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1

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

PubMed Central

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

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

2012-01-01

2

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

3

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

4

Water, Water Everywhere! Research the Water Cycle  

NSDL National Science Digital Library

Water, Water Everywhere! Research the Water Cycle asks students to conduct their own research on the water cycle (hydrologic cycle). Working collaboratively in small groups, students will research and write about the relationships between stages in the water cycle and the three states of matter relating to water. After completing this lesson, students will be prepared to create a model of the water cycle.

Bale, Regina

2012-07-17

5

The Water Cycle: Water Storage  

NSDL National Science Digital Library

This interactive, animated graphic helps explain the water cycle to younger students. The animation, with sound, explains the various parts of the water cycle and show how water moves from one part to another.

6

Water Cycle Webquest  

NSDL National Science Digital Library

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

7

The Water Cycle  

NSDL National Science Digital Library

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

8

The Water Cycle  

NSDL National Science Digital Library

This demonstration introduces the concept of water phases and cycling to younger students through observation, drawing, and writing. They will be able to explain how the Earth's water supply is recycled, form a hypothesis as to how/why the water cycle works, and use writing and drawing to explain how the cycle works.

1998-01-01

9

Discover the Water Cycle!  

NSDL National Science Digital Library

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

10

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

11

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

12

The Water Cycle  

NSDL National Science Digital Library

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

13

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

14

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

15

Exploring the Water Cycle  

NSDL National Science Digital Library

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

16

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. This brief clip, (6:05-6:20 beginning with diagram of water cycle and ending with narration Âover and over againÂ), reinforces the idea that water continually moves between Earth's atmosphere and its land and water.

17

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

18

The Water Cycle  

NSDL National Science Digital Library

This Classroom Connectors lesson plan discusses the continuous movement of water from Earth to air and back to Earth. Students list areas of the Earth where water circulates, explain evaporation and condensation, list the steps of the water cycle and explain what happens in each step. The site provides goals, objectives, an outline, time required, materials, activities, and closure ideas for the lesson. The Classroom Connectors address content with an activity approach while incorporating themes necessary to raise the activity to a higher cognition level. The major motivation is to employ instructional strategies that bring the students physically and mentally into touch with the science they are studying.

19

Thermochemical hydrogen production from a two-step solar-driven water-splitting cycle based on cerium oxides  

Microsoft Academic Search

A new thermochemical cycle for H2 production based on CeO2\\/Ce2O3 oxides has been successfully demonstrated. It consists of two chemical steps: (1) reduction, 2CeO2?Ce2O3+0.5O2; (2) hydrolysis, Ce2O3+H2O?2CeO2+H2. The thermal reduction of Ce(IV) to Ce(III) (endothermic step) is performed in a solar reactor featuring a controlled inert atmosphere. The feasibility of this first step has been demonstrated and the operating conditions

Stéphane Abanades; Gilles Flamant

2006-01-01

20

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

21

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

22

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

23

Biological water oxidation.  

PubMed

Photosystem II (PSII), a multisubunit pigment-protein supercomplex found in cyanobacteria, algae, and plants, catalyzes a unique reaction in nature: the light-driven oxidation of water. Remarkable recent advances in the structural analysis of PSII now give a detailed picture of the static supercomplex on the molecular level. These data provide a solid foundation for future functional studies, in particular the mechanism of water oxidation and oxygen release. The catalytic core of the PSII is a tetramanganese-calcium cluster (Mn?O?Ca), commonly referred to as the oxygen-evolving complex (OEC). The function of the OEC rests on its ability to cycle through five metastable states (Si, i = 0-4), transiently storing four oxidizing equivalents, and in so doing, facilitates the four electron water splitting reaction. While the latest crystallographic model of PSII gives an atomic picture of the OEC, the exact connectivity within the inorganic core and the S-state(s) that the X-ray model represents remain uncertain. In this Account, we describe our joint experimental and theoretical efforts to eliminate these ambiguities by combining the X-ray data with spectroscopic constraints and introducing computational modeling. We are developing quantum chemical methods to predict electron paramagnetic resonance (EPR) parameters for transition metal clusters, especially focusing on spin-projection approaches combined with density functional theory (DFT) calculations. We aim to resolve the geometric and electronic structures of all S-states, correlating their structural features with spectroscopic observations to elucidate reactivity. The sequence of manganese oxidations and concomitant charge compensation events via proton transfer allow us to rationalize the multielectron S-state cycle. EPR spectroscopy combined with theoretical calculations provides a unique window into the tetramangenese complex, in particular its protonation states and metal ligand sphere evolution, far beyond the scope of static techniques such as X-ray crystallography. This approach has led, for example, to a detailed understanding of the EPR signals in the S?-state of the OEC in terms of two interconvertible, isoenergetic structures. These two structures differ in their valence distribution and spin multiplicity, which has important consequences for substrate binding and may explain its low barrier exchange with solvent water. New experimental techniques and innovative sample preparations are beginning to unravel the complex sequence of substrate uptake/inclusion, which is coupled to proton release. The introduction of specific site perturbations, such as replacing Ca²? with Sr²?, provides discrete information about the ligand environment of the individual Mn ions. In this way, we have identified a potential open coordination site for one Mn center, which may serve as a substrate binding site in the higher S-states, such as S? and S?. In addition, we can now monitor the binding of the substrate water in the lower S-states (S? and S?) using new EPR-detected NMR spectroscopies. These studies provided the first evidence that one of the substrates is subsumed into the complex itself and forms an oxo-bridge between two Mn ions. This result places important new restrictions on the mechanism of O-O bond formation. These new insights from nature's water splitting catalyst provide important criteria for the rational design of bioinspired synthetic catalysts. PMID:23506074

Cox, Nicholas; Pantazis, Dimitrios A; Neese, Frank; Lubitz, Wolfgang

2013-07-16

24

Oxidation and low cycle fatigue life prediction  

NASA Technical Reports Server (NTRS)

When a metallic material is exposed to a high temperature in an ambient atmosphere, oxidation takes place on the metallic surface. The formed oxides (both surface and grain boundary oxides) are mechanically brittle so that if the stress is high enough the oxides will be cracked. The grain boundary oxide formation in TAZ-8A nickel-base superalloy was studied. The effect of oxide crack nucleus on low cycle fatigue life will be analyzed. The TAZ-8A was subjected to high temperature oxidation tests in air under the stress-free condition. The oxidation temperatures were 600, 800, and 1000 C. The oxidation time varies from 10 to 1000 hours.

Oshida, Y.; Liu, H. W.

1984-01-01

25

The Water Cycle: Infiltration  

NSDL National Science Digital Library

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

26

Natural and Urban "Stormwater" Water Cycle Models  

NSDL National Science Digital Library

Students apply their understanding of the natural water cycle and the urban "stormwater" water cycle, as well as the processes involved in both cycles to hypothesize how the flow of water is affected by altering precipitation. Student groups consider different precipitation scenarios based on both intensity and duration. Once hypotheses and specific experimental steps are developed, students use both a natural water cycle model and an urban water cycle model to test their hypotheses. To conclude, students explain their results, tapping their knowledge of both cycles and the importance of using models to predict water flow in civil and environmental engineering designs. The natural water cycle model is made in advance by the teacher, using simple supplies; a minor adjustment to the model easily turns it into the urban water cycle model.

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

27

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...

28

Ch.9 Water Resources ! Hydrologic cycle  

E-print Network

(PET) ! Potential evapotranspiration (PET) is the amount of water that would evaporate and transpire #12;Potential Evapotranspiration (PET) ! Potential evapotranspiration (PET) is the amount of waterCh.9 Water Resources #12;! Hydrologic cycle ! Water-budget concept and water balance equation

Pan, Feifei

29

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.

30

Water Cycle Missions for the Next Decade  

NASA Astrophysics Data System (ADS)

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

Houser, P. R.

2013-12-01

31

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

32

Natural and Urban "Stormwater" Water Cycles  

NSDL National Science Digital Library

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

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

33

The Water Cycle - Back and Forth  

NSDL National Science Digital Library

This is the first of three lessons on the water cycle. Students create a model (drawing) after learning the parts of the water cycle. The drawing will be in their science notebooks and will be something they will build on in future lessons. At the end of the unit they will display larger finished models. Vocabulary words are defined and connected to a model of melting ice in a water bottle.

Magdaleno, Maribel

2012-07-17

34

Hydrogen production from a combination of the water-gas shift and redox cycle process of methane partial oxidation via lattice oxygen over LaFeO3 perovskite catalyst.  

PubMed

A redox cycle process, in which CH4 and air are periodically brought into contact with a solid oxide packed in a fixed-bed reactor, combined with the water-gas shift (WGS) reaction, is proposed for hydrogen production. The sole oxidant for partial oxidation of methane (POM) is found to be lattice oxygen instead of gaseous oxygen. A perovskite-type LaFeO3 oxide was prepared by a sol-gel method and employed as an oxygen storage material in this process. The results indicate that, under appropriate reaction conditions, methane can be oxidized to CO and H2 by the lattice oxygen of LaFeO3 perovskite oxide with a selectivity higher than 95% and the consumed lattice oxygen can be replenished in a reoxidation procedure by a redox operation. It is suggested that the POM to H2/CO by using the lattice oxygen of the oxygen storage materials instead of gaseous oxygen should be possibly applicable. The LaFeO3 perovskite oxide maintained relatively high catalytic activity and structural stability, while the carbonaceous deposits, which come from the dissociation of CH4 in the pulse reaction, occurred due to the low migration rate of lattice oxygen from the bulk toward the surface. A new dissociation-oxidation mechanism for this POM without gaseous oxygen is proposed based on the transient responses of the products checked at different surface states via both pulse reaction and switch reaction over the LaFeO3 catalyst. In the absence of gaseous-phase oxygen, the rate-determining step of methane conversion is the migration rate of lattice oxygen, but the process can be carried out in optimized cycles. The product distribution for POM over LaFeO3 catalyst in the absence of gaseous oxygen was determined by the concentration of surface oxygen, which is relevant with the migration rate of lattice oxygen from the bulk toward the surface. This process of hydrogen production via selective oxidation of methane by lattice oxygen is better in avoiding the deep oxidation (to CO2) and enhancing the selectivity. Therefore, this new route is superior to general POM in stability (resistance to carbonaceous deposition), safety (effectively avoiding accidental explosion), ease of operation and optimization, and low cost (making use of air not oxygen). PMID:17181232

Dai, Xiao Ping; Wu, Qiong; Li, Ran Jia; Yu, Chang Chun; Hao, Zheng Ping

2006-12-28

35

Observing the Global Water Cycle from Space  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

36

Efficiency analysis for a manganese-oxide-based thermochemical cycle  

Microsoft Academic Search

A thermochemical cycle for the solar production of hydrogen is proposed. The cycle includes: (1) the conversion of solar to chemical energy by the thermal reduction of manganese(III) oxide to manganese(II) oxide at temperatures below 1900K, (2) the production of hydrogen by reacting manganese(II) oxide with sodium hydroxide, and (3) the separation of manganese oxide from sodium hydroxide by a

M Sturzenegger; P Nüesch

1999-01-01

37

Designing Green Oxidation Catalysts for Purifying Environmental Waters  

E-print Network

Designing Green Oxidation Catalysts for Purifying Environmental Waters W. Chadwick Ellis, Camly T,o-NC6H4NCO)2CMe2}(OH2)- ] (2d), which have been designed to be especially suitable for purifying water peroxidase-like cycles to rapidly and efficiently5 purify water of many chemicals, including EDs,6-8 as well

Blumberg, Bruce

38

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

39

WaterNet: The NASA Water Cycle Solutions Network  

NASA Astrophysics Data System (ADS)

Water is essential to life and directly impacts and constrains society's welfare, progress, and sustainable growth, and is continuously being transformed by climate change, erosion, pollution, and engineering practices. The water cycle is a critical resource for industry, agriculture, natural ecosystems, fisheries, aquaculture, hydroelectric power, recreation, and water supply, and is central to drought, flood, transportation-aviation, and disease hazards. It is therefore a national priority to use advancements in scientific observations and knowledge to develop solutions to the water challenges faced by society. NASA's unique role is to use its view from space to improve water and energy cycle monitoring and prediction. NASA has collected substantial water cycle information and knowledge that must be transitioned to develop solutions for all twelve National Priority Application (NPA) areas. NASA cannot achieve this goal alone -it must establish collaborations and interoperability with existing networks and nodes of research organizations, operational agencies, science communities, and private industry. Therefore, WaterNet: The NASA Water Cycle Solutions Network 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. WaterNet is a catalyst for discovery and sharing of creative solutions to water problems. It serves as a creative, discovery process that is the entry-path for a research-to-solutions systems engineering NASA framework, with the end result to ultimately improve decision support.

Houser, P. R.; Belvedere, D. R.; Pozzi, W. H.; Imam, B.; Schiffer, R.; Lawford, R.; Schlosser, C. A.; Gupta, H.; Welty, C.; Vorosmarty, C.; Matthews, D.

2007-12-01

40

SUPERCRITICAL WATER PARTIAL OXIDATION  

E-print Network

;OBJECTIVESOBJECTIVES · Develop a gasification technology that can convert biomass wastes of all types into hydrogen for gasification of biomass. · Show that high hydrogen yields and gasification efficiencies can be reliably aid in separation/storage of hydrogen · Develop Supercritical Water Gasification System in a four

41

Based on the Water Cycle of Water Resource Assessment  

Microsoft Academic Search

This paper takes annual water cycle in 1980~2004 of Tianjin city in China as an example to describe a method of integrated assessment on water resource, which is divided into four categories: genera,special, national economy available and quality qualified in functional zone. Distributed hydrology model is used to couple artificial water balance, and precipitation is taken as full aperture flux

Huaibin Wei; Zuhao Zhou

2011-01-01

42

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

DOE Data Explorer

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

Jenna N. Schroeder

43

Under the Lawn: Engaging the Water Cycle  

Microsoft Academic Search

This paper explores how several water technologies mediate people's relationship with nature in the domestic sphere. While septic systems are critical to the built environment in exurban North America, they remain largely unacknowledged. Their hidden participation in the backyards of private homes silently facilitates—yet outwardly denies—people's continued engagement in the water cycle. Now, a growing array of alternative practices (e.g.

Sharon Moran

2008-01-01

44

WaterNet: The NASA Water Cycle Solutions Network  

NASA Astrophysics Data System (ADS)

The water cycle is continuously being transformed by climate change, erosion, pollution, salinization, and engineering practices, and is central to drought, flood, and disease hazards. Therefore, it is a national priority is to use advancements in scientific observations and knowledge to develop solutions to society's water challenges. NASA's unique role in this national priority is to exploit its unique view from space to improve water and energy cycle monitoring and prediction. As such, NASA's Earth science programs have collected substantial water cycle information and knowledge that must be integrated and shared to develop solutions in all twelve national priority application areas. However, NASA alone cannot achieve the ultimate goal of improved operational environmental assessments, predictions and applications and therefore must establish collaborations and interoperability with existing networks and nodes of research organizations, operational agencies, the scientific community, and private industry. Therefore, we propose to develop WaterNet: The NASA Water Cycle Solutions Network whose 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. We will develop WaterNet by engaging relevant NASA water and energy cycle resources and community-of-practice organizations to develop what we term an "actionable database" that can be used to communicate and connect NASA Water and energy cycle focus area research Results (NWRs) towards the improvement of water-related Decision Support Tools (DSTs). Recognizing the many existing highly valuable water-related science and application networks, we will focus a balance of our efforts to enable their interoperability in a solutions network context. We will initially focus on identifying, collecting information about, and analyzing the two end points, these being the NWRs and water related DSTs. We will then develop strategies to connect these two end points via innovative communication strategies, improved user access to NASA resources, improved water cycle research community appreciation for DST requirements, improved policymaker, management and stakeholder knowledge of NASA research and application products, and identifying pathways for progress. Finally, we will develop relevant benchmarking and metrics, to understand the network's characteristics, to optimize its performance, and to establish sustainability.

Belvedere, D. R.; Houser, P. R.; Imam, B.; Schiffer, R.; Schlosser, C. A.; Gupta, H. V.; Welty, C.; Vorosmarty, C.; Matthews, D.; Lawford, R.

2006-05-01

45

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

46

Uranium oxidation: characterization of oxides formed by reaction with water  

SciTech Connect

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 at the oxide/metal interface. Single laminae are released if liquid water is present due to the prizing penetration at the reaction zone. The rate of reaction of water with uranium is directly proportional to the amount of adsorbed water on the oxide product. Rapid transport is effected through the open hydrous oxide product. Dehydration of the hydrous oxide irreversibly forms a more inert oxide which cannot be rehydrated to the degree that prevails in the original hydrous product of uranium oxidation with water. 27 figures.

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

1983-04-27

47

The artificial water cycle: emergy analysis of waste water treatment.  

PubMed

The artificial water cycle can be divided into the phases of water capture from the environment, potabilisation, distribution, waste water collection, waste water treatment and discharge back into the environment. The terminal phase of this cycle, from waste water collection to discharge into the environment, was assessed by emergy analysis. Emergy is the quantity of solar energy needed directly or indirectly to provide a product or energy flow in a given process. The emergy flow attributed to a process is therefore an index of the past and present environmental cost to support it. Six municipalities on the western side of the province of Bologna were analysed. Waste water collection is managed by the municipal councils and treatment is carried out in plants managed by a service company. Waste water collection was analysed by compiling a mass balance of the sewer system serving the six municipalities, including construction materials and sand for laying the pipelines. Emergy analysis of the water treatment plants was also carried out. The results show that the great quantity of emergy required to treat a gram of water is largely due to input of non renewable fossil fuels. As found in our previous analysis of the first part of the cycle, treatment is likewise characterised by high expenditure of non renewable resources, indicating a correlation with energy flows. PMID:12817633

Bastianoni, Simone; Fugaro, Laura; Principi, Ilaria; Rosini, Marco

2003-04-01

48

THE WATER CYCLE REVISITED:THE WATER CYCLE REVISITED: LINKAGES WITH ELEMENTLINKAGES WITH ELEMENT  

E-print Network

understanding of the effect of human influences on natural systems and to provide information will variability and changes in the cycling of water though terrestrial and freshwater ecosystems be linked

Slatton, Clint

49

The DOE Water Cycle Pilot Study  

SciTech Connect

A Department of Energy (DOE) multi-laboratory Water Cycle Pilot Study (WCPS) investigated components of the local water budget at the Walnut River Watershed in Kansas to study the relative importance of various processes and to determine the feasibility of observational water budget closure. An extensive database of local meteorological time series and land surface characteristics was compiled. Numerical simulations of water budget components were generated and, to the extent possible, validated for three nested domains within the Southern Great Plains; the DOE Atmospheric Radiation Measurement/Cloud Atmospheric Radiation Testbed (ARM/CART), the Walnut River Watershed (WRW), and the Whitewater Watershed (WW), Kansas A 2-month Intensive Observation Period (IOP) was conducted to gather detailed observations relevant to specific details of the water budget, including fine-scale precipitation, streamflow, and soil moisture measurements not made routinely by other programs. Event and season al water isotope (delta 18O, delta D) sampling in rainwater, streams, soils, lakes, and wells provided a means of tracing sources and sinks within and external to the WW, WRW, and the ARM/CART domains. The WCPS measured changes in leaf area index for several vegetation types, deep groundwater variations at two wells, and meteorological variables at a number of sites in the WRW. Additional activities of the WCPS include code development toward a regional climate model with water isotope processes, soil moisture transect measurements, and water level measurements in ground water wells.

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

2003-09-20

50

Carbon footprint estimation of municipal water cycle  

NASA Astrophysics Data System (ADS)

This research investigates the embodied energy associated with water use. A geographic information system (GIS) was tested using data from Loudoun County, Virginia. The objective of this study is to estimate the embodied energy and carbon emission levels associated with water service at a geographical location and to improve for sustainability planning. Factors that affect the carbon footprint were investigated and the use of a GIS based model as a sustainability planning framework was evaluated. The carbon footprint metric is a useful tool for prediction and measurement of a system's sustainable performance over its expected life cycle. Two metrics were calculated: tons of carbon dioxide per year to represent the contribution to global warming and watt-hrs per gallon to show the embodied energy associated with water consumption. The water delivery to the building, removal of wastewater from the building and associated treatment of water and wastewater create a sizable carbon footprint; often the energy attributed to this water service is the greatest end use of electrical energy. The embodied energy in water depends on topographical characteristics of the area's local water supply, the efficiency of the treatment systems, and the efficiency of the pumping stations. The questions answered by this research are: What is the impact of demand side sustainable water practices on the embodied energy as represented by a comprehensive carbon footprint? What are the major energy consuming elements attributed to the system? What is a viable and visually identifiable tool to estimate the carbon footprint attributed to those Greenhouse Gas (GHG) producing elements? What is the embodied energy and emission associated with water use delivered to a building? Benefits to be derived from a standardized GIS applied carbon footprint estimation approach include: (1) Improved environmental and economic information for the developers, water and wastewater processing and municipal planners; (2) Improved energy use reporting and conservation planning; (3) Establishment of a benchmark for GHG emissions attributed to the water and wastewater industry; (4) Ability to quantify relative impacts of building design options using carbon emission equivalents. The GIS based model was applied to the Dulles South and Brambelton regions in Loudoun County, Virginia. The GIS revealed the customer's embodied energy to be in the range of 4.41MWh/Mgal to 8.0 MWh/Mgal. The customer's carbon footprint is between 0.008 and18.0 Tons of CO2 for year 2008. The results of this study contributed to development of a standardized approach to estimate the GHG impact of a total water cycle, and provided a viable GIS tool resulting in visual maps as a decision support. It also showed the use of derived empirical formulas in predication of GHG impact for end users in a specific geographical area. The embodied energy in delivered water can be estimated using the devised model and be considered by the building sustainability ranking programs such as the USGBC LEED rating system. KEYWORDS. Water Life Cycle, Embodied Energy, Global Warming Potential, Energy Intensity, Energy Intensity Matrix, Emission Intensity, Emission Coefficient, Carbon Dioxide Emission, Water and Wastewater, Collection, Treatment and Distribution, Carbon Footprint, Topography, Municipality, Environmental Indicator, ArcGIS, LEED, GHG, ESI, LCA, LCEA, LCI, Sustainability, End Use, Potable Water

Bakhshi, Ali A.

51

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

52

Beyond Weather and the Water Cycle  

NSDL National Science Digital Library

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

2011-06-30

53

The Passive Microwave Water Cycle (PMWC) Product: Closing the Water Cycle Using a Constellation of Satellites  

NASA Astrophysics Data System (ADS)

We have developed a water cycle product as part of the NASA Energy and Water Cycle Study (NEWS). The purpose of the product is to integrate passive microwave retrievals from a variety of different sensors on different satellites including SSMI (F08, F10, F11, F13, F14, and F15), SSMIS (F16 and F17), AMSR (Aqua and Midori-II), TMI on TRMM, WindSat, and eventually AMSU (NOAA-15 and NOAA-16). The water cycle over a particular location averaged over a time scale of one month is given by: E-P=WVTD; where E is evaporation, P is precipitation, and WVTD is water vapor transport divergence. The new and unique feature of our product is that we make use of the large quantity of accurately intercalibrated water vapor and wind observations in order to estimate WVTD. As part of developing this product we have evaluated our new intercalibrated microwave rain rates, developed a procedure for estimating evaporation, and developed a procedure for estimating water vapor transport and its divergence. The Version-01 Passive Microwave Water Cycle (PMWC) dataset will contain maps of evaporation, precipitation, water vapor transport, water vapor transport divergence, and water vapor. Uncertainty estimates for each parameter will also be supplied. Currently, the product is a 20-year (1987-2007), 0.25-degree, monthly average product over the global oceans. One of our principle motivations is to obtain estimates of the uncertainty in "direct" physically-based retrievals of precipitation. Direct physically-based rain retrievals are subject to large uncertainties that are hard to quantify, such as horizontal inhomogeneity (beamfilling), cloud and rain water partitioning, rain column height and the rain vertical profile, drop size distribution, and the effects of frozen hydrometeors. By using the balanced water cycle, we can estimate precipitation uncertainties in P by estimating uncertainties in E and WVTD. Estimating uncertainties in E can be done with a straight-forward classical uncertainty analysis. Uncertainties in WVTD can easily be estimated using on-orbit simulation experiments with model data. In addition to uncertainty estimates, we also note that estimating precipitation through balancing the water cycle provides a new and independent estimate of precipitation. The errors with this technique are independent from the errors in passive microwave, active microwave, and infrared precipitation retrievals. This will be of great value as we enter the Global Precipitation Measurement (GPM) era. Moreover, consistency among hydrological parameters (evaporation, precipitation, water vapor transport divergence) and especially their trends provides indirect validation of the retrievals. Currently, we have evaluated trends in our evaporation, precipitation, and water vapor datasets on a global average basis. We find water vapor trends of 7 Percent/degree as the world warms - consistent with the Clausius-Clapeyron (C-C) relationship and with climate models. We also find that our evaporation and precipitation measurements both increase at close to the C-C rate. This is in contrast with climate models that predict a muted response of precipitation to global warming with rates between 1 to 3 Percent/degree. These water cycle relationships will be discussed in terms of their implications for the global energy balance.

Hilburn, K.; Wentz, F.

2007-12-01

54

Terrestrial nitrous oxide cycles and atmospheric effects  

NASA Technical Reports Server (NTRS)

The basic processes that cause N2O emission from soils are briefly discussed, and the rate of the processes is shown to vary widely in space and time, depending on soil, climate, and agrotechnical conditions. Although significant amounts of N2O are indeed emitted from the land, the complexity of the soil processes involved and the wide variation of measured rates still prevents the quantitative evaluation, global budgeting, and reliable prediction of atmospheric N2O. Increased atmospheric N2O abundance increases the levels of odd-nitrogen in the stratosphere, which, in turn, decreases the stratospheric ozone density via a catalytic cycle. Using appropriate atmospheric models and current chemical kinetic data, it has been found that the dependence of ozone reduction on N2O increase is nearly linear; a simulated doubling of N2O leads to a predicted decrease of about 14 percent in total ozone column density. A 10 percent increase in N2O yields a predicted increase in nonmelanoma skin cancer of several percent, and a possible raising of surface temperature of 0.03 K.

Whitten, R. C.; Lawless, J. G.; Banin, A.

1984-01-01

55

Plumbing the Global Carbon Cycle: Integrating Inland Waters into the  

E-print Network

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

Berkowitz, Alan R.

56

Alternating electron and proton transfer steps in photosynthetic water oxidation  

PubMed Central

Water oxidation by cyanobacteria, algae, and plants is pivotal in oxygenic photosynthesis, the process that powers life on Earth, and is the paradigm for engineering solar fuel–production systems. Each complete reaction cycle of photosynthetic water oxidation requires the removal of four electrons and four protons from the catalytic site, a manganese–calcium complex and its protein environment in photosystem II. In time-resolved photothermal beam deflection experiments, we monitored apparent volume changes of the photosystem II protein associated with charge creation by light-induced electron transfer (contraction) and charge-compensating proton relocation (expansion). Two previously invisible proton removal steps were detected, thereby filling two gaps in the basic reaction-cycle model of photosynthetic water oxidation. In the S2 ? S3 transition of the classical S-state cycle, an intermediate is formed by deprotonation clearly before electron transfer to the oxidant (). The rate-determining elementary step (?, approximately 30 µs at 20?°C) in the long-distance proton relocation toward the protein–water interface is characterized by a high activation energy (Ea = 0.46 ± 0.05 eV) and strong H/D kinetic isotope effect (approximately 6). The characteristics of a proton transfer step during the S0 ? S1 transition are similar (?, approximately 100 µs; Ea = 0.34 ± 0.08 eV; kinetic isotope effect, approximately 3); however, the proton removal from the Mn complex proceeds after electron transfer to . By discovery of the transient formation of two further intermediate states in the reaction cycle of photosynthetic water oxidation, a temporal sequence of strictly alternating removal of electrons and protons from the catalytic site is established. PMID:22988080

Klauss, André; Haumann, Michael; Dau, Holger

2012-01-01

57

The Future of Earth Observation and Water Cycle Science  

Microsoft Academic Search

Observation of the water cycle at various scales is critical in managing our water resources, through better understanding of the processes involved and improved predictions of the various aspects of the water cycle, such as precipitation, flooding, droughts etc.. With the \\

Petrus J. van Oevelen

2010-01-01

58

The human cycle of water: water management and anthropogenic contaminant pathways in Pótam, Sonora, Mexico’s water cycle  

Microsoft Academic Search

Women are the primary decision makers regarding household water sources in many developing nations, but are often overlooked\\u000a by researchers and organizations as primary water managers. This study took place in Pótam, Sonora, Mexico, during the summer\\u000a of 2007, with a follow-up visit in February 2008. The study aimed at understand the human cycle of water by identifying potential\\u000a exposure

Stacey A. Pilling

2011-01-01

59

Rethinking the light water reactor fuel cycle  

E-print Network

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

Shwageraus, Evgeni, 1973-

2004-01-01

60

An Overview of Water Cycle Research Needs and Initiatives  

NASA Astrophysics Data System (ADS)

Understanding, measuring and modeling the Global Water Cycle are central issues and themes for a number of international and national environmental programs. For example, the Integrated Global Observing Strategy (IGOS) Partners recently adopted the Global Water Cycle as a new theme. In the USA, the United States Global Change Research Program (USGCRP) is developing a water cycle program and possible initiatives based on a science plan developed by an independent study group and a range of inputs from other learned sources such as the National Academy of Sciences. After a brief review of federal and international water cycle research programs and critical gaps in our knowledge of the Global Water Cycle based on these recent studies, this talk will discuss the needs for new water cycle research activities based on emerging scientific and technical capabilities; and current social, environmental and economic developments. A number of scientific water cycle issues that are critical for resolving other issues such as climate change, coastal processes, and disaster prevention and mitigation will also be described. In the light of these issues some priorities are suggested for future water cycle research and program development.

Lawford, R. G.; Eden, S.

2002-05-01

61

Water pulses and biogeochemical cycles in arid and semiarid ecosystems  

Microsoft Academic Search

The episodic nature of water availability in arid and semiarid ecosystems has significant consequences on belowground carbon and nutrient cycling. Pulsed water events directly control belowground processes through soil wet-dry cycles. Rapid soil microbial response to incident moisture availability often results in almost instantaneous C and N mineralization, followed by shifts in C\\/N of microbially available substrate, and an offset

Amy T. Austin; Laura Yahdjian; John M. Stark; Jayne Belnap; Amilcare Porporato; Urszula Norton; Damián A. Ravetta; Sean M. Schaeffer

2004-01-01

62

Water clustering on nanostructured iron oxide films  

NASA Astrophysics Data System (ADS)

The adhesion of water to solid surfaces is characterized by the tendency to balance competing molecule-molecule and molecule-surface interactions. Hydroxyl groups form strong hydrogen bonds to water molecules and are known to substantially influence the wetting behaviour of oxide surfaces, but it is not well-understood how these hydroxyl groups and their distribution on a surface affect the molecular-scale structure at the interface. Here we report a study of water clustering on a moiré-structured iron oxide thin film with a controlled density of hydroxyl groups. While large amorphous monolayer islands form on the bare film, the hydroxylated iron oxide film acts as a hydrophilic nanotemplate, causing the formation of a regular array of ice-like hexameric nanoclusters. The formation of this ordered phase is localized at the nanometre scale; with increasing water coverage, ordered and amorphous water are found to coexist at adjacent hydroxylated and hydroxyl-free domains of the moiré structure.

Merte, Lindsay R.; Bechstein, Ralf; Peng, Guowen; Rieboldt, Felix; Farberow, Carrie A.; Zeuthen, Helene; Knudsen, Jan; Lægsgaard, Erik; Wendt, Stefan; Mavrikakis, Manos; Besenbacher, Flemming

2014-06-01

63

A Satellite View of Global Water and Energy Cycling  

NASA Astrophysics Data System (ADS)

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

Houser, P. R.

2012-12-01

64

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

Microsoft Academic Search

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

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

2009-01-01

65

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

66

Nuclear Production of Hydrogen Using Thermochemical Water-Splitting Cycles  

Microsoft Academic Search

The purpose of this work is to determine the potential for efficient, cost-effective, large-scale production of hydrogen utilizing high-temperature heat from an advanced nuclear power station in a thermochemical water-splitting cycle. We carried out a detailed literature search to create a searchable database with 115 cycles and 822 references. We developed screening criteria to reduce the list to 25 cycles.

L. C. Brown; G. E. Besenbruch; K. R. Schultz; A. C. Marshall; S. K. Showalter; P. S. Pickard; J. F. Funk

2002-01-01

67

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

68

Soar's basic operation cycle Water-Jug Problem  

E-print Network

Components Soar Rules Soar's basic operation cycle Tools Water-Jug Problem Eaters Cognitive Systems Christopher Wennhold Cognitive Systems II 1/33 #12;Components Soar Rules Soar's basic operation cycle Tools for food Christopher Wennhold Cognitive Systems II 2/33 #12;Components Soar Rules Soar's basic operation

Bremen, Universität

69

Collaboration essential for an energy neutral urban water cycle.  

PubMed

Two Dutch water boards prepared a Master Plan with measures to substantially reduce their energy use by 2027. In total, more than 100 measures were identified such as bubble aeration and heat recovery from effluent. Together these measures result in a 90-95% reduction in energy use at the water boards. However, for the whole urban water cycle, thus including the energy required for warm water use in households, the total energy reduction from these measures at the water boards is only 5-6%. To attain the objective to have an energy neutral urban water cycle, collaboration with other sectors such as housing, energy, agriculture and industry will be essential. Active collaboration of the water boards through the incorporation of energy efficient water measures as part of the carbon neutral effort of cities is recognized to be a promising strategy. PMID:23676381

Frijns, Jos; Mulder, Mirabella; Roorda, Jelle; Schepman, Hans; Voskamp, Tom

2013-01-01

70

The Water Cycle: Snowmelt Runoff to Streams  

NSDL National Science Digital Library

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

71

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

PubMed

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

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

2014-10-15

72

Water Decontamination With New Porous Oxide Photocatalysts  

NASA Astrophysics Data System (ADS)

Water pollution is major environmental problem worldwide. Many common industrial organic compounds that make their way into water systems can be carcinogenic at trace levels and are difficult and costly to remove completely with conventional technologies. Heterogeneous photocatalysts like titanium dioxide have the potential to completely mineralize organic compounds in water under ultraviolet light. We are proposing to develop new porous oxide semiconductor materials made up of titanium and niobium mixed oxide nanocomposites. The porous catalysts retain high catalytic activity while being easy to handle and filter out of product streams. New synthetic methods are to be developed that optimize physical properties and the catalyst's ability to photo-degrade organic contaminants in water.

Zarei Chaleshtori, M.; Saupe, G. B.

2008-12-01

73

Changes in the global water cycle Water in a Changing World 211  

E-print Network

of the world's rivers. Global warming is expected to have substantial effects on energy flows and matterChanges in the global water cycle Water in a Changing World 211 3 Part Key messages In many places changes in the global water cycle that analysed more than 100 studies (based on observations) found ris

Olden, Julian D.

74

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

75

A Porphyrin-Stabilized Iridium Oxide Water Oxidation Catalyst  

SciTech Connect

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

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

2011-01-01

76

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

E-print Network

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

De Roo, Guillaume

2009-01-01

77

The sulfur cycle in lake waters during thermal stratification  

Microsoft Academic Search

The sulfur cycle in Linsley Pond, Connecticut, was studied in 1963 and 1964 with sulfur-35 labelled sulfuric acid as a tracer. During the summer large quantities of the tracer disappeared from the hypolimnion and metalimnion. The loss of sulfate dissolved in water occurred predominantly at the mud-water interface. The reduction took place in the region of the hypolimnion as well

M. Stuiver

1967-01-01

78

Estimated Seasonal Cycle of North Atlantic Eighteen Degree Water Volume  

E-print Network

The seasonal cycle in the volume and formation rate of Eighteen Degree Water (EDW) in the North Atlantic is quantified over the 3-yr period from 2004 to 2006. The EDW layer is defined as all waters that have a temperature ...

Forget, Gael

79

Method of removing oxidized contaminants from water  

DOEpatents

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

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

1998-07-21

80

Method of removing oxidized contaminants from water  

DOEpatents

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

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

1998-01-01

81

LifeCycle Water Consumption of  

E-print Network

IWMI, 2007 #12;Biofuel Policy Primer 1. Biofuels are a good thing ­ GHG, Energy security, Farm ­ LCAbased policies ­ CA LCFS 3. But a good GHG LCA does not a responsible product make "Sustainability" standards ­ Landuse/deforestation, food vs. fuel, biodiversity, labor, WATER...etc. #12;Sustainability

Keller, Arturo A.

82

Life Cycle Assessment of Three Water Scenarios  

E-print Network

Screen DisinfectionFiltrationAeration Reverse Osmosis Microfiltration Aquifer Storage and Recovery the Sea of Cortez Treatment Processes Filtration Reverse Osmosis Steel pipeline conveying water from the Sea of Cortez to Phoenix, AZ #12;Desalination Plant - System Diagram Screen Filtration Reverse Osmosis

Keller, Arturo A.

83

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...

84

Nitric oxide cycle in mammals and the cyclicity principle.  

PubMed

This paper continues a series of reports considering nitric oxide (NO) and its cyclic conversions in mammals. Numerous facts are summarized with the goal of developing a general concept that would allow the statement of the multiple effects of NO on various systems of living organisms in the form of a short and comprehensive law. The current state of biological aspects of NO research is analyzed in term of elucidation of possible role of these studies in the system of biological sciences. The general concept is based on a notion on cyclic conversions of NO and its metabolites. NO cycles in living organisms and nitrogen turnover in the biosphere and also the Bethe nitrogen-carbon cycle in star matter are considered. A hypothesis that the cyclic organization of processes in living organisms and the biosphere reflects the evolution of life is proposed: the development of physiological functions and metabolism are suggested to be closely related to space and evolution of the Earth as a planet of the Solar System. PMID:11970729

Reutov, V P

2002-03-01

85

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

86

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

87

Supercritical water oxidation of ammonium picrate  

SciTech Connect

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

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

1994-11-01

88

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

89

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

90

Biotransformations Utilizing ?-Oxidation Cycle Reactions in the Synthesis of Natural Compounds and Medicines.  

PubMed

?-Oxidation cycle reactions, which are key stages in the metabolism of fatty acids in eucaryotic cells and in processes with a significant role in the degradation of acids used by microbes as a carbon source, have also found application in biotransformations. One of the major advantages of biotransformations based on the ?-oxidation cycle is the possibility to transform a substrate in a series of reactions catalyzed by a number of enzymes. It allows the use of sterols as a substrate base in the production of natural steroid compounds and their analogues. This route also leads to biologically active compounds of therapeutic significance. Transformations of natural substrates via ?-oxidation are the core part of the synthetic routes of natural flavors used as food additives. Stereoselectivity of the enzymes catalyzing the stages of dehydrogenation and addition of a water molecule to the double bond also finds application in the synthesis of chiral biologically active compounds, including medicines. Recent advances in genetic, metabolic engineering, methods for the enhancement of bioprocess productivity and the selectivity of target reactions are also described. PMID:23443116

Swizdor, Alina; Panek, Anna; Milecka-Tronina, Natalia; Ko?ek, Teresa

2012-01-01

91

Biotransformations Utilizing ?-Oxidation Cycle Reactions in the Synthesis of Natural Compounds and Medicines  

PubMed Central

?-Oxidation cycle reactions, which are key stages in the metabolism of fatty acids in eucaryotic cells and in processes with a significant role in the degradation of acids used by microbes as a carbon source, have also found application in biotransformations. One of the major advantages of biotransformations based on the ?-oxidation cycle is the possibility to transform a substrate in a series of reactions catalyzed by a number of enzymes. It allows the use of sterols as a substrate base in the production of natural steroid compounds and their analogues. This route also leads to biologically active compounds of therapeutic significance. Transformations of natural substrates via ?-oxidation are the core part of the synthetic routes of natural flavors used as food additives. Stereoselectivity of the enzymes catalyzing the stages of dehydrogenation and addition of a water molecule to the double bond also finds application in the synthesis of chiral biologically active compounds, including medicines. Recent advances in genetic, metabolic engineering, methods for the enhancement of bioprocess productivity and the selectivity of target reactions are also described. PMID:23443116

OEwizdor, Alina; Panek, Anna; Milecka-Tronina, Natalia; Kolek, Teresa

2012-01-01

92

Daily training with high carbohydrate availability increases exogenous carbohydrate oxidation during endurance cycling.  

PubMed

We determined the effects of varying daily carbohydrate intake by providing or withholding carbohydrate during daily training on endurance performance, whole body rates of substrate oxidation, and selected mitochondrial enzymes. Sixteen endurance-trained cyclists or triathletes were pair matched and randomly allocated to either a high-carbohydrate group (High group; n = 8) or an energy-matched low-carbohydrate group (Low group; n = 8) for 28 days. Immediately before study commencement and during the final 5 days, subjects undertook a 5-day test block in which they completed an exercise trial consisting of a 100 min of steady-state cycling (100SS) followed by a 7-kJ/kg time trial on two occasions separated by 72 h. In a counterbalanced design, subjects consumed either water (water trial) or a 10% glucose solution (glucose trial) throughout the exercise trial. A muscle biopsy was taken from the vastus lateralis muscle on day 1 of the first test block, and rates of substrate oxidation were determined throughout 100SS. Training induced a marked increase in maximal citrate synthase activity after the intervention in the High group (27 vs. 34 micromol x g(-1) x min(-1), P < 0.001). Tracer-derived estimates of exogenous glucose oxidation during 100SS in the glucose trial increased from 54.6 to 63.6 g (P < 0.01) in the High group with no change in the Low group. Cycling performance improved by approximately 6% after training. We conclude that altering total daily carbohydrate intake by providing or withholding carbohydrate during daily training in trained athletes results in differences in selected metabolic adaptations to exercise, including the oxidation of exogenous carbohydrate. However, these metabolic changes do not alter the training-induced magnitude of increase in exercise performance. PMID:20466803

Cox, Gregory R; Clark, Sally A; Cox, Amanda J; Halson, Shona L; Hargreaves, Mark; Hawley, John A; Jeacocke, Nikki; Snow, Rodney J; Yeo, Wee Kian; Burke, Louise M

2010-07-01

93

The displacement of the thermally grown oxide in thermal barrier systems upon temperature cycling  

E-print Network

barrier coatings; Thermal cycling; Oxidation 1. Introduction Thermal barrier systems used in gas turbinesO3, that forms between the thermal barrier coating (TBC) and the bond coat (Fig. 1). This thin layerThe displacement of the thermally grown oxide in thermal barrier systems upon temperature cycling A

Hutchinson, John W.

94

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

95

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

Microsoft Academic Search

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

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

2009-01-01

96

Theoretical and experimental investigation of an ammonia–water power and refrigeration thermodynamic cycle  

Microsoft Academic Search

A combined thermal power and cooling cycle proposed by Goswami is under intensive investigation, both theoretically and experimentally. The proposed cycle combines the Rankine and absorption refrigeration cycles, using a binary ammonia–water mixture as the working fluid. This cycle can be used as a bottoming cycle using waste heat from a conventional power cycle or an independent cycle using low

G Tamm; D. Y Goswami; S Lu; A. A Hasan

2004-01-01

97

Land surface water cycles observed with satellite sensors  

NASA Technical Reports Server (NTRS)

Acceleration of the global water cycle may lead to increased global precipitation, faster evaporation and a consequent exacerbation of hydrologic extreme. In the U.S. national assessment of the potential consequences of climate variability and change, two GCMs (CGCM1 and HadCM2) show a large increase in precipitation in the future over the southwestern U.S. particularly during winter (Felzer and Heard, 1999). Increased precipitation potentially has important impacts on agricultural and water use in the southeast U.S. (Hatch et al., 1999) and in the central Great Plains (Nielsen, 1997). A hurricane model predicts a 40% precipitation increase for severe hurricanes affecting southeastern Florida, which provokes substantially greater flooding that could negate most of the benefits of present water-management practices in this basin (Gutowski et al., 1994). Thus, it is important to observe the hydroclimate on a continuous longterm basis to address the question of increased precipitation in the enhanced water cycle.

Nghiem, Son V.; Njoku, E. G.; Brakenridge, G. R.; Kim, Y.

2005-01-01

98

Water oxidation reaction in natural and artificial photosynthetic systems  

SciTech Connect

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

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

2013-12-10

99

Linking plant identity and interspecific competition to soil nitrogen cycling through ammonia oxidizer communities  

Microsoft Academic Search

Both plants and microbes influence soil nutrient cycling. However, the links between plants, microbes and nutrient cycling are poorly understood. In this study, we investigated how plant identity and interspecific competition influence soil nitrogen cycling and attempted to link plant identity and interspecific competition to community structures of bacterial and archaeal ammonia oxidizers based on terminal restriction fragment length polymorphism

Fenliang Fan; Fusuo Zhang; Yahai Lu

2011-01-01

100

Membranes and the water cycle: challenges and opportunities  

Microsoft Academic Search

Membrane technology for the water cycle has been around for about 50 years and is taking an increasingly important role in\\u000a the provision of safe water supply and treatment and reuse of wastewater. It is timely to examine the challenges and the future\\u000a of the technology. The challenges are both technical and socio-political and they provide the drivers for new developments.

A. G. Fane

101

A Seamless Framework for Global Water Cycle Monitoring and Prediction  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

102

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

103

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...

104

Nano-confined water on surfaces of metal oxide nanoparticles  

Microsoft Academic Search

Nanolayers of water interacting with metal oxide surfaces demonstrate physical properties that are significantly different from those of bulk water and ice. Our recent water adsorption experiments suggest that the entropy of surface water is lower than those of bulk water and ice implying restricted motion of the water on the surface. We have studied dynamics of water on nanoparticles

Andrey Levchenko; Juliana Boerio-Goates; Brian Woodfield; Alexander Kolesnikov; Nancy Ross; David Wesolowski; David Cole; Alexandra Navrotsky

2008-01-01

105

Coupled reductive and oxidative sulfur cycling in the phototrophic plate of a meromictic lake.  

PubMed

Mahoney Lake represents an extreme meromictic model system and is a valuable site for examining the organisms and processes that sustain photic zone euxinia (PZE). A single population of purple sulfur bacteria (PSB) living in a dense phototrophic plate in the chemocline is responsible for most of the primary production in Mahoney Lake. Here, we present metagenomic data from this phototrophic plate--including the genome of the major PSB, as obtained from both a highly enriched culture and from the metagenomic data--as well as evidence for multiple other taxa that contribute to the oxidative sulfur cycle and to sulfate reduction. The planktonic PSB is a member of the Chromatiaceae, here renamed Thiohalocapsa sp. strain ML1. It produces the carotenoid okenone, yet its closest relatives are benthic PSB isolates, a finding that may complicate the use of okenone (okenane) as a biomarker for ancient PZE. Favorable thermodynamics for non-phototrophic sulfide oxidation and sulfate reduction reactions also occur in the plate, and a suite of organisms capable of oxidizing and reducing sulfur is apparent in the metagenome. Fluctuating supplies of both reduced carbon and reduced sulfur to the chemocline may partly account for the diversity of both autotrophic and heterotrophic species. Collectively, the data demonstrate the physiological potential for maintaining complex sulfur and carbon cycles in an anoxic water column, driven by the input of exogenous organic matter. This is consistent with suggestions that high levels of oxygenic primary production maintain episodes of PZE in Earth's history and that such communities should support a diversity of sulfur cycle reactions. PMID:24976102

Hamilton, T L; Bovee, R J; Thiel, V; Sattin, S R; Mohr, W; Schaperdoth, I; Vogl, K; Gilhooly, W P; Lyons, T W; Tomsho, L P; Schuster, S C; Overmann, J; Bryant, D A; Pearson, A; Macalady, J L

2014-09-01

106

Nitrous Oxide Cycling and its Isotopic Signatures in South West Pacific Ocean  

NASA Astrophysics Data System (ADS)

Nitrous oxide (N2O) is a significant greenhouse gas and is also involved in ozone depletion. The contribution of N2O to both these processes is expected to increase this century. The ocean contributes about 30% to the atmospheric N2O budget so there is strong interest in the oceanic N2O cycle. In the ocean N2O is produced via a number of different processes (e.g. bacterial nitrification, and denitrification). While coastal regions are well-studied there are limited data available for open ocean N2O especially in the Southern Ocean, with few studies of the relative contribution of different bacterial processes. Here we apply new stable isotope techniques and present a detailed overview of the distribution and fate of dissolved nitrous oxide from sampling sites in the southwest Pacific Ocean near New Zealand. Samples for nitrous oxide and nutrients were collected along the depth profiles from two biophysical mooring stations (subtropical and sub- Antarctic), four Geotraces stations (GP13, subtropical Pacific) and two bloom voyage stations in the subtropical front and subtropical pacific waters. The N2O saturation ranged from near equilibrium with air at the surface to a maximum value in the oxygen minimum zone. Thus the surface water masses are not a significant sink or atmospheric source for N2O .Multi-isotope characterization of N2O including d15Nbulk, d18O, d15N? and its site preference (SP, the difference between d15N? and d15N?)indicates that nitrification is the primary process responsible for nitrous oxide production in oxic waters whereas coupling between nitrification and denitrification may be an important mechanism for production in the oxygen minimum zone with a minor contribution by nitrification.

Mullungal, M.; Van Hale, R.; Frew, R. D.; Law, C. S.

2013-12-01

107

Proton release during the redox cycle of the water oxidase  

Microsoft Academic Search

Old and very recent experiments on the extent and the rate of proton release during the four reaction steps of photosynthetic water oxidation are reviewed. Proton release is discussed in terms of three main sources, namely the chemical production upon electron abstraction from water, protolytic reactions of Mn-ligands (e.g. oxo-bridges), and electrostatic response of neighboring amino acids. The extent of

Jérôme Lavergne; Wolfgang Junge

1993-01-01

108

Supercritical water oxidation of products of human metabolism  

NASA Technical Reports Server (NTRS)

Although the efficient destruction of organic material was demonstrated in the supercritical water oxidation process, the reaction kinetics and mechanisms are unknown. The kinetics and mechanisms of carbon monoxide and ammonia oxidation in and reaction with supercritical water were studied experimentally. Experimental oxidation of urine and feces in a microprocessor controlled system was performed. A minaturized supercritical water oxidation process for space applications was design, including preliminary mass and energy balances, power, space and weight requirements.

Tester, Jefferson W.; Orge A. achelling, Richard K. ADTHOMASSON; Orge A. achelling, Richard K. ADTHOMASSON

1986-01-01

109

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

110

How Do Higher Temperatures Affect the Water Cycle?  

NSDL National Science Digital Library

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

111

Water defluoridation by aluminium oxide-manganese oxide composite material.  

PubMed

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

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

2014-08-01

112

Density functional investigation of the water oxidation by iron complexes based on tetradentate nitrogen ligands.  

PubMed

Recently it was discovered that the iron coordination complex L(N4)Fe(II)(OTf)(2) (1) (L(N4) = neutral tetraazadendate ligand and OTf = OSO(2)CF(3)) and its analogues are efficient water oxidizing catalysts (WOCs) in aqueous acidic solution with excess amount of ceric(IV) ammonium nitrate (CAN), [Ce(IV)(NO(3))(6)](NH(4))(2), as sacrificial oxidants. The probable mechanism of water oxidation by these catalysts was explored on the basis of density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations for 1 as a representative WOC. We examined the conversion of 1 to the resting intermediate [L(N4)Fe(IV)(O)(OH(2))](2+) [2(IV)] as well as two catalytic cycles involving 2(IV): one proposed by Fillol et al. [Nat. Chem. 2011, 3, 1] in which the Fe oxidation states of the intermediate species vary from +2 to +5, and the alternative cycle in which they remain constant at +4. In addition, we investigated the role of the sacrificial oxidant CAN in driving the catalytic cycle. Our DFT and TD-DFT calculations confirm the experimental observation that 2(IV) is the resting species, and indicate that the catalytic cycle in which the Fe oxidation states of the intermediate species remain at +4 is energetically more favorable. PMID:23025899

Kasapbasi, Esra E; Whangbo, Myung-Hwan

2012-10-15

113

Change in Water Cycle- Important Issue on Climate Earth System  

NASA Astrophysics Data System (ADS)

Change in Water Cycle- Important Issue on Climate Earth System PRATIK KUMAR SINGH1 1BALDEVRAM MIRDHA INSTITUTE OF TECHNOLOGY,JAIPUR (RAJASTHAN) ,INDIA Water is everywhere on Earth and is the only known substance that can naturally exist as a gas, liquid, and solid within the relatively small range of air temperatures and pressures found at the Earth's surface.Changes in the hydrological cycle as a consequence of climate and land use drivers are expected to play a central role in governing a vast range of environmental impacts.Earth's climate will undergo changes in response to natural variability, including solar variability, and to increasing concentrations of green house gases and aerosols.Further more, agreement is widespread that these changes may profoundly affect atmospheric water vapor concentrations, clouds and precipitation patterns.As we know that ,a warmer climate, directly leading to increased evaporation, may well accelerate the hydrological cycle, resulting in an increase in the amount of moisture circulating through the atmosphere.The Changing Water Cycle programmer will develop an integrated, quantitative understanding of the changes taking place in the global water cycle, involving all components of the earth system, improving predictions for the next few decades of regional precipitation, evapotranspiration, soil moisture, hydrological storage and fluxes.The hydrological cycle involves evaporation, transpiration, condensation, precipitation, and runoff. NASA's Aqua satellite will monitor many aspects of the role of water in the Earth's systems, and will do so at spatial and temporal scales appropriate to foster a more detailed understanding of each of the processes that contribute to the hydrological cycle. These data and the analyses of them will nurture the development and refinement of hydrological process models and a corresponding improvement in regional and global climate models, with a direct anticipated benefit of more accurate weather and climate forecasts. Aqua is a major mission of the Earth Observing System (EOS), an international program centered in NASA's Earth Science Enterprise to study the Earth in detail from the unique vantage point of space. Focused on key measurements identified by a consensus of U.S. and international scientists, EOS is further enabling studies of the complex interactions amongst the Earth's land, ocean, air, ice and biological systems. Aqua's contributions to monitoring water in the Earth's environment will involve all six of Aqua's instruments: the Atmospheric Infrared Sounder (AIRS), the Advanced Microwave Sounding Unit (AMSU), the Humidity Sounder for Brazil (HSB), the Advanced Microwave Scanning Radiometer- Earth Observing System (AMSR-E), the Moderate Resolution Imaging Spectroradiometer (MODIS), and Clouds and the Earth's Radiant Energy System (CERES). Frozen water in the oceans, in the form of sea ice, will be examined with both AMSR-E and MODIS data, the former allowing routine monitoring of sea ice at a coarse resolution and the latter providing greater spatial resolution but only under cloud-free conditions. Sea ice can insulate the underlying liquid water against heat loss to the often frigid overlying polar atmosphere and also reflects sunlight that would otherwise be available to warm the ocean. AMSR-E measurements will allow the routine derivation of sea ice concentrations in both polar regions, through taking advantage of the marked contrast in microwave emissions of sea ice and liquid water. This will continue, with improved resolution and accuracy, a 22-year satellite record of changes in the extent of polar ice. MODIS, with its finer resolution, will permit the identification of individual ice flows, when unobscured by clouds. AMSR-E and MODIS will also provide monitoring, the AIRS/AMSU/HSB combination will provide more-accurate space-based measurements of atmospheric temperature and water vapor than have ever been obtained before, with the highest vertical resolution to date as well. Since water vapor is the Earth's primary greenhouse gas and co

Singh, Pratik

114

Containment system for supercritical water oxidation reactor  

DOEpatents

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

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

1994-01-01

115

Cobalt selenium oxohalides: catalysts for water oxidation.  

PubMed

Two new oxohalides Co4Se3O9Cl2 and Co3Se4O10Cl2 have been synthesized by solid state reactions. They crystallize in the orthorhombic space group Pnma and the monoclinic space group C2/m respectively. The crystal structure of the two compounds are made up of similar building blocks; Co4Se3O9Cl2 is made up of [CoO4Cl2], [CoO5Cl] and [SeO3] polyhedra and Co3Se4O10Cl2 is made up of [CoO4Cl2] and [SeO3] polyhedra. As several Co-containing compounds have proved to be good catalysts for water oxidation, the activities of the two new compounds were compared with the previously found oxohalide Co5Se4O12Cl2 in reference to CoO and CoCl2. The one electron oxidant Ru(bpy)3(3+) was used as oxidizing species in a phosphate buffer and it was found that the activities of the oxohalide species were in between CoO and CoCl2. The roles of Cl(-) and PO4(3-) ions are discussed. PMID:24452596

Rabbani, Faiz; Svengren, Henrik; Zimmermann, Iwan; Hu, Shichao; Laine, Tanja; Hao, Wenming; Akermark, Björn; Akermark, Torbjörn; Johnsson, Mats

2014-03-14

116

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

117

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

118

Water Cycling in the North Polar Region of Mars  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

119

Oxidation of graphite surface: the role of water  

E-print Network

Based on density functional calculations, we demonstrate a significant difference in oxidation patterns between graphene and graphite and the formation of defects after oxidation. Step-by-step modeling demonstrates that oxidation of 80% of the graphite surface is favorable. Oxidation above half of the graphite surface significantly decreases the energy costs of vacancy formation with CO2 production. The presence of water is crucial in the transformation of epoxy groups to hydroxyl, the intercalation with further bundle and exfoliation. In water-rich conditions, water intercalates graphite at the initial stages of oxidation and oxidation, which is similar to the oxidation process of free-standing graphene; in contrast, in water-free conditions, large molecules intercalate graphite only after oxidation occurs on more than half of the surface.

Boukhvalov, D W

2014-01-01

120

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.

121

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

Microsoft Academic Search

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

Junying Chu; Hao Wang; Jianhua Wang; Dayong Qin

2010-01-01

122

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

123

Life cycle water use of low-carbon transport fuels  

Microsoft Academic Search

In society’s quest to mitigate climate change it is important to consider potential trade-offs in climate solutions impacting other environmental issues. This analysis explores the life cycle water consumption of alternative low-carbon energy sources for transportation. Energy sources analyzed include both biofuels used in internal combustion engines and low-carbon electricity generation methods used in conjunction with electric vehicles. Biofuels considered

Christopher Harto; Robert Meyers; Eric Williams

2010-01-01

124

Oxidation of scandium by oxygen and water studied by XPS  

Microsoft Academic Search

Reaction of scandium with water at 293 K gives initially the oxide and, above -50 L, also the hydroxide. The ratio of hydroxide to oxide is approximately constant in the later stages of reaction. The reaction of water with scandium is slower and less extensive then with the lantha- nides. At low exposures of water at 80 K only the

J. K. GIMZEWSKI; S. AFFROSSMAN; M. T. GIBSON; L. M. WATSON; D. J. FABIAN

1979-01-01

125

Nano-sized layered aluminium or zinc-manganese oxides as efficient water oxidizing catalysts.  

PubMed

Nano-sized layered aluminium or zinc-manganese oxides were synthesized and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectrometry, dynamic light scattering and atomic absorption spectroscopy. These oxides showed efficient water oxidizing activity in the presence of cerium(IV) ammonium nitrate as a non-oxo transfer oxidant. Amounts of dissolved manganese, zinc or aluminium, and water oxidation activities of these oxides were reported and compared with other manganese oxides. A mechanism for oxygen evolution and possible roles for zinc or aluminium ions are also proposed. PMID:22565665

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

2012-06-21

126

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

127

Degradation in supercritical water oxidation systems  

SciTech Connect

Supercritical water oxidation (SCWO) can effectively destroy various civilian and military wastes; however, the system will generally need to withstand a corrosive environment. To improve our understanding of degradation within such systems, systematic exposure testing is being carried out in conjunction with analysis of failed components. Various alloys have been exposed to environments ranging from deionized water to highly chlorinated organic compounds and to temperatures from 300 to 600{degrees}C. Although, not surprisingly, high corrosion rates are encountered for the chlorinated feed streams, even deionized water can be aggressive at these conditions. In chlorinated feed streams, Hastelloy C-276 exhibits premature failure at subcritical conditions as a result of dealloying and cracking. At supercritical conditions (600{degrees}C) in chlorinated environments, the high-nickel alloys and stainless steels exhibited significant corrosion. To date, titanium appears to be the most promising candidate material for use in chlorinated organics. Analysis suggests that it may be possible to alter feed characteristics to reduce degradation to an acceptable level. This may permit the use of less costly materials for construction.

Mitton, D.B.; Han, E.H.; Zhang, S.H. [Massachusetts Inst. of Technology, Cambridge, MA (United States)

1996-10-01

128

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

129

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

130

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

E-print Network

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

Jaramillo, Paulina

131

Water oxidation by amorphous cobalt-based oxides: volume activity and proton transfer to electrolyte bases.  

PubMed

Water oxidation in the neutral pH regime catalyzed by amorphous transition-metal oxides is of high interest in energy science. Crucial determinants of electrocatalytic activity were investigated for a cobalt-based oxide film electrodeposited at various thicknesses on inert electrodes. For water oxidation at low current densities, the turnover frequency (TOF) per cobalt ion of the bulk material stayed fully constant for variation of the thickness of the oxide film by a factor of 100 (from about 15?nm to 1.5??m). Thickness variation changed neither the nanostructure of the outer film surface nor the atomic structure of the oxide catalyst significantly. These findings imply catalytic activity of the bulk hydrated oxide material. Nonclassical dependence on pH was observed. For buffered electrolytes with pKa values of the buffer base ranging from 4.7 (acetate) to 10.3 (hydrogen carbonate), the catalytic activity reflected the protonation state of the buffer base in the electrolyte solution directly and not the intrinsic catalytic properties of the oxide itself. It is proposed that catalysis of water oxidation occurs within the bulk hydrated oxide film at the margins of cobalt oxide fragments of molecular dimensions. At high current densities, the availability of a proton-accepting base at the catalyst-electrolyte interface controls the rate of water oxidation. The reported findings may be of general relevance for water oxidation catalyzed at moderate pH by amorphous transition-metal oxides. PMID:24449514

Klingan, Katharina; Ringleb, Franziska; Zaharieva, Ivelina; Heidkamp, Jonathan; Chernev, Petko; Gonzalez-Flores, Diego; Risch, Marcel; Fischer, Anna; Dau, Holger

2014-05-01

132

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

PubMed

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

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

2014-09-01

133

Influence of oxidative environments on damage in c\\/epoxy laminates subjected to thermal cycling  

Microsoft Academic Search

The aim of this study is to characterise damage processes in carbon\\/epoxy laminates submitted to thermal cycling in neutral (nitrogen) and oxidative (air, oxygen) atmospheres. Observations of the polished edges of the specimens by optical microscopy and SEM have revealed the presence of matrix shrinkage and fibre\\/matrix debondings only on samples tested under oxidative atmospheres. Quantitative analyses of transverse matrix

M. C Lafarie-Frenot; S Rouquie

2004-01-01

134

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

PubMed

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

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

2014-07-28

135

Iron-oxide catalyzed silicon photoanode for water splitting  

E-print Network

This thesis presents an integrated study of high efficiency photoanodes for water splitting using silicon and iron-oxide. The fundamental limitations of silicon to water splitting applications were overcome by an ultrathin ...

Jun, Kimin

2011-01-01

136

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

137

Supercritical water: Powerful oxidation for toxic organics  

SciTech Connect

Systems that use supercritical water oxidation (SCWO) are effective in destroying aqueous organic waste streams and pumpable sludges. Since March 1991, EcoWaste Technologies (EWT; Austin, TX) has operated an SCWO pilot plant at the University of Texas (Austin), which is designed to treat 40 gal/h of organic waste. Last May, EWT started up what is said to be the world`s first commercial SCWO unit at the Austin, TX research laboratory of Huntsman Corp. (formerly Texaco, Inc.). The continuous, 300-gal/h unit is designed to treat roughly 20 million lb/yr of the firm`s organic wastes. SCWO systems convert carbon to carbon dioxide, hydrogen to water, chlorine atoms from chlorinated organics to chloride ions, and nitro-compounds to nitrates and nitrogen. EWT`s process can handle waste streams with organics concentrations ranging from ppb levels to 25 wt. %. Destruction efficiencies to 99.99% are routinely reached for compounds such as 2-butanone, o-cresol, pentachlorophenol and trichloroethylene.

Shelley, S.

1995-05-01

138

Subaquatic oxidation of coal by water-dissolved oxygen  

Microsoft Academic Search

Subaquatic oxidation of two bituminous coals by water-dissolved oxygen was investigated using batch reactor equipped with membrane oxygen sensor. Effects of time, temperature and coal grain size were studied as basic parameters influencing the oxidation process. Obtained results showed the subaquatic coal oxidation can be considered as interaction of the first reaction order with respect to oxygen. From temperature dependence

Boleslav Taraba; Jan Kupka

2010-01-01

139

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

E-print Network

Mechanistic Studies of Water Electrolysis and Hydrogen Electro- Oxidation on High Temperature Ceria of simple hydrogen electro-oxidation and water electrolysis on oxide surfaces of solid oxide electrochemical of electrocatalytic splitting of water (H2O + 2e- H2 + O2- ) and electro-oxidation of hydrogen (H2 + O2- H2O + 2e

Li, Weixue

140

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

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

141

The cadence and water temperature effect on physiological responses during water cycling.  

PubMed

The aim of the study was to compare the maximal physiological responses during three protocols: maximal test on land cycle ergometer, maximal test on water cycling in an indoor pool at 27 °C (WC27) and at 31 °C (WC31). Moreover, the submaximal physiological responses were compared according cycling cadences and water temperatures during the water protocols. Ten young men were included and performed the protocols in separate days. Blood lactate (BL) concentration, heart rate (HR), oxygen uptake (VO2), ventilation (VE) and thermal comfort (TC) were collected during the exercise. The maximal HR and VO2 showed no significant differences between the protocols: HRmax: 189 ± 7 (Land), 188 ± 14 (WC27), 185 ± 9 bpm (WC31) and VO2max: 4.2 ± 0.4 (Land), 4.1 ± 0.5 (WC27) and 4.3 ± 0.5 l min(-1) (WC31). However, the maximal BL demonstrated significant lower values during the water protocols compared to the land protocol (p=0.018). All the submaximal physiological responses showed significant differences between the cadences (60, 70, 80 and 90 rpm). The effect of water temperature was significant for TC response (p=0.001) showing higher values at 31 °C than 27 °C (TCW27: 7 ± 1 and TCW31:9 ± 1). In conclusion, higher physiological responses were showed by increasing the cadence by 10 rpm and the subjects were more comfortable when cycling in the lower water temperature. PMID:24175730

Yazigi, Flávia; Pinto, Stephanie; Colado, Juan; Escalante, Yolanda; Armada-da-Silva, Paulo A S; Brasil, Roxana; Alves, Francisco

2013-01-01

142

Water footprint of European cars: potential impacts of water consumption along automobile life cycles.  

PubMed

Due to global increase of freshwater scarcity, knowledge about water consumption in product life cycles is important. This study analyzes water consumption and the resulting impacts of Volkswagen's car models Polo, Golf, and Passat and represents the first application of impact-oriented water footprint methods on complex industrial products. Freshwater consumption throughout the cars' life cycles is allocated to material groups and assigned to countries according to import mix shares or location of production sites. Based on these regionalized water inventories, consequences for human health, ecosystems, and resources are determined by using recently developed impact assessment methods. Water consumption along the life cycles of the three cars ranges from 52 to 83 m(3)/car, of which more than 95% is consumed in the production phase, mainly resulting from producing iron, steel, precious metals, and polymers. Results show that water consumption takes place in 43 countries worldwide and that only 10% is consumed directly at Volkswagen's production sites. Although impacts on health tend to be dominated by water consumption in South Africa and Mozambique, resulting from the production of precious metals and aluminum, consequences for ecosystems and resources are mainly caused by water consumption of material production in Europe. PMID:22390631

Berger, Markus; Warsen, Jens; Krinke, Stephan; Bach, Vanessa; Finkbeiner, Matthias

2012-04-01

143

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

144

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

Microsoft Academic Search

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

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

2007-01-01

145

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

146

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

PubMed

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

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

2014-08-22

147

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

148

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

Microsoft Academic Search

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

L. H. Rogers; D. H. Archer

1993-01-01

149

Anticipated SWOT Observations of Human Impacts on the Water Cycle  

NASA Astrophysics Data System (ADS)

The impoundment of water behind dams alters the timing and magnitude of the discharge of rivers to the ocean, and hence sea level, as well as evaporation from the global land areas, and, through irrigation, the storage of water on land in the soil column. The impact of these effects on the global hydrologic cycle globally is difficult to estimate given currently available (and shared) observations of temporally varying reservoir storage. The upcoming joint U.S.-France Surface Water and Ocean Topography (SWOT) mission* will measure terrestrial surface water storage dynamics with unprecedented global coverage for managed reservoirs, as well as natural lakes and rivers. Previous studies have investigated SWOT's potential ability to measure storage change for some lakes; however, because reservoirs are typically located in flooded river valleys, they tend to be more elongate than the high latitude lakes that have been studied, and have more complex shorelines (and hence a longer land-water boundary). Furthermore, for reservoirs in mountainous regions, SWOT observations will be prone to topographic layover effects. Finally, the temporal variability of water levels in reservoirs is determined by management goals (i.e., hydropower, flood control, irrigation, supply, recreation), rather than climate, as in the case of natural lakes. We report an investigation of the potential accuracy of SWOT observations of storage change over selected managed reservoirs in the United States. First, we developed a time series of water height maps over each reservoir by combining available bathymetry data with observations of reservoir storage. We then simulated realistic SWOT observations of water level over these water bodies, given the planned SWOT orbital parameters, anticipated noise, and topographic layover errors. We also simulated a realistic tropospheric delay, modeled from daily MERRA reanalysis data. From these synthetic observations, we estimate the number of overpasses needed to construct accurate area-elevation-volume curves. We discuss the accuracy of absolute volume estimated from an extrapolation of the smoothed elevation-volume relationship, as well as the accuracy of the directly observed storage change. SWOT performs better in terms of storage change accuracy over large reservoirs with regular boundaries and relatively flat topography. In addition, we assess the ability of SWOT's planned sampling schedule to reconstruct the variability in storage change for U.S. reservoirs as a function of their storage capacity. Estimates of absolute storage are most accurate for reservoirs that experience the most water level variation during the anticipated SWOT sampling period. *The SWOT mission has not been formally approved by NASA. The decision to proceed with the mission will not occur until the completion of the National Environmental Policy Act (NEPA) process. Material in this paper related to SWOT is for information purposes only.

Clark, E.; Andreadis, K.; Moller, D.; Lettenmaier, D. P.

2012-12-01

150

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. PMID:22330720

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

2011-01-01

151

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

152

The Urban Water Cycle and how it Modulates the Microclimate and the Energy Cycle  

NASA Astrophysics Data System (ADS)

Urbanization is the land-use modification with the largest and most manifest impacts on hydrologic storage and fluxes. This perturbation of the water cycle also has considerable ramifications on the surface energy budget and the microclimatology in built terrain: reducing the potential for water storage and subsequent evaporation reduces the fraction of incoming radiative energy dissipated through surface evaporation, and consequently increases the sensible heating of the urban atmosphere and solid surfaces (buildings, roads, …). However, the complexity of the involved physical processes and their interactions have so far been oversimplified, leading to considerable biases in model output when compared to observations. Using novel sensing techniques that include wireless sensor networks, this study seeks to build a better understanding of the Urban Water Cycle. Our findings indicate that "impervious surfaces" in urban area are not really impervious and not always dry. The role of evaporation from gravel-covered roofs and from concrete, brick, stone and asphalt surfaces can be considerable, leading to lower sensible heating. In addition, the different thermal properties of the various urban materials lead to extreme spatial heterogeneity in surface conditions that is much higher than over natural terrain. Building on this understanding, an improved urban canopy model is developed that includes much better representation of surface heterogeneity and of hydrological and thermal storage and transport processes, including analytical solutions of the heat equation and numerical solutions of the Richards equation in the urban surface. The model development will be detailed and applications focusing on the role of evaporation in mitigating summer building cooling needs and urban heat island effects will be presented.

Bou-Zeid, E.; Wang, Z.; Ramamurthy, P.; Li, D.; Sun, T.; Smith, J. A.

2012-12-01

153

Oxidation of methane in the water column of Lake Baikal  

NASA Astrophysics Data System (ADS)

The rate of aerobic oxidation of methane was calculated based on average profiles of the tritiumhelium age of the Baikal waters and concentrations of the dissolved methane in the water column. In the deep lake zone (>200 m), the intensity of oxidation vertically decreases and is (2-0.3) × 10-2 nl CH4l-1 days-1 in southern and central Baikal and (2.8-1.0) × 10-2 nl CH4 l-1 days-1 in northern Baikal. The effective coefficient of the oxidation rate in the lake depressions is 3.6 × 10-4, 3.3 × 10-4, and 3.7 × 10-4 days-1, respectively. At current methane concentrations in the water column, about 80 t of methane is oxidized per year. Oxidation of the dissolved methane in the water column was estimated at a possible increase of its concentration.

Granin, N. G.; Mizandrontsev, I. B.; Obzhirov, A. I.; Vereshchagina, O. F.; Gnatovskii, R. Yu.; Zhdanov, A. A.

2013-07-01

154

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

155

A Review of RedOx Cycling of Solid Oxide Fuel Cells Anode  

PubMed Central

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

Faes, Antonin; Hessler-Wyser, Aicha; Zryd, Amedee; Van Herle, Jan

2012-01-01

156

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

157

Highly efficient and robust molecular ruthenium catalysts for water oxidation  

PubMed Central

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

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

2012-01-01

158

Degradation of phenolic waste waters over Ni-oxide.  

PubMed

The low-temperature oxidation of phenol in an aqueous phase in the presence of Ni-oxide system has been studied. The effects of pH, temperature and the catalyst amount on the efficiency of the oxidation process have been investigated. The results obtained show that phenol is completely oxidized to harmless products--carboxylic acids and CO2 at ambient temperature and pH 6.0-7.0. The simple scheme for this synthesis of the Ni-oxide system and its regeneration is a prerequisite for its application to the purification of waste waters containing toxic compounds. PMID:11337856

Christoskova, S; Stoyanova, M

2001-06-01

159

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

2012-11-21

160

First Principles Studies of Water and Ice on Oxide Surfaces  

E-print Network

the fundamental properties of water adsorption, dissociation, and proton transfer on oxide surfaces. These studies reveal that the water adsorption energy and the tendency to dissociate both increase as one moves down transfer within clusters of just two water molecules, made possible by facile dissociation

Alavi, Ali

161

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

162

Multimodal science teachers' discourse in modeling the water cycle  

NASA Astrophysics Data System (ADS)

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 role do the different communicative modes play within teacher's discourse?, and (c) what are the relationships among communicative modes being used by the teacher? Theoretical framework is developed based on three strands: multimodal communication, science teaching and learning as modeling, and social semotics and Halliday's functional grammar. An analytic scheme guiding teachers' discourse analysis is presented and results discussed. Implications for science teacher education are drawn that would contribute to the improvement of science teacher education.

Márquez, Conxita; Izquierdo, Mercè; Espinet, Mariona

2006-03-01

163

Perspectives on reservoir storage and the global water cycle (Invited)  

NASA Astrophysics Data System (ADS)

The storage of water in man-made reservoirs is an important term in the global hydrological cycle. The total capacity of reservoirs globally has been estimated at 6000-8000 km3, or slightly less than 20% of annual river runoff to the oceans. The dynamics of reservoir storage at global, or even continental, scales is not well known, but rough estimates suggest that its interseasonal and interannual variability could be very roughly ¼ - 1/2 that of soil moisture. Yet aside from the very largest global reservoirs (which account for about 15% of total global capacity), and a few countries (e.g., USA) from which at least some reservoir storage data are publically available, information about global reservoir dynamics is surprisingly scarce. This is the case even though over the second half of the 20th Century, filling of reservoirs globally is estimated to have had a negative effect on sea level rise of as much as 0.5 mm/yr, reducing the amount of sea level rise that otherwise would have occurred by about 20%. Yet, as reservoir construction rates have slowed globally, and reservoir infilling by sedimentation has occurred, there no longer is consensus even as to the sign of the reservoir effect on sea level rise. In this overview talk, I review the potential for remote sensing, current and future, to provide better information about the role of reservoirs in the global water cycle, as well as the potential for modeling to provide and/or augment in situ and remote sensing data.

Lettenmaier, D. P.

2013-12-01

164

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

165

Rapid thermal cycling of metal-supported solid oxide fuel cellmembranes  

SciTech Connect

Solid oxide fuel cell (SOFC) membranes were developed inwhich zirconia-based electrolyte thin films were supported by a compositemetal/ceramic electrode, and were subjected to rapid thermal cyclingbetween 200 and 800 0C. The effects of this cycling on membraneperformance were evaluated. The membranes, not yet optimized forperformance, showed a peak power density of 350mW/cm2at 900 0C inlaboratory-sized SOFCs that was not affected by the thermal cycling. Thisresistance to cycling degradation is attributed to the close matching ofthermal expansion coefficient of the cermet support electrode with thatof the zirconia electrolyte.

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

2004-01-02

166

Water activation by small free ruthenium oxide clusters.  

PubMed

The reactions of ruthenium clusters, Rux(+) (x = 2-5), and ruthenium oxide clusters, RuxOy(+) (x = 2-5, y = 1-2), with water molecules have been investigated by gas phase ion trap mass spectrometry and first principle density functional calculations. The joint experimental and theoretical study reveals that the reactions of the ruthenium oxide clusters with water are considerably more efficient. This is assigned theoretically to the stronger binding of the water molecules to RuxOy(+) and, more importantly, to water activation leading to an efficient hydrogen transfer reaction from the water molecules to the oxygen atoms of the ruthenium oxide clusters. The theoretically predicted hydrogen shift reaction has been confirmed experimentally through (16)O/(18)O isotope exchange experiments. Calculated energy profiles for the reactions of selected oxide clusters with water illustrate that the oxygen isotope exchange relies on the facile transfer of hydrogen atoms via [1,3] shift reactions between the oxygen atoms of the complexes due to the relatively low barriers involved. These findings might open perspectives for the future realization of water oxidation driven by ruthenium oxide clusters. PMID:25146165

Lang, Sandra M; Bernhardt, Thorsten M; Krsti?, Marjan; Bona?i?-Koutecký, Vlasta

2014-11-19

167

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

PubMed

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

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

2014-02-18

168

Theoretical investigation of solar energy conversion and water oxidation catalysis  

E-print Network

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

Wang, Lee-Ping

2011-01-01

169

Oxidative decoupling mechanisms of monomer recovery from waste tires via partial supercritical water oxidation  

SciTech Connect

Ground waste tires can be oxidatively decomposed into recoverable useful chemical species via a controlled, partial supercritical water oxidation. The process feasibility has been demonstrated using a 1-liter semi-batch supercritical water oxidation system that is fabricated of Hastelloy C-276. The typical operating conditions are 370-400{degrees}C and 220-260 atm. The products include C{sub 1}-C{sub 10} hydrocarbons, including isoprene, the monomer of natural rubber. Possible oxidative decoupling mechanisms for the recovery of monomer and preliminary process engineering results are presented in this paper.

Lanterman, H.B.; Kocher, B.S.; Lee, S. [Univ. of Akron, OH (United States)

1996-12-31

170

Copper oxide incorporated mesoporous alumina for defluoridation of drinking water  

Microsoft Academic Search

In the present study mesoporous alumina was modified by coating copper oxide to enhance the defluoridation of water. The copper oxide coated alumina (COCA) was synthesised by impregnating alumina with copper sulphate solution followed by calcination at 450°C in presence of air. The COCA was thoroughly characterised using powder XRD, SEM and BET surface area analysis. It was observed that

Amit Bansiwal; Pradnya Pillewan; Rajesh B. Biniwale; Sadhana S. Rayalu

2010-01-01

171

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

172

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

173

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

174

Surface catalysis of water oxidation by the blue ruthenium dimer.  

PubMed

Single-electron activation of multielectron catalysis has been shown to be viable in catalytic water oxidation with stepwise proton-coupled electron transfer, leading to high-energy catalytic precursors. For the blue dimer, cis,cis-[(bpy)(2)(H(2)O)Ru(III)ORu(III)(H(2)O)(bpy)(2)](4+), the first well-defined molecular catalyst for water oxidation, stepwise 4e(-)/4H(+) oxidation occurs to give the reactive precursor [(O)Ru(V)ORu(V)(O)](4+). This key intermediate is kinetically inaccessible at an unmodified metal oxide surface, where the only available redox pathway is electron transfer. We report here a remarkable surface activation of indium-tin oxide (In(2)O(3):Sn) electrodes toward catalytic water oxidation by the blue dimer at electrodes derivatized by surface phosphonate binding of [Ru(4,4'-((HO)(2)P(O)CH(2))(2)bpy)(2)(bpy)](2+). Surface binding dramatically improves the rate of surface oxidation of the blue dimer and induces water oxidation catalysis. PMID:20377256

Jurss, Jonah W; Concepcion, Javier C; Norris, Michael R; Templeton, Joseph L; Meyer, Thomas J

2010-05-01

175

Subcritical and supercritical water oxidation of CELSS model wastes.  

PubMed

Controlled-Ecological-Life-Support-System (CELSS) model wastes were wet-oxidized at temperatures from 250 to 500 degrees C, i.e., below and above the critical point of water (374 degrees C and 218 kg/cm2 or 21.4 MPa). A solution of ammonium hydroxide and acetic acid and a slurry of human urine, feces, and wipes were used as model wastes. Almost all of the organic matter in the model wastes was oxidized in the temperature range from 400 to 500 degrees C, i.e., above the critical conditions for water. In contrast, only a small portion of the organic matter was oxidized at subcritical conditions. Although the extent of nitrogen oxidation to nitrous oxide (N2O) and/or nitrogen gas (N2) increased with reaction temperature, most of the nitrogen was retained in solution as ammonia near 400 degrees C. This important finding suggests that most of the nitrogen in the waste feed can be retained in solution as ammonia during oxidation at low supercritical temperatures and be subsequently used as a nitrogen source for plants in a CELSS while at the same time organic matter is almost completely oxidized to carbon dioxide and water. It was also found in this study the Hastelloy C-276 alloy reactor corroded during waste oxidation. The rate of corrosion was lower above than below the critical temperature for water. PMID:11537396

Takahashi, Y; Wydeven, T; Koo, C

1989-01-01

176

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

E-print Network

Ecological Modelling xxx (2005) xxx­xxx Modelling carbon and water cycles in a beech forest Part II and heterotrophic respirations, net ecosystem exchange, wood and root growth) and the water cycle (transpiration, soil evaporation, interception, drainage and soil water status) is tested with data from a young beech

Boyer, Edmond

177

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

178

Process for treating effluent from a supercritical water oxidation reactor  

DOEpatents

A method for treating a gaseous effluent from a supercritical water oxidation reactor containing entrained solids is provided comprising the steps of expanding the gas/solids effluent from a first to a second lower pressure at a temperature at which no liquid condenses; separating the solids from the gas effluent; neutralizing the effluent to remove any acid gases; condensing the effluent; and retaining the purified effluent to the supercritical water oxidation reactor.

Barnes, Charles M. (Idaho Falls, ID); Shapiro, Carolyn (Idaho Falls, ID)

1997-01-01

179

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

PubMed

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

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

2014-02-01

180

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

181

Connecting oxidative stress, auxin, and cell cycle regulation through a plant mitogen-activated  

E-print Network

Commentary Connecting oxidative stress, auxin, and cell cycle regulation through a plant mitogen of Vienna, Dr. Bohrgasse 9, 1030 Vienna, Austria Like all living organisms, plants must respond to many external stimuli. Mi- togen-activated protein kinases (MAPKs) mediate signal transduction of stress, cell

Hirt, Heribert

182

Performance analysis of ammonia absorption GAX cycle for combined cooling and hot water supply modes  

Microsoft Academic Search

An ammonia Generator–Absorber heat eXchange (GAX) absorption cycle with combined cooling and hot water supply modes is developed in this study. This paper proposes new multi-modes GAX cycles which function in three different modes (case 1, case 2 and case 3) of cooling and hot water supply with one hardware (ammonia\\/water GAX absorption heat pump), and finds the best cycle

Chan Woo Park; Junemo Koo; Yong Tae Kang

2008-01-01

183

[Inactivation of viruses in water by anodic oxidation (author's transl)].  

PubMed

The inactivating effect of anodic oxidation on viruses performed in an experimental electrolytic polarization unit was investigated with 11 different viruses suspended in tap and superficial water. Furthermore attempts were made to define the influence of factors important in experimental and water respect. Using concentrations up to 10(4) infectious units per ml representing a multiple quantity of the virus demonstrable in contaminated environmental waters all the viruses investigated could be inactivated reliably and rationally when suspended in tap water, more easily however in water of improved conductivity, by passing the current leading unit once. Anodic oxidation represents a fast and rational not denaturating method for decontamination of virus containing waters. Varying conditions of a water as well as bacterial contamination, so far remaining within naturally occurring scope, have only little or no influence on the inactivating effect on viruses. The applicability of the method is discussed briefly. PMID:211753

Mahnel, H

1978-06-01

184

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

185

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

186

Efficient water oxidation catalyzed by mononuclear ruthenium(II) complexes incorporating Schiff base ligands.  

PubMed

Four new charge-neutral ruthenium(II) complexes containing dianionic Schiff base and isoquinoline or 4-picoline ligands were synthesized and characterized by NMR and ESI-MS spectroscopies, elemental analysis, and X-ray diffraction. The complexes exhibited excellent chemical water oxidation activity and high stability under acidic conditions (pH?1.0) using (NH4)2Ce(NO3)6 as a sacrificial electron acceptor. The high catalytic activities of these complexes for water oxidation were sustained for more than 10?h at low concentrations. High turnover numbers of up to 3200 were achieved. A water nucleophilic attack mechanism was proposed. A Ru(V)=O intermediate was detected during the catalytic cycle by high-resolution mass spectrometry. PMID:24888489

Li, Ting-Ting; Chen, Yong; Li, Fu-Min; Zhao, Wei-Liang; Wang, Chuan-Jun; Lv, Xiao-Jun; Xu, Quan-Qing; Fu, Wen-Fu

2014-06-23

187

A Co(II)-Ru(II) dyad relevant to light-driven water oxidation catalysis.  

PubMed

Artificial photosynthesis aims at efficient water splitting into hydrogen and oxygen, by exploiting solar light. As a priority requirement, this process entails the integration of suitable multi-electron catalysts with light absorbing units, where charge separation is generated in order to drive the catalytic routines. The final goal could be the transposition of such an asset into a photoelectrocatalytic cell, where the two half-reactions, proton reduction to hydrogen and water oxidation to oxygen, take place at two appropriately engineered photoelectrodes. We herein report a covalent approach to anchor a Co(II) water oxidation catalyst to a Ru(II) polypyridine photosensitizer unit; photophysical characterisation and the catalytic activity of such a dyad in a light activated cycle are reported, and implications for the development of regenerative systems are discussed. PMID:24664104

López, Alejandro Montellano; Natali, Mirco; Pizzolato, Erica; Chiorboli, Claudio; Bonchio, Marcella; Sartorel, Andrea; Scandola, Franco

2014-06-28

188

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

189

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

190

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

191

Direct-Coupling O? Bond Forming Pathway in Cobalt Oxide Water Oxidation Catalysts  

E-print Network

We report a catalytic mechanism for water oxidation in a cobalt oxide cubane model compound, in which the crucial O–O bond formation step takes place by direct coupling between two CoIV(O) metal oxo groups. Our results are ...

Wang, Lee-Ping

192

Self-inhibition of water dissociation on magnesium oxide surfaces  

Microsoft Academic Search

Hydroxylated MgO surfaces have been prepared by exposure to water vapour of MgO crystals at room temperature. High hydroxyl coverages were achieved on freshly cleaved surfaces. However, upon adsorption–desorption cycles of the hydroxyl adlayer, the ability of the MgO surfaces to dissociate water was seen to be dramatically inhibited. Reduced reactivities have also been observed on both air- and water-exposed

D. Abriou; J. Jupille

1999-01-01

193

Multiple Observation Types Jointly Constrain Terrestrial Carbon and Water Cycles  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

194

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

195

Time-resolved observations of water oxidation intermediates on a cobalt oxide nanoparticle catalyst.  

PubMed

In any artificial photosynthetic system, the oxidation of water to molecular oxygen provides the electrons needed for the reduction of protons or carbon dioxide to a fuel. Understanding how this four-electron reaction works in detail is important for the development of improved robust catalysts made of Earth-abundant materials, like first-row transition-metal oxides. Here, using time-resolved Fourier-transform infrared spectroscopy and under reaction conditions, we identify intermediates of water oxidation catalysed by an abundant metal-oxide catalyst, cobalt oxide (Co3O4). One intermediate is a surface superoxide (three-electron oxidation intermediate absorbing at 1,013 cm(-1)), whereas a second observed intermediate is attributed to an oxo Co(IV) site (one-electron oxidation intermediate absorbing at 840 cm(-1)). The temporal behaviour of the intermediates reveals that they belong to different catalytic sites. Knowledge of the structure and kinetics of surface intermediates will enable the design of improved metal-oxide materials for more efficient water oxidation catalysis. PMID:24651205

Zhang, Miao; de Respinis, Moreno; Frei, Heinz

2014-04-01

196

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

197

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

198

Light-driven water oxidation for solar fuels  

PubMed Central

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

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

2014-01-01

199

Fatigue oxidation interaction in a superalloy—application to life prediction in high temperature low cycle fatigue  

Microsoft Academic Search

A study of the interaction between fatigue and oxidation has been carried out in the case of a cast cobalt base superalloy\\u000a MARM 509 tested in laboratory air at 900 C. The influence of fatigue cycling on oxidation of this alloy has been studied\\u000a by quantitative metallography on polished specimens exposed to air in a furnace and on strain-cycled low-cycle

J. Reuchet; L. Remy

1983-01-01

200

Using MGS TES Data to Understand Water Cycling in Mars' North Polar Region  

NASA Technical Reports Server (NTRS)

The Martian water cycle is one of the three annual cycles on Mars, dust and CO2 being the other two. Despite the fact that detailed spacecraft data, including global and annual coverage in a variety of wavelengths, have been taken of Mars spanning more than 25 years, there are many outstanding questions regarding the water cycle. There is very little exposed water on Mars today, in either the atmosphere or on the surface although there is geological evidence of catastrophic flooding and continuously running water in past epochs in Mars' history as well as recent (within about 10,000 years ago) evidence for running water in the form of gullies. While there is little water in the atmosphere, water- ice clouds do form and produce seasonal clouds caused by general circulation and by storms. These clouds may in turn be controlling the cycling of the water within the general circulation.

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

2003-01-01

201

The diel cycle of water vapor in west Greenland  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

202

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

PubMed

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

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

2012-10-01

203

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

PubMed Central

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

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

2012-01-01

204

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

205

TRMM and Its Connection to the Global Water Cycle  

NASA Technical Reports Server (NTRS)

The importance of quantitative knowledge of tropical rainfall, its associated latent heating and variability is summarized in the context of the global hydrologic cycle. Much of the tropics is covered by oceans. What land exists, is covered largely by rainforests that are only thinly populated. The only way to adequately measure the global tropical rainfall for climate and general circulation models is from space. The TRMM orbit is inclined 35 degrees leading to good sampling in the tropics and a rapid precession to study the diurnal cycle of precipitation. The precipitation instrument complement consists of the first rain radar to be flown in space (PR), a multi-channel passive microwave sensor (TMI) and a five-channel VIS/IR (VIRS) sensor. The precipitation radar operates at a frequency of 13.6 GHz. The swath width is 220 km, with a horizontal resolution of 4 km and the vertical resolution of 250 m. The minimum detectable signal from the precipitation radar has been measured at 17 dBZ. The TMI instrument is designed similar to the SSM/I with two important changes. The 22.235 GHz water vapor absorption channel of the SSM/I was moved to 21.3 GHz in order to avoid saturation in the tropics and 10.7 GHz V&H polarized channels were added to expand the dynamic range of rainfall estimates. The resolution of the TMI varies from 4.6 km at 85 GHz to 36 km at 10.7 GHz. The visible and infrared sensor (VIRS) measures radiation at 0.63, 1.6, 3.75, 10.8 and 12.0 microns. The spatial resolution of all five VIRS channels is 2 km at nadir. In addition to the three primary rainfall instruments, TRMM will also carry a Lightning Imaging Sensor (LIS) and a Clouds and the Earth's Radiant Energy System (CERES) instrument. This presentation will focus primarily on the advances in our understanding of tropical rain systems needed to interpret the TRMM data. Global averages, as well as case studies from TRMM radar (PR), the TRMM Microwave Imager (TMI) and Visible and Infrared Sensor (VIRS) will be presented. Comparisons and contrasts among the different sensors will be drawn. Results will also be compared to previous rainfall climatologies generated from the SSM/I instrument. In particular this paper will focus on the synergy between the TRMM radar and passive microwave radiometer and what we have learned from is synergy.

Kummerow, Chiristian

1999-01-01

206

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

PubMed

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

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

2013-06-12

207

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

E-print Network

& Mechanisms Scatterometer & Radiometer The Aquarius mission will make new discoveries about the oceanSea Surface Salinity Understanding the Interactions Between the Global Water Cycle, Ocean to discover how our oceans respond to climate change and the water cycle. Routine Ship and Buoy Observations

Waliser, Duane E.

208

Vol. 16, No. 2 May 2006Global Energy and Water Cycle Experiment World Climate Research Programme  

E-print Network

's climate system is an energy cycle that converts absorbed solar radiation into heat and associated by the exchanges of energy and water. Although some statistics of these varia- tions may be static, the energyNEWSNEWS Vol. 16, No. 2 May 2006Global Energy and Water Cycle Experiment World Climate Research

209

Photoelectrochemical oxidation of water at transparent ferric oxide film electrodes.  

PubMed

The fabrication of thin-film Fe(2)O(3) photoanodes from the spray pyrolysis of Fe(III)-containing solutions is reported along with their structural characterization and application to the photoelectrolysis of water. These films combine good performance, measured in terms of photocurrent density, with excellent mechanical stability. A full investigation into the effects that modifications of the spray-pyrolysis method, such as the addition of dopants or structure-directing agents and changes in precursor species or carrier solvent, have on the performance of the photoanodes has been realized. The largest photocurrents were obtained from photoanodes prepared from ferric chloride precursor solutions, simultaneously doped with Ti(4+) (5%) and Al(3+) (1%). Doping with Zn(2+) also shows promise, cathodically shifting the onset potential by approximately 0.22 V. PMID:16852715

Jorand Sartoretti, Chantal; Alexander, Bruce D; Solarska, Renata; Rutkowska, Iwona A; Augustynski, Jan; Cerny, Radovan

2005-07-21

210

Characteristics of plutonium-topped thorium cycles in heavy-water-moderated pressure tube reactors  

Microsoft Academic Search

Thorium cycles in heavy-water-moderated pressure tube reactors are expected to lead to much better nuclear fuel utilization than the current natural uranium once-through fuel cycle. The extent to which various parameters affect fuel cycle economics and uranium requirements during the approach to equilibrium conditions for first-generation plutonium-topped thorium cycle reactors has been studied. The results are compared with systems in

S. Banerjee; F. W. Barclay

1979-01-01

211

XENOWAC 2009 International Conference on Xenobiotics in the Urban Water Cycle  

E-print Network

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

Boyer, Edmond

212

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

213

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

Microsoft Academic Search

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

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

2011-01-01

214

Subcritical and supercritical water oxidation of CELSS model wastes  

NASA Technical Reports Server (NTRS)

A mixture of ammonium hydroxide with acetic acid and a slurry of human feces, urine, and wipes were used as CELSS model wastes to be wet-oxidized at temperatures from 250 to 500 C, i.e. below and above the critical point of water (374 C and 218 kg/sq cm or 21.4 MPa). The effects of oxidation temperature ( 250-500 C) and residence time (0-120 mn) on carbon and nitrogen and on metal corrosion from the reactor material were studied. Almost all of the organic matter in the model wastes was oxidized in the temperature range from 400 to 500 C, above the critical conditions for water. In contrast, only a small portion of the organic matter was oxidized at subcritical conditions. A substantial amount of nitrogen remained in solution in the form of ammonia at temperatures ranging from 350 to 450 C suggesting that, around 400 C, organic carbon is completely oxidized and most of the nitrogen is retained in solution. The Hastelloy C-276 alloy reactor corroded during subcritical and supercritical water oxidation.

Takahashi, Y.; Wydeven, T.; Koo, C.

1989-01-01

215

Thermal cycling of carbon\\/epoxy laminates in neutral and oxidative environments  

Microsoft Academic Search

Dealing with the “French Supersonic Aircraft Research Program”, thermal cycling tests in two environments, neutral (nitrogen) and oxidative (air), were performed on three different carbon\\/epoxy laminates: [03\\/903]S, [453\\/?453]S and QI [45\\/0\\/?45\\/90]S. This experimental study was conducted following a local approach through microscopic observations and X-radiographs and showed a significant effect of the oxygen level on the damage development. In fact,

S. Rouquie; M. C. Lafarie-Frenot; J. Cinquin; A. M. Colombaro

2005-01-01

216

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

Microsoft Academic Search

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

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

2010-01-01

217

Attenuated total reflectance infrared spectroscopy study of hysteresis of water and n-alcohol coadsorption on silicon oxide.  

PubMed

The structure and thickness of the binary adsorbate layers formed on silicon oxide exposed in n-propanol/water and n-pentanol/water vapor mixtures under atmospheric pressure and room temperature conditions were investigated using attenuated total reflectance infrared spectroscopy (ATR-IR). The ATR-IR spectra of the adsorbate layers were analyzed while the vapor composition was varied stepwise by changing the mixing ratios of (a) n-propanol vapor stream with a 94% relative partial pressure (P/P(sat)) and 94% P/P(sat) water stream and (b) 83% P/P(sat)n-pentanol and 85% P/P(sat) water streams. The amount of the adsorbed water with solid-like structure in the binary adsorbate layer was larger in successive cycles of the water/alcohol vapor composition change, while n-alcohol showed negligible hysteresis in the amount adsorbed. The hysteresis behavior of the solid-like water structure was amplified in the coadsorption cycles of alcohol and water as compared to the water-only case. The origin of this behavior must be attributed to the structure of the alcohol/water binary adsorbate layer. The n-alcohol molecules present at the adsorbate/vapor interface can lower the surface energy of the system and stabilize the solid-like water structure in the alcohol-water binary adsorbate layer on silicon oxide. PMID:23098071

Barnette, Anna L; Kim, Seong H

2012-11-01

218

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

PubMed Central

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

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

2011-01-01

219

What are the oxidation states of manganese required to catalyze photosynthetic water oxidation?  

PubMed

Photosynthetic O(2) production from water is catalyzed by a cluster of four manganese ions and a tyrosine residue that comprise the redox-active components of the water-oxidizing complex (WOC) of photosystem II (PSII) in all known oxygenic phototrophs. Knowledge of the oxidation states is indispensable for understanding the fundamental principles of catalysis by PSII and the catalytic mechanism of the WOC. Previous spectroscopic studies and redox titrations predicted the net oxidation state of the S(0) state to be (Mn(III))(3)Mn(IV). We have refined a previously developed photoassembly procedure that directly determines the number of oxidizing equivalents needed to assemble the Mn(4)Ca core of WOC during photoassembly, starting from free Mn(II) and the Mn-depleted apo-WOC complex. This experiment entails counting the number of light flashes required to produce the first O(2) molecules during photoassembly. Unlike spectroscopic methods, this process does not require reference to synthetic model complexes. We find the number of photoassembly intermediates required to reach the lowest oxidation state of the WOC, S(0), to be three, indicating a net oxidation state three equivalents above four Mn(II), formally (Mn(III))(3)Mn(II), whereas the O(2) releasing state, S(4), corresponds formally to (Mn(IV))(3)Mn(III). The results from this study have major implications for proposed mechanisms of photosynthetic water oxidation. PMID:22853909

Kolling, Derrick R J; Cox, Nicholas; Ananyev, Gennady M; Pace, Ron J; Dismukes, G Charles

2012-07-18

220

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

221

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

222

Water formation via HCl oxidation on Cu(1 0 0)  

NASA Astrophysics Data System (ADS)

Using density functional theory and periodic slabs, we have studied water formation via HCl oxidation on the Cu(1 0 0) surface. We show that while adsorbed chlorine increases the stability of water on the Cu(1 0 0) surface, water molecules dissociate immediately when located next to an oxygen atom. We also show that these competing interactions, when arising from HCl reacting with oxygen on Cu(1 0 0), lead to water formation according to two different pathways depending on the temperature and oxygen coverage.

Suleiman, Ibrahim A.; Radny, Marian W.; Gladys, Michael J.; Smith, Phillip V.; Mackie, John C.; Stockenhuber, Michael; Kennedy, Eric M.; Dlugogorski, Bogdan Z.

2014-04-01

223

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

224

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

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

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

2013-11-19

225

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

226

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

PubMed

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

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

2014-11-15

227

Pulsed-laser deposition of nanostructured iron oxide catalysts for efficient water oxidation.  

PubMed

Amorphous iron oxide nanoparticles were synthesized by pulsed-laser deposition (PLD) for functionalization of indium-tin oxide surfaces, resulting in electrodes capable of efficient catalysis in water oxidation. These electrodes, based on earth-abundant and nonhazardous iron metal, are able to sustain high current densities (up to 20 mA/cm2) at reasonably low applied potential (1.64 V at pH 11.8 vs reversible hydrogen electrode) for more than 1 h when employed as anodes for electrochemical water oxidation. The good catalytic performance proves the validity of PLD as a method to prepare nanostructured solid-state materials for catalysis, enabling control over critical properties such as surface coverage and morphology. PMID:24742340

Orlandi, Michele; Caramori, Stefano; Ronconi, Federico; Bignozzi, Carlo A; El Koura, Zakaria; Bazzanella, Nicola; Meda, Laura; Miotello, Antonio

2014-05-14

228

Cycle oxidation behavior of nanostructured Ni60-TiB 2 composite coating sprayed by HVOF technique  

NASA Astrophysics Data System (ADS)

Cycle oxidation resistance at 800 °C in static air was investigated for a nanostructured Ni60-TiB 2 composite coating sprayed by high velocity oxy-fuel (HVOF). For comparison, a Ni60-TiB 2 conventional composite coating was also studied. The results indicate that, the oxidation processes of both composite coatings are controlled by diffusion mechanism, and the nanostructured composite coating has better cycle oxidation resistance than that of the conventional composite coating. The reasons for this improvement can be attributed to the formation of the intact SiO 2 and Cr 2O 3 protective layer, and the enhanced adhesion between oxide film and nanostructure coating.

Wu, Y. S.; Qiu, W. Q.; Yu, H. Y.; Zhong, X. C.; Liu, Z. W.; Zeng, D. C.; Li, S. Z.

2011-09-01

229

Vibrational properties of water retained in graphene oxide  

NASA Astrophysics Data System (ADS)

Vibrational properties of water molecules retained in the interlayer space of graphene oxide were studied by combining inelastic neutron scattering spectroscopy with density functional theory calculations. The credibility of Lerf-Klinowski model in the description of the amplitude weighted vibrational density of states has been successfully examined. The solid-state plane-wave DFT computations have delivered satisfying qualitative interpretation of the INS spectrum, which was found to be mainly driven by the vibrational dynamics of the retained water.

Dru?bicki, Kacper; Natkaniec, Ireneusz

2014-04-01

230

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

231

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

232

Mobility of Water on Oxide Surfaces Studied by QENS  

SciTech Connect

Although neutron scattering is often considered a bulk probe, we demonstrate that the mobility of surface water on oxide nano-powders can be investigated using quasielastic neutron scattering. We discuss how the reduced number of hydrogen bonds per water molecule associated with surface confinement leads to a qualitative modification of single-particle translational dynamics compared to bulk water. The mobility of surface water in zirconium oxide with two hydration layers present is discussed in detail. The outer hydration layer exhibits translational dynamics on the time scale of tens of picoseconds, and thus can be studied using time-of-flight neutron spectrometry. The translational dynamics of the inner hydration layer in the range of hundreds of picoseconds can be assessed with backscattering neutron spectrometry. Interestingly, despite being slower by two orders of magnitude, the translational motion of the molecules of the inner hydration layer may share more common traits with bulk water compared to the motion of the outer hydration layer, the dynamics of which is slower than that of bulk water by just one order of magnitude. Similar to bulk water, the temperature dependence of the residence time for the water molecules of the inner hydration layer is non-Arrhenius, and can be described by a Vogel-Fulcher-Tammann (VFT) law. On the other hand, the molecules of the outer hydration layer demonstrate Arrhenius-type temperature dependence indicative of thermally activated surface jump diffusion. Our recent study of surface water on cerium oxide, which exhibits faster dynamics compared to water on zirconium oxide, has ventured into the low-temperature region (down to 200 K). Below 215 K, we have found a deviation from the VFT temperature dependence for the residence time indicative of a surprise "fragile"-to-"strong" transition in the surface water. While "fragile"-to-"strong" transition has been predicted in supercooled bulk water, there has been no prediction of such a transition in surface water. We discuss the links between our results and recent work on hydration water in carbon nanotubes and proteins.

Mamontov, Eugene [ORNL

2007-01-01

233

Photochemical water oxidation by crystalline polymorphs of manganese oxides: structural requirements for catalysis.  

PubMed

Manganese oxides occur naturally as minerals in at least 30 different crystal structures, providing a rigorous test system to explore the significance of atomic positions on the catalytic efficiency of water oxidation. In this study, we chose to systematically compare eight synthetic oxide structures containing Mn(III) and Mn(IV) only, with particular emphasis on the five known structural polymorphs of MnO2. We have adapted literature synthesis methods to obtain pure polymorphs and validated their homogeneity and crystallinity by powder X-ray diffraction and both transmission and scanning electron microscopies. Measurement of water oxidation rate by oxygen evolution in aqueous solution was conducted with dispersed nanoparticulate manganese oxides and a standard ruthenium dye photo-oxidant system. No Ru was absorbed on the catalyst surface as observed by XPS and EDX. The post reaction atomic structure was completely preserved with no amorphization, as observed by HRTEM. Catalytic activities, normalized to surface area (BET), decrease in the series Mn2O3 > Mn3O4 ? ?-MnO2, where the latter is derived from spinel LiMn2O4 following partial Li(+) removal. No catalytic activity is observed from LiMn2O4 and four of the MnO2 polymorphs, in contrast to some literature reports with polydispersed manganese oxides and electro-deposited films. Catalytic activity within the eight examined Mn oxides was found exclusively for (distorted) cubic phases, Mn2O3 (bixbyite), Mn3O4 (hausmannite), and ?-MnO2 (spinel), all containing Mn(III) possessing longer Mn-O bonds between edge-sharing MnO6 octahedra. Electronically degenerate Mn(III) has antibonding electronic configuration e(g)(1) which imparts lattice distortions due to the Jahn-Teller effect that are hypothesized to contribute to structural flexibility important for catalytic turnover in water oxidation at the surface. PMID:23391134

Robinson, David M; Go, Yong Bok; Mui, Michelle; Gardner, Graeme; Zhang, Zhijuan; Mastrogiovanni, Daniel; Garfunkel, Eric; Li, Jing; Greenblatt, Martha; Dismukes, G Charles

2013-03-01

234

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

235

Water Oxidation Catalysis DOI: 10.1002/anie.201106337  

E-print Network

energy is envisioned to drive the chemical reduction of carbon dioxide to ultimately give commodity chemicals that may be used as fuel. Inspired by natural photosynthesis, water oxidation is considered the ideal source for the electrons required to reduce one molecule of carbon dioxide. Recently, much

Baik, Mu-Hyun

236

Cobalt porphyrin electrode films for electrocatalytic water oxidation.  

PubMed

Catalysts play very important roles in artificial photosynthesis for solar energy conversion. In this present study, two water-insoluble cobalt porphyrin complexes, cobalt(II) meso-tetraphenylporphyrin (CoP-1) and cobalt(II) 5,10,15,20-tetrakis-(4-bromophenyl)porphyrin (CoP-2), were synthesized and coated as thin films on the FTO working electrode. The films showed good activities for electrocatalytic water oxidation in aqueous solutions at pH 9.2. The Faradaic efficiencies of both films approached to ~100%, measured using a fluorescence-based oxygen sensor. The turnover frequencies were close to 0.50 s(?1) and 0.40 s(?1) for CoP-1 and CoP-2, respectively, under an applied anodic potential of 1.3 V (vs. Ag/AgCl) at pH 9.2. Importantly, no cobalt oxide particles were observed on the working electrode after catalysis. The stability of the catalyst films was further evaluated by UV-vis spectroscopy, inhibition measurements, mass spectrometry, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The pH dependence of water oxidation on CoP-1 and CoP-2 suggested a proton-coupled electron transfer (PCET) mechanism. The catalyst films could be recycled and showed almost unchanged catalytic activities when they were reused in new electrocatalytic studies of water oxidation. PMID:24777036

Han, Ali; Jia, Hongxing; Ma, Hao; Ye, Shifan; Wu, Haotian; Lei, Haitao; Han, Yongzhen; Cao, Rui; Du, Pingwu

2014-06-21

237

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

238

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

239

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

E-print Network

Ecological Modelling xxx (2005) xxx­xxx Modelling carbon and water cycles in a beech forest Part I, stems, branches, coarse and fine roots, evapotranspira- tion, soil heterotrophic respiration, water on simulated NEE. Finally 17 parameters, linked to photosynthesis, vegetative respiration and soil water

Boyer, Edmond

240

Modelling and simulation of a water desalination station with solar multiple condensation evaporation cycle technique  

Microsoft Academic Search

This paper presents the study of a new generation of water desalination installation by solar energy using the SMCEC principle (Solar Multiple Condensation Evaporation Cycle). The good quality of distilled water obtained by this new concept favours its use for producing water for drinking and irrigation. The work presented in this paper includes modelling, simulation and experimental validation for this

H. Ben Bacha; M. Bouzguenda; M. S. Abid; A. y. Maalej

1999-01-01

241

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

PubMed Central

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

Wilcox, Christopher S.

2010-01-01

242

?-Oxidation and Glyoxylate Cycle Coupled to NADH: Cytochrome c and Ferricyanide Reductases in Glyoxysomes 1  

PubMed Central

Glyoxysomes isolated from castor bean (Ricinus communis L., var Hale) endosperm had NADH:ferricyanide reductase and NADH:cytochrome c reductase activities averaging 720 and 140 nanomole electrons/per minute per milligram glyoxysomal protein, respectively. These redox activities were greater than could be attributed to contamination of the glyoxysomal fractions in which 1.4% of the protein was mitochondrial and 5% endoplasmic reticulum. The NADH:ferricyanide reductase activity in the glyoxysomes was greater than the palmitoyl-coenzyme A (CoA) oxidation activity which generated NADH at a rate of 340 nanomole electrons per minute per milligram glyoxysomal protein. Palmitoyl-CoA oxidation could be coupled to ferricyanide or cytochrome c reduction. Complete oxidation of palmitoyl-CoA, yielding 14 nanomole electrons/per nanomole palmitoyl-CoA, was demonstrated with the acceptors, NAL, cytochrome c, and ferricyanide. Malate was also oxidized by glyoxysomes, if acetyl-CoA, ferricyanide, or cytochrome c was present. Glyoxysomal NADH:ferricyanide reductase activity has the capacity to support the combined rates of NADH generation by ?-oxidation and the glyoxylate cycle. PMID:16665778

Donaldson, Robert P.; Fang, Tung K.

1987-01-01

243

Thermodynamic analysis of injected water recovery systems for the humid air turbine (HAT) cycle  

SciTech Connect

The Humid Air Turbine (HAT) cycle is an inter-cooled gas turbine cycle, having an air-water mixing evaporator before the combustion chamber, and a heat recovering system for the exhaust gases. The considerable amount of water consumed in the mixing evaporator (about 1,200--2,400 m{sup 3} daily for a 100 MW unit), represents a significant drawback to the use of the HAT cycle as well as of other steam injected gas turbines. In fact, this means high operational costs for water treatment, and eventual legislative restrictions limiting the use of water, not to mention the environmental impact of the depletion of water resources. The aim of this paper is to evaluate the changes in the performance of the HAT cycle when a water recovery system is added in the exhaust gases, and to determine the heat exchangers conditions for maximum water and heat recovery. Finally, the size of a surface condenser for water recovery is determined for a given HAT cycle power output. The results show the possibility to recover up to 85% of the consumed water and up to 30% of input heat from the condensation of the water contained in the exhaust gas. The paper also examines all the thermodynamic processes in each cycle component from the viewpoint of recovering water from the exhaust gas. Since part of the water contained in the exhaust gas is due to the inlet air humidity and the combustion process, the relative amount of water and their contributions to the overall heat recovery are also calculated.

Bidini, G.; Desideri, U.; Di Maria, F. [Univ. di Perugia (Italy). Ist. di Energetica

1996-12-31

244

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

245

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

246

An Intensified Arctic Water Cycle? Trend Analysis of the Arctic System Freshwater Cycle: Observations and Expectations  

Microsoft Academic Search

It is expected that a warming climate will be attended by an intensification of the global hydrological cycle. While there are signs of positive trends in several hydrological quantities emerging at the global scale, the scope, character, and quantitative significance of these changes are not well established. In particular, long-term increases in river discharge across Arctic Eurasia are assumed to

M. A. Rawlins; J. C. Adam; C. J. Vorosmarty; M. C. Serreze; L. D. Hinzman; M. Holland; A. Shiklomanov

2007-01-01

247

Natural streamflow cycles and effects on water supply reliability  

E-print Network

is not explicitly considered in the WAM Project. The main objective of this thesis is to assess the significance of potential impacts of climate change trends and cycles in the Texas WAM. The study focuses on the Brazos River Basin that constitutes one...

Felden, Fabrice

2012-06-07

248

Light-harvesting photocatalysis for water oxidation using mesoporous organosilica.  

PubMed

An organic-based photocatalysis system for water oxidation, with visible-light harvesting antennae, was constructed using periodic mesoporous organosilica (PMO). PMO containing acridone groups in the framework (Acd-PMO), a visible-light harvesting antenna, was supported with [Ru(II)(bpy)3(2+)] complex (bpy = 2,2'-bipyridyl) coupled with iridium oxide (IrO(x)) particles in the mesochannels as photosensitizer and catalyst, respectively. Acd-PMO absorbed visible light and funneled the light energy into the Ru complex in the mesochannels through excitation energy transfer. The excited state of Ru complex is oxidatively quenched by a sacrificial oxidant (Na2S2O8) to form Ru(3+) species. The Ru(3+) species extracts an electron from IrO(x) to oxidize water for oxygen production. The reaction quantum yield was 0.34?%, which was improved to 0.68 or 1.2?% by the modifications of PMO. A unique sequence of reactions mimicking natural photosystem?II, 1)?light-harvesting, 2)?charge separation, and 3)?oxygen generation, were realized for the first time by using the light-harvesting PMO. PMID:24890840

Takeda, Hiroyuki; Ohashi, Masataka; Goto, Yasutomo; Ohsuna, Tetsu; Tani, Takao; Inagaki, Shinji

2014-07-14

249

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

250

Reaction of catalytic oxidation by liquid water and its application to waste water purification  

SciTech Connect

In this paper the results of experiments and some considerations of theoretical and practical problems devoted to a new type of chemical reaction--oxidation of organic substances by liquid water with the aid of noble metal catalyst--are given. Some problems of application such as reaction to self-purification of industrial waste waters are also considered.

Ioffe, I.I. [All-Union Inst. of Pulp and Paper Industry, Leningrad (Russian Federation)] [All-Union Inst. of Pulp and Paper Industry, Leningrad (Russian Federation); Rubinskaya, E.V. [All-Union Inst. of Petrochemical Processes, Leningrad (Russian Federation)] [All-Union Inst. of Petrochemical Processes, Leningrad (Russian Federation)

1997-06-01

251

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

252

Paralinear Oxidation of CVD SiC in Water Vapor  

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

253

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

254

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

NSDL National Science Digital Library

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

255

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

256

Concept for a small, colocated fuel cycle facility for oxide breeder fuels  

SciTech Connect

As part of a United States Department of Energy (USDOE) program to examine innovative liquid-metal reactor (LMR) system designs over the past three years, the Oak Ridge National Laboratory (ORNL) and the Westinghouse Hanford Company (WHC) collaborated on studies of mixed oxide fuel cycle options. A principal effort was an advanced concept for a small integrated fuel cycle colocated with a 1300-MW(e) reactor station. The study provided a scoping design, capital and operating cost estimates, and a basis on which to proceed with implementation of such a facility if future plans so dictate. The facility integrated reprocessing, waste management, and refabrication functions in a single facility of nominal 35-t/year capacity utilizing the latest technology developed in fabrication programs at WHC and in reprocessing at ORNL. The concept was based on many years of work at both sites and extensive design studies of prior years.

Burch, W.D.; Lerch, R.E.; Stradley, J.G.

1987-01-01

257

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

NASA Astrophysics Data System (ADS)

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 (?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, Rene; Jansz, Melan; Mossaddad, Mitra; Raghavan, Seetha; Okasinski, John; Almer, Jonathan; Pelaez-Perez, Hugo; Imbrie, Peter

2012-03-01

258

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

259

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

260

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

PubMed

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

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

2013-11-01

261

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

PubMed Central

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. 15NO2? 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. 15NO2? 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 (r2=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, 15NO2? oxidation rates were decoupled from 15NH4+ oxidation rates, but correlated with Nitrospina (r2=0.246, P<0.05) and NO2? concentrations (r2=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

2013-01-01

262

Time-resolved observations of water oxidation intermediates on a cobalt oxide  

E-print Network

, using time-resolved Fourier-transform infrared spectroscopy and under reaction conditions, we identify to molecular oxygen is a step common to all approaches to converting sunlight to fuel, whether biological, understanding Nature's water oxidation mechanism in photosystem II (from green plants and bacteria) has been

Cai, Long

263

Solubility of lead(II) oxide and copper(II) oxide in subcritical and supercritical water  

SciTech Connect

The solubilities of lead oxide (PbO) and copper oxide (CuO) in subcritical and supercritical water were measured at temperatures from 250 C to 500 C and pressures from 26 MPa to 34 MPa, in a flow-type apparatus. The solubility of lead oxide varied from 351 {micro}mol/kg H{sub 2}O at 424.9 C and 25.9 MPa to 4,406 {micro}mol/kg H{sub 2}O at 350.3 C and 30.2 MPa. The solubility of copper oxide varied from 1.3 {micro}mol/kg H{sub 2}O at 339.8 C and 28.0 MPa to 8.0 {micro}mol/kg H{sub 2}O at 324.9 C and 28.1 MPa. A hydration reaction model was applied to correlate the data.

Sue, Kiwamu; Hakuta, Yukiya; Smith, R.L. Jr.; Adschiri, Tadafumi; Arai, Kunio

1999-12-01

264

Photochemical route for accessing amorphous metal oxide materials for water oxidation catalysis.  

PubMed

Large-scale electrolysis of water for hydrogen generation requires better catalysts to lower the kinetic barriers associated with the oxygen evolution reaction (OER). Although most OER catalysts are based on crystalline mixed-metal oxides, high activities can also be achieved with amorphous phases. Methods for producing amorphous materials, however, are not typically amenable to mixed-metal compositions. We demonstrate that a low-temperature process, photochemical metal-organic deposition, can produce amorphous (mixed) metal oxide films for OER catalysis. The films contain a homogeneous distribution of metals with compositions that can be accurately controlled. The catalytic properties of amorphous iron oxide prepared with this technique are superior to those of hematite, whereas the catalytic properties of a-Fe(100-y-z)Co(y)Ni(z)O(x) are comparable to those of noble metal oxide catalysts currently used in commercial electrolyzers. PMID:23539180

Smith, Rodney D L; Prévot, Mathieu S; Fagan, Randal D; Zhang, Zhipan; Sedach, Pavel A; Siu, Man Kit Jack; Trudel, Simon; Berlinguette, Curtis P

2013-04-01

265

Methane oxidation in water-spreading and compost biofilters.  

PubMed

This study evaluated two biofilter designs to mitigate methane emissions from landfill vents. Water-spreading biofilters were designed to use the capillarity of coarse sand overlain by a finer sand to increase the active depth for methane oxidation. Compost biofilters consisted of 238-L barrels containing a 1:1 mixture (by volume) of compost to expanded polystyrene pellets. Two replicates of each type of biofilter were tested at an outdoor facility. Gas inflow consisted of an approximately 1:1 mixture (by volume) of CH4 and CO2. Methane output rates (J(out); g m(-2) day(-1)) were measured using the static chamber technique and the Pedersen et al. (2001) diffusion model. Methane oxidation rate (J(ox); g m(-2) day(-1)) and fraction of methane oxidized (f(ox)) were determined by mass balance. For methane inflow rates (J(in)) between 250 and 500 g m(-2) day(-1), the compost biofilter J(ox), 242 g m(-2) day(-1), was not significantly different (P = 0.0647) than the water-spreading biofilter J(ox), 203 g m(-2) day(-1); and the compost f(ox), 69%, was not significantly different (P = 0.7354) than water-spreading f(ox), 63%. The water-spreading biofilter was shown to generally perform as well as the compost biofilter, and it may be easier to implement at a landfill and require less maintenance. PMID:17252999

Powelson, David K; Chanton, Jeffery; Abichou, Tarek; Morales, Jose

2006-12-01

266

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

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

267

Understanding Global Water Cycle Variability From Satellite, In-situ and Model Reanalysis  

NASA Astrophysics Data System (ADS)

This study quantifies the global water cycle variability using the Global Precipitation Climatology Project (GPCP), gauge measurement, the National Centers for Environmental Prediction (NCEP) and the National Center for Atmospheric Research (NCAR) reanalysis and the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis. Preliminary results demonstrate that the occurrences of water cycle extreme variability increase globally with the time. The climate date suites consistently display wet trend over the northwestern Pacific, Atlantic Ocean, the southern Pacific, Amazon basin, and western Australian, whereas tremendous dry trend is noticed over mid-Africa, east Asia and western America. Globally speaking, the trend of water cycle variation is strong in winter but weak in fall although the trend exhibits regional dependent behavior. For instance, over the contiguous United States, significant wet trend is noted over the southern region in summer, while southwest region exhibits persistent dry trend during the entire four seasons. Further analysis will investigate the trend variation in evaporation, runoff and soil moisture. Spatial patterns of water cycle variability at region and global scales will also be identified to explore the relationship of sea surface temperature and soil moisture anomalies with the water cycle variation to further gain insight into the utility of slow varying boundary conditions for the useful prediction of water cycle variability.

Feng, X.; Houser, P.

2008-05-01

268

Water Sorption and Gamma Radiolysis Studies for Uranium Oxides  

SciTech Connect

Experiments have been performed in our laboratory on water sorption and radiolysis for uranium oxides. For the water sorption experiments, uranium oxide samples were prepared and exposed to known levels of humidity to establish the water uptake rate. Subsequently, the amount of water removed was studied by heating samples in an oven at fixed temperatures and by differential thermal analysis/thermogravimetric analysis. It was demonstrated that heating at 650 deg. C adequately removes all moisture from the samples. Uranium-238 oxides were irradiated in a {sup 60}Co source and in the high-gamma-radiation fields provided by spent nuclear fuel elements of the High Flux Isotope Reactor. For hydrated samples of UO{sub 3}, the primary gas produced was H{sub 2}; however, the maximum pressure increase reached a steady-state value of {approx}500 torr (10 psi). This H{sub 2} production appears to be a function of the dose and the amount of water present. Oxygen in the hydrated UO{sub 3} sample atmosphere was typically depleted, and no significant pressure rise was observed. Heat treatment of the UO{sub 3}.xH{sub 2}O at 650 deg. C results in conversion to U{sub 3}O{sub 8} and eliminates the H{sub 2} production. For all of the U{sub 3}O{sub 8} samples loaded in air and irradiated with gamma radiation, a pressure decrease was seen and little, if any, H{sub 2} was produced - even for samples with up to 9 wt% moisture content. Hence, these results demonstrated that the efforts to remove trace moisture from U{sub 3}O{sub 8} are not necessary to avoid pressurization of stored uranium oxides caused by gamma-induced radiolysis. In fact, this system can tolerate several percent of sorbed moisture.

Icenhour, Alan S.; Toth, L. M.; Luo Huimin [Oak Ridge National Laboratory (United States)

2004-08-15

269

Rapid thermal oxidation of silicon with different thermal annealing cycles in nitrogen: Influence on surface microroughness and electrical characteristics  

Microsoft Academic Search

The influence of two different thermal annealing cycles on the microroughness of the Si-SiO2 interface and on the electrical characteristics of the Si-SiO2 system has been investigated. Experiments were performed growing oxides by rapid thermal oxidation (RTO) and post-oxidation annealing in N2 using a slow cooling ramp recipe (SCRR) or a conventional pulsed thermal annealing recipe (PTAR). Compared to PTAR,

S. G. dos Santos Filho; C. M. Hasenack; M. C. V. Lopes; V. Baranauskas

1995-01-01

270

Advances In Understanding Global Water Cycle With Advent of GPM Mission  

NASA Technical Reports Server (NTRS)

During the coming decade, the internationally organized Global Precipitation Measurement (GPM) Mission will take an important step in creating a global precipitation observing system from space based on an international fleet of satellites operated as a constellation. One perspective for understanding the nature of GPM is that it will be a hierarchical system of datastreams beginning with very high caliber combined dual frequency radar/passive microwave (PMW) rain-radiometer retrievals, to high caliber PMW rain-radiometer only retrievals, and then on to blends of the former datastreams with additional lower-caliber PMW-based and IR-based rain retrievals. Within the context of the now emerging global water & energy cycle (GWEC) programs of a number of research agencies throughout the world, GPM serves as a centerpiece space mission for improving our understanding of the Earth's water cycle from a global measurement perspective and on down to regional scales and below. One of the salient problems within our current understanding of the global water and energy cycle is determining whether a change in the rate of the water cycle is accompanying changes in climate, e.g., climate warming. As there are a number of ways in which to define a rate-change of the global water cycle, it is not entirely clear as to what constitutes such a determination. This paper first presents an overview of the GPM Mission and how its overriding scientific objectives for climate, weather, and hydrology flow from the anticipated improvements that are being planned for the constellation-based measuring system. Next, the paper shows how the GPM observations can be used within the framework of the oceanic and continental water budget equations to determine whether a given perturbation in precipitation is indicative of an actual rate change in the water cycle, consistent with required responses in water storage and/or water flux transport processes, or whether it is simply part of the natural variability of a fixed rate cycle.

Smith, Eric A.

2002-01-01

271

Advances in Understanding Global Water Cycle with Advent of Global Precipitation Measurement (GPM) Mission  

NASA Technical Reports Server (NTRS)

Within this decade the internationally organized Global Precipitation Measurement (GPM) Mission will take an important step in creating a global precipitation observing system from space. One perspective for understanding the nature of GPM is that it will be a hierarchical system of datastreams beginning with very high caliber combined dual frequency radar/passive microwave (PMW) rain-radiometer retrievals, to high caliber PMW rain-radiometer only retrievals, and then on to blends of the former datastreams with additional lower-caliber PMW-based and IR-based rain retrievals. Within the context of the now emerging global water & energy cycle (GWEC) programs of a number of research agencies throughout the world, GPM serves as a centerpiece space mission for improving our understanding of the global water cycle from a global measurement perspective. One of the salient problems within our current understanding of the global water and energy cycle is determining whether a change in the rate of the water cycle is accompanying changes in climate, e.g., climate warming. As there are a number of ways in which to define a rate-change of the global water cycle, it is not entirely clear as to what constitutes such a determination. This paper presents an overview of the GPM Mission and how its observations can be used within the framework of the oceanic and continental water budget equations to determine whether a given perturbation in precipitation is indicative of an actual rate change in the global water cycle, consistent with required responses in water storage and/or water flux transport processes, or whether it is the natural variability of a fixed rate cycle.

Smith, Eric A.; Starr, David (Technical Monitor)

2002-01-01

272

Relationship Between GPM Mission and NASA's Global Water Cycle Research Program  

NASA Technical Reports Server (NTRS)

During the coming decade, the internationally organized Global Precipitation Measurement (GPM) Mission will take an important step in creating a global precipitation observing system from space based on an international fleet of satellites operated as a constellation of opportunity. One perspective for understanding the nature of GPM is that it will be a hierarchical system of datastreams beginning with very high caliber combined dual frequency radar/passive microwave (PMW) rain-radiometer retrievals, to high caliber PMW rain- radiometer only retrievals, and then on to blends of the former datastreams with additional lower-caliber PMW-based and IR-based rain retrievals. Within the context of the now emerging global water & energy cycle (GWEC) programs of a number of research agencies throughout the world, GPM serves as a centerpiece space mission for improving our understanding of the Earth's water cycle from a global measurement perspective and on down to regional scales and below. One of the salient problems within our current understanding of the global water and energy cycle is determining whether a change in the rate of the water cycle is accompanying changes in climate, e.g., climate warming. As there are a number of ways in which to define a rate- change of the global water cycle, it is not entirely clear as to what constitutes such a determination. This paper first presents an overview of the GPM Mission and how its overriding scientific objectives for climate, weather, and hydrology flow from the anticipated improvements that are being planned for the constellation-based measuring system. Next, the paper shows how the GPM observations can be used within the framework of the oceanic and continental water budget equations to determine whether a given perturbation in precipitation is indicative of an actual rate change in the water cycle, consistent with required responses in water storage and/or water flux transport processes, or whether it is simply part of the natural variability of a fixed rate cycle.

Smith, Eric A.

2002-01-01

273

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

274

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

275

A self-propelling cycle mediated by reactive oxide species and nitric oxide exists in LPS-activated microglia.  

PubMed

It has been widely accepted that microglia, the innate immune cells in the brain, can be chronically activated in response to neuron death, fuelling a self-renewing cycle of microglial activation followed by further neuron damage (reactive microgliosis), which has been considered as the main reason responsible for the progressive nature of neurodegenerative diseases. In the present study, it was found that LPS (lipopolysaccharide) significantly induced the activation of N9 microglia, and the increase of NO level induced by pretreatment of LPS could last after the removal of LPS. The culture medium of activated microglia significantly decreased the viability of rat primary cortical neuron. These results can be blocked by the antioxidant N-acetylcysteine (NAC) and nicotinamide adenine dinucleotide phosphate reduced (NADPH) oxidase inhibitor diphenyleneiodonium sulfate (DPI), suggesting that intracellular reactive oxide species (iROS) released from the activated microglial cells may continue to further activate microglia. Next, it was shown that the iROS level increased rapidly after the LPS treatment in microglia cells followed by the NO production through the regulation of iNOS (inducible nitric oxide synthase) expression. The increase of iROS could be reversed by gp91phox (the critical and catalytic subunit of NADPH oxidase) siRNA. Moreover, NO released from sodium nitroprusside (SNP) was able to increase the iROS production of N9 microglia by regulating of the activity and the expression of NADPH oxidase. In conclusion, our research suggests for the first time that there may exist a self-propelling cycle in microglial cells possibly mediated by iROS and NO when they become activated by LPS. It may be responsible partially for the ongoing microglial activation and the progressive nature of neurodegenerative diseases. PMID:23000131

Lijia, Zhang; Zhao, Siqi; Wang, Xiaoxiao; Wu, Chunfu; Yang, Jingyu

2012-12-01

276

Two bismuth sulfate-sulfuric acid hybrid water-splitting cycles. Proposed antimonyl sulfate cycle  

SciTech Connect

Some experimental work is presented that is related to two hybrid thermochemical cycles for the production of hydrogen which involve bismuth trisulfate and/or bismuth oxysulfates. Omitting statement of the steps for decomposition of SO/sub 3/ and the electrochemical formation of H/sub 2/ and H/sub 2/SO/sub 4/ from SO/sub 2/ and H/sub 2/O, the high and low temperature reactions are: Cycle I - Bi/sub 2/(SO/sub 4/)/sub 3/ = Bi/sub 2/O/sub 2/ /sub 3/ (SO/sub 4/)/sub 0/ /sub 7/ + 2.3 SO/sub 3/; and Bi/sub 2/O/sub 2/ /sub 3/(SO/sub 4/)/sub 0/ /sub 7/ + 2.3 H/sub 2/SO/sub 4/ = Bi/sub 2/(SO/sub 4/)/sub 3/ + 2.3 H/sub 2/O. Cycle II - Bi/sub 2/O(SO/sub 4/)/sub 2/ = Bi/sub 2/O/sub 2/ /sub 3/(SO/sub 4/)/sub 0/ /sub 7/ + 1.3 SO/sub 3/; and Bi/sub 2/O/sub 2/ /sub 3/(SO/sub 4/)/sub 0/ /sub 7/ + 1.3 H/sub 2/SO/sub 4/ = Bi/sub 2/O(SO/sub 4/)/sub 2/ + 1.3 H/sub 2/O. Equilibrium sulfur trioxide pressures are given graphically for three solid-gas equilibria involving Bi/sub 2/(SO/sub 4/)/sub 3/, ..cap alpha..- and ..beta..-Bi/sub 2/O(SO/sub 4/)/sub 2/, and Bi/sub 2/O/sub 2/SO/sub 4/. An improved method of carrying out the low temperature step for Cycle I is presented which may provide a remedy to a problem of sorption of sulfuric acid solution by the solids. An antimonyl sulfate - sulfuric acid hybrid cycle is outlined in which SO/sub 2/ and O/sub 2/ are evolved at different temperatures, simplifying the usual SO/sub 3/-SO/sub 2/-O/sub 2/ separation problem.

Jones, W.M.

1982-01-01

277

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

PubMed

Two mononuclear ruthenium complexes [Ru(H2 tcbp)(isoq)2 ] (1) and [Ru(H2 tcbp)(pic)2 ] (2) (H4 tcbp=4,4',6,6'-tetracarboxy-2,2'-bipyridine, isoq=isoquinoline, pic=4-picoline) are synthesized and fully characterized. Two spare carboxyl groups on the 4,4'-positions are introduced to enhance the solubility of 1 and 2 in water and to simultaneously allow them to tether to the electrode surface by an ester linkage. The photochemical, electrochemical, and photoelectrochemical water oxidation performance of 1 in neutral aqueous solution is investigated. Under electrochemical conditions, water oxidation is conducted on the deposited indium-tin-oxide anode, and a turnover number higher than 15,000 per water oxidation catalyst (WOC) 1 is obtained during 10?h of electrolysis under 1.42?V vs. NHE, corresponding to a turnover frequency of 0.41?s(-1) . The low overpotential (0.17?V) of electrochemical water oxidation for 1 in the homogeneous solution enables water oxidation under visible light by using [Ru(bpy)3 ](2+) (P1) (bpy=2,2'-bipyridine) or [Ru(bpy)2 (4,4'-(COOEt)2 -bpy)](2+) (P2) as a photosensitizer. In a three-component system containing 1 or 2 as a light-driven WOC, P1 or P2 as a photosensitizer, and Na2 S2 O8 or [CoCl(NH3 )5 ]Cl2 as a sacrificial electron acceptor, a high turnover frequency of 0.81?s(-1) and a turnover number of up to 600 for 1 under different catalytic conditions are achieved. In a photoelectrochemical system, the WOC 1 and photosensitizer are immobilized together on the photoanode. The electrons efficiently transfer from the WOC to the photogenerated oxidizing photosensitizer, and a high photocurrent density of 85??A?cm(-2) is obtained by applying 0.3?V bias vs. NHE. PMID:25205065

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

2014-10-20

278

Low-Temperature Oxidation of silicon nitride by water in supercritical condition  

Microsoft Academic Search

Oxidation tests carried out in supercritical water (400–500 °C) revealed a noticeable corrosion attack on the silicon nitride surface in spite of the low temperatures. Increasing water pressure generally caused an increase in the oxidation phenomena. Oxidation scale evolution depended strictly on the silicon nitride sintering process, sintering aids, porosity and impurities, which influenced oxidation kinetics and surface morphology. In

Edoardo Proverbio; Fabio Carassiti

1996-01-01

279

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

280

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

PubMed

Microbial activities drive the global nitrogen cycle, and in the past few years, our understanding of nitrogen cycling processes and the micro-organisms that mediate them has changed dramatically. During this time, the processes of anaerobic ammonium oxidation (anammox), and ammonia oxidation within the domain Archaea, have been recognized as two new links in the global nitrogen cycle. All available evidence indicates that these processes and organisms are critically important in the environment, and particularly in the ocean. Here we review what is currently known about the microbial ecology of anaerobic and archaeal ammonia oxidation, highlight relevant unknowns and discuss the implications of these discoveries for the global nitrogen and carbon cycles. PMID:18043610

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

2007-05-01

281

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

282

Water-table height and microtopography control biogeochemical cycling in an Arctic coastal tundra ecosystem  

NASA Astrophysics Data System (ADS)

Drained thaw lake basins (DTLB's) are the dominant land form of the Arctic Coastal Plain in northern Alaska. The presence of continuous permafrost prevents drainage and so water tables generally remain close to the soil surface, creating saturated, suboxic soil conditions. However, ice wedge polygons produce microtopographic variation in these landscapes, with raised areas such as polygon rims creating more oxic microenvironments. The peat soils in this ecosystem store large amounts of organic carbon which is vulnerable to loss as arctic regions continue to rapidly warm, and so there is great motivation to understand the controls over microbial activity in these complex landscapes. Here we report the effects of experimental flooding, along with seasonal and spatial variation in soil chemistry and microbial activity in a DTLB. The flooding treatment generally mirrored the effects of natural landscape variation in water-table height due to microtopography. The flooded portion of the basin had lower dissolved oxygen, lower oxidation-reduction potential (ORP) and higher pH, as did lower elevation areas throughout the entire basin. Similarly, soil pore water concentrations of organic carbon and aromatic compounds were higher in flooded and low elevation areas. Dissolved ferric iron (Fe(III)) concentrations were higher in low elevation areas and responded to the flooding treatment in low areas, only. The high concentrations of soluble Fe(III) in soil pore water were explained by the presence of siderophores, which were much more concentrated in low elevation areas. All the aforementioned variables were correlated, showing that Fe(III) is solubilized in response to anoxic conditions. Dissolved carbon dioxide (CO2) and methane (CH4) concentrations were higher in low elevation areas, but showed only subtle and/or seasonally dependent effects of flooding. In anaerobic laboratory incubations, more CH4 was produced by soils from low and flooded areas, whereas anaerobic CO2 production only responded to flooding in high elevation areas. Seasonal changes in the oxidation state of solid phase Fe minerals showed that net Fe reduction occurred, especially in topographically low areas. The effects of Fe reduction were also seen in the topographic patterns of pH, as protons were consumed where this process was prevalent. This suite of results can all be attributed to the effect of water table on oxygen availability: flooded conditions promote anoxia, stimulating dissolution and reduction of Fe(III), and to some extent, methanogenesis. However, two lines of evidence indicated the inhibition of methanogenesis by alternative e- acceptors such as Fe(III) and humic substances: (1) ratios of CO2:CH4 evolved from anaerobic soil incubations and dissolved in soil pore water were high; (2) CH4 concentrations were negatively correlated with the oxidation state of the soluble Fe pool in both topographically high and low areas. A second set of results could be explained by increased soil temperature in the flooding treatment, which presumably arose from the increased thermal conductivity of the soil surface: higher N mineralization rates and dissolved P concentrations were observed in flooded areas. Overall, these results could have implications for C and nutrient cycling in high Arctic areas where warming and flooding are likely consequences of climate change.

Lipson, D. A.; Zona, D.; Raab, T. K.; Bozzolo, F.; Mauritz, M.; Oechel, W. C.

2012-01-01

283

Water Sorption and Gamma Radiolysis Studies for Uranium Oxides  

SciTech Connect

During the development of a standard for the safe, long-term storage of {sup 233}U-containing materials, several areas were identified that needed additional experimental studies. These studies were related to the perceived potential for the radiolytic generation of large pressures or explosive concentrations of gases in storage containers. This report documents the results of studies on the sorption of water by various uranium oxides and on the gamma radiolysis of uranium oxides containing various amounts of sorbed moisture. In all of the experiments, {sup 238}U was used as a surrogate for the {sup 233}U. For the water sorption experiments, uranium oxide samples were prepared and exposed to known levels of humidity to establish the water uptake rate. Subsequently, the amount of water removed was studied by heating samples in a oven at fixed temperatures and by thermogravimetric analysis (TGA)/differential thermal analysis (DTA). It was demonstrated that heating at 650 C adequately removes all moisture from the samples. Uranium-238 oxides were irradiated in a {sup 60}Co source and in the high-gamma-radiation fields provided by spent nuclear fuel elements of the High Flux Isotope Reactor. For hydrated samples of UO{sub 3}, H{sub 2} was the primary gas produced; but the total gas pressure increase reached steady value of about 10 psi. This production appears to be a function of the dose and the amount of water present. Oxygen in the hydrated UO{sub 3} sample atmosphere was typically depleted, and no significant pressure rise was observed. Heat treatment of the UO{sub 3} {center_dot} xH{sub 2}O at 650 C would result in conversion to U{sub 3}O{sub 8} and eliminate the H{sub 2} production. For all of the U{sub 3}O{sub 8} samples loaded in air and irradiated with gamma radiation, a pressure decrease was seen and little, if any, H{sub 2} was produced--even for samples with up to 9 wt % moisture content. Hence, these results demonstrated that the efforts to remove trace moisture from U{sub 3}O{sub 8} are not necessary to avoid pressurization of stored uranium oxides caused by gamma-induced radiolysis. In fact, this system can tolerate several percent of sorbed moisture--most of which can be easily removed by heating to only 150 C. To complete the picture of the radiolytic response of uranium oxides that have sorbed moisture, alpha radiolysis experiments have been initiated.

Icenhour, A.S.

2002-02-27

284

Oxidation kinetics of Fe(II) in sea water  

Microsoft Academic Search

The oxidation of Fe(II) has been studied as a function of pH (5 to 9), temperature (5 to 45°C), and salinity (0 to 35). The pseudo-first-order rate constant, kâ, in water and sea water was found to be a second degree function of pH over the pH range of 7.5 to 8.5 at 5°C and 6.0 to 8.0 at 25°C.

F. J. Millero; S. Sotolongo; M. Izaguirre

1987-01-01

285

Breakdown of fast water transport in graphene oxides  

NASA Astrophysics Data System (ADS)

Fast slip flow was identified for water inside the interlayer gallery between graphene layers or carbon nanotubes. We report here that this significant flow rate enhancement (over two orders) breaks down with the presence of chemical functionalization and relaxation of nanoconfinement in graphene oxides. Molecular dynamics simulation results show that hydrodynamics applies in this circumstance, even at length scales down to nanometers. However, corrections to the slip boundary condition and apparent viscosity of nanoconfined flow must be included to make quantitative predictions. These results were discussed with the structural characteristics of liquid water and hydrogen-bond networks.

Wei, Ning; Peng, Xinsheng; Xu, Zhiping

2014-01-01

286

Breakdown of fast water transport in graphene oxides.  

PubMed

Fast slip flow was identified for water inside the interlayer gallery between graphene layers or carbon nanotubes. We report here that this significant flow rate enhancement (over two orders) breaks down with the presence of chemical functionalization and relaxation of nanoconfinement in graphene oxides. Molecular dynamics simulation results show that hydrodynamics applies in this circumstance, even at length scales down to nanometers. However, corrections to the slip boundary condition and apparent viscosity of nanoconfined flow must be included to make quantitative predictions. These results were discussed with the structural characteristics of liquid water and hydrogen-bond networks. PMID:24580178

Wei, Ning; Peng, Xinsheng; Xu, Zhiping

2014-01-01

287

Catalytic Water Oxidation on Derivatized nanoITO  

SciTech Connect

Electrocatalytic water oxidation occurs on high surface area, nanocrystalline ITO (nanoITO) surface-derivatized by phosphonate-binding of the catalyst [Ru(Mebimpy)(4,4?-((HO){sub 2}OPCH{sub 2}){sub 2}bpy)(OH{sub 2})]{sup 2+} (Mebimpy is 2,6-bis(1-methylbenzimidazol-2-yl)pyridine; bpy is 2,2?-bipyridine). With nanoITO, spectral data can be acquired on electrochemically generated intermediates and voltammograms monitored spectrophotometrically.

Chen, Zuofeng; Concepcion, Javier J; Hull, Jonathan Frazer; Hoertz, Paul G.; Meyer, Thomas J.

2010-01-01

288

Catalytic water oxidation on derivatized nanoITO.  

PubMed

Electrocatalytic water oxidation occurs on high surface area, nanocrystalline ITO (nanoITO) surface-derivatized by phosphonate-binding of the catalyst [Ru(Mebimpy)(4,4'-((HO)(2)OPCH(2))(2)bpy)(OH(2))](2+) (Mebimpy is 2,6-bis(1-methylbenzimidazol-2-yl)pyridine; bpy is 2,2'-bipyridine). With nanoITO, spectral data can be acquired on electrochemically generated intermediates and voltammograms monitored spectrophotometrically. PMID:20571709

Chen, Zuofeng; Concepcion, Javier J; Hull, Jonathan F; Hoertz, Paul G; Meyer, Thomas J

2010-08-14

289

The climate is changing and world popula4on is growing. These are increasing demands on the Earth's water resources and uncertainty on water availability. Advances in water cycle  

E-print Network

these challenges. With this in mind, JPL's Center for Climate Sciences February to May 2012 at JPL. A separate workshop on Water Resource Management water cycle science ques4ons; - integrate water cycle science across JPL

290

Reaction kinetics for the high temperature oxidation of Pu1wt%Ga in water vapor  

Microsoft Academic Search

Oxidation of plutonium metal is greatly accelerated by the presence of water vapor. The magnitude of the effect of water vapor on oxidation kinetics is determined by temperature, water concentration, and oxygen concentration. Most of the previous work has been directed toward evaluating the effect of moisture on the atmospheric oxidation of plutonium. Work on the isolation and characterization of

J. L. Stakebake; M. A. Saba

1988-01-01

291

Photoassembly of the Water-Oxidizing Complex in Photosystem II  

PubMed Central

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

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

2008-01-01

292

[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

293

Anaerobic oxidation of methane in tropical and boreal soils: Ecological significance in terrestrial methane cycling  

NASA Astrophysics Data System (ADS)

Anaerobic oxidation of methane (AOM) is a considerable sink for the greenhouse gas methane (CH4) in marine systems, but the importance of this process in terrestrial systems is less clear. Lowland boreal soils and wet tropical soils are two hot spots for CH4 cycling, yet AOM has been essentially uncharacterized in these systems. We investigated AOM in soils from sites in Alaska and Puerto Rico. Isotope tracers were utilized in vitro to enable the simultaneous quantification of CH4 production and consumption without use of biological inhibitors. Boreal peat soil and tropical mineral soil oxidized small but significant quantities of CH4 to CO2 under anoxic conditions (p < 0.001). Potential AOM rates were 21 ± 2 nmol gdw-1 d-1 and 2.9 ± 0.5 nmol gdw-1 d-1 for the boreal and tropical soils, respectively. The addition of terminal electron acceptors (NO3-, Fe(III), and SO42-) inhibited AOM and methanogenesis in both soils. In all incubations, CH4 production occurred simultaneously with AOM, and CH4 production rates were always greater than AOM rates. There was a strong correlation between the quantity of CH4 produced and the amount of CH4 oxidized under anoxic conditions (Alaska: r = 0.875, p < 0.0001; Puerto Rico: r = 0.817, p < 0.0001). CH4 oxidation under anoxic conditions was biological and likely mediated by methanogenic archaea. While only a small percentage of the total CH4 produced in these soils was oxidized under anoxic conditions (0.3% and 0.8% for Alaskan and Puerto Rican Soils), this process is important to understand since it could play a measurable role in controlling net CH4 flux.

Blazewicz, Steven J.; Petersen, Dorthe G.; Waldrop, Mark P.; Firestone, Mary K.

2012-06-01

294

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

PubMed

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

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

2014-01-21

295

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

EPA Science Inventory

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

296

GLOWA-DANUBE: INTEGRATIVE MODELLING OF GLOBAL CHANGE EFFECTS ON THE WATER CYCLE -THE GROUNDWATER PERSPECTIVE  

E-print Network

GLOWA-DANUBE: INTEGRATIVE MODELLING OF GLOBAL CHANGE EFFECTS ON THE WATER CYCLE - THE GROUNDWATER in a variety of medium sized watersheds. The Upper Danube Basin (A ~ 77.000 km²) represents a mountain-foreland situation in the temperate mid-latitudes. The major goal of "GLOWA-Danube" is the development of new water

Cirpka, Olaf Arie

297

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

Microsoft Academic Search

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

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

1978-01-01

298

Thermochemical hydrogen production via a cycle using barium and sulfur - Reaction between barium sulfide and water  

NASA Technical Reports Server (NTRS)

The reaction between barium sulfide and water, a reaction found in several sulfur based thermochemical cycles, was investigated kinetically at 653-866 C. Gaseous products were hydrogen and hydrogen sulfide. The rate determining step for hydrogen formation was a surface reaction between barium sulfide and water. An expression was derived for the rate of hydrogen formation.

Ota, K.; Conger, W. L.

1977-01-01

299

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

300

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

301

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

302

Humans Altering the Water Cycle GTN-Hydrology Meeting  

E-print Network

and resettlement ­ The Mekong Delta #12;Climate Change Mitigation & Adaptation Impacts · Biofuel plantations · Water management infrastructure · Land cover change · Institutions & pricing · Climate change for conservation due to biodiversity. #12;LAND COVER CHANGE #12;Land Cover Change · Affects: ­ Evapotranspiration

Columbia University

303

Emerging Contaminants in the Drinking Water Cycle - MCEARD  

EPA Science Inventory

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

304

EMERGING CONTAMINANTS IN THE WATER CYCLE: FATE AND TRANSPORT  

EPA Science Inventory

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

305

Assessment of hidden sulfur cycling processes through modeling of sulfur and oxygen isotope signatures of pore-water sulfate  

NASA Astrophysics Data System (ADS)

We developed a numerical model to simulate/predict the sulfur and oxygen isotope composition of pore-water sulfate in sediment pore-water profiles where sulfate concentrations decrease linearly with depth, presumably under steady-state conditions. We considered the effects of sulfate consumption due to the anaerobic oxidation of methane (AOM) alone and in combination with organoclastic sulfate reduction Linear sulfate concentration profiles are commonly associated with sulfate loss at depth driven by sulfate reduction coupled to AOM presumably under steady-state conditions. During this reaction the net consumption of sulfate and methane are balanced. The general assumption is that under steady-state conditions there is little to no sulfate loss due to organoclastic sulfate reduction and negligible sulfate gain due to other sulfur cycling processes above the sulfate-methane transition zone (SMTZ). When model results are compared to pore-water sulfate data from sediment cores obtained from the Argentine Basin, we see that sulfate reduction coupled to AOM alone cannot produce the measured sulfur and oxygen isotope patterns. Modeled isotope profiles including organoclastic sulfate reduction above the SMTZ provide a good match to the observations. The model comparison to our data reveals large sulfur isotope fractionation effects, with sulfur isotope enrichment factors (?34S) exceeding 50‰, consistent with the observed sulfur isotope offset between sulfate and sulfide. Furthermore, our model requires oxygen isotope exchange factors (?O) equal to or exceeding 10. Linear sulfate concentration profiles do not readily reveal the complexity and richness of sulfur cycling processes above the SMTZ and are able to 'hide' the effects of organoclastic sulfate reduction and additional sulfur cycling. Hence, the use of combined sulfur and oxygen isotope analysis is a valuable tool that can be used to gain insight into sulfur cycling not revealed by traditional means.

Arnold, G. L.; Liu, B.; Henkel, S.; Sawicka, J.; Kasten, S.; Khalili, A.; Brunner, B.

2012-12-01

306

Conventional and Advanced Silicagel-water Adsorption Cycles Driven by Near - environmental Temperature Heat  

NASA Astrophysics Data System (ADS)

This work aims at clarifying the possible operating temperature ranges for silica gel-water adsorption refrigeration cycles driven by near-environmental temperature heat sources (between 50°C and 85°C), with relatively small regenerating temperature lifts (10 K to 65 K). A newly developed three stage advanced silica gel-water cycle, which is operational with 50°C driving heat source and 30°C cooling source is introduced and compared with a conventional single stage cycle. The cycles are evaluated in terms of cooling capacity, COP and the viability of operation with near-environmental temperature driving heat sources. The analysis is based on experimental and cycle simulation work. The results showed the advanced three stage cycle to be particularly suited for operation with low grade waste heat driving sources, since it worked with small regenerating temperature lifts (?Tregen)of 10K to 30K. Another significant advantage of operation with small ?Tregen is the possibility to reduce irreversible heat losses from batched cycle operation. Experiments carried out on full-size machine suggested that, even with small?Tregen, adsorber /desorber heat exchanger improvements such as higher thermal conductance and smaller heat capacitance can contribute to reduce heat losses while improving cycle performance in terms of cooling capacity and COP.

Boelman, Elisa; B. Saha, Bidyut; Tanaka, Aiharu; Kashiwagi, Takao

307

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

PubMed

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

Zhang, Chao; Anadon, Laura Diaz

2013-12-17

308

EVALUATION OF THE DIURNAL CYCLE OF MODEL PREDICTED CLOUD LIQUID WATER PATH WITH MSG-SEVIRI OBSERVATIONS  

E-print Network

EVALUATION OF THE DIURNAL CYCLE OF MODEL PREDICTED CLOUD LIQUID WATER PATH WITH MSG Liquid Water path (LWP) in climate models receives relatively little attention. This is partly due on diurnal cycles of LWP over land and ocean surfaces. This paper evaluates diurnal cycles of LWP

Haak, Hein

309

Water oxidation by manganese oxides formed from tetranuclear precursor complexes: the influence of phosphate on structure and activity.  

PubMed

Two types of manganese oxides have been prepared by hydrolysis of tetranuclear Mn(iii) complexes in the presence or absence of phosphate ions. The oxides have been characterized structurally using X-ray absorption spectroscopy and functionally by O2 evolution measurements. The structures of the oxides prepared in the absence of phosphate are dominated by di-?-oxo bridged manganese ions that form layers with limited long-range order, consisting of edge-sharing MnO6 octahedra. The average manganese oxidation state is +3.5. The structure of these oxides is closely related to other manganese oxides reported as water oxidation catalysts. They show high oxygen evolution activity in a light-driven system containing [Ru(bpy)3](2+) and S2O8(2-) at pH 7. In contrast, the oxides formed by hydrolysis in the presence of phosphate ions contain almost no di-?-oxo bridged manganese ions. Instead the phosphate groups are acting as bridges between the manganese ions. The average oxidation state of manganese ions is +3. This type of oxide has much lower water oxidation activity in the light-driven system. Correlations between different structural motifs and the function as a water oxidation catalyst are discussed and the lower activity in the phosphate containing oxide is linked to the absence of protonable di-?-oxo bridges. PMID:24647521

Shevchenko, Denys; Anderlund, Magnus F; Styring, Stenbjörn; Dau, Holger; Zaharieva, Ivelina; Thapper, Anders

2014-06-28

310

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

311

The water dissociation reaction on clean and oxidized iron (110)  

NASA Astrophysics Data System (ADS)

The interaction of H2O with the clean Fe(110) surface, Fe(110) surfaces with absorbed oxygen, and Fe(110) surfaces after bulk oxygen penetration were investigated using UPS. At 225 K, surface absorbed hydroxyl groups are present on all surfaces studied. On initially clean Fe(110) and surfaces with up to half monolayer of absorbed oxygen, heating the hydroxyl layer produced at 225 to 360 K causes hydrogen and water desorption and additional oxygen deposition relative to the starting surface. Beyond one-half monolayer of initial oxygen coverage, dehydroxylation proceeded exclusively via water desorption with the quantitative restoration of the initial surface composition. These results demonstrate that the (110) surface of iron is passive toward oxidation by water alone below 360 K, after the first monolayer.

Dwyer, D. J.; Kelemen, S. R.; Kaldor, A.

1982-02-01

312

Efficient water oxidation at carbon nanotube-polyoxometalate electrocatalytic interfaces.  

PubMed

Water is the renewable, bulk chemical that nature uses to enable carbohydrate production from carbon dioxide. The dream goal of energy research is to transpose this incredibly efficient process and make an artificial device whereby the catalytic splitting of water is finalized to give a continuous production of oxygen and hydrogen. Success in this task would guarantee the generation of hydrogen as a carbon-free fuel to satisfy our energy demands at no environmental cost. Here we show that very efficient and stable nanostructured, oxygen-evolving anodes are obtained by the assembly of an oxygen-evolving polyoxometalate cluster (a totally inorganic ruthenium catalyst) with a conducting bed of multiwalled carbon nanotubes. Our bioinspired electrode addresses the one major challenge of artificial photosynthesis, namely efficient water oxidation, which brings us closer to being able to power the planet with carbon-free fuels. PMID:20861897

Toma, Francesca M; Sartorel, Andrea; Iurlo, Matteo; Carraro, Mauro; Parisse, Pietro; Maccato, Chiara; Rapino, Stefania; Gonzalez, Benito Rodriguez; Amenitsch, Heinz; Da Ros, Tatiana; Casalis, Loredana; Goldoni, Andrea; Marcaccio, Massimo; Scorrano, Gianfranco; Scoles, Giacinto; Paolucci, Francesco; Prato, Maurizio; Bonchio, Marcella

2010-10-01

313

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

314

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

315

Water Cycle Dynamics in the Snake River Basin, Alaska  

NASA Astrophysics Data System (ADS)

Alaska’s Seward Peninsula is underlain in the south by areas of near-freezing, continuous and discontinuous permafrost. These conditions make it susceptible to changing climatic conditions such as acceleration of the hydrologic cycle or general atmospheric warming. This study looks at the hydrologic record of the Snake River over the mid-twentieth century through present. The Snake River basin drains an area of about 22 square kilometers into Norton Sound near the Bering Strait, off the western coast of Alaska. Climate for this area is maritime in summer and somewhat continental in winter once the sea ice forms. Hydrometeorological parameters have been measured locally for more than fifty years with temperature being measured regularly over the last 100 years. Discharge has been measured in the Snake River intermittently over that time period as well. This study looks closely at drivers of inter-annual variations in soil moisture in the basin over the observational record using a physically based numerical hydrological model. Unlike many areas of Alaska, the meteorological record at Nome, located at the mouth of the watershed, shows no statistically significant increase in precipitation over either the last 30 years or the last 100 years. However, there has been a small increase in temperature over the 100 year time period.

Busey, R.; Hinzman, L. D.

2009-12-01

316

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

PubMed

We utilized gas-phase diffusion flame synthesis, which has potential for large-scale production of metal oxide nanoparticles, to produce iron oxide nanoparticles (IONPs) with variable oxidation states. The efficacy of these materials in removal of arsenate (As(V) ) from water was assessed. Two different flame configurations, a diffusion flame (DF) and an inverse diffusion flame (IDF), were employed to synthesize six different IONPs by controlling flame conditions. The IONPs produced in the IDF configuration (IDF-IONPs) had smaller particle diameters (4.8 - 8.2 nm) and larger surface areas (141-213 m(2)/g) than the IONPs produced in the DF configuration (29 nm, 36 m(2)/g), which resulted in their higher adsorption capacities. As(V) adsorption capacities of the IDF-IONPs increased when the IONPs were synthesized in more oxidizing conditions. The fully oxidized IDF-IONPs, maghemite (?-Fe2O3), showed the highest As(V) adsorption capacity, comparable to that of magnetite nanocrystals synthesized by thermal decomposition of iron pentacarbonyl and equivalent to three to four times higher capacity than that of a commonly used goethite-based adsorbent. All IONPs were magnetically responsive, which is of great importance for solid-liquid separation. This study demonstrates that the IONPs synthesized in gas-phase flame, particularly IDF-IONPs, are excellent adsorbents because of their high As(V) sorption capacity, potential for large-scale production, and useful magnetic property. PMID:23645964

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

2013-02-01

317

Thermodynamic properties of ammonia–water mixtures for power-cycle applications  

Microsoft Academic Search

Ammonia–water mixtures have been used as working fluids in absorption–refrigeration cycles for several decades. Their use as multi-component working fluids for power cycles has been investigated recently. The thermodynamic properties required are known or may be calculated at elevated temperatures and pressures. We present a new method for these computations using Gibbs free energies and empirical equations for bubble and

Feng Xu; D. Yogi Goswami

1999-01-01

318

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

SciTech Connect

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

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

2012-10-24

319

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

SciTech Connect

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

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

1980-06-01

320

Climate change mitigation by recovery of energy from the water cycle: a new challenge for water management.  

PubMed

Waternet is responsible for drinking water treatment and distribution, wastewater collection and treatment, and surface water management and control (quality and quantity) in and around Amsterdam. Waternet has the ambition to operate climate neutral in 2020. To realise this ambition, measures are required to compensate for the emission of 53,000 ton CO(2)-eq/year. Energy recovery from the water cycle looks very promising. First, calculations reveal that energy recovery from the water cycle in and around Amsterdam may contribute to a total reduction in greenhouse gas emissions up to 148,000 ton CO(2)-eq/year. The challenge for the coming years is to choose combinations of all the possibilities to fulfil the energy demand as much as possible. Only then the use of fossil fuel can be minimized and inevitable greenhouse gas emissions can be compensated, supporting the target to operate climate neutral in 2020. PMID:22173417

van der Hoek, J P

2012-01-01

321

Method and apparatus for waste destruction using supercritical water oxidation  

SciTech Connect

The invention relates to an improved apparatus and method for initiating and sustaining an oxidation reaction. A hazardous waste, is introduced into a reaction zone within a pressurized containment vessel. An oxidizer, preferably hydrogen peroxide, is mixed with a carrier fluid, preferably water, and the mixture is heated until the fluid achieves supercritical conditions of temperature and pressure. The heating means comprise cartridge heaters placed in closed-end tubes extending into the center region of the pressure vessel along the reactor longitudinal axis. A cooling jacket surrounds the pressure vessel to remove excess heat at the walls. Heating and cooling the fluid mixture in this manner creates a limited reaction zone near the center of the pressure vessel by establishing a steady state density gradient in the fluid mixture which gradually forces the fluid to circulate internally. This circulation allows the fluid mixture to oscillate between supercritical and subcritical states as it is heated and cooled.

NONE

2000-02-29

322

Degradation of conazole fungicides in water by electrochemical oxidation.  

PubMed

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

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

2013-11-01

323

Definition of water droplets "strain cycles" in air times dependences on their sizes and movement velocities  

NASA Astrophysics Data System (ADS)

Experimental investigation of water droplets deformation regularities during their motion in the air by the action of gravitational forces was executed. Characteristic sizes of droplets were varied in the range from 3 mm to 6 mm. Velocities of droplets movement attained to 5 m/s. The cross-correlation system of video registration was used. More than ten characteristic "strain cycles" of droplets during the 1 m distance motion by them thought the air were established. Characteristic of droplets forms, periods, dimensions and ranges were determined for all "strain cycles". "Strain cycle" times dependences on velocity and sizes of droplets were established.

Volkov, Roman; Zhdanova, Alena; Zabelin, Maxim; Kuznetsov, Geniy; Strizhak, Pavel

2014-08-01

324

Fundamental kinetics and mechanistic pathways for oxidation reactions in supercritical water  

NASA Technical Reports Server (NTRS)

Oxidation of the products of human metabolism in supercritical water has been shown to be an efficient way to accomplish the on-board water/waste recycling in future long-term space flights. Studies of the oxidation kinetics of methane to carbon dioxide in supercritical water are presented in this paper in order to enhance the fundamental understanding of the oxidation of human waste compounds in supercritical water. It is concluded that, although the elementary reaction models remain the best hope for simulating oxidation in supercritical water, several modifications to existing mechanisms need to be made to account for the role of water in the reaction mechanism.

Webley, Paul A.; Tester, Jefferson W.

1988-01-01

325

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

326

Studies on the Photoactivation of the Water-Oxidizing Enzyme  

PubMed Central

Inactivation of the water splitting enzyme complex in leaves or isolated chloroplasts results in increased susceptibility of photosystem II (PSII) to damage by light. Photoinhibition under this condition occurs in very weak light. The site of damage is exclusive of the water splitting complex yet still on the oxidizing side of PSII, as the QB locus is unaffected while photoreduction of silicomolybdate is inhibited. The kinetics of loss in PSII activity are more complex than apparent first-order, and the quantum efficiency is low. We observe no evidence of deletion from thylakoid membranes of any PSII polypeptide as a consequence of photoinhibition, although recovery from the photoinhibition is dependent upon both light and 70S protein synthesis. Enhanced synthesis of two proteins occurs during recovery, only one of which (D2) appears to be causally related to the recovery. We present a model which describes the relationship of weak light photoinhibition and its recovery to photoactivation of the S-state water oxidizing complex. Images Fig. 9 PMID:16665003

Callahan, Franklin E.; Becker, David W.; Cheniae, George M.

1986-01-01

327

Electrostatics and proton transfer in photosynthetic water oxidation.  

PubMed

Photosystem II (PSII) oxidizes two water molecules to yield dioxygen plus four protons. Dioxygen is released during the last out of four sequential oxidation steps of the catalytic centre (S(0) --> S(1), S(1) --> S(2), S(2) --> S(3), S(3) --> S(4) --> S(0)). The release of the chemically produced protons is blurred by transient, highly variable and electrostatically triggered proton transfer at the periphery (Bohr effect). The extent of the latter transiently amounts to more than one H(+)/e(-) under certain conditions and this is understood in terms of electrostatics. By kinetic analyses of electron-proton transfer and electrochromism, we discriminated between Bohr-effect and chemically produced protons and arrived at a distribution of the latter over the oxidation steps of 1 : 0 : 1 : 2. During the oxidation of tyr-161 on subunit D1 (Y(Z)), its phenolic proton is not normally released into the bulk. Instead, it is shared with and confined in a hydrogen-bonded cluster. This notion is difficult to reconcile with proposed mechanisms where Y(Z) acts as a hydrogen acceptor for bound water. Only in manganese (Mn) depleted PSII is the proton released into the bulk and this changes the rate of electron transfer between Y(Z) and the primary donor of PSII P(+)(680) from electron to proton controlled. D1-His190, the proposed centre of the hydrogen-bonded cluster around Y(Z), is probably further remote from Y(Z) than previously thought, because substitution of D1-Glu189, its direct neighbour, by Gln, Arg or Lys is without effect on the electron transfer from Y(Z) to P(+)(680) (in nanoseconds) and from the Mn cluster to Y(ox)(Z). PMID:12437879

Junge, Wolfgang; Haumann, Michael; Ahlbrink, Ralf; Mulkidjanian, Armen; Clausen, Jürgen

2002-10-29

328

Electrostatics and proton transfer in photosynthetic water oxidation.  

PubMed Central

Photosystem II (PSII) oxidizes two water molecules to yield dioxygen plus four protons. Dioxygen is released during the last out of four sequential oxidation steps of the catalytic centre (S(0) --> S(1), S(1) --> S(2), S(2) --> S(3), S(3) --> S(4) --> S(0)). The release of the chemically produced protons is blurred by transient, highly variable and electrostatically triggered proton transfer at the periphery (Bohr effect). The extent of the latter transiently amounts to more than one H(+)/e(-) under certain conditions and this is understood in terms of electrostatics. By kinetic analyses of electron-proton transfer and electrochromism, we discriminated between Bohr-effect and chemically produced protons and arrived at a distribution of the latter over the oxidation steps of 1 : 0 : 1 : 2. During the oxidation of tyr-161 on subunit D1 (Y(Z)), its phenolic proton is not normally released into the bulk. Instead, it is shared with and confined in a hydrogen-bonded cluster. This notion is difficult to reconcile with proposed mechanisms where Y(Z) acts as a hydrogen acceptor for bound water. Only in manganese (Mn) depleted PSII is the proton released into the bulk and this changes the rate of electron transfer between Y(Z) and the primary donor of PSII P(+)(680) from electron to proton controlled. D1-His190, the proposed centre of the hydrogen-bonded cluster around Y(Z), is probably further remote from Y(Z) than previously thought, because substitution of D1-Glu189, its direct neighbour, by Gln, Arg or Lys is without effect on the electron transfer from Y(Z) to P(+)(680) (in nanoseconds) and from the Mn cluster to Y(ox)(Z). PMID:12437879

Junge, Wolfgang; Haumann, Michael; Ahlbrink, Ralf; Mulkidjanian, Armen; Clausen, Jurgen

2002-01-01

329

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

330

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

NASA Technical Reports Server (NTRS)

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

Juhasz, A. J.

1982-01-01

331

Improving Representation of the Nitrous Oxide Cycle in Ocean Biogeochemical Models  

NASA Astrophysics Data System (ADS)

The processes governing the marine nitrous oxide cycle, oceanic distribution, and flux to the atmosphere display distinct heterogeneity. The primary pathway for N2O production in the oxygenated open ocean is believed to be nitrification during the oxidation of ammonium to nitrate. However, mechanisms of marine N2O production and consumption display significant sensitivity to local oxygen concentration. Oxygen minimum zones such as the Arabian Sea and Eastern Equatorial Pacific are characterized by large gradients in sub-surface N2O, and high rates of N2O turnover that significantly exceed those observed in the open ocean. A range of processes is believed to govern N2O formation in these regions, including enhanced nitrification, and a coupling of nitrification and denitrification pathways. N2O is also depleted via denitrification in anoxic zones. This spatial heterogeneity presents challenges to the development of effective model parameterizations for ocean N2O; i.e., parameterizations that also display reliable predictive capability under conditions of changing ocean circulation, productivity, and oxygen distribution. In this analysis we use the ocean biogeochemistry model NEMO-PlankTOM to evaluate a range of recent empirical parameterizations for marine N2O formation. We contrast these parameterizations with a recently developed process-based model of oceanic N2O. Simulations are evaluated using a global database of oceanic N2O measurements. Evaluation metrics include surface concentrations, depth profiles, and regional averages. We also discuss the challenges of developing a successful representation of the marine N2O cycle, given specific limitations of the present generation of global ocean biogeochemistry models.

Suntharalingam, P.; Buitenhuis, E.; Le Quere, C.; O'Meara, S.; Nevison, C. D.; Bange, H. W.; Butler, J. H.; Elkins, J. W.

2011-12-01

332

Nitric oxide synthases catalyze the activation of redox cycling and bioreductive anticancer agents.  

PubMed

Nitric oxide synthases (NOSs) play a crucial role in the control of blood flow, memory formation, and the immune response. These proteins can be structurally divided into oxygenase and reductase domains. The reductase domain shares a high degree of sequence homology with P450 reductase, which is thought to be the major enzyme responsible for the one-electron reduction of foreign compounds, including bioreductive antitumor agents currently undergoing clinical trials. In view of the structural similarities between NOS and P450 reductase, we investigated the capacity of NOS to reduce the hypoxic cytotoxin tirapazamine, the antitumor agent doxorubicin, and also the redox cycling compound menadione. All three isoforms exhibited high levels of activity toward these compounds. In the case of doxorubicin and menadione, the activity of NOS II was 5-10-fold higher than the other enzymes, whereas with tirapazamine, the activities were broadly similar. NOS-mediated metabolism of tirapazamine resulted in a large increase in plasmid DNA strand breaks, demonstrating that the reduction was a bioactivation process. In addition, tirapazamine inhibited NOS activity. Because nitric oxide is implicated in maintaining tumor vascular homeostasis, it is conceivable that tirapazamine could potentiate its own toxicity by increasing the degree of hypoxia. This study suggests that the NOSs could play a key role in the therapeutic effects of tirapazamine, particularly because NOS activity is markedly increased in several human tumors. In addition, the presence of NOS in the heart indicates that these enzymes may contribute to the cardiotoxicity of redox cycling drugs, such as doxorubicin. PMID:10213502

Garner, A P; Paine, M J; Rodriguez-Crespo, I; Chinje, E C; Ortiz De Montellano, P; Stratford, I J; Tew, D G; Wolf, C R

1999-04-15

333

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

PubMed Central

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

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

2011-01-01

334

Generation of hydrogen from aluminum and water – Effect of metal oxide nanocrystals and water quality  

Microsoft Academic Search

Metal Oxides nanocrystals such as TiO2, Co3O4, Cr2O3, Fe2O3, Mn2O3, NiO, CuO and ZnO were used as modifiers on the metallic aluminum (Al) powders for the production of hydrogen in deionized water or tap water at room temperature. In particular, the influences of TiO2 nanocrystals with various crystal sizes on the production of hydrogen from the reaction in tap water

Hong-Wen Wang; Hsing-Wei Chung; Hsin-Te Teng; Guozhong Cao

2011-01-01

335

Comparison of two thorium fuel cycles for use in light water prebreeder\\/breeder reactor systems (AWBA Development Program)  

Microsoft Academic Search

Light water prebreeder\\/breeder conceptual reactor systems have been developed which have the potential to significantly improve the fuel utilization of present generation light water reactors. The purpose of this study is to describe and compare two possible types of thorium fuel cycles for use in these light water prebreeder and breeder concepts. The two types of thorium fuel cycles basically

F. C. Merriman; D. F. McCoy; W. A. Boyd; J. R. Dwyer

1983-01-01

336

Genetic variation in pigeon pea ( Cajanus cajan (L.) Mill sp.) in response to successive cycles of water stress  

Microsoft Academic Search

Four pigeon pea [Cajanus cajan (L.) Mill sp.] cultivars were studied during two cycles of development of water stress and recovery. During these two cycles the genetic variation in vegetative development, leaf water potential, relative water content, photosynthesis, and stomatal conductance was followed. Plants were grown in a greenhouse and irrigated every seventh day. On two occasions (30 days and

P. M. Kimani; A. Benzioni; M. Ventura

1994-01-01

337

Manganese peroxidase from the basidiomycete Phanerochaete chrysosporium: spectral characterization of the oxidized states and the catalytic cycle  

Microsoft Academic Search

Manganese peroxidase (MnP), an extracellular heme enzyme from the lignin-degrading fungus Phanerochaete chrysosporium, catalyzes the Mn(II)-dependent oxidation of a variety of phenols. Herein, the authors spectroscopically characterize the oxidized states of MnP compounds I, II, and III and clarify the role of Mn in the catalytic cycle of the enzyme. Addition of 1 equiv of HâOâ to the native ferric

Hiroyuki Wariishi; Lakshmi Akileswaran; Michael H. Gold

1988-01-01

338

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

339

Interactions of Water Vapor with Oxides at Elevated Temperatures  

NASA Technical Reports Server (NTRS)

Many volatile metal hydroxides form by reaction of the corresponding metal oxide with water vapor. These reactions are important in a number of high temperature corrosion processes. Experimental methods for studying the thermodynamics of metal hydroxides include: gas leak Knudsen cell mass spectrometry, free jet sampling mass spectrometry, transpiration and hydrogen-oxygen flame studies. The available experimental information is reviewed and the most stable metal hydroxide species are correlated with position in the periodic table. Current studies in our laboratory on the Si-O-H system are discussed.

Jacobson, Nathan; Opila, Elizabeth; Copland, Evan; Myers, Dwight

2003-01-01

340

Oxidation of copper(I) in sea water  

Microsoft Academic Search

The oxidation of Cu(I) in air-saturated solutions of sea water has been measured as a function of pH (5.3-8.6), temperature (5-45 °C), and salinity (5-44). The overall rate constant k (kg mol⁻¹ min⁻¹) d(Cu(I))\\/dt = -k(Cu(I))(Oâ) has been fitted to log k = 10.73 + 0.23 pH - 2373\\/T - 3.33I¹² + 1.45I with a standard error of 0.08 in

V. K. Sharma; F. J. Millero

1988-01-01

341

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

PubMed

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

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

2013-10-01

342

Networked solid oxide fuel cell stacks combined with a gas turbine cycle  

NASA Astrophysics Data System (ADS)

An improved design of fuel cells stacks arrangement has been suggested before for MCFC where reactant streams are ducted such that they are fed and recycled among multiple MCFC stacks in series. By networking fuel cell stacks, increased efficiency, improved thermal balance, and higher total reactant utilisation can be achieved. In this study, a combination of networked solid oxide fuel cell (SOFC) stacks and a gas turbine (GT) has been modelled and analysed. In such a combination, the stacks are operating in series with respect to the fuel flow. In previous studies, conducted on hybrid SOFC/GT cycles by the authors, it was shown that the major part of the output of such cycles can be addressed to the fuel cell. In those studies, a single SOFC with parallel gas flows to individual cells were assumed. It can be expected that if the performance of the fuel cell is enhanced by networking, the overall system performance will improve. In the first part of this paper, the benefit of the networked stacks is demonstrated for a stand alone stack while the second part analyses and discusses the impact networking of the stacks has on the SOFC/GT system performance and design. For stacks with both reactant streams in series, a significant increase of system efficiency was found (almost 5% points), which, however, can be explained mainly by an improved thermal management.

Selimovic, Azra; Palsson, Jens

343

Tricarboxylic acid cycle-sustained oxidative phosphorylation in isolated myelin vesicles.  

PubMed

The Central Nervous System (CNS) function was shown to be fueled exclusively by oxidative phosphorylation (OXPHOS). This is in line with the sensitivity of brain to hypoxia, but less with the scarcity of the mitochondria in CNS. Consistently with the ectopic expression of FoF1-ATP synthase and the electron transfer chain in myelin, we have reported data demonstrating that isolated myelin vesicles (IMV) conduct OXPHOS. It may suggest that myelin sheath could be a site for the whole aerobic degradation of glucose. In this paper, we assayed the functionality of glycolysis and of TCA cycle enzymes in IMV purified from bovine forebrain. We found the presence and activity of all of the glycolytic and TCA cycle enzymes, comparable to those in mitochondria-enriched fractions, in the same experimental conditions. IMV also contain consistent carbonic anhydrase activity. These data suggest that myelin may be a contributor in energy supply for the axon, performing an extra-mitochondrial aerobic OXPHOS. The vision of myelin as the site of aerobic metabolism may shed a new light on many demyelinating pathologies, that cause an a yet unresolved axonal degeneration and whose clinical onset coincides with myelin development completion. PMID:23851157

Ravera, Silvia; Bartolucci, Martina; Calzia, Daniela; Aluigi, Maria Grazia; Ramoino, Paola; Morelli, Alessandro; Panfoli, Isabella

2013-11-01

344

Structure of zirconium alloy oxides formed in pure water studied with synchrotron radiation and  

E-print Network

Structure of zirconium alloy oxides formed in pure water studied with synchrotron radiation Abstract A detailed study was undertaken of oxides formed in 360 °C water on four Zr-based alloys (Zircaloy alloys. These results are discussed in terms of a model of oxide growth based on the periodic breakdown

Motta, Arthur T.

345

Recommendations for Cycle II of National Water-Quality Assessment (NAWQA) Program  

USGS Publications Warehouse

The Planning Team for the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Program defines a successful NAWQA Program as one that makes a balanced contribution to study-unit issues, national issues, and to the pursuit of scientific knowledge. Using this criterion, NAWQA has been a success. The program has provided important new knowledge and understanding of scientific processes, and insights into the occurrence and distribution of contaminants that have been key to local and national policy decisions. Most of the basic design characteristics of NAWQA's first decade (1991-2000), hereafter called cycle I) remain appropriate as the program enters its second decade (cycle II) in 2001. In cycle II, the program has the opportunity to build on its successful base and to evolve to take advantage of the knowledge generated in cycle I. In addition to this expected evolution, NAWQA must also make some changes to compensate for the fact that program funding has not kept pace with inflation. An important theme for the second cycle of NAWQA will be the integration of knowledge across scales and across disciplines. The question that drove the NAWQA design in the first cycle was "How is water quality related to land use?" Cycle II will build upon what was learned in cycle I and use land-use and water-quality gradients to identify and understand potential sources of various constituents and the processes affecting transport and fate of those constituents and their effects on receptors. The understanding we gain from applying this approach will be relevant to the interests of policymakers, regulatory agencies, and resource managers.

Mallard, Gail E.; Armbruster, Jeffrey T.; Broshears, Robert E.; Evenson, Eric J.; Luoma, Samuel N.; Phillips, Patrick J.; Prince, Keith R.

1999-01-01

346

Water and the oxidation state of subduction zone magmas.  

PubMed

Mantle oxygen fugacity exerts a primary control on mass exchange between Earth's surface and interior at subduction zones, but the major factors controlling mantle oxygen fugacity (such as volatiles and phase assemblages) and how tectonic cycles drive its secular evolution are still debated. We present integrated measurements of redox-sensitive ratios of oxidized iron to total iron (Fe3+/SigmaFe), determined with Fe K-edge micro-x-ray absorption near-edge structure spectroscopy, and pre-eruptive magmatic H2O contents of a global sampling of primitive undegassed basaltic glasses and melt inclusions covering a range of plate tectonic settings. Magmatic Fe3+/SigmaFe ratios increase toward subduction zones (at ridges, 0.13 to 0.17; at back arcs, 0.15 to 0.19; and at arcs, 0.18 to 0.32) and correlate linearly with H2O content and element tracers of slab-derived fluids. These observations indicate a direct link between mass transfer from the subducted plate and oxidation of the mantle wedge. PMID:19644118

Kelley, Katherine A; Cottrell, Elizabeth

2009-07-31

347

Water and the Oxidation State of Subduction Zone Magmas  

SciTech Connect

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

Kelley, K.; Cottrell, E

2009-01-01

348

The cycling of iron and manganese in the water column of Lake Sammamish, Washington  

USGS Publications Warehouse

Inventories of dissolved Mn and Fe in the bottom waters increase as the redox potential lowers with dissolved Mn inventories during stagnation being much larger than inventories of dissolved Fe. The shapes of the dissolved metal profiles indicate that dissolved Fe is supplied to the hypolimnion during stratification by diffusion of Fe(II) from the sediments into the overlying anoxic water as well as reduction of Fe oxide particles settling through the anoxic water column, while the dominant source of dissolved Mn to the anoxic bottom waters during most of the stratification period appears to be reduction of settling Mn-oxide particles. Inventories of particulate Fe in the hypolimnion during the latter stages of stratification are significantly larger than inventories of particulate Mn. Peaks of particulate Fe and Mn occur in the water column from July through November and particulate Mn peaks always occur at shallower depths than peaks of particulate Fe. -from Authors

Balistrieri, L.S.; Murray, J.W.; Paul, B.

1992-01-01

349

Domestic water uses: characterization of daily cycles in the north region of Portugal.  

PubMed

Nowadays, there is an increasing discussion among specialists about water use efficiency and the best measures to improve it. In Portugal, there have been a few attempts to expand the implementation of in situ water reuse projects. However, there is a lack of information about indoor water uses and how they are influenced by sociodemographic characteristics. There are several studies that investigate per capita global water usage, but the partitioning of this volume per domestic device and daily cycles is yet unknown. Identified as one of the key questions in sustainable building design, the water end-use is of primary importance to the design of hydraulic networks in buildings. In order to overcome this lack, a quantitative characterization of daily water uses for each domestic device was performed, based on a weekly monitoring program in fifty-two different dwellings in the northern region of Portugal (Vila Real, Valpaços and Oporto). For forty of them, each water usage of different domestic devices of each dwelling was recorded. At the same time, the remaining twelve dwellings were also monitored in order to register the volume of water consumed in each utilization of each domestic device. This paper presents the results of this complete monitoring program, using collected data to establish indoor water use patterns for each domestic device, aiming to support a more realistic approach to residential water use. The daily cycles in the different cities, where the monitoring program was performed, are also presented, in order to evaluate possible influences of sociodemographic characteristics. PMID:23685370

Matos, Cristina; Teixeira, Carlos A; Duarte, A A L S; Bentes, I

2013-08-01

350

Life cycle assessment of buildings technologies: High-efficiency commercial lighting and residential water heaters  

SciTech Connect

In this study the life cycle emissions and energy use are estimated for two types of energy technologies. The first technology evaluated is the sulfur lamp, a high-efficiency lighting system under development by the US Department of Energy (DOE) and Fusion Lighting, the inventor of the technology. The sulfur lamp is compared with conventional metal halide high-intensity discharge lighting systems. The second technology comparison is between standard-efficiency and high-efficiency gas and electric water heaters. In both cases the life cycle energy use and emissions are presented for the production of an equivalent level of service by each of the technologies. For both analyses, the energy use and emissions from the operation of the equipment are found to dominate the life cycle profile. The life cycle emissions for the water heating systems are much more complicated. The four systems compared include standard- and high-efficiency gas water heaters, standard electric resistance water heaters, and heat pump water heaters.

Freeman, S.L.

1997-01-01

351

Transpiring wall supercritical water oxidation test reactor design report  

SciTech Connect

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

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

1996-02-01

352

A vision for an ultra-high resolution integrated water cycle observation and prediction system  

NASA Astrophysics Data System (ADS)

Society's welfare, progress, and sustainable economic growth—and life itself—depend on the abundance and vigorous cycling and replenishing of water throughout the global environment. The water cycle operates on a continuum of time and space scales and exchanges large amounts of energy as water undergoes phase changes and is moved from one part of the Earth system to another. We must move toward an integrated observation and prediction paradigm that addresses broad local-to-global science and application issues by realizing synergies associated with multiple, coordinated observations and prediction systems. A central challenge of a future water and energy cycle observation strategy is to progress from single variable water-cycle instruments to multivariable integrated instruments in electromagnetic-band families. The microwave range in the electromagnetic spectrum is ideally suited for sensing the state and abundance of water because of water's dielectric properties. Eventually, a dedicated high-resolution water-cycle microwave-based satellite mission may be possible based on large-aperture antenna technology that can harvest the synergy that would be afforded by simultaneous multichannel active and passive microwave measurements. A partial demonstration of these ideas can even be realized with existing microwave satellite observations to support advanced multivariate retrieval methods that can exploit the totality of the microwave spectral information. The simultaneous multichannel active and passive microwave retrieval would allow improved-accuracy retrievals that are not possible with isolated measurements. Furthermore, the simultaneous monitoring of several of the land, atmospheric, oceanic, and cryospheric states brings synergies that will substantially enhance understanding of the global water and energy cycle as a system. The multichannel approach also affords advantages to some constituent retrievals—for instance, simultaneous retrieval of vegetation biomass would improve soil-moisture retrieval by avoiding the need for auxiliary vegetation information. This multivariable water-cycle observation system must be integrated with high-resolution, application relevant prediction systems to optimize their information content and utility is addressing critical water cycle issues. One such vision is a real-time ultra-high resolution locally-moasiced global land modeling and assimilation system, that overlays regional high-fidelity information over a baseline global land prediction system. Such a system would provide the best possible local information for use in applications, while integrating and sharing information globally for diagnosing larger water cycle variability. In a sense, this would constitute a hydrologic telecommunication system, where the best local in-situ gage, Doppler radar, and weather station can be shared internationally, and integrated in a consistent manner with global observation platforms like the multivariable water cycle mission. To realize such a vision, large issues must be addressed, such as international data sharing policy, model-observation integration approaches that maintain local extremes while achieving global consistency, and methods for establishing error estimates and uncertainty.

Houser, P. R.

2013-05-01

353

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

354

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

PubMed

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

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

2007-07-31

355

Unraveling ?1-Pyrroline-5-Carboxylate-Proline Cycle in Plants by Uncoupled Expression of Proline Oxidation Enzymes*  

PubMed Central

The two-step oxidation of proline in all eukaryotes is performed at the inner mitochondrial membrane by the consecutive action of proline dehydrogenase (ProDH) that produces ?1-pyrroline-5-carboxylate (P5C) and P5C dehydrogenase (P5CDH) that oxidizes P5C to glutamate. This catabolic route is down-regulated in plants during osmotic stress, allowing free Pro accumulation. We show here that overexpression of MsProDH in tobacco and Arabidopsis or impairment of P5C oxidation in the Arabidopsis p5cdh mutant did not change the cellular Pro to P5C ratio under ambient and osmotic stress conditions, indicating that P5C excess was reduced to Pro in a mitochondrial-cytosolic cycle. This cycle, involving ProDH and P5C reductase, exists in animal cells and now demonstrated in plants. As a part of the cycle, Pro oxidation by the ProDH-FAD complex delivers electrons to the electron transport chain. Hyperactivity of the cycle, e.g. when an excess of exogenous l-Pro is provided, generates mitochondrial reactive oxygen species (ROS) by delivering electrons to O2, as demonstrated by the mitochondria-specific MitoSox staining of superoxide ions. Lack of P5CDH activity led to higher ROS production under dark and light conditions in the presence of Pro excess, as well as rendered plants hypersensitive to heat stress. Balancing mitochondrial ROS production during increased Pro oxidation is therefore critical for avoiding Pro-related toxic effects. Hence, normal oxidation of P5C to Glu by P5CDH is key to prevent P5C-Pro intensive cycling and avoid ROS production from electron run-off. PMID:19635803

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

2009-01-01

356

Efficient water oxidation with organometallic iridium complexes as precatalysts.  

PubMed

Catalytic water oxidation has been investigated using five iridium complexes as precatalysts and NaIO4 as an oxidant at various pH conditions. An increase in the activity of all complexes was observed with increasing pH. A detailed analysis of spectroscopic data together with O2-evolution experiments using Cp*Ir(6,6?-dihydroxy-2,2?-bipyridine)(OH2)(2+) as a precatalyst indicate that the high catalytic activity is closely connected with transient species (A) that exhibits an absorption band at ?max 590 nm. The formation of this active form is strongly dependent on reaction conditions, and the species was distinctly observed using a small excess of periodate. However, another species absorbing at 600 nm (B), which seems to be a less active catalyst, was also observed and was more prominent at high oxidant concentration. Dynamic light scattering analysis and transmission electron microscopy have identified species B as 120 nm nanoparticles. The ultrafiltration method has revealed that species A can be attributed to particles with size in the range of 0.5–2 nm, possibly small IrOx clusters similar to those described previously by Harriman and co-workers (J. Phys. Chem., 1991, 95, 616–621). PMID:24549266

Lewandowska-Andralojc, Anna; Polyansky, Dmitry E; Wang, Chiu-Hui; Wang, Wan-Hui; Himeda, Yuichiro; Fujita, Etsuko

2014-06-28

357

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

PubMed

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

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

2013-11-01

358

Atmospheric chemistry of nitrogen on Mars: A link between oxidants in the soil and chlorine cycling  

NASA Astrophysics Data System (ADS)

NO and NO2, collectively denoted NOx, are generated in the Earth's atmosphere mainly from the photochemistry of biogenic nitrogen-containing gases whereas on Mars they form through the oxidation of products derived from ionospheric dissociation of N2. NOx disappears from both atmospheres when acids form from further oxidation and deposit to the surface. We show that peroxynitric acid (PNA), HO2NO2, dominates the removal of NOx from the atmosphere of Mars in contrast to nitric acid, HNO3, in the Earth's atmosphere because PNA is stabile against thermal decomposition at the colder temperatures of Mars. Following the dry deposition of PNA, peroxynitrate or peroxynitrite minerals are possible, while a proportion of PNA may also decompose and recycle NOx back to the atmosphere. Deposition of PNA must have been delivering nitrogen to the martian surface since at least ~3 Ga (during the Amazonian) when Mars has been predominantly cold and dry. In aqueous solution, peroxynitrates or peroxynitrites decompose and release O2. Thus, their inevitable formation from atmospheric chemistry could explain the release of O2 when water was added to the martian soil in the Viking Lander (VL) Gas Exchange experiment. Furthermore, PNA could interact with chlorides to liberate chlorine volatiles, enabling cyclic oxidation of chlorine compounds into perchlorate even in the absence of volcanic chlorine volatiles.

Catling, D. C.; Smith, M. L.; Claire, M. W.; Zahnle, K. J.

2013-09-01

359

Electroreduction-based electrochemical-enzymatic redox cycling for the detection of cancer antigen 15-3 using graphene oxide-modified indium-tin oxide electrodes.  

PubMed

We compare herein biosensing performance of two electroreduction-based electrochemical-enzymatic (EN) redox-cycling schemes [the redox cycling combined with simultaneous enzymatic amplification (one-enzyme scheme) and the redox cycling combined with preceding enzymatic amplification (two-enzyme scheme)]. To minimize unwanted side reactions in the two-enzyme scheme, ?-galactosidase (Gal) and tyrosinase (Tyr) are selected as an enzyme label and a redox enzyme, respectively, and Tyr is selected as a redox enzyme label in the one-enzyme scheme. The signal amplification in the one-enzyme scheme consists of (i) enzymatic oxidation of catechol into o-benzoquinone by Tyr and (ii) electroreduction-based EN redox cycling of o-benzoquinone. The signal amplification in the two-enzyme scheme consists of (i) enzymatic conversion of phenyl ?-d-galactopyranoside into phenol by Gal, (ii) enzymatic oxidation of phenol into catechol by Tyr, and (iii) electroreduction-based EN redox cycling of o-benzoquinone including further enzymatic oxidation of catechol to o-benzoquinone by Tyr. Graphene oxide-modified indium-tin oxide (GO/ITO) electrodes, simply prepared by immersing ITO electrodes in a GO-dispersed aqueous solution, are used to obtain better electrocatalytic activities toward o-benzoquinone reduction than bare ITO electrodes. The detection limits for mouse IgG, measured with GO/ITO electrodes, are lower than when measured with bare ITO electrodes. Importantly, the detection of mouse IgG using the two-enzyme scheme allows lower detection limits than that using the one-enzyme scheme, because the former gives higher signal levels at low target concentrations although the former gives lower signal levels at high concentrations. The detection limit for cancer antigen (CA) 15-3, a biomarker of breast cancer, measured using the two-enzyme scheme and GO/ITO electrodes is ca. 0.1 U/mL, indicating that the immunosensor is highly sensitive. PMID:24428396

Park, Seonhwa; Singh, Amardeep; Kim, Sinyoung; Yang, Haesik

2014-02-01

360

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

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

361

Life cycle assessment of three water systems in Copenhagen--a management tool of the future.  

PubMed

Environmental life-cycle assessment (LCA) was applied to evaluate three different water systems of the water sector in Copenhagen, Denmark, including technologies within water supply, facilities recycling water and treatment of sewer overflow. In these three water systems LCA was used to evaluate the environmental impacts of each of the processes involved. The overall conclusion was that LCA is suitable as a decision support tool in the water sector as it provides a holistic evaluation platform of the considered alternatives categorised in environmental impact categories. The use of LCA in the water sector of this region has limitations since it does not yet consider impact categories assessing freshwater scarcity and ecological sustainability. PMID:21278481

Godskesen, B; Zambrano, K C; Trautner, A; Johansen, N-B; Thiesson, L; Andersen, L; Clauson-Kaas, J; Neidel, T L; Rygaard, M; Kløverpris, N H; Albrechtsen, H-J

2011-01-01

362

Effects of Gravity on Supercritical Water Oxidation (SCWO) Processes  

NASA Technical Reports Server (NTRS)

The effects of gravity on the fluid mechanics of supercritical water jets are being studied at NASA to develop a better understanding of flow behaviors for purposes of advancing supercritical water oxidation (SCWO) technologies for applications in reduced gravity environments. These studies provide guidance for the development of future SCWO experiments in new experimental platforms that will extend the current operational range of the DECLIC (Device for the Study of Critical Liquids and Crystallization) Facility on board the International Space Station (ISS). The hydrodynamics of supercritical fluid jets is one of the basic unit processes of a SCWO reactor. These hydrodynamics are often complicated by significant changes in the thermo-physical properties that govern flow behavior (e.g., viscosity, thermal conductivity, specific heat, compressibility, etc), particularly when fluids transition from sub-critical to supercritical conditions. Experiments were conducted in a 150 ml reactor cell under constant pressure with water injections at various flow rates. Flow configurations included supercritical jets injected into either sub-critical or supercritical water. Profound gravitational influences were observed, particularly in the transition to turbulence, for the flow conditions under study. These results will be presented and the parameters of the flow that control jet behavior will be examined and discussed.

Hegde, Uday; Hicks, Michael

2013-01-01

363

Screening of water-splitting thermochemical cycles potentially attractive for hydrogen production by concentrated solar energy  

Microsoft Academic Search

Hydrogen, a promising and clean energy carrier, could potentially replace the use of fossil fuels in the transportation sector. Currently, no environmentally attractive, large-scale, low-cost and high-efficiency hydrogen production process is available for commercialization. Solar-driven water-splitting thermochemical cycles may constitute one of the ultimate options for CO2-free production of hydrogen. The method is environmentally friendly since it uses only water

Stéphane Abanades; Patrice Charvin; Gilles Flamant; Pierre Neveu

2006-01-01

364

Life cycle assessment of water reuse systems in an industrial park.  

PubMed

The rapid development of industrial parks in China has resulted in large resource consumption and pollutant emissions, especially freshwater use and wastewater discharge. Water reuse has attracted much attention from governments because of its potential to conserve freshwater and reduce pollutant emissions. However, water reuse usually means adding advanced treatment which consumes chemicals, materials and energy. Is the water reuse beneficial for the environment from a life cycle perspective? To answer this question, we quantified the environmental impacts of reusing treated wastewater at industrial parks under different scenarios through a comparative life-cycle assessment (LCA). Four scenarios are assessed: wastewater is treated and discharged, 20% and 99% of wastewater is treated and reused as industrial process water, and treated wastewater is used for horticulture. Inventory data were mainly obtained from a facility which manages the wastewater treatment and reuse system of an industrial park in Jiangsu Province. Environmental impacts were evaluated using the CML2001 method built into the GaBi version 4.3 database. The results show the water reuse is beneficial and the reuse rate significantly affects environmental performance of the system. It is also found that using the reclaimed water for higher value applications results in larger environmental credit. Decision makers in water management should consider both water quantity and quality and associated environmental impacts for different water reuse applications. PMID:24012874

Tong, Le; Liu, Xin; Liu, Xuewei; Yuan, Zengwei; Zhang, Qiong

2013-11-15

365

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

SciTech Connect

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

D. E. Shropshire

2009-01-01

366

Corrosion of high temperature alloys in supercritical water oxidation systems  

SciTech Connect

Supercritical water oxidation (SCWO) is a promising and very effective method for the oxidation of organic wastes. Its high solubility for organic compounds and its special physical properties (i.e. density, viscosity) resulting in a key advantage over standard processes like incineration. Due to the formation of HCl during oxidation of chlorine organics, a severe corrosion attack of most of the materials has been observed. This paper describes the results of investigations of high temperature alloys like alloy No. 214, alloy 602 CA, G-30 alloy, alloy 625, and alloy 686, exposed at 400 bar and 420 C for 24 hours in a CH{sub 2}Cl{sub 2}/H{sub 2}O{sub 2} mixture with about 2,000 wppm of chloride. The weight losses of all, samples varied between 3 mg/cm{sup 2} for G-30 alloy and about 73 mg/cm{sup 2} for alloy 686. The alloy No. 214 showed an increased corrosion for the preoxidized material, whereas the corrosion rate of alloy 602 CA was reduced by a factor of 3 due to the preoxidation at 900 C, prior to SCWO-exposure. The post mortem analysis revealed that alloy 686 has lost most of its nickel down to a depth of about 150 pm. The G-30 alloy showed a good corrosion behavior because of the formation of a protective oxide layer during the exposure. The layer was homogeneous with a thickness of about 12 pm, but a slight nickel leaching was observed, too.

Fodi, S.; Konys, J.; Hausselt, J.; Schmidt, H.; Casal, V. [Forschungszentrum Karlsruhe (Germany)

1998-12-31

367

Nanostructured Titanium Oxide Film- And Membrane-Based Photocatalysis For Water Treatment  

EPA Science Inventory

Titanium Oxide (TiO2) photocatalysis, one of the ultraviolet (UV)-based advanced oxidation technologies (AOTs) and nanotechnologies (AONs), has attracted great attention for the development of efficient water treatment and purification systems due to the effectiveness ...

368

Biological water-oxidizing complex: a nano-sized manganese-calcium oxide in a protein environment.  

PubMed

The resolution of Photosystem II (PS II) crystals has been improved using isolated PS II from the thermophilic cyanobacterium Thermosynechococcus vulcanus. The new 1.9 Å resolution data have provided detailed information on the structure of the water-oxidizing complex (Umena et al. Nature 473: 55-61, 2011). The atomic level structure of the manganese-calcium cluster is important for understanding the mechanism of water oxidation and to design an efficient catalyst for water oxidation in artificial photosynthetic systems. Here, we have briefly reviewed our knowledge of the structure and function of the cluster. PMID:22941557

Najafpour, Mohammad Mahdi; Moghaddam, Atefeh Nemati; Yang, Young Nam; Aro, Eva-Mari; Carpentier, Robert; Eaton-Rye, Julian J; Lee, Choon-Hwan; Allakhverdiev, Suleyman I

2012-10-01

369

Progress in the Los Alamos Scientific Laboratory program to develop thermochemical processes for hydrogen production. [Oxide-sulfate cycles; sulfuric acid cycles; bromide-sulfate cycles; sulfuric acid-sulfur cycles; hybrid cycles  

Microsoft Academic Search

The Los Alamos Scientific Laboratory Program to develop thermochemical processes for hydrogen production is based on attempts to develop criteria required of an ideal process and to search for types of thermochemical cycles that approximate these criteria. The advantages of reactions with large entropy changes have been demonstrated. The necessity for experimental verification of conceptual cycles has become apparent from

1976-01-01

370

PBO H2O: Plate Boundary Observatory Studies of the Water Cycle  

NASA Astrophysics Data System (ADS)

The EarthScope Plate Boundary Observatory was built to measure the deformation of the North American continent. PBO stations can also be used to measure ground displacements at much higher frequencies (5-Hz) for studies of fault slip during large earthquakes and for warnings of volcanic eruptions. There is also a long history of using atmospheric delays on the GPS signals to estimate precipitable water vapor (for weather and climate studies) and total electron content (space weather studies). Recently the PBO H2O research group has demonstrated that GPS signals that reflect from the nearby environment can be used for water cycle research. These GPS reflections measure how much water is in the top layer of the soil, how much snow is on its surface, and water content of nearby vegetation. Observing and monitoring spatial and temporal changes in the water cycle is critical for both understanding and predicting Earth's climate. Since GPS reflections encompass an area of ~1000 m^2, they provide a spatial footprint that complements satellite systems which sense much larger areas and in situ systems that sense regions < 1 m^2. Water cycle products are produced from PBO data each day and updated on the PBO H2O website.

Larson, K. M.; Small, E. E.; Chew, C. C.; Nievinski, F. G.; Pratt, J.; McCreight, J. L.; Braun, J.; Boniface, K.; Evans, S. G.

2013-12-01

371

Comparative simulations of dissolved organic matter cycling in idealized oceanic, coastal, and estuarine surface waters  

NASA Astrophysics Data System (ADS)

In this paper we used a steady-state ecosystem model that simulates both dissolved organic carbon (DOC) and nitrogen (DON) cycling to study how the planktonic community structure, nutrient availability, and dissolved organic matter (DOM) loading affect these cycles in idealized oceanic, coastal, and estuarine surface waters. The model was able to reproduce DOM and planktonic biomass distributions, uptake rates, and production rates (including DOM) that fell within ranges reported for oceanic, coastal, and estuarine systems. Using a sensitivity analysis we show that DOM cycling was intricately tied to the biomass concentration, distribution, and productivity of plankton. The efficiency of nutrient remineralization and the availability of inflowing nutrients and DON also played a large role in DOM cycling. In these simulations the largest autochthonous source of DOC was always phytoplankton exudation while important sources of DON varied considerably. In the oceanic simulations heterotrophic bacteria were particularly important for mediating DOM cycling because they were the primary agents that controlled nutrient recycling and supply (i.e., strong bottom-up control). In contrast, in the estuarine simulations mortality (mainly from grazing and viral lysis) had the most influence on DOM production. However, DOM cycling was generally less dependent on interactions between plankton in the estuarine case because of high nutrient and DOM loading. The coastal simulations were somewhere in between. In all simulations competition between different size classes of phytoplankton also played an important role in DOM cycling.

Keller, David P.; Hood, Raleigh R.

2013-01-01

372

Southern Ocean Iron Enrichment Experiment: Carbon Cycling in High and Low-Si Waters  

Microsoft Academic Search

The availability of iron is known to exert a controlling influence on biological productivity in surface waters over large areas of the ocean and may have been an important factor in the variation of the concentration of atmospheric carbon dioxide over glacial cycles. The effect of iron in the Southern Ocean is particularly important because of its large area and

Kenneth H. Coale; Kenneth S. Johnson; Francisco P. Chavez; Ken O. Buesseler; Richard T. Barber; Mark A. Brzezinski; William P. Cochlan; Frank J. Millero; Paul G. Falkowski; James E. Bauer; Rik H. Wanninkhof; Raphael M. Kudela; Mark A. Altabet; Burke E. Hales; Taro Takahashi; Michael R. Landry; Robert R. Bidigare; Xiujun Wang; Zanna Chase; Pete G. Strutton; Gernot E. Friederich; Maxim Y. Gorbunov; Veronica P. Lance; Anna K. Hilting; Michael R. Hiscock; Mark Demarest; William T. Hiscock; Kevin F. Sullivan; Sara J. Tanner; R. Mike Gordon; Craig N. Hunter; Virginia A. Elrod; Steve E. Fitzwater; Janice L. Jones; Sasha Tozzi; Michal Koblizek; Alice E. Roberts; Julian Herndon; Jodi Brewster; Nicolas Ladizinsky; Geoffrey Smith; David Cooper; David Timothy; Susan L. Brown; Karen E. Selph; Cecelia C. Sheridan; Benjamin S. Twining; Zackary I. Johnson

2004-01-01

373

THE EFFECTS OF CHANGING ECONOMIC CONDITIONS ON FUEL CYCLE COSTS IN PRESSURIZED WATER REACTORS  

Microsoft Academic Search

The effects of changing economic conditions on fuel cycle costs in an ; advsnced pressurized-water power reactor with free-standing stainless steel or ; Zircaloy fuel cladding are analyzed for eight different cost bases. These cost ; bases represent the effect of most of the combinations of economic conditions ; likely to occur during the life of the 461 Mw(e) reactor.

M. Benedict; H. Fenech; M. C. Richardson

1963-01-01

374

Production and Cycling of Methylated Mercury Species in Arctic Marine Waters  

Microsoft Academic Search

Monomethyl mercury (MMHg), a vertebrate neurotoxin which bioaccumulates through foodwebs, is found in some Arctic marine mammals at levels that may be harmful to northern peoples consuming them as food. Unfortunately, sources of MMHg to polar marine food webs remain unknown, in part due to the complex nature of Hg cycling in polar marine waters. Since 2005, we have been

I. Lehnherr; V. L. St. Louis; H. Hintelmann

2009-01-01

375

Studying the Water Cycle in an Environmental Context: The "Blue Planet" Program.  

ERIC Educational Resources Information Center

The Blue Planet program aims to develop an understanding of and insight into the environment among students by introducing environmental problems such as pollution. This paper presents a study investigating junior high school students' previous knowledge and understanding of environmental issues and perceptions on the nature of the water cycle

Ben-zvi-assaraf, Orit; Orion, Nir

376

The optimum design of air cycle refrigeration system with high pressure water separation  

Microsoft Academic Search

A mathematical model is developed for designing air-cycle refrigeration systems with known performance parameters and functional characteristics. The refrigeration systems considered are designed with high-pressure water separation, and attention is given to the attendant problems of freezing at the condenser outlet and design strategies for the cooling turbine. The design point selected for the model is at the maximum flight

Yu Wang; Xiu-Gan Yuan

1992-01-01

377

CHLORINATION BY-PRODUCTS IN DRINKING WATER AND MENSTRUAL CYCLE FUNCTION  

EPA Science Inventory

Chlorination by-Products in Drinking Water and Menstrual Cycle Function Gayle C. Windham1, Kirsten Waller2, Meredith Anderson2, Laura Fenster1, Pauline Mendola3, Shanna Swan4 1California Department of Health Services, Division of Environmental and Occupational Disea...

378

Studies on water-steam Rankine-cycle solar central receiver power plants. Final report  

Microsoft Academic Search

Cost estimates are provided for four 150 MWe solar hybrid central receiver power plants, based on the updating of conceptual designs developed in a previous EPRI solar hybrid power plant cost study, Water\\/Steam Rankine Cycle Solar Central Receiver Power Plant Cost Estimates. The power plants are hybrid in that main steam is generated in a central receiver and a conventional

J. R. Darnell; R. L. Lessley; J. A. Paffenbarger; A. A. Agur

1985-01-01

379

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

E-print Network

Short note Water, carbon and nitrogen cycling in a rendzina soil cropped with winter oilseed rape: the Châlons Oilseed Rape Database Ghislain Gosse Pierre Cellier Pascal Denoroy Benoit Gabriellea Patricia January 1999) Abstract - The Châlons Oilseed Rape Database holds the results of a comprehensive experiment

Paris-Sud XI, Université de

380

The Mackenzie GEWEX Study: The Water and Energy Cycles of a Major North American River Basin  

Microsoft Academic Search

The Mackenzie River is the largest North American source of freshwater for the Arctic Ocean. This basin is subjected to wide fluctuations in its climate and it is currently experiencing a pronounced warming trend. As a major Canadian contribution to the Global Energy and Water Cycle Experiment (GEWEX), the Mackenzie GEWEX Study (MAGS) is focusing on understanding and modeling the

R. E. Stewart; R. W. Crawford; H. G. Leighton; P. Marsh; G. S. Strong; G. W. K. Moore; H. Ritchie; W. R. Rouse; E. D. Soulis; B. Kochtubajda

1998-01-01

381

Pleistocene water cycle and eastern boundary current processes along the California continental margin  

Microsoft Academic Search

Coastal marine sediments contain mixtures of terrestrial and marine paleoclimate proxies that record how the coastal water cycle has behaved over long time frames. We explore a 600 kyr marine record from ODP Site 1018, located due west of Santa Cruz, California, to identify coastal wet and dry periods and to associate them with oceanographic processes. Wet periods in central

Mitchell Lyle; Linda Heusser; Christina Ravelo; Dyke Andreasen; Annette Olivarez Lyle; Noah Diffenbaugh

2010-01-01

382

Synthesis and Characterization of Oxide Feedstock Powders for the Fuel Cycle R&D Program  

SciTech Connect

Nuclear fuel feedstock properties, such as physical, chemical, and isotopic characteristics, have a significant impact on the fuel fabrication process and, by extension, the in-reactor fuel performance. This has been demonstrated through studies with UO{sub 2} spanning greater than 50 years. The Fuel Cycle R&D Program with The Department of Energy Office of Nuclear Energy has initiated an effort to develop a better understanding of the relationships between oxide feedstock, fresh fuel properties, and in-reactor fuel performance for advanced mixed oxide compositions. Powder conditioning studies to enable the use of less than ideal powders for ceramic fuel pellet processing are ongoing at Los Alamos National Laboratory (LANL) and an understanding of methods to increase the green density and homogeneity of pressed pellets has been gained for certain powders. Furthermore, Oak Ridge National Laboratory (ORNL) is developing methods for the co-conversion of mixed oxides along with techniques to analyze the degree of mixing. Experience with the fabrication of fuel pellets using co-synthesized multi-constituent materials is limited. In instances where atomically mixed solid solutions of two or more species are needed, traditional ceramic processing methods have been employed. Solution-based processes may be considered viable synthesis options, including co-precipitation (AUPuC), direct precipitation, direct-conversion (Modified Direct Denitration or MDD) and internal/external gelation (sol-gel). Each of these techniques has various advantages and disadvantages. The Fiscal Year 2010 feedstock development work at ORNL focused on the synthesis and characterization of one batch of UO{sub x} and one batch of U{sub 80}Ce{sub 20}O{sub x}. Oxide material synthesized at ORNL is being shipped to LANL for fuel fabrication process development studies. The feedstock preparation was performed using the MDD process which utilizes a rotary kiln to continuously thermally denitrate double salts of ammonium and metals to produce free-flowing powders that have good ceramic properties for fuel fabrication. Feedstock powder properties of interest include: particle size and distribution, surface area, phase purity, morphology, tap and bulk density, and flow characteristics.

Voit, Stewart L [ORNL; Vedder, Raymond James [ORNL; Johnson, Jared A [ORNL

2010-09-01

383

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

EPA Science Inventory

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

384

Saliva-Serum Ratios of Deuterium Oxide after Administration of Heavy Water  

Microsoft Academic Search

TOTAL body water may be estimated by administering a known weight of deuterium oxide and, after equilibration has occurred, determining its concentration in water obtained from some body fluid. Faller et al.1 have shown that, within the limits of experimental error, the same values are obtained for total body water whether the deuterium oxide is administered orally or intravenously. Serum

Nan Taggart; F. E. Hytten

1959-01-01

385

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

Microsoft Academic Search

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

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

2011-01-01

386

Oxidation of Ultra High Temperature Ceramics in Water Vapor  

NASA Technical Reports Server (NTRS)

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 (90 percent) using a cyclic vertical furnace at 1 atm. The total exposure time was 10 h at temperatures of 1200, 1300, and 1400 C. CVD SiC was also evaluated as a baseline for comparison. Weight change, X-ray diffraction analyses, surface and cross-sectional SEM and EDS were performed. These results are compared with tests ran in a stagnant air furnace at temperatures of 1327 C for 100 min, and with high pressure burner rig (HPBR) results at 1100 and 1300 C at 6 atm for 50 h. Low velocity water vapor does not make a significant contribution to the oxidation rates of UHTCs when compared to stagnant air. The parabolic rate constants at 1300 C, range from 0.29 to 16.0 mg(sup 2)cm(sup 4)/h for HS and ZCS, respectively, with ZS results between these two values. Comparison of results for UHTCs tested in the furnace in 90 percent water vapor with HPBR results was difficult due to significant sample loss caused by spallation in the increased velocity of the HPBR. Total recession measurements are also reported for the two test environments.

Nguyen, QuynhGiao N.; Opila, Elizabeth J.; Robinson, Raymond C.

2004-01-01

387

Advanced Oxidation Treatment of Drinking Water: Part II. Turbidity, Particles and Organics Removal from Lake Huron Water  

Microsoft Academic Search

Pre-coagulation ozonation has been reported to be effective in drinking water treatment processes. Limited data are available on the impact of advanced oxidation processes (AOPs) on Lake Huron water which serves as a primary source of drinking water for many communities around the Great Lakes region. Impact of ozone\\/hydrogen peroxide based AOP on Lake Huron water was studied. The results

M. F. Rahman; S. Y. Jasim; E. K. Yanful; S. Ndiongue; D. Borikar

2010-01-01

388

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

NASA Astrophysics Data System (ADS)

Large terrestrial planets are expected to have muted topography and deep oceans, implying they should be entirely covered in water, so-called waterworlds. Quantitatively, a planet ten times the mass of Earth is not expected to have exposed continents unless it has a water mass fraction less than 3×10-5, roughly ten times drier than Earth. This is important because waterworlds lack a silicate weathering thermostat so their climate is predicted to be less stable than that of planets with exposed continents. Water is partitioned, however, between a surface reservoir, the ocean, and an interior reservoir, the mantle. Plate tectonics transports water between these reservoirs on geological timescales. Degassing of melt at mid-ocean ridges and serpentinization of oceanic crust are mediated by sea-floor pressure, providing a stabilizing feedback on long-term ocean volume. Motivated by Earth's approximately steady-state deep water cycle, we develop a two-box model of the hydrosphere and derive steady-state solutions to the water-partitioning on terrestrial planets. Since hydrostatic pressure is proportional to gravity, super-Earths with a deep water cycle will tend to store most of their water in the mantle. We conclude that tectonically active terrestrial planets with H2O mass fractions less than 3×10-3 will have both oceans and exposed continents. The circumstellar habitable zone is therefore equally wide for any tectonically active planet.

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

2014-01-01

389

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

Microsoft Academic Search

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

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

2007-01-01

390

Fragments of layered manganese oxide are the real water oxidation catalyst after transformation of molecular precursor on clay.  

PubMed

A binuclear manganese molecular complex [(OH2)(terpy)Mn(?-O)2Mn(terpy)(OH2)](3+) (1) is the most prominent structural and functional model of the water-oxidizing Mn complex operating in plants and cyanobacteria. Supported on montmorillonite clay and using Ce(IV) as a chemical oxidant, 1 has been reported to be one of the best Mn-based molecular catalysts toward water oxidation. By X-ray absorption spectroscopy and kinetic analysis of the oxygen evolution reaction, we show that [(OH2)(terpy)Mn(?-O)2Mn(terpy)(OH2)](3+) is transformed into layered type Mn-oxide particles which are the actual water oxidation catalyst. PMID:24798550

Najafpour, M M; Moghaddam, Atefeh N; Dau, Holger; Zaharieva, Ivelina

2014-05-21

391

Possible Links Between Biomass Burning And The Water Cycle In Northern Sub-Saharan Africa  

NASA Astrophysics Data System (ADS)

The northern sub-Saharan African (NSSA) region, bounded on the north and south by the Sahara and the Equator, respectively, and stretching East-West across Africa, is very vulnerable because of the highly active environmental and meteorological processes associated with its unique location and human activities that potentially impact the regional water cycle. Over the years, this region has suffered frequent severe droughts that have caused tremendous hardship and loss of life to millions of its inhabitants due to the rapid depletion of the regional water resources, as exemplified by the dramatic drying of Lake Chad. On the other hand, the NSSA region shows one of the highest biomass-burning rates per unit land area among all regions of the world. Because of the high concentration and frequency of fires in this region, with the associated abundance of heat release and gaseous and particulate smoke emissions, biomass-burning activity is believed to be one of the drivers of the regional carbon and energy cycles, with serious implications for the water cycle. An interdisciplinary research effort sponsored by NASA is presently being focused on the NSSA region, to better understand possible connections between the intense biomass burning observed from satellite year after year across the region and the water cycle, through associated changes in land-cover, albedo, soil moisture, evapotranspiration, emissions, atmospheric processes, precipitation, surface runoff, and groundwater recharge. A combination of remote sensing and modeling approaches is being utilized to investigate these multiple processes to clarify possible links between them. We are finding significant covariance (positive or negative) between them, although we are yet to establish cause-and-effect relationships. In this presentation, we will discuss interesting results as well as the path toward improved understanding of the interrelationships and feedbacks between the water cycle components and the environmental change dynamics due to biomass burning and related processes in the NSSA region.

Ichoku, C. M.; Gatebe, C. K.; Lee, J.; Wang, J.; Bolten, J. D.; Policelli, F.; Wilcox, E. M.; Adegoke, J. O.; Habib, S.

2012-12-01

392

Integrated supercritical water gasification combined cycle (IGCC) systems for improved performance and reduced operating costs in existing plants  

SciTech Connect

A revolutionary hydrothermal heat recovery steam generator (HRSG) is being developed to produce clean fuels for gas turbines from slurries and emulsions of opportunity fuels. Water can be above 80% by weight and solids below 20%, including coal fines, coal water fuels, biomass, composted municipal refuse, sewage sludge and bitumen/Orimulsion. The patented HRSG tubes use a commercial method of particle scrubbing to improve heat transfer and prevent corrosion and deposition on heat transfer surfaces. A continuous-flow pilot plant is planned to test the HRSG over a wide range of operating conditions, including the supercritical conditions of water, above 221 bar (3,205 psia) and 374 C (705 F). Bench scale data shows, that supercritical water gasification below 580 C (1,076 F) and low residence time without catalysts or an oxidizer can produce a char product that can contain carbon up to the amount of fixed carbon in the proximate analysis of the solids in the feed. This char can be burned with coal in an existing combustion system to provide the heat required for gasification. The new HRSG tubes can be retrofitted into existing power plant boilers for repowering of existing plants for improved performance and reduced costs. A special condensing turbine allows final low-temperature cleaning and maintains quality and combustibility of the fuel vapor for modern gas turbine in the new Vapor Transmission Cycle (VTC). Increased power output and efficiency can be provided for existing plants, while reducing fuel costs. A preliminary computer-based process simulation model has been prepared that includes material and energy balances that simulate commercial-scale operations of the VTC on sewage sludge and coal. Results predict over 40% HHV thermal efficiency to electric power from sewage sludge at more than 83% water by weight. The system appears to become autothermal (no supplemental fuel required) at about 35% fixed carbon in the feed. Thus, bituminous and lignite coal slurries could be gasified at less than 25% coal and more than 75% water. Preliminary life cycle cost analyses indicate that disposal fees for sewage sludge improve operating economics over fuel that must be purchased, the cost and schedule advantages of natural gas-fired combined cycle systems are preserved. Sensitivity analyses show that increasing capital costs by 50% can be offset by an increase in sewage sludge disposal fees of $10/metric ton.

Tolman, R.; Parkinson, W.J.

1999-07-01

393

Roles of Oxygen and Water Vapor in the Oxidation of Halogen Terminated Ge(111) Surfaces  

SciTech Connect

The initial stage of the oxidation of Cl and Br terminated Ge(111) surfaces is studied using photoelectron spectroscopy. The authors perform controlled experiments to differentiate the effects of different factors in oxidation, and find that water vapor and oxygen play different roles. Water vapor effectively replaces the halogen termination layers with the hydroxyl group, but does not oxidize the surfaces further. In contrast, little oxidation is observed for Cl and Br terminated surfaces with dry oxygen alone. However, with the help of water vapor, oxygen oxidizes the surface by breaking the Ge-Ge back bonds instead of changing the termination layer.

Sun, Shiyu; /Stanford U., Phys. Dept.; Sun, Yun; Liu, Zhi; Lee, Dong-Ick; Pianette, Piero; /SLAC, SSRL

2006-12-18

394

Differences in fungicidal efficiency against Aspergillus flavus for neutralized and acidic electrolyzed oxidizing waters  

Microsoft Academic Search

Neutralized electrolyzed oxidizing water (NEW) and acidic electrolyzed oxidizing water (AcEW) are electrolyzed oxidizing waters (EOW) that have significantly different fungicidal efficiencies against Aspergillus flavus (A. flavus) (The actuation durations of no survival population to NEW and AcEW were 90s and 120s, respectively.), even when used at the same available chlorine concentration (30ppm). It has been verified by our previous

Ke Xiong; Hai-jie Liu; Rong Liu; Li-te Li

2010-01-01

395

Swirl injectors for oxidizer-rich staged combustion cycle engines and hypergolic propellants  

NASA Astrophysics Data System (ADS)

Presented here are two efforts concerning the application of swirl injectors to rocket engine main chamber injectors. The first study was undertaken to develop a liquid/liquid bi-centrifugal swirl injector for use with new hypergolic propellants in conjunction with KB Sciences and China Lake. The second study focuses on gas/liquid swirl injectors typically used for main chamber elements in oxidizer-rich staged combustion engines. The design, development and testing of hypergolic liquid/liquid bi-centrifugal swirl injector for use with rocket grade hydrogen peroxide (RGHP) and non-toxic hypergolic miscible fuels (NHMF) are discussed first. Cold flow tests were conducted to measure the spray cone angle and discharge coefficient of the injector, and allow for comparison with theoretical predictions to evaluate the design model. The goal of this effort was to establish a method to design swirl injectors operating in a thrust regime of 35 lbf, characteristic lengths of 30 in, and c* efficiencies above 90%. A literature review of existing inviscid swirl models is provided. The bi-centrifugal swirler design process is described, along with the design features of the series of bicentrifugal swirl injectors that were built. Results from cold flow experiments are compared to the theoretical predictions of the models reviewed. Characteristic velocity (c*) efficiencies of 70-92% were measured. Next an introduction will be made to the transition of the study into the research regarding swirl injectors for the oxidizer rich staged combustion (ORSC) cycle. The goals of the effort described here are to establish an empirical knowledge base to provide a fundamental understanding of main chamber injectors and for verification of an injector design methodology for the ORSC cycle. The derivation of the baseline operating conditions is discussed. The liquid oxygen/hydrogen (LOX/H2) preburner and GOX/RP-1 injector design and hardware are detailed. Two alternative injector designs chosen to explore the stability margins of this type of injector and give a quantitative comparison of the dynamic response to the baseline injector geometry are presented. The hydrogen/oxygen torch igniter with established heritage used in the preburner is briefly discussed. Finally, the results of igniter and preburner testing are presented.

Long, Matthew R.

396

Oxidation of Ultra-High Temperature Ceramics in Water Vapor  

NASA Technical Reports Server (NTRS)

Ultra high temperature ceramics (UHTCs) including HfB2 + SiC (20% by volume), ZrB2 + SiC (20% by volume) and ZrB2 + SiC (14% by volume) + C (30% by volume) have historically been evaluated as reusable thermal protection systems for hypersonic vehicles. This study investigates UHTCs for use as potential combustion and aeropropulsion engine materials. These materials were oxidized in water vapor (90%) using a cyclic vertical furnace at 1 atm. The total exposure time was 10 hours at temperatures of 1200, 1300, and 1400 C. CVD SiC was also evaluated as a baseline comparison. Weight change measurements, X-ray diffraction analyses, surface and cross-sectional SEM and EDS were performed. These results will be compared with tests ran in static air at temperatures of 1327, 1627, and 1927 C. Oxidation comparisons will also be made to the study by Tripp. A small number of high pressure burner rig (HPBR) results at 1100 and 1300 C will also be discussed. Specific weight changes at all three temperatures along with the SIC results are shown. SiC weight change is negligible at such short duration times. HB2 + SiC (HS) performed the best out of all the tested UHTCS for all exposure temperatures. ZrB2 + Sic (ZS) results indicate a slightly lower oxidation rate than that of ZrBl + SiC + C (ZCS) at 1200 and 1400 C, but a clear distinction can not be made based on the limited number of tested samples. Scanning electron micrographs of the cross-sections of all the UHTCs were evaluated. A representative area for HS is presented at 1400 C for 26 hours which was the composition with the least amount of oxidation. A continuous SiO2 scale is present in the outer most edge of the surface. An image of ZCS is presented at 1400 C for 10 hours, which shows the most degradation of all the compositions studied. Here, the oxide surface is a mixture of ZrSiO4, ZrO2 and SO2.

Nguyen, QuynhGiao N.; Opila, Elizabeth J.; Robinson, Raymond C.

2003-01-01

397

Destruction of explosives and rocket fuels by supercritical water oxidation  

SciTech Connect

Traditional methods for disposing of PEPs have been open burning or open detonation (OB/OD); however, regulatory agencies are likely to prohibit OB/OD because of the uncontrolled air emissions and soil contaminations. Likewise, controlled incineration carries a liability for air pollution because large quantities of NO{sub x} are produced in the conventional combustion chemistry of PEPS. Soil and ground water have already been contaminated with PEPs through normal operations at manufacturing plants and military bases. Incineration can be used for decontamination of these soils, with the associated liability for air pollution, but few satisfactory and economic methods exist for ground water decontamination. A clear need exists for improved disposal and destruction methods. The destruction of energetic materials, including propellants, explosives and pyrotechnics (PEPS) by oxidation in supercritical water is described. The focus is on the chemistry of the process. The destruction efficiencies and products of reaction contained in the aqueous and gaseous effluents of several representative PEPs are reported.

Dyer, R.B.; Buelow, S.J.; Harradine, D.M.; Robinson, J.M.; Foy, B.R.; Atencio, J.H.; Dell'Orco, P.C.; Funk, K.A.; McInroy, R.E.; Rofer, C.K.; Counce, D.A.; Trujillo, P.E. Jr. (Los Alamos National Lab., NM (United States)); Wander, J.D. (Hq. AFB Civil Engineering Support Agency, Tyndall AFB, FL (United States))

1992-01-01

398

Destruction of explosives and rocket fuels by supercritical water oxidation  

SciTech Connect

Traditional methods for disposing of PEPs have been open burning or open detonation (OB/OD); however, regulatory agencies are likely to prohibit OB/OD because of the uncontrolled air emissions and soil contaminations. Likewise, controlled incineration carries a liability for air pollution because large quantities of NO{sub x} are produced in the conventional combustion chemistry of PEPS. Soil and ground water have already been contaminated with PEPs through normal operations at manufacturing plants and military bases. Incineration can be used for decontamination of these soils, with the associated liability for air pollution, but few satisfactory and economic methods exist for ground water decontamination. A clear need exists for improved disposal and destruction methods. The destruction of energetic materials, including propellants, explosives and pyrotechnics (PEPS) by oxidation in supercritical water is described. The focus is on the chemistry of the process. The destruction efficiencies and products of reaction contained in the aqueous and gaseous effluents of several representative PEPs are reported.

Dyer, R.B.; Buelow, S.J.; Harradine, D.M.; Robinson, J.M.; Foy, B.R.; Atencio, J.H.; Dell`Orco, P.C.; Funk, K.A.; McInroy, R.E.; Rofer, C.K.; Counce, D.A.; Trujillo, P.E. Jr. [Los Alamos National Lab., NM (United States); Wander, J.D. [Hq. AFB Civil Engineering Support Agency, Tyndall AFB, FL (United States)

1992-09-01

399

Numerical Simulation of the Water Cycle Change Over the 20th Century  

NASA Technical Reports Server (NTRS)

We have used numerical models to test the impact of the change in Sea Surface Temperatures (SSTs) and carbon dioxide (CO2) concentration on the global circulation, particularly focusing on the hydrologic cycle, namely the global cycling of water and continental recycling of water. We have run four numerical simulations using mean annual SST from the early part of the 20th century (1900-1920) and the later part (1980-2000). In addition, we vary the CO2 concentrations for these periods as well. The duration of the simulations is 15 years, and the spatial resolution is 2 degrees. We use passive tracers to study the geographical sources of water. Surface evaporation from predetermined continental and oceanic regions provides the source of water for each passive tracer. In this way, we compute the percent of precipitation of each region over the globe. This can also be used to estimate precipitation recycling. In addition, we are using the passive tracers to independently compute the global cycling of water (compared to the traditional, Q/P calculation).

Bosilovich, Michael G.; Schubert, Siegfried D.

2003-01-01

400

Importance of Rain Evaporation and Continental Convection in the Tropical Water Cycle  

NASA Technical Reports Server (NTRS)

Atmospheric moisture cycling is an important aspect of the Earth's climate system, yet the processes determining atmospheric humidity are poorly understood. For example, direct evaporation of rain contributes significantly to the heat and moisture budgets of clouds, but few observations of these processes are available. Similarly, the relative contributions to atmospheric moisture over land from local evaporation and humidity from oceanic sources are uncertain. Lighter isotopes of water vapour preferentially evaporate whereas heavier isotopes preferentially condense and the isotopic composition of ocean water is known. Here we use this information combined with global measurements of the isotopic composition of tropospheric water vapour from the Tropospheric Emission Spectrometer (TES) aboard the Aura spacecraft, to investigate aspects of the atmospheric hydrological cycle that are not well constrained by observations of precipitation or atmospheric vapour content. Our measurements of the isotopic composition of water vapour near tropical clouds suggest that rainfall evaporation contributes significantly to lower troposphere humidity, with typically 20% and up to 50% of rainfall evaporating near convective clouds. Over the tropical continents the isotopic signature of tropospheric water vapour differs significantly from that of precipitation, suggesting that convection of vapour from both oceanic sources and evapotranspiration are the dominant moisture sources. Our measurements allow an assessment of the intensity of the present hydrological cycle and will help identify any future changes as they occur.

Worden, John; Noone, David; Bowman, Kevin; Beer, R.; Eldering, A.; Fisher, B.; Gunson, M.; Goldman, Aaron; Kulawik, S. S.; Lampel, Michael; Osterman, Gregory; Rinsland, Curtis P.; Rogders, Clive; Sander, Stanley; Shepard, Mark; Webster, Christopher R.; Worden, H. M.

2007-01-01

401

Evaluation of Fe oxide-coated GAC for removal and recovery of Cu(II) from water  

SciTech Connect

A composite solid, prepared by precipice an Fe oxide onto granular activated carbon (GAC), was evaluated as an adsorbent for the removal and recovery of Cu(II) from water. Relative to adsorption onto uncoated GAC, Cu(II) adsorption capacity increased as the amount of Fe oxide increased, from about 1.4 mg/g for GAC to 5 mg/g for GAC coated with 37 mg Fe oxide/g GAC. Tests in a column process for Cu(II) removal demonstrated that the composite adsorbent could be reused through at least 15 adsorption and desorption cycles. Although a fraction of the adsorbed Cu(II) was retained by the solid, there was no apparent loss in adsorption capacity. Treatment of low concentration solutions was effective; a 100 {mu}g Cu(II)/L solution was reduced to no more than 3 {mu}g/L through 1,000 bed volumes processed.

Wang, T.C.; Chandra, K.P.; Anderson, P.R. [Illinois Inst. of Technology, Chicago, IL (United States). I. Pritzker Dept. of Environmental Engineering

1994-12-31

402

The Conceptual Design of an Integrated Nuclearhydrogen Production Plant Using the Sulfur Cycle Water Decomposition System  

NASA Technical Reports Server (NTRS)

A hydrogen production plant was designed based on a hybrid electrolytic-thermochemical process for decomposing water. The sulfur cycle water decomposition system is driven by a very high temperature nuclear reactor that provides 1,283 K helium working gas. The plant is sized to approximately ten million standard cubic meters per day of electrolytically pure hydrogen and has an overall thermal efficiently of 45.2 percent. The economics of the plant were evaluated using ground rules which include a 1974 cost basis without escalation, financing structure and other economic factors. Taking into account capital, operation, maintenance and nuclear fuel cycle costs, the cost of product hydrogen was calculated at $5.96/std cu m for utility financing. These values are significantly lower than hydrogen costs from conventional water electrolysis plants and competitive with hydrogen from coal gasification plants.

Farbman, G. H.

1976-01-01

403

Linking carbon and water cycles using stable isotopes across scales: progress and challenges  

NASA Astrophysics Data System (ADS)

Stable isotope analysis is a powerful tool for tracing biogeochemical processes in the carbon and water cycles. One particularly powerful approach is to employ multiple isotopes where the simultaneous assessment of the D/H,18O/16O and/or 13C/12C in different compounds provide a unique means to investigate the coupling of water and carbon fluxes at various temporal and spatial scales. Here, we present a research update on recent advances in our process-based understanding of the utilization of carbon, oxygen and hydrogen isotopes to lend insight into carbon and water cycling. We highlight recent technological developments and approaches, their strengths and methodological precautions with examples covering scales from minutes to centuries and from the leaf to the globe.

Werner, C.; Badeck, F.; Brugnoli, E.; Cohn, B.; Cuntz, M.; Dawson, T.; Gessler, A.; Ghashghaie, J.; Grams, T. E. E.; Kayler, Z.; Keitel, C.; Lakatos, M.; Lee, X.; Máguas, C.; Ogée, J.; Rascher, K. G.; Schnyder, H.; Siegwolf, R.; Unger, S.; Welker, J.; Wingate, L.; Zeeman, M. J.

2011-03-01

404

Maintenance Cycle Extension in the IRIS Advanced Light Water Reactor Plant Design  

SciTech Connect

New nuclear power generation in the United States will be realized only if the economic performance can be made competitive with other methods of electrical power generation. The economic performance of a nuclear power plant can be significantly improved by increasing the time spent on-line generating electricity relative to the time spent off-line conducting maintenance and refueling. Maintenance includes planned actions (surveillances) and unplanned actions (corrective maintenance) to respond to component degradation or failure. A methodology is described that can be used to resolve, in the design phase, maintenance-related operating cycle length barriers. A primary goal was to demonstrate the applicability and utility of the methodology in the context of the International Reactor, Innovative and Secure (IRIS) design. IRIS is an advanced light water nuclear power plant that is being designed to maximize this on-line generating time by increasing the operating cycle length. This is consequently a maintenance strategy paper using the IRIS plant as the example.Potential IRIS operating cycle length maintenance-related barriers, determined by modification of an earlier operating pressurized water reactor (PWR) plant cycle length analysis to account for differences between the design of IRIS and this operating PWR, are presented. The proposed methodology to resolve these maintenance-related barriers by the design process is described. The results of applying the methodology to two potential IRIS cycle length barriers, relief valve testing and emergency heat removal system testing, are presented.

Galvin, Mark R. [United States Navy (United States); Todreas, Neil E. [Massachusetts Institute of Technology (United States); Conway, Larry E. [Westinghouse Science and Technology (United States)

2003-09-15

405

Removal of H 2S via an iron catalytic cycle and iron sulfide precipitation in the water column of dead end tributaries  

NASA Astrophysics Data System (ADS)

The oxidation and precipitation of H 2S were investigated in Torquay Canal and Bald Eagle Creek, two tributaries of northern Rehoboth Bay, one of the Delaware Inland Bays. These man-made dead end canals develop seasonal anoxia and have been the site of past fish kills and harmful algal blooms. The canals have multiple holes over 5.5 m deep compared to an average low tide depth of 2 m. In situ determination for dissolved O 2, H 2S and other Fe and S redox species were conducted with a solid-state Au/Hg microelectrode in 2003 and 2004. Laboratory analyses of discrete samples were also performed to measure dissolved and particulate Fe, Mn, and S 8 to follow the seasonal dynamics of O, S, Fe and Mn redox species. Our results indicate that the water in the holes becomes stratified with O 2 decreasing with depth and H 2S increasing with depth. Dissolved Fe was as high as 30 ?M whereas dissolved Mn was only 0.2 ?M in the water column, indicating that Fe is the dominant metal involved in S redox cycling and precipitation. In surface oxic waters, the dominant form of Fe was particulate Fe(III) (oxy)hydroxides. When seasonal anoxia developed, Fe(III) (oxy)hydroxides were reduced by H 2S to Fe(II) at the oxic-anoxic interface. The Fe(II) reduced from particulate Fe can be re-oxidized to Fe(III) by O 2 above and at the interface to form a catalytic cycle to oxidize H 2S. Elemental S is the predominant oxidation product and was as high as 30 ?M level (as S 0) at the interface. When the system was stable, the Fe catalytic cycle prevented H 2S from being released into surface water