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1

Use of Oxides in Thermochemical Water-Splitting Cycles for Solar Heat Sources. Cobalt Oxides.  

National Technical Information Service (NTIS)

The concept of utilizing oxide decompositions in advanced thermochemical hydrogen cycles for solar heat sources is introduced. It has particular interest in allowing direct transmission of energy to the process through an air window. A cycle for the Co su...

W. M. Jones M. G. Bowman

1982-01-01

2

Water Cycle  

NSDL National Science Digital Library

Students will use this short interactive activity to check their understanding on what they learned about the water cycle Do you drink the same water as your great grandparents did? Check this website then answer the following questions. COLLECTION 1. How many times does water go through the cycle? 2. Explain each part of the cycle and why it is important. 3. Construct a model or diagram based off the information from this ...

Peterson, Lori

2009-09-28

3

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

PubMed Central

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

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

2012-01-01

4

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

PubMed

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

2012-06-12

5

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

SciTech Connect

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

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

1984-01-01

6

Analysis of the hybrid copper oxide–copper sulfate cycle for the thermochemical splitting of water for hydrogen production  

Microsoft Academic Search

The hybrid copper oxide–copper sulfate water-splitting thermochemical cycle involves two principal steps: (1) hydrogen production from the electrolysis of water, SO2(g) and CuO(s) at room temperature and (2) the thermal decomposition of the CuSO4 product to form oxygen and SO2, which is recycled to the first step. A four-reaction version of the cycle (known in the literature as Cycle H-5)

Ross B. Gonzales; Victor J. Law; John C. Prindle

2009-01-01

7

Thirstin's Water Cycle  

NSDL National Science Digital Library

The representation is an animation of the water cycle. The user can select individual parts, such as: rain, water vapor, water storage and clouds. The user can observe water as it cycles through the various parts of the water cycle.

8

Dissociation of manganese(III) oxide as part of a thermochemical water splitting cycle  

Microsoft Academic Search

A three-step thermochemical cycle to produce renewable hydrogen was proposed, which utilizes manganese(III) oxide and thermal energy to produce hydrogen. Most work on the cycle has focused on the hydrogen generating and product recovery steps with little work on the dissociation. It is essential to understand the dissociation because the feasibility of the cycle is based on this reaction having

Todd Michael Francis

2008-01-01

9

The Water Cycle  

NSDL National Science Digital Library

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

Amanda, Miss

2011-02-14

10

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

11

Engineering design of a thermochemical water-splitting cycle. Final report. [Sulfuric acid--sulfur oxide--sulfide cycle  

Microsoft Academic Search

In consultation with Los Alamos Scientific Laboratory, the LASL baseline sulfuric acid-sulfur-oxide-sulfide cycle for thermochemical hydrogen production was selected for preliminary engineering design. Using LASL data, or values estimated in collaboration with LASL where data were incomplete, process conditions for all primary reactions were established. Conceptual solutions for separation and recycle processes were developed and combined with the primary reactions

J. De Graaf; L. Halvers; J. Porter; J. Russell

1976-01-01

12

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.

13

Human Water Cycle  

NSDL National Science Digital Library

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

Integrated Teaching And Learning Program

14

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.

15

The Water Cycle  

NSDL National Science Digital Library

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

16

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

17

Water Cycle Animation  

NSDL National Science Digital Library

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

18

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

19

Two-step water splitting thermochemical cycle based on iron oxide redox pair for solar hydrogen production  

Microsoft Academic Search

This study deals with solar hydrogen production from the two-step iron oxide thermochemical cycle (Fe3O4\\/FeO). This cycle involves the endothermic solar-driven reduction of the metal oxide (magnetite) at high temperature followed by the exothermic steam hydrolysis of the reduced metal oxide (wustite) for hydrogen generation. Thermodynamic and experimental investigations have been performed to quantify the performances of this cycle for

Patrice Charvin; Stéphane Abanades; Gilles Flamant; Florent Lemort

2007-01-01

20

Water Cycle Model Building  

NSDL National Science Digital Library

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

21

Global water cycle  

NASA Technical Reports Server (NTRS)

This research is the MSFC component of a joint MSFC/Pennsylvania State University Eos Interdisciplinary Investigation on the global water cycle extension across the earth sciences. The primary long-term objective of this investigation is to determine the scope and interactions of the global water cycle with all components of the Earth system and to understand how it stimulates and regulates change on both global and regional scales. Significant accomplishments in the past year are presented and include the following: (1) water vapor variability; (2) multi-phase water analysis; (3) global modeling; and (4) optimal precipitation and stream flow analysis and hydrologic processes.

Robertson, Franklin; Goodman, Steven J.; Christy, John R.; Fitzjarrald, Daniel E.; Chou, Shi-Hung; Crosson, William; Wang, Shouping; Ramirez, Jorge

1993-01-01

22

Global water cycle  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

23

The Water Cycle  

NSDL National Science Digital Library

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

24

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.

25

Engineering design of a thermochemical water-splitting cycle. Quarterly report, September 1November 30, 1975. [Sulfuric acid-sulfur oxide-sulfide cycle  

Microsoft Academic Search

The flowsheet and heat and mass balance calculations for the Los Alamos baseline sulfuric acid-sulfur-oxide-sulfide cycle have been completed. The overall efficiency is 27 percent, based on the higher heating value of hydrogen. This value includes the heat required to supply power for helium circulators of the nuclear heat source and the compression of the product hydrogen to 70 atm.

J. DeGraaf; J. Porter; J. Russell

1975-01-01

26

Analysis of supercritical water oxidation for detoxification of waste organic solvent in university based on life cycle assessment.  

PubMed

Spray incineration and supercritical water oxidation (SCWO) processes have been used for detoxifying waste organic fluids in the University of Tokyo. In this study, we aim to elucidate the environmental aspects of these waste treatment processes by life cycle assessment (LCA). Through the investigation of actual plants, the inventory data and other characteristics of actual plants were collected and analyzed. To confirm the potential of SCWO, three modification types of the process and operation were considered and assessed on the basis of estimated inventory data. The results demonstrate that spray incineration has less environmental impact than SCWO in all scenarios. However, SCWO has various advantages for installation as a treatment process in universities such as negligible risk of creating dioxins and particulate matter. Proper choice of the treatment method for organic waste fluid requires a comprehensive analysis of risks. Spray incineration poses the risk of providing dioxins and particulate matter, while SCWO has such risk at negligible level. This means that waste including concerned materials related to such emission should be treated by SCWO. Using the right technologies for the right tasks in the detoxification of hazardous materials should be implemented for sustainable universities. PMID:21868159

Kikuchi, Yasunori; Kurata, Kohjiro; Nakatani, Jun; Hirao, Masahiko; Oshima, Yoshito

2011-10-30

27

GEOSS Water Cycle Integrator  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

28

Studies of thermochemical water-splitting cycles  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

29

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

30

Precipitation and the Water Cycle.  

National Technical Information Service (NTIS)

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

K. Browning

1991-01-01

31

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

32

Cycling Water Through the Environment  

NSDL National Science Digital Library

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

2005-01-01

33

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

34

Studies on thermochemical water-splitting cycles  

Microsoft Academic Search

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

R. J. Remick; S. E. Foh

1979-01-01

35

The NEWS Water Cycle Climatology  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

36

The Mars water cycle  

NASA Technical Reports Server (NTRS)

A model has been developed to test the hypothesis that the observed seasonal and latitudinal distribution of water on Mars is controlled by the sublimation and condensation of surface ice deposits in the Arctic and Antarctic, and the meridional transport of water vapor. Besides reproducing the observed water vapor distribution, the model correctly reproduces the presence of a large permanent ice cap in the Arctic and not in the Antarctic. No permanent ice reservoirs are predicted in the temperate or equatorial zones. Wintertime ice deposits in the Arctic are shown to be the source of the large water vapor abundances observed in the Arctic summertime, and the moderate water vapor abundances in the northern temperate region. Model calculations suggest that a year without dust storms results in very little change in the water vapor distribution. The current water distribution appears to be the equilibrium distribution for present atmospheric conditions.

Davies, D. W.

1981-01-01

37

Water Cycle Research  

NSF Publications Database

... and its function as a transport agent for energy and mass (water and biologically/geochemically ... specific attention to (1) mass and energy transfer across the interfaces between land-atmosphere ...

38

Water 2: The Hydrologic Cycle  

NSDL National Science Digital Library

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

Vanasupa, Linda

39

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.

40

Droplet and the Water Cycle  

NSDL National Science Digital Library

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

2001-01-01

41

Copper-catalyzed hydroquinone oxidation and associated redox cycling of copper under conditions typical of natural saline waters.  

PubMed

A detailed kinetic model has been developed to describe the oxidation of Cu(I) by O2 and the reduction of Cu(II) by 1,4-hydroquinone (H2Q) in the presence of O2 in 0.7 M NaCl solution over a pH range of 6.5-8.0. The reaction between Cu(I) and O2 is shown to be the most important pathway in the overall oxidation of Cu(I), with the rate constant for this oxidation process increasing with an increasing pH. In 0.7 M NaCl solutions, Cu(II) is capable of catalyzing the oxidation of H2Q in the presence of O2 with the monoanion, HQ(-), the kinetically active hydroquinone form, reducing Cu(II) with an intrinsic rate constant of (5.0 ± 0.4) × 10(7) M(-1) s(-1). Acting as a chain-propagating species, the deprotonated semiquinone radical (SQ(•)?(-)) generated from both the one-electron oxidation of H2Q and the one-electron reduction of 1,4-benzoquinone (BQ) also reacts rapidly with Cu(II) and Cu(I), with the same rate constant of (2.0 ± 0.5) × 10(7) M(-1) s(-1). In addition to its role in reformation of Cu(II) via continuous oxidation of Cu(I), O2 rapidly removes SQ(•)?(-), resulting in the generation of O2(•)?(-). Agreement between half-cell reduction potentials of different redox couples provides confirmation of the veracity of the proposed model describing the interactions of copper and quinone species in circumneutral pH saline solutions. PMID:23796190

Yuan, Xiu; Pham, A Ninh; Miller, Christopher J; Waite, T David

2013-08-01

42

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),

43

Water Cycling &the GPM Mission  

NASA Astrophysics Data System (ADS)

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

Smith, E. A.

2003-04-01

44

Molecular water oxidation catalyst  

DOEpatents

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

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

1993-01-01

45

Studies on thermochemical water-splitting cycles  

NASA Astrophysics Data System (ADS)

The electrochemical oxidation of sulfur dioxide in relative dilute (less than 50 weight percent) sulfuric acid was assessed, and the preferred operating conditions (acid concentration, temperature, electrode materials) for such a cell to be mated with a metal oxide metal sulfate water splitting cycle was determined. Rough performance goals were 200 mA/sq cm at 0.5 V. A sulfuric acid concentration of 33 weight percent was chosen for the experiments. As both anode and cathode performance increased with temperature in the range investigated (0 to 75 C), a temperature of 75 C or higher appears to be optimal. Of the five materials examined, smooth or platinized platinum gave the best anode kinetics for a given potential.

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

1981-03-01

46

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

Microsoft Academic Search

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

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

2006-01-01

47

EMERGING CONTAMINANTS IN THE DRINKING WATER CYCLE  

EPA Science Inventory

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

48

Understanding the Material Thermodynamics of Two-Step Solar Thermochemical Water-Splitting Cycles  

Microsoft Academic Search

Metal oxide materials may be used in two-step solar thermochemical water-splitting cycles to renewably produce hydrogen: At high temperature, the oxide material is reduced, and at a lower temperature, the material re-oxidizes upon contact with water vapor producing hydrogen gas. Here, we present the first completely general analysis of the equilibrium thermodynamics of a two-step metal oxide water splitting cycle.

Bryce Meredig; Chris Wolverton

2009-01-01

49

The Water Cycle in Volusia County  

USGS Publications Warehouse

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

German, Edward R.

2009-01-01

50

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.

51

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

52

The NASA Energy and Water cycle Study  

Microsoft Academic Search

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,

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

2010-01-01

53

Global Changes of the Water Cycle Intensity.  

National Technical Information Service (NTIS)

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

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

2003-01-01

54

Supercritical Water Oxidation Data Acquisition Testing.  

National Technical Information Service (NTIS)

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. Super...

K. M. Garcia

1996-01-01

55

Water Cycle. K-6 Science Curriculum.  

ERIC Educational Resources Information Center

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

Blueford, J. R.; And Others

56

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),

57

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

58

WaterNet the NASA water cycle solutions network  

Microsoft Academic Search

The goal of the WaterNet project 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 being build by engaging relevant NASA water cycle research resources and community-of-practice organizations to develop what we term

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

2007-01-01

59

Observing the Global Water Cycle from Space  

NASA Technical Reports Server (NTRS)

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

Hildebrand, P. H.

2004-01-01

60

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

61

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

PubMed Central

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

Asada, K

2000-01-01

62

Understanding the boiling water reactor limit cycle  

SciTech Connect

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

March-Leuba, J.

1989-01-01

63

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

64

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

65

The seasonal cycle of water on Mars  

NASA Technical Reports Server (NTRS)

A review of the behavior of water in the Mars atmosphere and subsurface is appropriate now that data from the Mariner and Viking spacecraft have been analyzed and discussed for several years following completion of those missions. Observations and analyses pertinent to the seasonal cycle of water vapor in the atmosphere of Mars are reviewed, with attention toward transport of water and the seasonal exchange of water between the atmosphere and various non-atmospheric reservoirs. Possible seasonally-accessible sources and sinks for water include water ice on or within the seasonal and residual polar caps; surface or subsurface ice in the high-latitude regions of the planet; adsorbed or chemically-bound water within the near-surface regolith; or surface or subsurface liquid water. The stability of water within each of these reservoirs is discussed, as are the mechanisms for driving exchange of the water with the atmosphere and the timescales for exchange. Specific conclusions are reached about the distribution of water and the viability of each mechanism as a seasonal reservoir. Discussion is also included of the behavior of water on longer timescales, driven by the variations in solar forcing due to the quasi-periodic variations of the orbital obliquity. Finally, specific suggestions are made for future observations from spacecraft which would further define or constrain the seasonal cycle of water.

Jakosky, B. M.

1985-01-01

66

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

PubMed

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

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

2014-05-01

67

Water, Water Everywhere... and Oxidants too!  

NASA Astrophysics Data System (ADS)

The current predominant scientific strategy to find evidence for the existence of extraterrestrial life has been to "follow the water". Life on Earth requires the availability of water, so it makes sense that this is a good place to start when trying to evidence of extant or extinct signatures of life beyond our planet. However, life on Earth also requires redox gradients. Respiration and photosynthesis are two such examples of redox chemistry that is essential for life. Planetary surfaces and atmospheres are naturally oxidized by photolytic and radiolytic processes. Even on early Earth and Titan, the natural oxidation of primordial ammonia presumably created the present nitrogen atmospheres, respectively as real and potential abodes for life. In the cases of Mars, Europa and Enceladus, three bodies of intense astrobiological interest, the natural oxidation processes driven by space environment interactions can produce significant quantities of oxidants, which could potentially be utilized to sustain life. We propose, that in addition to the "follow the water" strategy, the scientific community should start to "follow the oxidants", as a potentially important avenue of research and exploration. We address models for oxidant formation in planetary surface irradiation environments, as simulated by laboratory investigations, and apply results to past, recent and ongoing planetary observations of Mars and icy bodies of potential astrobiological interest in the outer solar system.

Cooper, P. D.; Cooper, J. F.

2007-12-01

68

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

69

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

70

WaterNet: The NASA Water Cycle Solutions Network  

Microsoft Academic Search

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

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

2006-01-01

71

Does GRACE see the water cycle 'intensifying'?  

NASA Astrophysics Data System (ADS)

Several researchers have postulated that, under a changing climate due to anthropogenic forcing, an intensification of the water cycle is already under way (Huntington, 2006). This is usually related to increases in hydrological fluxes such as precipitation (P), evapotranspiration (E), and river discharge (R). It is under debate, however, whether such observed or reconstructed flux changes are real and on what scales. Large-scale increase or decrease of the flux deficit (P-E) would lead to acceleration or deceleration of water storage anomalies possibly visible in GRACE time series, when discharge variability is small or properly accounted for. We investigate to what extent such accelerations, which are indeed found in maps of global gridded GRACE water storage anomalies, can be explained using output fields derived from global and regional atmospheric (re-)analyses and from hydrological models. We find this analysis challenging, since the GRACE time series is short and dominated by ENSO-type natural variability. Observed accelerations strongly depend on the analysis time frame, and may be explained to a large percentage by natural variability, thus masking a possible anthropogenically driven intensification of the terrestrial water cycle. This motivates us to apply statistical decomposition techniques in order to identify modes of natural variabilities and to remove them from the GRACE time series prior to the estimation of accelerations. Huntington T.G. (2006): Evidence for intensification of the global water cycle: Review and synthesis. J. Hydrology, 319:83-95

Eicker, Annette; Kusche, Jürgen; Forootan, Ehsan; Springer, Anne; Schumacher, Maike; Ohlwein, Christian

2014-05-01

72

Following the Water Cycle to Sustainability  

NASA Astrophysics Data System (ADS)

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

Lutz, T. M.

2012-12-01

73

Circadian Clock NAD+ Cycle Drives Mitochondrial Oxidative Metabolism in Mice  

PubMed Central

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

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

2014-01-01

74

Bioelectrochemical oxidation of water.  

PubMed

The electrolysis of water provides a link between electrical energy and hydrogen, a high energy density fuel and a versatile energy carrier, but the process is very expensive. Indeed, the main challenge is to reduce energy consumption for large-scale applications using efficient renewable catalysts that can be produced at low cost. Here we present for the first time that laccase can catalyze electrooxidation of H2O to molecular oxygen. Native and laboratory-evolved laccases immobilized onto electrodes serve as bioelectrocatalytic systems with low overpotential and a high O2 evolution ratio against H2O2 production during H2O electrolysis. Our results open new research ground on H2O splitting, as they overcome serious practical limitations associated with artificial electrocatalysts currently used for O2 evolution. PMID:24725275

Pita, Marcos; Mate, Diana M; Gonzalez-Perez, David; Shleev, Sergey; Fernandez, Victor M; Alcalde, Miguel; De Lacey, Antonio L

2014-04-23

75

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

Microsoft Academic Search

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

K. Hilburn; F. Wentz

2007-01-01

76

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

77

Super critical water oxidation on energetic materials.  

National Technical Information Service (NTIS)

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 des...

J. A. Sanchez

1993-01-01

78

Recent developments in research on water oxidation by photosystem II.  

PubMed

Photosynthetic water oxidation chemistry at the unique manganese-calcium complex of photosystem II (PSII) is of fundamental importance and serves as a paragon in the development of efficient synthetic catalysts. A recent crystal structure of PSII shows the atoms of the water-oxidizing complex; its Mn4CaO5 core resembles inorganic manganese-calcium oxides. Merging of crystallographic and spectroscopic information reverses radiation-induced modifications at the Mn-complex in silico and facilitates discussion of the O-O bond chemistry. Coordinated proton movements are promoted by a water network connecting the Mn4CaO5 core with the oxidant, a tyrosine radical and one possibly mobile chloride ion. A basic reaction-cycle model predicts an alternating proton and electron removal from the catalytic site, which facilitates energetically efficient water oxidation. PMID:22387134

Dau, Holger; Zaharieva, Ivelina; Haumann, Michael

2012-04-01

79

Serpentine and the subduction zone water cycle  

NASA Astrophysics Data System (ADS)

This study explores a chemo-thermo-dynamic subduction zone model that solves for slab dehydration during subduction. We investigate how changes in the incoming plate's hydration and thermal structure may effect the efficiency of sub-arc water release from sediments, crust, and serpentinized mantle. We find that serpentinized lithospheric mantle may not only be an important fluid source to trigger arc melting but is also an efficient 'transport-lithology' to recycle chemically bound water into the deeper mantle. In fact, an old slab may remain sufficiently cold during subduction to retain up to 40% of its initial 'mantle' water at 8 GPa (˜240-km depth) after serpentine transforms to higher pressure hydrous phase A. Furthermore, deep water recycling at subduction zones is parameterized in terms of slab age and speed. Coupling this parameterization to a parameterized mantle convection evolution model allows us to calculate the mantle-surface geologic water cycle throughout the Earth's history. We find that the present-day Earth mantle may be highly outgassed containing only a small fraction of the Earth's water, which would mostly be recycled water from the exosphere.

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

2004-06-01

80

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

81

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

82

Hydrologic Cycle and Water Balance Equation  

NSDL National Science Digital Library

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

Peterson, Eric

83

Supercritical water oxidation of sulfide.  

PubMed

Supercritical water oxidation (SCWO) of sulfide wastewater with oxygen as the oxidant was investigated using ammonium sulfide solution as the model waste. The experiments, which were conducted in a bench-scale continuous SCWO installation, indicated that S2- could be completely oxidized to SO4(2-) within the residence time of less than 10 s under the supercritical water conditions at 698.2-773.2 K and 22.0 MPa-30.0 MPa. The reaction pathway of S2- in SCWO was determined to be S2- --> S2O3(2-) --> SO3(2-) --> SO4(2-). The effects of temperature, pressure, and oxygen content on SCWO of S2- were also studied. The kinetic model based on this pathway was established with the reaction rate constants and orders found by fitting the experimental data. The dependence of the rate constants on the temperature can be described with Arrhenius' law. The rate constants are dependent on the density of SCW, and the dependence is logarithmically linear. PMID:12775071

Wang, Tao; Xiang, Botao; Liu, Jun; Shen, Zhongyao

2003-05-01

84

Anticipated changes in the global atmospheric water cycle  

Microsoft Academic Search

The atmospheric branch of the water cycle, although containing just a tiny fraction of the Earth's total water reserves, presents a crucial interface between the physical climate (such as large-scale rainfall patterns) and the ecosystems upon which human societies ultimately depend. Because of the central importance of water in the Earth system, the question of how the water cycle is

Richard P Allan; Beate G Liepert

2010-01-01

85

INTRODUCTION: Anticipated changes in the global atmospheric water cycle  

Microsoft Academic Search

The atmospheric branch of the water cycle, although containing just a tiny fraction of the Earth's total water reserves, presents a crucial interface between the physical climate (such as large-scale rainfall patterns) and the ecosystems upon which human societies ultimately depend. Because of the central importance of water in the Earth system, the question of how the water cycle is

Richard P. Allan; Beate G. Liepert

2010-01-01

86

Thermodynamic Properties of Ammonia–Water Mixtures for Power Cycles  

Microsoft Academic Search

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

E. Thorin; C. Dejfors; G. Svedberg

1998-01-01

87

Highly efficient 6-stroke engine cycle with water injection  

DOEpatents

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

Szybist, James P; Conklin, James C

2012-10-23

88

The Water Cycle and Global Warming  

NSDL National Science Digital Library

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

89

The Water Cycle - Back and Forth (part 2)  

NSDL National Science Digital Library

Students will learn more about the water cycle components and how they work together. They will learn it is a closed system and the importance of the ocean in the cycle. Reading for understanding is a focus in this lesson.

Magdaleno, Maribel

2012-07-17

90

Thermodynamic Analysis of the Sulphur Cycle Water Splitting Process.  

National Technical Information Service (NTIS)

The Westinghouse hybrid sulphur cycle and the oxygen production stage of the purely thermochemical General Atomic sulphur-iodine cycle for water splitting were investigated. Detailed mass, energy and exergy balances were set up by a computer program syste...

H. Schepers

1983-01-01

91

A macro-scale natural hydrologic cycle water availability model  

Microsoft Academic Search

Long-term water usage can be no more than that which is naturally available through the hydrologic cycle. To help in the determination of the hydrologically desirable water usage from surface and groundwater sources, a simple, idealized long-term analysis of water availability based solely on the natural hydrologic cycle is suggested. The concept of a hydrologic replacement time is introduced to

Adam H. Slutsky; Ben C. Yen

1997-01-01

92

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

Microsoft Academic Search

Skillful predictions of water and energy cycle extremes (flood and drought) are elusive. To better understand the mechanisms responsible for water and energy extremes, and to make decisive progress in predicting these extremes, the collaborative NASA Energy and Water cycle Extremes (NEWSE) Integration Project, is studying these extremes in the U.S. Southern Great Plains (SGP) during 2006-2007, including their relationships

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

2008-01-01

93

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

NASA Astrophysics Data System (ADS)

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

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

94

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

SciTech Connect

The reaction of iodine with dry magnesium oxide and magnesium sulfite hexahydrate was studied experimentally as a possible means of improving the efficiency of the sulfur dioxide-iodine cycle. When no extra water was introduced, the maximum product yield was 67% obtained at 423 K. With excess water vapor, a nonporous plug was formed which prevented complete reaction. In the second case, maximum yield was 62% measured at 433 K showing that added water does not increase reaction products. This reaction gives an alternate route for producing hydrogen from water via the sulfur dioxide-iodine process.

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

1981-01-01

95

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

96

Alternating electron and proton transfer steps in photosynthetic water oxidation.  

PubMed

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 S(2) ? S(3) transition of the classical S-state cycle, an intermediate is formed by deprotonation clearly before electron transfer to the oxidant (Y Z OX). 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 (E(a) = 0.46 ± 0.05 eV) and strong H/D kinetic isotope effect (approximately 6). The characteristics of a proton transfer step during the S(0) ? S(1) transition are similar (?, approximately 100 µs; E(a) = 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

2012-10-01

97

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.

Klauss, Andre; Haumann, Michael; Dau, Holger

2012-01-01

98

A direct-cycle, supercritical light-water-cooled FBR, SCFBR-D  

Microsoft Academic Search

We have been studying supercritical-pressure light-water-cooled reactors (SCLWRS) for improving thermal efficiency, simplifying the light water reactor (LWR) system, and moving toward a low-cost fast breeder reactor (FBR) based on long-standing water coolant technology of a fossil-fired power plants and LWRs. This paper summarizes the conceptual design of a direct-cycle, supercritical-pressure FBR, the SCFBR-D. The fuel is U-Pu mixed oxides

Yoshiaki Oka; Tatjana Jevremovic; Seiichi Koshizuka; Yasushi Okano

1993-01-01

99

The NASA Energy and Water cycle Study (NEWS)  

Microsoft Academic Search

With their unprecedented new observation capacity combined with revolutions in modeling capability, satellite observations have great potential to make huge advances in water and energy cycle prediction. To realize this goal, we must develop a discipline of prediction and verification through the integration of water and energy cycle observations and models, and to verify model predictions against observed phenomena to

P. Houser; J. Entin

2008-01-01

100

Study group assists in global water cycle program  

Microsoft Academic Search

The U.S. Global Change Research Program (USGCRP) has appointed a Water Cycle Study Group (WCSG),chaired by George Hornberger of the University of Virginia, to advise the USGCRP agencies on development of a Global Water Cycle Program within the USGCRPThe aim is to define a USGCRP initiative for fiscal years 2001 and beyond. In appointing the group, Robert Corell (then chair

George M. Hornberger

2000-01-01

101

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

102

Light driven water oxidation by a single site cobalt salophen catalyst.  

PubMed

A salophen cobalt(II) complex enables water oxidation at neutral pH in photoactivated sacrificial cycles under visible light, thus confirming the high appeal of earth abundant single site catalysis for artificial photosynthesis. PMID:24036577

Pizzolato, Erica; Natali, Mirco; Posocco, Bianca; Montellano López, Alejandro; Bazzan, Irene; Di Valentin, Marilena; Galloni, Pierluca; Conte, Valeria; Bonchio, Marcella; Scandola, Franco; Sartorel, Andrea

2013-11-01

103

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

104

Stability of supported platinum sulfuric acid decomposition catalysts for use in thermochemical water splitting cycles  

Microsoft Academic Search

The activity and stability of several metal oxide supported platinum catalysts were explored for the sulfuric acid decomposition reaction. The acid decomposition reaction is common to several sulfur based thermochemical water splitting cycles. Reactions were carried out using a feed of concentrated liquid sulfuric acid (96wt%) at atmospheric pressure at temperatures between 800 and 850?C and a weight hour space

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

2007-01-01

105

Biochemical mechanism of oxidative damage by redox-cycling drugs.  

PubMed Central

Biochemical mechanisms of production of redox intermediates of redox-cycling drugs include: photochemical events, either photoionization process or electron transfer from photoexcited states; electron exchange of reduced form of a drug with the oxy state of oxygen-binding hemoproteins; oxidation by catalytic metal centers (oxidases, peroxidases, oxygenases) of the reduced forms of drugs; or electron transfer to the oxidized form of a drug from activated intracellular electron transfer chain (mitochondria, microsomes, etc.). Further reaction of these drug free radicals can lead to oxidative damage by either direct attack of biological macromolecules or via oxygen reduction, giving O2-, H2O2, and OH. The reaction pathway depends on the presence of metal ions, natural scavengers, enzymes that control relative concentrations of reactive species, and availability of oxygen in the environment.

Rotilio, G; Mavelli, I; Rossi, L; Ciriolo, M R

1985-01-01

106

Investigating the water cycle "snow fun"  

NSDL National Science Digital Library

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

107

Mars Water Cycle Simulations with the NASA\\/Ames GCM  

Microsoft Academic Search

We re-assess the role of the north residual water ice cap in the present water cycle on Mars in light of the downward revision of atmospheric water vapor column abundances as observed by TES. We find that models must pay closer attention to the distribution and temperature of ice in order to properly represent the contribution of the north residual

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

2007-01-01

108

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

109

Ammonia-Water Absorption-Heat-Pump Cycle.  

National Technical Information Service (NTIS)

The state-of-art in ammonia-water absorption cooling has been applied to an air-source heating-only heat-pump cycle which delivers its heat indoors via circulating liquid. The cycle is described, differences from the cooling application noted, and test re...

D. Kuhlenschmidt R. H. Merrick

1983-01-01

110

Thermodynamic properties of ammonia-water mixtures for power cycles  

SciTech Connect

Power cycles with ammonia-water mixtures as working fluids have been shown to reach higher thermal efficiencies than the traditional steam turbine (Rankine) cycle with water as the working fluid. Different correlations for the thermodynamic properties of ammonia-water mixtures have been used in studies of ammonia-water mixture cycles described in the literature. Four of these correlations are compared in this paper. The differences in thermal efficiencies for a bottoming Kalina cycle when these four property correlations are used are in the range 0.5 to 3.3%. The properties for saturated liquid and vapor according to three of the correlations and available experimental data are also compared at high pressures and temperatures [up to 20 MPa and 337 C (610 K)]. The difference in saturation temperature for the different correlations is up to 20%, and the difference in saturation enthalpy is as high as 100% when the pressure is 20 MPa.

Thorin, E. [Royal Inst. of Technology, Stockholm (Sweden)] [Royal Inst. of Technology, Stockholm (Sweden); [Maelardalen Univ., Vaesteraas (Sweden). Dept. of Energy; Dejfors, C.; Svedberg, G. [Royal Inst. of Technology, Stockholm (Sweden)] [Royal Inst. of Technology, Stockholm (Sweden)

1998-03-01

111

Nitrogen Cycle in Surface and Subsurface Waters.  

National Technical Information Service (NTIS)

The objectives of the Nitrogen Cycle studies are: to determine sources of nitrogen and phosphorus which limnologists consider to be contributing factors to lake eutrophication, i.e. to determine what part comes from natural sources, such as snow and rain;...

S. A. Witzel E. McCoy O. J. Attoe L. J. Polkowski K. T. Crabtree

1968-01-01

112

Chloride-assisted catalytic water oxidation.  

PubMed

Rates of electrocatalytic water oxidation to oxygen by Ru(ii) polypyridyl complexes are enhanced by added NaCl. Observations based on the single-site catalyst [Ru(II)(Mebimpy)(bpy)(OH2)](2+) (Mebimpy is 2,6-bis(1-methylbenzimidazol-2-yl)pyridine; bpy is 2,2'-bipyridine) at pH 7.0 in a phosphate buffer suggest a mechanism involving initial oxidation of the catalyst to Ru(V)(O)(3+) followed by Cl(-) oxidation to HOCl. Once formed, HOCl is oxidized to O2. PMID:24924315

Chen, Zuofeng; Concepcion, Javier J; Song, Na; Meyer, Thomas J

2014-06-26

113

OPA oxidation rates in supercritical water.  

PubMed

Supercritical water oxidation can effectively destroy a large variety of high-risk wastes resulting from munitions demilitarization and complex industrial chemical. An important design consideration in the development of supercritical water oxidation is the information on the oxidation rate. In this paper, the oxidation rate of isopropyl amine (OPA), one of high-risk wastes resulting from munitions demilitarization, was investigated under supercritical water oxidation (SCWO) conditions in an isothermal tubular reactor. H2O2 was used as the oxidant. The reaction temperatures were ranged from 684 to 891 K and the residence times varied from 9 to 18s at a fixed pressure of 25 MPa. The conversion of OPA was monitored by analyzing total organic carbon (TOC) on the liquid effluent samples. The initial TOC concentrations of OPA varied from 7.21 to 143.78 mmol/l at the conversion efficiencies from 88.94 to 99.98%. By taking into account the dependence of reaction rate on oxidant and TOC concentration, a global power-law rate expression was regressed from 38 OPA experimental data. The resulting pre-exponential factor was 2.46(+/-0.65)x10(3)l(1.37)mmol(-0.37)s(-1); the activation energy was 64.12+/-1.94 kJ/mol; and the reaction orders for OPA (based on TOC) and oxidant were 1.13+/-0.02 and 0.24+/-0.01, respectively. PMID:15941618

Veriansyah, Bambang; Kim, Jae-Duck; Lee, Jong-Chol; Lee, Youn-Woo

2005-09-30

114

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.

115

EDITORIAL: The global atmospheric water cycle  

Microsoft Academic Search

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

Lennart Bengtsson

2010-01-01

116

The ocean component of the global water cycle  

NASA Astrophysics Data System (ADS)

The distribution of evaporation and precipitation over the ocean (its hydrologic cycle) is one of the least understood elements of the climate system. However, it is now considered one of the most important, especially for ocean circulation changes on decadal to millennial time-scales. The ocean covers 70% of the Earth's surface and contains nearly all (97%) of its free water, thus, it plays a dominant role in the global water cycle. The atmosphere only holds a few centimeters of liquid water, or 0.001% of the total. However, most discussions of the water cycle focus on the rather small component associated with terrestrial processes [Chahine, 1992]. This is understandable, since the water cycle is so vital to agriculture and all of man's activities. Yet current estimates indicate that 86% of global evaporation and 78% of global precipitation occurs over the oceans [Baumgartner and Reichel, 1975]; (Figure 1 ). Since the oceans are the source of most rainwater, it behooves us to work toward a better understanding of the ocean hydrologic cycle; small changes in ocean evaporation and precipitation patterns may have dramatic consequences for the much smaller terrestrial water cycle. For example, if less than 1% of the rain falling on the Atlantic Ocean were to be concentrated in the central US, it would double the discharge of the Mississippi river!

Schmitt, Raymond W.

1995-07-01

117

Nuclear Production of Hydrogen Using Thermochemical Water-Splitting Cycles  

SciTech Connect

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. We used detailed evaluation to select two cycles that appear most promising, the Adiabatic UT-3 cycle and the Sulfur-Iodine cycle. We have selected the Sulfur-Iodine thermochemical water-splitting cycle for further development. We then assessed the suitability of various nuclear reactor types to the production of hydrogen from water using the Sulfur-Iodine cycle. A basic requirement is to deliver heat to the process interface heat exchanger at temperatures up to 900 deg. C. We considered nine categories of reactors: pressurized water-cooled, boiling water-cooled, organic-cooled, alkali metal-cooled, heavy metal-cooled, gas-cooled, molten salt-cooled, liquid-core and gas-core reactors. We developed requirements and criteria to carry out the assessment, considering design, safety, operational, economic and development issues. This assessment process led to our choice of the helium gas-cooled reactor for coupling to the Sulfur-Iodine cycle. In continuing work, we are investigating the improvements that have been proposed to the Sulfur-Iodine cycle and will generate an integrated flowsheet describing a hydrogen production plant powered by a high-temperature helium gas-cooled nuclear reactor. This will allow us to size process equipment and calculate hydrogen production efficiency and capital cost, and to estimate the cost of the hydrogen produced as a function of nuclear reactor cost. (authors)

Brown, L.C.; Besenbruch, G.E.; Schultz, K.R. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States); Marshall, A.C.; Showalter, S.K.; Pickard, P.S. [Sandia National Laboratories, PO Box 5800, Albuquerque, NM 87185 (United States); Funk, J.F. [University of Kentucky, Lexington, KY 40506 (United States)

2002-07-01

118

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

Microsoft Academic Search

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

A Berman; M Epstein

2000-01-01

119

Modeling Nitrogen Cycle at the Surface-Subsurface Water Interface  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

120

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

121

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

NASA Astrophysics Data System (ADS)

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

Greco, Francesca

2014-05-01

122

Supercritical water oxidation - Microgravity solids separation  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

123

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

124

Global water cycle and Earth's thermal evolution  

Microsoft Academic Search

Convergent margin processes play an important role in the distribution of terrestrial volatile species. During subduction processes volatiles are filtered from the subducting package and are restricted to return to the mantle. Water is the most abundant volatile and plays an important role in these processes. There is a number of geochemical investigations to determine the subduction, regassing, and recycling

Siegfried Franck; Christine Bounama

2001-01-01

125

Emerging Contaminants in the Drinking Water Cycle.  

EPA Science Inventory

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

126

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

127

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

128

Solar cycle variation of thermospheric nitric oxide at solstice  

NASA Technical Reports Server (NTRS)

A coupled, two-dimensional, chemical-diffusive model of the thermosphere is used to study the role of solar activity in the global distribution of nitric oxide. The model calculates self-consistently the zonally averaged temperature, circulation, and composition for solstice under solar maximum and solar minimum conditions. A decrease of the NO density by a factor of three to four in the E region is predicted from solar maximum to solar minimum. It is found that the main features of the overall morphology and the changes induced by the solar cycle are well reproduced in the model, although some details are not satisfactorily predicted. The sensitivity of the NO distribution to eddy transport and to the quenching of metastable N(2D) atoms by atomic oxygen is also described.

Gerard, J.-C.; Fesen, C. G.; Rusch, D. W.

1990-01-01

129

OXIDATION-REDUCTION POTENTIAL MEASUREMENTS OF IMPORTANT OXIDANTS IN DRINKING WATER  

EPA Science Inventory

Oxidation-reduction (redox) reactions are important in drinking water treatment and distribution. Oxidation-reduction potential (ORP) measurements of water reflect the tendency of major constituents in the water to accept or lose electrons. Although ORP measurements are valuable...

130

Nature and Stability of the Martian Seasonal Water Cycle  

NASA Astrophysics Data System (ADS)

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

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

2001-12-01

131

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

132

NASA's Earth Science Enterprise's Water and Energy Cycle Focus Area  

NASA Astrophysics Data System (ADS)

Understanding the Water and Energy cycles is critical towards improving our understanding of climate change, as well as the consequences of climate change. In addition, using results from water and energy cycle research can help improve water resource management, agricultural efficiency, disaster management, and public health. To address this, NASA's Earth Science Enterprise (ESE) has an end-to-end Water and Energy Cycle Focus Area, which along with the ESE's other five focus areas will help NASA answer key Earth Science questions. In an effort to build upon the pre-existing discipline programs, which focus on precipitation, radiation sciences, and terrestrial hydrology, NASA has begun planning efforts to create an implementation plan for integrative research to improve our understanding of the water and energy cycles. The basics of this planning process and the core aspects of the implementation plan will be discussed. Roadmaps will also be used to show the future direction for the entire focus area. Included in the discussion, will be aspects of the end-to-end nature of the Focus Area that encompass current and potential actives to extend research results to operational agencies to enable improved performance of policy and management decision support systems.

Entin, J. K.

2004-05-01

133

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

134

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

135

Water clustering on nanostructured iron oxide films.  

PubMed

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. PMID:24979078

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

2014-01-01

136

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

137

Carbon and water cycles in tropical papyrus wetlands  

Microsoft Academic Search

Highly productive papyrus (Cyperus papyrus L.) wetlands dominate many permanently flooded areas of tropical East Africa; however, the cycling of carbon and water within\\u000a these ecosystems is poorly understood. The objective of this study was to utilise Eddy Covariance (EC) techniques to measure\\u000a the fluxes of carbon dioxide and water vapour between papyrus vegetation and the atmosphere in a wetland

M. J. Saunders; M. B. Jones; F. Kansiime

2007-01-01

138

Nano-sized layered Mn oxides as promising and biomimetic water oxidizing catalysts for water splitting in artificial photosynthetic systems.  

PubMed

One challenge in artificial photosynthetic systems is the development of artificial model compounds to oxidize water. The water-oxidizing complex of Photosystem II which is responsible for biological water oxidation contains a cluster of four Mn ions bridged by five oxygen atoms. Layered Mn oxides as efficient, stable, low cost, environmentally friendly and easy to use, synthesize, and manufacture compounds could be considered as functional and structural models for the site. Because of the related structure of these Mn oxides and the catalytic centre of the active site of the water oxidizing complex of Photosystem II, the study of layered Mn oxides may also help to understand more about the mechanism of water oxidation by the natural site. This review provides an overview of the current status of layered Mn oxides in artificial photosynthesis and discuss the sophisticated design strategies for Mn oxides as water oxidizing catalysts. PMID:24727405

Najafpour, Mohammad Mahdi; Heidari, Sima; Amini, Emad; Khatamian, Masoumeh; Carpentier, Robert; Allakhverdiev, Suleyman I

2014-04-01

139

Light water breeder reactor using a uranium-plutonium cycle  

Microsoft Academic Search

This patent describes a light water receptor (LWR) for breeding fissile material using a uranium-plutonium cycle. It comprises: a prebreeder section having plutonium fuel containing a Pu-241 component, the prebreeder section being operable to produce enriched plutonium having an increased Pu-241 component; and a breeder section for receiving the enriched plutonium from the prebreeder section, the breeder section being operable

A. Radkowsky; R. Chen

1990-01-01

140

Plans and Activities for NASA's Global Water Cycle Research  

Microsoft Academic Search

Strictly speaking, the water (or hydrologic) cycle is by definition a global phenomenon. To observe, analyze, characterize, understand, and predict its structure and variations requires a coordinated, global effort of observations as well as global prediction systems which can assimilate and predict key fluxes and quantities. The National Aeronautics and Space Administration (NASA) has the unique capability of space-based experimental

C. A. Schlosser

2002-01-01

141

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

142

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

143

Thermo-Oxidative Stability of High Performance Composites under Thermal Cycling Conditions  

Microsoft Academic Search

Thermo-oxidative stability of high performance composites was investigated under thermal cycling conditions between room and 177°C curing temperature. For the analysis of thermal cycling experimental results, an equivalent cycle time (ECT) was developed by applying degradation-reaction kinetic theories to thermal-cycling conditions. Applying this methodology to the weight loss measurements of composite specimens, thermal cycling was found to exhibit a slower

Sang-Ho Lee; Jae-Do Nam; Kyujong Ahn; Ki-Mo Chung; James C. Seferis

2001-01-01

144

Destruction of Navy Hazardous Wastes by Supercritical Water Oxidation.  

National Technical Information Service (NTIS)

The objective of this study was to investigate the feasibility of using supercritical water oxidation (SCWO) to destroy organic hazardous wastes generated by Navy industrial activities. Supercritical water oxidation is the low temperature combustion of or...

R. E. Kirts

1994-01-01

145

Water and Energy Cycle EOS House web portal (WECHO)  

NASA Astrophysics Data System (ADS)

Water is the origin of life, the vast amount of water related Earth observation is of great value to water community users. This paper reports our research and development in providing the Water and Energy Cycle EOS House web portal (WECHO), a web-based tool, for the community to access water resource archived in EOS ClearingHouse (ECHO). WECHO aims to provide users the capabilities to search, browse and visualize data through common browsers, such as Internet Explore and Firefox. WECHO supports users to 1) access all ECHO functionalities, including registering as a new user, querying metadata and ordering delivery of earth observing data, subscribing to updates of interested metadata items and specific events; 2) semantically search ECHO with water ontologies integrated; 3) interactively access Earth Information Exchange (EIE) with the support of Semantic Web for Earth and Environmental Terminology (SWEET) and NOESIS.

Li, Z.; Huang, Q.; Li, W.; Zhu, H.; Yang, C.; Houser, P.; Larko, M.

2008-12-01

146

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

147

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

148

WaterNet: The NASA water cycle solutions network - Danubian regional applications  

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. This paper provides an overview and it discusses the concept of solutions networks focusing on the WaterNet. It invites Danubian research and applications teams to join our WaterNet network. The NASA Water cycle Solutions Network's goal is

Dave Matthews; Mitja Brilly; Mira Kobold; Mark Zagar; Paul Houser

2008-01-01

149

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.

150

WaterNet:The NASA Water Cycle Solutions Network  

Microsoft Academic Search

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. Projections of the effects of such factors will remain speculative until more effective global prediction systems and applications are implemented. NASA's unique role is to use its view from space to improve

D. R. Belvedere; P. R. Houser; W. Pozzi; B. Imam; R. Schiffer; C. A. Schlosser; H. Gupta; G. Martinez; V. Lopez; C. Vorosmarty; B. Fekete; D. Matthews; R. Lawford; C. Welty; A. Seck

2008-01-01

151

The water-oxidation complex in photosynthesis  

PubMed Central

Studies of the photosynthetic water-oxidation complex of photosystem II (PS II) using spectroscopic techniques have characterized not only important structural features, but also changes that occur in oxidation state of the Mn4 cluster and in its internal organization during the accumulation of oxidizing equivalents leading to O2 formation. Combining this spectroscopic information with that from the recently published relatively low-resolution X-ray diffraction studies, we have succeeded in limiting the range of likely cluster arrangements. This evidence strongly supports several options proposed earlier by DeRose et al. [J. Am. Chem. Soc. 116 (1994) 5239] and these can be further narrowed using compatibility with electron paramagnetic resonance (EPR) data.

Sauer, Kenneth; Yachandra, Vittal K.

2014-01-01

152

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

PubMed

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

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

2014-02-28

153

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

Microsoft Academic Search

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

Tetsuya Tokano

2003-01-01

154

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

Microsoft Academic Search

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

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

2010-01-01

155

Electrolysis of water on (oxidized) metal surfaces  

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

156

Pentachlorophenol oxidation rates in supercritical water.  

PubMed

The oxidation rate of pentachlorophenol, [C(6)HCl(5)O] which is used to control termites and as a general herbicide and also as the probable human's carcinogen, was investigated in an isothermal continuous tubular reactor under supercritical water oxidation (SCWO) conditions. The experiments were conducted at a temperature of 400-550 degrees C and a fixed pressure of 25 MPa, with a residence time that ranged from 6 s to 26 s. The conversion of PCP was monitored by analyzing total organic carbon (TOC) on the liquid effluent samples. The initial TOC concentrations of PCP were varied from 0.74 mmol/L to 2.91 mmol/L and the oxygen concentrations were varied from 0.46 mmol/L to 3.52 mmol/L. By taking into account the dependence of the oxidant and TOC concentration on the reaction rate, a global PCP oxidation rate was regressed from the data of 48 experiments, to a 95% confidence level. The resulting activation energy was determined to be 43.56 +/- 1.47 kJ/mol, and the pre-exponential factor was (1.92 +/- 0.46) x 10(2) L(1.16) mmol(-0.16) s(-1). The reaction orders for the PCP (based on TOC) and the oxidant were 0.74 +/- 0.02 and 0.42 +/- 0.05, respectively. PMID:18074281

Han, Seung Ho; Veriansyah, Bambang; Kim, Jae-Duck; Lee, Jong-Chol

2007-12-01

157

Challenges and Opportunities in Water Cycle Research: WCRP Contributions  

NASA Astrophysics Data System (ADS)

The state of knowledge and outstanding challenges and opportunities in global water cycle observations, research and modeling are briefly reviewed to set the stage for the reasons behind the new thrusts promoted by the World Climate Research Programme (WCRP) as Grand Challenges to be addressed on a 5- to 10-year time frame. Those focused on water are led by the GEWEX (Global Energy and Water Exchanges) project. A number of GEWEX science questions are being brought forward within GEWEX and the WCRP under guidance of the Joint Scientific Committee. Here, we describe what are some imperatives and opportunities for major advancements in observations, understanding, modeling and product development for water resources and climate that will enable a wide range of climate services and inform decisions on water resources management and practices.

Trenberth, Kevin E.; Asrar, Ghassem R.

2014-05-01

158

[Membrane cholesterol oxidation effects on synaptic vesicle cycle in frog (RANA ridibunda) motor nerve terminals].  

PubMed

In experiments on frog (Rana ridibunda) neuromuscular junction the influence of cholesterol oxidation on the presynaptic vesicular cycle was investigated. Application of cholesterol oxidase (1 u. a.) during 1/2 hour led to the oxidation of - 0.007 mg cholesterol per 1 g tissue and reduced stability of lipid rafts in the nerve terminals. Using electrophysiological techniques it was shown that the cholesterol oxidation decreases the evoked neurotransmitter release. In experiments with fluorescent FM-dyes the depression of the synaptic vesicles exo-endocytosis and the dispersion of synaptic vesicles clusters were revealed. Comparative analysis of electrophysiological and optical data, as well as experiments with water soluble quencher of FM-dye indicated the possibility of some neurotransmitter release by "kiss-and-run" pathway, when short-lived fusion pore is formed. It was concluded that cholesterol oxidation inhibit evoked exocytosis, and also synaptic vesicle delivery from reserve pool to cites of exocytosis probably by break of the clusterization. Perhaps the synaptic vesicles of recycling pool release the neurotransmitter using the kiss-and-run mechanism. PMID:23650738

Petrov, A M; Kasimov, M R; Giniatullin, A R; Zefirov, A L

2013-02-01

159

Superhalogen oxidizers capable of ionizing water molecules  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

160

Diurnal Cycles in Water Quality Across the Periodic Table  

NASA Astrophysics Data System (ADS)

Diurnal cycles in water quality can provide important clues to the processes that regulate aquatic chemistry, but they often are masked by longer-term, larger-amplitude variability, making their detection and quantification difficult. Here I outline several methods that can detect diurnal cycles even when they are massively obscured by statistically ill-behaved noise. I demonstrate these methods using high-frequency water quality data from the Plylimon catchment in mid-Wales (Neal et al., 2013; Kirchner and Neal, 2013). Several aspects combine to make the Plynlimon data set unique worldwide. Collected at 7-hour intervals, the Plynlimon data set is much more densely sampled than typical long-term weekly or monthly water quality data. This 7-hour sampling was also continued for two years, much longer than typical intensive sampling campaigns, and the resulting time series encompass a wide range of climatic and hydrological conditions. Furthermore, each sample was analyzed for a wide range of solutes with diverse sources in the natural environment. However, the 7-hour sampling frequency is both coarse and irregular in comparison to diurnal cycles, making their detection and quantification difficult. Nonetheless, the methods outlined here enable detection of statistically significant diurnal cycles in over 30 solutes at Plynlimon, including alkali metals (Li, Na, K, Rb, and Cs), alkaline earths (Be, Mg, Ca, Sr, and Ba), transition metals (Al, Ti, Mn, Fe, Co, Ni, Zn, Mo, Cd, and Pb), nonmetals (B, NO3, Si, As, and Se), lanthanides and actinides (La, Ce, Pr, and U), as well as total dissolved nitrogen (TDN), dissolved organic carbon (DOC), Gran alkalinity, pH, and electrical conductivity. These solutes span every row of the periodic table, and more than six orders of magnitude in concentration. Many of these diurnal cycles are subtle, representing only a few percent, at most, of the total variance in the concentration time series. Nonetheless they are diagnostically useful, because their amplitude and phase contain important clues to the mechanisms controlling these solutes in streamwater. Examples of these cycles and their likely origins will be discussed. Neal, C., B. Reynolds, J. W. Kirchner, P. Rowland, D. Norris, D. Sleep, A. Lawlor, C. Woods, S. Thacker, H. Guyatt, C. Vincent, K. Lehto, S. Grant, J. Williams, M. Neal, H. Wickham, S. Harman, and L. Armstrong. 2013. High-frequency precipitation and stream water quality time series from Plynlimon, Wales: an openly accessible data resource spanning the periodic table. Hydrological Processes 27:2531-2539. Kirchner, J. W., and C. Neal. 2013. Universal fractal scaling in stream chemistry and its implications for solute transport and water quality trend detection. Proceedings of the National Academy of Sciences of the United States of America 110:12213-12218.

Kirchner, J. W.

2013-12-01

161

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

PubMed

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

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

2002-01-01

162

Water cycles in closed ecological systems: effects of atmospheric pressure  

NASA Technical Reports Server (NTRS)

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

Rygalov, Vadim Y.; Fowler, Philip A.; Metz, Joannah M.; Wheeler, Raymond M.; Bucklin, Ray A.; Sager, J. C. (Principal Investigator)

2002-01-01

163

Oxidation of oily sludge in supercritical water.  

PubMed

The oxidation of oily sludge in supercritical water is performed in a batch reactor at reaction temperatures between 663 and 723 K, the reaction times between 1 and 10 min and pressure between 23 and 27 MPa. Effect of reaction parameters such as reaction time, temperature, pressure, O(2) excess and initial COD on oxidation of oily sludge is investigated. The results indicate that chemical oxygen demand (COD) removal rate of 92% can be reached in 10 min. COD removal rate increases as the reaction time, temperature and initial COD increase. Pressure and O(2) excess have no remarkable affect on reaction. By taking into account the dependence of reaction rate on COD concentration, a global power-law rate expression was regressed from experimental data. The resulting pre-exponential factor was 8.99 x 10(14)(mol L(-1))(-0.405)s(-1); the activation energy was 213.13+/-1.33 kJ/mol; and the reaction order for oily sludge (based on COD) is 1.405. It was concluded that supercritical water oxidation (SCWO) is a rapidly emerging oily sludge processing technology. PMID:19019533

Cui, Baochen; Cui, Fuyi; Jing, Guolin; Xu, Shengli; Huo, Weijing; Liu, Shuzhi

2009-06-15

164

Water Vapor Tracers as Diagnostics of the Regional Hydrologic Cycle  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

165

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

166

The Water Cycle (title provided or enhanced by cataloger)  

NSDL National Science Digital Library

This Classroom Connectors lesson plan discusses the steps of the water cycle, factors which affect runoff, underground water, and stalactities and stalagmites. 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.

167

Tetrametallic molecular catalysts for photochemical water oxidation.  

PubMed

Among molecular water oxidation catalysts (WOCs), those featuring a reactive set of four multi-redox transition metals can leverage an extraordinary interplay of electronic and structural properties. These are of particular interest, owing to their close structural, and possibly functional, relationship to the oxygen evolving complex of natural photosynthesis. In this review, special attention is given to two classes of tetrametallic molecular WOCs: (i) M(4)O(4) cubane-type structures stabilized by simple organic ligands, and (ii) systems in which a tetranuclear metal core is stabilized by coordination of two polyoxometalate (POM) ligands. Recent work in this rapidly evolving field is reviewed, with particular emphasis on photocatalytic aspects. Special attention is given to studies addressing the mechanistic complexity of these systems, sometimes overlooked in the rush for oxygen evolving performance. The complementary role of molecular WOCs and their relationship with bulk oxides and heterogeneous catalysis are discussed. PMID:23011384

Sartorel, Andrea; Bonchio, Marcella; Campagna, Sebastiano; Scandola, Franco

2013-03-21

168

Supercritical water oxidation of landfill leachate.  

PubMed

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

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

2011-01-01

169

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

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

170

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

171

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

172

Superconductor made by electrolyzed and oxidized water  

Microsoft Academic Search

By deintercalation of Na+ followed by inserting bilayers of water molecules into the host lattice, the layered cobalt oxide of gamma-Na0.7CoO2 undergoes a topotactic transformation to a layered cobalt oxyhydrate of Na0.35(H2O)1.3CoO2-delta with the c-axis expanded from c = 10.9 anstrom to c = 19.6 anstrom. In this paper, we demonstrate that the superconducting phase of c = 19.6 anstrom

Chia-Jyi Liu; Tsung-Hsien Wu; Lin-Li Hsu; Jung-Sheng Wang; Shu-Yo Chen; Wei Jen Chang; Jiunn-Yuan Lin

2006-01-01

173

Supercritical water oxidation technology for DWPF  

SciTech Connect

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

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

1992-02-07

174

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

Microsoft Academic Search

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

Evangelos Rozos; Christos Makropoulos

2011-01-01

175

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

Microsoft Academic Search

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

Evangelos Rozos; Christos Makropoulos

2012-01-01

176

Effects of Impoundments on Water Quality in the Southwest. Discussion - Bacterial Cycles and Water Quality.  

National Technical Information Service (NTIS)

In the determination of bacterial counts for the detection of cycles of presence in a large body of water, one must take into account several sources of error, such as a period of heavy rainfall, producing extensive runoff into the water impoundment. A st...

R. K. Guthrie

1969-01-01

177

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

178

Fundamental kinetics of methane oxidation in supercritical water. Summary report  

SciTech Connect

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

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

1989-05-22

179

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

Microsoft Academic Search

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

Ashish Gupta

2002-01-01

180

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

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

181

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

182

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

183

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

184

Can Continental Scale Basins Be Used For Detecting Trends and Intensification of The Global Water Cycle?  

Microsoft Academic Search

Evaluation of trends in the global water cycle and determining whether the global water cycle is intensifying are central to prediction and assessment of the effects of anthropogenic climate change. To address these questions, the water cycle compo- nents to be evaluated must first be identified, along with the time scale of evaluation. For instance, over the land areas of

J. Sheffield; D. P. Lettenmaier; E. Maurer; S. Rao; E. F. Wood; C. Zhu; A. Ziegler

2002-01-01

185

Analysis of alternative light water reactor (LWR) fuel cycles  

SciTech Connect

Nine alternative LWR fuel cycles are analyzed in terms of the isotopic content of the fuel material, the relative amounts of primary and recycled material, the uranium and thorium requirements, the fuel cycle costs and the fraction of energy which must be generated at secured sites. The fuel materials include low-enriched uranium (LEU), plutonium-uranium (MOX), highly-enriched uranium-thorium (HEU-Th), denatured uranium-thorium (DU-Th) and plutonium-thorium (Pu-Th). The analysis is based on tracing the material requirements of a generic pressurized water reactor (PWR) for a 30-year period at constant annual energy output. During this time period all the created fissile material is recycled unless its reactivity worth is less than 0.2% uranium enrichment plant tails.

Heeb, C.M.; Aaberg, R.L.; Boegel, A.J.; Jenquin, U.P.; Kottwitz, D.A.; Lewallen, M.A.; Merrill, E.T.; Nolan, A.M.

1979-12-01

186

Supercritical Water Reactor Cycle for Medium Power Applications  

SciTech Connect

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

BD Middleton; J Buongiorno

2007-04-25

187

Diurnal cycles in water quality across the periodic table  

NASA Astrophysics Data System (ADS)

Diurnal cycles in water quality can provide important clues to the processes that regulate aquatic chemistry, but they often are masked by longer-term, larger-amplitude variability, making their detection and quantification difficult. Here I outline methods that can detect diurnal cycles even when they are massively obscured by statistically ill-behaved noise. I demonstrate these methods using high-frequency water quality data from the Plylimon catchment in mid-Wales (Neal et al., 2013; Kirchner and Neal, 2013). Several aspects combine to make the Plynlimon data set unique worldwide. Collected at 7-hour intervals, the Plynlimon data set is much more densely sampled than typical long-term weekly or monthly water quality data. This 7-hour sampling was also continued for two years, much longer than typical intensive sampling campaigns, and the resulting time series encompass a wide range of climatic and hydrological conditions. Furthermore, each sample was analyzed for a wide range of solutes with diverse sources in the natural environment. However, the 7-hour sampling frequency is both coarse and irregular in comparison to diurnal cycles, making their detection and quantification difficult. Nonetheless, the methods outlined here enable detection of statistically significant diurnal cycles in over 30 solutes at Plynlimon, including alkali metals (Li, Na, K, Rb, and Cs), alkaline earths (Be, Mg, Ca, Sr, and Ba), transition metals (Al, Ti, Mn, Fe, Co, Ni, Zn, Mo, Cd, and Pb), nonmetals (B, NO3, Si, As, and Se), lanthanides and actinides (La, Ce, Pr, and U), as well as total dissolved nitrogen (TDN), dissolved organic carbon (DOC), Gran alkalinity, pH, and electrical conductivity. These solutes span every row of the periodic table, and more than six orders of magnitude in concentration. Many of these diurnal cycles are subtle, representing only a few percent, at most, of the total variance in the concentration time series. Nonetheless they are diagnostically useful, because their amplitude and phase contain important clues to the mechanisms controlling these solutes in streamwater. The amplitudes of these cycles vary seasonally, and from wet to dry conditions; the phases are typically much more consistent over time. Under low-flow conditions, the diurnal cycle phases of different elements vary systematically with their electronic structure, as reflected in their placement in the periodic table. Potential mechanisms for this surprising pattern will be discussed. Neal, C., B. Reynolds, J. W. Kirchner, P. Rowland, D. Norris, D. Sleep, A. Lawlor, C. Woods, S. Thacker, H. Guyatt, C. Vincent, K. Lehto, S. Grant, J. Williams, M. Neal, H. Wickham, S. Harman, and L. Armstrong. 2013. High-frequency precipitation and stream water quality time series from Plynlimon, Wales: an openly accessible data resource spanning the periodic table. Hydrological Processes 27:2531-2539. Kirchner, J. W., and C. Neal. 2013. Universal fractal scaling in stream chemistry and its implications for solute transport and water quality trend detection. Proceedings of the National Academy of Sciences of the United States of America 110:12213-12218.

Kirchner, James

2014-05-01

188

Microbial As(III) Oxidation in Water Treatment Plant Filters  

EPA Science Inventory

Arsenic exists in two oxidation states in water - arsenite [As(III)] and arsenate [As(V)]. As(III) is relatively mobile in water and difficult to remove by arsenic-removal treatment processes. Source waters that contain As(III) must add a strong oxidant such as free chlorine or p...

189

Oxidation of Carbon Monoxide by Metal Ions and Homogeneous Catalysis of the Water Gas Shift Reaction and Related Processes  

Microsoft Academic Search

A variety of metal ions and complexes oxidize CO in aqueous solution through mechanisms that differ in detail but have in common the involvement of an intermediate hydroxycarbonyl complex (MCOOH). Such oxidation reactions can also be incorporated into various catalytic cycles including the homogeneously catalyzed water gas shift reaction.

Jack Halpern

1981-01-01

190

Reductive Pentose Phosphate Cycle and Oxidative Carbohydrate Metabolic Activities in Pea Chloroplast Stroma Extracts 1  

PubMed Central

Oxidative and reductive carbohydrate metabolism was studied in reaction mixtures based on chlorophyll-free stromal extracts from chloroplasts of Pisum sativum. A new assay system for the reductive pentose phosphate cycle was characterized. When provided with ATP, an enzymic ATP-regenerating system and reduced pyridine nucleotide, substantial rates of CO2 fixation and pyridine nucleotide oxidation were observed following the addition of millimolar concentrations of reductive pentose phosphate cycle intermediates. The reduced pyridine nucleotide requirement could be met either by NADPH, or by NADH plus the added enzymes NAD+-glyceraldehyde phosphate dehydrogenase and phosphoglycerate kinase. When the assay system was primed with small amounts of reductive pentose phosphate cycle intermediates, lower rates of pyridine nucleotide oxidation were observed, but turnover of the complete cycle was demonstrated. Autocatalytic effects were not evident. The optimum pH and Mg concentrations for cycle turnover were similar to those believed to exist in the stroma of intact chloroplasts in the light. Oxidative carbohydrate metabolism was studied by supplying oxidized pyridine nucleotide and measuring its rate of reduction in the presence of sugar phosphates. Glycolytic activity, estimated as the rate of fructose-6-phosphate entry to the phosphofructokinase reaction was 2.7 micromoles per milligram chlorophyll per hour when fructose-6-phosphate was provided as substrate. Evidence based on glucose-6-phosphate and ribose-5-phosphate-dependent NADP+ reduction showed that the oxidative pentose phosphate cycle was also active. Apparent oxidative pentose phosphate cycle turnover in the presence of ribose-5-phosphate, estimated as the rate of glucose-6-phosphate entry to the glucose-6-phosphate dehydrogenase reaction, was 1.7 micromoles per milligram chlorophyll per hour. It was concluded that under the defined conditions, reductive pentose phosphate cycle activity could be measured without interference from oxidative carbohydrate metabolism in this experimental system.

Furbank, Robert T.; Lilley, Ross McC.

1981-01-01

191

A learning process of water cycle as complex system  

NASA Astrophysics Data System (ADS)

Water cycle is a very good example of a complex geosystem which has many societal impacts and drivers. A permanent and ubiquitous question is how to increase public awareness and understanding of its extreme behaviours, as well as of the related uncertainties. For instance, CEREVE is highly solicited to help the general public, particularly the youth, and the local politicians to get better acquainted with the new water culture in general and with flood risks in particular, in the nearby county Val-de-Marne. Since 2001, May is the month of the "Festival de l'Oh"(which sounds like "Festival de l'Eau", i.e. the water festival co-organized by the county council and city of Paris. "Oh » at the same time partly displays the chemical composition of water and is an exclamation for atonishment). This festival starts with the Scientific Days of Environment that involve researchers and students of the county, as well as collaborators of all around the world. This conference is open to the public who can be informed from the latest research developments, in particular with the help of some general synthesis and panel discussions. On the other hand, (young) researchers can present their own works to a large public. This conference is followed by a Professional Forum where students, heads of water public services or private operators can meet. In the framework of the water festival preparation, there are several water forums for the secondary schools. All along the year, there are regular pedagogical activities for secondary schools, in particular in the framework of Water Houses scattered across the county. We will discuss the importance to better evaluate the effective impact of these pedagogical events on the public awareness and understanding, and to make the learning process more adaptive and interactive, as well as to better address the underlying fundamental problems, e.g. the present limitations of current modelling and data processing.

Schertzer, D.; Deroubaix, J. F.; Tchiguirinskaia, I.; Tassin, B.; Thevenot, D.

2009-04-01

192

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

NASA Astrophysics Data System (ADS)

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

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

1999-08-01

193

Think Scientifically: The Sun and The Water Cycle  

NSDL National Science Digital Library

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

194

GEWEX - The Global Energy and Water Cycle Experiment  

NASA Technical Reports Server (NTRS)

GEWEX, which is part of the World Climate Research Program, has as its goal an order-of-magnitude improvement in the ability to model global precipitation and evaporation and furnish an accurate assessment of the sensitivity of atmospheric radiation and clouds. Attention will also be given to the response of the hydrological cycle and water resources to climate change. GEWEX employs a single program to coordinate all aspects of climatology from model development to the deployment and operation of observational systems. GEWEX will operate over the next two decades.

Chahine, Moustafa T.

1992-01-01

195

[Fundamental studies in oxidation reduction in relation to water photolysis  

SciTech Connect

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

Hurst, J.K.

1992-01-01

196

The Martian Water Cycle Based on 3-D Modeling  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

197

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

198

A general circulation model study of the Mars water cycle  

NASA Astrophysics Data System (ADS)

This study has focused on the development and application of the first fully three-dimensional model of the current Mars water cycle. Previous models of the water cycle have suggested the importance of transport processes in determining the observed variations in atmospheric water [Jakosky and Haberle (1992)]. This work addresses questions regarding the relative importance of water reservoirs, transport of water, control of global average vapour amounts, and the importance of clouds. The results of this work show that model transport out of the northern polar region during summer occurs primarily in surface forced, zonally asymmetric currents. Significantly more hemispheric transport is predicted than expected with zonal average models. Transport capacity is higher for south to north flow during southern summer than for north to south flow in northern summer. Houben et al. (1997) suggested that a model without regolith would ``flood'' with vapour. Our model does riot show this behaviour, thus the regolith may not provide sole control over global vapour amounts. The mechanism of ``equilibration'' for the model without regolith pivots on an annual average vapour flux balance across the northern high-latitude/polar latitude boundary. However, as there is always net loss to the south polar cold tap the ``equilibrium'' is only approximate. Simulations suggest that an exposed southern water cap would be unstable with respect to the northern cap. Comparison with zonal-average vapour data suggests that the residual cap provides <= 40% of the vapour observed to accrue after L S = 80°. Simulations employing seasonal ice show improved ``fits,'' but additional (regolith) sources are needed. As suggested by Kahn (1990), agreement with data requires cloud ice precipitation. Precipitation allows water to be removed from a cold atmosphere more rapidly than diffusion of ice or vapour. Simulations also suggest that cloud formation may reduce interhemispheric water transport [Clancy et al. (1996)]. The model evolution of zonal-average vapour distributions is in rough agreement with data. Cloudiness is generally overpredicted, likely due to defects in the cloud microphysics scheme. The spatial distribution of clouds compare reasonably well with the limited observations, however errors do occur in the tropics and winter hemisphere. These likely result from errors in the vertical wind field and local scale vapour transport. Differences between the true and model topography and surface temperatures are the most likely causes. Detailed modeling of vapour transport will require very close attention to the surface prescription.

Richardson, Mark Ian

1999-10-01

199

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

Microsoft Academic Search

Plasma electrolytic oxidation (PEO) was applied on the surface of commercially pure titanium substrates in a mixed aluminate-phosphate electrolyte in the presence of silicon nitride nanoparticles as suspension in the electrolyte in order to fabricate nanocomposite coatings. Pulsed current was applied based on variable duty cycle in order to synthesize functionally gradient coatings (FGC). Different rates of variable duty cycle

M. Aliofkhazraei; A. Sabour Rouhaghdam

200

Nanoscale manganese oxide within Faujasite zeolite as an efficient and biomimetic water oxidizing catalyst.  

PubMed

Nanoscale manganese oxides within Faujasite zeolite have been synthesized with a simple method and characterized by scanning electron microscopy, X-ray diffraction spectrometry, N(2) adsorption-desorption isotherms, transmission electron microscopy, 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. PMID:22833185

Najafpour, Mohammad Mahdi; Pashaei, Babak

2012-09-14

201

Problems with modelling crops in the water cycle  

NASA Astrophysics Data System (ADS)

Vegetation plays a major role both in the atmospheric and terrestrial water cycle. Cropland covers a large proportion of the global terrestrial area (i.e. 38% globally in 2005, FAOSTAT). Accordingly, crop models have become increasingly prominent for studying the impact of Global Change both on economic welfare and on the influence of vegetation on climate and feedback mechanisms with hydrological processes. By doing so, it is implied that crop models properly reflect the crop-soil interactions, soil water balance and vertical exchange with the atmosphere - and that parameters are to some degree portable. In this research we used data from eight lysimeters located at Brandis (Saxony, Germany), which have been planted with the crops of the surrounding farm to test the capability of the crop model in SWAP. The lysimeters contain different natural soil cores, leading to substantially different yield. This experiment gives the opportunity to test the crop model with regard to yield and the water cycle - i.e. whether a model calibrated with one crop and one climate can be moved to a different soil. When using the default parameters for the respective environment, the model does neither quantitatively nor qualitatively reproduce the dynamics of the yield and the water-balance for the different lysimeters. A joint calibration of plant and soil parameters performed much better than that of a sequential calibration of the same parameters. Moreover, the cross validation of parameter sets for the same crop to a different soil indicates strong interrelations between the two parameter sets. This suggests that the model is not portable, and needs to be calibrated at each location. As we aim on dynamic crop modelling at the mesoscale with regionalized parameters, we propose to work on understanding the orgin and effect of these discrepancies.

Jackisch, C.; Samaniego, L.; Hildebrandt, A.

2009-04-01

202

Electrode-assisted catalytic water oxidation by a flavin derivative  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

203

Supercritical water oxidation of solid particulates  

SciTech Connect

In the application of supercritical water oxidation (SCWO) to the treatment of aqueous solid wastes, particle size will be an important processing parameter. The particle size will impact feed preparation requirements such as slurry concentration, pumping requirements, and, in terms of the destruction of the solid particles, rate of reaction and reactor size. To address these issues, an experimental research program was undertaken to evaluate the effect of particle size on the reaction kinetics in SCWO of solid particulates (wheat straw and cellulose particles in this case). The experiments also included evaluation of the effects of temperature, pressure, and agitation rate. A two-step reaction mechanism was revealed, with a very rapid initial dissolution period followed by a longer particle reaction period. Empirically based mathematical relationships were developed that can be used for SCWO system design.

Pisharody, S.A.; Fisher, J.W. [NASA Ames Research Center, Moffett Field, CA (United States)] [NASA Ames Research Center, Moffett Field, CA (United States); Abraham, M.A. [Univ. of Tulsa, OK (United States). Dept. of Chemical Engineering] [Univ. of Tulsa, OK (United States). Dept. of Chemical Engineering

1996-12-01

204

Metal oxide photoanodes for water splitting.  

PubMed

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

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

2011-01-01

205

GEWEX: The Global Energy and Water Cycle Experiment  

NASA Astrophysics Data System (ADS)

The need for better quantitative understanding of energy fluxes and water exchanges is basic to all climate studies, yet our quantitative knowledge of the global hydrological cycle remains surprisingly poor. Evaporation minus precipitation or, similarly, the net flow of water from land to oceans and the net advection of moisture from the marine atmosphere to the terrestrial atmosphere is known at best to a factor of two to three (J. Schaake, personal communication, 1991). The regional and temporal distribution of the components of the hydrological budget are even more uncertain.Improved understanding of the global hydrological cycle has been limited in part by the absence of reliable global data on such essential quantities as precipitation, evaporation, and atmospheric transport; acquisition of these data is a prerequisite for the study of global energetics and hydrology. Space agencies in the United States, Europe, and Japan have announced plans to launch a series of global Earth observing satellites in the late 1990s to monitor these essential atmospheric and surface parameters and to complement existing operational meteorological and hydrological networks.

Chahine, Moustafa T.

206

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

PubMed

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

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

2006-08-01

207

Heat-Sterilized Silver Oxide-Zinc Cells Cycle Life Studies.  

National Technical Information Service (NTIS)

A JPL study was conducted to evaluate the cell design parameters that contribute to the cycle life of sealed, heat-sterilized silver oxide-zinc cells. Test cells having a rated capacity of 4.2 A-h were fabricated using zinc oxide electrodes prepared by th...

J. T. Arms

1973-01-01

208

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

209

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

210

Nanostructured transition metal oxides useful for water oxidation catalysis  

DOEpatents

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

Frei, Heinz M; Jiao, Feng

2013-12-24

211

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

212

Potential Seasonal Predictability of Water Cycle in Observations and Reanalysis  

NASA Astrophysics Data System (ADS)

Identification of predictability of water cycle variability is crucial for climate prediction, water resources availability, ecosystem management and hazard mitigation. An analysis that can assess the potential skill in seasonal prediction was proposed by the authors, named as analysis of covariance (ANOCOVA). This method tests whether interannual variability of seasonal means exceeds that due to weather noise under the null hypothesis that seasonal means are identical every year. It has the advantage of taking into account autocorrelation structure in the daily time series but also accounting for the uncertainty of the estimated parameters in the significance test. During the past several years, multiple reanalysis datasets have become available for studying climate variability and understanding climate system. We are motivated to compare the potential predictability of water cycle variation from different reanalysis datasets against observations using the newly proposed ANOCOVA method. The selected eight reanalyses include the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP/NCAR) 40-year Reanalysis Project (NNRP), the National Centers for Environmental Prediction-Department of Energy (NCEP/DOE) Reanalysis Project (NDRP), the European Centre for Medium-Range Weather Forecasts (ECMWF) 40-year Reanalysis, The Japan Meteorological Agency 25-year Reanalysis Project (JRA25), the ECMWF) Interim Reanalysis (ERAINT), the NCEP Climate Forecast System Reanalysis (CFSR), the National Aeronautics and Space Administration (NASA) Modern-Era Retrospective Analysis for Research and Applications (MERRA), and the National Oceanic and Atmospheric Administration-Cooperative Institute for Research in Environmental Sciences (NOAA/CIRES) 20th Century Reanalysis Version 2 (20CR). For key water cycle components, precipitation and evaporation, all reanalyses consistently show high fraction of predictable variance in the tropics, low predictability over the extratropics, more potential predictability over the ocean than land, and a stronger seasonal variation in potential predictability over land than ocean. The substantial differences are observed especially over the extropical areas where boundary-forced signal is not as significant as in tropics. We further evaluate the accuracy of reanalysis in estimating seasonal predictability over several selected regions, where rain gauge measurement or land surface data assimilation product is available and accurate, to gain insight on the strength and weakness of reanalysis products.

Feng, X.; Houser, P.

2012-12-01

213

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

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

214

Failure and life cycle evaluation of watering valves.  

PubMed

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

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

2011-09-01

215

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

216

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

Microsoft Academic Search

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

Andrew J. Frierdich; Yun Luo; Jeffrey G. Catalano

2011-01-01

217

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

218

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

2014-06-24

219

Catalytic decomposition of sulfuric acid on mixed Cr\\/Fe oxide samples and its application in sulfur–iodine cycle for hydrogen production  

Microsoft Academic Search

The present paper deals with the catalytic decomposition of sulfuric acid reaction which is common to several sulfur based thermochemical water splitting cycles including the sulfur–iodine thermochemical cycle. The activity and stability of Cr substituted Fe oxide catalysts were studied for the sulfuric acid decomposition reaction. The samples Fe2(1-x)Cr2xO3 were synthesized using ceramic route and characterized by XRD, N2-BET and

A. M. Banerjee; M. R. Pai; K. Bhattacharya; A. K. Tripathi; V. S. Kamble; S. R. Bharadwaj; S. K. Kulshreshtha

2008-01-01

220

Improved efficiency in thermochemical hydrogen cycles through decreasing the use of solvent water. Consideration of the sulfur dioxide: iodine cycle  

Microsoft Academic Search

This paper considers the relationship between evaporation and efficiency and examines experimentally an adaptation of the sulfur dioxide-iodine cycle where little water needs to be evaporated or condensed.

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

1982-01-01

221

Hydrogen Production Using Solid-Polymer-Electrolyte Technology for Water Electrolysis and Hybrid Sulfur Cycle.  

National Technical Information Service (NTIS)

An evaluation was made of the comparative technoeconomics of hydrogen production using the General Electric Company's solid polymer electrolyte technology in two advanced processes: Water Electrolysis and Hybrid Sulfur Cycle Water Decomposition. In water ...

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

1979-01-01

222

Kyuto heat pump cycle-no kokoritsuka ni kansuru ichikosatsu. Fukugo hatsuden(prime)yo joki cycle tono hikaku. (Study on performance of heat pump cycle for hot tap water supply. Comparison with steam cycle in combined cycle).  

National Technical Information Service (NTIS)

The performance of the advanced two-stage compression heat pump cycle was studied which is being developed to save energy in hot tap water supply. After functions of an intermediate heat exchanger essential to the heat pump cycle were analyzed precisely, ...

M. Saikawa T. Hamamatsu T. Iwatsubo H. Hasegawa

1990-01-01

223

Water soluble oxidized starches by peroxide reactive extrusion  

Microsoft Academic Search

Oxidation of starches of different amylose content was investigated to increase carboxyl and carbonyl content and to increase water solubility. Three types of cornstarches containing up to 70% amylose were oxidized by a reactive extrusion-drum drying process, using hydrogen peroxide and a ferrous–cupric sulfate catalyst. Increasing the peroxide level increased oxidation and solubility. Starches with higher amylose content gave reduced

R. E Wing; J. L Willett

1997-01-01

224

Heat Pump Cycle with an Air--Water Working Fluid.  

National Technical Information Service (NTIS)

A new thermodynamic cycle for heat pumps is discussed. The cycle resembles the Joule cycle in that it consists of an isentropic compression, a constant pressure heat rejection, an isentropic expansion with work recovery, and a constant pressure heat addit...

E. C. Hise J. V. Wilson

1977-01-01

225

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

226

Tunable single-site ruthenium catalysts for efficient water oxidation.  

PubMed

The catalytic water oxidation activity of mononuclear ruthenium complexes comprising a pyridine-functionalized abnormal triazolylidene ligand can be adjusted by modification of the triazolylidene substituents, which is readily achieved through click-type cycloaddition chemistry, affording some of the most active ruthenium catalysts known thus far for water oxidation (TONs > 400, TOFs close to 7000 h(-1)). PMID:21677991

Bernet, Lucile; Lalrempuia, Ralte; Ghattas, Wadih; Mueller-Bunz, Helge; Vigara, Laura; Llobet, Antoni; Albrecht, Martin

2011-07-28

227

Our Environment in Hot Water: Comparing Water Heaters, A Life Cycle Approach Comparing Tank and Tankless Water Heaters in California  

SciTech Connect

Residential water heating is a large source of energy use in California homes. This project took a life cycle approach to comparing tank and tankless water heaters in Northern and Southern California. Information about the life cycle phases was calculated using the European Union?s Methodology study for EcoDesign of Energy-using Products (MEEUP) and the National Renewable Energy Laboratory?s Life Cycle Inventory (NREL LCI) database. In a unit-to-unit comparison, it was found that tankless water heaters would lessen impacts of water heating by reducing annual energy use by 2800 MJ/year (16% compared to tank), and reducing global warming emissions by 175 kg CO2 eqv./year (18% reduction). Overall, the production and combustion of natural gas in the use phase had the largest impact. Total waste, VOCs, PAHs, particulate matter, and heavy-metals-to-air categories were also affected relatively strongly by manufacturing processes. It was estimated that tankless water heater users would have to use 10 more gallons of hot water a day (an increased usage of approximately 20%) to have the same impact as tank water heaters. The project results suggest that if a higher percentage of Californians used tankless water heaters, environmental impacts caused by water heating would be smaller.

Lu, Alison; McMahon, James; Masanet, Eric; Lutz, Jim

2008-08-13

228

Exploring the limits of the terrestrial fresh water cycle  

NASA Astrophysics Data System (ADS)

Precipitation is the ultimate source of life on this planet: it makes our crops grow, provides drinking water, feeds rivers and replenishes groundwater aquifers. Climate modelling studies estimate changes in precipitation due to increased greenhouse gas emissions and climate impact studies use those estimates as input to their (hydrological) models to predict future water availability and societal impact. However, humans also significantly alter the land surface by, for example, deforestation and irrigation, which is not frequently taken into account in our climate studies. Here, we present an overview of several papers in the field of moisture recycling, published by our group, that show the extent to which terrestrial evaporation influences terrestrial precipitation. It is found that 38% of the terrestrial precipitation originates from terrestrial evaporation and that 58% of all terrestrial evaporation recycles, and return again as terrestrial precipitation. Knowing this, it is clear that evaporation is not necessary a loss to the hydrological cycle. We show that in some cases even transpiration during the dry season can act as a moisture source for a distant region. To assess the vulnerability of a region to local and remote land use changes we propose the concept of the precipitationshed, which maps out a region's precipitation sources. Our results are useful in mapping out possible land use change threats, but also opportunities to safeguard our water resources in the Anthropocene.

van der Ent, Ruud; Wang-Erlandsson, Lan; Keys, Patrick; Savenije, Hubert

2014-05-01

229

A New Method for Regional Water Environmental Capacity Estimation Based on Natural-Social Water Cycle Analysis  

Microsoft Academic Search

Human's social-economic activities have significantly interrupted the natural water cycle, particularly in urban area. The so-called binary natural-social water cycle issue has highly increased the complexity of urban water system. Traditional method to calculate water environmental capacity (WEC) depending on water quality model and long time series of monitoring data is sometimes not practical, especially at the planning stage or

Pan Li; Siyu Zeng; Jining Chen

2010-01-01

230

Homogeneous oxidation of water by iron complexes with macrocyclic ligands.  

PubMed

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

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

2014-06-01

231

Nitrogen cycling in the offshore waters of the Black Sea  

NASA Astrophysics Data System (ADS)

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

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

2007-09-01

232

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

233

Life Cycle Assesment of Daugavgriva Waste Water Treatment Plant  

NASA Astrophysics Data System (ADS)

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

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

2009-01-01

234

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

235

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

NASA Astrophysics Data System (ADS)

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

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

2008-05-01

236

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

EPA Science Inventory

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

237

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

238

Effect of oestrous cycle on the oxidative burst activity of blood polymorphonuclear leucocytes in cows.  

PubMed

Blood polymorphonuclear leucocyte (PMN) oxidative burst activity, plasma cortisol levels, and the total and differential white blood cells counts (WBC) of six cycled dairy cows were evaluated for a period of 24 days, three times a week; on Mondays, Wednesdays and Fridays. The PMN oxidative burst was indirectly evaluated by flow cytometry, measuring the intracellular oxidation of 2',7'-dichlorofluorescein diacetate to 2',7' dichlorofluorescein (DCF) by H2O2-production. Results are presented as the mean fluorescence intensity (MFI) of DCF. Cow's oestrous cycle was evaluated by following the plasma progesterone levels using a radioimmunoassay method. Levels of cortisol in the plasma were measured using a fluorimetric method. The oxidative burst activity of PMN, represented a maximum value (MFI=117.6+/-7.4) during the oestrous period. A fall was then observed, in which a steady state was observed during the lutheinic phase of the oestrous cycle, reaching the minimum value [MFI=73.2+/-11.2 (poxidative burst activity was observed. Our results demonstrated that the oestrous cycle might influence directly, or indirectly, the immune system of cows, by altering the oxidative burst of PMN. PMID:19000223

Chaveiro, A; Moreira da Silva, F

2009-12-01

239

Preliminary analysis of the effects of sea water leakage on the performance of the ammonia cycle  

Microsoft Academic Search

The effects of water contamination on an OTEC power plant utilizing ammonia as the working fluid were investigated with reference to power cycles with and without recycle around the evaporator. The thermodynamic effects of increasing the water concentration in an optimized ammonia cycle plant were analyzed by means of the Han-Starling generalized correlation with appropriate parameters for ammonia-water mixtures. In

H. Hafezzadah; D. W. Johnson; K. E. Starling

1977-01-01

240

Simultaneous production of desalinated water and power using a hybrid-cycle OTEC plant  

SciTech Connect

A systems study for simultaneous production of desalinated water and electric power using the hybrid-cycle OTEC system was carried out. The hybrid cycle is a combination of open and closed-cycle OTEC systems. A 10 MWe shore-based hybrid-cycle OTEC plant is discussed and corresponding operating parameters are presented. Design and plant operating criteria for adjusting the ratio of water production to power generation are described and their effects on the total system were evaluated. The systems study showed technical advantages of the hybrid-cycle power system as compared to other leading OTEC systems for simultaneous production of desalinated water and electric power generation.

Panchal, C.B.; Bell, K.J.

1987-05-01

241

Ice haze, snow, and the Mars water cycle  

NASA Technical Reports Server (NTRS)

Light curves and extinction profiles derived from Martian limb observations are used to constrain the atmospheric temperature structure in regions of the atmosphere with thin haze and to analyze the haze particle properties and atmospheric eddy mixing. Temperature between 170 and 190 K are obtained for three cases at levels in the atmosphere ranging from 20 to 50 km. Eddy diffusion coefficients around 100,000 sq cm/s, typical of a nonconvecting atmosphere, are derived in the haze regions at times when the atmosphere is relatively clear of dust. This parameter apparently changes by more than three orders of magnitude with season and local conditions. The derived particle size parameter varies systematically by more than an order of magnitude with condensation level, in such a way that the characteristic fall time is always about one Martian day. Ice hazes provide a mechanism for scavenging water vapor in the thin Mars atmosphere and may play a key role in the seasonal cycle of water on Mars.

Kahn, Ralph

1990-01-01

242

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

243

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

NASA Astrophysics Data System (ADS)

The cycling and oxidation pathways of organic carbon were investigated at a single shallow water estuarine site in Trinity Bay, Texas, the uppermost lobe of Galveston Bay, during November 2000. Radio-isotopes were used to estimate sediment mixing and accumulation rates, and benthic chamber and pore water measurements were used to determine sediment-water exchange fluxes of oxygen, nutrients and metals, and infer carbon oxidation rates. Using 7Be and 234Th XS, the sediment-mixing coefficient ( Db) was 4.3 ± 1.8 cm 2 y -1, a value that lies at the lower limit for marine environments, indicating that mixing was not important in these sediments at this time. Sediment accumulation rates ( Sa), estimated using 137Cs and 210Pb XS, were 0.16 ± 0.02 g cm -2 y -1. The supply rate of organic carbon to the sediment-water interface was 30 ± 3.9 mmol C m -2 d -1, of which ˜10% or 2.9 ± 0.44 mmol C m -2 d -1was lost from the system through burial below the 1-cm thick surface mixed layer. Measured fluxes of O 2 were 26 ± 3.8 mmol m -2 d -1 and equated to a carbon oxidation rate of 20 ± 3.3 mmol C m -2 d -1, which is an upper limit due to the potential for oxidation of additional reduced species. Using organic carbon gradients in the surface mixed layer, carbon oxidation was estimated at 2.6 ± 1.1 mmol C m -2 d -1. Independent estimates made using pore water concentration gradients of ammonium and C:N stoichiometry, equaled 2.8 ± 0.46 mmol C m -2 d -1. The flux of DOC out of the sediments (DOC efflux) was 5.6 ± 1.3 mmol C m -2 d -1. In general, while mass balance was achieved indicating the sediments were at steady state during this time, changes in environmental conditions within the bay and the surrounding area, mean this conclusion might not always hold. These results show that the majority of carbon oxidation occurred at the sediment-water interface, via O 2 reduction. This likely results from the high frequency of sediment resuspension events combined with the shallow sediment mixing zone, leaving anaerobic oxidants responsible for only ˜10-15% of the carbon oxidized in these sediments.

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

2008-01-01

244

Closing the Water Cycle over the Ocean Using a Constellation of Satellites  

Microsoft Academic Search

We have completed the Version-1 Passive Microwave Water Cycle (PMWC) product for the NASA Energy and Water Cycle Study (NEWS). The purpose of this product is a full characterization of the atmospheric branch of the water cycle over the global oceans using accurately intercalibrated data from the SSM\\/I, TMI, and AMSR passive microwave sensors. The product is a monthly, 0.25-degree

K. Hilburn; F. Wentz

2008-01-01

245

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.

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

2012-01-01

246

A Review of RedOx Cycling of Solid Oxide Fuel Cells Anode.  

PubMed

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

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

2012-01-01

247

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

PubMed

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

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

2012-01-01

248

In situ coupled oxidation cycle catalyzed by highly active and reusable Pt-catalysts: dehydrogenative oxidation reactions in the presence of a catalytic amount of o-chloranil using molecular oxygen as the terminal oxidant.  

PubMed

An in situ coupled oxidation cycle that allows catalytic oxidation of a substrate with catalytic amounts of o-chloranil and novel reusable polymer-immobilized platinum nanocluster catalysts using molecular oxygen as the terminal oxidant was developed. PMID:20871889

Miyamura, Hiroyuki; Maehata, Kanako; Kobayashi, Shu

2010-11-14

249

Analyses of oxide films grown on Alloy 625 in oxidizing supercritical water  

Microsoft Academic Search

Morphologies, microstructures and chemical composition of oxide films grown on Alloy 625 at 400°C, 450°C and 500°C in oxidizing supercritical water containing 2.0% H2O2 were investigated using weight measurement, grazing incidence X-ray diffractometry, scanning electron microscopy, X-ray photoelectron spectroscopy and transmission electron microscopy. It was found that the mass gain of the alloy in oxidizing supercritical water increased with exposure

Mingcheng Sun; Xinqiang Wu; Zhaoen Zhang; En-Hou Han

2008-01-01

250

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' 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 in. 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.

Kummerow, Christian; Hong, Ye

1999-01-01

251

Highly efficient and robust molecular ruthenium catalysts for water oxidation.  

PubMed

Water oxidation catalysts are essential components of light-driven water splitting systems, which could convert water to H(2) driven by solar radiation (H(2)O + h? ? 1/2O(2) + H(2)). The oxidation of water (H(2)O ? 1/2O(2) + 2H(+) + 2e(-)) provides protons and electrons for the production of dihydrogen (2H(+) + 2e(-) ? H(2)), a clean-burning and high-capacity energy carrier. One of the obstacles now is the lack of effective and robust water oxidation catalysts. Aiming at developing robust molecular Ru-bda (H(2)bda = 2,2'-bipyridine-6,6'-dicarboxylic acid) water oxidation catalysts, we carried out density functional theory studies, correlated the robustness of catalysts against hydration with the highest occupied molecular orbital levels of a set of ligands, and successfully directed the synthesis of robust Ru-bda water oxidation catalysts. A series of mononuclear ruthenium complexes [Ru(bda)L(2)] (L = pyridazine, pyrimidine, and phthalazine) were subsequently synthesized and shown to effectively catalyze Ce(IV)-driven [Ce(IV) = Ce(NH(4))(2)(NO(3))(6)] water oxidation with high oxygen production rates up to 286 s(-1) and high turnover numbers up to 55,400. PMID:22753518

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

2012-09-25

252

Highly efficient and robust molecular ruthenium catalysts for water oxidation  

PubMed Central

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

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

2012-01-01

253

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

NASA Technical Reports Server (NTRS)

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

Arms, J. T.

1973-01-01

254

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

Microsoft Academic Search

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

Michael Shapira; Eran Segal; David Botstein

2004-01-01

255

Pressurized solid oxide fuel cell\\/gas turbine combined cycle systems  

Microsoft Academic Search

Over the last 10 years, Westinghouse Electric Corporation has made great strides in advancing tubular solid oxide fuel cell (SOFC) technology towards commercialization by the year 2001. In 1993, Westinghouse initiated a program to develop pressurized solid oxide fuel cell\\/gas turbine (PSOFC\\/GT) combined cycle power systems because of the ultra-high electrical efficiencies, 60-75% (net AC\\/LHV CH4), inherent with these systems.

1997-01-01

256

Oxidation of Melatonin and Tryptophan by an HRP Cycle Involving Compound III  

Microsoft Academic Search

We recently described that horseradish peroxidase (HRP) and myeloperoxidase (MPO) catalyze the oxidation of melatonin, forming the respective indole ring-opening product N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK) (Biochem. Biophys. Res. Commun. 279, 657–662, 2001). Although the classic peroxidatic enzyme cycle is expected to participate in the oxidation of melatonin, the requirement of a low HRP:H2O2 ratio suggested that other enzyme paths might also be

Valdecir F. Ximenes; Luiz H. Catalani; Ana Campa

2001-01-01

257

Salty-ocean water cycle variability and change (Invited)  

NASA Astrophysics Data System (ADS)

Previous work has highlighted a clear long-term salinity pattern amplification (PA) in both observations and modelled historical and future climate simulations. These results suggest that fresh ocean regions are becoming fresher, and salty regions saltier in response to evaporation minus precipitation (E-P) changes driven by a warming Earth - an ocean proxy for the ';rich get richer' (wet gets wetter, dry gets drier) mechanism. These global evaporation (E) and precipitation (P) surface fluxes over the ocean comprise 75-85% of the climatological annual mean global water cycle across the entire Earth surface and so are clearly a good place to look for temporal variations in the observed record. Using CMIP models we extend upon previous work to investigate the influence of climate variability on previously resolved PA estimates. Using the CMIP (Coupled Model Intercomparison Project phase 3 & 5) 20C3M/historical (20th century), SRES/RCP (future 21st century) and pre-industrial (piControl; unforced) simulations, we diagnose the relationship between the simulated ocean surface salinity and the simulated E-P (water cycle) changes. We investigate the intrinsic variability of both the modelled salinity and E-P fields to ascertain an envelope of modelled unforced (piControl) climate variability. We compare these unforced distributions to those of weakly- (20C3M/historical) and strongly-forced (SRES/RCP) simulations to determine the emergence of an anthropogenic-forced fingerprint from intrinsic variability as defined by the models. Using these forced-signal versus variability estimates from models, we revisit the observed salinity PA, investigate differences between the CMIP5 and CMIP3 models suites, and investigate the significance of resolved changes over 1950-present and discuss any implications to previous conclusions discovered by this updated analysis. Work undertaken at Lawrence Livermore National Laboratory is supported by the U.S. Department of Energy under contract DE-AC52-07NA27344. LLNL IM release number: LLNL-CONF-641935

Durack, P. J.; Gleckler, P. J.; Bindoff, N. L.

2013-12-01

258

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

259

Kinetics of zero valent iron nanoparticle oxidation in oxygenated water.  

PubMed

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

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

2012-12-01

260

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

NASA Astrophysics Data System (ADS)

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

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

261

Infrared Spectra of Water Bending Bands of Propylene Oxide-Water Complexes: Sequential Solvation of a Chiral Molecule in Water  

Microsoft Academic Search

Sequential solvation of propylene oxide (C3H6O), an prototypical chiral molecule, with water has been investigated using high resolution infrared spectroscopy and ab initio methods. In a number of low resolution studies, the vibrational and vibrational circular dichroism spectral features at the water bending vibration region had been shown to be highly sensitive to the water solvation structures around propylene oxide

Xunchen Liu; Yunjie Xu

2011-01-01

262

Catalytic water oxidation by mononuclear Ru complexes with an anionic ancillary ligand.  

PubMed

Mononuclear Ru-based water oxidation catalysts containing anionic ancillary ligands have shown promising catalytic efficiency and intriguing properties. However, their insolubility in water restricts a detailed mechanism investigation. In order to overcome this disadvantage, complexes [Ru(II)(bpc)(bpy)OH2](+) (1(+), bpc = 2,2'-bipyridine-6-carboxylate, bpy = 2,2'-bipyridine) and [Ru(II)(bpc)(pic)3](+) (2(+), pic = 4-picoline) were prepared and fully characterized, which features an anionic tridentate ligand and has enough solubility for spectroscopic study in water. Using Ce(IV) as an electron acceptor, both complexes are able to catalyze O2-evolving reaction with an impressive rate constant. On the basis of the electrochemical and kinetic studies, a water nucleophilic attack pathway was proposed as the dominant catalytic cycle of the catalytic water oxidation by 1(+), within which several intermediates were detected by MS. Meanwhile, an auxiliary pathway that is related to the concentration of Ce(IV) was also revealed. The effect of anionic ligand regarding catalytic water oxidation was discussed explicitly in comparison with previously reported mononuclear Ru catalysts carrying neutral tridentate ligands, for example, 2,2':6',2?-terpyridine (tpy). When 2(+) was oxidized to the trivalent state, one of its picoline ligands dissociated from the Ru center. The rate constant of picoline dissociation was evaluated from time-resolved UV-vis spectra. PMID:23409776

Tong, Lianpeng; Inge, A Ken; Duan, Lele; Wang, Lei; Zou, Xiaodong; Sun, Licheng

2013-03-01

263

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

264

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

265

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

266

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

267

Oxidation of Ammonia in Water by Ferrates (VI) and (IV).  

National Technical Information Service (NTIS)

The objective of the exploratory study was to determine the feasibility of application of ferrates (VI) to oxidation of ammonia to elemental nitrogen in pure water solutions and sewage treatment plant secondary effluent. Two competing reactions, the oxida...

K. Svanks

1976-01-01

268

Kinetics of Supercritical Water Oxidation. SERDP Compliance Technical Thrust Area.  

National Technical Information Service (NTIS)

This project consists of experiments and theoretical modeling designed to improve our understanding of the detailed chemical kinetics of supercritical water oxidation processes. The objective of the four-year project is to develop working models that accu...

S. F. Rice R. R. Steeper R. G. Hanush J. D. Aiken E. Croiset

1996-01-01

269

Fouling Study of Silicon Oxide Pores Exposed to Tap Water  

SciTech Connect

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

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

2007-07-12

270

Oxidation of hydrocarbons and oxygenates in supercritical water  

Microsoft Academic Search

The project, Supercritical Oxidation of Hazardous Chemical Wastes,'' is a Hazardous Waste Remedial Program Research and Development task being carried out by the Los Alamos National Laboratory. Its objective is to achieve an understanding of the technology for use in scaling up and applying oxidation in supercritical water as a viable process for treating a variety of Department of Energy

C. K. Rofer; G. E. Streit

1989-01-01

271

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

272

Optically transparent water oxidation catalysts based on copper nanowires.  

PubMed

Let the light shine through: A transparent film of copper nanowires was transformed into an electrocatalyst for water oxidation by electrodepostion of Ni or Co onto the surface of the nanowires. These core-shell nanowire networks exhibit electrocatalytic performance equivalent to metal oxide films of similar composition, but are several times more transparent. PMID:24136831

Chen, Zuofeng; Rathmell, Aaron R; Ye, Shengrong; Wilson, Adria R; Wiley, Benjamin J

2013-12-16

273

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

274

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

275

Effect of cardiopulmonary bypass on urea cycle intermediates and nitric oxide levels after congenital heart surgery  

Microsoft Academic Search

Objective To test the hypothesis that cardiopulmonary bypass used for repair of ventricular septal defects and atrioventricular septal defects would decrease availability of urea cycle intermediates including arginine and subsequent nitric oxide availability. Study design Consecutive infants (n = 26) undergoing cardiopulmonary bypass for repair of an unrestrictive ventricular septal defect or atrioventricular septal defect were studied. Blood samples were

Frederick E. Barr; Heidi Beverley; Kristin VanHook; Emma Cermak; Karla Christian; Davis Drinkwater; Karrie Dyer; Noel T. Raggio; Jason H. Moore; Brian Christman; Marshall Summar

2003-01-01

276

Comparison between two optimization strategies for solid oxide fuel cell–gas turbine hybrid cycles  

Microsoft Academic Search

This paper compares the performance characteristics of a combined power system with solid oxide fuel cell (SOFC) and gas turbine (GT) working under two thermodynamic optimization strategies. Expressions of the optimized power output and efficiency for both the subsystems and the SOFC-GT hybrid cycle are derived. Optimal performance characteristics are discussed and compared in detail through a parametric analysis to

Yingru Zhao; Nilay Shah; Nigel Brandon

2011-01-01

277

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

National Technical Information Service (NTIS)

A notional 440 kW auxiliary power unit has been developed for 300 passenger commercial transport aircraft in 2015AD. A hybrid engine using solid-oxide fuel cell stacks and a gas turbine bottoming cycle has been considered. Steady-state performance analysi...

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

2005-01-01

278

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

279

The Effects of Radiatively Active Water Ice Clouds on the Martian Global Seasonal Water Cycle  

NASA Astrophysics Data System (ADS)

Recently, Mars General Circulation Models (MGCM) have begun implementing cloud microphysics packages to better account for their role in the water cycle. Here, we discuss the importance of their radiative effects. For the past several years we have been implementing and testing a state-of-the-art cloud microphysics package into the NASA/Ames MGCM. This package accounts for the nucleation, growth, transport, and settling of a size distribution water ice cloud particles in a self-consistent fashion. The model also has flags to activate their solar and infrared radiative effects, which depend on the size and dust content of the ice particles. We have performed two simulations of the global water cycle on Mars: one in which the clouds are radiatively inert, and one in which they are radiatively active. We find that the thermal structure of the atmosphere in the radiatively active cloud run compares better with MGS TES and MRO MCS data. However, the water cycle dries out considerably with radiatively active clouds. There are several reasons for this but the main reason appears to be related to a cooling of the North Polar Residual Cap (NPRC) in the model that is brought about by the reflective nature of the clouds that develop in the lower atmosphere immediately above the NPRC. These clouds increase the planetary albedo at these latitudes and reduce the solar flux at the surface, which is not sufficiently compensated for by an increase in downward infrared emission. Our conclusion at this point, based upon comparison with MRO MCS and MARCI data, is that the model is overpredicting the cloud fields in the vicinity of the NPRC.

Haberle, Robert M.; Montmessin, F.; Kahre, M. A.; Hollingsworth, J. L.; Schaeffer, J.; de Brouchoven de Bergeyck, A.; Wilson, J.

2010-10-01

280

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

281

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 Tropical Rainfall Measuring Mission (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 its synergy.

Kummerow, Christian; Hong, Ye

1999-01-01

282

A Testbed for Integrated Water Cycle Observations: A Grand Challenge for the Community  

Microsoft Academic Search

As more space-borne sensors for components of the water cycle are launched by NASA, ESA and JAXA, there is a critical need by the community to integrate the measurements into coherent data sets useful for global water cycle analyses. The hydrology community must recognize the potential of these measurements to address basic research and application questions related to the global

E. F. Wood; M. Pan; J. Sheffield

2009-01-01

283

Use of Water Vapor as a Refrigerant: Impact of Cycle Modifications on Commercial Feasibility.  

National Technical Information Service (NTIS)

This project investigated the economic viability of using water as the refrigerant in a 1000-ton chiller application. The most attractive water cycle configuration was found to be a flash-intercooled, two-stage cycle using centrifugal compressors and dire...

2004-01-01

284

Investigation of sulfur based thermochemical cycles for hydrogen production by water decomposition. [Sulfur-based cycles  

Microsoft Academic Search

Preliminary screening of ten thermochemical cycles showed that only three cycles, all based on sulfur, had > 30% efficiency. A cost analysis of these cycles, assuming a high temperature nuclear reactor as primary energy source showed a production cost of $10.83\\/million Btu in a plant of 100,000 cu m\\/hr hydrogen capacity, which would have an investment cost of $207 to

Natarajan

1976-01-01

285

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

PubMed

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

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

2014-01-01

286

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

PubMed Central

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

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

2014-01-01

287

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

NASA Technical Reports Server (NTRS)

The atmospheric water cycle at the present epoch involves summertime sublimation of water from the north polar cap, transport of water through the atmosphere, and condensation on one or both winter CO2 caps. Exchange with the regolith is important seasonally, but the water content of the atmosphere appears to be controlled by the polar caps. The net annual transport through the atmosphere, integrated over long timescales, must be the driving force behind the long-term evolution of the polar caps; clearly, this feeds back into the evolution of the layered terrain. We have investigated the behavior of the seasonal water cycle and the net integrated behavior at the pole for the last 10 exp 7 years. Our model of the water cycle includes the solar input, CO2 condensation and sublimation, and summertime water sublimation through the seasonal cycles, and incorporates the long-term variations in the orbital elements describing the Martian orbit.

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

1992-01-01

288

Arabidopsis peroxisomal malate dehydrogenase functions in beta-oxidation but not in the glyoxylate cycle.  

PubMed

The aim was to determine the function of peroxisomal NAD(+)-malate dehydrogenase (PMDH) in fatty acid beta-oxidation and the glyoxylate cycle in Arabidopsis. Seeds in which both PMDH genes are disrupted by T-DNA insertions germinate, but seedling establishment is dependent on exogenous sugar. Mutant seedlings mobilize their triacylglycerol very slowly and growth is insensitive to 2,4-dichlorophenoxybutyric acid. Thus mutant seedlings are severely impaired in beta-oxidation, even though microarray analysis shows that beta-oxidation genes are expressed normally. The mutant phenotype was complemented by expression of a cDNA encoding PMDH with either its native peroxisome targeting signal-2 (PTS2) targeting sequence or a heterologous PTS1 sequence. In contrast to the block in beta-oxidation in mutant seedlings, [(14)C]acetate is readily metabolized into sugars and organic acids, thereby demonstrating normal activity of the glyoxylate cycle. We conclude that PMDH serves to reoxidize NADH produced from fatty acid beta-oxidation and does not participate directly in the glyoxylate cycle. PMID:17376163

Pracharoenwattana, Itsara; Cornah, Johanna E; Smith, Steven M

2007-05-01

289

Supercritical-pressure direct-cycle light water reactor - concept and design  

Microsoft Academic Search

The concept of a direct-cycle light water reactor operating at supercritical pressure was presented in other papers. The critical pressure of water is 22.1 MPa (221 bars). The density of water changes continuously above it, and the concept of boiling does not exist. The water coolant is heated up in the core and can be directly fed to turbines. The

Yoshiaki Oka; Seiichi Koshizuka

1992-01-01

290

Annual cycle of dense water cascading in the north-eastern Barents Sea  

Microsoft Academic Search

Dense water cascading, which moves cold and\\/or salty water down the continental slope, is an efficient way of communication between the coastal and the deep ocean. In the Arctic with respect to its extensive shelf waters, annual freeze-thaw cycle and associated salination and freshening the contribution by cascading in ventilation of the deep water masses was always considered to be

V. V. Ivanov; G. I. Shapiro

2004-01-01

291

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

292

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

293

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

2014-05-28

294

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 )2 Ce(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

295

Surface treatment of hematite photoanodes with zinc acetate for water oxidation.  

PubMed

A simple and inexpensive method to form a hematite photoanode for efficient water oxidation is reported. A very thin ZnO overlayer was deposited on top of a thin film of hematite and found, compared with non-treated hematite, to increase the photocurrent and reduce the onset potential for generating oxygen from water. After 3 cycles of ZnAc treatment, the photocurrent increased more than 40% to 1.08 mA cm(-2) at 0.23 V vs. Ag/AgCl and onset potential for water oxidation shifted by -170 mV. It is proposed that the ZnO overlayer changes the flat band potential of hematite and reduces the surface defects. PMID:22688799

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

2012-08-01

296

Status report on sulfur iodine thermochemical water-splitting cycle  

Microsoft Academic Search

Major process improvements which had been identified in an earlier phase of this program were investigated and their feasibility demonstrated. The engineering process flowsheet was revised to incorporate the newest process improvements. It is now being used for an estimate of hydrogen production cost from the General Atomic Company (GAC) cycle. An energy storage cycle for a solar adaptation of

G. E. Besenbruch; L. C. Brown; M. Yoshimoto; J. H. Norman; D. R. OKeefe; M. Endo; C. L. Allen; M. L. Kelly; P. W. Trester

1981-01-01

297

Aircraft Water Vapor Measurements Utilizing an Aluminum Oxide Hygrometer  

Microsoft Academic Search

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

Ernest Hilsenrath

1974-01-01

298

Hydration behavior and dynamics of water molecules in graphite oxide  

Microsoft Academic Search

In contrast to graphite intercalation compounds, graphite oxide (GO) is hydrophilic. However, the information about the mobility of the water molecules is still sparse. We show in this report that the degree of hydration and the kinetics of water uptake depend crucially on the preparation and aging conditions. The best sample we have ever got shows layer distances of 8,

A. Lerf; A. Buchsteiner; J. Pieper; S. Schöttl; I. Dekany; T. Szabo; H. P. Boehm

2006-01-01

299

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

PubMed Central

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

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

2013-01-01

300

Properties of nanostructured oxide formed during oxidation of a zirconium wire by supercritical water  

NASA Astrophysics Data System (ADS)

Synthesis of ZrO2 during oxidation of a zirconium wire by supercritical water at P = 25 MPa and T = 500 or 525°C has been investigated. It is established that an inhomogeneous nanostructured ZrO2 layer is formed as a result of oxidation. Rate of oxidation, oxide porosity and morphology, and average size and structure of crystallites are determined. The thermal conductivity of the synthesized ZrO2 layer in supercritical water and in nitrogen is determined by pulsed electric heating of a partially oxidized wire. The low values of thermal conductivity (about 0.2 W/(m K)) correspond to a layered structure of porous material, with layers orientated parallel to the oxidized-metal surface.

Vostrikov, A. A.; Dubov, D. Yu.; Sokol, M. Ya.

2014-04-01

301

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

PubMed

Previous measurements show that calcium manganese oxide nanoparticles are better water oxidation catalysts than binary manganese oxides (Mn3O4, Mn2O3, and MnO2). The probable reasons for such enhancement involve a combination of factors: The calcium manganese oxide materials have a layered structure with considerable thermodynamic stability and a high surface area, their low surface energy suggests relatively loose binding of H2O on the internal and external surfaces, and they possess mixed-valent manganese with internal oxidation enthalpy independent of the Mn(3+)/Mn(4+) ratio and much smaller in magnitude than the Mn2O3-MnO2 couple. These factors enhance catalytic ability by providing easy access for solutes and water to active sites and facile electron transfer between manganese in different oxidation states. PMID:23667149

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

2013-05-28

302

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

PubMed

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

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

2013-12-28

303

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

304

Nanolayered manganese oxide/C60 composite: a good water-oxidizing catalyst for artificial photosynthetic systems.  

PubMed

For the first time, we considered Mn oxide/C60 composites as water-oxidizing catalysts. The composites were synthesized by easy and simple procedures, and characterized by some methods. The water-oxidizing activities of these composites were also measured in the presence of cerium(iv) ammonium nitrate. We found that the nanolayered Mn oxide/C60 composites show promising activity toward water oxidation. PMID:24984108

Najafpour, Mohammad Mahdi; Abasi, Mahnaz; Tomo, Tatsuya; Allakhverdiev, Suleyman I

2014-07-15

305

Smooth Transition from Light Water Reactors to Fast Breeder Reactors by Flexible Fuel Cycle initiative (FFCI)  

SciTech Connect

In order to reasonably manage the transition period from existing light water reactors (LWR) to future fast breeder reactors (FBR), the authors propose an innovative fuel cycle system called Flexible Fuel Cycle Initiative (FFCI) which consists of LWR and FBR spent fuels reprocessing. LWR fuel reprocessing provides about 90% uranium removal from LWR spent fuel, then the composition of remaining spent fuel (recycle material) is about 50% uranium, 15% plutonium and 35% other nuclides. Recycle material is transferred to FBR fuel reprocessing to recover plutonium and uranium followed by mixed oxide (MOX) fuel fabrication for FBR. Depending on the introduction time of FBR, recycle material (about 1/10 volume of original spent fuel) may be stored until the construction of FBR. The FFCI has some advantages compared to full reprocessing facilities for LWR and FBR spent fuels to produce FBR fresh fuels. The LWR reprocessing facility becomes much smaller due to no Pu-U recovery and fabrication. The recycle materials can be reprocessed in the FBR reprocessing facility by using its surplus capacity without disturbing the FBR spent fuel reprocessing. The recycle materials can supply higher content of plutonium to FBR and can be compactly stored in case of FBR introduction delay. The plutonium balance was calculated under several conditions, which revealed that the FFCI system could meet the plutonium demand while creating no excess plutonium. (authors)

Yamashita, J.; Fukasawa, T.; Kawamura, F.; Hoshino, K. [Hitachi Works, Hitachi, Ltd., 3-1-1 Saiwai, Hitachi, Ibaraki, 317-8511 (Japan); Sasahira, A. [Power and Industrial Systems R and D Laboratory, Hitachi, Ltd., 7-2-1 Omika, Hitachi, Ibaraki, 319-1221 (Japan)

2006-07-01

306

Cyanamide route to calcium-manganese oxide foams for water oxidation.  

PubMed

In nature, photosynthetic water oxidation is efficiently catalysed at a protein-bound ?-oxido Mn4Ca cluster. This cluster consists of earth abundant, non-toxic elements and serves as a paragon for development of synthetic catalysts. In this study we developed porous calcium-manganese oxides with a unique foam-like nanostructure prepared via a facile and robust synthetic route using cyanamide as a porogen. A series of such oxide foams annealed at different temperatures was characterized by TEM, SEM, XRD, N2 physisorption, and X-ray absorption spectroscopy (XAS) in order to correlate crystallinity, atomic structure, surface area and oxidation state of the materials with catalytic activity. Some of the resulting Ca-Mn oxides show high activity as catalysts for water oxidation in the presence of cerium(iv) ammonium nitrate as a non-oxo transfer oxidant. An amorphous calcium-manganese-oxide foam with 130 m(2) g(-1) surface area and Mn oxidation state of +3.6 was identified to be most active; its activity is superior to previously reported Ca-Mn oxides. At the atomic level, this material shares structural motifs with the biological paragon as revealed by dual-edge XAS at the Mn and Ca K-edge. Rather than nanostructure and surface area, the atomic structure of the Ca-Mn oxide and the extent of structural order appear to be crucial determinants of catalytic activity. Fully disordered low-valent Mn materials as well as high-valent but crystalline Mn-Ca oxides are unreactive. Highly disordered variants of layered manganese oxide with Ca and water molecules interfacing layer fragments are most reactive. PMID:24091767

Baktash, Elham; Zaharieva, Ivelina; Schröder, Marc; Goebel, Caren; Dau, Holger; Thomas, Arne

2013-12-28

307

DRINKING IN SNAKES: KINEMATIC CYCLING AND WATER TRANSPORT  

Microsoft Academic Search

Snakes are purported to drink by sucking water into their mouths and then compressing the oral cavity to force water into the oesophagus. Video recordings of drinking behaviour in 23 snakes representing 14 species from three families, combined with simultaneous recordings of water volumes consumed, show that all the snakes vary widely in the amount of water taken in when

DAVID CUNDALL

308

Investigating the First-Cycle Irreversibility of Lithium Metal Oxide Cathodes for Li Batteries  

SciTech Connect

Layered lithium metal oxide cathodes typically exhibit irreversibility during the first cycle in lithium cells when cycled in conventional voltage ranges (e.g., 3-4.3 V vs. Li+/Li). In this work, we have studied the first-cycle irreversibility of lithium cells containing various layered cathode materials using galvanostatic cycling and in situ synchrotron X-ray diffraction. When cycled between 3.0 and 4.3 V vs. Li+/Li, the cells containing LiCoO2, LiNi0.8Co0.15Al0.05O2, and Li1.048(Ni1/3Co1/3Mn1/3)0.952O2 as cathodes showed initial coulombic efficiencies of 98.0, 87.0, and 88.6%, respectively, at relatively slow current (8 mA/g). However, the 'lost capacity' could be completely recovered by discharging the cells to low voltages (<2 V vs Li+/Li). During this deep discharge, the same cells exhibited voltage plateaus at 1.17, 1.81, and 1.47 V, respectively, which is believed to be associated with formation of a Li2MO2-like phase (M = Ni, Co, Mn) on the oxide particle surface due to very sluggish lithium diffusion in LieMO2 with {var_epsilon}{yields} 1 (i.e., near the end of discharge). The voltage relaxation curve and in situ X-ray diffraction patterns, obtained from a Li/Li1.048(Ni1/3Co1/3Mn1/3)0.952O2 cell, showed that the oxide cathode reversibly returned to its original state [i.e., Li1.048(Ni1/3Co1/3Mn1/3)0.952O2] during relaxation following the deep discharge to achieve 100% cycle efficiency.

Kang,S.; Yoon , W.; Nam, K.; Yang, X.; Abraham, D.

2008-01-01

309

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

310

GEWEX: The Global Energy and Water Cycle Experiment  

NASA Technical Reports Server (NTRS)

GEWEX is one of the world's largest global change research programs. Its purpose is to observe and understand the hydrological cycle and energy fluxes in the atmosphere, at land surfaces and in the upper oceans.

Chahine, M.; Vane, D.

1994-01-01

311

NASA Contributions to Improve Understanding of Extreme Events in the Global Energy and Water Cycle  

NASA Technical Reports Server (NTRS)

The U.S. Climate Change Science Program (CCSP) has established the water cycle goals of the Nation's climate change program. Accomplishing these goals will require, in part, an accurate accounting of the key reservoirs and fluxes associated with the global water and energy cycle, including their spatial and temporal variability. through integration of all necessary observations and research tools, To this end, in conjunction with NASA's Earth science research strategy, the overarching long-term NASA Energy and Water Cycle Study (NEWS) grand challenge can he summarized as documenting and enabling improved, observationally based, predictions of water and energy cycle consequences of Earth system variability and change. This challenge requires documenting and predicting trends in the rate of the Earth's water and energy cycling that corresponds to climate change and changes in the frequency and intensity of naturally occurring related meteorological and hydrologic events, which may vary as climate may vary in the future. The cycling of water and energy has obvious and significant implications for the health and prosperity of our society. The importance of documenting and predicting water and energy cycle variations and extremes is necessary to accomplish this benefit to society.

Lapenta, William M.

2008-01-01

312

Analysis of alternative light water reactor (LWR) fuel cycles  

Microsoft Academic Search

Nine alternative LWR fuel cycles are analyzed in terms of the isotopic content of the fuel material, the relative amounts of primary and recycled material, the uranium and thorium requirements, the fuel cycle costs and the fraction of energy which must be generated at secured sites. The fuel materials include low-enriched uranium (LEU), plutonium-uranium (MOX), highly-enriched uranium-thorium (HEU-Th), denatured uranium-thorium

C. M. Heeb; R. L. Aaberg; A. J. Boegel; U. P. Jenquin; D. A. Kottwitz; M. A. Lewallen; E. T. Merrill; A. M. Nolan

1979-01-01

313

eWaterCycle: A high resolution global hydrological model  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

314

Sunlight-induced photochemical decay of oxidants in natural waters: implications in ballast water treatment.  

PubMed

The transport and discharge of ship ballast water has been recognized as a major vector for the introduction of invasive species. Chemical oxidants, long used in drinking water and wastewater treatment, are alternative treatment methods for the control of invasive species currently being tested for use on ships. One concern when a ballasted vessel arrives in port is the adverse effects of residual oxidant in the treated water. The most common oxidants include chlorine (HOCl/OCl-), bromine (HOBr/OBr-), ozone (03), hydrogen peroxide (H2O2), chlorine dioxide (ClO2), and monochloramine (NH2Cl). The present study was undertaken to evaluate the sunlight-mediated photochemical decomposition of these oxidants. Sunlight photodecomposition was measured at various pH using either distilled water or oligotrophic Gulf Stream water for specific oxidants. For selected oxidants, quantum yields at specific wavelengths were obtained. An environmental photochemical model, GCSOLAR, also provided predictions of the fate (sunlight photolysis half-lives) of HOCI/OCl-, HOBr/OBr-, ClO2, and NH2Cl for two different seasons at latitude 40 degrees and in water with two different concentrations of chromophoric dissolved organic matter. These data are useful in assessing the environmental fate of ballast water treatment oxidants if they were to be discharged in port. PMID:17547204

Cooper, William J; Jones, Adam C; Whitehead, Robert F; Zika, Rod G

2007-05-15

315

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

316

A biomimetic copper water oxidation catalyst with low overpotential.  

PubMed

Simply mixing a Cu(II) salt and 6,6'-dihydroxy-2,2'-bipyridine (H2L) in a basic aqueous solution afforded a highly active water oxidation catalyst (WOC). Cyclic voltammetry of the solution at pH = 12-14 shows irreversible catalytic current with an onset potential of ~0.8 V versus NHE. Catalytic oxygen evolution takes place in controlled potential electrolysis at a relatively low overpotential of 640 mV. Experimental and computational studies suggest that the L ligand participates in electron transfer processes to facilitate the oxidation of the Cu center to lead to an active WOC with low overpotential, akin to the use of the tyrosine radical by Photosystem II to oxidize the CaMn4 center for water oxidation. PMID:24325734

Zhang, Teng; Wang, Cheng; Liu, Shubin; Wang, Jin-Liang; Lin, Wenbin

2014-01-01

317

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

Microsoft Academic Search

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

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

1981-01-01

318

Water oxidation chemistry of a synthetic dinuclear ruthenium complex containing redox-active quinone ligands.  

PubMed

We investigated theoretically the catalytic mechanism of electrochemical water oxidation in aqueous solution by a dinuclear ruthenium complex containing redox-active quinone ligands, [Ru2(X)(Y)(3,6-tBu2Q)2(btpyan)](m+) [X, Y = H2O, OH, O, O2; 3,6-tBu2Q = 3,6-di-tert-butyl-1,2-benzoquinone; btpyan =1,8-bis(2,2':6',2?-terpyrid-4'-yl)anthracene] (m = 2, 3, 4) (1). The reaction involves a series of electron and proton transfers to achieve redox leveling, with intervening chemical transformations in a mesh scheme, and the entire molecular structure and motion of the catalyst 1 work together to drive the catalytic cycle for water oxidation. Two substrate water molecules can bind to 1 with simultaneous loss of one or two proton(s), which allows pH-dependent variability in the proportion of substrate-bound structures and following pathways for oxidative activation of the aqua/hydroxo ligands at low thermodynamic and kinetic costs. The resulting bis-oxo intermediates then undergo endothermic O-O radical coupling between two Ru(III)-O(•) units in an anti-coplanar conformation leading to bridged ?-peroxo or ?-superoxo intermediates. The ?-superoxo species can liberate oxygen with the necessity for the preceding binding of a water molecule, which is possible only after four-electron oxidation is completed. The magnitude of catalytic current would be limited by the inherent sluggishness of the hinge-like bending motion of the bridged ?-superoxo complex that opens up the compact, hydrophobic active site of the catalyst and thereby allows water entry under dynamic conditions. On the basis of a newly proposed mechanism, we rationalize the experimentally observed behavior of electrode kinetics with respect to potential and discuss what causes a high overpotential for water oxidation by 1. PMID:24694023

Isobe, Hiroshi; Tanaka, Koji; Shen, Jian-Ren; Yamaguchi, Kizashi

2014-04-21

319

Comparison of two thorium fuel cycles for use in an advanced water breeder reactor  

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. These conceptual reactor systems were developed by the Advanced Water Breeder Applications (AWBA) program. The purpose of this study is to describe and compare two possible types of thorium fuel cycles for use in these

D. F. McCoy; F. C. Merriman; G. J. Stankiewkz

1983-01-01

320

Research and Development of an Air-Cycle Heat-Pump Water Heater. Final Report.  

National Technical Information Service (NTIS)

A prototype reverse Brayton air cycle heat pump water heater has been designed and built for residential applications. The system consists of a compressor/expander, an air-water heat exchanger, an electric motor, a water circulation pump, a thermostat, an...

J. T. Dieckmann A. J. Erickson A. C. Harvey W. M. Toscano

1979-01-01

321

Quantitative analysis of solid oxide fuel cell anode microstructure change during redox cycles  

NASA Astrophysics Data System (ADS)

In the present study, correlation between solid oxide fuel cell anode microstructure and electrochemical performance during redox cycles was investigated. Electrolyte-support cell with nickel/yttria stabilized zirconia composite anode was prepared and tested under discharge process with redox cycles. Redox treatment was basically conducted every 20 h during discharge process. Polarization resistance decreased just after redox treatment and increased during discharge process. Enhancement of cell performance after every redox cycles and faster degradation in the following discharge process were observed. Polarization resistance gradually increased as redox cycles were repeated. Focused ion beam-scanning electron microscopy (FIB-SEM) observation was conducted for reconstructing the three dimensional microstructures of the tested samples. From the three dimensional microstructure reconstruction, it is found that the shape of nickel particle got thinner and complicated after redox cycles. Triple phase boundary (TPB) length increased after redox treatment and decreased after discharge process. This TPB change was highly associated with Ni connectivity and Ni specific surface area. These microstructure changes are consistent with the change of cell performance enhancement after redox treatment and degradation after discharge process. However, TPB length density kept on increasing as redox cycles are repeated, which is inconsistent with the gradual degradation of anode performance.

Shimura, Takaaki; Jiao, Zhenjun; Hara, Shotaro; Shikazono, Naoki

2014-12-01

322

Treatment of gasoline-contaminated waters by advanced oxidation processes  

Microsoft Academic Search

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

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

2005-01-01

323

Paralinear oxidation of CVD SiC in water vapor  

Microsoft Academic Search

Silicon carbide-based composites are currently being developed for use in the complex environments of heat engines. The oxidation kinetics of CVD SiC were monitored by thermogravimetric analysis (TGA) in a 50% HâO\\/50% Oâ gas mixture flowing at 4.4 cm\\/s for temperatures between 1,200 and 1,400 C. Paralinear weight change kinetics were observed as the water vapor oxidized the SiC and

Elizabeth J. Opila; Raiford E. Hann

1997-01-01

324

Supercritical water oxidation of phenol and 2,4-dinitrophenol  

Microsoft Academic Search

The oxidation of high concentrations of phenol and 2,4-dinitrophenol (DNP) was investigated in a pilot-scale supercritical water oxidation (SCWO) system. Treatment for approximately 40s at a pressure of 25MPa, temperatures of 666–778K and oxygen excess of 0–34%, resulted in phenol destruction from 94 to 99.98%, consistent with extrapolations of some global rate laws proposed in the literature. Destruction of total

Ivette Vera Pérez; Steven Rogak; Richard Branion

2004-01-01

325

Direct partial oxidation of methane to methanol in supercritical water  

Microsoft Academic Search

The direct partial oxidation of methane to methanol in supercritical water has been investigated in an isothermal, laminar reactor over the temperature range of 400 to 450°C at 250 bar. Methane was mainly oxidized to CO, CO2, CH3OH, and H2. The highest selectivity to methanol obtained was approximately 35% with methane conversion of 1–3% at 400–410°C. Since oxygen was the

Joo H. Lee; Neil R. Foster

1996-01-01

326

Photoreductive dissolution of colloidal iron oxides in natural waters  

Microsoft Academic Search

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

T. David Waite; Francois M. M. Morel

1984-01-01

327

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

NASA Astrophysics Data System (ADS)

Two hybrid thermochemical cycles for the production of hydrogen which involve bismuth trisulfate and/or bismuth oxysulfates were investigated. Equilibrium sulfur trioxide pressure are given graphically for three solid gas equilibria involving Bi2(SO4)3 alpha- and beta-Bi2O(SO4)2, and Bi2O2SO4. An improved method of carrying out the low temperature step for Cycle 1 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 SO2 and O2 are evolved at different temperatures, simplifying the usual SO3-SO2-O2 separation problem.

Jones, W. M.

328

Residual stress and redox cycling of segmented-in-series solid oxide fuel cells  

Microsoft Academic Search

Residual stresses in the electrolytes of segmented-in-series solid oxide fuel cells (SIS-SOFCs) and anode-supported cells (ASCs) were estimated at room temperature by X-ray diffraction. In the SIS-SOFCs, the residual stresses in the electrolyte were smaller than in the ASCs and did not change significantly after redox cycling. For both designs, numerically calculated values of the residual stresses in the electrolyte

K. Fujita; T. Somekawa; T. Hatae; Y. Matsuzaki

2011-01-01

329

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

330

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

PubMed Central

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

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

2011-01-01

331

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

332

Interdisciplinary research in global biogeochemical cycling Nitrous oxide in terrestrial ecosystems  

NASA Technical Reports Server (NTRS)

NASA has begun an interdisciplinary research program to investigate various aspects of Global Biology and Global Habitability. An important element selected for the study of global phenomena is related to biogeochemical cycling. The studies involve a collaboration with recognized scientists in the areas of plant physiology, microbiology, nutrient cycling theory, and related areas. Selected subjects of study include nitrogen cycling dynamics in terrestrial ecosystems with special attention to biosphere/atmosphere interactions, and an identification of sensitive response variables which can be used in ecosystem models based on parameters derived from remotely sensed variables. A description is provided of the progress and findings over the past two years. Attention is given to the characteristics of nitrous oxide emissions, the approach followed in the investigations, the selection of study sites, radiometric measurements, and research in Sequoia.

Norman, S. D.; Peterson, D. L.

1984-01-01

333

Oxidation and Volatilization of Silica-Formers in Water Vapor  

NASA Technical Reports Server (NTRS)

At high temperatures SiC and Si3N4 react with water vapor to form a silica scale. Silica scales also react with water vapor to form a volatile Si(OH)4 species. These simultaneous reactions, one forming silica and the other removing silica, are described by paralinear kinetics. A steady state, in which these reactions occur at the same rate, is eventually achieved, After steady state is achieved, the oxide found on the surface is a constant thickness and recession of the underlying material occurs at a linear rate. The steady state oxide thickness, the time to achieve steady state, and the steady state recession rate can all be described in terms of the rate constants for the oxidation and volatilization reactions. In addition, the oxide thickness, the time to achieve steady state, and the recession rate can also be determined from parameters that describe a water vapor-containing environment. Accordingly, maps have been developed to show these steady state conditions as a function of reaction rate constants, pressure, and gas velocity. These maps can be used to predict the behavior of silica formers in water-vapor containing environments such as combustion environments. Finally, these maps are used to explore the limits of the paralinear oxidation model for SiC and Si3N4

Opila, E. J.; Gray, Hugh R. (Technical Monitor)

2002-01-01

334

Climate Change and Expected Impacts on the Global Water Cycle  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

335

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

NASA Astrophysics Data System (ADS)

In this study, the water cycles of nine water-soluble organic salts of atmospheric interest were studied using an electrodynamic balance (EDB) at 25°C. Sodium formate, sodium acetate, sodium succinate, sodium pyruvate and sodium methanesulfonate (Na-MSA) particles crystallize as the relative humidity (RH) decreases and they deliquesce as the RH increases. Sodium oxalate and ammonium oxalate form supersaturated particles at low RH before crystallization but they do not deliquesce even at RH=90%. Sodium malonate and sodium maleate particles neither crystallize nor deliquesce. These two salts absorb and evaporate water reversibly without hysteresis. In most cases, the solid states of single particles resulting from the crystallization of supersaturated droplets do not form the most thermodynamically stable state found in bulk studies. Sodium formate, sodium oxalate, ammonium oxalate, sodium succinate, sodium pyruvate and Na-MSA form anhydrous particles after crystallization. Sodium acetate forms particles with a water/salt molar ratio of 0.5 after crystallization. In salts with several hydrated states including sodium formate and sodium acetate, the particles deliquesce at the lowest deliquescence relative humidity (DRH) of the hydrates. Except sodium oxalate and ammonium oxalate, all the salts studied here are as hygroscopic as typical inorganic hygroscopic aerosols. The hygroscopic organic salts have a growth factor of 1.76-2.18 from RH=10-90%, comparable to that of typical hygroscopic inorganic salts such as NaCl and (NH 4) 2SO 4. Further study of other atmospheric water-soluble organic compounds and their mixtures with inorganic salts is needed to explain the field observations of the hygroscopic growth of ambient aerosols.

Peng, Changgeng; Chan, Chak K.

336

Aircraft water vapor measurements utilizing an aluminum oxide hygrometer  

NASA Technical Reports Server (NTRS)

A hygrometer for water vapor measurements from an aircraft was developed. An aluminum oxide hygrometer mounted in an aircraft Rosemount air temperature scoop was flown on the NASA Convair 990 and on a USAF B-57 aircraft. Water vapor measurements from the Convair 990 were conducted up to 40,000 ft with penetration into the stratosphere. Good agreement was obtained with simultaneously flown remote sounders of water vapor. During transcontinental flights the hygrometer demonstrated adequate response to measure the natural variability of water vapor near the tropopause. Rapid response was demonstrated in pursuit of the jet wake of an F-104 at 35,000 ft.

Hilsenrath, E.

1974-01-01

337

Aircraft water vapor measurements utilizing an aluminum oxide hygrometer  

NASA Technical Reports Server (NTRS)

A hygrometer for water vapor measurements from an aircraft has been developed. An aluminum oxide hygrometer mounted in an aircraft Rosemount air temperature scoop was flown on NASA and USAF aircraft. Water vapor measurements were conducted up to 40,000 feet with penetration into the stratosphere. Good agreement was obtained with simultaneously flown remote sounders of water vapor. During transcontinental flights the hygrometer demonstrated adequate response to measure the natural variability of water vapor near the tropopause. Rapid response was demonstrated in pursuit of the jet wake of an F-104 at 35,000 feet.

Hilsenrath, E.

1973-01-01

338

Relative worth of /sup 233/U and /sup 235/U in light water reactor fuel cycles  

SciTech Connect

The equivalence between /sup 235/U and /sup 233/U for use in light water reactors has been determined by comparing the performance of the two isotopes over the complete length of the fuel cycle. The method developed in this work has been applied to a uranium cycle as well as to a denatured thorium cycle. A basic price based on the initial substitution method has also been estimated for /sup 233/U.

Parvez, A.; Becker, M.

1983-10-01

339

High-temperature thermochemical water splitting cycle fusion reactor design considerations  

Microsoft Academic Search

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

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

1980-01-01

340

Development of a sulfur-iodine thermochemical water-splitting cycle for hydrogen production  

Microsoft Academic Search

A three-step thermochemical water-splitting cycle is being developed for the producing hydrogen from nonfossil energy sources. This cycle, which employs sulfur and iodine, can be conducted as an all liquid-and-gas process using concentrated solar heat or heat from a high-temperature gas-cooled reactor (HTGR). All chemical reactions have been shown to proceed rapidly and cleanly. In coupling the cycle to an

J. R. Schuster; J. L. Rusell Jr.; K. H. McCorkle; K. J. Mysels; J. H. Norman; D. R. Okeefe; R. Sharp; S. A. Stowell; P. W. Trester; D. G. Williamson

1977-01-01

341

Surfactant manganese complexes as models for the oxidation of water  

SciTech Connect

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

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

1984-02-01

342

The structure of graphene oxide membranes in liquid water, ethanol and water-ethanol mixtures.  

PubMed

The structure of graphene oxide (GO) membranes was studied in situ in liquid solvents using synchrotron radiation X-ray diffraction in a broad temperature interval. GO membranes are hydrated by water similarly to precursor graphite oxide powders but intercalation of alcohols is strongly hindered, which explains why the GO membranes are permeated by water and not by ethanol. Insertion of ethanol into the membrane structure is limited to only one monolayer in the whole studied temperature range, in contrast to precursor graphite oxide powders, which are intercalated with up to two ethanol monolayers (Brodie) and four ethanol monolayers (Hummers). As a result, GO membranes demonstrate the absence of "negative thermal expansion" and phase transitions connected to insertion/de-insertion of alcohols upon temperature variations reported earlier for graphite oxide powders. Therefore, GO membranes are a distinct type of material with unique solvation properties compared to parent graphite oxides even if they are composed of the same graphene oxide flakes. PMID:24189605

Talyzin, Alexandr V; Hausmaninger, Tomas; You, Shujie; Szabó, Tamás

2014-01-01

343

Concept of an innovative water management system with decentralized water reclamation and cascading material-cycle for agricultural areas.  

PubMed

Unlike in urban areas where intensive water reclamation systems are available, development of decentralized technologies and systems is required for water use to be sustainable in agricultural areas. To overcome various water quality issues in those areas, a research project entitled 'Development of an innovative water management system with decentralized water reclamation and cascading material-cycle for agricultural areas under the consideration of climate change' was launched in 2009. This paper introduces the concept of this research and provides detailed information on each of its research areas: (1) development of a diffuse agricultural pollution control technology using catch crops; (2) development of a decentralized differentiable treatment system for livestock and human excreta; and (3) development of a cascading material-cycle system for water pollution control and value-added production. The author also emphasizes that the innovative water management system for agricultural areas should incorporate a strategy for the voluntary collection of bio-resources. PMID:22828292

Fujiwara, T

2012-01-01

344

Smooth Transition from Light Water Reactors to Fast Breeder Reactors by Flexible Fuel Cycle initiative (FFCI)  

Microsoft Academic Search

In order to reasonably manage the transition period from existing light water reactors (LWR) to future fast breeder reactors (FBR), the authors propose an innovative fuel cycle system called Flexible Fuel Cycle Initiative (FFCI) which consists of LWR and FBR spent fuels reprocessing. LWR fuel reprocessing provides about 90% uranium removal from LWR spent fuel, then the composition of remaining

J. Yamashita; T. Fukasawa; F. Kawamura; K. Hoshino; A. Sasahira

2006-01-01

345

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

Microsoft Academic Search

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

Nirmal Jayaram; K. Srinivasan

2008-01-01

346

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

347

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

Microsoft Academic Search

The nitrogen cycle is comprised predominantly of biologically mediated pathways, leading to a series of negative feedbacks that stabilize the cycle. Sedimentary denitrification, the major sink in the nitrogen budget, is regulated by the rate of organic carbon rain to the sea floor, as well as oxygen concentrations in overlying bottom waters. The sensitivity of sedimentary denitrification as a negative

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

2008-01-01

348

Highly active oxide photocathode for photoelectrochemical water reduction.  

PubMed

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 H(2) 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%. PMID:21552270

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

2011-06-01

349

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

350

Improved Wrede Stand-Alone ORC (Organic Rankine-Cycle) Solar Water Pump with Tracking Concentrators.  

National Technical Information Service (NTIS)

This paper describes the Wrede organic Rankine-cycle solar water pump employing tracking parabolic troughs. System principles and improvements introduced with the fifth-generation pump-unit and the concentrators are briefly discussed. Previous field tests...

P. D. Lund T. C. W. Wrede

1984-01-01

351

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

352

Apoptotic response and cell cycle transition in ataxia telangiectasia cells exposed to oxidative stress.  

PubMed

The recently identified ATM gene plays a role in a signal transduction network activating multiple cellular functions in response to DNA damage. An attractive hypothesis is that the ATM protein is involved in a specialized antioxidant system responsible for detoxifying reactive oxygen intermediate and that the absence or dysfunction of this protein in AT cells would render them less capable of dealing with oxidative stress. In order to investigate the role of the ATM gene in cell cycle control and programmed cell death, Lymphoblastoid cell lines derived from four Ataxia-Telangiectasia (AT) patients and six controls have been analyzed. All cell lines were incubated with 2-deoxy-D-ribose (dRib), a reducing sugar that induces apoptosis through oxidative stress. The result showed an impaired response to dRib-induced apoptosis in AT cells, as well as a defect of cellular cycle arrest in G1/S phase and a normal expression of p53 protein. This indicate that the kinase activity of ATM gene product plays a very important role in the cellular response to oxidative stress. In conclusion the altered response of AT cells to oxidative stress and particularly their resistance to apoptotic cell death, could explain the high predisposition of these cells to progress toward malignant transformation. PMID:10821114

Formichi, P; Battisti, C; Tripodi, S A; Tosi P; Federico, A

2000-04-01

353

Water oxidation by manganese oxides, a new step towards a complete picture: simplicity is the ultimate sophistication.  

PubMed

We, for the first time, report that many Mn oxides (Mn3O4, ?-Mn2O3, ?-MnO2, CaMnO3, Ca2Mn3O8, CaMn3O6 and CaMn4O8) in the presence of cerium(IV) ammonium nitrate, in the water oxidation, convert to layered Mn oxide. This layered Mn oxide is an efficient water oxidizing catalyst. PMID:23838901

Najafpour, Mohammad Mahdi; Sedigh, Davood Jafarian

2013-09-14

354

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

355

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

Microsoft Academic Search

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

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

1995-01-01

356

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

Microsoft Academic Search

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

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

1981-01-01

357

Thermodynamic performance assessment of an ammonia–water Rankine cycle for power and heat production  

Microsoft Academic Search

In this paper, an ammonia–water based Rankine cycle is thermodynamically analyzed for renewable-based power production, e.g. solar, geothermal, biomass, oceanic-thermal, and nuclear as well as industrial waste heat. Due to the nature of the ammonia–water mixture, changes in its concentration allow thermodynamic cycles to adapt to fluctuations in renewable energy sources, which is an important advantage with respect to other

W. R. Wagar; C. Zamfirescu; I. Dincer

2010-01-01

358

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.

359

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

360

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

361

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

362

Removal of Nitrosamines from Waste Water by Potassium Ferrate Oxidation  

Microsoft Academic Search

Potassium ferrate (K2FeO4) is useful in the advanced treatment of waste water. Additional evidence of this capability is presented in this study. Potassium ferrate is a very strong oxidant and is highly soluble in water. The nitrosamine studied in this work was toxic and was a potent pancreatic tumorigen in laboratory animals. Nitrosamines, which are potent carcinogens, are widespread throughout

Ronald Bartzatt; Donald Nagel

1991-01-01

363

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

PubMed Central

The impact of climate variability on the water cycle in desert ecosystems is controlled by biospheric feedback at interannual to millennial timescales. This paper describes a unique field dataset from weighing lysimeters beneath nonvegetated and vegetated systems that unequivocally demonstrates the role of vegetation dynamics in controlling water cycle response to interannual climate variability related to El Niño southern oscillation in the Mojave Desert. Extreme El Niño winter precipitation (2.3-2.5 times normal) typical of the U.S. Southwest would be expected to increase groundwater recharge, which is critical for water resources in semiarid and arid regions. However, lysimeter data indicate that rapid increases in vegetation productivity in response to elevated winter precipitation reduced soil water storage to half of that in a nonvegetated lysimeter, thereby precluding deep drainage below the root zone that would otherwise result in groundwater recharge. Vegetation dynamics have been controlling the water cycle in interdrainage desert areas throughout the U.S. Southwest, maintaining dry soil conditions and upward soil water flow since the last glacial period (10,000-15,000 yr ago), as shown by soil water chloride accumulations. Although measurements are specific to the U.S. Southwest, correlations between satellite-based vegetation productivity and elevated precipitation related to El Niño southern oscillation indicate this model may be applicable to desert basins globally. Understanding the two-way coupling between vegetation dynamics and the water cycle is critical for predicting how climate variability influences hydrology and water resources in water-limited landscapes.

Scanlon, B. R.; Levitt, D. G.; Reedy, R. C.; Keese, K. E.; Sully, M. J.

2005-01-01

364

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

365

Nitrogen cycling in the offshore waters of the Black Sea  

Microsoft Academic Search

The purpose of this study was to measure directly the rates of several of the processes responsible for the production and utilization of nitrogenous nutrients, and to use these rates and other data to generate an annual nitrogen budget for the Black Sea. Water column samples and experimentation with 15N labeled nutrients in the offshore waters of the Black Sea

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

2007-01-01

366

The Global Enery and Water Cycle Experiment Science Strategy  

NASA Technical Reports Server (NTRS)

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

Chahine, M. T.

1997-01-01

367

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

Microsoft Academic Search

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

Joanna Vaile; Shona Halson; Nicholas Gill; Brian Dawson

2008-01-01

368

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

369

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

370

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

371

Teaching the Krebs Cycle.  

ERIC Educational Resources Information Center

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

Akeroyd, F. Michael

1983-01-01

372

Oxidation of Carbon Fibers in Water Vapor Studied  

NASA Technical Reports Server (NTRS)

T-300 carbon fibers (BP Amoco Chemicals, Greenville, SC) are a common reinforcement for silicon carbide composite materials, and carbon-fiber-reinforced silicon carbide composites (C/SiC) are proposed for use in space propulsion applications. It has been shown that the time to failure for C/SiC in stressed oxidation tests is directly correlated with the fiber oxidation rate (ref. 1). To date, most of the testing of these fibers and composites has been conducted in oxygen or air environments; however, many components for space propulsion, such as turbopumps, combustors, and thrusters, are expected to operate in hydrogen and water vapor (H2/H2O) environments with very low oxygen contents. The oxidation rate of carbon fibers in conditions representative of space propulsion environments is, therefore, critical for predicting component lifetimes for real applications. This report describes experimental results that demonstrate that, under some conditions, lower oxidation rates of carbon fibers are observed in water vapor and H2/H2O environments than are found in oxygen or air. At the NASA Glenn Research Center, the weight loss of the fibers was studied as a function of water pressure, temperature, and gas velocity. The rate of carbon fiber oxidation was determined, and the reaction mechanism was identified.

Opila, Elizabeth J.

2003-01-01

373

Efficient and sustained photoelectrochemical water oxidation by cobalt oxide/silicon photoanodes with nanotextured interfaces.  

PubMed

Plasma-enhanced atomic layer deposition of cobalt oxide onto nanotextured p(+)n-Si devices enables efficient photoelectrochemical water oxidation and effective protection of Si from corrosion at high pH (pH 13.6). A photocurrent density of 17 mA/cm(2) at 1.23 V vs RHE, saturation current density of 30 mA/cm(2), and photovoltage greater than 600 mV were achieved under simulated solar illumination. Sustained photoelectrochemical water oxidation was observed with no detectable degradation after 24 h. Enhanced performance of the nanotextured structure, compared to planar Si, is attributed to a reduced silicon oxide thickness that provides more intimate interfacial contact between the light absorber and catalyst. This work highlights a general approach to improve the performance and stability of Si photoelectrodes by engineering the catalyst/semiconductor interface. PMID:24720554

Yang, Jinhui; Walczak, Karl; Anzenberg, Eitan; Toma, Francesca M; Yuan, Guangbi; Beeman, Jeffrey; Schwartzberg, Adam; Lin, Yongjing; Hettick, Mark; Javey, Ali; Ager, Joel W; Yano, Junko; Frei, Heinz; Sharp, Ian D

2014-04-30

374

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/cm(2)) 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; Koura, Zakaria El; Bazzanella, Nicola; Meda, Laura; Miotello, Antonio

2014-05-14

375

Cycles  

NSDL National Science Digital Library

Just about anywhere you look in the natural sciences you'll find a cycle of some description. From cells to individuals to populations and beyond, cyclical patterns exist on every scale. The following collection of Web sites follows on this theme: The first site (1) is an excellent, animated introduction to the cell cycle from Cells Alive! Users can also get a closer look at the stages of mitosis by following the links provided. The next site from the Center for Biological Timing contains a tutorial on chronobiology, the study of biological rhythms (2). Visitors will find a thorough overview of the human clock and related concepts, with emphasis on our 24-hour sleep-wake cycle. Speaking of internal cycles, the next site contains an interesting article from BBC News, relating how a woman's choice of men may vary in accordance with her menstrual cycle (3). The next site moves from internal to externally-evident cycles, namely the life cycle of the monarch butterfly. Monarch Watch provides a detailed description of the butterfly life cycle, from egg to larva to pupa to adult (4). Perhaps not quite as appealing as the monarch butterfly, but nevertheless intriguing, Schistosoma flatworms have a complicated life cycle involving humans and a particular group of snails. The University of California-Los Angeles Institute of the Environment offers an illustrated explanation of this highly specialized life cycle (5). The following site from Science New Online describes how global climate change is accelerating the annual life cycles of plants and animals around the world (6). On the level of population, the Natural History Museum of Los Angeles County offers the familiar example of the Canada lynx and the hare -- the same example used by countless textbooks to demonstrate the cyclical nature of predator-prey dynamics (7). And finally, Georgia State University provides a nicely simplified introduction to the energy cycle in living things, focusing on the transfer of energy from the sun to plants to animals (8).

Sohmer, Rachel.

376

Global Energy and Water Cycle Experiment (GEWEX) and the Continental-scale International Project (GCIP)  

NASA Technical Reports Server (NTRS)

A discussion of the objectives of the Global Energy and Water Cycle Experiment (GEWEX) and the Continental-scale International Project (GCIP) is presented in vugraph form. The objectives of GEWEX are as follows: determine the hydrological cycle by global measurements; model the global hydrological cycle; improve observations and data assimilation; and predict response to environmental change. The objectives of GCIP are as follows: determine the time/space variability of the hydrological cycle over a continental-scale region; develop macro-scale hydrologic models that are coupled to atmospheric models; develop information retrieval schemes; and support regional climate change impact assessment.

Vane, Deborah

1993-01-01

377

SUPERCRITICAL WATER OXIDATION MODEL DEVELOPMENT FOR SELECTED EPA PRIORITY POLLUTANTS  

EPA Science Inventory

Supercritical Water Oxidation (SCWO) evaluated for five compounds: acetic acid, 2,4-dichlorophenol, pentachlorophenol, pyridine, 2,4-dichlorophenoxyacetic acid (methyl ester). inetic models were developed for acetic acid, 2,4-dichlorophenol, and pyridine. he test compounds were e...

378

Design requirements for the supercritical water oxidation test bed.  

National Technical Information Service (NTIS)

This report describes the design requirements for the supercritical water oxidation (SCWO) test bed that will be located at the Idaho National Engineering Laboratory (INEL). The test bed will process a maximum of 50 gph of waste plus the required volume o...

J. M. Svoboda D. J. Valentich

1994-01-01

379

Kinetics and mechanism of methane oxidation in supercritical water. [HAZWRAP  

Microsoft Academic Search

This project, is a Hazardous Waste Remedial Actions Program (HAZWRAP) Research and Development task being carried out by the Los Alamos National Laboratory. Its objective is to achieve an understanding of the technology for use in scaling up and applying oxidation in supercritical water as a viable process for treating a variety of Department of Energy Defense Programs (DOE-DP) waste

C. K. Rofer; G. E. Streit

1988-01-01

380

High temperature water electrolysis in solid oxide cells  

Microsoft Academic Search

Hydrogen production via high temperature steam electrolysis is a promising technology as it involves less electrical energy consumption compared to conventional low temperature water electrolysis, as consequence of the more favourable thermodynamic and electrochemical kinetic conditions for the reaction. This paper reports on the Solid Oxide Electrolyser Cell (SOEC) performance as function of the operating parameters temperature, humidity and current

Annabelle Brisse; Josef Schefold; Mohsine Zahid

2008-01-01

381

Electrophotolysis oxidation system for measurement of organic concentration in water  

NASA Technical Reports Server (NTRS)

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

Winkler, H. E. (inventor)

1981-01-01

382

Kinetics and mechanism of methane oxidation in supercritical water  

Microsoft Academic Search

We oxidized methane in supercritical water at 250 atm and at temperatures between 525 and 587 °C. The methane conversions ranged from 3 to 70%. CO was the product present in the highest yields at low conversions (< 10%), but CO2 became the most abundant product at higher conversions. These experimental results were used to test the predictions of a

Phillip E. Savage; Jianli Yu; Nicole Stylski; Eric E. Brock

1998-01-01

383

Oxidation kinetics for methane\\/methanol mixtures in supercritical water  

Microsoft Academic Search

A detailed chemical kinetics model that had been previously validated for the oxidation of methane and methanol, individually, in supercritical water predicted that the presence of methanol in the reactor feed stream would accelerate the rate of methane disappearance. For example, the methane conversions at 540°C, 273 atm., and 1.0 s were predicted to be 5, 15, 37, and 53%

Phillip E. Savage; Johanna Rovira; Nicole Stylski; Christopher J. Martino

2000-01-01

384

Conversion of Tire Waste Using Subcritical and Supercritical Water Oxidation  

Microsoft Academic Search

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

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

1999-01-01

385

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

386

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

Microsoft Academic Search

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

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

2007-01-01

387

Ni based mixed oxide materials for CH 4 oxidation under redox cycle conditions  

Microsoft Academic Search

The preparation, characterization and redox properties of Ni–Al–O and Ni–Mg–Al–O mixed oxides for CH4 chemical looping combustion (CLC) is addressed in this study. Ni–Al–O samples having different Ni\\/Al ratios (0.5–2.25), prepared by coprecipitation, consist after calcination at 1000°C of cubic NiO and NiAl2O4 spinel. A similar phase composition is obtained for Ni–Mg–Al–O, with Mg partitioned in the two phases. The

Raffaella Villa; Cinzia Cristiani; Gianpiero Groppi; Luca Lietti; Pio Forzatti; Ugo Cornaro; Stefano Rossini

2003-01-01

388

Destruction of energetic materials by supercritical water oxidation  

SciTech Connect

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

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

1993-10-01

389

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

390

Advanced treatment of sodium acetate in water by ozone oxidation.  

PubMed

Ozone oxidation is an advanced oxidation process for treatment of organic and inorganic wastewater. In this paper, sodium acetate (according to chemical oxygen demand [COD]) was selected as the model pollutant in water, and the degradation efficiencies and mechanism of sodium acetate in water by ozone oxidation were investigated. The results showed that the ozone oxidation was an effective treatment technology for advanced treatment of sodium acetate in water; the COD removal rate obtained the maximum value of 45.89% from sodium acetate solution when the pH value was 10.82, ozone concentration was 100 mg/L, reaction time was 30 minutes, and reaction temperature was 25 degrees C. The COD removal rate increased first and decreased subsequently with the bicarbonate (HCO3-) concentration from 0 to 200 mg/L, the largest decline being 20.35%. The COD removal rate declined by 25.38% with the carbonate (CO3(2-)) concentration from 0 to 200 mg/L; CO3(2-) has a more obvious scavenging effect to inhibit the formation of hydroxyl free radicals than HCO3-. Calcium chloride (CaCl2) and calcium hydroxide (Ca(OH)2) could enhance the COD removal rate greatly; they could reach 77.35 and 96.53%, respectively, after a reaction time of 30 minutes, which was increased by 31.46 and 50.64%, respectively, compared with only ozone oxidation. It was proved that the main ozone oxidation product of sodium acetate was carbon dioxide (CO2), and the degradation of sodium acetate in the ozone oxidation process followed the mechanism of hydroxyl free radicals. PMID:24645544

Yang, De-Min; Yuan, Jian-Mei

2014-02-01

391

Water and dust daily cycles: IRIS Mariner 9 data revisited  

NASA Astrophysics Data System (ADS)

IRIS Mariner 9 data have been studied, as function of season and local time, searching for a relation between water cont ent of the atmosphere and dust. After averaging data for different local time bins, the vertical temperature profile and atmospheric dust content were retrieved. The temperature profile was then used for evaluation of water mixing ratio. This last procedure was without ambiguity only when no thermal inversion was found in the vertical profile. This fact limits our basic results only on the dayside. Our results indicate that the ground temperature and the atmospheric temperature (in the low altitudes mainly) show a strong modulation during the day, with a peak temperature around 12-14 local time. Together with the temperature the atmospheric water content show a strong modulation: the peak of the water content, around 140 ppm, is observed with the peak of the temperature. The integrated atmospheric dust opacity computed at 1000 cm- 1 shows an anti-correlated behaviour: peaks are observed at early morning and late evening, while a local minimum is observed around noon. Our observations, with the integrated dust opacity decreasing around noon, are consistent with a model in which a large part of atmospheric water vapour is adsorbed by dust and soil , and is released as water vapour during the hot hours. In the afternoon, water is adsorbed quickly again as new dust is added by dust devils. The vertical temperature profile does not allow, during the entire day, ice condensation around dust. The water lines and the continuum around 200 - 400 cm-1 give spectral evidence of frost on soil only very early in the morning or very late in the evening . The 200 -400 cm-1 region is a very good indicator of the presence of frost .

Formisano, V.; Grassi, D.; Ignatiev, N.; Zasova, L.

392

Atmospheric Water-Cycle Regimes and Cloud Regimes  

NASA Astrophysics Data System (ADS)

The relationship between the atmospheric water vapor budget and cloud properties is investigated by collocated reanalysis fields from Modern Era Retrospective-analysis for Research and Applications (MERRA) and the observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite instrument. Intensities of surface water exchange (precipitation minus evaporation) are analyzed in the space of 'dynamical regimes', which are defined by combination of large-scale water vapor advection and convergence calculated from the MERRA. The atmospheric water vapor sinks associated with mid-latitude storm systems and precipitation in the west coast of United States are mainly driven by the large-scale dynamical advection, while those associated with tropical deep convection and summertime monsoons are mainly driven by water vapor convergence. Subtropical subsidence area over the eastern ocean basins is dominated by strong water vapor divergence. These dynamical regimes are then connected to the collocated MODIS cloud top pressure and cloud optical thickness. Probability density distributions of these MODIS cloud properties associated with each dynamical regime will be presented.

Wong, S.; Fetzer, E. J.; L'Ecuyer, T. S.

2013-12-01

393

Paleoecology of cool-water, subtidal cycles in mid-cenozoic limestones, Eucla Platform, Southern Australia  

SciTech Connect

The open-shelf, subtidal, bryozoan-rich Abrakurrie Limestone beneath the Nullarbor Plain (Eucla Platform) is cyclic at the meter-scale. Best developed cycles are asymmetric and comprise three distinct parts with a capping hardground. The basal part (A) is a thin, coarse, grainstone or rudstone that is rich in robust bryosoan and epifaunal echinoid fragments and pecten bivalves, reflecting growth and accumulation in generally high energy, hard bottom environments. The middle part (B), intepreted as a low-energy, sub-swellbase accumulation, is a burrowed to planar cross-laminated fine grainstone or packstone with a low diversity, delicate-branching bryozoan assemblage and little else except scattered infaunal echinoids and pectens. The upper part (C) is a burrowed, abundantly fossilferous (bryozoan, bivalve, echinoid) rudstone or floatstone. Upward increases in the numbers and diversity of Mg-calcite and aragonitic cheilostome bryozoans (especially erect rigid, flat robust branching and nodular/arborescent types), gastropods, infaunal bivalves, and infaunal echinoids points to a high-energy environment. Sediments at the top of C are variably cemented by inclusion-rich marine cement (now calcite) that formed a hardground which was subsequently physically and biologically eroded and stained by iron oxides during a period of non-deposition. Sediments from the next overlying cycle succeed cements in uppermost intergranular pores and fill open crustacean burrows. Variably developed cyclicity is interpreted, on the basis of comparable Holocene cool-water shelf sediments, to reflect deposition in generally sub-photic environments that ranged from just below swell base (B) upwards towards the zone of wave abrasion (A and C). Hardgrounds (H) formed when the seafloor was within the zone of wave abrasion. Shallowing and deepening of these critical interfaces was controlled by fluctuating sea level and/or climatic change. 55 refs., 12 figs.

James, N.P. [Queen`s Univ., Kingston, Ontario (Canada); Bone, Y. [Univ. of Adelaide (Australia)

1994-10-01

394

The Radiosensitivity of Satellite Cells: Cell Cycle Regulation, Apoptosis and Oxidative Stress  

PubMed Central

Skeletal muscles are the organ of movement, and their growth, regeneration and maintenance are dependent in large part on a population of myogenic stem cells known as satellite cells. Skeletal muscles and these resident myogenic stem cells (i.e., satellite cells) are commonly exposed to significant doses of radiation during diagnostic procedures and/or during the radiotherapeutic management of cancer. The main objective of this study was to examine the effects of clinically relevant doses of ? radiation on satellite cell survival and proliferation, cell cycle regulation, apoptosis, DNA double-strand break repair, oxidative stress and NO production. Overall, our findings demonstrate that doses of ? radiation ?5 Gy reduced satellite cell numbers by at least 70% due in part to elevated apoptosis and the inhibition of cell cycle progression. Radiation was also found to cause a significant and persistent increase in the level of reactive oxygen and nitrogen species. Interestingly, and within this backdrop of elevated oxidative stress, similar doses were found to produce substantial reductions in the levels of nitric oxide (NO). Proliferation of satellite cells has been shown to depend in part on the production of NO, and our findings give rise to the possibility that radiation-induced reductions in NO levels may provide a mechanism for the inhibition of satellite cell proliferation in vitro and possibly the regrowth of skeletal muscle exposed during clinical irradiation procedures.

Caiozzo, Vincent J.; Giedzinski, Erich; Baker, Mike; Suarez, Tatiana; Izadi, Atefeh; Lan, Mary; Cho-Lim, Jennie; Tseng, Bertrand P.; Limoli, Charles L.

2014-01-01

395

High temperature oxidation of molybdenum in water vapor environments  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

396

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

SciTech Connect

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

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

2008-04-01

397

Advances in Global Water Cycle Science Made Possible by Global Precipitation Mission (GPM)  

NASA Technical Reports Server (NTRS)

Within this decade the internationally sponsored Global Precipitation Mission (GPM) 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 from very high caliber combined dual frequency radar/passive microwave (PMW) rain-radiometer retrievals, to high caliber PMW rain-radiometer only retrievals, and on to blends of the former datastreams with other less-high caliber PMW-based and IR-based rain retrievals. Within the context of NASA's role in global water cycle science and its own Global Water & Energy Cycle (GWEC) program, GPM is the centerpiece mission for improving our understanding of the global water cycle from a space-based 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 global temperature. 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 Global Precipitation Mission and how its datasets can be used in a set of quantitative tests within the framework of the oceanic and continental water budget equations to determine comprehensively whether substantive rate changes do accompany perturbations in global temperatures and how such rate changes manifest themselves in both water storage and water flux transport processes.

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

2001-01-01

398

Survey of Bunsen reaction routes to improve the sulfur–iodine thermochemical water-splitting cycle  

Microsoft Academic Search

A large excess of water and iodine is typically employed in the Bunsen reaction step of the sulfur–iodine thermochemical cycle in order to induce liquid–liquid phase separation of the two acid products. This paper presents an overview of some alternative routes for carrying out the Bunsen reaction. The use of a reaction solvent other than water is first discussed, and

Alberto Giaconia; Giampaolo Caputo; Salvatore Sau; Pier Paolo Prosini; Alfonso Pozio; Massimo De Francesco; Pietro Tarquini; Luigi Nardi

2009-01-01

399

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

Microsoft Academic Search

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

Khaled Shahata; Tarek Zayed

2011-01-01

400

Multiple Staging of the Cold Water in the Open Cycle OTEC Systems.  

National Technical Information Service (NTIS)

Using the cooling water of the open cycle OTEC systems in a multiple stage fashion results in its most effective utilization. Such use increases by 2-1/3 times the power production capability per unit mass of cold water, thus reducing the cost of the most...

A. E. Molini C. Zener T. Fort

1979-01-01

401

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

Microsoft Academic Search

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

Yoshiaki OKA; Seiichi KOSHIZUKA

2001-01-01

402

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

403

Passive regulation of soil biogeochemical cycling by root water transport  

NASA Astrophysics Data System (ADS)

Surface and subsurface moisture dynamics are strongly influenced by the ability of vegetation to take up and redistribute soil moisture using hydraulic redistribution (HR). These dynamics in turn affect soil biogeochemical cycling through controls on decomposition and mineralization rates and ion transport. The goal of this study is to explore this coupling between HR and biogeochemistry using a numerical model. We examine decomposition and mineralization of organic matter and analyze whether differences in decomposition rates induced by HR influence the long-term storage of carbon in the soil and the movement of nitrate (NO 3-) and ammonium (NH 4+) in the rhizosphere. These dynamics are studied in a framework that incorporates the interaction between multiple plant species. The net effect of HR on decomposition is controlled by a trade-off between the resultant moisture and temperature states. This trade-off is conditioned by the availability of fine roots near the surface, and it impacts the long-term storage and vertical distribution of carbon in the soil. HR also impacts the transport and uptake of ions from the soil. It reduces the leaching of nitrate considerably, and, therefore facilitates the uptake of nitrate by vegetation roots. Furthermore, the magnitude and patterns of the feedbacks induced by HR are also influenced by the presence of different plant species that coexist. These results suggest that the alteration of soil moisture by plants through associated processes such as HR can have considerable impact on the below-ground biogeochemical cycling of carbon and nitrogen.

Quijano, Juan C.; Kumar, Praveen; Drewry, Darren T.

2013-06-01

404

Photocatalytic oxygen evolution from non-potable water by a bioinspired molecular water oxidation catalyst  

Microsoft Academic Search

We report that a model complex of the Photosystem II-Water Oxidizing Complex (PSII-WOC) facilitates, exclusively, photocatalytic water oxidation from non-potable water sources like seawater, under suitable conditions. When the manganese cubane cluster [Mn4O4L6]+, (L=(p-MeO-Ph)2PO2), 1+, is incorporated within a Nafion membrane deposited on an electrolytic anode that is poised at 1.00V (vs. Ag\\/AgCl) and illuminated with light, catalysis of only

Robin Brimblecombe; Jun Chen; Pawel Wagner; Timothy Buchhorn; G. Charles Dismukes; Leone Spiccia; Gerhard F. Swiegers

2011-01-01

405

Development and Validation of Water Vapor Tracers as Diagnostics for the Atmospheric Hydrologic Cycle  

NASA Technical Reports Server (NTRS)

Understanding of the local and remote sources of water vapor can be a valuable diagnostic in understanding the regional atmospheric hydrologic cycle. In the present study, we have implemented passive tracers as prognostic variables to follow water vapor evaporated in predetermined regions until the water tracer precipitates. The formulation of the sources and sinks of tracer water is generally proportional to the prognostic water vapor variable. Because all water has been accounted for in tracers, the water vapor variable provides the validation of the tracer water and the formulation of the sources and sinks. The tracers have been implemented in a GEOS General Circulation Model (GCM) simulation consisting of several summer periods to determine the source regions of precipitation for the United States and India. The recycling of water and interannual variability of the sources of water will be examined. Potential uses in GCM sensitivity studies, predictability studies and data assimilation will be discussed.

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

2000-01-01

406

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

SciTech Connect

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

Oshima, Yoshito; Tomita, Kengo; Koda, Seiichiro

1999-11-01

407

Manganese cluster in photosynthesis: Where plants oxidize water to dioxygen  

SciTech Connect

The essential involvement of manganese in photosynthetic water oxidation was implicit in the observation by Pirson in 1937 that plants and algae deprived of Mn in their growth medium lost the ability to evolve O{sub 2}. Addition of this essential element to the growth medium resulted in the restoration of water oxidation within 30 min. There is increased interest in the study of Mn in biological chemistry and dioxygen metabolism in the last two decades with the discovery of several Mn redox enzymes. The list of enzymes where Mn is required for redox activity includes a Mn superoxide dismutase, a binuclear Mn-containing catalase, a binuclear Mn-containing ribonucleotide reductase, a proposed binuclear Mn site in thiosulfate oxidase, a Mn peroxidase that is capable of oxidative degradation of lignin, and perhaps the most complex and important, the tetranuclear Mn-containing oxygen-evolving complex in photosystem II (Mn-OEC). Mn is well suited for the redox role with accessible oxidation states of II, III, and IV, and possibly V: oxidation states that have all been proposed to explain the mechanisms of the Mn redox enzymes.

Yachandra, V.K.; Klein, M.P. [Lawrence Berkeley National Lab., CA (United States). Structural Biology Div.] [Lawrence Berkeley National Lab., CA (United States). Structural Biology Div.; Sauer, K. [Lawrence Berkeley National Lab., CA (United States). Structural Biology Div.] [Lawrence Berkeley National Lab., CA (United States). Structural Biology Div.; [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry

1996-11-01

408

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 (IrOx ) 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 (Na2 S2 O8 ) to form Ru(3+) species. The Ru(3+) species extracts an electron from IrOx 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

409

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

NASA Astrophysics Data System (ADS)

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

Aliofkhazraei, M.; Rouhaghdam, A. Sabour

2012-01-01

410

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

411

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

SciTech Connect

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

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

2012-01-01

412

Stress variation with thermal cycling in the thermally grown oxide of an EB-PVD thermal barrier coating  

Microsoft Academic Search

A measurement approach for detecting thermal barrier coating (TBC) damage and assessing remaining life is described in this study. This is based on an experimental study of the oxide stress evolution as a function of thermal cycling. Residual stress in the thermally grown oxide (TGO) has been measured using photo-stimulated luminescence piezo spectroscopy (PLPS) for electron beam physical vapor deposited

Swetha Sridharan; Liangde Xie; Eric H. Jordan; Maurice Gell

2004-01-01

413

Pilot-scale laboratory waste treatment by supercritical water oxidation.  

PubMed

Supercritical water oxidation (SCWO) is a reaction in which organics in an aqueous solution can be oxidized by O2 to CO2 and H2O at a very high reaction rate. In 2003, The University of Tokyo constructed a facility for the SCWO process, the capacity of which is approximately 20 kl/year, for the purpose of treating organic laboratory waste. Through the operation of this facility, we have demonstrated that most of the organics in laboratory waste including halogenated organic compounds can be successfully treated without the formation of dioxines, suggesting that SCWO is useful as an alternative technology to the conventional incineration process. PMID:17095994

Oshima, Yoshito; Hayashi, Rumiko; Yamamoto, Kazuo

2006-01-01

414

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

415

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

416

Dimensionality dependent water splitting mechanisms on free manganese oxide clusters.  

PubMed

The interaction of ligand-free manganese oxide nanoclusters with water is investigated, aiming at uncovering phenomena which could aid the design of artificial water-splitting molecular catalysts. Gas phase measurements in an ion trap in conjunction with first-principles calculations provide new mechanistic insight into the water splitting process mediated by bi- and tetra-nuclear singly charged manganese oxide clusters, Mn2O2(+) and Mn4O4(+). In particular, a water-induced dimensionality change of Mn4O4(+) is predicted, entailing transformation from a two-dimensional ring-like ground state structure of the bare cluster to a cuboidal octa-hydroxy-complex for the hydrated one. It is further predicted that the water splitting process is facilitated by the cluster dimensionality crossover. The vibrational spectra calculated for species occurring along the predicted pathways of the reaction of Mn4O4(+) with water provide the impetus for future explorations, including vibrational spectroscopic experiments. PMID:24164444

Lang, Sandra M; Fleischer, Irene; Bernhardt, Thorsten M; Barnett, Robert N; Landman, Uzi

2013-11-13

417

Seasonal and diurnal cycles of liquid water in snow  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

418

Photosynthesis and the Enzymes of Photosynthetic Carbon Reduction Cycle in Mulberry During Water Stress and Recovery  

Microsoft Academic Search

Net photosynthetic rate (PN), stomatal conductance (gS), transpiration rate (E), intercellular CO2 concentration (Ci), leaf water potential (?w), leaf area, chlorophyll (Chl) content, and the activities of photosynthetic carbon reduction cycle (PCR) enzymes in two mulberry (Morus alba L.) cultivars (drought tolerant Anantha and drought sensitive M-5) were studied during water stress and recovery. During water stress, PN, gS, and

S. Thimmanaik; S. Giridara Kumar; G. Jyothsna Kumari; N. Suryanarayana; C. Sudhakar

2002-01-01