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1

Water Cycle  

NSDL National Science Digital Library

Water Cycle fun From water cycle Web Quest Links Introduction Task Process Evaluation Conclusion Resources Teacher Guide Introduction Luke Warm, a weather man, and you will help two baseball players understand why the big game might be rained out. You will explore the Water cycle and ...

Mrs. Terry

2009-04-03

2

Low-temperature, manganese oxide-based, thermochemical water splitting cycle  

PubMed Central

Thermochemical cycles that split water into stoichiometric amounts of hydrogen and oxygen below 1,000?°C, and do not involve toxic or corrosive intermediates, are highly desirable because they can convert heat into chemical energy in the form of hydrogen. We report a manganese-based thermochemical cycle with a highest operating temperature of 850?°C that is completely recyclable and does not involve toxic or corrosive components. The thermochemical cycle utilizes redox reactions of Mn(II)/Mn(III) oxides. The shuttling of Na+ into and out of the manganese oxides in the hydrogen and oxygen evolution steps, respectively, provides the key thermodynamic driving forces and allows for the cycle to be closed at temperatures below 1,000?°C. The production of hydrogen and oxygen is fully reproducible for at least five cycles. PMID:22647608

Xu, Bingjun; Bhawe, Yashodhan; Davis, Mark E.

2012-01-01

3

Water-sensitive low-frequency vibrations of reaction intermediates during S-state cycling in photosynthetic water oxidation.  

PubMed

In photosynthetic water oxidation, two water molecules are converted to an oxygen molecule through five reaction intermediates, designated S(n) (n = 0-4), at the catalytic Mn cluster of photosystem II. To understand the mechanism of water oxidation, changes in the chemical nature of the substrate water as well as the Mn cluster need to be defined during S-state cycling. Here, we report for the first time a complete set of Fourier transform infrared difference spectra during S-state cycling in the low-frequency (670-350 cm(-1)) region, in which interactions between the Mn cluster and its ligands can be detected directly, in PS II core particles from Thermosynechococcus elongatus. Furthermore, vibrations from oxygen and/or hydrogen derived from the substrate water and changes in them during S-state cycling were identified using multiplex isotope-labeled water, including H2(18)O, D2(16)O, and D2(18)O. Each water isotope affected the low-frequency S-state cycling spectra, characteristically. The bands sensitive only to (16)O/(18)O exchange were assigned to the modes from structures involving Mn and oxygen having no interactions with hydrogen, while the bands sensitive only to H/D exchange were assigned to modes from amino acid side chains and/or polypeptide backbones that associate with water hydrogen. The bands sensitive to both (16)O/(18)O and H/D exchanges were attributed to the structure involving Mn and oxygen structurally coupled with hydrogen in a direct or an indirect manner through hydrogen bonds. These bands include the changes of intermediate species derived from substrate water during the process of photosynthetic water oxidation. PMID:15909976

Kimura, Yukihiro; Ishii, Asako; Yamanari, Toshihiro; Ono, Taka-aki

2005-05-31

4

The Water Cycle  

NSDL National Science Digital Library

Students will learn the process of the water cycle. Alabama Course of Study: Science. Second Grade: Standard 9: Describe evaporation, condensation, and precipitation in the water cycle. What is the water cycle? On the worksheet provided, list the 4 parts of the water cycle. Between the parts draw a small picture to represent what is happening during this cycle. The Water Cycle See how we use the water in the water cycle. Thirstins Water Cycle Name 3 ways water changes form. This is an animated diagram of the Water Cycle Here is a ...

Lopez, Mrs.

2009-07-09

5

Redox cycle stability of mixed oxides used for hydrogen generation in the cyclic water gas shift process  

SciTech Connect

Graphical abstract: - Highlights: • Fe{sub 2}O{sub 3} modified with CaO, SiO{sub 2} and Al{sub 2}O{sub 3} was studied in cyclic water gas shift reactor. • For the first time stability of such oxides were tested for 100 redox cycles. • Optimally added oxides significantly improved the activity and the stability of Fe{sub 2}O{sub 3}. • Increased stability was attributed to the impediment of neck formation. - Abstract: Repeated cycles of the reduction of Fe{sub 3}O{sub 4} with reductive gas, e.g. hydrogen and subsequent oxidation of the reduced iron material with water vapor can be harnessed as a process for the production of pure hydrogen. The redox behavior of iron oxide modified with various amounts of SiO{sub 2}, CaO and Al{sub 2}O{sub 3} was investigated in the present study. The total amount of the additional metal oxides was always below 15 wt%. The samples were prepared by co-precipitation using urea hydrolysis method. The influence of various metal oxides on the hydrogen production capacity and the material stability was studied in detail in terms of temperature-programmed reduction (TPR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and BET analysis. Furthermore, the activity and the stability of the samples were tested in repeated reduction with diluted H{sub 2} and re-oxidation cycles with H{sub 2}O. The results indicate that combination of several oxides as promoter increases the stability of the iron oxide material by mitigating the sintering process. The positive influence of the oxides in stabilizing the iron oxide material is attributed to the impediment of neck formation responsible for sintering.

Datta, Pradyot, E-mail: pradyot.datta@gmail.com

2013-10-15

6

Water Cycle Webquest  

NSDL National Science Digital Library

Students are introduced to the Global Precipitation Measurement (GPM) satellite mission and its role in studying the water cycle. This webquest provides links to eight websites, allowing middle school students to explore the water cycle and its impacts on Earth's weather and climate. Through online videos and articles, students follow a water molecule through the cycle, discover the connection between the water cycle and global water/heat distribution, examine the role of solar energy, and assess the importance of fresh water.

7

The Water Cycle  

NSDL National Science Digital Library

The representation is a detailed, labeled diagram of the water cycle. Included in the representation are the major concepts of evaporation, precipitation and ground infiltration, as well as more advanced ideas. Above and below the diagram are several paragraphs that provide an introduction to the water cycle, a quick summary of the parts of the water cycle and information about global water distribution.

8

Human Water Cycle  

NSDL National Science Digital Library

Students learn about the human water cycle, or how humans impact the water cycle by settling down in civilizations. Specifically, they learn how people obtain, use and dispose of water. Students also learn about shortages of treated, clean and safe water and learn about ways that engineers address this issue through water conservation and graywater recycling.

Integrated Teaching and Learning Program,

9

The Water Cycle  

NSDL National Science Digital Library

What happens in each stage of the water cycle? First, watch this video to learn about each stage of the water cycle. video Next, click on this link to read more facts about each stages of the water cycle.

Baker, Ms.

2011-04-18

10

Discover the Water Cycle!  

NSDL National Science Digital Library

This interactive tour of the water cycle allows students to follow a water molecule from a home's plumbing system as it follows different routes through the hydrologic cycle. Students learn about how water is used, treated, and returned to the natural environment where it can cycle through liquid, solid, and gas phases.

11

The Water Cycle  

NSDL National Science Digital Library

This interactive diagram of the water cycle invites students to click on a part of the cycle to get information about streamflow, surface runoff, freshwater storage, ground-water discharge, ground-water storage, infiltration, precipitation, snowmelt, runoff to streams, springs, condensation, evaporation, transpiration, water in the atmosphere, ice and snow, and oceans. A summary of the water cycle on a single webpage is also available as text with pictures in about fifty languages, text only in thirteen languages, or diagram only.

2007-12-12

12

Amazon Water Cycle Roleplay  

NSDL National Science Digital Library

In this creative roleplay activity, learners will explore the various processes of the water cycle using movement, sound, and props to aid in comprehension. Learners will understand that water changes forms throughout the water cycle, and that this cycle runs continuously throughout all the cycles at the same time. This standards-based lesson, which is great for the classroom, camps, or afterschool programs, includes roleplay cards and ideas for props.

California Academy of Sciences

2008-01-01

13

The Water Cycle  

NSDL National Science Digital Library

This lesson was developed to give participants an understanding of Earth's water cycle. In this one-hour long activity, students participate in a webquest to learn about the water cycle, and then build a mini-model of the water cycle to observe how water moves through Earth's four systems. The activity uses the 5E instructional model and is part of the "Survivor Earth" series of one-hour lessons.

14

THE WATER CYCLE  

NSDL National Science Digital Library

DESK Standard: Understand the processes of evaporation, condensation, and precipitation as they relate to the water cycle. Water Cycle Diagram DATES: You can begin this activity on October 16. You should complete it by October 20. OBJECTIVE: You have been learning about the water cycle in class. This activity gives you the chance to review some important vocabulary: evaporation condensation precipitation collection You will watch a short video and complete a water ...

Hughes, Mr.

2006-02-18

15

The Water Cycle  

NSDL National Science Digital Library

Did you know that the water we use today is the same water found on Earth millions of years ago? The Earth constantly uses and recycles water in a process called the water cycle. In this lesson, learners explore the four phases of the water cycle. In the investigation Rain in a Jar, learners use hot water and ice to create condensation and a tiny cloud. In Making a Terrarium, learners create an ecosystem and water cycle by growing plants in a closed environment. Investigation spans several days.

2013-12-18

16

Exploring the Water Cycle  

NSDL National Science Digital Library

In this lesson, students will learn about the water cycle and how energy from the sun and the force of gravity drive this cycle. The emphasis in this lesson will be on having students understand the processes that take place in moving water through Earthâs system.

17

NOAA Water Cycle Game  

NSDL National Science Digital Library

The resource is a role-playing game in which students take on the role of a water molecule and travel through nine compartments of the water cycle to gain a better understanding for the true complexity of the movement of water.

18

Global water cycle  

NASA Technical Reports Server (NTRS)

The primary objective is to determine the scope and interactions of the global water cycle with all components of the Earth system and to understand how it stimulates and regulates changes on both global and regional scales. The following subject areas are covered: (1) water vapor variability; (2) multi-phase water analysis; (3) diabatic heating; (4) MSU (Microwave Sounding Unit) temperature analysis; (5) Optimal precipitation and streamflow analysis; (6) CCM (Community Climate Model) hydrological cycle; (7) CCM1 climate sensitivity to lower boundary forcing; and (8) mesoscale modeling of atmosphere/surface interaction.

Robertson, Franklin R.; Christy, John R.; Goodman, Steven J.; Miller, Tim L.; Fitzjarrald, Dan; Lapenta, Bill; Wang, Shouping

1991-01-01

19

The Other Water Cycle  

NSDL National Science Digital Library

For students who have already been introduced to the water cycle, this lesson is intended as a logical follow-up. Students learn about human impacts on the water cycle that create a pathway for pollutants beginning with urban development and joining the natural water cycle as surface runoff. The extent of surface runoff in an area depends on the permeability of the materials in the ground. Permeability is the degree to which water or other liquids are able to flow through a material. Different substances such as soil, gravel, sand and asphalt have varying levels of permeability. In this lesson, along with the associated activity, students learn about permeability and compare the permeability of several different materials for the purpose of engineering landscape drainage systems.

Engineering K-Phd Program

20

The Water Cycle  

NSDL National Science Digital Library

This site provides information about precipitation, evaporation, condensation, surface runoff, infiltration and transpiration, which are all part of the water cycle, a complex process that not only gives us water to drink and fish to eat, but also weather patterns that help grow our crops. The site has four sections. The introduction presents the overall concept while the second section covers each of the six parts of the cycle in detail. In the third part, The Cycle, the dynamic process is stressed and a diagram is included. Cloud Formation is the final section and it covers factors that control the size and shape of clouds such as heat, seasons, mountain ranges, bodies of water, volcanic eruptions, and even global warming. In addition, cloud nomenclature is discussed with an explanation of the advent of such cloud names as cumulonimbus, nimbostratus, cirrocumulus, and altostratus.

21

GEOSS Water Cycle Integrator  

NASA Astrophysics Data System (ADS)

It is critically important to recognize and co-manage the fundamental linkages across the water-dependent domains; land use, including deforestation; ecosystem services; and food-, energy- and health-securities. Sharing coordinated, comprehensive and sustained observations and information for sound decision-making is a first step; however, to take full advantage of these opportunities, we need to develop an effective collaboration mechanism for working together across different disciplines, sectors and agencies, and thereby gain a holistic view of the continuity between environmentally sustainable development, climate change adaptation and enhanced resilience. To promote effective multi-sectoral, interdisciplinary collaboration based on coordinated and integrated efforts, the Global Earth Observation System of Systems (GEOSS) is now developing a "GEOSS Water Cycle Integrator (WCI)", which integrates "Earth observations", "modeling", "data and information", "management systems" and "education systems". GEOSS/WCI sets up "work benches" by which partners can share data, information and applications in an interoperable way, exchange knowledge and experiences, deepen mutual understanding and work together effectively to ultimately respond to issues of both mitigation and adaptation. (A work bench is a virtual geographical or phenomenological space where experts and managers collaborate to use information to address a problem within that space). GEOSS/WCI enhances the coordination of efforts to strengthen individual, institutional and infrastructure capacities, especially for effective interdisciplinary coordination and integration. GEO has established the GEOSS Asian Water Cycle Initiative (AWCI) and GEOSS African Water Cycle Coordination Initiative (AfWCCI). Through regional, inter-disciplinary, multi-sectoral integration and inter-agency coordination in Asia and Africa, GEOSS/WCI is now leading to effective actions and public awareness in support of water security and sustainable development.

Koike, T.; Lawford, R. G.; Cripe, D.

2012-12-01

22

GEOSS Water Cycle Integrator  

NASA Astrophysics Data System (ADS)

It is critically important to recognize and co-manage the fundamental linkages across the water-dependent domains; land use, including deforestation; ecosystem services; and food-, energy- and health-securities. Sharing coordinated, comprehensive and sustained observations and information for sound decision-making is a first step; however, to take full advantage of these opportunities, we need to develop an effective collaboration mechanism for working together across different disciplines, sectors and agencies, and thereby gain a holistic view of the continuity between environmentally sustainable development, climate change adaptation and enhanced resilience. To promote effective multi-sectoral, interdisciplinary collaboration based on coordinated and integrated efforts, the intergovernmental Group on Earth Observations (GEO) is implementing the Global Earth Observation System of Systems (GEOSS). A component of GEOSS now under development is the "GEOSS Water Cycle Integrator (WCI)", which integrates Earth observations, modeling, data and information, management systems and education systems. GEOSS/WCI sets up "work benches" by which partners can share data, information and applications in an interoperable way, exchange knowledge and experiences, deepen mutual understanding and work together effectively to ultimately respond to issues of both mitigation and adaptation. (A work bench is a virtual geographical or phenomenological space where experts and managers collaborate to use information to address a problem within that space). GEOSS/WCI enhances the coordination of efforts to strengthen individual, institutional and infrastructure capacities, especially for effective interdisciplinary coordination and integration. GEO has established the GEOSS Asian Water Cycle Initiative (AWCI) and GEOSS African Water Cycle Coordination Initiative (AfWCCI). Through regional, inter-disciplinary, multi-sectoral integration and inter-agency coordination in Asia and Africa, GEOSS/WCI is now leading to effective actions and public awareness in support of water security and sustainable development.

Koike, Toshio; Lawford, Richard; Cripe, Douglas

2013-04-01

23

Studies of thermochemical water-splitting cycles  

NASA Technical Reports Server (NTRS)

Higher temperatures and more isothermal heat profiles of solar heat sources are developed. The metal oxide metal sulfate class of cycles were suited for solar heat sources. Electrochemical oxidation of SO2 and thermochemical reactions are presented. Electrolytic oxidation of sulfur dioxide in dilute sulfuric acid solutions were appropriate for metal oxide metal sulfate cycles. The cell voltage at workable current densities required for the oxidation of SO2 was critical to the efficient operation of any metal oxide metal sulfate cycle. A sulfur dioxide depolarized electrolysis cell for the splitting of water via optimization of the anode reaction is discussed. Sulfuric acid concentrations of 30 to 35 weight percent are preferred. Platinized platinum or smooth platinum gave the best anode kinetics at a given potential of the five materials examined.

Remick, R. J.; Foh, S. E.

1980-01-01

24

Behavior of oxide scales on 2. 25Cr-1Mo steel during thermal cycling. II. Scales grown in water vapor  

SciTech Connect

The acoustic emission (AE) technique has been applied to identify scale cracking during thermal cycling of tubes of 2.25Cr-1Mo steel. The scale morphology and failure mode were investigated by light and electron optical method. The scale formed at 600/degree/C in water vapor consists of an outer magnetite and an inner, chromium-containing spinel layer. Cooling leads to tensile stresses in the scale that cause macro- and microcrack formation in the scale. At constant-cycle parameters, a characteristic set of crack length and crack density is established. Changes in the cycle parameters also change the crack length and crack density. The experimental results can be described by a model developed by Hasselmann assuming a large number of noninteracting microcracks in a ceramic plate.

Christl, W.; Rahmel, A.; Schuetze, M.

1989-02-01

25

Fun with the Water Cycle  

NSDL National Science Digital Library

Science - 4th Grade Students will understand that water changes state as it moves through the water cycle. Note: this lesson plan can easily take more than one day for students to complete. Materials needed: Computers, frisbee, 2 clear plastic cups, tape, graduated cylinder, water, condensation data worksheet, 2 matches, 1 clear empty 2-liter pop bottle, 1/2 cup of warm water, flashlight, measuring cup 1. Click on the link below, then click "Thristin's Water Cycle: Water". Watch the short video about the water cycle. ...

Wirthlin, Ms.

2009-11-16

26

Cycling Water Through the Environment  

NSDL National Science Digital Library

In this lesson, students recognize the different forms that water takes and learn about where it exists in the environment. Using class discussion, multimedia resources, and experiments, students model the water cycle and explore how it can be used to create fresh water. They will identify the ways that water moves through the environment, recognize that most of Earth's surface is covered by water (but only a small amount is fresh water), and produce fresh water from salty water by distilling it.

2005-01-01

27

Water Cycle in a Bag  

NSDL National Science Digital Library

In this activity, learners create a biosphere in a baggie. Learners add soil, seeds and a little water in a ziplock bag, tape the bag to a sunny window and observe a microcosm of the water cycle (hydrologic cycle) that sustains life on Earth. This resource includes tips for using this activity with older children as well as useful web links.

Garden, Queens B.

2012-06-26

28

Water Cycling &the GPM Mission  

Microsoft Academic Search

The GPM mission is currently planned for start in the late'07 - early'08 time frame. Its main scientific goal is to help answer pressing scientific problems arising within the context of global and regional water cycles. These problems cut across a hierarchy of scales and include climate-water cycle interactions, techniques for improving weather and climate predictions, and better methods for

E. A. Smith

2003-01-01

29

The NEWS Water Cycle Climatology  

NASA Technical Reports Server (NTRS)

NASA's Energy and Water Cycle Study (NEWS) program fosters collaborative research towards improved quantification and prediction of water and energy cycle consequences of climate change. In order to measure change, it is first necessary to describe current conditions. The goal of the first phase of the NEWS Water and Energy Cycle Climatology project was to develop "state of the global water cycle" and "state of the global energy cycle" assessments based on data from modern ground and space based observing systems and data integrating models. The project was a multi-institutional collaboration with more than 20 active contributors. This presentation will describe the results of the water cycle component of the first phase of the project, which include seasonal (monthly) climatologies of water fluxes over land, ocean, and atmosphere at continental and ocean basin scales. The requirement of closure of the water budget (i.e., mass conservation) at various scales was exploited to constrain the flux estimates via an optimization approach that will also be described. Further, error assessments were included with the input datasets, and we examine these in relation to inferred uncertainty in the optimized flux estimates in order to gauge our current ability to close the water budget within an expected uncertainty range.

Rodell, Matthew; Beaudoing, Hiroko Kato; L'Ecuyer, Tristan; William, Olson

2012-01-01

30

The Water Cycle  

NSDL National Science Digital Library

The representation features a detailed six minute animated lesson about the major processes that move water between land, the ocean and the atmosphere, and convert water between states. Evaporation, condensation, transpiration and water reservoirs are major topics covered by the animation. The portion of the video (05:40 to 06:05 beginning with a drawn scene of mountains, oceans and sky to narration Âdissolved minerals in ground water carried to the ocean for billions of yearsÂ) describes pollutants being filtered out of water while minerals, such as sodium and arsenic, are Âpicked up by the water.

31

Water 2: The Hydrologic Cycle  

NSDL National Science Digital Library

This video looks at how water is provided for our use through the hydrologic cycle. It also explains how global climate change disturbs the storage of water in the various global compartments. This video is part of the Sustainability Learning Suites, made possible in part by a grant from the National Science Foundation. See 'Learn more about this resource' for Learning Objectives and Activities.

Vanasupa, Linda

32

SUPERCRITICAL WATER PARTIAL OXIDATION  

Microsoft Academic Search

In 2000, General Atomics was selected by DOE's Hydrogen Program to perform cooperatively- funded research on supercritical water partial oxidation (SWPO) of biomass, municipal solid waste (MSW), and high-sulfur coal to generate hydrogen. Phase I of this research is being performed in GA's privately-funded supercritical water (SCW) pilot plant at its San Diego, CA facilities. This pilot plant is a

N. W. Johanson; M. H. Spritzer; G. T. Hong; W. S. Rickman

33

The Water Cycle: Infiltration  

NSDL National Science Digital Library

This site provides a discussion of the downward movement, or infiltration, of water from the surface into soil or porous rock. Graphics illustrate the processes affecting infiltration, including precipitation, soil characteristics and saturation, land cover, slope, and evapotranspiration. Links to additional sources of information are also provided.

34

Oxidative photosynthetic carbon cycle or C2 cycle  

SciTech Connect

The oxidative photosynthetic carbon cycle (or C2 cycle) is the metabolic pathway responsible for photosynthetic oxygen uptake and the light-dependent production of carbon dioxide that is termed photorespiration. The C2 and reductive C3 cycles coexist, and combined, represent total photosynthetic carbon metabolism. A brief historical review is presented beginning with the early observations of the oxygen inhibition of photosynthesis up to the discovery of the oxygenase-activity associated with ribulose 1.5-bisphosphate carboxylase/oxygenase. The properties and the role of the compartmentalization of the enzymes involved with the pathway and the transport of C2, cycle intermediates are reviewed. The relationship of the C2 cycle to photorespiratory nitrogen metabolism and other associated metabolic pathways and the properties and regulation of the C2 cycle in diverse photosynthetic organisms are discussed. (Refs. 382).

Husic, D.W.; Husic, H.D.; Tolbert, N.E.

1987-01-01

35

Droplet and the Water Cycle  

NSDL National Science Digital Library

From NASA's For Kids Only Earth Science Enterprise Web site comes the interactive learning game, Droplet and the Water Cycle. Using Flash Macromedia, kids get to control an animated droplet of water falling from the sky in hopes of learning more about the water cycle. Controls are described on the first page, which allow you to move the droplet through a forest, a river, and an ocean while avoiding things, like butterflies and insects, which are very thirsty. The game can be downloaded to PC and Macintosh computers for free or played online. Although it is fun and challenging to play, it could use some more questions or other means of reinforcing the learning.

2001-01-01

36

Molecular water oxidation catalyst  

DOEpatents

A dimeric composition of the formula: ##STR1## wherein L', L", L'", and L"" are each a bidentate ligand having at least one functional substituent, the ligand selected from bipyridine, phenanthroline, 2-phenylpyridine, bipyrimidine, and bipyrazyl and the functional substituent selected from carboxylic acid, ester, amide, halogenide, anhydride, acyl ketone, alkyl ketone, acid chloride, sulfonic acid, phosphonic acid, and nitro and nitroso groups. An electrochemical oxidation process for the production of the above functionally substituted bidentate ligand diaqua oxo-bridged ruthenium dimers and their use as water oxidation catalysts is described.

Gratzel, Michael (St. Sulpice, CH); Munavalli, Shekhar (Bel Air, MD); Pern, Fu-Jann (Lakewood, CO); Frank, Arthur J. (Lakewood, CO)

1993-01-01

37

Simulating the urban water and contaminant cycle  

Microsoft Academic Search

This paper presents the water and contaminant daily simulation model of the total water cycle, called UVQ. The model has been developed to provide a means for rapidly assessing the impacts of conventional and non-conventional urban water supply, stormwater and wastewater development options on the total water cycle. UVQ provides a valuable insight into the viability of prospective alternative water

V. G. Mitchell; C. Diaper

2006-01-01

38

Water Cycling &the GPM Mission  

NASA Astrophysics Data System (ADS)

The GPM mission is currently planned for start in the late'07 - early'08 time frame. Its main scientific goal is to help answer pressing scientific problems arising within the context of global and regional water cycles. These problems cut across a hierarchy of scales and include climate-water cycle interactions, techniques for improving weather and climate predictions, and better methods for combining observed precipitation with hydrometeorological prediction models for applications to hazardous flood-producing storms, seasonal flood/draught conditions, and fresh water resource assessments. The GPM mission will expand the scope of precipitation measurement through the use of a constellation of some 9 satellites, one of which will be an advanced TRMM-like "core" satellite carrying a dual-frequency Ku-Ka band precipitation radar and an advanced, multifrequency passive microwave radiometer with vertical-horizontal polarization discrimination. The other constellation members will include new dedicated satellites and co-existing operational/research satellites carrying similar (but not identical) passive microwave radiometers. The goal of the constellation is to achieve 3-hour sampling at any spot on the globe - continuously. The constellation's orbit architecture will consist of a mix of sun-synchronous and non-sun-synchronous satellites with the "core" satellite providing measurements of cloud-precipitation microphysical processes plus calibration-quality rainrates to be used with the other retrieval information to ensure bias-free constellation coverage. GPM is organized internationally, involving existing, pending, projected, and under-study partnerships which will link NASA and NOAA in the US, NASDA in Japan, ESA in Europe, ISRO in India, CNES in France, and possibly ASI in Italy, KARI in South Korea, CSA in Canada, and AEB in Brazil. Additionally, the program is actively pursuing agreements with other international collaborators and domestic scientific agencies and institutions, as well as participation by individual scientists from academia, government, and the private sector to fulfill mission goals and to pave the way for what ultimately is expected to become an internationally-organized operational global precipitation observing system. Notably, the broad societal applications of GPM are reflected in the United Nation's identification of this mission as a foremost candidate for its Peaceful Uses of Space Program. An overview of the GPM mission design is given, followed by an explanation of its scientific agenda as an outgrowth of making improvements in rain retrieval accuracy, microphysics dexterity, sampling frequency, and global coverage. All of these improvements offer new means to observe variability in precipitation and water cycle fluxes, to improve water budget closure at regional and global scales, and to leverage these improvements in achieving improved predictability of weather, climate, and hydrometeorology. Specifically, the scientific agenda of GPM has been designed to leverage the measurement improvements to improve prognostic model performance, particularly quantitative precipitation forecasting and its linked phenomena at short, intermediate, and extended time scales. The talk addresses how GPM measurements will enable more accurate satellite-based calculations of the water cycle relative to where things stand today (two examples will be provided), and how such measurements can be used to evaluate accelerations and decelerations in regional and global water cycle processes and thus improve our understanding of water-driven climatic shifts. These improvements become possible by using more accurate, more microphysically-centric, more frequent, and fully global precipitation observations to achieve better water budget closure and to provide more realistic forcing and assessment of prediction models.

Smith, E. A.

2003-04-01

39

The Water Cycle in Volusia County  

USGS Publications Warehouse

Earth's water is always in motion. The water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above, and below the Earth's surface. This fact sheet provides information about how much water moves into and out of Volusia County, and where it is stored. It also illustrates the seasonal variation in water quantity and movement using data from some of the hydrologic data collection sites in or near Volusia County, Florida.

German, Edward R.

2009-01-01

40

Getting up to Speed: The Water Cycle and Water Conservation  

NSDL National Science Digital Library

This is an introduction to a module on water conservation. It presents the concepts of limited supply, the water cycle, and the impact by and on populations. It gives an overview of water conservation and what would happen without it.

41

Water Cycle Missions for the Next Decade  

NASA Astrophysics Data System (ADS)

The global water cycle describes the circulation of water as a vital and dynamic substance in its liquid, solid, and vapor phases as it moves through the atmosphere, oceans and land. Life in its many forms exists because of water, and modern civilization depends on learning how to live within the constraints imposed by the availability of water. The scientific challenge posed by the need to observe the global water cycle is to integrate in situ and space-borne observations to quantify the key water-cycle state variables and fluxes. The vision to address that challenge is a series of Earth observation missions that will measure the states, stocks, flows, and residence times of water on regional to global scales followed by a series of coordinated missions that will address the processes, on a global scale, that underlie variability and changes in water in all its three phases. The accompanying societal challenge is to foster the improved use of water data and information as a basis for enlightened management of water resources, to protect life and property from effects of extremes in the water cycle. A major change in thinking about water science that goes beyond its physics to include its role in ecosystems and society is also required. Better water-cycle observations, especially on the continental and global scales, will be essential. Water-cycle predictions need to be readily available globally to reduce loss of life and property caused by water-related natural hazards. Building on the 2007 Earth Science Decadal Survey, NASA's Plan for a Climate-Centric Architecture for Earth Observations and Applications from Space , and the 2012 Chapman Conference on Remote Sensing of the Terrestrial Water Cycle, a workshop was held in April 2013 to gather wisdom and determine how to prepare for the next generation of water cycle missions in support of the second Earth Science Decadal Survey. This talk will present the outcomes of the workshop including the intersection between science questions, technology readiness and satellite design optimization. A series of next-generation water cycle mission working groups were proposed and white papers, designed to identify capacity gaps and inform NASA were developed. The workshop identified several visions for the next decade of water cycle satellite observations, and developed a roadmap and action plan for developing the foundation for these missions. Achieving this outcome will result in optimized community investments and better functionality of these future missions, and will help to foster broader range of scientists and professionals engaged in water cycle observation planning and development around the country, and the world.

Houser, P. R.

2013-12-01

42

Water Cycle. K-6 Science Curriculum.  

ERIC Educational Resources Information Center

Water Cycle is one of the units of a K-6 unified science curriculum program. The unit consists of four organizing sub-themes: (1) atmosphere (highlighting the processes of evaporation, condensation, convection, wind movement and air pollution); (2) water (examining the properties of liquids, water distribution, use, and quality, and the water…

Blueford, J. R.; And Others

43

Nitrous oxide cycling in the water column and sediments of the oxygen minimum zone, eastern subtropical North Pacific, Southern California, and Northern Mexico (23°N-34°N)  

NASA Astrophysics Data System (ADS)

sources and sinks of N2O can illuminate N cycling processes in marine systems, particularly where changes in dissolved O2 can lead to changes in N cycling pathways (i.e., nitrification versus denitrification). We measured N2O and NO3- concentration and their stable isotope ratios (?15N and ?18O) in the water column and sediments of the oxygen minimum zone in the nearshore eastern subtropical North Pacific (23°N-34°N). Atmospheric efflux of N2O ranged from 2.2 to 17.9 ?mol m-2 d-1 or about 2-20 times higher than in oxygenated regions of the North Pacific. Surface waters were a source of 15N-depleted and 18O-enriched N2O to the atmosphere, indicating a bacterial, not archaeal, nitrification N2O source. Stable isotopes indicated that nitrification in both surface and intermediate waters (˜0-200 m) was the major source of N2O in this study area, with denitrification acting as a small N2O sink in strongly O2-depleted waters. Denitrification had a larger impact on observed patterns of N2O and NO3- concentrations and isotope ratios in the southern oxygen minimum zone. Sediments were generally neutral or a weak sink for N2O, with only one site (Soledad basin) showing a positive efflux of +3.5 ± 1.0 ?mol N2O-N m-2 d-1. Sediment fluxes of N2O at all sites were several orders of magnitude smaller than fluxes of dinitrogen, nitrate, and ammonium measured in previous studies and did not appear to impact water column N2O concentrations. N2O was less than 0.1% of the N2 efflux from sedimentary denitrification.

Townsend-Small, Amy; Prokopenko, Maria G.; Berelson, William M.

2014-05-01

44

Natural and Urban "Stormwater" Water Cycles  

NSDL National Science Digital Library

Through an overview of the components of the hydrologic cycle and the important roles they play in the design of engineered systems, students' awareness of the world's limited fresh water resources is heightened. The hydrologic cycle affects everyone and is the single most critical component to life on Earth. Students examine in detail the water cycle components and phase transitions, and then learn how water moves through the human-made urban environment. This urban "stormwater" water cycle is influenced by the pervasive existence of impervious surfaces that limit the amount of infiltration, resulting in high levels of stormwater runoff, limited groundwater replenishment and reduced groundwater flow. Students show their understanding of the process by writing a description of the path of a water droplet through the urban water cycle, from the droplet's point of view. The lesson lays the groundwork for rest of the unit, so students can begin to think about what they might do to modify the urban "stormwater" water cycle so that it functions more like the natural water cycle. A PowerPoint® presentation and handout are provided.

Water Awareness Research and Education (WARE) Research Experience for Teachers (RET),

45

Supramolecular Water Oxidation with Ru-bda-Based Catalysts.  

PubMed

Extremely slow and extremely fast new water oxidation catalysts based on the Ru-bda (bda=2,2'-bipyridine-6,6'-dicarboxylate) systems are reported with turnover frequencies in the range of 1 and 900 cycles?s(-1) , respectively. Detailed analyses of the main factors involved in the water oxidation reaction have been carried out and are based on a combination of reactivity tests, electrochemical experiments, and DFT calculations. These analyses give a convergent interpretation that generates a solid understanding of the main factors involved in the water oxidation reaction, which in turn allows the design of catalysts with very low energy barriers in all the steps involved in the water oxidation catalytic cycle. We show that for this type of system ?-stacking interactions are the key factors that influence reactivity and by adequately controlling them we can generate exceptionally fast water oxidation catalysts. PMID:25377430

Richmond, Craig J; Matheu, Roc; Poater, Albert; Falivene, Laura; Benet-Buchholz, Jordi; Sala, Xavier; Cavallo, Luigi; Llobet, Antoni

2014-12-22

46

Water oxidation by an electropolymerized catalyst on derivatized mesoporous metal oxide electrodes.  

PubMed

A general electropolymerization/electro-oligomerization strategy is described for preparing spatially controlled, multicomponent films and surface assemblies having both light harvesting chromophores and water oxidation catalysts on metal oxide electrodes for applications in dye-sensitized photoelectrosynthesis cells (DSPECs). The chromophore/catalyst ratio is controlled by the number of reductive electrochemical cycles. Catalytic rate constants for water oxidation by the polymer films are similar to those for the phosphonated molecular catalyst on metal oxide electrodes, indicating that the physical properties of the catalysts are not significantly altered in the polymer films. Controlled potential electrolysis shows sustained water oxidation over multiple hours with no decrease in the catalytic current. PMID:24735242

Ashford, Dennis L; Lapides, Alexander M; Vannucci, Aaron K; Hanson, Kenneth; Torelli, Daniel A; Harrison, Daniel P; Templeton, Joseph L; Meyer, Thomas J

2014-05-01

47

Combined cycle power plants - water chemistry  

SciTech Connect

Water chemistry guidelines are provided for combined cycle power plants. These plants utilize a gas and steam turbine to generate electric power. The gas turbine exhaust is passed through a heat recovery steam generator to produce steam. The steam is then expanded through a steam turbine for added power generation. This cycle comprises key features such as low feedwater temperature, large makeup water requirements, and low exhaust steam pressure. The steam purity and water chemistry guidelines address these features to provide a protective cycle chemistry environment.

Gabrielli, F. [Combustion Engineering, Inc., Windsor, CT (United States); Sandmann, H.; Svoboda, R. [ABB Kraftwerke AG, Baden (Switzerland)

1995-01-01

48

Deep water cycle: Mantle hydration  

NASA Astrophysics Data System (ADS)

The fate of water that enters the mantle within subducting slabs is unclear. Laboratory experiments indicate that subducted crust can transport large amounts of water into the deep Earth, and the lower mantle may become more hydrated over time.

Nishi, Masayuki

2015-01-01

49

Observing the Global Water Cycle from Space  

NASA Technical Reports Server (NTRS)

This paper presents an approach to measuring all major components of the water cycle from space. Key elements of the global water cycle are discussed in terms of the storage of water-in the ocean, air, cloud and precipitation, in soil, ground water, snow and ice, and in lakes and rivers, and in terms of the global fluxes of water between these reservoirs. Approaches to measuring or otherwise evaluating the global water cycle are presented, and the limitations on known accuracy for many components of the water cycle are discussed, as are the characteristic spatial and temporal scales of the different water cycle components. Using these observational requirements for a global water cycle observing system, an approach to measuring the global water cycle from space is developed. The capabilities of various active and passive microwave instruments are discussed, as is the potential of supporting measurements from other sources. Examples of space observational systems, including TRMM/GPM precipitation measurement, cloud radars, soil moisture, sea surface salinity, temperature and humidity profiling, other measurement approaches and assimilation of the microwave and other data into interpretative computer models are discussed to develop the observational possibilities. The selection of orbits is then addressed, for orbit selection and antenna size/beamwidth considerations determine the sampling characteristics for satellite measurement systems. These considerations dictate a particular set of measurement possibilities, which are then matched to the observational sampling requirements based on the science. The results define a network of satellite instrumentation systems, many in low Earth orbit, a few in geostationary orbit, and all tied together through a sampling network that feeds the observations into a data-assimilative computer model.

Hildebrand, P. H.

2004-01-01

50

Observing the Global Water Cycle from Space  

NASA Technical Reports Server (NTRS)

This paper presents an approach to measuring all major components of the water cycle from space. The goal of the paper is to explore the concept of using a sensor-web of satellites to observe the global water cycle. The details of the required measurements and observation systems are therefore only an initial approach and will undergo future refinement, as their details will be highly important. Key elements include observation and evaluation of all components of the water cycle in terms of the storage of water-in the ocean, air, cloud and precipitation, in soil, ground water, snow and ice, and in lakes and rivers-and in terms of the global fluxes of water between these reservoirs. For each component of the water cycle that must be observed, the appropriate temporal and spatial scales of measurement are estimated, along with the some of the frequencies that have been used for active and passive microwave observations of the quantities. The suggested types of microwave observations are based on the heritage for such measurements, and some aspects of the recent heritage of these measurement algorithms are listed. The observational requirements are based on present observational systems, as modified by expectations for future needs. Approaches to the development of space systems for measuring the global water cycle can be based on these observational requirements.

Hildebrand, Peter H.; Houser, Paul; Schlosser, C. Adam

2003-01-01

51

Geothermal Water Use: Life Cycle Water Consumption, Water Resource Assessment, and Water Policy Framework  

DOE Data Explorer

This report examines life cycle water consumption for various geothermal technologies to better understand factors that affect water consumption across the life cycle (e.g., power plant cooling, belowground fluid losses) and to assess the potential water challenges that future geothermal power generation projects may face. Previous reports in this series quantified the life cycle freshwater requirements of geothermal power-generating systems, explored operational and environmental concerns related to the geochemical composition of geothermal fluids, and assessed future water demand by geothermal power plants according to growth projections for the industry. This report seeks to extend those analyses by including EGS flash, both as part of the life cycle analysis and water resource assessment. A regional water resource assessment based upon the life cycle results is also presented. Finally, the legal framework of water with respect to geothermal resources in the states with active geothermal development is also analyzed.

Schroeder, Jenna N.

52

Geothermal Water Use: Life Cycle Water Consumption, Water Resource Assessment, and Water Policy Framework  

SciTech Connect

This report examines life cycle water consumption for various geothermal technologies to better understand factors that affect water consumption across the life cycle (e.g., power plant cooling, belowground fluid losses) and to assess the potential water challenges that future geothermal power generation projects may face. Previous reports in this series quantified the life cycle freshwater requirements of geothermal power-generating systems, explored operational and environmental concerns related to the geochemical composition of geothermal fluids, and assessed future water demand by geothermal power plants according to growth projections for the industry. This report seeks to extend those analyses by including EGS flash, both as part of the life cycle analysis and water resource assessment. A regional water resource assessment based upon the life cycle results is also presented. Finally, the legal framework of water with respect to geothermal resources in the states with active geothermal development is also analyzed.

Schroeder, Jenna N.

2014-06-10

53

Annual cycle and temperature dependence of pinene oxidation products and other water-soluble organic compounds in coarse and fine aerosol samples  

NASA Astrophysics Data System (ADS)

Filter samples of fine and coarse particulate matter were collected over a period of one year and analyzed for water-soluble organic compounds, including the pinene oxidation products pinic acid, pinonic acid, 3-methyl-1,2,3-butanetricarboxylic acid (3-MBTCA) and a variety of dicarboxylic acids (C5-C16) and nitrophenols. Seasonal variations and other characteristic features are discussed with regard to aerosol sources and sinks and data from other studies and regions. The ratios of adipic acid (C6) and phthalic acid (Ph) to azelaic acid (C9) indicate that the investigated aerosols samples were mainly influenced by biogenic sources. An Arrhenius-type correlation was found between the 3-MBTCA concentration and inverse temperature. Model calculations suggest that the temperature dependence is largely due to enhanced emissions and OH radical concentrations at elevated temperatures, whereas the influence of gas-particle partitioning appears to play a minor role. Enhanced ratios of pinic acid to 3-MBTCA indicate strong chemical aging of the investigated aerosols in summer and spring. Acknowledgment: The authors would like to thank M. Claeys for providing synthetic 3-methyl-1,2,3-butanetricarboxylic acid standards for LC-MS analysis and J. Fröhlich for providing filter samples and related information.

Zhang, Y.; Müller, L.; Winterhalter, R.; Moortgat, G. K.; Hoffmann, T.; Pöschl, U.

2010-05-01

54

General characteristics of thermally cycled tin oxide gas sensors  

Microsoft Academic Search

The response, measured as conductance, of thermally cycled tin oxide gas sensors was studied to determine the potential inherent in this technique with respect to increased selectivity and sensitivity. It was found that the range of cycle temperature as well as the period of the cycle had a critical effect on the amount of information that could be extracted from

W. M. Sears; K. Colbow; F. Consadori

1989-01-01

55

Atmospheric cycles of nitrogen oxides and ammonia  

NASA Astrophysics Data System (ADS)

The atmospheric cycles of nitrogenous trace compounds for the Northern and Southern Hemispheres are discussed. Source strengths and destruction rates for the nitrogen oxides: NO, NO2 and HNO3 -(NOX) and ammonia (NH3) are given as a function of latitude over continents and oceans. The global amounts of NOX-N and NH3-N produced annually in the period 1950 to 1975 (34 + 5 x one trillion g NOx-N/yr and 29 + or - 6 x one trillion g NH3-N/yr) are much less than previously assumed. Globally, natural and anthropogenic emissions are of similar magnitude. The NOx emission from anthropogenic sources is 1.5 times that from natural processes in the Northern Hemisphere, whereas in the Southern Hemisphere, it is a factor of 3 or 4 less. More than 80% of atmospheric ammonia seems to be derived from excrements of domestic animals, mostly by bulk deposition: 24 + or - 9 x one trillion g NO3 -N/yr and 21 + or - 9 x one trillion g NH4+-N/yr. Another fraction may be removed by absorption on vegetation and soils.

Bottger, A.; Ehhalt, D. H.; Gravenhorst, G.

1981-12-01

56

Solar High Temperature Water-Splitting Cycle with Quantum Boost  

SciTech Connect

A sulfur family chemical cycle having ammonia as the working fluid and reagent was developed as a cost-effective and efficient hydrogen production technology based on a solar thermochemical water-splitting cycle. The sulfur ammonia (SA) cycle is a renewable and sustainable process that is unique in that it is an all-fluid cycle (i.e., with no solids handling). It uses a moderate temperature solar plant with the solar receiver operating at 800°C. All electricity needed is generated internally from recovered heat. The plant would operate continuously with low cost storage and it is a good potential solar thermochemical hydrogen production cycle for reaching the DOE cost goals. Two approaches were considered for the hydrogen production step of the SA cycle: (1) photocatalytic, and (2) electrolytic oxidation of ammonium sulfite to ammonium sulfate in aqueous solutions. Also, two sub-cycles were evaluated for the oxygen evolution side of the SA cycle: (1) zinc sulfate/zinc oxide, and (2) potassium sulfate/potassium pyrosulfate. The laboratory testing and optimization of all the process steps for each version of the SA cycle were proven in the laboratory or have been fully demonstrated by others, but further optimization is still possible and needed. The solar configuration evolved to a 50 MW(thermal) central receiver system with a North heliostat field, a cavity receiver, and NaCl molten salt storage to allow continuous operation. The H2A economic model was used to optimize and trade-off SA cycle configurations. Parametric studies of chemical plant performance have indicated process efficiencies of ~20%. Although the current process efficiency is technically acceptable, an increased efficiency is needed if the DOE cost targets are to be reached. There are two interrelated areas in which there is the potential for significant efficiency improvements: electrolysis cell voltage and excessive water vaporization. Methods to significantly reduce water evaporation are proposed for future activities. Electrolysis membranes that permit higher temperatures and lower voltages are attainable. The oxygen half cycle will need further development and improvement.

Taylor, Robin [SAIC] [SAIC; Davenport, Roger [SAIC] [SAIC; Talbot, Jan [UCSD] [UCSD; Herz, Richard [UCSD] [UCSD; Genders, David [Electrosynthesis Co.] [Electrosynthesis Co.; Symons, Peter [Electrosynthesis Co.] [Electrosynthesis Co.; Brown, Lloyd [TChemE] [TChemE

2014-04-25

57

Circadian Clock NAD+ Cycle Drives Mitochondrial Oxidative Metabolism in Mice  

PubMed Central

Circadian clocks are self-sustained cellular oscillators that synchronize oxidative and reductive cycles in anticipation of the solar cycle. We found that the clock transcription feedback loop produces cycles of nicotinamide adenine dinucleotide (NAD+) biosynthesis, adenosine triphosphate production, and mitochondrial respiration through modulation of mitochondrial protein acetylation to synchronize oxidative metabolic pathways with the 24-hour fasting and feeding cycle. Circadian control of the activity of the NAD+-dependent deacetylase sirtuin 3 (SIRT3) generated rhythms in the acetylation and activity of oxidative enzymes and respiration in isolated mitochondria, and NAD+ supplementation restored protein deacetylation and enhanced oxygen consumption in circadian mutant mice. Thus, circadian control of NAD+ bioavailability modulates mitochondrial oxidative function and organismal metabolism across the daily cycles of fasting and feeding. PMID:24051248

Peek, Clara Bien; Affinati, Alison H.; Ramsey, Kathryn Moynihan; Kuo, Hsin-Yu; Yu, Wei; Sena, Laura A.; Ilkayeva, Olga; Marcheva, Biliana; Kobayashi, Yumiko; Omura, Chiaki; Levine, Daniel C.; Bacsik, David J.; Gius, David; Newgard, Christopher B.; Goetzman, Eric; Chandel, Navdeep S.; Denu, John M.; Mrksich, Milan; Bass, Joseph

2014-01-01

58

A Cryptic Sulfur Cycle in Oxygen-Minimum-Zone Waters off the Chilean Coast  

NASA Astrophysics Data System (ADS)

Nitrogen cycling is normally thought to dominate the biogeochemistry and microbial ecology of oxygen-minimum zones in marine environments. Through a combination of molecular techniques and process rate measurements, we showed that both sulfate reduction and sulfide oxidation contribute to energy flux and elemental cycling in oxygen-free waters off the coast of northern Chile. These processes may have been overlooked because in nature, the sulfide produced by sulfate reduction immediately oxidizes back to sulfate. This cryptic sulfur cycle is linked to anammox and other nitrogen cycling processes, suggesting that it may influence biogeochemical cycling in the global ocean.

Canfield, Don E.; Stewart, Frank J.; Thamdrup, Bo; De Brabandere, Loreto; Dalsgaard, Tage; Delong, Edward F.; Revsbech, Niels Peter; Ulloa, Osvaldo

2010-12-01

59

Children's Views about the Water Cycle.  

ERIC Educational Resources Information Center

Israeli children's (kindergarten to grade nine) explanations about the water cycle are described. Reports the children's views about the source of clouds and the mechanism of rainfall. It was concluded that understanding evaporation is a necessary condition for explaining a mechanism of rain containing the ideas of condensation and heaviness. (YP)

Bar, Varda

1989-01-01

60

Multi-cycle boiling water reactor fuel cycle optimization  

SciTech Connect

In this work a new computer code, BWROPT (Boiling Water Reactor Optimization), is presented. BWROPT uses the Parallel Simulated Annealing (PSA) algorithm to solve the out-of-core optimization problem coupled with an in-core optimization that determines the optimum fuel loading pattern. However it uses a Haling power profile for the depletion instead of optimizing the operating strategy. The result of this optimization is the optimum new fuel inventory and the core loading pattern for the first cycle considered in the optimization. Several changes were made to the optimization algorithm with respect to other nuclear fuel cycle optimization codes that use PSA. Instead of using constant sampling probabilities for the solution perturbation types throughout the optimization as is usually done in PSA optimizations the sampling probabilities are varied to get a better solution and/or decrease runtime. The new fuel types available for use can be sorted into an array based on any number of parameters so that each parameter can be incremented or decremented, which allows for more precise fuel type selection compared to random sampling. Also, the results are sorted by the new fuel inventory of the first cycle for ease of comparing alternative solutions. (authors)

Ottinger, K.; Maldonado, G.I. [University of Tennessee, 311 Pasqua Engineering Building, Knoxville, TN 37996-2300 (United States)

2013-07-01

61

Following the Water Cycle to Sustainability  

NASA Astrophysics Data System (ADS)

For scientists, modeling the connections among the parts of complex, dynamic systems is crucial. Doing so lets us understand emergent phenomena such as ecosystem behavior and climate patterns that could not otherwise be predicted. Emergent phenomena can typically only be understood or appreciated when we stand "outside" the system. When scientists take such an outsiders view of earth's systems they can propose many ways that human activities modify the climate system (e.g., increasing or reducing GHG emissions). But what should we do to achieve a sustainable future? Sustainability is an emergent property that arises at the level of the planetary management system, of which the scientific establishment is just a part. We are "insiders" and it is impossible to completely envision the conditions for sustainability or to plan for it. The crises in our atmosphere, biosphere, oceans, and in the natural and energy resource sectors are based in science and do call for urgent changes in science education. But education that focuses solely on science to meet the challenges of sustainability may be as likely to harm humanity's long-term prospects as to improve them. I present activities and teaching strategies that I use in general education classes at West Chester University, a comprehensive institution of roughly 14,000 undergraduates. The overarching concept is to extend "modeling the connections" to the sustainability level and to train students to think outside the system. To make the ideas more accessible, I have the students become sensors at their particular point in the web of connections that constitute the planetary management system. I ask them to evaluate their connection in three domains proposed by John Ehrenfeld (Sustainability by Design, Yale University Press, 2008): sense of place in the natural world; sense of responsibility for our actions, and sense of what it is to be a human being. I have them analyze their sense of connection with reference to a systems learning model based on feedback and limits to perception. I focus on a part of the course that builds on connections that start in the hydrosphere and that includes some basic experiential learning about the water cycle and students' reliance on it. We measure and visualize aspects of the water cycle in nearby areas of campus (designated as an outdoor classroom and demonstration garden). The evapotranspiration flow is used to introduce notions of what can happen when flows are not sensed (e.g., invisible to us). Students use an online water footprint calculator to discover how large their water reliance is, particularly through energy generation, food consumption and food waste; and how far their water reach extends (virtual water trade). They consider the ethical implications of their water use in a world in which it is becoming a more rare resource and in some cases a valued commodity. They learn about non-utilitarian values of water based on an activity on the values of nature. They look at local, community-based efforts to improve water quality and to re-localize water dependence. A reading from Aldo Leopold puts the water cycle in a historical and cultural perspective. The water cycle is strongly interwoven with natural and human energy systems, the climate system, the carbon cycle, nutrient cycles, the rock cycle, and serves as a starting point to reach many other topics.

Lutz, T. M.

2012-12-01

62

The Doe Water Cycle Pilot Study.  

NASA Astrophysics Data System (ADS)

A Department of Energy (DOE) multilaboratory Water Cycle Pilot Study (WCPS) investigated components of the local water budget at the Walnut River watershed in Kansas to study the relative importance of various processes and to determine the feasibility of observational water budget closure. An extensive database of local meteorological time series and land surface characteristics was compiled. Numerical simulations of water budget components were generated and, to the extent possible, validated for three nested domains within the Southern Great Plains-the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Cloud Atmospheric Radiation Testbed (CART), the Walnut River watershed (WRW), and the Whitewater watershed (WW), in Kansas.A 2-month intensive observation period (IOP) was conducted to gather extensive observations relevant to specific details of the water budget, including finescale precipitation, streamflow, and soil moisture measurements that were not made routinely by other programs. Event and seasonal water isotope (d18O, dD) sampling in rainwater, streams, soils, lakes, and wells provided a means of tracing sources and sinks within and external to the WW, WRW, and the ARM CART domains. The WCPS measured changes in the leaf area index for several vegetation types, deep groundwater variations at two wells, and meteorological variables at a number of sites in the WRW. Additional activities of the WCPS include code development toward a regional climate model that includes water isotope processes, soil moisture transect measurements, and water-level measurements in groundwater wells.

Miller, N. L.; King, A. W.; Miller, M. A.; Springer, E. P.; Wesely, M. L.; Bashford, K. E.; Conrad, M. E.; Costigan, K.; Foster, P. N.; Gibbs, H. K.; Jin, J.; Klazura, J.; Lesht, B. M.; Machavaram, M. V.; Pan, F.; Song, J.; Troyan, D.; Washington-Allen, R. A.

2005-03-01

63

EDITORIAL: The global atmospheric water cycle  

NASA Astrophysics Data System (ADS)

Water vapour plays a key role in the Earth's energy balance. Almost 50% of the absorbed solar radiation at the surface is used to cool the surface, through evaporation, and warm the atmosphere, through release of latent heat. Latent heat is the single largest factor in warming the atmosphere and in transporting heat from low to high latitudes. Water vapour is also the dominant greenhouse gas and contributes to a warming of the climate system by some 24°C (Kondratev 1972). However, water vapour is a passive component in the troposphere as it is uniquely determined by temperature and should therefore be seen as a part of the climate feedback system. In this short overview, we will first describe the water on planet Earth and the role of the hydrological cycle: the way water vapour is transported between oceans and continents and the return of water via rivers to the oceans. Generally water vapour is well observed and analysed; however, there are considerable obstacles to observing precipitation, in particular over the oceans. The response of the hydrological cycle to global warming is far reaching. Because different physical processes control the change in water vapour and evaporation/precipitation, this leads to a more extreme distribution of precipitation making, in general, wet areas wetter and dry areas dryer. Another consequence is a transition towards more intense precipitation. It is to be expected that the changes in the hydrological cycle as a consequence of climate warming may be more severe that the temperature changes. Water on planet Earth The total amount of available water on the Earth amounts to some 1.5 x 109 km3. The dominant part of this, 1.4 x 109 km3, resides in the oceans. About 29 x 106 km3 are locked up in land ice and glaciers and some 15 x 106 km3 are estimated to exist as groundwater. If all land ice and glaciers were to melt the sea level would rise some 80 m (Baumgartner and Reichel 1975). 13 x 103 km3 of water vapour are found in the atmosphere corresponding to a global average of 26 kg m-2 or 26 mm m-2 of water for each column of air on the surface of the Earth. There are large geographical differences such as between low and high latitudes. Figure 1 shows an estimate of the global water exchange between ocean and land, an annual average in units of 103 km3 (Baumgartner and Reichel 1975). An updated version can be found in Trenberth et al 2007 (their figure 1) showing broadly similar results. There is a net transport of some 38 units from ocean to land with about the same amount returning by the rivers to the ocean. However the amount of precipitation over the continents is almost three times as high, indicating a considerable recirculation of water over land. As shown by Trenberth et al (2007) the recirculation has a marked annual cycle as well as having large variations between continents. The recirculation is larger during the summer and for tropical land areas. The hydrological cycle of the world's oceans interacts differently with that of the continents. Most of the water from the Pacific Ocean recirculates between different parts of the Pacific itself, as and there is little net transport towards land. The pattern of water exchange between ocean and land is different in the Atlantic and Indian Oceans. Two thirds of the total net transport of water towards the continents comes from the Atlantic Ocean, with the rest essentially from the Indian Ocean. Most of the continental water for North and South America, Europe and Africa emanates from the Atlantic and is also returned to the Atlantic by the rivers. Figure 1 Figure 1. The global water cycle following Baumgartner and Reichel (1975). Annual values are in units of 103 km3 year-1. There is widespread evaporation (maximum some 2 m year-1) on each side of the inter-tropical convergence zone (ITCZ), transporting water vapour into the ITCZ and into the storm tracks of high latitudes. Conversely, in regions of net evaporation ocean salinity is increasing, leading to increased ocean vertical mixing. In the ITCZ and in the extra-tropical storm

Bengtsson, Lennart

2010-06-01

64

Structural and oxidation state changes of the photosystem II manganese complex in four transitions of the water oxidation cycle (S0 --> S1, S1 --> S2, S2 --> S3, and S3,4 --> S0) characterized by X-ray absorption spectroscopy at 20 K and room temperature.  

PubMed

Structural and electronic changes (oxidation states) of the Mn(4)Ca complex of photosystem II (PSII) in the water oxidation cycle are of prime interest. For all four transitions between semistable S-states (S(0) --> S(1), S(1) --> S(2), S(2) --> S(3), and S(3),(4) --> S(0)), oxidation state and structural changes of the Mn complex were investigated by X-ray absorption spectroscopy (XAS) not only at 20 K but also at room temperature (RT) where water oxidation is functional. Three distinct experimental approaches were used: (1) illumination-freeze approach (XAS at 20 K), (2) flash-and-rapid-scan approach (RT), and (3) a novel time scan/sampling-XAS method (RT) facilitating particularly direct monitoring of the spectral changes in the S-state cycle. The rate of X-ray photoreduction was quantitatively assessed, and it was thus verified that the Mn ions remained in their initial oxidation state throughout the data collection period (>90%, at 20 K and at RT, for all S-states). Analysis of the complete XANES and EXAFS data sets (20 K and RT data, S(0)-S(3), XANES and EXAFS) obtained by the three approaches leads to the following conclusions. (i) In all S-states, the gross structural and electronic features of the Mn complex are similar at 20 K and room temperature. There are no indications for significant temperature-dependent variations in structure, protonation state, or charge localization. (ii) Mn-centered oxidation likely occurs on each of the three S-state transitions, leading to the S(3) state. (iii) Significant structural changes are coupled to the S(0) --> S(1) and the S(2) --> S(3) transitions which are identified as changes in the Mn-Mn bridging mode. We propose that in the S(2) --> S(3) transition a third Mn-(mu-O)(2)-Mn unit is formed, whereas the S(0) --> S(1) transition involves deprotonation of a mu-hydroxo bridge. In light of these results, the mechanism of accumulation of four oxidation equivalents by the Mn complex and possible implications for formation of the O-O bond are considered. PMID:15697215

Haumann, M; Müller, C; Liebisch, P; Iuzzolino, L; Dittmer, J; Grabolle, M; Neisius, T; Meyer-Klaucke, W; Dau, H

2005-02-15

65

The cycling and oxidation pathways of organic carbon in a shallow estuary along the Texas Gulf Coast  

Microsoft Academic Search

The cycling and oxidation pathways of organic carbon were investigated at a single shallow water estuarine site in Trinity Bay, Texas, the uppermost lobe of Galveston Bay, during November 2000. Radio-isotopes were used to estimate sediment mixing and accumulation rates, and benthic chamber and pore water measurements were used to determine sediment-water exchange fluxes of oxygen, nutrients and metals, and

Kent W. Warnken; Peter H. Santschi; Kimberly A. Roberts; Gary A. Gill

2008-01-01

66

Beyond Weather and the Water Cycle  

NSDL National Science Digital Library

Beyond Weather and the Water Cycle is an online professional development magazine which focuses on preparing elementary teachers to teach climate science concepts while also integrating inquiry-based science and literacy instruction. The project draws on research showing that an integrated approach can improve student achievement in science, as well as in reading comprehension and oral and written discourse abilities. Structured around the seven essential principles of climate literacy, instructional and professional resources will improve elementary teacher understanding of climate science and change through an Earth systems approach and, by doing so, teachers will be able to more effectively prepare our youngest students to study and shape climate policy in the future.

2011-06-30

67

The cycling and oxidation pathways of organic carbon in a shallow estuary along the Texas Gulf Coast  

SciTech Connect

The cycling and oxidation pathways of organic carbon were investigated at a single shallow water estuarine site in Trinity Bay, Texas, the uppermost lobe of Galveston Bay, during November 2000. Radio-isotopes were used to estimate sediment mixing and accumulation rates, and benthic chamber and pore water measurements were used to determine sediment-water exchange fluxes of oxygen, nutrients and metals, and infer carbon oxidation rates.

Warnken, Kent W.; Santschi, Peter H.; Roberts, Kimberly A.; Gill, Gary A.

2007-08-08

68

Thermodynamic Properties of Ammonia–Water Mixtures for Power Cycles  

Microsoft Academic Search

Power cycles with ammonia–water mixtures as working fluids have been shown to reach higher thermal efficiencies than the traditional steam turbine (Rankine) cycle with water as the working fluid. Different correlations for the thermo-dynamic properties of ammonia–water mixtures have been used in studies of ammonia–water mixture cycles described in the literature. Four of these correlations are compared in this paper.

E. Thorin; C. Dejfors; G. Svedberg

1998-01-01

69

Plumbing the Global Carbon Cycle: Integrating Inland Waters into the  

E-print Network

Plumbing the Global Carbon Cycle: Integrating Inland Waters into the Terrestrial Carbon Budget J. J components of the carbon cycle at either global or regional scales. By taking published estimates of gas constructed a budget for the role of inland water ecosystems in the global carbon cycle. Our analysis

Berkowitz, Alan R.

70

Highly efficient 6-stroke engine cycle with water injection  

DOEpatents

A six-stroke engine cycle having improved efficiency. Heat is recovered from the engine combustion gases by using a 6-stroke engine cycle in which combustion gases are partially vented proximate the bottom-dead-center position of the fourth stroke cycle, and water is injected proximate the top-dead-center position of the fourth stroke cycle.

Szybist, James P; Conklin, James C

2012-10-23

71

Improved efficiency in the sulfur dioxide - Iodine hydrogen cycle through the use of magnesium oxide  

NASA Astrophysics Data System (ADS)

The reaction of iodine with dry magnesium oxide and magnesium sulfite hexahydrate was studied experimentally as a possible means of improving the efficiency of the sulfur dioxide-iodine cycle. When no extra water was introduced, the maximum product yield was 67% obtained at 423 K. With excess water vapor, a nonporous plug was formed which prevented complete reaction. In the second case, maximum yield was 62% measured at 423 K showing that added water does not increase reaction products. This reaction gives an alternate route for producing hydrogen from water via the sulfur dioxide-iodine process.

Mason, C. F. V.; Bowman, M. G.

72

Iridium oxide-polymer nanocomposite electrode materials for water oxidation.  

PubMed

Nanocomposite anode materials for water oxidation have been readily synthesized by electrodeposition of iridium oxide nanoparticles into poly(pyrrole-alkylammonium) films, previously deposited onto carbon electrodes by oxidative electropolymerization of a pyrrole-alkylammonium monomer. The nanocomposite films were characterized by electrochemistry, transmission electron microscopy, and atomic force microscopy. They showed an efficient electrocatalytic activity toward the oxygen evolution reaction. Data from Tafel plots have demonstrated that the catalytic activity of the iridium oxide nanoparticles is maintained following their inclusion in the polymer matrix. Bulk electrolysis of water at carbon foam modified electrodes have shown that the iridium oxide-polymer composite presents a higher catalytic activity and a better operational stability than regular oxide films. PMID:25045786

Lattach, Youssef; Rivera, Juan Francisco; Bamine, Tahya; Deronzier, Alain; Moutet, Jean-Claude

2014-08-13

73

Fuel-cycle cost comparisons with oxide and silicide fuels  

SciTech Connect

This paper addresses fuel cycle cost comparisons for a generic 10 MW reactor with HEU aluminide fuel and with LEU oxide and silicide fuels in several fuel element geometries. The intention of this study is to provide a consistent assessment of various design options from a cost point of view. Fuel cycle cost benefits could result if a number of reactors were to utilize fuel elements with the same number or different numbers of the same standard fuel plate. Data are presented to quantify these potential cost benefits. This analysis shows that there are a number of fuel element designs using LEU oxide or silicide fuels that have either the same or lower total fuel cycle costs than the HEU design. Use of these fuels with the uranium densities considered requires that they are successfully demonstrated and licensed.

Matos, J.E.; Freese, K.E.

1982-01-01

74

The Water Cycle and Global Warming  

NSDL National Science Digital Library

The Baylor University College of Medicine continues to work at a furious pace on their delightful BioEd Online site, and educators everywhere love them for their work and dedication. Recently, they placed this ââ¬ÃÂready-to-goââˆlessson on the water cycle and global warming online, and itâ≢s a true delight. As with the other lessons in this series, the materials here include a brief description of the lessonâ≢s objective, along with information on the intended audience, the materials required to complete the lesson, and so on. Teachers will note that they will need to download a slide set, several activity sheets, and a ââ¬ÃÂState of the Climate Reportââˆoffered from the National Climatic Data Center.

75

Regular paper Search for intermediates of photosynthetic water oxidation  

E-print Network

Key words: intermediate, photosynthesis, Photosystem II, S-state, water oxidation Abstract PhotosystemRegular paper Search for intermediates of photosynthetic water oxidation Juergen Clausen & Wolfgang II of cyanobacteria and plants incorporates the catalytic centre of water oxidation. Powered

Junge, Wolfgang

76

Rethinking the light water reactor fuel cycle  

E-print Network

The once through nuclear fuel cycle adopted by the majority of countries with operating commercial power reactors imposes a number of concerns. The radioactive waste created in the once through nuclear fuel cycle has to ...

Shwageraus, Evgeni, 1973-

2004-01-01

77

Supercritical water oxidation of ammonium picrate  

Microsoft Academic Search

This study demonstrates the feasibility of using supercritical water oxidation to destroy ammonium picrate. Analyses of reactor effluent composition at various temperatures, residence times, and oxidant concentrations were used to design an improved reactor configuration for achieving destruction with minimum corrosion. The engineering evaluation reactor, a room-sized laboratory scale reactor, was reconfigured to incorporate this design change. Destruction of ammonium

C. A. LaJeunesse; B. E. Mills; B. G. Brown

1994-01-01

78

A Satellite View of Global Water and Energy Cycling  

NASA Astrophysics Data System (ADS)

The global water cycle describes liquid, solid and vapor water dynamics as it moves through the atmosphere, oceans and land. Life exists because of water, and civilization depends on adapting to the constraints imposed by water availability. The carbon, water and energy cycles are strongly interdependent - energy is moved through evaporation and condensation, and photosynthesis is closely related to transpiration. There are significant knowledge gaps about water storage, fluxes and dynamics - we currently do not really know how much water is stored in snowpacks, groundwater or reservoirs. The view from space offers a vision for water science advancement. This vision includes observation, understanding, and prediction advancements that will improve water management and to inform water-related infrastructure that planning to provide for human needs and to protect the natural environment. The water cycle science challenge is to deploy a series of coordinated earth observation satellites, and to integrate in situ and space-borne observations to quantify the key water-cycle state variables and fluxes. The accompanying societal challenge is to integrate this information along with water cycle physics, and ecosystems and societal considerations as a basis for enlightened water resource management and to protect life and property from effects of water cycle extremes. Better regional to global scale water-cycle observations and predictions need to be readily available to reduce loss of life and property caused by water-related hazards. To this end, the NASA Energy and Water cycle Study (NEWS) has been documenting the satellite view of the water cycle with a goal of enabling improved, observationally based, predictions of water and energy cycle consequences of Earth system variability and change. NEWS has fostered broad interdisciplinary collaborations to study experimental and operational satellite observations and has developed analysis tools for characterizing air/sea fluxes, ocean circulation, atmospheric states, radiative balances, land surface states, sub-surface hydrology, snow and ice. This presentation will feature an overview of recent progress towards this challenge, and lay out the plan for coordination with complementary international efforts.

Houser, P. R.

2012-12-01

79

Presence of Ammonia-oxidizing Archaea and Their Influence on Nitrogen Cycling in Ilica Bay, Turkey  

NASA Astrophysics Data System (ADS)

Recenlty, the processes of anaerobic ammonium oxidation (anammox), and ammonia oxidation within the domain Archaea, have been recognized as two new links in the global nitrogen cycle. The distribution and ubiquity of marine Archaea an important role in global carbon and nitrogen cycling (Ingalls et al., 2006; Leininger et al., 2006; Wuchter et al.,2006a). However, our knowledge on archaeal distribution in aquatic ecosystem was largely confined to the extreme environments for a long time until DeLong (1992, 1998) revealed the ubiquity of archaea in common marine environments. Despite the great progress, more efforts need to be given to the study of archaeal diversity in the vast oceans and of the variations in the ecological environment from coastal to oceanic waters (Massana et al.,2000). Our studying area which Ilica Bay in Izmir (Turkey) has a lot of thermal springs. The aim of study was to investigate the presence of ammonia-oxidizing Archaea and their roles of nitrogen cycling in marine enviroments.We have not only used the geochemical analyses but also genetic tools. This study will supply knowledge for marine nitrogen cycling to understanding very well, in addition how Archea genes players in the process of anammox in shallow coastal marine environments.

Gulecal, Y.; Temel, M.

2011-12-01

80

Homogeneous and heterogenized iridium water oxidation catalysts  

NASA Astrophysics Data System (ADS)

The development of an efficient catalyst for the oxidative splitting of water into molecular oxygen, protons and electrons is of key importance for producing solar fuels through artificial photosynthesis. We are facing the problem by means of a rational approach aimed at understanding how catalytic performance may be optimized by the knowledge of the reaction mechanism of water oxidation and the fate of the catalytic site under the inevitably harsh oxidative conditions. For the purposes of our study we selected iridium water oxidation catalysts, exhibiting remarkable performance (TOF > 5 s-1 and TON > 20000). In particular, we recently focused our attention on [Cp*Ir(N,O)X] (N,O = 2-pyridincarboxylate; X = Cl or NO3) and [IrCl(Hedta)]Na water oxidation catalysts. The former exhibited a remarkable TOF whereas the latter showed a very high TON. Furthermore, [IrCl(Hedta)]Na was heterogenized onto TiO2 taking advantage of the presence of a dandling -COOH functionality. The heterogenized catalyst maintained approximately the same catalytic activity of the homogeneous analogous with the advantage that could be reused many times. Mechanistic studies were performed in order to shed some light on the rate-determining step and the transformation of catalysts when exposed to "oxidative stress". It was found that the last oxidative step, preceding oxygen liberation, is the rate-determining step when a small excess of sacrificial oxidant is used. In addition, several intermediates of the oxidative transformation of the catalyst were intercepted and characterized by NMR, X-Ray diffractometry and ESI-MS.

Macchioni, Alceo

2014-10-01

81

Nanostructured anodic iron oxide film as photoanode for water oxidation  

NASA Astrophysics Data System (ADS)

Two different configurations of photoanodes based on anodic iron oxide were investigated for photoelectrochemical water oxidation. A self-ordered and vertically oriented array of iron oxide nanotubes was obtained by anodization of pure iron substrate in an ethylene glycol based electrolyte containing 0.1M NH4F + 3 vol% water (EGWF solution) at 50 V for 15 min. Annealing of the oxide nanotubes in a hydrogen environment at 500 °C for 1 h resulted in a predominantly hematite phase. The second type of photoanode was obtained by a two-step anodization procedure. This process resulted in a two-layered oxide structure, a top layer of nano-dendrite morphology and a bottom layer of nanoporous morphology. This electrode configuration combined the better photocatalytic properties of the nano-dendritic iron oxide and better electron transportation behaviour of vertically oriented nano-channels. Annealing of these double anodized samples in an acetylene environment at 550 °C for 10 min resulted in a mixture of maghemite and hematite phases. Photocurrent densities of 0.74 mA cm-2 at 0.2 VAg/AgCl and 1.8 mA cm-2 at 0.5 VAg/AgCl were obtained under AM 1.5 illumination in 1M KOH solution. The double anodized samples showed high photoconductivity and more negative flat band potential (-0.8 VAg/AgCl), which are the properties required for promising photoanode materials.

Rangaraju, R. R.; Panday, A.; Raja, K. S.; Misra, M.

2009-07-01

82

Supercritical water oxidation - Microgravity solids separation  

NASA Technical Reports Server (NTRS)

This paper discusses the application of supercritical water oxidation (SCWO) waste treatment and water recycling technology to the problem of waste disposal in-long term manned space missions. As inorganic constituents present in the waste are not soluble in supercritical water, they must be removed from the organic-free supercritical fluid reactor effluent. Supercritical water reactor/solids separator designs capable of removing precipitated solids from the process' supercritical fluid in zero- and low- gravity environments are developed and evaluated. Preliminary experiments are then conducted to test the concepts. Feed materials for the experiments are urine, feces, and wipes with the addition of reverse osmosis brine, the rejected portion of processed hygiene water. The solid properties and their influence on the design of several oxidation-reactor/solids-separator configurations under study are presented.

Killilea, William R.; Hong, Glenn T.; Swallow, Kathleen C.; Thomason, Terry B.

1988-01-01

83

Ceramic coating system or water oxidation environments  

DOEpatents

A process for water oxidation of combustible materials in which during at least a part of the oxidation corrosive material is present and makes contact with at least a portion of the apparatus over a contact area on the apparatus. At least a portion of the contact surface area comprises titanium dioxide coated onto a titanium metal substrate. Such ceramic composites have been found to be highly resistant to environments encountered in the process of supercritical water oxidation. Such environments typically contain greater than 50 mole percent water, together with oxygen, carbon dioxide, and a wide range of acids, bases, and salts. Pressures are typically about 27.5 to about 1000 bar while temperatures range as high as 700.degree. C. The ceramic composites are also resistant to degradation mechanisms caused by thermal stresses.

Hong, Glenn T. (Tewksbury, MA)

1996-01-01

84

The water-oxidation complex in photosynthesis  

SciTech Connect

Studies of the photosynthetic water-oxidation complex of PSII using spectroscopic techniques have characterized not only important structural features, but also changes that occur in oxidation state of the Mn4 cluster and in its internal organization during the accumulation of oxidizing equivalents leading to O2 formation. Combining this spectroscopic information with that from the recently published relatively low-resolution X-ray diffraction studies, we have succeeded in limiting the range of likely cluster arrangements. This evidence strongly supports several options proposed earlier in DeRose et al. [1] and these can be further narrowed using compatibility with EPR data.

VKYachandra@lbl.gov

2003-03-27

85

Earth's Deep Water Cycle as a possible explanation of the Wilson Cycle (Invited)  

NASA Astrophysics Data System (ADS)

It is possible that a fraction of the water usually incorporated in subducting oceanic lithosphere does not escape the subducting slab when it passes through the mantle wedge. This water can then progress into the deeper mantle until it is released and might become part of an upwelling, thus taking part in a deep water cycle. We explore whether such a deep water cycle may be related to the Wilson cycle by investigating a weak, but persistent low S-velocity anomaly in the upper mantle beneath the US east coast. This anomaly sits above the high-velocity lower-mantle S-velocity structure generally interpreted as relatively cool, subducted Farallon lithosphere. We argue that the most likely explanation for the lowered S velocities is an elevated water content, with hydrogen incorporated in defects and oxygen at regular lattice sites in the crystal structure of major mantle minerals olivine, wadsleyite, and ringwoodite. The subducted Farallon lithosphere is a likely source for this water while the lithosphere at the Atlantic-North America margin is a likely recipient of the water. This water may be the vital element needed to allow the margin lithosphere to break and initiate subduction of the Atlantic lithosphere. In a broader geodynamic context we have proposed that a deep water cycle may be responsible for the longevity of plate tectonics in general and the Wilson Cycle in particular. We combine the latest mineral physics data with seismic velocity models to investigate the present feasibility of this idea.

van der Lee, S.; Jacobsen, S. D.; Lou, X.; Chang, Y.; Regenauer-Lieb, K.; Yuen, D. A.

2010-12-01

86

Plans and Activities for NASA's Global Water Cycle Research  

NASA Astrophysics Data System (ADS)

Strictly speaking, the water (or hydrologic) cycle is by definition a global phenomenon. To observe, analyze, characterize, understand, and predict its structure and variations requires a coordinated, global effort of observations as well as global prediction systems which can assimilate and predict key fluxes and quantities. The National Aeronautics and Space Administration (NASA) has the unique capability of space-based experimental and research measurements that observe the Earth's system as well as core modelling activities to exploit these space-based observations for assimilation in diagnostic studies and initialization in weather and climate predictions. A summary of NASA's current water-cycle activities and implementation plans will be presented. Currently, NASA's Global Water and Energy Cycle and Terrestrial Hydrology (formally known as the Land Surface Hydrology) Programs are the key funding sources which support relevant scientific research. These programs not only fund individual scientists, but also support large-scale field missions (for example the Cold Land Processes Experiment, CLPX, and the Soil Moisture Experiment, SMEx) which are critical for calibration/validation of space instruments and retrievals as well as gaining fundamental understanding of local-scale processes which comprise the global system. In addition, a new initiative for Water and Energy cycle Research (WatER) is being formulated which responds to the recent charge of USGCRP and NRC scientific panels calling for focused and prioritized research plans that serve to make significant strides in our understanding and prediction of the global water cycle. Following NASA's unique vocation, the WatER initative sets priorities for science/research support for key observable quantities of the water cycle (precipitation and surface wetness) whose instrument technology is tactable and scientfic end-returns not only benefit water-cycle predictions, but also serve to benefit other critical cross-cutting themes (such as the carbon cycle).

Schlosser, C. A.

2002-05-01

87

Arsenic(III) detection using electrochemical-chemical-chemical redox cycling at bare indium-tin oxide electrodes.  

PubMed

Sensitive As(III) detection in ground water is of great importance for evaluating the quality of drinking water. We report a sensitive electrochemical method for As(III) detection based on electrochemical-chemical-chemical (ECC) redox cycling involving Ru(IV) [an oxidized species of Ru(III)(NH3)5NH2(2+)], As(III), and tris(3-carboxyethyl)phosphine (TCEP). Electrochemical oxidation of Ru(III)(NH3)5NH2(2+) formed from Ru(III)(NH3)6(3+) generates Ru(IV), which quickly oxidizes As(III). This electro-mediated oxidation of As(III) produces As(V), which is reduced back to As(III) by TCEP. Electrochemically generated Ru(IV) then reoxidizes As(III), allowing ECC redox cycling to occur at a high rate on bare indium-tin oxide (ITO) electrodes without modifying the surfaces with electrocatalytic materials. Because most interfering metal ions precipitate in a carbonate buffer, water samples are mixed with carbonate buffers prior to electrochemical measurements, rendering the effects of Cu(+), Cu(2+), Fe(2+), Fe(3+), and Pb(2+) insignificant. The detection limit calculated by ECC redox cycling using a chronocoulogram is 1.2 ?M, much lower than that obtained using only the electro-mediated oxidation of As(III) (90 ?M). PMID:25209319

Jeong, Jinkyo; Das, Jagotamoy; Choi, Moonjung; Jo, Jinkyung; Aziz, Md Abdul; Yang, Haesik

2014-11-21

88

Water in Terrestrial Planets: Always an Oxidant?  

NASA Technical Reports Server (NTRS)

Water is commonly assumed to be an oxidant in many planetary settings. Because it can affect Fe-FeO-Fe2O3 equilibria and thus bulk compositional properties of planets and asteroids, this is an important ingredient to understand. The role of water in two settings will be addressed - magmas, and mantles during accretion - along with the implications for planet growth and evolution.

Righter, K.

2004-01-01

89

Modeling Nitrogen Cycle at the Surface-Subsurface Water Interface  

NASA Astrophysics Data System (ADS)

Anthropogenic activities, primarily food and energy production, have altered the global nitrogen cycle, increasing reactive dissolved inorganic nitrogen, Nr, chiefly ammonium NH4+ and nitrate NO3-, availability in many streams worldwide. Increased Nr promotes biological activity often with negative consequences such as water body eutrophication and emission of nitrous oxide gas, N2O, an important greenhouse gas as a by-product of denitrification. The hyporheic zone may play an important role in processing Nr and returning it to the atmosphere. Here, we present a process-based three-dimensional semi-analytical model, which couples hyporheic hydraulics with biogeochemical reactions and transport equations. Transport is solved by means of particle tracking with negligible local dispersion and biogeochemical reactions modeled by linearized Monod's kinetics with temperature dependant reaction rate coefficients. Comparison of measured and predicted N2O emissions from 7 natural stream shows a good match. We apply our model to gravel bed rivers with alternate bar morphology to investigate the role of hyporheic hydraulic, depth of alluvium, relative availability of stream concentration of NO3- and NH4+ and water temperature on nitrogen gradients within the sediment. Our model shows complex concentration dynamics, which depend on hyporheic residence time distribution and consequently on streambed morphology, within the hyporheic zone. Nitrogen gas emissions from the hyporheic zone increase with alluvium depth in large low-gradient streams but not in small steep streams. On the other hand, hyporheic water temperature influences nitrification/denitrification processes mainly in small-steep than large low-gradient streams, because of the long residence times, which offset the slow reaction rates induced by low temperatures in the latter stream. The overall conclusion of our analysis is that river morphology has a major impact on biogeochemical processes such as nitrification and denitrification with a direct impact on the stream nutrient removal and transport.

Marzadri, A.; Tonina, D.; Bellin, A.

2011-12-01

90

Oxidative treatment of pharmaceuticals in water  

Microsoft Academic Search

Environmentally relevant pharmaceuticals were chosen according to human consumption and occurrence in the aquatic environment like sewage plant effluents, rivers and groundwater to investigate their behavior during oxidative water treatment. Derived from data compilation in literature the lipid lowering agent clofibric acid and the analgesic agents ibuprofen and diclofenac were selected. Analyses of the acidic compounds were carried out after

C. Zwiener; F. H. Frimmel

2000-01-01

91

Supercritical water oxidation: An engineering update  

Microsoft Academic Search

This paper reviews the need for innovative treatment technologies and describes a wastewater treatment system capable of completely destroying toxic organic substances and biological sludges. The basic concepts of supercritical water oxidation (SCWO), associated engineering research, and technology development are examined. During the last few years a growing body of SCWO knowledge has been assembled. A number of universities, federal

E. F. Gloyna; Lixiong Li

1993-01-01

92

A Porphyrin-Stabilized Iridium Oxide Water Oxidation Catalyst  

SciTech Connect

Colloidal solutions of iridium oxide hydrate (IrO{sub 2}·NH{sub 2}O) were formed using porphyrin stabilizers bearing malonate-like functional groups at each of the four meso positions of the porphyrin ring. Cyclic voltammetry and monitoring of solution oxygen concentrations under constant applied potential demonstrated the electrochemical catalytic activity of the porphyrin–IrO{sub 2}·NH{sub 2}O complexes for the oxidation of water to oxygen. Quenching of the porphyrin fluorescence in the complex implies strong interaction between the porphyrin and the IrO{sub 2}·NH{sub 2}O. These results mark a step toward developing a porphyrin-based photoanode for use in a photoelectrochemical water-splitting cell.

Sherman, Ben; Pillai, Smitha; Kodis, Gerdenis; Bergkamp, Jesse; Mallouk, Thomas E.; Gust, Devens; Moore, Thomas A.; Moore, Ana L.

2011-01-01

93

Massive swings in the marine N cycle during the Great Oxidation Event  

NASA Astrophysics Data System (ADS)

Nitrogen isotope values preserved in sedimentary organic matter show a general increase sometime between 2.5 and 2.1 Ga (e.g., Beaumont and Robert, 1999), coincident with the initial rise of O2 in the Earth's atmosphere (the Great Oxidation Event; Holland, 2002). This shift is commonly interpreted to represent a major change in the global N cycle related to oxygenation of Earth's surficial environments. Despite the invoked connection between ?15N values and the GOE, high resolution studies of N isotopes across this critical time interval are lacking. Here we present ?15N data for kerogens from the ~2.32 Ga Rooihoogte and Timeball Hill formations, South Africa. These sediments were deposited during the GOE, when the disappearance of S-isotope mass-independent fractionation first indicates O2 levels consistently greater than 10-5 times present atmospheric level (e.g., Bekker et al., 2004). We interpret these data in the context of paleoredox indicators for ocean chemistry (Fe speciation analysis), further allowing us to explore changes in the N cycle under evolving environmental conditions. Our data show unusually 15N-depleted values (down to -13‰) at the bottom of the stratigraphic succession, in sediments deposited under a water column with dynamic redox conditions that fluctuated between oxic, ferruginous, and sulfidic states (possibly related to a shifting chemocline). The ?15N values increase dramatically (up to +14‰) across the boundary between the Rooihoogte and Timeball Hill formations, before settling to near modern values (+6‰) in sediments that were deposited under persistently oxygenated waters. We suggest that this record reflects the permanent onset of the oxidative N cycle (nitrification), which would have produced sufficient oxidized N compounds to establish denitrification and anammox as the dominant controls on ?15N values of marine organic matter. We also estimate the N fluxes required to produce this record using a global marine nitrogen cycle model.

Zerkle, A.; Poulton, S.; Newton, R.; Claire, M.; Bekker, A.

2012-12-01

94

EDITORIAL: The global atmospheric water cycle  

Microsoft Academic Search

Water vapour plays a key role in the Earth's energy balance. Almost 50% of the absorbed solar radiation at the surface is used to cool the surface, through evaporation, and warm the atmosphere, through release of latent heat. Latent heat is the single largest factor in warming the atmosphere and in transporting heat from low to high latitudes. Water vapour

Lennart Bengtsson

2010-01-01

95

Carbon footprint estimation of municipal water cycle  

Microsoft Academic Search

This research investigates the embodied energy associated with water use. A geographic information system (GIS) was tested using data from Loudoun County, Virginia. The objective of this study is to estimate the embodied energy and carbon emission levels associated with water service at a geographical location and to improve for sustainability planning. Factors that affect the carbon footprint were investigated

Ali A. Bakhshi

2009-01-01

96

The Water Cycle: Snowmelt Runoff to Streams  

NSDL National Science Digital Library

This site describes how snow and ice runoff become surface water and emphasizes how runoff from snowmelt is a major component of the global movement of water. A hydrograph from the U.S. Geological Survey shows a four-year time series of streamflow and illustrates how runoff from snowmelt affects the daily mean values, particularly at certain times of the year.

97

Toward a hydro-political water cycle: virtual water,hydrology and international political economy  

NASA Astrophysics Data System (ADS)

At the light of global food trade, no water cycle can be considered "closed" under a political point of view. While the hydrological cycle is a circular closed environment, if we open up our perspectives to social sciences, we will demonstrate how, thanks to virtual water, it is today possible to elaborate how much water 'enters or leave' any water body under the form crop-export, in terms of " water used for the production of agri-food products'. This new 'hydro-political cycle' will be discussed at the light of different theoretical perspectives: food trade theories, hydrology, international water law, socio-economic metabolism, material flow analysis.

Greco, Francesca

2014-05-01

98

Detecting oxidized contaminants in water using sulfur-oxidizing bacteria.  

PubMed

For the rapid and reliable detection of oxidized contaminants (i.e., nitrite, nitrate, perchlorate, dichromate) in water, a novel toxicity detection methodology based on sulfur-oxidizing bacteria (SOB) has been developed. The methodology exploits the ability of SOB to oxidize elemental sulfur to sulfuric acid in the presence of oxygen. The reaction results in an increase in electrical conductivity (EC) and a decrease in pH. When oxidized contaminants were added to the system, the effluent EC decreased and the pH increased due to the inhibition of the SOB. We found that the system can detect these contaminants in the 5-50 ppb range (in the case of NO(3)(-), 10 ppm was detected), which is lower than many whole-cell biosensors to date. At low pH, the oxidized contaminants are mostly in their acid or nonpolar, protonated form which act as uncouplers and make the SOB biosensor more sensitive than other whole-cell biosensors which operate at higher pH values where the contaminants exist as dissociated anions. The SOB biosensor can detect toxicity on the order of minutes to hours which can serve as an early warning so as to not pollute the environment and affect public health. PMID:21417357

Van Ginkel, Steven W; Hassan, Sedky H A; Ok, Yong Sik; Yang, Jae E; Kim, Yong-Seong; Oh, Sang-Eun

2011-04-15

99

Method of removing oxidized contaminants from water  

DOEpatents

The present invention is a method for removing oxidized contaminant(s) from water. More specifically, the invention has the steps of contacting water containing the oxidized contaminant(s) with a layered aluminosilicate having Fe(II). The aluminosilicate may contain naturally occurring Fe(II), or the Fe(II) may be produced by reducing Fe(III) that is initially present. Reduction may be either by exposure to a chemical or biological reductant. Contacting the water containing oxidized contaminant(s) may be by (1) injection of Fe(II)-containing layered aluminosilicate, via a well, into a saturated zone where it is likely to intercept the contaminated water; (2) injection of contaminated water into a vessel containing the Fe(II)-bearing layered aluminosilicate; and (3) first reducing Fe(III) in the layered aluminosilicate to Fe(II) by injection of a biological or chemical reductant, into an aquifer or vessel having sufficient Fe(III)-bearing aluminosilicate to produce the necessary Fe(II).

Amonette, James E. (Richland, WA); Fruchter, Jonathan S. (Richland, WA); Gorby, Yuri A. (Richland, WA); Cole, Charles R. (West Richmond, WA); Cantrell, Kirk J. (West Richmond, WA); Kaplan, Daniel I. (Richland, WA)

1998-01-01

100

Method of removing oxidized contaminants from water  

DOEpatents

The present invention is a method for removing oxidized contaminant(s) from water. More specifically, the invention has the steps of contacting water containing the oxidized contaminant(s) with a layered aluminosilicate having Fe(II). The aluminosilicate may contain naturally occurring Fe(II), or the Fe(II) may be produced by reducing Fe(III) that is initially present. Reduction may be either by exposure to a chemical or biological reductant. Contacting the water containing oxidized contaminant(s) may be by (1) injection of Fe(II)-containing layered aluminosilicate, via a well, into a saturated zone where it is likely to intercept the contaminated water; (2) injection of contaminated water into a vessel containing the Fe(II)-bearing layered aluminosilicate; and (3) first reducing Fe(III) in the layered aluminosilicate to Fe(II) by injection of a biological or chemical reductant, into an aquifer or vessel having sufficient Fe(III)-bearing aluminosilicate to produce the necessary Fe(II). 8 figs.

Amonette, J.E.; Fruchter, J.S.; Gorby, Y.A.; Cole, C.R.; Cantrell, K.J.; Kaplan, D.I.

1998-07-21

101

New Mars Water Cycle Simulations Constrained by Laboratory Microphysical Results  

NASA Astrophysics Data System (ADS)

Water ice clouds have an important role within the martian climate. While these clouds in general contain much less water mass and are optically thinner than their terrestrial counterparts, the thin martian atmosphere is very susceptible to their radiative effects. Furthermore, water ice clouds have a critical role in moderating the atmospheric transport of water vapor (via sedimentation of cloud particles) and dust (via scavenging of dust as cloud nuclei). Understanding the current climate of Mars and its water cycle requires a thorough understanding of martian water ice clouds. The microphysical processes that govern their formation and growth largely determine the effective role of water ice clouds. However, in most studies of martian water ice clouds these microphysics have been either neglected or greatly simplified. In those models that do attempt a more detailed treatment of cloud growth, the implementation of the critical parameters most important to martian clouds, namely the critical supersaturation, contact parameter and growth rate, is still handicapped by having only terrestrial analogs and data sets from which to derive constraints. The work presented here utilizes new laboratory measurements of cloud formation and growth in martian conditions to constrain a sophisticated hybrid-moment cloud model incorporated into the NASA Ames GCM. Significant differences are seen between water cycle predictions using traditional assumptions to those using the new cloud model and laboratory constraints. These differences, including changes in total water vapor and cloud column amount and surface frost distribution and seasonality, and the implication to water cycle processes and observations will be discussed.

Colaprete, A.; Iraci, L. T.; Phebus, B. D.

2007-12-01

102

What Goes Around Comes Around: Water Cycle  

NSDL National Science Digital Library

This resource guide from the Middle School Portal 2 project, written specifically for teachers, provides links to exemplary resources including background information, lessons, career information, and related national science education standards. The resources here will provide you with content information as well as lessons and activities to guide your students to deeper understandings of the nature of water, the need for and intricacies of its management, and why water management issues can be difficult and emotional.

Lefever, Mary

2007-07-01

103

Economics of nuclear fuel cycles : option valuation and neutronics simulation of mixed oxide fuels  

E-print Network

In most studies aiming at the economic assessment of nuclear fuel cycles, a primary concern is to keep scenarios economically comparable. For Uranium Oxide (UOX) and Mixed Oxide (MOX) fuels, a traditional way to achieve ...

De Roo, Guillaume

2009-01-01

104

Supercritical water oxidation of ammonium picrate  

SciTech Connect

This study demonstrates the feasibility of using supercritical water oxidation to destroy ammonium picrate. Analyses of reactor effluent composition at various temperatures, residence times, and oxidant concentrations were used to design an improved reactor configuration for achieving destruction with minimum corrosion. The engineering evaluation reactor, a room-sized laboratory scale reactor, was reconfigured to incorporate this design change. Destruction of ammonium picrate with minimized corrosion was demonstrated on this reconfigured reactor. Factors that must be considered in scaling up to pilot plant size are discussed.

LaJeunesse, C.A.; Mills, B.E.; Brown, B.G.

1994-11-01

105

Super critical water oxidation on energetic materials  

SciTech Connect

Supercritical water oxidation (SCWO) is an innovative process for the destruction of hazardous wastes that occurs above the critical temperature and pressure of water. In this paper we present results for the oxidation of simple organic wastes and the destruction of explosives. We have tested a 50 gal./day mobile tubular reactor using both acetone and hexane as surrogate aqueous wastes in reaction with excess oxygen. For acetone, our results indicate that the fuel and oxidant can be conveniently premixed before heating and the acetone effectively destroyed (>99.999%). By contrast, hexane, and likely other insoluble flammable organics must be separately preheated to above the critical temperature of water to avoid detonation. With regards to the treatment of explosives, we have demonstrated detection-sensitivity-limited destruction (typically >99.9%) of five explosives, HMX, RDX, TNT, NQ, and PETN, in a smaller scale SCWO reactor. Two alternative methods of increasing processing throughput for explosives, which have very low solubility in water at room temperature, were also investigated. They are the use of slurries and the SCWO postprocessing of the products of explosives hydrolyzed in low-temperature, basic solutions.

Sanchez, J.A.

1993-01-01

106

Super critical water oxidation on energetic materials  

SciTech Connect

Supercritical water oxidation (SCWO) is an innovative process for the destruction of hazardous wastes that occurs above the critical temperature and pressure of water. In this paper we present results for the oxidation of simple organic wastes and the destruction of explosives. We have tested a 50 gal./day mobile tubular reactor using both acetone and hexane as surrogate aqueous wastes in reaction with excess oxygen. For acetone, our results indicate that the fuel and oxidant can be conveniently premixed before heating and the acetone effectively destroyed (>99.999%). By contrast, hexane, and likely other insoluble flammable organics must be separately preheated to above the critical temperature of water to avoid detonation. With regards to the treatment of explosives, we have demonstrated detection-sensitivity-limited destruction (typically >99.9%) of five explosives, HMX, RDX, TNT, NQ, and PETN, in a smaller scale SCWO reactor. Two alternative methods of increasing processing throughput for explosives, which have very low solubility in water at room temperature, were also investigated. They are the use of slurries and the SCWO postprocessing of the products of explosives hydrolyzed in low-temperature, basic solutions.

Sanchez, J.A.

1993-04-01

107

Seasonal cycles of mitochondrial ADP sensitivity and oxidative capacities in trout oxidative muscle.  

PubMed

Mitochondria from red myotomal muscle of rainbow trout, Oncorhynchus mykiss, showed seasonal cycles of their maximal rates of substrate oxidation (nmol.min-1 mg-1 mitochondrial protein) and their apparent ADP affinity (Kmapp), as well as in the thermal sensitivity of these properties. Increases in the maximal capacity of pyruvate oxidation were sufficient to compensate for seasonal changes in temperature, except during the winter months when rates at habitat temperature were depressed relative to other periods. The ADP affinity of isolated mitochondria was highest during cold months. Thus, the Kmapp for ADP at habitat temperature showed less seasonal variation than the ADP Kmapp at a given temperature. A loss in ADP affinity with decreasing temperature occurred through much of the year, and only was definitively suppressed in December and July. Both the ADP affinity and the maximal oxidative capacities of muscle mitochondria seem to be regulated parameters. PMID:10595316

Guderley, H; St Pierre, J

1999-10-01

108

A model for the water-oxidation and recovery systems of the oxygen-evolving complex.  

PubMed

We propose a model for the water-oxidation and recovery systems of the oxygen-evolving complex (OEC) of the photosystem II (PSII) enzyme. The whole system is constructed from two catalytic cycles, conducted as a tandem reaction: (i) a water-oxidation loop uses cerium(IV) ammonium nitrate as an oxidant to activate a dimanganese complex for water-oxidation and thereby liberate a molecule of O2 and (ii) a recovery loop begins with photoinhibition of the dimanganese complex but then uses O2 to reactivate the manganese centre. The net result is a catalytic water-oxidation catalyst that can use self-generated O2 for recovery. PMID:24323354

Yatabe, Takeshi; Kikkawa, Mitsuhiro; Matsumoto, Takahiro; Nakai, Hidetaka; Kaneko, Kenji; Ogo, Seiji

2014-02-28

109

Emerging Contaminants in the Drinking Water Cycle.  

EPA Science Inventory

In the past decade, the scientific community and general public have become increasingly aware of the potential for the presence of unregulated, and generally unmonitored contaminants, found at low concentrations (sub-¿g/L) in surface, ground and drinking water. The most common...

110

Emerging Contaminants in the Drinking Water Cycle  

EPA Science Inventory

In the past decade, the scientific community and general public have become increasingly aware of the potential for the presence of unregulated, and generally unmonitored contaminants, found at low concentrations (sub-µg/L) in surface, ground and drinking water. The most common...

111

Greenlighting photoelectrochemical oxidation of water by iron oxide.  

PubMed

Hematite (?-Fe2O3) is one of just a few candidate electrode materials that possess all of the following photocatalyst-essential properties for scalable application to water oxidation: excellent stability, earth-abundance, suitability positive valence-band-edge energy, and significant visible light absorptivity. Despite these merits, hematite's modest oxygen evolution reaction kinetics and its poor efficiency in delivering photogenerated holes, especially holes generated by green photons, to the electrode/solution interface, render it ineffective as a practical water-splitting catalyst. Here we show that hole delivery and catalytic utilization can be substantially improved through Ti alloying, provided that the alloyed material is present in ultrathin-thin-film form. Notably, the effects are most pronounced for charges photogenerated by photons with energy comparable to the band gap for excitation of Fe(3d) ? Fe(3d) transitions (i.e., green photons). Additionally, at the optimum Ti substitution level the lifetimes of surface-localized holes, competent for water oxidation, are extended. Together these changes explain an overall improvement in photoelectrochemical performance, especially enhanced internal quantum efficiencies, observed upon Ti(IV) incorporation. PMID:25414974

Kim, Dong Wook; Riha, Shannon C; DeMarco, Erica J; Martinson, Alex B F; Farha, Omar K; Hupp, Joseph T

2014-12-23

112

Electrolysis of water on (oxidized) metal surfaces  

NASA Astrophysics Data System (ADS)

Density functional theory calculations are used as the basis for an analysis of the electrochemical process, where by water is split to form molecular oxygen and hydrogen. We develop a method for obtaining the thermochemistry of the electrochemical water splitting process as a function of the bias directly from the electronic structure calculations. We consider electrodes of Pt(1 1 1) and Au(1 1 1) in detail and then discuss trends for a series of different metals. We show that the difficult step in the water splitting process is the formation of superoxy-type (OOH) species on the surface by the splitting of a water molecule on top an adsorbed oxygen atom. One conclusion is that this is only possible on metal surfaces that are (partly) oxidized. We show that the binding energies of the different intermediates are linearly correlated for a number of metals. In a simple analysis, where the linear relations are assumed to be obeyed exactly, this leads to a universal relationship between the catalytic rate and the oxygen binding energy. Finally, we conclude that for systems obeying these relations, there is a limit to how good a water splitting catalyst an oxidized metal surface can become.

Rossmeisl, J.; Logadottir, A.; Nørskov, J. K.

2005-12-01

113

Water oxidation chemistry of photosystem II.  

PubMed Central

The O(2)-evolving complex of photosystem II catalyses the light-driven four-electron oxidation of water to dioxygen in photosynthesis. In this article, the steps leading to photosynthetic O(2) evolution are discussed. Emphasis is given to the proton-coupled electron-transfer steps involved in oxidation of the manganese cluster by oxidized tyrosine Z (Y(*)(Z)), the function of Ca(2+) and the mechanism by which water is activated for formation of an O-O bond. Based on a consideration of the biophysical studies of photosystem II and inorganic manganese model chemistry, a mechanism for photosynthetic O(2) evolution is presented in which the O-O bond-forming step occurs via nucleophilic attack on an electron-deficient Mn(V)=O species by a calcium-bound water molecule. The proposed mechanism includes specific roles for the tetranuclear manganese cluster, calcium, chloride, Y(Z) and His190 of the D1 polypeptide. Recent studies of the ion selectivity of the calcium site in the O(2)-evolving complex and of a functional inorganic manganese model system that test key aspects of this mechanism are also discussed. PMID:12437878

Vrettos, John S; Brudvig, Gary W

2002-01-01

114

Water oxidation reaction in natural and artificial photosynthetic systems  

SciTech Connect

Understanding the structure and mechanism of water oxidation catalysts is an essential component for developing artificial photosynthetic devices. In the natural water oxidation catalyst, the geometric and electronic structure of its inorganic core, the Mn{sub 4}CaO{sub 5} cluster, has been studied by spectroscopic and diffraction measurements. In inorganic systems, metal oxides seem to be good candidates for water oxidation catalysts. Understanding the reaction mechanism in both natural and oxide-based catalysts will helpin further developing efficient and robust water oxidation catalysts.

Yano, Junko; Yachandra, Vittal [Physical Biosciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720 (United States)

2013-12-10

115

The Global Water Cycle Geochemistry, and Environment  

NASA Astrophysics Data System (ADS)

In the preface the authors state, as reasons for producing this book, the need for an appropriate undergraduate-level text on water chemistry and the desire to provide broader coverage of atmospheric and environmental chemistry than is found in other existing books on this topic. They have attempted to write a book that could be understood by almost anyone with an elementarv knowledge of science, yet could still serve as a source of geochemical and environmental data for researchers in a variety of fields. The authors have succeeded admirably in achieving these difficult goals.

Bricker, Owen P.

116

Whole life cycle of femtosecond ultraviolet filaments in water  

NASA Astrophysics Data System (ADS)

We present measurements fully characterizing the whole life cycle of femtosecond pulses undergoing filamentation in water at 400 nm. The complete pulse dynamics is monitored by means of a four-dimensional mapping technique for the intensity distribution I (x,y,z,t) during the nonlinear interaction. Measured events (focusing or defocusing cycles, pulse splitting and replenishment, supercontinuum generation, conical emission, nonlinear absorption peaks) are mutually connected.The filament evolution from laser energy deposition in water, which is of paramount importance for a wide range of technological and medical applications, is interpreted in light of simulation results.

Jarnac, Amélie; Tamosauskas, Gintaras; Majus, Donatas; Houard, Aurélien; Mysyrowicz, André; Couairon, Arnaud; Dubietis, Audrius

2014-03-01

117

Nature and Stability of the Martian Seasonal Water Cycle  

NASA Astrophysics Data System (ADS)

Which components control the contemporary water cycle and what is the nature of the control mechanisms? These questions are at the heart of understanding how the Martian exchangeable water budget adjusts to perturbations and changes in the climate system. Analysis of a water cycle model embedded in the GFDL Mars GCM provides a paradigm for the water cycle as a feedback system, providing information on the important control points and response times. Much information on this system derives from monitoring the evolution towards steady state--one that resembles the observed water vapour and ice cloud distributions. The most important exchange balance in the system is that between the northern polar atmosphere and the rest of the planet. As the major net source for water, the northern residual water ice cap is active during summer, in the window of time between the sublimation and recondensation of the seasonal CO2 cap. At this time, water is exported from the northern polar atmosphere at a rate determined by the mixing capacity of the atmosphere and the amount of water held in the polar atmosphere. The latter is determined by the cap surface temperature. During the remainder of the year, water is returned to the pole. This return flux is determined by the atmospheric mixing capacity and the amount of water vapour held in the tropical and winter extratropical atmosphere. Steady-state is achieved when these fluxes balance. For a given climate state (and a roughly repeatable annual cycle of mixing), the outflux and influx of polar water are controlled by separate variables. Holding the cap temperature constant, the outflux will remain constant. Any perturbation to the global water budget will result in a change in the return flux that tends to oppose the sense of the perturbation--the perturbation will be damped. In the same way, a change in cap temperature (e.g. associated with a change in albedo) will result in changed water outflow. Again, this will tend to change the non-polar water vapour budget and hence the polar water influx so as to develop a new steady-state. It is important to note that only in this case is the steady-state global humidity changed: a given cap temperature and seasonal cycle of mixing capacity specifies a bulk steady-state atmospheric humidity. In all cases, the regolith acts as a damper on the system and adjusts to the global water distribution dictated ultimately by the northern cap. The model also suggests fast adjustment times, on order decades. A number of factors can affect atmospheric mixing capacity. As climate forcing factors change (associated with obliquity or greenhouse gas loading) the mixing capacity will change--an area for future study. The current mixing capacity of the atmosphere is also different from one that would obtain without atmospheric water condensation and sedimentation. Model clouds play important roles in returning water to the residual ice cap in northern summer, and significantly altering interhemispheric transport from that which would occur without clouds. As with previous studies, the southern polar cap acts as a permanent sink for water. The model and resulting paradigm for the water cycle can be used in very preliminary studies of past climate states. Forcing the model with an obliquity of 45 deg., the seasonal water ice caps become significantly more extended, reaching into the summer hemisphere. In fact, the seasonal caps "overlap" in the northern tropics, generating a year-round surface ice belt. Much work remains to be done in understanding water ice transport and exchange processes before models of paleoclimate can be of widespread utility--of which analysis of data from MGS and future missions will be key.

Richardson, M. I.; Wilson, R. J.

2001-12-01

118

DIURNAL CYCLE OF PRECIPITABLE WATER VAPOR OVER SPAIN  

SciTech Connect

Despite the importance of the diurnal cycle of precipitable water vapor (PWV), its knowledge is very limited due to the lack of data with sufficient temporal resolution. Currently, from GPS receivers, PWV can be obtained with high temporal resolution in all weather conditions for all hours of the day. In this study we have calculated the diurnal cycle of PWV for ten GPS stations over Spain. The minimum value is reached approximately at the same time at all the stations, ~0400-0500 UTC, whereas the maximum is reached in the second half of the day, but with a larger dispersion of its occurrence between stations. The amplitude of the cycle ranges between 0.72 mm and 1.78 mm. The highest values are recorded at the stations on the Mediterranean coast, with a doubling of the values of the stations on the Atlantic coast or inland. The amplitude of the PWV cycle, relative to the annual mean value, ranges between 8.8 % on the Mediterranean coast and 3.6 % on the Atlantic coast. Two distinctly different seasonal diurnal cycles have been identified, one in winter and other in summer, with spring and autumn being only transition states. The winter cycle is quite similar at all locations, whereas in summer, local effects are felt strongly, making the diurnal cycle quite different between stations. The amplitude of the summer cycle is 1.69 mm, it is almost double the winter one (0.93 mm). Analogous to the annual cycles, the seasonal cycles of the different stations are more similar during the night and early morning hours than during the afternoon. The observed features of the PWV diurnal cycle are explained in a qualitative way on the basis of the air temperature, the transport of moisture by local winds, and the turbulent vertical mixing.

Ortiz de Galisteo, J. P.; Cachorro, V. E.; Toledano, C.; Torres, B.; Laulainen, Nels S.; Bennouna, Yasmine; de Frutos, A. M.

2011-05-20

119

Anaerobic Ammonium Oxidation (Anammox) A new sink in the marine nitrogen cycle  

E-print Network

Term paper Anaerobic Ammonium Oxidation (Anammox) ­ A new sink in the marine nitrogen cycle. By finding a new key process in the marine nitrogen cycle the question arises how important it is in a global be discussed. By looking at the "new" marine nitrogen cycle we are developing the foundation for discussing

Fischlin, Andreas

120

Black Carbon in the Soil Carbon Cycle: Is it an Oxidation Resistant End-Product?  

E-print Network

Black Carbon in the Soil Carbon Cycle: Is it an Oxidation Resistant End-Product? Simone;1 Introduction Soils represent a large carbon pool in the global carbon cycle. Estimates suggest that this pool is twice as large as the atmospheric pool. But its role in the global carbon cycle remains unclear

Fischlin, Andreas

121

A Seamless Framework for Global Water Cycle Monitoring and Prediction  

NASA Astrophysics Data System (ADS)

The Global Earth Observation System of Systems (GEOSS) Water Strategy ('From Observations to Decisions') recognizes that 'water is essential for ensuring food and energy security, for facilitating poverty reduction and health security, and for the maintenance of ecosystems and biodiversity', and that water cycle data and observations are critical for improved water management and water security - especially in less developed regions. The GEOSS Water Strategy has articulated a number of goals for improved water management, including flood and drought preparedness, that include: (i) facilitating the use of Earth Observations for water cycle observations; (ii) facilitating the acquisition, processing, and distribution of data products needed for effective management; (iii) providing expertise, information systems, and datasets to the global, regional, and national water communities. There are several challenges that must be met to advance our capability to provide near real-time water cycle monitoring, early warning of hydrological hazards (floods and droughts) and risk assessment under climate change, regionally and globally. Current approaches to monitoring and predicting hydrological hazards are limited in many parts of the world, and especially in developing countries where national capacity is limited and monitoring networks are inadequate. This presentation describes the development of a seamless monitoring and prediction framework at all time scales that allows for consistent assessment of water variability from historic to current conditions, and from seasonal and decadal predictions to climate change projections. At the center of the framework is an experimental, global water cycle monitoring and seasonal forecast system that has evolved out of regional and continental systems for the US and Africa. The system is based on land surface hydrological modeling that is driven by satellite remote sensing precipitation to predict current hydrological conditions, flood potential and the state of drought. Seasonal climate model forecasts are downscaled and bias-corrected to drive the land surface model to provide hydrological forecasts and drought products out 6-9 months. The system relies on historic reconstructions of water variability over the 20th century, which forms the background climatology to which current conditions can be assessed. Future changes in water availability and drought risk are quantified based on bias-corrected and downscaled climate model projections that are used to drive the land surface models. For regions with lack of on-the-ground data we are field-testing low-cost environmental sensors and along with new satellite products for terrestrial hydrology and vegetation, integrating these into the system for improved monitoring and prediction. We provide an overview of the system and some examples of real-world applications to flood and drought events, with a focus on Africa.

Sheffield, J.; Wood, E. F.; Chaney, N.; Fisher, C. K.; Caylor, K. K.

2013-12-01

122

PHOTOREACTIONS IN SURFACE WATERS AND THEIR ROLE IN BIOGEOCHEMICAL CYCLES  

EPA Science Inventory

During the past decade significant interest has developed in the influence of photochemical reactions on biogeochemical cycles in surface waters of lakes and the sea. A major portion of recent research on these photoreactions has focused on the colored component of dissolved org...

123

Water defluoridation by aluminium oxide-manganese oxide composite material.  

PubMed

In this study, aluminium oxide-manganese oxide (AOMO) composite material was synthesized, characterized, and tested for fluoride removal in batch experiments. AOMO was prepared from manganese(II) chloride and aluminium hydroxide. The surface area of AOMO was found to be 30.7m2/g and its specific density was determined as 2.78 g/cm3. Detailed investigation of the adsorbent by inductively coupled plasma-optical emission spectrometry, inductively coupled plasma-mass spectrometry, and ion chromatography (for sulphate only) showed that it is composed of Al, Mn, SO4, and Na as major components and Fe, Si, Ca, and Mg as minor components. Thermogravimetric analysis was used to study the thermal behaviour of AOMO. X-ray diffraction analysis showed that the adsorbent is poorly crystalline. The point of zero charge was determined as 9.54. Batch experiments (by varying the proportion of MnO, adsorbent dose, contact time, initial F concentration, and raw water pH) showed that fluoride removal efficiency ofAOMO varied significantly with percentage of MnO with an optimum value of about I11% of manganese oxide in the adsorbent. The optimum dose of the adsorbent was 4 g/L which corresponds to the equilibrium adsorption capacity of 4.8 mg F-/g. Both the removal efficiency and adsorption capacity showed an increasing trend with an increase in initial fluoride concentration of the water. The pH for optimum fluoride removal was found to be in the range between 5 and 7. The adsorption data were analysed using the Freundlich, Langmuir, and Dubinirn-Radushkevich models. The minimum adsorption capacity obtained from the non-linear Freundlich isotherm model was 4.94 mg F-/g and the maximum capacity from the Langmuir isotherm method was 19.2mg F-/g. The experimental data of fluoride adsorption on AOMO fitted well to the Freundlich isotherm model. Kinetic studies showed that the adsorption is well described by a non-linear pseudo-second-order reaction model with an average rate constant of 3.1 x 10(-2) g/min mg. It is concluded that AOMO is a highly promising adsorbent for the removal of excess fluoride from drinking water. PMID:24956783

Alemu, Sheta; Mulugeta, Eyobel; Zewge, Feleke; Chandravanshi, Bhagwan Singh

2014-08-01

124

INTRODUCTION: Anticipated changes in the global atmospheric water cycle  

NASA Astrophysics Data System (ADS)

The atmospheric branch of the water cycle, although containing just a tiny fraction of the Earth's total water reserves, presents a crucial interface between the physical climate (such as large-scale rainfall patterns) and the ecosystems upon which human societies ultimately depend. Because of the central importance of water in the Earth system, the question of how the water cycle is changing, and how it may alter in future as a result of anthropogenic changes, present one of the greatest challenges of this century. The recent Intergovernmental Panel on Climate Change report on Climate Change and Water (Bates et al 2008) highlighted the increasingly strong evidence of change in the global water cycle and associated environmental consequences. It is of critical importance to climate prediction and adaptation strategies that key processes in the atmospheric water cycle are precisely understood and determined, from evaporation at the surface of the ocean, transport by the atmosphere, condensation as cloud and eventual precipitation, and run-off through rivers following interaction with the land surface, sub-surface, ice, snow and vegetation. The purpose of this special focus issue of Environmental Research Letters on anticipated changes in the global atmospheric water cycle is to consolidate the recent substantial advances in understanding past, present and future changes in the global water cycle through evidence built upon theoretical understanding, backed up by observations and borne out by climate model simulations. Thermodynamic rises in water vapour provide a central constraint, as discussed in a guest editorial by Bengtsson (2010). Theoretical implications of the Clausius-Clapeyron equation are presented by O'Gorman and Muller (2010) and with reference to a simple model (Sherwood 2010) while observed humidity changes confirm these anticipated responses at the land and ocean surface (Willett et al 2008). Rises in low-level moisture are thought to fuel an intensification of precipitation (O'Gorman and Schneider 2009) and analysis of observed and simulated changes in extreme rainfall for Europe (Lenderink and van Mijgaard 2008) and over tropical oceans by Allan et al (2010) appear to corroborate this. Radiative absorption by water vapour (Previdi 2010, Stephens and Ellis 2008) also provides a thermodynamic feedback on the water cycle, and explains why climate model projections of global precipitation and evaporation of around 1-3% K-1 are muted with respect to the expected 7% K-1 increases in low-level moisture. Climate models achieve dynamical responses through reductions in strength of the Walker circulation (Vecchi et al 2006) and small yet systematic changes in the atmospheric boundary layer over the ocean that modify evaporation (Richter and Xie 2008). A further consequence is anticipated sub-tropical drying (Neelin et al 2006, Chou et al 2007); Allan et al (2010) confirm a decline in dry sub-tropical precipitation while the wet regions become wetter both in model simulations and satellite-based observations. Discrepancies between observed and climate model simulated hydrological response to warming (Wentz et al 2007, Yu and Weller 2007) are of immediate concern in understanding and predicting future responses. Over decadal time-scales it is important to establish whether such discrepancies relate to the observing system, climate modeling deficiencies, or are a statistical artifact of the brevity of the satellite records (Liepert and Previdi 2009). Techniques for extracting information on century-scale changes in precipitation are emerging (Smith et al 2009) but are also subject to severe limitations. Past decadal-scale changes in the water cycle may be further influenced by regionally and temporally varying forcings and resulting feedbacks which must be represented realistically by models (Andrews et al 2009). The radiative impact of aerosols and their indirect effects on clouds and precipitation (Liepert et al 2004) provide an important example. Understanding surface solar 'dimming' and 'brightening' trends in th

Allan, Richard P.; Liepert, Beate G.

2010-06-01

125

Using NASA Products of the Water Cycle for Improved Water Resources Management  

Microsoft Academic Search

NASA Water Resources works within the Earth sciences and GEO community to leverage investments of space-based observation and modeling results including components of the hydrologic cycle into water resources management decision support tools for the goal towards the sustainable use of water. These Earth science hydrologic related observations and modeling products provide a huge volume of valuable data in both

D. L. Toll; B. Doorn; E. T. Engman; R. G. Lawford

2010-01-01

126

Supercritical water oxidation technology for DWPF  

SciTech Connect

At the request of Mr. H.L. Brandt and others in the Savannah River Field Office High Level Waste Division office, DWPF, and SRL personnel have reviewed two potential applications for supercritical water oxidation technology in DWPF. The first application would replace the current hydrolysis process by destroying the organic fractions of the precipitated cesium / potassium tetraphenylborate slurry. The second application pertains to liquid benzene destruction. After a thorough evaluation the first application is not recommended. The second is ready to be tested if needed.

Carter, J.T.; Gentilucci, J.A.

1992-02-07

127

How Do Higher Temperatures Affect the Water Cycle?  

NSDL National Science Digital Library

This demonstration shows that an increase in temperature will speed up the water cycle. One outcome will be an increase in rainfall. A second outcome will be the increase in total evaporation of water and subsequent drought. Materials required include two aquariums, plastic wrap, 2 clamp lamps with 60 watt light bulbs, pebbles and rocks, modeling clay, blue food coloring, and water. Student worksheets, background information for teachers, and a scoring rubric are included. This is Activity 2 in Too Many Blankets, a module in the lesson series, Potential Consequences of Climate Variability and Change.

128

Containment system for supercritical water oxidation reactor  

DOEpatents

A system for containment of a supercritical water oxidation reactor in the event of a rupture of the reactor. The system includes a containment for housing the reaction vessel and a communicating chamber for holding a volume of coolant, such as water. The coolant is recirculated and sprayed to entrain and cool any reactants that might have escaped from the reaction vessel. Baffles at the entrance to the chamber prevent the sprayed coolant from contacting the reaction vessel. An impact-absorbing layer is positioned between the vessel and the containment to at least partially absorb momentum of any fragments propelled by the rupturing vessel. Remote, quick-disconnecting fittings exterior to the containment, in cooperation with shut-off valves, enable the vessel to be isolated and the system safely taken off-line. Normally-closed orifices throughout the containment and chamber enable decontamination of interior surfaces when necessary.

Chastagner, Philippe (3134 Natalie Cir., Augusta, GA 30909-2748)

1994-01-01

129

Containment system for supercritical water oxidation reactor  

DOEpatents

A system is described for containment of a supercritical water oxidation reactor in the event of a rupture of the reactor. The system includes a containment for housing the reaction vessel and a communicating chamber for holding a volume of coolant, such as water. The coolant is recirculated and sprayed to entrain and cool any reactants that might have escaped from the reaction vessel. Baffles at the entrance to the chamber prevent the sprayed coolant from contacting the reaction vessel. An impact-absorbing layer is positioned between the vessel and the containment to at least partially absorb momentum of any fragments propelled by the rupturing vessel. Remote, quick-disconnecting fittings exterior to the containment, in cooperation with shut-off valves, enable the vessel to be isolated and the system safely taken off-line. Normally-closed orifices throughout the containment and chamber enable decontamination of interior surfaces when necessary. 2 figures.

Chastagner, P.

1994-07-05

130

Abiotic and biogeochemical signals derived from the seasonal cycles of tropospheric nitrous oxide  

NASA Astrophysics Data System (ADS)

Seasonal cycles in the mixing ratios of tropospheric nitrous oxide (N2O) are derived by detrending long-term measurements made at sites across four global surface monitoring networks. These cycles are examined for physical and biogeochemical signals. The detrended monthly data display large interannual variability, which at some sites challenges the concept of a "mean" seasonal cycle. The interannual variability in the seasonal cycle is not always correlated among networks that share common sites. In the Northern Hemisphere, correlations between detrended N2O seasonal minima and polar winter lower stratospheric temperature provide compelling evidence for a stratospheric influence, which varies in strength from year to year and can explain much of the interannual variability in the surface seasonal cycle. Even at sites where a strong, competing, regional N2O source exists, such as from coastal upwelling at Trinidad Head, California, the stratospheric influence must be understood in order to interpret the biogeochemical signal in monthly mean data. In the Southern Hemisphere, detrended surface N2O monthly means are correlated with polar lower stratospheric temperature in months preceding the N2O minimum, suggesting a coherent stratospheric influence in that hemisphere as well. A decomposition of the N2O seasonal cycle in the extratropical Southern Hemisphere suggests that ventilation of deep ocean water (microbially enriched in N2O) and the stratospheric influx make similar contributions in phasing, and may be difficult to disentangle. In addition, there is a thermal signal in N2O due to seasonal ingassing and outgassing of cooling and warming surface waters that is out of phase and thus competes with the stratospheric and ventilation signals. All the seasonal signals discussed above are subtle and are generally better quantified in high-frequency in situ data than in data from weekly flask samples, especially in the Northern Hemisphere. The importance of abiotic influences (thermal, stratospheric influx, and tropospheric transport) on N2O seasonal cycles suggests that, at many sites, surface N2O mixing ratio data by themselves are unlikely to provide information about seasonality in surface sources (e.g., for atmospheric inversions), but may be more powerful if combined with complementary data such as CFC-12 mixing ratios or N2O isotopes.

Nevison, C. D.; Dlugokencky, E.; Dutton, G.; Elkins, J. W.; Fraser, P.; Hall, B.; Krummel, P. B.; Langenfelds, R. L.; Prinn, R. G.; Steele, L. P.; Weiss, R. F.

2010-11-01

131

The effect of different metal ions between nanolayers of manganese oxide on water oxidation.  

PubMed

Here, we used a strategy to answer to the question that whether Ca(II) ion is specific for water oxidation or not? In the procedure, first we synthesized layered Mn oxides with K(I) between layers and then replaced K(I) by Ca(II), K(I), Mg(II), La(III) or Ni(II). We proposed that Ca(II), K(I), Mg(II), La(III) and Ni(II), between layers are important to form efficient water-oxidizing catalyst, but not specific in water oxidation. However, Cu(II) ions decrease water-oxidizing activity of layered Mn oxides. The result is important to find critical factors in water oxidation by low-cost and environmentally friendly nanolayered Mn oxides. PMID:25463674

Najafpour, Mohammad Mahdi; Isaloo, Mohsen Abbasi; Ghobadi, Mohadeseh Zarei; Amini, Emad; Haghighi, Behzad

2014-12-01

132

[Fundamental studies in oxidation reduction in relation to water photolysis  

SciTech Connect

Objectives were to understand 3 elementary processes central to developing membrane-based integrated chemical systems for water photolysis: role of interfaces in charge separation/recombination reactions, pathways for transmembrane charge separation, and mechanisms of water oxidation catalyzed by transition metal coordination complexes. Research during this period is arranged under the headings transmembrane oxidation-reduction mechanisms, optically gated transmembrane redox, and mechanisms of water oxidation catalysis. Viologens are involved.

Hurst, J.K.

1992-01-01

133

Water Cycling in the North Polar Region of Mars  

NASA Technical Reports Server (NTRS)

To date, there has been no comprehensive study to understand the partitioning of water into vapor and ice clouds, and the associated effects of dust and surface temperature in the north polar region. Ascertaining the degree to which water is transported out of the cap region versus within the cap region will give much needed insight into the overall story of water cycling on a seasonal basis. In particular, understanding the mechanism for the polar cap surface albedo changes would go along way in comprehending the sources and sinks of water in the northern polar region. We approach this problem by examining Thermal Emission Spectrometer (TES) atmospheric and surface data acquired in the northern summer season and comparing it to Viking data when possible. Because the TES instrument spans the absorption bands of water vapor, water ice, dust, and measures surface temperature, all three aerosols and surface temperature can be retrieved simultaneously. This presentation will show our latest results on the water vapor, water-ice clouds seasonal and spatial distributions, as well as surface temperatures and dust distribution which may lend insight into where the water is going.

Tamppari, L. K.; Smith, M. D.; Bass, D. S.

2003-01-01

134

Enhancing water cycle measurements for future hydrologic research  

USGS Publications Warehouse

The Consortium of Universities for the Advancement of Hydrologic Sciences, Inc., established the Hydrologic Measurement Facility to transform watershed-scale hydrologic research by facilitating access to advanced instrumentation and expertise that would not otherwise be available to individual investigators. We outline a committee-based process that determined which suites of instrumentation best fit the needs of the hydrological science community and a proposed mechanism for the governance and distribution of these sensors. Here, we also focus on how these proposed suites of instrumentation can be used to address key scientific challenges, including scaling water cycle science in time and space, broadening the scope of individual subdisciplines of water cycle science, and developing mechanistic linkages among these subdisciplines and spatio-temporal scales. ?? 2007 American Meteorological Society.

Loescher, H.W.; Jacobs, J.M.; Wendroth, O.; Robinson, D.A.; Poulos, G.S.; McGuire, K.; Reed, P.; Mohanty, B.P.; Shanley, J.B.; Krajewski, W.

2007-01-01

135

Electrochemical Quartz Crystal Microbalance Studies of Electron Addition at Nanocrystalline Tin Oxide/Water and Zinc Oxide/Water Interfaces: Evidence for  

E-print Network

Oxide/Water and Zinc Oxide/Water Interfaces: Evidence for Band-Edge-Determining Proton Uptake Buford I at nanocrystalline zinc oxide/ water and tin oxide/water interfaces is similarly accompanied by uptake of charge intercalation is a general mode of reactivity for metal oxide semiconductors. Finally, the new observations

136

Water Vapor Tracers as Diagnostics of the Regional Hydrologic Cycle  

NASA Technical Reports Server (NTRS)

Numerous studies suggest that local feedback of evaporation on precipitation, or recycling, is a significant source of water for precipitation. Quantitative results on the exact amount of recycling have been difficult to obtain in view of the inherent limitations of diagnostic recycling calculations. The current study describes a calculation of the amount of local and remote sources of water for precipitation, based on the implementation of passive constituent tracers of water vapor (termed water vapor tracers, WVT) in a general circulation model. In this case, the major limitation on the accuracy of the recycling estimates is the veracity of the numerically simulated hydrological cycle, though we note that this approach can also be implemented within the context of a data assimilation system. In this approach, each WVT is associated with an evaporative source region, and tracks the water until it precipitates from the atmosphere. By assuming that the regional water is well mixed with water from other sources, the physical processes that act on the WVT are determined in proportion to those that act on the model's prognostic water vapor. In this way, the local and remote sources of water for precipitation can be computed within the model simulation, and can be validated against the model's prognostic water vapor. Furthermore, estimates of precipitation recycling can be compared with bulk diagnostic approaches. As a demonstration of the method, the regional hydrologic cycles for North America and India are evaluated for six summers (June, July and August) of model simulation. More than 50% of the precipitation in the Midwestern United States came from continental regional tracers, and the local source was the largest of the regional tracers (14%). The Gulf of Mexico and Atlantic 2 regions contributed 18% of the water for Midwestern precipitation, but further analysis suggests that the greater region of the Tropical Atlantic Ocean may also contribute significantly. In general, most North American land regions showed a positive correlation between evaporation and recycling ratio (except the Southeast United States) and negative correlations of recycling ratio with precipitation and moisture transport (except the Southwestern United States). The Midwestern local source is positively correlated with local evaporation, but it is not correlated with water vapor transport. This is contrary to bulk diagnostic estimates of precipitation recycling. In India, the local source of precipitation is a small percentage of the precipitation owing to the dominance of the atmospheric transport of oceanic water. The southern Indian Ocean provides a key source of water for both the Indian continent and the Sahelian region.

Bosilovich, Michael G.; Schubert, Siegfried; Einaudi, Franco (Technical Monitor)

2001-01-01

137

Climate change and the water cycle in newly irrigated areas.  

PubMed

Climate change is affecting agriculture doubly: evapotranspiration is increasing due to increments in temperature while the availability of water resources is decreasing. Furthermore, irrigated areas are expanding worldwide. In this study, the dynamics of climate change impacts on the water cycle of a newly irrigated watershed are studied through the calculation of soil water balances. The study area was a 752-ha watershed located on the left side of the Ebro river valley, in Northeast Spain. The soil water balance procedures were carried out throughout 1827 consecutive days (5 years) of hydrological and agronomical monitoring in the study area. Daily data from two agroclimatic stations were used as well. Evaluation of the impact of climate change on the water cycle considered the creation of two future climate scenarios for comparison: 2070 decade with climate change and 2070 decade without climate change. The main indicators studied were precipitation, irrigation, reference evapotranspiration, actual evapotranspiration, drainage from the watershed, and irrigation losses. The aridity index was also applied. The results represent a baseline scenario in which adaptation measures may be included and tested to reduce the impacts of climate change in the studied area and other similar areas. PMID:25626569

Abrahão, Raphael; García-Garizábal, Iker; Merchán, Daniel; Causapé, Jesús

2015-02-01

138

Exploring causes of interannual variability in the seasonal cycles of tropospheric nitrous oxide  

E-print Network

Seasonal cycles in the mixing ratios of tropospheric nitrous oxide (N[subscript 2]O) are derived by detrending long-term measurements made at sites across four global surface monitoring networks. The detrended monthly data ...

Prinn, Ronald G.

139

Water exchange in manganese-based water-oxidizing catalysts in photosynthetic systems: from the water-oxidizing complex in photosystem II to nano-sized manganese oxides.  

PubMed

The water-oxidizing complex (WOC), also known as the oxygen-evolving complex (OEC), of photosystem II in oxygenic photosynthetic organisms efficiently catalyzes water oxidation. It is, therefore, responsible for the presence of oxygen in the Earth's atmosphere. The WOC is a manganese-calcium (Mn?CaO?(H?O)?) cluster housed in a protein complex. In this review, we focus on water exchange chemistry of metal hydrates and discuss the mechanisms and factors affecting this chemical process. Further, water exchange rates for both the biological cofactor and synthetic manganese water splitting are discussed. The importance of fully unveiling the water exchange mechanism to understand the chemistry of water oxidation is also emphasized here. This article is part of a special issue entitled: photosynthesis research for sustainability: keys to produce clean energy. PMID:24685431

Najafpour, Mohammad Mahdi; Isaloo, Mohsen Abbasi; Eaton-Rye, Julian J; Tomo, Tatsuya; Nishihara, Hiroshi; Satoh, Kimiyuki; Carpentier, Robert; Shen, Jian-Ren; Allakhverdiev, Suleyman I

2014-09-01

140

Nanostructured transition metal oxides useful for water oxidation catalysis  

DOEpatents

The present invention provides for a composition comprising a nanostructured transition metal oxide capable of oxidizing two H.sub.2O molecules to obtain four protons. In some embodiments of the invention, the composition further comprises a porous matrix wherein the nanocluster of the transition metal oxide is embedded on and/or in the porous matrix.

Frei, Heinz M; Jiao, Feng

2013-12-24

141

DESIGN OF HYBRID POWER GENERATION CYCLES EMPLOYING AMMONIA-WATER-CARBON DIOXIDE MIXTURES  

Microsoft Academic Search

A power cycle generates electricity from the heat of combustion of fossil fuels. Its efficiency is governed by the cycle configuration, the operating parameters, and the working fluid. Typical. designs use pure water as the fluid. in the last two decades, hybrid cycles based on ammonia-water, and carbon-dioxide mixtures as the working fluid have been proposed. These cycles may improve

Ashish Gupta

2002-01-01

142

WATER USE IN LCA Life cycle consumptive water use for oil shale development  

E-print Network

WATER USE IN LCA Life cycle consumptive water use for oil shale development and implications Heidelberg 2013 Abstract Purpose Oil shale is an unconventional petroleum source that can be produced domestically in the USA. Oil shale resources are primarily located in Utah, Wyoming, and Colorado, within

Jaramillo, Paulina

143

Cycling of gaseous elemental mercury: Importance of water vapor  

NASA Astrophysics Data System (ADS)

Gaseous elemental mercury is typically not thought of as a soluble compound, but its Henry’s law constant of 0.11 - 0.14 M atm-1 at 298K indicates enough water solubility that it must be considered in chemical cycling of Hg(0). We included mass transfer between the gaseous-aqueous phases and mercury aqueous reactions into our gas phase mercury chemical box model in order to better understand loss of Hg0 during nighttime. Mass transfer between the gaseous-aqueous phases was significantly influenced by water solubility of Hg(0) and the amount of liquid water content (LWC). The impact of water solubility of Hg(0) was examined through two sensitivity experiments; with and without aerosol chemistry. Ten hours of simulation showed that ~3.8 ppqv and ~11.5 ppqv of Hg(0) were decreased without and with aerosol chemistry respectively. The amount of Hg(0) lost indicated that aerosol uptake into its liquid water could be very important to mercury cycling compared to loss by dry deposition of Hg(0) alone. The sensitivity experiments showed also that Hg(aq) was increased to 9-102 ppqv with variable LWC ranging from 2exp(-12)-2exp(-10) after 10 hours of simulation. Finally, we conducted sensitivity experiments with consideration of dry deposition of speciated mercury. The sensitivity experiments indicated that dry deposition of particulate mercury (PHg) is critical to generate typical ambient levels of PHg compared to Hg0 and RGM. The loss of Hg(0) by aerosol uptake and dry deposition suggested that aerosol uptake of Hg(0) could play an important role in mercury cycling in the atmosphere.

Kim, S.; Talbot, R. W.; Mao, H.

2010-12-01

144

Nanostructured manganese oxide/carbon nanotubes, graphene and graphene oxide as water-oxidizing composites in artificial photosynthesis.  

PubMed

Herein, we report on nano-sized Mn oxide/carbon nanotubes, graphene and graphene oxide as water-oxidizing compounds in artificial photosynthesis. The composites are synthesized by different and simple procedures and characterized by a number of methods. The water-oxidizing activities of these composites are also considered in the presence of cerium(IV) ammonium nitrate. Some composites are efficient Mn-based catalysts with TOF (mmol O2 per mol Mn per second) ~ 2.6. PMID:24898625

Najafpour, Mohammad Mahdi; Rahimi, Fahime; Fathollahzadeh, Maryam; Haghighi, Behzad; Ho?y?ska, Ma?gorzata; Tomo, Tatsuya; Allakhverdiev, Suleyman I

2014-07-28

145

The NASA Energy and Water Cycle Extreme (NEWSE) Integration Project  

NASA Technical Reports Server (NTRS)

Skillful predictions of water and energy cycle extremes (flood and drought) are elusive. To better understand the mechanisms responsible for water and energy extremes, and to make decisive progress in predicting these extremes, the collaborative NASA Energy and Water cycle Extremes (NEWSE) Integration Project, is studying these extremes in the U.S. Southern Great Plains (SGP) during 2006-2007, including their relationships with continental and global scale processes, and assessment of their predictability on multiple space and time scales. It is our hypothesis that an integrative analysis of observed extremes which reflects the current understanding of the role of SST and soil moisture variability influences on atmospheric heating and forcing of planetary waves, incorporating recently available global and regional hydro- meteorological datasets (i.e., precipitation, water vapor, clouds, etc.) in conjunction with advances in data assimilation, can lead to new insights into the factors that lead to persistent drought and flooding. We will show initial results of this project, whose goals are to provide an improved definition, attribution and prediction on sub-seasonal to interannual time scales, improved understanding of the mechanisms of decadal drought and its predictability, including the impacts of SST variability and deep soil moisture variability, and improved monitoring/attributions, with transition to applications; a bridging of the gap between hydrological forecasts and stakeholders (utilization of probabilistic forecasts, education, forecast interpretation for different sectors, assessment of uncertainties for different sectors, etc.).

House, P. R.; Lapenta, W.; Schiffer, R.

2008-01-01

146

Selective oxidations of activated alcohols in water at room temperature.  

PubMed

Allylic and benzylic alcohols can be selectively oxidized to their corresponding aldehydes or ketones in water containing nanoreactors composed of the designer surfactant TPGS-750-M. The oxidation relies on catalytic amounts of CuBr, bpy, and TEMPO, with N-methyl-imidazole; air is the stoichiometric oxidant. PMID:25126656

Lipshutz, B H; Hageman, M; Fennewald, J C; Linstadt, R; Slack, E; Voigtritter, K

2014-10-01

147

34 Study of land surface heat fluxes and water cycle over the Tibetan plateau  

Microsoft Academic Search

The energy and water cycles over the Tibetan Plateau play an important role in the Asian monsoon system, which in turn is a major component of both the energy and water cycles of the global climate system. Using field observational data observed from the GAME\\/Tibet (Global Energy and Water cycle Experiment [GEWEX] Asian Monsoon Experiment on the Tibetan Plateau) and

Yaoming Ma; Tandong Yao; Hirohiko Ishikawa; Toshio Koike

2007-01-01

148

Ecological controls on water-cycle response to climate variability in deserts  

E-print Network

Ecological controls on water-cycle response to climate variability in deserts B. R. Scanlon* , D. G variability on the water cycle in desert ecosystems is controlled by biospheric feedback at interannual in controlling water cycle response to interannual climate variability related to El Nin~ o southern oscillation

Scanlon, Bridget R.

149

Cobalt-substituted Polyoxometalates as Viable WaterOxidation Catalysts.  

E-print Network

??Abstract Cobalt-substituted Polyoxometalates as Viable Water Oxidation Catalysts By Jeffrey Miles Tan The cobalt-substituted polyoxometalate K10[Co4(H2O)2(PW9O34)2]·22H2O was studied and evaluated for catalytic water oxidation activity.… (more)

Tan, Jeffrey Miles Tiu

2009-01-01

150

Semiconductor photocatalysts for water oxidation: current status and challenges.  

PubMed

Artificial photosynthesis is a highly-promising strategy to convert solar energy into hydrogen energy for the relief of the global energy crisis. Water oxidation is the bottleneck for its kinetic and energetic complexity in the further enhancement of the overall efficiency of the artificial photosystem. Developing efficient and cost-effective photocatalysts for water oxidation is a growing desire, and semiconductor photocatalysts have recently attracted more attention due to their stability and simplicity. This article reviews the recent advancement of semiconductor photocatalysts with a focus on the relationship between material optimization and water oxidation efficiency. A brief introduction to artificial photosynthesis and water oxidation is given first, followed by an explanation of the basic rules and mechanisms of semiconductor particulate photocatalysts for water oxidation as theoretical references for discussions of componential, surface structure, and crystal structure modification. O2-evolving photocatalysts in Z-scheme systems are also introduced to demonstrate practical applications of water oxidation photocatalysts in artificial photosystems. The final part proposes some challenges based on the dynamics and energetics of photoholes which are fundamental to the enhancement of water oxidation efficiency, as well as on the simulation of natural water oxidation that will be a trend in future research. PMID:24599528

Yang, Lingling; Zhou, Han; Fan, Tongxiang; Zhang, Di

2014-04-21

151

Water Vapor Tracers as Diagnostics of the Regional Hydrologic Cycle  

NASA Technical Reports Server (NTRS)

Numerous studies suggest that local feedback of surface evaporation on precipitation, or recycling, is a significant source of water for precipitation. Quantitative results on the exact amount of recycling have been difficult to obtain in view of the inherent limitations of diagnostic recycling calculations. The current study describes a calculation of the amount of local and remote geographic sources of surface evaporation for precipitation, based on the implementation of three-dimensional constituent tracers of regional water vapor sources (termed water vapor tracers, WVT) in a general circulation model. The major limitation on the accuracy of the recycling estimates is the veracity of the numerically simulated hydrological cycle, though we note that this approach can also be implemented within the context of a data assimilation system. In the WVT approach, each tracer is associated with an evaporative source region for a prognostic three-dimensional variable that represents a partial amount of the total atmospheric water vapor. The physical processes that act on a WVT are determined in proportion to those that act on the model's prognostic water vapor. In this way, the local and remote sources of water for precipitation can be predicted within the model simulation, and can be validated against the model's prognostic water vapor. As a demonstration of the method, the regional hydrologic cycles for North America and India are evaluated for six summers (June, July and August) of model simulation. More than 50% of the precipitation in the Midwestern United States came from continental regional sources, and the local source was the largest of the regional tracers (14%). The Gulf of Mexico and Atlantic regions contributed 18% of the water for Midwestern precipitation, but further analysis suggests that the greater region of the Tropical Atlantic Ocean may also contribute significantly. In most North American continental regions, the local source of precipitation is correlated with total precipitation. There is a general positive correlation between local evaporation and local precipitation, but it can be weaker because large evaporation can occur when precipitation is inhibited. In India, the local source of precipitation is a small percentage of the precipitation owing to the dominance of the atmospheric transport of oceanic water. The southern Indian Ocean provides a key source of water for both the Indian continent and the Sahelian region.

Bosilovich, Michael G.; Schubert, Siegfried D.; Einaudi, Franco (Technical Monitor)

2001-01-01

152

Homogeneous oxidation of water by iron complexes with macrocyclic ligands.  

PubMed

The activity of eleven separated iron complexes and nine in situ-generated iron complexes towards catalytic water oxidation have been examined in aqueous solutions with Ce(NH4)2(NO3)6 as the oxidant. Two iron complexes bearing tridentate and tetradentate macrocyclic ligands were found to be novel water oxidation catalysts. The one with tetradentate ligand exhibited a promising activity with a turnover number of 65 for oxygen evolution. PMID:24777911

Zhang, Biaobiao; Li, Fei; Yu, Fengshou; Cui, Honghua; Zhou, Xu; Li, Hua; Wang, Yong; Sun, Licheng

2014-06-01

153

Supercritical Water Reactor Cycle for Medium Power Applications  

SciTech Connect

Scoping studies for a power conversion system based on a direct-cycle supercritical water reactor have been conducted. The electric power range of interest is 5-30 MWe with a design point of 20 MWe. The overall design objective is to develop a system that has minimized physical size and performs satisfactorily over a broad range of operating conditions. The design constraints are as follows: Net cycle thermal efficiency {ge}20%; Steam turbine outlet quality {ge}90%; and Pumping power {le}2500 kW (at nominal conditions). Three basic cycle configurations were analyzed. Listed in order of increased plant complexity, they are: (1) Simple supercritical Rankine cycle; (2) All-supercritical Brayton cycle; and (3) Supercritical Rankine cycle with feedwater preheating. The sensitivity of these three configurations to various parameters, such as reactor exit temperature, reactor pressure, condenser pressure, etc., was assessed. The Thermoflex software package was used for this task. The results are as follows: (a) The simple supercritical Rankine cycle offers the greatest hardware simplification, but its high reactor temperature rise and reactor outlet temperature may pose serious problems from the viewpoint of thermal stresses, stability and materials in the core. (b) The all-supercritical Brayton cycle is not a contender, due to its poor thermal efficiency. (c) The supercritical Rankine cycle with feedwater preheating affords acceptable thermal efficiency with lower reactor temperature rise and outlet temperature. (d) The use of a moisture separator improves the performance of the supercritical Rankine cycle with feedwater preheating and allows for a further reduction of the reactor outlet temperature, thus it was selected for the next step. Preliminary engineering design of the supercritical Rankine cycle with feedwater preheating and moisture separation was performed. All major components including the turbine, feedwater heater, feedwater pump, condenser, condenser pump and pipes were modeled with realistic assumptions using the PEACE module of Thermoflex. A three-dimensional layout of the plant was also generated with the SolidEdge software. The results of the engineering design are as follows: (i) The cycle achieves a net thermal efficiency of 24.13% with 350/460 C reactor inlet/outlet temperatures, {approx}250 bar reactor pressure and 0.75 bar condenser pressure. The steam quality at the turbine outlet is 90% and the total electric consumption of the pumps is about 2500 kWe at nominal conditions. (ii) The overall size of the plant is attractively compact and can be further reduced if a printed-circuit-heat-exchanger (vs shell-and-tube) design is used for the feedwater heater, which is currently the largest component by far. Finally, an analysis of the plant performance at off-nominal conditions has revealed good robustness of the design in handling large changes of thermal power and seawater temperature.

BD Middleton; J Buongiorno

2007-04-25

154

Exploring causes of interannual variability in the seasonal cycles of tropospheric nitrous oxide  

NASA Astrophysics Data System (ADS)

Seasonal cycles in the mixing ratios of tropospheric nitrous oxide (N2O) are derived by detrending long-term measurements made at sites across four global surface monitoring networks. The detrended monthly data display large interannual variability, which at some sites challenges the concept of a "mean" seasonal cycle. In the Northern Hemisphere, correlations between polar winter lower stratospheric temperature and detrended N2O data, around the month of the seasonal minimum, provide empirical evidence for a stratospheric influence, which varies in strength from year to year and can explain much of the interannual variability in the surface seasonal cycle. Even at sites where a strong, competing, regional N2O source exists, such as from coastal upwelling at Trinidad Head, California, the stratospheric influence must be understood to interpret the biogeochemical signal in monthly mean data. In the Southern Hemisphere, detrended surface N2O monthly means are correlated with polar spring lower stratospheric temperature in months preceding the N2O minimum, providing empirical evidence for a coherent stratospheric influence in that hemisphere as well, in contrast to some recent atmospheric chemical transport model (ACTM) results. Correlations between the phasing of the surface N2O seasonal cycle in both hemispheres and both polar lower stratospheric temperature and polar vortex break-up date provide additional support for a stratospheric influence. The correlations discussed above are generally more evident in high-frequency in situ data than in data from weekly flask samples. Furthermore, the interannual variability in the N2O seasonal cycle is not always correlated among in situ and flask networks that share common sites, nor do the mean seasonal amplitudes always agree. The importance of abiotic influences such as the stratospheric influx and tropospheric transport on N2O seasonal cycles suggests that, at sites remote from local sources, surface N2O mixing ratio data by themselves are unlikely to provide information about seasonality in surface sources, e.g., for atmospheric inversions, unless the ACTMs employed in the inversions accurately account for these influences. An additional abioitc influence is the seasonal ingassing and outgassing of cooling and warming surface waters, which creates a thermal signal in tropospheric N2O that is of particular importance in the extratropical Southern Hemisphere, where it competes with the biological ocean source signal.

Nevison, C. D.; Dlugokencky, E.; Dutton, G.; Elkins, J. W.; Fraser, P.; Hall, B.; Krummel, P. B.; Langenfelds, R. L.; O'Doherty, S.; Prinn, R. G.; Steele, L. P.; Weiss, R. F.

2011-04-01

155

Reliability of sintered silver layer obtained using silver-oxide paste in power cycling test  

NASA Astrophysics Data System (ADS)

To investigate the reliability of a sintered silver bonding layer obtained using silver-oxide paste, a power cycling test was performed. The module obtained using silver-oxide paste achieved 73,400 power cycles in a test with Tjmax = 150 °C (?Tj = 120 °C), while a soldered (Pb3.5Sn1.5Ag) power module failed at 24,600 cycles. After the cycling test, a crack was observed in the Pb3.5Sn1.5Ag solder layer but not in the sintered silver layer. These results reveal that the sintered silver layer obtained using silver-oxide paste can treble the lifetime of a power module.

Yasuda, Yusuke; Tokoo, Naoya; Morita, Toshiaki; Suzuki, Kazuhiro

2015-01-01

156

Tracing the water cycle using measurements of stable water isotopes in ambient water vapour  

NASA Astrophysics Data System (ADS)

Short-term measurement series of the stable water isotope (SWI) composition of vapour can contribute to enhancing our process-based understanding of the spatio-temporal variability of the isotope signal in the atmospheric branch of the water cycle. Advanced knowledge about this variable can in turn give some hints on important moist atmospheric mechanisms like cloud formation, evaporation and transpiration at the land surface. In this sense, SWIs can be regarded as naturally available tracers of phase change processes in the atmosphere. There are still many open questions related to the processes determining isotope variability in atmospheric waters, in particular with regard to short-term variations and non-equilibrium fractionation. Furthermore, there is a need for measurements in order to constrain and validate simulations from isotope-enabled numerical weather and climate prediction models. The objective of this work is to explore short-term variations in isotope measurements in near-surface water vapour over land and to improve our understanding of the processes which influence the variability of isotope signals at different temporal scales. Our focus is set upon the investigation of the importance of single meteorological events (frontal rain showers, dry periods) for monthly mean water isotope values. The influence of upstream processes during evaporation at the source location and transport of the air parcel on the measured isotope signal as well as its link with land-atmosphere exchange fluxes are central aspects in the present investigation. Measurements of stable water isotopes with high (sub-hourly) temporal resolution have been performed in water vapour using a commercial laser spectrometer (Picarro, L1115-i) in an urban environment as well as in a pre-alpine catchment at an already existing extensive hydro-meteorological measurement station. The instrument and sampling system was assessed in terms of measurement precision, response time, instrument drift and system memory. First qualitative event-based analyses have been performed and the isotope measurements have been linked to the prevailing meteorological conditions.

Aemisegger, F.; Pfahl, S.; Wernli, H.

2010-09-01

157

Solid Oxide Fuel Cell/Gas Turbine Hybrid Cycle Technology for Auxiliary Aerospace Power  

NASA Technical Reports Server (NTRS)

A notional 440 kW auxiliary power unit has been developed for 300 passenger commercial transport aircraft in 2015AD. A hybrid engine using solid-oxide fuel cell stacks and a gas turbine bottoming cycle has been considered. Steady-state performance analysis during cruise operation has been presented. Trades between performance efficiency and system mass were conducted with system specific energy as the discriminator. Fuel cell performance was examined with an area specific resistance. The ratio of fuel cell versus turbine power was explored through variable fuel utilization. Area specific resistance, fuel utilization, and mission length had interacting effects upon system specific energy. During cruise operation, the simple cycle fuel cell/gas turbine hybrid was not able to outperform current turbine-driven generators for system specific energy, despite a significant improvement in system efficiency. This was due in part to the increased mass of the hybrid engine, and the increased water flow required for on-board fuel reformation. Two planar, anode-supported cell design concepts were considered. Designs that seek to minimize the metallic interconnect layer mass were seen to have a large effect upon the system mass estimates.

Steffen, Christopher J., Jr.; Freeh, Joshua E.; Larosiliere, Louis M.

2005-01-01

158

Iron oxidation kinetics and phosphorus immobilization at the groundwater-surface water interface  

NASA Astrophysics Data System (ADS)

Eutrophication of freshwater environments following diffuse nutrient loads is a widely recognized water quality problem in catchments. Fluxes of non-point P sources to surface waters originate from surface runoff and flow from soil water and groundwater into surface water. The availability of P in surface waters is controlled strongly by biogeochemical nutrient cycling processes at the soil-water interface. The mechanisms and rates of the iron oxidation process with associated binding of phosphate during exfiltration of anaerobic Fe(II) bearing groundwater are among the key unknowns in P retention processes in surface waters in delta areas where the shallow groundwater is typically pH-neutral to slightly acid, anoxic, iron-rich. We developed an experimental field set-up to study the dynamics in Fe(II) oxidation and mechanisms of P immobilization at the groundwater-surface water interface in an agricultural experimental catchment of a small lowland river. We physically separated tube drain effluent from groundwater discharge before it entered a ditch in an agricultural field. The exfiltrating groundwater was captured in in-stream reservoirs constructed in the ditch. Through continuous discharge measurements and weekly water quality sampling of groundwater, tube drain water, exfiltrated groundwater, and ditch water, we quantified Fe(II) oxidation kinetics and P immobilization processes across the seasons. This study showed that seasonal changes in climatic conditions affect the Fe(II) oxidation process. In winter time the dissolved iron concentrations in the in-stream reservoirs reached the levels of the anaerobic groundwater. In summer time, the dissolved iron concentrations of the water in the reservoirs are low, indicating that dissolved Fe(II) is completely oxidized prior to inflow into the reservoirs. Higher discharges, lower temperatures and lower pH of the exfiltrated groundwater in winter compared to summer shifts the location of the redox transition zone, with Fe(II) oxidation taking place in the soil surrounding the ditch during summer and in the surface water during winter. The dynamics in Fe(II) oxidation did not affect the dissolved P concentrations. The dissolved P concentrations of the in-stream reservoirs water were an order of magnitude lower than observed in the groundwater and have no seasonal trend. Our data showed preferential binding of P during initial stage of the Fe(II) oxidation process, indicating the formation of Fe(III)-phosphate precipitates. The formation of Fe(III)-phosphates at the groundwater-surface water interface is an important geochemical mechanism in the transformation of dissolved phosphate to particulate phosphate and therefore a major control on the P retention in natural waters that drain anaerobic aquifers.

van der Grift, Bas; Rozemeijer, Joachim; Griffioen, Jasper; van der Velde, Ype

2014-05-01

159

Think Scientifically: The Sun and The Water Cycle  

NSDL National Science Digital Library

Learners will read or listen to a story about two sisters, Marisol and Sofia, as they explore the Sun's role in the water cycle. Additionally, numerous extension resources are included in the accompanying educator guide, such as suggestions for no-cost language arts activities, links to further science activities, a book walk cue chart to guide classroom discussion before, during, and after the story, a graphic organizer, and alignments to the National Science Education Standards (NSES) and the Next Generation Science Standards (NGSS).

160

[Oxidation of Krebs cycle substrates by Eurytrema pancreaticum mitochondria].  

PubMed

From tissues of E. pancreaticum were isolated mitochondria capable to swell under the effect of some factors. The intensive oxidation of succinate, isocitrate, cisaconitate, oxalacetate and alpha-ketoglutarate by mitochondria and less intensive one of malate, fumarate, citrate and pyruvate were shown. NAD caused the rise in oxidation intensity of isocitrate, cis-aconitate, oxalacetate, alpha-ketoglutarate, malate, fumarate and pyruvate while NADP--of isocitrate and citrate. PMID:909726

Shestak, E A

1977-01-01

161

New processes and players in the nitrogen cycle: the microbial ecology of anaerobic and archaeal ammonia oxidation  

Microsoft Academic Search

Microbial activities drive the global nitrogen cycle, and in the past few years, our understanding of nitrogen cycling processes and the micro-organisms that mediate them has changed dramatically. During this time, the processes of anaerobic ammonium oxidation (anammox), and ammonia oxidation within the domain Archaea, have been recognized as two new links in the global nitrogen cycle. All available evidence

Christopher A Francis; J Michael Beman; Marcel M M Kuypers

2007-01-01

162

The Martian Water Cycle Based on 3-D Modeling  

NASA Technical Reports Server (NTRS)

Understanding the distribution of Martian water is a major goal of the Mars Surveyor program. However, until the bulk of the data from the nominal missions of TES, PMIRR, GRS, MVACS, and the DS2 probes are available, we are bound to be in a state where much of our knowledge of the seasonal behavior of water is based on theoretical modeling. We therefore summarize the results of this modeling at the present time. The most complete calculations come from a somewhat simplified treatment of the Martian climate system which is capable of simulating many decades of weather. More elaborate meteorological models are now being applied to study of the problem. The results show a high degree of consistency with observations of aspects of the Martian water cycle made by Viking MAWD, a large number of ground-based measurements of atmospheric column water vapor, studies of Martian frosts, and the widespread occurrence of water ice clouds. Additional information is contained in the original extended abstract.

Houben, H.; Haberle, R. M.; Joshi, M. M.

1999-01-01

163

Single-Crystal Tungsten Oxide Nanosheets: Photochemical Water Oxidation in the Quantum Confinement Regime  

E-print Network

Single-Crystal Tungsten Oxide Nanosheets: Photochemical Water Oxidation in the Quantum Confinement, catalysis, WO3, tungsten oxide, nanosheet, nanocrystal, quantum confinement, solar energy conversion INTRODUCTION Tungsten trioxide crystallizes in the ReO3 structure type and is an n-type semiconductor with a 2

Osterloh, Frank

164

Polyoxometalate water oxidation catalysts and methods of use thereof  

DOEpatents

Homogeneous water oxidation catalysts (WOCs) for the oxidation of water to produce hydrogen ions and oxygen, and methods of making and using thereof are described herein. In a preferred embodiment, the WOC is a polyoxometalate WOC which is hydrolytically stable, oxidatively stable, and thermally stable. The WOC oxidized waters in the presence of an oxidant. The oxidant can be generated photochemically, using light, such as sunlight, or electrochemically using a positively biased electrode. The hydrogen ions are subsequently reduced to form hydrogen gas, for example, using a hydrogen evolution catalyst (HEC). The hydrogen gas can be used as a fuel in combustion reactions and/or in hydrogen fuel cells. The catalysts described herein exhibit higher turn over numbers, faster turn over frequencies, and/or higher oxygen yields than prior art catalysts.

Hill, Craig L.; Gueletii, Yurii V.; Musaev, Djamaladdin G.; Yin, Qiushi; Botar, Bogdan

2014-09-02

165

Carbon cycle. Sunlight controls water column processing of carbon in arctic fresh waters.  

PubMed

Carbon in thawing permafrost soils may have global impacts on climate change; however, the factors that control its processing and fate are poorly understood. The dominant fate of dissolved organic carbon (DOC) released from soils to inland waters is either complete oxidation to CO2 or partial oxidation and river export to oceans. Although both processes are most often attributed to bacterial respiration, we found that photochemical oxidation exceeds rates of respiration and accounts for 70 to 95% of total DOC processed in the water column of arctic lakes and rivers. At the basin scale, photochemical processing of DOC is about one-third of the total CO2 released from surface waters and is thus an important component of the arctic carbon budget. PMID:25146289

Cory, Rose M; Ward, Collin P; Crump, Byron C; Kling, George W

2014-08-22

166

Community of Practice Applications from WaterNet: The NASA Water Cycle Solutions Network  

NASA Astrophysics Data System (ADS)

WaterNet is a new international network of researchers, stakeholders, and end-users of remote sensing tools that will benefit the water resources management community. It addresses a means for enhancing the social and economic developments of nations by increased use of practical research products from the terrestrial water cycle for making informed decisions. This paper provides a summary of the Water Cycle Community of Practice (CoP) plans and examples of Land Surface Model (LSM) applications for extreme events - floods, droughts, and heavy snowstorms in Europe. It discusses the concept of NASA's solutions networks focusing on the WaterNet. It invites EGU teams to join our WaterNet network. The NASA Water cycle Solutions Network's goal is to improve and optimize the sustained ability of water cycle researchers, stakeholders, organizations and networks to interact, identify, harness, and extend NASA research results to augment decision support tools and meet national needs. Our team is developing WaterNet by engaging relevant NASA water cycle research and community-of-practice organizations, to develop what we term an "actionable database" that can be used to communicate and connect NASA Water cycle research Results (NWRs) towards the improvement of water-related Decision Support Tools (DSTs). Recognizing that the European Commission and European Space Agency have also developed many related research products (EWRs), we seek to learn about these and network with the EU teams to include their information in the WaterNet actionable data base. Recognizing the many existing highly valuable water-related science and application networks in the US and EU, we focus the balance of our efforts on enabling their interoperability - facilitating access and communications among decision-makers and scientists. We present results of our initial focus on identification, collection, and analysis of the two end points, these being the NWRs and EWRs and water related DSTs. We discuss strategies to connect these two end points via innovative communication strategies, improved user access to NASA resources, improved water cycle research community appreciation for user DST requirements, improved policymaker, management and stakeholder knowledge of NASA and EU research and application products, and improved identification of pathways for progress. Extreme event analysis and prediction is important to water managers, emergency managers-civil defense and local law enforcement, and the public. The paper presents examples from the extreme flash flood event of 18 September 2007 which cost over 200 M Euro in damages to roads, homes, and other infrastructure in the mountains west of Ljubljana. Results from NASA's Global Land Data Assimilation System - Land Surface Model show the precipitation, runoff, and soil moisture simulated in this extreme local flood event highlighting the limitations of coarse grid ¼ degree grid and 1 km grid spacing models. Drought simulations over Southeastern Europe also provide examples of model capabilities for drought management decision-making focusing on soil moisture, soil temperature, and precipitation simulations from GLDAS. Extreme snowfall events also pose a serious problem for emergency managers, ski industry and transportation managers. An example of GLDAS simulations of a heavy snow event in the Alps shows the capabilities of GLDAS, and contrasts results from the SLF snow and avalanche research. We seek to build on existing partnerships with EU scientific teams that represent a cross-section of individual and networked NWRs, EWRs and DSTs from government, private, and academic domains, that will enable us to quickly establish an operational solutions network, entrain more partner nodes and networks, and move WaterNet toward self-sustainability in the US and EU. EU projects like AWARE, and the flood and drought forecasting research efforts (DMCSEE) and GMES projects are potential projects that may directly benefit from this WaterNet networking. Specific goals and objectives, methods of communication,

Matthews, D.; Brilly, M.; Gregoric, G.; Polajnar, J.; Houser, P.; Rodell, M.; Lehning, M.

2009-04-01

167

Manganese oxidation induced by water table fluctuations in a sand column.  

PubMed

On-off cycles of production wells, especially in bank filtration settings, cause oscillations in the local water table, which can deliver significant amounts of dissolved oxygen (DO) to the shallow groundwater. The potential for DO introduced in this manner to oxidize manganese(II) (Mn(II)), mediated by the obligate aerobe Pseudomonas putida GB-1, was tested in a column of quartz sand fed with anoxic influent solution and subject to 1.3 m water table changes every 30-50 h. After a period of filter ripening, 100 ?M Mn was rapidly removed during periods of low water table and high dissolved oxygen concentrations. The accumulation of Mn in the column was confirmed by XRF analysis of the sand at the conclusion of the study, and both measured net oxidation rates and XAS analysis suggest microbial oxidation as the dominant process. The addition of Zn, which inhibited GB-1 Mn oxidation but not its growth, interrupted the Mn removal process, but Mn oxidation recovered within one water table fluctuation. Thus transient DO conditions could support microbially mediated Mn oxidation, and this process could be more relevant in shallow groundwater than previously thought. PMID:22126514

Farnsworth, Claire E; Voegelin, Andreas; Hering, Janet G

2012-01-01

168

Life cycle assessment for sustainable metropolitan water systems planning.  

PubMed

Life Cycle Assessment (LCA) is useful as an information tool for the examination of alternative future scenarios for strategic planning. Developing a life cycle assessment for a large water and wastewater system involves making methodological decisions about the level of detail which is retained through different stages of the process. In this article we discuss a methodology tailored to strategic planning needs which retains a high degree of model segmentation in order to enhance modeling of a large, complex system. This is illustrated by a case study of Sydney Water, which is Australia's largest water service provider. A prospective LCA was carried out to examine the potential environmental impacts of Sydney Water's total operations in the year 2021. To our knowledge this is the first study to create an LCA model of an integrated water and wastewater system with this degree of complexity. A "base case" system model was constructed to represent current operating assets as augmented and upgraded to 2021. The base case results provided a basis for the comparison of alternative future scenarios and for conclusions to be drawn regarding potential environmental improvements. The scenarios can be roughly classified in two categories: (1) options which improve the environmental performance across all impact categories and (2) options which improve one indicator and worsen others. Overall environmental improvements are achieved in all categories by the scenarios examining increased demand management, energy efficiency, energy generation, and additional energy recovery from biosolids. The scenarios which examined desalination of seawater and the upgrades of major coastal sewage treatment plants to secondary and tertiary treatment produced an improvement in one environmental indicator but deteriorations in all the other impact categories, indicating the environmental tradeoffs within the system. The desalination scenario produced a significant increase in greenhouse gas emissions due to coal-fired electricity generation for a small increase in water supply. Assessment of a greenfield scenario incorporating water demand management, on-site treatment, local irrigation, and centralized biosolids treatment indicates significant environmental improvements are possible relative to the assessment of a conventional system of corresponding scale. PMID:15296294

Lundie, Sven; Peters, Gregory M; Beavis, Paul C

2004-07-01

169

Highly efficient and robust molecular ruthenium catalysts for water oxidation  

PubMed Central

Water oxidation catalysts are essential components of light-driven water splitting systems, which could convert water to H2 driven by solar radiation (H2O + h? ? 1/2O2 + H2). The oxidation of water (H2O ? 1/2O2 + 2H+ + 2e-) provides protons and electrons for the production of dihydrogen (2H+ + 2e- ? H2), a clean-burning and high-capacity energy carrier. One of the obstacles now is the lack of effective and robust water oxidation catalysts. Aiming at developing robust molecular Ru-bda (H2bda = 2,2?-bipyridine-6,6?-dicarboxylic acid) water oxidation catalysts, we carried out density functional theory studies, correlated the robustness of catalysts against hydration with the highest occupied molecular orbital levels of a set of ligands, and successfully directed the synthesis of robust Ru-bda water oxidation catalysts. A series of mononuclear ruthenium complexes [Ru(bda)L2] (L = pyridazine, pyrimidine, and phthalazine) were subsequently synthesized and shown to effectively catalyze CeIV-driven [CeIV = Ce(NH4)2(NO3)6] water oxidation with high oxygen production rates up to 286 s-1 and high turnover numbers up to 55,400. PMID:22753518

Duan, Lele; Araujo, Carlos Moyses; Ahlquist, Mårten S.G.; Sun, Licheng

2012-01-01

170

The use of ozone and associated oxidation processes in drinking water treatment  

Microsoft Academic Search

This paper summarizes the main applications of ozonation and associated oxidation processes in the treatment of natural waters (surface and ground waters) for drinking water production. In fact, oxidants may be added at several points throughout the treatment: pre-oxidation, intermediate oxidation or final disinfection. So, the numerous effects of chemical oxidation are discussed along the water treatment: removal of inorganic

V Camel; A Bermond

1998-01-01

171

Water, carbon and nitrogen cycling in a rendzina soil cropped with winter oilseed rape  

E-print Network

Short note Water, carbon and nitrogen cycling in a rendzina soil cropped with winter oilseed rape.) Internet database / nitrogen cycle / rendzina / oilseed rape Résumé - Une base de données sur les cycles on the dynamic fluxes of water, carbon and nitrogen within a soil-crop system at the field-scale, conducted

Paris-Sud XI, Université de

172

Oxidation behavior of Incoloy 800 under simulated supercritical water conditions  

NASA Astrophysics Data System (ADS)

For a correct design of supercritical water-cooled reactor (SCWR) components, data regarding the behavior of candidate materials in supercritical water are necessary. Corrosion has been identified as a critical problem because the high temperature and the oxidative nature of supercritical water may accelerate the corrosion kinetics. The goal of this paper is to investigate the oxidation behavior of Incoloy 800 exposed in autoclaves under supercritical water conditions for up to 1440 h. The exposure conditions (thermal deaerated water, temperatures of 723, 773, 823 and 873 K and a pressure of 25 MPa) have been selected as relevant for a supercritical power plant concept. To investigate the structural changes of the oxide films, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX) and electrochemical impedance spectroscopy (EIS) analyses were used. Results show changes in the oxides chemical composition, microstructure and thickness versus testing conditions (pressure, temperature and time). The oxide films are composed of two layers: an outer layer enriched in Fe oxide and an inner layer enriched in Cr and Ni oxides corresponding to small cavities supposedly due to internal oxidation.

Fulger, M.; Ohai, D.; Mihalache, M.; Pantiru, M.; Malinovschi, V.

2009-03-01

173

Kinetics of zero valent iron nanoparticle oxidation in oxygenated water.  

PubMed

Zero valent iron (ZVI) nanoparticles are versatile in their ability to remove a wide variety of water contaminants, and ZVI-based bimetallic nanoparticles show increased reactivity above that of ZVI alone. ZVI nanoparticles degrade contaminants through the reactive species (e.g., OH*, H(2(g)), H(2)O(2)) that are produced during iron oxidation. Measurement and modeling of aqueous ZVI nanoparticle oxidation kinetics are therefore necessary to optimize nanoparticle design. Stabilized ZVI and iron-nickel nanoparticles of approximately 150 nm in diameter were synthesized through solution chemistry, and nanoparticle oxidation kinetics were determined via measured mass change using a quartz crystal microbalance (QCM). Under flowing aerated water, ZVI nanoparticles had an initial exponential growth behavior indicating surface-dominated oxidation controlled by migration of species (H(2)O and O(2)) to the surface. A region of logarithmic growth followed the exponential growth which, based on the Mott-Cabrera model of thin oxide film growth, suggests a reaction dominated by movement of species (e.g., iron cations and oxygen anions) through the oxide layer. The presence of ethanol or a nickel shell on the ZVI nanoparticles delayed the onset of iron oxidation and reduced the extent of oxidation. In oxygenated water, ZVI nanoparticles oxidized primarily to the iron oxide-hydroxide lepidocrocite. PMID:23130994

Greenlee, Lauren F; Torrey, Jessica D; Amaro, Robert L; Shaw, Justin M

2012-12-01

174

Molecular water oxidation mechanisms followed by transition metals: state of the art.  

PubMed

One clean alternative to fossil fuels would be to split water using sunlight. However, to achieve this goal, researchers still need to fully understand and control several key chemical reactions. One of them is the catalytic oxidation of water to molecular oxygen, which also occurs at the oxygen evolving center of photosystem II in green plants and algae. Despite its importance for biology and renewable energy, the mechanism of this reaction is not fully understood. Transition metal water oxidation catalysts in homogeneous media offer a superb platform for researchers to investigate and extract the crucial information to describe the different steps involved in this complex reaction accurately. The mechanistic information extracted at a molecular level allows researchers to understand both the factors that govern this reaction and the ones that derail the system to cause decomposition. As a result, rugged and efficient water oxidation catalysts with potential technological applications can be developed. In this Account, we discuss the current mechanistic understanding of the water oxidation reaction catalyzed by transition metals in the homogeneous phase, based on work developed in our laboratories and complemented by research from other groups. Rather than reviewing all of the catalysts described to date, we focus systematically on the several key elements and their rationale from molecules studied in homogeneous media. We organize these catalysts based on how the crucial oxygen-oxygen bond step takes place, whether via a water nucleophilic attack or via the interaction of two M-O units, rather than based on the nuclearity of the water oxidation catalysts. Furthermore we have used DFT methodology to characterize key intermediates and transition states. The combination of both theory and experiments has allowed us to get a complete view of the water oxidation cycle for the different catalysts studied. Finally, we also describe the various deactivation pathways for these catalysts. PMID:24328498

Sala, Xavier; Maji, Somnath; Bofill, Roger; García-Antón, Jordi; Escriche, Lluís; Llobet, Antoni

2014-02-18

175

Ubiquity and diversity of ammonia-oxidizing archaea in water columns and sediments of the ocean  

PubMed Central

Nitrification, the microbial oxidation of ammonia to nitrite and nitrate, occurs in a wide variety of environments and plays a central role in the global nitrogen cycle. Catalyzed by the enzyme ammonia monooxygenase, the ability to oxidize ammonia was previously thought to be restricted to a few groups within the ?- and ?-Proteobacteria. However, recent metagenomic studies have revealed the existence of unique ammonia monooxygenase ?-subunit (amoA) genes derived from uncultivated, nonextremophilic Crenarchaeota. Here, we report molecular evidence for the widespread presence of ammonia-oxidizing archaea (AOA) in marine water columns and sediments. Using PCR primers designed to specifically target archaeal amoA, we find AOA to be pervasive in areas of the ocean that are critical for the global nitrogen cycle, including the base of the euphotic zone, suboxic water columns, and estuarine and coastal sediments. Diverse and distinct AOA communities are associated with each of these habitats, with little overlap between water columns and sediments. Within marine sediments, most AOA sequences are unique to individual sampling locations, whereas a small number of sequences are evidently cosmopolitan in distribution. Considering the abundance of nonextremophilic archaea in the ocean, our results suggest that AOA may play a significant, but previously unrecognized, role in the global nitrogen cycle. PMID:16186488

Francis, Christopher A.; Roberts, Kathryn J.; Beman, J. Michael; Santoro, Alyson E.; Oakley, Brian B.

2005-01-01

176

Dynamics of nitric oxide and nitrous oxide emission during full-scale reject water treatment.  

PubMed

Emission of NO and N2O from a full-scale two-reactor nitritation-anammox process was determined during a measurement campaign at the Dokhaven-Sluisjesdijk municipal WWTP (Rotterdam, NL). The NO and N2O levels in the off-gas responded to the aeration cycles and the aeration rate of the nitritation reactor, and to the nitrite and dissolved oxygen concentration. Due to the strong fluctuations in the NO and N2O levels in both the nitritation and the anammox reactor, only time-dependent measurements could yield a reliable estimate of the overall NO and N2O emissions. The NO emission from the nitritation reactor was 0.2% of the nitrogen load and the N2O emission was 1.7%. The NO emission from the anammox reactor was determined to be 0.003% of the nitrogen load and the N2O emission was 0.6%. Emission of NO2 could not be detected from the nitritation-anammox system. Denitrification by ammonia-oxidizing bacteria was considered to be the most probable cause of NO and N2O emission from the nitritation reactor. Since anammox bacteria have not been shown to produce N2O under physiological conditions, it is also suspected that ammonia-oxidizing bacteria contribute most to N2O production in the anammox reactor. The source of NO production in the anammox reactor can be either anammox bacteria or denitrification by heterotrophs or ammonia-oxidizing bacteria. Based on the results and previous work, it seems that a low dissolved oxygen or a high nitrite concentration are the most likely cause of elevated NO and N2O emission by ammonia-oxidizing bacteria. The emission was compared with measurements at other reject water technologies and with the main line of the Dokhaven-Sluisjesdijk WWTP. The N2O emission levels in the reject water treatment seem to be in the same range as for the main stream of activated sludge processes. Preliminary measurements of the N2O emission from a one-reactor nitritation-anammox system indicate that the emission is lower than in two-reactor systems. PMID:17920100

Kampschreur, Marlies J; van der Star, Wouter R L; Wielders, Hubert A; Mulder, Jan Willem; Jetten, Mike S M; van Loosdrecht, Mark C M

2008-02-01

177

A Review of RedOx Cycling of Solid Oxide Fuel Cells Anode  

PubMed Central

Solid oxide fuel cells are able to convert fuels, including hydrocarbons, to electricity with an unbeatable efficiency even for small systems. One of the main limitations for long-term utilization is the reduction-oxidation cycling (RedOx cycles) of the nickel-based anodes. This paper will review the effects and parameters influencing RedOx cycles of the Ni-ceramic anode. Second, solutions for RedOx instability are reviewed in the patent and open scientific literature. The solutions are described from the point of view of the system, stack design, cell design, new materials and microstructure optimization. Finally, a brief synthesis on RedOx cycling of Ni-based anode supports for standard and optimized microstructures is depicted. PMID:24958298

Faes, Antonin; Hessler-Wyser, Aïcha; Zryd, Amédée; Van Herle, Jan

2012-01-01

178

Unification of catalytic water oxidation and oxygen reduction reactions: amorphous beat crystalline cobalt iron oxides.  

PubMed

Catalytic water splitting to hydrogen and oxygen is considered as one of the convenient routes for the sustainable energy conversion. Bifunctional catalysts for the electrocatalytic oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are pivotal for the energy conversion and storage, and alternatively, the photochemical water oxidation in biomimetic fashion is also considered as the most useful way to convert solar energy into chemical energy. Here we present a facile solvothermal route to control the synthesis of amorphous and crystalline cobalt iron oxides by controlling the crystallinity of the materials with changing solvent and reaction time and further utilize these materials as multifunctional catalysts for the unification of photochemical and electrochemical water oxidation as well as for the oxygen reduction reaction. Notably, the amorphous cobalt iron oxide produces superior catalytic activity over the crystalline one under photochemical and electrochemical water oxidation and oxygen reduction conditions. PMID:25469760

Indra, Arindam; Menezes, Prashanth W; Sahraie, Nastaran Ranjbar; Bergmann, Arno; Das, Chittaranjan; Tallarida, Massimo; Schmeißer, Dieter; Strasser, Peter; Driess, Matthias

2014-12-17

179

ARSENIC CYCLING WITHIN THE WATER COLUMN OF A SMALL LAKE RECEIVING CONTAMINATED GROUND WATER DISCHARGE  

EPA Science Inventory

The fate of arsenic discharged from contaminated ground water to a small, shallow lake at a hazardous waste site is controlled, in part, by the rate of ferrous iron oxidation-precipitation and arsenic sorption occurring near the lake chemocline. Laboratory experiments were condu...

180

Theoretical investigation of solar energy conversion and water oxidation catalysis  

E-print Network

Solar energy conversion and water oxidation catalysis are two great scientific and engineering challenges that will play pivotal roles in a future sustainable energy economy. In this work, I apply electronic structure ...

Wang, Lee-Ping

2011-01-01

181

Polyoxometalates as Water Oxidation Catalysts and Their Use in Light-Driven Water Splitting.  

E-print Network

??Abstract Polyoxometalates as Water Oxidation Catalysts and Their Use in Light-Driven Water Splitting By Qiushi Yin Transition-metal substituted polyoxometalates are used to construct molecular analogues… (more)

Yin, Qiushi

2010-01-01

182

Supercritical water oxidation data acquisition testing. Final report, Volume I  

SciTech Connect

This report discusses the phase one testing of a data acquisition system for a supercritical water waste oxidation system. The system is designed to destroy a wide range of organic materials in mixed wastes. The design and testing of the MODAR Oxidizer is discussed. An analysis of the optimized runs is included.

NONE

1996-11-01

183

Mechanisms for synergistic oxidation of organics in ultrapure water systems  

Microsoft Academic Search

A mechanistic model is developed for the distribution, oxidation, and removal of organic impurities in typical polishing loops of ultrapure water (UPW) plants. The model is applied to the case of the oxidation of organics by ultraviolet (UV), ozone, and a unique method of adding ozone to the UV unit. The model is validated with direct experimental measurements using various

Kon-Tsu Kin; Farhang Shadman

2000-01-01

184

Control of methanol oxidation by ionic behavior in supercritical water.  

PubMed

In supercritical water the rate of methanol oxidation was controlled by ionic behavior as follows: the oxidation rate of methanol decreased with increasing proton and hydroxide ion concentration, possibly due to stabilization of the reactant, while that of CO was suppressed by added protons and enhanced by added hydroxide ions. PMID:12240145

Watanabe, M; Sue, K; Adschiri, T; Inomata, H; Smith, R L; Arai, K

2001-11-01

185

Anodic oxidation of phenol for waste water treatment  

Microsoft Academic Search

The electrochemical oxidation of phenol for waste water treatment was studied at a platinum anode. Analysis of reaction intermediates and a carbon balance has shown that the reaction occurs by two parallel pathways; chemical oxidation with electrogenerated hydroxyl radicals and direct combustion of adsorbed phenol or\\/and its aromatic intermediates to CO2.

Ch. Comninellis; C. Pulgarin

1991-01-01

186

Nitrogen cycling in the offshore waters of the Black Sea  

NASA Astrophysics Data System (ADS)

The purpose of this study was to measure directly the rates of several of the processes responsible for the production and utilization of nitrogenous nutrients, and to use these rates and other data to generate an annual nitrogen budget for the Black Sea. Water column samples and experimentation with 15N labeled nutrients in the offshore waters of the Black Sea reveal strong seasonal cycles in the utilization of different forms of N, the regeneration of NH 4+ and the production of NO 2- in and below the surface mixed layer. There was no opportunity to sample during winter, but historical data and contemporary satellite ocean color data for the study period allow us to make extrapolations to a full annual cycle for the Black Sea N budget. The processes supplying N to, and the microbial processes within, the Cold Intermediate Layer (CIL), which lies below the surface mixed layer, figure prominently in determining the sources of N available for primary production. The uptake of NO 3- by phytoplankton in this system was less sensitive to NH 4+ concentration than has been observed in many oceanic waters. The seasonal shift in nutrient uptake kinetics was consistent with seasonality of nutrient availability. Rates of in situ NO 2- production (and inferred nitrification) for the offshore waters was 1.6 × 10 11 mol y -1, three times the published estimates for NO 3- supplied from the NW Shelf (NWS) region, which originates from riverine discharges. Measured rates of nitrification in the CIL are about 60% of phytoplankton NO 3- + NO 2- uptake (2.8 × 10 11 mol y -1). Remineralization is about 25% of the NH 4+ phytoplankton utilization rate (3.8 × 10 11 mol y -1). Within the CIL NH 4+ is utilized in NO 2- production (and implied nitrification) at a rate that is similar to the rate of NH 4+ remineralization from organic matter. By preserving the rates that are determined with the most confidence, and making adjustments to the rates least confidently determined, nitrification (+60%, which is within the range of published values) and ammonium remineralization (+13%), the Black Sea N budget can be brought into balance. A balanced annual budget for N cycling in the offshore waters of the Black Sea estimates a particle export rate from the oxygenated surface layer to the deep anoxic waters equivalent to 8% of the total N production. We extrapolate an annual mean f-ratio of 0.38 by the conventional formulation (NO 3- uptake: total N uptake). However, the balanced N budget permits a direct comparison of allochthonous sources of N to total N production in this unusual aquatic ecosystem, resulting in an f-ratio of 0.17, which is reconciled with particulate export when the budgeted losses due to anammox and denitrification are included. The NO 3- content of the CIL is sensitive to year-to-year fluctuations in the source of N from the NWS. These processes plus the intensity of winter mixing, which supplies new N for the fall-winter bloom, are influenced by climate. Oscillations in winter temperature over the past few decades allow inference as to how the Black Sea N budget may be affected by future warmer conditions for this region.

McCarthy, James J.; Yilmaz, Aysen; Coban-Yildiz, Yesim; Nevins, John L.

2007-09-01

187

Heat-sterilized silver oxide-zinc cells: Cycle life studies  

NASA Technical Reports Server (NTRS)

A JPL study was conducted to evaluate the cell design parameters that contribute to the cycle life of sealed, heat-sterilized silver oxide-zinc cells. Test cells having a rated capacity of 4.2 A-h were fabricated using zinc oxide electrodes prepared by the sintered Teflon process. Two separator variations were evaluated, one having acrylic acid and the other methacrylic acid grafted to irradiated polyethylene film. Significant results of this study include the following: (1) cycle life in excess of 300 cycles was attained; (2) a zinc oxide/silver stoichiometric ratio of 1.5 resulted in greater cycle life than a ratio of 1.1, and similar cycle life to cells having a ratio of 2; (3) cells having methacrylic acid grafted separators suffered somewhat less in capacity loss due to zinc electrode shape change than cells having acrylic acid type; (4) use of acrylic acid grafted separators was slightly superior to the methacrylic acid type in respect to silver penetration; and (5) the inclusion of a layer of potassium titanate paper adjacent to the zinc electrodes resulted in cells that achieved higher cycle life before any of the group failed than that reached by cells of any other construction.

Arms, J. T.

1973-01-01

188

The NASA Energy and Water cycle Extreme (NEWSE) Integration Project  

NASA Astrophysics Data System (ADS)

Skillful predictions of water and energy cycle extremes (flood and drought) are elusive. To better understand the mechanisms responsible for water and energy extremes, and to make decisive progress in predicting these extremes, the collaborative NASA Energy and Water cycle Extremes (NEWSE) Integration Project, is studying these extremes in the U.S. Southern Great Plains (SGP) during 2006-2007, including their relationships with continental and global scale processes, and assessment of their predictability on multiple space and time scales. It is our hypothesis that an integrative analysis of observed extremes which reflects the current understanding of the role of SST and soil moisture variability influences on atmospheric heating and forcing of planetary waves, incorporating recently available global and regional hydro- meteorological datasets (i.e., precipitation, water vapor, clouds, etc.) in conjunction with advances in data assimilation, can lead to new insights into the factors that lead to persistent drought and flooding. We will show initial results of this project, whose goals are toprovide an improved definition, attribution and prediction on sub-seasonal to interannual time scales, improved understanding of the mechanisms of decadal drought and its predictability, including the impacts of SST variability and deep soil moisture variability, and improved monitoring/attributions, with transition to applications; a bridging of the gap between hydrological forecasts and stakeholders (utilization of probabilistic forecasts, education, forecast interpretation for different sectors, assessment of uncertainties for different sectors, etc.). *The NEWSE Team is: Romanou, Anastasiam, Columbia U.; Brian Soden, U. Miami; William Lapenta, NASA- MSFC; Megan Larko, CREW; Bing Lin, NASA-LaRC; Christa Peters-Lidard, NASA-GSFC; Xiquan Dong, U. North Dakota; Debbie Belvedere, CREW; Mathew Sapiano, U. Maryland; Duane Waliser, NASA-JPL; Eni Njoku, NASA/JPL; Eric Fetzer, NASA-JPL; Eyal Amitai, NASA-GSFC; Xiaogang Gao, U. California, Irvine; George Huffman, NASA-GSFC & SSAI; Jared Entin, NASA; Joseph Santanello, NASA-GSFC; John Roads, UCSD; W. Timothy Liu, NASA-JPL; Lixin Lu, Colorado State U.; Zhengzhao Luo, Colorado State U.; Michael Bosilovich, NASA-GSFC; Michael Jasinski, NASA-GSFC; William Olson, NASA-GSFC & UMBC-GEST; Pete Robertson, NASA-MSFC; Phil Arkin, U. Maryland; Paul Houser, CREW & GMU; Ralph Ferraro, NOAA; Pete Robertson, NASA-MSFC; Robert Schiffer; UMBC-GEST; Sujay Kumar, NASA-GSFC; Joseph A. Santanello, NASA-GSFC; Tristan L'Ecuyer, Colorado State U.; Wei-Kuo Tao; NASA-GSFC; Xia Feng; George Mason U.

Houser, P. R.; Lapenta, W.; Schiffer, R.

2008-05-01

189

Capacity and cycle-life of batteries using bismuth-bearing oxide  

NASA Astrophysics Data System (ADS)

An examination is made of the capacity performance of lead-acid positive electrodes which are prepared from bismuth (Bi)-bearing oxide. This oxide is produced from Pasminco VRLA Refined™ lead which contains 0.05 wt.% Bi. For comparison, benchmark tests are performed on electrodes made from oxide with virtually no bismuth (<0.005 wt.%). The change in capacity is investigated by means of a purpose-built `compression cell'. With this design, the positive active-material is constrained under the action of a desirable, constant force during charge-discharge cycling. In general, the capacity increases with the compressive force. Importantly, the use of Bi-bearing oxide yields higher initial capacity and then a significantly faster rise in capacity to the full value with subsequent cycling. Commercial VRLA batteries made with Bi-bearing oxide exhibit a lower rate of self-discharge than those fabricated with conventional factory oxide. In addition, Bi-bearing batteries provide good cycle-life under the International Electrotechnical Commission (IEC) test.

Lam, L. T.; Haigh, N. P.; Lim, O. V.; Rand, D. A. J.; Manders, J. E.

190

Nosocomial contamination by Mycobacterium gordonae in hospital water supply and super-oxidized water.  

PubMed

We experienced contamination by Mycobacterium gordonae of the hospital water of our surgical ward. The contamination was discovered following detection of the organism in operative lung samples, washed with super-oxidized water. Repeated examination of water demonstrated contamination by M. gordonae occurred only in the surgical ward, related to the apparatus for making super-oxidized water. No patients were infected by M. gordonae. After changing the water supply equipment and cleaning the water tubes, M. gordonae in the water disappeared. PMID:12009823

Fujita, Jiro; Nanki, N; Negayama, K; Tsutsui, S; Taminato, T; Ishida, T

2002-05-01

191

Infiltrated Phlogopite Micas with Superior Thermal Cycle Stability as Compressive Seals for Solid Oxide Fuel Cells  

SciTech Connect

Thermal cycle stability is one of the most stringent requirements for sealants in solid oxide fuel cell stacks. The sealants have to survive several hundreds to thousands of thermal cycles during lifetime operation in stationary and transportation applications. Recently, researchers at the Pacific Northwest National Laboratory have developed a novel method to infiltrate the mica flakes with a wetting or liquid forming material such that the leak path will be reduced from 3-D to 2-D and achieve good thermal cycle stability with low leak rates.

Chou, Y S.; Stevenson, Jeffry W.

2005-03-01

192

Nitric oxide alleviates aluminum-induced oxidative damage through regulating the ascorbate-glutathione cycle in roots of wheat.  

PubMed

The possible association with nitric oxide (NO) and ascorbate-glutathione (AsA-GSH) cycle in regulating aluminum (Al) tolerance of wheat (Triticum aestivum L.) was investigated using two genotypes with different Al resistance. Exposure to Al inhibited root elongation, and triggered lipid peroxidation and oxidation of AsA to dehydroascorbate and GSH to glutathione disulfide in wheat roots. Exogenous NO significantly increased endogenous NO levels, and subsequently alleviated Al-induced inhibition of root elongation and oxidation of AsA and GSH to maintain the redox molecules in the reduced form in both wheat genotypes. Under Al stress, significantly increased activities and gene transcriptional levels of ascorbate peroxidase, glutathione reductase, and dehydroascorbate reductase, were observed in the root tips of the Al-tolerant genotype Jian-864. Nitric oxide application enhanced the activity and gene transcriptional level of these enzymes in both wheat genotypes. ?-Glutamylcysteine synthetase was not significantly affected by Al or NO, but NO treatments increased the activity of glutathione peroxidase and glutathione S-transferase to a greater extent than the Al-treated wheat seedlings. Proline was significantly decreased by Al, while it was not affected by NO. These results clearly suggest that NO protects wheat root against Al-induced oxidative stress, possibly through its regulation of the AsA-GSH cycle. PMID:25319364

Sun, Chengliang; Liu, Lijuan; Yu, Yan; Liu, Wenjing; Lu, Lingli; Jin, Chongwei; Lin, Xianyong

2014-10-16

193

Conversions of Mn oxides to nanolayered Mn oxide in electrochemical water oxidation at near neutral pH, all to a better catalyst: catalyst evolution.  

PubMed

Here, for the first time, it is reported that some Mn oxides after a few hours convert to a nanolayered Mn oxide when the compounds are used as water-oxidizing catalysts in a water electrolysis device at near neutral pH and in the presence of LiClO4. The new nanolayered Mn oxide is more active than other Mn oxides toward water oxidation. This result is very important for artificial photosynthetic systems that use Mn oxides as water-oxidizing catalysts. PMID:24149796

Najafpour, Mohammad Mahdi; Haghighi, Behzad; Sedigh, Davood Jafarian; Ghobadi, Mohadeseh Zarei

2013-12-28

194

Copper as a robust and transparent electrocatalyst for water oxidation.  

PubMed

Copper metal is in theory a viable oxidative electrocatalyst based on surface oxidation to Cu(III) and/or Cu(IV) , but its use in water oxidation has been impeded by anodic corrosion. The in?situ formation of an efficient interfacial oxygen-evolving Cu catalyst from Cu(II) in concentrated carbonate solutions is presented. The catalyst necessitates use of dissolved Cu(II) and accesses the higher oxidation states prior to decompostion to form an active surface film, which is limited by solution conditions. This observation and restriction led to the exploration of ways to use surface-protected Cu metal as a robust electrocatalyst for water oxidation. Formation of a compact film of CuO on Cu surface prevents anodic corrosion and results in sustained catalytic water oxidation. The Cu/CuO surface stabilization was also applied to Cu nanowire films, which are transparent and flexible electrocatalysts for water oxidation and are an attractive alternative to ITO-supported catalysts for photoelectrochemical applications. PMID:25581365

Du, Jialei; Chen, Zuofeng; Ye, Shengrong; Wiley, Benjamin J; Meyer, Thomas J

2015-02-01

195

Energetic basis of catalytic activity of layered nanophase calcium manganese oxides for water oxidation  

PubMed Central

Previous measurements show that calcium manganese oxide nanoparticles are better water oxidation catalysts than binary manganese oxides (Mn3O4, Mn2O3, and MnO2). The probable reasons for such enhancement involve a combination of factors: The calcium manganese oxide materials have a layered structure with considerable thermodynamic stability and a high surface area, their low surface energy suggests relatively loose binding of H2O on the internal and external surfaces, and they possess mixed-valent manganese with internal oxidation enthalpy independent of the Mn3+/Mn4+ ratio and much smaller in magnitude than the Mn2O3-MnO2 couple. These factors enhance catalytic ability by providing easy access for solutes and water to active sites and facile electron transfer between manganese in different oxidation states. PMID:23667149

Birkner, Nancy; Nayeri, Sara; Pashaei, Babak; Najafpour, Mohammad Mahdi; Casey, William H.; Navrotsky, Alexandra

2013-01-01

196

Rare earth element partitioning between hydrous ferric oxides and acid mine water during iron oxidation  

USGS Publications Warehouse

Ferrous iron rapidly oxidizes to Fe (III) and precipitates as hydrous Fe (III) oxides in acid mine waters. This study examines the effect of Fe precipitation on the rare earth element (REE) geochemistry of acid mine waters to determine the pH range over which REEs behave conservatively and the range over which attenuation and fractionation occur. Two field studies were designed to investigate REE attenuation during Fe oxidation in acidic, alpine surface waters. To complement these field studies, a suite of six acid mine waters with a pH range from 1.6 to 6.1 were collected and allowed to oxidize in the laboratory at ambient conditions to determine the partitioning of REEs during Fe oxidation and precipitation. Results from field experiments document that even with substantial Fe oxidation, the REEs remain dissolved in acid, sulfate waters with pH below 5.1. Between pH 5.1 and 6.6 the REEs partitioned to the solid phases in the water column, and heavy REEs were preferentially removed compared to light REEs. Laboratory experiments corroborated field data with the most solid-phase partitioning occurring in the waters with the highest pH. ?? 2004 Elsevier Ltd. All rights reserved.

Verplanck, P.L.; Nordstrom, D.K.; Taylor, H.E.; Kimball, B.A.

2004-01-01

197

The Global Terrestrial Water Cycle Earth System Data Record  

NASA Astrophysics Data System (ADS)

A new balanced global terrestrial water cycle information has been created for NASAs' Making Earth Science Data Records for use in Research Environments (MEaSURE) project. It is comprised of multiple remotely-sensed and model generated data, and has been merged into a single unified multi-decade, high spatial resolution, climate consistent Earth Science Data Record (ESDR). In addition to the unified ESDR, the seven remotely-sensed and model generated input datasets are also available as ESDRs. These are: (1) VIC model derived water cycle variables, (3 hourly, from 1948 - 2010, on a 0.25 degree grid); (2) Satellite derived precipitation data from two separate sources: (a) GPCC data, (monthly, from 1983 - 1998, on a 0.5 degree grid), and (b) TRMM TMPA data (3 hourly, from 1998 - 2010, on a 0.25 degree grid); (3) Satellite derived evapotranspiration data, based on the SRB/ISCCP radiation forcings (3 hourly, from 1983 - 2007, on a 0.5 degree spatial resolution; (4) Satellite based soil moisture is derived from multiple satellite sensors, but, primarily the TRMM TMI and AMSR-E (daily, from 1998 - 2011, on a 0.25 degree grid); (5) Satellite derived water management variables (monthly, from 1992 - 2010, on a variable degree grid); (6) Satellite derived surface radiations, based on ISCCP-DX data, (3 hourly, from 1983 - 2009, on a 0.5 degree grid) (7) Model derived Surface Meteorological Forcing Fields (3 hourly, from 1948 - 2010, on a 0.25 degree grid). This poster illustrates the methodology used to generate the final unified ESDR. The poster gives an overview of the input datasets and the components of the output dataset. Additionally, some of the major challenges in the creation of this dataset are also illustrated, such as understanding where sources of temporal and spatial differences occur between datasets, and biases and uncertainties along with how these challenges were reconciled. These datasets are available through the NASA Goddard Earth Sciences (GES) Data and Information Services Center (DISC), as well as from a dedicated project server, at George Mason University, and are made available to the public, using such tools as FTP and the GrADS-DODS data server. This server provides the web infrastructure to communicate and distribute the large amount of data and documentations/metadata to the community. Along with these distribution tools, metrics were put in place to track user information, such as origins and number of visits and datasets downloaded.

MacCracken, R. F.; Wood, E. F.; Sheffield, J.; Houser, P. R.; Lettenmaier, D. P.; Pinker, R. T.; Pan, M.; Kummerow, C. D.; Gao, H.; Coccia, G.; Bytheway, J. L.

2013-12-01

198

CP12-mediated protection of Calvin-Benson cycle enzymes from oxidative stress.  

PubMed

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and phosphoribulokinase (PRK) are two energy-consuming enzymes of the Calvin-Benson cycle, whose regulation is crucial for the global balance of the photosynthetic process under different environmental conditions. In oxygen phototrophs, GAPDH and PRK regulation involves the redox-sensitive protein CP12. In the dark, oxidized chloroplast thioredoxins trigger the formation of a GAPDH/CP12/PRK complex in which both enzyme activities are down-regulated. In this report, we show that free GAPDH (A4-isoform) and PRK are also inhibited by oxidants like H2O2, GSSG and GSNO. Both in the land plant Arabidopsis thaliana and in the green microalga Chlamydomonas reinhardtii, both enzymes can be glutathionylated as shown by biotinylated-GSSG assay and MALDI-ToF mass spectrometry. CP12 is not glutathionylated but homodisulfides are formed upon oxidant treatments. In Arabidopsis but not in Chlamydomonas, the interaction between oxidized CP12 and GAPDH provides full protection from oxidative damage. In both organisms, preformed GAPDH/CP12/PRK complexes are protected from GSSG or GSNO oxidation, and in Arabidopsis also from H2O2 treatment. Overall, the results suggest that the role of CP12 in oxygen phototrophs needs to be extended beyond light/dark regulation, and include protection of enzymes belonging to Calvin-Benson cycle from oxidative stress. PMID:24211189

Marri, Lucia; Thieulin-Pardo, Gabriel; Lebrun, Régine; Puppo, Rémy; Zaffagnini, Mirko; Trost, Paolo; Gontero, Brigitte; Sparla, Francesca

2014-02-01

199

Free amino acids in marine rains: evidence for oxidation and potential role in nitrogen cycling  

Microsoft Academic Search

Previous studies of dissolved organic nitrogen (DON) in precipitation have addressed various aspects of nutrient transport and global nitrogen cycling1. In most of these studies however, the detailed chemical composition of DON was not determined. Analyses of specific organic nitrogen compounds within precipitation can yield new information about sources and transformations of DON as well as about heterogeneous oxidative processes

Kenneth Mopper; Rod G. Zika

1987-01-01

200

Thaumarchaeal ammonium oxidation and evidence for a nitrogen cycle in a subsurface radioactive thermal spring in the Austrian Central Alps.  

PubMed

Previous studies had suggested the presence of ammonium oxidizing Thaumarchaeota as well as nitrite oxidizing Bacteria in the subsurface spring called Franz Josef Quelle (FJQ), a slightly radioactive thermal mineral spring with a temperature of 43.6-47°C near the alpine village of Bad Gastein, Austria. The microbiological consortium of the FJQ was investigated for its utilization of nitrogen compounds and the putative presence of a subsurface nitrogen cycle. Microcosm experiments made with samples from the spring water, containing planktonic microorganisms, or from biofilms, were used in this study. Three slightly different media, enriched with vitamins and trace elements, and two incubation temperatures (30 and 40°C, respectively) were employed. Under aerobic conditions, high rates of conversion of ammonium to nitrite, as well as nitrite to nitrate were measured. Under oxygen-limited conditions nitrate was converted to gaseous compounds. Stable isotope probing with (15)NH4Cl or ((15)NH4)2SO4as sole energy sources revealed incorporation of (15)N into community DNA. Genomic DNA as well as RNA were extracted from all microcosms. The following genes or fragments of genes were successfully amplified, cloned and sequenced by standard PCR from DNA extracts: Ammonia monooxygenase subunit A (amoA), nitrite oxidoreductase subunits A and B (nxrA and nxrB), nitrate reductase (narG), nitrite reductase (nirS), nitric oxide reductases (cnorB and qnorB), nitrous oxide reductase (nosZ). Reverse transcription of extracted total RNA and real-time PCR suggested the expression of each of those genes. Nitrogen fixation (as probed with nifH and nifD) was not detected. However, a geological origin of NH(+) 4 in the water of the FJQ cannot be excluded, considering the silicate, granite and gneiss containing environment. The data suggested the operation of a nitrogen cycle in the subsurface environment of the FJQ. PMID:24904540

Gerbl, Friedrich W; Weidler, Gerhard W; Wanek, Wolfgang; Erhardt, Angelika; Stan-Lotter, Helga

2014-01-01

201

Plumbing the global carbon cycle: Integrating inland waters into the terrestrial carbon budget  

USGS Publications Warehouse

Because freshwater covers such a small fraction of the Earth's surface area, inland freshwater ecosystems (particularly lakes, rivers, and reservoirs) have rarely been considered as potentially important quantitative components of the carbon cycle at either global or regional scales. By taking published estimates of gas exchange, sediment accumulation, and carbon transport for a variety of aquatic systems, we have constructed a budget for the role of inland water ecosystems in the global carbon cycle. Our analysis conservatively estimates that inland waters annually receive, from a combination of background and anthropogenically altered sources, on the order of 1.9 Pg C y-1 from the terrestrial landscape, of which about 0.2 is buried in aquatic sediments, at least 0.8 (possibly much more) is returned to the atmosphere as gas exchange while the remaining 0.9 Pg y-1 is delivered to the oceans, roughly equally as inorganic and organic carbon. Thus, roughly twice as much C enters inland aquatic systems from land as is exported from land to the sea. Over prolonged time net carbon fluxes in aquatic systems tend to be greater per unit area than in much of the surrounding land. Although their area is small, these freshwater aquatic systems can affect regional C balances. Further, the inclusion of inland, freshwater ecosystems provides useful insight about the storage, oxidation and transport of terrestrial C, and may warrant a revision of how the modern net C sink on land is described. ?? 2007 Springer Science+Business Media, LLC.

Cole, J.J.; Prairie, Y.T.; Caraco, N.F.; McDowell, W.H.; Tranvik, L.J.; Striegl, R.G.; Duarte, C.M.; Kortelainen, P.; Downing, J.A.; Middelburg, J.J.; Melack, J.

2007-01-01

202

Transpiring wall supercritical water oxidation test reactor design report  

Microsoft Academic Search

Sandia National Laboratories is working with GenCorp, Aerojet and Foster Wheeler Development Corporation to develop a transpiring wall supercritical water oxidation reactor. The transpiring wall reactor promises to mitigate problems of salt deposition and corrosion by forming a protective boundary layer of pure supercritical water. A laboratory scale test reactor has been assembled to demonstrate the concept. A 1\\/4 scale

B. L. Haroldsen; D. Y. Ariizumi; B. E. Mills; B. G. Brown; D. C. Rousar

1996-01-01

203

THE FORMATION OF PB(IV) OXIDES IN CHLORINATED WATER  

EPA Science Inventory

Recent research has shown that Pb(IV) oxides can play an important geochemical role in drinking water distribution systems. The basis of most guidance for lead control in drinking water, however, presumes that Pb(II) solids control lead solubility. Therefore, it is important that...

204

Supercritical water fuel cleaning for improved combined cycle performance  

SciTech Connect

A revolutionary hydrothermal heat recovery steam generator (HRSG) is being developed by a federal, state university and industry partnership to produce clean fuels for gas turbines. The patented hydrothermal HRSG will accept solutions and emulsions without corrosion and deposition on heat transfer surfaces. An advanced continuous-flow pilot plant is being designed to test the HRSG over a wide range of operating conditions, including the supercritical conditions of water, above 221 bar (3205 psia) and 374 C (705 F). Water at these conditions can be used to clean emulsions of crude oil, composted refuse derived fuel, coal fines, and coal water fuels. Data shows that fuel nitrogen will be converted to nitrogen gas. Inorganic materials, such as sulfur, chlorine, alkali metals, ash, vanadium and other metals can be separated and removed for recycle or disposal. Carbon can be sequestered in char for decreased carbon dioxide emissions and activated for use as an adsorbent. Combining the new HRSG with a special condensing turbine and a modern gas turbine promises to increase power output, efficiency, availability and reliability in a new Vapor Transmission Cycle (VTC). The condensing turbine reduces the pressure of steam and fuel vapor to the gas turbine combustor inlet pressure, driving a generator and high-pressure feed pump. The condensing turbine reduces the temperature for final removal of contaminants while maintaining combustibility of the vapor for high turbine inlet temperature. Water is condensed for recycling to the process, eliminating water treatment costs and effluents. An Engineering Study is being prepared at the University of North Dakota Energy and Environmental Research Center (EERC). An Aspen Technology, Inc. computer-based process simulation model has been prepared in collaboration with a consultant from the Los Alamos National Laboratory and EERC. The process simulation model includes materials and energy balances that simulate commercial-scale operations for system optimization, using test data. Preliminary bench-scale test data at subcritical conditions for lignite, refuse derived fuel, and tire rubber are presented, including yield data incorporated in the process model. The model has been used to compare the VTC to commercially available technologies. These results are presented, with conclusions affecting the design of the pilot plant.

Tolman, R.; Timpe, R.C.; Parkinson, W.J.

1998-07-01

205

Position in Cell Cycle Controls the Sensitivity of Colon Cancer Cells to Nitric Oxide-Dependent Programmed Cell Death  

Microsoft Academic Search

Mounting evidence suggests that the position in the cell cycle of cells exposed to an oxidative stress could determine their survival or apoptotic cell death. This study aimed at determining whether nitric oxide (NO)- induced cell death in colon cancer cells might depend on their position in the cell cycle, based on a clone of the cancer cell line HT29

Anne Jarry; Laetitia Charrier; Chantal Bou-Hanna; Marie-Claire Devilder; Veronique Crussaire; Marc G. Denis; Genevieve Vallette; Christian L. Laboisse

2004-01-01

206

Light-driven water oxidation for solar fuels  

PubMed Central

Light-driven water oxidation is an essential step for conversion of sunlight into storable chemical fuels. Fujishima and Honda reported the first example of photoelectrochemical water oxidation in 1972. In their system, TiO2 was irradiated with ultraviolet light, producing oxygen at the anode and hydrogen at a platinum cathode. Inspired by this system, more recent work has focused on functionalizing nanoporous TiO2 or other semiconductor surfaces with molecular adsorbates, including chromophores and catalysts that absorb visible light and generate electricity (i.e., dye-sensitized solar cells) or trigger water oxidation at low overpotentials (i.e., photocatalytic cells). The physics involved in harnessing multiple photochemical events for multielectron reactions, as required in the four-electron water oxidation process, has been the subject of much experimental and computational study. In spite of significant advances with regard to individual components, the development of highly efficient photocatalytic cells for solar water splitting remains an outstanding challenge. This article reviews recent progress in the field with emphasis on water-oxidation photoanodes inspired by the design of functionalized thin film semiconductors of typical dye-sensitized solar cells. PMID:25364029

Young, Karin J.; Martini, Lauren A.; Milot, Rebecca L.; III, Robert C. Snoeberger; Batista, Victor S.; Schmuttenmaer, Charles A.; Crabtree, Robert H.; Brudvig, Gary W.

2014-01-01

207

Oxidation of arsenate(III) with manganese oxides in water treatment  

Microsoft Academic Search

Arsenate(III) is the more toxic form of inorganic arsenic and its removal from drinking water is less effective as compared to arsenate(V). Arsenate(III) persists in aerated water, even at high pH, but is easily oxidized by managanese dioxides. The oxidation of As(III) follows a second order rate law with respect to As(III). The reaction rate is effected by the initial

Wolfgang Driehaus; Reiner Seith; Martin Jekel

1995-01-01

208

Sensitivity Analysis of Reprocessing Cooling Times on Light Water Reactor and Sodium Fast Reactor Fuel Cycles  

SciTech Connect

The purpose of this study is to quantify the effects of variations of the Light Water Reactor (LWR) Spent Nuclear Fuel (SNF) and fast reactor reprocessing cooling time on a Sodium Fast Reactor (SFR) assuming a single-tier fuel cycle scenario. The results from this study show the effects of different cooling times on the SFR’s transuranic (TRU) conversion ratio (CR) and transuranic fuel enrichment. Also, the decay heat, gamma heat and neutron emission of the SFR’s fresh fuel charge were evaluated. A 1000 MWth commercial-scale SFR design was selected as the baseline in this study. Both metal and oxide CR=0.50 SFR designs are investigated.

R. M. Ferrer; S. Bays; M. Pope

2008-04-01

209

Nonlinear Source -" Receptor Relationship due to Interactions between Atmospheric Constituents, Water Cycle and Biogenic Emissions  

NASA Astrophysics Data System (ADS)

Specific economic sectors or source regions emit a wide variety of air pollutants which influence climate and air quality. This includes emissions of greenhouse gases, chemical species which affect the oxidation capacity of the atmosphere and the concentrations of ozone and methane, and aerosol particles or aerosol precursors. Regional climate respectively weather controls transport and removal of pollutants, chemical transformation pathways, particle formation rate and sink processes as well as emissions from natural sources. Interactions between aerosols and trace gases modify their global and regional distributions. Thus, climatic and environmental impacts are not only controlled by amount and chemical composition of pollutant emissions but in addition also by their interactions and the local meteorological conditions in the source region. For the development of mitigation strategies to minimize adverse conditions attributed to climate change and air pollution we need a better understanding of the role of source location, impact of interactions and feedbacks and of the influence of climate change on the chemical composition of the atmosphere. To demonstrate interactions and feedbacks between the cycles of gaseous and particulate atmospheric constituents, the water cycle, the biosphere and the changing climate we will present results of a series of numerical model simulations. Investigations include interactions between greenhouse gas warming, water cycle and aerosol cycle (Feichter et al., 2004), between aerosol cycles (Stier et al., 2006), between marine biogeochemistry and aerosol cycles (Kloster et al., 2006), and between gas-phase air chemistry and aerosol constituents (Pozzoli et al., 2007). The presentation discusses possible interactions and feedbacks and emphasizes the need for a better integration of the different Earth system components in climate and air quality models. Finally, the question whether anthropogenic emissions from different regions result in different climate sensitivity will be raised. Feichter J, Roeckner E, Lohmann U., Liepert B (2004): Nonlinear aspects of the climate response to greenhouse gas and aerosol forcing, Journal of Climate; 17, No 12, 2384-2398. Kloster, S. , Feichter, J., Maier-Reimer, E., Roeckner, Wetzel, P., Six, K.D., Stier, P. and Esch, M., (2007): Response of dimethylsulfide (DMS) in the ocean and atmosphere to global warming, J. Geophys. Res. (subm). Stier, P., J. Feichter, S. Kloster, E. Vignati, and J. Wilson (2006): Emission-Induced Nonlinearities in the Global Aerosol System - Results from the ECHAM5-HAM Aerosol-Climate Model, J. Clim Pozzoli L, I Bey, S Rast, M Schultz, P Stier and Feichter, (2007): Trace gas and aerosol interactions in a global coupled model of chemistry-aerosol-climate (to be subm.).

Kinne, S.; Feichter, J.; Rast, S.; Bey, I.; Folberth, G.; Pozzoli, L.; Kloster, S.; Stier, P.

2007-05-01

210

Dissolved N2/Ar Ratios in Sedimentary Pore Waters: A New Twist in Marine Nitrogen Cycle  

NASA Astrophysics Data System (ADS)

The nitrogen cycle is comprised predominantly of biologically mediated pathways, leading to a series of negative feedbacks that stabilize the cycle. Sedimentary denitrification, the major sink in the nitrogen budget, is regulated by the rate of organic carbon rain to the sea floor, as well as oxygen concentrations in overlying bottom waters. The sensitivity of sedimentary denitrification as a negative feedback can be expressed as a ratio between total denitrification (including nitrification sub-cycle) rates integrated over depth (fluxes) and fluxes of remineralized organic carbon out of the sediments, Ndenitr/Coxid_total. We have investigated benthic nitrogen cycling in three, semi-enclosed basins of the California Borderlands: Santa Monica, San Pedro and Santa Barbara located in the regime of seasonal coastal upwelling. Deep water in these basins is separated from the open ocean by sills of various depths, contributing to the low [O2], <1 to10 uM. In this study, we developed a method to sample pore waters for dissolved gas analysis. Ratios between O2, Ar and N2 were determined on extracted pore waters with 1) offline cryogenic extraction and subsequent analysis on Finnigan Delta Plus IRMS with 8 collectors; 2) Membrane Inlet Mass Spectrometery (MIMS). Vertical profiles of pore water N2/Ar in the three basins indicate N2 production at depth horizons which exceed by a factor of 5 to 20 the depth of nitrate penetration supported solely by diffusive flux. At depths of maximum subsurface N2 production, we discovered large pools of intracellular nitrate. The relationship between ?15N and ?18O of nitrate are consistent with the activity of a membrane-bound nitrate reductase affecting the measured isotopic composition of the nitrate pool (Granger et al., 2008, in press). In addition, increases in ?15N of pore water NH4 at this depth suggests that at least some of the nitrate might be used for anaerobic ammonium oxidation. Our model estimates up to 25 % of the measured total nitrate flux into the sediments must be transported by non-diffusive processes to support the subsurface N2 production rate. We hypothesize that nitrate is transported to depth by motile microorganisms, bacteria or protists, for use in yet to be identified reactions with sulfide, dissolved metals or organic matter. We propose that the non-local transport of nitrate also sustains the population of Anammox performing bacteria, living in close association with nitrate transporting organisms and contributing to the subsurface N2 production. This process presents yet another pathway for nitrate losses from the oceans, increasing sensitivity of sedimentary denitrification as a stabilizing feedback in the nitrogen cycle, as the conversion of transported nitrate to N2 may not be directly linked to oxidation of the organic carbon.

Berelson, W.; Prokopenko, M. G.; Sigman, D. M.; Hammond, D.

2008-12-01

211

Nano-sized manganese oxides as biomimetic catalysts for water oxidation in artificial photosynthesis: a review  

PubMed Central

There has been a tremendous surge in research on the synthesis of various metal compounds aimed at simulating the water-oxidizing complex (WOC) of photosystem II (PSII). This is crucial because the water oxidation half reaction is overwhelmingly rate-limiting and needs high over-voltage (approx. 1 V), which results in low conversion efficiencies when working at current densities required for hydrogen production via water splitting. Particular attention has been given to the manganese compounds not only because manganese has been used by nature to oxidize water but also because manganese is cheap and environmentally friendly. The manganese–calcium cluster in PSII has a dimension of about approximately 0.5 nm. Thus, nano-sized manganese compounds might be good structural and functional models for the cluster. As in the nanometre-size of the synthetic models, most of the active sites are at the surface, these compounds could be more efficient catalysts than micrometre (or bigger) particles. In this paper, we focus on nano-sized manganese oxides as functional and structural models of the WOC of PSII for hydrogen production via water splitting and review nano-sized manganese oxides used in water oxidation by some research groups. PMID:22809849

Najafpour, Mohammad Mahdi; Rahimi, Fahimeh; Aro, Eva-Mari; Lee, Choon-Hwan; Allakhverdiev, Suleyman I.

2012-01-01

212

Roles of surface water areas for water and solute cycle in Hanoi city, Viet Nam  

NASA Astrophysics Data System (ADS)

Hanoi city, the capital of Viet Nam, has developed beside the Red river. Recent rapid urbanization of this city has reduced a large number of natural water areas such as lakes, ponds and canals not only in the central area but the suburban area. Contrary, the urbanization has increased artificial water areas such as pond for fish cultivation and landscaping. On the other hand, the urbanization has induced the inflow of waste water from households and various kinds of factories to these water areas because of delay of sewerage system development. Inflow of the waste water has induced eutrophication and pollution of these water areas. Also, there is a possibility of groundwater pollution by infiltration of polluted surface water. However, the role of these water areas for water cycle and solute transport is not clarified. Therefore, this study focuses on the interaction between surface water areas and groundwater in Hanoi city to evaluate appropriate land development and groundwater resource management. We are carrying out three approaches: a) understanding of geochemical characteristics of surface water and groundwater, b) monitoring of water levels of pond and groundwater, c) sampling of soil and pond sediment. Correlation between d18O and dD of precipitation (after GNIP), the Red River (after GNIR) and the water samples of this study showed that the groundwater is composed of precipitation, the Red River and surface water that has evaporation process. Contribution of the surface water with evaporation process was widely found in the study area. As for groundwater monitoring, the Holocene aquifers at two sites were in unconfined condition in dry season and the groundwater levels in the aquifer continued to increase through rainy season. The results of isotopic analysis and groundwater level monitoring showed that the surface water areas are one of the major groundwater sources. On the other hand, concentrations of dissolved Arsenic (filtered by 0.45um) in the pore water of the pond sediments were much higher than the pond water and closed to that of groundwater. Also, other metal elements showed the same trend. This result suggested that Arsenic and other metal elements recharged to these ponds is probably adsorbed and removed by sediments (including organic matters). That is, pond sediment plays an important role for solute transport as a filter of Arsenic and metal elements. The results of this study strongly suggest that the natural and artificial surface water areas have important roles for water cycle and solute transport in Hanoi city. Although the number of the natural water areas is decreasing, dredging of artificial water areas increases the infiltration from the surface to aquifers. Therefore, qualitative and quantitative preservation of the surface water areas is important for conservation of groundwater environment and contribute to sustainable groundwater management in Hanoi city.

Hayashi, Takeshi; Kuroda, Keisuke; Do Thuan, An; Tran Thi Viet, Nga; Takizawa, Satoshi

2013-04-01

213

Structural Characterization of Biogenic Manganese Oxides Produced in Sea Water  

NASA Astrophysics Data System (ADS)

Manganese oxides have been coined as the "scavengers of the sea" and play important roles in both marine and freshwater systems. Natural manganese oxide nanoparticles and grain coatings are ubiquitous in the environment and profoundly impact the quality of sediments via their ability to degrade and sequester contaminants. These oxides are believed to form dominantly via oxidation of Mn(II) by marine and freshwater bacteria and have extremely high sorptive capacities for heavy metals. We have used XANES, EXAFS, and synchrotron (SR)-XRD techniques to study biogenic manganese oxides produced by spores of the marine Bacillus sp., strain SG-1 in seawater as a function of reaction time under fully in-situ conditions. The primary biogenic solid-phase Mn oxide product is a hexagonal layered phyollomanganate with an oxidation state similar to that in delta-MnO2. XRD data show the biooxides to have a phyllomanganate 10 basal plane spacing, suggesting the interlayer is hydrated and contains calcium. As the experiment continues, the initial biooxide changes to show triclinic symmetry. Fits to these EXAFS spectra suggest the octahedral layers have low Mn octahedral site vacancies in the lattice and the latyers bend to accommodate Jahn-Teller distortions creating the change in symmetry. The oxides observed in this study as models of Mn(II) bio-oxidation may be representative of the most abundant manganese oxide phase suspended in the oxic and sub-oxic zones of the oceanic water column.

Webb, S. M.; Bargar, J. R.; Tebo, B. M.

2003-12-01

214

SHORTER MENSTRUAL CYCLES ASSOCIATED WITH CHLORINATION BY-PRODUCTS IN DRINKING WATER  

EPA Science Inventory

Shorter Menstrual Cycles Associated with Chlorination by-Products in Drinking Water. Gayle Windham, Kirsten Waller, Meredith Anderson, Laura Fenster, Pauline Mendola, Shanna Swan. California Department of Health Services. In previous studies of tap water consumption we...

215

Multiple Observation Types Jointly Constrain Terrestrial Carbon and Water Cycles  

NASA Astrophysics Data System (ADS)

Information about the carbon cycle potentially constrains the water cycle, and vice versa. This paper explores the utility of multiple observation sets to constrain carbon and water fluxes and stores in a land surface model, and a resulting determination of the Australian terrestrial carbon budget. Observations include streamflow from 416 gauged catchments, measurements of evapotranspiration (ET) and net ecosystem production (NEP) from 12 eddy-flux sites, litterfall data, and data on carbon pools. The model is a version of CABLE (the Community Atmosphere-Biosphere-Land Exchange model), coupled with CASAcnp (a biogeochemical model) and SLI (Soil-Litter-Iso, a soil hydrology model including liquid and vapour water fluxes and the effects of litter). By projecting observation-prediction residuals onto model uncertainty, we find that eddy flux measurements provide a significantly tighter constraint on Australian continental net primary production (NPP) than the other data types. However, simultaneous constraint by multiple data types is important for mitigating bias from any single type. Results emerging from the multiply-constrained model are as follows (with all values applying over 1990-2011 and all ranges denoting ±1 standard error): (1) on the Australian continent, a predominantly semi-arid region, over half (0.64±0.05) of the water loss through ET occurs through soil evaporation and bypasses plants entirely; (2) mean Australian NPP is 2200±400 TgC/y, making the NPP/precipitation ratio about the same for Australia as the global land average; (3) annually cyclic ("grassy") vegetation and persistent ("woody") vegetation respectively account for 0.56±0.14 and 0.43±0.14 of NPP across Australia; (4) the average interannual variability of Australia's NEP (±180 TgC/y) is larger than Australia's total anthropogenic greenhouse gas emissions in 2011 (149 TgCeq/y), and is dominated by variability in desert and savannah regions. The mean carbon budget over 1990-2011 reveals that climate variability and rising CO2 respectively contributed 12±29 and 68±35 TgC/y to Net Biosphere Productivity (NBP, positive to land). However these terrestrial carbon gains were partially offset by fire and land use change (mainly clearing of woody savannah), which caused net losses of 31±5 TgC/y and 18±7 TgC/y respectively. The resultant overall NBP of 31±35 TgC/y offset fossil fuel emissions (95±6 TgC/y) by 32±36%. However, territorial fossil fuel emissions are increasingly being dwarfed by fossil fuel exports: in 2009-2010, Australia exported 2.5 times more carbon in fossil fuels than it emitted by burning fossil fuels for domestic use.

Raupach, M. R.; Haverd, V.; Briggs, P. R.; Canadell, J.; Davis, S. J.; Isaac, P. R.; Law, R.; Meyer, M.; Peters, G. P.; Pickett Heaps, C.; Roxburgh, S. H.; Sherman, B.; van Gorsel, E.; Viscarra Rossel, R.; Wang, Z.

2012-12-01

216

Trace element cycling through iron oxide minerals during redox-driven dynamic recrystallization  

SciTech Connect

Microbially driven iron redox cycling in soil and sedimentary systems, including during diagenesis and fluid migration, may activate secondary abiotic reactions between aqueous Fe(II) and solid Fe(III) oxides. These reactions catalyze dynamic recrystallization of iron oxide minerals through localized and simultaneous oxidative adsorption of Fe(II) and reductive dissolution of Fe(III). Redox-active trace elements undergo speciation changes during this process, but the impact redox-driven recrystallization has on redox-inactive trace elements associated with iron oxides is uncertain. Here we demonstrate that Ni is cycled through the minerals goethite and hematite during redox-driven recrystallization. X-ray absorption spectroscopy demonstrates that during this process adsorbed Ni becomes progressively incorporated into the minerals. Kinetic studies using batch reactors containing aqueous Fe(II) and Ni preincorporated into iron oxides display substantial release of Ni to solution. We conclude that iron oxide recrystallization activated by aqueous Fe(II) induces cycling of Ni through the mineral structure, with adsorbed Ni overgrown in regions of Fe(II) oxidative adsorption and incorporated Ni released in regions of reductive dissolution of structural Fe(III). The redistribution of Ni among the mineral bulk, mineral surface, and aqueous solution appears to be thermodynamically controlled and catalyzed by Fe(II). Our work suggests that important proxies for ocean composition on the early Earth may be invalid, identifies new processes controlling micronutrient availability in soil, sedimentary, and aquatic ecosystems, and points toward a mechanism for trace element mobilization during diagenesis and enrichment in geologic fluids.

Frierdich, Andrew J.; Luo, Yun; Catalano, Jeffrey G. (WU)

2011-11-17

217

Water oxidation and oxygen monitoring by cobalt-modified fluorine-doped tin oxide electrodes.  

PubMed

Electrocatalytic water oxidation occurs at fluoride-doped tin oxide (FTO) electrodes that have been surface-modified by addition of Co(II). On the basis of X-ray photoelectron spectroscopy and transmission electron microscopy measurements, the active surface site appears to be a single site or small-molecule assembly bound as Co(II), with no evidence for cobalt oxide film or cluster formation. On the basis of cyclic voltammetry measurements, surface-bound Co(II) undergoes a pH-dependent 1e(-)/1H(+) oxidation to Co(III), which is followed by pH-dependent catalytic water oxidation. O2 reduction at FTO occurs at -0.33 V vs NHE, allowing for in situ detection of oxygen as it is formed by water oxidation on the surface. Controlled-potential electrolysis at 1.61 V vs NHE at pH 7.2 resulted in sustained water oxidation catalysis at a current density of 0.16 mA/cm(2) with 29,000 turnovers per site over an electrolysis period of 2 h. The turnover frequency for oxygen production per Co site was 4 s(-1) at an overpotential of 800 mV at pH 7.2. Initial experiments with Co(II) on a mesoporous, high-surface-area nanoFTO electrode increased the current density by a factor of ~5. PMID:23692429

Kent, Caleb A; Concepcion, Javier J; Dares, Christopher J; Torelli, Daniel A; Rieth, Adam J; Miller, Andrew S; Hoertz, Paul G; Meyer, Thomas J

2013-06-12

218

Emerging contaminants of public health significance as water quality indicator compounds in the urban water cycle.  

PubMed

The contamination of the urban water cycle (UWC) with a wide array of emerging organic compounds (EOCs) increases with urbanization and population density. To produce drinking water from the UWC requires close examination of their sources, occurrence, pathways, and health effects and the efficacy of wastewater treatment and natural attenuation processes that may occur in surface water bodies and groundwater. This paper researches in details the structure of the UWC and investigates the routes by which the water cycle is increasingly contaminated with compounds generated from various anthropogenic activities. Along with a thorough survey of chemicals representing compound classes such as hormones, antibiotics, surfactants, endocrine disruptors, human and veterinary pharmaceuticals, X-ray contrast media, pesticides and metabolites, disinfection-by-products, algal toxins and taste-and-odor compounds, this paper provides a comprehensive and holistic review of the occurrence, fate, transport and potential health impact of the emerging organic contaminants of the UWC. This study also illustrates the widespread distribution of the emerging organic contaminants in the different aortas of the ecosystem and focuses on future research needs. PMID:24972248

Pal, Amrita; He, Yiliang; Jekel, Martin; Reinhard, Martin; Gin, Karina Yew-Hoong

2014-10-01

219

The diel cycle of water vapor in west Greenland  

NASA Astrophysics Data System (ADS)

present a study of the dynamics of small-scale (~100 km) atmospheric circulation in west Greenland which is dominated by interactions of marine and continental air masses. Water vapor concentration and isotopic ratios measured continuously over a 25 day period in Kangerlussuaq, Greenland were used to monitor the convergence of easterly katabatic winds and westerly sea breezes that form a front between the dry, isotopically depleted, glacial air mass and the moist, isotopically enriched, marine air mass. During the latter 16 days of the measurement period, an interval with no large-scale synoptic interference, the inland penetration of the sea breeze controlled the largest day-to-day humidity and vapor isotopic variations. Kangerlussuaq experienced sea breezes in the afternoon on 9 days, consistent with the long-term average of such occurrences on 56% of days in July and August. The inland position of the sea breeze front is controlled by the katabatic wind strength, which is stronger during times of reduced cloud coverage and/or higher-pressure gradient between the coast and the Greenland ice sheet. The position and movement of the front will likely respond to changes in the general atmospheric circulation and regional radiation balance resulting from global warming, which will, in turn, impact the local hydrological cycle and ecosystem processes.

Kopec, B. G.; Lauder, A. M.; Posmentier, E. S.; Feng, X.

2014-08-01

220

Ecological Modelling xxx (2005) xxxxxx Modelling carbon and water cycles in a beech forest  

E-print Network

Ecological Modelling xxx (2005) xxx­xxx Modelling carbon and water cycles in a beech forest Part I to assess the role of forested areas in the global carbon cycle and in the continental water balance. During with a carbon allocation model and coupled with a soil model. CASTANEA describes canopy photosynthesis

Boyer, Edmond

221

Ecological Modelling xxx (2005) xxxxxx Modelling carbon and water cycles in a beech forest  

E-print Network

Ecological Modelling xxx (2005) xxx­xxx Modelling carbon and water cycles in a beech forest Part II A forest ecosystem model (CASTANEA) simulating the carbon balance (canopy photosynthesis, autotrophic and heterotrophic respirations, net ecosystem exchange, wood and root growth) and the water cycle (transpiration

Boyer, Edmond

222

Oxidation of a polycrystalline titanium surface by oxygen and water  

NASA Astrophysics Data System (ADS)

Reactions of a well-characterized polycrystalline titanium surface with oxygen and water molecules at 150-850 K were studied in UHV by X-ray photoelectron spectroscopy (XPS), thermal desorption spectroscopy (TDS) and Fourier transform reflectance-absorption infrared spectroscopy (FT-RAIRS). At 150 K, O 2 oxidizes Ti 0 to Ti IV, Ti III and Ti II, but Ti exposure to H 2O at this temperature produces only Ti II species. At temperatures above 300 K, further oxidation of Ti by H 2O was observed. Maximum oxidation by either molecule is achieved at 550-600 K. Upon heating the oxidized titanium above 850 K, the oxide layer is completely reduced to Ti 0. Hydroxyl species are identified on the Ti surface after reaction with H 2O; they appear to be mostly hydrogen bonded between 250 and 350 K, and isolated in the 450-650 K surface temperature range. Depth profiling of the O 2-oxidized Ti surface shows that Ti IV/Ti III species account for about 20% of the total thickness of the oxide layers and are located near the surface, while Ti II has a broader distribution, and is concentrated close to the oxide-metal interface. The OH group concentration is maximized at 550 K on the sample surface and accounts for about 16% of the total surface oxygen, with a decreasing concentration of OH into the bulk of the titanium oxides.

Lu, Gang; Bernasek, Steven L.; Schwartz, Jeffrey

2000-06-01

223

Treatment of gasoline-contaminated waters by advanced oxidation processes  

Microsoft Academic Search

In this study, the efficiency of advanced oxidative processes (AOPs) was investigated toward the degradation of aqueous solutions containing benzene, toluene and xylenes (BTX) and gasoline-contaminated waters. The results indicated that BTX can be effectively oxidized by near UV-assisted photo-Fenton process. The treatment permits almost total degradation of BTX and removal of more than 80% of the phenolic intermediates at

Elaine Regina Lopes Tiburtius; Patricio Peralta-Zamora; Alexandre Emmel

2005-01-01

224

Photoreductive dissolution of colloidal iron oxides in natural waters  

Microsoft Academic Search

Size-separation (0.1-pm filtration and ultrafiltration) techniques and coulometric procedures have been used to investigate the photoreductive dissolution of iron oxides under conditions typical of natural waters. In the absence of organic agents, iron oxides are solubilized to varying degrees through photodissociation of ferric hydroxy groups at the colloid surface. The degree of dissolution is de- pendent principally on the chromophore

T. David Waite; Francois M. M. Morel

1984-01-01

225

Patterns, structures and regulations of domestic water cycle systems in China  

NASA Astrophysics Data System (ADS)

Domestic water cycle systems serving as one critical component of artificial water cycle at the catchment's scale, is so closely related to public healthy, human rights and social-economic development, and has gained the highest priority in strategic water resource and municipal infrastructure planning. In this paper, three basic patterns of domestic water cycle systems are identified and analyzed, including rural domestic water system (i.e. primary level), urban domestic water system (i.e. intermediate level) and metropolitan domestic water system (i.e. senior level), with different "abstract-transport-consume-discharge" mechanisms and micro-components of water consumption (such as drinking, cooking, toilet flushing, showering or cleaning). The rural domestic water system is general simple with three basic "abstract-consume-discharge" mechanisms and micro-components of basic water consumption such as drinking, cooking, washing and sanitation. The urban domestic water system has relative complex mechanisms of "abstract-supply-consume-treatment-discharge" and more micro-components of water consumption such as bath, dishwashing or car washing. The metropolitan domestic water system (i.e. senior level) has the most complex mechanisms by considering internal water reuse, external wastewater reclamation, and nutrient recycling processes. The detailed structures for different water cycle pattern are presented from the aspects of water quantity, wastewater quality and nutrients flow. With the speed up of urbanization and development of social-economy in China, those three basic patterns are interacting, transforming and upgrading. According to the past experiences and current situations, urban domestic water system (i.e. intermediate level) is the dominant pattern based on indicator of system number or system scale. The metropolitan domestic water system (i.e. senior level) is the idealized model for the future development and management. Current domestic water system management efforts typically fail in China, because the approach is generally narrowly-focused and fragmented. This paper put forward a total-process control framework following the water and pollutants (or nutrients) flows along the dualistic domestic water cycle process. Five key objectives of domestic water cycle system regulation are identified including water use safety, water use equity, water saving, wastewater reduction and nutrient recycling. Comprehensive regulatory framework regarding administrative, economic, technical and social measures is recommended to promote sustainable domestic water usage and demand management. Considering the relatively low affordability in rural area, economic measures should be mainly applied in urban domestic water systems and metropolitan domestic water systems. Engineering or technological measures which are suitable to the three domestic water cycle systems are discussed respectively.

Chu, Junying; Wang, Hao; Wang, Jianhua; Qin, Dayong

2010-05-01

226

XENOWAC 2009 International Conference on Xenobiotics in the Urban Water Cycle  

E-print Network

XENOWAC 2009 International Conference on Xenobiotics in the Urban Water Cycle 11th ­ 13th March 2009, Cyprus TYLOSIN ABATEMENT IN WATER BY PHOTOCATALYTIC PROCESS LAOUFI N.A1,4 , ALATRACHE A.2 water and rivers by organic pollutants is of great concern and requires a constant improvement of water

Boyer, Edmond

227

Improvement of chemical control in the water-steam cycle of thermal power plants  

Microsoft Academic Search

A more effective chemical control in the water-steam cycle (WSC) of thermal power plants (TPP) is proposed in this paper. Minimization of corrosion effects by the production of ultra pure water and its strict control is the basis of all the investigated processes. The research involved the analysis of water samples in the WSC through key water quality parameters and

Vladana N. Rajakovi?-Ognjanovi?; Dragana Z. Živojinovic; Branimir N. Grgur; Ljubinka V. Rajakovi?

2011-01-01

228

Bark Beetles and Watersheds Workshop: Impacts to the Hydrologic Cycle and Water  

E-print Network

Bark Beetles and Watersheds Workshop: Impacts to the Hydrologic Cycle and Water A. Ray Olpin Assessment Tim Bardsley, Western Water Assessment Utah Liaison Overview of WWA's work on bark beetles and water Eric Gordon, Western Water Assessment 9:30am--The Beetle Epidemic in Utah: Where are We

Tipple, Brett

229

Biogeochemical cycling of C, N, and water in paddy rice agriculture in Monsoon Asia  

NASA Astrophysics Data System (ADS)

We report latest results of an ongoing project to evaluate the biogeochemical cycling of C, N, and water in paddy rice agriculture in Monsoon Asia. The core project focus is application of the DNDC biogeochemical model to estimate greenhouse gas emissions from paddy rice, and possible impacts of changes in agricultural management on those emissions. Simulations are done at the scale of sub-national political units (county equivalents and/or provinces/states). One effort has been to develop geospatial input data sets of agricultural land use and management, including crop rotations, cropping intensity, water management (irrigated or rainfed), fertilizer use. We have worked with both statistical census data and MODIS space-borne remote sensing data to map paddy rice across the domain. A second effort has been model development for application to rainfed paddy agriculture, and model testing against field data from paddy sites in India. The final thrust is model application across the domain to estimate water use, crop yield, net C-sequestration in soils, and emissions of methane and nitrous oxide.

Frolking, S.; Li, C.; Xiao, X.; Babu, J. Y.; Boles, S.; Salas, W.

2006-05-01

230

In vitro antimicrobial activity of Medilox® super-oxidized water  

PubMed Central

Aim Super-oxidized water is one of the broad spectrum disinfectants, which was introduced recently. There are many researches to find reliable chemicals which are effective, inexpensive, easy to obtain and use, and effective for disinfection of microorganisms leading hospital infections. Antimicrobial activity of super-oxidized water is promising. The aim of this study was to investigate the in-vitro antimicrobial activity of different concentrations of Medilox® super-oxidized water that is approved by the Food and Drug Administration (FDA) as high level disinfectant. Material and methods In this study, super-oxidized water obtained from Medilox® [Soosan E & C, Korea] device, which had been already installed in our hospital, was used. Antimicrobial activities of different concentrations of super-oxidized water (1/1, 1/2, 1/5, 1/10, 1/20, 1/50, 1/100) at different exposure times (1, 2, 5, 10, 30 min) against six ATCC strains, eight antibiotic resistant bacteria, yeasts and molds were evaluated using qualitative suspension test. Dey-Engley Neutralizing Broth [Sigma-Aldrich, USA] was used as neutralizing agent. Results Medilox® was found to be effective against all standard strains (Acinetobacter baumannii 19606, Escherichia coli 25922, Enterococcus faecalis 29212, Klebsiella pneumoniae 254988, Pseudomonas aeruginosa 27853, Staphylococcus aureus 29213), all clinical isolates (Acinetobacter baumannii, Escherichia coli, vancomycin-resistant Enterococcus faecium, Klebsiella pneumoniae, Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus, Bacillus subtilis, Myroides spp.), and all yeastsat 1/1 dilution in ??1 minute. It was found to be effective on Aspergillus flavus at 1/1 dilution in ??2 minutes and on certain molds in ??5 minutes. Conclusion Medilox® super-oxidized water is a broad spectrum, on-site producible disinfectant, which is effective on bacteria and fungi and can be used for the control of nosocomial infection. PMID:25023905

2014-01-01

231

Caffeinated Nitric Oxide-releasing Lozenge Improves Cycling Time Trial Performance.  

PubMed

Boosting nitric oxide production during exercise by various means has been found to improve exercise performance. We investigated the effects of a nitric oxide releasing lozenge with added caffeine (70?mg) on oxygen consumption during steady-state exercise and cycling time trial performance using a double-blinded randomized, crossover experimental design. 15 moderately trained cyclists (7 females and 8 males) were randomly assigned to ingest the caffeinated nitric oxide lozenge or placebo 5?min before exercise. Oxygen consumption and blood lactate were assessed at rest and at 50%, 65% and 75% maximal oxygen consumption. Exercise performance was assessed by time to complete a simulated 20.15?km cycling time-trial course. No significant treatment effects for oxygen consumption or blood lactate at rest or during steady-state exercise were observed. However, time-trial performance was improved by 2.1% (p<0.01) when participants consumed the nitric oxide lozenge (2?424±69?s) compared to placebo (2?476±78?s) and without a significant difference in rating of perceived exertion. These results suggest that acute supplementation with a caffeinated nitric oxide releasing lozenge may be a practical and effective means of improving aerobic exercise performance. PMID:25285468

Lee, J; Kim, H T; Solares, G J; Kim, K; Ding, Z; Ivy, J L

2015-02-01

232

Impact of ocean acidification on benthic and water column ammonia oxidation  

NASA Astrophysics Data System (ADS)

Ammonia oxidation is a key microbial process within the marine N-cycle. Sediment and water column samples from two contrasting sites in the English Channel (mud and sand) were incubated (up to 14 weeks) in CO2-acidified seawater ranging from pH 8.0 to pH 6.1. Additional observations were made off the island of Ischia (Mediterranean Sea), a natural analogue site, where long-term thermogenic CO2 ebullition occurs (from pH 8.2 to pH 7.6). Water column ammonia oxidation rates in English Channel samples decreased under low pH with near-complete inhibition at pH 6.5. Water column Ischia samples showed a similar though not statistically significant trend. However, sediment ammonia oxidation rates at all three locations were not affected by reduced pH. These observations may be explained by buffering within sediments or low-pH adaptation of the microbial ammonia oxidizing communities. Our observations have implications for modeling the future impact of ocean acidification on marine ecosystems.

Kitidis, Vassilis; Laverock, Bonnie; McNeill, Louise C.; Beesley, Amanda; Cummings, Denise; Tait, Karen; Osborn, Mark A.; Widdicombe, Stephen

2011-11-01

233

Calvin-Benson cycle and sulphide oxidation enzymes in animals from sulphide-rich habitats  

Microsoft Academic Search

The role of sulphide oxidation-driven production of reduced carbon in the nutrition of animals adapted to life in sulphide-rich habitats such as the deep-sea hydrothermal vents and intertidal mudflats has been a topic of recent interest1-4. Chemoautotrophic sulphide-oxidizing bacteria have been isolated from samples of sulphide-rich vent water5-8, and it has been suggested that these could provide a food source

Horst Felbeck; James J. Childress; George N. Somero

1981-01-01

234

A Study of Junior High Students' Perceptions of the Water Cycle  

NSDL National Science Digital Library

This study explores junior high school students' perceptions of the water cycle. Data were collected from 1,000 7th and 9th grade students in Israel using a series of quantitative and qualitative research tools that were specifically developed for the study. The findings indicated that the students understood some of the processes involved, but most lacked the dynamic, cyclic, and systemic perceptions of the system. Moreover, they possessed an incomplete picture of the water cycle including many preconceptions and misconceptions about it. Most of the students were aware of the atmospheric part of the water cycle, but ignored its groundwater part. Moreover, those who included part of the underground system in the water cycle perceived the underground water as static, subsurface lakes which reflect the traditional teaching of the subject of water in the science curricula.

Ben-Zvi-Assarf, Orit; Orion, Nir

235

Size-dependent subnanometer Pd cluster (Pd4, Pd6, and Pd17) water oxidation electrocatalysis.  

PubMed

Water oxidation is a key catalytic step for electrical fuel generation. Recently, significant progress has been made in synthesizing electrocatalytic materials with reduced overpotentials and increased turnover rates, both key parameters enabling commercial use in electrolysis or solar to fuels applications. The complexity of both the catalytic materials and the water oxidation reaction makes understanding the catalytic site critical to improving the process. Here we study water oxidation in alkaline conditions using size-selected clusters of Pd to probe the relationship between cluster size and the water oxidation reaction. We find that Pd4 shows no reaction, while Pd6 and Pd17 deposited clusters are among the most active (in terms of turnover rate per Pd atom) catalysts known. Theoretical calculations suggest that this striking difference may be a demonstration that bridging Pd-Pd sites (which are only present in three-dimensional clusters) are active for the oxygen evolution reaction in Pd6O6. The ability to experimentally synthesize size-specific clusters allows direct comparison to this theory. The support electrode for these investigations is ultrananocrystalline diamond (UNCD). This material is thin enough to be electrically conducting and is chemically/electrochemically very stable. Even under the harsh experimental conditions (basic, high potential) typically employed for water oxidation catalysts, UNCD demonstrates a very wide potential electrochemical working window and shows only minor evidence of reaction. The system (soft-landed Pd4, Pd6, or Pd17 clusters on a UNCD Si-coated electrode) shows stable electrochemical potentials over several cycles, and synchrotron studies of the electrodes show no evidence for evolution or dissolution of either the electrode material or the clusters. PMID:23799858

Kwon, Gihan; Ferguson, Glen A; Heard, Christopher J; Tyo, Eric C; Yin, Chunrong; DeBartolo, Janae; Seifert, Sönke; Winans, Randall E; Kropf, A Jeremy; Greeley, Jeffrey; Johnston, Roy L; Curtiss, Larry A; Pellin, Michael J; Vajda, Stefan

2013-07-23

236

Effects of water flow rate, salt concentration and water temperature on efficiency of an electrolyzed oxidizing water generator  

Microsoft Academic Search

A three-factor central composite design was adopted to investigate the effects of water flow rate, water temperature and salt concentration on electrolysis efficiency and separation efficiency of an electrolyzed oxidizing water generator. Results indicated that electric potential (7.9–15.7 V) and power consumption (16–120 W) of the electrolysis cell were not affected by water flow rate, water temperature or salt concentration

S. Y. Hsu

2003-01-01

237

Metal Oxide Photoanodes for Water Splitting  

Microsoft Academic Search

\\u000a Solar hydrogen production through photocatalytically assisted water splitting has attracted a great deal of attention since\\u000a its first discovery almost 30 years ago. The publication of investigations into the use of TiO2 photoanodes has continued apace since and a critical review of current trends is reported herein. Recent advances in the\\u000a understanding of the behaviour of nanoparticulate TiO2 films is summarized

J. Augusty?ski; B. Alexander; R. Solarska

238

Sirt3 promotes the urea cycle and fatty acid oxidation during dietary restriction  

PubMed Central

Summary Emerging evidence suggests that protein acetylation is a broad-ranging regulatory mechanism. Here we utilize acetyl-peptide arrays and metabolomic analyses to identify substrates of mitochondrial deacetylase Sirt3. We identified ornithine transcarbamoylase (OTC) from the urea cycle, and enzymes involved in ?-oxidation. Metabolomic analyses of fasted mice lacking Sirt3 (sirt3?/?) revealed alterations in ?-oxidation and the urea cycle. Biochemical analysis demonstrated that Sirt3 directly deacetylates OTC and stimulates its activity. Mice under caloric restriction (CR) increased Sirt3 protein levels, leading to deacetylation and stimulation of OTC activity. In contrast, sirt3?/? mice failed to deacetylate OTC in response to CR. Inability to stimulate OTC under CR led to a failure to reduce orotic acid levels, a known outcome of OTC deficiency. Thus, Sirt3 directly regulates OTC activity and promotes the urea cycle during CR, and the results suggest that under low energy input, Sirt3 modulates mitochondria by promoting amino-acid catabolism and ?-oxidation. PMID:21255725

Hallows, William C.; Yu, Wei; Smith, Brian C.; Devries, Mark K.; Ellinger, James J.; Someya, Shinichi; Shortreed, Michael R.; Prolla, Tomas; Markley, John L.; Smith, Lloyd M.; Zhao, Shimin; Guan, Kun-Liang; Denu, John M.

2011-01-01

239

The generation and inactivation mechanism of oxidation–reduction potential of electrolyzed oxidizing water  

Microsoft Academic Search

The Nernst equations between the oxidation–reduction potential (ORP), the concentration of hypochlorous acid and chlorine and the value of pH in electrolyzed oxidizing water (EOW) were developed in three parts, which were in agreement in the measured values. The role of ORP in EOW for killing Escherichia coli O157:H7 was studied. The inactivation effect of EOW on E. coli O157:H7

Long B. Liao; Wei M. Chen; Xian M. Xiao

2007-01-01

240

How surface potential determines the kinetics of the first hole transfer of photocatalytic water oxidation.  

PubMed

Interfacial hole transfer between n-SrTiO3 and OH(-) was investigated by surface sensitive transient optical spectroscopy of an in situ photoelectrochemical cell during water oxidation. The kinetics reveal a single rate constant with an exponential dependence on the surface hole potential, spanning time scales from 3 ns to 8 ps over a ?1 V increase. A voltage- and laser illumination-induced process moves the valence band edge at the n-type semiconductor/water interface to continuously change the surface hole potential. This single step of the water oxidation reaction is assigned to the first hole transfer h(+) + OH(-) ? OH(•). The kinetics quantify how much a change in the free energy difference driving this first hole transfer reduces the activation barrier. They are also used to extrapolate the kinetic rate due to the activation barrier when that free energy difference is zero, or the Nernstian potential. This is the first time transient spectroscopy has enabled the separation of the first hole transfer from the full four hole transfer cycle and a direct determination of these two quantities. The Nernstian potential for OH(-)/OH(•) is also suggested, in rough agreement with gas-phase studies. The observation of a distinct, much longer time scale upon picosecond hole transfer to OH(-) suggests that a dominant, more stable intermediate of the water oxidation reaction, possibly a surface bound oxo, may result. PMID:25029360

Waegele, Matthias M; Chen, Xihan; Herlihy, David M; Cuk, Tanja

2014-07-30

241

Oxidation behavior of a ferritic stainless steel Crofer22 APU with thermal cycling  

NASA Astrophysics Data System (ADS)

Crofer22 APU specimens were prepared by grinding with grit 80 and 120 SiC grinding papers and were thermally cycled. The variation in oxidation behavior with thermal cycling was then investigated. Observation of microstructure, measurement of area specific resistance (ASR), analysis of the atomic percentages of the elements by EDX, and XRD analysis were performed. XRD patterns showed that the (Cr, Mn)3O4 spinel phase grew on the surface of the Crofer22 APU samples ground with grit 120. For the samples ground with grit 80, the ASR increased as the number of thermal cycles increased. Plots of ln (ASR/T) vs. 1/T for the samples ground with grit 80 after n = 4, 20 and 40 exhibited good linearity, and the apparent activation energies were between 63.7 kJ/mole and 76.3 kJ/mole.

Song, MyoungYoup; Duong, Anh T.; Mumm, Daniel R.

2013-01-01

242

Seasonal variations of gene expression biomarkers in Mytilus galloprovincialis cultured populations: temperature, oxidative stress and reproductive cycle as major modulators.  

PubMed

The blue mussel Mytilus galloprovincialis has been used as monitoring organism in many biomonitoring programs because of its broad distribution in South European sea waters and its physiological characteristics. Different pollution-stress biomarkers, including gene expression biomarkers, have been developed to determine its physiological response to the presence of different pollutants. However, the existing information about basal expression profiles is very limited, as very few biomarker-based studies were designed to reflect the natural seasonal variations. In the present study, we analyzed the natural expression patterns of several genes commonly used in biomonitoring, namely ferritin, metallothionein, cytochrome P450, glutathione S-transferase, heat shock protein and the kinase responsive to stress KRS, during an annual life cycle. Analysis of mantle-gonad samples of cultured populations of M. galloprovincialis from the Delta del Ebro (North East Spain) showed natural seasonal variability of these biomarkers, pointing to temperature and oxidative stress as major abiotic modulators. In turn, the reproductive cycle, a process that can be tracked by VCLM7 expression, and known to be influenced by temperature, seems to be the major biotic factor involved in seasonality. Our results illustrate the influence of environmental factors in the physiology of mussels through their annual cycle, a crucial information for the correct interpretation of responses under stress conditions. PMID:25203829

Jarque, Sergio; Prats, Eva; Olivares, Alba; Casado, Marta; Ramón, Montserrat; Piña, Benjamin

2014-11-15

243

Conversion of Tire Waste Using Subcritical and Supercritical Water Oxidation  

Microsoft Academic Search

The properties designed into tires that make them strong and chemically resistant also inhibit their ability to be recycled easily Conventional liquid solvents do not sufficiently dissolve waste tires and tire production material for convenient separation. Supercritical water oxidation (SCWO) may provide an alternative solution to this environmental problem. Partial SCWO can be used as a means to partially break

J. Todd Reaves; Christine W. Curtis; Christopher B. Roberts

1999-01-01

244

Electrophotolysis oxidation system for measurement of organic concentration in water  

NASA Technical Reports Server (NTRS)

Methods and apparatus for determining organic carbon in aqueous solution are described. The method comprises subjecting the aqueous solution to electrolysis, for generating oxygen from water, and simultaneously to ultraviolet radiation, for oxidation of substantially all organic carbon to carbon dioxide. The carbon dioxide is measured and the value is related to the concentration of organic carbon in the aqueous solution.

Winkler, H. E. (inventor)

1981-01-01

245

Origin and role of water ice clouds in the Martian water cycle as inferred from a general circulation model  

Microsoft Academic Search

In this paper, we present the results obtained by the general circulation model developed at the Laboratoire de Météorologie Dynamique which has been used to simulate the Martian hydrological cycle. Our model, which employs a simplified cloud scheme, reproduces the observed Martian water cycle with unprecedented agreement. The modeled seasonal evolution of cloudiness, which also compares well with data, is

F. Montmessin; F. Forget; P. Rannou; M. Cabane; R. M. Haberle

2004-01-01

246

Study of nickel electrode oxidation as a function of 80% depth of discharge cycling  

SciTech Connect

Oxidation of nickel sinter used in nickel oxide electrodes in aerospace nickel cadmium cells leads to hydrogen gassing and the potential for cell rupture. The oxidation is directly related to loss of overcharge protection built into the cell during manufacturing. In nickel hydrogen cells, excessive oxidation of the nickel sinter can eventually lead to a burst before leak situation and is a potential source of failure. It is well known that nickel cadmium cells having nylon separators contribute to loss of overcharge via a hydrolysis reaction of the nylon in the potassium hydroxide electrolyte environment in the cell. The hydrolysis reaction produces lower chain organics which are oxidized by the positive electrode and oxygen. Oxidation of the organics diminishes the overcharge protection. With introduction of the Super NiCd{trademark} and the Magnum{trademark} nickel cadmium cells the nylon hydrolysis reaction is eliminated, but any reducing agent in the cell such as nickel or an organic additive can contribute to loss of overcharge protection. The present effort describes chemical analyses made to evaluate the extent of overcharge protection loss in nickel cadmium cells which do not have nylon hydrolysis, and quantifies the amount of hydrogen buildup in nickel hydrogen cells which are subjected to 80% depth of discharge cycling with and without the presence of cadmium in the positive electrode.

Pickett, D.F. Jr.; Scoles, D.L.; Johnson, Z.W.; Hayden, J.W.; Pennington, R.D. [Eagle-Picher Industries, Inc., Colorado Springs, CO (United States)

1997-12-31

247

Steam Oxidation of Fossil Power Plant Materials: Collaborative Research to Enable Advanced Steam Power Cycles  

Research into improved materials systems and associated manufacturing and reliability issues is a major part of initiatives to produce cleaner and cheaper energy systems in the UK and the USA. Under the auspices of a Memorandum of Understanding on Energy R&D, a work programme concerned with steam oxidation has been conducted. The focus was on the generation of definitive information regarding the oxidation behaviour in steam of current and developmental ferritic steels, austenitic steels, and nickelbased alloys required to enable advanced steam power cycles. The results were intended to provide a basis for quantifying the rate of metal loss expected under advanced steam cycle conditions, as well as understanding of the evolution of oxide scale morphologies with time and temperature to identify features that could influence scale exfoliation characteristics. This understanding and acquired data were used to develop and validate models of oxide growth and loss by exfoliation. This paper provides an overview of the activity and highlights a selection of the results coming from the programme.

A. T. Fry; I. G Wright; N. J Simms; B. McGhee; G. R. Holcomb

2013-11-19

248

Hybrid Gas Water Heater Combined with Adsorption Heat Pump Cycle for Commercial Use  

Microsoft Academic Search

To improve the heat efficiency of gas water heaters, we studied a hybrid type water heater that combines a conventional gas-fired water heater and an adsorption heat pump cycle. With a target heat efficiency of approximately 120%—a dramatic increase over the 85% efficiency of a conventional gas water heater—this hybrid gas water heater (HGWH) is expected to be an energy-saving

Atsuya Tajima; Yuji Ozawa; Hideo Kawaguchi

2006-01-01

249

K562 cells display different vulnerability to H2 O2 induced oxidative stress in differing cell cycle phases.  

PubMed

Oxidative stress can be defined as the increase of oxidizing agents like reactive oxygen and nitrogen species, or the imbalance between the antioxidative defense mechanism and oxidants. Cell cycle checkpoint response can be defined as the arrest of the cell cycle functioning after damaging chemical exposure. This temporary arrest may be a period of time given to the cells to repair the DNA damage before entering the cycle again and completing mitosis. In order to determine the effects of oxidative stress on several cell cycle phases, human erytroleukemia cell line (K562) was synchronized with mimosine and genistein, and cell cycle analysis carried out. Synchronized cells were exposed to oxidative stress with hydrogen peroxide (H2 O2 ) at several concentrations and different times. Changes on mitochondria membrane potential (??m) of K562 cells were analyzed in G1 , S, and G2 /M using Rhodamine 123 (Rho 123). To determine apoptosis and necrosis, stressed cells were stained with Annexin V (AnnV) and propidium iodide (PI) for flow cytometry. Changes were observed in the ??m of synchronized and asynchronized cells that were exposed to oxidative stress. Synchronized cells in S phase proved resistant to the effects of oxidative stress and synchronized cells at G2 /M phase were sensitive to the effects of H2 O2 -induced oxidative stress at 500??M and above. PMID:25181960

Akcakaya, Handan; Dal, Fulya; Tok, Sabiha; Cinar, Suzan-Adin; Nurten, Rustem

2015-02-01

250

eWaterCycle: A high resolution global hydrological model  

NASA Astrophysics Data System (ADS)

In 2013, the eWaterCycle project was started, which has the ambitious goal to run a high resolution global hydrological model. Starting point was the PCR-GLOBWB built by Utrecht University. The software behind this model will partially be re-engineered in order to enable to run it in a High Performance Computing (HPC) environment. The aim is to have a spatial resolution of 1km x 1km. The idea is also to run the model in real-time and forecasting mode, using data assimilation. An on-demand hydraulic model will be available for detailed flow and flood forecasting in support of navigation and disaster management. The project faces a set of scientific challenges. First, to enable the model to run in a HPC environment, model runs were analyzed to examine on which parts of the program most CPU time was spent. These parts were re-coded in Open MPI to allow for parallel processing. Different parallelization strategies are thinkable. In our case, it was decided to use watershed logic as a first step to distribute the analysis. There is rather limited recent experience with HPC in hydrology and there is much to be learned and adjusted, both on the hydrological modeling side and the computer science side. For example, an interesting early observation was that hydrological models are, due to their localized parameterization, much more memory intensive than models of sister-disciplines such as meteorology and oceanography. Because it would be deadly to have to swap information between CPU and hard drive, memory management becomes crucial. A standard Ensemble Kalman Filter (enKF) would, for example, have excessive memory demands. To circumvent these problems, an alternative to the enKF was developed that produces equivalent results. This presentation shows the most recent results from the model, including a 5km x 5km simulation and a proof of concept for the new data assimilation approach. Finally, some early ideas about financial sustainability of an operational global hydrological model are presented.

van de Giesen, Nick; Bierkens, Marc; Drost, Niels; Hut, Rolf; Sutanudjaja, Edwin

2014-05-01

251

Water-Mediated Proton Hopping on an Iron Oxide Surface  

SciTech Connect

The diffusion of hydrogen atoms across solid oxide surfaces is often assumed to be accelerated by the presence of water molecules. Here we present a high-resolution, high-speed scanning tunneling microscopy (STM) study of the diffusion of H atoms on an FeO thin film. STM movies directly reveal a water-mediated hydrogen diffusion mechanism on the oxide surface at temperatures between 100 and 300 kelvin. Density functional theory calculations and isotope-exchange experiments confirm the STM observations, and a proton-transfer mechanism that proceeds via an H3O+-like transition state is revealed. This mechanism differs from that observed previously for rutile TiO2(110), where water dissociation is a key step in proton diffusion.

Merte, L. R.; Peng, Guowen; Bechstein, Ralf; Rieboldt, Felix; Farberow, Carrie A.; Grabow, Lars C.; Kudernatsch, Wilhelmine; Wendt, Stefen; Laegsgaard, E.; Mavrikakis, Manos; Besenbacher, Fleming

2012-05-18

252

MODERN WATER TREATMENT BY ELECTROCHEMICAL OXIDATION- A REVIEW  

E-print Network

Electrochemical oxidation (EO) as electrochemical method is unique by three aspects. The first is that is the most versatility process in water treatment area and covers: various industrial effluent treatment including, amongst others, distillery, agrochemical, pulp and paper, textile dyes, oilfield and metalplating wastes; hazardous effluent treatment including hospital wastes; removal of pathogens and persistent, pharmaceutical residues and biological from municipal wastewater treatment plant; removal of organic micro-pollutants such as pesticides and heavy metals such as arsenic and chromium from water. Another aspect is that EO is complementary with most other methods: chemical or electrochemical, and is often combined with one or more of them. And finally, this procedure is the most interdisciplinary of all. It includes: material science, (micro)biology, (electro)chemistry, environmental protection, water supply systems, etc. Key words: electrochemical oxidation, electrooxidation, wastewaters, synergistic methods, interdisciplinary approach, ecology.

Silvana B. Dimitrijevi?; Stevan P. Dimitrijevi?; Milovan D. Vukovi?

253

Water-mediated proton hopping on an iron oxide surface.  

PubMed

The diffusion of hydrogen atoms across solid oxide surfaces is often assumed to be accelerated by the presence of water molecules. Here we present a high-resolution, high-speed scanning tunneling microscopy (STM) study of the diffusion of H atoms on an FeO thin film. STM movies directly reveal a water-mediated hydrogen diffusion mechanism on the oxide surface at temperatures between 100 and 300 kelvin. Density functional theory calculations and isotope-exchange experiments confirm the STM observations, and a proton-transfer mechanism that proceeds via an H(3)O(+)-like transition state is revealed. This mechanism differs from that observed previously for rutile TiO(2)(110), where water dissociation is a key step in proton diffusion. PMID:22605771

Merte, Lindsay R; Peng, Guowen; Bechstein, Ralf; Rieboldt, Felix; Farberow, Carrie A; Grabow, Lars C; Kudernatsch, Wilhelmine; Wendt, Stefan; Lægsgaard, Erik; Mavrikakis, Manos; Besenbacher, Flemming

2012-05-18

254

Oxidation of dithiocarbamates to yield N-nitrosamines by water disinfection oxidants.  

PubMed

Two most commonly used dithiocarbamate (DTC) pesticides, dimethyldithiocarbamate (DMDTC) and diethyldithiocarbamate (DEDTC), were examined in this study to evaluate their potential to form nitrosamines when in contact with various water disinfection oxidants. Results show that DTCs can serve as nitrosamine precursors, by release of secondary amines through hydrolysis or through reactions with oxidants. The reactions of DTCs with monochloramine and ozone were found to be particularly problematic in the risk of generating nitrosamines, though all four tested oxidants, including free chlorine and chlorine dioxide, formed nitrosamines. NDEA yield from DEDTC was lower, by different degrees, than NDMA yield from DMDTC for all four oxidants, which was attributed to the steric hindrance associated with bulkier reaction intermediate that are more difficult to be further oxidized to form nitrosamine. The yield of nitrosamines increased with the oxidant dosage for both monochloramination and ozonation of DTCs. Results for nitrosamine formation from DTCs at varying pH were found to be consistent with the pH trend of nitrosamine formation from ozonation and monochloramination of secondary amines. Kinetic study results and identification and quantification of reaction products suggest that the DTCs were not significant direct precursors of nitrosamines during monochloramination or ozonation, but rather nitrosamines formed were primarily from reaction of oxidants with the amine which may be generated either through hydrolysis or through oxidation of DTCs. PMID:23176828

Padhye, Lokesh P; Kim, Jae-Hong; Huang, Ching-Hua

2013-02-01

255

High temperature oxidation of molybdenum in water vapor environments  

NASA Astrophysics Data System (ADS)

Molybdenum has recently gained attention as a candidate cladding material for use in light water reactors. Its excellent high temperature mechanical properties and stability under irradiation suggest that it could offer benefits to performance under a wide range of reactor conditions, but little is known about its oxidation behavior in water vapor containing atmospheres. The current study was undertaken to elucidate the oxidation behavior of molybdenum in water vapor environments to 1200 °C in order to provide an initial assessment of its feasibility as a light water reactor cladding. Initial observations indicate that at temperatures below 1000 °C, the kinetics of mass loss in water vapor would not be detrimental to cladding integrity during an off-normal event. Above 1000 °C, degradation is more rapid but remains slower than observed for optimized zirconium cladding alloys. The effect of hydrogen-water vapor and oxygen-water vapor mixtures on material loss was also explored at elevated temperatures. Parts-per-million levels of either hydrogen or oxygen will minimally impact performance, but hydrogen contents in excess of 1000 ppm were observed to limit volatilization at 1000 °C.

Nelson, A. T.; Sooby, E. S.; Kim, Y.-J.; Cheng, B.; Maloy, S. A.

2014-05-01

256

Nitrite oxidation in the upper water column and oxygen minimum zone of the eastern tropical North Pacific Ocean.  

PubMed

Nitrogen (N) is an essential nutrient in the sea and its distribution is controlled by microorganisms. Within the N cycle, nitrite (NO2(-)) has a central role because its intermediate redox state allows both oxidation and reduction, and so it may be used by several coupled and/or competing microbial processes. In the upper water column and oxygen minimum zone (OMZ) of the eastern tropical North Pacific Ocean (ETNP), we investigated aerobic NO2(-) oxidation, and its relationship to ammonia (NH3) oxidation, using rate measurements, quantification of NO2(-)-oxidizing bacteria via quantitative PCR (QPCR), and pyrosequencing. (15)NO2(-) oxidation rates typically exhibited two subsurface maxima at six stations sampled: one located below the euphotic zone and beneath NH3 oxidation rate maxima, and another within the OMZ. (15)NO2(-) oxidation rates were highest where dissolved oxygen concentrations were <5??M, where NO2(-) accumulated, and when nitrate (NO3(-)) reductase genes were expressed; they are likely sustained by NO3(-) reduction at these depths. QPCR and pyrosequencing data were strongly correlated (r(2)=0.79), and indicated that Nitrospina bacteria numbered up to 9.25% of bacterial communities. Different Nitrospina groups were distributed across different depth ranges, suggesting significant ecological diversity within Nitrospina as a whole. Across the data set, (15)NO2(-) oxidation rates were decoupled from (15)NH4(+) oxidation rates, but correlated with Nitrospina (r(2)=0.246, P<0.05) and NO2(-) concentrations (r(2)=0.276, P<0.05). Our findings suggest that Nitrospina have a quantitatively important role in NO2(-) oxidation and N cycling in the ETNP, and provide new insight into their ecology and interactions with other N-cycling processes in this biogeochemically important region of the ocean. PMID:23804152

Beman, J Michael; Leilei Shih, Joy; Popp, Brian N

2013-11-01

257

Ferrates: greener oxidants with multimodal action in water treatment technologies.  

PubMed

Conspectus One of the biggest challenges for humanity in the 21st century is easy access to purified and potable water. The presence of pathogens and toxins in water causes more than two million deaths annually, mostly among children under the age of five. Identifying and deploying effective and sustainable water treatment technologies is critical to meet the urgent need for clean water globally. Among the various agents used in the purification and treatment of water, iron-based materials have garnered particular attention in view of their special attributes such as their earth-abundant and environmentally friendly nature. In recent years, higher-valent tetraoxy iron(VI) (Fe(VI)O4(2-), Fe(VI)), commonly termed, ferrate, is being explored for a broad portfolio of applications, including a greener oxidant in synthetic organic transformations, a water oxidation catalyst, and an efficient agent for abatement of pollutants in water. The use of Fe(VI) as an oxidant/disinfectant and further utilization of the ensuing iron(III) oxides/hydroxide as coagulants are other additional attributes of ferrate for water treatment. This multimodal action and environmentally benign character of Fe(VI) are key advantages over other commonly used oxidants (e.g., chlorine, chlorine dioxide, permanganate, hydrogen peroxide, and ozone). This Account discusses current state-of-the-art applications of Fe(VI) and the associated unique chemistry of these high-valence states of iron. The main focus centers around the description and salient properties of ferrate species involving various electron transfer and oxygen-atom transfer pathways in terms of presently accepted mechanisms. The mechanisms derive the number of electron equivalents per Fe(VI) (i.e., oxidation capacity) in treating various contaminants. The role of pH in the kinetics of the reactions and in determining the removal efficiency of pollutants is highlighted; the rates of competing reactions of Fe(VI) with itself, water, and the contaminants, which are highly pH dependent, determine the optimum pH range of maximum efficacy. The main emphasis of this account is placed on cases where various modes of ferrate action are utilized, including the treatment of nitrogen- and sulfur-containing waste products, antibiotics, viruses, bacteria, arsenic, and heavy metals. For example, the oxidative degradation of N- and S-bearing contaminants by Fe(VI) yields either Fe(II) or Fe(III) via the intermediacy of Fe(IV) and Fe(V) species, respectively (e.g., Fe(VI) ? Fe(IV) ? Fe(II) and Fe(VI) ? Fe(V) ? Fe(III)). Oxidative transformations of antibiotics such as trimethoprim by Fe(VI) generate products with no residual antibiotic activity. Disinfection and inactivation of bacteria and viruses can easily be achieved by Fe(VI). Advanced applications involve the use of ferrate for the degradation of cyanobacteria and microcystin originating from algal blooms and for covalently embedding arsenic and heavy metals into the structure of formed magnetic iron(III) oxides, therefore preventing their leaching. Applications of state-of-the-art analytical techniques, namely, in situ Mössbauer spectroscopy, rapid-freeze electron paramagnetic resonance, nuclear forward scattering of synchrotron radiation, and mass spectrometry will enhance the mechanistic understanding of ferrate species. This will make it possible to unlock the true potential of ferrates for degrading emerging toxins and pollutants, and in the sustainable production and use of nanomaterials in an energy-conserving environment. PMID:25668700

Sharma, Virender K; Zboril, Radek; Varma, Rajender S

2015-02-17

258

Oxide-carbon composites and porous oxides prepared via water-swellable polymer networks  

SciTech Connect

Water-swellable polymer networks (WSPN) were employed as media for lodging metal nitrate salts or partially hydrolyzed tetraethyl orthosilicate (TEOS), which are precursors for inorganic oxides. The loading achieved either via the polymerization of a suitable monomer and a cross-linker in an aqueous solution of the precursor or, in the case of TEOS, via the simultaneous polymerization of both monomers. The pyrolysis of the precursor loaded network under N{sub 2} flow generated interpenetrating networks of carbon and metal oxide. The combustion of the composite in air removed the carbon network and a porous metal oxide framework remained. On the basis of the methodology, a coating layer of C-SiO{sub 2} composite was generated on a carbon-fiber, and a porous powders of SiO{sub 2}, ZrO{sub 2}, MgO, and CuO-ZnO-Al{sub 2}O{sub 3} oxide(s) were synthesized. It was found that the specific surface area of the oxides is affected by the nature of the WSPN. Two methodologies which lead to particles were developed. In one of them, sedimentation polymerization, large particles of about 1 mm size were obtained. In the other one, which starts from an emulsion of a water solution in an organic liquid (toluene, cyclohexane), micrometer size particles were prepared. 16 refs., 10 figs., 6 tabs.

Ruckenstein, E.; Hong, L. [State Univ. of New York, Buffalo, NY (United States)] [State Univ. of New York, Buffalo, NY (United States)

1996-02-01

259

Paralinear Oxidation of CVD SiC in Water Vapor  

NASA Technical Reports Server (NTRS)

The oxidation kinetics of CVD SiC were monitored by thermogravimetric analysis (TGA) in a 50% H2O/50% O2 gas mixture flowing at 4.4 cm/s for temperatures between 1200 and 1400 C. Paralinear weight change kinetics were observed as the water vapor oxidized the SiC and simultaneously volatilized the silica scale. The long-term degradation rate of SiC is determined by the volatility of the silica scale. Rapid SiC surface recession rates were estimated from these data for actual aircraft engine combustor conditions.

Opila, Elizabeth J.; Hann, Raiford E., Jr.

1997-01-01

260

Effects of tempol and redox-cycling nitroxides in models of oxidative stress  

PubMed Central

Tempol is a redox cycling nitroxide that promotes the metabolism of many reactive oxygen species (ROS) and improves nitric oxide bioavailability. It has been studied extensively in animal models of oxidative stress. Tempol has been shown to preserve mitochondria against oxidative damage and improve tissue oxygenation. Tempol improved insulin responsiveness in models of diabetes mellitus and improved the dyslipidemia, reduced the weight gain and prevented diastolic dysfunction and heart failure in fat-fed models of the metabolic syndrome. Tempol protected many organs, including the heart and brain, from ischemia/reperfusion damage. Tempol prevented podocyte damage, glomerulosclerosis, proteinuria and progressive loss of renal function in models of salt and mineralocorticosteroid excess. It reduced brain or spinal cord damage after ischemia or trauma and exerted a spinal analgesic action. Tempol improved survival in several models of shock. It protected normal cells from radiation while maintaining radiation sensitivity of tumor cells. Its paradoxical pro-oxidant action in tumor cells accounted for a reduction in spontaneous tumor formation. Tempol was effective in some models of neurodegeneration. Thus, tempol has been effective in preventing several of the adverse consequences of oxidative stress and inflammation that underlie radiation damage and many of the diseases associated with aging. Indeed, tempol given from birth prolonged the life span of normal mice. However, presently tempol has been used only in human subjects as a topical agent to prevent radiation-induced alopecia. PMID:20153367

Wilcox, Christopher S.

2010-01-01

261

On the Design of Oxide Films, Nanomaterials, and Heterostructures for Solar Water Oxidation Photoanodes  

NASA Astrophysics Data System (ADS)

Photoelectrochemistry and its associated technologies show unique potential to facilitate the large-scale production of solar fuels—those energy-rich chemicals obtained through conversion processes driven by solar energy, mimicking the photosynthetic process of green plants. The critical component of photoelectrochemical devices designed for this purpose is the semiconductor photoelectrode, which must be optically absorptive, chemically stable, and possess the required electronic band alignment with respect to the redox couple of the electrolyte to drive the relevant electrochemical reactions. After many decades of investigation, the primary technological obstacle remains the development of photoelectrode structures capable of efficient and stable conversion of light with visible frequencies, which is abundant in the solar spectrum. Metal oxides represent one of the few material classes that can be made photoactive and remain stable to perform the required functions. The unique range of functional properties of oxides, and especially the oxides of transition metals, relates to their associated diversity of cation oxidation states, cation electronic configurations, and crystal structures. In this dissertation, the use of metal oxide films, nanomaterials, and heterostructures in photoelectrodes enabling the solar-driven oxidation of water and generation of hydrogen fuel is examined. A range of transition- and post-transition-metal oxide material systems and nanoscale architectures is presented. The first chapters present results related to electrodes based on alpha-phase iron(III) oxide, a promising visible-light-active material widely investigated for this application. Studies of porous films fabricated by physical vapor deposition reveal the importance of structural quality, as determined by the deposition substrate temperature, on photoelectrochemical performance. Heterostructures with nanoscale feature dimensionality are explored and reviewed in a later chapter, which describes the methodologies to combine the unique and complimentary functional properties of dissimilar oxides to optimize the water photo-oxidation process Experimental results based on an iron(III) oxide-tungsten(VI) oxide system show enhancements associated with the heterostructure, which may indicate the presence of unexpected minority carrier dynamics, as observed additionally by ultrafast transient absorption spectroscopy. Next, a new conceptual framework for the design of solar water oxidation photoelectrodes based on the spatially inhomogeneous doping of wide-bandgap metal oxide nanostructures is introduced and experimentally verified. It is found that optical absorption and electronic conduction can be decoupled and optimized by spatially segregating the functional impurity species that facilitate their associated physical processes. In the final chapters of this dissertation the electronic structures of key oxide-oxide interfaces, relevant to the operation of efficient photoanodes, are examined using synchrotron-based soft x-ray spectroscopy. These studies indicate that the interfacial regions of electrodes possess distinct electronic structures, which deviate in terms of orbital character and occupancy from those of their constituent bulk oxides. These observations inform methodology to address certain operational deficiencies associated with the use of metal oxides for solar energy conversion applications.

Kronawitter, Coleman Xaver

262

Thorium fuel for light water reactors—reducing proliferation potential of nuclear power fuel cycle  

Microsoft Academic Search

The proliferation potential of the light water reactor fuel cycle may be significantly reduced by utilization of thorium as a fertile component of the nuclear fuel. The main challenge of thorium utilization is to design a core and a fuel cycle, which would be proliferation?resistant and economically feasible. This challenge is met by the Radkowsky Thorium Reactor (RTR) concept presented

Alex Galperin; Paul Reichert; Alvin Radkowsky

1997-01-01

263

Germanium cycling in the waters across a frontal zone: the Chatham Rise, New Zealand  

E-print Network

Germanium cycling in the waters across a frontal zone: the Chatham Rise, New Zealand Michael J for inorganic Ge, the profiles for monomethyl and dimethyl germanium (MMGe and DMGe) are conservative (Lewis et

Canberra, University of

264

Examining Language To Capture Scientific Understandings: The Case of the Water Cycle.  

ERIC Educational Resources Information Center

Presents units that address states of matter and changes of states of matter linked with the water cycle and integrates literacy and science. Discusses the language in science books. Lists characteristics of good science inquiry units. (Contains 11 references.) (ASK)

Varelas, Maria; Pappas, Christine; Barry, Anne; O'Neill, Amy

2001-01-01

265

Climate Change and Expected Impacts on the Global Water Cycle  

NASA Technical Reports Server (NTRS)

How the elements of the global hydrologic cycle may respond to climate change is reviewed, first from a discussion of the physical sensitivity of these elements to changes in temperature, and then from a comparison of observations of hydrologic changes over the past 100 million years. Observations of current changes in the hydrologic cycle are then compared with projected future changes given the prospect of global warming. It is shown that some of the projections come close to matching the estimated hydrologic changes that occurred long ago when the earth was very warm.

Rind, David; Hansen, James E. (Technical Monitor)

2002-01-01

266

Ground Water Sampling at ISCO Sites - Residual Oxidant Impact on Sample Quality and Sample Preservation Guideline  

EPA Science Inventory

In-situ chemical oxidation (ISCO) involves the delivery of a chemical oxidant into the subsurface where oxidative reactions transform ground water contaminants into less toxic or harmless byproducts. Due to oxidant persistence, ground water samples collected at hazardous waste si...

267

Theoretical study of catalytic mechanism for single-site water oxidation process  

PubMed Central

Water oxidation is a linchpin in solar fuels formation, and catalysis by single-site ruthenium complexes has generated significant interest in this area. Combining several theoretical tools, we have studied the entire catalytic cycle of water oxidation for a single-site catalyst starting with [RuII(tpy)(bpm)(OH2)]2+ (i.e., [RuII-OH2]2+; tpy is 2,2??6?,2??-terpyridine and bpm is 2,2?-bypyrimidine) as a representative example of a new class of single-site catalysts. The redox potentials and pKa calculations for the first two proton-coupled electron transfers (PCETs) from [RuII-OH2]2+ to [RuIV = O]2+ and the following electron-transfer process to [RuV = O]3+ suggest that these processes can proceed readily in acidic or weakly basic conditions. The subsequent water splitting process involves two water molecules, [RuV = O]3+ to generate [RuIII-OOH]2+, and H3O+ with a low activation barrier (?10 kcal/mol). After the key O---O bond forming step in the single-site Ru catalysis, another PECT process oxidizes [RuIII-OOH]2+ to [RuIV-OO]2+ when the pH is lower than 3.7. Two possible forms of [RuIV-OO]2+, open and closed, can exist and interconvert with a low activation barrier (< 7 kcal/mol) due to strong spin-orbital coupling effects. In Pathway 1 at pH = 1.0, oxygen release is rate-limiting with an activation barrier ?12 kcal/mol while the electron-transfer step from [RuIV-OO]2+ to [RuV - OO]3+ becomes rate-determining at pH = 0 (Pathway 2) with Ce(IV) as oxidant. The results of these theoretical studies with atomistic details have revealed subtle details of reaction mechanisms at several stages during the catalytic cycle. This understanding is helpful in the design of new catalysts for water oxidation. PMID:22615356

Lin, Xiangsong; Hu, Xiangqian; Concepcion, Javier J.; Chen, Zuofeng; Liu, Shubin; Meyer, Thomas J.; Yang, Weitao

2012-01-01

268

Interfacial properties of oxidized polystyrene and its interaction with water.  

PubMed

All-atom molecular dynamics simulations have been carried out to study the wetting of atactic polystyrene (aPS) thin films by water droplets. The effect of oxidation of the aPS surface on the contact angle has been studied as a function of oxygen concentration. Oxidation of aPS has been achieved by randomly replacing with oxygen the ortho and/or meta hydrogens on the aromatic rings within 1 nm of the aPS surface until the desired concentration of oxygen is reached. The simulated contact angle is found to decrease monotonically with increasing degree of oxidation, consistent with recent experimental results. The number of hydrogen bonds between water molecules and polystyrene at the interface is found to monotonically increase with oxygen concentration. By use of a modified Good-Girafalco-Fowkes-Young equation, the contribution of nondispersion interactions, ?sl(P), to the interfacial energy at the aPS/water interface has been determined as a function of the degree of oxidation. The values of ?sl(P) extracted appear to follow a quadratic dependence on oxygen concentration of the aPS surface. The roughness of the polystyrene surface appears to be independent of oxygen concentration when the polystyrene is exposed to vacuum, and it appears to increase slightly when it is in contact with water. The orientational ordering of the phenyl rings at the polystyrene surface exhibits no dependence on oxygen concentration for polystyrene in vacuum. However, the ordering appears to decrease slightly with increasing oxygen concentration when the polystyrene is in contact with water. PMID:24073691

Bekele, Selemon; Tsige, Mesfin

2013-10-29

269

Atmospheric cycling and air-water exchange of mercury over mid-continental lacustrine regions  

Microsoft Academic Search

Atmospheric mobilization and exchange at the air-water interface are significant features of biogeochemical cycling of Hg\\u000a at the Earth's surface. Our marine studies of Hg have been extended to terrestrial aquatic systems, where we are investigating\\u000a the tropospheric cycling, deposition and air-water exchange of Hg in the mid-continental lacustrine environs of northcentral\\u000a Wisconsin. This program is part of a multidisciplinary

William F. Fitzgerald; R. P. Mason; G. M. Vandal

1991-01-01

270

Methylated and elemental mercury cycling in surface and deep ocean waters of the North Atlantic  

Microsoft Academic Search

Biogeochemical cycling of mercury (Hg) in the ocean and air-sea exchange are integral parts of the global Hg cycle. Ionic Hg (i.e. reactive Hg-Hg°) is converted in ocean surface waters to elemental Hg (Hg°) with the subsequent loss, via gas evasion, of the Hg° to the atmosphere. During a recent cruise in the North Atlantic Ocean, Hg° in surface waters

R. P. Mason; K. R. Rolfhus; W. F. Fitzgerald

1995-01-01

271

The Water Cycle: Now You See It, Now You Don't  

NSDL National Science Digital Library

This is a hands-on lab activity about the water cycle, specifically evaporation and condensation. Using materials such as clay, ice and a lamp, learners will observe the relationship between temperature and condensation and temperature and evaporation. They will then draw a diagram or a concept map of the water cycle. Background information, common preconceptions, a glossary and more is included. This activity is part of the Aquarius Hands-on Laboratory Activities.

272

Life cycle water use for electricity generation: a review and harmonization of literature estimates  

NASA Astrophysics Data System (ADS)

This article provides consolidated estimates of water withdrawal and water consumption for the full life cycle of selected electricity generating technologies, which includes component manufacturing, fuel acquisition, processing, and transport, and power plant operation and decommissioning. Estimates were gathered through a broad search of publicly available sources, screened for quality and relevance, and harmonized for methodological differences. Published estimates vary substantially, due in part to differences in production pathways, in defined boundaries, and in performance parameters. Despite limitations to available data, we find that: water used for cooling of thermoelectric power plants dominates the life cycle water use in most cases; the coal, natural gas, and nuclear fuel cycles require substantial water per megawatt-hour in most cases; and, a substantial proportion of life cycle water use per megawatt-hour is required for the manufacturing and construction of concentrating solar, geothermal, photovoltaic, and wind power facilities. On the basis of the best available evidence for the evaluated technologies, total life cycle water use appears lowest for electricity generated by photovoltaics and wind, and highest for thermoelectric generation technologies. This report provides the foundation for conducting water use impact assessments of the power sector while also identifying gaps in data that could guide future research.

Meldrum, J.; Nettles-Anderson, S.; Heath, G.; Macknick, J.

2013-03-01

273

Photochemical, electrochemical, and photoelectrochemical water oxidation catalyzed by water-soluble mononuclear ruthenium complexes.  

PubMed

Two mononuclear ruthenium complexes [Ru(H2tcbp)(isoq)2] (1) and [Ru(H2tcbp)(pic)2] (2) (H4tcbp=4,4',6,6'-tetracarboxy-2,2'-bipyridine, isoq=isoquinoline, pic=4-picoline) are synthesized and fully characterized. Two spare carboxyl groups on the 4,4'-positions are introduced to enhance the solubility of 1 and 2 in water and to simultaneously allow them to tether to the electrode surface by an ester linkage. The photochemical, electrochemical, and photoelectrochemical water oxidation performance of 1 in neutral aqueous solution is investigated. Under electrochemical conditions, water oxidation is conducted on the deposited indium-tin-oxide anode, and a turnover number higher than 15,000 per water oxidation catalyst (WOC) 1 is obtained during 10?h of electrolysis under 1.42?V vs. NHE, corresponding to a turnover frequency of 0.41?s(-1). The low overpotential (0.17?V) of electrochemical water oxidation for 1 in the homogeneous solution enables water oxidation under visible light by using [Ru(bpy)3](2+) (P1) (bpy=2,2'-bipyridine) or [Ru(bpy)2(4,4'-(COOEt)2-bpy)](2+) (P2) as a photosensitizer. In a three-component system containing 1 or 2 as a light-driven WOC, P1 or P2 as a photosensitizer, and Na2S2O8 or [CoCl(NH3)5]Cl2 as a sacrificial electron acceptor, a high turnover frequency of 0.81?s(-1) and a turnover number of up to 600 for 1 under different catalytic conditions are achieved. In a photoelectrochemical system, the WOC 1 and photosensitizer are immobilized together on the photoanode. The electrons efficiently transfer from the WOC to the photogenerated oxidizing photosensitizer, and a high photocurrent density of 85??A?cm(-2) is obtained by applying 0.3?V bias vs. NHE. PMID:25205065

Li, Ting-Ting; Zhao, Wei-Liang; Chen, Yong; Li, Fu-Min; Wang, Chuan-Jun; Tian, Yong-Hua; Fu, Wen-Fu

2014-10-20

274

Origin and role of water ice clouds in the Martian water cycle as inferred from a general circulation model  

NASA Astrophysics Data System (ADS)

In this paper, we present the results obtained by the general circulation model developed at the Laboratoire de Météorologie Dynamique which has been used to simulate the Martian hydrological cycle. Our model, which employs a simplified cloud scheme, reproduces the observed Martian water cycle with unprecedented agreement. The modeled seasonal evolution of cloudiness, which also compares well with data, is described in terms of the meteorological phenomena that control the Martian cloud distribution. Whereas cloud formation in the tropical region results from seasonal changes in the overturning circulation, Polar Hood clouds are mostly driven by variations of atmospheric wave activity. A sensitivity study allows us to quantify the effects of the transport of water ice clouds on the seasonal evolution of the water cycle. The residence time of cloud particles is long enough to allow cloud advection over great distances (typically thousands of kilometers). Despite the relatively low proportion of clouds (~10%) in the total atmospheric inventory of water, their ability to be transported over large distances generally acts at the expense of the north polar cap and generates a water cycle globally wetter by a factor of 2 than a cycle produced by a model neglecting cloud transport. Around aphelion season, clouds modulate the north to south migration of water in a significant fashion and participate just as much as vapor in the cross-equatorial transport of total water. Most of the year, atmospheric waves generate an equatorward motion of water ice clouds near the polar vortex boundaries, partially balancing the opposite poleward flux of water vapor. The combination of both effects delays the return of water to the north polar cap and allows water to build up in the Martian tropics.

Montmessin, F.; Forget, F.; Rannou, P.; Cabane, M.; Haberle, R. M.

2004-10-01

275

The Water Cycle from Space: Use of Satellite Data in Land Surface Hydrology and Water Resource Management  

NASA Technical Reports Server (NTRS)

This slide presentation reviews how our understanding of the water cycle is enhanced by our use of satellite data, and how this informs land surface hydrology and water resource management. It reviews how NASA's current and future satellite missions will provide Earth system data of unprecedented breadth, accuracy and utility for hydrologic analysis.

Laymon, Charles; Blankenship, Clay; Khan, Maudood; Limaye, Ashutosh; Hornbuckle, Brian; Rowlandson, Tracy

2010-01-01

276

Microbial ammonia oxidation and enhanced nitrogen cycling in the Endeavour hydrothermal plume  

NASA Astrophysics Data System (ADS)

Ammonium was injected from the subseafloor hydrothermal system at the Endeavour Segment, Juan de Fuca Ridge, into the deep-sea water column resulting in an NH4+-rich (?177 nM) neutrally buoyant hydrothermal plume. This NH4+ was quickly removed by both autotrophic ammonia oxidation and assimilation. The former accounted for at least 93% of total net NH4+ removal, with its maximum rate in the neutrally buoyant plume (?53 nM d -1) up to 10-fold that in background deep water. Ammonia oxidation in this plume potentially added 26-130 mg NO3-md into the deep-sea water column. This oxidation process was heavily influenced by the presence of organic-rich particles, with which ammonia-oxidizing bacteria (AOB) were often associated (40-68%). AOB contributed up to 10.8% of the total microbial communities within the plume, and might constitute a novel lineage of ?-proteobacterial AOB based on 16S rRNA and amoA phylogenetic analyses. Meanwhile, NH4+ assimilation rates were also substantially enhanced within the neutrally buoyant plume (?26.4 nM d -1) and accounted for at least 47% of total net NH4+ removal rates. The combined NH4+ oxidation and assimilation rates always exceeded total net removal rates, suggesting active in situNH4+regeneration rates of at least an order of magnitude greater than the particulate nitrogen flux from the euphotic zone. Ammonia oxidation is responsible for NH4+ turnover of 0.7-13 days and is probably the predominant in situ organic carbon production process (0.6-13 mg C m -2 d -1) at early stages of Endeavour neutrally buoyant plumes.

Lam, Phyllis; Cowen, James P.; Popp, Brian N.; Jones, Ronald D.

2008-05-01

277

Effect of cold water immersion on repeat cycling performance and thermoregulation in the heat  

Microsoft Academic Search

To assess the effect of cold water immersion and active recovery on thermoregulation and repeat cycling performance in the heat, ten well-trained male cyclists completed five trials, each separated by one week. Each trial consisted of a 30-min exercise task, one of five 15-min recoveries (intermittent cold water immersion in 10°C, 15°C and 20°C water, continuous cold water immersion in

Joanna Vaile; Shona Halson; Nicholas Gill; Brian Dawson

2008-01-01

278

The water cycle in closed ecological systems: Perspectives from the Biosphere 2 and Laboratory Biosphere systems  

Microsoft Academic Search

To achieve sustainable, healthy closed ecological systems requires solutions to challenges of closing the water cycle - recycling wastewater\\/irrigation water\\/soil medium leachate and evaporated water and supplying water of required quality as needed for different needs within the facility. Engineering Biosphere 2, the first multi-biome closed ecological system within a total airtight footprint of 12,700 m2 with a combined volume

Mark Nelson; W. F. Dempster; J. P. Allen

2009-01-01

279

The water cycle in closed ecological systems: Perspectives from the Biosphere 2 and Laboratory Biosphere systems  

Microsoft Academic Search

To achieve sustainable, healthy closed ecological systems requires solutions to challenges of closing the water cycle – recycling wastewater\\/irrigation water\\/soil medium leachate and evaporated water and supplying water of required quality as needed for different needs within the facility. Engineering Biosphere 2, the first multi-biome closed ecological system within a total airtight footprint of 12,700m2 with a combined volume of

Mark Nelson; W. F. Dempster; J. P. Allen

2009-01-01

280

Oxidation kinetics of antibiotics during water treatment with potassium permanganate.  

PubMed

The ubiquitous occurrence of antibiotics in aquatic environments raises concerns about potential adverse effects on aquatic ecology and human health, including the promotion of increased antibiotic resistance. This study examined the oxidation of three widely detected antibiotics (ciprofloxacin, lincomycin, and trimethoprim) by potassium permanganate [KMnO(4); Mn(VII)]. Reaction kinetics were described by second-order rate laws, with apparent second-order rate constants (k(2)) at pH 7 and 25 degrees C in the order of 0.61 +/- 0.02 M(-1) s(-1) (ciprofloxacin) < 1.6 +/- 0.1 M(-1) s(-1) (trimethoprim) < 3.6 +/- 0.1 M(-1) s(-1) (lincomycin). Arrhenius temperature dependence was observed with apparent activation energies (E(a)) ranging from 49 kJ mol(-1) (trimethoprim) to 68 kJ mol(-1) (lincomycin). Rates of lincomycin and trimethoprim oxidation exhibited marked pH dependences, whereas pH had only a small effect on rates of ciprofloxacin oxidation. The effects of pH were quantitatively described by considering parallel reactions between KMnO(4) and individual acid-base species of the target antibiotics. Predictions from a kinetic model that included temperature, KMnO(4) dosage, pH, and source water oxidant demand as input parameters agreed reasonably well with measurements of trimethoprim and lincomycin oxidation in six drinking water utility sources. Although Mn(VII) reactivity with the antibiotics was lower than that reported for ozone and free chlorine, its high selectivity and stability suggests a promising oxidant for treating sensitive micropollutants in organic-rich matrices (e.g., wastewater). PMID:20704243

Hu, Lanhua; Martin, Heather M; Strathmann, Timothy J

2010-08-15

281

Fabrication of functionally gradient nanocomposite coatings by plasma electrolytic oxidation based on variable duty cycle  

NASA Astrophysics Data System (ADS)

Plasma electrolytic oxidation (PEO) was applied on the surface of commercially pure titanium substrates in a mixed aluminate-phosphate electrolyte in the presence of silicon nitride nanoparticles as suspension in the electrolyte in order to fabricate nanocomposite coatings. Pulsed current was applied based on variable duty cycle in order to synthesize functionally gradient coatings (FGC). Different rates of variable duty cycle (3, 1.5 and 1%/min), applied current densities (0.06-0.14 A/cm2) and concentrations of nanoparticles in the electrolyte (2, 4, 6, 8 and 10 g l-1) were investigated. The nanopowder and coated samples were analyzed by atomic force microscope, scanning electron microscope and transmission electron microscope. The influence of different rates of variable duty cycle (or treatment times) on the growth rate of nanocomposite coatings and their microhardness values was investigated. The experimental results revealed that the content of Si3N4 nanoparticulates in the layer increases with the increase of its concentration in the plasma electrolysis bath. Nanocomposite coatings fabricated with lower rate of variable duty cycle have higher microhardness with smoother microhardness profile.

Aliofkhazraei, M.; Rouhaghdam, A. Sabour

2012-01-01

282

The persistence of oceans on Earth-like planets: insights from the deep-water cycle  

E-print Network

In this paper we present a series of models for the deep water cycle on super-Earths experiencing plate tectonics. The deep water cycle can be modeled through parameterized convection models coupled with a volatile recycling model. The convection of the silicate mantle is linked to the volatile cycle through the water-dependent viscosity. Important differences in surface water content are found for different parameterizations of convection. Surface oceans are smaller and more persistent for single layer convection, rather than convection by boundary layer instability. Smaller planets have initially larger oceans but also return that water to the mantle more rapidly than larger planets. Super-Earths may therefore be less habitable in their early years than smaller planets, but their habitability (assuming stable surface conditions), will persist much longer.

Schaefer, Laura

2015-01-01

283

Pt/TiO2 (Rutile) Catalysts for Sulfuric Acid Decomposition in Sulfur-Based Thermochemical Water-Splitting Cycles  

SciTech Connect

Thermochemical cycles consist of a series of chemical reactions to produce hydrogen from water at lower temperatures than by direct thermal decomposition. All the sulfur-based cycles for water splitting employ the sulfuric acid decomposition reaction. This work reports the studies performed on platinum supported on titania (rutile) catalysts to investigate the causes of catalyst deactivation under sulfuric acid decomposition reaction conditions. Samples of 1 wt% Pt/TiO2 (rutile) catalysts were submitted to flowing concentrated sulfuric acid at 1123 K and atmospheric pressure for different times on stream (TOS) between 0 and 548 h. Post-operation analyses of the spent catalyst samples showed that Pt oxidation and sintering occurred under reaction conditions and some Pt was lost by volatilization. Pt loss rate was higher at initial times but total loss appeared to be independent of the gaseous environment. Catalyst activity showed an initial decrease that lasted for about 66 h, followed by a slight recovery of activity between 66 and 102 h TOS, and a period of slower deactivation after 102 h TOS. Catalyst sulfation did not seem to be detrimental to catalyst activity and the activity profile suggested that a complex dynamical situation involving platinum sintering, volatilization, and oxidation, along with TiO2 morphological changes affected catalyst activity in a non-monotonic way.

L. M. Petkovic; D. M. Ginosar; H. W. Rollins; K. C. Burch; P. J. Pinhero; H. H. Farrell

2008-04-01

284

A new method for tracing the Sahel water cycle  

E-print Network

cientifica Actualité scientifique Water vapour is the primary greenhouse gas, itself causing around 60% of the effect. Nevertheless, the cloud processes linked to it are one of the primary sources of uncertainty, based on the absorption spectra of the different water molecules that make up atmospheric vapour

285

The Global Enery and Water Cycle Experiment Science Strategy  

NASA Technical Reports Server (NTRS)

The distribution of water in the atmosphere and at the surface of the Earth is the most influential factor regulating our environment, not only because water is essential for life but also because through phase transitions it is the main energy source that control clouds and radiation and drives the global circulation of the atmosphere.

Chahine, M. T.

1997-01-01

286

Nonstoichiometric Titanium Oxides via Pulsed Laser Ablation in Water  

PubMed Central

Titanium oxide compounds TiO,Ti2O3, and TiO2 with a considerable extent of nonstoichiometry were fabricated by pulsed laser ablation in water and characterized by X-ray/electron diffraction, X-ray photoelectron spectroscopy and electron energy loss spectroscopy. The titanium oxides were found to occur as nanoparticle aggregates with a predominant 3+ charge and amorphous microtubes when fabricated under an average power density of ca. 1 × 108W/cm2 and 1011W/cm2, respectively followed by dwelling in water. The crystalline colloidal particles have a relatively high content of Ti2+ and hence a lower minimum band gap of 3.4 eV in comparison with 5.2 eV for the amorphous state. The protonation on both crystalline and amorphous phase caused defects, mainly titanium rather than oxygen vacancies and charge and/or volume-compensating defects. The hydrophilic nature and presumably varied extent of undercoordination at the free surface of the amorphous lamellae accounts for their rolling as tubes at water/air and water/glass interfaces. The nonstoichiometric titania thus fabricated have potential optoelectronic and catalytic applications in UV–visible range and shed light on the Ti charge and phase behavior of titania-water binary in natural shock occurrence. PMID:20672115

2010-01-01

287

Destruction of representative submarine food waste using supercritical water oxidation.  

PubMed

In this study, 13 types of organic materials were oxidized using H2O2 in a continuous flow reactor under the condition of supercritical water. The effect of the operational parameters on the conversion of total organic carbon (TOC) and total nitrogen (TN) was investigated, and the resulting quality of treated water was analyzed. It was found that these materials were easily oxidized with a TOC conversion achieving 99 % at temperature of 460 °C and TN conversion reaching 94 % at temperature of 500 °C. Rice decomposition was rapid, with TOC and TN decomposition rates of 99 % obtained within residence of 100 s at temperature of 460 °C. At temperature of 460 °C, pressure of 24 MPa, residence time of 100 s, and excess oxygen of 100 %, the quality of treated water attained levels commensurate with China's Standards for Drinking Water Quality. Reaction rate equation parameters were obtained by fitting the experimental data to the differential equation obtained using the Runge-Kutta algorithm. The decrease of the TOC in water samples exhibited reaction orders of 0.95 for the TOC concentration and 0.628 for the oxygen concentration. The activation energy was 83.018 kJ/mol. PMID:25315932

Chen, Shiying; Qu, Xuan; Zhang, Rong; Bi, Jicheng

2014-10-15

288

Oxidation and dissolution of tungsten carbide powder in water  

Microsoft Academic Search

The oxidation and dissolution of tungsten carbide powder dispersed in water was investigated using X-ray photoelectron spectroscopy (XPS) and leaching studies. We found that the WO3 surface layer on the oxidised tungsten carbide powder dissolves readily at pH>3 with the tungsten concentration increasing linearly with time. Adding cobalt powder to the tungsten carbide suspension resulted in a significant reduction of

Karin M. Andersson; Lennart Bergström

2000-01-01

289

Water dissolved nitrous oxide from paddy agroecosystem in China  

Microsoft Academic Search

Although nitrous oxide emission from agricultural leaching and runoff is thought to constitute a globally important source of this greenhouse gas, water dissolved N2O in paddy ecosystems is poorly understood and scarcely reported where large amounts of fertilizer nitrogen are applied. This paper gives the results of a study assessing variability of the relationships between N2O and NO3? concentration in

Z. Q. Xiong; G. X. Xing; Z. L. Zhu

2006-01-01

290

Conversion of hazardous materials using supercritical water oxidation  

DOEpatents

A process for destruction of hazardous materials in a medium of supercritical water without the addition of an oxidant material. The harzardous material is converted to simple compounds which are relatively benign or easily treatable to yield materials which can be discharged into the environment. Treatment agents may be added to the reactants in order to bind certain materials, such as chlorine, in the form of salts or to otherwise facilitate the destruction reactions.

Rofer, Cheryl K. (Los Alamos, NM); Buelow, Steven J. (Los Alamos, NM); Dyer, Richard B. (Los Alamos, NM); Wander, Joseph D. (Parker, FL)

1992-01-01

291

Photochemical water oxidation and origin of nonaqueous uranyl peroxide complexes.  

PubMed

Sunlight photolysis of uranyl nitrate and uranyl acetate solutions in pyridine produces uranyl peroxide complexes. To answer longstanding questions about the origin of these complexes, we conducted a series of mechanistic studies and demonstrate that these complexes arise from photochemical oxidation of water. The peroxo ligands are easily removed by protonolysis, allowing regeneration of the initial uranyl complexes for potential use in catalysis. PMID:24635209

McGrail, Brendan T; Pianowski, Laura S; Burns, Peter C

2014-04-01

292

Tunable water desalination across graphene oxide framework membranes.  

PubMed

The performance of graphene oxide framework (GOF) membranes for water desalination is assessed using classical molecular dynamics (MD) simulations. The coupling between water permeability and salt rejection of GOF membranes is studied as a function of linker concentration n, thickness h and applied pressure ?P. The simulations reveal that water permeability in GOF-(n,h) membranes can be tuned from ?5 (n = 32 and h = 6.5 nm) to 400 L cm(-2) day(-1) MPa(-1) (n = 64 and h = 2.5 nm) and follows a Cnh(-?n) law. For a given pore size (n = 16 or 32), water permeability of GOF membranes increases when the pore spacing decreases, whereas for a given pore spacing (n = 32 or 64), water permeability increases by up to two orders of magnitude when the pore size increases. Furthermore, for linker concentrations n ? 32, the high water permeability corresponds to a 100% salt rejection, elevating this type of GOF membrane as an ideal candidate for water desalination. Compared to experimental performance of reverse osmosis membranes, our calculations suggest that under the same conditions of applied pressure and characteristics of membranes (?P ? 10 MPa and h ? 100 nm), one can expect a perfect salt rejection coupled to a water permeability two orders of magnitude higher than existing technologies, i.e., from a few cL cm(-2) day(-1) MPa(-1) to a few L cm(-2) day(-1) MPa(-1). PMID:24675972

Nicolaï, Adrien; Sumpter, Bobby G; Meunier, Vincent

2014-05-14

293

Several perspectives on water-chemical cycles for nuclear power stations equipped with type VVER and RBMK reactors  

Microsoft Academic Search

Water-chemical cycles for loops I and II of VVER reactors are discussed. These cycles are mixed ammonia-sodium with a variable concentration of boric acid and ammonia hydrazine with a pH factor of 9.1 +\\/- 0.1. New water-chemical cycles are considered for use in both existing and new nuclear power plants. Application of these new water-chemical cycles showed produce a significant

A. P. Mamet; V. A. Mamet; V. I. Pashevich; P. N. Nazarenko

1982-01-01

294

Photoassembly of the Water-Oxidizing Complex in Photosystem II  

PubMed Central

The light-driven steps in the biogenesis and repair of the inorganic core comprising the O2-evolving center of oxygenic photosynthesis (photosystem II water-oxidation complex, PSII-WOC) are reviewed. These steps, known collectively as photoactivation, involve the photoassembly of the free inorganic cofactors to the cofactor-depleted PSII-(apo-WOC) driven by light and produce the active O2-evolving core comprised of Mn4CaOxCly. We focus on the functional role of the inorganic components as seen through the competition with non-native cofactors (“inorganic mutants”) on water oxidation activity, the rate of the photoassembly reaction, and on structural insights gained from EPR spectroscopy of trapped intermediates formed in the initial steps of the assembly reaction. A chemical mechanism for the initial steps in photoactivation is given that is based on these data. Photoactivation experiments offer the powerful insights gained from replacement of the native cofactors, which together with the recent X-ray structural data for the resting holoenzyme provide a deeper understanding of the chemistry of water oxidation. We also review some new directions in research that photoactivation studies have inspired that look at the evolutionary history of this remarkable catalyst. PMID:19190725

Dasgupta, Jyotishman; Ananyev, Gennady M; Dismukes, G. Charles

2008-01-01

295

DESIGN OF HYBRID POWER GENERATION CYCLES EMPLOYING AMMONIA-WATER-CARBON DIOXIDE MIXTURES  

SciTech Connect

A power cycle generates electricity from the heat of combustion of fossil fuels. Its efficiency is governed by the cycle configuration, the operating parameters, and the working fluid. Typical. designs use pure water as the fluid. in the last two decades, hybrid cycles based on ammonia-water, and carbon-dioxide mixtures as the working fluid have been proposed. These cycles may improve the power generation efficiency of Rankine cycles by 15%. Improved efficiency is important for two reasons: it lowers the cost of electricity being produced, and by reducing the consumption of fossil fuels per unit power, it reduces the generation of environmental pollutants. The goal of this project is to develop a computational optimization-based method for the design and analysis of hybrid bottoming power cycles to minimize the usage of fossil fuels. The development of this methodology has been achieved by formulating this task as that of selecting the least cost power cycle design from all possible configurations. They employ a detailed thermodynamic property prediction package they have developed under a DOE-FETC grant to model working fluid mixtures. Preliminary results from this work suggest that a pure NH{sub 3} cycle outperforms steam or the expensive Kalina cycle.

Ashish Gupta

2002-06-01

296

Artificial photosynthesis: from nanosecond electron transfer to catalytic water oxidation.  

PubMed

Human society faces a fundamental challenge as energy consumption is projected to increase due to population and economic growth as fossil fuel resources decrease. Therefore the transition to alternative and sustainable energy sources is of the utmost importance. The conversion of solar energy into chemical energy, by splitting H2O to generate molecular O2 and H2, could contribute to solving the global energy problem. Developing such a system will require the combination of several complicated processes, such as light-harvesting, charge separation, electron transfer, H2O oxidation, and reduction of the generated protons. The primary processes of charge separation and catalysis, which occur in the natural photosynthetic machinery, provide us with an excellent blueprint for the design of such systems. This Account describes our efforts to construct supramolecular assemblies capable of carrying out photoinduced electron transfer and to develop artificial water oxidation catalysts (WOCs). Early work in our group focused on linking a ruthenium chromophore to a manganese-based oxidation catalyst. When we incorporated a tyrosine unit into these supramolecular assemblies, we could observe fast intramolecular electron transfer from the manganese centers, via the tyrosine moiety, to the photooxidized ruthenium center, which clearly resembles the processes occurring in the natural system. Although we demonstrated multi-electron transfer in our artificial systems, the bottleneck proved to be the stability of the WOCs. Researchers have developed a number of WOCs, but the majority can only catalyze H2O oxidation in the presence of strong oxidants such as Ce(IV), which is difficult to generate photochemically. By contrast, illumination of ruthenium(II) photosensitizers in the presence of a sacrificial acceptor generates [Ru(bpy)3](3+)-type oxidants. Their oxidation potentials are significantly lower than that of Ce(IV), but our group recently showed that incorporating negatively charged groups into the ligand backbone could decrease the oxidation potential of the catalysts and, at the same time, decrease the potential for H2O oxidation. This permitted us to develop both ruthenium- and manganese-based WOCs that can operate under neutral conditions, driven by the mild oxidant [Ru(bpy)3](3+). Many hurdles to the development of viable systems for the production of solar fuels remain. However, the combination of important features from the natural photosynthetic machinery and novel artificial components adds insights into the complicated catalytic processes that are involved in splitting H2O. PMID:23957573

Kärkäs, Markus D; Johnston, Eric V; Verho, Oscar; Akermark, Björn

2014-01-21

297

Ground water geochemistry of short-term aquifer thermal energy storage test cycles  

SciTech Connect

The changes in the concentrations of Ca, dissolved silica, and alkalinity of the recovery waters of four short-term aquifer thermal energy storage test cycles with respect to the injection waters and the correlation of these concentrations with recovery water temperatures indicate that quartz and calcite dissolved during hot water storage. This hypothesis was supported by chemical equilibrium modeling and mass balance calculations. Magnesium concentrations were lower in recovery waters than in injection waters. Chemical modeling indicated that a Mg silicate (talc) could have precipitated. Potassium concentrations correlated well with temperatures, probably because of ion exchange involving potassium feldspars in the aquifer.

Holms, T.R.; Eisenreich, S.J.; Rosenberg, H.L.; Holm, N.P.

1987-06-01

298

Stability of Supported Platinum Sulfuric Acid Decomposition Catalysts for use in Thermochemical Water Splitting Cycles  

SciTech Connect

The activity and stability of several metal oxide supported platinum catalysts were explored for the sulfuric acid decomposition reaction. The acid decomposition reaction is common to several sulfur based thermochemical water splitting cycles. Reactions were carried out using a feed of concentrated liquid sulfuric acid (96 wt%) at atmospheric pressure at temperatures between 800 and 850 °C and a weight hour space velocity of 52 g acid/g catalyst/hr. Reactions were run at these high space velocities such that variations in kinetics were not masked by surplus catalyst. The influence of exposure to reaction conditions was explored for three catalysts; 0.1-0.2 wt% Pt supported on alumina, zirconia and titania. The higher surface area Pt/Al2O3 and Pt/ZrO2 catalysts were found to have the highest activity but deactivated rapidly. A low surface area Pt/TiO2 catalyst was found to have good stability in short term tests, but slowly lost activity for over 200 hours of continuous operation.

Daniel M. Ginosar; Lucia M. Petkovic; Anne W. Glenn; Kyle C. Burch

2007-03-01

299

Sea Surface Salinity Understanding the Interactions Between the Global Water Cycle, Ocean Circulation and Climate  

E-print Network

Sea Surface Salinity Understanding the Interactions Between the Global Water Cycle, Ocean Circulation and Climate Aquarius will provide unprecedented global maps of surface sea water salinity?" Sea surface salinity is the primary surface tracer of freshwater input and output to the ocean

Waliser, Duane E.

300

AN AMMONIA-WATER ABSORPTION-HIAT-PUMP CYCLE Donald Kuhlenschmidt, Member ASHRAE  

E-print Network

#12;AN AMMONIA-WATER ABSORPTION-HIAT-PUMP CYCLE BY Donald Kuhlenschmidt, Member ASHRAE Richard H. Merrick, Member ASHRAE ABSTRACT The scate-of-art in ammonia-water absorption cooling has been applied,000 Btuh) input unit reported. KLY WORDS Absorption Heat-pump Air conditioning heating Ammonia Donald

Oak Ridge National Laboratory

301

Economic comparison of hydrogen production using sulfuric acid electrolysis and sulfur cycle water decomposition. Final report  

Microsoft Academic Search

An evaluation of the relative economics of hydrogen production using two advanced techniques was performed. The hydrogen production systems considered were the Westinghouse Sulfur Cycle Water Decomposition System and a water electrolysis system employing a sulfuric acid electrolyte. The former is a hybrid system in which hydrogen is produced in an electrolyzer which uses sulfur dioxide to depolarize the anode.

G. H. Farbman; B. R. Krasicki; C. C. Hardman; S. S. Lin; G. H. Parker

1978-01-01

302

Interactions Among Water, Carbon, And Nutrient Cycles With Woody Plant Encroachment Into Grasslands  

Microsoft Academic Search

The expansion of woody plants into deserts, grasslands, and savannas alters water and nutrient cycling, affecting some one-fifth of the world's population. In this talk, research along precipitation gradients in North and South America will be used to examine interactions among water, carbon and nutrients in the southwestern U.S. and in grasslands of Argentina and Uruguay. Those interactions include groundwater

R. B. Jackson; V. Engel; E. G. Jobbagy; A. J. McElrone; W. T. Pockman

2003-01-01

303

Carbon Dioxide and Water Cycling in a Semiarid Savanna in Southern Arizona, USA  

Microsoft Academic Search

The consequences of recent woody plant encroachment on the carbon and water cycling of semiarid ecosystems are not well understood. In this presentation, we present measurements made from 2004 - 2006 using sap flow and eddy covariance techniques to examine the carbon dioxide and water fluxes that occurred over a semiarid savanna on the Santa Rita Experimental Range in southern

R. L. Scott; K. Hultine; G. Barron-Gafford; T. Huxman

2007-01-01

304

Mercury cycling in the water column of a seasonally anoxic urban lake (Onondaga Lake, NY)  

Microsoft Academic Search

Onondaga Lake, New York, is a hypereutrophic, urban lake that was subjected to industrial discharges of mercury (Hg) between 1947 and 1988. Water samples were collected from April through November 1992 and analyzed for filtered and unfiltered total Hg, methylmercury (CH3Hg), dimethylmercury, ionic Hg, and elemental Hg to characterize the biogeochemical cycling of Hg during water column stratification and hypolimnetic

L. A. Jacobs; S. M. Klein; E. A. Henry

1995-01-01

305

Economic Input-Output Life Cycle Assessment of Water Reuse Strategies in Residential Buildings  

EPA Science Inventory

This paper evaluates the environmental sustainability and economic feasibility of four water reuse designs through economic input-output life cycle assessments (EIO-LCA) and benefit/cost analyses. The water reuse designs include: 1. Simple Greywater Reuse System for Landscape Ir...

306

Supercritical-pressure, Once-through Cycle Light Water Cooled Reactor Concept  

Microsoft Academic Search

The purpose of the study is to develop new reactor concepts for the innovation of light water reactors (LWR) and fast reactors. Concept of the once-through coolant cycle, supercritical-pressure light water cooled reactor was developed. Major aspects of reactor design and safety were analysed by the computer codes which were developed by ourselves. It includes core design of thermal and

Yoshiaki OKA; Seiichi KOSHIZUKA

2001-01-01

307

Global Energy and Water Cycle Experiment mate models appear to systematically under-predict  

E-print Network

. Regional skew in search of a parent, Water Resources Research 11, 815-826. Milly, P. C. D., J. Betancourt for the Global Energy and Water Cycle Experiment, Geneva. Collateral Damage from the Death of Stationarity Roger article assert that the cause of the death of stationarity is human-caused climate change

Colorado at Boulder, University of

308

2-Phenyl-beta-lapachone can affect mitochondrial function by redox cycling mediated oxidation.  

PubMed

2-Phenyl-beta-lapachone (3,4-dihydro-2-methyl-2-phenyl-2H-naphtho[1,2b]pyran-5,6-dione) (2PBL) is a o-naphthoquinone synthesized as a possible antitumoral agent. The addition of micromolar concentrations of 2PBL to rat liver mitochondria (in the presence of malate-glutamate or succinate, as respiratory substrates): (1) stimulated O(2) consumption in state 4 and inhibited O(2) consumption in state 3, thus decreasing respiratory control index (RCI); and (2) collapsed the mitochondrial membrane potential. The addition of 2PBL to rat liver submitochondrial particles: (1) stimulated NADH oxidation in the presence of rotenone, antimycin, myxothiazol or cyanide; (2) stimulated (.-)O(2)(-) production in the presence of NADH and antimycin; and (3) led to 2PBL semiquinone radical production. Control studies carried out with two p-naphthoquinones, menadione and atovaquone, did not produced equivalent effects. These findings support the hypothesis that 2PBL, undergoes redox cycling and affects mitochondrial function. The 2PBL effect is complex, involving inhibition of electron transfer, uncoupling of oxidative phosphorylation, collapse of mitochondrial membrane potential and (.-)O(2)(-) production by redox cycling. The mitochondrion could be a target organelle for 2PBL cytotoxicity. PMID:15542051

de Witte, Natacha V; Stoppani, Andrés O M; Dubin, Marta

2004-12-15

309

Life cycle assessments of urban water systems: A comparative analysis of selected peer-reviewed literature.  

PubMed

Water is a growing concern in cities, and its sustainable management is very complex. Life cycle assessment (LCA) has been increasingly used to assess the environmental impacts of water technologies during the last 20 years. This review aims at compiling all LCA papers related to water technologies, out of which 18 LCA studies deals with whole urban water systems (UWS). A focus is carried out on these 18 case studies which are analyzed according to criteria derived from the four phases of LCA international standards. The results show that whereas the case studies share a common goal, i.e., providing quantitative information to policy makers on the environmental impacts of urban water systems and their forecasting scenarios, they are based on different scopes, resulting in the selection of different functional units and system boundaries. A quantitative comparison of life cycle inventory and life cycle impact assessment data is provided, and the results are discussed. It shows the superiority of information offered by multi-criteria approaches for decision making compared to that derived from mono-criterion. From this review, recommendations on the way to conduct the environmental assessment of urban water systems are given, e.g., the need to provide consistent mass balances in terms of emissions and water flows. Remaining challenges for urban water system LCAs are identified, such as a better consideration of water users and resources and the inclusion of recent LCA developments (territorial approaches and water-related impacts). PMID:25282088

Loubet, Philippe; Roux, Philippe; Loiseau, Eleonore; Bellon-Maurel, Veronique

2014-12-15

310

Calcium manganese(IV) oxides: biomimetic and efficient catalysts for water oxidation.  

PubMed

CaMnO(3) and Ca(2)Mn(3)O(8) were synthesized and characterized by SEM, XRD, FTIR and BET. Both oxides showed oxygen evolution activity in the presence of oxone, cerium(IV) ammonium nitrate and H(2)O(2). Oxygen evolution from water during irradiation with visible light (? > 400 nm) was also observed upon adding these manganese oxides to an aqueous solution containing tris(2,2'-bipyridyl) ruthenium(II), as photosensitizer, and chloro pentaammine cobalt(III) chloride, as electron acceptor, in an acetate buffer. The amounts of dissolved manganese and calcium from CaMnO(3) and Ca(2)Mn(3)O(8) in the oxygen evolving reactions were reported and compared with other (calcium) manganese oxides. Proposed mechanisms of oxygen evolution and proposed roles for the calcium ions are also considered. PMID:22382465

Najafpour, Mohammad Mahdi; Pashaei, Babak; Nayeri, Sara

2012-04-28

311

Triggering a Wet Climate on Mars: The Role of Outflow Channels in Martian Water Cycles  

NASA Astrophysics Data System (ADS)

The triggering of a robust water cycle on Mars has been hypothesized to be caused by gigantic flooding events evidenced by outflow channels. Here we use the Ames Mars General Circulation Model (MGCM) to study how these presumably abrupt eruptions of water (Carr,1996) affected the climate of Mars. We model where the water ultimately went as part of a transient hydrologic cycle. Chryse Planitia, east of Tharsis, has evidence for multiple water outflow channels. One of the largest channels is Ares Valles, which was carved by floods with estimated water volumes of order 10^5 km^2 (Andrews-Hanna, 2007 & Carr, 1996). Outflow discharge rate estimates range from 10^6 to 10^7 m^3/seconds or greater (Andrews-Hanna & Phillips, 2007, Harrison & Grimm, 2008). Studies suggest that outflow channels formed with smaller, successive floods instead of a single large flood (Wilson, et al.,2004). Warner et al. (2009) suggest up to six outflow events for the formation of Ares Valles, while estimates for another large outflow, Kasei Valles, might have been flooded by over two thousand floods with a total water volume of 5.5 x 10^5 km^3 (Harrison & Grimm, 2008). By adding water to the surface of Mars at the given outflow rate, as an expanding one-layer lake, we are able to study quantitatively how these outflow events influenced Mars climate, particularly the hydrologic cycle. In particular: Could sudden introductions of large amounts of water on the Martian surface lead to a new equilibrated water cycle? Can we tie certain fluvial surface features to transient or sustained water cycles? What are the roles of water vapor and water ice clouds to sudden changes in the water cycle on Mars? How are radiative feedbacks involved with this? What is the ultimate fate of the outflow water? This work uses the NASA Ames MGCM version 2.1 and other schemes that are part of the NASA Ames MGCM suite of tools. Various versions of the MGCM developed at Ames have been used extensively to examine dust and volatile distributions on Mars (e.g., Kahre et al., 2006, 2008). The MGCM 2.1 currently has a well-developed water ice cloud formation scheme (Montmessin et al., 2002, 2004a), which includes calculation of cloud particle concentrations, nucleation, growth, and gravitational sedimentation. For examining the effect of a large water outflow on the climate of Mars, we include water tracers, with an advanced cloud particle scheme Preliminary results suggest that water may have been transported globally for years post-outflow. Post-outflow water cloud formation increases dramatically, with water ice clouds and water vapor potentially transporting water globally. The global mass of water vapor and of water ice clouds increases substantially, with the post-outflow patterns settling into annual cycles, with increasing water entering the atmosphere from the surface over time. Future work will examine the radiative effects of the water vapor and water ice clouds, and the longer-term persistence of a new hydrological or climate regime Detailed comparisons of post-outflow precipitation locations with fluvial features on Mars will be done.

Santiago, D.; Asphaug, E. I.; Colaprete, A.

2011-12-01

312

Life cycle water use of energy production and its environmental impacts in China.  

PubMed

The energy sector is a major user of fresh water resources in China. We investigate the life cycle water withdrawals, consumptive water use, and wastewater discharge of China's energy sectors and their water-consumption-related environmental impacts, using a mixed-unit multiregional input-output (MRIO) model and life cycle impact assessment method (LCIA) based on the Eco-indicator 99 framework. Energy production is responsible for 61.4 billion m(3) water withdrawals, 10.8 billion m(3) water consumption, and 5.0 billion m(3) wastewater discharges in China, which are equivalent to 12.3%, 4.1% and 8.3% of the national totals, respectively. The most important feature of the energy-water nexus in China is the significantly uneven spatial distribution of consumptive water use and its corresponding environmental impacts caused by the geological discrepancy among fossil fuel resources, fresh water resources, and energy demand. More than half of energy-related water withdrawals occur in the east and south coastal regions. However, the arid north and northwest regions have much larger water consumption than the water abundant south region, and bear almost all environmental damages caused by consumptive water use. PMID:24125477

Zhang, Chao; Anadon, Laura Diaz

2013-12-17

313

Water oxidation mechanism for synthetic Co-oxides with small nuclearity.  

PubMed

Hybrid DFT model calculations have been performed for some cobalt complexes capable of oxidizing water. Since a very plausible mechanism for the oxygen-evolving complex involving the cuboidal Mn4Ca structure in photosystem II (PSII) has recently been established, the most important part of the present study concerns a detailed comparison between cobalt and manganese as water oxidation catalysts. One similarity found is that a M(IV)-O(•) state is the key precursor for O-O bond formation in both cases. This means that simply getting a M(IV) state is not enough; a formal M(V)?O state is required, with two oxidations on one center from M(III). For cobalt, not even that is enough. A singlet coupled state is required at this oxidation level, which is not the ground state. It is shown that there are also more fundamental differences between catalysts based on these metals. The favorable low-barrier direct coupling mechanism found for PSII is not possible for the corresponding cobalt complexes. The origin of this difference is explained. For the only oxygen-evolving cubic Co4O4 complex with a defined structure, described by Dismukes et al., the calculated results are in good agreement with experiments. For the Co4 models of the amorphous cobalt-oxo catalyst found by Nocera et al., higher barriers are found than the one obtained experimentally. The reasons for this are discussed. PMID:23968287

Li, Xichen; Siegbahn, Per E M

2013-09-18

314

Solar-thermal Water Splitting Using the Sodium Manganese Oxide Process & Preliminary H2A Analysis  

SciTech Connect

There are three primary reactions in the sodium manganese oxide high temperature water splitting cycle. In the first reaction, Mn2O3 is decomposed to MnO at 1,500°C and 50 psig. This reaction occurs in a high temperature solar reactor and has a heat of reaction of 173,212 J/mol. Hydrogen is produced in the next step of this cycle. This step occurs at 700°C and 1 atm in the presence of sodium hydroxide. Finally, water is added in the hydrolysis step, which removes NaOH and regenerates the original reactant, Mn2O3. The high temperature solar�driven step for decomposing Mn2O3 to MnO can be carried out to high conversion without major complication in an inert environment. The second step to produce H2 in the presence of sodium hydroxide is also straightforward and can be completed. The third step, the low temperature step to recover the sodium hydroxide is the most difficult. The amount of energy required to essentially distill water to recover sodium hydroxide is prohibitive and too costly. Methods must be found for lower cost recovery. This report provides information on the use of ZnO as an additive to improve the recovery of sodium hydroxide.

Todd M. Francis, Paul R. Lichty, Christopher Perkins, Melinda Tucker, Peter B. Kreider, Hans H. Funke, Allan Lewandowski, and Alan W. Weimer

2012-10-24

315

Evolutionary mixed-oxide fuel performance in pressurized water reactors  

SciTech Connect

Investigations of an advanced fuel form are currently under way at Los Alamos National Laboratory. This new fuel form, referred to as evolutionary mixed oxide (EMOX), is a slight perturbation on standard mixed-oxide (MOX) fuel, and analyses show that it can be an effective plutonium management tool in existing light water reactors. The addition of a small fraction of calcia-stabilized zirconia to the uranium-plutonium oxide matrix allows for greater plutonium conversion while also providing a licensing path forward toward eventual implementation of higher plutonium destruction fuels. These fuels, referred to as nonfertile (NF) fuels, achieve their high destruction rates through the absence of uranium, which breeds plutonium, in the fuel composition. Extensive calculations have been performed to assess the feasibility of incorporating the EMOX fuel form into existing pressurized water reactor (PWR) systems, and the results are presented in this paper. Specifically, calculations have been made to determine the plutonium consumption achievable by the EMOX concept, and comparisons have been made of this performance with that of typical MOX and NF fuels.

Eaton, S.L.; Beard, C.A.; Buksa, J.J. [Los Alamos National Laboratory, NM (United States)

1996-12-31

316

Interrelationship Between the Dust and Water Cycles in the Martian Atmosphere: Numerical Modeling Studies  

NASA Astrophysics Data System (ADS)

Mars' low-mass, primarily carbon dioxide atmosphere contains quantities of both water vapor and suspended dust particles. Suspended dust can have a significant impact upon the atmospheric thermal state as the dust warms and cools via absorption and emission of radiant energy. Water vapor condensing onto the dust grains will change the radiative characteristics of both. Small dust particles can potentially be carried to great altitudes and affect the temperatures there. One potential limiting factor in the vertical extent of the dust is water vapor condensation. If water vapor present in the atmosphere condenses upon a dust particle, the particle's gravitational sedimentation speed can be increased, and the likelihood of it being transported to high altitudes is diminished. Thus, water can act as a controlling mechanism with regard to the vertical extent of dust mixing. At the same time, the atmosphere's water vapor holding capacity is very strongly temperature dependent: the greater the temperature, the greater the potential water vapor mixing ratio (if a source of water or ice is available). Thus, there is a potentially significant interplay between the Martian dust and water cycles. Previous research done using computer modeling to better understand the Martian atmosphere treat the dust and the water cycles as two separate and independent processes. The existing numerical model will be improved to simulate the relationship between the Martian dust and water cycles by actually coupling the two cycles. The model will condense the water onto the dust allowing the particles radiative characteristics, fall speeds, and as a result, their vertical distribution to change. Data obtained from the Viking, Mars Pathfinder, and especially the Mars Global Surveyor missions will be used to determine the accuracy of the model results. Preliminary results will be presented at the June 2002 meeting.

Nelli, S. M.; Murphy, J. R.

2002-05-01

317

The water cycle in closed ecological systems: perspectives from the Biosphere 2 and Laboratory Biosphere systems  

Microsoft Academic Search

To achieve sustainable and healthy closed ecological systems requires successful solutions to the challenge of closing the water cycle - recycling wastewater\\/soil leachate and evaporateed water and supplying water of required quality as needed for different needs within the facility. Engineering Biosphere 2, the first multi-biome closed ecological system, total footprint of the airtight area is 12,700 m2 with a

Mark Nelson; William Dempster; John P. Allen

2008-01-01

318

Earth Science (A Process Approach), Section 1: The Water Cycle.  

ERIC Educational Resources Information Center

Included is a collection of earth science laboratory activities, which may provide the junior or senior high school science teacher with ideas for activities in his program. The included 48 experiments are grouped into these areas: properties of matter; evaporation; atmospheric moisture and condensation; precipitation; moving water, subsurface…

Campbell, K. C.; And Others

319

EMERGING CONTAMINANTS IN THE WATER CYCLE: FATE AND TRANSPORT  

EPA Science Inventory

In the past decade, the scientific community and general public have become increasingly aware of the potential for the presence of unregulated, and generally unmonitored contaminants, found at low concentrations in surface, ground and drinking water. The most common pathway for...

320

Emerging Contaminants in the Drinking Water Cycle - MCEARD  

EPA Science Inventory

In the past decade, the scientific community and general public have become increasingly aware of the potential for the presence of unregulated, and generally unmonitored contaminants, found at low concentrations (sub-¿g/L) in surface, ground and drinking water. The most common...

321

Arsenic removal from water using flame-synthesized iron oxide nanoparticles with variable oxidation states  

PubMed Central

We utilized gas-phase diffusion flame synthesis, which has potential for large-scale production of metal oxide nanoparticles, to produce iron oxide nanoparticles (IONPs) with variable oxidation states. The efficacy of these materials in removal of arsenate (As(V) ) from water was assessed. Two different flame configurations, a diffusion flame (DF) and an inverse diffusion flame (IDF), were employed to synthesize six different IONPs by controlling flame conditions. The IONPs produced in the IDF configuration (IDF-IONPs) had smaller particle diameters (4.8 – 8.2 nm) and larger surface areas (141–213 m2/g) than the IONPs produced in the DF configuration (29 nm, 36 m2/g), which resulted in their higher adsorption capacities. As(V) adsorption capacities of the IDF-IONPs increased when the IONPs were synthesized in more oxidizing conditions. The fully oxidized IDF-IONPs, maghemite (?-Fe2O3), showed the highest As(V) adsorption capacity, comparable to that of magnetite nanocrystals synthesized by thermal decomposition of iron pentacarbonyl and equivalent to three to four times higher capacity than that of a commonly used goethite-based adsorbent. All IONPs were magnetically responsive, which is of great importance for solid?liquid separation. This study demonstrates that the IONPs synthesized in gas-phase flame, particularly IDF-IONPs, are excellent adsorbents because of their high As(V) sorption capacity, potential for large-scale production, and useful magnetic property. PMID:23645964

Abid, Aamir D.; Kanematsu, Masakazu; Young, Thomas M.; Kennedy, Ian M.

2013-01-01

322

Comparison Between Crystalline and Amorphous Surfaces of Transition Metal Oxide Water Oxidation Catalysts: a Theoretical Perspective  

NASA Astrophysics Data System (ADS)

Amorphous films of transition-metal oxide water oxidation catalysts (WOCs) often show an enhanced catalytic activity compared to their crystalline counterparts [1-4]. In particular, in the case of cobalt-oxide based WOCs the observed similarity in their electrochemical properties and catalytic activity, under oxidative conditions, has been correlated with the formation of similar amorphous surface morphologies, suggesting the presence of a common, catalytically active amorphous structural motif [3,4]. We present ab initio calculations of cobalt oxide based material surfaces and we compare the electronic properties of crystalline and amorphous surfaces, with the aim of identifying differences related to their different catalytic activity.[4pt] [1] Blakemore, J. D., Schley, N. D., Kushner-Lenhoff, M. N., Winter, A. M., D'Souza, F., Crabtree, R. H., and Brudvig, G. W. Inorg. Chem. 51, 7749 (2012); [2] Tsuji, E., Imanishi, A., Fukui, K.-I. and Nakato, Y. Electrochimica Acta 56, 2009 (2011); [3] Jia, H., Stark, J., Zhou, L. Q., Ling, C., Takeshi, S., and Markin, Z. RSC Advances 2, 10874 (2012); [4] Lee, S. W., Carlton, C., Risch, M., Surendranath, Y., Chen, S., Furutsuki, S., Yamada, A., Nocera, D. G., and Shao-Horn, Y. J. Am. Chem. Soc. 134, 16959 (2012).

Skone, Jonathan H.; Galli, Giulia

2013-03-01

323

Microbial dissimilatory sulfur cycle in acid mine water.  

PubMed

Ferric, sulfate, and hydrogen ions are produced from pyritic minerals associated with coal as a result of autotrophic bacterial metabolism. Water carrying these ions accumulated behind a porous dam composed of wood dust originating at a log-cutting mill. As water seeped through the porous dam, it was enriched in organic nutrients which then supported growth and metabolism of heterotrophic bacteria in the water downstream from the dam. The heterotrophic microflora within and below the sawdust dam included dissimilatory sulfate-reducing anaerobic bacteria which reduce sulfate to sulfide. The sulfide produced caused the chemical reduction of ferric to ferrous ion, and black FeS precipitate was deposited on the pond bottom. A net increase in the pH of the lower pond water was observed when compared to the upper pond water. Microbial activity in the wood dust was demonstrated, and a sequence of cellulose degradation processes was inferred on the basis of sugar accumulation in mixed cultures in the laboratory, ultimately yielding fermentation products which serve as nutrients for sulfate-reducing bacteria. Some of the microorganisms were isolated and characterized. The biochemical and growth characteristics of pure culture isolates were generally consistent with observed reactions in the acidic environment, with the exception of sulfate-reducing bacteria. Mixed cultures which contained sulfate-reducing bacteria reduced sulfate at pH 3.0 in the laboratory with sawdust as the only nutrient. Pure cultures of sulfate-reducing bacteria isolated from the mixed cultures did not reduce sulfate below pH 5.5. PMID:5773013

Tuttle, J H; Dugan, P R; Macmillan, C B; Randles, C I

1969-02-01

324

Effect of mixing water magnetic activation cycle on cement stone structure  

NASA Astrophysics Data System (ADS)

The paper presents results of investigations of hydration processes and structure formation of the cement paste matrix mixed with water activated by magneto static field using water treatment cycle technology. It is shown that crystallization of phases occurs in the cement-water system at different rates, and phase redistribution in the structure of the cement paste matrix is described before and after magnetic activation of mixing water. Also, modeling of the cement-water system and calculations of amorphous and crystalline phases using the Rietveld refinement method before and after magnetic activation show that strength properties of the cement paste matrix depend not only on quantitative but also qualitative relationship between phases.

Kugaevskaya, S. A.; Abzaev, Yu A.; Safronov, V. N.; Sarkisov, Yu S.; Gorlenko, N. P.; Ermilova, T. A.

2015-01-01

325

Open Cycle OTEC System with Fresh Water Product  

NASA Astrophysics Data System (ADS)

An open-cycle ocean thermal energy conversion (OC-OTEC) system is one of energy conversion methods to generate electricity from ocean thermal energy. For OC-OTEC system, steam evaporated from the surface seawater due to flash evaporation drives the turbine. At that time, dissolved gas such as air is introduced into the low-pressure system (OC-OTEC system) as the non-condensable gas, which degrades the performance of condensation heat transfer. In this paper, a small scale OC-OTEC experimental unit experimentally investigates the effect of non-condensable gas on the heat transfer performance in a condenser. The experimental results are discussed in comparison with theoretical estimation by Sparrow-Lin method. It is shown that the condensation is occupied by heat and mass transfer near a condensation surface and that the condensation efficiency is affected by exhaust quantity of non-condensable gas at relative high concentration ratio of condensable gas.

Amano, Masatugu; Tanaka, Tadayosi

326

The life cycle of iron Fe(III) oxide: impact of fungi and bacteria  

NASA Astrophysics Data System (ADS)

Iron oxides are ubiquitous reactive constituents of soils, sediments and aquifers. They exhibit vast surface areas which bind a large array of trace metals, nutrients and organic molecules hence controlling their mobility/reactivity in the subsurface. In this context, understanding the "life cycle" of iron oxide in soils is paramount to many biogeochemical processes. Soils environments are notorious for their extreme heterogeneity and variability of chemical, physical conditions and biological agents at play. Here, we present studies investigating the role of two biological agents driving iron oxide dynamics in soils, root-associated fungi (mycorrhiza) and bacteria. Mycorrhiza filaments (hypha) grow preferentially around, and on the surface of nutrient-rich minerals, making mineral-fungi contact zones, hot-spots of chemical alteration in soils. However, because of the microscopic nature of hyphae (only ~ 5 µm wide for up to 1 mm long) and their tendency to strongly adhere to mineral surface, in situ observations of this interfacial micro-environment are scarce. In a microcosm, ectomycorrhiza (Paxillus involutus) was grown symbiotically with a pine tree (Pinus sylvestris) in the presence of freshly-cleaved biotite under humid, yet undersaturated, conditions typical of soils. Using spatially-resolved ion milling technique (FIB), transmission electron microscopy and spectroscopy (TEM/STEM-EDS), synchrotron based X-ray microscopy (STXM), we were able to quantify the speciation of Fe at the biotite-hypha interface. The results shows that substantial oxidation of biotite structural-Fe(II) into Fe(III) subdomains occurs at the contact zone between mycorrhiza and biotite. Once formed, iron(III) oxides can reductively dissolve under suboxic conditions via several abiotic and microbial pathways. In particular, they serve as terminal electron acceptors for the oxidation of organic matter by iron reducing bacteria. We aimed here to understand the role of Fe(III) mineral properties, in particular the influence of solubility, in the kinetics of microbial iron reduction. We used the facultative anaerobic gram-positive bacterium Shewanella putrefaciens as model iron reducing bacterium, with several ferrihydrite, hematite, goethite or lepidocrocite as electron acceptor, and lactate as electron donor. Maximum microbial Fe(III) reduction rates and solubility of Fe(III) phases were found to positively correlated in a Linear Free Energy Relationship suggesting a rate limitation by the electron transfer between iron reductases and a Fe(III) center, or by the subsequent desorption of Fe2+ from the iron oxide mineral surface.

Bonneville, Steeve

2014-05-01

327

Degradation of conazole fungicides in water by electrochemical oxidation.  

PubMed

The electrochemical oxidation (EO) treatment in water of three conazole fungicides, myclobutanil, triadimefon and propiconazole, has been carried out at constant current using a BDD/SS system. First, solutions of each fungicide were electrolyzed to assess the effect of the experimental parameters such as current, pH and fungicide concentration on the decay of each compound and total organic carbon abatement. Then a careful analysis of the degradation by-products was made by high performance liquid chromatography, ion chromatography and gas chromatography coupled with mass spectrometry in order to provide a detailed discussion on the original reaction pathways. Thus, during the degradation of conazole fungicides by the electrochemical oxidation process, aromatic intermediates, aliphatic carboxylic acids and Cl(-) were detected prior to their complete mineralization to CO2 while NO3(-) anions remained in the treated solution. This is an essential preliminary step towards the applicability of the EO processes for the treatment of wastewater containing conazole fungicides. PMID:24140400

Urzúa, J; González-Vargas, C; Sepúlveda, F; Ureta-Zañartu, M S; Salazar, R

2013-11-01

328

Net charge oscillation and proton release during water oxidation in photosynthesis. An electrochromic band shift study at pH 5.5–7.0  

Microsoft Academic Search

In the S-state cycle of water oxidation, a local electric field was measured in states S2 and S3. This was indicated by the strongly retarded reduction kinetics of the oxidized primary electron donor of PS II in these states (Brettel, K., Schlodder, E. and Witt, H.T. (1984) Biochim. Biophys. Acta 766, 403–415) as well as by electrochromic band shifts in

H. Kretschmann; E. Schlodder; H. T. Witt

1996-01-01

329

Seasonal and diurnal cycles of liquid water in snow  

NASA Astrophysics Data System (ADS)

The combination of upward-looking ground-penetrating radar (upGPR), automatic weather station (AWS) and lysimeter allows for continuous monitoring of bulk volumetric liquid water content (?w) within the snowpack and direct comparison with measurements of the corresponding outflow. The AWS data can be utilized to calculate energy fluxes between atmosphere and snowpack at the location of the station. While combining all data sets, we were able to quantify diurnal and seasonal changes in residual water content and relate modeled energy fluxes to water outflow. Since upGPR is a non-destructive monitoring technique, it is possible to continuously observe the snowpack and results are not biased through spatial variability of pit locations. Data analysis conducted for three consecutive years at the flat test site Weissfluhjoch, Davos, Switzerland showed that diurnal ?w variations never exceeded 2%. Without regard to days with new snow accumulation or refreezing, the diurnal patterns in ?w were very similar, with always daily peaks in the late afternoon (at about 17:00h) at the site. Although ?w values varied during a day up to 2%, the gradients during the season were very small. In 2012, for the whole melting period (>100 days), increases in ?w from day to day were 0.4% liquid water content on average. After the snowpack has become isothermal, positive energy fluxes result in outflow and increase the residual water content (?r). Our data showed that as long as potential melt - calculated for the determined energy fluxes - was exceeding measured outflow, ?r values were increasing but only until reaching a certain threshold. For all three years, the thresholds were similar at about ?r=4-5%. Only shortly before full ablation, these thresholds were surpassed. In two sloped test sites (about 22 degree slope angle) in Boise, Idaho, USA and above Davos, we installed upGPR systems as well. AWS data and energy-flux calculations for both slopes were extrapolated for the respective aspect and slope angle. Our data showed that snow stratigraphy highly influences ?r in slopes. As long as e.g. crusts ponded the vertical water flow, residual ?w of the whole snowpack was fairly low (

Heilig, Achim; Mitterer, Christoph; Schmid, Lino; Marshall, Hans-Peter; Schweizer, Jürg; Okorn, Robert; Eisen, Olaf

2014-05-01

330

Comparative simulation and investigation of ammonia-water: absorption cycles for heat pump applications  

Microsoft Academic Search

Several recent programs in absorption research have focused on technology for domestic heating and cooling utilizing natural gas. In residential and small commercial size applications, ammonia-water cycles offer the possibility of a gas-fired heat pump for both winter heating and summer cooling, at better year-round COPS than currently available by various alternatives. Several cycles have been considered for this purpose,

M Engler; G Grossman; H.-M Hellmann

1997-01-01

331

Nitrogen cycling in different types of sediments from Danish waters  

Microsoft Academic Search

Variations in sediment N:C ratios were correlated with water depth and season. ¹⁴NHâ\\/sup +\\/ was used to measure the rates of NHâ\\/sup +\\/ production (d) and incorporation into bacterial cells (i) in sediments from different stations, at different seasons. The validity of the rates d and i was indicated by the predicted correlation of d:i ratios with N:C ratios of

T. H. Blackburn; K. Henridsen

1983-01-01

332

Comparative assessment of nuclear fuel cycles. Light-water reactor once-through, classical fast breeder reactor, and symbiotic fast breeder reactor cycles  

SciTech Connect

The object of the Alternative Nuclear Fuel Cycle Study is to perform comparative assessments of nuclear power systems. There are two important features of this study. First, this evaluation attempts to encompass the complete, integrated fuel cycle from mining of uranium ore to disposal of waste rather than isolated components. Second, it compares several aspects of each cycle - energy use, economics, technological status, proliferation, public safety, and commercial potential - instead of concentrating on one or two assessment areas. This report presents assessment results for three fuel cycles. These are the light-water reactor once-through cycle, the fast breeder reactor on the classical plutonium cycle, and the fast breeder reactor on a symbiotic cycle using plutonium and /sup 233/U as fissile fuels. The report also contains a description of the methodology used in this assessment. Subsequent reports will present results for additional fuel cycles.

Hardie, R.W.; Barrett, R.J.; Freiwald, J.G.

1980-06-01

333

Evolution of the global water cycle on Mars: The geological evidence  

NASA Technical Reports Server (NTRS)

The geological evidence for active water cycling early in the history of Mars (Noachian geological system or heavy bombardment) consists almost exclusively of fluvial valley networks in the heavily cratered uplands of the planet. It is commonly assumed that these landforms required explanation by atmospheric processes operating above the freezing point of water and at high pressure to allow rainfall and liquid surface runoff. However, it has also been documented that nearly all valley networks probably formed by subsurface outflow and sapping erosion involving groundwater outflow prior to surface-water flow. The prolonged ground-water flow also requires extensive water cycling to maintain hydraulic gradients, but is this done via rainfall recharge, as in terrestrial environments?

Baker, V. R.; Gulick, V. C.

1993-01-01

334

The role of water ice clouds in the Martian hydrologic cycle  

NASA Technical Reports Server (NTRS)

A one-dimensional model for the seasonal cycle of water on Mars has been used to investigate the direction of the net annual transport of water on the planet and to study the possible role of water ice clouds, which are included as an independent phase in addition to ground ice and water vapor, in the cycle. The calculated seasonal and spatial patterns of occurrence of water ice clouds are qualitatively similar to the observed polar hoods, suggesting that these polar clouds are, in fact, an important component of water cycle. A residual dry ice in the south acts as a cold trap which, in the absence of sources other than the caps, will ultimately attract the water ice from the north cap; however, in the presence of a source of water in northern midlatitudes during spring, it is possible that the observed distribution of vapor and ice can be in a steady state even if a residual CO2 cap is a permanent feature of the system.

James, Philip B.

1990-01-01

335

Coupling Mars' Dust and Water Cycles: Effects on Dust Lifting Vigor, Spatial Extent and Seasonality  

NASA Technical Reports Server (NTRS)

The dust cycle is an important component of Mars' current climate system. Airborne dust affects the radiative balance of the atmosphere, thus greatly influencing the thermal and dynamical state of the atmosphere. Dust raising events on Mars occur at spatial scales ranging from meters to planet-wide. Although the occurrence and season of large regional and global dust storms are highly variable from one year to the next, there are many features of the dust cycle that occur year after year. Generally, a low-level dust haze is maintained during northern spring and summer, while elevated levels of atmospheric dust occur during northern autumn and winter. During years without global-scale dust storms, two peaks in total dust loading were observed by MGS/TES: one peak occurred before northern winter solstice at Ls 200-240, and one peak occurred after northern winter solstice at L(sub s) 305-340. These maxima in dust loading are thought to be associated with transient eddy activity in the northern hemisphere, which has been observed to maximize pre- and post-solstice. Interactive dust cycle studies with Mars General Circulation Models (MGCMs) have included the lifting, transport, and sedimentation of radiatively active dust. Although the predicted global dust loadings from these simulations capture some aspects of the observed dust cycle, there are marked differences between the simulated and observed dust cycles. Most notably, the maximum dust loading is robustly predicted by models to occur near northern winter solstice and is due to dust lifting associated with down slope flows on the flanks of the Hellas basin. Thus far, models have had difficulty simulating the observed pre- and post- solstice peaks in dust loading. Interactive dust cycle studies typically have not included the formation of water ice clouds or their radiative effects. Water ice clouds can influence the dust cycle by scavenging dust from atmosphere and by interacting with solar and infrared radiation, thereby modifying the thermal structure of the atmosphere and its circulation. Results presented in other papers at this workshop show that including the radiative effects of water ice clouds greatly influence the water cycle and the vigor of weather systems in both the northern and southern hemispheres. Our goal is to investigate the effects of fully coupling the dust and water cycles on the dust cycle. We show that including water ice clouds and their radiative effects greatly affect the magnitude, spatial extent and seasonality of dust lifting and the season of maximum atmospheric dust loading.

Kahre, M. A.; Hollingsworth, J. L.; Haberle, R. M.; Montmessin, F.

2012-01-01

336

Ru complexes that can catalytically oxidize water to molecular dioxygen.  

PubMed

The main objective of this review is to give a general overview of the structure, electrochemistry (when available), and catalytic performance of the Ru complexes, which are capable of oxidizing water to molecular dioxygen, and to highlight their more relevant features. The description of the Ru catalysts is mainly divided into complexes that contain a Ru-O-Ru bridging group and those that do not. Finally a few conclusions are drawn from the global description of all of the catalysts presented here, and some guidelines for future catalyst design are given. PMID:18330973

Romero, Isabel; Rodríguez, Montserrat; Sens, Cristina; Mola, Joaquim; Rao Kollipara, Mohan; Francàs, Laia; Mas-Marza, Elena; Escriche, Lluís; Llobet, Antoni

2008-03-17

337

Life cycle water consumption and wastewater generation impacts of a Marcellus shale gas well.  

PubMed

This study estimates the life cycle water consumption and wastewater generation impacts of a Marcellus shale gas well from its construction to end of life. Direct water consumption at the well site was assessed by analysis of data from approximately 500 individual well completion reports collected in 2010 by the Pennsylvania Department of Conservation and Natural Resources. Indirect water consumption for supply chain production at each life cycle stage of the well was estimated using the economic input-output life cycle assessment (EIO-LCA) method. Life cycle direct and indirect water quality pollution impacts were assessed and compared using the tool for the reduction and assessment of chemical and other environmental impacts (TRACI). Wastewater treatment cost was proposed as an additional indicator for water quality pollution impacts from shale gas well wastewater. Four water management scenarios for Marcellus shale well wastewater were assessed: current conditions in Pennsylvania; complete discharge; direct reuse and desalination; and complete desalination. The results show that under the current conditions, an average Marcellus shale gas well consumes 20,000 m(3) (with a range from 6700 to 33,000 m(3)) of freshwater per well over its life cycle excluding final gas utilization, with 65% direct water consumption at the well site and 35% indirect water consumption across the supply chain production. If all flowback and produced water is released into the environment without treatment, direct wastewater from a Marcellus shale gas well is estimated to have 300-3000 kg N-eq eutrophication potential, 900-23,000 kg 2,4D-eq freshwater ecotoxicity potential, 0-370 kg benzene-eq carcinogenic potential, and 2800-71,000 MT toluene-eq noncarcinogenic potential. The potential toxicity of the chemicals in the wastewater from the well site exceeds those associated with supply chain production, except for carcinogenic effects. If all the Marcellus shale well wastewater is treated to surface discharge standards by desalination, $59,000-270,000 per well would be required. The life cycle study results indicate that when gas end use is not considered hydraulic fracturing is the largest contributor to the life cycle water impacts of a Marcellus shale gas well. PMID:24380628

Jiang, Mohan; Hendrickson, Chris T; VanBriesen, Jeanne M

2014-02-01

338

A global model of the coupled sulfur/oxidant chemistry in the troposphere: The sulfur cycle  

NASA Astrophysics Data System (ADS)

A sulfur cycle chemistry scheme with dimethyl sulfide (DMS), SO2, sulfate, H2S, and methanesulfonic acid (MSA) is included in the OsloCTM2 model, and concentrations of sulfur are calculated interactively with the oxidant chemistry. This allows more consistent estimates of aqueous phase oxidation of SO2 to sulfate by O3, H2O2, and HO2NO2. The year 1996 is chosen as the standard, and a model run with 1996 meteorology and emissions is compared with 1996 observations. The results agree well with observations overall, although the model tends to overestimate SO2 and underestimate sulfate in Northern Hemisphere winter owing to an oxidation limitation. A global budget for 1996 quantifying the various processes is investigated. Our model results give a global lifetime (global burden) of 1 day (0.25 Tg(S)) and 3.8 days (0.5 3 Tg(S)) for SO2 and sulfate. Differences between the Southern Hemisphere, characterized by natural emissions and by loss of SO2 by O3 and H2O2 oxidation, and the Northern Hemisphere, characterized by anthropogenic emissions and by large loss by dry deposition, are revealed. Significant changes in sulfur emissions have occurred over the last decades with decrease in the Unites States and Europe and increase in Southeast Asia. U.S., European, and Chinese SO2 emissions have changed by -17.6%, -47.5%, and +93%, respectively. To study the impact of emission changes on the atmospheric composition, we have calculated distributions using the Global Emissions Inventory Activity (GEIA) 1985 inventory. The changes in sulfur emissions have significant changes on the sulfur concentrations and also some effect upon the oxidants. Increased emissions of NOx and hydrocarbons in China enhance O3, but increased sulfur inhibit the increase. The SO2 oxidation by OH, which can lead to formation of new sulfate particles, is given special attention. The model run using GEIA 1985 anthropogenic emission inventory is compared with other model studies.

Berglen, Tore F.; Berntsen, Terje K.; Isaksen, Ivar S. A.; Sundet, Jostein K.

2004-10-01

339

Oxidation resistant high temperature thermal cycling resistant coatings on silicon-based substrates and process for the production thereof  

DOEpatents

An oxidation resistant, high temperature thermal cycling resistant coated ceramic article for ceramic heat engine applications is disclosed. The substrate is a silicon-based material, i.e. a silicon nitride- or silicon carbide-based monolithic or composite material. The coating is a graded coating of at least two layers: an intermediate AlN or Al[sub x]N[sub y]O[sub z] layer and an aluminum oxide or zirconium oxide outer layer. The composition of the coating changes gradually from that of the substrate to that of the AlN or Al[sub x]N[sub y]O[sub z] layer and further to the composition of the aluminum oxide or zirconium oxide outer layer. Other layers may be deposited over the aluminum oxide layer. A CVD process for depositing the graded coating on the substrate is also disclosed.

Sarin, V.K.

1990-08-21

340

Oxidation resistant high temperature thermal cycling resistant coatings on silicon-based substrates and process for the production thereof  

DOEpatents

An oxidation resistant, high temperature thermal cycling resistant coated ceramic article for ceramic heat engine applications. The substrate is a silicon-based material, i.e. a silicon nitride- or silicon carbide-based monolithic or composite material. The coating is a graded coating of at least two layers: an intermediate AlN or Al.sub.x N.sub.y O.sub.z layer and an aluminum oxide or zirconium oxide outer layer. The composition of the coating changes gradually from that of the substrate to that of the AlN or Al.sub.x N.sub.y O.sub.z layer and further to the composition of the aluminum oxide or zirconium oxide outer layer. Other layers may be deposited over the aluminum oxide layer. A CVD process for depositing the graded coating on the substrate is also disclosed.

Sarin, Vinod K. (Lexington, MA)

1990-01-01

341

Long-Term Thermal Cycling of Phlogopite Mica-Based Compressive Seals for Solid Oxide Fuel Cells  

SciTech Connect

Reliable sealants are one of the toughest challenges in advancing solid oxide fuel cell technologies. One of the most stringent requirements for sealants is the thermal cycle stability. The sealants have to survive multiple thermal cycles during operation in stationary and transportation applications. Recently, researchers at the Pacific Northwest National Laboratory have developed a hybrid mica-based compressive seal with which leak rates were reduced...

Chou, Y S.; Stevenson, Jeffry W.

2005-03-01

342

Water and the Oxidation State of Subduction Zone Magmas  

SciTech Connect

Mantle oxygen fugacity exerts a primary control on mass exchange between Earth's surface and interior at subduction zones, but the major factors controlling mantle oxygen fugacity (such as volatiles and phase assemblages) and how tectonic cycles drive its secular evolution are still debated. We present integrated measurements of redox-sensitive ratios of oxidized iron to total iron (Fe{sup 3+}/{Sigma}Fe), determined with Fe K-edge micro-x-ray absorption near-edge structure spectroscopy, and pre-eruptive magmatic H{sub 2}O contents of a global sampling of primitive undegassed basaltic glasses and melt inclusions covering a range of plate tectonic settings. Magmatic Fe{sup 3+}/{Sigma}Fe ratios increase toward subduction zones (at ridges, 0.13 to 0.17; at back arcs, 0.15 to 0.19; and at arcs, 0.18 to 0.32) and correlate linearly with H{sub 2}O content and element tracers of slab-derived fluids. These observations indicate a direct link between mass transfer from the subducted plate and oxidation of the mantle wedge.

Kelley, K.; Cottrell, E

2009-01-01

343

A bipolar perspective on MIS2 climate and water cycle  

NASA Astrophysics Data System (ADS)

This presentation will be dedicated to the comparison of sets of information on polar climate extracted from an array of deep ice cores from Greenland (GISP2, GRIP, NGRIP, NEEM) and from East Antarctica (EDML, EDC, Vostok and TALDICE). This comparison will benefit from the synchronised AICC2012/GICC05 chronologies which have recently been established (Bazin et al, Clim. Past, submitted). It will rely on water stable isotope records, estimates of past accumulation rates derived from ice core chronologies, and estimates of past Greenland Summit temperature change derived from firn gas fractionation. The sequences of events between Greenland and Antarctic temperature, d18O, deuterium excess and accumulation will be investigated and discussed. The inter-ice core spread will be assessed throughout the time period from 30 to 11 ka, in order to extract the common climatic signals and the local deposition noise. The timing of the coldest period in polar temperature, water stable isotopes, and deuterium excess will be compared to the timing of the driest period as indicated by estimates of past accumulation rates. The bipolar sequence of events including changes in moisture sources and changes in polar climate will be identified and discussed in relationship with information on past changes in sea level, marine circulation and atmospheric composition.

Masson-Delmotte, Valérie; Bazin, Lucie; Guillevic, Myriam; Landais, Amaelle; Jouzel, Jean; Stenni, Barbara; Oerter, Hans; Vinther, Bo; Rasmussen, Sune; Gkinis, Vasileos; Popp, Trevor

2013-04-01

344

Transpiring wall supercritical water oxidation test reactor design report  

SciTech Connect

Sandia National Laboratories is working with GenCorp, Aerojet and Foster Wheeler Development Corporation to develop a transpiring wall supercritical water oxidation reactor. The transpiring wall reactor promises to mitigate problems of salt deposition and corrosion by forming a protective boundary layer of pure supercritical water. A laboratory scale test reactor has been assembled to demonstrate the concept. A 1/4 scale transpiring wall reactor was designed and fabricated by Aerojet using their platelet technology. Sandia`s Engineering Evaluation Reactor serves as a test bed to supply, pressurize and heat the waste; collect, measure and analyze the effluent; and control operation of the system. This report describes the design, test capabilities, and operation of this versatile and unique test system with the transpiring wall reactor.

Haroldsen, B.L.; Ariizumi, D.Y.; Mills, B.E.; Brown, B.G. [Sandia National Labs., Livermore, CA (United States). Engineering for Transportation and Environment Dept.; Rousar, D.C. [GenCorp Aerojet, Sacramento, CA (United States)

1996-02-01

345

Life cycle-based water assessment of a hand dishwashing product: opportunities and limitations.  

PubMed

It is only recently that life cycle-based indicators have been used to evaluate products from a water use impact perspective. The applicability of some of these methods has been primarily demonstrated on agricultural materials or products, because irrigation requirements in food production can be water-intensive. In view of an increasing interest on life cycle-based water indicators from different products, we ran a study on a hand dishwashing product. A number of water assessment methods were applied with the purpose of identifying both product improvement opportunities, as well as understanding the potential for underlying database and methodological improvements. The study covered the entire life cycle of the product and focused on environmental issues related to water use, looking in-depth at inventory, midpoint, and endpoint methods. "Traditional" water emission driven methods, such as freshwater eutrophication, were excluded from the analysis. The use of a single formula with the same global supply chain, manufactured in 1 location was evaluated in 2 countries with different water scarcity conditions. The study shows differences ranging up to 4 orders in magnitude for indicators with similar units associated with different water use types (inventory methods) and different cause-effect chain models (midpoint and endpoint impact categories). No uncertainty information was available on the impact assessment methods, whereas uncertainty from stochastic variability was not available at the time of study. For the majority of the indicators studied, the contribution from the consumer use stage is the most important (>90%), driven by both direct water use (dishwashing process) as well as indirect water use (electricity generation to heat the water). Creating consumer awareness on how the product is used, particularly in water-scarce areas, is the largest improvement opportunity for a hand dishwashing product. However, spatial differentiation in the inventory and impact assessment model may lead to very different results for the product used under exactly the same consumer use conditions, making the communication of results a real challenge. From a practitioner's perspective, the data collection step in relation to the goal and scope of the study sets high requirements for both foreground and background data. In particular, databases covering a broad spectrum of inventory data with spatially differentiated water use information are lacking. For some impact methods, it is unknown as to whether or not characterization factors should be spatially differentiated, which creates uncertainty in their interpretation and applicability. Finally, broad application of life cycle-based water assessment will require further development of commercial life cycle assessment software. PMID:23907994

Van Hoof, Gert; Buyle, Bea; Kounina, Anna; Humbert, Sebastien

2013-10-01

346

Long-term Thermal Cycling of Phlogopite Mica-based Compressive Seals for Solid Oxide Fuel Cells  

SciTech Connect

Planar solid oxide fuel cells (SOFC) require sealants to function properly in harsh environments at elevated temperatures. The SOFC stacks are expected to experience multiple thermal cycles (perhaps thousands of cycles for some applications) during their life time service in stationary or transportation applications. As a result, thermal cycle stability is considered a top priority for SOFC sealant development. In previous work, we have developed a hybrid mica-based compressive seal with very low leak rates of 2-4 x 10-2 to 10-3 sccm/cm at 800 C, and showed stable leak rates over limited thermal cycles In this paper we present results of long-term thermal cycle testing (> 1000 thermal cycles) of Phlogopite mica-based compressive seals. Open circuit voltage (OCV) was measured on a 2? x 2? 8-YSZ plate with the hybrid Phlogopite mica seals during thermal cycling in a dual environment (2.75% H2/Ar vs. air). During two long-term cycling tests, the measured OCVs were found to be consistent with the calculated Nernst voltages. The hybrid mica seal showed excellent thermal cycle stability over 1000 thermal cycles and can be considered a strong candidate for SOFC applications.

Chou, Y S.; Stevenson, Jeffry W.

2005-02-02

347

Gold or silver deposited on layered manganese oxide: a functional model for the water-oxidizing complex in photosystem II.  

PubMed

In this report, gold or silver deposited on layered manganese oxide has been synthesized by a simple method and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectrometry, atomic absorption spectroscopy, and energy-dispersive X-ray mapping. The gold deposited on layered manganese oxide showed efficient catalytic activity toward water oxidation in the presence of cerium(IV) ammonium nitrate. The properties associated with this compound suggest it is a functional model for the water-oxidizing complex in photosystem II. PMID:23896796

Najafpour, Mohammad Mahdi; Rahimi, Fahimeh; Sedigh, Davood Jafarian; Carpentier, Robert; Eaton-Rye, Julian J; Shen, Jian-Ren; Allakhverdiev, Suleyman I

2013-11-01

348

Optimization of the oxidant supply system for combined cycle MHD power plants  

NASA Technical Reports Server (NTRS)

An in-depth study was conducted to determine what, if any, improvements could be made on the oxidant supply system for combined cycle MHD power plants which could be reflected in higher thermal efficiency and a reduction in the cost of electricity, COE. A systematic analysis of air separation process varitions which showed that the specific energy consumption could be minimized when the product stream oxygen concentration is about 70 mole percent was conducted. The use of advanced air compressors, having variable speed and guide vane position control, results in additional power savings. The study also led to the conceptual design of a new air separation process, sized for a 500 MW sub e MHD plant, referred to a internal compression is discussed. In addition to its lower overall energy consumption, potential capital cost savings were identified for air separation plants using this process when constructed in a single large air separation train rather than multiple parallel trains, typical of conventional practice.

Juhasz, A. J.

1982-01-01

349

Oxidation of metal sulfites by iodine for use in thermochemical hydrogen cycles  

NASA Astrophysics Data System (ADS)

It is noted that thermochemical hydrogen cycles involving metal sulfates offer an alternative to sulfuric acid which is corrosive and has high energy requirements for drying prior to its thermal decomposition. The formation of such metal sulfates in conjunction with a low temperature hydrogen formation step is discussed. The following reaction was studied: MgSO3(c) + MgO(c) + I2(g) yields MgSO4(c) + MgI2(c). Although magnesium sulfite appears promising for this oxidation, a search was conducted for alternative metal sulfites which fit the following criteria for use: (1) sulfate must decompose in the temperature range available ( 1400 K); (2) iodide must hydrolyze easily; and (3) salts must not be rare, toxic, or expensive. Lanthanum and titanium fit these criteria.

Mason, C. F. V.; Bowman, M. G.

1981-09-01

350

Wet peroxide oxidation and catalytic wet oxidation of stripped sour water produced during oil shale refining.  

PubMed

Catalytic wet oxidation (CWO) and wet peroxide oxidation (WPO) of stripped sour water (SSW) from an oil shale refinery was investigated. Greater than 70% total organic carbon (TOC) removal from SSW was achieved using Cu(NO(3))(2) catalysed WO under the following conditions using a glass lined reaction vessel: 200 degrees C, pO(2)=0.5MPa, 3h, [Cu(NO(3))(2)]=67mmol/L. Significant TOC removal ( approximately 31%) also occurred in the system without added oxygen. It is proposed that this is predominantly due to copper catalysed oxidative decarboxylation of organics in SSW based on observed changes in copper oxidation state. Greater than 80% TOC removal was achieved using WPO under the following conditions: 150 degrees C, t=1.5h, [H(2)O(2)]=64g/L. Significantly more TOC could be removed from SSW by adding H(2)O(2) in small doses as opposed to adding the same total amount in one single dose. It was concluded that WPO was a far more effective process for removing odorous compounds from SSW. PMID:17537573

Prasad, Jaidev; Tardio, James; Jani, Harit; Bhargava, Suresh K; Akolekar, Deepak B; Grocott, Stephen C

2007-07-31

351

Contributions of the Peroxisome and ?-Oxidation Cycle to Biotin Synthesis in Fungi*  

PubMed Central

The first step in the synthesis of the bicyclic rings of d-biotin is mediated by 8-amino-7-oxononanoate (AON) synthase, which catalyzes the decarboxylative condensation of l-alanine and pimelate thioester. We found that the Aspergillus nidulans AON synthase, encoded by the bioF gene, is a peroxisomal enzyme with a type 1 peroxisomal targeting sequence (PTS1). Localization of AON to the peroxisome was essential for biotin synthesis because expression of a cytosolic AON variant or deletion of pexE, encoding the PTS1 receptor, rendered A. nidulans a biotin auxotroph. AON synthases with PTS1 are found throughout the fungal kingdom, in ascomycetes, basidiomycetes, and members of basal fungal lineages but not in representatives of the Saccharomyces species complex, including Saccharomyces cerevisiae. A. nidulans mutants defective in the peroxisomal acyl-CoA oxidase AoxA or the multifunctional protein FoxA showed a strong decrease in colonial growth rate in biotin-deficient medium, whereas partial growth recovery occurred with pimelic acid supplementation. These results indicate that pimeloyl-CoA is the in vivo substrate of AON synthase and that it is generated in the peroxisome via the ?-oxidation cycle in A. nidulans and probably in a broad range of fungi. However, the ?-oxidation cycle is not essential for biotin synthesis in S. cerevisiae or Escherichia coli. These results suggest that alternative pathways for synthesis of the pimelate intermediate exist in bacteria and eukaryotes and that Saccharomyces species use a pathway different from that used by the majority of fungi. PMID:21998305

Magliano, Pasqualina; Flipphi, Michel; Arpat, Bulak A.; Delessert, Syndie; Poirier, Yves

2011-01-01

352

The water cycle in a bottle: simulation of a hydrogeological basin  

NASA Astrophysics Data System (ADS)

THE WATER CYCLE IN A BOTTLE: simulation of a hydrogeological basin Author: Mª Roser Nebot (Institut Manuel Blancafort, La Garriga, Barcelona, Spain) Co-author: Sílvia Leiva Hevia (Institut Llicà d'Amunt, Lliça d'Amunt, Barcelona, Spain) The activity can be implemented in a great range of ages, because it has many different levels of depth. It is based on the construction of an analogical model of a hydrogeological basin using a 5L or 8L empty bottle. There are also other hands-on experiences that can be done in relation to the central one, such as creating a fountain, making a cloud, fog, a breeze… The use of a model that the students have to build and interact with enhances the possibility of cooperative and dialogic learning. The set of activities begins with an introduction to see what the students know about the water cycle and to focus on what they are going to work on. It also makes them think about underground water, which is frequently forgotten when drawing and studying the water cycle. Then, the building of the water cycle simulation from an empty bottle is presented, see http://www.xtec.cat/cirel/pla_le/nottingham/roser_nebot/index.htm (Unit 5). You will also find other activities related to the water cycle at the site. The students build the model, water the soil, and observe infiltration and the formation of a lake. Using a syringe they overexploit the well and dry the lake. By making the students label the underground water level and observe how water percolates through the holes in the aquifer we are making them aware that underground water doesn't circulate in rivers inside underground tunnels, but through the interconnected holes and crevices. Inside the bottle there is a little plant to observe evapotranspiration but, because it is very difficult to see the water droplets in the small plant that is inside the set-up, it is advisable to do a parallel experiment using bigger plants in a pot, covering them with a plastic bag tied around the stem, with the soil exposed to air, leaving some of them in the shade and some in the sun. The origin of condensation is thoroughly discussed so that the students understand that evapotranspiration comes from the addition of transpiration (plants) to evaporation. The students also add colouring to simulate contamination and salt to simulate marine intrusion. These activities, together with the overexploitation, help to understand how humans affect nature and how the effects are not the same in different parts of the world. To finish, there are different exercises to review, summarize and complement all that has been learnt through the lesson. To acknowledge the fact that many times underground water is forgotten, as homework they have to surf the net to see the many water cycle drawings and animations that don't show the water in the aquifers, and sometimes when the water is seen, the rocks that contain it are not depicted. They are also encouraged to realize that in water cycle representations, it never rains over the sea and that to adjust to what really happens and that there should also be rain over the oceans and seas. To finish, the idea that within the water cycle model there are many interrelated processes is discussed

Nebot Castelló, M. R.; Leiva Hevia, S.

2012-04-01

353

Electrochemical hydrogen production from thermochemical cycles using a proton exchange membrane electrolyzer  

Microsoft Academic Search

The electrochemical step in two thermochemical cycles for hydrogen production is reported. One cycle involves the electrochemical oxidation of sulfur dioxide to sulfuric acid (both water and SO2 are reactants). The other cycle involves the oxidation of anhydrous hydrogen bromide to bromine (anhydrous HBr is the only reactant). In both cycles, protons are reduced at the cathode to produce hydrogen.

PremKumar Sivasubramanian; Ramaraja P. Ramasamy; Francisco J. Freire; Charles E. Holland; John W. Weidner

2007-01-01

354

A novel marine nitrite-oxidizing Nitrospira species from Dutch coastal North Sea water  

PubMed Central

Marine microorganisms are important for the global nitrogen cycle, but marine nitrifiers, especially aerobic nitrite oxidizers, remain largely unexplored. To increase the number of cultured representatives of marine nitrite-oxidizing bacteria (NOB), a bioreactor cultivation approach was adopted to first enrich nitrifiers and ultimately nitrite oxidizers from Dutch coastal North Sea water. With solely ammonia as the substrate an active nitrifying community consisting of novel marine Nitrosomonas aerobic ammonia oxidizers (ammonia-oxidizing bacteria) and Nitrospina and Nitrospira NOB was obtained which converted a maximum of 2 mmol of ammonia per liter per day. Switching the feed of the culture to nitrite as a sole substrate resulted in a Nitrospira NOB dominated community (approximately 80% of the total microbial community based on fluorescence in situ hybridization and metagenomic data) converting a maximum of 3 mmol of nitrite per liter per day. Phylogenetic analyses based on the 16S rRNA gene indicated that the Nitrospira enriched from the North Sea is a novel Nitrospira species with Nitrospira marina as the next taxonomically described relative (94% 16S rRNA sequence identity). Transmission electron microscopy analysis revealed a cell plan typical for Nitrospira species. The cytoplasm contained electron light particles that might represent glycogen storage. A large periplasmic space was present which was filled with electron dense particles. Nitrospira-targeted polymerase chain reaction analyses demonstrated the presence of the enriched Nitrospira species in a time series of North Sea genomic DNA samples. The availability of this new Nitrospira species enrichment culture facilitates further in-depth studies such as determination of physiological constraints, and comparison to other NOB species. PMID:23515432

Haaijer, Suzanne C. M.; Ji, Ke; van Niftrik, Laura; Hoischen, Alexander; Speth, Daan; Jetten, Mike S. M.; Damsté, Jaap S. Sinninghe; Op den Camp, Huub J. M.

2013-01-01

355

cGMP-independent nitric oxide signaling and regulation of the cell cycle  

PubMed Central

Background Regulatory functions of nitric oxide (NO•) that bypass the second messenger cGMP are incompletely understood. Here, cGMP-independent effects of NO• on gene expression were globally examined in U937 cells, a human monoblastoid line that constitutively lacks soluble guanylate cyclase. Differentiated U937 cells (>80% in G0/G1) were exposed to S-nitrosoglutathione, a NO• donor, or glutathione alone (control) for 6 h without or with dibutyryl-cAMP (Bt2cAMP), and then harvested to extract total RNA for microarray analysis. Bt2cAMP was used to block signaling attributable to NO•-induced decreases in cAMP. Results NO• regulated 110 transcripts that annotated disproportionately to the cell cycle and cell proliferation (47/110, 43%) and more frequently than expected contained AU-rich, post-transcriptional regulatory elements (ARE). Bt2cAMP regulated 106 genes; cell cycle gene enrichment did not reach significance. Like NO•, Bt2cAMP was associated with ARE-containing transcripts. A comparison of NO• and Bt2cAMP effects showed that NO• regulation of cell cycle genes was independent of its ability to interfere with cAMP signaling. Cell cycle genes induced by NO• annotated to G1/S (7/8) and included E2F1 and p21/Waf1/Cip1; 6 of these 7 were E2F target genes involved in G1/S transition. Repressed genes were G2/M associated (24/27); 8 of 27 were known targets of p21. E2F1 mRNA and protein were increased by NO•, as was E2F1 binding to E2F promoter elements. NO• activated p38 MAPK, stabilizing p21 mRNA (an ARE-containing transcript) and increasing p21 protein; this increased protein binding to CDE/CHR promoter sites of p21 target genes, repressing key G2/M phase genes, and increasing the proportion of cells in G2/M. Conclusion NO• coordinates a highly integrated program of cell cycle arrest that regulates a large number of genes, but does not require signaling through cGMP. In humans, antiproliferative effects of NO• may rely substantially on cGMP-independent mechanisms. Stress kinase signaling and alterations in mRNA stability appear to be major pathways by which NO• regulates the transcriptome. PMID:16269079

Cui, Xiaolin; Zhang, Jianhua; Ma, Penglin; Myers, Daniela E; Goldberg, Ilana G; Sittler, Kelly J; Barb, Jennifer J; Munson, Peter J; Cintron, Ana del Pilar; McCoy, J Philip; Wang, Shuibang; Danner, Robert L

2005-01-01

356

Mechanistic Studies of Water Electrolysis and Hydrogen Electro-Oxidation on High Temperature Ceria-Based Solid Oxide  

E-print Network

Mechanistic Studies of Water Electrolysis and Hydrogen Electro- Oxidation on High Temperature Ceria-solid interface exclusively in the electrochemically active region of the SOC. During water electrolysis on ceria+ Ce4+ + OH- + H· ) is rate limiting in both the forward (water electrolysis) and reverse (H2 electro

Li, Weixue

357

Environmental assessment of supercritical water oxidation and other sewage sludge handling options.  

PubMed

Sustainable development relies on the eco-efficient use of all flows in society; more value created out of each resource unit. Supercritical water oxidation (SCWO) can be used for treatment of wet organic waste. The technology has been under development for over 20 years but has not yet been fully commercialized. SCWO allows for complete oxidation of all organics in sewage sludge and almost complete recovery of the inherent energy, essentially without harmful emissions. In this paper, a life-cycle assessment (LCA) of sewage sludge SCWO (Aqua-Critox) is presented and the results are compared with LCA results for other sludge handling options: agricultural use, co-incineration with municipal solid waste, incineration with subsequent phosphorus extraction (Bio-Con) and sludge fractionation with phosphorus recovery (Cambi-KREPRO). For SCWO, beneficial utilization of the heat of reaction is of crucial importance for the outcome. The electricity consumed by pumping and the nitrous oxide produced are other important parameters. The best sludge handling option from an environmental point of view depends on what aspect is considered more important in the impact assessment. Regarding global warming, the energy recovery methods perform better than agricultural use. PMID:16200986

Svanström, Magdalena; Fröling, Morgan; Olofsson, Mattias; Lundin, Margareta

2005-08-01

358

The Effect of Oxidant and Redox Potential on Metal Corrosion in Drinking Water  

EPA Science Inventory

Future drinking water regulatory action may require some water utilities to consider additional and/or alternative oxidation and disinfection practices. There is little known about the effect of oxidant changes on the corrosion of drinking water distribution system materials and ...

359

Warm Water Oxidation Verification - Scoping and Stirred Reactor Tests  

SciTech Connect

Scoping tests to evaluate the effects of agitation and pH adjustment on simulant sludge agglomeration and uranium metal oxidation at {approx}95 C were performed under Test Instructions(a,b) and as per sections 5.1 and 5.2 of this Test Plan prepared by AREVA. (c) The thermal testing occurred during the week of October 4-9, 2010. The results are reported here. For this testing, two uranium-containing simulant sludge types were evaluated: (1) a full uranium-containing K West (KW) container sludge simulant consisting of nine predominant sludge components; (2) a 50:50 uranium-mole basis mixture of uraninite [U(IV)] and metaschoepite [U(VI)]. This scoping study was conducted in support of the Sludge Treatment Project (STP) Phase 2 technology evaluation for the treatment and packaging of K-Basin sludge. The STP is managed by CH2M Hill Plateau Remediation Company (CHPRC) for the U.S. Department of Energy. Warm water ({approx}95 C) oxidation of sludge, followed by immobilization, has been proposed by AREVA and is one of the alternative flowsheets being considered to convert uranium metal to UO{sub 2} and eliminate H{sub 2} generation during final sludge disposition. Preliminary assessments of warm water oxidation have been conducted, and several issues have been identified that can best be evaluated through laboratory testing. The scoping evaluation documented here was specifically focused on the issue of the potential formation of high strength sludge agglomerates at the proposed 95 C process operating temperature. Prior hydrothermal tests conducted at 185 C produced significant physiochemical changes to genuine sludge, including the formation of monolithic concretions/agglomerates that exhibited shear strengths in excess of 100 kPa (Delegard et al. 2007).

Braley, Jenifer C.; Sinkov, Sergey I.; Delegard, Calvin H.; Schmidt, Andrew J.

2011-06-15

360

Oxidation kinetics of micron-sized aluminum powder in high-temperature boiling water  

Microsoft Academic Search

A new efficient method of hydrogen, heat and aluminum oxide\\/hydroxide co-production is proposed. Only micron-sized aluminum powder (without any chemical activation) and usual water are used as initial reagents. For aluminum to be effectively oxidized, water is converted into the high-temperature boiling state that creates high pressure inside oxidation reactor. Paper describes the oxidation kinetics of aluminum micron powder in

M. S. Vlaskin; E. I. Shkolnikov; A. V. Bersh

2011-01-01

361

Transgenic Introduction of a Glycolate Oxidative Cycle into A. thaliana Chloroplasts Leads to Growth Improvement  

PubMed Central

The photorespiratory pathway helps illuminated C3-plants under conditions of limited CO2 availability by effectively exporting reducing equivalents in form of glycolate out of the chloroplast and regenerating glycerate-3-P as substrate for RubisCO. On the other hand, this pathway is considered as probably futile because previously assimilated CO2 is released in mitochondria. Consequently, a lot of effort has been made to reduce this CO2 loss either by reducing fluxes via engineering RubisCO or circumventing mitochondrial CO2 release by the introduction of new enzyme activities. Here we present an approach following the latter route, introducing a complete glycolate catabolic cycle in chloroplasts of Arabidopsis thaliana comprising glycolate oxidase (GO), malate synthase (MS), and catalase (CAT). Results from plants bearing both GO and MS activities have already been reported (Fahnenstich et al., 2008). This previous work showed that the H2O2 produced by GO had strongly negative effects. These effects can be prevented by introducing a plastidial catalase activity, as reported here. Transgenic lines bearing all three transgenic enzyme activities were identified and some with higher CAT activity showed higher dry weight, higher photosynthetic rates, and changes in glycine/serine ratio compared to the wild type. This indicates that the fine-tuning of transgenic enzyme activities in the chloroplasts seems crucial and strongly suggests that the approach is valid and that it is possible to improve the growth of A. thaliana by introducing a synthetic glycolate oxidative cycle into chloroplasts. PMID:22639647

Maier, Alexandra; Fahnenstich, Holger; von Caemmerer, Susanne; Engqvist, Martin K. M.; Weber, Andreas P. M.; Flügge, Ulf-Ingo; Maurino, Veronica G.

2012-01-01

362

Anoxic nitric oxide cycling in plants: participating reactions and possible mechanisms.  

PubMed

At sufficiently low oxygen concentrations, hemeproteins are deoxygenated and become capable of reducing nitrite to nitric oxide (NO), in a reversal of the reaction in which NO is converted to nitrate or nitrite by oxygenated hemeproteins. The maximum rates of NO production depend on the oxygen avidity. The hemeproteins with the highest avidity, such as hexacoordinate hemoglobins, retain oxygen even under anoxic conditions resulting in their being extremely effective NO scavengers but essentially incapable of producing NO. Deoxyhemeprotein-related NO production can be observed in mitochondria (at the levels of cytochrome c oxidase, cytochrome c, complex III and possibly other sites), in plasma membrane, cytosol, endoplasmic reticulum and peroxisomes. In mitochondria, the use of nitrite as an alternative electron acceptor can contribute to a limited rate of ATP synthesis. Non-heme metal-containing proteins such as nitrate reductase and xanthine oxidase can also be involved in NO production. This will result in a strong anoxic redox flux of nitrogen through the hemoglobin-NO cycle involving nitrate reductase, nitrite: NO reductase, and NO dioxygenase. In normoxic conditions, NO is produced in very low quantities, mainly for signaling purposes and this nitrogen cycling is inoperative. PMID:19929898

Igamberdiev, Abir U; Bykova, Natalia V; Shah, Jay K; Hill, Robert D

2010-04-01

363

Benefits of neutral electrolyzed oxidizing water as a drinking water additive for broiler chickens.  

PubMed

In the wake of discussion about the use of drugs in food-producing farms, it seems to be more and more important to search for alternatives and supportive measures to improve health. In this field trial, the influence of electrolyzed oxidizing (EO) water on water quality, drug consumption, mortality, and performance parameters such as BW and feed conversion rate was investigated on 2 broiler farms. At each farm, 3 rearing periods were included in the study. With EO water as the water additive, the total viable cell count and the number of Escherichia coli in drinking water samples were reduced compared with the respective control group. The frequency of treatment days was represented by the number of used daily doses per population and showed lower values in EO-water-treated groups at both farms. Furthermore, the addition of EO water resulted in a lower mortality rate. In terms of analyzed performance parameters, no significant differences were determined. In this study, the use of EO water improved drinking water quality and seemed to reduce the drug use without showing negative effects on performance parameters and mortality rates. PMID:25037820

Bügener, E; Kump, A Wilms-Schulze; Casteel, M; Klein, G

2014-09-01

364

Global Water Cycle Agreement in the Climate Models Assessed in the IPCC AR4  

NASA Technical Reports Server (NTRS)

This study examines the fidelity of the global water cycle in the climate model simulations assessed in the IPCC Fourth Assessment Report. The results demonstrate good model agreement in quantities that have had a robust global observational basis and that are physically unambiguous. The worst agreement occurs for quantities that have both poor observational constraints and whose model representations can be physically ambiguous. In addition, components involving water vapor (frozen water) typically exhibit the best (worst) agreement, and fluxes typically exhibit better agreement than reservoirs. These results are discussed in relation to the importance of obtaining accurate model representation of the water cycle and its role in climate change. Recommendations are also given for facilitating the needed model improvements.

Waliser, D.; Seo, K. -W.; Schubert, S.; Njoku, E.

2007-01-01

365

Water cycle meets media cycle: Hydrology engagement and social media in New Zealand  

NASA Astrophysics Data System (ADS)

The dispersal of scientific knowledge is an on-going challenge for the research community, particularly for the more applied disciplines such as hydrology. To a large degree this arises because key stakeholders do not readily follow the peer-reviewed scientific literature. Even publicly accessible technical reports may be out of sight from many in both the research and stakeholder communities. The challenge to science communication is further compounded by an increasing pressure to raise the hydrological literacy of the public, as water resource management decisions become increasingly collaborative. In these situations, the diversification of communication channels and more rapid interactions between stakeholders and scientists can be of great value. The use of social media in the communication and advancement of hydrological science in New Zealand is a case in point. Two such initiatives are described here: a hydrology blog and a crowd-sourcing data collection campaign using Facebook. The hydrology blog, Waiology (a variant of "hydrology" with the Greek prefix for water replaced by its Maori equivalent), was set up with two main goals in mind: to foster greater understanding and appreciation of hydrology among the New Zealand public, and to more rapidly share new hydrological knowledge within the New Zealand hydrological community. In part, it has also been an experiment to test whether this mode of engagement is worthwhile. Measuring the success of the initiative has proven difficult, but has led to a suite of metrics that collectively gauge popular and professional interest and use of the material. To name a few, this includes visit statistics (taking note of the institution of the visitor), subscriptions, and non-internet citations. Results indicate that, since the blog's inception in mid-2011, it has become a valued resource for the NZ hydrological community and an interesting website for the general public. The second example centered on the use of Facebook, in conjunction with the blog, to encourage the public to gather snow depth data during significant and rare low-elevation snow storms in 2011 and 2012. Not only did this citizen science initiative contribute data to a research program, but it was also widely popular. Indeed, scientific interest from the New Zealand public consistently spiked during rare and significant natural phenomena such as snow storms and earthquakes. These two vignettes thus shed light on how to connect scientists to one another and to the public via social media, highlighting in particular the importance of the audiences' affinities with both the medium and the message.

Collins, D. B.; Woods, R. A.

2012-12-01

366

Nitric oxide sensitive-guanylyl cyclase subunit expression changes during estrous cycle in anterior pituitary glands.  

PubMed

17beta-estradiol (E2) exerts inhibitory actions on the nitric oxide pathway in rat adult pituitary glands. Previously, we reported that in vivo E2 acute treatment had opposite effects on soluble guanylyl cyclase (sGC) subunits, increasing alpha1- and decreasing beta1-subunit protein and mRNA expression and decreasing sGC activity in immature rats. Here we studied the E2 effect on sGC protein and mRNA expression in anterior pituitary gland from adult female rats to address whether the maturation of the hypothalamus-pituitary axis influences its effects and to corroborate whether these effects occur in physiological conditions such as during estrous cycle. E2 administration causes the same effect on sGC as seen in immature rats, and these effects are estrogen receptor dependent. These results suggest that E2 is the main effector of these changes. Since the sGC alpha-subunit increases while the sGC activity decreases, we studied if other less active isoforms of the sGC alpha-subunit are expressed. Here we show for the first time that sGCalpha2 and sGCalpha2 inhibitory (alpha2i) isoforms are expressed in this gland, but only sGCalpha2i mRNA increased after E2 acute treatment. Finally, to test whether E2 effects take place under a physiological condition, sGC subunit expression was monitored over estrous cycle. sGCalpha1, -beta1, and -alpha2i fluctuate along estrous cycle, and these changes are directly related with E2 level fluctuations rather than to NO level variations. These findings show that E2 physiologically regulates sGC expression and highlight a novel mechanism by which E2 downregulates sGC activity in rat anterior pituitary gland. PMID:19141686

Cabilla, Jimena P; Ronchetti, Sonia A; Nudler, Silvana I; Miler, Eliana A; Quinteros, Fernanda A; Duvilanski, Beatriz H

2009-04-01

367

A new Ru complex capable of catalytically oxidizing water to molecular dioxygen.  

PubMed

We have prepared three new dinuclear ruthenium complexes having the formulas [Ru2II(bpp)(trpy)2(mu-L)]2+ (L = Cl, 1; L = AcO, 2) and [Ru2II(bpp)(trpy)2(H2O)2]3+ (3). The three complexes have been characterized through the usual spectroscopic and electrochemical techniques and, in the cases of 1 and 2, the X-ray crystal structures have been solved. In aqueous acidic solution, the acetato bridge of 2 is replaced by aqua ligands, generating the bis(aqua) complex 3 which, upon oxidation to its RuIVRuIV state, has been shown to catalytically oxidize water to molecular oxygen. The measured pseudo-first-order rate constant for the O2-evolving process is 1.4 x 10-2 s-1, more than 3 times larger than the higher one previously reported for Ru-O-Ru type catalysts. This new water-splitting catalyst also has improved stability with regard to any previously described, achieving a total of 18.6 metal cycles. PMID:15212526

Sens, Cristina; Romero, Isabel; Rodríguez, Montserrat; Llobet, Antoni; Parella, Teodor; Benet-Buchholz, Jordi

2004-06-30

368

Sustained water oxidation by [Mn4O4]7+ core complexes inspired by oxygenic photosynthesis.  

PubMed

The bioinspired Mn-oxo cubane complex, [Mn(4)O(4)L(6)](+) 1b(+) (L = (p-MeO-Ph)(2)PO(2)), is a model of the photosynthetic O(2)-evolving complex. It is able to electro-oxidize water at 1.00 V (vs Ag/AgCl) under illumination by UV-visible light when suspended in a proton-conducting membrane (Nafion) coated onto a conducting electrode. Electrochemical measurements, and UV-visible, NMR, and EPR spectroscopies are interpreted to indicate that 1b(+) is the dominant electro-active species in the Nafion, both before and after catalytic cycling, and thus correlates closely with activity. The observation of a possible intermediate and free phosphinate ligand within the Nafion suggests a catalytic mechanism involving photolytic disruption of a phosphinate ligand, followed by O(2) formation, and subsequent reassembly of the cubane structure. Several factors that influence catalytic turnover such as the applied potential, illumination wavelength, and energy have been examined in respect of attaining optimum catalytic activity. Catalytic turnover frequencies of 20-270 molecules O(2) h(-1) catalyst(-1) at an overpotential of 0.38 V plus light (275-750 nm) and turnovers numbers >1000 molecules O(2) catalyst(-1) are observed. The 1b(+)-Nafion system is among the most active and durable molecular water oxidation catalysts known. PMID:19572724

Brimblecombe, Robin; Kolling, Derrick R J; Bond, Alan M; Dismukes, G Charles; Swiegers, Gerhard F; Spiccia, Leone

2009-08-01

369

N-Oxidation of 4-chloroaniline by prostaglandin synthase. Redox cycling of radical intermediate(s).  

PubMed

4-Chloroaniline undergoes N-oxidation in ram seminal-vesicle microsomal preparations supplemented with arachidonic acid to yield N-(4-chlorophenyl)-hydroxylamine and 1-chloro-4-nitrosobenzene. H2O2 also supports metabolism of the amine substrate to the same organic-solvent-extractable products, suggesting that the hydroperoxidase activity of prostaglandin synthase is responsible for the co-oxidation. Analysis of the reaction mixtures by e.s.r. spectrometry reveals the formation of a radical intermediate bearing the characteristics of a strongly immobilized nitroxide. Arylamine-stimulated O2.- release can be observed when the arachidonic acid-containing incubation media are supplemented with NADPH. Redox cycling of the nitroxide/hydroxylamine couple is presumed to represent the major source of O2.-, but additional mechanisms, such as redox changes of nitro anion radicals resulting from potential further metabolism of 1-chloro-4-nitrosobenzene, cannot be excluded. The concerted action of carrier-bound nitroxides and O2.- in initiating damage of cellular macromolecules is discussed. PMID:2985047

Golly, I; Hlavica, P

1985-03-15

370

N-Oxidation of 4-chloroaniline by prostaglandin synthase. Redox cycling of radical intermediate(s).  

PubMed Central

4-Chloroaniline undergoes N-oxidation in ram seminal-vesicle microsomal preparations supplemented with arachidonic acid to yield N-(4-chlorophenyl)-hydroxylamine and 1-chloro-4-nitrosobenzene. H2O2 also supports metabolism of the amine substrate to the same organic-solvent-extractable products, suggesting that the hydroperoxidase activity of prostaglandin synthase is responsible for the co-oxidation. Analysis of the reaction mixtures by e.s.r. spectrometry reveals the formation of a radical intermediate bearing the characteristics of a strongly immobilized nitroxide. Arylamine-stimulated O2.- release can be observed when the arachidonic acid-containing incubation media are supplemented with NADPH. Redox cycling of the nitroxide/hydroxylamine couple is presumed to represent the major source of O2.-, but additional mechanisms, such as redox changes of nitro anion radicals resulting from potential further metabolism of 1-chloro-4-nitrosobenzene, cannot be excluded. The concerted action of carrier-bound nitroxides and O2.- in initiating damage of cellular macromolecules is discussed. PMID:2985047

Golly, I; Hlavica, P

1985-01-01

371

Glutamate Utilization Couples Oxidative Stress Defense and the Tricarboxylic Acid Cycle in Francisella Phagosomal Escape  

PubMed Central

Intracellular bacterial pathogens have developed a variety of strategies to avoid degradation by the host innate immune defense mechanisms triggered upon phagocytocis. Upon infection of mammalian host cells, the intracellular pathogen Francisella replicates exclusively in the cytosolic compartment. Hence, its ability to escape rapidly from the phagosomal compartment is critical for its pathogenicity. Here, we show for the first time that a glutamate transporter of Francisella (here designated GadC) is critical for oxidative stress defense in the phagosome, thus impairing intra-macrophage multiplication and virulence in the mouse model. The gadC mutant failed to efficiently neutralize the production of reactive oxygen species. Remarkably, virulence of the gadC mutant was partially restored in mice defective in NADPH oxidase activity. The data presented highlight links between glutamate uptake, oxidative stress defense, the tricarboxylic acid cycle and phagosomal escape. This is the first report establishing the role of an amino acid transporter in the early stage of the Francisella intracellular lifecycle. PMID:24453979

Ramond, Elodie; Gesbert, Gael; Rigard, Mélanie; Dairou, Julien; Dupuis, Marion; Dubail, Iharilalao; Meibom, Karin; Henry, Thomas; Barel, Monique; Charbit, Alain

2014-01-01

372

Design of Mononuclear Ruthenium Catalysts for Low-Overpotential Water Oxidation.  

PubMed

Water oxidation is a key reaction in natural photosynthesis and in many schemes for artificial photosynthesis. Inspired by energy challenges and the emerging understanding of photosystem II, the development of artificial molecular catalysts for water oxidation has become a highly active area of research in recent years. In this Focus Review, we describe recent achievements in the development of single-site ruthenium catalysts for water oxidation with a particular focus on the overpotential of water oxidation. First, we introduce the general scheme to access the high-valent ruthenium-oxo species, the key species of the water-oxidation reaction. Next, the mechanisms of the O?O bond formation from the active ruthenium-oxo species are described. We then discuss strategies to decrease the onset potentials of the water-oxidation reaction. We hope this Focus Review will contribute to the further development of efficient catalysts toward sustainable energy-conversion systems. PMID:25318678

Okamura, Masaya; Masaoka, Shigeyuki

2014-10-16

373

Unraveling delta1-pyrroline-5-carboxylate-proline cycle in plants by uncoupled expression of proline oxidation enzymes.  

PubMed

The two-step oxidation of proline in all eukaryotes is performed at the inner mitochondrial membrane by the consecutive action of proline dehydrogenase (ProDH) that produces Delta(1)-pyrroline-5-carboxylate (P5C) and P5C dehydrogenase (P5CDH) that oxidizes P5C to glutamate. This catabolic route is down-regulated in plants during osmotic stress, allowing free Pro accumulation. We show here that overexpression of MsProDH in tobacco and Arabidopsis or impairment of P5C oxidation in the Arabidopsis p5cdh mutant did not change the cellular Pro to P5C ratio under ambient and osmotic stress conditions, indicating that P5C excess was reduced to Pro in a mitochondrial-cytosolic cycle. This cycle, involving ProDH and P5C reductase, exists in animal cells and now demonstrated in plants. As a part of the cycle, Pro oxidation by the ProDH-FAD complex delivers electrons to the electron transport chain. Hyperactivity of the cycle, e.g. when an excess of exogenous l-Pro is provided, generates mitochondrial reactive oxygen species (ROS) by delivering electrons to O(2), as demonstrated by the mitochondria-specific MitoSox staining of superoxide ions. Lack of P5CDH activity led to higher ROS production under dark and light conditions in the presence of Pro excess, as well as rendered plants hypersensitive to heat stress. Balancing mitochondrial ROS production during increased Pro oxidation is therefore critical for avoiding Pro-related toxic effects. Hence, normal oxidation of P5C to Glu by P5CDH is key to prevent P5C-Pro intensive cycling and avoid ROS production from electron run-off. PMID:19635803

Miller, Gad; Honig, Arik; Stein, Hanan; Suzuki, Nobuhiro; Mittler, Ron; Zilberstein, Aviah

2009-09-25

374

A fully coupled model for water-gas-heat reactive transport with methane oxidation in landfill covers.  

PubMed

Methane oxidation in landfill covers is a complex process involving water, gas and heat transfer as well as microbial oxidation. The coupled phenomena of microbial oxidation, water, gas, and heat transfer are not fully understood. In this study, a new model is developed that incorporates water-gas-heat coupled reactive transport in unsaturated soil with methane oxidation. Effects of microbial oxidation-generated water and heat are included. The model is calibrated using published data from a laboratory soil column test. Moreover, a series of parametric studies are carried out to investigate the influence of microbial oxidation-generated water and heat, initial water content on methane oxidation efficiency. Computed and measured results of gas concentration and methane oxidation rate are consistent. It is found that the coupling effects between water-gas-heat transfer and methane oxidation are significant. Ignoring microbial oxidation-generated water and heat can result in a significant difference in methane oxidation efficiency by 100%. PMID:25489976

Ng, C W W; Feng, S; Liu, H W

2015-03-01

375

Vapor compression CuCl heat pump integrated with a thermochemical water splitting cycle  

Microsoft Academic Search

In this paper, the feasibility of using cuprous chloride (CuCl) as a working fluid in a new high temperature heat pump with vapor compression is analyzed. The heat pump is integrated with a copper–chlorine (Cu–Cl) thermochemical water splitting cycle for internal heat recovery, temperature upgrades and hydrogen production. The minimum temperature of heat supply necessary for driving the water splitting

C. Zamfirescu; G. F. Naterer; I. Dincer

2011-01-01

376

Pharmaceutical Contaminants in Urban Water Cycles: A Discussion of Novel Concepts for Environmental Risk Assessment  

Microsoft Academic Search

\\u000a Urban water cycles are threatened in many ways by human activities, including the discharge of chemicals by industrial and\\u000a household effluents. Since more than a decade it has been recognised that the active ingredients of human pharmaceuticals\\u000a contribute to the chemical contamination of urban surface waters and may pose a serious risk to the environment. Pharmaceuticals\\u000a reach the aquatic environment

Stefan Scholz; Kristin Schirmer; Rolf Altenburger

377

Mars Water Cycle Simulations - Sensitivity to Model Physics and Dynamics, and Local Behaviour  

NASA Astrophysics Data System (ADS)

Simulation of the water cycle on Mars is sensitive to the representation of physical processes and the representation of transport by model dynamics. It is also complicated because, through radiative effects, the phyical processes of the water cycle can influence dynamics - such as via the radiative feedback of clouds and surface ice on the thermal state and hence the circulation. The problem is complicated by the fact that the water cycle is arguably the least well observed of the three major climate cycles on Mars (the others being dust and carbon dioxide). While several GCM studies have taken on the water cycle problem, they have yielded only "spot samples" of the system, where each model represents a unique combination of dynamical solver and physics suite. Under such circumstances it is difficult to isolate the effect of (say) regolith source from cloud feedback and errors in transportive dynamics. In this study, we use a range of different physical processes within a common physics package that is shared between the MarsWRF and Ashima's version of the Mars MITgcm. The former is a latitude-longitude finite difference model which has the advantage of allowing interactive nesting such that local observations of water vapour near the surface at the Phoenix and Curiosity landing sites can be examined. The latter is a finite volume model that can be run with a latitude-longitude or cubed-sphere computational grid. We have already shown that for the case of transport across the southern winter polar jet the finite volume core performs significantly better than any of the extant finite difference core models for Mars. The common model physics package includes radiative effects of water ice, regolith exchange involving surface condendation (frost) and subsurface diffusion, adsorption and freezing (ground ice), and a bulk cloud microphysics scheme.

Richardson, M.; Lee, C.; Lian, Y.; Mischna, M. A.; Newman, C. E.; Toigo, A. D.

2012-12-01

378

Global climate modeling of the Martian water cycle with improved microphysics and radiatively active water ice clouds  

NASA Astrophysics Data System (ADS)

Water ice clouds play a key role in the radiative transfer of the Martian atmosphere, impacting its thermal structure, its circulation, and, in turn, the water cycle. Recent studies including the radiative effects of clouds in global climate models (GCMs) have found that the corresponding feedbacks amplify the model defaults. In particular, it prevents models with simple microphysics from reproducing even the basic characteristics of the water cycle. Within that context, we propose a new implementation of the water cycle in GCMs, including a detailed cloud microphysics taking into account nucleation on dust particles, ice particle growth, and scavenging of dust particles due to the condensation of ice. We implement these new methods in the Laboratoire de Météorologie Dynamique GCM and find satisfying agreement with the Thermal Emission Spectrometer observations of both water vapor and cloud opacities, with a significant improvement when compared to GCMs taking into account radiative effects of water ice clouds without this implementation. However, a lack of water vapor in the tropics after Ls = 180° is persistent in simulations compared to observations, as a consequence of aphelion cloud radiative effects strengthening the Hadley cell. Our improvements also allow us to explore questions raised by recent observations of the Martian atmosphere. Supersaturation above the hygropause is predicted in line with Spectroscopy for Investigation of Characteristics of the Atmosphere of Mars observations. The model also suggests for the first time that the scavenging of dust by water ice clouds alone fails to fully account for the detached dust layers observed by the Mars Climate Sounder.

Navarro, T.; Madeleine, J.-B.; Forget, F.; Spiga, A.; Millour, E.; Montmessin, F.; Määttänen, A.

2014-07-01

379

Advanced Fuel Cycle Economic Analysis of Symbiotic Light-Water Reactor and Fast Burner Reactor Systems  

SciTech Connect

The Advanced Fuel Cycle Economic Analysis of Symbiotic Light-Water Reactor and Fast Burner Reactor Systems, prepared to support the U.S. Advanced Fuel Cycle Initiative (AFCI) systems analysis, provides a technology-oriented baseline system cost comparison between the open fuel cycle and closed fuel cycle systems. The intent is to understand their overall cost trends, cost sensitivities, and trade-offs. This analysis also improves the AFCI Program’s understanding of the cost drivers that will determine nuclear power’s cost competitiveness vis-a-vis other baseload generation systems. The common reactor-related costs consist of capital, operating, and decontamination and decommissioning costs. Fuel cycle costs include front-end (pre-irradiation) and back-end (post-iradiation) costs, as well as costs specifically associated with fuel recycling. This analysis reveals that there are large cost uncertainties associated with all the fuel cycle strategies, and that overall systems (reactor plus fuel cycle) using a closed fuel cycle are about 10% more expensive in terms of electricity generation cost than open cycle systems. The study concludes that further U.S. and joint international-based design studies are needed to reduce the cost uncertainties with respect to fast reactor, fuel separation and fabrication, and waste disposition. The results of this work can help provide insight to the cost-related factors and conditions needed to keep nuclear energy (including closed fuel cycles) economically competitive in the U.S. and worldwide. These results may be updated over time based on new cost information, revised assumptions, and feedback received from additional reviews.

D. E. Shropshire

2009-01-01

380

Fragments of layered manganese oxide are the real water oxidation catalyst after transformation of molecular precursor on clay.  

PubMed

A binuclear manganese molecular complex [(OH2)(terpy)Mn(?-O)2Mn(terpy)(OH2)](3+) (1) is the most prominent structural and functional model of the water-oxidizing Mn complex operating in plants and cyanobacteria. Supported on montmorillonite clay and using Ce(IV) as a chemical oxidant, 1 has been reported to be one of the best Mn-based molecular catalysts toward water oxidation. By X-ray absorption spectroscopy and kinetic analysis of the oxygen evolution reaction, we show that [(OH2)(terpy)Mn(?-O)2Mn(terpy)(OH2)](3+) is transformed into layered type Mn-oxide particles which are the actual water oxidation catalyst. PMID:24798550

Najafpour, M M; Moghaddam, Atefeh N; Dau, Holger; Zaharieva, Ivelina

2014-05-21

381

PBO H2O: Plate Boundary Observatory Studies of the Water Cycle  

NASA Astrophysics Data System (ADS)

The EarthScope Plate Boundary Observatory was built to measure the deformation of the North American continent. PBO stations can also be used to measure ground displacements at much higher frequencies (5-Hz) for studies of fault slip during large earthquakes and for warnings of volcanic eruptions. There is also a long history of using atmospheric delays on the GPS signals to estimate precipitable water vapor (for weather and climate studies) and total electron content (space weather studies). Recently the PBO H2O research group has demonstrated that GPS signals that reflect from the nearby environment can be used for water cycle research. These GPS reflections measure how much water is in the top layer of the soil, how much snow is on its surface, and water content of nearby vegetation. Observing and monitoring spatial and temporal changes in the water cycle is critical for both understanding and predicting Earth's climate. Since GPS reflections encompass an area of ~1000 m^2, they provide a spatial footprint that complements satellite systems which sense much larger areas and in situ systems that sense regions < 1 m^2. Water cycle products are produced from PBO data each day and updated on the PBO H2O website.

Larson, K. M.; Small, E. E.; Chew, C. C.; Nievinski, F. G.; Pratt, J.; McCreight, J. L.; Braun, J.; Boniface, K.; Evans, S. G.

2013-12-01

382

Atmospheric chemistry of nitrogen on Mars: A link between oxidants in the soil and chlorine cycling  

NASA Astrophysics Data System (ADS)

NO and NO2, collectively denoted NOx, are generated in the Earth's atmosphere mainly from the photochemistry of biogenic nitrogen-containing gases whereas on Mars they form through the oxidation of products derived from ionospheric dissociation of N2. NOx disappears from both atmospheres when acids form from further oxidation and deposit to the surface. We show that peroxynitric acid (PNA), HO2NO2, dominates the removal of NOx from the atmosphere of Mars in contrast to nitric acid, HNO3, in the Earth's atmosphere because PNA is stabile against thermal decomposition at the colder temperatures of Mars. Following the dry deposition of PNA, peroxynitrate or peroxynitrite minerals are possible, while a proportion of PNA may also decompose and recycle NOx back to the atmosphere. Deposition of PNA must have been delivering nitrogen to the martian surface since at least ~3 Ga (during the Amazonian) when Mars has been predominantly cold and dry. In aqueous solution, peroxynitrates or peroxynitrites decompose and release O2. Thus, their inevitable formation from atmospheric chemistry could explain the release of O2 when water was added to the martian soil in the Viking Lander (VL) Gas Exchange experiment. Furthermore, PNA could interact with chlorides to liberate chlorine volatiles, enabling cyclic oxidation of chlorine compounds into perchlorate even in the absence of volcanic chlorine volatiles.

Catling, D. C.; Smith, M. L.; Claire, M. W.; Zahnle, K. J.

2013-09-01

383

Unraveling the mechanism of water oxidation catalyzed by nonheme iron complexes.  

PubMed

Density functional theory (DFT) is employed to: 1)?propose a viable catalytic cycle consistent with our experimental results for the mechanism of chemically driven (Ce(IV) ) O2 generation from water, mediated by nonheme iron complexes; and 2)?to unravel the role of the ligand on the nonheme iron catalyst in the water oxidation reaction activity. To this end, the key features of the water oxidation catalytic cycle for the highly active complexes [Fe(OTf)2 (Pytacn)] (Pytacn: 1-(2'-pyridylmethyl)-4,7-dimethyl-1,4,7-triazacyclononane; OTf: CF3 SO3 (?) ) (1) and [Fe(OTf)2 (mep)] (mep: N,N'-bis(2-pyridylmethyl)-N,N'-dimethyl ethane-1,2-diamine) (2) as well as for the catalytically inactive [Fe(OTf)2 (tmc)] (tmc: N,N',N'',N'''-tetramethylcyclam) (3) and [Fe(NCCH3 )((Me) Py2 CH-tacn)](OTf)2 ((Me) Py2 CH-tacn: N-(dipyridin-2-yl)methyl)-N',N''-dimethyl-1,4,7-triazacyclononane) (4) were analyzed. The DFT computed catalytic cycle establishes that the resting state under catalytic conditions is a [Fe(IV) (O)(OH2 )(LN4 )](2+) species (in which LN4 =Pytacn or mep) and the rate-determining step is the O?O bond-formation event. This is nicely supported by the remarkable agreement between the experimental (?G(?) =17.6±1.6?kcal?mol(-1) ) and theoretical (?G(?) =18.9?kcal?mol(-1) ) activation parameters obtained for complex 1. The O?O bond formation is performed by an iron(V) intermediate [Fe(V) (O)(OH)(LN4 )](2+) containing a cis-Fe(V) (O)(OH) unit. Under catalytic conditions (Ce(IV) , pH?0.8) the high oxidation state Fe(V) is only thermodynamically accessible through a proton-coupled electron-transfer (PCET) process from the cis-[Fe(IV) (O)(OH2 )(LN4 )](2+) resting state. Formation of the [Fe(V) (O)(LN4 )](3+) species is thermodynamically inaccessible for complexes 3 and 4. Our results also show that the cis-labile coordinative sites in iron complexes have a beneficial key role in the O?O bond-formation process. This is due to the cis-OH ligand in the cis-Fe(V) (O)(OH) intermediate that can act as internal base, accepting a proton concomitant to the O?O bond-formation reaction. Interplay between redox potentials to achieve the high oxidation state (Fe(V) ?O) and the activation energy barrier for the following O?O bond formation appears to be feasible through manipulation of the coordination environment of the iron site. This control may have a crucial role in the future development of water oxidation catalysts based on iron. PMID:24668499

Acuña-Parés, Ferran; Codolà, Zoel; Costas, Miquel; Luis, Josep M; Lloret-Fillol, Julio

2014-05-01

384

Assessing a Satellite-Era Perspective of the Global Water Cycle  

Microsoft Academic Search

The capability of a global data compilation, largely satellite based, is assessed to depict the global atmospheric water cycle's mean state and variability. Monthly global precipitation estimates from the Global Precipitation Climatology Project (GPCP) and the Climate Prediction Center (CPC) Merged Analy- sis of Precipitation (CMAP) span from 1979 to 1999. Monthly global Special Sensor Microwave Imager (SSM\\/I)-based bulk aerodynamic

C. Adam Schlosser; Paul R. Houser

2007-01-01

385

Hydrological consistency using multi-sensor remote sensing data for water and energy cycle studies  

E-print Network

and feedback of land surface and atmospheric processes over large space and time scales. Remote sensingHydrological consistency using multi-sensor remote sensing data for water and energy cycle studies for future remote observation and analysis of the coupled land surface­atmosphere system. © 2007 Elsevier Inc

Pan, Ming

386

The Global Water Cycle Drives Volcanism on Seasonal to Millennial Timescales  

Microsoft Academic Search

Global rates of occurrence of volcanic eruptions show periodic behaviour on timescales ranging from 106 years. At long timescales (>106 to 107 years), rates of eruption are controlled by plate tectonics. At shorter timescales, the periodic nature of volcanism is forced by the global water cycle. Historical records of the rates of onset of eruption for the past 300 years

D. M. Pyle; B. G. Mason; T. E. Jupp; W. B. Dade

2005-01-01

387

Issues and Solutions for Bringing Heterogeneous Water Cycle Data Sets Together  

NASA Technical Reports Server (NTRS)

The water cycle research community has generated many regional to global scale products using data from individual NASA missions or sensors (e.g., TRMM, AMSR-E); multiple ground- and space-based data sources (e.g., Global Precipitation Climatology Project [GPCP] products); and sophisticated data assimilation systems (e.g., Land Data Assimilation Systems [LDAS]). However, it is often difficult to access, explore, merge, analyze, and inter-compare these data in a coherent manner due to issues of data resolution, format, and structure. These difficulties were substantiated at the recent Collaborative Energy and Water Cycle Information Services (CEWIS) Workshop, where members of the NASA Energy and Water cycle Study (NEWS) community gave presentations, provided feedback, and developed scenarios which illustrated the difficulties and techniques for bringing together heterogeneous datasets. This presentation reports on the findings of the workshop, thus defining the problems and challenges of multi-dataset research. In addition, the CEWIS prototype shown at the workshop will be presented to illustrate new technologies that can mitigate data access roadblocks encountered in multi-dataset research, including: (1) Quick and easy search and access of selected NEWS data sets. (2) Multi-parameter data subsetting, manipulation, analysis, and display tools. (3) Access to input and derived water cycle data (data lineage). It is hoped that this presentation will encourage community discussion and feedback on heterogeneous data analysis scenarios, issues, and remedies.

Acker, James; Kempler, Steven; Teng, William; Belvedere, Deborah; Liu, Zhong; Leptoukh, Gregory

2010-01-01

388

Southern Ocean Iron Enrichment Experiment: Carbon Cycling in High and Low-Si Waters  

Microsoft Academic Search

The availability of iron is known to exert a controlling influence on biological productivity in surface waters over large areas of the ocean and may have been an important factor in the variation of the concentration of atmospheric carbon dioxide over glacial cycles. The effect of iron in the Southern Ocean is particularly important because of its large area and

Kenneth H. Coale; Kenneth S. Johnson; Francisco P. Chavez; Ken O. Buesseler; Richard T. Barber; Mark A. Brzezinski; William P. Cochlan; Frank J. Millero; Paul G. Falkowski; James E. Bauer; Rik H. Wanninkhof; Raphael M. Kudela; Mark A. Altabet; Burke E. Hales; Taro Takahashi; Michael R. Landry; Robert R. Bidigare; Xiujun Wang; Zanna Chase; Pete G. Strutton; Gernot E. Friederich; Maxim Y. Gorbunov; Veronica P. Lance; Anna K. Hilting; Michael R. Hiscock; Mark Demarest; William T. Hiscock; Kevin F. Sullivan; Sara J. Tanner; R. Mike Gordon; Craig N. Hunter; Virginia A. Elrod; Steve E. Fitzwater; Janice L. Jones; Sasha Tozzi; Michal Koblizek; Alice E. Roberts; Julian Herndon; Jodi Brewster; Nicolas Ladizinsky; Geoffrey Smith; David Cooper; David Timothy; Susan L. Brown; Karen E. Selph; Cecelia C. Sheridan; Benjamin S. Twining; Zackary I. Johnson

2004-01-01

389

Hydrogen-oxygen closed cycle MHD power generation system based upon thermochemical decomposition of water  

Microsoft Academic Search

A new closed cycle energy conversion system in which an MHD generator operates on hydrogen and oxygen produced from water by means of multi-step thermochemical decomposition processes is proposed. It is shown that the MHD generator and the thermochemical decomposer can be combined effectively in the power generation process and that the conversion of nuclear heat available from already existing

T. Nakamura; W. Riedmueller

1975-01-01

390

Cycling of mercury between water, air, and soil compartments of the environment  

Microsoft Academic Search

The propensity to resist chemical, photo-chemical or biological degradation processes, coupled with a high degree of mobility — due to favorable physical-chemical properties such as relatively high vapor pressure and low solubility in water - bestows upon some chemical substances the necessary pre-requisites for extensive cycling among environmental compartments. Certain inorganic and organometallic species of Hg exhibit the aforementioned characteristics.

W. H. Schroeder; J. Munthe; O. Lindqvist

1989-01-01

391

Studying the Water Cycle in an Environmental Context: The "Blue Planet" Program.  

ERIC Educational Resources Information Center

The Blue Planet program aims to develop an understanding of and insight into the environment among students by introducing environmental problems such as pollution. This paper presents a study investigating junior high school students' previous knowledge and understanding of environmental issues and perceptions on the nature of the water cycle

Ben-zvi-assaraf, Orit; Orion, Nir

392

Nutrient Cycling at the Land-Water Interface: the Importance of the Riparian Zone!  

E-print Network

Nutrient Cycling at the Land-Water Interface: the Importance of the Riparian Zone! DOUGLAS M. GREEN 97331 USA Abstract.-Riparian ecosystems are sites ofimportant biogeochemical processes that affect with the slow diffusion of oxygen in waterlogged riparian soils, causes anaerobic conditions and reduction

393

Studies on water-steam Rankine-cycle solar central receiver power plants. Final report  

Microsoft Academic Search

Cost estimates are provided for four 150 MWe solar hybrid central receiver power plants, based on the updating of conceptual designs developed in a previous EPRI solar hybrid power plant cost study, Water\\/Steam Rankine Cycle Solar Central Receiver Power Plant Cost Estimates. The power plants are hybrid in that main steam is generated in a central receiver and a conventional

J. R. Darnell; R. L. Lessley; J. A. Paffenbarger; A. A. Agur

1985-01-01

394

Comparison of electrolyzed oxidizing water with other antimicrobial interventions to reduce pathogens on fresh pork  

Microsoft Academic Search

To date, the effectiveness of electrolyzed oxidizing (EO) water against bacteria associated with fresh pork has not been determined. Using a hand-held, food-grade garden sprayer, distilled water (W), chlorinated water (CL; 25 ppm), 2% lactic acid (LA), acidic EO water (EOA), or “aged” acidic EO water (AEOA; stored at 4 °C for 24 h) was sprayed (15 s) onto pork

K. A Fabrizio; C. N Cutter

2004-01-01

395

Effect of water quality on residential water heater life-cycle efficiency. Annual report, September 1983-August 1984  

SciTech Connect

A 3-year field test program is under way for the Gas Research Institute to quantify the effect of scale buildup on the performance of residential water heaters, and to determine the benefits and limitations of common water-treatment methods. In this program, the performance of gas and electric heaters is being monitored in test laboratories set up in selected U.S. cities. The efficiency of heaters operating on hard water is measured and compared with the performance of heaters operating on treated water. Corrosion tests are also being conducted on each type of water tested to determine the effect of water treatment on the corrosion of the water heating system. During this reporting period Battelle has established operating hard water test facilities at four test sites: (1) Battelle, (2) the Roswell Test Facility in Roswell, New Mexico, (3) the Water Quality Association in Lisle, Illinois, and (4) the Marshall Municipal Utilities in Marshall, Minnesota. At each of these sites 12 water heaters have been installed and are operating on accelerated draw cycles. The recovery efficiency of each heater has been carefully measured, and the heaters have been operating from 4 months at one site to 7 months at another. At two of the test sites, the recovery efficiency of each heater has been remeasured after 6 months of operation. No significant degradation in heater performance due to scale buildup was observed in these heaters for the equivalent of 2 to 3 years of typical residential use.

Stickford, G.H.; Talbert, S.G.; Newman, D.C.; Payer, J.H.; Vigon, B.W.

1984-10-01

396

Archaea Dominate Ammonia Oxidizers in the Permian Water Ecosystem of Midland Basin  

PubMed Central

We investigated the existence and characteristics of ammonia oxidizers in Permian water from Midland Basin. Molecular surveys targeting the amoA gene showed that only ammonia-oxidizing archaea (AOA) exist and have potential activity in this special environment. In contrast, no ammonia-oxidizing bacteria (AOB) were detected in the water. Phylogenetic analysis indicated that 72–89% of the total screened AOA clones were affiliated with those found in underground water, and 10–24% of the AOA clones were related to those found in marine water or sediments. Our results indicate AOA might be the most abundant ammonia-oxidizing microbes in this ecological niche. PMID:24005842

Hong, Yiguo; Youshao, Wang; Chen, Feng

2013-01-01

397

Destruction of explosives and rocket fuels by supercritical water oxidation  

SciTech Connect

Traditional methods for disposing of PEPs have been open burning or open detonation (OB/OD); however, regulatory agencies are likely to prohibit OB/OD because of the uncontrolled air emissions and soil contaminations. Likewise, controlled incineration carries a liability for air pollution because large quantities of NO{sub x} are produced in the conventional combustion chemistry of PEPS. Soil and ground water have already been contaminated with PEPs through normal operations at manufacturing plants and military bases. Incineration can be used for decontamination of these soils, with the associated liability for air pollution, but few satisfactory and economic methods exist for ground water decontamination. A clear need exists for improved disposal and destruction methods. The destruction of energetic materials, including propellants, explosives and pyrotechnics (PEPS) by oxidation in supercritical water is described. The focus is on the chemistry of the process. The destruction efficiencies and products of reaction contained in the aqueous and gaseous effluents of several representative PEPs are reported.

Dyer, R.B.; Buelow, S.J.; Harradine, D.M.; Robinson, J.M.; Foy, B.R.; Atencio, J.H.; Dell'Orco, P.C.; Funk, K.A.; McInroy, R.E.; Rofer, C.K.; Counce, D.A.; Trujillo, P.E. Jr. (Los Alamos National Lab., NM (United States)); Wander, J.D. (Hq. AFB Civil Engineering Support Agency, Tyndall AFB, FL (United States))

1992-01-01

398

Destruction of explosives and rocket fuels by supercritical water oxidation  

SciTech Connect

Traditional methods for disposing of PEPs have been open burning or open detonation (OB/OD); however, regulatory agencies are likely to prohibit OB/OD because of the uncontrolled air emissions and soil contaminations. Likewise, controlled incineration carries a liability for air pollution because large quantities of NO{sub x} are produced in the conventional combustion chemistry of PEPS. Soil and ground water have already been contaminated with PEPs through normal operations at manufacturing plants and military bases. Incineration can be used for decontamination of these soils, with the associated liability for air pollution, but few satisfactory and economic methods exist for ground water decontamination. A clear need exists for improved disposal and destruction methods. The destruction of energetic materials, including propellants, explosives and pyrotechnics (PEPS) by oxidation in supercritical water is described. The focus is on the chemistry of the process. The destruction efficiencies and products of reaction contained in the aqueous and gaseous effluents of several representative PEPs are reported.

Dyer, R.B.; Buelow, S.J.; Harradine, D.M.; Robinson, J.M.; Foy, B.R.; Atencio, J.H.; Dell`Orco, P.C.; Funk, K.A.; McInroy, R.E.; Rofer, C.K.; Counce, D.A.; Trujillo, P.E. Jr. [Los Alamos National Lab., NM (United States); Wander, J.D. [Hq. AFB Civil Engineering Support Agency, Tyndall AFB, FL (United States)

1992-09-01

399

A highly efficient six-stroke internal combustion engine cycle with water injection for in-cylinder exhaust heat recovery  

Microsoft Academic Search

A concept adding two strokes to the Otto or Diesel engine cycle to increase fuel efficiency is presented here. It can be thought of as a four-stroke Otto or Diesel cycle followed by a two-stroke heat recovery steam cycle. A partial exhaust event coupled with water injection adds an additional power stroke. Waste heat from two sources is effectively converted

James C. Conklin; James P. Szybist

2010-01-01

400

Water oxidation catalysis by Co(II) impurities in Co(III)4O4 cubanes.  

PubMed

The observed water oxidation activity of the compound class Co4O4(OAc)4(Py-X)4 emanates from a Co(II) impurity. This impurity is oxidized to produce the well-known Co-OEC heterogeneous cobaltate catalyst, which is an active water oxidation catalyst. We present results from electron paramagnetic resonance spectroscopy, nuclear magnetic resonance line broadening analysis, and electrochemical titrations to establish the existence of the Co(II) impurity as the major source of water oxidation activity that has been reported for Co4O4 molecular cubanes. Differential electrochemical mass spectrometry is used to characterize the fate of glassy carbon at water oxidizing potentials and demonstrate that such electrode materials should be used with caution for the study of water oxidation catalysis. PMID:25407218

Ullman, Andrew M; Liu, Yi; Huynh, Michael; Bediako, D Kwabena; Wang, Hongsen; Anderson, Bryce L; Powers, David C; Breen, John J; Abruña, Héctor D; Nocera, Daniel G

2014-12-17

401

The effects of the martian regolith on GCM water cycle simulations  

NASA Astrophysics Data System (ADS)

This paper describes General Circulation Model (GCM) simulations of the martian water cycle focusing on the effects of an adsorbing regolith. We describe the 10-layer regolith model used in this study which has been adapted from the 1-D model developed by Zent, A.P., Haberle, R.M., Houben, H.C., Jakosky, B.M. [1993. A coupled subsurface-boundary layer model of water on Mars. J. Geophys. Res. 98 (E2), 3319-3337, February]. Even with a 30-min timestep and taking into account the effect of surface water ice, our fully implicit scheme compares well with the results obtained by Zent, A.P., Haberle, R.M., Houben, H.C., Jakosky, B.M. [1993. A coupled subsurface-boundary layer model of water on Mars. J. Geophys. Res. 98 (E2), 3319-3337, February]. This means, however, that the regolith is not able to reproduce the diurnal variations in column water vapour abundance of up to a factor of 2-3 as seen in some observations, with only about 10% of the atmospheric water vapour column exchanging with the subsurface on a daily basis. In 3-D simulations we find that the regolith adsorbs water preferentially in high latitudes. This is especially true in the northern hemisphere, where perennial subsurface water ice builds up poleward of 60° N at depths which are comparable to the Odyssey observations. Much less ice forms in the southern high latitudes, which suggests that the water ice currently present in the martian subsurface is not stable under present conditions and is slowly subliming and being deposited in the northern hemisphere. When initialising the model with an Odyssey-like subsurface water ice distribution the model is capable of forcing the simulated water cycle from an arbitrary state close to the Mars Global Surveyor Thermal Emission Spectrometer observations. Without the actions of the adsorbing regolith the equilibrated water cycle is found to be a factor of 2-4 too wet. The process by which this occurs is by adsorption of water during northern hemisphere summer in northern mid and high latitudes where it remains locked in until northern spring when the seasonal CO 2 ice cap retreats. At this time the water diffuses out of the regolith in response to increased temperature and is returned to the residual water ice cap by eddie transport.

Böttger, H. M.; Lewis, S. R.; Read, P. L.; Forget, F.

2005-09-01

402

Importance of Rain Evaporation and Continental Convection in the Tropical Water Cycle  

NASA Technical Reports Server (NTRS)

Atmospheric moisture cycling is an important aspect of the Earth's climate system, yet the processes determining atmospheric humidity are poorly understood. For example, direct evaporation of rain contributes significantly to the heat and moisture budgets of clouds, but few observations of these processes are available. Similarly, the relative contributions to atmospheric moisture over land from local evaporation and humidity from oceanic sources are uncertain. Lighter isotopes of water vapour preferentially evaporate whereas heavier isotopes preferentially condense and the isotopic composition of ocean water is known. Here we use this information combined with global measurements of the isotopic composition of tropospheric water vapour from the Tropospheric Emission Spectrometer (TES) aboard the Aura spacecraft, to investigate aspects of the atmospheric hydrological cycle that are not well constrained by observations of precipitation or atmospheric vapour content. Our measurements of the isotopic composition of water vapour near tropical clouds suggest that rainfall evaporation contributes significantly to lower troposphere humidity, with typically 20% and up to 50% of rainfall evaporating near convective clouds. Over the tropical continents the isotopic signature of tropospheric water vapour differs significantly from that of precipitation, suggesting that convection of vapour from both oceanic sources and evapotranspiration are the dominant moisture sources. Our measurements allow an assessment of the intensity of the present hydrological cycle and will help identify any future changes as they occur.

Worden, John; Noone, David; Bowman, Kevin; Beer, R.; Eldering, A.; Fisher, B.; Gunson, M.; Goldman, Aaron; Kulawik, S. S.; Lampel, Michael; Osterman, Gregory; Rinsland, Curtis P.; Rogders, Clive; Sander, Stanley; Shepard, Mark; Webster, Christopher R.; Worden, H. M.

2007-01-01

403

Numerical Simulation of the Water Cycle Change Over the 20th Century  

NASA Technical Reports Server (NTRS)

We have used numerical models to test the impact of the change in Sea Surface Temperatures (SSTs) and carbon dioxide (CO2) concentration on the global circulation, particularly focusing on the hydrologic cycle, namely the global cycling of water and continental recycling of water. We have run four numerical simulations using mean annual SST from the early part of the 20th century (1900-1920) and the later part (1980-2000). In addition, we vary the CO2 concentrations for these periods as well. The duration of the simulations is 15 years, and the spatial resolution is 2 degrees. We use passive tracers to study the geographical sources of water. Surface evaporation from predetermined continental and oceanic regions provides the source of water for each passive tracer. In this way, we compute the percent of precipitation of each region over the globe. This can also be used to estimate precipitation recycling. In addition, we are using the passive tracers to independently compute the global cycling of water (compared to the traditional, Q/P calculation).

Bosilovich, Michael G.; Schubert, Siegfried D.

2003-01-01

404

Progress in the Los Alamos Scientific Laboratory program to develop thermochemical processes for hydrogen production. [Oxide-sulfate cycles; sulfuric acid cycles; bromide-sulfate cycles; sulfuric acid-sulfur cycles; hybrid cycles  

Microsoft Academic Search

The Los Alamos Scientific Laboratory Program to develop thermochemical processes for hydrogen production is based on attempts to develop criteria required of an ideal process and to search for types of thermochemical cycles that approximate these criteria. The advantages of reactions with large entropy changes have been demonstrated. The necessity for experimental verification of conceptual cycles has become apparent from

1976-01-01

405

The Conceptual Design of an Integrated Nuclearhydrogen Production Plant Using the Sulfur Cycle Water Decomposition System  

NASA Technical Reports Server (NTRS)

A hydrogen production plant was designed based on a hybrid electrolytic-thermochemical process for decomposing water. The sulfur cycle water decomposition system is driven by a very high temperature nuclear reactor that provides 1,283 K helium working gas. The plant is sized to approximately ten million standard cubic meters per day of electrolytically pure hydrogen and has an overall thermal efficiently of 45.2 percent. The economics of the plant were evaluated using ground rules which include a 1974 cost basis without escalation, financing structure and other economic factors. Taking into account capital, operation, maintenance and nuclear fuel cycle costs, the cost of product hydrogen was calculated at $5.96/std cu m for utility financing. These values are significantly lower than hydrogen costs from conventional water electrolysis plants and competitive with hydrogen from coal gasification plants.

Farbman, G. H.

1976-01-01

406

Development of long-life-cycle tablet ceramic adsorbent for geosmin removal from water solution  

Microsoft Academic Search

In this study, the tablet ceramic adsorbent (TCA), a silica\\/iron(III) oxide composite material, has been developed for geosmin (GSM) removal from the water solution. The physicochemical characteristics of TCA were examined with XRD, SEM, EDX and BET analyses. The sorption characteristics of GSM on TCA were investigated in a batch system. Attempts have been made to understand the adsorption kinetics,

Rongzhi Chen; Qiang Xue; Zhenya Zhang; Norio Sugiura; Yingnan Yang; Miao Li; Nan Chen; Zhao Ying; Zhongfang Lei

2011-01-01

407

Supercritical water oxidation of acrylic acid production wastewater.  

PubMed

Supercritical water oxidation (SCWO) of wastewater from an acrylic acid manufacturing plant has been studied on a continuous flow experimental system, whose reactor was made of Hastelloy C-276. Experimental conditions included a reaction temperature (T) ranging from 673 to 773K, a residence time (t) ranging from 72.7 to 339s, a constant pressure (P) of 25 MPa and a fixed oxidation coefficient (alpha) of 2.0. Experimental results indicated that reaction temperature and residence time had significant influences on the oxidation reaction, and increasing the two operation parameters could improve both degradation of chemical oxygen demand (COD) and ammonia nitrogen (NH3-N). The COD removal efficiency could reach up to 98.73% at 25 MPa, 773 K and 180.1 s, whereas the destruction efficiency of NH3-N was only 43.71%. We further carried out a kinetic analysis considering the induction period through free radical chain mechanism. It confirms that the power-law rate equation for COD removal was 345 exp(-52200/RT)[COD]1.98[O2]0.17 and for NH3-N removal was 500 exp(-64492.19/RT)[NH3-N]1.87 [O2]0.03. Moreover, the induction time formulations for COD and NH3-N were suspected to be exp(38250/RT)/173 and exp(55690/RT)/15231, respectively. Correspondingly, induction time changed from 2.22 to 5.38 s for COD and 0.38 to 1.38 s for NH3-N. Owing to the catalysis of reactor inner wall surface, more than 97% COD removal was achieved in all samples. PMID:24645473

Gong, Y M; Wang, S Z; Tang, X Y; Xu, D H; Ma, H H

2014-01-01

408

Techniques for determining total body water using deuterium oxide  

NASA Technical Reports Server (NTRS)

The measurement of total body water (TBW) is fundamental to the study of body fluid changes consequent to microgravity exposure or treatment with microgravity countermeasures. Often, the use of radioactive isotopes is prohibited for safety or other reasons. It was selected and implemented for use by some Johnson Space Center (JCS) laboratories, which permitted serial measurements over a 14 day period which was accurate enough to serve as a criterion method for validating new techniques. These requirements resulted in the selection of deuterium oxide dilution as the method of choice for TBW measurement. The development of this technique at JSC is reviewed. The recommended dosage, body fluid sampling techniques, and deuterium assay options are described.

Bishop, Phillip A.

1990-01-01

409

Water oxidation catalyzed by a dinuclear cobalt-polypyridine complex.  

PubMed

The dinuclear Co complex [(TPA)Co(?-OH)(?-O2 )Co(TPA)](ClO4 )3 (1, TPA=tris(2-pyridylmethyl)amine) catalyzes the oxidation of water. In the presence of [Ru(bpy)3 ](2+) and S2 O8 (2-) , photoinduced oxygen evolution can be observed with a turnover frequency (TOF) of 1.4±0.1?mol(O2 )?mol(1)(-1) ?s(-1) and a maximal turnover number (TON) of 58±5?mol(O2 )?mol(1)(-1) . The complex is shown to act as a molecular and homogeneous catalyst and a mechanism is proposed based on the combination of EPR data and light-driven O2 evolution kinetics. PMID:25348687

Wang, Hong-Yan; Mijangos, Edgar; Ott, Sascha; Thapper, Anders

2014-12-22

410

Supercritical water oxidation benchscale testing metallurgical analysis report  

SciTech Connect

This report describes metallurgical evaluation of witness wires from a series of tests using supercritical water oxidation (SCWO) to process cutting oil containing a simulated radionuclide. The goal of the tests was to evaluate the technology`s ability to process a highly chlorinated waste representative of many mixed waste streams generated in the DOE complex. The testing was conducted with a bench-scale SCWO system developed by the Modell Development Corporation. Significant test objectives included process optimization for adequate destruction efficiency, tracking the radionuclide simulant and certain metals in the effluent streams, and assessment of reactor material degradation resulting from processing a highly chlorinated waste. The metallurgical evaluation described herein includes results of metallographic analysis and Scanning Electron Microscopy analysis of witness wires exposed to the SCWO environment for one test series.

Norby, B.C.

1993-02-01