Monte Carlo simulation of the operational quantities at the realistic mixed neutron-photon radiation fields CANEL and SIGMA.

PubMed

Lacoste, V; Gressier, V

2007-01-01

The Institute for Radiological Protection and Nuclear Safety owns two facilities producing realistic mixed neutron-photon radiation fields, CANEL, an accelerator driven moderator modular device, and SIGMA, a graphite moderated americium-beryllium assembly. These fields are representative of some of those encountered at nuclear workplaces, and the corresponding facilities are designed and used for calibration of various instruments, such as survey meters, personal dosimeters or spectrometric devices. In the framework of the European project EVIDOS, irradiations of personal dosimeters were performed at CANEL and SIGMA. Monte Carlo calculations were performed to estimate the reference values of the personal dose equivalent at both facilities. The Hp(10) values were calculated for three different angular positions, 0 degrees, 45 degrees and 75 degrees, of an ICRU phantom located at the position of irradiation.

FIRE Arctic Clouds Experiment

NASA Technical Reports Server (NTRS)

Curry, J. A.; Hobbs, P. V.; King, M. D.; Randall, D. A.; Minnis, P.; Issac, G. A.; Pinto, J. O.; Uttal, T.; Bucholtz, A.; Cripe, D. G.;

Space radiation incident on SATS missions

NASA Technical Reports Server (NTRS)

Stassinopoulos, E. G.

1973-01-01

A special orbital radiation study was conducted in order to evaluate mission encountered energetic particle fluxes. This information is to be supplied to the project subsystem engineers for their guidance in designing flight hardware to withstand the expected radiation levels. Flux calculations were performed for a set of 20 nominal trajectories placed at several altitudes and inclinations. Temporal variations in the ambient electron environment were considered and partially accounted for. Magnetic field calculations were performed with a current field model, extrapolated to the tentative SATS launch epoch with linear time terms. Orbital flux integrations ware performed with the latest proton and electron environment models, using new computational methods. The results are presented in graphical and tabular form. Estimates of energetic solar proton fluxes are given for a one year mission at selected integral energies ranging from 10 to 100 Mev, calculated for a year of maximum solar activity during the next solar cycle.

The effect of unsteady blade loading on the aeroacoustics of a pusher propeller

NASA Astrophysics Data System (ADS)

Mauk, Clay S.; Farokhi, Saeed

1993-06-01

A theoretical/computational approach is developed to predict the change in near-field noise due to a momentum-deficit upstream of a propeller plane, specifically for a pylon wake in a pusher configuration. The acoustic pressure is computed using blade geometry and unsteady blade surface pressure history. The steady blade surface pressure is predicted using blade-momentum theory and two-dimensional airfoil characteristics. Unsteady blade pressures are derived from in-flight measurements. In-flight acoustic measurements are used for code validation purposes. Overall sound pressure levels (OSPL) are computed for an array of observer locations parallel to the propeller axis of rotation. In order to clearly realize the effect of the wake encounter on the radiated sound, the wake signature is eliminated from the unsteady blade pressures. By subtracting the OSPL computed with the smoothed data from that computed with the original unsteady data, the change in noise resulting from the wake encounter is deduced. In general, the noise was increased due to the propeller-wake chopping activity. For all flight conditions, the largest increase in radiated noise occurred for a highly loaded propeller. The results indicate that the propeller noise due to periodic wake encounter may possess a unique directivity pattern.

Three-dimensional aspects of radiative transfer in remote sensing of precipitation: Application to the 1986 COHMEX storm

NASA Technical Reports Server (NTRS)

Haferman, J. L.; Krajewski, W. F.; Smith, T. F.

1994-01-01

Several multifrequency techniques for passive microwave estimation of precipitation based on the absorption and scattering properties of hydrometers have been proposed in the literature. In the present study, plane-parallel limitations are overcome by using a model based on the discrete-ordinates method to solve the radiative transfer equation in three-dimensional rectangular domains. This effectively accounts for the complexity and variety of radiation problems encountered in the atmosphere. This investigation presents result for plane-parallel and three-dimensional radiative transfer for a precipitating system, discusses differences between these results, and suggests possible explanations for these differences. Microphysical properties were obtained from the Colorado State University Regional Atmospehric Modeling System and represent a hailstorm observed during the 1986 Cooperative Huntsville Meteorological Experiment. These properties are used as input to a three-dimensional radiative transfer model in order to simulate satellite observation of the storm. The model output consists of upwelling brightness temperatures at several of the frequencies on the Special Sensor Microwave/Imager. The radiative transfer model accounts for scattering and emission of atmospheric gases and hydrometers in liquid and ice phases. Brightness temperatures obtained from the three-dimensional model of this investigation indicate that horizontal inhomogeneities give rise to brightness temperature fields that can be quite different from fields obtained using plane-parallel radiative transfer theory. These differences are examined for various resolutions of the satellite sensor field of view. In adddition, the issue of boundary conditions for three-dimensional atmospheric radiative transfer is addressed.

Avionics electromagnetic interference immunity and environment

NASA Technical Reports Server (NTRS)

Clarke, C. A.

1986-01-01

Aircraft electromagnetic spectrum and radio frequency (RF) field strengths are charted, profiling the higher levels of electromagnetic voltages encountered by the commercial aircraft wiring. Selected military, urban, and rural electromagnetic field levels are plotted and provide a comparison of radiation amplitudes. Low frequency magnetic fields and electric fields from 400 H(Z) power systems are charted versus frequency and wire separation to indicate induced voltages on adjacent or neighboring circuits. Induced EMI levels and attenuation characteristics of electric, magnetic, RF fields, and transients are plotted and graphed for common types of wire circuits. The significance of wire circuit returns and shielding is emphasized to highlight the techniques that help block the paths of electromagnetic interference and maintain avionic interface signal quality.

Birth of millisecond pulsars in globular clusters

NASA Technical Reports Server (NTRS)

Grindlay, J. E.; Bailyn, C. D.

1988-01-01

It is argued here that accretion-induced collapse of white dwarfs in binaries can form millisecond pulsars directly without requiring a precursor low-mass X-ray binary stage. Ablation of the precollapse binary companion by the millisecond pulsar's radiation field, a process invoked to explain some of the characteristics of the recently discovered eclipsing millisecond pulsar, can then yield isolated neutron stars witout requiring an additional stellar encounter.

On The Detection Of Footprints From Strong Electron Acceleration In High-Intensity Laser Fields, Including The Unruh Effect

NASA Astrophysics Data System (ADS)

Thirolf, P. G.; Habs, D.; Homma, K.; Hörlein, R.; Karsch, S.; Krausz, F.; Maia, C.; Osterhoff, J.; Popp, A.; Schmid, K.; Schreiber, J.; Schützhold, R.; Tajima, T.; Veisz, L.; Wulz, J.; Yamazaki, T.

2010-04-01

The ultra-high fields of high-power short-pulse lasers are expected to contribute to understanding fundamental properties of the quantum vacuum and quantum theory in very strong fields. For example, the neutral QED vacuum breaks down at the Schwinger field strength of 1.3 1018V/m, where a virtual e+e- pair gains its rest mass energy over a Compton wavelength and materializes as a real pair. At such an ultra-high field strength, an electron experiences an acceleration of as = 2 1028 g and hence fundamental phenomena such as the long predicted Unruh effect start to play a role. The Unruh effect implies that the accelerated electron experiences the vacuum as a thermal bath with the Unruh temperature. In its accelerated frame the electron scatters photons off the thermal bath, corresponding to the emission of an entangled pair of photons in the laboratory frame. In upcoming experiments with intense accelerating fields, we will encounter a set of opportunities to experimentally study the radiation from electrons under extreme fields. Even before the Unruh radiation detection, we should run into the copious Larmor radiation. The detection of Larmor radiation and its characterization themselves have never been experimentally carried out to the best of our knowledge, and thus this amounts to a first serious study of physics at extreme acceleration. For example, we can study radiation damping effects like the Landau-Lifshitz radiation. Furthermore, the experiment should be able to confirm or disprove whether the Larmor and Landau-Lifshitz radiation components may be enhanced by a collective (N2) radiation, if a tightly clumped cluster of electrons is accelerated. The technique of laser driven dense electron sheet formation by irradiating a thin DLC foil target should provide such a coherent electron cluster with a very high density. If and when such mildly relativistic electron sheets are realized, a counterpropagating second laser can interact with them coherently. Under these conditions enhanced Larmor and Unruh radiation signals may be observed. Detection of the Unruh photons (together with its competing radiation components) is envisaged via Compton polarimetry in a novel highly granular 2D-segmented position-sensitive germanium detector.

Comparison of vibrational conductivity and radiative energy transfer methods

NASA Astrophysics Data System (ADS)

Le Bot, A.

2005-05-01

This paper is concerned with the comparison of two methods well suited for the prediction of the wideband response of built-up structures subjected to high-frequency vibrational excitation. The first method is sometimes called the vibrational conductivity method and the second one is rather known as the radiosity method in the field of acoustics, or the radiative energy transfer method. Both are based on quite similar physical assumptions i.e. uncorrelated sources, mean response and high-frequency excitation. Both are based on analogies with some equations encountered in the field of heat transfer. However these models do not lead to similar results. This paper compares the two methods. Some numerical simulations on a pair of plates joined along one edge are provided to illustrate the discussion.

Background radiation measurements at high power research reactors

NASA Astrophysics Data System (ADS)

Ashenfelter, J.; Balantekin, B.; Baldenegro, C. X.; Band, H. R.; Barclay, G.; Bass, C. D.; Berish, D.; Bowden, N. S.; Bryan, C. D.; Cherwinka, J. J.; Chu, R.; Classen, T.; Davee, D.; Dean, D.; Deichert, G.; Dolinski, M. J.; Dolph, J.; Dwyer, D. A.; Fan, S.; Gaison, J. K.; Galindo-Uribarri, A.; Gilje, K.; Glenn, A.; Green, M.; Han, K.; Hans, S.; Heeger, K. M.; Heffron, B.; Jaffe, D. E.; Kettell, S.; Langford, T. J.; Littlejohn, B. R.; Martinez, D.; McKeown, R. D.; Morrell, S.; Mueller, P. E.; Mumm, H. P.; Napolitano, J.; Norcini, D.; Pushin, D.; Romero, E.; Rosero, R.; Saldana, L.; Seilhan, B. S.; Sharma, R.; Stemen, N. T.; Surukuchi, P. T.; Thompson, S. J.; Varner, R. L.; Wang, W.; Watson, S. M.; White, B.; White, C.; Wilhelmi, J.; Williams, C.; Wise, T.; Yao, H.; Yeh, M.; Yen, Y.-R.; Zhang, C.; Zhang, X.; Prospect Collaboration

2016-01-01

Research reactors host a wide range of activities that make use of the intense neutron fluxes generated at these facilities. Recent interest in performing measurements with relatively low event rates, e.g. reactor antineutrino detection, at these facilities necessitates a detailed understanding of background radiation fields. Both reactor-correlated and naturally occurring background sources are potentially important, even at levels well below those of importance for typical activities. Here we describe a comprehensive series of background assessments at three high-power research reactors, including γ-ray, neutron, and muon measurements. For each facility we describe the characteristics and identify the sources of the background fields encountered. The general understanding gained of background production mechanisms and their relationship to facility features will prove valuable for the planning of any sensitive measurement conducted therein.

Merging Black Holes

NASA Technical Reports Server (NTRS)

Centrella, Joan; Baker, John G.; Kelly, Bernard J.; vanMeter, James R.

2010-01-01

Black-hole mergers take place in regions of very strong and dynamical gravitational fields, and are among the strongest sources of gravitational radiation. Probing these mergers requires solving the full set of Einstein's equations of general relativity numerically. For more than 40 years, progress towards this goal has been very slow, as numerical relativists encountered a host of difficult problems. Recently, several breakthroughs have led to dramatic progress, enabling stable and accurate calculations of black-hole mergers. This article presents an overview of this field, including impacts on astrophysics and applications in gravitational wave data analysis.

Evaluation of an automated karyotyping system for chromosome aberration analysis

NASA Technical Reports Server (NTRS)

Prichard, Howard M.

1987-01-01

Chromosome aberration analysis is a promising complement to conventional radiation dosimetry, particularly in the complex radiation fields encountered in the space environment. The capabilities of a recently developed automated karyotyping system were evaluated both to determine current capabilities and limitations and to suggest areas where future development should be emphasized. Cells exposed to radiometric chemicals and to photon and particulate radiation were evaluated by manual inspection and by automated karyotyping. It was demonstrated that the evaluated programs were appropriate for image digitization, storage, and transmission. However, automated and semi-automated scoring techniques must be advanced significantly if in-flight chromosome aberration analysis is to be practical. A degree of artificial intelligence may be necessary to realize this goal.

Radiation damage and annealing of lithium-doped silicon solar cells

NASA Technical Reports Server (NTRS)

Statler, R. L.

1971-01-01

Evidence has been presented that a lithium-diffused crucible-grown silicon solar cell can be made with better efficiency than the flight-quality n p 10 ohms-cm solar cell. When this lithium cell is exposed to a continuous radiation evironment at 60 C (electron spectrum from gamma rays) it has a higher power output than the N/P cell after a fluence equivalent to 1 MeV. A comparison of annealing of proton- and electron-damage in this lithium cell reveals a decidedly faster rate of recovery and higher level of recoverable power from the proton effects. Therefore, the lithium cell shows a good potential for many space missions where the proton flux is a significant fraction of the radiation field to be encountered.

Getting ready for the manned mission to Mars: the astronauts' risk from space radiation

NASA Astrophysics Data System (ADS)

Hellweg, Christine E.; Baumstark-Khan, Christa

2007-07-01

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.

Getting ready for the manned mission to Mars: the astronauts' risk from space radiation.

PubMed

Hellweg, Christine E; Baumstark-Khan, Christa

2007-07-01

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.

Hodgkin's disease: thyroid dysfunction following external irradiation

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

Tamura, K.; Shimaoka, K.

1981-01-01

The thyroid gland is commonly included in the field of radiation therapy for patients with malignant lymphoma and with head and neck tumors. The radiation dose for malignant diseases varies considerably depending on the purpose of treatment and the institutional policies. A substantial number of these patients are developing subclinical and clinical hypothyroidism. The risk of developing hypothyroidism after a moderate radiation dose of 2000 to 4500 rads has been reported to be 10 to 20 percent. In addition, subclinical hypothyroidism is induced further in one third of the patients. There are also suggestions that external irradiation of the thyroidmore » gland in patients with malignant lymphomas, as well as internal irradiation with radioiodine of the normal and hyperthyroid human thyroid glands, would induce elevations of serum antithyroid autoantibody titers. However, only a few cases of Graves disease following irradiation to the thyroid gland have been reported. We encountered a young woman who received radiation therapy to the mantle field for her Hodgkin's disease and developed hypothyroxinemia without overt signs and symptoms of hypothyroidism, followed by appearance of nodular goiter and then full-blown Graves disease.« less

Electric Field Distortion in Electro-Optical Devices Subjected to Ionizing Radiation.

DTIC Science & Technology

1983-12-26

applies- ties of scientif ic advances to nam military spae system . Versatilty and flaxibility hews beon developed to a high degree by the lehoratory...personel In deeling with the many problems encountered ina the nation’s rapidly dsvelopnas space system . 1expertise In the latest scientific developments is...desiga, distributed architectures for spacoerne m o putars, fault-tolerant c.speter system , artificia intelligence. end microelectronics applications

Project SOLWIND: Space radiation exposure. [evaluation of particle fluxes

NASA Technical Reports Server (NTRS)

Stassinopoulos, E. G.

1975-01-01

A special orbital radiation study was conducted for the SOLWIND project to evaluate mission-encountered energetic particle fluxes. Magnetic field calculations were performed with a current field model, extrapolated to the tentative spacecraft launch epoch with linear time terms. Orbital flux integrations for circular flight paths were performed with the latest proton and electron environment models, using new improved computational methods. Temporal variations in the ambient electron environment are considered and partially accounted for. Estimates of average energetic solar proton fluences are given for a one year mission duration at selected integral energies ranging from E greater than 10 to E greater than 100 MeV; the predicted annual fluence is found to relate to the period of maximum solar activity during the next solar cycle. The results are presented in graphical and tabular form; they are analyzed, explained, and discussed.

Background radiation measurements at high power research reactors

DOE PAGES

Ashenfelter, J.; Yeh, M.; Balantekin, B.; ...

2015-10-23

Research reactors host a wide range of activities that make use of the intense neutron fluxes generated at these facilities. Recent interest in performing measurements with relatively low event rates, e.g. reactor antineutrino detection, at these facilities necessitates a detailed understanding of background radiation fields. Both reactor-correlated and naturally occurring background sources are potentially important, even at levels well below those of importance for typical activities. Here we describe a comprehensive series of background assessments at three high-power research reactors, including γ-ray, neutron, and muon measurements. For each facility we describe the characteristics and identify the sources of the backgroundmore » fields encountered. Furthermore, the general understanding gained of background production mechanisms and their relationship to facility features will prove valuable for the planning of any sensitive measurement conducted therein.« less

Hydrogen therapy may reduce the risks related to radiation-induced oxidative stress in space flight.

PubMed

Schoenfeld, Michael P; Ansari, Rafat R; Zakrajsek, June F; Billiar, Timothy R; Toyoda, Yoshiya; Wink, David A; Nakao, Atsunori

2011-01-01

Cosmic radiation is known to induce DNA and lipid damage associated with increased oxidative stress and remains a major concern in space travel. Hydrogen, recently discovered as a novel therapeutic medical gas in a variety of biomedical fields, has potent antioxidant and anti-inflammatory activities. It is expected that space mission activities will increase in coming years both in numbers and duration. It is therefore important to estimate and prevent the risks encountered by astronauts due to oxidative stress prior to developing clinical symptoms of disease. We hypothesize that hydrogen administration to the astronauts by either inhalation or drinking hydrogen-rich water may potentially yield a novel and feasible preventative/therapeutic strategy to prevent radiation-induced adverse events. Copyright © 2010 Elsevier Ltd. All rights reserved.

New geometric and field theoretic aspects of a radiation dominated universe

NASA Astrophysics Data System (ADS)

Modak, Sujoy K.

2018-05-01

The homogeneous and isotropic radiation dominated universe, following the inflationary stage, is expressed as a spherically symmetric and inhomogeneous spacetime upon a power-law-type conformal transformation of the null (cosmological) coordinates. This new spacetime metric has many interesting properties. While the static observers, at a fixed position in this new spacetime, do not see any horizon, some nonstatic observers encounter a horizon due to their motion which is analogous to the situation of Rindler observers in Minkowski spacetime. The symmetry of the new metric offers a unitarily inequivalent quantization of the massless scalar field and provides a new example of particle creation. We calculate the particle content of the cosmological vacuum state with respect to the static observer in this new spacetime who, with respect to cosmological time, is freely falling in the asymptotic past and future but accelerated in between.

Mariner 10 mercury encounter.

PubMed

Dunne, J A

1974-07-12

Mariner 10's closet approach to Mercury on 29 March 1974 occurred on the dark side of the planet at a range of approximately 700 kilometers. The spacecraft trajectory passed through the shadows of both the sun and Earth. Experiments conducted included magnetic fields, plasma and charged particle studies of the solar wind interaction region, television photography, extreme ultraviolet spectroscopy of the atmosphere, the detection of infrared thermal radiation from the surface, and a dual-frequency radio occultation in search of an ionosphere.

Development of a Space Radiation Monte Carlo Computer Simulation

NASA Technical Reports Server (NTRS)

Pinsky, Lawrence S.

1997-01-01

The ultimate purpose of this effort is to undertake the development of a computer simulation of the radiation environment encountered in spacecraft which is based upon the Monte Carlo technique. The current plan is to adapt and modify a Monte Carlo calculation code known as FLUKA, which is presently used in high energy and heavy ion physics, to simulate the radiation environment present in spacecraft during missions. The initial effort would be directed towards modeling the MIR and Space Shuttle environments, but the long range goal is to develop a program for the accurate prediction of the radiation environment likely to be encountered on future planned endeavors such as the Space Station, a Lunar Return Mission, or a Mars Mission. The longer the mission, especially those which will not have the shielding protection of the earth's magnetic field, the more critical the radiation threat will be. The ultimate goal of this research is to produce a code that will be useful to mission planners and engineers who need to have detailed projections of radiation exposures at specified locations within the spacecraft and for either specific times during the mission or integrated over the entire mission. In concert with the development of the simulation, it is desired to integrate it with a state-of-the-art interactive 3-D graphics-capable analysis package known as ROOT, to allow easy investigation and visualization of the results. The efforts reported on here include the initial development of the program and the demonstration of the efficacy of the technique through a model simulation of the MIR environment. This information was used to write a proposal to obtain follow-on permanent funding for this project.

Large Amplitude Whistler Waves and Electron Acceleration in the Earth's Radiation Belts: A Review of STEREO and Wind Observations

NASA Technical Reports Server (NTRS)

Cattell, Cynthia; Breneman, A.; Goetz, K.; Kellogg, P.; Kersten, K.; Wygant, J.; Wilson, L. B., III; Looper, Mark D.; Blake, J. Bernard; Roth, I.

2012-01-01

One of the critical problems for understanding the dynamics of Earth's radiation belts is determining the physical processes that energize and scatter relativistic electrons. We review measurements from the Wind/Waves and STEREO S/Waves waveform capture instruments of large amplitude whistler-mode waves. These observations have provided strong evidence that large amplitude (100s mV/m) whistler-mode waves are common during magnetically active periods. The large amplitude whistlers have characteristics that are different from typical chorus. They are usually nondispersive and obliquely propagating, with a large longitudinal electric field and significant parallel electric field. We will also review comparisons of STEREO and Wind wave observations with SAMPEX observations of electron microbursts. Simulations show that the waves can result in energization by many MeV and/or scattering by large angles during a single wave packet encounter due to coherent, nonlinear processes including trapping. The experimental observations combined with simulations suggest that quasilinear theoretical models of electron energization and scattering via small-amplitude waves, with timescales of hours to days, may be inadequate for understanding radiation belt dynamics.

Measurement of Thermal Radiation Properties of Solids

NASA Technical Reports Server (NTRS)

Richmond, J. C. (Editor)

1963-01-01

The overall objectives of the Symposium were to afford (1) an opportunity for workers in the field to describe the equipment and procedures currently in use for measuring thermal radiation properties of solids, (2) an opportunity for constructive criticism of the material presented, and (3) an open forum for discussion of mutual problems. It was also the hope of the sponsors that the published proceedings of the Symposium would serve as a valuable reference on measurement techniques for evaluating thermal radiation properties of solids, partic.ularly for those with limited experience in the field. Because of the strong dependence of emitted flux upon temperature, the program committee thought it advisable to devote the first session to a discussion of the problems of temperature measurement. All of the papers in Session I were presented at the request of and upon topics suggested by the Committee. Because of time and space limitations, it, was impossible to consider all temperature measurement problems that might arise--the objective was rather to call to the attention of the reader some of the problems that might be encountered, and to provide references that might provide solutions.

The Application of FLUKA to Dosimetry and Radiation Therapy

NASA Technical Reports Server (NTRS)

Wilson, Thomas L.; Andersen, Victor; Pinsky, Lawrence; Ferrari, Alfredo; Battistoni, Giusenni

2005-01-01

Monte Carlo transport codes like FLUKA are useful for many purposes, and one of those is the simulation of the effects of radiation traversing the human body. In particular, radiation has been used in cancer therapy for a long time, and recently this has been extended to include heavy ion particle beams. The advent of this particular type of therapy has led to the need for increased capabilities in the transport codes used to simulate the detailed nature of the treatment doses to the Y O U S tissues that are encountered. This capability is also of interest to NASA because of the nature of the radiation environment in space.[l] While in space, the crew members bodies are continually being traversed by virtually all forms of radiation. In assessing the risk that this exposure causes, heavy ions are of primary importance. These arise both from the primary external space radiation itself, as well as fragments that result from interactions during the traversal of that radiation through any intervening material including intervening body tissue itself. Thus the capability to characterize the details of the radiation field accurately within a human body subjected to such external 'beams" is of critical importance.

Investigating Undergraduate Students’ Conceptions of Radiation

NASA Astrophysics Data System (ADS)

Romine, James M.; Buxner, Sanlyn; Impey, Chris; Nieberding, Megan; Antonellis, Jessie C.

2014-11-01

Radiation is an essential topic to the physical sciences yet is often misunderstood by the general public. The last time most people have formal instruction about radiation is as students in high school and this knowledge will be carried into adulthood. Peoples’ conceptions of radiation influence their attitude towards research regarding radiation, radioactivity, and other work where radiation is prevalent. In order to understand students’ ideas about radiation after having left high school, we collected science surveys from nearly 12,000 undergraduates enrolled in introductory science courses over a span of 25 years. This research investigates the relationship between students’ conceptions of radiation and students’ personal beliefs and academic field of study.Our results show that many students in the sample were unable to adequately describe radiation. Responses were typically vague, brief, and emotionally driven. Students’ field of study was found to significantly correlate with their conceptions. Students pursuing STEM majors were 60% more likely to describe radiation as an emission and/or form of energy and cited atomic or radioactive sources of radiation twice as often as non-STEM students. Additionally, students’ personal beliefs also appear to relate to their conceptions of radiation. The most prominent misconception shown was that radiation is a generically harmful substance, which was found to be consistent throughout the duration of the study. In particular, non-science majors in our sample had higher rates of misconceptions, often generalized the idea of radiation into a broad singular topic, and had difficulty properly identifying sources.Generalized ideas of radiation and the inability to properly recognize sources of radiation may contribute to the prevalent misconception that radiation is an inexplicably dangerous substance. A basic understanding of both electromagnetic and particulate radiation and the existence of radiation at various energy levels may substantially deter fear-based generalizations and increase students’ abilities to make rational decisions when encountering various types of radiation in daily life.

Exposing exposure: automated anatomy-specific CT radiation exposure extraction for quality assurance and radiation monitoring.

PubMed

Sodickson, Aaron; Warden, Graham I; Farkas, Cameron E; Ikuta, Ichiro; Prevedello, Luciano M; Andriole, Katherine P; Khorasani, Ramin

2012-08-01

To develop and validate an informatics toolkit that extracts anatomy-specific computed tomography (CT) radiation exposure metrics (volume CT dose index and dose-length product) from existing digital image archives through optical character recognition of CT dose report screen captures (dose screens) combined with Digital Imaging and Communications in Medicine attributes. This institutional review board-approved HIPAA-compliant study was performed in a large urban health care delivery network. Data were drawn from a random sample of CT encounters that occurred between 2000 and 2010; images from these encounters were contained within the enterprise image archive, which encompassed images obtained at an adult academic tertiary referral hospital and its affiliated sites, including a cancer center, a community hospital, and outpatient imaging centers, as well as images imported from other facilities. Software was validated by using 150 randomly selected encounters for each major CT scanner manufacturer, with outcome measures of dose screen retrieval rate (proportion of correctly located dose screens) and anatomic assignment precision (proportion of extracted exposure data with correctly assigned anatomic region, such as head, chest, or abdomen and pelvis). The 95% binomial confidence intervals (CIs) were calculated for discrete proportions, and CIs were derived from the standard error of the mean for continuous variables. After validation, the informatics toolkit was used to populate an exposure repository from a cohort of 54 549 CT encounters; of which 29 948 had available dose screens. Validation yielded a dose screen retrieval rate of 99% (597 of 605 CT encounters; 95% CI: 98%, 100%) and an anatomic assignment precision of 94% (summed DLP fraction correct 563 in 600 CT encounters; 95% CI: 92%, 96%). Patient safety applications of the resulting data repository include benchmarking between institutions, CT protocol quality control and optimization, and cumulative patient- and anatomy-specific radiation exposure monitoring. Large-scale anatomy-specific radiation exposure data repositories can be created with high fidelity from existing digital image archives by using open-source informatics tools.

Age as a risk factor for the disruption of cognitive performance by exposure to the types of radiation encounted on exploratory class missions to other planets

USDA-ARS?s Scientific Manuscript database

Exposure to the types of radiation encountered in space (particles of high energy and charge [HZE particles]) produces changes in neurocognitive performance similar to those observed in the aged organism. As such, it is possible that there would be an interaction between the effects of exposure to ...

Convergence of nanotechnology with radiation therapy—insights and implications for clinical translation

PubMed Central

Chatterjee, Dev Kumar; Wolfe, Tatiana; Lee, Jihyoun; Brown, Aaron P; Singh, Pankaj Kumar; Bhattarai, Shanta Raj; Diagaradjane, Parmeswaran; Krishnan, Sunil

2014-01-01

Improvements in accuracy and efficacy in treating tumors with radiation therapy (RT) over the years have been fueled by parallel technological and conceptual advances in imaging and image-guidance techniques, radiation treatment machines, computational methods, and the understanding of the biology of tumor response to RT. Recent advances in our understanding of the hallmarks of cancer and the emergence of strategies to combat these traits of cancer have resulted in an expanding repertoire of targeted therapeutics, many of which can be exploited for enhancing the efficacy of RT. Complementing this advent of new treatment options is the evolution of our knowledge of the interaction between nanoscale materials and human tissues (nanomedicine). As with the changes in RT paradigms when the field has encountered newer and maturing disciplines, the incorporation of nanotechnology innovations into radiation oncology has the potential to refine or redefine its principles and revolutionize its practice. This review provides a summary of the principles, applications, challenges and outlook for the use of metallic nanoparticles in RT. PMID:25279336

The Influence of Modulated Signal Risetime in Flight Electronics Radiated Immunity Testing with a Mode-Stirred Chamber

NASA Technical Reports Server (NTRS)

Ely, Jay J.; Nguyen, Truong X.; Scearce, Stephen A.

2000-01-01

For electromagnetic immunity testing of an electronic system, it is desirable to demonstrate its functional integrity when exposed to the full range and intensity of environmental electromagnetic threats that may be encountered over its operational life. As part of this, it is necessary to show proper system operation when exposed to representative threat signal modulations. Modulated signal transition time is easily overlooked, but can be highly significant to system susceptibility. Radiated electromagnetic field immunity testing is increasingly being performed in Mode Stirred Chambers. Because the peak field vs. time relationship is affected by the operation of a reverberating room, it is important to understand how the room may influence any input signal modulation characteristics. This paper will provide insight into the field intensity vs. time relationship within the test environment of a mode stirred chamber. An understanding of this relationship is important to EMC engineers in determining what input signal modulation characteristics will be transferred to the equipment under test. References will be given for the development of this topic, and experimental data will be presented

High-Performance, Radiation-Hardened Electronics for Space Environments

NASA Technical Reports Server (NTRS)

Keys, Andrew S.; Watson, Michael D.; Frazier, Donald O.; Adams, James H.; Johnson, Michael A.; Kolawa, Elizabeth A.

2007-01-01

The Radiation Hardened Electronics for Space Environments (RHESE) project endeavors to advance the current state-of-the-art in high-performance, radiation-hardened electronics and processors, ensuring successful performance of space systems required to operate within extreme radiation and temperature environments. Because RHESE is a project within the Exploration Technology Development Program (ETDP), RHESE's primary customers will be the human and robotic missions being developed by NASA's Exploration Systems Mission Directorate (ESMD) in partial fulfillment of the Vision for Space Exploration. Benefits are also anticipated for NASA's science missions to planetary and deep-space destinations. As a technology development effort, RHESE provides a broad-scoped, full spectrum of approaches to environmentally harden space electronics, including new materials, advanced design processes, reconfigurable hardware techniques, and software modeling of the radiation environment. The RHESE sub-project tasks are: SelfReconfigurable Electronics for Extreme Environments, Radiation Effects Predictive Modeling, Radiation Hardened Memory, Single Event Effects (SEE) Immune Reconfigurable Field Programmable Gate Array (FPGA) (SIRF), Radiation Hardening by Software, Radiation Hardened High Performance Processors (HPP), Reconfigurable Computing, Low Temperature Tolerant MEMS by Design, and Silicon-Germanium (SiGe) Integrated Electronics for Extreme Environments. These nine sub-project tasks are managed by technical leads as located across five different NASA field centers, including Ames Research Center, Goddard Space Flight Center, the Jet Propulsion Laboratory, Langley Research Center, and Marshall Space Flight Center. The overall RHESE integrated project management responsibility resides with NASA's Marshall Space Flight Center (MSFC). Initial technology development emphasis within RHESE focuses on the hardening of Field Programmable Gate Arrays (FPGA)s and Field Programmable Analog Arrays (FPAA)s for use in reconfigurable architectures. As these component/chip level technologies mature, the RHESE project emphasis shifts to focus on efforts encompassing total processor hardening techniques and board-level electronic reconfiguration techniques featuring spare and interface modularity. This phased approach to distributing emphasis between technology developments provides hardened FPGA/FPAAs for early mission infusion, then migrates to hardened, board-level, high speed processors with associated memory elements and high density storage for the longer duration missions encountered for Lunar Outpost and Mars Exploration occurring later in the Constellation schedule.

The Development of a Beta-Gamma Personnel Dosimeter

NASA Astrophysics Data System (ADS)

Tsakeres, Frank Steven

The assessment of absorbed dose in mixed beta and gamma radiation fields is an extremely complex task. For many years, the assessment of the absorbed dose to tissue from the weakly penetrating components of a radiation field (i.e., beta particles, electrons) has been largely ignored. Beta radiation fields are encountered routinely in a nuclear facility and may represent the major radiation component under certain accident or emergency conditions. Many attempts have been made to develop an accurate mixed field personnel dosimeter. However, all of these dosimeters have exhibited numerous response problems which have limited their usefulness for personnel dose assessment. Consequently, the determination of the absorbed dose at the epidermal depth (i.e., 7 mg/cm('2)) has been difficult to measure accurately. The objective of this research project was to design, build, and test a sensitive and accurate personnel dosimeter for mixed field applications. The selection of the various dosimeter elements were determined by evaluating several types of phosphors, filters, and backscatter materials. After evaluating the various response characteristics of the badge components, a prototype dosimeter, the CHEMM (CaF(,2):Dy Highly Efficient Multiple Element Multiple Filter) personnel dosimeter, was developed and tested at Georgia Tech, Emory University and the National Bureau of Standards. This dosimeter was comprised of four large CaF(,2):Dy (TLD-200) TLD's and a standard LiF (TLD-100) chip. The weakly penetrating and penetrating components of a radiation field were separated using a series of TLD/filter combinations and a new dose assessment algorithm. The large TLD-200 chips, along with a series of tissue-equivalent filters, were used to determine the absorbed dose due to the weakly penetrating radiation while a LiF/filter combination was used to measure the penetrating component. In addition, a new backscatter material was included in the badge design to better simulate a tissue-equivalent response. The CHEMM personnel dosimeter performance tests were conducted to simulate actual mixed radiation field environments. This dosimeter provided a high degree of sensitivity with accuracies well within the ANSI recommended performance standards for personnel dosimeters. In addition, it was concluded that the CHEMM dosimetry system provided a practical dosimeter alternative with a higher dose assessment accuracy and measurement sensitivity than the personnel dosimetry systems presently used in the nuclear power industry.

Stationary radiation hydrodynamics of accreting magnetic white dwarfs.

NASA Astrophysics Data System (ADS)

Woelk, U.; Beuermann, K.

1996-02-01

Using an artificial viscosity, we solved the one-dimensional time-independent two-fluid hydrodynamic equations simultaneously to the fully frequency and angle dependent radiation transport in an accretion flow directed towards the surface of a magnetic white dwarf. We consider energy transfer from ions to electrons by Coulomb encounters and cooling by bremsstrahlung and by cyclotron radiation in fields between B=5 and 70MG. Electron and ion temperatures relax in the post-shock regime and the cooling flow settles onto the white dwarf surface. For high mass flow rates ˙(m) (in g/cm^2^/s), cooling takes place mainly by bremsstrahlung and the solutions approach the non-magnetic case. For low ˙(m) and high B, cooling is dominated by cyclotron radiation which causes the thickness of the cooling region to collapse by 1-2 orders of magnitude compared to the non-magnetic case. The electron temperature behind the shock drops from a few 10^8^ to a few 10^7^K and the ratio of cyclotron vs. total radiative flux approaches unity. For high ˙(m) and low B values, bremsstrahlung dominates, but cyclotron losses can never be neglected. We find a smooth transition from particle-heated to shock-heated atmospheres in the maximum electron temperature and also in the thickness of the heated layer. With these results, the stationary radiation-hydrodynamics of accreting magnetic white dwarfs with cyclotron and bremsstrahlung cooling has been solved for the whole range of observed mass flow rates and field strengths.

Neutron/ γ-ray digital pulse shape discrimination with organic scintillators

NASA Astrophysics Data System (ADS)

Kaschuck, Y.; Esposito, B.

2005-10-01

Neutrons and γ-rays produce light pulses with different shapes when interacting with organic scintillators. This property is commonly used to distinguish between neutrons (n) and γ-rays ( γ) in mixed n/ γ fields as those encountered in radiation physics experiments. Although analog electronic pulse shape discrimination (PSD) modules have been successfully used for many years, they do not allow data reprocessing and are limited in count rate capability (typically up to 200 kHz). The performance of a n/ γ digital pulse shape discrimination (DPSD) system by means of a commercial 12-bit 200 MSamples/s transient recorder card is investigated here. Three organic scintillators have been studied: stilbene, NE213 and anthracene. The charge comparison method has been used to obtain simultaneous n/ γ discrimination and pulse height analysis. The importance of DPSD for high-intensity radiation field measurements and its advantages with respect to analog PSD are discussed. Based on post-experiment simulations with acquired data, the requirements for fast digitizers to provide DPSD with organic scintillators are also analyzed.

Surface plasmon transmission through discontinuous conducting surfaces: Plasmon amplitude modulation by grazing scattered fields

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

Mayoral-Astorga, L. A.; Gaspar-Armenta, J. A.; Ramos-Mendieta, F.

2016-04-15

We have studied numerically the diffraction of a surface plasmon polariton (SPP) when it encounters a wide multi-wavelength slit in conducting films. As a jump process a SPP is excited beyond the slit by wave scattering at the second slit edge. The exciting radiation is produced when the incident SPP collapses at the first slit edge. We have found that the transmitted SPP supports inherent and unavoidable interference with grazing scattered radiation; the spatial modulation extends to the fields in the diffraction region where a series of low intensity spots arises. We demonstrate that the SPP generated on the secondmore » slab depends on the frequency but not on the wave vector of the collapsed SPP; a SPP is transmitted even when the two metals forming the slit are different. The numerical results were obtained using the Finite Difference Time Domain (FDTD) method with a grid size λ/100.« less

Single event effects in high-energy accelerators

NASA Astrophysics Data System (ADS)

García Alía, Rubén; Brugger, Markus; Danzeca, Salvatore; Cerutti, Francesco; de Carvalho Saraiva, Joao Pedro; Denz, Reiner; Ferrari, Alfredo; Foro, Lionel L.; Peronnard, Paul; Røed, Ketil; Secondo, Raffaello; Steckert, Jens; Thurel, Yves; Toccafondo, Iacocpo; Uznanski, Slawosz

2017-03-01

The radiation environment encountered at high-energy hadron accelerators strongly differs from the environment relevant for space applications. The mixed-field expected at modern accelerators is composed of charged and neutral hadrons (protons, pions, kaons and neutrons), photons, electrons, positrons and muons, ranging from very low (thermal) energies up to the TeV range. This complex field, which is extensively simulated by Monte Carlo codes (e.g. FLUKA) is due to beam losses in the experimental areas, distributed along the machine (e.g. collimation points) and deriving from the interaction with the residual gas inside the beam pipe. The resulting intensity, energy distribution and proportion of the different particles largely depends on the distance and angle with respect to the interaction point as well as the amount of installed shielding material. Electronics operating in the vicinity of the accelerator will therefore be subject to both cumulative damage from radiation (total ionizing dose, displacement damage) as well as single event effects which can seriously compromise the operation of the machine. This, combined with the extensive use of commercial-off-the-shelf components due to budget, performance and availability reasons, results in the need to carefully characterize the response of the devices and systems to representative radiation conditions.

Development and Characterization of a High Throughput Screen to investigate the delayed Effects of Radiations Commonly Encountered in Space

NASA Astrophysics Data System (ADS)

Morgan, W. F.

Astronauts based on the space station or on long-term space missions will be exposed to high Z radiations in the cosmic environment In order to evaluate the potentially deleterious effects of exposure to radiations commonly encountered in space we have developed and characterized a high throughput assay to detect mutation deletion events and or hyperrecombination in the progeny of exposed cells This assay is based on a plasmid vector containing a green fluorescence protein reporter construct We have shown that after stable transfection of the vector into human or hamster cells this construct can identify mutations specifically base changes and deletions as well as recombination events e g gene conversion or homologous recombination occurring as a result of exposure to ionizing radiation Our focus has been on those events occurring in the progeny of an irradiated cell that are potentially associated with radiation induced genomic instability rather than the more conventional assays that evaluate the direct immediate effects of radiation exposure Considerable time has been spent automating analysis of surviving colonies as a function of time after irradiation in order to determine when delayed instability is induced and the consequences of this delayed instability The assay is now automated permitting the evaluation of potentially rare events associated with low dose low dose rate radiations commonly encountered in space

An experimental measurement of galactic cosmic radiation dose in conventional aircraft between San Francisco and London compared to theoretical values for conventional and supersonic aircraft

NASA Technical Reports Server (NTRS)

Wallace, R.; Boyer, M. F.

1972-01-01

These direct measurements are in fair agreement with computations made using a program which considers both basic cosmic ray atmospheric physics and the focusing effect of the earth's magnetic field. These measurements also agree with those made at supersonic jet aircraft altitudes in Rb-57 aircraft. It is concluded that experiments and theory show that the doses received at conventional jet aircraft altitudes are slightly higher than those encountered in supersonic flights at much higher altitudes.

Space radiation research in the new millenium--from where we come and where we go.

PubMed

Kiefer, J

2001-01-01

Space radiation research had a significant impact in the past. The physical interaction of heavy charged particles with living matter and the development of models, including microdosimetry, were stimulated by problems encountered in space. New phenomena were discovered. Advanced dosimetric techniques had to be developed and computational methods to describe the radiation field in space. The understanding of the radiobiology of heavy ions, necessary for a well-founded risk assessment and prompted by space radiation research, constitutes also the basis for heavy ion radiotherapy. So far unknown areas like the interaction of microgravity and radiation were opened. The space station will give even more opportunities. For the first time it will be possible to investigate animals for a longer time under the influence of both microgravity and radiation. Living systems can be exposed under well defined conditions with parallel physical measurements. Solar particle events are still an unsolved problem. Significant improvement in their predictability and quantitative description can be expected. All this will not only give exciting opportunities for research but will also translate into immediate benefit for human beings. This paper will attempt to give an overview of the past achievements and glance into the future.

The Comet Halley dust and gas environment

NASA Technical Reports Server (NTRS)

Divine, N.; Hanner, M. S.; Newburn, R. L., Jr.; Sekanina, Z.; Yeomans, D. K.

1986-01-01

Quantitative descriptions of environments near the nucleus of comet P/Halley have been developed to support spacecraft and mission design for the flyby encounters in March, 1986. To summarize these models as they exist just before the encounters, the relevant data from prior Halley apparitions and from recent cometary research are reviewed. Orbital elements, visual magnitudes, and parameter values and analysis for the nucleus, gas and dust are combined to predict Halley's position, production rates, gas and dust distributions, and electromagnetic radiation field for the current perihelion passage. The predicted numerical results have been useful for estimating likely spacecraft effects, such as impact damage and attitude perturbations. Sample applications are cited, including design of a dust shield for spacecraft structure, and threshold and dynamic range selection for flight experiments. It is expected that the comet's activity may be more irregular than these smoothly varying models predict, and that comparison with the flyby data will be instructive.

Ionizing radiation

NASA Technical Reports Server (NTRS)

Tobias, C. A.; Grigoryev, Y. G.

1975-01-01

The biological effects of ionizing radiation encountered in space are considered. Biological experiments conducted in space and some experiences of astronauts during space flight are described. The effects of various levels of radiation exposure and the determination of permissible dosages are discussed.

Exposing Exposure: Automated Anatomy-specific CT Radiation Exposure Extraction for Quality Assurance and Radiation Monitoring

PubMed Central

Warden, Graham I.; Farkas, Cameron E.; Ikuta, Ichiro; Prevedello, Luciano M.; Andriole, Katherine P.; Khorasani, Ramin

2012-01-01

Purpose: To develop and validate an informatics toolkit that extracts anatomy-specific computed tomography (CT) radiation exposure metrics (volume CT dose index and dose-length product) from existing digital image archives through optical character recognition of CT dose report screen captures (dose screens) combined with Digital Imaging and Communications in Medicine attributes. Materials and Methods: This institutional review board–approved HIPAA-compliant study was performed in a large urban health care delivery network. Data were drawn from a random sample of CT encounters that occurred between 2000 and 2010; images from these encounters were contained within the enterprise image archive, which encompassed images obtained at an adult academic tertiary referral hospital and its affiliated sites, including a cancer center, a community hospital, and outpatient imaging centers, as well as images imported from other facilities. Software was validated by using 150 randomly selected encounters for each major CT scanner manufacturer, with outcome measures of dose screen retrieval rate (proportion of correctly located dose screens) and anatomic assignment precision (proportion of extracted exposure data with correctly assigned anatomic region, such as head, chest, or abdomen and pelvis). The 95% binomial confidence intervals (CIs) were calculated for discrete proportions, and CIs were derived from the standard error of the mean for continuous variables. After validation, the informatics toolkit was used to populate an exposure repository from a cohort of 54 549 CT encounters; of which 29 948 had available dose screens. Results: Validation yielded a dose screen retrieval rate of 99% (597 of 605 CT encounters; 95% CI: 98%, 100%) and an anatomic assignment precision of 94% (summed DLP fraction correct 563 in 600 CT encounters; 95% CI: 92%, 96%). Patient safety applications of the resulting data repository include benchmarking between institutions, CT protocol quality control and optimization, and cumulative patient- and anatomy-specific radiation exposure monitoring. Conclusion: Large-scale anatomy-specific radiation exposure data repositories can be created with high fidelity from existing digital image archives by using open-source informatics tools. ©RSNA, 2012 Supplemental material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12111822/-/DC1 PMID:22668563

Investigating the effects of external fields polarization on the coupling of pure magnetic waves in the human body in very low frequencies

PubMed Central

2007-01-01

In this paper we studied the effects of external fields' polarization on the coupling of pure magnetic fields into human body. Finite Difference Time Domain (FDTD) method is used to calculate the current densities induced in a 1 cm resolution anatomically based model with proper tissue conductivities. Twenty different tissues have been considered in this investigation and scaled FDTD technique is used to convert the results of computer code run in 15 MHz to low frequencies which are encountered in the vicinity of industrial induction heating and melting devices. It has been found that external magnetic field's orientation due to human body has a pronounced impact on the level of induced currents in different body tissues. This may potentially help developing protecting strategies to mitigate the situations in which workers are exposed to high levels of external magnetic radiation. PMID:17504520

Project GALILEO: Farewell to the Major Moons of Jupiter

NASA Astrophysics Data System (ADS)

Theilig, E.

2002-01-01

After a six year odyssey, Galileo has completed its survey of the large moons of Jupiter. In the four years since the end of the primary mission, Galileo provided new insights into the fundamental questions concerning Jupiter and its moons and magnetosphere. Longevity, changing orbital geometry, and multiple flybys afforded the opportunity to distinguish intrinsic versus induced magnetic fields on the Galilean moons, to characterize the dusk side of the magnetosphere, to acquire high resolution observations supporting the possibility of subsurface water within Europa, Ganymede, and Callisto, and to monitor the highly dynamic volcanic activity of Io. In January 2002, a final gravity assist placed the spacecraft on a two-orbit trajectory culminating in a Jupiter impact in September 2003. With the successful completion of the Io encounters, plans are being made for the final encounter of the mission. In November 2002, the spacecraft will fly one Jupiter radius above the planet's cloud-tops, sampling the inner magnetosphere and the gossamer rings. The trajectory will take Galileo close enough to Amalthea, (a small inner moon) to obtain the first gravity data for this body. Because a radiation dose of 73 krads is expected on this encounter, which will bring the total radiation dose to greater than four times the spacecraft design limits, the command sequence has to account for the possibility of subsystem failure and the loss of spacecraft control after this perijove passage. One of the primary objectives this year has been to place the spacecraft on a trajectory to impact Jupiter on orbit 35. Galileo's discovery of water beneath the frozen surface of Europa raised concerns about forward contamination by inadvertently impacting that moon and resulted in an end of mission requirement to dispose of the spacecraft. A risk assessment of the final two Io encounters was performed to manage the project's ability to meet this requirement. Radiation affected the extended mission through damage to electronic parts in the attitude control subsystem, the computer memory and some science instruments and by causing transient bus reset indications. Software patches and changed operating strategies were implemented to work around most of the radiation effects. Recovery efforts to enhance the robustness of the Solid State Imaging camera paid off in the acquisition of images at both Io 32 and Io 33. Data on spacecraft performance in the harsh jovian environment may be useful to designers of future missions to Jupiter and its moons.

Electromagnetic fields and the public: EMF standards and estimation of risk

NASA Astrophysics Data System (ADS)

Grigoriev, Yury

2010-04-01

Mobile communications are a relatively new and additional source of electromagnetic exposure for the population. Standard daily mobile-phone use is known to increase RF-EMF (radiofrequency electromagnetic field) exposure to the brains of users of all ages, whilst mobile-phone base stations, and base station units for cordless phones, can regularly increase the exposures of large numbers of the population to RF-EMF radiation in everyday life. The need to determine appropriate standards stipulating the maximum acceptable short-term and long-term RF-EMF levels encountered by the public, and set such levels as general guidelines, is of great importance in order to help preserve the general public's health and that of the next generation of humanity.

MAJOR-MERGER GALAXY PAIRS AT Z = 0: DUST PROPERTIES AND COMPANION MORPHOLOGY

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

Domingue, Donovan L.; Ronca, Joseph; Hill, Emily

We present an analysis of dust properties of a sample of close major-merger galaxy pairs selected by K {sub s} magnitude and redshift. The pairs represent the two populations of spiral–spiral (S+S) and mixed morphology spiral–elliptical (S+E). The Code Investigating GALaxy Emission software is used to fit dust models to the Two Micron All Sky Survey, Wide-Field Infrared Survey Explorer , and Herschel flux density measurements, and to derive the parameters describing the polycyclic aromatic hydrocarbons contribution, interstellar radiation field, and photodissociation regions. Model fits verify our previous Spitzer Space Telescope analysis that S+S and S+E pairs do not havemore » the same level of enhancement of star formation and differ in dust composition. The spirals of mixed-morphology galaxy pairs do not exhibit the enhancements in interstellar radiation field and therefore dust temperature for spirals in S+S pairs in contrast to what would be expected according to standard models of gas redistribution due to encounter torques. This suggests the importance of the companion environment/morphology in determining the dust properties of a spiral galaxy in a close major-merger pair.« less

Method for calculating internal radiation and ventilation with the ADINAT heat-flow code

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

Butkovich, T.R.; Montan, D.N.

1980-04-01

One objective of the spent fuel test in Climax Stock granite (SFTC) is to correctly model the thermal transport, and the changes in the stress field and accompanying displacements from the application of the thermal loads. We have chosen the ADINA and ADINAT finite element codes to do these calculations. ADINAT is a heat transfer code compatible to the ADINA displacement and stress analysis code. The heat flow problem encountered at SFTC requires a code with conduction, radiation, and ventilation capabilities, which the present version of ADINAT does not have. We have devised a method for calculating internal radiation andmore » ventilation with the ADINAT code. This method effectively reproduces the results from the TRUMP multi-dimensional finite difference code, which correctly models radiative heat transport between drift surfaces, conductive and convective thermal transport to and through air in the drifts, and mass flow of air in the drifts. The temperature histories for each node in the finite element mesh calculated with ADINAT using this method can be used directly in the ADINA thermal-mechanical calculation.« less

Development of a statewide hospital plan for radiologic emergencies

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

Dainiak, Nicholas; Delli Carpini, Domenico; Bohan, Michael

Although general guidelines have been developed for triage of victims in the field and for hospitals to plan for a radiologic event, specific information for clinicians and administrators is not available for guidance in efficient management of radiation victims during their early encounter in the hospital. A consensus document was developed by staff members of four Connecticut hospitals, two institutions of higher learning, and the State of Connecticut Department of Environmental Protection and Office of Emergency Preparedness, with assistance of the American Society for Therapeutic Radiology and Oncology. The objective was to write a practical manual for clinicians (including radiationmore » oncologists, emergency room physicians, and nursing staff), hospital administrators, radiation safety officers, and other individuals knowledgeable in radiation monitoring that would be useful for evaluation and management of radiation injury. The rationale for and process by which the radiation response plan was developed and implemented in the State of Connecticut are reviewed. Hospital admission pathways are described, based on classification of victims as exposed, contaminated, and/or physically injured. This manual will be of value to those involved in planning the health care response to a radiologic event.« less

Dynamic implicit 3D adaptive mesh refinement for non-equilibrium radiation diffusion

NASA Astrophysics Data System (ADS)

Philip, B.; Wang, Z.; Berrill, M. A.; Birke, M.; Pernice, M.

2014-04-01

The time dependent non-equilibrium radiation diffusion equations are important for solving the transport of energy through radiation in optically thick regimes and find applications in several fields including astrophysics and inertial confinement fusion. The associated initial boundary value problems that are encountered often exhibit a wide range of scales in space and time and are extremely challenging to solve. To efficiently and accurately simulate these systems we describe our research on combining techniques that will also find use more broadly for long term time integration of nonlinear multi-physics systems: implicit time integration for efficient long term time integration of stiff multi-physics systems, local control theory based step size control to minimize the required global number of time steps while controlling accuracy, dynamic 3D adaptive mesh refinement (AMR) to minimize memory and computational costs, Jacobian Free Newton-Krylov methods on AMR grids for efficient nonlinear solution, and optimal multilevel preconditioner components that provide level independent solver convergence.

An analysis of blade vortex interaction aerodynamics and acoustics

NASA Technical Reports Server (NTRS)

Lee, D. J.

1985-01-01

The impulsive noise associated with helicopter flight due to Blade-Vortex Interaction, sometimes called blade slap is analyzed especially for the case of a close encounter of the blade-tip vortex with a following blade. Three parts of the phenomena are considered: the tip-vortex structure generated by the rotating blade, the unsteady pressure produced on the following blade during the interaction, and the acoustic radiation due to the unsteady pressure field. To simplify the problem, the analysis was confined to the situation where the vortex is aligned parallel to the blade span in which case the maximum acoustic pressure results. Acoustic radiation due to the interaction is analyzed in space-fixed coordinates and in the time domain with the unsteady pressure on the blade surface as the source of chordwise compact, but spanwise non-compact radiation. Maximum acoustic pressure is related to the vortex core size and Reynolds number which are in turn functions of the blade-tip aerodynamic parameters. Finally noise reduction and performance are considered.

Detecting axion stars with radio telescopes

NASA Astrophysics Data System (ADS)

Bai, Yang; Hamada, Yuta

2018-06-01

When axion stars fly through an astrophysical magnetic background, the axion-to-photon conversion may generate a large electromagnetic radiation power. After including the interference effects of the spacially-extended axion-star source and the macroscopic medium effects, we estimate the radiation power when an axion star meets a neutron star. For a dense axion star with 10-13M⊙, the radiated power is at the order of 1011W ×(100 μeV /ma) 4(B /1010Gauss) 2 with ma as the axion particle mass and B the strength of the neutron star magnetic field. For axion stars occupy a large fraction of dark matter energy density, this encounter event with a transient O (0.1s) radio signal may happen in our galaxy with the averaged source distance of one kiloparsec. The predicted spectral flux density is at the order of μJy for a neutron star with B ∼1013 Gauss. The existing Arecibo, GBT, JVLA and FAST and the ongoing SKA radio telescopes have excellent discovery potential of dense axion stars.

Evaluation of the dosimetric properties of a diode detector for small field proton radiosurgery.

PubMed

McAuley, Grant A; Teran, Anthony V; Slater, Jerry D; Slater, James M; Wroe, Andrew J

2015-11-08

The small fields and sharp gradients typically encountered in proton radiosurgery require high spatial resolution dosimetric measurements, especially below 1-2 cm diameters. Radiochromic film provides high resolution, but requires postprocessing and special handling. Promising alternatives are diode detectors with small sensitive volumes (SV) that are capable of high resolution and real-time dose acquisition. In this study we evaluated the PTW PR60020 proton dosimetry diode using radiation fields and beam energies relevant to radiosurgery applications. Energies of 127 and 157 MeV (9.7 to 15 cm range) and initial diameters of 8, 10, 12, and 20mm were delivered using single-stage scattering and four modulations (0, 15, 30, and 60mm) to a water tank in our treatment room. Depth dose and beam profile data were compared with PTW Markus N23343 ionization chamber, EBT2 Gafchromic film, and Monte Carlo simulations. Transverse dose profiles were measured using the diode in "edge-on" orientation or EBT2 film. Diode response was linear with respect to dose, uniform with dose rate, and showed an orientation-dependent (i.e., beam parallel to, or perpendicular to, detector axis) response of less than 1%. Diodevs. Markus depth-dose profiles, as well as Markus relative dose ratio vs. simulated dose-weighted average lineal energy plots, suggest that any LET-dependent diode response is negligible from particle entrance up to the very distal portion of the SOBP for the energies tested. Finally, while not possible with the ionization chamber due to partial volume effects, accurate diode depth-dose measurements of 8, 10, and 12 mm diameter beams were obtained compared to Monte Carlo simulations. Because of the small SV that allows measurements without partial volume effects and the capability of submillimeter resolution (in edge-on orientation) that is crucial for small fields and high-dose gradients (e.g., penumbra, distal edge), as well as negligible LET dependence over nearly the full the SOBP, the PTW proton diode proved to be a useful high-resolution, real-time metrology device for small proton field radiation measurements such as would be encountered in radiosurgery applications.

[Application Progress of Three-dimensional Laser Scanning Technology in Medical Surface Mapping].

PubMed

Zhang, Yonghong; Hou, He; Han, Yuchuan; Wang, Ning; Zhang, Ying; Zhu, Xianfeng; Wang, Mingshi

2016-04-01

The booming three-dimensional laser scanning technology can efficiently and effectively get spatial three-dimensional coordinates of the detected object surface and reconstruct the image at high speed,high precision and large capacity of information.Non-radiation,non-contact and the ability of visualization make it increasingly popular in three-dimensional surface medical mapping.This paper reviews the applications and developments of three-dimensional laser scanning technology in medical field,especially in stomatology,plastic surgery and orthopedics.Furthermore,the paper also discusses the application prospects in the future as well as the biomedical engineering problems it would encounter with.

Current clinical trials testing combinations of immunotherapy and radiation.

PubMed

Crittenden, Marka; Kohrt, Holbrook; Levy, Ronald; Jones, Jennifer; Camphausen, Kevin; Dicker, Adam; Demaria, Sandra; Formenti, Silvia

2015-01-01

Preclinical evidence of successful combinations of ionizing radiation with immunotherapy has inspired testing the translation of these results to the clinic. Interestingly, the preclinical work has consistently predicted the responses encountered in clinical trials. The first example came from a proof-of-principle trial started in 2001 that tested the concept that growth factors acting on antigen-presenting cells improve presentation of tumor antigens released by radiation and induce an abscopal effect. Granulocyte-macrophage colony-stimulating factor was administered during radiotherapy to a metastatic site in patients with metastatic solid tumors to translate evidence obtained in a murine model of syngeneic mammary carcinoma treated with cytokine FLT-3L and radiation. Subsequent clinical availability of vaccines and immune checkpoint inhibitors has triggered a wave of enthusiasm for testing them in combination with radiotherapy. Examples of ongoing clinical trials are described in this report. Importantly, most of these trials include careful immune monitoring of the patients enrolled and will generate important data about the proimmunogenic effects of radiation in combination with a variety of immune modulators, in different disease settings. Results of these studies are building a platform of evidence for radiotherapy as an adjuvant to immunotherapy and encourage the growth of this novel field of radiation oncology. Copyright © 2015 Elsevier Inc. All rights reserved.

Transfer of line radiation in differentially expanding atmospheres. VI The plane parallel atmosphere with expanding and contracting regions

NASA Technical Reports Server (NTRS)

Noerdlinger, P. D.

1981-01-01

The non-LTE radiative transfer problem for a two level atom with complete redistribution over a Doppler profile is solved for a plane parallel slab (overlying a radiating photosphere) that has a velocity field which rises symmetrically from zero at either face to a central maximum. Since the velocity gradient reverses, distant layers of the slab become coupled by radiation that jumps intervening layers. The Feautrier method is used, but an iterative variant is also employed as a check in cases where poorly conditioned matrices are encountered. Approximations are developed to explain some of the principal features. It is found that the source function S tends to have two plateaus with values near 2/3 I sub 0 and 1/3 I sub 0, where I sub 0 is the photospheric continuum incident from below; the larger value lies nearer the photosphere. The upper layers sometimes exhibit a rise in S owing to interconnection by radiation to the base. It is noted that the radiation force is largest at the two faces and the midplane. Some line profiles are found to have unusually steep absorptions at rest frequency because of the low excitation in the uppermost, stationary layers.

Quantum structures for recombination control in the light-emitting transistor

NASA Astrophysics Data System (ADS)

Chen, Kanuo; Hsiao, Fu-Chen; Joy, Brittany; Dallesasse, John M.

2017-02-01

Recombination of carriers in the direct-bandgap base of a transistor-injected quantum cascade laser (TI-QCL) is shown to be controllable through the field applied across the quantum cascade region located in the transistor's base-collector junction. The influence of the electric field on the quantum states in the cascade region's superlattice allows free flow of electrons out of the transistor base only for field values near the design field that provides optimal QCL gain. Quantum modulation of base recombination in the light-emitting transistor is therefore observed. In a GaAs-based light-emitting transistor, a periodic superlattice is grown between the p-type base and the n-type collector. Under different base-collector biasing conditions the distribution of quantum states, and as a consequence transition probabilities through the wells and barriers forming the cascade region, leads to strong field-dependent mobility for electrons in transit through the base-collector junction. The radiative base recombination, which is influenced by minority carrier transition lifetime, can be modulated through the quantum states alignment in the superlattice. A GaAs-based transistor-injected quantum cascade laser with AlGaAs/GaAs superlattice is designed and fabricated. Radiative base recombination is measured under both common-emitter and common-base configuration. In both configurations the optical output from the base is proportional to the emitter injection. When the quantum states in the superlattice are aligned the optical output in the base is reduced as electrons encounter less impedance entering the collector; when the quantum states are misaligned electrons have longer lifetime in the base and the radiative base recombination process is enhanced.

Strong Magnetic Field Fluctuations within Filamentary Auroral Density Cavities Interpreted as VLF Saucer Sources

NASA Technical Reports Server (NTRS)

Knudsen, D. L.; Kabirzadeh, R.; Burchill, J. K.; Pfaff, Robert F.; Wallis, D. D.; Bounds, S. R.; Clemmons, J. H.; Pincon, J.-L.

2012-01-01

The Geoelectrodynamics and Electro-Optical Detection of Electron and SuprathermalIon Currents (GEODESIC) sounding rocket encountered more than 100 filamentary densitycavities associated with enhanced plasma waves at ELF (3 kHz) and VLF (310 kHz)frequencies and at altitudes of 800990 km during an auroral substorm. These cavities weresimilar in size (20 m diameter in most cases) to so-called lower-hybrid cavities (LHCs)observed by previous sounding rockets and satellites; however, in contrast, many of theGEODESIC cavities exhibited up to tenfold enhancements in magnetic wave powerthroughout the VLF band. GEODESIC also observed enhancements of ELF and VLFelectric fields both parallel and perpendicular to the geomagnetic field B0 within cavities,though the VLF E field increases were often not as large proportionally as seen in themagnetic fields. This behavior is opposite to that predicted by previously published theoriesof LHCs based on passive scattering of externally incident auroral hiss. We argue thatthe GEODESIC cavities are active wave generation sites capable of radiating VLF wavesinto the surrounding plasma and producing VLF saucers, with energy supplied by cold,upward flowing electron beams composing the auroral return current. This interpretation issupported by the observation that the most intense waves, both inside and outside cavities,occurred in regions where energetic electron precipitation was largely inhibited orabsent altogether. We suggest that the wave-enhanced cavities encountered by GEODESICwere qualitatively different from those observed by earlier spacecraft because of thefortuitous timing of the GEODESIC launch, which placed the payload at apogee within asubstorm-related return current during its most intense phase, lasting only a few minutes.

RadNuc: A graphical user interface to deliver dose rate patterns encountered in nuclear medicine with a 137Cs irradiator

PubMed Central

Pasternack, Jordan B.; Howell, Roger W.

2012-01-01

The temporal variations in absorbed dose rates to organs and tissues in the body are very large in diagnostic and therapeutic nuclear medicine. The response of biological endpoints of relevance to radiation safety and therapeutic efficacy are generally modulated by dose rate. Therefore, it is important to understand how the complex dose rate patterns encountered in nuclear medicine impact relevant biological responses. Accordingly, a graphical user interface (GUI) was created to control a cesium-137 irradiator to deliver such dose rate patterns. Methods Visual Basic 6.0 was used to create a user-friendly GUI to control the dose rate by varying the thickness of a mercury attenuator. The GUI facilitates the delivery of a number of dose rate patterns including constant, exponential increase or decrease, and multi-component exponential. Extensive visual feedback is provided by the GUI during both the planning and delivery stages. Results The GUI controlled irradiator can achieve a maximum dose rate of 40 cGy/hr and a minimum dose rate of 0.01 cGy/hr. Addition of machined lead blocks can be used to further reduce the minimum dose rate to 0.0001 cGy/hr. Measured dose rate patterns differed from programmed dose rate patterns in total dose by 3.2% to 8.4%. Conclusion The GUI controlled irradiator is able to accurately create dose rate patterns encountered in nuclear medicine and other related fields. This makes it an invaluable tool for studying the effects of chronic constant and variable low dose rates on biological tissues in the contexts of both radiation protection and clinical administration of internal radionuclides. PMID:23265668

RadNuc: a graphical user interface to deliver dose rate patterns encountered in nuclear medicine with a 137Cs irradiator.

PubMed

Pasternack, Jordan B; Howell, Roger W

2013-02-01

The temporal variations in absorbed dose rates to organs and tissues in the body are very large in diagnostic and therapeutic nuclear medicine. The response of biological endpoints of relevance to radiation safety and therapeutic efficacy is generally modulated by dose rate. Therefore, it is important to understand how the complex dose rate patterns encountered in nuclear medicine impact relevant biological responses. Accordingly, a graphical user interface (GUI) was created to control a cesium-137 irradiator to deliver such dose rate patterns. Visual Basic 6.0 was used to create a user-friendly GUI to control the dose rate by varying the thickness of a mercury attenuator. The GUI facilitates the delivery of a number of dose rate patterns including constant, exponential increase or decrease, and multi-component exponential. Extensive visual feedback is provided by the GUI during both the planning and delivery stages. The GUI controlled irradiator can achieve a maximum dose rate of 40 cGy/h and a minimum dose rate of 0.01 cGy/h. Addition of machined lead blocks can be used to further reduce the minimum dose rate to 0.0001 cGy/h. Measured dose rate patterns differed from programmed dose rate patterns in total dose by 3.2% to 8.4%. The GUI controlled irradiator is able to accurately create dose rate patterns encountered in nuclear medicine and other related fields. This makes it an invaluable tool for studying the effects of chronic constant and variable low dose rates on biological tissues in the contexts of both radiation protection and clinical administration of internal radionuclides. Copyright © 2013 Elsevier Inc. All rights reserved.

Radiation environment for ATS-F. [including ambient trapped particle fluxes

NASA Technical Reports Server (NTRS)

Stassinopoulos, E. G.

1974-01-01

The ambient trapped particle fluxes incident on the ATS-F satellite were determined. Several synchronous circular flight paths were evaluated and the effect of parking longitude on vehicle encountered intensities was investigated. Temporal variations in the electron environment were considered and partially accounted for. Magnetic field calculations were performed with a current field model extrapolated to a later epoch with linear time terms. Orbital flux integrations were performed with the latest proton and electron environment models using new improved computational methods. The results are presented in graphical and tabular form; they are analyzed, explained, and discussed. Estimates of energetic solar proton fluxes are given for a one year mission at selected integral energies ranging from 10 to 100 Mev, calculated for a year of maximum solar activity during the next solar cycle.

Modern Radiation Therapy for Hodgkin Lymphoma: Field and Dose Guidelines From the International Lymphoma Radiation Oncology Group (ILROG)

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

Specht, Lena, E-mail: lena.specht@regionh.dk; Yahalom, Joachim; Illidge, Tim

2014-07-15

Radiation therapy (RT) is the most effective single modality for local control of Hodgkin lymphoma (HL) and an important component of therapy for many patients. These guidelines have been developed to address the use of RT in HL in the modern era of combined modality treatment. The role of reduced volumes and doses is addressed, integrating modern imaging with 3-dimensional (3D) planning and advanced techniques of treatment delivery. The previously applied extended field (EF) and original involved field (IF) techniques, which treated larger volumes based on nodal stations, have now been replaced by the use of limited volumes, based solelymore » on detectable nodal (and extranodal extension) involvement at presentation, using contrast-enhanced computed tomography, positron emission tomography/computed tomography, magnetic resonance imaging, or a combination of these techniques. The International Commission on Radiation Units and Measurements concepts of gross tumor volume, clinical target volume, internal target volume, and planning target volume are used for defining the targeted volumes. Newer treatment techniques, including intensity modulated radiation therapy, breath-hold, image guided radiation therapy, and 4-dimensional imaging, should be implemented when their use is expected to decrease significantly the risk for normal tissue damage while still achieving the primary goal of local tumor control. The highly conformal involved node radiation therapy (INRT), recently introduced for patients for whom optimal imaging is available, is explained. A new concept, involved site radiation therapy (ISRT), is introduced as the standard conformal therapy for the scenario, commonly encountered, wherein optimal imaging is not available. There is increasing evidence that RT doses used in the past are higher than necessary for disease control in this era of combined modality therapy. The use of INRT and of lower doses in early-stage HL is supported by available data. Although the use of ISRT has not yet been validated in a formal study, it is more conservative than INRT, accounting for suboptimal information and appropriately designed for safe local disease control. The goal of modern smaller field radiation therapy is to reduce both treatment volume and treatment dose while maintaining efficacy and minimizing acute and late sequelae. This review is a consensus of the International Lymphoma Radiation Oncology Group (ILROG) Steering Committee regarding the modern approach to RT in the treatment of HL, outlining a new concept of ISRT in which reduced treatment volumes are planned for the effective control of involved sites of HL. Nodal and extranodal non-Hodgkin lymphomas (NHL) are covered separately by ILROG guidelines.« less

Modern radiation therapy for Hodgkin lymphoma: field and dose guidelines from the international lymphoma radiation oncology group (ILROG).

PubMed

Specht, Lena; Yahalom, Joachim; Illidge, Tim; Berthelsen, Anne Kiil; Constine, Louis S; Eich, Hans Theodor; Girinsky, Theodore; Hoppe, Richard T; Mauch, Peter; Mikhaeel, N George; Ng, Andrea

2014-07-15

Radiation therapy (RT) is the most effective single modality for local control of Hodgkin lymphoma (HL) and an important component of therapy for many patients. These guidelines have been developed to address the use of RT in HL in the modern era of combined modality treatment. The role of reduced volumes and doses is addressed, integrating modern imaging with 3-dimensional (3D) planning and advanced techniques of treatment delivery. The previously applied extended field (EF) and original involved field (IF) techniques, which treated larger volumes based on nodal stations, have now been replaced by the use of limited volumes, based solely on detectable nodal (and extranodal extension) involvement at presentation, using contrast-enhanced computed tomography, positron emission tomography/computed tomography, magnetic resonance imaging, or a combination of these techniques. The International Commission on Radiation Units and Measurements concepts of gross tumor volume, clinical target volume, internal target volume, and planning target volume are used for defining the targeted volumes. Newer treatment techniques, including intensity modulated radiation therapy, breath-hold, image guided radiation therapy, and 4-dimensional imaging, should be implemented when their use is expected to decrease significantly the risk for normal tissue damage while still achieving the primary goal of local tumor control. The highly conformal involved node radiation therapy (INRT), recently introduced for patients for whom optimal imaging is available, is explained. A new concept, involved site radiation therapy (ISRT), is introduced as the standard conformal therapy for the scenario, commonly encountered, wherein optimal imaging is not available. There is increasing evidence that RT doses used in the past are higher than necessary for disease control in this era of combined modality therapy. The use of INRT and of lower doses in early-stage HL is supported by available data. Although the use of ISRT has not yet been validated in a formal study, it is more conservative than INRT, accounting for suboptimal information and appropriately designed for safe local disease control. The goal of modern smaller field radiation therapy is to reduce both treatment volume and treatment dose while maintaining efficacy and minimizing acute and late sequelae. This review is a consensus of the International Lymphoma Radiation Oncology Group (ILROG) Steering Committee regarding the modern approach to RT in the treatment of HL, outlining a new concept of ISRT in which reduced treatment volumes are planned for the effective control of involved sites of HL. Nodal and extranodal non-Hodgkin lymphomas (NHL) are covered separately by ILROG guidelines. Copyright © 2014 Elsevier Inc. All rights reserved.

Late effects of 1H irradiation on hippocampal physiology

NASA Astrophysics Data System (ADS)

Kiffer, Frederico; Howe, Alexis K.; Carr, Hannah; Wang, Jing; Alexander, Tyler; Anderson, Julie E.; Groves, Thomas; Seawright, John W.; Sridharan, Vijayalakshmi; Carter, Gwendolyn; Boerma, Marjan; Allen, Antiño R.

2018-05-01

NASA's Missions to Mars and beyond will expose flight crews to potentially dangerous levels of charged-particle radiation. Of all charged nuclei, 1H is the most abundant charged particle in both the galactic cosmic ray (GCR) and solar particle event (SPE) spectra. There are currently no functional spacecraft shielding materials that are able to mitigate the charged-particle radiation encountered in space. Recent studies have demonstrated cognitive injuries due to high-dose 1H exposures in rodents. Our study investigated the effects of 1H irradiation on neuronal morphology in the hippocampus of adult male mice. 6-month-old mice received whole-body exposure to 1H at 0.5 and 1 Gy (150 MeV/n; 0.35-0.55 Gy/min) at NASA's Space Radiation Laboratory in Upton, NY. At 9-months post-irradiation, we tested each animal's open-field exploratory performance. After sacrifice, we dissected the brains along the midsagittal plane, and then either fixed or dissected further and snap-froze them. Our data showed that exposure to 0.5 Gy or 1 Gy 1H significantly increased animals' anxiety behavior in open-field testing. Our micromorphometric analyses revealed significant decreases in mushroom spine density and dendrite morphology in the Dentate Gyrus, Cornu Ammonis 3 and 1 of the hippocampus, and lowered expression of synaptic markers. Our data suggest 1H radiation significantly increased exploration anxiety and modulated the dendritic spine and dendrite morphology of hippocampal neurons at a dose of 0.5 or 1 Gy.

Role of CT in Congenital Heart Disease.

PubMed

Rajiah, Prabhakar; Saboo, Sachin S; Abbara, Suhny

2017-01-01

Congenital heart diseases (CHD) are being increasingly encountered in cardiac imaging due to improved outcomes from surgical and interventional techniques. Imaging plays an important role in the evaluation of CHD, both prior to and after surgeries and interventions. Computed tomography (CT) has several advantages in the evaluation of these disorders, particularly its high spatial resolution, multi-planar reconstruction capabilities at sub-millimeter isotropic resolution, good temporal resolution, wide field of view, and rapid turnaround time, which minimizes the need for sedation and anesthesia in young children or children with disabilities. With modern scanners, images can be acquired as fast as within one heartbeat. Although there is a risk of ionizing radiation, the radiation dose can be minimized by using several dose reduction strategies. There is a risk of contrast nephrotoxicity in patients with renal dysfunction. In this article, we will review the role of CT in the evaluation of several congenital heart diseases, both in children and adults.

Superradiant effects on pulse propagation in resonant media. [atomic excitations/coherent radiation - operators (mathematics)/matrices (mathematics)

NASA Technical Reports Server (NTRS)

Lee, C.

1975-01-01

Adopting the so-called genealogical construction, the eigenstates of collective operators can be expressed corresponding to a specified mode for an N-atom system in terms of those for an (N-1)-atom system. Matrix element of a collective operator of an arbitrary mode is presented which can be written as the product of an m-dependent factor and an m-independent reduced matrix element (RME). A set of recursion formulas for the RME was obtained. A graphical representation of the RME on the branching diagram for binary irreducible representations of permutation groups was then introduced. This gave a simple and systematic way of calculating the RME. Results show explicitly the geometry dependence of superradiance and the relative importance of r-conserving and r-nonconserving processes and clears up the chief difficulty encounted in the problem of N two-level atoms, spread over large regions, interacting with a multimode radiation field.

A survey of trapped low energy electrons near the inner boundary of the inner radiation zone from the OSO-7

NASA Technical Reports Server (NTRS)

Neighbours, J. E.; Clark, G. W.

1974-01-01

Data from the MIT X-ray experiment on the OSO-7 satellite were used to delineate the regions in B-L and geographic spaces where trapped radiation was encountered. The results pertain specifically to electrons with energies in a range of 10 keV centered on 55 keV which were encountered in an orbit between altitudes of 330 and 570 km and latitudes of 33.3 degrees. A typical pitch angle distribution is fitted by a Gaussian with a FWHM of 28 degrees.

UK-5 Van Allen belt radiation exposure: A special study to determine the trapped particle intensities on the UK-5 satellite with spatial mapping of the ambient flux environment

NASA Technical Reports Server (NTRS)

Stassinopoulos, E. G.

1972-01-01

Vehicle encountered electron and proton fluxes were calculated for a set of nominal UK-5 trajectories with new computational methods and new electron environment models. Temporal variations in the electron data were considered and partially accounted for. Field strength calculations were performed with an extrapolated model on the basis of linear secular variation predictions. Tabular maps for selected electron and proton energies were constructed as functions of latitude and longitude for specified altitudes. Orbital flux integration results are presented in graphical and tabular form; they are analyzed, explained, and discussed.

Fading Correction To Be Used In Clinical Thermoluminescence Dosimetry

NASA Astrophysics Data System (ADS)

Furetta, C.; Azorin, J.; Rivera, T.

2004-09-01

This paper presents some useful expressions for fading correction, which can be used in practical situations as they can be encountered in clinical dosimetry. The situations took into consideration can be encountered in hospital environments during and after radiotherapeutic treatments of patients as well as for radiation protection procedures concerning staff members.

Neutrophil-inspired propulsion in a combined acoustic and magnetic field.

PubMed

Ahmed, Daniel; Baasch, Thierry; Blondel, Nicolas; Läubli, Nino; Dual, Jürg; Nelson, Bradley J

2017-10-03

Systems capable of precise motion in the vasculature can offer exciting possibilities for applications in targeted therapeutics and non-invasive surgery. So far, the majority of the work analysed propulsion in a two-dimensional setting with limited controllability near boundaries. Here we show bio-inspired rolling motion by introducing superparamagnetic particles in magnetic and acoustic fields, inspired by a neutrophil rolling on a wall. The particles self-assemble due to dipole-dipole interaction in the presence of a rotating magnetic field. The aggregate migrates towards the wall of the channel due to the radiation force of an acoustic field. By combining both fields, we achieved a rolling-type motion along the boundaries. The use of both acoustic and magnetic fields has matured in clinical settings. The combination of both fields is capable of overcoming the limitations encountered by single actuation techniques. We believe our method will have far-reaching implications in targeted therapeutics.Devising effective swimming and propulsion strategies in microenvironments is attractive for drug delivery applications. Here Ahmed et al. demonstrate a micropropulsion strategy in which a combination of magnetic and acoustic fields is used to assemble and propel colloidal particles along channel walls.

Radiation hazards to synchronous satellites: The IUE (SAS-D) mission

NASA Technical Reports Server (NTRS)

Stassinopoulos, E. G.

1973-01-01

The ambient trapped particle fluxes incident on the IUE (SAS-D) satellite were studied. Several synchronous elliptical and circular flight paths were evaluated and the effect of inclination, eccentricity, and parking longitude on vehicle encountered intensities was investigated. Temporal variations in the electron environment were considered and partially accounted for. Magnetic field calculations were performed with a current field model extrapolated to a later epoch with linear time terms. Orbital flux integrations were performed with the latest proton and electron environment models using new improved computational methods. The results are presented in graphical and tabular form; they are analyzed, explained, and discussed. Estimates of energetic solar proton fluxes are given for a one year mission at selected integral energies ranging from 10 to 100 MeV, calculated for a year of maximum solar activity during the next solar cycle.

The effect of anatomical modeling on space radiation dose estimates: a comparison of doses for NASA phantoms and the 5th, 50th, and 95th percentile male and female astronauts.

PubMed

Bahadori, Amir A; Van Baalen, Mary; Shavers, Mark R; Dodge, Charles; Semones, Edward J; Bolch, Wesley E

2011-03-21

The National Aeronautics and Space Administration (NASA) performs organ dosimetry and risk assessment for astronauts using model-normalized measurements of the radiation fields encountered in space. To determine the radiation fields in an organ or tissue of interest, particle transport calculations are performed using self-shielding distributions generated with the computer program CAMERA to represent the human body. CAMERA mathematically traces linear rays (or path lengths) through the computerized anatomical man (CAM) phantom, a computational stylized model developed in the early 1970s with organ and body profiles modeled using solid shapes and scaled to represent the body morphometry of the 1950 50th percentile (PCTL) Air Force male. With the increasing use of voxel phantoms in medical and health physics, a conversion from a mathematical-based to a voxel-based ray-tracing algorithm is warranted. In this study, the voxel-based ray tracer (VoBRaT) is introduced to ray trace voxel phantoms using a modified version of the algorithm first proposed by Siddon (1985 Med. Phys. 12 252-5). After validation, VoBRAT is used to evaluate variations in body self-shielding distributions for NASA phantoms and six University of Florida (UF) hybrid phantoms, scaled to represent the 5th, 50th, and 95th PCTL male and female astronaut body morphometries, which have changed considerably since the inception of CAM. These body self-shielding distributions are used to generate organ dose equivalents and effective doses for five commonly evaluated space radiation environments. It is found that dosimetric differences among the phantoms are greatest for soft radiation spectra and light vehicular shielding.

Radiation Effects: Core Project

NASA Technical Reports Server (NTRS)

Dicello, John F.

1999-01-01

The risks to personnel in space from the naturally occurring radiations are generally considered to be one of the most serious limitations to human space missions, as noted in two recent reports of the National Research Council/National Academy of Sciences. The Core Project of the Radiation Effects Team for the National Space Biomedical Research Institute is the consequences of radiations in space in order to develop countermeasure, both physical and pharmaceutical, to reduce the risks of cancer and other diseases associated with such exposures. During interplanetary missions, personnel in space will be exposed to galactic cosmic rays, including high-energy protons and energetic ions with atomic masses of iron or higher. In addition, solar events will produce radiation fields of high intensity for short but irregular durations. The level of intensity of these radiations is considerably higher than that on Earth's surface, and the biological risks to astronauts is consequently increased, including increased risks of carcinogenesis and other diseases. This group is examining the risk of cancers resulting from low-dose, low-dose rate exposures of model systems to photons, protons, and iron by using ground-based accelerators which are capable of producing beams of protons, iron, and other heavy ions at energies comparable to those encountered in space. They have begun the first series of experiments using a 1-GeV iron beam at the Brookhaven National Laboratory and 250-MeV protons at Loma Linda University Medical Center's proton synchrotron facility. As part of these studies, this group will be investigating the potential for the pharmaceutical, Tamoxifen, to reduce the risk of breast cancer in astronauts exposed to the level of doses and particle types expected in space. Theoretical studies are being carried out in a collaboration between scientists at NASA's Johnson Space Center and Johns Hopkins University in parallel with the experimental program have provided methods and predictions which are being used to assess the levels of risks to be encountered and to evaluate appropriate strategies for countermeasures. Although the work in this project is primarily directed toward problems associated with space travel, the problem of protracted exposures to low-levels of radiation is one of national interest in our energy and defense programs, and the results may suggest new paradigms for addressing such risks.

In vivo space radiation-induced non-targeted responses: late effects on molecular signaling in mitochondria.

PubMed

Jain, Mohit R; Li, Min; Chen, Wei; Liu, Tong; de Toledo, Sonia M; Pandey, Badri N; Li, Hong; Rabin, Bernard M; Azzam, Edouard I

2011-06-01

The lack of clear knowledge about space radiation-induced biological effects has been singled out as the most important factor limiting the prediction of radiation risk associated with human space exploration. The expression of space radiation-induced non-targeted effects is thought to impact our understanding of the health risks associated with exposure to low fluences of particulate radiation encountered by astronauts during prolonged space travel. Following a brief review of radiation-induced bystander effects and the growing literature for the involvement of oxidative metabolism in their expression, we show novel data on the induction of in vivo non-targeted effects following exposure to 1100 MeV/nucleon titanium ions. Analyses of proteins by two-dimensional gel electrophoresis in non-targeted liver of cranially-irradiated Sprague Dawley rats revealed that the levels of key proteins involved in mitochondrial fatty acid metabolism are decreased. In contrast, those of proteins involved in various cellular defense mechanisms, including antioxidation, were increased. These data contribute to our understanding of the mechanisms underlying the biological responses to space radiation, and support the involvement of mitochondrial processes in the expression of radiation induced non-targeted effects. Significantly, they reveal the cross-talk between propagated stressful effects and induced adaptive responses. Together, with the accumulating data in the field, our results may help reduce the uncertainty in the assessment of the health risks to astronauts. They further demonstrate that 'network analyses' is an effective tool towards characterizing the signaling pathways that mediate the long-term biological effects of space radiation.

Evaluation of the dosimetric properties of a diode detector for small field proton radiosurgery

PubMed Central

Teran, Anthony V.; Slater, Jerry D.; Slater, James M.; Wroe, Andrew J.

2015-01-01

The small fields and sharp gradients typically encountered in proton radiosurgery require high spatial resolution dosimetric measurements, especially below 1–2 cm diameters. Radiochromic film provides high resolution, but requires postprocessing and special handling. Promising alternatives are diode detectors with small sensitive volumes (SV) that are capable of high resolution and real‐time dose acquisition. In this study we evaluated the PTW PR60020 proton dosimetry diode using radiation fields and beam energies relevant to radiosurgery applications. Energies of 127 and 157 MeV (9.7 to 15 cm range) and initial diameters of 8, 10, 12, and 20 mm were delivered using single‐stage scattering and four modulations (0, 15, 30, and 60 mm) to a water tank in our treatment room. Depth dose and beam profile data were compared with PTW Markus N23343 ionization chamber, EBT2 Gafchromic film, and Monte Carlo simulations. Transverse dose profiles were measured using the diode in "edge‐on" orientation or EBT2 film. Diode response was linear with respect to dose, uniform with dose rate, and showed an orientation‐dependent (i.e., beam parallel to, or perpendicular to, detector axis) response of less than 1%. Diode vs. Markus depth‐dose profiles, as well as Markus relative dose ratio vs. simulated dose‐weighted average lineal energy plots, suggest that any LET‐dependent diode response is negligible from particle entrance up to the very distal portion of the SOBP for the energies tested. Finally, while not possible with the ionization chamber due to partial volume effects, accurate diode depth‐dose measurements of 8, 10, and 12 mm diameter beams were obtained compared to Monte Carlo simulations. Because of the small SV that allows measurements without partial volume effects and the capability of submillimeter resolution (in edge‐on orientation) that is crucial for small fields and high‐dose gradients (e.g., penumbra, distal edge), as well as negligible LET dependence over nearly the full the SOBP, the PTW proton diode proved to be a useful high‐resolution, real‐time metrology device for small proton field radiation measurements such as would be encountered in radiosurgery applications. PACS numbers: 87.56.‐v, 87.56.jf, 87.56.Fc PMID:26699554

Long term dose monitoring onboard the European Columbus module of the International Space Station (ISS) in the frame of the DOSIS and DOSIS 3D project

NASA Astrophysics Data System (ADS)

Berger, Thomas

The radiation environment encountered in space differs in nature from that on earth, consisting mostly of high energetic ions from protons up to iron, resulting in radiation levels far exceeding the ones present on earth for occupational radiation workers. Accurate knowledge of the physical characteristics of the space radiation field in dependence on the solar activity, the orbital parameters and the different shielding configurations of the International Space Station (ISS) is therefore needed. For the investigation of the spatial and temporal distribution of the radiation field inside the European Columbus module the experiment “Dose Distribution Inside the ISS” (DOSIS), under the project and science lead of the German Aerospace Center (DLR), was launched on July 15th 2009 with STS-127 to the ISS. The DOSIS experiment consists of a combination of “Passive Detector Packages” (PDP) distributed at eleven locations inside Columbus for the measurement of the spatial variation of the radiation field and two active Dosimetry Telescopes (DOSTELs) with a Data and Power Unit (DDPU) in a dedicated nomex pouch mounted at a fixed location beneath the European Physiology Module rack (EPM) for the measurement of the temporal variation of the radiation field parameters. The DOSIS experiment suite measured during the lowest solar minimum conditions in the space age from July 2009 to June 2011. In July 2011 the active hardware was transferred to ground for refurbishment and preparation for the follow up DOSIS 3D experiment. The hardware for DOSIS 3D was launched with Soyuz 30S to the ISS on May 15th 2012. The PDPs are replaced with each even number Soyuz flight starting with Soyuz 30S. Data from the active detectors is transferred to ground via the EPM rack which is activated once a month for this action. The presentation will give an overview of the DOSIS and DOSIS 3D experiment and focus on the results from the passive radiation detectors from the DOSIS 3D experiment (2012 - 2014) in comparison to the data of the DOSIS experiment (2009 - 2011). The Polish contribution was supported by the National Science Centre (No DEC-2012/06/M/ST9/00423). The CAU contributions to DOSIS and DOSIS 3D are financially supported by BMWi under Grants 50WB0826, 50WB1026 and 50WB1232.

A Gaussian beam method for ultrasonic non-destructive evaluation modeling

NASA Astrophysics Data System (ADS)

Jacquet, O.; Leymarie, N.; Cassereau, D.

2018-05-01

The propagation of high-frequency ultrasonic body waves can be efficiently estimated with a semi-analytic Dynamic Ray Tracing approach using paraxial approximation. Although this asymptotic field estimation avoids the computational cost of numerical methods, it may encounter several limitations in reproducing identified highly interferential features. Nevertheless, some can be managed by allowing paraxial quantities to be complex-valued. This gives rise to localized solutions, known as paraxial Gaussian beams. Whereas their propagation and transmission/reflection laws are well-defined, the fact remains that the adopted complexification introduces additional initial conditions. While their choice is usually performed according to strategies specifically tailored to limited applications, a Gabor frame method has been implemented to indiscriminately initialize a reasonable number of paraxial Gaussian beams. Since this method can be applied for an usefully wide range of ultrasonic transducers, the typical case of the time-harmonic piston radiator is investigated. Compared to the commonly used Multi-Gaussian Beam model [1], a better agreement is obtained throughout the radiated field between the results of numerical integration (or analytical on-axis solution) and the resulting Gaussian beam superposition. Sparsity of the proposed solution is also discussed.

Supervision Challenges Encountered during Kenyan University Students' Practicum Attachment

ERIC Educational Resources Information Center

Kathuri-Ogola, Lucy; VanLeeuwen, Charlene; Kabaria-Muriithi, Joan; Weeks, Lori E.; Kieru, Jane; Ndayala, Phoebe

2015-01-01

There is little published research that examines the supervision experience of field attachment supervisors in Kenya. In this study, we identify the challenges encountered by field supervisors during student field attachments with community organizations. Fifteen organizations that had hosted third year students from the Department of Community…

Evaluation of 2 possible further developments of the UK in-flight radiation warning meter for SSTS

NASA Technical Reports Server (NTRS)

Wilson, I. J.; Eustace, R. C.

1972-01-01

A mass reduction of the moderator and the response to the nucleon flux, responsible for the tissue-star component of the total-dose equivalent rate using a high atomic number material, are discussed. Radiation situations at SST cruising altitudes (approximately 20 km) due to solar proton flares were simulated in the stratosphere and on the ground. Actual stratospheric situations due to galactic cosmic radiation with a limited range of quality factor values (2-4) were encountered during slow ascents by balloons to 36 km. Synthetic situations obtained from high and low energy acclerator radiations were used to obtain radiation distributions having a larger range of quality factor values (11/2-9) than experienced in the stratosphere. The measurements made in these simulations related to the directly ionizing, neutron and tissue-star components of dose-equivalent rate. Due to the restricted range of neutron spectra encountered in the stratosphere, a significant mass reduction of the moderator by 4 kg was made, with the moderator clad with cadmium or some other slow neutron absorber.

Manned Mars mission radiation environment and radiobiology

NASA Technical Reports Server (NTRS)

Nachtwey, D. S.

1986-01-01

Potential radiation hazards to crew members on manned Mars missions are discussed. It deals briefly with radiation sources and environments likely to be encountered during various phases of such missions, providing quantitative estimates of these environments. Also provided are quantitative data and discussions on the implications of such radiation on the human body. Various sorts of protective measures are suggested. Recent re-evaluation of allowable dose limits by the National Council of Radiation Protection is discussed, and potential implications from such activity are assessed.

Predicted levels of human radiation tolerance extrapolated from clinical studies of radiation effects

NASA Technical Reports Server (NTRS)

Lushbaugh, C. C.

1972-01-01

Results of clinical studies of radiation effects on man are used to evaluate space radiation hazards encountered during manned space travel. Considered are effects of photons as well as of mixed fission neutrons and gamma irradiations in establishing body radiosensitivity and tolerance levels. Upper and lower dose-response-time relations for acute radiation syndromes in patients indicate that man is more than sufficiently radioresistant to make the risks of an early radiation effect during one short space mission intangibly small in relation to the other nonradiation risks involved.

Simulator study of vortex encounters by a twin-engine, commercial, jet transport airplane

NASA Technical Reports Server (NTRS)

Hastings, E. C., Jr.; Keyser, G. L., Jr.

1982-01-01

A simulator study of vortex encounters was conducted for a twin-engine, commercial, jet transport airplane encountering the vortex flow field of a heavy, four-engine, commercial, jet transport airplane in the final-approach configuration. The encounters were conducted with fixed controls and with a pilot using a state-of-the-art, manual-control system. Piloted encounters with the base-line vortex flow field out of ground effect (unattenuated) resulted in initial bank-angle excursions greater than 40 deg, coupled with initial sideslip-angle excursions greater than 10 deg. The severity of these initial upsets was significantly reduced when the vortex center was moved laterally or vertically away from the flight path of the encountering airplane. Smaller reductions occurred when the flow field was attenuated by the flight spoilers on the generating airplane. The largest reduction in the severity of the initial upsets, however, was from aging in ground effect. The severity of the initial upsets of the following airplane was relatively unaffected by the approach speed. Increasing the lift coefficient of the generating airplane resulted in an increase in the severity of the initial upsets.

Examining Relativistic Electron Loss in the Outer Radiation Belt

NASA Astrophysics Data System (ADS)

Green, J. C.; Onsager, T. G.; O'Brien, P.

2003-12-01

Since the discovery of earth's radiation belts researchers have sought to identify the mechanisms that dictate the seemingly erratic relativistic electron flux levels in the outer belt. Contrary to intuition, relativistic electron flux levels do not always increase during geomagnetic storms even though these storms signify enhanced energy input from the solar wind to the magnetosphere [Reeves et al., 2003; O'Brien et al., 2001]. The fickle response of the radiation belt electrons to geomagnetic activity suggests that flux levels are determined by the outcome of a continuous competition between acceleration and loss. Some progress has been made developing and testing acceleration mechanisms but little is known about how relativistic electrons are lost. We examine relativistic electron losses in the outer belt focusing our attention on flux decrease events of the type first described by Onsager et al. [2002]. The study showed a sudden decrease of geosynchronous >2MeV electron flux occurring simultaneously with local stretching of the magnetic field. The decrease was first observed near 15:00 MLT and progressed to all local times after a period of ˜10 hours. Expanding on the work of Onsager et al. [2002], we have identified ˜ 51 such flux decrease events in the GOES and LANL data and present the results of a superposed epoch analysis of solar wind data, geomagnetic activity indicators, and locally measured magnetic field and plasma data. The analysis shows that flux decreases occur after 1-2 days of quiet condition. They begin when either the solar wind dynamic pressure increases or Bz turns southward pushing hot dense plasma earthward to form a partial ring current and stretched magnetic field at dusk. Adiabatic electron motion in response to the stretched magnetic field may explain the initial flux reduction; however, often the flux does not recover with the magnetic field recovery, indicating that true loss from the magnetosphere is occurring. Using Polar and SAMPEX data, we examine whether precipitation to the atmosphere or magnetopause encounters can account for the additional loss.

Visual cueing considerations in Nap-of-the-Earth helicopter flight head-slaved helmet-mounted displays

NASA Technical Reports Server (NTRS)

Grunwald, Arthur J.; Kohn, Silvia

1993-01-01

The pilot's ability to derive Control-Oriented Visual Field Information from teleoperated Helmet-Mounted displays in Nap-of-the-Earth flight, is investigated. The visual field with these types of displays, commonly used in Apache and Cobra helicopter night operations, originates from a relatively narrow field-of-view Forward Looking Infrared Radiation Camera, gimbal-mounted at the nose of the aircraft and slaved to the pilot's line-of-sight, in order to obtain a wide-angle field-of-regard. Pilots have encountered considerable difficulties in controlling the aircraft by these devices. Experimental simulator results presented here indicate that part of these difficulties can be attributed to head/camera slaving system phase lags and errors. In the presence of voluntary head rotation, these slaving system imperfections are shown to impair the Control-Oriented Visual Field Information vital in vehicular control, such as the perception of the anticipated flight path or the vehicle yaw rate. Since, in the presence of slaving system imperfections, the pilot will tend to minimize head rotation, the full wide-angle field-of-regard of the line-of-sight slaved Helmet-Mounted Display, is not always fully utilized.

Ground Penetrating Radar as a Contextual Sensor for Multi-Sensor Radiological Characterisation

PubMed Central

Ukaegbu, Ikechukwu K.; Gamage, Kelum A. A.

2017-01-01

Radioactive sources exist in environments or contexts that influence how they are detected and localised. For instance, the context of a moving source is different from a stationary source because of the effects of motion. The need to incorporate this contextual information in the radiation detection and localisation process has necessitated the integration of radiological and contextual sensors. The benefits of the successful integration of both types of sensors is well known and widely reported in fields such as medical imaging. However, the integration of both types of sensors has also led to innovative solutions to challenges in characterising radioactive sources in non-medical applications. This paper presents a review of such recent applications. It also identifies that these applications mostly use visual sensors as contextual sensors for characterising radiation sources. However, visual sensors cannot retrieve contextual information about radioactive wastes located in opaque environments encountered at nuclear sites, e.g., underground contamination. Consequently, this paper also examines ground-penetrating radar (GPR) as a contextual sensor for characterising this category of wastes and proposes several ways of integrating data from GPR and radiological sensors. Finally, it demonstrates combined GPR and radiation imaging for three-dimensional localisation of contamination in underground pipes using radiation transport and GPR simulations. PMID:28387706

Stability analysis for the background equations for inflation with dissipation and in a viscous radiation bath

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

Bastero-Gil, Mar; Cerezo, Rafael; Berera, Arjun

2012-11-01

The effects of bulk viscosity are examined for inflationary dynamics in which dissipation and thermalization are present. A complete stability analysis is done for the background inflaton evolution equations, which includes both inflaton dissipation and radiation bulk viscous effects. Three representative approaches of bulk viscous irreversible thermodynamics are analyzed: the Eckart noncausal theory, the linear and causal theory of Israel-Stewart and a more recent nonlinear and causal bulk viscous theory. It is found that the causal theories allow for larger bulk viscosities before encountering an instability in comparison to the noncausal Eckart theory. It is also shown that the causalmore » theories tend to suppress the radiation production due to bulk viscous pressure, because of the presence of relaxation effects implicit in these theories. Bulk viscosity coefficients derived from quantum field theory are applied to warm inflation model building and an analysis is made of the effects to the duration of inflation. The treatment of bulk pressure would also be relevant to the reheating phase after inflation in cold inflation dynamics and during the radiation dominated regime, although very little work in both areas has been done; the methodology developed in this paper could be extended to apply to these other problems.« less

Three Misconceptions About Radiation — And What We Teachers Can Do to Confront Them

NASA Astrophysics Data System (ADS)

Neumann, Susanne

2014-09-01

During the last few years teaching physics, I have noticed that my students are becoming more and more interested in the topic of radiation. Mobile phones, modern game consoles, and WiFi—all of these devices involving some kind of radiation are part of our students' everyday lives. Students are also frequently confronted in the media with debates relating to different types of radiation: What are the effects of nuclear contamination going to be after the Fukushima accident? Can radiation from mobile phones really cause cancer? Should the use of tanning booths be forbidden for teenagers? Although students seem to be very motivated to learn about the topic of radiation, I have encountered several misconceptions about this topic that my students bring into the physics classroom. Some of these misconceptions might be caused by biased media reports, while others can be attributed to a different usage of the word radiation in everyday language (when compared to the scientific usage of this term). In this paper, I would like to present the most common misconceptions about radiation that I have encountered in my physics courses and I would like to give some ideas how to confront these ideas in teaching. A detailed description of these misconceptions discovered through empirical research can be found in one of my research articles.1

Consistent approach to describing aircraft HIRF protection

NASA Technical Reports Server (NTRS)

Rimbey, P. R.; Walen, D. B.

1995-01-01

The high intensity radiated fields (HIRF) certification process as currently implemented is comprised of an inconsistent combination of factors that tend to emphasize worst case scenarios in assessing commercial airplane certification requirements. By examining these factors which include the process definition, the external HIRF environment, the aircraft coupling and corresponding internal fields, and methods of measuring equipment susceptibilities, activities leading to an approach to appraising airplane vulnerability to HIRF are proposed. This approach utilizes technically based criteria to evaluate the nature of the threat, including the probability of encountering the external HIRF environment. No single test or analytic method comprehensively addresses the full HIRF threat frequency spectrum. Additional tools such as statistical methods must be adopted to arrive at more realistic requirements to reflect commercial aircraft vulnerability to the HIRF threat. Test and analytic data are provided to support the conclusions of this report. This work was performed under NASA contract NAS1-19360, Task 52.

The excitation of electronic transverse energy levels in an intense magnetic field

NASA Technical Reports Server (NTRS)

Bussard, R. W.

1978-01-01

Observations of the X-ray pulsar Hercules X-1 show a line emission feature at about 60 keV, which has been interpreted as the fundamental electron cyclotron line in a magnetic field of around six trillion gauss. In this interpretation, the line radiation results from transitions between transverse energy levels, which are quantized by the field. The expected line luminosity from the excitation of these levels by protons which are falling into the polar cap of a neutron star are calculated. They are assumed to attain kinetic energies up to around 200 MeV, the gravitational potential energy at the surface. The cross sections for high energy Coulomb encounters between small pitch angle protons and electrons in a strong field are measured and used to calculate the energy loss rate of the infalling protons. This rate, together with the rate of elastic nuclear proton collisions, is then used to calculate the number of line photons an infalling proton can be expected to produce, directly or indirectly. The results are applied to Hercules X-1.

Electrical Characteristics of Simulated Tornadoes and Dust Devils

NASA Technical Reports Server (NTRS)

Zimmerman, Michael I.; Farrell, William M.; Barth, E. L.; Lewellen, W. S.; Perlongo, N. J.; Jackson, T. L.

2012-01-01

It is well known that tornadoes and dust devils have the ability to accumulate significant, visible clouds of debris. Collisions between sand-like debris species produce different electric charges on different types of grains, which convect along different trajectories around the vortex. Thus, significant charge separations and electric currents are possible, which as the vortex fluctuates over time are thought to produce ULF radiation signatures that have been measured in the field. These electric and magnetic fields may contain valuable information about tornado structure and genesis, and may be critical in driving electrochemical processes within dust devils on Mars. In the present work, existing large eddy simulations of debris-laden tornadoes performed at West Virginia University are coupled with a new debris-charging and advection code developed at Goddard Space Flight Center to investigate the detailed (meter-resolution) fluid-dynamic origins of electromagnetic fields within terrestrial vortices. First results are presented, including simulations of the electric and magnetic fields that would be observed by a near-surface, instrument-laden probe during a direct encounter with a tornado.

Hazards to space workers from ionizing radiation

NASA Technical Reports Server (NTRS)

Lyman, J. T.

1980-01-01

A compilation of background information and a preliminary assessment of the potential risks to workers from the ionizing radiation encountered in space is provided. The report: (1) summarizes the current knowledge of the space radiation environment to which space workers will be exposed; (2) reviews the biological effects of ionizing radiation considered of major importance to a SPS project; and (3) discusses the health implications of exposure of populations of space workers to the radiations likely to penetrate through the shielding provided by the SPS work stations and habitat shelters of the SPS Reference System.

Developments in Radiation-Hardened Electronics Applicable to the Vision for Space Exploration

NASA Technical Reports Server (NTRS)

Keys, Andrew S.; Frazier, Donald O.; Patrick , Marshall C.; Watson, Michael D.; Johnson, Michael A.; Cressler, John D.; Kolawa, Elizabeth A.

2007-01-01

The Radiation Hardened Electronics for Space Exploration (RHESE) project develops the advanced technologies required to produce radiation hardened electronics, processors, and devices in support of the anticipated requirements of NASA's Constellation program. Methods of protecting and hardening electronics against the encountered space environment are discussed. Critical stages of a spaceflight mission that are vulnerable to radiation-induced interruptions or failures are identified. Solutions to mitigating the risk of radiation events are proposed through the infusion of RHESE technology products and deliverables into the Constellation program's spacecraft designs.

Testing of Photomultiplier Tubes in a Magnetic Field

NASA Astrophysics Data System (ADS)

Waldron, Zachary; A1 Collaboration

2016-09-01

The A1 collaboration at MAMI in Mainz, Germany has designed a neutron detector that can be used in experiments to measure the electric form factor of the neutron. They will measure elastic scattering from the neutron, using the polarized electron beam from MAMI at A1's experimental hall. The detector will be composed of two walls of staggered scintillator bars which will be read out by photomultiplier tubes (PMT), connected to both ends of each scintillator via light guides. The experiment requires a magnetic field with strength of 1 Tesla, 2m away from the first scintillator wall. The resulting fringe field is sufficient to disrupt the PMTs, despite the addition of Mu Metal shielding. The effects of the fringe field on these PMTs was tested to optimize the amplification of the PMTs. A Helmholtz Coil was designed to generate a controlled magnetic field with equivalent strength to the field that the PMTs will encounter. The PMTs were read out using a multi-channel analyzer, were tested at various angles relative to the magnetic field in order to determine the optimal orientation to minimize signal disruption. Tests were also performed to determine: the neutron detector response to cosmic radiation; and the best method for measuring a magnetic field's strength in two dimensions. National Science Foundation Grant No. IIA-1358175.

Evaluation of Bulk Charging in Geostationary Transfer Orbit and Earth Escape Trajectories Using the Numit 1-D Charging Model

NASA Technical Reports Server (NTRS)

Minow, Joseph I.; Coffey, Victoria N.; Parker, Linda N.; Blackwell, William C., Jr.; Jun, Insoo; Garrett, Henry B.

2007-01-01

The NUMIT 1-dimensional bulk charging model is used as a screening to ol for evaluating time-dependent bulk internal or deep dielectric) ch arging of dielectrics exposed to penetrating electron environments. T he code is modified to accept time dependent electron flux time serie s along satellite orbits for the electron environment inputs instead of using the static electron flux environment input originally used b y the code and widely adopted in bulk charging models. Application of the screening technique ts demonstrated for three cases of spacecraf t exposure within the Earth's radiation belts including a geostationa ry transfer orbit and an Earth-Moon transit trajectory for a range of orbit inclinations. Electric fields and charge densities are compute d for dielectric materials with varying electrical properties exposed to relativistic electron environments along the orbits. Our objectiv e is to demonstrate a preliminary application of the time-dependent e nvironments input to the NUMIT code for evaluating charging risks to exposed dielectrics used on spacecraft when exposed to the Earth's ra diation belts. The results demonstrate that the NUMIT electric field values in GTO orbits with multiple encounters with the Earth's radiat ion belts are consistent with previous studies of charging in GTO orb its and that potential threat conditions for electrostatic discharge exist on lunar transit trajectories depending on the electrical proper ties of the materials exposed to the radiation environment.

Radiation dosimetry for the Gemini program

NASA Technical Reports Server (NTRS)

Richmond, R. G.

1972-01-01

The principal source of radiation for low-earth-orbit, low inclination space flights is in the area of the South Atlantic magnetic anomaly. None of the Gemini dose measurements reported in the paper are of high enough intensity to be considered hazardous. There is a trend toward larger doses as missions are flown higher and longer. Extended orbital operations between 1400 and 4400 kilometers would encounter high interior radiation levels. Pronounced spacecraft geometry effects have been measured in manned spacecraft. Instrumentation for radiation measurements on Gemini spacecraft is described.

RBE of radiations in space and the implications for space travel.

PubMed

Edwards, A A

2001-01-01

Space travellers are irradiated with cosmic rays to a dose rate considerably higher than that received on earth. In order to make sensible judgements about space exploration, the risks to health of such radiation need to be assessed. Part of the assessment of risk is to allow for the enhanced biological effectiveness of high LET radiations with respect to others. In space the high LET radiations of concern are high energy neutrons and charged particles. At the doses and dose rates encountered in space, the important risk is the induction of cancer in the astronauts. For this biological end-point there is no direct human evidence for the relative effectiveness of these radiations. There are some data for neutrons for cancer and life-shortening in laboratory animals but these are for fission spectra neutrons, which are of lower energy than those encountered in space. There is a small amount of data for protons and high energy heavier charged particles. The remaining evidence comes from cellular experiments observing chromosome aberrations and gene mutations. From this sparse information, pragmatic choices need to be made for application to protection in space. The data are reviewed and the bases for the pragmatic choices discussed.

Evaluation of computed tomography numbers for treatment planning of lung cancer

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

Mira, J.G.; Fullerton, G.D.; Ezekiel, J.

1982-09-01

Computerized tomography numbers (CTN) were evaluated in 32 computerized tomography scans performed on patients with carcinoma of the lung, with the aim of evaluating CTN in normal (lung, blood, muscle, etc) and pathologic tissues (tumor, atelectasis, effusion, post-radiation fibrosis). Our main findings are: 1. Large individual CTN variations are encountered in both normal and pathologic tissues, above and below mean values. Hence, absolute numbers are meaningless. Measurements of any abnormal intrathoracic structure should be compared in relation to normal tissue CTN values in the same scan. 2. Tumor and complete atelectasis have CTN basically similar to soft tissue. Hence, thesemore » numbers are not useful for differential diagnosis. 3. Effusions usually have lower CTN and can be distinguished from previous situations. 4. Dosimetry based on uniform lung density assumptions (i.e., 300 mg/cm/sup 3/) might produce substantial dose errors as lung CTN exhibit variations indicating densities well above and below this value. 5. Preliminary information indicates that partial atelectasis and incipient post-radiation fibrosis can have very low CTN. Hence, they can be differentiated from solid tumors in certain cases, and help in differential diagnosis of post radiation recurrence within the radiotherapy field versus fibrosis.« less

A simulation study of fast neutron interrogation for standoff detection of improvised explosive devices

NASA Astrophysics Data System (ADS)

Heider, S. A.; Dunn, W. L.

2015-11-01

The signature-based radiation-scanning technique utilizes radiation detector responses, called "signatures," and compares these to "templates" in order to differentiate targets that contain certain materials, such as explosives or drugs, from those that do not. Our investigations are aimed at the detection of nitrogen-rich explosives contained in improvised explosive devices. We use the term "clutter" to refer to any non-explosive materials with which the interrogating radiation may interact between source and detector. To deal with the many target types and clutter configurations that may be encountered in the field, the use of "artificial templates" is proposed. The MCNP code was used to simulate 14.1 MeV neutron source beams incident on one type of target containing various clutter and sample materials. Signatures due to inelastic-scatter and prompt-capture gamma rays from hydrogen, carbon, nitrogen, and oxygen and two scattered neutron signatures were considered. Targets containing explosive materials in the presence of clutter were able to be identified from targets that contained only non-explosive ("inert") materials. This study demonstrates that a finite number of artificial templates is sufficient for IED detection with fairly good sensitivity and specificity.

Observations of the magnetic field and plasma flow in Jupiter's magnetosheath

NASA Technical Reports Server (NTRS)

Lepping, R. P.; Burlaga, L. F.; Klein, L. W.; Jessen, J. M.; Goodrich, G. C.

1980-01-01

Large scale (many minutes to 10 hours) magnetic field structures consisting predominantly of nearly north-south field direction were discovered in Jupiter's magnetosheath from the data of Voyagers 1 and 2 and Pioneer 10 during their outbound encounter trajectories. The Voyager 2 data, and that of Voyager 1 to a lesser extent, show evidence of a quasi-period of 10 hours (and occasionally 5 hours) for these structures. The north-south components of the field and plasma velocity were strongly correlated in the outbound magnetosheath as observed by Voyagers 1 and 2, and the components orthogonal to the north-south direction showed weak correlations. For both Voyager encounters the sense (positive and negative) of the north-south correlations were directly related to the direction of the ecliptic plane component of the interplanetary magnetic field using the field and plasma measurements of the non-encountering spacecraft.

Preliminary science results of Voyager 1 Saturn encounter

NASA Technical Reports Server (NTRS)

Bane, D.

1981-01-01

Preliminary science results of the Voyager 1 encounter of the planet Saturn are reported. On August 22, 1980, the spacecraft was 109 million km (68 million mi) from Saturn. Closest approach to Saturn took place on November 12, at 3:46 p.m. (PDT), when the spacecraft passed 126,000 km (78,000 mi) from the cloud tops. Measurements of the atmosphere, wind speed, radiation, six surrounding rings, and the planet's old and newly found satellites were recorded. The encounter ended December 15, 1980. The spacecraft took more than 17,500 photographs of Saturn and its satellites.

10 CFR 32.74 - Manufacture and distribution of sources or devices containing byproduct material for medical use.

Code of Federal Regulations, 2012 CFR

2012-01-01

... pertinent to an evaluation of its radiation safety, including: (i) The byproduct material contained, its... maintain its integrity under stresses likely to be encountered in normal use and accidents; (iv) For devices containing byproduct material, the radiation profile of a prototype device; (v) Details of quality...

10 CFR 32.74 - Manufacture and distribution of sources or devices containing byproduct material for medical use.

Code of Federal Regulations, 2011 CFR

2011-01-01

... pertinent to an evaluation of its radiation safety, including: (i) The byproduct material contained, its... maintain its integrity under stresses likely to be encountered in normal use and accidents; (iv) For devices containing byproduct material, the radiation profile of a prototype device; (v) Details of quality...

The DOSIS and DOSIS 3D Experiments onboard the International Space Station - Results from the Active DOSTEL Instruments

NASA Astrophysics Data System (ADS)

Burmeister, Soenke; Berger, Thomas; Reitz, Guenther; Beaujean, Rudolf; Boehme, Matthias; Haumann, Lutz; Labrenz, Johannes; Kortmann, Onno

2012-07-01

Besides the effects of the microgravity environment, and the psychological and psychosocial problems experienced in confined spaces, radiation is the main health detriment for long duration human space missions. The radiation environment encountered in space differs in nature from that on earth, consisting mostly of high energetic ions from protons up to iron, resulting in radiation levels far exceeding the ones present on earth for occupational radiation workers. Accurate knowledge of the physical characteristics of the space radiation field in dependence on the solar activity, the orbital parameters and the different shielding configurations of the International Space Station ISS is therefore needed. For the investigation of the spatial and temporal distribution of the radiation field inside the European COLUMBUS module the experiment DOSIS (Dose Distribution Inside the ISS) under the lead of DLR was launched on July 15th 2009 with STS-127 to the ISS. The experimental package was transferred from the Space Shuttle into COLUMBUS on July 18th. It consists of a combination of passive detector packages (PDP) distributed at 11 locations inside the European Columbus Laboratory and two active radiation detectors (DOSTELs) with a DDPU (DOSTEL Data and Power Unit) in a nomex pouch (DOSIS MAIN BOX) mounted at a fixed location beneath the European Physiology Module rack (EPM) inside COLUMBUS. The DOSTELs measured during the lowest solar minimum conditions in the space age from July 18th 2009 to June 16th 2011. In July 2011 the active hardware was transferred to ground for refurbishment and preparation for the DOSIS-3D experiment. The hardware will be launched with the Soyuz 30S flight to the ISS on May 15th 2012 and activated approximately ten days later. Data will be transferred from the DOSTEL units to ground via the EPM rack which is activated approximately every four weeks for this action. First Results for the active DOSIS-3D measurements such as count rate profiles, dose rates and LET spectra will be presented in comparison to the data of the DOSIS experiment as well as the DOSMAP experiment which has been performed during solar maximum in 2001.

Consumer Products Containing Radioactive Materials

MedlinePlus

Fact Sheet Adopted: February 2010 Health Physics Society Specialists in Radiation Safety Consumer Products Containing Radioactive Materials Everything we encounter in our daily lives contains some radioactive material, ...

Pedagogical encounters between nurses and patients in a medical ward--a field study.

PubMed

Friberg, F; Andersson, E Pilhammar; Bengtsson, J

2007-05-01

Patient teaching is regarded as an important aspect of nursing care as well as an essential part of the nursing profession. In nursing practice, a distinction can be made between formal (planned) and informal (spontaneous) patient teaching. The major part of patient teaching research is within the area of formal teaching. In spite of the fact that spontaneous teaching occurs in everyday nursing practice, there is a lack of knowledge in this area. The aim was to illuminate pedagogical dimensions in nursing situations and informal teaching. The study is a fieldwork study within the frames of a life-world phenomenological tradition. Fifteen registered nurses in a general medical ward of a university hospital in Sweden were followed in their daily work with patients. Twelve patients suffering from various chronic diseases were interviewed. The observations comprised a total of 173 h on 34 separate occasions. Informal dialogues with nurses were carried through. Further, formal interviews were conducted with 12 of the observed patients. The data were analysed by means of a life-world phenomenological approach. Two different pedagogical encounters are presented: "Players in different field pedagogical encounters", in which there is a breakdown in the pedagogical dialogue, and "Players in same field pedagogical encounters", in which the pedagogical dialogue develops. Patients' experiences of seeking and acquiring knowledge within these two types of encounter are characterised as "worry" versus "preparedness". Patients' dignity is either threatened or supported, depending on the type of encounter. Health care organisations have to create a pedagogical climate where "Same field pedagogical encounters" can be created. The nurse has to view the patient as a learning person in order to help the patient to achieve "preparedness". "Preparedness" is described as a cognitive-emotive-existential state and emphasised as an important goal of patient teaching.

Kinetic and spectral descriptions of autoionization phenomena associated with atomic processes in plasmas

NASA Astrophysics Data System (ADS)

Jacobs, Verne L.

2017-06-01

This investigation has been devoted to the theoretical description and computer modeling of atomic processes giving rise to radiative emission in energetic electron and ion beam interactions and in laboratory plasmas. We are also interested in the effects of directed electron and ion collisions and of anisotropic electric and magnetic fields. In the kinetic-theory description, we treat excitation, de-excitation, ionization, and recombination in electron and ion encounters with partially ionized atomic systems, including the indirect contributions from processes involving autoionizing resonances. These fundamental collisional and electromagnetic interactions also provide particle and photon transport mechanisms. From the spectral perspective, the analysis of atomic radiative emission can reveal detailed information on the physical properties in the plasma environment, such as non-equilibrium electron and charge-state distributions as well as electric and magnetic field distributions. In this investigation, a reduced-density-matrix formulation is developed for the microscopic description of atomic electromagnetic interactions in the presence of environmental (collisional and radiative) relaxation and decoherence processes. Our central objective is a fundamental microscopic description of atomic electromagnetic processes, in which both bound-state and autoionization-resonance phenomena can be treated in a unified and self-consistent manner. The time-domain (equation-of-motion) and frequency-domain (resolvent-operator) formulations of the reduced-density-matrix approach are developed in a unified and self-consistent manner. This is necessary for our ultimate goal of a systematic and self-consistent treatment of non-equilibrium (possibly coherent) atomic-state kinetics and high-resolution (possibly overlapping) spectral-line shapes. We thereby propose the introduction of a generalized collisional-radiative atomic-state kinetics model based on a reduced-density-matrix formulation. It will become apparent that the full atomic data needs for the precise modeling of extreme non-equilibrium plasma environments extend beyond the conventional radiative-transition-probability and collisional-cross-section data sets.

Influence of Dust Loading on Atmospheric Ionizing Radiation on Mars

NASA Technical Reports Server (NTRS)

Norman, Ryan B.; Gronoff, Guillaume; Mertens, Christopher J.

2014-01-01

Measuring the radiation environment at the surface of Mars is the primary goal of the Radiation Assessment Detector on the NASA Mars Science Laboratory's Curiosity rover. One of the conditions that Curiosity will likely encounter is a dust storm. The objective of this paper is to compute the cosmic ray ionization in different conditions, including dust storms, as these various conditions are likely to be encountered by Curiosity at some point. In the present work, the Nowcast of Atmospheric Ionizing Radiation for Aviation Safety model, recently modified for Mars, was used along with the Badhwar & O'Neill 2010 galactic cosmic ray model. In addition to galactic cosmic rays, five different solar energetic particle event spectra were considered. For all input radiation environments, radiation dose throughout the atmosphere and at the surface was investigated as a function of atmospheric dust loading. It is demonstrated that for galactic cosmic rays, the ionization depends strongly on the atmosphere profile. Moreover, it is shown that solar energetic particle events strongly increase the ionization throughout the atmosphere, including ground level, and can account for the radio blackout conditions observed by the Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument on the Mars Express spacecraft. These results demonstrate that the cosmic rays' influence on the Martian surface chemistry is strongly dependent on solar and atmospheric conditions that should be taken into account for future studies.

Use of Advanced Solar Cells for Commercial Communication Satellites

NASA Technical Reports Server (NTRS)

Bailey, Sheila G.; Landis, Geoffrey A.

1995-01-01

The current generation of communications satellites are located primarily in geosynchronous Earth orbit (GEO). Over the next decade, however, a new generation of communications satellites will be built and launched, designed to provide a world-wide interconnection of portable telephones. For this mission, the satellites must be positioned in lower polar and near-polar orbits. To provide complete coverage, large numbers of satellites will be required. Because the required number of satellites decreases as the orbital altitude is increased, fewer satellites would be required if the orbit chosen were raised from low to intermediate orbit. However, in intermediate orbits, satellites encounter significant radiation due to trapped electrons and protons. Radiation tolerant solar cells may be necessary to make such satellites feasible. We analyze the amount of radiation encountered in low and intermediate polar orbits at altitudes of interest to next-generation communication satellites, calculate the expected degradation for silicon, GaAs, and InP solar cells, and show that the lifetimes can be significantly increased by use of advanced solar cells.

Use of advanced solar cells for commerical communication satellites

NASA Astrophysics Data System (ADS)

Landis, Geoffrey A.; Bailey, Sheila G.

1995-01-01

The current generation of communications satellites are located primarily in geosynchronous Earth orbit (GEO). Over the next decade, however, a new generation of communications satellites will be built and launched, designed to provide a world-wide interconnection of portable telephones. For this mission, the satellites must be positioned in lower polar- and near-polar orbits. To provide complete coverage, large numbers of satellites will be required. Because of the required number of satellites decreases as the orbital altitude is increased, fewer satellites would be required if the orbit chosen were raised from Low to intermediate orbit. However, in intermediate orbits, satellites encounter significant radiation due to trapped electrons and protons. Radiation tolerant solar cells may be necessary to make such satellites feasible. We analyze the amount of radiation encountered in low and intermediate polar orbits at altitudes of interest to next-generation communication satellites, calculate the expected degradation for silicon, GaAs, and InP solar cells, and show that the lifetimes can be significantly increased by use of advanced solar cells.

Use of advanced solar cells for commercial communication satellites

NASA Astrophysics Data System (ADS)

Bailey, Sheila G.; Landis, Geoffrey A.

1995-03-01

The current generation of communications satellites are located primarily in geosynchronous Earth orbit (GEO). Over the next decade, however, a new generation of communications satellites will be built and launched, designed to provide a world-wide interconnection of portable telephones. For this mission, the satellites must be positioned in lower polar and near-polar orbits. To provide complete coverage, large numbers of satellites will be required. Because the required number of satellites decreases as the orbital altitude is increased, fewer satellites would be required if the orbit chosen were raised from low to intermediate orbit. However, in intermediate orbits, satellites encounter significant radiation due to trapped electrons and protons. Radiation tolerant solar cells may be necessary to make such satellites feasible. We analyze the amount of radiation encountered in low and intermediate polar orbits at altitudes of interest to next-generation communication satellites, calculate the expected degradation for silicon, GaAs, and InP solar cells, and show that the lifetimes can be significantly increased by use of advanced solar cells.

Extreme Environment Technologies for Space and Terrestrial Applications

NASA Technical Reports Server (NTRS)

Balint, Tibor S.; Cutts, James A.; Kolawa, Elizabeth A.; Peterson, Craig E.

2008-01-01

Over the next decades, NASA's planned solar system exploration missions are targeting planets, moons and small bodies, where spacecraft would be expected to encounter diverse extreme environmental (EE) conditions throughout their mission phases. These EE conditions are often coupled. For instance, near the surface of Venus and in the deep atmospheres of giant planets, probes would experience high temperatures and pressures. In the Jovian system low temperatures are coupled with high radiation. Other environments include thermal cycling, and corrosion. Mission operations could also introduce extreme conditions, due to atmospheric entry heat flux and deceleration. Some of these EE conditions are not unique to space missions; they can be encountered by terrestrial assets from the fields of defense,oil and gas, aerospace, and automotive industries. In this paper we outline the findings of NASA's Extreme Environments Study Team, including discussions on state of the art and emerging capabilities related to environmental protection, tolerance and operations in EEs. We will also highlight cross cutting EE mitigation technologies, for example, between high g-load tolerant impactors for Europa and instrumented projectiles on Earth; high temperature electronics sensors on Jupiter deep probes and sensors inside jet engines; and pressure vessel technologies for Venus probes and sea bottom monitors. We will argue that synergistic development programs between these fields could be highly beneficial and cost effective for the various agencies and industries. Some of these environments, however, are specific to space and thus the related technology developments should be spear headed by NASA with collaboration from industry and academia.

Corona And Ultraviolet Equipment For Testing Materials

NASA Technical Reports Server (NTRS)

Laue, Eric G.

1993-01-01

Two assemblies of laboratory equipment developed for use in testing abilities of polymers, paints, and other materials to withstand ultraviolet radiation and charged particles. One is vacuum ultraviolet source built around commercial deuterium lamp. Other exposes specimen in partial vacuum to both ultraviolet radiation and brush corona discharge. Either or both assemblies used separately or together to simulate approximately combination of solar radiation and charged particles encountered by materials aboard spacecraft in orbit around Earth. Also used to provide rigorous environmental tests of materials exposed to artificial ultraviolet radiation and charged particles in industrial and scientific settings or to natural ultraviolet radiation and charged particles aboard aircraft at high altitudes.

A general method for computing the total solar radiation force on complex spacecraft structures

NASA Technical Reports Server (NTRS)

Chan, F. K.

1981-01-01

The method circumvents many of the existing difficulties in computational logic presently encountered in the direct analytical or numerical evaluation of the appropriate surface integral. It may be applied to complex spacecraft structures for computing the total force arising from either specular or diffuse reflection or even from non-Lambertian reflection and re-radiation.

Simulation of planetary entry radiative heating with a CO2 gasdynamic laser

NASA Technical Reports Server (NTRS)

Lundell, J. H.; Dickey, R. R.; Howe, J. T.

1975-01-01

Heating encountered during entry into the atmospheres of Jupiter, Saturn, and Uranus is described, followed by a discussion of the use of a CO2 gasdynamic laser to simulate the radiative component of the heating. Operation and performance of the laser is briefly described. Finally, results of laser tests of some candidate heat-shield materials are presented.

Fast-Neutron Survey With Compact Plastic Scintillation Detectors.

PubMed

Preston, Rhys M; Tickner, James R

2017-07-01

With the rise of the Silicon Photomultiplier (SiPM), it is now practical to build compact scintillation detectors well suited to portable use. A prototype survey meter for fast-neutrons and gamma-rays, based around an EJ-299-34 plastic scintillator with SiPM readout, has been developed and tested. A custom digital pulse processor was used to perform pulse shape discrimination on-the-fly. Ambient dose equivalent H*(10) was calculated by means of two energy-dependent 'G-functions'. The sensitivity was calculated to be between 0.10 and 0.22 cps/(µSv/hr) for fast-neutrons with energies above 2.5 MeV. The prototype was used to survey various laboratory radiation fields, with the readings compared with commercial survey meters. The high sensitivity and lightweight nature of this detector makes it promising for rapid survey of the mixed neutron/gamma-ray fields encountered in industry and homeland security. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Protons and Electrons in Jupiter's Magnetic Field: Results from the University of Chicago Experiment on Pioneer 10.

PubMed

Simpson, J A; Hamilton, D; Lentz, G; McKibben, R B; Mogro-Campero, A; Perkins, M; Pyle, K R; Tuzzolino, A J; O'gallagher, J J

1974-01-25

Fluxes of high energy electrons and protons are found to be highly concentrated near the magnetic equatorial plane from distances of ~ 30 to ~ 100 Jovian radii (R(J)). The 10-hour period of planetary rotation is observed as an intensity variation, which indicates that the equatorial zone of high particle fluxes is inclined with respect to the rotation axis of the planet. At radial distances [unknown] 20 R(J) the synchrotron-radiation-producing electrons with energies greater, similar 3 million electron volts rise steeply to a maximum intensity of ~ 5 x 10(8) electrons per square centimeter per second near the periapsis at 2.8 R(J). The flux of protons with energies greater, similar 30 million electron volts reaches a maximum intensity of ~ 4 x 10(6) protons per square centimeter per second at ~ 3.5 R(J) with the intensity decreasing inside this radial distance. Only for radial distances [unknown] 20 R(J) does the radiation behave in a manner which is similar to that at the earth. Burst of electrons with energies up to 30 million electron volts, each lasting about 2 days, were observed in interplanetary space beginning approximately 1 month before encounter. This radiation appears to have escaped from the Jovian bow shock or magnetosphere.

The Capture of Interstellar Dust: The Pure Poynting-Robertson Case

NASA Technical Reports Server (NTRS)

Jackson, A. A.

2001-01-01

Ulysses and Galileo spacecraft have discovered interstellar dust particles entering the solar system. In general, particles trajectories not altered by Lorentz forces or radiation pressure should encounter the sun on open orbits. Under Newtonian forces alone these particles return to the interstellar medium. Dissipative forces, such as Poynting Robertson (PR) and corpuscular drag and non-dissipative Lorentz forces can modify open orbits to become closed. In particular, it is possible for the orbits of particles that pass close to the Sun to become closed due to PR drag. Further, solar irradiation will cause modification of the size of the dust particle by evaporation. The combination of these processes gives rise a class of capture orbits and bound orbits with evaporation. Considering only the case of pure PR drag a minimum impact parameter is derived for initial capture by Poynting-Robertson drag. Orbits in the solar radiation field are computed numerically accounting for evaporation with optical and material properties for ideal interstellar particles modeled. The properties of this kind of particle capture are discussed for the Sun but is applicable to other stars.

Guest-Host Encounters in Diaspora-Heritage Tourism: The Taglit-Birthright Israel Mifgash (Encounter)

ERIC Educational Resources Information Center

Sasson, Theodore; Mittelberg, David; Hecht, Shahar; Saxe, Leonard

2011-01-01

More than 300,000 diaspora Jewish young adults and tens of thousands of their Israeli peers have participated in structured, cross-cultural encounters--"mifgashim"--in the context of an experiential education program known as Taglit-Birthright Israel. Drawing on field observations, interviews, and surveys, the formal and informal…

Emergence of encounter networks due to human mobility.

PubMed

Riascos, A P; Mateos, José L

2017-01-01

There is a burst of work on human mobility and encounter networks. However, the connection between these two important fields just begun recently. It is clear that both are closely related: Mobility generates encounters, and these encounters might give rise to contagion phenomena or even friendship. We model a set of random walkers that visit locations in space following a strategy akin to Lévy flights. We measure the encounters in space and time and establish a link between walkers after they coincide several times. This generates a temporal network that is characterized by global quantities. We compare this dynamics with real data for two cities: New York City and Tokyo. We use data from the location-based social network Foursquare and obtain the emergent temporal encounter network, for these two cities, that we compare with our model. We found long-range (Lévy-like) distributions for traveled distances and time intervals that characterize the emergent social network due to human mobility. Studying this connection is important for several fields like epidemics, social influence, voting, contagion models, behavioral adoption and diffusion of ideas.

Quantum-mechanical transport equation for atomic systems.

NASA Technical Reports Server (NTRS)

Berman, P. R.

1972-01-01

A quantum-mechanical transport equation (QMTE) is derived which should be applicable to a wide range of problems involving the interaction of radiation with atoms or molecules which are also subject to collisions with perturber atoms. The equation follows the time evolution of the macroscopic atomic density matrix elements of atoms located at classical position R and moving with classical velocity v. It is quantum mechanical in the sense that all collision kernels or rates which appear have been obtained from a quantum-mechanical theory and, as such, properly take into account the energy-level variations and velocity changes of the active (emitting or absorbing) atom produced in collisions with perturber atoms. The present formulation is better suited to problems involving high-intensity external fields, such as those encountered in laser physics.

GCR Simulator Reference Field and a Spectral Approach for Laboratory Simulation

NASA Technical Reports Server (NTRS)

Slaba, Tony C.; Blattnig, Steve R.; Norbury, John W.; Rusek, Adam; La Tessa, Chiara; Walker, Steven A.

2015-01-01

The galactic cosmic ray (GCR) simulator at the NASA Space Radiation Laboratory (NSRL) is intended to deliver the broad spectrum of particles and energies encountered in deep space to biological targets in a controlled laboratory setting. In this work, certain aspects of simulating the GCR environment in the laboratory are discussed. Reference field specification and beam selection strategies at NSRL are the main focus, but the analysis presented herein may be modified for other facilities. First, comparisons are made between direct simulation of the external, free space GCR field and simulation of the induced tissue field behind shielding. It is found that upper energy constraints at NSRL limit the ability to simulate the external, free space field directly (i.e. shielding placed in the beam line in front of a biological target and exposed to a free space spectrum). Second, variation in the induced tissue field associated with shielding configuration and solar activity is addressed. It is found that the observed variation is likely within the uncertainty associated with representing any GCR reference field with discrete ion beams in the laboratory, given current facility constraints. A single reference field for deep space missions is subsequently identified. Third, an approach for selecting beams at NSRL to simulate the designated reference field is presented. Drawbacks of the proposed methodology are discussed and weighed against alternative simulation strategies. The neutron component and track structure characteristics of the simulated field are discussed in this context.

Generation and Radiation of Acoustic Waves from a 2-D Shear Layer

NASA Technical Reports Server (NTRS)

Agarwal, Anurag; Morris, Philip J.

2000-01-01

A parallel numerical simulation of the radiation of sound from an acoustic source inside a 2-D jet is presented in this paper. This basic benchmark problem is used as a test case for scattering problems that are presently being solved by using the Impedance Mismatch Method (IMM). In this technique, a solid body in the domain is represented by setting the acoustic impedance of each medium, encountered by a wave, to a different value. This impedance discrepancy results in reflected and scattered waves with appropriate amplitudes. The great advantage of the use of this method is that no modifications to a simple Cartesian grid need to be made for complicated geometry bodies. Thus, high order finite difference schemes may be applied simply to all parts of the domain. In the IMM, the total perturbation field is split into incident and scattered fields. The incident pressure is assumed to be known and the equivalent sources for the scattered field are associated with the presence of the scattering body (through the impedance mismatch) and the propagation of the incident field through a non-uniform flow. An earlier version of the technique could only handle uniform flow in the vicinity of the source and at the outflow boundary. Scattering problems in non-uniform mean flow are of great practical importance (for example, scattering from a high lift device in a non-uniform mean flow or the effects of a fuselage boundary layer). The solution to this benchmark problem, which has an acoustic wave propagating through a non-uniform mean flow, serves as a test case for the extensions of the IMM technique.

Identifying Student and Teacher Difficulties in Interpreting Atomic Spectra Using a Quantum Model of Emission and Absorption of Radiation

ERIC Educational Resources Information Center

Savall-Alemany, Francisco; Domènech-Blanco, Josep Lluís; Guisasola, Jenaro; Martínez-Torregrosa, Joaquín

2016-01-01

Our study sets out to identify the difficulties that high school students, teachers, and university students encounter when trying to explain atomic spectra. To do so, we identify the key concepts that any quantum model for the emission and absorption of electromagnetic radiation must include to account for the gas spectra and we then design two…

Space radiation dosimetry in low-Earth orbit and beyond.

PubMed

Benton, E R; Benton, E V

2001-09-01

Space radiation dosimetry presents one of the greatest challenges in the discipline of radiation protection. This is a result of both the highly complex nature of the radiation fields encountered in low-Earth orbit (LEO) and interplanetary space and of the constraints imposed by spaceflight on instrument design. This paper reviews the sources and composition of the space radiation environment in LEO as well as beyond the Earth's magnetosphere. A review of much of the dosimetric data that have been gathered over the last four decades of human space flight is presented. The different factors affecting the radiation exposures of astronauts and cosmonauts aboard the International Space Station (ISS) are emphasized. Measurements made aboard the Mir Orbital Station have highlighted the importance of both secondary particle production within the structure of spacecraft and the effect of shielding on both crew dose and dose equivalent. Roughly half the dose on ISS is expected to come from trapped protons and half from galactic cosmic rays (GCRs). The dearth of neutron measurements aboard LEO spacecraft and the difficulty inherent in making such measurements have led to large uncertainties in estimates of the neutron contribution to total dose equivalent. Except for a limited number of measurements made aboard the Apollo lunar missions, no crew dosimetry has been conducted beyond the Earth's magnetosphere. At the present time we are forced to rely on model-based estimates of crew dose and dose equivalent when planning for interplanetary missions, such as a mission to Mars. While space crews in LEO are unlikely to exceed the exposure limits recommended by such groups as the NCRP, dose equivalents of the same order as the recommended limits are likely over the course of a human mission to Mars. c2001 Elsevier Science B.V. All rights reserved.

Charged particle spectra measured during the transit to Mars with the Mars Science Laboratory Radiation Assessment Detector (MSL/RAD)

NASA Astrophysics Data System (ADS)

Ehresmann, Bent; Hassler, Donald M.; Zeitlin, Cary; Guo, Jingnan; Köhler, Jan; Wimmer-Schweingruber, Robert F.; Appel, Jan K.; Brinza, David E.; Rafkin, Scot C. R.; Böttcher, Stephan I.; Burmeister, Sönke; Lohf, Henning; Martin, Cesar; Böhm, Eckart; Matthiä, Daniel; Reitz, Günther

2016-08-01

The Mars Science Laboratory (MSL) started its 253-day cruise to Mars on November 26, 2011. During cruise the Radiation Assessment Detector (RAD), situated on board the Curiosity rover, conducted measurements of the energetic-particle radiation environment inside the spacecraft. This environment consists mainly of galactic cosmic rays (GCRs), as well as secondary particles created by interactions of these GCRs with the spacecraft. The RAD measurements can serve as a proxy for the radiation environment a human crew would encounter during a transit to Mars, for a given part of the solar cycle, assuming that a crewed vehicle would have comparable shielding. The measurements of radiological quantities made by RAD are important in themselves, and, the same data set allow for detailed analysis of GCR-induced particle spectra inside the spacecraft. This provides important inputs for the evaluation of current transport models used to model the free-space (and spacecraft) radiation environment for different spacecraft shielding and different times in the solar cycle. Changes in these conditions can lead to significantly different radiation fields and, thus, potential health risks, emphasizing the need for validated transport codes. Here, we present the first measurements of charged particle fluxes inside a spacecraft during the transit from Earth to Mars. Using data obtained during the last two month of the cruise to Mars (June 11-July 14, 2012), we have derived detailed energy spectra for low-Z particles stopping in the instrument's detectors, as well as integral fluxes for penetrating particles with higher energies. Furthermore, we analyze the temporal changes in measured proton fluxes during quiet solar periods (i.e., when no solar energetic particle events occurred) over the duration of the transit (December 9, 2011-July 14, 2012) and correlate them with changing heliospheric conditions.

Patient perspectives of telemedicine quality

PubMed Central

LeRouge, Cynthia M; Garfield, Monica J; Hevner, Alan R

2015-01-01

Background The purpose of this study was to explore the quality attributes required for effective telemedicine encounters from the perspective of the patient. Methods We used a multi-method (direct observation, focus groups, survey) field study to collect data from patients who had experienced telemedicine encounters. Multi-perspectives (researcher and provider) were used to interpret a rich set of data from both a research and practice perspective. Results The result of this field study is a taxonomy of quality attributes for telemedicine service encounters that prioritizes the attributes from the patient perspective. We identify opportunities to control the level of quality for each attribute (ie, who is responsible for control of each attribute and when control can be exerted in relation to the encounter process). This analysis reveals that many quality attributes are in the hands of various stakeholders, and all attributes can be addressed proactively to some degree before the encounter begins. Conclusion Identification of the quality attributes important to a telemedicine encounter from a patient perspective enables one to better design telemedicine encounters. This preliminary work not only identifies such attributes, but also ascertains who is best able to address quality issues prior to an encounter. For practitioners, explicit representation of the quality attributes of technology-based systems and processes and insight on controlling key attributes are essential to implementation, utilization, management, and common understanding. PMID:25565781

Teaching evolution in the Australian classroom

NASA Astrophysics Data System (ADS)

Vozzo, Les

A summary of the key issues of controversy encountered by science teachers in Australian classrooms. Evolution, cloning and gene manipulation, fertility control, artificial intelligence, irradiation of food, the use of nuclear energy, radiation from powerlines are some of the topics discussed and debated in classrooms. What are some of the difficulties encountered by teachers when students ask questions that raise moral dilemmas and challenges entrenched beliefs and views of the world. What are some of the teaching strategies used that deal with these difficulties.

A comparative study between shielded and open coplanar waveguide discontinuities

NASA Technical Reports Server (NTRS)

Dib, Nihad I.; Harokopus, W. P., Jr.; Ponchak, G. E.; Katehi, L. P. B.

1993-01-01

A comparative study between open and shielded coplanar waveguide (CPW) discontinuities is presented. The space domain integral equation method is used to characterize several discontinuities such as the open-end CPW and CPW series stubs. Two different geometries of CPW series stubs (straight and bent stubs) are compared with respect to resonant frequency and radiation loss. In addition, the encountered radiation loss due to different CPW shunt stubs is evaluated experimentally. The notion of forced radiation simulation is presented, and the results of such a simulation are compared to the actual radiation loss obtained rigorously. It is shown that such a simulation cannot give reliable results concerning radiation loss from printed circuits.

Evaluation of Superconducting Magnet Shield Configurations for Long Duration Manned Space Missions.

PubMed

Ambroglini, Filippo; Battiston, Roberto; Burger, William J

2016-01-01

A manned mission to Mars would present an important long-term health risk to the crew members due to the prolonged exposure to the ionizing radiation of galactic cosmic-rays. The radiation levels would largely exceed those encountered in the Apollo missions. An increase in the passive shielding provided by the spacecraft implies a significant increase of the mass. The advent of superconducting magnets in the early 1960s was considered an attractive alternative. The technology allows to generate magnetic fields capable to deflect the cosmic-rays in a manner analogous to the reduction of the particle fluxes in the upper atmosphere due to the Earth's dipole magnetic field. A series of the three studies have been conducted over the last 5 years, funded successively by European Space Agency (ESA), the NASA Innovative Advanced Concepts (NIAC) program, and the Union European's Seventh Framework Programme (FP7). The shielding configurations studied are based on high-temperature superconductors, which eliminate the need to operate with liquid helium. The mass estimates of the coils and supporting structure of the engineering designs are based on the current and expected near-future performance of the superconducting materials. In each case, the shield performance, in terms of dose reduction, is provided by a 3-dimensional Monte Carlo simulation, which treats in detail the electromagnetic and hadronic interactions of the galactic-cosmic rays, and the secondary particles they produce in the materials of the shield and spacecraft. A summary of the results of the studies, representing one of the most detailed and comprehensive efforts made in the field, is presented.

Encounter Group Effects of Soccer Team Performance.

ERIC Educational Resources Information Center

Magen, Zipora

1980-01-01

Suggests that a positive relationship exists between encounter group experience and the soccer team performance--a conclusion worthy of consideration in further research in the fields of psychology and sociology of sports. (Author)

Brief Communication: Is there a wind connection to freaque wave occurrences?

NASA Astrophysics Data System (ADS)

Liu, P. C.; Bouchard, R.; Rogers, W. E.; Babanin, A. V.; Wang, D. W.

2015-01-01

There was a recent freaque wave encounter near Scituate, Massachusetts by a local transport ferry en route from Provincetown to Boston. The encounter resulted in minimal damages, fortunately, and provided us a chance to examine a possible connection between the freaque wave occurrence and the ambient wind field, since the place of encounter was in the vicinity of a NOAA NDBC buoy where wind and wave data were recorded. Here we present a brief analysis. In particular, we found it is plausible that the freaque wave was the result of a wind speed reduction in the wind field that preceded its occurrence.

Computational chemistry and aeroassisted orbital transfer vehicles

NASA Technical Reports Server (NTRS)

Cooper, D. M.; Jaffe, R. L.; Arnold, J. O.

1985-01-01

An analysis of the radiative heating phenomena encountered during a typical aeroassisted orbital transfer vehicle (AOTV) trajectory was made to determine the potential impact of computational chemistry on AOTV design technology. Both equilibrium and nonequilibrium radiation mechanisms were considered. This analysis showed that computational chemistry can be used to predict (1) radiative intensity factors and spectroscopic data; (2) the excitation rates of both atoms and molecules; (3) high-temperature reaction rate constants for metathesis and charge exchange reactions; (4) particle ionization and neutralization rates and cross sections; and (5) spectral line widths.

Planetary quarantine. Space research and technology

NASA Technical Reports Server (NTRS)

1973-01-01

Planetary quarantine strategies for advanced spacecraft consider effects of satellite encounter, Jupiter atmosphere entry, space radiation, and cleaning and decontamination techniques on microbiological growth probability. Analytical restructuring is developed for microbial burden prediction and planetary contamination.

Overview of the Martian radiation environment experiment

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

Zeitlin, C.; Cleghorn, T.F.; Cucinotta, F.A.

Space radiation presents a hazard to astronauts, particularly those journeying outside the protective influence of the geomagnetosphere. Crews on future missions to Mars will be exposed to the harsh radiation environment of deep space during the transit between Earth and Mars. Once on Mars, they will encounter radiation that is only slightly reduced, compared to free space, by the thin Martian atmosphere. NASA is obliged to minimize, where possible, the radiation exposures received by astronauts. Thus, as a precursor to eventual human exploration, it is necessary to measure the Martian radiation environment in detail. The MARIE experiment, aboard the 2001more » Mars Odyssey spacecraft, is returning the first data that bear directly on this problem. Here we provide an overview of the experiment, including introductory material on space radiation and radiation dosimetry, a description of the detector, model predictions of the radiation environment at Mars, and preliminary dose-rate data obtained at Mars.« less

Seasonal Distributions of Global Ocean Chlorophyll and Nutrients: Analysis with a Coupled Ocean General Circulation Biogeochemical, and Radiative Model

NASA Technical Reports Server (NTRS)

Gregg, Watson W.

1999-01-01

A coupled general ocean circulation, biogeochemical, and radiative model was constructed to evaluate and understand the nature of seasonal variability of chlorophyll and nutrients in the global oceans. The model is driven by climatological meteorological conditions, cloud cover, and sea surface temperature. Biogeochemical processes in the model are determined from the influences of circulation and turbulence dynamics, irradiance availability, and the interactions among three functional phytoplankton groups (diatoms, chorophytes, and picoplankton) and three nutrient groups (nitrate, ammonium, and silicate). Phytoplankton groups are initialized as homogeneous fields horizontally and vertically, and allowed to distribute themselves according to the prevailing conditions. Basin-scale model chlorophyll results are in very good agreement with CZCS pigments in virtually every global region. Seasonal variability observed in the CZCS is also well represented in the model. Synoptic scale (100-1000 km) comparisons of imagery are also in good conformance, although occasional departures are apparent. Agreement of nitrate distributions with in situ data is even better, including seasonal dynamics, except for the equatorial Atlantic. The good agreement of the model with satellite and in situ data sources indicates that the model dynamics realistically simulate phytoplankton and nutrient dynamics on synoptic scales. This is especially true given that initial conditions are homogenous chlorophyll fields. The success of the model in producing a reasonable representation of chlorophyll and nutrient distributions and seasonal variability in the global oceans is attributed to the application of a generalized, processes-driven approach as opposed to regional parameterization, and the existence of multiple phytoplankton groups with different physiological and physical properties. These factors enable the model to simultaneously represent the great diversity of physical, biological, chemical, and radiative environments encountered in the global oceans.

REPEATING FAST RADIO BURSTS FROM HIGHLY MAGNETIZED PULSARS TRAVELING THROUGH ASTEROID BELTS

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

Dai, Z. G.; Wang, J. S.; Huang, Y. F.

Very recently, Spitler et al. and Scholz et al. reported their detections of 16 additional bright bursts in the direction of the fast radio burst (FRB) 121102. This repeating FRB is inconsistent with all of the catastrophic event models put forward previously for hypothetically non-repeating FRBs. Here, we propose a different model, in which highly magnetized pulsars travel through the asteroid belts of other stars. We show that a repeating FRB could originate from such a pulsar encountering a large number of asteroids in the belt. During each pulsar-asteroid impact, an electric field induced outside of the asteroid has suchmore » a large component parallel to the stellar magnetic field that electrons are torn off the asteroidal surface and accelerated to ultra-relativistic energies instantaneously. The subsequent movement of these electrons along magnetic field lines will cause coherent curvature radiation, which can account for all of the properties of an FRB. In addition, this model can self-consistently explain the typical duration, luminosity, and repetitive rate of the 17 bursts of FRB 121102. The predicted occurrence rate of repeating FRB sources may imply that our model would be testable in the next few years.« less

Investigations of a simulated geomagnetic field experienced by the International Space Station on attentional performance

NASA Astrophysics Data System (ADS)

Del Seppia, C.; Mezzasalma, L.; Messerotti, M.; Cordelli, A.; Ghione, S.

2009-01-01

We have previously reported that the exposure to an abnormal magnetic field simulating the one encountered by the International Space Station (ISS) orbiting around the Earth may enhance autonomic response to emotional stimuli. Here we report the results of the second part of that study which tested whether this field also affects cognitive functions. Twenty-four volunteers participated in the study, 12 exposed to the natural geomagnetic field and 12 to the magnetic field encountered by ISS. The test protocol consisted of a set of eight tests chosen from a computerized test battery for the assessment of attentional performance. The duration of exposure was 90 min. No effect of exposure to ISS magnetic field was observed on attentional performance.

Visual field information in Nap-of-the-Earth flight by teleoperated Helmet-Mounted displays

NASA Technical Reports Server (NTRS)

Grunwald, Arthur J.; Kohn, S.; Merhav, S. J.

1991-01-01

The human ability to derive Control-Oriented Visual Field Information from teleoperated Helmet-Mounted displays in Nap-of-the-Earth flight, is investigated. The visual field with these types of displays originates from a Forward Looking Infrared Radiation Camera, gimbal-mounted at the front of the aircraft and slaved to the pilot's line-of-sight, to obtain wide-angle visual coverage. Although these displays are proved to be effective in Apache and Cobra helicopter night operations, they demand very high pilot proficiency and work load. Experimental work presented in the paper has shown that part of the difficulties encountered in vehicular control by means of these displays can be attributed to the narrow viewing aperture and head/camera slaving system phase lags. Both these shortcomings will impair visuo-vestibular coordination, when voluntary head rotation is present. This might result in errors in estimating the Control-Oriented Visual Field Information vital in vehicular control, such as the vehicle yaw rate or the anticipated flight path, or might even lead to visuo-vestibular conflicts (motion sickness). Since, under these conditions, the pilot will tend to minimize head rotation, the full wide-angle coverage of the Helmet-Mounted Display, provided by the line-of-sight slaving system, is not always fully utilized.

Electrical characteristics of simulated tornadoes

NASA Astrophysics Data System (ADS)

Zimmerman, M. I.; Farrell, W. M.; Barth, E. L.; Lewellen, D. C.; Lewellen, W. S.; Perlongo, N. J.; Jackson, T.

2012-12-01

It is well known that tornadoes and dust devils have the ability to accumulate significant, visible clouds of debris. Collisions between sand-like debris species produce different electric charges on different types of grains, which convect along different trajectories around the vortex. Thus, significant charge separations and electric currents are possible, which as the vortex fluctuates over time are thought to produce ULF radiation signatures that have been measured in the field. These electric and magnetic fields may contain valuable information about tornado structure and genesis, and may be critical in driving electrochemical processes within dust devils on Mars. In the present work, existing large eddy simulations of debris-laden tornadoes performed at West Virginia University are coupled with a new debris-charging and advection code developed at Goddard Space Flight Center to investigate the detailed (meter-resolution) fluid-dynamic origins of electromagnetic fields within terrestrial vortices. First results are presented, including simulations of the electric and magnetic fields that would be observed by a near-surface, instrument-laden probe during a direct encounter with a tornado. This research was supported by an appointment to the NASA Postdoctoral Program at the Goddard Space Flight Center, administered by Oak Ridge Associated Universities through a contract with NASA. The generous allocation of computing resources by Dr. Timothy J. Stubbs is gratefully acknowledged.

Strong field QED in lepton colliders and electron/laser interactions

NASA Astrophysics Data System (ADS)

Hartin, Anthony

2018-05-01

The studies of strong field particle physics processes in electron/laser interactions and lepton collider interaction points (IPs) are reviewed. These processes are defined by the high intensity of the electromagnetic fields involved and the need to take them into account as fully as possible. Thus, the main theoretical framework considered is the Furry interaction picture within intense field quantum field theory. In this framework, the influence of a background electromagnetic field in the Lagrangian is calculated nonperturbatively, involving exact solutions for quantized charged particles in the background field. These “dressed” particles go on to interact perturbatively with other particles, enabling the background field to play both macroscopic and microscopic roles. Macroscopically, the background field starts to polarize the vacuum, in effect rendering it a dispersive medium. Particles encountering this dispersive vacuum obtain a lifetime, either radiating or decaying into pair particles at a rate dependent on the intensity of the background field. In fact, the intensity of the background field enters into the coupling constant of the strong field quantum electrodynamic Lagrangian, influencing all particle processes. A number of new phenomena occur. Particles gain an intensity-dependent rest mass shift that accounts for their presence in the dispersive vacuum. Multi-photon events involving more than one external field photon occur at each vertex. Higher order processes which exchange a virtual strong field particle resonate via the lifetimes of the unstable strong field states. Two main arenas of strong field physics are reviewed; those occurring in relativistic electron interactions with intense laser beams, and those occurring in the beam-beam physics at the interaction point of colliders. This review outlines the theory, describes its significant novel phenomenology and details the experimental schema required to detect strong field effects and the simulation programs required to model them.

The signatures of the parental cluster on field planetary systems

NASA Astrophysics Data System (ADS)

Cai, Maxwell Xu; Portegies Zwart, Simon; van Elteren, Arjen

2018-03-01

Due to the high stellar densities in young clusters, planetary systems formed in these environments are likely to have experienced perturbations from encounters with other stars. We carry out direct N-body simulations of multiplanet systems in star clusters to study the combined effects of stellar encounters and internal planetary dynamics. These planetary systems eventually become part of the Galactic field population as the parental cluster dissolves, which is where most presently known exoplanets are observed. We show that perturbations induced by stellar encounters lead to distinct signatures in the field planetary systems, most prominently, the excited orbital inclinations and eccentricities. Planetary systems that form within the cluster's half-mass radius are more prone to such perturbations. The orbital elements are most strongly excited in the outermost orbit, but the effect propagates to the entire planetary system through secular evolution. Planet ejections may occur long after a stellar encounter. The surviving planets in these reduced systems tend to have, on average, higher inclinations and larger eccentricities compared to systems that were perturbed less strongly. As soon as the parental star cluster dissolves, external perturbations stop affecting the escaped planetary systems, and further evolution proceeds on a relaxation time-scale. The outer regions of these ejected planetary systems tend to relax so slowly that their state carries the memory of their last strong encounter in the star cluster. Regardless of the stellar density, we observe a robust anticorrelation between multiplicity and mean inclination/eccentricity. We speculate that the `Kepler dichotomy' observed in field planetary systems is a natural consequence of their early evolution in the parental cluster.

Aeroacoustic interaction of a distributed vortex with a lifting Joukowski airfoil

NASA Technical Reports Server (NTRS)

Hardin, J. C.; Lamkin, S. L.

1984-01-01

A first principles computational aeroacoustics calculation of the flow and noise fields produced by the interaction of a distributed vortex with a lifting Joukowski airfoil is accomplished at the Reynolds number of 200. The case considered is that where the circulations of the vortex and the airfoil are of opposite sign, corresponding to blade vortex interaction on the retreating side of a single helicopter rotor. The results show that the flow is unsteady, even in the absence of the incoming vortex, resulting in trailing edge noise generation. After the vortex is input, it initially experiences a quite rapid apparent diffusion rate produced by stretching in the airfoil velocity gradients. Consideration of the effects of finite vortex size and viscosity causes the noise radiation during the encounter to be much less impulsive than predicted by previous analyses.

Transonic Resonance Demonstrated To Be a Source of Internal Noise From Mixer-Ejector Nozzles

NASA Technical Reports Server (NTRS)

Zaman, Khairul B.

2002-01-01

During noise field studies with mixer-ejector nozzles in NASA's High-Speed Research program, tones were often encountered. The tones would persist in the simulated "cutback" condition (shortly after takeoff). Unfortunately, we did not understand their origin and, thus, could not develop a logical approach for suppressing them. We naturally questioned whether or not some of those tones were due to the transonic resonance. This was studied with a 1/13th scale model of the High-Speed Civil Transport nozzle. The first objective was to determine if indeed tones could be detected in the radiated noise. The next objective was to diagnose if those tones were due to the transonic resonance. Agreement of the frequencies with the correlation equation and the effect of boundary layer tripping were to be used in the diagnosis.

A Binary-Encounter-Bethe Approach to Simulate DNA Damage by the Direct Effect

NASA Technical Reports Server (NTRS)

Plante, Ianik; Cucinotta, Francis A.

2013-01-01

The DNA damage is of crucial importance in the understanding of the effects of ionizing radiation. The main mechanisms of DNA damage are by the direct effect of radiation (e.g. direct ionization) and by indirect effect (e.g. damage by.OH radicals created by the radiolysis of water). Despite years of research in this area, many questions on the formation of DNA damage remains. To refine existing DNA damage models, an approach based on the Binary-Encounter-Bethe (BEB) model was developed[1]. This model calculates differential cross sections for ionization of the molecular orbitals of the DNA bases, sugars and phosphates using the electron binding energy, the mean kinetic energy and the occupancy number of the orbital. This cross section has an analytic form which is quite convenient to use and allows the sampling of the energy loss occurring during an ionization event. To simulate the radiation track structure, the code RITRACKS developed at the NASA Johnson Space Center is used[2]. This code calculates all the energy deposition events and the formation of the radiolytic species by the ion and the secondary electrons as well. We have also developed a technique to use the integrated BEB cross section for the bases, sugar and phosphates in the radiation transport code RITRACKS. These techniques should allow the simulation of DNA damage by ionizing radiation, and understanding of the formation of double-strand breaks caused by clustered damage in different conditions.

Direct Radiative Effect of Intense Dust Outbreaks in the Mediterranean

NASA Astrophysics Data System (ADS)

Gkikas, A.; Obiso, V.; Basart, S.; Jorba, O.; Pérez García-Pando, C.; Hatzianastassiou, N.; Gassó, S.; Baldasano, J. M.

2015-12-01

The broader Mediterranean basin is affected by intense desert dust outbreaks in spring. In the present study, we make use of satellite observations and modelling to investigate dust radiative impacts during three consecutive dust outbreaks occurred over the Mediterranean in the period 9/4-15/4/2008. The direct radiative effect (DRE) is estimated by using two simulations run with the NMMB/BSC-Dust model, where the interaction between dust aerosols and radiation is activated and deactivated, respectively. The simulation domain covers the North Africa, the Middle East and Europe at 0.25ºx0.25° and 40σ-layers. The first outbreak took place over the central and eastern Mediterranean on the 9th reaching aerosol optical depths (AODs) close to 1. The second one, with AODs up to 2, lasted from 10th to 14th affecting mainly the central Mediterranean. The third one, with AODs up to 5, affected the Iberian Peninsula on the 15th. DREs are computed for the outgoing radiation at the top of the atmosphere (TOA), the absorbed radiation into the atmosphere (ATMAB), for the downwelling (SURF) and the absorbed (NETSURF) radiation at surface, for the shortwave (SW), longwave (LW) and NET (SW+LW) radiation. According to our results, it is evident that DREs' spatial patterns are driven by those of AOD. Negative (cooling) instantaneous DRETOA, DRESURF and DRENETSURF values up to -500W/m2, -700W/m2 and -600W/m2, respectively, and positive (warming) instantaneous DREATMAB up to 340W/m2 are found for the SW spectrum, during daytime. Opposite but less pronounced effects are encountered for the LW radiation and during nightime. Due to these perturbations on the radiation field, the surface temperature is reduced locally by up to 8°C during daytime and increased by up to 4°C during nightime. It is found that the regional average NET DREs can be as large as -12W/m2, -45W/m2, -30W/m2 and 27W/m2 for TOA, SURF, NETSURF and ATMAB, respectively. Impacts on atmospheric stability and dust emissions are also investigated.

Numerical simulations of electromagnetic scattering by Solar system objects

NASA Astrophysics Data System (ADS)

Dlugach, Janna M.

2016-11-01

Having been profoundly stimulated by the seminal work of Viktor V. Sobolev, I have been involved in multi-decadal research in the fields of radiative transfer, electromagnetic scattering by morphologically complex particles and particulate media, and planetary remote sensing. Much of this research has been done in close collaboration with other "descendants" of Academician Sobolev. This tutorial paper gives a representative overview of the results of extensive numerical simulations (in the vast majority carried out in collaboration with Michael Mishchenko) used to analyze remote-sensing observations of Solar system objects and based on highly accurate methods of the radiative transfer theory and direct computer solvers of the Maxwell equations. Using the atmosphere of Jupiter as a proving ground and performing T-matrix and radiative-transfer calculations helps demonstrate the strong effect of aerosol-particle shapes on the accuracy of remote-sensing retrievals. I then discuss the application of the T-matrix method, a numerically exact solution of the vector radiative transfer equation, and the theory of coherent backscattering to an analysis of polarimetric radar observations of Saturn's rings. Numerical modeling performed by using the superposition T-matrix method in application to cometary dust in the form of aggregates serves to reproduce the results of polarimetric observations of the distant comet C/2010 S1. On the basis of direct computer solutions of the Maxwell equations, it is demonstrated that all backscattering effects predicted by the low-density theories of radiative transfer and coherent backscattering can also be identified for media with volume packing densities typically encountered in natural and artificial environments. This result implies that spectacular opposition effects observed for some high-albedo atmoshereless Solar system bodies can be attributed to coherent backscattering of sunlight by regolith layers composed of microscopic particles.

Cooling Timescales and Temporal Structure of Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

Sari, Re'em; Narayan, Ramesh; Piran, Tsvi

1996-12-01

A leading mechanism for producing cosmological gamma-ray bursts (GRBs) is via ultrarelativistic particles in an expanding fireball. The kinetic energy of the particles is converted into thermal energy in two shocks, a forward shock and a reverse shock, when the outward flowing particles encounter the interstellar medium. The thermal energy is then radiated via synchrotron emission and Comptonization. We estimate the synchrotron cooling timescale of the shocked material in the forward and reverse shocks for electrons of various Lorentz factors, focusing in particular on those electrons whose radiation falls within the energy detection range of the BATSE detectors. We find that in order to produce the rapid variability observed in most bursts, the energy density of the magnetic field in the shocked material must be greater than about 1% of the thermal energy density. In addition, the electrons must be nearly in equipartition with the protons, since otherwise we do not have reasonable radiative efficiencies of GRBs. Inverse Compton scattering can increase the cooling rate of the relevant electrons, but the Comptonized emission itself is never within the BATSE range. These arguments allow us to pinpoint the conditions within the radiating regions in GRBs and to determine the important radiation processes. In addition, they provide a plausible explanation for several observations. The model predicts that the duty cycle of intensity variations in GRB light curves should be nearly independent of burst duration and should scale inversely as the square root of the observed photon energy. Both correlations are in agreement with observations. The model also provides a plausible explanation for the bimodal distribution of burst durations. There is no explanation, however, for the presence of a characteristic break energy in GRB spectra.

Area X-ray or UV camera system for high-intensity beams

DOEpatents

Chapman, Henry N.; Bajt, Sasa; Spiller, Eberhard A.; Hau-Riege, Stefan , Marchesini, Stefano

2010-03-02

A system in one embodiment includes a source for directing a beam of radiation at a sample; a multilayer mirror having a face oriented at an angle of less than 90 degrees from an axis of the beam from the source, the mirror reflecting at least a portion of the radiation after the beam encounters a sample; and a pixellated detector for detecting radiation reflected by the mirror. A method in a further embodiment includes directing a beam of radiation at a sample; reflecting at least some of the radiation diffracted by the sample; not reflecting at least a majority of the radiation that is not diffracted by the sample; and detecting at least some of the reflected radiation. A method in yet another embodiment includes directing a beam of radiation at a sample; reflecting at least some of the radiation diffracted by the sample using a multilayer mirror; and detecting at least some of the reflected radiation.

Investigations of a simulated geomagnetic field experienced by the International Space Station on attentional performance.

PubMed

Del Seppia, Cristina; Mezzasalma, Lorena; Messerotti, Mauro; Cordelli, Alessandro; Ghione, Sergio

2009-01-01

We have previously reported that the exposure to an abnormal magnetic field simulating the one encountered by the International Space Station (ISS) orbiting around the Earth may enhance autonomic response to emotional stimuli. Here we report the results of the second part of that study which tested whether this field also affects cognitive functions. Twenty-four volunteers participated in the study, 12 exposed to the natural geomagnetic field and 12 to the magnetic field encountered by ISS. The test protocol consisted of a set of eight tests chosen from a computerized test battery for the assessment of attentional performance. The duration of exposure was 90 min. No effect of exposure to ISS magnetic field was observed on attentional performance. (c) 2008 Wiley-Liss, Inc.

ISEE 1 charged particle observations indicative of open magnetospheric field lines near the subsolar region

NASA Technical Reports Server (NTRS)

Williams, D. J.; Frank, L. A.

1980-01-01

On November 20, 1977, at 0230-0300 UT, ISEE 1 encountered unusual charged particle distributions within the magnetosphere. The three-dimensional distribution observations for energetic (greater than 24 keV) ions and plasma show the development of field-aligned asymmetries in the energetic ion distributions simultaneously with a marked change in plasma flow. It is concluded that the most likely explanation for these observations is that ISEE 1 encountered open magnetospheric field lines at its position within the magnetosphere (1030 LT and 1200 plus or minus 300 km from the magnetopause). Field lines were open near the geomagnetic equator, and the geometry was spatially or temporally variable. Other features of the field line topology are presented.

Survey of the supporting research and technology for the thermal protection of the Galileo Probe

NASA Technical Reports Server (NTRS)

Howe, J. T.; Pitts, W. C.; Lundell, J. H.

1981-01-01

The Galileo Probe, which is scheduled to be launched in 1985 and to enter the hydrogen-helium atmosphere of Jupiter up to 1,475 days later, presents thermal protection problems that are far more difficult than those experienced in previous planetary entry missions. The high entry speed of the Probe will cause forebody heating rates orders of magnitude greater than those encountered in the Apollo and Pioneer Venus missions, severe afterbody heating from base-flow radiation, and thermochemical ablation rates for carbon phenolic that rival the free-stream mass flux. This paper presents a comprehensive survey of the experimental work and computational research that provide technological support for the Probe's heat-shield design effort. The survey includes atmospheric modeling; both approximate and first-principle computations of flow fields and heat-shield material response; base heating; turbulence modelling; new computational techniques; experimental heating and materials studies; code validation efforts; and a set of 'consensus' first-principle flow-field solutions through the entry maneuver, with predictions of the corresponding thermal protection requirements.

Evaluation of SPE and GCR Radiation Effects in Inflatable, Space Suit and Composite Habitat Materials Project

NASA Technical Reports Server (NTRS)

Waller, Jess M.; Nichols, Charles

2016-01-01

The radiation resistance of polymeric and composite materials to space radiation is currently based on irradiating materials with Co-60 gamma-radiation to the equivalent total ionizing dose (TID) expected during mission. This is an approximation since gamma-radiation is not truly representative of the particle species; namely, Solar Particle Event (SPE) protons and Galactic Cosmic Ray (GCR) nucleons, encountered in space. In general, the SPE and GCR particle energies are much higher than Co-60 gamma-ray photons, and since the particles have mass, there is a displacement effect due to nuclear collisions between the particle species and the target material. This effort specifically bridges the gap between estimated service lifetimes based on decades old Co-60 gamma-radiation data, and newer assessments of what the service lifetimes actually are based on irradiation with particle species that are more representative of the space radiation environment.

Evaluation of Superconducting Magnet Shield Configurations for Long Duration Manned Space Missions

PubMed Central

Ambroglini, Filippo; Battiston, Roberto; Burger, William J.

2016-01-01

A manned mission to Mars would present an important long-term health risk to the crew members due to the prolonged exposure to the ionizing radiation of galactic cosmic-rays. The radiation levels would largely exceed those encountered in the Apollo missions. An increase in the passive shielding provided by the spacecraft implies a significant increase of the mass. The advent of superconducting magnets in the early 1960s was considered an attractive alternative. The technology allows to generate magnetic fields capable to deflect the cosmic-rays in a manner analogous to the reduction of the particle fluxes in the upper atmosphere due to the Earth’s dipole magnetic field. A series of the three studies have been conducted over the last 5 years, funded successively by European Space Agency (ESA), the NASA Innovative Advanced Concepts (NIAC) program, and the Union European’s Seventh Framework Programme (FP7). The shielding configurations studied are based on high-temperature superconductors, which eliminate the need to operate with liquid helium. The mass estimates of the coils and supporting structure of the engineering designs are based on the current and expected near-future performance of the superconducting materials. In each case, the shield performance, in terms of dose reduction, is provided by a 3-dimensional Monte Carlo simulation, which treats in detail the electromagnetic and hadronic interactions of the galactic-cosmic rays, and the secondary particles they produce in the materials of the shield and spacecraft. A summary of the results of the studies, representing one of the most detailed and comprehensive efforts made in the field, is presented. PMID:27376023

Radiation effects control: Eyes, skin. [space environment simulation

NASA Technical Reports Server (NTRS)

Hightower, D.; Smathers, J. B.

1974-01-01

Adverse effects on the lens of the eye and the skin due to exposure to proton radiation during manned space flight were evaluated. Actual proton irradiation which might be encountered in space was simulated. Irradiation regimes included single acute exposures, daily fractionated exposures, and weekly fractionated exposures. Animals were exposed and then maintained and examined periodically until data sufficient to meet the objective were obtained. No significant skin effects were noted and no serious sight impairment was exhibited.

Radiation Exposure Effects and Shielding Analysis of Carbon Nanotube Materials

NASA Technical Reports Server (NTRS)

Wilkins, Richard; Armendariz, Lupita (Technical Monitor)

2002-01-01

Carbon nanotube materials promise to be the basis for a variety of emerging technologies with aerospace applications. Potential applications to human space flight include spacecraft shielding, hydrogen storage, structures and fixtures and nano-electronics. Appropriate risk analysis on the properties of nanotube materials is essential for future mission safety. Along with other environmental hazards, materials used in space flight encounter a hostile radiation environment for all mission profiles, from low earth orbit to interplanetary space.

Spacecraft Environments Interactive: Space Radiation and Its Effects on Electronic System

NASA Technical Reports Server (NTRS)

Howard, J. W., Jr.; Hardage, D. M.

1999-01-01

The natural space environment is characterized by complex and subtle phenomena hostile to spacecraft. Effects of these phenomena impact spacecraft design, development, and operation. Space systems become increasingly susceptible to the space environment as use of composite materials and smaller, faster electronics increases. This trend makes an understanding of space radiation and its effects on electronic systems essential to accomplish overall mission objectives, especially in the current climate of smaller/better/cheaper faster. This primer outlines the radiation environments encountered in space, discusses regions and types of radiation, applies the information to effects that these environments have on electronic systems, addresses design guidelines and system reliability, and stresses the importance of early involvement of radiation specialists in mission planning, system design, and design review (part-by-part verification).

Biological countermeasures in space radiation health.

PubMed

Kennedy, Ann R; Todd, Paul

2003-06-01

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. The major types of radiation considered to be of importance during space travel are protons and particles of high atomic number and high energy (HZE particles). It is now clear that biological countermeasures can be used to prevent or reduce the levels of biological consequences resulting from exposure to protons or HZE particles, including the induction of cancer, immunosuppression and neurological defects caused by these types of ionizing radiation. Research related to the dietary additions of agents to minimize the risks of developing health-related problems which can result from exposure to space radiations is reviewed.

Biological countermeasures in space radiation health

NASA Technical Reports Server (NTRS)

Kennedy, Ann R.; Todd, Paul

2003-01-01

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. The major types of radiation considered to be of importance during space travel are protons and particles of high atomic number and high energy (HZE particles). It is now clear that biological countermeasures can be used to prevent or reduce the levels of biological consequences resulting from exposure to protons or HZE particles, including the induction of cancer, immunosuppression and neurological defects caused by these types of ionizing radiation. Research related to the dietary additions of agents to minimize the risks of developing health-related problems which can result from exposure to space radiations is reviewed.

Overview of the Martian radiation environment experiment

NASA Technical Reports Server (NTRS)

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

2004-01-01

Space radiation presents a hazard to astronauts, particularly those journeying outside the protective influence of the geomagnetosphere. Crews on future missions to Mars will be exposed to the harsh radiation environment of deep space during the transit between Earth and Mars. Once on Mars, they will encounter radiation that is only slightly reduced, compared to free space, by the thin Martian atmosphere. NASA is obliged to minimize, where possible, the radiation exposures received by astronauts. Thus, as a precursor to eventual human exploration, it is necessary to measure the Martian radiation environment in detail. The MARIE experiment, aboard the 2001 Mars Odyssey spacecraft, is returning the first data that bear directly on this problem. Here we provide an overview of the experiment, including introductory material on space radiation and radiation dosimetry, a description of the detector, model predictions of the radiation environment at Mars, and preliminary dose-rate data obtained at Mars. c2003 COSPAR. Published by Elsevier Ltd. All rights reserved.

The charged particle radiation environment on Mars measured by MSL/RAD from November 15, 2015 to January 15, 2016

NASA Astrophysics Data System (ADS)

Ehresmann, Bent; Zeitlin, Cary J.; Hassler, Donald M.; Matthiä, Daniel; Guo, Jingnan; Wimmer-Schweingruber, Robert F.; Appel, Jan K.; Brinza, David E.; Rafkin, Scot C. R.; Böttcher, Stephan I.; Burmeister, Sönke; Lohf, Henning; Martin, Cesar; Böhm, Eckart; Reitz, Günther

2017-08-01

The Radiation Assessment Detector (RAD) on board the Mars Science Laboratory (MSL) Curiosity rover has been measuring the radiation environment in Gale crater on Mars since August, 2012. These first in-situ measurements provide an important data set for assessing the radiation-associated health risks for future manned missions to Mars. Mainly, the radiation field on the Martian surface stems from Galactic Cosmic Rays (GCRs) and secondary particles created by the GCRs' interactions with the Martian atmosphere and soil. RAD is capable of measuring differential particle fluxes for lower-energy ions and isotopes of hydrogen and helium (up to hundreds of MeV/nuc). Additionally, RAD also measures integral particle fluxes for higher energies of these ions. Besides providing insight on the current Martian radiation environment, these fluxes also present an essential input for particle transport codes that are used to model the radiation to be encountered during future manned missions to Mars. Comparing simulation results with actual ground-truth measurements helps to validate these transport codes and identify potential areas of improvements in the underlying physics of these codes. At the First Mars Radiation Modeling Workshop (June 2016 in Boulder, CO), different groups of modelers were asked to calculate the Martian surface radiation environment for the time of November 15, 2015 to January 15, 2016. These model results can then be compared with in-situ measurements of MSL/RAD conducted during the same time frame. In this publication, we focus on presenting the charged particle fluxes measured by RAD between November 15, 2015 and January 15, 2016, providing the necessary data set for the comparison to model outputs from the modeling workshop. We also compare the fluxes to initial GCR intensities, as well as to RAD measurements from an earlier time period (August 2012 to January 2013). Furthermore, we describe how changes and updates in RAD on board processing and the on ground analysis tools effect and improve the flux calculations. An in-depth comparison of modeling results from the workshop and RAD fluxes of this publication is presented elsewhere in this issue (Matthiä et al., 2017).

The Use of Heavy Ion Radiation as an Analog for Space Radiation Environment and Its Effects on Drug Stability

NASA Technical Reports Server (NTRS)

Vaksman, Z.; Du, B.; Daniels, V.; Putcha, L.

2007-01-01

While it is common knowledge that electromagnetic radiation such as x-rays and gamma rays affect physical-chemical characteristics (PC) of compounds in addition to their toxic and mutagenic effects on biological systems, there are no reports on the effects of cosmic radiation encountered during space missions on stability of pharmaceuticals. Alterations in PC of drug formulations can adversely affect treatment with medications in space. Preliminary evaluation of stability and shelf-life of select pharmaceuticals (12) flown on space missions revealed that 37% and 40% of the formulations failed to meet USP requirements after shuttle and ISS flights, respectively. Based on these results, the current investigation is designed to examine the effect of proton (P) and heavy ion (Fe) radiation on 20 pharmaceutical preparations flown aboard the shuttle and ISS. The objectives of this project are: 1) Examine susceptibility of pharmaceuticals to short acute bouts of high intensity ionizing radiation species encountered during space flights; 2) Estimate extent of degradation of susceptible formulations as a function of intensity of each beam (P & Fe); and 3) compare and contrast the effects of single beam irradiation to that of a combined beam (P + Fe) that simulates space craft environment on drug stability. Irradiations were conducted at the Brookhaven National Laboratories (BNL) with beam strengths of 10 cGy, 10 or 50Gy of P and Fe beams separately. Preliminary evaluation of results revealed a reduction in the chemical content of label claim ranging 12-55 % for Augmentin, 7% for promethzine tablets and 9% for ciprofloxacin ointment. These results are in agreement, although less in magnitude than those observed during space flight and after gamma irradiation.

Novel reference radiation fields for pulsed photon radiation installed at PTB.

PubMed

Klammer, J; Roth, J; Hupe, O

2012-09-01

Currently, ∼70 % of the occupationally exposed persons in Germany are working in pulsed radiation fields, mainly in the medical sector. It has been known for a few years that active electronic dosemeters exhibit considerable deficits or can even fail completely in pulsed fields. Type test requirements for dosemeters exist only for continuous radiation. Owing to the need of a reference field for pulsed photon radiation and accordingly to the upcoming type test requirements for dosemeters in pulsed radiation, the Physikalisch-Technische Bundesanstalt has developed a novel X-ray reference field for pulsed photon radiation in cooperation with a manufacturer. This reference field, geared to the main applications in the field of medicine, has been well characterised and is now available for research and type testing of dosemeters in pulsed photon radiation.

47 CFR 27.70 - Information exchange.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES MISCELLANEOUS WIRELESS... activated or an existing base or fixed station is modified: (1) Location; (2) Effective radiated power; (3... identify the source if interference is encountered when the base or fixed station is activated. [72 FR...

No Flares from Gamma-Ray Burst Afterglow Blast Waves Encountering Sudden Circumburst Density Change

NASA Astrophysics Data System (ADS)

Gat, Ilana; van Eerten, Hendrik; MacFadyen, Andrew

2013-08-01

Afterglows of gamma-ray bursts are observed to produce light curves with the flux following power-law evolution in time. However, recent observations reveal bright flares at times on the order of minutes to days. One proposed explanation for these flares is the interaction of a relativistic blast wave with a circumburst density transition. In this paper, we model this type of interaction computationally in one and two dimensions, using a relativistic hydrodynamics code with adaptive mesh refinement called RAM, and analytically in one dimension. We simulate a blast wave traveling in a stellar wind environment that encounters a sudden change in density, followed by a homogeneous medium, and compute the observed radiation using a synchrotron model. We show that flares are not observable for an encounter with a sudden density increase, such as a wind termination shock, nor for an encounter with a sudden density decrease. Furthermore, by extending our analysis to two dimensions, we are able to resolve the spreading, collimation, and edge effects of the blast wave as it encounters the change in circumburst medium. In all cases considered in this paper, we find that a flare will not be observed for any of the density changes studied.

Automated Design of the Europa Orbiter Tour

NASA Technical Reports Server (NTRS)

Heaton, Andrew F.; Strange, Nathan J.; Longusaki, James M.; Bonfiglio, Eugene P.

2000-01-01

In this paper we investigate tours of the Jovian satellites Europa, Ganymede, and Callisto for the Europa Orbiter Mission. The principal goal of the tour design is to lower arrival V(sub infinity) for the final Europa encounter while meeting all of the design constraints. Key constraints arise from considering the total time of the tour and the radiation dosage of a tour. These tours may employ 14 or more encounters with the Jovian satellites, hence there is an enormous number of possible sequences of these satellites to investigate. We develop a graphical method that greatly aids the design process.

Automated Design of the Europa Orbiter Tour

NASA Technical Reports Server (NTRS)

Heaton, Andrew F.; Strange, Nathan J.; Longuski, James M.; Bonfiglio, Eugene P.; Taylor, Irene (Technical Monitor)

2000-01-01

In this paper we investigate tours of the Jovian satellites Europa Ganymede, and Callisto for the Europa Orbiter Mission. The principal goal of the tour design is to lower arrival V_ for the final Europa encounter while meeting all of the design constraints. Key constraints arise from considering the total time of the tour and the radiation dosage of a tour. These tours may employ 14 or more encounters with the Jovian satellites. hence there is an enormous number of possible sequences of these satellites to investigate. We develop a graphical method that greatly aids the design process.

Surface profiling interferometer

DOEpatents

Takacs, Peter Z.; Qian, Shi-Nan

1989-01-01

The design of a long-trace surface profiler for the non-contact measurement of surface profile, slope error and curvature on cylindrical synchrotron radiation (SR) mirrors. The optical system is based upon the concept of a pencil-beam interferometer with an inherent large depth-of-field. The key feature of the optical system is the zero-path-difference beam splitter, which separates the laser beam into two colinear, variable-separation probe beams. A linear array detector is used to record the interference fringe in the image, and analysis of the fringe location as a function of scan position allows one to reconstruct the surface profile. The optical head is mounted on an air bearing slide with the capability to measure long aspheric optics, typical of those encountered in SR applications. A novel feature of the optical system is the use of a transverse "outrigger" beam which provides information on the relative alignment of the scan axis to the cylinder optic symmetry axis.

High-performance fiber optic link for ECM antenna remoting

NASA Astrophysics Data System (ADS)

Edge, Colin; Burgess, John W.; Wale, Michael J.; Try, Nicholas W.

1998-11-01

The ability to remotely radiate microwave signals has become an essential feature of modern electronic counter-measures (ECM) systems. The use of fiber optics allows remote microwave links to be constructed which have very low propagation loss and dispersion, are very flexible and light in weight, and have a high degree of immunity from external electromagnetic fields, crosstalk and environmental effects. This combination of desirable characteristics are very beneficial to avionic ECM antenna remoting as well as many other applications. GEC-Marconi have developed high performance fiber components for use in a towed radar decoy. The resulting rugged and compact optical transmitter and receiver modules have been developed and proven to maintain the required performance over the full hostile range of environmental conditions encountered on a fast jet. Packaged fiber optic links have been produced which can achieve a compression dynamic range of greater than 87 dB in 1 MHz bandwidth over a 2 to 18 GHz.

Thunderstorm hazards flight research: Storm hazards 1980 overview

NASA Technical Reports Server (NTRS)

Deal, P. L.; Keyser, G. L.; Fisher, B. D.; Crabill, N. L.

1981-01-01

A highly instrumented NASA F-106B aircraft, modified for the storm hazards mission and protected against direct lightning strikes, was used in conjunction with various ground based radar and lightning measurement systems to collect data during thunderstorm penetration flights. During 69 thunderstorm penetrations, there were 10 direct lightning strikes to the aircraft. No problems were encountered with any of the aircraft's systems as a result of the strikes and the research instrumentation performed as designed. Electromagnetic characteristics of nine strikes were recorded, and the results of other experiments confirm the theory that X-ray radiation and nitrous oxide gas are being produced by processes associated directly with thunderstorm electric fields and lightning discharges. A better understanding of aircraft lightning attachment mechanisms and strike zones is being accomplished by careful inspection, identification, and documentation of lightning attachment points and swept stroke paths following each strike to the aircraft.

Validation of Shock Layer Radiation: Perspectives for Test Cases

NASA Technical Reports Server (NTRS)

Brandis, Aaron

2012-01-01

This paper presents a review of the analysis and measurement of radiation data obtained in the NASA Ames Research Center's Electric Arc Shock Tube (EAST) facility. The goal of these experiments was to measure the level of radiation encountered during atmospheric entry. The data obtained from these experiments is highlighted by providing the first spectrally and spatially resolved data for high speed Earth entry and measurements of the CO 4th positive band for conditions relevant to Mars entry. Comparisons of the EAST data with experimental results obtained from shock tunnels at JAXA and the University of Queensland are presented. Furthermore, the paper will detail initial analyses in to the influence and characterization of the measure non-equilibrium radiation.

Qualification and Testing of Quantum Cascade Lasers for Harsh Environments

NASA Astrophysics Data System (ADS)

Brauer, C. S.; Myers, T. L.; Cannon, B. D.; Anderson, C. G.; Crowther, B. G.; Hansen, S.

2014-12-01

Quantum cascade lasers (QCLs) offer the potential for the development of novel, laser-based instruments for both terrestrial and space applications. In order to withstand harsh conditions encountered in these environments, lasers must be robust, and rigorous testing is required before new systems can be utilized. A particular concern for space applications is the potential damage to laser performance caused by radiation exposure. While the effects of radiation exposure in diode lasers have been studied extensively, the effect on QCLs, which are fundamentally different from diode lasers, is not well known. We thus present work to quantify the performance of QCLs after exposure to moderate and high levels of radiation from different sources, including protons and gamma rays, to determine the effects of radiation damage.

Understanding metropolitan patterns of daily encounters.

PubMed

Sun, Lijun; Axhausen, Kay W; Lee, Der-Horng; Huang, Xianfeng

2013-08-20

Understanding of the mechanisms driving our daily face-to-face encounters is still limited; the field lacks large-scale datasets describing both individual behaviors and their collective interactions. However, here, with the help of travel smart card data, we uncover such encounter mechanisms and structures by constructing a time-resolved in-vehicle social encounter network on public buses in a city (about 5 million residents). Using a population scale dataset, we find physical encounters display reproducible temporal patterns, indicating that repeated encounters are regular and identical. On an individual scale, we find that collective regularities dominate distinct encounters' bounded nature. An individual's encounter capability is rooted in his/her daily behavioral regularity, explaining the emergence of "familiar strangers" in daily life. Strikingly, we find individuals with repeated encounters are not grouped into small communities, but become strongly connected over time, resulting in a large, but imperceptible, small-world contact network or "structure of co-presence" across the whole metropolitan area. Revealing the encounter pattern and identifying this large-scale contact network are crucial to understanding the dynamics in patterns of social acquaintances, collective human behaviors, and--particularly--disclosing the impact of human behavior on various diffusion/spreading processes.

Biomedical research

NASA Technical Reports Server (NTRS)

1981-01-01

Biomedical problems encountered by man in space which have been identified as a result of previous experience in simulated or actual spaceflight include cardiovascular deconditioning, motion sickness, bone loss, muscle atrophy, red cell alterations, fluid and electrolyte loss, radiation effects, radiation protection, behavior, and performance. The investigations and the findings in each of these areas were reviewed. A description of how biomedical research is organized within NASA, how it is funded, and how it is being reoriented to meet the needs of future manned space missions is also provided.

Commercial Nuclear Power Industry: Assessing and Meeting the Radiation Protection Workforce Needs.

PubMed

Hiatt, Jerry W

2017-02-01

This paper will provide an overview of the process used by the commercial nuclear power industry in assessing the status of existing industry staffing and projecting future supply demand needs. The most recent Nuclear Energy Institute-developed "Pipeline Survey Results" will be reviewed with specific emphasis on the radiation protection specialty. Both radiation protection technician and health physicist specialties will be discussed. The industry-initiated Nuclear Uniform Curriculum Program will be reviewed as an example of how the industry has addressed the need for developing additional resources. Furthermore, the reality of challenges encountered in maintaining the needed number of health physicists will also be discussed.

Charged particle spectra measured during the transit to Mars with the Mars Science Laboratory Radiation Assessment Detector (MSL/RAD).

PubMed

Ehresmann, Bent; Hassler, Donald M; Zeitlin, Cary; Guo, Jingnan; Köhler, Jan; Wimmer-Schweingruber, Robert F; Appel, Jan K; Brinza, David E; Rafkin, Scot C R; Böttcher, Stephan I; Burmeister, Sönke; Lohf, Henning; Martin, Cesar; Böhm, Eckart; Matthiä, Daniel; Reitz, Günther

2016-08-01

The Mars Science Laboratory (MSL) started its 253-day cruise to Mars on November 26, 2011. During cruise the Radiation Assessment Detector (RAD), situated on board the Curiosity rover, conducted measurements of the energetic-particle radiation environment inside the spacecraft. This environment consists mainly of galactic cosmic rays (GCRs), as well as secondary particles created by interactions of these GCRs with the spacecraft. The RAD measurements can serve as a proxy for the radiation environment a human crew would encounter during a transit to Mars, for a given part of the solar cycle, assuming that a crewed vehicle would have comparable shielding. The measurements of radiological quantities made by RAD are important in themselves, and, the same data set allow for detailed analysis of GCR-induced particle spectra inside the spacecraft. This provides important inputs for the evaluation of current transport models used to model the free-space (and spacecraft) radiation environment for different spacecraft shielding and different times in the solar cycle. Changes in these conditions can lead to significantly different radiation fields and, thus, potential health risks, emphasizing the need for validated transport codes. Here, we present the first measurements of charged particle fluxes inside a spacecraft during the transit from Earth to Mars. Using data obtained during the last two month of the cruise to Mars (June 11-July 14, 2012), we have derived detailed energy spectra for low-Z particles stopping in the instrument's detectors, as well as integral fluxes for penetrating particles with higher energies. Furthermore, we analyze the temporal changes in measured proton fluxes during quiet solar periods (i.e., when no solar energetic particle events occurred) over the duration of the transit (December 9, 2011-July 14, 2012) and correlate them with changing heliospheric conditions. Copyright © 2016 The Committee on Space Research (COSPAR). All rights reserved.

The use of computed radiography plates to determine light and radiation field coincidence.

PubMed

Kerns, James R; Anand, Aman

2013-11-01

Photo-stimulable phosphor computed radiography (CR) has characteristics that allow the output to be manipulated by both radiation and optical light. The authors have developed a method that uses these characteristics to carry out radiation field and light field coincidence quality assurance on linear accelerators. CR detectors from Kodak were used outside their cassettes to measure both radiation and light field edges from a Varian linear accelerator. The CR detector was first exposed to a radiation field and then to a slightly smaller light field. The light impinged on the detector's latent image, removing to an extent the portion exposed to the light field. The detector was then digitally scanned. A MATLAB-based algorithm was developed to automatically analyze the images and determine the edges of the light and radiation fields, the vector between the field centers, and the crosshair center. Radiographic film was also used as a control to confirm the radiation field size. Analysis showed a high degree of repeatability with the proposed method. Results between the proposed method and radiographic film showed excellent agreement of the radiation field. The effect of varying monitor units and light exposure time was tested and found to be very small. Radiation and light field sizes were determined with an uncertainty of less than 1 mm, and light and crosshair centers were determined within 0.1 mm. A new method was developed to digitally determine the radiation and light field size using CR photo-stimulable phosphor plates. The method is quick and reproducible, allowing for the streamlined and robust assessment of light and radiation field coincidence, with no observer interpretation needed.

Factors modifying the response of large animals to low-intensity radiation exposure

NASA Technical Reports Server (NTRS)

Page, N. P.; Still, E. T.

1972-01-01

In assessing the biological response to space radiation, two of the most important modifying factors are dose protraction and dose distribution to the body. Studies are reported in which sheep and swine were used to compare the hematology and lethality response resulting from radiation exposure encountered in a variety of forms, including acute (high dose-rate), chronic (low dose-rate), combinations of acute and chronic, and whether received as a continuous or as fractionated exposure. While sheep and swine are basically similar in response to acute radiation, their sensitivity to chronic irradiation is markedly different. Sheep remain relatively sensitive as the radiation exposure is protracted while swine are more resistant and capable of surviving extremely large doses of chronic irradiation. This response to chronic irradiation correlated well with changes in radiosensitivity and recovery following an acute, sublethal exposure.

Characterisation of neutron-sensitive bubble detectors for application in the measurement of jet aircrew exposure to natural background radiation.

PubMed

Tume, P; Lewis, B J; Bennett, L G; Cousins, T

1998-01-01

A survey of the natural background dose equivalent received by Canadian Forces aircrew was conducted using neutron-sensitive bubble detectors (BDs) as the primary detection tool. Since this study was a new application for these detectors, the BD response to neutron dose equivalent (RD) was extended from thermal to 500 MeV in neutron energy. Based upon the extended RD, it was shown that the manufacturer's calibration can be scaled by 1.5 +/- 0.5 to give a BD sensitivity that takes into account recently recommended fluence-to-neutron dose equivalent conversion functions and the cosmogenic neutron spectrum encountered at jet altitudes. An investigation of the effects of systematic bias caused by the cabin environment (i.e., temperature, pressure and relative humidity) on the in-flight measurements was also conducted. Both simulated and actual aircraft climate tests indicated that the detectors are insensitive to the pressure and relative humidity variations encountered during routine jet aircraft operations. Long term conditioning tests also confirmed that the BD-PND model of detector is sensitive to variations in temperature to within +/- 20%. As part of the testing process, the in-flight measurements also demonstrated that the neutron dose equivalent is distributed uniformly throughout a Boeing 707 jet aircraft, indicating that both pilots and flight attendants are exposed to the same neutron field intensity to within experimental uncertainty.

Light-Cone Effect of Radiation Fields in Cosmological Radiative Transfer Simulations

NASA Astrophysics Data System (ADS)

Ahn, Kyungjin

2015-02-01

We present a novel method to implement time-delayed propagation of radiation fields in cosmo-logical radiative transfer simulations. Time-delayed propagation of radiation fields requires construction of retarded-time fields by tracking the location and lifetime of radiation sources along the corresponding light-cones. Cosmological radiative transfer simulations have, until now, ignored this "light-cone effect" or implemented ray-tracing methods that are computationally demanding. We show that radiative trans-fer calculation of the time-delayed fields can be easily achieved in numerical simulations when periodic boundary conditions are used, by calculating the time-discretized retarded-time Green's function using the Fast Fourier Transform (FFT) method and convolving it with the source distribution. We also present a direct application of this method to the long-range radiation field of Lyman-Werner band photons, which is important in the high-redshift astrophysics with first stars.

A New Time-dependent Model for the Martian Radiation Environment

NASA Technical Reports Server (NTRS)

DeAngelis, G.; Clowdsley, M. S.; Singleterry, R. C., Jr.; Wilson, J. W.

2003-01-01

Manned space activities have been until present time limited to the near-Earth environment, most of them to low Earth orbit (LEO) scenarios, with only some of the Apollo missions targeted to the Moon. In current times most human exploration and development of space (HEDS) activities are related to the development of the International Space Station (ISS), and therefore take place in the LEO environment. A natural extension of HEDS activities will be going beyond LEO, and reach asteroids, Mars, Jupiter, Saturn, the Kuiper belt and the outskirts of the Solar System. Such long journeys onboard spacecraft outside the protective umbrella of the geomagnetic field will require higher levels of protection from the radiation environment found in the deep space for both astronauts and equipment. So, it is important to have available a tool for radiation shielding which takes into account the radiation environments found all along the interplanetary space and at the different bodies encountered in the Solar System. Moreover, the radiation protection is one of the two NASA highest concerns and priorities. A tool integrating different radiation environments with shielding computation techniques especially tailored for deep space mission scenario is instrumental in view of this exigency. In view of manned missions targeted to Mars, for which radiation exposure is one of the greatest problems and challenges to be tackled, it is of fundamental importance to have available a tool which allows to know which are the particle flux and spectra at any time at any point of the Martian surface. With this goal in mind, a new model for the radiation environment to be found on the planet Mars due to Galactic Cosmic Rays (GCR) has been developed. Solar modulated primary particles rescaled for Mars conditions are transported within the Martian atmosphere, with temporal properties modeled with variable timescales, down to the surface, with altitude and backscattering patterns taken into account. The tool allows analysis for manned Mars landing missions, as well as planetary science studies, e.g. subsurface water and volatile inventory studies. This Mars environmental model is available through the SIREST website, a project of NASA Langley Research Center.

Difficult Knowledge and Social Studies (Teacher) Education

ERIC Educational Resources Information Center

Garrett, H. James

2010-01-01

Social studies education is a field in which those involved--teachers and students--encounter what can be called "difficult knowledge". Difficult knowledge is a theoretical construct suggesting that when an individual encounters representations of social and historical trauma in a learning situation there exists a host of emotional and pedagogical…

Operation and performance of the New Horizons Long-Range Reconnaissance Imager during the Pluto encounter

NASA Astrophysics Data System (ADS)

Conard, S. J.; Weaver, H. A.; Núñez, J. I.; Taylor, H. W.; Hayes, J. R.; Cheng, A. F.; Rodgers, D. J.

2017-09-01

The Long-Range Reconnaissance Imager (LORRI) is a high-resolution imaging instrument on the New Horizons spacecraft. LORRI collected over 5000 images during the approach and fly-by of the Pluto system in 2015, including the highest resolution images of Pluto and Charon and the four much smaller satellites (Styx, Nix, Kerberos, and Hydra) near the time of closest approach on 14 July 2015. LORRI is a narrow field of view (0.29°), Ritchey-Chrétien telescope with a 20.8 cm diameter primary mirror and a three-lens field flattener. The telescope has an effective focal length of 262 cm. The focal plane unit consists of a 1024 × 1024 pixel charge-coupled device (CCD) detector operating in frame transfer mode. LORRI provides panchromatic imaging over a bandpass that extends approximately from 350 nm to 850 nm. The instrument operates in an extreme thermal environment, viewing space from within the warm spacecraft. For this reason, LORRI has a silicon carbide optical system with passive thermal control, designed to maintain focus without adjustment over a wide temperature range from -100 C to +50 C. LORRI operated flawlessly throughout the encounter period, providing both science and navigation imaging of the Pluto system. We describe the preparations for the Pluto system encounter, including pre-encounter rehearsals, calibrations, and navigation imaging. In addition, we describe LORRI operations during the encounter, and the resulting imaging performance. Finally, we also briefly describe the post-Pluto encounter imaging of other Kuiper belt objects and the plans for the upcoming encounter with KBO 2014 MU69.

Implementation of Adaptive Digital Controllers on Programmable Logic Devices

NASA Technical Reports Server (NTRS)

Gwaltney, David A.; King, Kenneth D.; Smith, Keary J.; Ormsby, John (Technical Monitor)

2002-01-01

Much has been made of the capabilities of FPGA's (Field Programmable Gate Arrays) in the hardware implementation of fast digital signal processing (DSP) functions. Such capability also makes and FPGA a suitable platform for the digital implementation of closed loop controllers. There are myriad advantages to utilizing an FPGA for discrete-time control functions which include the capability for reconfiguration when SRAM- based FPGA's are employed, fast parallel implementation of multiple control loops and implementations that can meet space level radiation tolerance in a compact form-factor. Other researchers have presented the notion that a second order digital filter with proportional-integral-derivative (PID) control functionality can be implemented in an FPGA. At Marshall Space Flight Center, the Control Electronics Group has been studying adaptive discrete-time control of motor driven actuator systems using digital signal processor (DSF) devices. Our goal is to create a fully digital, flight ready controller design that utilizes an FPGA for implementation of signal conditioning for control feedback signals, generation of commands to the controlled system, and hardware insertion of adaptive control algorithm approaches. While small form factor, commercial DSP devices are now available with event capture, data conversion, pulse width modulated outputs and communication peripherals, these devices are not currently available in designs and packages which meet space level radiation requirements. Meeting our goals requires alternative compact implementation of such functionality to withstand the harsh environment encountered on spacecraft. Radiation tolerant FPGA's are a feasible option for reaching these goals.

Robust Tracking of Small Displacements with a Bayesian Estimator

PubMed Central

Dumont, Douglas M.; Byram, Brett C.

2016-01-01

Radiation-force-based elasticity imaging describes a group of techniques that use acoustic radiation force (ARF) to displace tissue in order to obtain qualitative or quantitative measurements of tissue properties. Because ARF-induced displacements are on the order of micrometers, tracking these displacements in vivo can be challenging. Previously, it has been shown that Bayesian-based estimation can overcome some of the limitations of a traditional displacement estimator like normalized cross-correlation (NCC). In this work, we describe a Bayesian framework that combines a generalized Gaussian-Markov random field (GGMRF) prior with an automated method for selecting the prior’s width. We then evaluate its performance in the context of tracking the micrometer-order displacements encountered in an ARF-based method like acoustic radiation force impulse (ARFI) imaging. The results show that bias, variance, and mean-square error performance vary with prior shape and width, and that an almost one order-of-magnitude reduction in mean-square error can be achieved by the estimator at the automatically-selected prior width. Lesion simulations show that the proposed estimator has a higher contrast-to-noise ratio but lower contrast than NCC, median-filtered NCC, and the previous Bayesian estimator, with a non-Gaussian prior shape having better lesion-edge resolution than a Gaussian prior. In vivo results from a cardiac, radiofrequency ablation ARFI imaging dataset show quantitative improvements in lesion contrast-to-noise ratio over NCC as well as the previous Bayesian estimator. PMID:26529761

Implanted Cardiac Defibrillator Care in Radiation Oncology Patient Population

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

Gelblum, Daphna Y.; Amols, Howard

2009-04-01

Purpose: To review the experience of a large cancer center with radiotherapy (RT) patients bearing implantable cardiac defibrillators (ICDs) to propose some preliminary care guidelines as we learn more about the devices and their interaction with the therapeutic radiation environment. Methods and Materials: We collected data on patients with implanted ICDs treated with RT during a 2.5-year period at any of the five Memorial Sloan-Kettering clinical campuses. Information regarding the model, location, and dose detected from the device, as well as the treatment fields, fraction size, and treatment energy was collected. During this time, a new management policy for thesemore » patients had been implemented requiring treatment with low-energy beams (6 MV) and close surveillance of the patients in partnership with their electrophysiologist, as they received RT. Results: During the study period, 33 patients were treated with an ICD in place. One patient experienced a default of the device to its initial factory setting that was detected by the patient hearing an auditory signal from the device. This patient had initially been treated with a 15-MV beam. After this episode, his treatment was replanned to be completed with 6-MV photons, and he experienced no further events. Conclusion: Patients with ICDs and other implanted computer-controlled devices will be encountered more frequently in the RT department, and proper management is important. We present a policy for the safe treatment of these patients in the radiation oncology environment.« less

Magnetic Reconnection in Extreme Astrophysical Environments

NASA Astrophysics Data System (ADS)

Uzdensky, Dmitri

Magnetic reconnection is a fundamental plasma physics process of breaking ideal-MHD's frozen-in constraints on magnetic field connectivity and of dramatic rearranging of the magnetic topol-ogy, which often leads to a violent release of the free magnetic energy. Reconnection has long been acknowledged to be of great importance in laboratory plasma physics (magnetic fusion) and in space and solar physics (responsible for solar flares and magnetospheric substorms). In addition, its importance in Astrophysics has been increasingly recognized in recent years. However, due to a great diversity of astrophysical environments, the fundamental physics of astrophysical magnetic reconnection can be quite different from that of the traditional recon-nection encountered in the solar system. In particular, environments like the solar corona and the magnetosphere are characterized by relatively low energy densities, where the plasma is ad-equately described as a mixture of electrons and ions whose numbers are conserved and where the dissipated magnetic energy basically stays with the plasma. In contrast, in many high-energy astrophysical phenomena the energy density is so large that photons play as important a role as electrons and ions and, in particular, radiation pressure and radiative cooling become dominant. In this talk I focus on the most extreme case of high-energy-density astrophysical reconnec-tion — reconnection of magnetar-strength (1014 - 1015 Gauss) magnetic fields, important for giant flares in soft-gamma repeaters (SGRs), and for rapid magnetic energy release in either the central engines or in the relativistic jets of Gamma Ray Bursts (GRBs). I outline the key relevant physical processes and present a new theoretical picture of magnetic reconnection in these environments. The corresponding magnetic energy density is so enormous that, when suddenly released, it inevitably heats the plasma to relativistic temperatures, resulting in co-pious production of electron-positron pairs. The pairs make the reconnection layer optically thick, efficiently trapping gamma-ray photons and ensuring a local thermodynamic equilibrium between the radiation and the plasma. The plasma pressure inside the layer is then dominated by the radiation and pair pressure. At the same time, the timescale for radiation diffusion across the layer may still be much shorter than the global Alfven transit time along the layer, and hence the effects of radiative cooling on the thermodynamics of the layer need to be taken into account. In other words, the reconnection problem in this regime necessarily becomes a radiative transfer problem. In addition, the extremely high pair density, set by the local ther-modynamic equilibrium essentially independently of the upstream plasma density, can make the reconnection layer highly collisional, thereby justifying the use of resistive MHD (with Spitzer and Compton resistivities). The presence of all these processes calls for a substantial revision of our traditional physical picture of reconnection when applied to these environments. I will de-scribe how the corresponding new theory of reconnection of magnetar-strength magnetic fields ought to be constructed and will conclude by discussing its observational consequences and the prospects for future research.

Coherent Leinard-Wiechert fields produced by FELs (free-electron laser). Technical report, 14 January 1981-13 January 1982

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

Elias, L.R.

1981-12-01

Results are presented of a three-dimensional numerical analysis of the radiation fields produced in a free-electron laser. The method used here to obtain the spatial and temporal behavior of the radiated fields is based on the coherent superposition of the radiated fields is based on the coherent superposition of the exact Lienard-Wiechert fields produced by each electron in the beam. Interference effects are responsible for the narrow angular radiation patterns obtained and for the high degree of monochromaticity of the radiated fields.

Biomedical research publications: 1980 - 1982

NASA Technical Reports Server (NTRS)

Pleasant, L. G.; Limbach, L.

1982-01-01

Publications concerning the major physiological and psychological problems encountered by man when he undertakes space flight are listed. Nine research areas are included: cardiovascular deconditioning, motion sickness, bone alterations, muscle atrophy, blood cell alterations, fluid and eletrolyte changes, radiation effects and protection, behavior and performance, and general biomedical research.

Tracking reflective practice-based learning by medical students during an ambulatory clerkship.

PubMed

Thomas, Patricia A; Goldberg, Harry

2007-11-01

To explore the use of web and palm digital assistant (PDA)-based patient logs to facilitate reflective learning in an ambulatory medicine clerkship. Thematic analysis of convenience sample of three successive rotations of medical students' patient log entries. Johns Hopkins University School of Medicine. MS3 and MS4 students rotating through a required block ambulatory medicine clerkship. Students are required to enter patient encounters into a web-based log system during the clerkship. Patient-linked entries included an open text field entitled, "Learning Need." Students were encouraged to use this field to enter goals for future study or teaching points related to the encounter. The logs of 59 students were examined. These students entered 3,051 patient encounters, and 51 students entered 1,347 learning need entries (44.1% of encounters). The use of the "Learning Need" field was not correlated with MS year, gender or end-of-clerkship knowledge test performance. There were strong correlations between the use of diagnostic thinking comments and observations of therapeutic relationships (Pearson's r=.42, p<0.001), and between diagnostic thinking and primary interpretation skills (Pearson's r=.60, p<0.001), but not between diagnostic thinking and factual knowledge (Pearson's r =.10, p=.46). We found that when clerkship students were cued to reflect on each patient encounter with the electronic log system, student entries grouped into categories that suggested different levels of reflective thinking. Future efforts should explore the use of such entries to encourage and track habits of reflective practice in the clinical curriculum.

Understanding metropolitan patterns of daily encounters

PubMed Central

Sun, Lijun; Axhausen, Kay W.; Lee, Der-Horng; Huang, Xianfeng

2013-01-01

Understanding of the mechanisms driving our daily face-to-face encounters is still limited; the field lacks large-scale datasets describing both individual behaviors and their collective interactions. However, here, with the help of travel smart card data, we uncover such encounter mechanisms and structures by constructing a time-resolved in-vehicle social encounter network on public buses in a city (about 5 million residents). Using a population scale dataset, we find physical encounters display reproducible temporal patterns, indicating that repeated encounters are regular and identical. On an individual scale, we find that collective regularities dominate distinct encounters’ bounded nature. An individual’s encounter capability is rooted in his/her daily behavioral regularity, explaining the emergence of “familiar strangers” in daily life. Strikingly, we find individuals with repeated encounters are not grouped into small communities, but become strongly connected over time, resulting in a large, but imperceptible, small-world contact network or “structure of co-presence” across the whole metropolitan area. Revealing the encounter pattern and identifying this large-scale contact network are crucial to understanding the dynamics in patterns of social acquaintances, collective human behaviors, and—particularly—disclosing the impact of human behavior on various diffusion/spreading processes. PMID:23918373

A simple quality assurance test tool for the visual verification of light and radiation field congruent using electronic portal images device and computed radiography

PubMed Central

2012-01-01

Background The radiation field on most megavoltage radiation therapy units are shown by a light field projected through the collimator by a light source mounted inside the collimator. The light field is traditionally used for patient alignment. Hence it is imperative that the light field is congruent with the radiation field. Method A simple quality assurance tool has been designed for rapid and simple test of the light field and radiation field using electronic portal images device (EPID) or computed radiography (CR). We tested this QA tool using Varian PortalVision and Elekta iViewGT EPID systems and Kodak CR system. Results Both the single and double exposure techniques were evaluated, with double exposure technique providing a better visualization of the light-radiation field markers. The light and radiation congruency could be detected within 1 mm. This will satisfy the American Association of Physicists in Medicine task group report number 142 recommendation of 2 mm tolerance. Conclusion The QA tool can be used with either an EPID or CR to provide a simple and rapid method to verify light and radiation field congruence. PMID:22452821

High temperature strain measurement with a resistance strain gage

NASA Technical Reports Server (NTRS)

Lei, Jih-Fen; Fichtel, ED; Mcdaniel, Amos

1993-01-01

A PdCr based electrical resistance strain gage was demonstrated in the laboratory to be a viable sensor candidate for static strain measurement at high temperatures. However, difficulties were encountered while transferring the sensor to field applications. This paper is therefore prepared for recognition and resolution of the problems likely to be encountered with PdCr strain gages in field applications. Errors caused by the measurement system, installation technique and lead wire attachment are discussed. The limitations and some considerations related to the temperature compensation technique used for this gage are also addressed.

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

Adams, Fred C.; Coppess, Katherine R.; Bloch, Anthony M., E-mail: fca@umich.edu, E-mail: kcoppess@umich.edu, E-mail: abloch@umich.edu

Motivated by the possibility that different versions of the laws of physics could be realized within other universes, this paper delineates the galactic structure parameters that allow for habitable planets and revisits constraints on the amplitude Q of the primordial density fluctuations. Previous work indicates that large values of Q lead to galaxies so dense that planetary orbits cannot survive long enough for life to develop. Small values of Q lead to delayed star formation, loosely bound galaxies, and compromised heavy element retention. This work generalizes previous treatments in the following directions: [A] We consider models for the internal structuremore » of the galaxies, including a range of stellar densities, and find the fraction of the resulting galactic real estate that allows for stable, long-lived planetary orbits. [B] For high velocity encounters, we perform a large ensemble of numerical simulations to estimate cross sections for the disruption of planetary orbits due to interactions with passing stars. [C] We consider the background radiation fields produced by the galaxies: if a galaxy is too compact, the night sky seen from a potentially habitable planet can provide more power than the host star. [D] One consequence of intense galactic background radiation fields is that some portion of the galaxy, denoted as the Galactic Habitable Zone, will provide the right flux levels to support habitable planets for essentially any planetary orbit including freely floating bodies (but excluding close-in planets). As the value of Q increases, the fraction of stars in a galaxy that allow for (traditional) habitable planets decreases due to both orbital disruption and the intense background radiation. However, the outer parts of the galaxy always allow for habitable planets, so that the value of Q does not have a well-defined upper limit (due to scattering or radiation constraints). Moreover, some Galactic Habitable Zones are large enough to support more potentially habitable planets than the galaxies found in our universe. These results suggest that the possibilities for habitability in other universes are somewhat more favorable and far more diverse than previously imagined.« less

Environmental Catastrophes in the Earth's History Due to Solar Systems Encounters with Giant Molecular Clouds

NASA Technical Reports Server (NTRS)

Pavlov, Alexander A.

2011-01-01

In its motion through the Milky Way galaxy, the solar system encounters an average density (>=330 H atoms/cubic cm) giant molecular cloud (GMC) approximately every 108 years, a dense (approx 2 x 103 H atoms/cubic cm) GMC every approx 109 years and will inevitably encounter them in the future. However, there have been no studies linking such events with severe (snowball) glaciations in Earth history. Here we show that dramatic climate change can be caused by interstellar dust accumulating in Earth's atmosphere during the solar system's immersion into a dense (approx ,2 x 103 H atoms/cubic cm) GMC. The stratospheric dust layer from such interstellar particles could provide enough radiative forcing to trigger the runaway ice-albedo feedback that results in global snowball glaciations. We also demonstrate that more frequent collisions with less dense GMCs could cause moderate ice ages.

Adaptive Controller for Compact Fourier Transform Spectrometer with Space Applications

NASA Astrophysics Data System (ADS)

Keymeulen, D.; Yiu, P.; Berisford, D. F.; Hand, K. P.; Carlson, R. W.; Conroy, M.

2014-12-01

Here we present noise mitigation techniques developed as part of an adaptive controller for a very compact Compositional InfraRed Interferometric Spectrometer (CIRIS) implemented on a stand-alone field programmable gate array (FPGA) architecture with emphasis on space applications in high radiation environments such as Europa. CIRIS is a novel take on traditional Fourier Transform Spectrometers (FTS) and replaces linearly moving mirrors (characteristic of Michelson interferometers) with a constant-velocity rotating refractor to variably phase shift and alter the path length of incoming light. The design eschews a monochromatic reference laser typically used for sampling clock generation and instead utilizes constant time-sampling via internally generated clocks. This allows for a compact and robust device, making it ideal for spaceborne measurements in the near-IR to thermal-IR band (2-12 µm) on planetary exploration missions. The instrument's embedded microcontroller is implemented on a VIRTEX-5 FPGA and a PowerPC with the aim of sampling the instrument's detector and optical rotary encoder in order to construct interferograms. Subsequent onboard signal processing provides spectral immunity from the noise effects introduced by the compact design's removal of a reference laser and by the radiation encountered during space flight to destinations such as Europa. A variety of signal processing techniques including resampling, radiation peak removal, Fast Fourier Transform (FFT), spectral feature alignment, dispersion correction and calibration processes are applied to compose the sample spectrum in real-time with signal-to-noise-ratio (SNR) performance comparable to laser-based FTS designs in radiation-free environments. The instrument's FPGA controller is demonstrated with the FTS to characterize its noise mitigation techniques and highlight its suitability for implementation in space systems.

Implementation of Adaptive Digital Controllers on Programmable Logic Devices

NASA Technical Reports Server (NTRS)

Gwaltney, David A.; King, Kenneth D.; Smith, Keary J.; Monenegro, Justino (Technical Monitor)

2002-01-01

Much has been made of the capabilities of FPGA's (Field Programmable Gate Arrays) in the hardware implementation of fast digital signal processing. Such capability also makes an FPGA a suitable platform for the digital implementation of closed loop controllers. Other researchers have implemented a variety of closed-loop digital controllers on FPGA's. Some of these controllers include the widely used proportional-integral-derivative (PID) controller, state space controllers, neural network and fuzzy logic based controllers. There are myriad advantages to utilizing an FPGA for discrete-time control functions which include the capability for reconfiguration when SRAM-based FPGA's are employed, fast parallel implementation of multiple control loops and implementations that can meet space level radiation tolerance requirements in a compact form-factor. Generally, a software implementation on a DSP (Digital Signal Processor) or microcontroller is used to implement digital controllers. At Marshall Space Flight Center, the Control Electronics Group has been studying adaptive discrete-time control of motor driven actuator systems using digital signal processor (DSP) devices. While small form factor, commercial DSP devices are now available with event capture, data conversion, pulse width modulated (PWM) outputs and communication peripherals, these devices are not currently available in designs and packages which meet space level radiation requirements. In general, very few DSP devices are produced that are designed to meet any level of radiation tolerance or hardness. The goal of this effort is to create a fully digital, flight ready controller design that utilizes an FPGA for implementation of signal conditioning for control feedback signals, generation of commands to the controlled system, and hardware insertion of adaptive control algorithm approaches. An alternative is required for compact implementation of such functionality to withstand the harsh environment encountered on spacecraft. Radiation tolerant FPGA's are a feasible option for reaching this goal.

Implementation of Adaptive Digital Controllers on Programmable Logic Devices

NASA Technical Reports Server (NTRS)

Gwaltney, David A.; King, Kenneth D.; Smith, Keary J.; Montenegro, Justino (Technical Monitor)

2002-01-01

Much has been made of the capabilities of Field Programmable Gate Arrays (FPGA's) in the hardware implementation of fast digital signal processing functions. Such capability also makes an FPGA a suitable platform for the digital implementation of closed loop controllers. Other researchers have implemented a variety of closed-loop digital controllers on FPGA's. Some of these controllers include the widely used Proportional-Integral-Derivative (PID) controller, state space controllers, neural network and fuzzy logic based controllers. There are myriad advantages to utilizing an FPGA for discrete-time control functions which include the capability for reconfiguration when SRAM- based FPGA's are employed, fast parallel implementation of multiple control loops and implementations that can meet space level radiation tolerance requirements in a compact form-factor. Generally, a software implementation on a Digital Signal Processor (DSP) device or microcontroller is used to implement digital controllers. At Marshall Space Flight Center, the Control Electronics Group has been studying adaptive discrete-time control of motor driven actuator systems using DSP devices. While small form factor, commercial DSP devices are now available with event capture, data conversion, Pulse Width Modulated (PWM) outputs and communication peripherals, these devices are not currently available in designs and packages which meet space level radiation requirements. In general, very few DSP devices are produced that are designed to meet any level of radiation tolerance or hardness. An alternative is required for compact implementation of such functionality to withstand the harsh environment encountered on spacemap. The goal of this effort is to create a fully digital, flight ready controller design that utilizes an FPGA for implementation of signal conditioning for control feedback signals, generation of commands to the controlled system, and hardware insertion of adaptive-control algorithm approaches. Radiation tolerant FPGA's are a feasible option for reaching this goal.

Tips for Novice Researchers: Operational Difficulties Encountered in Underdeveloped Countries.

ERIC Educational Resources Information Center

Belcher El-Nahhas, Susan M.

This paper provides a general overview of the type of problems encountered in the field of research so that individuals who are contemplating conducting research in an underdeveloped country for the first time are better prepared, and hence, better able to complete their research. The paper recounts a female researcher's personal experiences in…

The “Gray Zone” of Police Work During Mental Health Encounters: Findings from an Observational Study in Chicago

PubMed Central

Wood, Jennifer D; Watson, Amy C; Fulambarker, Anjali J

2016-01-01

Although improving police responses to mental health crises has received significant policy attention, most encounters between police and persons with mental illnesses do not involve major crimes or violence, nor do they rise to the level of requiring emergency apprehension. Here, we report on field observations of police officers handling mental health-related encounters in Chicago. Findings confirm that these encounters often occur in the “gray zone”, where the problems at hand do not call for formal or legalistic interventions including arrest and emergency apprehension. In examining how police resolved such situations, we observed three core features of police work: (1) accepting temporary solutions to chronic vulnerability; (2) using local knowledge to guide decision-making; and (3) negotiating peace with complainants and call subjects. Study findings imply the need to advance field-based studies using systematic social observations of gray zone decision-making within and across distinct geographic and place-based contexts. Policy implications for supporting police interventions, including place-based enhancements of gray zone resources, are also discussed. PMID:28286406

Capture of exocomets and the erosion of the Oort cloud due to stellar encounters in the Galaxy

NASA Astrophysics Data System (ADS)

Hanse, J.; Jílková, L.; Portegies Zwart, S. F.; Pelupessy, F. I.

2018-02-01

The Oort cloud (OC) probably formed more than 4 Gyr ago and has been moving with the Sun in the Galaxy since, exposed to external influences, most prominently to the Galactic tide and passing field stars. Theories suggest that other stars might possess exocomets distributed similarly to our OC. We study the erosion of the OC and the possibility for capturing exocomets during the encounters with such field stars. We carry out simulations of flybys, where both stars are surrounded by a cloud of comets. We measure how many exocomets are transferred to the OC, how many OC's comets are lost, and how this depends on the other star's mass, velocity and impact parameter. Exocomets are transferred to the OC only during relatively slow (≲0.5 km s-1) and close (≲105 au) flybys and these are expected to be extremely rare. Assuming that all passing stars are surrounded by a cloud of exocomets, we derive that the fraction of exocomets in the OC has been about 10-5-10-4. Finally, we simulate the OC for the whole lifetime of the Sun, taking into account the encounters and the tidal effects. The OC has lost 25-65 per cent of its mass, mainly due to stellar encounters, and at most 10 per cent (and usually much less) of its mass can be captured. However, exocomets are often lost shortly after the encounter that delivers them, due to the Galactic tide and consecutive encounters.

Potential theory of radiation

NASA Technical Reports Server (NTRS)

Chiu, Huei-Huang

1989-01-01

A theoretical method is being developed by which the structure of a radiation field can be predicted by a radiation potential theory, similar to a classical potential theory. The introduction of a scalar potential is justified on the grounds that the spectral intensity vector is irrotational. The vector is also solenoidal in the limits of a radiation field in complete radiative equilibrium or in a vacuum. This method provides an exact, elliptic type equation that will upgrade the accuracy and the efficiency of the current CFD programs required for the prediction of radiation and flow fields. A number of interesting results emerge from the present study. First, a steady state radiation field exhibits an optically modulated inverse square law distribution character. Secondly, the unsteady radiation field is structured with two conjugate scalar potentials. Each is governed by a Klein-Gordon equation with a frictional force and a restoring force. This steady potential field structure and the propagation of radiation potentials are consistent with the well known results of classical electromagnetic theory. The extension of the radiation potential theory for spray combustion and hypersonic flow is also recommended.

Influence of Hydroponically Grown Hoyt Soybeans and Radiation Encountered on Mars Missions on the Yield and Quality of Soymilk and Tofu

NASA Technical Reports Server (NTRS)

Wilson, Lester A.

2005-01-01

Soybeans were chosen for hmar and planetary missions due to their nutritive value and ability to produce oil and protein for further food applications. However, soybeans must be processed into foods prior to crew consumption. Wilson et al. (2003) raised questions about (1) the influence of radiation (on germination and functional properties) that the soybeans would be exposed to during bulk storage for a Mars mission, and (2) the impact of using hydroponically grown versus field grown soybeans on the yield and quality of soyfoods. The influence of radiation can be broken down into two components: (A) affect of surface pasteurization to ensure the astronauts safety from food-borne illnesses (a Hazard Analysis Critical Control Point), and (B) affect of the amount of radiation the soybeans receive during a Mars mission. Decreases in the amount of natural antioxidants and free radical formation and oxidation induced changes in the soybean (lipid, protein, etc.) will influence the nutritional value, texture, quality, and safety of soyfoods made from them. The objectives of this project are to (1) evaluate the influence of gamma and electron beam radiation on bulk soybeans (HACCP, CCP) on the microbial load, germination, ease of processing, and quality of soymilk and tofu; (2) provide scale up and mass balance data for Advanced Life Support subsystems including Biomass, Solid Waste Processing, and Water Recovery Systems; and (3) to compare Hoyt field grown to hydroponically grown Hoyt soybeans for soymilk and tofu production. The soybean cultivar Hoyt, a small standing, high protein cultivar that could grow hydroponically in the AIMS facility on Mars) was evaluated for the production of soymilk and tofu. The quality and yield of the soymilk and tofu from hydroponic Hoyt, was compared to Vinton 81 (a soyfood industry standard), field Hoyt, IA 2032LS (lipoxygenase-free), and Proto (high protein and antioxidant potential). Soymilk and tofu were produced using the Japanese method. The soymilk was coagulated with calcium sulfate dihydrate. Soybeans and tofu were evaluated using chemical, microbial, and instrumental sensory methods. The surface radiation of whole dry soybeans using electron beam or gamma rays at 10 or 30 kGy did provide microbial safety for the astronauts. However, these doses caused oxidative changes that resulted in tofu with rancid aroma, darkening of the tofu, lower tofu yields, more solid waste, and loss of the ability of the seeds to germinate. While lower doses may reduce these problems, we lose the ability to insure microbial safety (cross-contamination) of bulk soybeans for the astronauts. Counter measures could include vacuum packaging, radiating under freezing conditions. A No Effect Dose for food quality, below 10 kGy needs to be determined. Better estimates of the radiation that the food will be exposed to need to determined and shared. Appropriate shielding for the food as well as the astronauts needs to be developed. The Hoyt soybean did not provide a high yielding, high quality tofu. A new small scale system for evaluating soybeans was developed using 50 g quantities of soybeans.

Fireproofing and heat insulating performance improvement of EG/ATH modified intumescent flame retardant coating treated under Co-60 radiation

NASA Astrophysics Data System (ADS)

Zhang, Yuehong; Luan, Weiling; Jiang, Tao

2017-12-01

New intumescent flame retardant (IFR) coatings with different fire retardants were prepared in this paper. Expandable graphite (EG) and Aluminium hydroxide (ATH) were respectively added into the conventional IFR coating system, which included ammonium polyphosphate (APP) / pentaerythritol (PER) / melamine (MEL). The fireproofing time and heat insulating properties of the additives acted as fire retardants were investigated via thermogravimetry analysis (TGA) and fire resistance test of homemade big panel test. The morphology of the char layer structure was achieved by scanning electron microscopy (SEM). The highlight of the paper was that the coating samples were pretreated under Co-60 radiation. The influence of radiation on the fire resistance time and char layer height was investigated. The results showed that the prepared IFR coatings can be used in Co-60 radiation for more than 90 min when encountering fire. It would be a reference for radiation shielding in nuclear environment.

ReactorHealth Physics operations at the NIST center for neutron research.

PubMed

Johnston, Thomas P

2015-02-01

Performing health physics and radiation safety functions under a special nuclear material license and a research and test reactor license at a major government research and development laboratory encompasses many elements not encountered by industrial, general, or broad scope licenses. This article reviews elements of the health physics and radiation safety program at the NIST Center for Neutron Research, including the early history and discovery of the neutron, applications of neutron research, reactor overview, safety and security of radiation sources and radioactive material, and general health physics procedures. These comprise precautions and control of tritium, training program, neutron beam sample processing, laboratory audits, inventory and leak tests, meter calibration, repair and evaluation, radioactive waste management, and emergency response. In addition, the radiation monitoring systems will be reviewed including confinement building monitoring, ventilation filter radiation monitors, secondary coolant monitors, gaseous fission product monitors, gas monitors, ventilation tritium monitor, and the plant effluent monitor systems.

Delayed effects of proton irradiation in Macaca Mulatta (22-year summary)

NASA Astrophysics Data System (ADS)

Woods, D. H.; Hardy, K. A.; Cox, A. B.; Salmon, Y. L.; Yochmowitz, M. G.; Cordts, R. E.

1989-05-01

Lifetime observations on a group of rhesus monkeys indicate that life expectancy loss from exposure to protons in the energy range encountered in the Van Allen belts and solar proton events can be correlated with the dose and energy of radiation. The primary cause of life shortening is nonleukemic cancers. Radiation also increased the rise of endometriosis (an abnormal proliferation of the lining of the uterus in females). Other effects associated with radiation exposures are lowered glucose tolerance and increased incidence of cataracts. Calculations of the relative risk of fatal cancers in the irradiated subjects reveal that the total body surface dose required to double the risk of death from cancer over a 20-year post exposure period varies with the linear energy transfer (LET) of the radiation. The ability to determine the integrated dose and LET spectrum in space radiation exposures of humans is, therefore, critical to the assessment of lifetime cancer risk.

NO FLARES FROM GAMMA-RAY BURST AFTERGLOW BLAST WAVES ENCOUNTERING SUDDEN CIRCUMBURST DENSITY CHANGE

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

Gat, Ilana; Van Eerten, Hendrik; MacFadyen, Andrew

2013-08-10

Afterglows of gamma-ray bursts are observed to produce light curves with the flux following power-law evolution in time. However, recent observations reveal bright flares at times on the order of minutes to days. One proposed explanation for these flares is the interaction of a relativistic blast wave with a circumburst density transition. In this paper, we model this type of interaction computationally in one and two dimensions, using a relativistic hydrodynamics code with adaptive mesh refinement called RAM, and analytically in one dimension. We simulate a blast wave traveling in a stellar wind environment that encounters a sudden change inmore » density, followed by a homogeneous medium, and compute the observed radiation using a synchrotron model. We show that flares are not observable for an encounter with a sudden density increase, such as a wind termination shock, nor for an encounter with a sudden density decrease. Furthermore, by extending our analysis to two dimensions, we are able to resolve the spreading, collimation, and edge effects of the blast wave as it encounters the change in circumburst medium. In all cases considered in this paper, we find that a flare will not be observed for any of the density changes studied.« less

Delayed cerebral radiation necrosis following treatment for a plasmacytoma of the skull.

PubMed

Chambless, Lola B; Angel, Federica B; Abel, Ty W; Xia, Fen; Weaver, Kyle D

2010-10-25

Cerebral radiation necrosis is a relatively common complication of radiation therapy for intracranial malignancies which can also rarely be encountered after radiation of extracranial lesions of the head and neck. We present the first reported case of cerebral radiation necrosis in a patient who underwent radiation therapy for a plasmacytoma of the skull. A 68-year-old male with multiple myeloma presented with an enhancing right frontal mass, 8 years after receiving radiation therapy for a plasmacytoma of the left frontal skull. The patient underwent a diagnostic and therapeutic craniotomy for a presumed neoplastic lesion. The pathologic diagnosis made in this case was delayed radiation necrosis. The patient was followed for over a year during which this process continued to evolve before the ultimate resolution of his clinical symptoms and radiographic abnormality. This case highlights the importance of considering radiation necrosis in the differential diagnosis of any patient with an intracranial mass and a history of radiation for an extracranial head and neck malignancy, regardless of timing and laterality. This case also provides unique insights into the ongoing debate regarding the role of the aberrant immune response in the pathogenesis of delayed cerebral radiation necrosis.

Magnetized or Unmagnetized: Ambiguity Persists Following Galileo's Encounters with Io in 1999 and 2000

NASA Technical Reports Server (NTRS)

Kivelson, Margaret G.; Khurana, Krishan K.; Russell, Christopher T.; Joy, Steven P.; Volwerk, Martin; Walker, Raymond J.; Zimmer, Christophe; Linker, Jon A.

2001-01-01

Magnetometer data from Galileo's close encounters with Io do not establish absolutely either the existence or absence of an internal magnetic moment because the measurements were made in regions where plasma currents contribute sizable magnetic perturbations. Data from an additional encounter where the closest approaches were made beneath Io's south polar regions, were lost. The recent passes enhance our understanding of the interaction of Io and its flux tube with the torus, and narrows the limits on possible internal sources of magnetic fields. Simple field-draping arguments account for some aspects of the observed rotations. Analyses in terms of both a magnetized and an unmagnetized Io are considered. Data from the February 2000 pass disqualify a strongly magnetized Io (surface equatorial field stronger than the background field) but do not disqualify a weakly magnetized Io (surface equatorial field of the order of Ganymede's but smaller than the background field at Io). Models imply that if Io is magnetized, its magnetic moment is not absolutely antialigned with the rotation axis. The inferred tilt is consistent with contributions from an inductive field on the order of those observed at Europa and Callisto. The currents would flow in the outer mantle or aesthenosphere if an induced field is present. Wave perturbations differing on flux tubes that do or do not link directly to Io and its ionosphere suggest the following: (1) the latter flux tubes are almost stagnant in Io's frame; and (2) a unipolar inductor correctly models the currents linking Io to Jupiter's ionosphere.

Radiative transfer theory for active remote sensing of a layer of small ellipsoidal scatterers. [of vegetation

NASA Technical Reports Server (NTRS)

Tsang, L.; Kubacsi, M. C.; Kong, J. A.

1981-01-01

The radiative transfer theory is applied within the Rayleigh approximation to calculate the backscattering cross section of a layer of randomly positioned and oriented small ellipsoids. The orientation of the ellipsoids is characterized by a probability density function of the Eulerian angles of rotation. The radiative transfer equations are solved by an iterative approach to first order in albedo. In the half space limit the results are identical to those obtained via the approach of Foldy's and distorted Born approximation. Numerical results of the theory are illustrated using parameters encountered in active remote sensing of vegetation layers. A distinctive characteristic is the strong depolarization shown by vertically aligned leaves.

Mariner 10 magnetic field observations of the Venus wake

NASA Technical Reports Server (NTRS)

Lepping, R. P.; Behannon, K. W.

1977-01-01

Magnetic field measurements made over a 21-hour interval during the Mariner 10 encounter with Venus were used to study the down-stream region of the solar wind-Venus interaction over a distance of approximately 100 R sub v. For most of the day before closest approach the spacecraft was located in a sheath-like region which was apparently bounded by planetary bow shock on the outer side and either a planetary wake boundary or transient boundary-like feature on the inner side. The spacecraft made multiple encounters with the wake-like boundary during the 21-hour interval with an increasing frequency as it approached the planet. Each pass into the wake boundary from the sheath region was consistently characterized by a slight decrease in magnetic field magnitude, a marked increase in the frequency and amplitude of field fluctuations, and a systematic clockwise rotation of the field direction when viewed from above the plane of the planet orbit.

Do pediatric and adult disaster victims differ? A descriptive analysis of clinical encounters from four natural disaster DMAT deployments.

PubMed

Gnauck, Katherine A; Nufer, Kevin E; LaValley, Jonathon M; Crandall, Cameron S; Craig, Frances W; Wilson-Ramirez, Gina B

2007-01-01

The differences between pediatric (< or = 17 years of age) and adult clinical field encounters were analyzed from four deployments of Disaster Medical Assistance Teams (DMATs). A retrospective cohort review of all patients who presented to DMAT field clinics during two hurricanes, one earthquake, and one flood was conducted. Descriptive statistics were used to analyze: (1) age; (2) gender; (3) severity category level; (4) chief complaint; (5) treatments provided; (6) discharge diagnosis; and (7) disposition. Five subsets of pediatric patients were analyzed further. Of the 2,196 patient encounters reviewed, 643 (29.5%) encounters were pediatric patients. Pediatric patients had a greater number of blank severity category levels than adults. Pediatric patients also were: (1) more likely to present with chief complaints of upper respiratory infections or wounds; (2) less likely to present with musculoskeletal pain or abdominal pain; and (3) equally likely to present with rashes. Pediatric patients were more likely to receive antibiotics, pain medication, and antihistamines, but were equally likely to need treatment for wounds. Dispositions to the hospital were less frequent for pediatric patients than for adults. Pediatric patients represent a substantial proportion of disaster victims at DMAT field clinics. They often necessitate special care requirements different from their adult counterparts. Pediatric-specific severity category criteria, treatment guidelines, equipment/medication stocks, and provider training are warranted for future DMAT response preparations.

Nanocrystalline zirconia can be amorphized by ion irradiation.

PubMed

Meldrum, A; Boatner, L A; Ewing, R C

2002-01-14

Nanocrystalline composites are finding applications in high-radiation environments due to their excellent mechanical and electronic properties. We show, however, that at the smallest particle sizes, radiation damage effects can be so strongly enhanced that under the right conditions, materials that have never been made amorphous can become highly susceptible to irradiation-induced amorphization. Because light-weight, high-strength nanocomposites are potential materials for spacecraft shielding and sensor systems, these fundamental results have significant implications for the design and selection of materials to be used in environments where a large ion flux will be encountered.

The Effect of a Mars Mission on Chromosome Damage in the Blood Lymphocytes of Astronauts

NASA Technical Reports Server (NTRS)

George, Kerry A.; Durante, M.; Cucinnotta, F. A.

2006-01-01

The radiation environment encountered during a manned mission to Mars will lead to significant elevation of biological damage in astronauts. Here we present estimates of the increased frequencies of chromosome aberrations in the peripheral blood lymphocytes of astronauts after a hypothetical Mars mission using radiation dose estimations and lymphocyte biology. Results will incorporate previously published data on in vivo induced chromosome damage in the blood lymphocytes of crewmembers after ISS and Mir missions, along with recent findings on the time dependant decay of chromosome aberrations after space flight.

Polymer-composite materials for radiation protection.

PubMed

Nambiar, Shruti; Yeow, John T W

2012-11-01

Unwanted exposures to high-energy or ionizing radiation can be hazardous to health. Prolonged or accumulated radiation dosage from either particle-emissions such as alpha/beta, proton, electron, neutron emissions, or high-energy electromagnetic waves such as X-rays/γ rays, may result in carcinogenesis, cell mutations, organ failure, etc. To avoid occupational hazards from these kinds of exposures, researchers have traditionally used heavy metals or their composites to attenuate the radiation. However, protective gear made of heavy metals are not only cumbersome but also are capable of producing more penetrative secondary radiations which requires additional shielding, increasing the cost and the weight factor. Consequently, significant research efforts have been focused toward designing efficient, lightweight, cost-effective, and flexible shielding materials for protection against radiation encountered in various industries (aerospace, hospitals, and nuclear reactors). In this regard, polymer composites have become attractive candidates for developing materials that can be designed to effectively attenuate photon or particle radiation. In this paper, we review the state-of-the-art of polymer composites reinforced with micro/nanomaterials, for their use as radiation shields.

Radiation-Induced Skin Injuries to Patients: What the Interventional Radiologist Needs to Know.

PubMed

Jaschke, Werner; Schmuth, Matthias; Trianni, Annalisa; Bartal, Gabriel

2017-08-01

For a long time, radiation-induced skin injuries were only encountered in patients undergoing radiation therapy. In diagnostic radiology, radiation exposures of patients causing skin injuries were extremely rare. The introduction of fast multislice CT scanners and fluoroscopically guided interventions (FGI) changed the situation. Both methods carry the risk of excessive high doses to the skin of patients resulting in skin injuries. In the early nineties, several reports of epilation and skin injuries following CT brain perfusion studies were published. During the same time, several papers reported skin injuries following FGI, especially after percutaneous coronary interventions and neuroembolisations. Thus, CT and FGI are of major concern regarding radiation safety since both methods can apply doses to patients exceeding 5 Gy (National Council on Radiation Protection and Measurements threshold for substantial radiation dose level). This paper reviews the problem of skin injuries observed after FGI. Also, some practical advices are given how to effectively avoid skin injuries. In addition, guidelines are discussed how to deal with patients who were exposed to a potentially dangerous radiation skin dose during medically justified interventional procedures.

Electromagnetic field radiation model for lightning strokes to tall structures

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

Motoyama, H.; Janischewskyj, W.; Hussein, A.M.

1996-07-01

This paper describes observation and analysis of electromagnetic field radiation from lightning strokes to tall structures. Electromagnetic field waveforms and current waveforms of lightning strokes to the CN Tower have been simultaneously measured since 1991. A new calculation model of electromagnetic field radiation is proposed. The proposed model consists of the lightning current propagation and distribution model and the electromagnetic field radiation model. Electromagnetic fields calculated by the proposed model, based on the observed lightning current at the CN Tower, agree well with the observed fields at 2km north of the tower.

Study on the electromagnetic radiation characteristics of discharging excimer laser system

NASA Astrophysics Data System (ADS)

Zhao, Duliang; Liang, Xu; Fang, Xiaodong; Wang, Qingsheng

2016-10-01

Excimer laser in condition of high voltage, large current and fast discharge will produce strong electromagnetic pulse radiation and electromagnetic interference on the around electrical equipment. The research on characteristics and distribution of excimer laser electromagnetic radiation could provide important basis for electromagnetic shielding and suppressing electromagnetic interference, and further improving the electromagnetic compatibility of system. Firstly, electromagnetic radiation source is analyzed according to the working principle of excimer laser. The key test points of the electromagnetic radiation, hydrogen thyratron, main discharge circuit and laser outlet, are determined by the mechanical structure and the theory of electromagnetic radiation. Secondly, characteristics of electromagnetic field were tested using a near field probe on the key positions of the vertical direction at 20, 50, and 80 cm, respectively. The main radiation frequencies and the radiation field characteristics in the near field are obtained. The experimental results show that the main radiation frequencies distribute in 47, 65, and 130 MHz for electric field and the main radiation frequencies distribute in 34, 100, and 165 MHz for magnetic field. The intensity of electromagnetic field decreases rapidly with the increase of test distance. The higher the frequency increases, the faster the amplitude attenuate. Finally, several electromagnetic interference suppression measurement methods are proposed from the perspective of electromagnetic compatibility according to the test results.

Studies of radiative transfer in the earth's atmosphere with emphasis on the influence of the radiation budget in the joint institute for advancement of flight sciences at the NASA-Langley Research Center

NASA Technical Reports Server (NTRS)

1979-01-01

Earth and solar radiation budget measurements were examined. Sensor calibration and measurement accuracy were emphasized. Past works on the earth's radiation field that must be used in reducing observations of the radiation field were reviewed. Using a finite difference radiative transfer algorithm, models of the angular and spectral dependence of the earth's radiation field were developed.

Estimation of missing values in solar radiation data using piecewise interpolation methods: Case study at Penang city

NASA Astrophysics Data System (ADS)

Zainudin, Mohd Lutfi; Saaban, Azizan; Bakar, Mohd Nazari Abu

2015-12-01

The solar radiation values have been composed by automatic weather station using the device that namely pyranometer. The device is functions to records all the radiation values that have been dispersed, and these data are very useful for it experimental works and solar device's development. In addition, for modeling and designing on solar radiation system application is needed for complete data observation. Unfortunately, lack for obtained the complete solar radiation data frequently occur due to several technical problems, which mainly contributed by monitoring device. Into encountering this matter, estimation missing values in an effort to substitute absent values with imputed data. This paper aimed to evaluate several piecewise interpolation techniques likes linear, splines, cubic, and nearest neighbor into dealing missing values in hourly solar radiation data. Then, proposed an extendable work into investigating the potential used of cubic Bezier technique and cubic Said-ball method as estimator tools. As result, methods for cubic Bezier and Said-ball perform the best compare to another piecewise imputation technique.

Simulating synchrotron radiation in accelerators including diffuse and specular reflections

DOE PAGES

Dugan, G.; Sagan, D.

2017-02-24

An accurate calculation of the synchrotron radiation flux within the vacuum chamber of an accelerator is needed for a number of applications. These include simulations of electron cloud effects and the design of radiation masking systems. To properly simulate the synchrotron radiation, it is important to include the scattering of the radiation at the vacuum chamber walls. To this end, a program called synrad3d has been developed which simulates the production and propagation of synchrotron radiation using a collection of photons. Photons generated by a charged particle beam are tracked from birth until they strike the vacuum chamber wall wheremore » the photon is either absorbed or scattered. Both specular and diffuse scattering is simulated. If a photon is scattered, it is further tracked through multiple encounters with the wall until it is finally absorbed. This paper describes the synrad3d program, with a focus on the details of its scattering model, and presents some examples of the program’s use.« less

Space radiation effects on plant and mammalian cells

NASA Astrophysics Data System (ADS)

Arena, C.; De Micco, V.; Macaeva, E.; Quintens, R.

2014-11-01

The study of the effects of ionizing radiation on organisms is related to different research aims. The current review emphasizes the studies on the effects of different doses of sparsely and densely ionizing radiation on living organisms, with the final purpose of highlighting specific and common effects of space radiation in mammals and plants. This topic is extremely relevant in the context of radiation protection from space environment. The response of different organisms to ionizing radiation depends on the radiation quality/dose and/or the intrinsic characteristics of the living system. Macromolecules, in particular DNA, are the critical targets of radiation, even if there is a strong difference between damages encountered by plant and mammalian cells. The differences in structure and metabolism between the two cell types are responsible for the higher resistance of the plant cell compared with its animal counterpart. In this review, we report some recent findings from studies performed in Space or on Earth, simulating space-like levels of radiation with ground-based facilities, to understand the effect of ionizing radiation on mammalian and plant cells. In particular, our attention is focused on genetic alterations and repair mechanisms in mammalian cells and on structures and mechanisms conferring radioresistance to plant cells.

What Can the Semantic Web Do for Adaptive Educational Hypermedia?

ERIC Educational Resources Information Center

Cristea, Alexandra I.

2004-01-01

Semantic Web and Adaptive Hypermedia come from different backgrounds, but it turns out that actually, they can benefit from each other, and that their confluence can lead to synergistic effects. This encounter can influence several fields, among which an important one is Education. This paper presents an analysis of this encounter, first from a…

The magnetospheric lobe at geosynchronous orbit

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

Thomsen, M.F.; Bame, S.J.; McComas, D.J.

1994-09-01

On rare occasions, satellites at geosynchronous altitude enter the magnetospheric lobe, characterized by extremely low ion fluxes between 1 eV and 40 keV and electron fluxes above a few hundred eV. One year of plasma observations from two simultaneously operating spacecraft at synchronous orbit is surveyed for lobe encounters. A total of 34 full encounters and 56 apparent near encounters are identified, corresponding to {approximately}0.06% of the total observation time. Unlike energetic particle (E>40 keV) dropouts studied earlier, there is a strong tendency for the lobe encounters to occur postmidnight, as late as 07 local time. The two spacecraft encountermore » the lobe with different rates and in different seasons. These occurrence properties are not simply explicable in terms of the orbital geometry in either the solar magnetic or the geocentric solar magnetospheric coordinate system. A composite coordinate system which previously organized more energetic particle dropouts is somewhat more successful in organizing the lobe encounters, suggesting that solar wind distortion of the magnetic equatorial plane away from the dipole location and toward the antisolar direction may be largely responsible for these dropouts. The authors results further suggest that this distortion persists even sunward of the dawn-dusk terminator. However, a simple dawn-dusk symmetric distortion does not fully account for all the seasonal and local time asymmetries in the occurrence of the lobe encounters; thus there is probably an additional dawn-dusk asymmetry in the distorted field. The lobe encounters are strongly associated with magnetospheric activity and tend to occur in association with rare magnetosheath encounters at synchronous orbit. It thus appears that the presence of the lobe at geosynchronous orbit is the result of major, probably asymmetric modifications of the magnetospheric field geometry in times of strong disturbance. 19 refs., 7 figs., 1 tab.« less

Couplings between the seasonal cycles of surface thermodynamics and radiative fluxes in the semi-arid Sahel

NASA Astrophysics Data System (ADS)

Guichard, F.; Kergoat, L.; Mougin, E.; Timouk, F.; Bock, O.; Hiernaux, P.

2009-04-01

A good knowledge of surface fluxes and atmospheric low levels is central to improving our understanding of the West African monsoon. This study provides a quantitative analysis of the peculiar seasonal and diurnal cycles of surface thermodynamics and radiative fluxes encountered in Central Sahel. It is based on a multi-year dataset collected in the Malian Gourma over a sandy soil at 1.5°W-15.3°N (a site referred to as Agoufou) with an automated weather station and a sunphotometer (AERONET), complemented by observations from the AMMA field campaign. The seasonal cycle of this Tropical region is characterized by a broad maximum of temperature in May, following the first minimum of the solar zenith angle by a few weeks, when Agoufou lies within the West African Heat-Low, and a late summer maximum of equivalent potential temperature within the core of the monsoon season, around the second yearly maximum of solar zenith angle, as the temperature reaches its Summer minimum. More broadly, subtle balances between surface air temperature and moisture fields are found on a range of scales. For instance, during the monsoon, apart from August, their opposite daytime fluctuations (warming, drying) lead to an almost flat diurnal cycle of the equivalent potential temperature at the surface. This feature stands out in contrast to other more humid continental regions. Here, the strong dynamics associated with the transition from a drier hot Spring to a brief cooler wet tropical Summer climate involves very large transformations of the diurnal cycles. The Summer increase of surface net radiation, Rnet, is also strong; typically 10-day mean Rnet reaches about 5 times its Winter minimum (~30 W.m-2) in August (~150 W.m-2). A major feature revealed by observations is that this increase is mostly driven by modifications of the surface upwelling fluxes shaped by rainfall events and vegetation phenology (surface cooling and darkening), while the direct impact of atmospheric changes on the total incoming radiation is limited to shorter time scales in Summer over this Central Sahelian location. However, observations also reveal astonishing radiative signatures of the monsoon on the surface incoming radiative flux. The incoming longwave flux does not reach its maximum during the monsoon season when the atmosphere is the most cloudy and humid, but earlier, prior to the onset of rainfall, as the dry and warmer atmosphere suddenly becomes moist. This feature points to the significance of the atmospheric cooling during the monsoon season and of the aerosol amounts in Spring. It also reveals that prior to the rainfall onset, the monsoon flow plays a major role on the diurnal cycle of the low-level temperature, due to its radiative properties. Conversely, the incoming solar radiation at the surface increases slightly from late Spring to the core monsoon season even though the atmosphere becomes moister and cloudier; this again involves the high aerosol optical thickness prevailing in late Spring and early Summer against a weaker shortwave forcing by monsoon clouds. The climatological combination of thermodynamic and radiative variations taking place during the monsoon eventually leads to a positive correlation between the equivalent potential temperature and Rnet. This correlation is, in turn, broadly consistent with an overall positive soil moisture rainfall feedback at this scale. Beyond these Sahelian-specific features, and in agreement with some previous studies, strong links are found between the atmospheric humidity and the net longwave flux, LWnet at the surface all year long, even across the much lower humidity ranges encountered in this region. They point to, and locally quantify the major control of water vapour and water-related processes on the surface-atmosphere thermal coupling as measured by LWnet. Namely, they are found to be more tightly coupled (LWnet closer to 0) when the atmosphere is moister and cloudier. Observational results such as presented here provide valuable ground truth for assessing models over a continental area displaying a challenging variety of surface-atmosphere regimes throughout the year, from a desert-like to a rainy tropical-like climate during the core of the monsoon. Indeed, the mechanisms emphasized by these data do not all comply to existing conceptual schemes.

The charged particle radiation environment on Mars measured by MSL/RAD from November 15, 2015 to January 15, 2016.

PubMed

Ehresmann, Bent; Zeitlin, Cary J; Hassler, Donald M; Matthiä, Daniel; Guo, Jingnan; Wimmer-Schweingruber, Robert F; Appel, Jan K; Brinza, David E; Rafkin, Scot C R; Böttcher, Stephan I; Burmeister, Sönke; Lohf, Henning; Martin, Cesar; Böhm, Eckart; Reitz, Günther

2017-08-01

The Radiation Assessment Detector (RAD) on board the Mars Science Laboratory (MSL) Curiosity rover has been measuring the radiation environment in Gale crater on Mars since August, 2012. These first in-situ measurements provide an important data set for assessing the radiation-associated health risks for future manned missions to Mars. Mainly, the radiation field on the Martian surface stems from Galactic Cosmic Rays (GCRs) and secondary particles created by the GCRs' interactions with the Martian atmosphere and soil. RAD is capable of measuring differential particle fluxes for lower-energy ions and isotopes of hydrogen and helium (up to hundreds of MeV/nuc). Additionally, RAD also measures integral particle fluxes for higher energies of these ions. Besides providing insight on the current Martian radiation environment, these fluxes also present an essential input for particle transport codes that are used to model the radiation to be encountered during future manned missions to Mars. Comparing simulation results with actual ground-truth measurements helps to validate these transport codes and identify potential areas of improvements in the underlying physics of these codes. At the First Mars Radiation Modeling Workshop (June 2016 in Boulder, CO), different groups of modelers were asked to calculate the Martian surface radiation environment for the time of November 15, 2015 to January 15, 2016. These model results can then be compared with in-situ measurements of MSL/RAD conducted during the same time frame. In this publication, we focus on presenting the charged particle fluxes measured by RAD between November 15, 2015 and January 15, 2016, providing the necessary data set for the comparison to model outputs from the modeling workshop. We also compare the fluxes to initial GCR intensities, as well as to RAD measurements from an earlier time period (August 2012 to January 2013). Furthermore, we describe how changes and updates in RAD on board processing and the on ground analysis tools effect and improve the flux calculations. An in-depth comparison of modeling results from the workshop and RAD fluxes of this publication is presented elsewhere in this issue (Matthiä et al., 2017). Copyright © 2017 The Committee on Space Research (COSPAR). All rights reserved.

The mechanism of the effect of a plasma layer with negative permittivity on the antenna radiation field

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

Wang, Chunsheng, E-mail: wangcs@hit.edu.cn; Liu, Hui; Jiang, Binhao

A model of a plasma–antenna system is developed to study the mechanism of the effect of the plasma layer on antenna radiation. Results show a plasma layer with negative permittivity is inductive, and thus affects the phase difference between electric and magnetic fields. In the near field of antenna radiation, a plasma layer with proper parameters can compensate the capacitivity of the vacuum and enhance the radiation power. In the far field of antenna radiation, the plasma layer with negative permittivity increases the inductivity of the vacuum and reduces the radiation power.

EFFECTS OF LASER RADIATION ON MATTER: Spectrum of the barium atom in a laser radiation field

NASA Astrophysics Data System (ADS)

Bondar', I. I.; Suran, V. V.

1990-08-01

An experimental investigation was made of the influence of a laser radiation field on the spectrum of barium atoms. The investigation was carried out by the method of three-photon ionization spectroscopy using dye laser radiation (ω = 14 800-18 700 cm - 1). The electric field intensity of the laser radiation was 103-106 V/cm. This laser radiation field had a strong influence on a number of bound and autoionizing states. The nature of this influence depended on the ratio of the excitation frequencies of bound and autoionizing states.

Coherent Lienard-Wiechert fields produced by free electron lasers

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

Elias, L.R.; Gallardo, J.C.

1981-12-01

Results are presented here of a three-dimensional numerical analysis of the radiation fields produced in a free electron laser. The method used here to obtain the spatial and temporal behavior of the radiated fields is based on the coherent superposition of the exact Lienard-Wiechert fields produced by each electron in the beam. Interference effects are responsible for the narrow angular radiation patterns obtained and for the high degree of monochromaticity of the radiated field.

Characteristic of the radiation field in low Earth orbit and in deep space.

PubMed

Reitz, Guenther

2008-01-01

The radiation exposure in space by cosmic radiation can be reduced through careful mission planning and constructive measures as example the provision of a radiation shelter, but it cannot be completely avoided. The reason for that are the extreme high energies of particles in this field and the herewith connected high penetration depth in matter. For missions outside the magnetosphere ionizing radiation is recognized as the key factor through its impact on crew health and performance. In absence of sporadic solar particle events the radiation exposure in Low Earth orbit (LEO) inside Spacecraft is determined by the galactic cosmic radiation (protons and heavier ions) and by the protons inside the South Atlantic Anomaly (SAA), an area where the radiation belt comes closer to the earth surface due to a displacement of the magnetic dipole axes from the Earth's center. In addition there is an albedo source of neutrons produced as interaction products of the primary galactic particles with the atoms of the earth atmosphere. Outside the spacecraft the dose is dominated by the electrons of the horns of the radiation belt located at about 60" latitude in Polar Regions. The radiation field has spatial and temporal variations in dependence of the Earth magnetic field and the solar cycle. The complexity of the radiation field inside a spacecraft is further increased through the interaction of the high energy components with the spacecraft shielding material and with the body of the astronauts. In interplanetary missions the radiation belt will be crossed in a couple of minutes and therefore its contribution to their radiation exposure is quite small, but subsequently the protection by the Earth magnetic field is lost, leaving only shielding measures as exposure reduction means. The report intends to describe the radiation field in space, the interaction of the particles with the magnetic field and shielding material and give some numbers on the radiation exposure in low earth orbits and in interplanetary missions.

Qualification of quantum cascade lasers for space environments

NASA Astrophysics Data System (ADS)

Myers, Tanya L.; Cannon, Bret D.; Brauer, Carolyn S.; Crowther, Blake G.; Hansen, Stewart

2014-06-01

Laser-based instruments are enabling a new generation of scientific instruments for space environments such as those used in the exploration of Mars. The lasers must be robust and able to withstand the harsh environment of space, including radiation exposure. Quantum cascade lasers (QCLs), which are semiconductor lasers that emit in the infrared spectral region, offer the potential for the development of novel laser-based instruments for space applications. The performance of QCLs after radiation exposure, however, has not been reported. We report on work to quantify the performance of QCLs after exposure to two different radiation sources, 64 MeV protons and Cobalt-60 gamma rays, at radiation levels likely to be encountered during a typical space flight mission. No significant degradation in threshold current or slope efficiency is observed for any of the seven Fabry-Perot QCLs that are tested.

Space shuttle rendezous, radiation and reentry analysis code

NASA Technical Reports Server (NTRS)

Mcglathery, D. M.

1973-01-01

A preliminary space shuttle mission design and analysis tool is reported emphasizing versatility, flexibility, and user interaction through the use of a relatively small computer (IBM-7044). The Space Shuttle Rendezvous, Radiation and Reentry Analysis Code is used to perform mission and space radiation environmental analyses for four typical space shuttle missions. Included also is a version of the proposed Apollo/Soyuz rendezvous and docking test mission. Tangential steering circle to circle low-thrust tug orbit raising and the effects of the trapped radiation environment on trajectory shaping due to solar electric power losses are also features of this mission analysis code. The computational results include a parametric study on single impulse versus double impulse deorbiting for relatively low space shuttle orbits as well as some definitive data on the magnetically trapped protons and electrons encountered on a particular mission.

Potential scattering in the presence of a static magnetic field and a radiation field of arbitrary polarization

NASA Astrophysics Data System (ADS)

Ferrante, G.; Zarcone, M.; Nuzzo, S.; McDowell, M. R. C.

1982-05-01

Expressions are obtained for the total cross sections for scattering of a charged particle by a potential in the presence of a static uniform magnetic field and a radiation field of arbitrary polarization. For a Coulomb field this is closely related to the time reverse of photoionization of a neutral atom in a magnetic field, including multiphoton effects off-resonance. The model is not applicable when the radiation energy approaches one of the quasi-Landau state separations. The effects of radiation field polarization are examined in detail.

Environmental Health concerns in natural and man-made environments

NASA Technical Reports Server (NTRS)

Bergtholdt, C. P.

1975-01-01

Industrial hygene and environmental health aspects of ground operation at the Jet Propulsion Laboratory were investigated. Major areas of concern are: (1) toxic substances, (2) noise pollution, (3) electromagnetic radiation; and (4) biohazards and sanitation. Each of these categories are also studied in a closed environment, such as encountered aboard of a spacecraft.

Environmental radiation and the lung

PubMed Central

Hamrick, Philip E.; Walsh, Phillip J.

1974-01-01

Environmental sources of radioactive materials and their relation to lung doses and lung burdens are described. The approaches used and the problems encountered in estimating lung doses are illustrated. Exposure to radon daughter products is contrasted to exposure to plutonium as particular examples of the hazards associated with radioactive materials of different chemical and physical characteristics. PMID:4620334

[Nonionizing radiation and electromagnetic fields].

PubMed

Bernhardt, J H

1991-01-01

Nonionising radiation comprises all kinds of radiation and fields of the electromagnetic spectrum where biological matter is not ionised, as well as mechanical waves such as infrasound and ultrasound. The electromagnetic spectrum is subdivided into individual sections and includes: Static and low-frequency electric and magnetic fields including technical applications of energy with mains frequency, radio frequency fields, microwaves and optic radiation (infrared, visible light, ultraviolet radiation including laser). The following categories of persons can be affected by emissions by non-ionising radiation: Persons in the environment and in the household, workers, patients undergoing medical diagnosis or treatment. If the radiation is sufficiently intense, or if the fields are of appropriate strength, a multitude of effects can occur (depending on the type of radiation), such as heat and stimulating or irritating action, inflammations of the skin or eyes, changes in the blood picture, burns or in some cases cancer as a late sequel. The ability of radiation to penetrate into the human body, as well as the types of interaction with biological tissue, with organs and organisms, differs significantly for the various kinds of nonionising radiation. The following aspects of nonionising radiation are discussed: protection of humans against excessive sunlight rays when sunbathing and when exposed to UV radiation (e.g. in solaria); health risks of radio and microwaves (safety of microwave cookers and mobile radio units); effects on human health by electric and magnetic fields in everyday life.

Gravitational scattering of electromagnetic radiation

NASA Technical Reports Server (NTRS)

Brooker, J. T.; Janis, A. I.

1980-01-01

The scattering of electromagnetic radiation by linearized gravitational fields is studied to second order in a perturbation expansion. The incoming electromagnetic radiation can be of arbitrary multipole structure, and the gravitational fields are also taken to be advanced fields of arbitrary multipole structure. All electromagnetic multipole radiation is found to be scattered by gravitational monopole and time-varying dipole fields. No case has been found, however, in which any electromagnetic multipole radiation is scattered by gravitational fields of quadrupole or higher-order multipole structure. This lack of scattering is established for infinite classes of special cases, and is conjectured to hold in general. The results of the scattering analysis are applied to the case of electromagnetic radiation scattered by a moving mass. It is shown how the mass and velocity may be determined by a knowledge of the incident and scattered radiation.

The Io Volcano Observer (IVO) for NASA Discovery 2015

NASA Astrophysics Data System (ADS)

McEwen, Alfred S.; Turtle, Elizabeth P.; Thomas, Nicolas

2015-04-01

IVO was first proposed as a NASA Discovery mission in 2010, powered by the Advanced Sterling Radioisotope Generators (ASRGs) to provide a compact spacecraft that points and settles quickly. The 2015 IVO uses advanced lightweight solar arrays and a 1-dimensional pivot to achieve similar observing flexibility during a set of fast (~18 km/s) flybys of Io. The John Hopkins University Applied Physics Lab (APL) leads mission implementation, with heritage from MESSENGER, New Horizons, and the Van Allen Probes. All science objectives from the Io Observer New Frontiers concept recommended in the 2011 Decadal Survey are addressed by IVO. There are 5 instruments plus gravity science: Narrow- and wide-angle cameras (NAC and WAC), Dual fluxgate magnetometers (DMAG), a thermal mapper (TMAP, from DLR), and particle environment package for Io (PEPI) consisting of an ion and neutral mass spectrometer (INMS, from UBE) and a plasma ion analyzer (PIA, from IRF). A student collaboration hotspot mapper (HOTMAP) is an option. The NAC and TMAP are on a ± 90° pivot for off-nadir targeting during encounters and for distant monitoring. The DMAG sensors are on the end and middle of 3.8-m boom and collect data continuously. WAC and HOTMAP are mounted on the S/C nadir deck, and observe during ±20 minutes of each Io closest approach, except orbits I0 and I2. PEPI is mounted on the S/C structure with the INMS field of view in the ram direction when the S/C nadir deck points at Io, and the PIA and has a large (hemispheric) field of view that will often include the upstream direction. Gravity science requires pointing the high-gain antenna at Earth during the I0 and I2 encounters. IVO launches in 2021 and arrives at Jupiter in early 2026. A close Io flyby (I0) ~1.5 hrs. after Jupiter orbit insertion lowers the orbit period, followed by 8 additional encounters achieving the suite of science objectives. The highly elliptical orbit with perijove near Io is inclined >40° to Jupiter's orbital plane, which minimizes total ionizing radiation dose compared to other Jupiter orbiters (<10% that of JUICE). The apoapse period of each orbit provides extended monitoring of Io and Europa at high phase angles (>120°), best to detect and monitor volcanic plumes as well as high-temperature hot spots on Io. Four of the encounters are designed for optimal measurement of induced magnetic signature from mantle melt. IVO will collect at least 20 Gb of science data per encounter: 100 times the Io data from the 8-year Galileo tour. Encounters last ~1 week, including global monitoring and four Io eclipses, with distant monitoring and data playback near apojove. I8 includes a flythrough of Pele's plume, if it is active, for gas composition. IVO team: F. Bagenal, S. Bailey, S. Barabash, J. Boldt, D. Breuer, A. Davies, I. de Pater, K.-H. Glassmeier, C. Hamilton, J. Helbert, R. Heyd, D. Heyner, K. Hibbard, S. Hörst, D. Humm, L. Iess, X. Jia, L. Kestay, K. Khurana, R. Kirk, R. Lorenz, J. Moses, O. Mousis, F. Nimmo, S. Osterman, C. Paranicas, C. Parker, J. Perry, E. Reynolds, A. Showman, B. Spence, J. Spencer, T. Spohn, S. Sutton, N. Thomas, M. Wieser, P. Wurz.

Deficiencies of active electronic radiation protection dosimeters in pulsed fields.

PubMed

Ankerhold, U; Hupe, O; Ambrosi, P

2009-07-01

Nowadays nearly all radiation fields used for X-ray diagnostics are pulsed. These fields are characterised by a high dose rate during the pulse and a short pulse duration in the range of a few milliseconds. The use of active electronic dosimeters has increased in the past few years, but these types of dosimeters might possibly not measure reliably in pulsed radiation fields. Not only personal dosimeters but also area dosimeters that are used mainly for dose rate measurements are concerned. These cannot be substituted by using passive dosimeter types. The characteristics of active electronic dosimeters determined in a continuous radiation field cannot be transferred to those in pulsed fields. Some provisional measurements with typical electronic dosimeters in pulsed radiation fields are presented to reveal this basic problem.

Graphene Field Effect Transistor for Radiation Detection

NASA Technical Reports Server (NTRS)

Li, Mary J. (Inventor); Chen, Zhihong (Inventor)

2016-01-01

The present invention relates to a graphene field effect transistor-based radiation sensor for use in a variety of radiation detection applications, including manned spaceflight missions. The sensing mechanism of the radiation sensor is based on the high sensitivity of graphene in the local change of electric field that can result from the interaction of ionizing radiation with a gated undoped silicon absorber serving as the supporting substrate in the graphene field effect transistor. The radiation sensor has low power and high sensitivity, a flexible structure, and a wide temperature range, and can be used in a variety of applications, particularly in space missions for human exploration.

Fundamental mechanisms in premixed flame propagation via vortex-flame interactions: Numerical simulations

NASA Technical Reports Server (NTRS)

Mantel, Thierry

1994-01-01

The goal of the present study is to assess numerically the ability of single-step and two-step chemical models to describe the main features encountered during the interaction between a two-dimensional vortex pair and a premixed laminar flame. In the two-step mechanism, the reaction kinetics are represented by a first chain branching reaction A + X yields 2X and a second chain termination reaction X + X yields P. This paper presents the fundamental mechanisms occurring during vortex-flame interactions and the relative impact of the major parameters encountered in turbulent premixed flames and suspected of playing a role in quenching mechanism: (1) Influence of stretch is investigated by analyzing the contribution of curvature and tangential strain on the local structure of the flame. The effect of Lewis number on the flame response to a strained field is analyzed. (2) Radiative heat losses which are suspected to be partially or totally responsible for quenching are also investigated. (3) The effect of the diffusion of the radicals is studied using a two-step mechanism in which an intermediate species is present. The parameters of the two-step mechanism are entirely determined from physical arguments. (4) Precise quantitative comparisons between the DNS and the experimental results of Samaniego et al are performed. These comparisons concern the evolution of the minimum heat release rate found along the flame front during the interaction and the distribution of the heat release rate along the flame front.

FIRE - Flyby of Io with Repeat Encounters: A conceptual design for a New Frontiers mission to Io

NASA Astrophysics Data System (ADS)

Suer, Terry-Ann; Padovan, Sebastiano; Whitten, Jennifer L.; Potter, Ross W. K.; Shkolyar, Svetlana; Cable, Morgan; Walker, Catherine; Szalay, Jamey; Parker, Charles; Cumbers, John; Gentry, Diana; Harrison, Tanya; Naidu, Shantanu; Trammell, Harold J.; Reimuller, Jason; Budney, Charles J.; Lowes, Leslie L.

2017-09-01

A conceptual design is presented for a low complexity, heritage-based flyby mission to Io, Jupiter's innermost Galilean satellite and the most volcanically active body in the Solar System. The design addresses the 2011 Decadal Survey's recommendation for a New Frontiers class mission to Io and is based upon the result of the June 2012 NASA-JPL Planetary Science Summer School. A science payload is proposed to investigate the link between the structure of Io's interior, its volcanic activity, its surface composition, and its tectonics. A study of Io's atmospheric processes and Io's role in the Jovian magnetosphere is also planned. The instrument suite includes a visible/near-IR imager, a magnetic field and plasma suite, a dust analyzer, and a gimbaled high gain antenna to perform radio science. Payload activity and spacecraft operations would be powered by three Advanced Stirling Radioisotope Generators (ASRG). The primary mission includes 10 flybys with close-encounter altitudes as low as 100 km. The mission risks are mitigated by ensuring that relevant components are radiation tolerant and by using redundancy and flight-proven parts in the design. The spacecraft would be launched on an Atlas V rocket with a delta-v of 1.3 km/s. Three gravity assists (Venus, Earth, Earth) would be used to reach the Jupiter system in a 6-year cruise. The resulting concept demonstrates the rich scientific return of a flyby mission to Io.

The Goshawk - Robert Kenward [Book Review

Treesearch

John R. Squires

2008-01-01

Your first encounter with goshawks (Accipter gentilis) often leaves an impression that lasts a lifetime, especially if it involves being attacked by an angry female as you approach too close to her nest. I still clearly remember my first encounter when, as a 7th grader, I was invited to the field by two falconers who were hunting a brace of goshawks...

Watercraft user characteristics, management preferences, and user encounters on the upper Delaware scenic and recreational river: 1979-1996

Treesearch

Stephen M. Bowes; Chad P. Dawson

1998-01-01

Recreational boaters on the National Park Service managed Upper Delaware Scenic and Recreational River were surveyed about their characteristics, management preferences, and user encounters. Field interviews were conducted from Memorial Day weekend through Labor Day weekend during the summer of 1996. A total of 650 boaters were contacted at public and commercial access...

The sources of inspiration in research on position-sensitive detectors

NASA Astrophysics Data System (ADS)

Charpak, G.

1988-12-01

The high-energy experimental physicist is constantly confronted with the problem of identifying and localizing particles, charged or neutral. The community of high-energy physicists has thus produced a variety of original methods which have found, or are beginning to find, applications in many fields that are remote from this discipline. New hadron accelerators which are foreseen for the year 2000 raise formidable problems. To take an extreme case, beams crossing at 5 ns intervals are being considered, with several interactions per crossing and with collision multiplicities close to 100. Should a high-energy experimental physicist who is interested in research on particle detectors, limit his horizon to these questions? Even if most of his effort is legitimately concentrated on solving the specific problems encountered with the projected accelerators, it would be a mistake for him to limit his activity to reaching only this goal. In many fields there is considerable demand for improvement in the methods of radiation imaging. I will list some of them, and illustrate my point — which is that contributing of this field is both fruitful and cross-fertilizing — with examples from the activity of our own group at CERN. I apologize for not doing justice to the many other efforts made in the same direction by other groups or laboratories, but the proceedings of this conference will already be illuminating in this respect.

Beauty is distractive: particle production during multifield inflation

NASA Astrophysics Data System (ADS)

Battefeld, Diana; Battefeld, Thorsten; Byrnes, Christian; Langlois, David

2011-08-01

We consider a two-dimensional model of inflation, where the inflationary trajectory is ``deformed'' by a grazing encounter with an Extra Species/Symmetry Point (ESP) after the observable cosmological scales have left the Hubble radius. The encounter entails a sudden production of particles, whose backreaction causes a bending of the trajectory and a temporary decrease in speed, both of which are sensitive to initial conditions. This ``modulated'' effect leads to an additional contribution to the curvature perturbation, which can be dominant if the encounter is close. We compute associated non-Gaussianities, the bispectrum and its scale dependence as well as the trispectrum, which are potentially detectable in many cases. In addition, we consider a direct modulation of the coupling to the light field at the ESP via a modulaton field, a mixed scenario whereby the modulaton is identified with a second inflaton, and an extended Extra Species Locus (ESL); all of these scenarios lead to similar additional contributions to observables. We conclude that inflaton interactions throughout inflation are strongly constrained if primordial non-Gaussianities remain unobserved in current experiments such as PLANCK. If they are observed, an ESP encounter leaves additional signatures on smaller scales which may be used to identify the model.

Method and apparatus for shadow aperture backscatter radiography (SABR) system and protocol

NASA Technical Reports Server (NTRS)

Shedlock, Daniel (Inventor); Jacobs, Alan M. (Inventor); Jacobs, Sharon Auerback (Inventor); Dugan, Edward (Inventor)

2010-01-01

A shadow aperture backscatter radiography (SABR) system includes at least one penetrating radiation source for providing a penetrating radiation field, and at least one partially transmissive radiation detector, wherein the partially transmissive radiation detector is interposed between an object region to be interrogated and the radiation source. The partially transmissive radiation detector transmits a portion of the illumination radiation field. A shadow aperture having a plurality of radiation attenuating regions having apertures therebetween is disposed between the radiation source and the detector. The apertures provide illumination regions for the illumination radiation field to reach the object region, wherein backscattered radiation from the object is detected and generates an image by the detector in regions of the detector that are shadowed by the radiation attenuation regions.

Deconvolution and analysis of wide-angle longwave radiation data from Nimbus 6 Earth radiation budget experiment for the first year

NASA Technical Reports Server (NTRS)

Bess, T. D.; Green, R. N.; Smith, G. L.

1980-01-01

One year of longwave radiation data from July 1975 through June 1976 from the Nimbus 6 satellite Earth radiation budget experiment is analyzed by representing the radiation field by a spherical harmonic expansion. The data are from the wide field of view instrument. Contour maps of the longwave radiation field and spherical harmonic coefficients to degree 12 and order 12 are presented for a 12 month data period.

Study of the dose rate effect of 180 nm nMOSFETs

NASA Astrophysics Data System (ADS)

He, Bao-Ping; Yao, Zhi-Bin; Sheng, Jiang-Kun; Wang, Zu-Jun; Huang, Shao-Yan; Liu, Min-Bo; Xiao, Zhi-Gang

2015-01-01

Radiation induced offstate leakage in the shallow trench isolation regions of SIMC 0.18 μm nMOSFETs is studied as a function of dose rate. A “true” dose rate effect (TDRE) is observed. Increased damage is observed at low dose rate (LDR) than at high dose rate (HDR) when annealing is taken into account. A new method of simulating radiation induced degradation in shallow trench isolation (STI) is presented. A comparison of radiation induced offstate leakage current in test nMOSFETs between total dose irradiation experiments and simulation results exhibits excellent agreement. The investigation results imply that the enhancement of the leakage current may be worse for the dose rate encountered in the environment of space.

Electric-field distribution near rectangular microstrip radiators for hyperthermia heating: theory versus experiment in water.

PubMed

Underwood, H R; Peterson, A F; Magin, R L

1992-02-01

A rectangular microstrip antenna radiator is investigated for its near-zone radiation characteristics in water. Calculations of a cavity model theory are compared with the electric-field measurements of a miniature nonperturbing diode-dipole E-field probe whose 3 mm tip was positioned by an automatic three-axis scanning system. These comparisons have implications for the use of microstrip antennas in a multielement microwave hyperthermia applicator. Half-wavelength rectangular microstrip patches were designed to radiate in water at 915 MHz. Both low (epsilon r = 10) and high (epsilon r = 85) dielectric constant substrates were tested. Normal and tangential components of the near-zone radiated electric field were discriminated by appropriate orientation of the E-field probe. Low normal to transverse electric-field ratios at 3.0 cm depth indicate that the radiators may be useful for hyperthermia heating with an intervening water bolus. Electric-field pattern addition from a three-element linear array of these elements in water indicates that phase and amplitude adjustment can achieve some limited control over the distribution of radiated power.

Enhancing radiative energy transfer through thermal extraction

NASA Astrophysics Data System (ADS)

Tan, Yixuan; Liu, Baoan; Shen, Sheng; Yu, Zongfu

2016-06-01

Thermal radiation plays an increasingly important role in many emerging energy technologies, such as thermophotovoltaics, passive radiative cooling and wearable cooling clothes [1]. One of the fundamental constraints in thermal radiation is the Stefan-Boltzmann law, which limits the maximum power of far-field radiation to P0 = σT4S, where σ is the Boltzmann constant, S and T are the area and the temperature of the emitter, respectively (Fig. 1a). In order to overcome this limit, it has been shown that near-field radiations could have an energy density that is orders of magnitude greater than the Stefan-Boltzmann law [2-7]. Unfortunately, such near-field radiation transfer is spatially confined and cannot carry radiative heat to the far field. Recently, a new concept of thermal extraction was proposed [8] to enhance far-field thermal emission, which, conceptually, operates on a principle similar to oil immersion lenses and light extraction in light-emitting diodes using solid immersion lens to increase light output [62].Thermal extraction allows a blackbody to radiate more energy to the far field than the apparent limit of the Stefan-Boltzmann law without breaking the second law of thermodynamics. Thermal extraction works by using a specially designed thermal extractor to convert and guide the near-field energy to the far field, as shown in Fig. 1b. The same blackbody as shown in Fig. 1a is placed closely below the thermal extractor with a spacing smaller than the thermal wavelength. The near-field coupling transfers radiative energy with a density greater than σT4. The thermal extractor, made from transparent and high-index or structured materials, does not emit or absorb any radiation. It transforms the near-field energy and sends it toward the far field. As a result, the total amount of far-field radiative heat dissipated by the same blackbody is greatly enhanced above SσT4, where S is the area of the emitter. This paper will review the progress in thermal extraction. It is organized as follows. In Section 1, we will discuss the theory of thermal extraction [8]. In Section 2, we review an experimental implementation based on natural materials as the thermal extractor [8]. Lastly, in Section 3, we review the experiment that uses structured metamaterials as thermal extractors to enhance optical density of states and far-field emission [9].

A Coupled Ocean General Circulation, Biogeochemical, and Radiative Model of the Global Oceans: Seasonal Distributions of Ocean Chlorophyll and Nutrients

NASA Technical Reports Server (NTRS)

Gregg, Watson W.; Busalacchi, Antonio (Technical Monitor)

2000-01-01

A coupled ocean general circulation, biogeochemical, and radiative model was constructed to evaluate and understand the nature of seasonal variability of chlorophyll and nutrients in the global oceans. Biogeochemical processes in the model are determined from the influences of circulation and turbulence dynamics, irradiance availability. and the interactions among three functional phytoplankton groups (diatoms. chlorophytes, and picoplankton) and three nutrients (nitrate, ammonium, and silicate). Basin scale (greater than 1000 km) model chlorophyll results are in overall agreement with CZCS pigments in many global regions. Seasonal variability observed in the CZCS is also represented in the model. Synoptic scale (100-1000 km) comparisons of imagery are generally in conformance although occasional departures are apparent. Model nitrate distributions agree with in situ data, including seasonal dynamics, except for the equatorial Atlantic. The overall agreement of the model with satellite and in situ data sources indicates that the model dynamics offer a reasonably realistic simulation of phytoplankton and nutrient dynamics on synoptic scales. This is especially true given that initial conditions are homogenous chlorophyll fields. The success of the model in producing a reasonable representation of chlorophyll and nutrient distributions and seasonal variability in the global oceans is attributed to the application of a generalized, processes-driven approach as opposed to regional parameterization and the existence of multiple phytoplankton groups with different physiological and physical properties. These factors enable the model to simultaneously represent many aspects of the great diversity of physical, biological, chemical, and radiative environments encountered in the global oceans.

Method and means for measuring the anisotropy of a plasma in a magnetic field

DOEpatents

Shohet, J.L.; Greene, D.G.S.

1973-10-23

Anisotropy is measured of a free-free-bremsstrahlungradiation-generating plasma in a magnetic field by collimating the free-free bremsstrahlung radiation in a direction normal to the magnetic field and scattering the collimated free- free bremsstrahlung radiation to resolve the radiation into its vector components in a plane parallel to the electric field of the bremsstrahlung radiation. The scattered vector components are counted at particular energy levels in a direction parallel to the magnetic field and also normal to the magnetic field of the plasma to provide a measure of anisotropy of the plasma. (Official Gazette)

The non-radiating component of the field generated by a finite monochromatic scalar source distribution

NASA Astrophysics Data System (ADS)

Hoenders, Bernhard J.; Ferwerda, Hedzer A.

1998-09-01

We separate the field generated by a spherically symmetric bounded scalar monochromatic source into a radiative and non-radiative part. The non-radiative part is obtained by projecting the total field on the space spanned by the non-radiating inhomogeneous modes, i.e. the modes which satisfy the inhomogeneous wave equation. Using residue techniques, introduced by Cauchy, we obtain an explicit analytical expression for the non-radiating component. We also identify the part of the source distribution which corresponds to this non-radiating part. The analysis is based on the scalar wave equation.

Automatic Suppression of Intense Monochromatic Light in Electro-Optical Sensors

PubMed Central

Ritt, Gunnar; Eberle, Bernd

2012-01-01

Electro-optical imaging sensors are widely distributed and used for many different tasks. Due to technical improvements, their pixel size has been steadily decreasing, resulting in a reduced saturation capacity. As a consequence, this progress makes them susceptible to intense point light sources. Developments in laser technology have led to very compact and powerful laser sources of any wavelength in the visible and near infrared spectral region, offered as laser pointers. The manifold of wavelengths makes it difficult to encounter sensor saturation over the complete operating waveband by conventional measures like absorption or interference filters. We present a concept for electro-optical sensors to suppress overexposure in the visible spectral region. The key element of the concept is a spatial light modulator in combination with wavelength multiplexing. This approach allows spectral filtering within a localized area in the field of view of the sensor. The system offers the possibility of automatic reduction of overexposure by monochromatic laser radiation. PMID:23202039

Quantum information erasure inside black holes

DOE PAGES

Lowe, David A.; Thorlacius, Larus

2015-12-15

An effective field theory for infalling observers in the vicinity of a quasi-static black hole is given in terms of a freely falling lattice discretization. The lattice model successfully reproduces the thermal spectrum of outgoing Hawking radiation, as was shown by Corley and Jacobson, but can also be used to model observations made by a typical low-energy observer who enters the black hole in free fall at a prescribed time. The explicit short distance cutoff ensures that, from the viewpoint of the infalling observer, any quantum information that entered the black hole more than a scrambling time earlier has beenmore » erased by the black hole singularity. Furthermore, this property, combined with the requirement that outside observers need at least of order the scrambling time to extract quantum information from the black hole, ensures that a typical infalling observer does not encounter drama upon crossing the black hole horizon in a theory where black hole information is preserved for asymptotic observers.« less

Black-Hole Binaries, Gravitational Waves, and Numerical Relativity

NASA Technical Reports Server (NTRS)

Kelly, Bernard J.; Centrella, Joan; Baker, John G.; Kelly, Bernard J.; vanMeter, James R.

2010-01-01

Understanding the predictions of general relativity for the dynamical interactions of two black holes has been a long-standing unsolved problem in theoretical physics. Black-hole mergers are monumental astrophysical events ' releasing tremendous amounts of energy in the form of gravitational radiation ' and are key sources for both ground- and spacebased gravitational wave detectors. The black-hole merger dynamics and the resulting gravitational waveforms can only he calculated through numerical simulations of Einstein's equations of general relativity. For many years, numerical relativists attempting to model these mergers encountered a host of problems, causing their codes to crash after just a fraction of a binary orbit cnuld be simulated. Recently ' however, a series of dramatic advances in numerical relativity has ' for the first time, allowed stable / robust black hole merger simulations. We chronicle this remarkable progress in the rapidly maturing field of numerical relativity, and the new understanding of black-hole binary dynamics that is emerging. We also discuss important applications of these fundamental physics results to astrophysics, to gravitationalwave astronomy, and in other areas.

Revised prediction of LDEF exposure to trapped protons

NASA Technical Reports Server (NTRS)

Watts, John W.; Armstrong, T. W.; Colborn, B. L.

1993-01-01

The Long Duration Exposure Facility (LDEF) spacecraft flew in a 28.5 deg inclination circular orbit with an altitude in the range from 319.4 to 478.7 km. For this orbital altitude and inclination, two components contribute most of the penetrating charge particle radiation encountered - the galactic cosmic rays and the geomagnetically trapped Van Allen protons. Where shielding is less than 1.0 g/sq cm geomagnetically trapped electrons make a significant contribution. The 'Vette' models together with the associated magnetic field models and the solar conditions were used to obtain the trapped electron and proton omnidirectional fluences reported previously. Results for directional proton spectra using the MSFC anisotropy model for solar minimum and 463 km altitude (representative for the LDEF mission) were also reported. The directional trapped proton flux as a function of mission time is presented considering altitude and solar activity variation during the mission. These additional results represent an extension of previous calculations to provide a more definitive description of the LDEF trapped proton exposure.

Dark solitons in laser radiation build-up dynamics.

PubMed

Woodward, R I; Kelleher, E J R

2016-03-01

We reveal the existence of slowly decaying dark solitons in the radiation build-up dynamics of bright pulses in all-normal dispersion mode-locked fiber lasers, numerically modeled in the framework of a generalized nonlinear Schrödinger equation. The evolution of noise perturbations to quasistationary dark solitons is examined, and the significance of background shape and soliton-soliton collisions on the eventual soliton decay is established. We demonstrate the role of a restoring force in extending soliton interactions in conservative systems to include the effects of dissipation, as encountered in laser cavities, and generalize our observations to other nonlinear systems.

Hydrogen-Helium shock Radiation tests for Saturn Entry Probes

NASA Technical Reports Server (NTRS)

Cruden, Brett A.

2016-01-01

This paper describes the measurement of shock layer radiation in Hydrogen/Helium mixtures representative of that encountered by probes entering the Saturn atmosphere. Normal shock waves are measured in Hydrogen-Helium mixtures (89:11% by volume) at freestream pressures between 13-66 Pa (0.1-0.5 Torr) and velocities from 20-30 km/s. Radiance is quantified from the Vacuum Ultraviolet through Near Infrared. An induction time of several centimeters is observed where electron density and radiance remain well below equilibrium. Radiance is observed in front of the shock layer, the characteristics of which match the expected diffusion length of Hydrogen.

Magnetosphere-Regolith/Exosphere Coupling: Differences and Similarities to the Earth Magnetosphere-Ionosphere Coupling

NASA Technical Reports Server (NTRS)

Gjerleov, J. W.; Slavin, J. A.

2001-01-01

Of the three Mercury passes made by Mariner 10, the first and third went through the Mercury magnetosphere. The third encounter which occurred during northward IMF (interplanetary magnetic field) showed quiet time magnetic fields. In contrast the third encounter observed clear substorm signatures including dipolarization, field-aligned currents (FACs) and injection of energetic electrons at geosynchronous orbit. However, the determined cross-tail potential drop and the assumed height integrated conductance indicate that the FAC should be 2-50 times weaker than observed. We address this inconsistency and the fundamental problem of FAC closure whether this takes place in the regolith or in the exosphere. The current state of knowledge of the magnetosphere-exosphere/regolith coupling is addressed and similarities and differences to the Earth magnetosphere-ionosphere coupling are discussed.

Plasma-tail activity and the interplanetary medium at Halley's Comet during Armada Week: 6-14 March 1986

NASA Technical Reports Server (NTRS)

Niedner, Malcolm B., Jr.; Schwingenschuh, Konrad; Hoeksema, J. Todd; Dryer, Murray; Mcintosh, Patrick S.

1987-01-01

The encounters of five spacecraft with Halley's Comet during 6-14 March 1986 offered a unique opportunity to calibrate the solar-wind interaction with cometary plasmas as recorded by remote wide-field and narrow-field/narrowband imaging. Perhaps not generally recognized in the comet community is the additional opportunity offered by the Halley Armada to study the structure of the solar-wind and interplanetary magnetic field (IMF) in three dimensions using five sets of data obtained over similar time intervals and heliocentric distances, but at somewhat different heliolatitudes. In fact, the two problems, i.e., comet physics and the structure of the interplanetary medium, are coupled if one wants to understand what conditions pertained at the comet between the encounters. This relationship is discussed.

Pioneer 10 and 11 (Jupiter and Saturn) magnetic field experiments

NASA Technical Reports Server (NTRS)

Jones, D. E.

1986-01-01

Magnet field data obtained by the vector helium magnetometer (VHM) during the encounters of Jupiter (Pioneer 10 and 11) and Saturn (Pioneer 11) was analyzed and interpreted. The puzzling characteristics of the Jovian and Saturnian magnetospheric magnetic fields were studied. An apparent substorm (including thinning of the dayside tail current sheet) was observed at Jupiter, as well as evidence suggesting that at the magnetopause the cusp is at an abnormally low latitude. The characteristics of Saturn's ring current as observed by Pioneer 11 were dramatically different from those suggested by the Voyager observations. Most importantly, very strong perturbations in the azimuthal ring current magnetic field suggest that the plane of the ring was not in the dipole equatorial plane, being tilted 5 to 10 deg. relative to the dipole and undergoing significant changes during the encounter. When these changing currents were corrected for, an improved planetary field determination was obtained. In addition, the ring and azimuthal currents at Saturn displayed significantly different time dependences.

Gamma irradiation of Fabry–Perot interband cascade lasers

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

Myers, Tanya L.; Cannon, Bret D.; Brauer, Carolyn S.

Two Fabry-Perot interband cascade lasers (ICLs) were exposed to Cobalt-60 gamma rays for a dosage of 500 krad(Si) each, which is higher than is typically encountered in space applications. The ICLs do not show any significant changes in threshold current or slope efficiency, suggesting the suitability of ICLs for use in radiation environments.

Qualification of quantum cascade lasers for space environments

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

Myers, Tanya L.; Cannon, Bret D.; Brauer, Carolyn S.

2014-06-11

Laser-based instruments are enabling a new generation of scientific instruments for space environments such as those used in the exploration of Mars. The lasers must be robust and able to withstand the harsh environment of space, including radiation exposure. Quantum cascade lasers (QCLs), which are semiconductor lasers that emit in the infrared spectral region, offer the potential for the development of novel laser-based instruments for space applications. The performance of QCLs after radiation exposure, however, has not been reported. We report on work to quantify the performance of QCLs after exposure to two different radiation sources, 64 MeV protons andmore » Cobalt-60 gamma rays, at radiation levels likely to be encountered during a typical space flight mission. No significant degradation in threshold current or slope efficiency is observed for any of the seven Fabry-Perot QCLs that are tested.« less

Orbital measurements of the Earth's radiation budget during the first decade of the space program

NASA Technical Reports Server (NTRS)

Bandeen, W. R.

1982-01-01

The instrumentation and data analysis methods applied to data from the Explorer 7, TIROS 2, 3, 4, and 7, and Nimbus 2 and 3 experimental satellites are summarized. Problems encountered in analyzing these data included: determining the value of the solar constant, inaccuracies introduced by degradation of the sensors in orbit, the need to infer the total reflected and emitted radiation from filtered measurements, the development of corrections for anisotropy in order to determine the outgoing flux densities at the moment of measurement, and the development of corrections to account for diurnal variability. The corrections for long- and shortwave anisotropy and historical determinations of the solar constant and albedo are treated in detail. These early measurements indicated that the planetary albedo was lower, the emitted radiation higher, and the equator-to-pole gradient of net radiation greater than previously supposed.

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

Zainudin, Mohd Lutfi, E-mail: mdlutfi07@gmail.com; Institut Matematik Kejuruteraan; Saaban, Azizan, E-mail: azizan.s@uum.edu.my

The solar radiation values have been composed by automatic weather station using the device that namely pyranometer. The device is functions to records all the radiation values that have been dispersed, and these data are very useful for it experimental works and solar device’s development. In addition, for modeling and designing on solar radiation system application is needed for complete data observation. Unfortunately, lack for obtained the complete solar radiation data frequently occur due to several technical problems, which mainly contributed by monitoring device. Into encountering this matter, estimation missing values in an effort to substitute absent values with imputedmore » data. This paper aimed to evaluate several piecewise interpolation techniques likes linear, splines, cubic, and nearest neighbor into dealing missing values in hourly solar radiation data. Then, proposed an extendable work into investigating the potential used of cubic Bezier technique and cubic Said-ball method as estimator tools. As result, methods for cubic Bezier and Said-ball perform the best compare to another piecewise imputation technique.« less

Delayed effects of proton irradiation in Macaca Mulatta (22-year summary)

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

Woods, D.H.; Hardy, K.A.; Cox, A.B.

1989-05-15

Lifetime observations on a group of rhesus monkeys indicate that life expectancy loss from exposure to protons in the energy range encountered in the Van Allen belts and solar proton events can be correlated with the dose and energy of radiation. The primary cause of life shortening is nonleukemic cancers. Radiation also increased the rise of endometriosis (an abnormal proliferation of the lining of the uterus in females). Other effects associated with radiation exposures are lowered glucose tolerance and increased incidence of cataracts. Calculations of the relative risk of fatal cancers in the irradiated subjects reveal that the total bodymore » surface dose required to double the risk of death from cancer over a 20-year post exposure period varies with the linear energy transfer (LET) of the radiation. The ability to determine the integrated dose and LET spectrum in space radiation exposures of humans is, therefore, critical to the assessment of lifetime cancer risk.« less

Treatment planning systems for external whole brain radiation therapy: With and without MLC (multi leaf collimator) optimization

NASA Astrophysics Data System (ADS)

Budiyono, T.; Budi, W. S.; Hidayanto, E.

2016-03-01

Radiation therapy for brain malignancy is done by giving a dose of radiation to a whole volume of the brain (WBRT) followed by a booster at the primary tumor with more advanced techniques. Two external radiation fields given from the right and left side. Because the shape of the head, there will be an unavoidable hotspot radiation dose of greater than 107%. This study aims to optimize planning of radiation therapy using field in field multi-leaf collimator technique. A study of 15 WBRT samples with CT slices is done by adding some segments of radiation in each field of radiation and delivering appropriate dose weighting using a TPS precise plan Elekta R 2.15. Results showed that this optimization a more homogeneous radiation on CTV target volume, lower dose in healthy tissue, and reduced hotspots in CTV target volume. Comparison results of field in field multi segmented MLC technique with standard conventional technique for WBRT are: higher average minimum dose (77.25% ± 0:47%) vs (60% ± 3:35%); lower average maximum dose (110.27% ± 0.26%) vs (114.53% ± 1.56%); lower hotspot volume (5.71% vs 27.43%); and lower dose on eye lenses (right eye: 9.52% vs 18.20%); (left eye: 8.60% vs 16.53%).

Radiation Hormesis: Historical Perspective and Implications for Low-Dose Cancer Risk Assessment

PubMed Central

Vaiserman, Alexander M.

2010-01-01

Current guidelines for limiting exposure of humans to ionizing radiation are based on the linear-no-threshold (LNT) hypothesis for radiation carcinogenesis under which cancer risk increases linearly as the radiation dose increases. With the LNT model even a very small dose could cause cancer and the model is used in establishing guidelines for limiting radiation exposure of humans. A slope change at low doses and dose rates is implemented using an empirical dose and dose rate effectiveness factor (DDREF). This imposes usually unacknowledged nonlinearity but not a threshold in the dose-response curve for cancer induction. In contrast, with the hormetic model, low doses of radiation reduce the cancer incidence while it is elevated after high doses. Based on a review of epidemiological and other data for exposure to low radiation doses and dose rates, it was found that the LNT model fails badly. Cancer risk after ordinarily encountered radiation exposure (medical X-rays, natural background radiation, etc.) is much lower than projections based on the LNT model and is often less than the risk for spontaneous cancer (a hormetic response). Understanding the mechanistic basis for hormetic responses will provide new insights about both risks and benefits from low-dose radiation exposure. PMID:20585444

Hawking radiation of five-dimensional charged black holes with scalar fields

NASA Astrophysics Data System (ADS)

Miao, Yan-Gang; Xu, Zhen-Ming

2017-09-01

We investigate the Hawking radiation cascade from the five-dimensional charged black hole with a scalar field coupled to higher-order Euler densities in a conformally invariant manner. We give the semi-analytic calculation of greybody factors for the Hawking radiation. Our analysis shows that the Hawking radiation cascade from this five-dimensional black hole is extremely sparse. The charge enhances the sparsity of the Hawking radiation, while the conformally coupled scalar field reduces this sparsity.

Non-thermal continuous and modulated electromagnetic radiation fields effects on sleep EEG of rats☆

PubMed Central

Mohammed, Haitham S.; Fahmy, Heba M.; Radwan, Nasr M.; Elsayed, Anwar A.

2012-01-01

In the present study, the alteration in the sleep EEG in rats due to chronic exposure to low-level non-thermal electromagnetic radiation was investigated. Two types of radiation fields were used; 900 MHz unmodulated wave and 900 MHz modulated at 8 and 16 Hz waves. Animals has exposed to radiation fields for 1 month (1 h/day). EEG power spectral analyses of exposed and control animals during slow wave sleep (SWS) and rapid eye movement sleep (REM sleep) revealed that the REM sleep is more susceptible to modulated radiofrequency radiation fields (RFR) than the SWS. The latency of REM sleep increased due to radiation exposure indicating a change in the ultradian rhythm of normal sleep cycles. The cumulative and irreversible effect of radiation exposure was proposed and the interaction of the extremely low frequency radiation with the similar EEG frequencies was suggested. PMID:25685416

47 CFR 2.1053 - Measurements required: Field strength of spurious radiation.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 1 2011-10-01 2011-10-01 false Measurements required: Field strength of spurious radiation. 2.1053 Section 2.1053 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL... Procedures Certification § 2.1053 Measurements required: Field strength of spurious radiation. (a...

47 CFR 2.1053 - Measurements required: Field strength of spurious radiation.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 1 2014-10-01 2014-10-01 false Measurements required: Field strength of spurious radiation. 2.1053 Section 2.1053 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL... Procedures Certification § 2.1053 Measurements required: Field strength of spurious radiation. (a...

47 CFR 2.1053 - Measurements required: Field strength of spurious radiation.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 1 2013-10-01 2013-10-01 false Measurements required: Field strength of spurious radiation. 2.1053 Section 2.1053 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL... Procedures Certification § 2.1053 Measurements required: Field strength of spurious radiation. (a...

Predictions for Radiation Shielding Materials

NASA Technical Reports Server (NTRS)

Kiefer, Richard L.

2002-01-01

Radiation from galactic cosmic rays (GCR) and solar particle events (SPE) is a serious hazard to humans and electronic instruments during space travel, particularly on prolonged missions outside the Earth s magnetic fields. Galactic cosmic radiation (GCR) is composed of approx. 98% nucleons and approx. 2% electrons and positrons. Although cosmic ray heavy ions are 1-2% of the fluence, these energetic heavy nuclei (HZE) contribute 50% of the long-term dose. These unusually high specific ionizations pose a significant health hazard acting as carcinogens and also causing microelectronics damage inside spacecraft and high-flying aircraft. These HZE ions are of concern for radiation protection and radiation shielding technology, because gross rearrangements and mutations and deletions in DNA are expected. Calculations have shown that HZE particles have a strong preference for interaction with light nuclei. The best shield for this radiation would be liquid hydrogen, which is totally impractical. For this reason, hydrogen-containing polymers make the most effective practical shields. Shielding is required during missions in Earth orbit and possibly for frequent flying at high altitude because of the broad GCR spectrum and during a passage into deep space and LunarMars habitation because of the protracted exposure encountered on a long space mission. An additional hazard comes from solar particle events (SPEs) which are mostly energetic protons that can produce heavy ion secondaries as well as neutrons in materials. These events occur at unpredictable times and can deliver a potentially lethal dose within several hours to an unshielded human. Radiation protection for humans requires safety in short-term missions and maintaining career exposure limits within acceptable levels on future long-term exploration missions. The selection of shield materials can alter the protection of humans by an order of magnitude. If improperly selected, shielding materials can actually increase radiation damage due to penetration properties and nuclear fragmentation. Protecting space-borne microelectronics from single event upsets (SEUs) by transmitted radiation will benefit system reliability and system design cost by using optimal shield materials. Long-term missions on the surface of the Moon or Mars will require the construction of habitats to protect humans during their stay. One approach to the construction is to make structural materials from lunar or Martian regolith using a polymeric material as a binder. The hydrogen-containing polymers are considerably more effective for radiation protection than the regolith, but the combination minimizes the amount of polymer to be transported. We have made composites of simulated lunar regolith with two different polymers, LaRC-SI, a high-performance polyimide thermoset, and polyethylene, a thermoplastic.

Field Incidence of Mycotoxins in Commercial Popcorn and Potential Environmental Influences

USDA-ARS?s Scientific Manuscript database

Insect ear damage and mycotoxin levels were monitored in several commercial popcorn fields in Central Illinois over a four-year period. Aflatoxin was rare, but fumonisin and deoxynivalenol (DON) were commonly encountered each year and occurred at mean levels in fields up to 1.7 ppm (sample max 2.77...

Magnetic anomalies in east Pacific using MAGSAT data

NASA Technical Reports Server (NTRS)

Harrison, C. G. A. (Principal Investigator)

1983-01-01

Methods for solving problems encountered in separating the core field from the crustal field are summarized as well as those methods developed for inverting total magnetic field data to obtain source functions for oceanic areas. Accounting for magnetization contrasts and the magnetization values measured in rocks of marine origin are also discussed.

A method for photon beam Monte Carlo multileaf collimator particle transport

NASA Astrophysics Data System (ADS)

Siebers, Jeffrey V.; Keall, Paul J.; Kim, Jong Oh; Mohan, Radhe

2002-09-01

Monte Carlo (MC) algorithms are recognized as the most accurate methodology for patient dose assessment. For intensity-modulated radiation therapy (IMRT) delivered with dynamic multileaf collimators (DMLCs), accurate dose calculation, even with MC, is challenging. Accurate IMRT MC dose calculations require inclusion of the moving MLC in the MC simulation. Due to its complex geometry, full transport through the MLC can be time consuming. The aim of this work was to develop an MLC model for photon beam MC IMRT dose computations. The basis of the MC MLC model is that the complex MLC geometry can be separated into simple geometric regions, each of which readily lends itself to simplified radiation transport. For photons, only attenuation and first Compton scatter interactions are considered. The amount of attenuation material an individual particle encounters while traversing the entire MLC is determined by adding the individual amounts from each of the simplified geometric regions. Compton scatter is sampled based upon the total thickness traversed. Pair production and electron interactions (scattering and bremsstrahlung) within the MLC are ignored. The MLC model was tested for 6 MV and 18 MV photon beams by comparing it with measurements and MC simulations that incorporate the full physics and geometry for fields blocked by the MLC and with measurements for fields with the maximum possible tongue-and-groove and tongue-or-groove effects, for static test cases and for sliding windows of various widths. The MLC model predicts the field size dependence of the MLC leakage radiation within 0.1% of the open-field dose. The entrance dose and beam hardening behind a closed MLC are predicted within +/-1% or 1 mm. Dose undulations due to differences in inter- and intra-leaf leakage are also correctly predicted. The MC MLC model predicts leaf-edge tongue-and-groove dose effect within +/-1% or 1 mm for 95% of the points compared at 6 MV and 88% of the points compared at 18 MV. The dose through a static leaf tip is also predicted generally within +/-1% or 1 mm. Tests with sliding windows of various widths confirm the accuracy of the MLC model for dynamic delivery and indicate that accounting for a slight leaf position error (0.008 cm for our MLC) will improve the accuracy of the model. The MLC model developed is applicable to both dynamic MLC and segmental MLC IMRT beam delivery and will be useful for patient IMRT dose calculations, pre-treatment verification of IMRT delivery and IMRT portal dose transmission dosimetry.

Changes in Liver Metabolic Gene Expression from Radiation Exposure

NASA Technical Reports Server (NTRS)

Peters, C. P.; Wotring, Virginia E.

2011-01-01

Radiation exposure is one of the unique physiological challenges of human spaceflight that is not encountered on earth. While radiation exposure is known to impart physiological stresses and alter normal function, it is unclear how it specifically affects drug metabolism. A major concern is that the actions of medications used in spaceflight may deviate from the expectations formed from terrestrial use. This concern was investigated at the molecular level by analyzing how gamma radiation exposure affected gene expression in the livers of mice. Three different doses of radiation were administered and after various intervals of recovery time, gene expression was measured with RT-qPCR screening arrays for drug metabolism and DNA repair. After examining the results of 192 genes total from each of 72 mice, 65 genes were found to be significantly affected by at least one of the doses of radiation. In general, the genes affected are involved in the metabolism of drugs with lipid or steroid hormone-like structures, as well as the maintenance of redox homeostasis and repair of DNA damage.

Effects of radiation on DNA's double helix

NASA Technical Reports Server (NTRS)

2003-01-01

The blueprint of life, DNA's double helix is found in the cells of everything from bacteria to astronauts. Exposure to radiation(depicted at right) such as X-rays (upper) or heavy ion particles (lower), can damage DNA and cause dire consequences both to the organism itself and to future generations. One of NASA's main goals is to develop better radiation shielding materials to protect astronauts from destructive radiation in space. This is particularly important for long space missions. NASA has selected researchers to study materials that provide better shielding. This research is managed by NASA's Office of Biological and Physical Research and is supported by the Microgravity Science and Applications Department at NASA's Marshall Center. During International Space Station Expedition Six, the Extravehicular Activity Radiation Monitoring (EVARM) will continue to measure radiation dosage encountered by the eyes, internal organs and skin during specific spacewalks, and relate it to the type of activity, location and other factors. An analysis of this information may be useful in mitigating potential exposure to space walkers in the future. (Illustration by Dr. Frank Cucinotta, NASA/Johnson Space Center, and Prem Saganti, Lockheed Martin)

Dental consultation in patients planned for/undergoing/post radiation therapy for head and neck cancers: a questionnaire-based survey.

PubMed

Mainali, Apeksha; Sumanth, K N; Ongole, Ravikiran; Denny, Ceena

2011-01-01

Mouth and pharyngeal cancers account for approximately 6% of cancers worldwide. Radiotherapy is one of the means of treatment of head and neck cancer. Consultation with a dental team experienced in caring for patients undergoing treatment for head and neck cancer will improve the quality of life of such patients. To evaluate the attitude of oncologists toward dental consultation to patients planning for/prior to/undergoing/post radiation therapy for head and neck cancers and to evaluate the number of radiation oncologists who encounter oral complaints and consider worth referring to a dentist. A questionnaire-based study was carried out following mailing of covering letter and self-administered questionnaire comprising 11 items, to 25 radiation oncology centers selected in India based on convenient sampling. Out of the 25 centers, we received response from 20 centers with 60 completely filled questionnaires. Five centers did not respond for further correspondences. The study indicated a need for awareness and education among radiation oncologists regarding dental consultation in patients planned/undergoing /post radiation therapy for head and neck cancer.

Radiation pneumonitis in breast cancer patients treated with conservative surgery and radiation therapy

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

Lingos, T.I.; Recht, A.; Vicini, F.

1991-07-01

The likelihood of radiation pneumonitis and factors associated with its development in breast cancer patients treated with conservative surgery and radiation therapy have not been well established. To assess these, the authors retrospectively reviewed 1624 patients treated between 1968 and 1985. Median follow-up for patients without local or distant failure was 77 months. Patients were treated with either tangential fields alone (n = 508) or tangents with a third field to the supraclavicular (SC) or SC-axillary (AX) region (n = 1116). Lung volume treated in the tangential fields was generally limited by keeping the perpendicular distance (demagnified) at the isocentermore » from the deep field edges to the posterior chest wall (CLD) to 3 cm or less. Seventeen patients with radiation pneumonitis were identified (1.0%). Radiation pneumonitis was diagnosed when patients presented with cough (15/17, 88%), fever (9/17, 53%), and/or dyspnea (6/17, 35%) and radiographic changes (17/17) following completion of RT. Radiographic infiltrates corresponded to treatment portals in all patients, and in 12 of the 17 patients, returned to baseline within 1-12 months. Five patients had permanent scarring on chest X ray. No patient had late or persistent pulmonary symptoms. The incidence of radiation pneumonitis was correlated with the combined use of chemotherapy (CT) and a third field. Three percent (11/328) of patients treated with a 3-field technique who received chemotherapy developed radiation pneumonitis compared to 0.5% (6 of 1296) for all other patients (p = 0.0001). When patients treated with a 3-field technique received chemotherapy concurrently with radiation therapy, the incidence of radiation pneumonitis was 8.8% (8/92) compared with 1.3% (3/236) for those who received sequential chemotherapy and radiation therapy (p = 0.002).« less

Predicting the Earth encounters of (99942) Apophis

NASA Technical Reports Server (NTRS)

Giorgini, Jon D.; Benner, Lance A. M.; Ostro, Steven J.; Nolan, Michael C.; Busch, Michael W.

2007-01-01

Arecibo delay-Doppler measurements of (99942) Apophis in 2005 and 2006 resulted in a five standard-deviation trajectory correction to the optically predicted close approach distance to Earth in 2029. The radar measurements reduced the volume of the statistical uncertainty region entering the encounter to 7.3% of the pre-radar solution, but increased the trajectory uncertainty growth rate across the encounter by 800% due to the closer predicted approach to the Earth. A small estimated Earth impact probability remained for 2036. With standard-deviation plane-of-sky position uncertainties for 2007-2010 already less than 0.2 arcsec, the best near-term ground-based optical astrometry can only weakly affect the trajectory estimate. While the potential for impact in 2036 will likely be excluded in 2013 (if not 2011) using ground-based optical measurements, approximations within the Standard Dynamical Model (SDM) used to estimate and predict the trajectory from the current era are sufficient to obscure the difference between a predicted impact and a miss in 2036 by altering the dynamics leading into the 2029 encounter. Normal impact probability assessments based on the SDM become problematic without knowledge of the object's physical properties; impact could be excluded while the actual dynamics still permit it. Calibrated position uncertainty intervals are developed to compensate for this by characterizing the minimum and maximum effect of physical parameters on the trajectory. Uncertainty in accelerations related to solar radiation can cause between 82 and 4720 Earth-radii of trajectory change relative to the SDM by 2036. If an actionable hazard exists, alteration by 2-10% of Apophis' total absorption of solar radiation in 2018 could be sufficient to produce a six standard-deviation trajectory change by 2036 given physical characterization; even a 0.5% change could produce a trajectory shift of one Earth-radius by 2036 for all possible spin-poles and likely masses. Planetary ephemeris uncertainties are the next greatest source of systematic error, causing up to 23 Earth-radii of uncertainty. The SDM Earth point-mass assumption introduces an additional 2.9 Earth-radii of prediction error by 2036. Unmodeled asteroid perturbations produce as much as 2.3 Earth-radii of error. We find no future small-body encounters likely to yield an Apophis mass determination prior to 2029. However, asteroid (144898) 2004 VD17, itself having a statistical Earth impact in 2102, will probably encounter Apophis at 6.7 lunar distances in 2034, their uncertainty regions coming as close as 1.6 lunar distances near the center of both SDM probability distributions.

Hepatic radioembolization with yttrium-90 containing glass microspheres: Preliminary results and clinical follow-up

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

Andrews, J.C.; Walker, S.C.; Ackermann, R.J.

1994-10-01

The treatment of hepatic tumors remains unsatisfactory. These lesions receive most of their blood supply from the hepatic artery, therefore the hepatic artery administration of beta-emitting particulate radiopharmaceuticals is an attractive approach to deliver therapeutic irradiation to the liver and differentially to tumors within the liver. A Phase 1 dose escalation study of the hepatic tolerance to radiation delivered by {sup 90}Y containing glass microspheres was carried out in 24 patients with hepatic malignancy. Doses of {sup 90}Y microspheres to achieve an estimated whole-liver nominal absorbed radiation dose of 5000 cGy (two patients), 7500cGy (six patients), 10,000 cGy (seven patients),more » 12,500 cGy (six patients), and 15,000 cGy (three patients) were administered via the hepatic artery. The administered nominal absorbed radiation dose (NARD) was estimated based on liver volume determined from CT scans and the assumption of uniform distribution of microspheres throughout the liver. No hematologic, hepatic or pulmonary toxicity was encountered in the dose range examined during a mean follow-up period of up to 53 mo. Reversible gastritis or duodenitis was encountered in four patients without imaging or biopsy evidence for extra-hepatic deposition of microspheres. Response data, based on CT scans obtained 16 wk after treatment, showed progressive disease in eight patients, stable disease in seven patients, minimal response in four patients and partial response in five patients. Subsequent follow-up revealed three long-term survivors at 204, 216 and 228 wk. These preliminary data demonstrates that in the examined dose range, radiation may be safely delivered to liver tumors by means of {sup 90}Y glass microspheres with encouraging response data. 39 refs., 3 figs., 1 tab.« less

Terahertz Radiation from Laser Created Plasma by Applying a Transverse Static Electric Field

NASA Astrophysics Data System (ADS)

Fukuda, Takuya; Katahira, Koji; Yugami, Noboru; Sentoku, Yasuhiko; Sakagami, Hitoshi; Nagatomo, Hideo

2016-10-01

Terahertz (THz) radiation, which is emitted in narrow cone in the forward direction from laser created plasma has been observed by N.Yugami et al.. Additionally, Löffler et al. have observed that a significantly increased THz emission intensity in the forward direction when the transverse static electric field is applied to the plasma. The purpose of our study is to derive the mechanism of the THz radiation from laser created plasma by applying the transverse static electric field. To study the radiation mechanism, we conducted 2D-PIC simulation. With the static electric field of 10 kV/cm and gas density of 1020 cm-3, we obtain 1.2 THz single cycle pulse radiation, whose intensity is 1.3 ×105 W/cm2. The magnetic field called ``picket fence mode'' is generated in the laser created plasma. At the boundary surface between the plasma and vacuum, the magnetic field is canceled because eddy current flows. We conclude that the temporal behavior of the magnetic field at the boundary surface radiates the THz wave.

Dehydration and Lagrangian Cold Point in the extratropical Tropopause region

NASA Astrophysics Data System (ADS)

Hoor, P.; Wernli, H.

2012-04-01

The tropopause region of the tropics and extratropics is sensitive to modifications of the radiation budget through changes of radiatively active substances like ozone and water vapour. Both may also modify the temperature structure and the strengths of the tropopause inversion layer (TIL). Stratospheric water vapour is mainly controlled by dehydration in the tropics. Ascending air masses encounter their minimum temperature in the TTL region (tropical tropopause layer) which determines the water vapour fraction which enters the stratosphere. In the lowermost stratosphere of the extratropics however, the tropical signal might be lost due to mixing with airmasses which crossed the tropopause (TST: troposphere to stratosphere) at higher temperatures, therefore carrying more water vapour to the extratropical stratosphere. We investigate statistical 90 day backward trajectories to investigate the role of dehydration at the extratropical tropopause for the water vapour budget at the tropopause at mid and high latitudes. We use a set of 800000 trajectories for summer and winter, respectively, on the basis of ECMWF-T799L91 operational data (kinematic wind fields). We analyze the trajectories for the time and locations of their cold point and TST. Our results indicate that : 1) TST and dehydration occur at different locations 2) Dehydration occurs in general before trajectories enter the stratosphere 3) Dehydration of TST trajectories can occur in northern winter after TST in the region of high tropopauses over Siberia

Tuning near field radiative heat flux through surface excitations with a metal insulator transition.

PubMed

van Zwol, P J; Ranno, L; Chevrier, J

2012-06-08

The control of heat flow is a formidable challenge due to lack of good thermal insulators. Promising new opportunities for heat flow control were recently theoretically discovered for radiative heat flow in near field, where large heat flow contrasts may be achieved by tuning electronic excitations on surfaces. Here we show experimentally that the phase transition of VO2 entails a change of surface polariton states that significantly affects radiative heat transfer in near field. In all cases the Derjaguin approximation correctly predicted radiative heat transfer in near field, but it underestimated the far field limit. Our results indicate that heat flow contrasts can be realized in near field that can be larger than those obtained in far field.

A Review of Tunable Wavelength Selectivity of Metamaterials in Near-Field and Far-Field Radiative Thermal Transport

PubMed Central

Tian, Yanpei; Ricci, Matt; Hyde, Mikhail; Gregory, Otto; Zheng, Yi

2018-01-01

Radiative thermal transport of metamaterials has begun to play a significant role in thermal science and has great engineering applications. When the key features of structures become comparable to the thermal wavelength at a particular temperature, a narrowband or wideband of wavelengths can be created or shifted in both the emission and reflection spectrum of nanoscale metamaterials. Due to the near-field effect, the phenomena of radiative wavelength selectivity become significant. These effects show strong promise for applications in thermophotovoltaic energy harvesting, nanoscale biosensing, and increased energy efficiency through radiative cooling in the near future. This review paper summarizes the recent progress and outlook of both near-field and far-field radiative heat transfer, different design structures of metamaterials, applications of unique thermal and optical properties, and focuses especially on exploration of the tunable radiative wavelength selectivity of nano-metamaterials. PMID:29786650

A summary of the OV1-19 satellite dose, depth dose, and linear energy transfer spectral measurements

NASA Technical Reports Server (NTRS)

Cervini, J. T.

1972-01-01

Measurements of the biophysical and physical parameters in the near earth space environment, specifically, the Inner Van Allen Belt are discussed. This region of space is of great interest to planners of the Skylab and the Space Station programs because of the high energy proton environment, especially during periods of increased solar activity. Many physical measurements of charged particle flux, spectra, and pitch angle distribution have been conducted and are programmed in the space radiation environment. Such predictions are not sufficient to accurately predict the effects of space radiations on critical biological and electronic systems operating in these environments. Some of the difficulties encountered in transferring from physical data to a prediction of the effects of space radiation on operational systems are discussed.

Poisoning of Heat Pipes

NASA Technical Reports Server (NTRS)

Gillies, Donald; Lehoczky, Sandor; Palosz, Witold; Carpenter, Paul; Salvail, Pat

2007-01-01

Thermal management is critical to space exploration efforts. In particular, efficient transfer and control of heat flow is essential when operating high energy sources such as nuclear reactors. Thermal energy must be transferred to various energy conversion devices, and to radiators for safe and efficient rejection of excess thermal energy. Applications for space power demand exceptionally long periods of time with equipment that is accessible for limited maintenance only. Equally critical is the hostile and alien environment which includes high radiation from the reactor and from space (galactic) radiation. In space or lunar applications high vacuum is an issue, while in Martian operations the systems will encounter a CO2 atmosphere. The effect of contact at high temperature with local soil (regolith) in surface operations on the moon or other terrestrial bodies (Mars, asteroids) must be considered.

Crystal regularity with high-resolution synchrotron X-radiation diffraction imaging

NASA Technical Reports Server (NTRS)

Steiner, Bruce; Dobbyn, Ronald C.

1991-01-01

New, high-resolution sources of X-radiation such as monochromatic synchrotron radiation beams with subarcsec divergence allow observation of regularities in a range of crystals with sufficient clarity for comprehensive analyses, whose results can deepen understanding of the nature of various crystal irregularities, their sources, and their effects on device performance. An account is presented of the results thus achievable with irregularities encountered in lattice orientation and strain, grain and subgrain boundaries, dislocations, domain boundaries, additional phases, and surface scratches. Significant achievements to date encompass the observation of critical anomalies in lead tin telluride, the reconciliation of disparate observations of GaAs, the determination of the performance effects of irregularities in mercuric iodide, and the characterization of the origins of crystal growth in bismuth silicon oxide.

Setting radon-specific release criteria and demonstrating compliance for land affected by NORM.

PubMed

García-Talavera, M; Martínez, M; Matarranz, J L M; Ramos, L

2008-11-01

Residues from industrial activities involving naturally occurring radioactive materials (NORMs) may cause radiation exposures to members of the public, particularly when NORM-affected land is brought into residential use. To provide an adequate protection against radiation in such situations, the following limiting criteria are currently required in Spain for releasing NORM-affected land: (i) no more than a 300 microSv yr(-1) increase (excluding radon doses) over the natural background; (ii) (222)Rn concentrations in hypothetical future dwellings lower than 200 Bq m(-3); and (iii) reduction of all radiation exposures to as low as reasonable achievable. This paper addresses some of the problems encountered in translating the (222)Rn criterion into site-specific release limits and in demonstrating compliance with them.

Starbursts triggered by central overpressure in interacting galaxies

NASA Technical Reports Server (NTRS)

Jog, Chanda J.; Das, Mousumi

1993-01-01

A triggering mechanism for the origin of enhanced, massive-star formation in the central regions of interacting spiral galaxy pairs is proposed. Our mechanism is based on the detailed evolution of a realistic interstellar medium in a galaxy following an encounter. As a disk giant molecular cloud (GMC) tumbles into the central region following a galaxy encounter, it undergoes a radiative shock compression via the pre-existing high pressure of the central intercloud medium. The shocked outer shell of a GMC becomes gravitationally unstable and begins to fragment thus resulting in a burst of star formation, when the growth time for the gravitational instabilities in the shell becomes smaller than the crossing time of the shock. The resulting values of typical infrared luminosity agree with observations.

A bimodal dust grain distribution in the IC 434 H ii region

NASA Astrophysics Data System (ADS)

Ochsendorf, B. B.; Tielens, A. G. G. M.

2015-04-01

Context. Studies of dust evolution and processing in different phases of the interstellar medium (ISM) is essential to understanding the lifecycle of dust in space. Recent results have challenged the capabilities and validity of current dust models, indicating that the properties of interstellar dust evolve as it transits between different phases of the ISM. Aims: We characterize the dust content from the IC 434 H ii region, and present a scenario that results in the large-scale structure of the region seen to date. Methods: We conduct a multi-wavelength study of the dust emission from the ionized gas, and combine this with modeling, from large scales that provide insight into the history of the IC 434/L1630 region, to small scales that allow us to infer quantitative properties of the dust content inside the H ii region. Results: The dust enters the H ii region through momentum transfer with a champagne flow of ionized gas, set up by a chance encounter between the L1630 molecular cloud and the star cluster of σ Ori. We observe two clearly separated dust populations inside the ionized gas, that show different observational properties, as well as contrasting optical properties. Population A is colder (~25 K) than predicted by widely-used dust models, its temperature is insensitive to an increase of the impinging radiation field, it is momentum-coupled to the gas, and efficiently absorbs radiation pressure to form a dust wave at 1.0 pc ahead of σ Ori AB. Population B is characterized by a constant [20/30] flux ratio throughout the H ii region, heats up to ~75 K close to the star, and is less efficient in absorbing radiation pressure, forming a dust wave at 0.1 pc from the star. Conclusions: The dust inside IC 434 is bimodal. The characteristics of population A are remarkable and cannot be explained by current dust models. We argue that large porous grains or fluffy aggregates are potential candidates to explain much of the observational characteristics. Population B are grains that match the classical description of spherical, compact dust. The inferred optical properties are consistent with either very small grains, or large grains in thermal equilibrium with the radiation field. Our results confirm recent work that stress the importance of variations in the dust properties between different regions of the ISM.

Reference field specification and preliminary beam selection strategy for accelerator-based GCR simulation

NASA Astrophysics Data System (ADS)

Slaba, Tony C.; Blattnig, Steve R.; Norbury, John W.; Rusek, Adam; La Tessa, Chiara

2016-02-01

The galactic cosmic ray (GCR) simulator at the NASA Space Radiation Laboratory (NSRL) is intended to deliver the broad spectrum of particles and energies encountered in deep space to biological targets in a controlled laboratory setting. In this work, certain aspects of simulating the GCR environment in the laboratory are discussed. Reference field specification and beam selection strategies at NSRL are the main focus, but the analysis presented herein may be modified for other facilities and possible biological considerations. First, comparisons are made between direct simulation of the external, free space GCR field and simulation of the induced tissue field behind shielding. It is found that upper energy constraints at NSRL limit the ability to simulate the external, free space field directly (i.e. shielding placed in the beam line in front of a biological target and exposed to a free space spectrum). Second, variation in the induced tissue field associated with shielding configuration and solar activity is addressed. It is found that the observed variation is likely within the uncertainty associated with representing any GCR reference field with discrete ion beams in the laboratory, given current facility constraints. A single reference field for deep space missions is subsequently identified. Third, a preliminary approach for selecting beams at NSRL to simulate the designated reference field is presented. This approach is not a final design for the GCR simulator, but rather a single step within a broader design strategy. It is shown that the beam selection methodology is tied directly to the reference environment, allows facility constraints to be incorporated, and may be adjusted to account for additional constraints imposed by biological or animal care considerations. The major biology questions are not addressed herein but are discussed in a companion paper published in the present issue of this journal. Drawbacks of the proposed methodology are discussed and weighed against alternative simulation strategies.

SU-F-T-486: A Simple Approach to Performing Light Versus Radiation Field Coincidence Quality Assurance Using An Electronic Portal Imaging Device (EPID)

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

Herchko, S; Ding, G

2016-06-15

Purpose: To develop an accurate, straightforward, and user-independent method for performing light versus radiation field coincidence quality assurance utilizing EPID images, a simple phantom made of readily-accessible materials, and a free software program. Methods: A simple phantom consisting of a blocking tray, graph paper, and high-density wire was constructed. The phantom was used to accurately set the size of a desired light field and imaged on the electronic portal imaging device (EPID). A macro written for use in ImageJ, a free image processing software, was then use to determine the radiation field size utilizing the high density wires on themore » phantom for a pixel to distance calibration. The macro also performs an analysis on the measured radiation field utilizing the tolerances recommended in the AAPM Task Group #142. To verify the accuracy of this method, radiochromic film was used to qualitatively demonstrate agreement between the film and EPID results, and an additional ImageJ macro was used to quantitatively compare the radiation field sizes measured both with the EPID and film images. Results: The results of this technique were benchmarked against film measurements, which have been the gold standard for testing light versus radiation field coincidence. The agreement between this method and film measurements were within 0.5 mm. Conclusion: Due to the operator dependency associated with tracing light fields and measuring radiation fields by hand when using film, this method allows for a more accurate comparison between the light and radiation fields with minimal operator dependency. Removing the need for radiographic or radiochromic film also eliminates a reoccurring cost and increases procedural efficiency.« less

Electrochromic Radiator Coupon Level Testing and Full Scale Thermal Math Modeling for Use on Altair Lunar Lander

NASA Technical Reports Server (NTRS)

Bannon, Erika T.; Bower, Chad E.; Sheth, Rubik; Stephan, Ryan

2010-01-01

In order to control system and component temperatures, many spacecraft thermal control systems use a radiator coupled with a pumped fluid loop to reject waste heat from the vehicle. Since heat loads and radiation environments can vary considerably according to mission phase, the thermal control system must be able to vary the heat rejection. The ability to "turn down" the heat rejected from the thermal control system is critically important when designing the system. Electrochromic technology as a radiator coating is being investigated to vary the amount of heat rejected by a radiator. Coupon level tests were performed to test the feasibility of this technology. Furthermore, thermal math models were developed to better understand the turndown ratios required by full scale radiator architectures to handle the various operation scenarios encountered during a mission profile for the Altair Lunar Lander. This paper summarizes results from coupon level tests as well as the thermal math models developed to investigate how electrochromics can be used to increase turn down ratios for a radiator. Data from the various design concepts of radiators and their architectures are outlined. Recommendations are made on which electrochromic radiator concept should be carried further for future thermal vacuum testing.

Looking into future: challenges in radiation protection in medicine.

PubMed

Rehani, M M

2015-07-01

Radiation protection in medicine is becoming more and more important with increasing wider use of X-rays, documentation of effects besides the potential for long-term carcinogenic effects. With computed tomography (CT) likely to become sub-mSv in coming years, positron emission tomography (PET), single photon emission computed tomography (SPECT) and some of the nuclear medical examination will become focus of attraction as high-dose examinations, even though they are less-frequent ones. Clarity will be needed on radiation effects at levels of radiation doses encountered in a couple of CT scans and if effects are really cumulative. There is challenge to develop radiation metrics that can be used as easily as units of temperature and length and avoidance of multiple meaning of a single dose metric. Other challenges include development of biological indicators of radiation dose, transition from dose to a representative phantom to dose to individual patient, system for tracking of radiation exposure history of patient, avoidance of radiation-induced skin injury in patients and radiation cataract in staff, cutting down inappropriate referrals for radiological examinations, confidence building in patient and patient safety in radiotherapy. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

An Introduction to Atmospheric Radiation: Review for the Bulletin of AMS

NASA Technical Reports Server (NTRS)

Marshak, Alexander

2003-01-01

Whether you like a certain geophysical book or not, largely depends on your background. The field of radiative transfer and atmospheric radiation, in particular, combines people with a wide range of mathematical skills: from theoretical astrophysicists and nuclear physicists to meteorologists and ecologists. There is always a delicate balance between physical explanations and their mathematical interpretations. This balance is very personal and is based on your background. I came to the field of atmospheric radiative transfer as a mathematician with little knowledge of atmospheric physics. After being in the field for more than a decade, I still have gaps in my atmospheric science education. Thus I assess a radiative transfer book fi-om two main criteria: how well does it describe the material that is familiar to me (the radiative transfer equation and its numerical solutions) and how well does it help me to fill the gaps in my personal knowledge. So I present this review fi-om the perspective of a former mathematician working in the field of atmospheric radiation. . After being asked to review the book, my first intention was to compare the new edition with the previous one (Liou, 1980). In doing so, you can clearly follow the progress made in the field of atmospheric radiation over the past two decades. If there are few changes (as in Fundamental Radiative Transfer) or no changes at all (as in the Maxwell s equations), then the field has not seen much development. To the contrary, many differences between the two editions illustrate areas of major progress in the field, such as evidenced in Thermal Ineared Radiative Transfer and even in the creations of completely new fields like Three-Dimensional Radiative Transfer or Light Scattering by Nonspherical Particles. Obviously, the major changes happened not in the theory, which is at least half a century old, but in data quality and completely new measurements (mostly due to new satellite data) with higher accuracy and more reliability. The new edition illustrates this progress well.

The physics of polarization

NASA Astrophysics Data System (ADS)

Landi Degl'Innocenti, Egidio

This course is intended to give a description of the basic physical concepts which underlie the study and the interpretation of polarization phenomena. Apart from a brief historical introduction (Sect. 1), the course is organized in three parts. A first part (Sects. 2 - 6) covers the most relevant facts about the polarization phenomena that are typically encountered in laboratory applications and in everyday life. In Sect. 2, the modern description of polarization in terms of the Stokes parameters is recalled, whereas Sect. 3 is devoted to introduce the basic tools of laboratory polarimetry, such as the Jones calculus and the Mueller matrices. The polarization phenomena which are met in the reflection and refraction of a beam of radiation at the separation surface between two dielectrics, or between a dielectric and a metal, are recalled in Sect. 4. Finally, Sect. 5 gives an introduction to the phenomena of dichroism and of anomalous dispersion and Sect. 6 summarizes the polarization phenomena that are commonly encountered in everyday life. The second part of this course (Sects. 7-14) deals with the description, within the formalism of classical physics, of the spectro-polarimetric properties of the radiation emitted by accelerated charges. Such properties are derived by taking as starting point the Liénard and Wiechert equations that are recalled and discussed in Sect. 7 both in the general case and in the non-relativistic approximation. The results are developed to find the percentage polarization, the radiation diagram, the cross-section and the spectral characteristics of the radiation emitted in different phenomena particularly relevant from the astrophysical point of view. The emission of a linear antenna is derived in Sect. 8. The other Sections are devoted to Thomson scattering (Sect. 9), Rayleigh scattering (Sect. 10), Mie scattering (Sect. 11), bremsstrahlung radiation (Sect. 12), cyclotron radiation (Sect. 13), and synchrotron radiation (Sect. 14). Finally, the third part (Sects. 15-19) is devoted to give a sketch of the theory of the generation and transfer of polarized radiation in spectral lines. After a general introduction to the argument (Sect. 15), the concepts of density-matrix and of atomic polarization are illustrated in Sect. 16. In Sect. 17, a parallelism is established, within the framework of the theory of stellar atmospheres, between the usual formalism, which neglects polarization phenomena, and the more involved formalism needed for the interpretation of spectro-polarimetric observations. Some consequences of the radiative transfer equations for polarized radiation, pointing to the importance of dichroism phenomena in establishing the amplification condition via stimulated emission, are discussed in Sect. 18. The last section (Sect. 19) is devoted to introduce the problem of finding a self-consistent solution of the radiative transfer equations for polarized radiation and of the statistical equilibrium equations for the density matrix (non-LTE of the 2nd kind).

FIRST EURADOS INTERCOMPARISON EXERCISE OF EYE LENS DOSEMETERS FOR MEDICAL APPLICATIONS.

PubMed

Clairand, I; Ginjaume, M; Vanhavere, F; Carinou, E; Daures, J; Denoziere, M; Silva, E H; Roig, M; Principi, S; Van Rycheghem, L

2016-09-01

In the context of the decrease in the eye lens dose limit for occupational exposure to 20 mSv per year stated by the recent revision of the European Basic Safety Standards Directive 2013/59/EURATOM, the European Radiation Dosimetry Group (EURADOS) has organised in 2014, for the first time, an intercomparison exercise for eye lens dosemeters. The main objective was to assess the capabilities of the passive eye lens dosemeters currently in use in Europe for occupational monitoring in medical fields. A total of 20 European individual monitoring services from 15 different countries have participated. The dosemeters provided by the participants were all composed of thermoluminescent detectors, of various types and designs. The irradiations were carried out with several photon fields chosen to cover the energy and angle ranges encountered in medical workplace. Participants were asked to report the doses in terms of Hp(3) using their routine protocol. The results provided by each participant were compared with the reference delivered doses. All the results were anonymously analysed. Results are globally satisfactory since, among the 20 participants, 17 were able to provide 90 % of their response in accordance with the ISO 14146 standard requirements. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

OSIRIS-REx Orbit Determination Covariance Studies at Bennu

NASA Technical Reports Server (NTRS)

Antreasian, P. G.; Moreau, M.; Jackman, C.; Williams, K.; Page, B.; Leonard, J. M.

2016-01-01

The Origins Spectral Interpretation Resource Identification Security Regolith Explorer (OSIRIS-REx) mission is a NASA New Frontiers mission launching in 2016 to rendezvous with the small, Earth-crossing asteroid (101955) Bennu in late 2018, and ultimately return a sample of regolith to Earth. Approximately 3 months before the encounter with Bennu, the asteroid finally becomes detectable in the narrow field PolyCam imager. The spacecraft's rendezvous with Bennu begins with a series of four Asteroid Approach Maneuvers, which slow the spacecraft's speed relative to Bennu beginning two and a half months prior to closest approach, ultimately delivering the spacecraft to a point 18 km from Bennu on Nov 18, 2018. An extensive campaign of proximity operations activities to characterize the properties of Bennu and select a suitable sample site will follow. This paper will discuss the challenges of navigating near a small 500-m diameter asteroid. The navigation at close proximity is dependent on the accurate mathematical model or digital terrain map of the asteroids shape. Predictions of the spacecraft state are very sensitive to spacecraft small forces, solar radiation pressure, and mis-modeling of Bennu's gravity field. Uncertainties in the physical parameters of the central body Bennu create additional challenges. The navigation errors are discussed and their impact on science planning will be presented.

Enhanced retroviral gene delivery in ultrasonic standing wave fields.

PubMed

Lee, Y-H; Peng, C-A

2005-04-01

Enhancement of retroviral transduction efficiency has been achieved by several physical and chemical approaches. However, the application of those methods is hampered by not easily scalable configurations. In this study, instead of looking into the effect of sonoporation, the potential of ultrasonic standing wave fields (USWF) to facilitate retroviral transduction rate was explored. We reasoned that, driven by the primary acoustic radiation force, suspended cells moved to the pressure nodal planes first and formed cell bands. Nanometer-sized retroviruses, circulated between nodal planes by acoustic microstreaming, then used the preformed cell bands as the nucleating sites to attach on. As a result, the encounter opportunity between retroviruses and cells was increased and further facilitated the gene delivery efficiency. Our results showed that mega-Hertz USWF brought K562 erythroleukemia cells (10(6) cells/ml) and vesicular stomatitis virus G-protein (VSV-G) pseudotyped retroviruses (titer of 5 x 10(6) CFU/ml) into close contact at the pressure nodal planes, yielding a four-fold increment of enhanced green fluorescent protein transgene expression after 5-min USWF exposure in the presence of Polybrene. Furthermore, with a fixed titer of retrovirus, the transduction rate was augmented with the increase of cell concentration. In summary, USWF offer a feasible means to enhance retroviral transduction efficiency in large-scale settings.

OSIRIS-REx Orbit Determination Covariance Studies at Bennu

NASA Technical Reports Server (NTRS)

Antreasian, P. G.; Moreau, M.; Jackman, C.; Williams, K.; Page, B.; Leonard, J. M.

2016-01-01

The Origins Spectral Interpretation Resource Identification Security Regolith Explorer (OSIRIS-REx) mission is a NASA New Frontiers mission launching in 2016 to rendezvous with the small, Earth-crossing asteroid (101955) Bennu in late 2018, ultimately returning a sample of regolith to Earth. Approximately three months before the encounter with Bennu, the asteroid becomes detectable in the narrow field PolyCam imager. The spacecraft's rendezvous with Bennu begins with a series of four Asteroid Approach Maneuvers, slowing the spacecraft's speed relative to Bennu beginning two and a half months prior to closest approach, ultimately delivering the spacecraft to a point 18 km from Bennu in Nov, 2018. An extensive campaign of proximity operations activities to characterize the properties of Bennu and select a suitable sample site will follow. This paper will discuss the challenges of navigating near a small 500-m diameter asteroid. The navigation at close proximity is dependent on the accurate mathematical model or digital terrain map of the asteroid's shape. Predictions of the spacecraft state are very sensitive to spacecraft small forces, solar radiation pressure, and mis-modeling of Bennu's gravity field. Uncertainties in the physical parameters of the central body Bennu create additional challenges. The navigation errors are discussed and their impact on science planning will be presented.

Biophysics and medical effects of enhanced radiation weapons.

PubMed

Reeves, Glen I

2012-08-01

Enhanced radiation weapons (ERW) are fission-fusion devices where the massive numbers of neutrons generated during the fusion process are intentionally allowed to escape rather than be confined to increase yield (and fallout products). As a result, the energy partition of the weapon output shifts from blast and thermal energies toward prompt radiation. The neutron/gamma output ratio is also increased. Neutrons emitted from ERW are of higher energy than the Eave of neutrons from fission weapons. These factors affect the patterns of injury distribution; delay wound healing in combined injuries; reduce the therapeutic efficacy of medical countermeasures; and increase the dose to radiation-only casualties, thus potentiating the likelihood of encountering radiation-induced incapacitation. The risk of radiation-induced carcinogenesis is also increased. Radiation exposure to first responders from activation products is increased over that expected from a fission weapon of similar yield. However, the zone of dangerous fallout is significantly reduced in area. At least four nations have developed the potential to produce such weapons. Although the probability of detonation of an ERW in the near future is very small, it is nonzero, and clinicians and medical planners should be aware of the medical effects of ERW.

Radiation Forces and Torques without Stress (Tensors)

ERIC Educational Resources Information Center

Bohren, Craig F.

2011-01-01

To understand radiation forces and torques or to calculate them does not require invoking photon or electromagnetic field momentum transfer or stress tensors. According to continuum electromagnetic theory, forces and torques exerted by radiation are a consequence of electric and magnetic fields acting on charges and currents that the fields induce…

14 CFR 29.1317 - High-intensity Radiated Fields (HIRF) Protection.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false High-intensity Radiated Fields (HIRF...-intensity Radiated Fields (HIRF) Protection. (a) Except as provided in paragraph (d) of this section, each electrical and electronic system that performs a function whose failure would prevent the continued safe...

14 CFR 25.1317 - High-intensity Radiated Fields (HIRF) Protection.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false High-intensity Radiated Fields (HIRF...-intensity Radiated Fields (HIRF) Protection. (a) Except as provided in paragraph (d) of this section, each electrical and electronic system that performs a function whose failure would prevent the continued safe...

14 CFR 27.1317 - High-intensity Radiated Fields (HIRF) Protection.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false High-intensity Radiated Fields (HIRF...-intensity Radiated Fields (HIRF) Protection. (a) Except as provided in paragraph (d) of this section, each electrical and electronic system that performs a function whose failure would prevent the continued safe...

14 CFR 27.1317 - High-intensity Radiated Fields (HIRF) Protection.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false High-intensity Radiated Fields (HIRF...-intensity Radiated Fields (HIRF) Protection. (a) Except as provided in paragraph (d) of this section, each electrical and electronic system that performs a function whose failure would prevent the continued safe...

14 CFR 25.1317 - High-intensity Radiated Fields (HIRF) Protection.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false High-intensity Radiated Fields (HIRF...-intensity Radiated Fields (HIRF) Protection. (a) Except as provided in paragraph (d) of this section, each electrical and electronic system that performs a function whose failure would prevent the continued safe...

14 CFR 23.1308 - High-intensity Radiated Fields (HIRF) Protection.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false High-intensity Radiated Fields (HIRF... Equipment General § 23.1308 High-intensity Radiated Fields (HIRF) Protection. (a) Except as provided in paragraph (d) of this section, each electrical and electronic system that performs a function whose failure...

14 CFR 29.1317 - High-intensity Radiated Fields (HIRF) Protection.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false High-intensity Radiated Fields (HIRF...-intensity Radiated Fields (HIRF) Protection. (a) Except as provided in paragraph (d) of this section, each electrical and electronic system that performs a function whose failure would prevent the continued safe...

14 CFR 23.1308 - High-intensity Radiated Fields (HIRF) Protection.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false High-intensity Radiated Fields (HIRF... Equipment General § 23.1308 High-intensity Radiated Fields (HIRF) Protection. (a) Except as provided in paragraph (d) of this section, each electrical and electronic system that performs a function whose failure...

Wave field synthesis of moving virtual sound sources with complex radiation properties.

PubMed

Ahrens, Jens; Spors, Sascha

2011-11-01

An approach to the synthesis of moving virtual sound sources with complex radiation properties in wave field synthesis is presented. The approach exploits the fact that any stationary sound source of finite spatial extent radiates spherical waves at sufficient distance. The angular dependency of the radiation properties of the source under consideration is reflected by the amplitude and phase distribution on the spherical wave fronts. The sound field emitted by a uniformly moving monopole source is derived and the far-field radiation properties of the complex virtual source under consideration are incorporated in order to derive a closed-form expression for the loudspeaker driving signal. The results are illustrated via numerical simulations of the synthesis of the sound field of a sample moving complex virtual source.

High-time resolution measurements of upstream magnetic field and plasma conditions during flux transfer events at the Earth's dayside magnetopause

NASA Technical Reports Server (NTRS)

Jacob, Jamey D.; Carrell, Cynthia

1993-01-01

We present preliminary results of a study of upstream magnetic field and plasma conditions measured by IRM during flux transfer events observed at the Earth's magnetopause by CCE. This study was designed to determine the importance of various upstream factors in the formation of bipolar magnetic field signatures called flux transfer events (FTEs). Six FTE encounters were examined. In three cases, the two satellites were on similar magnetic field lines. Preliminary investigation showed that fluctuations occurred in the Bz component of the interplanetary magnetic field (IMF) resulting in a southward field preceding the FTE in all three of these cases. In two of these cases, the changes were characterized by a distinct rotation from a strong southward to a strong northward field. There were also accompanying changes in the dynamic and thermal pressure in the solar wind immediately before the FTE was encountered. Examination of the 3D plasma distributions showed that these pulses were due to the addition of energetic upstreaming foreshock particles. There were no consistent changes in either Bz or the plasma pressure at IRM for the three events when the satellites were not connected by the IMF.

Destruction of a Magnetized Star

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-01-01

What happens when a magnetized star is torn apart by the tidal forces of a supermassive black hole, in a violent process known as a tidal disruption event? Two scientists have broken new ground by simulating the disruption of stars with magnetic fields for the first time.The magnetic field configuration during a simulation of the partial disruption of a star. Top left: pre-disruption star. Bottom left: matter begins to re-accrete onto the surviving core after the partial disruption. Right: vortices form in the core as high-angular-momentum debris continues to accrete, winding up and amplifying the field. [Adapted from Guillochon McCourt 2017]What About Magnetic Fields?Magnetic fields are expected to exist in the majority of stars. Though these fields dont dominate the energy budget of a star the magnetic pressure is a million times weaker than the gas pressure in the Suns interior, for example they are the drivers of interesting activity, like the prominences and flares of our Sun.Given this, we can wonder what role stars magnetic fields might play when the stars are torn apart in tidal disruption events. Do the fields change what we observe? Are they dispersed during the disruption, or can they be amplified? Might they even be responsible for launching jets of matter from the black hole after the disruption?Star vs. Black HoleIn a recent study, James Guillochon (Harvard-Smithsonian Center for Astrophysics) and Michael McCourt (Hubble Fellow at UC Santa Barbara) have tackled these questions by performing the first simulations of tidal disruptions of stars that include magnetic fields.In their simulations, Guillochon and McCourt evolve a solar-mass star that passes close to a million-solar-mass black hole. Their simulations explore different magnetic field configurations for the star, and they consider both what happens when the star barely grazes the black hole and is only partially disrupted, as well as what happens when the black hole tears the star apart completely.Amplifying EncountersFor stars that survive their encounter with the black hole, Guillochon and McCourt find that the process of partial disruption and re-accretion can amplify the magnetic field of the star by up to a factor of 20. Repeated encounters of the star with the black hole could amplify the field even more.The authors suggest an interesting implication of this idea: a population of highly magnetized stars may have formed in our own galactic center, resulting from their encounters with the supermassive black hole Sgr A*.A turbulent magnetic field forms after a partial stellar disruption and re-accretion of the tidal tails. [Adapted from Guillochon McCourt 2017]Effects in DestructionFor stars that are completely shredded and form a tidal stream after their encounter with the black hole, the authors find that the magnetic field geometry straightens within the stream of debris. There, the pressure of the magnetic field eventually dominates over the gas pressure and self-gravity.Guillochon and McCourt find that the fields new configuration isnt ideal for powering jets from the black hole but it is strong enough to influence how the stream interacts with itself and its surrounding environment, likely affecting what we can expect to see from these short-lived events.These simulations have clearly demonstrated the need to further explore the role of magnetic fields in the disruptions of stars by black holes.BonusCheck out the full (brief) video from one of the simulations by Guillochon and McCourt (be sure to watch it in high-res!). It reveals the evolution of a stars magnetic field configuration as the star is partially disrupted by the forces of a supermassive black hole and then re-accretes.CitationJames Guillochon and Michael McCourt 2017 ApJL 834 L19. doi:10.3847/2041-8213/834/2/L19

Trajectories and distribution of interstellar dust grains in the heliosphere

DOE PAGES

Slavin, Jonathan D.; Frisch, Priscilla C.; Müller, Hans-Reinhard; ...

2012-11-01

The solar wind carves a bubble in the surrounding interstellar medium (ISM) known as the heliosphere. Charged interstellar dust grains (ISDG) encountering the heliosphere may be diverted around the heliopause or penetrate it depending on their charge-to-mass ratio. Here, we present new calculations of trajectories of ISDG in the heliosphere, and the dust density distributions that result. We include up-to-date grain charging calculations using a realistic UV radiation field and full three-dimensional magnetohydrodynamic fluid + kinetic models for the heliosphere. Models with two different (constant) polarities for the solar wind magnetic field (SWMF) are used, with the grain trajectory calculationsmore » done separately for each polarity. Small grains a gr ≲ 0.01 μm are completely excluded from the inner heliosphere. Large grains, a gr ≳ 1.0 μm, pass into the inner solar system and are concentrated near the Sun by its gravity. Trajectories of intermediate size grains depend strongly on the SWMF polarity. When the field has magnetic north pointing to ecliptic north, the field de-focuses the grains resulting in low densities in the inner heliosphere, while for the opposite polarity the dust is focused near the Sun. The ISDG density outside the heliosphere inferred from applying the model results to in situ dust measurements is inconsistent with local ISM depletion data for both SWMF polarities but is bracketed by them. Our result points to the need to include the time variation in the SWMF polarity during grain propagation. This provides valuable insights for interpretation of the in situ dust observations from Ulysses.« less

An outbreak of chickenpox in a military field hospital--the implications for biological warfare.

PubMed Central

Hepburn, N C; Brooks, T J

1991-01-01

An outbreak of chickenpox with spread to patients and staff on the isolation ward of a British field hospital during the Gulf war is described. The implications for the design and operation of field hospital isolation units should transmissible biological warfare agents be encountered in any future conflict are discussed. PMID:1774746

Polymer materials and component evaluation in acidic-radiation environments

NASA Astrophysics Data System (ADS)

Celina, M.; Gillen, K. T.; Malone, G. M.; Clough, R. L.; Nelson, W. H.

2001-07-01

Polymeric materials used for cable/wire insulation, electrical connectors, O-rings, seals, and in critical components such as motors, level switches and resistive thermo-devices were evaluated under accelerated degradation conditions in combined radiation-oxidative elevated-temperature acidic-vapor (nitric/oxalic) environments relevant to conditions in isotope processing facilities. Experiments included the assessment of individual materials such as PEEK, polyimides, polyolefin based cable insulation, EPDM rubbers, various epoxy systems, commercial caulking materials as well as some functional testing of components. We discuss how to conduct laboratory experiments to simulate such complex hostile environments, describe some degradation effects encountered, and evaluate the impact on appropriate material and component selection.

Volcanism-Climate Interactions

NASA Technical Reports Server (NTRS)

Walter, Louis S. (Editor); Desilva, Shanaka (Editor)

1991-01-01

The range of disciplines in the study of volcanism-climate interactions includes paleoclimate, volcanology, petrology, tectonics, cloud physics and chemistry, and climate and radiation modeling. Questions encountered in understanding the interactions include: the source and evolution of sulfur and sulfur-gaseous species in magmas; their entrainment in volcanic plumes and injection into the stratosphere; their dissipation rates; and their radiative effects. Other issues include modeling and measuring regional and global effects of such large, dense clouds. A broad-range plan of research designed to answer these questions was defined. The plan includes observations of volcanoes, rocks, trees, and ice cores, as well as satellite and aircraft observations of erupting volcanoes and resulting lumes and clouds.

Radiation Protection

NASA Astrophysics Data System (ADS)

Grupen, Claus

Radiation protection is a very important aspect for the application of particle detectors in many different fields, like high energy physics, medicine, materials science, oil and mineral exploration, and arts, to name a few. The knowledge of radiation units, the experience with shielding, and information on biological effects of radiation are vital for scientists handling radioactive sources or operating accelerators or X-ray equipment. This article describes the modern radiation units and their conversions to older units which are still in use in many countries. Typical radiation sources and detectors used in the field of radiation protection are presented. The legal regulations in nearly all countries follow closely the recommendations of the International Commission on Radiological Protection (ICRP). Tables and diagrams with relevant information on the handling of radiation sources provide useful data for the researcher working in this field.

The effect of simulated altitude on the visual fields of glaucoma patients and the elderly.

DOT National Transportation Integrated Search

1991-01-01

This study tests whether mild hypoxia, that is typically encountered in civilian aircraft, causes temporary visual field defects in elderly persons or temporarily increases pre-existing defects in persons with glaucoma. The central 24-2 program on th...

The generation of gravitational waves. I - Weak-field sources

NASA Technical Reports Server (NTRS)

Thorne, K. S.; Kovacs, S. J.

1975-01-01

This paper derives and summarizes a 'plug-in-and-grind' formalism for calculating the gravitational waves emitted by any system with weak internal gravitational fields. If the internal fields have negligible influence on the system's motions, the formalism reduces to standard 'linearized theory'. Independent of the effects of gravity on the motions, the formalism reduces to the standard 'quadrupole-moment formalism' if the motions are slow and internal stresses are weak. In the general case, the formalism expresses the radiation in terms of a retarded Green's function for slightly curved spacetime and breaks the Green's function integral into five easily understood pieces: direct radiation, produced directly by the motions of the source; whump radiation, produced by the 'gravitational stresses' of the source; transition radiation, produced by a time-changing time delay ('Shapiro effect') in the propagation of the nonradiative 1/r field of the source; focusing radiation, produced when one portion of the source focuses, in a time-dependent way, the nonradiative field of another portion of the source; and tail radiation, produced by 'back-scatter' of the nonradiative field in regions of focusing.

The generation of gravitational waves. 1. Weak-field sources: A plug-in-and-grind formalism

NASA Technical Reports Server (NTRS)

Thorne, K. S.; Kovacs, S. J.

1974-01-01

A plug-in-and-grind formalism is derived for calculating the gravitational waves emitted by any system with weak internal gravitational fields. If the internal fields have negligible influence on the system's motions, then the formalism reduces to standard linearized theory. Whether or not gravity affects the motions, if the motions are slow and internal stresses are weak, then the new formalism reduces to the standard quadrupole-moment formalism. In the general case the new formalism expresses the radiation in terms of a retarded Green's function for slightly curved spacetime, and then breaks the Green's-function integral into five easily understood pieces: direct radiation, produced directly by the motions of the sources; whump radiation, produced by the the gravitational stresses of the source; transition radiation, produced by a time-changing time delay (Shapiro effect) in the propagation of the nonradiative, 1/r field of the source; focussing radiation produced when one portion of the source focusses, in a time-dependent way, the nonradiative field of another portion of the source, and tail radiation, produced by backscatter of the nonradiative field in regions of focussing.

Super-Planckian far-field radiative heat transfer

NASA Astrophysics Data System (ADS)

Fernández-Hurtado, V.; Fernández-Domínguez, A. I.; Feist, J.; García-Vidal, F. J.; Cuevas, J. C.

2018-01-01

We present here a theoretical analysis that demonstrates that the far-field radiative heat transfer between objects with dimensions smaller than the thermal wavelength can overcome the Planckian limit by orders of magnitude. To guide the search for super-Planckian far-field radiative heat transfer, we make use of the theory of fluctuational electrodynamics and derive a relation between the far-field radiative heat transfer and the directional absorption efficiency of the objects involved. Guided by this relation, and making use of state-of-the-art numerical simulations, we show that the far-field radiative heat transfer between highly anisotropic objects can largely overcome the black-body limit when some of their dimensions are smaller than the thermal wavelength. In particular, we illustrate this phenomenon in the case of suspended pads made of polar dielectrics like SiN or SiO2. These structures are widely used to measure the thermal transport through nanowires and low-dimensional systems and can be employed to test our predictions. Our work illustrates the dramatic failure of the classical theory to predict the far-field radiative heat transfer between micro- and nanodevices.

First Stage Solid Propellant Multi Debris Thermal Analysis

NASA Technical Reports Server (NTRS)

Toleman, Benjamin M.

2011-01-01

The crew launch vehicle considered for the Constellation (Cx) Program utilizes a first stage solid rocket motor. If an abort is initiated in first stage flight the Crew Module (CM) will separate and be pulled away from the launch vehicle via a Launch Abort System (LAS) in order to safely and quickly carry the crew away from the malfunction launch vehicle. Having aborted the mission, the launch vehicle will likely be destroyed via a Flight Termination System (FTS) in order to prevent it from errantly traversing back over land and posing a risk to the public. The resulting launch vehicle debris field, composed primarily of first stage solid propellant, poses a threat to the CM. The harsh radiative thermal environment induced by surrounding burning propellant debris may lead to CM parachute failure. A methodology, detailed herein, has been developed to address this concern and quantify the risk of first stage propellant debris leading to radiative thermal demise of the CM parachutes. Utilizing basic thermal radiation principles, a software program was developed to calculate parachute temperature as a function of time for a given abort trajectory and debris piece trajectory set. Two test cases, considered worst-case aborts with regard to launch vehicle debris environments, were analyzed using the simulation: an abort declared at Mach 1 and an abort declared at maximum dynamic pressure (Max Q). For both cases, the resulting temperature profiles indicated that thermal limits for the parachutes were not exceeded. However, short duration close encounters by single debris pieces did have a significant effect on parachute temperature, with magnitudes on the order of 10 s of degrees Fahrenheit. Therefore while these two test cases did not indicate exceedance of thermal limits, in order to quantify the risk of parachute failure due to radiative effects from the abort environment, a more thorough probability-based analysis using the methodology demonstrated herein must be performed.

First Stage Solid Propellant Multiply Debris Thermal Analysis

NASA Technical Reports Server (NTRS)

Toleman, Benjamin M.

2011-01-01

Destruction of a solid rocket stage of a launch vehicle can create a thermal radiation hazard for an aborting crew module. This hazard was assessed for the Constellation Program (Cx) crew and launch vehicle concept. For this concept, if an abort was initiated in first stage flight, the Crew Module (CM) will separate and be pulled away from the malfunctioning launch vehicle via a Launch Abort System (LAS). Having aborted the mission, the launch vehicle will likely be destroyed via a Flight Termination System (FTS) in order to prevent it from errantly traversing back over land and posing a risk to the public. The resulting launch vehicle debris field, composed primarily of first stage solid propellant, poses a threat to the CM. The harsh radiative thermal environment, caused by surrounding burning propellant debris, may lead to CM parachute failure. A methodology, detailed herein, has been developed to address this concern and to quantify the risk of first stage propellant debris leading to the thermal demise of the CM parachutes. Utilizing basic thermal radiation principles, a software program was developed to calculate parachute temperature as a function of time for a given abort trajectory and debris piece trajectory set. Two test cases, considered worst case aborts with regard to launch vehicle debris environments, were analyzed using the simulation: an abort declared at Mach 1 and an abort declared at maximum dynamic pressure (Max Q). For both cases, the resulting temperature profiles indicated that thermal limits for the parachutes were not exceeded. However, short duration close encounters by single debris pieces did have a significant effect on parachute temperature. Therefore while these two test cases did not indicate exceedance of thermal limits, in order to quantify the risk of parachute failure due to radiative effects from the abort environment, a more thorough probability-based analysis using the methodology demonstrated herein must be performed.

Assessing contextual factors that influence acceptance of pedestrian alerts by a night vision system.

PubMed

Källhammer, Jan-Erik; Smith, Kip

2012-08-01

We investigated five contextual variables that we hypothesized would influence driver acceptance of alerts to pedestrians issued by a night vision active safety system to inform the specification of the system's alerting strategies. Driver acceptance of automotive active safety systems is a key factor to promote their use and implies a need to assess factors influencing driver acceptance. In a field operational test, 10 drivers drove instrumented vehicles equipped with a preproduction night vision system with pedestrian detection software. In a follow-up experiment, the 10 drivers and 25 additional volunteers without experience with the system watched 57 clips with pedestrian encounters gathered during the field operational test. They rated the acceptance of an alert to each pedestrian encounter. Levels of rating concordance were significant between drivers who experienced the encounters and participants who did not. Two contextual variables, pedestrian location and motion, were found to influence ratings. Alerts were more accepted when pedestrians were close to or moving toward the vehicle's path. The study demonstrates the utility of using subjective driver acceptance ratings to inform the design of active safety systems and to leverage expensive field operational test data within the confines of the laboratory. The design of alerting strategies for active safety systems needs to heed the driver's contextual sensitivity to issued alerts.

First indication of the coherent unipolar diffraction radiation generated by relativistic electrons

NASA Astrophysics Data System (ADS)

Naumenko, G.; Shevelev, M.

2018-05-01

As is generally known, the integral of the electric field strength over all time for usual (bipolar) radiation is zero. The first demonstration of the possibility of unipolar radiation generation has been considered theoretically by Bessonov in 1981 [E.G. Bessonov, Zh. Eksp. Teor. Fiz. 80 (1981) 852]. According to this work, the unipolar radiation (or strange electromagnetic waves) is radiation for which the integral of the electric field strength over the entire duration of a pulse differs significantly from zero. Later, several theoretical papers devoted to this phenomenon have appeared in the literature, where authors investigated mainly synchrotron radiation. However, despite the critical interest, the experimental investigations ignored this effect. In this paper we present results of the first experimental investigation of the unipolar radiation generated by a relativistic electron beam. To detect the unipolar radiation the detector that is sensitive to the selected direction of the electric field strength has been elaborated and tested. We used a designed detector to observe the coherent backward diffraction radiation appearing when a bunched electron beam travels in the vicinity of a flat conductive target. The asymmetry of the electric field strength of the coherent backward diffraction radiation has been demonstrated.

Voyager 1: Encounter with Saturn

NASA Technical Reports Server (NTRS)

Panagakos, N.

1980-01-01

The history of the Voyager Project is reviewed as well as known facts about Saturn and its satellites. Important results of encounters with Jupiter are summarized. Scientific objectives of the flyby of Saturn involve the planet's atmosphere, rings, and magnetic field interactions with the solar wind and satellites. The search for additional satellites, and various aspects of Titan, Rhea, Dione, Mimas, Iapetus, Hyperion, and Enceladas are also of interest. The instruments developed to obtain these goals are described.

Juno Magnetometer Observations in the Earth's Magnetosphere

NASA Astrophysics Data System (ADS)

Connerney, J. E.; Oliversen, R. J.; Espley, J. R.; MacDowall, R. J.; Schnurr, R.; Sheppard, D.; Odom, J.; Lawton, P.; Murphy, S.; Joergensen, J. L.; Joergensen, P. S.; Merayo, J. M.; Denver, T.; Bloxham, J.; Smith, E. J.; Murphy, N.

2013-12-01

The Juno spacecraft enjoyed a close encounter with Earth on October 9, 2013, en route to Jupiter Orbit Insertion (JOI) on July 5, 2016. The Earth Flyby (EFB) provided a unique opportunity for the Juno particles and fields instruments to sample mission relevant environments and exercise operations anticipated for orbital operations at Jupiter, particularly the period of intense activity around perijove. The magnetic field investigation onboard Juno is equipped with two magnetometer sensor suites, located at 10 and 12 m from the spacecraft body at the end of one of the three solar panel wings. Each contains a vector fluxgate magnetometer (FGM) sensor and a pair of co-located non-magnetic star tracker camera heads which provide accurate attitude determination for the FGM sensors. This very capable magnetic observatory sampled the Earth's magnetic field at 64 vector samples/second throughout passage through the Earth's magnetosphere. We present observations of the Earth's magnetic field and magnetosphere obtained throughout the encounter and compare these observations with those of other Earth-orbiting assets, as available, and with particles and fields observations acquired by other Juno instruments operated during EFB.

Delivering accessible fieldwork: preliminary findings from a collaborative international study

NASA Astrophysics Data System (ADS)

Stokes, Alison; Atchison, Christopher; Feig, Anthony; Gilley, Brett

2017-04-01

Students with disabilities are commonly excluded from full participation in geoscience programs, and encounter significant barriers when accessing field-learning experiences. In order to increase talent and diversity in the geoscience workforce, more inclusive learning experiences must be developed that will enable all students to complete the requirements of undergraduate degree programs, including fieldwork. We discuss the outcomes of a completely accessible field course developed through the collaborative effort of geoscience education practitioners from the US, Canada and the UK. This unique field workshop has brought together current geoscience academics and students with disabilities to share perspectives on commonly-encountered barriers to learning in the field, and explore methods and techniques for overcoming them. While the student participants had the opportunity to learn about Earth processes while situated in the natural environment, participating geoscience instructors began to identify how to improve the design of field courses, making them fully inclusive of learners with disabilities. The outcomes from this experience will be used to develop guidelines to facilitate future development and delivery of accessible geoscience fieldwork.

Dose accuracy of a durable insulin pen with memory function, before and after simulated lifetime use and under stress conditions.

PubMed

Xue, Ligang; Mikkelsen, Kristian Handberg

2013-03-01

The objective of this study was to assess the dose accuracy of NovoPen® 5 in delivering low, medium and high doses of insulin before and after simulated lifetime use. A secondary objective was to evaluate the durability of the pen and its memory function under various stress conditions designed to simulate conditions that may be encountered in everyday use of an insulin pen. All testing was conducted according to International Organization for Standardization guideline 11608-1, 2000 for pen injectors. Dose accuracy was measured for the delivery of 1 unit (U) (10 mg), 30 U (300 mg) and 60 U (600 mg) test medium in standard, cool and hot conditions and before and after simulated lifetime use. Dose accuracy was also tested after preconditioning in dry heat storage; cold storage; damp cyclical heat; shock, bump and vibration; free fall and after electrostatic charge and radiated field test. Memory function was tested under all temperature and physical conditions. NovoPen 5 maintained dosing accuracy and memory function at minimum, medium and maximum doses in standard, cool and hot conditions, stress tests and simulated lifetime use. The pens remained intact and retained dosing accuracy and a working memory function at all doses after exposure to variations in temperature and after physical challenge. NovoPen 5 was accurate at all doses tested and under various functionality tests. Its durable design ensured that the dose accuracy and memory function were retained under conditions of stress likely to be encountered in everyday use.

A laboratory investigation of the variability of cloud reflected radiance fields

NASA Technical Reports Server (NTRS)

Mckee, T. B.; Cox, S. K.

1986-01-01

A method to determine the radiative properties of complex cloud fields was developed. A Cloud field optical simulator (CFOS) was constructed to simulate the interaction of cloud fields with visible radiation. The CFOS was verified by comparing experimental results from it with calculations performed with a Monte Carlo radiative transfer model. A software library was developed to process, reduce, and display CFOS data. The CFSOS was utilized to study the reflected radiane patterns from simulated cloud fields.

Near Field Radiation Characteristics of Implantable Square Spiral Chip Inductor Antennas for Bio-Sensors

NASA Technical Reports Server (NTRS)

Nessel, James A.; Simons, Rainee N.; Miranda, Felix A.

2007-01-01

The near field radiation characteristics of implantable Square Spiral Chip Inductor Antennas (SSCIA) for Bio-Sensors have been measured. Our results indicate that the measured near field relative signal strength of these antennas agrees with simulated results and confirm that in the near field region the radiation field is fairly uniform in all directions. The effects of parameters such as ground-plane, number of turns and microstrip-gap width on the performance of the SSCIA are presented. Furthermore, the SSCIA antenna with serrated ground plane produce a broad radiation pattern, with a relative signal strength detectable at distances within the range of operation of hand-held devices for self-diagnosis.

Properties of an ultrarelativistic charged particle radiation in a constant homogeneous crossed electromagnetic field

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

Bogdanov, O.V., E-mail: bov@tpu.ru; Department of Higher Mathematics and Mathematical Physics, Tomsk Polytechnic University, Tomsk, 634050; Kazinski, P.O., E-mail: kpo@phys.tsu.ru

The properties of radiation created by a classical ultrarelativistic scalar charged particle in a constant homogeneous crossed electromagnetic field are described both analytically and numerically with radiation reaction taken into account in the form of the Landau–Lifshitz equation. The total radiation naturally falls into two parts: the radiation formed at the entrance point of a particle into the crossed field (the synchrotron entrance radiation), and the radiation coming from the late-time asymptotics of a particle motion (the de-excited radiation). The synchrotron entrance radiation resembles, although does not coincide with, the ultrarelativistic limit of the synchrotron radiation: its distribution over energiesmore » and angles possesses almost the same properties. The de-excited radiation is soft, not concentrated in the plane of motion of a charged particle, and almost completely circularly polarized. The photon energy delivering the maximum to its spectral angular distribution decreases with increasing the initial energy of a charged particle, while the maximum value of this distribution remains the same at the fixed photon observation angle and entrance angle of a charged particle. The ultraviolet and infrared asymptotics of the total radiation are also described. - Highlights: • Properties of an electron radiation in a crossed electromagnetic field are studied. • Spectral angular distribution of the synchrotron entrance radiation is described. • Spectral angular distribution of the de-excited radiation is described. • De-excited radiation is almost completely circularly polarized. • Photon energy at the maximum of the de-excited radiation decreases with increasing the initial energy of an electron.« less

Application of the planar-scanning technique to the near-field dosimetry of millimeter-wave radiators.

PubMed

Zhao, Jianxun; Lu, Hongmin; Deng, Jun

2015-02-01

The planar-scanning technique was applied to the experimental measurement of the electric field and power flux density (PFD) in the exposure area close to the millimeter-wave (MMW) radiator. In the near-field region, the field and PFD were calculated from the plane-wave spectrum of the field sampled on a scan plane far from the radiator. The measurement resolution was improved by reducing the spatial interval between the field samples to a fraction of half the wavelength and implementing multiple iterations of the fast Fourier transform. With the reference to the results from the numerical calculation, an experimental evaluation of the planar-scanning measurement was made for a 50 GHz radiator. Placing the probe 1 to 3 wavelengths from the aperture of the radiator, the direct measurement gave the near-field data with significant differences from the numerical results. The planar-scanning measurement placed the probe 9 wavelengths away from the aperture and effectively reduced the maximum and averaged differences in the near-field data by 70.6% and 65.5%, respectively. Applied to the dosimetry of an open-ended waveguide and a choke ring antenna for 60 GHz exposure, the technique proved useful to the measurement of the PFD in the near-field exposure area of MMW radiators. © 2015 Wiley Periodicals, Inc.

Conducting international nursing research: challenges and opportunities.

PubMed

Opollo, Jackline Gloria; Opollo, Diana Alaka; Gray, Jennifer; Spies, Lori

2014-11-01

To describe practical experiences before, during and after gaining entry into research fields in Kenya and Uganda. Planning, conducting and implementing international research can be an arduous task. Novice researchers need practical guides to accessing international fields and mitigating challenges met in the field. The researchers conducted three different studies in two developing nations. This paper reviews challenges encountered when conducting international research. Solutions used to overcome these challenges are discussed. Establishing and maintaining effective partnerships is critical to the success of international research efforts. Researchers must be tactful, flexible and creative when handling methodological, ethical and logistical challenges encountered in settings poor in resources. International research provides opportunities for increasing dedication, building cross-cultural competence and advancing health professional practice globally. This paper contributes to nursing scholarship by highlighting the practical challenges of conducting international research. Illustrations aimed at lending insight and encouraging others to expand their dedication to conducting international research are offered.

Voyager 2 Saturn encounter attitude and articulation control experience

NASA Technical Reports Server (NTRS)

Hill, M.

1982-01-01

A description is given of the Voyager Attitude and Articulation Control System (AACS). The complex series of maneuvers required for Voyager 2 during the near encounter period to obtain fields and particle data, track the limb of Saturn during the earth occultation period, and reflect the RF beam off the Saturnian ring system are discussed. It is noted that some of these maneuvers involved rotating the spacecraft simultaneously about multiple axes while maintaining accurate pointing of the scan platform, a first for interplanetary missions. Also described are two anomalies experienced by the AACS during the near encounter period. The first was the significant roll attitude error that occurred shortly after all axis inertial control and that continued to grow until celestial reacquisition. The second was that the scan platform slewing in the azimuth axis stopped midway through the near encounter. These anomalies are analyzed, and their effect on future missions is assessed.

Redistribution of resonance radiation. II - The effect of magnetic fields.

NASA Technical Reports Server (NTRS)

Omont, A.; Cooper, J.; Smith, E. W.

1973-01-01

Previously obtained results for scattering of radiation in the presence of collisions are restated in a density matrix formalism which employs an irreducible-tensor description of the radiation field. This formalism is particularly useful for problems associated with radiative transfer theory. The redistribution is then extended to include the effect of a weak magnetic field. By averaging over a finite bandwidth which is on the order of the Doppler width, simplified expressions of physical significance for the scattering in the Doppler core and the Lorentz wings are obtained. Expressions are also obtained for the corresponding source function of radiative transfer theory.

Electromagnetic radiation from beam-plasma instabilities

NASA Technical Reports Server (NTRS)

Stenzel, R. L.; Whelan, D. A.

1982-01-01

The mechanism by which unstable electrostatic waves of an electron-beam plasma system are converted into observed electromagnetic waves is of great current interest in space plasma physics. Electromagnetic radiation arises from both natural beam-plasma systems, e.g., type III solar bursts and kilometric radiation, and from man-made electron beams injected from rockets and spacecraft. In the present investigation the diagnostic difficulties encountered in space plasmas are overcome by using a large laboratory plasma. A finite diameter (d approximately equal to 0.8 cm) electron beam is injected into a uniform quiescent magnetized afterglow plasma of dimensions large compared with electromagnetic wavelength. Electrostatic waves grow, saturate and decay within the uniform central region of the plasma volume so that linear mode conversion on density gradients can be excluded as a possible generation mechanism for electromagnetic waves.

Vibration analysis and sound field characteristics of a tubular ultrasonic radiator.

PubMed

Liang, Zhaofeng; Zhou, Guangping; Zhang, Yihui; Li, Zhengzhong; Lin, Shuyu

2006-12-01

A sort of tubular ultrasonic radiator used in ultrasonic liquid processing is studied. The frequency equation of the tubular radiator is derived, and its radiated sound field in cylindrical reactor is calculated using finite element method and recorded by means of aluminum foil erosion. The results indicate that sound field of tubular ultrasonic radiator in cylindrical reactor appears standing waves along both its radial direction and axial direction, and amplitudes of standing waves decrease gradually along its radial direction, and the numbers of standing waves along its axial direction are equal to the axial wave numbers of tubular radiator. The experimental results are in good agreement with calculated results.

Peering Inside the Pillars of Creation

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2018-06-01

On 1 April 1995, Hubble captured one of its most well-known images: a stunning photo of towering features known as the Pillars of Creation, located in the Eagle Nebula just 7,000 light-years away. A new study explores how these iconic columns are influenced by the magnetic fields within them.Pillars from ShocksAn illustrative figure of the BISTRO magnetic-field vectors observed in the Pillars of Creation, overlaid on a Hubble composite of the pillars. [Pattle et al. 2018]In the Hubble image, we see the result of young, hot stars that have driven a photoionization shock into the cloud around them, forming complex structures in the dense gas at the shock interfaces. These structures in this case, dense columns of neutral gas and dust are then bombarded with hot radiation from the young stars, giving the structures a misty, ethereal look as they photoevaporate.Though we have a rough picture, the specifics of how the Pillars of Creation were formed and how they evolve in this harsh radiation environment arent yet fully understood. In particular, the role of magnetic fields in shaping and sustaining these pillars is poorly constrained, both observationally and theoretically.To address this problem, a team of scientists led by Kate Pattle (University of Central Lancashire, UK and National Tsing Hua University, Taiwan), has now made the first direct observations of the magnetic-field morphology within the Pillars of Creation.The authors proposed formation scenario: a) an ionization front approaches an overdensity in the molecular gas, b) the front is slowed at the overdensity, causing the magnetic field lines to bend, c) the compressed magnetic field supports the pillar against radial collapse, but cant support against longitudinal erosion. [Adapted from Pattle et al. 2018]Observing FieldsPattle and collaborators imaged the pillars as a part of the B-Fields in Star-Forming Region Observations (BISTRO) project, which uses a camera and polarimeter mounted on the James Clerk Maxwell Telescope in Hawaii. The high-resolution, submillimeter-wavelength polarimetric observations allowed the team to measure the orientations of the magnetic fields within the pillars.Pattle and collaborators found that the magnetic fields inside the Pillars of Creation are actually quite organized: they generally run along the length of the pillars, perpendicular to and decoupled from the field in the surrounding cloud. The authors use their observations to estimate the strength of the fields: roughly 170320 G in the pillars.Magnetic SupportWhat do these results tell us? First, the strength of the fields is consistent with a formation scenario in which very weakly magnetized gas was compressed to form columns. The authors propose that the Pillars of Creation were formed when an ionization front driven by radiation from nearby young, hot stars encountered a dense clump as it moved through the cloud of molecular gas. The overdensity slowed the front, causing the magnetic field to bend as the surrounding gas moved. The compressed magnetic field then supported the resulting column from collapse.Pattle and collaborators argue that the magnetic fields in the Pillars of Creation are supporting the pillars radially against collapse even now. They may also be preventing the pillar ends from breaking off into disconnected clumps known as cometary globules, a process that could eventually disintegrate the pillars.So whats BISTRO up to now? The project is continuing to survey magnetic fields in the dense gas of other nearby high-mass star-forming regions. This may help confirm the results found for the Pillars of Creation, bringing us another step closer to understanding how magnetic fields influence the some of the striking features that Hubble and other telescopes have revealed in our astronomical backyard.CitationKate Pattle et al 2018 ApJL 860 L6. doi:10.3847/2041-8213/aac771

SU-E-T-361: Energy Dependent Radiation/light-Field Misalignment On Truebeam Linear Accelerator

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

Sperling, N; Tanny, S; Parsai, E

2015-06-15

Purpose: Verifying the co-incidence of the radiation and light field is recommended by TG-142 for monthly and annual checks. On a digital accelerator, it is simple to verify that beam steering settings are consistent with accepted and commissioned values. This fact should allow for physicists to verify radiation-light-field co-incidence for a single energy and accept that Result for all energies. We present a case where the radiation isocenter deviated for a single energy without any apparent modification to the beam steering parameters. Methods: The radiation isocenter was determined using multiple Methods: Gafchromic film, a BB test, and radiation profiles measuredmore » with a diode. Light-field borders were marked on Gafchromic film and then irradiated for all photon energies. Images of acceptance films were compared with films taken four months later. A phantom with a radio-opaque BB was aligned to isocenter using the light-field and imaged using the EPID for all photon energies. An unshielded diode was aligned using the crosshairs and then beam profiles of multiple field sizes were obtained. Field centers were determined using Omni-Pro v7.4 software, and compared to similar scans taken during commissioning. Beam steering parameter files were checked against backups to determine that the steering parameters were unchanged. Results: There were no differences between the configuration files from acceptance. All three tests demonstrated that a single energy had deviated from accepted values by 0.8 mm in the inline direction. The other two energies remained consistent with previous measurements. The deviated energy was re-steered to be within our clinical tolerance. Conclusions: Our study demonstrates that radiation-light-field coincidence is an energy dependent effect for modern linacs. We recommend that radiation-light-field coincidence be verified for all energies on a monthly basis, particularly for modes used to treat small fields, as these may drift without influencing results from other tests.« less

MSFC Stream Model Preliminary Results: Modeling the 1998-2002 Leonid Encounters and the 1993,1994, and 2004 Perseid Encounters

NASA Technical Reports Server (NTRS)

Moser, D. E.; Cooke, W. J.

2004-01-01

The cometary meteoroid ejection models of Jones (1996) and Crifo (1997) were used to simulate ejection from comets 55P/Tempel-Tuttle during the last 12 revolutions, and the 1862, 1737, and 161 0 apparitions of 1 OSP/Swift-Tuttle. Using cometary ephemerides generated by the JPL HORIZONS Solar System Data and Ephemeris Computation Service, ejection was simulated in 1 hour time steps while the comet was within 2.5 AU of the Sun. Also simulated was ejection occurring at the hour of perihelion passage. An RK4 variable step integrator was then used to integrate meteoroid position and velocity forward in time, accounting for the effects of radiation pressure, Poynting-Robertson drag, and the gravitational forces of the planets, which were computed using JPL's DE406 planetary ephemerides. An impact parameter is computed for each particle approaching the Earth, and the results are compared to observations of the 1998-2002 Leonid showers, and the 1993-1 994 Perseids. A prediction for Earth's encounter with the Perseid stream in 2004 is also presented.

'Full dose' reirradiation of human cervical spinal cord.

PubMed

Ryu, S; Gorty, S; Kazee, A M; Bogart, J; Hahn, S S; Dalal, P S; Chung, C T; Sagerman, R H

2000-02-01

With the progress of modern multimodality cancer treatment, retreatment of late recurrences or second tumors became more commonly encountered in management of patients with cancer. Spinal cord retreatment with radiation is a common problem in this regard. Because radiation myelopathy may result in functional deficits, many oncologists are concerned about radiation-induced myelopathy when retreating tumors located within or immediately adjacent to the previous radiation portal. The treatment decision is complicated because it requires a pertinent assessment of prognostic factors with and without reirradiation, radiobiologic estimation of recovery of occult spinal cord damage from the previous treatment, as well as interactions because of multimodality treatment. Recent studies regarding reirradiation of spinal cord in animals using limb paralysis as an endpoint have shown substantial and almost complete recovery of spinal cord injury after a sufficient time after the initial radiotherapy. We report a case of "full" dose reirradiation of the entire cervical spinal cord in a patient who has not developed clinically detectable radiation-induced myelopathy on long-term follow-up of 17 years after the first radiotherapy and 5 years after the second radiotherapy.

Biotechnology

NASA Image and Video Library

2003-01-22

The blueprint of life, DNA's double helix is found in the cells of everything from bacteria to astronauts. Exposure to radiation(depicted at right) such as X-rays (upper) or heavy ion particles (lower), can damage DNA and cause dire consequences both to the organism itself and to future generations. One of NASA's main goals is to develop better radiation shielding materials to protect astronauts from destructive radiation in space. This is particularly important for long space missions. NASA has selected researchers to study materials that provide better shielding. This research is managed by NASA's Office of Biological and Physical Research and is supported by the Microgravity Science and Applications Department at NASA's Marshall Center. During International Space Station Expedition Six, the Extravehicular Activity Radiation Monitoring (EVARM) will continue to measure radiation dosage encountered by the eyes, internal organs and skin during specific spacewalks, and relate it to the type of activity, location and other factors. An analysis of this information may be useful in mitigating potential exposure to space walkers in the future. (Illustration by Dr. Frank Cucinotta, NASA/Johnson Space Center, and Prem Saganti, Lockheed Martin)

Environment of Space Interactions with Space Systems

NASA Technical Reports Server (NTRS)

2004-01-01

The primary product of this research project was a computer program named SAVANT. This program uses the Displacement Damage Dose (DDD) method of calculating radiation damage to solar cells. This calculation method was developed at the Naval Research Laboratory, and uses fundamental physical properties of the solar cell materials to predict radiation damage to the solar cells. This means that fewer experimental measurements are required to characterize the radiation damage to the cells, which results in a substantial cost savings to qualify solar cells for orbital missions. In addition, the DDD method makes it easier to characterize cells that are already being used, but have not been fully tested using the older technique of characterizing radiation damage. The computer program combines an orbit generator with NASA's AP-8 and AE-8 models of trapped protons and electrons. This allows the user to specify an orbit, and the program will calculate how the spacecraft moves during the mission, and the radiation environment that it encounters. With the spectrum of the particles, the program calculates how they would slow down while traversing the coverglass, and provides a slowed-down spectrum.

Structural biologists capture detailed image of gene regulator’s fleeting form | Center for Cancer Research

Cancer.gov

Using an ultrafast, high-intensity radiation source called an X-ray free-electron laser (XFEL), scientists have captured an atomic-level picture of an RNA structure called a riboswitch as it reorganizes itself to regulate protein production. The structure they visualized has never before been seen, and likely exists for only milliseconds after the riboswitch first encounters

Analysis of the Radiated Field in an Electromagnetic Reverberation Chamber as an Upset-Inducing Stimulus for Digital Systems

NASA Technical Reports Server (NTRS)

Torres-Pomales, Wilfredo

2012-01-01

Preliminary data analysis for a physical fault injection experiment of a digital system exposed to High Intensity Radiated Fields (HIRF) in an electromagnetic reverberation chamber suggests a direct causal relation between the time profile of the field strength amplitude in the chamber and the severity of observed effects at the outputs of the radiated system. This report presents an analysis of the field strength modulation induced by the movement of the field stirrers in the reverberation chamber. The analysis is framed as a characterization of the discrete features of the field strength waveform responsible for the faults experienced by a radiated digital system. The results presented here will serve as a basis to refine the approach for a detailed analysis of HIRF-induced upsets observed during the radiation experiment. This work offers a novel perspective into the use of an electromagnetic reverberation chamber to generate upset-inducing stimuli for the study of fault effects in digital systems.

An improved radiation metric. [for radiation pressure in strong gravitational fields

NASA Technical Reports Server (NTRS)

Noerdlinger, P. D.

1976-01-01

An improved radiation metric is obtained in which light rays make a small nonzero angle with the radius, thus representing a source of finite size. Kaufmann's previous solution is criticized. The stabilization of a scatterer near a source of gravitational field and radiation is slightly enhanced for sources of finite size.

Hawking radiation of a vector field and gravitational anomalies

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

Murata, Keiju; Miyamoto, Umpei

2007-10-15

Recently, the relation between Hawking radiation and gravitational anomalies has been used to estimate the flux of Hawking radiation for a large class of black objects. In this paper, we extend the formalism, originally proposed by Robinson and Wilczek, to the Hawking radiation of vector particles (photons). It is explicitly shown, with the Hamiltonian formalism, that the theory of an electromagnetic field on d-dimensional spherical black holes reduces to one of an infinite number of massive complex scalar fields on 2-dimensional spacetime, for which the usual anomaly-cancellation method is available. It is found that the total energy emitted from themore » horizon for the electromagnetic field is just (d-2) times that for a scalar field. The results support the picture that Hawking radiation can be regarded as an anomaly eliminator on horizons. Possible extensions and applications of the analysis are discussed.« less

Slope effects on shortwave radiation components and net radiation

NASA Technical Reports Server (NTRS)

Walter-Shea, Elizabeth A.; Blad, Blaine L.; Hays, Cynthia J.; Mesarch, Mark A.

1992-01-01

The main objective of the International Satellite Land Surface Climatology Project (ISLSCP) has been stated as 'the development of techniques that may be applied to satellite observations of the radiation reflected and emitted from the Earth to yield quantitative information concerning land surface climatological conditions.' The major field study, FIFE (the First ISLSCP Field Experiment), was conducted in 1978-89 to accomplish this objective. Four intensive field campaigns (IFC's) were carried out in 1987 and one in 1989. Factors contributing to observed reflected radiation from the FIFE site must be understood before the radiation observed by satellites can be used to quantify surface processes. Analysis since our last report has focused on slope effects on incoming and outgoing shortwave radiation and net radiation from data collected in 1989.

Multi-mode horn antenna simulation

NASA Technical Reports Server (NTRS)

Dod, L. R.; Wolf, J. D.

1980-01-01

Radiation patterns were computed for a circular multimode horn antenna using waveguide electric field radiation expressions. The circular multimode horn was considered as a possible reflector feed antenna for the Large Antenna Multifrequency Microwave Radiometer (LAMMR). This horn antenna uses a summation of the TE sub 11 deg and TM sub 11 deg modes to generate far field primary radiation patterns with equal E and H plane beamwidths and low sidelobes. A computer program for the radiation field expressions using the summation of waveguide radiation modes is described. The sensitivity of the multimode horn antenna radiation patterns to phase variations between the two modes is given. Sample radiation pattern calculations for a reflector feed horn for LAMMR are shown. The multimode horn antenna provides a low noise feed suitable for radiometric applications.

Radiative heat transfer in the extreme near field.

PubMed

Kim, Kyeongtae; Song, Bai; Fernández-Hurtado, Víctor; Lee, Woochul; Jeong, Wonho; Cui, Longji; Thompson, Dakotah; Feist, Johannes; Reid, M T Homer; García-Vidal, Francisco J; Cuevas, Juan Carlos; Meyhofer, Edgar; Reddy, Pramod

2015-12-17

Radiative transfer of energy at the nanometre length scale is of great importance to a variety of technologies including heat-assisted magnetic recording, near-field thermophotovoltaics and lithography. Although experimental advances have enabled elucidation of near-field radiative heat transfer in gaps as small as 20-30 nanometres (refs 4-6), quantitative analysis in the extreme near field (less than 10 nanometres) has been greatly limited by experimental challenges. Moreover, the results of pioneering measurements differed from theoretical predictions by orders of magnitude. Here we use custom-fabricated scanning probes with embedded thermocouples, in conjunction with new microdevices capable of periodic temperature modulation, to measure radiative heat transfer down to gaps as small as two nanometres. For our experiments we deposited suitably chosen metal or dielectric layers on the scanning probes and microdevices, enabling direct study of extreme near-field radiation between silica-silica, silicon nitride-silicon nitride and gold-gold surfaces to reveal marked, gap-size-dependent enhancements of radiative heat transfer. Furthermore, our state-of-the-art calculations of radiative heat transfer, performed within the theoretical framework of fluctuational electrodynamics, are in excellent agreement with our experimental results, providing unambiguous evidence that confirms the validity of this theory for modelling radiative heat transfer in gaps as small as a few nanometres. This work lays the foundations required for the rational design of novel technologies that leverage nanoscale radiative heat transfer.

Spectral tuning of near-field radiative heat transfer by graphene-covered metasurfaces

NASA Astrophysics Data System (ADS)

Zheng, Zhiheng; Wang, Ao; Xuan, Yimin

2018-03-01

When two gratings are respectively covered by a layer of graphene sheet, the near-field radiative heat transfer between two parallel gratings made of silica (SiO2) could be greatly improved. As the material properties of doped silicon (n-type doping concentration is 1020 cm-3, marked as Si-20) and SiO2 differ greatly, we theoretically investigate the near-field radiative heat transfer between two parallel graphene-covered gratings made of Si-20 to explore some different phenomena, especially for modulating the spectral properties. The radiative heat flux between two parallel bulks made of Si-20 can be enhanced by using gratings instead of bulks. When the two gratings are respectively covered by a layer of graphene sheet, the radiative heat flux between two gratings made of Si-20 can be further enhanced. By tuning graphene chemical potential μ and grating filling factor f, due to the interaction between surface plasmon polaritons (SPPs) of graphene sheets and grating structures, the spectral properties of the radiative heat flux between two parallel graphene-covered gratings can be effectively regulated. This work will develop and supplement the effects of materials on the near-field radiative heat transfer for this kind of system configuration, paving a way to modulate the spectral properties of near-field radiative heat transfer.

Continental cichlid radiations: functional diversity reveals the role of changing ecological opportunity in the Neotropics.

PubMed

Arbour, Jessica Hilary; López-Fernández, Hernán

2016-08-17

Adaptive radiations have been hypothesized to contribute broadly to the diversity of organisms. Models of adaptive radiation predict that ecological opportunity and ecological release, the availability of empty ecological niches and the response by adapting lineages to occupy them, respectively, drive patterns of phenotypic and lineage diversification. Adaptive radiations driven by 'ecological opportunity' are well established in island systems; it is less clear if ecological opportunity influences continent-wide diversification. We use Neotropical cichlid fishes to test if variation in rates of functional evolution is consistent with changing ecological opportunity. Across a functional morphological axis associated with ram-suction feeding traits, evolutionary rates declined through time as lineages diversified in South America. Evolutionary rates of ram-suction functional morphology also appear to have accelerated as cichlids colonized Central America and encountered renewed opportunity. Our results suggest that ecological opportunity may play an important role in shaping patterns of morphological diversity of even broadly distributed lineages like Neotropical cichlids. © 2016 The Author(s).

Continental cichlid radiations: functional diversity reveals the role of changing ecological opportunity in the Neotropics

PubMed Central

López-Fernández, Hernán

2016-01-01

Adaptive radiations have been hypothesized to contribute broadly to the diversity of organisms. Models of adaptive radiation predict that ecological opportunity and ecological release, the availability of empty ecological niches and the response by adapting lineages to occupy them, respectively, drive patterns of phenotypic and lineage diversification. Adaptive radiations driven by ‘ecological opportunity’ are well established in island systems; it is less clear if ecological opportunity influences continent-wide diversification. We use Neotropical cichlid fishes to test if variation in rates of functional evolution is consistent with changing ecological opportunity. Across a functional morphological axis associated with ram–suction feeding traits, evolutionary rates declined through time as lineages diversified in South America. Evolutionary rates of ram–suction functional morphology also appear to have accelerated as cichlids colonized Central America and encountered renewed opportunity. Our results suggest that ecological opportunity may play an important role in shaping patterns of morphological diversity of even broadly distributed lineages like Neotropical cichlids. PMID:27512144

Radiation and Plasma Environments for Lunar Missions

NASA Technical Reports Server (NTRS)

Minow, Joseph I.; Edwards, David L.; Altstatt, Richard L.; Diekmann, Anne M.; Blackwell, William C., Jr.; Harine, Katherine J.

2006-01-01

Space system design for lunar orbit and extended operations on the lunar surface requires analysis of potential system vulnerabilities to plasma and radiation environments to minimize anomalies and assure that environmental failures do not occur during the mission. Individual environments include the trapped particles in Earth s radiation belts, solar energetic particles and galactic cosmic rays, plasma environments encountered in transit to the moon and on the lunar surface (solar wind, terrestrial magnetosheath and magnetotail, and lunar photoelectrons), and solar ultraviolet and extreme ultraviolet photons. These are the plasma and radiation environments which contribute to a variety of effects on space systems including total ionizing dose and dose rate effects in electronics, degradation of materials in the space environment, and charging of spacecraft and lunar dust. This paper provides a survey of the relevant charged particle and photon environments of importance to lunar mission design ranging from the lowest (approx.few 10 s eV) photoelectron energies to the highest (approx.GeV) cosmic ray energies.

Fine needle aspiration cytology of radiation-induced changes in nonneoplastic breast lesions. Possible pitfalls in cytodiagnosis

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

Peterse, J.L.; Thunnissen, F.B.; van Heerde, P.

1989-03-01

The range of radiation-induced changes in fine needle aspiration (FNA) smears of the breast is described. In 41 of more than 800 patients who underwent breast-conserving treatment, a palpable breast lesion developed, and FNA was performed. In six cases, a recurrent carcinoma was present. In the remaining cases, three patterns of nonneoplastic lesions could be discerned: epithelial atypia (14 cases), fat necrosis (10 cases) and poorly cellular smears without epithelial atypia or fat necrosis (13 cases). It is important to be familiar with the patterns of radiation-induced epithelial atypia, since such atypia may lead to a misdiagnosis of recurrent carcinoma.more » These atypical cells may show impressive anisocytosis and anisonucleosis; however, the nuclear/cytoplasmic ratio remains normal and an admixture of bipolar cells is present. Cell dissociation and necrotic cell debris, as often seen in breast cancer smears, were never encountered in FNA smears from radiated nonneoplastic breasts.« less

Stage III Melanoma in the Axilla: Patterns of Regional Recurrence After Surgery With and Without Adjuvant Radiation Therapy

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

Pinkham, Mark B., E-mail: mark.pinkham@health.qld.gov.au; University of Queensland, Brisbane; Foote, Matthew C.

Purpose: To describe the anatomic distribution of regionally recurrent disease in patients with stage III melanoma in the axilla after curative-intent surgery with and without adjuvant radiation therapy. Methods and Materials: A single-institution, retrospective analysis of a prospective database of 277 patients undergoing curative-intent treatment for stage III melanoma in the axilla between 1992 and 2012 was completed. For patients who received radiation therapy and those who did not, patterns of regional recurrence were analyzed, and univariate analyses were performed to assess for potential factors associated with location of recurrence. Results: There were 121 patients who received adjuvant radiation therapymore » because their clinicopathologic features conferred a greater risk of regional recurrence. There were 156 patients who received no radiation therapy. The overall axillary control rate was 87%. There were 37 patients with regional recurrence; 17 patients had received adjuvant radiation therapy (14%), and 20 patients (13%) had not. The likelihood of in-field nodal recurrence was significantly less in the adjuvant radiation therapy group (P=.01) and significantly greater in sites adjacent to the axilla (P=.02). Patients with high-risk clinicopathologic features who did not receive adjuvant radiation therapy also tended to experience in-field failure rather than adjacent-field failure. Conclusions: Patients who received adjuvant radiation therapy were more likely to experience recurrence in the adjacent-field regions rather than in the in-field regions. This may not simply reflect higher-risk pathology. Using this data, it may be possible to improve outcomes by reducing the number of adjacent-field recurrences after adjuvant radiation therapy.« less

The Experiences and Challenges in Drilling into Semi molten or Molten Intrusive in Menengai Geothermal Field

NASA Astrophysics Data System (ADS)

Mortensen, A. K.; Mibei, G. K.

2017-12-01

Drilling in Menengai has experienced various challenges related to drilling operations and the resource itself i.e. quality discharge fluids vis a vis gas content. The main reason for these challenges is related to the nature of rocks encountered at depths. Intrusives encountered within Menengai geothermal field have been group into three based on their geological characteristics i.e. S1, S2 and S3.Detailed geology and mineralogical characterization have not been done on these intrusive types. However, based on physical appearances, S1 is considered as a diorite dike, S2 is syenite while S3 is molten rock material. This paper summarizes the experiences in drilling into semi molten or molten intrusive (S3).

Europa's differentiated internal structure: inferences from two Galileo encounters.

PubMed

Anderson, J D; Lau, E L; Sjogren, W L; Schubert, G; Moore, W B

1997-05-23

Doppler data generated with the Galileo spacecraft's radio carrier wave during two Europa encounters on 19 December 1996 (E4) and 20 February 1997 (E6) were used to measure Europa's external gravitational field. The measurements indicate that Europa has a predominantly water ice-liquid outer shell about 100 to 200 kilometers thick and a deep interior with a density in excess of about 4000 kilograms per cubic meter. The deep interior could be a mixture of metal and rock or it could consist of a metal core with a radius about 40 percent of Europa's radius surrounded by a rock mantle with a density of 3000 to 3500 kilograms per cubic meter. The metallic core is favored if Europa has a magnetic field.

Growing the Nuclear Workforce Through Outreach

NASA Astrophysics Data System (ADS)

Kilburn, Micha

2015-10-01

Many students don't encounter physics in the classroom until college or the end of high school. Most college students never encounter nuclear physics in the classroom. In order to grow the nuclear science workforce, students need to be aware of the field much earlier in the education. However, teaching teens about nuclear science can be a daunting task at the outset. I will present and describe successful outreach curricula and programs that can be duplicated by any college, university or laboratory. These include workshops for boy scouts and girl scouts as well as teaching nuclear science with magnetic marbles. I will also present some results from assessments of JINA-CEE's more intensive programs aimed at recruiting youth to the field. JINA-CEE

Pomegranate Supplementation Improves Affective and Motor Behavior in Mice after Radiation Exposure

PubMed Central

Dulcich, Melissa S.; Hartman, Richard E.

2013-01-01

Currently, NASA has plans for extended space travel, and previous research indicates that space radiation can have negative effects on cognitive skills as well as physical and mental health. With long-term space travel, astronauts will be exposed to greater radiation levels. Research shows that an antioxidant-enriched diet may offer some protection against the cellular effects of radiation and may provide significant neuroprotection from the effects of radiation-induced cognitive and behavioral skill deficits. Ninety-six C57BL/6 mice (48 pomegranate fed and 48 control) were irradiated with proton radiation (2 Gy), and two-month postradiation behaviors were assessed using a battery of behavioral tests to measure cognitive and motor functions. Proton irradiation was associated with depression-like behaviors in the tail suspension test, but this effect was ameliorated by the pomegranate diet. Males, in general, displayed worse coordination and balance than females on the rotarod task, and the pomegranate diet ameliorated this effect. Overall, it appears that proton irradiation, which may be encountered in space, may induce a different pattern of behavioral deficits in males than females and that a pomegranate diet may confer protection against some of those effects. PMID:23662154

'A good fit?' Bringing the sociology of footwear to the clinical encounter in podiatry services: a narrative review.

PubMed

Nicholls, Emily; Robinson, Victoria; Farndon, Lisa; Vernon, Wesley

2018-01-01

This narrative review explores the ways in which drawing on theories and methods used in sociological work on footwear and identity can contribute to healthcare research with podiatrists and their patients, highlighting recent research in this field, implications for practice and potential areas for future development.Traditionally, research within Podiatry Services has tended to adopt a quantitative, positivist focus, developing separately from a growing body of sociological work exploring the importance of shoes in constructing identity and self-image. Bringing qualitative research drawing on sociological theory and methods to the clinical encounter has real potential to increase our understanding of patient values, motivations and - crucially - any barriers to adopting 'healthier' footwear that they may encounter. Such work can help practitioners to understand why patients may resist making changes to their footwear practices, and help us to devise new ways for practitioners to explore and ultimately break down individual barriers to change (including their own preconceptions as practitioners). This, in turn, may lead to long-term, sustainable changes to footwear practices and improvements in foot health for those with complex health conditions and the wider population. A recognition of the complex links between shoes and identity is opening up space for discussion of patient resistance to footwear changes, and paving the way for future research in this field beyond the temporary 'moment' of the clinical encounter.

An Assessment of an Oral Examination Format for Evaluating Clinical Competence in Emergency Medicine.

ERIC Educational Resources Information Center

Solomon, David J.; And Others

1990-01-01

In July 1989 the American Board of Emergency Medicine conducted a field test of the oral recertification examination process. Sixteen examiners and 25 examinees participated in the field test. The examination included 3 chart-stimulated recall and 3 simulated-patient encounter cases. (MLW)

Process Improvement Education with Professionals in the Addiction Treatment Field

ERIC Educational Resources Information Center

Pulvermacher, Alice

2006-01-01

Continuing education is being provided to professionals in the addiction treatment field to help them develop skills in process improvement and better meet the needs and requests they encounter. Access and retention of individuals seeking addiction treatment have been two of the greatest challenges addiction treatment professionals face.…

Nimbus 7 earth radiation budget wide field of view climate data set improvement. II - Deconvolution of earth radiation budget products and consideration of 1982-1983 El Nino event

NASA Technical Reports Server (NTRS)

Ardanuy, Phillip E.; Hucek, Richard R.; Groveman, Brian S.; Kyle, H. Lee

1987-01-01

A deconvolution technique is employed that permits recovery of daily averaged earth radiation budget (ERB) parameters at the top of the atmosphere from a set of the Nimbus 7 ERB wide field of view (WFOV) measurements. Improvements in both the spatial resolution of the resultant fields and in the fidelity of the time averages is obtained. The algorithm is evaluated on a set of months during the period 1980-1983. The albedo, outgoing long-wave radiation, and net radiation parameters are analyzed. The amplitude and phase of the quasi-stationary patterns that appear in the spatially deconvolved fields describe the radiation budget components for 'normal' as well as the El Nino/Southern Oscillation (ENSO) episode years. They delineate the seasonal development of large-scale features inherent in the earth's radiation budget as well as the natural variability of interannual differences. These features are underscored by the powerful emergence of the 1982-1983 ENSO event in the fields displayed. The conclusion is that with this type of resolution enhancement, WFOV radiometers provide a useful tool for the observation of the contemporary climate and its variability.

Fluid dynamic aspects of jet noise generation

NASA Technical Reports Server (NTRS)

1974-01-01

The location of the noise sources within jet flows, their relative importance to the overall radiated field, and the mechanisms by which noise generation occurs, are studied by detailed measurements of the level and spectral composition of the radiated sound in the far field. Directional microphones are used to isolate the contribution to the radiated sound of small regions of the flow, and for cross-correlation between the radiated acoustic field and either the velocity fluctuations or the pressure fluctuations in the source field. Acquired data demonstrate the supersonic convection of the acoustic field and the resulting limited upstream influence of the signal source, as well as a possible increase of signal strength as it propagates toward the centerline of the flow.

Engineering Near-Field Transport of Energy using Nanostructured Materials

DTIC Science & Technology

2015-12-12

increasingly important for a wide range of nanotechnology applications. Recent computational studies on near- field radiative heat transfer (NFRHT) suggest...SECURITY CLASSIFICATION OF: The transport of heat at the nanometer scale is becoming increasingly important for a wide range of nanotechnology...applications. Recent computational studies on near- field radiative heat transfer (NFRHT) suggest that radiative energy transport between suitably chosen

Identification of the Radiative and Nonradiative Parts of a Wave Field

NASA Astrophysics Data System (ADS)

Hoenders, B. J.; Ferwerda, H. A.

2001-08-01

We present a method for decomposing a wave field, described by a second-order ordinary differential equation, into a radiative component and a nonradiative one, using a biorthonormal system related to the problem under consideration. We show that it is possible to select a special system such that the wave field is purely radiating. We discuss the differences and analogies with approaches which, unlike our approach, start from the corresponding sources of the field.

Regulatory aspects of radiation protection.

PubMed

Janssens, A; Sarro Vaquero, M

2005-01-01

The paper introduces the projects launched by the European Community to foster prospects in dosimetry, radiation protection and best use of equipment in the medical field. These projects are put in perspective with the European legal framework for radiation protection, in particular, the Basic Safety Standards Directive, the Medical Exposures Directive and the Directive on High-Activity Sealed Sources. A summary is given of the overall mission statements of the commission services in the field of radiation protection, including the field of research, and how they relate to other actions in the overall health policy of the EU. In conclusion, a number of priority areas for future work in the medical field are highlighted.

An analysis of the radiation from apertures in curved surfaces by the geometrical theory of diffraction. [ray technique for electromagnetic fields

NASA Technical Reports Server (NTRS)

Pathak, P. H.; Kouyoumjian, R. G.

1974-01-01

In this paper the geometrical theory of diffraction is extended to treat the radiation from apertures of slots in convex perfectly conducting surfaces. It is assumed that the tangential electric field in the aperture is known so that an equivalent infinitesimal source can be defined at each point in the aperture. Surface rays emanate from this source which is a caustic of the ray system. A launching coefficient is introduced to describe the excitation of the surface ray modes. If the field radiated from the surface is desired, the ordinary diffraction coefficients are used to determine the field of the rays shed tangentially from the surface rays. The field of the surface ray modes is not the field on the surface; hence if the mutual coupling between slots is of interest, a second coefficient related to the launching coefficient must be employed. In the region adjacent to the shadow boundary, the component of the field directly radiated from the source is represented by Fock-type functions. In the illuminated region the incident radiation from the source (this does not include the diffracted field components) is treated by geometrical optics. This extension of the geometrical theory of diffraction is applied to calculate the radiation from slots on elliptic cylinders, spheres, and spheroids.

Next-to-next-to-leading order gravitational spin-orbit coupling via the effective field theory for spinning objects in the post-Newtonian scheme

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

Levi, Michele; Steinhoff, Jan, E-mail: michele.levi@upmc.fr, E-mail: jan.steinhoff@aei.mpg.de

2016-01-01

We implement the effective field theory for gravitating spinning objects in the post-Newtonian scheme at the next-to-next-to-leading order level to derive the gravitational spin-orbit interaction potential at the third and a half post-Newtonian order for rapidly rotating compact objects. From the next-to-next-to-leading order interaction potential, which we obtain here in a Lagrangian form for the first time, we derive straightforwardly the corresponding Hamiltonian. The spin-orbit sector constitutes the most elaborate spin dependent sector at each order, and accordingly we encounter a proliferation of the relevant Feynman diagrams, and a significant increase of the computational complexity. We present in detail themore » evaluation of the interaction potential, going over all contributing Feynman diagrams. The computation is carried out in terms of the ''nonrelativistic gravitational'' fields, which are advantageous also in spin dependent sectors, together with the various gauge choices included in the effective field theory for gravitating spinning objects, which also optimize the calculation. In addition, we automatize the effective field theory computations, and carry out the automated computations in parallel. Such automated effective field theory computations would be most useful to obtain higher order post-Newtonian corrections. We compare our Hamiltonian to the ADM Hamiltonian, and arrive at a complete agreement between the ADM and effective field theory results. Finally, we provide Hamiltonians in the center of mass frame, and complete gauge invariant relations among the binding energy, angular momentum, and orbital frequency of an inspiralling binary with generic compact spinning components to third and a half post-Newtonian order. The derivation presented here is essential to obtain further higher order post-Newtonian corrections, and to reach the accuracy level required for the successful detection of gravitational radiation.« less

Drilling into Rhyolitic Magma at Shallow depth at Krafla Volcanic Complex, NE-Iceland

NASA Astrophysics Data System (ADS)

Mortensen, A. K.; Markússon, S. H.; Gudmundsson, Á.; Pálsson, B.

2017-12-01

Krafla volcanic complex in NE-Iceland is an active volcano but the latest eruption was the Krafla Fires in 1975-1984. Though recent volcanic activity has consisted of basaltic fissure eruptions, then it is rhyolitic magma that has been intercepted on at least two occasions while drilling geothermal production wells in the geothermal field suggesting a layered magma plumbing system beneath the Krafla volcanic complex. In 2008 quenched rhyolitic glass was retrieved from the bottom of well KJ-39, which is 2865 m deep ( 2571 m true vertical depth). In 2009 magma was again encountered at an even shallower depth and in more than 2,5 km distance from the bottom of well KJ-39, but in 2009 well IDDP-1 was drilled into magma three times just below 2100 m depth. Only on the last occasion was quenched glass retrieved to confirm that magma had been encountered. In well KJ-39 the quenched glass was rhyolitic in composition. The glass contained resorbed minerals of plagioclase, clinopyroxene and titanomagnetite, but the composition of the glass resembles magma that has formed by partial melting of hydrated basalt. The melt was encountered among cuttings from impermeable, coarse basaltic intrusives at a depth, where the well was anticipated to penetrate the Hólseldar volcanic fissure. In IDDP-1 the quenched glass was also rhyolitic in composition. The glass contained less than 5% of phenocrysts, but the phenocryst assemblage included andesine plagioclase, augite, pigeonite, and titanomagnetite. At IDDP-1 the melt was encountered below a permeable zone composed of fine to coarse grained felsite and granophyre. The disclosure of magma in two wells at Krafla volcanic complex verify that rhyolitic magma can be encountered at shallow depth across a larger area within the caldera. The encounter of magma at shallow depth conforms with that superheated conditions have been found at >2000 m depth in large parts of Krafla geothermal field.

Declining Orangutan Encounter Rates from Wallace to the Present Suggest the Species Was Once More Abundant

PubMed Central

Meijaard, Erik; Welsh, Alan; Ancrenaz, Marc; Wich, Serge; Nijman, Vincent; Marshall, Andrew J.

2010-01-01

Background Bornean orangutans (Pongo pygmaeus) currently occur at low densities and seeing a wild one is a rare event. Compared to present low encounter rates of orangutans, it is striking how many orangutan each day historic collectors like Alfred Russel Wallace were able to shoot continuously over weeks or even months. Does that indicate that some 150 years ago encounter rates with orangutans, or their densities, were higher than now? Methodology/Principal Findings We test this hypothesis by quantifying encounter rates obtained from hunting accounts, museum collections, and recent field studies, and analysing whether there is a declining trend over time. Logistic regression analyses of our data support such a decline on Borneo between the mid-19th century and the present. Even when controlled for variation in the size of survey and hunting teams and the durations of expeditions, mean daily encounter rates appear to have declined about 6-fold in areas with little or no forest disturbance. Conclusions/Significance This finding has potential consequences for our understanding of orangutans, because it suggests that Bornean orangutans once occurred at higher densities. We explore potential explanations—habitat loss and degradation, hunting, and disease—and conclude that hunting fits the observed patterns best. This suggests that hunting has been underestimated as a key causal factor of orangutan density and distribution, and that species population declines have been more severe than previously estimated based on habitat loss only. Our findings may require us to rethink the biology of orangutans, with much of our ecological understanding possibly being based on field studies of animals living at lower densities than they did historically. Our approach of quantifying species encounter rates from historic data demonstrates that this method can yield valuable information about the ecology and population density of species in the past, providing new insight into species' conservation needs. PMID:20711451

Thirty-sixth Lauriston S. Taylor Lecture on radiation protection and measurements--from the field to the laboratory and back: the what ifs, wows, and who cares of radiation biology.

PubMed

Brooks, Antone L

2013-11-01

My scientific journey started at the University of Utah chasing fallout. It was on everything, in everything, and was distributed throughout the ecosystem. This resulted in radiation doses to humans and caused me great concern. From this concern I asked the question, "Are there health effects from these radiation doses and levels of radioactive contamination?" I have invested my scientific career trying to address this basic question. While conducting research, I got acquainted with many of the What ifs of radiation biology. The major What if in my research was, "What if we have underestimated the radiation risk for internally-deposited radioactive material?" While conducting research to address this important question, many other What ifs came up related to dose, dose rate, and dose distribution. I also encountered a large number of Wows. One of the first was when I went from conducting environmental fallout studies to research in a controlled laboratory. The activity in fallout was expressed as pCi L⁻¹, whereas it was necessary to inject laboratory animals with μCi g⁻¹ body weight to induce measurable biological changes, chromosome aberrations, and cancer. Wow! That is seven to nine orders of magnitude above the activity levels found in the environment. Other Wows have made it necessary for the field of radiation biology to make important paradigm shifts. For example, one shift involved changing from "hit theory" to total tissue responses as the result of bystander effects. Finally, Who cares? While working at U.S. Department of Energy headquarters and serving on many scientific committees, I found that science does not drive regulatory and funding decisions. Public perception and politics seem to be major driving forces. If scientific data suggested that risk had been underestimated, everyone cared. When science suggested that risk had been overestimated, no one cared. This result-dependent Who cares? was demonstrated as we tried to generate interactions by holding meetings with individuals involved in basic low-dose research, regulators, and the news media. As the scientists presented their "exciting data" that suggested that risk was overestimated, many of the regulators simply said, "We cannot use such data." The newspaper people said, "It is not possible to get such information by my editors." In spite of these difficulties, research results from basic science must be made available and considered by members of the public as well as by those that make regulatory recommendations. Public outreach of the data is critical and must continue to be a future focus to address properly the question of, "Who cares?" My journey in science, like many of yours, has been a mixture of chasing money, beatings, and the joys of unique and interesting research results. Perhaps through our experiences, we can improve research environments, funding, and use of the valuable information that is generated. Scientists that study at all levels of biological organization, from the environment to the laboratory and human epidemiology, must share expertise and data to address the What Ifs, Wows, and Who Cares of radiation biology.

Vulnerability of OFDR-based distributed sensors to radiations

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

Rizzolo, S.; Dipartimento di Fisica e Chimica, Universita di Palermo, Viale delle Scienze Parco d'Orleans II, Ed. 17, 90128 Palermo; Areva Centre Technique, Boulevard de l'Industrie, 71200, Le Creusot

2015-07-01

Silica-based optical fibers have recently attracted much interest for their use in harsh environments such as the ones encountered in space, military or high energy physics applications. Small size, fast response, light weight and immunity to electromagnetic fields are favorable advantages that often become decisive for fiber sensing to be chosen over other conventional sensing technologies. As an important and representative example, Fukushima's accident highlighted weaknesses in the safety of nuclear power plants. Since, one of the strategic research axis of the nuclear industry is devoted to the development of novel technologies and sensors to enhance and reinforce the safetymore » in nuclear power plants, especially in the case of accidental conditions associated with a strong increase of the constraints applied to the fiber-based system. The objective of this research field is to develop classes of distributed fiber-based sensors using scattering-based techniques, powerful solutions for various measurands measurement. Optical fiber properties, indeed, depend on several external parameters such as temperature, strain and therefore the fiber itself can be used as the sensitive element. Different classes of fiber-based sensing techniques have been recently investigated such as Fiber Bragg Gratings (FBGs) for discrete measurements and Brillouin, Raman and Rayleigh [8,9] scattering based techniques for distributed measurements of various environmental parameters. Whereas Brillouin and Raman sensor resolutions remain in the range of one meter, the advantage of Rayleigh scattering based technique is that it offers very high spatial resolution from 1 cm down to few μm over several hundred meters of fiber length down to few meters respectively. For nuclear industry, integrating fibers-based sensors has to improve the performances (resolution, operating range,...) of security systems in current nuclear power plants (NPPs) and offers new alternative technologies that may overcome the issues identified for next generation of NPPs. Such integration will only be possible if the OFDR based systems are able to resist to the constraints associated with industrial environments, one of the most constraining being the presence of high level of radiations. In this work, we carry out a systematic study to highlight the OFDR interest and sensitivity to probe the optical samples at high irradiation dose levels. The responses of five optical fibers types, from radiation hardened to radiation sensitive ones, are investigated to explore the influence of both the material compositions and the γ-irradiation on the ODFR sensors. Using these samples, we should highlight the influence of the core dopant concentration on the observed radiation-induced changes as well as the difference observed when the cladding is either radiation resistant or radiation sensitive. Our samples were irradiated using a {sup 60}Co source facility reaching total doses varying from 1 MGy up to a maximum of 10 MGy. All the measurements are performed after diverse months from irradiation to study permanents effects induced from these high γ-rays doses. We'll present at the conference all the experimental results acquired and use them to estimate the potential of OFDR-based systems for operation in radiation environments. (authors)« less

Understanding Radiation Thermometry. Part II

NASA Technical Reports Server (NTRS)

Risch, Timothy K.

2015-01-01

This document is a two-part course on the theory and practice of radiation thermometry. Radiation thermometry is the technique for determining the temperature of a surface or a volume by measuring the electromagnetic radiation it emits. This course covers the theory and practice of radiative thermometry and emphasizes the modern application of the field using commercially available electronic detectors and optical components. The course covers the historical development of the field, the fundamental physics of radiative surfaces, along with modern measurement methods and equipment.

Understanding Radiation Thermometry. Part I

NASA Technical Reports Server (NTRS)

Risch Timothy K.

2015-01-01

This document is a two-part course on the theory and practice of radiation thermometry. Radiation thermometry is the technique for determining the temperature of a surface or a volume by measuring the electromagnetic radiation it emits. This course covers the theory and practice of radiative thermometry and emphasizes the modern application of the field using commercially available electronic detectors and optical components. The course covers the historical development of the field, the fundamental physics of radiative surfaces, along with modern measurement methods and equipment.

Optical fibres in the radiation environment of CERN

NASA Astrophysics Data System (ADS)

Guillermain, E.

2017-11-01

CERN, the European Organization for Nuclear Research (in Geneva, Switzerland), is home to a complex scientific instrument: the 27-kilometre Large Hadron Collider (LHC) collides beams of high-energy particles at close to the speed of light. Optical fibres are widely used at CERN, both in surface areas (e.g. for inter-building IT networks) and in the accelerator complex underground (e.g. for cryogenics, vacuum, safety systems). Optical fibres in the accelerator are exposed to mixed radiation fields (mainly composed of protons, pions, neutrons and other hadrons, gamma rays and electrons), with dose rates depending on the particular installation zone, and with radiation levels often significantly higher than those encountered in space. In the LHC and its injector chain radiation levels range from relatively low annual doses of a few Gy up to hundreds of kGy. Optical fibres suffer from Radiation Induced Attenuation (RIA, expressed in dB per unit length) that affect light transmission and which depends on the irradiation conditions (e.g. dose rate, total dose, temperature). In the CERN accelerator complex, the failure of an optical link can affect the proper functionality of control or monitoring systems and induce the interruption of the accelerator operation. The qualification of optical fibres for installation in critical radiation areas is therefore crucial. Thus, all optical fibre types installed in radiation areas at CERN are subject to laboratory irradiation tests, in order to evaluate their RIA at different total dose and dose rates. This allows the selection of the appropriate optical fibre type (conventional or radiation resistant) compliant with the requirements of each installation. Irradiation tests are performed in collaboration with Fraunhofer INT (irradiation facilities and expert team in Euskirchen, Germany). Conventional off-the-shelf optical fibres can be installed for optical links exposed to low radiation levels (i.e. annual dose typically below few kGy). Nevertheless, the conventional optical fibres must be carefully qualified as a spread in RIA of factor 10 is observed among optical fibres of different types and dopants. In higher radiation areas, special radiation resistant optical fibres are installed. For total dose above 1 kGy, the RIA of these special optical fibres is at least 10 times lower than the conventional optical fibres RIA at same irradiation conditions. 2400 km of these special radiation resistant optical fibres were recently procured at CERN. As part of this procurement process, a quality assurance plan including the irradiation testing of all 65 produced batches was set up. This presentation will review the selection process of the appropriate optical fibre types to be installed in the radiation environment of CERN. The methodology for choosing the irradiation parameters for the laboratory tests will be discussed together with an overview of the RIA of different optical fibre types under several irradiation conditions.

radiation and electric field induced effects on the order-disorder phase in lithium sodium sulphate crystals

NASA Astrophysics Data System (ADS)

Hamed, A. E.; Kassem, M. E.; El-Wahidy, E. F.; El-Abshehy, M. A.

1995-03-01

The temperature dependence of specific heat at constant pressure, Cp(T), has been measured for lithium sodium sulphate, LiNaSo4 crystals, at different ?-radiation doses and external bias electric field (Eb), in the temperature range 300-900 K. A nonlinear dependence of transition temperature, T1 and a remarkable change in the thermodynamic parameters, were obtained as the effect of both electric field and ?-radiation. The effect of ?-radiation doses on the phase transition in LiNaSO4 crystals was explained as due to an internal bias field, Eb, originating from the interaction of polar defects with the order parameter of the host lattice. The internal bias field effect on the behaviour of Cp(T) in LiNaSO4 crystals was similar to that of the external electric field (E).

Basic theory for polarized, astrophysical maser radiation in a magnetic field

NASA Technical Reports Server (NTRS)

Watson, William D.

1994-01-01

Fundamental alterations in the theory and resulting behavior of polarized, astrophysical maser radiation in the presence of a magnetic field have been asserted based on a calculation of instabilities in the radiative transfer. I reconsider the radiative transfer and find that the relevant instabilities do not occur. Calculational errors in the previous investigation are identified. In addition, such instabilities would have appeared -- but did not -- in the numerous numerical solutions to the same radiative transfer equations that have been presented in the literature. As a result, all modifications that have been presented in a recent series of papers (Elitzur 1991, 1993) to the theory for polarized maser radiation in the presence of a magnetic field are invalid. The basic theory is thus clarified.

Parameter estimation applied to Nimbus 6 wide-angle longwave radiation measurements

NASA Technical Reports Server (NTRS)

Green, R. N.; Smith, G. L.

1978-01-01

A parameter estimation technique was used to analyze the August 1975 Nimbus 6 Earth radiation budget data to demonstrate the concept of deconvolution. The longwave radiation field at the top of the atmosphere is defined from satellite data by a fifth degree and fifth order spherical harmonic representation. The variations of the major features of the radiation field are defined by analyzing the data separately for each two-day duty cycle. A table of coefficient values for each spherical harmonic representation is given along with global mean, gradients, degree variances, and contour plots. In addition, the entire data set is analyzed to define the monthly average radiation field.

Physical activity communication between oncology providers and patients with early-stage breast, colon, or prostate cancer.

PubMed

Nyrop, Kirsten A; Deal, Allison M; Williams, Grant R; Guerard, Emily J; Pergolotti, Mackenzi; Muss, Hyman B

2016-02-01

National guidelines recommend that patients with a cancer diagnosis engage in regular physical activity to reduce cancer-related fatigue, maintain quality of life and physical function, and improve overall prognosis and survival. This study investigates oncology provider communications about physical activity during routine clinic visits with patients with early-stage breast, colon, or prostate cancer. This study used a retrospective chart review for documentation of inquiries or recommendations pertaining to physical activity in clinician notes and after-visit patient summaries. In a 1-month period, 55 oncology providers had 361 encounters (clinic visits) with early-stage cancer patients. Thirty-five percent of these encounters included a provider communication about "physical activity," "exercise," or "activity." Encounters with a medical oncologist resulted in a physical activity communication 55% of the time, whereas encounters with other clinician specialties did so 20% of the time (P < .0001). The likelihood of a physical activity communication increased with patient age (P < .001). When the encounter was with a patient who was being seen for surveillance, chemotherapy, or endocrine treatment, the rate of physical activity communications was significantly higher (46%, 37%, and 58%, respectively) than the rate when the visit was during radiation treatment or surgery (6% and 19%, respectively; P < .0001). This study shows that it is feasible for oncology providers to have physical activity communications during routine clinic visits; however, the frequency of physical activity communications varies among providers. Interventions are needed to remind and encourage all oncology providers to encourage their patients with early-stage cancer to be physically active. . © 2015 American Cancer Society.

Modeling of Dynamic Behavior of Carbon Fiber-Reinforced Polymer (CFRP) Composite under X-ray Radiation.

PubMed

Zhang, Kun; Tang, Wenhui; Fu, Kunkun

2018-01-16

Carbon fiber-reinforced polymer (CFRP) composites have been increasingly used in spacecraft applications. Spacecraft may encounter highenergy-density X-ray radiation in outer space that can cause severe damage. To protect spacecraft from such unexpected damage, it is essential to predict the dynamic behavior of CFRP composites under X-ray radiation. In this study, we developed an in-house three-dimensional explicit finite element (FEM) code to investigate the dynamic responses of CFRP composite under X-ray radiation for the first time, by incorporating a modified PUFF equation-of-state. First, the blow-off impulse (BOI) momentum of an aluminum panel was predicted by our FEM code and compared with an existing radiation experiment. Then, the FEM code was utilized to determine the dynamic behavior of a CFRP composite under various radiation conditions. It was found that the numerical result was comparable with the experimental one. Furthermore, the CFRP composite was more effective than the aluminum panel in reducing radiation-induced pressure and BOI momentum. The numerical results also revealed that a 1 keV X-ray led to vaporization of surface materials and a high-magnitude compressive stress wave, whereas a low-magnitude stress wave was generated with no surface vaporization when a 3 keV X-ray was applied.

Modeling of Dynamic Behavior of Carbon Fiber-Reinforced Polymer (CFRP) Composite under X-ray Radiation

PubMed Central

Zhang, Kun; Tang, Wenhui; Fu, Kunkun

2018-01-01

Carbon fiber-reinforced polymer (CFRP) composites have been increasingly used in spacecraft applications. Spacecraft may encounter highenergy-density X-ray radiation in outer space that can cause severe damage. To protect spacecraft from such unexpected damage, it is essential to predict the dynamic behavior of CFRP composites under X-ray radiation. In this study, we developed an in-house three-dimensional explicit finite element (FEM) code to investigate the dynamic responses of CFRP composite under X-ray radiation for the first time, by incorporating a modified PUFF equation-of-state. First, the blow-off impulse (BOI) momentum of an aluminum panel was predicted by our FEM code and compared with an existing radiation experiment. Then, the FEM code was utilized to determine the dynamic behavior of a CFRP composite under various radiation conditions. It was found that the numerical result was comparable with the experimental one. Furthermore, the CFRP composite was more effective than the aluminum panel in reducing radiation-induced pressure and BOI momentum. The numerical results also revealed that a 1 keV X-ray led to vaporization of surface materials and a high-magnitude compressive stress wave, whereas a low-magnitude stress wave was generated with no surface vaporization when a 3 keV X-ray was applied. PMID:29337891

Graphite and ablative material response to CO2 laser, carbon-arc, and xenon-arc radiation

NASA Technical Reports Server (NTRS)

Brewer, W. D.

1976-01-01

The behavior was investigated of graphite and several charring ablators in a variety of high-radiative heat-flux environments. A commercial-grade graphite and nine state-of-the-art charring ablators were subjected to various radiative environments produced by a CO2 laser and a carbon arc. Graphite was also tested in xenon-arc radiation. Heat-flux levels ranged from 10 to 47 MW/sq m. Tests were conducted in air, nitrogen, helium, and a CO2-N2 mixture which simulated the Venus atmosphere. The experimental results were compared with theoretical results obtained with a one-dimensional charring-ablator analysis and a two-dimensional subliming-ablator analysis. Neither the graphite nor the charring ablators showed significant differences in appearance or microstructure after testing in the different radiative environments. The performance of phenolic nylon and graphite was predicted satisfactorily with existing analyses and published material property data. Good agreement between experimental and analytical results was obtained by using sublimation parameters from a chemical nonequilibrium analysis of graphite sublimation. Some charring ablators performed reasonably well and could withstand radiative fluxes of the level encountered in certain planetary entries. Other materials showed excessive surface recession and/or large amounts of cracking and spalling, and appear to be unsuitable for severe radiative environments.

A possible pole problem in the formula for klystron gap fields

NASA Technical Reports Server (NTRS)

Kosmahl, H. G.

1977-01-01

In isolated cases a pole may be encountered in a previously published solution for the fields in a klystron gap. Formulas, permitting the critical combinations of parameters to be defined, are presented. It is noted that the region of inaccuracy surrounding the pole is sufficiently small and that a 0.1% change in the field changing parameter is enough to avoid it.

Gamma radiation field intensity meter

DOEpatents

Thacker, Louis H.

1994-01-01

A gamma radiation intensity meter measures dose rate of a radiation field. The gamma radiation intensity meter includes a tritium battery emitting beta rays generating a current which is essentially constant. Dose rate is correlated to an amount of movement of an electroscope element charged by the tritium battery. Ionizing radiation decreases the voltage at the element and causes movement. A bleed resistor is coupled between the electroscope support element or electrode and the ionization chamber wall electrode.

Gamma radiation field intensity meter

DOEpatents

Thacker, Louis H.

1995-01-01

A gamma radiation intensity meter measures dose rate of a radiation field. The gamma radiation intensity meter includes a tritium battery emitting beta rays generating a current which is essentially constant. Dose rate is correlated to an amount of movement of an electroscope element charged by the tritium battery. Ionizing radiation decreases the voltage at the element and causes movement. A bleed resistor is coupled between the electroscope support element or electrode and the ionization chamber wall electrode.

TH-EF-204-00: AAPM-AMPR (Russia)-SEFM (Spain) Joint Course On Challenges and Advantages of Small Field Radiation Treatment Techniques

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

NONE

Joanna E. Cygler, Jan Seuntjens, J. Daniel Bourland, M. Saiful Huq, Josep Puxeu Vaque, Daniel Zucca Aparicio, Tatiana Krylova, Yuri Kirpichev, Eric Ford, Caridad Borras Stereotactic Radiation Therapy (SRT) utilizes small static and dynamic (IMRT) fields, to successfully treat malignant and benign diseases using techniques such as Stereotactic Radiosurgery (SRS) and Stereotactic Body Radiation Therapy (SBRT). SRT is characterized by sharp dose gradients for individual fields and their resultant dose distributions. For appropriate targets, small field radiotherapy offers improved treatment quality by allowing better sparing of organs at risk while delivering the prescribed target dose. Specialized small field treatment deliverymore » systems, such as robotic-controlled linear accelerators, gamma radiosurgery units, and dynamic arc linear accelerators may utilize rigid fixation, image guidance, and tumor tracking, to insure precise dose delivery to static or moving targets. However, in addition to great advantages, small field delivery techniques present special technical challenges for dose calibration due to unique geometries and small field sizes not covered by existing reference dosimetry protocols such as AAPM TG-51 or IAEA TRS 398. In recent years extensive research has been performed to understand small field dosimetry and measurement instrumentation. AAPM, IAEA and ICRU task groups are expected to provide soon recommendations on the dosimetry of small radiation fields. In this symposium we will: 1] discuss the physics, instrumentation, methodologies and challenges for small field radiation dose measurements; 2] review IAEA and ICRU recommendations on prescribing, recording and reporting of small field radiation therapy; 3] discuss selected clinical applications and technical aspects for specialized image-guided, small field, linear accelerator based treatment techniques such as IMRT and SBRT. Learning Objectives: To learn the physics of small fields in contrast to dosimetry of conventional fields To learn about detectors suitable for small fields To learn about the role of Monte Carlo simulations in determination of small field output factors To provide an overview of the IAEA small field dosimetry recommendations To provide an overview of the content of the ICRU report on Prescribing, Reporting and Recording of Small Field Radiation Therapy. To learn about special technical considerations in delivering IMRT and SBRT treatments To appreciate specific challenges of IMRT implementation J. Seuntjens, Natural Sciences and Engineering Research Council; Canadian Institutes of Health Research.« less

TH-EF-204-02: Small Field Radiation Therapy: Physics and Recent Recommendations From IAEA and ICRU

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

Seuntjens, J.

Joanna E. Cygler, Jan Seuntjens, J. Daniel Bourland, M. Saiful Huq, Josep Puxeu Vaque, Daniel Zucca Aparicio, Tatiana Krylova, Yuri Kirpichev, Eric Ford, Caridad Borras Stereotactic Radiation Therapy (SRT) utilizes small static and dynamic (IMRT) fields, to successfully treat malignant and benign diseases using techniques such as Stereotactic Radiosurgery (SRS) and Stereotactic Body Radiation Therapy (SBRT). SRT is characterized by sharp dose gradients for individual fields and their resultant dose distributions. For appropriate targets, small field radiotherapy offers improved treatment quality by allowing better sparing of organs at risk while delivering the prescribed target dose. Specialized small field treatment deliverymore » systems, such as robotic-controlled linear accelerators, gamma radiosurgery units, and dynamic arc linear accelerators may utilize rigid fixation, image guidance, and tumor tracking, to insure precise dose delivery to static or moving targets. However, in addition to great advantages, small field delivery techniques present special technical challenges for dose calibration due to unique geometries and small field sizes not covered by existing reference dosimetry protocols such as AAPM TG-51 or IAEA TRS 398. In recent years extensive research has been performed to understand small field dosimetry and measurement instrumentation. AAPM, IAEA and ICRU task groups are expected to provide soon recommendations on the dosimetry of small radiation fields. In this symposium we will: 1] discuss the physics, instrumentation, methodologies and challenges for small field radiation dose measurements; 2] review IAEA and ICRU recommendations on prescribing, recording and reporting of small field radiation therapy; 3] discuss selected clinical applications and technical aspects for specialized image-guided, small field, linear accelerator based treatment techniques such as IMRT and SBRT. Learning Objectives: To learn the physics of small fields in contrast to dosimetry of conventional fields To learn about detectors suitable for small fields To learn about the role of Monte Carlo simulations in determination of small field output factors To provide an overview of the IAEA small field dosimetry recommendations To provide an overview of the content of the ICRU report on Prescribing, Reporting and Recording of Small Field Radiation Therapy. To learn about special technical considerations in delivering IMRT and SBRT treatments To appreciate specific challenges of IMRT implementation J. Seuntjens, Natural Sciences and Engineering Research Council; Canadian Institutes of Health Research.« less

Turbulence detection using radiosondes: plugging the gaps in the observation of turbulence

NASA Astrophysics Data System (ADS)

Marlton, Graeme; Harrison, Giles; Williams, Paul; Nicoll, Keri

2014-05-01

Turbulence costs the airline industry tens of millions of dollars each year, through damage to aircraft and injury to passengers. Clear-air turbulence (CAT) is particularly problematic, as it cannot be detected using remote sensing methods and we lack consistent observations to validate forecast models. Here we describe two specially adapted meteorological radiosondes that are used to measure turbulence. The first sensor consists of a Hall-effect magnetometer, which uses the Earth's magnetic field as a reference point, allowing the motion of the sonde to be measured. The second consists of an accelerometer that measures the accelerations the balloon encounters. A solar radiation sensor is mounted at the top of the package, to determine whether the sonde is in cloud. Results from multiple flights over Reading, UK in different conditions, show both sensors detecting turbulent regions near jet boundaries and above cloud tops, with the accelerometer recording values in excess of 6g in these regions. Case studies will show how these observations can be used to test the performance of a selection of empirical turbulence diagnostics initialised from ERA-interim data.

Voyager: Neptune Encounter Highlights

NASA Technical Reports Server (NTRS)

1989-01-01

Voyager encounter data are presented in computer animation (CA) and real (R) animation. The highlights include a view of 2 full rotations of Neptune. It shows spacecraft trajectory 'diving' over Neptune and intercepting Triton's orbit, depicting radiation and occulation zones. Also shown are a renegade orbit of Triton and Voyager's encounter with Neptune's Magnetopause. A model of the spacecraft's complex maneuvers during close encounters of Neptune and Triton is presented. A view from Earth of Neptune's occulation experiment is is shown as well as a recreation of Voyager's final pass. There is detail of Voyager's Image Compensation technique which produces Voyager images. Eighteen images were produced on June 22 - 23, 1989, from 57 million miles away. A 68 day sequence which provides a stroboscopic view - colorization approximates what is seen by the human eye. Real time images recorded live from Voyager on 8/24/89 are presented. Photoclinometry produced the topography of Triton. Three images are used to create a sequence of Neptune's rings. The globe of Neptune and 2 views of the south pole are shown as well as Neptune rotating. The rotation of a scooter is frozen in images showing differential motion. There is a view of rotation of the Great Dark Spot about its own axis. Photoclinometry provides a 3-dimensional perspective using a color mosaic of Triton images. The globe is used to indicate the orientation of Neptune's crescent. The east and west plumes on Triton are shown.

Neptune encounter highlights

NASA Astrophysics Data System (ADS)

1989-11-01

Voyager encounter data are presented in computer animation (CA) and real (R) animation. The highlights include a view of 2 full rotations of Neptune. It shows spacecraft trajectory 'diving' over Neptune and intercepting Triton's orbit, depicting radiation and occulation zones. Also shown are a renegade orbit of Triton and Voyager's encounter with Neptune's Magnetopause. A model of the spacecraft's complex maneuvers during close encounters of Neptune and Triton is presented. A view from Earth of Neptune's occulation experiment is is shown as well as a recreation of Voyager's final pass. There is detail of Voyager's Image Compensation technique which produces Voyager images. Eighteen images were produced on June 22 - 23, 1989, from 57 million miles away. A 68 day sequence which provides a stroboscopic view - colorization approximates what is seen by the human eye. Real time images recorded live from Voyager on 8/24/89 are presented. Photoclinometry produced the topography of Triton. Three images are used to create a sequence of Neptune's rings. The globe of Neptune and 2 views of the south pole are shown as well as Neptune rotating. The rotation of a scooter is frozen in images showing differential motion. There is a view of rotation of the Great Dark Spot about its own axis. Photoclinometry provides a 3-dimensional perspective using a color mosaic of Triton images. The globe is used to indicate the orientation of Neptune's crescent. The east and west plumes on Triton are shown.

Numerical simulation of runaway electrons: 3-D effects on synchrotron radiation and impurity-based runaway current dissipation

NASA Astrophysics Data System (ADS)

del-Castillo-Negrete, D.; Carbajal, L.; Spong, D.; Izzo, V.

2018-05-01

Numerical simulations of runaway electrons (REs) with a particular emphasis on orbit dependent effects in 3-D magnetic fields are presented. The simulations were performed using the recently developed Kinetic Orbit Runaway electron Code (KORC) that computes the full-orbit relativistic dynamics in prescribed electric and magnetic fields including radiation damping and collisions. The two main problems of interest are synchrotron radiation and impurity-based RE dissipation. Synchrotron radiation is studied in axisymmetric fields and in 3-D magnetic configurations exhibiting magnetic islands and stochasticity. For passing particles in axisymmetric fields, neglecting orbit effects might underestimate or overestimate the total radiation power depending on the direction of the radial shift of the drift orbits. For trapped particles, the spatial distribution of synchrotron radiation exhibits localized "hot" spots at the tips of the banana orbits. In general, the radiation power per particle for trapped particles is higher than the power emitted by passing particles. The spatial distribution of synchrotron radiation in stochastic magnetic fields, obtained using the MHD code NIMROD, is strongly influenced by the presence of magnetic islands. 3-D magnetic fields also introduce a toroidal dependence on the synchrotron spectra, and neglecting orbit effects underestimates the total radiation power. In the presence of magnetic islands, the radiation damping of trapped particles is larger than the radiation damping of passing particles. Results modeling synchrotron emission by RE in DIII-D quiescent plasmas are also presented. The computation uses EFIT reconstructed magnetic fields and RE energy distributions fitted to the experimental measurements. Qualitative agreement is observed between the numerical simulations and the experiments for simplified RE pitch angle distributions. However, it is noted that to achieve quantitative agreement, it is necessary to use pitch angle distributions that depart from simplified 2-D Fokker-Planck equilibria. Finally, using the guiding center orbit model (KORC-GC), a preliminary study of pellet mitigated discharges in DIII-D is presented. The dependence of RE energy decay and current dissipation on initial energy and ionization levels of neon impurities is studied. The computed decay rates are within the range of experimental observations.

The Topology and Properties of Mercury's Tail Current Sheet

NASA Astrophysics Data System (ADS)

Al Asad, M.; Johnson, C.; Philpott, L. C.

2017-12-01

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft orbited Mercury from March 2011 until April 2015, measuring the vector magnetic field inside and outside the magnetosphere. MESSENGER repeatedly encountered the tail current sheet (TCS) on the nightside of the planet. We examined 1s magnetic field data within 20 minutes of the magnetic equator position on 2435 orbit to characterize the shape and properties of Mercury's TCS and investigate its response to solar wind conditions. Identification of the TCS from vector magnetic field data used the following criteria: (1) a rapid rotation in the field direction from anti-sunward in the southern tail lobe to sunward in the northern lobe, accompanied by (2) a decrease in the field magnitude and (3) an increase in field variability. The current sheet was encountered on 606 orbits allowing the probability of encountering the tail current sheet in the equatorial plane to be mapped. Orbits on which the TCS was identified were binned spatially and superposed epoch analysis used to determine the field magnitude at the edge of the TCS, from which its time-averaged 3D shape was extracted. The TCS has an inner edge at 1.5 RM downtail in the midnight plane with a thickness of 0.34 RM, extends to the observation limit of 2.8 RM, decreasing in thickness to 0.28 RM. The thickness of the TCS increases in the dawn/dusk directions to 0.7 RM at 1.8 RM downtail and ± 1.5 RM from the noon-midnight plane and it warps towards the planet in the dawn/dusk directions. No strong correlations were found between the time-averaged shape and position of the TCS and solar wind conditions such as the solar wind ram pressure and the magnetic disturbance index, nor with parameters that control these conditions such as heliocentric distance. However, it is likely that the TCS does respond to these conditions on time scales too short to be characterized with MESSENGER data. In addition to mapping the shape of the current sheet, we observed that many TCS crossings exhibit the magnetic characteristics of a bifurcated current sheet rather than a typical Harris-type structure. In fact, we found that more TCS encounters can be classified as bifurcated (34%) than Harris-like (15%). This suggests the bifurcated TCS structure may be more stable and common in Mercury's magnetosphere than at Earth.

Finite element-integral simulation of static and flight fan noise radiation from the JT15D turbofan engine

NASA Technical Reports Server (NTRS)

Baumeister, K. J.; Horowitz, S. J.

1982-01-01

An iterative finite element integral technique is used to predict the sound field radiated from the JT15D turbofan inlet. The sound field is divided into two regions: the sound field within and near the inlet which is computed using the finite element method and the radiation field beyond the inlet which is calculated using an integral solution technique. The velocity potential formulation of the acoustic wave equation was employed in the program. For some single mode JT15D data, the theory and experiment are in good agreement for the far field radiation pattern as well as suppressor attenuation. Also, the computer program is used to simulate flight effects that cannot be performed on a ground static test stand.

Pioneers 10 and 11 deep space missions

NASA Technical Reports Server (NTRS)

Dyal, Palmer

1990-01-01

Pioneers 10 and 11 were launched from Earth, 2 March 1972, and 5 April 1973, respectively. The Pioneers were the first spacecraft to explore the asteroid belt and the first to encounter the giant planets, Jupiter and Saturn. The Pioneer 10 spacecraft is now the most distant man-made object in our solar system and is farther from the Sun than all nine planets. It is 47 AU from the Sun and is moving in a direction opposite to that of the Sun's motion through the galaxy. Pioneer 11 is 28 AU from the Sun and is traveling in the direction opposite of Pioneer 10, in the same direction as the Sun moves in the galaxy. These two Pioneer spacecraft provided the first large-scale, in-situ measurements of the gas and dust surrounding a star, the Sun. Since launch, the Pioneers have measured large-scale properties of the heliosphere during more than one complete 11-year solar sunspot cycle, and have measured the properties of the expanding solar atmosphere, the transport of cosmic rays into the heliosphere, and the high-energy trapped radiation belts and magnetic fields associated with the planets Jupiter and Saturn. Accurate Doppler tracking of these spin-stabilized spacecraft was used to search for differential gravitational forces from a possible trans-Neptunian planet and to search for gravitational radiation. Future objectives of the Pioneer 10 and 11 missions are to continue measuring the large-scale properties of the heliosphere and to search for its boundary with interstellar space.

Radiation from particles moving in small-scale magnetic fields created in solid-density laser-plasma laboratory experiments

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

Keenan, Brett D., E-mail: bdkeenan@ku.edu; Medvedev, Mikhail V.

2015-11-15

Plasmas created by high-intensity lasers are often subject to the formation of kinetic-streaming instabilities, such as the Weibel instability, which lead to the spontaneous generation of high-amplitude, tangled magnetic fields. These fields typically exist on small spatial scales, i.e., “sub-Larmor scales.” Radiation from charged particles moving through small-scale electromagnetic (EM) turbulence has spectral characteristics distinct from both synchrotron and cyclotron radiation, and it carries valuable information on the statistical properties of the EM field structure and evolution. Consequently, this radiation from laser-produced plasmas may offer insight into the underlying electromagnetic turbulence. Here, we investigate the prospects for, and demonstrate themore » feasibility of, such direct radiative diagnostics for mildly relativistic, solid-density laser plasmas produced in lab experiments.« less

Estimating net solar radiation using Landsat Thematic Mapper and digital elevation data

NASA Technical Reports Server (NTRS)

Dubayah, R.

1992-01-01

A radiative transfer algorithm is combined with digital elevation and satellite reflectance data to model spatial variability in net solar radiation at fine spatial resolution. The method is applied to the tall-grass prairie of the 16 x 16 sq km FIFE site (First ISLSCP Field Experiment) of the International Satellite Land Surface Climatology Project. Spectral reflectances as measured by the Landsat Thematic Mapper (TM) are corrected for atmospheric and topographic effects using field measurements and accurate 30-m digital elevation data in a detailed model of atmosphere-surface interaction. The spectral reflectances are then integrated to produce estimates of surface albedo in the range 0.3-3.0 microns. This map of albedo is used in an atmospheric and topographic radiative transfer model to produce a map of net solar radiation. A map of apparent net solar radiation is also derived using only the TM reflectance data, uncorrected for topography, and the average field-measured downwelling solar irradiance. Comparison with field measurements at 10 sites on the prairie shows that the topographically derived radiation map accurately captures the spatial variability in net solar radiation, but the apparent map does not.

Radiation Hardened Electronics for Extreme Environments

NASA Technical Reports Server (NTRS)

Keys, Andrew S.; Watson, Michael D.

2007-01-01

The Radiation Hardened Electronics for Space Environments (RHESE) project consists of a series of tasks designed to develop and mature a broad spectrum of radiation hardened and low temperature electronics technologies. Three approaches are being taken to address radiation hardening: improved material hardness, design techniques to improve radiation tolerance, and software methods to improve radiation tolerance. Within these approaches various technology products are being addressed including Field Programmable Gate Arrays (FPGA), Field Programmable Analog Arrays (FPAA), MEMS Serial Processors, Reconfigurable Processors, and Parallel Processors. In addition to radiation hardening, low temperature extremes are addressed with a focus on material and design approaches.

Reality and Surreality of 3-D Displays: Holodeck and Beyond

DTIC Science & Technology

2000-01-01

are 2-D interference patterns and may, in principal, be written on a 2-D recording medium whose response is a function of intensity (e.g. photographic...devices based on reflective digital micromirror devices ( DMD ), or 1-D grading light valves. Photorefractive crystals include tantalum dioxide, lithium...Hologram readout is a diffractive interference phenomenon, which becomes significant when electromagnetic radiation encounters structures (e.g. pixels of

Structural biologists capture detailed image of gene regulator’s fleeting form | Center for Cancer Research

Cancer.gov

Using an ultrafast, high-intensity radiation source called an X-ray free-electron laser (XFEL), scientists have captured an atomic-level picture of an RNA structure called a riboswitch as it reorganizes itself to regulate protein production. The structure they visualized has never before been seen, and likely exists for only milliseconds after the riboswitch first encounters its activating molecule.  Read more...  

Simulation study of geometric shape factor approach to estimating earth emitted flux densities from wide field-of-view radiation measurements

NASA Technical Reports Server (NTRS)

Weaver, W. L.; Green, R. N.

1980-01-01

A study was performed on the use of geometric shape factors to estimate earth-emitted flux densities from radiation measurements with wide field-of-view flat-plate radiometers on satellites. Sets of simulated irradiance measurements were computed for unrestricted and restricted field-of-view detectors. In these simulations, the earth radiation field was modeled using data from Nimbus 2 and 3. Geometric shape factors were derived and applied to these data to estimate flux densities on global and zonal scales. For measurements at a satellite altitude of 600 km, estimates of zonal flux density were in error 1.0 to 1.2%, and global flux density errors were less than 0.2%. Estimates with unrestricted field-of-view detectors were about the same for Lambertian and non-Lambertian radiation models, but were affected by satellite altitude. The opposite was found for the restricted field-of-view detectors.

Three dimensional radiation fields in free electron lasers using Lienard-Wiechert fields

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

Elias, L.R.; Gallardo, J.

1981-10-28

In a free electron laser a relativistic electron beam is bunched under the action of the ponderomotive potential and is forced to radiate in close phase with the input wave. Until recently, most theories of the FEL have dealt solely with electron beams of infinite transverse dimension radiating only one-dimensional E.M. waves (plane waves). Although these theories describe accurately the dynamics of the electrons during the FEL interaction process, neither the three dimensional nature of the radiated fields nor its non-monochromatic features can be properly studied by them. As a result of this, very important practical issues such as themore » gain per gaussian-spherical optical mode in a free electron laser have not been well addressed, except through a one dimensional field model in which a filling factor describes crudely the coupling of the FEL induced field to the input field.« less

Basic Principles of Spectroscopy

NASA Astrophysics Data System (ADS)

Penner, Michael H.

Spectroscopy deals with the production, measurement, and interpretation of spectra arising from the interaction of electromagnetic radiation with matter. There are many different spectroscopic methods available for solving a wide range of analytical problems. The methods differ with respect to the species to be analyzed (such as molecular or atomic spectroscopy), the type of radiation-matter interaction to be monitored (such as absorption, emission, or diffraction), and the region of the electromagnetic spectrum used in the analysis. Spectroscopic methods are very informative and widely used for both quantitative and qualitative analyses. Spectroscopic methods based on the absorption or emission of radiation in the ultraviolet (UV), visible (Vis), infrared (IR), and radio (nuclear magnetic resonance, NMR) frequency ranges are most commonly encountered in traditional food analysis laboratories. Each of these methods is distinct in that it monitors different types of molecular or atomic transitions. The basis of these transitions is explained in the following sections.

A Search for Early High-Energy Afterglows in BATSE Gamma-Ray Bursts

NASA Technical Reports Server (NTRS)

Giblin, Timothy W.

2003-01-01

The scope of this project was to perform a detailed search for the early high-energy afterglow component of gamma-ray bursts (GRBs) in the BATSE GRB data archive. GRBs are believed to be the product of shock waves generated in a relativistic outflow from the demise of extremely massive stars and/or binary neutron star mergers. The outflow undeniably encounters the ambient medium of the progenitor object and another shock wave is set up. A forward shock propagates into the medium and a reverse shock propagates through the ejecta. This "external" shock dissipates the kinetic energy of the ejecta in the form of radiation via synchrotron losses and slows the outflow eventually to a non-relativistic state. Radiation from the forward external shock is therefore expected to be long-lived, lasting days, weeks, and even months. This radiation is referred to as the 'afterglow'.

Intensity-Modulated Radiation Therapy (IMRT) for Head and Neck Surgeons

PubMed Central

Gutiontov, Stanley I.; Shin, Edward J.; Lok, Benjamin; Lee, Nancy Y.; Cabanillas, Ruben

2016-01-01

The development of intensity-modulated radiation therapy has played a major role in improving outcomes and decreasing morbidity in head and neck cancer patients. This review addresses this vital modality with a focus on the important role of the head and neck surgeon. The technique as well as its benefits and points of caution are outlined, the definitions of tumor and treatment volumes are discussed, and the dose and fractionation are detailed. Following this are several sections dedicated to the role of the head and neck surgeon in the planning of both definitive and post-operative radiation therapy to the primary site and neck. There is a focus throughout on anatomic and surgical considerations; commonly encountered situations are illustrated. With a deeper understanding of this technique and their own pivotal contribution to target delineation, head and neck surgeons will be poised to expand their role and improve cancer care for their patients. PMID:26705685

Effects of radiation and temperature on gallium nitride (GaN) metal-semiconductor-metal ultraviolet photodetectors

NASA Astrophysics Data System (ADS)

Chiamori, Heather C.; Angadi, Chetan; Suria, Ateeq; Shankar, Ashwin; Hou, Minmin; Bhattacharya, Sharmila; Senesky, Debbie G.

2014-06-01

The development of radiation-hardened, temperature-tolerant materials, sensors and electronics will enable lightweight space sub-systems (reduced packaging requirements) with increased operation lifetimes in extreme harsh environments such as those encountered during space exploration. Gallium nitride (GaN) is a ceramic, semiconductor material stable within high-radiation, high-temperature and chemically corrosive environments due to its wide bandgap (3.4 eV). These material properties can be leveraged for ultraviolet (UV) wavelength photodetection. In this paper, current results of GaN metal-semiconductor-metal (MSM) UV photodetectors behavior after irradiation up to 50 krad and temperatures of 15°C to 150°C is presented. These initial results indicate that GaN-based sensors can provide robust operation within extreme harsh environments. Future directions for GaN-based photodetector technology for down-hole, automotive and space exploration applications are also discussed.

Redundant drive current imbalance problem of the Automatic Radiator Inspection Device (ARID)

NASA Technical Reports Server (NTRS)

Latino, Carl D.

1992-01-01

The Automatic Radiator Inspection Device (ARID) is a 4 Degree of Freedom (DOF) robot with redundant drive motors at each joint. The device is intended to automate the labor intensive task of space shuttle radiator inspection. For safety and redundancy, each joint is driven by two independent motor systems. Motors driving the same joint, however, draw vastly different currents. The concern was that the robot joints could be subjected to undue stress. It was the objective of this summer's project to determine the cause of this current imbalance. In addition it was to determine, in a quantitative manner, what was the cause, how serious the problem was in terms of damage or undue wear to the robot and find solutions if possible. It was concluded that most problems could be resolved with a better motor control design. This document discusses problems encountered and possible solutions.

Divergent Roles of RPA Homologs of the Model Archaeon Halobacterium salinarum in Survival of DNA Damage.

PubMed

Evans, Jessica J; Gygli, Patrick E; McCaskill, Julienne; DeVeaux, Linda C

2018-04-20

The haloarchaea are unusual in possessing genes for multiple homologs to the ubiquitous single-stranded DNA binding protein (SSB or replication protein A, RPA) found in all three domains of life. Halobacterium salinarum contains five homologs: two are eukaryotic in organization, two are prokaryotic and are encoded on the minichromosomes, and one is uniquely euryarchaeal. Radiation-resistant mutants previously isolated show upregulation of one of the eukaryotic-type RPA genes. Here, we have created deletions in the five RPA operons. These deletion mutants were exposed to DNA-damaging conditions: ionizing radiation, UV radiation, and mitomycin C. Deletion of the euryarchaeal homolog, although not lethal as in Haloferax volcanii , causes severe sensitivity to all of these agents. Deletion of the other RPA/SSB homologs imparts a variable sensitivity to these DNA-damaging agents, suggesting that the different RPA homologs have specialized roles depending on the type of genomic insult encountered.

Advancements in Afterbody Radiative Heating Simulations for Earth Entry

NASA Technical Reports Server (NTRS)

Johnston, Christopher O.; Panesi, Marco; Brandis, Aaron M.

2016-01-01

Four advancements to the simulation of backshell radiative heating for Earth entry are presented. The first of these is the development of a flow field model that treats electronic levels of the dominant backshell radiator, N, as individual species. This is shown to allow improvements in the modeling of electron-ion recombination and two-temperature modeling, which are shown to increase backshell radiative heating by 10 to 40%. By computing the electronic state populations of N within the flow field solver, instead of through the quasi-steady state approximation in the radiation code, the coupling of radiative transition rates to the species continuity equations for the levels of N, including the impact of non-local absorption, becomes feasible. Implementation of this additional level of coupling between the flow field and radiation codes represents the second advancement presented in this work, which is shown to increase the backshell radiation by another 10 to 50%. The impact of radiative transition rates due to non-local absorption indicates the importance of accurate radiation transport in the relatively complex flow geometry of the backshell. This motivates the third advancement, which is the development of a ray-tracing radiation transport approach to compute the radiative transition rates and divergence of the radiative flux at every point for coupling to the flow field, therefore allowing the accuracy of the commonly applied tangent-slab approximation to be assessed for radiative source terms. For the sphere considered at lunar-return conditions, the tangent-slab approximation is shown to provide a sufficient level of accuracy for the radiative source terms, even for backshell cases. This is in contrast to the agreement between the two approaches for computing the radiative flux to the surface, which differ by up to 40%. The final advancement presented is the development of a nonequilibrium model for NO radiation, which provides significant backshell radiation at velocities below 10 km/s. The developed model reduces the nonequilibrium NO radiation by 50% relative to the previous model.

Terahertz radiation generation by beating of two laser beams in a collisional plasma with oblique magnetic field

NASA Astrophysics Data System (ADS)

Hematizadeh, Ayoob; Jazayeri, Seyed Masud; Ghafary, Bijan

2018-02-01

A scheme for excitation of terahertz (THz) radiation is presented by photo mixing of two super-Gaussian laser beams in a rippled density collisional magnetized plasma. Lasers having different frequencies and wave numbers but the same electric fields create a ponderomotive force on the electrons of plasma in the beating frequency. Super-Gaussian laser beam has the exclusive features such as steep gradient in laser intensity distribution, wider cross-section in comparison with Gaussian profiles, which make stronger ponderomotive force and higher THz radiation. The magnetic field is considered oblique to laser beams propagation direction; in this case, depending on the phase matching conditions different mode waves can propagate in plasma. It is found that amplitude and efficiency of the emitted THz radiation not only are sensitive to the beating frequency, collision frequency, and magnetic field strength but to the angle between laser beams and static magnetic field. The efficiency of THz radiation can be optimized in a certain angle.

Aha Malawi! Envisioning Field Experiences That Nurture Cultural Competencies for Preservice Teachers

ERIC Educational Resources Information Center

Talbot, Patricia A.

2011-01-01

This theoretical study uses the context of the writer's personal encounters in Malawi, Africa, to propose a conceptual model for creating diverse field experiences based on best practices in critical pedagogy, service learning, and the underpinnings of transformational learning theory, for the purpose of increasing the probability of meaningful…

Evaluating the Learning Outcomes of An International Field Trip in Postgraduate Lighting Design Courses

ERIC Educational Resources Information Center

Isoardi, Gillian

2010-01-01

Lighting industry professionals work in an international marketplace and encounter a range of social, geographical and cultural challenges associated with this. Education in lighting should introduce students to aspects of these challenges. To achieve this, an international field trip was recently undertaken that sought to provide an authentic…

Encouraging Reflexivity in Urban Geography Fieldwork: Study Abroad Experiences in Singapore and Malaysia

ERIC Educational Resources Information Center

Glass, Michael R.

2014-01-01

Fieldwork in urban geography courses can encourage reflexivity among students regarding the cities they encounter. This article outlines how student reflexivity was encouraged within a new international field research course in Singapore and Malaysia. Drawing on examples from students' field exercises written during an intensive and occasionally…

Elites, Bureaucrats, Ostriches, and Pussycats: Managing Research in Policy Settings.

ERIC Educational Resources Information Center

Marshall, Catherine

Female researchers conducting field research in educational politics encounter special problems of access, entry, reciprocity, and ethics. Accordingly, this study focuses first on field research methods in policy settings as a general topic, then on problems specific to women in this area. A researcher must be aware of informal coalitions or…

Challenges Social Work Students Encounter in International Field Placements and Recommendations for Responsible Management

ERIC Educational Resources Information Center

Matthew, Lenore E.; Lough, Benjamin J.

2017-01-01

Social work students often face personal and institutional challenges prior to, during, and after international field placements. If not managed, these challenges may compromise students' professional development and hinder their meaningful contribution to placements abroad, which is of particular concern when students from the Global North are…

Radiation from Relativistic Jets

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Mizuno, Y.; Hardee, P.; Sol, H.; Medvedev, M.; Zhang, B.; Nordlund, A.; Frederiksen, J. T.; Fishman, G. J.; Preece, R.

2008-01-01

Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., gamma-ray bursts (GRBs), active galactic nuclei (AGNs), and Galactic microquasar systems usually have power-law emission spectra. Recent PIC simulations of relativistic electron-ion (electron-positron) jets injected into a stationary medium show that particle acceleration occurs within the downstream jet. In the presence of relativistic jets, instabilities such as the Buneman instability, other two-streaming instability, and the Weibel (filamentation) instability create collisionless shocks, which are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The 'jitter' radiation from deflected electrons in small-scale magnetic fields has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation, a case of diffusive synchrotron radiation, may be important to understand the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

Modal propagation angles in a cylindrical duct with flow and their relation to sound radiation

NASA Technical Reports Server (NTRS)

Rice, E. J.; Heidmann, M. F.; Sofrin, T. G.

1979-01-01

The main emphasis is upon the propagation angle with respect to the duct axis and its relation to the far-field acoustic radiation pattern. When the steady flow Mach number is accounted for in the duct, the propagation angle in the duct is shown to be coincident with the angle of the principal lobe of far-field radiation obtained using the Wiener-Hopf technique. Different Mach numbers are allowed within the duct and in the external field. For static tests with a steady flow in an inlet but with no external Mach number the far-field radiation pattern is shifted considerably toward the inlet axis when compared to zero Mach number radiation theory. As the external Mach number is increased the noise radiation pattern is shifted away from the inlet axis. The theory is developed using approximations for sound propagation in circular ducts. An exact analysis using Hankel function solutions for the zero Mach number case is given to provide a check of the simpler approximate theory.

The Tordo 1 polar cusp barium plasma injection experiment

NASA Technical Reports Server (NTRS)

Wescott, E. M.; Stenbaek-Nielsen, H. C.; Davis, T. N.; Jeffries, R. A.; Roach, W. H.

1978-01-01

In January 1975, two barium plasma injection experiments were carried out with rockets launched into the upper atmosphere where field lines from the dayside cusp region intersect the ionosphere. The Tordo 1 experiment took place near the beginning of a worldwide magnetic storm. It became a polar cap experiment almost immediately as convection perpendicular to the magnetic field moved the fluorescent plasma jet away from the cusp across the polar cap in an antisunward direction. Convection across the polar cap with an average velocity of more than 1 km/s was observed for nearly 40 min until the barium flux tubes encountered large electron fields associated with a poleward bulge of the auroral oval near Greenland. Prior to the encounter with the aurora near Greenland there is evidence of upward acceleration of the barium ions while they were in the polar cap. The three-dimensional observations of the plasma orientation and motion give an insight into convection from the cusp region across the polar cap, the orientation of the polar cap magnetic field lines out to several earth radii, the causes of polar cap magnetic perturbations, and parallel acceleration processes.

Gamma radiation field intensity meter

DOEpatents

Thacker, L.H.

1995-10-17

A gamma radiation intensity meter measures dose rate of a radiation field. The gamma radiation intensity meter includes a tritium battery emitting beta rays generating a current which is essentially constant. Dose rate is correlated to an amount of movement of an electroscope element charged by the tritium battery. Ionizing radiation decreases the voltage at the element and causes movement. A bleed resistor is coupled between the electroscope support element or electrode and the ionization chamber wall electrode. 4 figs.

Gamma radiation field intensity meter

DOEpatents

Thacker, L.H.

1994-08-16

A gamma radiation intensity meter measures dose rate of a radiation field. The gamma radiation intensity meter includes a tritium battery emitting beta rays generating a current which is essentially constant. Dose rate is correlated to an amount of movement of an electroscope element charged by the tritium battery. Ionizing radiation decreases the voltage at the element and causes movement. A bleed resistor is coupled between the electroscope support element or electrode and the ionization chamber wall electrode. 4 figs.

Micro Penning Trap for Continuous Magnetic Field Monitoring in High Radiation Environments

NASA Astrophysics Data System (ADS)

Latorre, Javiera; Bollen, Georg; Gulyuz, Kerim; Ringle, Ryan; Bado, Philippe; Dugan, Mark; Lebit Team; Translume Collaboration

2016-09-01

As new facilities for rare isotope beams, like FRIB at MSU, are constructed, there is a need for new instrumentation to monitor magnetic fields in beam magnets that can withstand the higher radiation level. Currently NMR probes, the instruments used extensively to monitor magnetic fields, do not have a long lifespans in radiation-high environments. Therefore, a radiation-hard replacement is needed. We propose to use Penning trap mass spectrometry techniques to make high precision magnetic field measurements. Our Penning microtrap will be radiation resistant as all of the vital electronics will be at a safe distance from the radiation. The trap itself is made from materials not subject to radiation damage. Penning trap mass spectrometers can determine the magnetic field by measuring the cyclotron frequency of an ion with a known mass and charge. This principle is used on the Low Energy Beam Ion Trap (LEBIT) minitrap at NSCL which is the foundation for the microtrap. We have partnered with Translume, who specialize in glass micro-fabrication, to develop a microtrap in fused-silica glass. A microtrap is finished and ready for testing at NSCL with all of the electronic and hardware components setup. DOE Phase II SBIR Award No. DE-SC0011313, NSF Award Number 1062410 REU in Physics, NSF under Grant No. PHY-1102511.

Reverberation Chamber Uniformity Validation and Radiated Susceptibility Test Procedures for the NASA High Intensity Radiated Fields Laboratory

NASA Technical Reports Server (NTRS)

Koppen, Sandra V.; Nguyen, Truong X.; Mielnik, John J.

2010-01-01

The NASA Langley Research Center's High Intensity Radiated Fields Laboratory has developed a capability based on the RTCA/DO-160F Section 20 guidelines for radiated electromagnetic susceptibility testing in reverberation chambers. Phase 1 of the test procedure utilizes mode-tuned stirrer techniques and E-field probe measurements to validate chamber uniformity, determines chamber loading effects, and defines a radiated susceptibility test process. The test procedure is segmented into numbered operations that are largely software controlled. This document is intended as a laboratory test reference and includes diagrams of test setups, equipment lists, as well as test results and analysis. Phase 2 of development is discussed.

Scale models: A proven cost-effective tool for outage planning

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

Lee, R.; Segroves, R.

1995-03-01

As generation costs for operating nuclear stations have risen, more nuclear utilities have initiated efforts to improve cost effectiveness. Nuclear plant owners are also being challenged with lower radiation exposure limits and new revised radiation protection related regulations (10 CFR 20), which places further stress on their budgets. As source term reduction activities continue to lower radiation fields, reducing the amount of time spent in radiation fields becomes one of the most cost-effective ways of reducing radiation exposure. An effective approach for minimizing time spent in radiation areas is to use a physical scale model for worker orientation planning andmore » monitoring maintenance, modifications, and outage activities. To meet the challenge of continued reduction in the annual cumulative radiation exposures, new cost-effective tools are required. One field-tested and proven tool is the physical scale model.« less

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

Chow, Edward; Makhani, Leila; Culleton, Shaelyn

Purpose: Hemibody irradiation has been shown to relieve bony metastatic pain within 24-48 hours of treatment, whereas for local external beam radiation, onset of pain relief is 1-4 weeks after radiation. The primary objective of this study is to examine whether there is a relationship between the areas of radiation treatment and onset of pain relief. Methods and Materials: From Jan 1999 to Jan 2002, a total of 653 patients with symptomatic bone metastases were treated with external beam radiation. Pain scores and analgesic consumption were recorded at baseline and Weeks 1, 2, 4, 8, and 12. The areas ofmore » radiation treatment for all patients were calculated, then correlated with the response and analyzed in various ways. We first compared pain score alone with mean radiation field size. Second, we combined pain score and analgesic consumption. Last, we implemented the International Consensus end points for pain score and analgesic intake. Results: Assessment of 653 patients showed no significant correlation comparing pain scores alone with radiation field area, with the exception of Week 4 for partial responders. Again, no significant correlation was found when combining both analgesic intake and pain score against radiation field size. Even when implementing the International Consensus end point definitions for radiation response, the only significant correlation between radiation field size and response was observed in Week 2 for partial response. Conclusion: There was no statistical significance between mean areas of radiation treatment with the onset of pain relief.« less

The development of remote wireless radiation dose monitoring system

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

Lee, Jin-woo; Chonbuk National University, Jeonjoo-Si; Jeong, Kyu-hwan

Internet of things (IoT) technology has recently shown a large flow of IT trends in human life. In particular, our lives are now becoming integrated with a lot of items around the 'smart-phone' with IoT, including Bluetooth, Near Field Communication (NFC), Beacons, WiFi, and Global Positioning System (GPS). Our project focuses on the interconnection of radiation dosimetry and IoT technology. The radiation workers at a nuclear facility should hold personal dosimeters such as a Thermo-Luminescence Dosimeter (TLD), an Optically Stimulated Luminescence Dosimeter (OSL), pocket ionization chamber dosimeters, an Electronic Personal Dosimeter (EPD), or an alarm dosimeter on their body. Somemore » of them have functions that generate audible or visible alarms to radiation workers in a real working area. However, such devices used in radiation fields these days have no functions for communicating with other areas or the responsible personnel in real time. In particular, when conducting a particular task in a high dose area, or a number of repair works within a radiation field, radiation dose monitoring is important for the health of the workers and the work efficiency. Our project aims at the development of a remote wireless radiation dose monitoring system (RWRD) that can be used to monitor the radiation dose in a nuclear facility for radiation workers and a radiation protection program In this project, a radiation dosimeter is the detection device for personal radiation dose, a smart phone is the mobile wireless communication tool, and, Beacon is the wireless starter for the detection, communication, and position of the worker using BLE (Bluetooth Low Energy). In this report, we report the design of the RWRD and a demonstration case in a real radiation field. (authors)« less

Active Control of Sound Radiation due to Subsonic Wave Scattering from Discontinuities on Thin Elastic Beams.

NASA Astrophysics Data System (ADS)

Guigou, Catherine Renee J.

1992-01-01

Much progress has been made in recent years in active control of sound radiation from vibrating structures. Reduction of the far-field acoustic radiation can be obtained by directly modifying the response of the structure by applying structural inputs rather than by adding acoustic sources. Discontinuities, which are present in many structures are often important in terms of sound radiation due to wave scattering behavior at their location. In this thesis, an edge or boundary type discontinuity (clamped edge) and a point discontinuity (blocking mass) are analytically studied in terms of sound radiation. When subsonic vibrational waves impinge on these discontinuities, large scattered sound levels are radiated. Active control is then achieved by applying either control forces, which approximate shakers, or pairs of control moments, which approximate piezoelectric actuators, near the discontinuity. Active control of sound radiation from a simply-supported beam is also examined. For a single frequency, the flexural response of the beam subject to an incident wave or an input force (disturbance) and to control forces or control moments is expressed in terms of waves of both propagating and near-field types. The far-field radiated pressure is then evaluated in terms of the structural response, using Rayleigh's formula or a stationary phase approach, depending upon the application. The control force and control moment magnitudes are determined by optimizing a quadratic cost function, which is directly related to the control performance. On determining the optimal control complex amplitudes, these can be resubstituted in the constitutive equations for the system under study and the minimized radiated fields can be evaluated. High attenuation in radiated sound power and radiated acoustic pressure is found to be possible when one or two active control actuators are located near the discontinuity, as is shown to be mostly associated with local changes in beam response near the discontinuity. The effect of the control actuators on the far-field radiated pressure, the wavenumber spectrum, the flexural displacement and the near-field time averaged intensity and pressure distributions are studied in order to further understand the control mechanisms. The influence of the near-field structural waves is investigated as well. Some experimental results are presented for comparison.

Tailoring Thermal Radiative Properties with Doped-Silicon Nanowires

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

Zhang, Zhuomin

Aligned doped-silicon nanowire (D-SiNW) arrays form a hyperbolic metamaterial in the mid-infrared and have unique thermal radiative properties, such as broadband omnidirectional absorption, low-loss negative refraction, etc. A combined theoretical and experimental investigation will be performed to characterize D-SiNW arrays and other metamaterials for tailoring thermal radiative properties. Near-field thermal radiation between anisotropic materials with hyperbolic dispersions will also be predicted for potential application in energy harvesting. A new kind of anisotropic metamaterial with a hyperbolic dispersion in a broad infrared region has been proposed and demonstrated based on aligned doped-silicon nanowire (D-SiNW) arrays. D-SiNW-based metamaterials have unique thermal radiativemore » properties, such as broadband omnidirectional absorption whose width and location can be tuned by varying the filling ratio and/or doping level. Furthermore, high figure of merit (FOM) can be achieved in a wide spectral region, suggesting that D-SiNW arrays may be used as a negative refraction material with much less loss than other structured materials, such as layered semiconductor materials. We have also shown that D-SiNWs and other nanostructures can significantly enhance near-field thermal radiation. The study of near-field radiative heat transfer between closely spaced objects and the electromagnetic wave interactions with micro/nanostructured materials has become an emerging multidisciplinary field due to its importance in advanced energy systems, manufacturing, local thermal management, and high spatial resolution thermal sensing and mapping. We have performed extensive study on the energy streamlines involving anisotropic metamaterials and the applicability of the effective medium theory for near-field thermal radiation. Graphene as a 2D material has attracted great attention in nanoelectronics, plasmonics, and energy harvesting. We have shown that graphene can be used to tailor the transmittance, reflectance, and absorptance of nanostructured materials. Furthermore, graphene can be used to enhance near-field coupling to increase the phonon tunneling probability. We have performed analysis of near-field thermophotovoltaic devices with backside reflecting mirror and with tungsten gratings. We have predicted a large enhancement of electroluminescent refrigeration at a separation distance down to 10 nm due to near-field thermal radiation effect. A heat flux measurement system is developed to measure the near-field radiation in vacuum. We have fabricated doped Si plates separated by sparsely distributed posts to create a 200-800 nm vacuum gap. Our measurement results demonstrate that 11 times enhancement of near-field thermal radiation between parallel doped-Si plates with a lateral dimension 1 cm by 1 cm.« less

RADIATION BIOLOGY: CONCEPTS FOR RADIATION PROTECTION

EPA Science Inventory

ABSTRACT

The opportunity to write a historical review of the field of radiation biology allows for the viewing of the development and maturity of a field of study, thereby being able to provide the appropriate context for the earlier years of research and its findings. The...

ATTENUATION OF COBALT-60 RADIATION FROM A SOURCE DISTRIBUTED AROUND A CONCRETE BLOCKHOUSE

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

Batter, J.F.; Starbird, A.W.

1961-06-15

Two radiation-shielding experiments were performed upon a simple blockhouse structure. The blockhouse was exposed to a simulated fallout field, and the radiation penetrating the structure was measured. The radiation field was produced by circulating a sealed cobalt-60 source through polyethylene tubing predistributed over an octant centered on the test building. Experimental details are described and results tabulated. (auth)

Microwave sintering of ceramic materials

NASA Astrophysics Data System (ADS)

Karayannis, V. G.

2016-11-01

In the present study, the potential of microwave irradiation as an innovative energy- efficient alternative to conventional heating technologies in ceramic manufacturing is reviewed, addressing the advantages/disadvantages, while also commenting on future applications of possible commercial interest. Ceramic materials have been extensively studied and used due to several advantages they exhibit. Sintering ceramics using microwave radiation, a novel technology widely employed in various fields, can be an efficient, economic and environmentally-friendlier approach, to improve the consolidation efficiency and reduce the processing cycle-time, in order to attain substantial energy and cost savings. Microwave sintering provides efficient internal heating, as energy is supplied directly and penetrates the material. Since energy transfer occurs at a molecular level, heat is generated throughout the material, thus avoiding significant temperature gradients between the surface and the interior, which are frequently encountered at high heating rates upon conventional sintering. Thus, rapid, volumetric and uniform heating of various raw materials and secondary resources for ceramic production is possible, with limited grain coarsening, leading to accelerated densification, and uniform and fine-grained microstructures, with enhanced mechanical performance. This is particularly important for manufacturing large-size ceramic products of quality, and also for specialty ceramic materials such as bioceramics and electroceramics. Critical parameters for the process optimization, including the electromagnetic field distribution, microwave-material interaction, heat transfer mechanisms and material transformations, should be taken into consideration.

Effects of gamma irradiations on reactive pulsed laser deposited vanadium dioxide thin films

NASA Astrophysics Data System (ADS)

Madiba, I. G.; Émond, N.; Chaker, M.; Thema, F. T.; Tadadjeu, S. I.; Muller, U.; Zolliker, P.; Braun, A.; Kotsedi, L.; Maaza, M.

2017-07-01

Vanadium oxide films are considered suitable coatings for various applications such as thermal protective coating of small spacecrafts because of their thermochromic properties. While in outer space, such coating will be exposed to cosmic radiations which include γ-rays. To study the effect of these γ-rays on the coating properties, we have deposited vanadium dioxide (VO2) films on silicon substrates and subjected them to extensive γ-irradiations with typical doses encountered in space missions. The prevalent crystallographic phase after irradiation remains the monoclinic VO2 phase but the films preferential orientation shifts to lower angles due to the presence of disordered regions caused by radiations. Raman spectroscopy measurements also evidences that the VO2 structure is slightly affected by gamma irradiation. Indeed, increasing the gamma rays dose locally alters the crystalline and electronic structures of the films by modifying the V-V inter-dimer distance, which in turns favours the presence of the VO2 metallic phase. From the XPS measurements of V2p and O1s core level spectra, an oxidation of vanadium from V4+ towards V5+ is revealed. The data also reveal a hydroxylation upon irradiation which is corroborated by the vanishing of a low oxidation state peak near the Fermi energy in the valence band. Our observations suggest that gamma radiations induce the formation of Frenkel pairs. Moreover, THz transmission measurements show that the long range structure of VO2 remains intact after irradiation whilst the electrical measurements evidence that the coating resistivity decreases with gamma irradiation and that their transition temperature is slightly reduced for high gamma ray doses. Even though gamma rays are only one of the sources of radiations that are encountered in space environment, these results are very promising with regards to the potential of integration of such VO2 films as a protective coating for spacecrafts.

NASA's Biomedical Research Program

NASA Technical Reports Server (NTRS)

Ahn, Chung-Hae

1981-01-01

The biomedical research program has been established to investigate the major physiological and psychological problems encountered by man when he undertakes spaceflight. The program seeks to obtain a better definition of each problem, an understanding of its underlying mechanism, and ultimately a means of prevention. In pursuing these goals the program also includes a major effort to develop the research tools and procedures it needs where these are not being developed elsewhere. After almost twenty years of manned spaceflight activities and after a much longer period of space related ground-based research, the program now recognizes two characteristics of spaceflight which are truly unique to space. These are weightlessness and one specific form of radiation. In its present stage of maturity much of the research focuses on mechanisms underlying the basic responses of man and animals to weightlessness. The program consists of nine elements. Eight of these are referable to specific physiological problems that have either been encountered in previous manned spaceflight or which are anticipated to occur as spaceflights last longer, traverse steeper orbital inclinations, or are otherwise different from previous missions. The ninth addresses problems that have neither arisen nor can be reasonably predicted but are suspected on the basis of theoretical models, ground-based animal research, or for other reasons. The program's current emphasis is directed toward the motion sickness problem because of its relevance to Space Shuttle operations. Increased awareness and understanding of the radiation hazard has resulted in more emphasis being placed on the biological effects of high energy, high mass number particulate radiation and upon radiation protection . Cardiovascular and musculoskeleta1 studies are pursued in recognition of the considerable fundamental knowledge that must be acquired in these areas before effective countermeasures to the effects of repetitive or long-term flight can be devised. Major new avenues of research will deal with the psychological accompaniments of spaceflight and with mathematical modelling of physiological systems.

Thin-film CdTe detector for microdosimetric study of radiation dose enhancement at gold-tissue interface.

PubMed

Paudel, Nava Raj; Shvydka, Diana; Parsai, E Ishmael

2016-09-08

Presence of interfaces between high and low atomic number (Z) materials, often encountered in diagnostic imaging and radiation therapy, leads to radiation dose perturbation. It is characterized by a very narrow region of sharp dose enhancement at the interface. A rapid falloff of dose enhancement over a very short distance from the interface makes the experimental dosimetry nontrivial. We use an in-house-built inexpensive thin-film Cadmium Telluride (CdTe) photodetector to study this effect at the gold-tissue interface and verify our experimental results with Monte Carlo (MC) modeling. Three-micron thick thin-film CdTe photodetectors were fabricated in our lab. One-, ten- or one hundred-micron thick gold foils placed in a tissue-equivalent-phantom were irradiated with a clinical Ir-192 high-dose-rate (HDR) source and current measured with a CdTe detector in each case was compared with the current measured for all uniform tissue-equivalent phantom. Percentage signal enhancement (PSE) due to each gold foil was then compared against MC modeled percentage dose enhancement (PDE), obtained from the geometry mimicking the experimental setup. The experimental PSEs due to 1, 10, and 100 μm thick gold foils at the closest measured distance of 12.5μm from the interface were 42.6 ± 10.8 , 137.0 ± 11.9, and 203.0 ± 15.4, respectively. The corresponding MC modeled PDEs were 38.1 ± 1, 164 ± 1, and 249 ± 1, respectively. The experimental and MC modeled values showed a closer agreement at the larger distances from the interface. The dose enhancement in the vicinity of gold-tissue interface was successfully measured using an in-house-built, high-resolution CdTe-based photodetector and validated with MC simulations. A close agreement between experimental and the MC modeled results shows that CdTe detector can be utilized for mapping interface dose distribution encountered in the application of ionizing radiation. © 2016 The Authors.

Feasibility of Tactical Air Delivery Resupply Using Gliders

DTIC Science & Technology

2016-12-01

using modern design and manufacturing techniques including AutoCAD, 3D printing , laser cutting and CorelDraw, and conducting field testing and...Sparrow,” using modern design and manufacturing techniques including AutoCAD, 3D printing , laser cutting and CorelDraw, and conducting field testing and...the desired point(s) of impact due to the atmospheric three-dimensional ( 3D ) wind and density field encountered by the descending load under canopy

Magnetic Fields and Multiple Protostar Formation

NASA Astrophysics Data System (ADS)

Boss, A. P.

2001-12-01

Recent observations of star-forming regions suggest that binary and multiple young stars are the rule rather than the exception, and implicate fragmentation as the likely mechanism for their formation. Most numerical hydrodynamical calculations of fragmentation have neglected the possibly deleterious effects of magnetic fields, in spite of ample evidence for the importance of magnetic support of pre-collapse clouds. We present here the first numerical hydrodynamical survey of the full effects of magnetic fields on the collapse and fragmentation of dense cloud cores. The models are calculated with a three dimensional, finite differences code which solves the equations of hydrodynamics, gravitation, and radiative transfer in the Eddington and diffusion approximations. Magnetic field effects are included through two simple approximations: magnetic pressure is added to the gas pressure, and magnetic tension is approximated by gravity dilution once collapse is well underway. Ambipolar diffusion of the magnetic field leading to cloud collapse is treated approximately as well. Models are calculated for a variety of initial cloud density profiles, shapes, and rotation rates. We find that in spite of the inclusion of magnetic field effects, dense cloud cores are capable of fragmenting into binary and multiple protostar systems. Initially prolate clouds tend to fragment into binary protostars, while initially oblate clouds tend to fragment into multiple protostar systems containing a small number (of order four) of fragments. The latter are likely to be subject to rapid orbital evolution, with close encounters possibly leading to the ejection of fragments. Contrary to expectation, magnetic tension effects appear to enhance fragmentation, allowing lower mass fragments to form than would otherwise be possible, because magnetic tension helps to prevent a central density singularity from forming and producing a dominant single object. Magnetically-supported dense cloud cores thus seem to be capable of collapsing and fragmenting into sufficient numbers of binary and multiple protostar systems to be compatible with observations of the relative rarity of single protostars. This work was partially supported by NSF grants AST-9983530 and MRI-9976645.

Collapse and Fragmentation of Molecular Cloud Cores. VII. Magnetic Fields and Multiple Protostar Formation

NASA Astrophysics Data System (ADS)

Boss, Alan P.

2002-04-01

Recent observations of star-forming regions suggest that binary and multiple young stars are the rule rather than the exception and implicate fragmentation as the likely mechanism for their formation. Most numerical hydrodynamic calculations of fragmentation have neglected the possibly deleterious effects of magnetic fields, despite ample evidence for the importance of magnetic support of precollapse clouds. We present here the first numerical hydrodynamic survey of the collapse and fragmentation of initially magnetically supported clouds that takes into account several magnetic field effects in an approximate manner. The models are calculated with a three-dimensional, finite differences code that solves the equations of hydrodynamics, gravitation, and radiative transfer in the Eddington and diffusion approximations. Magnetic field effects are included through two simple approximations: magnetic pressure is added to the gas pressure, and magnetic tension is approximated by gravity dilution once collapse is well underway. Ambipolar diffusion of the magnetic field leading to cloud collapse is treated approximately as well. Models are calculated for a variety of initial cloud density profiles, shapes, and rotation rates. We find that in spite of the inclusion of magnetic field effects, dense cloud cores are capable of fragmenting into binary and multiple protostar systems. Initially prolate clouds tend to fragment into binary protostars, while initially oblate clouds tend to fragment into multiple protostar systems containing a small number (of the order of 4) of fragments. The latter are likely to be subject to rapid orbital evolution, with close encounters possibly leading to the ejection of fragments. Contrary to expectation, magnetic tension effects appear to enhance fragmentation, allowing lower mass fragments to form than would otherwise be possible, because magnetic tension helps to prevent a central density singularity from forming and producing a dominant single object. Magnetically supported dense cloud cores thus seem to be capable of collapsing and fragmenting into sufficient numbers of binary and multiple protostar systems to be compatible with observations of the relative rarity of single protostars.

Simulation of Relativistic Shocks and Associated Radiation from Turbulent Magnetic Fields

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Mizuno, Y.; Niemiec, J.; Medvedev, M.; Zhang, B.; Hardee, P.; Frederiksen, J.; Sol, H.; Pohl, M.; Hartmann, D. H.;

Radiation Electrodynamics of the Photo-Electron Cloud Produced By an Arbitrary Photon Pulse Incident on a Planar Emitting Surface in Vacuum

DTIC Science & Technology

1994-06-01

charge clouds. These finitely-remote fields are then used to compute asymptotic radiation fields in the limit of the field point going to infinity in a 0...like to thank Doug Beason for providing an environment conducive to performing the research reported on here and Michelle Tafoya for her excellent...radiation quantities, however, are obtained only in the limit of the field point going to infinity ; we thus demonstrate the existence of this limit and

[Saccharomyces cerevisiae as a model organism for studying the carcinogenicity of non-ionizing electromagnetic fields and radiation].

PubMed

Voĭchuk, S I

2014-01-01

Medical and biological aspects of the effects of non-ionizing electromagnetic (EM) fields and radiation on human health are the important issues that have arisen as a result of anthropogenic impact on the biosphere. Safe use of man-made sources of non-ionizing electromagnetic fields and radiation in a broad range of frequencies--static, radio-frequency and microwave--is a subject of discussions and speculations. The main problem is the lack of understanding of the mechanism(s) of reception of EMFs by living organisms. In this review we have analyzed the existing literature data regarding the effects of the electromagnetic radiation on the model eukaryotic organism--yeast Saccharomyces cerevisiae. An attempt was made to estimate the probability of induction of carcinogenesis in humans under the influence of magnetic fields and electromagnetic radiation of extremely low frequency, radio frequency and microwave ranges.

Use of an electric field in an electrostatic liquid film radiator.

PubMed

Bankoff, S G; Griffing, E M; Schluter, R A

2002-10-01

Experimental and numerical work was performed to further the understanding of an electrostatic liquid film radiator (ELFR) that was originally proposed by Kim et al.(1) The ELFR design utilizes an electric field that exerts a normal force on the interface of a flowing film. The field lowers the pressure under the film in a space radiator and, thereby, prevents leakage through a puncture in the radiator wall. The flowing film is subject to the Taylor cone instability, whereby a cone of fluid forms underneath an electrode and sharpens until a jet of fluid is pulled toward the electrode and disintegrates into droplets. The critical potential for the instability is shown to be as much as an order of magnitude higher than that used in previous designs.(2) Furthermore, leak stoppage experiments indicate that the critical field is adequate to stop leaks in a working radiator.

Characterisation of ionisation chambers for a mixed radiation field and investigation of their suitability as radiation monitors for the LHC.

PubMed

Theis, C; Forkel-Wirth, D; Perrin, D; Roesler, S; Vincke, H

2005-01-01

Monitoring of the radiation environment is one of the key tasks in operating a high-energy accelerator such as the Large Hadron Collider (LHC). The radiation fields consist of neutrons, charged hadrons as well as photons and electrons with energy spectra extending from those of thermal neutrons up to several hundreds of GeV. The requirements for measuring the dose equivalent in such a field are different from standard uses and it is thus necessary to investigate the response of monitoring devices thoroughly before the implementation of a monitoring system can be conducted. For the LHC, it is currently foreseen to install argon- and hydrogen-filled high-pressure ionisation chambers as radiation monitors of mixed fields. So far their response to these fields was poorly understood and, therefore, further investigation was necessary to prove that they can serve their function well enough. In this study, ionisation chambers of type IG5 (Centronic Ltd) were characterised by simulating their response functions by means of detailed FLUKA calculations as well as by calibration measurements for photons and neutrons at fixed energies. The latter results were used to obtain a better understanding and validation of the FLUKA simulations. Tests were also conducted at the CERF facility at CERN in order to compare the results with simulations of the response in a mixed radiation field. It is demonstrated that these detectors can be characterised sufficiently enough to serve their function as radiation monitors for the LHC.

The enhancement mechanism of thin plasma layer on antenna radiation

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

Wang, Chunsheng, E-mail: wangcs@hit.edu.cn; Jiang, Binhao; Li, Xueai

A model of plasma-antenna is carried out to study the radiation enhancement mechanism of antenna covered by thin plasma layer. The results show when the radiation intensity achieves maximum, a region of equal electric field is formed due to the reflection of electric field at the interface of plasma and air. The plasma layer acted as an extension of the antenna. Furthermore, the shape of plasma layer is changed to verify the effect of plasma boundary on antenna radiation. The study shows the effect of thin plasma layer on electromagnetic field and provides a type of plasma antenna.

Radiative Efficiency of Collisionless Accretion

NASA Astrophysics Data System (ADS)

Gruzinov, Andrei V.

1998-07-01

The radiative efficiency, η≡L/Ṁc2, of a slowly accreting black hole is estimated using a two-temperature model of accretion. The radiative efficiency depends on the magnetic field strength near the Schwarzschild radius. For weak magnetic fields, i.e., β-1 ≡ B2/8πp <~ 10-3, the low efficiency η ~ 10-4 that is assumed in some theoretical models is achieved. For β-1 > 10-3, a significant fraction of viscous heat is dissipated by electrons and radiated away resulting in η > 10-4. At equipartition magnetic fields, β-1 ~ 1, we estimate η ~ 10-1.

Relativistic tidal interaction of a white dwarf with a massive black hole

NASA Technical Reports Server (NTRS)

Frolov, V. P.; Khokhlov, A. M.; Novikov, I. D.; Pethick, C. J.

1994-01-01

We compute encounters of a realistic white dwarf model with a massive black hole in the regime where relativistic effects are important, using a three-dimensional, finite-difference, Eulerian, piecewise parabolic method (PPM) hydrodynamical code. Both disruptive and nondisruptive encounters are considered. We identify and discuss relativistic effects important for the problem: relativistic shift of the pericenter distance, time delay, relativistic precession, and the tensorial structure of the tidal forces. In the nondisruptive case, stripping of matter takes place. In the surface layers of the surviving core, complicated hydrodynamical phenomena are revealed. In both disruptive and nondispruptive encounters, material flows out in the form of two thin, S-shaped, supersonic jets. Our results provide realistic initial conditions for the subsequent investigation of the dynamics of the debris in the field of the black hole. We evaluate the critical conditions for complete disruption of the white dwarf, and compare our results with the corresponding results for nonrelativistic encounters.

The quest for extraterrestrial life: what about the viruses?

USGS Publications Warehouse

Griffin, Dale Warren

2013-01-01

Recently, viruses have been recognized as the most numerous entities and the primary drivers of evolution on Earth. Historically, viruses have been mostly ignored in the field of astrobiology due to the view that they are not alive in the classical sense and if encountered would not present risk due to their host-specific nature. What we currently know of viruses is that we are most likely to encounter them on other life-bearing planets; that while some are exquisitely host-specific, many viruses can utilize hundreds of different host species; that viruses are known to exist in our planet's most extreme environments; and that while many do not survive long outside their hosts, some can survive for extended periods, especially in the cold. In our quest for extraterrestrial life, we should be looking for viruses; and while any encountered may pose no risk, the possibility of an encounter with a virus capable of accessing multiple cell types exists, and any prospective contact with such an organism should be treated accordingly.

The quest for extraterrestrial life: what about the viruses?

PubMed

Griffin, Dale Warren

2013-08-01

Recently, viruses have been recognized as the most numerous entities and the primary drivers of evolution on Earth. Historically, viruses have been mostly ignored in the field of astrobiology due to the view that they are not alive in the classical sense and if encountered would not present risk due to their host-specific nature. What we currently know of viruses is that we are most likely to encounter them on other life-bearing planets; that while some are exquisitely host-specific, many viruses can utilize hundreds of different host species; that viruses are known to exist in our planet's most extreme environments; and that while many do not survive long outside their hosts, some can survive for extended periods, especially in the cold. In our quest for extraterrestrial life, we should be looking for viruses; and while any encountered may pose no risk, the possibility of an encounter with a virus capable of accessing multiple cell types exists, and any prospective contact with such an organism should be treated accordingly.

AOI 1— COMPUTATIONAL ENERGY SCIENCES:MULTIPHASE FLOW RESEARCH High-fidelity multi-phase radiation module for modern coal combustion systems

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

Modest, Michael

The effects of radiation in particle-laden flows were the object of the present research. The presence of particles increases optical thickness substantially, making the use of the “optically thin” approximation in most cases a very poor assumption. However, since radiation fluxes peak at intermediate optical thicknesses, overall radiative effects may not necessarily be stronger than in gas combustion. Also, the spectral behavior of particle radiation properties is much more benign, making spectral models simpler (and making the assumption of a gray radiator halfway acceptable, at least for fluidized beds when gas radiation is not large). On the other hand, particlesmore » scatter radiation, making the radiative transfer equation (RTE) much more di fficult to solve. The research carried out in this project encompassed three general areas: (i) assessment of relevant radiation properties of particle clouds encountered in fluidized bed and pulverized coal combustors, (ii) development of proper spectral models for gas–particulate mixtures for various types of two-phase combustion flows, and (iii) development of a Radiative Transfer Equation (RTE) solution module for such applications. The resulting models were validated against artificial cases since open literature experimental data were not available. The final models are in modular form tailored toward maximum portability, and were incorporated into two research codes: (i) the open-source CFD code OpenFOAM, which we have extensively used in our previous work, and (ii) the open-source multi-phase flow code MFIX, which is maintained by NETL.« less

Research on the electromagnetic radiation characteristics of the gas main switch of a capacitive intense electron-beam accelerator

NASA Astrophysics Data System (ADS)

Qiu, Yongfeng; Liu, Jinliang; Yang, Jianhua; Cheng, Xinbing; Li, Guolin

2017-11-01

Strong electromagnetic fields are radiated during the operation of the intense electron-beam accelerator (IEBA), which may lead to the nearby electronic devices out of order. In this paper, the research on the electromagnetic radiation characteristic of the gas main switch of a capacitive IEBA is carried out by the methods of theory analysis and experiment investigation. It is obtained that the gas main switch is the dominating radiation resource. In the absence of electromagnetic shielding for the gas main switch, when the pulse forming line of the IEBA is charged to 700 kV, the radiation field with amplitude of 3280 V/m, dominant frequency of 84 MHz and high frequency 100 MHz is obtained at a distance of 10 meters away from the gas main switch. The experimental results of the radiation field agree with the theoretical calculations. We analyze the achievements of several research groups and find that there is a relationship between the rise time (T) of the transient current of the gas main switch and the dominant frequency (F) of the radiation field, namely, F*T=1. Contrast experiment is carried out with a metal shield cover for the gas main switch. Experimental results show that for the shielded setup the radiation field reduces to 115 V/m, the dominant frequency increases to 86.5 MHz at a distance of 10 away meters from the gas main switch. These conclusions are beneficial for further research on the electromagnetic radiation and protection of the IEBA.

Radiation-like scalar field and gauge fields in cosmology for a theory with dynamical time

NASA Astrophysics Data System (ADS)

Benisty, David; Guendelman, E. I.

2016-09-01

Cosmological solutions with a scalar field behaving as radiation are obtained, in the context of gravitational theory with dynamical time. The solution requires the spacial curvature of the universe k, to be zero, unlike the standard radiation solutions, which do not impose any constraint on the spatial curvature of the universe. This is because only such k = 0 radiation solutions pose a homothetic Killing vector. This kind of theory can be used to generalize electromagnetism and other gauge theories, in curved spacetime, and there are no deviations from standard gauge field equation (like Maxwell equations) in the case there exist a conformal Killing vector. But there could be departures from Maxwell and Yang-Mills equations, for more general spacetimes.

Operational Prototype Development of a Global Aircraft Radiation Exposure Nowcast

NASA Astrophysics Data System (ADS)

Mertens, Christopher; Kress, Brian; Wiltberger, Michael; Tobiska, W. Kent; Bouwer, Dave

Galactic cosmic rays (GCR) and solar energetic particles (SEP) are the primary sources of human exposure to high linear energy transfer (LET) radiation in the atmosphere. High-LET radiation is effective at directly breaking DNA strands in biological tissue, or producing chemically active radicals in tissue that alter the cell function, both of which can lead to cancer or other adverse health effects. A prototype operational nowcast model of air-crew radiation exposure is currently under development and funded by NASA. The model predicts air-crew radiation exposure levels from both GCR and SEP that may accompany solar storms. The new air-crew radiation exposure model is called the Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) model. NAIRAS will provide global, data-driven, real-time exposure predictions of biologically harmful radiation at aviation altitudes. Observations are utilized from the ground (neutron monitors), from the atmosphere (the NCEP Global Forecast System), and from space (NASA/ACE and NOAA/GOES). Atmospheric observations characterize the overhead mass shielding and the ground-and space-based observations provide boundary conditions on the incident GCR and SEP particle flux distributions for transport and dosimetry calculations. Radiation exposure rates are calculated using the NASA physics-based HZETRN (High Charge (Z) and Energy TRaNsport) code. An overview of the NAIRAS model is given: the concept, design, prototype implementation status, data access, and example results. Issues encountered thus far and known and/or anticipated hurdles to research to operations transition are also discussed.

RITRACKS: A Software for Simulation of Stochastic Radiation Track Structure, Micro and Nanodosimetry, Radiation Chemistry and DNA Damage for Heavy Ions

NASA Technical Reports Server (NTRS)

Plante, I; Wu, H

2014-01-01

The code RITRACKS (Relativistic Ion Tracks) has been developed over the last few years at the NASA Johnson Space Center to simulate the effects of ionizing radiations at the microscopic scale, to understand the effects of space radiation at the biological level. The fundamental part of this code is the stochastic simulation of radiation track structure of heavy ions, an important component of space radiations. The code can calculate many relevant quantities such as the radial dose, voxel dose, and may also be used to calculate the dose in spherical and cylindrical targets of various sizes. Recently, we have incorporated DNA structure and damage simulations at the molecular scale in RITRACKS. The direct effect of radiations is simulated by introducing a slight modification of the existing particle transport algorithms, using the Binary-Encounter-Bethe model of ionization cross sections for each molecular orbitals of DNA. The simulation of radiation chemistry is done by a step-by-step diffusion-reaction program based on the Green's functions of the diffusion equation]. This approach is also used to simulate the indirect effect of ionizing radiation on DNA. The software can be installed independently on PC and tablets using the Windows operating system and does not require any coding from the user. It includes a Graphic User Interface (GUI) and a 3D OpenGL visualization interface. The calculations are executed simultaneously (in parallel) on multiple CPUs. The main features of the software will be presented.

PLANT PROTECTIVE RESPONSE TO ENHANCED UV-B RADIATION UNDER FIELD CONDITIONS: LEAF OPTICAL PROPERTIES AND PHOTOSYNTHESIS

EPA Science Inventory

Plants of Vicia faba were grown in the field during early to midsummer while receiving two levels of supplemental UV-B radiation. Light-saturated photosynthesis and stomatal diffusive conductance of intact leaves did not show any indications of UV-radiation damage. Supplemental U...

Magnetic field amplification by the r-mode instability

NASA Astrophysics Data System (ADS)

Chugunov, A. I.; Friedman, J. L.; Lindblom, L.; Rezzolla, L.

2017-12-01

We discuss the magnetic field enhancement by unstable r-modes (driven by the gravitational radiation reaction force) in rotating stars. In the absence of a magnetic field, gravitational radiation exponentially increases the r-mode amplitude α, and accelerates differential rotation (secular motion of fluid elements). For a magnetized star, differential rotation enhances the magnetic field energy. Rezzolla et al (2000-2001) argued that if the magnetic energy grows faster than the gravitational radiation reaction force pumps energy into the r-modes, then the r-mode instability is suppressed. Chugunov (2015) demonstrated that without gravitational radiation, differential rotation can be treated as a degree of freedom decoupled from the r-modes and controlled by the back reaction of the magnetic field. In particular, the magnetic field windup does not damp r-modes. Here we discuss the effect of the back reaction of the magnetic field on differential rotation of unstable r-modes, and show that it limits the generated magnetic field and the magnetic energy growth rate preventing suppression of the r-mode instability by magnetic windup at low saturation amplitudes, α ≪ 1, predicted by current models.

The Role of Mass Spectrometry-Based Metabolomics in Medical Countermeasures Against Radiation

PubMed Central

Patterson, Andrew D.; Lanz, Christian; Gonzalez, Frank J.; Idle, Jeffrey R.

2013-01-01

Radiation metabolomics can be defined as the global profiling of biological fluids to uncover latent, endogenous small molecules whose concentrations change in a dose-response manner following exposure to ionizing radiation. In response to the potential threat of nuclear or radiological terrorism, the Center for High-Throughput Minimally Invasive Radiation Biodosimetry (CMCR) was established to develop field-deployable biodosimeters based, in principle, on rapid analysis by mass spectrometry of readily and easily obtainable biofluids. In this review, we briefly summarize radiation biology and key events related to actual and potential nuclear disasters, discuss the important contributions the field of mass spectrometry has made to the field of radiation metabolomics, and summarize current discovery efforts to use mass spectrometry-based metabolomics to identify dose-responsive urinary constituents, and ultimately to build and deploy a noninvasive high-throughput biodosimeter. PMID:19890938

Exploring the effects of individual customer incivility encounters on employee incivility: the moderating roles of entity (in)civility and negative affectivity.

PubMed

Walker, David D; van Jaarsveld, Danielle D; Skarlicki, Daniel P

2014-01-01

Incivility between customers and employees is common in many service organizations. These encounters can have negative outcomes for employees, customers, and the organization. To date, researchers have tended to study incivility as an aggregated and accumulated phenomenon (entity perspective). In the present study, we examined incivility as it occurs during a specific service encounter (event perspective) alongside the entity perspective. Using a mixed-method multilevel field study of customer service interactions, we show that individual customer incivility encounters (i.e., events) trigger employee incivility as a function of the employee's overall accumulated impression of the (in)civility in his or her customer interactions, such that the effects are more pronounced among employees who generally perceive their customer interactions to be more versus less civil. We also find that these interactive effects occur only among employees who are lower (vs. higher) in negative affectivity. Our results show that, in order to expand the understanding of customer incivility, it is important to study the incivility encounter, the social context in which negative customer interactions occur, and individual differences. PsycINFO Database Record (c) 2014 APA, all rights reserved

Evaluation of the trade-offs encountered in planning and treating locally advanced head and neck cancer: intensity-modulated radiation therapy vs dual-arc volumetric-modulated arc therapy

PubMed Central

Oliver, M; McConnell, D; Romani, M; McAllister, A; Pearce, A; Andronowski, A; Wang, X; Leszczynski, K

2012-01-01

Objective The primary purpose of this study was to assess the practical trade-offs between intensity-modulated radiation therapy (IMRT) and dual-arc volumetric-modulated arc therapy (DA-VMAT) for locally advanced head and neck cancer (HNC). Methods For 15 locally advanced HNC data sets, nine-field step-and-shoot IMRT plans and two full-rotation DA-VMAT treatment plans were created in the Pinnacle3 v. 9.0 (Philips Medical Systems, Fitchburg, WI) treatment planning environment and then delivered on a Clinac iX (Varian Medical Systems, Palo Alto, CA) to a cylindrical detector array. The treatment planning goals were organised into four groups based on their importance: (1) spinal cord, brainstem, optical structures; (2) planning target volumes; (3) parotids, mandible, larynx and brachial plexus; and (4) normal tissues. Results Compared with IMRT, DA-VMAT plans were of equal plan quality (p>0.05 for each group), able to be delivered in a shorter time (3.1 min vs 8.3 min, p<0.0001), delivered fewer monitor units (on average 28% fewer, p<0.0001) and produced similar delivery accuracy (p>0.05 at γ2%/2mm and γ3%/3mm). However, the VMAT plans took more planning time (28.9 min vs 7.7 min per cycle, p<0.0001) and required more data for a three-dimensional dose (20 times more, p<0.0001). Conclusions Nine-field step-and-shoot IMRT and DA-VMAT are both capable of meeting the majority of planning goals for locally advanced HNC. The main trade-offs between the techniques are shorter treatment time for DA-VMAT but longer planning time and the additional resources required for implementation of a new technology. Based on this study, our clinic has incorporated DA-VMAT for locally advanced HNC. Advances in knowledge DA-VMAT is a suitable alternative to IMRT for locally advanced HNC. PMID:22806619

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

Fu,; Chen, Y; Yu, Y

Purpose: Orthogonal kV image pairs are used for target localization when fiducial markers are implanted. CBCT is used to verify cone SRS setup. Therefore it is necessary to evaluate the isocenter congruence between radiation fields and kV imaging center. This study used a simple method to evaluate the isocenter congruence, and compared the results for MLC and cone fields on two different Linacs. Methods: Varian OBI block was attached on the couch. It has a central 1mm BB with markers on three surfaces to align with laser. KV and MV images were taken at four cardinal angles. A 3x3cm2 MLCmore » field and a 20mm cone field were irradiated respectively. On each kV image, the distance from BB center to the kV graticule center were measured. On the MV image of MLC field, the center of radiation field was determined manually, while for cone field, the Varian AM maintenance software was used to analyze the distance between BB and radiation field. The subtraction of the two distances gives the discrepancy between kV and radiation centers. Each procedure was repeated on five days at Trilogy and TrueBeam respectively. Results: The maximum discrepancy was found in the longitudinal direction at 180° gantry angel. It was 1.5±0.1mm for Trilogy and 0.6±0.1mm for TrueBeam. For Trilogy, although radiation center wobbled only 0.7mm and image center wobbled 0.8mm, they wobbled to the opposite direction. KV Pair using gantry 180° should be avoided in this case. Cone vs. kV isocenter has less discrepancy than MLC for Trilogy. Conclusion: Radiation isocenter of MLC and cone field is different, so is between Trilogy and TrueBeam. The method is simple and reproducible to check kV and radiation isocenter congruence.« less

Convergence of the Bouguer-Beer law for radiation extinction in particulate media

NASA Astrophysics Data System (ADS)

Frankel, A.; Iaccarino, G.; Mani, A.

2016-10-01

Radiation transport in particulate media is a common physical phenomenon in natural and industrial processes. Developing predictive models of these processes requires a detailed model of the interaction between the radiation and the particles. Resolving the interaction between the radiation and the individual particles in a very large system is impractical, whereas continuum-based representations of the particle field lend themselves to efficient numerical techniques based on the solution of the radiative transfer equation. We investigate radiation transport through discrete and continuum-based representations of a particle field. Exact solutions for radiation extinction are developed using a Monte Carlo model in different particle distributions. The particle distributions are then projected onto a concentration field with varying grid sizes, and the Bouguer-Beer law is applied by marching across the grid. We show that the continuum-based solution approaches the Monte Carlo solution under grid refinement, but quickly diverges as the grid size approaches the particle diameter. This divergence is attributed to the homogenization error of an individual particle across a whole grid cell. We remark that the concentration energy spectrum of a point-particle field does not approach zero, and thus the concentration variance must also diverge under infinite grid refinement, meaning that no grid-converged solution of the radiation transport is possible.

Radiation and Internal Charging Environments for Thin Dielectrics in Interplanetary Space

NASA Technical Reports Server (NTRS)

Minow, Joseph I.; Parker, Linda Neergaard; Altstatt, Richard L.

2004-01-01

Spacecraft designs using solar sails for propulsion or thin membranes to shade instruments from the sun to achieve cryogenic operating temperatures are being considered for a number of missions in the next decades. A common feature of these designs are thin dielectric materials that will be exposed to the solar wind, solar energetic particle events, and the distant magnetotail plasma environments encountered by spacecraft in orbit about the Earth-Sun L2 point. This paper will discuss the relevant radiation and internal charging environments developed to support spacecraft design for both total dose radiation effects as well as dose rate dependent phenomenon, such as internal charging in the solar wind and distant magnetotail environments. We will describe the development of radiation and internal charging environment models based on nearly a complete solar cycle of Ulysses solar wind plasma measurements over a complete range of heliocentric latitudes and the early years of the Geotail mission where distant magnetotail plasma environments were sampled beyond X(sub GSE) = -100 Re to nearly L2 (X(sub GSE) -236 Re). Example applications of the environment models are shown to demonstrate the radiation and internal charging environments of thin materials exposed to the interplanetary space plasma environments.

Animal studies of life shortening and cancer risk from space radiation

NASA Astrophysics Data System (ADS)

Wood, D. H.; Yochmowitz, M. G.; Hardy, K. A.; Salmon, Y. L.

The U. S. Air Force study of the delayed effects of single, total body exposures to simulated space radiation in rhesus monkeys is now in its 21st year. Observations on 301 irradiated and 57 age-matched control animals indicate that life expectancy loss from exposure to protons in the energy range encountered in the Van Allen belts and solar proton events can be expressed as a logarithmic function of the dose. The primary causes of life shortening are cancer and endometriosis (an abnormal proliferation of the lining of the uterus in females). Life shortening estimates permit comparison of the risk associated with space radiation exposures to be compared with that of other occupational and environmental hazards, thereby facilitating risk/benefit decisions in the planning and operational phases of manned space missions. Calculations of the relative risk of fatal cancers in the irradiated subjects reveal that the total body surface dose required to double the risk of death from cancer over a 20-year post exposure period varies with the linear energy transfer (LET) of the radiation. The ability to determine the integrated dose and LET spectrum in space radiation exposures of human is, therefore, critical to the assessment of life-time cancer risk.

A NOVEL EMISSION SPECTRUM FROM A RELATIVISTIC ELECTRON MOVING IN A RANDOM MAGNETIC FIELD

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

Teraki, Yuto; Takahara, Fumio, E-mail: teraki@vega.ess.sci.osaka-u.ac.jp

2011-07-10

We numerically calculate the radiation spectrum from relativistic electrons moving in small-scale turbulent magnetic fields expected in high-energy astrophysical sources. Such a radiation spectrum is characterized by the strength parameter a = {lambda}{sub B} e|B|/mc {sup 2}, where {lambda}{sub B} is the length scale of the turbulent field. When a is much larger than the Lorentz factor of a radiating electron {gamma}, synchrotron radiation is realized, while a << 1 corresponds to the so-called jitter radiation regime. Because for 1 < a < {gamma} we cannot use either approximations, we should have recourse to the Lienard-Wiechert potential to evaluate themore » radiation spectrum, which is performed in this Letter. We generate random magnetic fields assuming Kolmogorov turbulence, inject monoenergetic electrons, solve the equation of motion, and calculate the radiation spectrum. We perform numerical calculations for several values of a with {gamma} = 10. We obtain various types of spectra ranging between jitter radiation and synchrotron radiation. For a {approx} 7, the spectrum takes a novel shape which had not been noticed up to now. It is like a synchrotron spectrum in the middle energy region, but in the low frequency region it is a broken power law and in the high frequency region an extra power-law component appears beyond the synchrotron cutoff. We give a physical explanation of these features.« less

Preliminary investigation of proton and helium ion radiation effects on fluorescent dyes for use in astrobiology applications.

PubMed

Thompson, Daniel P; Wilson, Paul K; Sims, Mark R; Cullen, David C; Holt, John M C; Parker, David J; Smith, Mike D

2006-04-15

The Specific Molecular Identification of Life Experiment (SMILE) instrument (Sims et al. Planet. Space Science 2005, 53, 781-791) proposes to use specific molecular receptors for the detection of organic biomarkers on future astrobiology missions (e.g., to Mars). Such receptors will be used in assays with fluorescently labeled assay reagents. A key uncertainty of this approach is whether the fluorescent labels used in the system will survive exposure to levels of solar and galactic particle radiation encountered during a flight to Mars. Therefore, two fluorescent dyes (fluorescein and Alexa Fluor 633) have been exposed to low-energy proton and alpha radiation with total fluences comparable or exceeding that expected during an unshielded cruise to Mars. The results of these initial experiments are presented, which show that both dyes retain their fluorescent properties after irradiation. No significant alteration in the absorption and emission wavelengths or the quantum yields of the dyes with either radiation exposure was found. These results suggest other structurally similar fluorophores will likely retain their fluorescent properties after exposure to similar levels of proton and alpha radiation. However, more extensive radiation fluorophore testing is needed before their suitability for astrobiology missions to Mars can be fully confirmed.

Quantitative Proteomic Profiling of Low-Dose Ionizing Radiation Effects in a Human Skin Model

PubMed Central

Hengel, Shawna M.; Aldrich, Joshua T.; Waters, Katrina M.; Pasa-Tolic, Ljiljana; Stenoien, David L.

2014-01-01

To assess responses to low-dose ionizing radiation (LD-IR) exposures potentially encountered during medical diagnostic procedures, nuclear accidents or terrorist acts, a quantitative proteomic approach was used to identify changes in protein abundance in a reconstituted human skin tissue model treated with 0.1 Gy of ionizing radiation. To improve the dynamic range of the assay, subcellular fractionation was employed to remove highly abundant structural proteins and to provide insight into radiation-induced alterations in protein localization. Relative peptide quantification across cellular fractions, control and irradiated samples was performing using 8-plex iTRAQ labeling followed by online two-dimensional nano-scale liquid chromatography and high resolution MS/MS analysis. A total of 107 proteins were detected with statistically significant radiation-induced change in abundance (>1.5 fold) and/or subcellular localization compared to controls. The top biological pathways identified using bioinformatics include organ development, anatomical structure formation and the regulation of actin cytoskeleton. From the proteomic data, a change in proteolytic processing and subcellular localization of the skin barrier protein, filaggrin, was identified, and the results were confirmed by western blotting. This data indicate post-transcriptional regulation of protein abundance, localization and proteolytic processing playing an important role in regulating radiation response in human tissues. PMID:28250387

Integrating the healthcare enterprise in radiation oncology plug and play--the future of radiation oncology?

PubMed

Abdel-Wahab, May; Rengan, Ramesh; Curran, Bruce; Swerdloff, Stuart; Miettinen, Mika; Field, Colin; Ranjitkar, Sunita; Palta, Jatinder; Tripuraneni, Prabhakar

2010-02-01

To describe the processes and benefits of the integrating healthcare enterprises in radiation oncology (IHE-RO). The IHE-RO process includes five basic steps. The first step is to identify common interoperability issues encountered in radiation treatment planning and the delivery process. IHE-RO committees partner with vendors to develop solutions (integration profiles) to interoperability problems. The broad application of these integration profiles across a variety of vender platforms is tested annually at the Connectathon event. Demonstration of the seamless integration and transfer of patient data to the potential users are then presented by vendors at the public demonstration event. Users can then integrate these profiles into requests for proposals and vendor contracts by institutions. Incorporation of completed integration profiles into requests for proposals can be done when purchasing new equipment. Vendors can publish IHE integration statements to document the integration profiles supported by their products. As a result, users can reference integration profiles in requests for proposals, simplifying the systems acquisition process. These IHE-RO solutions are now available in many of the commercial radiation oncology-related treatment planning, delivery, and information systems. They are also implemented at cancer care sites around the world. IHE-RO serves an important purpose for the radiation oncology community at large. Copyright 2010 Elsevier Inc. All rights reserved.

RADECS Short Course Session I: The Space Radiation Environment

NASA Technical Reports Server (NTRS)

Xapsos, Michael; Bourdarie, Sebastien

2007-01-01

The presented slides and accompanying paper focus on radiation in the space environment. Since space exploration has begun it has become evident that the space environment is a highly aggressive medium. Beyond the natural protection provided by the Earth's atmosphere, various types of radiation can be encountered. Their characteristics (energy and nature), origins and distributions in space are extremely variable. This environment degrades electronic systems and on-board equipment in particular and creates radiobiological hazards during manned space flights. Based on several years of space exploration, a detailed analysis of the problems on satellites shows that the part due to the space environment is not negligible. It appears that the malfunctions are due to problems linked to the space environment, electronic problems, design problems, quality problems, other issues, and unexplained reasons. The space environment is largely responsible for about 20% of the anomalies occurring on satellites and a better knowledge of that environment could only increase the average lifetime of space vehicles. This naturally leads to a detailed study of the space environment and of the effects that it induces on space vehicles and astronauts. Sources of radiation in the space environment are discussed here and include the solar activity cycle, galactic cosmic rays, solar particle events, and Earth radiation belts. Future challenges for space radiation environment models are briefly addressed.

Characterisation and optimisation of Ground Penetrating Radar antennas

NASA Astrophysics Data System (ADS)

Warren, Craig; Giannopoulos, Antonios

2014-05-01

Research on the characterisation and optimisation of Ground Penetrating Radar (GPR) antennas will be presented as part of COST Action TU1208 "Civil Engineering Applications of Ground Penetrating Radar". This work falls within the remit of Working Group 1 - "Novel GPR instrumentation" which focuses on the design of innovative GPR equipment for Civil Engineering (CE) applications, on the building of prototypes and on the testing and optimisation of new systems. The diversity of applications of GPR has meant there are a number of different GPR antenna designs available to the end-user as well as those being used in the research community. The type and size of a GPR antenna is usually dependent on the application, e.g. low frequency antennas, which are physically larger, are used where significant depth of penetration is important, whereas high frequency antennas, which are physically smaller, are used where less penetration and better resolution are required. Understanding how energy is transmitted and received by a particular GPR antenna has many benefits: it could lead to more informed usage of the antenna in GPR surveys; improvements in antenna design; and better interpretation of GPR signal returns from the ground/structure. The radiation characteristics of a particular antenna are usually investigated by studying the radiation patterns and directivity. For GPR antennas it is also important to study these characteristics when the antenna is in different environments that would typically be encountered in GPR surveys. In this work Finite-Difference Time-Domain (FDTD) numerical models of GPR antennas have been developed. These antenna models replicate all the detailed geometry and main components of the real antennas. The models are representative of typical high-frequency, high-resolution GPR antennas primarily used in CE for the evaluation of structural features in concrete: the location of rebar, conduits, and post-tensioned cables, as well as the estimation of material thickness on bridge decks and pavements. Radiation patterns obtained using the antenna models as well as physical measurements have been used to investigate the radiation characteristics of high-frequency GPR antennas. Studies were conducted with homogeneous materials of different dielectric constants (Er=3, 10, 30, & 72) and at a range of observation distances. The first objective was to compare, using the FDTD antenna model, 'traditional' transmitted field patterns with field patterns obtained using responses from a target spaced at regular intervals around the circumference of a circle, i.e. received energy. Our initial results show, for the same dielectric and observation distance, E- and H-field patterns obtained using the received energy approach have a significantly narrower main lobe than the traditional transmitted patterns. This raises the question of which approach is more beneficial for the characterisation of GPR antennas, and hence better interpretation of GPR responses. The second objective was to compare modelled field patterns with measured patterns obtained from a commercial high-frequency GPR antenna using the received energy approach. The measurements were made in different oil-in-water emulsions which were used to simulate materials with different permittivities and conductivities. Initial comparisons of the measured and modelled data show a very good correlation, which validates use of the antenna model for further studies.

Effect of Field Size and Length of Plantar Spur on Treatment Outcome in Radiation Therapy of Plantar Fasciitis: The Bigger the Better?

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

Hermann, Robert Michael, E-mail: hermann@strahlentherapie-westerstede.com; Abteilung Strahlentherapie und Spezielle Onkologie, Medizinische Hochschule Hannover; Meyer, Andreas

2013-12-01

Purpose: Radiation therapy is well established in the treatment of painful plantar fasciitis or heel spur. A retrospective analysis was conducted to investigate the effect of field definition on treatment outcome and to determine the impact of factors potentially involved. Methods and Materials: A review of treatment data of 250 patients (285 heels) with a mean follow-up time of 11 months showed that complete symptom remission occurred in 38%, partial remission in 32%, and no change in 19% (11% were lost to follow-up). Variables such as radiologic evidence of plantar spurs, their length, radiation dose, field size, age, sex, andmore » onset of pain before administration of radiation therapy were investigated in univariate and multivariate regression analyses. Results: Treatment response depended upon age >53 years, length of heel spur ≤6.5 mm (or no radiologic evidence of a heel spur), and onset of pain <12 months before radiation therapy. Patients with these clinical prerequisites stood a 93% chance of clinical response. Without these prerequisites, only 49% showed any impact. No influence of field size on treatment outcome became evident. Conclusion: Patients with short plantar heel spurs benefit from radiation therapy equally well as patients without any radiologic evidence. Moreover, smaller field sizes have the same positive effect as commonly used large field definitions covering the entire calcaneal bone. This leads to a recommendation of a considerable reduction of field size in future clinical practice.« less

Investigation of the radiation properties of magnetospheric ELF waves induced by modulated ionospheric heating

NASA Astrophysics Data System (ADS)

Wang, Feng; Ni, Binbin; Zhao, Zhengyu; Zhao, Shufan; Zhao, Guangxin; Wang, Min

2017-05-01

Electromagnetic extremely low frequency (ELF) waves play an important role in modulating the Earth's radiation belt electron dynamics. High-frequency (HF) modulated heating of the ionosphere acts as a viable means to generate artificial ELF waves. The artificial ELF waves can reside in two different plasma regions in geo-space by propagating in the ionosphere and penetrating into the magnetosphere. As a consequence, the entire trajectory of ELF wave propagation should be considered to carefully analyze the wave radiation properties resulting from modulated ionospheric heating. We adopt a model of full wave solution to evaluate the Poynting vector of the ELF radiation field in the ionosphere, which can reflect the propagation characteristics of the radiated ELF waves along the background magnetic field and provide the initial condition of waves for ray tracing in the magnetosphere. The results indicate that the induced ELF wave energy forms a collimated beam and the center of the ELF radiation shifts obviously with respect to the ambient magnetic field with the radiation power inversely proportional to the wave frequency. The intensity of ELF wave radiation also shows a weak correlation with the size of the radiation source or its geographical location. Furthermore, the combination of ELF propagation in the ionosphere and magnetosphere is proposed on basis of the characteristics of the ELF radiation field from the upper ionospheric boundary and ray tracing simulations are implemented to reasonably calculate magnetospheric ray paths of ELF waves induced by modulated ionospheric heating.

Radiation Characteristics of Antennas Embedded in a Layer with Two-Temperature Electron Population

DTIC Science & Technology

2013-10-01

high that the microwave signals are completely cut off. This is the famous `` communication blackout’’ encountered during the Apollo missions in the...1960s. Indeed issues with communication with reentry vehicles were studied even before Apollo missions [3]. Such communication blackout problems are...during Apollo missions [24], [25]. Although there are now other means to communicate (via satellite) the sensor needs for modern hypersonic vehicles

Basalt models for the Mars penetrator mission: Geology of the Amboy Lava Field, California

NASA Technical Reports Server (NTRS)

Greeley, R.; Bunch, T. E.

1976-01-01

Amboy lava field (San Bernardino County, California) is a Holocene basalt flow selected as a test site for potential Mars Penetrators. A discussion is presented of (1) the general relations of basalt flow features and textures to styles of eruptions on earth, (2) the types of basalt flows likely to be encountered on Mars and the rationale for selection of the Amboy lava field as a test site, (3) the general geology of the Amboy lava field, and (4) detailed descriptions of the target sites at Amboy lava field.

The radiation from slots in truncated dielectric-covered surfaces

NASA Technical Reports Server (NTRS)

Hwang, Y. M.; Kouyoumjian, R. G.; Pathak, P. H.

1974-01-01

A theoretical approach based on the geometrical theory of diffraction is used to study the electromagnetic radiation from a narrow slot in a dielectric-covered perfectly-conducting surface terminated at an edge. The total far-zone field is composed of a geometrical optics field and a diffracted field. The geometrical optics field is the direct radiation from the slot to the field point. The slot also generates surface waves which are incident at the termination of the dielectric cover, where singly-diffracted rays and reflected surface waves are excited. The diffraction and reflection coefficients are obtained from the canonical problem of the diffraction of a surface wave by a right-angle wedge where the dielectric-covered surface is approximated by an impedance surface. This approximation is satisfactory for a very thin cover; however, the radiation from its vertical and faces cannot be neglected in treating the thicker dielectric cover. This is taken into account by using a Kirchhoff-type approximation, which contributes a second term to the diffraction coefficient previously obtained. The contributions from the geometrical optics field, the singly-diffracted rays and all significant multiply-diffracted rays are summed to give the total radiation. Calculated and measured patterns are found to be in good agreement.

Low-frequency electromagnetic plasma waves at comet P/Grigg-Skjellerup: Analysis and interpretation

NASA Technical Reports Server (NTRS)

Neubauer, Fritz M.; Glassmeier, Karl-Heinz; Coates, A. J.; Johnstone, A. D.

1993-01-01

The propagation and polarization characteristic of low-frequency electromagnetic wave fields near comet P/Grigg-Skjellerup (P/GS) are analyzed using magnetic field and plasma observations obtained by the Giotto magnetometer experiment and the Johnstone plasma analyzer during the encounter at the comet on July 10, 1992. The results have been physically interpreted.

The Content of Educational Psychology: An Analysis of Top Ranked Journals from 2003 through 2007

ERIC Educational Resources Information Center

Nolen, Amanda L.

2009-01-01

Educational psychology as a field of study has encountered a lack of distinction by overlapping with other fields of study or disciplines. Consequently, educational psychology continues to have difficulty claiming jurisdiction over bodies of research knowledge and has been encroached upon by other more crystallized disciplines. The purpose of this…