These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Overview of the Graphical User Interface for the GERMcode (GCR Event-Based Risk Model)  

NASA Technical Reports Server (NTRS)

The descriptions of biophysical events from heavy ions are of interest in radiobiology, cancer therapy, and space exploration. The biophysical description of the passage of heavy ions in tissue and shielding materials is best described by a stochastic approach that includes both ion track structure and nuclear interactions. A new computer model called the GCR Event-based Risk Model (GERM) code was developed for the description of biophysical events from heavy ion beams at the NASA Space Radiation Laboratory (NSRL). The GERMcode calculates basic physical and biophysical quantities of high-energy protons and heavy ions that have been studied at NSRL for the purpose of simulating space radiobiological effects. For mono-energetic beams, the code evaluates the linear-energy transfer (LET), range (R), and absorption in tissue equivalent material for a given Charge (Z), Mass Number (A) and kinetic energy (E) of an ion. In addition, a set of biophysical properties are evaluated such as the Poisson distribution of ion or delta-ray hits for a specified cellular area, cell survival curves, and mutation and tumor probabilities. The GERMcode also calculates the radiation transport of the beam line for either a fixed number of user-specified depths or at multiple positions along the Bragg curve of the particle. The contributions from primary ion and nuclear secondaries are evaluated. The GERMcode accounts for the major nuclear interaction processes of importance for describing heavy ion beams, including nuclear fragmentation, elastic scattering, and knockout-cascade processes by using the quantum multiple scattering fragmentation (QMSFRG) model. The QMSFRG model has been shown to be in excellent agreement with available experimental data for nuclear fragmentation cross sections, and has been used by the GERMcode for application to thick target experiments. The GERMcode provides scientists participating in NSRL experiments with the data needed for the interpretation of their experiments, including the ability to model the beam line, the shielding of samples and sample holders, and the estimates of basic physical and biological outputs of the designed experiments. We present an overview of the GERMcode GUI, as well as providing training applications.

Kim, Myung-Hee Y.; Cucinotta, Francis A.

2010-01-01

2

Mixed-field GCR Simulations for Radiobiological Research Using Ground Based Accelerators  

NASA Technical Reports Server (NTRS)

Space radiation is comprised of a large number of particle types and energies, which have differential ionization power from high energy protons to high charge and energy (HZE) particles and secondary neutrons produced by galactic cosmic rays (GCR). Ground based accelerators such as the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL) are used to simulate space radiation for radiobiology research and dosimetry, electronics parts, and shielding testing using mono-energetic beams for single ion species. As a tool to support research on new risk assessment models, we have developed a stochastic model of heavy ion beams and space radiation effects, the GCR Event-based Risk Model computer code (GERMcode). For radiobiological research on mixed-field space radiation, a new GCR simulator at NSRL is proposed. The NSRL-GCR simulator, which implements the rapid switching mode and the higher energy beam extraction to 1.5 GeV/u, can integrate multiple ions into a single simulation to create GCR Z-spectrum in major energy bins. After considering the GCR environment and energy limitations of NSRL, a GCR reference field is proposed after extensive simulation studies using the GERMcode. The GCR reference field is shown to reproduce the Z and LET spectra of GCR behind shielding within 20% accuracy compared to simulated full GCR environments behind shielding. A major challenge for space radiobiology research is to consider chronic GCR exposure of up to 3-years in relation to simulations with cell and animal models of human risks. We discuss possible approaches to map important biological time scales in experimental models using ground-based simulation with extended exposure of up to a few weeks and fractionation approaches at a GCR simulator.

Kim, Myung-Hee Y.; Rusek, Adam; Cucinotta, Francis A.

2014-01-01

3

Mixed-field GCR Simulations for Radiobiological Research using Ground Based Accelerators  

NASA Astrophysics Data System (ADS)

Space radiation is comprised of a large number of particle types and energies, which have differential ionization power from high energy protons to high charge and energy (HZE) particles and secondary neutrons produced by galactic cosmic rays (GCR). Ground based accelerators such as the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL) are used to simulate space radiation for radiobiology research and dosimetry, electronics parts, and shielding testing using mono-energetic beams for single ion species. As a tool to support research on new risk assessment models, we have developed a stochastic model of heavy ion beams and space radiation effects, the GCR Event-based Risk Model computer code (GERMcode). For radiobiological research on mixed-field space radiation, a new GCR simulator at NSRL is proposed. The NSRL-GCR simulator, which implements the rapid switching mode and the higher energy beam extraction to 1.5 GeV/u, can integrate multiple ions into a single simulation to create GCR Z-spectrum in major energy bins. After considering the GCR environment and energy limitations of NSRL, a GCR reference field is proposed after extensive simulation studies using the GERMcode. The GCR reference field is shown to reproduce the Z and LET spectra of GCR behind shielding within 20 percents accuracy compared to simulated full GCR environments behind shielding. A major challenge for space radiobiology research is to consider chronic GCR exposure of up to 3-years in relation to simulations with cell and animal models of human risks. We discuss possible approaches to map important biological time scales in experimental models using ground-based simulation with extended exposure of up to a few weeks and fractionation approaches at a GCR simulator.

Kim, Myung-Hee Y.; Rusek, Adam; Cucinotta, Francis

4

Overview of the Graphical User Interface for the GERM Code (GCR Event-Based Risk Model  

NASA Technical Reports Server (NTRS)

The descriptions of biophysical events from heavy ions are of interest in radiobiology, cancer therapy, and space exploration. The biophysical description of the passage of heavy ions in tissue and shielding materials is best described by a stochastic approach that includes both ion track structure and nuclear interactions. A new computer model called the GCR Event-based Risk Model (GERM) code was developed for the description of biophysical events from heavy ion beams at the NASA Space Radiation Laboratory (NSRL). The GERM code calculates basic physical and biophysical quantities of high-energy protons and heavy ions that have been studied at NSRL for the purpose of simulating space radiobiological effects. For mono-energetic beams, the code evaluates the linear-energy transfer (LET), range (R), and absorption in tissue equivalent material for a given Charge (Z), Mass Number (A) and kinetic energy (E) of an ion. In addition, a set of biophysical properties are evaluated such as the Poisson distribution of ion or delta-ray hits for a specified cellular area, cell survival curves, and mutation and tumor probabilities. The GERM code also calculates the radiation transport of the beam line for either a fixed number of user-specified depths or at multiple positions along the Bragg curve of the particle. The contributions from primary ion and nuclear secondaries are evaluated. The GERM code accounts for the major nuclear interaction processes of importance for describing heavy ion beams, including nuclear fragmentation, elastic scattering, and knockout-cascade processes by using the quantum multiple scattering fragmentation (QMSFRG) model. The QMSFRG model has been shown to be in excellent agreement with available experimental data for nuclear fragmentation cross sections, and has been used by the GERM code for application to thick target experiments. The GERM code provides scientists participating in NSRL experiments with the data needed for the interpretation of their experiments, including the ability to model the beam line, the shielding of samples and sample holders, and the estimates of basic physical and biological outputs of the designed experiments. We present an overview of the GERM code GUI, as well as providing training applications.

Kim, Myung-Hee; Cucinotta, Francis A.

2010-01-01

5

GCR environmental models I: Sensitivity analysis for GCR environments  

NASA Astrophysics Data System (ADS)

galactic cosmic ray (GCR) models are required to assess crew exposure during long-duration missions to the Moon or Mars. Many of these models have been developed and compared to available measurements, with uncertainty estimates usually stated to be less than 15%. However, when the models are evaluated over a common epoch and propagated through to effective dose, relative differences exceeding 50% are observed. This indicates that the metrics used to communicate GCR model uncertainty can be better tied to exposure quantities of interest for shielding applications. This is the first of three papers focused on addressing this need. In this work, the focus is on quantifying the extent to which each GCR ion and energy group, prior to entering any shielding material or body tissue, contributes to effective dose behind shielding. Results can be used to more accurately calibrate model-free parameters and provide a mechanism for refocusing validation efforts on measurements taken over important energy regions. Results can also be used as references to guide future nuclear cross-section measurements and radiobiology experiments. It is found that GCR with Z > 2 and boundary energies below 500 MeV/n induce less than 5% of the total effective dose behind shielding. This finding is important given that most of the GCR models are developed and validated against Advanced Composition Explorer/Cosmic Ray Isotope Spectrometer (ACE/CRIS) measurements taken below 500 MeV/n. It is therefore possible for two models to very accurately reproduce the ACE/CRIS data while inducing very different effective dose values behind shielding.

Slaba, Tony C.; Blattnig, Steve R.

2014-04-01

6

GCR Environmental Models I: Sensitivity Analysis for GCR Environments  

NASA Technical Reports Server (NTRS)

Accurate galactic cosmic ray (GCR) models are required to assess crew exposure during long-duration missions to the Moon or Mars. Many of these models have been developed and compared to available measurements, with uncertainty estimates usually stated to be less than 15%. However, when the models are evaluated over a common epoch and propagated through to effective dose, relative differences exceeding 50% are observed. This indicates that the metrics used to communicate GCR model uncertainty can be better tied to exposure quantities of interest for shielding applications. This is the first of three papers focused on addressing this need. In this work, the focus is on quantifying the extent to which each GCR ion and energy group, prior to entering any shielding material or body tissue, contributes to effective dose behind shielding. Results can be used to more accurately calibrate model-free parameters and provide a mechanism for refocusing validation efforts on measurements taken over important energy regions. Results can also be used as references to guide future nuclear cross-section measurements and radiobiology experiments. It is found that GCR with Z>2 and boundary energies below 500 MeV/n induce less than 5% of the total effective dose behind shielding. This finding is important given that most of the GCR models are developed and validated against Advanced Composition Explorer/Cosmic Ray Isotope Spectrometer (ACE/CRIS) measurements taken below 500 MeV/n. It is therefore possible for two models to very accurately reproduce the ACE/CRIS data while inducing very different effective dose values behind shielding.

Slaba, Tony C.; Blattnig, Steve R.

2014-01-01

7

Nuclear interactions in heavy ion transport and event-based risk models.  

PubMed

The physical description of the passage of heavy ions in tissue and shielding materials is of interest in radiobiology, cancer therapy and space exploration, including a human mission to Mars. Galactic cosmic rays (GCRs) consist of a large number of ion types and energies. Energy loss processes occur continuously along the path of heavy ions and are well described by the linear energy transfer (LET), straggling and multiple scattering algorithms. Nuclear interactions lead to much larger energy deposition than atomic-molecular collisions and alter the composition of heavy ion beams while producing secondary nuclei often in high multiplicity events. The major nuclear interaction processes of importance for describing heavy ion beams was reviewed, including nuclear fragmentation, elastic scattering and knockout-cascade processes. The quantum multiple scattering fragmentation model is shown to be in excellent agreement with available experimental data for nuclear fragmentation cross sections and is studied for application to thick target experiments. A new computer model, which was developed for the description of biophysical events from heavy ion beams at the NASA Space Radiation Laboratory (NSRL), called the GCR Event Risk-Based Model (GERMcode) is described. PMID:21242169

Cucinotta, Francis A; Plante, Ianik; Ponomarev, Artem L; Kim, Myung-Hee Y

2011-02-01

8

Isotopic Dependence of GCR Fluence behind Shielding  

NASA Technical Reports Server (NTRS)

In this paper we consider the effects of the isotopic composition of the primary galactic cosmic rays (GCR), nuclear fragmentation cross-sections, and isotopic-grid on the solution to transport models used for shielding studies. Satellite measurements are used to describe the isotopic composition of the GCR. For the nuclear interaction data-base and transport solution, we use the quantum multiple-scattering theory of nuclear fragmentation (QMSFRG) and high-charge and energy (HZETRN) transport code, respectively. The QMSFRG model is shown to accurately describe existing fragmentation data including proper description of the odd-even effects as function of the iso-spin dependence on the projectile nucleus. The principle finding of this study is that large errors (+/-100%) will occur in the mass-fluence spectra when comparing transport models that use a complete isotopic-grid (approx.170 ions) to ones that use a reduced isotopic-grid, for example the 59 ion-grid used in the HZETRN code in the past, however less significant errors (<+/-20%) occur in the elemental-fluence spectra. Because a complete isotopic-grid is readily handled on small computer workstations and is needed for several applications studying GCR propagation and scattering, it is recommended that they be used for future GCR studies.

Cucinotta, Francis A.; Wilson, John W.; Saganti, Premkumar; Kim, Myung-Hee Y.; Cleghorn, Timothy; Zeitlin, Cary; Tripathi, Ram K.

2006-01-01

9

GCR Environmental Models III: GCR Model Validation and Propagated Uncertainties in Effective Dose  

NASA Technical Reports Server (NTRS)

This is the last of three papers focused on quantifying the uncertainty associated with galactic cosmic rays (GCR) models used for space radiation shielding applications. In the first paper, it was found that GCR ions with Z>2 and boundary energy below 500 MeV/nucleon induce less than 5% of the total effective dose behind shielding. This is an important finding since GCR model development and validation have been heavily biased toward Advanced Composition Explorer/Cosmic Ray Isotope Spectrometer measurements below 500 MeV/nucleon. Weights were also developed that quantify the relative contribution of defined GCR energy and charge groups to effective dose behind shielding. In the second paper, it was shown that these weights could be used to efficiently propagate GCR model uncertainties into effective dose behind shielding. In this work, uncertainties are quantified for a few commonly used GCR models. A validation metric is developed that accounts for measurements uncertainty, and the metric is coupled to the fast uncertainty propagation method. For this work, the Badhwar-O'Neill (BON) 2010 and 2011 and the Matthia GCR models are compared to an extensive measurement database. It is shown that BON2011 systematically overestimates heavy ion fluxes in the range 0.5-4 GeV/nucleon. The BON2010 and BON2011 also show moderate and large errors in reproducing past solar activity near the 2000 solar maximum and 2010 solar minimum. It is found that all three models induce relative errors in effective dose in the interval [-20%, 20%] at a 68% confidence level. The BON2010 and Matthia models are found to have similar overall uncertainty estimates and are preferred for space radiation shielding applications.

Slaba, Tony C.; Xu, Xiaojing; Blattnig, Steve R.; Norman, Ryan B.

2014-01-01

10

Isotopic Effects in Nuclear Fragmentation and GCR Transport Problems  

NASA Technical Reports Server (NTRS)

Improving the accuracy of the galactic cosmic ray (GCR) environment and transport models is an important goal in preparing for studies of the projected risks and the efficiency of potential mitigations methods for space exploration. In this paper we consider the effects of the isotopic composition of the primary cosmic rays and the isotopic dependence of nuclear fragmentation cross sections on GCR transport models. Measurements are used to describe the isotopic composition of the GCR including their modulation throughout the solar cycle. The quantum multiple-scattering approach to nuclear fragmentation (QMSFRG) is used as the data base generator in order to accurately describe the odd-even effect in fragment production. Using the Badhwar and O'Neill GCR model, the QMSFRG model and the HZETRN transport code, the effects of the isotopic dependence of the primary GCR composition and on fragment production for transport problems is described for a complete GCR isotopic-grid. The principle finding of this study is that large errors ( 100%) will occur in the mass-flux spectra when comparing the complete isotopic-grid (141 ions) to a reduced isotopic-grid (59 ions), however less significant errors 30%) occur in the elemental-flux spectra. Because the full isotopic-grid is readily handled on small computer work-stations, it is recommended that they be used for future GCR studies.

Cucinotta, Francis A.

2002-01-01

11

Host Event Based Network Monitoring  

SciTech Connect

The purpose of INL’s research on this project is to demonstrate the feasibility of a host event based network monitoring tool and the effects on host performance. Current host based network monitoring tools work on polling which can miss activity if it occurs between polls. Instead of polling, a tool could be developed that makes use of event APIs in the operating system to receive asynchronous notifications of network activity. Analysis and logging of these events will allow the tool to construct the complete real-time and historical network configuration of the host while the tool is running. This research focused on three major operating systems commonly used by SCADA systems: Linux, WindowsXP, and Windows7. Windows 7 offers two paths that have minimal impact on the system and should be seriously considered. First is the new Windows Event Logging API, and, second, Windows 7 offers the ALE API within WFP. Any future work should focus on these methods.

Jonathan Chugg

2013-01-01

12

Modulation of GCR in Various Types of Helispheric Magnetic Field  

NASA Astrophysics Data System (ADS)

We make an attempt to compare the modulation of galactic cosmic rays (GCR) as the result of various assumptions referred to heliospheric magnetic field (HMF). The steady state version of 3D Parker cosmic ray transport equation (TPE), with drift included, is solved num erically in the spherically symmetric heliosphere. We take into account four cases of the possible magnetic field configuration: standard Parker HMF, Parker field with modifications in polar direction done by Jokippi and K ta (2) and Smith ando Bieber (3) , Fisk type of field (4). In the last one we assume the existence north and south polar coronal holes in the inner corona with central point inclined from the rotation of the Sun. At the polar regions of the heliosphere the isotropic diffusion of GCR is assumed. The results of calculation s will be discussed in detail. The (4) model more reduces an acces s of galactic particles from polar direction into solar system than others.

Kobylinski, Z.; Bochorishvili, T.

13

A SIMPLE EVENT-BASED PID CONTROLLER  

Microsoft Academic Search

A simple event-based PID controller is presented. It is shown that it is possible to obtain large reductions in CPU utilization with only minor control performance degradation. Simulations on a double-tank process are presented.

Karl-Erik Årzén

1999-01-01

14

Event-based control for memristive systems  

NASA Astrophysics Data System (ADS)

This paper studies the event-based control for memristive systems. Consider the state-dependent properties of the memristor, a new fuzzy model employing parallel distributed compensation (PDC) gives a new way to linearize complicated memristive system with only two subsystems. As the existence of uncertainties of memristor and to reduce the amount of communication, event-based control algorithm to stabilize memristive systems and extend the results to systems with signal quantization and networked induced delays. Through the fuzzy modeling and distributed event-based control, there are three main advantages: (1) only two linear subsystems are considered to reduce the numbers of fuzzy rules from 2n to 2×n as for traditional Takagi-Sugeno fuzzy model, n is the number of memristive subsystems; (2) the memristive subsystem is triggered at its own event time, which reduces communication burdens and lowers the controller updating frequency; (3) the effects of quantization and time delays are taken into account.

Wen, Shiping; Zeng, Zhigang; Huang, Tingwen

2014-10-01

15

Model Estimated GCR Particle Flux Variation - Assessment with CRIS Data  

NASA Astrophysics Data System (ADS)

We present model calculated particle flux as a function of time during the current solar cycle along with the comparisons from the ACE/CRIS data and the Mars/MARIE data. In our model calculations we make use of the NASA's HZETRN (High Z and Energy Transport) code along with the nuclear fragmentation cross sections that are described by the quantum multiple scattering (QMSFRG) model. The time dependant variation of the GCR environment is derived making use of the solar modulation potential, phi. For the past ten years, Advanced Composition Explorer (ACE) has been in orbit at the Sun- Earth libration point (L1). Data from the Cosmic Ray Isotope Spectrometer (CRIS) instrument onboard the ACE spacecraft has been available from 1997 through the present time. Our model calculated particle flux showed high degree of correlation during the earlier phase of the current solar cycle (2003) in the lower Z region within 15

Saganti, Premkumar

16

Landscape of international event-based biosurveillance  

PubMed Central

Event-based biosurveillance is a scientific discipline in which diverse sources of data, many of which are available from the Internet, are characterized prospectively to provide information on infectious disease events. Biosurveillance complements traditional public health surveillance to provide both early warning of infectious disease events and situational awareness. The Global Health Security Action Group of the Global Health Security Initiative is developing a biosurveillance capability that integrates and leverages component systems from member nations. This work discusses these biosurveillance systems and identifies needed future studies. PMID:22460393

Hartley, DM; Nelson, NP; Walters, R; Arthur, R; Yangarber, R; Madoff, L; Linge, JP; Mawudeku, A; Collier, N; Brownstein, JS; Thinus, G; Lightfoot, N

2010-01-01

17

Event-Based Science: Remote Sensing Activities  

NSDL National Science Digital Library

Event-Based Science is a new way to teach science by using newsworthy events to establish the relevance of science topics. Interviews, photographs, web pages, and inquiry-based science activities create a desire to know more about these topics. This collection of activities deals with such topics as damage to agriculture caused by drought, the recovery of forests after a fire, and flooding and the migration of river channels. There are also activities on earthquake hazards, hurricane tracking, the impacts of oil spills, and how to plan an escape route to avoid a volcanic mudflow. Each of these activities uses NASA imagery, in particular LandSat images.

2007-03-15

18

CENDA: Camouflage Event Based Malicious Node Detection Architecture  

E-print Network

CENDA: Camouflage Event Based Malicious Node Detection Architecture Kanthakumar Pongaliur Li Xiao type of attack and lacks a unified architecture to identify multiple attack types. Camouflage Event Based Malicious Node Detection Architecture (CENDA) is a proactive architecture that uses camouflage

Liu, Alex X.

19

A New gcrR-Deficient Streptococcus mutans Mutant for Replacement Therapy of Dental Caries  

PubMed Central

Background. gcrR gene acts as a negative regulator related to sucrose-dependent adherence in S. mutans. It is constructive to test the potential capacity of mutans with gcrR gene deficient in bacteria replacement therapy. Methods. In this study, we constructed the mutant by homologous recombination. The morphological characteristics of biofilms were analyzed by confocal laser scanning microscopy. S. mutans UA159 and the mutant MS-gcrR-def were inoculated, respectively, or together for competitive testing in vitro and in rat model. Results. Adhesion assay showed that the adhesion ability of the mutant increased relative to the wild type, especially in the early stage. MS-gcrR-def out-competed S. mutans UA159 in vitro biofilm, and correspondingly coinfection displayed significantly fewer caries in vivo. The former possessed both a lower level of acid production and a stronger colonization potential than S. mutans UA159. Conclusion. These findings demonstrate that MS-gcrR-def appears to be a good candidate for replacement therapy. PMID:24453853

Pan, Wenting; Mao, Tiantian; Xu, Qing-an; Shao, Jin; Liu, Chang; Fan, Mingwen

2013-01-01

20

An Event-Based PID Controller With Low Computational Cost  

E-print Network

An Event-Based PID Controller With Low Computational Cost Sylvain Durand and Nicolas Marchand Ne.marchand@gipsa-lab.inpg.fr Abstract: In this paper, some improvements of event-based PID controllers are proposed. These controllers, contrary to a time-triggered one which calculates the control signal at each sampling time, calculate

Paris-Sud XI, Université de

21

Discrete-event based simulation conceptual modeling of systems biology  

Microsoft Academic Search

The protein production from DNA to protein via RNA is a very complicated process, which could be called central dogma. In this paper, we used event based simulation to model, simulate, analyze and specify the three main processes that are involved in the process of protein production: replication, transcription, and translation. The whole control flow of event-based simulation is composed

Joe W. Yeol; Issac Barjis; Yeong S. Ryu; Joseph Barjis

2005-01-01

22

On the GCR intensity and the inversion of the heliospheric magnetic field during the periods of the high solar activity  

E-print Network

We consider the long-term behavior of the solar and heliospheric parameters and the GCR intensity in the periods of high solar activity and the inversions of heliospheric magnetic field (HMF). The classification of the HMF polarity structures and the meaning of the HMF inversion are discussed. The procedure is considered how to use the known HMF polarity distribution for the GCR intensity modeling during the periods of high solar activity. We also briefly discuss the development and the nearest future of the sunspot activity and the GCR intensity in the current unusual solar cycle 24.

Krainev, M B

2014-01-01

23

Badhwar-O'Neil 2007 Galactic Cosmic Ray (GCR) Model Using Advanced Composition Explorer (ACE) Measurements for Solar Cycle 23  

NASA Technical Reports Server (NTRS)

Advanced Composition Explorer (ACE) satellite measurements of the galactic cosmic ray flux and correlation with the Climax Neutron Monitor count over Solar Cycle 23 are used to update the Badhwar O'Neill Galactic Cosmic Ray (GCR) model.

ONeill, P. M.

2007-01-01

24

Study of Static Recrystallization Behaviors of GCr15 Steel Under Two-Pass Hot Compression Deformation  

NASA Astrophysics Data System (ADS)

In order to study the static recrystallization behavior of GCr15 steel during hot deformation process, two-pass hot compression experiments were conducted on Gleeble-3500 thermo-simulation system at the test temperatures from 850 to 1150 °C strain rate from 0.01 to 1 s-1, strain from 0.05 to 0.15 and inter-stage delay time from 1 to 100 s, respectively. The effects of temperature, strain rate and strain on static recrystallization of GCr15 steel were discussed in details. And the kinetic equations, in which the tension-time index n was 0.35 and the activation energy Q was 225.86 kJ/mol, were proposed. The comparison between the experimental results and predicted results was performed and the research results indicated that the effects of deformation parameters on the static recrystallization in multi-stage hot deformation are significant. The predicted results are in good agreement with the experimental ones, which indicates that the proposed kinetic equations can give an accurate estimate of the static recrystallization behaviors and microstructural evolutions for GCr15 steel.

Mao, Huajie; Zhang, Rui; Hua, Lin; Yin, Fei

2014-12-01

25

Integrated network construction using event based text mining  

E-print Network

Integrated network construction using event based text mining Yvan Saeys, Sofie Van Landeghem numerous interactions between biological entities. Text mining techniques have been increasingly useful mining in the systems biology field has been restricted mostly to the discovery of protein

Gent, Universiteit

26

Event-Based Learning: Educational and Technological Perspectives  

Microsoft Academic Search

Teachers have traditionally introduced current events in the classroom to leverage news topics relevant to the curriculum; however, to my knowledge no studies have attempted to provide a comprehensive research view on these event-related teaching activities. This paper presents an introductory event-based learning analysis from educational and technological research perspectives. This research effort provides a broad characterization of event-based learning

Sebastian de la Chica

27

Static Analysis for Event-Based XML Processing  

Microsoft Academic Search

Event-based processing of XML data - as exemplified by the pop - ular SAX framework - is a powerful alternative to using W3C's DOM or similar tree-based APIs. The event-based approach is particularly superior when processing large XML documents in a streaming fashion with minimal memory consumption. This paper discusses challenges for creating program analy ses for SAX applications. In

Anders Møller

28

Asynchronous visual event-based time-to-contact.  

PubMed

Reliable and fast sensing of the environment is a fundamental requirement for autonomous mobile robotic platforms. Unfortunately, the frame-based acquisition paradigm at the basis of main stream artificial perceptive systems is limited by low temporal dynamics and redundant data flow, leading to high computational costs. Hence, conventional sensing and relative computation are obviously incompatible with the design of high speed sensor-based reactive control for mobile applications, that pose strict limits on energy consumption and computational load. This paper introduces a fast obstacle avoidance method based on the output of an asynchronous event-based time encoded imaging sensor. The proposed method relies on an event-based Time To Contact (TTC) computation based on visual event-based motion flows. The approach is event-based in the sense that every incoming event adds to the computation process thus allowing fast avoidance responses. The method is validated indoor on a mobile robot, comparing the event-based TTC with a laser range finder TTC, showing that event-based sensing offers new perspectives for mobile robotics sensing. PMID:24570652

Clady, Xavier; Clercq, Charles; Ieng, Sio-Hoi; Houseini, Fouzhan; Randazzo, Marco; Natale, Lorenzo; Bartolozzi, Chiara; Benosman, Ryad

2014-01-01

29

Asynchronous visual event-based time-to-contact  

PubMed Central

Reliable and fast sensing of the environment is a fundamental requirement for autonomous mobile robotic platforms. Unfortunately, the frame-based acquisition paradigm at the basis of main stream artificial perceptive systems is limited by low temporal dynamics and redundant data flow, leading to high computational costs. Hence, conventional sensing and relative computation are obviously incompatible with the design of high speed sensor-based reactive control for mobile applications, that pose strict limits on energy consumption and computational load. This paper introduces a fast obstacle avoidance method based on the output of an asynchronous event-based time encoded imaging sensor. The proposed method relies on an event-based Time To Contact (TTC) computation based on visual event-based motion flows. The approach is event-based in the sense that every incoming event adds to the computation process thus allowing fast avoidance responses. The method is validated indoor on a mobile robot, comparing the event-based TTC with a laser range finder TTC, showing that event-based sensing offers new perspectives for mobile robotics sensing. PMID:24570652

Clady, Xavier; Clercq, Charles; Ieng, Sio-Hoi; Houseini, Fouzhan; Randazzo, Marco; Natale, Lorenzo; Bartolozzi, Chiara; Benosman, Ryad

2014-01-01

30

Galactic Cosmic Ray (GCR) Model of Titan and Formation of HCNO Exobiological Molecules  

NASA Astrophysics Data System (ADS)

Saturn as a system has two very exotic moons Titan and Enceladus. Space radiation effects at both moons, and as coupled by the Saturn magnetosphere, could lead to the evolution of exobiological models at Titan composed of HCNO molecules. At Titan Cassini discovered that 1) keV oxygen ions, evidently from Enceladus, are bombarding Titan’s upper atmosphere (Hartle et al., 2006a,b) and 2) heavy positive and negative ions exist in significant abundances within Titan’s upper atmosphere (Coates et al., 2007). Polycyclic Aromatic Hydrocarbons (PAHs) and fullerenes could form in Titan’s ionosphere. Laboratory measurements indicate that fullerenes, which are hollow carbon shells, can trap the keV oxygen ions. Clustering of the fullerenes with PAHs and the dominant nitrogen molecules could form larger aerosols enriched in trapped oxygen. Aerosol precipitation could then convey these chemically complex structures deeper into the atmosphere and to the moon surface. We estimate that GCR irradiation should dominate the chemical processing of the aerosols on the surface into more complex organic forms such as tholins and amino acids. To further quantify our results, we have developed an advanced model of GCR interaction with Titan’s atmosphere, surface and sub-surface. The model shows dose rates ~ 8x10-6 ergs/cm2/s at the surface which is ~ 4.2x10-9 erg/gm/s for tholin mass density ~ 1.8 gm/cm3. The GCR are found to penetrate ~ 50-100 m below the surface and may therefore also reach the bottom of Titan’s methane-ethane lakes. Reggie Hudson et al. (2008) showed that G-factor ~ 0.001 for Glycine. They used pure Acetonitrile CH3CN ices with very small water levels ~ 0.01% for O. So using G ~ 0.001 and GCR surface energy flux noted above at Titan’s surface we estimate abundance levels ~ 2-10 ppb of amino acids such as Glycine over 450 Myr period. Therefore, we conclude that this synergy of Saturn system, exogenic irradiation, and molecular processes provide a potential pathway for accumulation of prebiotic chemicals on the surface of Titan.

Sittler, Edward C.; Cooper, J. F.

2014-01-01

31

Abstracting event-based control models for high autonomy systems  

NASA Technical Reports Server (NTRS)

A high autonomy system needs many models on which to base control, management, design, and other interventions. These models differ in level of abstraction and in formalism. Concepts and tools are needed to organize the models into a coherent whole. The paper deals with the abstraction processes for systematic derivation of related models for use in event-based control. The multifaceted modeling methodology is briefly reviewed. The morphism concepts needed for application to model abstraction are described. A theory for supporting the construction of DEVS models needed for event-based control is then presented. An implemented morphism on the basis of this theory is also described.

Luh, Cheng-Jye; Zeigler, Bernard P.

1993-01-01

32

Comparison of Transport Codes, HZETRN, HETC and FLUKA, Using 1977 GCR Solar Minimum Spectra  

NASA Technical Reports Server (NTRS)

The HZETRN deterministic radiation transport code is one of several tools developed to analyze the effects of harmful galactic cosmic rays (GCR) and solar particle events (SPE) on mission planning, astronaut shielding and instrumentation. This paper is a comparison study involving the two Monte Carlo transport codes, HETC-HEDS and FLUKA, and the deterministic transport code, HZETRN. Each code is used to transport ions from the 1977 solar minimum GCR spectrum impinging upon a 20 g/cm2 Aluminum slab followed by a 30 g/cm2 water slab. This research is part of a systematic effort of verification and validation to quantify the accuracy of HZETRN and determine areas where it can be improved. Comparisons of dose and dose equivalent values at various depths in the water slab are presented in this report. This is followed by a comparison of the proton fluxes, and the forward, backward and total neutron fluxes at various depths in the water slab. Comparisons of the secondary light ion 2H, 3H, 3He and 4He fluxes are also examined.

Heinbockel, John H.; Slaba, Tony C.; Tripathi, Ram K.; Blattnig, Steve R.; Norbury, John W.; Badavi, Francis F.; Townsend, Lawrence W.; Handler, Thomas; Gabriel, Tony A.; Pinsky, Lawrence S.; Reddell, Brandon; Aumann, Aric R.

2009-01-01

33

Elemental GCR Observations during the 2009-2010 Solar Minimum Period  

NASA Technical Reports Server (NTRS)

Using observations from the Cosmic Ray Isotope Spectrometer (CRIS) onboard the Advanced Composition Explorer (ACE), we present new measurements of the galactic cosmic ray (GCR) elemental composition and energy spectra for the species B through Ni in the energy range approx. 50-550 MeV/nucleon during the record setting 2009-2010 solar minimum period. These data are compared with our observations from the 1997-1998 solar minimum period, when solar modulation in the heliosphere was somewhat higher. For these species, we find that the intensities during the 2009-2010 solar minimum were approx. 20% higher than those in the previous solar minimum, and in fact were the highest GCR intensities recorded during the space age. Relative abundances for these species during the two solar minimum periods differed by small but statistically significant amounts, which are attributed to the combination of spectral shape differences between primary and secondary GCRs in the interstellar medium and differences between the levels of solar modulation in the two solar minima. We also present the secondary-to-primary ratios B/C and (Sc+Ti+V)/Fe for both solar minimum periods, and demonstrate that these ratios are reasonably well fit by a simple "leaky-box" galactic transport model that is combined with a spherically symmetric solar modulation model.

Lave, K. A.; Israel, M. H.; Binns, W. R.; Christian, E. R.; Cummings, A. C.; Davis, A. J.; deNolfo, G. A.; Leske, R. A.; Mewaldt, R. A.; Stone, E. C.; vonRosenvinge, T. T.; Wiedenbeck, M. E.

2013-01-01

34

Some experimental studies on GCr15 steel by nitrogen ion overlap-implantation  

NASA Astrophysics Data System (ADS)

Timken wear test samples and contact fatigue samples of thrust bearing washers of GCr15 steel have been overlap-implanted by different energies and N + dosages. AES-PRO analysis, Timken wear tests and contact fatigue tests have been conducted. The results have shown that both the saturated concentration region of the nitrogen ion implantation and the implantation depth can be suitably extended by the overlap-implantation method. Thus, the total quantity of implantative elements can be increased and the modification potential of the matrix surface can be further enhanced. It is well-known that the greater the actual amount of N atoms which enter the Fe matrix, the better the effect of surface modification. Our preliminary work shows that in the Fe matrix there obviously exists a concentration limit of N, which is above 23%. When the implantation dose is increased from 6 × 10 17 to 12 × 10 17 N +/cm 2, there is no obvious increase in the total amount of N atoms which enter the Fe matrix. They are limited by the saturated concentration [1]. On this basis, we develop our experimental studies on GCr15 steel by N + ion overlap-implantation.

Jiucheng, Jin; Yingming, Luo; Chuanguo, Zhao; Huanzheng, Chen

35

Comparative Study on Different Phonon Frequency Spectra of Graphite in GCR  

NASA Astrophysics Data System (ADS)

A GCR (Gas Cooled Reactor) employs graphite as a neutron moderator and a reflector. At thermal energies, the scattering of the neutrons is affected by the binding characteristics of the scattering nucleus in the moderator. Thus, these effects should be carefully described by well defined scattering laws. The calculations for the scattering laws require an exact shape of the phonon frequency distribution of a material as an input parameter, as well as its lattice structure. Currently several variations of the phonon frequency spectra are available. We have generated different sets of temperature dependent scattering laws for graphite with the module LEAPR of the NJOY using the available phonon frequency spectra. The temperature range of the generated data sets was from 300 to 2000 °K. To observe the effect of these different scattering laws on the criticality of a GCR core, MCNP calculations were carried out and their results were compared with each other. As the basis of a comparison, the keff and the temperature coefficients for the moderator and reflector were used.

Cho, Young-Sik; Kim, Kang-Seog; Kim, Do Heon; Lee, Young-Ouk; Chang, Jonghwa

2006-04-01

36

Refactoring Using Event-based Profiling Adithya Nagarajan  

E-print Network

refactoring. As event interactions are dynamic, one source of information that can be used for refactoringRefactoring Using Event-based Profiling Adithya Nagarajan Department of Computer Science University to improve it, e.g., to make it more reusable, reliable and maintainable. The source of infor- mation

Memon, Atif M.

37

Generating Time Space Diagram Using Event-Based Traffic Data  

E-print Network

Generating Time Space Diagram Using Event-Based Traffic Data Presented by: Heng Hu, PhD Jianfeng rely on Synchro TS-Diagram · Field verification is done via probe vehicles, which is time consuming Det A B C Time Space Delayed arrivals Link Entrance Dummy Vehicle QOD vf Back of Queue Queue Departure

Minnesota, University of

38

Heft 175 Sachin Ramesh Patil Regionalization of an Event Based  

E-print Network

Heft 175 Sachin Ramesh Patil Regionalization of an Event Based Nash Cascade Model for Flood Sachin Ramesh Patil aus Jalgaon, Indien Hauptberichter: Prof. Dr. rer.nat. Dr.-Ing. habil. András Model for Flood Predictions in Ungauged Basins von Dr.-Ing. Sachin Ramesh Patil Eigenverlag des

Cirpka, Olaf Arie

39

An AES and ESCA study of GCr15 steel coated with Ti, Cr and bombarded by N + and Ar +  

NASA Astrophysics Data System (ADS)

GCr15 steel specimens coated with Ti, Cr and bombarded with N +, Ar + were analyzed by AES and ESCA (PHI-550). The results show that (1) the specimens bombarded with N + have improved surface mechanical properties compared to those bombarded with Ar +; (2) the changes in the surface properties are related to the composition of the surface layer, mainly to TiO 2, TiN, Cr 2O 3, and other compounds. Also, the presence of carbon is found to be advantageous in modifying GCr15 bearing steel.

Jie, Zhao; Wang, Li; Yawen, Su; Srivastava, S. C.

1988-07-01

40

Event-Based Monitoring of Open Source Software Projects Dindin Wahyudin, A Min Tjoa  

E-print Network

Event-Based Monitoring of Open Source Software Projects Dindin Wahyudin, A Min Tjoa Institute and Process Monitoring, Event-Based System, Event- Based Project Monitoring; Open Source Software Project. 1 subscribe schema in an event-based system. The development processes in an Open Source Software project can

41

Mars Science Laboratory; A Model for Event-Based EPO  

NASA Astrophysics Data System (ADS)

The NASA Mars Science Laboratory (MSL) and its Curiosity Rover, a part of NASA's Mars Exploration Program, represent the most ambitious undertaking to date to explore the red planet. MSL/Curiosity was designed primarily to determine whether Mars ever had an environment capable of supporting microbial life. NASA's MSL education program was designed to take advantage of existing, highly successful event based education programs to communicate Mars science and education themes to worldwide audiences through live webcasts, video interviews with scientists, TV broadcasts, professional development for teachers, and the latest social media frameworks. We report here on the success of the MSL education program and discuss how this methodological framework can be used to enhance other event based education programs.

Mayo, Louis; Lewis, E.; Cline, T.; Stephenson, B.; Erickson, K.; Ng, C.

2012-10-01

42

ADEES: An Adaptable and Extensible Event Based Infrastructure  

Microsoft Academic Search

This paper describes ADEES, an open and evolutionary event-based architecture to develop complex distributed information systems.\\u000a Different from most existing event supports that provide limited event description models and fixed management models, ADEES\\u000a can be extendedandcustomizedon a per-application basis. It is not another “one-size-fits-all” event manager! It is usedto\\u000a generate event managers adopted by components to produce and consume events

Genoveva Vargas-solar; Christine Collet

2002-01-01

43

Secondary Cosmic Ray Particles Due to GCR Interactions in the Earth's Atmosphere  

SciTech Connect

Primary GCR interact with the Earth's atmosphere originating atmospheric showers, thus giving rise to fluxes of secondary particles in the atmosphere. Electromagnetic and hadronic interactions interplay in the production of these particles, whose detection is performed by means of complementary techniques in different energy ranges and at different depths in the atmosphere, down to the Earth's surface. Monte Carlo codes are essential calculation tools which can describe the complexity of the physics of these phenomena, thus allowing the analysis of experimental data. However, these codes are affected by important uncertainties, concerning, in particular, hadronic physics at high energy. In this paper we shall report some results concerning inclusive particle fluxes and atmospheric shower properties as obtained using the FLUKA transport and interaction code. Some emphasis will also be given to the validation of the physics models of FLUKA involved in these calculations.

Battistoni, G.; /Milan U. /INFN, Milan; Cerutti, F.; /CERN; Fasso, A.; /SLAC; Ferrari, A.; /CERN; Garzelli, M.V.; /Milan U. /INFN, Milan; Lantz, M.; /Goteborg, ITP; Muraro, S. /Milan U. /INFN, Milan; Pinsky, L.S.; /Houston U.; Ranft, J.; /Siegen U.; Roesler, S.; /CERN; Sala, P.R.; /Milan U. /INFN, Milan; ,

2009-06-16

44

Secondary Cosmic Ray Particles due to GCR Interactions in the Earth's Atmosphere  

SciTech Connect

Primary GCR interact with the Earth's atmosphere originating atmospheric showers, thus giving rise to fluxes of secondary particles in the atmosphere. Electromagnetic and hadronic interactions interplay in the production of these particles, whose detection is performed by means of complementary techniques in different energy ranges and at different depths in the atmosphere, down to the Earth's surface.Monte Carlo codes are essential calculation tools which can describe the complexity of the physics of these phenomena, thus allowing the analysis of experimental data. However, these codes are affected by important uncertainties, concerning, in particular, hadronic physics at high energy. In this paper we shall report some results concerning inclusive particle fluxes and atmospheric shower properties as obtained using the FLUKA transport and interaction code. Some emphasis will also be given to the validation of the physics models of FLUKA involved in these calculations.

Battistoni, G.; Garzelli, M. V.; Muraro, S.; Sala, P. R. [University of Milano, Department of Physics, and INFN, Milan (Italy); Cerutti, F.; Ferrari, A.; Roesler, S. [CERN, Geneva (Switzerland); Fasso, A. [SLAC, Stanford, CA (United States); Lantz, M. [Chalmers University, Department of Fundamental Physics, Goteborg (Sweden); Pinsky, L. S. [University of Houston, Department of Physics, Houston, TX (United States); Ranft, J. [Siegen University, Fachbereich 7-Physik, Siegen (Germany)

2008-01-24

45

Nuclear fragmentation of GCR-like ions: comparisons between data and PHITS  

NASA Astrophysics Data System (ADS)

We present a summary of results from recent work in which we have compared nuclear fragmentation cross section data to predictions of the PHITS Monte Carlo simulation. The studies used beams of 12 C, 35 Cl, 40 Ar, 48 Ti, and 56 Fe at energies ranging from 290 MeV/nucleon to 1000 MeV/nucleon. Some of the data were obtained at the Brookhaven National Laboratory, others at the National Institute of Radiological Sciences in Japan. These energies and ion species are representative of the heavy ion component of the Galactic Cosmic Rays (GCR), which contribute significantly to the dose and dose equivalent that will be received by astronauts on deep-space missions. A critical need for NASA is the ability to accurately model the transport of GCR heavy ions through matter, including spacecraft walls, equipment racks, and other shielding materials, as well as through tissue. Nuclear interaction cross sections are of primary importance in the GCR transport problem. These interactions generally cause the incoming ion to break up (fragment) into one or more lighter ions, which continue approximately along the initial trajectory and with approximately the same velocity the incoming ion had prior to the interaction. Since the radiation dose delivered by a particle is proportional to the square of the quantity (charge/velocity), i.e., to (Z/?)2 , fragmentation reduces the dose (and, typically, dose equivalent) delivered by incident ions. The other mechanism by which dose can be reduced is ionization energy loss, which can lead to some particles stopping in the shielding. This is the conventional notion of shielding, but it is not applicable to human spaceflight, since the particles in the GCR tend to be highly energetic and because shielding must be relatively thin in order to keep overall mass as low as possible, keeping launch costs within reason. To support these goals, our group has systematically measured a large number of nuclear cross sections, intended to be used as either input to, or validation of, NASA transport models. A database containing over 200 charge-changing cross sections, and over 2000 fragment production cross sections, is nearing completion, with most results available online. In the past year, we have been investigating the PHITS (Particle and Heavy Ion Transport System) model of Niita et al. For purposes of modeling nuclear interactions, PHITS combines the Jet AA Microscopic Transport Model (JAM) hadron cascade model, the Jaeri Quantum Molecular Dynamics (JQMD) model, and the Generalized Evaporation Model (GEM). We will present detailed comparisons of our data to the cross sections and fragment angular distributions that arise from this model. The model contains some significant deficiencies, but, as we will show, also represents a significant advance over older, simpler models of fragmentation. 504b030414000600080000002100828abc13fa0000001c020000130000005b436f6e74656e745f54797065735d2e78

Zeitlin, Cary; Guetersloh, Stephen; Heilbronn, Lawrence; Miller, Jack; Sihver, Lembit; Mancusi, Davide; Fukumura, Aki; Iwata, Yoshi; Murakami, Takeshi

46

Secondary Cosmic Ray particles due to GCR interactions in the Earth's atmosphere  

E-print Network

Primary GCR interact with the Earth's atmosphere originating atmospheric showers, thus giving rise to fluxes of secondary particles in the atmosphere. Electromagnetic and hadronic interactions interplay in the production of these particles, whose detection is performed by means of complementary techniques in different energy ranges and at different depths in the atmosphere, down to the Earth's surface. Monte Carlo codes are essential calculation tools which can describe the complexity of the physics of these phenomena, thus allowing the analysis of experimental data. However, these codes are affected by important uncertainties, concerning, in particular, hadronic physics at high energy. In this paper we shall report some results concerning inclusive particle fluxes and atmospheric shower properties as obtained using the FLUKA transport and interaction code. Some emphasis will also be given to the validation of the physics models of FLUKA involved in these calculations.

G. Battistoni; F. Cerutti; A. Fassò; A. Ferrari; M. V. Garzelli; M. Lantz; S. Muraro; L. S. Pinsky; J. Ranft; S. Roesler; P. R. Sala

2007-11-13

47

GCR flux reconstruction during the last three centuries validated by the Ti-44 in meteorites and Be-10 in ice  

NASA Astrophysics Data System (ADS)

In a previous work [1] we deduced that during prolonged minima of solar activity since 1700 the galactic cosmic rays (GCR) flux was much higher (˜2 times) respect to what we can infer from GCR modulation deduced solely by the Sunspot Number series. This flux was higher respect to what we observe in the last decades by Neutron Monitor or balloon and spacecraft-borne detectors and confirmed by the three fresh-fall meteorites that we have measured during solar cycle 22. Recently we have deduced the GCR annual mean spectra for the last 300 years [2], starting from the open solar magnetic flux proposed by Solanki et al. [3]. Utilizing the GCR flux we have calculated the 44Ti (T1/2 = 59.2 y) activity in meteorites taking into account the cross sections for its production from the main target element Fe and Ni. We compare the calculated activity with our measurements of the cosmogenic 44Ti in different chondrites fell in the period 1810-1997. The results are in close agreement both in phase and amplitude. The same procedure has been adopted for calculating the production rate of 10Be in atmosphere. Normalizing to the concentration in ice in the solar cycles 20 and 21 we obtain a good agreement with the 10Be profile in Dye3 core [4]. These results demonstrate that our inference of the GCR flux in the past 300 years is reliable. [1] Bonino G., Cini Castagnoli G., Bhandari N., Taricco C., textit {Science}, 270, 1648, 1995 [2] Bonino G., Cini Castagnoli G., Cane D., Taricco C. and Bhandari N., textit {Proc. XXVII Intern. Cosmic Ray Conf.} (Hamburg, 2001) 3769-3772. [3] Solanki S.K., Schüssler M. and Fligge M.,Nature, 408, 445, 2000 [4] Beer J. et al., private communication

Cini Castagnoli, G.; Cane, D.; Taricco, C.; Bhandari, N.

2003-04-01

48

GCR Transport in the Brain: Assessment of Self-Shielding, Columnar Damage, and Nuclear Reactions on Cell Inactivation Rates  

NASA Technical Reports Server (NTRS)

Radiation shield design is driven by the need to limit radiation risks while optimizing risk reduction with launch mass/expense penalties. Both limitation and optimization objectives require the development of accurate and complete means for evaluating the effectiveness of various shield materials and body-self shielding. For galactic cosmic rays (GCR), biophysical response models indicate that track structure effects lead to substantially different assessments of shielding effectiveness relative to assessments based on LET-dependent quality factors. Methods for assessing risk to the central nervous system (CNS) from heavy ions are poorly understood at this time. High-energy and charge (HZE) ion can produce tissue events resulting in damage to clusters of cells in a columnar fashion, especially for stopping heavy ions. Grahn (1973) and Todd (1986) have discussed a microlesion concept or model of stochastic tissue events in analyzing damage from HZE's. Some tissues, including the CNS, maybe sensitive to microlesion's or stochastic tissue events in a manner not illuminated by either conventional dosimetry or fluence-based risk factors. HZE ions may also produce important lateral damage to adjacent cells. Fluences of high-energy proton and alpha particles in the GCR are many times higher than HZE ions. Behind spacecraft and body self-shielding the ratio of protons, alpha particles, and neutrons to HZE ions increases several-fold from free-space values. Models of GCR damage behind shielding have placed large concern on the role of target fragments produced from tissue atoms. The self-shielding of the brain reduces the number of heavy ions reaching the interior regions by a large amount and the remaining light particle environment (protons, neutrons, deuterons. and alpha particles) may be the greatest concern. Tracks of high-energy proton produce nuclear reactions in tissue, which can deposit doses of more than 1 Gv within 5 - 10 cell layers. Information on rates of cell killing from GCR, including patterns of cell killing from single particle tracks. can provide useful information on expected differences between proton and HZE tracks and clinical experiences with photon irradiation. To model effects on cells in the brain, it is important that transport models accurately describe changes in the GCR due to interactions in the cranium and proximate tissues. We describe calculations of the attenuated GCR particle fluxes at three dose-points in the brain and associated patterns of cell killing using biophysical models. The effects of the brain self-shielding and bone-tissue interface of the skull in modulating the GCR environment are considered. For each brain dose-point, the mass distribution in the surrounding 4(pi) solid angle is characterized using the CAM model to trace 512 rays. The CAM model describes the self-shielding by converting the tissue distribution to mass-equivalent aluminum, and nominal values of spacecraft shielding is considered. Particle transport is performed with the proton, neutron, and heavy-ion transport code HZETRN with the nuclear fragmentation model QMSFRG. The distribution of cells killed along the path of individual GCR ions is modeled using in vitro cell inactivation data for cells with varying sensitivity. Monte Carlo simulations of arrays of inactivated cells are considered for protons and heavy ions and used to describe the absolute number of cell killing events of various magnitude in the brain from the GCR. Included are simulations of positions of inactivated cells from stopping heavy ions and nuclear stars produced by high-energy ions most importantly, protons and neutrons.

Shavers, M. R.; Atwell, W.; Cucinotta, F. A.; Badhwar, G. D. (Technical Monitor)

1999-01-01

49

Event-Based Science: Remote-Sensing Activities  

NSDL National Science Digital Library

These activities enable students to use remotely-sensed data- as they tackle the real-world problems and tasks found in existing Event-Based Science (EBS) modules. Remotely-sensed data are employed as an integral part of both the presentation of Earth system science concepts, and in the solutions to real-world problems. The activities emphasize the use of NASA remote-sensing data from satellites and sensors including: Landsat, GOES, and MODIS, and SeaWiFS. The EBS remote-sensing activities enhance EBS modules, including: Blight! Earthquake! Fire! Flood! Hurricane! Oil Spill! and Volcano!

2011-01-01

50

Event-based Simulation Model for Quantum Optics Experiments  

SciTech Connect

We present a corpuscular simulation model of optical phenomena that does not require the knowledge of the solution of a wave equation of the whole system and reproduces the results of Maxwell's theory by generating detection events one-by-one. The event-based corpuscular model gives a unified description of multiple-beam fringes of a plane parallel plate and single-photon Mach-Zehnder interferometer, Wheeler's delayed choice, photon tunneling, quantum eraser, two-beam interference, double-slit, Einstein-Podolsky-Rosen-Bohm and Hanbury Brown-Twiss experiments. We also discuss the possibility to refute our corpuscular model.

De Raedt, H. [Department of Applied Physics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, NL-9747 AG Groningen (Netherlands); Michielsen, K. [Institute for Advanced Simulation, Juelich Supercomputing Centre, Research Centre Juelich, D-52425 Juelich (Germany)

2011-03-28

51

Event-Based Simulation of Quantum Physics Experiments  

NASA Astrophysics Data System (ADS)

We review an event-based simulation approach which reproduces the statistical distributions of wave theory not by requiring the knowledge of the solution of the wave equation of the whole system but by generating detection events oneby- one according to an unknown distribution. We illustrate its applicability to various single photon and single neutron interferometry experiments and to two Bell-test experiments, a single-photon Einstein-Podolsky-Rosen experiment employing post-selection for photon pair identification and a single-neutron Bell test interferometry experiment with nearly 100% detection efficiency.

Michielsen, Kristel; de Raedt, Hans

2015-10-01

52

Model Calculations with Excited Nuclear Fragmentations and Implications of Current GCR Spectra  

NASA Astrophysics Data System (ADS)

As a result of the fragmentation process in nuclei, energy from the excited states may also contribute to the radiation damage on the cell structure. Radiation induced damage to the human body from the excited states of oxygen and several other nuclei and its fragments are of a concern in the context of the measured abundance of the current galactic cosmic rays (GCR) environment. Nuclear Shell model based calculations of the Selective-Core (Saganti-Cucinotta) approach are being expanded for O-16 nuclei fragments into N-15 with a proton knockout and O-15 with a neutron knockout are very promising. In our on going expansions of these nuclear fragmentation model calculations and assessments, we present some of the prominent nuclei interactions from a total of 190 isotopes that were identified for the current model expansion based on the Quantum Multiple Scattering Fragmentation Model (QMSFRG) of Cucinotta. Radiation transport model calculations with the implementation of these energy level spectral characteristics are expected to enhance the understanding of radiation damage at the cellular level. Implications of these excited energy spectral calculations in the assessment of radiation damage to the human body may provide enhanced understanding of the space radiation risk assessment.

Saganti, Premkumar

53

Assessment and Requirements of Nuclear Reaction Databases for GCR Transport in the Atmosphere and Structures  

NASA Technical Reports Server (NTRS)

The transport properties of galactic cosmic rays (GCR) in the atmosphere, material structures, and human body (self-shielding) am of interest in risk assessment for supersonic and subsonic aircraft and for space travel in low-Earth orbit and on interplanetary missions. Nuclear reactions, such as knockout and fragmentation, present large modifications of particle type and energies of the galactic cosmic rays in penetrating materials. We make an assessment of the current nuclear reaction models and improvements in these model for developing required transport code data bases. A new fragmentation data base (QMSFRG) based on microscopic models is compared to the NUCFRG2 model and implications for shield assessment made using the HZETRN radiation transport code. For deep penetration problems, the build-up of light particles, such as nucleons, light clusters and mesons from nuclear reactions in conjunction with the absorption of the heavy ions, leads to the dominance of the charge Z = 0, 1, and 2 hadrons in the exposures at large penetration depths. Light particles are produced through nuclear or cluster knockout and in evaporation events with characteristically distinct spectra which play unique roles in the build-up of secondary radiation's in shielding. We describe models of light particle production in nucleon and heavy ion induced reactions and make an assessment of the importance of light particle multiplicity and spectral parameters in these exposures.

Cucinotta, F. A.; Wilson, J. W.; Shinn, J. L.; Tripathi, R. K.

1998-01-01

54

MHD compressor---expander conversion system integrated with GCR inside a deployable reflector  

SciTech Connect

This work originates from the proposal MHD Compressor-Expander Conversion System Integrated with a GCR Inside a Deployable Reflector''. The proposal concerned an innovative concept of nuclear, closed-cycle MHD converter for power generation on space-based systems in the multi-megawatt range. The basic element of this converter is the Power Conversion Unit (PCU) consisting of a gas core reactor directly coupled to an MHD expansion channel. Integrated with the PCU, a deployable reflector provides reactivity control. The working fluid could be either uranium hexafluoride or a mixture of uranium hexafluoride and helium, added to enhance the heat transfer properties. The original Statement of Work, which concerned the whole conversion system, was subsequently redirected and focused on the basic mechanisms of neutronics, reactivity control, ionization and electrical conductivity in the PCU. Furthermore, the study was required to be inherently generic such that the study was required to be inherently generic such that the analysis an results can be applied to various nuclear reactor and/or MHD channel designs''.

Tuninetti, G. (Ansaldo S.p.A., Genoa (Italy). Research Div.); Botta, E.; Criscuolo, C.; Riscossa, P. (Ansaldo S.p.A., Genoa (Italy). Nuclear Div.); Giammanco, F. (Pisa Univ. (Italy). Dipt. di Fisica); Rosa-Clot, M. (Florence Univ. (Italy). Dipt. di Fisica)

1989-04-20

55

Assessment and requirements of nuclear reaction databases for GCR transport in the atmosphere and structures.  

PubMed

The transport properties of galactic cosmic rays (GCR) in the atmosphere, material structures, and human body (self-shielding) are of interest in risk assessment for supersonic and subsonic aircraft and for space travel in low-Earth orbit and on interplanetary missions. Nuclear reactions, such as knockout and fragmentation, present large modifications of particle type and energies of the galactic cosmic rays in penetrating materials. We make an assessment of the current nuclear reaction models and improvements in these model for developing required transport code data bases. A new fragmentation data base (QMSFRG) based on microscopic models is compared to the NUCFRG2 model and implications for shield assessment made using the HZETRN radiation transport code. For deep penetration problems, the build-up of light particles, such as nucleons, light clusters and mesons from nuclear reactions in conjunction with the absorption of the heavy ions, leads to the dominance of the charge Z = 0, 1, and 2 hadrons in the exposures at large penetration depths. Light particles are produced through nuclear or cluster knockout and in evaporation events with characteristically distinct spectra which play unique roles in the build-up of secondary radiation's in shielding. We describe models of light particle production in nucleon and heavy ion induced reactions and make an assessment of the importance of light particle multiplicity and spectral parameters in these exposures. PMID:11542895

Cucinotta, F A; Wilson, J W; Shinn, J L; Tripathi, R K

1998-01-01

56

Determining the Magnitude of Neutron and Galactic Cosmic Ray (GCR) Fluxes at the Moon using the Lunar Exploration Neutron Detector during the Historic Space-Age Era of High GCR Flux  

NASA Astrophysics Data System (ADS)

The Lunar Reconnaissance Orbiter (LRO) was launched June 18, 2009 during an historic space-age era of minimum solar activity [1]. The lack of solar sunspot activity signaled a complex set of heliospheric phenomena [2,3,4] that also gave rise to a period of unprecedentedly high Galactic Cosmic Ray (GCR) flux [5]. These events coincided with the primary mission of the Lunar Exploration Neutron Detector (LEND, [6]), onboard LRO in a nominal 50-km circular orbit of the Moon [7]. Methods to calculate the emergent neutron albedo population using Monte Carlo techniques [8] rely on an estimate of the GCR flux and spectra calibrated at differing periods of solar activity [9,10,11]. Estimating the actual GCR flux at the Moon during the LEND's initial period of operation requires a correction using a model-dependent heliospheric transport modulation parameter [12] to adjust the GCR flux appropriate to this unique solar cycle. These corrections have inherent uncertainties depending on model details [13]. Precisely determining the absolute neutron and GCR fluxes is especially important in understanding the emergent lunar neutrons measured by LEND and subsequently in estimating the hydrogen/water content in the lunar regolith [6]. LEND is constructed with a set of neutron detectors to meet differing purposes [6]. Specifically there are two sets of detector systems that measure the flux of epithermal neutrons: a) the uncollimated Sensor for Epi-Thermal Neutrons (SETN) and b) the Collimated Sensor for Epi-Thermal Neutrons (CSETN). LEND SETN and CSETN observations form a complementary set of simultaneous measurements that determine the absolute scale of emergent lunar neutron flux in an unambiguous fashion and without the need for correcting to differing solar-cycle conditions. LEND measurements are combined with a detailed understanding of the sources of instrumental back-ground, and the performance of CSETN and SETN. This comparison allows us to calculate a constant scale factor that determines the absolute flux of neutrons at the Moon and then subsequently to deduce the proper scale of the GCR flux. References: [1] H. S. Ahluwakia and R. C. Ygbuhay (2010) Twelfth International Solar Wind Conference, 699-702. [2] F. B. McDonald et al. (2010) JRL, 37, L18101. [3] H. Moraal and P. H. Stoker (2010) JGR, 115, 12109-12118. [4] R. Kataoka et al. (2012) Space Weather, 10, 11001-11007. [4] C-L. Huang et al. (2009), JRL, 37, L09109-L09104. [5] R. A. Mewaldt et al. (2010) Ap. J Lett., 723, L1-L6. [6] I. G. Mitrofanov et al. (2010) Space Science Rev., 150, 283-207. [7] C. R. Tooley et al. (2010) Space Science Rev., 150, 23-62. [8] G. W. McKinney et al. (2006) JGR, 111, 6004-6018. [9] P. M. O'Neil (2010) IEEE Trans. Nucl. Sci., 57(6), 3148-3153. [10] American National Standards Institute Tech. Rep. ISO 15390 (2004). [11] I. G. Usokin et al. (2008) JGR, 110, A12108. [12] M. D. Looper et al. (2013) Space Weather, 11, 142-152. [13] A. I. Mrigakshi et al. (2012) JGR, 117, A08109-A08121.

Chin, G.; Sagdeev, R.; Boynton, W. V.; Mitrofanov, I. G.; Milikh, G. M.; Su, J. J.; Livengood, T. A.; McClanahan, T. P.; Evans, L.; Starr, R. D.; litvak, M. L.; Sanin, A.

2013-12-01

57

Event-Based User Classification in Weibo Media  

PubMed Central

Weibo media, known as the real-time microblogging services, has attracted massive attention and support from social network users. Weibo platform offers an opportunity for people to access information and changes the way people acquire and disseminate information significantly. Meanwhile, it enables people to respond to the social events in a more convenient way. Much of the information in Weibo media is related to some events. Users who post different contents, and exert different behavior or attitude may lead to different contribution to the specific event. Therefore, classifying the large amount of uncategorized social circles generated in Weibo media automatically from the perspective of events has been a promising task. Under this circumstance, in order to effectively organize and manage the huge amounts of users, thereby further managing their contents, we address the task of user classification in a more granular, event-based approach in this paper. By analyzing real data collected from Sina Weibo, we investigate the Weibo properties and utilize both content information and social network information to classify the numerous users into four primary groups: celebrities, organizations/media accounts, grassroots stars, and ordinary individuals. The experiments results show that our method identifies the user categories accurately. PMID:25133235

Wang, Wendong; Cheng, Shiduan; Que, Xirong

2014-01-01

58

Event based classification of Web 2.0 text streams  

E-print Network

Web 2.0 applications like Twitter or Facebook create a continuous stream of information. This demands new ways of analysis in order to offer insight into this stream right at the moment of the creation of the information, because lots of this data is only relevant within a short period of time. To address this problem real time search engines have recently received increased attention. They take into account the continuous flow of information differently than traditional web search by incorporating temporal and social features, that describe the context of the information during its creation. Standard approaches where data first get stored and then is processed from a peristent storage suffer from latency. We want to address the fluent and rapid nature of text stream by providing an event based approach that analyses directly the stream of information. In a first step we want to define the difference between real time search and traditional search to clarify the demands in modern text filtering. In a second s...

Bauer, Andreas

2012-01-01

59

DNA Binding of the Cell Cycle Transcriptional Regulator GcrA Depends on N6-Adenosine Methylation in Caulobacter crescentus and Other Alphaproteobacteria  

PubMed Central

Several regulators are involved in the control of cell cycle progression in the bacterial model system Caulobacter crescentus, which divides asymmetrically into a vegetative G1-phase (swarmer) cell and a replicative S-phase (stalked) cell. Here we report a novel functional interaction between the enigmatic cell cycle regulator GcrA and the N6-adenosine methyltransferase CcrM, both highly conserved proteins among Alphaproteobacteria, that are activated early and at the end of S-phase, respectively. As no direct biochemical and regulatory relationship between GcrA and CcrM were known, we used a combination of ChIP (chromatin-immunoprecipitation), biochemical and biophysical experimentation, and genetics to show that GcrA is a dimeric DNA–binding protein that preferentially targets promoters harbouring CcrM methylation sites. After tracing CcrM-dependent N6-methyl-adenosine promoter marks at a genome-wide scale, we show that these marks recruit GcrA in vitro and in vivo. Moreover, we found that, in the presence of a methylated target, GcrA recruits the RNA polymerase to the promoter, consistent with its role in transcriptional activation. Since methylation-dependent DNA binding is also observed with GcrA orthologs from other Alphaproteobacteria, we conclude that GcrA is the founding member of a new and conserved class of transcriptional regulators that function as molecular effectors of a methylation-dependent (non-heritable) epigenetic switch that regulates gene expression during the cell cycle. PMID:23737758

Mohapatra, Saswat S.; Bompard, Coralie; Brilli, Matteo; Frandi, Antonio; Castric, Vincent; Villeret, Vincent; Viollier, Patrick H.; Biondi, Emanuele G.

2013-01-01

60

Database of Gene Co-Regulation (dGCR): A Web Tool for Analysing Patterns of Gene Co-regulation across Publicly Available Expression Data.  

PubMed

The database of Gene Co-Regulation (dGCR) is a web tool for the analysis of gene relationships based on correlated patterns of gene expression over publicly available transcriptional data. The motivation behind dGCR is that genes whose expression patterns correlate across many experiments tend to be co-regulated and hence share biological function. In addition to revealing functional connections between individual gene pairs, extended sets of co-regulated genes can also be assessed for enrichment of gene ontology classes and interaction pathways. This functionality provides an insight into the biological function of the query gene itself. The dGCR web tool extends the range of expression data curated by existing co-regulation databases and provides additional insights into gene function through the analysis of pathways, gene ontology classes and co-regulation modules. PMID:25628763

Williams, Gareth

2015-01-01

61

Database of Gene Co-Regulation (dGCR): A Web Tool for Analysing Patterns of Gene Co-regulation across Publicly Available Expression Data  

PubMed Central

The database of Gene Co-Regulation (dGCR) is a web tool for the analysis of gene relationships based on correlated patterns of gene expression over publicly available transcriptional data. The motivation behind dGCR is that genes whose expression patterns correlate across many experiments tend to be co-regulated and hence share biological function. In addition to revealing functional connections between individual gene pairs, extended sets of co-regulated genes can also be assessed for enrichment of gene ontology classes and interaction pathways. This functionality provides an insight into the biological function of the query gene itself. The dGCR web tool extends the range of expression data curated by existing co-regulation databases and provides additional insights into gene function through the analysis of pathways, gene ontology classes and co-regulation modules.

Williams, Gareth

2015-01-01

62

Inner heliosphere spatial gradients of GCR protons and alpha particles in the low GeV range  

NASA Astrophysics Data System (ADS)

The spacecraft Ulysses was launched in October 1990 in the maximum phase of solar cycle 22, reached its final, highly inclined (80.2°) Keplerian orbit around the Sun in February 1992, and was finally switched off in June 2009. The Kiel Electron Telescope (KET) aboard Ulysses measures electrons from 3 MeV to a few GeV and protons and helium in the energy range from 6 MeV/nucleon to above 2 GeV/nucleon. In order to investigate the radial and latitudinal gradients of galactic cosmic rays (GCR), it is essential to know their intensity variations for a stationary observer in the heliosphere because the Ulysses measurements reflect not only the spatial but also the temporal variation of the energetic particle intensities. This was accomplished in the past with the Interplanetary Monitoring Platform-J (IMP 8) until it was lost in 2006. Fortunately, the satellite-borne experiment PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) was launched in June 2006 and can be used as a reliable 1 AU baseline for measurements of the KET aboard Ulysses. With these tools at hand, we have the opportunity to determine the spatial gradients of GCR protons and alpha particles at about 0.1 to 1 GeV/n in the inner heliosphere during the extended minimum of solar cycle 23. We then compare these A<0 magnetic epoch results with previous Ulysses/KET findings from the preceding A>0 cycle.

Gieseler, J.; Boezio, M.; Casolino, M.; De Simone, N.; Di Felice, V.; Heber, B.; Martucci, M.; Picozza, P.

2013-12-01

63

Optimization of Correlated Source Coding for Event-Based Monitoring in Sensor Networks  

E-print Network

Optimization of Correlated Source Coding for Event-Based Monitoring in Sensor Networks Jaspreet of joint coding of correlated sources under a cost criterion that is appropriately conditioned on event oc}@ece.ucsb.edu Abstract Motivated by the paradigm of event-based monitoring, which can poten- tially alleviate

Madhow, Upamanyu

64

Understanding JavaScript Event-Based Interactions Saba Alimadadi Sheldon Sequeira Ali Mesbah Karthik Pattabiraman  

E-print Network

Understanding JavaScript Event-Based Interactions Saba Alimadadi Sheldon Sequeira Ali Mesbah of the JavaScript language. We propose a generic technique for capturing low-level event-based interactions, related JavaScript code executions, and their impact on the dynamic DOM state. Our approach, implemented

Pulfrey, David L.

65

Oil Spill!: An Event-Based Science Module. Teacher's Guide. Oceanography Module.  

ERIC Educational Resources Information Center

This book is designed for middle school earth science or general science teachers to help their students learn scientific literacy through event-based science. Unlike traditional curricula, the event- based earth science module is a student-centered, interdisciplinary, inquiry-oriented program that emphasizes cooperative learning, teamwork,…

Wright, Russell G.

66

Oil Spill! An Event-Based Science Module. Student Edition. Oceanography Module.  

ERIC Educational Resources Information Center

This book is designed for middle school students to learn scientific literacy through event-based science. Unlike traditional curricula, the event-based earth science module is a student-centered, interdisciplinary, inquiry-oriented program that emphasizes cooperative learning, teamwork, independent research, hands-on investigations, and…

Wright, Russell G.

67

Toxic Leak!: An Event-Based Science Module. Student Edition. Groundwater Module.  

ERIC Educational Resources Information Center

This book is designed for the middle school students to learn scientific literacy through event-based science. Unlike traditional curricula, the event-based earth science module is a student-centered, interdisciplinary, inquiry-oriented program that emphasizes cooperative learning, teamwork, independent research, hands-on investigations, and…

Wright, Russell G.

68

Further Results on Event-Based PID Controller Sylvain Durand and Nicolas Marchand  

E-print Network

Further Results on Event-Based PID Controller Sylvain Durand and Nicolas Marchand Abstract-- In this paper, some improvements of the simple event-based PID controller presented by K-E °Arz´en in [2] are proposed. This controller, contrary to a time-triggered con- troller which calculates the control signal

Paris-Sud XI, Université de

69

First Flight!: An Event-Based Science Module. Student Edition. Physics Module.  

ERIC Educational Resources Information Center

This book is designed for middle school students to learn scientific literacy through event-based science. Unlike traditional curricula, the event-based earth science module is a student-centered, interdisciplinary, inquiry-oriented program that emphasizes cooperative learning, teamwork, independent research, hands-on investigations, and…

Wright, Russell G.

70

First Flight!: An Event-Based Science Module Teacher's Guide. Physics Module.  

ERIC Educational Resources Information Center

This book is designed for middle school life science or physical science teachers to help their students learn scientific literacy through event-based science. Unlike traditional curricula, the event- based earth science module is a student-centered, interdisciplinary, inquiry-oriented program that emphasizes cooperative learning, teamwork,…

Wright, Russell G.

71

Asteroid! An Event-Based Science Module. Teacher's Guide. Astronomy Module.  

ERIC Educational Resources Information Center

This book is designed for middle school earth science or general science teachers to help their students learn scientific literacy through event-based science. Unlike traditional curricula, the event- based earth science module is a student-centered, interdisciplinary, inquiry-oriented program that emphasizes cooperative learning, teamwork,…

Wright, Russell G.

72

Asteroid! An Event-Based Science Module. Student Edition. Astronomy Module.  

ERIC Educational Resources Information Center

This book is designed for middle school students to learn scientific literacy through event-based science. Unlike traditional curricula, the event-based earth science module is a student-centered, interdisciplinary, inquiry-oriented program that emphasizes cooperative learning, teamwork, independent research, hands-on investigations, and…

Wright, Russell G.

73

Lecture 12: Distributed and saturated event-based control Lecture 12 Outline  

E-print Network

-based PID control #12;4/25/13 2 Distributed event-based control · How to implement event-based control over a distributed system? ­ E.g., control of mul7-roboton control for non-holonomic mobile robots #12;4/25/13 11 Summary · Mul7-agent

Johansson, Karl Henrik

74

Event-based Approach to Money Laundering Data Analysis and Visualization  

E-print Network

Event-based Approach to Money Laundering Data Analysis and Visualization Tat-Man Cheong Faculty, an event-based approach to money laundering data analysis and visualization is proposed in this paper. The effectiveness of the proposed method is demonstrated on a money laundering case from Taiwan. Categories

Si, Yain Whar "Lawrence"

75

Tornado! An Event-Based Science Module. Student Edition. Meteorology Module.  

ERIC Educational Resources Information Center

This book is designed for middle school students to learn scientific literacy through event-based science. Unlike traditional curricula, the event-based earth science module is a student-centered, interdisciplinary, inquiry-oriented program that emphasizes cooperative learning, teamwork, independent research, hands-on investigations, and…

Wright, Russell G.

76

Tornado! An Event-Based Science Module. Teacher's Guide. Meteorology Module.  

ERIC Educational Resources Information Center

This book is designed for middle school earth science teachers to help their students learn about problems with tornadoes and scientific literacy through event-based science. Unlike traditional curricula, the event-based earth science module is a student-centered, interdisciplinary, inquiry-oriented program that emphasizes cooperative learning,…

Wright, Russell G.

77

Draft Title 40 CFR 191 compliance certification application for the Waste Isolation Pilot Plant. Volume 6: Appendix GCR Volume 1  

SciTech Connect

The Geological Characterization Report (GCR) for the WIPP site presents, in one document, a compilation of geologic information available to August, 1978, which is judged to be relevant to studies for the WIPP. The Geological Characterization Report for the WIPP site is neither a preliminary safety analysis report nor an environmental impact statement; these documents, when prepared, should be consulted for appropriate discussion of safety analysis and environmental impact. The Geological Characterization Report of the WIPP site is a unique document and at this time is not required by regulatory process. An overview is presented of the purpose of the WIPP, the purpose of the Geological Characterization Report, the site selection criteria, the events leading to studies in New Mexico, status of studies, and the techniques employed during geological characterization.

NONE

1995-03-31

78

Differential regulation of the overlapping Kaposi's sarcoma-associated herpesvirus vGCR (orf74) and LANA (orf73) promoters.  

PubMed

Similar to that of other herpesviruses, Kaposi's sarcoma-associated herpesvirus (KSHV/HHV-8) lytic replication destroys the host cell, while the virus can persist in a latent state in synchrony with the host. During latency only a few genes are transcribed, and the question becomes one of what determines latent versus lytic gene expression. Here we undertake a detailed analysis of the latency-associated nuclear antigen (LANA [orf73]) promoter (LANAp). We characterized a minimal region that is necessary and sufficient to maintain high-level transcription in all tissues tested, including primary endothelial cells and B cells, which are the suspected natural host for KSHV. We show that in transient-transfection assays LANAp mimics the expression pattern observed for the authentic promoter in the context of the KSHV episome. Unlike other KSHV promoters tested thus far, LANAp is not affected by tetradecanoyl phorbol acetate or viral lytic cycle functions. It is, however, subject to control by LANA itself and cellular regulatory factors, such as p53. This is in contrast to the K14/vGCR (orf74) promoter, which overlaps LANAp and directs transcription on the opposite strand. We isolated a minimal cis-regulatory region sufficient for K14/vGCR promoter activity and show that it, too, mimics the regulation observed for the authentic viral promoter. In particular, we demonstrate that its activity is absolutely dependent on the immediate-early transactivator orf50, the KSHV homolog of the Epstein-Barr virus Rta transactivator. PMID:11160678

Jeong, J; Papin, J; Dittmer, D

2001-02-01

79

Differential Regulation of the Overlapping Kaposi's Sarcoma-Associated Herpesvirus vGCR (orf74) and LANA (orf73) Promoters  

PubMed Central

Similar to that of other herpesviruses, Kaposi's sarcoma-associated herpesvirus (KSHV/HHV-8) lytic replication destroys the host cell, while the virus can persist in a latent state in synchrony with the host. During latency only a few genes are transcribed, and the question becomes one of what determines latent versus lytic gene expression. Here we undertake a detailed analysis of the latency-associated nuclear antigen (LANA [orf73]) promoter (LANAp). We characterized a minimal region that is necessary and sufficient to maintain high-level transcription in all tissues tested, including primary endothelial cells and B cells, which are the suspected natural host for KSHV. We show that in transient-transfection assays LANAp mimics the expression pattern observed for the authentic promoter in the context of the KSHV episome. Unlike other KSHV promoters tested thus far, LANAp is not affected by tetradecanoyl phorbol acetate or viral lytic cycle functions. It is, however, subject to control by LANA itself and cellular regulatory factors, such as p53. This is in contrast to the K14/vGCR (orf74) promoter, which overlaps LANAp and directs transcription on the opposite strand. We isolated a minimal cis-regulatory region sufficient for K14/vGCR promoter activity and show that it, too, mimics the regulation observed for the authentic viral promoter. In particular, we demonstrate that its activity is absolutely dependent on the immediate-early transactivator orf50, the KSHV homolog of the Epstein-Barr virus Rta transactivator. PMID:11160678

Jeong, Joseph; Papin, James; Dittmer, Dirk

2001-01-01

80

Concepts and models for typing events for event-based systems  

Microsoft Academic Search

Event-based systems are increasingly gaining widespread attention for applications that require integration with loosely coupled and distributed systems for time-critical business solutions. In this paper, we show concepts and models for representing, structuring and typing events. We discuss existing event models in the field and introduce the event model of the event-based system SARI for illustrating various typing concepts. The

Szabolcs Rozsnyai; Josef Schiefer; Alexander Schatten

2007-01-01

81

In vitro Manganese-Dependent Cross-Talk between Streptococcus mutans VicK and GcrR: Implications for Overlapping Stress Response Pathways  

PubMed Central

Streptococcus mutans, a major acidogenic component of the dental plaque biofilm, has a key role in caries etiology. Previously, we demonstrated that the VicRK two-component signal transduction system modulates biofilm formation, oxidative stress and acid tolerance responses in S. mutans. Using in vitro phosphorylation assays, here we demonstrate for the first time, that in addition to activating its cognate response regulator protein, the sensor kinase, VicK can transphosphorylate a non-cognate stress regulatory response regulator, GcrR, in the presence of manganese. Manganese is an important micronutrient that has been previously correlated with caries incidence, and which serves as an effector of SloR-mediated metalloregulation in S. mutans. Our findings supporting regulatory effects of manganese on the VicRK, GcrR and SloR, and the cross-regulatory networks formed by these components are more complex than previously appreciated. Using DNaseI footprinting we observed overlapping DNA binding specificities for VicR and GcrR in native promoters, consistent with these proteins being part of the same transcriptional regulon. Our results also support a role for SloR as a positive regulator of the vicRK two component signaling system, since its transcription was drastically reduced in a SloR-deficient mutant. These findings demonstrate the regulatory complexities observed with the S. mutans manganese-dependent response, which involves cross-talk between non-cognate signal transduction systems (VicRK and GcrR) to modulate stress response pathways. PMID:25536343

Downey, Jennifer S.; Mashburn-Warren, Lauren; Ayala, Eduardo A.; Senadheera, Dilani B.; Hendrickson, Whitney K.; McCall, Lathan W.; Sweet, Julie G.; Cvitkovitch, Dennis G.; Spatafora, Grace A.; Goodman, Steven D.

2014-01-01

82

An Event-Based Approach to Distributed Diagnosis of Continuous Systems  

NASA Technical Reports Server (NTRS)

Distributed fault diagnosis solutions are becoming necessary due to the complexity of modern engineering systems, and the advent of smart sensors and computing elements. This paper presents a novel event-based approach for distributed diagnosis of abrupt parametric faults in continuous systems, based on a qualitative abstraction of measurement deviations from the nominal behavior. We systematically derive dynamic fault signatures expressed as event-based fault models. We develop a distributed diagnoser design algorithm that uses these models for designing local event-based diagnosers based on global diagnosability analysis. The local diagnosers each generate globally correct diagnosis results locally, without a centralized coordinator, and by communicating a minimal number of measurements between themselves. The proposed approach is applied to a multi-tank system, and results demonstrate a marked improvement in scalability compared to a centralized approach.

Daigle, Matthew; Roychoudhurry, Indranil; Biswas, Gautam; Koutsoukos, Xenofon

2010-01-01

83

An event-based approach to validating solar wind speed predictions: High-speed  

E-print Network

An event-based approach to validating solar wind speed predictions: High-speed enhancements in the Wang-Sheeley-Arge model M. J. Owens Center for Space Physics, Boston University, Boston, Massachusetts, Massachusetts, USA H. E. Spence and A. Pembroke Center for Space Physics, Boston University, Boston

California at Berkeley, University of

84

Tuning of event-based industrial controllers with simple stability guarantees  

E-print Network

sampling to actuating, is triggered all together by a single, periodic26 source of events. Correspondingly, and (b) there can be multiple28 sources of events.29 Referring to Figure 1, a variety of event: Event-based control loop. ing on how the event source(s) and triggering rule(s) make the sensor

Como, Giacomo

85

SUPERVISED MODEL TRAINING FOR OVERLAPPING SOUND EVENTS BASED ON UNSUPERVISED SOURCE SEPARATION  

E-print Network

SUPERVISED MODEL TRAINING FOR OVERLAPPING SOUND EVENTS BASED ON UNSUPERVISED SOURCE SEPARATION Toni event detection is addressed in the presence of overlapping sounds. Unsupervised sound source separation percentage units in the detection accuracy. Index Terms-- acoustic event detection, sound source separa- tion

Virtanen, Tuomas

86

Event-based simulation of interference with alternatingly blocked particle sources  

E-print Network

We analyze the predictions of an event-based corpuscular model for interference in the case of two-beam interference experiments in which the two sources are alternatingly blocked. We show that such experiments may be used to test specific predictions of the corpuscular model.

K. Michielsen; S. Mohanty; L. Arnold; H. De Raedt

2011-12-12

87

A THREADED EVENT-BASED SIMULATION APPROACH TO ANALYZING THE INTELLI-  

E-print Network

Chapter 1 A THREADED EVENT-BASED SIMULATION APPROACH TO ANALYZING THE INTELLI- GENCE ON WMD ATTACKS help with intelligence analysis of WMD attacks against critical infrastructure. Keywords: Intelligence attacks against critical infrastructures. There are different types of WMD attacks [?], including chemical

Ritter, Frank

88

Autonomous Indoor Exploration with an Event-Based Visual SLAM System  

E-print Network

Autonomous Indoor Exploration with an Event-Based Visual SLAM System Raoul Hoffmann1, David to systems that autonomously localize themselves on a map while simultaneously creating and maintaining a purely visual solution would be preferred. Any such vision based system to date requires highly optimized

Kuehnlenz, Kolja

89

Event-Based Data Control in Healthcare Jatinder Singh and Jean Bacon  

E-print Network

Event-Based Data Control in Healthcare Jatinder Singh and Jean Bacon Computer Laboratory University transmission. Categories and Subject Descriptors C.2.4 [Computer-Communication Networks]: Distrib- uted Systems Keywords Data Control, Healthcare, Middleware, Publish/Subscribe 1. HEALTHCARE DIRECTIONS Health services

Cambridge, University of

90

A QUALITATIVE EVENT-BASED APPROACH TO FAULT DIAGNOSIS OF HYBRID SYSTEMS  

E-print Network

A QUALITATIVE EVENT-BASED APPROACH TO FAULT DIAGNOSIS OF HYBRID SYSTEMS By Matthew J. Daigle and multiple faults, (iii) developing an integrated framework for diagnosis of parametric, sensor, and discrete of the approach is demonstrated on two practical systems. First, the single fault diagnosis method for continuous

Daigle, Matthew

91

An Event-based Approach to Integrated Parametric and Discrete Fault Diagnosis in Hybrid Systems  

E-print Network

An Event-based Approach to Integrated Parametric and Discrete Fault Diagnosis in Hybrid Systems.j.daigle@nasa.gov, {xenofon.koutsoukos,gautam.biswas}@vanderbilt.edu Abstract Fault diagnosis is crucial for ensuring the safe for hybrid diagnosis of parametric and discrete faults by incorporating the effects of both types of faults

Daigle, Matthew

92

Foundations for Event-Based Process Analysis in Heterogeneous Software Engineering Environments  

E-print Network

Foundations for Event-Based Process Analysis in Heterogeneous Software Engineering Environments engineering processes. In this paper we build on a service-oriented platform for technically and semantically-based engineering processes. We empirically evaluate the approach using the "continuous integration and test

93

NASA Space Radiation Program Integrative Risk Model Toolkit  

NASA Technical Reports Server (NTRS)

NASA Space Radiation Program Element scientists have been actively involved in development of an integrative risk models toolkit that includes models for acute radiation risk and organ dose projection (ARRBOD), NASA space radiation cancer risk projection (NSCR), hemocyte dose estimation (HemoDose), GCR event-based risk model code (GERMcode), and relativistic ion tracks (RITRACKS), NASA radiation track image (NASARTI), and the On-Line Tool for the Assessment of Radiation in Space (OLTARIS). This session will introduce the components of the risk toolkit with opportunity for hands on demonstrations. The brief descriptions of each tools are: ARRBOD for Organ dose projection and acute radiation risk calculation from exposure to solar particle event; NSCR for Projection of cancer risk from exposure to space radiation; HemoDose for retrospective dose estimation by using multi-type blood cell counts; GERMcode for basic physical and biophysical properties for an ion beam, and biophysical and radiobiological properties for a beam transport to the target in the NASA Space Radiation Laboratory beam line; RITRACKS for simulation of heavy ion and delta-ray track structure, radiation chemistry, DNA structure and DNA damage at the molecular scale; NASARTI for modeling of the effects of space radiation on human cells and tissue by incorporating a physical model of tracks, cell nucleus, and DNA damage foci with image segmentation for the automated count; and OLTARIS, an integrated tool set utilizing HZETRN (High Charge and Energy Transport) intended to help scientists and engineers study the effects of space radiation on shielding materials, electronics, and biological systems.

Kim, Myung-Hee Y.; Hu, Shaowen; Plante, Ianik; Ponomarev, Artem L.; Sandridge, Chris

2015-01-01

94

Event-based Transmission Line Matrix Method for Simulating Site-Specific Multipath Propagation Characteristics  

SciTech Connect

Accurate radio channel modeling is essential for deploying advanced wireless sensors in harsh industrial and urban environments. Site-specific propagation modeling tools are required to understand the channel parameters with in these environments. Multipath delay spread determines the frequency-selective fading characteristics of the channel. This paper describes a novel computationally inexpensive technique to determine multipath delay spread. Event-based transmission line matrix-based method is used to simulate the channel.

Kuruganti, Phani Teja [ORNL] [ORNL; Nutaro, James J [ORNL] [ORNL; Djouadi, Seddik M [ORNL] [ORNL

2012-01-01

95

An Energy Efficient Layer for Event-Based Communications in Web-of-Things Frameworks  

E-print Network

to the concept of Internet-of-Things (IoT) [1]. This idiom includes the concept of Wireless Sensor Networks (WSN the energy consumption of things connected to the Internet through Wi-Fi. We rely on the Web-of-ThingsAn Energy Efficient Layer for Event-Based Communications in Web-of-Things Frameworks Gérôme Bovet1

Boyer, Edmond

96

The GCR All-Particle Spectrum in the 0.1-100 TeV Energy Range  

NASA Astrophysics Data System (ADS)

The results of direct measurements of the all particle spectra by five different instruments on satellites and balloons are considered. It is shown, that is the representatio as the flux multiplied by energy to the power of 2.6 the all-particle spectrum shows a 'step'. The parameters of this 'step' and its origin are analyzed. Historically it has so happ ened that the all-particle spectrum obtained as the sum individual components, the energy range 1 < E < (5 - 10) TeV in the proton spectrum is not covered by direct measurements. Usually this energy interval in the all-particle spectrum is filled via interp olation, which is bases on the assumption that the proton spectrum is similar to the spectrum of nuclei. This spectrum is usually considered to be the all-particle GCR spectrum Io (E ) [1]. Direct information on the all-particle spectrum in the energy range from 1 to 10 TeV can be obtained using direct measurements of the of the all-particle spectrum by electronic instruments. For the first time such information was obtained in 1972 as a result of the all-particle spectrum measurements by the SEZ-14 instrument on the 'Proton1,2,3' satellites and the SEZ-15 instrument on the 'Proton-4' satellite [2,3]. These measurements revealed an anomaly in the all-particle spectrum in the 1-10 TeV energy range. In 1997 the spectrum was measured again by the TIC instrument [4]. The TIC instrument measured the energy release of all-particles arriving from arbitrary directions. As it was shown by the authors in [4,5] the energy release spectrum revealed the same anomaly in the all-particle spectrum, previously observed in the measurements made on 'Proton' satellites [2]. The results of the measurements made by the TIC, SEZ-14 and SEZ-15 are shown in Fig.1. The solid line in Fig.1 shows the function ?(E ), which gives a good approximation of the experimental all-particle spectrum at a =0.4 TeV. ?(E ) = E 2.6 Io (E ) (E /a)3 0.11 } + 0.130m-2s-1 sr -1 T eV 1.6 (1) {1 + 0.37 = [1 + (E /a)3 ]0.2 1 + (E /a)3 It can be seen from Fig.1 that the anomaly in the all-particle spectrum shows a

Tolstaya, Ekaterina D.; Grigorov, N. L.

2003-07-01

97

An efficient causative event-based approach for deriving the annual flood frequency distribution  

NASA Astrophysics Data System (ADS)

In ungauged catchments or catchments without sufficient streamflow data, derived flood frequency methods are often applied to provide the basis for flood risk assessment. The most commonly used event-based methods, such as design storm and joint probability approaches are able to give fast estimation, but can also lead to prediction bias and uncertainties due to the limitations of inherent assumptions and difficulties in obtaining input information (rainfall and catchment wetness) related to events that cause extreme floods. An alternative method is a long continuous simulation which produces more accurate predictions, but at the cost of massive computational time. In this study a hybrid method was developed to make the best use of both event-based and continuous approaches. The method uses a short continuous simulation to provide inputs for a rainfall-runoff model running in an event-based fashion. The total probability theorem is then combined with the peak over threshold method to estimate annual flood distribution. A synthetic case study demonstrates the efficacy of this procedure compared with existing methods of estimating annual flood distribution. The main advantage of the hybrid method is that it provides estimates of the flood frequency distribution with an accuracy similar to the continuous simulation approach, but with dramatically reduced computation time. This paper presents the method at the proof-of-concept stage of development and future work is required to extend the method to more realistic catchments.

Li, Jing; Thyer, Mark; Lambert, Martin; Kuczera, George; Metcalfe, Andrew

2014-03-01

98

The Design and Implementation of Real-time Event-based Applications with Damien Masson and Serge Midonnet  

E-print Network

The Design and Implementation of Real-time Event-based Applications with RTSJ Damien Masson This paper presents a framework to design real-time event-based applications using Java. The Real-Time Spec- ification for Java (RTSJ) is well designed for hard periodic real-time systems. Though it also proposes

Paris-Sud XI, Université de

99

Measuring pesticides in surface waters - continuous versus event-based sampling design  

NASA Astrophysics Data System (ADS)

Monitoring pesticides in surface waters is still a work- and cost-intensive procedure. Therefore, studies are normally carried out with a low monitoring frequency or with only a small selection of substances to be analyzed. In this case, it is not possible to picture the high temporal variability of pesticide concentrations, depending on application dates, weather conditions, cropping seasons and other factors. In 2007 the Institute of Landscape Ecology and Resource Management at Giessen University implemented a monitoring program during two pesticide application periods aiming to produce a detailed dataset of pesticide concentration for a wide range of substances, and which would also be suitable for the evaluation of catchment-scale pesticide exposure models. The Weida catchment in Thuringia (Eastern Germany) was selected as study area due to the availability of detailed pesticide application data for this region. The samples were taken from the river Weida at the gauge Zeulenroda, where it flows into a drinking water reservoir. The catchment area is 102 km². 67% of the area are in agricultural use, the main crops being winter wheat, maize, winter barley and winter rape. Dominant soil texture classes are loamy sand and loamy silt. About one third of the agricultural area is drained. The sampling was carried out in cooperation with the water supply agency of Thuringia (Fernwasserversorgung Thueringen). The sample analysis was done by the Institute of Environmental Research at Dortmund University. Two sampling schemes were carried out using two automatic samplers: continuous sampling with composite samples bottled two times per week and event-based sampling triggered by a discharge threshold. 53 samples from continuous sampling were collected. 19 discharge events were sampled with 45 individual samples (one to six per event). 34 pesticides and two metabolites were analyzed. 21 compounds were detected, nine of which having concentrations above the drinking water limit (0.1 µg/l). Pesticide loads were calculated separately from continuous and event-based samples. Only three pesticides dominated the total load. These were the herbicides metazachlor, terbuthylazine and quinmerac amounting to 75 % of the total load. This result seems to be plausible considering the fact that these three substances are the pesticides with the highest applied amounts in the Weida catchment. The highest pesticide loads of single pesticides were observed during or shortly after their application period, mostly accompanied by larger discharge events. They can be explained as surface runoff and drainage inputs from treated fields, since spray-drift inputs would be detected during the application periods without dependency on discharge events, and inputs from point-sources are usually independent of discharge as well. Annual loads calculated from continuous samples were mainly higher than those of event-based samples due to the fact that they represent a much longer time period. On the other hand, the highest concentrations were found in the event-based samples; in many cases they double the maximum concentrations of continuous samples. The monitoring study presented shows that different sampling strategies lead to different results and can answer different questions. If the intention is to detect maximum concentrations caused by surface runoff or drainage inputs, e.g. to assess the resulting risk to the aquatic community, the event based sampling method can be recommended. If one is rather interested in calculating annual pesticide loads and assessing which fractions of applied amounts finally enter the surface water network, continuous sampling is advisable. The dataset of continuous and event-based pesticide concentrations offers the possibility to evaluate and improve pesticide exposure models at the catchment scale. Further work is scheduled on this issue.

Eyring, J.; Bach, M.; Frede, H.-G.

2009-04-01

100

Fast vision through frameless event-based sensing and convolutional processing: application to texture recognition.  

PubMed

Address-event representation (AER) is an emergent hardware technology which shows a high potential for providing in the near future a solid technological substrate for emulating brain-like processing structures. When used for vision, AER sensors and processors are not restricted to capturing and processing still image frames, as in commercial frame-based video technology, but sense and process visual information in a pixel-level event-based frameless manner. As a result, vision processing is practically simultaneous to vision sensing, since there is no need to wait for sensing full frames. Also, only meaningful information is sensed, communicated, and processed. Of special interest for brain-like vision processing are some already reported AER convolutional chips, which have revealed a very high computational throughput as well as the possibility of assembling large convolutional neural networks in a modular fashion. It is expected that in a near future we may witness the appearance of large scale convolutional neural networks with hundreds or thousands of individual modules. In the meantime, some research is needed to investigate how to assemble and configure such large scale convolutional networks for specific applications. In this paper, we analyze AER spiking convolutional neural networks for texture recognition hardware applications. Based on the performance figures of already available individual AER convolution chips, we emulate large scale networks using a custom made event-based behavioral simulator. We have developed a new event-based processing architecture that emulates with AER hardware Manjunath's frame-based feature recognition software algorithm, and have analyzed its performance using our behavioral simulator. Recognition rate performance is not degraded. However, regarding speed, we show that recognition can be achieved before an equivalent frame is fully sensed and transmitted. PMID:20181543

Perez-Carrasco, Jose Antonio; Acha, Begona; Serrano, Carmen; Camunas-Mesa, Luis; Serrano-Gotarredona, Teresa; Linares-Barranco, Bernabe

2010-04-01

101

Lessons Learned from Real-Time, Event-Based Internet Science Communications  

NASA Technical Reports Server (NTRS)

For the last several years the Science Directorate at Marshall Space Flight Center has carried out a diverse program of Internet-based science communication. The Directorate's Science Roundtable includes active researchers, NASA public relations, educators, and administrators. The Science@NASA award-winning family of Web sites features science, mathematics, and space news. The program includes extended stories about NASA science, a curriculum resource for teachers tied to national education standards, on-line activities for students, and webcasts of real-time events. The focus of sharing science activities in real-time has been to involve and excite students and the public about science. Events have involved meteor showers, solar eclipses, natural very low frequency radio emissions, and amateur balloon flights. In some cases, broadcasts accommodate active feedback and questions from Internet participants. Through these projects a pattern has emerged in the level of interest or popularity with the public. The pattern differentiates projects that include science from those that do not, All real-time, event-based Internet activities have captured public interest at a level not achieved through science stories or educator resource material exclusively. The worst event-based activity attracted more interest than the best written science story. One truly rewarding lesson learned through these projects is that the public recognizes the importance and excitement of being part of scientific discovery. Flying a camera to 100,000 feet altitude isn't as interesting to the public as searching for viable life-forms at these oxygen-poor altitudes. The details of these real-time, event-based projects and lessons learned will be discussed.

Phillips, T.; Myszka, E.; Gallagher, D. L.; Adams, M. L.; Koczor, R. J.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

102

Valenced Cues and Contexts Have Different Effects on Event-Based Prospective Memory  

PubMed Central

This study examined the separate influence and joint influences on event-based prospective memory task performance due to the valence of cues and the valence of contexts. We manipulated the valence of cues and contexts with pictures from the International Affective Picture System. The participants, undergraduate students, showed higher performance when neutral compared to valenced pictures were used for cueing prospective memory. In addition, neutral pictures were more effective as cues when they occurred in a valenced context than in the context of neutral pictures, but the effectiveness of valenced cues did not vary across contexts that differed in valence. The finding of an interaction between cue and context valence indicates that their respective influence on event-based prospective memory task performance cannot be understood in isolation from each other. Our findings are not consistent with by the prevailing view which holds that the scope of attention is broadened and narrowed, respectively, by positively and negatively valenced stimuli. Instead, our findings are more supportive of the recent proposal that the scope of attention is determined by the motivational intensity associated with valenced stimuli. Consistent with this proposal, we speculate that the motivational intensity associated with different retrieval cues determines the scope of attention, that contexts with different valence values determine participants’ task engagement, and that prospective memory task performance is determined jointly by attention scope and task engagement. PMID:25647484

Graf, Peter; Yu, Martin

2015-01-01

103

Event-based plausibility immediately influences on-line language comprehension.  

PubMed

In some theories of sentence comprehension, linguistically relevant lexical knowledge, such as selectional restrictions, is privileged in terms of the time-course of its access and influence. We examined whether event knowledge computed by combining multiple concepts can rapidly influence language understanding even in the absence of selectional restriction violations. Specifically, we investigated whether instruments can combine with actions to influence comprehension of ensuing patients of (as in Rayner, Warren, Juhuasz, & Liversedge, 2004; Warren & McConnell, 2007). Instrument-verb-patient triplets were created in a norming study designed to tap directly into event knowledge. In self-paced reading (Experiment 1), participants were faster to read patient nouns, such as hair, when they were typical of the instrument-action pair (Donna used the shampoo to wash vs. the hose to wash). Experiment 2 showed that these results were not due to direct instrument-patient relations. Experiment 3 replicated Experiment 1 using eyetracking, with effects of event typicality observed in first fixation and gaze durations on the patient noun. This research demonstrates that conceptual event-based expectations are computed and used rapidly and dynamically during on-line language comprehension. We discuss relationships among plausibility and predictability, as well as their implications. We conclude that selectional restrictions may be best considered as event-based conceptual knowledge rather than lexical-grammatical knowledge. PMID:21517222

Matsuki, Kazunaga; Chow, Tracy; Hare, Mary; Elman, Jeffrey L; Scheepers, Christoph; McRae, Ken

2011-07-01

104

On event-based PI control of first-order processes Ubaldo Tiberi, Jose Araujo, Karl Henrik Johansson  

E-print Network

On event-based PI control of first-order processes Ubaldo Tiberi, Jos´e Ara´ujo, Karl Henrik-mail:{ubaldot,araujo,kallej}@ee.kth.se) Abstract: In this paper the design of an event-based proportional-integral (PI) control scheme for stable instants based on an estimate of the PI control signal is proposed. This mechanism addresses some side

Johansson, Karl Henrik

105

Event-based knowledge extraction from free-text descriptions for art images by using semantic role labeling approaches  

Microsoft Academic Search

Purpose – The purpose of this paper is to show how previous studies have demonstrated that non-professional users prefer using event-based conceptual descriptions, such as “a woman wearing a hat”, to describe and search images. In many art image archives, these conceptual descriptions are manually annotated in free-text fields. This study aims to explore technologies to automate event-based knowledge extractions

Chia-hung Lin; Chia-wei Yen; Jen-shin Hong; Samuel Cruz-lara

2008-01-01

106

GCR and SPE organ doses in deep space with different shielding: Monte Carlo simulations based on the FLUKA code coupled to anthropomorphic phantoms  

NASA Astrophysics Data System (ADS)

Astronauts' exposure to space radiation is of high concern for long-term missions, especially for those in deep space such as possible travels to Mars. In these cases shielding optimization is a crucial issue, and simulations based on radiation transport codes and anthropomorphic model phantoms can be of great help. In this work the FLUKA Monte Carlo code was coupled with two anthropomorphic phantoms (a mathematical model and a "voxel" model) to calculate organ-averaged dose, dose equivalent and "biological dose" in the various tissues and organs following exposure to the August 1972 Solar Particle Event and to Galactic Cosmic Rays under different shielding conditions. The "biological dose" was characterized by the average number of induced "Complex Lesions" (CLs) per cell in a given organ or tissue, where CLs are clustered DNA breaks which can play an important role in chromosome aberration induction. Separate calculation of the contributions from secondary hadrons - in particular neutrons - with respect to primary particles allowed us to quantify the role played by nuclear interactions occurring in the shield and in the human body. Specifically for GCR, the contributions from the different components of the incident primary spectra were calculated separately as well. As expected, the SPE doses showed a dramatic decrease with increasing Al shielding. Furthermore, for SPEs internal organs received much lower doses with respect to skin, and nuclear interactions were found to be of minor importance. A 10 g/cm 2 Al storm shelter turned out to be sufficient to respect the NCRP limits for 30-days LEO missions in case of a SPE similar to the August 1972 event. In contrast with SPEs, GCR absorbed doses remained roughly constant with increasing Al shielding. The organ-averaged dose equivalent and biological dose showed a (slight) decrease starting from a shield thickness of 2 g/cm 2, probably due the lower LET of projectile fragments.

Ballarini, F.; Battistoni, G.; Cerutti, F.; Fassò, A.; Ferrari, A.; Gadioli, E.; Garzelli, M. V.; Mairani, A.; Ottolenghi, A.; Paretzke, H. G.; Parini, V.; Pelliccioni, M.; Pinsky, L.; Sala, P. R.; Scannicchio, D.; Trovati, S.; Zankl, M.

107

Simulation of greenhouse climate monitoring and control with wireless sensor network and event-based control.  

PubMed

Monitoring and control of the greenhouse environment play a decisive role in greenhouse production processes. Assurance of optimal climate conditions has a direct influence on crop growth performance, but it usually increases the required equipment cost. Traditionally, greenhouse installations have required a great effort to connect and distribute all the sensors and data acquisition systems. These installations need many data and power wires to be distributed along the greenhouses, making the system complex and expensive. For this reason, and others such as unavailability of distributed actuators, only individual sensors are usually located in a fixed point that is selected as representative of the overall greenhouse dynamics. On the other hand, the actuation system in greenhouses is usually composed by mechanical devices controlled by relays, being desirable to reduce the number of commutations of the control signals from security and economical point of views. Therefore, and in order to face these drawbacks, this paper describes how the greenhouse climate control can be represented as an event-based system in combination with wireless sensor networks, where low-frequency dynamics variables have to be controlled and control actions are mainly calculated against events produced by external disturbances. The proposed control system allows saving costs related with wear minimization and prolonging the actuator life, but keeping promising performance results. Analysis and conclusions are given by means of simulation results. PMID:22389597

Pawlowski, Andrzej; Guzman, Jose Luis; Rodríguez, Francisco; Berenguel, Manuel; Sánchez, José; Dormido, Sebastián

2009-01-01

108

Simulation of Greenhouse Climate Monitoring and Control with Wireless Sensor Network and Event-Based Control  

PubMed Central

Monitoring and control of the greenhouse environment play a decisive role in greenhouse production processes. Assurance of optimal climate conditions has a direct influence on crop growth performance, but it usually increases the required equipment cost. Traditionally, greenhouse installations have required a great effort to connect and distribute all the sensors and data acquisition systems. These installations need many data and power wires to be distributed along the greenhouses, making the system complex and expensive. For this reason, and others such as unavailability of distributed actuators, only individual sensors are usually located in a fixed point that is selected as representative of the overall greenhouse dynamics. On the other hand, the actuation system in greenhouses is usually composed by mechanical devices controlled by relays, being desirable to reduce the number of commutations of the control signals from security and economical point of views. Therefore, and in order to face these drawbacks, this paper describes how the greenhouse climate control can be represented as an event-based system in combination with wireless sensor networks, where low-frequency dynamics variables have to be controlled and control actions are mainly calculated against events produced by external disturbances. The proposed control system allows saving costs related with wear minimization and prolonging the actuator life, but keeping promising performance results. Analysis and conclusions are given by means of simulation results. PMID:22389597

Pawlowski, Andrzej; Guzman, Jose Luis; Rodríguez, Francisco; Berenguel, Manuel; Sánchez, José; Dormido, Sebastián

2009-01-01

109

Selection of intense rainfall events based on intensity thresholds and lightning data in Switzerland  

NASA Astrophysics Data System (ADS)

This paper presents a method to identify intense warm season storms of convective character based on intensity thresholds and lightning, and analyzes their statistical properties. Long records of precipitation and lightning data at 4 stations and 10 min resolution in different climatological regions in Switzerland are used. Our premise is that thunderstorms associated with lightning generate bursts of high rainfall intensity. We divided all storms into those accompanied by lightning and those without lightning and found the threshold I* that separates intense events based on peak 10 min intensity Ip ? I* for a chosen misclassification rate ?. The performance and robustness of the selection method was tested by investigating the inter-annual variability of I* and its relation to the frequency of lightning strikes. The probability distributions of the main storm properties (rainfall depth R, event duration D, average storm intensity Ia and peak 10 min intensity Ip) for the intense storm subsets show that the event average and peak intensities are significantly different between the stations, and highest in Lugano in southern Switzerland. Non-parametric correlations between the main storm properties were estimated for the subsets of intense storms and all storms including stratiform rain. The differences in the correlations between storm subsets are greater than those between stations, which indicates that care must be exercised not to mix events when they are sampled for multivariate analysis, e.g. copula fitting to rainfall data.

Gaal, L.; Molnar, P.; Szolgay, J.

2014-01-01

110

Selection of intense rainfall events based on intensity thresholds and lightning data in Switzerland  

NASA Astrophysics Data System (ADS)

This paper presents a method to identify intense warm season storms with convective character based on intensity thresholds and the presence of lightning, and analyzes their statistical properties. Long records of precipitation and lightning data at 4 stations and 10 min resolution in different climatological regions in Switzerland are used. Our premise is that thunderstorms associated with lightning generate bursts of high rainfall intensity. We divided all recorded storms into those accompanied by lightning and those without lightning and found the threshold I* that separates intense events based on peak 10 min intensity Ip ? I* for a chosen misclassification rate ?. The performance and robustness of the selection method was tested by investigating the inter-annual variability of I* and its relation to the frequency of lightning strikes. The probability distributions of the main storm properties (rainfall depth R, event duration D, average storm intensity Ia and peak 10 min intensity Ip) for the intense storm subsets show that the event average and peak intensities are significantly different between the stations. Non-parametric correlations between the main storm properties were estimated for intense storms and all storms including stratiform rain. The differences in the correlations between storm subsets are greater than those between stations, which indicates that care must be exercised not to mix events of different origin when they are sampled for multivariate analysis, for example, copula fitting to rainfall data.

Gaál, L.; Molnar, P.; Szolgay, J.

2014-05-01

111

Assessing the Continuum of Event-Based Biosurveillance Through an Operational Lens  

SciTech Connect

This research follows the Updated Guidelines for Evaluating Public Health Surveillance Systems, Recommendations from the Guidelines Working Group, published by the Centers for Disease Control and Prevention nearly a decade ago. Since then, models have been developed and complex systems have evolved with a breadth of disparate data to detect or forecast chemical, biological, and radiological events that have significant impact in the One Health landscape. How the attributes identified in 2001 relate to the new range of event-based biosurveillance (EBB) technologies is unclear. This manuscript frames the continuum of EBB methods, models, and constructs through an operational lens (i.e., aspects and attributes associated with operational considerations in the development, testing, and validation of the EBB methods and models and their use in an operational environment). A 2-day subject matter expert workshop was held to scientifically identify, develop, and vet a set of attributes for the broad range of such operational considerations. Workshop participants identified and described comprehensive attributes for the characterization of EBB. The identified attributes are: (1) event, (2) readiness, (3) operational aspects, (4) geographic coverage, (5) population coverage, (6) input data, (7) output, and (8) cost. Ultimately, the analyses herein discuss the broad scope, complexity, and relevant issues germane to EBB useful in an operational environment.

Corley, Courtney D.; Lancaster, Mary J.; Brigantic, Robert T.; Chung, James S.; Walters, Ronald A.; Arthur, Ray; Bruckner-Lea, Cindy J.; Calapristi, Augustin J.; Dowling, Glenn; Hartley, David M.; Kennedy, Shaun; Kircher, Amy; Klucking, Sara; Lee, Eva K.; McKenzie, Taylor K.; Nelson, Noele P.; Olsen, Jennifer; Pancerella, Carmen M.; Quitugua, Teresa N.; Reed, Jeremy T.; Thomas, Carla S.

2012-03-28

112

A Review of Evaluations of Electronic Event-Based Biosurveillance Systems  

PubMed Central

Electronic event-based biosurveillance systems (EEBS’s) that use near real-time information from the internet are an increasingly important source of epidemiologic intelligence. However, there has not been a systematic assessment of EEBS evaluations, which could identify key uncertainties about current systems and guide EEBS development to most effectively exploit web-based information for biosurveillance. To conduct this assessment, we searched PubMed and Google Scholar to identify peer-reviewed evaluations of EEBS’s. We included EEBS’s that use publicly available internet information sources, cover events that are relevant to human health, and have global scope. To assess the publications using a common framework, we constructed a list of 17 EEBS attributes from published guidelines for evaluating health surveillance systems. We identified 11 EEBS’s and 20 evaluations of these EEBS’s. The number of published evaluations per EEBS ranged from 1 (Gen-Db, GODsN, MiTAP) to 8 (GPHIN, HealthMap). The median number of evaluation variables assessed per EEBS was 8 (range, 3–15). Ten published evaluations contained quantitative assessments of at least one key variable. No evaluations examined usefulness by identifying specific public health decisions, actions, or outcomes resulting from EEBS outputs. Future EEBS assessments should identify and discuss critical indicators of public health utility, especially the impact of EEBS’s on public health response. PMID:25329886

Gajewski, Kimberly N.; Peterson, Amy E.; Chitale, Rohit A.; Pavlin, Julie A.; Russell, Kevin L.; Chretien, Jean-Paul

2014-01-01

113

Models and Monte Carlo simulations of GCR and SPE organ doses with different shielding, based on the FLUKA code coupled with anthropomorphic phantoms  

NASA Astrophysics Data System (ADS)

Astronauts' exposure to space radiation is of major concern for long-term missions, especially for those in deep space such as a possible mission to Mars. Shielding optimization is therefore a crucial issue, and simulations based on radiation transport codes coupled with anthropomorphic model phantoms can be of great help. In this work, carried out with the FLUKA MC code and two anthropomorphic phantoms (a mathematical model and a "voxel" model), distributions of physical (i.e. absorbed), equivalent and "biological" dose in the various tissues and organs were calculated in different shielding conditions for solar minimum and solar maximum GCR spectra, as well as for the August 1972 Solar Particle Event. The biological dose was modeled as the average number of "Complex Lesions" (CL) per cell in a given organ. CLs are clustered DNA breaks previously calculated with "event-by-event" track structure simulations and integrated in the condensed-history FLUKA code. This approach is peculiar in that it is an example of a mechanistically-based quantification of the ionizing radiation action in biological targets; indeed CLs have been shown to play a fundamental role in chromosome aberration induction. The contributions of primary particles and secondary hadrons were calculated separately, thus allowing quantification of the role of nuclear reactions in the shield and in the human body. As expected, the doses calculated for the 1972 SPE decrease dramatically with increasing the Al shielding; nuclear reactions were found to be of minor importance, although their role is higher for internal organs and large shielding. An Al shield thickness of 10 g/cm2 appears sufficient to respect the 30-day deterministic limits recommended by NCRP for missions in Low Earth Orbit. In contrast with the results obtained for SPE, GCR doses to internal organs are not significantly lower than skin doses. However, the relative contribution of secondary hadrons was found to be more important for internal organs due to nuclear interactions in the human body. Both for skin and for internal organs, the physical dose was found to be essentially independent of the shield thickness. The equivalent and biological doses to skin show a significant decrease starting from 5 g/cm2, whereas internal organs show more complex trends characterized by minima and maxima mainly dependent on the organ type. Polyethylene shielding resulted to be more effective with respect to Aluminum.

Ballarini, F.; Fluka-Phantoms Team

114

Event-based Green Scheduling of Radiant Systems in Buildings Truong X. Nghiem, George J. Pappas and Rahul Mangharam  

E-print Network

, the building's thermal mass can be utilized to flatten out peaks in energy demand. Nowadays, radiant systems predictive control was shown to improve the comfort and energy consumption of radiant systems in [4Event-based Green Scheduling of Radiant Systems in Buildings Truong X. Nghiem, George J. Pappas

Pappas, George J.

115

Modulation of a Fronto-Parietal Network in Event-Based Prospective Memory: An rTMS Study  

ERIC Educational Resources Information Center

Event-based prospective memory (PM) is a multi-component process that requires remembering the delayed execution of an intended action in response to a pre-specified PM cue, while being actively engaged in an ongoing task. Some neuroimaging studies have suggested that both prefrontal and parietal areas are involved in the maintenance and…

Bisiacchi, P. S.; Cona, G.; Schiff, S.; Basso, D.

2011-01-01

116

Determination of Time and Order for Event-Based Middleware in Mobile Peer-to-Peer Environments  

E-print Network

mobile P2P environments. Event correlation will be a multi-step operation from event sources to the finalDetermination of Time and Order for Event-Based Middleware in Mobile Peer-to-Peer Environments Eiko, UK Email: {eiko.yoneki, jean.bacon}@cl.cam.ac.uk Abstract An event correlation is becoming

Cambridge, University of

117

Submission to International Journal of Control, Automation, and Systems 1 Event-Based Control of the Inverted Pendulum  

E-print Network

of the Inverted Pendulum: Swing up and Stabilization Sylvain Durand, J. Fermi Guerrero-Castellanos, Nicolas to control a nonlinear and unstable system, that is the inverted pendulum. We are first interested on the stabilization of the pendulum near its inverted position and propose an event-based control approach

Boyer, Edmond

118

Event-based knowledge elicitation of operating room management decision-making using scenarios adapted from information systems data  

Microsoft Academic Search

BACKGROUND: No systematic process has previously been described for a needs assessment that identifies the operating room (OR) management decisions made by the anesthesiologists and nurse managers at a facility that do not maximize the efficiency of use of OR time. We evaluated whether event-based knowledge elicitation can be used practically for rapid assessment of OR management decision-making at facilities,

Franklin Dexter; Ruth E Wachtel; Richard H Epstein

2011-01-01

119

Using Event Based Data to Assess Vehicle Pedestrian Crash Risk in the Absence of All-Red  

E-print Network

Using Event Based Data to Assess Vehicle Pedestrian Crash Risk in the Absence of All-Red Phase decision making at a signalized intersection? Ã? How effective is the signal timing (particularly "All-Red lane.) #12;4 4 Ã?Data analyzed between 10:30 am to 5 pm. Ã?Typical Yellow duration = 3 secs, All-Red

Minnesota, University of

120

A Computationally Fast and Parametric Model to Estimate Protein-Ligand Docking Time for Stochastic Event Based Simulation  

Microsoft Academic Search

This paper presents a computationally fast analytical model to estimate the time taken for protein-ligand docking in biological\\u000a pathways. The environment inside the cell has been reported to be unstable with a considerable degree of randomness creating\\u000a a stochastic resonance. To facilitate the understanding of the dynamic behavior of biological systems, we propose an “in silico”\\u000a stochastic event based simulation.

Preetam Ghosh; Samik Ghosh; Kalyan Basu; Sajal K. Das

2007-01-01

121

Observer Agreement for Timed-Event Sequential Data: A Comparison of Time-Based and Event-Based Algorithms  

PubMed Central

Observer agreement is often regarded as the sine qua non of observational research. Cohen’s kappa is a widely-used index and is appropriate when discrete entities, such as a turn-of-talk or a demarcated time-interval, are presented to pairs of observers to code. Kappa-like statistics and agreement matrixes are also used for the timed-event sequential data produced when observers first segment and then code events detected in the stream of behavior, noting onset and offset times. Such kappas are of two kinds, time-based and event-based. Available for download is a computer program (OASTES, Observer Agreement for Simulated Timed Event Sequences) that simulates the coding of observers of a stated accuracy, and then computes agreement statistics for two time-based kappas (with and without tolerance) and three event-based kappas (one implemented in The Observer, one in INTERACT, and one in GSEQ). Based on simulation results presented here, and due to the somewhat different information provide by each, reporting of both a time-based and an event-based kappa is recommended. PMID:19182133

Bakeman, Roger; Quera, Vicenç; Gnisci, Augusto

2009-01-01

122

Effective utilization of flue gases in raceway reactor with event-based pH control for microalgae culture.  

PubMed

This work addresses effective utilization of flue gases through the proper pH control in raceway reactors. The pH control problem has been addressed with an event-based control approach using a Generalized Predictive Controller (GPC) with actuator deadband. Applying this control strategy it is possible to reduce the control effort, and at the same time saving control resources. In the pH process case, the event-based controller with actuator deadband can be tuned to supply only necessary amount of CO2 to keep the pH close to its optimal value. On the other hand, the evaluated control algorithm significantly improves the pH control accuracy, what has a direct influence on biomass production. In order to test the performance of the event-based GPC controller, several experiments have been performed on a real raceway reactor. Additionally, several control performance indexes have been used to compare the analyzed technique with commonly used on/off controller. PMID:25113401

Pawlowski, A; Mendoza, J L; Guzmán, J L; Berenguel, M; Acién, F G; Dormido, S

2014-10-01

123

NIST GCR 02841 Between Invention  

E-print Network

_branscomb@harvard.edu Philip E. Auerswald Assistant Director, Science, Technology, and Public Policy Program Kennedy School OF STANDARDS AND TECHNOLOGY Arden L. Bement, Jr., Director #12;#12;Page iii Table of Contents PROJECT ADVISORY a project-level definition of technology-based innovation . . . . . 27 B. Applied research? Seed investment

Magee, Joseph W.

124

Concentration of electrostatic solitary waves around magnetic nulls within magnetic reconnection diffusion region: single-event-based statistics  

NASA Astrophysics Data System (ADS)

It is important to study the `concentrated' electrostatic solitary waves/structures (ESWs) associated with the magnetic reconnection. In the literature published as regards this topic, very few studies have reported the observation of such a large number of ESWs in a single magnetic reconnection event. In this work, we report our observation of a large number of ESWs around the magnetic null-pairs within the magnetic reconnection ion diffusion region of Earth's magnetosphere on 10 September 2001. With more than 9,600 cases of ESWs observed around magnetic null-pairs and more than 97,600 cases observed during the ion diffusion region crossing time span, the observation of such a large number of ESWs in the diffusion region has not been reported often in published works. We further perform single-event-based statistical analysis of the characteristics of the ESWs around magnetic null-pairs. Based on the statistical result, we speculate that the two-stream instability originating from the magnetic null and traveling outward along the plasma sheet boundary layer (PSBL) is the candidate mechanism of the large number of observed ESWs. Our observation and analysis in this work suggests that even with the presence of a complex magnetic structure around a magnetic null-pair in the three-dimensional regime, concentrated ESWs can be observed. This single-reconnection-event-based statistical result of ESWs around the magnetic null-pairs can aid in understanding the microdynamics associated with three-dimensional (3D) magnetic reconnection.

Li, Shiyou; Zhang, Shifeng; Cai, Hong; Yu, Sufang

2014-12-01

125

Monetary Incentive Effects on Event-Based Prospective Memory Three Months after Traumatic Brain Injury in Children  

PubMed Central

Information regarding the remediation of event-based prospective memory (EB-PM) impairments following pediatric traumatic brain injury (TBI) is scarce. Addressing this, two levels of monetary incentives were used to improve EB-PM in children ages 7 to 16 years with orthopedic injuries (OI, n = 51), or moderate (n = 25), and severe (n = 39) TBI at approximately three months postinjury. The EB-PM task consisted of the child giving a specific verbal response to a verbal cue from the examiner while performing a battery of neuropsychological measures (ongoing task). Significant effects were found for Age-at-Test, Motivation Condition, Period, and Group. Within-group analyses indicated OI and moderate TBI groups performed significantly better under the high-versus low-incentive condition, but the severe TBI group demonstrated no significant improvement. These results indicate EB-PM can be significantly improved at three months postinjury in children with moderate, but not severe, TBI. PMID:21347945

Pedroza, Claudia; Chapman, Sandra B.; Cook, Lori G.; Vásquez, Ana C.; Levin, Harvey S.

2011-01-01

126

Estimating the length of waits: a description of the period lifetable method and comparison with census and event based methods.  

PubMed

To discover whether the period lifetable provides more valid estimates of length of wait in prospect than are obtained using the lengths either of (current) waits captured at the time of the mid-period census or of the (prior) waits of those extracted over a specified period. We determined whether there was a surplus (or a deficiency) of extractions within the cross-classification of cohort and waiting time category which straddled each census. We used census-, event- and lifetable-based methods to produce three period-specific estimates of the percentage of waits of 0-2 months, and we determined whether length of wait grew shorter (or longer) from one period to the next. We used Lambda B to indicate the extent to which we were able to predict the direction of change in length of wait once we knew the direction of change in size of list. We found a direct correlation between change in length of wait and change in size of list, as expected under the stock-flow model, when length of wait was estimated using the lifetable for the period (L(B) = 58.33, 95% confidence interval [CI] = 29-88), but we obtained a null correlation when we used census-based estimates (L(B) = 6.45) and we obtained an inverse correlation when we used event-based estimates (L(B) = 57.14, 95% CI = 31-83). The period lifetable appears to provide more valid estimates of length of wait and should therefore be substituted for census- and event-based methods of estimation, wherever possible. PMID:22673699

Armstrong, Paul W

2012-05-01

127

Comparison of Patients with Parkinson's Disease or Cerebellar Lesions in the Production of Periodic Movements Involving Event-Based or Emergent Timing  

ERIC Educational Resources Information Center

We have hypothesized a distinction between the processes required to control the timing of different classes of periodic movements. In one class, salient events mark successive cycles. For these movements, we hypothesize that the temporal goal is a requisite component of the task representation, what we refer to as event-based timing. In the other…

Spencer, R.M.C.; Ivry, R.B.

2005-01-01

128

Time-Based and Event-Based Prospective Memory in Autism Spectrum Disorder: The Roles of Executive Function and Theory of Mind, and Time-Estimation  

ERIC Educational Resources Information Center

Prospective memory (remembering to carry out an action in the future) has been studied relatively little in ASD. We explored time-based (carry out an action at a pre-specified time) and event-based (carry out an action upon the occurrence of a pre-specified event) prospective memory, as well as possible cognitive correlates, among 21…

Williams, David; Boucher, Jill; Lind, Sophie; Jarrold, Christopher

2013-01-01

129

Time-based and event-based prospective memory in autism spectrum disorder: the roles of executive function and theory of mind, and time-estimation.  

PubMed

Prospective memory (remembering to carry out an action in the future) has been studied relatively little in ASD. We explored time-based (carry out an action at a pre-specified time) and event-based (carry out an action upon the occurrence of a pre-specified event) prospective memory, as well as possible cognitive correlates, among 21 intellectually high-functioning children with ASD, and 21 age- and IQ-matched neurotypical comparison children. We found impaired time-based, but undiminished event-based, prospective memory among children with ASD. In the ASD group, time-based prospective memory performance was associated significantly with diminished theory of mind, but not with diminished cognitive flexibility. There was no evidence that time-estimation ability contributed to time-based prospective memory impairment in ASD. PMID:23179340

Williams, David; Boucher, Jill; Lind, Sophie; Jarrold, Christopher

2013-07-01

130

Unit-specific event-based continuous-time approach for short-term scheduling of batch plants using RTN framework  

Microsoft Academic Search

The problem of short-term scheduling of batch plants has received remarkable attention in the past two decades. The state-task-network (STN) and resource-task-network (RTN) process representations are extensively used in modeling scheduling problems. In this paper, we propose a new model to investigate the RTN representation for unit-specific event-based models. For handling dedicated finite storage, a novel formulation is proposed without

Munawar A. Shaik; Christodoulos A. Floudas

2008-01-01

131

Limited correlation between conventional pathologist and automatic computer-assisted quantification of hepatic steatosis due to difference between event-based and surface-based analysis.  

PubMed

Computer-assisted automatic quantification (CAQ) was developed as an alternative method for the diagnosis of hepatic steatosis in order to compensate for observer-dependent bias. Here, we aim to demonstrate that CAQ can provide an accurate and precise result in analysis of fatty content, but that it is inappropriate to validate CAQ by comparison with conventional pathologist estimation (PE). Male rats were fed with a methionine-choline-deficient plus high-fat diet for three days, one week, or two weeks to induce mild, moderate, or severe steatosis. Samples were collected from all liver lobes. Severity of hepatic steatosis was assessed by an experienced pathologist who estimated the percentage of hepatocytes containing lipid droplets. Fatty content was quantified by PE, CAQ, and biochemical analysis (BA). CAQ, PE, and BA can correctly reflect severe fatty change. However, in the case of mild and moderate steatosis, PE could not reflect the true fatty content ( r between PE and BA was <0). The result of CAQ correlated well with that of BA among the various degrees of severity of hepatic steatosis. In conclusion, due to a difference between event-based and surface-based analysis, it is inappropriate to validate the CAQ of hepatic steatosis by comparison with PE. PMID:24235313

Deng, Meihong; Dahmen, Uta; Sun, Jian; Huang, Hai; Sehestedt, Christian; Homeyer, Andre; Schenk, Andrea; Dirsch, Olaf

2014-07-01

132

Event-based speed control on a sensor-less miniature thruster Thibaut Raharijaona1, Lorris Dola1, Bruno Boisseau2, John-Jairo Martinez-Molina2, Nicolas Marchand2  

E-print Network

derivative (PID) controller is presented with the simulation results applied to a double tank process period is removed and different event-based PID algorithms without safety limit condition were also for disturbed linear systems. In this paper, using miniature actuators which equipped the bio-inspired robot

Paris-Sud XI, Université de

133

Fitting an ex-Gaussian function to examine costs in event-based prospective memory: evidence for a continuous monitoring profile.  

PubMed

Event-based prospective memory (PM) tasks require individuals to remember to perform a deferred action when a target event occurs. PM task requirements can slow ongoing task responses on non-target trials ('costs') under conditions where the defining features of targets are non-focal to the ongoing task, which is indicative that individuals have allocated some form of cognitive control process to the PM task. Recent fits of the ex-Gaussian mathematical function to non-target trial response distributions by prior studies have indicated that these control processes are transiently allocated. In the current paper, fits of the ex-Gaussian function to data reported by Loft and Humphreys (2012) demonstrate a shift in the entire response time distribution (?) and an increase in skew (?) for a non-focal PM condition required to remember to make a PM response if presented with category exemplars, compared to a control condition. This change in ? is indicative of a more continuous PM monitoring profile than that reported by prior studies. In addition, within-subject variability in ? was reliably correlated with PM accuracy, suggesting that these control processes allocated on a regular basis were functional to PM accuracy. In contrast, when the ongoing task directed attention to the defining features of targets (focal PM) there was a trend level increase in ?, but the within-subject variability in ? was not correlated with PM accuracy, consistent with the theoretical premise that focal PM tasks are not as dependent on cognitive control as non-focal PM tasks. PMID:25247678

Loft, Shayne; Bowden, Vanessa K; Ball, B Hunter; Brewer, Gene A

2014-10-01

134

Modeller subjectivity and calibration impacts on hydrological model applications: an event-based comparison for a road-adjacent catchment in south-east Norway.  

PubMed

Identifying a 'best' performing hydrologic model in a practical sense is difficult due to the potential influences of modeller subjectivity on, for example, calibration procedure and parameter selection. This is especially true for model applications at the event scale where the prevailing catchment conditions can have a strong impact on apparent model performance and suitability. In this study, two lumped models (CoupModel and HBV) and two physically-based distributed models (LISEM and MIKE SHE) were applied to a small catchment upstream of a road in south-eastern Norway. All models were calibrated to a single event representing typical winter conditions in the region and then applied to various other winter events to investigate the potential impact of calibration period and methodology on model performance. Peak flow and event-based hydrographs were simulated differently by all models leading to differences in apparent model performance under this application. In this case-study, the lumped models appeared to be better suited for hydrological events that differed from the calibration event (i.e., events when runoff was generated from rain on non-frozen soils rather than from rain and snowmelt on frozen soil) while the more physical-based approaches appeared better suited during snowmelt and frozen soil conditions more consistent with the event-specific calibration. This was due to the combination of variations in subsurface conditions over the eight events considered, the subsequent ability of the models to represent the impact of the conditions (particularly when subsurface conditions varied greatly from the calibration event), and the different approaches adopted to calibrate the models. These results indicate that hydrologic models may not only need to be selected on a case-by-case basis but also have their performance evaluated on an application-by-application basis since how a model is applied can be equally important as inherent model structure. PMID:25262294

Kalantari, Zahra; Lyon, Steve W; Jansson, Per-Erik; Stolte, Jannes; French, Helen K; Folkeson, Lennart; Sassner, Mona

2015-01-01

135

Modeling rates of bank erosion in sinuous tidal channel derived from event-based terrestrial lidar surveys in the Mont Saint Michel Bay  

NASA Astrophysics Data System (ADS)

The Mont-Saint-Michel (MSM) bay is characterized by a semi-diurnal regime with a tidal range of 14 meter. Understanding river bank migration of tidal channels in such mega tidal salt marshes requires a precise quantification of the relative contribution of frequent and infrequent bank erosion events to the longer term dynamics. We use terrestrial lidar scanner (TLS) which overcomes the limitations of traditional bank measurement approaches (e.g. aerial photography, GPS measurements) with high resolution and high precision topographic data. We use 30 TLS measurements and traditional data sources to quantify the annual and daily dynamics of bank erosion for a sinuous salt marsh channel near the island of the MSM. We present the results of a 2 years study that begun in September 2010. We compare annual bank retreat with daily surveys focused on spring tides in order to calculate "event-based" volume of bank erosion. For active steep banks, the volume of sediment eroded is computed between 2 set of point cloud that are classified by the CANUPO algorithm to remove vegetation (Brodu and Lague, 2012). A new algorithm allows a direct comparison of point clouds in 3D based on surface normal computation and measurement of mean surface change along the normal direction. On a 5 centimeter resolution grid, the changes between 2 banks point cloud is computed and used to calculate volume of eroded bank. Measured rates of bank retreat varied between no detectable change to 2 m/tide, which correspond roughly to 100 cubic meters/tide. We also document a non-homothetic pattern of bank erosion during spring tides : erosion is focused in narrow zones of the meander and shifts spatially at daily timescales. To relate bank erosion to hydraulic characteristics of the channel, an ADCP was used to measure flow velocity during tides. The measurements highlights two main points that only occurs when tides overcomes the salt marsh: (i) the ebb flow is stronger than flood flow with velocities up to 2.2 m/s and (ii) the maximum ebb velocity (MEV) increase linearly with the maximum tide height. The dominant role of the ebb was also noted during field observations : during the ebb, the flow is focused on a narrow zone of the bank due to rapid bathymetric modifications at daily timescales. This could explain the non-homothetic behavior of bank erosion. The daily volume of eroded bank is only significant when the tide overcome the salt marsh which occurs 10 % of time. From the linear relationship between tide height and MEV, we can relate bank erosion to flow velocity. We show that the eroded volume increases exponentially with the MEV. This new physical model of bank erosion is applied on daily tides records. From Sept 2010 to June 2012, the model succeeds to estimate the volume of bank eroded. However, the model fails to reproduce the dynamics before Sept 2010, which can be explained by a significant change in channel curvature and morphology. The study shows that the combination of TLS and hydrosedimentary measurements can be used to construct 'field' models of tidal channel dynamics. Our data highlights a strong non-linearity between bank erosion, tidal amplitude and ebb flow velocity that results in spring tide events representing 95.7 % of the total erosion for a duration of 10 % of time.

Leroux, J.; Lague, D.

2012-12-01

136

Event Based Mobility Model for Subway Scenarios  

Microsoft Academic Search

High cost and complexity of mobile ad hoc networks (MANETs) testbeds let simulation as the best solution to experiment MANETs protocols and applications. Thus improving current simulation tools become crucial to provide valuable results. Mobility and propagation models are key element to realistically simulate user's behaviour and wave propagations and therefore assure the validity of the simulations results. Unfortunately, accurate

Vincent Toubiana; Houda Labiod; Bennet Fischer

2007-01-01

137

An Event-Based Architecture Definition Language  

Microsoft Academic Search

This paper discusses general requirements forarchitecture definition languages, and describes the syntaxand semantics of the subset of the Rapide language that is designedto satisfy these requirements. Rapide is a concurrentevent-based simulation language for defining and simulatingthe behavior of system architectures. Rapide is intended formodelling the architectures of concurrent and distributedsystems, both hardware and software. In order to representthe behavior of

David C. Luckham; James Vera

1995-01-01

138

Event based Control for Distributed Systemsy  

E-print Network

Controller Ore Waste #12;SAP OPC-UA ClientWireless control demonstration integrating Web services Siemans Wireless control demonstration integrating ABB Siemens SAP systems 17 18 Jun 2008 Gateway: OPC-UA Server Supervisory control ABB 800xA OPC-UA Server Tank Process Real time control Se nso P Blackfin rs u m p Froth

Johansson, Karl Henrik

139

Production of neutrons from interactions of GCR-like particles  

NASA Technical Reports Server (NTRS)

In order to help assess the risk to astronauts due to the long-term exposure to the natural radiation environment in space, an understanding of how the primary radiation field is changed when passing through shielding and tissue materials must be obtained. One important aspect of the change in the primary radiation field after passing through shielding materials is the production of secondary particles from the breakup of the primary. Neutrons are an important component of the secondary particle field due to their relatively high biological weighting factors, and due to their relative abundance, especially behind thick shielding scenarios. Because of the complexity of the problem, the estimation of the risk from exposure to the secondary neutron field must be handled using calculational techniques. However, those calculations will need an extensive set of neutron cross section and thicktarget neutron yield data in order to make an accurate assessment of the risk. In this paper we briefly survey the existing neutron-production data sets that are applicable to the space radiation transport problem, and we point out how neutron production from protons is different than neutron production from heavy ions. We also make comparisons of one the heavy-ion data sets with Boltzmann-Uehling-Uhlenbeck (BUU) calculations.

Heilbronn, L.; Frankel, K.; Holabird, K.; Zeitlin, C.; McMahan, M. A.; Rathbun, W.; Cronqvist, M.; Gong, W.; Madey, R.; Htun, M.; Elaasar, M.; Anderson, B. D.; Baldwin, A. R.; Jiang, J.; Keane, D.; Scott, A.; Shao, Y.; Watson, J. W.; Zhang, W. M.; Galonsky, A.; Ronningen, R.; Zecher, P.; Kruse, J.; Wang, J.; Miller, J. (Principal Investigator)

1998-01-01

140

GCR-Induced Photon Luminescence of the Moon  

NASA Technical Reports Server (NTRS)

It is shown that the Moon has a ubiquitous photon luminescence induced by Galactic cosmic-rays (GCRs), using the Monte Carlo particle-physics program FLUKA. Both the fluence and the flux of the radiation can be determined by this method, but only the fluence will be presented here. This is in addition to thermal radiation emitted due to the Moon s internal temperature and radioactivity. This study is a follow-up to an earlier discussion [1] that addressed several misconceptions regarding Moonshine in the Earth-Moon system (Figure 1) and predicted this effect. There also exists a related x-ray fluorescence induced by solar energetic particles (SEPs, <350 MeV) and solar photons at lower x-ray energies, although this latter fluorescence was studied on Apollo 15 and 16 [2- 5], Lunar Prospector [6], and even EGRET [7].

Lee, K. T.; Wilson, T. L.

2008-01-01

141

INVITED SESSION NUMBER: 157 Event-Based Feedback Control  

E-print Network

to- ward a closed-loop form of electrical deep brain stimulation, a treatment for neuromotor disorders such as Parkinson's disease, with symptoms characterized by pathological neural synchronization. I. INTRODUCTION Symptoms of neuromotor disorders, such as Parkinson's Disease (PD), have been linked

Moehlis, Jeff

142

Assessment and Event Based Analysis of Dynamic Wireless Networks  

E-print Network

partial information on the network state, they need to collaborate and agree on a time varying assessment behavior. In this paper, we propose an assessment index (SA) based on nodes' satisfaction and its self dynamic wireless networks of collaborative nodes. More specifically, our work is focused on the evaluation

Paris-Sud XI, Université de

143

Home Photo Content Modeling for Personalized Event-Based Retrieval  

Microsoft Academic Search

Rapid advances in sensor, storage, processor, and communication technologies let consumers store large digital photo collections. Consumers need effective tools to organize and access photos in a semantically meaningful way. We address the semantic gap between feature-based indexes computed automatically and human query and retrieval preferences.

Joo-hwee Lim; Qi Tian; Philippe Mulhem

2003-01-01

144

Event-based data dissemination control in healthcare  

E-print Network

in healthcare towards preventative care. This shift involves using technology to assist in care provision outside tra- ditional care institutions -- for instance, in a patient's home. To support such an environment, care providers require notification of incidents as they occur. However, health information

Cambridge, University of

145

Tsunami Warning Criteria for Cascadia events based on Tsunami models  

NASA Astrophysics Data System (ADS)

Initial tsunami warning, advisory, and watch zones for potential Cascadia earthquakes have been revised based on maximum expected threat for tsunamis generated by earthquakes in this region. Presently, alert zones are initially based on travel time for earthquakes greater than magnitude 7.8 with all areas less than three hours away from the source being put into a tsunami warning. The impact of this change is to reduce the length of coastline which is immediately put it into a warning status. Tsunami Warning Centers often delineate initial tsunami alert zones based on pre-set criteria dependent on earthquake magnitude, location, depth, and tsunami travel time. In many cases, this approach can lead to over-warning. Over the last several years, the West Coast/Alaska Tsunami Warning Center (WCATWC) has attempted to refine the amount of coastline immediately placed in a warning status based on maximum expected threat instead of travel time. Tsunami forecast models used to predict impacts during events (for example, Alaska Tsunami Forecast Model (ATFM), Short-term Inundation Forecasting for Tsunamis (SIFT), and Rapid Inundation Forecasting of Tsunamis (RIFT)) can also be used a-priori to delineate zones at-risk for specified source zones. forecast models have proven reasonably accurate during recent events. For the Cascadia Subduction zone, several rupture scenarios ranging from magnitude 7.9 to 9.2, were computed. Forecasted wave heights at various points are then used to set the initial Warning/Watch/Advisory regions. This procedure is more efficient than a blanket warning - or a refined warning based on travel times - as appropriate threat levels are assigned based on expected impact. For example, after a magnitude 8.7 earthquake in the southern Cascadia Subduction zone, southern and most of central California can be left out of the warning zone and placed in an advisory, as none of this region contains expected impacts in the warning threshold (tsunami amplitude over 1m). Under previous criteria, these zones would have been placed in a warning. Several examples are shown which help refine criteria used by the Tsunami Warning Center during hypothetical Cascadia events.

Huang, P. Y.; Nyland, D. L.; Knight, W.; Gately, K.; Hale, D.; Urban, G.; Waddell, J.; Carrick, J.; Popham, C.; Bahng, B.; Kim, Y.; Burgy, M.; Langley, S.; Preller, C. C.; Whitmore, P.

2013-12-01

146

Event-based predictive control strategy for teleoperation via Internet  

Microsoft Academic Search

The variable time delay and the packet loss degrade the performance of Internet based teleoperation system severely, even make the system unstable. Most of the previous work on Internet-based teleoperations rest on many assumptions, for example, time delay is constant or has upper bound, control is not in real-time. This paper presents a new predictive control strategy for the Internet

Dan Chen; Ning Xi; Yuechao Wang; Hongyi Li; Xusheng Tang

2008-01-01

147

Galactic Cosmic Ray Event-Based Risk Model (GERM) Code  

NASA Technical Reports Server (NTRS)

This software describes the transport and energy deposition of the passage of galactic cosmic rays in astronaut tissues during space travel, or heavy ion beams in patients in cancer therapy. Space radiation risk is a probability distribution, and time-dependent biological events must be accounted for physical description of space radiation transport in tissues and cells. A stochastic model can calculate the probability density directly without unverified assumptions about shape of probability density function. The prior art of transport codes calculates the average flux and dose of particles behind spacecraft and tissue shielding. Because of the signaling times for activation and relaxation in the cell and tissue, transport code must describe temporal and microspatial density of functions to correlate DNA and oxidative damage with non-targeted effects of signals, bystander, etc. These are absolutely ignored or impossible in the prior art. The GERM code provides scientists data interpretation of experiments; modeling of beam line, shielding of target samples, and sample holders; and estimation of basic physical and biological outputs of their experiments. For mono-energetic ion beams, basic physical and biological properties are calculated for a selected ion type, such as kinetic energy, mass, charge number, absorbed dose, or fluence. Evaluated quantities are linear energy transfer (LET), range (R), absorption and fragmentation cross-sections, and the probability of nuclear interactions after 1 or 5 cm of water equivalent material. In addition, a set of biophysical properties is evaluated, such as the Poisson distribution for a specified cellular area, cell survival curves, and DNA damage yields per cell. Also, the GERM code calculates the radiation transport of the beam line for either a fixed number of user-specified depths or at multiple positions along the Bragg curve of the particle in a selected material. The GERM code makes the numerical estimates of basic physical and biophysical quantities of high-energy protons and heavy ions that have been studied at the NASA Space Radiation Laboratory (NSRL) for the purpose of simulating space radiation biological effects. In the first option, properties of monoenergetic beams are treated. In the second option, the transport of beams in different materials is treated. Similar biophysical properties as in the first option are evaluated for the primary ion and its secondary particles. Additional properties related to the nuclear fragmentation of the beam are evaluated. The GERM code is a computationally efficient Monte-Carlo heavy-ion-beam model. It includes accurate models of LET, range, residual energy, and straggling, and the quantum multiple scattering fragmentation (QMSGRG) nuclear database.

Cucinotta, Francis A.; Plante, Ianik; Ponomarev, Artem L.; Kim, Myung-Hee Y.

2013-01-01

148

Event-based text mining for biology and functional genomics.  

PubMed

The assessment of genome function requires a mapping between genome-derived entities and biochemical reactions, and the biomedical literature represents a rich source of information about reactions between biological components. However, the increasingly rapid growth in the volume of literature provides both a challenge and an opportunity for researchers to isolate information about reactions of interest in a timely and efficient manner. In response, recent text mining research in the biology domain has been largely focused on the identification and extraction of 'events', i.e. categorised, structured representations of relationships between biochemical entities, from the literature. Functional genomics analyses necessarily encompass events as so defined. Automatic event extraction systems facilitate the development of sophisticated semantic search applications, allowing researchers to formulate structured queries over extracted events, so as to specify the exact types of reactions to be retrieved. This article provides an overview of recent research into event extraction. We cover annotated corpora on which systems are trained, systems that achieve state-of-the-art performance and details of the community shared tasks that have been instrumental in increasing the quality, coverage and scalability of recent systems. Finally, several concrete applications of event extraction are covered, together with emerging directions of research. PMID:24907365

Ananiadou, Sophia; Thompson, Paul; Nawaz, Raheel; McNaught, John; Kell, Douglas B

2014-06-01

149

The principle of immanence in event-based distributed systems  

E-print Network

of elements in the system filtered from an over-complex environment. Niklas Luhmann considers mutual considering in its communication what is meaningful and what is not. According to the sociologist Niklas Luhmann, social systems are autopoietically closed in the sense that they use and rely on resources from

Paris-Sud XI, Université de

150

An Event-Based Approach to Spatial Information  

Microsoft Academic Search

The notion of the location of an object at a moment of time is relatively straightforward, it is the region of space occupied by the object at that time. However, we are often concerned with the location of something over an extended period of time, as in Alice was in the room for ten minutes. Conceptualizing the location of an

Michael J. Almeida

1997-01-01

151

"The GCR Collection: from Alaska to Antarctica and from Martinique to Macquarie Ridge"  

E-print Network

Layer 3 A B 0 Depth (km) Seismic wave velocity (km/s) A Basalt Diabase Gabbro Peridotite Seismic models Diabase Gabbro Peridotite #12;#12;Peridotite, Gabbro, and Diabase/Layer 2b Cores from DSDP, ODP, IODP

152

NIST GCR 02-831 The Art of Telling Your Story  

E-print Network

Drive Morrisville, NC 27560 PreFlight Ventures, Inc 919-806-1166 rking@preflightventures.com Grant 43 . . . . . . . . . . 27 #12;4. Wrap Up . . . . . . . . . . . . . . . . . . . . . . . 29 5. Preparing to Make Your

Magee, Joseph W.

153

No-migration variance petition: Draft. Volume 4, Appendices DIF, GAS, GCR (Volume 1)  

SciTech Connect

The Department of Energy is responsible for the disposition of transuranic (TRU) waste generated by national defense-related activities. Approximately 2.6 million cubic feet of the se waste have been generated and are stored at various facilities across the country. The Waste Isolation Pilot Plant (WIPP), was sited and constructed to meet stringent disposal requirements. In order to permanently dispose of TRU waste, the DOE has elected to petition the US EPA for a variance from the Land Disposal Restrictions of RCRA. This document fulfills the reporting requirements for the petition. This report is volume 4 of the petition which presents details about the transport characteristics across drum filter vents and polymer bags; gas generation reactions and rates during long-term WIPP operation; and geological characterization of the WIPP site.

NONE

1995-05-31

154

Draft Title 40 CFR 191 compliance certification application for the Waste Isolation Pilot Plant. Volume 7: Appendix GCR Volume 2  

SciTech Connect

This report contains the second part of the geological characterization report for the Waste Isolation Pilot Plant. Both hydrology and geochemistry are evaluated. The following aspects of hydrology are discussed: surface hydrology; ground water hydrology; and hydrology drilling and testing. Hydrologic studies at the site and adjacent site areas have concentrated on defining the hydrogeology and associated salt dissolution phenomena. The geochemical aspects include a description of chemical properties of geologic media presently found in the surface and subsurface environments of southeastern New Mexico in general, and of the proposed WIPP withdrawal area in particular. The characterization does not consider any aspect of artificially-introduced material, temperature, pressure, or any other physico-chemical condition not native to the rocks of southeastern New Mexico.

NONE

1995-03-31

155

Event-Based Plausibility Immediately Influences On-Line Language Comprehension  

ERIC Educational Resources Information Center

In some theories of sentence comprehension, linguistically relevant lexical knowledge, such as selectional restrictions, is privileged in terms of the time-course of its access and influence. We examined whether event knowledge computed by combining multiple concepts can rapidly influence language understanding even in the absence of selectional…

Matsuki, Kazunaga; Chow, Tracy; Hare, Mary; Elman, Jeffrey L.; Scheepers, Christoph; McRae, Ken

2011-01-01

156

A Program Structure for Event-Based Speech Synthesis by Rules within a Flexible Segmental Framework.  

ERIC Educational Resources Information Center

A program structure based on recently developed techniques for operating system simulation has the required flexibility for use as a speech synthesis algorithm research framework. This program makes synthesis possible with less rigid time and frequency-component structure than simpler schemes. It also meets real-time operation and memory-size…

Hill, David R.

1978-01-01

157

Event-Based Monitoring of Sediment Flux Following Removal of Oregon's Marmot Dam  

Microsoft Academic Search

Breaching of Oregon's Marmot Dam in October 2007 allowed the 80-km-long Sandy River to flow freely from Mount Hood to the Columbia River for the first time in nearly 100 years. When breached, the dam was brimful with sediment. As part of an analysis examining the redistribution of ~730,000 m3 of stored sediment following the dam removal, we measured suspended-sediment

J. J. Major; J. E. O'Connor; K. R. Spicer; H. M. Bragg; J. R. Wallick; R. L. Kittleson; K. K. Lee; D. Cushman; D. Piatt; D. Q. Tanner; T. Hale; M. A. Uhrich; A. Rhode

2008-01-01

158

You Never Walk Alone: Recommending Academic Events Based on Social Network Analysis  

NASA Astrophysics Data System (ADS)

Combining Social Network Analysis and recommender systems is a challenging research field. In scientific communities, recommender systems have been applied to provide useful tools for papers, books as well as expert finding. However, academic events (conferences, workshops, international symposiums etc.) are an important driven forces to move forwards cooperation among research communities. We realize a SNA based approach for academic events recommendation problem. Scientific communities analysis and visualization are performed to provide an insight into the communities of event series. A prototype is implemented based on the data from DBLP and EventSeer.net, and the result is observed in order to prove the approach.

Klamma, Ralf; Cuong, Pham Manh; Cao, Yiwei

159

An event-based approach to understanding decadal fluctuations in the Atlantic meridional overturning circulation  

NASA Astrophysics Data System (ADS)

Many previous studies have shown that unforced climate model simulations exhibit decadal-scale fluctuations in the Atlantic meridional overturning circulation (AMOC), and that this variability can have impacts on surface climate fields. However, the robustness of these surface fingerprints across different models is less clear. Furthermore, with the potential for coupled feedbacks that may amplify or damp the response, it is not known whether the associated climate signals are linearly related to the strength of the AMOC changes, or if the fluctuation events exhibit nonlinear behaviour with respect to their strength or polarity. To explore these questions, we introduce an objective and flexible method for identifying the largest natural AMOC fluctuation events in multicentennial/multimillennial simulations of a variety of coupled climate models. The characteristics of the events are explored, including their magnitude, meridional coherence and spatial structure, as well as links with ocean heat transport and the horizontal circulation. The surface fingerprints in ocean temperature and salinity are examined, and compared with the results of linear regression analysis. It is found that the regressions generally provide a good indication of the surface changes associated with the largest AMOC events. However, there are some exceptions, including a nonlinear change in the atmospheric pressure signal, particularly at high latitudes, in HadCM3. Some asymmetries are also found between the changes associated with positive and negative AMOC events in the same model. Composite analysis suggests that there are signals that are robust across the largest AMOC events in each model, which provides reassurance that the surface changes associated with one particular event will be similar to those expected from regression analysis. However, large differences are found between the AMOC fingerprints in different models, which may hinder the prediction and attribution of such events in reality.

Allison, Lesley; Hawkins, Ed; Woollings, Tim

2014-09-01

160

Event based neutron activation spectroscopy and analysis algorithm using MLE and metaheuristics  

NASA Astrophysics Data System (ADS)

Techniques used in neutron activation analysis are often dependent on the experimental setup. In the context of developing a portable and high efficiency detection array, good energy resolution and half-life discrimination are difficult to obtain with traditional methods [1] given the logistic and financial constraints. An approach different from that of spectrum addition and standard spectroscopy analysis [2] was needed. The use of multiple detectors prompts the need for a flexible storage of acquisition data to enable sophisticated post processing of information. Analogously to what is done in heavy ion physics, gamma detection counts are stored as two-dimensional events. This enables post-selection of energies and time frames without the need to modify the experimental setup. This method of storage also permits the use of more complex analysis tools. Given the nature of the problem at hand, a light and efficient analysis code had to be devised. A thorough understanding of the physical and statistical processes [3] involved was used to create a statistical model. Maximum likelihood estimation was combined with metaheuristics to produce a sophisticated curve-fitting algorithm. Simulated and experimental data were fed into the analysis code prompting positive results in terms of half-life discrimination, peak identification and noise reduction. The code was also adapted to other fields of research such as heavy ion identification of the quasi-target (QT) and quasi-particle (QP). The approach used seems to be able to translate well into other fields of research.

Wallace, Barton

2014-03-01

161

A 1-year long event-based isotopic composition of precipitation in Bolivia: observations and modelling  

NASA Astrophysics Data System (ADS)

Over the last years, an increasing number of studies combining both observations and modelling works has been carried out to determine and to decipher the different climate controls on the isotopic composition of tropical precipitation. Most of those studies have dealt with seasonal to interannual timescales. We present here the isotopic composition of precipitation collected on an event basis from September 1999 to August 2000 in the Zongo Valley (16 degrees S, 67 degrees W) from 945 to 4750 m. The delta records are fairly similar from one station to another and clearly show an intra-month variability superimposed on the seasonal cycle. Conversely, precipitation distribution and occurrence of extremes largely differ from one station to another, revealing that local precipitation has no control on delta. We thus explore potential regional controls (origin of airmasses, precipitation history along trajectories) using back-trajectories calculations. Deuterium excess available from one station is also examined as a proxy of water vapor recycling. Based on a simulation zoomed over South America (60km resolution) and nudged by reanalyzed winds performed with the LMDZ-iso model, which is able to reproduce well the observations in the Zongo Valley, we examine in deeper details the climate controls that could explain the strong intra-seasonal variations in the isotopic composition of precipitation.

Vimeux, Francoise; Tremoy, Guillaume; Risi, Camille

2010-05-01

162

Team-Teaching a Current Events-Based Biology Course for Nonmajors  

ERIC Educational Resources Information Center

Rice University has created a team-taught interactive biology course for nonmajors with a focus on cutting edge biology in the news--advances in biotechnology, medicine, and science policy, along with the biological principles and methodology upon which these advances are based. The challenges inherent to teaching current topics were minimized by…

Bondos, Sarah E.; Phillips, Dereth

2008-01-01

163

An event-based neural network architecture with an asynchronous programmable synaptic memory.  

PubMed

We present a hybrid analog/digital very large scale integration (VLSI) implementation of a spiking neural network with programmable synaptic weights. The synaptic weight values are stored in an asynchronous Static Random Access Memory (SRAM) module, which is interfaced to a fast current-mode event-driven DAC for producing synaptic currents with the appropriate amplitude values. These currents are further integrated by current-mode integrator synapses to produce biophysically realistic temporal dynamics. The synapse output currents are then integrated by compact and efficient integrate and fire silicon neuron circuits with spike-frequency adaptation and adjustable refractory period and spike-reset voltage settings. The fabricated chip comprises a total of 32 × 32 SRAM cells, 4 × 32 synapse circuits and 32 × 1 silicon neurons. It acts as a transceiver, receiving asynchronous events in input, performing neural computation with hybrid analog/digital circuits on the input spikes, and eventually producing digital asynchronous events in output. Input, output, and synaptic weight values are transmitted to/from the chip using a common communication protocol based on the Address Event Representation (AER). Using this representation it is possible to interface the device to a workstation or a micro-controller and explore the effect of different types of Spike-Timing Dependent Plasticity (STDP) learning algorithms for updating the synaptic weights values in the SRAM module. We present experimental results demonstrating the correct operation of all the circuits present on the chip. PMID:24681923

Moradi, Saber; Indiveri, Giacomo

2014-02-01

164

An events based algorithm for distributing concurrent tasks on multi-core architectures  

E-print Network

In this paper, a programming model is presented which enables scalable parallel performance on multi-core shared memory architectures. The model has been developed for application to a wide range of numerical simulation ...

Holmes, David W.

165

Using Event-Based Style for Developing M2M Applications  

E-print Network

]. It covers a wide array of applications including automotive, meter- ing, remote management, IP multimedia predict that there will be 25 billion connected IP devices by 2015, with M2M traffic expected to grow subsystem, industrial data collection, health care, etc [16, 23]. For example, in agriculture, M2M

Boyer, Edmond

166

Generic-Events Architecture: Integrating Real-World Aspects in Event-Based Systems  

Microsoft Academic Search

In a future networked physical world, a myriad of smart sensors and actuators assess and control aspects of their environments\\u000a and autonomously act in response to it. To a large extent, such systems operate proactively and independently of direct human\\u000a control. They include computer hardware and software parts mixed with mechanical devices. Besides the regular computer communication\\u000a channels, they also

Antonio Casimiro; Jörg Kaiser; Paulo Veríssimo

2006-01-01

167

An event-based model of braided river system aquifers heterogeneity based on Multiple Points Statistics  

NASA Astrophysics Data System (ADS)

Braided-rivers are common in mountainous regions like the Swiss Alps. These dynamic systems generate highly heterogeneous deposits and form an important part of alluvial aquifers which are tapped for agriculture and drinking water supply. In this presentation, we propose to integrate large scale and high resolution LIDAR data in a pseudo genetic approach embedding Multiple Points Statistics (MPS) to model the heterogeneity of such aquifers. A way to build 3D sedimentary models is to use descriptive methods, which translate data into conceptual facies models but do not offer uncertainty quantification. Another possibility is the use of stochastic models but most of them do not include strong geological knowledge and their degree of realism can be rather weak. Another approach is to use process-based methods. In this work, we imitate the processes occurring during flood events, by building successive topographies with the Direct Sampling (DS) multiple point statistics algorithm. Each successive topography is conditioned by the previous one. All those steps are constrained by a series of LIDAR data sets allowing to train the algorithm. This is different from classical MPS models, since we do not directly use MPS to model the lithofacies directly, but instead to simulate the processes that lead to the heterogeneity in order to ensure that higher statistics that can be inferred from field data are accurately reproduced. The use of the DS is motivated by the fact that it an MPS technique allowing to co-simulate continuous variables. It is easy to condition to field data and offers a high degree of realism in the simulations. The underlying erosion-deposition process leaves some records of each event in the form of remaining layers, which are populated with facies of different granulometry, according to some predefined rules function of the geobody's shape and dimensions. Input parameters allow controlling the aggradation/degradation intensity.

Renard, P.; Pirot, G.

2012-12-01

168

Kernel support for the event-based cooperation of distributed resource managers  

Microsoft Academic Search

Multimedia and real-time applications require end-to-end QoS support based on the cooperative management of their distributed resources. This paper introduces a kernel-level facility, called Q(uality)-channel, which provides a flexible fabric with which Operating System developers can efficiently implement policies for managing the resources used by distributed applications. The inherent complexity of resource management in large-scale distributed applications is addressed by

Christian Poellabauer; Karsten Schwan

2002-01-01

169

Classification of cyclogenesis events based on a comprehensive set of potential precursors  

NASA Astrophysics Data System (ADS)

Case studies indicate a large variability of the involved atmospheric structures and physical processes responsible for cyclogenesis. Historical classifications focus on the relative importance of low-level baroclinicity and upper-level disturbances, and a more recent threefold classification also considers the role of diabatically produced low-tropospheric potential vorticity. In this study, a large set of potential precursors for cyclogenesis will be systematically investigated on a statistical basis. Cyclones are objectively identified during 2010 in the operational analyses and deterministic forecasts from the European Centre for Medium-Range Weather Forecasts (ECMWF) and then tracked along their life cycle. The starting points of these tracks are considered as the location of cyclogenesis. In the environment of these locations a set of about 20 precursors is determined. The set includes the following parameters: (a) temperature and heat fluxes at the surface; (b) characteristic conditions in the troposphere (e.g., integrated water vapor, amplitude of low-level potential vorticity); (c) measures of baroclinic and convective stability (e.g., Eady growth rate and CAPE); and (d) flow patterns at and forcing from the tropopause level (e.g., jet streams and streaks, potential vorticity anomalies, height of the tropopause). In addition to these relatively simple Eulerian characteristics, more advanced diagnostic approaches will be applied, including a Lagrangian moisture source diagnostic and quasigeostrophic omega forcing. These parameters will be determined for a multitude of cyclones and build the basis for an in-depth statistical analysis in this precursor phase space. A clustering approach will be applied to this precursor phase space in order to determine the main categories of cyclogenesis, and their geographical and seasonal variability.

Graf, M.; Sprenger, M.; Wernli, H.

2012-04-01

170

Estimating the frequency of extremely energetic solar events, based on solar, stellar, lunar, and terrestrial records  

E-print Network

The most powerful explosions on the Sun [...] drive the most severe space-weather storms. Proxy records of flare energies based on SEPs in principle may offer the longest time base to study infrequent large events. We conclude that one suggested proxy, nitrate concentrations in polar ice cores, does not map reliably to SEP events. Concentrations of select radionuclides measured in natural archives may prove useful in extending the time interval of direct observations up to ten millennia, but as their calibration to solar flare fluences depends on multiple poorly known properties and processes, these proxies cannot presently be used to help determine the flare energy frequency distribution. Being thus limited to the use of direct flare observations, we evaluate the probabilities of large-energy solar explosions by combining solar flare observations with an ensemble of stellar flare observations. We conclude that solar flare energies form a relatively smooth distribution from small events to large flares, while...

Schrijver, C J; Baltensperger, U; Cliver, E W; Guedel, M; Hudson, H S; McCracken, K G; Osten, R A; Peter, Th; Soderblom, D R; Usoskin, I G; Wolff, E W

2012-01-01

171

Event based statistics from high spatial and temporal resolution gauge and radar data  

NASA Astrophysics Data System (ADS)

Studies of extreme precipitation is often focused on daily resolution and for point measurements, i.e. gauge data. A main problem with this coarse temporal resolution is the strong averaging effect on short events. Here we present a study based on high temporal resolution (five minutes) data from radar (1x1 km horizontal resolution) and a high spatial density gauge data set over southwestern Germany. For the gauge data, an event is defined as a sequence of consecutive precipitation measurements above the measurement threshold, while for radar data the events are defined as continuous horizontal regions with above measurement limit intensities. With samples from about two years of data for the radar and from about 90 gauges each with 8 years of data, we get solid statistics for different aspects of the event distributions. A strong relationship between the temporal and spatial definitions of events is found. Additional use of synoptic observations allow the distinction of convective and stratiform precipitation types. The two types show largely different intensity distributions and characteristics for both spatial and temporal statistics. With probability and intensity distributions of the events, it is possible to calculate statistics of the precipitation yield from different duration (or size) events. We found that the yield from stratiform events decrease in a near power-law manner, while convective precipitation shows a concave dependence an a log-log scale, with the largest yields for events of around 20 minutes duration or 30 km2 area. The results emphasise the utility of high temporal resolution data of less than one hour, which allows proper resolution of convective showers and additionally to derive event statistics, which are important for impact assessments.

Berg, Peter; Eggert, Bastian; Haerter, Jan; Moseley, Christopher

2013-04-01

172

Prediction of solar proton events based on flare and CME parameters  

NASA Astrophysics Data System (ADS)

In this study we have examined the probability of solar proton events (SPEs) and their peak fluxes depending on flare (flux, longitude and impulsive time) and CME parameters (linear speed and angular width). For this we used the NOAA SPE list and their associated flare data from 1976 to 2006 and CME data from 1997 to 2006. We found that about 3.5% (1.9% for M-class and 21.3% for X-class) of the flares are associated with SPEs. It is also found that this fraction strongly depends on longitude; for example, the fraction for 30W° < L < 90W° is about three times larger than that for 30°E < L < 90°E. The occurrence probability of SPEs for flares with long duration (? 0.3 hours) is about 2 (X-class flare) to 7 (M-class flare) times larger than that for flares with short duration (< 0.3 hours). In the case of halo CMEs with V ? 1500km/s, 36.1% are associated with SPEs but in the case of partial halo CME (120° ? AW < 359°) with 400 km/s ? V < 1000 km/s, only 0.9% are associated with SPEs. The relationships between X-ray flare peak flux and SPE peak flux are strongly dependent on longitude and impulsive time. The relationships between CME speed and SPE peak flux depend on longitude as well as direction parameter. From this study, we suggest a new SPE forecast method with three-steps: (1) SPE occurrence probability prediction according to the contingency tables depending on flare and CME parameters, (2) SPE flux prediction depending on flare and CME parameters, and (3) SPE peak time.

Park, J.; Moon, Y.

2011-12-01

173

Event-Based Monitoring of Sediment Flux Following Removal of Oregon's Marmot Dam  

NASA Astrophysics Data System (ADS)

Breaching of Oregon's Marmot Dam in October 2007 allowed the 80-km-long Sandy River to flow freely from Mount Hood to the Columbia River for the first time in nearly 100 years. When breached, the dam was brimful with sediment. As part of an analysis examining the redistribution of ~730,000 m3 of stored sediment following the dam removal, we measured suspended-sediment load and bedload at sites 10 km upstream and 0.5 to 18 km downstream of the dam before, during and after breaching, and during five subsequent high-water events. Prior to breaching of the dam, suspended-sediment and bedload mass fluxes along the Sandy River both upstream and downstream of the dam were of the order of a few to a few tens of kg/s. Suspended sediment upstream was composed chiefly of sand in contrast to mostly silt and clay passing measurement sites 0.5 and 18 km below the dam. In all reaches bedload consisted chiefly (>90%) of sand. Breaching of the dam released a pulse of turbid water having an instantaneous suspended-sediment flux of 5200 kg/s. The initial sediment pulse consisted predominantly of silt and clay, presumably eroded from thin, fine-grained topset beds at the downstream end of the reservoir. However, the suspended load coarsened rapidly as the Sandy River incised into the stored sand and gravel that filled the former reservoir. Following the initial peak value, median fluxes of sandy suspended sediment 0.5 km below the dam site hovered around several tens to hundreds of kg/s for at least 24 hours, whereas the median suspended- sediment flux remained about 30 kg/s both 10 km upstream and 18 km downstream. Bedload transport also increased following breaching, but its response was slower than for suspended sediment. Bedload flux 0.5 km below the dam site increased from ~1 kg/s before breaching to 60 kg/s by 6 hours and to about 70 kg/s by 18 hours after breaching, in contrast to the steady, low (<10 kg/s) flux of sandy bedload passing upstream and farther downstream before and after breaching. Initially, the near-field bedload consisted predominantly of sand transported in large dunes. Significant gravel transport did not begin until 18 to 20 hours after breaching, in conjunction with rapid bed aggradation and downstream propagation of mid- channel gravel bars. This enhanced sediment transport occurred under a median flow just 30% greater than the river's mean annual flow at Marmot Dam. Within 3 months of breaching, the near-field high-flow-driven bedload flux remained significantly elevated above both upstream and downstream fluxes, but the suspended-sediment flux had declined substantially. Near-field bedload flux was persistently 10 to 100 times greater than that upstream and farther downstream, and remained gravel-rich compared to the sandy bedload passing stations upstream and 18 km distant. In contrast, near-field suspended-sediment concentrations declined approximately logarithmically, and by January 2008 the associated sandy suspended-sediment flux was comparable in both composition and magnitude to the suspended-sediment flux 18 km distant. The newly energetic Sandy River thus rapidly flushed sandy suspended-sediment downstream. Gravel-rich bedload continues to disperse downstream, but has yet to reach distal reaches of the river system. The majority of gravel transported thus far is stored chiefly along the 2-km-long channel reach below the dam site and within the Sandy River gorge 2-8 km downstream from the dam site.

Major, J. J.; O'Connor, J. E.; Spicer, K. R.; Bragg, H. M.; Wallick, J. R.; Kittleson, R. L.; Lee, K. K.; Cushman, D.; Piatt, D.; Tanner, D. Q.; Hale, T.; Uhrich, M. A.; Rhode, A.

2008-12-01

174

Event-Based Analysis of Video Lihi Zelnik-Manor Michal Irani  

E-print Network

by the Israeli Science Foundation (ISF), Technion Funds for Security Research, the Technion Autonomous Systems Program (TASP), the Intel Collaborative Research Institute for Computational Intelligence (ICRI

Zelnik-Manor, Lihi - Zelnik-Manor, Lihi

175

Loss Modeling with a Data-Driven Approach in Event-Based Rainfall-Runoff Analysis  

NASA Astrophysics Data System (ADS)

Mathematical models require the estimation of rainfall abstractions for accurate predictions of runoff. Although loss models such as the constant loss and exponential loss models are commonly used, these methods are based on simplified assumptions of the physical process. A new approach based on the data driven paradigm to estimate rainfall abstractions is proposed in this paper. The proposed data driven model, based on the artificial neural network (ANN) does not make any assumptions on the loss behavior. The estimated discharge from a physically-based model, obtained from the kinematic wave (KW) model assuming zero losses, was used as the only input to the ANN. The output is the measured discharge. Thus, the ANN functions as a black-box loss model. Two sets of data were analyzed for this study. The first dataset consists of rainfall and runoff data, measured from an artificial catchment (area = 25 m2) comprising two overland planes (slope = 11%), 25m long, transversely inclined towards a rectangular channel (slope = 2%) which conveyed the flow, recorded using calibrated weigh tanks, to the outlet. Two rain gauges, each placed 6.25 m from either ends of the channel, were used to record rainfall. Data for six storm events over the period between October 2002 and December 2002 were analyzed. The second dataset was obtained from the Upper Bukit Timah catchment (area = 6.4 km2) instrumented with two rain gauges and a flow measuring station. A total of six events recorded between November 1987 and July 1988 were selected for this study. The runoff predicted by the ANN was compared with the measured runoff. In addition, results from KW models developed for both the catchments were used as a benchmark. The KW models were calibrated assuming the loss rate for an average event for each of the datasets. The results from both the ANN and KW models agreed well with the runoff measured from the artificial catchment. The KW model is expected to perform well since the catchment is completely impervious and the losses are small. Thus, the good agreement of results between the ANN with the KW model results demonstrates the applicability of the ANN model in modeling the loss rate. Comparing the modeled runoff with the measured runoff for the Upper Bukit Timah catchment, it was found that the KW model was not able to produce the runoff from the catchment accurately due to the improper prescription of the loss rate. This is because the loss rate varies over a wide range of values in a real catchment and using the loss rate for an average event did not provide truly representative values for the catchment. Although the same dataset was used in the training of the ANN model, the ANN model was able to produce hydrographs with significantly higher Nash-Sutcliffe coefficients compared to the KW model. This analysis demonstrates that the ANN model is better able to model the highly variable loss rate during storm events, especially if the data used for calibration is limited. ACKNOWLEDGEMENT Funding received from the DHI-NTU Water & Environment Research Centre and Education Hub is gratefully acknowledged.

Chua, L. H. C.

2012-04-01

176

An event-based approach to understanding decadal fluctuations in the Atlantic meridional overturning circulation  

NASA Astrophysics Data System (ADS)

Many previous studies have shown that unforced climate model simulations exhibit decadal-scale fluctuations in the Atlantic meridional overturning circulation (AMOC), and that this variability can have impacts on surface climate fields. However, the robustness of these surface fingerprints across different models is less clear. Furthermore, with the potential for coupled feedbacks that may amplify or damp the response, it is not known whether the associated climate signals are linearly related to the strength of the AMOC changes, or if the fluctuation events exhibit nonlinear behaviour with respect to their strength or polarity. To explore these questions, we introduce an objective and flexible method for identifying the largest natural AMOC fluctuation events in multicentennial/multimillennial simulations of a variety of coupled climate models. The characteristics of the events are explored, including their magnitude, meridional coherence and spatial structure, as well as links with ocean heat transport and the horizontal circulation. The surface fingerprints in ocean temperature and salinity are examined, and compared with the results of linear regression analysis. It is found that the regressions generally provide a good indication of the surface changes associated with the largest AMOC events. However, there are some exceptions, including a nonlinear change in the atmospheric pressure signal, particularly at high latitudes, in HadCM3. Some asymmetries are also found between the changes associated with positive and negative AMOC events in the same model. Composite analysis suggests that there are signals that are robust across the largest AMOC events in each model, which provides reassurance that the surface changes associated with one particular event will be similar to those expected from regression analysis. However, large differences are found between the AMOC fingerprints in different models, which may hinder the prediction and attribution of such events in reality.

Allison, Lesley; Hawkins, Ed; Woollings, Tim

2015-01-01

177

Event-Based Interaction Management for Composite E-Services in eFlow  

Microsoft Academic Search

The Web is rapidly becoming the platform through which many companies deliver e-services to businesses and individual customers. E-Services are typically delivered in their primitive forms, called basic services. However, today's business environment creates the opportunity for providing value-added, integrated services, delivered by composing existing e-services, possibly offered by different providers.

Fabio Casati; Ming-chien Shan

2002-01-01

178

Internet-based Software Engineering Enables and Requires Event-Based Management Tools  

Microsoft Academic Search

Distributed software engineering (DSE) eorts oer dicult challenges to those whoneed to monitor and manage the overall process. Without the capability to know whatis happening in the process, the risk of failing to produce a quality product on scheduleincreases greatly. With Internet-based DSE, the opportunity exists to capture data fromthe process at relatively low cost, since so much of the

Jonathan E. Cook

2000-01-01

179

Simulation of the ATIC-2 Silicon Matrix for Protons and Helium GCR Primaries at 0.3, 10, and 25 TeV/Nucleon  

NASA Technical Reports Server (NTRS)

The energy deposition distribution for protons and helium galactic cosmic ray primaries at 0.3, 10, and 25 TeV/nucleon in the ATIC-2 silicon matrix detector are simulated with GEANT4. The GEANT3 geometrical model of ATIC developed by the University of Maryland was combined with a GEANT4 application developed for the Deep Space Test Bed (DSTB) detector package. The new code included relatively minor modifications to completely describe the ATIC materials and a more detailed model of the Silicon Matrix detector. For this analysis all particles were started as a unidirectional beam at a single point near the center of the Silicon Matrix front surface. The point was selected such that each primary passed through at least two of the overlapping silicon pixels.

Watts, J.; Adams, J. H.; Bashindzhagyan, G.; Batkov, K. E.; Chang, J.; Christl, M.; Fazely, A. R.; Ganel, O.; Gunasingha R. M.; Guzik, T. G.

2005-01-01

180

US\\/FRG Umbrella Agreement for Cooperation in GCR Development: fuel, fission products and graphite subprogram. Quarterly status report, January 1, 1981March 31, 1981  

Microsoft Academic Search

The status of progress on the major milestones, as defined in Revision 2 of the Subprogram Plan, is summarized for the second quarter of FY-81. Technical highlights of the period were: continued successful operation of fuel capsule R2K13 (PWS FD-15); reports written on irradiation induced permeability change in pyrocarbon (FD-12) and post-irradiation analysis technique comparison on coated particles (FD-13); and

1981-01-01

181

Models and Monte Carlo simulations of GCR and SPE organ doses with different shielding, based on the FLUKA code coupled with anthropomorphic phantoms  

Microsoft Academic Search

Astronauts' exposure to space radiation is of major concern for long-term missions, especially for those in deep space such as a possible mission to Mars. Shielding optimization is therefore a crucial issue, and simulations based on radiation transport codes coupled with anthropomorphic model phantoms can be of great help. In this work, carried out with the FLUKA MC code and

F. Ballarini

2004-01-01

182

Reducing Inter-Cell Handover Events based on Cell ID Information in Multi-hop Relay Systems  

E-print Network

and Technology (KAIST) Email: ginny@kaist.ac.kr Ki-Young Han Telecommunication R&D Center Samsung Electronics Co and Computer Science Korea Advanced Institute of Science and Technology (KAIST) Email: dhcho@ee.kaist

Kim, Yong Jung

183

A plan for community event-based surveillance to reduce ebola transmission - sierra leone, 2014-2015.  

PubMed

Ebola virus disease (Ebola) was first detected in Sierra Leone in May 2014 and was likely introduced into the eastern part of the country from Guinea. The disease spread westward, eventually affecting Freetown, Sierra Leone's densely populated capital. By December 2014, Sierra Leone had more Ebola cases than Guinea and Liberia, the other two West African countries that have experienced widespread transmission. As the epidemic intensified through the summer and fall, an increasing number of infected persons were not being detected by the county's surveillance system until they had died. Instead of being found early in the disease course and quickly isolated, these persons remained in their communities throughout their illness, likely spreading the disease. PMID:25632956

Crowe, Sam; Hertz, Darren; Maenner, Matt; Ratnayake, Ruwan; Baker, Pieter; Lash, Ryan; Klena, John; Lee-Kwan, Seung Hee; Williams, Candice; Jonnie, Gabriel T; Gorina, Yelena; Anderson, Alicia; Saffa, Gbessay; Carr, Dana; Tuma, Jude; Miller, Laura; Turay, Alhajie; Belay, Ermias

2015-01-30

184

Robotic goalie with 3 ms reaction time at 4% CPU load using event-based dynamic vision sensor  

PubMed Central

Conventional vision-based robotic systems that must operate quickly require high video frame rates and consequently high computational costs. Visual response latencies are lower-bound by the frame period, e.g., 20 ms for 50 Hz frame rate. This paper shows how an asynchronous neuromorphic dynamic vision sensor (DVS) silicon retina is used to build a fast self-calibrating robotic goalie, which offers high update rates and low latency at low CPU load. Independent and asynchronous per pixel illumination change events from the DVS signify moving objects and are used in software to track multiple balls. Motor actions to block the most “threatening” ball are based on measured ball positions and velocities. The goalie also sees its single-axis goalie arm and calibrates the motor output map during idle periods so that it can plan open-loop arm movements to desired visual locations. Blocking capability is about 80% for balls shot from 1 m from the goal even with the fastest-shots, and approaches 100% accuracy when the ball does not beat the limits of the servo motor to move the arm to the necessary position in time. Running with standard USB buses under a standard preemptive multitasking operating system (Windows), the goalie robot achieves median update rates of 550 Hz, with latencies of 2.2 ± 2 ms from ball movement to motor command at a peak CPU load of less than 4%. Practical observations and measurements of USB device latency are provided1. PMID:24311999

Delbruck, Tobi; Lang, Manuel

2013-01-01

185

A novel application of a neuro-fuzzy computational technique in event-based rainfall-runoff modeling  

Microsoft Academic Search

Intelligent computing tools based on fuzzy logic and Artificial Neural Networks (ANN) have been successfully applied in various problems with superior performances. A new approach of combining these two powerful AI tools, known as neuro-fuzzy systems, has increasingly attracted scientists in different fields. Although many studies have been carried out using this approach in pattern recognition and signal processing, few

Amin Talei; Lloyd Hock Chye Chua; Chai Quek

2010-01-01

186

Controls of event-based pesticide leaching in natural soils: A systematic study based on replicated field scale irrigation experiments  

NASA Astrophysics Data System (ADS)

Tile drains strongly influence the water cycle in agricultural catchment in terms of water quantity and quality. The connectivity of preferential flow to tile drains can create shortcuts for rapid transport of solutes into surface waters. The leaching of pesticides can be linked to a set of main factors including, rainfall characteristics, soil moisture, chemical properties of the pesticides, soil properties, and preferential flow paths. The connectivity of the macropore system to the tile drain is crucial for pesticide leaching. Concurring influences of the main factors, threshold responses and the role of flow paths are still poorly understood. The objective of this study is to investigate these influences by a replica series of three irrigation experiments on a tile drain field site using natural and artificial tracers together with applied pesticides. We found a clear threshold behavior in the initialization of pesticide transport that was different between the replica experiments. Pre-event soil water contributed significantly to the tile drain flow, and creates a flow path for stored pesticides from the soil matrix to the tile drain. This threshold is controlled by antecedent soil moisture and precipitation characteristics, and the interaction between the soil matrix and preferential flow system. Fast transport of pesticides without retardation and the remobilization could be attributed to this threshold and the interaction between the soil matrix and the preferential flow system. Thus, understanding of the detailed preferential flow processes clearly enhances the understanding of pesticide leaching on event and long term scale, and can further improve risk assessment and modeling approaches.

Klaus, Julian; Zehe, Erwin; Elsner, Martin; Palm, Juliane; Schneider, Dorothee; Schröder, Boris; Steinbeiss, Sibylle; van Schaik, Loes; West, Stephanie

2014-05-01

187

Integrated Data Products to Forecast, Mitigate, and Educate for Natural Hazard Events Based on Recent and Historical Observations  

NASA Astrophysics Data System (ADS)

Immediately following a damaging or fatal natural hazard event there is interest to access authoritative data and information. The National Geophysical Data Center (NGDC) maintains and archives a comprehensive collection of natural hazards data. The NGDC global historic event database includes all tsunami events, regardless of intensity, as well as earthquakes and volcanic eruptions that caused fatalities, moderate damage, or generated a tsunami. Examining the past record provides clues to what might happen in the future. NGDC also archives tide gauge data from stations operated by the NOAA/NOS Center for Operational Oceanographic Products and Services and the NOAA Tsunami Warning Centers. In addition to the tide gauge data, NGDC preserves deep-ocean water-level, 15-second sampled data as collected by the Deep-ocean Assessment and Reporting of Tsunami (DART) buoys. Water-level data provide evidence of sea-level fluctuation and possible inundation events. NGDC houses an extensive collection of geologic hazards photographs available online as digital images. Visual media provide invaluable pre- and post-event data for natural hazards. Images can be used to illustrate inundation and possible damage or effects. These images are organized by event or hazard type (earthquake, volcano, tsunami, landslide, etc.), along with description and location. They may be viewed via interactive online maps and are integrated with historic event details. The planning required to achieve collection and dissemination of hazard event data is extensive. After a damaging or fatal event, NGDC begins to collect and integrate data and information from many people and organizations into the hazards databases. Sources of data include the U.S. NOAA Tsunami Warning Centers, the U.S. Geological Survey, the U.S. NOAA National Data Buoy Center, the UNESCO Intergovernmental Oceanographic Commission (IOC), Smithsonian Institution's Global Volcanism Program, news organizations, etc. NGDC then works to promptly distribute data and information for the appropriate audience. For example, when a major tsunami occurs, all of the related tsunami data are combined into one timely resource. NGDC posts a publicly accessible online report which includes: 1) event summary; 2) eyewitness and instrumental recordings from preliminary field surveys; 3) regional historical observations including similar past events and effects; 4) observed water heights and calculated tsunami travel times; and 5) near-field effects. This report is regularly updated to incorporate the most recent news and observations. Providing timely access to authoritative data and information ultimately benefits researchers, state officials, the media and the public.

McCullough, H. L.; Dunbar, P. K.; Varner, J. D.

2011-12-01

188

Development of an open, event-based and platform independent architecture for distributed and intelligent control systems  

Microsoft Academic Search

New developments confirm the trend of autonomous distributed control systems in the field of manufacturing and automation. To fulfill this demand a new concept of the design of control systems is required in which the structure, the interfaces and communication and interaction opportunities with no restrictions to the platform or hardware are defined. The concept presented in this paper is

K. Feldmann; W. Wolf; M. Weber

2004-01-01

189

A performance evaluation of pattern-based and event-based methods of historic biogeography: recovering the historical signal  

Microsoft Academic Search

The performance of three different methodologies of historical biogeography, Brook's parsimony analysis (BPA), reconciled tree analysis (RTA) and dispersal vicariance analysis (DIVA), was assessed based on their ability to recover a previously known area relationship. To test the methods a series of theoretical data sets containing different effects (such as missing areas, polytomic clades, redundant taxa, different phylogenetic relationships and

Federico Villalobos

2006-01-01

190

conference on limestone hydrogeology, 2011, Besanon, France 91 Infiltration processes in karst using an event-based conceptual  

E-print Network

performances, but are not necessarily able to simulate hydrochemistry, which is commonly used to establish functioning, but is still qualitative. Consequently, hydrochemistry appears to be a powerful additional tool

Paris-Sud XI, Université de

191

Stable Isotope Ratios of Hydrogen and Oxygen in Event-based Precipitation at Linze, the Hexi Corridor, Northwestern China  

NASA Astrophysics Data System (ADS)

The stable isotope ratios of single precipitation events were investigated during the period June 2008 to August 2012 at Linze, which is located in the Hexi Corridor and adjacent to the northern Tibetan Plateau. The local meteoric water line (LMWL) for Linze, ?2H = 8.270?18O + 6.215 (r2 = 0.954, n = 45), was derived using amount-weighted monthly average ?2H and ?18O values to be consistent with International Atomic Energy Agency (IAEA) established practice. The correlation equation between ?2H and ?18O values from individual samples was found to be ?2H = 8.053?18O + 2.535 (r2 = 0.944, n = 165), which is different from the LMWL, exhibiting lower slope value and intercept value. The ?18O temperature dependences at Linze was 0.514‰/oC, smaller than the global values based on monthly average temperature. No marked amount effect was found in this study. These isotopic characteristics of precipitation may be attributed to the incorporation of inland recycled moisture into clouds and secondary evaporation during precipitations. Clear seasonal trends were identified in both oxygen isotope ratios and the deuterium-excess, and these were ascribed to the intraannual variation of moisture transport to this region. The deuterium-excess values were high in summer and autumn, when moisture was derived from westerly transport. The deuterium-excess values were low during the cold and dry periods, when moisture originated from the humid ocean surface. This finding reveals that the air mass from the westerly transport dominates the precipitation in the Hexi Corridor, while the southwest monsoon contributes little to the annual precipitation because it is blocked by Tibetan Plateau. Our data also suggest that the moisture derived from local evapotranspiration may contribute greatly to the precipitation.

Sun, Z.; Ma, R.; Zhou, A.

2013-12-01

192

Medical mitigation strategies for acute radiation exposure during spaceflight.  

PubMed

The United States Government has recently refocused their space program on manned missions to the Moon by 2018 and later to Mars. While there are many potential risks associated with exploration-class missions, one of the most serious and unpredictable is the effect of acute space radiation exposure, and the space program must make every reasonable effort to mitigate this risk. The two cosmic sources of radiation that could impact a mission outside the Earth's magnetic field are solar particle events (SPE) and galactic cosmic radiation (GCR). Either can cause acute and chronic medical illness. Numerous researchers are currently examining the ability of GCR exposure to induce the development of genetic changes that lead to malignancies and other delayed effects. However, relatively little has been published on the medical management of an acute SPE event and the potential impact on the mission and crew. This review paper will provide the readers with medical management options for an acute radiation event based on recommendations from the Department of Homeland Security (DHS), Centers for Disease Control (CDC), and evidence-based critical analysis of the scientific literature. It is the goal of this paper to stimulate debate regarding the definition of safety parameters for exploration-class missions to determine the level of medical care necessary to provide for the crew that will undertake such missions. PMID:16491581

Epelman, Slava; Hamilton, Douglas R

2006-02-01

193

Event-based measurement of boundary-layer winds and topographic effects with a small unmanned aircraft system (sUas)  

NASA Astrophysics Data System (ADS)

Numerical models are invaluable tools for developing and testing hypotheses about interactions and feedbacks between wind and topography. However, field-based measurements are equally important for building and enhancing confidence in model output. Several field methods are available, including conventional approaches using tall masts equipped with an array of anemometers, as well as weather balloons, but few methods are able to match the level of detail available in model simulations of topographically-modified windflow. Here we propose an alternative method that may enhance numerical models. The method involves a small unmanned aircraft system (sUas) equipped with a meteorological sensor payload. The sUas is a two blade helicopter that weighs 5.5 kg, and has a length of 1.32 m. We designed a simple measurement and control system using an Arduino micro-controller, which acquired measurements at pre-defined coordinates autonomously. The entire survey was pre-configured and uploaded to the aircraft, effectively avoiding the need for manual aircraft operation and data collection. We collected raw measurements at each waypoint, yielding a point cloud of windspeed data. During test flights the sUas was able to maintain a stable position (± 0.6 m vertical and horizontal) in wind speeds up to 50 km/h. We used the raw data to map the wind speed-up ratio relative to a reference anemometer. Although it would be preferable to acquire continuous measurements at each waypoint, the sUas method only provides a snapshot of wind at each location. However, despite this limitation, the sUas does fill a void in terms of spatial measurements within the boundary layer. It may be possible to enhance this method in the future through deployment of sUas swarms that measure wind concurrently at many locations. Furthermore, other sensors can be deployed on sUas for measuring aeolian processes such as dust.

Riddell, K.; Hugenholtz, C.

2012-12-01

194

Executive and Theory-of-Mind Contributions to Event-Based Prospective Memory in Children: Exploring the Self-Projection Hypothesis  

ERIC Educational Resources Information Center

In two studies, 4- to 6-year-olds were asked to name pictures of animals for the benefit of a watching hand puppet (the ongoing task) but to refrain from naming and to remove from view any pictures of dogs (the prospective memory [PM] task). Children also completed assessments of verbal ability, cognitive inhibition, working memory, and…

Ford, Ruth M.; Driscoll, Timothy; Shum, David; Macaulay, Catrin E.

2012-01-01

195

A System For Event-Based Film Browsing Bart Lehane, Noel E. O'Connor, Alan F. Smeaton, and Hyowon Lee  

E-print Network

Lee Centre for Digital Video Processing and Adaptive Information Cluster, Dublin City University://www.cdvp.dcu.ie Abstract. The recent past has seen a proliferation in the amount of digital video content being created with which production, reproduction and consumption is now possible. The widespread use of digital video

Lee, Hyowon

196

Monitoring of event-based mobilization of hydrophobic pollutants in rivers: calibration of turbidity as a proxy for particle facilitated transport in field and laboratory.  

PubMed

Transport of many pollutants in rivers is coupled to mobilization of suspended particles which typically occurs during floods. Since the amount of total suspended solids (TSS) in rivers can be monitored by turbidity measurements this may be used as a proxy for the total concentration of particle associated pollutants such as PAHs, PCBs, etc. and several heavy metals. Online turbidity measurements (e.g. by optical backscattering sensors) would then also allow for an assessment of particle and pollutant flux dynamics if once calibrated against TSS and total pollutant concentrations for a given catchment. In this study, distinct flood and thus turbidity events were sampled at high temporal resolution in three contrasting sub-catchments of the River Neckar in Southwest Germany (Ammer, Goldersbach, Steinlach) as well as in the River Neckar itself and investigated for the total amount of PAHs and TSS in water; turbidity (NTU) and grain size distributions of suspended solids were determined as well. Laboratory experiments were performed with natural river bed sediments from different locations (Ammer) to investigate PAH concentrations, TSS and turbidity during sedimentation of suspended particles under controlled conditions (yielding smaller and smaller suspended particles and TSS with time). Laboratory and field results agreed very well and showed that turbidity and TSS were linearly correlated over an extended turbidity range up to 2000 NTU for the field samples and up to 8000 NTU in lab experiments. This also holds for total PAH concentrations which can be reasonably well predicted based on turbidity measurements and TSS vs. PAHs relationships - even for high turbidity values observed during flood events (>2000 NTU). Total PAH concentrations on suspended solids were independent of grain size of suspended particles. This implies that for the rivers investigated the sorption capacity of particles did not change significantly during the observed events. PMID:24858216

Rügner, Hermann; Schwientek, Marc; Egner, Marius; Grathwohl, Peter

2014-08-15

197

Executive and theory-of-mind contributions to event-based prospective memory in children: exploring the self-projection hypothesis.  

PubMed

In two studies, 4- to 6-year-olds were asked to name pictures of animals for the benefit of a watching hand puppet (the ongoing task) but to refrain from naming and to remove from view any pictures of dogs (the prospective memory [PM] task). Children also completed assessments of verbal ability, cognitive inhibition, working memory, and false-belief understanding (both studies), empathy (Study 1 only), and performance on false-sign tests that matched the false-belief tests in narrative content and structure (Study 2 only). Both studies found that inhibition and false-belief performance made unique contributions to the variance in PM, although in Study 1 the influence of inhibition was evident only when children needed to withhold naming. Study 2 further demonstrated that false-belief performance was the only reliable predictor of whether children remembered to return to the researcher an object that had been loaned to them prior to the picture-naming game. Both experiments uncovered moderate relations between PM and chronological age, but such relations were rarely significant after taking account of cognitive ability. We consider the implications of the findings for (a) current views regarding frontal/executive contributions to PM development and (b) the suggestion that the same brain network underlies various forms of mental self-projection, including envisioning the future and understanding the minds of other people. PMID:22169353

Ford, Ruth M; Driscoll, Timothy; Shum, David; Macaulay, Catrin E

2012-03-01

198

Executive and theory-of-mind contributions to event-based prospective memory in children: Exploring the self-projection hypothesis  

Microsoft Academic Search

In two studies, 4- to 6-year-olds were asked to name pictures of animals for the benefit of a watching hand puppet (the ongoing task) but to refrain from naming and to remove from view any pictures of dogs (the prospective memory [PM] task). Children also completed assessments of verbal ability, cognitive inhibition, working memory, and false-belief understanding (both studies), empathy

Ruth M. Ford; Timothy Driscoll; David Shum; Catrin E. Macaulay

199

What controls the isotopic composition of the African monsoon precipitation? Insights from event-based precipitation collected during the 2006 AMMA field campaign  

NASA Astrophysics Data System (ADS)

The stable isotopic composition of the tropical precipitation constitutes a useful tool for paleoclimate reconstructions and to better constrain the water cycle. To better understand what controls the isotopic composition of tropical precipitation, we analyze the ? 18O and deuterium-excess of the precipitation of individual events collected in the Niamey area (Niger) during the monsoon season, as part of the 2006 AMMA field campaign. During the monsoon onset, the abrupt increase of convective activity over the Sahel is associated with an abrupt change in the isotopic composition. Before the onset, when convective activity is scarce, the rain composition records the intensity and the organization of individual convective systems. After the onset, on the contrary, it records a regional-scale intra-seasonal variability over the Sahel, by integrating convective activity both spatially and temporally over the previous days.

Risi, Camille; Bony, Sandrine; Vimeux, Francoise; Descroix, Luc; Ibrahim, Boubacar; Lebreton, Eric; Mamadou, Ibrahim; Sultan, Benjamin

2008-12-01

200

Tampa Bay Times Top Workplaces 2013 -Univ. of Florida GCREC http://www.topworkplaces.com/frontend.php/regional-list/company/tampabay/univ-of-florida-gcr[1/28/2014 8:22:22 AM  

E-print Network

Tampa Bay Times Top Workplaces 2013 - Univ. of Florida GCREC http://www.topworkplaces.com/frontend a lot from What employees say Related Articles What it takes to be among Tampa Bay's top workplaces How the survey Tampa Bay's Top 100 Workplaces was done Beyond perks of pizza and Ping-Pong, what really makes

Jawitz, James W.

201

Calculation of The Ti Activity In 44 Chondrites Which Fell In The Last Two Centuries and Comparison With Measurements  

Microsoft Academic Search

The cosmogenic radioisotopes in meteorites, produced by nuclear interactions of the galactic cosmic rays (GCR) with the meteoroids in the interplanetary space are good proxies of both the GCR flux and the solar activity. Different cosmogenic radionu- clides with different half-lives give information over different time scales. Recently we have inferred the GCR annual mean spectra for the last 300

G. Bonino; D. Cane; G. Cini Castagnoli; C. Taricco; N. Bhandari

2002-01-01

202

Do Plants Contain G Protein-Coupled Receptors?1[C][W][OPEN  

PubMed Central

Whether G protein-coupled receptors (GPCRs) exist in plants is a fundamental biological question. Interest in deorphanizing new GPCRs arises because of their importance in signaling. Within plants, this is controversial, as genome analysis has identified 56 putative GPCRs, including G protein-coupled receptor1 (GCR1), which is reportedly a remote homolog to class A, B, and E GPCRs. Of these, GCR2 is not a GPCR; more recently, it has been proposed that none are, not even GCR1. We have addressed this disparity between genome analysis and biological evidence through a structural bioinformatics study, involving fold recognition methods, from which only GCR1 emerges as a strong candidate. To further probe GCR1, we have developed a novel helix-alignment method, which has been benchmarked against the class A-class B-class F GPCR alignments. In addition, we have presented a mutually consistent set of alignments of GCR1 homologs to class A, class B, and class F GPCRs and shown that GCR1 is closer to class A and/or class B GPCRs than class A, class B, or class F GPCRs are to each other. To further probe GCR1, we have aligned transmembrane helix 3 of GCR1 to each of the six GPCR classes. Variability comparisons provide additional evidence that GCR1 homologs have the GPCR fold. From the alignments and a GCR1 comparative model, we have identified motifs that are common to GCR1, class A, B, and E GPCRs. We discuss the possibilities that emerge from this controversial evidence that GCR1 has a GPCR fold. PMID:24246381

Taddese, Bruck; Upton, Graham J.G.; Bailey, Gregory R.; Jordan, Siân R.D.; Abdulla, Nuradin Y.; Reeves, Philip J.; Reynolds, Christopher A.

2014-01-01

203

Analyses of static energy conversion systems for small nuclear power plants  

Microsoft Academic Search

Small, Gas Cooled Reactor (GCR) nuclear power plants with static energy conversion could meet the energy mix in underdeveloped countries, including electricity, residential and industrial space heating, seawater desalination, and\\/or high temperature process heat or steam for industrial uses. Analyses are performed of one high-temperature GCR and three intermediate-temperature GCR power plants with co-generation options to calculate and compare the

Mohamed S. El-Genk; Jean-Michel P. Tournier

2003-01-01

204

Alterations of glucocorticoid receptor expression during glucocorticoid hormone therapy in renal transplant patients  

Microsoft Academic Search

Previous studies have demonstrated that glucocorticoid resistance develops in some patients during glucocorticoid therapy due to the down-regulation of glucocorticoid receptor (GCR) expression. A new flow cytometric method has been used for monitoring the intracellular GCR level in peripheral blood mononuclear cells (PBMCs). GCR expression by different lymphocyte subpopulations (bearing surface CD4+ CD8+ or CD19+) in steroid-treated (ST) and non-treated

Timea Berki; Afshin Tavakoli; Károly Nagy; Gergely Nagy; Péter Németh

2002-01-01

205

Galactic cosmic ray transport methods and radiation quality issues  

NASA Technical Reports Server (NTRS)

An overview of galactic cosmic ray (GCR) interaction and transport methods, as implemented in the Langley Research Center GCR transport code, is presented. Representative results for solar minimum, exo-magnetospheric GCR dose equivalents in water are presented on a component by component basis for various thicknesses of aluminum shielding. The impact of proposed changes to the currently used quality factors on exposure estimates and shielding requirements are quantified. Using the cellular track model of Katz, estimates of relative biological effectiveness (RBE) for the mixed GCR radiation fields are also made.

Townsend, L. W.; Wilson, J. W.; Cucinotta, F. A.; Shinn, J. L.

1992-01-01

206

Glucocorticoid receptors in the retina, Müller glia and the formation of Müller glia-derived progenitors.  

PubMed

Identification of the signaling pathways that influence the reprogramming of Müller glia into neurogenic retinal progenitors is key to harnessing the potential of these cells to regenerate the retina. Glucocorticoid receptor (GCR) signaling is commonly associated with anti-inflammatory responses and GCR agonists are widely used to treat inflammatory diseases of the eye, even though the cellular targets and mechanisms of action in the retina are not well understood. We find that signaling through GCR has a significant impact upon the ability of Müller glia to become proliferating Müller glia-derived progenitor cells (MGPCs). The primary amino acid sequence and pattern of GCR expression in the retina is highly conserved across vertebrate species, including chickens, mice, guinea pigs, dogs and humans. In all of these species we find GCR expressed by the Müller glia. In the chick retina, we find that GCR is expressed by progenitors in the circumferential marginal zone (CMZ) and is upregulated by Müller glia in acutely damaged retinas. Activation of GCR signaling inhibits the formation of MGPCs and antagonizes FGF2/MAPK signaling in the Müller glia. By contrast, we find that inhibition of GCR signaling stimulates the formation of proliferating MGPCs in damaged retinas, and enhances the neuronal differentiation while diminishing glial differentiation. Given the conserved expression pattern of GCR in different vertebrate retinas, we propose that the functions and mechanisms of GCR signaling are highly conserved and are mediated through the Müller glia. We conclude that GCR signaling directly inhibits the formation of MGPCs, at least in part, by interfering with FGF2/MAPK signaling. PMID:25085975

Gallina, Donika; Zelinka, Christopher; Fischer, Andy J

2014-09-01

207

44Ti in meteorites and Galactic Cosmic Ray flux over the past 235 years  

Microsoft Academic Search

The solar magnetic field modulates the galactic cosmic ray GCR flux in the heliosphere and hence one approach to determine solar activity variations in the past is to study the isotopes produced in the matter exposed to GCR flux Isotopic concentration of radionuclides like 10 Be and 14 C produced in the atmosphere and deposited in sediments or ice cores

C. Taricco; N. Bhandari; D. Cane; P. Colombetti; N. Verma; G. Vivaldi

2006-01-01

208

Development of a Miniaturized Hollow-Waveguide Gas Correlation Radiometer for Trace Gas Measurements in the Martian Atmosphere  

NASA Technical Reports Server (NTRS)

We present preliminary results in the development of a miniaturized gas correlation radiometer (GCR) for column trace gas measurements in the Martian atmosphere. The GCR is designed as an orbiting instrument capable of mapping multiple trace gases and identifying active regions on the Mars surface.

Wilson, Emily L.; Georgieva, E. M.; Blalock, G. W.; Marx, C. T.; Heaps, W. S.

2012-01-01

209

Guiding Preservice Teachers to Critically Reflect: Towards a Renewed Sense about English Learners  

ERIC Educational Resources Information Center

The purpose of this practitioner inquiry was to explore the use of Guided Critical Reflection (GCR) in preparing preservice teachers for English learners (ELs). As a teacher researcher, I documented, analyzed, and discussed the ways in which students in my course used the process of GCR to transform their passively held understandings about ELs.…

Markos, Amy Michele

2011-01-01

210

Corotating interaction regions and the 27 day variation of galactic cosmic rays intensity at 1 AU during the cycle 23/24 solar minimum  

NASA Astrophysics Data System (ADS)

We investigate the formation and evolution of corotating interaction regions (CIRs) in the solar wind and their effects on galactic cosmic rays (GCR) during the recent solar cycle 23/24 solar minimum. The output from a three-dimensional MHD model serves as background for kinetic time-dependent simulations of GCR transport based on the Parker equation. The results show that the CIR forward/reverse shock pairs or compression/rarefaction regions play important roles in the transport of GCR particles and directly control the observed 27 day periodic intensity variations. We find that stream interfaces (SIs) in CIRs and the heliospheric current sheet (HCS) are both closely associated with the GCR depression onset, in agreement with the observations at 1 AU. The HCS is more important when its tilt angle becomes small during the declining phase of the solar minimum, while the passages of SIs control the onset of GCR depressions for larger HCS tilt angles. The mechanism of GCR intensity variation near 1 AU can be explained through an interplay between the effects of particle drift and diffusion. The simulated plasma background and GCR intensity are compared with the observations from spacecraft and a neutron monitor on the ground, to find good qualitative agreement. Evidently, CIRs had a substantial modulational effect on GCR during the recent solar minimum.

Guo, X.; Florinski, V.

2014-04-01

211

The role of martensite reorientation in the fretting behaviour of nickel titanium shape memory alloy  

E-print Network

887 The role of martensite reorientation in the fretting behaviour of nickel titanium shape memory.1243/13506501JET427 Abstract: In this study, fretting tests of a GCr15 steel ball against a nickel titanium (NiTi) shape memory alloy plate (NiTi/GCr15) are performed on a horizontal servo-hydraulic fretting machine

Sun, Qing-Ping

212

Light ion components of the galactic cosmic rays: Nuclear interactions and transport theory  

Microsoft Academic Search

Light nuclei are present in the primary galactic cosmic rays (GCR) and are produced in thick targets due to projectile or target fragmentation from both nucleon and heavy ion induced reactions. In the primary GCR, 4He is the most abundant nucleus after 1H. However, there are also a substantial fluxes of 2H and 3He. In this paper we describe theoretical

L. W Townsend; J. W Wilson; J. L Shinn; G. D Badhwar; R. R Dubey

1996-01-01

213

Light ion components of the galactic cosmic rays: Nuclear interactions and transport theory  

Microsoft Academic Search

Light nuclei are present in the primary galactic cosmic rays (GCR) and are produced in thick targets due to projectile or target fragmentation from both nucleon and heavy induced reactions. In the primary GCR, He-4 is the most abundant nucleus after H-1. However, there are also a substantial fluxes of H-2 and He-3. In this paper we describe theoretical models

F. A. Cucinotta; L. W. Townsend; J. W. Wilson; J. L. Shinn; G. D. Badhwar; R. R. Dubey

1996-01-01

214

Interpreting 10 Be changes during the Maunder Minimum  

E-print Network

rays (GCR) is modulated by the strength of the solar magnetic field [Lal and Peters, 1967; Masarik Minimum complicate the process of estimating changes in the solar modulation strength during that time and Beer, 1999]. (Changes in geomagnetic field strength also affect GCR flux, but generally on much longer

215

Influence of cosmic-ray variability on the monsoon rainfall and temperature  

NASA Astrophysics Data System (ADS)

We study the role of galactic cosmic ray (GCR) variability in influencing the rainfall variability in Indian Summer Monsoon Rainfall (ISMR) season. We find that on an average during 'drought' (low ISMR) periods in India, GCR flux is decreasing, and during 'flood' (high ISMR) periods, GCR flux is increasing. The results of our analysis suggest for a possibility that the decreasing GCR flux during the summer monsoon season in India may suppress the rainfall. On the other hand, increasing GCR flux may enhance the rainfall. We suspect that in addition to real environmental conditions, significant levitation/dispersion of low clouds and hence reduced possibility of collision/coalescence to form raindrops suppresses the rainfall during decreasing GCR flux in monsoon season. On the other hand, enhanced collision/coalescence efficiency during increasing GCR flux due to electrical effects may contribute to enhancing the rainfall. Based on the observations, we put forward the idea that, under suitable environmental conditions, changing GCR flux may influence precipitation by suppressing/enhancing it, depending upon the decreasing/increasing nature of GCR flux variability during monsoon season in India, at least. We further note that the rainfall variability is inversely related to the temperature variation during ISMR season. We suggest an explanation, although speculative, how a decreasing/increasing GCR flux can influence the rainfall and the temperature. We speculate that the proposed hypothesis, based on the Indian climate data can be extended to whole tropical and sub-tropical belt, and that it may contribute to global temperature in a significant way. If correct, our hypothesis has important implication for the sun - climate link.

Badruddin; Aslam, O. P. M.

2015-01-01

216

Modulation of Galactic Cosmic Rays Observed at L1 in Solar Cycle 23  

NASA Astrophysics Data System (ADS)

We analyze a unique 15 yr record of galactic cosmic-ray (GCR) measurements made by the SOHO Coronal Diagnostic Spectrometer NIS detectors, recording integrated GCR numbers with energies above 1.0 GeV between 1996 July and 2011 June. We are able to closely reproduce the main features of the SOHO/CDS GCR record using the modulation potential calculated from neutron monitor data by Usoskin et al. The GCR numbers show a clear solar cycle modulation: they decrease by 50% from the 1997 minimum to the 2000 maximum of the solar cycle, then return to the 1997 level in 2007 and continue to rise, in 2009 December reaching a level 25% higher than in 1997. This 25% increase is in contrast with the behavior of Ulysses/KET GCR protons extrapolated to 1 AU in the ecliptic plane, showing the same level in 2008-2009 as in 1997. The GCR numbers are inversely correlated with the tilt angle of the heliospheric current sheet. In particular, the continued increase of SOHO/CDS GCRs from 2007 until 2009 is correlated with the decrease of the minimum tilt angle from 30° in mid-2008 to 5° in late 2009. The GCR level then drops sharply from 2010 January, again consistent with a rapid increase of the tilt angle to over 35°. This shows that the extended 2008 solar minimum was different from the 1997 minimum in terms of the structure of the heliospheric current sheet.

Fludra, A.

2015-01-01

217

Voyager 1 UVS measurements of Galactic cosmic rays  

NASA Astrophysics Data System (ADS)

Detectors of the Ultra-Violet Spectrographs (UVS) on board the Voyagers provide independent measurements of galactic cosmic ray (GCR) fluxes. The energy and angular response are derived from correlative studies with other Voyager Instruments. We show the evolution of the GCR flux and anisotropy during and after the abrupt increases in 2012. Using data from UVS and other instruments we show strong evidence for the end of the GCR heliospheric modulation in the 300 MeV range at the present location of Voyager 1, in line with the flux steadiness since September 2012. This suggests that Voyager already entered the interstellar medium, and we discuss potential reasons.

Lallement, R.; Quemerais, E.; Bertaux, J.; Sandel, B. R.

2013-12-01

218

Pulsed Magnetic Field Driven Gas Core Reactors for Space Power & Propulsion Applications  

NASA Technical Reports Server (NTRS)

The present results indicated that: 1. A pulsed magnetic driven fission power concept, PMD-GCR is developed for closed (NER) and semi-open (NTR) operations. 2. In power mode, power is generated at alpha less than 1 for power levels of hundreds of KW or higher 3. IN semi open NTR mode, PMD-GCR generates thrust at I(sub sp) approx. 5,000 s and jet power approx. 5KW/Kg. 4. PMD-GCR is highly subcritical and is actively driven to critically. 5. Parallel path with fusion R&D needs in many areas including magnet and plasma.

Anghaie, Samim; Smith, Blair; Knight, Travis; Butler, Carey

2003-01-01

219

Comparison of Space Radiation Calculations from Deterministic and Monte Carlo Transport Codes  

NASA Technical Reports Server (NTRS)

The presentation outline includes motivation, radiation transport codes being considered, space radiation cases being considered, results for slab geometry, results from spherical geometry, and summary. ///////// main physics in radiation transport codes hzetrn uprop fluka geant4, slab geometry, spe, gcr,

Adams, J. H.; Lin, Z. W.; Nasser, A. F.; Randeniya, S.; Tripathi, r. K.; Watts, J. W.; Yepes, P.

2010-01-01

220

Identification of Licopyranocoumarin and Glycyrurol from Herbal Medicines as Neuroprotective Compounds for Parkinson's Disease  

PubMed Central

In the course of screening for the anti-Parkinsonian drugs from a library of traditional herbal medicines, we found that the extracts of choi-joki-to and daio-kanzo-to protected cells from MPP+-induced cell death. Because choi-joki-to and daio-kanzo-to commonly contain the genus Glycyrrhiza, we isolated licopyranocoumarin (LPC) and glycyrurol (GCR) as potent neuroprotective principals from Glycyrrhiza. LPC and GCR markedly blocked MPP+-induced neuronal PC12D cell death and disappearance of mitochondrial membrane potential, which were mediated by JNK. LPC and GCR inhibited MPP+-induced JNK activation through the suppression of reactive oxygen species (ROS) generation, thereby inhibiting MPP+-induced neuronal PC12D cell death. These results indicated that LPC and GCR derived from choi-joki-to and daio-kanzo-to would be promising drug leads for PD treatment in the future. PMID:24960051

Fujimaki, Takahiro; Saiki, Shinji; Tashiro, Etsu; Yamada, Daisuke; Kitagawa, Mitsuhiro; Hattori, Nobutaka; Imoto, Masaya

2014-01-01

221

Observations of the Li, Be, and B isotopes and Constraints on Cosmic-ray Propagation  

SciTech Connect

The abundance of Li, Be, and B isotopes in galactic cosmic rays (GCR) between E=50-200 MeV/nucleon has been observed by the Cosmic Ray Isotope Spectrometer (CRIS) on NASA's ACE mission since 1997 with high statistical accuracy. Precise observations of Li, Be, B can be used to constrain GCR propagation models. We find that a diffusive reacceleration model with parameters that best match CRIS results (e.g. B/C, Li/C, etc) are also consistent with other GCR observations. A {approx}15-20% overproduction of Li and Be in the model predictions is attributed to uncertainties in the production cross-section data. The latter becomes a significant limitation to the study of rare GCR species that are generated predominantly via spallation.

de Nolfo, Georgia A.; Moskalenko, I.V.; Binns, W.R.; Christian, E.R.; Cummings, A.C.; Davis, A.J.; George, J.S.; Hink, P.L.; Israel, M.H.; Leske, R.A.; Lijowski, M.; Mewaldt, R.A.; Stone, E.C.; Strong, A.W.; von Rosenvinge, T.T.; Wiedenbeck, M.E.; Yanasak, N.E.; /NASA, Goddard /Stanford U., HEPL /Washington U., St. Louis /NASA, Headquarters/Caltech, SRL /Aerospace Corp. /Garching, Max Planck Inst., MPE /Caltech, JPL; ,

2006-11-15

222

DEVELOPING METHODS FOR ANTAGONIZING TNF-? AND IL-1? IN THE CENTRAL NERVOUS SYSTEM  

E-print Network

harvested to examine the development of glucocorticoid resistance (GCR), a hallmark of SDR, in the TNF-? study only. The ELISA assay was not sensitive enough to the tissue levels of TNF-?, therefore successful antagonism was undetectable. In contrast, IL-1...

Hardin, Elizabeth Ashley

2006-08-16

223

Observations of the Li, Be, and B Isotopes and Constraints on Cosmic-ray Propagation  

NASA Technical Reports Server (NTRS)

The abundance of Li, Be, and B isotopes in galactic cosmic rays (GCR) between E=50-200 MeV/nucleon has been observed by the Cosmic Ray Isotope Spectrometer (CRIS) on NASA's ACE mission since 1997 with high statistical accuracy. Precise observations of Li, Be, B can be used to constrain GCR propagation models. We find that a diffusive reacceleration model with parameters that best match CRIS results (e.g. B/C, Li/C, etc) are also consistent with other GCR observations. A approx. 15-20% overproduction of Li and Be in the model predictions is attributed to uncertainties in the production cross-section data. The latter becomes a significant limitation to the study of rare GCR species that are generated predominantly via spallation.

deNolfo, G. A.; Moskalenko, I. V.; Binns, W. R.; Christian, E. R.; Cummings, A. C.; Davis, A. J.; George, J. S.; Hink, P. L.; Israel, M. H.; Leske, R. A.; Lijowski, M.; Mewaldt, R. A.; Stone, E. C.; Strong, A. W.; vonRosenvinge, T. T.; Wiedenbeck, M. E.; Yanasak, N. E.

2007-01-01

224

Composite Materials for Radiation Shielding During Deep Space Missions  

NASA Technical Reports Server (NTRS)

Minimizing radiation exposure from the galactic cosmic ray (GCR) environment during deep space missions is essential to human health and sensitive instrument survivability. Given the fabrication constraints of space transportation vehicles protective shielding is, consequently, a complicated materials issue. These concerns are presented and considered in view of some novel composite materials being developed/suggested for GCR shielding applications. Advantages and disadvantages of the composites will be discussed as well as the need for coordinated testing/evaluation and modeling efforts.

Grugel, R. N.; Watts, J.; Adams, J. H.; Rose, M. Franklin (Technical Monitor)

2001-01-01

225

On the depth-dependent production of radionuclides (44?A?59) by solar protons in extraterrestrial matter  

Microsoft Academic Search

In order to interpret cosmogenic radionuclides in extraterrestrial matter one has to differentiate between p- and ?-induced\\u000a reactions with solar (SCR) and with galactic (GCR) cosmic rays. Our earlier studies have shown that for a satisfactory description\\u000a of GCR-interactions with dense matter rather few but characteristic high energy cross sections are required. In contrast,\\u000a for the low and medium energy

R. Michel; G. Brinkmann

1980-01-01

226

Modeling And Analysis Of The Diskund Generator Component Of A Gas Core Reactor\\/MHD Rankine Cycle Space Power System  

Microsoft Academic Search

A gas core nuclear reactor (GCR)\\/disk magnetohydrodynamic (MHD) generator direct closed Rankine space power system concept is described. The GCR\\/disk MHD generator marriage facilitates efficient high electric power density system performance at relatively high operating temperatures. The aystem concept promises high specific power levels, on the order of 1 kWe\\/kg. An overview of the disk MHD generator component magnetofluiddynamic and

Gerard E. Welch; Edward T. Dugan; W. E. Lear; J. G. Appelbaum

1990-01-01

227

G-Protein Complex Mutants Are Hypersensitive to Abscisic Acid Regulation of Germination and Postgermination Development1[W  

PubMed Central

Abscisic acid (ABA) plays regulatory roles in a host of physiological processes throughout plant growth and development. Seed germination, early seedling development, stomatal guard cell functions, and acclimation to adverse environmental conditions are key processes regulated by ABA. Recent evidence suggests that signaling processes in both seeds and guard cells involve heterotrimeric G proteins. To assess new roles for the Arabidopsis (Arabidopsis thaliana) G? subunit (GPA1), the G? subunit (AGB1), and the candidate G-protein-coupled receptor (GCR1) in ABA signaling during germination and early seedling development, we utilized knockout mutants lacking one or more of these components. Our data show that GPA1, AGB1, and GCR1 each negatively regulates ABA signaling in seed germination and early seedling development. Plants lacking AGB1 have greater ABA hypersensitivity than plants lacking GPA1, suggesting that AGB1 is the predominant regulator of ABA signaling and that GPA1 affects the efficacy of AGB1 execution. GCR1 acts upstream of GPA1 and AGB1 for ABA signaling pathways during germination and early seedling development: gcr1 gpa1 double mutants exhibit a gpa1 phenotype and agb1 gcr1 and agb1 gcr1 gpa1 mutants exhibit an agb1 phenotype. Contrary to the scenario in guard cells, where GCR1 and GPA1 have opposite effects on ABA signaling during stomatal opening, GCR1 acts in concert with GPA1 and AGB1 in ABA signaling during germination and early seedling development. Thus, cell- and tissue-specific functional interaction in response to a given signal such as ABA may determine the distinct pathways regulated by the individual members of the G-protein complex. PMID:16581874

Pandey, Sona; Chen, Jin-Gui; Jones, Alan M.; Assmann, Sarah M.

2006-01-01

228

The influence of galactic cosmic ray on all India annual rainfall and temperature  

NASA Astrophysics Data System (ADS)

The inverse relation between galactic cosmic ray (GCR) and sunspot numbers (SSN) suggests that the increase (decrease) in GCR count is linked with low (high) solar activity. The present study attempts to reveal the influence of GCR on all India annual rainfall and temperature during the period from 1953 to 2005. The inter-annual variation depicts that during the transition from maximum to minimum count of GCR, the rainfall anomaly shows alternative variation over India. Similar variation has also been observed for maximum temperature. Implementation of Fourier analysis shows an 11 year cycle of cosmic ray and depicts an increase in GCR count in the 11 year interval during the study period. The Fourier analysis of all India annual rainfall (AIR) and temperature also shows an 11 year cycle with a decreasing trend during the 11 year interval. The inter-decadal variation shows that during high GCR count there is a possibility of decrease in rainfall and minimum temperature but an increase in maximum temperature. The seasonal correlation shows a possible proportional association between cosmic ray and rainfall during the post monsoon season. The result further depicts that the sunspot number and temperature is positively correlated during the post-monsoon season. The correlation map of rainfall and temperature shows a meager but significant correlation with cosmic ray over some parts of West and East Indian coasts.

Chaudhuri, Sutapa; Pal, Jayanti; Guhathakurta, Suchandra

2015-02-01

229

Analysis distribution of galactic cosmic rays particle energy with polar orbit satellite for Geant4 application  

NASA Astrophysics Data System (ADS)

Galactic Cosmic Rays (GCR) are photon waves originating from astrophysical sources which traverse through the interstellar/interplanetary medium and reaching the terrestrial atmosphere. The energies of Galactic Cosmic Ray particles up to and exceeding 1012 eV, and this spectrum are peaked around 1 GeV. The National Aeronautics and Space Administration (NASA) provide satellite mission for monitoring the energy GCR particles in polar orbit, so-called the ACE and OMNI. In this paper, we analyze results from measurement error of GCR sensor. The error result is obtained by comparing the measurements from GCR sensor with ground-based neutron monitors at Bartol University. The measurements were taken for two periods during a Solar Particle Event (SPE) maximum on 14 July 2000 and 28 October 2003. The largest value of measurement error from GCR sensor in this study is OMNI satellites. After the error results were obtained, they were applied into Geant4 simulation. This simulation shows the shape of particle energy distribution of GCR sensors. The simulation has been tested and can be operated very well under Linux based platform.

Suparta, W.; Putro, W. S.

2014-04-01

230

Effects of Cutoffs on Galactic Cosmic-Ray Interactions in Solar-System Matter  

NASA Technical Reports Server (NTRS)

The energetic particles in the galactic cosmic rays (GCR) induce many interactions in a variety of solar-system matter. Cosmogenic nuclides are used to study the histories of meteorites and lunar samples. Gamma rays and neutrons are used to map the compositions of planetary surfaces, such as Mars, the Moon, and asteroids. In almost all of these cases, the spectra of incident GCR particles are fairly similar, with only some modulation by the Sun over an 11-year cycle. Strong magnetic fields can seriously affect the energy spectrum of GCR particles hitting the surface of objects inside the magnetic fields. The Earth s geomagnetic field is strong enough that only GCR particles with magnetic rigidities above approx. 17 GV (a proton energy of approx. 17 GeV) reach the atmosphere over certain regions near the equator. This effect of removing lower-energy GCR particles is called a cutoff. The jovian magnetic fields are so strong that the fluxes of GCR particles hitting the 4 large Galilean satellites are similarly affected. The cutoff at Europa is estimated to be similar to or a little higher than at the Earth s equator.

Kim, K. J.; Reedy, R. C.; Masarik, J.

2005-01-01

231

Computational and Genetic Reduction of a Cell Cycle to Its Simplest, Primordial Components  

PubMed Central

What are the minimal requirements to sustain an asymmetric cell cycle? Here we use mathematical modelling and forward genetics to reduce an asymmetric cell cycle to its simplest, primordial components. In the Alphaproteobacterium Caulobacter crescentus, cell cycle progression is believed to be controlled by a cyclical genetic circuit comprising four essential master regulators. Unexpectedly, our in silico modelling predicted that one of these regulators, GcrA, is in fact dispensable. We confirmed this experimentally, finding that ?gcrA cells are viable, but slow-growing and elongated, with the latter mostly due to an insufficiency of a key cell division protein. Furthermore, suppressor analysis showed that another cell cycle regulator, the methyltransferase CcrM, is similarly dispensable with simultaneous gcrA/ccrM disruption ameliorating the cytokinetic and growth defect of ?gcrA cells. Within the Alphaproteobacteria, gcrA and ccrM are consistently present or absent together, rather than either gene being present alone, suggesting that gcrA/ccrM constitutes an independent, dispensable genetic module. Together our approaches unveil the essential elements of a primordial asymmetric cell cycle that should help illuminate more complex cell cycles. PMID:24415923

Fumeaux, Coralie; Viollier, Patrick H.; Howard, Martin

2013-01-01

232

Implementing Badhwar-O'Neill Galactic Cosmic Ray Model for the Analysis of Space Radiation Exposure  

NASA Technical Reports Server (NTRS)

For the analysis of radiation risks to astronauts and planning exploratory space missions, accurate energy spectrum of galactic cosmic radiation (GCR) is necessary. Characterization of the ionizing radiation environment is challenging because the interplanetary plasma and radiation fields are modulated by solar disturbances and the radiation doses received by astronauts in interplanetary space are likewise influenced. A model of the Badhwar-O'Neill 2011 (BO11) GCR environment, which is represented by GCR deceleration potential theta, has been derived by utilizing all of the GCR measurements from balloons, satellites, and the newer NASA Advanced Composition Explorer (ACE). In the BO11 model, the solar modulation level is derived from the mean international sunspot numbers with time-delay, which has been calibrated with actual flight instrument measurements to produce better GCR flux data fit during solar minima. GCR fluxes provided by the BO11 model were compared with various spacecraft measurements at 1 AU, and further comparisons were made for the tissue equivalent proportional counters measurements at low Earth orbits using the high-charge and energy transport (HZETRN) code and various GCR models. For the comparison of the absorbed dose and dose equivalent calculations with the measurements by Radiation Assessment Detector (RAD) at Gale crater on Mars, the intensities and energies of GCR entering the heliosphere were calculated by using the BO11 model, which accounts for time-dependent attenuation of the local interstellar spectrum of each element. The BO11 model, which has emphasized for the last 24 solar minima, showed in relatively good agreement with the RAD data for the first 200 sols, but it was resulted in to be less well during near the solar maximum of solar cycle 24 due to subtleties in the changing heliospheric conditions. By performing the error analysis of the BO11 model and the optimization in reducing overall uncertainty, the resultant BO13 model corrects the fit at solar maxima as well as being accurate at solar minima. The BO13 model is implemented to the NASA Space Cancer Risk model for the assessment of radiation risks. Overall cumulative probability distribution of solar modulation parameters represents the percentile rank of the average interplanetary GCR environment, and the probabilistic radiation risks can be assessed for various levels of GCR environment to support mission design and operational planning for future manned space exploration missions.

Kim, Myung-Hee Y.; O'Neill, Patrick M.; Slaba, Tony C.

2014-01-01

233

Calculation of The Ti Activity In 44 Chondrites Which Fell In The Last Two Centuries and Comparison With Measurements  

NASA Astrophysics Data System (ADS)

The cosmogenic radioisotopes in meteorites, produced by nuclear interactions of the galactic cosmic rays (GCR) with the meteoroids in the interplanetary space are good proxies of both the GCR flux and the solar activity. Different cosmogenic radionu- clides with different half-lives give information over different time scales. Recently we have inferred the GCR annual mean spectra for the last 300 years [1]. The most prominent result concerns the cosmic ray flux during prolonged solar quiet periods. We deduced that during the Maunder minimum of solar acivity (1700), the Dal- ton minimum (1800) and the Modern minimum (1900) the GCR flux was much higher (2 times) respect to the flux observed in the last decades. Utilizing these GCR spectra we have calculated the 44 Ti (T1/2 = 59.2 y) activity in meteorites taking into account its exitation function for production from the main target element Fe, Ni and Ti [2]. Furthermore, in the last years we have measured the very low activity of the cosmogenic 44Ti in different fell chondrites and now our data cover the interval 1810 to present. The calculated 44Ti profile is in close agreement with the observed mea- surements. This result demonstrates that our inference of the GCR flux in the past 300 years is reliable. The cosmogenic 44Ti in meteorites is a unique tool, free from ter- restrial influences, for validation of both the GCR flux and the heliospheric behaviour over century time scale. [1] G. Bonino, G. Cini Castagnoli, D. Cane, C. Taricco and N. Bhandari, Proc. XXVII Intern. Cosmic Ray Conf. (Hamburg, 2001) 3769-3772. [2] R. Michel and S. Neumann (1998) Proc. Indian Acad. Sci. Earth Planet. Sci. , 107, 441-457.

Bonino, G.; Cane, D.; Cini Castagnoli, G.; Taricco, C.; Bhandari, N.

234

Badhwar-O'Neill 2011 Galactic Cosmic Ray Model Update and Future Improvements  

NASA Technical Reports Server (NTRS)

The Badhwar-O'Neill Galactic Cosmic Ray (GCR) Model based on actual GCR measurements is used by deep space mission planners for the certification of microelectronic systems and the analysis of radiation health risks to astronauts in space missions. The BO GCR Model provides GCR flux in deep space (outside the earth's magnetosphere) for any given time from 1645 to present. The energy spectrum from 50 MeV/n - 20 GeV/n is provided for ions from hydrogen to uranium. This work describes the most recent version of the BO GCR model (BO'11). BO'11 determined the GCR flux at a given time applying an emperical time delay function to past sunspot activity. We describe the GCR measurement data used in the BO'11 update - modern data from BESS, PAMELA, CAPRICE, and ACE emphasized more than the older balloon data used for the previous BO model (BO'10). We look at the GCR flux for the last 24 solar minima and show how much greater the flux was for the cycle 24 minimum in 2010. The BO'11 Model uses the traditional, steady-state Fokker-Planck differential equation to account for particle transport in the heliosphere due to diffusion, convection, and adiabatic deceleration. It assumes a radially symmetrical diffusion coefficient derived from magnetic disturbances caused by sunspots carried outward by a constant solar wind. A more complex differential equation is now being tested to account for particle transport in the heliosphere in the next generation BO model. This new model is time-dependent (no longer a steady state model). In the new model, the dynamics and anti-symmetrical features of the actual heliosphere are accounted for so emperical time delay functions will no longer be required. The new model will be capable of simulating the more subtle features of modulation - such as the Sun's polarity and modulation dependence on gradient and curvature drift. This improvement is expected to significantly improve the fidelity of the BO GCR model. Preliminary results of its performance will be presented.

O'Neill, Pat M.; Kim, Myung-Hee Y.

2014-01-01

235

Evaluating Shielding Effectiveness for Reducing Space Radiation Cancer Risks  

NASA Technical Reports Server (NTRS)

We discuss calculations of probability distribution functions (PDF) representing uncertainties in projecting fatal cancer risk from galactic cosmic rays (GCR) and solar particle events (SPE). The PDF s are used in significance tests of the effectiveness of potential radiation shielding approaches. Uncertainties in risk coefficients determined from epidemiology data, dose and dose-rate reduction factors, quality factors, and physics models of radiation environments are considered in models of cancer risk PDF s. Competing mortality risks and functional correlations in radiation quality factor uncertainties are treated in the calculations. We show that the cancer risk uncertainty, defined as the ratio of the 95% confidence level (CL) to the point estimate is about 4-fold for lunar and Mars mission risk projections. For short-stay lunar missions (<180 d), SPE s present the most significant risk, however one that is mitigated effectively by shielding, especially for carbon composites structures with high hydrogen content. In contrast, for long duration lunar (>180 d) or Mars missions, GCR risks may exceed radiation risk limits, with 95% CL s exceeding 10% fatal risk for males and females on a Mars mission. For reducing GCR cancer risks, shielding materials are marginally effective because of the penetrating nature of GCR and secondary radiation produced in tissue by relativistic particles. At the present time, polyethylene or carbon composite shielding can not be shown to significantly reduce risk compared to aluminum shielding based on a significance test that accounts for radiobiology uncertainties in GCR risk projection.

Cucinotta, Francis A.; Kim, Myung-Hee Y.; Ren, Lei

2007-01-01

236

The orphan protein bis-?-glutamylcystine reductase joins the pyridine nucleotide-disulfide reductase family  

PubMed Central

Facile DNA sequencing became possible decades after many enzymes had been purified and characterized. Consequently, there are still “orphan” enyzmes whose activity is known but the genes that encode them have not been identified. Identification of the genes encoding orphan enzymes is important because it allows correct annotation of genes of unknown function or with mis-assigned function. Bis-?-glutamylcystine reductase (GCR) is an orphan protein that was purified in 1988. This enzyme catalyzes the reduction of bis-?-glutamylcystine. ?-Glutamylcysteine (?-Glu-Cys) is the major low molecular weight thiol in halobacteria. We purified GCR from Halobacterium sp. NRC-1 and identified the sequence of 23 tryptic peptides by NanoLC electrospray ionization tandem mass spectrometry. These peptides cover 62% of the protein predicted to be encoded by a gene in Halobacterium sp. NRC-1 that is annotated as mercuric reductase. GCR and mercuric reductase activities were assayed using enzyme that was expressed in E. coli and re-folded from inclusion bodies. The enzyme had robust GCR activity, but no mercuric reductase activity. The genomes of most, but not all, halobacteria for which whole genome sequences are available have close homologs of GCR, suggesting that there is more to be learned about the low molecular weight thiols used in halobacteria. PMID:23560638

Kim, Juhan; Copley, Shelley D.

2014-01-01

237

Super-TIGER: A Balloon-Borne Instrument to Probe Galactic Cosmic Ray Origins  

NASA Astrophysics Data System (ADS)

Super-TIGER (Super Trans-Iron Galactic Element Recorder) is a balloon-borne instrument under construction for a long-duration flight from Antarctica in 2012. It is designed to measure the relative abundances of the ultra-heavy (UH) Galactic cosmic rays (GCR) with individual-element resolution from _{30}Zn to _{42}Mo and make exploratory measurements through _{56}Ba, as well as the energy spectra of the GCR from _{10}Ne to _{29}Cu between 0.8 and 10 GeV/nucleon. The UH measurements will test the OB association origin model of the GCR, as well as the model of preferential acceleration of refractory elements. The GCR spectrum measurements will probe for microquasars or other sources that could superpose spectral features. Super-TIGER is a ˜ 4 × larger evolution of the preceding TIGER instrument, and is comprised of two independent modules with a total area of 5.4 m^{2}. A combination of plastic scintillation detectors, acrylic and silica-aerogel Cherenkov detectors, and scintillating fiber hodoscopes are used to resolve particle charge, kinetic energy per nucleon, and trajectory. Refinements in the Super-TIGER design over TIGER, including reduced material in the beam, give it a collecting power that is ˜ 6.4× larger. This paper will report on the instrument development status, the expected flight performance, and the scientific impact of the anticipated Super-TIGER GCR measurements. This research was supported by NASA under Grant NNX09AC17G

Rauch, Brian

2012-07-01

238

Diffusion coefficient and radial gradient of galactic cosmic rays  

E-print Network

We present the temporal changes of the diffusion coefficient K of galactic cosmic rays (GCRs) at the Earth orbit calculated based on the experimental data using two different methods. The first approach is based on the Parker convection-diffusion approximation of GCR modulation [1]: i.e. K~Vr=dI where dI is the variation of the GCR intensity measured by neutron monitors (NM),V is the solar wind velocity and r is the radial distance. The second approach is based on the interplanetary magnetic field (IMF) data. It was suggested that parallel mean free path can be expressed in terms of B as in [2]-[4]. Using data of the product of the parallel mean free path and radial gradient of GCR calculated based on the GCR anisotropy data (Ahluwalia et al., this conference ICRC 2013, poster ID: 487 [5]), we estimate the temporal changes of the radial gradient of GCR at the Earth orbit. We show that the radial gradient exhibits a strong solar cycle dependence (11-year variation) and a weak solar magnetic cycle dependence (2...

Modzelewska, Renata

2015-01-01

239

Study the effect of gray component replacement level on reflectance spectra and color reproduction accuracy  

NASA Astrophysics Data System (ADS)

The aim of this study is investigation of gray component replacement (GCR) levels on reflectance spectrum for different overprints of the inks and color reproduction accuracy. The most commonly implemented method in practice for generation of achromatic composition is gray component replacement (GCR). The experiments in this study, have been performed in real production conditions with special test form generated by specialized software. The measuring of reflection spectrum of printed colors, gives a complete conception for the effect of different gray component replacement levels on color reproduction accuracy. For better data analyses and modeling of processes, we have calculated (converted) the CIEL*a*b* color coordinates from the reflection spectra data. The assessment of color accuracy by using different GCR amount has been made by calculation of color difference ?E* ab. In addition for the specific printing conditions we have created ICC profiles with different GCR amounts. A comparison of the color gamuts has been performed. For a first time a methodology is implemented for examination and estimation of effect of GCR levels on color reproduction accuracy by studying a big number of colors in entire visible spectrum. Implementation in practice of the results achieved in this experiment, will lead to improved gray balance and better color accuracy. Another important effect of this research is reduction of financial costs of printing production by decreasing of ink consumption, indirect reduction of emissions during the manufacture of inks and facilitates the process of deinking during the recycling paper.

Spiridonov, I.; Shopova, M.; Boeva, R.

2013-03-01

240

Depth-dose equivalent relationship for cosmic rays at various solar minima  

NASA Technical Reports Server (NTRS)

Galactic cosmic rays (GCR) pose a serious radiation hazard for long-duration missions. In designing a lunar habitat or a Mars transfer vehicle, the radiation exposure determines the GCR shielding thickness, and hence the weight of spacecraft. Using the spherically symmetric diffusion theory of the solar modulation of GCR, and data on the differential energy spectra of H, He, O, and Fe, from 1965 to 1989, it has been shown that (1) the flux is determined by the diffusion parameter which is a function of the time in the solar cycle, and (2) the fluxes in the 1954 and 1976-1977 solar minima were similar and higher than those in 1965. In this paper, we have extended the spherical solar modulation theory back to 1954. The 1954-1955 GCR flux was nearly the same as that from 1976 to 1977; the 1965 flux values were nearly the same as those in 1986. Using this theory we have obtained the GCR spectra for all the nuclei, and calculated the depth dose as a function of Al thickness. It is shown that the shielding required to stay below 0.5 Sv is 17.5 -3/+8 g/sq cm of Al, and 9 -1.5/+5 g/sq cm to stay below 0.6 Sv. The calculated dose equivalent using the ICRP 60 values for quality factors is about 15 percent higher than that calculated using the ICRP 26 value.

Badhwar, G. D.; Cucinotta, F. A.; O'Neill, P. M.

1993-01-01

241

Stratospheric polar vortex as a possible reason for temporal variations of solar activity and galactic cosmic ray effects on the lower atmosphere circulation  

NASA Astrophysics Data System (ADS)

Possible reasons for the temporal instability of long-term effects of solar activity (SA) and galactic cosmic ray (GCR) variations on the lower atmosphere circulation were studied. It was shown that the detected earlier ?60-year oscillations of the amplitude and sign of SA/GCR effects on the troposphere pressure at high and middle latitudes (Veretenenko and Ogurtsov, Adv.Space Res., 2012) are closely related to the state of a cyclonic vortex forming in the polar stratosphere. The intensity of the vortex was found to reveal a roughly 60-year periodicity affecting the evolution of the large-scale atmospheric circulation and the character of SA/GCR effects. An intensification of both Arctic anticyclones and mid-latitudinal cyclones associated with an increase of GCR fluxes at minima of the 11-year solar cycles is observed in the epochs of a strong polar vortex. In the epochs of a weak polar vortex SA/GCR effects on the development of baric systems at middle and high latitudes were found to change the sign. The results obtained provide evidence that the mechanism of solar activity and cosmic ray influences on the lower atmosphere circulation involves changes in the evolution of the stratospheric polar vortex.

Veretenenko, S.; Ogurtsov, M.

2014-12-01

242

The Development of Materials for Structures and Radiation Shielding in Aerospace  

NASA Technical Reports Server (NTRS)

Polymeric materials on space vehicles and high-altitude aircraft win be exposed to highly penetrating radiations. These radiations come from solar flares and galactic cosmic rays (GCR). Radiation from solar flares consists primarily of protons with energies less than 1 GeV. On the other hand, GCR consist of nuclei with energies as high as 10(exp 10) GeV. Over 90% of the nuclei in GCR are protons and alpha particles, however there is a small but significant component of particles with atomic numbers greater than ten. Particles with high atomic number (Z) and high energy interact with very high specific ionization and thus represent a serious hazard for humans and electronic equipment on a spacecraft or on high-altitude commercial aircraft (most importantly for crew members who would have long exposures). Neutrons generated by reactions with the high energy particles also represent a hazard both for humans and electronic equipment.

Kiefer, Richard L.; Orwoll, Robert A.

2001-01-01

243

Cosmic-Ray Modulation due to High-Speed Solar-Wind Streams of Different Sources, Speed, and Duration  

NASA Astrophysics Data System (ADS)

We study the modulation of galactic cosmic rays (GCR) due to high-speed streams (HSS) identified in the solar wind. We compare the GCR modulation due to i) streams with different speed, ii) streams of different duration, and iii) streams from different solar sources. We apply the method of superposed-epoch analysis to analyze the interplanetary plasma and field parameters during the passage of streams with distinct plasma and field characteristics. We use the plasma/field characteristics to distinguish various features of solar sources and interplanetary structures, and discuss the observed differences in the cosmic-ray response. We study the influence of speed, duration, and solar sources of the streams on the GCR modulation. We discuss the relative importance of different solar-wind parameters in the modulation process.

Kumar, Anand; Badruddin

2014-11-01

244

Stopping powers and cross sections due to two-photon processes in relativistic nucleus-nucleus collision  

NASA Technical Reports Server (NTRS)

The radiation dose received from high energy galactic cosmic rays (GCR) is a limiting factor in the design of long duration space flights and the building of lunar and martian habitats. It is of vital importance to have an accurate understanding of the interactions of GCR in order to assess the radiation environment that the astronauts will be exposed to. Although previous studies have concentrated on the strong interaction process in GCR, there are also very large effects due to electromagnetic (EM) interactions. In this report we describe our first efforts at understanding these EM production processes due to two-photon collisions. More specifically, we shall consider particle production processes in relativistic heavy ion collisions (RHICs) through two-photon exchange.

Cheung, Wang K.; Norbury, John W.

1992-01-01

245

Revised Production Rates for Na-22 and Mn-54 in Meteorites Using Cross Sections Measured for Neutron-induced Reactions  

NASA Technical Reports Server (NTRS)

The interactions of galactic cosmic rays (GCR) with extraterrestrial bodies produce small amounts of radionuclides and stable isotopes. The production rates of many relatively short-lived radionuclides, including 2.6-year Na-22 and 312-day Mn-54, have been measured in several meteorites collected very soon after they fell. Theoretical models used to calculate production rates for comparison with the measured values rely on input data containing good cross section measurements for all relevant reactions. Most GCR particles are protons, but secondary neutrons make most cosmogenic nuclides. Calculated production rates using only cross sections for proton-induced reactions do not agree well with measurements. One possible explanation is that the contribution to the production rate from reactions initiated by secondary neutrons produced in primary GCR interactions should be included explicitly. This, however, is difficult to do because so few of the relevant cross sections for neutron-induced reactions have been measured.

Sisterson, J. M.; Kim, K. J.; Reedy, R. C.

2004-01-01

246

Modulation of UK lightning by heliospheric magnetic field polarity  

NASA Astrophysics Data System (ADS)

Observational studies have reported solar magnetic modulation of terrestrial lightning on a range of time scales, from days to decades. The proposed mechanism is two-step: lightning rates vary with galactic cosmic ray (GCR) flux incident on Earth, either via changes in atmospheric conductivity and/or direct triggering of lightning. GCR flux is, in turn, primarily controlled by the heliospheric magnetic field (HMF) intensity. Consequently, global changes in lightning rates are expected. This study instead considers HMF polarity, which doesn?t greatly affect total GCR flux. Opposing HMF polarities are, however, associated with a 40–60% difference in observed UK lightning and thunder rates. As HMF polarity skews the terrestrial magnetosphere from its nominal position, this perturbs local ionospheric potential at high latitudes and local exposure to energetic charged particles from the magnetosphere. We speculate as to the mechanism(s) by which this may, in turn, redistribute the global location and/or intensity of thunderstorm activity.

Owens, M. J.; Scott, C. J.; Lockwood, M.; Barnard, L.; Harrison, R. G.; Nicoll, K.; Watt, C.; Bennett, A. J.

2014-11-01

247

Cellular track model of biological damage to mammalian cell cultures from galactic cosmic rays  

NASA Technical Reports Server (NTRS)

The assessment of biological damage from the galactic cosmic rays (GCR) is a current interest for exploratory class space missions where the highly ionizing, high-energy, high-charge ions (HZE) particles are the major concern. The relative biological effectiveness (RBE) values determined by ground-based experiments with HZE particles are well described by a parametric track theory of cell inactivation. Using the track model and a deterministic GCR transport code, the biological damage to mammalian cell cultures is considered for 1 year in free space at solar minimum for typical spacecraft shielding. Included are the effects of projectile and target fragmentation. The RBE values for the GCR spectrum which are fluence-dependent in the track model are found to be more severe than the quality factors identified by the International Commission on Radiological Protection publication 26 and seem to obey a simple scaling law with the duration period in free space.

Cucinotta, Francis A.; Katz, Robert; Wilson, John W.; Townsend, Lawrence W.; Nealy, John E.; Shinn, Judy L.

1991-01-01

248

Updated Computational Model of Cosmic Rays Near Earth  

NASA Technical Reports Server (NTRS)

An updated computational model of the galactic-cosmic-ray (GCR) environment in the vicinity of the Earth, Earth s Moon, and Mars has been developed, and updated software has been developed to implement the updated model. This model accounts for solar modulation of the cosmic-ray contribution for each element from hydrogen through iron by computationally propagating the local interplanetary spectrum of each element through the heliosphere. The propagation is effected by solving the Fokker-Planck diffusion, convection, energy-loss boundary-value problem. The Advanced Composition Explorer NASA satellite has provided new data on GCR energy spectra. These new data were used to update the original model and greatly improve the accuracy of prediction of interplanetary GCR.

ONeill, Patrick M.

2006-01-01

249

Oscillations in the open solar magnetic flux with a period of 1.68years: imprint on galactic cosmic rays and implications for heliospheric shielding  

NASA Astrophysics Data System (ADS)

An understanding of how the heliosphere modulates galactic cosmic ray (GCR) fluxes and spectra is important, not only for studies of their origin, acceleration and propagation in our galaxy, but also for predicting their effects (on technology and on the Earth's environment and organisms) and for interpreting abundances of cosmogenic isotopes in meteorites and terrestrial reservoirs. In contrast to the early interplanetary measurements, there is growing evidence for a dominant role in GCR shielding of the total open magnetic flux, which emerges from the solar atmosphere and enters the heliosphere. In this paper, we relate a strong 1.68-year oscillation in GCR fluxes to a corresponding oscillation in the open solar magnetic flux and infer cosmic-ray propagation paths confirming the predictions of theories in which drift is important in modulating the cosmic ray flux.

Rouillard, A.; Lockwood, M.

2004-12-01

250

Galactic cosmic ray modulation for sunspot cycle 24  

NASA Astrophysics Data System (ADS)

The galactic cosmic ray (GCR) modulation at earth orbit is studied for the sunspot cycle 24 using data from the global network of neutron monitors, balloon measurements at high latitudes in Russia, and directional muon telescopes at Nagoya. The observed decrease in GCR intensity is modest compared to previous cycles. The tilt angle of heliospheric current sheet is at its maximum value for a cycle, solar polar fields have reversed, interplanetary magnetic field intensity at earth orbit is at peak (lower than prior cycles). So, one expects GCR intensity to be most depressed. A determination is made of rigidity dependence of the observed modulation. It is a power law with an exponent not too different from that observed for prior cycles (20-23).

Ahluwalia, H. S.

251

Occurrence of Antimicrobial-Resistant Escherichia coli and Salmonella enterica in the Beef Cattle Production and Processing Continuum.  

PubMed

Specific concerns have been raised that 3(rd)-generation cephalosporin-resistant (3GC(r)) Escherichia coli, trimethoprim-sulfamethoxazole-resistant (COT(r)) E. coli, 3GC(r) Salmonella enterica, and nalidixic acid-resistant (NAL(r)) S. enterica, may be present in cattle production environments, persist through beef processing, and contaminate final products. The prevalences and concentrations of these organisms were determined in feces and hides (at feedlot and processing plant), pre-evisceration carcasses, and final carcasses from three lots of fed cattle (n=184). Prevalences and concentrations were further determined for strip loins from 103 of the carcasses. 3GC(r) Salmonella were detected on 7.6 % of hides during processing and were not detected on final carcasses or strip loins. NAL(r) S. enterica was detected on only one hide. 3GC(r) E. coli and COT(r) E. coli were detected on 100.0 % of hides during processing. Concentrations of 3GC(r) E. coli and COT(r) E. coli on hides were correlated with pre-evisceration carcass contamination. 3GC(r) E. coli and COT(r) E. coli were each detected on only 0.5 % of final carcasses and were not detected on strip loins. Five hundred and forty-two isolates were screened for extraintestinal pathogenic E. coli (ExPEC) virulence-associated markers. Only two COT(r) E. coli isolated from hides were ExPEC, indicating that fed cattle products are not a significant source of ExPEC causing human urinary tract infections. The very low prevalences of these organisms on final carcasses, and their absence on strip loins demonstrate that current sanitary dressing procedures and processing interventions are effective against antimicrobial-resistant bacteria. PMID:25398858

Schmidt, John W; Agga, Getahun E; Bosilevac, Joseph M; Brichta-Harhay, Dayna M; Shackelford, Steven D; Wang, Rong; Wheeler, Tommy L; Arthur, Terrance M

2014-11-14

252

Assessment of Galactic Cosmic Ray Models and Implications on the Estimation of Radiation Exposure in Space  

NASA Astrophysics Data System (ADS)

Astronauts are subjected to elevated levels of high-energy ionizing radiation in space which poses a substantial risk to their health. Therefore, the assessment of the radiation exposure for long duration manned spaceflight is essential. This is done by measuring dose using various detector techniques and by performing numerical simulations utilizing radiation transport codes which allow to predict radiation exposure for future missions and for conditions where measurements are not feasible or available. A necessary prerequisite for an accurate estimation of the exposure using the latter approach is a reliable description of the radiation spectra. Accordingly, in order to estimate the exposure from the Galactic Cosmic Rays (GCRs), which are one of the major sources of radiation exposure in space, GCR models are required. This work presents an evaluation of GCR models for dosimetry purposes and the effect of applying these models on the estimation of GCR exposure in space outside and inside the Earth's magnetosphere. To achieve this, widely used GCR models - Badhwar-O'Neill2010, Burger-Usoskin, CREME2009 and CREME96, were evaluated by comparing model spectra for light and heavy nuclei with measurements from various high-altitude balloon and space missions over several decades. Additionally a new model, based on the GCR-ISO model, developed at the German Aerospace Centre (DLR) was also investigated. The differences arising in the radiation exposure by applying these models are quantified in terms of absorbed dose and dose equivalent rates that were estimated numerically using the GEANT4 Monte-Carlo framework. During certain epochs in the last decade, there are large discrepancies between the model and the measured spectra. All models exhibit weaknesses in describing the increased GCR flux that was observed in 2009-2010. The differences in the spectra, described by the models, result in considerable differences in the estimated dose quantities.

Mrigakshi, A. I.; Matthiä, D.; Berger, T.; Reitz, G.; Wimmer-Schweingruber, R. F.

2012-12-01

253

A membrane glucocorticoid receptor mediates the rapid/non-genomic actions of glucocorticoids in mammalian skeletal muscle fibres  

PubMed Central

Glucocorticoids (GCs) are steroid hormones released from the adrenal gland in response to stress. They are also some of the most potent anti-inflammatory and immunosuppressive drugs currently in clinical use. They exert most of their physiological and pharmacological actions through the classical/genomic pathway. However, they also have rapid/non-genomic actions whose physiological and pharmacological functions are still poorly understood. Therefore, the primary aim of this study was to investigate the rapid/non-genomic effects of two widely prescribed glucocorticoids, beclomethasone dipropionate (BDP) and prednisolone acetate (PDNA), on force production in isolated, intact, mouse skeletal muscle fibre bundles. The results show that the effects of both GCs on maximum isometric force (Po) were fibre-type dependent. Thus, they increased Po in the slow-twitch fibre bundles without significantly affecting that of the fast-twitch fibre bundles. The increase in Po occurred within 10 min and was insensitive to the transcriptional inhibitor actinomycin D. Also, it was maximal at ?250 nm and was blocked by the glucocorticoid receptor (GCR) inhibitor RU486 and a monoclonal anti-GCR, suggesting that it was mediated by a membrane (m) GCR. Both muscle fibre types expressed a cytosolic GCR. However, a mGCR was present only in the slow-twitch fibres. The receptor was more abundant in oxidative than in glycolytic fibres and was confined mainly to the periphery of the fibres where it co-localised with laminin. From these findings we conclude that the rapid/non-genomic actions of GCs are mediated by a mGCR and that they are physiologically/therapeutically beneficial, especially in slow-twitch muscle fibres. PMID:23878367

Pérez, María Hernández-Alcalá; Cormack, Jonathan; Mallinson, David; Mutungi, Gabriel

2013-01-01

254

Badhwar-O'Neill 2011 Galactic Cosmic Ray Model Update and Future Improvements  

NASA Technical Reports Server (NTRS)

The Badhwar-O'Neill Galactic Cosmic Ray (GCR) Model based on actual GR measurements is used by deep space mission planners for the certification of micro-electronic systems and the analysis of radiation health risks to astronauts in space missions. The BO GCR Model provides GCR flux in deep space (outside the earth's magnetosphere) for any given time from 1645 to present. The energy spectrum from 50 MeV/n-20 GeV/n is provided for ions from hydrogen to uranium. This work describes the most recent version of the BO GCR model (BO'11). BO'11 determines the GCR flux at a given time applying an empirical time delay function to past sunspot activity. We describe the GCR measurement data used in the BO'11 update - modern data from BESS, PAMELA, CAPRICE, and ACE emphasized for than the older balloon data used for the previous BO model (BO'10). We look at the GCR flux for the last 24 solar minima and show how much greater the flux was for the cycle 24 minimum in 2010. The BO'11 Model uses the traditional, steady-state Fokker-Planck differential equation to account for particle transport in the heliosphere due to diffusion, convection, and adiabatic deceleration. It assumes a radially symmetrical diffusion coefficient derived from magnetic disturbances caused by sunspots carried onward by a constant solar wind. A more complex differential equation is now being tested to account for particle transport in the heliosphere in the next generation BO model. This new model is time-dependent (no longer a steady state model). In the new model, the dynamics and anti-symmetrical features of the actual heliosphere are accounted for so empirical time delay functions will no longer be required. The new model will be capable of simulating the more subtle features of modulation - such as the Sun's polarity and modulation dependence on the gradient and curvature drift. This improvement is expected to significantly improve the fidelity of the BO GCR model. Preliminary results of its performance will be presented.

O'Neill, Pat M.; Kim, Myung-Hee Y.

2014-01-01

255

An Improved Analytic Model for Microdosimeter Response  

NASA Technical Reports Server (NTRS)

An analytic model used to predict energy deposition fluctuations in a microvolume by ions through direct events is improved to include indirect delta ray events. The new model can now account for the increase in flux at low lineal energy when the ions are of very high energy. Good agreement is obtained between the calculated results and available data for laboratory ion beams. Comparison of GCR (galactic cosmic ray) flux between Shuttle TEPC (tissue equivalent proportional counter) flight data and current calculations draws a different assessment of developmental work required for the GCR transport code (HZETRN) than previously concluded.

Shinn, Judy L.; Wilson, John W.; Xapsos, Michael A.

2001-01-01

256

The Flux of Galactic Cosmic Rays over the last 200,000 Years calculated from Beryllium-10 Records in deep Sea Sediments  

NASA Astrophysics Data System (ADS)

The production of cosmogenic radionuclides like 10Be and 14C in the Earth's atmosphere is directly related to the flux of galactic cosmic rays (GCR) reaching the Earth's orbit. Measuring the depositional flux of 10Be, as deposited in marine sediments, therefore provides a good tool to reconstruct the GCR-flux and to study the presumed GCR-climate connection on millennial time scales. However, the deposition of 10Be into deep sea sediments also can be influenced strongly by climatically induced oceanic transport processes like sediment redistribution of adsorbed 10Be and lateral transport of dissolved 10Be. Consequently, the bulk deposition of 10Be can not be used to reconstruct the global GCR-flux. The global 10Be-production is separated from the transport signal by applying a correction procedure. While sediment redistribution is corrected by using the well established 230Thex-normalization methoda, the transport of dissolved 10Be is quantified by using a simple box model that is able to describe water mass transport and sedimentation of 10Be in the ocean. The transport-corrected 10Be-profiles represent global production changes. They can be used to calculate the flux of GCRs during the last 200,000 years (based on simulations presented by Masarik and Beerb). The comparison of the GCR-flux with climate records from stalagmites from lowc and midd latitudes shows a correlation between the growth periodes of stalagmites and times of low GCR-flux. The 10Be-based record of the GCR-flux also can be used in paleoclimate models to study the presumed GCR-climate connection on millennial timescales. begin{small} aFrank et al., in Use of Proxies in Paleoceanography: Examples from the South Atlantic (eds. Fischer, G. &Wefer, G.), 409-426 (Springer-Verlag, New York, 1999). bMasarik and Beer, Simulation of particle fluxes and cosmogenic nuclide production in the Earth's atmosphere. JGR-Atmospheres 104, 12099-12111 (1999). cNeff et al., Strong coherence between solar variability and the monsoon in Oman between 9 and 6 kyr ago. Nature 411, 290-293 (2001). dSpoetl et al., Start of the last interglacial period at 135 ka: Evidence from a high Alpine speleothem. Geology 30, 815-818 (2002).

Christl, M.; Strobl, C.; Mangini, A.; Kubik, P.

2003-04-01

257

Issues in deep space radiation protection  

NASA Technical Reports Server (NTRS)

The exposures in deep space are largely from the Galactic Cosmic Rays (GCR) for which there is as yet little biological experience. Mounting evidence indicates that conventional linear energy transfer (LET) defined protection quantities (quality factors) may not be appropriate for GCR ions. The available biological data indicates that aluminum alloy structures may generate inherently unhealthy internal spacecraft environments in the thickness range for space applications. Methods for optimization of spacecraft shielding and the associated role of materials selection are discussed. One material which may prove to be an important radiation protection material is hydrogenated carbon nanofibers. c 2001. Elsevier Science Ltd. All rights reserved.

Wilson, J. W.; Shinn, J. L.; Tripathi, R. K.; Singleterry, R. C.; Clowdsley, M. S.; Thibeault, S. A.; Cheatwood, F. M.; Schimmerling, W.; Cucinotta, F. A.; Badhwar, G. D.; Noor, A. K.; Kim, M. Y.; Badavi, F. F.; Heinbockel, J. H.; Miller, J.; Zeitlin, C.; Heilbronn, L.

2001-01-01

258

Managing Lunar and Mars Mission Radiation Risks. Part 1; Cancer Risks, Uncertainties, and Shielding Effectiveness  

NASA Technical Reports Server (NTRS)

This document addresses calculations of probability distribution functions (PDFs) representing uncertainties in projecting fatal cancer risk from galactic cosmic rays (GCR) and solar particle events (SPEs). PDFs are used to test the effectiveness of potential radiation shielding approaches. Monte-Carlo techniques are used to propagate uncertainties in risk coefficients determined from epidemiology data, dose and dose-rate reduction factors, quality factors, and physics models of radiation environments. Competing mortality risks and functional correlations in radiation quality factor uncertainties are treated in the calculations. The cancer risk uncertainty is about four-fold for lunar and Mars mission risk projections. For short-stay lunar missins (<180 d), SPEs present the most significant risk, but one effectively mitigated by shielding. For long-duration (>180 d) lunar or Mars missions, GCR risks may exceed radiation risk limits. While shielding materials are marginally effective in reducing GCR cancer risks because of the penetrating nature of GCR and secondary radiation produced in tissue by relativisitc particles, polyethylene or carbon composite shielding cannot be shown to significantly reduce risk compared to aluminum shielding. Therefore, improving our knowledge of space radiobiology to narrow uncertainties that lead to wide PDFs is the best approach to ensure radiation protection goals are met for space exploration.

Cucinotta, Francis A.; Kim, Myung-Hee Y.; Ren, Lei

2005-01-01

259

Radiation shielding of astronauts in interplanetary flights: the CREAM surveyor to Mars and the magnetic lens system for a spaceship  

Microsoft Academic Search

The radiation absorbed by astronauts during interplanetary flights is mainly due to cosmic rays of solar origin (SCR). In the most powerful solar flares the dose absorbed in few hours can exceed that cumulated in one year of exposition to the galactic component of cosmic rays (GCR). At energies above the minimum one needed to cross the walls of the

P. Spillantini; F. Taccetti; P. Papini; L. Rossi; M. Casolino

260

Space Radiation Transport Codes: A Comparative Study for Galactic Cosmic Rays Environment  

NASA Astrophysics Data System (ADS)

For long duration and/or deep space human missions, protection from severe space radiation exposure is a challenging design constraint and may be a potential limiting factor. The space radiation environment consists of galactic cosmic rays (GCR), solar particle events (SPE), trapped radiation, and includes ions of all the known elements over a very broad energy range. These ions penetrate spacecraft materials producing nuclear fragments and secondary particles that damage biological tissues, microelectronic devices, and materials. In deep space missions, where the Earth's magnetic field does not provide protection from space radiation, the GCR environment is significantly enhanced due to the absence of geomagnetic cut-off and is a major component of radiation exposure. Accurate risk assessments critically depend on the accuracy of the input information as well as radiation transport codes used, and so systematic verification of codes is necessary. In this study, comparisons are made between the deterministic code HZETRN2006 and the Monte Carlo codes HETC-HEDS and FLUKA for an aluminum shield followed by a water target exposed to the 1977 solar minimum GCR spectrum. Interaction and transport of high charge ions present in GCR radiation environment provide a more stringent constraint in the comparison of the codes. Dose, dose equivalent and flux spectra are compared; details of the comparisons will be discussed, and conclusions will be drawn for future directions.

Tripathi, Ram; Wilson, John W.; Townsend, Lawrence W.; Gabriel, Tony; Pinsky, Lawrence S.; Slaba, Tony

261

Evaluating shielding effectiveness for reducing space radiation cancer risks  

Microsoft Academic Search

We discuss calculations of probability distribution functions (PDF) representing uncertainties in projecting fatal cancer risk from galactic cosmic rays (GCR) and solar particle events (SPE). The PDFs are used in significance tests for evaluating the effectiveness of potential radiation shielding approaches. Uncertainties in risk coefficients determined from epidemiology data, dose and dose–rate reduction factors, quality factors, and physics models of

Francis A. Cucinotta; Myung-Hee Y. Kim; Lei Ren

2006-01-01

262

Estimation of Galactic Cosmic Ray exposure inside and outside the Earth's magnetosphere during the recent solar minimum between solar cycles 23 and 24  

NASA Astrophysics Data System (ADS)

The evidently low solar activity observed between solar cycles 23 and 24 during the years 2008-2010 led to a substantial increase in the Galactic Cosmic Ray (GCR) intensity in comparison with preceding solar minima. As the GCRs consist of highly-ionizing charged particles having the potential to cause biological damage, they are a subject of concern for manned missions to space. With the enhanced particle fluxes observed between 2008 and 2010, it is reasonable to assume that the radiation exposure from GCR must have also increased to unusually high levels. In this paper, the GCR exposure outside and inside the Earth's magnetosphere is numerically calculated for time periods starting from 1970 to the end of 2011 in order to investigate the increase in dose levels during the years 2008-2010 in comparison with the last three solar minima. The dose rates were calculated in a water sphere, used as a surrogate for the human body, either unshielded or surrounded by aluminium shielding of 0.3, 10 or 40 g/cm2. By performing such a long-term analysis, it was estimated that the GCR exposure during the recent solar minimum was indeed the largest in comparison with previous minima and that the increase was more pronounced for locations outside the magnetosphere.

Mrigakshi, Alankrita Isha; Matthiä, Daniel; Berger, Thomas; Reitz, Günther; Wimmer-Schweingruber, Robert F.

2013-09-01

263

Analysis of MIR18 results for physical and biological dosimetry: radiation shielding effectiveness in LEO  

Microsoft Academic Search

We compare models of radiation transport and biological response to physical and biological dosimetry results from astronauts on the Mir space station. Transport models are shown to be in good agreement with physical measurements and indicate that the ratio of equivalent dose from the Galactic Cosmic Rays (GCR) to protons is about 3\\/2:1 and that this ratio will increase for

F. A Cucinotta; J. W Wilson; J. R Williams; J. F Dicello

2000-01-01

264

Lunar soil as shielding against space radiation J. Miller a,*, L. Taylor b  

E-print Network

Lunar soil as shielding against space radiation J. Miller a,*, L. Taylor b , C. Zeitlin c , L January 2009 Keywords: Lunar soil Lunar regolith Space radiation shielding Galactic cosmic radiation (GCR be mitigated in part by radiation shielding. The spacecraft, spacesuits and rovers will provide only modest

Perfect, Ed

265

Computational trigonometry  

SciTech Connect

By means of the author`s earlier theory of antieigenvalues and antieigenvectors, a new computational approach to iterative methods is presented. This enables an explicit trigonometric understanding of iterative convergence and provides new insights into the sharpness of error bounds. Direct applications to Gradient descent, Conjugate gradient, GCR(k), Orthomin, CGN, GMRES, CGS, and other matrix iterative schemes will be given.

Gustafson, K. [Univ. of Colorado, Boulder, CO (United States)

1994-12-31

266

Progress and Status on the Development of NASA's Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) model  

Microsoft Academic Search

The NASA Applied Sciences Program recently selected a project for funding through the Research Opportunities in Space and Earth Sciences (ROSES) solicitation. The project objective is to develop a nowcast prediction of air-crew radiation exposure from both background galactic cosmic rays (GCR) and solar energetic particle events (SEP) that may accompany solar storms. The new air-crew radiation exposure model is

C. J. Mertens; W. K. Tobiska; S. R. Blattnig; B. T. Kress; M. J. Wiltberger; S. C. Solomon; J. Kunches; J. J. Murray

2008-01-01

267

Sex differences in operant responding and survivability following exposure to space radiation  

Technology Transfer Automated Retrieval System (TEKTRAN)

On exploratory class missions, such as a mission to Mars, astronauts will be exposed to types and doses of radiation (galactic cosmic rays [GCR]) which are not experienced in low earth orbit where the space shuttle and International Space Station operate. Despite the fact that the crew on such a mi...

268

Probing the heliosphere with the directional anisotropy of galactic cosmic-ray intensity  

NASA Astrophysics Data System (ADS)

Because of the large detector volume that can be deployed, ground-based detectors remain state-of-the-art instrumentation for measuring high-energy galactic cosmic-rays (GCRs). This paper demonstrates how useful information can be derived from observations of the directional anisotropy of the high-energy GCR intensity, introducing the most recent results obtained from the ground-based observations. The anisotropy observed with the global muon detector network (GMDN) provides us with a unique information of the spatial gradient of the GCR density which reflects the large-scale magnetic structure in the heliosphere. The solar cycle variation of the gradient gives an important information on the GCR transport in the heliosphere, while the short-term variation of the gradient enables us to deduce the large-scale geometry of the magnetic flux rope and the interplanetary coronal mass ejection (ICME). Real-time monitoring of the precursory anisotropy which has often been observed at the Earth preceding the arrival of the ICME accompanied by a strong shock may provide us with useful tools for forecasting the space weather with a long lead time. The solar cycle variation of the Sun's shadow observed in the TeV GCR intensity is also useful for probing the large-scale magnetic structure of the solar corona.

Munakata, Kazuoki

2012-07-01

269

Special applications of gas-cooled reactors  

SciTech Connect

The HTGR technology has been demonstrated by Peach Bottom, Fort St. Vrain, and AVR. Another member of the GCR family is the GCFR. Energy requirements for process heat applications of the HTGR high-temperature nuclear heat source are tabulated. 2 tables. (DLC)

Peinado, C.O.

1981-02-01

270

Gas Core Reactor-MHD Power System with Cascading Power Cycle  

Microsoft Academic Search

The US Department of Energy initiative Gen-IV aim is to produce an entire nuclear energy production system with next generation features for certification before 2030. A Generation 4 capable system must have superior sustainability, safety and reliability, and economic cost advantages in comparison with third generation light water reactors. A gas core reactor (GCR) with magnetohydrodynamic (MHD) power converter and

Blair M. Smith; Samim Anghaie; Travis W. Knight

2002-01-01

271

Preparing nurses to use standardized nursing language in the electronic health record.  

PubMed

Research demonstrated nurses' education needs to be able to document nursing diagnoses, interventions and patient outcomes in the EHR. The aim of this study is to investigate the effect of Guided Clinical Reasoning, a learning method to foster nurses' abilities in using standardized language. In a cluster randomized experimental study, nurses from 3 wards received Guided Clinical Reasoning (GCR), a learning method to foster nurses in stating nursing diagnoses, related interventions and outcomes. Three wards, receiving Classic Case Discussions, functioned as control group. The learning effect was measured by assessing the quality of 225 nursing documentations by applying 18 Likert-type items with a 0-4 scale of the measurement instrument "Quality of Nursing Diagnoses, Interventions and Outcomes" (Q-DIO). T-tests were applied to analyze pre-post intervention scores. GCR led to significantly higher quality of nursing diagnosis documentation; to etiology-specific nursing interventions and to enhanced nursing-sensitive patient outcomes. Before GCR, the pre-intervention mean in quality of nursing documentation was = 2.69 (post-intervention = 3.70; p<.0001). Similar results were found for nursing interventions and outcomes. In the control group, the quality remained unchanged. GCR supported nurses' abilities to state accurate nursing diagnoses, to select effective nursing interventions and to reach enhanced patient outcomes. Nursing diagnoses (NANDA-I) with related interventions and patient outcomes provide a knowledgebase for nurses to use standardized language in the EHR. PMID:19592861

Müller-Staub, Maria

2009-01-01

272

Mechanical behaviour of HTR materials: Developments in support of defect assessment, structural integrity and lifetime evaluation  

Microsoft Academic Search

Mod 9Cr–1Mo steel (T91) is a candidate material for pressure vessels and for some internal structures of GCR (Gas Cooled Reactors). In order to validate this choice, it is necessary, firstly to verify that it is able to withstand the planned environmental and operating conditions, and secondly to check if it is covered by the existing design codes, concerning its

O. Ancelet; S. Marie

2010-01-01

273

CHEMICAL TECHNOLOGY DIVISION, UNIT OPERATIONS SECTION MONTHLY PROGRESS REPORT FOR FEBRUARY 1960  

Microsoft Academic Search

Vibratory compaction using air-operated piston type vibrators with ; accelerations up to 150 gees and frequencies up to 85 cycles\\/sec produced ; densities up to 8.2 g\\/cc. A test facility is being installed to study helium ; coolant purification for the GCR. Thorium dioxide particle size obtained by ; flame preparation appears to be Ilinited by particle division within the

M. E. Whatley; P. A. Haas; R. W. Horton; A. D. Ryon; J. C. Suddath; C. D. Watson

1960-01-01

274

Dispatch R539 Cytokinin action: Two receptors better than one?  

E-print Network

of plants [4]. To investigate the function of GCR1, Plakidou-Dymock et al. [4] generated transgenic of the transgenic lines, Plakidou-Dymock et al. [4] went on to show that the Dainty phenotype segregated of a hormonal defect, so Plakidou-Dymock et al. [4] examined the responses of the transgenic plants to a nu

Estelle, Mark

275

Predictors of Satisfaction in Geographically Close and Long-Distance Relationships  

ERIC Educational Resources Information Center

In this study, the authors examined geographically close (GCRs) and long-distance (LDRs) romantic relationship satisfaction as explained by insecure attachment, self-disclosure, gossip, and idealization. After college student participants (N = 536) completed a Web survey, structural equation modeling (SEM) multigroup analysis revealed that the GCR

Lee, Ji-yeon; Pistole, M. Carole

2012-01-01

276

Commitment Predictors: Long-Distance versus Geographically Close Relationships  

ERIC Educational Resources Information Center

In this web-based study, the authors examined long-distance relationships (LDRs) and geographically close relationships (GCRs). Two hierarchical multiple regressions (N = 138) indicated that attachment predicted LDR and GCR commitment in Step 1. Final equations indicated that high satisfaction and investments predicted LDR commitment, whereas low…

Pistole, M. Carole; Roberts, Amber; Mosko, Jonathan E.

2010-01-01

277

Mars surface radiation exposure for solar maximum conditions and 1989 solar proton events  

NASA Technical Reports Server (NTRS)

The Langley heavy-ion/nucleon transport code, HZETRN, and the high-energy nucleon transport code, BRYNTRN, are used to predict the propagation of galactic cosmic rays (GCR's) and solar flare protons through the carbon dioxide atmosphere of Mars. Particle fluences and the resulting doses are estimated on the surface of Mars for GCR's during solar maximum conditions and the Aug., Sep., and Oct. 1989 solar proton events. These results extend previously calculated surface estimates for GCR's at solar minimum conditions and the Feb. 1956, Nov. 1960, and Aug. 1972 solar proton events. Surface doses are estimated with both a low-density and a high-density carbon dioxide model of the atmosphere for altitudes of 0, 4, 8, and 12 km above the surface. A solar modulation function is incorporated to estimate the GCR dose variation between solar minimum and maximum conditions over the 11-year solar cycle. By using current Mars mission scenarios, doses to the skin, eye, and blood-forming organs are predicted for short- and long-duration stay times on the Martian surface throughout the solar cycle.

Simonsen, Lisa C.; Nealy, John E.

1992-01-01

278

THE ASTROPHYSICAL JOURNAL, 551:478485, 2001 April 10 ( 2001. The American Astronomical Society. All rights reserved. Printed in U.S.A.  

E-print Network

is based on spallation reactions between low-energy (10Ã?30 MeV) carbon and oxygen nuclei and interstellar: circumstellar matter Ã? dust, extinction Ã? nuclear reactions, nucleosynthesis, abundances Ã? supernovae: general 1 reactions between high-energy ([100 MeV) Galactic cosmic rays (GCR) and abundant target nuclei such as 12C

Fegley Jr., Bruce

279

Biological Production of an Integrin ?v?3 Targeting Imaging Probe and Functional Verification.  

PubMed

The aim of the present study is to establish a bacterial clone capable of secreting an integrin ?v?3 targeting probe with bioluminescent and fluorescent activities, and to verify its specific targeting and optical activities using molecular imaging. A bacterial vector expressing a fusion of secretory Gaussia luciferase (sGluc), mCherry, and RGD (sGluc-mCherry-RGDX3; GCR), and a control vector expressing a fusion of secretory Gaussia luciferase and mCherry (sGluc-mCherry; GC) were constructed. The GCR and GC proteins were expressed in E. coli and secreted into the growth medium, which showed an approximately 10-fold higher luciferase activity than the bacterial lysate. Successful purification of GCR and GC was achieved using the 6X His-tag method. The GCR protein bound with higher affinity to U87MG cells than CHO cells in confocal microscopy and IVIS imaging, and also showed a high affinity for integrin ?v?3 expressing tumor xenografts in an in vivo animal model. An E. coli clone was established to secrete an integrin ?v?3 targeting imaging probe with bioluminescent and fluorescent activities. The probe was produced feasibly and at low cost, and has shown to be useful for the assessment of angiogenesis in vitro and in vivo. PMID:25654118

Hwang, Mi-Hye; Kim, Jung Eun; Kim, Sang-Yeob; Kalimuthu, Senthilkumar; Jeong, Shin Young; Lee, Sang-Woo; Lee, Jaetae; Ahn, Byeong-Cheol

2015-01-01

280

Cosmic Ray 11-Year Modulation for Sunspot Cycle 24  

NASA Astrophysics Data System (ADS)

Galactic cosmic-ray (GCR) modulation at 1 AU for sunspot (SSN) Cycle 24 is studied using data from a global network of detectors and balloon measurements of low-energy ions at high latitudes in Russia. The observed modulation is modest compared with previous cycles. The tilt angle of the heliospheric current sheet reached a maximum value for Cycle 24 even though the peak of the interplanetary magnetic-field intensity at 1 AU has a much lower value (? 5 nT). The solar polar field in the northern hemisphere reversed in June 2012 and again in March 2014 while that in the southern hemisphere reversed in July 2013. The double field reversal in northern hemisphere after SSN maximum is not expected from dynamo theory. GCR modulation is at maximum phase in 2013. We have also studied the anomalous GCR recovery in 2009 using data from a low-energy proton channel on Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA). The rigidity dependence of the Cycle 24 modulation is computed using data from neutron monitors, directional muon telescopes at Nagoya, Japan, and detectors on balloons at high latitudes in Russia. It is a power law with an exponent -1.29, similar to previous solar cycles (-1.2±0.1); the nearly linear dependence of the modulation on the rigidity over a wide range poses a challenge to the quasi-linear theory (QLT) of GCR modulation.

Ahluwalia, H. S.; Ygbuhay, R. C.

2015-02-01

281

Designing a Complex Fragmentation Block for Simulating the Galactic Environment by Using a Single Accelerator Beam in PHITS (Practicle and Heavy Ion Transport Code System)  

E-print Network

the linear energy transfer (LET) spectrum found in the GCR. The purpose of this thesis research is to use a Monte Carlo transport code to study the fragmentation of a combined iron and proton beam source using a multi-depth moderator block to reproduce...

Chen, Gary

2011-10-21

282

Cancer risk from exposure to galactic cosmic rays: implications for space exploration by human beings  

Microsoft Academic Search

must be balanced with the cost, safety, and ethical concerns when deciding acceptable risks for astronauts. The main health concerns are exposure to galactic cosmic rays (GCR) and solar proton events, which lead to substantial, but poorly understood, risks of carcinogenesis and degenerative disease. 2,3 Spacefl ights in low Earth orbit, such as missions on a space shuttle and at

Marco Durante

2006-01-01

283

G-Protein Complex Mutants Are Hypersensitive to Abscisic Acid Regulation of Germination  

E-print Network

throughout plant growth and development. Seed germination, early seedling development, stomatal guard cell, AGB1, and GCR1 each negatively regulates ABA signaling in seed germination and early seedling network involving a number of different signals and effectors. For example, during seed germination

Jones, Alan M.

284

The production of cosmogenic nuclides in stony meteoroids by galactic cosmic ray particles  

Microsoft Academic Search

We present a purely physical model for the calculation of depth- and size-dependent production rates of cosmogenic nuclides by galactic cosmic ray particles. Besides the spectra of primary and secondary particles and the excitation functions of the underlying nuclear reactions the model is based on only one free parameter, the integral number of GCR particles in the meteoroid orbits. We

Ingo Leya; Hans-Jürgen Lange; Sonja Neumann; Rainer Wieler; Rolf Michel

2000-01-01

285

Invited Editorial: Radiation exposures of aircrew in high altitude flight  

Microsoft Academic Search

Introduction Background radiation levels in the atmosphere vary in intensity with latitude, altitude and phase of the solar cycle. These background levels are generated primarily by galactic cosmic rays (GCR), consisting of energetic nuclei of all naturally occurring elements, interacting with atmospheric constituents, primarily through atomic and nuclear collisions. Cosmic rays were discovered in 1912, about the same time that

Lawrence W. Townsend

2001-01-01

286

Radiation Dose Analysis of Galactic Cosmic Ray in Low Earth Orbit/Near Equatorial Orbit  

NASA Astrophysics Data System (ADS)

Space environment contained harmful radiation that posed risk to spacecraft orbiting the Earth. In this paper, we looked into radiation doses caused by galactic cosmic ray (GCR) towards satellites orbiting in low earth orbit (LEO) near Earth's equator (NEqO) and compared them with doses caused by solar energetic particles (SEP) and trapped particles to determine the damage level of GCR. The radiation doses included linear energy transfer (LET) and nonionizing energy loss (NIEL) through a 1mm gallium arsenide (GaAs) planar geometry by using Space Environment Information System (SPENVIS) method. The orbital data followed Malaysian Razaksat satellite at 685km altitude and 9° inclination during selected solar minimum and solar maximum from solar cycles 21 to 24. We found that trapped particles gave the highest LET and no SEP was detected in SPENVIS. The LET values tend to be higher during solar minimum for trapped particles and GCR, corresponding to their anti-correlated fluxes with the solar activity. However, the NIEL values for GCR in solar cycle 23 did not follow the anti-correlation pattern.

Suparta, W.; Zulkeple, S. K.

2014-10-01

287

Annales Geophysicae (2004) 22: 43814395 SRef-ID: 1432-0576/ag/2004-22-4381  

E-print Network

, there is growing evi- dence for a dominant role in GCR shielding of the total open magnetic flux, which emerges: imprint on galactic cosmic rays and implications for heliospheric shielding A. Rouillard1 and M. Lockwood1 the implied links between solar irradiance variations and cosmic ray shielding by the helio- sphere

Boyer, Edmond

288

Oscillations in the open solar magnetic flux with a period of 1.68years: imprint on galactic cosmic rays and implications for heliospheric shielding  

Microsoft Academic Search

An understanding of how the heliosphere modulates galactic cosmic ray (GCR) fluxes and spectra is important, not only for studies of their origin, acceleration and propagation in our galaxy, but also for predicting their effects (on technology and on the Earth's environment and organisms) and for interpreting abundances of cosmogenic isotopes in meteorites and terrestrial reservoirs. In contrast to the

A. Rouillard; M. Lockwood

2004-01-01

289

Biological Production of an Integrin ?v?3 Targeting Imaging Probe and Functional Verification  

PubMed Central

The aim of the present study is to establish a bacterial clone capable of secreting an integrin ?v?3 targeting probe with bioluminescent and fluorescent activities, and to verify its specific targeting and optical activities using molecular imaging. A bacterial vector expressing a fusion of secretory Gaussia luciferase (sGluc), mCherry, and RGD (sGluc-mCherry-RGDX3; GCR), and a control vector expressing a fusion of secretory Gaussia luciferase and mCherry (sGluc-mCherry; GC) were constructed. The GCR and GC proteins were expressed in E. coli and secreted into the growth medium, which showed an approximately 10-fold higher luciferase activity than the bacterial lysate. Successful purification of GCR and GC was achieved using the 6X His-tag method. The GCR protein bound with higher affinity to U87MG cells than CHO cells in confocal microscopy and IVIS imaging, and also showed a high affinity for integrin ?v?3 expressing tumor xenografts in an in vivo animal model. An E. coli clone was established to secrete an integrin ?v?3 targeting imaging probe with bioluminescent and fluorescent activities. The probe was produced feasibly and at low cost, and has shown to be useful for the assessment of angiogenesis in vitro and in vivo. PMID:25654118

Hwang, Mi-Hye; Kim, Jung Eun; Kim, Sang-Yeob; Kalimuthu, Senthilkumar; Jeong, Shin Young; Lee, Sang-Woo; Lee, Jaetae; Ahn, Byeong-Cheol

2015-01-01

290

Modeling production and climate-related impacts on Be concentration in ice cores  

E-print Network

strength and the solar activity modulation parameter (f), CO2, sea surface temperatures, and volcanic of the Sun) on the 11 year timescale are positively linked with changes in solar magnetic activity [Willson and Hudson, 1988; Radick et al., 1990]. In turn, the Sun's magnetic field modulates galactic cosmic rays (GCR

291

The proposed connection between clouds and cosmic rays: Cloud  

E-print Network

flux grows. Thus modulation of the strength of the interplanetary magnetic field by solar activity by the magnetic field of the Sun via the solar wind. Because GCR are ionized particles, they are deflected to the inner solar system. When solar activity is at a maximum, the Sun's magnetic field is strong and fewer

292

Author's personal copy Reconstruction of global 10  

E-print Network

timescales is mainly modulated by the Earths' magnetic dipole field. During periods with low dipole strength caused by geomagnetic variability and by a potential long-term variability of the solar magnetic field Rays (GCR), (ii) a proxy for past geomagnetic dipole strength, and (iii) as a global matching tool

Wehrli, Bernhard

293

The Projection of Space Radiation Environments with a Solar Cycle Statistical Model  

NASA Technical Reports Server (NTRS)

A solar cycle statistical model has been developed to project sunspot numbers which represent the variations in the space radiation environment. The resultant projection of sunspot numbers in near future were coupled to space-related quantities of interest in radiation protection, such as the galactic cosmic radiation (GCR) deceleration potential (f) and the mean occurrence frequency of solar particle event (SPE). Future GCR fluxes have been derived from a predictive model, in which GCR temporal dependence represented by f was derived from GCR flux and ground-based Climax neutron monitor rate measurements over the last four decades. Results showed that the point dose equivalent inside a typical spacecraft in interplanetary radiation fields was influenced by solar modulation up to a factor of three. One important characteristic of sporadic SPEs is their mean frequency of occurrence, which is dependent on solar activity. Projections of future mean frequency of SPE occurrence were estimated from a power law function of sunspot number. Furthermore, the cumulative probabilities of SPE during short-period missions were defined with the continuous database of proton fluences of SPE. The analytic representation of energy spectra of SPE was constructed by the Weibull distribution for different event sizes. The representative exposure level at each event size was estimated for the guideline of protection systems for astronauts during future space exploration missions.

Kim, Myung-Hee; Cucinotta, Francis A.; Wilson, John W.

2006-01-01

294

Assessment of the radiation environment on the Moon  

Microsoft Academic Search

In connection with projects on a manned base on the Moon, the assessment of radiation risk to staff of the base owing to galactic (GCR) and solar (SEP) cosmic radiation becomes very relevant. The paper describes the methodology for assessing the radiation environment on the lunar surface and in the depths of lunar soil taking into account the primary and

A. N. Denisov; N. V. Kuznetsov; R. A. Nymmik; M. I. Panasyuk; N. M. Sobolevsky

2011-01-01

295

First Results From the Martian Radiation Environment Experiment MARIE  

NASA Astrophysics Data System (ADS)

The Martian Radiation Environment Experiment (MARIE), aboard the 2001 Mars Odyssey spacecraft, is returning the first detailed radiation data from Mars orbit. Characterization of the Martian radiation environment is a necessary precursor to eventual human exploration of Mars. MARIE, which consists primarily of an 8-element silicon detector telescope, is providing high-quality measurements of Solar Energetic Particles (SEP) from a unique vantage point, and is also able to measure a significant portion of the spectrum of Galactic Cosmic Rays (GCR). The GCR are composed of atomic nuclei with kinetic energies ranging from tens of MeV per nucleon to hundreds of GeV per nucleon and higher. Energy distributions typically peak in the region of several hundred MeV per nucleon. These highly charged and energetic particles can penetrate tens of centimeters of matter, including tissue and practical depths of spacecraft shielding. The combination of high energy and high ionization associated with heavy nuclei in the GCR make these particles much more effective in causing biological damage than a comparable dose of sparsely-ionizing radiation such as muons or X-rays. These particles therefore present a potentially serious long-term health risk to astronauts, particularly on missions outside the protection of the geomagnetosphere. At Mars, the GCR spectrum is expected to be substantially the same as seen at Earth, modulated slightly by variations in the solar magnetic field. The spectrum of SEP tends to be dominated by low-energy protons; though less exotic than heavy ions in the GCR, these particles, produced in Coronal Mass Ejections, pose the risk of acute radiation exposure, owing to the high fluxes that are often generated. SEP spectra for a given CME may be entirely different at Earth and Mars, for a variety of reasons. MARIE has been operational in Mars orbit since March 2002. Several solar events have been observed, in addition to GCR ions. We will present dosimetric results as well as preliminary particle spectra from SEP and GCR.

Zeitlin, C.; Cleghorn, T. F.; Cucinotta, F. A.; Saganti, P.; Pinsky, L. S.; Andersen, V.; Lee, K. T.; Turner, R.; Atwell, W.

2002-12-01

296

Nibrella saemangeumensis gen. nov., sp. nov. and Nibrella viscosa sp. nov., novel members of the family Cytophagaceae, isolated from seawater.  

PubMed

Two strains, designated GCR0103(T) and GYR3121(T), were isolated from seawater of the Saemangeum Embankment in Jeollabuk-do, Korea. The cells of the two strains were Gram-reaction-negative and non-motile, and formed multicellular filaments. The colonies of the two strains were pink-pigmented and able to grow at 15-37 °C (optimum 25 °C) on R2A and NA medium. Strains GCR0103(T) and GYR3121(T) grew at pH 6.5-10 (optimum pH 7.5) and pH 5.5-9.5 (optimum pH 7.5), and within NaCl ranges of 0-0.4% and 0-1%, respectively. The polar lipid profiles of the two strains contained phosphatidylethanolamine, five unknown aminolipids, an unknown phospholipid and four or five unknown lipids. The DNA G+C contents of strains GCR0103(T) and GYR3121(T) were 56.0 and 54.5 mol%, respectively. The respiratory quinone detected in both strains was MK-7. The 16S rRNA gene sequence similarity between GCR0103(T) and GYR3121(T) was 95.5?%. The 16S rRNA gene sequence similarities of the two strains to closely related reference strains were less than 89?%. Phylogenetic analysis based on 16S rRNA genes showed that GCR0103(T) and GYR3121(T) formed a distinct phyletic line in the family Cytophagaceae. On the basis of the phenotypic, chemotaxonomic and phylogenetic properties, strains GCR0103(T) and GYR3121(T) represent two novel species in a new genus within the family Cytophagaceae, for which the names Nibrella saemangeumensis gen. nov., sp. nov. and Nibrella viscosa sp. nov. are proposed. The type strain of Nibrella saemangeumensis is GCR0103(T) (?=?KACC 16453(T)?=?JCM 17927(T)) and the type strain of Nibrella viscosa is GYR3121(T) (?=?KACC 16447(T)?=?JCM 17925(T)). PMID:23907222

Kang, Ji Young; Chun, Jeesun; Choi, Ahyoung; Cho, Jang-Cheon; Jahng, Kwang Yeop

2013-12-01

297

27-day Variation of the Three Dimensional Solar Anisotropy of Galactic Cosmic Ray: 1965-2013  

NASA Astrophysics Data System (ADS)

The temporal evaluation of the 27-day variation of the three dimensional (3D) galactic cosmic ray (GCR) anisotropy has been studied for 1965-2013. 3D anisotropy vector, obtained based on the neutron monitors and Nagoya muon telescopes data, is used to study north-south asymmetry of the heliosphere. We analyze the 27-day variation of the (1) two dimensional (2D) GCR anisotropy in the ecliptic plane and (2) North-South anisotropy normal to the ecliptic plane. Studying the timeline of the 27-day variation of the 2D GCR anisotropy, we confirm that the average amplitude in the minimum epoch of solar activity is polarity dependent, as it is expected from the drift theory. The amplitude of the 27-day variation in the negative polarity epochs is less as we had shown before. The feeble 11-year variation connected with solar cycle and strong 22-year pattern connected with solar magnetic cycle is visible in the 27-day variation of the 2D anisotropy for 1965-2013. We show that the 27-day variation of the North-South anisotropy varies in accordance to solar cycle with a period of 11-years. Relationships of the 27-day variation of the 3D GCR anisotropy with solar activity and solar wind parameters were studied, as well. Furthermore, a study of the interplanetary magnetic field (IMF) sector structure in the period 1965-2013 has been carried out. We find that number of days with the sign of the IMF of northern hemisphere is about 10% larger than of southern hemisphere for all the solar activity minima since 1965, providing an independent evidence of a persistent southward offset of heliospheric neutral sheet (HNS), as observed by the Ulysses mission. We, also study an influence of the southward displacement of the HNS in behavior of the 27-day variation of the GCR intensity expected from the theoretical modeling.

Modzelewska, Renata; Alania, Michael

298

Corotating Solar Wind Structures and Recurrent Trains of Enhanced Diurnal Variation in Galactic Cosmic Rays  

NASA Astrophysics Data System (ADS)

Data from the Princess Sirindhorn Neutron Monitor at Doi Inthanon, Thailand, with a vertical cutoff rigidity of 16.8 GV, were utilized to determine the diurnal anisotropy (DA) of Galactic cosmic rays (GCRs) near Earth during solar minimum conditions between 2007 November and 2010 November. We identified trains of enhanced DA over several days, which often recur after a solar rotation period (~27 days). By investigating solar coronal holes as identified from synoptic maps and solar wind parameters, we found that the intensity and anisotropy of cosmic rays are associated with the high-speed streams (HSSs) in the solar wind, which are in turn related to the structure and evolution of coronal holes. An enhanced DA was observed after the onset of some, but not all, HSSs. During time periods of recurrent trains, the DA was often enhanced or suppressed according to the sign of the interplanetary magnetic field B, which suggests a contribution from a mechanism involving a southward gradient in the GCR density, n, and a gradient anisotropy along B × ?n. In one non-recurrent and one recurrent sequence, an HSS from an equatorial coronal hole was merged with that from a trailing mid-latitude extension of a polar coronal hole, and the slanted HSS structure in space with suppressed GCR density can account for the southward GCR gradient. We conclude that the gradient anisotropy is a source of temporary changes in the GCR DA under solar minimum conditions, and that the latitudinal GCR gradient can sometimes be explained by the coronal hole morphology.

Yeeram, T.; Ruffolo, D.; Sáiz, A.; Kamyan, N.; Nutaro, T.

2014-04-01

299

May 2005 Halo CMEs and Galactic Cosmic Ray Flux Changes at Earth's Orbit  

NASA Astrophysics Data System (ADS)

The pressure corrected hourly data from the global network of cosmic ray detectors, measurements of the interplanetary magnetic field (IMF) intensity ( B) at Earth's orbit and its components B x , B y , B z (in the geocentric solar ecliptic coordinates) are used to conduct a comprehensive study of the galactic cosmic ray (GCR) intensity fluctuations caused by the halo coronal mass ejection of 13 May 2005. Distinct differences exist in GCR timelines recorded by neutron monitors (NMs) and multidirectional muon telescopes (MTs), the latter respond to the high rigidity portion of the GCR differential rigidity spectrum. The Forbush decrease (FD) onset in MTs is delayed (˜5 h) with respect to the onset of a geomagnetic storm sudden commencement (SSC) and a large pre-increase is present in MT data before, during, and after the SSC onset, of unknown origin. The rigidity spectrum, for a range of GCR rigidities (?200 GV), is a power law in rigidity (R) with a negative exponent ( ?=-1.05) at GCR minimum intensity, leading us to infer that the quasi-linear theory of modulation is inconsistent with observations at high rigidities (>1 GV); the results support the force field theory of modulation. At present, we do not have a comprehensive model for the FD explaining quantitatively all the observational features but we present a preliminary model listing physical processes that may contribute to a FD timeline. We explored the connections between different phases of the FD and the power spectra of IMF components but did not find a sustained relationship.

Ahluwalia, H. S.; Alania, M. V.; Wawrzynczak, A.; Ygbuhay, R. C.; Fikani, M. M.

2014-05-01

300

A field assessment of long-term laboratory sediment toxicity tests with the amphipod Hyalella azteca  

USGS Publications Warehouse

Response of the amphipod Hyalella azteca exposed to contaminated sediments for 10 to 42 d in laboratory toxicity tests was compared to responses observed in controlled three-month invertebrate colonization exposures conducted in a pond. Sediments evaluated included a sediment spiked with dichlorodiphenyldichloroethane (DDD) or dilutions of a field sediment collected from the Grand Calumet River (GCR) in Indiana (USA) (contaminated with organic compounds and metals). Consistent effects were observed at the highest exposure concentrations (400 ??g DDD/goc [DDD concentrations normalized to grams of organic carbon (goc) in sedimentl or 4% GCR sediment) on survival, length, and reproduction of amphipods in the laboratory and on abundance of invertebrates colonizing sediments in the field. Effect concentrations for DDD observed for 10-d length and 42-d reproduction of amphipods (e.g., chronic value [ChV] of 66 ??g DDD/goc and 25% inhibition concentration [IC25] of 68 ??g DDD/goc for reproduction) were similar to the lowest effect concentrations for DDD measured on invertebrates colonizing sediment the field. Effect concentrations for GCR sediment on 28-d survival and length and 42-d reproduction and length of amphipods (i.e., ChVs of 0.20-0.66% GCR sediment) provided more conservative effect concentrations compared to 10-d survival or length of amphipods in the laboratory or the response of invertebrates colonizing sediment in the field (e.g., ChVs of 2.2% GCR sediment). Results of this study indicate that use of chronic laboratory toxicity tests with H. azteca and benthic colonization studies should be used to provide conservative estimates of impacts on benthic communities exposed to contaminated sediments. Bioaccumulation of DDD by oligochaetes colonizing the DDD-spiked sediment was similar to results of laboratory sediment tests previously conducted with the oligochaete Lumbriculus variegates, confirming that laboratory exposures can be used to estimate bioaccumulation by oligochaetes exposed in the field. ?? 2005 SETAC.

Ingersoll, C.G.; Wang, N.; Hayward, J.M.R.; Jones, J.R.; Jones, S.B.; Ireland, D.S.

2005-01-01

301

Physics of the Isotopic Dependence of Galactic Cosmic Ray Fluence Behind Shielding  

NASA Technical Reports Server (NTRS)

For over 25 years, NASA has supported the development of space radiation transport models for shielding applications. The NASA space radiation transport model now predicts dose and dose equivalent in Earth and Mars orbit to an accuracy of plus or minus 20%. However, because larger errors may occur in particle fluence predictions, there is interest in further assessments and improvements in NASA's space radiation transport model. In this paper, we consider the effects of the isotopic composition of the primary galactic cosmic rays (GCR) and the isotopic dependence of nuclear fragmentation cross-sections on the solution to transport models used for shielding studies. Satellite measurements are used to describe the isotopic composition of the GCR. Using NASA's quantum multiple-scattering theory of nuclear fragmentation (QMSFRG) and high-charge and energy (HZETRN) transport code, we study the effect of the isotopic dependence of the primary GCR composition and secondary nuclei on shielding calculations. The QMSFRG is shown to accurately describe the iso-spin dependence of nuclear fragmentation. The principal finding of this study is that large errors (plus or minus 100%) will occur in the mass-fluence spectra when comparing transport models that use a complete isotope grid (approximately 170 ions) to ones that use a reduced isotope grid, for example the 59 ion-grid used in the HZETRN code in the past, however less significant errors (less than 20%) occur in the elemental-fluence spectra. Because a complete isotope grid is readily handled on small computer workstations and is needed for several applications studying GCR propagation and scattering, it is recommended that they be used for future GCR studies.

Cucinotta, Francis A.; Saganti, Premkumar B.; Hu, Xiao-Dong; Kim, Myung-Hee Y.; Cleghorn, Timothy F.; Wilson, John W.; Tripathi, Ram K.; Zeitlin, Cary J.

2003-01-01

302

Simulation and Comparison of Martian Surface Ionization Radiation  

NASA Technical Reports Server (NTRS)

The spectrum of energetic particle radiation and corresponding doses at the surface of Mars is being characterized by the Radiation Assessment Detector (RAD), one of ten science instruments on the Mars Science Laboratory (MSL) Curiosity Rover. The time series of dose rate for the first 300 Sols after landing on Mars on August 6, 2012 is presented here. For the comparison to RAD measurements of dose rate, Martian surface ionization radiation is simulated by utilizing observed space quantities. The GCR primary radiation spectrum is calculated by using the Badhwar-O'Neill 2011 (BO11) galactic cosmic ray (GCR) model, which has been developed by utilizing all balloon and satellite GCR measurements since 1955 and the newer 1997-2012 Advanced Composition Explorer (ACE) measurements. In the BO11 model, solar modulation of the GCR primary radiation spectrum is described in terms of the international smoothed sunspot number and a time delay function. For the transport of the impingent GCR primary radiation through Mars atmosphere, a vertical distribution of atmospheric thickness at each elevation is calculated using the vertical profiles of atmospheric temperature and pressure made by Mars Global Surveyor measurements. At Gale Crater in the southern hemisphere, the seasonal variation of atmospheric thickness is accounted for the daily atmospheric pressure measurements of the MSL Rover Environmental Monitoring Station (REMS) by using low- and high-density models for cool- and warm-season, respectively. The spherically distributed atmospheric distance is traced along the slant path, and the resultant directional shielding by Martian atmosphere is coupled with Curiosity vehicle for dose estimates. We present predictions of dose rate and comparison to the RAD measurements. The simulation agrees to within +/- 20% with the RAD measurements showing clearly the variation of dose rate by heliospheric conditions, and presenting the sensitivity of dose rate by atmospheric pressure, which has been found from the RAD experiments and driven by thermal tides on Martian surface.

Kim, Myung-Hee Y.; Zeitlin, Cary; Hassler, Donald M.; Cucinotta, Francis A.

2013-01-01

303

Simulation and Comparison of Martian Surface Ionization Radiation  

NASA Astrophysics Data System (ADS)

The spectrum of energetic particle radiation and corresponding doses at the surface of Mars is being characterized by the Radiation Assessment Detector (RAD), one of ten science instruments on the Mars Science Laboratory (MSL) Curiosity Rover. The time series of dose rate for the first 300 Sols after landing on Mars on August 6, 2012 is presented here. For the comparison to RAD measurements of dose rate, Martian surface ionization radiation is simulated by utilizing observed space quantities. The GCR primary radiation spectrum is calculated by using the Badhwar-O'Neill 2011 (BO11) galactic cosmic ray (GCR) model, which has been developed by utilizing all balloon and satellite GCR measurements since 1955 and the newer 1997-2012 Advanced Composition Explorer (ACE) measurements. In the BO11 model, solar modulation of the GCR primary radiation spectrum is described in terms of the international smoothed sunspot number and a time delay function. For the transport of the impingent GCR primary radiation through Mars atmosphere, a vertical distribution of atmospheric thickness at each elevation is calculated using the vertical profiles of atmospheric temperature and pressure made by Mars Global Surveyor measurements. At Gale Crater in the southern hemisphere, the seasonal variation of atmospheric thickness is accounted for the daily atmospheric pressure measurements of the MSL Rover Environmental Monitoring Station (REMS) by using low- and high-density models for cool- and warm-season, respectively. The spherically distributed atmospheric distance is traced along the slant path, and the resultant directional shielding by Martian atmosphere is coupled with Curiosity vehicle for dose estimates. We present predictions of dose rate and comparison to the RAD measurements. The simulation agrees to within +-20% with the RAD measurements showing clearly the variation of dose rate by heliospheric conditions, and presenting the sensitivity of dose rate by atmospheric pressure, which has been found from the RAD experiments and driven by thermal tides on Martian surface.

Kim, M. Y.; Zeitlin, C. J.; Hassler, D.; Cucinotta, F.

2013-12-01

304

Large Galactic Cosmic Ray Anisotropies in the Heliosheath  

NASA Astrophysics Data System (ADS)

The angular distribution of galactic cosmic ray (GCR) intensities had been observed to be nearly isotropic throughout the space age, with even the largest anisotropies falling well short of 1%. Voyager 1, after the initial GCR intensity enhancement in May 2012 and upon sustainably entering a region depleted of hot plasma on 25 August 2012 (Burlaga et al. 2013; Krimigis et al. 2013; Stone et al. 2013; Webber & McDonald 2013), has uncovered a new regime where large GCR anisotropies prevail. We recently reported on the largest GCR anisotropies observed (Krimigis et al., 2013; Hill et al., 2013), with the second order anisotropy of >200 MeV GCRs reaching ~3.5%. We developed a new technique to extract bi-directional intensities from a double-ended particle telescope that has asymmetric viewing geometry (i.e., the geometric factor for particle detection with one end is unequal to the geometric factor of the other end). Applying this technique we report here on the variation of GCR anisotropies at Voyager 1 and 2 in the depletion region, in the hot heliosheath, and upstream of the termination shock. Burlaga, L.F. et al, 2013, Science 341, 147-150, DOI: 10.1126/science.1235451. Hill, M.E. et al, 2013, presented at the 12th Ann. Inter. Astrophys. Conf., Myrtle Beach, SC, 15-19 April 2013. Krimigis, S.M. et al., 2013, Science 341, 144-147, DOI: 10.1126/science.1235721. Stone, E.C. et al., 2013, Science 341, 150-153, DOI: 10.1126/science.1236408. Webber & McDonald, 2013, Geophys. Res. Let. 40, 1665-1668, DOI: 10.1002/grl.50383.

Hill, M. E.; Decker, R. B.; Hamilton, D. C.; Brown, L. E.; Krimigis, S. M.; Roelof, E. C.

2013-12-01

305

Radiation effects in space: The Clementine I mission  

SciTech Connect

The space radiation environment for the CLEMENTINE I mission was investigated using a new calculational model, CHIME, which includes the effects of galactic cosmic rays (GCR), anomalous component (AC) species and solar energetic particle (SEP) events and their variations as a function of time. Unlike most previous radiation environment models, CHIME is based upon physical theory and is {open_quotes}calibrated{close_quotes} with energetic particle measurements made over the last two decades. Thus, CHIME provides an advance in the accuracy of estimating the interplanetary radiation environment. Using this model we have calculated particle energy spectra, fluences and linear energy transfer (LET) spectra for all three major components of the CLEMENTINE I mission during 1994: (1) the spacecraft in lunar orbit, (2) the spacecraft during asteroid flyby, and (3) the interstate adapter USA in Earth orbit. Our investigations indicate that during 1994 the level of solar modulation, which dominates the variation in the GCR and AC flux as a function of time, will be decreasing toward solar minimum levels. Consequently the GCR and AC flux will be increasing during Y, the year and, potentially, will rise to levels seen during previous solar minimums. The estimated radiation environment also indicates that the AC will dominate the energetic particle spectra for energies below 30-50 MeV/nucleon, while the GCR have a peak flux at {approximately}300 MeV/nucleon and maintain a relatively high flux level up to >1000 MeV/nucleon. The AC significantly enhances the integrated flux for LET in the range 1 to 10 MeV/(mg/cm{sup 2}), but due to the steep energy spectra of the AC a relatively small amount of material ({approximately}50 mils of Al) can effectively shield against this component. The GCR are seen to be highly penetrating and require massive amounts of shielding before there is any appreciable decrease in the LET flux.

Guzik, T. G.; Clayton, E.; Wefel, J. P.

1994-12-20

306

The Average Quality Factors by TEPC for Charged Particles  

NASA Technical Reports Server (NTRS)

The quality factor used in radiation protection is defined as a function of LET, Q(sub ave)(LET). However, tissue equivalent proportional counters (TEPC) measure the average quality factors as a function of lineal energy (y), Q(sub ave)(Y). A model of the TEPC response for charged particles considers energy deposition as a function of impact parameter from the ion s path to the volume, and describes the escape of energy out of sensitive volume by delta-rays and the entry of delta rays from the high-density wall into the low-density gas-volume. A common goal for operational detectors is to measure the average radiation quality to within accuracy of 25%. Using our TEPC response model and the NASA space radiation transport model we show that this accuracy is obtained by a properly calibrated TEPC. However, when the individual contributions from trapped protons and galactic cosmic rays (GCR) are considered; the average quality factor obtained by TEPC is overestimated for trapped protons and underestimated for GCR by about 30%, i.e., a compensating error. Using TEPC's values for trapped protons for Q(sub ave)(y), we obtained average quality factors in the 2.07-2.32 range. However, Q(sub ave)(LET) ranges from 1.5-1.65 as spacecraft shielding depth increases. The average quality factors for trapped protons on STS-89 demonstrate that the model of the TEPC response is in good agreement with flight TEPC data for Q(sub ave)(y), and thus Q(sub ave)(LET) for trapped protons is overestimated by TEPC. Preliminary comparisons for the complete GCR spectra show that Q(sub ave)(LET) for GCR is approximately 3.2-4.1, while TEPC measures 2.9-3.4 for QQ(sub ave)(y), indicating that QQ(sub ave)(LET) for GCR is underestimated by TEPC.

Kim, Myung-Hee Y.; Nikjoo, Hooshang; Cucinotta, Francis A.

2004-01-01

307

Assessing the experience in complex hepatopancreatobiliary surgery among graduating chief residents: Is the operative experience enough?  

PubMed Central

Introduction Resident operative autonomy and case volume is associated with posttraining confidence and practice plans. Accreditation Council for Graduate Medical Education requirements for graduating general surgery residents are four liver and three pancreas cases. We sought to evaluate trends in resident experience and autonomy for complex hepatopancreatobiliary (HPB) surgery over time. Methods We queried the Accreditation Council for Graduate Medical Education General Surgery Case Log (2003–2012) for all cases performed by graduating chief residents (GCR) relating to liver, pancreas, and the biliary tract (HPB); simple cholecystectomy was excluded. Mean (±SD), median [10th–90th percentiles] and maximum case volumes were compared from 2003 to 2012 using R2 for all trends. Results A total of 252,977 complex HPB cases (36% liver, 43% pancreas, 21% biliary) were performed by 10,288 GCR during the 10-year period examined (Mean = 24.6 per GCR). Of these, 57% were performed during the chief year, whereas 43% were performed as postgraduate year 1–4. Only 52% of liver cases were anatomic resections, whereas 71% of pancreas cases were major resections. Total number of cases increased from 22,516 (mean = 23.0) in 2003 to 27,191 (mean = 24.9) in 2012. During this same time period, the percentage of HPB cases that were performed during the chief year decreased by 7% (liver: 13%, pancreas 8%, biliary 4%). There was an increasing trend in the mean number of operations (mean ± SD) logged by GCR on the pancreas (9.1 ± 5.9 to 11.3 ± 4.3; R2 = .85) and liver (8.0 ± 5.9 to 9.4 ± 3.4; R2 = .91), whereas those for the biliary tract decreased (5.9 ± 2.5 to 3.8 ± 2.1; R2 = .96). Although the median number of cases [10th:90th percentile] increased slightly for both pancreas (7.0 [4.0:15] to 8.0 [4:20]) and liver (7.0 [4:13] to 8.0 [5:14]), the maximum number of cases preformed by any given GCR remained stable for pancreas (51 to 53; R2 = .18), but increased for liver (38 to 45; R2 = .32). The median number of HPB cases that GCR performed as teaching assistants (TAs) remained at zero during this time period. The 90th percentile of cases performed as TA was less than two for both pancreas and liver. Conclusion Roughly one-half of GCR have performed fewer than 10 cases in each of the liver, pancreas, or biliary categories at time of completion of residency. Although the mean number of complex liver and pancreatic operations performed by GCR increased slightly, the median number remained low, and the number of TA cases was virtually zero. Most GCR are unlikely to be prepared to perform complex HPB operations. PMID:24953270

Sachs, Teviah E.; Ejaz, Aslam; Weiss, Matthew; Spolverato, Gaya; Ahuja, Nita; Makary, Martin A.; Wolfgang, Christopher L.; Hirose, Kenzo; Pawlik, Timothy M.

2015-01-01

308

An analytical model for the prediction of a micro-dosimeter response function  

NASA Astrophysics Data System (ADS)

A rapid analytical procedure for the prediction of a micro-dosimeter response function in Low Earth Orbit (LEO), correlated with the Space Transportation System (STS, shuttle) Tissue Equivalent Proportional Counter (TEPC) measurements is presented. The analytical model takes into consideration the energy loss straggling and chord length distribution of the detector, and is capable of predicting energy deposition fluctuations in a cylindrical micro-volume of arbitrary aspect ratio (height/diameter) by incoming ions through both direct and indirect (? rays) events. At any designated (ray traced) target point within the vehicle, the model as input accepts the differential flux spectrum of Galactic Cosmic Rays (GCR) and/or trapped protons at LEO. On a desktop PC, the response function of TEPC for each ion in the GCR/trapped field is computed at the average rate of 30 seconds/ion. The ionizing radiation environment at LEO is represented by O'Neill's GCR model (2004), covering charge particles in the 1?Z?28 range. O'Neill's free space GCR model is coupled with the Langley Research Center (LaRC) cutoff model with angular dependency compensation to compute the transmission coefficient at LEO. The trapped proton environment is represented by a LaRC developed time dependent procedure which couples the AP8min/AP8max, Deep River Neutron Monitor (DRNM) and F10.7 solar radio frequency measurements. The albedo neutron environment is represented by the extrapolation of the Atmospheric Ionizing Radiation (AIR) measurements. The charged particle transport calculations correlated with STS 56, 51, 110 and 114 flights are accomplished by using the most recent version (2005) of LaRC's deterministic ionized particle transport code High charge (Z) and Energy TRaNsport (HZETRN). Herein, we present the correlations between the TEPC model predictions (response function) and TEPC measured differential/integral spectra in the lineal energy (y) domain for both GCR and trapped protons, with the conclusion that the model correctly accounts for the increase in flux at low y values where energetic ions are the primary contributor. We further discuss that even with the incorporation of angular dependency in the cutoffs, comparison of the GCR differential/integral flux in the y domain between STS 56, 51, 110 and 114 TEPC measured data and current calculations indicates that there still exists an underestimation by the simulations (model) at low to mid range y values. This underestimation is argued to be partly related the exclusion of the secondary pion and kaon particle production from the current version of HZETRN.

Badavi, Francis; Michael, Michael; Wilson, John W.

309

Validity of the Aluminum Equivalent Approximation in Space Radiation Shielding  

NASA Technical Reports Server (NTRS)

The origin of the aluminum equivalent shield approximation in space radiation analysis can be traced back to its roots in the early years of the NASA space programs (Mercury, Gemini and Apollo) wherein the primary radiobiological concern was the intense sources of ionizing radiation causing short term effects which was thought to jeopardize the safety of the crew and hence the mission. Herein, it is shown that the aluminum equivalent shield approximation, although reasonably well suited for that time period and to the application for which it was developed, is of questionable usefulness to the radiobiological concerns of routine space operations of the 21 st century which will include long stays onboard the International Space Station (ISS) and perhaps the moon. This is especially true for a risk based protection system, as appears imminent for deep space exploration where the long-term effects of Galactic Cosmic Ray (GCR) exposure is of primary concern. The present analysis demonstrates that sufficiently large errors in the interior particle environment of a spacecraft result from the use of the aluminum equivalent approximation, and such approximations should be avoided in future astronaut risk estimates. In this study, the aluminum equivalent approximation is evaluated as a means for estimating the particle environment within a spacecraft structure induced by the GCR radiation field. For comparison, the two extremes of the GCR environment, the 1977 solar minimum and the 2001 solar maximum, are considered. These environments are coupled to the Langley Research Center (LaRC) deterministic ionized particle transport code High charge (Z) and Energy TRaNsport (HZETRN), which propagates the GCR spectra for elements with charges (Z) in the range I <= Z <= 28 (H -- Ni) and secondary neutrons through selected target materials. The coupling of the GCR extremes to HZETRN allows for the examination of the induced environment within the interior' of an idealized spacecraft as approximated by a spherical shell shield, and the effects of the aluminum equivalent approximation for a good polymeric shield material such as genetic polyethylene (PE). The shield thickness is represented by a 25 g/cm spherical shell. Although one could imagine the progression to greater thickness, the current range will be sufficient to evaluate the qualitative usefulness of the aluminum equivalent approximation. Upon establishing the inaccuracies of the aluminum equivalent approximation through numerical simulations of the GCR radiation field attenuation for PE and aluminum equivalent PE spherical shells, we Anther present results for a limited set of commercially available, hydrogen rich, multifunctional polymeric constituents to assess the effect of the aluminum equivalent approximation on their radiation attenuation response as compared to the generic PE.

Badavi, Francis F.; Adams, Daniel O.; Wilson, John W.

2009-01-01

310

Full Mission Astronaut Radiation Exposure Assessments for Long Duration Lunar Surface Missions  

NASA Technical Reports Server (NTRS)

Risk to astronauts due to ionizing radiation exposure is a primary concern for missions beyond Low Earth Orbit (LEO) and will drive mission architecture requirements, mission timelines, and operational practices. Both galactic cosmic ray (GCR) and solar particle event (SPE) environments pose a risk to astronauts for missions beyond LEO. The GCR environment, which is made up of protons and heavier ions covering a broad energy spectrum, is ever present but varies in intensity with the solar cycle, while SPEs are sporadic events, consisting primarily of protons moving outward through the solar system from the sun. The GCR environment is more penetrating and is more difficult to shield than SPE environments, but lacks the intensity to induce acute effects. Large SPEs are rare, but they could result in a lethal dose, if adequate shielding is not provided. For short missions, radiation risk is dominated by the possibility of a large SPE. Longer missions also require planning for large SPEs; adequate shielding must be provided and operational constraints must allow astronauts to move quickly to shielded locations. The dominant risk for longer missions, however, is GCR exposure, which accumulates over time and can lead to late effects such as cancer. SPE exposure, even low level SPE exposure received in heavily shielded locations, will increase this risk. In addition to GCR and SPE environments, the lunar neutron albedo resulting mainly from the interaction of GCRs with regolith will also contribute to astronaut risk. Full mission exposure assessments were performed for proposed long duration lunar surface mission scenarios. In order to accomplish these assessments, radiation shielding models were developed for a proposed lunar habitat and rover. End-to-End mission exposure assessments were performed by first calculating exposure rates for locations in the habitat, rover, and during extra-vehicular activities (EVA). Subsequently, total mission exposures were evaluated for proposed timelines. A number of computational tools and mathematical models, which have been incorporated into NASA's On-Line Tool for the Assessment of Radiation In Space (OLTARIS), were used for this study. These tools include GCR and SPE environment models, human body models, and the HZETRN space radiation transport code, which is used to calculate the transport of the charged particles and neutrons through shielding materials and human tissue. Mission exposure results, assessed in terms of effective dose, are presented for proposed timelines and recommendations are made for improved astronaut shielding and safer operational practice.

Adamczyk, Anne M.; Clowdsley, Martha S.; Qualls, Garry D.; Blattnig, Steve B.; Lee, Kerry T.; Fry, Dan J.; Stoffle, Nicholas N.; Simonsen, Lisa C.; Slaba, Tony C.; Walker, Steven A.; Zapp, Edward N.

2010-01-01

311

On the validity of the aluminum equivalent approximation in space radiation shielding applications  

NASA Astrophysics Data System (ADS)

The origin of the aluminum equivalent shield approximation in space radiation analysis can be traced back to its roots in the early years of the NASA space programs (Mercury, Gemini and Apollo) wherein the primary radiobiological concern was the intense sources of ionizing radiation causing short term effects which was thought to jeopardize the safety of the crew and hence the mission. Herein, it is shown that the aluminum equivalent shield approximation, although reasonably well suited for that time period and to the application for which it was developed, is of questionable usefulness to the radiobiological concerns of routine space operations of the 21st century which will include long stays onboard the International Space Station (ISS) and perhaps the moon. This is especially true for a risk based protection system, as appears imminent for deep space exploration where the long-term effects of Galactic Cosmic Ray (GCR) exposure is of primary concern. The present analysis demonstrates that sufficiently large errors in the interior particle environment of a spacecraft result from the use of the aluminum equivalent approximation, and such approximations should be avoided in future astronaut risk estimates. In this study, the aluminum equivalent approximation is evaluated as a means for estimating the particle environment within a spacecraft structure induced by the GCR radiation field. For comparison, the two extremes of the GCR environment, the 1977 solar minimum and the 2001 solar maximum, are considered. These environments are coupled to the Langley Research Center (LaRC) deterministic ionized particle transport code High charge ( Z) and Energy TRaNsport (HZETRN), which propagates the GCR spectra for elements with charges ( Z) in the range 1 ? Z ? 28 (H-Ni) and secondary neutrons through selected target materials. The coupling of the GCR extremes to HZETRN allows for the examination of the induced environment within the interior of an idealized spacecraft as approximated by a spherical shell shield, and the effects of the aluminum equivalent approximation for a good polymeric shield material such as generic polyethylene (PE). The shield thickness is represented by a 25 g/cm 2 spherical shell. Although, one could imagine the progression to greater thickness, the current range will be sufficient to evaluate the qualitative usefulness of the aluminum equivalent approximation. Upon establishing the inaccuracies of the aluminum equivalent approximation through numerical simulations of the GCR radiation field attenuation for PE and aluminum equivalent PE spherical shells, we further present results for a limited set of commercially available, hydrogen rich, multifunctional polymeric constituents to assess the effect of the aluminum equivalent approximation on their radiation attenuation response as compared to the generic PE.

Badavi, Francis F.; Adams, Daniel O.; Wilson, John W.

2010-09-01

312

Radiation characteristics in the spherical tissue-equivalent phantom on the ISS during solar activity minimum according to the data from Liulin-5 experiment  

NASA Astrophysics Data System (ADS)

The Liulin-5 charged particle telescope observes the radiation characteristics in the spherical tissue-equivalent phantom of MATROSHKA-R international project on the International Space Station (ISS). Liulin-5 measures time resolved deposited energy spectra, linear energy transfer (LET) spectrum, flux and absorbed dose rates for electrons, protons and the biologically relevant heavy ion components of the cosmic radiation at three depths along the phantom's radius. We present some new results of Liulin-5 experiment obtained from June 2007 to March 2010. The average quality factor for different time intervals is between 2.7 and 4.4. Due to the heavy ions in LET spectrum of the galactic cosmic rays (GCR), the GCR quality factor is bigger than that of the trapped protons. The absorbed dose rates measured at depths in the phantom corresponding to the depths of blood forming organs in human body are 7.75-9.6 ?Gy/h and the dose equivalent rates are 24.6-36.7 ?Sv/h. Usually the trapped protons contribute about 60% of the total absorbed dose at 40 mm depth in the phantom and about 40% at 165 mm depth. The rest of the dose comes from GCR. Space Shuttle docking and the change of ISS attitude preformed for that purpose lead to a decrease in the total doses and to decreasing the trapped protons contributions. The doses from GCR are not affected neither by the depth of measurement not by Shuttle docking. At 165 mm depth in the phantom the largest fluxes along the ISS orbit are obtained from the trapped protons in the South Atlantic Anomaly (SAA) at L values 1.26-1.27, B?0.198 Gs, geographical longitude ?-51° to -55°, latitude ?-28° to -29° and altitudes 361-363 km. Minimal values about 0.1 particles/cm2s were recorded at L?1 from GCR, at L?4 the GCR flux reaches 2.1 particles/cm2s.

Semkova, J.; Koleva, R.; Maltchev, St.; Bankov, N.; Benghin, V.; Chernykh, I.; Shurshakov, V.; Petrov, V.

2013-07-01

313

Effect of polarity reversal of solar magnetic field in cosmic ray fluctuations  

NASA Astrophysics Data System (ADS)

The transition process of decay of the large-scale magnetic field of the Sun at the stage of its polarity reversal is manifested as a giant wave of polarity reversal with the period of a half-year. Maximums of a wave in the GCR scintillation index are ~3 Bartels rotations of the Sun before GCR intensity minimums. The revealed relationship are used both for the longterm forecast of geoeffective solar activity periods ?=3±1 solar rotations in advance and for the operative forecast of geoeffective events of Space Weather from several hours to ~1 day in advance. The semi-annual wave is also detected in the interplanetary magnetic field (IMF) parameters. The presence of the wave of polarity reversal explains a "gap" in the majority of parameters uniformly both in the maximum of solar activity ("Gnevyshev effect") and in the beginning of a declining branch of the 11-year cycle.

Kozlov, V. I.; Kozlov, V. V.; Markov, V. V.

2003-09-01

314

A space radiation shielding model of the Martian radiation environment experiment (MARIE)  

NASA Technical Reports Server (NTRS)

The 2001 Mars Odyssey spacecraft was launched towards Mars on April 7, 2001. Onboard the spacecraft is the Martian radiation environment experiment (MARIE), which is designed to measure the background radiation environment due to galactic cosmic rays (GCR) and solar protons in the 20-500 MeV/n energy range. We present an approach for developing a space radiation-shielding model of the spacecraft that includes the MARIE instrument in the current mapping phase orientation. A discussion is presented describing the development and methodology used to construct the shielding model. For a given GCR model environment, using the current MARIE shielding model and the high-energy particle transport codes, dose rate values are compared with MARIE measurements during the early mapping phase in Mars orbit. The results show good agreement between the model calculations and the MARIE measurements as presented for the March 2002 dataset. c2003 COSPAR. Published by Elsevier Ltd. All rights reserved.

Atwell, W.; Saganti, P.; Cucinotta, F. A.; Zeitlin, C. J.

2004-01-01

315

Galactic cosmic ray abundances and spectra behind defined shielding  

NASA Technical Reports Server (NTRS)

Linear Energy Transfer (LET) spectra have been measured for lunar missions and for several near Earth orbits ranging from 28 deg to 83 deg inclination. In some of the experiments the flux of Galactic Cosmic Rays (GCR) was determined separately from contributions caused by interactions in the detector material. Results of these experiments are compared to model calculations. The general agreement justifies the use of the model to calculate GCR fluxes. The magnitude of variations caused by solar modulation, geomagnetic shielding, and shielding by matter determined from calculated LET spectra is generally in agreement with experimental data. However, more detailed investigations show that there are some weak points in modeling solar modulation and shielding by material. These points are discussed in more detail.

Heinrich, W.; Benton, E. V.; Wiegel, B.; Zens, R.; Rusch, G.

1994-01-01

316

Solar modulation and nuclear fragmentation effects in galactic cosmic ray transport through shielding  

NASA Technical Reports Server (NTRS)

Crews of manned interplanetary missions may accumulate significant radiation exposures from the Galactic Cosmic Ray (GCR) environment in space. Estimates of how these dose levels are affected by the assumed temporal and spatial variations in the composition of the GCR environment, and by the effects of the spacecraft and body self-shielding on the transported fields are presented. In this work, the physical processes through which shielding alters the transported radiation fields are described. We then present estimates of the effects on model calculations of (1) nuclear fragmentation model uncertainties, (2) solar modulation, (3) variations between solar cycles, and (4) proposed changes to the quality factors which relate dose equivalent to absorbed dose.

Townsend, L. W.; Cucinotta, C. F.; Wilson, J. W.; Shinn, J. L.; Badhwar, G.

1994-01-01

317

Optimized Shielding for Space Radiation Protection  

NASA Technical Reports Server (NTRS)

Abstract. Future deep space mission and International Space Station exposures will be dominated by the high-charge and -energy (HZE) ions of the Galactic Cosmic Rays (GCR). A few mammalian systems have been extensively tested over a broad range of ion types and energies. For example, C3H10T1/2 cells, V79 cells, and Harderian gland tumors have been described by various track-structure dependent response models. The attenuation of GCR induced biological effects depends strongly on the biological endpoint, response model used, and material composition. Optimization of space shielding is then driven by the nature of the response model and the transmission characteristics of the given material.

Wilson, J. W.; Cucinotta, F. A.; Kim, M.-H. Y.; Schimmerling, W.

2000-01-01

318

Revisited modeling of Titan’s middle atmosphere electrical conductivity  

NASA Astrophysics Data System (ADS)

The atmospheric electrical conductivity measured by the Permittivity, Wave and Altimetry (PWA) subsystem on board the Huygens probe, during the landing mission on Titan, has been modeled in the present work. Previous modeling studies showed a Galactic Cosmic Ray (GCR) peak of conductivity at a higher altitude and a quantitative overestimation in the altitude range 0-100 km compared to that observed by the PWA instrument. Recently the PWA data was revisited and provided new constraints on the conductivity at altitudes 100-180 km. Because the aerosols in the atmosphere are known to alter the electron concentration, using a detailed distribution of the aerosols at all altitudes, the electron conductivity has been calculated in the altitude range 0-180 km. By using a variable range of photoemission threshold for the aerosols, the present model is able to reasonably predict the altitude at which the GCR peak of conductivity occurs and to meet the new constraints for the conductivity profile.

Mishra, Alabhya; Michael, Marykutty; Tripathi, Sachchida Nand; Béghin, Christian

2014-08-01

319

Galactic Cosmic Rays from Superbubbles and the Abundances of Lithium, Beryllium, and Boron  

E-print Network

In this article we study the galactic evolution of the LiBeB elements within the framework of a detailed model of the chemical evolution of the Galaxy that includes galactic cosmic ray nucleosynthesis by particles accelerated in superbubbles. The chemical composition of the superbubble consists of varying proportions of ISM and freshly supernova synthesized material. The observational trends of 6 LiBeB evolution are nicely reproduced by models in which GCR come from a mixture of 25% of supernova material with 75% of ISM, except for 6 Li, for which maybe an extra source is required at low metallicities. To account for 7 Li evolution several additional sources have been considered (neutrino-induced nucleosynthesis, nova outbursts, C-stars). The model fulfills the energetic requirements for GCR acceleration.

Andreu Alibes; Javier Labay; Ramon Canal

2002-02-05

320

Light ion components of the galactic cosmic rays: nuclear interactions and transport theory.  

PubMed

Light nuclei are present in the primary galactic cosmic rays (GCR) and are produced in thick targets due to projectile or target fragmentation from both nucleon and heavy ion induced reactions. In the primary GCR, 4He is the most abundant nucleus after 1H. However, there are also a substantial fluxes of 2H and 3He. In this paper we describe theoretical models based on quantum multiple scattering theory for the description of light ion nuclear interactions. The energy dependence of the light ion fragmentation cross section is considered with comparisons of inclusive yields and secondary momentum distributions to experiments described. We also analyze the importance of a fast component of lights ions from proton and neutron induced target fragmentation. These theoretical models have been incorporated into the cosmic ray transport code HZETRN and will be used to analyze the role of shielding materials in modulating the production and the energy spectrum of light ions. PMID:11540375

Cucinotta, F A; Townsend, L W; Wilson, J W; Shinn, J L; Badhwar, G D; Dubey, R R

1996-01-01

321

Radiation Physics for Space and High Altitude Air Travel  

NASA Technical Reports Server (NTRS)

Galactic cosmic rays (GCR) are of extra-solar origin consisting of high-energy hydrogen, helium, and heavy ions. The GCR are modified by physical processes as they traverse through the solar system, spacecraft shielding, atmospheres, and tissues producing copious amounts of secondary radiation including fragmentation products, neutrons, mesons, and muons. We discuss physical models and measurements relevant for estimating biological risks in space and high-altitude air travel. Ambient and internal spacecraft computational models for the International Space Station and a Mars mission are discussed. Risk assessment is traditionally based on linear addition of components. We discuss alternative models that include stochastic treatments of columnar damage by heavy ion tracks and multi-cellular damage following nuclear fragmentation in tissue.

Cucinotta, F. A.; Wilson, J. W.; Goldhagen, P.; Saganti, P.; Shavers, M. R.; McKay, Gordon A. (Technical Monitor)

2000-01-01

322

Study - Radiation Shielding Effectiveness of the Prototyped High Temperature Superconductivity (HTS) 'Artificial' Magnetosphere for Deep Space Missions  

NASA Technical Reports Server (NTRS)

The high temperature superconductor (HTS) is being used to develop the magnets for the Variable Specific Impulse Magneto-plasma Rocket (VASIMR ) propulsion system and may provide lightweight magnetic radiation shielding to protect spacecraft crews from radiation caused by GCR and SPEs on missions to Mars. A study is being planned to assess the radiation shielding effectiveness of the artificial magnetosphere produced by the HTS magnet. VASIMR is an advanced technology propulsion engine which is being touted as enabling one way transit to Mars in 90 days or less. This is extremely important to NASA. This technology would enable a significant reduction in the number of days in transit to and from Mars and significantly reduce the astronauts exposure to a major threat - high energy particles from solar storms and GCR during long term deep space missions. This paper summarizes the plans for the study and the subsequent testing of the VASIMR technology onboard the ISS slated for 2013.

Denkins, Pamela

2010-01-01

323

A Saccharomyces cerevisiae RNase H2 Interaction Network Functions To Suppress Genome Instability  

PubMed Central

Errors during DNA replication are one likely cause of gross chromosomal rearrangements (GCRs). Here, we analyze the role of RNase H2, which functions to process Okazaki fragments, degrade transcription intermediates, and repair misincorporated ribonucleotides, in preventing genome instability. The results demonstrate that rnh203 mutations result in a weak mutator phenotype and cause growth defects and synergistic increases in GCR rates when combined with mutations affecting other DNA metabolism pathways, including homologous recombination (HR), sister chromatid HR, resolution of branched HR intermediates, postreplication repair, sumoylation in response to DNA damage, and chromatin assembly. In some cases, a mutation in RAD51 or TOP1 suppressed the increased GCR rates and/or the growth defects of rnh203? double mutants. This analysis suggests that cells with RNase H2 defects have increased levels of DNA damage and depend on other pathways of DNA metabolism to overcome the deleterious effects of this DNA damage. PMID:24550002

Allen-Soltero, Stephanie; Martinez, Sandra L.; Putnam, Christopher D.

2014-01-01

324

Numerical Study of the Generation of Linear Energy Transfer Spectra for Space Radiation Applications  

NASA Technical Reports Server (NTRS)

In analyzing charged particle spectra in space due to galactic cosmic rays (GCR) and solar particle events (SPE), the conversion of particle energy spectra into linear energy transfer (LET) distributions is a convenient guide in assessing biologically significant components of these spectra. The mapping of LET to energy is triple valued and can be defined only on open energy subintervals where the derivative of LET with respect to energy is not zero. Presented here is a well-defined numerical procedure which allows for the generation of LET spectra on the open energy subintervals that are integrable in spite of their singular nature. The efficiency and accuracy of the numerical procedures is demonstrated by providing examples of computed differential and integral LET spectra and their equilibrium components for historically large SPEs and 1977 solar minimum GCR environments. Due to the biological significance of tissue, all simulations are done with tissue as the target material.

Badavi, Francis F.; Wilson, John W.; Hunter, Abigail

2005-01-01

325

Effects of Nuclear Cross Sections at Different Energies on the Radiation Hazard from Galactic Cosmic Rays  

NASA Technical Reports Server (NTRS)

The radiation hazard for astronauts from galactic cosmic rays is a major obstacle in long duration human space explorations. Space radiation transport codes have been developed to calculate radiation environment on missions to the Moon, Mars or beyond. We have studied how uncertainties in fragmentation cross sections at different energies affect the accuracy of predictions from such radiation transport. We find that, in deep space, cross sections between 0.3 and 0.85 GeV/u usually have the largest effect on dose-equivalent behind shielding in solar minimum GCR environments, and cross sections between 0.85 and 1.2 GeV/u have the largest effect in solar maximum GCR environments. At the International Space Station, cross sections at higher energies have the largest effect due to the geomagnetic cutoff.

Lin, Z. W.; Adams, J. H., Jr.

2006-01-01

326

Galactic Cosmic Rays in the Outer Heliosphere  

NASA Technical Reports Server (NTRS)

We report a next generation model of galactic cosmic ray (GCR) transport in the three dimensional heliosphere. Our model is based on an accurate three-dimensional representation of the heliospheric interface. This representation is obtained by taking into account the interaction between partially ionized, magnetized plasma flows of the solar wind and the local interstellar medium. Our model reveals that after entering the heliosphere GCRs are stored in the heliosheath for several years. The preferred GCR entry locations are near the nose of the heliopause and at high latitudes. Low-energy (hundreds of MeV) galactic ions observed in the heliosheath have spent, on average, a longer time in the solar wind than those observed in the inner heliosphere, which would explain their cooled-off spectra at these energies. We also discuss radial gradients in the heliosheath and the implications for future Voyager observations

Florinski, V.; Washimi, H.; Pogorelov, N. V.; Adams, J. H.

2010-01-01

327

Cosmic Ray Modulation in the Outer Heliosphere During the Minimum of Solar Cycle 23/24  

NASA Technical Reports Server (NTRS)

We report a next generation model of galactic cosmic ray (GCR) transport in the three dimensional heliosphere. Our model is based on an accurate three-dimensional representation of the heliospheric interface. This representation is obtained by taking into account the interaction between partially ionized, magnetized plasma flows of the solar wind and the local interstellar medium. Our model reveals that after entering the heliosphere GCRs are stored in the heliosheath for several years. The preferred GCR entry locations are near the nose of the heliopause and at high latitudes. Low-energy (hundreds of MeV) galactic ions observed in the heliosheath have spent, on average, a longer time in the solar wind than those observed in the inner heliosphere, which would explain their cooled-off spectra at these energies. We also discuss radial gradients in the heliosheath and the implications for future Voyager observations.

Adams, James H., Jr.; Florinski, V.; Washimi, H.; Pogorelov, N. V.

2011-01-01

328

Different glassy states, as indicated by a violation of the generalized Cauchy relation  

NASA Astrophysics Data System (ADS)

Using Brillouin spectroscopy as a probe for high-frequency clamped acoustic properties, a shear modulus c44infty can be measured in addition to the longitudinal modulus c11infty already well above the thermal glass transition. On slow cooling of the liquid through the thermal glass transition temperature Tg, both moduli show a kink-like behaviour and the function c11infty = c11infty(c44infty) follows a generalized Cauchy relation (gCR) defined by the linear relation c11infty = 3c44infty + constant, which completely hides the glass transition. In this work we show experimentally that on fast cooling this linear transformation becomes violated within the glassy state, but that thermal ageing drives the elastic coefficients towards the gCR, i.e. towards a unique glassy state.

Krüger, J. K.; Britz, T.; le Coutre, A.; Baller, J.; Possart, W.; Alnot, P.; Sanctuary, R.

2003-07-01

329

Effects of radiobiological uncertainty on vehicle and habitat shield design for missions to the moon and Mars  

NASA Technical Reports Server (NTRS)

Some consequences of uncertainties in radiobiological risk due to galactic cosmic ray (GCR) exposure are analyzed for their effect on engineering designs for the first lunar outpost and a mission to explore Mars. This report presents the plausible effect of biological uncertainties, the design changes necessary to reduce the uncertainties to acceptable levels for a safe mission, and an evaluation of the mission redesign cost. Estimates of the amount of shield mass required to compensate for radiobiological uncertainty are given for a simplified vehicle and habitat. The additional amount of shield mass required to provide a safety factor for uncertainty compensation is calculated from the expected response to GCR exposure. The amount of shield mass greatly increases in the estimated range of biological uncertainty, thus, escalating the estimated cost of the mission. The estimates are used as a quantitative example for the cost-effectiveness of research in radiation biophysics and radiation physics.

Wilson, John W.; Nealy, John E.; Schimmerling, Walter; Cucinotta, Francis A.; Wood, James S.

1993-01-01

330

The Heavy Nuclei Explorer (HNX) Mission  

NASA Technical Reports Server (NTRS)

The Heavy Nuclei eXplorer (HNX) mission was recently selected by NASA for a Small Explorer (SMEX) Mission Concept Study to begin in 2001. The primary scientific objectives of HNX are to measure the age of the galactic cosmic rays (GCR) since nucleosynthesis, determine the injection mechanism for the GCR accelerator (Volatility or FIP), and study the mix of nucleosynthetic processes that contribute to the source of GCRs. The experimental goal of HNX is to measure the elemental abundances of all individual stable nuclei from neon through the actinides and possibly beyond. HNX is composed of two instruments: ECCO, which measures elemental abundances of nuclei with Z(sup 3)72, and ENTICE, which measures elemental abundances of nuclei with 10(f)Z(f)82. We will discuss the mission and the science that can be addressed by HNX.

Binns, W. R.

2001-01-01

331

The Heavy Nuclei eXplorer (HNX) Mission  

NASA Technical Reports Server (NTRS)

The primary scientific objectives of HNX, which was recently selected by NASA for a Small Explorer (SMEX) Mission Concept Study, are to measure the age of the galactic cosmic rays (GCR) since nucleosynthesis, determine the injection mechanism for the GCR accelerator (Volatility or FIP), and study the mix of nucleosynthetic processes that contribute to the source of GCRs. The experimental goal of HNX is to measure the elemental abundances of all individual stable nuclei from neon through the actinides and possibly beyond. HNX is composed of two instruments: ECCO, which measures elemental abundances of nuclei with Z greater than or equal to 72, and ENTICE. which measures elemental abundances of nuclei with Z between 10 and 82. We describe the mission and the science that can be addressed by HNX.

Binns, W. R.; Adams, J. H.; Barbier, L. M.; Craig, N.; Cummings, A. C.; Cummings, J. R.; Doke, T.; Hasebe, N.; Hayashi, T.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

332

Radiation quality of cosmic ray nuclei studied with Geant4-based simulations  

NASA Astrophysics Data System (ADS)

In future missions in deep space a space craft will be exposed to a non-negligible flux of high charge and energy (HZE) particles present in the galactic cosmic rays (GCR). One of the major concerns of manned missions is the impact on humans of complex radiation fields which result from the interactions of HZE particles with the spacecraft materials. The radiation quality of several ions representing GCR is investigated by calculating microdosimetry spectra. A Geant4-based Monte Carlo model for Heavy Ion Therapy (MCHIT) is used to simulate microdosimetry data for HZE particles in extended media where fragmentation reactions play a certain role. Our model is able to reproduce measured microdosimetry spectra for H, He, Li, C and Si in the energy range of 150-490 MeV/u. The effect of nuclear fragmentation on the relative biological effectiveness (RBE) of He, Li and C is estimated and found to be below 10%.

Burigo, Lucas N.; Pshenichnov, Igor A.; Mishustin, Igor N.; Bleicher, Marcus

2014-04-01

333

Quiet-Time Spectra and Abundances of Energetic Particles During the 1996 Solar Minimum  

NASA Technical Reports Server (NTRS)

We report the energy spectra and abundances of ions with atomic number, Z, in the interval Z is greater than or equal to 2 and Z is less than or equal to 36 and energies approximately 3-20 MeV/amu for solar and interplanetary quiet periods between 1994 November and 1998 April as measured by the large-geometry Low Energy Matrix Telescope (LEMT) telescope on the Wind spacecraft near Earth. The energy spectra show the presence of galactic (GCR) and "anomalous" cosmic ray (ACR) components, depending on the element. ACR components are reported for Mg and Si for the first time at 1 AU and the previous observation of S and Ar is confirmed. However, only GCR components are clearly apparent for the elements Ca, Ti, Cr, Fe, as well as for C. New limits are placed on a possible ACR contribution for other elements, including Kr.

Reames, Donald V.

1999-01-01

334

Quiet-Time Spectra and Abundances of Energetic Particles During the 1996 Solar Minimum  

NASA Technical Reports Server (NTRS)

This report concerns the energy spectra and abundances of ions with atomic number, Z, in the interval 2 greater than or equal to Z and Z less than or equal to 36 and energies approximately 3-20 MeV/amu for solar and interplanetary quiet periods between November 1994 and April 1998 as measured by the large-geometry LEMT telescope on the Wind spacecraft near Earth. The energy spectra show the presence of galactic (GCR) and 'anomalous' cosmic ray (ACR) components, depending on the element. ACR components are reported for Mg and Si for the first time at 1 AU and the previous observation of S and Ar is confirmed. However, only GCR components are clearly apparent for the elements Ca, Ti, Cr, Fe, as well as for C. New limits are placed on a possible ACR contribution for other elements, including Kr.

Reames, Donald V.

1998-01-01

335

The descent of the solar cycle 24 cosmic ray modulation  

NASA Astrophysics Data System (ADS)

The descending phase of the galactic cosmic ray (GCR) modulation at earth orbit, for the sunspot number (SSN) cycle 24 is studied, using data from the global network of neutron monitors and the balloon measurements at high latitudes in Russia. The decrease in intensity, two years after the onset of modulation, is modest compared to earlier cycles. The tilt angle of the heliospheric current sheet is very close to its maximum value for a cycle and the solar polar field has reversed in the northern hemisphere. So, one should expect the GCR modulation to be close to its maximum value. A preliminary determination is made of the rigidity dependence of the observed modulation for two years. It is a power law with an exponent -1.11, similar to that observed for earlier cycles (20-23).

Ahluwalia, H. S.; Ygbuhay, R. C.

2013-06-01

336

Preliminary Design of a Galactic Cosmic Ray Shielding Materials Testbed for the International Space Station  

NASA Technical Reports Server (NTRS)

The preliminary design of a testbed to evaluate the effectiveness of galactic cosmic ray (GCR) shielding materials, the MISSE Radiation Shielding Testbed (MRSMAT) is presented. The intent is to mount the testbed on the Materials International Space Station Experiment-X (MISSE-X) which is to be mounted on the International Space Station (ISS) in 2016. A key feature is the ability to simultaneously test nine samples, including standards, which are 5.25 cm thick. This thickness will enable most samples to have an areal density greater than 5 g/sq cm. It features a novel and compact GCR telescope which will be able to distinguish which cosmic rays have penetrated which shielding material, and will be able to evaluate the dose transmitted through the shield. The testbed could play a pivotal role in the development and qualification of new cosmic ray shielding technologies.

Gaier, James R.; Berkebile, Stephen; Sechkar, Edward A.; Panko, Scott R.

2012-01-01

337

Galactic Cosmic Ray Modulation near the Heliospheric Current Sheet  

NASA Astrophysics Data System (ADS)

Galactic cosmic rays (GCRs) are modulated by the heliospheric magnetic field (HMF) both over decadal time scales (due to long-term, global HMF variations), and over time scales of a few hours (associated with solar wind structures such as coronal mass ejections or the heliospheric current sheet, HCS). Due to the close association between the HCS, the streamer belt, and the band of slow solar wind, HCS crossings are often associated with corotating interaction regions where fast solar wind catches up and compresses slow solar wind ahead of it. However, not all HCS crossings are associated with strong compressions. In this study we categorize HCS crossings in two ways: Firstly, using the change in magnetic polarity, as either away-to-toward (AT) or toward-to-away (TA) magnetic field directions relative to the Sun and, secondly, using the strength of the associated solar wind compression, determined from the observed plasma density enhancement. For each category, we use superposed epoch analyses to show differences in both solar wind parameters and GCR flux inferred from neutron monitors. For strong-compression HCS crossings, we observe a peak in neutron counts preceding the HCS crossing, followed by a large drop after the crossing, attributable to the so-called `snow-plough' effect. For weak-compression HCS crossings, where magnetic field polarity effects are more readily observable, we instead observe that the neutron counts have a tendency to peak in the away magnetic field sector. By splitting the data by the dominant polarity at each solar polar region, we find that the increase in GCR flux prior to the HCS crossing is primarily from strong compressions in cycles with negative north polar fields due to GCR drift effects. Finally, we report on unexpected differences in GCR behavior between TA weak compressions during opposing polarity cycles.

Thomas, S. R.; Owens, M. J.; Lockwood, M.; Scott, C. J.

2014-07-01

338

Radiation risk predictions for Space Station Freedom orbits  

NASA Technical Reports Server (NTRS)

Risk assessment calculations are presented for the preliminary proposed solar minimum and solar maximum orbits for Space Station Freedom (SSF). Integral linear energy transfer (LET) fluence spectra are calculated for the trapped proton and GCR environments. Organ dose calculations are discussed using the computerized anatomical man model. The cellular track model of Katz is applied to calculate cell survival, transformation, and mutation rates for various aluminum shields. Comparisons between relative biological effectiveness (RBE) and quality factor (QF) values for SSF orbits are made.

Cucinotta, Francis A.; Atwell, William; Weyland, Mark; Hardy, Alva C.; Wilson, John W.; Townsend, Lawrence W.; Shinn, Judy L.; Katz, Robert

1991-01-01

339

ISOLATED WOLF-RAYET STARS AND O SUPERGIANTS IN THE GALACTIC CENTER REGION IDENTIFIED VIA PASCHEN-{alpha} EXCESS  

SciTech Connect

We report the discovery of 19 hot, evolved, massive stars near the Galactic center region (GCR). These objects were selected for spectroscopy owing to their detection as strong sources of Paschen-{alpha} (P{alpha}) emission-line excess, following a narrowband imaging survey of the central 0.{sup 0}65 x 0.{sup 0}25 (l, b) around Sgr A* with the Hubble Space Telescope. Discoveries include six carbon-type (WC) and five nitrogen-type (WN) Wolf-Rayet stars, six O supergiants, and two B supergiants. Two of the O supergiants have X-ray counterparts having properties consistent with solitary O stars and colliding-wind binaries. The infrared photometry of 17 stars is consistent with the Galactic center distance, but 2 of them are located in the foreground. Several WC stars exhibit a relatively large infrared excess, which is possibly thermal emission from hot dust. Most of the stars appear scattered throughout the GCR, with no relation to the three known massive young clusters; several others lie near the Arches and Quintuplet clusters and may have originated within one of these systems. The results of this work bring the total sample of Wolf-Rayet (WR) stars in the GCR to 88. All sources of strong P{alpha} excess have been identified in the area surveyed with HST, which implies that the sample of WN stars in this region is near completion, and is dominated by late (WNL) types. The current WC sample, although probably not complete, is almost exclusively dominated by late (WCL) types. The observed WR subtype distribution in the GCR is a reflection of the intrinsic rarity of early subtypes (WNE and WCE) in the inner Galaxy, an effect that is driven by metallicity.

Mauerhan, J. C.; Stolovy, S. R. [Infrared Processing and Analysis Center, California Institute of Technology, Mail Code 220-6, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Cotera, A. [SETI Institute, 515 North Whisman Road, Mountain View, CA 94043 (United States); Dong, H.; Wang, Q. D. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Morris, M. R. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Lang, C., E-mail: mauerhan@ipac.caltech.edu [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52245 (United States)

2010-12-10

340

The Feasibility of Multipole Electrostatic Radiation Shielding  

NASA Technical Reports Server (NTRS)

Although passive shielding appears to be the only workable solution for galactic cosmic radiation (GCR), active shielding may play an important augmenting role to control the dose from solar particle events (SPEs). It has been noted that, to meet the guidelines of NCRP Report No. 98 through the six SPEs of 1989, a crew member would need roughly double the passive shielding that is necessary to control the GCR dose . This would dramatically increase spacecraft mass, and so it has been proposed that a small but more heavily shielded storm shelter may be used to protect the crew during SPEs. Since a gradual SPE may last 5 or more days, staying in a storm shelter may be psychologically and physiologically distressing to the crew. Storm shelters do not provide shielding for the spacecraft itself against the SPE radiation, and radiation damage to critical electronics may result in loss of mission and life. Single-event effects during the radiation storm may require quick crew response to maintain the integrity of the spacecraft, and confining the crew to a storm shelter prohibits their attending to the spacecraft at the precise time when that attention is needed the most. Active shielding cannot protect against GCR because the particle energies are too high. Although lower energy particles are easier to stop in a passive shield, such shielding is more satisfactory against GCR than against SPE radiation because of the tremendous difference in their initial fluences. Even a small fraction of the SPE fluence penetrating the passive shielding may result in an unacceptably high dose. Active shielding is more effective than passive shielding against SPE radiation because it offers 100% shielding effectiveness up to the cutoff energy, and significant shielding effectiveness beyond the cutoff as well.

Metzger, Philip T.; Lane, John E.; Youngquist, Robert C.

2004-01-01

341

Radiation Transport Properties of Potential In Situ-Developed Regolith-Epoxy Materials for Martian Habitats  

NASA Technical Reports Server (NTRS)

Mission crews in space outside the Earth s magnetic field will be exposed to high energy heavy charged particles in the galactic cosmic radiation (GCR). These highly ionizing particles will be a source of radiation risk to crews on extended missions to the Moon and Mars, and the biological effects of and countermeasures to the GCR have to be investigated as part of the planning of exploration-class missions. While it is impractical to shield spacecraft and planetary habitats against the entire GCR spectrum, biological and physical studies indicate that relatively modest amounts of shielding are effective at reducing the radiation dose. However, nuclear fragmentation in the shielding materials produces highly penetrating secondary particles, which complicates the problem: in some cases, some shielding is worse than none at all. Therefore the radiation transport properties of potential shielding materials need to be carefully investigated. One intriguing option for a Mars mission is the use of material from the Martian surface, in combination with chemicals carried from Earth and/or fabricated from elements found in the Martian atmosphere, to construct crew habitats. We have measured the transmission properties of epoxy-Martian regolith composites with respect to heavy charged particles characteristic of the GCR ions which bombard the Martian surface. The composites were prepared at NASA Langley Research Center using simulated Martian regolith, in the process also evaluating fabrication methods which could lead to technologies for in situ fabrication on Mars. Initial evaluation of the radiation shielding properties is made using radiation transport models developed at NASA-LaRC, and the results of these calculations are used to select the composites with the most favorable radiation transmission properties. These candidates are then evaluated at particle accelerators which produce beams of heavy charged particles representative in energy and charge of the radiation at the surface of Mars. The ultimate objective is to develop the models into a design tool for use by mission planners, flight surgeons and radiation health specialists.

Miller, Jack; Heilbronn, Lawrence H.; Zeitlin, Cary J.; Wilson, John W.; Singleterry, Robert C., Jr.; Thibeault, Sheila Ann

2003-01-01

342

Gas Core Reactor with Magnetohydrodynamic Power System and Cascading Power Cycle  

Microsoft Academic Search

The U.S. Department of Energy initiative Generation IV aim is to produce an entire nuclear energy production system with next-generation features for certification before 2030. A Generation IV-capable system must have superior sustainability, safety and reliability, and economic cost advantages in comparison with third generation light water reactors (LWRs). A gas core reactor (GCR) with magnetohydrodynamic (MHD) power converter and

Blair M. Smith; Samim Anghaie

2004-01-01

343

A comparison of clinician-rated neuropsychological and self-rated cognitive assessments in patients with asthma and rheumatologic disorders.  

PubMed

Although data are mixed, asthma and rheumatologic conditions may be associated with cognitive impairment. Medications may play a role because corticosteroids are associated with memory impairment. Therefore, an easily administered assessment of cognition would be useful in these patients. We assessed relationships between self-rated and clinician-rated cognitive performance and mood in patients with asthma and rheumatologic diseases. Participants included 31adults treated for asthma or rheumatologic disorders (17 receiving chronic prednisone therapy, and 14 not receiving prednisone). An objective assessment of a variety of cognitive domains was administered through clinician and patient-rated assessments of cognition. Composite scores for the objective (Global Clinical Rating [GCR]) and subjective (Neuropsychological Impairment Scale: Global Measure of Impairment [GMI]) measures of cognition were derived. Depression was assessed with the 17-item Hamilton Rating Scale for Depression (HRSD-17). A linear regression was conducted with GMI scores as dependent variable and GCR, HRSD-17 scores, and prednisone-use status, as independent variables. Significant differences between prednisone-treated patients and other patients were observed on the GCR, GMI, and HRSD-17. In the regression analysis, HRSD-17 scores, but not GCR scores, significantly predicted GMI scores. Prednisone-treated patients had higher levels of depressive symptoms and subjective and objective cognitive deficits than those not taking prednisone. In the combined patient groups, subjective cognitive assessment was more strongly related to depressive symptoms than objective cognition. Findings suggest physicians should be aware of the potential for cognitive deficits in patients taking corticosteroids and, when appropriate, should consider the use of objective neurocognitive tests or neuropsychology consultation to better characterize its presence and severity. PMID:23484893

Frol, Alan B; Vasquez, Aracely; Getahun, Yonatan; Pacheco, Maria; Khan, David A; Brown, E Sherwood

2013-01-01

344

Multi-Scale Model of Galactic Cosmic Ray Effects on the Hippocampus  

NASA Astrophysics Data System (ADS)

An important concern for risk assessment from galactic cosmic ray (GCR) exposures is impacts to the central nervous systems including changes in cognition, and associations with increased risk of Alzheimer’s disease (AD). AD, which affects about 50 percent of the population above age 80-yr, is a degenerative disease that worsens with time after initial onset leading to death, and has no known cure. AD is difficult to detect at early stages, and the small number of epidemiology studies that have considered the possibility have not identified an association with low dose radiation. However, experimental studies in transgenic mice suggest the possibility exits. We discuss modeling approaches to consider mechanisms whereby GCR would accelerate the occurrence of AD to earlier ages. Biomarkers of AD include Amyloid beta plaques, and neurofibrillary tangles (NFT) made up of aggregates of the hyper-phosphorylated form of the micro-tubule associated, tau protein. Related markers include synaptic degeneration, dendritic spine loss, and neuronal cell loss through apoptosis. GCR may affect these processes by causing oxidative stress, aberrant signaling following DNA damage, and chronic neuro-inflammation. Cell types considered in multi-scale models are neurons, astrocytes, and microglia. We developed biochemical and cell kinetics models of DNA damage signaling related to glycogen synthase kinase-3 beta and neuro-inflammation, and considered approaches to develop computer simulations of GCR induced cell interactions and their relationships to Amyloid beta plaques and NFTs. Comparison of model results to experimental data for the age specific development of plaques in transgenic mice and predictions of space radiation effects will be discussed.

Cucinotta, Francis

345

Matrix models and graph colouring  

NASA Astrophysics Data System (ADS)

We study an edge-colouring problem on random planar graphs which is one of the simplest vertex models that may be analyzed by standard methods of large N matrix models. The main features of the saddle point solution and its critical behaviour are described. At the critical value of the coupling gcr the eigen value density u(?)M is found to vanish at the border of the support as ?-a2/3.

Cicuta, Giovanni M.; Molinari, Luca; Montaldi, Emilio

1993-06-01

346

Intact and permeabilized cells of the yeast Hansenula polymorpha as bioselective elements for amperometric assay of formaldehyde  

Microsoft Academic Search

Intact and permeabilized yeast cells were tested as the biorecognition elements for amperometric assay of formaldehyde (FA). For this aim, the mutant C-105 (gcr1 catX) of the methylotrophic yeast Hansenula polymorpha with a high activity of AOX was chosen. Different approaches were used for monitoring FA-dependent cell response including analysis of their oxygen consumption rate by the use of a

Maria Khlupova; Boris Kuznetsov; Olha Demkiv; Mykhailo Gonchar; Elisabeth Csöregi; Sergey Shleev

2007-01-01

347

Minimizing Astronauts' Risk from Space Radiation during Future Lunar Missions  

NASA Technical Reports Server (NTRS)

This viewgraph presentation reviews the risk factors from space radiation for astronauts on future lunar missions. Two types of radiation are discussed, Galactic Cosmic Radiation (GCR) and Solar Particle events (SPE). Distributions of Dose from 1972 SPE at 4 DLOCs inside Spacecraft are shown. A chart with the organ dose quantities is also given. Designs of the exploration class spacecraft and the planned lunar rover are shown to exhibit radiation protections features of those vehicles.

Kim, Myung-Hee Y.; Hayat, Mathew; Nounu, Hatem N.; Feiveson, Alan H.; Cucinotta, Francis A.

2007-01-01

348

Preliminary design of a small air loop for system analysis  

Microsoft Academic Search

In its R&D program for Gas-Cooled nuclear Reactors (GCR), CEA is considering the construction of a Small Air Loop for System Analysis, SALSA, in order to validate thermal hydraulic simulation codes like CATHARE in a direct-cycle configuration for the exploration of a wide range of transients at the scale of the whole nuclear reactor. The objective of the loop is

Nicolas TAUVERON; Manuel SAEZ; Jean-Paul RUBY; Genevieve GEFFRAYE; Denis TENCHINE; Thierry GERMAIN; Eric HERVIEU

349

Turbo-EEPRML: An EEPR4 channel with an error-correcting post-processor designed for 16\\/17 rate quasi-MTR code  

Microsoft Academic Search

An EEPRML channel with a post processor has been developed for compensating for the degradation in performance due to noise correlation. This Turbo-EEPRML is designed for 16\\/17 rate quasi-MTR (QMTR) code. The proposed method has high performance and simple circuitry. Simulation showed that Turbo-EEPRML has a 2.0-2.5 dB coding gain over a conventional EPRML channel for 16\\/17 GCR code

Takushi Nishiya; Kyoko Tsukano; T. Hirai; Takashi Nara; Seiichi Mita

1998-01-01

350

MCNP6 Cosmic-Source Option  

SciTech Connect

MCNP is a Monte Carlo radiation transport code that has been under development for over half a century. Over the last decade, the development team of a high-energy offshoot of MCNP, called MCNPX, has implemented several physics and algorithm improvements important for modeling galactic cosmic-ray (GCR) interactions with matter. In this presentation, we discuss the latest of these improvements, a new Cosmic-Source option, that has been implemented in MCNP6.

McKinney, Gregg W [Los Alamos National Laboratory; Armstrong, Hirotatsu [Los Alamos National Laboratory; James, Michael R [Los Alamos National Laboratory; Clem, John [University of Delaware, BRI; Goldhagen, Paul [DHS, National Urban Security Technology Laboratory

2012-06-19

351

An Algorithm for the Transport of Anisotropic Neutrons  

NASA Technical Reports Server (NTRS)

One major obstacle to human space exploration is the possible limitations imposed by the adverse effect of long-term exposure to the space environment. Even before human spaceflight began, the potentially brief exposure of astronauts to the very intense random solar particle events (SPE) were of great concern. A new challenge appears in deep space exploration from exposure to the low-intensity heavy-ion flux of the galactic cosmic rays (GCR) since the missions are of long duration and the accumulated GCR exposures can be high. Because cancer induction rates increase behind low to rather large thicknesses of aluminum shielding, according to available biological data on mammalian exposures to GCR like ions, the shield requirements for a Mars mission are prohibitively expensive in terms of mission launch costs. Therefore, a critical issue in the Human Exploration and Development of Space enterprise is cost effective mitigation of risk associated with ionizing radiation exposure. In order to estimate astronaut risk to GCR exposure and associated cancer risks and health hazards, it is necessary to do shield material studies. To determine an optimum radiation shield material it is necessary to understand nuclear interaction processes such as fragmentation and secondary particle production which is a function of energy dependent cross sections. This requires knowledge of material transmission characteristics either through laboratory testing or improved theoretical modeling. Here ion beam transport theory is of importance in that testing of materials in the laboratory environment generated by particle accelerators is a necessary step in materials development and evaluation for space use. The approximations used in solving the Boltzmann transport equation for the space setting are often not sufficient for laboratory work and those issues are a major emphasis of the present work.

Tweed, J.

2005-01-01

352

The influence of cosmic rays on the size of the Antarctic Ozone Hole  

E-print Network

The Antarctic region in which severe ozone depletion has taken place is known as the ozone hole. This region has two basic indicators: the area, where the ozone abundance is low (size), and the quantity of ozone mass deficit (depth). The energetic particles that penetrate deeply into the atmosphere and galactic cosmic rays (GCR) modify the ozone abundance in the stratosphere. With this research project, we are looking for evidence of a connection between variations in the cosmic ray flux and variations in the size of the ozone hole. In addition, we are looking for signs of the kind of processes that physically connect GCR fluxes with variations in the stratospheric ozone hole size (OHS) in the Antarctic region. With this goal in mind, we also analyze here the atmospheric temperature (AT) anomalies, which have often been linked with such variations. Using Morlet's wavelet spectral analysis to compute the coherence between two time series, we found that during the analyzed period (1982-2005), there existed a common signal of around 3 and 5 years between the OHS and GCR time series, during September and November, respectively. In both cases, the relationship showed a time-dependent anti-correlation between the two series. On the other hand, for October the analysis showed a time-dependent correlation that occurs around 1.7 years. These results seem to indicate that there exist at least two kinds of modulation processes of GCR fluxes on the OHS that work simultaneously but that change their relative relevance along the timeline.

M. Alvarez Madrigal; J. Perez Peraza; V. M. Velasco

2010-01-15

353

Sunspot activity and cosmic ray modulation at 1 a.u. for 1900-2013  

NASA Astrophysics Data System (ADS)

The descent of sunspot cycle 23 to an unprecedented minimum of long duration in 2006-2009 led to a prolonged galactic cosmic ray (GCR) recovery to the highest level observed in the instrumental era for a variety of energetic charged particle species on Earth, over a wide range of rigidities. The remarkable GCR increase measured by several ground-based, balloon-borne, and detectors on a satellite is described and discussed. It is accompanied by a decrease in solar wind velocity and interplanetary magnetic field at 1 a.u., reaching the lowest values since measurements of the solar wind began in October 1963; the solar polar field strength (?T) measured at the Wilcox Solar Observatory (WSO) is also significantly reduced compared to prior cycles since the start of the program in 1976, the polar field in the northern hemisphere reversed in June 2012 and again in February 2014, that in the southern hemisphere reversed in July 2013. If updates of WSO data confirm the second reversal in northern solar hemisphere, it would pose a serious challenge to the Dynamo Theory. The long-term change in solar behavior may have begun in 1992, perhaps earlier. The physical underpinnings of these solar changes need to be understood and their effect on GCR modulation processes clarified. The study discusses the recent phenomena in the context of GCR modulation since 1900. These happenings affected our empirical predictions for the key parameters for the next two sunspot cycles (they may be progressively less active than sunspot cycle 24) but it enhanced support for our prediction that solar activity is descending into a Dalton-like grand minimum in the middle of the twentyfirst century, reducing the frequency of the coronal mass ejections; they determine the space weather affecting the quality of life on Earth, radiation dose for hardware and human activities in space as well as the frequency of large Forbush decreases at 1 a.u.

Ahluwalia, H. S.

2014-10-01

354

Status of experimental data base development relevant to spaceradiation transport and protection  

SciTech Connect

This report describes the highlights and progress made in aprogram of measurements studying radiation transport through materials ofinterest to NASA. All measurements were preformed at acceleratorfacilities, primarily using GCR-like heavy-ion beams incident uponvarious elemental and composite targets. Both primary and secondaryparticles exiting the target were measured. The secondary particlesinclude both charged particles and neutrons. These measurements serve asuseful benchmarks and input to transport model calculations.

Heilbronn, Lawrence H.; Guetersloh, Stephen; Zeitlin, Cary; Miller, Jack

2004-04-01

355

Polymeric Materials With Additives for Durability and Radiation Shielding in Space  

NASA Technical Reports Server (NTRS)

Polymeric materials are attractive for use in space structures because of their light weight and high strength In addition, polymers are made of elements with low atomic numbers (Z), primarily carbon (C), hydrogen (H), oxygen (0), and nitrogen (N) which provide the best shielding from galactic cosmic rays (GCR) (ref. 1). Galactic cosmic rays are composed primarily of nuclei (i.e., fully ionized atoms) plus a contribution of about 2% from electrons and positrons. There is a small but significant component of GCR particles with high charge (Z > 10) and high energy (E >100 GeV) (ref. 2). These so-called HZE particles comprise only 1 to 2% of the cosmic ray fluence but they interact with very high specific ionization and contribute 50% of the long- term dose to humans. The best shield for this radiation would be liquid hydrogen, which is not feasible. For this reason, hydrogen-containing polymers make the most effective practical shields. Moreover, neutrons are formed in the interactions of GCR particles with materials. Neutrons can only lose energy by collisions or reactions with a nucleus since they are uncharged. This is a process that is much less probable than the Coulombic interactions of charged particles. Thus, neutrons migrate far from the site of the reaction in which they were formed. This increases the probability of neutrons reaching humans or electronic equipment. Fast neutrons (> 1 MeV) can interact with silicon chips in electronic equipment resulting in the production of recoil ions which can cause single event upsets (SEU) in sensitive components (ref. 3). Neutrons lose energy most effectively by elastic collisions with light atoms, particularly hydrogen atoms. Therefore, hydrogen-containing polymers are not only effective in interacting with GCR particles; they are also effective in reducing the energy of the neutrons formed in the interactions.

Kiefer, Richard

2011-01-01

356

Comparisons of Integrated Radiation Transport Models with Microdosimetry Data in Spaceflight  

NASA Technical Reports Server (NTRS)

Astronauts are exposed to galactic cosmic rays (GCR), trapped protons, and possible solar particle events (SPE) during spaceflight. For such complicated mixtures of radiation types and kinetic energies, tissue equivalent proportional counters (TEPC's) represent a simple time-dependent approach for radiation monitoring. Of interest in radiation protection is the average quality factor of a radiation field defined as a function of linear energy transfer, LET, Q(sub ave)(LET). However TEPC's measure the average quality factors as a function of lineal energy (y), Q(sub ave)(y) defined as the average energy deposition in a volume divided by the average chord length of the volume. Lineal energy, y deviates from LET due to energy straggling, delta-ray escape or entry, and nuclear fragments produced in the detector. Using integrated space radiation models that includes the transport code HZETRN/BRYNTRN, the quantum nuclear interaction model, QMSFRG, and results from Monte-Carlo track simulations of TEPC's response to ions, we consider comparisons of model calculations to TEPC results from NASA missions in low Earth orbit and make predictions for lunar and Mars missions. Good agreement between the model and measured spectra from past NASA missions is found. A finding of this work is that TEPC's values for trapped or solar protons of Q(sub ave)(y) range from 1.9-2.5, overestimating Q(sub ave)(LET), which ranges from 1.4-1.6 with both quantities increasing with shielding depth due to nuclear secondaries Comparisons for the complete GCR spectra show that Q(sub ave)(LET) for GCR is approximately 3.5-4.5, while TEPC's measure 2.9-3.4 for Q(sub ave)(y) with the GCR values decreasing with depth as heavy ions are absorbed in shielding material. Our results support the use of TEPC's for space radiation environmental monitoring when computational analysis is used for proper data interpretation.

Cucinotta, Francis A.; Nikjoo, H.; Kim, M. Y.; Hu, X.; Dicello, J. F.; Pisacane, V. L.

2006-01-01

357

ANISOTROPY AS A PROBE OF THE GALACTIC COSMIC-RAY PROPAGATION AND HALO MAGNETIC FIELD  

SciTech Connect

The anisotropy of cosmic rays (CRs) in the solar vicinity is generally attributed to CR streaming due to the discrete distribution of CR sources or local magnetic field modulation. Recently, the two-dimensional large-scale CR anisotropy has been measured by many experiments in the TeV-PeV energy range in both hemispheres. The tail-in excess along the tangential direction of the local spiral arm and the loss cone deficit pointing to the north Galactic pole direction agree with what have been obtained in tens to hundreds of GeV. The persistence of the two large-scale anisotropy structures in such a wide energy range suggests that the anisotropy might be due to global streaming of the Galactic CRs (GCRs). This work tries to extend the observed CR anisotropy picture from the solar system to the whole galaxy. In such a case, we can find a new interesting signature, a loop of GCR streaming, of the GCR propagation. We further calculate the overall GCR streaming induced magnetic field, and find a qualitative consistency with the observed structure of the halo magnetic field.

Qu, Xiao-bo; Zhang, Yi; Liu, Cheng; Hu, Hong-bo [Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Xue, Liang, E-mail: zhangyi@mail.ihep.ac.cn [School of Physics, Shandong University, Ji'nan 250100 (China)

2012-05-01

358

Initiation-promotion model of tumor prevalence in mice from space radiation exposures.  

PubMed

Exposures in space consist of low-level background components from galactic cosmic rays (GCR), occasional intense-energetic solar-particle events, periodic passes through geomagnetic-trapped radiation, and exposure from possible onboard nuclear-propulsion engines. Risk models for astronaut exposure from such diverse components and modalities must be developed to assure adequate protection in future NASA missions. The low-level background exposures (GCR), including relativistic heavy ions (HZE), will be the ultimate limiting factor for astronaut career exposure. We consider herein a two-mutation, initiation-promotion, radiation-carcinogenesis model in mice in which the initiation stage is represented by a linear kinetics model of cellular repair/misrepair, including the track-structure model for heavy ion action cross-sections. The model is validated by comparison with the harderian gland tumor experiments of Alpen et al. for various ion beams. We apply the initiation-promotion model to exposures from galactic cosmic rays, using models of the cosmic-ray environment and heavy ion transport, and consider the effects of the age of the mice prior to and after the exposure and of the length of time in space on predictions of relative risk. Our results indicate that biophysical models of age-dependent radiation hazard will provide a better understanding of GCR risk than models that rely strictly on estimates of the initial slopes of these radiations. PMID:7480628

Cucinotta, F A; Wilson, J W

1995-08-01

359

Solar-Cosmic-Ray-Produced Nuclides in Extraterrestrial Matter  

NASA Technical Reports Server (NTRS)

There are two main types of cosmic rays that have sufficient energy to induce nuclear reactions -- the galactic cosmic rays (GCR) and solar cosmic rays (also called solar energetic particles). Both types of particles can have production rates and production ratios in the small objects often found in cold and hot deserts that are different from those seen for most meteorites, which typically have radii of approx. 10-100 centimeters. GCR production rates are often lower than those for most meteorites. GCR production ratios, such as Ne-22/Ne-21, are also often different in small objects. Smaller meteoroids also are more likely to have nuclides made by solar-cosmic-ray (SCR) particles than typically-sized meteorites. The very small meteorite Salem had large amounts of SCR-produced radionuclides. Meteorites recovered in Antarctica are more likely to contain SCR-produced nuclides than other meteorites. Martian and lunar meteorites are also likely to have SCR-produced nuclides. Production rates and profiles for SCR-produced nuclides in meteoroids have been calculated previously. However, the cross sections for the nuclear reactions making many SCR-produced nuclides, such as Be-10 were not well measured then. New rates and profiles are calculated here using good cross sections for the reactions making these nuclides.

Reedy, Robert C.

1999-01-01

360

Solar-Cosmic-Ray-Produced Nuclides in Extraterrestrial Matter  

NASA Technical Reports Server (NTRS)

There are two main types of cosmic rays that have sufficient energy to induce nuclear reactions -- the galactic cosmic rays (GCR) and solar cosmic rays (also called solar energetic particles). Both types of particles can have production rates and production ratios in the small objects often found in cold and hot deserts that are different from those seen for most meteorites, which typically have radii of approx.10-100 centimeters. GCR production rates are often lower than those for most meteorites. GCR production ratios, such as Ne-22/Ne-21, are also often different in small objects. Smaller meteoroids also are more likely to have nuclides made by solar-cosmic-ray (SCR) particles than typically-sized meteorites. The very small meteorite Salem had large amounts of SCR-produced radionuclides. Meteorites recovered in Antarctica are more likely to contain SCR-produced nuclides than other meteorites. Martian and lunar meteorites are also likely to have SCR-produced nuclides. Production rates and profiles for SCR-produced nuclides in meteoroids have been calculated previously. However, the cross sections for the nuclear reactions making many SCR-produced nuclides, such as Be-10, were not well measured then. New rates and profiles are calculated here using good cross sections for the reactions making these nuclides.

Reedy, Robert C.

2000-01-01

361

Materials for Shielding Astronauts from the Hazards of Space Radiations  

NASA Technical Reports Server (NTRS)

One major obstacle to human space exploration is the possible limitations imposed by the adverse effects of long-term exposure to the space environment. Even before human spaceflight began, the potentially brief exposure of astronauts to the very intense random solar energetic particle (SEP) events was of great concern. A new challenge appears in deep space exploration from exposure to the low-intensity heavy-ion flux of the galactic cosmic rays (GCR) since the missions are of long duration and the accumulated exposures can be high. Because cancer induction rates increase behind low to rather large thickness of aluminum shielding according to available biological data on mammalian exposures to GCR like ions, the shield requirements for a Mars mission are prohibitively expensive in terms of mission launch costs. Preliminary studies indicate that materials with high hydrogen content and low atomic number constituents are most efficient in protecting the astronauts. This occurs for two reasons: the hydrogen is efficient in breaking up the heavy GCR ions into smaller less damaging fragments and the light constituents produce few secondary radiations (especially few biologically damaging neutrons). An overview of the materials related issues and their impact on human space exploration will be given.

Wilson, J. W.; Cucinotta, F. A.; Miller, J.; Shinn, J. L.; Thibeault, S. A.; Singleterry, R. C.; Simonsen, L. C.; Kim, M. H.

1997-01-01

362

Rigidity Dependence of the Long-Term Variations of Galactic Cosmic-Ray Intensity in Relation to the Interplanetary Magnetic-Field Turbulence: 1968 - 2002  

NASA Astrophysics Data System (ADS)

We studied the relationship between the power-law exponent ? on the rigidity R of the spectrum of galactic cosmic-ray (GCR) intensity variation ( ?D( R)/ D( R)? R - ? ) and the exponents ? y and ? z of the power spectral density (PSD) of the B y and B z components of the interplanetary magnetic field (IMF) turbulence (PSD˜ f - ? , where f is the frequency). We used the data from neutron monitors and IMF for the period of 1968 - 2002. The exponents ? y and ? z were calculated in the frequency interval ? f= f 2- f 1=3×10-6 Hz of the resonant frequencies ( f 1=1×10-6 Hz, f 2=4×10-6 Hz) that are responsible for the scattering of GCR particles with the rigidity range detected by neutron monitors. We found clear inverse correlations between ? and ? y or ? z when the time variations of the resonant frequencies were derived from in situ measurements of the solar wind velocity U sw and IMF strength B during 1968 - 2002. We argue that these inverse relations are a fundamental feature in the GCR modulation that is not restricted to the analyzed years of 1968 - 2002.

Siluszyk, M.; Iskra, K.; Alania, M. V.

2014-11-01

363

Probabilistic Assessment of Radiation Risk for Astronauts in Space Missions  

NASA Technical Reports Server (NTRS)

Accurate predictions of the health risks to astronauts from space radiation exposure are necessary for enabling future lunar and Mars missions. Space radiation consists of solar particle events (SPEs), comprised largely of medium energy protons, (less than 100 MeV); and galactic cosmic rays (GCR), which include protons and heavy ions of higher energies. While the expected frequency of SPEs is strongly influenced by the solar activity cycle, SPE occurrences themselves are random in nature. A solar modulation model has been developed for the temporal characterization of the GCR environment, which is represented by the deceleration potential, phi. The risk of radiation exposure from SPEs during extra-vehicular activities (EVAs) or in lightly shielded vehicles is a major concern for radiation protection, including determining the shielding and operational requirements for astronauts and hardware. To support the probabilistic risk assessment for EVAs, which would be up to 15% of crew time on lunar missions, we estimated the probability of SPE occurrence as a function of time within a solar cycle using a nonhomogeneous Poisson model to fit the historical database of measurements of protons with energy > 30 MeV, (phi)30. The resultant organ doses and dose equivalents, as well as effective whole body doses for acute and cancer risk estimations are analyzed for a conceptual habitat module and a lunar rover during defined space mission periods. This probabilistic approach to radiation risk assessment from SPE and GCR is in support of mission design and operational planning to manage radiation risks for space exploration.

Kim, Myung-Hee; DeAngelis, Giovanni; Cucinotta, Francis A.

2009-01-01

364

Early Energetic Particle Irradiation of the HED Parent Body Regolith  

NASA Technical Reports Server (NTRS)

Previous studies have shown that many individual grains within the dark phase of the Kapoeta howardite were irradiated with energetic particles while residing on the surface of the early HED regolith. Particle tracks in these grains vary in density by more than an order of magnitude and undoubtedly were formed by energetic heavy (Fe) ions associated with early solar flares. Early Irradiation of HED Regolith: Concentrations of excess Ne alone are not sufficient to decide between competing galactic and solar irradiation models. However, from recent studies of depth samples of oriented lunar rocks, we have shown that the cosmogenic 21-Ne/22-Ne ratio produced in feldspar differs substantially between Galactic Cosmic Radiation (GCR) and solar protons, and that this difference is exactly that predicted from cross-section data. Using Ne literature data and new isotopic data we obtained on acid-etched, separated feldspar from both the light and dark phases of Kapoeta, we derive 21-Ne/22-Ne = 0.80 for the recent GCR irradiation and 21-Ne/22-Ne = 0.68 for the early regolith irradiation. This derived ratio indicates that the early Ne production in the regolith occurred by both galactic and solar protons. If we adopt a likely one-component regolith model in which all grains were exposed to galactic protons but individual grains had variable exposure to solar protons, we estimate that this early GCR irradiation lasted for about 3-6 m.y. More complex two-component regolith models involving separate solar and galactic irradiation would permit this GCR age to be longer. Higher-energy solar protons would permit the GCR to be longer. Higher-energy solar protons would permit the GCR age to be shorter. Further, cosmogenic 126(Xe) in Kapoeta dark is no more than a factor of about 2 higher than that observed in Kapoeta light. Because 126(Xe) can only be formed by galactic protons and not solar protons, these data support a short GCR irradiation for the HED regolith. This would also be the maximum time peRiod for the solar irradiation. Various asteroidal regolith models, based on Monte Carlo modeling of impact rates as a function of size and on irradiation features of meteorites, predict surface exposure times of about 0.1 to 10 m.y., and depend on such factors as gravity, rock mechanical properties, and micrometeoroid flux. Because the depth at which solar Fe tracks are produced (is much less than 1 micrometer) is much less than the depth at which Solar Cosmic Rays (SCR) Ne is produced (about 1 cm), for a reasonably well-stirred HED regolith the "surface exposure time" for SCR 21-Ne production should be significantly longer than that for solar tracks and some other surface irradiation features. Enhanced Solar Proton Irradiation: For bulk samples of Kapoeta dark feldspar and a one-component regolith model, the derived ratio of 21-Ne/22-Ne = 0.68 implies that the early production ratio of SCR 21-Ne to GCR 21-Ne was about 0.5-1.5. This ratio is independent of any assumptions about the fraction of dark grains that are irradiated or of the variability in the degree of solar irradiation among grains. The 21-Ne SCR/GCR ratio indirectly derived from bulk Kapoeta pyroxene is somewhat larger, as is the ratio derived for simple two-component regolith models. Individual feldspar grains that were extensively solar irradiated would require even larger 21-Ne SCR/GCR production ratios. In contrast, the theoretical SCR/GCR production ratio for lunar feldspar with 0 g/CM2 shield ing is is less than or equal to 2, and the lowest ratio observed in near-surface samples of lunar anorthosites is less than or equal to 1. Considering the greater solar distance of Vesta (compared to the Moon), the likelihood that SCR 21-Ne was acquired under some shielding where production rates are lower, and the likelihood that the exposure time to galactic protons exceeded the exposure time to solar protons because of their very different penetration depths, the 21-Ne SCR/GCR production ratio on the HED parent body was probably < 0.1. The relatively large difference be

Bogard, D. D.; Garrison, D. H.; Rao, M. N.

1996-01-01

365

Short-term and Long-term Variations of Dose Rate measured by MSL/RAD  

NASA Astrophysics Data System (ADS)

The Radiation Assessment Detector (RAD), onboard Mars Science Laboratory’s (MSL) rover Curiosity, measures the spectra of both energetic charged and neutral particles along with radiation dose rate at the surface of Mars. Several effects have been observed for the first time to influence the Galactic Cosmic Ray (GCR)-driven particle radiation on the surface: [a] short-term diurnal variations of the Martian atmospheric pressure caused by daily thermal tides [Rafkin 2014]; [b] long-term seasonal pressure changes in the Martian atmosphere; and [c] the modulation of the primary GCR fluxes by the heliospheric magnetic field, which correlates with long-term solar activities and heliospheric rotation. These concurrent factors affect the dose rate variations measured by RAD on the Martian surface. RAD also recorded the dose rate during the 253-day cruise phase of MSL from the Earth to Mars. The variations of the GCR-induced dose rates during quiet time period without the direct detection of Solar Particle Events (SPE) were solely driven by the changes of heliospheric conditions (i.e. [c]). The RAD cruise and surface dose measurements, along with the surface pressure data and the solar modulation factor, are analysed in order to understand how the long-term influences ([b] and [c]) individually correlate with the measured dose rates.

Guo, Jingnan; Zeitlin, Cary; Rafkin, Scot; Boettcher, Stephan; Reitz, Guenther; Koehler, Jan; Ehresmann, Bent; Martin, Cesar; Burmeister, Soenke; Posner, Arik; Wimmer-Schweingruber, Robert; Hassler, Donald M.; Brinza, David; Boehm, Henning Eckart; Lohf, Henning; Appel, Jan

366

ISSCREM: International Space Station cosmic radiation exposure model  

NASA Astrophysics Data System (ADS)

A semi-empirical model is derived from operational data collected aboard the International Space Station (ISS) with the U.S. tissue equivalent proportional counter (TEPC). The model provides daily and cumulative mission predictions of the operational dose equivalent that space-crew may receive from galactic cosmic radiation (GCR) and trapped radiation (TR) sources as a function of the ISS orbit. The parametric model for GCR exposure correlates the TEPC dose equivalent rate to the cutoff rigidity at ISS altitudes while the TR parametric model relates this quantity to the mean atmospheric density at the crossing of the South Atlantic Anomaly (SAA). The influences of solar activity, flux asymmetry inside the SAA, detector orientation, and position aboard the ISS on the dose equivalent have been examined. The model has been successfully benchmarked against measured data for GCR and TR exposures to within ± 10% and ± 20%, respectively, over periods of time ranging from a single day to a full mission. In addition, preliminary estimates of the protection quantity of effective dose equivalent have been simulated using the PHITS Monte Carlo transport code. These simulations indicate that the TEPC dose equivalent is a conservative estimate of the effective dose equivalent.

El-Jaby, Samy; Lewis, Brent J.; Tomi, Leena; Sihver, Lembit; Sato, Tatsuhiko; Lee, Kerry T.; Johnson, A. Steve

367

Radiation Shielding Optimization on Mars  

NASA Technical Reports Server (NTRS)

Future space missions to Mars will require radiation shielding to be optimized for deep space transit and an extended stay on the surface. In deep space, increased shielding levels and material optimization will reduce the exposure from most solar particle events (SPE) but are less effective at shielding against galactic cosmic rays (GCR). On the surface, the shielding provided by the Martian atmosphere greatly reduces the exposure from most SPE, and long-term GCR exposure is a primary concern. Previous work has shown that in deep space, additional shielding of common materials such as aluminum or polyethylene does not significantly reduce the GCR exposure. In this work, it is shown that on the Martian surface, almost any amount of aluminum shielding increases exposure levels for humans. The increased exposure levels are attributed to neutron production in the shield and Martian regolith as well as the electromagnetic cascade induced in the Martian atmosphere. This result is significant for optimization of vehicle and shield designs intended for the surface of Mars.

Slaba, Tony C.; Mertens, Chris J.; Blattnig, Steve R.

2013-01-01

368

[Galactic heavy charged particles damaging effect on biological structures].  

PubMed

A concept of the radiation risk of the manned interplanetary flights is proposed and substantiated. Heavy charged particles that are a component of the galactic cosmic rays (GCR) have a high damaging effect on the biological structures as great amount of energy is deposited in heavy particle tracks. The high biological effectiveness of heavy ions is observed in their action on cell genetic structures and the whole organism, including the brain structures. The hippocampus is the part of the central nervous system that is the most sensitive to radiation--first of all, to heavy charged particles. Irradiation of animals with accelerated iron ions at doses corresponding to the real fluxes of GCR heavy nuclei, to which Mars mission crews can be exposed, leads to marked behavioral function disorders in the post-irradiation period. To evaluate the radiation risk for the interplanetary flight crews, the concept of successful mission accomplishment is introduced. In these conditions, the central nervous system structures can be the critical target of GCR heavy nuclei. Their damage can modify the higher integrative functions of the brain and cause disorders in the crew members' operator performances. PMID:23789432

Grigor'ev, A I; Krasavin, E A; Ostrovski?, M A

2013-03-01

369

Dielectronic recombination data for dynamic finite-density plasmas I. Goals and methodology  

E-print Network

A programme is outlined for the assembly of a comprehensive dielectronic recombination database within the generalized collisional--radiative (GCR) framework. It is valid for modelling ions of elements in dynamic finite-density plasmas such as occur in transient astrophysical plasmas such as solar flares and in the divertors and high transport regions of magnetic fusion devices. The resolution and precision of the data are tuned to spectral analysis and so are sufficient for prediction of the dielectronic recombination contributions to individual spectral line emissivities. The fundamental data are structured according to the format prescriptions of the Atomic Data and Analysis Structure (ADAS) and the production of relevant GCR derived data for application is described and implemented following ADAS. The requirements on the dielectronic recombination database are reviewed and the new data are placed in context and evaluated with respect to older and more approximate treatments. Illustrative results validate the new high-resolution zero-density dielectronic recombination data in comparison with measurements made in heavy-ion storage rings utilizing an electron cooler. We also exemplify the role of the dielectronic data on GCR coefficient behaviour for some representative light and medium weight elements.

N. R. Badnell; M. G. O'Mullane; H. P. Summers; Z. Altun; M. A. Bautista; J. Colgan; T. W. Gorczyca; D. M. Mitnik; M. S. Pindzola; O. Zatsarinny

2003-04-15

370

Designing Spacecraft and Mission Operations Plans to Meet Flight Crew Radiation Dose Requirements: Why is this an "Epic Challenge" for Long-Term Manned Interplanetary Flight  

NASA Technical Reports Server (NTRS)

Outline of presentation: (1) Radiation Shielding Concepts and Performance - Galactic Cosmic Rays (GCRs) (1a) Some general considerations (1b) Galactic Cosmic Rays (2)GCR Shielding I: What material should I use and how much do I need? (2a) GCR shielding materials design and verification (2b) Spacecraft materials point dose cosmic ray shielding performance - hydrogen content and atomic number (2c) Accelerator point dose materials testing (2d) Material ranking and selection guidelines (2e) Development directions and return on investment (point dose metric) (2f) Secondary particle showers in the human body (2f-1) limited return of investment for low-Z, high-hydrogen content materials (3) GCR shielding II: How much will it cost? (3a) Spacecraft design and verification for mission radiation dose to the crew (3b) Habitat volume, shielding areal density, total weight, and launch cost for two habitat volumes (3c) It's All about the Money - Historical NASA budgets and budget limits (4) So, what can I do about all this? (4a) Program Design Architecture Trade Space (4b) The Vehicle Design Trade Space (4c) Some Near Term Recommendations

Koontz, Steven

2012-01-01

371

Initiation-promotion model of tumor prevalence in mice from space radiation exposures  

NASA Technical Reports Server (NTRS)

Exposures in space consist of low-level background components from galactic cosmic rays (GCR), occasional intense-energetic solar-particle events, periodic passes through geomagnetic-trapped radiation, and exposure from possible onboard nuclear-propulsion engines. Risk models for astronaut exposure from such diverse components and modalities must be developed to assure adequate protection in future NASA missions. The low-level background exposures (GCR), including relativistic heavy ions (HZE), will be the ultimate limiting factor for astronaut career exposure. We consider herein a two-mutation, initiation-promotion, radiation-carcinogenesis model in mice in which the initiation stage is represented by a linear kinetics model of cellular repair/misrepair, including the track-structure model for heavy ion action cross-sections. The model is validated by comparison with the harderian gland tumor experiments of Alpen et al. for various ion beams. We apply the initiation-promotion model to exposures from galactic cosmic rays, using models of the cosmic-ray environment and heavy ion transport, and consider the effects of the age of the mice prior to and after the exposure and of the length of time in space on predictions of relative risk. Our results indicate that biophysical models of age-dependent radiation hazard will provide a better understanding of GCR risk than models that rely strictly on estimates of the initial slopes of these radiations.

Cucinotta, F. A.; Wilson, J. W.

1995-01-01

372

Cosmogenic nuclides in the Martian surface: Constraints for sample recovery and transport  

NASA Technical Reports Server (NTRS)

Stable and radioactive cosmogenic nuclides and radiation damage effects such as cosmic ray tracks can provide information on the surface history of Mars. A recent overview on developments in cosmogenic nuclide research for historical studies of predominantly extraterrestrial materials was published previously. The information content of cosmogenic nuclides and radiation damage effects produced in the Martian surface is based on the different ways of interaction of the primary galactic and solar cosmic radiation (GCR, SCR) and the secondary particle cascade. Generally the kind and extent of interactions as seen in the products depend on the following factors: (1) composition, energy and intensity of the primary SCR and GCR; (2) composition, energy and intensity of the GCR-induced cascade of secondary particles; (3) the target geometry, i.e., the spatial parameters of Martian surface features with respect to the primary radiation source; (4) the target chemistry, i.e., the chemical composition of the Martian surface at the sampling location down to the minor element level or lower; and (5) duration of the exposure. These factors are not independent of each other and have a major influence on sample taking strategies and techniques.

Englert, Peter A. J.

1988-01-01

373

Space Radiation Cancer Risks and Uncertainities for Different Mission Time Periods  

NASA Technical Reports Server (NTRS)

Space radiation consists of solar particle events (SPEs), comprised largely of medium energy protons (less than several hundred MeV); and galactic cosmic ray (GCR), which includes high energy protons and high charge and energy (HZE) nuclei. For long duration missions, space radiation presents significant health risks including cancer mortality. Probabilistic risk assessment (PRA) is essential for radiation protection of crews on long term space missions outside of the protection of the Earth s magnetic field and for optimization of mission planning and costs. For the assessment of organ dosimetric quantities and cancer risks, the particle spectra at each critical body organs must be characterized. In implementing a PRA approach, a statistical model of SPE fluence was developed, because the individual SPE occurrences themselves are random in nature while the frequency distribution of SPEs depends strongly upon the phase within the solar activity cycle. Spectral variability of SPEs was also examined, because the detailed energy spectra of protons are important especially at high energy levels for assessing the cancer risk associated with energetic particles for large events. An overall cumulative probability of a GCR environment for a specified mission period was estimated for the temporal characterization of the GCR environment represented by the deceleration potential (theta). Finally, this probabilistic approach to space radiation cancer risk was coupled with a model of the radiobiological factors and uncertainties in projecting cancer risks. Probabilities of fatal cancer risk and 95% confidence intervals will be reported for various periods of space missions.

Kim,Myung-Hee Y.; Cucinotta, Francis A.

2012-01-01

374

Use of Apollo 17 Epoch Neutron Spectrum as a Benchmark in Testing LEND Collimated Sensor  

NASA Technical Reports Server (NTRS)

The Apollo 17 neutron experiment LPNE provided a unique set of data on production of neutrons in the Lunar soil bombarded by Galactic Cosmic Rays (GCR). It serves as valuable "ground-truth" in the age of orbital remote sensing. We used the neutron data attributed to Apollo 17 epoch as a benchmark for testing the LEND's collimated sensor, as introduced by the geometry of collimator and efficiency of He3 counters. The latter is defined by the size of gas counter and pressure inside it. The intensity and energy spectrum of neutrons escaping the lunar surface are dependent on incident flux of Galactic Cosmic Rays (GCR) whose variability is associated with Solar Cycle and its peculiarities. We obtain first the share of neutrons entering through the field of view of collimator as a fraction of the total neutron flux by using the angular distribution of neutron exiting the Moon described by our Monte Carlo code. We computed next the count rate of the 3He sensor by using the neutron energy spectrum from McKinney et al. [JGR, 2006] and by consider geometry and gas pressure of the LEND sensor. Finally the neutron count rate obtained for the Apollo 17 epoch characterized by intermediate solar activity was adjusted to the LRO epoch characterized by low solar activity. It has been done by taking into account solar modulation potential, which affects the GCR flux, and in turn changes the neutron albedo flux.

Chin, Gordon; Sagdeev, R.; Milikh, G.

2011-01-01

375

Effects of Nuclear Cross Sections at Different Energies on Space Radiation Exposure from Galactic Cosmic Rays  

NASA Technical Reports Server (NTRS)

Space radiation from galactic cosmic rays (GCR) is a major hazard to space crews, especially in long duration human space explorations. For this reason, they will be protected by radiation shielding that fragments the GCR heavy ions. Here we investigate how sensitive the crew's radiation exposure is to nuclear fragmentation cross sections at different energies. We find that in deep space cross sections between about 0.2 and 1.2 GeV/u have the strongest effect on dose equivalent behind shielding in solar minimum GCR environments, and cross sections between about 0.6 and 1.7 GeV/u are the most important at solar maximum'. On the other hand, at the location of the International Space Station, cross sections at_higher -energies, between about 0.6 and 1.7 GeV /u at solar minimum and between about 1.7 and 3.4 GeV/u'at,solar maximum, are the most important This is. due-to the average geomagnetic cutoff for the ISS orbit. We also show the effect of uncertainties in the fragmentation cross sections on the elemental energy spectra behind shielding. These results help to focus the studies of fragmentation cross sections on the proper energy range in order to improve our predictions of crew exposures.

Li, Zi-Wei; Adams, James H., Jr.

2007-01-01

376

Calibration of the Galactic Cosmic Ray Flux  

NASA Technical Reports Server (NTRS)

We report first Xe data on the cross-calibration of I-129-Xe-129(sub n) ages with conventional CRE ages, a method which is expected to provide information on the long-term constancy of the galactic cosmic ray (GCR) flux. We studied isotopic signatures of Xe released in stepwise heating, decomposition and melting of troilites in the Cape York iron meteorite to identify isotopic shifts in Xe-129 and Xe-131 due to neutron capture in Te-128 and Te-130. We also resolve components due to extinct 129I, spallation and fission Xe. There has recently been much speculation on the constancy of GCR over long time scales, as may be inferred from iron meteorites. If GCRs originate from supernova events, this provides the basis for postulating increased fluxes at locations with higher than average densities of supernovae, specifically in OB-associations. The solar system at present appears to be inside a local bubble between spiral arms and may experience an increased GCR flux.

Mathew, K. J.; Marti, K.

2004-01-01

377

The role of the ejecta magnetic flux on the two-step Forbush decreases  

NASA Astrophysics Data System (ADS)

A Forbush Decrease (FD) is a depression in the Galactic Cosmic Ray (GCR) background intensity, and are usually associated to the passage of an Interplanetary Coronal Mass Ejection (ICME). Magnetic Clouds (MCs) are a subset of ICMEs that are well studied, and are known to cause the deepest FDs. Usually, FDs present two steps in the depression profile, one associated to the shock arrival, and a steeper one restricted to the duration of the ejecta passage. There is a wide variety of processes responsible for the GCR depressions. For instance: the enhanced solar wind (SW) convection, reduced diffusion coefficients, enhanced adiabatic cooling, increase of the coherent magnetic field, etc. Our aim is to make a selection of FD events filtering those associated to well studied magnetic structures, such as Magnetic Clouds (MCs), in order to minimize the mixing processes involved in the ICME-GCR interactions in the resulting sample, and to study statistical properties. We determine the parameters of each FD profile and look for correlations with the associated MC parameters. We propose a method to decompose the FD profile into shock and ejecta components, and investigate correlations with the associated amplitudes of the ejecta components. We introduce the parameter, ``magnetic flux per unit length F/L'', and investigate its importance in the context of a simple ``diffusive barrier'' model. According to the correlations found, the two-step events are better represented by the ``diffusive barrier'' model, and the flux F/L is the parameter that better correlates with these events.

Masías Meza, Jimmy; Dasso, Sergio

378

Galactic cosmic ray exposure estimates for SAGE-3 mission in polar orbit  

NASA Technical Reports Server (NTRS)

An analysis of the effects of galactic cosmic ray (GCR) exposures on charge-coupled devices (CCDs) was performed for the SAGE-III 5-year mission in sun-synchronous orbit between 1996 and 2001. A detailed environment model used in conjunction with a geomagnetic vertical cut-off code provides the predicted 5-year fluence of GCR ions. A computerized solid model of the spacecraft was used to define the effective shield thickness distribution around the CCD detector. The particle fluences at the detector location are calculated with the Langley heavy-ion transport code, and these fluences are used in conjunction with estimated nuclear stopping powers to evaluate dosimetric quantities related to the detector degradation. A previous study analyzing effects of trapped particle and solar flare protons indicated an approximate 20 percent reduction in detector sensitivity for the mission. The galactic cosmic ray contribution was thought to be relatively small and therefore was not previously analyzed. The present study provides quantification of the GCR effects, which are found to contribute less than 1 percent of the total environment degradation.

Nealy, John E.; Tipton, Bryan E.

1992-01-01

379

Polyethylene as a Radiation Shielding Standard in SimulatedCosmic-Ray Environments  

SciTech Connect

Radiation risk management for human space missions dependson accurate modeling of high-energy heavy ion transport in matter. Theprocess of nuclear fragmentation can play a key role in reducing both thephysical dose and the biological effectiveness of the radiationencountered in deep space. Hydrogenous materials and light elements areexpected to be more effective shields against the deleterious effects ofGalactic Cosmic Rays (GCR) than aluminum, which is used in currentspacecraft hulls. NASA has chosen polyethylene, CH2, as the referencematerial for accelerator-based radiation testing of multi-functioncomposites that are currently being developed. A detailed discussion ofthe shielding properties of polyethylene under a variety of relevantexperimental conditions is presented, along with Monte Carlo simulationsof the experiments and other Monte Carlo calculations in which the entireGCR flux is simulated. The Monte Carlo results are compared to theaccelerator data and we assess the usefulness of 1 GeV/amu 56Fe as aproxy for GCR heavy ions. We conclude that additional accelerator-basedmeasurements with higher beam energies would be useful.

Guetersloh, Stephen B.; Zeitlin, Cary; Heilbronn, Lawrence H.; Miller, Jack; Komiyama, Tatsudo; Fukumura, A.; Iwata, Y.; Murakami, T.; Bhattacharya M.

2006-08-19

380

Monte Carlo transport model comparison with 1A GeV accelerated iron experiment: heavy-ion shielding evaluation of NASA space flight-crew foodstuff  

NASA Technical Reports Server (NTRS)

Deep-space manned flight as a reality depends on a viable solution to the radiation problem. Both acute and chronic radiation health threats are known to exist, with solar particle events as an example of the former and galactic cosmic rays (GCR) of the latter. In this experiment Iron ions of 1A GeV are used to simulate GCR and to determine the secondary radiation field created as the GCR-like particles interact with a thick target. A NASA prepared food pantry locker was subjected to the iron beam and the secondary fluence recorded. A modified version of the Monte Carlo heavy ion transport code developed by Zeitlin at LBNL is compared with experimental fluence. The foodstuff is modeled as mixed nuts as defined by the 71st edition of the Chemical Rubber Company (CRC) Handbook of Physics and Chemistry. The results indicate a good agreement between the experimental data and the model. The agreement between model and experiment is determined using a linear fit to ordered pairs of data. The intercept is forced to zero. The slope fit is 0.825 and the R2 value is 0.429 over the resolved fluence region. The removal of an outlier, Z=14, gives values of 0.888 and 0.705 for slope and R2 respectively. c2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

Stephens, D. L. Jr; Townsend, L. W.; Miller, J.; Zeitlin, C.; Heilbronn, L.

2002-01-01

381

LISA Pathfinder test-mass charging during galactic cosmic-ray flux short-term variations  

NASA Astrophysics Data System (ADS)

Metal free-floating test masses aboard the future interferometers devoted to gravitational wave detection in space are charged by galactic and solar cosmic rays with energies \\gt 100 MeV/n. This process represents one of the main sources of noise in the lowest frequency band (\\lt 10-3 Hz) of these experiments. We study here the charging of the LISA Pathfinder (LISA-PF) gold-platinum test masses due to galactic cosmic-ray (GCR) protons and helium nuclei with the Fluka Monte Carlo toolkit. Projections of the energy spectra of GCRs during the LISA-PF operations in 2015 are considered. This work was carried out on the basis of the solar activity level and solar polarity epoch expected for LISA-PF. The effects of GCR short-term variations are evaluated here for the first time. Classical Forbush decreases, GCR variations induced by the Sun rotation, and fluctuations in the LISA-PF frequency bandwidth are discussed.

Grimani, C.; Fabi, M.; Lobo, A.; Mateos, I.; Telloni, D.

2015-02-01

382

First Cosmic Ray Proton Albedo Map of the Moon  

NASA Astrophysics Data System (ADS)

The Lunar Reconnaissance Orbiter (LRO) has been observing the surface and environment of the Moon since June of 2009. The CRaTER instrument (Cosmic Ray Telescope for the Effects of Radiation) on LRO is designed to characterize the lunar radiation environment and its effects on simulated human tissue. CRaTER's multiple solid-state detectors can be used to discriminate the different elements in the galactic cosmic ray (GCR) population above ~10 MeV/nucleon, and can also distinguish between primary GCR protons arriving from deep space from some secondary particles backscattered from the lunar surface (i.e., "albedo"). We use the previously reported strong presence of > 10 MeV protons coming up from the lunar surface to construct a proton albedo map of the Moon. The map accounts for time variation in the secondary particles driven by time variations in the primary GCR population, thus revealing any true spatial variation of the proton albedo with lunar surface properties such as gross mineralogical abundance differences between regolith in maria and highlands.

Wilson, J. K.; Spence, H.; Kasper, J.; Golightly, M.; Blake, J.; Mazur, J. E.; Townsend, L.; Case, A.; Looper, M. D.

2010-12-01

383

[Results of statistical analysis of the dynamics of ionizing radiation dose fields in the service module of the International Space Station in 2000-2012].  

PubMed

The on-going 24th solar cycle (SC) is distinguished from the previous ones by low activity. On the contrary, levels of proton fluxes from galactic cosmic rays (GCR) are high, which increases the proton flow striking the Earth's radiation belts (ERB). Therefore, at present the absorbed dose from ERB protons should be calculated with consideration of the tangible increase of protons intensity built into the model descriptions based on experimental measurements during the minimum between cycles 19 and 20, and the cycle 21 maximum. The absorbed dose from GCR and ERB protons copies galactic protons dynamics, while the ERB electrons dose copies SC dynamics. The major factors that determine the absorbed dose value are SC phase, ISS orbital altitude and shielding of the dosimeter readings of which are used in analysis. The paper presents the results of dynamic analysis of absorbed doses measured by a variety of dosimeters, namely, R-16 (2 ionization chambers), DB8-1, DB8-2, DB8-3, DB8-4 as a function of ISS orbit altitude and SC phase. The existence of annual variation in the absorbed dose dynamics has been confirmed; several additional variations with the periods of 17 and 52 months have been detected. Modulation of absorbed dose variations by the SC and GCR amplitudes has been demonstrated. PMID:25035897

Mitrikas, V G

2014-01-01

384

The Event Tunnel: Interactive Visualization of Complex Event Streams for Business Process Pattern Analysis  

Microsoft Academic Search

Event-based systems are gaining increasing popularity for building loosely coupled and distributed systems. Since business processes are becoming more interconnected and event-driven, event-based systems fit well for supporting and monitoring business processes. In this paper, we present an event-based business intelligence tool, the Event Tunnel framework. It provides an interactive visualiza- tion of event streams to support business analysts in

Martin Suntinger; Hannes Obweger; Josef Schiefer; M. Eduard Gröller

2008-01-01

385

Schema-based Scheduling of Event Processors and Buffer Minimization for Queries on Structured Data Streams  

Microsoft Academic Search

We introduce an extension of the XQuery lan- guage, FluX, that supports event-based query processing and the conscious handling of main memory buffers. Purely event-based queries of this language can be executed on stream- ing XML data in a very direct way. We then develop an algorithm that allows to efficiently rewrite XQueries into the event-based FluX language. This algorithm

Christoph Koch; Stefanie Scherzinger; Nicole Schweikardt; Bernhard Stegmaier

2004-01-01

386

An analytical model for the prediction of a micro-dosimeter response function  

NASA Astrophysics Data System (ADS)

A rapid analytical procedure for the prediction of a micro-dosimeter response function in low Earth orbit (LEO), correlated with the Space Transportation System (STS, shuttle) Tissue Equivalent Proportional Counter (TEPC) measurements is presented. The analytical model takes into consideration the energy loss straggling and chord length distribution of the detector, and is capable of predicting energy deposition fluctuations in a cylindrical micro-volume of arbitrary aspect ratio (height/diameter) by incoming ions through both direct and indirect (? ray) events. At any designated (ray traced) target point within the vehicle, the model accepts the differential flux spectrum of Galactic Cosmic Rays (GCRs) and/or trapped protons at LEO as input. On a desktop PC, the response function of TEPC for each ion in the GCR/trapped field is computed at the average rate of 30 s/ion. The ionizing radiation environment at LEO is represented by O'Neill's GCR model (2004), covering charged particles in the 1 ? Z ? 28 range. O'Neill's free space GCR model is coupled with the Langley Research Center (LaRC) angular dependent geomagnetic cutoff model to compute the transmission coefficient in LEO. The trapped proton environment is represented by a LaRC developed time dependent procedure which couples the AP8MIN/AP8MAX, Deep River Neutron Monitor (DRNM) and F10.7 solar radio frequency measurements. The albedo neutron environment is represented by the extrapolation of the Atmospheric Ionizing Radiation (AIR) measurements. The charged particle transport calculations correlated with STS 51 and 114 flights are accomplished by using the most recent version (2005) of the LaRC deterministic High charge ( Z) and Energy TRaNsport (HZETRN) code. We present the correlations between the TEPC model predictions (response function) and TEPC measured differential/integral spectra in the lineal energy ( y) domain for both GCR and trapped protons, with the conclusion that the model correctly accounts for the increase in flux at low y values where energetic ions are the primary contributor. We further discuss that, even with the incorporation of angular dependency in the cutoffs, comparison of the GCR differential/integral flux between STS 51 and 114 TEPC measured data and current calculations indicates that there still exists an underestimation by the simulations at low to mid range y values. This underestimation is partly related the exclusion of the secondary pion particle production from the current version of HZETRN.

Badavi, F. F.; Xapsos, M. A.; Wilson, J. W.

2009-07-01

387

A comparative study of continuous-time modelings for scheduling of crude oil operations  

E-print Network

A comparative study of continuous-time modelings for scheduling of crude oil operations Xuan Chena and formulations for the crude oil scheduling problem. We compare the event-based model, the unit slot model on its efficient performance for industrial problems. Keywords: Crude oil scheduling; event-based model

Grossmann, Ignacio E.

388

Coupled W-Os-Pt isotope systematics in IVB iron meteorites: In situ neutron dosimetry for W isotope chronology  

NASA Astrophysics Data System (ADS)

Tungsten isotope compositions of magmatic iron meteorites yield ages of differentiation that are within ±2 Ma of the formation of CAIs, with the exception of IVB irons that plot to systematically less radiogenic compositions yielding erroneously old ages. Secondary neutron capture due to galactic cosmic ray (GCR) irradiation is known to lower the ?182W of iron meteorites, adequate correction of which requires a measure of neutron dosage which has not been available, thus far. The W, Os and Pt isotope systematics of 12 of the 13 known IVB iron meteorites were determined by MC-ICP-MS (W, Os, Pt) and TIMS (Os). On the same dissolutions that yield precise ?182W, stable Os and Pt isotopes were determined as in situ neutron dosimeters for empirical correction of the ubiquitous cosmic-ray induced burn-out of 182W in iron meteorites. The W isotope data reveal a main cluster with ?182W of ˜-3.6, but a much larger range than observed in previous studies including irons (Weaver Mountains and Warburton Range) that show essentially no cosmogenic effect on their ?182W. The IVB data exhibits resolvable negative anomalies in ?189Os (-0.6?) and complementary ?190Os anomalies (+0.4?) in Tlacotepec due to neutron capture on 189Os which has approximately the same neutron capture cross section as 182W, and captures neutrons to produce 190Os. The least irradiated IVB iron, Warburton Range, has ?189Os and ?190Os identical to terrestrial values. Similarly, Pt isotopes, which are presented as ?192Pt, ?194Pt and ?196Pt range from +4.4? to +53?, +1.54? to -0.32? and +0.73? to -0.20?, respectively, also identify Tlacotepec and Dumont as the most GCR-damaged samples. In W-Os and W-Pt isotope space, the correlated isotope data back-project toward a 0-epsilon value of ?192Pt, ?189Os and ?190Os from which a pre-GCR irradiation ?182W of -3.42±0.09 (2?) is derived. This pre-GCR irradiation ?182W is within uncertainty of the currently accepted CAI initial ?182W. The Pt and Os isotope correlations in the IVB irons are in good agreement with a nuclear model for spherical irons undergoing GCR spallation, although this model over-predicts the change of ?182W by ˜2×, indicating a need for better W neutron capture cross section determinations. A nucleosynthetic effect in ?184W in these irons of -0.14±0.08 is confirmed, consistent with the presence of Mo and Ru isotope anomalies in IVB irons. The lack of a non-GCR Os isotope anomaly in these irons requires more complex explanations for the production of W, Ru and Mo anomalies than nebular heterogeneity in the distribution of s-process to r-process nuclides.

Wittig, N.; Humayun, M.; Brandon, A. D.; Huang, S.; Leya, I.

2013-01-01

389

Solar Drivers of 11-yr and Long-Term Cosmic Ray Modulation  

NASA Astrophysics Data System (ADS)

In the current paradigm for the modulation of galactic cosmic rays (GCRs), diffusion is taken to be the dominant process during solar maxima while drift dominates at minima. Observations during the recent solar minimum challenge the pre-eminence of drift at such times. In 2009, the ˜2 GV GCR intensity measured by the Newark neutron monitor increased by ˜5% relative to its maximum value two cycles earlier even though the average tilt angle in 2009 was slightly larger than that in 1986 (˜20° vs. ˜14°), while solar wind B was significantly lower (˜3.9 nT vs. ˜5.4 nT). A decomposition of the solar wind into high-speed streams, slow solar wind, and coronal mass ejections (CMEs; including post-shock flows) reveals that the Sun transmits its message of changing magnetic field (diffusion coefficient) to the heliosphere primarily through CMEs at solar maximum and high-speed streams at solar minimum. Long-term reconstructions of solar wind B are in general agreement for the ˜1900-present interval and can be used to reliably estimate GCR intensity over this period. For earlier epochs, however, a recent 10Be-based reconstruction covering the past ˜104 years shows nine abrupt and relatively short-lived drops of B to ?0 nT, with the first of these corresponding to the Spörer minimum. Such dips are at variance with the recent suggestion that B has a minimum or floor value of ˜2.8 nT. A floor in solar wind B implies a ceiling in the GCR intensity (a permanent modulation of the local interstellar spectrum) at a given energy/rigidity. The 30-40% increase in the intensity of 2.5 GV electrons observed by Ulysses during the recent solar minimum raises an interesting paradox that will need to be resolved.

Cliver, E. W.; Richardson, I. G.; Ling, A. G.

2013-06-01

390

Probabilistic Assessment of Cancer Risk from Solar Particle Events  

NASA Astrophysics Data System (ADS)

For long duration missions outside of the protection of the Earth's magnetic field, space radi-ation presents significant health risks including cancer mortality. Space radiation consists of solar particle events (SPEs), comprised largely of medium energy protons (less than several hundred MeV); and galactic cosmic ray (GCR), which include high energy protons and heavy ions. While the frequency distribution of SPEs depends strongly upon the phase within the solar activity cycle, the individual SPE occurrences themselves are random in nature. We es-timated the probability of SPE occurrence using a non-homogeneous Poisson model to fit the historical database of proton measurements. Distributions of particle fluences of SPEs for a specified mission period were simulated ranging from its 5th to 95th percentile to assess the cancer risk distribution. Spectral variability of SPEs was also examined, because the detailed energy spectra of protons are important especially at high energy levels for assessing the cancer risk associated with energetic particles for large events. We estimated the overall cumulative probability of GCR environment for a specified mission period using a solar modulation model for the temporal characterization of the GCR environment represented by the deceleration po-tential (?). Probabilistic assessment of cancer fatal risk was calculated for various periods of lunar and Mars missions. This probabilistic approach to risk assessment from space radiation is in support of mission design and operational planning for future manned space exploration missions. In future work, this probabilistic approach to the space radiation will be combined with a probabilistic approach to the radiobiological factors that contribute to the uncertainties in projecting cancer risks.

Kim, Myung-Hee Y.; Cucinotta, Francis A.

391

Neutron density profile in the lunar subsurface produced by galactic cosmic rays  

NASA Astrophysics Data System (ADS)

Neutron production by galactic cosmic rays (GCR) in the lunar subsurface is very important when performing lunar and planetary nuclear spectroscopy and space dosimetry. Further im-provements to estimate the production with increased accuracy is therefore required. GCR, which is a main contributor to the neutron production in the lunar subsurface, consists of not only protons but also of heavy components such as He, C, N, O, and Fe. Because of that, it is important to precisely estimate the neutron production from such components for the lunar spectroscopy and space dosimetry. Therefore, the neutron production from GCR particles in-cluding heavy components in the lunar subsurface was simulated with the Particle and Heavy ion Transport code System (PHITS), using several heavy ion interaction models. This work presents PHITS simulations of the neutron density as a function of depth (neutron density profile) in the lunar subsurface and the results are compared with experimental data obtained by Apollo 17 Lunar Neutron Probe Experiment (LNPE). From our previous study, it has been found that the accuracy of the proton-induced neutron production models is the most influen-tial factor when performing precise calculations of neutron production in the lunar subsurface. Therefore, a benchmarking of proton-induced neutron production models against experimental data was performed to estimate and improve the precision of the calculations. It was found that the calculated neutron production using the best model of Cugnon Old (E < 3 GeV) and JAM (E > 3 GeV) gave up to 30% higher values than experimental results. Therefore, a high energy nuclear data file (JENDL-HE) was used instead of the Cugnon Old model at the energies below 3 GeV. Then, the calculated neutron density profile successfully reproduced the experimental data from LNPE within experimental errors of 15% (measurement) + 30% (systematic). In this presentation, we summarize and discuss our calculated results of neutron production in the lunar subsurface.

Ota, Shuya; Sihver, Lembit; Kobayashi, Shingo; Hasebe, Nobuyuki

392

Daytime restricted feeding modifies 24 h rhythmicity and subcellular distribution of liver glucocorticoid receptor and the urea cycle in rat liver.  

PubMed

The timing system in mammals is formed by a set of peripheral biological clocks coordinated by a light-entrainable pacemaker located in the suprachiasmatic nucleus. Daytime restricted feeding (DRF) modifies the circadian control and uncouples the light-dependent physiological rhythmicity, food access becoming the principal external time cue. In these conditions, an alternative biological clock is expressed, the food-entrainable oscillator (FEO). Glucocorticoid hormones are an important part of the humoral mechanisms in the daily synchronisation of the metabolic response of peripheral oscillators by the timing system. A peak of circulating corticosterone has been reported before food access in DRF protocols. In the present study we explored in the liver the 24 h variations of: (1) the subcellular distribution of glucocorticoid receptor (GCR), (2) the activities of the corticosterone-forming and NADPH-generating enzymes (11?-hydroxysteroid dehydrogenase type 1 (11?-HSD-1) and hexose-6-phosphate dehydrogenase (H6PDH)), and, (3) parameters related with the urea cycle (circulating urea and activities of carbamoyl phosphate synthetase and ornithine transcarbamylase) elicited by DRF. The results showed that DRF promoted an increase of more than two times of the hepatic GCR, but exclusively in the cytosolic compartment, since the GCR in the nuclear fraction showed a reduction. No changes were observed in the activities of 11?-HSD-1 and H6PDH, but the rhythmicity of all of the urea cycle-related parameters was modified. It is concluded that liver glucocorticoid signalling and the urea cycle are responsive to feeding-restricted schedules and could be part of the FEO. PMID:22456310

Luna-Moreno, Dalia; García-Ayala, Braulio; Díaz-Muñoz, Mauricio

2012-12-14

393

Solar Drivers of 11-yr and Long-Term Cosmic Ray Modulation  

NASA Technical Reports Server (NTRS)

In the current paradigm for the modulation of galactic cosmic rays (GCRs), diffusion is taken to be the dominant process during solar maxima while drift dominates at minima. Observations during the recent solar minimum challenge the pre-eminence of drift: at such times. In 2009, the approx.2 GV GCR intensity measured by the Newark neutron monitor increased by approx.5% relative to its maximum value two cycles earlier even though the average tilt angle in 2009 was slightly larger than that in 1986 (approx.20deg vs. approx.14deg), while solar wind B was significantly lower (approx.3.9 nT vs. approx.5.4 nT). A decomposition of the solar wind into high-speed streams, slow solar wind, and coronal mass ejections (CMEs; including postshock flows) reveals that the Sun transmits its message of changing magnetic field (diffusion coefficient) to the heliosphere primarily through CMEs at solar maximum and high-speed streams at solar minimum. Long-term reconstructions of solar wind B are in general agreement for the approx. 1900-present interval and can be used to reliably estimate GCR intensity over this period. For earlier epochs, however, a recent Be-10-based reconstruction covering the past approx. 10(exp 4) years shows nine abrupt and relatively short-lived drops of B to < or approx.= 0 nT, with the first of these corresponding to the Sporer minimum. Such dips are at variance with the recent suggestion that B has a minimum or floor value of approx.2.8 nT. A floor in solar wind B implies a ceiling in the GCR intensity (a permanent modulation of the local interstellar spectrum) at a given energy/rigidity. The 30-40% increase in the intensity of 2.5 GV electrons observed by Ulysses during the recent solar minimum raises an interesting paradox that will need to be resolved.

Cliver, E. W.; Richardson, I. G.; Ling, A. G.

2011-01-01

394

Space Weather Nowcasting of Atmospheric Ionizing Radiation for Aviation Safety  

NASA Technical Reports Server (NTRS)

There is a growing concern for the health and safety of commercial aircrew and passengers due to their exposure to ionizing radiation with high linear energy transfer (LET), particularly at high latitudes. The International Commission of Radiobiological Protection (ICRP), the EPA, and the FAA consider the crews of commercial aircraft as radiation workers. During solar energetic particle (SEP) events, radiation exposure can exceed annual limits, and the number of serious health effects is expected to be quite high if precautions are not taken. There is a need for a capability to monitor the real-time, global background radiations levels, from galactic cosmic rays (GCR), at commercial airline altitudes and to provide analytical input for airline operations decisions for altering flight paths and altitudes for the mitigation and reduction of radiation exposure levels during a SEP event. The Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) model is new initiative to provide a global, real-time radiation dosimetry package for archiving and assessing the biologically harmful radiation exposure levels at commercial airline altitudes. The NAIRAS model brings to bear the best available suite of Sun-Earth observations and models for simulating the atmospheric ionizing radiation environment. Observations are utilized from ground (neutron monitors), from the atmosphere (the METO analysis), and from space (NASA/ACE and NOAA/GOES). Atmospheric observations provide the overhead shielding information and the ground- and space-based observations provide boundary conditions on the GCR and SEP energy flux distributions for transport and dosimetry simulations. Dose rates are calculated using the parametric AIR (Atmospheric Ionizing Radiation) model and the physics-based HZETRN (High Charge and Energy Transport) code. Empirical models of the near-Earth radiation environment (GCR/SEP energy flux distributions and geomagnetic cut-off rigidity) are benchmarked against the physics-based CMIT (Coupled Magnetosphere- Ionosphere-Thermosphere) and SEP-trajectory models.

Mertens, Christopher J.; Wilson, John W.; Blattnig, Steve R.; Solomon, Stan C.; Wiltberger, J.; Kunches, Joseph; Kress, Brian T.; Murray, John J.

2007-01-01

395

NAIRAS aircraft radiation model development, dose climatology, and initial validation  

NASA Astrophysics Data System (ADS)

The Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) is a real-time, global, physics-based model used to assess radiation exposure to commercial aircrews and passengers. The model is a free-running physics-based model in the sense that there are no adjustment factors applied to nudge the model into agreement with measurements. The model predicts dosimetric quantities in the atmosphere from both galactic cosmic rays (GCR) and solar energetic particles, including the response of the geomagnetic field to interplanetary dynamical processes and its subsequent influence on atmospheric dose. The focus of this paper is on atmospheric GCR exposure during geomagnetically quiet conditions, with three main objectives. First, provide detailed descriptions of the NAIRAS GCR transport and dosimetry methodologies. Second, present a climatology of effective dose and ambient dose equivalent rates at typical commercial airline altitudes representative of solar cycle maximum and solar cycle minimum conditions and spanning the full range of geomagnetic cutoff rigidities. Third, conduct an initial validation of the NAIRAS model by comparing predictions of ambient dose equivalent rates with tabulated reference measurement data and recent aircraft radiation measurements taken in 2008 during the minimum between solar cycle 23 and solar cycle 24. By applying the criterion of the International Commission on Radiation Units and Measurements (ICRU) on acceptable levels of aircraft radiation dose uncertainty for ambient dose equivalent greater than or equal to an annual dose of 1 mSv, the NAIRAS model is within 25% of the measured data, which fall within the ICRU acceptable uncertainty limit of 30%. The NAIRAS model predictions of ambient dose equivalent rate are generally within 50% of the measured data for any single-point comparison. The largest differences occur at low latitudes and high cutoffs, where the radiation dose level is low. Nevertheless, analysis suggests that these single-point differences will be within 30% when a new deterministic pion-initiated electromagnetic cascade code is integrated into NAIRAS, an effort which is currently underway.

Mertens, Christopher J.; Meier, Matthias M.; Brown, Steven; Norman, Ryan B.; Xu, Xiaojing

2013-10-01

396

Probabilistic Assessment of Cancer Risk from Solar Particle Events  

NASA Technical Reports Server (NTRS)

For long duration missions outside of the protection of the Earth s magnetic field, space radiation presents significant health risks including cancer mortality. Space radiation consists of solar particle events (SPEs), comprised largely of medium energy protons (less than several hundred MeV); and galactic cosmic ray (GCR), which include high energy protons and heavy ions. While the frequency distribution of SPEs depends strongly upon the phase within the solar activity cycle, the individual SPE occurrences themselves are random in nature. We estimated the probability of SPE occurrence using a non-homogeneous Poisson model to fit the historical database of proton measurements. Distributions of particle fluences of SPEs for a specified mission period were simulated ranging from its 5 th to 95th percentile to assess the cancer risk distribution. Spectral variability of SPEs was also examined, because the detailed energy spectra of protons are important especially at high energy levels for assessing the cancer risk associated with energetic particles for large events. We estimated the overall cumulative probability of GCR environment for a specified mission period using a solar modulation model for the temporal characterization of the GCR environment represented by the deceleration potential (^). Probabilistic assessment of cancer fatal risk was calculated for various periods of lunar and Mars missions. This probabilistic approach to risk assessment from space radiation is in support of mission design and operational planning for future manned space exploration missions. In future work, this probabilistic approach to the space radiation will be combined with a probabilistic approach to the radiobiological factors that contribute to the uncertainties in projecting cancer risks.

Kim, Myung-Hee Y.; Cucinotta, Francis A.

2010-01-01

397

Estimation of Effective Doses for Radiation Cancer Risks on ISS, Lunar, and Mars Missions with Space Radiation Measurement  

NASA Technical Reports Server (NTRS)

Radiation protection practices define the effective dose as a weighted sum of equivalent dose over major sites for radiation cancer risks. Since a crew personnel dosimeter does not make direct measurement of effective dose, it has been estimated with skin-dose measurements and radiation transport codes for ISS and STS missions. The Phantom Torso Experiment (PTE) of NASA s Operational Radiation Protection Program has provided the actual flight measurements of active and passive dosimeters which were placed throughout the phantom on STS-91 mission for 10 days and on ISS Increment 2 mission. For the PTE, the variation in organ doses, which is resulted by the absorption and the changes in radiation quality with tissue shielding, was considered by measuring doses at many tissue sites and at several critical body organs including brain, colon, heart, stomach, thyroid, and skins. These measurements have been compared with the organ dose calculations obtained from the transport models. Active TEPC measurements of lineal energy spectra at the surface of the PTE also provided the direct comparison of galactic cosmic ray (GCR) or trapped proton dose and dose equivalent. It is shown that orienting the phantom body as actual in ISS is needed for the direct comparison of the transport models to the ISS data. One of the most important observations for organ dose equivalent of effective dose estimates on ISS is the fractional contribution from trapped protons and GCR. We show that for most organs over 80% is from GCR. The improved estimation of effective doses for radiation cancer risks will be made with the resultant tissue weighting factors and the modified codes.

Kim, M.Y.; Cucinotta, F.A.

2005-01-01

398

EXPOSE-R cosmic radiation time profile  

NASA Astrophysics Data System (ADS)

The aim of the paper is to present the time profile of cosmic radiation exposure obtained by the radiation risks radiometer-dosimeter (R3DR) during the ESA exposition facility for EXPOSE-R mission (EXPOSE-R) in the EXPOSE-R facility outside the Russian Zvezda module of the International Space Station (ISS). Another aim is to make the obtained results available to other EXPOSE-R teams for use in their data analysis. R3DR is a low mass and small dimensions automated device, which measures solar radiation in four channels and in addition cosmic ionizing radiation. The main results of cosmic ionizing radiation measurements are: three different radiation sources were detected and quantified: galactic cosmic rays (GCR), energetic protons from the inner radiation belt (IRB) in the region of the South Atlantic anomaly and energetic electrons from the outer radiation belt (ORB). The highest daily averaged absorbed dose rate of 506 ?Gy day-1 came from IRB protons; GCR delivered much smaller daily absorbed dose rates of 81.4 ?Gy day-1 on average, and ORB source delivered on average a dose rate of 89 ?Gy day-1. The IRB and ORB daily averaged absorbed dose rates were higher than those observed during the ESA exposition facility for EXPOSE-E mission (EXPOSE-E), whereas the GCR rate was smaller than that measured during the EXPOSE-E mission. The reason for this difference is much less surrounding constructions shielding of the R3DR instrument in comparison with the R3DE instrument.

Dachev, Tsvetan; Horneck, Gerda; Häder, Donat-Peter; Schuster, Martin

2015-01-01

399

Evaluations of Risks from the Lunar and Mars Radiation Environments  

NASA Technical Reports Server (NTRS)

Protecting astronauts from the space radiation environments requires accurate projections of radiation in future space missions. Characterization of the ionizing radiation environment is challenging because the interplanetary plasma and radiation fields are modulated by solar disturbances and the radiation doses received by astronauts in interplanetary space are likewise influenced. The galactic cosmic radiation (GCR) flux for the next solar cycle was estimated as a function of interplanetary deceleration potential, which has been derived from GCR flux and Climax neutron monitor rate measurements over the last 4 decades. For the chaotic nature of solar particle event (SPE) occurrence, the mean frequency of SPE at any given proton fluence threshold during a defined mission duration was obtained from a Poisson process model using proton fluence measurements of SPEs during the past 5 solar cycles (19-23). Analytic energy spectra of 34 historically large SPEs were constructed over broad energy ranges extending to GeV. Using an integrated space radiation model (which includes the transport codes HZETRN [1] and BRYNTRN [2], and the quantum nuclear interaction model QMSFRG[3]), the propagation and interaction properties of the energetic nucleons through various media were predicted. Risk assessment from GCR and SPE was evaluated at the specific organs inside a typical spacecraft using CAM [4] model. The representative risk level at each event size and their standard deviation were obtained from the analysis of 34 SPEs. Risks from different event sizes and their frequency of occurrences in a specified mission period were evaluated for the concern of acute health effects especially during extra-vehicular activities (EVA). The results will be useful for the development of an integrated strategy of optimizing radiation protection on the lunar and Mars missions. Keywords: Space Radiation Environments; Galactic Cosmic Radiation; Solar Particle Event; Radiation Risk; Risk Analysis; Radiation Protection.

Kim, Myung-Hee; Hayat, Matthew J.; Feiveson, Alan H.; Cucinotta, Francis A.

2008-01-01

400

Temporal Changes in the Rigidity Spectrum of Forbush Decreases Based on Neutron Monitor Data  

NASA Astrophysics Data System (ADS)

The Forbush decrease (Fd) of the Galactic cosmic ray (GCR) intensity and disturbances in the Earth's magnetic field generally take place simultaneously and are caused by the same phenomenon, namely a coronal mass ejection (CME) or a shock wave created after violent processes in the solar atmosphere. The magnetic cut-off rigidity of the Earth's magnetic field changes because of the disturbances, leading to additional changes in the GCR intensity observed by neutron monitors and muon telescopes. Therefore, one may expect distortion in the temporal changes in the power-law exponent of the rigidity spectrum calculated from neutron monitor data without correcting for the changes in the cut-off rigidity of the Earth's magnetic field. We compare temporal changes in the rigidity spectrum of Fds calculated from neutron monitor data corrected and uncorrected for the geomagnetic disturbances. We show some differences in the power-law exponent of the rigidity spectrum of Fds, particularly during large disturbances of the cut-off rigidity of the Earth's magnetic field. However, the general features of the temporal changes in the rigidity spectrum of Fds remain valid as they were found in our previous study. Namely, at the initial phase of the Fd, the rigidity spectrum is relatively soft and it gradually becomes hard up to the time of the minimum level of the GCR intensity. Then during the recovery phase of the Fd, the rigidity spectrum gradually becomes soft. This confirms that the structural changes of the interplanetary magnetic field turbulence in the range of frequencies of 10-6 - 10-5 Hz are generally responsible for the time variations in the rigidity spectrum we found during the Fds.

Alania, M. V.; Wawrzynczak, A.; Sdobnov, V. E.; Kravtsova, M. V.

2013-09-01

401

A stochastic simulation of the propagation of Galactic cosmic rays reflecting the discreteness of cosmic ray sources Age and path length distribution  

NASA Astrophysics Data System (ADS)

Aims: The path length distribution of Galactic cosmic rays (GCRs) is the fundamental ingredient for modeling the propagation process of GCRs based on the so-called weighted slab method. We try to derive this distribution numerically by taking into account the discreteness in both space and time of occurrences of supernova explosions where GCRs are suspected to be born. The resultant age distribution and ratio of B/C are to be compared with recent observations. Methods: We solve numerically the stochastic differential equations equivalent to the Parker diffusion-convection equation which describes the propagation process of GCR in the Galaxy. We assume the three-dimensional diffusion is an isotropic one without any free escape boundaries. We ignore any energy change of GCRs and the existence of the Galactic wind for simplicity. We also assume axisymmetric configurations for the density distributions of the interstellar matter and for the surface density of supernovae. We have calculated age and path length of GCR protons arriving at the solar system with this stochastic method. The obtained age is not the escape time of GCRs from the Galaxy as usually assumed, but the time spent by GCRs during their journey to the solar system from the supernova remnants where they were born. Results: The derived age and path length show a distribution spread in a wide range even for GCR protons arriving at the solar system with the same energy. The distributions show a cut-off at a lower range in age or path length depending on the energy of GCRs. These cut-offs clearly come from the discreteness of occurrence of supernovae. The mean age of GeV particles obtained from the distributions is consistent with the age obtained by direct observation of radioactive secondary nuclei. The energy dependence of the B/C ratio estimated with the path length distribution reproduces reliably the energy dependence of B/C obtained by recent observations in space.

Miyake, S.; Muraishi, H.; Yanagita, S.

2015-01-01

402

Validation of Galactic Cosmic Radiation and Geomagnetic Transmissions  

NASA Technical Reports Server (NTRS)

The Alpha Magnet Spectrometer (AMS) was flown on Shuttle flight STS-91 in June 1998 near solar minimum. This unique spectrometer has provided very high resolution, calibrated data on the galactic hydrogen and helium rigidity spectra form approx. 100 MeV/n to approx. 200 GeV/n as a function of magnetic latitude. This paper describes a comparison of the AMS data with the Badhwar-O'Neill GCR model and the geomagnetic transmission calculated using the quiescent DGRF 1990 cutoffs. The results have strong bearing on radiation modeling for the International Space Station.

Badhwar, Gautam D.; Troung, A.; ONeill, P.; Bman, B.

2000-01-01

403

Galactic cosmic rays measured by UVS on Voyager 1 and the end of the modulation. Is the upwind heliopause a collapsed charge-exchange layer?  

NASA Astrophysics Data System (ADS)

The detectors of the Ultraviolet Spectrographs (UVS) on Voyager 1/2 are recording a background intensity that was earlier assigned mainly to disintegrations in the radio-isotope thermoelectric generator and systematically subtracted from the signal to infer photon counting. Here, we show that it arises instead from galactic cosmic rays (GCRs). We show the GCR flux measured by UVS on Voyager 1 from 1992 to August 2013, and by comparing to data from the GCR dedicated detectors, we estimate the energy range responsible for this UVS signal, which is around 300 MeV, and the response of UVS to the GCR anisotropy. After the abrupt jumps of May and August 2012, the count rate has been only slightly fluctuating around a constant value. However, comparing it to the data from the Low Energy Charge Particle Experiment (LECP) and the Cosmic Ray Subsystem (CRS) shows that those small variations are only responses to a varying anisotropy and not to a flux change. Taking advantage of the similarity in energy range to one of the products of the CRS instrument suite, we use the ratio between the two independent signals as a proxy for the temporal evolution of the GCR spectral slope around the 300 MeV range. We show that this slope remained unchanged since August 2012 and find strong evidence that it will no longer vary, implying the end of the heliospheric modulation at those energies, and that Voyager 1 at this date is near or past the heliopause. The origin of this unexpectedly narrow and stagnating inner heliosheath is still unclear, and we discuss the potential effects of low solar wind speed episodes and subsequent self-amplified charge-exchange with interstellar neutrals, as a source of deceleration and collapse. We suggest that the quasi-static region encountered by Voyager 1 may be related to such effects, triggered by the strong solar-maximum variability. This did not happen for Voyager 2 due to its trajectory at an angle further from the heliosphere axis and a later termination shock crossing. The existence on the upwind side of a mixing layer formed by charge transfer instead of a pure plasma contact discontinuity could explain various Voyager 1 observations.

Lallement, R.; Bertaux, J. L.; Quémerais, E.; Sandel, B. R.

2014-03-01

404

Gas Core Reactor-MHD Power System with Cascading Power Cycle  

SciTech Connect

The US Department of Energy initiative Gen-IV aim is to produce an entire nuclear energy production system with next generation features for certification before 2030. A Generation 4 capable system must have superior sustainability, safety and reliability, and economic cost advantages in comparison with third generation light water reactors. A gas core reactor (GCR) with magnetohydrodynamic (MHD) power converter and cascading power cycle forms the basis for a Generation IV concept that is expected to set the upper performance limits in sustainability and power conversion efficiency among all existing and proposed fission powered systems. A gaseous core reactor delivering 1000's MW fission power acts as the heat source for a high temperature magnetohydrodynamic power converter. A uranium tetrafluoride fuel mix, with {approx}95% mole fraction helium gas, provides a stable working fluid for the primary MHD-Brayton cycle. A helium Brayton cycle extracts waste heat from the MHD generator with about 20% energy efficiency, but the low temperature side is still hot enough ({approx}1600 K) to drive a second conventional helium Brayton cycle with about 35% efficiency. There is enough heat at the low temperature side of the He-Brayton cycle to generate steam, and so another heat recovery cycle can be added, this time a Rankine steam cycle with up to 40% efficiency. The proof of concept does not require a tremendously efficient (first law) MHD cycle, the high temperature direct energy conversion capability of an MHD dynamo, combined with already sophisticated steam powered turbine industry knowledge base allows the cascading cycle design to achieve break-through first law energy efficiencies previously unheard of in the nuclear power industry. Although simple in concept, the gas core reactor design has not achieved the state of technological maturity that, say, molten salt or high-temperature gas-cooled reactors have pioneered. However, even on paper the GCR-MHD concept holds considerable promise, for example, like molten salt reactors the fuel is continuously cycled, allowing high-burnup, and continuous burning of actinides, and hence greatly improved fuel utilization. The fuel inventory is two orders of magnitude lower than LWR's of comparable power output and fissile plutonium production is likewise lower than in spent LWR fuel. Besides these features this paper discusses specific GCR-MHD design challenges such as fission enhanced gas conductivity in the MHD channel, GCR safety issues and related engineering problems. (authors)

Smith, Blair M.; Anghaie, Samim; Knight, Travis W. [Innovative Nuclear Space Power and Propulsion Institute, University of Florida, PO Box 116502, Gainesville, FL, 32611 (United States)

2002-07-01

405

Miniaturized Gas Correlation Radiometer for the Detection of Trace Gases in the Martian Atmosphere  

NASA Technical Reports Server (NTRS)

We present a miniaturized and simplified version of a gas correlation radiometer (GCR) capable of simultaneously mapping multiple trace gases and identifying active regions on the Mars surface. Gas correlation radiometry (GCR) has been shown to be a sensitive and versatile method for detecting trace gases in Earth's atmosphere. Reduction of the size and mass of the GCR was achieved by implementing compact, light-weight 1 mm inner diameter hollow-core optical fibers (hollow waveguides) as the gas correlation cells. In a comparison with an Earth orbiting CO2 GCR instrument, exchanging the 10 m multipass cells with hollow waveguide gas correlation cells of equivalent path length reduces the mass from approximately 150 kg to approximately 0.5 kg, and reduces the volume from 1.9 m x 1.3 m x 0.86 m to a small bundle of fiber coils approximately 1 meter in diameter by 0.05 m in height (mass and volume reductions of greater than 99%). A unique feature of this instrument is its stackable module design, with a single module for each trace gas. Each of the modules is self-contained, and fundamentally identical; differing by the bandpass filter wavelength range and gas mixtures inside the hollow-waveguide absorption cells. The current configuration contains four stacked modules for simultaneous measurements of methane (CH4), formaldehyde (H2CO), water vapor (H2O), and deuterated water vapor (HDO) but could easily be expanded to include measurements of additional species of interest including nitrous oxide (N2O), hydrogen sulfide (H2S), methanol (CH3OH), and sulfur dioxide (SO2), as well as carbon dioxide (CO2) for a simultaneous measure of mass balance. Preliminary results indicate that a 1 ppb detection limit is possible for both formaldehyde and methane with one second of averaging. Using non-optimized components, we have demonstrated an instrument sensitivity equivalent to approximately 30 ppb for formaldehyde, and approximately 500 ppb for methane. We expect custom bandpass filters and 6 m long waveguides to significantly improve these promising results. Ongoing testing is being conducted on water vapor and deuterated water vapor.

Melroy, Hilary R.; Wilson, Emily L.; Georgieva, Elena

2012-01-01

406

Computational Nuclear Forensics Analysis of Weapons-grade Plutonium Separated from Fuel Irradiated in a Thermal Reactor  

E-print Network

Energies. ............................................................................................................. 19 4 Description of Indian 220 MWe PHWR Full Core.23 ........................................ 21 5 Sketch of a Single 19... of Spent Fuel Discharged From Power Reactors2 Reactor Type Fuel burn-up (GWd/tU) Isotopic Composition (%) 239Pu 240Pu 241Pu 242Pu GCR 3.6 77.9 18.1 3.5 0.5 PHWR 7.5 66.4 26.9 5.1 1.5 AGR 18 53.7 30.8 9.9 5.0 RBMK 20 50.2 33.7 10.2 3.3 BWR...

Coles, Taylor Marie

2014-04-27

407

[Individual characteristics of correction of the cosmonauts' vegetative status with a method of adaptive biofeedback  

NASA Technical Reports Server (NTRS)

The ability of 4 cosmonauts to voluntarily control their physiological parameters during the standing test was evaluated following a series of the adaptive feedback (AF) training sessions. Vegetative status of the cosmonauts during voluntary "relaxation" and "straining" was different when compared with its indices determined before these sessions. In addition, there was a considerable individual variability in the intensity and direction of the AF effects, and the range of parameters responding to AF. It was GCR which was the easiest one for the AF control.

Kornilova, L. N.; Cowings, P.; Arlashchenko, N. I.; Korneev, D. Iu; Sagalovich, S. V.; Sarantseva, A. V.; Toscano, W.; Kozlovskaia, I. B.

2003-01-01

408

MARIE Measurements and Model Predictions of Solar Modulation of Galactic Cosmic Rays at Mars  

NASA Technical Reports Server (NTRS)

Recent data from the MARIE (Martian Radiation Environment Experiment) instrument on board the 2001 Mars Odyssey spacecraft currently in Mars orbit are presented. It is shown that the short-term modulations of galactic cosmic rays (GCR) are well described by correlating the so lar modulation parameter, <1>, with Earth-based neutron monitor counts using a 85-day time lag and the NASA Models - HZETRN (High Z and Energy Transport) and QMSFRG (Quantum Multiple Scattering theory of nuclear Fragmentation). The dose rates observed by the MARIE instrument are within 10% of the model calculations.

Saganti, P. B.; Cucinotta, F. A.; Zeitlin, C. J.; Cleghorn, T. F.; Hu, X.; Lee, K. T.

2003-01-01

409

Radiation: Physical Characterization and Environmental Measurements  

NASA Technical Reports Server (NTRS)

In this session, Session WP4, the discussion focuses on the following topics: Production of Neutrons from Interactions of GCR-Like Particles; Solar Particle Event Dose Distributions, Parameterization of Dose-Time Profiles; Assessment of Nuclear Events in the Body Produced by Neutrons and High-Energy Charged Particles; Ground-Based Simulations of Cosmic Ray Heavy Ion Interactions in Spacecraft and Planetary Habitat Shielding Materials; Radiation Measurements in Space Missions; Radiation Measurements in Civil Aircraft; Analysis of the Pre-Flight and Post-Flight Calibration Procedures Performed on the Liulin Space Radiation Dosimeter; and Radiation Environment Monitoring for Astronauts.

1997-01-01

410

Charge spectra of cosmic ray nuclei measured with CR-39 detectors in low earth orbit  

NASA Astrophysics Data System (ADS)

Galactic Cosmic Rays (GCR) nuclei play an important role in the radiation exposure of humans in Low Earth Orbit (LEO). CR-39 nuclear track detectors have been successfully used to measure the charge spectrum of cosmic rays and related radiation dose in LEO. The method for measuring charge spectrum is based on the analysis of the etch rate gradient and effective etch rate ratio, along with calibration by high-energy heavy ions at particle accelerators. Here we report our results obtained in the interior of spacecraft for the STS-108, STS-112 and ISS-7S missions. Comparisons have been made between experimental and theoretical predictions and show good agreement.

Zhou, D.; O'Sullivan, D.; Semones, E.; Weyland, M.

2006-08-01

411

Monte Carlo Analysis of Pion Contribution to Absorbed Dose from Galactic Cosmic Rays  

NASA Technical Reports Server (NTRS)

Accurate knowledge of the physics of interaction, particle production and transport is necessary to estimate the radiation damage to equipment used on spacecraft and the biological effects of space radiation. For long duration astronaut missions, both on the International Space Station and the planned manned missions to Moon and Mars, the shielding strategy must include a comprehensive knowledge of the secondary radiation environment. The distribution of absorbed dose and dose equivalent is a function of the type, energy and population of these secondary products. Galactic cosmic rays (GCR) comprised of protons and heavier nuclei have energies from a few MeV per nucleon to the ZeV region, with the spectra reaching flux maxima in the hundreds of MeV range. Therefore, the MeV - GeV region is most important for space radiation. Coincidentally, the pion production energy threshold is about 280 MeV. The question naturally arises as to how important these particles are with respect to space radiation problems. The space radiation transport code, HZETRN (High charge (Z) and Energy TRaNsport), currently used by NASA, performs neutron, proton and heavy ion transport explicitly, but it does not take into account the production and transport of mesons, photons and leptons. In this paper, we present results from the Monte Carlo code MCNPX (Monte Carlo N-Particle eXtended), showing the effect of leptons and mesons when they are produced and transported in a GCR environment.

Aghara, S.K.; Battnig, S.R.; Norbury, J.W.; Singleterry, R.C.

2009-01-01

412

Space Radiation Cancer Risks and Uncertainties for Mars Missions  

NASA Technical Reports Server (NTRS)

Projecting cancer risks from exposure to space radiation is highly uncertain because of the absence of data for humans and because of the limited radiobiology data available for estimating late effects from the high-energy and charge (HZE) ions present in the galactic cosmic rays (GCR). Cancer risk projections involve many biological and physical factors, each of which has a differential range of uncertainty due to the lack of data and knowledge. We discuss an uncertainty assessment within the linear-additivity model using the approach of Monte Carlo sampling from subjective error distributions that represent the lack of knowledge in each factor to quantify the overall uncertainty in risk projections. Calculations are performed using the space radiation environment and transport codes for several Mars mission scenarios. This approach leads to estimates of the uncertainties in cancer risk projections of 400-600% for a Mars mission. The uncertainties in the quality factors are dominant. Using safety standards developed for low-Earth orbit, long-term space missions (>90 days) outside the Earth's magnetic field are currently unacceptable if the confidence levels in risk projections are considered. Because GCR exposures involve multiple particle or delta-ray tracks per cellular array, our results suggest that the shape of the dose response at low dose rates may be an additional uncertainty for estimating space radiation risks.

Cucinotta, F. A.; Schimmerling, W.; Wilson, J. W.; Peterson, L. E.; Badhwar, G. D.; Saganti, P. B.; Dicello, J. F.

2001-01-01

413

Radiation environment at LEO orbits: MC simulation and experimental data.  

NASA Astrophysics Data System (ADS)

The evaluations of the different components of the radiation environment in spacecraft, both in LEO orbits and in deep space is of great importance because the biological effect on humans and the risk for instrumentation strongly depends on the kind of radiation (high or low LET). That is important especially in view of long term manned or unmanned space missions, (mission to Mars, solar system exploration). The study of space radiation field is extremely complex and not completely solved till today. Given the complexity of the radiation field, an accurate dose evaluation should be considered an indispensable part of any space mission. Two simulation codes (MCNPX and GEANT4) have been used to assess the secondary radiation inside FO-TON M3 satellite and ISS. The energy spectra of primary radiation at LEO orbits have been modelled by using various tools (SPENVIS, OMERE, CREME96) considering separately Van Allen protons, the GCR protons and the GCR alpha particles. This data are used as input for the two MC codes and transported inside the spacecraft. The results of two calculation meth-ods have been compared. Moreover some experimental results previously obtained on FOTON M3 satellite by using TLD, Bubble dosimeter and LIULIN detector are considered to check the performances of the two codes. Finally the same experimental device are at present collecting data on the ISS (ASI experiment BIOKIS -nDOSE) and at the end of the mission the results will be compared with the calculation.

Zanini, Alba; Borla, Oscar; Damasso, Mario; Falzetta, Giuseppe

414

Getting ready for the manned mission to Mars: the astronauts' risk from space radiation.  

PubMed

Space programmes are shifting towards planetary exploration and, in particular, towards missions by human beings to the Moon and to Mars. Radiation is considered to be one of the major hazards for personnel in space and has emerged as the most critical issue to be resolved for long-term missions both orbital and interplanetary. The two cosmic sources of radiation that could impact a mission outside the Earth's magnetic field are solar particle events (SPE) and galactic cosmic rays (GCR). Exposure to the types of ionizing radiation encountered during space travel may cause a number of health-related problems, but the primary concern is related to the increased risk of cancer induction in astronauts. Predictions of cancer risk and acceptable radiation exposure in space are extrapolated from minimal data and are subject to many uncertainties. The paper describes present-day estimates of equivalent doses from GCR and solar cosmic radiation behind various shields and radiation risks for astronauts on a mission to Mars. PMID:17235598

Hellweg, Christine E; Baumstark-Khan, Christa

2007-07-01

415

Benchmark Evaluation of the HTR-PROTEUS Absorber Rod Worths (Core 4)  

SciTech Connect

PROTEUS was a zero-power research reactor at the Paul Scherrer Institute (PSI) in Switzerland. The critical assembly was constructed from a large graphite annulus surrounding a central cylindrical cavity. Various experimental programs were investigated in PROTEUS; during the years 1992 through 1996, it was configured as a pebble-bed reactor and designated HTR-PROTEUS. Various critical configurations were assembled with each accompanied by an assortment of reactor physics experiments including differential and integral absorber rod measurements, kinetics, reaction rate distributions, water ingress effects, and small sample reactivity effects [1]. Four benchmark reports were previously prepared and included in the March 2013 edition of the International Handbook of Evaluated Reactor Physics Benchmark Experiments (IRPhEP Handbook) [2] evaluating eleven critical configurations. A summary of that effort was previously provided [3] and an analysis of absorber rod worth measurements for Cores 9 and 10 have been performed prior to this analysis and included in PROTEUS-GCR-EXP-004 [4]. In the current benchmark effort, absorber rod worths measured for Core Configuration 4, which was the only core with a randomly-packed pebble loading, have been evaluated for inclusion as a revision to the HTR-PROTEUS benchmark report PROTEUS-GCR-EXP-002.

John D. Bess; Leland M. Montierth

2014-06-01

416

Time Profile of Cosmic Radiation Exposure During the EXPOSE-E Mission: The R3DE Instrument  

PubMed Central

Abstract The aim of this paper is to present the time profile of cosmic radiation exposure obtained by the Radiation Risk Radiometer-Dosimeter during the EXPOSE-E mission in the European Technology Exposure Facility on the International Space Station's Columbus module. Another aim is to make the obtained results available to other EXPOSE-E teams for use in their data analysis. Radiation Risk Radiometer-Dosimeter is a low-mass and small-dimension automatic device that measures solar radiation in four channels and cosmic ionizing radiation as well. The main results of the present study include the following: (1) three different radiation sources were detected and quantified—galactic cosmic rays (GCR), energetic protons from the South Atlantic Anomaly (SAA) region of the inner radiation belt, and energetic electrons from the outer radiation belt (ORB); (2) the highest daily averaged absorbed dose rate of 426 ?Gy d?1 came from SAA protons; (3) GCR delivered a much smaller daily absorbed dose rate of 91.1 ?Gy d?1, and the ORB source delivered only 8.6 ?Gy d?1. The analysis of the UV and temperature data is a subject of another article (Schuster et al., 2012). Key Words: Ionizing radiation—R3D—ISS. Astrobiology 12, 403–411. PMID:22680687

Horneck, Gerda; Häder, Donat-Peter; Schuster, Martin; Richter, Peter; Lebert, Michael; Demets, Rene

2012-01-01

417

Depth Dependency of Neutron Density Produced by Galactic Cosmic Rays in the Lunar Subsurface  

NASA Astrophysics Data System (ADS)

Neutron production by galactic cosmic rays (GCR) in the lunar subsurface plays an important role in the radiation environment on the surface and subsurface of the Moon and to make its accurate estimation is therefore very important for lunar and planetary nuclear spectroscopy and space dosimetry. In this work, the depth dependency of neutron production from protons and alpha particles in galactic cosmic ray (GCR) was estimated using the three-dimensional particle and heavy ion transport simulation code PHITS incorporating the latest high energy nuclear data, JENDL-HE. Our estimation of equilibrium neutron density profiles in the lunar subsurface was compared with the experimental data obtained by Apollo 17 Lunar Neutron Probe Experiment (LNPE). In our former study, it was shown that the proton-induced neutron production cross sections had the largest influence on the accuracy of the neutron production estimation. Therefore, we made an extensive comparison of proton-nucleus reaction models incorporated in PHITS using some experimental data and selected the best combination of JENDL-HE at the energy < 3 GeV and JAM model above it. As the results, our calculation successfully reproduced the LNPE data within experimental errors of 15% (measurement) + 30% (systematic).

Ota, Shuya

2012-07-01

418

Analysis of MIR-18 results for physical and biological dosimetry: radiation shielding effectiveness in LEO  

NASA Technical Reports Server (NTRS)

We compare models of radiation transport and biological response to physical and biological dosimetry results from astronauts on the Mir space station. Transport models are shown to be in good agreement with physical measurements and indicate that the ratio of equivalent dose from the Galactic Cosmic Rays (GCR) to protons is about 3/2:1 and that this ratio will increase for exposures to internal organs. Two biological response models are used to compare to the Mir biodosimetry for chromosome aberration in lymphocyte cells; a track-structure model and the linear-quadratic model with linear energy transfer (LET) dependent weighting coefficients. These models are fit to in vitro data for aberration formation in human lymphocytes by photons and charged particles. Both models are found to be in reasonable agreement with data for aberrations in lymphocytes of Mir crew members: however there are differences between the use of LET dependent weighting factors and track structure models for assigning radiation quality factors. The major difference in the models is the increased effectiveness predicted by the track model for low charge and energy ions with LET near 10 keV/micrometers. The results of our calculations indicate that aluminum shielding, although providing important mitigation of the effects of trapped radiation, provides no protective effect from the galactic cosmic rays (GCR) in low-earth orbit (LEO) using either equivalent dose or the number of chromosome aberrations as a measure until about 100 g/cm 2 of material is used.

Cucinotta, F. A.; Wilson, J. W.; Williams, J. R.; Dicello, J. F.

2000-01-01

419

IDAHO NATIONAL LABORATORY PROGRAM TO OBTAIN BENCHMARK DATA ON THE FLOW PHENOMENA IN A SCALED MODEL OF A PRISMATIC GAS-COOLED REACTOR LOWER PLENUM FOR THE VALIDATION OF CFD CODES  

SciTech Connect

The experimental program that is being conducted at the Matched Index-of-Refraction (MIR) Flow Facility at Idaho National Laboratory (INL) to obtain benchmark data on measurements of flow phenomena in a scaled model of a typical prismatic gas-cooled (GCR) reactor lower plenum using 3-D Particle Image Velocimetry (PIV) is presented. A detailed description of the model, scaling, the experimental facility, 3-D PIV system, measurement uncertainties and analysis, experimental procedures and samples of the data sets that have been obtained are included. Samples of the data set that are presented include mean-velocity-field and turbulence data in an approximately 1:7 scale model of a region of the lower plenum of a typical prismatic GCR design. This experiment has been selected as the first Standard Problem endorsed by the Generation IV International Forum. Results concentrate on the region of the lower plenum near its far reflector wall (away from the outlet duct). Inlet jet Reynolds numbers (based on the jet diameter and the time-mean average flow rate) are approximately 4,300 and 12,400. The measurements reveal undeveloped, non-uniform flow in the inlet jets and complicated flow patterns in the model lower plenum. Data include three-dimensional vector plots, data displays along the coordinate planes (slices) and charts that describe the component flows at specific regions in the model. Information on inlet flow is also presented.

Hugh M. McIlroy Jr.; Donald M. McEligot; Robert J. Pink

2008-09-01

420

Benchmark Analysis of Pion Contribution from Galactic Cosmic Rays  

NASA Technical Reports Server (NTRS)

Shielding strategies for extended stays in space must include a comprehensive resolution of the secondary radiation environment inside the spacecraft induced by the primary, external radiation. The distribution of absorbed dose and dose equivalent is a function of the type, energy and population of these secondary products. A systematic verification and validation effort is underway for HZETRN, which is a space radiation transport code currently used by NASA. It performs neutron, proton and heavy ion transport explicitly, but it does not take into account the production and transport of mesons, photons and leptons. The question naturally arises as to what is the contribution of these particles to space radiation. The pion has a production kinetic energy threshold of about 280 MeV. The Galactic cosmic ray (GCR) spectra, coincidentally, reaches flux maxima in the hundreds of MeV range, corresponding to the pion production threshold. We present results from the Monte Carlo code MCNPX, showing the effect of lepton and meson physics when produced and transported explicitly in a GCR environment.

Aghara, Sukesh K.; Blattnig, Steve R.; Norbury, John W.; Singleterry, Robert C., Jr.

2008-01-01

421

Low dose radiation hypersensitivity and clustered DNA damages in human fibroblasts exposed to low dose and dose rate protons or 137CS y-rays  

SciTech Connect

Effective radioprotection for human space travelers hinges upon understanding the individual properties of charged particles. A significant fraction of particle radiation astronauts will encounter in space exploratory missions will come from high energy protons in galactic cosmic radiation (GCR) and/or possible exposures to lower energy proton flux from solar particle events (SPEs). These potential exposures present major concerns for NASA and others, in planning and executing long term space exploratory missions. We recently reported cell survival and transformation (acquisition of anchorage-independent growth in soft agar) frequencies in apparently normal NFF-28 primary human fibroblasts exposed to 0-30 cGy of 50MeV, 100MeV (SPE-like), or 1000 MeV (GCR-like) monoenergetic protons. These were modeled after 1989 SPE energies at an SPE-like low dose-rate (LDR) of 1.65 cGy/min or high dose rate (HDR) of 33.3 cGy/min delivered at the NASA Space Radiation Laboratory (NSRL) at BNL.

Bennett P. V.; Bennett, P.V.; Keszenman, D.J.; Johnson, A.M.; Sutherland, B.M.; Wilson, P.F.

2013-05-14

422

Cosmic Ray Origin: Lessons from Ultra-High-Energy Cosmic Rays and the Galactic/Extragalactic Transition  

NASA Astrophysics Data System (ADS)

We examine the question of the origin of the Galactic cosmic-rays (GCRs) in the light of the data available at the highest energy end of the spectrum. We argue that the data of the Pierre Auger Observatory and of the KASCADE-Grande experiment suggest that the transition between the Galactic and the extragalactic components takes place at the energy of the ankle in the all-particle cosmic-ray spectrum, and at an energy of the order of 1017 eV for protons. Such a high energy for Galactic protons appears difficult to reconcile with the general view that GCRs are accelerated by the standard diffusive shock acceleration process at the forward shock of individual supernova remnants (SNRs). We also review various difficulties of the standard SNR-GCR connection, related to the evolution of the light element abundances and to significant isotopic anomalies. We point out that most of the power injected by the supernovæ in the Galaxy is actually released inside superbubbles, which may thus play an important role in the origin of cosmic-rays, and could solve some persistent problems of the standard SNR-GCR scenario in a rather natural way.

Parizot, Etienne

2014-11-01

423

Response of the Earth’s lower ionosphere to the Ground Level Enhancement event of December 13, 2006  

NASA Astrophysics Data System (ADS)

In this study we analyze the Ground Level Enhancement Event No 70 observed on December 13, 2006, by correlating the observations from two research topics: Cosmic rays and Very Low Frequency (VLF < 30 kHz) wave propagation, as two ground based techniques for the detection of solar proton events, and their impact on the lower ionosphere. The observations have been endorsed from recordings of worldwide network ground based Neutron Monitors as well as by satellite data from the satellites GOES 12 (www.swpc.noaa.gov) and Pamela (www.pamela.roma2infn.it). We have evaluated the ionization rate for protons in the altitude range relevant to VLF propagation, and for galactic cosmic ray (GCR) background, finding that at energies up to ˜2 GeV the ionization rate of solar protons exceeded the GCR ionization by 1.5 orders of magnitude. We have applied the Long Wave Propagation Capability (LWPC) code to evaluate the enhancement of the electron density from VLF signal perturbation and have inferred corresponding electron densities from the evaluated ionization rates and effective recombination coefficients from literature, to find the two independent sets in good agreement.

Žigman, Vida; Kudela, Karel; Grubor, Davorka

2014-03-01

424

Solar-flare implanted He-4/He-3 and solar-proton-produced Ne and Ar concentration profiles preserved in lunar rock 61016  

NASA Technical Reports Server (NTRS)

Depth profiles for Ne-21, Ne-22, and Ar-38 isotopes from oriented lunar rock 61016 are reported. Concentration profiles of cosmogenic GCR+SCR (Galactic cosmic ray and solar cosmic ray-produced) isotopes are determined, quantitatively resolving neon and argon produced by energetic solar flares from that produced by Galactic cosmic rays. The SCR component is resolved from the GCR component as a function of shielding, and excellent agreement is found between experimental SCR production profiles for the isotopes and theoretically calculated values. A characteristic SW He-4/He-3 ratio of 3450 +/- 81, representing energies down to as few keV/amu. In slightly deeper samples an SRF He-4/He-3 ratio of 3450 +/- 725 is found for He particles with E larger than about 1 MeV/amu. These results indicate that the isotopic composition of SF He, averaged over the long term, is energy-dependent. An implanted Ne-20/Ne-22 ratio of 12.4 is measured in unetched samples, representing E greater than 1 MeV/amu, and a ratio of 11.6 is inferred in the samples, representing E larger than about 5 MeV/amu.

Rao, M. N.; Garrison, D. H.; Bogard, D. D.; Reedy, R. C.

1993-01-01

425

3D Visualization of Solar Disk: Mars Radiation Environment 2003-2008  

NASA Astrophysics Data System (ADS)

During 2002 and 2003, MARIE (Martian Radiation Environment Experiment) instrument onboard the 2001 Mars Odyssey spacecraft provided some unique data from the Martian orbit. The orbit alignment of Mars- Sun-Earth provided an opportunity between 180° (August 2002) and 0° (October 2003). During this time, the MARIE data included the background GCR (Galactic Cosmic Rays) and several SPE (Solar Particle Events) enhanced radiation dose-rate measurements at Mars. Nearly 40 times increase in the quiet- time GCR dose-rate was noted from 25 mrad/day to nearly 1000 mrad/day at Mars. Understanding the active regions on the Sun that are likely to result into SPE on the far side will also be of concern for future deep space explorations beyond LEO. We present our approach in depicting SPE with 3D visualization of solar disks facing Mars and Earth. We present the assessment of SPE activity between 2003 and 2008 towards Mars along with an estimated dose-rate during an SPE at Mars along with heliosphere distribution.

Saganti, P. B.; Erickson, G. M.; Cucinotta, F. A.

2008-12-01

426

Biomarker Response to Galactic Cosmic Ray-Induced NOx and the Methane Greenhouse Effect in the Atmosphere of an Earthlike Planet Orbiting an M-Dwarf Star  

E-print Network

Planets orbiting in the habitable zone (HZ) of M-Dwarf stars are subject to high levels of galactic cosmic rays (GCRs) which produce nitrogen oxides in earthlike atmospheres. We investigate to what extent this NOx may modify biomarker compounds such as ozone (O3) and nitrous oxide (N2O), as well as related compounds such as water (H2O) (essential for life) and methane (CH4) (which has both abiotic and biotic sources) . Our model results suggest that such signals are robust, changing in the M-star world atmospheric column by up to 20% due to the GCR NOx effects compared to an M-star run without GCR effects and can therefore survive at least the effects of galactic cosmic rays. We have not however investigated stellar cosmic rays here. CH4 levels are about 10 times higher than on the Earth related to a lowering in hydroxyl (OH) in response to changes in UV. The increase is less than reported in previous studies. This difference arose partly because we used different biogenic input. For example, we employed 23% ...

Grenfell, J L; Patzer, B; Rauer, H; Segura, A; Stadelmann, A; Stracke, B; Titz, R; Von Paris, P; Grenfell, John Lee; Griessmeier, Jean-Mathias; Patzer, Beate; Rauer, Heike; Segura, Antigona; Stadelmann, Anja; Stracke, Barbara; Titz, Ruth; Paris, Philip von

2007-01-01

427