurements, especially at the field scale or larger. So far, pedotransfer functions do not offer an especially reliable alternative since published approaches exhibit poor prediction performances. In our study we aimed at building pedotransfer functions by growing random forests (a statistical learning approach) on 486 datasets from the meta-database on tension-disk infiltrometer measurements collected from peer-reviewed literature and recently presented by Jarvis et al. (2013, Influence of soil, land use and climatic factors on the hydraulic conductivity of soil. Hydrol. Earth Syst. Sci. 17(12), 5185-5195). When some data from a specific source publication were allowed to enter the training set whereas others were used for validation, the results of a 10-fold cross-validation showed reasonable coefficients of determination of 0.53 for hydraulic conductivity at 10 cm tension, K10, and 0.41 for saturated conductivity, Ks. The estimated average annual temperature and precipitation at the site were the most important predictors for K10, while bulk density and estimated average annual temperature were most important for Ks prediction. The soil organic carbon content and the diameter of the disk infiltrometer were also important for the prediction of both K10 and Ks. However, coefficients of determination were around zero when all datasets of a specific source publication were excluded from the training set and exclusively used for validation. This may indicate experimenter bias, or that better predictors have to be found or that a larger dataset has to be used to infer meaningful pedotransfer functions for saturated and near-saturated hydraulic conductivities. More research is in progress

Riverine N2O concentrations, exports to estuary and emissions to atmosphere from the Changjiang River in response to increasing nitrogen loads

NASA Astrophysics Data System (ADS)

Yan, Weijin; Yang, Libiao; Wang, Fang; Wang, Jianing; Ma, Pei

2012-12-01

This study investigated the variations of dissolved N2O and emissions over diurnal and seasonal temporal scales in 2009, as well as the time series of riverine N2O export to estuary and emission to atmosphere in response to increasing anthropogenic nitrogen loads in the Changjiang River. For the diurnal study, N2O concentrations ranged from 0.26 to 0.34 and from 0.44 to 0.52 μg N-N2O L-1 in August and October 2009, respectively. The dissolved N2O was supersaturated with a mean value of 197%. Studies on N2O emissions, also taken in August and October, ranged from 2.67 to 11.6 and from 6.72 to 15.2 μg N-N2O m-2 h-1, respectively. For the seasonal study (June through December 2009), N2O concentrations ranged from 0.34 to 0.72 μg N-N2O L-1 and were supersaturated in all the samples (average 212%). N2O emissions ranged from 1.87 to 40.8 μg N-N2O m-2 h-1. Our study found no significant differences in diurnal patterns of N2O saturation but detected significant difference in seasonal patterns of N2O saturation: higher during summer while lower during autumn and winter. We found a significant relationship between dissolved N2O and river nitrate, which can predict the variation of N2O concentrations in the River. The net production of N2 ranged from 0.01 to 0.47 mg N-N2 L-1. These excess N2 values were significantly correlated to the N2O production and are suggestive of denitrification in the river. Applying the Global News model to the river system using measures taken during the 1970 to 2002 period, we estimated N2O emissions to atmosphere increased from 330 to 3650 ton N-N2O yr-1. During that same 1970-2002 period, N2O exports to estuary increased from 91 to 470 ton N-N2O yr-1. Taken together, the findings reported here suggest that both the river N2O concentrations and emissions would increase in response to rising anthropogenic nitrogen loads. Our study showed that the mean emission factor based on the ratio of the total N2O flux to NO3- flux is four times greater

Fate and Transport of Nitrogen and Carbon with Decomposition of Organic Matter in a Reduced Paddy Field Based on a Coupled Nitrogen-Carbon Cycling Model Using the HP1 Code

NASA Astrophysics Data System (ADS)

Toride, N.; Matsuoka, K.

2017-12-01

In order to predict the fate and transport of nitrogen in a reduced paddy field as a result of decomposition of organic matter, we implemented within the PHREEQC program a modified coupled carbon and nitrogen cycling model based on the LEACHM code. SOM decay processes from organic carbon (Org-C) to biomass carbon (Bio-C), humus carbon (Hum-C), and carbon dioxide (CO2) were described using first-order kinetics. Bio-C was recycled into the organic pool. When oxygen was available in an aerobic condition, O2 was used to produce CO2 as an electron accepter. When O2 availability is low, other electron acceptors such as NO3-, Mn4+, Fe3+, SO42-, were used depending on the redox potential. Decomposition of Org-N was related to the carbon cycle using the C/N ratio. Mineralization and immobilization were determined based on available NH4-N and the nitrogen demand for the formation of biomass and humus. Although nitrification was independently described with the first-order decay process, denitrification was linked with the SOM decay since NO3- was an electron accepter for the CO2 production. Proton reactions were coupled with the nitrification from NH4+ to NO3-, and the ammonium generation from NH3 to NH4+. Furthermore, cation and anion exchange reactions were included with the permanent negative charges and the pH dependent variable charges. The carbon and nitrogen cycling model described with PHREEQC was linked with HYDRUS-1D using the HP1 code. Various nitrogen and carbon transport scenarios were demonstrated for the application of organic matter to a saturated paddy soil.

Soil Microbial Responses to Elevated CO2 and O3 in a Nitrogen-Aggrading Agroecosystem

PubMed Central

Cheng, Lei; Booker, Fitzgerald L.; Burkey, Kent O.; Tu, Cong; Shew, H. David; Rufty, Thomas W.; Fiscus, Edwin L.; Deforest, Jared L.; Hu, Shuijin

2011-01-01

Climate change factors such as elevated atmospheric carbon dioxide (CO2) and ozone (O3) can exert significant impacts on soil microbes and the ecosystem level processes they mediate. However, the underlying mechanisms by which soil microbes respond to these environmental changes remain poorly understood. The prevailing hypothesis, which states that CO2- or O3-induced changes in carbon (C) availability dominate microbial responses, is primarily based on results from nitrogen (N)-limiting forests and grasslands. It remains largely unexplored how soil microbes respond to elevated CO2 and O3 in N-rich or N-aggrading systems, which severely hinders our ability to predict the long-term soil C dynamics in agroecosystems. Using a long-term field study conducted in a no-till wheat-soybean rotation system with open-top chambers, we showed that elevated CO2 but not O3 had a potent influence on soil microbes. Elevated CO2 (1.5×ambient) significantly increased, while O3 (1.4×ambient) reduced, aboveground (and presumably belowground) plant residue C and N inputs to soil. However, only elevated CO2 significantly affected soil microbial biomass, activities (namely heterotrophic respiration) and community composition. The enhancement of microbial biomass and activities by elevated CO2 largely occurred in the third and fourth years of the experiment and coincided with increased soil N availability, likely due to CO2-stimulation of symbiotic N2 fixation in soybean. Fungal biomass and the fungi∶bacteria ratio decreased under both ambient and elevated CO2 by the third year and also coincided with increased soil N availability; but they were significantly higher under elevated than ambient CO2. These results suggest that more attention should be directed towards assessing the impact of N availability on microbial activities and decomposition in projections of soil organic C balance in N-rich systems under future CO2 scenarios. PMID:21731722

Co3O4 nanocrystals with exposed low-surface-energy planes anchored on chemically integrated graphitic carbon nitride-modified nitrogen-doped graphene: A high-performance anode material for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Zhang, Wenyao; Fu, Yongsheng; Wang, Xin

2018-05-01

A facile strategy to synthesize a composite composed of cubic Co3O4 nanocrystals anchored on chemically integrated g-C3N4-modified N-graphene (CN-NG) as an advanced anode material for high-performance lithium-ion batteries is reported. It is found that the morphology of the Co3O4 nanocrystals contains blunt-edge nanocubes with well-demarcated boundaries and numerous exposed low-index (1 1 1) crystallographic facets. These planes can be directly involved in the electrochemical reactions, providing rapid Li-ion transport channels for charging and discharging and thus enhancing the round-trip diffusion efficiency. On the other hand, the CN-NG support displays unusual textural features, such as superior structural stability, accessible active sites, and good electrical conductivity. The experimental results reveal that the chemical and electronic coupling of graphitic carbon nitride and nitrogen-doped graphene synergistically facilitate the anchoring of Co3O4 nanocrystals and prevents their migration. The resulting Co3O4/CN-NG composite exhibits a high specific reversible capacity of up to 1096 mAh g-1 with excellent cycling stability and rate capability. We believe that such a hybrid carbon support could open a new path for applications in electrocatalysis, sensors, supercapacitors, etc., in the near future.

Sensitivity of terrestrial N2O emission to atmospheric nitrogen deposition

NASA Astrophysics Data System (ADS)

Ito, A.; Sudo, K.; Nishina, K.; Ishijima, K.; Inatomi, M. I.

2015-12-01

Terrestrial N2O emission is generated from several nitrogen sources including biological fixation, agricultural fertilizer, and atmospheric deposition. There remain large uncertainties how much N2O is produced from atmospheric deposition. This is a crosscutting issue between global warming and atmospheric pollution. In this study, we assessed the sensitivity of global terrestrial N2O emission to atmospheric deposition, using a process-based model VISIT. In the model, N2O emission is estimated separately for nitrification and denitrfication with the NGAS parameterization. The global simulations were conducted from 1901 to 2014 at spatial resolution of 0.5 degree. Atmospheric deposition of ammonium, NOy, and organic nitrogen simulated by the atmospheric chemistry model CHASER from the pre-industrial time to the present was used. Annual total nitrogen deposition was estimated to increase from 27 Tg N in 1901 to 77 Tg N in 2014. The total N2O emission was also estimated to increase in the period, but it was largely attributable to the increased emission from croplands. We need further investigations for the N2O emission from natural soils, which may be nitrogen-limited.

Critical Evaluations and Thermodynamic Optimizations of the MnO-Mn2O3-SiO2 and FeO-Fe2O3-MnO-Mn2O3-SiO2 Systems

NASA Astrophysics Data System (ADS)

Kang, Youn-Bae; Jung, In-Ho

2017-06-01

A critical evaluation and thermodynamic modeling for thermodynamic properties of all oxide phases and phase diagrams in the Fe-Mn-Si-O system (MnO-Mn2O3-SiO2 and FeO-Fe2O3-MnO-Mn2O3-SiO2 systems) are presented. Optimized Gibbs energy parameters for the thermodynamic models of the oxide phases were obtained which reproduce all available and reliable experimental data within error limits from 298 K (25°C) to above the liquidus temperatures at all compositions covering from known oxide phases, and oxygen partial pressure from metal saturation to 0.21 bar. The optimized thermodynamic properties and phase diagrams are believed to be the best estimates presently available. Slag (molten oxide) was modeled using the modified quasichemical model in the pair approximation. Olivine (Fe2SiO4-Mn2SiO4) was modeled using two-sublattice model in the framework of the compound energy formalism (CEF), while rhodonite (MnSiO3-FeSiO3) and braunite (Mn7SiO_{12} with excess Mn2O3) were modeled as simple Henrian solutions. It is shown that the already developed models and databases of two spinel phases (cubic- and tetragonal-(Fe, Mn)3O4) using CEF [Kang and Jung, J. Phys. Chem. Solids (2016), vol. 98, pp. 237-246] can successfully be integrated into a larger thermodynamic database to be used in practically important higher order system such as silicate. The database of the model parameters can be used along with a software for Gibbs energy minimization in order to calculate any type of phase diagram section and thermodynamic properties.

Oxygen Saturation in Closed-Globe Blunt Ocular Trauma

PubMed Central

Long, Chongde; Wen, Xin; Gao, Qianying

2016-01-01

Purpose. To evaluate the oxygen saturation in retinal blood vessels in patients after closed-globe blunt ocular trauma. Design. Retrospective observational case series. Methods. Retinal oximetry was performed in both eyes of 29 patients with unilateral closed-globe blunt ocular trauma. Arterial oxygen saturation (SaO2), venous oxygen saturation (SvO2), arteriovenous difference in oxygen saturation (SO2), arteriolar diameter, venular diameter, and arteriovenous difference in diameter were measured. Association parameters including age, finger pulse oximetry, systolic pressure, diastolic pressure, and heart rate were analyzed. Results. The mean SaO2 in traumatic eyes (98.1% ± 6.8%) was not significantly different from SaO2 in unaffected ones (95.3% ± 7.2%) (p = 0.136). Mean SvO2 in traumatic eyes (57.1% ± 10.6%) was significantly lower than in unaffected ones (62.3% ± 8.4%) (p = 0.044). The arteriovenous difference in SO2 in traumatic eyes (41.0% ± 11.2%) was significantly larger than in unaffected ones (33.0% ± 6.9%) (p = 0.002). No significant difference was observed between traumatic eyes and unaffected ones in arteriolar (p = 0.249) and venular diameter (p = 0.972) as well as arteriovenous difference in diameter (p = 0.275). Conclusions. Oxygen consumption is increased in eyes after cgBOT, associated with lower SvO2 and enlarged arteriovenous difference in SO2 but not with changes in diameter of retinal vessels. PMID:27699174

Nitrogen saturation in experimental forested watersheds

Treesearch

Ivan J. Fernandez; Mary Beth Adams

2000-01-01

Daniel Rutherford is credited with the discovery of nitrogen (N) in 1772. A.L. Lavoisier, the 18th century French chemist, called this element "azote" which translates to "without life" because free N is incapable of supporting life: a fitting name for this element given the paradoxes it presents to society and its role in global ecology.

Effects of long-term (10 years) exposure to elevated CO2 and O3 on trembling Aspen carbon and nitrogen metabolism at the aspen FACE (Free-Air Carbon Dioxide Enrichment) study site

Treesearch

Rakesh Minocha; Stephanie Long; Subhash Minocha; Paula Marquardt; Neil Nelson; Mark. Kubiske

2010-01-01

This study was conducted at the Aspen Free-Air Carbon Dioxide Enrichment (FACE) experimental site, Rhinelander, WI, (USA). Since 1998, 12 experimental rings planted in 1997 underwent four different treatments: control; elevated CO2 (560 ppm); elevated O3 (1.5X ambient) and elevated CO2 (560 ppm) + O...

Spin-Coating and Characterization of Multiferroic MFe2O4 (M=Co, Ni) / BaTiO3 Bilayers

NASA Astrophysics Data System (ADS)

Quandt, Norman; Roth, Robert; Syrowatka, Frank; Steimecke, Matthias; Ebbinghaus, Stefan G.

2016-01-01

Bilayer films of MFe2O4 (M=Co, Ni) and BaTiO3 were prepared by spin coating of N,N-dimethylformamide/acetic acid solutions on platinum coated silicon wafers. Five coating steps were applied to get the desired thickness of 150 nm for both the ferrite and perovskite layer. XRD, IR and Raman spectroscopy revealed the formation of phase-pure ferrite spinels and BaTiO3. Smooth surfaces with roughnesses in the order of 3 to 5 nm were found in AFM investigations. Saturation magnetization of 347 emu cm-3 for the CoFe2O4/BaTiO3 and 188 emu cm-3 for the NiFe2O4/BaTiO3 bilayer, respectively were found. For the CoFe2O4/BaTiO3 bilayer a strong magnetic anisotropy was observed with coercivity fields of 5.1 kOe and 3.3 kOe (applied magnetic field perpendicular and parallel to film surface), while for the NiFe2O4/BaTiO3 bilayer this effect is less pronounced. Saturated polarization hysteresis loops prove the presence of ferroelectricity in both systems.

The distribution of hydrogen, nitrogen, and chlorine radicals in the lower stratosphere: Implications for changes in O3 due to emission of NO(y) from supersonic aircraft

NASA Technical Reports Server (NTRS)

Salawitch, R. J.; Wofsy, S. C.; We-Nnberg, P. O.; Cohen, R. C.; Anderson, J. G.; Fahey, D. W.; Gao, R. S.; Keim, E. R.; Woodbridge, E. L.; Stimpfle, R. M.

1994-01-01

In situ measurements of hydrogen, nitrogen, and chlorine radicals obtained in the lower statosphere during SPADE are compared to results from a photochemical model that assimilates measurements of radical precursors and environmental conditions. Models allowing for heterogeneous hydrolysis of N2O5 agree well with measured concentrations of NO and ClO, but concentrations of HO2 and OH are underestimated by 10 to 25%, concentrations of NO2 are overestimated by 10 to 30%, and concentrations of HCl are overestimated by a factor of 2. Discrepancies for (OH) and (HO2) are reduced if we allow for higher yields of O((1)D) from O2 photolysis and for heterogeneous production of HNO2. The data suggest more efficent catalytic removal of O3 by hydrogen and halogen radicals relative to nitrogen oxide radicals than predicted by models using recommendend rates and cross sections. Increased in (O3) in the lower stratosphere may be larger in response to inputs of NO(y) from supersonic aircraft than estimated by current assessment models.

Responses of CH(4), CO(2) and N(2)O fluxes to increasing nitrogen deposition in alpine grassland of the Tianshan Mountains.

PubMed

Li, Kaihui; Gong, Yanming; Song, Wei; He, Guixiang; Hu, Yukun; Tian, Changyan; Liu, Xuejun

2012-06-01

To assess the effects of nitrogen (N) deposition on greenhouse gas (GHG) fluxes in alpine grassland of the Tianshan Mountains in central Asia, CH(4), CO(2) and N(2)O fluxes were measured from June 2010 to May 2011. Nitrogen deposition tended to significantly increase CH(4) uptake, CO(2) and N(2)O emissions at sites receiving N addition compared with those at site without N addition during the growing season, but no significant differences were found for all sites outside the growing season. Air temperature, soil temperature and water content were the important factors that influence CO(2) and N(2)O emissions at year-round scale, indicating that increased temperature and precipitation in the future will exert greater impacts on CO(2) and N(2)O emissions in the alpine grassland. In addition, plant coverage in July was also positively correlated with CO(2) and N(2)O emissions under elevated N deposition rates. The present study will deepen our understanding of N deposition impacts on GHG balance in the alpine grassland ecosystem, and help us assess the global N effects, parameterize Earth System models and inform decision makers. Copyright © 2012 Elsevier Ltd. All rights reserved.

Transparent Cu4O3/ZnO heterojunction photoelectric devices

NASA Astrophysics Data System (ADS)

Kim, Hong-Sik; Yadav, Pankaj; Patel, Malkeshkumar; Kim, Joondong; Pandey, Kavita; Lim, Donggun; Jeong, Chaehwan

2017-12-01

The present article reports the development of flexible, self-biased, broadband, high speed and transparent heterojunction photodiode, which is essentially important for the next generation electronic devices. We grow semitransparent p-type Cu4O3 using the reactive sputtering method at room temperature. The structural and optical properties of the Cu4O3 film were investigated by using the X-ray diffraction and UV-visible spectroscopy, respectively. The p-Cu4O3/n-ZnO heterojunction diode under dark condition yields rectification behavior with an extremely low saturation current value of 1.8 × 10-10 A and a zero bias photocurrent under illumination condition. The transparent p-Cu4O3/n-ZnO heterojunction photodetector can be operated without an external bias, due to the light-induced voltage production. The metal oxide heterojunction based on Cu4O3/ZnO would provide a route for the transparent and flexible photoelectric devices, including photodetectors and photovoltaics.

Nitrogen line spectroscopy in O-stars. III. The earliest O-stars

NASA Astrophysics Data System (ADS)

Rivero González, J. G.; Puls, J.; Massey, P.; Najarro, F.

2012-07-01

produced by abundance effects. Conclusions: Our findings suggest that the Walborn et al. (2002, AJ, 123, 2754) classification scheme is able to provide a meaningful relation between spectral type and effective temperature, as long as it is possible to discriminate for the luminosity class. In terms of spectral morphology, this might be difficult to achieve in low-Z environments such as the SMC, owing to rather low wind-strengths. According to our predictions, the major bias of the classification scheme is due to nitrogen content, and the overall spectral type-Teff relation for low-metallicity (e.g., SMC) O-stars might be non-monotonic around O3.5/O4. Based on (i) observations collected at the European Southern Observatory Very Large Telescope, under programmes 68.D-0369, 171.D-0237 (FLAMES), and 67.D-0238, 70.D-0164, 074.D-0109 (UVES); (ii) observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programmes 6417, 7739, and 9412; and (iii) observations gathered with the 6.5 m Magellan telescopes at the Las Campanas Observatory, Chile.Appendices A and B are available in electronic form at http://www.aanda.org

Drained coastal peatlands: A potential nitrogen source to marine ecosystems under prolonged drought and heavy storm events-A microcosm experiment.

PubMed

Wang, Hongjun; Richardson, Curtis J; Ho, Mengchi; Flanagan, Neal

2016-10-01

Over the past several decades there has been a massive increase in coastal eutrophication, which is often caused by increased runoff input of nitrogen from landscape alterations. Peatlands, covering 3% of land area, have stored about 12-21% of global soil organic nitrogen (12-20Pg N) around rivers, lakes and coasts over millennia and are now often drained and farmed. Their huge nitrogen pools may be released by intensified climate driven hydrologic events-prolonged droughts followed by heavy storms-and later transported to marine ecosystems. In this study, we collected peat monoliths from drained, natural, and restored coastal peatlands in the Southeastern U.S., and conducted a microcosm experiment simulating coupled prolonged-drought and storm events to (1) test whether storms could trigger a pulse of nitrogen export from drought-stressed peatlands and (2) assess how differentially hydrologic managements through shifting plant communities affect nitrogen export by combining an experiment of nitrogen release from litter. During the drought phase, we observed a significant temporal variation in net nitrogen mineralization rate (NMR). NMR spiked in the third month and then decreased rapidly. This pattern indicates that drought duration significantly affects nitrogen mineralization in peat. NMR in the drained site reached up to 490±110kgha(-1)year(-1), about 5 times higher than in the restored site. After the 14-month drought phase, we simulated a heavy storm by bringing peat monoliths to saturation. In the discharge waters, concentrations of total dissolved nitrogen in the monoliths from the drained site (72.7±16.3mgL(-1)) was about ten times as high as from the restored site. Our results indicate that previously drained peatlands under prolonged drought are a potent source of nitrogen export. Moreover, drought-induced plant community shifts to herbaceous plants substantially raise nitrogen release with lasting effects by altering litter quality in peatlands

Surface-Tuned Co3O4 Nanoparticles Dispersed on Nitrogen-Doped Graphene as an Efficient Cathode Electrocatalyst for Mechanical Rechargeable Zinc-Air Battery Application.

PubMed

Singh, Santosh K; Dhavale, Vishal M; Kurungot, Sreekumar

2015-09-30

The most vital component of the fuel cells and metal-air batteries is the electrocatalyst, which can facilitate the oxygen reduction reaction (ORR) at a significantly reduced overpotential. The present work deals with the development of surface-tuned cobalt oxide (Co3O4) nanoparticles dispersed on nitrogen-doped graphene as a potential ORR electrocatalyst possessing some unique advantages. The thermally reduced nitrogen-doped graphene (NGr) was decorated with three different morphologies of Co3O4 nanoparticles, viz., cubic, blunt edged cubic, and spherical, by using a simple hydrothermal method. We found that the spherical Co3O4 nanoparticle supported NGr catalyst (Co3O4-SP/NGr-24h) has acquired a significant activity makeover to display the ORR activity closely matching with the state-of-the-art Pt supported carbon (PtC) catalyst in alkaline medium. Subsequently, the Co3O4-SP/NGr-24h catalyst has been utilized as the air electrode in a Zn-air battery, which was found to show comparable performance to the system derived from PtC. Co3O4-SP/NGr-24h catalyst has shown several hours of flat discharge profile at the discharge rates of 10, 20, and 50 mA/cm(2) with a specific capacity and energy density of ~590 mAh/g-Zn and ~840 Wh/kg-Zn, respectively, in the primary Zn-air battery system. In conjunction, Co3O4-SP/NGr-24h has outperformed as an air electrode in mechanical rechargeable Zn-air battery as well, which has shown consistent flat discharge profile with minimal voltage loss at a discharge rate of 50 mA/cm(2). The present results, thus demonstrate that the proper combination of the tuned morphology of Co3O4 with NGr will be a promising and inexpensive material for efficient and ecofriendly cathodes for Zn-air batteries.

Polaronic deformation at the Fe2+/3 + impurity site in Fe:LiNbO3 crystals

NASA Astrophysics Data System (ADS)

Sanson, A.; Zaltron, A.; Argiolas, N.; Sada, C.; Bazzan, M.; Schmidt, W. G.; Sanna, S.

2015-03-01

Iron doped LiNbO3 crystals with different iron valence states are investigated. An extended x-ray absorption fine structure (EXAFS) spectroscopy study highlights evident changes in the local structure around iron that can be ascribed to the presence of small polarons. In particular, when a Fe3+ replaced a Li ion, the oxygen octahedron shrinked with respect to the pure material, with an average iron-oxygen bond value very similar to that of Fe2O3 hematite. When adding an electron, it localizes at the Fe site in a configuration very close to the atomic Fe d orbitals, inducing a relaxation of the oxygen cage. The same system was modelled by spin-polarized density functional theory (DFT). Several local as well as hybrid exchange-correlation functionals were probed on the bulk LiNbO3 structural properties. The computation is then extended to the case of hematite and finally to the Fe defect in LiNbO3. The calculations reproduced with good accuracy the large lattice relaxation of the oxygen ligands associated to the electronic capture at the Fe center that can be interpreted as due to the polaron formation. The calculations reproduce satisfactorily the available EXAFS data, and allow for the estimation of the polaron energies and the optical properties of the defect.

Strain and Ni substitution induced ferromagnetism in LaCoO3 thin films

NASA Astrophysics Data System (ADS)

Kumar, Ashok; Kumar, Vinod; Kumar, Rajesh; Kumar, Ravi

2018-05-01

We have grown epitaxial strained films of LaCoO3 and LaCo0.7Ni0.3O3 on LaAlO3 (100) substrate via pulsed laser deposition. Superconducting quantum interference device magnetization measurements show that, unlike its bulk counterpart, the ground state of the strained LaCoO3 on LAO is ferromagnetic. The saturation magnetization has been found increase strongly from a value of 118 emu/cm3 to 350 emu/ cm3 for Ni substituted thin film. Present study reveals that strain can stabilize FM order in these thin films down to low temperature, which can further be tuned to higher saturation magnetization with the Ni substitution.

Influences of Root Hydraulic Redistribution on N2O Emissions at AmeriFlux Sites

NASA Astrophysics Data System (ADS)

Fu, Congsheng; Lee, Xuhui; Griffis, Timothy J.; Wang, Guiling; Wei, Zhongwang

2018-05-01

It has long been suspected that root hydraulic redistribution (HR) affects the carbon and nitrogen cycles. Nitrous oxide (N2O) is an important greenhouse gas and is the primary stratospheric ozone-depleting substance. To our knowledge, the influences of HR on N2O emissions have not been investigated. Here we use the HR schemes of Ryel et al. and Amenu and Kumar incorporated into CLM4.5 to examine N2O emissions at five AmeriFlux sites. The results show that HR reduced N2O emissions by 28-92% in the four natural ecosystems experiencing a dry season, whereas it had a very limited effect on the Corn Belt site that has strong emissions but with no distinct dry season. We hypothesize that N2O emissions in ecosystems with a distinct dry season are likely overestimated by CENTURY-based Earth system models.

Efficient removal of arsenite through photocatalytic oxidation and adsorption by ZrO2-Fe3O4 magnetic nanoparticles

NASA Astrophysics Data System (ADS)

Sun, Tianyi; Zhao, Zhiwei; Liang, Zhijie; Liu, Jie; Shi, Wenxin; Cui, Fuyi

2017-09-01

Bifunctional ZrO2-Fe3O4 magnetic nanoparticles were synthesized and characterized, to remove As(III) through photocatalyic oxidation and adsorption. With a saturation magnetization of 27.39 emu/g, ZrO2-Fe3O4 nanoparticles with size of 10-30 nm could be easily separated from solutions with a simple magnetic process. Under UV light, As(III) could be completely oxidized to less toxic As(V) by ZrO2-Fe3O4 nanoparticles within 40 min in the photocatalytic reaction. Simultaneously, As(V) could be adsorbed onto the surface of nanoparticles with high efficiency. The adsorption of As(V) was well fitted by the pseudo-second-order model and the Freundlich isotherm model, respectively, and the maximum adsorption capacities of the nanoparticles was 133.48 mg/g at pH 7.0. As(III) could be effectively removed by ZrO2-Fe3O4 nanoparticles at initial pH range from 4 to 8. Among all the common coexisting ions investigated, except for chloride and sulfate, carbonate, silicate and phosphate decreased the As(III) removal by competing with arsenic species for adsorption sites. The synthesized magnetic ZrO2-Fe3O4 combined the photocatalytic oxidation property of ZrO2 and the high adsorption capacity of both ZrO2 and Fe3O4, which make it have significant potential applications in the As(III)-contaminated water treatment.

Optical investigation of variability in body region dependent transcutaneous oxygen saturation

NASA Astrophysics Data System (ADS)

Philimon, Sheena P.; Huong, Audrey K. C.; Hafizah, W. M.; Ong, P. E.; Ngu, Xavier T. I.

2016-11-01

This paper presents the use of multispectral imaging system to investigate variability in transcutaneous oxygen saturation (StO2) amongst different individuals and at different skin sites. Noncontact reflectance data are collected from central forehead, posterior forearm, thenar region of palm and proximal ankle of three healthy Asians. The prediction of the required StO2 value is via fitting Extended Modified Lambert (EMLB) model to the measured attenuation data using extinction coefficient of hemoglobin components in the wavelength range of 520 - 600 nm as its priori knowledge. The obtained results revealed a relatively high mean StO2 of 54 ± 1.9% at the palm of the hand site. This is followed by measurement at foot ankle and forehead with StO2 of 52.3 ± 2.4% and 51.2 ± 7.7%, respectively. Meanwhile the lowest reading of StO2 of 48.8 ± 5.1% is observed at the posterior forearm. Based on these findings, this work concluded that palm of the hand would provide considerably consistent measurement of StO2 among individuals. This is largely owing to the higher density of circulatory anastomosis at this skin site. This implied viability of using the developed strategy in the studies of microcirculation mechanism especially on wound at this skin region.

Nitrogen mineralization and nitrification in a mixed-conifer forest in southern California: controlling factors, fluxes, and nitrogen fertilization response at a high and low nitrogen deposition site

Treesearch

Mark E. Fenn; Mark A. Poth; Joseph D. Terry; Timothy J. Blubaugh

2005-01-01

Net fluxes of nitrogen (N) mineralization and nitrification were measured in situ on a monthly basis for 3 years at a high (HN) and low (LN) N deposition site in the San Bernardino Mountains, California. Mean N mineralization fluxes in the forest floor and top 10 cm of mineral soil were 19.0 and 59.8 kg N·ha–1·year–1 at LN...

Magnetic properties of nitrogen-doped ZrO2: Theoretical evidence of absence of room temperature ferromagnetism

PubMed Central

Albanese, Elisa; Leccese, Mirko; Di Valentin, Cristiana; Pacchioni, Gianfranco

2016-01-01

N-dopants in bulk monoclinic ZrO2 and their magnetic interactions have been investigated by DFT calculations, using the B3LYP hybrid functional. The electronic and magnetic properties of the paramagnetic N species, substitutionals and interstitials, are discussed. Their thermodynamic stability has been estimated as a function of the oxygen partial pressure. At 300 K, N prefers interstitial sites at any range of oxygen pressure, while at higher temperatures (700–1000 K), oxygen poor-conditions facilitate substitutional dopants. We have considered the interaction of two N defects in various positions in order to investigate the possible occurrence of ferromagnetic ordering. A very small magnetic coupling constant has been calculated for several 2N-ZrO2 configurations, thus demonstrating that magnetic ordering can be achieved only at very low temperatures, well below liquid nitrogen. Furthermore, when N atoms replace O at different sites, resulting in slightly different positions of the corresponding N 2p levels, a direct charge transfer can occur between the two dopants with consequent quenching of the magnetic moment. Another mechanism that contributes to the quenching of the N magnetic moments is the interplay with oxygen vacancies. These effects contribute to reduce the concentration of magnetic impurities, thus limiting the possibility to establish magnetic ordering. PMID:27527493

The Distribution of Hydrogen, Nitrogen, and Chlorine Radicals in the Lower Stratosphere: Implications for Changes in O3 due to Emission of NO(y) from Supersonic Aircraft

NASA Technical Reports Server (NTRS)

Salawitch, R. J.; Wofsy, S. C.; Wennberg, P. O.; Cohen, R. C.; Anderson, J. G.; Fahey, D. W.; Gao, R. S.; Keim, E. R.; Woodbridge, E. L.; Stimpfle, R. M.;

Seasonal variations and cycling of nitrous oxide using nitrogen isotopes and concentrations from an unsaturated zone of a floodplain

NASA Astrophysics Data System (ADS)

Bill, M.; Conrad, M. E.; Kolding, S.; Williams, K. H.; Tokunaga, T. K.

2014-12-01

Nitrous oxide (N2O) concentrations and isotope ratios of 15N to 14N of N2O in the vadose zone mainly depend on atmospheric deposition, symbiotic or non-symbiotic N2 fixation, and nitrification/denitrification processes in underlying groundwater. In an effort to quantify N2O seasonal variations, cycling and N budgets in an alluvial aquifer in western Colorado (Rifle, CO), the concentrations and nitrogen stable isotopes of N2O within the pore space of partially saturated sediments have been monitored over the 2013-2014 years. Vertically resolved profiles spanning from 0m to 3m depth were sampled at 0.5m increments at a periodicity of one month. At each of the profile locations, N2O concentrations decreased from 3m depth to the surface. The maximum concentrations were observed at the interface between the unsaturated zone and groundwater, with minimum values observed in the near surface samples. The d15N values tend to increase from the unsaturated zone/groundwater interface to the surface. Both variation of N2O concentrations and d15N values suggest that denitrification is the main contribution to N2O production and both parameters exhibited a strong seasonal variation. The maximum concentrations (~10ppmv) were observed at the beginning of summer, during the annual maximum in water table elevation. The minimum N2O concentrations were observed in the period from January to May and coincided with low water table elevations. Additionally, nitrogen concentrations and d15N values of the shallowest sediments within the vertical profiles do not show variation, suggesting that the main source of N2O is associated with groundwater denitrification, with the shallower, partially saturated sediments acting as a sink for N2O.

Impact of isoprene and nitrogen oxides on O3 chemistry at the local and the regional scale : the ESCOMPTE experiment

NASA Astrophysics Data System (ADS)

Cortinovis, J.; Solmon, F.; Personne, E.; Serça, D.; Rosset, R.

2003-04-01

Concentrations of nitrogen oxides (NOx = NO+NO2) and volatile organic compounds (VOCs) play a crucial role in the atmospheric chemistry through the production-destruction of tropospheric O3. In rural areas, NOx concentrations are much lower than in urban areas, whereas VOCs emissions can be relatively high. This is due to a relative longer residence time of VOCs, and to the substantial contribution of Biogenic VOCs (BVOCs) representing more than 85% of all the VOCs emitted at the Earth surface (half of it being isoprene). For these reasons, O3 production in rural areas is most of the time NOx-limited. Taking into account biogenic emissions of isoprene in global scale atmospheric chemistry modeling adds from 10 to 40% to the ozone produced when compared to the same simulation without isoprene. This suggests that BVOCs and NOx emissions must be accounted for in models of atmospheric pollution forecasting at local and regional scales. In this study, we present a sensitivity analysis on the impact of the isoprene and nitrogen oxides emissions at the local and the regional scale. This study is done from data collected during the ESCOMPTE campaign which took place in June and July 2001 in the Marseille region (Southwest France) characterized by both strong natural and anthropogenic sources of trace gases. Isoprene emission experimental data from a Quercus Pubescens Mediterranean forest are used to constrain the 1Dz Soil-Vegetation-Atmospheric-Transfer ISBA model. This SVAT is used in the 3D MESO-NH-Chemistry model to simulate scenarios of pollution at the regional scale including the measured biogenic source for isoprene, and GENEMIS anthropogenic sources for other trace gases. To focus on the chemistry aspect of these simulations, the atmospheric dynamics are set to an "ideal" configuration. We have investigated the impact of the relative position and distance between the biogenic and anthropogenic sources on the O3 budget. According to this, and to the intensity of the

Indium vacancy induced d0 ferromagnetism in Li-doped In2O3 nanoparticles

NASA Astrophysics Data System (ADS)

Cao, Haiming; Xing, Pengfei; Zhou, Wei; Yao, Dongsheng; Wu, Ping

2018-04-01

Li-doped In2O3 nanoparticles with room temperature d0 ferromagnetism were prepared by a sol-gel method. X-ray diffraction, X-ray photoelectron spectroscopy and photoluminescence were carried out to investigate the effects of Li incorporation on the lattice defects. As the content of Li increases, non-monotonic changes in shifts of XRD peak (2 2 2) and the intensity ratios of indium vacancies related photoluminescence peak (PII) with respect to oxygen vacancies related peak (PI) are observed. Results show that at low doping level (≤2 at.%) Li prefers to occupy In sites, while with further doping the interstitial sites are more favorable for Li. Combined with the consistent non-monotonic change in saturation magnetization, we think that indium vacancies resulting from Li-doping play an important role in inducing d0 ferromagnetism in our Li-doped In2O3 nanoparticles, and the FM coupling is mainly mediated by the LiIn-ONN-VIn-ONN-LiIn chains.

Ecosystem processes and nitrogen export in northern U.S. watersheds.

USGS Publications Warehouse

Stottlemyer, R.

2001-01-01

There is much interest in the relationship of atmospheric nitrogen (N) inputs to ecosystem outputs as an indicator of possible "nitrogen saturation" by human activity. Longer-term, ecosystem-level mass balance studies suggest that the relationship is not clear and that other ecosystem processes may dominate variation in N outputs. We have been studying small, forested watershed ecosystems in five northern watersheds for periods up to 35 years. Here I summarize the research on ecosystem processes and the N budget. During the past 2 decades, average wet-precipitation N inputs ranged from about 0.1 to 6 kg N ha(-1) year(-1) among sites. In general, sites with the lowest N inputs had the highest output-to-input ratios. In the Alaska watersheds, streamwater N output exceeded inputs by 70 to 250%. The ratio of mean monthly headwater nitrate (NO3-) concentration to precipitation NO3- concentration declined with increased precipitation concentration. A series of ecosystem processes have been studied and related to N outputs. The most important appear to be seasonal change in hydrologic flowpath, soil freezing, seasonal forest-floor inorganic N pools resulting from over-winter mineralization beneath the snowpack, spatial variation in watershed forest-floor inorganic N pools, the degree to which snowmelt percolates soils, and gross soil N mineralization rates.

Magnetic transition in Y-site doped multiferroic YMnO3

NASA Astrophysics Data System (ADS)

Thakur, Rajesh K.; Thakur, Rasna; Gaur, N. K.

2016-05-01

We have synthesized polycrystalline hexagonal Y1-xSrxMnO3 (x=0.02, 0.1) compounds by using conventional solid state reaction method. The detailed structural investigations are carried out by using XRD studies which reveals the single phase formation of the reported compounds with hexagonal structure and space group P63cm (JCPDS: 25-1079). Further the XRD data of reported compounds were analyzed by RIETVELD (FULLPROFF) method which shows the decrease in the lattice parameter with increasing concentration of divalent strontium to Y-site. The observed pointed kinks in the specific heat study are indicative of the probable coupling in between the electric and magnetic orders in this class of materials. The reported systematic specific heat studies shows that the antiferromagnetic (AFM) transition temperature (TN) shifts to higher value with increasing concentration of Sr2+ ion in the YMnO3 compound which is attributed to the enhanced lattice contribution to the specific heat in the this compound. The present compound shows the independence of specific heat and magnetic transition temperature with applied magnetic field of 8T and 12T.

Au nanocage/SiO2 saturable absorber for passive Q-switching Yb-doped fiber laser

NASA Astrophysics Data System (ADS)

Bai, Jinxi; Li, Ping; Guo, Lei; Zhang, Baitao; Hu, Qiongyu; Wang, Lili; Liu, Binghai; Chen, Xiaohan

2018-05-01

Au nanocages/SiO2 (Au-NCs/SiO2) with the surface plasmon resonance peak at 1060 nm were fabricated and experimentally exploited as the saturable absorber in an all-fiber passively Q-switched ytterbium-doped fiber laser for the first time. Under a pump power of 440 mW, the average output power of 10.6 mW was obtained with the pulse duration 1.4 µs and the repetition rate of 126.9 kHz at 1060.5 nm with the 3 dB spectral width of 0.131 nm. The results indicate that Au-NCs/SiO2 exhibits the potential for applications in the field of pulse lasers.

On the substitution of Sr ions at Y sites in YB(suba2)Cu3O(sub7-d)

NASA Astrophysics Data System (ADS)

Siddiqi, S. A.; Sreedhar, K.; Drobac, D.; Infante, C.; Matacotta, F. C.; Ganguly, P.

1989-10-01

The effect of Sr substitution at the Ba sites in YBa2 Cu3 O sub 7-d has been studied; attempts to substitute Sr exclusively at Y sites have not been successful. We have been able to substitute Sr at Y sites only when the Ba ions are simultaneously substituted by Sr to give solid solutions of the type Y sub 1-x Sr sub x Ba sub 2-2x Sr sub 2x Cu3 O(sub 7-)x(sub /2-d). These examples show superconducting transitions higher than 78 K without significant deterioration in the magnitude of the ac susceptibility. The substitutions are best understood in terms of site constraints on the ions occupying the Y and Ba sites.

Enhanced magnetoelectric properties of BiFeO{sub 3} on formation of BiFeO{sub 3}/SrFe{sub 12}O{sub 19} nanocomposites

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

Das, Anusree; Chatterjee, Souvik; Das, Dipankar, E-mail: ddas@alpha.iuc.res.in

2016-06-21

Nanocomposites (NCs) comprising (1−x) BiFeO{sub 3} (BFO) and x SrFe{sub 12}O{sub 19} (SRF) (x = 0.1, 0.2, 0.3, and 0.4) have been prepared by a sol-gel route. Presence of pure phases of both BiFeO{sub 3} (BFO) and SrFe{sub 12}O{sub 19} (SRF) in the NCs for x = 0.3 and 0.4 has been confirmed by Rietveld analysis of XRD data though a minor impurity phase is observed in the case of x = 0.1 and 0.2 NCs. Transmission electron micrographs of the NCs show that particles are mostly spherical with average size of 30 nm. M-H measurements at 300 and 10 K indicate predominantly ferrimagnetic behavior of all themore » NCs with an increasing trend of saturation magnetization values with increasing content of SRF. Dielectric constant (ε{sub r}) of the NCs at room temperature shows a dispersive behavior with frequency and attains a constant value at higher frequency. ε{sub r} − T measurements reveal an increasing trend of dielectric constant of the NCs with increasing temperature and show an anomaly around the antiferromagnetic transition temperature of BFO, which indicates magnetoelectric coupling in the NCs. The variation of capacitance in the presence of magnetic field confirms the enhancement of magnetoelectric effect in the NCs. {sup 57}Fe Mössbauer spectroscopy results indicate the presence of only Fe{sup 3+} ions in usual crystallographic sites of BFO and SRF.« less

Correlation between ionic size and valence state of tetra, penta and hexavalent B-site substitution with solubility limit, phase transformation and multiferroic properties of Bi0.875Eu0.125FeO3

NASA Astrophysics Data System (ADS)

Mumtaz, Fiza; Jaffari, G. Hassnain; Hassan, Qadeer ul; Shah, S. Ismat

2018-06-01

We present detailed comparative study of effect of isovalent i.e. Eu+3 substitution at A-site and tetra (Ti+4, Zr+4), penta (V+5) and hexavalent (W+6) substitutions at B-site in BiFeO3. Eu+3 substitution led to phase transformation and exhibited mixed phases i.e. rhombohedral and orthorhombic, while tetravalent substituents (Ti+4 and Zr+4) led to stabilization of cubic phase. In higher valent (i.e. V+5 and W+6) cases solubility limit was significantly reduced where orthorhombic phase was observed as in the case of parent compound. Phase transformation as a consequence of increase in microstrain and chemical pressure induced by the substituent has been discussed. Solubility limit of different B-site dopants i.e. Zr, W and V was extracted to 5%, 2% and 2%, respectively. Extra phases in various cases were Bi2Fe4O9, Bi25FeO40, Bi14W2O27, and Bi23V4O44.5 and their fractional amount have been quantified. Ti was substituted up to 15% and has been observed to be completely soluble in the parent compound. Solubility limits depends on ionic radii mismatch and valance difference of Fe+3 and dopant, in which valance difference plays more dominant role. Solubility limit and phase transformation has been explained in terms of change in bond strength and tolerance factor induced by incorporation of dopant which depend on its size and valence state. Detail optical, dielectric, ferroelectric, magnetic and transport properties of Eu and Ti co-doped samples and selected low concentration B-site doped compositions (i.e. 2%) have presented and discussed. Two d-d transitions and three charge transfer transitions were observed within UV-VIS range. Both change in cell volume for the same phase and transformation in crystal structure affects the band gap. Increase in room temperature dielectric constant and saturation polarization was also found to increase in case of Eu-Ti co-doped samples with increasing concentration of Ti. Substitution of Eu at A-site and Ti at B-site led to

Fine-scale Phenology and Nitrogen-Fixing Microbes at a GLORIA Site in Southwestern Montana, USA

NASA Astrophysics Data System (ADS)

Apple, M. E.; Prince, J.; Morales, S.; Apple, C.; Gallagher, J.

2010-12-01

Global climate change is predicted to have a major impact on alpine environments and plants, including changes in the phenology of alpine plants in western North America. The GLORIA( Global Research Initiative in Alpine Environments) project is an international network of alpine sites for long-term monitoring of naturally-occurring alpine plants in the context of climate change. We established a GLORIA site in southwestern Montana in 2008 with four sub-summits of ascending elevation from treeline to the upper alpine with surveys of plants in quadrats at each cardinal direction and installed -20° to 50° C temperature loggers (Onset TB132). This GLORIA site is immediately east of the Continental Divide at Mt. Fleecer, (45°49”36.06”N, 112°48’08.18”W), a 2873 m (9425 ft.) peak situated between the Pintlar and Pioneer Mts., and at Mt. Keokirk, 2987.3 m, (9801 ft.), 45°35’37.94” N, 112°57”03.89” W, south of Mt. Fleecer in the Pioneer Mts. Phenology is an important aspect of life in the mountains. Herbaceous plants appear at different times throughout the growing season but can be virtually undetectable at other times. To determine when particular species can be detected, we constructed a time-series of photographs of plants at the 3m2 and 1m2 quadrats at the sub-summits at Mt. Fleecer in the summer of 2010, with the first set of photographs taken on July 9, just after snowmelt and the final set taken on August 28, just before snowfall. The photographs demonstrate that apparently new species are found when early and late season images are compared. Data on the timing intervals of vegetative growth, anthesis, fruiting, and seed dispersal as well as visualizations of the seasonal appearance and disappearance of the aboveground parts of different species can be extracted from the photographs in the time series. As a result of this study, several new species will be added to the Southwestern Montana GLORIA species list, including Gentiana calycosa and

POSTFLAME BEHAVIOR OF NITROGENOUS SPECIES IN THE PRESENCE OF FUEL SULFUR: I. RICH, MOIST, CO/AR/O2

EPA Science Inventory

The paper gives results of experimental measurements of NO, N2, and other nitrogenous species in the postflame games of rich (phi = 2.17) premixed laminar CO/Ar/O2 (trace H2) flames, with fuel nitrogen as NO, C2N2, and NH3 and fuel sulfur as SO2, which allowed the nitrogen balanc...

Assessing variable rate nitrogen fertilizer strategies within an extensively instrument field site using the MicroBasin model

NASA Astrophysics Data System (ADS)

Ward, N. K.; Maureira, F.; Yourek, M. A.; Brooks, E. S.; Stockle, C. O.

2014-12-01

The current use of synthetic nitrogen fertilizers in agriculture has many negative environmental and economic costs, necessitating improved nitrogen management. In the highly heterogeneous landscape of the Palouse region in eastern Washington and northern Idaho, crop nitrogen needs vary widely within a field. Site-specific nitrogen management is a promising strategy to reduce excess nitrogen lost to the environment while maintaining current yields by matching crop needs with inputs. This study used in-situ hydrologic, nutrient, and crop yield data from a heavily instrumented field site in the high precipitation zone of the wheat-producing Palouse region to assess the performance of the MicroBasin model. MicroBasin is a high-resolution watershed-scale ecohydrologic model with nutrient cycling and cropping algorithms based on the CropSyst model. Detailed soil mapping conducted at the site was used to parameterize the model and the model outputs were evaluated with observed measurements. The calibrated MicroBasin model was then used to evaluate the impact of various nitrogen management strategies on crop yield and nitrate losses. The strategies include uniform application as well as delineating the field into multiple zones of varying nitrogen fertilizer rates to optimize nitrogen use efficiency. We present how coupled modeling and in-situ data sets can inform agricultural management and policy to encourage improved nitrogen management.

Atmosphere-Forest Exchange: Important Questions Regarding the Atmosphere's Role in the Delivery of Nutrient Nitrogen and Impacts on Nitrogen and Carbon Cycling

NASA Astrophysics Data System (ADS)

Carroll, M.; Shepson, P. B.; Bertman, S. B.; Sparks, J. P.; Holland, E. A.

2002-12-01

Atmosphere-Forest Exchange: Important Questions Regarding the Atmosphere's Role in the Delivery of Nutrient Nitrogen and Impacts on Nitrogen and Carbon Cycling Atmospheric composition and chemistry directly affect ecosystem nitrogen cycling and indirectly affect ecosystem carbon cycling and storage. Current understanding of atmosphere-forest nitrogen exchange and subsequent impacts is based almost exclusively on nitrogen deposition data obtained from networks using buckets placed in open areas, studies involving inorganic nitrogen, frequently with enhanced N deposition inputs applied only to soils, and that ignore multiple stresses (e.g., the combined effects of aerosols, ozone exposure, elevated CO2, and drought). Current models of nitrogen cycling treat deposited nitrogen (e.g., HNO3 and NO3-) as a permanent sink whereas data appear to indicate that photolytic and heterogeneous chemical processes occurring on surfaces and in dew can result in the re-evolution of gaseous species such as NO and HONO. Similarly, the direct uptake of gaseous nitrogen compounds by foliage has been neglected, compromising conclusions drawn from deposition experiments and ignoring a mechanism that may significantly affect nitrogen cycling and carbon storage, one that may become more significant with future atmospheric and climate change. We hypothesize that the atmosphere plays a significant role in the delivery of nutrient nitrogen to the N-limited mixed hardwood forest at the PROPHET research site at the University of Michigan Biological Station. We assert that a complete understanding of atmosphere- biosphere interactions and feedbacks is required to develop a predictive capability regarding forest response to increasing atmospheric CO2, reactive nitrogen, oxidants, and aerosols, increasing nitrogen and acidic deposition, and anticipated climate change. We further assert that conclusions drawn from studies that are limited to inorganic nitrogen, fertilization of soils, and/or that

A-site Ordered Chromium Perovskites, ACu3Cr4O12 with A = Trivalent Ions

NASA Astrophysics Data System (ADS)

Sugiyama, Jun; Nozaki, Hiroshi; Umegaki, Izumi; Higemoto, Wataru; Isobe, Masahiko; Takagi, Hidenori; Sakurai, Hiroya; Ansaldo, Eduardo J.; Brewer, Jess H.; Sassa, Yasmine; Forslund, Ola Kenji; Månsson, Martin

The magnetic ground state of the A-site ordered chromium perovskites, ACu3Cr4O12 with A = Y, La, Eu, and Lu has been investigated with μ+SR using powder samples prepared by a high-pressure technique. Weak transverse field measurements revealed that the four compounds enter into a magnetic phase below 230-260 K. Moreover, the transition temperature (TN) was found to decrease with increasing the size of A3+ ions. Zero field measurements indicated the formation of static antiferromagnetic (AF) order in ACu3Cr4O12 below TN. Furthermore, since the internal magnetic field in the AF phase is independent of A, the role of 4f electrons on the AF state is very limited and/or eventually absence in ACu3Cr4O12.

Non-equilibrium nitrogen DC-arc plasma treatment of TiO2 nanopowder.

PubMed

Suzuki, Yoshikazu; Gonzalez-Aguilar, José; Traisnel, Noel; Berger, Marie-Hélène; Repoux, Monique; Fulcheri, Laurent

2009-01-01

Non-equilibrium nitrogen DC-arc plasma treatment of a commercial TiO2 anatase nanopowder was examined to obtain nitrogen-doped TiO2. By using a non-thermal discharge at low current (150 mA) and high voltage (1200 V) using pure N2 gas, light yellowish-gray TiO2 powder was successfully obtained within a short period of 5-10 min. XPS and TEM-EELS studies confirmed the existence of doped nitrogen. Due to the relatively mild conditions (plasma power of 180 W), metastable anatase structure and fine crystallite size of TiO2 (ca. 10 nm) were maintained after the plasma treatment. The in-flight powder treatment system used in this study is promising for various type of powder treatment.

Synthesis, Characterization, and Study of In Vitro Cytotoxicity of ZnO-Fe3O4 Magnetic Composite Nanoparticles in Human Breast Cancer Cell Line (MDA-MB-231) and Mouse Fibroblast (NIH 3T3).

PubMed

Bisht, Gunjan; Rayamajhi, Sagar; Kc, Biplab; Paudel, Siddhi Nath; Karna, Deepak; Shrestha, Bhupal G

2016-12-01

Novel magnetic composite nanoparticles (MCPs) were successfully synthesized by ex situ conjugation of synthesized ZnO nanoparticles (ZnO NPs) and Fe 3 O 4 NPs using trisodium citrate as linker with an aim to retain key properties of both NPs viz. inherent selectivity towards cancerous cell and superparamagnetic nature, respectively, on a single system. Successful characterization of synthesized nanoparticles was done by XRD, TEM, FTIR, and VSM analyses. VSM analysis showed similar magnetic profile of thus obtained MCPs as that of naked Fe 3 O 4 NPs with reduction in saturation magnetization to 16.63 emu/g. Also, cell viability inferred from MTT assay showed that MCPs have no significant toxicity towards noncancerous NIH 3T3 cells but impart significant toxicity at similar concentration to breast cancer cell MDA-MB-231. The EC50 value of MCPs on MDA-MB-231 is less than that of naked ZnO NPs on MDA-MB-231, but its toxicity on NIH 3T3 was significantly reduced compared to ZnO NPs. Our hypothesis for this prominent difference in cytotoxicity imparted by MCPs is the synergy of selective cytotoxicity of ZnO nanoparticles via reactive oxygen species (ROS) and exhausting scavenging activity of cancerous cells, which further enhance the cytotoxicity of Fe 3 O 4 NPs on cancer cells. This dramatic difference in cytotoxicity shown by the conjugation of magnetic Fe 3 O 4 NPs with ZnO NPs should be further studied that might hold great promise for the development of selective and site-specific nanoparticles. Schematic representation of the conjugation, characterization and cytotoxicity analysis of Fe 3 O 4 -ZnO magnetic composite particles (MCPs).

17O excess transfer during the NO2 + O3 → NO3 + O2 reaction.

PubMed

Berhanu, Tesfaye Ayalneh; Savarino, Joël; Bhattacharya, S K; Vicars, Willliam C

2012-01-28

The ozone molecule possesses a unique and distinctive (17)O excess (Δ(17)O), which can be transferred to some of the atmospheric molecules via oxidation. This isotopic signal can be used to trace oxidation reactions in the atmosphere. However, such an approach depends on a robust and quantitative understanding of the oxygen transfer mechanism, which is currently lacking for the gas-phase NO(2) + O(3) reaction, an important step in the nocturnal production of atmospheric nitrate. In the present study, the transfer of Δ(17)O from ozone to nitrate radical (NO(3)) during the gas-phase NO(2) + O(3) → NO(3) + O(2) reaction was investigated in a series of laboratory experiments. The isotopic composition (δ(17)O, δ(18)O) of the bulk ozone and the oxygen gas produced in the reaction was determined via isotope ratio mass spectrometry. The Δ(17)O transfer function for the NO(2) + O(3) reaction was determined to be: Δ(17)O(O(3)∗) = (1.23 ± 0.19) × Δ(17)O(O(3))(bulk) + (9.02 ± 0.99). The intramolecular oxygen isotope distribution of ozone was evaluated and results suggest that the excess enrichment resides predominantly on the terminal oxygen atoms of ozone. The results obtained in this study will be useful in the interpretation of high Δ(17)O values measured for atmospheric nitrate, thus leading to a better understanding of the natural cycling of atmospheric reactive nitrogen. © 2012 American Institute of Physics

Effect of watershed urbanization on N2O emissions from the Chongqing metropolitan river network, China

NASA Astrophysics Data System (ADS)

He, Yixin; Wang, Xiaofeng; Chen, Huai; Yuan, Xingzhong; Wu, Ning; Zhang, Yuewei; Yue, Junsheng; Zhang, Qiaoyong; Diao, Yuanbin; Zhou, Lilei

2017-12-01

Watershed urbanization, an integrated anthropogenic perturbation, is another considerable global concern in addition to that of global warming and may significantly enrich the N loadings of watersheds, which then greatly influences the nitrous oxide (N2O) production and fluxes of these aquatic systems. However, little is known about the N2O dynamics in human-dominated metropolitan river networks. In this study, we present the temporal and spatial variations in N2O saturation and emission in the Chongqing metropolitan river network, which is undergoing intensified urbanization. The N2O saturation and fluxes at 84 sampling sites ranged from 126% to 10536% and from 4.5 to 1566.8 μmol N2O m-2 d-1, with means of 1780% and 261 μmol N2O m-2 d-1. The riverine N2O saturation and fluxes increased along with the urbanization gradient and urbanization rate, with disproportionately higher values in urban rivers due to the N2O-rich sewage inputs and enriched in situ N substrates. We found a clear seasonal pattern of N2O saturation, which was co-regulated by both water temperature and precipitation. Regression analysis indicated that the N substrates and dissolved oxygen (DO) that controlled nitrogen metabolism acted as good predictors of the N2O emissions of urban river networks. Particularly, phosphorus (P) and hydromorphological factors (water velocity, river size and bottom substrate) had stronger relationships with the N2O saturation and could also be used to predict the N2O emission hotspots in regions with rapid urbanization. In addition, the default emission factors (EF5-r) used in the Intergovernmental Panel on Climate Change (IPCC) methodology may need revision given the differences among the physical and chemical factors in different rivers, especially urban rivers.

Well-Defined Metal-O6 in Metal-Catecholates as a Novel Active Site for Oxygen Electroreduction.

PubMed

Liu, Xuan-He; Hu, Wei-Li; Jiang, Wen-Jie; Yang, Ya-Wen; Niu, Shuai; Sun, Bing; Wu, Jing; Hu, Jin-Song

2017-08-30

Metal-nitrogen coordination sites, M-N x (M = Fe, Co, Ni, etc.), have shown great potential to replace platinum group materials as electrocatalysts for oxygen reduction reaction (ORR). However, the real active site in M-N x is still vague to date due to their complicated structure and composition. It is therefore highly desirable but challenging to develop ORR catalysts with novel and clear active sites, which could meet the needs of comprehensive understanding of structure-function relationships and explore new cost-effective and efficient ORR electrocatalysts. Herein, well-defined M-O 6 coordination in metal-catecholates (M-CATs, M = Ni or Co) is discovered to be catalytically active for ORR via a four-electron-dominated pathway. In view of no pyrolysis involved and unambiguous crystalline structure of M-CATs, the M-O 6 octahedral coordination site with distinct structure is determined as a new type of active site for ORR. These findings extend the scope of metal-nonmetal coordination as an active site for ORR and pave a way for bottom-up design of novel electrocatalysts containing M-O 6 coordination.

A study of nitrogen behavior in the formation of Ta/TaN and Ti/TaN alloyed metal electrodes on SiO2 and HfO2 dielectrics

NASA Astrophysics Data System (ADS)

Gassilloud, R.; Maunoury, C.; Leroux, C.; Piallat, F.; Saidi, B.; Martin, F.; Maitrejean, S.

2014-04-01

We studied Ta, TaN, and sub-stoichiometric TaNx electrodes (obtained by nitrogen redistribution in Ta/TaN or Ti/TaN bilayers) deposited on thermal SiO2 and HfO2/IL (0.8 nm SiO2 IL, i.e., interlayer) stacks. Effective work-functions (WF) were extracted on MOS capacitor structures on SiO2 bevelled insulator of 4.2 eV for pure Ta, 4.6 eV for TaN, and 4.3 eV for sub-stoichiometric TaNx. This intermediate WF value is explained by TaN nitrogen redistribution with reactive Ta or Ti elements shifting the gate work-function toward the Si conduction band. The same electrodes deposited on an HfO2/IL dielectric showed different behavior: First, the Ta/HfO2/IL stack shows a +200 meV WF increase (towards the Si valence band) compared to the SiO2 dielectric stack. This increase is explained by the well-known HfO2/IL dipole formation. Second, in contrast to electrodes deposited on SiO2, sub-stoichiometric TaNx/HfO2 is found to have a lower WF (4.3 eV), than pure Ta on HfO2 (4.4 eV). This inversion in work-function behavior measured on SiO2 vs. HfO2 is explained by the nitrogen redistribution in Ta/TaN bilayer together with diffusion of nitrogen through the HfO2 layer, leading to Si-N formation which prevents dipole formation at the HfO2/IL interface.

Ferroelectric and Piezoelectric Properties of KNbO3 Ceramics Containing Small Amounts of LaFeO3

NASA Astrophysics Data System (ADS)

Kakimoto, Ken-ichi; Masuda, Izumi; Ohsato, Hitoshi

2003-09-01

Dense KNbO3 ceramics have been successfully synthesized by pressure-less sintering under optimized heat-treatment conditions using a small amount of La2O3 and Fe2O3 additives. KNbO3 forms (K1-xLax)(Nb1-xFex)O3 solid solutions and changes in the crystal system, depending on the additive content, from orthorhombic to tetragonal at x of 0.020, and from tetragonal to cubic at x of 0.200 or higher. When only 0.002 mol of La2O3 and Fe2O3 (x=0.002) was added into KNbO3, the highest value (98.8%) of the theoretical density was obtained. This specimen showed orthorhombic symmetry with a high Curie temperature of 420°C, and demonstrated a well-saturated ferroelectric hysteresis loop with large remanent polarization (Pr) of 18 μC/cm2, which is comparable to the value reported for pure KNbO3 ceramics fabricated by hot pressing. Furthermore, the x=0.002 specimen showed a planar electromechanical coupling ratio (kp) of 0.17 and piezoelectric d33 constant of 98 pC/N, regardless of the unsaturated poling state.

No significant interactions between nitrogen stimulation and ozone inhibition of isoprene emission in Cathay poplar.

PubMed

Yuan, Xiangyang; Shang, Bo; Xu, Yansen; Xin, Yue; Tian, Yuan; Feng, Zhaozhong; Paoletti, Elena

2017-12-01

Isoprene emission from plants subject to a combination of ozone (O 3 ) and nitrogen (N) has never been investigated. Cathay poplar (Populus cathayana) saplings were exposed to O 3 (CF, charcoal-filtered air, NF, non-filtered ambient air and E-O 3 , non-filtered air +40ppb) and N treatments (N0, 0kgNha -1 year -1 , N50, 50kgNha -1 year -1 and N100, 100kgNha -1 year -1 ) for 96days. Increasing O 3 exposure decreased isoprene emission (11.5% in NF and 57.9% in E-O 3 ), as well as light-saturated photosynthetic rate (A sat ) and chlorophyll content, while N load increased isoprene emission (19.6% in N50 and 33.4% in N100) as well as A sat and chlorophyll content. Although O 3 and N interacted significantly in A sat , N did not mitigate the negative effects of O 3 on isoprene emission, i.e. the combined effects were additive and did not interact. These results warrant more research on the combined effects of co-existing global change factors on future isoprene emission and atmospheric chemical processes. Copyright © 2017 Elsevier B.V. All rights reserved.

A-site- and/or B-site-modified PbZrTiO3 materials and (Pb, Sr, Ca, Ba, Mg) (Zr, Ti, Nb, Ta)O3 films having utility in ferroelectric random access memories and high performance thin film microactuators

NASA Technical Reports Server (NTRS)

Bilodeau, Steven (Inventor); Baum, Thomas H. (Inventor); Roeder, Jeffrey F. (Inventor); Chen, Ing-Shin (Inventor)

2001-01-01

A modified PbZrTiO.sub.3 perovskite crystal material thin film, wherein the PbZrTiO.sub.3 perovskite crystal material includes crystal lattice A-sites and B-sites at least one of which is modified by the presence of a substituent selected from the group consisting of (i) A-site substituents consisting of Sr, Ca, Ba and Mg, and (ii) B-site substituents selected from the group consisting of Nb and Ta. The perovskite crystal thin film material may be formed by liquid delivery MOCVD from metalorganic precursors of the metal components of the thin film, to form PZT and PSZT, and other piezoelectric and ferroelectric thin film materials. The thin films of the invention have utility in non-volatile ferroelectric memory devices (NV-FeRAMs), and in microelectromechanical systems (MEMS) as sensor and/or actuator elements, e.g., high speed digital system actuators requiring low input power levels.

Carbon and nitrogen isotopes unravels sources of aerosol contamination at Caribbean rural and urban coastal sites.

PubMed

Morera-Gómez, Yasser; Santamaría, Jesús Miguel; Elustondo, David; Alonso-Hernández, Carlos Manuel; Widory, David

2018-06-15

The constant increase of anthropogenic emissions of aerosols, usually resulting from a complex mixture from various sources, leads to a deterioration of the ambient air quality. The stable isotope compositions (δ 13 C and δ 15 N) of total carbon (TC) and nitrogen (TN) in both PM 10 and emissions from potential sources were investigated for first time in a rural and an urban Caribbean costal sites in Cuba to better constrain the origin of the contamination. Emissions from road traffic, power plant and shipping emissions were discriminated by coupling their C and N contents and corresponding isotope signatures. Other sources (soil, road dust and cement plant), in contrast, presented large overlapping ranges for both C and N isotope compositions. δ 13 C PM10 isotope compositions in the rural (average of -25.4 ± 1.2‰) and urban (average of -24.8 ± 1.2‰) sites were interpreted as a mixture of contributions from two main contributors: i) fossil fuel combustion and ii) cement plant and quarries. Results also showed that this last source is impacting more air quality at the urban site. A strong influence from local wood burning was also identified at the rural site. These conclusions were comforted by a statistical analysis using a conditional bivariate probability function. TN and δ 15 N values from the urban site demonstrated that nitrogen in PM 10 was generated by secondary processes through the formation of (NH 4 ) 2 SO 4 . The exchange in the (NH 4 ) 2 SO 4 molecule between gaseous NH 3 and particle NH 4 + under stoichiometric equilibrium may control the observed 15 N enrichment. At low nitrogen concentrations in the aerosols, representing PM 10 with both the highest primary N and lowest secondary N proportions, comparison with the δ 15 N of potential sources indicate that emissions from diesel car and power plant emissions may represent the major vectors of primary nitrogen. Copyright © 2018 Elsevier B.V. All rights reserved.

Tunable emission and excited state absorption induced optical limiting in Tb2(MoO4)3: Sm3+/Eu3+ nanophosphors

NASA Astrophysics Data System (ADS)

Mani, Kamal P.; Sreekanth, Perumbilavil; Vimal, G.; Biju, P. R.; Unnikrishnan, N. V.; Ittyachen, M. A.; Philip, Reji; Joseph, Cyriac

2016-12-01

Photoluminescence properties and optical limiting behavior of pure and Sm3+/Eu3+ doped Tb2(MoO4)3 nanophosphors are investigated. The prepared nanophosphors exhibit excellent emission when excited by UV light. Color-tunable emissions in Tb2-xSmx(MoO4)3 and Tb2-xEux(MoO4)3 are realized by employing different excitation wavelengths or by controlling the doping concentration of Sm3+ and Eu3+. Luminescence quantum yield and CIE chromatic coordinates of the prepared phosphors were also presented. Optical limiting properties of the samples are investigated by open aperture Z-scan technique using 5 ns laser pulses at 532 nm. Numerical fitting of the measured Z-scan data to the relevant nonlinear transmission equations reveals that the nonlinear absorption is arising from strong excited state absorption, along with weak absorption saturation and it is found that the optical nonlinearity of Tb2(MoO4)3 increases with Sm3+/Eu3+doping. Parameters such as saturation fluence, excited state absorption cross section and ground state absorption cross section of the samples have been determined numerically, from which the figure of merit for nonlinear absorption is calculated. The excited state absorption cross-section of the samples is found to be one order of magnitude higher than that of the ground state absorption cross-section, indicating strong reverse saturable absorption. These results indicate that Sm3+/Eu3+ doped Tb2(MoO4)3 nanophosphors are efficient media for UV/n-UV pumped LEDs, and are also potential candidates for designing efficient optical limiting devices for the protection of human eyes and sensitive optical detectors from harmful laser radiation.

Site-selective doping and superconductivity in (La1-yPry)(Ba2-xLax)Cu3O7+δ

NASA Astrophysics Data System (ADS)

Mitzi, D. B.; Feffer, P. T.; Newsam, J. M.; Webb, D. J.; Klavins, P.; Jacobson, A. J.; Kapitulnik, A.

1988-10-01

Samples in the quaternary system (La1-yPry)(Ba2-xLax)Cu3O7+δ have been prepared and characterized using x-ray and neutron diffraction, thermogravimetric analysis, and transport and magnetic measurements. Pr substitutes on the oxygen-depleted La layers for y>0.0, while La substitutes on the Ba sites for x>0.0. The effect of doping on each site is inferred to be primarily local, affecting immediately adjacent Cu-O layers. The similar suppression of superconductivity that accompanies doping on each of the two distinct sites apparently correlates with the degree of oxidation of the Cu-O sheets (and not the chains), indicating that the sheets support the high temperature superconductivity. Comparison of orthorhombic and tetragonal samples with similar Ba:La ratios (and y=0) demonstrates that the orthorhombic phase yields the largest Meissner signals and highest transition temperatures in the La(Ba2-xLax)Cu3O7+δ system. The effect on superconductivity of oxygen-vacancy configuration in the Cu-O chain layers is proposed to derive, indirectly, from their influence on the Cu-O sheets. In addition, optimally superconducting La(Ba2-xLax)Cu3O7+δ samples exhibit interesting normal-state magnetic properties, with a paramagnetic susceptibility that decreases steadily with temperature between 350 K and Tc.

Enhanced paramagnetism of mesoscopic graphdiyne by doping with nitrogen.

PubMed

Zhang, Mingjia; Wang, Xiaoxiong; Sun, Huijuan; Wang, Ning; Lv, Qing; Cui, Weiwei; Long, Yunze; Huang, Changshui

2017-09-14

The new two-dimensional graphitic material, graphdiyne, has attracted great interest recently due to the superior intrinsic semiconductor properties. Here we investigate the magnetism of pure graphdiyne material and find it demonstrating a remarkable paramagnetic characteristic, which can be attributed to the appearance of special sp-hybridized carbon atoms. On this basis, we further introduce nitrogen with 5.29% N/C ratio into graphdiyne followed by simply annealing in a dopant source and realize a twofold enhancement of saturation moment at 2 K. Associate with the density of states calculation, we investigate the influence of the nitrogen atom doping sites on paramagnetism, and further reveal the important role of doped nitrogen atom on benzene ring in improving local magnetic moment. These results can not only help us deeply understand the intrinsic magnetism of graphdiyne, but also open an efficient way to improve magnetism of graphdiyne by hetero atom doping, like nitrogen doping, which may promote the potential application of graphdiyne in spintronics.

Controls on Highly Siderophile Element Concentrations in Martian Basalt: Sulfide Saturation and Under-Saturation

NASA Technical Reports Server (NTRS)

Righter, Kevin

2009-01-01

Highly siderophile elements (HSE; Re, Au and the platinum group elements) in shergottites exhibit a wide range from very high, similar to the terrestrial mantle, to very low, similar to sulfide saturated mid ocean ridge basalt (e.g., [1]). This large range has been difficult to explain without good constraints on sulfide saturation or under-saturation [2]. A new model for prediction of sulfide saturation places new constraints on this problem [3]. Shergottite data: For primitive shergottites, pressure and temperature estimates are between 1.2-1.5 GPa, and 1350-1470 C [4]. The range of oxygen fugacities is from FMQ-2 to IW, where the amount of Fe2O3 is low and thus does not have a significant effect on the S saturation values. Finally, the bulk compositions of shergottites have been reported in many recent studies (e.g., [5]). All of this information will be used to test whether shergottites are sulfide saturated [3]. Modeling values and results: The database for HSE partition coefficients has been growing with many new data for silicates and oxides [6-8] to complement a large sulfide database [9- 11]. Combining these data with simple batch melting models allows HSE contents of mantle melts to be estimated for sulfide-bearing vs. sulfide-free mantle. Combining such models with fractional crystallization modeling (e.g., [12]) allows HSE contents of more evolved liquids to be modeled. Most primitive shergottites have high HSE contents (and low S contents) that can be explained by sulfide under-saturated melting of the mantle. An exception is Dhofar 019 which has high S contents and very low HSE contents suggesting sulfide saturation. Most evolved basaltic shergottites have lower S contents than saturation, and intermediate HSE contents that can be explained by olivine, pyroxene, and chromite fractionation. An exception is EET A79001 lithology B, which has very low HSE contents and S contents higher than sulfide saturation values . evidence for sulfide saturation

Modification of a deoxynivalenol-antigen-mimicking nanobody to improve immunoassay sensitivity by site-saturation mutagenesis.

PubMed

Qiu, Yu-Lou; He, Qing-Hua; Xu, Yang; Wang, Wei; Liu, Yuan-Yuan

2016-01-01

A nanobody (N-28) which can act as a deoxynivalenol (DON) antigen has been generated, and its residues Thr102-Ser106 were identified to bind with anti-DON monoclonal antibody by alanine-scanning mutagenesis. Site-saturation mutagenesis was used to analyze the plasticity of five residues and to improve the sensitivity of the N-28-based immunoassay. After mutagenesis, three mutants were selected by phage immunoassay and were sequenced. The half-maximal inhibitory concentrations of the immunoassay based on mutants N-28-T102Y, N-28-V103L, and N-28-Y105F were 24.49 ± 1.0, 51.83 ± 2.5, and 35.65 ± 1.6 ng/mL, respectively, showing the assay was, respectively, 3.2, 1.5, and 2.2 times more sensitive than the wild-type-based assay. The best mutant, N-28-T102Y, was used to develop a competitive phage ELISA to detect DON in cereals with high specificity and accuracy. In addition, the structural properties of N-28-T102Y and N-28 were investigated, revealing that the affinity of N-28-T102Y decreased because of increased steric hindrance with the large side chain. The lower-binding-affinity antigen mimetic may contribute to the improvement of the sensitivity of competitive immunoassays. These results demonstrate that nanobodies would be a favorable tool for engineering. Moreover, our results have laid a solid foundation for site-saturation mutagenesis of antigen-mimicking nanobodies to improve immunoassay sensitivity for small molecules.

Dissolved organic nitrogen budgets for upland, forested ecosystems in New England

USGS Publications Warehouse

Campbell, J.L.; Hornbeck, J.W.; McDowell, W.H.; Buso, D.C.; Shanley, J.B.; Likens, G.E.

2000-01-01

Relatively high deposition of nitrogen (N) in the northeastern United States has caused concern because sites could become N saturated. In the past, mass-balance studies have been used to monitor the N status of sites and to investigate the impact of increased N deposition. Typically, these efforts have focused on dissolved inorganic forms of N (DIN = NH4-N + NO3-N) and have largely ignored dissolved organic nitrogen (DON) due to difficulties in its analysis. Recent advances in the measurement of total dissolved nitrogen (TDN) have facilitated measurement of DON as the residual of TDN - DIN. We calculated DON and DIN budgets using data on precipitation and streamwater chemistry collected from 9 forested watersheds at 4 sites in New England. TDN in precipitation was composed primarily of DIN. Net retention of TDN ranged from 62 to 89% (4.7 to 10 kg ha-1 yr-1) of annual inputs. DON made up the majority of TDN in stream exports, suggesting that inclusion of DON is critical to assessing N dynamics even in areas with large anthropogenic inputs of DIN. Despite the dominance of DON in streamwater, precipitation inputs of DON were approximately equal to outputs. DON concentrations in streamwater did not appear significantly influenced by seasonal biological controls, but did increase with discharge on some watersheds. Streamwater NO3-N was the only fraction of N that exhibited a seasonal pattern, with concentrations increasing during the winter months and peaking during snowmelt runoff. Concentrations of NO3-N varied considerably among watersheds and are related to DOC:DON ratios in streamwater. Annual DIN exports were negatively correlated with streamwater DOC:DON ratios, indicating that these ratios might be a useful index of N status of upland forests.

Irreversibility and carriers control in two-dimensional electron gas at LaTiO3/SrTiO3 interface

NASA Astrophysics Data System (ADS)

Bergeal, N.; Biscaras, J.; Hurand, S.; Feuillet-Palma, C.; Lesueur, J.; Rastogi, A.; Budhani, R. C.; Reyren, N.; Lesne, E.; Leboeuf, D.; Proust, C.

2013-03-01

It has been shown recently that a two-dimensional electron gas 2DEG could form at the interface of two insulators such as LaAlO3 and SrTiO3, or LaTiO3 (a Mott insulator) and SrTiO3. We present low temperature transport measurements on LaTiO3/SrTiO3 and LaAlO3/SrTiO3 hetero-structures, whose properties can be modulated by field effect using a metallic gate on the back of the substrate. Here we show that when the carrier density is electrostatically increased beyond a critical value, the added electrons escape into the SrTiO3 leading to an irreversible doping regime where all the electronic properties of the 2DEG saturate (carrier density, resistivity, superconducting transition...). The dynamic of leakage was studied using time resolved measurement. Based on a complete self-consistent description of the confinement well, a thermal model for the carriers escape has been developed, which quantitatively accounts for the data.

Nb K-edge x-ray absorption investigation of the pressure induced amorphization in A-site deficient double perovskite La1/3NbO3.

PubMed

Marini, C; Noked, O; Kantor, I; Joseph, B; Mathon, O; Shuker, R; Kennedy, B J; Pascarelli, S; Sterer, E

2016-02-03

Nb K-edge x-ray absorption spectroscopy is utilized to investigate the changes in the local structure of the A-site deficient double perovskite La1/3NbO3 which undergoes a pressure induced irreversible amorphization. EXAFS results show that with increasing pressure up to 7.5 GPa, the average Nb-O bond distance decreases in agreement with the expected compression and tilting of the NbO6 octahedra. On the contrary, above 7.5 GPa, the average Nb-O bond distance show a tendency to increase. Significant changes in the Nb K-edge XANES spectrum with evident low energy shift of the pre-peak and the absorption edge is found to happen in La1/3NbO3 above 6.3 GPa. These changes evidence a gradual reduction of the Nb cations from Nb(5+) towards Nb(4+) above 6.3 GPa. Such a valence change accompanied by the elongation of the average Nb-O bond distances in the octahedra, introduces repulsion forces between non-bonding adjacent oxygen anions in the unoccupied A-sites. Above a critical pressure, the Nb reduction mechanism can no longer be sustained by the changing local structure and amorphization occurs, apparently due to the build-up of local strain. EXAFS and XANES results indicate two distinct pressure regimes having different local and electronic response in the La1/3NbO3 system before the occurence of the pressure induced amorphization at  ∼14.5 GPa.

Field-dependent magnetization of BiFeO 3 in ultrathin La 0.7Sr 0.3MnO 3/BiFeO 3 superlattice

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

Fitzsimmons, Michael R.; Jia, Quanxi X.; Singh, Surendra

2015-12-02

We report the observation of field-induced magnetization of BiFeO 3 (BFO) in an ultrathin La 0.7Sr 0.3MnO 3 (LSMO)/BFO superlattice using polarized neutron reflectivity (PNR). The depth dependent structure and magnetic characterization of subnano layer thick (thickness ~ 0.7 nm each) LSMO/BFO hetrostructure is carried out using X-ray reflectivity and PNR techniques. Our PNR results indicate parallel alignment of magnetization as well as enhancement in magnetic moment across LSMO/BFO interfaces. The study showed an increase in average magnetization on increasing applied magnetic field at 10K. As a result, we observed a saturation magnetization of 110 ± 15 kA/m (~0.8 μmore » B/Fe) for ultrathin BFO layer (~2 unit cell) sandwiched between ultrathin LSMO layers (~ 2 unit cell).« less

Acoustoelectric current saturation in c-axis fiber-textured polycrystalline zinc oxide films

NASA Astrophysics Data System (ADS)

Pompe, T.; Srikant, V.; Clarke, D. R.

1996-12-01

Acoustoelectric current saturation, which until now has only been observed in piezoelectric single crystals, is observed in thin polycrystalline zinc oxide films. Epitaxial ZnO films on c-plane sapphire and textured ZnO polycrystalline films on fused silica both exhibit current saturation phenomenon. The values of the saturation current densities are in the range 105-106 A/cm2, depending on the carrier concentration in the film, with corresponding saturation electric fields of 3-5×103 V/cm. In addition to the current saturation, the electrical properties of the films degraded with the onset of the acoustoelectric effect but could be restored by annealing at 250 °C in a vacuum for 30 min.

Short tests to couple N₂O emission mitigation and nitrogen removal strategies for landfill leachate recirculation.

PubMed

Wu, Dong; Wang, Chao; Dolfing, Jan; Xie, Bing

2015-04-15

Landfills implemented with onsite leachate recirculation can efficiently remove pollutants, but currently they are reckoned as N2O emission hot spots. In this project, we evaluated the relationship between N2O emission and nitrogen (N) removal efficiency with different types of leachate recirculated. Nitrate supplemented leachate showed low N2O emission rates with the highest N removal efficiency (~70%), which was equivalent to ~1% nitrogen emitted as N2O. Although in nitrite containing leachates' N removal efficiencies also reached to ~60%, their emitted N2O comprised ~40% of total removed nitrogen. Increasing nitrogen load promoted N2O emission and N removal efficiency, except in ammonia type leachate. When the ratio of BOD to total nitrogen increased from 0.2 to 0.4, the N2O emission flux from nitrate supplemented leachate decreased from ~25 to <0.5 μg N/kg-soil·h. We argue prior to leachate in situ recirculation, sufficient pre-aeration is critical to mitigate N2O surges and simultaneously enhance nitrogen removal efficiency. Copyright © 2015 Elsevier B.V. All rights reserved.

Experimental Study on the Behavior of TiN and Ti2O3 Inclusions in Contact with CaO‐Al2O3‐SiO2‐MgO Slags

PubMed Central

Bernhard, C.

2017-01-01

TiN and Ti2O3 are the predominant inclusion types in Ti-alloyed ferritic chromium stainless steels. In order to ensure the required steel cleanness level, an effective removal of such inclusions in the slag during secondary metallurgy is essential. This inclusion removal predominantly takes place via dissolution of the inclusion in the slag. The dissolution behavior of TiN and Ti2O3 in CaO-SiO2-Al2O3-MgO slags as well as their agglomeration behavior in the liquid steel is investigated using High Temperature Laser Scanning Confocal Microscopy and Tammann Furnace experiments. Thermodynamic calculations are performed using FactSage 7.0. The behavior of TiN is observed to be completely different to that of oxides. Ti2O3 dissolves quickly in slags, and its dissolution behavior is comparable to that of other already well examined oxides. In contrast, TiN shows a very intense gas reaction which is attributed to the release of nitrogen during contact with slag. Slags with higher SiO2 content show a significantly higher ability for the dissolution of TiN as compared to Al2O3-rich slags. The gas reaction is found to also significantly influence the final steel cleanness. Despite the easy absorption of TiN in the slag, the formed nitrogen supports the formation of pinholes in the steel. PMID:29109805

Lower tropospheric distributions of O3 and aerosol over Raoyang, a rural site in the North China Plain

NASA Astrophysics Data System (ADS)

Wang, Rui; Xu, Xiaobin; Jia, Shihui; Ma, Ruisheng; Ran, Liang; Deng, Zhaoze; Lin, Weili; Wang, Ying; Ma, Zhiqiang

2017-03-01

The North China Plain (NCP) has become one of the most polluted regions in China, with the rapidly increasing economic growth in the past decades. High concentrations of ambient O3 and aerosol have been observed at urban as well as rural sites in the NCP. Most of the in situ observations of air pollutants have been conducted near the ground so that current knowledge about the vertical distributions of tropospheric O3 and aerosol over the NCP region is still limited. In this study, vertical profiles of O3 and size-resolved aerosol concentrations below 2.5 km were measured in summer 2014 over a rural site in the NCP, using an unmanned aerial vehicle (UAV) equipped with miniature analyzers. In addition, vertical profiles of aerosol scattering property in the lower troposphere and vertical profiles of O3 below 1 km were also observed at the site using a lidar and tethered balloon, respectively. The depths of the mixed layer and residual layer were determined according to the vertical gradients of lidar particle extinction and aerosol number concentration. Average O3 and size-resolved aerosol number concentration in both the mixed and residual layer were obtained from the data observed in seven UAV flights. The results show that during most of the flights the O3 levels above the top of mixed layer were higher than those below. Such a positive gradient in the vertical distribution of O3 makes the residual layer an important source of O3 in the mixed layer, particularly during the morning when the top of mixed layer is rapidly elevated. In contrast to O3, aerosol number concentration was normally higher in the mixed layer than in the residual layer, particularly in the early morning. Aerosol particles were overwhelmingly distributed in the size range < 1 µm, showing slight differences between the mixed and residual layers. Our measurements confirm that the lower troposphere over the rural area of the NCP is largely impacted by anthropogenic pollutants locally emitted or

Low temperature magnetic properties of GdFeO3

NASA Astrophysics Data System (ADS)

Paul, Pralay; Prajapat, C. L.; Rajarajan, A. K.; Rao, T. V. Chandrasekhar

2018-04-01

Polycrystalline GdFeO3 was prepared using conventional solid state reaction method. Magnetization studies at low temperatures show antiferromagnetic ordering of Gd moments at ˜2.5K. Saturation in magnetization is noted at 2K under moderate magnetic fields, a result hitherto unreported. We conjecture that such a saturation is indicative of weakening of Dzyaloshinskii-Moriya interaction between Gd and Fe sublattices.

Exchange-coupled Fe3O4/CoFe2O4 nanoparticles for advanced magnetic hyperthermia

NASA Astrophysics Data System (ADS)

Robles, J.; Das, R.; Glassell, M.; Phan, M. H.; Srikanth, H.

2018-05-01

We report a systematic study of the effects of core and shell size on the magnetic properties and heating efficiency of exchange-coupled Fe3O4/CoFe2O4 core/shell nanoparticles. The nanoparticles were synthesized using thermal decomposition of organometallic precursors. Transmission electron microscopy (TEM) confirmed the formation of spherical Fe3O4 and Fe3O4/CoFe2O4 nanoparticles. Magnetic measurements showed high saturation magnetization for the nanoparticles at room temperature. Increasing core diameter (6.4±0.7, 7.8±0.1, 9.6±1.2 nm) and/or shell thickness (˜1, 2, 4 nm) increased the coercive field (HC), while an optimal value of saturation magnetization (MS) was achieved for the Fe3O4 (7.8±0.1nm)/CoFe2O4 (2.1±0.1nm) nanoparticles. Magnetic hyperthermia measurements indicated a large increase in specific absorption rate (SAR) for 8.2±1.1 nm Fe3O4/CoFe2O4 compared to Fe3O4 nanoparticles of same size. The SAR of the Fe3O4/CoFe2O4 nanoparticles increased from 199 to 461 W/g for 800 Oe as the thickness of the CoFe2O4 shell was increased from 0.9±0.5 to 2.1±0.1 nm. The SAR enhancement is attributed to a combination of the large MS and the large HC. Therefore, these Fe3O4/CoFe2O4 core/shell nanoparticles can be a good candidate for advanced hyperthermia application.

An Explosive Bomb-Inspired Method to Prepare Collapsed and Ruptured Fe2 O3 /Nitrogen-Doped Carbon Capsules as Catalyst Support.

PubMed

Wu, Jie; Zhang, Hui; Feng, Yan; Zhang, Xiao; Yao, Tongjie; Lian, Yongfu

2017-12-01

Compared with integrated capsules, ruptured ones have better mass diffusion and transport properties due to large gaps in the shells. However, most studies focus on integrated capsules, whereas little attention has been paid to the ruptured counterparts. Herein, an explosive bomb-inspired method was employed to prepare collapsed and ruptured Fe 2 O 3 /nitrogen-doped carbon (CR-Fe 2 O 3 /NC) capsules by using polystyrene (PS) nanoparticles (NPs) as a hard template, and polypyrrole (PPy) with embedded Prussian blue (PB) NPs as the shell. During pyrolysis, PB is converted into Fe 2 O 3 , and PPy is carbonized to form NC. Importantly, the PS core decomposes into gas molecules, leading to high pressure inside of the capsule, which explodes the thin shell into pieces. The roles of shell thickness and amount of Fe 2 O 3 on determining the spherical or collapsed, and integrated or ruptured morphology were revealed. Taking advantage of structural merits, including large gaps, thin shells, low density, and high surface area, CR-Fe 2 O 3 /NC capsules were used as supports for Pd NPs. These capsules exhibited better catalytic activity than that of integrated ones. Due to the magnetic properties, they could be reused at least five times. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Discrepancies between arterial oxygen saturation and functional oxygen saturation measured with pulse oximetry in very preterm infants.

PubMed

Rosychuk, Rhonda J; Hudson-Mason, Ann; Eklund, Dianne; Lacaze-Masmonteil, Thierry

2012-01-01

Discrepancies between pulse oximetry saturation (SpO(2)) and arterial saturation (SaO(2)) at low blood oxygenation values have been previously reported with significant variations among instruments and studies. Whether pulse oximeters that attenuate motion artifact are less prone to such discrepancies is not well known. To prospectively assess the agreement of the Masimo V4 pulse oximeter within the critical 85-95% SpO(2) target range. For all consecutive babies with gestational age <33 weeks, postnatal age <7 days, and an umbilical arterial line, SpO(2) was measured continuously and SaO(2) analyzed on an as-needed basis. Bland-Altman techniques provided estimates of the difference (D = SaO(2) - SpO(2)), standard deviation (SD), and 95% limits of agreement (D ± 2*SD). There were 1,032 measurements (114 babies) with SpO(2) between 85 and 95%. The 95% limits of agreement were -2.0 ± 5.8, -2.4 ± 9.2, and -1.9 ± 5.3 in the SpO(2) categories 85-95, 85-89, and 91-95%, respectively. For the SpO(2) categories 85-89% and 91-95%, only 52% (53/101) and 59% (523/886) of SpO(2) values, respectively, corresponded to the analogous SaO(2) categories. In the 85-89% SpO(2) category, SaO(2) was lower than 85% in 39 of the 101 (39%) measurements. SaO(2) was lower on average than SpO(2) with an increased bias at lower saturation. The -2.4 ± 9.2 95% limits of agreement for SaO(2) - SpO(2) in the 85-89% SpO(2) category suggest that SpO(2) and SaO(2) are not interchangeable and intermittent SaO(2) assessments are warranted when the targeted SpO(2) is within this range. Copyright © 2011 S. Karger AG, Basel.

Improved accuracy in high-temperature conversion elemental analyzer δ18O measurements of nitrogen-rich organics.

PubMed

Hunsinger, Glendon B; Stern, Libby A

2012-03-15

The use of high-temperature conversion (HTC) reduction systems interfaced with isotope ratio mass spectrometers for δ(18)O measurements of nitrogen-containing organic materials is complicated by isobaric interference from (14)N(16)O(+). This ion is produced in the ion source when N(2) reacts with trace oxygen shifting the m/z 30 baseline prior to elution of CO. We compared adaptations to a typical HTC system (TC/EA) to determine the best method to measure the δ(18)O values of nitrogen-rich organic substrates including: (1) 0.6 and 1.5 m 5 Å molecular sieve GC columns; (2) reduction of N(2) peak via He dilution; and (3) diversion of N(2) to waste via an automated four-port valve. These methods were applied to caffeine (IAEA-600), glycine, 4-nitroacetanilide, pentaerythritol tetranitrate (PETN) and cyclotrimethylene trinitramine (RDX), as well as pure and sodium azide-doped benzoic acid (IAEA-601) and sucrose (IAEA-CH6). The efficiency of N(2) production in the HTC interface was highly variable among these compounds. Both the longer column and the dilutor improved, but did not eliminate, the adverse effects of nitrogen. The diversion of N(2) adequately addressed the nitrogen-induced problems as indicated by: (1) consistent m/z 30 background offset between reference and sample CO for both N-free and N-rich materials; (2) production of the highest δ(18)O values; and (3) high correlation between the increase in the δ(18)O values relative to the GC-only measurements and the N(2) peak area. Additional validation would require N-rich oxygen isotope standards for inter-laboratory comparisons. Further, more stringent methodology may improve the poor inter-laboratory δ(18)O reproducibility of IAEA-600. Published in 2012 by John Wiley & Sons, Ltd.

Saturation-resolved-fluorescence spectroscopy of Cr3+:mullite glass ceramic

NASA Astrophysics Data System (ADS)

Liu, Huimin; Knutson, Robert; Yen, W. M.

1990-01-01

We present a saturation-based technique designed to isolate and uncouple individual components of inhomogeneously broadened spectra that are simultaneously coupled to each other through spectral overlap and energy-transfer interactions. We have termed the technique saturation-resolved-fluorescence spectroscopy; we demonstrate its usefulness in deconvoluting the complex spectra of Cr3+:mullite glass ceramic.

Magnetic transition in Y-site doped multiferroic YMnO{sub 3}

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

Thakur, Rajesh K., E-mail: thakur.rajesh2009@gmail.com; Thakur, Rasna, E-mail: rasnathakur@yahoo.com; Gaur, N. K., E-mail: srl-nkgaur@yahoo.co.in

2016-05-06

We have synthesized polycrystalline hexagonal Y{sub 1-x}Sr{sub x}MnO{sub 3} (x=0.02, 0.1) compounds by using conventional solid state reaction method. The detailed structural investigations are carried out by using XRD studies which reveals the single phase formation of the reported compounds with hexagonal structure and space group P6{sub 3}cm (JCPDS: 25-1079). Further the XRD data of reported compounds were analyzed by RIETVELD (FULLPROFF) method which shows the decrease in the lattice parameter with increasing concentration of divalent strontium to Y-site. The observed pointed kinks in the specific heat study are indicative of the probable coupling in between the electric and magneticmore » orders in this class of materials. The reported systematic specific heat studies shows that the antiferromagnetic (AFM) transition temperature (T{sub N}) shifts to higher value with increasing concentration of Sr{sup 2+} ion in the YMnO{sub 3} compound which is attributed to the enhanced lattice contribution to the specific heat in the this compound. The present compound shows the independence of specific heat and magnetic transition temperature with applied magnetic field of 8T and 12T.« less

Cobalt nanoparticles/nitrogen-doped graphene with high nitrogen doping efficiency as noble metal-free electrocatalysts for oxygen reduction reaction.

PubMed

Liang, Jingwen; Hassan, Mehboob; Zhu, Dongsheng; Guo, Liping; Bo, Xiangjie

2017-03-15

Nitrogen-doped graphene (N/GR) has been considered as active metal-free electrocatalysts for oxygen reduction reaction (ORR). However, the nitrogen (N) doping efficiency is very low and only few N atoms are doped into the framework of GR. To boost the N doping efficiency, in this work, a confined pyrolysis method with high N doping efficiency is used for the preparation of cobalt nanoparticles/nitrogen-doped GR (Co/N/GR). Under the protection of SiO 2 , the inorganic ligand NH 3 in cobalt amine complex ([Co(NH 3 ) 6 ] 3+ ) is trapped in the confined space and then can be effectively doped into the framework of GR without the introduction of any carbon residues. Meanwhile, due to the redox reaction between the cobalt ions and carbon atoms of GR, Co nanoparticles are supported into the framework of N/GR. Due to prevention of GR layer aggregation with SiO 2 , the Co/N/GR with high dispersion provides sufficient surface area and maximum opportunity for the exposure of Co nanoparticles and active sites of N dopant. By combination of enhanced N doping efficiency, Co nanoparticles and high dispersion of GR sheets, the Co/N/GR is remarkably active, cheap and selective noble-metal free catalysts for ORR. Copyright © 2016 Elsevier Inc. All rights reserved.

Effects of background oxygen pressure on dielectric and ferroelectric properties of epitaxial (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 thin films on SrTiO3

NASA Astrophysics Data System (ADS)

Abazari, M.; Akdoǧan, E. K.; Safari, A.

2008-11-01

Oxygen partial pressure (PO_2) in pulsed laser deposition significantly influences the composition, microstructure, and electrical properties of epitaxial misfit strain-relieved 450nm ⟨001⟩ oriented epitaxial (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 thin films on SrRuO3 coated SrTiO3. Films deposited at 400mTorr exhibit high remnant and saturated polarization of 7.5 and 16.5μC /cm2, respectively, which is ˜100% increase over the ones grown at 100mTorr. The dielectric constant linearly increases from 220 to 450 with increasing PO2. The observed changes in surface morphology of the films and their properties are shown to be due to the suppression of volatile A-site cation loss.

Saturation sampling for spatial variation in multiple air pollutants across an inversion-prone metropolitan area of complex terrain

PubMed Central

2014-01-01

Background Characterizing intra-urban variation in air quality is important for epidemiological investigation of health outcomes and disparities. To date, however, few studies have been designed to capture spatial variation during select hours of the day, or to examine the roles of meteorology and complex terrain in shaping intra-urban exposure gradients. Methods We designed a spatial saturation monitoring study to target local air pollution sources, and to understand the role of topography and temperature inversions on fine-scale pollution variation by systematically allocating sampling locations across gradients in key local emissions sources (vehicle traffic, industrial facilities) and topography (elevation) in the Pittsburgh area. Street-level integrated samples of fine particulate matter (PM2.5), black carbon (BC), nitrogen dioxide (NO2), sulfur dioxide (SO2), and ozone (O3) were collected during morning rush and probable inversion hours (6-11 AM), during summer and winter. We hypothesized that pollution concentrations would be: 1) higher under inversion conditions, 2) exacerbated in lower-elevation areas, and 3) vary by season. Results During July - August 2011 and January - March 2012, we observed wide spatial and seasonal variability in pollution concentrations, exceeding the range measured at regulatory monitors. We identified elevated concentrations of multiple pollutants at lower-elevation sites, and a positive association between inversion frequency and NO2 concentration. We examined temporal adjustment methods for deriving seasonal concentration estimates, and found that the appropriate reference temporal trend differs between pollutants. Conclusions Our time-stratified spatial saturation approach found some evidence for modification of inversion-concentration relationships by topography, and provided useful insights for refining and interpreting GIS-based pollution source indicators for Land Use Regression modeling. PMID:24735818

Saturation sampling for spatial variation in multiple air pollutants across an inversion-prone metropolitan area of complex terrain.

PubMed

Shmool, Jessie Lc; Michanowicz, Drew R; Cambal, Leah; Tunno, Brett; Howell, Jeffery; Gillooly, Sara; Roper, Courtney; Tripathy, Sheila; Chubb, Lauren G; Eisl, Holger M; Gorczynski, John E; Holguin, Fernando E; Shields, Kyra Naumoff; Clougherty, Jane E

2014-04-16

Characterizing intra-urban variation in air quality is important for epidemiological investigation of health outcomes and disparities. To date, however, few studies have been designed to capture spatial variation during select hours of the day, or to examine the roles of meteorology and complex terrain in shaping intra-urban exposure gradients. We designed a spatial saturation monitoring study to target local air pollution sources, and to understand the role of topography and temperature inversions on fine-scale pollution variation by systematically allocating sampling locations across gradients in key local emissions sources (vehicle traffic, industrial facilities) and topography (elevation) in the Pittsburgh area. Street-level integrated samples of fine particulate matter (PM2.5), black carbon (BC), nitrogen dioxide (NO2), sulfur dioxide (SO2), and ozone (O3) were collected during morning rush and probable inversion hours (6-11 AM), during summer and winter. We hypothesized that pollution concentrations would be: 1) higher under inversion conditions, 2) exacerbated in lower-elevation areas, and 3) vary by season. During July - August 2011 and January - March 2012, we observed wide spatial and seasonal variability in pollution concentrations, exceeding the range measured at regulatory monitors. We identified elevated concentrations of multiple pollutants at lower-elevation sites, and a positive association between inversion frequency and NO2 concentration. We examined temporal adjustment methods for deriving seasonal concentration estimates, and found that the appropriate reference temporal trend differs between pollutants. Our time-stratified spatial saturation approach found some evidence for modification of inversion-concentration relationships by topography, and provided useful insights for refining and interpreting GIS-based pollution source indicators for Land Use Regression modeling.

Nitrogen and carbon dynamics beneath on-site wastewater treatment systems in Pitt County, North Carolina.

PubMed

Del Rosario, Katie L; Humphrey, Charles P; Mitra, Siddhartha; O'Driscoll, Michael A

2014-01-01

On-site wastewater treatment systems (OWS) are a potentially significant non-point source of nutrients to groundwater and surface waters, and are extensively used in coastal North Carolina. The goal of this study was to determine the treatment efficiency of four OWS in reducing total dissolved nitrogen (TDN) and dissolved organic carbon (DOC) concentrations before discharge to groundwater and/or adjacent surface water. Piezometers were installed for groundwater sample collection and nutrient analysis at four separate residences that use OWS. Septic tank effluent, groundwater, and surface water samples (from an adjacent stream) were collected four times during 2012 for TDN and DOC analysis and pH, temperature, electrical conductivity, and dissolved oxygen measurements. Treatment efficiencies from the tank to the groundwater beneath the drainfields ranged from 33 to 95% for TDN and 45 to 82% for DOC, although dilution accounted for most of the concentration reductions. There was a significant positive correlation between nitrate concentration and separation distance from trench bottom to water table and a significant negative correlation between DOC concentration and separation distance. The TDN and DOC transport (>15 m) from two OWS with groundwater saturated drainfield trenches was significant.

Structural transitions in hybrid improper ferroelectric C a3T i2O7 tuned by site-selective isovalent substitutions: A first-principles study

NASA Astrophysics Data System (ADS)

Li, C. F.; Zheng, S. H.; Wang, H. W.; Gong, J. J.; Li, X.; Zhang, Y.; Yang, K. L.; Lin, L.; Yan, Z. B.; Dong, Shuai; Liu, J.-M.

2018-05-01

C a3T i2O7 is an experimentally confirmed hybrid improper ferroelectric material, in which the electric polarization is induced by a combination of the coherent Ti O6 octahedral rotation and tilting. In this work, we investigate the tuning of ferroelectricity of C a3T i2O7 using isovalent substitutions on Ca sites. Due to the size mismatch, larger/smaller alkaline earths prefer A'/A sites, respectively, allowing the possibility for site-selective substitutions. Without extra carriers, such site-selected isovalent substitutions can significantly tune the Ti O6 octahedral rotation and tilting, and thus change the structure and polarization. Using the first-principles calculations, our study reveals that three substituted cases (Sr, Mg, and Sr+Mg) show divergent physical behaviors. In particular, (CaTiO3) 2SrO becomes nonpolar, which can reasonably explain the suppression of polarization upon Sr substitution observed in experiment. In contrast, the polarization in (MgTiO3) 2CaO is almost doubled upon substitutions, while the estimated coercivity for ferroelectric switching does not change. The (MgTiO3) 2SrO remains polar but its structural space group changes, with moderate increased polarization and possible different ferroelectric switching paths. Our study reveals the subtle ferroelectricity in the A3T i2O7 family and suggests one more practical route to tune hybrid improper ferroelectricity, in addition to the strain effect.

Evaluation of dihydroquercetin-3-O-glucoside from Malbec grapes as copigment of malvidin-3-O-glucoside.

PubMed

Fanzone, Martín; González-Manzano, Susana; Pérez-Alonso, Joaquín; Escribano-Bailón, María Teresa; Jofré, Viviana; Assof, Mariela; Santos-Buelga, Celestino

2015-05-15

Malbec is a wine grape variety of great phenolic potential characterized for its high levels of anthocyanins and dihydroflavonols. To evaluate the possible implication of dihydroflavonols in the expression of red wine color through reactions of copigmentation or condensation, assays were carried out in wine model systems with different malvidin-3-O-glucoside:dihydroquercetin-3-O-glucoside molar ratios. The addition of increasing levels of dihydroquercetin-3-O-glucoside to a constant malvidin-3-O-glucoside concentration resulted in a hyperchromic effect associated with a darkening of the anthocyanin solutions, greater quantity of color and visual saturation, perceptible to the human eye. Copigmentation and thermodynamic measurements showed that dihydroquercetin-3-O-glucoside can act as an anthocyanin copigment, similar to other usual wine components like flavanols or phenolic acids, although apparently less efficient than flavonols. The high levels of dihydroflavonols existing in Malbec wines in relation to other non-anthocyanin phenolics should make this family of compounds particularly important to explain the color expression in Malbec young red wines. Copyright © 2014 Elsevier Ltd. All rights reserved.

[3H]MK-801 binding sites in post-mortem human frontal cortex.

PubMed

Kornhuber, J; Mack-Burkhardt, F; Kornhuber, M E; Riederer, P

1989-03-29

The binding of [3H]MK-801 ((+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate) was investigated in extensively washed homogenates of post-mortem human frontal cortex. The association of [3H]MK-801 proceeded slowly (t1/2 = 553 min) and reached equilibrium only after a prolonged incubation (greater than 24 h). The dissociation of [3H]MK-801 from the binding site was also slow (t1/2 = 244 min). Glutamate, glycine and magnesium markedly increased the rate of association (t1/2 = 14.8 min) and dissociation (t1/2 = 36.5 min). At equilibrium, the binding was not altered by these substances. Specific binding was linear with protein concentration, was saturable, reversible, stereoselective, heat-labile and was nearly absent in the white matter. Scatchard analysis of the saturation curves obtained at equilibrium indicated that there was a high-affinity (Kd1 1.39 +/- 0.21 nM, Bmax1 0.483 +/- 0.084 pmol/mg protein) and a low-affinity (Kd2 116.25 +/- 50.79 nM, Bmax2 3.251 +/- 0.991 pmol/mg protein) binding site. All competition curves obtained with (+)-MK-801, (-)-MK-801, phencyclidine and ketamine had Hill coefficients of less than unity and were best explained by a two-site model. Thus, our results demonstrate the presence of binding sites for MK-801 in post-mortem human brains and provide evidence for binding site heterogeneity. Furthermore, glutamate, glycine and magnesium accelerate the association and dissociation of [3H]MK-801 to and from its binding sites. The results add support to the hypothesis that MK-801, glutamate, glycine and magnesium all bind to different sites on the NMDA receptor-ion channel complex.

Precision saturated absorption spectroscopy of H3+

NASA Astrophysics Data System (ADS)

Guan, Yu-Chan; Chang, Yung-Hsiang; Liao, Yi-Chieh; Peng, Jin-Long; Wang, Li-Bang; Shy, Jow-Tsong

2018-03-01

In our previous work on the Lamb-dips of the ν2 fundamental band transitions of H3+, the saturated absorption spectrum was obtained by third-derivative spectroscopy using frequency modulation with an optical parametric oscillator (OPO). However, frequency modulation also caused errors in the absolute frequency determination. To solve this problem, we built a tunable offset locking system to lock the pump frequency of the OPO to an iodine-stabilized Nd:YAG laser. With this improvement, we were able to scan the OPO idler frequency precisely and obtain the saturated absorption profile using intensity modulation. Furthermore, ion concentration modulation was employed to subtract the background noise and increase the signal-to-noise ratio. To determine the absolute frequency of the idler wave, the OPO signal frequency was locked to an optical frequency comb. The absolute frequency accuracy of our spectrometer was better than 7 kHz, demonstrated by measuring the wavelength standard transition of methane at 3.39 μm. Finally, we measured 16 transitions of H3+ and our results agree very well with other precision measurements. This work successfully resolved the discrepancies between our previous measurements and other precision measurements.

Anthropogenic imprints on nitrogen and oxygen isotopic composition of precipitation nitrate in a nitrogen-polluted city in southern China

NASA Astrophysics Data System (ADS)

Fang, Y. T.; Koba, K.; Wang, X. M.; Wen, D. Z.; Li, J.; Takebayashi, Y.; Liu, X. Y.; Yoh, M.

2010-09-01

Nitric acid (HNO3) or nitrate (NO3-) is the dominant sink for reactive nitrogen oxides (NOx = NO + NO2) in the atmosphere. In many Chinese cities, HNO3 is becoming a significant contributor to acid deposition. In the present study, we used the denitrifier method to measure nitrogen (N) and oxygen (O) isotopic composition of NO3- in 113 precipitation samples collected from Guangzhou City in southern China over a two-year period (2008 and 2009). We attempted to better understand the spatial and seasonal variability of atmospheric NOx sources and the NO3- formation pathways in this N-polluted city in the Pearl River Delta region. The δ15N values of NO3- (versus air N2) ranged from -4.9 to +10.1‰, and averaged +3.9‰ in 2008 and +3.3‰ in 2009. Positive δ15N values were observed throughout the year, indicating the anthropogenic contribution of NOx emissions, particularly from coal combustion. Different seasonal patterns of δ15N-NO3- were observed between 2008 and 2009, which might reflect different human activities associated with the global financial crisis and the intensive preparations for the 16th Asian Games. Nitrate δ18O values (versus Vienna Standard Mean Ocean Water) varied from +33.4 to +86.5‰ (average +65.0‰ and +67.0‰ in 2008 and 2009, respectively), a range being lower than those reported for high altitude and polar areas. Several δ18O values were observed lower than the expected minimum of 50‰ at our study site. This was likely caused by the reaction of NO with peroxy radicals; peroxy radicals can compete with O3 to convert NO to NO2, thereby donate O atoms with much lower δ18O value than that of O3 to atmospheric NO3-. Our results highlight that the influence of human activities on atmospheric chemistry can be recorded by the N and O isotopic composition of atmospheric NO3- in a N-polluted city.

Anthropogenic imprints on nitrogen and oxygen isotopic composition of precipitation nitrate in a nitrogen-polluted city in southern China

NASA Astrophysics Data System (ADS)

Fang, Y. T.; Koba, K.; Wang, X. M.; Wen, D. Z.; Li, J.; Takebayashi, Y.; Liu, X. Y.; Yoh, M.

2011-02-01

Nitric acid (HNO3) or nitrate (NO3-) is the dominant sink for reactive nitrogen oxides (NOx = NO + NO2) in the atmosphere. In many Chinese cities, HNO3 is becoming a significant contributor to acid deposition. In the present study, we measured nitrogen (N) and oxygen (O) isotopic composition of NO3- in 113 precipitation samples collected from Guangzhou City in southern China over a two-year period (2008 and 2009). We attempted to better understand the spatial and seasonal variability of atmospheric NOx sources and the NO3- formation pathways in this N-polluted city in the Pearl River Delta region. The δ15N values of NO3- (versus air N2) ranged from -4.9 to +10.1‰, and averaged +3.9‰ in 2008 and +3.3‰ in 2009. Positive δ15N values were observed throughout the year, indicating the anthropogenic contribution of NOx emissions, particularly from coal combustion. Different seasonal patterns of δ15N-NO3- were observed between 2008 and 2009, which might reflect different human activities associated with the global financial crisis and the intensive preparations for the 16th Asian Games. Nitrate δ18O values (versus Vienna Standard Mean Ocean Water) varied from +33.4 to +86.5‰ (average +65.0‰ and +67.0‰ in 2008 and 2009, respectively), a range being lower than those reported for high latitude and polar areas. Sixteen percent of δ18O values was observed lower than the expected minimum of +55‰ at our study site. This was likely caused by the reaction of NO with peroxy radicals; peroxy radicals can compete with O3 to convert NO to NO2, thereby donate O atoms with much lower δ18O value than that of O3 to atmospheric NO3-. Our results highlight that the influence of human activities on atmospheric chemistry can be recorded by the N and O isotopic composition of atmospheric NO3- in a N-polluted city.

Viscosity of SiO2-"FeO"-Al2O3 System in Equilibrium with Metallic Fe

NASA Astrophysics Data System (ADS)

Chen, Mao; Raghunath, Sreekanth; Zhao, Baojun

2013-08-01

The present study delivered the measurements of viscosities in SiO2-"FeO"-Al2O3 system in equilibrium with metallic Fe. The rotational spindle technique was used in the measurements at the temperature range of 1473 K to 1773 K (1200 °C to 1500 °C). Molybdenum crucibles and spindles were employed in all measurements. The Fe saturation condition was maintained by an iron plate placed at the bottom of the crucible. The equilibrium compositions of the slags were measured by EPMA after the viscosity measurements. The effect of up to 20 mol. pct Al2O3 on the viscosity of the SiO2-"FeO" slag was investigated. The "charge compensation effect" of the Al2O3 and FeO association has been discussed. The modified quasi-chemical viscosity model has been optimized in the SiO2-"FeO"-Al2O3 system in equilibrium with metallic Fe to describe the viscosity measurements of the present study.

Effect of temperature on hydration kinetics and polymerization of tricalcium silicate in stirred suspensions of CaO-saturated solutions

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

Grant, Steven A.; Boitnott, Ginger E.; Korhonen, Charles J.

2006-04-15

Tricalcium silicate was hydrated at 274, 278, 283, 298, and 313 K in stirred suspensions of saturated CaO solutions under a nitrogen-gas atmosphere until the end of deceleratory period. The suspension conductivities and energy flows were measured continuously. The individual reaction rates for tricalcium silicate dissolution, calcium silicate hydrate precipitation, and calcium hydroxide precipitation were calculated from these measurements. The results suggest that the proportion of tricalcium silicate dissolved was determined by the rate of tricalcium silicate dissolution and the time to very rapid calcium hydroxide precipitation. The time to very rapid calcium hydroxide precipitation was more sensitive to changesmore » in temperature than was the rate of tricalcium silicate dissolution, so that the proportion of tricalcium silicate hydration dissolved by the deceleratory period increased with decreasing temperature. The average chain length of the calcium silicate hydrate ascertained by magic-angle spinning nuclear magnetic resonance spectroscopy increased with increasing temperature.« less

Distinct Effects of Humic Acid on Transport and Retention of TiO2 Rutile Nanoparticles in Saturated Sand Column

EPA Science Inventory

Distinct effects of humic acid (HA, 0 – 10 mg L-1) on the transport of titanium dioxide (rutile) nanoparticles (nTiO2) through saturated sand columns were observed under conditions of environmental relevance (ionic strength 3 – 200 mM NaCl, pH 5.7 and 9.0). Specifical...

O3 flux-related responsiveness of photosynthesis, respiration, and stomatal conductance of adult Fagus sylvatica to experimentally enhanced free-air O3 exposure.

PubMed

Löw, M; Häberle, K-H; Warren, C R; Matyssek, R

2007-03-01

Knowledge of responses of photosynthesis, respiration, and stomatal conductance to cumulative ozone uptake (COU) is still scarce, and this is particularly the case for adult trees. The effect of ozone (O(3)) exposure on trees was examined with 60-year-old beech trees (FAGUS SYLVATICA) at a forest site of southern Germany. Trees were exposed to the ambient O(3) regime (1 x O(3)) or an experimentally elevated twice-ambient O(3) regime (2 x O(3)). The elevated 2 x O (3) regime was provided by means of a free-air O(3) canopy exposure system. The hypotheses were tested that (1) gas exchange is negatively affected by O(3) and (2) the effects of O(3) are dose-dependent and thus the sizes of differences between treatments are positively related to COU. Gas exchange (light-saturated CO(2) uptake rate A(max), stomatal conductance g (s), maximum rate of carboxylation Vc (max), ribulose-1,5-bisphosphate turnover limited rate of photosynthesis J (max), CO(2) compensation point CP, apparent quantum yield of net CO(2) uptake AQ, carboxylation efficiency CE, day- and nighttime respiration) and chlorophyll fluorescence (electron transfer rate, ETR) were measured IN SITU on attached sun and shade leaves. Measurements were made periodically throughout the growing seasons of 2003 (an exceptionally dry year) and 2004 (a year with average rainfall). In 2004 Vc(max), J(max), and CE were lower in trees receiving 2 x O(3) compared with the ambient O(3) regime (1 x O(3)). Treatment differences in Vc (max), J (max), CE were rather small in 2004 (i.e., parameter levels were lower by 10 - 30 % in 2 x O(3) than 1 x O(3)) and not significant in 2003. In 2004 COU was positively correlated with the difference between treatments in A (max), g (s), and ETR (i.e., consistent with the dose-dependence of O(3)'s deleterious effects). However, in 2003, differences in A(max), g (s), and ETR between the two O(3) regimes were smaller at the end of the dry summer 2003 (i.e., when COU was greatest). The

Magnetic properties of transition metal substituted La 0.85Ag 0.15Mn 1-yM yO 3 compounds (M=Co, Cr and Al)

NASA Astrophysics Data System (ADS)

Srivastava, S. K.; Ravi, S.

2009-12-01

In this paper we report a systematic study of Mn-site substitution by M=Co, Cr and Al in La 0.85Ag 0.15MnO 3 series to understand the magnetic interactions between Mn and other transition metals. The long-range ferromagnetic (FM) ordering of the parent compound was significantly affected by Mn-site substitution. The measured magnetic properties of Co-doped samples have been explained on the basis of FM interactions in Mn 3+-O-Mn 4+, Co 2+-O-Mn 4+, Co 3+-O-Mn 4+ networks and simultaneous antiferromagnetic (AFM) interactions in Mn 4+-O-Mn 4+, Co 2+-O-Mn 3+ networks. The magnetic properties of Cr-doped compounds could be understood on the basis of double exchange FM interactions in Mn 3+-O 2--Mn 4+ networks and competing AFM in Cr 3+-O-Mn 4+, Mn 4+-O-Mn 4+, Cr 3+-O-Mn 3+ networks. However, it is found that the doping of Al ions play a role of magnetic dilution, without contributing any other competing magnetic interaction. The field variations of magnetization of all the above three series could be analysed by fitting to Brillouin function model and the effective spin contribution for FM has been determined. The measured saturation magnetization has been explained quantitatively.

Metal-insulator transition in Ba3Fe1 -xRu2 +xO9 : Interplay between site disorder, chemical percolation, and electronic structure

NASA Astrophysics Data System (ADS)

Middey, S.; Aich, Payel; Meneghini, C.; Mukherjee, K.; Sampathkumaran, E. V.; Siruguri, V.; Mahadevan, P.; Ray, Sugata

2016-11-01

Perovskites containing barium metal at the A site often take up unusual hexagonal structures having more than one type of possible sites for the B cation to occupy. This opens up various different B -B - or B -O-B -type connectivities and consequent physical properties which are naturally missing in cubic perovskites. BaRuO3 is one such system where doping of Ru (4 d4 ) by other transition metals (Mn +) creates similar conditions, giving rise to various M -Ru interactions. Interestingly, the 6 H hexagonal structure of doped barium ruthenate triple perovskite (Ba3M Ru2O9 ) seems to possess some internal checks because within the structure M ion always occupies the 2 a site and Ru goes to the 4 f site, allowing only M -O-Ru 180∘ and Ru-O-Ru 90∘ interactions to occur. The only exception is observed in the case of the Fe dopant, which allows us to study almost the full Ba3Fe1 -xRu2 +xO9 series of compounds with wide ranges of x because here Fe ions have the ability to freely go to the 4 f sites and Ru readily takes up the 2 a positions. Therefore, here one has the opportunity to probe the evolution of electronic and magnetic properties as a function of doping by going from BaRuO3 (paramagnetic metal) to BaFeO3 (ferromagnetic insulator). Our detailed experimental and theoretical results show that the series does exhibit a percolative metal-insulator transition with an accompanying but not coincidental magnetic transition as a function of x .

Temporal and spatial variation of nitrogen transformations in nitrogen-saturated soils of a central Appalachian hardwood forest

Treesearch

Frank S. Gilliam; Bradley M. Yurish; Mary Beth Adams

2001-01-01

We studied temporal and spatial patterns of soil nitrogen (N) dynamics from 1993 to 1995 in three watersheds of Fernow Experimental Forest, W.V.: WS7 (24-year-old, untreated); WS4 (mature, untreated); and WS3 (24- year-old, treated with (NH4)2SO4 since 1989 at the rate of 35 kg N·ha–1...

Facile transformation of FeO/Fe3O4 core-shell nanocubes to Fe3O4 via magnetic stimulation

NASA Astrophysics Data System (ADS)

Lak, Aidin; Niculaes, Dina; Anyfantis, George C.; Bertoni, Giovanni; Barthel, Markus J.; Marras, Sergio; Cassani, Marco; Nitti, Simone; Athanassiou, Athanassia; Giannini, Cinzia; Pellegrino, Teresa

2016-09-01

Here, we propose the use of magnetic hyperthermia as a means to trigger the oxidation of Fe1-xO/Fe3-δO4 core-shell nanocubes to Fe3-δO4 phase. As a first relevant consequence, the specific absorption rate (SAR) of the initial core-shell nanocubes doubles after exposure to 25 cycles of alternating magnetic field stimulation. The improved SAR value was attributed to a gradual transformation of the Fe1-xO core to Fe3-δO4, as evidenced by structural analysis including high resolution electron microscopy and Rietveld analysis of X-ray diffraction patterns. The magnetically oxidized nanocubes, having large and coherent Fe3-δO4 domains, reveal high saturation magnetization and behave superparamagnetically at room temperature. In comparison, the treatment of the same starting core-shell nanocubes by commonly used thermal annealing process renders a transformation to γ-Fe2O3. In contrast to other thermal annealing processes, the method here presented has the advantage of promoting the oxidation at a macroscopic temperature below 37 °C. Using this soft oxidation process, we demonstrate that biotin-functionalized core-shell nanocubes can undergo a mild self-oxidation transformation without losing their functional molecular binding activity.

Doping Li-rich cathode material Li2MnO3 : Interplay between lattice site preference, electronic structure, and delithiation mechanism

NASA Astrophysics Data System (ADS)

Hoang, Khang

2017-12-01

We report a detailed first-principles study of doping in Li2MnO3 , in both the dilute doping limit and heavy doping, using hybrid density-functional calculations. We find that Al, Fe, Mo, and Ru impurities are energetically most favorable when incorporated into Li2MnO3 at the Mn site, whereas Mg is most favorable when doped at the Li sites. Nickel, on the other hand, can be incorporated at the Li site and/or the Mn site, and the distribution of Ni over the lattice sites can be tuned by tuning the material preparation conditions. There is a strong interplay among the lattice site preference and charge and spin states of the dopant, the electronic structure of the doped material, and the delithiation mechanism. The calculated electronic structure and voltage profile indicate that in Ni-, Mo-, or Ru-doped Li2MnO3 , oxidation occurs on the electrochemically active transition-metal ion(s) before it does on oxygen during the delithiation process. The role of the dopants is to provide charge compensation and bulk electronic conduction mechanisms in the initial stages of delithiation, hence enabling the oxidation of the lattice oxygen in the later stages. This work thus illustrates how the oxygen-oxidation mechanism can be used in combination with the conventional mechanism involving transition-metal cations in design of high-capacity battery cathode materials.

Achieving low effluent NO3-N and TN concentrations in low influent chemical oxygen demand (COD) to total Kjeldahl nitrogen (TKN) ratio without using external carbon source

NASA Astrophysics Data System (ADS)

Cao, Jiashun; Oleyiblo, Oloche James; Xue, Zhaoxia; Otache, Y. Martins; Feng, Qian

2015-07-01

Two mathematical models were used to optimize the performance of a full-scale biological nutrient removal (BNR) activated treatment plant, a plug-flow bioreactors operated in a 3-stage phoredox process configuration, anaerobic anoxic oxic (A2/O). The ASM2d implemented on the platform of WEST2011 software and the BioWin activated sludge/anaerobic digestion (AS/AD) models were used in this study with the aim of consistently achieving the designed effluent criteria at a low operational cost. Four ASM2d parameters (the reduction factor for denitrification , the maximum growth rate of heterotrophs (µH), the rate constant for stored polyphosphates in PAOs ( q pp), and the hydrolysis rate constant ( k h)) were adjusted. Whereas three BioWin parameters (aerobic decay rate ( b H), heterotrophic dissolved oxygen (DO) half saturation ( K OA), and Y P/acetic) were adjusted. Calibration of the two models was successful; both models have average relative deviations (ARD) less than 10% for all the output variables. Low effluent concentrations of nitrate nitrogen (N-NO3), total nitrogen (TN), and total phosphorus (TP) were achieved in a full-scale BNR treatment plant having low influent chemical oxygen demand (COD) to total Kjeldahl nitrogen (TKN) ratio (COD/TKN). The effluent total nitrogen and nitrate nitrogen concentrations were improved by 50% and energy consumption was reduced by approximately 25%, which was accomplished by converting the two-pass aerobic compartment of the plug-flow bioreactor to anoxic reactors and being operated in an alternating mode. Findings in this work are helpful in improving the operation of wastewater treatment plant while eliminating the cost of external carbon source and reducing energy consumption.

Spin-Coating and Characterization of Multiferroic MFe{sub 2}O{sub 4} (M=Co, Ni) / BaTiO{sub 3} Bilayers

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

Quandt, Norman; Roth, Robert; Syrowatka, Frank

2016-01-15

Bilayer films of MFe{sub 2}O{sub 4} (M=Co, Ni) and BaTiO{sub 3} were prepared by spin coating of N,N-dimethylformamide/acetic acid solutions on platinum coated silicon wafers. Five coating steps were applied to get the desired thickness of 150 nm for both the ferrite and perovskite layer. XRD, IR and Raman spectroscopy revealed the formation of phase-pure ferrite spinels and BaTiO{sub 3}. Smooth surfaces with roughnesses in the order of 3 to 5 nm were found in AFM investigations. Saturation magnetization of 347 emu cm{sup −3} for the CoFe{sub 2}O{sub 4}/BaTiO{sub 3} and 188 emu cm{sup −3} for the NiFe{sub 2}O{sub 4}/BaTiO{submore » 3} bilayer, respectively were found. For the CoFe{sub 2}O{sub 4}/BaTiO{sub 3} bilayer a strong magnetic anisotropy was observed with coercivity fields of 5.1 kOe and 3.3 kOe (applied magnetic field perpendicular and parallel to film surface), while for the NiFe{sub 2}O{sub 4}/BaTiO{sub 3} bilayer this effect is less pronounced. Saturated polarization hysteresis loops prove the presence of ferroelectricity in both systems. - Graphical abstract: The SEM image of the CoFe{sub 2}O{sub 4}/BaTiO{sub 3} bilayer on Pt–Si-substrate (left), magnetization as a function of the magnetic field perpendicular and parallel to the film plane (right top) and P–E and I–V hysteresis loops of the bilayer at room temperature. - Highlights: • Ferrite and perovskite oxides grown on platinum using spin coating technique. • Columnar growth of cobalt ferrite particle on the substrate. • Surface investigation showed a homogenous and smooth surface. • Perpendicular and parallel applied magnetic field revealed a magnetic anisotropy. • Switching peaks and saturated P–E hysteresis loops show ferroelectricity.« less

Interaction between the APOC3 gene promoter polymorphisms, saturated fat intake and plasma lipoproteins.

PubMed

Brown, Sherine; Ordovás, José M; Campos, Hannia

2003-10-01

To test the hypothesis that APOC3 gene polymorphisms modulate the effect of saturated fat (SAT) intake on plasma lipoproteins and LDL size. We studied 336 randomly selected residents from Costa Rica. APOC3 polymorphisms were genotyped in the promoter region (T-455C, T-625del) and the C3238G 3' untranslated region (UTR). Dietary intake was assessed by a validated food-frequency questionnaire (FFQ) and median saturated fat intake (11%) was used to define low and high exposure to saturated fat. Allele frequencies were 0.49, 0.51 and 0.19 for the APOC3-455C, -625de1, and APOC3 3238G alleles, respectively. Significant gene-diet interactions were found for total (P<0.0004) and LDL cholesterol (P<0.01). In homozygotes for the APOC3-455T-625T alleles, saturated fat intake was associated with a 13% increase in total cholesterol (P<0.001) and a 20% increase in LDL cholesterol (P<0.001). In contrast, no association between plasma lipoproteins and saturated fat intake was found among carriers of the APOC3-455C-625del allele. The APOC3 3238G UTR allele did not modify the observed association. Compared to a diet high in saturated fat, a habitually low saturated fat diet is associated with a beneficial lipoprotein profile only among homozygotes of the APOC3 promoter 455T-625T polymorphism.

Preparation and photocatalytic activity of nitrogen-doped TiO2 hollow nanospheres

NASA Astrophysics Data System (ADS)

Cho, Hyung-Joon; Hwang, Poong-Gok; Jung, Dongwoon

2011-12-01

TiO2 hollow nanospheres were prepared using silicon oxide as a template. N-doped titanium oxide hollow spheres, TiO2-xNx were synthesized by reacting TiO2 hollow spheres with thiourea at 500 °C. XRD and XPS data showed that oxygen was successfully substituted by nitrogen through the nitrogen-doping reaction, and finally N-doped TiO2 hollow spheres were formed. The N-doped TiO2 hollow spheres showed new absorption shoulder in visible light region so that they were expected to exhibit photocatalytic activity in the visible light. The photocatalytic activity of N-doped TiO2 hollow spheres under visible light was similar to that of normal spherical TiO2-xNx in spite of the structural difference.

Distinct Effects of Humic Acid on Transport and Retention of TiO2 Rutile Nanoparticles in Saturated Sand Columns

EPA Science Inventory

The distinct effects of humic acid (HA, 0−10 mg L−1) on the transport of titanium dioxide (rutile) nanoparticles (nTiO2) through saturated sand columns were observed under conditions of environmental relevance (ionic strength 3−200 mM NaCl, pH 5.7 and 9.0). Specifically, the tra...

Minnealloy: a new magnetic material with high saturation flux density and low magnetic anisotropy

NASA Astrophysics Data System (ADS)

Mehedi, Md; Jiang, Yanfeng; Suri, Pranav Kumar; Flannigan, David J.; Wang, Jian-Ping

2017-09-01

We are reporting a new soft magnetic material with high saturation magnetic flux density, and low magnetic anisotropy. The new material is a compound of iron, nitrogen and carbon, α‧-Fe8(NC), which has saturation flux density of 2.8  ±  0.15 T and magnetic anisotropy of 46 kJ m-3. The saturation flux density is 27% higher than pure iron, a widely used soft magnetic material. Soft magnetic materials are very important building blocks of motors, generators, inductors, transformers, sensors and write heads of hard disk. The new material will help in the miniaturization and efficiency increment of the next generation of electronic devices.

Allosteric site-mediated active site inhibition of PBP2a using Quercetin 3-O-rutinoside and its combination.

PubMed

Rani, Nidhi; Vijayakumar, Saravanan; P T V, Lakshmi; Arunachalam, Annamalai

2016-08-01

Recent crystallographic study revealed the involvement of allosteric site in active site inhibition of penicillin binding protein (PBP2a), where one molecule of Ceftaroline (Cef) binds to the allosteric site of PBP2a and paved way for the other molecule (Cef) to bind at the active site. Though Cef has the potency to inhibit the PBP2a, its adverse side effects are of major concern. Previous studies have reported the antibacterial property of Quercetin derivatives, a group of natural compounds. Hence, the present study aims to evaluate the effect of Quercetin 3-o-rutinoside (Rut) in allosteric site-mediated active site inhibition of PBP2a. The molecular docking studies between allosteric site and ligands (Rut, Que, and Cef) revealed a better binding efficiency (G-score) of Rut (-7.790318) and Cef (-6.194946) with respect to Que (-5.079284). Molecular dynamic (MD) simulation studies showed significant changes at the active site in the presence of ligands (Rut and Cef) at allosteric site. Four different combinations of Rut and Cef were docked and their G-scores ranged between -6.320 and -8.623. MD studies revealed the stability of the key residue (Ser403) with Rut being at both sites, compared to other complexes. Morphological analysis through electron microscopy confirmed that combination of Rut and Cefixime was able to disturb the bacterial cell membrane in a similar fashion to that of Rut and Cefixime alone. The results of this study indicate that the affinity of Rut at both sites were equally good, with further validations Rut could be considered as an alternative for inhibiting MRSA growth.

Nitrogen excess in North American ecosystems: Predisposing factors, ecosystem responses, and management strategies

USGS Publications Warehouse

Fenn, M.E.; Poth, M.A.; Aber, J.D.; Baron, Jill S.; Bormann, B.T.; Johnson, D.W.; Lemly, A.D.; McNulty, S.G.; Ryan, D.F.; Stottlemyer, R.

1998-01-01

Most forests in North America remain nitrogen limited, although recent studies have identified forested areas that exhibit symptoms of N excess, analogous to overfertilization of arable land. Nitrogen excess in watersheds is detrimental because of disruptions in plant/soil nutrient relations, increased soil acidification and aluminum mobility, increased emissions of nitrogenous greenhouse gases from soil, reduced methane consumption in soil, decreased water quality, toxic effects on freshwater biota, and eutrophication of coastal marine waters. Elevated nitrate (NO3/-) loss to groundwater or surface waters is the primary symptom of N excess. Additional symptoms include increasing N concentrations and higher N:nutrient ratios in foliage (i.e., N:Mg, N:P), foliar accumulation of amino acids or NO3/-, and low soil C:N ratios. Recent nitrogen-fertilization studies in New England and Europe provide preliminary evidence that some forests receiving chronic N inputs may decline in productivity and experience greater mortality. Long-term fertilization at Mount Ascutney, Vermont, suggests that declining and slow N-cycling coniferous stands may be replaced by fast-growing and fast N-cycling deciduous forests. Symptoms of N saturation are particularly severe in high-elevation, nonaggrading spruce-fir ecosystems in the Appalachian Mountains and in eastern hardwood watersheds at the Fernow Experimental Forest near Parsons, West Virginia. In the Los Angeles Air Basin, mixed conifer forests and chaparral watersheds with high smog exposure are N saturated and exhibit the highest streamwater NO3/- concentrations for wildlands in North America. High-elevation alpine watersheds in the Colorado Front Range and a deciduous forest in Ontario, Canada, are N saturated, although N deposition is moderate (~8 kg??ha-1??yr-1). In contrast, the Harvard Forest hardwood stand in Massachusetts has absorbed >900 kg N/ha during 8 yr of N amendment studies without significant NO3/- leaching

Nitrogen trading tool

USDA-ARS?s Scientific Manuscript database

The nitrogen cycle is impacted by human activities, including those that increase the use of nitrogen in agricultural systems, and this impact can be seen in effects such as increased nitrate (NO3) levels in groundwater or surface water resources, increased concentration of nitrous oxide (N2O) in th...

Nonstoichiometric Zn Ferrite and ZnFe2O4/Fe2O3 Composite Spheres: Preparation, Magnetic Properties, and Chromium Removal

NASA Astrophysics Data System (ADS)

Hang, Chun-Liang; Yang, Li-Xia; Sun, Chang-Mei; Liang, Ying

2018-03-01

Monodisperse and porous nonstoichiometric Zn ferrite can be prepared by a solvothermal method. Such non-Zn ferrite was used to be the precursor for synthesis of ZnFe2O4/Fe2O3 composite via calcination at 600°C for 3 h in air. X-ray powder diffractometer (XRD) and Energy Dispersive Spectrometer (EDS) proved the nonstoichiometry of Zn ferrite synthesized by solvothermal method and the formation of ZnFe2O4/Fe2O3 composite via calcination. TEM image showed that non-Zn ferrite spheres with wormlike nanopore structure were made of primary nanocrystals. BET surface area of non-Zn ferrite was much higher than that of ZnFe2O4/Fe2O3 composite. Saturation magnetization of non-Zn ferrites was significantly higher than that of ZnFe2O4/Fe2O3 composites. Calcination of non-Zn ferrite resulted in the formation of large amount of non-magnetic Fe2O3,which caused a low magnetization of composite. Because of higher BET surface area and higher saturation magnetization, non-Zn ferrite presented better Cr6+ adsorption property than ZnFe2O4/Fe2O3 composites.

Ground-water flow, geochemistry, and effects of agricultural practices on nitrogen transport at study sites in the Piedmont and Coastal Plain physiographic provinces, Patuxent River Basin, Maryland

USGS Publications Warehouse

McFarland, Randolph E.

1995-01-01

The effects of agricultural practices on nitrogen transport were assessed at two 10-acre study sites in the Patuxent River Basin, Maryland, during 1986- 92. Nitrogen load was larger in ground water than in surface runoff at both sites. Denitrification and (or) long traveltimes of ground water at the study site in the Piedmont Province resulted in lower concentrations of nitrate than at the site in the Coastal Plain Province. The study period was brief compared to traveltimes of nitrogen in ground water of several decades. Therefore, the effects of agricultural practices were observed only in parts of both sites. At the Piedmont site, nitrate concentration in two springs was 7 mg/L (milligrams per liter) two years after corn was grown under no-till cultivation, and decreased to 3.5 mg/L during 4 years while cultivation practices and crops included no-till soybeans, continuous alfalfa, and contoured strips alternated among corn, alfalfa, and soybeans. Nitrogen load in ground water decreased from 12 to 6 (lb/acre)/yr (pounds per acre per year). At the Coastal Plain site, the concentration of nitrate in ground water decreased from 10 mg/L after soybeans were grown under no-till cultivation for 2 years, to 9 mg/L after soybeans were grown under conventional till cultivation for 3 years. No-till cultivation in 1988 resulted in a greater nitrogen load in ground water (12.55 (lbs/acre)/yr), as well as greater ground-water recharge and discharge, than conventional till cultivation in 1991 (11.51 (lbs/ acre)/yr), even though the amount and timing of precipitation for both years were similar.

Nitrogen grain-boundary passivation of In-doped ZnO transparent conducting oxide

NASA Astrophysics Data System (ADS)

Ali, D.; Butt, M. Z.; Coughlan, C.; Caffrey, D.; Shvets, I. V.; Fleischer, K.

2018-04-01

We have investigated the properties and conduction limitations of spray pyrolysis grown, low-cost transparent conducting oxide ZnO thin films doped with indium. We analyze the optical, electrical, and crystallographic properties as functions of In content with a specific focus on postgrowth heat treatment of these thin films at 320 ∘C in an inert, nitrogen atmosphere, which improves the films electrical properties considerably. The effect was found to be dominated by nitrogen-induced grain-boundary passivation, identified by a combined study using i n situ resistance measurement upon annealing, x-ray photoelectron spectroscopy, photoluminescence, and x-ray diffraction studies. We also highlight the chemical mechanism of morphologic and crystallographic changes found in films with high indium content. By optimizing growth conditions according to these findings, ZnO:In with a resistivity as low as 2 ×10 -3Ω cm , high optical quality (T ≈90 % ), and sheet resistance of 32 Ω /□ has been obtained without any need for postgrowth treatments.

[Interactions of straw, nitrogen fertilizer and bacterivorous nematodes on soil labile carbon and nitrogen and greenhouse gas emissions].

PubMed

Zhang, Teng-Hao; Wang, Nan; Liu, Man-Qiang; Li, Fang-Hui; Zhu, Kang-Li; Li, Hui-Xin; Hu, Feng

2014-11-01

A 3 x 2 factorial design of microcosm experiment was conducted to investigate the interactive effects of straw, nitrogen fertilizer and bacterivorous nematodes on soil microbial biomass carbon (C(mic)) and nitrogen (N(mic)), dissolved organic carbon (DOC) and nitrogen (DON), mineral nitrogen (NH(4+)-N and NO(3-)-N), and greenhouse gas (CO2, N2O and CH4) emissions. Results showed that straw amendment remarkably increased the numbers of bacterivorous nematodes and the contents of Cmic and Nmic, but Cmic and Nmic decreased with the increasing dose of nitrogen fertilization. The effects of bacterivorous nematodes strongly depended on either straw or nitrogen fertilization. The interactions of straw, nitrogen fertilization and bacterivorous nematodes on soil DOC, DON and mineral nitrogen were strong. Straw and nitrogen fertilization increased DOC and mineral nitrogen contents, but their influences on DON depended on the bacterivorous nematodes. The DOC and mineral nitrogen were negatively and positively influenced by the bacterivorous nematodes, re- spectively. Straw significantly promoted CO2 and N2O emissions but inhibited CH4 emission, while interactions between nematodes and nitrogen fertilization on emissions of greenhouse gases were obvious. In the presence of straw, nematodes increased cumulative CO2 emissions with low nitrogen fertilization, but decreased CO2 and N2O emissions with high nitrogen fertilization on the 56th day after incubation. In summary, mechanical understanding the soil ecological process would inevitably needs to consider the roles of soil microfauna.

Mapping Sites of O-Glycosylation and Fringe Elongation on Drosophila Notch*

PubMed Central

Harvey, Beth M.; Rana, Nadia A.; Moss, Hillary; Leonardi, Jessica; Jafar-Nejad, Hamed; Haltiwanger, Robert S.

2016-01-01

Glycosylation of the Notch receptor is essential for its activity and serves as an important modulator of signaling. Three major forms of O-glycosylation are predicted to occur at consensus sites within the epidermal growth factor-like repeats in the extracellular domain of the receptor: O-fucosylation, O-glucosylation, and O-GlcNAcylation. We have performed comprehensive mass spectral analyses of these three types of O-glycosylation on Drosophila Notch produced in S2 cells and identified peptides containing all 22 predicted O-fucose sites, all 18 predicted O-glucose sites, and all 18 putative O-GlcNAc sites. Using semiquantitative mass spectral methods, we have evaluated the occupancy and relative amounts of glycans at each site. The majority of the O-fucose sites were modified to high stoichiometries. Upon expression of the β3-N-acetylglucosaminyltransferase Fringe with Notch, we observed varying degrees of elongation beyond O-fucose monosaccharide, indicating that Fringe preferentially modifies certain sites more than others. Rumi modified O-glucose sites to high stoichiometries, although elongation of the O-glucose was site-specific. Although the current putative consensus sequence for O-GlcNAcylation predicts 18 O-GlcNAc sites on Notch, we only observed apparent O-GlcNAc modification at five sites. In addition, we performed mass spectral analysis on endogenous Notch purified from Drosophila embryos and found that the glycosylation states were similar to those found on Notch from S2 cells. These data provide foundational information for future studies investigating the mechanisms of how O-glycosylation regulates Notch activity. PMID:27268051

A Unique 3D Nitrogen-Doped Carbon Composite as High-Performance Oxygen Reduction Catalyst

PubMed Central

Karunagaran, Ramesh; Tung, Tran Thanh; Tran, Diana; Coghlan, Campbell; Doonan, Christian

2017-01-01

The synthesis and properties of an oxygen reduction catalyst based on a unique 3-dimensional (3D) nitrogen doped (N-doped) carbon composite are described. The composite material is synthesised via a two-step hydrothermal and pyrolysis method using bio-source low-cost materials of galactose and melamine. Firstly, the use of iron salts and galactose to hydrothermally produceiron oxide (Fe2O3) magnetic nanoparticle clusters embedded carbon spheres. Secondly, magnetic nanoparticles diffused out of the carbon sphere when pyrolysed in the presence of melamine as nitrogen precursor. Interestingly, many of these nanoparticles, as catalyst-grown carbon nanotubes (CNTs), resulted in the formation of N-doped CNTs and N-doped carbon spheres under the decomposition of carbon and a nitrogen environment. The composite material consists of integrated N-doped carbon microspheres and CNTs show high ORR activity through a predominantly four-electron pathway. PMID:28792432

N2O, NO, N2 and CO2 emissions from tropical savanna and grassland of northern Australia: an incubation experiment with intact soil cores

NASA Astrophysics Data System (ADS)

Werner, C.; Reiser, K.; Dannenmann, M.; Hutley, L. B.; Jacobeit, J.; Butterbach-Bahl, K.

2014-11-01

Strong seasonal variability of hygric and thermal soil conditions are a defining environmental feature in northern Australia. However, how such changes affect the soil-atmosphere exchange of nitrous oxide (N2O), nitric oxide (NO) and dinitrogen (N2) is still not well explored. By incubating intact soil cores from four sites (three savanna, one pasture) under controlled soil temperatures (ST) and soil moisture (SM) we investigated the release of the trace gas fluxes of N2O, NO and carbon dioxide (CO2). Furthermore, the release of N2 due to denitrification was measured using the helium gas flow soil core technique. Under dry pre-incubation conditions NO and N2O emissions were very low (<7.0 ± 5.0 μg NO-N m-2 h-1; <0.0 ± 1.4 μg N2O-N m-2 h-1) or in the case of N2O, even a net soil uptake was observed. Substantial NO (max: 306.5 μg N m-2 h-1) and relatively small N2O pulse emissions (max: 5.8 ± 5.0 μg N m-2 h-1) were recorded following soil wetting, but these pulses were short lived, lasting only up to 3 days. The total atmospheric loss of nitrogen was generally dominated by N2 emissions (82.4-99.3% of total N lost), although NO emissions contributed almost 43.2% to the total atmospheric nitrogen loss at 50% SM and 30 °C ST incubation settings (the contribution of N2 at these soil conditions was only 53.2%). N2O emissions were systematically higher for 3 of 12 sample locations, which indicates substantial spatial variability at site level, but on average soils acted as weak N2O sources or even sinks. By using a conservative upscale approach we estimate total annual emissions from savanna soils to average 0.12 kg N ha-1 yr-1 (N2O), 0.68 kg N ha-1 yr-1 (NO) and 6.65 kg N ha-1 yr-1 (N2). The analysis of long-term SM and ST records makes it clear that extreme soil saturation that can lead to high N2O and N2 emissions only occurs a few days per year and thus has little impact on the annual total. The potential contribution of nitrogen released due to pulse events

Magnetic Properties of Electron-Doped LaCoO3

NASA Astrophysics Data System (ADS)

Tomiyasu, Keisuke; Sato, Mika; Koyama, Shun-Ichi; Nojima, Tsutomu; Kajimoto, Ryoichi; Ji, Sungdae; Iwasa, Kazuaki

2017-09-01

We studied electron-doped LaCo1 - yTey6 + O3 by magnetization measurements and neutron scattering. The effective Bohr magneton, estimated by Curie-Weiss fitting around room temperature, is independent of y. This suggests that magnetic Co3+(HS), not nonmagnetic Co3+(LS), is mainly replaced by doped magnetic Co2+(HS). At the lowest temperatures, a Brillouin-function-like saturating behavior persists in the magnetization curves even in the high-y samples, and neither a clear magnetic reflection nor magnetic dispersion is observed by neutron scattering. These findings indicate that the magnetic correlation is very weak, in contrast to the well-known hole-doped LaCoO3 accompanied by a drastic transition to a ferromagnetic metal. However, we also found that the low-y samples exhibit nonnegligible enhancement of the saturated magnetization by ˜2μB per a doped electron. All these characteristics are discussed in the light of the activation and inactivation of a spin-state blockade.

Probing surface sites of TiO2: reactions with [HRe(CO)5] and [CH3Re(CO)5].

PubMed

Lobo-Lapidus, Rodrigo J; Gates, Bruce C

2010-10-04

Two carbonyl complexes of rhenium, [HRe(CO)(5)] and [CH(3)Re(CO)(5)], were used to probe surface sites of TiO(2) (anatase). These complexes were adsorbed from the gas phase onto anatase powder that had been treated in flowing O(2) or under vacuum to vary the density of surface OH sites. Infrared (IR) spectra demonstrate the variation in the number of sites, including Ti(+3)-OH and Ti(+4)-OH. IR and extended X-ray absorption fine structure (EXAFS) spectra show that chemisorption of the rhenium complexes led to their decarbonylation, with formation of surface-bound rhenium tricarbonyls, when [HRe(CO)(5)] was adsorbed, or rhenium tetracarbonyls, when [CH(3)Re(CO)(5)] was adsorbed. These reactions were accompanied by the formation of water and surface carbonates and removal of terminal hydroxyl groups associated with Ti(+3) and Ti(+4) ions on the anatase. Data characterizing the samples after adsorption of [HRe(CO)(5)] or [CH(3)Re(CO)(5)] determined a ranking of the reactivity of the surface OH sites, with the Ti(+3)-OH groups being the more reactive towards the rhenium complexes but the less likely to be dehydroxylated. The two rhenium pentacarbonyl probes provided complementary information, suggesting that the carbonate species originate from carbonyl ligands initially bonded to the rhenium and from hydroxyl groups of the titania surface, with the reaction leading to the formation of water and bridging hydroxyl groups on the titania. The results illustrate the value of using a family of organometallic complexes as probes of oxide surface sites.

Cerebral arterial oxygen saturation measurements using a fiber-optic pulse oximeter.

PubMed

Phillips, J P; Langford, R M; Chang, S H; Maney, K; Kyriacou, P A; Jones, D P

2010-10-01

A pilot investigation was undertaken to assess the performance of a novel fiber-optic cerebral pulse oximetry system. A fiber-optic probe designed to pass through the lumen of a cranial bolt of the type used to make intracranial pressure measurements was used to obtain optical reflectance signals directly from brain tissue. Short-duration measurements were made in six patients undergoing neurosurgery. These were followed by a longer duration measurement in a patient recovering from an intracerebral hematoma. Estimations of cerebral arterial oxygen saturation derived from a frequency domain-based algorithm are compared with simultaneous pulse oximetry (SpO2) and hemoximeter (SaO2) blood samples. The short-duration measurements showed that reliable photoplethysmographic signals could be obtained from the brain tissue. In the long-duration study, the mean (±SD) difference between cerebral oxygen saturation (ScaO2) and finger SpO2 (in saturation units) was -7.47(±3.4)%. The mean (±SD) difference between ScaO2 and blood SaO2 was -7.37(±2.8)%. This pilot study demonstrated that arterial oxygen saturation may be estimated from brain tissue via a fiber-optic pulse oximeter used in conjunction with a cranial bolt. Further studies are needed to confirm the clinical utility of the technique.

Probing the electronic structure and photoactivation process of nitrogen-doped TiO2 using DRS, PL, and EPR.

PubMed

Zhang, Zizhong; Long, Jinlin; Xie, Xiuqiang; Lin, Huan; Zhou, Yangen; Yuan, Rusheng; Dai, Wenxin; Ding, Zhengxin; Wang, Xuxu; Fu, Xianzhi

2012-04-23

The electronic structure and photoactivation process in N-doped TiO(2) is investigated. Diffuse reflectance spectroscopy (DRS), photoluminescence (PL), and electron paramagnetic resonance (EPR) are employed to monitor the change of optical absorption ability and the formation of N species and defects in the heat- and photoinduced N-doped TiO(2) catalyst. Under thermal treatment below 573 K in vacuum, no nitrogen dopant is removed from the doped samples but oxygen vacancies and Ti(3+) states are formed to enhance the optical absorption in the visible-light region, especially at wavelengths above 500 nm with increasing temperature. In the photoactivation processes of N-doped TiO(2), the DRS absorption and PL emission in the visible spectral region of 450-700 nm increase with prolonged irradiation time. The EPR results reveal that paramagnetic nitrogen species (N(s)·, oxygen vacancies with one electron (V(o)·), and Ti(3+) ions are produced with light irradiation and the intensity of N(s)· species is dependent on the excitation light wavelength and power. The combined characterization results confirm that the energy level of doped N species is localized above the valence band of TiO(2) corresponding to the main absorption band at 410 nm of N-doped TiO(2), but oxygen vacancies and Ti(3+) states as defects contribute to the visible-light absorption above 500 nm in the overall absorption of the doped samples. Thus, a detailed picture of the electronic structure of N-doped TiO(2) is proposed and discussed. On the other hand, the transfer of charge carriers between nitrogen species and defects is reversible on the catalyst surface. The presence of oxygen-vacancy-related defects leads to quenching of paramagnetic N(s)· species but they stabilize the active nitrogen species N(s)(-). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nitrogen in rock: Occurrences and biogeochemical implications

USGS Publications Warehouse

Holloway, J.M.; Dahlgren, R.A.

2002-01-01

There is a growing interest in the role of bedrock in global nitrogen cycling and potential for increased ecosystem sensitivity to human impacts in terrains with elevated background nitrogen concentrations. Nitrogen-bearing rocks are globally distributed and comprise a potentially large pool of nitrogen in nutrient cycling that is frequently neglected because of a lack of routine analytical methods for quantification. Nitrogen in rock originates as organically bound nitrogen associated with sediment, or in thermal waters representing a mixture of sedimentary, mantle, and meteoric sources of nitrogen. Rock nitrogen concentrations range from trace levels (>200 mg N kg -1) in granites to ecologically significant concentrations exceeding 1000 mg N kg -1 in some sedimentary and metasedimentary rocks. Nitrate deposits accumulated in arid and semi-arid regions are also a large potential pool. Nitrogen in rock has a potentially significant impact on localized nitrogen cycles. Elevated nitrogen concentrations in water and soil have been attributed to weathering of bedrock nitrogen. In some environments, nitrogen released from bedrock may contribute to nitrogen saturation of terrestrial ecosystems (more nitrogen available than required by biota). Nitrogen saturation results in leaching of nitrate to surface and groundwaters, and, where soils are formed from ammonium-rich bedrock, the oxidation of ammonium to nitrate may result in soil acidification, inhibiting revegetation in certain ecosystems. Collectively, studies presented in this article reveal that geologic nitrogen may be a large and reactive pool with potential for amplification of human impacts on nitrogen cycling in terrestrial and aquatic ecosystems.

Fabrication by Electrophoretic Deposition of Nano-Fe3O4 and Fe3O4@SiO2 3D Structure on Carbon Fibers as Supercapacitor Materials

NASA Astrophysics Data System (ADS)

Hajalilou, Abdollah; Abouzari-Lotf, Ebrahim; Etemadifar, Reza; Abbasi-Chianeh, Vahid; Kianvash, Abbas

2018-05-01

Core-shell nanostructured magnetic Fe3O4@SiO2 with particle size ranging from 3 nm to 40 nm has been synthesized via a facile precipitation method. Tetraethyl orthosilicate was employed as surfactant to prepare core-shell structures from Fe3O4 nanoparticles synthesized from pomegranate peel extract using a green method. X-ray diffraction analysis, Fourier-transform infrared and ultraviolet-visible (UV-Vis) spectroscopies, transmission electron microscopy, and scanning electron microscopy with energy-dispersive spectroscopy were employed to characterize the samples. The prepared Fe3O4 nanoparticles were approximately 12 nm in size, and the thickness of the SiO2 shell was 4 nm. Evaluation of the magnetic properties indicated lower saturation magnetization for Fe3O4@SiO2 powder ( 11.26 emu/g) compared with Fe3O4 powder ( 13.30 emu/g), supporting successful wrapping of the Fe3O4 nanoparticles by SiO2. As-prepared powders were deposited on carbon fibers (CFs) using electrophoretic deposition and their electrochemical behavior investigated. The rectangular-shaped cyclic voltagrams of Fe3O4@CF and Fe3O4@C@CF samples indicated electrochemical double-layer capacitor (EDLC) behavior. The higher specific capacitance of 477 F/g for Fe3O4@C@CF (at scan rate of 0.05 V/s in the potential range of - 1.13 to 0.45 V) compared with 205 F/g for Fe3O4@CF (at the same scan rate in the potential range of - 1.04 to 0.24 V) makes the former a superior candidate for use in energy storage applications.

Superparamagnetic Au-Fe3O4 nanoparticles: one-pot synthesis, biofunctionalization and toxicity evaluation

NASA Astrophysics Data System (ADS)

Pariti, A.; Desai, P.; Maddirala, S. K. Y.; Ercal, N.; Katti, K. V.; Liang, X.; Nath, M.

2014-09-01

Superparamagnetic Au-Fe3O4 bifunctional nanoparticles have been synthesized using a single step hot-injection precipitation method. The synthesis involved using Fe(CO)5 as iron precursor and HAuCl4 as gold precursor in the presence of oleylamine and oleic acid. Oleylamine helps in reducing Au3+ to Au0 seeds which simultaneously oxidizes Fe(0) to form Au-Fe3O4 bifunctional nanoparticles. Triton® X-100 was employed as a highly viscous solvent to prevent agglomeration of Fe3O4 nanoparticles. Detailed characterization of these nanoparticles was performed by using x-ray powder diffraction, transmission electron microscopy, scanning tunneling electron microscopy, UV-visible spectroscopy, Mössbauer and magnetometry studies. To evaluate these nanoparticles’ applicability in biomedical applications, L-cysteine was attached to the Au-Fe3O4 nanoparticles and cytotoxicity of Au-Fe3O4 nanoparticles was tested using CHO cells by employing MTS assay. L-cysteine modified Au-Fe3O4 nanoparticles were qualitatively characterized using Fourier transform infrared spectroscopy and Raman spectroscopy; and quantitatively using acid ninhydrin assay. Investigations reveal that that this approach yields Au-Fe3O4 bifunctional nanoparticles with an average particle size of 80 nm. Mössbauer studies indicated the presence of Fe in Fe3+ in A and B sites (tetrahedral and octahedral, respectively) and Fe2+ in B sites (octahedral). Magnetic measurements also indicated that these nanoparticles were superparamagnetic in nature due to Fe3O4 region. The saturation magnetization for the bifunctional nanoparticles was observed to be ˜74 emu g-1, which is significantly higher than the previously reported Fe3O4 nanoparticles. Mössbauer studies indicated that there was no significant Fe(0) impurity that could be responsible for the superparamagnetic nature of these nanoparticles. None of the investigations showed any presence of other impurities such as Fe2O3 and FeOOH. These Au-Fe3O4 bifunctional

Structural and Magnetic Properties of LaCoO3/SrTiO3 Multilayers.

PubMed

Zhang, Hongrui; Zhang, Jing; Yang, Huaiwen; Lan, Qianqian; Hong, Deshun; Wang, Shufang; Shen, Xi; Khan, Tahira; Yu, Richeng; Sun, Jirong; Shen, Baogen

2016-07-20

Structural and magnetic properties of the LaCoO3/SrTiO3 (LCO/STO) multilayers (MLs) with a fixed STO layer of 4 nm but varied LCO layer thicknesses have been systematically studied. The MLs grown on Sr0.7La0.3Al0.65Ta0.35O3 (LSAT) and SrTiO3 (STO) exhibit the in-plane lattice constant of the substrates, but those on LaAlO3 (LAO) show the in-plane lattice constant between those of the first two kinds of MLs. Compared with the LCO single layer (SL), the magnetic order of the MLs is significantly enhanced, as demonstrated by a very slow decrease, which is fast for the SL, of the Curie temperature and the saturation magnetization as the LCO layer thickness decreases. For example, clear ferromagnetic order is observed in the ML with the LCO layer of ∼1.5 nm, whereas it vanishes below ∼6 nm for the LCO SL. This result is consistent with the observation that the dark stripes, which are believed to be closely related to the magnetic order, remain clear in the MLs while they are vague in the corresponding LCO SL. The present work suggests a novel route to tune the magnetism of perovskite oxide films.

Multifunctional Fe3O4/ZnO nanocomposites with magnetic and optical properties.

PubMed

Zou, Peng; Hong, Xia; Chu, Xueying; Li, Yajun; Liu, Yichun

2010-03-01

Multifunctional Fe3O4/ZnO nanocomposites were successfully synthesized through two-step solution-based methods. Fe3O4 nanoparticles were used as seeds for the deposit and growth of ZnO nanocrystals. Transmission electron microscopy (TEM) images, X-ray diffraction (XRD) patterns, and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) were employed to observe the morphology, size, structure, and crystalline phase of the nanocomposites and confirm their chemical composition. The results of magnetization curves, resonant Raman scattering, and photoluminescence spectra revealed that the nanocomposites simultaneously possessed the super-paramagnetism of Fe3O4 and the multiphonon resonant Raman scattering and photoluminescence (PL) properties of ZnO. Compared with that of pure Fe3O4, the saturation magnetization of the Fe3O4 component within the nanocomposites was enhanced. The Raman spectroscopic fingerprint of ZnO component was preserved, and the fluorescent background was efficiently reduced. The interfacial effect was found to play an important role in modulating or improving the properties of the nanocomposites.

Multifractal detrended cross-correlation analysis on NO, NO2 and O3 concentrations at traffic sites

NASA Astrophysics Data System (ADS)

Xu, Weijia; Liu, Chunqiong; Shi, Kai; Liu, Yonghong

2018-07-01

NOX plays the important role for O3 production in atmospheric photochemical processes. In this paper, the cross-correlations between NO (NO2) and O3 at three traffic sites in Hong Kong are investigated, using the multifractal detrended cross-correlation analysis (MFDCCA). The results show that the cross-correlations between NO (NO2) and O3 have multifractal nature and long term persistent power-law decaying behavior. The sources of multifractality are discussed based on the shuffling and phase randomization procedure. The chi square test is applied to identify the contributions degree of NO and NO2 to multifractality due to its own long term correlations respectively. And the temporal evolutions of the local contributions degree of NO and NO2 to multifractality are investigated by the sliding windows method. The differences between them are explained by the self-organized criticality mechanism of air pollution, combined with global solar radiation. MFDCCA provides a helpful approach for understanding the quantitative relationship between the O3 and its precursors.

Isolated boron and nitrogen sites on porous graphitic carbon synthesized from nitrogen-containing chitosan for supercapacitors.

PubMed

Sun, Li; Fu, Yu; Tian, Chungui; Yang, Ying; Wang, Lei; Yin, Jie; Ma, Jing; Wang, Ruihong; Fu, Honggang

2014-06-01

Separated boron and nitrogen porous graphitic carbon (BNGC) is fabricated by a facile hydrothermal coordination/ZnCl2-activation process from renewable and inexpensive nitrogen-containing chitosan. In this synthetic pathway, chitosan, which has a high nitrogen content, first coordinates with Fe(3+) ions to form chitosan-Fe that subsequently reacts with boric acid (boron source) to generate the BNGC precursor. After simultaneous carbonization and ZnCl2 activation followed by removal of the Fe catalyst, BNGC, containing isolated boron and nitrogen centers and having a high surface area of 1567 m(2)  g(-1) and good conductivity, can be obtained. Results indicate that use of chitosan as a nitrogen-containing carbon source effectively prevents nitrogen atoms from direct combination with boron atoms. In addition, the incorporation of Fe(3+) ions not only endows BNGC with high graphitization, but also favors for nitrogen fixation. Remarkably, the unique microstructure of BNGC enables its use as an advanced electrode material for energy storage. As electrode material for supercapacitors, BNGC shows a high capacitance of 313 F g(-1) at 1 A g(-1), and also long-term durability and coulombic efficiency of >99.5 % after 5000 cycles. Notably, in organic electrolytes, the energy density could be up to 50.1 Wh kg(-1) at a power density of 10.5 kW kg(-1). The strategy developed herein opens a new avenue to prepare BNGC without inactive BN bonds from commercially available chitosan for high-performance supercapacitors. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Use of GIS-based Site-specific Nitrogen Management for Improving Energy Efficiency

USDA-ARS?s Scientific Manuscript database

To our knowledge, geographical information system (GIS)-based site-specific nitrogen management (SSNM) techniques have not been used to assess agricultural energy costs and efficiency. This chapter uses SSNM case studies for corn (Zea mays L.) grown in Missouri and cotton (Gossypium hirsutum L.) gro...

Retinal vessel oxygen saturation in a healthy young Chinese population.

PubMed

Yang, Wei; Fu, Yue; Dong, Yanmin; Lin, Leilei; Huang, Xia; Li, Yujie; Lin, Xiaofeng; Gao, Qianying

2016-06-01

To measure retinal vessel oxygen saturation in a healthy young Chinese population and to determine the effects of multiple factors (gender, age, dioptre, vessel diameter and ocular perfusion pressure - OPP) on retinal oxygen saturation. A total of 126 healthy Chinese individuals aged from 19 to 30 were included in this study. A retinal oximeter (Oxymap T1) was used to measure retinal vessel oxygen saturation by retinal imaging at two different wavelengths. The mean retinal vessel oxygen saturation (Sat_O2 ) of arterioles, venules and arteriovenous (AV) difference overall and in four separate quadrants were measured. Intra-ocular pressure, blood pressure, finger pulse oximetry value, vessel diameter and dioptre were also measured. The correlations between OPP and dioptre, OPP and vessel diameter, and dioptre and vessel diameter were analysed. And the effects of multiple factors on the retinal oxygen saturation were analysed. The mean oxygen saturation was 93.2 ± 6.3% in the retinal arterioles, 60.4 ± 5.3% in venules and 32.9 ± 6.4% in AV difference. The temporal quadrants had lower measurements of arteriolar and venular oxygen saturation and AV difference compared with nasal quadrants (p < 0.001). The oxygen saturation of the arterioles, venules and AV difference were unaffected by any unique factor. Arteriolar and venular retinal oxygen saturation correlated negatively with the product of dioptre and OPP. Arteriolar retinal oxygen saturation correlated positively with the product of dioptre and vessel diameter. This study provided a normal reference of Sat_O2 in healthy young Chinese individuals. It was a reflection of the normal state of retinal oxygen metabolism affected by several factors. © 2016 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Influence of phosphate and solution pH on the mobility of ZnO nanoparticles in saturated sand.

PubMed

Li, Lingxiangyu; Schuster, Michael

2014-02-15

The mobility of nanoparticles (NPs) strongly depends on the chemical characterization of the environmental medium. However, the influence of phosphate on NPs mobility was ignored by scientists despite the serious phosphate contamination in natural environments. Hence, the influence of phosphate and solution pH on the mobility of zinc oxide nanoparticles (ZnO-NPs) was investigated in water-saturated sand representative of groundwater aquifers, which encompassed a range of P/Zn molar ratios (P/Zn: 0-4) and pH (4.8-10.0). The transport of ZnO-NPs was dramatically enhanced in the presence of phosphate, even at a low P/Zn molar ratio namely 0.25, and the retention of ZnO-NPs in the saturated sand decreased with increasing P/Zn molar ratio. Moreover, attachment efficiencies (α) and deposition rates (kd) of ZnO-NPs rapidly decreased with increasing P/Zn molar ratio. In contrast, the solution pH had negligible effects on ZnO-NP transport behavior under phosphate-abundant condition (P/Zn: 4). The distinct effects may be explained by the energy interaction between ZnO-NPs and sand surface under different conditions. Interestingly, under phosphate-abundant condition (P/Zn: 4), solution pH could strongly affect the transport of Zn(2+) in the water-saturated sand. Overall, this study outlines the importance of taking account of phosphate into risk assessment of NPs in the environment. Copyright © 2013 Elsevier B.V. All rights reserved.

Mössbauer Studies of Core-Shell FeO/Fe3O4 Nanoparticles

NASA Astrophysics Data System (ADS)

Kamzin, A. S.; Valiullin, A. A.; Khurshid, H.; Nemati, Z.; Srikanth, H.; Phan, M. H.

2018-02-01

FeO/Fe3O4 nanoparticles were synthesized by thermal decomposition. Electron microscopy revealed that these nanoparticles were of the core-shell type and had a spherical shape with an average size of 20 nm. It was found that the obtained FeO/Fe3O4 nanoparticles had exchange coupling. The effect of anisotropy on the efficiency of heating (hyperthermic effect) of FeO/Fe3O4 nanoparticles by an external alternating magnetic field was examined. The specific absorption rate (SAR) of the studied nanoparticles was 135 W/g in the experiment with an external alternating magnetic field with a strength of 600 Oe and a frequency of 310 kHz. These data led to an important insight: the saturation magnetization is not the only factor governing the SAR, and the efficiency of heating of magnetic FeO/Fe3O4 nanoparticles may be increased by enhancing the effective anisotropy. Mössbauer spectroscopy of the phase composition of the synthesized nanoparticles clearly revealed the simultaneous presence of three phases: magnetite Fe3O4, maghemite γ-Fe2O3, and wustite FeO.

Measurement and Modeling of Site-specific Nitrogen and Oxygen Isotopic Composition of Atmospheric Nitrous Oxide at Mace Head, Ireland

NASA Astrophysics Data System (ADS)

McClellan, M. J.; Saikawa, E.; Prinn, R. G.; Ono, S.

2015-12-01

Global mixing ratios of atmospheric nitrous oxide (N2O), a potent greenhouse gas, have increased nearly linearly from the beginning of the modern industrial period to today, with the current global average in excess of 325 ppb. This increase can be largely attributed to anthropogenic activity above the level of N2O emissions from natural biotic sources. The effect of N2O on Earth's climate is twofold: in the troposphere, N2O is radiatively active and chemically inert, while it serves as a reactive source of ozone-destroying nitrogen oxides in the stratosphere. The marked altitudinal divide in its reactivity means that all stages in the N2O life cycle—emission, transport, and destruction—must be examined to understand the overall effect of N2O on Earth's climate. However, the understanding of the total impact of N2O is incomplete, as there remain significant uncertainties in the global budget of this gas. Due to unique isotopic substitutions (15N and 18O) made by different N2O sources and stratospheric chemical reactions, the measurement of N2O isotopic ratios in ambient air can help identify the distribution and magnitude of distinct source types. We present the first year of site-specific nitrogen and oxygen isotopic composition data from the MIT Stheno-tunable infrared direct absorption spectroscopy (TILDAS) instrument at Mace Head, Ireland. Aided by the Stheno preconcentration system, Stheno-TILDAS can achieve measurement precisions of 0.10‰ or greater for all isotopic ratios (δ15N and δ18O) in ambient N2O. We further compare these data to the results from Model for Ozone and Related Tracers version 4 (MOZART-4) simulations, including N2O isotopic fractionation processes and MERRA/GEOS-5 reanalysis meteorological fields. These results will form the basis of future Bayesian inverse modeling simulations that will constrain global N2O source, circulation, and sink dynamics better.

The Role of Lewis and Brønsted Acid Sites in NO Reduction with NH3 on Sulfur Modified TiO2-Supported V2O5 Catalyst

NASA Astrophysics Data System (ADS)

Zhao, Wei; Dou, Shengping; Zhong, Qin; Wu, Licheng; Wang, Qian; Wang, Aijian

2017-12-01

V2O5/S-doped TiO2 was prepared by the sol-gel and impregnation methods. The adsorption of NO, NH3, and O2 over the catalyst was studied by in situ DRIFTS spectroscopy to elucidate the reaction mechanism of the low-temperature selective catalytic reduction of NO with NH3. Exposing the catalyst to O2 and NO, three types of nitrates species appeared on the surface. The introduction of S to TiO2 could generate large amounts of acid sites for ammonia adsorption on the catalyst, which was believed to be an important role in the SCR reaction and hereby improved the catalytic activity. The results indicated two possible SCR reaction pathways for catalyst. One was that NO was absorbed to form nitrite species, which could react with NH3 on Lewis acid sites, producing N2 and H2O. Another way was that NH3 was adsorbed, then reacted with gas phase NO (E-R) and nitrite intermediates on the surface (L-H).

Atomic layer deposition and properties of ZrO2/Fe2O3 thin films

PubMed Central

Seemen, Helina; Ritslaid, Peeter; Rähn, Mihkel; Tamm, Aile; Kukli, Kaupo; Kasikov, Aarne; Link, Joosep; Stern, Raivo; Dueñas, Salvador; Castán, Helena; García, Héctor

2018-01-01

Thin solid films consisting of ZrO2 and Fe2O3 were grown by atomic layer deposition (ALD) at 400 °C. Metastable phases of ZrO2 were stabilized by Fe2O3 doping. The number of alternating ZrO2 and Fe2O3 deposition cycles were varied in order to achieve films with different cation ratios. The influence of annealing on the composition and structure of the thin films was investigated. Additionally, the influence of composition and structure on electrical and magnetic properties was studied. Several samples exhibited a measurable saturation magnetization and most of the samples exhibited a charge polarization. Both phenomena were observed in the sample with a Zr/Fe atomic ratio of 2.0. PMID:29441257

Nitrous oxide flux and nitrogen transformations across a landscape gradient in Amazonia

NASA Technical Reports Server (NTRS)

Livingston, Gerald P.; Vitousek, Peter M.; Matson, Pamela A.

1988-01-01

Nitrous oxide flux and nitrogen turnover were measured in three types of Amazonian forest ecosystems within Reserva Florestal Ducke near Manaus, Brazil. Nitrogen mineralization and nitrate production measured during 10-day laboratory incubations were 3-4 times higher in clay soils associated with 'terra firme' forests on ridge-top and slope positions than in 'campinarana' forests on bottomland sand soils. In contrast, nitrous oxide fluxes did not differ significantly among sites, but were highly variable in space and time. The observed frequency distribution of flux was positively skewed, with a mean overall sites and all sampling times of 1.3 ng N2O-N/sq cm per hr. Overall, the flux estimates were comparable to or greater than those of temperature forests, but less than others reported for Amazoonia. Results from a field fertilization experiment suggest that most nitrous oxide flux was associated with denitrification of soil nitrate.

Dynamics of CrO 3 –Fe 2 O 3 Catalysts during the High-Temperature Water-Gas Shift Reaction: Molecular Structures and Reactivity

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

Keturakis, Christopher J.; Zhu, Minghui; Gibson, Emma K.

2016-06-13

A series of supported CrO 3/Fe 2O 3 catalysts were investigated for the high-temperature water-gas shift (WGS) and reverse-WGS reactions and extensively characterized using in situ and operando IR, Raman, and XAS spectroscopy during the high-temperature WGS/RWGS reactions. The in situ spectroscopy examinations reveal that the initial oxidized catalysts contain surface dioxo (O=) 2Cr 6+O 2 species and a bulk Fe 2O 3 phase containing some Cr 3+ substituted into the iron oxide bulk lattice. Operando spectroscopy studies during the high-temperature WGS/RWGS reactions show that the catalyst transforms during the reaction. The crystalline Fe 2O 3 bulk phase becomes Femore » 3O 4 ,and surface dioxo (O=) 2Cr 6+O 2 species are reduced and mostly dissolve into the iron oxide bulk lattice. Consequently, the chromium–iron oxide catalyst surface is dominated by FeO x sites, but some minor reduced surface chromia sites are also retained. The Fe 3–-xCr xO 4 solid solution stabilizes the iron oxide phase from reducing to metallic Fe0 and imparts an enhanced surface area to the catalyst. Isotopic exchange studies with C 16O 2/H 2 → C 18O 2/H 2 isotopic switch directly show that the RWGS reaction proceeds via the redox mechanism and only O* sites from the surface region of the chromium–iron oxide catalysts are involved in the RWGS reaction. The number of redox O* sites was quantitatively determined with the isotope exchange measurements under appropriate WGS conditions and demonstrated that previous methods have undercounted the number of sites by nearly 1 order of magnitude. The TOF values suggest that only the redox O* sites affiliated with iron oxide are catalytic active sites for WGS/RWGS, though a carbonate oxygen exchange mechanism was demonstrated to exist, and that chromia is only a textural promoter that increases the number of catalytic active sites without any chemical promotion effect.« less

Effect of soil saturation on denitrification in a grassland soil

NASA Astrophysics Data System (ADS)

Maritza Cardenas, Laura; Bol, Roland; Lewicka-Szczebak, Dominika; Gregory, Andrew Stuart; Matthews, Graham Peter; Whalley, William Richard; Misselbrook, Thomas Henry; Scholefield, David; Well, Reinhard

2017-10-01

Nitrous oxide (N2O) is of major importance as a greenhouse gas and precursor of ozone (O3) destruction in the stratosphere mostly produced in soils. The soil-emitted N2O is generally predominantly derived from denitrification and, to a smaller extent, nitrification, both processes controlled by environmental factors and their interactions, and are influenced by agricultural management. Soil water content expressed as water-filled pore space (WFPS) is a major controlling factor of emissions and its interaction with compaction, has not been studied at the micropore scale. A laboratory incubation was carried out at different saturation levels for a grassland soil and emissions of N2O and N2 were measured as well as the isotopocules of N2O. We found that flux variability was larger in the less saturated soils probably due to nutrient distribution heterogeneity created from soil cracks and consequently nutrient hot spots. The results agreed with denitrification as the main source of fluxes at the highest saturations, but nitrification could have occurred at the lower saturation, even though moisture was still high (71 % WFSP). The isotopocules data indicated isotopic similarities in the wettest treatments vs. the two drier ones. The results agreed with previous findings where it is clear there are two N pools with different dynamics: added N producing intense denitrification vs. soil N resulting in less isotopic fractionation.

First-principles analysis of ferroelectric transition in MnSnO3 and MnTiO3 perovskites

NASA Astrophysics Data System (ADS)

Kang, Sung Gu

2018-06-01

The ferroelectric instabilities of an artificially adopted Pnma structure in low tolerance perovskites have been explored (Kang et al., 2017) [4], where an unstable A-site environment was reported to be the major driving source for the low tolerance perovskites to exhibit ferroelectric instability. This study examined the ferroelectric transition of two magnetic perovskite materials, MnSnO3 and MnTiO3, in Pnma phase. Phase transitions to the Pnma phase at elevated pressures were observed. MnSnO3, which has a lower (larger) tolerance factor (B-site cation radius), showed a higher ferroelectric mode amplitude than MnTiO3. The distribution of the bond length of Mn-O and the mean quadratic elongation (QE) of octahedra (SnO6 or TiO6) were investigated for structural analysis. However, MnTiO3 showed a larger spontaneous polarization than MnSnO3 due to high Born effective charges of titanium. This study is useful because it provides a valuable pathway to the design of promising multiferroic materials.

In-pile test of Li 2TiO 3 pebble bed with neutron pulse operation