Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Shared Responsibility”

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 1,081 records · Page 60

Integrating Ideas for International Data Collaborations Through The Committee on Earth Observation Satellites (CEOS) International Directory Network (IDN)

The capabilities of the International Directory Network's (IDN) version MD9.5, along with a new version of the metadata authoring tool, "docBUILDER", will be presented during the Technology and Services Subgroup session of the Working Group on Information Systems and Services (WGISS). Feedback provided through the international community has proven instrumental in positively influencing the direction of the IDN s development. The international community was instrumental in encouraging support for using the IS0 international character set that is now available through the directory. Supporting metadata descriptions in additional languages encourages extended use of the IDN. Temporal and spatial attributes often prove pivotal in the search for data. Prior to the new software release, the IDN s geospatial and temporal searches suffered from browser incompatibilities and often resulted in unreliable performance for users attempting to initiate a spatial search using a map based on aging Java applet technology. The IDN now offers an integrated Google map and date search that replaces that technology. In addition, one of the most defining characteristics in the search for data relates to the temporal and spatial resolution of the data. The ability to refine the search for data sets meeting defined resolution requirements is now possible. Data set authors are encouraged to indicate the precise resolution values for their data sets and subsequently bin these into one of the pre-selected resolution ranges. New metadata authoring tools have been well received. In response to requests for a standalone metadata authoring tool, a new shareable software package called "docBUILDER solo" will soon be released to the public. This tool permits researchers to document their data during experiments and observational periods in the field. interoperability has been enhanced through the use of the Open Archives Initiative s (OAI) Protocol for Metadata Harvesting (PMH). Harvesting of XML content through OAI-MPH has been successfully tested with several organizations. The protocol appears to be a prime candidate for sharing metadata throughout the international community. Data services for visualizing and analyzing data have become valuable assets in facilitating the use of data. Data providers are offering many of their data-related services through the directory. The IDN plans to develop a service-based architecture to further promote the use of web services. During the IDN Task Team session, ideas for further enhancements will be discussed.

Olsen, Lola M.↗

Surface-Induced Deprotonation of Thiol Ligands Impacts the Optical Response of CdS Quantum Dots

Cadmium chalcogenide quantum dots (QDs) passivated by thiol-based ligands exhibit several advantages in their applications in lighting, sensing, and imaging technologies. However, their emission is sensitive to thiol concentrations, pH conditions, and temperatures. Using calculations based on the density functional theory, we identify conditions for thiol/thiolate equilibrium at the CdS QD surface that either eliminate or introduce optically inactive hole trap states favoring or disfavoring the emission. Our calculations indicate much weaker interactions between the QD and protonated species (thiols), compared to their deprotonated counterparts (thiolates). Additionally, the surface of CdS QD facilitates the partial deprotonation of thiols, leading to the formation of an additional stable networking conformation where the proton is shared between the ligand and the QD surface. Thiolates strongly reduce the optical intensity of low-energy transitions in CdS QDs, contributing thiolate-localized hole trap states at the QD band gap. However, networking between the thiols and the surface, as well as the presence of native ligands such as primary amines, stabilize such trap states brightening the lowest optical transitions. This explains the increased emission of thiol-passivated QDs at lower concentrations in neutral or acidic solutions. Surface-mediated bias toward deprotonated species and their contribution to optically inactive states also rationalizes irreversible emission quenching and bleaching in the CdSe/CdS QDs exposed to high temperatures or intensive laser pulse.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Defining the Environmental Adaptations of Genus Devosia: Insights into its Expansive Short Peptide Transport System and Positively Selected Genes

Devosia are well known for their dominance in soil habitats contaminated with various toxins and are best characterized for their bioremediation potential. In this study, we compared the genomes of 27 strains of Devosia with aim to understand their metabolic abilities. The analysis revealed their adaptive gene repertoire which was bared from 52% unique pan-gene content. A striking feature of all genomes was the abundance of oligo- and di-peptide permeases (oppABCDF and dppABCDF) with each genome harboring an average of 60.7±19.1 and 36.5±10.6 operon associated genes respectively. Apart from their primary role in nutrition, these permeases may help Devosia to sense environmental signals and in chemotaxis at stressed habitats. Through sequence similarity network analyses, we identified 29 Opp and 19 Dpp sequences that shared very little homology with any other sequence suggesting an expansive short peptidic transport system within Devosia. The substrate determining components of these permeases viz. OppA and DppA further displayed a large diversity that separated into 12 and 9 homologous clusters respectively in addition to large number of isolated nodes. We also dissected the genome scale positive evolution and found genes associated with growth (exopolyphosphatase, HesB_IscA_SufA family protein), detoxification (moeB, nifU-like domain protein, alpha/beta hydrolase), chemotaxis (cheB, luxR) and stress response (phoQ, uspA, luxR, sufE) were positively selected. The study highlights the genomic plasticity of the Devosia spp. for conferring adaptation, bioremediation and the potential to utilize a wide range of substrates. The widespread toxin-antitoxin loci and ‘open’ state of the pangenome provided evidence of plastic genomes and a much larger genetic repertoire of the genus which is yet uncovered.

59 BASIC BIOLOGICAL SCIENCES↗

Optimizing multi-modal, non-axisymmetric plasma response metrics with additional coil rows on DIII-D

The expansion of the DIII-D tokamak operational space via the addition of new non-axisymmetric coil rows is investigated using the linear MHD plasma response code MARS-F. The plasma response to magnetic perturbations imposed by five distinct low- and high-field side coil geometries is modeled for toroidal mode numbers up to n = 6. A set of linear (~δB^2: resonant, kink mode amplitude) and quadratic (~δB: core and edge integrated NTV torque) plasma metrics are defined and compared directly for the various coil geometries. Coil size is also scanned as a secondary optimization variable. An in-vessel coil located at the low-field side midplane is identified as the most efficient plasma response actuator across all metrics and toroidal mode numbers. The multi-row combination of this new midplane (M) coil with the existing DIII-D non-axisymmetric coil set is considered in numerical optimization studies to quantify the impact of this new coil on modeled plasma response metrics. The addition of the M coil is shown to significantly increase the actuator efficiency in maximizing individual plasma response metrics as well as maximizing multi-modal ratios of response metrics, e.g. maximizing resonant modes or edge NTV torque while minimizing kink modes or core NTV torque. The ex-vessel midplane (C) coil is also observed to have an outsize effect on multi-modal optimization due to its uniquely narrow poloidal spectra, and the expansion of optimization space due to the combined use of the two existing in-vessel coil rows with both the M and C coils is notably larger than either coil's individual contribution even though both share similar poloidal locations. This four-row system is expected to greatly extend abilities to understand and optimize the control of transients and rotation on the DIII-D tokamak.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Redefining Resource Adequacy for Modern Power Systems: A Report of the Redefining Resource Adequacy Task Force

Today's rapidly increasing levels of wind, solar, storage, and load flexibility require the industry to rethink reliability planning and resource adequacy methods for modern power systems. Periods with a risk of shortfall often no longer coincide with peak demand - reliability risks are less about peak load and more about the daily setting of the sun, extended cloud cover, wind speeds, cold snaps, and heat waves. In addition, demand is increasingly flexible. Key resources are time-sensitive, as batteries need time to recharge and electricity customers can only be asked to provide demand response for just so long. And reliability failures are often correlated - with one another and with the weather. Two driving factors require the industry to reconsider its analytical approach for resource adequacy: (1) Chronological grid operations: The increasing importance of variable renewable resources (such as wind and solar) and of energy-limited resources (storage and demand response) make it essential to understand the full year of chronological operation of the grid. Specific attention must be paid to hourly, seasonal, and inter-annual resource variability. The sequence of the variability is key, as energy-limited resources such as batteries or demand response require either a preceding period or subsequent period of high production to be useful for grid reliability. (2) Correlated events: Historically, resource adequacy analysis focused on shortfalls caused by random, discrete mechanical failures of large generating units. In contrast, shortfalls today are often caused by multiple, correlated events caused by common weather patterns. Resource adequacy analysis must increasingly shift its focus to these correlated events. The redesign of resource adequacy methods will benefit from a set of guiding principles to better allow for sharing of insights and best practices, interregional resource coordination, and a smoother regulatory process for resource procurement. The objective of this report is to move this redesign forward. It provides an overview of key drivers changing the way resource adequacy needs to be evaluated, identifies shortcomings of conventional approaches, and outlines first principles for practitioners to consider as they adapt their approaches. The central message is: what got us here won't get us there.

24 POWER TRANSMISSION AND DISTRIBUTION↗

The Structure and Immune Regulatory Implications of the Ubiquitin-Like Tandem Domain Within an Avian 2’-5’ Oligoadenylate Synthetase-Like Protein

Post-translational modification of host and viral proteins by ubiquitin and ubiquitin-like proteins plays a key role in a host’s ability to mount an effective immune response. Avian species lack a ubiquitin-like protein found in mammals and other non-avian reptiles; interferon stimulated gene product 15 (ISG15). ISG15 serves as a messenger molecule and can be conjugated to both host and viral proteins leading them to be stabilized, degraded, or sequestered. Structurally, ISG15 is comprised of a tandem ubiquitin-like domain (Ubl), which serves as the motif for post-translational modification. The 2’-5’ oligoadenylate synthetase-like proteins (OASL) also encode two Ubl domains in series near its C-terminus which binds OASL to retinoic acid inducible gene-I (RIG-I). This protein-protein interaction increases the sensitivity of RIG-I and results in an enhanced production of type 1 interferons and a robust immune response. Unlike human and other mammalian OASL homologues, avian OASLs terminate their tandem Ubl domains with the same LRLRGG motif found in ubiquitin and ISG15, a motif required for their conjugation to proteins. Chickens, however, lack RIG-I, raising the question of structural and functional characteristics of chicken OASL (chOASL). By investigating chOASL, the evolutionary history of viruses with deubiquitinases can be explored and drivers of species specificity for these viruses may be uncovered. Here we show that the chOASL tandem Ubl domains shares structural characteristics with mammalian ISG15, and that chOASL can oligomerize and conjugate to itself. In addition, the ISG15-like features of avian OASLs and how they impact interactions with viral deubiquitinases and deISGylases are explored.

59 BASIC BIOLOGICAL SCIENCES↗

Validating (d,p gamma) as a Surrogate for Neutron Capture

The r-process is responsible for creating roughly half of the elements heavier than iron. It has recently become understood that the rates at which neutron capture reactions proceed at late times in the rprocess may dramatically affect the final abundance pattern. However, direct measurements of neutron capture reaction rates on exotic nuclei are exceptionally difficult, necessitating the development of indirect approaches such as the surrogate technique. The (d,py) reaction at low energies was identified as a promising surrogate for the (n,y) reaction, as both reactions share many characteristics. We report on a program to validate (d,py) as a surrogate for (n,y) using 95Mo as a target. The experimental campaign includes direct measurements of the y-ray intensities from the decay of excited states populated in the 95Mo(n,y) and 95Mo(d,py) reactions.

Ratkiewicz, A.↗

Nonparallel transcriptional divergence during parallel adaptation

Abstract How underlying mechanisms bias evolution toward predictable outcomes remains an area of active debate. In this study, we leveraged phenotypic plasticity and parallel adaptation across independent lineages of Trinidadian guppies ( Poecilia reticulata ) to assess the predictability of gene expression evolution during parallel adaptation. Trinidadian guppies have repeatedly and independently adapted to high‐ and low‐predation environments in the wild. We combined this natural experiment with a laboratory breeding design to attribute transcriptional variation to the genetic influences of population of origin and developmental plasticity in response to rearing with or without predators. We observed substantial gene expression plasticity, as well as the evolution of expression plasticity itself, across populations. Genes exhibiting expression plasticity within populations were more likely to also differ in expression between populations, with the direction of population differences more likely to be opposite those of plasticity. While we found more overlap than expected by chance in genes differentially expressed between high‐ and low‐predation populations from distinct evolutionary lineages, the majority of differentially expressed genes were not shared between lineages. Our data suggest alternative transcriptional configurations associated with shared phenotypes, highlighting a role for transcriptional flexibility in the parallel phenotypic evolution of a species known for rapid adaptation.

Fischer, Eva K.↗

Lands with Wilderness Characteristics, Resource Management Plan Constraints, and Land Exchanges: Cross-Jurisdictional Management and Impacts on Unconventional Fuel Development in Utah's Uinta Basin

Utah is rich in oil shale and oil sands resources. Chief among the challenges facing prospective unconventional fuel developers is the ability to access these resources. Access is heavily dependent upon land ownership and applicable management requirements. Understanding constraints on resource access and the prospect of consolidating resource holdings across a fragmented management landscape is critical to understanding the role Utah’s unconventional fuel resources may play in our nation’s energy policy. This Topical Report explains the historic roots of the “crazy quilt” of western land ownership, how current controversies over management of federal public land with wilderness character could impact access to unconventional fuels resources, and how land exchanges could improve management efficiency. Upon admission to the Union, the State of Utah received the right to title to more than one-ninth of all land within the newly formed state. This land is held in trust to support public schools and institutions, and is managed to generate revenue for trust beneficiaries. State trust lands are scattered across the state in mostly discontinuous 640-acre parcels, many of which are surrounded by federal land and too small to develop on their own. Where state trust lands are developable but surrounded by federal land, federal land management objectives can complicate state trust land development. The difficulty generating revenue from state trust lands can frustrate state and local government officials as well as citizens advocating for economic development. Likewise, the prospect of industrial development of inholdings within prized conservation landscapes creates management challenges for federal agencies. One major tension involves whether certain federal public lands possess wilderness character, and if so, whether management of those lands should emphasize wilderness values over other uses. On December 22, 2010, Secretary of the Interior Ken Salazar issued Secretarial Order 3310, Protecting Wilderness Characteristics on Lands Managed by the Bureau of Land Management. Supporters argue that the Order merely provides guidance regarding implementation of existing legal obligations without creating new rights or duties. Opponents describe Order 3310 as subverting congressional authority to designate Wilderness Areas and as closing millions of acres of public lands to energy development and commodity production. While opponents succeeded in temporarily defunding the Order’s implementation and forcing the Bureau of Land Management (BLM) to adopt a more collaborative approach, the fundamental questions remain: Which federal public lands possess wilderness characteristics and how should those lands be managed? The closely related question is: How might management of such resources impact unconventional fuel development within Utah? These questions remain pressing independent of the Order because the BLM, which manages the majority of federal land in Utah, is statutorily obligated to maintain an up-to-date inventory of federal public lands and the resources they contain, including lands with wilderness characteristics. The BLM is also legally obligated to develop and periodically update land use plans, relying on information obtained in its public lands inventory. The BLM cannot sidestep these hard choices, and failure to consider wilderness characteristics during the planning process will derail the planning effort. Based on an analysis of the most recent inventory data, lands with wilderness characteristics — whether already subject to mandatory protection under the Wilderness Act, subject to discretionary protections as part of BLM Resource Management Plan revisions, or potentially subject to new protections under Order 3310 — are unlikely to profoundly impact oil shale development within Utah’s Uinta Basin. Lands with wilderness characteristics are likely to v have a greater impact on oil sands resources, particularly those resources found in the southern part of the state. Management requirements independent of lands with wilderness characteristics far overshadow the challenges posed by wilderness issues. Wilderness character issues aside, a need to improve management integration remains. In researching past efforts to manage across the fragmented landscape we found that unilateral actions have been deeply divisive and engendered distrust among those impacted by the action. This distrust can linger for decades. Collaborative efforts, whether intended to protect lands, foster development, or do both, can represent an attractive alternative to unilateral action. Such collaborative efforts are more likely to succeed when they respond to strong incentives to act, evidence widespread involvement and support, and benefit from a committed champion. Projects are all but certain to fail where participants overreach or one of these elements is missing. For more than three decades, the state and federal government have cooperatively pursued land exchanges in order to “block up” isolated state trust lands and eliminate inholdings. These efforts can advance both conservation and development objectives, and are generally conducted in conjunction with efforts to protect extraordinary federal lands. Congress recognized the value of such exchanges and, as part of the Energy Policy Act of 2005, directed the Department of the Interior to pursue land exchanges as a means of facilitating environmentally responsible oil shale and oil sands recovery. But land exchanges are not without their challenges. Federal law requires equalizing the value of the lands and resources to be exchanged, and various means of equalizing value have been attempted. More flexible approaches have a higher likelihood of success, but are often criticized as resulting in an economic windfall for one party. Today challenges associated with appraisal and valuation stand as the most significant obstacles in the way of large-scale exchanges. Greater reliance on revenue sharing provisions that prevent an economic windfall to one party and avoid challenges inherent in valuing oil shale and oil sands resources may mark a promising path forward. The success or failure of these efforts could profoundly impact both the prospect of unconventional fuel development and wilderness character protection.

04 OIL SHALES AND TAR SANDS↗

International Governmental Collaboration on Best Practice in Aging Infrastructure Management - 18027

Legacy nuclear sites in the US, UK and Canada are all facing a similar challenge of completing their operational and cleanup missions in parallel in a safe, efficient and cost-effective manner. Compounding the challenge is the fact that many important facilities are old with a significant level of deferred maintenance/capital needs, resulting in the need for a strategic approach to infrastructure management to ensure that maintenance and capital funding is directed at the highest priority items and that neither operations nor ongoing Decontamination and Decommissioning (D and D) activities are compromised. To help address this challenge, a Technical Information Exchange meeting was held in Ottawa, Canada in early June 2017 which brought together responsible parties from; - Government agencies including the UK Nuclear Decommissioning Authority (NDA), US Department of Energy Environmental Management (DOE EM), US National Nuclear Security Administration (NNSA), Atomic Energy of Canada Ltd (AECL) and Canadian Department of Defense - Implementers and other Government entities including Savannah River National Laboratory, Idaho National Laboratory and Canadian Nuclear Laboratories (CNL) - Associations including representation on behalf of the Institute of Asset Management and; - Contractors including Mission Support Alliance, Mott McDonald, and Longenecker and Associates The objective of this meeting was to share information about respective 'best practices' and to begin to develop common approaches to the prioritization and management of aging infrastructure investment across the organizations. The exchange focused on identifying common critical issues which were discussed through a series of presentations and small group discussions. The outcome from the meeting was an improved understanding by all participants of the latest approaches being applied to Infrastructure Asset Management and the formation of four International Working Groups which now meet on a regular (4-6 week) basis to share lessons learned and to develop international best practice in their area of interest. This paper details; - the issues and challenges that were identified during the meeting - how these were assimilated and distilled into discrete areas to enable formation of specific Working Groups - progress made by the Working Groups to date. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

Real-Time Ammonia and Humidity Monitoring with Ultra-Fast Conductometric Sensors Based on Porphyrin and Phthalocyanine Complexes

Organic semiconductors like porphyrins and phthalocyanines are attracting a wide range of researchers due to their versatile electrical properties and sensing performances in conductometric sensors. In this study, we investigate two types of π-extended porphyrins, which share the same macrocyclic structure but differ in their central metal. These porphyrins are employed as sublayers in bilayer heterojunction devices, with the lutetium bisphthalocyanine complex, LuPc 2 , serving as the common top layer. Remarkably, the central metal in the porphyrin macrocycle significantly influences the solubility of the materials and, consequently, the surface topography of the resulting bilayer heterojunction devices. This structural variation translates into distinct electrical and sensing performances. The device incorporating nickel as metal centre (AM2) demonstrates superior sensitivity towards NH3, with a relative response (RR) of ca. -7% at 90 ppm, an ultra-fast response time of about 9 s, and an impressive limit of detection (LOD) of 250 ppb, whereas, the device that has zinc as metal centre in sublayer (AM3) exhibits RR value of ca. -0.9% at 90 ppm with t 90 of ca. 120 s and LOD of 2 ppm. Both devices are evaluated under randomly varying NH 3 concentration and RH value. The results shows that the AM2-based sensor allows following NH 3 in real-time, while the AM3-based sensor delivers an average concentration over time. On the other hand, the AM2-based sensor exhibits slow kinetics under RH exposure, while the AM3-based sensor precisely mirrors the pattern of random RH changes generated by the software, demonstrating its exceptional responsiveness and accuracy in tracking humidity fluctuations. In conclusion, these findings underscore the critical role of the metal centre in tuning the electrical and sensing properties of the heterojunction devices.

99 GENERAL AND MISCELLANEOUS↗

A microeconomic scheduler for parallel computers

We describe a scheduler based on the microeconomic paradigm for scheduling on-line a set of parallel jobs in a multiprocessor system. In addition to the classical objectives of increasing the system throughput and reducing the response time, we consider fairness in allocating system resources among the users, and providing the user with control over the relative performances of his jobs. We associate with every user a savings account in which he receives money at a constant rate. When a user wants to run a job, he creates an expense account for that job to which he transfers money from his savings account. The job uses the funds in its expense account to obtain the system resources it needs for execution. The share of the system resources allocated to the user is directly related to the rate at which the user receives money; the rate at which the user transfers money into a job expense account controls the job's performance. We prove that starvation is not possible in our model. Simulation results show that our scheduler improves both system and user performances in comparison with two different variable partitioning policies. It is also shown to be effective in guaranteeing fairness and providing control over the performance of jobs.

Stoica, Ion↗

Recovery and Resilience in the Pacific Northwest

Around the world, communities are wrestling with what it means to be resilient enough to recover from a catastrophic disaster. Emergency management agencies have come to recognize that response and recovery are only two phases along the road to resilience and that there is no real dividing line between response and recovery. Some response activities will continue into the recovery phase; however, recovery preparations need to begin during the response phase if communities are to limit the damage to the economy, a key driver affecting resilience. Since its inception in 2007, the Pacific Northwest National Laboratory’s (PNNL) Northwest Regional Technology Center (NWRTC) for Homeland Security in Seattle, Washington, has been working with state, local, and federal agencies; the private sector; and other organizations to develop approaches that foster resilience and support rapid recovery following an accidental, intentional, or natural disaster. This paper describes the NWRTC’s approach to building robust local and regional coalitions, shares some notable successes in improving recovery and increasing resilience, and identifies challenges and issues that still need to be addressed if communities are to be resilient in the face of disasters.

Resilience, Conference Proceedings, Recovery, NWRT↗

Diagnostic assessment of reservoir response to fracturing: a case study from Hydraulic Fracturing Test Site (HFTS) in Midland Basin

Abstract This paper outlines a data collection and diagnostics case study involving multiple horizontal shale wells. We look at well production profiles using rate transient analysis, differences in near wellbore complexity, geologic variations within the area of interest, as well as compositional differences in the rocks based on cores obtained from within the stimulated reservoir. The Hydraulic Fracturing Test Site is a multi-well experiment involving stimulation of unconventional shale wells in the southeastern Midland portion of the Permian Basin. The targeted formations include both the upper as well as the middle Wolfcamp formations, also referred alternatively as Wolfcamp A and Wolfcamp B. Data integration and analysis shared in this paper help us understand the various geologic controls impacting well productivity, particularly the wide variance observed between the Wolfcamp A and Wolfcamp B formations. Rate transient analysis indicates similar system permeabilities for stimulated wells. However, we observe higher effective fracture half-lengths for upper Wolfcamp wells. Using observations from 3D seismic interpretations (such as pad scale faults) as well as petrophysical and image log data, we highlight the substantial differences in stimulation as we move along the well laterals from the heel toward the toe sections. These differences are further reconciled with observations from zones with high data density at the core locations through stimulated rock, as well as independent data such as microseismic emissions. At the test site, Wolfcamp A was found to be relatively quartz rich with significant heterogeneity whereas Wolfcamp B is richer in clay and organic content. This impacts the geomechanical characteristics of the rock mass with much higher natural fracture density in the shallower interval. Thus, the fracture growth is more uniform in the deeper interval and more heterogeneous with branching likely in upper interval. Increased complexity also leads to consistently better productivity from the wells in the shallower interval as demonstrated from RTA results. This case study is unique because it provides valuable insights from actual sampling of the stimulated zones in hydraulically fractured wells and helps understand impact of various factors that contribute toward variability in well production. The findings from this study provides insights into need for optimization of completion designs in the various Wolfcamp landing zones, such as optimization of cluster or fracture spacing in various Wolfcamp intervals. In addition, it provides a useful template for data collection and research direction in future field test sites of similar nature in unconventional reservoirs.

Energy & Fuels↗

Conserved and Diversified Gene Families of Monovalent Cation/H+ Antiporters from Algae to Flowering Plants

All organisms have evolved strategies to regulate ion and pH homeostasis in response to developmental and environmental cues. One strategy is mediated by monovalent cation– proton antiporters (CPA) that are classified in two superfamilies. Many CPA1 genes from bacteria, fungi, metazoa, and plants have been functionally characterized; though roles of plant CPA2 genes encoding K+-efflux antiporter (KEA) and cation/H+ exchanger (CHX) families are largely unknown. Phylogenetic analysis showed that three clades of the CPA1 Na+–H+ exchanger (NHX) family have been conserved from single-celled algae to Arabidopsis. These are (i) plasma membrane-bound SOS1/AtNHX7 that share ancestry with prokaryote NhaP, (ii) endosomal AtNHX5/6 that is part of the eukaryote Intracellular-NHE clade, and (iii) a vacuolar NHX clade (AtNHX1–4) specific to plants. Early diversification of KEA genes possibly from an ancestral cyanobacterium gene is suggested by three types seen in all plants. Intriguingly, CHX genes diversified from three to four members in one subclade of early land plants to 28 genes in eight subclades of Arabidopsis. Homologs from Spirogyra or Physcomitrella share high similarity with AtCHX20, suggesting that guard cellspecific AtCHX20 and its closest relatives are founders of the family, and pollen-expressed CHX genes appeared later in monocots and early eudicots. AtCHX proteins mediate K+ transport and pH homeostasis, and have been localized to intracellular and plasma membrane.Thus KEA genes are conserved from green algae to angiosperms, and their presence in red algae and secondary endosymbionts suggest a role in plastids. In contrast, AtNHX1– 4 subtype evolved in plant cells to handle ion homeostasis of vacuoles. The great diversity of CHX genes in land plants compared to metazoa, fungi, or algae would imply a significant role of ion and pH homeostasis at dynamic endomembranes in the vegetative and reproductive success of flowering plants.

54 ENVIRONMENTAL SCIENCES↗

Coordination namespace processing

An approach is described that accesses data in a shared memory that is shared amongst nodes that include a local node and remote nodes. The local node receives a name corresponding to a named data element in a Coordination Namespace, the Coordination Namespace having been created in a memory distributed amongst the nodes. A hash function is applied to at least a portion of the name with a result of the hash function being a natural node indicator. Data corresponding to the named data element is requested from a natural node identified by the indicator. Based on the request, a response is received from the natural node.

Nair, Rishi↗

Spatiotemporal Metabolic Network Models Reveal Complex Autotroph-Heterotroph Biofilm Interactions Governed by Photon Incidences

Autotroph-heterotroph interactions are ubiquitous in natural environment and play a key role in controlling various essential ecosystem functions, such as production and utilization of organic matter, cycling of nitrogen, sulfur, and other chemical elements. Understanding how these biofilm metabolic interactions are constrained in space and time remains challenging because fully predictive models designed for this purpose are currently limited. Toward filling this gap, here we developed community metabolic network models for two autotroph-heterotroph biofilm consortia (termed UCC-A and UCC-O), which share a suite of common heterotrophic members but have a single distinct photoautotrophic cyanobacterium (Phormidesmis priestleyi str. ANA and Phormidium sp. OSCR) that provides organic carbon and nitrogen sources to support the growth of heterotrophic partners. After determining model parameters by data fitting using the spatiotemporal distributions of microbial abundances, we comparatively analyzed the resulting biofilm models to examine any fundamental differences in microbial interactions between the two consortia under the variation of key environmental variables: CO2 and photon levels. The UCC-A model predicted generally expected responses, i.e., the autotroph population increased in response to elevated levels of CO2 and photon, followed by increase in the heterotroph population. In contrast, the UCC-O model showed somewhat complicated dynamics, e.g., higher photon incidence rates resulted in the increase in autotroph population but decrease in heterotroph population due to the lowered provision of glucose from the autotroph. A further analysis showed that species coexistence was governed by the photon incidences rather than the carbon availability for UCC-O, which was the opposite for UCC-A.

Phalak, Poonam↗

Application of sensitivity analysis in DYMOND/Dakota to fuel cycle transition scenarios

The ability to perform sensitivity analysis has been enabled for the nuclear fuel cycle simulator DYMOND through its coupling with the design and analysis toolkit Dakota. To test and demonstrate these new capabilities, a transition scenario and multi-parameter study were devised. The transition scenario represents a partial transition from the US nuclear fleet to a closed fuel cycle with small modular LWRs and fast reactors fueled by reprocessed used nuclear fuel. Four uncertain parameters in this transition were studied – start date of reprocessing, total reprocessing capacity, the nuclear energy demand growth, and the rate at which the fast reactors are deployed – with respect to their impact on four response metrics. The responses – total natural uranium consumed, maximum annual enrichment capacity required, total disposed mass, and total cost of the nuclear fuel cycle – were chosen based on measures known to be of interest in transition scenarios and to be significantly impacted by the varying parameters. Furthermore, analysis of this study was performed both from the direct sampling and through surrogate models developed in Dakota to calculate the global sensitivity measures Sobol’ indices. This example application of this new capability showed that the most consequential parameter to most metrics was the share of new build capacity that is fast reactors. However, for the cost metric, the scaling factor of the energy demand growth was significant and had synergistic behavior with the fast reactor new build share.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗