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Last update: November 12, 2013.
1

Water Cycle  

NSDL National Science Digital Library

4th Grade Science - Water Cycle Water Cycle two day interactive lesson plan. DAY 1: Welcome to the Water Cycle! Today we are going to be exploring and finding out more about the wonderful Water Cycle! For starters we are going to start with a movie, click the following link and watch the video and ...

Staley, Mrs.

2009-11-09

2

Preliminary evaluation of hybrid electrochemical-thermochemical cycles for the production of hydrogen from water. [Lead oxide cycle  

Microsoft Academic Search

Water decomposition cycles, of the hybrid type, involving an electrochemical cell producing hydrogen, and an oxide, and a subsequent thermochemical process loop which liberates oxygen and regenerates the lower oxide (or metal), are evaluated. A prototype cycle based on the oxides of lead: HO + PbO H + PbO (electrolysis) PbO PbO + ¹\\/O (thermal decomposition) is presented. In principle,

Munger

1976-01-01

3

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.

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

2012-01-01

4

Use of oxides in thermochemical water-splitting cycles for solar heat sources. Copper oxides. Revision  

SciTech Connect

Several oxides can be decomposed to oxygen and a lower oxide at temperatures that might be feasible with a solar heat source. Heat might be directly transmitted to the solid through an air window, rather than quartz, with release of oxygen to the atmosphere. The cycle involving CuO, I/sub 2/, and Mg(OH)/sub 2/ is similar to the previous Co/sub 3/O/sub 4/-CoO cycle. The difficulty is the formation of CuI as a metastable intermediate. The oxidation of CuI is thermodynamically very favorable, but its rate limits completion. Excess Mg(OH)/sub 2/ appears to increase the rate but not to the point where IO/sub 3//sup -/ oxidation of CuI competes with oxidation of Cu/sub 2/O. Nevertheless, the batch runs suggest that about 98% of the maximum possible MgI/sub 2/ could be formed in the cycle reaction. Cuprous iodide complexes formed in the concentrated MgI/sub 2/ may give the necessary improvement by providing a solution path for their oxidation by iodate. Work of others pertaining to the cycle is briefly discussed.

Jones, W.M.; Bowman, M.G.

1984-01-01

5

Use of oxides in thermochemical water-splitting cycles for solar heat sources. Copper oxides  

SciTech Connect

Several oxides can be decomposed to oxygen and a lower oxide at temperatures that might be feasible with a solar heat source. Heat might be directly transmitted to the solid through an air window, rather than quartz, with release of oxygen to the atmosphere. The cycle utilizing CuO, I/sub 2/, and Mg (OH)/sub 2/ is similar to the previous Co/sub 3/O/sub 4/ - CoO cycle. We are concentrating on the reformation of CuO. At 448 K the rate is favorable; for example, the yield rises about linearly with time to 92% at 1.17 h and more slowly thereafter. The only difficulty is the formation of CuI as a metastable intermediate. The oxidation of CuI is thermodynamically very favorable, but its rate limits completion. Excess Mg(OH)/sub 2/ appears to increase the rate but not to the point where IO/sub 3//sup -/ oxidation of CuI competes with oxidation of Cu/sub 2/O. Nevertheless, the batch runs suggest that about 98% of the maximum possible MgI/sub 2/ could be formed. Cuprous iodide complexes formed in the concentrated MgI/sub 2/ may give the necessary improvement by providing a solution path for their oxidation by iodate. Work of others pertaining to the cycle is briefly discussed.

Jones, W.M.; Bowman, M.G.

1984-01-01

6

Water-oxidation catalysis by manganese in a geochemical-like cycle  

NASA Astrophysics Data System (ADS)

Water oxidation in all oxygenic photosynthetic organisms is catalysed by the Mn4CaO4 cluster of Photosystem II. This cluster has inspired the development of synthetic manganese catalysts for solar energy production. A photoelectrochemical device, made by impregnating a synthetic tetranuclear-manganese cluster into a Nafion matrix, has been shown to achieve efficient water oxidation catalysis. We report here in situ X-ray absorption spectroscopy and transmission electron microscopy studies that demonstrate that this cluster dissociates into Mn(II) compounds in the Nafion, which are then reoxidized to form dispersed nanoparticles of a disordered Mn(III/IV)-oxide phase. Cycling between the photoreduced product and this mineral-like solid is responsible for the observed photochemical water-oxidation catalysis. The original manganese cluster serves only as a precursor to the catalytically active material. The behaviour of Mn in Nafion therefore parallels its broader biogeochemistry, which is also dominated by cycles of oxidation into solid Mn(III/IV) oxides followed by photoreduction to Mn2+.

Hocking, Rosalie K.; Brimblecombe, Robin; Chang, Lan-Yun; Singh, Archana; Cheah, Mun Hon; Glover, Chris; Casey, William H.; Spiccia, Leone

2011-06-01

7

The Water Cycle  

NSDL National Science Digital Library

4th Grade Science Learn all about the Water Cycle! The Water Cycle: Water Storage Learn about Evaporation, Condensation, Precipitation, and Collection! The Water Cycle Here are some activites to learn about the water cycle. Hydrologic Cycle ...

Andrus, Ms.

2007-10-12

8

Discovering the Water Cycle!  

NSDL National Science Digital Library

We will be learning about what the water cycle is and how it works. Resources! The Hydrologic Cycle: Water's journey through time The Water Cycle Thirstin's Water Cycle Activity Water evaporates from the surface Water Wonders These are a collection of websites that are going to help us in our journey of discovering what the water cycle is. ...

Mortensen, Miss

2009-10-09

9

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

10

THE WATER CYCLE/ CLOUDS  

NSDL National Science Digital Library

Students will learn about the water cycle and how it works. You will explore many resources to find out many new factors about the water cycle. What is the water cycle? National water cycle Name the 4 water parts of the water cycle? Weather wonders Where are 3 places that the water cycle exists- What happens after condensation? animated water cycle Name 4 types of clouds? What is the highest level cloud called? Which cloud is associated with powerful thunderstorms? Cloud Types What do clouds have to do with the water cycle? National water cycle What is ...

Ms.brown

2009-04-06

11

The Water Cycle  

NSDL National Science Digital Library

Students will understand and explain parts of the water cycle. First watch the video to get a background about the water cycle: water cycle video Draw and explain the water cycle in your own words (include the terms: evaporation, condensation, precipitation, at least 3 bodies of water, the sun). Before reading the experiment record your predictions: If you put a small amount of water ...

Amanda, Miss

2011-02-14

12

The Water Cycle  

NSDL National Science Digital Library

Today you will explore the water cycle. Please visit the following websites (in order!) to gather information about the water cycle. Fill out your Information Sheet as you go. 1. Water cycle story 2. Water Cycle--heat 3. animation (Make sure to read the captions at the bottom!) ...

Hauck, Mrs.

2006-08-26

13

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

14

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 such as evapotranspiration, and water storage. 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.

15

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.

Sciences, California A.

2008-01-01

16

Water Cycle Animation  

NSDL National Science Digital Library

The water cycle is Earth's natural mechanism for transporting and recycling water between the surface and the atmosphere. Through the processes of condensation, precipitation, infiltration, runoff, transpiration, and evaporation, water continuously travels from the atmosphere to the ground and back again. In this animation from NASA, users can observe the steps of the water cycle. The segment is fifty-two seconds in length.

17

The Water Cycle  

NSDL National Science Digital Library

Students will work with interactive internet resources to learn all about the water cycle. Fourth Grade Science Standard 1 Objective 2: Describe the water cycle. Locate examples of evaporation and condensation in the water cycle (e.g., water evaporates when heated and clouds or dew forms when vapor is cooled). Describe the processes of evaporation, condensation, and precipitation as they relate to the water cycle. Identify locations that hold water as it passes through the water cycle (e.g., oceans, atmosphere, fresh surface water, snow, ice, and ground water). Construct a model or diagram to show how water continuously moves through the water cycle over time. Describe how the water cycle relates to the water supply in your community. Web Quest Links Introduction Task Resources Evaluation Conclusion Teacher Guide Introduction Have you ever wondered how water gets from oceans, lakes, streams, or clouds into your glass? Check out the following links to learn more about it! TASK Start out by learning the concepts in this song from Bill Nye! Bill Nye the Science Guy- Water Cycle Jump Look ...

Lish, Ms.

2009-04-06

18

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

19

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.

Jersey, New; Center, Liberty S.; Coalition, New J.

2006-01-01

20

Water Cycle Game  

NSDL National Science Digital Library

Through role-play as a molecule of water, students gain a better understanding for the complexity of the movement of water. Nine stations are set-up for each of the water cycle compartments (animal, cloud, glacier, ground water, lake, ocean, plant, river, soil). At each station, a roll of the dice tells each student where to move next. Colored trackers record each studentâs unique journey through the water cycle to compare to others' journeys later on. Students will identify the states of water, and when water changes states as it moves through its cycle. This game is meant to be played with a group of people, so that the path each player takes can be compared with everyone elseâs.

Usgs

2009-11-24

21

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.

22

Global Water Cycle.  

National Technical Information Service (NTIS)

This research is the MSFC component of a joint MSFC/Pennsylvania State University Eos Interdisciplinary Investigation on the global water cycle extension across the earth sciences. The primary long-term objective of this investigation is to determine the ...

F. Robertson S. J. Goodman J. R. Christy D. E. Fitzjarrald S. Chou

1993-01-01

23

The Water Cycle  

NSDL National Science Digital Library

We are about to enter into the world of science and discover many new things about the water cycle. Introduction Below is a list of websites I have created for you to go and do certain activities. I will give you directions of things I would like for you to do at each website. All About The Water Cycle Here is a game you can play. ...

Jenny

2008-11-17

24

Water Cycle Model Building  

NSDL National Science Digital Library

The resource is a model building activity which uses simple materials to create a working representation of the water cycle. The resource also includes background information on the water cycle for the teacher, learning goals, alignment to National Science Education Standards and AAAS Benchmarks for Science Literacy, and assessment ideas, including questions for students. The resource includes suggested modifications for classrooms with limited supplies and/or with non-English speaking students.

25

The Other Water Cycle  

NSDL National Science Digital Library

For students that have already been introduced to the water cycle this lesson is intended as a logical follow-up. Students will 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 activities, students will learn about permeability and compare the permeability of several different materials for the purpose of engineering landscape drainage systems.

Engineering K-Ph.d. Program

26

Wet oxidation of concentrated wastewaters of paper mills for water cycle closing  

Microsoft Academic Search

Experimental research into wet oxidation of concentrated wastewaters from paper mills was undertaken. Evaporation and membrane concentrates from paper mills were selected as experimental objects. The aim of the wet oxidation of the paper mill concentrates was to reduce the concentration of organics and to improve biodegradability of the concentrates. The effect of temperature, pH and the influence of homogeneous

S Verenich; A Laari; J Kallas

2000-01-01

27

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.

28

Global Water Cycle.  

National Technical Information Service (NTIS)

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 ar...

F. R. Robertson J. R. Christy S. J. Goodman T. L. Miller D. Fitzjarrald

1991-01-01

29

Reaction experiments for thermochemical water-splitting. [Classes of cycles: metal-metal oxide; metal oxide-metal hydroxide; metal oxide-metal sulfate; metal-metal halide; metal oxide-metal halide  

Microsoft Academic Search

Almost all known pure thermochemical hydrogen production cycles can be grouped into five generic classes, each involving either a metal oxide or a metal halide as an intermediate. In general, those cycles with the highest-temperature endothermic reactions and the least number of reactions are the most efficient. This is expected because thermochemical cycles are special types of heat engines. The

J. Gahimer; J. Pangborn; S. Foh; M. Mazumder; R. Stotz

1976-01-01

30

Make a Water Cycle Wristband  

NSDL National Science Digital Library

In this activity on page 4 of the PDF, learners thread colored beads onto string. Each beach represent a process of the water cycle. This resource contains a diagram showing the water cycle and provides definitions for related keywords.

Society, American C.

2013-07-08

31

The International Water Cycle Workshop  

Microsoft Academic Search

Scientists from Japan, Europe, and the United States met at the International Water Cycle Workshop, in Seattle, Washington, last summer. The goals of this workshop were to review a draft implementation of the water cycle component to the Global Earth Observing System of Systems (GEOSS), and to develop a companion ``water cycle road map'' that would provide specific actions and

Norman L. Miller; Toshio Koike; Eric F. Wood; Richard Lawford; Einar-Arne Herland

2005-01-01

32

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

33

Precipitation and the Water Cycle.  

National Technical Information Service (NTIS)

Details of the hydrological cycle are considered together with the Global Energy and Water Cycle Experiment (GEWEX) established to observe, understand, model and eventually predict variations of the global hydrological regimes, including changes in region...

K. Browning

1991-01-01

34

The water cycle for kids  

USGS Publications Warehouse

The U.S. Geological Survey (USGS) and the Food and Agriculture Organization of the United Nations (FAO) have created a water-cycle diagram for use in elementary and middle schools. The diagram is available in many languages. This diagram is part of the USGS's Water Science School, in which the water cycle is described in detail.

Neno, Stephanie; Morgan, Jim; Zonolli, Gabriele; Perlman, Howard; Gonthier, Gerard

2013-01-01

35

Weather and The Water Cycle  

NSDL National Science Digital Library

Students will be able to do activities dealing with weather and water cycles. Learn what makes weather wet and wild, forcast and predict weather. Webweather For Kids Learn about tornadoes and hurricanes. Kidstorm Learn about the water cycles. water Cycles Now click on the following link: Interactive weather maker 1. How much change in temperature is needed to make it snow? On the right side of the page click on Weather Detective Web Quest. Follow the ...

Merritt, Mrs.

2005-10-15

36

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

37

Studies on thermochemical water-splitting cycles  

Microsoft Academic Search

The purpose of this program was to assess the electrochemical oxidation of sulfur dioxide in relative dilute (less than 50 weight percent) sulfuric acid and to determine the preferred operating conditions (acid concentration, temperature, electrode materials) for such a cell to be mated with a metal oxide-metal sulfate water-splitting cycle. Our rough performance goals were 200 mA\\/cm² at 0.5 V.

R. J. Remick; S. E. Foh

1980-01-01

38

Studies on thermochemical water-splitting cycles  

Microsoft Academic Search

The electrochemical oxidation of sulfur dioxide in relative dilute (less than 50 weight percent) sulfuric acid was assessed, and the preferred operating conditions (acid concentration, temperature, electrode materials) for such a cell to be mated with a metal oxide metal sulfate water splitting cycle was determined. Rough performance goals were 200 mA\\/sq cm at 0.5 V. A sulfuric acid concentration

R. J. Remick; S. E. Foh

1981-01-01

39

Studies on thermochemical water-splitting cycles  

Microsoft Academic Search

Thermochemical water-splitting cycles that use solid metal sulfates instead of sulfuric acid appear to offer the advantage of allowing the electrolytic oxidation of sulfurous acid to take place in relatively dilute solutions where anodic overpotential is expected to be minimized. The Institute of Gas Technology is investigating such systems in order to define preferred operating conditions and performance for the

R. J. Remick; S. E. Foh

1979-01-01

40

The Mars water cycle  

Microsoft Academic Search

A model has been developed to test the hypothesis that the observed seasonal and latitudinal distribution of water on Mars is controlled by the sublimation and condensation of surface ice deposits in the Arctic and Antarctic, and the meridional transport of water vapor. Besides reproducing the observed water vapor distribution, the model correctly reproduces the presence of a large permanent

D. W. Davies

1981-01-01

41

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. From approximately 1:20 to 1:35 (narration of Âreservoir to "lies in the oceanÂ), the representation employs a diagram, narration and a pie chart to emphasize the key idea that water collects in rivers and lakes and most of it flows back into the oceans.

42

The Water Cycle  

NSDL National Science Digital Library

This is a Macromedia Flash Player enhanced website developed by the EPA. The website is divided into four sections: rain, water storage, vapor, and clouds. In the Rain section, students can discover the forms of precipitation and why it occurs. Through the short, interactive module, individuals can learn about the development of aquifers, transpiration, and condensation. This is a great website for young students to grasp the connections between different forms of water.

43

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

44

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

45

Grades 3-4 Water Cycle  

Microsoft Academic Search

This is a science lesson for students in grade three and four on the water cycle. Through this lesson students will be able to give an accurate and detailed description of the water cycle including the process that accompany it (evaporation, condensation, and precipitation). Students will understand that water changes into different forms of matter throughout the water cycle and

Gina Camilli

2009-01-01

46

Concept of innovative water reactor for flexible fuel cycle (FLWR)  

Microsoft Academic Search

In order to ensure sustainable energy supply in the future based on the matured light water reactor (LWR) and coming mixed oxide (MOX)-LWR technologies, a concept of innovative water reactor for flexible fuel cycle (FLWR) has been investigated in Japan Atomic Energy Research Agency (JAEA). The concept consists of two parts in the chronological sequence. The first part realizes a

T. Iwamura; S. Uchikawa; T. Okubo; T. Kugo; H. Akie; Y. Nakano; T. Nakatsuka

2006-01-01

47

EMERGING CONTAMINANTS IN THE DRINKING WATER CYCLE  

EPA Science Inventory

PRESENTATION OUTLINE: I. General overview of the water cycle; II. USEPA and USGS Research; a. Wastewater treatment plant (WWTP) effluents and downstream surface waters; b. Groundwater down gradient from WW lagoon; c. Source and finished water fro...

48

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

49

Catalytic water oxidation: Rugged water-oxidation anodes  

Microsoft Academic Search

The efficient catalytic oxidation of water to dioxygen in the solid state is one of the challenges to be overcome to build sun-driven and\\/or electrocatalytic water-splitting devices. Now, an effective water-oxidation hybrid catalyst system has been made by attaching a ruthenium-polyoxometallate complex to a carbon nanotube.

Antoni Llobet

2010-01-01

50

Nitric oxide in the human respiratory cycle  

Microsoft Academic Search

Interactions of nitric oxide (NO) with hemoglobin (Hb) could regulate the uptake and delivery of oxygen (O2) by subserving the classical physiological responses of hypoxic vasodilation and hyperoxic vasconstriction in the human respiratory cycle. Here we show that in in vitro and ex vivo systems as well as healthy adults alternately exposed to hypoxia or hyperoxia (to dilate or constrict

Timothy J. McMahon; Richard E. Moon; Ben P. Luschinger; Martha S. Carraway; Anne E. Stone; Bryant W. Stolp; Andrew J. Gow; John R. Pawloski; Paula Watke; David J. Singel; Claude A. Piantadosi; Jonathan S. Stamler

2002-01-01

51

Creative Writing and the Water Cycle.  

ERIC Educational Resources Information Center

Uses the story "The Life of a Drop of Water" to initiate a creative writing activity and teach about the water cycle. Attempts to stimulate students' understanding of a scientific concept by using their imaginations. (YDS)

Young, Rich; Virmani, Jyotika; Kusek, Kristen M.

2001-01-01

52

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.

53

Modeling the Martian seasonal water cycle  

Microsoft Academic Search

Ever since the observations of Percival Lowell, the annual cycle of Martian water has been a fascinating topic in planetary exploration. Observations by the Viking Orbiter, supplemented by Earth-based microwave and infrared observations, have given us a reasonable picture of this cycle. We are now also able to model the cycle using our Mars Climate Model, a simplified atmospheric general

Howard Houben; Robert M. Haberle; Richard E. Young; Aaron P. Zent

1997-01-01

54

Global Changes of the Water Cycle Intensity.  

National Technical Information Service (NTIS)

In this study, we evaluate numerical simulations of the twentieth century climate, focusing on the changes in the intensity of the global water cycle. A new diagnostic of atmospheric water vapor cycling rate is developed and employed, that relies on const...

M. G. Bosilovich S. D. Schubert G. K. Walker

2003-01-01

55

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

56

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

57

Modelling the Krebs cycle and oxidative phosphorylation.  

PubMed

The Krebs cycle and oxidative phosphorylation are the two most important sets of reactions in a eukaryotic cell that meet the major part of the total energy demands of a cell. In this paper, we present a computer simulation of the coupled reactions using open source tools for simulation. We also show that it is possible to model the Krebs cycle with a simple black box with a few inputs and outputs. However, the kinetics of the internal processes has been modelled using numerical tools. We also show that the Krebs cycle and oxidative phosphorylation together can be combined in a similar fashion - a black box with a few inputs and outputs. The Octave script is flexible and customisable for any chosen set-up for this model. In several cases, we had no explicit idea of the underlying reaction mechanism and the rate determining steps involved, and we have used the stoichiometric equations that can be easily changed as and when more detailed information is obtained. The script includes the feedback regulation of the various enzymes of the Krebs cycle. For the electron transport chain, the pH gradient across the membrane is an essential regulator of the kinetics and this has been modelled empirically but fully consistent with experimental results. The initial conditions can be very easily changed and the simulation is potentially very useful in a number of cases of clinical importance. PMID:23528175

Korla, Kalyani; Mitra, Chanchal K

2013-03-25

58

Modelling the urban water cycle  

Microsoft Academic Search

Current urban water management practices aim to remove stormwater and wastewater efficiently from urban areas. An alternative approach is to consider stormwater and wastewater as a potential resource substitute for a portion of the water imported via the reticulated supply system. A holistic view of urban water resources provides the framework for the evaluation of the demand for water supply,

V. G. Mitchell; R. G. Mein; T. A. Mcmahon

2001-01-01

59

Evolution of the Martian water cycle  

Microsoft Academic Search

The current Martian water cycle is extremely asymmetric, with large amounts of vapor subliming off a permanent north polar water ice cap in northern summer, but with no apparent major source of water vapor in the southern hemisphere. Detailed simulations of this process with a three-dimensional circulation model indicate that the summertime interhemispheric exchange (Hadley cell) is very much stronger

H. Houben; R. M. Haberle; R. E. Young; A. P. Zent

1997-01-01

60

The Doe Water Cycle Pilot Study  

Microsoft Academic Search

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

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

2005-01-01

61

The water-water cycle as alternative photon and electron sinks.  

PubMed Central

The water-water cycle in chloroplasts is the photoreduction of dioxygen to water in photosystem I (PS I) by the electrons generated in photosystem II (PS II) from water. In the water-water cycle, the rate of photoreduction of dioxygen in PS I is several orders of magnitude lower than those of the disproportionation of superoxide catalysed by superoxide dismutase, the reduction of hydrogen peroxide to water catalysed by ascorbate peroxidase, and the reduction of the resulting oxidized forms of ascorbate by reduced ferredoxin or catalysed by either dehydroascorbate reductase or monodehydroascorbate reductase. The water-water cycle therefore effectively shortens the lifetimes of photoproduced superoxide and hydrogen peroxide to suppress the production of hydroxyl radicals, their interactions with the target molecules in chloroplasts, and resulting photoinhibition. When leaves are exposed to photon intensities of sunlight in excess of that required to support the fixation of CO2, the intersystem electron carriers are over-reduced, resulting in photoinhibition. Under such conditions, the water-water cycle not only scavenges active oxygens, but also safely dissipates excess photon energy and electrons, in addition to downregulation of PS II and photorespiration. The dual functions of the water-water cycle for protection from photoinhibition under photon excess stress are discussed, along with its functional evolution.

Asada, K

2000-01-01

62

Understanding the boiling water reactor limit cycle  

SciTech Connect

This paper presents an interpretation of the physical mechanisms involved in the development of limit cycle oscillations in boiling water reactors (BWRs). Based on this interpretation, approximate correlations for some oscillation parameters are developed and shown to be largely independent of the particular reactor operating condition. The stability of the limit cycle is also studied in this paper. It is shown that the BWR limit cycle may become unstable and bifurcate. The bifurcation process leads to aperiodic (chaotic) behavior of the reactor power and causes the peak oscillation powers to be larger than those from a nonbifurcated limit cycle. 7 refs., 6 figs., 1 tab.

March-Leuba, J.

1989-01-01

63

ENGINEERING BULLETIN: SUPERCRITICAL WATER OXIDATION  

EPA Science Inventory

This engineering bulletin presents a description and status of supercritical water oxidation technology, a summary of recent performance tests, and the current applicability of this emerging technology. This information is provided to assist remedial project managers, contractors...

64

ENGINEERING BULLETIN: SUPERCRITICAL WATER OXIDATION  

EPA Science Inventory

This engineering bulletin presents a description and status of supercritical water oxidation technology, a summary of recent performance tests, and the current applicability of this emerging technology. his information is provided to assist remedial project managers, contractors ...

65

Life Cycle Assessment of Water Recycling Technology  

Microsoft Academic Search

Environmental performance of different water recycling technologies is compared on the basis of the associated potential environmental impacts using the technique of Life Cycle Assessment (LCA). The LCA method is used here to support decision making in water recycling in terms of (1) comparison and selection of suitable technology and (2) identification of opportunities to enhance the environmental performance of

N. Tangsubkul; P. Beavis; S. J. Moore; S. Lundie; T. D. Waite

2005-01-01

66

The NASA Energy and Water cycle Study  

NASA Astrophysics Data System (ADS)

In 2003 NASA established the NASA Energy and Water-cycle Study (NEWS), whose long-term grand challenge is to document and enable improved, observationally based, predictions of water and energy cycle consequences of Earth system variability and change. Over the past two years, the NEWS team has been working on how to refine its approach to science integration . To this end, NEWS has created four working groups that identify integration needs and make the needed connections to partner and coordinate with water & energy cycle research and application activities going on at other organizations within NASA, nationally, and internationally. The four groups are: (1) Drought & Flood Extremes- including water and energy aspects of abrupt climate change, (2) Evaporation & Latent Heating - including both land and ocean, (3) Water and Energy Cycle Climatology - to exploit and influence evolving observing systems, and (4) Modeling & Water Cycle Prediction - foster interaction with the global modeling community. The first phase of NEWS focuses on the first coordinated attempt to describe the complete global energy and water cycle using existing and forthcoming satellite and ground based observations, and laying the foundation for essential NEWS developments in model representations of atmospheric energy and water exchange processes. This comprehensive energy and water data analysis program must exploit crucial datasets, some still requiring complete re-processing, and new satellite measurements. These data products will then be evaluated for accuracy and consistency, in part by using them in the first diagnosis of the weather-scale (space and time) variations of the global energy and water cycle over the past one-two decades. The primary objective is to ensure that results of this analysis effort serve as a recognized data basis to compare with corresponding climate statistics produced by existing climate models, quantify systematic deficiencies, and identify needed improvements. The data records to be produced through these efforts are mandatory for developing and validating models that meet NEWS scientific requirements. At the same time, NEWS implementation calls for the development of radically new model representations of energy and water exchange processes that resolve significant process scales and spatial variability in ground boundary conditions. Such process-resolving models may be first constructed as independent stand-alone modules that can be tested against ad hoc field measurements and systematic observations at selected experimental sites. At a later stage, the codes may be simplified through statistical sampling of process-scale variables or otherwise reduced to generate integrated fluxes representative of each grid-element in a climate model. Finally, the implementation plan calls for broad exploration of potential new observing techniques concerning all aspects of the energy and water cycle, and initiating relevant technical feasibility and scientific benefit studies.

Houser, P. R.; Entin, J. K.; Schiffer, R. A.; Belvedere, D. R.

2010-12-01

67

Some alternatives to the mixed oxide fuel cycle  

Microsoft Academic Search

While on initial examination each of the six fuel cycle concepts (tandem cycle, extended burnup, fuel rejuvenation, coprocessing, partial reprocessing, and thorium) described in the report may have some potential for improving safeguards, none of the six appears to have any other major or compelling advantages over the mixed oxide (MOX) fuel cycle. Compared to the MOX cycle, all but

D. E. Deonigi; E. A. Eschbach; S. Goldsmith; P. J. Pankaskie; C. A. Rohrmann; R. D. Widrig

1977-01-01

68

Evolution of the Martian water cycle.  

PubMed

The current Martian water cycle is extremely asymmetric, with large amounts of vapor subliming off a permanent north polar water ice cap in northern summer, but with no apparent major source of water vapor in the southern hemisphere. Detailed simulations of this process with a three-dimensional circulation model indicate that the summertime interhemispheric exchange (Hadley cell) is very much stronger than transport by eddies in other seasons. As a result, water ice would be distributed globally were it not for the buffering action of regolith soil adsorption which limits the net flux of water vapor off the north polar cap to amounts that are insignificant even on the scale of thousands of years. It has been suggested that the polar layered deposits are the result of exchange on these long time scales, driven by changes in Martian orbital parameters. We therefore are conducting simulations to test the effect of varied orbital parameters on the Martian water cycle. We find that when the perihelion summer pole is charged with a polar water ice cap, large quantities of water are quickly transfered to the aphelion summer pole, setting up an annual cycle that resembles the present one. Thus, the adsorptivity of the Martian regolith may be in the narrow range where it can limit net transport from the aphelion but not the perihelion pole. PMID:11543274

Houben, H; Haberle, R M; Young, R E; Zent, A P

1997-01-01

69

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

70

Investigating the Water Cycle: Using Plants to Study Evaporation  

NSDL National Science Digital Library

In this science activity, students investigate the water cycle by testing the water evaporated from leaves (transpiration) in a field experience. Students use elements of this information to track the water cycle through it's various stages.

71

Modeling the Martian seasonal water cycle  

NASA Astrophysics Data System (ADS)

Ever since the observations of Percival Lowell, the annual cycle of Martian water has been a fascinating topic in planetary exploration. Observations by the Viking Orbiter, supplemented by Earth-based microwave and infrared observations, have given us a reasonable picture of this cycle. We are now also able to model the cycle using our Mars Climate Model, a simplified atmospheric general circulation model designed specifically for this purpose. We find that a thin adsorbing layer of the Martian regolith plays a fundamental role in the water cycle, limiting the lower atmospheric relative humidity and preventing the formation of widespread ice deposits at low latitudes. We are thus able to estimate a large-scale average value of the specific soil surface area of this regolith. Water which evaporates from the permanent north polar ice cap during summer is returned by a process of repeated evaporation and precipitation on the retreating seasonal cap the following spring, so that the global inventory of water outside the polar caps ranges within narrow limits. (There is a small net annual deposition of water ice at the south polar cap which is always at dry ice temperatures.) If ice on the residual south polar cap is exposed during the summer, it rapidly sublimes, generating vapor amounts similar to those observed in northern summer. Recovery to normal dry conditions in the southern atmosphere occurs very rapidly in the next year. Such an event could explain the otherwise anomalous Earth-based pre-Viking observations of a wet southern summer. If southern ice deposits at lower latitudes are exposed, the vapor can be transferred irreversibly through the strong Hadley cell to the north polar cap. We therefore speculate that the asymmetry of Mars' current orbit is responsible for the asymmetry of the present water distribution (with extensive permanent water ice deposits located only in the colder, aphelion summer, northern hemisphere).

Houben, Howard; Haberle, Robert M.; Young, Richard E.; Zent, Aaron P.

1997-04-01

72

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

73

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

74

Nature and Stability of the Martian Seasonal Water Cycle  

Microsoft Academic Search

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

M. I. Richardson; R. J. Wilson

2001-01-01

75

Circadian clock NAD+ cycle drives mitochondrial oxidative metabolism in mice.  

PubMed

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

2013-09-19

76

North American water and energy cycles  

NASA Astrophysics Data System (ADS)

Closure of the water and energy cycles for North America has been improved by combining several new data sets to provide an integrated view from 1979 to 2010. We use new global atmospheric reanalyses, top-of-atmosphere radiation, surface fluxes including evaporation E and precipitation P, streamflow and river discharge, and Gravity Recovery and Climate Experiment estimates of water storage and its tendency. The atmospheric moisture budget provides more reliable estimates and reproducible time series of E-P than separate estimates of E and P. The excess of P over E is greatest in winter largely because of changing evapotranspiration, whereas precipitation is largest in summer. The annual mean loss of energy to space of 33 W m-2 is compensated for nearly equally by transports of dry static energy and latent energy onto land. The annual cycle (amplitude of ~20 W m-2) of implied downward surface flux corresponds to changes in surface and soil temperatures and seasonal snowmelt.

Trenberth, Kevin E.; Fasullo, John T.

2013-01-01

77

Efficient generation of H2 by splitting water with an isothermal redox cycle.  

PubMed

Solar thermal water-splitting (STWS) cycles have long been recognized as a desirable means of generating hydrogen gas (H2) from water and sunlight. Two-step, metal oxide-based STWS cycles generate H2 by sequential high-temperature reduction and water reoxidation of a metal oxide. The temperature swings between reduction and oxidation steps long thought necessary for STWS have stifled STWS's overall efficiency because of thermal and time losses that occur during the frequent heating and cooling of the metal oxide. We show that these temperature swings are unnecessary and that isothermal water splitting (ITWS) at 1350°C using the "hercynite cycle" exhibits H2 production capacity >3 and >12 times that of hercynite and ceria, respectively, per mass of active material when reduced at 1350°C and reoxidized at 1000°C. PMID:23908235

Muhich, Christopher L; Evanko, Brian W; Weston, Kayla C; Lichty, Paul; Liang, Xinhua; Martinek, Janna; Musgrave, Charles B; Weimer, Alan W

2013-08-01

78

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

79

A general circulation model study of the Mars water cycle  

Microsoft Academic Search

This study has focused on the development and application of the first fully three-dimensional model of the current Mars water cycle. Previous models of the water cycle have suggested the importance of transport processes in determining the observed variations in atmospheric water [Jakosky and Haberle (1992)]. This work addresses questions regarding the relative importance of water reservoirs, transport of water,

Mark Ian Richardson

1999-01-01

80

Human–bacteria nitric oxide cycles in HIV1 infection  

Microsoft Academic Search

The human intestinal tract harbors a complex microbiotic environment containing commensal bacteria and immunocompetent mucosal cells. There is considerable communication between the bacteria and host cells through dietary constituents and metabolic cycles. We propose that in the pathogenesis of acquired immunodeficiency syndrome (AIDS), the human immunodeficiency virus-1 (HIV-1) triggers a change in a coupled transorganism (human–bacteria) nitric oxide interchange cycle,

H. Zhang; D. Boring; H. Haverkos

2002-01-01

81

Hydrologic Cycle and Water Balance Equation  

NSDL National Science Digital Library

This exercise is designed to evaluate the students' understanding of both the hydrologic cycle and the water budget (mass balance) equation. In my course, the exercise is the students' first exposure to models in the course. While the exercise may seem basic, students gain experience in creating conceptual models and then generating mathematical models from the conceptual model. The exercise provides students with an introduction (or refresher) to some basic Excel formulas. Finally, the exercise can be modified to include more "what if" scenarios that require critical thinking and analysis from the students.

Peterson, Eric

82

Uranium Oxidation: Characterization of Oxides Formed by Reaction with Water.  

National Technical Information Service (NTIS)

Three different uranium oxide samples have been characterized with respect to the different preparation techniques. Results show that the water reaction with uranium metal occurs cyclically forming laminar layers of oxide which spall off due to the strain...

E. L. Fuller J. B. Condon M. H. Eager N. R. Smyrl

1983-01-01

83

Fe-Oxides in Water Remediation Technologies  

NASA Astrophysics Data System (ADS)

Water is essential for life, a strategic resource for every country and population. Its availability and sanitary safety is highly connected with the health and economic status of a population. The burden of disease due to polluted water is a major public health problem throughout the world. Many pollutants in water streams have been identified as toxic and harmful to the environment and human health, and among them arsenic, mercury and cadmium are considered those with the highest priority. Iron is the fourth most abundant element in the Earth's crust, and reactions involving iron play a major role in the environmental cycling of a range of important contaminants. Our earlier research has shown that Fe oxides/oxyhydroxides are particularly effective adsorbents of a range of contaminants (toxic metals), due to their high (reactive) specific surface area. It has been proven that Fe is particularly effective in As removal as a chemical bond is created on Fe surface and As is stabilised and can be safely deposited. Removal of contaminants from waste streams through precipitation with (hydrous) ferric oxides is an established methodology in a number of industrial processes (high density sludge systems for arsenic control in effluents from the mining industry, and in the treatment of textile dye effluent).

Vaclavikova, M.; Stefusova, K.; Gallios, G. P.

84

Anticipated changes in the global atmospheric water cycle  

Microsoft Academic Search

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

Richard P Allan; Beate G Liepert

2010-01-01

85

INTRODUCTION: Anticipated changes in the global atmospheric water cycle  

Microsoft Academic Search

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

Richard P. Allan; Beate G. Liepert

2010-01-01

86

The Hydrologic Cycle: Water's journey through time  

NSDL National Science Digital Library

This module discusses the hydrologic cycle and its impacts on the planet Earth. Additionally, the module addresses connections between the hydrologic cycle, climate and the impacts humans have had on the cycle.

Egger, Anne

2003-08-26

87

Chromium cycling in soils and water: links, gaps, and methods.  

PubMed Central

The major links in the cycling of chromium in soils and in natural waters are between chromium(III) and chromium (VI). Between the larger links are lesser links involving processes of mobilization and oxidation of CrIII and reduction of CrVI. The gaps are mainly in our understanding of the factors that control these processes. If soluble CrIII is added to an "average" soil, a portion of it will become immediately oxidized by manganese oxides to CrVI. The rest of the CrIII may remain reduced for long periods of time, even in the presence of electron-accepting manganese oxides. However, this less available CrIII can be mobilized by low molecular weight organic complexers and then oxidized where redox conditions are optimal. Usually part of any CrVI added to a soil or sediment will be reduced instantly, especially under acid conditions. On the other hand, high concentrations of polluting CrVI may quickly exhaust the readily available reducing power of the matrix material and excess CrVI, the thermodynamically stable form in air, may persist for years in soils or lagoons without reduction. Cleanup of chromium pollution must involve the surrounding of both CrIII and CrVI with excesses of slowly available reducing substances and sealing them permanently from inputs of atmospheric oxygen. Monitoring the effectiveness of the measures is mandatory, but fortunately the chemical testing for CrVI in soil and water is simple and problem free compared with most colorimetric determinations.

Bartlett, R J

1991-01-01

88

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 âÂÂready-to-goâ lessson on the water cycle and global warming online, and itâÂÂs a true delight. As with the other lessons in this series, the materials here include a brief description of the lessonâÂÂs 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 âÂÂState of the Climate Reportâ offered from the National Climatic Data Center.

89

8 Water Cycle in the Atmosphere and Shallow Subsurface  

Microsoft Academic Search

The global water cycle on Earth constitutes one of the most relevant components of the terrestrial ecosystem. While the vast majority of terrestrial water is stored in the world oceans, the perpetual cycle of water between ocean, atmosphere and land in all three phases is recognised as one basic feature that characterises the Earth, and is contrasted to the rest

Tetsuya Tokano

2005-01-01

90

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

91

Methotrexate: pentose cycle and oxidative stress.  

PubMed

The effect of methotrexate (MTX) and leucovorin (LCV) on pentose cycle enzymes and the activity of enzymes involved in enzyme defence mechanisms against ROS in HeLa cells, were studied. The effect of MTX was also investigated on the cellular levels of glutathione. MTX inhibited the activity of glucose-6-phosphate and 6-phosphogluconate dehydrogenases. The activities of glutathione reductase and gamma-glutamylcysteine synthetase were also inhibited by the drug. No effect was observed on the activities of catalase, superoxide dismutase or transketolase. LCV had no effect on any of the enzymes studied. MTX decreased the cellular levels of glutathione (70 per cent), while the presence of LCV and glutamine did not interfere with the effect of MTX. The net results appear to show that the biological situation resulting from treatment with MTX leads to a reduction of effectiveness of the antioxidant enzyme defence system. PMID:9857491

Babiak, R M; Campello, A P; Carnieri, E G; Oliveira, M B

1998-12-01

92

Low Temperature Cycling of Partially Oxidized Submicron Magnetites  

NASA Astrophysics Data System (ADS)

In nature, the oxidation of magnetite to maghemite is the most common oxide mineral alteration. Small deviations from stoichiometry, such as surface oxidation in magnetite, have a considerable effect on the Verwey transition. The present work studies the effect of partial oxidation on the Verwey transition temperature Tv of submicron magnetites with mean particle sizes of 40 nm to 210 nm. Samples were heated in air at 100, 150 and 200 C. Saturation isothermal remanent magnetization (SIRM) given to the oxidized nanoparticles by a 2.5 T field at 10 K decreased steadily during zero-field warming to 300 K, with little or no indication of the Verwey transition. After completing the thermal cycle by cooling in zero field to 10 K the stoichiometric magnetites, which had lost 70-90 percent of their SIRM in warming through Tv, recovered very little of their initial remanence. However, the partially oxidized magnetites, which had lost 30-60 percent of their SIRM in the warming half-cycle, recovered 50-90 percent of the initial remanence after cooling to 10 K. A complete set of zero-field cooling-warming cycles of SIRM produced at 300 K was also carried out. These curves have more structure in both cooling and warming and are more diagnostic of degree of oxidation than the usually measured warming curve of SIRM produced below Tv. The 300 K SIRM of stoichiometric magnetites decreases steadily with cooling to the isotropic point, with variable amounts of recovery in cooling through Tv. The oxidized magnetites behave quite differently: the SIRM at first increases in zero-field cooling from 300 K, then decreases as Tv is approached. The hump-like form of the zero-field warming curve above Tv is even more pronounced. With complete oxidation to maghemite and the disappearance of the Verwey transition, the 300 K SIRM increases monotonically throughout zero-field cooling from 300 to 10 K.

Ozdemir, O.

2009-05-01

93

The Water Cycle of La Plata Basin  

NASA Astrophysics Data System (ADS)

The regional economies in subtropical South America hinge on vital water resources, which are significantly affected by climate variability. The subtropical region encompasses La Plata basin (LPB), recently endorsed as a GEWEX Continental Scale Experiment. This presentation describes a transferability experiment by which methodologies developed for data rich regions (e.g., the Mississippi basin) can be applied to data sparse regions of the world, and in particular to the La Plata basin. The mesoscale regional model employed for this activity is an adaptation to South America of NCEP's Eta model. Here, the short term forecasts for the period April 2001-October 2003 are employed to estimate the water cycle of the La Plata basin. During the period covered by this study there is a remarkable agreement between observed and forecast precipitation (both are 3.1 mm/day) despite some regional differences. A cautious assessment will include further evaluation of the uncertainties in both the model and the observed estimates. There is a slight imbalance (~ -0.28 mm/day) between P-E and moisture flux convergence partly due to not including the local changes of atmospheric water content in the computation. Nevertheless, this term is expected to be small, and indeed even if the water balance can be estimated with an uncertainty of about 0.3 mm/day, by itself this is a promising result for future activities. Still, the ultimate verification of the reliability of the model estimates is by comparison of P-E or MFC with river discharge. The long term river discharge is equivalent to 0.61 mm/day, which is very close to the MFC (0.60 mm/day). If river discharge values are representative of the more recent period covered by the model products, then the model produces a correct value for MFC and in turn it suggests that the model overestimates evaporation by about 0.2-0.3 mm/day in the annual average. The previous results are encouraging in our efforts to bridge the gap resulting from scarce observations; currently, we are employing the Eta model for seasonal simulations over South America, in particular to assess the effect of lower boundary conditions on the precipitation processes affecting La Plata basin as a first step toward studies of seasonal predictability. Results indicate that the model is stable and does not drift to an unknown climate.

Berbery, E. H.; Collini, E. A.; Barros, V.; Pyle, M.

2004-05-01

94

Thermodynamic Limitations of Photosynthetic Water Oxidation at High Proton Concentrations*  

PubMed Central

In oxygenic photosynthesis, solar energy drives the oxidation of water catalyzed by a Mn4Ca complex bound to the proteins of Photosystem II. Four protons are released during one turnover of the water oxidation cycle (S-state cycle), implying thermodynamic limitations at low pH. For proton concentrations ranging from 1 nm (pH 9) to 1 mm (pH 3), we have characterized the low-pH limitations using a new experimental approach: a specific pH-jump protocol combined with time-resolved measurement of the delayed chlorophyll fluorescence after nanosecond flash excitation. Effective pK values were determined for low-pH inhibition of the light-induced S-state transitions: pK1 = 3.3 ± 0.3, pK2 = 3.5 ± 0.2, and pK3 ? pK4 = 4.6 ± 0.2. Alkaline inhibition was not observed. An extension of the classical Kok model facilitated assignment of these four pK values to specific deprotonation steps in the reaction cycle. Our results provide important support to the extended S-state cycle model and criteria needed for assessment of quantum chemical calculations of the mechanism of water oxidation. They also imply that, in intact organisms, the pH in the lumen compartment can hardly drop below 5, thereby limiting the ?pH contribution to the driving force of ATP synthesis.

Zaharieva, Ivelina; Wichmann, Jorg M.; Dau, Holger

2011-01-01

95

Water Cycle in the Atmosphere and Shallow Subsurface  

NASA Astrophysics Data System (ADS)

The global water cycle on Earth constitutes one of the most relevant components of the terrestrial ecosystem. While the vast majority of terrestrial water is stored in the world oceans, the perpetual cycle of water between ocean, atmosphere and land in all three phases is recognised as one basic feature that characterises the Earth, and is contrasted to the rest of the Solar System. On the other hand, Mars is devoid of a liquid hydrological cycle in the atmosphere and on the surface in the form of rainfall, rivers or oceans, which favour life on Earth's surface. However, a subtle water cycle does exist on present Mars and elucidating the details of the water cycle is crucial in understanding the global water inventory.

Tokano, Tetsuya

96

Nitrogen Oxide Fluxes and Nitrogen Cycling during Postagricultural ...  

Treesearch

Description: The effects of changes in tropical land use on soil emissions of nitrous oxide (N2O) ... land use and forest composition, litterfall, soil nitrogen (N) pools and turnover, soil moisture, and patterns of carbon (C) cycling in a lower ... nitrification, soil nitrate, and net N mineralization and negatively to leaf litter C:N ratio.

97

Biological water oxidation: lessons from nature.  

PubMed

Hydrogen production by water splitting may be an appealing solution for future energy needs. To evolve hydrogen efficiently in a sustainable manner, it is necessary first to synthesize what we may call a 'super catalyst' for water oxidation, which is the more challenging half reaction of water splitting. An efficient system for water oxidation exists in the water oxidizing complex in cyanobacteria, algae and plants; further, recently published data on the Manganese-calcium cluster have provided details on the mechanism and structure of the water oxidizing complex. Here, we have briefly reviewed the characteristics of the natural system from the standpoint of what we could learn from it to produce an efficient artificial system. In short, to design an efficient water oxidizing complex for artificial photosynthesis, we must learn and use wisely the knowledge about water oxidation and the water oxidizing complex in the natural system. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial. PMID:22507946

Najafpour, Mohammad Mahdi; Moghaddam, Atefeh Nemati; Allakhverdiev, Suleyman I; Govindjee

2012-04-10

98

Nitrous oxide in coastal waters  

SciTech Connect

Measurements of dissolved and atmospheric nitrous oxide (N{sub 2}O) are presented for three coastal environments: (1) the central North Sea, (2) the German Bight, and (3) the Gironde estuary. The contribution of coastal regions to the oceanic emissions of atmospheric N{sub 2}O were also determined. N{sub 2}O was measured with a gas chromatograph equipped with an electron capture detector and analyzed. The surface waters of the central North Sea and the German bight were found to be near equilibrium with the overlying atmosphere, while the mean saturation in the Gironde estuary was 132%. Mean saturations in coastal regions without estuaries or upwelling phenomena were only slightly higher than in the open ocean. When estuaries and regions with upwelling are included, however, approximately 60% of the oceanic N{sub 2}O flux is attributable to coastal regions. A review of published data indicated that previous studies have seriously underestimated N{sub 2}O sea-to-air flux from coastal regions. 69 refs., 8 figs., 4 tabs.

Bange, H.W.; Rapsomanikis, S.; Andreae, M.O. [Max Planck Institute for Chemistry, Mainz (Germany)

1996-03-01

99

Life cycle assessment of nuclear-based hydrogen production via thermochemical water splitting using a copper-chlorine (Cu-Cl) cycle  

Microsoft Academic Search

The energy carrier hydrogen is expected to solve some energy challenges. Since its oxidation does not emit greenhouse gases (GHGs), its use does not contribute to climate change, provided that it is derived from clean energy sources. Thermochemical water splitting using a Cu-Cl cycle, linked with a nuclear super-critical water cooled reactor (SCWR), which is being considered as a Generation

Ahmet Ziyaettin Ozbilen

2010-01-01

100

Thermogravimetric analysis of the ZnO\\/Zn water splitting cycle  

Microsoft Academic Search

The endothermal dissociation of zinc oxide into its elements, followed by the exothermal hydrolysis of zinc, is considered as a two-step water splitting thermochemical cycle using high-temperature solar process heat. Thermogravimetric measurements were conducted on both reaction steps to elucidate the influence of temperature, oxygen partial pressure, inert gas flow rate, and chemical impurities on the reaction kinetics. The dissociation

A. Weidenkaff; A. W. Reller; A. Wokaun; A. Steinfeld

2000-01-01

101

Global Hydrological Cycles and World Water Resources  

Microsoft Academic Search

Water is a naturally circulating resource that is constantly recharged. Therefore, even though the stocks of water in natural and artificial reservoirs are helpful to increase the available water resources for human society, the flow of water should be the main focus in water resources assessments. The climate system puts an upper limit on the circulation rate of available renewable

Taikan Oki; Shinjiro Kanae

2006-01-01

102

The water cycle at the Phoenix landing site, Mars  

Microsoft Academic Search

The water cycle is critically important to understanding Mars system science, especially interactions between water and surface minerals or possible biological systems. In this thesis, the water cycle is examined at the Mars Phoenix landing site (68.22°N, 125.70°W), using data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), High-Resolution Imaging Science Experiment (HiRISE), the Phoenix Lander Surface Stereo Imager

Selby Cull

2010-01-01

103

Wet Air Oxidation of Waste Water.  

National Technical Information Service (NTIS)

In order to solve ecological problems, research in laboratories and technical schools on the purification of chemically contaminated waste water by wet air oxidation was carried out and resulted in the construction of a prototype technical plant. The plan...

G. Friedhofen H. Kerres J. Rosenbaum R. Thiel

1980-01-01

104

Towards an Integrated Global Water Cycle Observations (IGWCO) Strategy  

NASA Astrophysics Data System (ADS)

The Integrated Global Observing Strategy Partnership (IGOS-P), which consists of space agencies (represented by the Committee on Earth Observing Satellites) and international programs, adopted water as a priority in 2001. Subsequently, in November 2003, it adopted a Global Water Cycle Observations theme report and now is planning follow-on activities. The Integrated Global Water Cycle Observing (IGWCO) strategy provides an international framework for guiding decisions on priorities and strategies regarding water cycle observations for: a) monitoring climate variability and change; b) effective water management and sustainable development of the world's water resources; c) societal applications for resource development and environmental management; d) specification of initial conditions for weather and climate forecasts, and e) research directed at priority water cycle questions. It also promotes strategies that facilitate the processing, archiving and distribution of water cycle data and products. The IGWCO report contains a number of recommendations aimed at improving water cycle observations and products and supporting the further development of the theme. Since November 2003, a number of steps have been taken to develop a plan for implementing the theme. This implementation plan has identified activities and studies related to the Coordinated Enhanced Observing Period (CEOP), the Global Water System Project (GWSP), and the development of integrated precipitation and soil moisture products. Other activities under consideration involve building the capacity of developing countries to make measurements and analyze global water cycle variables thereby strengthening their ability to manage national water resources. The purpose of this presentation is to inform the scientific community of these activities and to solicit advice and assistance in the implementation of the strategy.

Lawford, R. G.

2004-12-01

105

Dynamics of the global water cycle of Biosphere 2  

Microsoft Academic Search

We investigate water usage and movement throughout the major reservoirs of Biosphere 2, Oracle AZ, over a period of 2 months. The data analyzed show reservoir turnover times ranging from hours to several years and the existence of three major water sub-cycles. A ‘fast pool’, or 60% of the available water used daily in Biosphere 2, is recycled within a

Francesco N. Tubiello; John W. Druitt; Bruno D. V. Marino

1999-01-01

106

Simulation of the water cycle in Biosphere 2  

Microsoft Academic Search

The budget of water flows and storages in Biosphere 2 was drawn in energy systems language to generate equations for a simple simulation model. Using data by others for calibration and a seasonal variation of sunlight, main features of the seasonal water cycle were analyzed. The model result coincided with the observed patterns of seasonal variation in the water level

Daeseok Kang

1999-01-01

107

Secular Changes in Great Lakes Water Level Seasonal Cycles  

Microsoft Academic Search

The three primary scales of Great Lakes water level fluctuations are interannual, seasonal, and episodic. Of these three, the seasonal water level fluctuations have received relatively little attention. The Great Lakes water levels have a well defined seasonal cycle driven primarily by snowmelt in the spring and summer and lake evaporation in the fall and winter. The present average seasonal

Frank H. Quinn

2002-01-01

108

Investigating the water cycle "snow fun"  

NSDL National Science Digital Library

In this activity students collect snow in a cup, predict how much water will be in the cup when the snow melts. Students are exposed to evaporation as the water "disappears" over time and try to stop this from happening.

109

Potassium vapor topping cycle gas-fired boiler water test  

Microsoft Academic Search

The potassium vapor topping cycle is a concept for increasing the efficiency of the Rankine vapor cycle by raising the peak temperature by employing a potassium vapor cycle with a turbine inlet temperature of 1500 to 1600°F (815 to 870°C) in which the waste heat rejected from the condensing potassium vapor is transferred to boiling water and steam in a

D. B. Lloyd; R. H. Guymon; R. S. Holcomb

1978-01-01

110

Water Quality Testing in your Local Water Cycle  

NSDL National Science Digital Library

Students analyze local water chemistry by identifying and collecting local water samples, deciding upon questions they want to answer about their local water sources, and then performing simple water quality tests on their samples.

Anderson, Jennifer L.

111

Continuous solar air conditioning with ammonia\\/water absorption cycle  

Microsoft Academic Search

The considered cycle involves the replacement of the vapor compression function of a conventional compressor with a generator, absorber, and a circulation pump. The generator utilizes heat to produce a refrigerant vapor at high pressure. This vapor is condensed and expanded for cooling. The refrigerant combines subsequently with an absorbant and is returned to the generator. The ammonia\\/water absorption cycle

E. A. Farber; C. A. Morrison; H. A. Ingley; J. A. Clark

1976-01-01

112

Water Cycling under Climate Change. Interactions between the water cycle, vegetation and a changing (sub)tropical climate  

Microsoft Academic Search

The water cycle is an essential component of the climate system because the physical properties of water in its liquid, solid and gaseous phases allow for the redistribution of energy in the oceans and atmosphere. At the scale of individual organisms, water and energy are also essential for the biochemical reactions required for life to develop. The terrestrial biosphere may

H. J. de Boer

2012-01-01

113

Try This at Home: Water Cycle in a Bag  

NSDL National Science Digital Library

In this activity, younger students will construct a model which will allow them to identify the components of the water cycle and observe processes involved in the movement of water through the various components of the cycle. This activity can be done at home with common household materials and could be used by students who are home schooled. They will be able to infer evaporation and observe condensation, precipitation, and runoff.

114

Pressurized Water Reactor Thorium Fuel Cycle Studies.  

National Technical Information Service (NTIS)

The use of a thorium fuel cycle in a PWR is studied. The thorium has no fissile isotope and a fissile nuclide must be added to the thorium fuel. This nuclide can be uranium 235, plutonium 239 or uranium 233. In this work we have kept the fuel assembly geo...

A. Aktogu

1981-01-01

115

Iron oxide formation in artificial ground waters  

Microsoft Academic Search

Artificial ground water containing 40 mg\\/l Ca and varying concentrations of Fe(II), Fe(III) and Si were rapidly oxidized with\\u000a air. The ferrihydrite forming is similar to those found in natural Finish ground waters.

U. Schwertmann; L. Carlson; H. Fechter

1984-01-01

116

The kinetics of hydrogen production in the oxidation of liquid zinc with water vapor  

Microsoft Academic Search

Thermochemical cycles where metal oxides are reduced and the elementary metal is reoxidized with water, thus generating hydrogen has been proposed for conversion of solar energy to chemical energy and fuels. The two steps of the cycle can be separated in time and place, thus providing also means for storage of solar energy in chemical form. The second step of

A Berman; M Epstein

2000-01-01

117

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

118

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

119

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

120

Earth observation Water Cycle Multi-Mission Observation Strategy (WACMOS)  

NASA Astrophysics Data System (ADS)

Observing and monitoring the different components of the global water cycle and their dynamics are essential steps to understand the climate of the Earth, forecast the weather, predict natural disasters like floods and droughts, and improve water resources management. Earth observation technology is a unique tool to provide a global understanding of many of the essential variables governing the water cycle and monitor their evolution over time from global to basin scales. In the coming years an increasing number of Earth observation missions will provide an unprecedented capacity to quantify several of these variables on a routine basis. In this context, the European Space Agency (ESA), in collaboration with the Global Energy and Water Cycle Experiment (GEWEX) of the World Climate Research Program (WCRP), launched the Water Cycle Multi-Mission Observation Strategy (WACMOS) project in 2009. The project aims at developing and validating a novel set of geo-information products relevant to the water cycle covering the following thematic areas: evapotranspiration, soil moisture, cloud characterization and water vapour. The generation of these products is based on a number of innovative techniques and methods aiming at exploiting the synergies of different types of Earth observation data available today to the science community. This paper provides an overview of the major findings of the project with the ultimate goal of demonstrating the potential of innovative multi-mission based strategies to improve current observations by maximizing the synergistic use of the different types of information provided by the currently available observation systems.

Su, Z.; Dorigo, W.; Fernández-Prieto, D.; van Helvoirt, M.; Hungershoefer, K.; de Jeu, R.; Parinussa, R.; Timmermans, J.; Roebeling, R.; Schröder, M.; Schulz, J.; van der Tol, C.; Stammes, P.; Wagner, W.; Wang, L.; Wang, P.; Wolters, E.

2010-10-01

121

Supercritical Water Oxidation Data Acquisition Testing  

SciTech Connect

Supercritical Water Oxidation (SCWO) is a high pressure oxidation process that blends air, water, and organic waste material in an oxidizer in which where the temperature and pressure in the oxidizer are maintained above the critical point of water. Supercritical water mixed with hydrocarbons, which would be insoluble at subcritical conditions, forms a homogeneous phase which possesses properties associated with both a gas and a liquid. Hydrocarbons in contact with oxygen and SCW are readily oxidized. These properties of SCW make it an attractive means for the destruction of waste streams containing organic materials. SCWO technology holds great promise for treating mixed wastes in an environmentally safe and efficient manner. In the spring of 1994 the U.S. Department of Energy (DOE) initiated a Supercritical Water Oxidation Data Acquisition Testing (SCWODAT) program. The SCWODAT program provided further information and operational data on the effectiveness of treating both simulated mixed waste and typical Navy hazardous waste using the SCWO technology. The program concentrated on the acquisition of data through pilot plant testing. The Phase I DOE testing used a simulated waste stream that contained a complex machine cutting oil and metals, that acted as surrogates for radionuclides. The Phase II Navy testing included pilot testing using hazardous waste materials to demonstrate the effectiveness of the SCWO technology. The SCWODAT program demonstrated that the SCWO process oxidized the simulated waste stream containing complex machine cutting oil, selected by DOE as representative of one of the most difficult of the organic waste streams for which SCWO had been applied. The simulated waste stream with surrogate metals in solution was oxidized, with a high destruction efficiency, on the order of 99.97%, in both the neutralized and unneutralized modes of operation.

K. M. Garcia

1996-08-01

122

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

123

Relationships between Cycling Hypoxia, HIF-1, Angiogenesis and Oxidative Stress  

PubMed Central

This Failla Lecture focused on the inter-relationships between tumor angiogenesis, HIF-1 expression and radiotherapy responses. A common thread that bonds all of these factors together is microenvironmental stress caused by reactive oxygen and nitrogen species formed during tumor growth and angiogenesis or in response to cytotoxic treatment. In this review we focus on one aspect of the crossroad between oxidative stress and angiogenesis, namely cycling hypoxia. Understanding of the relative importance of this feature of the tumor microenvironment has recently expanded; it influences tumor biology in ways that are separate from chronic hypoxia. Cycling hypoxia can influence angiogenesis, treatment responses and metastatic behavior. It represents an important and relatively less well understood feature of tumor biology that requires additional research.

Dewhirst, Mark W.

2009-01-01

124

Evidence for trends in the Northern Hemisphere water cycle  

Microsoft Academic Search

We have applied a unique water vapor tracing algorithm using observed precipitation and atmospheric analyses for the period 1979–2003 to estimate water budgets and recycling ratio (the fraction of precipitation over a region that originated as evaporation from the same region) over land areas across the globe. Over most mid- and high-latitude areas, a strong annual cycle of recycling ratio

Paul A. Dirmeyer; Kaye L. Brubaker

2006-01-01

125

Electrolysis of water on oxide surfaces  

Microsoft Academic Search

In this paper, density functional theory (DFT) calculations are performed to analyze the electrochemical water-splitting process producing molecular oxygen (O2) and hydrogen (H2). We investigate the trends in the electro-catalytic properties of (110) surfaces of three rutile-type oxides (RuO2, IrO2, and TiO2). The two first of these oxide anodes show lower O2-evolving over-potentials than metal anodes, due to weak O

J. Rossmeisl; Z.-W. Qu; H. Zhu; G.-J. Kroes; J. K. Nørskov

2007-01-01

126

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

127

Cycle Simulation of HotWater Fired Absorption Chiller  

NASA Astrophysics Data System (ADS)

The design limits were examined to determine the lowest temperature for hot water that can be used as a heat source to drive a hot water fired absorption chiller. Advantage was taken of the fact that the cycle calculation method using the minimum temperature difference is quite effective. This minimum temperature difference was the lower of the two temperature differences used to get the logarithmic mean temperature difference that need to design the evaporator, absorber, condenser and generator in an absorption refrigerator. This report proposes a new solution algorithm employing this minimum temperature difference to make a cycle simulation of the hot water fired absorption chiller. It shows the lowest usable temperature for hot water and makes clear the chilled water and cooling water temperature conditions that can provide the lowest temperature.

Esaki, Shuji; Iramina, Kazuyasu; Kobayashi, Takahiro; Ohnou, Masayuki; Kaneko, Toshiyuki; Soga, Takashi

128

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

129

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...

130

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...

131

Special Centrifugal Pumps for the Water Cycle.  

National Technical Information Service (NTIS)

There is a description of special centrifugal pumps for transporting mixtures of solid matter and water. There is an explanation of the type of stress and the wear mechanism. A detailed description is given of the hydraulic layout, high-wear components an...

1983-01-01

132

Micropollutant loads in the urban water cycle.  

PubMed

The assessment of micropollutants in the urban aquatic environment is a challenging task since both the water balance and the contaminant concentrations are characterized by a pronounced variability in time and space. In this study the water balance of a central European urban drainage catchment is quantified for a period of one year. On the basis of a concentration monitoring of several micropollutants, a contaminant mass balance for the study area's wastewater, surface water, and groundwater is derived. The release of micropollutants from the catchment was mainly driven by the discharge of the wastewater treatment plant. However, combined sewer overflows (CSO) released significant loads of caffeine, bisphenol A, and technical 4-nonylphenol. Since an estimated fraction of 9.9-13.0% of the wastewater's dry weather flow was lost as sewer leakages to the groundwater, considerable loads of bisphenol A and technical 4-nonylphenol were also released by the groundwater pathway. The different temporal dynamics of release loads by CSO as an intermittent source and groundwater as well as treated wastewater as continuous pathways may induce acute as well as chronic effects on the receiving aquatic ecosystem. This study points out the importance of the pollution pathway CSO and groundwater for the contamination assessments of urban water resources. PMID:20509608

Musolff, Andreas; Leschik, Sebastian; Reinstorf, Frido; Strauch, Gerhard; Schirmer, Mario

2010-07-01

133

Life cycle assessment of municipal waste water systems  

Microsoft Academic Search

Life Cycle Assessment was applied to municipal planning in a study of waste water systems in Bergsjön, a Göteborg suburb,\\u000a and Hamburgsund, a coastal village. Existing waste water treatment consists of mechanical, biological and chemical treatment.\\u000a The heat in the waste water from Bergsjön is recovered for the district heating system. One alternative studied encompassed\\u000a pretreatment, anaerobic digestion or drying

Anne-Marie Tillman; Mikael Svingby; Henrik Lundström

1998-01-01

134

Seismological constraints on Earth's Deep Water Cycle  

NASA Astrophysics Data System (ADS)

Water is a ubiquitous volatile, relatively small amounts of which can be present in the mantle in the form of hydrous melts, hydrous phases, or incorporated into the crystal structure of nominally anhydrous minerals of the major mantle mineralogy. In whichever form the water or another volatile is, even small amounts will likely affect the seismic properties of the mantle in various ways, such that seismic observations contain unique and valuable information on the amount and distribution of volatiles in the Earth's mantle. It is, however, challenging to extract this information because of limitations in the amount and density of available seismic data, multiple interpretations of similar observations, and limited quantification of the effects of volatiles and other parameters on the seismic properties. Wet polymorphs of olivine tend to lower the seismic velocity relatively gradually throughout the upper mantle, while deep carbon tends to be have fewer host mineralogies, leaving its signature more precipitous. Water can also stretch and elevate seismic discontinuities related to mineralogical phase changes. Overall in the mantle, the seismic effects of volatiles are small compared those of heat. Various types of observations have been combined to infer water content in the mantle, ranging from a few hundredths of weight percent to several weight percent. Altogether, the seismological literature suggests that the mantle is heterogeneously hydrated. There does not appear to be an obvious correlation between present tectonic environment and mantle water content, though a tendency exists to interpret possibly hydrous regions in the mid mantle as being related to past subduction of oceanic lithosphere. More recently, a new tendency relates possibly hydrous regions in the mid mantle to future subduction of oceanic lithosphere.

Van der Lee, S.

2011-12-01

135

Serpentine and the subduction zone water cycle  

Microsoft Academic Search

Abstract This study explores a chemo-thermo-dynamic subduction zone model that solves for slab dehydration during subduction. We investigate how,changes in the incoming,plate’s hydration and thermal structure may,effect the efficiency of sub-arc water release from sediments, crust, and serpentinized mantle. We find that serpentinized lithospheric mantle may not only be an important fluid source to trigger arc melting but is also

J. P. Morgan; M. Hort; J. A. D. Connolly

2004-01-01

136

Serpentine and the subduction zone water cycle  

Microsoft Academic Search

This study explores a chemo-thermo-dynamic subduction zone model that solves for slab dehydration during subduction. We investigate how changes in the incoming plate's hydration and thermal structure may effect the efficiency of sub-arc water release from sediments, crust, and serpentinized mantle. We find that serpentinized lithospheric mantle may not only be an important fluid source to trigger arc melting but

Lars H Rüpke; Jason Phipps Morgan; Matthias Hort; James A. D Connolly

2004-01-01

137

Remote-sensing-based estimates of the fundamental global water cycle: Annual cycle  

Microsoft Academic Search

The average annual cycle of the atmospheric branch of the fundamental global water cycle (FGWC) was studied with remote-sensing-based precipitation estimates from the Global Precipitation Climatology Project (GPCP; blended microwave-infrared-rain gauge) Version 2 and the Goddard Profiling algorithm (GPROF; passive microwave) Version 6 data sets and overocean evaporation estimates from the Goddard Satellite Surface Turbulent Fluxes Version 2 (passive microwave)

Vikram M. Mehta; Andrew J. DeCandis; Amita V. Mehta

2005-01-01

138

West African Monsoon water cycle: 1. A hybrid water budget data set  

Microsoft Academic Search

This study investigates the West African Monsoon water cycle with the help of a new hybrid water budget data set developed within the framework of the African Monsoon Multidisciplinary Analyses. Surface water and energy fluxes are estimated from an ensemble of land surface model simulations forced with elaborate precipitation and radiation products derived from satellite observations, while precipitable water tendencies

R. Meynadier; O. Bock; F. Guichard; A. Boone; P. Roucou; J.-L. Redelsperger

2010-01-01

139

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

140

An assessment of supercritical water oxidation (SCWO)  

Microsoft Academic Search

The process of supercritical water oxidation (SCWO) is a promising alternative to the incineration of aqueous organic waste streams and has received an enormous interest during the last decade. However, SCWO as an end-of-pipe technology has some disadvantages that have hindered an industrial application of the process. Beside technical problems due to reactor corrosion and salt precipitation, problems result from

Peter Kritzer; Eckhard Dinjus

2001-01-01

141

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

142

Supercritical water oxidation of landfill leachate  

SciTech Connect

Highlights: > Thermal analysis of NH{sub 3} in supercritical water oxidation reaction. > Research on the catalytic reaction of landfill leachate by using response surface method. > Kinetic research of supercritical water oxidation of NH{sub 3} with and without MnO{sub 2} catalyst. - Abstract: In this paper, ammonia as an important ingredient in landfill leachate was mainly studied. Based on Peng-Robinson formulations and Gibbs free energy minimization method, the estimation of equilibrium composition and thermodynamic analysis for supercritical water oxidation of ammonia (SCWO) was made. As equilibrium is reached, ammonia could be totally oxidized in SCW. N{sub 2} is the main product, and the formation of NO{sub 2} and NO could be neglected. The investigation on SCWO of landfill leachate was conducted in a batch reactor at temperature of 380-500 deg. C, reaction time of 50-300 s and pressure of 25 MPa. The effect of reaction parameters such as oxidant equivalent ratio, reaction time and temperature were investigated. The results showed that COD and NH{sub 3} conversion improved as temperature, reaction time and oxygen excess increased. Compared to organics, NH{sub 3} is a refractory compound in supercritical water. The conversion of COD and NH{sub 3} were higher in the presence of MnO{sub 2} than that without catalyst. The interaction between reaction temperature and time was analyzed by using response surface method (RSM) and the results showed that its influence on the NH{sub 3} conversion was relatively insignificant in the case without catalyst. A global power-law rate expression was regressed from experimental data to estimate the reaction rate of NH{sub 3}. The activation energy with and without catalyst for NH{sub 3} oxidation were 107.07 {+-} 8.57 kJ/mol and 83.22 {+-} 15.62 kJ/mol, respectively.

Wang Shuzhong, E-mail: s_z_wang@yahoo.cn [School of Energy and Power Engineering of Xi' an Jiao Tong University, Xi'an 710049 (China); Guo Yang [School of Energy and Power Engineering of Xi' an Jiao Tong University, Xi'an 710049 (China); Chen Chongming [Hebei Electric Power Research Institute, Shijizhuang, Hebei 050021 (China); Zhang Jie; Gong Yanmeng; Wang Yuzhen [School of Energy and Power Engineering of Xi' an Jiao Tong University, Xi'an 710049 (China)

2011-09-15

143

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

144

Method of removing oxidized contaminants from water  

US Patent & Trademark Office Database

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).

1998-07-21

145

Water oxidation intermediates applied to catalysis: benzyl alcohol oxidation.  

PubMed

Four distinct intermediates, Ru(IV)?O(2+), Ru(IV)(OH)(3+), Ru(V)?O(3+), and Ru(V)(OO)(3+), formed by oxidation of the catalyst [Ru(Mebimpy)(4,4'-((HO)(2)OPCH(2))(2)bpy)(OH(2))](2+) [Mebimpy = 2,6-bis(1-methylbenzimidazol-2-yl) and 4,4'-((HO)(2)OPCH(2))(2)bpy = 4,4'-bismethylenephosphonato-2,2'-bipyridine] on nanoITO (1-PO(3)H(2)) have been identified and utilized for electrocatalytic benzyl alcohol oxidation. Significant catalytic rate enhancements are observed for Ru(V)(OO)(3+) (~3000) and Ru(IV)(OH)(3+) (~2000) compared to Ru(IV)?O(2+). The appearance of an intermediate for Ru(IV)?O(2+) as the oxidant supports an O-atom insertion mechanism, and H/D kinetic isotope effects support net hydride-transfer oxidations for Ru(IV)(OH)(3+) and Ru(V)(OO)(3+). These results illustrate the importance of multiple reactive intermediates under catalytic water oxidation conditions and possible control of electrocatalytic reactivity on modified electrode surfaces. PMID:22309164

Vannucci, Aaron K; Hull, Jonathan F; Chen, Zuofeng; Binstead, Robert A; Concepcion, Javier J; Meyer, Thomas J

2012-02-22

146

A nickel containing polyoxometalate water oxidation catalyst.  

PubMed

A new pentanickel silicotungstate complex, K(10)H(2)[Ni(5)(OH)(6)(OH(2))(3)(Si(2)W(18)O(66))]·34H(2)O (KH-), has been synthesized and characterized by X-ray crystallography and several other methods. Dynamic light scattering, kinetics and other experiments confirm that in the presence of [Ru(bpy)(3)](2+) (the photosensitizer for light-driven water oxidations) and [Ru(bpy)(3)](3+) (the oxidant in the dark water oxidations) exists in an equilibrium between solution (soluble) and a [Ru(bpy)(3)](n+)- complex (minimally soluble) form. This new pentanickel polyoxometalate catalyzes efficient water oxidation in both the dark and on irradiation with 455 nm LED light with 1.0 mM [Ru(bpy)(3)](2+) photosensitizer and 5.0 mM Na(2)S(2)O(8), sacrificial electron acceptor. Four lines of evidence indicate that in this solution [symbol:see text] Ru(bpy)(3)](n+)- complex equilibrium remains molecular and does not decompose to nickel hydroxide particles. PMID:22986774

Zhu, Guibo; Glass, Elliot N; Zhao, Chongchao; Lv, Hongjin; Vickers, James W; Geletii, Yurii V; Musaev, Djamaladdin G; Song, Jie; Hill, Craig L

2012-11-14

147

Cycling of reduced trace gases and hydroxylamine in coastal waters  

SciTech Connect

The distributions and fluxes of methane, carbon monoxide, nitrous oxide, hydrogen, and hydroxylamine were examined in Yaquina Bay, a relatively unpolluted estuary on the coast of Oregon, and Big Lagoon, a meromictic, coastal lagoon in Northern California. Special emphasis was placed on measuring hydroxylamine, a potential precursor to nitrous oxide in aquatic systems. A gas chromatographic method that is independent of pH and salinity was developed, thus allowing measurement of nanomolar concentrations of hydroxylamine in euryhaline waters for the first time. The kinetics of this reaction involving oxidation of hydroxylamine by iron(III), were examined in detail and suggest a complex reaction sequence with a number of possible end products.

Butler, J.H.

1986-01-01

148

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...

149

Multimodal Science Teachers' Discourse in Modeling the Water Cycle  

ERIC Educational Resources Information Center

The paper presents an intensive study of a micro-event aiming at the characterization of teacher's discourse from a multimodal communication perspective in a secondary school science classroom dealing with the topic of "water cycle." The research addresses the following questions: (a) What communicative modes are used by the teacher?, (b) what…

Marquez, Conxita; Izquierdo, Merce; Espinet, Mariona

2006-01-01

150

Man and the water cycle: challenges for the 21st century  

Microsoft Academic Search

Water is essential to life. Modern, technological societies use huge quantities of this precious liquid. The hydrologic (water) cycle represents the movement of water through the earth's environmental systems. Humankind primarily makes use of three parts of the hydrologic cycle for its water needs: rivers, lakes, and groundwater. Our use of these components of the water cycle has had a

Philip P. Micklin

1996-01-01

151

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

152

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

153

[The presence of medications in the water cycle].  

PubMed

Medications and radiographic contrast dyes are sometimes detected in surface waters, ground water and drinking water; these have proven detrimental effects on organisms living in such waters The concentration of medications found in drinking water is at least a thousand times below their minimum therapeutic dosages. In humans, the long-term effects of daily exposure to low dosages of medications and 'mixture toxicity' is not known; based on the concentrations and substance toxicity, it is presumed that the risk is nil.. Physicians can play their part in controlling the problem of medications becoming part of the water cycle by taking this into account when prescribing medications. Users can make a difference by handling their medications with care and by returning all unused portions to the pharmacy. The pharmaceutical industry can also do its part by taking degradability, options for removal and the environmental effects of medications into account during their stages of development. PMID:23343740

van der Hoek, Jan Peter; van Alphen, Jacques; Kaas, Reinoutje; van der Oost, Ron

2013-01-01

154

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

155

Spatial inhomogeneity of the martian subsurface water distribution: implication from a global water cycle model  

Microsoft Academic Search

In an effort to test and to understand the global hydrogen distribution in the shallow subsurface of Mars retrieved by the Mars Odyssey gamma-ray spectrometer, the present state and movement of water are investigated by a coupled global subsurface–atmosphere water cycle model. It was found that the observed global subsurface hydrogen distribution is largely consistent with the modeled global water

Tetsuya Tokano

2003-01-01

156

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

157

Anaerobic oxidation of methane: an underappreciated aspect of methane cycling in peatland ecosystems?  

NASA Astrophysics Data System (ADS)

Despite a large body of literature on microbial anaerobic oxidation of methane (AOM) in marine sediments and saline waters and its importance to the global methane (CH4) cycle, until recently little work has addressed the potential occurrence and importance of AOM in non-marine systems. This is particularly true for peatlands, which represent both a massive sink for atmospheric CO2 and a significant source of atmospheric CH4. Our knowledge of this process in peatlands is inherently limited by the methods used to study CH4 dynamics in soil and sediment and the assumption that there are no anaerobic sinks for CH4 in these systems. Studies suggest that AOM is CH4-limited and difficult to detect in potential CH4 production assays against a background of CH4 production. In situ rates also might be elusive due to background rates of aerobic CH4 oxidation and the difficulty in separating net and gross process rates. Conclusive evidence for the electron acceptor in this process has not been presented. Nitrate and sulfate are both plausible and favorable electron acceptors, as seen in other systems, but there exist theoretical issues related to the availability of these ions in peatlands and only circumstantial evidence suggests that these pathways are important. Iron cycling is important in many wetland systems, but recent evidence does not support the notion of CH4 oxidation via dissimilatory Fe(III) reduction or a CH4 oxidizing archaea in consortium with an Fe(III) reducer. Calculations based on published rates demonstrate that AOM might be a significant and underappreciated constraint on the global CH4 cycle, although much about the process is unknown, in vitro rates may not relate well to in situ rates, and projections based on those rates are fraught with uncertainty. We suggest electron transfer mechanisms, C flow and pathways, and quantifying in situ peatland AOM rates as the highest priority topics for future research.

Smemo, K. A.; Yavitt, J. B.

2011-03-01

158

Process for treating effluent from a supercritical water oxidation reactor  

Microsoft Academic Search

The present invention relates generally to a method for treating and recycling the effluent from a supercritical water oxidation reactor and more specifically to a method for treating and recycling the effluent by expanding the effluent without extensive cooling. Supercritical water oxidation is the oxidation of fuel, generally waste material, in a body of water under conditions above the thermodynamic

C. M. Barnes; C. Shapiro

1995-01-01

159

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

160

BioCycle study: design of the longitudinal study of the oxidative stress and hormone variation during the menstrual cycle  

PubMed Central

Summary Studies in both human and animal species have suggested that oxidative stress may be associated with health outcomes, including the risk of infertility in both males and females. Sex hormones have been shown to have antioxidant properties. The difficulty in studying the role of oxidative stress in females is partly due to fluctuation in these endogenous sex hormones across the menstrual cycle. The aim of this study was to determine the association of oxidative stress levels with endogenous reproductive hormone levels and antioxidants, including vitamin levels, across the menstrual cycle in a prospective cohort of premenopausal women. The goal was to enrol 250 healthy, regularly menstruating premenopausal women for two menstrual cycles. Participants visited the clinic up to 8 times per cycle, at which time blood and urine were collected. The visits occurred at key hormonally defined phases of the menstrual cycle, with the help of an algorithm based on cycle length and data from a fertility monitor. In addition, participants were administered standardised questionnaires, had various physical measures taken, and had other pertinent data collected. A total of 259 women were enrolled in this study, with 250 completing two cycles, despite a demanding study protocol which participants were required to follow. This report describes the study design, baseline characteristics and visit completion rate for the BioCycle study.

Wactawski-Wende, Jean; Schisterman, Enrique F.; Hovey, Kathleen M.; Howards, Penelope P.; Browne, Richard W.; Hediger, Mary; Liu, Aiyi; Trevisan, Maurizio

2009-01-01

161

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.

Vrettos, John S; Brudvig, Gary W

2002-01-01

162

Cadmium-cadmium hydroxide thermochemical water-splitting cycle  

Microsoft Academic Search

The Institute of Gas Technology (IGT) has derived and developed a hybrid thermochemical water-splitting cycle based on cadmium chemistry: (1) Cd(s) + 2HâO(l) ..-->.. Cd(OH)â(s) + Hâ(g), (2) Cd(OH)â(s) ..-->.. CdO(s) + HâO(g), and (3) CdO(s) ..-->.. Cd(g) + 1\\/2 Oâ(g). All steps in this cycle have been tested in the laboratory and proven workable. Reaction 1 is an electrochemical

J. Schreiber; S. Foh; R. Remick

1980-01-01

163

Observe a raindrop traveling through various parts of the water cycle  

NSDL National Science Digital Library

The representation is an interactive resource in which students move a raindrop through different parts of the water cycle. In each part of the cycle, a drop of water represents where the water is. Clicking on the red arrows show the process as water travels through the cycle.

164

Cooperation of xanthophyll cycle with water-water cycle in the protection of photosystems 1 and 2 against inactivation during chilling stress under low irradiance  

Microsoft Academic Search

The xanthophyll cycle and the water-water cycle had different functional significance in chilling-sensitive sweet pepper upon exposure to chilling temperature (4 °C) under low irradiance (100 µmol m?2 s?1) for 6 h. During chilling stress, effects of non-photochemical quenching (NPQ) on photosystem 2 (PS2) in dithiothreitol (DTT) fed leaves remained distinguishable from that of the water-water cycle in diethyldithiocarbamate (DDTC)

X.-G. Li; Y.-P. Bi; S.-J. Zhao; Q.-W. Meng; Q. Zou; Q.-W. He

2005-01-01

165

The NASA Energy and Water Cycle Climatology (NEWCC) Integration Project  

NASA Astrophysics Data System (ADS)

To date, a truly self-consistent, quantitative description of the Earth's global water and energy cycles, based on the highest quality, independently-observed pieces of information that decipher each of the key storage terms, fluxes, and pathways has been elusive. Such a data compilation of adequate climate quality is of vital interest and an ultimate scientific need of the global observation, modeling, and prediction community. To meet this need, we present results from the first phase of a NASA Energy and Water Cycle Climatology (NEWCC) Integration Project, a collaborative effort whose aim is to construct a defensible, self-consistent, long-term climatology of the global energy and water cycles. Our working hypothesis is that an observationally-based estimate of water and energy fluxes and storages, derived from focused and independently observed components of these cycles, can be balanced and provide useful characterizations and evaluation data for climate prediction and predictability studies. The NEWCC team members are actively involved in key facets of this observational arena, and thus for the first phase of NEWCC, we bring together state-of-the-art, (predominantly) satellite-based observations that include: precipitation, ocean and land evaporation, runoff, atmospheric water storage, ocean and land storage changes, atmospheric transport, radiation, latent and sensible heat fluxes, and subsequently hope to include explicit snow/ice information, such as snow water equivalent and ice mass changes. Our current efforts focus on the period spanning the years 2003 to 2005, for which the most recent and highest-quality satellite-based information is available for all the aforementioned quantities. We present an assessment of the ability of these observational datasets to satisfy the water and energy budgets and the degree to which they show consistency in their mean annual cycles as well as geospatial variability. In doing so, we will highlight, where possible, the most egregious areas of imbalance and inconsistency while also providing a quantification of measurement errors to identify which algorithms and/or measurements hold the most promise for improvement.

Schlosser, C. A.; Lin, B.; NEWCC Team

2008-05-01

166

Superhalogen oxidizers capable of ionizing water molecules  

NASA Astrophysics Data System (ADS)

The ability of ionizing water molecules by chosen strong oxidizing agents of superhalogen nature is demonstrated. It is shown that two selected Gutsev-Boldyrev superhalogens, BF4 and AlF4 (whose corresponding daughter anions BF4- and AlF4- are known to strongly bind an excess electron), might be employed to ionize single water molecule and small water clusters ((H2O)n, n = 2-4) which results in forming [(H2O)n]+[BF4]- and [(H2O)n]+[AlF4]- stable species (n = 1-4). The [(H2O)n]+[BF4]- and [(H2O)n]+[AlF4]- molecules are characterized by large values of binding (interaction) energy (28-73 kcal/mol) and substantial charge flow (0.5-0.8 au) between the components which confirms their ionic nature.

Marchaj, Marzena; Freza, Sylwia; Rybacka, Olimpia; Skurski, Piotr

2013-06-01

167

New Capabilities for Studies Using Isotopes in the Water Cycle  

NASA Astrophysics Data System (ADS)

The characterization and quantification of hydrological fluxes within components of the water cycle and across interfaces (e.g., atmosphere/land surface, aquifer/river, soil/plant) are critical for assessing and managing water resources and for understanding the impacts of climate change and variability on the hydrological cycle. Stable isotopes of oxygen and hydrogen, and radioactive isotopes such as tritium and carbon-14, provide unique insights into hydrological and climatic processes at local, regional, and global scales, including the role of groundwater in rivers and lakes, groundwater recharge rates, and sources and recycling rates of atmospheric moisture [Aggarwal et al., 2005; Gat, 1996; Kendall and McDonnell, 1998]. Isotopes also provide critical insights into understanding feedbacks and interactions between physical and biological processes (e.g., ecohydrology).

Aggarwal, Pradeep K.; Alduchov, Oleg; Araguás, Luis Araguás; Dogramaci, Shawan; Katzlberger, Gernot; Kriz, Karel; Kulkarni, Kshitij M.; Kurttas, Türker; Newman, Brent D.; Pucher, Alexander

2007-12-01

168

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

169

Water cycles in closed ecological systems: effects of atmospheric pressure.  

PubMed

In bioregenerative life support systems that use plants to generate food and oxygen, the largest mass flux between the plants and their surrounding environment will be water. This water cycle is a consequence of the continuous change of state (evaporation-condensation) from liquid to gas through the process of transpiration and the need to transfer heat (cool) and dehumidify the plant growth chamber. Evapotranspiration rates for full plant canopies can range from ~1 to 10 L m-2 d-1 (~1 to 10 mm m-2 d-1), with the rates depending primarily on the vapor pressure deficit (VPD) between the leaves and the air inside the plant growth chamber. VPD in turn is dependent on the air temperature, leaf temperature, and current value of relative humidity (RH). Concepts for developing closed plant growth systems, such as greenhouses for Mars, have been discussed for many years and the feasibility of such systems will depend on the overall system costs and reliability. One approach for reducing system costs would be to reduce the operating pressure within the greenhouse to reduce structural mass and gas leakage. But managing plant growth environments at low pressures (e.g., controlling humidity and heat exchange) may be difficult, and the effects of low-pressure environments on plant growth and system water cycling need further study. We present experimental evidence to show that water saturation pressures in air under isothermal conditions are only slightly affected by total pressure, but the overall water flux from evaporating surfaces can increase as pressure decreases. Mathematical models describing these observations are presented, along with discussion of the importance for considering "water cycles" in closed bioregenerative life support systems. PMID:12481804

Rygalov, Vadim Y; Fowler, Philip A; Metz, Joannah M; Wheeler, Raymond M; Bucklin, Ray A

2002-01-01

170

DIRECT-CYCLE, BOILING-WATER NUCLEAR REACTOR  

DOEpatents

A direct-cycle boiling-water nuclear reactor is described that employs a closed vessel and a plurality of fuel assemblies, each comprising an outer tube closed at its lower end, an inner tube, fuel rods in the space between the tubes and within the inner tube. A body of water lying within the pressure vessel and outside the fuel assemblies is converted to saturated steam, which enters each fuel assembly at the top and is converted to superheated steam in the fuel assembly while it is passing therethrough first downward through the space between the inner and outer tubes of the fuel assembly and then upward through the inner tube. (AEC)

Harrer, J.M.; Fromm, L.W. Jr.; Kolba, V.M.

1962-08-14

171

The First Globally Integrated Water Cycle Data Sets by CEOP  

NASA Astrophysics Data System (ADS)

In an effort to achieve more accurate determination of the water cycle and its association with climate variability and change as well as to establish a baseline set of information on the impacts of this variability on water resources, the Coordinated Enhanced Observing Period (CEOP) was launched on July 1, 2001. The preliminary data period, EOP-1, was implemented from July to September in 2001. The first annual enhanced observing period, EOP-3, started on October 1, 2002. CEOP is seeking to achieve a database of common measurements from both in situ and satellite remote sensing, model output, and four-dimensional data analyses (4DDA; including global and regional reanalyses) for a specified period. In this context, a number of carefully selected reference stations are linked closely with the existing network of observing sites involved in the GEWEX Continental Scale Experiments, which are distributed across the world. The initial step of CEOP is to develop a pilot global hydro- climatological dataset with global consistency associated with climate variability that can be used to help validate satellite hydrology products and evaluate, develop and eventually predict water and energy cycle processes in global and regional models. The dataset, will be used to address studies on the inter-comparison and inter-connectivity of the monsoon systems and regional water and energy budgets, and will provide a means for down-scaling from the global climate to local water resources, as a secondary activity.

Koike, T.; Roads, J.

2003-12-01

172

The nocturnal water cycle in an open-canopy forest  

NASA Astrophysics Data System (ADS)

The movement of moisture into, out-of, and within forest ecosystems is modulated by feedbacks that stem from processes which couple plants, soil, and the atmosphere. While an understanding of these processes has been gleaned from Eddy Covariance techniques, the reliability of the method suffers at night because of weak turbulence. During the summer of 2011, continuous profiles of the isotopic composition (i.e., ?18O and ?D) of water vapor and periodic measurements of soil, leaf, and precipitation pools were measured in an open-canopy ponderosa pine forest in central Colorado to study within-canopy nocturnal water cycling. The isotopic composition of the nocturnal water vapor varies significantly based on the relative contributions of the three major hydrological processes acting on the forest: dewfall, exchange of moisture between leaf waters and canopy vapor, and periodic mixing between the canopy and background air. Dewfall proved to be surprisingly common (˜30% of the nights) and detectable on both the surface and within the canopy through the isotopic measurements. While surface dew could be observed using leaf wetness and soil moisture sensors, dew in the foliage was only measurable through isotopic analysis of the vapor and often occurred even when no dew accumulated on the surface. Nocturnal moisture cycling plays a critical role in water availability in forest ecosystems through foliar absorption and transpiration, and assessing these dynamics, as done here, is necessary for fully characterizing the hydrological controls on terrestrial productivity.

Berkelhammer, M.; Hu, J.; Bailey, A.; Noone, D. C.; Still, C. J.; Barnard, H.; Gochis, D.; Hsiao, G. S.; Rahn, T.; Turnipseed, A.

2013-09-01

173

Supercritical water oxidation of landfill leachate.  

PubMed

In this paper, ammonia as an important ingredient in landfill leachate was mainly studied. Based on Peng-Robinson formulations and Gibbs free energy minimization method, the estimation of equilibrium composition and thermodynamic analysis for supercritical water oxidation of ammonia (SCWO) was made. As equilibrium is reached, ammonia could be totally oxidized in SCW. N(2) is the main product, and the formation of NO(2) and NO could be neglected. The investigation on SCWO of landfill leachate was conducted in a batch reactor at temperature of 380-500 °C, reaction time of 50-300s and pressure of 25 MPa. The effect of reaction parameters such as oxidant equivalent ratio, reaction time and temperature were investigated. The results showed that COD and NH(3) conversion improved as temperature, reaction time and oxygen excess increased. Compared to organics, NH(3) is a refractory compound in supercritical water. The conversion of COD and NH(3) were higher in the presence of MnO(2) than that without catalyst. The interaction between reaction temperature and time was analyzed by using response surface method (RSM) and the results showed that its influence on the NH(3) conversion was relatively insignificant in the case without catalyst. A global power-law rate expression was regressed from experimental data to estimate the reaction rate of NH(3). The activation energy with and without catalyst for NH(3) oxidation were 107.07 ± 8.57 kJ/mol and 83.22 ± 15.62 kJ/mol, respectively. PMID:21705208

Wang, Shuzhong; Guo, Yang; Chen, Chongming; Zhang, Jie; Gong, Yanmeng; Wang, Yuzhen

2011-06-25

174

The reactor physics characteristics of a transuranic mixed oxide fuel in a heavy water moderated reactor  

Microsoft Academic Search

The reprocessing actinide materials extracted from spent fuel for use in mixed oxide fuels is a key component in maximizing the spent fuel repository utility. While fast spectrum reactor technologies are being considered in order to close the fuel cycle, and transmute these actinides, there is potential to utilize existing pressurized heavy water reactors such as the CANDU®11CANDU is a

A. C. Morreale; W. J. Garland; D. R. Novog

2011-01-01

175

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

NASA Astrophysics Data System (ADS)

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 near-real-time and extended back nearly 50 years. Observations of this type enable assessment of numerous water resources management issues including water scarcity, extreme events of drought and floods, and water quality. Examples of water cycle estimates make towards the contributions to the water management community include snow cover and snowpack, soil moisture, evapotranspiration, precipitation, streamflow and ground water. The availability of water is also contingent on the quality of water and hence water quality is an important part of NASA Water Resources. Water quality activities include both nonpoint source (agriculture land use, ecosystem disturbances, impervious surfaces, etc.) and direct remote sensing ( i.e., turbidity, algae, aquatic vegetation, temperature, etc.). . The NASA Water Resources Program organizes its projects under five functional themes: 1) stream-flow and flood forecasting; 2) water consumptive use and irrigation (includes evapotranspiration); 3) drought; 4) water quality; and 5) climate impacts on water resources. Currently NASA Water Resources is supporting 21 funded projects with 11 additional projects being concluded. To maximize the use of NASA water cycle measurements end to projects are supported with strong links with decision support systems. The NASA Water Resources Program works closely with other government agencies NOAA, USDA-FAS, USGS, AFWA, USAID, universities, and non-profit, international, and private sector organizations. International water cycle applications include: 1) Famine Early Warning System Network (FEWSNET) being expanded for famine relief to many developing nations of the world using a NASA Land Data Assimilation System (LDAS); 2) Air Force Weather Agency (AFWA) global hydrology mapping program that extends their global hydrology to much finer resolutions through use of an optimized LDAS; 3) 'SERVIR' a visualization and monitoring center of Earth science information in Central America and East Africa with plans for additional locations in developing countries of the world; 4) installing NASA Water Information System Platforms (WISPs) strategically located throughout the Middle East and North Africa (MENA) in partnerships with USAID and the World Bank; and 5) Latin American capacity building efforts within GEO.

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

2010-12-01

176

Assessing the combined benefits of water recycling technologies by modelling the total urban water cycle  

Microsoft Academic Search

This study investigates the potential benefits of new technologies, modern appliances, and innovative techniques that help to improve the performance of the urban water cycle. Urbanisation is a major source of additional pressures (both qualitative and quantitative) on the environment. For example abstractions to cover the increased demands for water supply or alterations of the topographic and geomorphologic properties of

Evangelos Rozos; Christos Makropoulos

2012-01-01

177

Assessing the combined benefits of water recycling technologies by modelling the total urban water cycle  

Microsoft Academic Search

This study investigates the potential benefits of new technologies, modern appliances, and innovative techniques that help to improve the performance of the urban water cycle. Urbanisation is a major source of additional pressures (both qualitative and quantitative) on the environment. For example abstractions to cover the increased demands for water supply or alterations of the topographic and geomorphologic properties of

Evangelos Rozos; Christos Makropoulos

2011-01-01

178

Alicante University, closed water cycle, reverse osmosis and water treatment plants  

Microsoft Academic Search

In this paper we will explain the major features which have been considered for the design of a brackish water reverse osmosis plant being constructed in Alicante, in the southeast of Spain. This plant will form part of an integral system cycle that will try to utilize and optimize the water resources of this area. The plant will have the

D. Prats; M. F. Chillón; M. Rubio; J. A. Reverter

1997-01-01

179

Sensitivity of the global water cycle to the water-holding capacity of land  

Microsoft Academic Search

The sensitivity of the global water cycle to the water-holding capacity of the plant-root zone of continental soils is estimated by simulations using a mathematical model of the general circulation of the atmosphere, with prescribed ocean surface temperatures and prescribed cloud. With an increase of the globally constant storage capacity, evaporation from the continents rises and runoff falls, because a

P. C. D. Milly; K. A. Dunne

1994-01-01

180

Influence of localized plasticity on oxidation behaviour of austenitic stainless steels under primary water reactor  

NASA Astrophysics Data System (ADS)

The sensitivity of precipitation-strengthened A286 austenitic stainless steel to stress corrosion cracking was studied by means of slow-strain-rate tests. First, alloy cold working by low cycle fatigue (LCF) was investigated. Fatigue tests under plastic strain control were performed at different strain levels (??p/2 = 0.2%, 0.5%, 0.8% and 2%) to establish correlations between stress softening and the deformation microstructure resulting from the LCF tests. Deformed microstructures were identified through TEM investigations. The interaction between oxidation and localized deformation bands was also studied and it resulted that localized deformation bands are not preferential oxide growth channels. The pre-cycling of the alloy did not modify its oxidation behaviour. However, intergranular oxidation in the subsurface under the oxide layer formed after exposure to PWR primary water was shown.

Cissé, Sarata; Laffont, Lydia; Lafont, Marie-Christine; Tanguy, Benoit; Andrieu, Eric

2013-02-01

181

The water cycle at the Phoenix landing site, Mars  

NASA Astrophysics Data System (ADS)

The water cycle is critically important to understanding Mars system science, especially interactions between water and surface minerals or possible biological systems. In this thesis, the water cycle is examined at the Mars Phoenix landing site (68.22°N, 125.70°W), using data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), High-Resolution Imaging Science Experiment (HiRISE), the Phoenix Lander Surface Stereo Imager (SSI), and employing non-linear spectral mixing models. The landing site is covered for part of the year by the seasonal ice cap, a layer of CO2 and H2O ice that is deposited in mid-fall and sublimates in mid-spring. During the mid-summer, H2O ice is deposited on the surface at the Phoenix landing site. CO2 ice forms at the site during fall. The onset date of seasonal ices varies annually, perhaps due to variable levels of atmospheric dust. During fall and winter, the CO2 ice layer thickens and sinters into a slab of ice, ˜30 cm thick. After the spring equinox, the CO2 slab breaks into smaller grains as it sublimates. Long before all of the CO2 ice is gone, H2O ice dominates the near-infrared spectra of the surface. Additional H2O ice is cold-trapped onto the surface of the CO2 ice deposit during this time. Sublimation during the spring is not uniform, and depends on the thermal inertia properties of the surface, including depth of ground ice. All of the seasonal ices have sublimated by mid-spring; however, a few permanent ice deposits remain throughout the summer. These are small water ice deposits on the north-facing slopes of Heimdal Crater and adjacent plateaus, and a small patch of mobile water ices that chases shadows in a small crater near the landing site. During the late spring and early summer, the site is free of surface ice. During this time, the water cycle is dominated by vapor exchange between the subsurface water ice deposits and the atmosphere. Two types of subsurface ice were found at the Phoenix landing site: a pore water ice that appears to be in diffusive equilibrium with the atmosphere, and an almost pure water ice deposit that is apparently not in equilibrium. In addition to vapor and solid phases of the water cycle, there is strong evidence of a liquid phase. Patches of concentrated perchlorate salt are observed in trenches dug by the lander. Perchlorate is believed to form at the landing site through atmospheric interactions, which deposit the salts on the surface. The salts are then dissolved and translocated to the subsurface by thin films of liquid water. These thin films may arise due to perchlorate interactions with the atmospheric water vapor or seasonal ices. It is possible that the winter CO2 ice slab may act as a greenhouse cap, trapping enough heat for the underlying fall-deposited water ice to react with the perchlorate to form thin films of brines. Alternatively, the brines may form when summertime water vapor interacts with perchlorate on the surface, when temperatures rise above the perchlorate brine eutectic.

Cull, Selby

2010-01-01

182

Life-cycle testing of receiving waters with Ceriodaphnia dubia  

SciTech Connect

Seven-day tests with Ceriodaphnia dubia are commonly used to estimate toxicity of effluents or receiving waters but can sometimes yield {open_quotes}no toxicity{close_quotes} outcomes even if pollutants are present. We conducted two sets of full life-cycle tests with C. dubia to (1) see if tests with longer exposure periods would reveal evidence for toxicity that might not be evident from 7-day tests, and (2) determine the relative importance of water quality versus food as factors influencing C. dubia reproduction. In the first set of tests, C. dubia was reared in diluted mineral water (negative control), water from a stream impacted by coal fly-ash, or water from a retention basin containing sediments contaminated with mercury, other metals and polychlorinated biphenyls. The second set of tests used water from the retention basin only, but this water was either filtered or not filtered, and food was either added or not added, prior to testing. C. dubia survival and reproduction did not differ much among the three water types in the first set of tests, but these two parameters were strongly affected by the filtering and food-addition treatments in the second set of tests. Thus, C. dubia appeared to be relatively insensitive to general water-quality factors, but quite sensitive to food-related factors. Regression analyses showed that the predictability of life-time reproduction by C. dubia from the results of 7-day tests was very low (R{sup 2}< 0.35) in five of the six experiments. The increase in predictability as a function of test duration also differed among water types in the first set of tests, and among treatments in the second set of tests. Thus, 7-day tests with C. dubia may be used to quantify water-quality problems, but it may not be possible to reliably extrapolate the results of these tests to longer time scales.

Stewart, A.J.; Konetsky, B.K.

1996-12-31

183

Fundamental kinetics of methane oxidation in supercritical water. Summary report  

SciTech Connect

Fundamental understanding of the oxidation of compounds in supercritical water is essential for the design, development and operation of a supercritical water oxidation unit. Previous work in our group determined the oxidation kinetics of carbon monoxide and ethanol in supercritical water for temperatures ranging from 400 to 540 C. Oxidation studies of methane up to 700 C have recently been completed and are presented in this report. Theoretical studies of fundamental kinetics and mechanistic pathways for the oxidation of methane in supercritical water are discussed. Application of current gas phase elementary reaction models are briefly presented and their limitations discussed.

Webley, P.A.; Tester, J.W. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Chemical Engineering

1989-05-22

184

RADIO OXIDATION OF IRRADIATED SUGARS IN DILUTE AERATED WATER SOLUTIONS  

Microsoft Academic Search

As an effect of ionizing radiaiion, water solutions of simple sugars ; undergo radiooxidation. This oxidation is caused by oxidizing radicals formed in ; water under the influence of radiation which, by attacking the chain end group -; CHâ--OH, produce unstable uronic peracids for glucose and fructose and ; stable uronic acids for alpha -methyl glucoside. The oxidation of glucose

G. Binder; A. Vincze

1957-01-01

185

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

186

Electrochemical water oxidation with carbon-grafted iridium complexes.  

PubMed

Hydrogen production from water splitting provides a potential solution to storing harvested solar energy in chemical fuels, but this process requires active and robust catalysts that can oxidize water to provide a source of electrons for proton reduction. Here we report the direct, covalent grafting of molecular Ir complexes onto carbon electrodes, with up to a monolayer coverage. Carbon-grafted Ir complexes electrochemically oxidize water with a turnover frequency of up to 3.3 s(-1) and a turnover number of 644 during the first hour. Electrochemical water oxidation with grafted catalysts gave enhanced rates and stability compared to chemically driven water oxidation with the corresponding molecular catalysts. This strategy provides a way to systematically evaluate catalysts under tunable conditions, potentially providing new insights into electrochemical water oxidation processes and water oxidation catalyst design. PMID:22292527

deKrafft, Kathryn E; Wang, Cheng; Xie, Zhigang; Su, Xin; Hinds, Bruce J; Lin, Wenbin

2012-02-06

187

Fourier transform infrared difference spectroscopy for studying the molecular mechanism of photosynthetic water oxidation.  

PubMed

The photosystem II reaction center mediates the light-induced transfer of electrons from water to plastoquinone, with concomitant production of O2. Water oxidation chemistry occurs in the oxygen-evolving complex (OEC), which consists of an inorganic Mn4CaO5 cluster and its surrounding protein matrix. Light-induced Fourier transform infrared (FTIR) difference spectroscopy has been successfully used to study the molecular mechanism of photosynthetic water oxidation. This powerful technique has enabled the characterization of the dynamic structural changes in active water molecules, the Mn4CaO5 cluster, and its surrounding protein matrix during the catalytic cycle. This mini-review presents an overview of recent important progress in FTIR studies of the OEC and implications for revealing the molecular mechanism of photosynthetic water oxidation. PMID:23734156

Chu, Hsiu-An

2013-05-21

188

The Relationship Between the Diagenetic Cycles of Reducible Iron and Manganese Oxides and Dissolved Organic Carbon (DOC)  

NASA Astrophysics Data System (ADS)

Field evidence suggests that the fate of sedimentary DOC is intimately linked to the diagenetic cycles of iron and manganese in marine sediments. Co-variations of their concentrations in sediment pore water [1], as well as the release of DOC upon the reductive dissolution of authigenic iron and manganese oxides [1] suggest that sorption (i.e., co-precipitation and/or adsorption) onto these oxides may play an important role on the diagenetic behavior of DOC. Whereas the diagenetic cycling of iron and manganese between oxic and suboxic sediments is well documented, DOC pore water gradients have most often been interpreted uniquely as indicative of a flux of DOC out of the sediments to the overlying bottom waters [2-5]. This interpretation stems from our inability to resolve a subsurface DOC sink from the vertical distribution of sedimentary particulate organic carbon (POC). This DOC sink, if it exists, would considerably alter our views of the mechanisms that regulate DOC fluxes across the sediment-water interface as well as their quantification. Sorption onto authigenic metal oxides may also lead to a molecular and isotopic fractionation of DOC. Furthermore, if DOC sorption to metal oxides is a reversible process, it may buffer pore water DOC concentrations and release to the overlying waters. Oxic surface sediments recovered from the St. Lawrence Estuary and the Saguenay Fjord were incubated under anaerobic conditions and extracted with a mild reducing agent to determine the amount and composition (molecular and isotopic) of the DOC associated with the authigenic iron and manganese oxides. Preliminary results from the study will be presented. References: [1] Deflandre et al. (2002) Geochim. Cosmochim. Acta, 66; 14, 2547-2558. [2] Alperin et. al., (1999) Geochim. Cosmochim. Acta, 63; 3-4, 427-448. [3] Burdige et al., (1999) Geochim. Cosmochim. Acta, 63; 10, 507-1515. [4] Holcombe et al., (2001) Limnol. Oceanogr., 46; 2, 298-308. [5] Papadimitriou et. al. (2002) Mar. Chem., 79, 37-47.

Barazzuol, L. N.; Mucci, A.; Gélinas, Y.

2004-05-01

189

Multiyear simulations of the Martian water cycle with the Ames General Circulation Model  

Microsoft Academic Search

Previous research done using global, 3-D computer modeling to better understand the Martian atmosphere treat the dust and the water cycles as two separate and independent processes. The existing Ames numerical model will be employed to simulate the relationship between the Martian dust and water cycles by actually coupling the two cycles. Water will condense onto the dust, allowing the

S. M. Nelli; J. R. Murphy; R. M. Haberle; J. R. Schaeffer

2003-01-01

190

Photoassisted oxidation of oil films on water  

SciTech Connect

The objective of the project is to develop a method for the solar assisted oxidation of oil slicks. A semiconducting photocatalyst, titanium dioxide, is used. Upon absorbing a photon, an electron-hole pair is generated in the TiO{sub 2} microcrystal. The electron reacts with surface-adsorbed oxygen, reducing it to hydrogen peroxide; the hole directly oxidizes adsorbed organic compounds. Titanium dioxide is denser than either oil or seawater; the density of its anatase phase is 3.8 and that of its rutile phase is 4.3. In order to keep the titanium dioxide at the air/oil interface, it is attached to a low density, floating material. The particles of the latter are sufficiently small to make the system economical. Specifically, the photocatalyst particles are attached to inexpensive hollow glass microbeads of about 100{mu}m diameter. Those areas of the microbeads that are not covered by photocatalyst are made oleophilic, so that the microbeads will follow the oil slick and not migrate to either the air/water or the water/oil interface.

Heller, A.; Brock, J.R.

1990-10-01

191

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

192

The neutronic and fuel cycle performance of interchangeable 3500 MWth metal and oxide fueled LMRs  

SciTech Connect

This study summarizes the neutronic and fuel cycle analysis performed at Argonne National Laboratory for an oxide and a metal fueled 3500 MWth LMR. The oxide and metal core designs were developed to meet reactor performance specifications that are constrained by requirements for core loading interchangeability and for small burnup reactivity swing. Differences in the computed performance parameters of the oxide and metal cores, arising from basic differences in their neutronic characteristics, were identified and discussed. It is shown that metal and oxide cores designed to the same ground rules exhibit many similar performance characteristics; however, they differ substantially in reactivity coefficients, control strategies, and fuel cycle options. 12 refs., 25 figs.

Fujita, E.K.; Wade, D.C.

1989-03-01

193

Role of Water Vapor in the Partial Oxidation of Propene  

Microsoft Academic Search

The role of water vapor was explored for the partial oxidation of propene over antimony–tin–vanadium oxide (SB\\/Sn\\/V oxide) catalyst at 1 atm pressure and 340°C using a microcatalytic packed bed reactor. Steady-state, transient kinetics, TPD, and isotopic transient experiments were performed. Water suppresses the formation of CO2by blocking the most active sites which are responsible for CO2formation but water also

Y. A. Saleh-Alhamed; R. R. Hudgins; P. L. Silveston

1996-01-01

194

[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

195

Alternative electron flows (water-water cycle and cyclic electron flow around PSI) in photosynthesis: molecular mechanisms and physiological functions.  

PubMed

An electron flow in addition to the major electron sinks in C(3) plants [both photosynthetic carbon reduction (PCR) and photorespiratory carbon oxidation (PCO) cycles] is termed an alternative electron flow (AEF) and functions in the chloroplasts of leaves. The water-water cycle (WWC; Mehler-ascorbate peroxidase pathway) and cyclic electron flow around PSI (CEF-PSI) have been studied as the main AEFs in chloroplasts and are proposed to play a physiologically important role in both the regulation of photosynthesis and the alleviation of photoinhibition. In the present review, I discuss the molecular mechanisms of both AEFs and their functions in vivo. To determine their physiological function, accurate measurement of the electron flux of AEFs in vivo are required. Methods to assay electron flux in CEF-PSI have been developed recently and their problematic points are discussed. The common physiological function of both the WWC and CEF-PSI is the supply of ATP to drive net CO(2) assimilation. The requirement for ATP depends on the activities of both PCR and PCO cycles, and changes in both WWC and CEF-PSI were compared with the data obtained in intact leaves. Furthermore, the fact that CEF-PSI cannot function independently has been demonstrated. I propose a model for the regulation of CEF-PSI by WWC, in which WWC is indispensable as an electron sink for the expression of CEF-PSI activity. PMID:21068108

Miyake, Chikahiro

2010-11-10

196

Growth and Characterization of Anodic Oxidized Films in Pure Water  

NASA Astrophysics Data System (ADS)

An anodic oxidized film has been deposited in pure water at room temperature. Film thickness increases linearly as a function of total charge during oxidation. High film deposition rate and low surface roughness are obtained by alternately changing the polarity of the applied voltage. The film growth mechanism is discussed and the model of anodic oxidation in pure water is proposed. The HF etching rate and the oxide thickness are reduced by an increase in annealing temperature. Though the electrical characteristics of the anodic oxide film are inferior to those of the film obtained by thermal oxidation, they can be improved by thermal annealing at a temperature of 400°C.

Ohnishi, Kazunori; Ito, Akira; Takahashi, Yoshihiro; Miyazaki, Syunsuke

2002-03-01

197

A comparative evaluation of cobalt chromium oxide, cobalt manganese oxide, cobalt manganese oxide, and copper manganese oxide as catalysts for the water-gas shift reaction  

Microsoft Academic Search

Cobalt chromium oxide, cobalt manganese oxide, and copper manganese oxide have been compared as catalysts for the water-gas shift reaction. Cobalt chromium oxide and cobalt manganese oxide catalysts can give both high activity and long lifetimes for this reaction. Cobalt chromium oxide catalysts display higher activity compared to the other catalyst systems and this is shown that both the cobalt

G. J. Hutchings; R. G. Copperthwaite; F. M. Gottschalk; R. Hunter; J. Mellor; S. W. Orchard; T. Sangiorgio

1992-01-01

198

Wet oxidation for enhanced oil recovery with produced water recycle  

SciTech Connect

Wet oxidation has been shown to be effective in enabling recycling of untreated produced water while generating 100% quality steam/CO/sub 2/ mixtures for enhanced oil recovery. Continuous pilot plant tests with several different fuels and produced water compositions showed no influence of the feed water composition on oxidation rates. Produced water of any quality, including high chlorides, can be used. Low grade fuels such as Syncrude coke are effectively oxidized with no atmospheric pollution emissions; no SOx or NOx is formed in the process. The wet oxidation process can be operated so as to generate only damp, dewatered solid wastes, thereby eliminating the need for disposal of liquid effluents.

Chowdhury, A.K.; Pradt, L.A.

1983-01-01

199

Nitrogen cycling following The Great Oxidation Event, evidence from the Paleoproterozoic of Fennoscandia.  

NASA Astrophysics Data System (ADS)

The Fennoscandia Arctic Russia - Drilling Early Earth Project (FAR-DEEP) recovered core materials spanning the early Paleoproterozoic of Arctic Russia under the auspices of the International Continental Scientific Drilling Program. Here we present N and C isotopic data documenting N and C cycle dynamics during this critical interval of Earth history. Additionally, we will discuss the challenges of nitrogen isotope studies in such ancient sediments and the methods that we have utilized to test the fidelity of our nitrogen isotope data. Nitrogen isotope studies in very ancient sedimentary rocks, like those recovered by the FAR-DEEP are plagued by the concerns of diagenetic and metamorphic overprinting. Nitrogen is often present in very low concentrations and in a variety of inorganic phases that may or may not be derived from the ambient organic matter. For these reasons, bulk sediment ?15N data can be at best, ambiguous. To overcome these issues we have utilized kerogens for ?15N and ?13C analyses. The large difference between bulk and kerogen ?15N data demonstrates that inorganic N is anomalously 15N-enriched, by up to 7% and bulk ?15N values substantially overestimate the magnitude of the 15N variability in the Onega Basin (OB) sediments. Metasomatic processes during basinal magamatic activity resulted in the addition of 15N-enriched inorganic-N. Authigenic K-bearing micas are common in intervals where bulk ?15N values are 15N-enriched, suggesting that secondary mineral phases have retained 15N-enriched ammonia generated during metsomatism. The FAR-DEEP drilling team has documented an anomalously large, and rapid ?13C shift of -17% in carbonates and organic matter of the Zhaoneskaya Formation (ZF) of the OB following the extended period of 13Ccarb-enrichment know as the Lomagundi-Jatuli event. The isotopic shift in reduced carbon has also been recognized in the Franceville Formation of Gabon, termed here as "Shunga-Francevillian" anomaly, and may reflect the global oxidation of organic matter buried during the buildup of atmospheric oxygen in response to Lomagundi-Jatuli carbon burial. The dynamic response of the nitrogen cycle in the ZF is consistent with increased availability of O2 in the water column and is similar to the response documented in Archean sequences. Kerogen ?15N values are below 2%, most likely reflecting a biological N2-fixation source for nutrient-nitrogen with little influence from denitrification. ?13C values increase from -26% to -19% signaling a transient increase in the burial of organic carbon and net production of O2. Transition from a largely anoxic OB water column to one that was oxidized in its surface waters would have allowed for redox cycling of nitrogen and accompanying 15N-enrichment. Thus, the observed ?15N increase of 5% reflects an expansion in denitrification and associated reactions and oxidation of the OB water column under elevated atmospheric O2. At the end of the precipitous decrease in ?13C values ?15N values return pre-excursion values of ~+2%. This drop in ?13C and ?15N suggests a return to less oxidizing conditions in the OB following drawdown of atmospheric O2 during organic matter oxidation.

Junium, C. K.; Kump, L.; Arthur, M. A.; Melezhik, V.; Lepland, A.; Members of the FAR-DEEP Drilling Team

2011-12-01

200

Arsenic cycling within the water column of a small lake receiving contaminated ground-water discharge  

SciTech Connect

The fate of arsenic discharged from contaminated ground water to a small, shallow lake at a hazardous waste site was examined to understand the role of iron (hydr)oxide precipitation-dissolution processes within the water column. Field and laboratory observations indicate that arsenic solubility was controlled, in part, by the extent of ferrous iron oxidation-precipitation and arsenic sorption occurring near the lake chemocline. Laboratory experiments were conducted using site-derived water to assess the impact of these coupled processes on the removal of dissolved arsenic from the water column. The measured concentration of organic carbon from epilimnetic and hypolimnetic water sampled from the lake was approximately 1.3 mM and 17.0 mM, respectively. Experiments conducted with these samples along with synthetic controls containing no organic carbon demonstrated that observed rates of formation and crystallinity of the precipitated iron (hydr)oxide were dependent on the concentration of organic carbon in the lake water. Increasing dissolved organic matter concentration did not significantly interfere with ferrous iron oxidation, but inhibited iron (hydr)oxide precipitation and subsequent sorption of arsenic. For experiments using water sampled from the lake hypolimnion there was a strong relationship between the fraction of precipitated iron and the fraction of sorbed arsenic. Laboratory- and field-derived iron (hydr)oxide precipitates were characterized to evaluate mineralogy and arsenic distribution. In-situ suspended solids and precipitates formed in laboratory experiments using hypolimnetic water were identified as poorly crystalline 2-line ferrihydrite. These solids were readily dissolved in the presence of dithionite indicating that elevated dissolved iron and arsenic observed in the hypolimnion resulted, in part, from in-situ reductive dissolution of settling 2-line ferrihydrite near the sediment-water interface. These observations support the contention that the levels of dissolved arsenic observed in the shallow lake can be attributed to ground-water discharge and internal recycling of arsenic within the water column. The efficiency of the process resulting in iron (hydr)oxide precipitation and arsenic sorption limits the downgradient export of arsenic derived from ground-water discharge.

Ford, Robert G.; Wilkin, Richard T.; Hernandez, Gina (EPA); (ECO)

2008-09-18

201

Cycling endurance of silicon-oxide-nitride-oxide-silicon nonvolatile memory stacks prepared with nitrided SiO2/Si(100) interfaces  

NASA Astrophysics Data System (ADS)

The effects of nitrided SiO2/Si(100) interfaces upon cycling endurance in silicon-oxide-nitride-oxide-silicon (SONOS) nonvolatile memory transistors are investigated. Analysis of metal-oxide-silicon field-effect transistor subthreshold characteristics indicate cycling degradation to be a manifestation of interface trap generation at the tunnel oxide/silicon interface. After 106 write/erase cycles, SONOS film stacks prepared with nitrided tunnel oxides exhibit enhanced cycling endurance over stacks prepared with non-nitrided tunnel oxides. If the capping oxide is formed by steam oxidation, rather than by deposition, SONOS stacks prepared with non-nitrided tunnel oxides exhibit endurance characteristics similar to stacks with nitrided tunnel oxides. For this case, a mechanism for latent nitridation of the tunnel oxide/silicon interface is proposed.

Habermehl, S.; Nasby, R. D.; Rightley, M. J.

1999-08-01

202

Efficiency, costs and benefits of AOPs for removal of pharmaceuticals from the water cycle.  

PubMed

Different advanced oxidation processes (AOP) were developed for the treatment of highly loaded wastewater streams. Optimisation of removal and improvement of efficiency were carried out on a laboratory, semiworks and pilot plant scale. The persistent cytostatic drug cyclophosphamide was selected as a reference substance regarding elimination and evaluation of the various oxidation processes because of its low degradability rate. The investigated processes are cost-efficient and suitable regarding the treatment of wastewater streams since they lead to efficient elimination of antibiotics and antineoplastics. A total reduction of toxicity was proven by means of the umuC-test. However, in order to reduce pharmaceuticals from the water cycle, it must be considered that the input of more than 80 % of the pharmaceuticals entering wastewater treatment systems results from private households. Therefore, advanced technologies should also be installed at wastewater treatment plants. PMID:20182078

Tuerk, J; Sayder, B; Boergers, A; Vitz, H; Kiffmeyer, T K; Kabasci, S

2010-01-01

203

Electrode-assisted catalytic water oxidation by a flavin derivative  

NASA Astrophysics Data System (ADS)

The success of solar fuel technology relies on the development of efficient catalysts that can oxidize or reduce water. All molecular water-oxidation catalysts reported thus far are transition-metal complexes, however, here we report catalytic water oxidation to give oxygen by a fully organic compound, the N(5)-ethylflavinium ion, Et-Fl+. Evolution of oxygen was detected during bulk electrolysis of aqueous Et-Fl+ solutions at several potentials above +1.9 V versus normal hydrogen electrode. The catalysis was found to occur on glassy carbon and platinum working electrodes, but no catalysis was observed on fluoride-doped tin-oxide electrodes. Based on spectroelectrochemical results and preliminary calculations with density functional theory, one possible mechanistic route is proposed in which the oxygen evolution occurs from a peroxide intermediate formed between the oxidized flavin pseudobase and the oxidized carbon electrode. These findings offer an organic alternative to the traditional water-oxidation catalysts based on transition metals.

Mirzakulova, Ekaterina; Khatmullin, Renat; Walpita, Janitha; Corrigan, Thomas; Vargas-Barbosa, Nella M.; Vyas, Shubham; Oottikkal, Shameema; Manzer, Samuel F.; Hadad, Christopher M.; Glusac, Ksenija D.

2012-10-01

204

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

205

Mercury cycling between the water column and surface sediments in a contaminated area.  

PubMed

Mercury cycling in the water column and upper sediments of a contaminated area, the Largo do Laranjo, Aveiro (Portugal), was evaluated after determination of reactive and non-reactive mercury concentrations in the water column and pore waters of sediments, collected in several places of this bay. In the water column, reactive mercury concentrations varied between 10 and 37 pmol dm(-3), the highest values being observed near the mercury anthropogenic source. However, reactive mercury was a narrowly constrained fraction of the total mercury, making up only 4-16% of the total, showing evidence of the importance of dissolved organic matter on mercury transport. In sediments, higher concentrations of mercury were also determined near industrial discharges. Results indicate the existence of an equilibrium between solid and liquid phases, determined by solid sediment/pore water distribution coefficients. Much of the mercury present in the solid fraction is associated with organic matter (r=0.837) and iron oxyhydroxides (r=0.919), but as oxides begin to dissolve in reduced sediments and organic matter decays, the adsorbed mercury is released. In fact, the mercury concentrations in pore waters of those contaminated sediments largely exceeded the values determined in the water column. As molecular diffusion may contribute to the dissolved mercury distribution in the overlying water column, this phenomenon was evaluated. However, the pore waters of Largo do Laranjo do not enrich the water column substantially in terms of reactive and non-reactive mercury. In fact, pore waters can contribute only to 0.2% and 0.5% of the reactive and non-reactive mercury present in the water column, respectively, showing that as long as mercury is being incorporated in sediments, it stays in stable forms. PMID:16854448

Ramalhosa, Elsa; Segade, Susana Río; Pereira, Eduarda; Vale, Carlos; Duarte, Armando

2006-07-18

206

Kinetics of simazine advanced oxidation in water.  

PubMed

Comparison of the effects and kinetics of UV photolysis and four advanced oxidation systems (ozone, ozone/hydrogen peroxide, ozone/UV radiation and UV radiation/hydrogen peroxide) for the removal of simazine from water has been investigated. At the conditions applied, the order of reactivity was ozone < ozone/hydrogen peroxide < UV radiation < ozone/UV radiation and UV radiation/hydrogen peroxide. Rate constants of the reactions between ozone and simazine and hydroxyl radical and simazine were found to be 8.7 M-1s-1 and 2.1 x 10(9) M-1s-1, respectively. Also, a quantum yield of 0.06 mol.photon-1 was found for simazine at 254 nm UV radiation. The high value of the quantum yield corroborated the importance of the direct photolysis process. Percentage contributions of direct reaction with ozone, reaction with hydroxyl radicals and direct photolysis were also quantified. PMID:10874621

Beltrán, F J; García-Araya, J F; Rivas, J; Alvarez, P M; Rodríguez, E

2000-07-01

207

Metal oxide photoanodes for water splitting.  

PubMed

Solar hydrogen production through photocatalytically assisted water splitting has attracted a great deal of attention since its first discovery almost 30 years ago. The publication of investigations into the use of TiO? photoanodes has continued apace since and a critical review of current trends is reported herein. Recent advances in the understanding of the behaviour of nanoparticulate TiO? films is summarized along with a balanced report into the utility and nature of titania films doped with non-metallic elements and ordered, nanostructured films such as those consisting of nanotubes. Both of these are areas that have generated a not insignificant degree of activity. One goal of doping TiO? has been to extend the photoresponse of the material to visible light. A similar goal has seen a resurgence in interest in Fe?O? photoanodes. Herein, the influence of dopants on the photocurrent density observed at Fe?O? photoanodes and, in this regard, the role of silicon has attracted much attention, and a little debate. Finally, we look beyond the binary oxides. Photoanodes made from new materials such as mixed metal oxides, perovskite structured semiconductors, metal (oxy)nitrides or composite electrodes offer the potential to either tailor the optical band gap or tune the conduction or valence band energetics. Recent work in this area is detailed here. PMID:21506001

Augusty?ski, J; Alexander, B D; Solarska, R

2011-01-01

208

Water vapor measurements at ALOMAR over a solar cycle compared with model calculations by LIMA  

NASA Astrophysics Data System (ADS)

Microwave water vapor measurements between 40 and 80 km over a solar cycle (1996-2007) were carried out in high latitudes at ALOMAR (69.290 N, 16.030 E), Norway. Some gapes and only few interruptions of monitoring occurred during this period. The observations are marked by a certain year-to-year variability not directly related to the solar activity. In the upper domain in winter the water vapor mixing ratios are anti-correlated to the solar activity whereas in summer minima occurred in the years after the solar maximum in 2000/01. In winter sudden stratospheric warmings modulate the water vapor mixing ratios. Within the stratopause region a middle atmospheric water vapor maximum was observed. It results from the methane oxidation and is a regular feature there. The maximum altitude increases toward summer by approximately 5 km. During this season a secondary water vapor maximum also occurred above 65 km most pronounced in late summer. A strong day-to-day variability connected with planetary wave activity was found over the whole year. Although model calculations by means of the real date model LIMA (Leibniz-Institute Middle Atmosphere model) reflect essential patterns of the water vapor variation the results also show that exchange processes between the stratosphere and troposphere not modeled by LIMA influences the long-term variability. We discuss the chemical and dynamical background of the variation of water vapor in the middle atmosphere.

Sonnemann, Gerd; Hartogh, Paul; Song, Li; Grygalashvyly, Mykhaylo; Berger, Uwe

209

Mars' Water Cycle: Interpreting Phoenix Lander Observations with a General Circulation Model  

Microsoft Academic Search

The water cycle is a key aspect of Mars' current climate system. Critical components of the water cycle include the exchange of water between the surface and atmosphere (i.e., surface water sources and sinks), cloud formation\\/dissipation, and atmospheric transport. Observations acquired by instruments on the Phoenix Lander and Mars Reconnaissance Orbiter (MRO) provide unique insights into many aspects of the

M. Kahre; R. M. Haberle; J. Hollingsworth; J. de Mûlenaere

2009-01-01

210

Earthquake cycle modulation via the redistribution of surface water mass  

NASA Astrophysics Data System (ADS)

Surface water bodies, from individual lakes to the global ocean, change in extent and mass over timescales ranging from a single year to a Milankovich cycle. Stress changes within the solid earth as a result of the redistribution of water mass have the potential to affect the seismic cycle on nearby faults through a combination of mechanisms, including deformation from the weight of the load and changes to effective normal stress via pore pressure diffusion. We present a model that quantifies these effects and their roles in modulating the seismic cycle. 3-D stress change from rebound is calculated using a semi-analytic method for a two-layer model including a thick elastic plate overlying a viscoelastic halfspace. The computational efficiency of the semi-analytic solution allows the true shape of the surface load to be accounted for without simplification. Effective normal stress from pore pressure diffusion is constrained by the hydrostatic end member. Two case studies are considered: 1) eustatic sea level rise since the Last Glacial Maximum and its ability to influence fault slip-rate in coastal regions during the late Pleistocene and early Holocene; and 2) intermittent floods of ancient Lake Cahuilla over the last 1200 years and their influence on fault rupture along the southern terminus of the San Andreas Fault. The sensitivity of a particular fault to water loading is highly dependent on both its geometry and its earthquake recurrence interval. The stresses imposed by these loads are generally an order of magnitude smaller than the tectonic stress accumulation over the same time period, such that redistributed surface loads can affect the timing of fault rupture but do not alter the structural or tectonic setting of a region. However, by advancing or delaying fault rupture, surface loads are able to perturb the apparent fault slip rate over the timescale of the redistribution. In particular, the long-term seismic cycle of a fault is more likely to be affected when a nearby flooding event recurs over a time period similar to the earthquake recurrence interval. These models are therefore helpful for understanding observations of fault slip-rate variability on a variety of systems.

Luttrell, K. M.; Brothers, D. S.

2011-12-01

211

Life cycle assessment of nuclear-based hydrogen production via thermochemical water splitting using a copper-chlorine (Cu-Cl) cycle  

NASA Astrophysics Data System (ADS)

The energy carrier hydrogen is expected to solve some energy challenges. Since its oxidation does not emit greenhouse gases (GHGs), its use does not contribute to climate change, provided that it is derived from clean energy sources. Thermochemical water splitting using a Cu-Cl cycle, linked with a nuclear super-critical water cooled reactor (SCWR), which is being considered as a Generation IV nuclear reactor, is a promising option for hydrogen production. In this thesis, a comparative environmental study is reported of the three-, four- and five-step Cu-Cl thermochemical water splitting cycles with various other hydrogen production methods. The investigation uses life cycle assessment (LCA), which is an analytical tool to identify and quantify environmentally critical phases during the life cycle of a system or a product and/or to evaluate and decrease the overall environmental impact of the system or product. The LCA results for the hydrogen production processes indicate that the four-step Cu-Cl cycle has lower environmental impacts than the three- and five-step Cu-Cl cycles due to its lower thermal energy requirement. Parametric studies show that acidification potentials (APs) and global warming potentials (GWPs) for the four-step Cu-Cl cycle can be reduced from 0.0031 to 0.0028 kg SO2-eq and from 0.63 to 0.55 kg CO2-eq, respectively, if the lifetime of the system increases from 10 to 100 years. Moreover, the comparative study shows that the nuclear-based S-I and the four-step Cu-Cl cycles are the most environmentally benign hydrogen production methods in terms of AP and GWP. GWPs of the S-I and the four-step Cu-Cl cycles are 0.412 and 0.559 kg CO2-eq for reference case which has a lifetime of 60 years. Also, the corresponding APs of these cycles are 0.00241 and 0.00284 kg SO2-eq. It is also found that an increase in hydrogen plant efficiency from 0.36 to 0.65 decreases the GWP from 0.902 to 0.412 kg CO 2-eq and the AP from 0.00459 to 0.00209 kg SO2-eq for the four-step Cu-Cl cycle. Keywords: Hydrogen production, nuclear energy, Cu-Cl cycle, environmental impact, LCA.

Ozbilen, Ahmet Ziyaettin

212

Iron-dependent changes in cellular energy metabolism: influence on citric acid cycle and oxidative phosphorylation  

Microsoft Academic Search

Iron modulates the expression of the critical citric acid cycle enzyme aconitase via a translational mechanism involving iron regulatory proteins. Thus, the present study was undertaken to investigate the consequences of iron perturbation on citric acid cycle activity, oxidative phosphorylation and mitochondrial respiration in the human cell line K-562. In agreement with previous data iron increases the activity of mitochondrial

Horst Oexle; Erich Gnaiger; Günter Weiss

1999-01-01

213

17Oexcess in meteoric water: as a new isotopic parameter to decipher water cycle processes  

Microsoft Academic Search

Classical water stable isotopes (dD and d18O) have been used for more than 50 years with the aim to understand the links between water cycle and climate. They provide information on either temperature or precipitation changes depending on the latitudes. Their combination, in the so-called d-excess, brings some information on climatic conditions occurring during non equilibrium processes along air masses

A. Landais; M. Guillevic; H. Steen-Larsen; F. Vimeux; A. Bouygues; S. Falourd; C. M. Risi; S. Bony

2009-01-01

214

The water cycles of water-soluble organic salts of atmospheric importance  

Microsoft Academic Search

In this study, the water cycles of nine water-soluble organic salts of atmospheric interest were studied using an electrodynamic balance (EDB) at 25°C. Sodium formate, sodium acetate, sodium succinate, sodium pyruvate and sodium methanesulfonate (Na-MSA) particles crystallize as the relative humidity (RH) decreases and they deliquesce as the RH increases. Sodium oxalate and ammonium oxalate form supersaturated particles at low

Changgeng Peng; Chak K Chan

2001-01-01

215

RELATIONSHIPS BETWEEN OXIDATION-REDUCTION POTENTIAL, OXIDANT, AND PH IN DRINKING WATER  

EPA Science Inventory

Oxidation and reduction (redox) reactions are very important in drinking water. Oxidation-reduction potential (ORP) measurements reflect the redox state of water. Redox measurements are not widely made by drinking water utilities in part because they are not well understood. The ...

216

RELATIONSHIPS BETWEEN OXIDATION-REDUCTION, OXIDANT, AND PH IN DRINKING WATER  

EPA Science Inventory

Oxidation and reduction (redox) reactions are very important in drinking water. Oxidation-reduction potential (ORP) measurements reflect the redox state of water. Redox measurements are not widely made by drinking water utilities in part because they are not well understood. The ...

217

Failure and life cycle evaluation of watering valves.  

PubMed

Automated watering systems provide a reliable source of ad libitum water to animal cages. Our facility uses an automated water delivery system to support approximately 95% of the housed population (approximately 14,000 mouse cages). Drinking valve failure rates from 2002 through 2006 never exceeded the manufacturer standard of 0.1% total failure, based on monthly cage census and the number of floods. In 2007, we noted an increase in both flooding and cases of clinical dehydration in our mouse population. Using manufacturer's specifications for a water flow rate of 25 to 50 mL/min, we initiated a wide-scale screening of all valves used. During a 4-mo period, approximately 17,000 valves were assessed, of which 2200 failed according to scoring criteria (12.9% overall; 7.2% low flow; 1.6% no flow; 4.1% leaky). Factors leading to valve failures included residual metal shavings, silicone flash, introduced debris or bedding, and (most common) distortion of the autoclave-rated internal diaphragm and O-ring. Further evaluation revealed that despite normal autoclave conditions of heat, pressure, and steam, an extreme negative vacuum pull caused the valves' internal silicone components (diaphragm and O-ring) to become distorted and water-permeable. Normal flow rate often returned after a 'drying out' period, but components then reabsorbed water while on the animal rack or during subsequent autoclave cycles to revert to a variable flow condition. On the basis of our findings, we recalibrated autoclaves and initiated a preventative maintenance program to mitigate the risk of future valve failure. PMID:22330720

Gonzalez, David M; Graciano, Sandy J; Karlstad, John; Leblanc, Mathias; Clark, Tom; Holmes, Scott; Reuter, Jon D

2011-09-01

218

Failure and Life Cycle Evaluation of Watering Valves  

PubMed Central

Automated watering systems provide a reliable source of ad libitum water to animal cages. Our facility uses an automated water delivery system to support approximately 95% of the housed population (approximately 14,000 mouse cages). Drinking valve failure rates from 2002 through 2006 never exceeded the manufacturer standard of 0.1% total failure, based on monthly cage census and the number of floods. In 2007, we noted an increase in both flooding and cases of clinical dehydration in our mouse population. Using manufacturer's specifications for a water flow rate of 25 to 50 mL/min, we initiated a wide-scale screening of all valves used. During a 4-mo period, approximately 17,000 valves were assessed, of which 2200 failed according to scoring criteria (12.9% overall; 7.2% low flow; 1.6% no flow; 4.1% leaky). Factors leading to valve failures included residual metal shavings, silicone flash, introduced debris or bedding, and (most common) distortion of the autoclave-rated internal diaphragm and O-ring. Further evaluation revealed that despite normal autoclave conditions of heat, pressure, and steam, an extreme negative vacuum pull caused the valves’ internal silicone components (diaphragm and O-ring) to become distorted and water-permeable. Normal flow rate often returned after a ‘drying out’ period, but components then reabsorbed water while on the animal rack or during subsequent autoclave cycles to revert to a variable flow condition. On the basis of our findings, we recalibrated autoclaves and initiated a preventative maintenance program to mitigate the risk of future valve failure.

Gonzalez, David M; Graciano, Sandy J; Karlstad, John; Leblanc, Mathias; Clark, Tom; Holmes, Scott; Reuter, Jon D

2011-01-01

219

Diel Studies of Hydrogen Peroxide Production and Cycling in Urban-Impacted Southern California Coastal Receiving Waters  

NASA Astrophysics Data System (ADS)

Microbial water quality in a watershed and its receiving waters is monitored through measurements of fecal indicator bacteria (FIB). Diel cycling in FIB have previously been observed, with a minimum at noon and maximum levels during the night. Hydrogen peroxide, a reactive oxidant produced photochemically from dissolved organic matter in natural water systems, has been suggested as a possible cause of bacterial mortality and resultant FIB diel variability. To assess the importance of H2O2 in coastal waters routinely monitored for FIB, we conducted four 24-h diel studies of surf zone concentrations at the height of the summer recreational season in July 2009 at Crystal Cove State Beach, a popular bathing beach in Orange County, Southern California. Concentrations showed diel cycling anti-correlated with typical FIB diel variability, consistent with cause and effect. Concentrations ranged from a noon high of 200 nM to a night-time low of 40 nM. We discuss trends observed between H2O2 levels, tide and DOM optical properties and potential DOM and H2O2 sources. Our concentrations, production and loss rates obtained in this dynamic surf zone environment are compared to previous off-shore seawater studies. This study has relevance for oxidant cycling and microbial water quality in the surface waters of watersheds.

Clark, C. D.; de Bruyn, W. J.; Hirsch, C.; Aiona, P.

2009-12-01

220

Validation of water cycle in GCM using water isotope data (Invited)  

Microsoft Academic Search

Water isotopes, HDO, H218O, are very powerful validation tools for hydrological cycle in the GCM. Their variability in the atmosphere is related to the source of moisture and the integrated histories of both condensation and evaporation during travel from source to deposition site. Hence good representation of observed global isotopic patterns and their seasonality indicate that GCM can reasonably simulate

N. Kurita

2010-01-01

221

Amorphous manganese oxide remains amorphous upon lithium intercalation and cycling  

Microsoft Academic Search

Lithium intercalation in amorphous manganese oxide, synthesized by a room temperature aqueous oxidation route, is analyzed. As reported before, the material yields a very high intercalation capacity and also shows promising rate capability as cathode for rechargeable lithium batteries. The present study investigates the structure of the material using X-ray powder diffraction conducted on composite cathode pellets at different stages

Xu Jun John; Ye Hui; Jain Gaurav; Yang Jingsi

2004-01-01

222

Endothelial nitric oxide synthase is differently expressed in human endometrial vessels during the menstrual cycle  

Microsoft Academic Search

Endogenous nitric oxide (NO) can be synthesized by endothelial cells and can act as a potent vasodilator. We investigated endothelial nitric oxide synthase (eNOS), one of the three different enzymes responsible for the synthesis of NO by immunohistochemical methods throughout the menstrual cycle on 34 endometrial samples and compared its detection with the von Willebrand Factor (vWF) as a reliable

M. Taguchi; J. Alfer; K. Chwalisz; H. M. Beier; I. Classen-Linke

2000-01-01

223

Proposal and analysis of a novel ammonia–water cycle for power and refrigeration cogeneration  

Microsoft Academic Search

Cogeneration has improved sustainability as it can improve the energy utilization efficiency significantly. In this paper, a novel ammonia-water cycle is proposed for the cogeneration of power and refrigeration. In order to meet the different concentration requirements in the cycle heat addition process and the condensation process, a splitting \\/absorption unit is introduced and integrated with an ammonia–water Rankine cycle

Meng Liu; Na Zhang

2007-01-01

224

Cycling of three solid oxide fuel cell types  

Microsoft Academic Search

One of the key problems of SOFCs is their slow start-up and cycling performance which is due to the thermal shock problems of zirconia electrolyte and its associated electrode and interconnect materials. Typical start-up times range from 2 to 6h. Faster cycles can cause degradation in performance and in material integrity. The purpose of this paper is to study the

Waldemar Bujalski; Chinnan M. Dikwal; Kevin Kendall

2007-01-01

225

Chemical and Biological Oxidation of Iron in Acid Mine Water  

Microsoft Academic Search

Prior to limestone neutralization of acid water, ferrous iron needs to be oxidized to prevent downstream oxidation and the formation of acid. This study assessed the effect of various parameters on the biological and chemical rate of iron oxidation, both chemically and biologically. In batch experiments, it was found that although the use of support media had no effect on

N. R. Nengovhela; C. A. Strydom; J. P. Maree; H. A. Greben

2004-01-01

226

A proposal for water oxidation in photosystem II  

Microsoft Academic Search

There has been much speculation concerning the mechanism for water oxidation by Photosystem 11. Based on recent work on the biophysics of Photosystem I1 and our own work on the reactivity of synthetic manganese complexes, we propose a chemically reasonable mechanistic model for the water oxidation function of this enzyme. An essential feature of the model is the nucleophilic attack

Vincent L. Pecoraro; Michael J. Baldwin; M. Tyler Caudle; Wen-Yuan Hsieh; Neil A. Law

1998-01-01

227

Stainless steel flow reactor for supercritical water oxidation: corrosion tests  

Microsoft Academic Search

One of the obstacles that is inhibiting the development of supercritical water oxidation (SCWO) into a viable industrial process, is the problem of corrosion. A bench scale stainless steel flow reactor for supercritical water oxidation studies was constructed. Corrosion of the reactor was studied under pressure of 400 bars and at temperatures of 250, 375 and 420°C. The concentrations of

Tina M. Hayward; Igor M. Svishchev; Ramesh C. Makhija

2003-01-01

228

Improved cycling performance of bismuth-modified amorphous manganese oxides as cathodes for rechargeable lithium batteries  

Microsoft Academic Search

Bismuth-modified amorphous manganese oxides were synthesized via a room temperature aqueous route. They were galvanostatically tested as intercalation cathodes for rechargeable lithium batteries at 1mAcm?2 between 1.5 and 4.3V. In sharp contrast to severe capacity fading of unmodified amorphous manganese oxide synthesized by the same route, a stable cycling performance of the bismuth-modified amorphous manganese oxide was observed. After an

Jingsi Yang; Terrill B Atwater; Jun John Xu

2005-01-01

229

Humans Transforming the Water Cycle and the 500-Year Challenge  

NASA Astrophysics Data System (ADS)

Humans are today embedded into the basic character of the water cycle, through a myriad of processes including water abstraction and flow diversion, land cover change, pollution, destruction of aquatic biodiversity, and climate change. A major scientific challenge is to understand how these changes manifest themselves and if they bear synergistic impacts across different scales. While the concept of human manipulation of the hydrologic cycle in the contemporary timeframe has been gaining general acceptance in the community, the notion of how this control has evolved, and evolved to regionally-significant scales, has been less well-developed. These issues can be tackled through an interdisciplinary synthesis goal: To quantify the widespread alteration of hydrologic systems over local-to-regional domains focusing on the Northeast Corridor of the United States over a 500-yr period (1600 to 2100)—The 500-Year Challenge. This discussion presents the rationale plus key findings of this team-based effort to understand the evolution of human-water systems over both retrospective and future time horizons. Our effort, organized through the work of the Northeast Regional Consortium for Hydrologic Synthesis, focuses on a region that serves as an ideal example of the major changes undergoing the hydrologic over the national and indeed global scales. The effort has yielded several important conceptual steps forward in our understanding of human-water systems. First, chief products have been a developed as a series of metrics of system state and at the fully regional scale. These include the quantification of legal, social, and economic dimension information as they specifically relate to hydrology. Next, we forward the concept of hydrologic space-time collapse, as a means to understand how populations across the region have created and subsequently shed hydrologic constraints through the use of technology and the co-option of water external to their locale. Third, addressing the 500-year challenge would be impossible without the crossing of disciplinary bounds. Organizing a multiple perspective approach on the 500-Year Challenge is being realized through development of a cross-disciplinary integrated digital data compendia. The Regional Consortium itself crosses disciplinary and career stage boundaries and essential links are actively being established with many academic and practitioner constituencies. Lessons will be shared on executing synthesis in this context.

Vorosmarty, C. J.; Green, M. B.; Hermans, C. M.

2009-12-01

230

Computational comparison of stepwise oxidation and O-O bond formation in mononuclear ruthenium water oxidation catalysts  

NASA Astrophysics Data System (ADS)

A computational comparison of key steps along proposed water oxidation pathways for eleven distinct mononuclear ruthenium catalysts is presented. Free energies are determined via density functional calculations and analyzed for catalyst structural stability, energetic comparisons to experimentally measured potentials in highly acidic conditions, and other features. A single feature for optimal catalyst design does not emerge; different steps along the oxidation cycle are impacted in subtle and sometimes divergent ways depending on the nature of the ligand modification on the catalyst. The results reinforce the notion observed in previous experimental studies - in such multi-step mechanisms with complex catalysts, a careful balance between energetic optimization and catalyst stability at multiple steps along the cycle may be critical for practical performance considerations. Whereas comparing catalysts at an individual step is likely to provide an incomplete picture, behavior of chemically modified catalysts can be distinguished computationally across multiple mechanistic steps.

Jarvis, Emily A. A.; Lee, Brian; Neddenriep, Bradley; Shoemaker, Wendy

2013-05-01

231

[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

232

Climatically induced sedimentary cycles in Pliocene deep-water carbonates  

SciTech Connect

Two DSDP sites (86 and 94) on the Campeche ramp in the southern Gulf of Mexico penetrated more than 100 m of Pliocene pelagic ooze. The ooze is primarily carbonate, with a much smaller volcanic ash component than occurs in some Pleistocene sediments at these sites. Cores recovered from these holes display variations in carbonate mineralogy as well as total carbonate and sand abundances that are correlated with the oxygen isotope stratigraphy. Diagenetic loss of Mg-calcite is complete by the base of the Pleistocene, but aragonite, especially high-Sr aragonite forming algal needles that were transported off the shelf to the slope, persists through upper Pliocene cores. Variations in oxygen isotope ratios in planktonic foraminifera occur throughout the Pliocene, although the amplitude of those cycles is smaller than for the Pleistocene, with its more dramatic glacial-interglacial contrasts. As in overlying Pleistocene slope sediments, cooler intervals correspond with greater abundances of aragonite in the upper Pliocene section, reflecting a shift of the shallow, productive shelf seaward across the ramp surface during times of relatively low sea level. However, the aragonite abundances in the Pliocene are reduced on average compared to the Pleistocene. This difference is due in part to diagenetic loss, but also it likely reflects the overall higher sea level that apparently characterized Pliocene oceans, trapping more algal aragonite landward. Although sea level and climatic fluctuations were indeed less extreme in the Pliocene, they were still sufficient to generate sedimentary cycles in deep-water carbonates.

Gardulski, A.F. (Tufts Univ., Medford, MA (United States))

1991-03-01

233

Life Cycle Assesment of Daugavgriva Waste Water Treatment Plant  

NASA Astrophysics Data System (ADS)

This paper presents the assessment of the environmental impacts caused by the treatment of Riga's waste water in the Daugavgriva plant with biogas energy cogeneration through the life cycle assessment (LCA). The LCA seems to be a good tool to assess and evaluate the most serious environmental impacts of a facility The results showed clearly that the impact category contributing the most to the total impact -eutrophicationcomes from the wastewater treatment stage. Climate change also seems to be a relevant impact coming from the wastewater treatment stage and the main contributor to the Climate change is N2O. The main environmental benefits, in terms of the percentages of the total impact, associated to the use of biogas instead of any other fossil fuel in the cogeneration plant are equal to: 3,11% for abiotic depletation, 1,48% for climate change, 0,51% for acidification and 0,12% for eutrophication.

Romagnoli, F.; Sampaio, F.; Blumberga, D.

2009-01-01

234

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...

235

Rapid thermal cycling of metal-supported solid oxide fuel cellmembranes  

SciTech Connect

Solid oxide fuel cell (SOFC) membranes were developed in which zirconia-based electrolyte thin films were supported by a composite metal/ceramic electrode, and were subjected to rapid thermal cycling between 200 and 800 C. The effects of this cycling on membrane performance were evaluated. The membranes, not yet optimized for performance, showed a peak power density of 350mW/cm2at 900 C in laboratory-sized SOFCs that was not affected by the thermal cycling. This resistance to cycling degradation is attributed to the close matching of thermal expansion coefficient of the cermet support electrode with that of the zirconia electrolyte.

Matus, Yuriy B.; De Jonghe, Lutgard C.; Jacobson, Craig P.; Visco, Steven J.

2004-01-02

236

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

237

Future climate change, the agricultural water cycle, and agricultural production in China  

Microsoft Academic Search

Climate change would have a major impact on the hydrological cycle and consequently on available water resources, the potential for flood and drought, and agricultural productivity. In this study, the impacts of climate change on the agricultural water cycle and their implications for agricultural production in the 2020s were assessed by water-balance calculations for Chinese croplands. Temporal and spatial changes

Fulu Tao; Masayuki Yokozawa; Yousay Hayashi; Erda Lina

2003-01-01

238

Evidence for intensification of the global water cycle: Review and synthesis  

Microsoft Academic Search

One of the more important questions in hydrology is: if the climate warms in the future, will there be an intensification of the water cycle and, if so, the nature of that intensification? There is considerable interest in this question because an intensification of the water cycle may lead to changes in water-resource availability, an increase in the frequency and

Thomas G. Huntington

2006-01-01

239

Simulation of Water Cycle With a Martian Weather Research and Forecast Model  

Microsoft Academic Search

The water cycle in the Martian atmosphere is influenced by exchange with the subsurface, condensation on the surface, mixing between the boundary layer and the free atmosphere, large-scale horizontal mixing of air masses and precipitation as water ice particles. We have installed a water cycle model with microphysics processes into the Martian Weather Research and Forecast (WRF) model. It treats

A. Inada; M. I. Richardson; M. A. Mischna; C. E. Newman; A. D. Toigo; A. R. Vasavada

2005-01-01

240

Thermophysical properties of copper compounds in copper–chlorine thermochemical water splitting cycles  

Microsoft Academic Search

This paper examines the relevant thermophysical properties of compounds of copper that are used in thermochemical water splitting cycles. There are four variants of such Cu–Cl cycles that use heat and electricity to split the water molecule and produce H2 and O2. Since the energy input is mainly in the form of thermal energy, the Cu–Cl water splitting cycle is

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

2010-01-01

241

Tensile cracking during thermal cycling of alumina films formed by high-temperature oxidation  

SciTech Connect

Plastic relaxation of the stresses, produced by high-temperature oxidation and thermal contraction mismatch on cooling, decreases residual compression in the oxide. For this reason, slow cooling from the oxidation temperature is expected to have a beneficial effect on spalling resistance of protective alumina films. However, there exists a possibility of creating tensile stress in the oxide upon subsequent heating. With increasing stress relaxation on cooling, the magnitude of the tensile stress also increases which may lead to cracking of the oxide at high temperature. Experimental evidence shows an adverse effect of stress relaxation on the mechanical integrity of alumina films formed on Fe-Cr-Al heat-resistant alloys. High cooling and heating rates between oxidation cycles are required to prevent tensile failure of the oxide.

Tolpygo, V.K.; Clarke, D.R.

1999-10-08

242

Cell cycle arrest by monochloramine through the oxidation of retinoblastoma protein.  

PubMed

Impairment of cell cycle control has serious effects on inflammation, tissue repair, and carcinogenesis. We report here the G1 cell cycle arrest by monochloramine (NH2Cl), a physiological oxidant derived from activated neutrophils, and its mechanism. When Jurkat cells were treated with NH2Cl (70 microM, 10 min) and incubated for 24 h, the S phase population decreased significantly with a slight increase in the hypodiploid cell population. The G0/ G1 phase and G2/M phase populations did not show marked changes. Three hours after NH2Cl treatment, the retinoblastoma protein (pRB) was dephosphorylated especially at Ser780 and Ser795, both of which are important phosphorylation sites for the G1 checkpoint function. The phosphorylation at Ser807/811 showed no apparent change. The expression of cyclins, cyclin-dependent kinases, and cyclin-dependent kinase inhibitors showed no apparent change. Moreover, the kinase activity that phosphorylates pRB remained constant even after NH2Cl treatment. The protein phosphatase activity that dephosphorylates pRB showed a marginal increase. Notably, when the recombinant pRB was oxidized by NH2Cl in vitro, the oxidized pRB became difficult to be phosphorylated by kinases, especially at Ser780 and Ser795, but not at Ser807/811. Amino acid analysis of oxidized pRB showed methionine oxidation to methionine sulfoxide. The NH2Cl-treated Jurkat cell proteins also showed a decrease in methionine. These observations suggested that direct pRB oxidation was the major cause of NH2Cl-induced cell cycle arrest. In the presence of 2 mM NH4+, NaOCl (200 microM) or activated neutrophils also induced a G1 cell cycle arrest. As protein methionine oxidation has been reported in inflammation and aging, cell cycle modulation by pRB oxidation may occur in various pathological conditions. PMID:14732295

Hosako, Mutsumi; Ogino, Tetsuya; Omori, Masako; Okada, Shigeru

2004-01-01

243

Stable cycling of thin-film vanadium oxide electrodes between 4 and 0 V in lithium batteries  

Microsoft Academic Search

Vanadium oxide prepared by plasma-enhanced chemical vapor deposition was cycled in different voltage ranges in a lithium battery. Electrochemical cycling results show a surprisingly low irreversibility during the first discharge and good stability for close to 1000 cycles between 4 and 0V. Raman spectroscopy results indicate that a major structural transformation takes place when the films are cycled down to

Ping Liu; Se-Hee Lee; C. Edwin Tracy; John A Turner

2003-01-01

244

Silicon and tungsten oxide nanostructures for water splitting  

Microsoft Academic Search

Inorganic semiconductors are promising materials for driving photoelectrochemical water-splitting reactions. However, there is not a single semiconductor material that can sustain the unassisted splitting of water into H2 and O2. Instead, we are developing a three part cell design where individual catalysts for water reduction and oxidation will be attached to the ends of a membrane. The job of splitting

Karla R. Reyes Gil; Joshua M. Spurgeon; Nathan S. Lewis

2009-01-01

245

Analysis of Mixed Oxide Fuel Loaded Cores in the Heavy Water Reactor FUGEN  

Microsoft Academic Search

Uranium-plutonium mixed oxide (MOX) fuel cores in the heavy water reactor, FUGEN, were analyzed using the Advanced Thermal Reactor (ATR) type core design code system WIMS-ATR\\/POLESTAR and the accuracy of this code system also has been evaluated by means of operational data through the 34 burnup cycles and on-site ?-scanning data. The root mean square errors of calculated thermal neutron

Tsukasa OHTANI; Takashi IIJIMA; Yoshitake SHIRATORI

2003-01-01

246

Analysis of Mixed Oxide Fuel Loaded Cores in the Heavy Water Reactor FUGEN  

Microsoft Academic Search

Uranium-plutonium mixed oxide (MOX) fuel cores in the heavy water reactor, FUGEN, were analyzed using the Advanced Thermal Reactor (ATR) type core design code system WIMS-ATR\\/POLESTAR and the accuracy of this code system also has been evaluated by means of operational data through the 34 burnup cycles and on-site ? -scanning data. The root mean square errors of calculated thermal

Tsukasa OHTANI; Takashi IIJIMA; Yoshitake SHIRATORI

2003-01-01

247

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.

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

2012-01-01

248

Highly efficient and robust molecular ruthenium catalysts for water oxidation.  

PubMed

Water oxidation catalysts are essential components of light-driven water splitting systems, which could convert water to H(2) driven by solar radiation (H(2)O + h? ? 1/2O(2) + H(2)). The oxidation of water (H(2)O ? 1/2O(2) + 2H(+) + 2e(-)) provides protons and electrons for the production of dihydrogen (2H(+) + 2e(-) ? H(2)), 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 (H(2)bda = 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)L(2)] (L = pyridazine, pyrimidine, and phthalazine) were subsequently synthesized and shown to effectively catalyze Ce(IV)-driven [Ce(IV) = Ce(NH(4))(2)(NO(3))(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

2012-07-02

249

A Model for Water Oxidation Complex in Photosystem II  

NASA Astrophysics Data System (ADS)

Ruthenium complexes containing ring-substituted bipryidine ligands and related structures have longbeen known to efficiently catalyze water oxidation by strong chemical oxidants and at electrode surfaces. However, despite considerable effort, the goal of identifying the underlying molecular mechanisms has not yet been realized. In this paper, ZINDO/1 theory has been used to study a Ru complex found to react with water and Ce(NH 4)2(NO3)6 to liberate molecular oxygen (O2). The complex indicates a robust catalyst as compared to other earlier reported systems also a proposal mechanism for water oxidation is reported.

Mahdi Najafpour, M.

250

Homogeneous water oxidation catalysts containing a single metal site.  

PubMed

The recent recognition that a single metal site is capable of mediating the multiple electron and proton transfer events associated with water oxidation represents a pivotal discovery for the field. This finding has led to a remarkable expansion of known synthetic water oxidation catalysts, and has provided the means to gain unprecedented insight into the reaction steps involved with O-O bond formation. This perspective reflects on the key studies that have advanced our understanding of water oxidation catalysis while summarizing molecular features that are integral to negotiating this complicated reaction pathway with the goal of helping identify new frontiers of discovery for the field. PMID:23133828

Wasylenko, Derek J; Palmer, Ryan D; Berlinguette, Curtis P

2012-11-07

251

Polyoxometalate water oxidation catalysts and the production of green fuel.  

PubMed

In the last five years and currently, research on solar fuels has been intense and no sub-area in this field has been more active than the development of water oxidation catalysts (WOCs). In this timeframe, a new class of molecular water oxidation catalysts based on polyoxometalates have been reported that combine the advantages of homogeneous and heterogeneous catalysts. This review addresses central issues in green energy generation, the challenges in water oxidation catalyst development, and the possible uses of polyoxometalates in green energy science. PMID:22972187

Lv, Hongjin; Geletii, Yurii V; Zhao, Chongchao; Vickers, James W; Zhu, Guibo; Luo, Zhen; Song, Jie; Lian, Tianquan; Musaev, Djamaladdin G; Hill, Craig L

2012-09-12

252

Coal Conversion Wastewater Treatment by Catalytic Oxidation in Supercritical Water  

SciTech Connect

In previous reports, we showed that CARULITE 150 from Carus Chemical Company was so effective with oxidation of phenol in supercritical water (SCW) that the results we obtained were likely influenced by internal mass-transfer resistance. We also reported that oxidation of phenol over MnO{sub 2} powder in SCW improved the conversions of both phenol and total organic carbon (TOC) relative to non-catalytic oxidation while the catalytic oxidation kinetics was free from mass-transfer limitation. In this report we continued the investigation of oxidation over the MnO{sub 2} powder in SCW.

Savage, P.E.

1997-08-25

253

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

254

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

255

Economic Comparison of Hydrogen Production Using Sulfuric Acid Electrolysis and Sulfur Cycle Water Decomposition. Final Report.  

National Technical Information Service (NTIS)

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 ...

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

1978-01-01

256

Three-Dimensional Modelling of the Early Martian Climate and Water Cycle  

Microsoft Academic Search

We perform GCM modelling of the early martian climate. CO2 condensation, cloud formation, and a water cycle are included. New CO2 continuum opacity data predicts reduced warming, but this is partially compensated by local water vapor feedbacks.

R. Wordsworth; F. Forget; E. Millour; J.-B. Madeleine; V. Eymet; R. Haberle

2010-01-01

257

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

258

Lipoic acid and moderate swimming improves the estrous cycle and oxidative stress in Wistar rats.  

PubMed

The generation of reactive oxygen species resulting from physical activity may trigger adaptive processes at the reproductive level and in the antioxidant defense system itself. The objective of this study was to investigate the effects of moderate daily swimming and lipoic acid (LA) supplementation on estrous cycle duration and pro-oxident and antioxidant markers in young Wistar rats. Animals were submitted to daily swimming (for 1 h) for 30 days, between 1300 h and 1400 h. The following study groups were formed: group 1, sedentary; group 2, submitted to swimming; group 3, sedentary supplemented with 100 mg·kg(-1)·day(-1) of LA; and group 4, submitted to swimming and supplementation with 100 mg·kg(-1)·day(-1) of LA. The estrous cycle of the animals was evaluated daily, and the following oxidative stress markers were measured: plasma thiobarbituric acid reactive substances (TBARS) and glutathione (GSH), erythrocyte superoxide dismutase (SOD), GSH peroxidase (GPx) and catalase (CAT) activity. The exercise protocol increased estrous cycle duration in group 2, especially in the diestrous phase. There was also a decrease in lipoperoxidation, with enhanced antioxidant activity of SOD and GPx. Group 4 showed no alteration in estrous cycle duration and maintained the beneficial effects on the antioxidant system observed in group 2. The increase in estrous cycle duration and improved oxidative stress markers may be an adaptive response to moderate exercise. LA impeded any exercise-induced alteration in the cycle but preserved improvements in the antioxidant system. PMID:21980960

Martins, Rand Randall; de Oliveira Macedo, Ulisvaldo Brunno; Leite, Lúcia Dantas; Rezende, Adriana Augusto; Brandão-Neto, José; Almeida, Maria das Graças

2011-10-07

259

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

260

Effect on Limestone of 15 Cycles of Immersion in Dead Sea Water  

Microsoft Academic Search

The standard BRE crystallization test using Dead Sea water (instead of hydrous sodium sulphate) has been applied on 10 limestone types. At the end of the 15th cycle, all the limestones have increased in weight. Most of the weight increase, being proportional to the porosity of limestone, occurred during the first five cycles. The 15 cycles of soaking and drying

Basem K. Mohd

2006-01-01

261

17Oexcess in meteoric water: as a new isotopic parameter to decipher water cycle processes  

NASA Astrophysics Data System (ADS)

Classical water stable isotopes (dD and d18O) have been used for more than 50 years with the aim to understand the links between water cycle and climate. They provide information on either temperature or precipitation changes depending on the latitudes. Their combination, in the so-called d-excess, brings some information on climatic conditions occurring during non equilibrium processes along air masses histories (evaporation over the Oceans, reevaporation of droplets in convective systems, continental recycling or ice crystals formation). Recently, the possibility to measure with high precision d17O in water has enabled to introduce a new parameter, 17Oexcess, resulting from the combination of d18O and d17O. According to both observations and modeling works, this new isotopic parameter is able to decipher some of the non equilibrium processes: when measured in ice core, it is expected to be a more direct tracer of relative humidity of the oceanic evaporative regions than d-excess. In order to better understand what controls this new parameter as well as to extract the maximum climatic information from the combination of 17Oexcess and d-excess, we present different original studies combining these two parameters in several key regions. First, data collected in Niger, West Africa, at scales ranging from the convective system to the seasonal cycle confirm the strong influence of relative humidity on 17Oexcess through the rain reevaporation process. Second, seasonal cycles in the Zongo Valley (Tropical Bolivia) suggest that rain recycling along air masses trajectories have different signatures on d-excess and 17Oexcess leading to decipher the different processes. Third, we study how local processes (precipitation, sublimation) in polar region (Greenland) can affect 17Oexcess archived in ice core with respect to d-excess records through (1) isotopic measurements of vapor versus precipitation collected at the NEEM station and (2) seasonal cycles measured from snow pits.

Landais, A.; Guillevic, M.; Steen-Larsen, H.; Vimeux, F.; Bouygues, A.; Falourd, S.; Risi, C. M.; Bony, S.

2009-12-01

262

The Use of Water Vapor as a Refrigerant: Impact of Cycle Modifications on Commercial Viability  

SciTech Connect

This project investigated the economic viability of using water as the refrigerant in a 1000-ton chiller application. The most attractive water cycle configuration was found to be a flash-intercooled, two-stage cycle using centrifugal compressors and direct contact heat exchangers. Component level models were developed that could be used to predict the size and performance of the compressors and heat exchangers in this cycle as well as in a baseline, R-134a refrigeration cycle consistent with chillers in use today. A survey of several chiller manufacturers provided information that was used to validate and refine these component models. The component models were integrated into cycle models that were subsequently used to investigate the life-cycle costs of both an R-134a and water refrigeration cycle. It was found that the first cost associated with the water as a refrigerant cycle greatly exceeded the savings in operating costs associated with its somewhat higher COP. Therefore, the water refrigeration cycle is not an economically attractive option to today's R-134a refrigeration system. There are a number of other issues, most notably the requirements associated with purging non-condensable gases that accumulate in a direct contact heat exchanger, which will further reduce the economic viability of the water cycle.

Brandon F. Lachner, Jr.; Gregory F. Nellis; Douglas T. Reindl

2004-08-30

263

Enhanced soil toxic metal fixation in iron (hydr)oxides by redox cycles  

Microsoft Academic Search

The possibility to foster toxic metals (Cd, Cu, Ni, Pb and Zn) fixation on Fe (hydr)oxides, either native or added as ameliorants, was investigated at the laboratory scale in two heavily polluted arable and grassland soils by inducing repeated cycles of the reduction and oxidation. Soil samples were treated with Fe-rich waste (FeW) alone or together with fresh organic waste

Marco Contin; Claudio Mondini; Liviana Leita; Maria De Nobili

2007-01-01

264

Potential roles of anaerobic ammonium and methane oxidation in the nitrogen cycle of wetland ecosystems  

Microsoft Academic Search

Anaerobic ammonium oxidation (anammox) and anaerobic methane oxidation (ANME coupled to denitrification) with nitrite as electron\\u000a acceptor are two of the most recent discoveries in the microbial nitrogen cycle. Currently the anammox process has been relatively\\u000a well investigated in a number of natural and man-made ecosystems, while ANME coupled to denitrification has only been observed\\u000a in a limited number of

Guibing Zhu; Mike S. M. Jetten; Peter Kuschk; Katharina F. Ettwig; Chengqing Yin

2010-01-01

265

Disruption of Yeast Forkhead-associated Cell Cycle Transcription by Oxidative Stress  

Microsoft Academic Search

The effects of oxidative stress on yeast cell cycle depend on the stress-exerting agent. We studied the effects of two oxidative stress agents, hydrogen peroxide (HP) and the superoxide-generating agent Menadione (MD). We found that two small co-expressed groups of genes regulated by the Mcm1-Fkh2-Ndd1 transcription regulatory complex are sufficient to account for the difference in the effects of HP

Michael Shapira; Eran Segal; David Botstein

2004-01-01

266

Nitrogen Oxide Fluxes and Nitrogen Cycling during Postagricultural Succession and Forest Fertilization in the Humid Tropics  

Microsoft Academic Search

The effects of changes in tropical land use on soil emissions of nitrous oxide (N2O) and nitric oxide (NO) are not well understood. We examined emissions of N2O and NO and their relationships to land use and forest composition, litterfall, soil nitrogen (N) pools and turnover, soil\\u000a moisture, and patterns of carbon (C) cycling in a lower montane, subtropical wet

Heather Erickson; Michael Keller; Eric A. Davidson

2001-01-01

267

Heat-sterilized silver oxide--zinc cells cycle life studies. [4. 2 Ah  

Microsoft Academic Search

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 Ah were fabricated from 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

Arms

1973-01-01

268

Stoichiometry of Reducing Equivalents and Splitting of Water in the Citric Acid Cycle.  

ERIC Educational Resources Information Center

|Presents a solution to the problem of finding the source of extra reducing equivalents, and accomplishing the stoichiometry of glucose oxidation reactions. Discusses the citric acid cycle and glycolysis. (CW)|

Madeira, Vitor M. C.

1988-01-01

269

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

National Technical Information Service (NTIS)

Supercritical Water Oxidation (SCWO) technology holds great promise for treating mixed wastes, in an environmentally safe and efficient manner. In the spring of 1994 the US Department of Energy (DOE), Idaho Operations Office awarded Stone & Webster Engine...

1996-01-01

270

New Advanced Oxidation Technologies for Destruction of Pollutants in Water.  

National Technical Information Service (NTIS)

The use of the set of advanced oxidation technologies (plasma, bio- and photochemical) for the purification and disinfection of the heavy contaminated water is proposed. The plasma and photochemical techniques are used for the destruction of complicated o...

A. Kravchenko A. Trokhymchuk V. Chernyak Y. Tarasova

2001-01-01

271

Fouling Study of Silicon Oxide Pores Exposed to Tap Water  

SciTech Connect

We report on the fouling of Focused Ion Beam (FIB)-fabricated silicon oxide nanopores after exposure to tap water for two weeks. Pore clogging was monitored by Scanning Electron Microscopy (SEM) on both bare silicon oxide and chemically functionalized nanopores. While fouling occurred on hydrophilic silicon oxide pore walls, the hydrophobic nature of alkane chains prevented clogging on the chemically functionalized pore walls. These results have implications for nanopore sensing platform design.

Nilsson, J.; Bourcier, W.L.; Lee, J.R.I.; Letant, S.E.; /LLNL, Livermore

2007-07-12

272

Trends and seasonal cycles in the isotopic composition of nitrous oxide since 1940  

NASA Astrophysics Data System (ADS)

The atmospheric nitrous oxide mixing ratio has increased by 20% since 1750 (ref. ). Given that nitrous oxide is both a long-lived greenhouse gas and a stratospheric ozone-depleting substance, this increase is of global concern. However, the magnitude and geographic distribution of nitrous oxide sources, and how they have changed over time, is uncertain. A key unknown is the influence of the stratospheric circulation, which brings air depleted in nitrous oxide to the surface. Here, we report the oxygen and intramolecular nitrogen isotopic compositions of nitrous oxide in firn air samples from Antarctica and archived air samples from Cape Grim, Tasmania, spanning 1940-2005. We detect seasonal cycles in the isotopic composition of nitrous oxide at Cape Grim. The phases and amplitudes of these seasonal cycles allow us to distinguish between the influence of the stratospheric sink and the oceanic source at this site, demonstrating that isotope measurements can help in the attribution and quantification of surface sources in general. Large interannual variations and long-term decreasing trends in isotope composition are also apparent. These long-term trends allow us to distinguish between natural and anthropogenic sources of nitrous oxide, and confirm that the rise in atmospheric nitrous oxide levels is largely the result of an increased reliance on nitrogen-based fertilizers.

Park, S.; Croteau, P.; Boering, K. A.; Etheridge, D. M.; Ferretti, D.; Fraser, P. J.; Kim, K.-R.; Krummel, P. B.; Langenfelds, R. L.; van Ommen, T. D.; Steele, L. P.; Trudinger, C. M.

2012-04-01

273

Oxidative decomposition of vitamin C in drinking water.  

PubMed

We have previously shown that vitamin C (ascorbic acid) can initiate hydroxyl radical formation in copper contaminated household drinking water. In the present study, we have examined the stability of vitamin C in copper and bicarbonate containing household drinking water. In drinking water samples, contaminated with copper from the pipes and buffered with bicarbonate, 35% of the added vitamin C was oxidized to dehydroascorbic acid within 15 min. After 3h incubation at room temperature, 93% of the added (2 mM) ascorbic acid had been oxidized. The dehydroascorbic acid formed was further decomposed to oxalic acid and threonic acid by the hydrogen peroxide generated from the copper (I) autooxidation in the presence of oxygen. A very modest oxidation of vitamin C occurred in Milli-Q water and in household water samples not contaminated by copper ions. Moreover, addition of vitamin C to commercially sold domestic bottled water samples did not result in vitamin C oxidation. Our results demonstrate that ascorbic acid is rapidly oxidized to dehydroascorbic acid and further decomposed to oxalic- and threonic acid in copper contaminated household tap water that is buffered with bicarbonate. The impact of consuming ascorbic acid together with copper and bicarbonate containing drinking water on human health is discussed. PMID:15493459

Jansson, Patric J; Jung, Hye R; Lindqvist, Christer; Nordström, Tommy

2004-08-01

274

Kinetics and mechanism of hydrogen sulfide oxidation in sea water  

SciTech Connect

This article provides a comprehensive chemical investigation on the oxidation of acid rain-transported hydrogen sulfides in sea water and on the environmental consequences of their oxidation products. Biochemical and microbiological mechanisms are discussed in detail. Implications and effects for the world's oceans in general are discussed and special emphasis is given to the Black Sea.

Leonov, A.V.; Aizatullin, T.A.

1987-11-01

275

Electrocatalytic Synthesis of Propylene Oxide During Water Electrolysis  

Microsoft Academic Search

A new method for the synthesis of propylene oxide using nascent oxygen generated during the electrolysis of water has been proposed. Among the noble metal blacks tested, the most active and selective anode electrocatalyst was Pt black. The oxidation of propylene was initiated at an applied voltage across the cell higher than ca. 1.1 V (anode potential higher than 1.1

Kiyoshi Otsuka; Tetsuya Ushiyama; Ichiro Yamanaka; K. Ebitani

1995-01-01

276

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

277

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

278

Towards a Global Water Cycle Theme within the Integrated Global Observing Strategy (IGOS) Framework  

Microsoft Academic Search

Over the past three years a number of scientists, international programs and national agencies have been working towards the establishment of a water cycle theme within the IGOS-Partnership. The current theme definition provides a framework for guiding decisions regarding priorities and strategies for the enhancement of water cycle observations in support of 1) monitoring climate variability and change, 2) effective

R. G. Lawford

2004-01-01

279

Perceptions of the Water Cycle among Primary School Children in Botswana.  

ERIC Educational Resources Information Center

Describes qualitative and quantitative methods used to elucidate the nature of the perception of the water cycle held by Botswana primary-grade pupils in three different geographic areas. Concludes that the students' perception of the water cycle was positively influenced by schooling but negatively impacted upon, to some extent, by the untutored…

Taiwo, A. A.; Motswiri, M. J.; Masene, R.

1999-01-01

280

The effect of a global dust storm on simulations of the Martian water cycle  

Microsoft Academic Search

Recent Mars Global Surveyor Thermal Emission Spectrometer (TES) observations have shown the effects of a global dust storm on the water cycle on Mars. Simulations using a Mars General Circulation Model were conducted to assess the influence of an arbitrary global dust storm on the modelled water cycle. Further, the effects of an adsorbing regolith during the dust storm were

H. M. Böttger; S. R. Lewis; P. L. Read; F. Forget

2004-01-01

281

Oxidation of Trace Contaminants in Drinking Water.  

National Technical Information Service (NTIS)

Contamination of drinking water by traces of organic chemicals is of special concern because of health effects of these materials. Louisiana waters are especially susceptible to this contamination because of industrial discharges stemming from large petro...

F. Groves

1985-01-01

282

Thermodynamic analysis of an integrated solid oxide fuel cell cycle with a rankine cycle  

Microsoft Academic Search

Hybrid systems consisting of solid oxide fuel cells (SOFC) on the top of a steam turbine (ST) are investigated. The plants are fired by natural gas (NG). A desulfurization reactor removes the sulfur content in the fuel while a pre-reformer breaks down the heavier hydro-carbons. The pre-treated fuel enters then into the anode side of the SOFC. The remaining fuels

Masoud Rokni

2010-01-01

283

Sonocatalytic Wet Oxidation for Water Purification.  

National Technical Information Service (NTIS)

This program was directed toward development of a suitable ultrasonic reactor design that will allow rapid oxidation of contaminant species under mild conditions thus reducing the capital cost for the equipment as well as the operating costs associated wi...

S. R. Taylor C. M. Rouse A. A. Hoffman

1991-01-01

284

Oxidation-Reduction Potential in Sea Water  

Microsoft Academic Search

In bacteriological studies much attention is now given to oxidation-reduction potentials. The systems studied have usually potentials at least 0'4 V. below that of the reversible oxygen electrode, are reasonably well poised and obey laws thermodynamically deduced. Owing to the irreversibility of the oxygen electrode and to difficulties of measurement no such attention has been given to oxidation-reduction potentials in

L. H. N. Cooper

1937-01-01

285

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

286

Geomorphological control of water tables in a blanket peat landscape: implications for carbon cycling  

Microsoft Academic Search

Water tables are an important control on carbon cycling and rates of carbon sequestration in peatland systems, and water table depth is therefore a key parameter in carbon models for blanket peat systems. Although there is a wide literature on blanket peat hydrology, including studies which specifically evaluate water table conditions, detailed data on water table behaviour and variability at

Tim Allott; Martin Evans; John Lindsay; Clive Agnew; Jim Freer

2010-01-01

287

Effects Of Urbanization On Interconnected Water Cycle, Microclimate And Energy Usage In Semi-Arid Regions  

Microsoft Academic Search

Landscape changes induced by urbanization have been found to influence urban water cycle components including evapotranspiration (ET), runoff and water use. For instance, residential areas in semi-arid regions with vegetation subjected to lawn watering have higher ET rates when compared to the other areas in an urban environment. This increase associated with lawn irrigation can contribute to water scarcity problems.

I. Jeyachandran; S. J. Burian; E. Pardyjak

2008-01-01

288

The Mars water cycle at other epochs: History of the polar caps and layered terrain  

Microsoft Academic Search

The atmospheric water cycle at the present epoch involves summertime sublimation of water from the north polar cap, transport of water through the atmosphere, and condensation on one or both winter CO2 caps. Exchange with the regolith is important seasonally, but the water content of the atmosphere appears to be controlled by the polar caps. The net annual transport through

Bruce M. Jakosky; Bradley G. Henderson; Michael T. Mellon

1992-01-01

289

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

National Technical Information Service (NTIS)

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 analysi...

C. J. Steffen J. E. Freeh L. M. Larosiliere

2005-01-01

290

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

291

The Science and Magic of Chemistry. A Learning Cycle Laboratory on Oxidation-Reduction.  

ERIC Educational Resources Information Center

|Discusses the goals of learning cycle laboratories in helping students acquire knowledge about a specific topic and to do so moving in a non-threatening way from the concrete operational level to the formal operational level. Describes an experiment designed for such laboratories dealing with the topic of oxidation-reduction. (TW)|

Silberman, Robert G.; Zipp, Arden P.

1986-01-01

292

Optimization of the Oxidant Supply System for Combined Cycle Mhd Power Plants.  

National Technical Information Service (NTIS)

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...

A. J. Juhasz

1982-01-01

293

An improvement in the use of plutonium in pressurized water reactors; The subassembly mixed-oxide fuel management concept  

Microsoft Academic Search

An unconventional mixed-oxide (MOX) fuel management concept for a pressurized water reactor core is proposed. Subassembly management (SAM) is an in-out reloading scheme applied within MOX assemblies that are reconstructed'' at each end of cycle. The SAM concept needs only one kind of MOX fuel pin instead of the three pins necessary in the standard MOX fuel management concept; it

C. Bangil; G. Gambier; M. Soldevila

1989-01-01

294

Electrode-assisted catalytic water oxidation by a flavin derivative.  

PubMed

The success of solar fuel technology relies on the development of efficient catalysts that can oxidize or reduce water. All molecular water-oxidation catalysts reported thus far are transition-metal complexes, however, here we report catalytic water oxidation to give oxygen by a fully organic compound, the N(5)-ethylflavinium ion, Et-Fl(+). Evolution of oxygen was detected during bulk electrolysis of aqueous Et-Fl(+) solutions at several potentials above +1.9 V versus normal hydrogen electrode. The catalysis was found to occur on glassy carbon and platinum working electrodes, but no catalysis was observed on fluoride-doped tin-oxide electrodes. Based on spectroelectrochemical results and preliminary calculations with density functional theory, one possible mechanistic route is proposed in which the oxygen evolution occurs from a peroxide intermediate formed between the oxidized flavin pseudobase and the oxidized carbon electrode. These findings offer an organic alternative to the traditional water-oxidation catalysts based on transition metals. PMID:23000992

Mirzakulova, Ekaterina; Khatmullin, Renat; Walpita, Janitha; Corrigan, Thomas; Vargas-Barbosa, Nella M; Vyas, Shubham; Oottikkal, Shameema; Manzer, Samuel F; Hadad, Christopher M; Glusac, Ksenija D

2012-08-26

295

Surface treatment of hematite photoanodes with zinc acetate for water oxidation  

NASA Astrophysics Data System (ADS)

A simple and inexpensive method to form a hematite photoanode for efficient water oxidation is reported. A very thin ZnO overlayer was deposited on top of a thin film of hematite and found, compared with non-treated hematite, to increase the photocurrent and reduce the onset potential for generating oxygen from water. After 3 cycles of ZnAc treatment, the photocurrent increased more than 40% to 1.08 mA cm-2 at 0.23 V vs. Ag/AgCl and onset potential for water oxidation shifted by -170 mV. It is proposed that the ZnO overlayer changes the flat band potential of hematite and reduces the surface defects.A simple and inexpensive method to form a hematite photoanode for efficient water oxidation is reported. A very thin ZnO overlayer was deposited on top of a thin film of hematite and found, compared with non-treated hematite, to increase the photocurrent and reduce the onset potential for generating oxygen from water. After 3 cycles of ZnAc treatment, the photocurrent increased more than 40% to 1.08 mA cm-2 at 0.23 V vs. Ag/AgCl and onset potential for water oxidation shifted by -170 mV. It is proposed that the ZnO overlayer changes the flat band potential of hematite and reduces the surface defects. Electronic supplementary information (ESI) available: Experimental details, characterizations and supporting figures. See DOI: 10.1039/c2nr30862b

Xi, Lifei; Bassi, Prince Saurabh; Chiam, Sing Yang; Mak, Wai Fatt; Tran, Phong D.; Barber, James; Chye Loo, Joachim Say; Wong, Lydia Helena

2012-07-01

296

Oxidative gating of water channels (aquaporins) in corn roots  

Microsoft Academic Search

An oxidative gating of water channels (aquaporins: AQPs) was observed in roots of corn seedlings as already found for the green alga Chara corallina . In the presence of 35 m M hydrogen peroxide (H 2 O 2 ) - a precursor of hydroxyl radicals (*OH) - half times of water flow (as measured with the aid of pressure probes)

Q. Ye; E. Steudle; QING YE

2005-01-01

297

Origin of Anomalous Water Permeation through Graphene Oxide Membrane  

NASA Astrophysics Data System (ADS)

Water inside the low dimensional carbon structures has been considered seriously owing to fundamental interest in its flow and structures as well as its practical impact. Recently, the anomalous perfect penetration of water through graphene oxide membrane was demonstrated although the membrane was impenetrable for other liquids and even gases. The unusual auxetic behavior of graphene oxide in the presence of water was also reported. Here, based on first-principles calculations, we establish atomistic models for hybrid systems composed of water and graphene oxides revealing the anomalous water behavior inside the stacked graphene oxides. We show that formation of hexagonal ice bilayer in between the flakes as well as melting transition of ice at the edges of flakes are crucial to realize the perfect water permeation across the whole stacked structures. The distance between adjacent layers that can be controlled either by oxygen reduction process or pressure is shown to determine the water flow thus highlighting a unique water dynamics in randomly connected two-dimensional spaces.

Boukhvalov, Danil W.; Katsnelson, Mikhail I.; Son, Young-Woo

2013-08-01

298

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...

299

The inorganic biochemistry of photosynthetic oxygen evolution\\/water oxidation  

Microsoft Academic Search

At the request of the organizer of this special edition, we have attempted to do several things in this manuscript: (1) we present a mini-review of recent, selected, works on the light-induced inorganic biogenesis (photoactivation), composition and structure of the inorganic core responsible for photosynthetic water oxidation; (2) we summarize a new proposal for the evolutionary origin of the water

G. M. Ananyev; L. Zaltsman; C. Vasko; G. C. Dismukes

2001-01-01

300

Aircraft Water Vapor Measurements Utilizing an Aluminum Oxide Hygrometer  

Microsoft Academic Search

A hygrometer for water vapor measurements from an aircraft was developed. An aluminum oxide hygrometer mounted in an aircraft Rosemount air temperature scoop was flown on the NASA Convair 990 and on a USAF B-57 aircraft. Water vapor measurements from the Convair 990 were conducted up to 40,000 ft with penetration into the stratosphere. Good agreement was obtained with simultaneously

Ernest Hilsenrath

1974-01-01

301

Combined carbon dioxide\\/water solid oxide electrolysis  

Microsoft Academic Search

Solid oxide electrolysis of a mixture of water and carbon dioxide has many applications in space exploration. It can be implemented in propellant production systems that use Martian resources or in closed-loop life support systems to cleanse the atmosphere of facilities in extraterrestrial bases and of cabin spacecrafts. This work endeavors to quantify the performance of combined water and carbon

Christine Schroeder Iacomini

2004-01-01

302

Insights into high-temperature nitrogen cycling from studies of the thermophilic ammonia-oxidizing archaeon Nitrosocaldus yellowstonii. (Invited)  

Microsoft Academic Search

Our understanding of the nitrogen cycle has advanced significantly in recent years with the discovery of new metabolic processes and the recognition that key processes such as aerobic ammonia oxidation are more broadly distributed among extant organisms and habitat ranges. Nitrification, the oxidation of ammonia to nitrite and nitrate, is a key component of the nitrogen cycle and, until recently,

J. R. de la Torre

2010-01-01

303

Biomimetic metal oxides for the extraction of nanoparticles from water  

NASA Astrophysics Data System (ADS)

Contamination of nanomaterials in the environment will pose significant health risks in the future. A viable purification method is necessary to address this problem. Here we report the synthesis and application of a series of metal oxides prepared using a biological template for the removal of nanoparticles from the aqueous environment. A simple synthesis of metal oxides such as ZnO, NiO, CuO, Co3O4 and CeO2 employing eggshell membrane (ESM) as a biotemplate is reported. The morphology of the metal oxide powders was characterized using electron microscopes and the lattice structure was established using X-ray diffraction methods. Extraction of nanoparticles from water was carried out to compare the efficiency of metal oxides. NiO showed good extraction efficiency in removing gold and silver nanoparticles from spiked water samples within an hour. Easy access and enhanced stability of metal oxides makes them interesting candidates for applications in industrial effluent treatments and water purifications.Contamination of nanomaterials in the environment will pose significant health risks in the future. A viable purification method is necessary to address this problem. Here we report the synthesis and application of a series of metal oxides prepared using a biological template for the removal of nanoparticles from the aqueous environment. A simple synthesis of metal oxides such as ZnO, NiO, CuO, Co3O4 and CeO2 employing eggshell membrane (ESM) as a biotemplate is reported. The morphology of the metal oxide powders was characterized using electron microscopes and the lattice structure was established using X-ray diffraction methods. Extraction of nanoparticles from water was carried out to compare the efficiency of metal oxides. NiO showed good extraction efficiency in removing gold and silver nanoparticles from spiked water samples within an hour. Easy access and enhanced stability of metal oxides makes them interesting candidates for applications in industrial effluent treatments and water purifications. Electronic supplementary information (ESI) available: XRD and EDS analysis of the prepared metal oxides, EDS analysis of nanoparticles adsorbed on the surface of metal oxides and SEM micrographs of metal oxides are included. See DOI: 10.1039/c3nr34221b

Mallampati, Ramakrishna; Valiyaveettil, Suresh

2013-03-01

304

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

305

A synthetic biology approach to engineer a functional reversal of the ?-oxidation cycle.  

PubMed

While we have recently constructed a functional reversal of the ?-oxidation cycle as a platform for the production of fuels and chemicals by engineering global regulators and eliminating native fermentative pathways, the system-level approach used makes it difficult to determine which of the many deregulated enzymes are responsible for product synthesis. This, in turn, limits efforts to fine-tune the synthesis of specific products and prevents the transfer of the engineered pathway to other organisms. In the work reported here, we overcome the aforementioned limitations by using a synthetic biology approach to construct and functionally characterize a reversal of the ?-oxidation cycle. This was achieved through the in vitro kinetic characterization of each functional unit of the core and termination pathways, followed by their in vivo assembly and functional characterization. With this approach, the four functional units of the core pathway, thiolase, 3-hydroxyacyl-CoA dehydrogenase, enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydratase, and acyl-CoA dehydrogenase/trans-enoyl-CoA reductase, were purified and kinetically characterized in vitro. When these four functional units were assembled in vivo in combination with thioesterases as the termination pathway, the synthesis of a variety of 4-C carboxylic acids from a one-turn functional reversal of the ?-oxidation cycle was realized. The individual expression and modular construction of these well-defined core components exerted the majority of control over product formation, with only highly selective termination pathways resulting in shifts in product formation. Further control over product synthesis was demonstrated by overexpressing a long-chain thiolase that enables the operation of multiple turns of the reversal of the ?-oxidation cycle and hence the synthesis of longer-chain carboxylic acids. The well-defined and self-contained nature of each functional unit makes the engineered reversal of the ?-oxidation cycle "chassis neutral" and hence transferrable to the host of choice for efficient fuel or chemical production. PMID:23656231

Clomburg, James M; Vick, Jacob E; Blankschien, Matthew D; Rodríguez-Moyá, María; Gonzalez, Ramon

2012-10-24

306

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

PubMed

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 Mn(3+)/Mn(4+) 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

2013-05-10

307

Silicon and tungsten oxide nanostructures for water splitting  

NASA Astrophysics Data System (ADS)

Inorganic semiconductors are promising materials for driving photoelectrochemical water-splitting reactions. However, there is not a single semiconductor material that can sustain the unassisted splitting of water into H2 and O2. Instead, we are developing a three part cell design where individual catalysts for water reduction and oxidation will be attached to the ends of a membrane. The job of splitting water is therefore divided into separate reduction and oxidation reactions, and each catalyst can be optimized independently for a single reaction. Silicon might be suitable to drive the water reduction. Inexpensive highly ordered Si wire arrays were grown on a single crystal wafer and transferred into a transparent, flexible polymer matrix. In this array, light would be absorbed along the longer axial dimension while the resulting electrons or holes would be collected along the much shorter radial dimension in a massively parallel array resembling carpet fibers on a microscale, hence the term "solar carpet". Tungsten oxide is a good candidate to drive the water oxidation. Self-organized porous tungsten oxide was successfully synthesized on the tungsten foil by anodization. This sponge-like structure absorbs light efficiently due to its high surface area; hence we called it "solar sponge".

Reyes Gil, Karla R.; Spurgeon, Joshua M.; Lewis, Nathan S.

2009-08-01

308

Atomic layer-deposited tunnel oxide stabilizes silicon photoanodes for water oxidation  

Microsoft Academic Search

A leading approach for large-scale electrochemical energy production with minimal global-warming gas emission is to use a renewable source of electricity, such as solar energy, to oxidize water, providing the abundant source of electrons needed in fuel synthesis. We report corrosion-resistant, nanocomposite anodes for the oxidation of water required to produce renewable fuels. Silicon, an earth-abundant element and an efficient

Yi Wei Chen; Jonathan D. Prange; Simon Dühnen; Yohan Park; Marika Gunji; Christopher E. D. Chidsey; Paul C. McIntyre

2011-01-01

309

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.

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

2012-01-01

310

Succession of Internal Sulfur Cycles and Sulfur-Oxidizing Bacterial Communities in Microaerophilic Wastewater Biofilms  

PubMed Central

The succession of sulfur-oxidizing bacterial (SOB) community structure and the complex internal sulfur cycle occurring in wastewater biofilms growing under microaerophilic conditions was analyzed by using a polyphasic approach that employed 16S rRNA gene-cloning analysis combined with fluorescence in situ hybridization, microelectrode measurements, and standard batch and reactor experiments. A complete sulfur cycle was established via S0 accumulation within 80 days in the biofilms in replicate. This development was generally split into two phases, (i) a sulfur-accumulating phase and (ii) a sulfate-producing phase. In the first phase (until about 40 days), since the sulfide production rate (sulfate-reducing activity) exceeded the maximum sulfide-oxidizing capacity of SOB in the biofilms, H2S was only partially oxidized to S0 by mainly Thiomicrospira denitirificans with NO3? as an electron acceptor, leading to significant accumulation of S0 in the biofilms. In the second phase, the SOB populations developed further and diversified with time. In particular, S0 accumulation promoted the growth of a novel strain, strain SO07, which predominantly carried out the oxidation of S0 to SO42? under oxic conditions, and Thiothrix sp. strain CT3. In situ hybridization analysis revealed that the dense populations of Thiothrix (ca. 109 cells cm?3) and strain SO07 (ca. 108 cells cm?3) were found at the sulfur-rich surface (100 ?m), while the population of Thiomicrospira denitirificans was distributed throughout the biofilms with a density of ca. 107 to 108 cells cm?3. Microelectrode measurements revealed that active sulfide-oxidizing zones overlapped the spatial distributions of different phylogenetic SOB groups in the biofilms. As a consequence, the sulfide-oxidizing capacities of the biofilms became high enough to completely oxidize all H2S produced by SRB to SO42? in the second phase, indicating establishment of the complete sulfur cycle in the biofilms.

Okabe, Satoshi; Ito, Tsukasa; Sugita, Kenichi; Satoh, Hisashi

2005-01-01

311

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

312

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

313

Iron-dependent changes in cellular energy metabolism: influence on citric acid cycle and oxidative phosphorylation.  

PubMed

Iron modulates the expression of the critical citric acid cycle enzyme aconitase via a translational mechanism involving iron regulatory proteins. Thus, the present study was undertaken to investigate the consequences of iron perturbation on citric acid cycle activity, oxidative phosphorylation and mitochondrial respiration in the human cell line K-562. In agreement with previous data iron increases the activity of mitochondrial aconitase while it is reduced upon addition of the iron chelator desferrioxamine (DFO). Interestingly, iron also positively affects three other citric acid cycle enzymes, namely citrate synthase, isocitric dehydrogenase, and succinate dehydrogenase, while DFO decreases the activity of these enzymes. Consequently, iron supplementation results in increased formation of reducing equivalents (NADH) by the citric acid cycle, and thus in increased mitochondrial oxygen consumption and ATP formation via oxidative phosphorylation as shown herein. This in turn leads to downregulation of glucose utilization. In contrast, all these metabolic pathways are reduced upon iron depletion, and thus glycolysis and lactate formation are significantly increased in order to compensate for the decrease in ATP production via oxidative phosphorylation in the presence of DFO. Our results point to a complex interaction between iron homeostasis, oxygen supply and cellular energy metabolism in human cells. PMID:10556622

Oexle, H; Gnaiger, E; Weiss, G

1999-11-10

314

Photoassisted oxidation of oil films on water  

SciTech Connect

The objective of the project is to develop TiO{sub 2}-based photocatalysts for the solar assisted oxidative dissolution of oil slicks. In a TiO{sub 2} crystal, absorption of a photon generates an electron-hole pair. The electron reacts with surface-adsorbed oxygen, reducing it to hydrogen peroxide; the hole directly oxidizes adsorbed organic compounds, usually via an intermediate OH radical. Since the density of TiO{sub 2} (3.8g/cc for anatase, 4.3 g/cc for rutile) is greater than that of either oil or seawater, TiO{sub 2} crystals are attached to inexpensive, engineered hollow glass microspheres to ensure flotation on the oil slick surface. Portions of the microsphere surface not covered by TiO{sub 2} are made oleophilic so that the microbeads will be preferentially attracted to the oil-air interface.

Heller, A.; Brock, J.R.

1991-08-01

315

Sensitivity of the global water cycle to the water-holding capacity of land  

SciTech Connect

The sensitivity of the global water cycle to the water-holding capacity of the plant-root zone of continental soils is estimated by simulations using a mathematical model of the general circulation of the atmosphere, with prescribed ocean surface temperatures and prescribed cloud. With an increase of the globally constant storage capacity, evaporation from the continents rises and runoff falls, because a high storage capacity enhances the ability of the soil to store water from periods of excess for later evaporation during periods of shortage. In addition, atmospheric feedbacks associated with higher precipitation and lower potential evaporation drive further changes in evaporation and runoff. Most changes in evaporation and runoff occur in the tropics and the northern middle-latitude rain belts. Global evaporation from land increases by 7 cm for each doubling of storage capacity. Sensitivity is negligible for capacity above 60 cm. In the tropics and in the extratropics,increased continental evaporation is split between increased continental precipitation and decreased convergence of atmospheric water vapor from ocean to land. In the tropics, this partitioning is strongly affected by induced circulation changes, which are themselves forced by changes in latent heating. In the northern middle and high latitudes, the increased continental evaporation moistens the atmosphere. This change in humidity of the atmosphere is greater above the continents than above the oceans, and the resulting reduction in the sea-land humidity gradient causes a decreased onshore transport of water vapor by transient eddies. Results here may have implications for problems in global hydrology and climate dynamics, including effects of water resource development on global precipitation, climatic control of plant rooting characteristics, climatic effects of tropical deforestation, and climate-model errors. 21 refs., 13 figs., 21 tabs.

Milly, P.C.D.; Dunne, K.A. (Geological Survey, Princeton, NJ (United States))

1994-04-01

316

Life-cycle analysis on biodiesel production from microalgae: Water footprint and nutrients balance  

Microsoft Academic Search

This research examines the life-cycle water and nutrients usage of microalgae-based biodiesel production. The influence of water types, operation with and without recycling, algal species, geographic distributions are analyzed. The results confirm the competitiveness of microalgae-based biofuels and highlight the necessity of recycling harvested water and using sea\\/wastewater as water source. To generate 1kg biodiesel, 3726kg water, 0.33kg nitrogen, and

Jia Yang; Ming Xu; Xuezhi Zhang; Qiang Hu; Milton Sommerfeld; Yongsheng Chen

2011-01-01

317

Process for treating effluent from a supercritical water oxidation reactor  

DOEpatents

The present invention relates generally to a method for treating and recycling the effluent from a supercritical water oxidation reactor and more specifically to a method for treating and recycling the effluent by expanding the effluent without extensive cooling. Supercritical water oxidation is the oxidation of fuel, generally waste material, in a body of water under conditions above the thermodynamic critical point of water. The current state of the art in supercritical water oxidation plant effluent treatment is to cool the reactor effluent through heat exchangers or direct quench, separate the cooled liquid into a gas/vapor stream and a liquid/solid stream, expand the separated effluent, and perform additional purification on gaseous, liquid, brine and solid effluent. If acid gases are present, corrosion is likely to occur in the coolers. During expansion, part of the condensed water will revaporize. Vaporization can damage the valves due to cavitation and erosion. The present invention expands the effluent stream without condensing the stream. Radionuclides and suspended solids are more efficiently separated in the vapor phase. By preventing condensation, the acids are kept in the much less corrosive gaseous phase thereby limiting the damage to treatment equipment. The present invention also reduces the external energy consumption, by utilizing the expansion step to also cool the effluent.

Barnes, C.M.; Shapiro, C.

1995-12-31

318

The Atmospheric Water Cycle Above a Tropical Closed Lake (Lake Ihotry, Southwestern Madagascar)  

Microsoft Academic Search

We present an indirect approach based on a lake isotope mass balance model to infer the seasonal evolution of the isotope composition of atmospheric water vapour, and to quantify the atmospheric water cycle above a lake. Starting from the lake water balance previously established, the isotope mass balance allows to calculate the isotopic composition of the moisture evaporated from the

C. Vallet-Coulomb; F. Gasse; C. Sonzogni

2008-01-01

319

Observation of isotopes in the water cycle—the Swiss National Network (NISOT)  

Microsoft Academic Search

The Swiss National Network for the Observation of Isotopes in the Water Cycle (NISOT) includes eleven precipitation, seven surface water (river) and three groundwater stations, where tritium, deuterium and oxygen-18 are monthly measured in composite samples. The network provides a good overview of the characteristic isotope signatures in recharge waters in Switzerland and of the relations between isotopes and altitude,

Marc Schürch; Ronald Kozel; Ulrich Schotterer; Jean-Pierre Tripet

2003-01-01

320

A preliminary study of the tropical water cycle and its sensitivity to surface warming  

Microsoft Academic Search

This paper presents preliminary findings of an investigation of the water budget of tropical cumulus convection using the Goddard Cumulus Ensemble Model (GCEM). Results of an experiment designed to obtain a [open quotes]fingerprint[close quotes] in the tropical hydrologic cycle in response to surface warming are also presented. The ensemble mean water budget shows the distribution of water vapor and cloud

K. M. Lau; W. K. Tao; C. H. Sui

1993-01-01

321

Mars Water Cycle at Other Epochs: History of the Polar Caps and Layered Terrain.  

National Technical Information Service (NTIS)

The atmospheric water cycle at the present epoch involves summertime sublimation of water from the north polar cap, transport of water through the atmosphere, and condensation on one or both winter CO2 caps. Exchange with the regolith is important seasona...

B. M. Jakosky B. G. Henderson M. T. Mellon

1992-01-01

322

Deep Water Cycle: its Role in Earth's Thermal Evolution and Plate Tectonics  

Microsoft Academic Search

Earth is unique among the terrestrial planets in our solar system because it has plate tectonics and abundant surface water. It has long been suggested that these two salient features are intimately related. New constraints on water concentrations in the Earth's interior and on mechanisms for mantle degassing and regassing have improved our knowledge of Earth's deep water cycle; however,

T. W. Becker; J. W. Crowley; M. Gérault; T. Höink; A. J. Schaeffer; P. H. Barry; J. Frost; J. Girard; M. Nunez-Valdez; M. Hirschmann; S. Hier-Majumder; R. J. O'Connell

2010-01-01

323

Atomic layer-deposited tunnel oxide stabilizes silicon photoanodes for water oxidation  

NASA Astrophysics Data System (ADS)

A leading approach for large-scale electrochemical energy production with minimal global-warming gas emission is to use a renewable source of electricity, such as solar energy, to oxidize water, providing the abundant source of electrons needed in fuel synthesis. We report corrosion-resistant, nanocomposite anodes for the oxidation of water required to produce renewable fuels. Silicon, an earth-abundant element and an efficient photovoltaic material, is protected by atomic layer deposition (ALD) of a highly uniform, 2?nm thick layer of titanium dioxide (TiO2) and then coated with an optically transmitting layer of a known catalyst (3?nm iridium). Photoelectrochemical water oxidation was observed to occur below the reversible potential whereas dark electrochemical water oxidation was found to have low-to-moderate overpotentials at all pH values, resulting in an inferred photovoltage of ~550?mV. Water oxidation is sustained at these anodes for many hours in harsh pH and oxidative environments whereas comparable silicon anodes without the TiO2 coating quickly fail. The desirable electrochemical efficiency and corrosion resistance of these anodes is made possible by the low electron-tunnelling resistance (<0.006???cm2 for p+-Si) and uniform thickness of atomic-layer deposited TiO2.

Chen, Yi Wei; Prange, Jonathan D.; Dühnen, Simon; Park, Yohan; Gunji, Marika; Chidsey, Christopher E. D.; McIntyre, Paul C.

2011-07-01

324

Atomic layer-deposited tunnel oxide stabilizes silicon photoanodes for water oxidation.  

PubMed

A leading approach for large-scale electrochemical energy production with minimal global-warming gas emission is to use a renewable source of electricity, such as solar energy, to oxidize water, providing the abundant source of electrons needed in fuel synthesis. We report corrosion-resistant, nanocomposite anodes for the oxidation of water required to produce renewable fuels. Silicon, an earth-abundant element and an efficient photovoltaic material, is protected by atomic layer deposition (ALD) of a highly uniform, 2 nm thick layer of titanium dioxide (TiO(2)) and then coated with an optically transmitting layer of a known catalyst (3 nm iridium). Photoelectrochemical water oxidation was observed to occur below the reversible potential whereas dark electrochemical water oxidation was found to have low-to-moderate overpotentials at all pH values, resulting in an inferred photovoltage of ~550 mV. Water oxidation is sustained at these anodes for many hours in harsh pH and oxidative environments whereas comparable silicon anodes without the TiO(2) coating quickly fail. The desirable electrochemical efficiency and corrosion resistance of these anodes is made possible by the low electron-tunnelling resistance (<0.006 ? cm(2) for p(+)-Si) and uniform thickness of atomic-layer deposited TiO(2). PMID:21685904

Chen, Yi Wei; Prange, Jonathan D; Dühnen, Simon; Park, Yohan; Gunji, Marika; Chidsey, Christopher E D; McIntyre, Paul C

2011-06-19

325

The burnup dependence of light water reactor spent fuel oxidation  

Microsoft Academic Search

The air oxidation of fragments of Light Water Reactor (LWR) spent fuel with burnup in the range 16-42 MWd\\/kg M was studied using thermogravimetric analysis. Experiments were conducted in dry air over the temperature range 255-325sp°C. Mass increases were generally followed until the calculated oxygen-to-metal ratio reached 2.7. LWR spent fuel was shown to oxidize via the two step reaction

Brady Dean Hanson

1998-01-01

326

A novel silver oxides oxygen evolving catalyst for water splitting  

Microsoft Academic Search

A novel silver oxides oxygen evolving catalyst (Ag-OEC) for hydrogen production by water splitting was formed in situ on an indium tin oxide anode, in a near-neutral potassium tetraborate (K2B4O7) electrolyte. The catalyst exhibited high activity and low overpotential for O2 evolution under mild conditions. The main functional composition of the catalyst was a redox couple of Ag2O\\/AgO. Catalytic activity

Wei Wang; Qiang Zhao; Jinxiang Dong; Jinping Li

2011-01-01

327

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

328

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

329

The oxidation of copper(I) in natural waters  

Microsoft Academic Search

The reduced forms of metals in natural waters can be formed by photochemical, biochemical and geochemical processes. The lifetime of these reduced metals will be determined by the rates of oxidation with O$\\\\sb2$ and H$\\\\sb2$O$\\\\sb2$.In my work, I have concentrated on the kinetics of oxidation of Cu(I) in aqueous solutions. By studying the rate in various media as a function

Virender Kumar Sharma

1989-01-01

330

Water vapor measurements at ALOMAR over a solar cycle compared with model calculations by LIMA  

NASA Astrophysics Data System (ADS)

Microwave water vapor measurements between 40 and 80 km altitude over a solar cycle (1996-2006) were carried out in high latitudes at Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR) (69.29°N, 16.03°E), Norway. Some smaller gaps and three interruptions of monitoring in the winters 1996/1997 and 2005/2006 and from spring 2001 to spring 2002 occurred during this period. The observations show a distinct year-to-year variability not directly related to solar Lyman-? radiation. In winter the water vapor mixing ratios in the upper domain were anticorrelated to the solar activity, whereas in summer, minima occurred in the years after the solar maximum in 2000/2001. In winter, sudden stratospheric warmings (SSWs) modulated the water vapor mixing ratios. Within the stratopause region a middle atmospheric water vapor maximum was observed, which results from the methane oxidation and is a regular feature there. The altitude of the maximum increased by approximately 5 km as summer approached. The largest mixing ratios were monitored in autumn. During the summer season a secondary water vapor maximum also occurred above 65 km most pronounced in late summer. The solar Lyman-? radiation impacts the water vapor mixing ratio particularly in winter above 65 km. In summer the correlation is positive below 70 km. The correlation is also positive in the lower mesosphere/stratopause region in winter due to the action of sudden stratospheric warmings, which occur more frequently under the condition of high solar activity and the enhancing the humidity. A strong day-to-day variability connected with planetary wave activity was found throughout the entire year. Model calculations by means of Leibniz-Institute Middle Atmosphere model (LIMA) reflect the essential patterns of the water vapor variation, but the results also show differences from the observations, indicating that exchange processes between the troposphere and stratosphere not modeled by LIMA could have influenced the long-term variability. We show results of measurements, compare these with calculations, and discuss the chemical and dynamical backgrounds of the variation of water vapor in the middle atmosphere.

Hartogh, P.; Sonnemann, G. R.; Grygalashvyly, M.; Song, Li; Berger, U.; Lübken, F.-J.

2010-01-01

331

Hallmarks of maghemitization in low-temperature remanence cycling of partially oxidized magnetite nanoparticles  

NASA Astrophysics Data System (ADS)

In environmental, soil, and sediment magnetism, it is important to be able to estimate the degree of oxidation of magnetite grains. We report a new method for finding the oxidation parameter z semiquantitatively from cooling-warming cycles of room temperature remanences. We measured magnetization M continuously for stoichiometric and partially oxidized magnetites with average grain sizes of 37 and 220 nm during zero-field cycling of 2.5 T saturation isothermal remanent magnetization (SIRM) from 300 K to 20 K and back to 300 K. Oxidized magnetites were obtained by heating stoichiometric magnetite in air at 100°C, 150°C, and 200°C. In other experiments, SIRM was given at 10 K, and M was monitored during zero-field warming to 300 K. In the oxidized magnetites, SIRM at first increases in cooling from 300 K and then decreases in approaching the Verwey transition. The hump-like form is even more pronounced in the warming curves above TV. For maghemite, the fully oxidized end member, we found reversible cooling-warming curves with no Verwey transition. In partially oxidized grains, consisting of a maghemite surface layer and a largely unoxidized core, a Verwey transition is resolvable up to high degrees of oxidation. Hallmarks of maghemitization include (1) a smeared-out Verwey transition shifted to lower temperatures when warming 20 K SIRM, (2) a shifted and broadened transition region in both cooling and warming of 300 K SIRM, and (3) humped cooling and warming curves of 300 K SIRM between 300 K and TV. Property 3 has excellent diagnostic value. It results from the combination of a slowly increasing M of maghemite and the rapid and nonlinear decrease in M of magnetite during cooling and is seen even for the slight initial oxidation of the reduced 37 nm magnetite. Certain properties, such as the change in M in warming from 20 K to TV and the change in initial and final M values in a complete cooling-warming cycle, are roughly proportional to the oxidation parameter z. However, the proportionality factors also depend on grain size d, which would have to be known independently in order to estimate z.

Özdemir, Özden; Dunlop, David J.

2010-02-01

332

Water vapor measurements in the mesosphere from Mauna Loa over solar cycle 23  

NASA Astrophysics Data System (ADS)

The Water Vapor Millimeter-wave Spectrometer (WVMS) system has been making measurements from the Network for the Detection of Atmospheric Composition Change site at Mauna Loa, Hawaii (19.5°N, 204.4°E), since 1996, covering nearly the complete period of solar cycle 23. The WVMS measurements are compared with Halogen Occultation Experiment (HALOE) (1992-2005), Microwave Limb Sounder (MLS) (2004 to present), and Atmospheric Chemistry Experiment (ACE) Fourier transform spectrometer (2004 to present) measurements in the mesosphere. In the upper mesosphere Lyman ? radiation photodissociates water vapor; hence, water vapor in the upper mesosphere varies with the solar cycle. We calculate fits to the WVMS and HALOE water vapor data in this region using the Lasp Interactive Solar Irradiance Datacenter Lyman ? data set. This is, to our knowledge, the only published validation of the sensitivity of HALOE water vapor measurements to the solar cycle, and the HALOE and WVMS water vapor measurements show a very similar sensitivity to the solar cycle. Once the solar cycle variations are taken into account, the primary water vapor variations at all of these altitudes from 1992 to the present are an increase from 1992 to 1996, a maximum in water vapor in 1996, and small changes from 1997 to the present. Measurements from 2004 to 2008, which are available from WVMS, MLS, and ACE, show not only good agreement in interannual variations but also excellent agreement in their absolute measurements (to within better than 3%) of the water vapor mixing ratio from 50 to 80 km.

Nedoluha, Gerald E.; Gomez, R. Michael; Hicks, Brian C.; Wrotny, Jonathan E.; Boone, Chris; Lambert, Alyn

2009-12-01

333

Surfactant manganese complexes as models for the oxidation of water  

SciTech Connect

Surfactant manganese complexes have been studied spectroscopically and electrochemically as models for the catalysts involved in the photooxidation of water to produce oxygen. Evidence has been obtained for the participation of the suggested redox cycle Mn/sup II/ to Mn/sup III/ to Mn/sup IV/ and back to Mn/sup II/ with the evolution of oxygen.

Wohlgemuth, R.; Otvos, J.W.; Calvin, M.

1984-02-01

334

High-temperature thermochemical water splitting cycle fusion reactor design considerations  

Microsoft Academic Search

The design considerations were explored for the adaptation of the high-temperature General Atomic sulfur-iodine thermochemical water splitting cycle to a fusion reactor heat source. This high-temperature cycle modification was found to have a good heat line match to the fusion heat source with an attractive possibility of process simplification compared to the reference HTGR-adapted cycle. The cost improvement due to

E. T. Cheng; C. P. C. Wong; K. H. McCorkle Jr.; P. W. Trester; K. R. Schultz

1980-01-01

335

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

336

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

337

Performance-based optimal design and rehabilitation of water distribution networks using life cycle costing  

Microsoft Academic Search

A new multiobjective formulation is proposed for the optimal design and rehabilitation of a water distribution network, with minimization of life cycle cost and maximization of performance as objectives. The life cycle cost is considered to comprise the initial cost of pipes, the cost of replacing old pipes with new ones, the cost of cleaning and lining existing pipes, the

Nirmal Jayaram; K. Srinivasan

2008-01-01

338

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

339

Effect of Internal Heat Recovery in Ammonia-Water Absorption Cooling Cycles: Exergy and Structural Analysis  

Microsoft Academic Search

First and second law analysis have been conducted for three low temperature driven ammonia-water absorption cooling cycles with increasing internal heat recovery. Based on the results of exergy analysis the structural analysis has been achieved. The obtained Coefficients of Structural Bonds (CSB) consider how the irreversibility of the whole cycle is affected by a change in the irreversibility related to

Dieter Boer; Berhane Hagos Gebreslassie; Marc Medrano; Miquel Nogués

340

Evolution of the Global Water Cycle on Mars: The Geological Evidence.  

National Technical Information Service (NTIS)

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 th...

V. R. Baker V. C. Gulick

1993-01-01

341

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

342

Highly active oxide photocathode for photoelectrochemical water reduction  

NASA Astrophysics Data System (ADS)

A clean and efficient way to overcome the limited supply of fossil fuels and the greenhouse effect is the production of hydrogen fuel from sunlight and water through the semiconductor/water junction of a photoelectrochemical cell, where energy collection and water electrolysis are combined into a single semiconductor electrode. We present a highly active photocathode for solar H2 production, consisting of electrodeposited cuprous oxide, which was protected against photocathodic decomposition in water by nanolayers of Al-doped zinc oxide and titanium oxide and activated for hydrogen evolution with electrodeposited Pt nanoparticles. The roles of the different surface protection components were investigated, and in the best case electrodes showed photocurrents of up to -7.6?mA?cm-2 at a potential of 0?V versus the reversible hydrogen electrode at mild pH. The electrodes remained active after 1?h of testing, cuprous oxide was found to be stable during the water reduction reaction and the Faradaic efficiency was estimated to be close to 100%.

Paracchino, Adriana; Laporte, Vincent; Sivula, Kevin; Grätzel, Michael; Thimsen, Elijah

2011-06-01

343

Highly water-soluble multi-walled carbon nanotubes amine-functionalized by supercritical water oxidation  

NASA Astrophysics Data System (ADS)

Multi-walled carbon nanotubes (MWNTs) have been amine-functionalized by eco-friendly supercritical water oxidation. The facilely functionalized MWNTs have high solubility (~84 mg L-1) in water and 78% transmittance at 30-fold dilution. The Tyndall effect is also shown for several liquids.Multi-walled carbon nanotubes (MWNTs) have been amine-functionalized by eco-friendly supercritical water oxidation. The facilely functionalized MWNTs have high solubility (~84 mg L-1) in water and 78% transmittance at 30-fold dilution. The Tyndall effect is also shown for several liquids. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03784c

Chun, Kyoung-Yong; Moon, In-Kyu; Han, Joo-Hee; Do, Seung-Hoe; Lee, Jin-Seo; Jeon, Seong-Yun

2013-10-01

344

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

345

Expression of endothelial nitric oxide synthase in the ovine ovary throughout the estrous cycle  

Microsoft Academic Search

This study was conducted to evaluate the expression of endothelial nitric oxide synthase (eNOS) in ovarian follicles and corpora lutea (CL) throughout the estrous cycle in sheep. Three experiments were conducted to (1) immunolocalize eNOS protein, (2) determine expression of mRNA for eNOS and its receptor guanylate cyclase 1 soluble b3 (GUCY1B3), and (3) co-localize eNOS and vascular endothelial growth

Anna T Grazul-Bilska; Chainarong Navanukraw; Mary Lynn Johnson; Daniel A Arnold; Lawrence P Reynolds; Dale A Redmer

2006-01-01

346

Lipid-oxidation catalyses by substances in water on lipid-water interface  

Microsoft Academic Search

Methyl linoleate and water containing heme, ferrous sulfate, cysteine, or ascorbic acid were shaken, and the oxidation was\\u000a measured by means of a Warburg manometer. In spite of a small area of the interface between the lipid and water, oxidation\\u000a was greatly accelerated by these catalysts. The catalyses occurred limitedly in the interface region, except for cysteine.\\u000a Triphenylphosphine added to

M. Morita; M. Mukunoki; F. Okubo; S. Tadokoro

1976-01-01

347

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

2013-07-12

348

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

349

Production of solar hydrogen by a novel, 2-step, water-splitting thermochemical cycle  

Microsoft Academic Search

A novel, two-step, water-splitting cycle is presented which, in contrast to previously proposed cycles that require upper operating temperatures above 2300 K, can be conducted at a moderate temperature. In the first endothermic step, Ni0.5Mn0.5Fe2O4 is thermally activated above 1073 K to form an oxygen-deficient ferrite. In the second step, activated ferrite is reacted with water below 1073 K to

A. Steinfeld; P. Kuhn; K. Ehrensberger

1995-01-01

350

The Use of Water Vapor as a Refrigerant: Impact of Cycle Modifications on Commercial Viability  

Microsoft Academic Search

This project investigated the economic viability of using water as the refrigerant in a 1000-ton chiller application. The most attractive water cycle configuration was found to be a flash-intercooled, two-stage cycle using centrifugal compressors and direct contact heat exchangers. Component level models were developed that could be used to predict the size and performance of the compressors and heat exchangers

Jr. Brandon F. Lachner; Gregory F. Nellis; Douglas T. Reindl

2004-01-01

351

Combined cycle with low-quality heat integration and water injection into the compressed air  

Microsoft Academic Search

The water injection after the compressor into the combustion air of a gas turbine and its evaporation by low-quality heat was analysed for different types of low-temperature heat sources and water-vapour contents of the pressurised air. To integrate low-quality heat—for example solar heat—into a conventional combined cycle efficiently and economically, the cycle must be changed in such a way that

Nikos Aronis; Reinhard Leithner

2004-01-01

352

Status of the development of the General Atomic thermochemical water-splitting cycle  

SciTech Connect

Progress in the development of the General Atomic (GA) sulfur-iodine thermochemical water-splitting cycle over the last 18 months is reported in this paper. The results of the work carried out during the last year have demonstrated that thermochemical water splitting by the suflur-iodine cycle is a feasible process and have provided some confidence that thermal efficiencies as high as 50% are achievable.

Besenbruch, G.; Caprioglio, G.; McCorkle, K.; Norman, J.; O'Keefe, D.; Yoshimoto, M.

1981-01-01

353

Status of the development of the general atomic thermochemical water-splitting cycle  

Microsoft Academic Search

Progress in the development of the General Atomic (GA) sulfur-iodine thermochemical water-splitting cycle over the last 18 months is reported in this paper. The results of the work carried out during the last year have demonstrated that thermochemical water splitting by the suflur-iodine cycle is a feasible process and have provided some confidence that thermal efficiencies as high as 50%

G. Besenbruch; G. Caprioglio; K. McCorkle; J. Norman; D. Okeefe; M. Yoshimoto

1981-01-01

354

Advanced steam cycles for light water reactors. Final report  

Microsoft Academic Search

An appraisal of the potential of adding superheat to improve the overall ; LWR plant cycle performance is presented. The study assesses the economic and ; technical problems associated with the addition of approximately 500°F of ; superheat to raise the steam temperature to 1000°F. The practicality of ; adding either nuclear or fossil superheat to LWR's is reviewed. The

1975-01-01

355

Modelling of a water\\/steam cycle of the combined cycle power plant \\  

Microsoft Academic Search

In order to improve the performance of its simulation tools while reducing their cost, EDF is studying the interest and feasibility to replace LEDA, a tool developed and maintained by EDF for the modelling and simulation of the normal or incidental operation of nuclear and conventional thermal plants, by off-the- shelf available tools. The combined cycle power plant \\

Baligh El Hefni; Daniel Bouskela

356

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

357

Supercritical water oxidation for the destruction of municipal excess sludge and alcohol distillery wastewater of molasses  

Microsoft Academic Search

Supercritical water oxidation has been focused as an environmentally attractive technology where organic materials are oxidized to carbon dioxide, water, and N2. We have applied the supercritical water oxidation to municipal excess sludge and alcohol distillery wastewater of molasses. The reaction was carried out in a batch reactor or a flow reactor with hydrogen peroxide as an oxidant in the

Motonobu Goto; Takatsugu Nada; Akane Ogata; Akio Kodama; Tsutomu Hirose

1998-01-01

358

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

359

Modeling and observations of the atmospheric water cycle and isotopic fractionation on Mars  

NASA Astrophysics Data System (ADS)

Detection of the water isotopic ratios (mainly HDO/H2O and H2O18/H2O16) on Mars will provide important information for the investigations of the history and visualization of water cycle. We are planning the observations of the water isotopic ratios by the sub-millimetre wavelength, as well as starting the 3-dimensional simulations of water cycle including the isotopic fractionations. Here we show our plan of the observation and current status of our Mars general circulation model (MGCM) including the preliminary results.

Kuroda, T.; Sagawa, H.; Nakagawa, H.; Kasai, Y.; Terada, N.; Kasaba, Y.

2012-09-01

360

Visible light water splitting using dye-sensitized oxide semiconductors.  

PubMed

Researchers are intensively investigating photochemical water splitting as a means of converting solar to chemical energy in the form of fuels. Hydrogen is a key solar fuel because it can be used directly in combustion engines or fuel cells, or combined catalytically with CO(2) to make carbon containing fuels. Different approaches to solar water splitting include semiconductor particles as photocatalysts and photoelectrodes, molecular donor-acceptor systems linked to catalysts for hydrogen and oxygen evolution, and photovoltaic cells coupled directly or indirectly to electrocatalysts. Despite several decades of research, solar hydrogen generation is efficient only in systems that use expensive photovoltaic cells to power water electrolysis. Direct photocatalytic water splitting is a challenging problem because the reaction is thermodynamically uphill. Light absorption results in the formation of energetic charge-separated states in both molecular donor-acceptor systems and semiconductor particles. Unfortunately, energetically favorable charge recombination reactions tend to be much faster than the slow multielectron processes of water oxidation and reduction. Consequently, visible light water splitting has only recently been achieved in semiconductor-based photocatalytic systems and remains an inefficient process. This Account describes our approach to two problems in solar water splitting: the organization of molecules into assemblies that promote long-lived charge separation, and catalysis of the electrolysis reactions, in particular the four-electron oxidation of water. The building blocks of our artificial photosynthetic systems are wide band gap semiconductor particles, photosensitizer and electron relay molecules, and nanoparticle catalysts. We intercalate layered metal oxide semiconductors with metal nanoparticles. These intercalation compounds, when sensitized with [Ru(bpy)(3)](2+) derivatives, catalyze the photoproduction of hydrogen from sacrificial electron donors (EDTA(2-)) or non-sacrificial donors (I(-)). Through exfoliation of layered metal oxide semiconductors, we construct multilayer electron donor-acceptor thin films or sensitized colloids in which individual nanosheets mediate light-driven electron transfer reactions. When sensitizer molecules are "wired" to IrO(2).nH(2)O nanoparticles, a dye-sensitized TiO(2) electrode becomes the photoanode of a water-splitting photoelectrochemical cell. Although this system is an interesting proof-of-concept, the performance of these cells is still poor (approximately 1% quantum yield) and the dye photodegrades rapidly. We can understand the quantum efficiency and degradation in terms of competing kinetic pathways for water oxidation, back electron transfer, and decomposition of the oxidized dye molecules. Laser flash photolysis experiments allow us to measure these competing rates and, in principle, to improve the performance of the cell by changing the architecture of the electron transfer chain. PMID:19905000

Youngblood, W Justin; Lee, Seung-Hyun Anna; Maeda, Kazuhiko; Mallouk, Thomas E

2009-12-21

361

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.

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

362

Oxidative capacity of the Mexico City atmosphere - Part 2: A ROx radical cycling perspective  

NASA Astrophysics Data System (ADS)

A box model using measurements from the Mexico City Metropolitan Area study in the spring of 2003 (MCMA-2003) is presented to study oxidative capacity (our ability to predict OH radicals) and ROx (ROx=OH+HO2+RO2+RO) radical cycling in a polluted (i.e., very high NOx=NO+NO2) atmosphere. Model simulations were performed using the Master Chemical Mechanism (MCMv3.1) constrained with 10 min averaged measurements of major radical sources (i.e., HCHO, HONO, O3, CHOCHO, etc.), radical sink precursors (i.e., NO, NO2, SO2, CO, and 102 volatile organic compounds (VOC)), meteorological parameters (temperature, pressure, water vapor concentration, dilution), and photolysis frequencies. Modeled HOx (=OH+HO2) concentrations compare favorably with measured concentrations for most of the day; however, the model under-predicts the concentrations of radicals in the early morning. This "missing reactivity" is highest during peak photochemical activity, and is least visible in a direct comparison of HOx radical concentrations. We conclude that the most likely scenario to reconcile model predictions with observations is the existence of a currently unidentified additional source for RO2 radicals, in combination with an additional sink for HO2 radicals that does not form OH. The true uncertainty due to "missing reactivity" is apparent in parameters like chain length. We present a first attempt to calculate chain length rigorously i.e., we define two parameters that account for atmospheric complexity, and are based on (1) radical initiation, n(OH), and (2) radical termination, ?. We find very high values of n(OH) in the early morning are incompatible with our current understanding of ROx termination routes. We also observe missing reactivity in the rate of ozone production (P(O3)). For example, the integral amount of ozone produced could be under-predicted by a factor of two. We argue that this uncertainty is partly accounted for in lumped chemical codes that are optimized to predict ozone concentrations; however, these codes do not reflect the true uncertainty in oxidative capacity that is relevant to other aspects of air quality management, such as the formation of secondary organic aerosol (SOA). Our analysis highlights that apart from uncertainties in emissions, and meteorology, there is an additional major uncertainty in chemical mechanisms that affects our ability to predict ozone and SOA formation with confidence.

Sheehy, P. M.; Volkamer, R.; Molina, L. T.; Molina, M. J.

2010-07-01

363

Polyethylene oxide does not necessarily aggregate in water  

Microsoft Academic Search

POLYETHYLENE oxide (PEO) is one of the most extensively studied of all water-soluble synthetic polymers, both for its wide range of applications1-4 and from the fundamental standpoint of understanding the behaviour of polymer solutions. The aggregation behaviour of PEO in water and its consequences have been a matter of concern in many studies5-11 of this system. It is not clear,

K. Devanand; J. C. Selser

1990-01-01

364

Hydrogen production using solid-polymer-electrolyte technology for water electrolysis and hybrid sulfur cycle  

Microsoft Academic Search

An evaluation was made of the comparative technoeconomics of hydrogen production using the General Electric Company's solid polymer electrolyte technology in two advanced processes: Water Electrolysis and Hybrid Sulfur Cycle Water Decomposition. In water electrolysis, based on the solid polymer electrolyte, only purified water is fed to the cell. The cell voltage is typically 1.65V at 1000 amp\\/ft² (ASF), 300

J. M. Sedlak; J. H. Russell; A. B. LaConti; D. K. Gupta; J. F. Austin; J. S. Nugent

1979-01-01

365

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

366

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

367

Bacterial Oxidation of Iron in Olivine: Implications for the Subsurface Biosphere, Global Chemical Cycles, and Life on Mars  

NASA Astrophysics Data System (ADS)

We isolated 21 species of bacteria from subseafloor and terrestrial basalt environments and which thrive on olivine at neutral pH. Cell numbers increase four to five orders of magnitude over three weeks in media where the only metabolic energy comes from the oxidation of Fe(II) in olivine. The subseafloor bacteria were isolated from a borehole on the flank of Juan de Fuca Ridge in the northeast Pacific basin where the temperature ranged from 4 up to 64 °C over four years. Terrestrial isolates originated from the basalt-ice boundary in a lava tube on the flank of Newberry Caldera in the Cascades of Oregon. The borehole water was either seawater or seawater plus subseafloor formation water and the lava tube ice was frozen meteoric or ground water. Although microorganisms capable of oxidizing iron for growth are known, microbes that oxidize iron from silicate minerals at neutral pH have not previously been cultured. The 21 species in this study are the first neutrophilic, iron-oxidizing bacteria (nFeOB) to be isolated and cultured that grow on olivine. These nFeOB are primary producers and we believe that they are a widespread component of the subsurface biosphere. In addition to their ability use iron from olivine, these microbes assimilate carbon from bicarbonate in solution and can grow when oxygen pressures are low. They also use nitrate as an alternative electron acceptor to oxygen in anaerobiosis. Since basalt is the most common rock in the Earth's crust and iron is the fourth most abundant element in the crust, we believe nFeOB are likely to be a significant portion of the subsurface biosphere. They are likely to affect, and perhaps in some environments control, the weathering rate of olivine and possibly of pyroxene and basalt glass. Olivine is a component of Mars's surface and it is present on other rocky bodies in the solar system. The ability of these bacteria to use Fe(II) from olivine, to assimilate carbon, to grow at low temperature, and to use low levels of oxygen and nitrate as oxidants would allow them to survive below the surface of Mars. These cultured organisms, which are the first known to oxidize iron from olivine at neutral pH, may be a major component of the subsurface biosphere, may affect global chemical cycles of elements in basalt, and could potentially, live in the Martian subsurface.

Fisk, M. R.; Popa, R.; Smith, A. R.; Popa, R.; Boone, J.

2011-12-01

368

Tropospheric odd nitrogen and the atmospheric water vapor cycle  

Microsoft Academic Search

A model for tropospheric odd nitrogen is presented. It is argued that the vertical profile of HNO3, a highly soluble gas, is similar to the vertical profile of water vapor, so that the volume mixing ratio of gaseous HNO3 to water vapor is constant with altitude. The value of this mixing ratio, deduced from the observed concentration of nitrates in

William Chameides

1975-01-01

369

Teaching the Krebs Cycle.  

ERIC Educational Resources Information Center

Outlines a simple but rigorous treatment of the Krebs Cycle suitable for A-level Biology students. The importance of the addition of water molecules in various stages of the cycle is stressed as well as the removal of hydrogen atoms by the oxidizing enzymes. (JN)

Akeroyd, F. Michael

1983-01-01

370

THE FORMATION OF PB (IV) OXIDES IN CHLORINATED WATER  

EPA Science Inventory

The foundation for lead control in drinking water distribution systems is based on Pb(II) chemistry. In recent years, however, Pb(IV) oxides have been identified in distribution systems, suggesting that they may be important relative to predicting and controlling lead concentrat...

371

Oxidation of Ultra High Temperature Ceramics in Water Vapor.  

National Technical Information Service (NTIS)

Ultra High Temperature Ceramics (UHTCs) including HfB2 + 20v/0 SiC (HS), ZrB2 + 20v/0 SiC (ZS), and ZrB2 + 30v/0 C + 14v/0 SiC (ZCS) have been investigated for use as potential aeropropulsion engine materials. These materials were oxidized in water vapor ...

Q. G. N. Nguyen E. J. Opila R. C. Robinson

2004-01-01

372

Nickel oxide water electrolysis diaphragm fabricated by a novel method  

Microsoft Academic Search

We have been studying small-scale, dispersed hydrogen production by water electrolysis by using renewable energy such as solar light. In order to fabricate the compact nickel oxide diaphragms used in such system, a novel method was devised where Ni deposition was applied in combination with a masking process. The method has the merits of being controllable in thickness and porous

Takashi Ohmori; Kenjiro Tachikawa; Katsuyuki Tsuji; Katsuhiro Anzai

2007-01-01

373

The role of manganese in photosynthetic water oxidation  

Microsoft Academic Search

Summary The process of photosynthetic water oxidation to dioxygen under proton release takes place via a sequence of four univalent redox steps in a manganese-containing unit. In this mini-review the current state of knowledge is briefly described with special emphasis on the following topics: (a) the nature of the catalytic site, (b) the structure of the redox chemistry of the

G. Renger; T. Wydrzynski

1991-01-01

374

Anthropogenic impacts on the global water cycle - a multi model approach.  

NASA Astrophysics Data System (ADS)

Humans activities have a large impact on the global water cycle. Through the building of dams and irrigation schemes large amounts of water are diverted from river systems. Through the emission of greenhouse gases causing global warming, also the rainfall and evaporation patterns are changed across the globe. It is, however, still difficult to quantify current and future impacts on the global water cycle due to limited data availability, model imperfections and large uncertainties in climate change projections. To partly overcome these limitations we used a multi-model approach to study anthropogenic impacts on the global water cycle. Four different global hydrological models (H08, VIC, WaterGAP and LPJml) were forced with an historical climate dataset (Watch Forcing Data) and bias corrected output of three different global climate models (Echam, IPSL and CNRM) using two emission scenarios (A2 and B1). In addition the LPJml model was also run with two different land use change scenarios. Combining the water availability simulations with the water demand scenarios developed within the Watch project we also analyzed current and future water scarcity. The analyses show that current human impacts and on the water cycle are especially high in Central Asia, parts of Europe, the Southwestern US and the Murray-Darling Basin in Australia. The model comparison of agricultural water use and demand showed that the differences in total global agricultural demand and water use were relatively smaller than the differences in simulated water availability. All models showed agricultural water extractions are high in South and East Asia in particular in Northern India and Pakistan and in Northeast China. The most important spatial differences between the different models was observed for Northern China where H08 showed much higher water demands than VIC. Future analyses showed that climate change impacts on the global water cycle are potentially high especially in the semi-arid regions. Although there were considerable differences in the four hydrological models in general all models predicted the same direction of change. In conclusion the analyses showed that both under the B1 and the A2 scenarios the percentage of agricultural water demand than cannot be fulfilled by surface and ground-water will increase. Water shortages will be much higher under the A2 than under the B1 scenario. In conclusion using a multi model approach gives a more robust quantification of possible future anthropogenic impacts on the global water cycle.

Ludwig, F.; haddeland, I.; Biemans, H.; Clark, D.; Fransen, W.; Voss, F.; Floerke, M.; Heinke, J.; Hagemann, S.; Hanasakki, N.; Gerten, D.; Kabat, P.

2012-04-01

375

North-south asymmetry of subsurface water distribution on Mars: implication from a global water cycle model  

Microsoft Academic Search

The Gammy-Ray spectrometer onboard Mars Odyssey recently detected in the near-surface soil of Martian polar region a high abundance of hydrogen, which is indicative of ground ice. In an effort to understand the observed global subsurface water distribution a global coupled atmosphere-subsurface water cycle model is developed. The simulation indicates that, regardless of the initial subsurface water distribution, the soil

Tetsuya Tokano

2002-01-01

376

Destruction of energetic materials by supercritical water oxidation  

SciTech Connect

Supercritical water oxidation is a relatively low-temperature process that can give high destruction efficiencies for a variety of hazardous chemical wastes. Results are presented examining the destruction of high explosives and propellants in supercritical water and the use of low temperature, low pressure hydrolysis as a pretreatment process. Reactions of cyclotrimethylene trinitramine (RDX), cyclotetramethylene tetranitramine (HMX), nitroguanidine (NQ), pentaerythritol tetranitrate (PETN), and 2,4,6-trinitrotoluene (TNT) are examined in a flow reactor operated at temperatures between 400{degrees}C and 650{degrees}C. Explosives are introduced into the reactor at concentrations below the solubility limits. For each of the compounds, over 99.9% is destroyed in less than 30 seconds at temperatures above 600{degrees}C. The reactions produce primarily N{sub 2}, N{sub 2}O,CO{sub 2}, and some nitrate and nitrite ions. The distribution of reaction products depends on reactor pressure, temperature, and oxidizer concentration. Kinetics studies of the reactions of nitrate and nitrite ions with various reducing reagents in supercritical water show that they can be rapidly and completely destroyed at temperatures above 525{degrees}C. The use of slurries and hydrolysis to introduce high concentrations of explosives into a supercritical water reactor is examined. For some compounds the rate of reaction depends on particle size. The hydrolysis of explosives at low temperatures (<100{degrees}C) and low pressures (<1 atm) under basic conditions produces water soluble, non-explosive products which are easily destroyed by supercritical water oxidation. Large pieces of explosives (13 cm diameter) have been successfully hydrolyzed. The rate, extent, and products of the hydrolysis depend on the type and concentration of base. Results from the base hydrolysis of triple base propellant M31A1E1 and the subsequent supercritical water oxidation of the hydrolysis products are presented.

Beulow, S.J.; Dyer, R.B.; Harradine, D.M.; Robinson, J.M.; Oldenborg, R.C.; Funk, K.A.; McInroy, R.E.; Sanchez, J.A.; Spontarelli, T.

1993-10-01

377

Mineralogical Characterization of Manganese Oxides in Mine Water Treatment Systems  

NASA Astrophysics Data System (ADS)

The removal of manganese(II) from mine water is a significant problem for both operating and abandoned mines across the United States. In many situations, manganese removal represents the most costly aspect of mine water treatment. Active treatment of Mn-containing mine water requires adjustment of pH to 9-10, and results in the abiotic precipitation of manganese oxides (MnOx). After manganese removal, this high pH water must be neutralized before release. Alternatively, passive limestone beds can be used for neutralization of low-pH mine water and subsequent manganese removal. Although limestone beds are effective for Mn removal, the processes involved are not clear (e.g., relative importance of biological Mn(II) oxidation versus surface mediated oxidation) and the characteristics of the manganese "crusts" formed are not well studied. In this field-based study, we have collected natural manganese oxides from two different limestone beds designed to treat mine water from abandoned coal strip mines in Pennsylvania. Samples were collected at different locations in the beds and at different seasons to capture possible variations in mineralogical characteristics. Water samples were also collected to measure the corresponding solution chemistry and revealed that manganese removal was strongly temperature dependent. Solid samples have been examined by scanning and transmission electron microscopy, and by X-ray diffraction. Micro-diffraction XRD has been used to tentatively identify disordered buserite as a predominant mineral in many of these crust samples. Additional characterizations will include particle size distribution and surface charge. Synchroton-based X-ray techniques such as scanning transmission X-ray microscopy (STXM) and X-ray spectroscopy (XAS) may also be pursued.

Tan, H.; Heaney, P.; Post, J.; Burgos, W.

2006-05-01

378

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

379

Equillbrating metal-oxide cluster ensembles for oxidation reactions using oxygen in water  

Microsoft Academic Search

. Particularly problematic is the fact that oxidation ofsubstrates by O2 involves radical chemistry, which is intrinsically non-selective and difficult to control. In addition, metallo-organic catalysts are inherently susceptible to degra- dation5 by oxygen-based radicals, while their transition-metal- ion active sites often react with water to give insoluble, and thus inactive, oxides or hydroxides7. Furthermore, pH control is often requiredto

Ira A. Weinstock; Elena M. G. Barbuzzi; Michael W. Wemple; Jennifer J. Cowan; Richard S. Reiner; Dan M. Sonnen; Robert A. Heintz; James S. Bond; Craig L. Hill

2001-01-01

380

Acid-base model for thy--mochemical water splitting. Results of experimental tests on manganese-based thermochemical cycles  

SciTech Connect

An acid-base model for thermochemical water splitting cycles is described, together with the results of its application to cycles based upon reactions of manganese oxides. Experiments confirmed that at least 12 acids-HCl, H/sub 2/SO/sub 4/, H/sub 3/PO/sub 4/, MoO/sub 3/, NaPO/sub 3/, Na/sub 4/P/sub 2/O/sub 7/, SiO/sub 2/, Cr/sub 2/O/sub 3/, TiO/sub 2/, Al/sub 2/O/sub 3/, SnO/sub 2/, and Fe/sub 2/Onumber-drive the thermal decomposition of NaMnO/sub 2/ at temperatures below 1400/sup 0/K. Only rather strong bases-NaOH, LiOH, BaO, Li/sub 2/CO/sub 3/, Na/sub 2/CO/sub 3/-can drive the steam oxidation of Mn(II) below 1300/sup 0/K. In accord with the model, the acids HCl, H/sub 2/SO/sub 4/, H/sub 3/PO/sub 4/, and MoO/sub 3/ are too strong to be used in Mn(III)/(II) cycles, because their Na, Li, and Ba salts are too stable. Cycles were demonstrated with the other 8 acids and either NaOH or Na/sub 2/CO/sub 3/. Because such cycles evolve O/sub 2(g)/ in the presence of air, solar furnaces are appropriate sources of thermal energy for them.

Robinson, P.R.; Kilyk, J. Jr.

1980-01-01

381

Water Vapor Tracers as Diagnostics of the Regional Hydrologic Cycle.  

National Technical Information Service (NTIS)

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 inhe...

M. G. Bosilovich S. D. Schubert

2001-01-01

382

Nitrous oxide cycling in the Black Sea inferred from stable isotope and isotopomer distributions  

NASA Astrophysics Data System (ADS)

The low-oxygen regions of the world's oceans have been shown to be major sources of nitrous oxide, a trace gas in the atmosphere that contributes to both greenhouse warming and the destruction of stratospheric ozone. Nitrous oxide can be produced as a by-product of nitrification or an intermediate of denitrification; low oxygen conditions enhance the yield of nitrous oxide from both pathways. We measured the concentration and isotopic composition of dissolved nitrous oxide at several stations in the Black Sea, an anoxic basin with a well-defined suboxic layer that separates the ventilated surface waters from the sulfidic deep waters. Our data show that in contrast to other low-oxygen marine regions, nitrous oxide does not accumulate in the Black Sea at significant levels. Moreover, whereas the reduction of nitrous oxide by denitrification usually yields residual gas that is enriched in both stable isotopes, in the Black Sea declining nitrous oxide concentrations are accompanied by enrichment in 18O-N 2O but depletion in 15N-N 2O. We measured a minimum ?15N-N 2O value of -10.8±0.8‰ vs. air N 2, by far the lowest measured to date for seawater. Measurements of the distribution of 15N within the linear nitrous oxide molecule reveal that this unusual isotopic signal is most pronounced in the end-position nitrogen, and that site preference, or the tendency for 15N to be found in the center-position nitrogen, co-varies positively with 18O-N 2O. We surmise that the highly unusual isotopic composition of Black Sea nitrous oxide is the result of two processes: production of 15N-depleted nitrous oxide by ammonium oxidation followed by its reduction by denitrification, which causes enrichment in 18O and enhancement of 15N-site preference. Bottle incubation experiments with 15N-ammonium and 15N-nitrite reveal that both oxidation and reduction pathways to nitrous oxide are active in the Black Sea suboxic zone.

Westley, Marian B.; Yamagishi, Hiroaki; Popp, Brian N.; Yoshida, Naohiro

2006-08-01

383

Nitrous oxide cycling in the Black Sea inferred from stable isotope and isotopomer distributions  

NASA Astrophysics Data System (ADS)

The low-oxygen regions of the world's oceans have been shown to be major sources of nitrous oxide, a trace gas in the atmosphere that contributes to both greenhouse warming and the destruction of stratospheric ozone. Nitrous oxide can be produced as a by-product of nitrification or an intermediate of denitrification; low oxygen conditions enhance the yield of nitrous oxide from both pathways. We measured the concentration and isotopic composition of dissolved nitrous oxide at several stations in the Black Sea, an anoxic basin with a well-defined suboxic layer that separates the ventilated surface waters from the sulfidic deep waters. Our data show that in contrast to other low-oxygen marine regions, nitrous oxide does not accumulate in the Black Sea at significant levels. Moreover, whereas the reduction of nitrous oxide by denitrification usually yields residual gas that is enriched in both stable isotopes, in the Black Sea declining nitrous oxide concentrations are accompanied by enrichment in 18O-N2O but depletion in 15N-N2O. We measured a minimum ?15N-N2O value of -10.8±0.8‰ vs. air N2, by far the lowest measured to date for seawater. Measurements of the distribution of 15N within the linear nitrous oxide molecule reveal that this unusual isotopic signal is most pronounced in the end-position nitrogen, and that site preference, or the tendency for 15N to be found in the center-position nitrogen, co-varies positively with 18O-N2O. We surmise that the highly unusual isotopic composition of Black Sea nitrous oxide is the result of two processes: production of 15N-depleted nitrous oxide by ammonium oxidation followed by its reduction by denitrification, which causes enrichment in 18O and enhancement of 15N-site preference. Bottle incubation experiments with 15N-ammonium and 15N-nitrite reveal that both oxidation and reduction pathways to nitrous oxide are active in the Black Sea suboxic zone.

Westley, Marian B.; Yamagishi, Hiroaki; Popp, Brian N.; Yoshida, Naohiro

2006-08-01

384

Highly water-soluble multi-walled carbon nanotubes amine-functionalized by supercritical water oxidation.  

PubMed

Multi-walled carbon nanotubes (MWNTs) have been amine-functionalized by eco-friendly supercritical water oxidation. The facilely functionalized MWNTs have high solubility (?84 mg L(-1)) in water and 78% transmittance at 30-fold dilution. The Tyndall effect is also shown for several liquids. PMID:24057096

Chun, Kyoung-Yong; Moon, In-Kyu; Han, Joo-Hee; Do, Seung-Hoe; Lee, Jin-Seo; Jeon, Seong-Yun

2013-09-12

385

Water Cycling Between Ocean and Mantle: Super-Earths Need Not be Waterworlds  

NASA Astrophysics Data System (ADS)

Simple scaling relations dictate that ocean depth should increase with planetary mass, with the generic prediction that large terrestrial planets should be entirely covered in water, so-called waterworlds. Water is partitioned, however, between a surface reservoir, the ocean, and an interior reservoir, the mantle. If a planet undergoes plate tectonics, then water can move between these reservoirs on geological timescales: ocean crust formation at mid-ocean ridges releases water into the ocean, while subduction of serpentinized crust carries water into the mantle. Motivated by Earth's approximately steady-state deep water cycle, we develop a two-box model of the hydrosphere including potential feedbacks from sea-floor pressure, as well as the effects of isostatic adjustment. Using this model, we derive analytic and numerical steady-state solutions to the water-partitioning on terrestrial planets. We show that isostatic adjustment allows for a wide range of ocean volumes without submerging continents. Since surface gravity does not affect the steady state isostatic balance, this leeway applies just as well to super-Earths, despite their reduced topography. Moreover, the deep water cycle is mediated by sea-floor pressure, which is proportional to gravity. Super-Earths with a deep water cycle should therefore store the majority of their water in the mantle. We conclude that tectonically active planets with water mass fractions below about 0.004 will have exposed continents like Earth.

Cowan, Nicolas B.; Abbot, D. S.

2013-10-01

386

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

387

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

388

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

389

Succession of internal sulfur cycles and sulfur-oxidizing bacterial communities in microaerophilic wastewater biofilms.  

PubMed

The succession of sulfur-oxidizing bacterial (SOB) community structure and the complex internal sulfur cycle occurring in wastewater biofilms growing under microaerophilic conditions was analyzed by using a polyphasic approach that employed 16S rRNA gene-cloning analysis combined with fluorescence in situ hybridization, microelectrode measurements, and standard batch and reactor experiments. A complete sulfur cycle was established via S(0) accumulation within 80 days in the biofilms in replicate. This development was generally split into two phases, (i) a sulfur-accumulating phase and (ii) a sulfate-producing phase. In the first phase (until about 40 days), since the sulfide production rate (sulfate-reducing activity) exceeded the maximum sulfide-oxidizing capacity of SOB in the biofilms, H(2)S was only partially oxidized to S(0) by mainly Thiomicrospira denitirificans with NO(3)(-) as an electron acceptor, leading to significant accumulation of S(0) in the biofilms. In the second phase, the SOB populations developed further and diversified with time. In particular, S(0) accumulation promoted the growth of a novel strain, strain SO07, which predominantly carried out the oxidation of S(0) to SO(4)(2-) under oxic conditions, and Thiothrix sp. strain CT3. In situ hybridization analysis revealed that the dense populations of Thiothrix (ca. 10(9) cells cm(-3)) and strain SO07 (ca. 10(8) cells cm(-3)) were found at the sulfur-rich surface (100 microm), while the population of Thiomicrospira denitirificans was distributed throughout the biofilms with a density of ca. 10(7) to 10(8) cells cm(-3). Microelectrode measurements revealed that active sulfide-oxidizing zones overlapped the spatial distributions of different phylogenetic SOB groups in the biofilms. As a consequence, the sulfide-oxidizing capacities of the biofilms became high enough to completely oxidize all H(2)S produced by SRB to SO(4)(2-) in the second phase, indicating establishment of the complete sulfur cycle in the biofilms. PMID:15870342

Okabe, Satoshi; Ito, Tsukasa; Sugita, Kenichi; Satoh, Hisashi

2005-05-01

390

Simulation-based life cycle cost modeling and maintenance plan for water mains  

Microsoft Academic Search

Life cycle cost (LCC) is an essential approach to decide on alternative rehabilitation strategies for infrastructure systems, such as water mains. The research presented in this article identifies several rehabilitation methods for water mains, which are classified into three main categories: repair, renovation and replacement. A simulation-based LCC (SLCC) model is developed to compare different rehabilitation scenarios\\/alternatives for various types

Khaled Shahata; Tarek Zayed

2011-01-01

391

Sampling Throughout The Hydrologic Cycle To Characterize Sources Of Volatile Organic Compounds In Ground Water  

Microsoft Academic Search

Results of three studies in New Jersey demonstrate that analysis of samples collected throughout the hydrologic cycle can improve understanding of the sources of volatile organic compounds (VOCs) in ambi- ent ground water. Results of the first study indicate that atmospheric concentrations of methyl-tert butyl ether (MTBE) are sufficiently high to cause detection in ground water, whereas atmospheric concentrations of

Arthur L. Baehr; Leon J. Kauffman; Emmanuel G. Charles; Ronald J. Baker

392

Sulfur cycling in the water column of Little Rock Lake, Wisconsin  

Microsoft Academic Search

The S cycle in the water column of a small, soft-water lake was studied for 9 years as part of an experimental study of the effects of acid rain on lakes. The two basins of the lake were artificially separated, and one basin was experimentally acidified with sulfuric acid while the other served as a reference or control. Spatial and

N. R. Urban; C. J. Sampson; P. L. Brezonik; L. A. Baker

2001-01-01

393

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

394

A New Look at Mars' Seasonal Water Cycle in the North  

Microsoft Academic Search

Mars water cycle variability is likely recorded in polar ice and layered terrains. Previously, we reported an increase in Mars north polar albedo as the northern summer season progresses and believe the albedo increase in Mariner 9 and Viking imaging data is due to the deposition of water ice onto the residual cap and polar layered deposits [Bass et al,

D. S. Bass; D. A. Paige

1996-01-01

395

Multiple staging of the cold water in the open cycle OTEC Systems  

Microsoft Academic Search

Using the cooling water of the open cycle OTEC Systems in a multiple stage fashion results in its most effective utilization. Such use increases by 2-1\\/3 times the power production capability per unit mass of cold water, thus reducing the cost of the most expensive single item of an original installation. Later stages could utilize the effluent from previously installed

A. E. Molini; C. Zener; T. Fort Jr.

1979-01-01

396

Application of solar hot water and geothermal principles to closed-cycle aquaculture  

Microsoft Academic Search

The design of an underground silo where warm water food fish could be raised to market size under controlled conditions. The building and solar concept analysis for the closed cycle aquaculture system are described. Energy conservation features of the design include Earth berming and insulation of the production silo and enclosure, a waste water reclaim system and a solar heating

R. A. Yanzito

1981-01-01

397

Use of solar energy for direct and two-step water decomposition cycles  

Microsoft Academic Search

The feasibility of using concentrated solar energy at high temperatures to decompose water is experimentally demonstrated. Preliminary studies show that direct decomposition of water at 2000-2500 C is possible and that the main development should be directed toward reactor design and the separation of product gases. On the other hand, it is shown that two-step thermochemical cycles for hydrogen production

E. Bilgen; M. Ducarroir; M. Foex; F. Sibieude; F. Trombe

1977-01-01

398

Sensitivity of a coupled dust and water cycle in the Ames General Circulation Model  

Microsoft Academic Search

Global, 3-D computer modeling of the Martian atmosphere is reaching a new level of maturity. The community is transitioning into an era where advancements in computational speed are allowing for the coupling of the dust and water cycles. This coupling allows water to condense onto the dust, changing the particle's radiative characteristics, fall speeds, and as a result, their spatial

S. Nelli; J. Murphy; F. Montmessin; A. Colaprete; R. Haberle; J. Schaeffer

2004-01-01

399

The contribution of condensation to the water cycle under high-mountain conditions  

Microsoft Academic Search

Little is known about the interaction between condensation, precipitation and evaporation as an integral part of the water cycle under high-mountain conditions. This paper focuses on methods of identification and measurement of condensation under natural conditions in high alpine valleys by example of the Dischma in eastern Switzerland. The role of different vegetation zones in transferring water from and to

Carmen de Jong

2005-01-01

400

The Tropical Water and Energy Cycles in a Cumulus Ensemble Model. Part I: Equilibrium Climate  

Microsoft Academic Search

A cumulus ensemble model is used to study the tropical water and energy cycles and their role in the climate system. The model includes cloud dynamics, radiative processes, and microphysics that incorporate all important production and conversion processes among water vapor and five species of hydrometeors. Radiative transfer in clouds is parameterized based on cloud contents and size distributions of

C. H. Sui; K. M. Lau; W. K. Tao; J. Simpson

1994-01-01

401

Combination split system air conditioner and compression cycle domestic hot water heating apparatus  

Microsoft Academic Search

A conventional split system air conditioner is combined with a compression cycle or heat pump system for supplying heat to a domestic water heater. The units are combined in such a way that significant energy savings can be achieved by circulating air in series through the outdoor evaporator coil of the hot water heating system and then through the condensing

V. O. Bahel; R. R. Kuehner; R. H. Rosenberg

1980-01-01

402

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

403

[Environment effects of algae-caused black spots: impacts on Fe-Mn-S cycles in water-sediment interface].  

PubMed

The driving effects of algal cells settlement in the water-sediment interface on Fe, Mn, S biogeochemistry in laboratory through static cultivation device. Results showed that dissolved oxygen would be exhausted by algae cells in 50 min after the cyanobacteria cells settled to the sediment surface. Soon the water-sediment interface formed the severe anoxia and Fe-Mn oxides and sulfides were deoxidized quickly in the strong reducing environment. The Fe2+, Mn2+ content in interface increased to the summit at the 4th day and their concentrations were 4.40 mg/L and 2.35 mg/L, respectively. When it comes to the end of the experiment, the Fe2+ content had a little reduction and Mn2+ reduced quickly, their concentrations were 3.37 mg/L and 0.97 mg/L at the end of experiment. However, S2- concentration in interface reached the highest at the 2nd day and its content was 0.63 mg/L, and its concentration was only 0.12 mg/L at the end since it has been reduced. The ORP was--150 mV in the sediment surface and indicated that the sediment environment was a strong reducing environment. Phenomenon of algal cells induced black spots in water bodies was the main driving factors on Fe/Mn oxides and sulfides biogeochemistry cycle, and also the extreme anoxia environment would have great harm on the water body's ecology. PMID:21250447

Liu, Guo-Feng; He, Jun; Fan, Cheng-Xin; Zhang, Lei; Shen, Qiu-Shi; Zhong, Ji-Cheng; Yan, Shao-Hua

2010-11-01

404

Measuring ecological impact of water consumption by bioethanol using life cycle impact assessment  

Microsoft Academic Search

Purpose  Though the development of biofuel has attracted numerous studies for quantifying potential water demand applying life cycle\\u000a thinking, the impacts of biofuel water consumption still remain unknown. In this study, we aimed to quantify ecological impact\\u000a associated with corn-based bioethanol water consumption in Minnesota in responding to different refinery expansion scenarios\\u000a by applying a life cycle impact assessment method.\\u000a \\u000a \\u000a \\u000a \\u000a Methods

Yi-Wen Chiu; Sangwon Suh; Stephan Pfister; Stefanie Hellweg; Annette Koehler

405

Water displacements in the Pacific and the genesis of El Nino cycles  

SciTech Connect

Sea level observations are used to estimate the amounts of warm water exchanged during the 1982 to 1983 El Nino event, indicating an eastward flux of about 40 x 10/sup 6/ m/sup 3/ s/sup -1/. At the end of El Nino the equatorial Pacific is depleted of warm water which is lost toward higher latitudes. The duration of a complete El Nino cycle is determined by the time required for the slow accumulation of warm water in the western Pacific. The cycle constitutes an energy relaxation of the ocean-atmosphere system.

Wyrtki, K.

1985-07-20

406

Effect of water density and air pressure on partial oxidation of bitumen in supercritical water  

Microsoft Academic Search

Partial oxidation of bitumen was examined in supercritical water from 653 to 723K at a water\\/oil ratio from 0 to 3 and up to 5.1MPa of initial air pressure. The contents in the reactor were separated into water rich phase and oil rich phase. Most of oxygen was quickly consumed within 30min and the main gases produced were CO, CO2

Takafumi Sato; Phan Hieu Trung; Tomoyuki Tomita; Naotsugu Itoh

407

Water oxidation by a ruthenium complex with noninnocent quinone ligands: possible formation of an O-O bond at a low oxidation state of the metal.  

PubMed

Tanaka and co-workers reported a novel dinuclear Ru complex, [Ru2(OH)2(3,6-Bu2Q)2(btpyan)](SbF6)2 (3,6-Bu2Q = 3,6-di tert-butyl-1,2-benzoquinone, btpyan = 1,8-bis(2,2':6',2''-terpyrid-4'-yl)anthracene), that contains redox active quinone ligands and has an excellent electrocatalytic activity for water oxidation when immobilized on an indium-tin-oxide electrode (Inorg. Chem., 2001, 40, 329-337). The novel features of the dinuclear and related mononuclear Ru species with quinone ligands, and comparison of their properties to those of the Ru analogues with the bpy ligand (bpy = 2,2'-bipyridine) replacing quinone, are summarized here together with new theoretical and experimental results that show striking features for both the dinuclear and mononuclear species. The identity and oxidation state of key mononuclear species, including the previously reported oxyl radical, have been reassigned. Our gas-phase theoretical calculations indicate that the Tanaka Ru-dinuclear catalyst seems to maintain predominantly Ru(II) centers while the quinone ligands and water moiety are involved in redox reactions throughout the entire catalytic cycle for water oxidation. Our theoretical study identifies [Ru2(O2(-))(Q(-1.5))2(btpyan)](0) as a key intermediate and the most reduced catalyst species that is formed by removal of all four protons before four-electron oxidation takes place. While our study toward understanding the complicated electronic and geometric structures of possible intermediates in the catalytic cycle is still in progress, the current status and new directions for kinetic and mechanistic investigations, and key issues and challenges in water oxidation with the Tanaka catalyst (and its analogues with Cl(-) or NO(2-)substituted quinones and a species with a xanthene bridge instead an antheracene) are discussed. PMID:18330970

Muckerman, James T; Polyansky, Dmitry E; Wada, Tohru; Tanaka, Koji; Fujita, Etsuko

2008-03-17

408

Upper Water Column Dimethylated Sulfur Biogeochemical Cycling in the Sargasso Sea - Assessing the Oceanic DMS Source  

Microsoft Academic Search

Once ventilated to the atmosphere, the oxidation products of biologically produced DMS are non sea salt sulfate and methane sulfonate aerosols which potentially exert considerable control on the global climate via alterations in radiative properties, acid-base chemistry, halogen cycles, and aerosol iron availability. The most significant obstacle to assessing and quantifying any associated climate feedbacks, beyond uncertainties associated with flux

D. A. Toole; J. W. Dacey; N. R. Bates; N. M. Levine; A. Neeley

2008-01-01

409

Kinetics of the catalytic oxidation of phenol over manganese oxide in supercritical water  

SciTech Connect

A kinetic analysis was made for the phenol disappearance rate in catalytic oxidation of phenol over MnO{sub 2} in supercritical water at a fixed temperature of 425 C and pressures between 22.7 and 27.2 MPa. The nonsupported MnO{sub 2} catalyst possessed a strong activity for promoting phenol oxidation, though the overall reaction rate was appreciably influenced by internal mass-transfer resistance. From the kinetic analysis on the reaction rate of the phenol disappearance, the global rate expression of the surface reaction was obtained, where the reaction orders with respect to phenol, oxygen, and water were almost unity, 0.7, and {minus}2.0, respectively. A Langmuir-type mechanism, in which phenol and oxygen adsorbed on the catalytic sites and water adsorbed on the same site to inhibit the phenol and oxygen adsorption, was proposed to explain the reaction orders for phenol, oxygen, and water.

Oshima, Yoshito; Tomita, Kengo; Koda, Seiichiro

1999-11-01

410

Water Uptake by Roots Controls Water Table Movement and Sediment Oxidation in Short Spartina Marsh  

NASA Astrophysics Data System (ADS)

Downward movement of the water table during both day and night in the short grass zone of intertidal salt marshes is due not to drainage but to water uptake by roots. Removal of water from the sediment results in the entry of air into the sediment, suggesting a feedback between plant growth, water uptake, and sediment oxidation. The water balance of Spartina alterniflora appears to influence the internal morphology of its roots, potentially giving rise to a new mechanism for the mass flow of gas in plants.

Dacey, John W. H.; Howes, Brian L.

1984-05-01

411

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

PubMed

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

2010-02-11

412

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

2012-11-06

413

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

2013-06-27

414

The radiation oxidation of aluminum in contact with water  

Microsoft Academic Search

The aluminum oxidation in the aluminum-water system under the action of radiation is studied using the radiothermoluminescence\\u000a and IR-reflection absorption spectroscopy methods. The specific features of the radiother moluminescence peaks observed in\\u000a a 100–250 K temperature range (the activation energy E\\u000a a = 0.38–0.65 eV) corroborate the significance role of superficial oxygen hole-type centers and chemisorbed oxygen in the oxide

N. N. Gadzhieva

2007-01-01

415

Mechanism of catalytic oxidation of water-lipid substrate  

NASA Astrophysics Data System (ADS)

The processes of ethyl oleate water-emulsion oxidation in the presence of copper (II) complexes with ?-alanine as a catalyst were investigated spectroscopically. UV spectra of the samples revealed the competitive nature of the formation and decomposition of hydroperoxides in the course of oxidation. Vis spectra of the aqueous phase revealed the constant presence of copper (II) complex with ?-alanine and the formation of a similar complex with copper (I) in organic phase. The involvement of these complexes in the reactions of chain nucleation and decay of hydroperoxides is suggested.

Kraynik, V. V.; Ushkalova, V. N.

2010-05-01

416

Solar-powered Rankine cycles for fresh water production  

Microsoft Academic Search

The lack of access to electricity grid and fresh water strongly limits the development and the quality of life to many rural locations. The distributed solar power generation can be applied to many basic needs, not only electricity generation, but also desalination, cooling, heating, etc. For this reason it provides opportunity of social and economic development and therefore promoting employment.

Lourdes García-Rodríguez; Agustín M. Delgado-Torres

2007-01-01

417

MULTIPLE SPACEBORNE WATER CYCLE OBSERVATIONS WOULD AID MODELING  

Technology Transfer Automated Retrieval System (TEKTRAN)

Land data assimilation systems (LDAS) are designed to provide continental-scale estimates of surface moisture and temperature states - and water and energy flux exchanges with the atmosphere - by propagating land surface models using observations of micrometeorological forcing data (e.g. surface pre...

418

Lidar Monitoring of the Water Vapor Cycle in the Troposphere  

Microsoft Academic Search

The water vapor mixing ratio distribution in the lower and middle troposphere has been continuously monitored, using an active lidar system. The methodology of the differential absorption laser method used for these measurements is summarized and related to the corresponding achievements of the experimental system set up at the Haute-Provence Observatory, France. The experimental results emphasize the unique aspect of

C. Cahen; G. Megie; P. Flamant

1982-01-01

419

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

420

Hallmarks of Maghemitization in Low-Temperature Remanence Cycling of Partially Oxidized Magnetite Nanoparticles  

NASA Astrophysics Data System (ADS)

We report continuous measurements of magnetization M for stoichiometric and partially oxidized magnetite samples with average grain sizes of 37 and 220 nm during thermal cycling from 300 K to 20 K and back to 300 K. Oxidized magnetites were produced by heating stoichiometric magnetite in air at 100, 150 and 200 C. Samples were given an initial saturation isothermal remanent magnetization (SIRM) in a 2.5 T field and then cooled and rewarmed in zero field. In other experiments, SIRM was given at 10 K and M was continuously monitored during zero-field warming to 300 K. SIRM cooling and warming curves of stoichiometric magnetites are irreversible for the high-temperature cubic phase but completely reversible at all temperatures below 90 K for the low-temperature monoclinic phase. In the oxidized magnetites, the SIRM first increases in cooling from 300 K, then decreases in approaching the Verwey transition. The hump-like form is even more pronounced in the warming curves above Tv. We also measured maghemite, the fully oxidized end member, and found reversible cooling/warming curves with no Verwey transition. In partially oxidized grains, which consist of a maghemite surface layer and a largely unoxidized core, a Verwey transition is resolvable up to high degrees of oxidation. Hallmarks of maghemitization include: (1) a smeared-out Verwey transition shifted to lower temperatures when warming 20-K SIRM; (2) a shifted and broadened transition region in both cooling and warming of 300-K SIRM; and (3) humped cooling and warming curves of 300-K SIRM between 300 K and Tv. Property 1 is often overshadowed by massive remanence unblocking between 10 and 50 K, making the broadened transition hard to resolve. Property 3 has excellent diagnostic value. It results from the combination of a slowly increasing M of maghemite and the rapid and nonlinear decrease in M of magnetite during cooling, and is seen even for the slight initial oxidation of the reduced 37 nm magnetite.

Ozdemir, O.

2009-12-01

421

Corrosion in supercritical water oxidation systems: A phenomenological analysis  

SciTech Connect

Supercritical water oxidation (SCWO) is now being actively developed as a means of destroying highly toxic organic waste (including physiological agents) and for reducing the volume of low level nuclear waste. Pronounced corrosion damage occurs in supercritical water oxidation reactors, and few materials are immune to attack. In this paper, the authors describe a phenomenological model for the corrosion process, and they discuss the effect of electrolyte dissociation and water density, as influenced by temperature and pressure, upon the kinetics of corrosion of metals and alloys in supercritical water. The corrosion process at near-critical temperatures is believed to involve acid attack, with the concentration of H{sup +} being a function of the dissociation constant of HCl, which is a major product of the oxidation of chlorinated organic waste, and of the density of the solution. The authors show that the competing effects of temperature on the heterogeneous rate constant and on the concentrations of H{sup +} and O{sub 2} leads to a pressure (and hence density)-dependent maximum in the corrosion rate in the vicinity of the critical temperature. This result is in general agreement with experimental data on corrosion in aqueous solutions at near-critical temperatures.

Kriksunov, L.B.; Macdonald, D.D. [Pennsylvania State Univ., University Park, PA (United States). Center for Advanced Materials

1995-12-01

422

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

423

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

PubMed

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 [Ru(II)(tpy)(bpm)(OH(2))](2+) (i.e., [Ru(II)-OH(2)](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 pK(a) calculations for the first two proton-coupled electron transfers (PCETs) from [Ru(II)-OH(2)](2+) to [Ru(IV) = O](2+) and the following electron-transfer process to [Ru(V) = O](3+) suggest that these processes can proceed readily in acidic or weakly basic conditions. The subsequent water splitting process involves two water molecules, [Ru(V) = O](3+) to generate [Ru(III)-OOH](2+), and H(3)O(+) 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 [Ru(III)-OOH](2+) to [Ru(IV)-OO](2+) when the pH is lower than 3.7. Two possible forms of [Ru(IV)-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 [Ru(IV)-OO](2+) to [Ru(V)-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

2012-05-21

424

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

2013-10-14

425

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

426

ESA's STSE WACMOS Project: Towards a Water Cycle Multimission Observation Strategy  

NASA Astrophysics Data System (ADS)

Understanding the role of the global water cycle in the Earth system it is essential to be able to measure from space hydro-climatic variables, such as radiation, precipitation, evapotranspiration, soil moisture, clouds, water vapour, surface water and runoff, vegetation state, albedo and surface temperature, etc. Such measurements are required to further increase not only our understanding of the different components of the water cycle and its variability, both spatially and temporally, but also to characterise the processes and interactions between the terrestrial and atmospheric branches of the water cycle, and how this coupling may influence climate variability and predictability. Moreover, enhancing the observational capacity and the model capabilities to predict in a reliable manner the variations in the global water cycle will be a key contribution to the improvement of water governance, the mitigation of water-related damages and the sustainable human development. In the last few years, EO has demonstrated the capacity to provide reliable measurements over oceans, land and atmosphere representing an unique tool for scientist to observe and monitor the earth system. Now, the earth observation panorama is getting into a new era where the increasing number of missions and sensors available for scientific and operational applications, besides the advances in computer science, modelling and data assimilation, open unprecedented opportunities to enhance human capacities to observe, understand and predict the water cycle and its variability in time. However, in order to fully exploit this increasing potential and bring this newly available capacity to practical operational levels, significant scientific efforts are required in order to: • Develop novel and enhanced geo-physical products exploiting available synergies among different observational system; • Consolidate the development of consistent long-term data sets integrating different EO systems in a synergic manner; • Develop robust methodologies to integrate and assimilate space observations and in situ measurements into advance coupled models being able to describe biophysical processes and interactions between ocean, land and atmosphere describing the water cycle and hydrological processes; In this context, the European Space Agency (ESA) in collaboration with the Global Energy and Water Experiment (GEWEX) of the World Climate Research Program (WCRP) launched the project Water Cycle Multi-mission Observation Strategy (WACMOS) early in 2009. The project, funded under the ESA's Support To Science Element, address the first of the above objectives. In particular, the project objective is twofold: • On the one hand, developing and validating a Product Portfolio of novel geo-information products responding to the GEWEX scientific priorities and exploiting the synergic capabilities between ESA EO data and other non-ESA missions. • Exploring and assessing different methodologies to exploit in a synergic manner different observations towards the development of long-term consistent datasets of key (essential) variables describing the water cycle. In this context, WACMOS is focused on four components of the above cycle that are also thematic priorities identified in close collaboration with the GEWEX scientific community: Evapotranspiration, soil moisture, clouds and water vapour. The product portfolio comprises: 1) AATSR-MERIS based evapotranspiration modelling approach; 2) Merged passive and active microwave first multi-decade soil moisture data set; 3) Novel MSG SEVIRI-SCIAMACHY cloud products and 4) Synergic SEVIRI-IASI and SEVIRI-MERIS water vapour products. In this paper, the methodologies and preliminary results of WACMOS are introduced. In the next phase of the project, consolidated methods, data products and validation results will be generated, so that a global water cycle product of evapotranpiration, soil moisture, clouds and water vapour with quantified uncertainties can be produced for climate research and water resources management uses.

Fernández Prieto, Diego; Su, Bob

2010-05-01

427

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)

1996-02-01

428

The water-water cycle in leaves is not a major alternative electron sink for dissipation of excess excitation energy when CO(2) assimilation is restricted.  

PubMed

Electron flux from water via photosystem II (PSII) and PSI to oxygen (water-water cycle) may provide a mechanism for dissipation of excess excitation energy in leaves when CO(2) assimilation is restricted. Mass spectrometry was used to measure O(2) uptake and evolution together with CO(2) uptake in leaves of French bean and maize at CO(2) concentrations saturating for photosynthesis and the CO(2) compensation point. In French bean at high CO(2) and low O(2) concentrations no significant water-water cycle activity was observed. At the CO(2) compensation point and 3% O(2) a low rate of water-water cycle activity was observed, which accounted for 30% of the linear electron flux from water. In maize leaves negligible water-water cycle activity was detected at the compensation point. During induction of photosynthesis in maize linear electron flux was considerably greater than CO(2) assimilation, but no significant water-water cycle activity was detected. Miscanthus × giganteus grown at chilling temperature also exhibited rates of linear electron transport considerably in excess of CO(2) assimilation; however, no significant water-water cycle activity was detected. Clearly the water-water cycle can operate in leaves under some conditions, but it does not act as a major sink for excess excitation energy when CO(2) assimilation is restricted. PMID:21332508

Driever, Steven M; Baker, Neil R

2011-03-15

429

Performance calculations and research direction for a water enhanced regenerative gas turbine cycle  

SciTech Connect

A cycle has been conceived that combines compressor cooling, humidification, and regenerative air heating with the added enhancement of direct injection of water into the air flow. In this cycle it is proposed that a fine mist of water be injected into the compressor air stream and a spray or film of water into the regenerator air stream. Water injection into the compressor air flow realizes several benefits: it cools the air flow, reducing the power required for compression and increasing the potential for exhaust heat recovery; it adds mass to the air stream, increasing the power produced by expansion; and it reduces the amount of cooling bleed air required by increasing the specific heat and decreasing the temperature of the cooling air stream. The greatest benefit would be derived from spraying a fine mist of water directly into the existing air flow into or before the compressor so that cooling and compression would occur simultaneously. This may be accomplished by entraining the water droplets in the inlet air flow or by introducing the water in stages during compression. An alternative and less technically challenging approach is to extract the air stream to a saturation chamber and then reintroduce the air stream into the compressor. This approach is not as desirable because it would increase the equipment cost and add a significant pressure drop penalty. The second use of water in this cycle is in water-assisted regeneration.

Rogers, L.H. [USDOE Morgantown Energy Technology Center, WV (United States); Archer, D.H. [Carnegie-Mellon Univ., Pittsburgh, PA (United States)

1993-09-01

430

Human alterations of the terrestrial water cycle through land management  

NASA Astrophysics Data System (ADS)

This study quantifies current and potential future changes in transpiration, evaporation, interception loss and river discharge in response to land use change, irrigation and climate change, by performing several distinct simulations within the consistent hydrology and biosphere modeling framework LPJmL (Lund-Potsdam-Jena managed Land). We distinguished two irrigation simulations: a water limited one in which irrigation was restricted by local renewable water resources (ILIM), and a potential one in which no such limitation was assumed but withdrawals from deep groundwater or remote rivers allowed (IPOT). We found that the effect of historical land use change as compared to potential natural vegetation was pronounced, including a reduction in interception loss and transpiration by 25.9% and 10.6%, respectively, whereas river discharge increased by 6.6% (climate conditions of 1991 2000). Furthermore, we estimated that about 1170 km3yr-1 of irrigation water could be withdrawn from local renewable water resources (in ILIM), which resulted in a reduction of river discharge by 1.5%. However, up to 1660 km3yr-1 of water withdrawals were required in addition under the assumption that optimal growth of irrigated crops was sustained (IPOT), which resulted in a slight net increase in global river discharge by 2.0% due to return flows. Under the HadCM3 A2 climate and emission scenario, climate change alone will decrease total evapotranspiration by 1.5% and river discharge by 0.9% in 2046 2055 compared to 1991 2000 average due to changes in precipitation patterns, a decrease in global precipitation amount, and the net effect of CO2 fertilization. A doubling of agricultural land in 2046 2055 compared to 1991 2000 average as proposed by the IMAGE land use change scenario will result in a decrease in total evapotranspiration by 2.5% and in an increase in river discharge by 3.9%. That is, the effects of land use change in the future will be comparable in magnitude to the effects of climate change in this particular scenario. On present irrigated areas future water withdrawal will increase especially in regions where climate changes towards warmer and dryer conditions will be pronounced.

Rost, S.; Gerten, D.; Heyder, U.

2008-06-01

431

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

432

A metallic fuel cycle concept from spent oxide fuel to metallic fuel  

SciTech Connect

A Metallic fuel cycle concept for Self-Consistent Nuclear Energy System (SCNES) has been proposed in a companion papers. The ultimate goal of the SCNES is to realize sustainable energy supply without endangering the environment and humans. For future transition period from LWR era to SCNES era, a new metallic fuel recycle concept from LWR spent fuel has been proposed in this paper. Combining the technology for electro-reduction of oxide fuels and zirconium recovery by electrorefining in molten salts in the nuclear recycling schemes, the amount of radioactive waste reduced in a proposed metallic fuel cycle concept. If the recovery ratio of zirconium metal from the spent zirconium waste is 95%, the cost estimation in zirconium recycle to the metallic fuel materials has been estimated to be less than 1/25. (authors)

Fujita, Reiko; Kawashima, Masatoshi; Yamaoka, Mitsuaki [Power and Industrial Systems Research and Development Center, Toshiba Corporation, 4-1, Ukishima-cho, Kawasaki-ku, Kawasaki, 210-0862 (Japan); Arie, Kazuo [Nuclear Energy Systems and Services Dev., Toshiba Corporation, 4-1, Ukishima-cho, Kawasaki-ku, Kawasaki, 210-0862 (Japan); Koyama, Tadafumi [Central research Institute of Electric Power Industry (Japan)

2007-07-01

433

Biochemical predetermination of the NO synthase and nitrite reductase components of the nitric oxide cycle.  

PubMed

This review presents some aspects of a concept of cellular evolution bearing a relationship to nitrate--nitrite respiration, the endosymbiosis theory, and the origin of NO synthase and nitrite reductase activity in heme-containing proteins. Analysis of structural and functional unity of the NO synthase and nitrite reductase systems suggests that these systems did not arise without any relation to evolutionarily ancient energetic systems of cells. The use of symmetry principles reveals commonalities among many electron transport chains which in the language of physics is called "invariance". This work also comparatively analyzes the nitric oxide cycle and the known nitrogen cycle. The ideas about evolution of the NO synthase and nitrite reductase systems developed here are clearly compatible with the endosymbiotic theory and the hypothesis that nitrate--nitrite respiration was a precursor of oxygen-dependent respiration. PMID:10381613

Reutov, V P

1999-05-01

434

Role of mechanical loads in inducing in-cycle tensile stress in thermally grown oxide  

SciTech Connect

Experimental in situ synchrotron x-ray diffraction results tracking the strain behavior of the various layers during a cycle, under thermo-mechanical conditions are presented in this work. The quantitative strain measurements here show that the thermally grown oxide briefly experiences in-plane tensile stress ({sigma}{sub 22} = +36.4 MPa) with increased mechanical loading during ramp-up in the thermal cycle. These findings are the first in situ experimental observations of these strains under thermo-mechanical conditions, envisaged to serve as a catalyst for crack initiation. The depth resolved measurements of strain taken during applied thermal and mechanical load in this work are a significant step towards achieving realistic testing conditions.

Diaz, R.; Jansz, M.; Mossaddad, M.; Raghavan, S.; Okasinski, J.S.; Almer, J.D.; Perez, H.P.; Imbrie, P. (X-Ray Science Division); (University of Central Florida); (Purdue University)

2012-01-01

435

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...

436

Ceria–zirconia mixed oxide prepared by continuous hydrothermal synthesis in supercritical water as catalyst support  

Microsoft Academic Search

A number of different synthetic methods have been applied to prepare ceria–zirconia and related mixed oxides. Continuous hydrothermal synthesis in supercritical water (supercritical synthesis) is a method to prepare metal oxide nanoparticles rapidly and continuously using supercritical water as anti-solvent. Highly crystallized nanoparticles of homogeneous complex metal oxides as well as single metal oxides could be produced easily by the

Jeong-Rang Kim; Ki-Yong Lee; Myung-Ji Suh; Son-Ki Ihm

437

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

438

Static Analysis of Double Effect Adsorption Refrigeration Cycle Using Silica gel/Water Pair  

NASA Astrophysics Data System (ADS)

In this paper,a static analysis of double effect adsorption refrigeration cycle utilizing condensation heat is discussed. Double effect adsorption refrigeration cycle consists of two cycles, High Temperature Cycle (HTC) which is driven from external heat sources, and Low Temperature Cycle (LTC) which is driven by condensation heat from HTC. Both of HTC and LTC are using silica gel and water as working pairs. The effect of heat source temperature on cycle performance was investigated in terms of coefficient of performance (COP) and specific cooling energy (SCE). Results showed that double effect cycle would produce higher COP than single effect cycle for driving temperature observed between 80-150°C with the same operating condition. However, the value of SCE is lower than single effect, despite that the SCE of double effect cycle is improved with heat source temperature higher than 100°C. Further, it was also observed that adsorbent mass ratio of HTC and LTC affected performance of chiller. When adsorbent mass ratio of HTC and LTC was unity, it was found that SCE and COP took the maximum.

Marlinda; Miyazaki, Takahiko; Ueda, Yuki; Akisawa, Atsushi

439

Advanced oxidation process based on the Cr(III)/Cr(VI) redox cycle.  

PubMed

Oxidative degradation of aqueous organic pollutants, using 4-chlorophenol (4-CP) as a main model substrate, was achieved with the concurrent H(2)O(2)-mediated transformation of Cr(III) to Cr(VI). The Fenton-like oxidation of 4-CP is initiated by the reaction between the aquo-complex of Cr(III) and H(2)O(2), which generates HO(•) along with the stepwise oxidation of Cr(III) to Cr(VI). The Cr(III)/H(2)O(2) system is inactive in acidic condition, but exhibits maximum oxidative capacity at neutral and near-alkaline pH. Since we previously reported that Cr(VI) can also activate H(2)O(2) to efficiently generate HO(•), the dual role of H(2)O(2) as an oxidant of Cr(III) and a reductant of Cr(VI) can be utilized to establish a redox cycle of Cr(III)-Cr(VI)-Cr(III). As a result, HO(•) can be generated using both Cr(III)/H(2)O(2) and Cr(VI)/H(2)O(2) reactions, either concurrently or sequentially. The formation of HO(•) was confirmed by monitoring the production of p-hydroxybenzoic acid from [benzoic acid + HO(•)] as a probe reaction and by quenching the degradation of 4-CP in the presence of methanol as a HO(•) scavenger. The oxidation rate of 4-CP in the Cr(III)/H(2)O(2) solution was highly influenced by pH, which is ascribed to the hydrolysis of Cr(III)(H(2)O)(n) into Cr(III)(H(2)O)(n-m)(OH)(m) and the subsequent condensation to oligomers. The present study proposes that the Cr(III)/H(2)O(2) combined with Cr(VI)/H(2)O(2) process is a viable advanced oxidation process that operates over a wide pH range using the reusable redox cycle of Cr(III) and Cr(VI). PMID:21988604

Bokare, Alok D; Choi, Wonyong

2011-10-11

440

Life cycle energy use and greenhouse gas emission analysis for a water resource recovery facility in India.  

PubMed

This paper quantifies life cycle energy use and greenhouse gas (GHG) emissions associated with water resource recovery facilities (WRRFs) in India versus water quality improvements achieved from infrastructure investments. A first such analysis is conducted using operating data for a WRRF, which employs upflow anaerobic sludge blanket (UASB) reactors and oxidation. On-site operations energy use, process GHG emissions, and embodied energy in infrastructure were quantified. The analysis showed energy use and GHG emissions of 0.2 watt-hours (Wh) and 0.3 gram carbon dioxide (CO2) equivalents per liter (gCO2e/L) wastewater treated, and 1.3 Wh and 2.1 gCO2e/gBOD removed, achieving 81% biochemical oxygen demand (BOD) and 999% fecal coliform removal annually. Process emissions of WRRFs contributed 44% of life cycle GHG emissions, similar in magnitude to those from electricity (46%), whereas infrastructure contributed 10%. Average WRRF-associated GHG emissions (0.9gCO2e/L) were lower than those expected if untreated wastewater was released to the river. Investments made by WRRFs in developing world cities improve water quality and may mitigate overall GHG emissions. PMID:23944144

Miller-Robbie, Leslie; Ramaswami, Anu; Kumar, Prasanna

2013-07-01

441

The effect of caffeine ingestion on neutrophil oxidative burst responses following prolonged cycling.  

PubMed

This study investigated the effect of caffeine ingestion on neutrophil oxidative burst responses to prolonged cycling. In a two part study, 19 endurance trained male cyclists (Part A--11; Part B--8) performed 90 min of exercise at 70% VO2max 1 h after ingesting 6 mg/kg body mass of caffeine (CAF) or placebo (PLA). CAF ingestion had no effect on the PMA-stimulated oxidative burst response (Part A), yet it attenuated the exercise-induced decline in f-MLP stimulated response that occurred with PLA (Part B). CAF ingestion significantly increased serum caffeine concentration and plasma adrenaline concentration following exercise. In addition, circulating lymphocyte count was increased following CAF ingestion whereas there was no effect on neutrophil number. Therefore, although CAF ingestion was associated with an increase in adrenaline, this was not associated with an expected decrease in neutrophil function. This suggests that in the present study, CAF ingestion influenced neutrophil function via alternative mechanisms. PMID:16676701

Walker, Gary J; Caudwell, Phillipa; Dixon, Natalie; Bishop, Nicolette C

2006-02-01

442