The Impact on Individualizing Student Models on Necessary Practice Opportunities

ERIC Educational Resources Information Center

Lee, Jung In; Brunskill, Emma

2012-01-01

When modeling student learning, tutors that use the Knowledge Tracing framework often assume that all students have the same set of model parameters. We find that when fitting parameters to individual students, there is significant variation among the individual's parameters. We examine if this variation is important in terms of instructional…

Quantifying errors in trace species transport modeling.

PubMed

Prather, Michael J; Zhu, Xin; Strahan, Susan E; Steenrod, Stephen D; Rodriguez, Jose M

2008-12-16

One expectation when computationally solving an Earth system model is that a correct answer exists, that with adequate physical approximations and numerical methods our solutions will converge to that single answer. With such hubris, we performed a controlled numerical test of the atmospheric transport of CO(2) using 2 models known for accurate transport of trace species. Resulting differences were unexpectedly large, indicating that in some cases, scientific conclusions may err because of lack of knowledge of the numerical errors in tracer transport models. By doubling the resolution, thereby reducing numerical error, both models show some convergence to the same answer. Now, under realistic conditions, we identify a practical approach for finding the correct answer and thus quantifying the advection error.

Developing Learning Progression-Based Teacher Knowledge Measures

ERIC Educational Resources Information Center

Jin, Hui; Shin, HyoJeong; Johnson, Michele E.; Kim, JinHo; Anderson, Charles W.

2015-01-01

This study developed learning progression-based measures of science teachers' content knowledge (CK) and pedagogical content knowledge (PCK). The measures focus on an important topic in secondary science curriculum using scientific reasoning (i.e., tracing matter, tracing energy, and connecting scales) to explain plants gaining weight and…

Cirrus: Inducing Subject Models from Protocol Data

DTIC Science & Technology

1988-08-16

behavior scientists, and more recently, by knowledge engineers who wish to embed the knowledge of human experts in an expert system. However, protocol...analysis is notoriously difficult and time comsuming . Several systems have been developed to aid in protocol analysis. Waterman and Newell (1971, 1973...developed a system that could read the natural langauge of the protocol and produce a formal trace of it (a problem behavior graph). The system, however

Designing a Knowledge Representation Approach for the Generation of Pedagogical Interventions by MTTs

ERIC Educational Resources Information Center

Paquette, Luc; Lebeau, Jean-François; Beaulieu, Gabriel; Mayers, André

2015-01-01

Model-tracing tutors (MTTs) have proven effective for the tutoring of well-defined tasks, but the pedagogical interventions they produce are limited and usually require the inclusion of pedagogical content, such as text message templates, in the model of the task. The capability to generate pedagogical content would be beneficial to MTT…

Global sensing of gaseous and aerosol trace species using automated instrumentation on 747 airliners

NASA Technical Reports Server (NTRS)

Perkins, P. J.; Papathakos, L. C.

1977-01-01

The Global Atmospheric Sampling Program (GASP) by NASA is collecting and analyzing data on gaseous and aerosol trace species in the upper troposphere and lower stratosphere. Measurements are obtained from automated systems installed on four 747 airliners flying global air routes. Advances were made in airborne sampling instrumentation. Improved instruments and analysis techniques are providing an expanding data base for trace species including ozone, carbon monoxide, water vapor, condensation nuclei and mass concentrations of sulfates and nitrates. Simultaneous measurements of several trace species obtained frequently can be used to uniquely identify the source of the air mass as being typically tropospheric or stratospheric. A quantitative understanding of the tropospheric-stratospheric exchange processes leads to better knowledge of the atmospheric impact of pollution through the development of improved simulation models of the atmosphere.

Local Semantic Trace: A Method to Analyze Very Small and Unstructured Texts for Propositional Knowledge

ERIC Educational Resources Information Center

Pirnay-Dummer, Pablo

2015-01-01

A local semantic trace is a certain quasi-propositional structure that can still be reconstructed from written content that is incomplete or does not follow a proper grammar. It can also retrace bits of knowledge from text containing only very few words, making the microstructure of these artifacts of knowledge externalization available for…

Taking a Closer Look at Science Teaching Orientations

ERIC Educational Resources Information Center

Friedrichsen, Patrica; Van Driel, Jan H.; Abell, Sandra K.

2011-01-01

In this position paper, we examine the science teaching orientation component of the S. Magnusson, J. Krajcik, and H. Borko (1999) pedagogical content knowledge (PCK) model for science teaching. We trace the origin of the construct in the literature, identifying multiple definitions that have lead to ambiguity. After examining published studies…

Modeling Microbial Processes in EPIC to Estimate Greenhouse Gas Emissions from soils

NASA Astrophysics Data System (ADS)

Schwab, D. E.; Izaurralde, R. C.; McGill, W. B.; Williams, J. R.; Schmid, E.

2009-12-01

Emissions of trace gases (CO2, N2O and CH4) to the atmosphere from managed terrestrial ecosystems have been contributing significantly to the warming of Earth. Trace gas production is dominated by biospheric processes. An improved knowledge of the soil-plant-atmosphere interface is of key importance for understanding trace gas dynamics. In soils, microbial metabolism plays a key role in the release or uptake of trace gases. Here we present work on the biophysical and biogeochemical model EPIC (Environmental Policy/Integrated Climate) to extend its capabilities to simulate CO2 and N2O fluxes in managed and unmanaged ecosystems. Emphasis will be given to recently developed, microbially-based, denitrification and nitrification modules. The soil-atmosphere exchange of trace gases can be measured by using various equipments, but often these measurements exhibit extreme space-time variability. We use hourly time steps to account for the variability induced by small changes in environmental conditions. Soils are often studied as macroscopic systems, although their functions are predominantly controlled at a microscopic level; i.e. the level of the microorganisms. We include these processes to the extent that these are known and can be quantitatively described. We represent soil dynamics mathematically with routines for gas diffusion, Michael Menten processes, electron budgeting and other processes such as uptake and transformations. We hypothesize that maximization of energy capture form scarce substrates using energetic favorable reactions drives evolution and that competitive advantage can result by depriving a competitor from a substrate. This Microbe Model changes concepts of production of N-containing trace gases; it unifies understanding of N oxidation and reduction, predicts production and evolution of trace gases and is consistent with observations of anaerobic ammonium oxidation.

Magazines as wilderness information sources: assessing users' general wilderness knowledge and specific leave no trace knowledge

Treesearch

John J. Confer; Andrew J. Mowen; Alan K. Graefe; James D. Absher

2000-01-01

The Leave No Trace (LNT) educational program has the potential to provide wilderness users with useful minimum impact information. For LNT to be effective, managers need to understand who is most/least aware of minimum impact practices and how to expose users to LNT messages. This study examined LNT knowledge among various user groups at an Eastern wilderness area and...

Interleaved Practice with Multiple Representations: Analyses with Knowledge Tracing Based Techniques

ERIC Educational Resources Information Center

Rau, Martina A.; Pardos, Zachary A.

2012-01-01

The goal of this paper is to use Knowledge Tracing to augment the results obtained from an experiment that investigated the effects of practice schedules using an intelligent tutoring system for fractions. Specifically, this experiment compared different practice schedules of multiple representations of fractions: representations were presented to…

Competitive Trace Theory: A Role for the Hippocampus in Contextual Interference during Retrieval.

PubMed

Yassa, Michael A; Reagh, Zachariah M

2013-01-01

Much controversy exists regarding the role of the hippocampus in retrieval. The two dominant and competing accounts have been the Standard Model of Systems Consolidation (SMSC) and Multiple Trace Theory (MTT), which specifically make opposing predictions as to the necessity of the hippocampus for retrieval of remote memories. Under SMSC, memories eventually become independent of the hippocampus as they become more reliant on cortical connectivity, and thus the hippocampus is not required for retrieval of remote memories, only recent ones. MTT on the other hand claims that the hippocampus is always required no matter the age of the memory. We argue that this dissociation may be too simplistic, and a continuum model may be better suited to address the role of the hippocampus in retrieval of remote memories. Such a model is presented here with the main function of the hippocampus during retrieval being "recontextualization," or the reconstruction of memory using overlapping traces. As memories get older, they are decontextualized due to competition among partially overlapping traces and become more semantic and reliant on neocortical storage. In this framework dubbed the Competitive Trace Theory (CTT), consolidation events that lead to the strengthening of memories enhance conceptual knowledge (semantic memory) at the expense of contextual details (episodic memory). As a result, remote memories are more likely to have a stronger semantic representation. At the same time, remote memories are also more likely to include illusory details. The CTT is a novel candidate model that may provide some resolution to the memory consolidation debate.

Competitive Trace Theory: A Role for the Hippocampus in Contextual Interference during Retrieval

PubMed Central

Yassa, Michael A.; Reagh, Zachariah M.

2013-01-01

Much controversy exists regarding the role of the hippocampus in retrieval. The two dominant and competing accounts have been the Standard Model of Systems Consolidation (SMSC) and Multiple Trace Theory (MTT), which specifically make opposing predictions as to the necessity of the hippocampus for retrieval of remote memories. Under SMSC, memories eventually become independent of the hippocampus as they become more reliant on cortical connectivity, and thus the hippocampus is not required for retrieval of remote memories, only recent ones. MTT on the other hand claims that the hippocampus is always required no matter the age of the memory. We argue that this dissociation may be too simplistic, and a continuum model may be better suited to address the role of the hippocampus in retrieval of remote memories. Such a model is presented here with the main function of the hippocampus during retrieval being “recontextualization,” or the reconstruction of memory using overlapping traces. As memories get older, they are decontextualized due to competition among partially overlapping traces and become more semantic and reliant on neocortical storage. In this framework dubbed the Competitive Trace Theory (CTT), consolidation events that lead to the strengthening of memories enhance conceptual knowledge (semantic memory) at the expense of contextual details (episodic memory). As a result, remote memories are more likely to have a stronger semantic representation. At the same time, remote memories are also more likely to include illusory details. The CTT is a novel candidate model that may provide some resolution to the memory consolidation debate. PMID:23964216

Genius or Dynamic Learner? Benjamin Franklin's Path to Greatness

ERIC Educational Resources Information Center

Marcum, James W.

2008-01-01

While the remarkable accomplishments of Benjamin Franklin are unparalleled, the means of their attainment can be considered more accessible to ordinary people and not necessarily attributable to a special genius. The steady development of Franklin's knowledge and skills is traced in light of a new model of "dynamic learning," which is a method…

Using Model-Tracing to Conduct Performance Assessment of Students' Inquiry Skills within a Microworld

ERIC Educational Resources Information Center

Gobert, Janice D.; Koedinger, Kenneth R.

2011-01-01

The National frameworks for science emphasize inquiry skills (NRC, 1996), however, in typical classroom practice, science learning often focuses on rote learning in part because science process skills are difficult to assess (Fadel, Honey, & Pasnick, 2007) and rote knowledge is prioritized on high-stakes tests. Short answer assessments of…

The top quark (20 years after the discovery)

DOE PAGES

Boos, Eduard; Brandt, Oleg; Denisov, Dmitri; ...

2015-09-10

On the twentieth anniversary of the observation of the top quark, we trace our understanding of this heaviest of all known particles from the prediction of its existence, through the searches and discovery, to the current knowledge of its production mechanisms and properties. We also discuss the central role of the top quark in the Standard Model and the windows that it opens for seeking new physics beyond the Standard Model.

Model description and evaluation of the mark-recapture survival model used to parameterize the 2012 status and threats analysis for the Florida manatee (Trichechus manatus latirostris)

USGS Publications Warehouse

Langtimm, Catherine A.; Kendall, William L.; Beck, Cathy A.; Kochman, Howard I.; Teague, Amy L.; Meigs-Friend, Gaia; Peñaloza, Claudia L.

2016-11-30

This report provides supporting details and evidence for the rationale, validity and efficacy of a new mark-recapture model, the Barker Robust Design, to estimate regional manatee survival rates used to parameterize several components of the 2012 version of the Manatee Core Biological Model (CBM) and Threats Analysis (TA).  The CBM and TA provide scientific analyses on population viability of the Florida manatee subspecies (Trichechus manatus latirostris) for U.S. Fish and Wildlife Service’s 5-year reviews of the status of the species as listed under the Endangered Species Act.  The model evaluation is presented in a standardized reporting framework, modified from the TRACE (TRAnsparent and Comprehensive model Evaluation) protocol first introduced for environmental threat analyses.  We identify this new protocol as TRACE-MANATEE SURVIVAL and this model evaluation specifically as TRACE-MANATEE SURVIVAL, Barker RD version 1. The longer-term objectives of the manatee standard reporting format are to (1) communicate to resource managers consistent evaluation information over sequential modeling efforts; (2) build understanding and expertise on the structure and function of the models; (3) document changes in model structures and applications in response to evolving management objectives, new biological and ecological knowledge, and new statistical advances; and (4) provide greater transparency for management and research review.

Automated knowledge-base refinement

NASA Technical Reports Server (NTRS)

Mooney, Raymond J.

1994-01-01

Over the last several years, we have developed several systems for automatically refining incomplete and incorrect knowledge bases. These systems are given an imperfect rule base and a set of training examples and minimally modify the knowledge base to make it consistent with the examples. One of our most recent systems, FORTE, revises first-order Horn-clause knowledge bases. This system can be viewed as automatically debugging Prolog programs based on examples of correct and incorrect I/O pairs. In fact, we have already used the system to debug simple Prolog programs written by students in a programming language course. FORTE has also been used to automatically induce and revise qualitative models of several continuous dynamic devices from qualitative behavior traces. For example, it has been used to induce and revise a qualitative model of a portion of the Reaction Control System (RCS) of the NASA Space Shuttle. By fitting a correct model of this portion of the RCS to simulated qualitative data from a faulty system, FORTE was also able to correctly diagnose simple faults in this system.

Knowledge engineering tools for reasoning with scientific observations and interpretations: a neural connectivity use case.

PubMed

Russ, Thomas A; Ramakrishnan, Cartic; Hovy, Eduard H; Bota, Mihail; Burns, Gully A P C

2011-08-22

We address the goal of curating observations from published experiments in a generalizable form; reasoning over these observations to generate interpretations and then querying this interpreted knowledge to supply the supporting evidence. We present web-application software as part of the 'BioScholar' project (R01-GM083871) that fully instantiates this process for a well-defined domain: using tract-tracing experiments to study the neural connectivity of the rat brain. The main contribution of this work is to provide the first instantiation of a knowledge representation for experimental observations called 'Knowledge Engineering from Experimental Design' (KEfED) based on experimental variables and their interdependencies. The software has three parts: (a) the KEfED model editor - a design editor for creating KEfED models by drawing a flow diagram of an experimental protocol; (b) the KEfED data interface - a spreadsheet-like tool that permits users to enter experimental data pertaining to a specific model; (c) a 'neural connection matrix' interface that presents neural connectivity as a table of ordinal connection strengths representing the interpretations of tract-tracing data. This tool also allows the user to view experimental evidence pertaining to a specific connection. BioScholar is built in Flex 3.5. It uses Persevere (a noSQL database) as a flexible data store and PowerLoom® (a mature First Order Logic reasoning system) to execute queries using spatial reasoning over the BAMS neuroanatomical ontology. We first introduce the KEfED approach as a general approach and describe its possible role as a way of introducing structured reasoning into models of argumentation within new models of scientific publication. We then describe the design and implementation of our example application: the BioScholar software. This is presented as a possible biocuration interface and supplementary reasoning toolkit for a larger, more specialized bioinformatics system: the Brain Architecture Management System (BAMS).

Knowledge engineering tools for reasoning with scientific observations and interpretations: a neural connectivity use case

PubMed Central

2011-01-01

Background We address the goal of curating observations from published experiments in a generalizable form; reasoning over these observations to generate interpretations and then querying this interpreted knowledge to supply the supporting evidence. We present web-application software as part of the 'BioScholar' project (R01-GM083871) that fully instantiates this process for a well-defined domain: using tract-tracing experiments to study the neural connectivity of the rat brain. Results The main contribution of this work is to provide the first instantiation of a knowledge representation for experimental observations called 'Knowledge Engineering from Experimental Design' (KEfED) based on experimental variables and their interdependencies. The software has three parts: (a) the KEfED model editor - a design editor for creating KEfED models by drawing a flow diagram of an experimental protocol; (b) the KEfED data interface - a spreadsheet-like tool that permits users to enter experimental data pertaining to a specific model; (c) a 'neural connection matrix' interface that presents neural connectivity as a table of ordinal connection strengths representing the interpretations of tract-tracing data. This tool also allows the user to view experimental evidence pertaining to a specific connection. BioScholar is built in Flex 3.5. It uses Persevere (a noSQL database) as a flexible data store and PowerLoom® (a mature First Order Logic reasoning system) to execute queries using spatial reasoning over the BAMS neuroanatomical ontology. Conclusions We first introduce the KEfED approach as a general approach and describe its possible role as a way of introducing structured reasoning into models of argumentation within new models of scientific publication. We then describe the design and implementation of our example application: the BioScholar software. This is presented as a possible biocuration interface and supplementary reasoning toolkit for a larger, more specialized bioinformatics system: the Brain Architecture Management System (BAMS). PMID:21859449

Trace Elements in River Waters

NASA Astrophysics Data System (ADS)

Gaillardet, J.; Viers, J.; Dupré, B.

2003-12-01

Trace elements are characterized by concentrations lower than 1 mg L-1 in natural waters. This means that trace elements are not considered when "total dissolved solids" are calculated in rivers, lakes, or groundwaters, because their combined mass is not significant compared to the sum of Na+, K+, Ca2+, Mg2+, H4SiO4, HCO3-, CO32-, SO42-, Cl-, and NO3-. Therefore, most of the elements, except about ten of them, occur at trace levels in natural waters. Being trace elements in natural waters does not necessarily qualify them as trace elements in rocks. For example, aluminum, iron, and titanium are major elements in rocks, but they occur as trace elements in waters, due to their low mobility at the Earth's surface. Conversely, trace elements in rocks such as chlorine and carbon are major elements in waters.The geochemistry of trace elements in river waters, like that of groundwater and seawater, is receiving increasing attention. This growing interest is clearly triggered by the technical advances made in the determination of concentrations at lower levels in water. In particular, the development of inductively coupled plasma mass spectrometry (ICP-MS) has considerably improved our knowledge of trace-element levels in waters since the early 1990s. ICP-MS provides the capability of determining trace elements having isotopes of interest for geochemical dating or tracing, even where their dissolved concentrations are extremely low.The determination of trace elements in natural waters is motivated by a number of issues. Although rare, trace elements in natural systems can play a major role in hydrosystems. This is particularly evident for toxic elements such as aluminum, whose concentrations are related to the abundance of fish in rivers. Many trace elements have been exploited from natural accumulation sites and used over thousands of years by human activities. Trace elements are therefore highly sensitive indexes of human impact from local to global scale. Pollution impact studies require knowledge of the natural background concentrations and knowledge of pollutant behavior. For example, it is generally accepted that rare earth elements (REEs) in waters behave as good analogues for the actinides, whose natural levels are quite low and rarely measured. Water quality investigations have clearly been a stimulus for measurement of toxic heavy metals in order to understand their behavior in natural systems.From a more fundamental point of view, it is crucial to understand the behavior of trace elements in geological processes, in particular during chemical weathering and transport by waters. Trace elements are much more fractionated by weathering and transport processes than major elements, and these fractionations give clues for understanding the nature and intensity of the weathering+transport processes. This has not only applications for weathering studies or for the past mobilization and transport of elements to the ocean (potentially recorded in the sediments), but also for the possibility of better utilization of trace elements in the aqueous environment as an exploration tool.In this chapter, we have tried to review the recent literature on trace elements in rivers, in particular by incorporating the results derived from recent ICP-MS measurements. We have favored a "field approach" by focusing on studies of natural hydrosystems. The basic questions which we want to address are the following: What are the trace element levels in river waters? What controls their abundance in rivers and fractionation in the weathering+transport system? Are trace elements, like major elements in rivers, essentially controlled by source-rock abundances? What do we know about the chemical speciation of trace elements in water? To what extent do colloids and interaction with solids regulate processes of trace elements in river waters? Can we relate the geochemistry of trace elements in aquatic systems to the periodic table? And finally, are we able to satisfactorily model and predict the behavior of most of the trace elements in hydrosystems?An impressive literature has dealt with experimental works on aqueous complexation, uptake of trace elements by surface complexation (inorganic and organic), uptake by living organisms (bioaccumulation) that we have not reported here, except when the results of such studies directly explain natural data. As continental waters encompass a greater range of physical and chemical conditions, we focus on river waters and do not discuss trace elements in groundwaters, lakes, and the ocean. In lakes and in the ocean, the great importance of life processes in regulating trace elements is probably the major difference from rivers.Section 5.09.2 of this chapter reports data. We will review the present-day literature on trace elements in rivers to show that our knowledge is still poor. By comparing with the continental abundances, a global mobility index is calculated for each trace element. The spatial and temporal variability of trace-element concentrations in rivers will be shown to be important. In Section 5.09.3, sources of trace elements in river waters are indicated. We will point out the great diversity of sources and the importance of global anthropogenic contamination for a number of elements. The question of inorganic and organic speciation of trace elements in river water will then be addressed in Section 5.09.4, considering some general relationships between speciation and placement in the periodic table. In Section 5.09.5, we will show that studies on organic-rich rivers have led to an exploration of the "colloidal world" in rivers. Colloids are small particles, passing through the conventional filters used to separate dissolved and suspended loads in rivers. They appear as major carriers of trace elements in rivers and considerably complicate aqueous-speciation calculation. Finally, in Section 5.09.6, the significance of interactions between solutes and solid surfaces in river waters will be reviewed. Regulation by surfaces is of major importance for a great range of elements. Although for both colloids and surface interactions, some progress has been made, we are still far from a unified model that can accurately predict trace-element concentrations in natural water systems. This is mainly due to our poor physical description of natural colloids, surface site complexation, and their interaction with solutes.

Validity of the Born approximation for beyond Gaussian weak lensing observables

DOE PAGES

Petri, Andrea; Haiman, Zoltan; May, Morgan

2017-06-06

Accurate forward modeling of weak lensing (WL) observables from cosmological parameters is necessary for upcoming galaxy surveys. Because WL probes structures in the nonlinear regime, analytical forward modeling is very challenging, if not impossible. Numerical simulations of WL features rely on ray tracing through the outputs of N-body simulations, which requires knowledge of the gravitational potential and accurate solvers for light ray trajectories. A less accurate procedure, based on the Born approximation, only requires knowledge of the density field, and can be implemented more efficiently and at a lower computational cost. In this work, we use simulations to show thatmore » deviations of the Born-approximated convergence power spectrum, skewness and kurtosis from their fully ray-traced counterparts are consistent with the smallest nontrivial O(Φ 3) post-Born corrections (so-called geodesic and lens-lens terms). Our results imply a cancellation among the larger O(Φ 4) (and higher order) terms, consistent with previous analytic work. We also find that cosmological parameter bias induced by the Born-approximated power spectrum is negligible even for a LSST-like survey, once galaxy shape noise is considered. When considering higher order statistics such as the κ skewness and kurtosis, however, we find significant bias of up to 2.5σ. Using the LensTools software suite, we show that the Born approximation saves a factor of 4 in computing time with respect to the full ray tracing in reconstructing the convergence.« less

Validity of the Born approximation for beyond Gaussian weak lensing observables

NASA Astrophysics Data System (ADS)

Petri, Andrea; Haiman, Zoltán; May, Morgan

2017-06-01

Accurate forward modeling of weak lensing (WL) observables from cosmological parameters is necessary for upcoming galaxy surveys. Because WL probes structures in the nonlinear regime, analytical forward modeling is very challenging, if not impossible. Numerical simulations of WL features rely on ray tracing through the outputs of N -body simulations, which requires knowledge of the gravitational potential and accurate solvers for light ray trajectories. A less accurate procedure, based on the Born approximation, only requires knowledge of the density field, and can be implemented more efficiently and at a lower computational cost. In this work, we use simulations to show that deviations of the Born-approximated convergence power spectrum, skewness and kurtosis from their fully ray-traced counterparts are consistent with the smallest nontrivial O (Φ3) post-Born corrections (so-called geodesic and lens-lens terms). Our results imply a cancellation among the larger O (Φ4) (and higher order) terms, consistent with previous analytic work. We also find that cosmological parameter bias induced by the Born-approximated power spectrum is negligible even for a LSST-like survey, once galaxy shape noise is considered. When considering higher order statistics such as the κ skewness and kurtosis, however, we find significant bias of up to 2.5 σ . Using the LensTools software suite, we show that the Born approximation saves a factor of 4 in computing time with respect to the full ray tracing in reconstructing the convergence.

Tolerance to cadmium in plants: the special case of hyperaccumulators.

PubMed

Verbruggen, Nathalie; Juraniec, Michal; Baliardini, Cecilia; Meyer, Claire-Lise

2013-08-01

On sols highly polluted by trace metallic elements the majority of plant species are excluders, limiting the entry and the root to shoot translocation of trace metals. However a rare class of plants called hyperaccumulators possess remarkable adaptation because those plants combine extremely high tolerance degrees and foliar accumulation of trace elements. Hyperaccumulators have recently gained considerable interest, because of their potential use in phytoremediation, phytomining and biofortification. On a more fundamental point of view hyperaccumulators of trace metals are case studies to understand metal homeostasis and detoxification mechanisms. Hyperaccumulation of trace metals usually depends on the enhancement of at least four processes, which are the absorption from the soil, the loading in the xylem in the roots and the unloading from the xylem in the leaves and the detoxification in the shoot. Cadmium is one of the most toxic trace metallic elements for living organisms and its accumulation in the environment is recognized as a worldwide concern. To date, only nine species have been recognized as Cd hyperaccumulators that is to say able to tolerate and accumulate more than 0.01 % Cd in shoot dry biomass. Among these species, four belong to the Brassicaceae family with Arabidopsis halleri and Noccaea caerulescens being considered as models. An update of our knowledge on the evolution of hyperaccumulators will be presented here.

Leveraging Semantic Labels for Multi-level Abstraction in Medical Process Mining and Trace Comparison.

PubMed

Leonardi, Giorgio; Striani, Manuel; Quaglini, Silvana; Cavallini, Anna; Montani, Stefania

2018-05-21

Many medical information systems record data about the executed process instances in the form of an event log. In this paper, we present a framework, able to convert actions in the event log into higher level concepts, at different levels of abstraction, on the basis of domain knowledge. Abstracted traces are then provided as an input to trace comparison and semantic process discovery. Our abstraction mechanism is able to manage non trivial situations, such as interleaved actions or delays between two actions that abstract to the same concept. Trace comparison resorts to a similarity metric able to take into account abstraction phase penalties, and to deal with quantitative and qualitative temporal constraints in abstracted traces. As for process discovery, we rely on classical algorithms embedded in the framework ProM, made semantic by the capability of abstracting the actions on the basis of their conceptual meaning. The approach has been tested in stroke care, where we adopted abstraction and trace comparison to cluster event logs of different stroke units, to highlight (in)correct behavior, abstracting from details. We also provide process discovery results, showing how the abstraction mechanism allows to obtain stroke process models more easily interpretable by neurologists. Copyright © 2018. Published by Elsevier Inc.

Trace-Based Microanalytic Measurement of Self-Regulated Learning Processes

ERIC Educational Resources Information Center

Siadaty, Melody; Gaševic, Dragan; Hatala, Marek

2016-01-01

To keep pace with today's rapidly growing knowledge-driven society, productive self-regulation of one's learning processes are essential. We introduce and discuss a trace-based measurement protocol to measure the effects of scaffolding interventions on self-regulated learning (SRL) processes. It guides tracing of learners' actions in a learning…

Musculoskeletal model-based control interface mimics physiologic hand dynamics during path tracing task

NASA Astrophysics Data System (ADS)

Crouch, Dustin L.; (Helen Huang, He

2017-06-01

Objective. We investigated the feasibility of a novel, customizable, simplified EMG-driven musculoskeletal model for estimating coordinated hand and wrist motions during a real-time path tracing task. Approach. A two-degree-of-freedom computational musculoskeletal model was implemented for real-time EMG-driven control of a stick figure hand displayed on a computer screen. After 5-10 minutes of undirected practice, subjects were given three attempts to trace 10 straight paths, one at a time, with the fingertip of the virtual hand. Able-bodied subjects completed the task on two separate test days. Main results. Across subjects and test days, there was a significant linear relationship between log-transformed measures of accuracy and speed (Pearson’s r  =  0.25, p  <  0.0001). The amputee subject could coordinate movement between the wrist and MCP joints, but favored metacarpophalangeal joint motion more highly than able-bodied subjects in 8 of 10 trials. For able-bodied subjects, tracing accuracy was lower at the extremes of the model’s range of motion, though there was no apparent relationship between tracing accuracy and fingertip location for the amputee. Our result suggests that, unlike able-bodied subjects, the amputee’s motor control patterns were not accustomed to the multi-joint dynamics of the wrist and hand, possibly as a result of post-amputation cortical plasticity, disuse, or sensory deficits. Significance. To our knowledge, our study is one of very few that have demonstrated the real-time simultaneous control of multi-joint movements, especially wrist and finger movements, using an EMG-driven musculoskeletal model, which differs from the many data-driven algorithms that dominate the literature on EMG-driven prosthesis control. Real-time control was achieved with very little training and simple, quick (~15 s) calibration. Thus, our model is potentially a practical and effective control platform for multifunctional myoelectric prostheses that could restore more life-like hand function for individuals with upper limb amputation.

Trace Analysis and Spatial Reasoning: An Example of Intensive Cognitive Diagnosis and Its Implications for Testing.

DTIC Science & Technology

1987-09-01

of Intensive Cognitive Diagnosis and Its Implications for Testing Stellan Ohisson Learning Research and Development Center, University of Pittsburgh...7a. NAME OF MONITORING ORGANIZATION Learning Research & Development (if applicable) Cognitive Science Program Center, University of Pittsburg Office of...GAGE All other eaitions are obolSete. UN CLASS " UNLASSI FIED Ohlsson 1 Trace Analysis Knowledge and Understanding in Human Learning Knowledge and

OceanRoute: Vessel Mobility Data Processing and Analyzing Model Based on MapReduce

NASA Astrophysics Data System (ADS)

Liu, Chao; Liu, Yingjian; Guo, Zhongwen; Jing, Wei

2018-06-01

The network coverage is a big problem in ocean communication, and there is no low-cost solution in the short term. Based on the knowledge of Mobile Delay Tolerant Network (MDTN), the mobility of vessels can create the chances of end-to-end communication. The mobility pattern of vessel is one of the key metrics on ocean MDTN network. Because of the high cost, few experiments have focused on research of vessel mobility pattern for the moment. In this paper, we study the traces of more than 4000 fishing and freight vessels. Firstly, to solve the data noise and sparsity problem, we design two algorithms to filter the noise and complement the missing data based on the vessel's turning feature. Secondly, after studying the traces of vessels, we observe that the vessel's traces are confined by invisible boundary. Thirdly, through defining the distance between traces, we design MR-Similarity algorithm to find the mobility pattern of vessels. Finally, we realize our algorithm on cluster and evaluate the performance and accuracy. Our results can provide the guidelines on design of data routing protocols on ocean MDTN.

Direct rapid analysis of trace bioavailable soil macronutrients by chemometrics-assisted energy dispersive X-ray fluorescence and scattering spectrometry.

PubMed

Kaniu, M I; Angeyo, K H; Mwala, A K; Mangala, M J

2012-06-04

Precision agriculture depends on the knowledge and management of soil quality (SQ), which calls for affordable, simple and rapid but accurate analysis of bioavailable soil nutrients. Conventional SQ analysis methods are tedious and expensive. We demonstrate the utility of a new chemometrics-assisted energy dispersive X-ray fluorescence and scattering (EDXRFS) spectroscopy method we have developed for direct rapid analysis of trace 'bioavailable' macronutrients (i.e. C, N, Na, Mg, P) in soils. The method exploits, in addition to X-ray fluorescence, the scatter peaks detected from soil pellets to develop a model for SQ analysis. Spectra were acquired from soil samples held in a Teflon holder analyzed using (109)Cd isotope source EDXRF spectrometer for 200 s. Chemometric techniques namely principal component analysis (PCA), partial least squares (PLS) and artificial neural networks (ANNs) were utilized for pattern recognition based on fluorescence and Compton scatter peaks regions, and to develop multivariate quantitative calibration models based on Compton scatter peak respectively. SQ analyses were realized with high CMD (R(2)>0.9) and low SEP (0.01% for N and Na, 0.05% for C, 0.08% for Mg and 1.98 μg g(-1) for P). Comparison of predicted macronutrients with reference standards using a one-way ANOVA test showed no statistical difference at 95% confidence level. To the best of the authors' knowledge, this is the first time that an XRF method has demonstrated utility in trace analysis of macronutrients in soil or related matrices. Copyright © 2012 Elsevier B.V. All rights reserved.

Analytic expressions for the black-sky and white-sky albedos of the cosine lobe model.

PubMed

Goodin, Christopher

2013-05-01

The cosine lobe model is a bidirectional reflectance distribution function (BRDF) that is commonly used in computer graphics to model specular reflections. The model is both simple and physically plausible, but physical quantities such as albedo have not been related to the parameterization of the model. In this paper, analytic expressions for calculating the black-sky and white-sky albedos from the cosine lobe BRDF model with integer exponents will be derived, to the author's knowledge for the first time. These expressions for albedo can be used to place constraints on physics-based simulations of radiative transfer such as high-fidelity ray-tracing simulations.

Domain-Specific Knowledge and Why Teaching Generic Skills Does Not Work

ERIC Educational Resources Information Center

Tricot, André; Sweller, John

2014-01-01

Domain-general cognitive knowledge has frequently been used to explain skill when domain-specific knowledge held in long-term memory may provide a better explanation. An emphasis on domain-general knowledge may be misplaced if domain-specific knowledge is the primary factor driving acquired intellectual skills. We trace the long history of…

Fate of Trace Metals in Anaerobic Digestion.

PubMed

Fermoso, F G; van Hullebusch, E D; Guibaud, G; Collins, G; Svensson, B H; Carliell-Marquet, C; Vink, J P M; Esposito, G; Frunzo, L

2015-01-01

A challenging, and largely uncharted, area of research in the field of anaerobic digestion science and technology is in understanding the roles of trace metals in enabling biogas production. This is a major knowledge gap and a multifaceted problem involving metal chemistry; physical interactions of metal and solids; microbiology; and technology optimization. Moreover, the fate of trace metals, and the chemical speciation and transport of trace metals in environments--often agricultural lands receiving discharge waters from anaerobic digestion processes--simultaneously represents challenges for environmental protection and opportunities to close process loops in anaerobic digestion.

Deficiencies and toxicities of trace elements and micronutrients in tropical soils: Limitations of knowledge and future research needs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davies, B.E.

1997-01-01

This article reviews present knowledge concerning deficiencies and toxicities of trace elements and micronutrients in tropical soils. The myth that all tropical soils are highly leached and nutrient-poor is challenged. Continuing use of the term laterite by ecologists and geologists is criticized and adoption of plinthite is urged. The trace element content of plinthite and its possible influence on micronutrient availability are described. Micronutrient limitations of tropical agriculture are related to soil type and formation, and the special problem of aluminum toxicity in acid soils is discussed in both agricultural and ecological contexts. Studies of micronutrient cycling in tropical forestsmore » or savannas are needed to supplement the emerging picture of the complexities of major element cycles in these ecosystems.« less

The Use of Pro/Engineer CAD Software and Fishbowl Tool Kit in Ray-tracing Analysis

NASA Technical Reports Server (NTRS)

Nounu, Hatem N.; Kim, Myung-Hee Y.; Ponomarev, Artem L.; Cucinotta, Francis A.

2009-01-01

This document is designed as a manual for a user who wants to operate the Pro/ENGINEER (ProE) Wildfire 3.0 with the NASA Space Radiation Program's (SRP) custom-designed Toolkit, called 'Fishbowl', for the ray tracing of complex spacecraft geometries given by a ProE CAD model. The analysis of spacecraft geometry through ray tracing is a vital part in the calculation of health risks from space radiation. Space radiation poses severe risks of cancer, degenerative diseases and acute radiation sickness during long-term exploration missions, and shielding optimization is an important component in the application of radiation risk models. Ray tracing is a technique in which 3-dimensional (3D) vehicle geometry can be represented as the input for the space radiation transport code and subsequent risk calculations. In ray tracing a certain number of rays (on the order of 1000) are used to calculate the equivalent thickness, say of aluminum, of the spacecraft geometry seen at a point of interest called the dose point. The rays originate at the dose point and terminate at a homogenously distributed set of points lying on a sphere that circumscribes the spacecraft and that has its center at the dose point. The distance a ray traverses in each material is converted to aluminum or other user-selected equivalent thickness. Then all equivalent thicknesses are summed up for each ray. Since each ray points to a direction, the aluminum equivalent of each ray represents the shielding that the geometry provides to the dose point from that particular direction. This manual will first list for the user the contact information for help in installing ProE and Fishbowl in addition to notes on the platform support and system requirements information. Second, the document will show the user how to use the software to ray trace a Pro/E-designed 3-D assembly and will serve later as a reference for troubleshooting. The user is assumed to have previous knowledge of ProE and CAD modeling.

Initial correlations in open-systems dynamics: The Jaynes-Cummings model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smirne, Andrea; Vacchini, Bassano; INFN, Sezione di Milano, Via Celoria 16, I-20133 Milano

2010-12-15

Employing the trace distance as a measure for the distinguishability of quantum states, we study the influence of initial correlations on the dynamics of open systems. We concentrate on the Jaynes-Cummings model for which the knowledge of the exact joint dynamics of system and reservoir allows the treatment of initial states with arbitrary correlations. As a measure for the correlations in the initial state we consider the trace distance between the system-environment state and the product of its marginal states. In particular, we examine the correlations contained in the thermal equilibrium state for the total system, analyze their dependence onmore » the temperature and on the coupling strength, and demonstrate their connection to the entanglement properties of the eigenstates of the Hamiltonian. A detailed study of the time dependence of the distinguishability of the open system states evolving from the thermal equilibrium state and its corresponding uncorrelated product state shows that the open system dynamically uncovers typical features of the initial correlations.« less

Leveraging Organizational Learning for Knowledge and Performance

ERIC Educational Resources Information Center

Cavaleri, Steven A.

2004-01-01

This article examines the alignment and fit between knowledge management and organizational learning to determine the potential feasibility of integrating the two approaches. The philosophical roots of both disciplines are traced to common ground in a philosophy known as "pragmatism". Early generation forms of knowledge management are critiqued…

To analyse a trace or not? Evaluating the decision-making process in the criminal investigation.

PubMed

Bitzer, Sonja; Ribaux, Olivier; Albertini, Nicola; Delémont, Olivier

2016-05-01

In order to broaden our knowledge and understanding of the decision steps in the criminal investigation process, we started by evaluating the decision to analyse a trace and the factors involved in this decision step. This decision step is embedded in the complete criminal investigation process, involving multiple decision and triaging steps. Considering robbery cases occurring in a geographic region during a 2-year-period, we have studied the factors influencing the decision to submit biological traces, directly sampled on the scene of the robbery or on collected objects, for analysis. The factors were categorised into five knowledge dimensions: strategic, immediate, physical, criminal and utility and decision tree analysis was carried out. Factors in each category played a role in the decision to analyse a biological trace. Interestingly, factors involving information available prior to the analysis are of importance, such as the fact that a positive result (a profile suitable for comparison) is already available in the case, or that a suspect has been identified through traditional police work before analysis. One factor that was taken into account, but was not significant, is the matrix of the trace. Hence, the decision to analyse a trace is not influenced by this variable. The decision to analyse a trace first is very complex and many of the tested variables were taken into account. The decisions are often made on a case-by-case basis. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Useful Knowledge? Concepts, Values, and Access in American Education, 1776-1840.

ERIC Educational Resources Information Center

Watkinson, James D.

1990-01-01

Traces changing concepts of what constituted useful knowledge, especially as revealed in journals, in the United States from 1776 to 1840. Identifies a widening knowledge gap--corresponding with industrialization--between increasingly elitist, specialized learned societies and mechanics/farmers. Argues that as science grew more professionalized,…

TB tracer teams in South Africa: knowledge, practices and challenges of tracing TB patients to improve adherence.

PubMed

Bristow, Claire C; Podewils, Laura Jean; Bronner, Liza Ellen; Bantubani, Nonkqubela; Walt, Martie van der; Peters, Annatjie; Mametja, David

2013-09-04

In 2008-2009 the South African National Tuberculosis (TB) Program (NTP) implemented a national pilot project, the TB Tracer Project, aiming to decrease default rates and improve patient outcomes. The current study aimed to inform the NTP by describing the knowledge, attitudes, and practices of TB program personnel involved with tracing activities. A self-administered written questionnaire was sent to TB staff, managers and tracer team leaders to assess basic TB knowledge, attitudes and practices. Descriptive statistics were used to summarize results and the chi-squared statistic was used to compare responses of staff at facilities that participated in the TB Tracer Project (tracer) and those that followed standard NTP care (non-tracer). Of 560 total questionnaires distributed, 270 were completed and returned (response rate 48%). Total TB knowledge ranged from 70.8-86.3% correct across all response groups. However, just over half (range 50-59.3%) of each respondent group was able to correctly identify the four components of a DOT encounter. A patient no longer feeling sick was cited by 72.1% of respondents as the reason patients fail to adhere to treatment. Tracer teams were viewed as an effective means to get patients to return to treatment by 96.3% of health facility level respondents. Tracer team leaders reported concerns including lack of logistical support (41.7%), insufficient physical safety precautions (41.7%), and inadequate protection from contracting TB (39.1%). Upon patients returning to treatment at the clinic, facilities included in the TB Tracer Project were significantly more likely to discuss alternate DOTS arrangements than non-tracer facilities (79.2 vs. 66.4%, p = 0.03). This study identified key components of knowledge, attitudes, and practices regarding TB patient tracing activities in South Africa. Educating patients on the essential need to complete treatment irrespective of clinical symptoms may help improve treatment adherence. Future scale-up and integration of TB tracing activities as part of standard TB management should include provisions for standardized training of personnel on the critical elements of DOTS, and for ensuring appropriate supervision, logistical support, and physical safety and TB transmission protection of tracing teams.

Both Trace and Delay Conditioning of Evaluative Responses Depend on Contingency Awareness

ERIC Educational Resources Information Center

Kattner, Florian; Ellermeier, Wolfgang; Tavakoli, Paniz

2012-01-01

Whereas previous evaluative conditioning (EC) studies produced inconsistent results concerning the role of contingency knowledge, there are classical eye-blink conditioning studies suggesting that declarative processes are involved in trace conditioning but not in delay conditioning. In two EC experiments pairing neutral sounds (conditioned…

Hydrological Modelling and Sensitivity Analysis Using Topmodel and Simulated Annealing Techniques.application To The Haute-mentue Catchment(switzerland).

NASA Astrophysics Data System (ADS)

Balin Talamba, D.; Higy, C.; Joerin, C.; Musy, A.

The paper presents an application concerning the hydrological modelling for the Haute-Mentue catchment, located in western Switzerland. A simplified version of Topmodel, developed in a Labview programming environment, was applied in the aim of modelling the hydrological processes on this catchment. Previous researches car- ried out in this region outlined the importance of the environmental tracers in studying the hydrological behaviour and an important knowledge has been accumulated dur- ing this period concerning the mechanisms responsible for runoff generation. In con- formity with the theoretical constraints, Topmodel was applied for an Haute-Mentue sub-catchment where tracing experiments showed constantly low contributions of the soil water during the flood events. The model was applied for two humid periods in 1998. First, the model calibration was done in order to provide the best estimations for the total runoff. Instead, the simulated components (groundwater and rapid flow) showed far deviations from the reality indicated by the tracing experiments. Thus, a new calibration was performed including additional information given by the environ- mental tracing. The calibration of the model was done by using simulated annealing (SA) techniques, which are easy to implement and statistically allow for converging to a global minimum. The only problem is that the method is time and computer consum- ing. To improve this, a version of SA was used which is known as very fast-simulated annealing (VFSA). The principles are the same as for the SA technique. The random search is guided by certain probability distribution and the acceptance criterion is the same as for SA but the VFSA allows for better taking into account the ranges of vari- ation of each parameter. Practice with Topmodel showed that the energy function has different sensitivities along different dimensions of the parameter space. The VFSA algorithm allows differentiated search in relation with the sensitivity of the param- eters. The environmental tracing was used in the aim of constraining the parameter space in order to better simulate the hydrological behaviour of the catchment. VFSA outlined issues for characterising the significance of Topmodel input parameters as well as their uncertainty for the hydrological modelling.

Technology needs assessment of an atmospheric observation system for tropospheric research missions, part 1

NASA Technical Reports Server (NTRS)

Alvarado, D. R.; Bortner, M. H.; Grenda, R. N.; Frippel, G. G.; Halsey, H.; Neste, S. L.; Kritikos, H.; Keafer, L. S.; Deryder, L. J.

1982-01-01

The technology advancements needed to implement the atmospheric observation satellite systems for air quality research were identified. Tropospheric measurements are considered. The measurements and sensors are based on a model of knowledge objectives in atmospheric science. A set of potential missions and attendant spacecraft and sensors is postulated. The results show that the predominant technology needs will be in passive and active sensors for accurate and frequent global measurements of trace gas concentration profiles.

Forests under climate change and air pollution: gaps in understanding and future directions for research.

PubMed

Matyssek, R; Wieser, G; Calfapietra, C; de Vries, W; Dizengremel, P; Ernst, D; Jolivet, Y; Mikkelsen, T N; Mohren, G M J; Le Thiec, D; Tuovinen, J-P; Weatherall, A; Paoletti, E

2012-01-01

Forests in Europe face significant changes in climate, which in interaction with air quality changes, may significantly affect forest productivity, stand composition and carbon sequestration in both vegetation and soils. Identified knowledge gaps and research needs include: (i) interaction between changes in air quality (trace gas concentrations), climate and other site factors on forest ecosystem response, (ii) significance of biotic processes in system response, (iii) tools for mechanistic and diagnostic understanding and upscaling, and (iv) the need for unifying modelling and empirical research for synthesis. This position paper highlights the above focuses, including the global dimension of air pollution as part of climate change and the need for knowledge transfer to enable reliable risk assessment. A new type of research site in forest ecosystems ("supersites") will be conducive to addressing these gaps by enabling integration of experimentation and modelling within the soil-plant-atmosphere interface, as well as further model development. Copyright © 2011 Elsevier Ltd. All rights reserved.

Listen to Your Inner Voice: Using Your Intuition in Outdoor Leadership.

ERIC Educational Resources Information Center

Cook, Janice

Intuition is knowledge of something without the conscious use of reasoning. The question of where intuitive knowledge comes from may be addressed from neurophysiological, spiritual, or philosophical perspectives. In some cases, hunches may be traced to the unconscious processing of immediate sensory input with previous knowledge. In other cases,…

Examining Multiple Dimensions of Word Knowledge for Content Vocabulary Understanding

ERIC Educational Resources Information Center

Cervetti, Gina N.; Tilson, Jennifer L.; Castek, Jill; Bravo, Marco A.; Trainin, Guy

2012-01-01

This study traces the development of a vocabulary measure designed to assess multiple types of word knowledge. The assessment, which was administered in conjunction with a science unit about weather and the water cycle for third-and-fourth graders, included items for six knowledge types--recognition, definition, classification/example, context,…

"The Voice inside Herself": Transforming Gendered Academic Identities in Educational Administration

ERIC Educational Resources Information Center

Wallace, Janice; Wallin, Dawn

2015-01-01

This paper traces the academic identity formation(s) of 10 Canadian female academics whose disciplinary knowledge is in the field of educational administration. We trace the ways in which discourses of gender, institutional power, and other cultural and social influences shaped their sense of themselves as academics in the highly patriarchal…

Trace Elements in Parenteral Nutrition: Considerations for the Prescribing Clinician

PubMed Central

Jin, Jennifer; Mulesa, Leanne; Carrilero Rouillet, Mariana

2017-01-01

Trace elements (TEs) are an essential component of parenteral nutrition (PN). Over the last few decades, there has been increased experience with PN, and with this knowledge more information about the management of trace elements has become available. There is increasing awareness of the effects of deficiencies and toxicities of certain trace elements. Despite this heightened awareness, much is still unknown in terms of trace element monitoring, the accuracy of different assays, and current TE contamination of solutions. The supplementation of TEs is a complex and important part of the PN prescription. Understanding the role of different disease states and the need for reduced or increased doses is essential. Given the heterogeneity of the PN patients, supplementation should be individualized. PMID:28452962

Trace elements in parenteral nutrition: a practical guide for dosage and monitoring for adult patients.

PubMed

Fessler, Theresa A

2013-12-01

Parenteral nutrition (PN) is a life-sustaining therapy for hundreds of thousands of people who have severe impairment of gastrointestinal function. Trace elements are a small but very important part of PN that can be overlooked during busy practice. Serious complications can result from trace element deficiencies and toxicities, and this is especially problematic during times of product shortages. Practical information on parenteral trace element use can be gleaned from case reports, some retrospective studies, and very few randomized controlled trials. A general knowledge of trace element metabolism and excretion, deficiency and toxicity symptoms, products, optimal dosages, and strategies for supplementation, restriction, and monitoring will equip practitioners to provide optimal care for their patients who depend on PN.

Trace Elements in Parenteral Nutrition: Considerations for the Prescribing Clinician.

PubMed

Jin, Jennifer; Mulesa, Leanne; Carrilero Rouillet, Mariana

2017-04-28

Trace elements (TEs) are an essential component of parenteral nutrition (PN). Over the last few decades, there has been increased experience with PN, and with this knowledge more information about the management of trace elements has become available. There is increasing awareness of the effects of deficiencies and toxicities of certain trace elements. Despite this heightened awareness, much is still unknown in terms of trace element monitoring, the accuracy of different assays, and current TE contamination of solutions. The supplementation of TEs is a complex and important part of the PN prescription. Understanding the role of different disease states and the need for reduced or increased doses is essential. Given the heterogeneity of the PN patients, supplementation should be individualized.

From position-specific isotope labeling towards soil fluxomics: a novel toolbox to assess the microbial impact on biogeochemical cycles

NASA Astrophysics Data System (ADS)

Apostel, C.; Dippold, M. A.; Kuzyakov, Y.

2015-12-01

Understanding the microbial impact on C and nutrient cycles is one of the most important challenges in terrestrial biogeochemistry. Transformation of low molecular weight organic substances (LMWOS) is a key step in all biogeochemical cycles because 1) all high molecular substances pass the LMWOS pool during their degradation and 2) only LMWOS can be taken up by microorganisms intact. Thus, the transformations of LMWOS are dominated by biochemical pathways of the soil microorganisms. Thus, understanding fluxes and transformations in soils requires a detailed knowledge on the microbial metabolic network and its control mechanism. Tracing C fate in soil by isotopes became on of the most applied and promising biogeochemistry tools but studies were nearly exclusively based on uniformly labeled substances. However, such tracers do not allow the differentiation of the intact use of the initial substances from its transformation to metabolites. The novel tool of position-specific labeling enables to trace molecule atoms separately and thus to determine the cleavage of molecules - a prerequisite for metabolic tracing. Position-specific labeling of basic metabolites and quantification of isotope incorporation in CO2 and bulk soil enabled following the basic metabolic pathways of microorganisms. However, the combination of position-specific 13C labeling with compound-specific isotope analysis of microbial biomarkers and metabolites like phospholipid fatty acids (PLFA) or amino sugars revealed new insights into the soil fluxome: First, it enables tracing specific anabolic pathways in diverse microbial communities in soils e.g. carbon starvation pathways versus pathways reflecting microbial growth. Second, it allows identification of specific pathways of individual functional microbial groups in soils in situ. Tracing metabolic pathways and understanding their regulating factors are crucial for soil C fluxomics i.e. the unravaling of the complex network of C transformations. Quantitative models to assess microbial group specific metabolic pathways can be generated and parameterized by this approach. The knowledge of submolecular C transformation steps and its regulating factors is essential for understanding C cycling and long-term C storage in soils.

Atmospheric refraction: a history.

PubMed

Lehn, Waldemar H; van der Werf, Siebren

2005-09-20

We trace the history of atmospheric refraction from the ancient Greeks up to the time of Kepler. The concept that the atmosphere could refract light entered Western science in the second century B.C. Ptolemy, 300 years later, produced the first clearly defined atmospheric model, containing air of uniform density up to a sharp upper transition to the ether, at which the refraction occurred. Alhazen and Witelo transmitted his knowledge to medieval Europe. The first accurate measurements were made by Tycho Brahe in the 16th century. Finally, Kepler, who was aware of unusually strong refractions, used the Ptolemaic model to explain the first documented and recognized mirage (the Novaya Zemlya effect).

Accounting for rainfall evaporation using dual-polarization radar and mesoscale model data

NASA Astrophysics Data System (ADS)

Pallardy, Quinn; Fox, Neil I.

2018-02-01

Implementation of dual-polarization radar should allow for improvements in quantitative precipitation estimates due to dual-polarization capability allowing for the retrieval of the second moment of the gamma drop size distribution. Knowledge of the shape of the DSD can then be used in combination with mesoscale model data to estimate the motion and evaporation of each size of drop falling from the height at which precipitation is observed by the radar to the surface. Using data from Central Missouri at a range between 130 and 140 km from the operational National Weather Service radar a rain drop tracing scheme was developed to account for the effects of evaporation, where individual raindrops hitting the ground were traced to the point in space and time where they interacted with the radar beam. The results indicated evaporation played a significant role in radar rainfall estimation in situations where the atmosphere was relatively dry. Improvements in radar estimated rainfall were also found in these situations by accounting for evaporation. The conclusion was made that the effects of raindrop evaporation were significant enough to warrant further research into the inclusion high resolution model data in the radar rainfall estimation process for appropriate locations.

Routes of Knowledge: Toward a Methodological Framework for Tracing the Historical Impact of International Organizations

ERIC Educational Resources Information Center

Christensen, Ivan Lind; Ydesen, Christian

2015-01-01

Recent trends in the historiography of international organizations are occupied with tracing their historical impact on national contexts. There is, however, no consensus on how to conduct this type of analysis methodologically. This article examines the methodological challenges arising from this type of research. While a great deal of…

A dual-trace model for visual sensory memory.

PubMed

Cappiello, Marcus; Zhang, Weiwei

2016-11-01

Visual sensory memory refers to a transient memory lingering briefly after the stimulus offset. Although previous literature suggests that visual sensory memory is supported by a fine-grained trace for continuous representation and a coarse-grained trace of categorical information, simultaneous separation and assessment of these traces can be difficult without a quantitative model. The present study used a continuous estimation procedure to test a novel mathematical model of the dual-trace hypothesis of visual sensory memory according to which visual sensory memory could be modeled as a mixture of 2 von Mises (2VM) distributions differing in standard deviation. When visual sensory memory and working memory (WM) for colors were distinguished using different experimental manipulations in the first 3 experiments, the 2VM model outperformed Zhang and Luck (2008) standard mixture model (SM) representing a mixture of a single memory trace and random guesses, even though SM outperformed 2VM for WM. Experiment 4 generalized 2VM's advantages of fitting visual sensory memory data over SM from color to orientation. Furthermore, a single trace model and 4 other alternative models were ruled out, suggesting the necessity and sufficiency of dual traces for visual sensory memory. Together these results support the dual-trace model of visual sensory memory and provide a preliminary inquiry into the nature of information loss from visual sensory memory to WM. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Traces and echoes of De Architectura by Marcus Vitruvius Pollio in the work of Xu Guangqi in 17th century China

NASA Astrophysics Data System (ADS)

Cigola, Michela; Fang, Yibing

2016-03-01

This study aims to investigate the role played by Xu Guangqi (1562-1633), minister of the Ming Dynasty, in the development of European scientific and technical knowledge in China between the 16th and 17th centuries by analyzing a book of Western technology that he wrote, namely, Taixi Shuifa ( On Western Hydraulics). Several Western books related to machine knowledge are searched to trace the source of the illustrations in Taixi Shuifa. We found that Archimedes' screw and Ctesibius' machine, which are included in Vitruvius' De Architectura volumes, also appear in the work of Xu Guangqi.

Current issues in atmospheric change

NASA Technical Reports Server (NTRS)

1987-01-01

In response to questions about the effects of long-term, global-scale changes in the atmosphere raised in congressional hearings, a group of leading experts held a two-day workshop to survey the state of current knowledge about atmospheric changes and their implications. The review focuses on the sources, concentrations, and changes of those gases most directly linked to human activities, i.e., carbon dioxide, ozone, and the chlorofluorocarbons; the direct physical effects of rising concentrations of trace gases. The review discusses the uncertainties associated with the knowledge of current trends and possible future changes, including ozone trends and the Antarctic ozone hole, and the impacts of rising concentrations of trace gases.

TB tracer teams in South Africa: knowledge, practices and challenges of tracing TB patients to improve adherence

PubMed Central

2013-01-01

Background In 2008–2009 the South African National Tuberculosis (TB) Program (NTP) implemented a national pilot project, the TB Tracer Project, aiming to decrease default rates and improve patient outcomes. The current study aimed to inform the NTP by describing the knowledge, attitudes, and practices of TB program personnel involved with tracing activities. Methods A self-administered written questionnaire was sent to TB staff, managers and tracer team leaders to assess basic TB knowledge, attitudes and practices. Descriptive statistics were used to summarize results and the chi-squared statistic was used to compare responses of staff at facilities that participated in the TB Tracer Project (tracer) and those that followed standard NTP care (non-tracer). Results Of 560 total questionnaires distributed, 270 were completed and returned (response rate 48%). Total TB knowledge ranged from 70.8-86.3% correct across all response groups. However, just over half (range 50–59.3%) of each respondent group was able to correctly identify the four components of a DOT encounter. A patient no longer feeling sick was cited by 72.1% of respondents as the reason patients fail to adhere to treatment. Tracer teams were viewed as an effective means to get patients to return to treatment by 96.3% of health facility level respondents. Tracer team leaders reported concerns including lack of logistical support (41.7%), insufficient physical safety precautions (41.7%), and inadequate protection from contracting TB (39.1%). Upon patients returning to treatment at the clinic, facilities included in the TB Tracer Project were significantly more likely to discuss alternate DOTS arrangements than non-tracer facilities (79.2 vs. 66.4%, p = 0.03). Conclusions This study identified key components of knowledge, attitudes, and practices regarding TB patient tracing activities in South Africa. Educating patients on the essential need to complete treatment irrespective of clinical symptoms may help improve treatment adherence. Future scale-up and integration of TB tracing activities as part of standard TB management should include provisions for standardized training of personnel on the critical elements of DOTS, and for ensuring appropriate supervision, logistical support, and physical safety and TB transmission protection of tracing teams. PMID:24007294

Application of graph-based semi-supervised learning for development of cyber COP and network intrusion detection

NASA Astrophysics Data System (ADS)

Levchuk, Georgiy; Colonna-Romano, John; Eslami, Mohammed

2017-05-01

The United States increasingly relies on cyber-physical systems to conduct military and commercial operations. Attacks on these systems have increased dramatically around the globe. The attackers constantly change their methods, making state-of-the-art commercial and military intrusion detection systems ineffective. In this paper, we present a model to identify functional behavior of network devices from netflow traces. Our model includes two innovations. First, we define novel features for a host IP using detection of application graph patterns in IP's host graph constructed from 5-min aggregated packet flows. Second, we present the first application, to the best of our knowledge, of Graph Semi-Supervised Learning (GSSL) to the space of IP behavior classification. Using a cyber-attack dataset collected from NetFlow packet traces, we show that GSSL trained with only 20% of the data achieves higher attack detection rates than Support Vector Machines (SVM) and Naïve Bayes (NB) classifiers trained with 80% of data points. We also show how to improve detection quality by filtering out web browsing data, and conclude with discussion of future research directions.

A new method for automatic discontinuity traces sampling on rock mass 3D model

NASA Astrophysics Data System (ADS)

Umili, G.; Ferrero, A.; Einstein, H. H.

2013-02-01

A new automatic method for discontinuity traces mapping and sampling on a rock mass digital model is described in this work. The implemented procedure allows one to automatically identify discontinuity traces on a Digital Surface Model: traces are detected directly as surface breaklines, by means of maximum and minimum principal curvature values of the vertices that constitute the model surface. Color influence and user errors, that usually characterize the trace mapping on images, are eliminated. Also trace sampling procedures based on circular windows and circular scanlines have been implemented: they are used to infer trace data and to calculate values of mean trace length, expected discontinuity diameter and intensity of rock discontinuities. The method is tested on a case study: results obtained applying the automatic procedure on the DSM of a rock face are compared to those obtained performing a manual sampling on the orthophotograph of the same rock face.

An Exploration of the Source of Key Concepts and Principles in Froebel's Educational Theory.

ERIC Educational Resources Information Center

Lee, Sang-Wook; Evans, Roy

1996-01-01

Traces the origins of Friedrich Froebel's views on children, curriculum, pedagogics, and didactics; the underpinnings of his beliefs concerning the nature of knowledge; and the kinds of knowledge and dispositions he believed were appropriate for children to acquire. (MDM)

Parallel labeling experiments for pathway elucidation and (13)C metabolic flux analysis.

PubMed

Antoniewicz, Maciek R

2015-12-01

Metabolic pathway models provide the foundation for quantitative studies of cellular physiology through the measurement of intracellular metabolic fluxes. For model organisms metabolic models are well established, with many manually curated genome-scale model reconstructions, gene knockout studies and stable-isotope tracing studies. However, for non-model organisms a similar level of knowledge is often lacking. Compartmentation of cellular metabolism in eukaryotic systems also presents significant challenges for quantitative (13)C-metabolic flux analysis ((13)C-MFA). Recently, innovative (13)C-MFA approaches have been developed based on parallel labeling experiments, the use of multiple isotopic tracers and integrated data analysis, that allow more rigorous validation of pathway models and improved quantification of metabolic fluxes. Applications of these approaches open new research directions in metabolic engineering, biotechnology and medicine. Copyright © 2015 Elsevier Ltd. All rights reserved.

Ray-tracing of shape metrology data of grazing incidence x-ray astronomy mirrors

NASA Astrophysics Data System (ADS)

Zocchi, Fabio E.; Vernani, Dervis

2008-07-01

A number of future X-ray astronomy missions (e.g. Simbol-X, eROSITA) plan to utilize high throughput grazing incidence optics with very lightweight mirrors. The severe mass specifications require a further optimization of the existing technology with the consequent need of proper optical numerical modeling capabilities for both the masters and the mirrors. A ray tracing code has been developed for the simulation of the optical performance of type I Wolter masters and mirrors starting from 2D and 3D metrology data. In particular, in the case of 2D measurements, a 3D data set is reconstructed on the basis of dimensional references and used for the optical analysis by ray tracing. In this approach, the actual 3D shape is used for the optical analysis, thus avoiding the need of combining the separate contributions of different 2D measurements that require the knowledge of their interactions which is not normally available. The paper describes the proposed approach and presents examples of application on a prototype engineering master in the frame of ongoing activities carried out for present and future X-ray missions.

Tracing Cosmic Dawn

NASA Astrophysics Data System (ADS)

Fialkov, Anastasia

2018-05-01

Observational effort is on the way to probe the 21-cm of neutral hydrogen from the epochs of Reionization and Cosmic Dawn. Our current poor knowledge of high redshift astrophysics results in a large uncertainty in the theoretically predicted 21-cm signal. A recent parameter study that is highlighted here explores the variety of 21-cm signals resulting from viable astrophysical scenarios. Model-independent relations between the shape of the signal and the underlying astrophysics are discussed. Finally, I briefly note on possible alternative probes of the high redshift Universe, specifically Fast Radio Bursts.

Screening wish theories: dream psychologies and early cinema.

PubMed

Marinelli, Lydia

2006-03-01

The analogy between dream and film represents a central thread in the psychoanalytic discussion of cinema. Using examples taken from films created between 1900 and 1906, this paper develops a typology of dream scenes in early film. The basis for the proposed typology is provided by the dream knowledge in circulation toward the end of the nineteenth century. This knowledge was fed by a great variety of sources, some of them in the proximity of scientific research and some of them far from it, including wish-fulfilling prognostic models and those based on the reservoir of memory or on bodily stimuli. By setting cinema in a context of contemporary dream psychologies, it is possible to trace the specific conditions under which the analogy between dream and cinema could become effective.

Modeling technology innovation: how science, engineering, and industry methods can combine to generate beneficial socioeconomic impacts.

PubMed

Stone, Vathsala I; Lane, Joseph P

2012-05-16

Government-sponsored science, technology, and innovation (STI) programs support the socioeconomic aspects of public policies, in addition to expanding the knowledge base. For example, beneficial healthcare services and devices are expected to result from investments in research and development (R&D) programs, which assume a causal link to commercial innovation. Such programs are increasingly held accountable for evidence of impact-that is, innovative goods and services resulting from R&D activity. However, the absence of comprehensive models and metrics skews evidence gathering toward bibliometrics about research outputs (published discoveries), with less focus on transfer metrics about development outputs (patented prototypes) and almost none on econometrics related to production outputs (commercial innovations). This disparity is particularly problematic for the expressed intent of such programs, as most measurable socioeconomic benefits result from the last category of outputs. This paper proposes a conceptual framework integrating all three knowledge-generating methods into a logic model, useful for planning, obtaining, and measuring the intended beneficial impacts through the implementation of knowledge in practice. Additionally, the integration of the Context-Input-Process-Product (CIPP) model of evaluation proactively builds relevance into STI policies and programs while sustaining rigor. The resulting logic model framework explicitly traces the progress of knowledge from inputs, following it through the three knowledge-generating processes and their respective knowledge outputs (discovery, invention, innovation), as it generates the intended socio-beneficial impacts. It is a hybrid model for generating technology-based innovations, where best practices in new product development merge with a widely accepted knowledge-translation approach. Given the emphasis on evidence-based practice in the medical and health fields and "bench to bedside" expectations for knowledge transfer, sponsors and grantees alike should find the model useful for planning, implementing, and evaluating innovation processes. High-cost/high-risk industries like healthcare require the market deployment of technology-based innovations to improve domestic society in a global economy. An appropriate balance of relevance and rigor in research, development, and production is crucial to optimize the return on public investment in such programs. The technology-innovation process needs a comprehensive operational model to effectively allocate public funds and thereby deliberately and systematically accomplish socioeconomic benefits.

Modeling technology innovation: How science, engineering, and industry methods can combine to generate beneficial socioeconomic impacts

PubMed Central

2012-01-01

Background Government-sponsored science, technology, and innovation (STI) programs support the socioeconomic aspects of public policies, in addition to expanding the knowledge base. For example, beneficial healthcare services and devices are expected to result from investments in research and development (R&D) programs, which assume a causal link to commercial innovation. Such programs are increasingly held accountable for evidence of impact—that is, innovative goods and services resulting from R&D activity. However, the absence of comprehensive models and metrics skews evidence gathering toward bibliometrics about research outputs (published discoveries), with less focus on transfer metrics about development outputs (patented prototypes) and almost none on econometrics related to production outputs (commercial innovations). This disparity is particularly problematic for the expressed intent of such programs, as most measurable socioeconomic benefits result from the last category of outputs. Methods This paper proposes a conceptual framework integrating all three knowledge-generating methods into a logic model, useful for planning, obtaining, and measuring the intended beneficial impacts through the implementation of knowledge in practice. Additionally, the integration of the Context-Input-Process-Product (CIPP) model of evaluation proactively builds relevance into STI policies and programs while sustaining rigor. Results The resulting logic model framework explicitly traces the progress of knowledge from inputs, following it through the three knowledge-generating processes and their respective knowledge outputs (discovery, invention, innovation), as it generates the intended socio-beneficial impacts. It is a hybrid model for generating technology-based innovations, where best practices in new product development merge with a widely accepted knowledge-translation approach. Given the emphasis on evidence-based practice in the medical and health fields and “bench to bedside” expectations for knowledge transfer, sponsors and grantees alike should find the model useful for planning, implementing, and evaluating innovation processes. Conclusions High-cost/high-risk industries like healthcare require the market deployment of technology-based innovations to improve domestic society in a global economy. An appropriate balance of relevance and rigor in research, development, and production is crucial to optimize the return on public investment in such programs. The technology-innovation process needs a comprehensive operational model to effectively allocate public funds and thereby deliberately and systematically accomplish socioeconomic benefits. PMID:22591638

Development of simulated and ovine models of extracorporeal life support to improve understanding of circuit-host interactions.

PubMed

Shekar, Kiran; Fung, Yoke L; Diab, Sara; Mullany, Daniel V; McDonald, Charles I; Dunster, Kimble R; Fisquet, Stephanie; Platts, David G; Stewart, David; Wallis, Steven C; Smith, Maree T; Roberts, Jason A; Fraser, John F

2012-06-01

Extracorporeal life support (ECLS) is a lifesaving technology that is being increasingly used in patients with severe cardiorespiratory failure. However, ECLS is not without risks. The biosynthetic interface between the patient and the circuit can significantly alter inflammation, coagulation, pharmacokinetics and disposition of trace elements. The relative contributions of the pump, disease and patient in propagating these alterations are difficult to quantify in critically ill patients with multiple organ failure. To design a model where the relevance of individual components could be assessed, in isolation and in combination. Four ECLS models were developed and tested - an in-vitro simulated ECLS circuit; and ECLS in healthy sheep, sheep with acute lung injury (ALI), and sheep with ALI together with transfusion of old or new blood. Successful design of in-vitro and in-vivo models. We successfully conducted multiple experiments in the simulated circuits and ECLS runs in healthy and ALI sheep. We obtained preliminary data on inflammation, coagulation, histology, pharmacokinetics and trace element disposition during ECLS. The establishment of in-vitro and in-vivo models provides a powerful means for enhancing knowledge of the pathophysiology associated with ECLS and identification of key factors likely to influence patient outcomes. A clearer description of the contribution of disease and therapeutic interventions may allow improved design of equipment, membranes, medicines and physiological goals for improved patient care.

Institutional Authority and Traces of Intergenerational Conflict

ERIC Educational Resources Information Center

Tufan, Ismail; Kilic, Sultan; Tokgoz, Nimet; Howe, Jurgen; Yaman, Hakan

2010-01-01

While society's level of education increases in a modernization process, the knowledge monopoly is taken over by the young. Increasing demand on knowledge attained through organized education leads to increasing power by the young. In the modernizing society of Turkey, this kind of struggle will occur between intellectual groups. Results of this…

Vertical Integration: Teachers' Knowledge and Teachers' Voice.

ERIC Educational Resources Information Center

Corrie, L.

1995-01-01

Traces the theoretical basis for vertical integration in early school years. Contrasts transmission-based pedagogy with a higher level of teacher control, and acquirer-based pedagogy with a higher level of student control. Suggests that early childhood pedagogy will be maintained when teachers are able to articulate their pedagogical knowledge and…

Unsettling Binary Thinking: Tracing an Analytic Trajectory of the Place of Indigenous Musical Knowledge in the Academy

ERIC Educational Resources Information Center

Hess, Juliet

2015-01-01

Six years ago, I wrote a composition about the state of indigenous music in the academy with an accompanying research paper. In this work, I attempted to trace the presence of indigenous music in the institution both musically and through an anti-colonial lens. The writing was structured around three musical snapshots entitled Subjugation,…

Self-Consistent Model of Magnetospheric Ring Current and Propagating Electromagnetic Ion Cyclotron Waves: Waves in Multi-Ion Magnetosphere

NASA Technical Reports Server (NTRS)

Khazanov, G. V.; Gamayunov, K. V.; Gallagher, D. L.; Kozyra, J. U.

2006-01-01

The further development of a self-consistent theoretical model of interacting ring current ions and electromagnetic ion cyclotron waves (Khazanov et al., 2003) is presented In order to adequately take into account wave propagation and refraction in a multi-ion magnetosphere, we explicitly include the ray tracing equations in our previous self-consistent model and use the general form of the wave kinetic equation. This is a major new feature of the present model and, to the best of our knowledge, the ray tracing equations for the first time are explicitly employed on a global magnetospheric scale in order to self-consistently simulate the spatial, temporal, and spectral evolution of the ring current and of electromagnetic ion cyclotron waves To demonstrate the effects of EMIC wave propagation and refraction on the wave energy distribution and evolution, we simulate the May 1998 storm. The main findings of our simulation can be summarized as follows. First, owing to the density gradient at the plasmapause, the net wave refraction is suppressed, and He+-mode grows preferably at the plasmapause. This result is in total agreement with previous ray tracing studies and is very clearly found in presented B field spectrograms. Second, comparison of global wave distributions with the results from another ring current model (Kozyra et al., 1997) reveals that this new model provides more intense and more highly plasmapause-organized wave distributions during the May 1998 storm period Finally, it is found that He(+)-mode energy distributions are not Gaussian distributions and most important that wave energy can occupy not only the region of generation, i.e., the region of small wave normal angles, but all wave normal angles, including those to near 90 . The latter is extremely crucial for energy transfer to thermal plasmaspheric electrons by resonant Landau damping and subsequent downward heat transport and excitation of stable auroral red arcs.

Self-Consistent Model of Magnetospheric Ring Current and Propagating Electromagnetic Ion Cyclotron Waves. 1; Waves in Multi Ion Magnetosphere

NASA Technical Reports Server (NTRS)

Khazanov, G. V.; Gumayunov, K. V.; Gallagher, D. L.; Kozyra, J. U.

2006-01-01

The further development of a self-consistent theoretical model of interacting ring current ions and electromagnetic ion cyclotron waves [Khazanov et al., 2003] is presented. In order to adequately take into account the wave propagation and refraction in a multi-ion plasmasphere, we explicitly include the ray tracing equations in our previous self-consistent model and use the general form of the wave kinetic equation. This is a major new feature of the present model and, to the best of our knowledge, the ray tracing equations for the first time are explicitly employed on a global magnetospheric scale in order to self-consistently simulate spatial, temporal, and spectral evolutions of the ring current and electromagnetic ion cyclotron waves. To demonstrate the effects of EMIC wave propagation and refraction on the EMIC wave energy distributions and evolution we simulate the May 1998 storm. The main findings of our simulation can be summarized as follows. First, due to the density gradient at the plasmapause, the net wave refraction is suppressed, and He(+)-mode grows preferably at plasmapause. This result is in a total agreement with the previous ray tracing studies, and very clear observed in presented B-field spectrograms. Second, comparison the global wave distributions with the results from other ring current model [Kozyra et al., 1997] reveals that our model provides more intense and higher plasmapause organized distributions during the May, 1998 storm period. Finally, the found He(+)-mode energy distributions are not Gaussian distributions, and most important that wave energy can occupy not only the region of generation, i. e. the region of small wave normal angles, but the entire wave normal angle region and even only the region near 90 degrees. The latter is extremely crucial for energy transfer to thermal plasmaspheric electrons by resonant Landau damping, and subsequent downward heat transport and excitation of stable auroral red arcs.

Phoneme restoration and empirical coverage of interactive activation and adaptive resonance models of human speech processing

PubMed Central

Magnuson, James S.

2015-01-01

Grossberg and Kazerounian [(2011). J. Acoust. Soc. Am. 130, 440–460] present a model of sequence representation for spoken word recognition, the cARTWORD model, which simulates essential aspects of phoneme restoration. Grossberg and Kazerounian also include simulations with the TRACE model presented by McClelland and Elman [(1986). Cognit. Psychol. 18, 1–86] that seem to indicate that TRACE cannot simulate phoneme restoration. Grossberg and Kazerounian also claim cARTWORD should be preferred to TRACE because of TRACE's implausible approach to sequence representation (reduplication of time-specific units) and use of non-modulatory feedback (i.e., without position-specific bottom-up support). This paper responds to Grossberg and Kazerounian first with TRACE simulations that account for phoneme restoration when appropriately constructed noise is used (and with minor changes to TRACE phoneme definitions), then reviews the case for reduplicated units and feedback as implemented in TRACE, as well as TRACE's broad and deep coverage of empirical data. Finally, it is argued that cARTWORD is not comparable to TRACE because cARTWORD cannot represent sequences with repeated elements, has only been implemented with small phoneme and lexical inventories, and has been applied to only one phenomenon (phoneme restoration). Without evidence that cARTWORD captures a similar range and detail of human spoken language processing as alternative models, it is premature to prefer cARTWORD to TRACE. PMID:25786959

The electronic encapsulation of knowledge in hydraulics, hydrology and water resources

NASA Astrophysics Data System (ADS)

Abbott, Michael B.

The rapidly developing practice of encapsulating knowledge in electronic media is shown to lead necessarily to the restructuring of the knowledge itself. The consequences of this for hydraulics, hydrology and more general water-resources management are investigated in particular relation to current process-simulation, real-time control and advice-serving systems. The generic properties of the electronic knowledge encapsulator are described, and attention is drawn to the manner in which knowledge 'goes into hiding' through encapsulation. This property is traced in the simple situations of pure mathesis and in the more complex situations of taxinomia using one example each from hydraulics and hydrology. The consequences for systems architectures are explained, pointing to the need for multi-agent architectures for ecological modelling and for more general hydroinformatics systems also. The relevance of these developments is indicated by reference to ongoing projects in which they are currently being realised. In conclusion, some more general epistemological aspects are considered within the same context. As this contribution is so much concerned with the processes of signification and communication, it has been partly shaped by the theory of semiotics, as popularised by Eco ( A Theory of Semiotics, Indiana University, Bloomington, 1977).

What We Have Learned About the Existing Trace Element Partitioning data During the Population Phase of traceDs

NASA Astrophysics Data System (ADS)

Nielsen, R. L.; Ghiorso, M. S.; Trischman, T.

2015-12-01

The database traceDs is designed to provide a transparent and accessible resource of experimental partitioning data. It now includes ~ 90% of all the experimental trace element partitioning data (~4000 experiments) produced over the past 45 years, and is accessible through a web based interface (using the portal lepr.ofm-research.org). We set a minimum standard for inclusion, with the threshold criteria being the inclusion of: Experimental conditions (temperature, pressure, device, container, time, etc.) Major element composition of the phases Trace element analyses of the phases Data sources that did not report these minimum components were not included. The rationale for not including such data is that the degree of equilibration is unknown, and more important, no rigorous approach to modeling the behavior of trace elements is possible without knowledge of composition of the phases, and the temperature and pressure of formation/equilibration. The data are stored using a schema derived from that of the Library of Experimental Phase Relations (LEPR), modified to account for additional metadata, and restructured to permit multiple analytical entries for various element/technique/standard combinations. In the process of populating the database, we have learned a number of things about the existing published experimental partitioning data. Most important are: ~ 20% of the papers do not satisfy one or more of the threshold criteria. The standard format for presenting data is the average. This was developed as the standard during the time where there were space constraints for publication in spite of fact that all the information can now be published as electronic supplements. The uncertainties that are published with the compositional data are often not adequately explained (e.g. 1 or 2 sigma, standard deviation of the average, etc.). We propose a new set of publication standards for experimental data that include the minimum criteria described above, the publication of all analyses with error based on peak count rates and background, plus information on the structural state of the mineral (e.g. orthopyroxene vs. pigeonite).

Nitrogen Fate in a Phreatic Fluviokarst Watershed: a Stable Isotope, Sediment Tracing, and Numerical Modeling Approach

NASA Astrophysics Data System (ADS)

Husic, A.; Fox, J.; Ford, W. I., III; Agouridis, C.; Currens, J. C.; Taylor, C. J.

2017-12-01

Sediment tracing tools provide an insight into provenance, fate, and transport of sediment and, when coupled to stable isotopes, can elucidate in-stream biogeochemical processes. Particulate nitrogen fate in fluviokarst systems is a relatively unexplored area of research partially due to the complex hydrodynamics at play in karst systems. Karst topography includes turbulent conduits that transport groundwater and contaminants at speeds more typical of open channel flows than laminar Darcian flows. While it is accepted that karst hydro-geomorphology represents a hybrid surface-subsurface system for fluid, further investigation is needed to determine whether, and to what extent, karst systems behave like surface agricultural streams or porous media aquifers with respect to their role in nitrogen cycling. Our objective is to gain an understanding of in-conduit nitrogen processes and their effect on net nitrogen-exports from karst springs to larger waterbodies. The authors apply water, sediment, carbon, and nitrogen tracing techniques to analyze water for nitrate, sediment carbon and nitrogen, and stable sediment nitrogen isotope (δ15N). Thereafter, a new numerical model is formulated that: simulates dissolved inorganic nitrogen and sediment nitrogen transformations in the phreatic karst conduit; couples carbon turnover and nitrogen transformations in the model structure; and simulates the nitrogen stable isotope mass balance for the dissolved and sediment phases. Nitrogen tracing data results show a significant increase in δ15N of sediment nitrogen at the spring outlet relative to karst inputs indicating the potential for isotope fractionation during dissolved N uptake by bed sediments in the conduit and during denitrification within bed sediments. The new numerical modeling structure is then used to reproduce the data results and provide an estimate of the relative dominance of N uptake and denitrification within the surficial sediments of the karst conduit system. For the first time to our knowledge, results shed light on sediment processes that help control nutrient retention in phreatic karst conduits and tend to suggest that the karst systems behave as an intermediate N conveyor relative to surface agricultural streams and porous media aquifers.

Correlation between some selected trace metal concentrations in six species of fish from the Arabian Sea

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ashraf, M.; Jaffar, M.

1988-07-01

The role of trace metals in marine ecosystems has been keenly investigated during recent years. It is known that abundance of essential trace metals regulates the metal content in the organisms by homeostatic control mechanisms, which when cease to function cause essential trace metals to act in an either acutely or chronically toxic manner. Therefore, a correlation study based on essential and non-essential trace metal concentrations is imperative for extending the existing knowledge of bioaccumulation of trace metals in marine organisms. An attempt has been made in the present investigation to bring out quantitative correlations between the concentrations of iron,more » copper, lead and zinc in the edible muscle tissue of six species of marine fish: Salmon (salmon sole); tuna (thunnus thynnus); pomfret silver (pampus argenteus); Pomfret black (formioniger); long tail tuna (thynnus tonggel) and Indian oil sardine (sardinella longiceps). These fish are abundantly available in Pakistan along the coastal line of the Arabian Sea and have great commercial value. The computational analysis on the trace metal correlation was conducted using an MSTAT statistical package.« less

Communicating Leave No Trace ethics and practices: Efficacy of two-day trainer courses

USGS Publications Warehouse

Daniels, M.L.; Marion, J.L.

2005-01-01

Heavy recreational visitation within protected natural areas has resulted in many ecological impacts. Many of these impacts may be avoided or minimized through adoption of low-impact hiking and camping practices. Although ?No Trace? messages have been promoted in public lands since the 1970s, few studies have documented the reception and effectiveness of these messages. The U.S. Leave No Trace Center for Outdoor Ethics develops and promotes two-day Trainer courses that teach Leave No Trace (LNT) skills and ethics to outdoor professionals, groups, and interested individuals. This study examined the change in knowledge, ethics, and behavior of LNT Trainer course participants. The respondents were a convenience sample of participants in Trainer courses offered from April through August 2003. Trainer course instructors administered pre-course and post-course questionnaires to their participants, and we contacted participants individually with a followup questionnaire 4 months after completion of their course. Scores for each of the sections increased immediately following the course, and decreased slightly over the 4 months following the course. Overall, more than half of the knowledge and behavior items, and half of the ethics items, showed significant improvement from pre-course measures to the follow-up. Age, reported LNT experience, and backpacking experience affected the participants? pre-course knowledge and behavior scores. Younger, less experienced respondents also showed a greater improvement in behavior following the course. Trainer course participants also shared their LNT skills and ethics with others both formally and informally. In summary, the LNT Trainer course was successful in increasing participants? knowledge, ethics, and behavior, which they then shared with others. Since many low impact skills taught in the LNT curriculum are supported by scientific research, LNT educational programs have the potential to effectively minimize the environmental impacts caused by outdoor recreationists. Research implications for improving LNT training and instruction are described.

Infrared radiation models for atmospheric methane

NASA Technical Reports Server (NTRS)

Cess, R. D.; Kratz, D. P.; Caldwell, J.; Kim, S. J.

1986-01-01

Mutually consistent line-by-line, narrow-band and broad-band infrared radiation models are presented for methane, a potentially important anthropogenic trace gas within the atmosphere. Comparisons of the modeled band absorptances with existing laboratory data produce the best agreement when, within the band models, spurious band intensities are used which are consistent with the respective laboratory data sets, but which are not consistent with current knowledge concerning the intensity of the infrared fundamental band of methane. This emphasizes the need for improved laboratory band absorptance measurements. Since, when applied to atmospheric radiation calculations, the line-by-line model does not require the use of scaling approximations, the mutual consistency of the band models provides a means of appraising the accuracy of scaling procedures. It is shown that Curtis-Godson narrow-band and Chan-Tien broad-band scaling provide accurate means of accounting for atmospheric temperature and pressure variations.

A Method for Assessing the Retention of Trace Elements in Human Body Using Neural Network Technology

PubMed Central

Ragimov, Aligejdar; Faizullin, Rashat; Valiev, Vsevolod

2017-01-01

Models that describe the trace element status formation in the human organism are essential for a correction of micromineral (trace elements) deficiency. A direct trace element retention assessment in the body is difficult due to the many internal mechanisms. The trace element retention is determined by the amount and the ratio of incoming and excreted substance. So, the concentration of trace elements in drinking water characterizes the intake, whereas the element concentration in urine characterizes the excretion. This system can be interpreted as three interrelated elements that are in equilibrium. Since many relationships in the system are not known, the use of standard mathematical models is difficult. The artificial neural network use is suitable for constructing a model in the best way because it can take into account all dependencies in the system implicitly and process inaccurate and incomplete data. We created several neural network models to describe the retentions of trace elements in the human body. On the model basis, we can calculate the microelement levels in the body, knowing the trace element levels in drinking water and urine. These results can be used in health care to provide the population with safe drinking water. PMID:29065586

Numerical simulation of trace element transport on subsurface environment pollution in coal mine spoil.

PubMed

Qiang, Xue; Bing, Liang; Hui-yun, Wang; Lei, Liu

2006-01-01

An understanding of the dynamic behavior of trace elements leaching from coal mine spoil is important in predicting the groundwater quality. The relationship between trace element concentrations and leaching times, pH values of the media is studied. Column leaching tests conducted in the laboratory showed that there was a close correlation between pH value and trace element concentrations. The longer the leaching time, the higher the trace element concentrations. Different trace elements are differently affected by pH values of leaching media. A numerical model for water flow and trace element transport has been developed based on analyzing the characteristics of migration and transformation of trace elements leached from coal mine spoil. Solutions to the coupled model are accomplished by Eulerian-Lagrangian localized adjoint method. Numerical simulation shows that rainfall intensity determined maximum leaching depth. As rainfall intensity is 3.6ml/s, the outflow concentrations indicate a breakthrough of trace elements beyond the column base, with peak concentration at 90cm depth. And the subsurface pollution range has a trend of increase with time. The model simulations are compared to experimental results of trace element concentrations, with reasonable agreement between them. The analysis and modeling of trace elements suggested that the infiltration of rainwater through the mine spoil might lead to potential groundwater pollution. It provides theoretical evidence for quantitative assessment soil-water quality of trace element transport on environment pollution.

Integrating ethnobiological knowledge into biodiversity conservation in the Eastern Himalayas.

PubMed

O'Neill, Alexander R; Badola, Hemant K; Dhyani, Pitamber P; Rana, Santosh K

2017-03-29

Biocultural knowledge provides valuable insight into ecological processes, and can guide conservation practitioners in local contexts. In many regions, however, such knowledge is underutilized due to its often-fragmented record in disparate sources. In this article, we review and apply ethnobiological knowledge to biodiversity conservation in the Eastern Himalayas. Using Sikkim, India as a case study, we: (i) traced the history and trends of ethnobiological documentation; (ii) identified priority species and habitat types; and, (iii) analyzed within and among community differences pertaining to species use and management. Our results revealed that Sikkim is a biocultural hotspot, where six ethnic communities and 1128 species engage in biocultural relationships. Since the mid-1800s, the number of ethnobiological publications from Sikkim has exponentially increased; however, our results also indicate that much of this knowledge is both unwritten and partitioned within an aging, gendered, and caste or ethnic group-specific stratum of society. Reviewed species were primarily wild or wild cultivated, native to subtropical and temperate forests, and pend IUCN Red List of Threatened Species assessment. Our results demonstrate the value of engaging local knowledge holders as active participants in conservation, and suggest the need for further ethnobiological research in the Eastern Himalayas. Our interdisciplinary approach, which included rank indices and geospatial modelling, can help integrate diverse datasets into evidence-based policy.

Designing effective animations for computer science instruction

NASA Astrophysics Data System (ADS)

Grillmeyer, Oliver

This study investigated the potential for animations of Scheme functions to help novice computer science students understand difficult programming concepts. These animations used an instructional framework inspired by theories of constructivism and knowledge integration. The framework had students make predictions, reflect, and specify examples to animate to promote autonomous learning and result in more integrated knowledge. The framework used animated pivotal cases to help integrate disconnected ideas and restructure students' incomplete ideas by illustrating weaknesses in their existing models. The animations scaffolded learners, making the thought processes of experts more visible by modeling complex and tacit information. The animation design was guided by prior research and a methodology of design and refinement. Analysis of pilot studies led to the development of four design concerns to aid animation designers: clearly illustrate the mapping between objects in animations with the actual objects they represent, show causal connections between elements, draw attention to the salient features of the modeled system, and create animations that reduce complexity. Refined animations based on these design concerns were compared to computer-based tools, text-based instruction, and simpler animations that do not embody the design concerns. Four studies comprised this dissertation work. Two sets of animated presentations of list creation functions were compared to control groups. No significant differences were found in support of animations. Three different animated models of traces of recursive functions ranging from concrete to abstract representations were compared. No differences in learning gains were found between the three models in test performance. Three models of animations of applicative operators were compared with students using the replacement modeler and the Scheme interpreter. Significant differences were found favoring animations that addressed causality and salience in their design. Lastly, two binary tree search algorithm animations designed to reduce complexity were compared with hand-tracing of calls. Students made fewer mistakes in predicting the tree traversal when guided by the animations. However, the posttest findings were inconsistent. In summary, animations designed based on the design concerns did not consistently add value to instruction in the form investigated in this research.

The Representation of Knowledge in Image Understanding.

DTIC Science & Technology

1985-03-01

for memory traces? It’s been quite a few years since Lashley wrote his famous paper "Search for the Engram ." That paper pinpointed the fundamental...34 engram hunters," mostly empirical neurobiologists guided by their own often powerful working hypotheses, ensued and has continued that search with...progress. What is an Engram ? (Some Informal Considerations) Memory, viewed as traces of experience, is necessarily massively . distributed. As an example

Stochastic and Deterministic Approaches to Gas-grain Modeling of Interstellar Sources

NASA Astrophysics Data System (ADS)

Vasyunin, Anton; Herbst, Eric; Caselli, Paola

During the last decade, our understanding of the chemistry on surfaces of interstellar grains has been significantly enchanced. Extensive laboratory studies have revealed complex structure and dynamics in interstellar ice analogues, thus making our knowledge much more detailed. In addition, the first qualitative investigations of new processes were made, such as non-thermal chemical desorption of species from dust grains into the gas. Not surprisingly, the rapid growth of knowledge about the physics and chemistry of interstellar ices led to the development of a new generation of astrochemical models. The models are typically characterized by more detailed treatments of the ice physics and chemistry than previously. The utilized numerical approaches vary greatly from microscopic models, in which every single molecule is traced, to ``mean field'' macroscopic models, which simulate the evolution of averaged characteristics of interstellar ices, such as overall bulk composition. While microscopic models based on a stochastic Monte Carlo approach are potentially able to simulate the evolution of interstellar ices with an account of most subtle effects found in a laboratory, their use is often impractical due to limited knowledge about star-forming regions and huge computational demands. On the other hand, deterministic macroscopic models that often utilize kinetic rate equations are computationally efficient but experience difficulties in incorporation of such potentially important effects as ice segregation or discreteness of surface chemical reactions. In my talk, I will review the state of the art in the development of gas-grain astrochemical models. I will discuss how to incorporate key features of ice chemistry and dynamics in the gas-grain astrochemical models, and how the incorporation of recent laboratory findings into gas-grain models helps to better match observations.

Writing Science and Objectification: Selecting, Organizing, and Decontextualing Knowledge

ERIC Educational Resources Information Center

Wright, Laura J.

2008-01-01

This analysis focuses on two writing activities required by a middle school science curriculum unit to demonstrate how particular forms of writing guide students to frame their knowledge in important ways. Following the completion of charts and "Think and Write" questions related to a single scientific phenomenon, I trace how students identify the…

Southern Ocean biological iron cycling in the pre-whaling and present ecosystems

NASA Astrophysics Data System (ADS)

Maldonado, Maria T.; Surma, Szymon; Pakhomov, Evgeny A.

2016-11-01

This study aimed to create the first model of biological iron (Fe) cycling in the Southern Ocean food web. Two biomass mass-balanced Ecopath models were built to represent pre- and post-whaling ecosystem states (1900 and 2008). Functional group biomasses (tonnes wet weight km-2) were converted to biogenic Fe pools (kg Fe km-2) using published Fe content ranges. In both models, biogenic Fe pools and consumption in the pelagic Southern Ocean were highest for plankton and small nektonic groups. The production of plankton biomass, particularly unicellular groups, accounted for the highest annual Fe demand. Microzooplankton contributed most to biological Fe recycling, followed by carnivorous zooplankton and krill. Biological Fe recycling matched previous estimates, and, under most conditions, could entirely meet the Fe demand of bacterioplankton and phytoplankton. Iron recycling by large baleen whales was reduced 10-fold by whaling between 1900 and 2008. However, even under the 1900 scenario, the contribution of whales to biological Fe recycling was negligible compared with that of planktonic consumers. These models are a first step in examining oceanic-scale biological Fe cycling, highlighting gaps in our present knowledge and key questions for future research on the role of marine food webs in the cycling of trace elements in the sea. This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'.

Southern Ocean biological iron cycling in the pre-whaling and present ecosystems.

PubMed

Maldonado, Maria T; Surma, Szymon; Pakhomov, Evgeny A

2016-11-28

This study aimed to create the first model of biological iron (Fe) cycling in the Southern Ocean food web. Two biomass mass-balanced Ecopath models were built to represent pre- and post-whaling ecosystem states (1900 and 2008). Functional group biomasses (tonnes wet weight km -2 ) were converted to biogenic Fe pools (kg Fe km -2 ) using published Fe content ranges. In both models, biogenic Fe pools and consumption in the pelagic Southern Ocean were highest for plankton and small nektonic groups. The production of plankton biomass, particularly unicellular groups, accounted for the highest annual Fe demand. Microzooplankton contributed most to biological Fe recycling, followed by carnivorous zooplankton and krill. Biological Fe recycling matched previous estimates, and, under most conditions, could entirely meet the Fe demand of bacterioplankton and phytoplankton. Iron recycling by large baleen whales was reduced 10-fold by whaling between 1900 and 2008. However, even under the 1900 scenario, the contribution of whales to biological Fe recycling was negligible compared with that of planktonic consumers. These models are a first step in examining oceanic-scale biological Fe cycling, highlighting gaps in our present knowledge and key questions for future research on the role of marine food webs in the cycling of trace elements in the sea.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'. © 2016 The Author(s).

Factors leading to the involvement of Forensic Advisors in the Belgian criminal justice system.

PubMed

Bitzer, Sonja

2018-04-01

Forensic Advisors at the National Institute for Criminalistics and Criminology in Brussels act as advising body to the magistrate regarding analytical possibilities and the usefulness of trace analysis in a case. Initially, their function was devised to assist in complex murder cases with unknown offender. However, in a previous study, the increasing diversity of the cases they are requested for has been observed (Bitzer et al., in press). In order to deepen our understanding of the decision steps in the criminal investigation process, the decision to involve a Forensic Advisor and the factors leading to their involvement were evaluated. The study focused on homicide, robbery and burglary cases with and without requests for a Forensic Advisor between January 2014 and June 2016. The factors were categorised into five knowledge dimensions: strategic, immediate, physical, criminal and utility. Decision tree modelling was carried out in order to identify the factors influencing the request for a Forensic Advisor in the case. The decision to request a Forensic Advisor differs between different types of offences. It also depends on the complexity of the case in terms of the number of traces and objects collected at the crime scene, and the availability of witness reports. Indeed, Forensic Advisors take the role of trace analysis coordinator by providing an overview of all available traces, objects, analyses and results. According to the principal implication factors and the performed case study, the contribution of Forensic Advisors consists mainly in summarising all information and advise on potential additional analyses. This might be explained by a loss of overview of the information and the possibilities regarding trace analysis by the magistrate responsible of the case. Copyright © 2018 Elsevier B.V. All rights reserved.

Data Prospecting with CORPRAL: Pre-attentive Vision Model at Work

NASA Astrophysics Data System (ADS)

Galkin, I. A.; Reinisch, B. W.; Khmyrov, G. M.; Kozlov, A. V.; Grinstein, J.; Fung, S. F.

2005-12-01

The Cognitive Online Rpi Plasmagram Rating Algorithm (CORPRAL) is the automated data prospecting tool developed to find interesting examples of signal propagation in the 1.2 million plasmagram image archive from the Radio Plasma Imager (RPI) onboard the IMAGE spacecraft. The RPI instrument is a spaceborne radar whose transmitted radio waves may reflect from important magnetospheric structures, such as the plasmapause and the magnetopause, and return to the spacecraft location to be detected. The CORPRAL prospector draws attention of the human analysts to the RPI plasmagrams that contain traces of remote reflections (~18% of all images), thus helping to relieve the search efforts in the otherwise overwhelming RPI data repository. To find the echo traces in plasmagrams, CORPRAL employs a pre-attentive vision model that replicates human ability to identify important objects in the field of view without willful concentration of attention. The importance of such objects is determined by their `saliency', the ability to stand out against the background. The saliency evaluation is done subconsciously, without a priori concepts of the object shape. The RPI imagery dataset providesd an excellent testbed for studies of the model performance on low saliency objects immersed in irregular background noise. The paper discusses results of statistical evaluation of the CORPRAL performance on a collection of ~25,000 plasmagram images interpreted manually. Overall accuracy of plasmagram interpretation varies depending on the applied measuring program but remains in the mid-90% range. As the prevalence of plasmagrams that contain traces goes below 10%, we do observe lower positive predicted values (PPV) of the CORPRAL analysis (~50%), indicating that automatically selected plasmagrams are interesting only with 50% chance. We will discuss future development efforts and provide examples and scenarios where RPI data prospecting is instrumental in knowledge discovery.

Development and testing of a new ray-tracing approach to GNSS carrier-phase multipath modelling

NASA Astrophysics Data System (ADS)

Lau, Lawrence; Cross, Paul

2007-11-01

Multipath is one of the most important error sources in Global Navigation Satellite System (GNSS) carrier-phase-based precise relative positioning. Its theoretical maximum is a quarter of the carrier wavelength (about 4.8 cm for the Global Positioning System (GPS) L1 carrier) and, although it rarely reaches this size, it must clearly be mitigated if millimetre-accuracy positioning is to be achieved. In most static applications, this may be accomplished by averaging over a sufficiently long period of observation, but in kinematic applications, a modelling approach must be used. This paper is concerned with one such approach: the use of ray-tracing to reconstruct the error and therefore remove it. In order to apply such an approach, it is necessary to have a detailed understanding of the signal transmitted from the satellite, the reflection process, the antenna characteristics and the way that the reflected and direct signal are processed within the receiver. This paper reviews all of these and introduces a formal ray-tracing method for multipath estimation based on precise knowledge of the satellite reflector antenna geometry and of the reflector material and antenna characteristics. It is validated experimentally using GPS signals reflected from metal, water and a brick building, and is shown to be able to model most of the main multipath characteristics. The method will have important practical applications for correcting for multipath in well-constrained environments (such as at base stations for local area GPS networks, at International GNSS Service (IGS) reference stations, and on spacecraft), and it can be used to simulate realistic multipath errors for various performance analyses in high-precision positioning.

Three-dimensional automatic computer-aided evaluation of pleural effusions on chest CT images

NASA Astrophysics Data System (ADS)

Bi, Mark; Summers, Ronald M.; Yao, Jianhua

2011-03-01

The ability to estimate the volume of pleural effusions is desirable as it can provide information about the severity of the condition and the need for thoracentesis. We present here an improved version of an automated program to measure the volume of pleural effusions using regular chest CT images. First, the lungs are segmented using region growing, mathematical morphology, and anatomical knowledge. The visceral and parietal layers of the pleura are then extracted based on anatomical landmarks, curve fitting and active contour models. The liver and compressed tissues are segmented out using thresholding. The pleural space is then fitted to a Bezier surface which is subsequently projected onto the individual two-dimensional slices. Finally, the volume of the pleural effusion is quantified. Our method was tested on 15 chest CT studies and validated against three separate manual tracings. The Dice coefficients were 0.74+/-0.07, 0.74+/-0.08, and 0.75+/-0.07 respectively, comparable to the variation between two different manual tracings.

Bernard J. Wood Receives 2013 Harry H. Hess Medal: Citation

NASA Astrophysics Data System (ADS)

Hofmann, Albrecht W.

2014-01-01

As Harry Hess recognized over 50 years ago, mantle melting is the fundamental motor for planetary evolution and differentiation. Melting generates the major divisions of crust mantle and core. The distribution of chemical elements between solids, melts, and gaseous phases is fundamental to understanding these differentiation processes. Bernie Wood, together with Jon Blundy, has combined experimental petrology and physicochemical theory to revolutionize the understanding of the distribution of trace elements between melts and solids in the Earth. Knowledge of these distribution laws allows the reconstruction of the source compositions of the melts (deep in Earth's interior) from their abundances in volcanic rocks. Bernie's theoretical treatment relates the elastic strain of the lattice caused by the substitution of a trace element in a crystal to the ionic radius and charge of this element. This theory, and its experimental calibrations, brought order to a literature of badly scattered, rather chaotic experimental data that allowed no satisfactory quantitative modeling of melting processes in the mantle.

Using Support Vector Machines to Automatically Extract Open Water Signatures from POLDER Multi-Angle Data Over Boreal Regions

NASA Technical Reports Server (NTRS)

Pierce, J.; Diaz-Barrios, M.; Pinzon, J.; Ustin, S. L.; Shih, P.; Tournois, S.; Zarco-Tejada, P. J.; Vanderbilt, V. C.; Perry, G. L.; Brass, James A. (Technical Monitor)

2002-01-01

This study used Support Vector Machines to classify multiangle POLDER data. Boreal wetland ecosystems cover an estimated 90 x 10(exp 6) ha, about 36% of global wetlands, and are a major source of trace gases emissions to the atmosphere. Four to 20 percent of the global emission of methane to the atmosphere comes from wetlands north of 4 degrees N latitude. Large uncertainties in emissions exist because of large spatial and temporal variation in the production and consumption of methane. Accurate knowledge of the areal extent of open water and inundated vegetation is critical to estimating magnitudes of trace gas emissions. Improvements in land cover mapping have been sought using physical-modeling approaches, neural networks, and active microwave, examples that demonstrate the difficulties of separating open water, inundated vegetation and dry upland vegetation. Here we examine the feasibility of using a support vector machine to classify POLDER data representing open water, inundated vegetation and dry upland vegetation.

Temporal variability in trace metal solubility in a paddy soil not reflected in uptake by rice (Oryza sativa L.).

PubMed

Pan, Yunyu; Koopmans, Gerwin F; Bonten, Luc T C; Song, Jing; Luo, Yongming; Temminghoff, Erwin J M; Comans, Rob N J

2016-12-01

Alternating flooding and drainage conditions have a strong influence on redox chemistry and the solubility of trace metals in paddy soils. However, current knowledge of how the effects of water management on trace metal solubility are linked to trace metal uptake by rice plants over time is still limited. Here, a field-contaminated paddy soil was subjected to two flooding and drainage cycles in a pot experiment with two rice plant cultivars, exhibiting either high or low Cd accumulation characteristics. Flooding led to a strong vertical gradient in the redox potential (Eh). The pH and Mn, Fe, and dissolved organic carbon concentrations increased with decreasing Eh and vice versa. During flooding, trace metal solubility decreased markedly, probably due to sulfide mineral precipitation. Despite its low solubility, the Cd content in rice grains exceeded the food quality standards for both cultivars. Trace metal contents in different rice plant tissues (roots, stem, and leaves) increased at a constant rate during the first flooding and drainage cycle but decreased after reaching a maximum during the second cycle. As such, the high temporal variability in trace metal solubility was not reflected in trace metal uptake by rice plants over time. This might be due to the presence of aerobic conditions and a consequent higher trace metal solubility near the root surface, even during flooding. Trace metal solubility in the rhizosphere should be considered when linking water management to trace metal uptake by rice over time.

Particulate and trace gas emissions from prescribed burns in southeastern U.S. fuel types: Summary of a 5-year project

Treesearch

David R. Weise; Timothy J. Johnson; James Reardon

2015-01-01

Management of smoke from prescribed fires requires knowledge of fuel quantity and the amount and composition of the smoke produced by the fire to minimize adverse impacts on human health. A five-year study produced new emissions information for more than 100 trace gases and particulate matter in smoke for fuel types found in the southern United States of America using...

Synthetic Image Generator Model; Application of View Angle Dependent Reflectivity Components and Performance Evaluation in the Visible Region

DTIC Science & Technology

1993-02-01

3.1.2. Modeling of Environment ....................... 6 3.1.3. Ray Tracing and Radiosity ..................... 8 3.2. Reflectivity Review...SIG modeling is dependent on proper treatment of its effects. 3.1.3 Ray Tracing and Radiosity Prior to reviewing reflectivity, a brief look is made of...methods of applying complex theoretical energy propagation algorithms. Two such methods are ray tracing and radiosity (Goral, et al, 1984). Ray tracing is a

Boolean network identification from perturbation time series data combining dynamics abstraction and logic programming.

PubMed

Ostrowski, M; Paulevé, L; Schaub, T; Siegel, A; Guziolowski, C

2016-11-01

Boolean networks (and more general logic models) are useful frameworks to study signal transduction across multiple pathways. Logic models can be learned from a prior knowledge network structure and multiplex phosphoproteomics data. However, most efficient and scalable training methods focus on the comparison of two time-points and assume that the system has reached an early steady state. In this paper, we generalize such a learning procedure to take into account the time series traces of phosphoproteomics data in order to discriminate Boolean networks according to their transient dynamics. To that end, we identify a necessary condition that must be satisfied by the dynamics of a Boolean network to be consistent with a discretized time series trace. Based on this condition, we use Answer Set Programming to compute an over-approximation of the set of Boolean networks which fit best with experimental data and provide the corresponding encodings. Combined with model-checking approaches, we end up with a global learning algorithm. Our approach is able to learn logic models with a true positive rate higher than 78% in two case studies of mammalian signaling networks; for a larger case study, our method provides optimal answers after 7min of computation. We quantified the gain in our method predictions precision compared to learning approaches based on static data. Finally, as an application, our method proposes erroneous time-points in the time series data with respect to the optimal learned logic models. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Divided multimodal attention sensory trace and context coding strategies in spatially congruent auditory and visual presentation.

PubMed

Kristjánsson, Tómas; Thorvaldsson, Tómas Páll; Kristjánsson, Arni

2014-01-01

Previous research involving both unimodal and multimodal studies suggests that single-response change detection is a capacity-free process while a discriminatory up or down identification is capacity-limited. The trace/context model assumes that this reflects different memory strategies rather than inherent differences between identification and detection. To perform such tasks, one of two strategies is used, a sensory trace or a context coding strategy, and if one is blocked, people will automatically use the other. A drawback to most preceding studies is that stimuli are presented at separate locations, creating the possibility of a spatial confound, which invites alternative interpretations of the results. We describe a series of experiments, investigating divided multimodal attention, without the spatial confound. The results challenge the trace/context model. Our critical experiment involved a gap before a change in volume and brightness, which according to the trace/context model blocks the sensory trace strategy, simultaneously with a roaming pedestal, which should block the context coding strategy. The results clearly show that people can use strategies other than sensory trace and context coding in the tasks and conditions of these experiments, necessitating changes to the trace/context model.

Tracing the Knowledge Building Process through Discussions Mediated by a CSCL Environment: A Case Study

ERIC Educational Resources Information Center

Adanir, Gülgün Afacan

2017-01-01

This case study demonstrates the use of interaction analysis techniques to explore students' knowledge building process evidenced in time-stamped logs of a CSCL environment that consists of chat, shared whiteboard, and wiki features. The study was performed in a graduate level course, which covers online assignments that expect students to…

Knowledge Activation versus Sentence Mapping When Representing Fictional Characters' Emotional States.

ERIC Educational Resources Information Center

Gernsbacher, Morton Ann; Robertson, Rachel R. W.

1992-01-01

In a study of knowledge activation and sentence mapping, subjects read stories that described concrete actions, and then the content of the stories was manipulated (i.e. stories were written that implied different emotional states). It is suggested that the more emotionally evoking situations one encounters the more memory traces are stored and…

An Evaluation on Signature Knowledge and Awareness of Turkish Teacher Candidates

ERIC Educational Resources Information Center

Sen, Ülker; Uysal, Basak

2016-01-01

Signature is developed by individuals different from other biological traces such as DNA and fingerprint. The development of signing ability that takes place in the main heading of writing education, is under the responsibility of individuals, peers of individuals and teachers of individuals. The aim of this study is to evaluate the knowledge and…

Extended professional development for systemic curriculum reform

NASA Astrophysics Data System (ADS)

Kubitskey, Mary Elizabeth

Education standards call for adopting inquiry science instruction. Successful adoption requires professional development (PD) to support teachers, increasing the need for research on PD. This dissertation examines the question: What is the influence of high quality, curriculum aligned, long-term group workshops and related practice on teacher learning? I focus on the following subquestions: (1) What is the influence of high quality, curriculum aligned, long-term, group workshops on teacher knowledge and beliefs? (2) What is the impact of the workshops on teacher practice? (3) What is the influence of practice on student response? (4) What is the impact of practice and student response on teacher knowledge and beliefs? I focus on an instance of PD nested within a long-term systemic change initiative, tracing eleven science teachers' learning from workshops and associated enactments. The data included pre and post-unit interviews (n=22), two post-workshop interviews (n=17), workshop observations (n=2), classroom observations (n=24) and student work (n=351). I used mixed-methods analysis. Quantitative analysis measured teacher learning by comparing pre and post-unit interview ratings. Qualitative components included two case study approaches: logic model technique and cross-case synthesis, examining teacher learning within and across teachers. The findings suggested a teacher-learning model incorporating PD, teacher knowledge, beliefs, practice and student response. PD impacts teachers' knowledge by providing teachers with new knowledge, adapting previous knowledge, or convincing them to value existing knowledge they chose not to use. The workshops can influence beliefs, providing teachers with confidence and motivation to adopt the practice. Beliefs can mediate how knowledge manifested itself in practice that, in turn, impacts students' response. Student response influences the teachers' beliefs, either reinforcing or motivating change. This teacher-learning model suggests a PD design model for long-term systemic change, incorporating teacher practice and student response, providing guidance for teachers making adaptations that maintain reform. This dissertation responds to the call for empirical research linking PD to learning outcomes. These models are unique because practice becomes a continuum of PD, rather than outcome and stresses the importance of addressing teachers' beliefs. This PD design provides mechanisms for maintaining equivalence between the written and enacted curriculum, sustaining the integrity of the reform.

Studying the precision of ray tracing techniques with Szekeres models

NASA Astrophysics Data System (ADS)

Koksbang, S. M.; Hannestad, S.

2015-07-01

The simplest standard ray tracing scheme employing the Born and Limber approximations and neglecting lens-lens coupling is used for computing the convergence along individual rays in mock N-body data based on Szekeres swiss cheese and onion models. The results are compared with the exact convergence computed using the exact Szekeres metric combined with the Sachs formalism. A comparison is also made with an extension of the simple ray tracing scheme which includes the Doppler convergence. The exact convergence is reproduced very precisely as the sum of the gravitational and Doppler convergences along rays in Lemaitre-Tolman-Bondi swiss cheese and single void models. This is not the case when the swiss cheese models are based on nonsymmetric Szekeres models. For such models, there is a significant deviation between the exact and ray traced paths and hence also the corresponding convergences. There is also a clear deviation between the exact and ray tracing results obtained when studying both nonsymmetric and spherically symmetric Szekeres onion models.

Reverse ray tracing for transformation optics.

PubMed

Hu, Chia-Yu; Lin, Chun-Hung

2015-06-29

Ray tracing is an important technique for predicting optical system performance. In the field of transformation optics, the Hamiltonian equations of motion for ray tracing are well known. The numerical solutions to the Hamiltonian equations of motion are affected by the complexities of the inhomogeneous and anisotropic indices of the optical device. Based on our knowledge, no previous work has been conducted on ray tracing for transformation optics with extreme inhomogeneity and anisotropicity. In this study, we present the use of 3D reverse ray tracing in transformation optics. The reverse ray tracing is derived from Fermat's principle based on a sweeping method instead of finding the full solution to ordinary differential equations. The sweeping method is employed to obtain the eikonal function. The wave vectors are then obtained from the gradient of that eikonal function map in the transformed space to acquire the illuminance. Because only the rays in the points of interest have to be traced, the reverse ray tracing provides an efficient approach to investigate the illuminance of a system. This approach is useful in any form of transformation optics where the material property tensor is a symmetric positive definite matrix. The performance and analysis of three transformation optics with inhomogeneous and anisotropic indices are explored. The ray trajectories and illuminances in these demonstration cases are successfully solved by the proposed reverse ray tracing method.

Producing knowledge about racial differences: tracing scientists' use of "race" and "ethnicity" from grants to articles.

PubMed

Friedman, Asia; Lee, Catherine

2013-01-01

The research and publication practices by which scientists produce biomedical knowledge about race and ethnicity remain largely unexamined, and most of the existing research looks at the knowledge production process at a single point in time. In light of this, we specifically focus on the questions of whether and in what ways researchers' discussions of race and ethnicity change over the course of the research process by comparing grant proposals to published articles. Using content analysis, we investigated the use of race and ethnicity in 72 grants funded by the National Cancer Institute of the National Institutes of Health between 1990 and 1999 and 144 matched articles published between 1996 and 2010, tracing the production of biomedical knowledge from study design to published findings. This is also the first study to look at whether the NIH Inclusion Mandate, which went into effect in June of 1994, changed the way investigators research and write about racial and ethnic differences. In following this knowledge production process, we explore how scientists "deliver" on their research proposal goals. In addition, we provide insight into whether and how state policies directed at guiding research practices can shape output. © 2013 American Society of Law, Medicine & Ethics, Inc.

Comparative Study of Raw and Boiled Silver Pomfret Fish from Coastal Area and Retail Market in Relation to Trace Metals and Proximate Composition

PubMed Central

Huque, Roksana; Munshi, M. Kamruzzaman; Khatun, Afifa; Islam, Mahfuza; Hossain, Afzal; Hossain, Arzina; Akter, Shirin; Kabir, Jamiul; Nahar Jolly, Yeasmin; Islam, Ashraful

2014-01-01

Trace metals concentration and proximate composition of raw and boiled silver pomfret (Pampus argenteus) from coastal area and retail market were determined to gain the knowledge of the risk and benefits associated with indiscriminate consumption of marine fishes. The effects of cooking (boiling) on trace metal and proximate composition of silver pomfret fish were also investigated. Trace element results were determined by the Energy Dispersive X-ray Fluorescence (EDXRF) Spectrometer wherein fish samples from both areas exceeded the standard limits set by FAO/WHO for manganese, lead, cadmiumm and chromium and boiling has no significant effects on these three metal concentrations. Long-term intake of these contaminated fish samples can pose a health risk to humans who consume them. PMID:26904650

Process tracing in political science: What's the story?

PubMed

Crasnow, Sharon

2017-04-01

Methodologists in political science have advocated for causal process tracing as a way of providing evidence for causal mechanisms. Recent analyses of the method have sought to provide more rigorous accounts of how it provides such evidence. These accounts have focused on the role of process tracing for causal inference and specifically on the way it can be used with case studies for testing hypotheses. While the analyses do provide an account of such testing, they pay little attention to the narrative elements of case studies. I argue that the role of narrative in case studies is not merely incidental. Narrative does cognitive work by both facilitating the consideration of alternative hypotheses and clarifying the relationship between evidence and explanation. I consider the use of process tracing in a particular case (the Fashoda Incident) in order to illustrate the role of narrative. I argue that process tracing contributes to knowledge production in ways that the current focus on inference tends to obscure. Copyright © 2017 Elsevier Ltd. All rights reserved.

On the advancement of therapeutic penality: therapeutic authority, personality science and the therapeutic community.

PubMed

McBride, Ruari-Santiago

2017-09-01

In this article I examine the advancement of therapeutic penality in the UK, a penal philosophy that reimagines prison policy, practices and environments utilising psychological knowledge. Adopting a historical approach, I show how modern therapeutic penality is linked to the emergence of personality science in the nineteenth century and the development of the democratic therapeutic community (DTC) model in the twentieth century. I outline how at the turn of the twenty-first century a catalytic event generated a moral panic that led the British government to mobilise psychological knowledge and technologies in an attempt to manage dangerous people with severe personality disorder. Tracing subsequent developments, I argue psychological ways of talking, thinking and acting have obtained unparalleled salience in domains of penality and, in turn, radically transformed the conditions of imprisonment. © 2017 Foundation for the Sociology of Health & Illness.

A ray tracing model for leaf bidirectional scattering studies

NASA Technical Reports Server (NTRS)

Brakke, T. W.; Smith, J. A.

1987-01-01

A leaf is modeled as a deterministic two-dimensional structure consisting of a network of circular arcs designed to represent the internal morphology of major species. The path of an individual ray through the leaf is computed using geometric optics. At each intersection of the ray with an arc, the specular reflected and transmitted rays are calculated according to the Snell and Fresnel equations. Diffuse scattering is treated according to Lambert's law. Absorption is also permitted but requires a detailed knowledge of the spectral attenuation coefficients. An ensemble of initial rays are chosen for each incident direction with the initial intersection points on the leaf surface selected randomly. The final equilibrium state after all interactions then yields the leaf bidirectional reflectance and transmittance distributions. The model also yields the internal two dimensional light gradient profile of the leaf.

Make Gestures to Learn: Reproducing Gestures Improves the Learning of Anatomical Knowledge More than Just Seeing Gestures

PubMed Central

Cherdieu, Mélaine; Palombi, Olivier; Gerber, Silvain; Troccaz, Jocelyne; Rochet-Capellan, Amélie

2017-01-01

Manual gestures can facilitate problem solving but also language or conceptual learning. Both seeing and making the gestures during learning seem to be beneficial. However, the stronger activation of the motor system in the second case should provide supplementary cues to consolidate and re-enact the mental traces created during learning. We tested this hypothesis in the context of anatomy learning by naïve adult participants. Anatomy is a challenging topic to learn and is of specific interest for research on embodied learning, as the learning content can be directly linked to learners' body. Two groups of participants were asked to look at a video lecture on the forearm anatomy. The video included a model making gestures related to the content of the lecture. Both groups see the gestures but only one also imitate the model. Tests of knowledge were run just after learning and few days later. The results revealed that imitating gestures improves the recall of structures names and their localization on a diagram. This effect was however significant only in long-term assessments. This suggests that: (1) the integration of motor actions and knowledge may require sleep; (2) a specific activation of the motor system during learning may improve the consolidation and/or the retrieval of memories. PMID:29062287

Mineralogy controls on reactive transport of Marcellus Shale waters.

PubMed

Cai, Zhang; Wen, Hang; Komarneni, Sridhar; Li, Li

2018-07-15

Produced or flowback waters from Marcellus Shale gas extraction (MSWs) typically are highly saline and contain chemicals including trace metals, which pose significant concerns on water quality. The natural attenuation of MSW chemicals in groundwater is poorly understood due to the complex interactions between aquifer minerals and MSWs, limiting our capabilities to monitor and predict. Here we combine flow-through experiments and process-based reactive transport modeling to understand mechanisms and quantify the retention of MSW chemicals in a quartz (Qtz) column, a calcite-rich (Cal) column, and a clay-rich (Vrm, vermiculite) column. These columns were used to represent sand, carbonate, and clay-rich aquifers. Results show that the types and extent of water-rock interactions differ significantly across columns. Although it is generally known that clay-rich media retard chemicals and that quartz media minimize water-rock interactions, results here have revealed insights that differ from previous thoughts. We found that the reaction mechanisms are much more complex than merely sorption and mineral precipitation. In clay rich media, trace metals participate in both ion exchange and mineral precipitation. In fact, the majority of metals (~50-90%) is retained in the solid via mineral precipitation, which is surprising because we typically expect the dominance of sorption in clay-rich aquifers. In the Cal column, trace metals are retained not only through precipitation but also solid solution partitioning, leading to a total of 75-99% retention. Even in the Qtz column, trace metals are retained at unexpectedly high percentages (~20-70%) due to precipitation. The reactive transport model developed here quantitatively differentiates the relative importance of individual processes, and bridges a limited number of experiments to a wide range of natural conditions. This is particularly useful where relatively limited knowledge and data prevent the prediction of complex rock-contaminant interactions and natural attenuation. Copyright © 2018 Elsevier B.V. All rights reserved.

A new method for automated discontinuity trace mapping on rock mass 3D surface model

NASA Astrophysics Data System (ADS)

Li, Xiaojun; Chen, Jianqin; Zhu, Hehua

2016-04-01

This paper presents an automated discontinuity trace mapping method on a 3D surface model of rock mass. Feature points of discontinuity traces are first detected using the Normal Tensor Voting Theory, which is robust to noisy point cloud data. Discontinuity traces are then extracted from feature points in four steps: (1) trace feature point grouping, (2) trace segment growth, (3) trace segment connection, and (4) redundant trace segment removal. A sensitivity analysis is conducted to identify optimal values for the parameters used in the proposed method. The optimal triangular mesh element size is between 5 cm and 6 cm; the angle threshold in the trace segment growth step is between 70° and 90°; the angle threshold in the trace segment connection step is between 50° and 70°, and the distance threshold should be at least 15 times the mean triangular mesh element size. The method is applied to the excavation face trace mapping of a drill-and-blast tunnel. The results show that the proposed discontinuity trace mapping method is fast and effective and could be used as a supplement to traditional direct measurement of discontinuity traces.

Ray Tracing and Modal Methods for Modeling Radio Propagation in Tunnels With Rough Walls

PubMed Central

Zhou, Chenming

2017-01-01

At the ultrahigh frequencies common to portable radios, tunnels such as mine entries are often modeled by hollow dielectric waveguides. The roughness condition of the tunnel walls has an influence on radio propagation, and therefore should be taken into account when an accurate power prediction is needed. This paper investigates how wall roughness affects radio propagation in tunnels, and presents a unified ray tracing and modal method for modeling radio propagation in tunnels with rough walls. First, general analytical formulas for modeling the influence of the wall roughness are derived, based on the modal method and the ray tracing method, respectively. Second, the equivalence of the ray tracing and modal methods in the presence of wall roughnesses is mathematically proved, by showing that the ray tracing-based analytical formula can converge to the modal-based formula through the Poisson summation formula. The derivation and findings are verified by simulation results based on ray tracing and modal methods. PMID:28935995

A trace map comparison algorithm for the discrete fracture network models of rock masses

NASA Astrophysics Data System (ADS)

Han, Shuai; Wang, Gang; Li, Mingchao

2018-06-01

Discrete fracture networks (DFN) are widely used to build refined geological models. However, validating whether a refined model can match to reality is a crucial problem, concerning whether the model can be used for analysis. The current validation methods include numerical validation and graphical validation. However, the graphical validation, aiming at estimating the similarity between a simulated trace map and the real trace map by visual observation, is subjective. In this paper, an algorithm for the graphical validation of DFN is set up. Four main indicators, including total gray, gray grade curve, characteristic direction and gray density distribution curve, are presented to assess the similarity between two trace maps. A modified Radon transform and loop cosine similarity are presented based on Radon transform and cosine similarity respectively. Besides, how to use Bézier curve to reduce the edge effect is described. Finally, a case study shows that the new algorithm can effectively distinguish which simulated trace map is more similar to the real trace map.

Trace elements as quantitative probes of differentiation processes in planetary interiors

NASA Technical Reports Server (NTRS)

Drake, M. J.

1980-01-01

The characteristic trace element signature that each mineral in the source region imparts on the magma constitutes the conceptual basis for trace element modeling. It is shown that abundances of trace elements in extrusive igneous rocks may be used as petrological and geochemical probes of the source regions of the rocks if differentiation processes, partition coefficients, phase equilibria, and initial concentrations in the source region are known. Although compatible and incompatible trace elements are useful in modeling, the present review focuses primarily on examples involving the rare-earth elements.

Parallel Ray Tracing Using the Message Passing Interface

DTIC Science & Technology

2007-09-01

software is available for lens design and for general optical systems modeling. It tends to be designed to run on a single processor and can be very...Cameron, Senior Member, IEEE Abstract—Ray-tracing software is available for lens design and for general optical systems modeling. It tends to be designed to...National Aeronautics and Space Administration (NASA), optical ray tracing, parallel computing, parallel pro- cessing, prime numbers, ray tracing

The Contribution of Vocabulary Knowledge and Semantic Orthographic Fluency to Text Quality through Elementary School in Catalan

ERIC Educational Resources Information Center

Castillo, Cristina; Tolchinsky, Liliana

2018-01-01

Building a text is a multidimensional endeavor. Writers must work simultaneously on the content of the text, its discursive organization, the structure of the sentences, and the individual words themselves. Knowledge of vocabulary is central to this endeavor. This study intends (1) to trace the development of writer's vocabulary depth, their…

Theory in Practice: Why "Good Medicine" and "Scientific Medicine" Are Not Necessarily the Same Thing

ERIC Educational Resources Information Center

De Camargo, Kenneth, Jr.; Coeli, Claudia Medina

2006-01-01

The term "scientific medicine", ubiquitous in medical literature although poorly defined, can be traced to a number of assumptions, three of which are examined in this paper: that medicine is a form of knowledge-driven practice, where the established body of proven medical knowledge determines what doctors do; if what doctors do is either…

Individual Differences in Students' Knowing and Learning about Fractions: Evidence from an In-Depth Qualitative Study

ERIC Educational Resources Information Center

Bempeni, Maria; Vamvakoussi, Xenia

2015-01-01

We present the results of an in-depth qualitative study that examined ninth graders' conceptual and procedural knowledge of fractions as well as their approach to mathematics learning, in particular fraction learning. We traced individual differences, even extreme, in the way that students combine the two kinds of knowledge. We also provide…

There and Back Again: From Research Methods to Principles of Learning, and Everything in Between: Consolidated Knowledge Using the Course Wiki

ERIC Educational Resources Information Center

Hogendoorn, Adrian

2017-01-01

A course wiki is an active environment in which students not only solve problems, but also find their own problems (Bransford, Brown, & Cocking, 1999). Wikis are novel, immersive environments requiring active participation, which enable students to build knowledge within a secure online setting (Hadjerrouit, 2011). This contribution traces a…

Beam-tracing model for predicting sound fields in rooms with multilayer bounding surfaces

NASA Astrophysics Data System (ADS)

Wareing, Andrew; Hodgson, Murray

2005-10-01

This paper presents the development of a wave-based room-prediction model for predicting steady-state sound fields in empty rooms with specularly reflecting, multilayer surfaces. A triangular beam-tracing model with phase, and a transfer-matrix approach to model the surfaces, were involved. Room surfaces were modeled as multilayers of fluid, solid, or porous materials. Biot theory was used in the transfer-matrix formulation of the porous layer. The new model consisted of the transfer-matrix model integrated into the beam-tracing algorithm. The transfer-matrix model was validated by comparing predictions with those by theory, and with experiment. The test surfaces were a glass plate, double drywall panels, double steel panels, a carpeted floor, and a suspended-acoustical ceiling. The beam-tracing model was validated in the cases of three idealized room configurations-a small office, a corridor, and a small industrial workroom-with simple boundary conditions. The number of beams, the reflection order, and the frequency resolution required to obtain accurate results were investigated. Beam-tracing predictions were compared with those by a method-of-images model with phase. The model will be used to study sound fields in rooms with local- or extended-reaction multilayer surfaces.

An examination of coherent structures in a lobed mixer using multifractal measures in conjunction with the proper orthogonal decomposition

NASA Technical Reports Server (NTRS)

Ukeiley, L.; Varghese, M.; Glauser, M.; Valentine, D.

1991-01-01

A 'lobed mixer' device that enhances mixing through secondary flows and streamwise vorticity is presently studied within the framework of multifractal-measures theory, in order to deepen understanding of velocity time trace data gathered on its operation. Proper orthogonal decomposition-based knowledge of coherent structures has been applied to obtain the generalized fractal dimensions and multifractal spectrum of several proper eigenmodes for data samples of the velocity time traces; this constitutes a marked departure from previous multifractal theory applications to self-similar cascades. In certain cases, a single dimension may suffice to capture the entire spectrum of scaling exponents for the velocity time trace.

TRAFIC: fiber tract classification using deep learning

NASA Astrophysics Data System (ADS)

Ngattai Lam, Prince D.; Belhomme, Gaetan; Ferrall, Jessica; Patterson, Billie; Styner, Martin; Prieto, Juan C.

2018-03-01

We present TRAFIC, a fully automated tool for the labeling and classification of brain fiber tracts. TRAFIC classifies new fibers using a neural network trained using shape features computed from previously traced and manually corrected fiber tracts. It is independent from a DTI Atlas as it is applied to already traced fibers. This work is motivated by medical applications where the process of extracting fibers from a DTI atlas, or classifying fibers manually is time consuming and requires knowledge about brain anatomy. With this new approach we were able to classify traced fiber tracts obtaining encouraging results. In this report we will present in detail the methods used and the results achieved with our approach.

Chirped Laser Dispersion Spectroscopy for Remote Open-Path Trace-Gas Sensing

PubMed Central

Nikodem, Michal; Wysocki, Gerard

2012-01-01

In this paper we present a prototype instrument for remote open-path detection of nitrous oxide. The sensor is based on a 4.53 μm quantum cascade laser and uses the chirped laser dispersion spectroscopy (CLaDS) technique for molecular concentration measurements. To the best of our knowledge this is the first demonstration of open-path laser-based trace-gas detection using a molecular dispersion measurement. The prototype sensor achieves a detection limit down to the single-ppbv level and exhibits excellent stability and robustness. The instrument characterization, field deployment performance, and the advantages of applying dispersion sensing to sensitive trace-gas detection in a remote open-path configuration are presented. PMID:23443389

Chirped laser dispersion spectroscopy for remote open-path trace-gas sensing.

PubMed

Nikodem, Michal; Wysocki, Gerard

2012-11-28

In this paper we present a prototype instrument for remote open-path detection of nitrous oxide. The sensor is based on a 4.53 μm quantum cascade laser and uses the chirped laser dispersion spectroscopy (CLaDS) technique for molecular concentration measurements. To the best of our knowledge this is the first demonstration of open-path laser-based trace-gas detection using a molecular dispersion measurement. The prototype sensor achieves a detection limit down to the single-ppbv level and exhibits excellent stability and robustness. The instrument characterization, field deployment performance, and the advantages of applying dispersion sensing to sensitive trace-gas detection in a remote open-path configuration are presented.

A single-trace dual-process model of episodic memory: a novel computational account of familiarity and recollection.

PubMed

Greve, Andrea; Donaldson, David I; van Rossum, Mark C W

2010-02-01

Dual-process theories of episodic memory state that retrieval is contingent on two independent processes: familiarity (providing a sense of oldness) and recollection (recovering events and their context). A variety of studies have reported distinct neural signatures for familiarity and recollection, supporting dual-process theory. One outstanding question is whether these signatures reflect the activation of distinct memory traces or the operation of different retrieval mechanisms on a single memory trace. We present a computational model that uses a single neuronal network to store memory traces, but two distinct and independent retrieval processes access the memory. The model is capable of performing familiarity and recollection-based discrimination between old and new patterns, demonstrating that dual-process models need not to rely on multiple independent memory traces, but can use a single trace. Importantly, our putative familiarity and recollection processes exhibit distinct characteristics analogous to those found in empirical data; they diverge in capacity and sensitivity to sparse and correlated patterns, exhibit distinct ROC curves, and account for performance on both item and associative recognition tests. The demonstration that a single-trace, dual-process model can account for a range of empirical findings highlights the importance of distinguishing between neuronal processes and the neuronal representations on which they operate.

Remote Sensing of Alpha and Beta Sources - Modeling Summary

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dignon, J; Frank, M; Cherepy, N

Evaluating the potential for optical detection of the products of interactions of energetic electrons or other particles with the background atmosphere depends on predictions of change in atmospheric concentrations of species which would generate detectable spectral signals within the range of observation. The solar blind region of the spectrum, in the ultra violet, would be the logical band for outdoor detection (see Figure 1). The chemistry relevant to these processes is composed of ion-molecule reactions involving the initially created N{sub 2}{sup +} and O{sub 2}{sup +} ions, and their subsequent interactions with ambient trace atmospheric constituents. Effective modeling of themore » atmospheric chemical system acted upon by energetic particles requires knowledge of the dominant mechanism that exchange charge and associate it with atmospheric constituents, kinetic parameters of the individual processes (see e.g. Brasseur and Solomon, 1995), and a solver for the coupled differential equations that is accurate for the very stiff set of time constants involved. The LLNL box model, VOLVO, simulates the diel cycle of trace constituent photochemistry for any point on the globe over the wide range of time scales present using a stiff Gear-type ODE solver, i.e. LSODE. It has been applied to problems such as tropospheric and stratospheric nitrogen oxides, stratospheric ozone production and loss, and tropospheric hydrocarbon oxidation. For this study we have included the appropriate ion flux.« less

Modeling the Impact of Value of Information on Situational Awareness using C3TRACE

DTIC Science & Technology

2016-05-01

ARL-TR-7684 ● MAY 2016 US Army Research Laboratory Modeling the Impact of Value of Information on Situational Awareness Using...US Army Research Laboratory Modeling the Impact of Value of Information on Situational Awareness using C3TRACE by John T Richardson...SUBTITLE Modeling the Impact of Value of Information on Situational Awareness Using C3TRACE 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM

Complex Road Intersection Modelling Based on Low-Frequency GPS Track Data

NASA Astrophysics Data System (ADS)

Huang, J.; Deng, M.; Zhang, Y.; Liu, H.

2017-09-01

It is widely accepted that digital map becomes an indispensable guide for human daily traveling. Traditional road network maps are produced in the time-consuming and labour-intensive ways, such as digitizing printed maps and extraction from remote sensing images. At present, a large number of GPS trajectory data collected by floating vehicles makes it a reality to extract high-detailed and up-to-date road network information. Road intersections are often accident-prone areas and very critical to route planning and the connectivity of road networks is mainly determined by the topological geometry of road intersections. A few studies paid attention on detecting complex road intersections and mining the attached traffic information (e.g., connectivity, topology and turning restriction) from massive GPS traces. To the authors' knowledge, recent studies mainly used high frequency (1 s sampling rate) trajectory data to detect the crossroads regions or extract rough intersection models. It is still difficult to make use of low frequency (20-100 s) and easily available trajectory data to modelling complex road intersections geometrically and semantically. The paper thus attempts to construct precise models for complex road intersection by using low frequency GPS traces. We propose to firstly extract the complex road intersections by a LCSS-based (Longest Common Subsequence) trajectory clustering method, then delineate the geometry shapes of complex road intersections by a K-segment principle curve algorithm, and finally infer the traffic constraint rules inside the complex intersections.

2-Dimensional B-Spline Algorithms with Applications to Ray Tracing in Media of Spatially-Varying Refractive Index

DTIC Science & Technology

2007-08-01

In the approach, photon trajectories are computed using a solution of the Eikonal equation (ray-tracing methods) rather than linear trajectories. The...coupling the radiative transport solution into heat transfer and damage models. 15. SUBJECT TERMS: B-Splines, Ray-Tracing, Eikonal Equation...multi-layer biological tissue model. In the approach, photon trajectories are computed using a solution of the Eikonal equation (ray-tracing methods

A novel tracing method for the segmentation of cell wall networks.

PubMed

De Vylder, Jonas; Rooms, Filip; Dhondt, Stijn; Inze, Dirk; Philips, Wilfried

2013-01-01

Cell wall networks are a common subject of research in biology, which are important for plant growth analysis, organ studies, etc. In order to automate the detection of individual cells in such cell wall networks, we propose a new segmentation algorithm. The proposed method is a network tracing algorithm, exploiting the prior knowledge of the network structure. The method is applicable on multiple microscopy modalities such as fluorescence, but also for images captured using non invasive microscopes such as differential interference contrast (DIC) microscopes.

Ontology development for provenance tracing in National Climate Assessment of the US Global Change Research Program

NASA Astrophysics Data System (ADS)

Fu, Linyun; Ma, Xiaogang; Zheng, Jin; Goldstein, Justin; Duggan, Brian; West, Patrick; Aulenbach, Steve; Tilmes, Curt; Fox, Peter

2014-05-01

This poster will show how we used a case-driven iterative methodology to develop an ontology to represent the content structure and the associated provenance information in a National Climate Assessment (NCA) report of the US Global Change Research Program (USGCRP). We applied the W3C PROV-O ontology to implement a formal representation of provenance. We argue that the use case-driven, iterative development process and the application of a formal provenance ontology help efficiently incorporate domain knowledge from earth and environmental scientists in a well-structured model interoperable in the context of the Web of Data.

Analysing neutron scattering data using McStas virtual experiments

NASA Astrophysics Data System (ADS)

Udby, L.; Willendrup, P. K.; Knudsen, E.; Niedermayer, Ch.; Filges, U.; Christensen, N. B.; Farhi, E.; Wells, B. O.; Lefmann, K.

2011-04-01

With the intention of developing a new data analysis method using virtual experiments we have built a detailed virtual model of the cold triple-axis spectrometer RITA-II at PSI, Switzerland, using the McStas neutron ray-tracing package. The parameters characterising the virtual instrument were carefully tuned against real experiments. In the present paper we show that virtual experiments reproduce experimentally observed linewidths within 1-3% for a variety of samples. Furthermore we show that the detailed knowledge of the instrumental resolution found from virtual experiments, including sample mosaicity, can be used for quantitative estimates of linewidth broadening resulting from, e.g., finite domain sizes in single-crystal samples.

Trace elements in coal. Environmental and health significance

USGS Publications Warehouse

Finkelman, R.B.

1999-01-01

Trace elements can have profound adverse effects on the health of people burning coal in homes or living near coal deposits, coal mines, and coal- burning power plants. Trace elements such as arsenic emitted from coal- burning power plants in Europe and Asia have been shown to cause severe health problems. Perhaps the most widespread health problems are caused by domestic coal combustion in developing countries where millions of people suffer from fluorosis and thousands from arsenism. Better knowledge of coal quality characteristics may help to reduce some of these health problems. For example, information on concentrations and distributions of potentially toxic elements in coal may help delineate areas of a coal deposit to be avoided. Information on the modes of occurrence of these elements and the textural relations of the minerals in coal may help to predict the behavior of the potentially toxic trace metals during coal cleaning, combustion, weathering, and leaching.

Conceptualising forensic science and forensic reconstruction. Part II: The critical interaction between research, policy/law and practice.

PubMed

Morgan, R M

2017-11-01

This paper builds on the FoRTE conceptual model presented in part I to address the forms of knowledge that are integral to the four components of the model. Articulating the different forms of knowledge within effective forensic reconstructions is valuable. It enables a nuanced approach to the development and use of evidence bases to underpin decision-making at every stage of a forensic reconstruction by enabling transparency in the reporting of inferences. It also enables appropriate methods to be developed to ensure quality and validity. It is recognised that the domains of practice, research, and policy/law intersect to form the nexus where forensic science is situated. Each domain has a distinctive infrastructure that influences the production and application of different forms of knowledge in forensic science. The channels that can enable the interaction between these domains, enhance the impact of research in theory and practice, increase access to research findings, and support quality are presented. The particular strengths within the different domains to deliver problem solving forensic reconstructions are thereby identified and articulated. It is argued that a conceptual understanding of forensic reconstruction that draws on the full range of both explicit and tacit forms of knowledge, and incorporates the strengths of the different domains pertinent to forensic science, offers a pathway to harness the full value of trace evidence for context sensitive, problem-solving forensic applications. Copyright © 2017 The Author. Published by Elsevier B.V. All rights reserved.

A Global Overview of Exposure Levels and Biological Effects of Trace Elements in Penguins.

PubMed

Espejo, Winfred; Celis, José E; GonzÃlez-Acuña, Daniel; Banegas, Andiranel; Barra, Ricardo; Chiang, Gustavo

2018-01-01

Trace elements are chemical contaminants that can be present almost anywhere on the planet. The study of trace elements in biotic matrices is a topic of great relevance for the implications that it can have on wildlife and human health. Penguins are very useful, since they live exclusively in the Southern Hemisphere and represent about 90% of the biomass of birds of the Southern Ocean. The levels of trace elements (dry weight) in different biotic matrices of penguins were reviewed here. Maps of trace element records in penguins were included. Data on exposure and effects of trace elements in penguins were collected from the literature. The most reported trace elements in penguins are aluminum, arsenic, cadmium, lead, mercury, copper, zinc, and manganese. Trace elements have been measured in 11 of the 18 species of penguins. The most studied biotic matrices are feathers and excreta. Most of the studies have been performed in Antarctica and subantarctic Islands. Little is known about the interaction among metals, which could provide better knowledge about certain mechanisms of detoxification in penguins. Future studies of trace elements in penguins must incorporate other metals such as vanadium, cobalt, nickel, and chromium. Data of metals in the species such as Eudyptes pachyrhynchus, Eudyptes moseleyi, Eudyptes sclateri, Eudyptes robustus, Eudyptes schlegeli, Spheniscus demersus, Spheniscus mendiculus, and Megadyptes antipodes are urged. It is important to correlate levels of metals in different biotic matrices with the effects on different species and in different geographic locations.

Modeling of contact tracing in social networks

NASA Astrophysics Data System (ADS)

Tsimring, Lev S.; Huerta, Ramón

2003-07-01

Spreading of certain infections in complex networks is effectively suppressed by using intelligent strategies for epidemic control. One such standard epidemiological strategy consists in tracing contacts of infected individuals. In this paper, we use a recently introduced generalization of the standard susceptible-infectious-removed stochastic model for epidemics in sparse random networks which incorporates an additional (traced) state. We describe a deterministic mean-field description which yields quantitative agreement with stochastic simulations on random graphs. We also discuss the role of contact tracing in epidemics control in small-world and scale-free networks. Effectiveness of contact tracing grows as the rewiring probability is reduced.

Present state of knowledge of the upper atmosphere: An assessment report; processes that control ozone and other climatically important trace gases

NASA Technical Reports Server (NTRS)

Watson, R. T.; Geller, M. A.; Stolarski, R. S.; Hampson, R. F.

1986-01-01

The state of knowledge of the upper atmosphere was assessed as of January 1986. The physical, chemical, and radiative processes which control the spatial and temporal distribution of ozone in the atmosphere; the predicted magnitude of ozone perturbations and climate changes for a variety of trace gas scenarios; and the ozone and temperature data used to detect the presence or absence of a long term trend were discussed. This assessment report was written by a small group of NASA scientists, was peer reviewed, and is based primarily on the comprehensive international assessment document entitled Atmospheric Ozone 1985: Assessment of Our Understanding of the Processes Controlling Its Present Distribution and Change, to be published as the World Meteorological Organization Global Ozone Research and Monitoring Project Report No. 16.

Use of sediment-trace element geochemical models for the identification of local fluvial baseline concentrations

USGS Publications Warehouse

Horowitz, A.J.; Elrick, K.A.; Demas, C.R.; Demcheck, D.K.

1991-01-01

Studies have demonstrated the utility of fluvial bed sediment chemical data in assesing local water-quality conditions. However, establishing local background trace element levels can be difficult. Reference to published average concentrations or the use of dated cores are often of little use in small areas of diverse local petrology, geology, land use, or hydrology. An alternative approach entails the construction of a series of sediment-trace element predictive models based on data from environmentally diverse but unaffected areas. Predicted values could provide a measure of local background concentrations and comparison with actual measured concentrations could identify elevated trace elements and affected sites. Such a model set was developed from surface bed sediments collected nationwide in the United States. Tests of the models in a small Louisiana basin indicated that they could be used to establish local trace element background levels, but required recalibration to account for local geochemical conditions outside the range of samples used to generate the nationwide models.

The Pursuit of Knowledge under Difficulties: From Self-Improvement to Adult Education in America, 1750-1990.

ERIC Educational Resources Information Center

Kett, Joseph F.

This book traces the history of adult and continuing education in the United States from 1750 through 1990. The following topics are among those examined in the book's 12 chapters: literature, philosophy, and self-education in the 18th century; uses of knowledge in the antebellum period (law and learning, piety and learning, commerce and culture);…

Risk perception and communication in vaccination decisions: a fuzzy-trace theory approach.

PubMed

Reyna, Valerie F

2012-05-28

The tenets of fuzzy-trace theory, along with prior research on risk perception and risk communication, are used to develop a process model of vaccination decisions in the era of Web 2.0. The theory characterizes these decisions in terms of background knowledge, dual mental representations (verbatim and gist), retrieval of values, and application of values to representations in context. Lack of knowledge interferes with the ability to extract the essential meaning, or gist, of vaccination messages. Prevention decisions have, by definition, a status quo option of "feeling okay." Psychological evidence from other prevention decisions, such as cancer screening, indicates that many people initially mentally represent their decision options in terms of simple, categorical gist: a choice between (a) a feeling-okay option (e.g., the unvaccinated status quo) versus (b) taking up preventive behavior that can have two potential categorical outcomes: feeling okay or not feeling okay. Hence, applying the same theoretical rules as used to explain framing effects and the Allais paradox, the decision to get a flu shot, for example, boils down to feeling okay (not sick) versus feeling okay (not sick) or not feeling okay (sick, side effects, or death). Because feeling okay is superior to not feeling okay (a retrieved value), this impoverished gist supports choosing not to have the flu vaccine. Anti-vaccination sources provide more coherent accounts of the gist of vaccination than official sources, filling a need to understand rare adverse outcomes. Copyright © 2011 Elsevier Ltd. All rights reserved.

Risk Perception and Communication in Vaccination Decisions: A Fuzzy-Trace Theory Approach

PubMed Central

Reyna, Valerie F.

2012-01-01

The tenets of fuzzy-trace theory, along with prior research on risk perception and risk communication, are used to develop a process model of vaccination decisions in the era of Web 2.0. The theory characterizes these decisions in terms of background knowledge, dual mental representations (verbatim and gist), retrieval of values, and application of values to representations in context. Lack of knowledge interferes with the ability to extract the essential meaning, or gist, of vaccination messages. Prevention decisions have, by definition, a status quo option of “feeling okay.” Psychological evidence from other prevention decisions, such as cancer screening, indicates that many people initially mentally represent their decision options in terms of simple, categorical gist: a choice between (a) a feeling-okay option (e.g., the unvaccinated status quo) versus (b) taking up preventive behavior that can have two potential categorical outcomes: feeling okay or not feeling okay. Hence, applying the same theoretical rules as used to explain framing effects and the Allais paradox, the decision to get a flu shot, for example, boils down to feeling okay (not sick) versus feeling okay (not sick) or not feeling okay (sick, side effects, or death). Because feeling okay is superior to not feeling okay (a retrieved value), this impoverished gist supports choosing not to have the flu vaccine. Anti-vaccination sources provide more coherent accounts of the gist of vaccination than official sources, filling a need to understand rare adverse outcomes. PMID:22133507

Mirabel: an integrated project for risk and cost/benefit analysis of peanut allergy.

PubMed

Crépet, A; Papadopoulos, A; Elegbede, C F; Ait-Dahmane, S; Loynet, C; Millet, G; Van Der Brempt, X; Bruyère, O; Marette, S; Moneret-Vautrin, D A

2015-03-01

Food allergy is a major public health issue. However, no regulatory measures exist when allergens are present at trace levels and the different risk components are poorly described. Thus, knowledge on exposure components such as the allergens present in foods and the consumption behaviour of allergic consumers and models to estimate the related risk need to be enriched. Mirabel proposes for the first time studying each risk component using an integrated approach in order to improve the quality of life of the allergic population. Field surveys were conducted in order to fill in the current gaps in unintentional allergen traces in food, allergic consumers' food behaviour, threshold doses of allergic reaction, allergy symptoms and severity. The aim is also to propose methodological and operational tools to quantify allergic risk, to test management scenarios and to produce a cost/benefit analysis. Medical data on the peanut allergies of 785 patients were collected in the MIRABEL survey and 443 patients answered the food consumption questionnaire. The population surveyed was mostly paediatric - 86% were children under 16 years of age, with a high percentage of males (60%). This project will generate tangible results on peanut allergen exposure and risk which could be used in future risk assessment work and particularly to provide science-based guidance to set up concentration limits for peanut traces on packages. Copyright © 2014 Elsevier Inc. All rights reserved.

Busting out of crystallography's Sisyphean prison: from pencil and paper to structure solving at the press of a button: past, present and future of crystallographic software development, maintenance and distribution.

PubMed

Cranswick, Lachlan Michael David

2008-01-01

The history of crystallographic computing and use of crystallographic software is one which traces the escape from the drudgery of manual human calculations to a world where the user delegates most of the travail to electronic computers. In practice, this involves practising crystallographers communicating their thoughts to the crystallographic program authors, in the hope that new procedures will be implemented within their software. Against this background, the development of small-molecule single-crystal and powder diffraction software is traced. Starting with the analogue machines and the use of Hollerith tabulators of the late 1930's, it is shown that computing developments have been science led, with new technologies being harnessed to solve pressing crystallographic problems. The development of software is also traced, with a final caution that few of the computations now performed daily are really understood by the program users. Unless a sufficient body of people continues to dismantle and re-build programs, the knowledge encoded in the old programs will become as inaccessible as the knowledge of how to build the Great Pyramid at Giza.

A Novel Hybrid Model for Drawing Trace Reconstruction from Multichannel Surface Electromyographic Activity.

PubMed

Chen, Yumiao; Yang, Zhongliang

2017-01-01

Recently, several researchers have considered the problem of reconstruction of handwriting and other meaningful arm and hand movements from surface electromyography (sEMG). Although much progress has been made, several practical limitations may still affect the clinical applicability of sEMG-based techniques. In this paper, a novel three-step hybrid model of coordinate state transition, sEMG feature extraction and gene expression programming (GEP) prediction is proposed for reconstructing drawing traces of 12 basic one-stroke shapes from multichannel surface electromyography. Using a specially designed coordinate data acquisition system, we recorded the coordinate data of drawing traces collected in accordance with the time series while 7-channel EMG signals were recorded. As a widely-used time domain feature, Root Mean Square (RMS) was extracted with the analysis window. The preliminary reconstruction models can be established by GEP. Then, the original drawing traces can be approximated by a constructed prediction model. Applying the three-step hybrid model, we were able to convert seven channels of EMG activity recorded from the arm muscles into smooth reconstructions of drawing traces. The hybrid model can yield a mean accuracy of 74% in within-group design (one set of prediction models for all shapes) and 86% in between-group design (one separate set of prediction models for each shape), averaged for the reconstructed x and y coordinates. It can be concluded that it is feasible for the proposed three-step hybrid model to improve the reconstruction ability of drawing traces from sEMG.

Trace organic solutes in closed-loop forward osmosis applications: influence of membrane fouling and modeling of solute build-up.

PubMed

D'Haese, Arnout; Le-Clech, Pierre; Van Nevel, Sam; Verbeken, Kim; Cornelissen, Emile R; Khan, Stuart J; Verliefde, Arne R D

2013-09-15

In this study, trace organics transport in closed-loop forward osmosis (FO) systems was assessed. The FO systems considered, consisted of an FO unit and a nanofiltration (NF) or reverse osmosis (RO) unit, with the draw solution circulating between both units. The rejection of trace organics by FO, NF and RO was tested. It was found that the rejection rates of FO were generally comparable with NF and lower than RO rejection rates. To assess the influence of fouling in FO on trace organics rejection, FO membranes were fouled with sodium alginate, bovine serum albumin or by biofilm growth, after which trace organics rejection was tested. A negative influence of fouling on FO rejection was found which was limited in most cases, while it was significant for some compounds such as paracetamol and naproxen, indicating specific compound-foulant interactions. The transport mechanism of trace organics in FO was tested, in order to differentiate between diffusive and convective transport. The concentration of trace organics in the final product water and the build-up of trace organics in the draw solution were modeled assuming the draw solution was reconcentrated by NF/RO and taking into account different transport mechanisms for the FO membrane and different rejection rates by NF/RO. Modeling results showed that if the FO rejection rate is lower than the RO rejection rate (as is the case for most compounds tested), the added value of the FO-RO cycle compared to RO only at steady-state was small for diffusively and negative for convectively transported trace organics. Modeling also showed that trace organics accumulate in the draw solution. Copyright © 2013 Elsevier Ltd. All rights reserved.

Mapping the audit traces of interdisciplinary collaboration: bridging and blending between choreography and cognitive science.

PubMed

Barnard, Philip; deLahunta, Scott

2017-01-01

Two long-term sci-art research projects are described and positioned in the broader conceptual landscape of interdisciplinary collaboration. Both projects were aimed at understanding and augmenting choreographic decision-making and both were grounded in research conducted within a leading contemporary dance company. In each case, the work drew upon methods and theory from the cognitive sciences, and both had a direct impact on the way in which the company made new work. In the synthesis presented here the concept of an audit trace is introduced. Audit traces identify how specific classes of knowledge are used and transformed not only within the arts or sciences but also when arts practice is informed by science or when arts practice informs science.

Middle Atmosphere Program. Handbook for MAP. Volume 31: Reference models of trace species for the COSPAR international reference atmosphere

NASA Technical Reports Server (NTRS)

Keating, G. M. (Editor)

1989-01-01

A set of preliminary reference atmosphere models of significant trace species which play important roles in controlling the chemistry, radiation budget, and circulation patterns of the atmosphere were produced. These models of trace species distributions are considered to be reference models rather than standard models; thus, it was not crucial that they be correct in an absolute sense. These reference models can serve as a means of comparison between individual observations, as a first guess in inversion algorithms, and as an approximate representation of observations for comparison to theoretical calculations.

An animal model of fetal alcohol spectrum disorder: Trace conditioning as a window to inform memory deficits and intervention tactics.

PubMed

Hunt, Pamela S; Barnet, Robert C

2015-09-01

Animal models of Fetal Alcohol Spectrum Disorders (FASD) afford the unique capacity to precisely control timing of alcohol exposure and alcohol exposure amounts in the developing animal. These models have powerfully informed neurophysiological alterations associated with fetal and perinatal alcohol. In two experiments presented here we expand use of the Pavlovian Trace Conditioning procedure to examine cognitive deficits and intervention strategies in a rat model of FASD. Rat pups were exposed to 5g/kg/day ethanol on postnatal days (PD) 4-9, simulating alcohol exposure in the third trimester in humans. During early adolescence, approximately PD 30, the rats were trained in the trace conditioning task in which a light conditioned stimulus (CS) and shock unconditioned stimulus (US) were paired but separated by a 10-s stimulus free trace interval. Learning was assessed in freezing behavior during shock-free tests. Experiment 1 revealed that neonatal ethanol exposure significantly impaired hippocampus-dependent trace conditioning relative to controls. In Experiment 2 a serial compound conditioning procedure known as 'gap filling' completely reversed the ethanol-induced deficit in trace conditioning. We also discuss prior data regarding the beneficial effects of supplemental choline and novel preliminary data regarding the pharmacological cognitive enhancer physostigmine, both of which mitigate the alcohol-induced cognitive deficit otherwise seen in trace conditioning controls. We suggest trace conditioning as a useful tool for characterizing some of the core cognitive deficits seen in FASD, and as a model for developing effective environmental as well as nutritional and pharmacological interventions. Copyright © 2014 Elsevier Inc. All rights reserved.

An Animal Model of Fetal Alcohol Spectrum Disorder: Trace Conditioning as a Window to Inform Memory Deficits and Intervention Tactics

PubMed Central

Hunt, Pamela S.; Barnet, Robert C.

2014-01-01

Animal models of Fetal Alcohol Spectrum Disorders (FASD) afford the unique capacity to precisely control timing of alcohol exposure and alcohol exposure amounts in the developing animal. These models have powerfully informed neurophysiological alterations associated with fetal and perinatal alcohol. In two experiments presented here we expand use of the Pavlovian Trace Conditioning procedure to examine cognitive deficits and intervention strategies in a rat model of FASD. Rat pups were exposed to 5 g/kg/day ethanol on postnatal days (PD) 4–9, simulating alcohol exposure in the third trimester in humans. During early adolescence, approximately PD 30, the rats were trained in the trace conditioning task in which a light conditioned stimulus (CS) and shock unconditioned stimulus (US) were paired but separated by a 10-s stimulus free trace interval. Learning was assessed in freezing behavior during shock-free tests. Experiment 1 revealed that neonatal ethanol exposure significantly impaired hippocampus-dependent trace conditioning relative to controls. In Experiment 2 a serial compound conditioning procedure known as ‘gap filling’ completely reversed the ethanol-induced deficit in trace conditioning. We also discuss prior data regarding the beneficial effects of supplemental choline and novel preliminary data regarding the pharmacological cognitive enhancer physostigmine, both of which mitigate the alcohol-induced cognitive deficit otherwise seen in trace conditioning controls. We suggest trace conditioning as a useful tool for characterizing some of the core cognitive deficits seen in FASD, and as a model for developing effective environmental as well as nutritional and pharmacological interventions. PMID:25477227

Cloud Chemistry in the United States: Problems and Prospects

NASA Astrophysics Data System (ADS)

Carlton, A. G.; Barth, M. C.; Lance, S.; Fahey, K.; McNeill, V. F.; Weber, R. J.

2017-12-01

Clouds cover 60% of the Earth's surface at a given time and are the primary means by which atmospheric trace species are lofted from the polluted boundary layer to the free troposphere. Clouds also play an important role as atmospheric aqueous phase reactors, scavenging soluble gas phase precursors and providing a medium for oxidation reactions that yield lower volatility products that contribute to increased aerosol mass when cloud drops evaporate. On a global average, most sulfate particles are formed during cloud processing, and organic particles known to form through aqueous phase pathways are found above clouds. However, atmospheric chemistry observations are generally biased for clear sky conditions. For example, aircraft field deployments typically avoid clouds. Satellite retrievals impacted by clouds are often screened from the final data products. This hinders knowledge of cloud chemistry and the impacts on tropospheric composition. In this work, we explore temporal and geospatial trends in trace species related to cloud processing in the U.S. with a focus on organic chemistry. We apply 3-dimensional and 0-dimensional models to recent campaigns and mountaintop cloud sampling sites, and compare to measurements.

Tools for knowledge acquisition within the NeuroScholar system and their application to anatomical tract-tracing data

PubMed Central

Burns, Gully APC; Cheng, Wei-Cheng

2006-01-01

Background Knowledge bases that summarize the published literature provide useful online references for specific areas of systems-level biology that are not otherwise supported by large-scale databases. In the field of neuroanatomy, groups of small focused teams have constructed medium size knowledge bases to summarize the literature describing tract-tracing experiments in several species. Despite years of collation and curation, these databases only provide partial coverage of the available published literature. Given that the scientists reading these papers must all generate the interpretations that would normally be entered into such a system, we attempt here to provide general-purpose annotation tools to make it easy for members of the community to contribute to the task of data collation. Results In this paper, we describe an open-source, freely available knowledge management system called 'NeuroScholar' that allows straightforward structured markup of the PDF files according to a well-designed schema to capture the essential details of this class of experiment. Although, the example worked through in this paper is quite specific to neuroanatomical connectivity, the design is freely extensible and could conceivably be used to construct local knowledge bases for other experiment types. Knowledge representations of the experiment are also directly linked to the contributing textual fragments from the original research article. Through the use of this system, not only could members of the community contribute to the collation task, but input data can be gathered for automated approaches to permit knowledge acquisition through the use of Natural Language Processing (NLP). Conclusion We present a functional, working tool to permit users to populate knowledge bases for neuroanatomical connectivity data from the literature through the use of structured questionnaires. This system is open-source, fully functional and available for download from [1]. PMID:16895608

An Assessment of Radiation Modification from a European Perspective

NASA Astrophysics Data System (ADS)

Kristjansson, J. E.; Lawrence, M. G.; Boucher, O.; Haywood, J. M.; Irvine, P. J.; Muri, H.; Schmidt, H.; Schulz, M.; Vaughan, N.; Watson, M.; Born, W.; Schaefer, S.; Stelzer, H.

2014-12-01

The European Transdisciplinary Assessment of Climate Engineering (EuTRACE) project (2012-2014) is funded by the European Commission (EC). In EuTRACE, researchers from the natural sciences, social sciences and the humanities have joined forces to assess various proposed geoengineering techniques concerning their radiative forcing potential and side effects, ethical aspects, economics aspects, as well as governance and regulation aspects. A comprehensive assessment report will be submitted to the EC in autumn 2014. We will present some highlights of the part of the EuTRACE assessment that deals with the natural science aspects of proposed Radiation Modification (RM) techniques. The techniques considered are: a) Stratospheric Sulfur Injections; b) Marine Cloud Brightening; c) Desert Brightening; d) Vegetation Brightening; and e) Cirrus Cloud Thinning. A large number of publications in the scientific literature has been considered, as well as recently published assessment reports by the Royal Society in the UK and the German Federal Ministry of Education and Research. Some of the findings of the assessment are: Globally averaged, the current anthropogenic radiative forcing could conceivably be offset by the RM techniques considered. The RM techniques could have a significant global effect already after 1 year or less. Model simulations consistently show that Solar RM leads to regional imbalances due to different spatial footprints of solar and carbon dioxide radiative forcings. This may have significant consequences for precipitation patterns and the hydrological cycle. Very rapid warming is virtually certain if RM were to be stopped abruptly or over a period of one to a few years. Model studies of RM usually assume that the techniques are technologically feasible. In fact, the technological challenges are poorly known, and in many cases the physical processes involved are poorly understood. We will end by discussing key research questions and knowledge gaps.

False memory for orthographically versus semantically similar words in adolescents with dyslexia: a fuzzy-trace theory perspective.

PubMed

Obidziński, Michał; Nieznański, Marek

2017-10-01

The presented research was conducted in order to investigate the connections between developmental dyslexia and the functioning of verbatim and gist memory traces-assumed in the fuzzy-trace theory. The participants were 71 high school students (33 with dyslexia and 38 without learning difficulties). The modified procedure and multinomial model of Stahl and Klauer (simplified conjoint recognition model) was used to collect and analyze data. Results showed statistically significant differences in four of the model parameters: (a) the probability of verbatim trace recollection upon presentation of orthographically similar stimulus was higher in the control than dyslexia group, (b) the probability of verbatim trace recollection upon presentation of semantically similar stimulus was higher in the control than dyslexia group, (c) the probability of gist trace retrieval upon presentation of semantically similar stimulus was higher in the dyslexia than control group, and (d) the probability of gist trace retrieval upon target stimulus presentation (in the semantic condition) was higher in the control than dyslexia group. The obtained results suggest differences of memory functioning in terms of verbatim and gist trace retrieval between people with and without dyslexia on specific, elementary cognitive processes postulated by the fuzzy-trace theory. These can indicate new approaches in the education of persons with developmental dyslexia, focused on specific impairments and the strengths of their memory functioning.

Atmospheric Research 2016 Technical Highlights

NASA Technical Reports Server (NTRS)

Platnick, Steven

2017-01-01

Atmospheric research in the Earth Sciences Division (610) consists of research and technology development programs dedicated to advancing knowledge and understanding of the atmosphere and its interaction with the climate of Earth. The Divisions goals are to improve understanding of the dynamics and physical properties of precipitation, clouds, and aerosols; atmospheric chemistry, including the role of natural and anthropogenic trace species on the ozone balance in the stratosphere and the troposphere; and radiative properties of Earth's atmosphere and the influence of solar variability on the Earth's climate. Major research activities are carried out in the Mesoscale Atmospheric Processes Laboratory, the Climate and Radiation Laboratory, the Atmospheric Chemistry and Dynamics Laboratory, and the Wallops Field Support Office. The overall scope of the research covers an end-to-end process, starting with the identification of scientific problems, leading to observation requirements for remote-sensing platforms, technology and retrieval algorithm development; followed by flight projects and satellite missions; and eventually, resulting in data processing, analyses of measurements, and dissemination from flight projects and missions. Instrument scientists conceive, design, develop, and implement ultraviolet, infrared, optical, radar, laser, and lidar technology to remotely sense the atmosphere. Members of the various laboratories conduct field measurements for satellite sensor calibration and data validation, and carry out numerous modeling activities. These modeling activities include climate model simulations, modeling the chemistry and transport of trace species on regional-to-global scales, cloud resolving models, and developing the next-generation Earth system models. Satellite missions, field campaigns, peer-reviewed publications, and successful proposals are essential at every stage of the research process to meeting our goals and maintaining leadership of the Earth Sciences Division in atmospheric science research. Figure 1.1 shows the 22-year record of peer-reviewed publications and proposals among the various laboratories.

A Bayesian computational model for online character recognition and disability assessment during cursive eye writing.

PubMed

Diard, Julien; Rynik, Vincent; Lorenceau, Jean

2013-01-01

This research involves a novel apparatus, in which the user is presented with an illusion inducing visual stimulus. The user perceives illusory movement that can be followed by the eye, so that smooth pursuit eye movements can be sustained in arbitrary directions. Thus, free-flow trajectories of any shape can be traced. In other words, coupled with an eye-tracking device, this apparatus enables "eye writing," which appears to be an original object of study. We adapt a previous model of reading and writing to this context. We describe a probabilistic model called the Bayesian Action-Perception for Eye On-Line model (BAP-EOL). It encodes probabilistic knowledge about isolated letter trajectories, their size, high-frequency components of the produced trajectory, and pupil diameter. We show how Bayesian inference, in this single model, can be used to solve several tasks, like letter recognition and novelty detection (i.e., recognizing when a presented character is not part of the learned database). We are interested in the potential use of the eye writing apparatus by motor impaired patients: the final task we solve by Bayesian inference is disability assessment (i.e., measuring and tracking the evolution of motor characteristics of produced trajectories). Preliminary experimental results are presented, which illustrate the method, showing the feasibility of character recognition in the context of eye writing. We then show experimentally how a model of the unknown character can be used to detect trajectories that are likely to be new symbols, and how disability assessment can be performed by opportunistically observing characteristics of fine motor control, as letter are being traced. Experimental analyses also help identify specificities of eye writing, as compared to handwriting, and the resulting technical challenges.

A Bayesian computational model for online character recognition and disability assessment during cursive eye writing

PubMed Central

Diard, Julien; Rynik, Vincent; Lorenceau, Jean

2013-01-01

This research involves a novel apparatus, in which the user is presented with an illusion inducing visual stimulus. The user perceives illusory movement that can be followed by the eye, so that smooth pursuit eye movements can be sustained in arbitrary directions. Thus, free-flow trajectories of any shape can be traced. In other words, coupled with an eye-tracking device, this apparatus enables “eye writing,” which appears to be an original object of study. We adapt a previous model of reading and writing to this context. We describe a probabilistic model called the Bayesian Action-Perception for Eye On-Line model (BAP-EOL). It encodes probabilistic knowledge about isolated letter trajectories, their size, high-frequency components of the produced trajectory, and pupil diameter. We show how Bayesian inference, in this single model, can be used to solve several tasks, like letter recognition and novelty detection (i.e., recognizing when a presented character is not part of the learned database). We are interested in the potential use of the eye writing apparatus by motor impaired patients: the final task we solve by Bayesian inference is disability assessment (i.e., measuring and tracking the evolution of motor characteristics of produced trajectories). Preliminary experimental results are presented, which illustrate the method, showing the feasibility of character recognition in the context of eye writing. We then show experimentally how a model of the unknown character can be used to detect trajectories that are likely to be new symbols, and how disability assessment can be performed by opportunistically observing characteristics of fine motor control, as letter are being traced. Experimental analyses also help identify specificities of eye writing, as compared to handwriting, and the resulting technical challenges. PMID:24273525

Vitamins and Microelement Bioavailability in Different Stages of Chronic Kidney Disease.

PubMed

Jankowska, Magdalena; Rutkowski, Bolesław; Dębska-Ślizień, Alicja

2017-03-15

Chronic kidney disease (CKD) predisposes one to either deficiency or toxic excess of different micronutrients. The knowledge on micronutrients-specifically water-soluble vitamins and trace elements-in CKD is very limited. Consequently, current guidelines and recommendations are mostly based on expert opinions or poor-quality evidence. Abnormalities of micronutrient resources in CKD develop for several reasons. Dietary restrictions and anorexia lead to an insufficient micronutrient intake, while diuretics use and renal replacement therapy lead to their excessive losses. Absorption is unpredictable, and metabolism impaired. Better understanding of the micronutrient needs of CKD patients could have an impact on many complications linked to vitamin and trace element disorders, including high mortality, increased risk of atherosclerosis, inflammation, oxidative stress, anemia, polyneuropathy, encephalopathy, weakness and fragility, muscle cramps, bone disease, depression, or insomnia. Here, we summarize the up-to-date knowledge on micronutrient resources in different stages of CKD, and share our experience with the assessment of micronutrient status.

Comparing TID simulations using 3-D ray tracing and mirror reflection

NASA Astrophysics Data System (ADS)

Huang, X.; Reinisch, B. W.; Sales, G. S.; Paznukhov, V. V.; Galkin, I. A.

2016-04-01

Measuring the time variations of Doppler frequencies and angles of arrival (AoA) of ionospherically reflected HF waves has been proposed as a means of detecting the occurrence of traveling ionospheric disturbances (TIDs). Simulations are made using ray tracing through the International Reference Ionosphere (IRI) electron density model in an effort to reproduce measured signatures. The TID is represented by a wavelike perturbation of the 3-D electron density traveling horizontally in the ionosphere with an amplitude that varies sinusoidally with time. By judiciously selecting the TID parameters the ray tracing simulation reproduces the observed Doppler frequencies and AoAs. Ray tracing in a 3-D realistic ionosphere is, however, excessively time consuming considering the involved homing procedures. It is shown that a carefully selected reflecting corrugated mirror can reproduce the time variations of the AoA and Doppler frequency. The results from the ray tracing through the IRI model ionosphere and the mirror model reflections are compared to assess the applicability of the mirror-reflection model.

Trace metal fractionation as a mean to improve on the management of contaminated sediments from runoff water in infiltration basins.

PubMed

Al Husseini, Amelène El-Mufleh; Béchet, Béatrice; Gaudin, Anne; Ruban, Véronique

2013-01-01

The management of stormwater sediment is a key issue for local authorities due to the pollution load and significant tonnages. In view of reuse, for example for civil engineering, the environmental evaluation of these highly aggregated sediments requires the study of the fractionation and mobility of trace metals. The distribution of trace metals (Cd, Cr, Cu, Ni, Pb, Zn) and their level of lability in three French stormwater sediments was determined using sequential and kinetic extractions (EDTA reagent) associated with mineralogical analysis and scanning electron microscopy observations. Using microanalysis, new data were acquired on the evolution of aggregate state during extractions, and on its significant role in the retention of trace metals. Trace metals were, in particular, observed to be very stable in small aggregates (10-50 microm). Comparison of the two extraction methods revealed that EDTA extraction was not convenient for evaluating the stable fraction of Cr, Ni and Zn. Moreover, the results were relevant for basins presenting similar sources of trace metals, whatever the physicochemical conditions in basins. The results suggest that the management of stormwater sediments could be improved by a better knowledge of metal mobility, as chemical extractions could highlight the localization of the mobile fraction of trace metals. Treatment could be therefore avoided, or specific treatment could be applied to a reduced volume of sediments.

Trace elements in Mediterranean seagrasses and macroalgae. A review.

PubMed

Bonanno, Giuseppe; Orlando-Bonaca, Martina

2018-03-15

This review investigates the current state of knowledge on the levels of the main essential and non-essential trace elements in Mediterranean vascular plants and macroalgae. The research focuses also on the so far known effects of high element concentrations on these marine organisms. The possible use of plants and algae as bioindicators of marine pollution is discussed as well. The presence of trace elements is overall well known in all five Mediterranean vascular plants, whereas current studies investigated element concentrations in only c. 5.0% of all native Mediterranean macroalgae. Although seagrasses and macroalgae can generally accumulate and tolerate high concentrations of trace elements, phytotoxic levels are still not clearly identified for both groups of organisms. Moreover, although the high accumulation of trace elements in seagrasses and macroalgae is considered as a significant risk for the associated food webs, the real magnitude of this risk has not been adequately investigated yet. The current research provides enough scientific evidence that seagrasses and macroalgae may act as effective bioindicators, especially the former for trace elements in sediments, and the latter in seawater. The combined use of seagrasses and macroalgae as bioindicators still lacks validated protocols, whose application should be strongly encouraged to biomonitor exhaustively the presence of trace elements in the abiotic and biotic components of coastal ecosystems. Copyright © 2017 Elsevier B.V. All rights reserved.

Modeling a 400 Hz Signal Transmission Through the South China Sea Basin

DTIC Science & Technology

2009-03-01

TRACING ..........................8 1. General Ray Theory and the Eikonal Approximation .....................8 2. Hamiltonian Ray Tracing...HAMILTONIAN RAY TRACING 1. General Ray Theory and the Eikonal Approximation In general, modeling acoustic propagation through the ocean necessitates... eikonal and represents the phase component of the solution. Since solutions of constant phase represent wave fronts, and rays travel in a direction

QSAR-like models: a potential tool for the selection of PhACs and EDCs for monitoring purposes in drinking water treatment systems--a review.

PubMed

Delgado, Luis F; Charles, Philippe; Glucina, Karl; Morlay, Catherine

2012-12-01

Recent studies have demonstrated the presence of trace-level pharmaceutically active compounds (PhACs) and endocrine disrupting compounds (EDCs) in a number of finished drinking waters (DWs). Since there is sparse knowledge currently available on the potential effects on human health associated with the chronic exposure to trace levels of these Emerging Contaminants (ECs) through routes such as DW, it is suggested that the most appropriate criterion is a treatment criterion in order to prioritize ECs to be monitored during DW preparation. Hence, only the few ECs showing the lowest removals towards a given DW Treatment (DWT) process would serve as indicators of the overall efficiency of this process and would be relevant for DW quality monitoring. In addition, models should be developed for estimating the removal of ECs in DWT processes, thereby overcoming the practical difficulties of experimentally assessing each compound. Therefore, the present review has two objectives: (1) to provide an overview of the recent scientific surveys on the occurrence of PhACs and EDCs in finished DWs; and (2) to propose the potential of Quantitative-Structure-Activity-Relationship-(QSAR)-like models to rank ECs found in environmental waters, including parent compounds, metabolites and transformation products, in order to select the most relevant compounds to be considered as indicators for monitoring purposes in DWT systems. Copyright © 2012 Elsevier Ltd. All rights reserved.

Why trace and delay conditioning are sometimes (but not always) hippocampal dependent: A computational model

PubMed Central

Moustafa, Ahmed A.; Wufong, Ella; Servatius, Richard J.; Pang, Kevin C. H.; Gluck, Mark A.; Myers, Catherine E.

2013-01-01

A recurrent-network model provides a unified account of the hippocampal region in mediating the representation of temporal information in classical eyeblink conditioning. Much empirical research is consistent with a general conclusion that delay conditioning (in which the conditioned stimulus CS and unconditioned stimulus US overlap and co-terminate) is independent of the hippocampal system, while trace conditioning (in which the CS terminates before US onset) depends on the hippocampus. However, recent studies show that, under some circumstances, delay conditioning can be hippocampal-dependent and trace conditioning can be spared following hippocampal lesion. Here, we present an extension of our prior trial-level models of hippocampal function and stimulus representation that can explain these findings within a unified framework. Specifically, the current model includes adaptive recurrent collateral connections that aid in the representation of intra-trial temporal information. With this model, as in our prior models, we argue that the hippocampus is not specialized for conditioned response timing, but rather is a general-purpose system that learns to predict the next state of all stimuli given the current state of variables encoded by activity in recurrent collaterals. As such, the model correctly predicts that hippocampal involvement in classical conditioning should be critical not only when there is an intervening trace interval, but also when there is a long delay between CS onset and US onset. Our model simulates empirical data from many variants of classical conditioning, including delay and trace paradigms in which the length of the CS, the inter-stimulus interval, or the trace interval is varied. Finally, we discuss model limitations, future directions, and several novel empirical predictions of this temporal processing model of hippocampal function and learning. PMID:23178699

A Methodology and Software Environment for Testing Process Model’s Sequential Predictions with Protocols

DTIC Science & Technology

1992-12-21

in preparation). Foundations of artificial intelligence. Cambridge, MA: MIT Press. O’Reilly, R. C. (1991). X3DNet: An X- Based Neural Network ...2.2.3 Trace based protocol analysis 19 2.2A Summary of important data features 21 2.3 Tools related to process model testing 23 2.3.1 Tools for building...algorithm 57 3. Requirements for testing process models using trace based protocol 59 analysis 3.1 Definition of trace based protocol analysis (TBPA) 59

Interaction in Spoken Word Recognition Models: Feedback Helps.

PubMed

Magnuson, James S; Mirman, Daniel; Luthra, Sahil; Strauss, Ted; Harris, Harlan D

2018-01-01

Human perception, cognition, and action requires fast integration of bottom-up signals with top-down knowledge and context. A key theoretical perspective in cognitive science is the interactive activation hypothesis: forward and backward flow in bidirectionally connected neural networks allows humans and other biological systems to approximate optimal integration of bottom-up and top-down information under real-world constraints. An alternative view is that online feedback is neither necessary nor helpful; purely feed forward alternatives can be constructed for any feedback system, and online feedback could not improve processing and would preclude veridical perception. In the domain of spoken word recognition, the latter view was apparently supported by simulations using the interactive activation model, TRACE, with and without feedback: as many words were recognized more quickly without feedback as were recognized faster with feedback, However, these simulations used only a small set of words and did not address a primary motivation for interaction: making a model robust in noise. We conducted simulations using hundreds of words, and found that the majority were recognized more quickly with feedback than without. More importantly, as we added noise to inputs, accuracy and recognition times were better with feedback than without. We follow these simulations with a critical review of recent arguments that online feedback in interactive activation models like TRACE is distinct from other potentially helpful forms of feedback. We conclude that in addition to providing the benefits demonstrated in our simulations, online feedback provides a plausible means of implementing putatively distinct forms of feedback, supporting the interactive activation hypothesis.

Interaction in Spoken Word Recognition Models: Feedback Helps

PubMed Central

Magnuson, James S.; Mirman, Daniel; Luthra, Sahil; Strauss, Ted; Harris, Harlan D.

2018-01-01

Human perception, cognition, and action requires fast integration of bottom-up signals with top-down knowledge and context. A key theoretical perspective in cognitive science is the interactive activation hypothesis: forward and backward flow in bidirectionally connected neural networks allows humans and other biological systems to approximate optimal integration of bottom-up and top-down information under real-world constraints. An alternative view is that online feedback is neither necessary nor helpful; purely feed forward alternatives can be constructed for any feedback system, and online feedback could not improve processing and would preclude veridical perception. In the domain of spoken word recognition, the latter view was apparently supported by simulations using the interactive activation model, TRACE, with and without feedback: as many words were recognized more quickly without feedback as were recognized faster with feedback, However, these simulations used only a small set of words and did not address a primary motivation for interaction: making a model robust in noise. We conducted simulations using hundreds of words, and found that the majority were recognized more quickly with feedback than without. More importantly, as we added noise to inputs, accuracy and recognition times were better with feedback than without. We follow these simulations with a critical review of recent arguments that online feedback in interactive activation models like TRACE is distinct from other potentially helpful forms of feedback. We conclude that in addition to providing the benefits demonstrated in our simulations, online feedback provides a plausible means of implementing putatively distinct forms of feedback, supporting the interactive activation hypothesis. PMID:29666593

Testing Linear Temporal Logic Formulae on Finite Execution Traces

NASA Technical Reports Server (NTRS)

Havelund, Klaus; Rosu, Grigore; Norvig, Peter (Technical Monitor)

2001-01-01

We present an algorithm for efficiently testing Linear Temporal Logic (LTL) formulae on finite execution traces. The standard models of LTL are infinite traces, reflecting the behavior of reactive and concurrent systems which conceptually may be continuously alive. In most past applications of LTL. theorem provers and model checkers have been used to formally prove that down-scaled models satisfy such LTL specifications. Our goal is instead to use LTL for up-scaled testing of real software applications. Such tests correspond to analyzing the conformance of finite traces against LTL formulae. We first describe what it means for a finite trace to satisfy an LTL property. We then suggest an optimized algorithm based on transforming LTL formulae. The work is done using the Maude rewriting system. which turns out to provide a perfect notation and an efficient rewriting engine for performing these experiments.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doug Blankenship

Archive of ArcGIS data from the West Flank FORGE site located in Coso, California. Archive contains the following eight shapefiles: Polygon of the 3D geologic model (WestFlank3DGeologicModelExtent) Polylines of the traces 3D modeled faults (WestFlank3DModeledFaultTraces) Polylines of the fault traces from Duffield and Bacon, 1980 (WestFlankFaultsfromDuffieldandBacon) Polygon of the West Flank FORGE site (WestFlankFORGEsite) Polylines of the traces of the geologic cross-sections (cross-sections in a separate archive in the GDR) (WestFlankGeologicCrossSections) Polylines of the traces of the seismic reflection profiles through and adjacent to the West Flank site (seismic reflection profiles in a separate archive in the GDR) (WestFlankSiesmicReflectionProfiles) Pointsmore » of the well collars in and around the West Flank site (WestFlankWellCollars) Polylines of the surface expression of the West Flank well paths (WestFlankWellPaths)« less

Mapping the audit traces of interdisciplinary collaboration: bridging and blending between choreography and cognitive science

PubMed Central

Barnard, Philip; deLahunta, Scott

2017-01-01

ABSTRACT Two long-term sci–art research projects are described and positioned in the broader conceptual landscape of interdisciplinary collaboration. Both projects were aimed at understanding and augmenting choreographic decision-making and both were grounded in research conducted within a leading contemporary dance company. In each case, the work drew upon methods and theory from the cognitive sciences, and both had a direct impact on the way in which the company made new work. In the synthesis presented here the concept of an audit trace is introduced. Audit traces identify how specific classes of knowledge are used and transformed not only within the arts or sciences but also when arts practice is informed by science or when arts practice informs science. PMID:29308084

Active engagement in a web-based tutorial to prevent obesity grounded in Fuzzy-Trace Theory predicts higher knowledge and gist comprehension.

PubMed

Brust-Renck, Priscila G; Reyna, Valerie F; Wilhelms, Evan A; Wolfe, Christopher R; Widmer, Colin L; Cedillos-Whynott, Elizabeth M; Morant, A Kate

2017-08-01

We used Sharable Knowledge Objects (SKOs) to create an Intelligent Tutoring System (ITS) grounded in Fuzzy-Trace Theory to teach women about obesity prevention: GistFit, getting the gist of healthy eating and exercise. The theory predicts that reliance on gist mental representations (as opposed to verbatim) is more effective in reducing health risks and improving decision making. Technical information was translated into decision-relevant gist representations and gist principles (i.e., healthy values). The SKO was hypothesized to facilitate extracting these gist representations and principles by engaging women in dialogue, "understanding" their responses, and replying appropriately to prompt additional engagement. Participants were randomly assigned to either the obesity prevention tutorial (GistFit) or a control tutorial containing different content using the same technology. Participants were administered assessments of knowledge about nutrition and exercise, gist comprehension, gist principles, behavioral intentions and self-reported behavior. An analysis of engagement in tutorial dialogues and responses to multiple-choice questions to check understanding throughout the tutorial revealed significant correlations between these conversations and scores on subsequent knowledge tests and gist comprehension. Knowledge and comprehension measures correlated with healthier behavior and greater intentions to perform healthy behavior. Differences between GistFit and control tutorials were greater for participants who engaged more fully. Thus, results are consistent with the hypothesis that active engagement with a new gist-based ITS, rather than a passive memorization of verbatim details, was associated with an array of known psychosocial mediators of preventive health decisions, such as knowledge acquisition, and gist comprehension.

Trace elements and radionuclides in palm oil, soil, water, and leaves from oil palm plantations: A review.

PubMed

Olafisoye, O B; Oguntibeju, O O; Osibote, O A

2017-05-03

Oil palm (Elaeisguineensis) is one of the most productive oil producing plant in the world. Crude palm oil is composed of triglycerides supplying the world's need of edible oils and fats. Palm oil also provides essential elements and antioxidants that are potential mediators of cellular functions. Experimental studies have demonstrated the toxicity of the accumulation of significant amounts of nonessential trace elements and radionuclides in palm oil that affects the health of consumers. It has been reported that uptake of trace elements and radionuclides from the oil palm tree may be from water and soil on the palm plantations. In the present review, an attempt was made to revise and access knowledge on the presence of some selected trace elements and radionuclides in palm oil, soil, water, and leaves from oil palm plantations based on the available facts and data. Existing reports show that the presence of nonessential trace elements and radionuclides in palm oil may be from natural or anthropogenic sources in the environment. However, the available literature is limited and further research need to be channeled to the investigation of trace elements and radionuclides in soil, water, leaves, and palm oil from oil palm plantations around the globe.

Factors influencing health care workers’ implementation of tuberculosis contact tracing in Kweneng, Botswana

PubMed Central

Tlale, Lebapotswe; Frasso, Rosemary; Kgosiesele, Onalenna; Selemogo, Mpho; Mothei, Quirk; Habte, Dereje; Steenhoff, Andrew

2016-01-01

Introduction TB contact tracing rates remain low in high burden settings and reasons for this are not well known. We describe factors that influence health care workers' (HCW) implementation of TB contact tracing (CT) in a high TB burden district of Botswana. Methods Data were collected using questionnaires and in-depth interviews in 31 of the 52 health facilities in Kweneng East Health District. Responses were summarized using summary statistics and comparisons between HCW groups were done using parametric or non-parametric tests as per normality of the data distribution. Results One hundred and four HCWs completed questionnaires. Factors that influenced HCW TB contact tracing were their knowledge, attitudes and practices as well as personal factors including decreased motivation and lack of commitment. Patient factors included living further away from the clinic, unknown residential address and high rates of migration and mobility. Administrative factors included staff shortages, lack of transport, poor reporting of TB cases and poor medical infrastructure e.g. suboptimal laboratory services. A national HCW strike and a restructuring of the health system emerged as additional factors during in-depth interviews of TB coordinators. Conclusion Multiple factors lead to poor TB contact tracing in this district. Interventions to increase TB contact tracing will be informed by these findings. PMID:27800084

Factors influencing health care workers' implementation of tuberculosis contact tracing in Kweneng, Botswana.

PubMed

Tlale, Lebapotswe; Frasso, Rosemary; Kgosiesele, Onalenna; Selemogo, Mpho; Mothei, Quirk; Habte, Dereje; Steenhoff, Andrew

2016-01-01

TB contact tracing rates remain low in high burden settings and reasons for this are not well known. We describe factors that influence health care workers' (HCW) implementation of TB contact tracing (CT) in a high TB burden district of Botswana. Data were collected using questionnaires and in-depth interviews in 31 of the 52 health facilities in Kweneng East Health District. Responses were summarized using summary statistics and comparisons between HCW groups were done using parametric or non-parametric tests as per normality of the data distribution. One hundred and four HCWs completed questionnaires. Factors that influenced HCW TB contact tracing were their knowledge, attitudes and practices as well as personal factors including decreased motivation and lack of commitment. Patient factors included living further away from the clinic, unknown residential address and high rates of migration and mobility. Administrative factors included staff shortages, lack of transport, poor reporting of TB cases and poor medical infrastructure e.g. suboptimal laboratory services. A national HCW strike and a restructuring of the health system emerged as additional factors during in-depth interviews of TB coordinators. Multiple factors lead to poor TB contact tracing in this district. Interventions to increase TB contact tracing will be informed by these findings.

Deception in plants: mimicry or perceptual exploitation?

PubMed

Schaefer, H Martin; Ruxton, Graeme D

2009-12-01

Mimicry involves adaptive resemblance between a mimic and a model. However, despite much recent research, it remains contentious in plants. Here, we review recent progress on studying deception by flowers, distinguishing between plants relying on mimicry to achieve pollination and those relying on the exploitation of the perceptual biases of animals. We disclose fundamental differences between both mechanisms and explain why the evolution of exploitation is less constrained than that of mimicry. Exploitation of perceptual biases might thus be a precursor for the gradual evolution of mimicry. Increasing knowledge on the sensory and cognitive filters in animals, and on the selective pressures that maintain them, should aid researchers in tracing the evolutionary dynamics of deception in plants.

Surface chemistry and mineralogy. [of planet Mars

NASA Technical Reports Server (NTRS)

Banin, A.; Clark, B. C.; Waenke, H.

1992-01-01

The accumulated knowledge on the chemistry and mineralogy of Martian surface materials is reviewed. Pertinent information obtained by direct analyses of the soil on Mars by the Viking Landers, by remote sensing of Mars from flyby and orbiting spacecraft, by telescopic observations from earth, and through detailed analyses of the SNC meteorites presumed to be Martian rocks are summarized and analyzed. A compositional model for Mars soil, giving selected average elemental concentrations of major and trace elements, is suggested. It is proposed that the fine surface materials on Mars are a multicomponent mixture of weathered and nonweathered minerals. Smectite clays, silicate mineraloids similar to palagonite, and scapolite are suggested as possible major candidate components among the weathered minerals.

Three-dimensional ray-tracing model for the study of advanced refractive errors in keratoconus.

PubMed

Schedin, Staffan; Hallberg, Per; Behndig, Anders

2016-01-20

We propose a numerical three-dimensional (3D) ray-tracing model for the analysis of advanced corneal refractive errors. The 3D modeling was based on measured corneal elevation data by means of Scheimpflug photography. A mathematical description of the measured corneal surfaces from a keratoconus (KC) patient was used for the 3D ray tracing, based on Snell's law of refraction. A model of a commercial intraocular lens (IOL) was included in the analysis. By modifying the posterior IOL surface, it was shown that the imaging quality could be significantly improved. The RMS values were reduced by approximately 50% close to the retina, both for on- and off-axis geometries. The 3D ray-tracing model can constitute a basis for simulation of customized IOLs that are able to correct the advanced, irregular refractive errors in KC.

An Analysis of Machine- and Human-Analytics in Classification.

PubMed

Tam, Gary K L; Kothari, Vivek; Chen, Min

2017-01-01

In this work, we present a study that traces the technical and cognitive processes in two visual analytics applications to a common theoretic model of soft knowledge that may be added into a visual analytics process for constructing a decision-tree model. Both case studies involved the development of classification models based on the "bag of features" approach. Both compared a visual analytics approach using parallel coordinates with a machine-learning approach using information theory. Both found that the visual analytics approach had some advantages over the machine learning approach, especially when sparse datasets were used as the ground truth. We examine various possible factors that may have contributed to such advantages, and collect empirical evidence for supporting the observation and reasoning of these factors. We propose an information-theoretic model as a common theoretic basis to explain the phenomena exhibited in these two case studies. Together we provide interconnected empirical and theoretical evidence to support the usefulness of visual analytics.

An architecture for the development of real-time fault diagnosis systems using model-based reasoning

NASA Technical Reports Server (NTRS)

Hall, Gardiner A.; Schuetzle, James; Lavallee, David; Gupta, Uday

1992-01-01

Presented here is an architecture for implementing real-time telemetry based diagnostic systems using model-based reasoning. First, we describe Paragon, a knowledge acquisition tool for offline entry and validation of physical system models. Paragon provides domain experts with a structured editing capability to capture the physical component's structure, behavior, and causal relationships. We next describe the architecture of the run time diagnostic system. The diagnostic system, written entirely in Ada, uses the behavioral model developed offline by Paragon to simulate expected component states as reflected in the telemetry stream. The diagnostic algorithm traces causal relationships contained within the model to isolate system faults. Since the diagnostic process relies exclusively on the behavioral model and is implemented without the use of heuristic rules, it can be used to isolate unpredicted faults in a wide variety of systems. Finally, we discuss the implementation of a prototype system constructed using this technique for diagnosing faults in a science instrument. The prototype demonstrates the use of model-based reasoning to develop maintainable systems with greater diagnostic capabilities at a lower cost.

Trace conditioning in insects—keep the trace!

PubMed Central

Dylla, Kristina V.; Galili, Dana S.; Szyszka, Paul; Lüdke, Alja

2013-01-01

Trace conditioning is a form of associative learning that can be induced by presenting a conditioned stimulus (CS) and an unconditioned stimulus (US) following each other, but separated by a temporal gap. This gap distinguishes trace conditioning from classical delay conditioning, where the CS and US overlap. To bridge the temporal gap between both stimuli and to form an association between CS and US in trace conditioning, the brain must keep a neural representation of the CS after its termination—a stimulus trace. Behavioral and physiological studies on trace and delay conditioning revealed similarities between the two forms of learning, like similar memory decay and similar odor identity perception in invertebrates. On the other hand differences were reported also, like the requirement of distinct brain structures in vertebrates or disparities in molecular mechanisms in both vertebrates and invertebrates. For example, in commonly used vertebrate conditioning paradigms the hippocampus is necessary for trace but not for delay conditioning, and Drosophila delay conditioning requires the Rutabaga adenylyl cyclase (Rut-AC), which is dispensable in trace conditioning. It is still unknown how the brain encodes CS traces and how they are associated with a US in trace conditioning. Insects serve as powerful models to address the mechanisms underlying trace conditioning, due to their simple brain anatomy, behavioral accessibility and established methods of genetic interference. In this review we summarize the recent progress in insect trace conditioning on the behavioral and physiological level and emphasize similarities and differences compared to delay conditioning. Moreover, we examine proposed molecular and computational models and reassess different experimental approaches used for trace conditioning. PMID:23986710

Linking genes to ecosystem trace gas fluxes in a large-scale model system

NASA Astrophysics Data System (ADS)

Meredith, L. K.; Cueva, A.; Volkmann, T. H. M.; Sengupta, A.; Troch, P. A.

2017-12-01

Soil microorganisms mediate biogeochemical cycles through biosphere-atmosphere gas exchange with significant impact on atmospheric trace gas composition. Improving process-based understanding of these microbial populations and linking their genomic potential to the ecosystem-scale is a challenge, particularly in soil systems, which are heterogeneous in biodiversity, chemistry, and structure. In oligotrophic systems, such as the Landscape Evolution Observatory (LEO) at Biosphere 2, atmospheric trace gas scavenging may supply critical metabolic needs to microbial communities, thereby promoting tight linkages between microbial genomics and trace gas utilization. This large-scale model system of three initially homogenous and highly instrumented hillslopes facilitates high temporal resolution characterization of subsurface trace gas fluxes at hundreds of sampling points, making LEO an ideal location to study microbe-mediated trace gas fluxes from the gene to ecosystem scales. Specifically, we focus on the metabolism of ubiquitous atmospheric reduced trace gases hydrogen (H2), carbon monoxide (CO), and methane (CH4), which may have wide-reaching impacts on microbial community establishment, survival, and function. Additionally, microbial activity on LEO may facilitate weathering of the basalt matrix, which can be studied with trace gas measurements of carbonyl sulfide (COS/OCS) and carbon dioxide (O-isotopes in CO2), and presents an additional opportunity for gene to ecosystem study. This work will present initial measurements of this suite of trace gases to characterize soil microbial metabolic activity, as well as links between spatial and temporal variability of microbe-mediated trace gas fluxes in LEO and their relation to genomic-based characterization of microbial community structure (phylogenetic amplicons) and genetic potential (metagenomics). Results from the LEO model system will help build understanding of the importance of atmospheric inputs to microorganisms pioneering fresh mineral matrix. Additionally, the measurement and modeling techniques that will be developed at LEO will be relevant for other investigators linking microbial genomics to ecosystem function in more well-developed soils with greater complexity.

The role of working memory and declarative memory in trace conditioning

PubMed Central

Connor, David A.; Gould, Thomas J.

2017-01-01

Translational assays of cognition that are similarly implemented in both lower and higher-order species, such as rodents and primates, provide a means to reconcile preclinical modeling of psychiatric neuropathology and clinical research. To this end, Pavlovian conditioning has provided a useful tool for investigating cognitive processes in both lab animal models and humans. This review focuses on trace conditioning, a form of Pavlovian conditioning typified by the insertion of a temporal gap (i.e., trace interval) between presentations of a conditioned stimulus (CS) and an unconditioned stimulus (US). This review aims to discuss pre-clinical and clinical work investigating the mnemonic processes recruited for trace conditioning. Much work suggests that trace conditioning involves unique neurocognitive mechanisms to facilitate formation of trace memories in contrast to standard Pavlovian conditioning. For example, the hippocampus and prefrontal cortex (PFC) appear to play critical roles in trace conditioning. Moreover, cognitive mechanistic accounts in human studies suggest that working memory and declarative memory processes are engaged to facilitate formation of trace memories. The aim of this review is to integrate cognitive and neurobiological accounts of trace conditioning from preclinical and clinical studies to examine involvement of working and declarative memory. PMID:27422017

Sediment source fingerprinting as an aid to catchment management: A review of the current state of knowledge and a methodological decision-tree for end-users

USGS Publications Warehouse

Collins, A.L; Pulley, S.; Foster, I.D.L; Gellis, Allen; Porto, P.; Horowitz, A.J.

2017-01-01

The growing awareness of the environmental significance of fine-grained sediment fluxes through catchment systems continues to underscore the need for reliable information on the principal sources of this material. Source estimates are difficult to obtain using traditional monitoring techniques, but sediment source fingerprinting or tracing procedures, have emerged as a potentially valuable alternative. Despite the rapidly increasing numbers of studies reporting the use of sediment source fingerprinting, several key challenges and uncertainties continue to hamper consensus among the international scientific community on key components of the existing methodological procedures. Accordingly, this contribution reviews and presents recent developments for several key aspects of fingerprinting, namely: sediment source classification, catchment source and target sediment sampling, tracer selection, grain size issues, tracer conservatism, source apportionment modelling, and assessment of source predictions using artificial mixtures. Finally, a decision-tree representing the current state of knowledge is presented, to guide end-users in applying the fingerprinting approach.

Bioaerosols from composting facilities—a review

PubMed Central

Wéry, Nathalie

2014-01-01

Bioaerosols generated at composting plants are released during processes that involve the vigorous movement of material such as shredding, compost pile turning, or compost screening. Such bioaerosols are a cause of concern because of their potential impact on both occupational health and the public living in close proximity to such facilities. The biological hazards potentially associated with bioaerosol emissions from composting activities include fungi, bacteria, endotoxin, and 1-3 β-glucans. There is a major lack of knowledge concerning the dispersal of airborne microorganisms emitted by composting plants as well as the potential exposure of nearby residents. This is due in part to the difficulty of tracing specifically these microorganisms in air. In recent years, molecular tools have been used to develop new tracers which should help in risk assessments. This review summarizes current knowledge of microbial diversity in composting aerosols and of the associated risks to health. It also considers methodologies introduced recently to enhance understanding of bioaerosol dispersal, including new molecular indicators and modeling. PMID:24772393

Tracing the trilobite tree from the root to the tips: a model marriage of fossils and phylogeny.

PubMed

Lieberman, Bruce S; Karim, Talia S

2010-01-01

Trilobites are a highly diverse group of extinct arthropods that persisted for nearly 300 million years. During that time, there was a profusion of morphological form, and they occupied a plethora of marine habitats. Their diversity, relative abundance, and complex morphology make them excellent candidates for phylogenetic analysis, and partly as a consequence they have been the subject of many cladistic studies. Although phylogenetic knowledge is certainly incomplete, our understanding of evolutionary patterns within the group has dramatically increased over the last 30 years. Moreover, trilobites have formed an important component of various studies of macroevolutionary processes. Here, we summarize the phylogenetic breadth of knowledge on the Trilobita, and present various hypotheses about phylogenetic patterns within the group, from the highest to the lowest taxonomic levels. Key topics we consider include the question of trilobite monophyly, the phylogenetic position of trilobites vis à vis extant arthropod groups, and inter- and intra-ordinal relationships. Copyright (c) 2009 Elsevier Ltd. All rights reserved.

A New Paradigm for Intelligent Tutoring Systems: Example-Tracing Tutors

ERIC Educational Resources Information Center

Aleven, Vincent; McLaren, Bruce M.; Sewall, Jonathan; Koedinger, Kenneth R.

2009-01-01

The Cognitive Tutor Authoring Tools (CTAT) support creation of a novel type of tutors called example-tracing tutors. Unlike other types of ITSs (e.g., model-tracing tutors, constraint-based tutors), example-tracing tutors evaluate student behavior by flexibly comparing it against generalized examples of problem-solving behavior. Example-tracing…

Accumulated energy norm for full waveform inversion of marine data

NASA Astrophysics Data System (ADS)

Shin, Changsoo; Ha, Wansoo

2017-12-01

Macro-velocity models are important for imaging the subsurface structure. However, the conventional objective functions of full waveform inversion in the time and the frequency domain have a limited ability to recover the macro-velocity model because of the absence of low-frequency information. In this study, we propose new objective functions that can recover the macro-velocity model by minimizing the difference between the zero-frequency components of the square of seismic traces. Instead of the seismic trace itself, we use the square of the trace, which contains low-frequency information. We apply several time windows to the trace and obtain zero-frequency information of the squared trace for each time window. The shape of the new objective functions shows that they are suitable for local optimization methods. Since we use the acoustic wave equation in this study, this method can be used for deep-sea marine data, in which elastic effects can be ignored. We show that the zero-frequency components of the square of the seismic traces can be used to recover macro-velocities from synthetic and field data.

Framework based on stochastic L-Systems for modeling IP traffic with multifractal behavior

NASA Astrophysics Data System (ADS)

Salvador, Paulo S.; Nogueira, Antonio; Valadas, Rui

2003-08-01

In a previous work we have introduced a multifractal traffic model based on so-called stochastic L-Systems, which were introduced by biologist A. Lindenmayer as a method to model plant growth. L-Systems are string rewriting techniques, characterized by an alphabet, an axiom (initial string) and a set of production rules. In this paper, we propose a novel traffic model, and an associated parameter fitting procedure, which describes jointly the packet arrival and the packet size processes. The packet arrival process is modeled through a L-System, where the alphabet elements are packet arrival rates. The packet size process is modeled through a set of discrete distributions (of packet sizes), one for each arrival rate. In this way the model is able to capture correlations between arrivals and sizes. We applied the model to measured traffic data: the well-known pOct Bellcore, a trace of aggregate WAN traffic and two traces of specific applications (Kazaa and Operation Flashing Point). We assess the multifractality of these traces using Linear Multiscale Diagrams. The suitability of the traffic model is evaluated by comparing the empirical and fitted probability mass and autocovariance functions; we also compare the packet loss ratio and average packet delay obtained with the measured traces and with traces generated from the fitted model. Our results show that our L-System based traffic model can achieve very good fitting performance in terms of first and second order statistics and queuing behavior.

Multi-trace element levels and arsenic speciation in urine of e-waste recycling workers from Agbogbloshie, Accra in Ghana.

PubMed

Asante, Kwadwo Ansong; Agusa, Tetsuro; Biney, Charles Augustus; Agyekum, William Atuobi; Bello, Mohammed; Otsuka, Masanari; Itai, Takaaki; Takahashi, Shin; Tanabe, Shinsuke

2012-05-01

To understand human contamination by multi-trace elements (TEs) in electrical and electronic waste (e-waste) recycling site at Agbogbloshie, Accra in Ghana, this study analyzed TEs and As speciation in urine of e-waste recycling workers. Concentrations of Fe, Sb, and Pb in urine of e-waste recycling workers were significantly higher than those of reference sites after consideration of interaction by age, indicating that the recycling workers are exposed to these TEs through the recycling activity. Urinary As concentration was relatively high, although the level in drinking water was quite low. Speciation analysis of As in human urine revealed that arsenobetaine and dimethylarsinic acid were the predominant As species and concentrations of both species were positively correlated with total As concentration as well as between each other. These results suggest that such compounds may be derived from the same source, probably fish and shellfish and greatly influence As exposure levels. To our knowledge, this is the first study on human contamination resulting from the primitive recycling of e-waste in Ghana. This study will contribute to the knowledge about human exposure to trace elements from an e-waste site in a less industrialized region so far scantly covered in the literature. Copyright © 2012 Elsevier B.V. All rights reserved.

Authoring Model-Tracing Cognitive Tutors

ERIC Educational Resources Information Center

Blessing, Stephen B.; Gilbert, Stephen B.; Ourada, Stephen; Ritter, Steven

2009-01-01

Intelligent Tutoring Systems (ITSs) that employ a model-tracing methodology have consistently shown their effectiveness. However, what evidently makes these tutors effective, the cognitive model embedded within them, has traditionally been difficult to create, requiring great expertise and time, both of which come at a cost. Furthermore, an…

TRACE Model for Simulation of Anticipated Transients Without Scram in a BWR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng L. Y.; Baek J.; Cuadra,A.

2013-11-10

A TRACE model has been developed for using theTRACE/PARCS computational package [1, 2] to simulate anticipated transients without scram (ATWS) events in a boiling water reactor (BWR). The model represents a BWR/5 housed in a Mark II containment. The reactor and the balance of plant systems are modeled in sufficient detail to enable the evaluation of plant responses and theeffectiveness of automatic and operator actions tomitigate this beyond design basis accident.The TRACE model implements features thatfacilitate the simulation of ATWS events initiated by turbine trip and closure of the main steam isolation valves (MSIV). It also incorporates control logic tomore » initiate actions to mitigate the ATWS events, such as water levelcontrol, emergency depressurization, and injection of boron via the standby liquid control system (SLCS). Two different approaches have been used to model boron mixing in the lower plenum of the reactor vessel: modulate coolant flow in the lower plenum by a flow valve, and use control logic to modular.« less

A Bayesian model for estimating population means using a link-tracing sampling design.

PubMed

St Clair, Katherine; O'Connell, Daniel

2012-03-01

Link-tracing sampling designs can be used to study human populations that contain "hidden" groups who tend to be linked together by a common social trait. These links can be used to increase the sampling intensity of a hidden domain by tracing links from individuals selected in an initial wave of sampling to additional domain members. Chow and Thompson (2003, Survey Methodology 29, 197-205) derived a Bayesian model to estimate the size or proportion of individuals in the hidden population for certain link-tracing designs. We propose an addition to their model that will allow for the modeling of a quantitative response. We assess properties of our model using a constructed population and a real population of at-risk individuals, both of which contain two domains of hidden and nonhidden individuals. Our results show that our model can produce good point and interval estimates of the population mean and domain means when our population assumptions are satisfied. © 2011, The International Biometric Society.

Trace Elements Affect Methanogenic Activity and Diversity in Enrichments from Subsurface Coal Bed Produced Water

PubMed Central

Ünal, Burcu; Perry, Verlin Ryan; Sheth, Mili; Gomez-Alvarez, Vicente; Chin, Kuk-Jeong; Nüsslein, Klaus

2012-01-01

Microbial methane from coal beds accounts for a significant and growing percentage of natural gas worldwide. Our knowledge of physical and geochemical factors regulating methanogenesis is still in its infancy. We hypothesized that in these closed systems, trace elements (as micronutrients) are a limiting factor for methanogenic growth and activity. Trace elements are essential components of enzymes or cofactors of metabolic pathways associated with methanogenesis. This study examined the effects of eight trace elements (iron, nickel, cobalt, molybdenum, zinc, manganese, boron, and copper) on methane production, on mcrA transcript levels, and on methanogenic community structure in enrichment cultures obtained from coal bed methane (CBM) well produced water samples from the Powder River Basin, Wyoming. Methane production was shown to be limited both by a lack of additional trace elements as well as by the addition of an overly concentrated trace element mixture. Addition of trace elements at concentrations optimized for standard media enhanced methane production by 37%. After 7 days of incubation, the levels of mcrA transcripts in enrichment cultures with trace element amendment were much higher than in cultures without amendment. Transcript levels of mcrA correlated positively with elevated rates of methane production in supplemented enrichments (R2 = 0.95). Metabolically active methanogens, identified by clone sequences of mcrA mRNA retrieved from enrichment cultures, were closely related to Methanobacterium subterraneum and Methanobacterium formicicum. Enrichment cultures were dominated by M. subterraneum and had slightly higher predicted methanogenic richness, but less diversity than enrichment cultures without amendments. These results suggest that varying concentrations of trace elements in produced water from different subsurface coal wells may cause changing levels of CBM production and alter the composition of the active methanogenic community. PMID:22590465

Retrieval of Vertical Aerosol and Trace Gas Distributions from Polarization Sensitive Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS)

NASA Astrophysics Data System (ADS)

Tirpitz, Jan-Lukas; Friess, Udo; Platt, Ulrich

2017-04-01

An accurate knowledge of the vertical distribution of trace gases and aerosols is crucial for our understanding of the chemical and dynamical processes in the lower troposphere. Their accurate determination is typically only possible by means of laborious and expensive airborne in-situ measurements but in the recent decades, numerous promising ground-based remote sensing approaches have been developed. One of them is to infer vertical distributions from "Differential Optical Absorption Spectroscopy" (DOAS) measurements. DOAS is a technique to analyze UV- and visible radiation spectra of direct or scattered sunlight, which delivers information on different atmospheric parameters, integrated over the light path from space to the instrument. An appropriate set of DOAS measurements, recorded under different viewing directions (Multi-Axis DOAS) and thus different light path geometries, provides information on the atmospheric state. The vertical profiles of aerosol properties and trace gas concentrations can be retrieved from such a set by numerical inversion techniques, incorporating radiative transfer models. The information content of measured data is rarely sufficient for a well-constrained retrieval, particularly for atmospheric layers above 1 km. We showed in first simulations that, apart from spectral properties, the polarization state of skylight is likely to provide a significant amount of additional information on the atmospheric state and thus to enhance retrieval quality. We present first simulations, expectations and ideas on how to implement and characterize a polarization sensitive Multi-Axis DOAS instrument and a corresponding profile retrieval algorithm.

I/O-aware bandwidth allocation for petascale computing systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Zhou; Yang, Xu; Zhao, Dongfang

In the Big Data era, the gap between the storage performance and an appli- cation's I/O requirement is increasing. I/O congestion caused by concurrent storage accesses from multiple applications is inevitable and severely harms the performance. Conventional approaches either focus on optimizing an ap- plication's access pattern individually or handle I/O requests on a low-level storage layer without any knowledge from the upper-level applications. In this paper, we present a novel I/O-aware bandwidth allocation framework to coordinate ongoing I/O requests on petascale computing systems. The motivation behind this innovation is that the resource management system has a holistic view ofmore » both the system state and jobs' activities and can dy- namically control the jobs' status or allocate resource on the y during their execution. We treat a job's I/O requests as periodical subjobs within its lifecycle and transform the I/O congestion issue into a classical scheduling problem. Based on this model, we propose a bandwidth management mech- anism as an extension to the existing scheduling system. We design several bandwidth allocation policies with different optimization objectives either on user-oriented metrics or system performance. We conduct extensive trace- based simulations using real job traces and I/O traces from a production IBM Blue Gene/Q system at Argonne National Laboratory. Experimental results demonstrate that our new design can improve job performance by more than 30%, as well as increasing system performance.« less

From biota to chemistry and climate: towards a comprehensive description of trace gas exchange between the biosphere and atmosphere

NASA Astrophysics Data System (ADS)

Arneth, A.; Sitch, S.; Bondeau, A.; Butterbach-Bahl, K.; Foster, P.; Gedney, N.; de Noblet-Ducoudré, N.; Prentice, I. C.; Sanderson, M.; Thonicke, K.; Wania, R.; Zaehle, S.

2010-01-01

Exchange of non-CO2 trace gases between the land surface and the atmosphere plays an important role in atmospheric chemistry and climate. Recent studies have highlighted its importance for interpretation of glacial-interglacial ice-core records, the simulation of the pre-industrial and present atmosphere, and the potential for large climate-chemistry and climate-aerosol feedbacks in the coming century. However, spatial and temporal variations in trace gas emissions and the magnitude of future feedbacks are a major source of uncertainty in atmospheric chemistry, air quality and climate science. To reduce such uncertainties Dynamic Global Vegetation Models (DGVMs) are currently being expanded to mechanistically represent processes relevant to non-CO2 trace gas exchange between land biota and the atmosphere. In this paper we present a review of important non-CO2 trace gas emissions, the state-of-the-art in DGVM modelling of processes regulating these emissions, identify key uncertainties for global scale model applications, and discuss a methodology for model integration and evaluation.

From biota to chemistry and climate: towards a comprehensive description of trace gas exchange between the biosphere and atmosphere

NASA Astrophysics Data System (ADS)

Arneth, A.; Sitch, S.; Bondeau, A.; Butterbach-Bahl, K.; Foster, P.; Gedney, N.; de Noblet-Ducoudré, N.; Prentice, I. C.; Sanderson, M.; Thonicke, K.; Wania, R.; Zaehle, S.

2009-07-01

Exchange of non-CO2 trace gases between the land surface and the atmosphere plays an important role in atmospheric chemistry and climate. Recent studies have highlighted its importance for interpretation of glacial-interglacial ice-core records, the simulation of the pre-industrial and present atmosphere, and the potential for large climate-chemistry and climate-aerosol feedbacks in the coming century. However, spatial and temporal variations in trace gas emissions and the magnitude of future feedbacks are a major source of uncertainty in atmospheric chemistry, air quality and climate science. To reduce such uncertainties Dynamic Global Vegetation Models (DGVMs) are currently being expanded to mechanistically represent processes relevant to non-CO2 trace gas exchange between land biota and the atmosphere. In this paper we present a review of important non-CO2 trace gas emissions, the state-of-the-art in DGVM modelling of processes regulating these emissions, identify key uncertainties for global scale model applications, and discuss a methodology for model integration and evaluation.

Three dimensional ray tracing of the Jovian magnetosphere in the low frequency range

NASA Technical Reports Server (NTRS)

Menietti, J. D.

1984-01-01

Ray tracing studies of Jovian low frequency emissions were studied. A comprehensive three-dimensional ray tracing computer code for examination of model Jovian decametric (DAM) emission was developed. The improvements to the computer code are outlined and described. The results of the ray tracings of Jovian emissions will be presented in summary form.

Optimizing detector geometry for trace element mapping by X-ray fluorescence.

PubMed

Sun, Yue; Gleber, Sophie-Charlotte; Jacobsen, Chris; Kirz, Janos; Vogt, Stefan

2015-05-01

Trace metals play critical roles in a variety of systems, ranging from cells to photovoltaics. X-Ray Fluorescence (XRF) microscopy using X-ray excitation provides one of the highest sensitivities available for imaging the distribution of trace metals at sub-100 nm resolution. With the growing availability and increasing performance of synchrotron light source based instruments and X-ray nanofocusing optics, and with improvements in energy-dispersive XRF detectors, what are the factors that limit trace element detectability? To address this question, we describe an analytical model for the total signal incident on XRF detectors with various geometries, including the spectral response of energy dispersive detectors. This model agrees well with experimentally recorded X-ray fluorescence spectra, and involves much shorter calculation times than with Monte Carlo simulations. With such a model, one can estimate the signal when a trace element is illuminated with an X-ray beam, and when just the surrounding non-fluorescent material is illuminated. From this signal difference, a contrast parameter can be calculated and this can in turn be used to calculate the signal-to-noise ratio (S/N) for detecting a certain elemental concentration. We apply this model to the detection of trace amounts of zinc in biological materials, and to the detection of small quantities of arsenic in semiconductors. We conclude that increased detector collection solid angle is (nearly) always advantageous even when considering the scattered signal. However, given the choice between a smaller detector at 90° to the beam versus a larger detector at 180° (in a backscatter-like geometry), the 90° detector is better for trace element detection in thick samples, while the larger detector in 180° geometry is better suited to trace element detection in thin samples. Copyright © 2015. Published by Elsevier B.V.

Optimizing detector geometry for trace element mapping by X-ray fluorescence

PubMed Central

Sun, Yue; Gleber, Sophie-Charlotte; Jacobsen, Chris; Kirz, Janos; Vogt, Stefan

2016-01-01

Trace metals play critical roles in a variety of systems, ranging from cells to photovoltaics. X-Ray Fluorescence (XRF) microscopy using X-ray excitation provides one of the highest sensitivities available for imaging the distribution of trace metals at sub-100 nm resolution. With the growing availability and increasing performance of synchrotron light source based instruments and X-ray nanofocusing optics, and with improvements in energy-dispersive XRF detectors, what are the factors that limit trace element detectability? To address this question, we describe an analytical model for the total signal incident on XRF detectors with various geometries, including the spectral response of energy dispersive detectors. This model agrees well with experimentally recorded X-ray fluorescence spectra, and involves much shorter calculation times than with Monte Carlo simulations. With such a model, one can estimate the signal when a trace element is illuminated with an X-ray beam, and when just the surrounding non-fluorescent material is illuminated. From this signal difference, a contrast parameter can be calculated and this can in turn be used to calculate the signal-to-noise ratio (S/N) for detecting a certain elemental concentration. We apply this model to the detection of trace amounts of zinc in biological materials, and to the detection of small quantities of arsenic in semiconductors. We conclude that increased detector collection solid angle is (nearly) always advantageous even when considering the scattered signal. However, given the choice between a smaller detector at 90° to the beam versus a larger detector at 180° (in a backscatter-like geometry), the 90° detector is better for trace element detection in thick samples, while the larger detector in 180° geometry is better suited to trace element detection in thin samples. PMID:25600825

Optimizing detector geometry for trace element mapping by X-ray fluorescence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Yue; Gleber, Sophie-Charlotte; Jacobsen, Chris

Trace metals play critical roles in a variety of systems, ranging from cells to photovoltaics. X-Ray Fluorescence (XRF) microscopy using X-ray excitation provides one of the highest sensitivities available for imaging the distribution of trace metals at sub-100 nm resolution. With the growing availability and increasing performance of synchrotron light source based instruments and X-ray nanofocusing optics, and with improvements in energy-dispersive XRF detectors, what are the factors that limit trace element detectability? To address this question, we describe an analytical model for the total signal incident on XRF detectors with various geometries, including the spectral response of energy dispersivemore » detectors. This model agrees well with experimentally recorded X-ray fluorescence spectra, and involves much shorter calculation times than with Monte Carlo simulations. With such a model, one can estimate the signal when a trace element is illuminated with an X-ray beam, and when just the surrounding non-fluorescent material is illuminated. From this signal difference, a contrast parameter can be calculated and this can in turn be used to calculate the signal-to-noise ratio (S/N) for detecting a certain elemental concentration. We apply this model to the detection of trace amounts of zinc in biological materials, and to the detection of small quantities of arsenic in semiconductors. We conclude that increased detector collection solid angle is (nearly) always advantageous even when considering the scattered signal. However, given the choice between a smaller detector at 90° to the beam versus a larger detector at 180° (in a backscatter-like geometry), the 90° detector is better for trace element detection in thick samples, while the larger detector in 180° geometry is better suited to trace element detection in thin samples.« less

The New Cellular Immunology

ERIC Educational Resources Information Center

Claman, Henry N.

1973-01-01

Discusses the nature of the immune response and traces many of the discoveries that have led to the present state of knowledge in immunology. The new cellular immunology is directing its efforts toward improving health by proper manipulation of the immune mechanisms of the body. (JR)

Comparing FDTD and Ray-Tracing Models in Numerical Simulation of HgCdTe LWIR Photodetectors

NASA Astrophysics Data System (ADS)

Vallone, Marco; Goano, Michele; Bertazzi, Francesco; Ghione, Giovanni; Schirmacher, Wilhelm; Hanna, Stefan; Figgemeier, Heinrich

2016-09-01

We present a simulation study of HgCdTe-based long-wavelength infrared detectors, focusing on methodological comparisons between the finite-difference time-domain (FDTD) and ray-tracing optical models. We performed three-dimensional simulations to determine the absorbed photon density distributions and the corresponding photocurrent and quantum efficiency spectra of isolated n-on- p uniform-composition pixels, systematically comparing the results obtained with FDTD and ray tracing. Since ray tracing is a classical optics approach, unable to describe interference effects, its applicability has been found to be strongly wavelength dependent, especially when reflections from metallic layers are relevant. Interesting cavity effects around the material cutoff wavelength are described, and the cases where ray tracing can be considered a viable approximation are discussed.

Virtual Ray Tracing as a Conceptual Tool for Image Formation in Mirrors and Lenses

ERIC Educational Resources Information Center

Heikkinen, Lasse; Savinainen, Antti; Saarelainen, Markku

2016-01-01

The ray tracing method is widely used in teaching geometrical optics at the upper secondary and university levels. However, using simple and straightforward examples may lead to a situation in which students use the model of ray tracing too narrowly. Previous studies show that students seem to use the ray tracing method too concretely instead of…

ENSO effects on stratospheric trace gases: How do we capture reality?

NASA Astrophysics Data System (ADS)

Braesicke, Peter; Kirner, Oliver; Versick, Stefan; Joeckel, Patrick; Stiler, Gabriele

2016-04-01

The El Niño/Southern Oscillation (ENSO) phenomenon is an important pacemaker for interannual variability in the Earth's atmosphere. ENSO impacts on trace gases have been observed and modelled for the stratosphere and the troposphere. However, unambiguous attribution is often difficult due to the limited length of homogenous observational records and thus long-term (decadal) trends are sometimes difficult to detect. Generally ENSO impacts in low latitudes are easier to detect, because the response emerges close (temporally and spatially) to the forcing. Moving from low to high latitudes it becomes increasingly difficult to isolate ENSO driven variability, due to time-lags involved and many other modes of variability playing a role as well. Here, we use a nudged version of the EMAC chemistry-climate model to evaluate ENSO impacts on trace gases over the last 35 years (a so-called Ref-C1SD integration) and contrast the nudged model with its free running counterpart. We use water vapour and ozone observations from the MIPAS instrument on ENVISAT from 2002 to 2012 to test the model performance. Using lagged correlations for the longer model time-series we trace the ENSO signal from the tropical lower troposphere to the polar lower and middle stratosphere and provide a framework for simple attribution of the ENSO signal in trace gases. This concise characterisation of the ENSO impact on trace gases aids improved trend detection in temporally limited time series.

Efficacy of a Web-based Intelligent Tutoring System for Communicating Genetic Risk of Breast Cancer: A Fuzzy-Trace Theory Approach

PubMed Central

Wolfe, Christopher R.; Reyna, Valerie F.; Widmer, Colin L.; Cedillos, Elizabeth M.; Fisher, Christopher R.; Brust-Renck, Priscila G.; Weil, Audrey M.

2014-01-01

Background Many healthy women consider genetic testing for breast cancer risk, yet BRCA testing issues are complex. Objective Determining whether an intelligent tutor, BRCA Gist, grounded in fuzzy-trace theory (FTT), increases gist comprehension and knowledge about genetic testing for breast cancer risk, improving decision-making. Design In two experiments, 410 healthy undergraduate women were randomly assigned to one of three groups: an online module using a web-based tutoring system (BRCA Gist) that uses artificial intelligence technology, a second group read highly similar content from the NCI web site, and a third completed an unrelated tutorial. Intervention BRCA Gist applied fuzzy trace theory and was designed to help participants develop gist comprehension of topics relevant to decisions about BRCA genetic testing, including how breast cancer spreads, inherited genetic mutations, and base rates. Measures We measured content knowledge, gist comprehension of decision-relevant information, interest in testing, and genetic risk and testing judgments. Results Control knowledge scores ranged from 54% to 56%, NCI improved significantly to 65% and 70%, and BRCA Gist improved significantly more to 75% and 77%, p<.0001. BRCA Gist scored higher on gist comprehension than NCI and control, p<.0001. Control genetic risk-assessment mean was 48% correct; BRCA Gist (61%), and NCI (56%) were significantly higher, p<.0001. BRCA Gist participants recommended less testing for women without risk factors (not good candidates), (24% and 19%) than controls (50%, both experiments) and NCI, (32%) Experiment 2, p<.0001. BRCA Gist testing interest was lower than controls, p<.0001. Limitations BRCA Gist has not been tested with older women from diverse groups. Conclusions Intelligent tutors, such as BRCA Gist, are scalable, cost effective ways of helping people understand complex issues, improving decision-making. PMID:24829276

Knowledge-based modelling of historical surfaces using lidar data

NASA Astrophysics Data System (ADS)

Höfler, Veit; Wessollek, Christine; Karrasch, Pierre

2016-10-01

Currently in archaeological studies digital elevation models are mainly used especially in terms of shaded reliefs for the prospection of archaeological sites. Hesse (2010) provides a supporting software tool for the determination of local relief models during the prospection using LiDAR scans. Furthermore the search for relicts from WW2 is also in the focus of his research. In James et al. (2006) the determined contour lines were used to reconstruct locations of archaeological artefacts such as buildings. This study is much more and presents an innovative workflow of determining historical high resolution terrain surfaces using recent high resolution terrain models and sedimentological expert knowledge. Based on archaeological field studies (Franconian Saale near Bad Neustadt in Germany) the sedimentological analyses shows that archaeological interesting horizon and geomorphological expert knowledge in combination with particle size analyses (Koehn, DIN ISO 11277) are useful components for reconstructing surfaces of the early Middle Ages. Furthermore the paper traces how it is possible to use additional information (extracted from a recent digital terrain model) to support the process of determination historical surfaces. Conceptual this research is based on methodology of geomorphometry and geo-statistics. The basic idea is that the working procedure is based on the different input data. One aims at tracking the quantitative data and the other aims at processing the qualitative data. Thus, the first quantitative data were available for further processing, which were later processed with the qualitative data to convert them to historical heights. In the final stage of the workflow all gathered information are stored in a large data matrix for spatial interpolation using the geostatistical method of Kriging. Besides the historical surface, the algorithm also provides a first estimation of accuracy of the modelling. The presented workflow is characterized by a high flexibility and the opportunity to include new available data in the process at any time.

Analysis of Asian Outflow over the Western Pacific using Observations from Trace-P

NASA Technical Reports Server (NTRS)

Jacob, Daniel J.

2004-01-01

Our analysis of the TRACE-P data focused on answering the following questions: 1) How do anthropogenic sources in Asia contribute to chemical outflow over the western Pacific in spring? 2) How does biomass burning in southeast Asia contribute to this outflow? 3) How can the TRACE-P observations be used to better quantify the sources of environmentally important gases in eastern Asia? Our strategy drew on a combination of data analysis and global 3-D modeling, as described below. We also contributed to the planning and execution of TRACE-P through service as mission scientist and by providing chemical model forecasts in the field.

Intelligence-led crime scene processing. Part I: Forensic intelligence.

PubMed

Ribaux, Olivier; Baylon, Amélie; Roux, Claude; Delémont, Olivier; Lock, Eric; Zingg, Christian; Margot, Pierre

2010-02-25

Forensic science is generally defined as the application of science to address questions related to the law. Too often, this view restricts the contribution of science to one single process which eventually aims at bringing individuals to court while minimising risk of miscarriage of justice. In order to go beyond this paradigm, we propose to refocus the attention towards traces themselves, as remnants of a criminal activity, and their information content. We postulate that traces contribute effectively to a wide variety of other informational processes that support decision making in many situations. In particular, they inform actors of new policing strategies who place the treatment of information and intelligence at the centre of their systems. This contribution of forensic science to these security oriented models is still not well identified and captured. In order to create the best condition for the development of forensic intelligence, we suggest a framework that connects forensic science to intelligence-led policing (part I). Crime scene attendance and processing can be envisaged within this view. This approach gives indications about how to structure knowledge used by crime scene examiners in their effective practice (part II). 2009 Elsevier Ireland Ltd. All rights reserved.

Predicting What Will Happen When You Intervene.

PubMed

Cartwright, Nancy; Hardie, Jeremy

2017-01-01

This paper offers some rules of thumb that practicing social workers can use for case studies that aim to construct, albeit not fully and never entirely reliably, models designed to help predict what will happen if they intervene in specific ways to help this particular client, here and now. We call these 'ex ante case-specific causal models'. 'Ex ante' because they are for before-the-fact prediction of what the likely effects of proposed actions are. 'Case-specific' because we are not concerned with studies that provide evidence for some general conclusion but rather with using what general and local knowledge one can get to predict what will happen to a specific client in the real settings in which they live. 'Causal' because this kind of case study aims to trace out as best possible the web of causal processes that will be responsible for what happens. In this sense our case studies resemble post facto realist evaluations.

Design of a Thermal Precipitator for the Characterization of Smoke Particles from Common Spacecraft Materials

NASA Technical Reports Server (NTRS)

Meyer, Marit Elisabeth

2015-01-01

A thermal precipitator (TP) was designed to collect smoke aerosol particles for microscopic analysis in fire characterization research. Information on particle morphology, size and agglomerate structure obtained from these tests supplements additional aerosol data collected. Modeling of the thermal precipitator throughout the design process was performed with the COMSOL Multiphysics finite element software package, including the Eulerian flow field and thermal gradients in the fluid. The COMSOL Particle Tracing Module was subsequently used to determine particle deposition. Modeling provided optimized design parameters such as geometry, flow rate and temperatures. The thermal precipitator was built and testing verified the performance of the first iteration of the device. The thermal precipitator was successfully operated and provided quality particle samples for microscopic analysis, which furthered the body of knowledge on smoke particulates. This information is a key element of smoke characterization and will be useful for future spacecraft fire detection research.

Source and Cycling of Trace Metals and Nutrients in a Microbial Coalbed Methane System

NASA Astrophysics Data System (ADS)

Earll, M. M.; Barnhart, E. P.; Ritter, D.; Vinson, D. S.; Orem, W. H.; Vengosh, A.; McIntosh, J. C.

2015-12-01

The source and cycling of trace metals and nutrients in coalbed methane (CBM) systems are controlled by both geochemical processes, such as dissolution or precipitation, and biological mediation by microbial communities. CBM production by the microbes is influenced by trace metals and macronutrients such as nitrogen (N) and phosphate (P). Previous studies have shown the importance of these nutrients to both enhance and inhibit methane production; however, it's not clear whether they are sourced from coal via in-situ biodegradation of organic matter or transported into the seams with groundwater recharge. To address this knowledge gap, trace metal and nutrient geochemistry and the organic content of solid coal and associated groundwater will be investigated across a hydrologic gradient in CBM wells in the Powder River Basin, MT. Sequential dissolution experiments (chemical extraction of organic and inorganic constituents) using 8 core samples of coal and sandstone will provide insight into the presence of trace metals and nutrients in coalbeds, the associated minerals present, and their mobilization. If significant concentrations of N, P, and trace metals are present in core samples, in-situ sourcing of nutrients by microbes is highly probable. The biogeochemical evolution of groundwater, as it relates to trace metal and nutrient cycling by microbial consortia, will be investigated by targeting core-associated coal seams from shallow wells in recharge areas to depths of at least 165 m and across a 28 m vertical profile that include overburden, coal, and underburden. If microbial-limiting trace metals and nutrients are transported into coal seams with groundwater recharge, we would expect to see higher concentrations of trace metals and nutrients in recharge areas compared to deeper coalbeds. The results of this study will provide novel understanding of where trace metals and nutrients are sourced and how they are cycled in CBM systems.

Ray Tracing Methods in Seismic Emission Tomography

NASA Astrophysics Data System (ADS)

Chebotareva, I. Ya.

2018-03-01

Highly efficient approximate ray tracing techniques which can be used in seismic emission tomography and in other methods requiring a large number of raypaths are described. The techniques are applicable for the gradient and plane-layered velocity sections of the medium and for the models with a complicated geometry of contrasting boundaries. The empirical results obtained with the use of the discussed ray tracing technologies and seismic emission tomography results, as well as the results of numerical modeling, are presented.

MODELING THE EFFECTS OF CLIMATE AND LAND USE CHANGE ON CARBON AND TRACE GAS BUDGETS OVER THE AMAZON REGION USING NASA SATELLITE PRODUCTS

EPA Science Inventory

As part of the LBA-ECO Phase III synthesis efforts for remote sensing and predictive modeling of Amazon carbon, water, and trace gas fluxes, we are evaluating results from the regional ecosystem model called NASA-CASA (Carnegie-Ames Stanford Approach). The NASA-CASA model has bee...

Current Status of Post-combustor Trace Chemistry Modeling and Simulation at NASA Glenn Research Center

NASA Technical Reports Server (NTRS)

Wey, Thomas; Liu, Nan-Suey

2003-01-01

The overall objective of the current effort at NASA GRC is to evaluate, develop, and apply methodologies suitable for modeling intra-engine trace chemical changes over post combustor flow path relevant to the pollutant emissions from aircraft engines. At the present time, the focus is the high pressure turbine environment. At first, the trace chemistry model of CNEWT were implemented into GLENN-HT as well as NCC. Then, CNEWT, CGLENN-HT, and NCC were applied to the trace species evolution in a cascade of Cambridge University's No. 2 rotor and in a turbine vane passage. In general, the results from these different codes provide similar features. However, the details of some of the quantities of interest can be sensitive to the differences of these codes. This report summaries the implementation effort and presents the comparison of the No. 2 rotor results obtained from these different codes. The comparison of the turbine vane passage results is reported elsewhere. In addition to the implementation of trace chemistry model into existing CFD codes, several pre/post-processing tools that can handle the manipulations of the geometry, the unstructured and structured grids as well as the CFD solutions also have been enhanced and seamlessly tied with NCC, CGLENN-HT, and CNEWT. Thus, a complete CFD package consisting of pre/post-processing tools and flow solvers suitable for post-combustor intra-engine trace chemistry study is assembled.

Critique of the Schema Concept.

ERIC Educational Resources Information Center

Dahlin, Bo

2001-01-01

Discusses the concept of schema and the role this concept plays in educational practice. Traces the historical development of the concept and how it came to be taken for granted that schemata exist. Suggests a return to a more phenomenological approach to learning and knowledge formation. (SLD)

Vitamins and Microelement Bioavailability in Different Stages of Chronic Kidney Disease

PubMed Central

Jankowska, Magdalena; Rutkowski, Bolesław; Dębska-Ślizień, Alicja

2017-01-01

Chronic kidney disease (CKD) predisposes one to either deficiency or toxic excess of different micronutrients. The knowledge on micronutrients—specifically water-soluble vitamins and trace elements—in CKD is very limited. Consequently, current guidelines and recommendations are mostly based on expert opinions or poor-quality evidence. Abnormalities of micronutrient resources in CKD develop for several reasons. Dietary restrictions and anorexia lead to an insufficient micronutrient intake, while diuretics use and renal replacement therapy lead to their excessive losses. Absorption is unpredictable, and metabolism impaired. Better understanding of the micronutrient needs of CKD patients could have an impact on many complications linked to vitamin and trace element disorders, including high mortality, increased risk of atherosclerosis, inflammation, oxidative stress, anemia, polyneuropathy, encephalopathy, weakness and fragility, muscle cramps, bone disease, depression, or insomnia. Here, we summarize the up-to-date knowledge on micronutrient resources in different stages of CKD, and share our experience with the assessment of micronutrient status. PMID:28294976

Where do field lines go in the quiet magnetosphere?

NASA Technical Reports Server (NTRS)

Stern, David P.; Alekseev, Igor' I.

1988-01-01

The state of knowledge concerning the global pattern of geomagnetic field lines is reviewed. Sources of information on that pattern include (1) magnetic-field models, derived directly from magnetic data or indirectly from generally observed properties and from physics; (2) the tracing of magnetospheric features (e.g., polar cusps or the inner edge of the plasma sheet); (3) matching of magnetic flux; and (4) analysis of magnetic fields. Field-line structure inside about 8 earth radii is known fairly well, but beyond that, especially in the tail, the situation becomes rather uncertain and variable. Two particularly difficult problems are the linkage between open field lines and the interplanetary field and the field-line structure of the quiescent magnetosphere following periods of prolonged northward Bz.

Social science and Sozialwissenschaft: Categorical and institutional boundaries of knowledge.

PubMed

Sonnert, Gerhard

2018-05-16

This article explores how linguistic categories affect boundary work in scholarly knowledge production. Whereas the German language knows the unified concept of Wissenschaft for all branches of scholarship represented at universities, the English language separates science from the arts or humanities and does not commonly engage an overarching concept. This has had consequences for American social science, which are traced both in the discourse shaping its development and in the deployment and distribution of institutional resources. © 2018 Wiley Periodicals, Inc.

Using Spring Water Nitrate to Monitor Spatiotemporal Trends in Nitrogen Deposition for the Santa Clara Valley Habitat Plan

NASA Astrophysics Data System (ADS)

Weiss, S. B.; Hastings, M. G.

2016-12-01

Atmospheric nitrogen deposition is a major acute threat to biodiversity, but has rarely been addressed in regulatory conservation plans. The Santa Clara Valley Habitat Plan is a Habitat Conservation Plan/Natural Communities Conservation Plan (HCP/NCCP) that addresses development impacts on 19 covered species, most of which inhabit nutrient-poor serpentine grasslands that are highly sensitive to N-deposition with a critical load of 6 kg-N ha-1 year-1. Increased N-deposition from highway improvements and development was a major regulatory nexus, and a novel nitrogen fee based on car trips generated is one of the funding mechanisms, driving a need for cost-effective and robust monitoring of N-deposition trends over the 50-year plan and beyond. In the high deposition zone (10-20 kg-N ha-1 year-1), spring water nitrate levels up to 25 ppm (as NO3-) were measured in baseflow, levels higher than any reported for non-agricultural sites in California. Nitrate measurements follow measured and modeled deposition gradients, and are affected by catchment soils, geomorphology, and vegetation. Existing knowledge of local nitrogen deposition using passive samplers, CMAQ models, N-cycling measurements, and emissions inventories/projections are used to generate hypotheses that can be tested with a combination of spring water nitrate sampled through the year and across deposition gradients, N and O isotopic analysis including 17O to trace atmospheric nitrate, modeled recharge rates, and groundwater dating. A set of sentinel springs for long-term monitoring will be identified and sampled on an interval commensurate with shallow groundwater residence times. The unique characteristics of serpentine grasslands (low productivity, shallow soils, highly fractured bedrock, and numerous springs) provide a model system for tracing N-deposition and its effects on protected species.

The Asian clam Corbicula fluminea as a biomonitor of trace element contamination: Accounting for different sources of variation using an hierarchical linear model

USGS Publications Warehouse

Shoults-Wilson, W. A.; Peterson, J.T.; Unrine, J.M.; Rickard, J.; Black, M.C.

2009-01-01

In the present study, specimens of the invasive clam, Corbicula fluminea, were collected above and below possible sources of potentially toxic trace elements (As, Cd, Cr, Cu, Hg, Pb, and Zn) in the Altamaha River system (Georgia, USA). Bioaccumulation of these elements was quantified, along with environmental (water and sediment) concentrations. Hierarchical linear models were used to account for variability in tissue concentrations related to environmental (site water chemistry and sediment characteristics) and individual (growth metrics) variables while identifying the strongest relations between these variables and trace element accumulation. The present study found significantly elevated concentrations of Cd, Cu, and Hg downstream of the outfall of kaolin-processing facilities, Zn downstream of a tire cording facility, and Cr downstream of both a nuclear power plant and a paper pulp mill. Models of the present study indicated that variation in trace element accumulation was linked to distance upstream from the estuary, dissolved oxygen, percentage of silt and clay in the sediment, elemental concentrations in sediment, shell length, and bivalve condition index. By explicitly modeling environmental variability, the Hierarchical linear modeling procedure allowed the identification of sites showing increased accumulation of trace elements that may have been caused by human activity. Hierarchical linear modeling is a useful tool for accounting for environmental and individual sources of variation in bioaccumulation studies. ?? 2009 SETAC.

Silurian trace fossils in carbonate turbidites from the Alexander Arc of southeastern Alaska

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soja, C.M.

Early to Late Silurian (Wenlock-Ludlow) body and trace fossils from the Heceta Formation are preserved in the oldest widespread carbonates in the Alexander terrane of southeastern Alaska. They represent the earliest shelly benthos to inhabit a diversity of marine environments and are important indicators of the early stages in benthic community development within this ancient island arc. The trace fossils are significant because they add to a small but growing body of knowledge about ichnofaunas in deep-water Paleozoic carbonates. Proximal to medial carbonate turbidites yield a low-diversity suite of trace fossils that comprises five distinct types of biogenic structures. Beddingmore » planes reveal simple epichnial burrows (Planolites), cross-cutting burrows (Fucusopsis), and tiny cylindrical burrows. These and other casts, including chondrites( )-like burrow clusters, represent the feeding activities (fodinichnia) of preturbidite animals. Hypichnial burrows and rare endichnial traces reflect the activities of postturbidite animals. Broken and offset traces indicate that infaunal biota commenced burrowing before slumping and subsequent soft-sediment deformation. The abundance and density of trace fossils increases offshore in the medial turbidites associated with a decrease in the size and amount of coarse particles and with an increase in mud and preserved organic material. Although diversity levels are similar in the proximal and medial turbidite facies, they are much lower than in Paleozoic siliciclastic turbidites. This may reflect unfavorable environmental conditions for infaunal biota or paleobiogeographic isolation of the Alexander terrane during the Silurian. A greater use of trace fossils in terrane analysis will help to resolve this issue and should provide new data for reconstructing the paleogeography of circum-Pacific terranes.« less

A knowledge-guided active model method of cortical structure segmentation on pediatric MR images.

PubMed

Shan, Zuyao Y; Parra, Carlos; Ji, Qing; Jain, Jinesh; Reddick, Wilburn E

2006-10-01

To develop an automated method for quantification of cortical structures on pediatric MR images. A knowledge-guided active model (KAM) approach was proposed with a novel object function similar to the Gibbs free energy function. Triangular mesh models were transformed to images of a given subject by maximizing entropy, and then actively slithered to boundaries of structures by minimizing enthalpy. Volumetric results and image similarities of 10 different cortical structures segmented by KAM were compared with those traced manually. Furthermore, the segmentation performances of KAM and SPM2, (statistical parametric mapping, a MATLAB software package) were compared. The averaged volumetric agreements between KAM- and manually-defined structures (both 0.95 for structures in healthy children and children with medulloblastoma) were higher than the volumetric agreement for SPM2 (0.90 and 0.80, respectively). The similarity measurements (kappa) between KAM- and manually-defined structures (0.95 and 0.93, respectively) were higher than those for SPM2 (both 0.86). We have developed a novel automatic algorithm, KAM, for segmentation of cortical structures on MR images of pediatric patients. Our preliminary results indicated that when segmenting cortical structures, KAM was in better agreement with manually-delineated structures than SPM2. KAM can potentially be used to segment cortical structures for conformal radiation therapy planning and for quantitative evaluation of changes in disease or abnormality. Copyright (c) 2006 Wiley-Liss, Inc.

An introduction of Markov chain Monte Carlo method to geochemical inverse problems: Reading melting parameters from REE abundances in abyssal peridotites

NASA Astrophysics Data System (ADS)

Liu, Boda; Liang, Yan

2017-04-01

Markov chain Monte Carlo (MCMC) simulation is a powerful statistical method in solving inverse problems that arise from a wide range of applications. In Earth sciences applications of MCMC simulations are primarily in the field of geophysics. The purpose of this study is to introduce MCMC methods to geochemical inverse problems related to trace element fractionation during mantle melting. MCMC methods have several advantages over least squares methods in deciphering melting processes from trace element abundances in basalts and mantle rocks. Here we use an MCMC method to invert for extent of melting, fraction of melt present during melting, and extent of chemical disequilibrium between the melt and residual solid from REE abundances in clinopyroxene in abyssal peridotites from Mid-Atlantic Ridge, Central Indian Ridge, Southwest Indian Ridge, Lena Trough, and American-Antarctic Ridge. We consider two melting models: one with exact analytical solution and the other without. We solve the latter numerically in a chain of melting models according to the Metropolis-Hastings algorithm. The probability distribution of inverted melting parameters depends on assumptions of the physical model, knowledge of mantle source composition, and constraints from the REE data. Results from MCMC inversion are consistent with and provide more reliable uncertainty estimates than results based on nonlinear least squares inversion. We show that chemical disequilibrium is likely to play an important role in fractionating LREE in residual peridotites during partial melting beneath mid-ocean ridge spreading centers. MCMC simulation is well suited for more complicated but physically more realistic melting problems that do not have analytical solutions.

Combining position-specific 13C labeling with compound-specific isotope analysis: first steps towards soil fluxomics

NASA Astrophysics Data System (ADS)

Dippold, Michaela; Kuzyakov, Yakov

2015-04-01

Understanding the soil organic matter (SOM) dynamics is one of the most important challenges in soil science. Transformation of low molecular weight organic substances (LMWOS) is a key step in biogeochemical cycles because 1) all high molecular substances pass this stage during their decomposition and 2) only LMWOS will be taken up by microorganisms. Previous studies on LMWOS were focused on determining net fluxes through the LMWOS pool, but they rarely identified transformations. As LMWOS are the preferred C and energy source for microorganisms, the transformations of LMWOS are dominated by biochemical pathways of the soil microorganisms. Thus, understanding fluxes and transformations in soils requires a detailed knowledge on the biochemical pathways and its controlling factors. Tracing C fate in soil by isotopes became on of the most applied and promising biogeochemistry tools. Up to now, studies on LMWOS were nearly exclusively based on uniformly labeled organic substances i.e. all C atoms in the molecules were labeled with 13C or 14C. However, this classical approach did not allow the differentiation between use of intact initial substances in any process, or whether they were transformed to metabolites. The novel tool of position-specific labeling enables to trace molecule atoms separately and thus to determine the cleavage of molecules - a prerequisite for metabolic tracing. Position-specific labeling of LMWOS and quantification of 13CO2 and 13C in bulk soil enabled following the basic metabolic pathways of soil microorganisms. However, only the combination of position-specific 13C labeling with compound-specific isotope analysis of microbial biomarkers and metabolites allowed 1) tracing specific anabolic pathways in diverse microbial communities in soils and 2) identification of specific pathways of individual functional microbial groups. So, these are the prerequisites for soil fluxomics. Our studies combining position-specific labeled glucose with amino sugar 13C analysis showed that oxidizing catabolic pathways and anabolic pathways, i.e. building-up new cellular compounds, occurred in soils simultaneously. This involved an intensive C recycling within the microorganisms that was observed not only for cytosolic compounds but also for cell wall polymers. Fungal metabolism and fluxes were slower than bacterial intracellular C recycling and turnover. Furthermore, position-specific labeling of glutamate and subsequent 13C analysis of microbial phospholipid fatty acids (PLFA) revealed starvation pathways, which were only active in specific microbial groups in soils. These studies revealed that position-specific labeling enables the reconstruction of metabolic pathways of LMWOS within diverse microbial communities in complex media such as soil. Processes occurring simultaneously in soil i.e. 1) within individual, reversible metabolic pathways and 2) in various microbial groups could be traced by position-specific labeling in soils in situ. Tracing these pathways and understanding their regulating factors are crucial for soil C fluxomics, the extremely complex network of transformations towards mineralization versus the formation of microbial biomass compounds. Quantitative models to assess microbial group specific metabolic networks can be generated and parameterized by this approach. The submolecular knowledge of transformation steps and biochemical pathways in soils and their regulating factors is essential for understanding C cycling and long-term C storage in soils.

Turbine Chemistry Modeling

NASA Technical Reports Server (NTRS)

Liu, Nan-Suey; Wey, Thomas

2001-01-01

Many of the engine exhaust species resulting in significant environmental impact exist in trace amounts. Recent research, e.g., conducted at MIT-AM, has pointed to the intra-engine environment as a possible site for important trace chemistry activity. In addition, the key processes affecting the trace species activity occurring downstream in the air passages of the turbine and exhaust nozzle are not well understood. Most recently, an effort has been initiated at NASA Glenn Research Center under the UEET Program to evaluate and further develop CFD-based technology for modeling and simulation of intra-engine trace chemical changes relevant to atmospheric effects of pollutant emissions from aircraft engines. This presentation will describe the current effort conducted at Glenn; some preliminary results relevant to the trace species chemistry in a turbine passage will also be presented to indicate the progress to date.

Development Of Knowledge Systems For Trouble Shooting Complex Production Machinery

NASA Astrophysics Data System (ADS)

Sanford, Richard L.; Novak, Thomas; Meigs, James R.

1987-05-01

This paper discusses the use of knowledge base system software for microcomputers to aid repairmen in diagnosing electrical failures in complex mining machinery. The knowledge base is constructed to allow the user to input initial symptoms of the failed machine, and the most probable cause of failure is traced through the knowledge base, with the software requesting additional information such as voltage or resistance measurements as needed. Although the case study presented is for an underground mining machine, results have application to any industry using complex machinery. Two commercial expert-system development tools (M1 TM and Insight 2+TM) and an Al language (Turbo PrologTM) are discussed with emphasis on ease of application and suitability for this study.

Verification technology of remote sensing camera satellite imaging simulation based on ray tracing

NASA Astrophysics Data System (ADS)

Gu, Qiongqiong; Chen, Xiaomei; Yang, Deyun

2017-08-01

Remote sensing satellite camera imaging simulation technology is broadly used to evaluate the satellite imaging quality and to test the data application system. But the simulation precision is hard to examine. In this paper, we propose an experimental simulation verification method, which is based on the test parameter variation comparison. According to the simulation model based on ray-tracing, the experiment is to verify the model precision by changing the types of devices, which are corresponding the parameters of the model. The experimental results show that the similarity between the imaging model based on ray tracing and the experimental image is 91.4%, which can simulate the remote sensing satellite imaging system very well.

Innovative interdisciplinary approaches in catchment hydrology: on the potential for diatoms and thermal infrared imagery for documenting spatio-temporal dynamics and connectivity of saturated areas in the hillslope-riparian zone-stream system

NASA Astrophysics Data System (ADS)

Pfister, L.; Martínez-Carreras, N.; Wetzel, C.; Ector, L.; Frentress, J.; McDonnell, J. J.

2012-04-01

Over the past decades, hydrologists have been relentlessly investigating water source, flowpaths and residence time. These issues are of paramount importance when it comes to both the quantitative and qualitative management of water resources. Support from the scientific community has indeed been repeatedly sollicited by the European Union in the context of an optimization of the implementation of its framework directives on water quality and floods. However, to date large uncertainties remain adjunct to our measurements of hydrological processes on the one hand and the modelling of the precipitation-runoff relationship on the other hand. Originally, investigations on the rainfall-runoff transformation were based on conventional geochemical and isotopic tracing techniques. Unfortunately, well-known and documented technical limitations (e.g. non-stable end-members, incomplete mixing assumptions) have rapidly stymied further progress in our understanding of the rainfall-runoff transformation. More recently, technological progress has created new potential for going well beyond the traditional sources of information, such as rainfall and discharge. New measuring techniques have been recently introduced (e.g. thermographic systems such as temperature fiber optic cables and thermal IR cameras for tracing water source and flowpaths, satellite aperture radar for measuring flood extents and/or soil humidity, laser spectrometers for stable isotope measurements, etc.). Indeed the rainfall-runoff transformation inside a catchment is the result of a plethora of interrelated processes that go well beyond water movements. As a consequence, it is crucial to the development of hydrological science to integrate the advances and knowledge from different disciplines. In other terms, knowledge from ecology, biology, as well as other sciences is needed to better understand the functioning of catchments. We need to work together on common problems to find better solutions In recent years, our research activities have been focusing on the exploration of new research avenues for untapping new insights on inherent hydrological processes, guiding water source and flowpaths. Here, we will present the most recent results obtained to date from interdisciplinary proof-of-concept studies carried out in the Weierbach experimental watershed. New research avenues, such as the introduction of terrestrial diatom tracing in flood waves, will hopefully contribute to reduce uncertainties in the determination of the onset/cessation of surface runoff and connectivity in the hillslope-riparian zone-stream system. Likewise, thermal infrared imaging has shown considerable potential for tracing surface water flowpaths, connectivity, as well as saturated area dynamics.

Layer detection and snowpack stratigraphy characterisation from digital penetrometer signals

NASA Astrophysics Data System (ADS)

Floyer, James Antony

Forecasting for slab avalanches benefits from precise measurements of snow stratigraphy. Snow penetrometers offer the possibility of providing detailed information about snowpack structure; however, their use has yet to be adopted by avalanche forecasting operations in Canada. A manually driven, variable rate force-resistance penetrometer is tested for its ability to measure snowpack information suitable for avalanche forecasting and for spatial variability studies on snowpack properties. Subsequent to modifications, weak layers of 5 mm thick are reliably detected from the penetrometer signals. Rate effects are investigated and found to be insignificant for push velocities between 0.5 to 100 cm s-1 for dry snow. An analysis of snow deformation below the penetrometer tip is presented using particle image velocimetry and two zones associated with particle deflection are identified. The compacted zone is a region of densified snow that is pushed ahead of the penetrometer tip; the deformation zone is a broader zone surrounding the compacted zone, where deformation is in compression and in shear. Initial formation of the compacted zone is responsible for pronounced force spikes in the penetrometer signal. A layer tracing algorithm for tracing weak layers, crusts and interfaces across transects or grids of penetrometer profiles is presented. This algorithm uses Wiener spiking deconvolution to detect a portion of the signal manually identified as a layer in one profile across to an adjacent profile. Layer tracing is found to be most effective for tracing crusts and prominent weak layers, although weak layers close to crusts were not well traced. A framework for extending this method for detecting weak layers with no prior knowledge of weak layer existence is also presented. A study relating the fracture character of layers identified in compression tests is presented. A multivariate model is presented that distinguishes between sudden and other fracture characters 80% of the time. Transects of penetrometer profiles are presented over several alpine terrain features commonly associated with spatial variability of snowpack properties. Physical processes relating to the variability of certain snowpack properties revealed in the transects is discussed. The importance of characteristic signatures for training avalanche practitioners to recognise potentially unstable terrain is also discussed.

Characterizing marine particles and their impact on biogeochemical cycles in the GEOTRACES program

NASA Astrophysics Data System (ADS)

Anderson, Robert F.; Hayes, Christopher T.

2015-04-01

Trace elements and their isotopes (TEIs) are of priority interest in several subdisciplines of oceanography. For example, the vital role of trace element micronutrients in regulating the growth of marine organisms, which, in turn, may influence the structure and composition of marine ecosystems, is now well established (Morel and Price, 2003; Twining and Baines, 2013). Natural distributions of some TEIs have been severely impacted by anthropogenic emissions, leading to substantial perturbations of natural ocean inventories. Pb and Hg, for example, (Lamborg et al., 2002; Schaule and Patterson, 1981), may represent a significant threat to human food supply. Furthermore, much of our knowledge of past variability in the ocean environment, including the ocean's role in climate change, has been developed using TEI proxies archived in marine substrates such as sediments, corals and microfossils. Research in each of these areas relies on a comprehensive knowledge of the distributions of TEIs in the ocean, and on the sensitivity of these distributions to changing environmental conditions. With numerous processes affecting the regional supply and removal of TEIs in the ocean, a comprehensive understanding of the marine biogeochemical cycles of TEIs can be attained only by a global, coordinated, international effort. GEOTRACES, an international program designed to study the marine biogeochemical cycles of trace elements and their isotopes (Anderson et al., 2014; Henderson et al., 2007), aims to achieve these goals.

["Migration of Thoughts". Ludwik Fleck's morphology of knowledge].

PubMed

Neumann, Michael

2014-01-01

This article traces some of the transformation that the fields of folk psychology (Völkerpsychologie) and anthropology underwent in the late nineteenth century. Ludwik Fleck, in developing his sociology of knowledge, drew on both of these fields; a legacy that makes it possible to conceive of his epistemology as a theory of communication. Fleck, in grounding his understanding of the relationship between sociality and communication on insights from these two disciplines, proposed the morphological concept of an organic formation of all scientific knowledge. Naturalising knowledge production in this manner, Fleck postulated a program of deciphering, reading, and translation that would relate all forms of knowledge back to the rules and conditions of its making. In this morphological conception of the processes of knowledge production, Fleck’s sociology bears significant similarities with the description of social institutions by French sociologists Marcel Mauss and Emile Durkheim, who also drew on insights from late-nineteenth-century folk psychology and anthropology.

Modeling a Miniaturized Scanning Electron Microscope Focusing Column - Lessons Learned in Electron Optics Simulation

NASA Technical Reports Server (NTRS)

Loyd, Jody; Gregory, Don; Gaskin, Jessica

2016-01-01

This presentation discusses work done to assess the design of a focusing column in a miniaturized Scanning Electron Microscope (SEM) developed at the NASA Marshall Space Flight Center (MSFC) for use in-situ on the Moon-in particular for mineralogical analysis. The MSFC beam column design uses purely electrostatic fields for focusing, because of the severe constraints on mass and electrical power consumption imposed by the goals of lunar exploration and of spaceflight in general. The resolution of an SEM ultimately depends on the size of the focused spot of the scanning beam probe, for which the stated goal here is a diameter of 10 nanometers. Optical aberrations are the main challenge to this performance goal, because they blur the ideal geometrical optical image of the electron source, effectively widening the ideal spot size of the beam probe. In the present work the optical aberrations of the mini SEM focusing column were assessed using direct tracing of non-paraxial rays, as opposed to mathematical estimates of aberrations based on paraxial ray-traces. The geometrical ray-tracing employed here is completely analogous to ray-tracing as conventionally understood in the realm of photon optics, with the major difference being that in electron optics the lens is simply a smoothly varying electric field in vacuum, formed by precisely machined electrodes. Ray-tracing in this context, therefore, relies upon a model of the electrostatic field inside the focusing column to provide the mathematical description of the "lens" being traced. This work relied fundamentally on the boundary element method (BEM) for this electric field model. In carrying out this research the authors discovered that higher accuracy in the field model was essential if aberrations were to be reliably assessed using direct ray-tracing. This led to some work in testing alternative techniques for modeling the electrostatic field. Ultimately, the necessary accuracy was attained using a BEM/Fourier series hybrid approach. The presentation will give background remarks about the MSFC mini Lunar SEM concept and electron optics modeling, followed by a description of the alternate field modeling techniques that were tried, along with their incorporation into a ray-trace simulation. Next, the validation of this simulation against commercially available software will be discussed using an example lens as a test case. Then, the efficacy of aberration assessment using direct ray-tracing will be demonstrated, using this same validation case. The discussion will include practical error checks of the field solution. Finally, the ray-trace assessment of the MSFC mini Lunar SEM concept will be shown and discussed. The authors believe this presentation will be of general interest to practitioners of modeling and simulation, as well as those with a general optics background. Because electron optics and photon optics share many basic concepts (e.g., lenses, images, aberrations, etc.), the appeal of this presentation need not be restricted to just those interested in charged particle optics.

Effects of Trace Amine-associated Receptor 1 Agonists on the Expression, Reconsolidation, and Extinction of Cocaine Reward Memory.

PubMed

Liu, Jian-Feng; Thorn, David A; Zhang, Yanan; Li, Jun-Xu

2016-07-01

As a modulator of dopaminergic system, trace amine-associated receptor 1 has been shown to play a critical role in regulating the rewarding properties of additive drugs. It has been demonstrated that activation of trace amine-associated receptor 1 decreased the abuse-related behaviors of cocaine in rats. However, the role of trace amine-associated receptor 1 in specific stages of cocaine reward memory is still unclear. Here, using a cocaine-induced conditioned place preference model, we tested the effects of a selective trace amine-associated receptor 1 agonist RO5166017 on the expression, reconsolidation, and extinction of cocaine reward memory. We found that RO5166017 inhibited the expression but not retention of cocaine-induced conditioned place preference. RO5166017 had no effect on the reconsolidation of cocaine reward memory. Pretreatment with RO5166017 before extinction hindered the formation of extinction long-term memory. RO5166017 did not affect the movement during the conditioned place preference test, indicating the inhibitory effect of RO5166017 on the expression of cocaine-induced conditioned place preference was not caused by locomotion inhibition. Using a cocaine i.v. self-administration model, we found that the combined trace amine-associated receptor 1 partial agonist RO5263397 with extinction had no effect on the following cue- and drug-induced reinstatement of cocaine-seeking behavior. Repeated administration of the trace amine-associated receptor 1 agonist during extinction showed a continually inhibitory effect on the expression of cocaine reward memory both in cocaine-induced conditioned place preference and cocaine self-administration models. Taken together, these results indicate that activation of trace amine-associated receptor 1 specifically inhibited the expression of cocaine reward memory. The inhibitory effect of trace amine-associated receptor 1 agonists on cocaine reward memory suggests that trace amine-associated receptor 1 agonists could be a promising agent to prevent cocaine relapse. © The Author 2016. Published by Oxford University Press on behalf of CINP.

Polar Processes in a 50-year Simulation of Stratospheric Chemistry and Transport

NASA Technical Reports Server (NTRS)

Kawa, S.R.; Douglass, A. R.; Patrick, L. C.; Allen, D. R.; Randall, C. E.

2004-01-01

The unique chemical, dynamical, and microphysical processes that occur in the winter polar lower stratosphere are expected to interact strongly with changing climate and trace gas abundances. Significant changes in ozone have been observed and prediction of future ozone and climate interactions depends on modeling these processes successfully. We have conducted an off-line model simulation of the stratosphere for trace gas conditions representative of 1975-2025 using meteorology from the NASA finite-volume general circulation model. The objective of this simulation is to examine the sensitivity of stratospheric ozone and chemical change to varying meteorology and trace gas inputs. This presentation will examine the dependence of ozone and related processes in polar regions on the climatological and trace gas changes in the model. The model past performance is base-lined against available observations, and a future ozone recovery scenario is forecast. Overall the model ozone simulation is quite realistic, but initial analysis of the detailed evolution of some observable processes suggests systematic shortcomings in our description of the polar chemical rates and/or mechanisms. Model sensitivities, strengths, and weaknesses will be discussed with implications for uncertainty and confidence in coupled climate chemistry predictions.

Privacy Vulnerability of Published Anonymous Mobility Traces

DOE PAGES

Ma, Chris Y. T.; Yau, David K. Y.; Yip, Nung Kwan; ...

2013-06-01

Mobility traces of people and vehicles have been collected and published to assist the design and evaluation of mobile networks, such as large-scale urban sensing networks. Although the published traces are often made anonymous in that the true identities of nodes are replaced by random identifiers, the privacy concern remains. This is because in real life, nodes are open to observations in public spaces, or they may voluntarily or inadvertently disclose partial knowledge of their whereabouts. Thus, snapshots of nodes’ location information can be learned by interested third parties, e.g., directly through chance/engineered meetings between the nodes and their observers,more » or indirectly through casual conversations or other information sources about people. In this paper, we investigate how an adversary, when equipped with a small amount of the snapshot information termed as side information, can infer an extended view of the whereabouts of a victim node appearing in an anonymous trace. Our results quantify the loss of victim nodes’ privacy as a function of the nodal mobility, the inference strategies of adversaries, and any noise that may appear in the trace or the side information. Generally, our results indicate that the privacy concern is significant in that a relatively small amount of side information is sufficient for the adversary to infer the true identity (either uniquely or with high probability) of a victim in a set of anonymous traces. For instance, an adversary is able to identify the trace of 30%-50% of the victims when she has collected 10 pieces of side information about a victim.« less

Trace elements in hazardous mineral fibres.

PubMed

Bloise, Andrea; Barca, Donatella; Gualtieri, Alessandro Francesco; Pollastri, Simone; Belluso, Elena

2016-09-01

Both occupational and environmental exposure to asbestos-mineral fibres can be associated with lung diseases. The pathogenic effects are related to the dimension, biopersistence and chemical composition of the fibres. In addition to the major mineral elements, mineral fibres contain trace elements and their content may play a role in fibre toxicity. To shed light on the role of trace elements in asbestos carcinogenesis, knowledge on their concentration in asbestos-mineral fibres is mandatory. It is possible that trace elements play a synergetic factor in the pathogenesis of diseases caused by the inhalation of mineral fibres. In this paper, the concentration levels of trace elements from three chrysotile samples, four amphibole asbestos samples (UICC amosite, UICC anthophyllite, UICC crocidolite and tremolite) and fibrous erionite from Jersey, Nevada (USA) were determined using inductively coupled plasma mass spectrometry (ICP-MS). For all samples, the following trace elements were measured: Li, Be, Sc, V, Cr, Mn, Co, Ni, Cu, Zn, As, Rb, Sr, Y, Sb, Cs, Ba, La, Pb, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, U. Their distribution in the various mineral species is thoroughly discussed. The obtained results indicate that the amount of trace metals such as Mn, Cr, Co, Ni, Cu and Zn is higher in anthophyllite and chrysotile samples, whereas the amount of rare earth elements (REE) is higher in erionite and tremolite samples. The results of this work can be useful to the pathologists and biochemists who use asbestos minerals and fibrous erionite in-vitro studies as positive cyto- and geno-toxic standard references. Copyright © 2016 Elsevier Ltd. All rights reserved.

Subcellular distribution of trace elements in the liver of sea turtles.

PubMed

Anan, Yasumi; Kunito, Takashi; Sakai, Haruya; Tanabe, Shinsuke

2002-01-01

Subcellular distribution of Cu, Zn, Se, Rb, Mo, Ag, Cd and Pb was determined in the liver of green turtles (Chelonia mydas) and hawksbill turtles (Eretmochelys imbricata) from Yaeyama Islands, Japan. Also, hepatic cytosol from sea turtles was applied on a Sephadex G-75 column and elution profiles of trace elements were examined. Copper, Zn, Se, Rb, Ag and Cd were largely present in cytosol in the liver of both species, indicating that cytosol was the significant site for the accumulation of these elements in sea turtles. In contrast, Mo and Pb were accumulated specifically in nuclear and mitochondrial fraction and microsomal fraction, respectively. Gel filtration analysis showed that Cu, Zn, Ag and Cd were bound to metallothionein (MT) in the cytosol of sea turtles. To our knowledge, this is the first report on the association of trace elements with MT in sea turtles.

Refrigeration Controls: Electrical & Mechanical; Appliance Repair 3: 9027.02.

ERIC Educational Resources Information Center

Dade County Public Schools, Miami, FL.

This booklet outlines a course designed to equip major appliance service students with the fundamental knowledge and understanding of procedures, basic electrical circuitry, and nomenclatures of components necessary in successfully tracing a circuit and repairing or replacing a malfunctioning component. Course content includes goals, specific…

Constructing Virtual Worlds: Tracing the Historical Development of Learner Practices.

ERIC Educational Resources Information Center

Barab, Sasha A.; Hay, Kenneth E.; Barnett, Michael; Squire, Kurt

2001-01-01

Explored learning and instruction within a technology-rich, collaborative, participatory learning environment by tracking the emergence of shared understanding and products through student and teacher practices. Found that becoming knowledgeably skillful with respect to a particular practice or concept is a multigenerational process, evolving in…

Towards a New Cartography of Curriculum Reform: Reflections on Educational Decentralization in Argentina.

ERIC Educational Resources Information Center

Dussel, Ines; Tiramonti, Guillermina; Birgin, Alejandra

2000-01-01

States that educational reforms in Argentina have reshaped both school knowledge and institutional patterns of school administration. Analyzes the process of "curriculum reterritorialization" in Argentina, the contradictions and displacements it produces, and the hybrid products that result. Traces reterritorialization through four…

A Synchronization Account of False Recognition

ERIC Educational Resources Information Center

Johns, Brendan T.; Jones, Michael N.; Mewhort, Douglas J. K.

2012-01-01

We describe a computational model to explain a variety of results in both standard and false recognition. A key attribute of the model is that it uses plausible semantic representations for words, built through exposure to a linguistic corpus. A study list is encoded in the model as a gist trace, similar to the proposal of fuzzy trace theory…

Trace elements and antioxidant enzymes in Behçet's disease.

PubMed

Saglam, K; Serce, A F; Yilmaz, M I; Bulucu, F; Aydin, A; Akay, C; Sayal, A

2002-07-01

Free oxygen radicals and insufficiency of antioxidant enzymes have been implicated in the pathogenesis of Behçet's disease (BD). Trace elements function as cofactors to antioxidant enzymes. The antioxidant system and trace elements were investigated in many different studies, including BD, but these subjects have not been investigated as a whole in these patients. The aim of the present study was to investigate the antioxidative system and trace elements in BD to contribute to the knowledge of pathogenesis and treatment of this disease. We examined glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) activities together with selenium (Se), copper (Cu), zinc (Zn), manganese (Mn), and iron (Fe) levels in plasma and erythrocytes of 50 patients with BD and 30 healthy controls. It was found that in patients with BD, erythrocyte GSH-Px and SOD activities and erythrocyte Se, plasma Fe, Mn, and Zn levels were significantly lower than those of controls and that plasma Cu, erythrocyte Zn, and Mn levels were significantly higher in patients with BD. Insufficient antioxidant enzyme activities were observed in patients with BD. The mechanism(s) of this phenomenon is not clear. Therefore, supplementation with trace elements involved in the antioxidative processes may increase scavenger enzyme activities, and consequently, an improvement in clinical symptoms may be expected.

Chemical Modeling for Studies of GeoTRACE Capabilities

NASA Technical Reports Server (NTRS)

2005-01-01

Geostationary measurements of tropospheric pollutants with high spatial and temporal resolution will revolutionize the understanding and predictions of the chemically linked global pollutants aerosols and ozone. However, the capabilities of proposed geostationary instruments, particularly GeoTRACE, have not been thoroughly studied with model simulations. Such model simulations are important to answer the questions and allay the concerns that have been expressed in the atmospheric sciences community about the feasibility of such measurements. We proposed a suite of chemical transport model simulations using the EPA Models 3 chemical transport model, which obtains its meteorology from the MM-5 mesoscale model. The model output consists of gridded abundances of chemical pollutants and meteorological parameters every 30-60 minutes for cases that have occurred in the Eastern United States. This output was intended to be used to test the GeoTRACE capability to retrieve the tropospheric columns of these pollutants.

Automatic parameter estimation of multicompartmental neuron models via minimization of trace error with control adjustment.

PubMed

Brookings, Ted; Goeritz, Marie L; Marder, Eve

2014-11-01

We describe a new technique to fit conductance-based neuron models to intracellular voltage traces from isolated biological neurons. The biological neurons are recorded in current-clamp with pink (1/f) noise injected to perturb the activity of the neuron. The new algorithm finds a set of parameters that allows a multicompartmental model neuron to match the recorded voltage trace. Attempting to match a recorded voltage trace directly has a well-known problem: mismatch in the timing of action potentials between biological and model neuron is inevitable and results in poor phenomenological match between the model and data. Our approach avoids this by applying a weak control adjustment to the model to promote alignment during the fitting procedure. This approach is closely related to the control theoretic concept of a Luenberger observer. We tested this approach on synthetic data and on data recorded from an anterior gastric receptor neuron from the stomatogastric ganglion of the crab Cancer borealis. To test the flexibility of this approach, the synthetic data were constructed with conductance models that were different from the ones used in the fitting model. For both synthetic and biological data, the resultant models had good spike-timing accuracy. Copyright © 2014 the American Physiological Society.

A FINITE-DIFFERENCE, DISCRETE-WAVENUMBER METHOD FOR CALCULATING RADAR TRACES

EPA Science Inventory

A hybrid of the finite-difference method and the discrete-wavenumber method is developed to calculate radar traces. The method is based on a three-dimensional model defined in the Cartesian coordinate system; the electromagnetic properties of the model are symmetric with respect ...

Vapor-deposited water and nitric acid ices

NASA Astrophysics Data System (ADS)

Leu, Ming-Taun; Keyser, Leon F.

Ices formed by vapor deposition have been the subject of numerous laboratory investigations in connection with snow and glaciers on the ground, ice clouds in the terrestrial atmosphere, surfaces of other planets and their satellites, and the interstellar medium. In this review we will focus on these specific subjects: (1) heterogeneous chemistry on the surfaces of polar stratospheric clouds (PSCs) and (2) surfaces of satellites of the outer planets in our solar system. Stratospheric ozone provides a protective shield for mankind and the global biosphere from harmful ultraviolet solar radiation. In past decades, theoretical atmospheric models for the calculation of ozone balance frequently used only homogeneous gas-phase reactions in their studies. Since the discovery of the Antarctic ozone hole in 1985, however, it has been demonstrated that knowledge of heterogeneous reactions on the surface of PSCs is definitely needed to understand this significant natural event due to the anthropogenic emission of chlorofluorocarbons (CFCs). We will briefly discuss the experimental techniques for the investigation of heterogeneous chemistry on ice surfaces carried out in our laboratories. The experimental apparatus used include: several flow-tube reactors, an electron-impact ionization mass spectrometer, a Fourier transform infrared spectrometer, a BET adsorption apparatus, and a scanning environmental electron microscope. The adsorption experiments and electron microscopic work have demonstrated that the vapor-deposited ices are highly porous. Therefore, it is necessary to develop theoretical models for the elucidation of the uptake and reactivity of trace gases in porous ice substrates. Several measurements of uptake and reaction probabilities of these trace gases on water ices and nitric acid ices have been performed under ambient conditions in the upper troposphere and lower stratosphere, mainly in the temperature range 180-220 K. The trace gases of atmospheric importance in heterogeneous chemistry include: ClONO2, HCl, HOCl, and HNO3. In addition, recent interest in the possible landing of a robotic spacecraft on the surface of Europa, one of the Galilean satellites of Jupiter, and ground based telescopic observations demand detailed knowledge of the physical properties of the icy surfaces of the outer planets and their satellites. Lower temperature studies in the range 77-150 K using both electron microscopy and adsorption isotherms (BET surface area measurements) have revealed some intriguing observations that may provide some insights for remote sensing of these satellite surfaces. Finally, we will attempt to summarize our recent results and suggest future research directions in both theoretical and laboratory investigations.

Vertex shading of the three-dimensional model based on ray-tracing algorithm

NASA Astrophysics Data System (ADS)

Hu, Xiaoming; Sang, Xinzhu; Xing, Shujun; Yan, Binbin; Wang, Kuiru; Dou, Wenhua; Xiao, Liquan

2016-10-01

Ray Tracing Algorithm is one of the research hotspots in Photorealistic Graphics. It is an important light and shadow technology in many industries with the three-dimensional (3D) structure, such as aerospace, game, video and so on. Unlike the traditional method of pixel shading based on ray tracing, a novel ray tracing algorithm is presented to color and render vertices of the 3D model directly. Rendering results are related to the degree of subdivision of the 3D model. A good light and shade effect is achieved by realizing the quad-tree data structure to get adaptive subdivision of a triangle according to the brightness difference of its vertices. The uniform grid algorithm is adopted to improve the rendering efficiency. Besides, the rendering time is independent of the screen resolution. In theory, as long as the subdivision of a model is adequate, cool effects as the same as the way of pixel shading will be obtained. Our practical application can be compromised between the efficiency and the effectiveness.

[Global Atmospheric Chemistry/Transport Modeling and Data-Analysis

NASA Technical Reports Server (NTRS)

Prinn, Ronald G.

1999-01-01

This grant supported a global atmospheric chemistry/transport modeling and data- analysis project devoted to: (a) development, testing, and refining of inverse methods for determining regional and global transient source and sink strengths for trace gases; (b) utilization of these inverse methods which use either the Model for Atmospheric Chemistry and Transport (MATCH) which is based on analyzed observed winds or back- trajectories calculated from these same winds for determining regional and global source and sink strengths for long-lived trace gases important in ozone depletion and the greenhouse effect; (c) determination of global (and perhaps regional) average hydroxyl radical concentrations using inverse methods with multiple "titrating" gases; and (d) computation of the lifetimes and spatially resolved destruction rates of trace gases using 3D models. Important ultimate goals included determination of regional source strengths of important biogenic/anthropogenic trace gases and also of halocarbons restricted by the Montreal Protocol and its follow-on agreements, and hydrohalocarbons now used as alternatives to the above restricted halocarbons.

Simulating intrafraction prostate motion with a random walk model.

PubMed

Pommer, Tobias; Oh, Jung Hun; Munck Af Rosenschöld, Per; Deasy, Joseph O

2017-01-01

Prostate motion during radiation therapy (ie, intrafraction motion) can cause unwanted loss of radiation dose to the prostate and increased dose to the surrounding organs at risk. A compact but general statistical description of this motion could be useful for simulation of radiation therapy delivery or margin calculations. We investigated whether prostate motion could be modeled with a random walk model. Prostate motion recorded during 548 radiation therapy fractions in 17 patients was analyzed and used for input in a random walk prostate motion model. The recorded motion was categorized on the basis of whether any transient excursions (ie, rapid prostate motion in the anterior and superior direction followed by a return) occurred in the trace and transient motion. This was separately modeled as a large step in the anterior/superior direction followed by a returning large step. Random walk simulations were conducted with and without added artificial transient motion using either motion data from all observed traces or only traces without transient excursions as model input, respectively. A general estimate of motion was derived with reasonable agreement between simulated and observed traces, especially during the first 5 minutes of the excursion-free simulations. Simulated and observed diffusion coefficients agreed within 0.03, 0.2 and 0.3 mm 2 /min in the left/right, superior/inferior, and anterior/posterior directions, respectively. A rapid increase in variance at the start of observed traces was difficult to reproduce and seemed to represent the patient's need to adjust before treatment. This could be estimated somewhat using artificial transient motion. Random walk modeling is feasible and recreated the characteristics of the observed prostate motion. Introducing artificial transient motion did not improve the overall agreement, although the first 30 seconds of the traces were better reproduced. The model provides a simple estimate of prostate motion during delivery of radiation therapy.

Modeling of laser interactions with composite materials

DOE PAGES

Rubenchik, Alexander M.; Boley, Charles D.

2013-05-07

In this study, we develop models of laser interactions with composite materials consisting of fibers embedded within a matrix. A ray-trace model is shown to determine the absorptivity, absorption depth, and optical power enhancement within the material, as well as the angular distribution of the reflected light. We also develop a macroscopic model, which provides physical insight and overall results. We show that the parameters in this model can be determined from the ray trace model.

Patella instability: building bridges across the ocean a historic review.

PubMed

Arendt, Elizabeth A; Dejour, David

2013-02-01

The diagnosis of and treatment for musculoskeletal disease and injuries have seen an explosion of new knowledge. More precise imaging, correlative injury anatomy, more focused physical examination features, among others, have led this upsurge of current insight. Crucial to this knowledge revolution is the expansion of international knowledge, which is aided by an adoption of a universal scientific language, electronic transfer of information, and personal communication of surgeons and scientists across national boundaries. One area where this is particularly evident is in our knowledge and treatment for patellofemoral disorders. This article will review the developments in the management of patellar dislocations by tracing their historical roots. This is not meant to be a comprehensive review, but rather to give current readers a "historical memory" upon which to judge and interpret our present-day bridge of knowledge. Level of evidence V.

Learning Probabilistic Logic Models from Probabilistic Examples

PubMed Central

Chen, Jianzhong; Muggleton, Stephen; Santos, José

2009-01-01

Abstract We revisit an application developed originally using abductive Inductive Logic Programming (ILP) for modeling inhibition in metabolic networks. The example data was derived from studies of the effects of toxins on rats using Nuclear Magnetic Resonance (NMR) time-trace analysis of their biofluids together with background knowledge representing a subset of the Kyoto Encyclopedia of Genes and Genomes (KEGG). We now apply two Probabilistic ILP (PILP) approaches - abductive Stochastic Logic Programs (SLPs) and PRogramming In Statistical modeling (PRISM) to the application. Both approaches support abductive learning and probability predictions. Abductive SLPs are a PILP framework that provides possible worlds semantics to SLPs through abduction. Instead of learning logic models from non-probabilistic examples as done in ILP, the PILP approach applied in this paper is based on a general technique for introducing probability labels within a standard scientific experimental setting involving control and treated data. Our results demonstrate that the PILP approach provides a way of learning probabilistic logic models from probabilistic examples, and the PILP models learned from probabilistic examples lead to a significant decrease in error accompanied by improved insight from the learned results compared with the PILP models learned from non-probabilistic examples. PMID:19888348

Learning Probabilistic Logic Models from Probabilistic Examples.

PubMed

Chen, Jianzhong; Muggleton, Stephen; Santos, José

2008-10-01

We revisit an application developed originally using abductive Inductive Logic Programming (ILP) for modeling inhibition in metabolic networks. The example data was derived from studies of the effects of toxins on rats using Nuclear Magnetic Resonance (NMR) time-trace analysis of their biofluids together with background knowledge representing a subset of the Kyoto Encyclopedia of Genes and Genomes (KEGG). We now apply two Probabilistic ILP (PILP) approaches - abductive Stochastic Logic Programs (SLPs) and PRogramming In Statistical modeling (PRISM) to the application. Both approaches support abductive learning and probability predictions. Abductive SLPs are a PILP framework that provides possible worlds semantics to SLPs through abduction. Instead of learning logic models from non-probabilistic examples as done in ILP, the PILP approach applied in this paper is based on a general technique for introducing probability labels within a standard scientific experimental setting involving control and treated data. Our results demonstrate that the PILP approach provides a way of learning probabilistic logic models from probabilistic examples, and the PILP models learned from probabilistic examples lead to a significant decrease in error accompanied by improved insight from the learned results compared with the PILP models learned from non-probabilistic examples.

Evaluation of Chemistry-Climate Model Results using Long-Term Satellite and Ground-Based Data

NASA Technical Reports Server (NTRS)

Stolarski, Richard S.

2005-01-01

Chemistry-climate models attempt to bring together our best knowledge of the key processes that govern the composition of the atmosphere and its response to changes in forcing. We test these models on a process by process basis by comparing model results to data from many sources. A more difficult task is testing the model response to changes. One way to do this is to use the natural and anthropogenic experiments that have been done on the atmosphere and are continuing to be done. These include the volcanic eruptions of El Chichon and Pinatubo, the solar cycle, and the injection of chlorine and bromine from CFCs and methyl bromide. The test of the model's response to these experiments is their ability to produce the long-term variations in ozone and the trace gases that affect ozone. We now have more than 25 years of satellite ozone data. We have more than 15 years of satellite and ground-based data of HC1, HN03, and many other gases. I will discuss the testing of models using long-term satellite data sets, long-term measurements from the Network for Detection of Stratospheric Change (NDSC) , long-term ground-based measurements of ozone.

Expectancies as a Determinant of Interference Phenomena

ERIC Educational Resources Information Center

Hasher, Lynn; Greenberg, Michael

1977-01-01

One version, by Lockhart, Craik, and Jacoby, of a levels-of-processing model of memory asserts the importance of the role of expectancies about forthcoming information in determining the elaborateness of a memory trace. Confirmed expectancies result in less-elaborated memory traces; disconfirmed expectancies result in elaborate memory traces.…

Experimental physical methods and theories--then and now.

PubMed

Schulte, Jurgen

2015-10-01

A first evaluation of fundamental research into the physics and physiology of Ultra high dilutions (UHDs) was conducted by the author in 1994(1). In this paper we revisit methods and theories from back then and follow their paths through their evolution and contribution to new knowledge in UHD research since then. Physical methods and theories discusses in our anthology on UHD in 1994(1) form the basis for tracing ideas and findings along their path of further development and impact on new knowledge in UHD. Experimental approaches to probe physical changes in homeopathic preparations have become more sophisticated over past two decades, so did the desire to report results to a scientific standard that is on par with those in specialist literature. The same cannot be said about underlying supporting theoretical models and simulations. Grant challenges in science often take a more targeted and more concerted approach to formulate a research question and then look for answers. A concerted effort to focus on one hypothesized physical aspect of a well-defined homeopathic preparation may help aligning experimental methods with theoretical models and, in doing so, help to gain a deeper understanding of the whole body of insights and data produced. Copyright © 2015 The Faculty of Homeopathy. Published by Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Yue; Gleber, Sophie-Charlotte; Jacobsen, Chris

Trace metals play critical roles in a variety of systems, ranging from cells to photovoltaics. X-Ray Fluorescence (XRF) microscopy using X-ray excitation provides one of the highest sensitivities available for imaging the distribution of trace metals at sub-100 nm resolution. With the growing availability and increasing performance of synchrotron light source based instruments and X-ray nanofocusing optics, and with improvements in energy-dispersive XRF detectors, what are the factors that limit trace element detectability? To address this question, we describe an analytical model for the total signal incident on XRF detectors with various geometries, including the spectral response of energy dispersivemore » detectors. This model agrees well with experimentally recorded X-ray fluorescence spectra, and involves much shorter calculation times than with Monte Carlo simulations. With such a model, one can estimate the signal when a trace element is illuminated with an X-ray beam, and when just the surrounding non-fluorescent material is illuminated. From this signal difference, a contrast parameter can be calculated and this can in turn be used to calculate the signal-to-noise ratio (S/N) for detecting a certain elemental concentration. We apply this model to the detection of trace amounts of zinc in biological materials, and to the detection of small quantities of arsenic in semiconductors. We conclude that increased detector collection solid angle is (nearly) always advantageous even when considering the scattered signal. However, given the choice between a smaller detector at 90° to the beam versus a larger detector at 180° (in a backscatter-like geometry), the 90° detector is better for trace element detection in thick samples, while the larger detector in 180° geometry is better suited to trace element detection in thin samples.« less

Illustrating phallic worship: uses of material objects and the production of sexual knowledge in eighteenth-century antiquarianism and early twentieth-century sexual science.

PubMed

Funke, Jana; Fisher, Kate; Grove, Jen; Langlands, Rebecca

2017-07-03

This article reveals previously overlooked connections between eighteenth-century antiquarianism and early twentieth-century sexual science by presenting a comparative reading of two illustrated books: An Account of the Remains of the Worship of Priapus , by British antiquarian scholar Richard Payne Knight (1750-1824), and Die Weltreise eines Sexualforschers (The World Journey of a Sexologist), by German sexual scientist Magnus Hirschfeld (1868-1935). A close analysis of these publications demonstrates the special status of material artefacts and the strategic engagement with visual evidence in antiquarian and scientific writings about sex. Through its exploration of the similarities between antiquarian and sexual scientific thought, the article demonstrates the centrality of material culture to the production of sexual knowledge in the Western world. It also opens up new perspectives on Western intellectual history and on the intellectual origins of sexual science. While previous scholarship has traced the beginnings of sexual science back to nineteenth-century medical disciplines, this article shows that sexual scientists drew upon different forms of evidence and varied methodologies to produce sexual knowledge and secure scientific authority. As such, sexual science needs to be understood as a field with diverse intellectual roots that can be traced back (at least) to the eighteenth century.

Illustrating phallic worship: uses of material objects and the production of sexual knowledge in eighteenth-century antiquarianism and early twentieth-century sexual science

PubMed Central

Funke, Jana; Fisher, Kate; Grove, Jen; Langlands, Rebecca

2017-01-01

Abstract This article reveals previously overlooked connections between eighteenth-century antiquarianism and early twentieth-century sexual science by presenting a comparative reading of two illustrated books: An Account of the Remains of the Worship of Priapus, by British antiquarian scholar Richard Payne Knight (1750–1824), and Die Weltreise eines Sexualforschers (The World Journey of a Sexologist), by German sexual scientist Magnus Hirschfeld (1868–1935). A close analysis of these publications demonstrates the special status of material artefacts and the strategic engagement with visual evidence in antiquarian and scientific writings about sex. Through its exploration of the similarities between antiquarian and sexual scientific thought, the article demonstrates the centrality of material culture to the production of sexual knowledge in the Western world. It also opens up new perspectives on Western intellectual history and on the intellectual origins of sexual science. While previous scholarship has traced the beginnings of sexual science back to nineteenth-century medical disciplines, this article shows that sexual scientists drew upon different forms of evidence and varied methodologies to produce sexual knowledge and secure scientific authority. As such, sexual science needs to be understood as a field with diverse intellectual roots that can be traced back (at least) to the eighteenth century. PMID:29393929

Quantifying trace element and isotope fluxes at the ocean-sediment boundary: a review.

PubMed

Homoky, William B; Weber, Thomas; Berelson, William M; Conway, Tim M; Henderson, Gideon M; van Hulten, Marco; Jeandel, Catherine; Severmann, Silke; Tagliabue, Alessandro

2016-11-28

Quantifying fluxes of trace elements and their isotopes (TEIs) at the ocean's sediment-water boundary is a pre-eminent challenge to understand their role in the present, past and future ocean. There are multiple processes that drive the uptake and release of TEIs, and properties that determine their rates are unevenly distributed (e.g. sediment composition, redox conditions and (bio)physical dynamics). These factors complicate our efforts to find, measure and extrapolate TEI fluxes across ocean basins. GEOTRACES observations are unveiling the oceanic distributions of many TEIs for the first time. These data evidence the influence of the sediment-water boundary on many TEI cycles, and underline the fact that our knowledge of the source-sink fluxes that sustain oceanic distributions is largely missing. Present flux measurements provide low spatial coverage and only part of the empirical basis needed to predict TEI flux variations. Many of the advances and present challenges facing TEI flux measurements are linked to process studies that collect sediment cores, pore waters, sinking material or seawater in close contact with sediments. However, such sampling has not routinely been viable on GEOTRACES expeditions. In this article, we recommend approaches to address these issues: firstly, with an interrogation of emergent data using isotopic mass-balance and inverse modelling techniques; and secondly, by innovating pursuits of direct TEI flux measurements. We exemplify the value of GEOTRACES data with a new inverse model estimate of benthic Al flux in the North Atlantic Ocean. Furthermore, we review viable flux measurement techniques tailored to the sediment-water boundary. We propose that such activities are aimed at regions that intersect the GEOTRACES Science Plan on the basis of seven criteria that may influence TEI fluxes: sediment provenance, composition, organic carbon supply, redox conditions, sedimentation rate, bathymetry and the benthic nepheloid inventory.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'. © 2015 The Authors.

Quantifying trace element and isotope fluxes at the ocean-sediment boundary: a review

NASA Astrophysics Data System (ADS)

Homoky, William B.; Weber, Thomas; Berelson, William M.; Conway, Tim M.; Henderson, Gideon M.; van Hulten, Marco; Jeandel, Catherine; Severmann, Silke; Tagliabue, Alessandro

2016-11-01

Quantifying fluxes of trace elements and their isotopes (TEIs) at the ocean's sediment-water boundary is a pre-eminent challenge to understand their role in the present, past and future ocean. There are multiple processes that drive the uptake and release of TEIs, and properties that determine their rates are unevenly distributed (e.g. sediment composition, redox conditions and (bio)physical dynamics). These factors complicate our efforts to find, measure and extrapolate TEI fluxes across ocean basins. GEOTRACES observations are unveiling the oceanic distributions of many TEIs for the first time. These data evidence the influence of the sediment-water boundary on many TEI cycles, and underline the fact that our knowledge of the source-sink fluxes that sustain oceanic distributions is largely missing. Present flux measurements provide low spatial coverage and only part of the empirical basis needed to predict TEI flux variations. Many of the advances and present challenges facing TEI flux measurements are linked to process studies that collect sediment cores, pore waters, sinking material or seawater in close contact with sediments. However, such sampling has not routinely been viable on GEOTRACES expeditions. In this article, we recommend approaches to address these issues: firstly, with an interrogation of emergent data using isotopic mass-balance and inverse modelling techniques; and secondly, by innovating pursuits of direct TEI flux measurements. We exemplify the value of GEOTRACES data with a new inverse model estimate of benthic Al flux in the North Atlantic Ocean. Furthermore, we review viable flux measurement techniques tailored to the sediment-water boundary. We propose that such activities are aimed at regions that intersect the GEOTRACES Science Plan on the basis of seven criteria that may influence TEI fluxes: sediment provenance, composition, organic carbon supply, redox conditions, sedimentation rate, bathymetry and the benthic nepheloid inventory. This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'.

Quantifying trace element and isotope fluxes at the ocean–sediment boundary: a review

PubMed Central

Berelson, William M.; Severmann, Silke

2016-01-01

Quantifying fluxes of trace elements and their isotopes (TEIs) at the ocean's sediment–water boundary is a pre-eminent challenge to understand their role in the present, past and future ocean. There are multiple processes that drive the uptake and release of TEIs, and properties that determine their rates are unevenly distributed (e.g. sediment composition, redox conditions and (bio)physical dynamics). These factors complicate our efforts to find, measure and extrapolate TEI fluxes across ocean basins. GEOTRACES observations are unveiling the oceanic distributions of many TEIs for the first time. These data evidence the influence of the sediment–water boundary on many TEI cycles, and underline the fact that our knowledge of the source–sink fluxes that sustain oceanic distributions is largely missing. Present flux measurements provide low spatial coverage and only part of the empirical basis needed to predict TEI flux variations. Many of the advances and present challenges facing TEI flux measurements are linked to process studies that collect sediment cores, pore waters, sinking material or seawater in close contact with sediments. However, such sampling has not routinely been viable on GEOTRACES expeditions. In this article, we recommend approaches to address these issues: firstly, with an interrogation of emergent data using isotopic mass-balance and inverse modelling techniques; and secondly, by innovating pursuits of direct TEI flux measurements. We exemplify the value of GEOTRACES data with a new inverse model estimate of benthic Al flux in the North Atlantic Ocean. Furthermore, we review viable flux measurement techniques tailored to the sediment–water boundary. We propose that such activities are aimed at regions that intersect the GEOTRACES Science Plan on the basis of seven criteria that may influence TEI fluxes: sediment provenance, composition, organic carbon supply, redox conditions, sedimentation rate, bathymetry and the benthic nepheloid inventory. This article is part of the themed issue ‘Biological and climatic impacts of ocean trace element chemistry’. PMID:29035270

An experimental study of trace element partitioning between perovskite, hibonite and melt: Equilibrium values

NASA Technical Reports Server (NTRS)

Kennedy, A. K.; Lofgren, G. E.; Wasserburg, G. J.

1993-01-01

The presence of perovskite (CATiO3) and hibonite (Ca Al12O19) within different regions of Calcium-, Aluminum-rich Inclusions (CAI) and the trace element concentrations of these minerals in each circumstance, constrain models of precursor formation, nebular condensation, the thermal history of inclusions with relict perovskite and hibonite, and the formation of the Wark-Lovering rim. At present mineral/melt partition coefficient data for hibonite are limited to a few elements in simple experimental systems, or to those derived from hibonite-glass pairs in hibonite/glass microspherules. Similarly, there is only limited data on perovskite D that are applicable to meteorite compositions. Apart from the importance of partitioning studies to meteorite research, D values also are invaluable in the development of thermodynamic models, especially when data is available for a large number of elements that have different ionic charge and radii. In addition, study of the effect of rapid cooling on partitioning is crucial to our understanding of meteorite inclusions. To expand our knowledge of mineral/melt D for perovskite and hibonite, a study was instituted where D values are obtained in both equilibrium and dynamic cooling experiments. As an initial phase of this study mineral/melt D was measured for major elements (Ca, Mg, Al, Ti, and Si), 15 rare earth elements (La-Lu) and 8 other elements (Ba, Sr, U, Th, Nb, Zr, Hf, and Ge) in perovskite and hibonite grown under equilibrium conditions, in bulk compositions that are respectively similar to Compact Type A (CTA) CAI and to a hibonite/glass microspherule. Experimental mixes were doped with REE at 20-50x chondritic (ch) abundances, Ba at 50 ppm, Sr, Hf, Nb, and Zr at 100 ppm and, U and Th at 200 ppm. Trace element abundances were measured with the PANURGE ion microprobe. Major element compositions were obtained by electron microprobe analysis.

Moving epithelia: Tracking the fate of mammalian limbal epithelial stem cells.

PubMed

Di Girolamo, Nick

2015-09-01

Lineage tracing allows the destiny of a stem cell (SC) and its progeny to be followed through time. In order to track their long-term fate, SC must be permanently marked to discern their distribution, division, displacement and differentiation. This information is essential for unravelling the mysteries that govern their replenishing activity while they remain anchored within their niche microenvironment. Modern-day lineage tracing uses inducible genetic recombination to illuminate cells within embryonic, newborn and adult tissues, and the advent of powerful high-resolution microscopy has enabled the behaviour of labelled cells to be monitored in real-time in a living organism. The simple structural organization of the mammalian cornea, including its accessibility and transparency, renders it the ideal tissue to study SC fate using lineage tracing assisted by non-invasive intravital microscopy. Despite more than a century of research devoted to understanding how this tissue is maintained and repaired, many limitations and controversies continue to plague the field, including uncertainties about the specificity of current SC markers, the number of SC within the cornea, their mode of division, their location, and importantly the signals that dictate cell migration. This communication will highlight historical discoveries as well as recent developments in the corneal SC field; more specifically how the progeny of these cells are mobilised to replenish this dynamic tissue during steady-state, disease and transplantation. Also discussed is how insights gleaned from animal studies can be used to advance our knowledge of the fundamental mechanisms that govern modelling and remodelling of the human cornea in health and disease. Copyright © 2015 Elsevier Ltd. All rights reserved.

Quantifying emerging local anthropogenic emissions in the Arctic region: the ACCESS aircraft campaign experiment (Invited)

NASA Astrophysics Data System (ADS)

Roiger, A.; Thomas, J. L.; Schlager, H.; Law, K.; Kim, J.; Reiter, A.; Schaefler, A.; Weinzierl, B.; Rose, M.; Raut, J.; Marelle, L.

2013-12-01

Arctic sea ice has decreased dramatically in the past few decades, which has opened the Arctic Ocean to transit shipping and hydrocarbon extraction. These anthropogenic activities are expected to increase emissions of air pollutants and climate forcers (e.g. aerosols, ozone) in the Arctic troposphere significantly in the future. However, large knowledge gaps exist how these emissions influence regional air pollution and Arctic climate. Here we present an overview on the ACCESS (Arctic Climate Change, Economy, and Society, a European Union Seventh Framework Programme project) aircraft campaign, which primarily focused on studying emissions from emerging Arctic pollution sources. During the ACCESS campaign in July 2012, the DLR Falcon was based in Andenes, Norway, and was equipped with a suite of trace gas and aerosol instruments (black carbon, ozone, as well as other trace species). During nine scientific flights, emissions from different ship types (e.g. cargo, passenger, and fishing vessels) and a variety of offshore extraction facilities (e.g. drilling rigs, production and storage platforms) were probed off the Norwegian Coast. The emissions from these increasing pollution sources showed distinct differences in chemical and aerosol composition. To put the emerging local pollution within a broader context, we also measured sulfur-rich emissions originating from industrial activities on the Kola Peninsula and black carbon containing biomass burning plumes imported from Siberian wildfires. We will present an overview on the trace gas and aerosol properties of the different emission sources, and discuss the influence of future local anthropogenic activities on the Arctic air composition by combining measurements with model simulations.

Optimizing detector geometry for trace element mapping by X-ray fluorescence

DOE PAGES

Sun, Yue; Gleber, Sophie -Charlotte; Jacobsen, Chris; ...

2015-01-01

We report that trace metals play critical roles in a variety of systems, ranging from cells to photovoltaics. X-Ray Fluorescence (XRF) microscopy using X-ray excitation provides one of the highest sensitivities available for imaging the distribution of trace metals at sub-100 nm resolution. With the growing availability and increasing performance of synchrotron light source based instruments and X-ray nanofocusing optics, and with improvements in energy-dispersive XRF detectors, what are the factors that limit trace element detectability? To address this question, we describe an analytical model for the total signal incident on XRF detectors with various geometries, including the spectral responsemore » of energy dispersive detectors. This model agrees well with experimentally recorded X-ray fluorescence spectra, and involves much shorter calculation times than with Monte Carlo simulations. With such a model, one can estimate the signal when a trace element is illuminated with an X-ray beam, and when just the surrounding non-fluorescent material is illuminated. From this signal difference, a contrast parameter can be calculated and this can in turn be used to calculate the signal-to-noise ratio (S/N) for detecting a certain elemental concentration. We apply this model to the detection of trace amounts of zinc in biological materials, and to the detection of small quantities of arsenic in semiconductors. In conclusion, we conclude that increased detector collection solid angle is (nearly) always advantageous even when considering the scattered signal. However, given the choice between a smaller detector at 90° to the beam versus a larger detector at 180° (in a backscatter-like geometry), the 90° detector is better for trace element detection in thick samples, while the larger detector in 180° geometry is better suited to trace element detection in thin samples.« less

Optimizing detector geometry for trace element mapping by X-ray fluorescence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Yue; Gleber, Sophie -Charlotte; Jacobsen, Chris

We report that trace metals play critical roles in a variety of systems, ranging from cells to photovoltaics. X-Ray Fluorescence (XRF) microscopy using X-ray excitation provides one of the highest sensitivities available for imaging the distribution of trace metals at sub-100 nm resolution. With the growing availability and increasing performance of synchrotron light source based instruments and X-ray nanofocusing optics, and with improvements in energy-dispersive XRF detectors, what are the factors that limit trace element detectability? To address this question, we describe an analytical model for the total signal incident on XRF detectors with various geometries, including the spectral responsemore » of energy dispersive detectors. This model agrees well with experimentally recorded X-ray fluorescence spectra, and involves much shorter calculation times than with Monte Carlo simulations. With such a model, one can estimate the signal when a trace element is illuminated with an X-ray beam, and when just the surrounding non-fluorescent material is illuminated. From this signal difference, a contrast parameter can be calculated and this can in turn be used to calculate the signal-to-noise ratio (S/N) for detecting a certain elemental concentration. We apply this model to the detection of trace amounts of zinc in biological materials, and to the detection of small quantities of arsenic in semiconductors. In conclusion, we conclude that increased detector collection solid angle is (nearly) always advantageous even when considering the scattered signal. However, given the choice between a smaller detector at 90° to the beam versus a larger detector at 180° (in a backscatter-like geometry), the 90° detector is better for trace element detection in thick samples, while the larger detector in 180° geometry is better suited to trace element detection in thin samples.« less

Long Term Association of Tropospheric Trace gases over Pakistan by exploiting satellite observations and development of Econometric Regression based Model

NASA Astrophysics Data System (ADS)

Zeb, Naila; Fahim Khokhar, Muhammad; Khan, Saud Ahmed; Noreen, Asma; Murtaza, Rabbia

2017-04-01

Air pollution is the expected key environmental issue of Pakistan as it is ranked among top polluted countries in the region. Ongoing rapid economic growth without any adequate measures is leading to worst air quality over time. The study aims to monitor long term atmospheric composition and association of trace gases over Pakistan. Tropospheric concentrations of CO, TOC, NO2 and HCHO derived from multiple satellite instruments are used for study from year 2005 to 2014. The study will provide first database for tropospheric trace gases over Pakistan. Spatio-temporal assessment identified hotspots and possible sources of trace gases over the Pakistan. High concentrations of trace gases are mainly observed over Punjab region, which may be attributed to its metropolitan importance. It is the major agricultural, industrialized and urbanized (nearly 60 % of the Pakistan's population) sector of the country. The expected sources are the agricultural fires, biomass/fossil fuel burning for heating purposes, urbanization, industrialization and meteorological variations. Seasonal variability is observed to explore seasonal patterns over the decade. Well defined seasonal cycles of trace gases are observed over the whole study period. The observed seasonal patterns also showed some noteworthy association among trace gases, which is further explored by different statistical tests. Seasonal Mann Kendall test is applied to test the significance of trend in series whereas correlation is carried out to measure the strength of association among trace gases. Strong correlation is observed for trace gases especially between CO and TOC. Partial Mann Kendall test is used to ideally identify the impact of each covariate on long term trend of CO and TOC by partialling out each correlating trace gas (covariate). It is observed that TOC, NO2 and HCHO has significant impact on long term trend of CO whereas, TOC critically depends on NO2 concentrations for long term increase over the region. Furthermore to explore causal relation, regression analysis is employed to estimate model for CO and TOC. This model numerically estimated the long term association of trace gases over the region.

Determination of equivalent sound speed profiles for ray tracing in near-ground sound propagation.

PubMed

Prospathopoulos, John M; Voutsinas, Spyros G

2007-09-01

The determination of appropriate sound speed profiles in the modeling of near-ground propagation using a ray tracing method is investigated using a ray tracing model which is capable of performing axisymmetric calculations of the sound field around an isolated source. Eigenrays are traced using an iterative procedure which integrates the trajectory equations for each ray launched from the source at a specific direction. The calculation of sound energy losses is made by introducing appropriate coefficients to the equations representing the effect of ground and atmospheric absorption and the interaction with the atmospheric turbulence. The model is validated against analytical and numerical predictions of other methodologies for simple cases, as well as against measurements for nonrefractive atmospheric environments. A systematic investigation for near-ground propagation in downward and upward refractive atmosphere is made using experimental data. Guidelines for the suitable simulation of the wind velocity profile are derived by correlating predictions with measurements.

Scaling properties of ballistic nano-transistors

PubMed Central

2011-01-01

Recently, we have suggested a scale-invariant model for a nano-transistor. In agreement with experiments a close-to-linear thresh-old trace was found in the calculated ID - VD-traces separating the regimes of classically allowed transport and tunneling transport. In this conference contribution, the relevant physical quantities in our model and its range of applicability are discussed in more detail. Extending the temperature range of our studies it is shown that a close-to-linear thresh-old trace results at room temperatures as well. In qualitative agreement with the experiments the ID - VG-traces for small drain voltages show thermally activated transport below the threshold gate voltage. In contrast, at large drain voltages the gate-voltage dependence is weaker. As can be expected in our relatively simple model, the theoretical drain current is larger than the experimental one by a little less than a decade. PMID:21711899

A FINITE-DIFFERENCE, DISCRETE-WAVENUMBER METHOD FOR CALCULATING RADAR TRACES

EPA Science Inventory

A hybrid of the finite-difference method and the discrete-wavenumber method is developed to calculate radar traces. The method is based on a three-dimensional model defined in the Cartesian coordinate system; the electromag-netic properties of the model are symmetric with respect...

Investigation of the roles of trace elements during hepatitis C virus infection using protein-protein interactions and a shortest path algorithm.

PubMed

Zhu, LiuCun; Chen, XiJia; Kong, Xiangyin; Cai, Yu-Dong

2016-11-01

Hepatitis is a type of infectious disease that induces inflammation of the liver without pinpointing a particular pathogen or pathogenesis. Type C hepatitis, as a type of hepatitis, has been reported to induce cirrhosis and hepatocellular carcinoma within a very short amount of time. It is a great threat to human health. Some studies have revealed that trace elements are associated with infection with and immune rejection against hepatitis C virus (HCV). However, the mechanism underlying this phenomenon is still unclear. In this study, we aimed to expand our knowledge of this phenomenon by designing a computational method to identify genes that may be related to both HCV and trace element metabolic processes. The searching procedure included three stages. First, a shortest path algorithm was applied to a large network, constructed by protein-protein interactions, to identify potential genes of interest. Second, a permutation test was executed to exclude false discoveries. Finally, some rules based on the betweenness and associations between candidate genes and HCV and trace elements were built to select core genes among the remaining genes. 12 lists of genes, corresponding to 12 types of trace elements, were obtained. These genes are deemed to be associated with HCV infection and trace elements metabolism. The analyses indicate that some genes may be related to both HCV and trace element metabolic processes, further confirming the associations between HCV and trace elements. The method was further tested on another set of HCV genes, the results indicate that this method is quite robustness. The newly found genes may partially reveal unknown mechanisms between HCV infection and trace element metabolism. This article is part of a Special Issue entitled "System Genetics" Guest Editor: Dr. Yudong Cai and Dr. Tao Huang. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of silicon on trace element partitioning in iron-bearing metallic melts

NASA Astrophysics Data System (ADS)

Chabot, Nancy L.; Safko, Trevor M.; McDonough, William F.

2010-08-01

Despite the fact that Si is considered a potentially important metalloid in planetary systems, little is known about the effect of Si in metallic melts on trace element partitioning behavior. Previous studies have established the effects of S, C, and P, nonmetals, through solid metal/liquid metal experiments in the corresponding Fe binary systems, but the Fe-Si system is not appropriate for similar experiments because of the high solubility of Si in solid metal. In this work, we present the results from 0.1MPa experiments with two coexisting immiscible metallic liquids in the Fe-S-Si system. By leveraging the extensive available knowledge about the effect of S on trace element partitioning behavior, we explore the effect of Si. Results for 22 trace elements are presented. Strong Si avoidance behavior is demonstrated by As, Au, Ga, Ge, Sb, Sn, and Zn. Iridium, Os, Pt, Re, Ru, and W exhibit weak Si avoidance tendencies. Silicon appears to have no significant effect on the partitioning behaviors of Ag, Co, Cu, Cr, Ni, Pd, and V, all of which had similar partition coefficients over a wide range of Si liquid concentrations from Si-free to 13 wt%. The only elements in our experiments to show evidence of a potentially weak attraction to Si were Mo and Rh. Applications of the newly determined effects of Si to problems in planetary science indicate that (1) The elements Ni, Co, Mo, and W, which are commonly used in planetary differentiation models, are minimally affected by the presence of Si in the metal, especially in comparison to other effects such as from oxygen fugacity. 2) Reduced enstatite-rich meteorites may record a chemical signature due to Si in the metallic melts during partial melting, and if so, elements identified by this study as having strong Si avoidance may offer unique insight into unraveling the history of these meteorites.

Intra- and interobserver agreement among obstetric experts in court regarding the review of abnormal fetal heart rate tracings and obstetrical management.

PubMed

Sabiani, Laura; Le Dû, Renaud; Loundou, Anderson; d'Ercole, Claude; Bretelle, Florence; Boubli, Léon; Carcopino, Xavier

2015-12-01

The objective of the study was to evaluate the intra- and interobserver agreement among obstetric experts in court regarding the retrospective review of abnormal fetal heart rate tracings and obstetrical management of patients with abnormal fetal heart rate during labor. A total of 22 French obstetric experts in court reviewed 30 cases of term deliveries of singleton pregnancies diagnosed with at least 1 hour of abnormal fetal heart rate, including 10 cases with adverse neonatal outcome. The experts reviewed all cases twice within a 3-month interval, with the first review being blinded to neonatal outcome. For each case reviewed, the experts were provided with the obstetric data and copies of the complete fetal heart rate recording and the partogram. The experts were asked to classify the abnormal fetal heart rate tracing and to express whether they agreed with the obstetrical management performed. When they disagreed, the experts were asked whether they concluded that an error had been made and whether they considered the obstetrical management as the cause of cerebral palsy in children if any. Compared with blinded review, the experts were significantly more likely to agree with the obstetric management performed (P < .001) and with the mode of delivery (P < .001) when informed about the neonatal outcome and were less likely to conclude that an error had been made (P < .001) or to establish a link with potential cerebral palsy (P = .003). The experts' intraobserver agreement for the review of abnormal fetal heart rate tracing and obstetrical management were both mediocre (kappa = 0.46-0.51 and kappa = 0.48-0.53, respectively). The interobserver agreement for the review of abnormal fetal heart rate tracing was low and was not improved by knowledge of the neonatal outcome (kappa = 0.11-0.18). The interobserver agreement for the interpretation of obstetrical management was also low (kappa = 0.08-0.19) but appeared to be improved by knowledge of the neonatal outcome (kappa = 0.15-0.32). The intra- and interobserver agreement among obstetric experts in court for the review of abnormal fetal heart rate tracing and the appropriateness of obstetrical care is poor, suggesting a lack of objectivity of obstetrical expertise as currently performed in court. Copyright © 2015 Elsevier Inc. All rights reserved.

IJS procedure for RELAP5 to TRACE input model conversion using SNAP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prosek, A.; Berar, O. A.

2012-07-01

The TRAC/RELAP Advanced Computational Engine (TRACE) advanced, best-estimate reactor systems code developed by the U.S. Nuclear Regulatory Commission comes with a graphical user interface called Symbolic Nuclear Analysis Package (SNAP). Much of efforts have been done in the past to develop the RELAP5 input decks. The purpose of this study is to demonstrate the Institut 'Josef Stefan' (IJS) conversion procedure from RELAP5 to TRACE input model of BETHSY facility. The IJS conversion procedure consists of eleven steps and is based on the use of SNAP. For calculations of the selected BETHSY 6.2TC test the RELAP5/MOD3.3 Patch 4 and TRACE V5.0more » Patch 1 were used. The selected BETHSY 6.2TC test was 15.24 cm equivalent diameter horizontal cold leg break in the reference pressurized water reactor without high pressure and low pressure safety injection. The application of the IJS procedure for conversion of BETHSY input model showed that it is important to perform the steps in proper sequence. The overall calculated results obtained with TRACE using the converted RELAP5 model were close to experimental data and comparable to RELAP5/MOD3.3 calculations. Therefore it can be concluded, that proposed IJS conversion procedure was successfully demonstrated on the BETHSY integral test facility input model. (authors)« less

From Charity School to Workhouse in the 1720's: The SPCK and Mr Marriott's Solution.

ERIC Educational Resources Information Center

Simon, Joan

1988-01-01

Traces the progress of the Society for Promoting Christian Knowledge's (England) charity school movement in the early eighteenth century and its shift from promotion of catechistical instruction to putting children to work in workhouses that served to banish idleness and beggary. (GEA)

International Handbook of Research on Conceptual Change

ERIC Educational Resources Information Center

Vosniadou, Stella

2008-01-01

The study of conceptual change traces its heritage to the notions of paradigm (networks of shared beliefs, concepts, practices) and paradigm shift made famous by Thomas Kuhn in his book, "The Structure of Scientific Revolutions". Kuhn's work was quickly linked to developmental psychology (how knowledge develops) and to science education (teaching…

A Longitudinal Study of Children's Developing Knowledge and Reasoning in Science

ERIC Educational Resources Information Center

Tytler, Russell; Peterson, Suzanne

2005-01-01

The growth in science understanding and reasoning of 12 children is being traced through their primary school years. The paper reports findings concerning children's growing understandings of evaporation, and their changing responses to exploration activities, that show the complexity and coherence of learning pathways. Children's responses to…

Mechanisms of antimony adsorption onto soybean stover-derived biochar in aqueous solutions

USDA-ARS?s Scientific Manuscript database

Limited mechanistic knowledge is available to understand how biochar interacts with trace elements that exist predominantly as oxoanions, such as antimony (Sb). Soybean stover biochars were produced at 300 degrees C (SBC300) and 700 degrees C (SBC700), and were characterized by BET, Boehm titration,...

The Development of Sociocultural Competence with the Help of Computer Technology

ERIC Educational Resources Information Center

Rakhimova, Alina E.; Yashina, Marianna E.; Mukhamadiarova, Albina F.; Sharipova, Astrid V.

2017-01-01

The article deals with the description of the process of development sociocultural knowledge and competences using computer technologies. On the whole the development of modern computer technologies allows teachers to broaden trainees' sociocultural outlook and trace their progress online. Observation of modern computer technologies and estimation…

Community Psychology in South Africa: Origins, Developments, and Manifestations

ERIC Educational Resources Information Center

Seedat, Mohamed; Lazarus, Sandy

2011-01-01

This article represents a South African contribution to the growing international body of knowledge on histories of community psychology. We trace the early antecedents of social-community psychology interventions and describe the social forces and academic influences that provided the impetus for the emergence and development of community…

The Mind's Staircase: Exploring the Conceptual Underpinnings of Children's Thought and Knowledge.

ERIC Educational Resources Information Center

Case, Robbie; And Others

This book, which contains 19 chapters, examines children's learning processes in light of reconceptualizations of Piagetian theory. Part one traces the theoretical question underpinning this examination and includes three chapters: "General and Specific Views of the Mind, its Structure, and its Development"; "A Neo-Piagetian…

Musical Knowledge, Musical Identity, and the Generalist Teacher: Vicki's Story.

ERIC Educational Resources Information Center

Russell, Joan

1996-01-01

Utilizes excerpts from an undergraduate elementary education student's journal to examine generalist teachers' attitudes towards musical competency and the necessary qualifications for teachers. Traces one teacher's recognition of her own musicality and the corresponding influence on her feelings of competency to teach this subject in an…

Tracking Back to the Big Bang.

ERIC Educational Resources Information Center

Peat, David

1983-01-01

Traces some astronomical history and considers how astronomers have arrived at their current knowledge of distance, size, and time as it applies to objects in the night sky. The information is provided as background to a discussion of the Hubble constant and its relationship to the age of the universe. (JN)

Educating Engineers in Information Utilization.

ERIC Educational Resources Information Center

Borovansky, Vladimir T.

1987-01-01

Traditionally engineers are not heaviest users of information resources. This can be traced to lack of emphasis on information sources in engineering education. Failure to use available knowledge leads to reinventing the wheel and losing the race for technological superiority. Few U.S. universities offer formal courses in information resources in…

A 100-year review: Carbohydrates - characterization, digestion, and utilization

USDA-ARS?s Scientific Manuscript database

Our knowledge of the role of carbohydrates in dairy cattle nutrition has advanced substantially during the 100 years in which the Journal of Dairy Science has been published. In this review, we traced the history of scientific investigation and discovery from crude fiber, nitrogen-free extract, and ...

Electromagnetic ray tracing model for line structures.

PubMed

Tan, C B; Khoh, A; Yeo, S H

2008-03-17

In this paper, a model for electromagnetic scattering of line structures is established based on high frequency approximation approach - ray tracing. This electromagnetic ray tracing (ERT) model gives the advantage of identifying each physical field that contributes to the total solution of the scattering phenomenon. Besides the geometrical optics field, different diffracted fields associated with the line structures are also discussed and formulated. A step by step addition of each electromagnetic field is given to elucidate the causes of a disturbance in the amplitude profile. The accuracy of the ERT model is also discussed by comparing with the reference finite difference time domain (FDTD) solution, which shows a promising result for a single polysilicon line structure with width of as narrow as 0.4 wavelength.

Co-occurrence profiles of trace elements in potable water systems: a case study.

PubMed

Andra, Syam S; Makris, Konstantinos C; Charisiadis, Pantelis; Costa, Costas N

2014-11-01

Potable water samples (N = 74) from 19 zip code locations in a region of Greece were profiled for 13 trace elements composition using inductively coupled plasma mass spectrometry. The primary objective was to monitor the drinking water quality, while the primary focus was to find novel associations in trace elements occurrence that may further shed light on common links in their occurrence and fate in the pipe scales and corrosion products observed in urban drinking water distribution systems. Except for arsenic at two locations and in six samples, rest of the analyzed elements was below maximum contaminant levels, for which regulatory values are available. Further, we attempted to hierarchically cluster trace elements based on their covariances resulting in two groups; one with arsenic, antimony, zinc, cadmium, and copper and the second with the rest of the elements. The grouping trends were partially explained by elements' similar chemical activities in water, underscoring their potential for co-accumulation and co-mobilization phenomena from pipe scales into finished water. Profiling patterns of trace elements in finished water could be indicative of their load on pipe scales and corrosion products, with a corresponding risk of episodic contaminant release. Speculation was made on the role of disinfectants and disinfection byproducts in mobilizing chemically similar trace elements of human health interest from pipe scales to tap water. It is warranted that further studies may eventually prove useful to water regulators from incorporating the acquired knowledge in the drinking water safety plans.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wuebbles, D.J.; Kinnison, D.E.; Lean, J.L.

Over the past decade, knowledge of the magnitude and temporal structure of the variations in the sun's ultraviolet irradiance has increased steadily. A number of theoretical modeling studies have shown that changes in the solar ultraviolet flux during the 11-year solar cycle can have a significant effect on stratospheric ozone concentrations. With the exception of Brasseur et al., who examined a very broad range of solar flux variations, all of these studies assumed much larger changes in the ultraviolet flux than measurements now indicate. These studies either calculated the steady-state effect at solar maximum and solar minimum or assumed sinusoidalmore » variations in the solar flux changes with time. It is now possible to narrow the uncertainty range of the expected effects on upper stratospheric ozone and temperature resulting from the 11-year solar cycle. A more accurate representation of the solar flux changes with time is used in this analysis, as compared to previous published studies. This study also evaluates the relative roles of solar flux variations and increasing concentrations of long-lived trace gases in determining the observed trends in upper stratospheric ozone and temperature. The LLNL two-dimensional chemical-radiative-transport model of the global atmosphere is used to evaluate the combined effects on the stratosphere from changes in solar ultraviolet irradiances and trace gas concentrations over the last several decades. Derived trends in upper stratospheric ozone concentrations and temperature are then compared with available analyses of ground-based and satellite measurements over this time period.« less

Understanding Biogenic and Anthropogenic Trace Gas Variations Measured Near Cool, CA in June 2010

NASA Astrophysics Data System (ADS)

Klein, B. Z.; Flowers, B. A.; Gorkowski, K.; Dubey, M. K.; Knighton, W. B.; Floerchinger, C.; Herndon, S. C.; Fast, J. D.; Zaveri, R. A.

2011-12-01

Trace gas signatures produced by forested and urban areas differ greatly. Forested areas are dominated by gases produced during photosynthesis and respiration: CO2 and volatile organic compounds (VOCs) including terpenes and isoprene. Urban areas are heavily influenced by vehicle exhaust emissions and have elevated levels of CO, NOx and aromatic hydrocarbons such as benzene. Ozone is produced as a byproduct of both of these sources; it is produced when NOx from urban areas reacts with either anthropogenic or biogenic hydrocarbons. The Carbonaceous Aerosol and Radiative Effects Study (CARES) campaign was conducted during June 2010, in part to observe the evolution of urban air masses as they mix into rural locations and to better understand anthropogenic-biogenic photochemical interactions. The campaign included two ground-based sampling sites, one in Sacramento, CA (T0) and one downwind, approximately 70km NE, rurally located near Cool, CA (T1). In situ measurements of CO2, CO, O3, NO and multiple different VOCs were performed at the T1 site during the study, and are analyzed here to gain insights into the chemistry and transport of these trace gases. Comparisons between these trace gases coupled with transport modeling is used to delineate biogenic and anthropogenic sources. Additionally, comparisons between trace gases produced predominately by biogenic sources provide valuable information on how meteorology affects their production. Two atmospheric models (HYSPLIT back-trajectories and WRF forecasts) are used to predict transport episodes, where polluted air masses from the Sacramento or more distant San Francisco areas are transported to Cool. The two models display significant overlap for eleven different transport episodes during the study period. Both models also agree on two transport-free multiple-day periods. By examining the periods during which the models are in agreement, we are able to characterize with high certainty the trace gas signatures of local biogenic sources and also the significance of short-range transported anthropogenic trace gases.

Sediment source fingerprinting as an aid to catchment management: A review of the current state of knowledge and a methodological decision-tree for end-users.

PubMed

Collins, A L; Pulley, S; Foster, I D L; Gellis, A; Porto, P; Horowitz, A J

2017-06-01

The growing awareness of the environmental significance of fine-grained sediment fluxes through catchment systems continues to underscore the need for reliable information on the principal sources of this material. Source estimates are difficult to obtain using traditional monitoring techniques, but sediment source fingerprinting or tracing procedures, have emerged as a potentially valuable alternative. Despite the rapidly increasing numbers of studies reporting the use of sediment source fingerprinting, several key challenges and uncertainties continue to hamper consensus among the international scientific community on key components of the existing methodological procedures. Accordingly, this contribution reviews and presents recent developments for several key aspects of fingerprinting, namely: sediment source classification, catchment source and target sediment sampling, tracer selection, grain size issues, tracer conservatism, source apportionment modelling, and assessment of source predictions using artificial mixtures. Finally, a decision-tree representing the current state of knowledge is presented, to guide end-users in applying the fingerprinting approach. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

What we know and how we know it: contributions from nursing to women's health research and scholarship.

PubMed

Taylor, D; Woods, N

2001-01-01

In this first chapter, we trace the historical roots of nursing research and scholarship focused on protecting and promoting women's health. Beginning with Florence Nightingale, modern nursing's first researcher, who focused on the health impact of women's daily lives through her detailed observations of human behavior. More recently, nursing's contributions to women's health over the past 30 years have redefined women's health, proposed new frameworks for understanding women's health; provided reviews of the women's health literature across disciplines; developed communities of nurse scholars and researchers focused on new areas of women's health research; generated and expanded the knowledge base for women's health practice and education; promoted a global view of women's health; and proposed new models for women's health care delivery. Clearly, a community of nursing scholars, developed over the past 25 years, has contributed to advancing women's health knowledge and improving the health and well-being of women. Without the benefit of a crystal ball, we suggest that nursing will continue to provide leadership in the conduct and the application of research to improve women's health and women's lives.

Modeling Academic Achievement by Self-Reported versus Traced Goal Orientation

ERIC Educational Resources Information Center

Zhou, Mingming; Winne, Philip H.

2012-01-01

We examined achievement goals measured by self-reports and by traces (behavioral indicators) gathered as undergraduates used software tools to study a multimedia-formatted article. Traces were operationalized by tags participants applied to selections of text and hyperlinks they clicked in the article. Tags and hyperlinks were titled to represent…

Improved specificity of hippocampal memory trace labeling.

PubMed

Cazzulino, Alejandro S; Martinez, Randy; Tomm, Nicole K; Denny, Christine A

2016-06-01

Recent studies have focused on the identification and manipulation of memory traces in rodent models. The two main mouse models utilized are either a CreER(T2) /loxP tamoxifen (TAM)- or a tetracycline transactivator/tetracycline-response element doxycycline-inducible system. These systems, however, could be improved to label a more specific population of activated neurons corresponding to behavior. Here, we sought to identify an improved selective estrogen receptor (ER) modulator (SERM) in which we could label an individual memory trace in ArcCreER(T2) mice. We found that 4-hydroxytamoxifen (4-OHT) is a selective SERM in the ArcCreER(T2) × Rosa26-CAG-stop(flox) -channelrhodospin (ChR2)-enhanced yellow fluorescent protein (eYFP) mice. The half-life of 4-OHT is shorter than TAM, allowing for more specificity of memory trace labeling. Furthermore, 4-OHT allowed for context-specific labeling in the dentate gyrus and CA3. In summary, we believe that 4-OHT improves the specificity of memory trace labeling and will allow for refined memory trace studies in the future. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Stoichiometry and kinetics of the anaerobic ammonium oxidation (Anammox) with trace hydrazine addition.

PubMed

Yao, Zongbao; Lu, Peili; Zhang, Daijun; Wan, Xinyu; Li, Yulian; Peng, Shuchan

2015-12-01

Purpose of this study is to investigate the stoichiometry and kinetics of anaerobic ammonium oxidation (Anammox) with trace hydrazine addition. The stoichiometry was established based on the electron balance of Anammox process with trace N2H4 addition. The stoichiometric coefficients were determined by the proton consumption and the changes in substrates and products. It was found that trace N2H4 addition can increase the yield of Anammox bacteria (AnAOB) and reduce NO3(-) yield, which enhances the Anammox. Subsequently, kinetic model of Anammox with trace N2H4 addition was developed, and the parameters of the anaerobic degradation model of N2H4 were obtained for the first time. The maximum specific substrate utilization rate, half-saturation constant and inhibition constant of N2H4 were 25.09mgN/g VSS/d, 10.42mgN/L and 1393.88mgN/L, respectively. These kinetic parameters might provide important information for the engineering applications of Anammox with trace N2H4 addition. Copyright © 2015 Elsevier Ltd. All rights reserved.

Conversion of the trace elements Zn, Cd, and Pb in the combustion of near-Moscow coals

DOE Office of Scientific and Technical Information (OSTI.GOV)

E.V. Samuilov; L.N. Lebedeva; L.S. Pokrovskaya

A model for the conversion of trace elements in the combustion of near-Moscow coals based on a complex approach combining the capabilities of geochemistry, chemical thermodynamics, phase analysis, and chemical kinetics is proposed. The conversion of the trace elements Zn, Cd, and Pb as the constituents of near-Moscow coal in the flow of coal combustion products along the line of the P-59 boiler at the Ryazanskaya Thermal Power Plant was calculated. Experimental data were used in the development of the model and in calculations.

Predicting risk of trace element pollution from municipal roads using site-specific soil samples and remotely sensed data.

PubMed

Reeves, Mari Kathryn; Perdue, Margaret; Munk, Lee Ann; Hagedorn, Birgit

2018-07-15

Studies of environmental processes exhibit spatial variation within data sets. The ability to derive predictions of risk from field data is a critical path forward in understanding the data and applying the information to land and resource management. Thanks to recent advances in predictive modeling, open source software, and computing, the power to do this is within grasp. This article provides an example of how we predicted relative trace element pollution risk from roads across a region by combining site specific trace element data in soils with regional land cover and planning information in a predictive model framework. In the Kenai Peninsula of Alaska, we sampled 36 sites (191 soil samples) adjacent to roads for trace elements. We then combined this site specific data with freely-available land cover and urban planning data to derive a predictive model of landscape scale environmental risk. We used six different model algorithms to analyze the dataset, comparing these in terms of their predictive abilities and the variables identified as important. Based on comparable predictive abilities (mean R 2 from 30 to 35% and mean root mean square error from 65 to 68%), we averaged all six model outputs to predict relative levels of trace element deposition in soils-given the road surface, traffic volume, sample distance from the road, land cover category, and impervious surface percentage. Mapped predictions of environmental risk from toxic trace element pollution can show land managers and transportation planners where to prioritize road renewal or maintenance by each road segment's relative environmental and human health risk. Published by Elsevier B.V.

Real-time tumor motion estimation using respiratory surrogate via memory-based learning

NASA Astrophysics Data System (ADS)

Li, Ruijiang; Lewis, John H.; Berbeco, Ross I.; Xing, Lei

2012-08-01

Respiratory tumor motion is a major challenge in radiation therapy for thoracic and abdominal cancers. Effective motion management requires an accurate knowledge of the real-time tumor motion. External respiration monitoring devices (optical, etc) provide a noninvasive, non-ionizing, low-cost and practical approach to obtain the respiratory signal. Due to the highly complex and nonlinear relations between tumor and surrogate motion, its ultimate success hinges on the ability to accurately infer the tumor motion from respiratory surrogates. Given their widespread use in the clinic, such a method is critically needed. We propose to use a powerful memory-based learning method to find the complex relations between tumor motion and respiratory surrogates. The method first stores the training data in memory and then finds relevant data to answer a particular query. Nearby data points are assigned high relevance (or weights) and conversely distant data are assigned low relevance. By fitting relatively simple models to local patches instead of fitting one single global model, it is able to capture highly nonlinear and complex relations between the internal tumor motion and external surrogates accurately. Due to the local nature of weighting functions, the method is inherently robust to outliers in the training data. Moreover, both training and adapting to new data are performed almost instantaneously with memory-based learning, making it suitable for dynamically following variable internal/external relations. We evaluated the method using respiratory motion data from 11 patients. The data set consists of simultaneous measurement of 3D tumor motion and 1D abdominal surface (used as the surrogate signal in this study). There are a total of 171 respiratory traces, with an average peak-to-peak amplitude of ∼15 mm and average duration of ∼115 s per trace. Given only 5 s (roughly one breath) pretreatment training data, the method achieved an average 3D error of 1.5 mm and 95th percentile error of 3.4 mm on unseen test data. The average 3D error was further reduced to 1.4 mm when the model was tuned to its optimal setting for each respiratory trace. In one trace where a few outliers are present in the training data, the proposed method achieved an error reduction of as much as ∼50% compared with the best linear model (1.0 mm versus 2.1 mm). The memory-based learning technique is able to accurately capture the highly complex and nonlinear relations between tumor and surrogate motion in an efficient manner (a few milliseconds per estimate). Furthermore, the algorithm is particularly suitable to handle situations where the training data are contaminated by large errors or outliers. These desirable properties make it an ideal candidate for accurate and robust tumor gating/tracking using respiratory surrogates.

The Gaussian Laser Angular Distribution in HYDRA's 3D Laser Ray Trace Package

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sepke, Scott M.

In this note, the angular distribution of rays launched by the 3D LZR ray trace package is derived for Gaussian beams (npower==2) with bm model=3±. Beams with bm model=+3 have a nearly at distribution, and beams with bm model=-3 have a nearly linear distribution when the spot size is large compared to the wavelength.

Modeling Trace Element Concentrations in the San Francisco Bay Estuary from Remote Measurement of Suspended Solids

NASA Astrophysics Data System (ADS)

Press, J.; Broughton, J.; Kudela, R. M.

2014-12-01

Suspended and dissolved trace elements are key determinants of water quality in estuarine and coastal waters. High concentrations of trace element pollutants in the San Francisco Bay estuary necessitate consistent and thorough monitoring to mitigate adverse effects on biological systems and the contamination of water and food resources. Although existing monitoring programs collect annual in situ samples from fixed locations, models proposed by Benoit, Kudela, & Flegal (2010) enable calculation of the water column total concentration (WCT) and the water column dissolved concentration (WCD) of 14 trace elements in the San Francisco Bay from a more frequently sampled metric—suspended solids concentration (SSC). This study tests the application of these models with SSC calculated from remote sensing data, with the aim of validating a tool for continuous synoptic monitoring of trace elements in the San Francisco Bay. Using HICO imagery, semi-analytical and empirical SSC algorithms were tested against a USGS dataset. A single-band method with statistically significant linear fit (p < 0.001) was chosen as the proxy for SSC values. The numerical models for WCT and the distribution ratio D were applied in MATLAB with terms to account for regional and seasonal effects, and results were used to calculate WCD. The modeled results were assessed against in situ data from the San Francisco Estuary Regional Monitoring Program. Quantile regression was used to evaluate model sensitivity to the distribution of regions, and outliers displaying regional aberrations were removed before robust regression was applied. Statistically significant and highly correlated results for WCT were found for 10 elements, with goodness of fit greater than or equal to that of the original models of seven elements. WCD was successfully modeled for six elements, with goodness of fit for each exceeding that of the original models. Concentrations of Arsenic, Iron, and Lead in the southern region of the Bay were found to exceed EPA water quality criteria for human health and aquatic life. The results of this study demonstrate the potential of monitoring programs using remote observation of trace element concentrations, and provide the foundation for investigation of pollutant sources and pathways over time.

Crew collaboration in space: a naturalistic decision-making perspective

NASA Technical Reports Server (NTRS)

Orasanu, Judith

2005-01-01

Successful long-duration space missions will depend on the ability of crewmembers to respond promptly and effectively to unanticipated problems that arise under highly stressful conditions. Naturalistic decision making (NDM) exploits the knowledge and experience of decision makers in meaningful work domains, especially complex sociotechnical systems, including aviation and space. Decision making in these ambiguous, dynamic, high-risk environments is a complex task that involves defining the nature of the problem and crafting a response to achieve one's goals. Goal conflicts, time pressures, and uncertain outcomes may further complicate the process. This paper reviews theory and research pertaining to the NDM model and traces some of the implications for space crews and other groups that perform meaningful work in extreme environments. It concludes with specific recommendations for preparing exploration crews to use NDM effectively.

A simple model for closure temperature of a trace element in cooling bi-mineralic systems

NASA Astrophysics Data System (ADS)

Liang, Yan

2015-09-01

Closure temperature is defined as the lower temperature limit at which the element of interest effectively ceases diffusive exchange with its surrounding medium during cooling. Here we generalize the classic equation of Dodson (1973) for cooling mono-mineralic systems to cooling bi-mineralic aggregates by considering diffusive exchange of a trace element between the two minerals in a closed system. We present a simple analytical model that includes key parameters affecting the closure temperature of a trace element in cooling bi-mineralic systems: cooling rate, temperature-dependent diffusion coefficients for the trace element in the two minerals, temperature-dependent partition coefficient of the trace element between the two minerals, effective grain sizes of the two minerals, and volume proportions of the minerals in the system. We show that closure temperatures of a trace element in cooling bi-mineralic systems are bounded by the closure temperatures of the trace element in the two mono-mineralic systems and that our generalized model reduces to Dodson's equation when one of the mineral serves as "an effective infinite" reservoir to the other mineral. Application to closure temperatures of REE in orthopyroxene and clinopyroxene bi-mineralic systems highlights the importance of REE diffusion and partitioning in the pyroxenes as well as clinopyroxene modal abundance and grain size in the systems. Closure temperatures for REE in two-pyroxene bearing equigranular rocks are controlled primarily by diffusion in orthopyroxene unless the modal abundance of clinopyroxene is very small. This has important bearings on the interpretation of temperatures derived from the REE-in-two-pyroxene thermometer.

Knowledge synthesis with maps of neural connectivity.

PubMed

Tallis, Marcelo; Thompson, Richard; Russ, Thomas A; Burns, Gully A P C

2011-01-01

This paper describes software for neuroanatomical knowledge synthesis based on neural connectivity data. This software supports a mature methodology developed since the early 1990s. Over this time, the Swanson laboratory at USC has generated an account of the neural connectivity of the sub-structures of the hypothalamus, amygdala, septum, hippocampus, and bed nucleus of the stria terminalis. This is based on neuroanatomical data maps drawn into a standard brain atlas by experts. In earlier work, we presented an application for visualizing and comparing anatomical macro connections using the Swanson third edition atlas as a framework for accurate registration. Here we describe major improvements to the NeuARt application based on the incorporation of a knowledge representation of experimental design. We also present improvements in the interface and features of the data mapping components within a unified web-application. As a step toward developing an accurate sub-regional account of neural connectivity, we provide navigational access between the data maps and a semantic representation of area-to-area connections that they support. We do so based on an approach called "Knowledge Engineering from Experimental Design" (KEfED) model that is based on experimental variables. We have extended the underlying KEfED representation of tract-tracing experiments by incorporating the definition of a neuronanatomical data map as a measurement variable in the study design. This paper describes the software design of a web-application that allows anatomical data sets to be described within a standard experimental context and thus indexed by non-spatial experimental design features.

A Program for Calculating and Plotting Synthetic Common-Source Seismic-Reflection Traces for Multilayered Earth Models.

ERIC Educational Resources Information Center

Ramananantoandro, Ramanantsoa

1988-01-01

Presented is a description of a BASIC program to be used on an IBM microcomputer for calculating and plotting synthetic seismic-reflection traces for multilayered earth models. Discusses finding raypaths for given source-receiver offsets using the "shooting method" and calculating the corresponding travel times. (Author/CW)

A bayesian approach for determining velocity and uncertainty estimates from seismic cone penetrometer testing or vertical seismic profiling data

USGS Publications Warehouse

Pidlisecky, Adam; Haines, S.S.

2011-01-01

Conventional processing methods for seismic cone penetrometer data present several shortcomings, most notably the absence of a robust velocity model uncertainty estimate. We propose a new seismic cone penetrometer testing (SCPT) data-processing approach that employs Bayesian methods to map measured data errors into quantitative estimates of model uncertainty. We first calculate travel-time differences for all permutations of seismic trace pairs. That is, we cross-correlate each trace at each measurement location with every trace at every other measurement location to determine travel-time differences that are not biased by the choice of any particular reference trace and to thoroughly characterize data error. We calculate a forward operator that accounts for the different ray paths for each measurement location, including refraction at layer boundaries. We then use a Bayesian inversion scheme to obtain the most likely slowness (the reciprocal of velocity) and a distribution of probable slowness values for each model layer. The result is a velocity model that is based on correct ray paths, with uncertainty bounds that are based on the data error. ?? NRC Research Press 2011.

Contact tracing of tuberculosis: a systematic review of transmission modelling studies.

PubMed

Begun, Matt; Newall, Anthony T; Marks, Guy B; Wood, James G

2013-01-01

The WHO recommended intervention of Directly Observed Treatment, Short-course (DOTS) appears to have been less successful than expected in reducing the burden of TB in some high prevalence settings. One strategy for enhancing DOTS is incorporating active case-finding through screening contacts of TB patients as widely used in low-prevalence settings. Predictive models that incorporate population-level effects on transmission provide one means of predicting impacts of such interventions. We aim to identify all TB transmission modelling studies addressing contact tracing and to describe and critically assess their modelling assumptions, parameter choices and relevance to policy. We searched MEDLINE, SCOPUS, COMPENDEX, Google Scholar and Web of Science databases for relevant English language publications up to February 2012. Of the 1285 studies identified, only 5 studies met our inclusion criteria of models of TB transmission dynamics in human populations designed to incorporate contact tracing as an intervention. Detailed implementation of contact processes was only present in two studies, while only one study presented a model for a high prevalence, developing world setting. Some use of relevant data for parameter estimation was made in each study however validation of the predicted impact of interventions was not attempted in any of the studies. Despite a large body of literature on TB transmission modelling, few published studies incorporate contact tracing. There is considerable scope for future analyses to make better use of data and to apply individual based models to facilitate more realistic patterns of infectious contact. Combined with a focus on high burden settings this would greatly increase the potential for models to inform the use of contract tracing as a TB control policy. Our findings highlight the potential for collaborative work between clinicians, epidemiologists and modellers to gather data required to enhance model development and validation and hence better inform future public health policy.

Contact Tracing of Tuberculosis: A Systematic Review of Transmission Modelling Studies

PubMed Central

Begun, Matt; Newall, Anthony T.; Marks, Guy B.; Wood, James G.

2013-01-01

The WHO recommended intervention of Directly Observed Treatment, Short-course (DOTS) appears to have been less successful than expected in reducing the burden of TB in some high prevalence settings. One strategy for enhancing DOTS is incorporating active case-finding through screening contacts of TB patients as widely used in low-prevalence settings. Predictive models that incorporate population-level effects on transmission provide one means of predicting impacts of such interventions. We aim to identify all TB transmission modelling studies addressing contact tracing and to describe and critically assess their modelling assumptions, parameter choices and relevance to policy. We searched MEDLINE, SCOPUS, COMPENDEX, Google Scholar and Web of Science databases for relevant English language publications up to February 2012. Of the 1285 studies identified, only 5 studies met our inclusion criteria of models of TB transmission dynamics in human populations designed to incorporate contact tracing as an intervention. Detailed implementation of contact processes was only present in two studies, while only one study presented a model for a high prevalence, developing world setting. Some use of relevant data for parameter estimation was made in each study however validation of the predicted impact of interventions was not attempted in any of the studies. Despite a large body of literature on TB transmission modelling, few published studies incorporate contact tracing. There is considerable scope for future analyses to make better use of data and to apply individual based models to facilitate more realistic patterns of infectious contact. Combined with a focus on high burden settings this would greatly increase the potential for models to inform the use of contract tracing as a TB control policy. Our findings highlight the potential for collaborative work between clinicians, epidemiologists and modellers to gather data required to enhance model development and validation and hence better inform future public health policy. PMID:24023742

Determining Hypocentral Parameters for Local Earthquakes in 1-D Using a Genetic Algorithm and Two-point ray tracing

NASA Astrophysics Data System (ADS)

Kim, W.; Hahm, I.; Ahn, S. J.; Lim, D. H.

2005-12-01

This paper introduces a powerful method for determining hypocentral parameters for local earthquakes in 1-D using a genetic algorithm (GA) and two-point ray tracing. Using existing algorithms to determine hypocentral parameters is difficult, because these parameters can vary based on initial velocity models. We developed a new method to solve this problem by applying a GA to an existing algorithm, HYPO-71 (Lee and Larh, 1975). The original HYPO-71 algorithm was modified by applying two-point ray tracing and a weighting factor with respect to the takeoff angle at the source to reduce errors from the ray path and hypocenter depth. Artificial data, without error, were generated by computer using two-point ray tracing in a true model, in which velocity structure and hypocentral parameters were known. The accuracy of the calculated results was easily determined by comparing calculated and actual values. We examined the accuracy of this method for several cases by changing the true and modeled layer numbers and thicknesses. The computational results show that this method determines nearly exact hypocentral parameters without depending on initial velocity models. Furthermore, accurate and nearly unique hypocentral parameters were obtained, although the number of modeled layers and thicknesses differed from those in the true model. Therefore, this method can be a useful tool for determining hypocentral parameters in regions where reliable local velocity values are unknown. This method also provides the basic a priori information for 3-D studies. KEY -WORDS: hypocentral parameters, genetic algorithm (GA), two-point ray tracing

Expanding Access to Knowledge: Continuing Higher Education. NUCEA 1915-1990.

ERIC Educational Resources Information Center

Rohfeld, Rae Wahl, Ed.

In honor of its 75th anniversary, the National University Continuing Education Association (NUCEA) presents this compendium of the history of continuing higher education. It traces the adult education movement from its beginnings and explores the role of continuing education and NUCEA in the 20th century. Articles, excerpts, and reports are…

Ties That Do Not Bind: Musings on the Specious Relevance of Academic Research.

ERIC Educational Resources Information Center

Bolton, Michael J.; Stolcis, Gregory B.

2003-01-01

Discusses the gap between academic research and practice in public administration and argues that it can be traced to conflicts such as theoretical vs. pragmatic knowledge, data-supported vs. logic-driven information, scientific method vs. case studies, academic vs. practitioner journals, and tenure vs. organizational effectiveness. Explores…

The Nature of Knowledge and the Structure of the University.

ERIC Educational Resources Information Center

Thompson, Patricia J.

This paper argues that women experience two realities, a "private sphere" and a "public sphere," and the implication of this dual perspective needs to be addressed by women scholars in all disciplines. The idea behind these two spheres of reality is traced back to the ancient Greeks where household management (oikos) was the…

Meaning in Mud: Yup'ik Eskimo Girls at Play.

ERIC Educational Resources Information Center

deMarrais, Kathleen Bennett; And Others

1992-01-01

Describes storyknifing, a traditional way of storytelling illustrated through pictures traced in mud, by young girls in a Yup'ik Eskimo village on the Kuskokwim River (Alaska). Storyknifing provides a forum in which young girls learn cultural and cognitive knowledge. Storyknifing maintains a link with traditional society in this village. (SLD)

A Critical Exploration of Changing Definitions of Public Good in Relation to Higher Education

ERIC Educational Resources Information Center

Williams, Joanna

2016-01-01

Discussion of the relationship between higher education (HE) and public good can be traced to Kant's argument that universities critically held society to account. Mill, Newman and Arnold suggested knowledge itself was a public good. In the twentieth century, economists argued education could drive national technological progress. More recently…

The Antieconomy Hypothesis (Part 3): Toward a Solution

ERIC Educational Resources Information Center

Vanderburg, Willem H.

2009-01-01

Parts 1 and 2 explore the hypothesis that the application of mainstream economics has led to economies becoming uneconomic, which is as close as a social science can get to experimentally disproving its theories. One of the primary reasons for this failure is traced to the characteristics of the knowledge infrastructures of contemporary societies,…

Equal Knowledge Is the Strong Root of Democratic Egalitarianism

ERIC Educational Resources Information Center

Palumbo, Anthony; Levitt, Roberta

2011-01-01

This article considers how to bridge the achievement gap by showing that reading methodology influenced American educational philosophy, primary-grade curricula, and American schools. It considers the impact of the romantic movement on progressive education and notes that the current academic achievement gap has two roots. The first can be traced,…

The Related Effects of Item Characteristics in Measures of Epistemological Beliefs

ERIC Educational Resources Information Center

Pope, Kathryn J.; Mooney, Gillian A.

2016-01-01

Personal epistemology is concerned with people's beliefs or assumptions about the nature of knowledge and knowing. Whilst contributions in this field can be traced back to the 1970s, fundamental questions about the ontology and epistemology of the construct still remain. The current study explored the effects of three characteristics of questions…

Police Reform, Task Force Rhetoric, and Traces of Dissent: Rethinking Consensus-as-Outcome in Collaborative Writing Situations

ERIC Educational Resources Information Center

Knievel, Michael

2008-01-01

Pedagogical and scholarly representations of collaborative writing and knowledge construction in technical communication have traditionally recognized consensus as the logical outcome of collaborative work, even as scholars and teachers have acknowledged the value of conflict and "dissensus" in the process of collaborative knowledge…

Teacher Reflection in a Hall of Mirrors: Historical Influences and Political Reverberations.

ERIC Educational Resources Information Center

Fendler, Lynn

2003-01-01

Traces the history of reflection in teacher education, focusing on its emergence through the influences of Descartes, Dewey, Schon, and feminism. Uses the critical lenses of Foucaultian genealogy and the sociology of scientific knowledge to investigate how the complicated meanings of reflection play out in complex ways through research practice.…

The Construction of the Self: A Developmental Perspective.

ERIC Educational Resources Information Center

Harter, Susan

Drawing upon extensive theoretical knowledge and decades of empirical research, this book traces changes in the structure and content of self-representations from early childhood through late adolescence. Chapter 1 includes a discussion of the self as subject (I-self) and object (Me-self) and describes the historical roots of contemporary issues…

Notions of "Rhetoric as Epistemic" in Ancient Greece.

ERIC Educational Resources Information Center

Benoit, William L.

The notion that rhetoric (and to a lesser extent, argument) is epistemic is an increasingly popular one today, although it can be traced to ancient Greece. The notion holds that rhetoric, or the art of persuasion, creates and shapes knowledge. Two ancient authors--Aristophanes and Plato--provide evidence that others had notions of rhetoric as…

Ghosts from the Nursery: Tracing the Roots of Violence.

ERIC Educational Resources Information Center

Karr-Morse, Robin; Wiley, Meredith S.

Noting that although the causes of violence are highly complex and multifaceted, this book argues that a growing body of scientific knowledge demonstrates that maltreatment during the 9 months of fetal growth and the first 24 months after birth often leads to violent older children and adults. Following an introduction, the book contains the…

The Knowledge That Matters in Professional Practices

ERIC Educational Resources Information Center

Edwards, Anne; Daniels, Harry

2012-01-01

We draw on the analytic resources of cultural historical activity theory and the work of (Basil) Bernstein and Knorr Cetina to examine evidence from a study of inter-professional practices in children's services in three English local authorities (local government systems). The study traced the horizontal (e.g. cross service) and vertical (e.g.…

Expanding Dimensions of the "Knowledge Society": Technology, Discourse Ethics and Agency in Coastal Communities.

ERIC Educational Resources Information Center

Harris, Carol

2002-01-01

Traces philosophical appraisals of technology, both as devices for human purposes and, as technological rationality, as ways of thinking and acting. Two applications of communication technology in the context of Canadian coastal communities illustrate the distinction between training and education, and the importance of public space in which to…

Advances in the application of amino acid nitrogen isotopic analysis in ecological and biogeochemical studies

USDA-ARS?s Scientific Manuscript database

Compound-specific isotopic analysis of amino acids (CSIA-AA) has emerged in the last decade as a powerful approach for tracing the origins and fate of nitrogen in ecological and biogeochemical studies. This approach is based on the empirical knowledge that source AAs (i.e., phenylalanine), fractiona...

Trace chemical contaminant generation rates for spacecraft contamination control system design

NASA Technical Reports Server (NTRS)

Perry, J. L.

1995-01-01

A spacecraft presents a unique design challenge with respect to providing a comfortable environment in which people can live and work. All aspects of the spacecraft environmental design including the size of the habitable volume, its temperature, relative humidity, and composition must be considered to ensure the comfort and health of the occupants. The crew members and the materials selected for outfitting the spacecraft play an integral part in designing a habitable spacecraft because material offgassing and human metabolism are the primary sources for continuous trace chemical contaminant generation onboard a spacecraft. Since these contamination sources cannot be completely eliminated, active control processes must be designed and deployed onboard the spacecraft to ensure an acceptably clean cabin atmosphere. Knowledge of the expected rates at which contaminants are generated is very important to the design of these processes. Data from past spacecraft missions and human contaminant production studies have been analyzed to provide this knowledge. The resulting compilation of contaminants and generation rates serve as a firm basis for past, present, and future contamination control system designs for space and aeronautics applications.

Dietary traces of neonicotinoid pesticides as a cause of population declines in honey bees: an evaluation by Hill's epidemiological criteria.

PubMed

Cresswell, James E; Desneux, Nicolas; vanEngelsdorp, Dennis

2012-06-01

Honey bees are important pollinators of both crops and wild plants. Pesticide regimes that threaten their sustainability should therefore be assessed. As an example, evidence that the agricultural use of neonicotinoid pesticides is a cause of the recently observed declines in honey bees is examined. The aim is to define exacting demographic conditions for a detrimental factor to precipitate a population decline, and Hill's epidemiological 'causality criteria' are employed as a structured process for making an expert judgement about the proposition that trace dietary neonicotinoids in nectar and pollen cause population declines in honey bees. In spite of the absence of decisive experimental results, the analysis shows that, while the proposition is a substantially justified conjecture in the context of current knowledge, it is also substantially contraindicated by a wide variety of circumstantial epidemiological evidence. It is concluded that dietary neonicotinoids cannot be implicated in honey bee declines, but this position is provisional because important gaps remain in current knowledge. Avenues for further investigations to resolve this longstanding uncertainty are therefore identified. Copyright © 2012 Society of Chemical Industry.

Newly-formed emotional memories guide selective attention processes: Evidence from event-related potentials.

PubMed

Schupp, Harald T; Kirmse, Ursula; Schmälzle, Ralf; Flaisch, Tobias; Renner, Britta

2016-06-20

Emotional cues can guide selective attention processes. However, emotional stimuli can both activate long-term memory representations reflecting general world knowledge and engage newly formed memory representations representing specific knowledge from the immediate past. Here, the self-completion feature of associative memory was utilized to assess the regulation of attention processes by newly-formed emotional memory. First, new memory representations were formed by presenting pictures depicting a person either in an erotic pose or as a portrait. Afterwards, to activate newly-built memory traces, edited pictures were presented showing only the head region of the person. ERP recordings revealed the emotional regulation of attention by newly-formed memories. Specifically, edited pictures from the erotic compared to the portrait category elicited an early posterior negativity and late positive potential, similar to the findings observed for the original pictures. A control condition showed that the effect was dependent on newly-formed memory traces. Given the large number of new memories formed each day, they presumably make an important contribution to the regulation of attention in everyday life.

Debugging expert systems using a dynamically created hypertext network

NASA Technical Reports Server (NTRS)

Boyle, Craig D. B.; Schuette, John F.

1991-01-01

The labor intensive nature of expert system writing and debugging motivated this study. The hypothesis is that a hypertext based debugging tool is easier and faster than one traditional tool, the graphical execution trace. HESDE (Hypertext Expert System Debugging Environment) uses Hypertext nodes and links to represent the objects and their relationships created during the execution of a rule based expert system. HESDE operates transparently on top of the CLIPS (C Language Integrated Production System) rule based system environment and is used during the knowledge base debugging process. During the execution process HESDE builds an execution trace. Use of facts, rules, and their values are automatically stored in a Hypertext network for each execution cycle. After the execution process, the knowledge engineer may access the Hypertext network and browse the network created. The network may be viewed in terms of rules, facts, and values. An experiment was conducted to compare HESDE with a graphical debugging environment. Subjects were given representative tasks. For speed and accuracy, in eight of the eleven tasks given to subjects, HESDE was significantly better.

Newly-formed emotional memories guide selective attention processes: Evidence from event-related potentials

PubMed Central

Schupp, Harald T.; Kirmse, Ursula; Schmälzle, Ralf; Flaisch, Tobias; Renner, Britta

2016-01-01

Emotional cues can guide selective attention processes. However, emotional stimuli can both activate long-term memory representations reflecting general world knowledge and engage newly formed memory representations representing specific knowledge from the immediate past. Here, the self-completion feature of associative memory was utilized to assess the regulation of attention processes by newly-formed emotional memory. First, new memory representations were formed by presenting pictures depicting a person either in an erotic pose or as a portrait. Afterwards, to activate newly-built memory traces, edited pictures were presented showing only the head region of the person. ERP recordings revealed the emotional regulation of attention by newly-formed memories. Specifically, edited pictures from the erotic compared to the portrait category elicited an early posterior negativity and late positive potential, similar to the findings observed for the original pictures. A control condition showed that the effect was dependent on newly-formed memory traces. Given the large number of new memories formed each day, they presumably make an important contribution to the regulation of attention in everyday life. PMID:27321471

Constraints on the bioavailability of trace elements to terrestrial fauna at mining and smelting sites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pastorok, R.; Schoof, R.; LaTier, A.

1995-12-31

At mining and smelting sites, the bioavailability of waste-related trace elements to terrestrial wildlife is limited by mineralogy of the waste material and the geochemistry of the waste-soil mixture. For example, encapsulation of trace elements in inert mineral matrices limits the assimilation of particle-associated trace elements that are ingested by wildlife. The bioavailability of arsenic, cadmium, copper, lead, silver, and zinc at mining and smelting sites in Oklahoma and Montana was evaluated based on analysis of waste material, soil chemistry, and concentrations of trace elements in whole-body samples of key food web species. Concentrations of trace elements were generally elevatedmore » relative to reference area values for selected species of vegetation, insects, spiders, and small mammals. Soil-to-tissue bioconcentration factors derived from field data at these sites were generally low (< 1), with the exception of cadmium in vegetation. For all of the trace elements evaluated, wildlife exposure models indicate that the potential for transfer of contaminants to wildlife species of public concern and high trophic-level predators is limited. Moreover, laboratory feeding experiments conducted with cadmium and lead indicate that the assimilation of waste-related trace elements by mammals is relatively low (24--47 percent for lead in blood and bone; 22--44 percent for cadmium in kidney). The relatively low bioavailability of trace elements at mining and smelting sites should be considered when estimating exposure of ecological receptors and when deriving soil cleanup criteria based on measured or modeled ecological risk.« less

Atmospheric, Climatic, and Environmental Research

NASA Technical Reports Server (NTRS)

Broecker, Wallace S.; Gornitz, Vivien M.

1994-01-01

The climate and atmospheric modeling project involves analysis of basic climate processes, with special emphasis on studies of the atmospheric CO2 and H2O source/sink budgets and studies of the climatic role Of CO2, trace gases and aerosols. These studies are carried out, based in part on use of simplified climate models and climate process models developed at GISS. The principal models currently employed are a variable resolution 3-D general circulation model (GCM), and an associated "tracer" model which simulates the advection of trace constituents using the winds generated by the GCM.

Review of chemical, medication, and anesthesia toxicity in the OR.

PubMed

Fiedler, M A; Biddle, C

1998-02-01

A host of toxic substances exist in the OR. The toxicity of prep solutions, cleaning chemicals, common medications, and trace anesthetic gases varies greatly. Nurses use, direct others in the use of, or administer potential toxins while breathing air that may be contaminated to some degree with anesthetic vapors. Often, the OR nurse is the neighborhood resource when questions about the toxicity of common chemicals and drugs arise. A general knowledge of the toxicity of these substances improves the nurse's ability to assess the risk from trace anesthetic gases, prevent injury to patients, provide first aid when potentially dangerous exposure occurs, and direct others in the safe use of OR chemicals.

Improved backward ray tracing with stochastic sampling

NASA Astrophysics Data System (ADS)

Ryu, Seung Taek; Yoon, Kyung-Hyun

1999-03-01

This paper presents a new technique that enhances the diffuse interreflection with the concepts of backward ray tracing. In this research, we have modeled the diffuse rays with the following conditions. First, as the reflection from the diffuse surfaces occurs in all directions, it is impossible to trace all of the reflected rays. We confined the diffuse rays by sampling the spherical angle out of the reflected rays around the normal vector. Second, the traveled distance of reflected energy from the diffuse surface differs according to the object's property, and has a comparatively short reflection distance. Considering the fact that the rays created on the diffuse surfaces affect relatively small area, it is very inefficient to trace all of the sampled diffused rays. Therefore, we set a fixed distance as the critical distance and all the rays beyond this distance are ignored. The result of this research is that as the improved backward ray tracing can model the illumination effects such as the color bleeding effects, we can replace the radiosity algorithm under the limited environment.

Improving Marine Ecosystem Models with Biochemical Tracers

NASA Astrophysics Data System (ADS)

Pethybridge, Heidi R.; Choy, C. Anela; Polovina, Jeffrey J.; Fulton, Elizabeth A.

2018-01-01

Empirical data on food web dynamics and predator-prey interactions underpin ecosystem models, which are increasingly used to support strategic management of marine resources. These data have traditionally derived from stomach content analysis, but new and complementary forms of ecological data are increasingly available from biochemical tracer techniques. Extensive opportunities exist to improve the empirical robustness of ecosystem models through the incorporation of biochemical tracer data and derived indices, an area that is rapidly expanding because of advances in analytical developments and sophisticated statistical techniques. Here, we explore the trophic information required by ecosystem model frameworks (species, individual, and size based) and match them to the most commonly used biochemical tracers (bulk tissue and compound-specific stable isotopes, fatty acids, and trace elements). Key quantitative parameters derived from biochemical tracers include estimates of diet composition, niche width, and trophic position. Biochemical tracers also provide powerful insight into the spatial and temporal variability of food web structure and the characterization of dominant basal and microbial food web groups. A major challenge in incorporating biochemical tracer data into ecosystem models is scale and data type mismatches, which can be overcome with greater knowledge exchange and numerical approaches that transform, integrate, and visualize data.

Monitoring Programs Using Rewriting

NASA Technical Reports Server (NTRS)

Havelund, Klaus; Rosu, Grigore; Lan, Sonie (Technical Monitor)

2001-01-01

We present a rewriting algorithm for efficiently testing future time Linear Temporal Logic (LTL) formulae on finite execution traces, The standard models of LTL are infinite traces, reflecting the behavior of reactive and concurrent systems which conceptually may be continuously alive in most past applications of LTL, theorem provers and model checkers have been used to formally prove that down-scaled models satisfy such LTL specifications. Our goal is instead to use LTL for up-scaled testing of real software applications, corresponding to analyzing the conformance of finite traces against LTL formulae. We first describe what it means for a finite trace to satisfy an LTL property end then suggest an optimized algorithm based on transforming LTL formulae. We use the Maude rewriting logic, which turns out to be a good notation and being supported by an efficient rewriting engine for performing these experiments. The work constitutes part of the Java PathExplorer (JPAX) project, the purpose of which is to develop a flexible tool for monitoring Java program executions.

Ebola virus disease contact tracing activities, lessons learned and best practices during the Duport Road outbreak in Monrovia, Liberia, November 2015.

PubMed

Wolfe, Caitlin M; Hamblion, Esther L; Schulte, Jacqueline; Williams, Parker; Koryon, Augustine; Enders, Jonathan; Sanor, Varlee; Wapoe, Yatta; Kwayon, Dash; Blackley, David J; Laney, Anthony S; Weston, Emily J; Dokubo, Emily K; Davies-Wayne, Gloria; Wendland, Annika; Daw, Valerie T S; Badini, Mehboob; Clement, Peter; Mahmoud, Nuha; Williams, Desmond; Gasasira, Alex; Nyenswah, Tolbert G; Fallah, Mosoka

2017-06-01

Contact tracing is one of the key response activities necessary for halting Ebola Virus Disease (EVD) transmission. Key elements of contact tracing include identification of persons who have been in contact with confirmed EVD cases and careful monitoring for EVD symptoms, but the details of implementation likely influence their effectiveness. In November 2015, several months after a major Ebola outbreak was controlled in Liberia, three members of a family were confirmed positive for EVD in the Duport Road area of Monrovia. The cluster provided an opportunity to implement and evaluate modified approaches to contact tracing. The approaches employed for improved contact tracing included classification and risk-based management of identified contacts (including facility based isolation of some high risk contacts, provision of support to persons being monitored, and school-based surveillance for some persons with potential exposure but not listed as contacts), use of phone records to help locate missing contacts, and modifications to data management tools. We recorded details about the implementation of these approaches, report the overall outcomes of the contact tracing efforts and the challenges encountered, and provide recommendations for management of future outbreaks. 165 contacts were identified (with over 150 identified within 48 hours of confirmation of the EVD cases) and all initially missing contacts were located. Contacts were closely monitored and promptly tested if symptomatic; no contacts developed disease. Encountered challenges related to knowledge gaps among contact tracing staff, data management, and coordination of contact tracing activities with efforts to offer Ebola vaccine. The Duport Road EVD cluster was promptly controlled. Missing contacts were effectively identified, and identified contacts were effectively monitored and rapidly tested. There is a persistent risk of EVD reemergence in Liberia; the experience controlling each cluster can help inform future Ebola control efforts in Liberia and elsewhere.

Robust Requirements Tracing via Internet Search Technology: Improving an IV and V Technique. Phase 2

NASA Technical Reports Server (NTRS)

Hayes, Jane; Dekhtyar, Alex

2004-01-01

There are three major objectives to this phase of the work. (1) Improvement of Information Retrieval (IR) methods for Independent Verification and Validation (IV&V) requirements tracing. Information Retrieval methods are typically developed for very large (order of millions - tens of millions and more documents) document collections and therefore, most successfully used methods somewhat sacrifice precision and recall in order to achieve efficiency. At the same time typical IR systems treat all user queries as independent of each other and assume that relevance of documents to queries is subjective for each user. The IV&V requirements tracing problem has a much smaller data set to operate on, even for large software development projects; the set of queries is predetermined by the high-level specification document and individual requirements considered as query input to IR methods are not necessarily independent from each other. Namely, knowledge about the links for one requirement may be helpful in determining the links of another requirement. Finally, while the final decision on the exact form of the traceability matrix still belongs to the IV&V analyst, his/her decisions are much less arbitrary than those of an Internet search engine user. All this suggests that the information available to us in the framework of the IV&V tracing problem can be successfully leveraged to enhance standard IR techniques, which in turn would lead to increased recall and precision. We developed several new methods during Phase II; (2) IV&V requirements tracing IR toolkit. Based on the methods developed in Phase I and their improvements developed in Phase II, we built a toolkit of IR methods for IV&V requirements tracing. The toolkit has been integrated, at the data level, with SAIC's SuperTracePlus (STP) tool; (3) Toolkit testing. We tested the methods included in the IV&V requirements tracing IR toolkit on a number of projects.

Ebola virus disease contact tracing activities, lessons learned and best practices during the Duport Road outbreak in Monrovia, Liberia, November 2015

PubMed Central

Schulte, Jacqueline; Williams, Parker; Koryon, Augustine; Enders, Jonathan; Sanor, Varlee; Wapoe, Yatta; Kwayon, Dash; Blackley, David J.; Laney, Anthony S.; Weston, Emily J.; Dokubo, Emily K.; Davies-Wayne, Gloria; Wendland, Annika; Daw, Valerie T. S.; Badini, Mehboob; Clement, Peter; Mahmoud, Nuha; Williams, Desmond; Gasasira, Alex; Nyenswah, Tolbert G.; Fallah, Mosoka

2017-01-01

Background Contact tracing is one of the key response activities necessary for halting Ebola Virus Disease (EVD) transmission. Key elements of contact tracing include identification of persons who have been in contact with confirmed EVD cases and careful monitoring for EVD symptoms, but the details of implementation likely influence their effectiveness. In November 2015, several months after a major Ebola outbreak was controlled in Liberia, three members of a family were confirmed positive for EVD in the Duport Road area of Monrovia. The cluster provided an opportunity to implement and evaluate modified approaches to contact tracing. Methods The approaches employed for improved contact tracing included classification and risk-based management of identified contacts (including facility based isolation of some high risk contacts, provision of support to persons being monitored, and school-based surveillance for some persons with potential exposure but not listed as contacts), use of phone records to help locate missing contacts, and modifications to data management tools. We recorded details about the implementation of these approaches, report the overall outcomes of the contact tracing efforts and the challenges encountered, and provide recommendations for management of future outbreaks. Results 165 contacts were identified (with over 150 identified within 48 hours of confirmation of the EVD cases) and all initially missing contacts were located. Contacts were closely monitored and promptly tested if symptomatic; no contacts developed disease. Encountered challenges related to knowledge gaps among contact tracing staff, data management, and coordination of contact tracing activities with efforts to offer Ebola vaccine. Conclusions The Duport Road EVD cluster was promptly controlled. Missing contacts were effectively identified, and identified contacts were effectively monitored and rapidly tested. There is a persistent risk of EVD reemergence in Liberia; the experience controlling each cluster can help inform future Ebola control efforts in Liberia and elsewhere. PMID:28575034

Elevated Arc/Arg 3.1 protein expression in the basolateral amygdala following auditory trace-cued fear conditioning.

PubMed

Chau, Lily S; Prakapenka, Alesia; Fleming, Stephen A; Davis, Ashley S; Galvez, Roberto

2013-11-01

The underlying neuronal mechanisms of learning and memory have been heavily explored using associative learning paradigms. Two of the more commonly employed learning paradigms have been contextual and delay fear conditioning. In fear conditioning, a subject learns to associate a neutral stimulus (conditioned stimulus; CS), such as a tone or the context of the room, with a fear provoking stimulus (unconditioned stimulus; US), such as a mild footshock. Utilizing these two paradigms, various analyses have elegantly demonstrated that the amygdala plays a role in both fear-related associative learning paradigms. However, the amygdala's involvement in trace fear conditioning, a forebrain-dependent fear associative learning paradigm that has been suggested to tap into higher cognitive processes, has not been closely investigated. Furthermore, to our knowledge, the specific amygdala nuclei involved with trace fear conditioning has not been examined. The present study used Arc expression as an activity marker to determine the amygdala's involvement in trace fear associative learning and to further explore involvement of specific amygdalar nuclei. Arc is an immediate early gene that has been shown to be associated with neuronal activation and is believed to be necessary for neuronal plasticity. Findings from the present study demonstrated that trace-conditioned mice, compared to backward-conditioned (stimulation-control), delay-conditioned and naïve mice, exhibited elevated amygdalar Arc expression in the basolateral (BLA) but not the central (CeA) or the lateral amygdala (LA). These findings are consistent with previous reports demonstrating that the amygdala plays a critical role in trace conditioning. Furthermore, these findings parallel studies demonstrating hippocampal-BLA activation following contextual fear conditioning, suggesting that trace fear conditioning and contextual fear conditioning may involve similar amygdala nuclei. Together, findings from this study demonstrate similarities in the pathway for trace and contextual fear conditioning, and further suggest possible underlying mechanisms for acquisition and consolidation of these two types of fear-related learning. Copyright © 2013 Elsevier Inc. All rights reserved.

Laser Ray Tracing in a Parallel Arbitrary Lagrangian-Eulerian Adaptive Mesh Refinement Hydrocode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masters, N D; Kaiser, T B; Anderson, R W

2009-09-28

ALE-AMR is a new hydrocode that we are developing as a predictive modeling tool for debris and shrapnel formation in high-energy laser experiments. In this paper we present our approach to implementing laser ray-tracing in ALE-AMR. We present the equations of laser ray tracing, our approach to efficient traversal of the adaptive mesh hierarchy in which we propagate computational rays through a virtual composite mesh consisting of the finest resolution representation of the modeled space, and anticipate simulations that will be compared to experiments for code validation.

Effects of Humidity Swings on Adsorption Columns for Air Revitalization: Modeling and Experiments

NASA Technical Reports Server (NTRS)

LeVan, M. Douglas; Finn, John E.

1997-01-01

Air purification systems are necessary to provide clean air in the closed environments aboard spacecraft. Trace contaminants are removed using adsorption. One major factor concerning the removal of trace contaminants is relative humidity. Water can reduce adsorption capacity and, due to constant fluctuations, its presence is difficult to incorporate into adsorption column designs. The purpose of the research was to allow for better design techniques in trace contaminant adsorption systems, especially for feeds with water present. Experiments and mathematical modeling research on effects of humidity swings on adsorption columns for air revitalization were carried out.

Application of RFID in the area of agricultural products quality traceability and tracking and the anti-collision algorithm

NASA Astrophysics Data System (ADS)

Wang, Zu-liang; Zhang, Ting; Xie, Shi-yang

2017-01-01

In order to improve the agricultural tracing efficiency and reduce tracking and monitoring cost, agricultural products quality tracking and tracing based on Radio-Frequency Identification(RFID) technology is studied, then tracing and tracking model is set up. Three-layer structure model is established to realize the high quality of agricultural products traceability and tracking. To solve the collision problems between multiple RFID tags and improve the identification efficiency a new reservation slot allocation mechanism is proposed. And then we analyze and optimize the parameter by numerical simulation method.

Modified batch anaerobic digestion assay for testing efficiencies of trace metal additives to enhance methane production of energy crops.

PubMed

Brulé, Mathieu; Bolduan, Rainer; Seidelt, Stephan; Schlagermann, Pascal; Bott, Armin

2013-01-01

Batch biochemical methane potential (BMP) assays to evaluate the methane yield of biogas substrates such as energy crops are usually carried out with undiluted inoculum. A BMP assay was performed on two energy crops (green cuttings and grass silage). Anaerobic digestion was performed both with and without supplementation of three commercial additives containing trace metals in liquid, solid or adsorbed form (on clay particles). In order to reveal positive effects of trace metal supplementation on the methane yield, besides undiluted inoculum, 3-fold and 10-fold dilutions of the inoculum were applied for substrate digestion. Diluted inoculum variants were supplemented with both mineral nutrients and pH-buffering substances to prevent a collapse of the digestion process. As expected, commercial additives had no effect on the digestion process performed with undiluted inoculum, while significant increases of methane production through trace element supplementation could be observed on the diluted variants. The effect of inoculum dilution may be twofold: (1) decrease in trace metal supplementation from the inoculum and (2) reduction in the initial number of bacterial cells. Bacteria require higher growth rates for substrate degradation and hence have higher trace element consumption. According to common knowledge of the biogas process, periods with volatile fatty acids accumulation and decreased pH may have occurred in the course ofanaerobic digestion. These effects may have led to inhibition, not only ofmethanogenes and acetogenes involved in the final phases of methane production, but also offibre-degrading bacterial strains involved in polymer hydrolysis. Further research is required to confirm this hypothesis.

Trace elements in winter snow of the Dolomites (Italy): a statistical study of natural and anthropogenic contributions.

PubMed

Gabrielli, P; Cozzi, G; Torcini, S; Cescon, P; Barbante, C

2008-08-01

Knowledge of the occurrence of trace elements deposited in fresh alpine snow is very limited. Although current sources of major ionic inorganic species have been well established, this is not the case for many trace elements. This manuscript attempts to reconstruct the origin of Ag, Ba, Bi, Cd, Co, Cr, Cu, Fe, Mo, Mn, Pb, Sb, Ti, U, V and Zn in winter surface snow, extensively collected in the Dolomites region (Eastern Alps, Italy). Sampling of surface snow was conducted weekly during the winter 1998 at 21 sites at altitudes ranging from approximately 1000 to approximately 3000 m. This led to a remarkable dataset of trace element concentrations in surface snow from low latitudes. Here we show a preliminary statistical investigation conducted on the 366 samples collected. It was found that V, Sb, Zn, Cd, Mo and Pb have a predominantly anthropogenic origin, linked to the road traffic in the alpine valleys and the nearby heavily industrialised area of the Po Valley. In addition, the occasionally strong Fe and Cr input may reflect the mechanical abrasion of ferrous components of the vehicles. However, much of the Fe along with Mn, U and Ti originates primarily from the geological background of the Dolomites. A marine contribution was found to be negligible for all the trace elements. The origin of other trace elements is less clear: Ag can be possibly attributed to a predominantly anthropogenic origin while Cr, Co, Cu and Ba are usually from crustal rocks but different than the Dolomites.

Modelling prehistoric terrain Models using LiDAR-data: a geomorphological approach

NASA Astrophysics Data System (ADS)

Höfler, Veit; Wessollek, Christine; Karrasch, Pierre

2015-10-01

Terrain surfaces conserve human activities in terms of textures and structures. With reference to archaeological questions, the geological archive is investigated by means of models regarding anthropogenic traces. In doing so, the high-resolution digital terrain model is of inestimable value for the decoding of the archive. The evaluation of these terrain models and the reconstruction of historical surfaces is still a challenging issue. Due to the data collection by means of LiDAR systems (light detection and ranging) and despite their subsequent pre-processing and filtering, recently anthropogenic artefacts are still present in the digital terrain model. Analysis have shown that elements, such as contour lines and channels, can well be extracted from a high-resolution digital terrain model. This way, channels in settlement areas show a clear anthropogenic character. This fact can also be observed for contour lines. Some contour lines representing a possibly natural ground surface and avoid anthropogenic artefacts. Comparable to channels, noticeable patterns of contour lines become visible in areas with anthropogenic artefacts. The presented workflow uses functionalities of ArcGIS and the programming language R.1 The method starts with the extraction of contour lines from the digital terrain model. Through macroscopic analyses based on geomorphological expert knowledge, contour lines are selected representing the natural geomorphological character of the surface. In a first step, points are determined along each contour line in regular intervals. This points and the corresponding height information which is taken from an original digital terrain model is saved as a point cloud. Using the programme library gstat, a variographic analysis and the use of a Kriging-procedure based on this follow.2-4 The result is a digital terrain model filtered considering geomorphological expert knowledge showing no human degradation in terms of artefacts, preserving the landscape-genetic character and can be called a prehistoric terrain model.

SilMush: A procedure for modeling of the geochemical evolution of silicic magmas and granitic rocks

NASA Astrophysics Data System (ADS)

Hertogen, Jan; Mareels, Joyce

2016-07-01

A boundary layer crystallization modeling program is presented that specifically addresses the chemical fractionation in silicic magma systems and the solidification of plutonic bodies. The model is a Langmuir (1989) type approach and does not invoke crystal settling in high-viscosity silicic melts. The primary aim is to model a granitic rock as a congealed crystal-liquid mush, and to integrate major element and trace element modeling. The procedure allows for some exploratory investigation of the exsolution of H2O-fluids and of the fluid/melt partitioning of trace elements. The procedure is implemented as a collection of subroutines for the MS Excel spreadsheet environment and is coded in the Visual Basic for Applications (VBA) language. To increase the flexibility of the modeling, the procedure is based on discrete numeric process simulation rather than on solution of continuous differential equations. The program is applied to a study of the geochemical variation within and among three granitic units (Senones, Natzwiller, Kagenfels) from the Variscan Northern Vosges Massif, France. The three units cover the compositional range from monzogranite, over syenogranite to alkali-feldspar granite. An extensive set of new major element and trace element data is presented. Special attention is paid to the essential role of accessory minerals in the fractionation of the Rare Earth Elements. The crystallization model is able to reproduce the essential major and trace element variation trends in the data sets of the three separate granitic plutons. The Kagenfels alkali-feldspar leucogranite couples very limited variation in major element composition to a considerable and complex variation of trace elements. The modeling results can serve as a guide for the reconstruction of the emplacement sequence of petrographically distinct units. Although the modeling procedure essentially deals with geochemical fractionation within a single pluton, the modeling results bring up a number of questions about the petrogenetic relationships among parental magmas of nearly coeval granitic units emplaced in close proximity.

Alleviation of environmental risks associated with severely contaminated mine tailings using amendments: Modeling of trace element speciation, solubility, and plant accumulation.

PubMed

Pardo, Tania; Bes, Cleménce; Bernal, Maria Pilar; Clemente, Rafael

2016-11-01

Tailings are considered one of the most relevant sources of contamination associated with mining activities. Phytostabilization of mine spoils may need the application of the adequate combination of amendments to facilitate plant establishment and reduce their environmental impact. Two pot experiments were set up to assess the capability of 2 inorganic materials (calcium carbonate and a red mud derivate, ViroBind TM ), alone or in combination with organic amendments, for the stabilization of highly acidic trace element-contaminated mine tailings using Atriplex halimus. The effects of the treatments on tailings and porewater physico-chemical properties and trace-element accumulation by the plants, as well as the processes governing trace elements speciation and solubility in soil solution and their bioavailability were modeled. The application of the amendments increased tailings pH and decreased (>99%) trace elements solubility in porewater, but also changed the speciation of soluble Cd, Cu, and Pb. All the treatments made A. halimus growth in the tailings possible; organic amendments increased plant biomass and nutritional status, and reduced trace-element accumulation in the plants. Tailings amendments modified trace-element speciation in porewater (favoring the formation of chlorides and/or organo-metallic forms) and their solubility and plant uptake, which were found to be mainly governed by tailing/porewater pH, electrical conductivity, and organic carbon content, as well as soluble/available trace-element concentrations. Environ Toxicol Chem 2016;35:2874-2884. © 2016 SETAC. © 2016 SETAC.

Zebrafish in the sea of mineral (iron, zinc, and copper) metabolism

PubMed Central

Zhao, Lu; Xia, Zhidan; Wang, Fudi

2014-01-01

Iron, copper, zinc, and eight other minerals are classified as essential trace elements because they present in minute in vivo quantities and are essential for life. Because either excess or insufficient levels of trace elements can be detrimental to life (causing human diseases such as iron-deficiency anemia, hemochromatosis, Menkes syndrome and Wilson's disease), the endogenous levels of trace minerals must be tightly regulated. Many studies have demonstrated the existence of systems that maintain trace element homeostasis, and these systems are highly conserved in multiple species ranging from yeast to mice. As a model for studying trace mineral metabolism, the zebrafish is indispensable to researchers. Several large-scale mutagenesis screens have been performed in zebrafish, and these screens led to the identification of a series of metal transporters and the generation of several mutagenesis lines, providing an in-depth functional analysis at the system level. Moreover, because of their developmental advantages, zebrafish have also been used in mineral metabolism-related chemical screens and toxicology studies. Here, we systematically review the major findings of trace element homeostasis studies using the zebrafish model, with a focus on iron, zinc, copper, selenium, manganese, and iodine. We also provide a homology analysis of trace mineral transporters in fish, mice and humans. Finally, we discuss the evidence that zebrafish is an ideal experimental tool for uncovering novel mechanisms of trace mineral metabolism and for improving approaches to treat mineral imbalance-related diseases. PMID:24639652

False Memory for Orthographically versus Semantically Similar Words in Adolescents with Dyslexia: A Fuzzy-Trace Theory Perspective

ERIC Educational Resources Information Center

Obidzinski, Michal; Nieznanski, Marek

2017-01-01

The presented research was conducted in order to investigate the connections between developmental dyslexia and the functioning of verbatim and gist memory traces--assumed in the fuzzy-trace theory. The participants were 71 high school students (33 with dyslexia and 38 without learning difficulties). The modified procedure and multinomial model of…

Strong spatial variability in trace gas dynamics following experimental drought in a humid tropical forest

Treesearch

Tana Wood; W. L. Silver

2012-01-01

[1] Soil moisture is a key driver of biogeochemical processes in terrestrial ecosystems, strongly affecting carbon (C) and nutrient availability as well as trace gas production and consumption in soils. Models predict increasing drought frequency in tropical forest ecosystems, which could feed back on future climate change directly via effects on trace gasdynamics and...

Reverse radiance: a fast accurate method for determining luminance

NASA Astrophysics Data System (ADS)

Moore, Kenneth E.; Rykowski, Ronald F.; Gangadhara, Sanjay

2012-10-01

Reverse ray tracing from a region of interest backward to the source has long been proposed as an efficient method of determining luminous flux. The idea is to trace rays only from where the final flux needs to be known back to the source, rather than tracing in the forward direction from the source outward to see where the light goes. Once the reverse ray reaches the source, the radiance the equivalent forward ray would have represented is determined and the resulting flux computed. Although reverse ray tracing is conceptually simple, the method critically depends upon an accurate source model in both the near and far field. An overly simplified source model, such as an ideal Lambertian surface substantially detracts from the accuracy and thus benefit of the method. This paper will introduce an improved method of reverse ray tracing that we call Reverse Radiance that avoids assumptions about the source properties. The new method uses measured data from a Source Imaging Goniometer (SIG) that simultaneously measures near and far field luminous data. Incorporating this data into a fast reverse ray tracing integration method yields fast, accurate data for a wide variety of illumination problems.

Is there still a TRACE of trace?

NASA Astrophysics Data System (ADS)

McClelland, James; Mirman, Daniel; Holt, Lori

2003-04-01

According to the TRACE model [McClelland and Elman, Cogn. Psychol. 18, 1-86 (1986)], speech recognition is an interactive activation process involving the integrated use of top-down (lexical) and bottom-up (acoustic) information. Although it is widely accepted that there are lexical influences on speech perception, there has been a disagreement over their exact nature. Two contested predictions of TRACE are that (a) lexical influences should delay or inhibit recognition of phonemes not consistent with lexical information and (b) a lexical influence on the identification of one phoneme can trigger compensation for co-articulation, affecting the identification of other phonemes. Others [Norris, McQueen, and Cutler, BBS 23, 299-370 (2000)] have argued that the predicted effects do not occur, taking this to support an alternative to the TRACE model in which lexical influences do not affect perception, but only a post-perceptual identification process. We re-examine the evidence on these points along with the recent finding that lexical information may lead to a lasting adjustment of category boundaries [McQueen, Norris, and Cutler, Psychonomics Abstract 255 (2001)]. Our analysis indicates that the existing evidence is completely consistent with TRACE, and we suggest additional research that will be necessary to resolve unanswered questions.

Within-Category VOT Affects Recovery from "Lexical" Garden-Paths: Evidence against Phoneme-Level Inhibition

ERIC Educational Resources Information Center

McMurray, Bob; Tanenhaus, Michael K.; Aslin, Richard N.

2009-01-01

Spoken word recognition shows gradient sensitivity to within-category voice onset time (VOT), as predicted by several current models of spoken word recognition, including TRACE (McClelland, J., & Elman, J. (1986). The TRACE model of speech perception. "Cognitive Psychology," 18, 1-86). It remains unclear, however, whether this sensitivity is…

Modeling impacts of management on carbon sequestration and trace gas emissions in forested wetland ecosystems

Treesearch

Changsheng Li; Jianbo Cui

2004-01-01

A process- based model, Wetland-DNDC, was modified to enhance its capacity to predict the impacts of management practices on carbon sequestration in and trace gas emissions from forested wetland ecosystems. The modifications included parameterization of management practices fe.g., forest harvest, chopping, burning, water management, fertilization, and tree planting),...

Cognitive Demand of Model Tracing Tutor Tasks: Conceptualizing and Predicting How Deeply Students Engage

ERIC Educational Resources Information Center

Kessler, Aaron M.; Stein, Mary Kay; Schunn, Christian D.

2015-01-01

Model tracing tutors represent a technology designed to mimic key elements of one-on-one human tutoring. We examine the situations in which such supportive computer technologies may devolve into mindless student work with little conceptual understanding or student development. To analyze the support of student intellectual work in the model…

Zebrafish Models of Human Leukemia: Technological Advances and Mechanistic Insights.

PubMed

Harrison, Nicholas R; Laroche, Fabrice J F; Gutierrez, Alejandro; Feng, Hui

2016-01-01

Insights concerning leukemic pathophysiology have been acquired in various animal models and further efforts to understand the mechanisms underlying leukemic treatment resistance and disease relapse promise to improve therapeutic strategies. The zebrafish (Danio rerio) is a vertebrate organism with a conserved hematopoietic program and unique experimental strengths suiting it for the investigation of human leukemia. Recent technological advances in zebrafish research including efficient transgenesis, precise genome editing, and straightforward transplantation techniques have led to the generation of a number of leukemia models. The transparency of the zebrafish when coupled with improved lineage-tracing and imaging techniques has revealed exquisite details of leukemic initiation, progression, and regression. With these advantages, the zebrafish represents a unique experimental system for leukemic research and additionally, advances in zebrafish-based high-throughput drug screening promise to hasten the discovery of novel leukemia therapeutics. To date, investigators have accumulated knowledge of the genetic underpinnings critical to leukemic transformation and treatment resistance and without doubt, zebrafish are rapidly expanding our understanding of disease mechanisms and helping to shape therapeutic strategies for improved outcomes in leukemic patients.

Zebrafish Models of Human Leukemia: Technological Advances and Mechanistic Insights

PubMed Central

Harrison, Nicholas R.; Laroche, Fabrice J.F.; Gutierrez, Alejandro

2016-01-01

Insights concerning leukemic pathophysiology have been acquired in various animal models and further efforts to understand the mechanisms underlying leukemic treatment resistance and disease relapse promise to improve therapeutic strategies. The zebrafish (Danio rerio) is a vertebrate organism with a conserved hematopoietic program and unique experimental strengths suiting it for the investigation of human leukemia. Recent technological advances in zebrafish research including efficient transgenesis, precise genome editing, and straightforward transplantation techniques have led to the generation of a number of leukemia models. The transparency of the zebrafish when coupled with improved lineage-tracing and imaging techniques has revealed exquisite details of leukemic initiation, progression, and regression. With these advantages, the zebrafish represents a unique experimental system for leukemic research and additionally, advances in zebrafish-based high-throughput drug screening promise to hasten the discovery of novel leukemia therapeutics. To date, investigators have accumulated knowledge of the genetic underpinnings critical to leukemic transformation and treatment resistance and without doubt, zebrafish are rapidly expanding our understanding of disease mechanisms and helping to shape therapeutic strategies for improved outcomes in leukemic patients. PMID:27165361

Remembering over the short-term: the case against the standard model.

PubMed

Nairne, James S

2002-01-01

Psychologists often assume that short-term storage is synonymous with activation, a mnemonic property that keeps information in an immediately accessible form. Permanent knowledge is activated, as a result of on-line cognitive processing, and an activity trace is established "in" short-term (or working) memory. Activation is assumed to decay spontaneously with the passage of time, so a refreshing process-rehearsal-is needed to maintain availability. Most of the phenomena of immediate retention, such as capacity limitations and word length effects, are assumed to arise from trade-offs between rehearsal and decay. This "standard model" of how we remember over the short-term still enjoys considerable popularity, although recent research questions most of its main assumptions. In this chapter I review the recent research and identify the empirical and conceptual problems that plague traditional conceptions of short-term memory. Increasingly, researchers are recognizing that short-term retention is cue driven, much like long-term memory, and that neither rehearsal nor decay is likely to explain the particulars of short-term forgetting.

Exploratory of society

NASA Astrophysics Data System (ADS)

Cederman, L.-E.; Conte, R.; Helbing, D.; Nowak, A.; Schweitzer, F.; Vespignani, A.

2012-11-01

A huge flow of quantitative social, demographic and behavioral data is becoming available that traces the activities and interactions of individuals, social patterns, transportation infrastructures and travel fluxes. This has caused, together with innovative computational techniques and methods for modeling social actions in hybrid (natural and artificial) societies, a qualitative change in the ways we model socio-technical systems. For the first time, society can be studied in a comprehensive fashion that addresses social and behavioral complexity. In other words we are in the position to envision the development of large data and computational cyber infrastructure defining an exploratory of society that provides quantitative anticipatory, explanatory and scenario analysis capabilities ranging from emerging infectious disease to conflict and crime surges. The goal of the exploratory of society is to provide the basic infrastructure embedding the framework of tools and knowledge needed for the design of forecast/anticipatory/crisis management approaches to socio technical systems, supporting future decision making procedures by accelerating the scientific cycle that goes from data generation to predictions.

Automated segmentation of chronic stroke lesions using LINDA: Lesion Identification with Neighborhood Data Analysis

PubMed Central

Pustina, Dorian; Coslett, H. Branch; Turkeltaub, Peter E.; Tustison, Nicholas; Schwartz, Myrna F.; Avants, Brian

2015-01-01

The gold standard for identifying stroke lesions is manual tracing, a method that is known to be observer dependent and time consuming, thus impractical for big data studies. We propose LINDA (Lesion Identification with Neighborhood Data Analysis), an automated segmentation algorithm capable of learning the relationship between existing manual segmentations and a single T1-weighted MRI. A dataset of 60 left hemispheric chronic stroke patients is used to build the method and test it with k-fold and leave-one-out procedures. With respect to manual tracings, predicted lesion maps showed a mean dice overlap of 0.696±0.16, Hausdorff distance of 17.9±9.8mm, and average displacement of 2.54±1.38mm. The manual and predicted lesion volumes correlated at r=0.961. An additional dataset of 45 patients was utilized to test LINDA with independent data, achieving high accuracy rates and confirming its cross-institutional applicability. To investigate the cost of moving from manual tracings to automated segmentation, we performed comparative lesion-to-symptom mapping (LSM) on five behavioral scores. Predicted and manual lesions produced similar neuro-cognitive maps, albeit with some discussed discrepancies. Of note, region-wise LSM was more robust to the prediction error than voxel-wise LSM. Our results show that, while several limitations exist, our current results compete with or exceed the state-of-the-art, producing consistent predictions, very low failure rates, and transferable knowledge between labs. This work also establishes a new viewpoint on evaluating automated methods not only with segmentation accuracy but also with brain-behavior relationships. LINDA is made available online with trained models from over 100 patients. PMID:26756101

Two years of CarboPerm: achievements and further steps of an interdisciplinary Russian-German project on the formation, turnover and release of carbon in Siberian permafrost landscape

NASA Astrophysics Data System (ADS)

Zubrzycki, S.

2015-12-01

Permafrost-affected soils of the northern hemisphere have accumulated large pools of soil organic carbon (SOC) since continuous low temperatures in the permafrost prevented organic matter (OM) decomposition. According to recent estimates these soils contain 1300 ± 200 Pg of SOC, or about twice as much the carbon within the global vegetation. Rising arctic temperatures will likely result in increased permafrost thawing with the consequence of increased mobilization and degradation of formerly frozen OM. This degradation process will presumably result in an increased formation of trace gases such as methane and carbon dioxide which can be released to the atmosphere. Rising trace gas concentrations due to permafrost thawing would thereby induce a positive feedback on climate warming. CarboPerm, is a joint German-Russian research project funded by the German Federal Ministry of Education and Research. It comprises multi-disciplinary investigations on the formation, turnover and release of SOC in Siberian permafrost. It aims to gain increased understanding of how permafrost-affected landscapes will respond to global warming and how this response will influence the local, regional and global trace gas balance. CarboPerm strengthens permafrost research in underrepresented areas which are hardly accessible to international researchers. The obtained results improve our understanding of the future development of the sensitive and economically relevant arctic permafrost regions. With this contribution we want to inform the interested community about the new knowledge resulting from results of all scientific work packages: (i) the origin, properties, and dynamics of fossil carbon, (ii) the age and quality of organic matter, (iii) the recent carbon dynamics in permafrost landscapes, (iv) the microbial transformation of organic carbon in permafrost, and (v) process-driven modeling of soil carbon dynamics in permafrost areas.

A functional-structural kiwifruit vine model integrating architecture, carbon dynamics and effects of the environment.

PubMed

Cieslak, Mikolaj; Seleznyova, Alla N; Hanan, Jim

2011-04-01

Functional-structural modelling can be used to increase our understanding of how different aspects of plant structure and function interact, identify knowledge gaps and guide priorities for future experimentation. By integrating existing knowledge of the different aspects of the kiwifruit (Actinidia deliciosa) vine's architecture and physiology, our aim is to develop conceptual and mathematical hypotheses on several of the vine's features: (a) plasticity of the vine's architecture; (b) effects of organ position within the canopy on its size; (c) effects of environment and horticultural management on shoot growth, light distribution and organ size; and (d) role of carbon reserves in early shoot growth. Using the L-system modelling platform, a functional-structural plant model of a kiwifruit vine was created that integrates architectural development, mechanistic modelling of carbon transport and allocation, and environmental and management effects on vine and fruit growth. The branching pattern was captured at the individual shoot level by modelling axillary shoot development using a discrete-time Markov chain. An existing carbon transport resistance model was extended to account for several source/sink components of individual plant elements. A quasi-Monte Carlo path-tracing algorithm was used to estimate the absorbed irradiance of each leaf. Several simulations were performed to illustrate the model's potential to reproduce the major features of the vine's behaviour. The model simulated vine growth responses that were qualitatively similar to those observed in experiments, including the plastic response of shoot growth to local carbon supply, the branching patterns of two Actinidia species, the effect of carbon limitation and topological distance on fruit size and the complex behaviour of sink competition for carbon. The model is able to reproduce differences in vine and fruit growth arising from various experimental treatments. This implies it will be a valuable tool for refining our understanding of kiwifruit growth and for identifying strategies to improve production.

Mid-Frequency Reverberation Measurements with Full Companion Environmental Support

DTIC Science & Technology

2014-12-30

acoustic modeling is based on measured stratification and observed wave amplitudes on the New Jersey shelf during the SWARM experiment.3 Ray tracing is...wave model then gives quantitative results for the clutter. 2. Swarm NLIW model and ray tracing Nonlinear internal waves are very common on the...receiver in order to give quantitative clutter to reverberation. To picture the mechanism, a set of rays was launched from a source at range zero and

Performance Prediction of Constrained Waveform Design for Adaptive Radar

DTIC Science & Technology

2016-11-01

Kullback - Leibler divergence. χ2 Goodness - of - Fit Test We compute the estimated CDF for both models with 10000 MC trials. For Model 1 we observed a p-value of ...was clearly similar in its physical attributes, but the measures used , ( Kullback - Leibler , Chi-Square Test and the trace of the covariance) showed...models goodness - of - fit we look at three measures (1) χ2- Test (2) Trace of the inverse

Tracing the influence of land-use change on water quality and coral reefs using a Bayesian model.

PubMed

Brown, Christopher J; Jupiter, Stacy D; Albert, Simon; Klein, Carissa J; Mangubhai, Sangeeta; Maina, Joseph M; Mumby, Peter; Olley, Jon; Stewart-Koster, Ben; Tulloch, Vivitskaia; Wenger, Amelia

2017-07-06

Coastal ecosystems can be degraded by poor water quality. Tracing the causes of poor water quality back to land-use change is necessary to target catchment management for coastal zone management. However, existing models for tracing the sources of pollution require extensive data-sets which are not available for many of the world's coral reef regions that may have severe water quality issues. Here we develop a hierarchical Bayesian model that uses freely available satellite data to infer the connection between land-uses in catchments and water clarity in coastal oceans. We apply the model to estimate the influence of land-use change on water clarity in Fiji. We tested the model's predictions against underwater surveys, finding that predictions of poor water quality are consistent with observations of high siltation and low coverage of sediment-sensitive coral genera. The model thus provides a means to link land-use change to declines in coastal water quality.

Contamination characteristics and source apportionment of trace metals in soils around Miyun Reservoir.

PubMed

Chen, Haiyang; Teng, Yanguo; Chen, Ruihui; Li, Jiao; Wang, Jinsheng

2016-08-01

Due to their toxicity and bioaccumulation, trace metals in soils can result in a wide range of toxic effects on animals, plants, microbes, and even humans. Recognizing the contamination characteristics of soil metals and especially apportioning their potential sources are the necessary preconditions for pollution prevention and control. Over the past decades, several receptor models have been developed for source apportionment. Among them, positive matrix factorization (PMF) has gained popularity and was recommended by the US Environmental Protection Agency as a general modeling tool. In this study, an extended chemometrics model, multivariate curve resolution-alternating least squares based on maximum likelihood principal component analysis (MCR-ALS/MLPCA), was proposed for source apportionment of soil metals and applied to identify the potential sources of trace metals in soils around Miyun Reservoir. Similar to PMF, the MCR-ALS/MLPCA model can incorporate measurement error information and non-negativity constraints in its calculation procedures. Model validation with synthetic dataset suggested that the MCR-ALS/MLPCA could extract acceptable recovered source profiles even considering relatively larger error levels. When applying to identify the sources of trace metals in soils around Miyun Reservoir, the MCR-ALS/MLPCA model obtained the highly similar profiles with PMF. On the other hand, the assessment results of contamination status showed that the soils around reservoir were polluted by trace metals in slightly moderate degree but potentially posed acceptable risks to the public. Mining activities, fertilizers and agrochemicals, and atmospheric deposition were identified as the potential anthropogenic sources with contributions of 24.8, 14.6, and 13.3 %, respectively. In order to protect the drinking water source of Beijing, special attention should be paid to the metal inputs to soils from mining and agricultural activities.

The Search for Efficiency in Arboreal Ray Tracing Applications

NASA Astrophysics Data System (ADS)

van Leeuwen, M.; Disney, M.; Chen, J. M.; Gomez-Dans, J.; Kelbe, D.; van Aardt, J. A.; Lewis, P.

2016-12-01

Forest structure significantly impacts a range of abiotic conditions, including humidity and the radiation regime, all of which affect the rate of net and gross primary productivity. Current forest productivity models typically consider abstract media to represent the transfer of radiation within the canopy. Examples include the representation forest structure via a layered canopy model, where leaf area and inclination angles are stratified with canopy depth, or as turbid media where leaves are randomly distributed within space or within confined geometric solids such as blocks, spheres or cones. While these abstract models are known to produce accurate estimates of primary productivity at the stand level, their limited geometric resolution restricts applicability at fine spatial scales, such as the cell, leaf or shoot levels, thereby not addressing the full potential of assimilation of data from laboratory and field measurements with that of remote sensing technology. Recent research efforts have explored the use of laser scanning to capture detailed tree morphology at millimeter accuracy. These data can subsequently be used to combine ray tracing with primary productivity models, providing an ability to explore trade-offs among different morphological traits or assimilate data from spatial scales, spanning the leaf- to the stand level. Ray tracing has a major advantage of allowing the most accurate structural description of the canopy, and can directly exploit new 3D structural measurements, e.g., from laser scanning. However, the biggest limitation of ray tracing models is their high computational cost, which currently limits their use for large-scale applications. In this talk, we explore ways to more efficiently exploit ray tracing simulations and capture this information in a readily computable form for future evaluation, thus potentially enabling large-scale first-principles forest growth modelling applications.

Experimental evaluation of radiosity for room sound-field prediction.

PubMed

Hodgson, Murray; Nosal, Eva-Marie

2006-08-01

An acoustical radiosity model was evaluated for how it performs in predicting real room sound fields. This was done by comparing radiosity predictions with experimental results for three existing rooms--a squash court, a classroom, and an office. Radiosity predictions were also compared with those by ray tracing--a "reference" prediction model--for both specular and diffuse surface reflection. Comparisons were made for detailed and discretized echograms, sound-decay curves, sound-propagation curves, and the variations with frequency of four room-acoustical parameters--EDT, RT, D50, and C80. In general, radiosity and diffuse ray tracing gave very similar predictions. Predictions by specular ray tracing were often very different. Radiosity agreed well with experiment in some cases, less well in others. Definitive conclusions regarding the accuracy with which the rooms were modeled, or the accuracy of the radiosity approach, were difficult to draw. The results suggest that radiosity predicts room sound fields with some accuracy, at least as well as diffuse ray tracing and, in general, better than specular ray tracing. The predictions of detailed echograms are less accurate, those of derived room-acoustical parameters more accurate. The results underline the need to develop experimental methods for accurately characterizing the absorptive and reflective characteristics of room surfaces, possible including phase.

Dispersion model on PM₂.₅ fugitive dust and trace metals levels in Kuwait Governorates.

PubMed

Bu-Olayan, A H; Thomas, B V

2012-03-01

Frequent dust storms and recent environmental changes were found to affect the human health especially in residents of arid countries. Investigations on the PM(2.5) fugitive dust in six Kuwait Governorate areas using dispersion Gaussian plume modeling revealed significant relationship between low rate of pollutant emission, low wind velocity, and stable weather conditions' matrix causing high rate of dust deposition in summer than in winter. The rate of dust deposition and trace metals levels in PM(2.5) were in the sequence of G-VI > G-I > G-II > G-V > G-III > G-IV. Trace metals were observed in the sequence of Al > Fe > Zn > Ni > Pb > Cd irrespective of the Governorate areas and the two seasons. The high rate of dust deposition and trace metals in PM(2.5) was reflected by the vast open area, wind velocity, and rapid industrialization besides natural and anthropogenic sources. A combination of air dispersion modeling and nephalometric and gravimetric studies of this kind not only determines the seasonal qualitative and quantitative analyses on the PM(2.5) dust deposition besides trace metals apportionment in six Kuwait Governorate areas, but also characterizes air pollution factors that could be used by environmentalist to deduce preventive measures.

Wide extragalactic (sub-)millimeter surveys with SCUBA and AzTEC

NASA Astrophysics Data System (ADS)

Aretxaga, I.; Hughes, D. H.; SHADES Collaboration; AzTEC Collaboration

2009-05-01

We summarize the present status of our knowledge of the millimeter galaxy population derived from extensive (sub-) millimeter extragalactic surveys like the SCUBA HAlf Degree Survey (SHADES), and the current status of the next generation of surveys traced with the AzTEC camera, that has, so far, surveyed more than 2 degrees at 1.1wavelengths.

Use and Exchange Value in Mathematics Education: Contemporary CHAT Meets Bourdieu's Sociology

ERIC Educational Resources Information Center

Williams, Julian

2012-01-01

Empirical work has shown how mathematics education exhibits certain tensions between its value as being practically useful to production and consumption on the one hand and in offering access to scarce resources on the other hand. These tensions can be ultimately traced to the contradictions in the way mathematical knowledge enhances the use value…

To Show Is to Know? The Conceptualization of Evidence and Discourses of Vision in Social Science and Education Research

ERIC Educational Resources Information Center

Baker, Bernadette

2017-01-01

The demand for evidence in particular forms shapes contemporary educational policy, curriculum studies' debates over the politics of knowledge "versus" wisdom, and research into classroom practice. This paper provides a genealogical trace that examines the arbitrary and historical linkage of discourses of vision (especially when vision…

Visualizing Communication Structures in Science Classrooms: Tracing Cumulativity in Teacher-Led Whole Class Discussions

ERIC Educational Resources Information Center

Lehesvuori, Sami; Viiri, Jouni; Rasku-Puttonen, Helena; Moate, Josephine; Helaakoski, Jussi

2013-01-01

Teacher-led whole class discussions are essential when it comes to guiding students' construction of knowledge, and recent studies on teaching and learning emphasize the need for more student-centered teaching methods. In previous studies, the extent to which different types of communication take place in the classroom have been extensively…

The Academy, Development, and Modernity's "Other"

ERIC Educational Resources Information Center

Haavelsrud, Magnus

2015-01-01

Epistemological preferences in Western academies over the centuries became the measuring rod for what is to count as valid knowledge in thinking about development. The genealogy of the sciences of law and economics can be traced back to the Roman and British empires. The problem is posed in this paper as to the question of how remnants of these…

The Consequences of Democratizing Knowledge: Reconsidering Richard Hofstadter and the History of Education

ERIC Educational Resources Information Center

De Simone, Deborah M.

2001-01-01

In his Pulitzer Prize winning work, "Anti-intellectualism in American Life," Richard Hofstadter set out to trace the social movements that altered the role of intellect in society from a virtue to a vice. In so doing, he explored questions regarding the purpose of education and whether the democratization of education altered that…

Antonio Gramsci and Feminism: The Elusive Nature of Power

ERIC Educational Resources Information Center

Ledwith, Margaret

2009-01-01

From a feminist perspective, I am interested in "women's ways of knowing" (Belenky et al., 1997) and the relationship between knowledge, difference and power (Goldberger et al., 1996). Here I trace the relevance of Gramsci to my own feminist consciousness, and the part he played in my journey to praxis. I also address feminism's intellectual…

Still-Video Photography: Tomorrow's Electronic Cameras in the Hands of Today's Photojournalists.

ERIC Educational Resources Information Center

Foss, Kurt; Kahan, Robert S.

This paper examines the still-video camera and its potential impact by looking at recent experiments and by gathering information from some of the few people knowledgeable about the new technology. The paper briefly traces the evolution of the tools and processes of still-video photography, examining how photographers and their work have been…

International Perspectives on Lifelong Learning: From Recurrent Education to the Knowledge Society.

ERIC Educational Resources Information Center

Istance, David, Ed.; Schuetze, Hans G., Ed.; Schuller, Tom, Ed.

This book, consisting of 17 chapters written by different authors, traces the progress that has been made in developing lifelong learning policies over the past 30 years and examines current challenges to lifelong learning policymakers. Focusing on a global agenda, the book is organized in six parts with thematic chapters following an introductory…

Labor and Technology: Union Response to Changing Environments.

ERIC Educational Resources Information Center

Kennedy, Donald, Ed.; And Others

This collection of papers, which is intended as a contribution to the body of knowledge known as labor studies, examines the ways in which labor unions have and are continuing to respond to technological change in the workplace. The introduction by Donald Kennedy, Charles Craypo, and Mary Lehman traces the impact of technological change on the…

English, Literacy and Neoliberal Policies: Mapping a Contested Moment in the United States

ERIC Educational Resources Information Center

Brass, Jory

2014-01-01

This essay maps some of the ways in which the professional knowledge of English teaching has been defined and positioned in the present moment in the United States. The first part of the essay traces multidisciplinary shifts in English education/literacy research that have expanded and shifted the discursive boundaries of teacher education and…

Higher Education Leadership: Enhancing Skills through Professional Development Programs. ASHE/ERIC Higher Education Report No. 5, 1987.

ERIC Educational Resources Information Center

McDade, Sharon A.

The responsibilities and skills of college administrators and training needs and programs are discussed. After tracing typical career paths of administrators, skills and knowledge that they need are identified, based in part on similar positions from government, service organizations, and the military. The list of administrators' responsibilities…

Student Teams' Development over Time: Tracing the Relationship between the Quality of Communication and Teams' Performance

ERIC Educational Resources Information Center

Pöysä-Tarhonen, Johanna; Elen, Jan; Tarhonen, Pasi

2016-01-01

Current discussions in higher education and alumni training acknowledge the challenges training programs face in responding to the authentic needs of the labor market. In addition to academic knowledge, higher education institutions are expected to provide general twenty-first-century skills, such as problem-solving, critical thinking,…

Dilution as a Model of Long-Term Forgetting

ERIC Educational Resources Information Center

Lansdale, Mark; Baguley, Thom

2008-01-01

This article presents a model of long term forgetting based on 3 ideas: (a) Memory for a stimulus can be described by a population of accessible traces; (b) probability of retrieval after a delay is predicted by the proportion of traces in this population that will be defined as correct if sampled; and (c) this population is diluted over time by…

Relationship of college student characteristics and inquiry-based geometrical optics instruction to knowledge of image formation with light-ray tracing

NASA Astrophysics Data System (ADS)

Isik, Hakan

This study is premised on the fact that student conceptions of optics appear to be unrelated to student characteristics of gender, age, years since high school graduation, or previous academic experiences. This study investigated the relationships between student characteristics and student performance on image formation test items and the changes in student conceptions of optics after an introductory inquiry-based physics course. Data was collected from 39 college students who were involved in an inquiry-based physics course teaching topics of geometrical optics. Student data concerning characteristics and previous experiences with optics and mathematics were collected. Assessment of student understanding of optics knowledge for pinholes, plane mirrors, refraction, and convex lenses was collected with, the Test of Image Formation with Light-Ray Tracing instrument. Total scale and subscale scores representing the optics instrument content were derived from student pretest and posttest responses. The types of knowledge, needed to answer each optics item correctly, were categorized as situational, conceptual, procedural, and strategic knowledge. These types of knowledge were associated with student correct and incorrect responses to each item to explain the existences and changes in student scientific and naive conceptions. Correlation and stepwise multiple regression analyses were conducted to identify the student characteristics and academic experiences that significantly predicted scores on the subscales of the test. The results showed that student experience with calculus was a significant predictor of student performance on the total scale as well as on the refraction subscale of the Test of Image Formation with Light-Ray Tracing. A combination of student age and previous academic experience with precalculus was a significant predictor of student performance on the pretest pinhole subscale. Student characteristic of years since high school graduation significantly predicted the gain in student scores on pinhole and plane-mirror items from the pretest to the posttest with those students who were most recent graduates from high school doing better. Multivariate and univariate analyses of variance of the Test of Image Formation with Light-Ray Tracing pinhole scale and individual item changes from the pretest to the posttest resulted in statistically significant mean differences between total scores as well as between various individual pinhole items. There were no significant changes for individual plane-mirror items from pretest to posttest. Results revealed that there is a perceivable relationship between student optics-content knowledge and the types of knowledge required by items. At the pretest, the greatest selection of wrong responses related to the items requiring situational type of knowledge and the fewest selection of wrong responses was relate to the items requiring procedural type of knowledge. Student selection of wrong options for each item revealed the following naive optics conceptions: pinholes do not create reversed images (pretest), size and sharpness of pinhole images are related to the focus of a pinhole camera (pretest and posttest); propagation of light rays are interpreted as being radial rather than directional (pretest and posttest); no conception of image formation and observation for parallel mirrors (pretest and posttest), the place of an image depends on the position of the observer (pretest and posttest), a plane mirror reflects the images of the objects placed at one side of the mirror and the observers who were positioned at the other side of the mirror can see them (pretest and posttest); applying the law of reflection to plane mirrors without considering the variations in angles of incidence and reflection (pretest and posttest), and image observation is confused with the image formation in mirrors placed perpendicular to one another (pretest and posttest). Future research should focus on the acquisition, development, and identification of reliable measures of optics concepts, processes, types of knowledge, and specific optics understanding (i.e., pinhole, plane-mirror). Future research should focus on the identification of the more critical concepts such as changes in size and sharpness of pinhole images, image observation, image formation in general, and image formation and observation in parallel mirrors. Future research can be conducted with a larger set of participants so as to compare different instructional methods and address instructional deficiencies using more efficient statistical methods. Comparative studies can be conducted to investigate the relations of various instructional strategies on student conceptions of optics.

Sharing and reusing cardiovascular anatomical models over the Web: a step towards the implementation of the virtual physiological human project.

PubMed

Gianni, Daniele; McKeever, Steve; Yu, Tommy; Britten, Randall; Delingette, Hervé; Frangi, Alejandro; Hunter, Peter; Smith, Nicolas

2010-06-28

Sharing and reusing anatomical models over the Web offers a significant opportunity to progress the investigation of cardiovascular diseases. However, the current sharing methodology suffers from the limitations of static model delivery (i.e. embedding static links to the models within Web pages) and of a disaggregated view of the model metadata produced by publications and cardiac simulations in isolation. In the context of euHeart--a research project targeting the description and representation of cardiovascular models for disease diagnosis and treatment purposes--we aim to overcome the above limitations with the introduction of euHeartDB, a Web-enabled database for anatomical models of the heart. The database implements a dynamic sharing methodology by managing data access and by tracing all applications. In addition to this, euHeartDB establishes a knowledge link with the physiome model repository by linking geometries to CellML models embedded in the simulation of cardiac behaviour. Furthermore, euHeartDB uses the exFormat--a preliminary version of the interoperable FieldML data format--to effectively promote reuse of anatomical models, and currently incorporates Continuum Mechanics, Image Analysis, Signal Processing and System Identification Graphical User Interface (CMGUI), a rendering engine, to provide three-dimensional graphical views of the models populating the database. Currently, euHeartDB stores 11 cardiac geometries developed within the euHeart project consortium.

Simple way to calculate a UV-finite one-loop quantum energy in the Randall-Sundrum model

NASA Astrophysics Data System (ADS)

Altshuler, Boris L.

2017-04-01

The surprising simplicity of Barvinsky-Nesterov or equivalently Gelfand-Yaglom methods of calculation of quantum determinants permits us to obtain compact expressions for a UV-finite difference of one-loop quantum energies for two arbitrary values of the parameter of the double-trace asymptotic boundary conditions. This result generalizes the Gubser and Mitra calculation for the particular case of difference of "regular" and "irregular" one-loop energies in the one-brane Randall-Sundrum model. The approach developed in the paper also allows us to get "in one line" the one-loop quantum energies in the two-brane Randall-Sundrum model. The relationship between "one-loop" expressions corresponding to the mixed Robin and to double-trace asymptotic boundary conditions is traced.

Trace metal speciation in natural waters: Computational vs. analytical

USGS Publications Warehouse

Nordstrom, D. Kirk

1996-01-01

Improvements in the field sampling, preservation, and determination of trace metals in natural waters have made many analyses more reliable and less affected by contamination. The speciation of trace metals, however, remains controversial. Chemical model speciation calculations do not necessarily agree with voltammetric, ion exchange, potentiometric, or other analytical speciation techniques. When metal-organic complexes are important, model calculations are not usually helpful and on-site analytical separations are essential. Many analytical speciation techniques have serious interferences and only work well for a limited subset of water types and compositions. A combined approach to the evaluation of speciation could greatly reduce these uncertainties. The approach proposed would be to (1) compare and contrast different analytical techniques with each other and with computed speciation, (2) compare computed trace metal speciation with reliable measurements of solubility, potentiometry, and mean activity coefficients, and (3) compare different model calculations with each other for the same set of water analyses, especially where supplementary data on speciation already exist. A comparison and critique of analytical with chemical model speciation for a range of water samples would delineate the useful range and limitations of these different approaches to speciation. Both model calculations and analytical determinations have useful and different constraints on the range of possible speciation such that they can provide much better insight into speciation when used together. Major discrepancies in the thermodynamic databases of speciation models can be evaluated with the aid of analytical speciation, and when the thermodynamic models are highly consistent and reliable, the sources of error in the analytical speciation can be evaluated. Major thermodynamic discrepancies also can be evaluated by simulating solubility and activity coefficient data and testing various chemical models for their range of applicability. Until a comparative approach such as this is taken, trace metal speciation will remain highly uncertain and controversial.

Effective holographic models for QCD: Glueball spectrum and trace anomaly

NASA Astrophysics Data System (ADS)

Ballon-Bayona, Alfonso; Boschi-Filho, Henrique; Mamani, Luis A. H.; Miranda, Alex S.; Zanchin, Vilson T.

2018-02-01

We investigate effective holographic models for QCD arising from five-dimensional dilaton gravity. The models are characterized by a dilaton with a mass term in the UV, dual to a CFT deformation by a relevant operator, and quadratic in the IR. The UV constraint leads to the explicit breaking of conformal symmetry, whereas the IR constraint guarantees linear confinement. We propose semianalytic interpolations between the UV and the IR and obtain a spectrum for scalar and tensor glueballs consistent with lattice QCD data. We use the glueball spectrum as a physical constraint to find the evolution of the model parameters as the mass term goes to 0. Finally, we reproduce the universal result for the trace anomaly of deformed CFTs and propose a dictionary between this result and the QCD trace anomaly. A nontrivial consequence of this dictionary is the emergence of a β function similar to the two-loop perturbative QCD result.

Scaling up in the face of uncertainty - controls on trace gas fluxes in heterogeneous landscapes (Invited)

NASA Astrophysics Data System (ADS)

Bernhardt, E. S.; Helton, A. M.; Morse, J. L.; Poole, G. C.

2013-12-01

Wetlands are the dominant natural source of methane to the global atmosphere and can be important sites of either N2O emission or consumption. Changes in the spatial extent or inundation frequency and duration may lead to substantial shifts in the contribution of wetland ecosystems to global CH4 and N2O emissions. Trace gases are produced at the scale of individual microbes, each of which respond dynamically to the local availability of electron donors and acceptors. Within landscape patches, substrate supply and redox conditions are strongly controlled by variation in water table elevation and vertical hydrologic exchange. At the landscape scale, lateral exchange between patches and the extent and duration of inundation. Accurate estimates of trace gas emissions from wetlands are hard to estimate given the dynamic patterns of redox potential within the soil column and across the landscape that redistribute electron donors and acceptors both vertically and laterally. In five years of trace gas flux measurement and modeling at TOWER, a 440 ha restored wetland in coastal NC, we have developed both simulation and statistical models to estimate landscape level trace gas fluxes. Yet, because trace gas emissions are highly variable in both time and space, our qualitative and quantitative attempts at upscaling trace gas emissions typically generate estimates with extremely high uncertainty. In this talk we will explore the challenges inherent to the estimation of landscape scale trace gas fluxes at the scale of our individual ecosystem as well as the difficulties in extrapolating across multiple ecosystem studies.

National Aeronautics and Space Administration (NASA)/american Society for Engineering Education (ASEE) Summer Faculty Fellowship Program, 1991, Volume 2

NASA Technical Reports Server (NTRS)

Hyman, William A. (Editor); Goldstein, Stanley H. (Editor)

1991-01-01

The objectives of the program are: (1) to further the professional knowledge of qualified engineering and science faculty members; (2) to stimulate an exchange of ideas between participants and NASA; (3) to enrich and refresh the research and teaching activities of participant's institutions; and (4) to contribute to the research objectives of the NASA Centers. A compilation of the final reports on the research projects done by the faculty fellows during the summer of 1991 are presented. Some of the topics covered include: collision avoidance for rover vehicles, bioinstrumentation, neural nets, total quality management of flexible space structures, project scheduling, nondestructive tests, orthostatic intolerance to bedrest, hypersonic reentry simulation, measuring human energy expenditure, tribological models, trace element movement in Anarctic ice, gastrointestinal function, and computer assisted instruction.

The Approximate Bayesian Computation methods in the localization of the atmospheric contamination source

NASA Astrophysics Data System (ADS)

Kopka, P.; Wawrzynczak, A.; Borysiewicz, M.

2015-09-01

In many areas of application, a central problem is a solution to the inverse problem, especially estimation of the unknown model parameters to model the underlying dynamics of a physical system precisely. In this situation, the Bayesian inference is a powerful tool to combine observed data with prior knowledge to gain the probability distribution of searched parameters. We have applied the modern methodology named Sequential Approximate Bayesian Computation (S-ABC) to the problem of tracing the atmospheric contaminant source. The ABC is technique commonly used in the Bayesian analysis of complex models and dynamic system. Sequential methods can significantly increase the efficiency of the ABC. In the presented algorithm, the input data are the on-line arriving concentrations of released substance registered by distributed sensor network from OVER-LAND ATMOSPHERIC DISPERSION (OLAD) experiment. The algorithm output are the probability distributions of a contamination source parameters i.e. its particular location, release rate, speed and direction of the movement, start time and duration. The stochastic approach presented in this paper is completely general and can be used in other fields where the parameters of the model bet fitted to the observable data should be found.

The Virtual Learning Commons (VLC): Enabling Co-Innovation Across Disciplines

NASA Astrophysics Data System (ADS)

Pennington, D. D.; Gandara, A.; Del Rio, N.

2014-12-01

A key challenge for scientists addressing grand-challenge problems is identifying, understanding, and integrating potentially relevant methods, models and tools that that are rapidly evolving in the informatics community. Such tools are essential for effectively integrating data and models in complex research projects, yet it is often difficult to know what tools are available and it is not easy to understand or evaluate how they might be used in a given research context. The goal of the National Science Foundation-funded Virtual Learning Commons (VLC) is to improve awareness and understanding of emerging methodologies and technologies, facilitate individual and group evaluation of these, and trace the impact of innovations within and across teams, disciplines, and communities. The VLC is a Web-based social bookmarking site designed specifically to support knowledge exchange in research communities. It is founded on well-developed models of technology adoption, diffusion of innovation, and experiential learning. The VLC makes use of Web 2.0 (Social Web) and Web 3.0 (Semantic Web) approaches. Semantic Web approaches enable discovery of potentially relevant methods, models, and tools, while Social Web approaches enable collaborative learning about their function. The VLC is under development and the first release is expected Fall 2014.

Modeling ECM fiber formation: structure information extracted by analysis of 2D and 3D image sets

NASA Astrophysics Data System (ADS)

Wu, Jun; Voytik-Harbin, Sherry L.; Filmer, David L.; Hoffman, Christoph M.; Yuan, Bo; Chiang, Ching-Shoei; Sturgis, Jennis; Robinson, Joseph P.

2002-05-01

Recent evidence supports the notion that biological functions of extracellular matrix (ECM) are highly correlated to its structure. Understanding this fibrous structure is very crucial in tissue engineering to develop the next generation of biomaterials for restoration of tissues and organs. In this paper, we integrate confocal microscopy imaging and image-processing techniques to analyze the structural properties of ECM. We describe a 2D fiber middle-line tracing algorithm and apply it via Euclidean distance maps (EDM) to extract accurate fibrous structure information, such as fiber diameter, length, orientation, and density, from single slices. Based on a 2D tracing algorithm, we extend our analysis to 3D tracing via Euclidean distance maps to extract 3D fibrous structure information. We use computer simulation to construct the 3D fibrous structure which is subsequently used to test our tracing algorithms. After further image processing, these models are then applied to a variety of ECM constructions from which results of 2D and 3D traces are statistically analyzed.

Nuclear microscopy in trace-element biology — from cellular studies to the clinic

NASA Astrophysics Data System (ADS)

Lindh, Ulf

1993-05-01

The concentration and distribution of trace and major elements in cells are of great interest in cell biology. PIXE can provide elemental concentrations in the bulk of cells or organelles as other bulk techniques such as atomic absorption spectrophotometry and nuclear activation analysis. Supplementary information, perhaps more exciting, on the intracellular distributions of trace elements can be provided using nuclear microscopy. Intracellular distributions of trace elements in normal and malignant cells are presented. The toxicity of mercury and cadmium can be prevented by supplementation of the essential trace element selenium. Some results from an experimental animal model are discussed. The intercellular distribution of major and trace elements in isolated blood cells, as revealed by nuclear microscopy, provides useful clinical information. Examples are given concerning inflammatory connective-tissue diseases and the chronic fatigue syndrome.

Trace elements in patients on continuous renal replacement therapy.

PubMed

Broman, M; Bryland, A; Carlsson, O

2017-07-01

Intensive care patients with acute kidney injury (AKI), treated with continuous renal replacement therapy (CRRT) are at great risk for disturbances in plasma levels of trace elements due to the underlying illness, AKI, and dialysis. This study was performed to increase our knowledge regarding eight different trace elements during CRRT. Thirty one stable patients with AKI, treated with CRRT, were included in the study. Blood, plasma and effluent samples were taken at the start of the study and 36 ± 12 h later. A group of 48 healthy volunteers were included as controls and exposed to one fasting blood sample. Samples were analysed for trace elements (Cr, Cu, Mn, Co, Zn, Rb, Mo, Se) and standard blood chemistry. Blood and plasma levels of selenium and rubidium were significantly reduced while the levels of chromium, cobalt, and molybdenum were significantly increased in the study group vs. healthy volunteers. There was an uptake of chromium, manganese, and zinc. Molybdenum mass balance was around zero. For selenium, copper, and rubidium there were a marked loss. The low levels of selenium and rubidium in blood and plasma from CRRT patients, together with the loss via CRRT effluent, raises the possibility of the need for selenium supplementation in this group of patients, despite the unchanged levels during the short study period. Further investigations on the effect of additional administration of trace elements to CRRT patients would be of interest. © 2017 The Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Concentrations of trace elements in marine fish and its risk assessment in Malaysia.

PubMed

Agusa, Tetsuro; Kunito, Takashi; Yasunaga, Genta; Iwata, Hisato; Subramanian, Annamalai; Ismail, Ahmad; Tanabe, Shinsuke

2005-01-01

Concentrations of trace elements (V, Cr, Mn, Co, Cu, Zn, Ga, Se, Rb, Sr, Mo, Ag, Cd, Sn, Sb, Cs, Ba, Hg, Tl, Pb and Bi) were determined in muscle and liver of 12 species of marine fish collected from coastal areas in Malaysia. Levels of V, Cr, Mn, Co, Cu, Zn, Ga, Sr, Mo, Ag, Cd, Sn, Ba and Pb in liver were higher than those in muscle, whereas Rb and Cs concentrations showed the opposite trend. Positive correlations between concentrations in liver and muscle were observed for all the trace elements except Cu and Sn. Copper, Zn, Se, Ag, Cd, Cs and Hg concentrations in bigeye scads from the east coast of the Peninsular Malaysia were higher than those from the west, whereas V showed the opposite trend. The high concentration of V in the west coast might indicate oil contamination in the Strait of Malacca. To evaluate the health risk to Malaysian population through consumption of fish, intake rates of trace elements were estimated on the basis of the concentrations of trace elements in muscle of fish and daily fish consumption. Some specimens of the marine fish had Hg levels higher than the guideline value by US Environmental Protection Agency (EPA), indicating that consumption of these fish at the present rate may be hazardous to Malaysian people. To our knowledge, this is the first study on multielemental accumulation in marine fish from the Malaysian coast.

Efficient use of single molecule time traces to resolve kinetic rates, models and uncertainties

NASA Astrophysics Data System (ADS)

Schmid, Sonja; Hugel, Thorsten

2018-03-01

Single molecule time traces reveal the time evolution of unsynchronized kinetic systems. Especially single molecule Förster resonance energy transfer (smFRET) provides access to enzymatically important time scales, combined with molecular distance resolution and minimal interference with the sample. Yet the kinetic analysis of smFRET time traces is complicated by experimental shortcomings—such as photo-bleaching and noise. Here we recapitulate the fundamental limits of single molecule fluorescence that render the classic, dwell-time based kinetic analysis unsuitable. In contrast, our Single Molecule Analysis of Complex Kinetic Sequences (SMACKS) considers every data point and combines the information of many short traces in one global kinetic rate model. We demonstrate the potential of SMACKS by resolving the small kinetic effects caused by different ionic strengths in the chaperone protein Hsp90. These results show an unexpected interrelation between conformational dynamics and ATPase activity in Hsp90.

Concept and analytical basis for revistas - A fast, flexible computer/graphic system for generating periodic satellite coverage patterns

NASA Technical Reports Server (NTRS)

King, J. C.

1976-01-01

The generation of satellite coverage patterns is facilitated by three basic strategies: use of a simplified physical model, permitting rapid closed-form calculation; separation of earth rotation and nodal precession from initial geometric analyses; and use of symmetries to construct traces of indefinite length by repetitive transposition of basic one-quadrant elements. The complete coverage patterns generated consist of a basic nadir trace plus a number of associated off-nadir traces, one for each sensor swath edge to be delineated. Each trace is generated by transposing one or two of the basic quadrant elements into a circle on a nonrotating earth model sphere, after which the circle is expanded into the actual 'helical' pattern by adding rotational displacements to the longitude coordinates. The procedure adapts to the important periodic coverage cases by direct insertion of the characteristic integers N and R (days and orbital revolutions, respectively, per coverage period).

Regional dust storm modeling for health services: The case of valley fever

NASA Astrophysics Data System (ADS)

Sprigg, William A.; Nickovic, Slobodan; Galgiani, John N.; Pejanovic, Goran; Petkovic, Slavko; Vujadinovic, Mirjam; Vukovic, Ana; Dacic, Milan; DiBiase, Scott; Prasad, Anup; El-Askary, Hesham

2014-09-01

On 5 July 2011, a massive dust storm struck Phoenix, Arizona (USA), raising concerns for increased cases of valley fever (coccidioidomycosis, or, cocci). A quasi-operational experimental airborne dust forecast system predicted the event and provides model output for continuing analysis in collaboration with public health and air quality communities. An objective of this collaboration was to see if a signal in cases of valley fever in the region could be detected and traced to the storm - an American haboob. To better understand the atmospheric life cycle of cocci spores, the DREAM dust model (also herein, NMME-DREAM) was modified to simulate spore emission, transport and deposition. Inexact knowledge of where cocci-causing fungus grows, the low resolution of cocci surveillance and an overall active period for significant dust events complicate analysis of the effect of the 5 July 2011 storm. In the larger context of monthly to annual disease surveillance, valley fever statistics, when compared against PM10 observation networks and modeled airborne dust concentrations, may reveal a likely cause and effect. Details provided by models and satellites fill time and space voids in conventional approaches to air quality and disease surveillance, leading to land-atmosphere modeling and remote sensing that clearly mark a path to advance valley fever epidemiology, surveillance and risk avoidance.

Acquisition and processing pitfall with clipped traces in surface-wave analysis

NASA Astrophysics Data System (ADS)

Gao, Lingli; Pan, Yudi

2016-02-01

Multichannel analysis of surface waves (MASW) is widely used in estimating near-surface shear (S)-wave velocity. In the MASW method, generating a reliable dispersion image in the frequency-velocity (f-v) domain is an important processing step. A locus along peaks of dispersion energy at different frequencies allows the dispersion curves to be constructed for inversion. When the offsets are short, the output seismic data may exceed the dynamic ranges of geophones/seismograph, as a result of which, peaks and (or) troughs of traces will be squared off in recorded shot gathers. Dispersion images generated by the raw shot gathers with clipped traces would be contaminated by artifacts, which might be misidentified as Rayleigh-wave phase velocities or body-wave velocities and potentially lead to incorrect results. We performed some synthetic models containing clipped traces, and analyzed amplitude spectra of unclipped and clipped waves. The results indicate that artifacts in the dispersion image are dependent on the level of clipping. A real-world example also shows how clipped traces would affect the dispersion image. All the results suggest that clipped traces should be removed from the shot gathers before generating dispersion images, in order to pick accurate phase velocities and set reasonable initial inversion models.

Eastern Denali Fault surface trace map, eastern Alaska and Yukon, Canada

USGS Publications Warehouse

Bender, Adrian M.; Haeussler, Peter J.

2017-05-04

We map the 385-kilometer (km) long surface trace of the right-lateral, strike-slip Denali Fault between the Totschunda-Denali Fault intersection in Alaska, United States and the village of Haines Junction, Yukon, Canada. In Alaska, digital elevation models based on light detection and ranging and interferometric synthetic aperture radar data enabled our fault mapping at scales of 1:2,000 and 1:10,000, respectively. Lacking such resources in Yukon, we developed new structure-from-motion digital photogrammetry products from legacy aerial photos to map the fault surface trace at a scale of 1:10,000 east of the international border. The section of the fault that we map, referred to as the Eastern Denali Fault, did not rupture during the 2002 Denali Fault earthquake (moment magnitude 7.9). Seismologic, geodetic, and geomorphic evidence, along with a paleoseismic record of past ground-rupturing earthquakes, demonstrate Holocene and contemporary activity on the fault, however. This map of the Eastern Denali Fault surface trace complements other data sets by providing an openly accessible digital interpretation of the location, length, and continuity of the fault’s surface trace based on the accompanying digital topography dataset. Additionally, the digitized fault trace may provide geometric constraints useful for modeling earthquake scenarios and related seismic hazard.

Size Effect of Ground Patterns on FM-Band Cross-Talks between Two Parallel Signal Traces of Printed Circuit Boards for Vehicles

NASA Astrophysics Data System (ADS)

Iida, Michihira; Maeno, Tsuyoshi; Wang, Jianqing; Fujiwara, Osamu

Electromagnetic disturbances in vehicle-mounted radios are mainly caused by conducted noise currents flowing through wiring-harnesses from vehicle-mounted printed circuit boards (PCBs) with common slitting ground patterns. To suppress these kinds of noise currents, we previously measured them for simple two-layer PCBs with two parallel signal traces and slitting or non-slitting ground patterns, and then investigated by the FDTD simulation the reduction characteristics of the FM-band cross-talk noise levels between two parallel signal traces on six simple PCB models having different slitting ground or different divided ground patterns parallel to the traces. As a result, we found that the contributory factor for the FM-band cross-talk reduction is the reduction of mutual inductance between the two parallel traces, and also the noise currents from PCBs can rather be suppressed even if the size of the return ground becomes small. In this study, to investigate this finding, we further simulated the frequency characteristics of cross-talk reduction for additional six simple PCB models with different dividing dimensions ground patterns parallel to the traces, which revealed an interesting phenomenon that cross-talk reduction characteristics do not always decrease with increasing the width between the divided ground patterns.

Understanding Genetic Breast Cancer Risk: Processing Loci of the BRCA Gist Intelligent Tutoring System

PubMed Central

Wolfe, Christopher R.; Reyna, Valerie F.; Widmer, Colin L.; Cedillos-Whynott, Elizabeth M.; Brust-Renck, Priscila G; Weil, Audrey M.; Hu, Xiangen

2016-01-01

The BRCA Gist Intelligent Tutoring System helps women understand and make decisions about genetic testing for breast cancer risk. BRCA Gist is guided by Fuzzy-Trace Theory, (FTT) and built using AutoTutor Lite. It responds differently to participants depending on what they say. Seven tutorial dialogues requiring explanation and argumentation are guided by three FTT concepts: forming gist explanations in one’s own words, emphasizing decision-relevant information, and deliberating the consequences of decision alternatives. Participants were randomly assigned to BRCA Gist, a control, or impoverished BRCA Gist conditions removing gist explanation dialogues, argumentation dialogues, or FTT images. All BRCA Gist conditions performed significantly better than controls on knowledge, comprehension, and risk assessment. Significant differences in knowledge, comprehension, and fine-grained dialogue analyses demonstrate the efficacy of gist explanation dialogues. FTT images significantly increased knowledge. Providing more elements in arguments against testing correlated with increased knowledge and comprehension. PMID:28008216

Understanding Genetic Breast Cancer Risk: Processing Loci of the BRCA Gist Intelligent Tutoring System.

PubMed

Wolfe, Christopher R; Reyna, Valerie F; Widmer, Colin L; Cedillos-Whynott, Elizabeth M; Brust-Renck, Priscila G; Weil, Audrey M; Hu, Xiangen

2016-07-01

The BRCA Gist Intelligent Tutoring System helps women understand and make decisions about genetic testing for breast cancer risk. BRCA Gist is guided by Fuzzy-Trace Theory, (FTT) and built using AutoTutor Lite. It responds differently to participants depending on what they say. Seven tutorial dialogues requiring explanation and argumentation are guided by three FTT concepts: forming gist explanations in one's own words, emphasizing decision-relevant information, and deliberating the consequences of decision alternatives. Participants were randomly assigned to BRCA Gist , a control, or impoverished BRCA Gist conditions removing gist explanation dialogues, argumentation dialogues, or FTT images. All BRCA Gist conditions performed significantly better than controls on knowledge, comprehension, and risk assessment. Significant differences in knowledge, comprehension, and fine-grained dialogue analyses demonstrate the efficacy of gist explanation dialogues. FTT images significantly increased knowledge. Providing more elements in arguments against testing correlated with increased knowledge and comprehension.

Effective removal of trace thallium from surface water by nanosized manganese dioxide enhanced quartz sand filtration.

PubMed

Huangfu, Xiaoliu; Ma, Chengxue; Ma, Jun; He, Qiang; Yang, Chun; Zhou, Jian; Jiang, Jin; Wang, Yaan

2017-12-01

Thallium (Tl) has drawn wide concern due to its high toxicity even at extremely low concentrations, as well as its tendency for significant accumulation in the human body and other organisms. The need to develop effective strategies for trace Tl removal from drinking water is urgent. In this study, the removal of trace Tl (0.5 μg L -1 ) by conventional quartz sand filtration enhanced by nanosized manganese dioxide (nMnO 2 ) has been investigated using typical surface water obtained from northeast China. The results indicate that nMnO 2 enhanced quartz sand filtration could remove trace Tl(I) and Tl(III) efficiently through the adsorption of Tl onto nMnO 2 added to a water matrix and onto nMnO 2 attached on quartz sand surfaces. Tl(III)-HA complexes might be responsible for higher residual Tl(III) in the effluent compared to residual Tl(I). Competitive Ca 2+ cations inhibit Tl removal to a certain extent because the Ca 2+ ions will occupy the Tl adsorption site on nMnO 2 . Moreover, high concentrations of HA (10 mgTOC L -1 ), which notably complexes with and dissolves nMnO 2 (more than 78%), resulted in higher residual Tl(I) and Tl(III). Tl(III)-HA complexes might also enhance Tl(III) penetration to a certain extent. Additionally, a higher pH level could enhance the removal of trace Tl from surface water. Finally, a slight increase of residual Tl was observed after backwash, followed by the reduction of the Tl concentration in the effluent to a "steady" state again. The knowledge obtained here may provide a potential strategy for drinking water treatment plants threatened by trace Tl. Copyright © 2017. Published by Elsevier Ltd.

A high-throughput solid-phase extraction microchip combined with inductively coupled plasma-mass spectrometry for rapid determination of trace heavy metals in natural water.

PubMed

Shih, Tsung-Ting; Hsieh, Cheng-Chuan; Luo, Yu-Ting; Su, Yi-An; Chen, Ping-Hung; Chuang, Yu-Chen; Sun, Yuh-Chang

2016-04-15

Herein, a hyphenated system combining a high-throughput solid-phase extraction (htSPE) microchip with inductively coupled plasma-mass spectrometry (ICP-MS) for rapid determination of trace heavy metals was developed. Rather than performing multiple analyses in parallel for the enhancement of analytical throughput, we improved the processing speed for individual samples by increasing the operation flow rate during SPE procedures. To this end, an innovative device combining a micromixer and a multi-channeled extraction unit was designed. Furthermore, a programmable valve manifold was used to interface the developed microchip and ICP-MS instrumentation in order to fully automate the system, leading to a dramatic reduction in operation time and human error. Under the optimized operation conditions for the established system, detection limits of 1.64-42.54 ng L(-1) for the analyte ions were achieved. Validation procedures demonstrated that the developed method could be satisfactorily applied to the determination of trace heavy metals in natural water. Each analysis could be readily accomplished within just 186 s using the established system. This represents, to the best of our knowledge, an unprecedented speed for the analysis of trace heavy metal ions. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of tubing length on the dispersion correction of an arterially sampled input function for kinetic modeling in PET.

PubMed

O'Doherty, Jim; Chilcott, Anna; Dunn, Joel

2015-11-01

Arterial sampling with dispersion correction is routinely performed for kinetic analysis of PET studies. Because of the the advent of PET-MRI systems, non-MR safe instrumentation will be required to be kept outside the scan room, which requires the length of the tubing between the patient and detector to increase, thus worsening the effects of dispersion. We examined the effects of dispersion in idealized radioactive blood studies using various lengths of tubing (1.5, 3, and 4.5 m) and applied a well-known transmission-dispersion model to attempt to correct the resulting traces. A simulation study was also carried out to examine noise characteristics of the model. The model was applied to patient traces using a 1.5 m acquisition tubing and extended to its use at 3 m. Satisfactory dispersion correction of the blood traces was achieved in the 1.5 m line. Predictions on the basis of experimental measurements, numerical simulations and noise analysis of resulting traces show that corrections of blood data can also be achieved using the 3 m tubing. The effects of dispersion could not be corrected for the 4.5 m line by the selected transmission-dispersion model. On the basis of our setup, correction of dispersion in arterial sampling tubing up to 3 m by the transmission-dispersion model can be performed. The model could not dispersion correct data acquired using a 4.5 m arterial tubing.

The evolution of concepts of vestibular peripheral information processing: toward the dynamic, adaptive, parallel processing macular model

NASA Technical Reports Server (NTRS)

Ross, Muriel D.

2003-01-01

In a letter to Robert Hooke, written on 5 February, 1675, Isaac Newton wrote "If I have seen further than certain other men it is by standing upon the shoulders of giants." In his context, Newton was referring to the work of Galileo and Kepler, who preceded him. However, every field has its own giants, those men and women who went before us and, often with few tools at their disposal, uncovered the facts that enabled later researchers to advance knowledge in a particular area. This review traces the history of the evolution of views from early giants in the field of vestibular research to modern concepts of vestibular organ organization and function. Emphasis will be placed on the mammalian maculae as peripheral processors of linear accelerations acting on the head. This review shows that early, correct findings were sometimes unfortunately disregarded, impeding later investigations into the structure and function of the vestibular organs. The central themes are that the macular organs are highly complex, dynamic, adaptive, distributed parallel processors of information, and that historical references can help us to understand our own place in advancing knowledge about their complicated structure and functions.

Knowledge Synthesis with Maps of Neural Connectivity

PubMed Central

Tallis, Marcelo; Thompson, Richard; Russ, Thomas A.; Burns, Gully A. P. C.

2011-01-01

This paper describes software for neuroanatomical knowledge synthesis based on neural connectivity data. This software supports a mature methodology developed since the early 1990s. Over this time, the Swanson laboratory at USC has generated an account of the neural connectivity of the sub-structures of the hypothalamus, amygdala, septum, hippocampus, and bed nucleus of the stria terminalis. This is based on neuroanatomical data maps drawn into a standard brain atlas by experts. In earlier work, we presented an application for visualizing and comparing anatomical macro connections using the Swanson third edition atlas as a framework for accurate registration. Here we describe major improvements to the NeuARt application based on the incorporation of a knowledge representation of experimental design. We also present improvements in the interface and features of the data mapping components within a unified web-application. As a step toward developing an accurate sub-regional account of neural connectivity, we provide navigational access between the data maps and a semantic representation of area-to-area connections that they support. We do so based on an approach called “Knowledge Engineering from Experimental Design” (KEfED) model that is based on experimental variables. We have extended the underlying KEfED representation of tract-tracing experiments by incorporating the definition of a neuronanatomical data map as a measurement variable in the study design. This paper describes the software design of a web-application that allows anatomical data sets to be described within a standard experimental context and thus indexed by non-spatial experimental design features. PMID:22053155

Rapid effective trace-back capability value: a case study of foot-and-mouth in the Texas High Plains.

PubMed

Hagerman, Amy D; Ward, Michael P; Anderson, David P; Looney, J Chris; McCarl, Bruce A

2013-07-01

In this study our aim was to value the benefits of rapid effective trace-back capability-based on a livestock identification system - in the event of a foot and mouth disease (FMD) outbreak. We simulated an FMD outbreak in the Texas High Plains, an area of high livestock concentration, beginning in a large feedlot. Disease spread was simulated under different time dependent animal tracing scenarios. In the specific scenario modeled (incursion of FMD within a large feedlot, detection within 14 days and 90% effective tracing), simulation suggested that control costs of the outbreak significantly increase if tracing does not occur until day 10 as compared to the baseline of tracing on day 2. In addition, control costs are significantly increased if effectiveness were to drop to 30% as compared to the baseline of 90%. Results suggest potential benefits from rapid effective tracing in terms of reducing government control costs; however, a variety of other scenarios need to be explored before determining in which situations rapid effective trace-back capability is beneficial. Copyright © 2012 Elsevier B.V. All rights reserved.

Polarization Considerations for the Laser Interferometer Space Antenna

NASA Technical Reports Server (NTRS)

Waluschka, Eugene; Pedersen, Tracy R.; McNamara, Paul

2005-01-01

A polarization ray trace model of the Laser Interferometer Space Antenna s (LISA) optical path is being created. The model will be able to assess the effects of various polarizing elements and the optical coatings on the required, very long path length, picometer level dynamic interferometry. The computational steps are described. This should eliminate any ambiguities associated with polarization ray tracing of interferometers and provide a basis for determining the computer model s limitations and serve as a clearly defined starting point for future work.

Ray tracing through a hexahedral mesh in HADES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henderson, G L; Aufderheide, M B

In this paper we describe a new ray tracing method targeted for inclusion in HADES. The algorithm tracks rays through three-dimensional tetrakis hexahedral mesh objects, like those used by the ARES code to model inertial confinement experiments.

An optimized chronology for a stalagmite using seasonal trace element cycles from Shihua Cave, Beijing, North China

NASA Astrophysics Data System (ADS)

Ban, F.; Baker, A.; Marjo, C.; Duan, W.; Li, X.; Coleborn, K.; Akter, R.; Nagra, G.

2017-12-01

Stalagmites play an increasingly important role in the paleoclimatic reconstruction from seasonal to orbital timescales. One of the important reasons is that 230Th-dating can provide an absolute age enabling more accurate knowledge of the stalagmite growth. Additionally, annual trace element and optical layers can provide complementary method for determining a precise age and seasonal resolution. The trace elements of a stalagmite (XMG) in Beijing Shihua Cave, which is located in the East Asian monsoon region, were analyzed by laser ablation ICP-MS and compared with stalagmite laminae. The results show that: (1) the polished section of the topmost 4 mm of stalagmite XMG has obvious bi-optical layers (fluorescence and visible light) under a conventional transmission microscope. In the rest of the sample laminae are not observed using this method. (2) The variations of P/Ca, Sr/Ca, Ba/Ca, U/Ca and Mg/Ca show seasonal cycles throughout the sample. Sr/Ca is inversely correlated to P/Ca, and its peaks correspond with the (non-fluorescing) white layers, which deposit in late winter and spring when the climate is dry. The peaks of P/Ca match closely with the (fluorescing) opaque layers, because P is a soil-derived element which increases in the high rainfall monsoon period. (3) The PCA of the five trace elements showed that the cycles of PC1 could represent the annual cycle. This stalagmite was deposited over 148 ± 4 years through peak counting and the cycles of PC1 correspond well with the annual layers. Trace element cyclicity as shown by PC1 can increase the accuracy of stalagmite dating, especially in the absence of obvious laminae. The trace elements can be used as the marker of seasonal changes in a strongly contrasting wet-dry monsoon climate regime. Keywords: high-precision dating; LA-ICP-MS; stalagmite; trace elements; seasonal cycles; Shihua Cave

Spatiotemporal dynamics of the Ebola epidemic in Guinea and implications for vaccination and disease elimination: a computational modeling analysis.

PubMed

Ajelli, Marco; Merler, Stefano; Fumanelli, Laura; Pastore Y Piontti, Ana; Dean, Natalie E; Longini, Ira M; Halloran, M Elizabeth; Vespignani, Alessandro

2016-09-07

Among the three countries most affected by the Ebola virus disease outbreak in 2014-2015, Guinea presents an unusual spatiotemporal epidemic pattern, with several waves and a long tail in the decay of the epidemic incidence. Here, we develop a stochastic agent-based model at the level of a single household that integrates detailed data on Guinean demography, hospitals, Ebola treatment units, contact tracing, and safe burial interventions. The microsimulation-based model is used to assess the effect of each control strategy and the probability of elimination of the epidemic according to different intervention scenarios, including ring vaccination with the recombinant vesicular stomatitis virus-vectored vaccine. The numerical results indicate that the dynamics of the Ebola epidemic in Guinea can be quantitatively explained by the timeline of the implemented interventions. In particular, the early availability of Ebola treatment units and the associated isolation of cases and safe burials helped to limit the number of Ebola cases experienced by Guinea. We provide quantitative evidence of a strong negative correlation between the time series of cases and the number of traced contacts. This result is confirmed by the computational model that suggests that contact tracing effort is a key determinant in the control and elimination of the disease. In data-driven microsimulations, we find that tracing at least 5-10 contacts per case is crucial in preventing epidemic resurgence during the epidemic elimination phase. The computational model is used to provide an analysis of the ring vaccination trial highlighting its potential effect on disease elimination. We identify contact tracing as one of the key determinants of the epidemic's behavior in Guinea, and we show that the early availability of Ebola treatment unit beds helped to limit the number of Ebola cases in Guinea.

Infrasound ray tracing models for real events

NASA Astrophysics Data System (ADS)

Averbuch, Gil; Applbaum, David; Price, Colin; Ben Horin, Yochai

2015-04-01

Infrasound ray tracing models for real events C. Price1, G. Averbuch1, D. Applbaum1, Y. Ben Horin2 (1) Department of Geosciences, Tel Aviv University, Israel (2) Soreq Nuclear Research Center, Yavne, Israel Ray tracing models for infrasound propagation require two atmospheric parameters: the speed of sound profile and the wind profile. The usage of global atmospheric models for the speed of sound and wind profiles raises a fundamental question: can these models provide accurate results for modeling real events that have been detected by the infrasound arrays? Moreover, can these models provide accurate results for events that occurred during extreme weather conditions? We use 2D and 3D ray tracing models based on a modified Hamiltonian for a moving medium. Radiosonde measurements enable us to update the first 20 km of both speed of sound and wind profiles. The 2009 and 2011 Sayarim calibration experiments in Israel served us as a test for the models. In order to answer the question regarding the accuracy of the model during extreme weather conditions, we simulate infrasound sprite signals that were detected by the infrasound array in Mt. Meron, Israel. The results from modeling the Sayarim experiment provided us sufficient insight to conclude that ray tracing modeling can provide accurate results for real events that occurred during fair weather conditions. We conclude that the time delay in the model of the 2009 experiment is due to lack of accuracy in the wind and speed of sound profiles. Perturbed profiles provide accurate results. Earlier arrivals in 2011 are a result of the assumption that the earth is flat (no topography) and the use of local radiosonde measurements for the entire model. Using local radiosonde measurements only for part of the model and neglecting them on other parts prevents the early arrivals. We were able to determine which sprite is the one that got detected in the infrasound array as well as providing a height range for the sprite's height or the sprite's most energetic part. Even though atmospheric wind has a strong influence on infrasound wave propagation, our estimation is that for high altitude sources, extreme weather in the troposphere below has low impact on the trajectories of the waves.

Disconnected Diagrams in Lattice QCD

NASA Astrophysics Data System (ADS)

Gambhir, Arjun Singh

In this work, we present state-of-the-art numerical methods and their applications for computing a particular class of observables using lattice quantum chromodynamics (Lattice QCD), a discretized version of the fundamental theory of quarks and gluons. These observables require calculating so called "disconnected diagrams" and are important for understanding many aspects of hadron structure, such as the strange content of the proton. We begin by introducing the reader to the key concepts of Lattice QCD and rigorously define the meaning of disconnected diagrams through an example of the Wick contractions of the nucleon. Subsequently, the calculation of observables requiring disconnected diagrams is posed as the computationally challenging problem of finding the trace of the inverse of an incredibly large, sparse matrix. This is followed by a brief primer of numerical sparse matrix techniques that overviews broadly used methods in Lattice QCD and builds the background for the novel algorithm presented in this work. We then introduce singular value deflation as a method to improve convergence of trace estimation and analyze its effects on matrices from a variety of fields, including chemical transport modeling, magnetohydrodynamics, and QCD. Finally, we apply this method to compute observables such as the strange axial charge of the proton and strange sigma terms in light nuclei. The work in this thesis is innovative for four reasons. First, we analyze the effects of deflation with a model that makes qualitative predictions about its effectiveness, taking only the singular value spectrum as input, and compare deflated variance with different types of trace estimator noise. Second, the synergy between probing methods and deflation is investigated both experimentally and theoretically. Third, we use the synergistic combination of deflation and a graph coloring algorithm known as hierarchical probing to conduct a lattice calculation of light disconnected matrix elements of the nucleon at two different values of the lattice spacing. Finally, we employ these algorithms to do a high-precision study of strange sigma terms in light nuclei; to our knowledge this is the first calculation of its kind from Lattice QCD.

Disconnected Diagrams in Lattice QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gambhir, Arjun

In this work, we present state-of-the-art numerical methods and their applications for computing a particular class of observables using lattice quantum chromodynamics (Lattice QCD), a discretized version of the fundamental theory of quarks and gluons. These observables require calculating so called \\disconnected diagrams" and are important for understanding many aspects of hadron structure, such as the strange content of the proton. We begin by introducing the reader to the key concepts of Lattice QCD and rigorously define the meaning of disconnected diagrams through an example of the Wick contractions of the nucleon. Subsequently, the calculation of observables requiring disconnected diagramsmore » is posed as the computationally challenging problem of finding the trace of the inverse of an incredibly large, sparse matrix. This is followed by a brief primer of numerical sparse matrix techniques that overviews broadly used methods in Lattice QCD and builds the background for the novel algorithm presented in this work. We then introduce singular value deflation as a method to improve convergence of trace estimation and analyze its effects on matrices from a variety of fields, including chemical transport modeling, magnetohydrodynamics, and QCD. Finally, we apply this method to compute observables such as the strange axial charge of the proton and strange sigma terms in light nuclei. The work in this thesis is innovative for four reasons. First, we analyze the effects of deflation with a model that makes qualitative predictions about its effectiveness, taking only the singular value spectrum as input, and compare deflated variance with different types of trace estimator noise. Second, the synergy between probing methods and deflation is investigated both experimentally and theoretically. Third, we use the synergistic combination of deflation and a graph coloring algorithm known as hierarchical probing to conduct a lattice calculation of light disconnected matrix elements of the nucleon at two different values of the lattice spacing. Finally, we employ these algorithms to do a high-precision study of strange sigma terms in light nuclei; to our knowledge this is the first calculation of its kind from Lattice QCD.« less

Clitoral Sexual Arousal: Neuronal Tracing Study From the Clitoris Through the Spinal Tracts

PubMed Central

Martin-Alguacil, Nieves; Schober, Justine M.; Sengelaub, Dale R.; Pfaff, Donald W.; Shelley, Deborah N.

2009-01-01

Purpose Although genital tactile stimulation is regarded as a precursor to sexual arousal and a recognized initiator of central nervous system arousal, specific afferent neural pathways transmit sensory stimuli of arousal, beginning at the epithelial level on the clitoris and following the course of arousal stimuli through the central nervous system. Limited knowledge exists of the pathway from the cutaneous receptors of nerves originating in the epithelial tissue of the clitoris and continuing to spinal cord afferents. Such information may contribute to an understanding of sexual arousal, particularly in female vertebrates. We further defined the neural pathways and mechanisms responsible for arousal originating in the epithelium of the clitoris as well as related neural pathways to the spinal cord in a murine model. Materials and Methods We performed a comprehensive review of the published relevant clinical and histological material from human and nonhuman vertebrate studies. In 29 adult female C57B1/6 mice the distribution of pelvic nerves and vessels was mapped. Gross dissection of 4 female mice was facilitated by resin injection of the vascular system in 2. Neuronal tracing was performed in 25 mice that received clitoral injection of wheat germ agglutinin-horseradish peroxidase into the clitoris and were sacrificed after 72 to 96 hours. The spinal cord and periclitoral tissue were removed and fixed. Immunohistochemistry was performed. Results Gross anatomy of the mouse clitoris showed that pudendal and hypogastric nerves have a major role in the innervation of the external genitalia. Neuronal tracing revealed that the greatest nerve density was noted in the L5/6 spinal cord. The distribution extended from S1 to L2 with no labeling seen in the L3 spinal cord. Wheat germ agglutinin-horseradish peroxidase labeling was seen caudal in levels S1 through L4 and rostral in L2. Conclusions Understanding the neuroanatomy of the clitoris using a murine model may provide a valuable tool for the study of sexual arousal disorders and the further understanding of sexual function related to neural pathologies and trauma. PMID:18707740

Behaviors, Knowledge, and Education of Leave No Trace Principles in the Red River Gorge Rock Climbing Community

ERIC Educational Resources Information Center

Clark, Brian Gregory

2017-01-01

Rock Climbing is becoming a very popular and mainstream outdoor activity. With the growth in rock climbing comes an increase in the numbers of visitors that this sport attracts. The increase in visitor usage undoubtedly leads to an impact on the natural environment surrounding these rock climbing areas. Rock climbers acknowledge the impacts that…

"Enactment of Sámi Past in School Textbooks: Towards Multiple Pasts for Future Making"

ERIC Educational Resources Information Center

Ekeland, Torun Granstrøm

2017-01-01

The article examines the use of archaeological knowledge in elementary history textbooks used in Norwegian schools today. The aim is to determine whether we can find any traces of colonialism by reviewing how these narratives perform in interrelations within and between the Sámi and Norse pasts, and how the narratives allow for hybridity and…

General Education or Vocational Education in College Programs: The Long View.

ERIC Educational Resources Information Center

Parker, Franklin

The origins of general education are traced to the seven liberal arts in ancient Greece, showing the influence of Socrates, Plato, the Sophists, and others. Examined are the early conflict over the sources of knowledge and the uses to which it should be put. Relevance to the college curriculum is shown, and it is told how this was broadened to…

Integrating Epistemological Perspectives on Chemistry in Chemical Education: The Cases of Concept Duality, Chemical Language, and Structural Explanations

ERIC Educational Resources Information Center

Kaya, Ebru; Erduran, Sibel

2013-01-01

In this paper, we trace the work of some philosophers of chemistry to draw some implications for the improvement of chemical education. We examine some key features of chemical knowledge, and how these features are relevant for school chemistry teaching and learning. In particular, we examine Laszlo's ("Foundations of Chemistry"…

Comparative Effectiveness or Evidence-Based Medical Practice: "A Rose by Any Other Name..."

ERIC Educational Resources Information Center

Langer, Menachem; Langer, Nieli

2009-01-01

The goal of education and research in all disciplines is to develop critical thinking skills as a method for improving clinical decisionmaking. The emphasis on critical thinking is nothing new and can be traced back to ancient times when Socrates challenged his students to think about their knowledge, beliefs, and behaviors by interrogating them.…

Reforming the School Curriculum and Assessment in England to Match the Best in the World--A Cautionary Tale

ERIC Educational Resources Information Center

Steers, John

2014-01-01

This article traces the development of a new National Curriculum in England following the general election of 2010. The prevailing political ideology of an approach based on securing "core knowledge" in a limited range of preferred "academic" subjects and its deleterious impact on the arts in schools is described. The vigorous…

Tracing the Evolution of Educational Development through the POD Network's Institute for New Faculty Developers

ERIC Educational Resources Information Center

DiPietro, Michele

2014-01-01

Educational development is a unique professional field in that it is not defined by content taught in a single degree that qualifies individuals to be in it. The resulting heterogeneity in newcomers' knowledge and skills is addressed in different ways by different national networks. Since 1997, the POD Network has held a biennial Institute for New…

Conceptual Representations for Transfer: A Case Study Tracing Back and Looking Forward

ERIC Educational Resources Information Center

Sinha, Suparna; Gray, Steven; Hmelo-Silver, Cindy E.; Jordan, Rebecca; Eberbach, Catherine; Goel, Ashok; Rugaber, Spencer

2013-01-01

A primary goal of instruction is to prepare learners to transfer their knowledge and skills to new contexts, but how far this transfer goes is an open question. In the research reported here, we seek to explain a case of transfer through examining the processes by which a conceptual representation used to reason about complex systems was…

Regional/Urban Air Quality Modeling Assessment over China Using the Models-3/CMAQ System

NASA Astrophysics Data System (ADS)

Fu, J. S.; Jang, C. C.; Streets, D. G.; Li, Z.; Wang, L.; Zhang, Q.; Woo, J.; Wang, B.

2004-12-01

China is the world's most populous country with a fast growing economy that surges in energy comsumption. It has become the second largest energy consumer after the United States although the per capita level is much lower than those found in developed or developing countries. Air pollution has become one of the most important problems of megacities such as Beijing and Shanghai and has serious impacts on public health, causes urban and regional haze. The Models-3/CMAQ modeling application that has been conducted to simulate multi-pollutants in China is presented. The modeling domains cover East Asia (36-kmx36-km) including Japan, South Korea, Korea DPR, Indonesia, Thailand, India and Mongolia, East China (12-kmx12-km) and Beijing/Tianjing, Shanghai (4-kmx4-km). For this study, the Asian emission inventory based on the emission estimates of the year 2000 that supported the NASA TRACE-P program is used. However, the TRACE-P emission inventory was developed for a different purpose such as global modeling. TRACE-P emission inventory may not be practical in urban area. There is no China national emission inventory available. Therefore, TRACE-P emission inventory is used on the East Asia and East China domains. The 8 districts of Beijing and Shanghai local emissions inventory are used to replace TRACE-P in 4-km domains. The meteorological data for the Models-3/CMAQ run are extracted from MM5. The model simulation is performed during the period January 1-20 and July 1-20, 2001 that presented the winter and summer time for China areas. The preliminary model results are shown O3 concentrations are in the range of 80 -120 ppb in the urban area. Lower urban O3 concentrations are shown in Beijing areas, possibly due to underestimation of urban man-made VOC emissions in the TRACE-P inventory and local inventory. High PM2.5 (70ug/m3 in summer and 150ug/m3 in winter) were simulated over metropolitan & downwind areas with significant secondary constituents. More comprehensive simulations in the Beijing, Shanghai areas are presented with sensitivity analysis. A comparison against available ozone and PM measurement data in Beijing, Shanghai is presented. The local emission inventory improvement in China is to be suggested to investigate. The modeling configuration of the Beijing 4-km x 4-km domain is to demonstrate the development of cost-effective control strategies for the air pollution control such as 2008 Olympic Game air quality management plan.

Tracing Technological Development Trajectories: A Genetic Knowledge Persistence-Based Main Path Approach.

PubMed

Park, Hyunseok; Magee, Christopher L

2017-01-01

The aim of this paper is to propose a new method to identify main paths in a technological domain using patent citations. Previous approaches for using main path analysis have greatly improved our understanding of actual technological trajectories but nonetheless have some limitations. They have high potential to miss some dominant patents from the identified main paths; nonetheless, the high network complexity of their main paths makes qualitative tracing of trajectories problematic. The proposed method searches backward and forward paths from the high-persistence patents which are identified based on a standard genetic knowledge persistence algorithm. We tested the new method by applying it to the desalination and the solar photovoltaic domains and compared the results to output from the same domains using a prior method. The empirical results show that the proposed method can dramatically reduce network complexity without missing any dominantly important patents. The main paths identified by our approach for two test cases are almost 10x less complex than the main paths identified by the existing approach. The proposed approach identifies all dominantly important patents on the main paths, but the main paths identified by the existing approach miss about 20% of dominantly important patents.

Tracing Technological Development Trajectories: A Genetic Knowledge Persistence-Based Main Path Approach

PubMed Central

2017-01-01

The aim of this paper is to propose a new method to identify main paths in a technological domain using patent citations. Previous approaches for using main path analysis have greatly improved our understanding of actual technological trajectories but nonetheless have some limitations. They have high potential to miss some dominant patents from the identified main paths; nonetheless, the high network complexity of their main paths makes qualitative tracing of trajectories problematic. The proposed method searches backward and forward paths from the high-persistence patents which are identified based on a standard genetic knowledge persistence algorithm. We tested the new method by applying it to the desalination and the solar photovoltaic domains and compared the results to output from the same domains using a prior method. The empirical results show that the proposed method can dramatically reduce network complexity without missing any dominantly important patents. The main paths identified by our approach for two test cases are almost 10x less complex than the main paths identified by the existing approach. The proposed approach identifies all dominantly important patents on the main paths, but the main paths identified by the existing approach miss about 20% of dominantly important patents. PMID:28135304

Neuronal Spike Timing Adaptation Described with a Fractional Leaky Integrate-and-Fire Model

PubMed Central

Teka, Wondimu; Marinov, Toma M.; Santamaria, Fidel

2014-01-01

The voltage trace of neuronal activities can follow multiple timescale dynamics that arise from correlated membrane conductances. Such processes can result in power-law behavior in which the membrane voltage cannot be characterized with a single time constant. The emergent effect of these membrane correlations is a non-Markovian process that can be modeled with a fractional derivative. A fractional derivative is a non-local process in which the value of the variable is determined by integrating a temporal weighted voltage trace, also called the memory trace. Here we developed and analyzed a fractional leaky integrate-and-fire model in which the exponent of the fractional derivative can vary from 0 to 1, with 1 representing the normal derivative. As the exponent of the fractional derivative decreases, the weights of the voltage trace increase. Thus, the value of the voltage is increasingly correlated with the trajectory of the voltage in the past. By varying only the fractional exponent, our model can reproduce upward and downward spike adaptations found experimentally in neocortical pyramidal cells and tectal neurons in vitro. The model also produces spikes with longer first-spike latency and high inter-spike variability with power-law distribution. We further analyze spike adaptation and the responses to noisy and oscillatory input. The fractional model generates reliable spike patterns in response to noisy input. Overall, the spiking activity of the fractional leaky integrate-and-fire model deviates from the spiking activity of the Markovian model and reflects the temporal accumulated intrinsic membrane dynamics that affect the response of the neuron to external stimulation. PMID:24675903

Critical issues in trace gas biogeochemistry and global change.

PubMed

Beerling, David J; Nicholas Hewitt, C; Pyle, John A; Raven, John A

2007-07-15

The atmospheric composition of trace gases and aerosols is determined by the emission of compounds from the marine and terrestrial biospheres, anthropogenic sources and their chemistry and deposition processes. Biogenic emissions depend upon physiological processes and climate, and the atmospheric chemistry is governed by climate and feedbacks involving greenhouse gases themselves. Understanding and predicting the biogeochemistry of trace gases in past, present and future climates therefore demands an interdisciplinary approach integrating across physiology, atmospheric chemistry, physics and meteorology. Here, we highlight critical issues raised by recent findings in all of these key areas to provide a framework for better understanding the past and possible future evolution of the atmosphere. Incorporating recent experimental and observational findings, especially the influence of CO2 on trace gas emissions from marine algae and terrestrial plants, into earth system models remains a major research priority. As we move towards this goal, archives of the concentration and isotopes of N2O and CH4 from polar ice cores extending back over 650,000 years will provide a valuable benchmark for evaluating such models. In the Pre-Quaternary, synthesis of theoretical modelling with geochemical and palaeontological evidence is also uncovering the roles played by trace gases in episodes of abrupt climatic warming and ozone depletion. Finally, observations and palaeorecords across a range of timescales allow assessment of the Earth's climate sensitivity, a metric influencing our ability to decide what constitutes 'dangerous' climate change.

Efficient Unsteady Flow Visualization with High-Order Access Dependencies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jiang; Guo, Hanqi; Yuan, Xiaoru

We present a novel high-order access dependencies based model for efficient pathline computation in unsteady flow visualization. By taking longer access sequences into account to model more sophisticated data access patterns in particle tracing, our method greatly improves the accuracy and reliability in data access prediction. In our work, high-order access dependencies are calculated by tracing uniformly-seeded pathlines in both forward and backward directions in a preprocessing stage. The effectiveness of our proposed approach is demonstrated through a parallel particle tracing framework with high-order data prefetching. Results show that our method achieves higher data locality and hence improves the efficiencymore » of pathline computation.« less

Statistical Models for Averaging of the Pump–Probe Traces: Example of Denoising in Terahertz Time-Domain Spectroscopy

NASA Astrophysics Data System (ADS)

Skorobogatiy, Maksim; Sadasivan, Jayesh; Guerboukha, Hichem

2018-05-01

In this paper, we first discuss the main types of noise in a typical pump-probe system, and then focus specifically on terahertz time domain spectroscopy (THz-TDS) setups. We then introduce four statistical models for the noisy pulses obtained in such systems, and detail rigorous mathematical algorithms to de-noise such traces, find the proper averages and characterise various types of experimental noise. Finally, we perform a comparative analysis of the performance, advantages and limitations of the algorithms by testing them on the experimental data collected using a particular THz-TDS system available in our laboratories. We conclude that using advanced statistical models for trace averaging results in the fitting errors that are significantly smaller than those obtained when only a simple statistical average is used.

Modelling Seasonal Carbon Dynamics on Fen Peatlands

NASA Astrophysics Data System (ADS)

Giebels, Michael; Beyer, Madlen; Augustin, Jürgen; Roppel, Mario; Juszczak, Radoszlav; Serba, Tomasz

2010-05-01

In Germany more than 99 % of fens have lost their carbon and nutrient sink function due to heavy drainage and agricultural land use especially during the last decades and thus resulted in compression and heavy peat loss (CHARMAN 2002; JOOSTEN & CLARKE 2002; SUCCOW & JOOSTEN 2001; AUGUSTIN et al. 1996; KUNTZE 1993). Therefore fen peatlands play an important part (4-5 %) in the national anthropogenic trace gas budget. But only a small part of drained and agricultural used fens in NE Germany can be restored. Knowledge of the influence of land use to trace gas exchange is important for mitigation of the climate impact of the anthropogenic peatland use. We study carbon exchanges between soil and atmosphere on several fen peatland use areas at different sites in NE-Germany. Our research covers peatlands of supposed strongly climate forcing land use (cornfield and intensive pasture) and of probably less forcing, alternative types (meadow and extensive pasture) as well as rewetted (formerly drained) areas and near-natural sites like a low-degraded fen and a wetted alder woodland. We measured trace gas fluxes with manual and automatic chambers in periodic routines since spring 2007. The used chamber technique bases on DROESLER (2005). In total we now do research at 22 sites situated in 5 different locations covering agricultural, varying states of rewetted and near-natural treatments. We present results of at least 2 years of measurements on our site of varying types of agricultural land use. There we found significant differences in the annual carbon balances depending on the genesis of the observed sites and the seasonal dynamics. Annual balances were constructed by applying single respiration and photosynthesis CO2 models for each measurement campaign. These models were based on LLOYD-TAYLOR (1994) and Michaelis-Menten-Kinetics respectively. Crosswise comparison of different site treatments combined with the seasonal environmental observations give good hints for the identification of main flux driving parameters. Based on this procedure we developed a specific methane efflux model, mainly driven by the observed groundwater fluctuation and soil temperature. Depending on the observed timescale initial starting points of the model showed up to be remarkably different. We also will present suggestions for an advanced CO2 modelling as the present approaches are both based on single parameters. Generally our experiences from our field studies show that mono-parameterized models often fail in reproducing measured flux values. References: Augustin, J., Merbach, W., Käding, H., Schnidt, W. & Schalitz, G. 1996. Lachgas- und Methanemissionen aus degradierten Niedermoorstandorten Nordostdeutschlands unter dem Einfluß unterschiedlicher Bewirtschaftung. Alfed-Wegener-Stiftung (ed.): Von den Ressourcen zum Recycling: Geoanalytik-Geomanagement-Geoinformatik. Ernst & Sohn Verlag. Berlin Charman, D. 2002: Peatland and environmental change. John Wiley & Sons, LTD, Chichester Droesler, M. 2005. Trace Gas Exchange and climatic relevance of bog ecosystems, Southern Germany, phD-thesis, TU München, München Joosten, H. & Clarke, D. 2002: Wise use of mires and peatlands-background and principles including a framework for decision-making. International Mire Conservation Group and International Peat Society (eds.), Finland Kuntze 1993: Moore als Senken und Quellen für C und N, Mitt. Deutsche Bodenkundliche Gesellschaft 69, 277-280 Lloyd, J., Taylor, J. A. 1994. On the Temperature Dependence of Soil Respiration, Functional Ecology, Vol. 8, No. 3, pp. 315-323 Succow, M. & Joosten, H. 2001: Landschaftsökologische Moorkunde, 2nd edition, Schweizerbart'sche Verlagsbuchhandlung, Stuttgart

Fast solar radiation pressure modelling with ray tracing and multiple reflections

NASA Astrophysics Data System (ADS)

Li, Zhen; Ziebart, Marek; Bhattarai, Santosh; Harrison, David; Grey, Stuart

2018-05-01

Physics based SRP (Solar Radiation Pressure) models using ray tracing methods are powerful tools when modelling the forces on complex real world space vehicles. Currently high resolution (1 mm) ray tracing with secondary intersections is done on high performance computers at UCL (University College London). This study introduces the BVH (Bounding Volume Hierarchy) into the ray tracing approach for physics based SRP modelling and makes it possible to run high resolution analysis on personal computers. The ray tracer is both general and efficient enough to cope with the complex shape of satellites and multiple reflections (three or more, with no upper limit). In this study, the traditional ray tracing technique is introduced in the first place and then the BVH is integrated into the ray tracing. Four aspects of the ray tracer were tested for investigating the performance including runtime, accuracy, the effects of multiple reflections and the effects of pixel array resolution.Test results in runtime on GPS IIR and Galileo IOV (In Orbit Validation) satellites show that the BVH can make the force model computation 30-50 times faster. The ray tracer has an absolute accuracy of several nanonewtons by comparing the test results for spheres and planes with the analytical computations. The multiple reflection effects are investigated both in the intersection number and acceleration on GPS IIR, Galileo IOV and Sentinel-1 spacecraft. Considering the number of intersections, the 3rd reflection can capture 99.12 %, 99.14 % , and 91.34 % of the total reflections for GPS IIR, Galileo IOV satellite bus and the Sentinel-1 spacecraft respectively. In terms of the multiple reflection effects on the acceleration, the secondary reflection effect for Galileo IOV satellite and Sentinel-1 can reach 0.2 nm /s2 and 0.4 nm /s2 respectively. The error percentage in the accelerations magnitude results show that the 3rd reflection should be considered in order to make it less than 0.035 % . The pixel array resolution tests show that the dimensions of the components have to be considered when choosing the spacing of the pixel in order not to miss some components of the satellite in ray tracing. This paper presents the first systematic and quantitative study of the secondary and higher order intersection effects. It shows conclusively the effect is non-negligible for certain classes of misson.

Effect of Ground Patterns Size on FM-Band Cross-Talks between Two Parallel Signal Traces of Printed Circuit Boards for Vehicles

NASA Astrophysics Data System (ADS)

Iida, Michihira; Maeno, Tsuyoshi; Fujiwara, Osamu

It is well known that electromagnetic disturbances in vehicle-mounted radios are mainly caused by conducted noise currents flowing through wiring-harnesses from vehicle-mounted printed circuit boards (PCBs) with common ground patterns containing slits. To suppress the noise currents outflow from PCBs of these kinds, we previously measured noise currents outflow from simple two-layer PCBs having two parallel signal traces and different ground patterns with/without slits to reveal that making slits with open ends on the ground patterns in parallel with the traces can reduce the conducted noise currents. In the present study, with FDTD simulation, we investigated reduction effects of ground patterns size on the FM-band cross-talk noise levels between two parallel signal traces, by using four types of simple PCB models having different ground patterns formed in different numbers but containing the same planar dimension slits parallel to the traces, in addition to two types of PCB models with different ground patterns divided into two parts parallel to the traces. As a result, we found that the cross-talk noise currents for the above six types of PCBs decrease by 6.9-8.5dB compared to the PCB which has a plain ground with no slits. From this study, we got the finding that the contributing factor for the above mentioned cross-talk reduction relies on the reduction of mutual inductance between the two parallel traces. In addition, in case of this study, it is interesting to note that the noise currents outflow from PCBs can rather be suppressed when the size of the return ground of each signal trace is small.

Analytical, Experimental, and Modelling Studies of Lunar and Terrestrial Rocks

NASA Technical Reports Server (NTRS)

Haskin, Larry A.

1997-01-01

The goal of our research has been to understand the paths and the processes of planetary evolution that produced planetary surface materials as we find them. Most of our work has been on lunar materials and processes. We have done studies that obtain geological knowledge from detailed examination of regolith materials and we have reported implications for future sample-collecting and on-surface robotic sensing missions. Our approach has been to study a suite of materials that we have chosen in order to answer specific geologic questions. We continue this work under NAG5-4172. The foundation of our work has been the study of materials with precise chemical and petrographic analyses, emphasizing analysis for trace chemical elements. We have used quantitative models as tests to account for the chemical compositions and mineralogical properties of the materials in terms of regolith processes and igneous processes. We have done experiments as needed to provide values for geochemical parameters used in the models. Our models take explicitly into account the physical as well as the chemical processes that produced or modified the materials. Our approach to planetary geoscience owes much to our experience in terrestrial geoscience, where samples can be collected in field context and sampling sites revisited if necessary. Through studies of terrestrial analog materials, we have tested our ideas about the origins of lunar materials. We have been mainly concerned with the materials of the lunar highland regolith, their properties, their modes of origin, their provenance, and how to extrapolate from their characteristics to learn about the origin and evolution of the Moon's early igneous crust. From this work a modified model for the Moon's structure and evolution is emerging, one of globally asymmetric differentiation of the crust and mantle to produce a crust consisting mainly of ferroan and magnesian igneous rocks containing on average 70-80% plagioclase, with a large, mafic, trace-element-rich geochemical province, and a regolith that globally contains trace-element-rich material distributed from this province by the Imbrium basin-forming impact. This contrasts with earlier models of a concentrically zoned Moon with a crust of ferroan anorthosite overlying a layer of urKREEP overlying ultramafic cumulates. From this work, we have learned lessons useful for developing strategies for studying regolith materials that help to maximize the information available about both the evolution of the regolith and the igneous differentiation of the planet. We believe these lessons are useful in developing strategies for on-surface geological, mineralogical, and geochemical studies, as well. The main results of our work are given in the following brief summaries of major tasks. Detailed accounts of these results have been submitted in the annual progress reports.

Male-specific DNA markers provide genetic evidence of an XY chromosome system, a recombination arrest and allow the tracing of paternal lineages in date palm.

PubMed

Cherif, Emira; Zehdi, Salwa; Castillo, Karina; Chabrillange, Nathalie; Abdoulkader, Sabira; Pintaud, Jean-Christophe; Santoni, Sylvain; Salhi-Hannachi, Amel; Glémin, Sylvain; Aberlenc-Bertossi, Frédérique

2013-01-01

Whether sex chromosomes are differentiated is an important aspect of our knowledge of dioecious plants, such as date palm (Phoenix dactylifera). In this crop plant, the female individuals produce dates, and are thus the more valuable sex. However, there is no way to identify the sex of date palm plants before reproductive age, and the sex-determining mechanism is still unclear. To identify sex-linked microsatellite markers, we surveyed a set of 52 male and 55 female genotypes representing the geographical diversity of the species. We found three genetically linked loci that are heterozygous only in males. Male-specific alleles allowed us to identify the gender in 100% of individuals. These results confirm the existence of an XY chromosomal system with a nonrecombining XY-like region in the date palm genome. The distribution of Y haplotypes in western and eastern haplogroups allowed us to trace two male ancestral paternal lineages that account for all known Y diversity in date palm. The very low diversity associated with Y haplotypes is consistent with clonal paternal transmission of a nonrecombining male-determining region. Our results establish the date palm as a biological model with one of the most ancient sex chromosomes in flowering plants. © 2012 IRD. New Phytologist © 2013 New Phytologist Trust.

Goal-Driven Autonomy and Robust Architecture for Long-Duration Missions (Year 1: 1 July 2013 - 31 July 2014)

DTIC Science & Technology

2014-09-30

Mental Domain = Ω Goal Management goal change goal input World =Ψ Memory Mission & Goals( ) World Model (-Ψ) Episodic Memory Semantic Memory ...Activations Trace Meta-Level Control Introspective Monitoring Memory Reasoning Trace ( ) Strategies Episodic Memory Metaknowledge Self Model...it is from incorrect or missing memory associations (i.e., indices). Similarly, correct information may exist in the input stream, but may not be

A theoretical framework for measuring knowledge in screening decision aid trials.

PubMed

Smith, Sian K; Barratt, Alexandra; Trevena, Lyndal; Simpson, Judy M; Jansen, Jesse; McCaffery, Kirsten J

2012-11-01

To describe a theoretical framework for assessing knowledge about the possible outcomes of participating in bowel cancer screening for the faecal occult blood test. The content of the knowledge measure was based on the UK General Medical Council's screening guidelines and a theory-based approach to assessing gist knowledge (Fuzzy Trace Theory). It comprised conceptual and numeric questions to assess knowledge of the underlying construct (e.g. false positive concept) and the approximate numbers affected (e.g. likelihood of a false positive). The measure was used in a randomised controlled trial involving 530 adults with low education, to compare the impact of a bowel screening decision aid with a screening information booklet developed for the Australian Government National Bowel Cancer Screening Program. The numeric knowledge scale was particularly responsive to the effects of the decision aid; at follow-up decision aid participants' numeric knowledge was significantly greater than the controls (P<0.001). This contrasts with the conceptual knowledge scale which improved significantly in both groups from baseline to follow-up (P<0.001). Our theory-based knowledge measure was responsive to change in conceptual knowledge and to the effect on numeric knowledge of a decision aid. This theoretical framework has the potential to guide the development of knowledge measures in other screening settings. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Dynamic rupture modeling of thrust faults with parallel surface traces.

NASA Astrophysics Data System (ADS)

Peshette, P.; Lozos, J.; Yule, D.

2017-12-01

Fold and thrust belts (such as those found in the Himalaya or California Transverse Ranges) consist of many neighboring thrust faults in a variety of geometries. Active thrusts within these belts individually contribute to regional seismic hazard, but further investigation is needed regarding the possibility of multi-fault rupture in a single event. Past analyses of historic thrust surface traces suggest that rupture within a single event can jump up to 12 km. There is also observational precedent for long distance triggering between subparallel thrusts (e.g. the 1997 Harnai, Pakistan events, separated by 50 km). However, previous modeling studies find a maximum jumping rupture distance between thrust faults of merely 200 m. Here, we present a new dynamic rupture modeling parameter study that attempts to reconcile these differences and determine which geometrical and stress conditions promote jumping rupture. We use a community verified 3D finite element method to model rupture on pairs of thrust faults with parallel surface traces. We vary stress drop and fault strength to determine which conditions produce jumping rupture at different dip angles and different separations between surface traces. This parameter study may help to understand the likelihood of jumping rupture in real-world thrust systems, and may thereby improve earthquake hazard assessment.

Improvements of the Ray-Tracing Based Method Calculating Hypocentral Loci for Earthquake Location

NASA Astrophysics Data System (ADS)

Zhao, A. H.

2014-12-01

Hypocentral loci are very useful to reliable and visual earthquake location. However, they can hardly be analytically expressed when the velocity model is complex. One of methods numerically calculating them is based on a minimum traveltime tree algorithm for tracing rays: a focal locus is represented in terms of ray paths in its residual field from the minimum point (namely initial point) to low residual points (referred as reference points of the focal locus). The method has no restrictions on the complexity of the velocity model but still lacks the ability of correctly dealing with multi-segment loci. Additionally, it is rather laborious to set calculation parameters for obtaining loci with satisfying completeness and fineness. In this study, we improve the ray-tracing based numerical method to overcome its advantages. (1) Reference points of a hypocentral locus are selected from nodes of the model cells that it goes through, by means of a so-called peeling method. (2) The calculation domain of a hypocentral locus is defined as such a low residual area that its connected regions each include one segment of the locus and hence all the focal locus segments are respectively calculated with the minimum traveltime tree algorithm for tracing rays by repeatedly assigning the minimum residual reference point among those that have not been traced as an initial point. (3) Short ray paths without branching are removed to make the calculated locus finer. Numerical tests show that the improved method becomes capable of efficiently calculating complete and fine hypocentral loci of earthquakes in a complex model.

Ray Tracing through the Edge Focusing of Rectangular Benders and an Improved Model for the Los Alamos Proton Storage Ring

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kolski, Jeffrey S.; Barlow, David B.; Macek, Robert J.

2011-01-01

Particle ray tracing through simulated 3D magnetic fields was executed to investigate the effective quadrupole strength of the edge focusing of the rectangular bending magnets in the Los Alamos Proton Storage Ring (PSR). The particle rays receive a kick in the edge field of the rectangular dipole. A focal length may be calculated from the particle tracking and related to the fringe field integral (FINT) model parameter. This tech note introduces the baseline lattice model of the PSR and motivates the need for an improvement in the baseline model's vertical tune prediction, which differs from measurement by .05. An improvedmore » model of the PSR is created by modifying the fringe field integral parameter to those suggested by the ray tracing investigation. This improved model is then verified against measurement at the nominal PSR operating set point and at set points far away from the nominal operating conditions. Lastly, Linear Optics from Closed Orbits (LOCO) is employed in an orbit response matrix method for model improvement to verify the quadrupole strengths of the improved model.« less

Atomistic simulation of trace element incorporation into garnets - comparison with experimental garnet-melt partitioning data

NASA Astrophysics Data System (ADS)

van Westrenen, W.; Allan, N. L.; Blundy, J. D.; Purton, J. A.; Wood, B. J.

2000-05-01

We have studied the energetics of trace element incorporation into pure almandine (Alm), grossular (Gros), pyrope (Py) and spessartine (Spes) garnets (X 3Al 2Si 3O 12, with X = Fe, Ca, Mg, Mn respectively), by means of computer simulations of perfect and defective lattices in the static limit. The simulations use a consistent set of interatomic potentials to describe the non-Coulombic interactions between the ions, and take explicit account of lattice relaxation associated with trace element incorporation. The calculated relaxation (strain) energies Urel are compared to those obtained using the Brice (1975) model of lattice relaxation, and the results compared to experimental garnet-melt trace element partitioning data interpreted using the same model. Simulated Urel associated with a wide range of homovalent (Ni, Mg, Co, Fe, Mn, Ca, Eu, Sr, Ba) and charge-compensated heterovalent (Sc, Lu, Yb, Ho, Gd, Eu, Nd, La, Li, Na, K, Rb) substitutions onto the garnet X-sites show a near-parabolic dependence on trace element radius, in agreement with the Brice model. From application of the Brice model we derived apparent X-site Young's moduli EX(1+, 2+, 3+) and the 'ideal' ionic radii r0(1+, 2+, 3+), corresponding to the minima in plots of Urel vs. radius. For both homovalent and heterovalent substitutions r0 increases in the order Py-Alm-Spes-Gros, consistent with crystallographic data on the size of garnet X-sites and with the results of garnet-melt partitioning studies. Each end-member also shows a marked increase in both the apparent EX and r0 with increasing trace element charge ( Zc). The increase in EX is consistent with values obtained by fitting to the Brice model of experimental garnet-melt partitioning data. However, the increase in r0 with increasing Zc is contrary to experimental observation. To estimate the influence of melt on the energetics of trace element incorporation, solution energies ( Usol) were calculated for appropriate exchange reactions between garnet and melt, using binary and other oxides to simulate cation co-ordination environment in the melt. Usol also shows a parabolic dependence on trace element radius, with inter-garnet trends in EX and r0 similar to those found for relaxation energies. However, r0( i+) obtained from minima in plots of Usol vs. radius are located at markedly different positions, especially for heterovalent substitutions ( i = 1, 3). For each end-member garnet, r0 now decreases with increasing Zc, consistent with experiment. Furthermore, although different assumptions for trace element environment in the melt, e.g., REE 3+ (VI) vs. REE 3+ (VIII), lead to parabolae with differing curvatures and minima, relative differences between end-members are always preserved. We conclude that: 1. The simulated variation in r0 and EX between garnets is largely governed by the solid phase. This stresses the overriding influence of crystal local environment on trace element partitioning. 2. Simulations suggest r0 in garnets varies with trace element charge, as experimentally observed. 3. Absolute values of r0 and EX can be influenced by the presence and structure of a coexisting melt. Thus, quantitative relations between r0, E and crystal chemistry should be derived from well-constrained systematic mineral-melt partitioning studies, and cannot be predicted from crystal-structural data alone.

Lagrangian water mass tracing from pseudo-Argo, model-derived salinity, tracer and velocity data: An application to Antarctic Intermediate Water in the South Atlantic Ocean

NASA Astrophysics Data System (ADS)

Blanke, Bruno; Speich, Sabrina; Rusciano, Emanuela

2015-01-01

We use the tracer and velocity fields of a climatological ocean model to investigate the ability of Argo-like data to estimate accurately water mass movements and transformations, in the style of analyses commonly applied to the output of ocean general circulation model. To this end, we introduce an algorithm for the reconstruction of a fully non-divergent three-dimensional velocity field from the simple knowledge of the model vertical density profiles and 1000-m horizontal velocity components. The validation of the technique consists in comparing the resulting pathways for Antarctic Intermediate Water in the South Atlantic Ocean to equivalent reference results based on the full model information available for velocity and tracers. We show that the inclusion of a wind-induced Ekman pumping and of a well-thought-out expression for vertical velocity at the level of the intermediate waters is essential for the reliable reproduction of quantitative Lagrangian analyses. Neglecting the seasonal variability of the velocity and tracer fields is not a significant source of errors, at least well below the permanent thermocline. These results give us confidence in the success of the adaptation of the algorithm to true gridded Argo data for investigating the dynamics of flows in the ocean interior.

Influence of dissolved organic matter and manganese oxides on metal speciation in soil solution: A modelling approach.

PubMed

Schneider, Arnaud R; Ponthieu, Marie; Cancès, Benjamin; Conreux, Alexandra; Morvan, Xavier; Gommeaux, Maxime; Marin, Béatrice; Benedetti, Marc F

2016-06-01

Trace element (TE) speciation modelling in soil solution is controlled by the assumptions made about the soil solution composition. To evaluate this influence, different assumptions using Visual MINTEQ were tested and compared to measurements of free TE concentrations. The soil column Donnan membrane technique (SC-DMT) was used to estimate the free TE (Cd, Cu, Ni, Pb and Zn) concentrations in six acidic soil solutions. A batch technique using DAX-8 resin was used to fractionate the dissolved organic matter (DOM) into four fractions: humic acids (HA), fulvic acids (FA), hydrophilic acids (Hy) and hydrophobic neutral organic matter (HON). To model TE speciation, particular attention was focused on the hydrous manganese oxides (HMO) and the Hy fraction, ligands not considered in most of the TE speciation modelling studies in soil solution. In this work, the model predictions of free ion activities agree with the experimental results. The knowledge of the FA fraction seems to be very useful, especially in the case of high DOM content, for more accurately representing experimental data. Finally, the role of the manganese oxides and of the Hy fraction on TE speciation was identified and, depending on the physicochemical conditions of the soil solution, should be considered in future studies. Copyright © 2016 Elsevier Ltd. All rights reserved.

Distance measurement based on light field geometry and ray tracing.

PubMed

Chen, Yanqin; Jin, Xin; Dai, Qionghai

2017-01-09

In this paper, we propose a geometric optical model to measure the distances of object planes in a light field image. The proposed geometric optical model is composed of two sub-models based on ray tracing: object space model and image space model. The two theoretic sub-models are derived on account of on-axis point light sources. In object space model, light rays propagate into the main lens and refract inside it following the refraction theorem. In image space model, light rays exit from emission positions on the main lens and subsequently impinge on the image sensor with different imaging diameters. The relationships between imaging diameters of objects and their corresponding emission positions on the main lens are investigated through utilizing refocusing and similar triangle principle. By combining the two sub-models together and tracing light rays back to the object space, the relationships between objects' imaging diameters and corresponding distances of object planes are figured out. The performance of the proposed geometric optical model is compared with existing approaches using different configurations of hand-held plenoptic 1.0 cameras and real experiments are conducted using a preliminary imaging system. Results demonstrate that the proposed model can outperform existing approaches in terms of accuracy and exhibits good performance at general imaging range.

Managing knowledge integration in a national health-care crisis: lessons learned from combating SARS in Singapore.

PubMed

Devadoss, Paul Raj; Pan, Shan Ling; Singh, Shreyan

2005-06-01

The outbreak of Severe Acute Respiratory Syndrome is the first severe and readily transmissible disease to emerge in the 21st century. Often one new infection meant tracing of several people to monitor their health conditions as well. In Singapore, several agencies coordinated their efforts to quickly bring the outbreak under control. The current breed of health-care information systems (HCIS) was not sufficient to handle new information-sharing needs during the crisis. In this paper, we take a look at the measures taken during the crisis in Singapore through a knowledge integration perspective. This perspective reveals interesting implications for HCIS.

Investigation of mesoscale trace gas distributions across an Arctic tropopause fold affected by gravity wave activity

NASA Astrophysics Data System (ADS)

Woiwode, Wolfgang; Oelhaf, Hermann; Dörnbrack, Andreas; Bramberger, Martina; Diekmann, Christopher; Friedl-Vallon, Felix; Höpfner, Michael; Hoor, Peter; Johansson, Sören; Krause, Jens; Kunkel, Daniel; Orphal, Johannes; Preusse, Peter; Ruhnke, Roland; Schlage, Romy; Schröter, Jennifer; Sinnhuber, Björn-Martin; Ungermann, Jörn; Zahn, Andreas

2017-04-01

Tropopause folds are known of enabling efficient exchange of trace constituents between the stratosphere and troposphere. In particular, the modification of the vertical distributions of radiatively important H2O and other reactive trace gases associated with tropopause folds is relevant for accurate model simulations of the upper troposphere and lower stratosphere composition. During the POLSTRACC/GW-LCYCLE/SALSA flight on 12 January 2016, the HALO (High Altitude LOng range) aircraft crossed twice an extended tropopause fold in the vicinity of the Arctic polar vortex. At the same time, the ECMWF operational analysis shows that the meteorological scenario probed above Italy was accompanied by wide-spread gravity wave activity induced by north-westerly winds. Using high spectral resolution limb-observations by the GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere) spectrometer aboard HALO and associated observations, we investigate the vertical distributions of H2O, O3, temperature, and associated parameters across the tropopause fold. In combination with a high-resolution simulation by the ICON-ART (ICOsahedral Nonhydrostatic- Aerosol and Reactive Trace gases) model, we search for indications for irreversible trace gas exchange between the stratosphere and troposphere and the potential influence of gravity waves.

The Antarctic cold desert and the search for traces of life on Mars.

PubMed

Friedmann, E I

1986-01-01

The cryptoendolithic microorganisms that live inside rocks in the frigid Ross Desert of Antarctica can serve as a terrestrial model for what may have happened to life forms on Mars when the planet became dry and cold. Trace fossils of microbial rock colonization exist in Antarctica, and similar structures could have formed on Mars. In some respects, such trace fossils could be an easier target for life-detection systems than fossils of cellular structures.

The Antarctic cold desert and the search for traces of life on Mars

NASA Technical Reports Server (NTRS)

Friedmann, E. I.

1986-01-01

The cryptoendolithic microoganisms that live inside rocks in the frigid Ross Desert of Antarctica can serve as a terrestrial model for what may have happened to life forms on Mars when the planet became dry and cold. Trace fossils of microbial rock colonization exist in Antarctica, and similar structures could have formed on Mars. In some respects, such trace fossils could be an easier target for life-detection systems than fossils of cellular structures.

Trace element partitioning between ionic crystal and liquid

NASA Technical Reports Server (NTRS)

Tsang, T.; Philpotts, J. A.; Yin, L.

1978-01-01

The partitioning of trace elements between ionic crystals and the melt has been correlated with lattice energy of the host. The solid-liquid partition coefficient has been expressed in terms of the difference in relative ionic radius of the trace element and the homogeneous and heterogeneous strain of the host lattice. Predictions based on this model appear to be in general agreement with data for alkali nitrates and for rare-earth elements in natural garnet phenocrysts.

Seasonal Cyclicity in Trace Elements and Stable Isotopes of Modern Horse Enamel.

PubMed

de Winter, Niels J; Snoeck, Christophe; Claeys, Philippe

2016-01-01

The study of stable isotopes in fossil bioapatite has yielded useful results and has shown that bioapatites are able to faithfully record paleo-environmental and paleo-climatic parameters from archeological to geological timescales. In an effort to establish new proxies for the study of bioapatites, intra-tooth records of enamel carbonate stable isotope ratios from a modern horse are compared with trace element profiles measured using laboratory micro X-Ray Fluorescence scanning. Using known patterns of tooth eruption and the relationship between stable oxygen isotopes and local temperature seasonality, an age model is constructed that links records from six cheek upper right teeth from the second premolar to the third molar. When plotted on this age model, the trace element ratios from horse tooth enamel show a seasonal pattern with a small shift in phase compared to stable oxygen isotope ratios. While stable oxygen and carbon isotopes in tooth enamel are forced respectively by the state of the hydrological cycle and the animal's diet, we argue that the seasonal signal in trace elements reflects seasonal changes in dust intake and diet of the animal. The latter explanation is in agreement with seasonal changes observed in carbon isotopes of the same teeth. This external forcing of trace element composition in mammal tooth enamel implies that trace element ratios may be used as proxies for seasonal changes in paleo-environment and paleo-diet.

Seasonal Cyclicity in Trace Elements and Stable Isotopes of Modern Horse Enamel

PubMed Central

Snoeck, Christophe; Claeys, Philippe

2016-01-01

The study of stable isotopes in fossil bioapatite has yielded useful results and has shown that bioapatites are able to faithfully record paleo-environmental and paleo-climatic parameters from archeological to geological timescales. In an effort to establish new proxies for the study of bioapatites, intra-tooth records of enamel carbonate stable isotope ratios from a modern horse are compared with trace element profiles measured using laboratory micro X-Ray Fluorescence scanning. Using known patterns of tooth eruption and the relationship between stable oxygen isotopes and local temperature seasonality, an age model is constructed that links records from six cheek upper right teeth from the second premolar to the third molar. When plotted on this age model, the trace element ratios from horse tooth enamel show a seasonal pattern with a small shift in phase compared to stable oxygen isotope ratios. While stable oxygen and carbon isotopes in tooth enamel are forced respectively by the state of the hydrological cycle and the animal’s diet, we argue that the seasonal signal in trace elements reflects seasonal changes in dust intake and diet of the animal. The latter explanation is in agreement with seasonal changes observed in carbon isotopes of the same teeth. This external forcing of trace element composition in mammal tooth enamel implies that trace element ratios may be used as proxies for seasonal changes in paleo-environment and paleo-diet. PMID:27875538

Retrieval of trace gas concentrations over Summit Station, Greenland using moderate-resolution spectral infrared radiances

NASA Astrophysics Data System (ADS)

Bahramvash Shams, S.; Walden, V. P.; Turner, D. D.

2017-12-01

Measurements of trace gases at high temporal resolution are important for understanding variations and trends at high latitudes. Trace gases over Greenland can be influenced by both long-range transport from pollution sources as well as local chemical processes. Satellite retrievals are an important data source in the polar regions, but accurate ground-based measurements are needed for proper validation, especially in data sparse regions. A moderate-resolution (0.5 cm-1) Fourier transform infrared spectrometer (FTIR), the Polar Atmospheric Emitted Radiance Interferometer (P-AERI), has been operated at Summit Station, Greenland as part of the ICECAPS project since 2010. In this study, trace gas concentrations, including ozone, nitrous oxide, and methane are retrieved using different optimal estimation retrieval codes. We first present results of retrieved gases using synthetic spectra (from a radiative transfer model) that mimic P-AERI measurements to evaluate systematic errors in the inverse models. We also retrieve time series of trace gas concentrations during periods of clear skies over Summit. We investigate the amount of vertical information that can be obtained with moderate resolution spectra for each of the trace gases, and also the impact of the seasonal variation of atmospheric water vapor on the retrievals. Data from surface observations and ozonesondes obtained by the NOAA Global Monitoring Division are used to improve the retrievals and as validation.

Evolution of the knowledge system for agricultural development in the Yaqui Valley, Sonora, Mexico.

PubMed

McCullough, Ellen B; Matson, Pamela A

2016-04-26

Knowledge systems-networks of linked actors, organizations, and objects that perform a number of knowledge-related functions that link knowledge and know how with action-have played a key role in fostering agricultural development over the last 50 years. We examine the evolution of the knowledge system of the Yaqui Valley, Mexico, a region often described as the home of the green revolution for wheat, tracing changes in the functions of critical knowledge system participants, information flows, and research priorities. Most of the knowledge system's key players have been in place for many decades, although their roles have changed in response to exogenous and endogenous shocks and trends (e.g., drought, policy shifts, and price trends). The system has been agile and able to respond to challenges, in part because of the diversity of players (evolving roles of actors spanning research-decision maker boundaries) and also because of the strong and consistent role of innovative farmers. Although the agricultural research agenda in the Valley is primarily controlled from within the agricultural sector, outside voices have become an important influence in broadening development- and production-oriented perspectives to sustainability perspectives.

Evolution of the knowledge system for agricultural development in the Yaqui Valley, Sonora, Mexico

PubMed Central

McCullough, Ellen B.; Matson, Pamela A.

2016-01-01

Knowledge systems—networks of linked actors, organizations, and objects that perform a number of knowledge-related functions that link knowledge and know how with action—have played a key role in fostering agricultural development over the last 50 years. We examine the evolution of the knowledge system of the Yaqui Valley, Mexico, a region often described as the home of the green revolution for wheat, tracing changes in the functions of critical knowledge system participants, information flows, and research priorities. Most of the knowledge system's key players have been in place for many decades, although their roles have changed in response to exogenous and endogenous shocks and trends (e.g., drought, policy shifts, and price trends). The system has been agile and able to respond to challenges, in part because of the diversity of players (evolving roles of actors spanning research–decision maker boundaries) and also because of the strong and consistent role of innovative farmers. Although the agricultural research agenda in the Valley is primarily controlled from within the agricultural sector, outside voices have become an important influence in broadening development- and production-oriented perspectives to sustainability perspectives. PMID:21606365

An expert system/ion trap mass spectrometry approach for life support systems monitoring

NASA Technical Reports Server (NTRS)

Palmer, Peter T.; Wong, Carla M.; Yost, Richard A.; Johnson, Jodie V.; Yates, Nathan A.; Story, Michael

1992-01-01

Efforts to develop sensor and control system technology to monitor air quality for life support have resulted in the development and preliminary testing of a concept based on expert systems and ion trap mass spectrometry (ITMS). An ITMS instrument provides the capability to identify and quantitate a large number of suspected contaminants at trace levels through the use of a variety of multidimensional experiments. An expert system provides specialized knowledge for control, analysis, and decision making. The system is intended for real-time, on-line, autonomous monitoring of air quality. The key characteristics of the system, performance data and analytical capabilities of the ITMS instrument, the design and operation of the expert system, and results from preliminary testing of the system for trace contaminant monitoring are described.

Double Dissociation of Amygdala and Hippocampal Contributions to Trace and Delay Fear Conditioning

PubMed Central

Raybuck, Jonathan D.; Lattal, K. Matthew

2011-01-01

A key finding in studies of the neurobiology of learning memory is that the amygdala is critically involved in Pavlovian fear conditioning. This is well established in delay-cued and contextual fear conditioning; however, surprisingly little is known of the role of the amygdala in trace conditioning. Trace fear conditioning, in which the CS and US are separated in time by a trace interval, requires the hippocampus and prefrontal cortex. It is possible that recruitment of cortical structures by trace conditioning alters the role of the amygdala compared to delay fear conditioning, where the CS and US overlap. To investigate this, we inactivated the amygdala of male C57BL/6 mice with GABA A agonist muscimol prior to 2-pairing trace or delay fear conditioning. Amygdala inactivation produced deficits in contextual and delay conditioning, but had no effect on trace conditioning. As controls, we demonstrate that dorsal hippocampal inactivation produced deficits in trace and contextual, but not delay fear conditioning. Further, pre- and post-training amygdala inactivation disrupted the contextual but the not cued component of trace conditioning, as did muscimol infusion prior to 1- or 4-pairing trace conditioning. These findings demonstrate that insertion of a temporal gap between the CS and US can generate amygdala-independent fear conditioning. We discuss the implications of this surprising finding for current models of the neural circuitry involved in fear conditioning. PMID:21283812

The role of the medial prefrontal cortex in trace fear extinction

PubMed Central

Kwapis, Janine L.; Jarome, Timothy J.

2015-01-01

The extinction of delay fear conditioning relies on a neural circuit that has received much attention and is relatively well defined. Whether this established circuit also supports the extinction of more complex associations, however, is unclear. Trace fear conditioning is a better model of complex relational learning, yet the circuit that supports extinction of this memory has received very little attention. Recent research has indicated that trace fear extinction requires a different neural circuit than delay extinction; trace extinction requires the participation of the retrosplenial cortex, but not the amygdala, as noted in a previous study. Here, we tested the roles of the prelimbic and infralimbic regions of the medial prefrontal cortex in trace and delay fear extinction by blocking NMDA receptors during extinction learning. We found that the prelimbic cortex is necessary for trace, but not for delay fear extinction, whereas the infralimbic cortex is involved in both types of extinction. These results are consistent with the idea that trace fear associations require plasticity in multiple cortical areas for successful extinction. Further, the infralimbic cortex appears to play a role in extinction regardless of whether the animal was initially trained in trace or delay conditioning. Together, our results provide new information about how the neural circuits supporting trace and delay fear extinction differ. PMID:25512576

Two-lattice models of trace element behavior: A response

NASA Astrophysics Data System (ADS)

Ellison, Adam J. G.; Hess, Paul C.

1990-08-01

Two-lattice melt components of Bottinga and Weill (1972), Nielsen and Drake (1979), and Nielsen (1985) are applied to major and trace element partitioning between coexisting immiscible liquids studied by RYERSON and Hess (1978) and Watson (1976). The results show that (1) the set of components most successful in one system is not necessarily portable to another system; (2) solution non-ideality within a sublattice severely limits applicability of two-lattice models; (3) rigorous application of two-lattice melt components may yield effective partition coefficients for major element components with no physical interpretation; and (4) the distinction between network-forming and network-modifying components in the sense of the two-lattice models is not clear cut. The algebraic description of two-lattice models is such that they will most successfully limit the compositional dependence of major and trace element solution behavior when the effective partition coefficient of the component of interest is essentially the same as the bulk partition coefficient of all other components within its sublattice.

Sleep on your memory traces: How sleep effects can be explained by Act-In, a functional memory model.

PubMed

Cherdieu, Mélaine; Versace, Rémy; Rey, Amandine E; Vallet, Guillaume T; Mazza, Stéphanie

2018-06-01

Numerous studies have explored the effect of sleep on memory. It is well known that a period of sleep, compared to a similar period of wakefulness, protects memories from interference, improves performance, and might also reorganize memory traces in a way that encourages creativity and rule extraction. It is assumed that these benefits come from the reactivation of brain networks, mainly involving the hippocampal structure, as well as from their synchronization with neocortical networks during sleep, thereby underpinning sleep-dependent memory consolidation and reorganization. However, this memory reorganization is difficult to explain within classical memory models. The present paper aims to describe whether the influence of sleep on memory could be explained using a multiple trace memory model that is consistent with the concept of embodied cognition: the Act-In (activation-integration) memory model. We propose an original approach to the results observed in sleep research on the basis of two simple mechanisms, namely activation and integration. Copyright © 2017 Elsevier Ltd. All rights reserved.

Interpretation of Trace Gas Data Using Inverse Methods and Global Chemical Transport Models

NASA Technical Reports Server (NTRS)

Prinn, Ronald G.

1997-01-01

This is a theoretical research project aimed at: (1) development, testing, and refining of inverse methods for determining regional and global transient source and sink strengths for long lived gases important in ozone depletion and climate forcing, (2) utilization of inverse methods to determine these source/sink strengths which use the NCAR/Boulder CCM2-T42 3-D model and a global 3-D Model for Atmospheric Transport and Chemistry (MATCH) which is based on analyzed observed wind fields (developed in collaboration by MIT and NCAR/Boulder), (3) determination of global (and perhaps regional) average hydroxyl radical concentrations using inverse methods with multiple titrating gases, and, (4) computation of the lifetimes and spatially resolved destruction rates of trace gases using 3-D models. Important goals include determination of regional source strengths of methane, nitrous oxide, and other climatically and chemically important biogenic trace gases and also of halocarbons restricted by the Montreal Protocol and its follow-on agreements and hydrohalocarbons used as alternatives to the restricted halocarbons.

Modeling the reflectance of the lunar regolith by a new method combining Monte Carlo Ray tracing and Hapke's model with application to Chang'E-1 IIM data.

PubMed

Wong, Un-Hong; Wu, Yunzhao; Wong, Hon-Cheng; Liang, Yanyan; Tang, Zesheng

2014-01-01

In this paper, we model the reflectance of the lunar regolith by a new method combining Monte Carlo ray tracing and Hapke's model. The existing modeling methods exploit either a radiative transfer model or a geometric optical model. However, the measured data from an Interference Imaging spectrometer (IIM) on an orbiter were affected not only by the composition of minerals but also by the environmental factors. These factors cannot be well addressed by a single model alone. Our method implemented Monte Carlo ray tracing for simulating the large-scale effects such as the reflection of topography of the lunar soil and Hapke's model for calculating the reflection intensity of the internal scattering effects of particles of the lunar soil. Therefore, both the large-scale and microscale effects are considered in our method, providing a more accurate modeling of the reflectance of the lunar regolith. Simulation results using the Lunar Soil Characterization Consortium (LSCC) data and Chang'E-1 elevation map show that our method is effective and useful. We have also applied our method to Chang'E-1 IIM data for removing the influence of lunar topography to the reflectance of the lunar soil and to generate more realistic visualizations of the lunar surface.

A New Stochastic Approach to Predict Peak and Residual Shear Strength of Natural Rock Discontinuities

NASA Astrophysics Data System (ADS)

Casagrande, D.; Buzzi, O.; Giacomini, A.; Lambert, C.; Fenton, G.

2018-01-01

Natural discontinuities are known to play a key role in the stability of rock masses. However, it is a non-trivial task to estimate the shear strength of large discontinuities. Because of the inherent complexity to access to the full surface of the large in situ discontinuities, researchers or engineers tend to work on small-scale specimens. As a consequence, the results are often plagued by the well-known scale effect. A new approach is here proposed to predict shear strength of discontinuities. This approach has the potential to avoid the scale effect. The rationale of the approach is as follows: a major parameter that governs the shear strength of a discontinuity within a rock mass is roughness, which can be accounted for by surveying the discontinuity surface. However, this is typically not possible for discontinuities contained within the rock mass where only traces are visible. For natural surfaces, it can be assumed that traces are, to some extent, representative of the surface. It is here proposed to use the available 2D information (from a visible trace, referred to as a seed trace) and a random field model to create a large number of synthetic surfaces (3D data sets). The shear strength of each synthetic surface can then be estimated using a semi-analytical model. By using a large number of synthetic surfaces and a Monte Carlo strategy, a meaningful shear strength distribution can be obtained. This paper presents the validation of the semi-analytical mechanistic model required to support the new approach for prediction of discontinuity shear strength. The model can predict both peak and residual shear strength. The second part of the paper lays the foundation of a random field model to support the creation of synthetic surfaces having statistical properties in line with those of the data of the seed trace. The paper concludes that it is possible to obtain a reasonable estimate of peak and residual shear strength of the discontinuities tested from the information from a single trace, without having access to the whole surface.

Trace fossils in diatomaceous strata of Miocene Monterey Formation: their character and implications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Savdra, C.E.; Bottjer, D.J.

Younger parts of the Miocene Monterey Formation are commonly characterized by relatively unaltered diatomaceous strata. A common characteristic of these deposits is the preservation of varvelike lamination, indicative of deposition under anoxic or nearly anoxic conditions. Although laminated rock types are volumetrically dominant, bioturbated intervals are by no means rare, but little attention has been paid to the trace fossils themselves. Our study of trace fossils in the Monterey Formation demonstrated the significance of these biogenic structures in paleoenvironmental and paleoecologic analyses. In particular, trace fossils provide a means for detailed reconstruction of paleo-oxygenation conditions during Monterey deposition. Trace fossilsmore » in several Monterey sections exposed in central and southern California were examined in detail. At all localities, three major ichnofossil assemblages or ichnofacies were recognized: (1) Chondrites, (2) Planolites, and (3) Thalassinoides. The size and diversity of the three major ichnofacies and their lithologic associations suggest that the distribution of these facies is controlled primarily by the level of paleo-bottom water oxygenation. The Chondrites ichnofacies represents very low paleo-oxygen levels just above the anoxic threshold. The Planolites ichnofacies, with greater variety of larger burrow types, is indicative of slightly higher levels of oxygenation. Moderately to well-oxygenated conditions are suggested by the Thalassinoides ichnofacies. More detailed information on paleoenvironmental conditions can be gleaned by applying a refined trace-fossil tiering model. When used in detailed (centimeter-scale) vertical sequence analyses, this tiering model permits the translation of data on the composition, size parameters, and cross-cutting relationships of trace-fossil assemblages into relative paleo-oxygenation curves.« less

Logistics of community smallpox control through contact tracing and ring vaccination: a stochastic network model.

PubMed

Porco, Travis C; Holbrook, Karen A; Fernyak, Susan E; Portnoy, Diane L; Reiter, Randy; Aragón, Tomás J

2004-08-06

Previous smallpox ring vaccination models based on contact tracing over a network suggest that ring vaccination would be effective, but have not explicitly included response logistics and limited numbers of vaccinators. We developed a continuous-time stochastic simulation of smallpox transmission, including network structure, post-exposure vaccination, vaccination of contacts of contacts, limited response capacity, heterogeneity in symptoms and infectiousness, vaccination prior to the discontinuation of routine vaccination, more rapid diagnosis due to public awareness, surveillance of asymptomatic contacts, and isolation of cases. We found that even in cases of very rapidly spreading smallpox, ring vaccination (when coupled with surveillance) is sufficient in most cases to eliminate smallpox quickly, assuming that 95% of household contacts are traced, 80% of workplace or social contacts are traced, and no casual contacts are traced, and that in most cases the ability to trace 1-5 individuals per day per index case is sufficient. If smallpox is assumed to be transmitted very quickly to contacts, it may at times escape containment by ring vaccination, but could be controlled in these circumstances by mass vaccination. Small introductions of smallpox are likely to be easily contained by ring vaccination, provided contact tracing is feasible. Uncertainties in the nature of bioterrorist smallpox (infectiousness, vaccine efficacy) support continued planning for ring vaccination as well as mass vaccination. If initiated, ring vaccination should be conducted without delays in vaccination, should include contacts of contacts (whenever there is sufficient capacity) and should be accompanied by increased public awareness and surveillance.

A ray tracing model of gravity wave propagation and breakdown in the middle atmosphere

NASA Technical Reports Server (NTRS)

Schoeberl, M. R.

1985-01-01

Gravity wave ray tracing and wave packet theory is used to parameterize wave breaking in the mesosphere. Rays are tracked by solving the group velocity equations, and the interaction with the basic state is determined by considering the evolution of the packet wave action density. The ray tracing approach has a number of advantages over the steady state parameterization as the effects of gravity wave focussing and refraction, local dissipation, and wave response to rapid changes in the mean flow are more realistically considered; however, if steady state conditions prevail, the method gives identical results. The ray tracing algorithm is tested using both interactive and noninteractive models of the basic state. In the interactive model, gravity wave interaction with the polar night jet on a beta-plane is considered. The algorithm produces realistic polar night jet closure for weak topographic forcing of gravity waves. Planetary scale waves forced by local transfer of wave action into the basic flow in turn transfer their wave action into the zonal mean flow. Highly refracted rays are also found not to contribute greatly to the climatology of the mesosphere, as their wave action is severely reduced by dissipation during their lateral travel.

Analysis of the Effect of Electron Density Perturbations Generated by Gravity Waves on HF Communication Links

NASA Astrophysics Data System (ADS)

Fagre, M.; Elias, A. G.; Chum, J.; Cabrera, M. A.

2017-12-01

In the present work, ray tracing of high frequency (HF) signals in ionospheric disturbed conditions is analyzed, particularly in the presence of electron density perturbations generated by gravity waves (GWs). The three-dimensional numerical ray tracing code by Jones and Stephenson, based on Hamilton's equations, which is commonly used to study radio propagation through the ionosphere, is used. An electron density perturbation model is implemented to this code based upon the consideration of atmospheric GWs generated at a height of 150 km in the thermosphere and propagating up into the ionosphere. The motion of the neutral gas at these altitudes induces disturbances in the background plasma which affects HF signals propagation. To obtain a realistic model of GWs in order to analyze the propagation and dispersion characteristics, a GW ray tracing method with kinematic viscosity and thermal diffusivity was applied. The IRI-2012, HWM14 and NRLMSISE-00 models were incorporated to assess electron density, wind velocities, neutral temperature and total mass density needed for the ray tracing codes. Preliminary results of gravity wave effects on ground range and reflection height are presented for low-mid latitude ionosphere.

Trace Uranium Partitioning in a Multiphase Nano-FeOOH System

DOE Office of Scientific and Technical Information (OSTI.GOV)

McBriarty, Martin E.; Soltis, Jennifer A.; Kerisit, Sebastien

The characterization of trace elements in nanomaterials using extended X-ray absorption fine structure (EXAFS) spectroscopy constitutes a first step toward understanding how impurities or dopants affect the properties of the host phase. However, limitations to EXAFS interpretation complicate the analysis of trace concentrations of impurities that are distributed across multiple phases in a heterogeneous system. Ab initio molecular dynamics (AIMD)-informed EXAFS analysis was employed to investigate the immobilization of trace uranium associated with nanophase iron (oxyhydr)oxides, a model system for the geochemical sequestration of radiotoxic contaminants. The reductive transformation of ferrihydrite (Fe(OH)3) to nano-particulate iron oxyhydroxide minerals in the presencemore » of uranyl (UO2)2+(aq) resulted in the preferential incorporation of U into goethite (a-FeOOH) over lepidocrocite (g-FeOOH), even though reaction conditions favored the formation of excess lepidocrocite. This unexpected result is supported by atomically resolved transmission electron microscopy. Using this model system, we demonstrate how AIMD-informed EXAFS analysis lifts the strict statistical limitations of traditional shell-by-shell EXAFS modeling, enabling the detailed analysis of the local bonding environment, charge compensation mechanisms, and oxidation states of polyvalent impurities in complex multi-phase nano-systems.« less

National Ignition Facility main laser stray light analysis and control

DOE Office of Scientific and Technical Information (OSTI.GOV)

English, R E; Miller, J L; Peterson, G

1998-06-26

Stray light analysis has been carried out for the main laser section of the National Ignition Facility main laser section using a comprehensive non-sequential ray trace model supplemented with additional ray trace and diffraction propagation modeling. This paper describes the analysis and control methodology, gives examples of ghost paths and required tilted lenses, baffles, absorbers, and beam dumps, and discusses analysis of stray light "pencil beams" in the system.

Mathematic models for a ray tracing method and its applications in wireless optical communications.

PubMed

Zhang, Minglun; Zhang, Yangan; Yuan, Xueguang; Zhang, Jinnan

2010-08-16

This paper presents a new ray tracing method, which contains a whole set of mathematic models, and its validity is verified by simulations. In addition, both theoretical analysis and simulation results show that the computational complexity of the method is much lower than that of previous ones. Therefore, the method can be used to rapidly calculate the impulse response of wireless optical channels for complicated systems.

Temperature and composition dependencies of trace element partitioning - Olivine/melt and low-Ca pyroxene/melt

NASA Technical Reports Server (NTRS)

Colson, R. O.; Mckay, G. A.; Taylor, L. A.

1988-01-01

This paper presents a systematic thermodynamic analysis of the effects of temperature and composition on olivine/melt and low-Ca pyroxene/melt partitioning. Experiments were conducted in several synthetic basalts with a wide range of Fe/Mg, determining partition coefficients for Eu, Ca, Mn, Fe, Ni, Sm, Cd, Y, Yb, Sc, Al, Zr, and Ti and modeling accurately the changes in free energy for trace element exchange between crystal and melt as functions of the trace element size and charge. On the basis of this model, partition coefficients for olivine/melt and low-Ca pyroxene/melt can be predicted for a wide range of elements over a variety of basaltic bulk compositions and temperatures. Moreover, variations in partition coeffeicients during crystallization or melting can be modeled on the basis of changes in temperature and major element chemistry.

HARPA: A versatile three-dimensional Hamiltonian ray-tracing program for acoustic waves in the atmosphere above irregular terrain

NASA Astrophysics Data System (ADS)

Jones, R. M.; Riley, J. P.; Georges, T. M.

1986-08-01

The modular FORTRAN 77 computer program traces the three-dimensional paths of acoustic rays through continuous model atmospheres by numerically integrating Hamilton's equations (a differential expression of Fermat's principle). The user specifies an atmospheric model by writing closed-form formulas for its three-dimensional wind and temperature (or sound speed) distribution, and by defining the height of the reflecting terrain vs. geographic latitude and longitude. Some general-purpose models are provided, or users can readily design their own. In addition to computing the geometry of each raypath, HARPA can calculate pulse travel time, phase time, Doppler shift (if the medium varies in time), absorption, and geometrical path length. The program prints a step-by-step account of a ray's progress. The 410-page documentation describes the ray-tracing equations and the structure of the program, and provides complete instructions, illustrated by a sample case.

Tracing how normative messages may influence physical activity intention

USDA-ARS?s Scientific Manuscript database

Normative messages have been shown to increase intention to do physical activity (PA). We traced how 'positive' and 'negative' normative messages influenced PA intention by comparing constructs of the model of goal-directed behaviour with descriptive norms (MGDB+DN) across control and treatment grou...

Key drivers of airline loyalty.

PubMed

Dolnicar, Sara; Grabler, Klaus; Grün, Bettina; Kulnig, Anna

2011-10-01

This study investigates drivers of airline loyalty. It contributes to the body of knowledge in the area by investigating loyalty for a number of a priori market segments identified by airline management and by using a method which accounts for the multi-step nature of the airline choice process. The study is based on responses from 687 passengers. Results indicate that, at aggregate level, frequent flyer membership, price, the status of being a national carrier and the reputation of the airline as perceived by friends are the variables which best discriminate between travellers loyal to the airline and those who are not. Differences in drivers of airline loyalty for a number of segments were identified. For example, loyalty programs play a key role for business travellers whereas airline loyalty of leisure travellers is difficult to trace back to single factors. For none of the calculated models satisfaction emerged as a key driver of airline loyalty.

Randomizing world trade. II. A weighted network analysis

NASA Astrophysics Data System (ADS)

Squartini, Tiziano; Fagiolo, Giorgio; Garlaschelli, Diego

2011-10-01

Based on the misleading expectation that weighted network properties always offer a more complete description than purely topological ones, current economic models of the International Trade Network (ITN) generally aim at explaining local weighted properties, not local binary ones. Here we complement our analysis of the binary projections of the ITN by considering its weighted representations. We show that, unlike the binary case, all possible weighted representations of the ITN (directed and undirected, aggregated and disaggregated) cannot be traced back to local country-specific properties, which are therefore of limited informativeness. Our two papers show that traditional macroeconomic approaches systematically fail to capture the key properties of the ITN. In the binary case, they do not focus on the degree sequence and hence cannot characterize or replicate higher-order properties. In the weighted case, they generally focus on the strength sequence, but the knowledge of the latter is not enough in order to understand or reproduce indirect effects.