Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “water structure”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Extreme Water Deficit in Brazil Detected from Space

Extreme droughts have caused significant socioeconomic and environmental damage worldwide. In Brazil, ineffective energy development and water management policies have magnified the impacts of recent severe droughts, which include massive agricultural losses, water supply restrictions, and energy rationing. Spaceborne remote sensing data advance our understanding of the spatiotemporal variability of large-scale droughts and enhance the detection and monitoring of extreme water-related events. In this study, data derived from the Gravity Recovery and Climate Experiment (GRACE) mission are used to detect and quantify an extended major drought over eastern Brazil and provide estimates of impacted areas and region-specific water deficits. Two structural breakpoint detection methods were applied to time series of GRACE-based terrestrial water storage anomalies (TWSA), determining when two abrupt changes occurred. One, in particular, defines the beginning of the current drought. Using TWSA, a water loss rate of 26.1 cmyr21 over southeastern Brazil was detected from 2012 to 2015. Based on analysis of Global Land Data Assimilation System(GLDAS) outputs, the extreme drought is mostly related to lower-than-usual precipitation rates, resulting in high soil moisture depletion and lower-than-usual rates of evapotranspiration. A reduction of 2023 of precipitation over an extended period of 3 years is enough to raise serious water scarcity conditions in the country. Correlations between monthly time series of both grid-based TWSA and ground-based water storage measurements at 16 reservoirs located within southeastern Brazil varied from 0.42 to 0.82. Differences are mainly explained by reservoir sizes and proximity to the drought nucleus.

terrestrial↗
NASA NTRS1991

Spectroscopic analyses of Fe and water in clays: A Martian surface weathering study

Martian surface morphology suggests the presence of liquid H2O on Mars in the past. Reflectance spectra of the Martian surface include features which correspond to the crystal field transitions of iron, as well as features supporting the presence of ice and minerals containing structural OH and surface water. Researchers initiated further spectroscopic studies of surface iron and water and structural OH in clays in order to determine what remotely obtained spectra can indicate about the presence of clays on Mars based on a clearer understanding of the factors influencing the spectral features. Current technology allows researchers to better correlate the low frequency fundamental stretching and bending vibrations of O-H bonds with the diagnostic near infrared overtone and combination bands used in mineral characterization and identification.

Bishop, J. L.↗
NASA NTRS1989

False-color display of special sensor microwave/imager (SSM/I) data

Displays of multifrequency passive microwave data from the Special Sensor Microwave/Imager (SSM/I) flying on the Defense Meteorological Satellite Program (DMSP) spacecraft are presented. Observed brightness temperatures at 85.5 GHz (vertical and horizontal polarizations) and 37 GHz (vertical polarization) are respectively used to 'drive' the red, green, and blue 'guns' of a color monitor. The resultant false-color images can be used to distinguish land from water, highlight precipitation processes and structure over both land and water, and detail variations in other surfaces such as deserts, snow cover, and sea ice. The observations at 85.5 GHz also add a previously unavailable frequency to the problem of rainfall estimation from space. Examples of mesoscale squall lines, tropical and extra-tropical storms, and larger-scale land and atmospheric features as 'viewed' by the SSM/I are shown.

Negri, Andrew J.↗
NASA NTRS2005

Bifunctional catalytic electrode

The present invention relates to an oxygen electrode for a unitized regenerative hydrogen-oxygen fuel cell and the unitized regenerative fuel cell having the oxygen electrode. The oxygen electrode contains components electrocatalytically active for the evolution of oxygen from water and the reduction of oxygen to water, and has a structure that supports the flow of both water and gases between the catalytically active surface and a flow field or electrode chamber for bulk flow of the fluids. The electrode has an electrocatalyst layer and a diffusion backing layer interspersed with hydrophilic and hydrophobic regions. The diffusion backing layer consists of a metal core having gas diffusion structures bonded to the metal core.

Cisar, Alan↗
NASA NTRS2007

Analysis of the Effects of Sea Disposal on a One-Ton Container

Excess and obsolete stocks of chemical warfare material (CWM) were sea disposed by the United States between 1919 and 1970. One-ton containers were used for bulk storage of CWM and were the largest containers sea disposed. Disposal depths ranged from 300 to 17,000 feet. Based on a Type D container assembly drawing, three independent analyses (one corrosion and two structural) were performed on the containers to address the corrosion resistance from prolonged exposure to sea water and the structural response during the descent. Corrosion predictions were made using information about corrosion rates and the disposal environment. The structural analyses employed two different finite element codes and were used to predict the buckling and material response of the container during sea disposal. The results of these investigations are summarized below. Detailed reports on each study are contained in the appendices.

Jackson, Wde C.↗
NASA NTRS2000

Computer Modeling of the Earliest Cellular Structures and Functions

In the absence of extinct or extant record of protocells (the earliest ancestors of contemporary cells). the most direct way to test our understanding of the origin of cellular life is to construct laboratory models of protocells. Such efforts are currently underway in the NASA Astrobiology Program. They are accompanied by computational studies aimed at explaining self-organization of simple molecules into ordered structures and developing designs for molecules that perform proto-cellular functions. Many of these functions, such as import of nutrients, capture and storage of energy. and response to changes in the environment are carried out by proteins bound to membrane< We will discuss a series of large-scale, molecular-level computer simulations which demonstrate (a) how small proteins (peptides) organize themselves into ordered structures at water-membrane interfaces and insert into membranes, (b) how these peptides aggregate to form membrane-spanning structures (eg. channels), and (c) by what mechanisms such aggregates perform essential proto-cellular functions, such as proton transport of protons across cell walls, a key step in cellular bioenergetics. The simulations were performed using the molecular dynamics method, in which Newton's equations of motion for each item in the system are solved iteratively. The problems of interest required simulations on multi-nanosecond time scales, which corresponded to 10(exp 6)-10(exp 8) time steps.

Pohorille, Andrew↗
NASA NTRS2010

Water in the Oceanic Lithosphere: Salt Lake Crater Xenoliths, Oahu, Hawaii

Water can be present in nominally anhydrous minerals of peridotites in the form of hydrogen bonded to structural oxygen. Such water in the oceanic upper mantle could have a significant effect on its physical and chemical properties. However, the water content of the MORB source has been inferred indirectly from the compositions of basalts. Direct determinations on abyssal peridotites are scarce because they have been heavily hydrothermally altered. Here we present the first water analyses of minerals from spinel peridotite xenoliths of Salt Lake Crater, Oahu, Hawaii, which are exceptionally fresh. These peridotites are thought to represent fragments of the Pacific oceanic lithosphere that was refertilized by alkalic Hawaiian melts. A few have unradiogenic Os and radiogenic Hf isotopes and may be fragments of an ancient (~2 Ga) depleted and recycled lithosphere. Water contents in olivine (Ol), orthopyroxene (Opx), and clinopyroxene (Cpx) were determined by FTIR spectrometry. Preliminary H_{2}O contents show ranges of 8-10 ppm for Ol, 151-277 ppm for Opx, and 337-603 ppm for Cpx. Reconstructed bulk rock H_{2}O contents range from 88-131 ppm overlapping estimates for the MORB source. Water contents between Ol minerals of the same xenolith are heterogeneous and individual OH infrared bands vary within a mineral with lower 3230 cm^{-1} and higher 3650-3400 cm^{-1} band heights from core to edge. This observation suggests disturbance of the hydrogen in Ol likely occurring during xenolith entrainment to the surface. Pyroxene water contents are higher than most water contents in pyroxenes from continental peridotite xenoliths and higher than those of abyssal peridotites. Cpx water contents decrease with increasing degree of depletion (e.g. increasing Fo in Ol and Cr# in spinel) consistent with an incompatible behavior of water. However Cpx water contents also show a positive correlation with LREE/HREE ratios and LREE concentrations consistent with refertilization. Opx water contents increase with increasing degree of depletion and decrease with LREE/HREE ratios which is inconsistent with the incompatible behavior of H. Calculated water contents of melts in equilibrium with Cpx or Opx range from 1.4 to 3.8 wt % which is higher than that of all Hawaiian lavas. Calculated melts in equilibrium with Cpx and Opx have variable but mostly high H_{2}O/Ce ratios (194 to 1146) consistent with those of rejuvenated stage lavas from Niihau and the South Arch volcanic field, but unlike the drier shield building stage tholeiites. Whether the high water contents recorded in Salt Lake Crater xenoliths were acquired before and/or during interaction of the oceanic lithosphere with the Hawaiian plume will be discussed.

Peslier, Anne H.↗
NASA NTRS1975

Water vapor weathering of Taurus-Littrow orange soil - A pore-structure analysis

A pore-volume analysis was performed on water vapor adsorption data previously obtained on a fresh sample of Taurus-Littrow orange soil, and the analysis was repeated on the same sample after its exposure to moist air for a period of approximately six months. The results indicate that exposure of an outgassed sample to high relative pressures of water vapor can result in the formation of substantial micropore structure, the precise amount being dependent on the sample pretreatment, particularly the outgassing temperature. Micropore formation is explained in terms of water penetration into surface defects. In contrast, long-term exposure to moist air at low relative pressures appears to reverse the process with the elimination of micropores and enlargement of mesopores possibly through surface diffusion of metastable adsorbent material. The results are considered with reference to the storage of lunar samples.

Cadenhead, D. A.↗
NASA NTRS2003

Structural Basis for "Flip-Flop" Action of Human Pyruvate Dehydrogenase

The derivative of vitamin B1, thiamin pyrophosphate is a cofactor of pyruvate dehydrogenase, a component enzyme of the mitochondrial pyruvate dehydrogenase multienzyme complex that plays a major role in directing energy metabolism in the cell. This cofactor is used to cleave the C(sup alpha)-C(=O) bond of pyruvate followed by reductive acetyl transfer to lipoyl-dihydrolipoamide acetyltransferase. In alpha(sub 2)beta(sub 2)-tetrameric human pyruvate dehydrogenase, there are two cofactor binding sites, each of them being a center of independently conducted, although highly coordinated enzymatic reactions. The dynamic nonequivalence of two, otherwise chemically equivalent, catalytic sites can now be understood based on the recently determined crystal structure of the holo-form of human pyruvate dehydrogenase at 1.95A resolution. The structure of pyruvate dehydrogenase was determined using a combination of MAD phasing and molecular replacement followed by rounds of torsion-angles molecular-dynamics simulated-annealing refinement. The final pyruvate dehydrogenase structure included coordinates for all protein amino acids two cofactor molecules, two magnesium and two potassium ions, and 742 water molecules. The structure was refined to R = 0.202 and R(sub free) = 0.244. Our structural analysis of the enzyme folding and domain assembly identified a simple mechanism of this protein motion required for the conduct of catalytic action.

Ciszak, Ewa↗
NASA NTRS2019

Emergence of Simple Ion Channels by Self-Assembly of Short Peptides

As protocells transitioned from structures bound by membranes made of simple amphiphiles, such as fatty acids, to structures containing phospholipid membranes, they became nearly impermeable to charged species. Yet, the ability to transport ions across membranes was vital to regulating cellular volume, pH homeostasis, generating energy and sensing the environment. For this reason, life evolved ion channels, protein structures surrounding water-filled pores in the membrane that facilitated ion transport. In contemporary cells, ion channels are complex protein assemblies. Could the same function be carried out, even if less efficiently and selectively, by much simpler peptides at the origins of life? To answer this question, we turned to trichogen (GAIV), an 11-residue peptide that was found to permeabilize membrane, causing leakage of the vesicle content including ions. Since GAIV is synthesized non-gnomically, it represents as excellent model for the earliest, poorly optimized channels. Understanding the mechanism by which short peptides, such as GAIV, mediate ion transport across membranes provides crucial information on the emergence, structure and the mechanism of action of the earliest ion channels. In this study, we used extensive molecular dynamics (MD) simulations to investigate directly spontaneous assembly of GAIV peptide and its structural dynamics, the formation of an induced water pore across the membrane and consequently ion conduction through the membrane.

Wei, Chenyu↗
NASA NTRS1979

Remote sensing of seasonal distribution of precipitable water vapor over the oceans and inference of boundary layer structure

Over the ocean satellite infrared spectral measurements in the 18 micrometer water vapor band and the 11 micrometer window region were used to derive precipitable water vapor, w, in the atmosphere and the sea surface temperature, SST. Seasonal maps of w on the oceans derived from these data reveal the dynamical influence of the large scale atmospheric circulation. With the help of a model for the vertical distribution of water vapor, the configuration of the atmospheric boundary layer over the oceans can be inferred from w when the information of SST is combined. The gross seasonal mean structure of the boundary layer inferred in this fashion reveals the broad areas of the trade wind inversion and the convectively active areas such as the intertropical convergence zones.

Prabhakara, C.↗
NASA NTRS2018

Are Water Markets Globally Applicable?

Water scarcity is a global concern that necessitates a global perspective, but it is also the product of multiple regional issues that require regional solutions. Water markets constitute a regionally applicable non-structural measure to counter water scarcity that has received the attention of academics and policy-makers, but there is no global view on their applicability. We present the global distribution of potential nations and states where water markets could be instituted in a legal sense, by investigating 296 water laws internationally, with special reference to a minimum set of key rules: legalization of water reallocation, the separation of water rights and landownership, and the modification of the cancellation rule for non-use. We also suggest two additional globally distributed prerequisites and policy implications: the predictability of the available water before irrigation periods and public control of groundwater pumping throughout its jurisdiction.

global water scarcity↗
NASA NTRS2023

Climate and Human Impacts on Hydrological Processes and Flood Risk in Southern Louisiana

Satellite observations of coastal Louisiana indicate an overall land loss over recent decades, which could be attributed to climate and human-induced factors, including sea level rise (SLR). Climate induced hydrological change (CHC) has impacted the way flood control structures are used, altering the spatiotemporal water distribution. Based on “what-if” scenarios, we determine relative impacts of SLR and CHC on increased flood risk over southern Louisiana and examine the role of water management, via flood control structures, in mitigating flood risk over the region. Our findings show that CHC has increased flood risk over the past 28 years. The number of affected people increases as extreme hydrological events become more exceptional. Water management reduces flood risk to urban areas and croplands, especially during exceptional hydrological events. For example, currently (i.e., 2016-2020 period), CHC-induced flooding puts an additional 73km2 of cropland under flood risk at least half of the time (median flood event) and 65km2 once a year (annual flood event), when compared to a past period (1993-1997). A ten- to twenty-fold increase relative to SLR-induced flooding. CHC also increases population vulnerability in southern Louisiana to flooding; additional 9900 residents currently live under flood risk at least half of the time, and that number increases to 27,400 for annual flood events. Residents vulnerable to SLR induced flooding is lower (6000 and 3300 residents, respectively). Conclusions are that CHC is a major factor that should be accounted for flood resilience and that water management interventions can mitigate risks to human life and activities.

Augusto Getirana↗
NASA NTRS1988

Cumulus convection and the terrestrial water-vapor distribution

Cumulus convection plays a significant role in determining the structure of the terrestrial water vapor field. Cumulus convection acts directly on the moisture field by condensing and precipitating water vapor and by redistributing water vapor through cumulus induced eddy circulations. The mechanisms by which cumulus convection influences the terrestrial water vapor distribution is outlined. Calculations using a theory due to Kuo is used to illustrate the mechanisms by which cumulus convection works. Understanding of these processes greatly aids the ability of researchers to interpret the seasonal and spatial distribution of atmospheric water vapor by providing information on the nature of sources and sinks and the global circulation.

Donner, Leo J.↗
NASA NTRS1993

The molecular matching problem

Molecular chemistry contains many difficult optimization problems that have begun to attract the attention of optimizers in the Operations Research community. Problems including protein folding, molecular conformation, molecular similarity, and molecular matching have been addressed. Minimum energy conformations for simple molecular structures such as water clusters, Lennard-Jones microclusters, and short polypeptides have dominated the literature to date. However, a variety of interesting problems exist and we focus here on a molecular structure matching (MSM) problem.

Kincaid, Rex K.↗
NASA NTRS1992

SPE water electrolyzers in support of the lunar outpost

During the 1970s, the SPE water electrolyzer, which uses ion exchange membranes as its sole electrolyte, was developed for nuclear submarine metabolic oxygen production. These developments included SPE water electrolyzer operation at up to 3,000 psia and at current densities in excess of 1,000 amps per square foot. The SPE water electrolyzer system is now fully qualified for both the U.S. and U.K. Navies with tens of thousands of system hours accumulated at sea. During the 1980s, the basic SPE water electrolyzer cell structure developed for the Navies was incorporated into several demonstrations for NASA's Space Station Program. Among these were: the SPE regenerative fuel cell for electrical energy storage; the SPE water electrolyzer for metabolic oxygen production; and the high pressure SPE water electrolyzer for reboost propulsion reactant production. In the 1990s, one emphasis will be the development of SPE water electrolyzers for the Lunar Outposts Currently defined potential Lunar Outpost applications for the SPE water electrolyzer include: SPE water electrolyzers for metabolic oxygen and potable water production from reclaimed water; and SPE water electrolyzers operating at high pressure as part of stationary and mobile surface energy storage systems.

Mcelroy, J. F.↗
NASA NTRS1991

SPE (tm) water electrolyzers in support of mission from planet Earth

During the 1970's, the Solid Polymer Electrolyte (SPE) water electrolyzer, which uses ion exchange membranes as its sole electrolyte, was developed for nuclear submarine metabolic oxygen production. SPE water electrolyzer developments included operation at up to 3,000 psia and at current densities in excess of 1,000 amps per square foot. The SPE water electrolyzer system has accumulated tens of thousands of system hours with the Navies of both the United States and the United Kingdom. During the 1980's, the basic SPE water electrolyzer cell structure developed for the Navies was incorporated into several demonstrators for NASA's Space Station Program. Among these were: (1) the SPE regenerative fuel cell for electrical energy storage; (2) the SPE water electrolyzer for metabolic oxygen production; and (3) the high pressure SPE water electrolyzer for reboost propellant production. In the 1990's, emphasis will be the development of SPE water electrolyzers for Mission from Planet Earth. Currently defined potential applications for the SPE water electrolyzer include: (1) SPE water electrolyzers operating at high pressure as part of a regenerative fuel cell extraterrestrial surface energy storage system; (2) SPE water electrolyzers for propellant production from extraterrestrial indigenous materials; and (3) SPE water electrolyzers for metabolic oxygen and potable water production from reclaimed water.

J F McElroy↗
NASA NTRS2000

The Structure of Ice Nanoclusters and Thin-films of Water Ice: Implications for Icy Grains in Cold Molecular Clouds

The cubic to hexagonal phase transformation in water ice (I(sub c) yields I(sub h)) is used to measure the extent to which surface structure and impurities control bulk properties. In pure crystalline (I(sub c)) water ice nanoclusters and in thin-films of impure water ice, I(sub c) yields I(sub h) occurs at lower temperatures than in thin-films of pure water ice. The disordered surface of the 20 nm diameter nanoclusters promotes transformations or reactions which would otherwise be kinetically hindered. Likewise, impurities such as methanol introduce defects into the ice network, thereby allowing sluggish structural transitions to proceed. Such surface-related phenomena play an important role in promoting chemical reactions on interstellar ice grains within cold molecular clouds, where the first organic compounds are formed.

Delzeit, Lance↗