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1

Diffuse UV Background Radiation  

NASA Astrophysics Data System (ADS)

The diffuse UV sky is expected to glow with significant amounts of starlight that is scattered from the interstellar dust. The albedo and scattering pattern of the dust in the ultraviolet are both well established, and are both fairly independent of wavelength from 912 Å to 3000 Å. We present 1943 Voyager spectra of the diffuse cosmic background radiation from 500 Å to 1200 Å, and we compare their brightnesses, and their distribution on the sky, to those observed (Murthy et al., ApJ 724, 1389, 2010) from the GALEX mission at longer wavelengths (1530 Å). Significant differences appear, suggesting that background radiation components in addition to dust-scattered starlight may be present in both spectral regions.

Conn Henry, Richard; Murthy, J.

2012-01-01

2

Models of diffuse solar radiation  

Microsoft Academic Search

For some locations both global and diffuse solar radiation are measured. However, for many locations, only global is measured, or inferred from satellite data. For modelling solar energy applications, the amount of radiation on a tilted surface is needed. Since only the direct component on a tilted surface can be calculated from trigonometry, we need to have diffuse on the

John Boland; Barbara Ridley; Bruce Brown

2008-01-01

3

Diffuse galactic radiation  

NASA Astrophysics Data System (ADS)

High-energy interstellar emission is produced by interactions of cosmic-ray electrons and nuclei with the interstellar medium and low-energy radiation fields in the Milky Way. This is not only a background for point-like and extended sources studies, but also a unique tool to learn about cosmic rays and the interstellar medium. Thanks to its energy range from 20 MeV to more than 300 GeV, its large effective area and field of view, its improved angular resolution, as well as an all-sky survey strategy, the Fermi Large Area Telescope (LAT) is the best instrument to study high-energy Galactic interstellar emission, which accounts for most of the photons it detects. To disentangle degeneracies in the GeV range, complementary observations are crucial at lower and higher energy, for example by INTEGRAL/SPI, CGRO/COMPTEL or HESS, as well as all-sky radio or sub-millimeter surveys. We provide an overview of the Galactic interstellar gamma-ray emission modeling and focus on ?-ray H I emissivity and large scale structures studies performed with the LAT.

Casandjian, Jean-Marc

2012-12-01

4

About diffusivity, radiative viscosity and particle transport  

NASA Astrophysics Data System (ADS)

It is shown that the process called radiative diffusivity by Morel & Thévenin (2002, 390, 611) does not exist as they describe it. Their description is based on a confusion between atomic diffusion and turbulent transport (often called turbulent diffusion in the context of particle transport in stars). We evaluate how ions are slowed down by photons and show that this may be neglected in atomic diffusion calculations. In their evolutionary model calculations, \\citet{MorelTh2002} made the {ad hoc} hypothesis that turbulent diffusion was proportional to radiative viscosity.

Alecian, G.; Michaud, G.

2005-02-01

5

Diffuse gallium-67 uptake in radiation pneumonitis  

SciTech Connect

To evaluate the clinical usefulness of Ga-67 imaging for the assessment of radiation pneumonitis, 12 patients who had developed radiation pneumonitis after receiving radiotherapy alone for non-small-cell lung cancer from 1979 through 1988 were reviewed. Diffuse bilateral Ga-67 uptake occurred in 5 out of the 12 cases; in the other 7 cases, Ga-67 uptake was confined to the irradiation lung. Conversely, chest radiography showed infiltrates only in the irradiated lung. Histopathology of the lung in four out of the five cases that showed diffuse Ga-67 uptake in the lung, however, revealed that the lung outside the radiation field with Ga-67 uptake was consistent with interstitial pneumonitis induced by radiation. These results suggest that radiation pneumonitis could extend beyond the irradiated lung and that Ga-67 imaging is more useful than chest radiography for the assessment of the spatial extent of radiography pneumonitis.

Kataoka, M.; Kawamura, M.; Ueda, N.; Itoh, H.; Iio, A.; Hamamoto, K. (Ehime Univ. School of Medicine, Onsen-gun (Japan))

1990-10-01

6

Diffusion processes in general relativistic radiating spheres  

SciTech Connect

The influence of diffusion processes on the dynamics of general relativistic radiating spheres is systematically studied by means of two examples. Differences between the streaming-out limit and the diffusion limit are exhibited, for both models, through the evolution curves of dynamical variables. In particular it is shown the Bondi mass decreases, for both models, in the diffusion limit as compared with its value at the streaming-out regime. 15 refs.

Barreto, W.; Herrera, L.; Santos, N.O. (Oriente Universidad, Cumana (Venezuela); Universidad Central de Venezuela, Caracas; Observatorio Nacional do Brasil, Rio de Janeiro (Brazil))

1989-09-01

7

Radiative diffusion in stellar atmospheres: diffusion velocities  

Microsoft Academic Search

Aims.The present paper addresses some of the problems in the buildup of element stratification in stellar magnetic atmospheres due to microscopic diffusion, in particular the redistribution of momentum among the various ionisation stages of a given element and the calculation of diffusion velocities in the presence of inclined magnetic fields. Methods: .We have considerably modified and extended our CARAT code

G. Alecian; M. J. Stift

2006-01-01

8

Assessment of diffuse radiation models in Azores  

NASA Astrophysics Data System (ADS)

Measured irradiance databases usually consist of global solar radiation data with limited spatial coverage. Hence, solar radiation models have been developed to estimate the diffuse fraction from the measured global irradiation. This information is critical for the assessment of the potential of solar energy technologies; for example, the decision to use photovoltaic systems with tracking system. The different solar radiation models for this purpose differ on the parameters used as input. The simplest, and most common, are models which use global radiation information only. More sophisticated models require meteorological parameters such as information from clouds, atmospheric turbidity, temperature or precipitable water content. Most of these models comprise correlations with the clearness index, kt (portion of horizontal extra-terrestrial radiation reaching the Earth's surface) to obtain the diffuse fraction kd (portion of diffuse component from global radiation). The applicability of these different models is related to the local atmospheric conditions and its climatic characteristics. The models are not of general validity and can only be applicable to locations where the albedo of the surrounding terrain and the atmospheric contamination by dust are not significantly different from those where the corresponding methods were developed. Thus, models of diffuse fraction exhibit a relevant degree of location dependence: e.g. models developed considering data acquired in Europe are mainly linked to Northern, Central or, more recently, Mediterranean areas. The Azores Archipelago, with its particular climate and cloud cover characteristics, different from mainland Europe, has not yet been considered for the development of testing of such models. The Azorean climate reveals large amounts of cloud cover in its annual cycle, with spatial and temporal variabilities more complex than the common Summer/Winter pattern. This study explores the applicability of different existing correlation models of diffuse fraction and clearness index or other plain parameters to the Azorean region. Reliable data provided by the Atmospheric Radiation Measurements (ARM) Climate Research Facility from the Graciosa Island deployment of the ARM Mobile Facility (http://www.arm.gov/sites/amf/grw) was used to perform the analysis. Model results showed a tendency to underestimate higher values of diffuse radiation. From the performance results of the correlation models reviewed it was clear that there is room for improvement.

Magarreiro, Clarisse; Brito, Miguel; Soares, Pedro; Azevedo, Eduardo

2014-05-01

9

Radiation  

Cancer.gov

DCEG researchers carry out a broad-based research program designed to identify, understand, and quantify the risk of cancer in populations exposed to medical, occupational, or environmental radiation. They study ionizing radiation exposures (e.g., x-rays,

10

Estimation of monthly mean hourly diffuse solar radiation  

Microsoft Academic Search

Measured hourly diffuse solar radiation data of Zhengzhou in 2004 were analyzed in this work. The solar model proposed by Liu and Jordan was used to estimate the monthly mean hourly diffuse solar radiation data at Zhengzhou in 2004. Comparison between estimated and measured values of the hourly diffuse solar radiation showed that Liu & Jordan model can predict the

Yingni Jiang

2009-01-01

11

Diffusion model for lightning radiative transfer  

SciTech Connect

A one-speed Boltzmann transport theory, with diffusion approximations, is applied to study the radiative transfer properties of lightning in optically thick thunderclouds. Near-infrared (lambda = 0.7774 micrometers) photons associated with a prominent oxygen emission triplet in the lightning spectrum are considered. Transient and spatially complex lightning radiation sources are placed inside a rectangular parallelepiped thundercloud geometry and the effects of multiple scattering are studied. The cloud is assumed to be composed of a homogeneous collection of identical spherical water droplets, each droplet a nearly conservative, anisotropic scatterer. Conceptually, we treat the thundercloud like a nuclear reactor, with photons replaced by neutrons, and utilize standard one-speed neutron diffusion techniques common in nuclear reactor analyses. Valid analytic results for the intensity distribution (expanded in spherical harmonics) are obtained for regions sufficiently far from sources. Model estimates of the arrival-time delay and pulse width broadening of lightning signals radiated from within the cloud are determined and the results are in good agreement with both experimental data and previous Monte Carlo estimates. Additional model studies of this kind will be used to study the general information content of cloud top lightning radiation signatures.

Koshak, W.J.; Solakiewicz, R.J.; Phanord, D.D.; Blakeslee, R.J. [NASA, Marshall Space Flight Center, Huntsville, AL (United States)]|[Chicago State Univ., Chicago, IL (United States)]|[Univ. of Alabama, Huntsville, AL (United States)

1994-07-01

12

Diffusion model for lightning radiative transfer  

NASA Technical Reports Server (NTRS)

A one-speed Boltzmann transport theory, with diffusion approximations, is applied to study the radiative transfer properties of lightning in optically thick thunderclouds. Near-infrared (lambda = 0.7774 micrometers) photons associated with a prominent oxygen emission triplet in the lightning spectrum are considered. Transient and spatially complex lightning radiation sources are placed inside a rectangular parallelepiped thundercloud geometry and the effects of multiple scattering are studied. The cloud is assumed to be composed of a homogeneous collection of identical spherical water droplets, each droplet a nearly conservative, anisotropic scatterer. Conceptually, we treat the thundercloud like a nuclear reactor, with photons replaced by neutrons, and utilize standard one-speed neutron diffusion techniques common in nuclear reactor analyses. Valid analytic results for the intensity distribution (expanded in spherical harmonics) are obtained for regions sufficiently far from sources. Model estimates of the arrival-time delay and pulse width broadening of lightning signals radiated from within the cloud are determined and the results are in good agreement with both experimental data and previous Monte Carlo estimates. Additional model studies of this kind will be used to study the general information content of cloud top lightning radiation signatures.

Koshak, William J.; Solakiewicz, Richard J.; Phanord, Dieudonne D.; Blakeslee, Richard J.

1994-01-01

13

Radiation  

NASA Video Gallery

Outside the protective cocoon of Earth's atmosphere, the universe is full of harmful radiation. Astronauts who live and work in space are exposed not only to ultraviolet rays but also to space radi...

14

Radiators  

SciTech Connect

A heat-exchange radiator is connected to a fluid flow circuit by a connector which provides one member of an interengageable spigot and socket pair for push-fit, fluid-tight, engagement between the connector and the radiator, with latching formations at least one of which is resilient. Preferably the connector carries the spigot which tapers and engages with a socket of corresponding shape, the spigot carrying an O-ring seal and either latching fingers or a resilient latching circlip.

Webster, D. M.

1985-07-30

15

Observations of the diffuse UV radiation field  

NASA Technical Reports Server (NTRS)

Spectra are presented for the diffuse UV radiation field between 1250 to 3100 A from eight different regions of the sky, which were obtained with the Johns Hopkins UVX experiment. UVX flew aboard the Space Shuttle Columbia (STS-61C) in January 1986 as part of the Get-Away Special project. The experiment consisted of two 1/4 m Ebert-Fastie spectrometers, covering the spectral range 1250 to 1700 A at 17 A resolution and 1600 to 3100 A at 27 A resolution, respectively, with a field of view of 4 x .25 deg, sufficiently small to pick out regions of the sky with no stars in the line of sight. Values were found for the diffuse cosmic background ranging in intensity from 300 to 900 photons/sq cm/sec/sr/A. The cosmic background is spectrally flat from 1250 to 3100 A, within the uncertainties of each spectrometer. The zodiacal light begins to play a significant role in the diffuse radiation field above 2000 A, and its brightness was determined relative to the solar emission. Observed brightnesses of the zodiacal light in the UV remain almost constant with ecliptic latitude, unlike the declining visible brightnesses, possibly indicating that those (smaller) grains responsible for the UV scattering have a much more uniform distribution with distance from the ecliptic plane than do those grains responsible for the visible scattering.

Murthy, Jayant; Henry, R. C.; Feldman, P. D.; Tennyson, P. D.

1989-01-01

16

Radiation enhanced diffusion in MgO  

NASA Astrophysics Data System (ADS)

Radiation enhanced diffusion and ion beam mixing of 18O, Ca, and Zn buried tracer layers in MgO, grown by molecular beam epitaxy, have been measured following irradiation with 2.0 MeV Kr+ and 1.0 MeV Ne+, He+, and H+ from 30 to 1500 °C. The ion beam mixing parameter varied between 1.0 and 5.0 Å5 eV-1 for the different tracers at 30 °C and increased slowly with increasing temperature. These results are consistent with ballistic mixing. In the highest temperature range investigated, 1350-1500 °C, the radiation enhanced diffusion coefficient for 18O was proportional to the square root of the irradiation flux and displayed an apparent activation enthalpy of 1.2 eV. These dependencies on flux and temperature are indicative of recombination-limited kinetics, with the measured activation enthalpy representing one-half the migration enthalpy of anion vacancies. From 1150 to 1350 °C an activation enthalpy of 4.1 eV was obtained. The unexpectedly high value is attributed to the dissociation energy of small vacancy clusters. Measurements on the cation sublattice were limited to temperatures below 900 °C owing to the excessive thermal diffusion associated with extrinsic vacancies, which are present for trivalent impurity charge compensation.

van Sambeek, A. I.; Averback, R. S.; Flynn, C. P.; Yang, M. H.; Jäger, W.

1998-06-01

17

Adaptive Implicit Non-Equilibrium Radiation Diffusion  

NASA Astrophysics Data System (ADS)

We describe methods for accurate and efficient long term time integration of non-equilibrium radiation diffusion systems: implicit time integration for efficient long term time integration of stiff multiphysics 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.

Philip, B.; Wang, Z.; Berrill, M.; Rodriguez, M.; Pernice, M.

2013-04-01

18

Radiation diffusion in the three-dimensional radiation-hydrodynamics code CTH  

Microsoft Academic Search

A treatment of radiation diffusion has been developed for implementation in the three-dimensional Eulerian radiation- hydrodynamics code CTH. The implicit energy flow model was derived using the one-temperature diffusion approximation to the radiation transport equation, i.e., the radiation energy is proportional to the fourth power of the material temperature. The Incomplete Choleski-Conjugate Gradient Method is used to solve the differenced

Rottler

1989-01-01

19

On the relationship between direct and anisotropic diffuse radiation  

NASA Astrophysics Data System (ADS)

The relationship between the direct and anisotropic diffuse radiation for discrete ordinates method (DOM) is analyzed. The solution of anisotropic diffuse radiation can be expressed as a summation of a series of the solution for direct radiation in multi-stream DOM. A wide range of accuracy checks for anisotropic diffuse radiation of a homogeneous layer is performed with respect to the "exact" results computed from the ?-128-stream scheme for radiative transfer. In addition, the results indicate that the increasing number of streams produces a decrease in error of reflection/transmission.

Zhang, Feng; Zhou, Xiuji; Zhang, Hua; Peng, Xindong; Wang, Zhili

2014-07-01

20

Global, direct and diffuse solar-radiation in Syria  

Microsoft Academic Search

Solar-radiation components, namely global, diffuse and direct, were calculated over the Syrian landmass using several mathematical equations starting from the Angström formula. An appropriate theoretical method and a computer program were specially designed and developed for these calculations. The program provides fast, direct and accurate information about the global, diffuse and direct solar-radiations on any site in the country. In

Ali Al-Mohamad

2004-01-01

21

Flux-limited diffusion models in radiation hydrodynamics  

SciTech Connect

The authors discuss certain flux-limited diffusion theories which approximately describe radiative transfer in the presence of steep spatial gradients. A new formulation is presented which generalizes a flux-limited description currently in widespread use for large radiation hydrodynamic calculations. This new formation allows more than one Case discrete mode to be described by a flux-limited diffusion equation. Such behavior is not extant in existing formulations. Numerical results predicted by these flux-limited diffusion models are presented for radiation penetration into an initially cold halfspace. 37 refs., 5 figs.

Pomraning, G.C.; Szilard, R.H. (Univ. of California, Los Angeles (United States))

1993-01-01

22

On the luminous efficacy of diffuse solar radiation  

Microsoft Academic Search

Models for diffuse illuminance and irradiance and for the luminous efficacy of diffuse solar radiation are developed, specifically for clear skies, and also for all sky types.All luminous efficacy models reported in the present work have the distinctive feature of being obtained from empirical models developed for diffuse illuminance and irradiance, looking in this way, apparently for the first time,

Luis Robledo; Alfonso Soler

2001-01-01

23

Correlation of total, diffuse, and direct solar radiation  

NASA Technical Reports Server (NTRS)

Present requirements for realistic solar energy system evaluations necessitate a comprehensive body of solar-radition data. The data should include both diffuse and direct solar radiation as well as their total on an hourly (or shorter) basis. In general, however, only the total solar radiation values were recorded. This report presents a correlation that relates the diffuse component of an hourly total solar radiation value to the total radiation ratio of the maximum value attainable. The data used were taken at the Blue Hill Observatory in Milton, Massachusetts, for the period 1952. The relation - in the form of the data plots - can be used in situations in which only the hourly total radiation data are available but the diffuse component is desired.

Buyco, E. H.; Namkoong, D.

1977-01-01

24

Consistent Solar Evolution Model Including Diffusion and Radiative Acceleration Effects  

Microsoft Academic Search

The solar evolution has been calculated including all the effects of the diffusion of helium and heavy elements. Monochromatic opacities are used to calculate radiative accelerations and Rosseland opacities at each evolution time step, taking into account the local abundance changes of all important (21) chemical elements. The OPAL monochromatic data are used for the opacities and the radiative accelerations.

S. Turcotte; J. Richer; G. Michaud; C. A. Iglesias; F. J. Rogers

1998-01-01

25

The Origin of the Diffuse Background gamma-Radiation.  

National Technical Information Service (NTIS)

Recent observations have now provided evidence for diffuse background gamma radiation extending to energies beyond 100 MeV. There is some evidence of isotropy and implied cosmological origin. Significant features in the spectrum of this background radiati...

F. W. Stecker J. L. Puget

1974-01-01

26

Radiation Diffusion:. AN Overview of Physical and Numerical Concepts  

NASA Astrophysics Data System (ADS)

An overview of the physical and mathematical foundations of radiation transport is given. Emphasis is placed on how the diffusion approximation and its transport corrections arise. An overview of the numerical handling of radiation diffusion coupled to matter is also given. Discussions center on partial temperature and grey methods with comments concerning fully implicit methods. In addition finite difference, finite element and Pert representations of the div-grad operator is also discussed

Graziani, Frank

2005-12-01

27

Self-diffusion and radiation damage in ?-phosphorus single crystals  

Microsoft Academic Search

The temperature dependence and pressure dependence of self-diffusion in ?-white phosphorus single crystals have been redetermined using radiotracer and plastic deformation techniques. The use of P-labelled tracer resulted in radiation damage to the solid by the emitted electrons (E? max= 1·71 MeV). This led to the evaluation of radiation-enhanced self-diffusion coefficients which show a similar anomalous temperature dependence to that

E. M. Hampton; P. McKay; J. N. Sherwood

1974-01-01

28

Numerical transport and diffusion methods in radiative transfer  

SciTech Connect

A numerical discretization scheme, in both space and time, is considered for the equation of radiative transfer and its corresponding diffusion approximation. Numerical results are presented for radiation penetration into a cold slab driven by a constant incident surface intensity. A comparison of results is made among solutions obtained from the discretization of the radiative transfer equation, a flux-limited diffusion approximation, and the classical diffusion approximation. By numerically studying the properties of the flux-limited diffusion approximation, we conclude that the treatment of the nonlinearities in such a description can significantly affect the results. Different iteration strategies of such nonlinearities are discussed and benchmark data for the converged solution are presented in three different time regimes. Finally, we conclude from this analysis that flux limiting is an important factor in solving these types of problems and must be included in an diffusive description.

Szilard, R.H.; Pomraning, G.C. (California Univ., Los Angeles, CA (United States). School of Engineering and Applied Science)

1992-11-01

29

Diffuse solar radiation and associated meteorological parameters in India  

NASA Astrophysics Data System (ADS)

Solar diffuse radiation data including global radiation, shortwave and longwave balances, net radiation and sunshine hours have been extensively analyzed to study the variation of diffuse radiation with turbidity and cloud discharges appearing in the form of atmospherics over the tropics. Results of surface radiation measurements at Calcutta, Poona, Delhi and Madras are presented together with some meteorological parameters. The monthly values of diffuse radiation and the monthly ratios of diffuse to global solar radiation have been examined, with a special emphasis in relation to the noise level of atmospherics at Calcutta in the very low frequency band. The results exhibit some definite seasonal changes which appear to be in close agreement with one another. Acknowledgements. We gratefully appreciate the on-line DMSP database facility at APL (Newell et al., 1991) from which this study has benefited greatly. We wish to thank E. Friis-Christensen for his encouragement and useful discussions. A. Y. would like to thank the Danish Meteorological Institute, where this work was done, for its hospitality during his stay there and the Nordic Baltic Scholarship Scheme for its financial support of this stay. Topical Editor K.-H. Glassmeier thanks M. J. Engebretson and H. Lühr for their help in evaluating this paper.--> Correspondence to: A. Yahnin-->

Bhattacharya, A. B.; Kar, S. K.; Bhattacharya, R.

1996-10-01

30

Observation of resonant diffusive radiation in random multilayered systems.  

PubMed

Diffusive radiation is a new type of radiation predicted to occur in randomly inhomogeneous media due to the multiple scattering of pseudophotons. This theoretical effect is now observed experimentally. The radiation is generated by the passage of electrons of energy 200 KeV-2.2 MeV through a random stack of films in the visible light region. The radiation intensity increases resonantly provided the Cerenkov condition is satisfied for the average dielectric constant of the medium. The observed angular dependence and electron resonance energy are in agreement with the theoretical predictions. These observations open a road to application of diffusive radiation in particle detection, astrophysics, soft-x-ray generation, etc. PMID:16907579

Gevorkian, Zh S; Harutyunyan, S R; Ananikian, N S; Arakelian, V H; Ayvazyan, R B; Gavalyan, V B; Grigorian, N K; Vardanyan, H S; Sahakian, V H; Hakobyan, A A

2006-07-28

31

DIFFUSION OF PROTONS IN THE OUTER RADIATION BELT  

Microsoft Academic Search

The diffusion of protons in the outer radiation belt due to violation of the third adiabatic invariant has been examined. The particular mechanism studied is one in which variations in the intensity of the solar wind produce magnetic disturbances causing motion of particles between L shells. A Fokker-Planck diffusion equation is used with terms describing Coulomb energy degradation and charge-exchange

M. P. Nakada; G. D. Mead

1965-01-01

32

Diffuse, global and extra-terrestrial solar radiation for Singapore  

Microsoft Academic Search

In this paper, equations have been developed to estimate diffuse fraction of the hourly, daily and monthly global insolation on a horizontal surface. These correlations are expressed in terms of Kd, the ratio of diffuse-to-total radiation, and KT, the clearness index. The hourly correlation equations, show a fairly similar trend to that of Orgill and Hollands (1) and Spencer (5)

M. N. A. Hawlader

1984-01-01

33

Outward diffusion of energetic particles from the Jovian radiation belt  

Microsoft Academic Search

It is suggested that energetic particles populating the Jovian outer magnetosphere and neighboring interplanetary space are flowing from the Jovian radiation belt by the outward diffusion process that violates both second and third adiabatic invariants. This cross-field diffusion process operates preferentially at low altitudes, and it does not cause serious degradation of particle energy. A model is constructed which combines

A. Nishida

1976-01-01

34

Radiative Extinction of Gaseous Spherical Diffusion Flames in Microgravity  

NASA Technical Reports Server (NTRS)

Radiative extinction of spherical diffusion flames was investigated experimentally and numerically. The experiments involved microgravity spherical diffusion flames burning ethylene and propane at 0.98 bar. Both normal (fuel flowing into oxidizer) and inverse (oxidizer flowing into fuel) flames were studied, with nitrogen supplied to either the fuel or the oxygen. Flame conditions were chosen to ensure that the flames extinguished within the 2.2 s of available test time; thus extinction occurred during unsteady flame conditions. Diagnostics included color video and thin-filament pyrometry. The computations, which simulated flow from a porous sphere into a quiescent environment, included detailed chemistry, transport and radiation, and yielded transient results. Radiative extinction was observed experimentally and simulated numerically. Extinction time, peak temperature, and radiative loss fraction were found to be independent of flow rate except at very low flow rates. Radiative heat loss was dominated by the combustion products downstream of the flame and was found to scale with flame surface area, not volume. For large transient flames the heat release rate also scaled with surface area and thus the radiative loss fraction was largely independent of flow rate. Peak temperatures at extinction onset were about 1100 K, which is significantly lower than for kinetic extinction. One observation of this work is that while radiative heat losses can drive transient extinction, this is not because radiative losses are increasing with time (flame size) but rather because the heat release rate is falling off as the temperature drops.

Santa, K. J.; Chao, B. H.; Sunderland, P. B.; Urban, D. L.; Stocker, D. P.; Axelbaum, R. L.

2007-01-01

35

Radiation diffusion in the three-dimensional radiation-hydrodynamics code CTH  

SciTech Connect

A treatment of radiation diffusion has been developed for implementation in the three-dimensional Eulerian radiation- hydrodynamics code CTH. The implicit energy flow model was derived using the one-temperature diffusion approximation to the radiation transport equation, i.e., the radiation energy is proportional to the fourth power of the material temperature. The Incomplete Choleski-Conjugate Gradient Method is used to solve the differenced equations. Ionization states are obtained using the average atom ionization model, and Rosseland mean opacities are obtained using a simple analytical expression associated with the ionization model. The paper presents a brief derivation of the energy flow model, and a discussion of the implementation of the model in CTH. 5 refs.

Rottler, J.S.

1989-01-01

36

The diffuse component of the cosmic X-radiation  

NASA Technical Reports Server (NTRS)

The A-2 experiment on HEAO-1 is specifically developed to study the diffuse radiation of the entire X-ray sky over a wide bandwidth, covering both the soft X-ray emission from nearby regions of the galaxy and the isotropic hard X-radiation indicative of remote extragalactic origins. A partial conclusion from the experiment is that a hot thermal plasma, on a scale comparable to that of the universe, may be the principal source of hard X-radiation characteristic of the extragalactic sky. Some key features of this background were defined.

Boldt, E. A.; Garmire, C.

1978-01-01

37

Theoretical and Numerical Investigation of Radiative Extinction of Diffusion Flames  

NASA Technical Reports Server (NTRS)

The influence of soot radiation on diffusion flames was investigated using both analytical and numerical techniques. Soot generated in diffusion flames dominate the flame radiation over gaseous combustion products and can significantly lower the temperature of the flame. In low gravity situations there can be significant accumulation of soot and combustion products in the vicinity of the primary reaction zone owing to the absence of any convective buoyant flow. Such situations may result in substantial suppression of chemical activities in a flame, and the possibility of a radiative extinction may also be anticipated. The purpose of this work was to not only investigate the possibility of radiative extinction of a diffusion flame but also to qualitatively and quantitatively analyze the influence of soot radiation on a diffusion flame. In this study, first a hypothetical radiative loss profile of the form of a sech(sup 2) was assumed to influence a pure diffusion flame. It was observed that the reaction zone can, under certain circumstances, move through the radiative loss zone and locate itself on the fuel side of the loss zone contrary to our initial postulate. On increasing the intensity and/or width of the loss zone it was possible to extinguish the flame, and extinction plots were generated. In the presence of a convective flow, however, the movement of the temperature and reaction rate peaks indicated that the flame behavior is more complicated compared to a pure diffusional flame. A comprehensive model of soot formation, oxidation and radiation was used in a more involved analysis. The soot model of Syed, Stewart and Moss was used for soot nucleation and growth and the model of Nagle and Strickland-Constable was used for soot oxidation. The soot radiation was considered in the optically thin limit. An analysis of the flame structure revealed that the radiative loss term is countered both by the reaction term and the diffusion term. The essential balance for the soot volume fraction was found to be between the processes of soot convection and soot growth. Such a balance yielded to analytical treatment and the soot volume fraction could be expressed in the form of an integral. The integral was evaluated using two approximate methods and the results agreed very well with the numerical solutions for all cases examined.

Ray, Anjan

1996-01-01

38

Statistical models for estimating hourly diffuse solar radiation in different regions of Thailand  

Microsoft Academic Search

In this study, four statistical models for estimating diffuse solar radiation from global solar radiation in different regions of Thailand have been developed. In developing the models, a 12-year period of global and diffuse solar radiation measured at four of our solar radiation monitoring stations, situated in different regions of Thailand have been analyzed. The statistical models estimate diffuse fraction

Serm Janjai; P. Phaprom; R. Wattan; I. Masiri

2010-01-01

39

Diffusion tensor imaging of the optic radiations after optic neuritis.  

PubMed

Trans-synaptic degeneration could exacerbate neurodegeneration in multiple sclerosis (MS). We aimed to assess whether anterograde trans-synaptic degeneration could be identified in the primary visual pathway in vivo. Diffusion tensor imaging (DTI) was used to assess the optic radiations in 15 patients with previous optic nerve inflammation and 9 healthy volunteers. A probabilistic atlas of the optic radiations was created from healthy diffusion tractography data. Lengthwise profiles for DTI parameters (axial [?(||) ], radial [?(?) ] and mean diffusivity [MD], fractional anisotropy [FA] and the angle of deviation of the principal eigenvector [?]) were analyzed for patients and controls. Patients also underwent multifocal visual evoked potential (mfVEP) assessments to characterize the latency and amplitude of cortical potentials. Correlations were performed between mfVEP latency and amplitude in the left and right visual hemi-fields and DTI parameters in the contra-lateral optic radiations. Patients displayed a significant decrease in ?(||) within the body of both optic radiations, which significantly correlated with loss of mfVEP amplitude. Abnormal ?(?) and FA were detected bilaterally throughout the optic radiations in patients but the abnormality was not associated with amplitude reduction or latency prolongation of the mfVEP. An abnormal ? value was observed in the left optic radiations of patients, and the ? value in the body of the optic radiations also correlated with mfVEP amplitude loss. The assocation between bilateral DTI abnormalities within the optic radiations and loss of afferent electrical activity could indicate anterograde trans-synaptic degeneration occurs following optic neuritis. PMID:21915943

Kolbe, Scott; Bajraszewski, Clare; Chapman, Caron; Nguyen, Tan; Mitchell, Peter; Paine, Mark; Butzkueven, Helmut; Johnston, Leigh; Kilpatrick, Trevor; Egan, Gary

2012-09-01

40

Consistent Solar Evolution Model Including Diffusion and Radiative Acceleration Effects  

NASA Astrophysics Data System (ADS)

The solar evolution has been calculated including all the effects of the diffusion of helium and heavy elements. Monochromatic opacities are used to calculate radiative accelerations and Rosseland opacities at each evolution time step, taking into account the local abundance changes of all important (21) chemical elements. The OPAL monochromatic data are used for the opacities and the radiative accelerations. The Opacity Project data are needed to calculate how chemical species and electrons share the momentum absorbed from the radiation flux. A detailed evaluation of the impact of atomic diffusion on solar models is presented. On some elements thermal diffusion adds approximately 50% to the gravitational settling velocity. While gravitational settling had been included in previous solar models, this is the first time that the impact of radiative accelerations is considered. Radiative accelerations can be up to 40% of gravity below the solar convection zone and thus affect chemical element diffusion significantly, contrary to current belief. Up to the solar age, the abundances of most metals change by 7.5% if complete ionization is assumed, but by 8.5%-10% if detailed ionization of each species is taken into account. If radiative accelerations are included, intermediate values are obtained. Diffusion leads to a change of up to 8% in the Rosseland opacities, compared to those of the original mixture. Most of this effect can be taken into account by using tables with several values of Z. If one isolates the effects of radiative accelerations, the abundance changes they cause alter the Rosseland opacity by up to 0.5%; the density is affected by up to 0.2%; the sound speed is affected by at most 0.06%. The inclusion of radiative accelerations leads to a reduction of 3% of neutrino fluxes measured with 37Cl detectors and 1% measured with 71Ga detectors. The partial transformation of C and O into N by nuclear reactions in the core causes a ~1% change in the opacities that cannot be modeled by a change in Z alone. The evolution is allowed to proceed to 1010 yr in order to determine the impact at the end of the main-sequence life of solar-type stars. It is found that immediately below the convection zone, the radiative acceleration on some iron peak elements is within a few percent of gravity. The abundance anomalies reach 18% for He in the convection zone but are kept within 12% and 15% for most because of grad. They would have reached 18% in the absence of grad.

Turcotte, S.; Richer, J.; Michaud, G.; Iglesias, C. A.; Rogers, F. J.

1998-09-01

41

Calculation of direct solar and diffuse radiation in Israel  

NASA Astrophysics Data System (ADS)

This study deals with the calculation of direct solar radiation and diffuse radiation for locations in Israel as hourly values. The model is based on the calculation of the Linke turbidity factors for the stations Bet-Dagan, Jerusalem, Beer Sheva, Sedom and Eilat, which have been determined from radiation measurements. The turbidity factors for clear sky conditions showed a characteristic yearly pattern and the differences between the stations were related to their geographical locations. The model requires different algorithms for calculations in the Rift Valley system and the rest of Israel. The calculations proved to be very accurate for clear sky conditions with high radiation values (average deviation: 7.3% or 61.6 W/m2 for values above 600 W/m2). The presence of clouds and lower sun angles lead to less accurate results, which are nevertheless still acceptable within the range for further applications.

Becker, Stefan

2001-10-01

42

Structure and radiation properties of turbulent diffusion flames  

SciTech Connect

A theoretical and experimental study of the flame structure and gas band radiation of carbon monoxide/hydrogen/air diffusion flames is described. The results have applications to analysis of the rate of spread of natural fires, design and development of furnaces, determination of radiant heat loads to engine components, development of rocket plume visibility, safe operations of industrial flares, development of material test codes for fire properties and development of fire detectors. The structure of the turbulent flames was studied using the Mie scattering technique to measure single and two-point mixture fraction statistics, and laser Doppler anemometery to measure single-point velocity statistics along the centerline. A stochastic methodology for treating the nonlinear flame radiation fluctuations caused by turbulence/radiation interactions was developed. The methodology was evaluated by comparison with high resolution emission spectroscopy measurements of gas-band radiation.

Kounalakis, M. E.

1990-01-01

43

Semiconductor detectors produced by lithium diffusion simulated by thermal radiation  

Microsoft Academic Search

A method for preparation of semiconductors (SD) with thin (10-20 micrometer) dead layers is described. Unlike the traditional technology, lithium diffusion by means of pulses of thermal radiation in the presence of a temperature gradient in the specimen is used to reduce the depth of the pn junction. The proposed method provides semiconductor detectors with parameters that bring the energy

M. G. Gornov; Yu. B. Gurov; Z. T. Kim; C. Y. Kim; B. P. Osipenko; J. Jurkowski

1988-01-01

44

Estimation of horizontal diffuse solar radiation in Egypt  

Microsoft Academic Search

The measured values of monthly average daily global H and diffuse Hd solar radiation on a horizontal surface, as well as the number of bright sunshine hours n?, for four Egyptian locations are analyzed. The selected locations include Matruh, Al-Arish, Rafah and Aswan to represent the weather conditions of the north and south of Egypt. First, second and third order

A. A El-Sebaii; A. A Trabea

2003-01-01

45

Radiation hydrodynamics of triggered star formation: the effect of the diffuse radiation field  

NASA Astrophysics Data System (ADS)

We investigate the effect of including diffuse field radiation when modelling the radiatively driven implosion of a Bonnor-Ebert sphere (BES). Radiation-hydrodynamical calculations are performed by using operator splitting to combine Monte Carlo photoionization with grid-based Eulerian hydrodynamics that includes self-gravity. It is found that the diffuse field has a significant effect on the nature of radiatively driven collapse which is strongly coupled to the strength of the driving shock that is established before impacting the BES. This can result in either slower or more rapid star formation than expected using the on-the-spot approximation depending on the distance of the BES from the source object. As well as directly compressing the BES, stronger shocks increase the thickness and density in the shell of accumulated material, which leads to short, strong, photoevaporative ejections that reinforce the compression whenever it slows. This happens particularly effectively when the diffuse field is included as rocket motion is induced over a larger area of the shell surface. The formation and evolution of 'elephant trunks' via instability is also found to vary significantly when the diffuse field is included. Since the perturbations that seed instabilities are smeared out elephant trunks form less readily and, once formed, are exposed to enhanced thermal compression.

Haworth, Thomas J.; Harries, Tim J.

2012-02-01

46

Radiation from Buoyant Turbulent Diffusion Flames  

Microsoft Academic Search

The relationship between the radiant fraction, X R, of the total heat release rate from buoyant turbulent diffusion flames and a fuel's laminar flame smoke point is refined and extended to include: additional hydrocarbon fuels, fuel dilution with nitrogen and a range of oxygen\\/nitrogen ambient environments. Correlation of the data allows one to predict X R in terms of the:

L. Orloff; J. DE RIS; M. A. DELICHATSIOS

1992-01-01

47

Comparison of the Radiative Two-Flux and Diffusion Approximations  

NASA Technical Reports Server (NTRS)

Approximate solutions are sometimes used to determine the heat transfer and temperatures in a semitransparent material in which conduction and thermal radiation are acting. A comparison of the Milne-Eddington two-flux approximation and the diffusion approximation for combined conduction and radiation heat transfer in a ceramic material was preformed to determine the accuracy of the diffusion solution. A plane gray semitransparent layer without a substrate and a non-gray semitransparent plane layer on an opaque substrate were considered. For the plane gray layer the material is semitransparent for all wavelengths and the scattering and absorption coefficients do not vary with wavelength. For the non-gray plane layer the material is semitransparent with constant absorption and scattering coefficients up to a specified wavelength. At higher wavelengths the non-gray plane layer is assumed to be opaque. The layers are heated on one side and cooled on the other by diffuse radiation and convection. The scattering and absorption coefficients were varied. The error in the diffusion approximation compared to the Milne-Eddington two flux approximation was obtained as a function of scattering coefficient and absorption coefficient. The percent difference in interface temperatures and heat flux through the layer obtained using the Milne-Eddington two-flux and diffusion approximations are presented as a function of scattering coefficient and absorption coefficient. The largest errors occur for high scattering and low absorption except for the back surface temperature of the plane gray layer where the error is also larger at low scattering and low absorption. It is shown that the accuracy of the diffusion approximation can be improved for some scattering and absorption conditions if a reflectance obtained from a Kubelka-Munk type two flux theory is used instead of a reflection obtained from the Fresnel equation. The Kubelka-Munk reflectance accounts for surface reflection and radiation scattered back by internal scattering sites while the Fresnel reflection only accounts for surface reflections.

Spuckler, Charles M.

2006-01-01

48

Radiation from Gas-Jet Diffusion Flames in Microgravity Environments  

NASA Technical Reports Server (NTRS)

This paper presents the first demonstration of quantitative flame-radiation measurement in microgravity environments, with the objective of studying the influences and characteristics of radiative transfer on the behavior of gas-jet diffusion flames with possible application to spacecraft fire detection. Laminar diffusion flames of propane, burning in quiescent air at atmospheric pressure, are studied in the 5.18-Second Zero-Gravity Facility of NASA Lewis Research Center. Radiation from these flames is measured using a wide-view angle, thermopile-detector radiometer, and comparisons are made with normal-gravity flames. The results show that the radiation level is significantly higher in microgravity compared to normal-gravity environments due to larger flame size, enhanced soot formation, and entrapment of combustion products in the vicinity of the flame. These effects are the consequences of the removal of buoyancy which makes diffusion the dominant mechanism of transport. The results show that longer test times may be needed to reach steady state in microgravity environments.

Bahadori, M. Yousef; Edelman, Raymond B.; Sotos, Raymond G.; Stocker, Dennis P.

1991-01-01

49

Spectrometer system for diffuse extreme ultraviolet radiation  

Microsoft Academic Search

A unique grazing incidence spectrometer system has been designed to study diffuse line emission between 80 and 650 A with 10-30 A resolution. The minimum detectable emission line strength during a 5-min observation ranges from 100-2000 ph\\/sq cm sec str. The instrument uses mechanically ruled reflection gratings placed in front of a linear array of mirrors. These mirrors focus the

Simon E. Labov

1989-01-01

50

Numerical analysis of time integration errors for nonequilibrium radiation diffusion  

SciTech Connect

Numerical analysis of time integration errors for nonequilibrium radiation diffusion is considered. Two first-order implicit time integration methods are studied. Asymptotic analysis and modified equation analysis are applied to both time integration methods. Numerical experiments are used to highlight the results of the analysis. Asymptotic analysis is used to highlight the source of temperature spiking when a hot radiation wave propagates into a cold material. Modified equation analysis is used to provide insight into the thermal wave speed coming from the two different first-order methods.

Knoll, D.A. [Los Alamos National Laboratory (United States)], E-mail: Dana.Knoll@inl.gov; Lowrie, R.B. [Los Alamos National Laboratory (United States); Morel, J.E. [Los Alamos National Laboratory (United States); Texas A and M University (United States)

2007-10-01

51

Shadow-band correction for diffuse ultraviolet radiation measurements  

NASA Astrophysics Data System (ADS)

the correction of shadow-band solar total diffuse measurements has been extensively studied, the case of diffuse ultraviolet measurements has not been properly addressed. This study analyzes the correction factor to be applied to experimental measurements performed adapting a shadow-band to a UV radiometer at a radiometric station in Badajoz (Spain). Three different models, based on approaches widely used for correcting total diffuse measurements, have been revised and adapted for the ultraviolet spectral range. Results reveal that some aspects of the correction proposed for total diffuse radiation are not suitable for ultraviolet diffuse radiation. The mathematical expressions are consequently modified to match the behavior in the ultraviolet range. Thus, three correction models particularized for ultraviolet diffuse measurements are proposed and validated against experimental data. The two models adapted from the original expressions proposed by Battles et al., and Steven show the best performance, with rRMSE of 2.74% and 2.20% and rMBE of 1.53% and 0.46%, respectively.

SáNchez, G.; Serrano, A.; Cancillo, M. L.

2013-05-01

52

VOYAGER OBSERVATIONS OF THE DIFFUSE FAR-ULTRAVIOLET RADIATION FIELD  

SciTech Connect

The two Voyager spacecraft have completed their planetary exploration mission and are now probing the outer realms of the heliosphere. The Voyager ultraviolet spectrometers continued to operate well after the Voyager 2 Neptune encounter in 1989. We present a complete database of diffuse radiation observations made by both Voyagers: a total of 1943 spectra (500-1600 A) scattered throughout the sky. These include observations of dust-scattered starlight, emission lines from the hot interstellar medium, and a number of locations where no diffuse radiation was detected, with the very low upper limit of about 25 photons cm{sup -2} s{sup -1} sr{sup -1} A{sup -1}. Many of these observations were from late in the mission when there was significantly less contribution from interplanetary emission lines and thus less contamination of the interstellar signal.

Murthy, Jayant [Indian Institute of Astrophysics, Bengalooru 560 034 (India); Henry, Richard Conn [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Holberg, Jay B., E-mail: jmurthy@yahoo.com [Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721 (United States)

2012-03-01

53

Diffuse Galactic Positron Annihilation Radiation and the Underlying Continuum  

Microsoft Academic Search

In this thesis we explore the origins of the diffuse Galactic positron annihilation line radiation at 0.511 MeV and the underlying gamma ray continuum. In order to determine the sources of the positrons responsible for the 0.511 MeV line emission we construct models for the spatial distribution of this emission. We find that it is not possible to model the

Jeffrey George Skibo

1993-01-01

54

Wireless in-house data communication via diffuse infrared radiation  

Microsoft Academic Search

A novel wireless broadcast\\/multi-access channel is described for flexibly interconnecting a cluster of data terminals located within the same room. The transmission medium is diffusively scattered infrared radiation at 950-nm wavelength. Transmission is low-to-medium speed and the range up to 50 m. Theoretical analysis indicates that the time dispersion limits the transmission bandwidth of the system to 260 Mbit ?

FRITZ R. GFELLER; URS BAPST

1979-01-01

55

Consistent Solar Evolution Model Including Diffusion and Radiative Acceleration Effects  

SciTech Connect

The solar evolution has been calculated including all the effects of the diffusion of helium and heavy elements. Monochromatic opacities are used to calculate radiative accelerations and Rosseland opacities at each evolution time step, taking into account the local abundance changes of all important (21) chemical elements. The OPAL monochromatic data are used for the opacities and the radiative accelerations. The Opacity Project data are needed to calculate how chemical species and electrons share the momentum absorbed from the radiation flux. A detailed evaluation of the impact of atomic diffusion on solar models is presented. On some elements thermal diffusion adds approximately 50{percent} to the gravitational settling velocity. While gravitational settling had been included in previous solar models, this is the first time that the impact of radiative accelerations is considered. Radiative accelerations can be up to 40{percent} of gravity below the solar convection zone and thus affect chemical element diffusion significantly, contrary to current belief. Up to the solar age, the abundances of most metals change by 7.5{percent} if complete ionization is assumed, but by 8.5{percent}{endash}10{percent} if detailed ionization of each species is taken into account. If radiative accelerations are included, intermediate values are obtained. Diffusion leads to a change of up to 8{percent} in the Rosseland opacities, compared to those of the original mixture. Most of this effect can be taken into account by using tables with several values of {ital Z}. If one isolates the effects of radiative accelerations, the abundance changes they cause alter the Rosseland opacity by up to 0.5{percent}; the density is affected by up to 0.2{percent}; the sound speed is affected by at most 0.06{percent}. The inclusion of radiative accelerations leads to a reduction of 3{percent} of neutrino fluxes measured with {sup 37}Cl detectors and 1{percent} measured with {sup 71}Ga detectors. The partial transformation of C and O into N by nuclear reactions in the core causes a {approximately}1{percent} change in the opacities that cannot be modeled by a change in {ital Z} alone. The evolution is allowed to proceed to 10{sup 10} yr in order to determine the impact at the end of the main-sequence life of solar-type stars. It is found that immediately below the convection zone, the radiative acceleration on some iron peak elements is within a few percent of gravity. The abundance anomalies reach 18{percent} for He in the convection zone but are kept within 12{percent} and 15{percent} for most because of {ital g}{sub rad}. They would have reached 18{percent} in the absence of {ital g}{sub rad}. {copyright} {ital {copyright} 1998.} {ital The American Astronomical Society}

Turcotte, S. [Departement de physique, Universite de Montreal, Montreal, Quebec H3C 3J7 (Canada)] [Departement de physique, Universite de Montreal, Montreal, Quebec H3C 3J7 (Canada); [Teoretisk Astrofysik Center, Aarhus Universitet, DK-8000, Aarhus C (Denmark); Richer, J. [Centre de Recherche en Calcul Applique (CERCA), 5160 boulevard Decarie, bureau 400, Montreal, PQ H3X 2H9 (Canada)] [Centre de Recherche en Calcul Applique (CERCA), 5160 boulevard Decarie, bureau 400, Montreal, PQ H3X 2H9 (Canada); Michaud, G. [Centre de Recherche en Calcul Applique (CERCA), 5160 boulevard Decarie, bureau 400, Montreal, PQ H3X 2H9 (Canada)] [Centre de Recherche en Calcul Applique (CERCA), 5160 boulevard Decarie, bureau 400, Montreal, PQ H3X 2H9 (Canada); [Departement de Physique, Universite de Montreal, Montreal, PC H3C 3J7 (Canada); Iglesias, C.A.; Rogers, F.J. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94550 (United States)] [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94550 (United States)

1998-09-01

56

Influence of radiation damage on xenon diffusion in silicon carbide  

NASA Astrophysics Data System (ADS)

Diffusion of xenon in poly and single crystalline silicon carbide and the possible influence of radiation damage on it are investigated. For this purpose 360 keV xenon ions were implanted in commercial 6H-SiC and CVD-SiC wafers at room temperature, 350 °C and 600 °C. Width broadening of the implantation profiles and xenon retention during isochronal and isothermal annealing up to temperatures of 1500 °C was determined by RBS-analysis, whilst in the case of 6H-SiC damage profiles were simultaneously obtained by ?-particle channelling. No diffusion or xenon loss was detected in the initially amorphized and eventually recrystallized surface layer of cold implanted 6H-SiC during annealing up to 1200 °C. Above that temperature serious erosion of the implanted surface occurred, which made any analysis impossible. No diffusion or xenon loss is detected in the hot implanted 6H-SiC samples during annealing up to 1400 °C. Radiation damage dependent grain boundary diffusion is observed at 1300 °C in CVD-SiC.

Friedland, E.; Gärtner, K.; Hlatshwayo, T. T.; van der Berg, N. G.; Thabethe, T. T.

2014-08-01

57

Radiation-enhanced self- and boron diffusion in germanium  

NASA Astrophysics Data System (ADS)

We report experiments on proton radiation-enhanced self- and boron (B) diffusion in germanium (Ge) for temperatures between 515 ?C and 720 ?C. Modeling of the experimental diffusion profiles measured by means of secondary ion mass spectrometry is achieved on the basis of the Frenkel pair reaction and the interstitialcy and dissociative diffusion mechanisms. The numerical simulations ascertain concentrations of Ge interstitials and B-interstitial pairs that deviate by several orders of magnitude from their thermal equilibrium values. The dominance of self-interstitial related defects under irradiation leads to an enhanced self- and B diffusion in Ge. Analysis of the experimental profiles yields data for the diffusion of self-interstitials (I) and the thermal equilibrium concentration of BI pairs in Ge. The temperature dependence of these quantities provides the migration enthalpy of I and formation enthalpy of BI that are compared with recent results of atomistic calculations. The behavior of self- and B diffusion in Ge under concurrent annealing and irradiation is strongly affected by the property of the Ge surface to hinder the annihilation of self-interstitials. The limited annihilation efficiency of the Ge surface can be caused by donor-type surface states favored under vacuum annealing, but the physical origin remains unsolved.

Schneider, S.; Bracht, H.; Klug, J. N.; Hansen, J. Lundsgaard; Larsen, A. Nylandsted; Bougeard, D.; Haller, E. E.

2013-03-01

58

A study of the diffuse galactic gamma radiation  

NASA Technical Reports Server (NTRS)

The observed diffuse galactic gamma radiation is compared to that predicted from galactic cosmic ray interactions with galactic matter and photons, assuming that on a broad scale the galactic cosmic rays in the plane are correlated with matter density. Recent considerations of the galactic diffuse matter distribution, particularly the molecular hydrogen, the galactic photon density, and a revised cosmic ray galactic scale height, are included. The predictions are compared to the observational gamma ray longitude distributions, the latitude distribution, and energy spectrum, including the COS-B satellite results, and the COS-B background estimate. Considering the uncertainties, the agreement between the theoretical predictions and the gamma ray data seems generally reasonable, suggesting that the general concepts are likely to be correct. Both the results determined here alone and in conjunction with other work calculating source functions assuming only cosmic ray matter contributions indicate no necessity for a significant point source contribution to the diffuse gamma radiation in the energy range being considered (E(gamma)10 MeV).

Fichtel, C. E.; Kniffen, D. A.

1984-01-01

59

Photoacoustic imaging of prostate cancer using cylinder diffuse radiation  

NASA Astrophysics Data System (ADS)

Prostate cancer is one of diseases with high mortality in man. Many clinical imaging modalities are utilized for the detection, grading and staging of prostate cancer, such as ultrasound, CT, MRI, etc. But they lacked adequate sensitivity and specificity for finding cancer in transition or central zone of prostate. To overcome these problems, we propose a photoacoustic imaging modality based on cylinder diffuse radiation through urethra for prostate cancer detection. We measure the related parameters about this system like lateral resolution (~2mm) and axial resolution(~333?m). Finally, simulated sample was imaged by our system. The results demonstrate the feasibility for detecting prostate cancer by our system.

Xie, Wenming; Li, Li; Li, Zhifang; Li, Hui

2012-12-01

60

General Variational Formulation for Problems of Heat Transfer by Diffuse Radiation.  

National Technical Information Service (NTIS)

A variational principle is shown which is suitable for the solution of any problems involving heat interchange by diffuse radiation in nonparticipating media. The basic radiation theory is briefly discussed, with the deduction of the system of integral eq...

R. M. S. Gama

1985-01-01

61

Effects of Refractive Index and Diffuse or Specular Boundaries on a Radiating Isothermal Layer.  

National Technical Information Service (NTIS)

Equilibrium temperatures of an absorbing-emitting layer were obtained for exposure to incident radiation and with the layer boundaries either specular or diffuse. For high refractive indices the surface condition can influence the radiative heat balance i...

R. Siegel C. M. Spuckler

1994-01-01

62

The product formula algorithm applied to linear and radiation diffusion  

SciTech Connect

We extend an unconditionally stable, explicit algorithm due to DeRaedt and Richardson, Farrell, and Long to include various linear and radiation diffusion problems in one and two dimensions with open and/or reflecting boundary conditions. We consider the ramifications of the ordering ambiguity problem (a feature that arises in the product formula scheme). In order to improve accuracy, we introduce a new type of subcycling based on the Lie-Trotter product formula. We consider a one-dimensional test problem which consists of a slab of material with a constant driving temperature source on one side. We compare the analytic and numerical results for the time evolution of the temperature profile in the linear and radiation diffusion problems as a function of Courant factor ({alpha}). We find excellent agreement except when {alpha} {much_gt} 1. For large {alpha}, the transient temperature profiles exhibit a {open_quotes}staircase{close_quote} like behavior. However, we show (albeit, not rigorously) that all solutions regardless of {alpha} approximately converge to the correct steady state solution. We also present results for a two-dimensional problem consisting of a constant driving temperature source on one side of a slab of material with an optically thick region interior to the slab.

Graziani, F.R. [Lawrence Livermore National Lab., CA (United States)] [Lawrence Livermore National Lab., CA (United States)

1995-04-01

63

Global radiation model and angular distribution of the diffuse irradiance  

Microsoft Academic Search

Horizontal global radiation computer codes for the evaluation of solar cell performance under various atmospheric conditions were developed. A numerical calculation method for the radiation transfer equation, including the doubling and adding method, was employed to reduce the computational effort. Extensive horizontal global radiation data sets including spectral energy distributions and angular distribution were generated. The spectral irradiances are presented

Yukiharu Miyake; Yuji Nakanishi; Ryuichi Shimokawa; Yoshihiro Hamakawa

1987-01-01

64

Distribution patterns of diffuse solar radiation in Yunnan Province, China  

Microsoft Academic Search

Yunnan Province, China, is situated in a very favorable region for solar energy utilization. Its unique “cubic climates” and geographic features make its distribution patterns of solar radiation vary considerably. It will be very beneficial to study, in detail, the characteristics of solar radiation climates in the province. Based on the correlations and the dry—wet season model of solar radiation

Lin Wenxian; Lu Enrong; Gao Wenfeng; Pu Shaoxuan; Liu Tao

1996-01-01

65

Soot and Radiation Measurements in Microgravity Jet Diffusion Flames  

NASA Technical Reports Server (NTRS)

The subject of soot formation and radiation heat transfer in microgravity jet diffusion flames is important not only for the understanding of fundamental transport processes involved but also for providing findings relevant to spacecraft fire safety and soot emissions and radiant heat loads of combustors used in air-breathing propulsion systems. Our objectives are to measure and model soot volume fraction, temperature, and radiative heat fluxes in microgravity jet diffusion flames. For this four-year project, we have successfully completed three tasks, which have resulted in new research methodologies and original results. First is the implementation of a thermophoretic soot sampling technique for measuring particle size and aggregate morphology in drop-tower and other reduced gravity experiments. In those laminar flames studied, we found that microgravity soot aggregates typically consist of more primary particles and primary particles are larger in size than those under normal gravity. Comparisons based on data obtained from limited samples show that the soot aggregate's fractal dimension varies within +/- 20% of its typical value of 1.75, with no clear trends between normal and reduced gravity conditions. Second is the development and implementation of a new imaging absorption technique. By properly expanding and spatially-filtering the laser beam to image the flame absorption on a CCD camera and applying numerical smoothing procedures, this technique is capable of measuring instantaneous full-field soot volume fractions. Results from this technique have shown the significant differences in local soot volume fraction, smoking point, and flame shape between normal and reduced gravity flames. We observed that some laminar flames become open-tipped and smoking under microgravity. The third task we completed is the development of a computer program which integrates and couples flame structure, soot formation, and flame radiation analyses together. We found good agreements between model predictions and experimental data for laminar and turbulent flames under both normal and reduced gravity. We have also tested in the laboratory the techniques of rapid-insertion fine-wire thermocouples and emission pyrometry for temperature measurements. These techniques as well as laser Doppler velocimetry and spectral radiative intensity measurement have been proposed to provide valuable data and improve the modeling analyses.

Ku, Jerry C.

1996-01-01

66

Diffusion of radiation belt protons by whistler waves  

SciTech Connect

Whistler waves propagating near the quasi-electrostatic limit can interact with energetic protons ({approximately}80-500 keV) that are transported into the radiation belts. The waves may be launched from either the ground or generated in the magnetosphere as a result of the resonant interactions with trapped electrons. The wave frequencies are significant fractions of the equatorial electron gyrofrequency, and they propagate oliquely to the geomagnetic field. A finite spectrum of waves compensates for the inhomogeneity of the geomagnetic field allowing the protons to stay in gyroresonance with the waves over long distances along magnetic field lines. The Fokker-Planck equation is integrated along the flux tube considering the contributions of multiple-resonance crossings. The quasi-linear diffusion coefficients in energy, cross energy/pitch angle, and pitch angle are obtained for second-order resonant interactions. They are shown to be proportional to the electric fields amplitudes. Numerical calculations for the second-order interactions show that diffusion dominates near the edge of the loss cone. For small pitch angles the largest diffusion coefficient is in energy, although the cross energy/pitch angle term is also important. This may explain the induced proton precipitation observed in active space experiments. 24 refs., 12 figs.

Villalon, E. [Northeastern Univ., Boston, MA (United States)] [Northeastern Univ., Boston, MA (United States); Burke, W.J. [Hanscom Air Force Base, MA (United States)] [Hanscom Air Force Base, MA (United States)

1994-11-01

67

Verification of SpacePy's radial diffusion radiation belt model  

NASA Astrophysics Data System (ADS)

Model verification, or the process of ensuring that the prescribed equations are properly solved, is a necessary step in code development. Careful, quantitative verification guides users when selecting grid resolution and time step and gives confidence to code developers that existing code is properly instituted. This work introduces the RadBelt radiation belt model, a new, open-source version of the Dynamic Radiation Environment Assimilation Model (DREAM) and uses the Method of Manufactured Solutions (MMS) to quantitatively verify it. Order of convergence is investigated for a plethora of code configurations and source terms. The ability to apply many different diffusion coefficients, including time constant and time varying, is thoroughly investigated. The model passes all of the tests, demonstrating correct implementation of the numerical solver. The importance of DLL and source term dynamics on the selection of time step and grid size is also explored. Finally, an alternative method to apply the source term is examined to illustrate additional considerations required when non-linear source terms are used.

Welling, D. T.; Koller, J.; Camporeale, E.

2011-09-01

68

Verification of SpacePy's radial diffusion radiation belt model  

NASA Astrophysics Data System (ADS)

Model verification, or the process of ensuring that the prescribed equations are properly solved, is a necessary step in code development. Careful, quantitative verification guides users when selecting grid resolution and time step and gives confidence to code developers that existing code is properly instituted. This work introduces the RadBelt radiation belt model, a new, open-source version of the Dynamic Radiation Environment Assimilation Model (DREAM) and uses the Method of Manufactured Solutions (MMS) to quantitatively verify it. Order of convergence is investigated for a plethora of code configurations and source terms. The ability to apply many different diffusion coefficients, including time constant and time varying, is thoroughly investigated. The model passes all of the tests, demonstrating correct implementation of the numerical solver. The importance of DLL and source term dynamics on the selection of time step and grid size is also explored. Finally, an alternative method to apply the source term is examined to illustrate additional considerations required when non-linear source terms are used.

Welling, D. T.; Koller, J.; Camporeale, E.

2012-03-01

69

Diffuse radiation unsteady transformation by thermal dynamic holograms  

NASA Astrophysics Data System (ADS)

The problem of the amplification of low intensity radiation pulses can be solved by the utilization of the optical amplifier based on the dynamic holograms (DH), as one of the methods. This permits to concentrate almost all the radiation from the illuminated object in the solid angle required for monitoring, thus, providing the decrease of the requirements to the sensitivity of the monitoring equipment, that is the photomaterials on the holographing of the diffuse reflecting objects, in particular. It is expedient to record the DH in the media with thermal nonlinearity, because in tnis case the effective transformation of the equal frequency beams on the small thicknesses ( less then 1 cm ) of the nonlinear medium under practicallj any crosz-section dimension :an be carried out, and the wide range of adjusting C 10+ i0s ) of the temporal scales of the Dii recording and reconstruction is possible just by c.angirg of the crossing angles between the incident beams.esides, under th certatr conditions the thermal DH can provide the image amplification with the increasing of their contrast.The investigation of the effectiie unsteady transformation of the plane waves has been carried out earlier, in this paper the results of the investigation of nstady mgification and phase abbezations (PA) of the difluse light beams durng their interaction in the thermal DH, re presented.

Berezinsky, Alexandra M.; Dukhovniy, Anatoliy M.

1991-02-01

70

BRIEF COMMUNICATIONS: Thermal diffusion separation of gas mixtures with the aid of laser radiation  

Microsoft Academic Search

An analysis is made of thermal diffusion processes in gas mixtures stimulated by laser radiation. It is shown that these processes may be characterized by high values of the separation coefficient. Complex dynamic regimes of thermal diffusion in a laser radiation field are revealed by the calculations. The results of an experimental study are also given.

F. V. Bunkin; N. A. Kirichenko; B. S. Luk'yanchuk; Georgii A. Shafeev

1982-01-01

71

Comparison of methods for estimating daily and hourly diffuse solar radiation  

Microsoft Academic Search

Daily and hourly diffuse radiations measured using a pyranometer and shading ring have been compared with the values calculated using several correlations. For the daily diffuse radiation, the correlation of Duffie & Beckman (Solar Engineering of Thermal Processes, John Wiley, 1980), Liu & Jordan (Solar Energy, 4(3) (1960) 1–19), Erts et al., (Solar Energy, 28 (1982) 293) and Bruno (Solar

S. K. Srivastava; A. Gaur; O. P. Singh; R. N. Tiwari

1995-01-01

72

Resonant electron diffusion as a saturation process of the synchrotron maser instability. [of auroral kilometric radiation  

NASA Technical Reports Server (NTRS)

The theory of resonant electron diffusion as an effective saturation process of the auroral kilometric radiation has been formulated. The auroral kilometric radiation is assumed to be amplified by the synchrotron maser instability that is driven by an electron distribution of the loss-cone type. The calculated intensity of the saturated radiation is found to have a significantly lower value in comparison with that caused by the quasi-linear diffusion process as an alternative saturation process. This indicates that resonant electron diffusion dominates over quasi-linear diffusion in saturating the synchrotron maser instability.

Lee, M. C.; Kuo, S. P.

1986-01-01

73

A comparison of discrete-ordinates and flux-limited-diffusion methods for modeling radiation transport in radiative shock tubes  

NASA Astrophysics Data System (ADS)

The Center for Radiative Shock Hydrodynamics (CRASH) seeks to improve the predictive capability for models of Omega laser experiments of radiative shock waves. The laser is used to shock, ionize, and accelerate a beryllium plate into a xenon-filled shock tube. These shocks, when driven above a threshold velocity of about 60 km/s, become strongly radiative and convert most of the incoming energy flux into radiation. Radiative shocks have properties that are significantly different from purely hydrodynamic shocks and, in modeling this phenomenon numerically, it is important to compute radiative effects accurately. In this presentation, we examine approaches to modeling radiation transport by comparing two methods: (i) a computationally efficient approximation (multigroup flux-limited diffusion), currently in use in the CRASH code, with (ii) a more accurate discrete-ordinates treatment that is offered by the code PDT. We present a selection of results from a suite of comparison tests, showing both idealized problems and those that are representative of conditions found in the CRASH experiment.

Myra, Eric S.; Hawkins, Wm. Daryl

2011-11-01

74

Diffusion in microgravity of macroparticles in a dusty plasma under solar radiation.  

PubMed

Diffusion of macroparticles, charged by solar radiation in microgravity, is studied by analyzing experimental data obtained on the MIR space station. Temperature, velocity distributions, friction coefficient, and diffusion constants were obtained for bronze particles. A comparison of experimental and theoretical estimates shows that the dynamic behavior of the macroparticles for short observation times can be determined by observing the ambipolar diffusion. PMID:11801065

Vaulina, O S; Nefedov, A P; Petrov, O F; Fortov, V E

2002-01-21

75

Modeling the luminous efficacy of diffuse solar radiation on inclined surfaces for all sky conditions  

Microsoft Academic Search

In the present work, we have undertaken a study of the luminous efficacy of diffuse solar radiation incident on vertical surfaces facing north, east, south and west for all sky conditions and mean hourly values of diffuse irradiance and diffuse illuminance. We have developed luminous efficacy models, of the type previously obtained for a horizontal surface, assuming that the surface

Luis Robledo; Alfonso Soler

2003-01-01

76

Effects of Refractive Index and Diffuse or Specular Boundaries on a Radiating Isothermal Layer  

NASA Technical Reports Server (NTRS)

Equilibrium temperatures of an absorbing-emitting layer were obtained for exposure to incident radiation and with the layer boundaries either specular or diffuse. For high refractive indices the surface condition can influence the radiative heat balance if the layer optical thickness is small. Hence for a spectrally varying absorption coefficient the layer temperature is affected if there is significant radiative energy in the spectral range with a small absorption coefficient. Similar behavior was obtained for transient radiative cooling of a layer where the results are affected by the initial temperature and hence the fraction of energy radiated in the short wavelength region where the absorption coefficient is small. The results are a layer without internal scattering. If internal scattering is significant, the radiation reaching the internal surface of a boundary is diffused and the effect of the two different surface conditions would become small.

Siegel, R.; Spuckler, C. M.

1994-01-01

77

Estimation of hourly global and diffuse solar radiation from hourly sunshine duration  

Microsoft Academic Search

A statistical procedure has been employed to develop correlations of monthly-mean-hourly global and diffuse solar radiation on a horizontal surface to hourly sunshine duration. Several years of measured data on solar radiation and sunshine duration, reported in the literature for two stations in the southern African region, is employed for this purpose. The applicability of the developed correlations is tested

K GOPINATHAN

1992-01-01

78

Comparative study of various correlations in estimating hourly diffuse fraction of global solar radiation  

Microsoft Academic Search

Proper design and performance predictions of solar energy systems require accurate information on the availability of solar radiation. The diffuse-to-global solar radiation correlation, originally developed by Liu and Jordan, has been extensively used as the technique providing accurate results, although it is latitude dependent. Thus, in the present study, empirical correlations of this type were developed to establish a relationship

C. P. Jacovides; F. S. Tymvios; V. D. Assimakopoulos; N. A. Kaltsounides

2006-01-01

79

Detailed modeling analysis for soot formation and radiation in microgravity gas jet diffusion flames  

NASA Technical Reports Server (NTRS)

Radiation heat transfer in combustion systems has been receiving increasing interest. In the case of hydrocarbon fuels, a significant portion of the radiation comes from soot particles, justifying the need for detailed soot formation model and radiation transfer calculations. For laminar gas jet diffusion flames, results from this project (4/1/91 8/22/95) and another NASA study show that flame shape, soot concentration, and radiation heat fluxes are substantially different under microgravity conditions. Our emphasis is on including detailed soot transport models and a detailed solution for radiation heat transfer, and on coupling them with the flame structure calculations. In this paper, we will discuss the following three specific areas: (1) Comparing two existing soot formation models, and identifying possible improvements; (2) A simple yet reasonably accurate approach to calculating total radiative properties and/or fluxes over the spectral range; and (3) Investigating the convergence of iterations between the flame structure solver and the radiation heat transfer solver.

Ku, Jerry C.; Tong, LI; Greenberg, Paul S.

1995-01-01

80

Soot formation and radiation in turbulent jet diffusion flames under normal and reduced gravity conditions  

NASA Technical Reports Server (NTRS)

Most practical combustion processes, as well as fires and explosions, exhibit some characteristics of turbulent diffusion flames. For hydrocarbon fuels, the presence of soot particles significantly increases the level of radiative heat transfer from flames. In some cases, flame radiation can reach up to 75 percent of the heat release by combustion. Laminar diffusion flame results show that radiation becomes stronger under reduced gravity conditions. Therefore, detailed soot formation and radiation must be included in the flame structure analysis. A study of sooting turbulent diffusion flames under reduced-gravity conditions will not only provide necessary information for such practical issues as spacecraft fire safety, but also develop better understanding of fundamentals for diffusion combustion. In this paper, a summary of the work to date and of future plans is reported.

Ku, Jerry C.; Tong, LI; Sun, Jun; Greenberg, Paul S.; Griffin, Devon W.

1993-01-01

81

A multigroup radiation diffusion test problem: Comparison of code results with analytic solution  

SciTech Connect

We consider a 1D, slab-symmetric test problem for the multigroup radiation diffusion and matter energy balance equations. The test simulates diffusion of energy from a hot central region. Opacities vary with the cube of the frequency and radiation emission is given by a Wien spectrum. We compare results from two LLNL codes, Raptor and Lasnex, with tabular data that define the analytic solution.

Shestakov, A I; Harte, J A; Bolstad, J H; Offner, S R

2006-12-21

82

Radiation Enhanced Silicon Self-Diffusion and the Silicon Vacancy at High Temperatures  

Microsoft Academic Search

We report proton radiation enhanced self-diffusion (RESD) studies on Si-isotope heterostructures. Self-diffusion experiments under irradiation were performed at temperatures between 780 °C and 872 °C for various times and proton fluxes. Detailed modeling of RESD provides direct evidence that vacancies at high temperatures diffuse with a migration enthalpy of HmV=(1.8±0.5) eV significantly more slowly than expected from their diffusion at

H. Bracht; J. Fage Pedersen; N. Zangenberg; A. Nylandsted Larsen; E. E. Haller; G. Lulli; M. Posselt

2003-01-01

83

Radiation Symbols  

MedlinePLUS

... Effects Ionizing & Non-Ionizing Radiation Understanding Radiation: Radiation Symbols Radiation Protection Basics Main Page History of Radiation ... Michigan's Radiation and Health Physics Page . United Nations Symbol In February of 2007, the United Nations introduced ...

84

Heat transfer including particle and gas radiation in subsonic MHD diffuser - II  

NASA Astrophysics Data System (ADS)

Heat transfer by convection and gas and slag particle radiation in subsonic MHD diffusers is analyzed by simultaneously solving the radiation transport equation and the quasi-three-dimensional gasdynamic equations. The efficiency factors for extinction and scattering by particles are calculated from the Mie theory. For a reference diffuser geometry, heat transfer by convection is found to be 25 MW, and radiative heat transfer varies from 44 MW to 79 MW, depending on the rate of ash carryover into the channel. Results reveal that the heat transfer is sensitive to the ash carryover into the channel, slag particle spectrum, electrical conductivity of ash, gas composition, and wall emissivity. It is observed that, because of multiple scattering, the particles shield the short-wavelength radiation emitted by potassium atoms. The impacts of heat transfer enhancement by gas radiation in the channel and by gas-plus-particles radiation in the diffuser on MHD system design are assessed. It is suggested that, from the systems design point of view, the diffuser be regarded as a part of the radiant boiler. No significant effect of radiation enhancement on the ability to decompose NO(x) is anticipated.

Ahluwalia, R. K.; Im, K. H.

1980-01-01

85

Diffuse radiation increases global ecosystem-level water-use efficiency  

NASA Astrophysics Data System (ADS)

Current environmental changes lead not only to rising atmospheric CO2 levels and air temperature but also to changes in air pollution and thus the light quality of the solar radiation reaching the land-surface. While rising CO2 levels are thought to enhance photosynthesis and closure of stomata, thus leading to relative water savings, the effect of diffuse radiation on transpiration by plants is less clear. It has been speculated that the stimulation of photosynthesis by increased levels of diffuse light may be counteracted by higher transpiration and consequently water depletion and drought stress. Ultimately, in water co-limited systems, the overall effect of diffuse radiation will depend on the sensitivity of canopy transpiration versus photosynthesis to diffuse light, i.e. whether water-use efficiency changes with relative levels of diffuse light. Our study shows that water-use efficiency increases significantly with higher fractions of diffuse light. It uses the ecosystem-atmosphere gas-exchange observations obtained with the eddy covariance method at 29 flux tower sites. In contrast to previous global studies, the analysis is based directly on measurements of diffuse radiation. Its effect on water-use efficiency was derived by analyzing the multivariate response of carbon and water fluxes to radiation and air humidity using a purely empirical approach based on artificial neural networks. We infer that per unit change of diffuse fraction the water-use efficiency increases up to 40% depending on diffuse fraction levels and ecosystem type. Hence, in regions with increasing diffuse radiation positive effects on primary production are expected even under conditions where water is co-limiting productivity.

Moffat, A. M.; Reichstein, M.; Cescatti, A.; Knohl, A.; Zaehle, S.

2012-12-01

86

Estimating the Diffuse Fraction of Hourly Global Solar Radiation in Southern Africa  

Microsoft Academic Search

Several years of hourly diffuse and global radiation data, reported for five Southern African locations, are used to establish a relationship between hourly diffuse fraction Dh\\/Gh and the hourly clearness index (KT). This relationship is compared to the correlations established by Orgill and Hollands (Solar Energy, 19, 357, 1977) and by Bruno (Solar Energy, 20, 97, 1978) and also to

K. K. Gopinathan

1989-01-01

87

Diffuse Galactic Radiation and its Application to CMB Observations  

NASA Astrophysics Data System (ADS)

In this thesis I describe work related to the investigation of CMB foregrounds, particularly at frequencies of ? 30 GHz where the Very Small Array (VSA) operates. During the commissioning period at Tenerife, the VSA was shown to approach the theoretical sensitivity. The first season (1 year) of CMB observations measures the ?-range 150-900. The first peak in the CMB power spectrum is clearly detected at ? ? 220 with ? T ? 80 ?K and there is evidence for a second peak at ? ? 550. At higher ?, the fluctuations drop in amplitude to ? 30 ?K at ? ? 800, in agreement with current inflationary cosmologies. The VSA results agree exceptionally well with other recent CMB experiments (BOOMERanG, MAXIMA, DASI, CBI). With priors from type Ia supernovae data, we find ?_{b}h^{2}=0.029_{-0.009}^{+0.009}, n_{s}=1.02_{-0.06}^{+0.12}, ?_{tot}=1.02_{-0.06}^{+0.08}, ?_{cdm}h^{2}=0.09_{-0.04}^{+0.05}, ?_{m}=0.32_{-0.06}^{+0.09} and ?_{?}=0.71_{-0.07}^{+0.07}. Foreground contamination from residual discrete radio sources is calculated to be less than 2.5% tep{Scott02}. This is achieved by measuring at the same frequency and time, the brightest sources in each VSA region using a dedicated source-subtraction baseline. We have opted to observe at a single frequency therefore it is critical to know the amplitude of Galactic emission. The contamination from diffuse Galactic radiation is calculated to be ? 5 ?K at angular scales of 1° using r.m.s. predictions from foreground maps. Further to this, I have developed a cross-correlation method to calculate the correlation of the interferometer data with foreground maps. I find no correlation with the 100 ?m map tep{Schlegel98}, with an upper limit of 0.84 ?K (2?) in the VSA data. A full-sky H? map at 1deg; resolution is produced by combining data from the WHAM and SHASSA surveys; the H? line is well-known to be a good tracer of free-free emission. A quantitative method of calculating the absorption of H? by dust is given, based on the 100 ?m maps of tet{Schlegel98}. The greatest uncertainty is the fraction of dust, f_{d}, along the line of sight actually absorbing. The conversion from H? to radio free-free continuum is re-evaluated and equations in the literature are corrected. The conversion can be applied to produce free-free template maps for frequencies 1-1000 GHz with a precision of ? 10%. The free-free template is tested for several regions of the sky using low frequency data. The free-free estimates appear to be too large by up to ˜ 30%. This can be largely explained by variations in the electron temperature. At high Galactic latitudes (|b|>20°), the 408 MHz synchrotron map has ˜ 6% in the form of free-free emission; the correction is therefore important. Finally, the power spectrum of H?/free-free seems to be much flatter (power-law index of ? 2) than previously thought, but is well below the CMB anisotropy for ?=10-70. I also describe work associated with the Manchester Wide-Field Camera (MWFC). The MWFC has a 32° field of view with 7 arcmin resolution which allows large-scale (? 1°) nebulosities to be imaged. H? observations of the Eridanus region are presented and the correlations with the far infrared and X-ray emission are described. There is evidence for a superposition of H? shells along the line of sight. The camera has been modified to allow stand-alone operation using its own mount and CCD.

Dickinson, Clive

2002-10-01

88

Modeling radiation belt electron dynamics during GEM challenge intervals with the DREAM3D diffusion model  

NASA Astrophysics Data System (ADS)

a response to the Geospace Environment Modeling (GEM) "Global Radiation Belt Modeling Challenge," a 3D diffusion model is used to simulate the radiation belt electron dynamics during two intervals of the Combined Release and Radiation Effects Satellite (CRRES) mission, 15 August to 15 October 1990 and 1 February to 31 July 1991. The 3D diffusion model, developed as part of the Dynamic Radiation Environment Assimilation Model (DREAM) project, includes radial, pitch angle, and momentum diffusion and mixed pitch angle-momentum diffusion, which are driven by dynamic wave databases from the statistical CRRES wave data, including plasmaspheric hiss, lower-band, and upper-band chorus. By comparing the DREAM3D model outputs to the CRRES electron phase space density (PSD) data, we find that, with a data-driven boundary condition at Lmax = 5.5, the electron enhancements can generally be explained by radial diffusion, though additional local heating from chorus waves is required. Because the PSD reductions are included in the boundary condition at Lmax = 5.5, our model captures the fast electron dropouts over a large L range, producing better model performance compared to previous published results. Plasmaspheric hiss produces electron losses inside the plasmasphere, but the model still sometimes overestimates the PSD there. Test simulations using reduced radial diffusion coefficients or increased pitch angle diffusion coefficients inside the plasmasphere suggest that better wave models and more realistic radial diffusion coefficients, both inside and outside the plasmasphere, are needed to improve the model performance. Statistically, the results show that, with the data-driven outer boundary condition, including radial diffusion and plasmaspheric hiss is sufficient to model the electrons during geomagnetically quiet times, but to best capture the radiation belt variations during active times, pitch angle and momentum diffusion from chorus waves are required.

Tu, Weichao; Cunningham, G. S.; Chen, Y.; Henderson, M. G.; Camporeale, E.; Reeves, G. D.

2013-10-01

89

Diffusive and Radiative Transport in Fires Experiment: DARTFire  

NASA Technical Reports Server (NTRS)

A low velocity, opposed-flow, flame spread experiment designed for execution on a sounding rocket is described. Early results of infrared and ultraviolet-visible imaging using video cameras and narrow band filters are described along with planned digital image data reduction. Measured and computed spread rates show that the classical thermal regime for flame spread over thick PMMA persists, for 50% O2, down to about 5 cm/s, at which point a transition to a microgravity regime in which radiation eventually leads to extinction in at least a quiescent environment. The microgravity regime of flame spread is then distinct from the thermal and kinetic regimes previously identified.

Olson, Sandra L.; Altenkirch, Robert A.; Bhattacharjee, Subrata; Tang, Lin; Hegde, Uday

1997-01-01

90

Solving the radiation diffusion and energy balance equations using pseudo-transient continuation  

Microsoft Academic Search

We develop a scheme for the system coupling the radiation diffusion and matter energy balance equations. The method is based on fully implicit, first-order, backward Euler differencing; Picard–Newton iterations solve the nonlinear system. We show that iterating on the radiation energy density and the emission source is more robust. Since the Picard–Newton scheme may not converge for all initial conditions

A. I. Shestakov; J. A. Greenough; L. H. Howell

2005-01-01

91

Radiative diffusivity factors in cirrus and stratocumulus clouds: Application to two-stream models  

NASA Technical Reports Server (NTRS)

A diffusion-like description of radiative transfer in clouds and the free atmosphere is often used. The two stream model is probably the best known example of such a description. The main idea behind the approach is that only the first few moments of radiance are needed to describe the radiative field correctly. Integration smooths details of the angular distribution of specific intensity and it is assumed that the closure parameters of the theory (diffusivity factors) are only weakly dependent on the distribution. The diffusivity factors are investigated using the results obtained from both Stratocumulus and Cirrus phases of FIRE experiment. A new theoretical framework is described in which two (upwards and downwards) diffusivity factors are used and a detailed multistream model is used to provide further insight about both the diffusivity factors and their dependence on scattering properties of clouds.

Stephens, Graeme L.; Flatau, P. J.; Tsay, S.-C.; Hein, Paul F.

1990-01-01

92

Effect of microwave radiation on diffusion behavior of anti-solvent during crystallization  

NASA Astrophysics Data System (ADS)

The effect of microwave radiation on anti-solvent crystallization was investigated by in situ observation of nanoparticle size in a reactor. The precipitation of sodium chloride by the addition of ethanol was accelerated by the increase in molecular diffusion caused by microwave radiation. The microwave power controlled the particle size because increasing the power increases the temperature, which leads to the dissolution of the precipitate. The salt concentration in the solution, and the anti-solvent concentration and volume were important factors in anti-solvent crystallization under microwave radiation.

Asakuma, Yusuke; Miura, Masataka

2014-09-01

93

Implicit Solution of Non-Equilibrium Radiation Diffusion Including Reactive Heating Source in Material Energy Equation  

SciTech Connect

In this paper, the authors investigate performance of a fully implicit formulation and solution method of a diffusion-reaction system modeling radiation diffusion with material energy transfer and a fusion fuel source. In certain parameter regimes this system can lead to a rapid conversion of potential energy into material energy. Accuracy in time integration is essential for a good solution since a major fraction of the fuel can be depleted in a very short time. Such systems arise in a number of application areas including evolution of a star and inertial confinement fusion. Previous work has addressed implicit solution of radiation diffusion problems. Recently Shadid and coauthors have looked at implicit and semi-implicit solution of reaction-diffusion systems. In general they have found that fully implicit is the most accurate method for difficult coupled nonlinear equations. In previous work, they have demonstrated that a method of lines approach coupled with a BDF time integrator and a Newton-Krylov nonlinear solver could efficiently and accurately solve a large-scale, implicit radiation diffusion problem. In this paper, they extend that work to include an additional heating term in the material energy equation and an equation to model the evolution of the reactive fuel density. This system now consists of three coupled equations for radiation energy, material energy, and fuel density. The radiation energy equation includes diffusion and energy exchange with material energy. The material energy equation includes reaction heating and exchange with radiation energy, and the fuel density equation includes its depletion due to the fuel consumption.

Shumaker, D E; Woodward, C S

2005-05-03

94

Process of defect formation and diffusion in metals induced by laser radiation  

NASA Astrophysics Data System (ADS)

There have been conducted researches for the presence of defects in specimens of repined carbonyl iron after the treatment by continuous radiation of C02-laser under subcritical conditions. High degree of presence of the defects is characterized by appearance of cellular dislocation structure and by considerable oversaturation of vacancies. There have been also investigated the conditions of realization of an accelerated diffusion of boron in iron and steels in treating by continuous radiation of CD2-- laser. It was revealed that the boron redistribution from the previously created layer of borides on the metal surface is accomplished in steels to the depthes of up to 3 mm. The accelerated oxygen diffusion stimulated by the laser radiation has been investigated on the basis of the obtained results of the process of internal oxidation of alloy Cu-Sn (0. 55 at 7. ). There has been proposed the model of process of accelerated transport. 2. FORMATION OF DEFECTS IN CARBONYL IRON UNDER CONTINUOUS LASER RADIATION The investigation of the defect formation under the continuous laser radiation 10. 6 sam) was conducted with the specimens (4x0. 8x80) mm of carbonyl iron 0. 008 C 0. 047 Mn Al + Si + S) refined in hydrogen atmosphere. The laser treatment was accomplished without flashing the metal surface. Treatment characteristics: radiation power P (0. 25-1. 1 kV. Specimen displacement speed under the laser beam V (10-2. 5) mm/s

Zvonkov, Alexander D.; Boranbaeva, H. M.

1990-10-01

95

Terahertz radiation from InAs induced by carrier diffusion and drift  

SciTech Connect

Terahertz (THz) radiation from a (100) oriented InAs surfaces is dominated by the photo-Dember effect. The strength of the radiation is influenced by screening the radiation with doped carriers. When irradiated by femtosecond pulses, the wafer with the lowest doping concentration radiates THz power nearly two orders higher than the wafer with highest doping concentration. With identical optical excitation and same doping concentration, a p-type InAs generates stronger THz waves than an n-type InAs due to the weaker screening effect. The low doping p-type InAs (1x10{sup 16} cm{sup -3}) sample is the strongest THz wave emitter among all the unbiased semiconductors we have ever tested with a Ti:sapphire laser oscillator. The drift-diffusion equation (DDE) is used in the study of carrier drift and diffusion as well as subsequent THz radiation from InAs wafers. The calculation explains well the experimental observation of the relationship between a THz electric field and the doping properties of InAs. The physical pictures of the carrier drift and diffusion characteristics in InAs surfaces are also clearly provided in this report.

Liu, Kai; Xu, Jingzhou; Yuan, Tao; Zhang, X.-C. [Center for THz Research, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

2006-04-15

96

An Experimental and Theoretical Study of Radiative Extinction of Diffusion Flames  

NASA Technical Reports Server (NTRS)

The objective of this research was to experimentally and theoretically investigate the radiation-induced extinction of gaseous diffusion flames in microgravity. The microgravity conditions were required because radiation-induced extinction is generally not possible in 1-g but is highly likely in microgravity. In 1-g, the flame-generated particulates (e.g. soot) and gaseous combustion products that are responsible for flame radiation, are swept away from the high temperature reaction zone by the buoyancy-induced flow and a steady state is developed. In microgravity, however, the absence of buoyancy-induced flow which transports the fuel and the oxidizer to the combustion zone and removes the hot combustion products from it enhances the flame radiation due to: (1) transient build-up of the combustion products in the flame zone which increases the gas radiation, and (2) longer residence time makes conditions appropriate for substantial amounts of soot to form which is usually responsible for most of the radiative heat loss. Numerical calculations conducted during the course of this work show that even non-radiative flames continue to become "weaker" (diminished burning rate per unit flame area) due to reduced rates of convective and diffusive transport. Thus, it was anticipated that radiative heat loss may eventually extinguish the already "weak" microgravity diffusion flame. While this hypothesis appears convincing and our numerical calculations support it, experiments for a long enough microgravity time could not be conducted during the course of this research to provide an experimental proof. Space shuttle experiments on candle flames show that in an infinite ambient atmosphere, the hemispherical candle flame in microgravity will burn indefinitely. It was hoped that radiative extinction can be experimentally shown by the aerodynamically stabilized gaseous diffusion flames where the fuel supply rate was externally controlled. While substantial progress toward this goal was made during this project, identifying the experimental conditions for which radiative extinction occurs for various fuels requires further study. Details concerning this research which are discussed in published articles are included in the appendices.

Atreya, Arvind

1995-01-01

97

Secondary production of neutral pi-mesons and the diffuse galactic gamma radiation  

NASA Technical Reports Server (NTRS)

Isobaric and scaling model predictions of the secondary spectra of neutral pi-mesons produced in proton-proton collisions, at energies between threshold and a few GeV, are compared on the basis of accelerator data and found to show the isobaric model to be superior. This model is accordingly used, in conjuction with a scaling model representation at high energies, in a recalculation of the pi exp (0) gamma-radiation's contribution to the diffuse galactic gamma background; the cosmic ray-induced production of photons (whose energy exceeds 100 MeV) by such radiation occurs at a rate of 1.53 x 10 to the -25 photons/(s-H atom). These results are compared with previous calculations of this process as well as with COS-B observations of the diffuse galactic gamma-radiation.

Dermer, C. D.

1986-01-01

98

Absorption and scattering of laser radiation by the diffusion flame of aviation kerosene  

SciTech Connect

The absorption coefficient of the radiation of a repetitively pulsed Nd : YAG laser with an average output power up to 6 W and of a cw ytterbium optical fibre laser with an output power up to 3 kW was measured in the diffusion flame of aviation kerosene burning on a free surface in the atmospheric air. The absorption coefficient as a function of flame length, radiation power, and radiation intensity, which was varied in the {approx}10{sup 3} - 5 Multiplication-Sign 10{sup 4} W cm{sup -2} range, was obtained for two distances (1 and 2 cm) between the laser beam axis and the surface. The coefficient of radiation absorption by kerosene flame was compared with that in ethanol and kerosene - ethanol mixture flames. The radiation power scattered by a small segment of the kerosene flame irradiated by Nd : YAG laser radiation was measured as a function of longitudinal and azimuthal coordinates. An estimate was made of the total scattered radiation power.

Gvozdev, S V; Glova, A F; Dubrovskii, V Yu; Durmanov, S T; Krasyukov, A G; Lysikov, A Yu; Smirnov, G V; Solomakhin, V B

2012-04-30

99

Discrete-Ordinates and Flux-Limited-Diffusion Methods for Radiation Transport: A Comparison Study  

NASA Astrophysics Data System (ADS)

The Center for Radiative Shock Hydrodynamics (CRASH) seeks to improve the predictive capability for models of Omega laser experiments of radiative shock waves. The laser is used to shock, ionize, and accelerate a beryllium plate into a xenon-filled shock tube. These shocks, when driven above a threshold velocity of about 60 km/s, become strongly radiative and convert most of the incoming energy flux into radiation. Radiative shocks have properties that are significantly different from purely hydrodynamic shocks and, in modeling this phenomenon numerically, it is important to compute radiative effects accurately. In this presentation, we examine approaches to modeling radiation transport by comparing two methods: (i) a computationally efficient approximation (multigroup flux-limited diffusion), currently in use in the CRASH code, with (ii) a more accurate discrete-ordinates treatment that is offered by the code PDT. We present a selection of updated results from a suite of comparison tests, showing both idealized problems and those that are representative of conditions found in the CRASH experiment. This research was supported by the DOE NNSA/ASC under the Predictive Science Academic Alliance Program by grant number DEFC52-08NA28616.

Myra, Eric S.; Hawkins, W. D.

2012-05-01

100

Monolithic, Radiation Hard Charge Sensitive Preamplifier Using Diffused N-channel Junction Field Effect Transistors  

Microsoft Academic Search

A monolithic preamplifier entirely based on epitaxial channel, diffused gate N-JFETs has been designed and thoroughly investigated by means of SPICE simulation and breadboard implement at ion. Integration of the circuit is now in progress on the base of the technological processes that expected to retain the characteristics of noise and radiation tolerance that these JFETs feature as discrete devices.

V. Radeka; S. Rescia; P. F. Manfredi; V. Speziali

1990-01-01

101

Monolithic, radiation hard charge sensitive preamplifier using diffused N-channel junction field effect transistors  

SciTech Connect

This paper reports on a monlithic preamplifier based on epitaxial channel, diffused gate N-JFETs designed and investigated by means of SPICE simulation and breadboard implementation. Integration of the circuit is now in progress on the base of the technological processes that expected to retain the characteristics of noise and radiation tolerance that these JFETs feature as discrete devices.

Radeka, V.; Rescia, S. (Brookhaven National Lab., Upton, NY (United States)); Manfredi, P.F.; Speziali, V. (Dipt. di Elettronica, Univ. di Pavia, Via Abbiategrasso 209, 27100 Pavia (IT))

1991-04-01

102

A Multigrid Newton-Krylov Method for Multimaterial Equilibrium Radiation Diffusion1  

Microsoft Academic Search

We focus on a fully implicit, nonlinearly converged, solution of multimaterial equilibrium radiation diffusion problems. The nonlinear method of solution is a Newton-Krylov (generalized minimum residual, GMRES) method preconditioned by a multigrid method. The multigrid iteration matrix results from a Picard-type linearization of the governing equations. The governing equation is highly nonlinear with the principal forms of nonlinearity found in

William J. Rider; Dana A. Knoll; Gordon L. Olsony

1999-01-01

103

A Multigrid Newton–Krylov Method for Multimaterial Equilibrium Radiation Diffusion  

Microsoft Academic Search

We focus on a fully implicit, nonlinearly converged, solution of multimaterial equilibrium radiation diffusion problems. The nonlinear method of solution is a Newton–Krylov (generalized minimum residual, GMRES) method preconditioned by a multigrid method. The multigrid iteration matrix results from a Picard-type linearization of the governing equations. The governing equation is highly nonlinear with the principal forms of nonlinearity found in

William J Rider; Dana A Knoll; Gordon L Olson

1999-01-01

104

Effects of Oxygen Concentration on Radiative Loss from Normal-Gravity and Microgravity Methane Diffusion Flames  

NASA Technical Reports Server (NTRS)

Laminar diffusion flames of methane, burning in quiescent oxidizing environments at atmospheric pressure, have been studied under both normal-gravity and microgravity conditions. Radiation from these flames is measured using a wide-view-angle, thermopile detector radiometer. The oxidizer was 18, 21, and 30 percent oxygen in nitrogen.

Bahadori, M. Y.; Edelman, Raymond B.; Stocker, Dennis P.; Sotos, Raymond G.; Vaughan, David F.

1992-01-01

105

A Cloud Layer-Sunshine Model for Estimating Direct, Diffuse and Total Solar Radiation  

Microsoft Academic Search

A previous study (Suckling and Hay, 1976a) described a method for cal- culating hourly values of the direct and diffuse solar radiation for cloud- less sky conditions. This paper pre- sents an extension which incorporates the effects of clouds through the use of hourly values of cloud amount and type for up to four layers and hourly bright sunshine totals.

P. W. Suckling; J. E. Hay

106

Proposal of a regressive model for the hourly diffuse solar radiation under all sky conditions  

Microsoft Academic Search

In this work, we propose a new regressive model for the estimation of the hourly diffuse solar irradiation under all sky conditions. This new model is based on the sigmoid function and uses the clearness index and the relative optical mass as predictors. The model performance was compared against other five regressive models using radiation data corresponding to 21 stations

J. A. Ruiz-Arias; H. Alsamamra; J. Tovar-Pescador; D. Pozo-Vázquez

2010-01-01

107

Predictions of soot and thermal radiation properties in confined turbulent jet diffusion flames  

Microsoft Academic Search

Computational modeling of well-documented jet diffusion flames, burning methane at atmospheric and elevated pressure, is presented. The main emphasis of the work is on the intimate coupling between the soot production rate and the flame radiative heat loss. This coupling is found to be vital for flame soot prediction. A number of methods for closing soot production source terms in

S. J. Brookes; J. B. Moss

1999-01-01

108

Estimating the horizontal diffuse solar radiation over the Central Anatolia Region of Turkey  

Microsoft Academic Search

The main objective of the present study is to develop new hybrid models to predict the monthly average daily diffuse solar radiation on a horizontal surface over Turkey’s Central Anatolia Region (CAR), which covers the 12 provinces (Afyon, Ankara, Cankiri, Corum, Eskisehir, Kayseri, Kirsehir, Konya, Nevsehir, Nigde, Sivas and Yozgat), as an example. The models proposed by many investigators to

Haydar Aras; Ozgur Balli; Arif Hepbasli

2006-01-01

109

Modeling hourly diffuse solar-radiation in the city of São Paulo using a neural-network technique  

Microsoft Academic Search

In this work, a perceptron neural-network technique is applied to estimate hourly values of the diffuse solar-radiation at the surface in São Paulo City, Brazil, using as input the global solar-radiation and other meteorological parameters measured from 1998 to 2001. The neural-network verification was performed using the hourly measurements of diffuse solar-radiation obtained during the year 2002. The neural network

Jacyra Soares; Amauri P. Oliveira; Marija Zlata Božnar; Primož Mlakar; João F. Escobedo; Antonio J. Machado

2004-01-01

110

Estimation of the diffuse radiation fraction for hourly, daily and monthly-average global radiation  

NASA Astrophysics Data System (ADS)

Hourly pyrheliometer and pyranometer data from four U.S. locations are used to establish a relationship between the hourly diffuse fraction and the hourly clearness index. This relationship is compared to the relationship established by Orgill and Hollands (1977) and to a set of data from Highett, Australia, and agreement is within a few percent in both cases. The transient simulation program TRNSYS is used to calculate the annual performance of solar energy systems using several correlations. For the systems investigated, the effect of simulating the random distribution of the hourly diffuse fraction is negligible. A seasonally dependent daily diffuse correlation is developed from the data, and this daily relationship is used to derive a correlation for the monthly-average diffuse fraction.

Erbs, D. G.; Klein, S. A.; Duffie, J. A.

111

Multifrequency radiation diffusion equations for homogeneous, refractive, lossy media and their interface conditions  

SciTech Connect

We derive time-dependent multifrequency diffusion equations for homogeneous, refractive lossy media. The equations are applicable for a domain composed of several materials with distinct refractive indexes. In such applications, the fundamental radiation variable, the intensity I, is discontinuous across material interfaces. The diffusion equations evolve a variable ?, the integral of I over all directions divided by the square of the refractive index. Attention is focused on boundary and internal interface conditions for ?. For numerical solutions using finite elements, it is shown that at material interfaces, the usual diffusion coefficient 1/3? of the multifrequency equation, where ? is the opacity, is modified by a tensor diffusion term consisting of integrals of the reflectivity. Numerical results are presented. For a single material simulation, the ? equations yield the same result as diffusion equations that evolve the spectral radiation energy density. A second simulation solves a test problem that models radiation transport in a domain comprised of materials with different refractive indexes. Results qualitatively agree with those previously published.

Shestakov, Aleksei I., E-mail: shestakov1@llnl.gov

2013-06-15

112

Radiation dosimetry.  

PubMed Central

This article summarizes the basic facts about the measurement of ionizing radiation, usually referred to as radiation dosimetry. The article defines the common radiation quantities and units; gives typical levels of natural radiation and medical exposures; and describes the most important biological effects of radiation and the methods used to measure radiation. Finally, a proposal is made for a new radiation risk unit to make radiation risks more understandable to nonspecialists.

Cameron, J

1991-01-01

113

Sources of cosmic rays and galactic diffuse gamma radiation  

NASA Astrophysics Data System (ADS)

The diffuse galactic gamma-ray spectrum measured by the EGRET experiment is interpreted within a scenario in which cosmic rays (CRs) are injected by three different kind of sources, (i) supernovae (SN) which explode into the interstellar medium (ISM), (ii) Red Supergiants (RSG), and (iii) Wolf-Rayet stars (WR), where the two latter explode into their pre-SN winds.

Casanova, S.; Biermann, P. L.; Engel, R.; Meli, A.; Ulrich, R.

114

Diffuse gamma radiation. [intensity, energy spectrum and spatial distribution from SAS 2 observations  

NASA Technical Reports Server (NTRS)

Results are reported for an investigation of the intensity, energy spectrum, and spatial distribution of the diffuse gamma radiation detected by SAS 2 away from the galactic plane in the energy range above 35 MeV. The gamma-ray data are compared with relevant data obtained at other wavelengths, including 21-cm emission, radio continuum radiation, and the limited UV and radio information on local molecular hydrogen. It is found that there are two quite distinct components to the diffuse radiation, one of which shows a good correlation with the galactic matter distribution and continuum radiation, while the other has a much steeper energy spectrum and appears to be isotropic at least on a coarse scale. The galactic component is interpreted in terms of its implications for both local and more distant regions of the Galaxy. The apparently isotropic radiation is discussed partly with regard to the constraints placed on possible models by the steep energy spectrum, the observed intensity, and an upper limit on the anisotropy.

Fichtel, C. E.; Simpson, G. A.; Thompson, D. J.

1978-01-01

115

Sources of Cosmic Rays and Galactic Diffuse Gamma Radiation  

NASA Astrophysics Data System (ADS)

The diffuse galactic gamma-ray spectrum measured by the EGRET experiment \\citep{Hunter:1997} are interpreted within a scenario in which cosmic rays (CRs) are injected by three different kind of sources, (i) supernovae (SN) which explode into the interstellar medium (ISM), (ii) Red Supergiants (RSG), and (iii) Wolf-Rayet stars (WR), where the two latter explode into their pre-SN winds (Biermann et al. 2001; Sina et al. 2001).

Casanova, S.; Biermann, P. L.; Engel, R.; Meli, A.; Ulrich, R.

2004-10-01

116

Differences in Brainstem Fiber Tract Response to Radiation: A Longitudinal Diffusion Tensor Imaging Study  

SciTech Connect

Purpose: To determine whether radiation-induced changes in white matter tracts are uniform across the brainstem. Methods and Materials: We analyzed serial diffusion tensor imaging data, acquired before radiation therapy and over 48 to 72 months of follow-up, from 42 pediatric patients (age 6-20 years) with medulloblastoma. FSL software (FMRIB, Oxford, UK) was used to calculate fractional anisotropy (FA) and axial, radial, and mean diffusivities. For a consistent identification of volumes of interest (VOIs), the parametric maps of each patient were transformed to a standard brain space (MNI152), on which we identified VOIs including corticospinal tract (CST), medial lemniscus (ML), transverse pontine fiber (TPF), and middle cerebellar peduncle (MCP) at the level of pons. Temporal changes of DTI parameters in VOIs were compared using a linear mixed effect model. Results: Radiation-induced white matter injury was marked by a decline in FA after treatment. The decline was often accompanied by decreased axial diffusivity, increased radial diffusivity, or both. This implied axonal damage and demyelination. We observed that the magnitude of the changes was not always uniform across substructures of the brainstem. Specifically, the changes in DTI parameters for TPF were more pronounced than in other regions (P<.001 for FA) despite similarities in the distribution of dose. We did not find a significant difference among CST, ML, and MCP in these patients (P>.093 for all parameters). Conclusions: Changes in the structural integrity of white matter tracts, assessed by DTI, were not uniform across the brainstem after radiation therapy. These results support a role for tract-based assessment in radiation treatment planning and determination of brainstem tolerance.

Uh, Jinsoo, E-mail: jinsoo.uh@stjude.org [Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee (United States)] [Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee (United States); Merchant, Thomas E. [Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee (United States)] [Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee (United States); Li, Yimei; Feng, Tianshu [Department of Biostatistics, St. Jude Children's Research Hospital, Memphis, Tennessee (United States)] [Department of Biostatistics, St. Jude Children's Research Hospital, Memphis, Tennessee (United States); Gajjar, Amar [Department of Oncology, St. Jude Children's Research Hospital, Memphis, Tennessee (United States)] [Department of Oncology, St. Jude Children's Research Hospital, Memphis, Tennessee (United States); Ogg, Robert J.; Hua, Chiaho [Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee (United States)] [Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee (United States)

2013-06-01

117

Influence of thermal radiation on soot production in Laminar axisymmetric diffusion flames  

NASA Astrophysics Data System (ADS)

The aim of this paper is to study the effect of radiative heat transfer on soot production in laminar axisymmetric diffusion flames. Twenty-four C1-C3 hydrocarbon-air flames, consisting of normal (NDF) and inverse (IDF) diffusion flames at both normal gravity (1 g) and microgravity (0 g), and covering a wide range of conditions affecting radiative heat transfer, were simulated. The numerical model is based on the Steady Laminar Flamelet (SLF) model, a semi-empirical two-equation acetylene/benzene based soot model and the Statistical Narrow Band Correlated K (SNBCK) model coupled to the Finite Volume Method (FVM) to compute thermal radiation. Predictions relative to velocity, temperature, soot volume fraction and radiative losses are on the whole in good agreement with the available experimental data. Model results show that, for all the flames considered, thermal radiation is a crucial process with a view to providing accurate predictions for temperatures and soot concentrations. It becomes increasingly significant from IDFs to NDFs and its influence is much greater as gravity is reduced. The radiative contribution of gas prevails in the weakly-sooting IDFs and in the methane and ethane NDFs, whereas soot radiation dominates in the other flames. However, both contributions are significant in all cases, with the exception of the 1 g IDFs investigated where soot radiation can be ignored. The optically-thin approximation (OTA) was also tested and found to be applicable as long as the optical thickness, based on flame radius and Planck mean absorption coefficient, is less than 0.05. The OTA is reasonable for the IDFs and for most of the 1 g NDFs, but it fails to predict the radiative heat transfer for the 0 g NDFs. The accuracy of radiative-property models was then assessed in the latter cases. Simulations show that the gray approximation can be applied to soot but not to combustion gases. Both the non-gray and gray soot versions of the Full Spectrum Correlated k (FSCK) model can be then substituted for the SNBCK with a reduction in CPU time by a factor of about 20 in the latter case.

Demarco, R.; Nmira, F.; Consalvi, J. L.

2013-05-01

118

Effects of Aerosol Optical Depth on diffuse UV and visible radiation  

NASA Astrophysics Data System (ADS)

Ultraviolet radiation (UV, 300-367nm) was measured with a UV-multifilter rotating shadowband radiometer (UV- MFRSR) at Yonsei University, Seoul (37.57°N, 126.97°) for 7 months from January to July 2006 and visible irradiance (400-700 nm) also measured with a MFRSR for 12 months of 2006 at the same station. Spectral UV_AOD and vis_AOD were retrieved using the Langley method and Beer-Bouguer-Lambert's law, and compared with AOD obtained from Skyradiometer to validate their values. The diffuse and direct irradiance were analyzed to investigate the dependence on total optical depth (TOD) and aerosol optical depth (AOD). The direct-horizontal solar irradiance decreases exponentially as the optical depth increases according to the Beer- Bouguer-Lambert's Law. As the TOD and AOD increase, the diffuse-horizontal UV radiation gradually increases and shows a maximum value at some critical optical depth for a given SZA. Similar analysis was performed on the relation between the diffuse irradiance and AOD. RAF(radiation amplification factor) was used to correct the ozone effects on UV. These results provide empirical equations for the amount of diffuse irradiance in UV and visible wavelengths.

Kim, Y.; Kim, J.; Cho, H.; Kim, Y.

2007-12-01

119

Computations of soot formation in ethylene/air counterflow diffusion flames and its interaction with radiation  

NASA Astrophysics Data System (ADS)

A methodology is presented which allows to predict soot levels produced in simple, one-dimensional laminar flames. The method is applied to the calculation of a set of well documented ethylene/air counterflow diffusion flames, using a detailed chemical mechanism (Davis et al., 1999 [1]) and a semi-empirical, two-equation soot model from Leung and Lindstedt (1991) [2]. Modifications of the original soot model are made in order to retrieve the experimental measurements of Hwang and Chung (2001) [3]. To account for radiative heat losses, a second series of fully coupled gas/soot/radiation simulations of the counterflow flames is performed. This allows to assess the effect of soot and gas radiation on soot formation and on the flame structure.

Hernández, Ignacio; Lecocq, Guillaume; Poitou, Damien; Riber, Eléonore; Cuenot, Bénédicte

2013-01-01

120

Polarization radiation in the planetary atmosphere delimited by a heterogeneous diffusely reflecting surface  

NASA Technical Reports Server (NTRS)

Spatial frequency characteristics (SFC) and the scattering functions were studied in the two cases of a uniform horizontal layer with absolutely black bottom, and an isolated layer. The mathematical model for these examples describes the horizontal heterogeneities in a light field with regard to radiation polarization in a three dimensional planar atmosphere, delimited by a heterogeneous surface with diffuse reflection. The perturbation method was used to obtain vector transfer equations which correspond to the linear and nonlinear systems of polarization radiation transfer. The boundary value tasks for the vector transfer equation that is a parametric set and one dimensional are satisfied by the SFC of the nonlinear system, and are expressed through the SFC of linear approximation. As a consequence of the developed theory, formulas were obtained for analytical calculation of albedo in solving the task of dissemination of polarization radiation in the planetary atmosphere with uniform Lambert bottom.

Strelkov, S. A.; Sushkevich, T. A.

1983-01-01

121

Comparative 2D Radiation MHD Simulations of Argon Gas Puff Z-pinch Plasma Experiments on the Sandia Z Machine Using the Radiative Diffusion and CRE Transport Models  

NASA Astrophysics Data System (ADS)

The recent development of the computationally efficient tabulated collisional radiative equilibrium (TCRE) radiation transport model(J.W. Thornhill, J.P. Apruzese, J. Davis, R.W. Clark, A.L. Velikovich, J.L. Giuliani, Jr., Y.K. Chong, K.G. Whitney, C. Deeney, C.A. Coverdale and F.L. Cochran, Phys. Plasmas 7, 3480 (2001).) has made possible full multidimensional radiation MHD simulations of hot dense Z-pinch plasmas with a realistic description of the non-LTE ionization dynamics and radiation transport physics. In this study, we focus on the implementation of the TCRE radiation transport model in the Mach2 2D radiation MHD code. An application of the model is made through a full dynamical simulation of an argon gas puff pinch driven by a circuit model of the Z generator. An analysis of the simulation, in particular, the K- and L-shell radiation yields, as well as the spectral and spatial characteristics of the radiation will be presented. In addition, a comparison of this multidimensional transport method will be made with the existing radiative diffusion model.

Chong, Y. K.; Thornhill Giuliani, J. W., Jr.; Apruzese, J. P.; Terry, R. E.; Davis, J.

2001-10-01

122

Thermal and radiation-enhanced diffusion in the bulk metallic glass Ni23Zr62Al15  

NASA Astrophysics Data System (ADS)

The temperature dependence of tracer diffusion in the three-component system NiZrAl was measured. For the composition Ni23Zr62Al15, it was possible to measure diffusion coefficients below and above the glass transition temperature. Similar to the binary metallic glass NiZr, the diffusion coefficient was strongly dependent on the atomic size of the tracer, varying by two orders of magnitude. The results are suggestive of a collective diffusion mechanism in bulk metallic glasses. Radiation-enhanced diffusion was also measured in this alloy and compared with measurements of radiation-induced viscous flow on similar alloys.

Flege, S.; Hahn, H.; Averback, R. S.

2004-01-01

123

The grand unified photon spectrum: A coherent view of the diffuse extragalactic background radiation  

NASA Technical Reports Server (NTRS)

The spectrum of diffuse extragalactic background radiation (DEBRA) at wavelengths from 10(exp 5) to 10(exp -24) cm is presented in a coherent fashion. Each wavelength region, from the radio to ultra-high energy photons and cosmic rays, is treated both separately and as part of the grand unified photon spectrum (GUPS). A discussion of, and references to, the relevant literature for each wavelength region is included. This review should provide a useful tool for those interested in diffuse backgrounds, the epoch of galaxy formation, astrophysical/cosmological constraints to particle properties, exotic early Universe processes, and many other astrophysical and cosmological enterprises. As a worked example, researchers derive the cosmological constraints to an unstable-neutrino spies (with arbitrary branching ratio to a radiative decay mode) that follow from the GUPS.

Ressell, M. Ted; Turner, Michael S.

1989-01-01

124

Solar UV-B in tropical forest gaps: Analysis using direct and diffuse radiation  

SciTech Connect

Experiments with natural levels of solar ultraviolet-B radiation (UV-B) have recently shown inhibition of the growth of some tropical forest tree seedlings. A knowledge of forest radiation environments is needed to help assess UV-B effects in natural situations. Although forest canopies strongly attenuate solar radiation, treefall gaps provide a very different radiation environment. We simultaneously measured both UV-B and photosynthetically active radiation (PAR) in forest gaps on Barro Colorado Island, Panama. Outside the forest, UV-B is predominately diffuse even under clear sky conditions. In sunflecks of small forest gaps, most of the UV-B was in the direct beam component. Compared to conditions outside the forest, the UV-B in these sunflecks was low relative to PAR. Shaded portions of the gap, in contrast, had proportionately high levels of UV-B relative to PAR. There are indications in the literature that relatively low UV-B levels may be effective under low PFD. Seasonal trends of PAR and UV-B in different locations in gaps can be inferred from hemispherical canopy photographs.

Flint, S.D.; Caldwell, M.M. [Utah State Univ., Logan, UT (United States)

1995-06-01

125

Effect of Radiative Heat Transfer on Three-Dimensional Double Diffusive Natural Convection  

Microsoft Academic Search

This work presents a numerical study of the effect of the radiative heat transfer on the three-dimensional double diffusive convection in a differentially heated cubic cavity for different optical parameters of the medium. This numerical study is conducted for fixed Prandtl, Rayleigh, and Lewis numbers, Pr = 13.6, Ra = 10, Le = 2, and buoyancy ratio N in the range [–2, 0]. The natural convection

A. Abidi; L. Kolsi; M. N. Borjini; H. Ben Aissia

2011-01-01

126

Multigrid Newton–Krylov method for radiation in diffusive semitransparent media  

Microsoft Academic Search

We present a fast multigrid solver for simplified PN (SPN) approximations to the diffusive radiation in non-grey semitransparent media. The method consists on reformulating the equations as a nonlinear fixed point problem in the temperature only. Given a mesh hierarchy, time and space discretizations are performed using second-order implicit and finite differencing methods, respectively. At each mesh level, a Newton–Krylov

2007-01-01

127

Radiation Medicine.  

National Technical Information Service (NTIS)

Contents: Physics and dosimetry of ionizing radiation; Pathophysiology of radiation affections; Infection and immunity in irradiated organisms; Toxicology of radioactive substances; Pathologoanatomy of radiation affections; Chemical protection against ion...

A. I. Burnazyan A. V. Lebedinskii

1965-01-01

128

Radiation therapy  

MedlinePLUS

Radiation therapy uses high-powered x-rays, particles, or radioactive seeds to kill cancer cells. ... faster than normal cells in the body. Because radiation is most harmful to quickly growing cells, radiation ...

129

Lasers Radiation  

MedlinePLUS

Lasers Radiation RadTown USA Topics Personal Exposure : Airport Security Scanning Cosmic Radiation During Flights CT Scans Dental X-ray Diagnostic Nuclear Medicine Electric and Magnetic Fields (EMF) Radiation from Power Lines Internal ...

130

Radiation Therapy  

MedlinePLUS

Radiation Therapy Radiation therapy (sometimes referred to as radiotherapy, x-ray therapy or irradiation) has been used to treat many types of cancer for more than 100 years. Radiation therapy refers to the careful use of various ...

131

Radiation Therapy  

MedlinePLUS

Radiation therapy is a cancer treatment. It uses high doses of radiation to kill cancer cells and stop them from ... half of all cancer patients receive it. The radiation may be external, from special machines, or internal, ...

132

A Comparison Between Modeled and Measured Clear-Sky Radiative Shortwave Fluxes in Arctic Environments, with Special Emphasis on Diffuse Radiation  

SciTech Connect

The ability of the SBDART radiative transfer model to predict clear-sky diffuse and direct normal broadband shortwave irradiances is investigated. Model calculations of these quantities are compared with data from the Atmospheric Radiation Measurement (ARM) program’s Southern Great Plains (SGP) and North Slope of Alaska (NSA) sites. The model tends to consistently underestimate the direct normal irradiances at both sites by about 1%. In regards to clear-sky diffuse irradiance, the model overestimates this quantity at the SGP site in a manner similar to what has been observed in other studies (Halthore and Schwartz, 2000). The difference between the diffuse SBDART calculations and Halthore and Schwartz’s MODTRAN calculations is very small, thus demonstrating that SBDART performs similarly to MODTRAN. SBDART is then applied to the NSA site, and here it is found that the discrepancy between the model calculations and corrected diffuse measurements (corrected for daytime offsets, Dutton et al., 2001) is 0.4 W/m2 when averaged over the 12 cases considered here. Two cases of diffuse measurements from a shaded “black and white” pyranometer are also compared with the calculations and the discrepancy is again minimal. Thus, it appears as if the “diffuse discrepancy” that exists at the SGP site does not exist at the NSA sites. We cannot yet explain why the model predicts diffuse radiation well at one site but not at the other.

Barnard, James C.; Flynn, Donna M.

2002-10-08

133

Atmospheric radiation  

SciTech Connect

Studies of atmospheric radiative processes are summarized for the period 1987-1990. Topics discussed include radiation modeling; clouds and radiation; radiative effects in dynamics and climate; radiation budget and aerosol effects; and gaseous absorption, particulate scattering and surface reflection. It is concluded that the key developments of the period are a defining of the radiative forcing to the climate system by trace gases and clouds, the recognition that cloud microphysics and morphology need to be incorporated not only into radiation models but also climate models, and the isolation of a few important unsolved theoretical problems in atmospheric radiation.

Harshvardhan, M.R. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States))

1991-01-01

134

MHD and Thermal Radiation Effects on Exponentially Accelerated Isothermal Vertical Plate with Uniform Mass Diffusion  

NASA Astrophysics Data System (ADS)

Thermal radiation effects on an unsteady free convective flow of a viscous incompressible flow of a past an exponentially accelerated infinite isothermal vertical plate with uniform mass diffusion in the presence magnetic field are considered. The fluid considered here is a gray, absorbing-emitting radiation but a non-scattering medium. The plate temperature is raised to Tw and the concentration level near the plate is also raised to C?w . An exact solution to the dimensionless governing equations is obtained by the Laplace transform method, when the plate is exponentially accelerated with a velocity u= u0 exp(a?t?) in its own plane against gravitational field. The effects of velocity, temperature and concentration fields are studied for different physical parameters such as the magnetic field parameter, thermal radiation parameter, Schmidt number, thermal Grashof number, mass Grashof number and time. It is observed that the velocity increases with decreasing magnetic field parameter or radiation parameter. But the trend is just reversed with respect to a or t .

Muthucumaraswamy, R.; Visalakshi, V.

2013-06-01

135

Thermal Diffusivity and Conductivity Measurements: Effect of Sample Length and Radiation  

NASA Astrophysics Data System (ADS)

Measurements of thermal diffusivity D and conductivity ? commonly show an upturn as a function of temperature. The upturn is very apparent in semi-transparent materials such as upper mantle minerals at absolute temperatures T of the order of 600-700 K. Although the effect is readily attributed to a radiative component, it shows a temperature dependence that is more characteristic of a black body (e.g., T3) than that expected from actual optical absorption spectra at high temperature for very large dimensions. When radiative conductivity ?r is obtained from optical methods, it tends begin at lower temperatures and to level off as absorption increases with T. Part of the discrepancy can be assigned to the fact that photon mean free path mfp( T) is usually comparable with sample dimensions. However, the problem is worsened in portions of the spectra by spectral path lengths (reciprocal absorption coefficients) substantially longer than sample lengths, an effect manifested in length-dependent radiative diffusion. For olivine (Mg0.91,Fe0.09)2SiO4 we have used a model of 1-dimensional spectral absorption and emission between volume elements to demonstrate that as sample length increases, ?r approaches that expected from spectral methods.

Shankland, T. J.; Schilling, F. R.; Gibert, B.; Gratz, K.

2005-12-01

136

Radiation view factor program  

NASA Technical Reports Server (NTRS)

Computer program, RAVFAC, calculates diffuse radiation view factors, using contour integrals. Technique is combined with finite difference /double summation/ technique to compose total program package.

Lovin, J. K.; Lubkowitz, A. W.

1971-01-01

137

Radial diffusion models of energetic electrons and Jupiter's synchrotron radiation. 2: Time variability  

NASA Technical Reports Server (NTRS)

We used a radial diffusion code for energetic electrons in Jupiter's magnetosphere to investigate variations in Jupiter's radio emission due to changes in the electron phase space density at L shells between 6 and 50, and due to changes in the radial diffusion parameters. We suggest that the observed variations in Jupiter's radio emission are likely caused by changes in the electron phase space density at some boundary L(sub 1) is greater than 6, if the primary mode of transport of energetic electrons is radial diffusion driven by fluctuating electric and/or magnetic fields induced by upper atmospheric turbulence. We noticed an excellent empirical correlation, both in phase and relative amplitude, between changes in the solar wind ram pressure and Jupiter's synchrotron radiation if the electron phase space density at the boundary L(sub 1) (L(sub 1) is approximately equal to 20-50) varies linearly with the square root of the solar wind ram pressure, f is approximately (N(sub s)nu(exp 2 sub s))(exp 1/2). The calculations were carried out with a diffusion coefficient D(sub LL) = D(sub n)L(exp n) with n = 3. The diffusion coefficient which best fit the observed variations in Jupiter's synchrotron radiation D(sub 3) = 1.3 +/- 0.2 x 10(exp -9)/s is approximately 0.041/yr, which corresponds to a lagtime of approximately 2 years. We further show that the observed short term (days-weeks) variations in Jupiter's radio emission cannot be explained adequately when radial diffusion is taken into account.

De Pater, Imke; Goertz, Christoph K.

1994-01-01

138

Nonlinear variants of the TR/BDF2 method for thermal radiative diffusion  

NASA Astrophysics Data System (ADS)

We apply the Trapezoidal/BDF2 (TR/BDF2) temporal discretization scheme to nonlinear grey radiative diffusion. This is a scheme that is not well-known within the radiation transport community, but we show that it offers many desirable characteristics relative to other second-order schemes. Several nonlinear variants of the TR/BDF2 scheme are defined and computationally compared with the Crank-Nicholson scheme. It is found for our test problems that the most accurate TR/BDF2 schemes are those that are fully iterated to nonlinear convergence, but the most efficient TR/BDF2 scheme is one based upon a single Newton iteration. It is also shown that neglecting the contributions to the Jacobian matrix from the cross-sections, which is often done due to a lack of smooth interpolations for tabular cross-section data, has a significant impact upon efficiency.

Edwards, Jarrod D.; Morel, Jim E.; Knoll, Dana A.

2011-02-01

139

A multigrid preconditioner and automatic differentiation for non-equilibrium radiation diffusion problems  

SciTech Connect

We study the efficient solution of non-equilibrium radiation diffusion problems. An implicit time discretization leads to the solution of systems of non-linear equations which couple radiation energy and material temperature. We consider the implicit Euler method, the mid-point scheme, the two-step backward differentiation formula, and a two-stage implicit Runge-Kutta method for time discretization. We employ a Newton-Krylov method in the solution of arising non-linear problems. We describe the computation of the Jacobian matrix for Newton's method using automatic differentiation based on the operator overloading in Fortran 90. For GMRES iterations, we propose a simple multigrid preconditioner applied directly to the coupled linearized problems. We demonstrate the efficiency and scalability of the proposed solution procedure by solving one-dimensional and two-dimensional model problems.

Glowinski, Roland [Department of Mathematics, PGH 651, University of Houston, Houston, TX 77204-3008 (United States)]. E-mail: roland@math.uh.edu; Toivanen, Jari [Center for Research in Scientific Computation, Box 8205, North Carolina State University, Raleigh, NC 27695-8205 (United States)]. E-mail: jatoivan@ncsu.edu

2005-07-20

140

Nonlinear variants of the TR/BDF2 method for thermal radiative diffusion  

SciTech Connect

We apply the Trapezoidal/BDF2 (TR/BDF2) temporal discretization scheme to nonlinear grey radiative diffusion. This is a scheme that is not well-known within the radiation transport community, but we show that it offers many desirable characteristics relative to other second-order schemes. Several nonlinear variants of the TR/BDF2 scheme are defined and computationally compared with the Crank-Nicholson scheme. It is found for our test problems that the most accurate TR/BDF2 schemes are those that are fully iterated to nonlinear convergence, but the most efficient TR/BDF2 scheme is one based upon a single Newton iteration. It is also shown that neglecting the contributions to the Jacobian matrix from the cross-sections, which is often done due to a lack of smooth interpolations for tabular cross-section data, has a significant impact upon efficiency.

Edwards, Jarrod D. [Department of Nuclear Engineering, 129 Zachry Engineering Center, TAMU 3133, Texas A and M University, College Station, Texas 77843 (United States); Morel, Jim E., E-mail: morel@tamu.ed [Department of Nuclear Engineering, 129 Zachry Engineering Center, TAMU 3133, Texas A and M University, College Station, Texas 77843 (United States); Knoll, Dana A. [Fluid Dynamics and Solid Mechanics Group T-3, Los Alamos National Laboratory, P.O. Box 1663, MS B216, Los Alamos, NM 87545 (United States)

2011-02-20

141

Predictions of soot and thermal radiation properties in confined turbulent jet diffusion flames  

SciTech Connect

Computational modeling of well-documented jet diffusion flames, burning methane at atmospheric and elevated pressure, is presented. The main emphasis of the work is on the intimate coupling between the soot production of rate and the flame radiative heat loss. This coupling is found to be vital for flame soot prediction. A number of methods for closing soot production source terms in the turbulent flow are presented and assessed. In particular it is shown that the degree of correlation assumed between soot particles and their oxidizing species exerts a large influence on both the growth of the soot and its subsequent burnout. Finally, predictions of the mean radiative emission spectra from these flames are presented.

Brookes, S.J.; Moss, J.B. [Cranfield Univ., Bedford (United Kingdom). School of Mechanical Engineering] [Cranfield Univ., Bedford (United Kingdom). School of Mechanical Engineering

1999-03-01

142

Dynamic Implicit 3D Adaptive Mesh Refinement for Non-Equilibrium Radiation Diffusion  

SciTech Connect

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 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 multiphysics systems: implicit time integration for efficient long term time integration of stiff multiphysics 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 linear solver convergence.

Philip, Bobby [ORNL] [ORNL; Wang, Zhen [ORNL] [ORNL; Berrill, Mark A [ORNL] [ORNL; Rodriguez Rodriguez, Manuel [ORNL] [ORNL; Pernice, Michael [Idaho National Laboratory (INL)] [Idaho National Laboratory (INL)

2014-01-01

143

An experimental and theoretical study of radiative extinction of diffusion flames  

NASA Technical Reports Server (NTRS)

Our work was primarily theoretical and numerical. We investigated the simplified modeling of heat losses in diffusion flames, then we 'ramped up' the level of complexity in each successive study until the final chapter discussed the general problem of soot/flame interaction. With regard to the specific objective of studying radiative extinction, we conclude that in the steady case a self-extinguishing zero-g flame is unlikely to occur. The soot volume fractions are too small. On the other hand, our work does provide rational means for assessing the mixture of chemical energy release and radiative heat release. It also provides clues for suitable 'tailoring' this balance. Thus heat fluxes to surrounding surfaces can be substantially increased by exploiting and modifying its sooting capability.

Wichman, Indrek S.; Atreya, A.

1994-01-01

144

Radiation Laws  

NSDL National Science Digital Library

This site lists physical laws that describe radiation. Topics covered include the Plank Radiation Law, and the Wien and Stefan-Boltzmann Laws. The site also features a table summarizing the blackbody temperatures necessary to give a peak for emitted radiation in various regions of the spectrum, and three Java applets illustrating important properties of blackbody radiation.

Astronomy, Department O.; Knoxville, University O.

145

Compound radiator  

NASA Astrophysics Data System (ADS)

Standard radiator design with a plate facing cold space on one side and the warm spacecraft at the other side suffers from considerable parasitic heat load to the radiator even when the back of the radiator is covered with the best Multi Layer Insulation (MLI) available. In addition, performance of the plate radiator depends crucially on its insulation which might well deteriorate over a long duration mission. In an attempt to address these manifest and potential problems the concept of a compound radiator was worked out. First tests confirm model calculations; the compound radiator marks a very significant improvement over a standard plate radiator.

Thomsen, Knud

1991-12-01

146

Shear mixing in stellar radiative zones. I. Effect of thermal diffusion and chemical stratification  

NASA Astrophysics Data System (ADS)

Context. Turbulent transport of chemical elements in radiative zones of stars is considered in current stellar evolution codes thanks to phenomenologically derived diffusion coefficients. Recent local numerical simulations suggest that the coefficient for radial turbulent diffusion due to radial differential rotation satisfies Dt ? 0.058?/Ri, in qualitative agreement with the model of Zahn (1992, A&A, 265, 115). However, this model does not apply (i) when differential rotation is strong with respect to stable thermal stratification or (ii) when chemical stratification has a significant dynamical effect, a situation encountered at the outer boundary of nuclear-burning convective cores. Aims: We extend our numerical study to consider the effects of chemical stratification and of strong shear, and compare the results with prescriptions used in stellar evolution codes. Methods: We performed local, direct numerical simulations of stably stratified, homogeneous, sheared turbulence in the Boussinesq approximation. The regime of high thermal diffusivities, typical of stellar radiative zones, is reached thanks to the so-called small-Péclet-number approximation, which is an asymptotic development of the Boussinesq equations in this regime. The dependence of the diffusion coefficient on chemical stratification was explored in this approximation. Results: Maeder's extension of Zahn's model in the strong-shear regime (Maeder 1995, A&A, 299, 84) is not supported by our results, which are better described by a model found in the geophysical literature. As regards the effect of chemical stratification, our quantitative estimate of the diffusion coefficient as a function of the mean gradient of mean molecular weight leads to the formula Dt ? 0.45?(0.12-Ri?) /Ri, which is compatible in the weak-shear regime with the model of Maeder & Meynet (1996, A&A, 313, 140) but not with Maeder's (1997, A&A, 321, 134).

Prat, V.; Lignières, F.

2014-06-01

147

Consistent Evolution of F Stars: Diffusion, Radiative Accelerations, and Abundance Anomalies  

NASA Astrophysics Data System (ADS)

Consistent stellar evolution models of F stars (1.1-1.5 M?) are calculated with radiative forces, opacities, and diffusion for all elements included in OPAL's opacity tables. The opacities and radiative forces are continuously recomputed during evolution from OPAL's monochromatic data (~1.5 Gbyte) in order to include all effects of abundance changes due to diffusion and nuclear evolution. TOPbase is also used for radiative accelerations. Iron surface overabundances occur in stars more massive than 1.3 M?. Local overabundances of iron peak elements increase the Rosseland opacity in a region at the base of the convection zone by a factor of 3-6; this increases the mass of the convective zone by up to a factor of 5. It is important to follow Cr, Mn, and Ni independently of Fe, since they peak at different temperatures within the star. The predicted abundance anomalies are much larger than observed in most F-type stars of open clusters. This suggests that atomic diffusion is not the only process responsible for the Li gap in open clusters. The predicted iron peak element overabundances indicate trends that are compatible with those observed in Fm stars. They however tend to be larger than the observed overabundances, leaving room for some perturbing hydrodynamical process. The present models, devoid of free parameters, are a necessary step in constraining the additional hydrodynamical processes required to better reproduce observed surface abundances. Since the abundances of 28 elements are calculated, one may have 27 constraints on stellar hydrodynamics, once the relative abundances of all species have been determined observationally.

Turcotte, S.; Richer, J.; Michaud, G.

1998-09-01

148

Radiative heating of interstellar grains falling toward the solar nebula: 1-D diffusion calculations.  

PubMed

As the dense molecular cloud that was the precursor of our Solar System was collapsing to form a protosun and the surrounding solar-nebula accretion disk, infalling interstellar grains were heated much more effectively by radiation from the forming protosun than by radiation from the disk's accretion shock. Accordingly, we have estimated the temperatures experienced by these infalling grains using radiative diffusion calculations whose sole energy source is radiation from the protosun. Although the calculations are 1-dimensional, they make use of 2-D, cylindrically symmetric models of the density structure of a collapsing, rotating cloud. The temperature calculations also utilize recent models for the composition and radiative properties of interstellar grains (Pollack et al. 1994. Astrophys. J. 421, 615-639), thereby allowing us to estimate which grain species might have survived, intact, to the disk accretion shock and what accretion rates and molecular-cloud rotation rates aid that survival. Not surprisingly, we find that the large uncertainties in the free parameter values allow a wide range of grain-survival results: (1) For physically plausible high accretion rates or low rotation rates (which produce small accretion disks), all of the infalling grain species, even the refractory silicates and iron, will vaporize in the protosun's radiation field before reaching the disk accretion shock. (2) For equally plausible low accretion rates or high rotation rates (which produce large accretion disks), all non-ice species, even volatile organics, will survive intact to the disk accretion shock. These grain-survival conclusions are subject to several limitations which need to be addressed by future, more sophisticated radiative-transfer models. Nevertheless, our results can serve as useful inputs to models of the processing that interstellar grains undergo at the solar nebula's accretion shock, and thus help address the broader question of interstellar inheritance in the solar nebula and present Solar System. These results may also help constrain the size of the accretion disk: for example, if we require that the calculations produce partial survival of organic grains into the solar nebula, we infer that some material entered the disk intact at distances comparable to or greater than a few AU. Intriguingly, this is comparable to the heliocentric distance that separates the C-rich outer parts of the current Solar System from the C-poor inner regions. PMID:11540163

Simonelli, D P; Pollack, J B; McKay, C P

1997-02-01

149

Radiative heating of interstellar grains falling toward the solar nebula: 1-D diffusion calculations  

NASA Technical Reports Server (NTRS)

As the dense molecular cloud that was the precursor of our Solar System was collapsing to form a protosun and the surrounding solar-nebula accretion disk, infalling interstellar grains were heated much more effectively by radiation from the forming protosun than by radiation from the disk's accretion shock. Accordingly, we have estimated the temperatures experienced by these infalling grains using radiative diffusion calculations whose sole energy source is radiation from the protosun. Although the calculations are 1-dimensional, they make use of 2-D, cylindrically symmetric models of the density structure of a collapsing, rotating cloud. The temperature calculations also utilize recent models for the composition and radiative properties of interstellar grains (Pollack et al. 1994. Astrophys. J. 421, 615-639), thereby allowing us to estimate which grain species might have survived, intact, to the disk accretion shock and what accretion rates and molecular-cloud rotation rates aid that survival. Not surprisingly, we find that the large uncertainties in the free parameter values allow a wide range of grain-survival results: (1) For physically plausible high accretion rates or low rotation rates (which produce small accretion disks), all of the infalling grain species, even the refractory silicates and iron, will vaporize in the protosun's radiation field before reaching the disk accretion shock. (2) For equally plausible low accretion rates or high rotation rates (which produce large accretion disks), all non-ice species, even volatile organics, will survive intact to the disk accretion shock. These grain-survival conclusions are subject to several limitations which need to be addressed by future, more sophisticated radiative-transfer models. Nevertheless, our results can serve as useful inputs to models of the processing that interstellar grains undergo at the solar nebula's accretion shock, and thus help address the broader question of interstellar inheritance in the solar nebula and present Solar System. These results may also help constrain the size of the accretion disk: for example, if we require that the calculations produce partial survival of organic grains into the solar nebula, we infer that some material entered the disk intact at distances comparable to or greater than a few AU. Intriguingly, this is comparable to the heliocentric distance that separates the C-rich outer parts of the current Solar System from the C-poor inner regions.

Simonelli, D. P.; Pollack, J. B.; McKay, C. P.

1997-01-01

150

Probabilistic diffusion tractography of the optic radiations and visual function in preterm infants at term equivalent age  

Microsoft Academic Search

Children born prematurely have a high incidence of visual disorders which cannot always be explained by focal retinal or brain lesions.The aim of this study was to test the hypothesis that visual function in preterm infants is related to the microstructural development of white matter in the optic radiations. We used diffusion tensor imaging (DTI) with probabilistic diffusion tractography to

Laura Bassi; Daniela Ricci; Anna Volzone; Joanna M. Allsop; Latha Srinivasan; Aakash Pai; Carmen Ribes; Luca A. Ramenghi; Eugenio Mercuri; Fabio Mosca; A. David Edwards; Frances M. Cowan; Mary A. Rutherford; Serena J. Counsell

2008-01-01

151

Measurement and modeled data of solar spectral global direct and diffuse radiation at Valencia (Spain)  

NASA Astrophysics Data System (ADS)

Since December, 1992 a continuing data bank of measurements of global, direct and diffuse solar irradiance for clear skies is being compiled at Valencia, Spain). The measurements are performed with the commercial LICOR spectroradiometer from 300 - 1100 nm with a spectral resolution of 6 nm. As a complementary work to irradiance measurements an extensive comparative task is being carried out between these experimental data and modelled ones. The chosen model is a detailed narrow band model developed at the Laboratoire d'Optique Atmospherique of the Universite of Lille, France) which uses a two-flux method to solve the radiative transfer equation. The multilayer model (17 atmospheric levels) considers the atmosphere as a plane-parallel absorbing and scattering medium where total, direct and diffuse spectral irradiance values are calculated at each level. Preliminary analysis shows promising results but the difficulty in modelling aerosol properties to fit experimental data is clearly manifested.

Cachorro, Victoria E.; de Frutos, Angel M.; Utrillas, Pilar; Martinez-Lozano, Jose A.

1994-12-01

152

Modeling Heat Conduction and Radiation Transport with the Diffusion Equation in NIF ALE-AMR  

SciTech Connect

The ALE-AMR code developed for NIF is a multi-material hydro-code that models target assembly fragmentation in the aftermath of a shot. The combination of ALE (Arbitrary Lagrangian Eulerian) hydro with AMR (Adaptive Mesh Refinement) allows the code to model a wide range of physical conditions and spatial scales. The large range of temperatures encountered in the NIF target chamber can lead to significant fluxes of energy due to thermal conduction and radiative transport. These physical effects can be modeled approximately with the aid of the diffusion equation. We present a novel method for the solution of the diffusion equation on a composite mesh in order to capture these physical effects.

Fisher, A C; Bailey, D S; Kaiser, T B; Gunney, B N; Masters, N D; Koniges, A E; Eder, D C; Anderson, R W

2009-10-06

153

Fabric radiators  

NASA Astrophysics Data System (ADS)

The design of large, high-temperature space radiators is still an evolving discipline. Researchers expanded the data base available to a designer by studying a novel class of radiators constructed of ceramic fabrics and/or composite materials. It appears that fabric radiators have features not available in more conventional radiator types, while offering the light weight and stowability of advanced radiators such as liquid droplet types. Experiments show that fabrics can be treated to become impermeable to the working fluid while retaining flexibility. This feature of fabrics, when allied to their low density, provides a material well-adapted to radiator construction.

Antoniak, Zenen I.; Jacox, Michael G.

154

Combination of magnetic resonance imaging and diffuse optical spectroscopy to predict radiation response in the breast: an exploratory pilot study  

NASA Astrophysics Data System (ADS)

Radiation therapy (RT) is a standard treatment after lumpectomy for breast cancer, involving a typical course of approximately 6-7 weeks of daily treatment. Many women find this cumbersome and costly, and therefore many are left with the option of mastectomy. Many groups are now investigating novel ways to deliver RT, by using different techniques and shortening the course of treatment. However, the efficacy and side effects of these strategies are not known. In this project, we wish to develop noninvasive imaging tools that would allow us to measure radiation dose effects in women with breast cancer. We hope this will lead to new ways to identify individuals who may not need radiation therapy, who may safely be treated with new accelerated techniques, or who should be treated with the standard radiation therapy approach. We propose to study the effect of radiation therapy using a combination of two imaging modalities: 1) magnetic resonance imaging (MRI) which will provide detailed information on breast structures and blood vessels and 2) near infra-red diffuse optical spectroscopy (DOS), which measures local biologic properties of breast tissue. Our hypothesis is that by using a combination of modalities we will be able to better characterize radiation effects in breast tissue, by measuring differences between the radiated and non-irradiated breast. The development of novel non-invasive tools providing information about how individuals respond to radiation therapy can lead to important improvement of radiation treatment, and ultimately help guide individualized treatment programs in the future.

Klifa, C.; Hattangadi, J.; Watkins, M.; Li, A.; Sakata, T.; Tromberg, B.; Hylton, N.; Park, C.

2007-03-01

155

New self-similar radiation-hydrodynamics solutions in the high-energy density, equilibrium diffusion limit  

NASA Astrophysics Data System (ADS)

This work presents semi-analytic solutions to a radiation-hydrodynamics problem of a radiation source driving an initially cold medium. Our solutions are in the equilibrium diffusion limit, include material motion and allow for radiation-dominated situations where the radiation energy is comparable to (or greater than) the material internal energy density. As such, this work is a generalization of the classical Marshak wave problem that assumes no material motion and that the radiation energy is negligible. Including radiation energy density in the model serves to slow down the wave propagation. The solutions provide insight into the impact of radiation energy and material motion, as well as present a novel verification test for radiation transport packages. As a verification test, the solution exercises the radiation-matter coupling terms and their v/c treatment without needing a hydrodynamics solve. An example comparison between the self-similar solution and a numerical code is given. Tables of the self-similar solutions are also provided.

Lane, Taylor K.; McClarren, Ryan G.

2013-09-01

156

Measuring Radiation  

MedlinePLUS

... or beta particles, gamma rays, x-rays, or neutrons, a quantity of radioactive material is expressed in ... larger than the absorbed dose for alpha and neutron radiation, because these types of radiation are more ...

157

Ionizing Radiation  

MedlinePLUS

... of Ionizing Radiation Sources Not Covered by Atomic Energy Act of 1954 . STD 01-04-001 [STD ... not the most current version. US Department of Energy (DOE) 10 CFR 835 , Occupational Radiation Protection Health ...

158

Radiation Emergencies  

MedlinePLUS

... bromide Methyl isocyanate Nicotine Nitrogen mustard Opioids Organic solvents Osmium tetroxide Paraquat Phosgene Phosgene oxime Phosphine Phosphorus ... Radiation Disasters Public Health Planning for Radiological and Nuclear Terrorism Radiation Basics Made Simple Radiological Terrorism: Just ...

159

Radiation Therapy  

MedlinePLUS

... get email updates Please leave this field empty Radiation Therapy SHARE Share on Facebook Preview your comments ... Treatment and Care > Treatments Listen The goal of radiation therapy is to destroy or stop brain tumor ...

160

Three-dimensional electron radiation belt simulations using the BAS Radiation Belt Model with new diffusion models for chorus, plasmaspheric hiss, and lightning-generated whistlers  

NASA Astrophysics Data System (ADS)

The flux of relativistic electrons in the Earth's radiation belts is highly variable and can change by orders of magnitude on timescales of a few hours. Understanding the drivers for these changes is important as energetic electrons can damage satellites. We present results from a new code, the British Antarctic Survey (BAS) Radiation Belt model, which solves a 3-D Fokker-Planck equation, following a similar approach to the Versatile Electron Radiation Belt (VERB) code, incorporating the effects of radial diffusion, wave-particle interactions, and collisions. Whistler mode chorus waves, plasmaspheric hiss, and lightning-generated whistlers (LGW) are modeled using new diffusion coefficients, calculated by the Pitch Angle and Energy Diffusion of Ions and Electrons (PADIE) code, with new wave models based on satellite data that have been parameterized by both the AE and Kp indices. The model for plasmaspheric hiss and LGW includes variation in the wave-normal angle distribution of the waves with latitude. Simulations of 100 days from the CRRES mission demonstrate that the inclusion of chorus waves in the model is needed to reproduce the observed increase in MeV flux during disturbed conditions. The model reproduces the variation of the radiation belts best when AE, rather than Kp, is used to determine the diffusion rates. Losses due to plasmaspheric hiss depend critically on the the wave-normal angle distribution; a model where the peak of the wave-normal angle distribution depends on latitude best reproduces the observed decay rates. Higher frequency waves (˜1-2 kHz) only make a significant contribution to losses for L?<3 and the highest frequencies (2-5 kHz), representing LGW, have a limited effect on MeV electrons for 2

Glauert, Sarah A.; Horne, Richard B.; Meredith, Nigel P.

2014-01-01

161

Role of land surface processes and diffuse/direct radiation partitioning in simulating the European climate  

NASA Astrophysics Data System (ADS)

The influence of land processes and in particular of diffuse/direct radiation partitioning on surface fluxes and associated regional-scale climate feedbacks is investigated. ERA-40 driven simulations over Europe are performed using the COSMO-CLM2 Regional Climate Model (RCM). Two alternative Land Surface Models (LSMs), a 2nd generation LSM (TERRA_ML) and a more advanced 3rd generation LSM (Community Land Model version 3.5), and two versions of the atmospheric component are tested, as well as a revised coupling procedure allowing for variations in diffuse/direct light partitioning at the surface, and their accounting by the land surface component. Overall, the RCM performance for various variables (e.g., surface fluxes, temperature and precipitation) is improved when using the more advanced 3rd generation LSM. These improvements are of the same order of magnitude as those arising from a new version of the atmospheric component, demonstrating the benefit of using a realistic representation of land surface processes for regional climate simulations. Taking into account variability in diffuse/direct light partitioning at the surface further improves the model performance in terms of summer temperature variability at the monthly and daily time scales. Comparisons with observations show that the RCM realistically captures temporal variations in diffuse/direct light partitioning as well as the evapotranspiration sensitivity to these variations. Our results suggest that a modest but consistent fraction (up to 3 %) of the overall variability in summer temperature can be explained by variations in the diffuse to direct ratio.

Davin, E. L.; Seneviratne, S. I.

2011-12-01

162

Role of land surface processes and diffuse/direct radiation partitioning in simulating the European climate  

NASA Astrophysics Data System (ADS)

The influence of land processes and in particular of diffuse/direct radiation partitioning on surface fluxes and associated regional-scale climate feedbacks is investigated using ERA-40 driven simulations over Europe performed with the COSMO-CLM2 Regional Climate Model (RCM). Two alternative Land Surface Models (LSMs), a 2nd generation LSM (TERRA_ML) and a more advanced 3rd generation LSM (Community Land Model version 3.5), and two versions of the atmospheric component are tested, as well as a revised coupling procedure allowing for variations in diffuse/direct light partitioning at the surface, and their accounting by the land surface component. Overall, the RCM performance for various variables (e.g., surface fluxes, temperature and precipitation) is improved when using the more advanced 3rd generation LSM. These improvements are of the same order of magnitude as those arising from a new version of the atmospheric component, demonstrating the benefit of using a realistic representation of land surface processes for regional climate simulations. Taking into account the variability in diffuse/direct light partitioning at the surface further improves the model performance in terms of summer temperature variability at the monthly and daily time scales. Comparisons with observations show that the RCM realistically captures temporal variations in diffuse/direct light partitioning as well as the evapotranspiration sensitivity to these variations. Our results suggest that a modest but consistent fraction (up to 3 %) of the overall variability in summer temperature can be explained by variations in the diffuse to direct ratio.

Davin, E. L.; Seneviratne, S. I.

2012-05-01

163

Identifying the human optic radiation using diffusion imaging and fiber tractography  

PubMed Central

Measuring the properties of the white matter pathways from retina to cortex in the living human brain will have many uses for understanding visual performance and guiding clinical treatment. For example, identifying the Meyer’s loop portion of the optic radiation (OR) has clinical significance because of the large number of temporal lobe resections. We use diffusion tensor imaging and fiber tractography (DTI-FT) to identify the most likely pathway between the lateral geniculate nucleus (LGN) and the calcarine sulcus in sixteen hemispheres of eight healthy volunteers. Quantitative population comparisons between DTI-FT estimates and published postmortem dissections match with a spatial precision of about 1 mm. The OR can be divided into three bundles that are segmented based on the direction of the fibers as they leave the LGN: Meyer’s loop, central, and direct. The longitudinal and radial diffusivities of the three bundles do not differ within the measurement noise; there is a small difference in the radial diffusivity between the right and left hemispheres. We find that the anterior tip of Meyer’s loop is 28 ± 3 mm posterior to the temporal pole, and the population range is 1 cm. Hence, it is important to identify the location of this bundle in individual subjects or patients.

Sherbondy, Anthony J.; Dougherty, Robert F.; Napel, Sandy; Wandell, Brian A.

2009-01-01

164

A new, coupled transport-diffusion method for radiative transfer calculations  

SciTech Connect

We derive and present a new frequency- and angle-integrated low-order system of equations designed to enhance the accuracy of a coupled, high-order (transport) solution of the thermal radiative transfer equations. In particular, our new low-order system is designed to use intensity-weighted opacities and anisotropic diffusion coefficients generated by a solution of the Implicit Monte Carlo (IMC) equations in order to predict the spatial dependence of the material temperature and radiation energies in the ensuing time cycle. The predicted temperature solution can then be exploited to generate appropriately time-centered opacities, specific heats, and Planck emission spectra for the upcoming IMC solution. Additionally, the relatively inexpensive solution of the low-order system can be iteratively solved to recommend an adaptive time step size before the IMC solution is computed. A test implementation has been implemented using existing software available from the Jayenne and Capsaicin projects at Los Alamos National Laboratory. We present initial results from a new driver code that has integrated these stochastic and deterministic software packages. (authors)

Wollaber, A. B.; Warsa, J. S. [Los Alamos National Laboratory, MS D409, P.O. Box 1663, Los Alamos NM, 87545 (United States)] [Los Alamos National Laboratory, MS D409, P.O. Box 1663, Los Alamos NM, 87545 (United States)

2013-07-01

165

Radiation therapy improves treatment outcome in patients with diffuse large B-cell lymphoma.  

PubMed

The effects of radiotherapy (RT) after chemotherapy in patients with diffuse large B-cell lymphoma (DLBCL) remain unclear; several trials have yielded conflicting results. This study examined the effect of RT after cyclophosphamide, doxorubicin, vincristine, and prednisone + rituximab (R-CHOP) treatment on event-free (EFS) and overall (OS) survival. Data from 216 patients with DLBCL who were enrolled in two clinical trials at Italian Lymphoma Study Group sites and were subjected to six R-CHOP cycles and involved-field radiotherapy (IFRT) were retrospectively analyzed. IFRT treatment yielded significant EFS benefit, with a 66% reduction in the risk of death and/or disease progression. Cox analysis, when adjusted for age, gender, stage, performance status (PS), lactate dehydrogenase (LDH), and disease bulk, confirmed the significant EFS benefit of IFRT. The role of RT in DLBCL in the rituximab era is unclear. Future studies must take into account new radiation techniques and the response to chemotherapy based on functional imaging. Prospective randomized trials incorporating response-adapted therapy and modern radiation techniques are needed. PMID:21663499

Marcheselli, Luigi; Marcheselli, Raffaella; Bari, Alessia; Liardo, Eliana Valentina; Morabito, Fortunato; Baldini, Luca; Brugiatelli, Maura; Merli, Francesco; Di Renzo, Nicola; Sacchi, Stefano

2011-10-01

166

On linearization and preconditioning for radiation diffusion coupled to material thermal conduction equations  

SciTech Connect

Jacobian-free Newton–Krylov (JFNK) method is an effective algorithm for solving large scale nonlinear equations. One of the most important advantages of JFNK method is that there is no necessity to form and store the Jacobian matrix of the nonlinear system when JFNK method is employed. However, an approximation of the Jacobian is needed for the purpose of preconditioning. In this paper, JFNK method is employed to solve a class of non-equilibrium radiation diffusion coupled to material thermal conduction equations, and two preconditioners are designed by linearizing the equations in two methods. Numerical results show that the two preconditioning methods can improve the convergence behavior and efficiency of JFNK method.

Feng, Tao, E-mail: fengtao2@mail.ustc.edu.cn [School of Mathematical Sciences, University of Science and Technology of China, Hefei 230052 (China) [School of Mathematical Sciences, University of Science and Technology of China, Hefei 230052 (China); Graduate School of China Academy Engineering Physics, Beijing 100083 (China); An, Hengbin, E-mail: an_hengbin@iapcm.ac.cn [National Key Laboratory of Computational Physics, Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China)] [National Key Laboratory of Computational Physics, Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China); Yu, Xijun, E-mail: yuxj@iapcm.ac.cn [National Key Laboratory of Computational Physics, Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China)] [National Key Laboratory of Computational Physics, Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China); Li, Qin, E-mail: liqin@lsec.cc.ac.cn [Chinese Academy of Mathematics and Systems Science, Beijing 100190 (China)] [Chinese Academy of Mathematics and Systems Science, Beijing 100190 (China); Zhang, Rongpei, E-mail: zhangrongpei@163.com [Graduate School of China Academy Engineering Physics, Beijing 100083 (China)] [Graduate School of China Academy Engineering Physics, Beijing 100083 (China)

2013-03-01

167

Directional Degradation of Spectralon Diffuser Under Ionizing Radiation for Calibration of Space-Based Sensors  

NASA Technical Reports Server (NTRS)

Assessment of the effect of Vacuum Ultra Violet (VUV) irradiation on the Bidirectional Reflectance Distribution Function (BRDF) of Spectralon is presented in this paper. The sample was a 99% white Spectralon calibration standard irradiated with VUV source positioned at 60o off the irradiation direction for a total of 20 hours. The BRDF before and after VUV irradiation was measured and compared at number of wavelengths in the UV, VIS and IR. Non-isotropic directional degradation of Spectralon diffuser under ionizing radiation was detected at different BRDF measurement geometries primarily at UV spectral range. The 8o directional/hemispherical reflectance of the same sample was also measured and compared from 200nm to 2500nm. Index Terms BRDF, Reflectance, Multiangular, Spectralon, Remote Sensing

Georgiev, G. T.; Butler, J. J.; Kowalewski, M. G.; Ding, L.

2012-01-01

168

On linearization and preconditioning for radiation diffusion coupled to material thermal conduction equations  

NASA Astrophysics Data System (ADS)

Jacobian-free Newton-Krylov (JFNK) method is an effective algorithm for solving large scale nonlinear equations. One of the most important advantages of JFNK method is that there is no necessity to form and store the Jacobian matrix of the nonlinear system when JFNK method is employed. However, an approximation of the Jacobian is needed for the purpose of preconditioning. In this paper, JFNK method is employed to solve a class of non-equilibrium radiation diffusion coupled to material thermal conduction equations, and two preconditioners are designed by linearizing the equations in two methods. Numerical results show that the two preconditioning methods can improve the convergence behavior and efficiency of JFNK method.

Feng, Tao; An, Hengbin; Yu, Xijun; Li, Qin; Zhang, Rongpei

2013-03-01

169

Laminar Smoke Point Based Subgrid Soot Radiation Modeling Applied to LES of Buoyant Turbulent Diffusion Flames  

NASA Astrophysics Data System (ADS)

Large eddy simulations (LES) of gaseous buoyant turbulent flames have been conducted with the application of a flamelet based soot-radiation model. The subgrid model applies a turbulent eddy description of soot formation, oxidation and radiation and is based on the laminar smoke point concept. Two parameters, a local turbulent strain rate and prior enthalpy loss/gain fraction influence the soot formation and radiation. Radiation heat transfer is simulated by solving the finite volume discretized form of the radiative transfer equation (RTE) with the subgrid soot-radiation model implemented. The radiant heating of surfaces in close proximity of the flames is computed and predicted heat fluxes and surface temperatures are compared against experimental data. Fire growth in a rack storage arrangement is simulated with the application of a pyrolysis model. Computed heat release rate (HRR) is compared against experimental data.

Chatterjee, Prateep; de Ris, John L.; Wang, Yi; Krishnamoorthy, Niveditha; Dorofeev, Sergey B.

2012-06-01

170

Comparing diffuse radiation models with one predictor for partitioning incident PAR radiation into its diffuse component in the eastern Mediterranean basin  

Microsoft Academic Search

In the photosynthesis process, solar radiation energy is converted to chemical energy by using atmospheric CO2. That is, almost all living species depend on energy produced through photosynthesis for their nourishing components thus making photosynthesis vital to the earth's life. Nevertheless, the knowledge of photosynthetic photon flux density QP (PAR, 400–700 nm) is important in several applications dealing with plants physiology,

C. P. Jacovides; J. Boland; D. N. Asimakopoulos; N. A. Kaltsounides

2010-01-01

171

Radial Diffusion of Outer Radiation Belt Electrons - Quantifying the Relative Importance of ULF wave Electric and Magnetic Fields  

NASA Astrophysics Data System (ADS)

MeV energy electrons are thought to be transported inwards from the plasma sheet into the radiation belts under the action of radial diffusion. Waves in the ultra-low frequency (ULF) band have frequencies which can be drift resonant with these electrons in the outer zone suggesting the potential for strong interactions, and enhanced radial diffusion. The diffusion coefficients depend on the power spectral density (PSD) of the waves electric and magnetic fields in space in the equatorial plane. Here we use over a solar cycle of ground magnetometer data to determined the electric field PSD in space and in-situ GOES and AMPTE data to obtain the magnetic field PSD. The diffusion coefficients derived from these PSD values allows us to quantify the relative importance of the electric and magnetic field diffusion terms. The commonly used analytic expressions presented in Brautigam and Albert [2000] indicate that magnetic diffusion dominates over the electric diffusion by over an order of magnitude. However, the magnetic diffusion coefficients we derive from the in-situ PSD measurements indicate that the Brautigam and Albert [2000] magnetic diffusion term is over an order of magnitude too high and that during high Kp intervals at L<4 the electric field diffusion term can become over two orders of magnitude greater than the magnetic diffusion term. In addition, radial diffusion simulations of electrons driven by these diffusion coefficients will be presented illustrating that both the electric and magnetic field diffusion coefficients may play an important role in the dynamics and energization of the Earth's outer radiation belt region.

Ozeke, L.; Mann, I. R.; Murphy, K. R.; Rae, J.; Milling, D. K.

2011-12-01

172

Comparison of LFM-test particle simulations and radial diffusion models of radiation belt electron injection into the slot region  

Microsoft Academic Search

The physics-based Lyon-Fedder-Mobarry (LFM) code simulates Earth's magnetospheric topology and dynamics by solving the equations of ideal MHD using input solar wind parameters at the upstream boundary. Comparison with electron phase space density evolution during storms using a radial diffusion code, as well as spacecraft measurements where available, will tell us when diffusion is insufficiently accurate for radiation belt simulation,

F. Chu; M. Hudson; B. Kress

2008-01-01

173

Radiation Chemistry  

NASA Astrophysics Data System (ADS)

Ionizing radiation causes chemical changes in the molecules of the interacting medium. The initial molecules change to new molecules, resulting in changes of the physical, chemical, and eventually biological properties of the material. For instance, water decomposes to its elements H2 and O2. In polymers, degradation and crosslinking take place. In biopolymers, e.g., DNS strand breaks and other alterations occur. Such changes are to be avoided in some cases (radiation protection), however, in other cases they are used for technological purposes (radiation processing). This chapter introduces radiation chemistry by discussing the sources of ionizing radiation (radionuclide sources, machine sources), absorption of radiation energy, techniques used in radiation chemistry research, and methods of absorbed energy (absorbed dose) measurements. Radiation chemistry of different classes of inorganic (water and aqueous solutions, inorganic solids, ionic liquids (ILs)) and organic substances (hydrocarbons, halogenated compounds, polymers, and biomolecules) is discussed in concise form together with theoretical and experimental backgrounds. An essential part of the chapter is the introduction of radiation processing technologies in the fields of polymer chemistry, food processing, and sterilization. The application of radiation chemistry to nuclear technology and to protection of environment (flue gas treatment, wastewater treatment) is also discussed.

Wojnárovits, L.

174

Time-independent hybrid enrichment for finite element solution of transient conduction–radiation in diffusive grey media  

SciTech Connect

We investigate the effectiveness of the partition-of-unity finite element method for transient conduction–radiation problems in diffusive grey media. The governing equations consist of a semi-linear transient heat equation for the temperature field and a stationary diffusion approximation to the radiation in grey media. The coupled equations are integrated in time using a semi-implicit method in the finite element framework. We show that for the considered problems, a combination of hyperbolic and exponential enrichment functions based on an approximation of the boundary layer leads to improved accuracy compared to the conventional finite element method. It is illustrated that this approach can be more efficient than using h adaptivity to increase the accuracy of the finite element method near the boundary walls. The performance of the proposed partition-of-unity method is analyzed on several test examples for transient conduction–radiation problems in two space dimensions.

Mohamed, M. Shadi, E-mail: m.s.mohamed@durham.ac.uk [School of Engineering and Computing Sciences, University of Durham, South Road, Durham DH1 3LE (United Kingdom); Seaid, Mohammed; Trevelyan, Jon [School of Engineering and Computing Sciences, University of Durham, South Road, Durham DH1 3LE (United Kingdom)] [School of Engineering and Computing Sciences, University of Durham, South Road, Durham DH1 3LE (United Kingdom); Laghrouche, Omar [Institute for Infrastructure and Environment, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom)] [Institute for Infrastructure and Environment, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom)

2013-10-15

175

Reanalysis of relativistic radiation belt electron fluxes using CRRES satellite data, a radial diffusion model, and a Kalman filter  

Microsoft Academic Search

In this study we perform a reanalysis of the sparse MEA CRRES relativistic electron data using a relatively simple one-dimensional radial diffusion model and a Kalman filtering approach. By combining observations with the model in an optimal way we produce a high time and space resolution reanalysis of the radiation belt electron fluxes over a 50-d period starting on 18

Yuri Shprits; Dmitri Kondrashov; Yue Chen; Richard Thorne; Michael Ghil; Reiner Friedel; Geoff Reeves

2007-01-01

176

Seasonal variations of diffuse solar radiation at Ilorin (8°32'N,4°46'E), Nigeria  

NASA Astrophysics Data System (ADS)

Hourly diffuse solar irradiance (Hd) and the corresponding global irradiance (H) falling on a horizontal surface at Ilorin (8°32'N,4°46'E), Nigeria has been measured for a period of fifteen months commencing from February, 1993. As expected, each monthly mean diurnal variation of Hd exhibits a mid-day maximum, while that of the ratio Hd/H exhibits a minimum. The month to month variations of these parameters are consequent on the dominant atmospheric conditions observed in the months concerned. The monthly average daily total of diffuse radiation (Hdm) was found to be highest in February, 1994 with a value of (3347 ± 45) Wm-2day-1, mainly due to the effects of Harmattan haze and thin clouds, while it was found to be lowest in November, 1993 and January, 1994 with a value of about 2500 Wm-2day-1. Similarly, the ratio of the monthly average daily total of diffuse radiation to the monthly average daily total of global radiation (Hdm/Hm) had the lowest value of 0.49 in the relatively clear sky month of November, 1993 and the highest value of 0.74 in the mainly cloudy month of August, 1993. On an annual average, the diffuse component constituted about 60% of the global solar radiation arriving on the ground at Ilorin, Nigeria primarily due to clouds and Harmattan haze which are seasonal, in addition to the constant background of molecular scattering.

Iziomon, Moses G.; Aro, Theophilus O.

1995-06-01

177

Anisotropic model for the diffuse biologically-effective irradiance of solar UV-radiation on inclined surfaces  

Microsoft Academic Search

A model for biologically-effective ultraviolet radiation (UVR) of the sun is described, which allows the calculation of diffuse irradiance on inclined surfaces. A model is presented, for which isotropic scattered and reflected radiance are assumed. Using the horizon as a borderline between the upper and lower hemisphere, the scattering phenomena in the atmosphere for UVR are discussed. In contrast to

G. Schauberger

1992-01-01

178

Solar radiation statistics for Iran  

Microsoft Academic Search

Various prediction methods for calculating the mean monthly solar radiation parameters are examined. A suitable method is proposed for predicting the mean monthly values of direct, diffuse, and total solar radiation at different locations in Iran. This method is based on the assumption that the direct and diffuse components of solar radiation are primarily functions of solar zenith angle and

M DANESHYAR

1978-01-01

179

Physics-based preconditioning and the Newton-Krylov method for non-equilibrium radiation diffusion  

SciTech Connect

An algorithm is presented for the solution of the time dependent reaction-diffusion systems which arise in non-equilibrium radiation diffusion applications. This system of nonlinear equations is solved by coupling three numerical methods, Jacobian-free Newton-Krylov, operator splitting, and multigrid linear solvers. An inexact Newton's method is used to solve the system of nonlinear equations. Since building the Jacobian matrix for problems of interest can be challenging, the authors employ a Jacobian-free implementation of Newton's method, where the action of the Jacobian matrix on a vector is approximated by a first order Taylor series expansion. Preconditioned generalized minimal residual (PGMRES) is the Krylov method used to solve the linear systems that come from the iterations of Newton's method. The preconditioner in this solution method is constructed using a physics-based divide and conquer approach, often referred to as operator splitting. This solution procedure inverts the scalar elliptic systems that make up the preconditioner using simple multigrid methods. The preconditioner also addresses the strong coupling between equations with local 2 x 2 block solves. The intra-cell coupling is applied after the inter-cell coupling has already been addressed by the elliptic solves. Results are presented using this solution procedure that demonstrate its efficiency while incurring minimal memory requirements.

Mousseau, V.A.; Knoll, D.A.; Rider, W.J.

2000-05-20

180

A case study of view-factor rectification procedures for diffuse-gray radiation enclosure computations  

NASA Technical Reports Server (NTRS)

The view factors which are used in diffuse-gray radiation enclosure calculations are often computed by approximate numerical integrations. These approximately calculated view factors will usually not satisfy the important physical constraints of reciprocity and closure. In this paper several view-factor rectification algorithms are reviewed and a rectification algorithm based on a least-squares numerical filtering scheme is proposed with both weighted and unweighted classes. A Monte-Carlo investigation is undertaken to study the propagation of view-factor and surface-area uncertainties into the heat transfer results of the diffuse-gray enclosure calculations. It is found that the weighted least-squares algorithm is vastly superior to the other rectification schemes for the reduction of the heat-flux sensitivities to view-factor uncertainties. In a sample problem, which has proven to be very sensitive to uncertainties in view factor, the heat transfer calculations with weighted least-squares rectified view factors are very good with an original view-factor matrix computed to only one-digit accuracy. All of the algorithms had roughly equivalent effects on the reduction in sensitivity to area uncertainty in this case study.

Taylor, Robert P.; Luck, Rogelio

1995-01-01

181

Diffuse fluorescence tomography based on the radiative transfer equation for small animal imaging  

NASA Astrophysics Data System (ADS)

Diffuse florescence tomography (DFT) as a high-sensitivity optical molecular imaging tool, can be applied to in vivo visualize interior cellular and molecular events for small-animal disease model through quantitatively recovering biodistributions of specific molecular probes. In DFT, the radiative transfer equation (RTE) and its approximation, such as the diffuse equation (DE), have been used as the forward models. The RTE-based DFT methodology is more suitable for biological tissue having void-like regions and the near-source area as in the situations of small animal imaging. We present a RTE-based scheme for the steady state DFT, which combines the discrete solid angle method and the finite difference method to obtain numerical solutions of the 2D steady RTE, with the natural boundary condition and collimating light source model. The approach is validated using the forward data from the Monte Carlo simulation for its better performances in the spatial resolution and reconstruction fidelity compared to the DE-based scheme.

Wang, Yihan; Zhang, Limin; Zhao, Huijuan; Gao, Feng; Li, Jiao

2014-02-01

182

Hawking radiation  

NASA Astrophysics Data System (ADS)

Hawking radiation is the thermal radiation predicted to be spontaneously emitted by black holes. It arises from the steady conversion of quantum vacuum fluctuations into pairs of particles, one of which escaping at infinity while the other is trapped inside the black hole horizon. It is named after the physicist Stephen Hawking who derived its existence in 1974. This radiation reduces the mass of black holes and is therefore also known as black hole evaporation.

Parentani, Renaud; Spindel, Philippe

2011-12-01

183

A radiometric model of an earth radiation budget radiometer optical system with diffuse-specular surfaces  

Microsoft Academic Search

The Earth Radiation Budget Experiment (ERBE) is to fly on NASA's Earth Radiation Budget Satellite (ERBS) and on NOAA F and NOAA G. Large spatial scale earth energy budget data will be derived primarily from measurements made by the ERBE nonscanning instrument (ERBE-NS). A description is given of a mathematical model capable of simulating the radiometric response of any of

M. R. Luther

1981-01-01

184

Application of a Reynolds stress turbulence model to a supersonic radiating hydrogen-air diffusion flame  

NASA Technical Reports Server (NTRS)

A second-order differential Reynolds Stress turbulence model has been applied to the Favre-averaged Navier-Stokes equations for the study of supersonic flows with finite-rate chemistry and radiation. An assumed Beta Probability Density Function is applied to account for the chemical source terms and the radiative flux terms in the conservation equations. A seven-species, seven-reaction finite rate chemistry mechanism is used to simulate the combustion process. The tangent slab approximation is used in radiative flux formulation. A pseudo-gray gas model is used to represent the absorption-emission characteristics of the participating species. The turbulence/radiation interaction is achieved via a new formulation. The resulting formulation is validated by comparison with experimental data on reacting supersonic axisymmetric jets. Results obtained for specific conditions indicate that the effect of chemical reaction on the turbulence is significant. Also, the radiative heat transfer is enhanced by the turbulence.

Chandrasekhar, R.; Tiwari, S. N.

1993-01-01

185

Estimation of hourly solar radiation for India  

Microsoft Academic Search

The ASHRAE constants predict high values of the hourly beam radiation and very low values of the hourly diffuse radiation when used to predict radiation at Indian locations. Hence a procedure has been developed for the estimation of direct, diffuse and global hourly solar radiation on a horizontal surface for any location in India. To calculate hourly solar radiation, an

G. V. Parishwad; R. K. Bhardwaj; V. K. Nema

1997-01-01

186

Radiation Measurements on Magnesium Flames.  

National Technical Information Service (NTIS)

The radiation of a diffusely radiating Mg0 flame is characterized by four parameters, which are initially unknown: temperature, optical thickness, and dispersion (wavelength dependence) of the absorption and scattering coefficients. The black body tempera...

F. Roessler

1968-01-01

187

Ionizing radiation  

NASA Technical Reports Server (NTRS)

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.

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

1975-01-01

188

Understanding Radiation.  

ERIC Educational Resources Information Center

Radiation is a natural energy force that has been a part of the environment since the Earth was formed. It takes various forms, none of which can be smelled, tasted, seen, heard, or felt. Nevertheless, scientists know what it is, where it comes from, how to measure and detect it, and how it affects people. Cosmic radiation from outer space and…

Department of Energy, Washington, DC. Nuclear Energy Office.

189

Radiation enteritis  

MedlinePLUS

... seeds to kill cancer cells. Along with the cancer cells, radiation therapy may also damage cells that make up the lining of the intestines. Anyone who receives radiation therapy to the belly or ... pancreatic, prostate, uterine, or colon and rectal cancer.

190

Combined heat transfer in floating zone growth of large silicon crystals with radiation on diffuse and specular surfaces  

NASA Astrophysics Data System (ADS)

Numerical analyses are conducted to investigate the combined heat transfer in floating zone growth of large Si crystals with needle-eye technique. The radiation element method, REM2, is employed to determine the radiative heat exchange, in which the view factors associated with the components in the float zone furnace and both the diffuse and specular reflection components are incorporated. The boundary element method and the finite difference method are adopted to calculate the electromagnetic field and the heat conduction, respectively. The effect of surface radiative characteristics of Si melt and crystal, i.e., diffuse and/or specular, is discussed in detail. It is found that the consideration of specular surfaces increases the Joulean heat and the radiative heat flux. The temperature fields are obtained for the cases of diffuse and specular, and the difference between the two different cases is obvious in the crystal and molten zone areas. The molten zone is enlarged when the specular surface is accounted for. The interface shape is examined and found to be in good agreement with the experiment.

Guo, Zhixiong; Maruyama, Shigenao; Togawa, Shinji

1998-01-01

191

Radiative processes  

NASA Technical Reports Server (NTRS)

Solar radiation and the processes that control its deposition in the Earth atmosphere are considered. The published data obtained since 1978 define a reference solar spectral irradiance for use in atmospheric chemical and dynamical studies, while long term satellite measurements are now providing information on variations in the output of the Sun over a range of time scales. As concerns absorption of solar radiation in the atmosphere, new cross section data for molecular oxygen and ozone are now available. Line-by-line calculations used to predict infrared flux divergences, both as regards assumptions made in radiative transfer calculations and in the spectroscopic parameters used as inputs are examined. Also examined are the influence of radiative processes on planetary scale wave activity, photochemical acceleration of radiative damping, and the breakdown of local thermodynamic equilibrium at mesospheric altitudes.

Frederick, J. E.; Leovy, C.; Anderson, D. E., Jr.; Anderson, G. P.; Dickinson, R. E.; Drayson, S. R.; Fels, S.; Hall, L. A.; Kiehl, J.; Mentall, J. E.

1985-01-01

192

Radiation detector  

DOEpatents

Apparatus is provided for detecting radiation such as gamma rays and x-rays generated in backscatter Moessbauer effect spectroscopy and x-ray spectrometry, which has a large window for detecting radiation emanating over a wide solid angle from a specimen and which generates substantially the same output pulse height for monoenergetic radiation that passes through any portion of the detection chamber. The apparatus includes a substantially toroidal chamber with conductive walls forming a cathode, and a wire anode extending in a circle within the chamber with the anode lying closer to the inner side of the toroid which has the least diameter than to the outer side. The placement of the anode produces an electric field, in a region close to the anode, which has substantially the same gradient in all directions extending radially from the anode, so that the number of avalanche electrons generated by ionizing radiation is independent of the path of the radiation through the chamber.

Fultz, B.T.

1980-12-05

193

Radiation detector  

DOEpatents

Apparatus is provided for detecting radiation such as gamma rays and X-rays generated in backscatter Mossbauer effect spectroscopy and X-ray spectrometry, which has a large "window" for detecting radiation emanating over a wide solid angle from a specimen and which generates substantially the same output pulse height for monoenergetic radiation that passes through any portion of the detection chamber. The apparatus includes a substantially toroidal chamber with conductive walls forming a cathode, and a wire anode extending in a circle within the chamber with the anode lying closer to the inner side of the toroid which has the least diameter than to the outer side. The placement of the anode produces an electric field, in a region close to the anode, which has substantially the same gradient in all directions extending radially from the anode, so that the number of avalanche electrons generated by ionizing radiation is independent of the path of the radiation through the chamber.

Fultz, Brent T. (Berkeley, CA)

1983-01-01

194

A theoretical analysis of the influence of turbulence on radiative emission in turbulent diffusion flames of methane  

NASA Astrophysics Data System (ADS)

A theoretical analysis is reported to quantify the increase of radiative emission due to turbulence for methane diffusion flames burning in air. The instantaneous thermochemical state of the reactive mixture is described by a flamelet model and a detailed chemical mechanism. Mean values of the absorption coefficient, blackbody radiation intensity and radiative emission are evaluated for different turbulence levels by assuming the pdf shape of mixture fraction. The results show that turbulent fluctuations generally contribute to reduce the Planck mean absorption coefficient of the medium, in contrast with the blackbody radiation intensity, which is significantly increased by turbulence. If the turbulence level is relatively small, the influence of turbulence on the absorption coefficient is marginal. Otherwise, fluctuations of the absorption coefficient of the medium should be taken into account. The mean radiative emission is underestimated if turbulent fluctuations are fully ignored and overestimated if only temperature fluctuations are considered, while neglecting fluctuations of the absorption coefficient of the medium, the error being generally higher in the latter case. The effects of turbulence on radiative emission are stronger in the fuel-lean region and close to stoichiometric conditions than in the fuel-rich region.

Coelho, P. J.

2012-06-01

195

Anisotropic model for the diffuse biologically-effective irradiance of solar UV-radiation on inclined surfaces  

NASA Astrophysics Data System (ADS)

A model for biologically-effective ultraviolet radiation (UVR) of the sun is described, which allows the calculation of diffuse irradiance on inclined surfaces. A model is presented, for which isotropic scattered and reflected radiance are assumed. Using the horizon as a borderline between the upper and lower hemisphere, the scattering phenomena in the atmosphere for UVR are discussed. In contrast to models for other solar spectral ranges, the radiation field of UVR is close to isotropic. Only the horizon darkening by the long optical pathlengths was included in the model. This term was quantified by the UV albedo.

Schauberger, G.

1992-03-01

196

Coupled radiative transfer equation and diffusion approximation model for photon migration in turbid medium with low-scattering and non-scattering regions  

Microsoft Academic Search

In this paper, a coupled radiative transfer equation and diffusion approximation model is extended for light propagation in turbid medium with low-scattering and non-scattering regions. The light propagation is modelled with the radiative transfer equation in sub-domains in which the assumptions of the diffusion approximation are not valid. The diffusion approximation is used elsewhere in the domain. The two equations

Tanja Tarvainen; Marko Vauhkonen; Ville Kolehmainen; Simon R. Arridge; Jari P. Kaipio

2005-01-01

197

Solar radiation on Mars  

SciTech Connect

Detailed information on solar radiation characteristics on Mars are necessary for effective design of future planned solar energy systems operating on the surface of Mars. In this paper the authors present a procedure and solar radiation related data from which the diurnally, hourly and daily variation of the global, direct beam and diffuse insolation on Mars are calculated. The radiation data are based on measured optical depth of the Martian atmosphere derived from images taken of the sun with a special diode on the Viking cameras; and computation based on multiple wavelength and multiple scattering of the solar radiation.

Appelbaum, J.; Flood, D.J. (National Aeronautics and Space Administration, Cleveland, OH (USA))

1990-01-01

198

Solar radiation on Mars  

NASA Technical Reports Server (NTRS)

Detailed information on solar radiation characteristics on Mars are necessary for effective design of future planned solar energy systems operating on the surface of Mars. Presented here is a procedure and solar radiation related data from which the diurnally, hourly and daily variation of the global, direct beam and diffuse insolation on Mars are calculated. The radiation data are based on measured optical depth of the Martian atmosphere derived from images taken of the sun with a special diode on the Viking cameras; and computation based on multiple wavelength and multiple scattering of the solar radiation.

Appelbaum, Joseph; Flood, Dennis J.

1990-01-01

199

Solar radiation on Mars  

NASA Technical Reports Server (NTRS)

Detailed information on solar radiation characteristics on Mars are necessary for effective design of future planned solar energy systems operating on the surface of Mars. Presented here is a procedure and solar radiation related data from which the diurnally, hourly and daily variation of the global, direct beam and diffuse insolation on Mars are calculated. The radiation data are based on measured optical depth of the Martian atmosphere derived from images taken of the sun with a special diode on the Viking cameras; and computation based on multiple wavelength and multiple scattering of the solar radiation.

Appelbaum, Joseph; Flood, Dennis J.

1989-01-01

200

Radiative transfer modeling of direct and diffuse sunlight in a Siberian pine forest  

NASA Astrophysics Data System (ADS)

We have expanded the Monte Carlo, ray-tracing model FLIGHT in order to simulate photosynthesis within three-dimensional, heterogeneous tree canopies. In contrast to the simple radiative transfer schemes adopted in many land-surface models (e.g., the Big Leaf approximation), our simulation calculates explicitly the leaf irradiance at different heights within the canopy and thus produces an accurate scale-up in photosynthesis from leaf to canopy level. We also account for both diffuse and direct sunlight. For a Siberian stand of Scots pine Pinus sylvestris, FLIGHT predicts observed carbon assimilation, across the full range of sky radiance, with an r.m.s. error of 12%. Our main findings for this sparse canopy, using both measurements and model, are as follows: (1) Observationally, we detect a light-use efficiency (LUE) increase of only ?10% for the canopy when the proportion of diffuse sky radiance is 75% rather than 25%. The corresponding enhancement predicted by our simulations is 10-20%. With such small increases in LUE, our site will not assimilate more carbon on overcast days compared to seasonally equivalent sunny days; (2) the scale-up in photosynthesis from top-leaf to canopy is less than unity. The Big Leaf approximation, based on Beer's law and light-acclimated leaf nitrogen, overpredicts this scale-up by ?60% for low sky radiance (?500 ?molPAR m-2 s-1); (3) when leaf nitrogen is distributed so as to maximize canopy photosynthesis, the increase in the canopy carbon assimilation, compared with a uniform nitrogen distribution, is small (?4%). Maximum assimilation occurs when the vertical gradient of leaf nitrogen is slightly shallower than that of the light profile.

Alton, P. B.; North, P.; Kaduk, J.; Los, S.

2005-12-01

201

Perturbative theory of grazing-incidence diffuse nuclear resonant scattering of synchrotron radiation  

SciTech Connect

Theoretical description of off-specular grazing-incidence nuclear resonant scattering of synchrotron radiation (synchrotron Moessbauer reflectometry, SMR) is presented. The recently developed SMR, similar to polarized neutron reflectometry (PNR), is an analytical tool for the determination of isotopic and magnetic structure of thin films and multilayers. It combines the sensitivity of Moessbauer spectroscopy to hyperfine interactions and the depth selectivity of x-ray reflectometry. Specular reflection provides information on the depth profile, while off-specular scattering on the lateral structure of scattering layers. Off-specular SMR and PNR intensity formulas of a rather general multilayer with different domains, based on a distorted incident-wave approximation (DIWA), are presented. The distorted-wave Born approximation results are given in an appendix. Physical and numerical implications, of using DIWA are explained. The temporal character of SMR imposes specific differences between SMR and PNR. In order to reveal the limits of DIWA and to compare the two analytical methods, two-dimensional diffuse SMR and PNR maps of an antiferromagnetic multilayer are calculated and critically compared. Experimental ''{omega}-2{theta}'' SMR map of a periodic [Fe/Cr]{sub 20} multilayer is presented and compared with simulations by the present theory.

Deak, L.; Bottyan, L.; Nagy, D. L. [KFKI Research Institute for Particle and Nuclear Physics, P.O. Box 49, H-1525 Budapest (Hungary); Spiering, H. [Institut fuer Anorganische und Analytische Chemie, Johannes Gutenberg Universitaet Mainz, Staudinger Weg 9, D-55099 Mainz (Germany); Khaidukov, Yu. N. [Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region (Russian Federation); Yoda, Y. [SPring-8 JASRI, 1-1-1 Kouto, Mikazuki-cho, Sayo-gun, Hyogo 679-5198 (Japan)

2007-12-01

202

WEE1 kinase inhibition enhances the radiation response of diffuse intrinsic pontine gliomas.  

PubMed

Diffuse intrinsic pontine glioma (DIPG) is a fatal pediatric disease. Thus far, no therapeutic agent has proven beneficial in the treatment of this malignancy. Therefore, conventional DNA-damaging radiotherapy remains the standard treatment, providing transient neurologic improvement without improving the probability of overall survival. During radiotherapy, WEE1 kinase controls the G(2) cell-cycle checkpoint, allowing for repair of irradiation (IR)-induced DNA damage. Here, we show that WEE1 kinase is one of the highest overexpressed kinases in primary DIPG tissues compared with matching non-neoplastic brain tissues. Inhibition of WEE1 by MK-1775 treatment of DIPG cells inhibited the IR-induced WEE1-mediated phosphorylation of CDC2, resulting in reduced G(2)-M arrest and decreased cell viability. Finally, we show that MK-1775 enhances the radiation response of E98-Fluc-mCherry DIPG mouse xenografts. Altogether, these results show that inhibition of WEE1 kinase in conjunction with radiotherapy holds potential as a therapeutic approach for the treatment of DIPG. PMID:23270927

Caretti, Viola; Hiddingh, Lotte; Lagerweij, Tonny; Schellen, Pepijn; Koken, Phil W; Hulleman, Esther; van Vuurden, Dannis G; Vandertop, W Peter; Kaspers, Gertjan J L; Noske, David P; Wurdinger, Thomas

2013-02-01

203

Thermodynamic and optical thickness corrections to diffusive radiative transfer formulations with application to planetary interiors  

NASA Astrophysics Data System (ADS)

transfer of high-frequency light under diffusive conditions is key to planetary heat flow and is important in astronomy and engineering. In geophysics, the effective radiative conductivity (krad) has been overestimated by threefold due to modeling refraction across planar interfaces as conical emanations of a point source. This assumption violates the second law of thermodynamics because heat can only flow down the thermal gradient. In addition to an extraneous factor of the index of refraction squared, calculations of krad need to address low absorbance in the near-infrared which cannot be quantified using small samples as required for diamond anvil cell experiments. We provide a new derivation and approximate krad in the Earth's mantle as 1.9 × 10-10T3 in Wm-1K-1, which is larger than previous estimates by a factor of up to 10, and will affect geodynamic models. It is also important in geodynamic models to incorporate the fast speed of the carriers, which cause this phenomenon to dominate transient events, and the relative flux of photons and phonons.

Hofmeister, A. M.

2014-05-01

204

Synchrotron Radiation  

SciTech Connect

This book covers the physical aspects of synchrotron radiation generation and is designed as a textbook and reference for graduate students, teachers and scientists utilizing synchrotron radiation. It is my hope that this text may help especially students and young researchers entering this exciting field to gain insight into the characteristics of synchrotron radiation. Discovered in 1945, synchrotron radiation has become the source of photons from the infrared to hard x-rays for a large community of researchers in basic and applied sciences. This process was particularly supported by the development of electron accelerators for basic research in high energy physics. Specifically, the development of the store ring and associated technologies resulted in the availability of high brightness photon beams far exceeding other sources. In this text, the physics of synchrotron radiation for a variety of magnets is derived from first principles resulting in useful formulas for the practitioner. Since the characteristics and quality of synchrotron radiation are intimately connected with the accelerator and electron beam producing this radiation, a short overview of relevant accelerator physics is included.

Wiedemann, Helmut

2003-08-11

205

Radiation damage of contact structures with diffusion barriers exposed to irradiation with {sup 60}Co{gamma}-ray photons  

SciTech Connect

The effect of ionizing radiation of {sup 60}Co {gamma}-ray photons in the dose range 10{sup 4}-2 x 10{sup 9} rad on metal-semiconductor Au-ZrB{sub x}-AlGaN/GaN and Au-TiB{sub x}-Al-Ti-n-GaN contacts and Au-ZrB{sub x}-n-GaN Schottky diodes is examined. The contacts with the TiB{sub x} and ZrB{sub x} diffusion barriers do not degrade under the effect of ionizing radiation if the dose does not exceed 10{sup 8} rad. The Au-ZrB{sub x}-n-GaN Schottky diodes remain stable in the dose range 10{sup 4}-10{sup 6} rad. As the radiation dose is increased to {>=}10{sup 8} rad, the damage to the contact metallization increases and is accompanied by formation of through pores, which is conducive to accumulation of oxygen at the Au-ZrB{sub x}(TiB{sub x}) interfaces and to an increase in mass transport of atoms in contact-forming layers. In this case, irradiation-caused degradation of the Schottky diodes is observed. Possible mechanisms of radiation damage of contact structures with diffusion barriers are analyzed.

Belyaev, A. E. [National Academy of Sciences of Ukraine, Lashkaryov Institute of Semiconductor Physics (Ukraine); Boltovets, N. S. [Orion State Enterprise Research Institute (Ukraine); Konakova, R. V., E-mail: konakova@isp.kiev.ua; Milenin, V. V. [National Academy of Sciences of Ukraine, Lashkaryov Institute of Semiconductor Physics (Ukraine); Sveshnikov, Yu. N. [Elma-Malachite Close Corporation (Russian Federation); Sheremet, V. N. [National Academy of Sciences of Ukraine, Lashkaryov Institute of Semiconductor Physics (Ukraine)

2010-04-15

206

Experimental measurements of a prototype high concentration Fresnel lens CPV module for the harvesting of diffuse solar radiation.  

PubMed

A prototype concentrator photovoltaic (CPV) module with high solar concentration, an added low-cost solar cell, and an adjoining multi-junction solar cell is fabricated and experimentally demonstrated. In the present CPV module, the low cost solar cell captures diffuse solar radiation penetrating the concentrator lens and the multi-junction cell captures concentrated direct solar radiation. On-sun test results show that the electricity generated by a Fresnel lens-based CPV module with an additional crystalline silicon solar cell is greater than that for a conventional CPV module by a factor of 1.44 when the mean ratio of diffuse normal irradiation to global normal irradiation at the module aperture is 0.4. Several fundamental optical characteristics are presented for the present module. PMID:24921997

Yamada, Noboru; Okamoto, Kazuya

2014-01-13

207

Radiation Fog  

NSDL National Science Digital Library

This is the first instructional component to be published in the Physical Processes Professional Competency Unit of the Forecasting Low-Altitude Clouds and Fog for Aviation Operations Professional Development Series. The learning modules in this professional competency unit will help aviation forecasters gain more familiarity with the physical concepts and atmospheric conditions related to fog and low stratus life cycles. Such understanding, in turn, can help forecasters more efficiently and accurately evaluate the ability of a given atmospheric environment to generate and/or maintain radiation fog. Radiation Fog presents presents the physical processes and life cycle of radiation fog, including its preconditioning environment, initiation, growth, and dissipation. The processes include radiation (both solar and longwave), soil-atmosphere thermal interactions, turbulent mixing, the roles of condensation nuclei, and droplet settling. Each section includes a set of interactive questions based on the learning content presented.

Spangler, Tim

2000-12-01

208

Radiation Therapy.  

National Technical Information Service (NTIS)

Guidelines are presented for the development of radiation therapy capability in northwestern Pennsylvania. A surplus of megavoltage (cobalt therapy, linear accelerator) capability exists in the area, (as of 1976) therefore recommendations are made for one...

1976-01-01

209

Radiation sterilization  

PubMed Central

The sterilization by radiation of disposable medical items has been investigated. Various vegetative and spore-bearing bacteria have been irradiated and results indicate that 2·5 Mrad can be recommended to give a high degree of sterility. Spores of B. pumilus (E.601) showed such resistance that it might be a suitable test organism for determining the efficiency of a radiation treatment. A high standard of packaging must be demanded for pre-sterilized products.

Darmady, E. M.; Hughes, K. E. A.; Burt, Margaret M.; Freeman, Barbara M.; Powell, D. B.

1961-01-01

210

R-CHOP with dose-attenuated radiation therapy could induce good prognosis in gastric diffuse large B cell lymphoma  

PubMed Central

Background The treatment strategy for gastric diffuse large cell lymphoma (DLBCL) has not been standardized in such as to the cycles of chemotherapy, dose of radiation, or necessity for the surgery. Although the results of CHOP or R-CHOP treatments have demonstrated the good prognosis, the treatments have been controversial in many cases. Methods We retrospectively analyzed 40 gastric DLBCL patients receiving chemotherapy with or without radiation in our institute. Those in stages II-IV were treated with six cycles of R-CHOP without radiation; for those in stage I, we administered three cycles of R-CHOP with radiation. Results The three-year overall survival (OS) and progression-free survival (PFS) rates were 95.2 and 91.8%, respectively. Those in stage I obtained 100% of OS. The radiation dose prescribed was 30.6?Gy for CR cases and 39.6 to 40?Gy for PR after chemotherapy. Although survival rates tended to correlate with staging groups or age-adjusted IPI classifications, multivariate statistical analysis did not show clear differences. All 14 patients with initial bleeding were successfully managed without surgery during treatment. Conclusion R-CHOP therapy was very effective for gastric DLBCL. It may be not necessary to use more than 30.6?Gy of radiotherapy in the highly chemo-sensitive cases. Less toxic treatments should be made available to gastric DLBCL patients.

2012-01-01

211

Diffusion tensor imaging tractography of the optic radiation for epilepsy surgical planning: A comparison of two methods  

PubMed Central

Summary The optic radiation is a key white matter structure at risk during epilepsy surgery involving the temporal, parietal or occipital lobes. It shows considerable anatomical variability, cannot be delineated on clinical MRI sequences and damage may cause a disabling visual field deficit. Diffusion tensor imaging tractography allows non-invasive mapping of this pathway. Numerous methods have been published but direct comparison is difficult as patient, acquisition and analysis parameters differ. Two methods for delineating the optic radiation were applied to 6 healthy controls and 4 patients with epileptogenic lesions near the optic radiation. By comparing methods with the same datasets, many of the parameters could be controlled. The first method was previously developed to accurately identify Meyer's loop for planning anterior temporal lobe resection. The second aimed to address limitations of this method by using a more automated technique to reduce operator time and to depict the entire optic radiation. Whilst the core of the tract was common to both methods, there was significant variability between the methods. Method 1 gave a more consistent depiction of Meyer's loop with fewer spurious tracts. Method 2 gave a better depiction of the entire optic radiation, particularly in more posterior portions, but did not identify Meyer's loop in one patient. These results show that whilst tractography is a promising technique, there is significant variability depending on the method chosen even when the majority of parameters are fixed. Different methods may need to be chosen for surgical planning depending on the individual clinical situation.

Winston, Gavin P.; Mancini, Laura; Stretton, Jason; Ashmore, Jonathan; Symms, Mark R.; Duncan, John S.; Yousry, Tarek A.

2011-01-01

212

Fully implicit solution of large-scale non-equilibrium radiation diffusion with high order time integration  

SciTech Connect

We present a solution method for fully implicit radiation diffusion problems discretized on meshes having millions of spatial zones. This solution method makes use of high order in time integration techniques, inexact Newton-Krylov nonlinear solvers, and multigrid preconditioners. We explore the advantages and disadvantages of high order time integration methods for the fully implicit formulation on both two- and three-dimensional problems with tabulated opacities and highly nonlinear fusion source terms.

Brown, Peter N. [Center for Applied Scientific Computing, Lawrence Livermore National Laboratory, PO Box 808, L-561, Livermore, CA 94551 (United States)]. E-mail: pnbrown@llnl.gov; Shumaker, Dana E. [Center for Applied Scientific Computing, Lawrence Livermore National Laboratory, PO Box 808, L-561, Livermore, CA 94551 (United States)]. E-mail: shumaker1@llnl.gov; Woodward, Carol S. [Center for Applied Scientific Computing, Lawrence Livermore National Laboratory, PO Box 808, L-561, Livermore, CA 94551 (United States)]. E-mail: cswoodward@llnl.gov

2005-04-10

213

Radiation Doses in Perspective  

MedlinePLUS

... Health Effects Ionizing & Non-Ionizing Radiation Understanding Radiation: Radiation Doses in Perspective Health Effects Main Page Exposure ... Sources Doses from Common Radiation Sources Average U.S. Radiation Doses and Sources All of us are exposed ...

214

Dependence of the bounce-averaged diffusion coefficients on magnetic field model in the outer radiation belt  

NASA Astrophysics Data System (ADS)

Bounce-averaged scattering rates computed in the dipole magnetic field are usually used for the diffusive simulations of the radiation belt diffusion codes. We present the results of calculations of the bounce-averaged pitch angle , mixed , and momentum diffusion coefficients in two Tsyganenko and dipole field models. We consider resonant interactions of the outer radiation belt electrons with oblique whistler-mode chorus waves. We assume the Gaussian wave frequency distribution and the Gaussian wave normal angle distribution. The bounce-averaged scattering rates are calculated for geomagnetically quiet and disturbed conditions at two MLT locations. We concentrate at distance of 7 Earth radii near the geostationary orbit. We demonstrate that on the day side the effects of taking into account a realistic magnetic field are only considerable for small equatorial pitch angles for energies larger than E=1 MeV. On the night side the differences in the bounce-averaged scattering rates calculated in Tsyganenko and dipole field models can reach several orders of magnitude at various equatorial pitch angles for E?0.5 MeV electrons. To explain the differences in , , and associated with a change of the magnetic field model on the day and night sides we present the contribution of various resonant harmonics to the diffusion and examine the changes in the resonance condition. We show that with increasing electron energy a larger numbers of resonances can significantly contribute to the bounce-averaged diffusion coefficients up to several tens of resonances in the realistic magnetic fields. Our study shows that it is crucially important for radiation belt modeling to compute the scattering rates in a realistic field model.

Orlova, K.; Shprits, Y.; Ni, B.

2012-04-01

215

Synchrotron Radiation  

NASA Astrophysics Data System (ADS)

As early as 1900, immediately after the pioneer formulation by Liénard and Wiechert of the retarded potentials of a point charge (electron), calculations of the characteristics of the radiation from an accelerated electron or electron beam have been performed. But it was not until 1947 when John Blewett actually observed the synchrotron radiation from the beam in the 70-MeV General Electric electron synchrotron, the phenomenon was accepted as physical reality instead of some interesting mathematical deduction. It was soon recognized that the synchrotron radiation provides an extremely brilliant photon beam over a very broad frequency range from infrared to hard x-ray, and hence makes an ideal tool for use in extranuclear research. By the end of the twentieth century there were dozens of electron storage rings operated around the world at energies from a few hundred MeV to 8 GeV for experiments. Here we will study first the properties of the synchrotron radiation and then the effects of the emission of synchrotron radiation on the electron beam.

Teng, Lee C.

2004-02-01

216

Anomalous Diffuse Interstellar Bands in the Spectrum of Herschel 36. II. Analysis of Radiatively Excited CH+, CH, and Diffuse Interstellar Bands  

NASA Astrophysics Data System (ADS)

Absorption spectra toward Herschel 36 (Her 36) for the \\tilde{A}^1\\Pi \\leftarrow \\tilde{X}^1\\Sigma transitions of CH+ in the J = 1 excited rotational level and for the \\tilde{A}^2\\Delta \\leftarrow \\tilde{X}^2\\Pi transitions of CH in the J = 3/2 excited fine structure level have been analyzed. These excited levels are above their ground levels by 40.1 K and ~25.7 K and indicate high radiative temperatures of the environment of 14.6 K and 6.7 K, respectively. The effect of the high radiative temperature is more spectacular in some diffuse interstellar bands (DIBs) observed toward Her 36; remarkable extended tails toward red (ETRs) were observed. We interpret these ETRs as being due to a small decrease of the rotational constants upon excitation of the excited electronic states. Along with radiative pumping of a great many high-J rotational levels, this causes the ETRs. In order to study this effect quantitatively, we have developed a model calculation in which the effects of collisions and radiation are treated simultaneously. The simplest case of linear molecules is considered. It has been found that the ETR is reproduced if the fraction of the variation of the rotational constant, ? ? (B' - B)/B, is sufficiently high (3%-5%) and the radiative temperature is high (T r > 50 K). Although modeling for general molecules is beyond the scope of this paper, the results indicate that the prototypical DIBs ?5780.5, ?5797.1, and ?6613.6 which show the pronounced ETRs are due to polar molecules that are sensitive to the radiative excitation. The requirement of high ? favors relatively small molecules with three to six heavy atoms. DIBs ?5849.8, ?6196.0, and ?6379.3 that do not show the pronounced ETRs are likely due to non-polar molecules or large polar molecules with small ?.

Oka, Takeshi; Welty, Daniel E.; Johnson, Sean; York, Donald G.; Dahlstrom, Julie; Hobbs, L. M.

2013-08-01

217

Radiation receiver  

DOEpatents

The apparatus for collecting radiant energy and converting same to alternate energy form includes a housing having an interior space and a radiation transparent window allowing, for example, solar radiation to be received in the interior space of the housing. Means are provided for passing a stream of fluid past said window and for injecting radiation absorbent particles in said fluid stream. The particles absorb the radiation and because of their very large surface area, quickly release the heat to the surrounding fluid stream. The fluid stream particle mixture is heated until the particles vaporize. The fluid stream is then allowed to expand in, for example, a gas turbine to produce mechanical energy. In an aspect of the present invention properly sized particles need not be vaporized prior to the entrance of the fluid stream into the turbine, as the particles will not damage the turbine blades. In yet another aspect of the invention, conventional fuel injectors are provided to inject fuel into the fluid stream to maintain the proper temperature and pressure of the fluid stream should the source of radiant energy be interrupted. In yet another aspect of the invention, an apparatus is provided which includes means for providing a hot fluid stream having hot particles disbursed therein which can radiate energy, means for providing a cooler fluid stream having cooler particles disbursed therein, which particles can absorb radiant energy and means for passing the hot fluid stream adjacent the cooler fluid stream to warm the cooler fluid and cooler particles by the radiation from the hot fluid and hot particles. 5 figs.

Hunt, A.J.

1983-09-13

218

Second order time evolution of the multigroup diffusion and P{sub 1} equations for radiation transport  

SciTech Connect

Highlights: {yields} An existing multigroup transport algorithm is extended to be second-order in time. {yields} A new algorithm is presented that does not require a grey acceleration solution. {yields} The two algorithms are tested with 2D, multi-material problems. {yields} The two algorithms have comparable computational requirements. - Abstract: An existing solution method for solving the multigroup radiation equations, linear multifrequency-grey acceleration, is here extended to be second order in time. This method works for simple diffusion and for flux-limited diffusion, with or without material conduction. A new method is developed that does not require the solution of an averaged grey transport equation. It is effective solving both the diffusion and P{sub 1} forms of the transport equation. Two dimensional, multi-material test problems are used to compare the solution methods.

Olson, Gordon L., E-mail: olson99@tds.net [Computer and Computational Sciences Division (CCS-2), Los Alamos National Laboratory, 5 Foxglove Circle, Madison, WI 53717 (United States)

2011-08-20

219

Hybrid model of light propagation in random media based on the time-dependent radiative transfer and diffusion equations  

NASA Astrophysics Data System (ADS)

Numerical modeling of light propagation in random media has been an important issue for biomedical imaging, including diffuse optical tomography (DOT). For high resolution DOT, accurate and fast computation of light propagation in biological tissue is desirable. This paper proposes a space-time hybrid model for numerical modeling based on the radiative transfer and diffusion equations (RTE and DE, respectively) in random media under refractive-index mismatching. In the proposed model, the RTE and DE regions are separated into space and time by using a crossover length and the time from the ballistic regime to the diffusive regime, ?DA~10/?t? and tDA~20/v?t? where ?t? and v represent a reduced transport coefficient and light velocity, respectively. The present model succeeds in describing light propagation accurately and reduces computational load by a quarter compared with full computation of the RTE.

Fujii, Hiroyuki; Okawa, Shinpei; Yamada, Yukio; Hoshi, Yoko

2014-11-01

220

Quantitative monitoring of radiation induced skin toxicities in nude mice using optical biomarkers measured from diffuse optical reflectance spectroscopy.  

PubMed

Monitoring the onset of erythema following external beam radiation therapy has the potential to offer a means of managing skin toxicities via biological targeted agents - prior to full progression. However, current skin toxicity scoring systems are subjective and provide at best a qualitative evaluation. Here, we investigate the potential of diffuse optical spectroscopy (DOS) to provide quantitative metrics for scoring skin toxicity. A DOS fiberoptic reflectance probe was used to collect white light spectra at two probing depths using two short fixed source-collector pairs with optical probing depths sensitive to the skin surface. The acquired spectra were fit to a diffusion theory model of light transport in tissue to extract optical biomarkers (hemoglobin concentration, oxygen saturation, scattering power and slope) from superficial skin layers of nude mice, which were subjected to erythema inducing doses of ionizing radiation. A statistically significant increase in oxygenated hemoglobin (p < 0.0016) was found in the skin post-irradiation - confirming previous reports. More interesting, we observed for the first time that the spectral scattering parameters, A (p = 0.026) and k (p = 0.011), were an indicator of erythema at day 6 and could potentially serve as an early detection optical biomarker of skin toxicity. Our data suggests that reflectance DOS may be employed to provide quantitative assessment of skin toxicities following curative doses of external beam radiation. PMID:24876997

Yohan, Darren; Kim, Anthony; Korpela, Elina; Liu, Stanley; Niu, Carolyn; Wilson, Brian C; Chin, Lee Cl

2014-05-01

221

Quantitative monitoring of radiation induced skin toxicities in nude mice using optical biomarkers measured from diffuse optical reflectance spectroscopy  

PubMed Central

Monitoring the onset of erythema following external beam radiation therapy has the potential to offer a means of managing skin toxicities via biological targeted agents – prior to full progression. However, current skin toxicity scoring systems are subjective and provide at best a qualitative evaluation. Here, we investigate the potential of diffuse optical spectroscopy (DOS) to provide quantitative metrics for scoring skin toxicity. A DOS fiberoptic reflectance probe was used to collect white light spectra at two probing depths using two short fixed source-collector pairs with optical probing depths sensitive to the skin surface. The acquired spectra were fit to a diffusion theory model of light transport in tissue to extract optical biomarkers (hemoglobin concentration, oxygen saturation, scattering power and slope) from superficial skin layers of nude mice, which were subjected to erythema inducing doses of ionizing radiation. A statistically significant increase in oxygenated hemoglobin (p < 0.0016) was found in the skin post-irradiation – confirming previous reports. More interesting, we observed for the first time that the spectral scattering parameters, A (p = 0.026) and k (p = 0.011), were an indicator of erythema at day 6 and could potentially serve as an early detection optical biomarker of skin toxicity. Our data suggests that reflectance DOS may be employed to provide quantitative assessment of skin toxicities following curative doses of external beam radiation.

Yohan, Darren; Kim, Anthony; Korpela, Elina; Liu, Stanley; Niu, Carolyn; Wilson, Brian C; Chin, Lee CL

2014-01-01

222

Optic Radiation Fiber Tractography in Glioma Patients Based on High Angular Resolution Diffusion Imaging with Compressed Sensing Compared with Diffusion Tensor Imaging - Initial Experience  

PubMed Central

Objective Up to now, fiber tractography in the clinical routine is mostly based on diffusion tensor imaging (DTI). However, there are known drawbacks in the resolution of crossing or kissing fibers and in the vicinity of a tumor or edema. These restrictions can be overcome by tractography based on High Angular Resolution Diffusion Imaging (HARDI) which in turn requires larger numbers of gradients resulting in longer acquisition times. Using compressed sensing (CS) techniques, HARDI signals can be obtained by using less non-collinear diffusion gradients, thus enabling the use of HARDI-based fiber tractography in the clinical routine. Methods Eight patients with gliomas in the temporal lobe, in proximity to the optic radiation (OR), underwent 3T MRI including a diffusion-weighted dataset with 30 gradient directions. Fiber tractography of the OR using a deterministic streamline algorithm based on DTI was compared to tractography based on reconstructed diffusion signals using HARDI+CS. Results HARDI+CS based tractography displayed the OR more conclusively compared to the DTI-based results in all eight cases. In particular, the potential of HARDI+CS-based tractography was observed for cases of high grade gliomas with significant peritumoral edema, larger tumor size or closer proximity of tumor and reconstructed fiber tract. Conclusions Overcoming the problem of long acquisition times, HARDI+CS seems to be a promising basis for fiber tractography of the OR in regions of disturbed diffusion, areas of high interest in glioma surgery.

Kuhnt, Daniela; Bauer, Miriam H. A.; Sommer, Jens; Merhof, Dorit; Nimsky, Christopher

2013-01-01

223

RADIATION MYELOPATHY  

Microsoft Academic Search

A survey was made of 38 cases of radiation myelopathy with regard to ; early symptoms and signs, differential diagnosis, prognosis, nature of the ; primary lesion irradiated, and latency between irradiation and the development of ; neurological symptoms. Death occurred in 17 of these cases, 1 month to 4 yr ; after the first neurologic symptoms, as a result

CHRISTOPHER A. PALLIS; SYDNEY LOUIS; ROWLAND L. MORGAN

1961-01-01

224

Radiation Therapy  

MedlinePLUS

... the body, making the person very sick. Radiation therapy kills cancer cells and keeps them from growing and multiplying. The ... people may first have surgery to remove cancer cells or tumors and then have ... depends on the kind of cancer he or she has. A doctor called an ...

225

Radiation Models  

ERIC Educational Resources Information Center

Discusses the historical development of both the wave and the corpuscular photon model of light. Suggests that students should be informed that the two models are complementary and that each model successfully describes a wide range of radiation phenomena. Cites 19 references which might be of interest to physics teachers and students. (LC)

James, W. G. G.

1970-01-01

226

Radiation accidents.  

PubMed

It is essential that emergency physicians understand ways to manage patients contaminated by radioactive materials and/or exposed to external radiation sources. Contamination accidents require careful surveys to identify the metabolic pathway of the radionuclides to guide prognosis and treatment. The level of treatment required will depend on careful surveys and meticulous decontamination. There is no specific therapy for the acute radiation syndrome. Prophylactic antibodies are desirable. For severely exposed patients treatment is similar to the supportive care given to patients undergoing organ transplantation. For high-dose extremity injury, no methods have been developed to reverse the fibrosing endarteritis that eventually leads to tissue death so frequently found with this type of injury. Although the Three Mile Island episode of March 1979 created tremendous public concern, there were no radiation injuries. The contamination outside the reactor building and the release of radioiodine were negligible. The accidental fuel element meltdown at Chernobyl, USSR, resulted in many cases of acute radiation syndrome. More than 100,000 people were exposed to high levels of radioactive fallout. The general principles outlined here are applicable to accidents of that degree of severity. PMID:3526994

Saenger, E L

1986-09-01

227

Radiation source  

Microsoft Academic Search

A method is described of generating X-radiation from an apparatus comprised of: (a) at least two electrodes mounted in an evacuable chamber with one of the electrodes positioned above the other electrode; (b) a quantity of a powder of at least one conducting or semi-conducting material supported on the lower of the electrodes when the electrodes have a potential difference

S. G. Szirmai; G. R. Newman; P. L. Kelly

1987-01-01

228

Radiation Therapy  

MedlinePLUS

... after radiation therapy has ended. Skin damage or changes. The skin around the treatment area may be red, sensitive, or easily irritated in the days, weeks, and months during and after treatment. ... texture may change. (Most symptoms of skin damage are temporary, although ...

229

Radiation cataract.  

PubMed

Until very recently, ocular exposure guidelines were based on the assumption that radiation cataract is a deterministic event requiring threshold doses generally greater than 2 Gy. This view was, in part, based on older studies which generally had short follow-up periods, failed to take into account increasing latency as dose decreased, had relatively few subjects with doses below a few Gy, and were not designed to detect early lens changes. Newer findings, including those in populations exposed to much lower radiation doses and in subjects as diverse as astronauts, medical workers, atomic bomb survivors, accidentally exposed individuals, and those undergoing diagnostic or radiotherapeutic procedures, strongly suggest dose-related lens opacification at significantly lower doses. These observations resulted in a recent re-evaluation of current lens occupational exposure guidelines, and a proposed lowering of the presumptive radiation cataract threshold to 0.5 Gy/year and the occupational lens exposure limit to 20 mSv/year, regardless of whether received as an acute, protracted, or chronic exposure. Experimental animal studies support these conclusions and suggest a role for genotoxicity in the development of radiation cataract. Recent findings of a low or even zero threshold for radiation-induced lens opacification are likely to influence current research efforts and directions concerning the cellular and molecular mechanisms underlying this pathology. Furthermore, new guidelines are likely to have significant implications for occupational and/or accidental exposure, and the need for occupational eye protection (e.g. in fields such as interventional medicine). PMID:23089007

Kleiman, N J

2012-01-01

230

Hypofractionation vs Conventional Radiation Therapy for Newly Diagnosed Diffuse Intrinsic Pontine Glioma: A Matched-Cohort Analysis  

SciTech Connect

Purpose: Despite conventional radiation therapy, 54 Gy in single doses of 1.8 Gy (54/1.8 Gy) over 6 weeks, most children with diffuse intrinsic pontine glioma (DIPG) will die within 1 year after diagnosis. To reduce patient burden, we investigated the role of hypofractionation radiation therapy given over 3 to 4 weeks. A 1:1 matched-cohort analysis with conventional radiation therapy was performed to assess response and survival. Methods and Materials: Twenty-seven children, aged 3 to 14, were treated according to 1 of 2 hypofractionation regimens over 3 to 4 weeks (39/3 Gy, n=16 or 44.8/2.8 Gy, n=11). All patients had symptoms for {<=}3 months, {>=}2 signs of the neurologic triad (cranial nerve deficit, ataxia, long tract signs), and characteristic features of DIPG on magnetic resonance imaging. Twenty-seven patients fulfilling the same diagnostic criteria and receiving at least 50/1.8 to 2.0 Gy were eligible for the matched-cohort analysis. Results: With hypofractionation radiation therapy, the overall survival at 6, 9, and 12 months was 74%, 44%, and 22%, respectively. Progression-free survival at 3, 6, and 9 months was 77%, 43%, and 12%, respectively. Temporary discontinuation of steroids was observed in 21 of 27 (78%) patients. No significant difference in median overall survival (9.0 vs 9.4 months; P=.84) and time to progression (5.0 vs 7.6 months; P=.24) was observed between hypofractionation vs conventional radiation therapy, respectively. Conclusions: For patients with newly diagnosed DIPG, a hypofractionation regimen, given over 3 to 4 weeks, offers equal overall survival with less treatment burden compared with a conventional regimen of 6 weeks.

Janssens, Geert O., E-mail: g.janssens@rther.umcn.nl [Department of Radiation Oncology, Radboud University Nijmegen Medical Centre, Nijmegen (Netherlands); Jansen, Marc H. [Pediatric Oncology/Hematology, VU University Medical Center, Amsterdam (Netherlands)] [Pediatric Oncology/Hematology, VU University Medical Center, Amsterdam (Netherlands); Lauwers, Selmer J. [Department of Radiation Oncology, Radboud University Nijmegen Medical Centre, Nijmegen (Netherlands)] [Department of Radiation Oncology, Radboud University Nijmegen Medical Centre, Nijmegen (Netherlands); Nowak, Peter J. [Department of Radiation Oncology, Erasmus Medical Centre, Rotterdam (Netherlands)] [Department of Radiation Oncology, Erasmus Medical Centre, Rotterdam (Netherlands); Oldenburger, Foppe R. [Department of Radiation Oncology, Academic Medical Centre, Amsterdam (Netherlands)] [Department of Radiation Oncology, Academic Medical Centre, Amsterdam (Netherlands); Bouffet, Eric [Department of Hematology/Oncology, The Hospital for Sick Children, University of Toronto, Toronto (Canada)] [Department of Hematology/Oncology, The Hospital for Sick Children, University of Toronto, Toronto (Canada); Saran, Frank [Department of Pediatric Oncology, The Royal Marsden NHS Foundation Trust, Sutton (United Kingdom)] [Department of Pediatric Oncology, The Royal Marsden NHS Foundation Trust, Sutton (United Kingdom); Kamphuis-van Ulzen, Karin [Department of Radiology, Radboud University Nijmegen Medical Centre, Nijmegen (Netherlands)] [Department of Radiology, Radboud University Nijmegen Medical Centre, Nijmegen (Netherlands); Lindert, Erik J. van [Department of Neurosurgery, Radboud University Nijmegen Medical Centre, Nijmegen (Netherlands)] [Department of Neurosurgery, Radboud University Nijmegen Medical Centre, Nijmegen (Netherlands); Schieving, Jolanda H. [Department of Neurology, Radboud University Nijmegen Medical Centre, Nijmegen (Netherlands)] [Department of Neurology, Radboud University Nijmegen Medical Centre, Nijmegen (Netherlands); Boterberg, Tom [Department of Radiation Oncology, Ghent University Hospital, Ghent (Belgium)] [Department of Radiation Oncology, Ghent University Hospital, Ghent (Belgium); Kaspers, Gertjan J. [Pediatric Oncology/Hematology, VU University Medical Center, Amsterdam (Netherlands)] [Pediatric Oncology/Hematology, VU University Medical Center, Amsterdam (Netherlands); Span, Paul N.; Kaanders, Johannes H. [Department of Radiation Oncology, Radboud University Nijmegen Medical Centre, Nijmegen (Netherlands)] [Department of Radiation Oncology, Radboud University Nijmegen Medical Centre, Nijmegen (Netherlands); Gidding, Corrie E. [Department of Pediatric Oncology, Radboud University Nijmegen Medical Centre, Nijmegen (Netherlands)] [Department of Pediatric Oncology, Radboud University Nijmegen Medical Centre, Nijmegen (Netherlands); Hargrave, Darren [Department of Oncology, Great Ormond Street Hospital, London (United Kingdom)] [Department of Oncology, Great Ormond Street Hospital, London (United Kingdom)

2013-02-01

231

A faster algorithm for smoothed particle hydrodynamics with radiative transfer in the flux-limited diffusion approximation  

NASA Astrophysics Data System (ADS)

We describe a new, faster implicit algorithm for solving the radiation hydrodynamics equations in the flux-limited diffusion approximation for smoothed particle hydrodynamics. This improves on the method elucidated in Whitehouse and Bate by using a Gauss-Seidel iterative method rather than iterating over the exchange of energy between pairs of particles. The new algorithm is typically many thousands of times faster than the old one, which will enable more complex problems to be solved. The new algorithm is tested using the same tests performed by Turner and Stone for ZEUS-2D, and repeated by Whitehouse and Bate.

Whitehouse, Stuart C.; Bate, Matthew R.; Monaghan, Joe J.

2005-12-01

232

Sound Radiation from Cylindrical Radiators  

NSDL National Science Digital Library

The following animations illustrate the radiation of sound waves from a vibrating source in 2-D. The source is a long cylinder which is oscillating in the radial direction only (all vibrations along the length of the cylinder are ignored). In particular, the animations show the vibration of the cylinder in its various modes and the resulting particle displacements of the surrounding fluid.

Russell, Dan

233

Change in Diffusing Capacity After Radiation as an Objective Measure for Grading Radiation Pneumonitis in Patients Treated for Non-Small-Cell Lung Cancer  

SciTech Connect

Purpose: Scoring of radiation pneumonitis (RP), a dose-limiting toxicity after thoracic radiochemotherapy, is subjective and thus inconsistent among studies. Here we investigated whether the extent of change in diffusing capacity of the lung for carbon monoxide (DLCO) after radiation therapy (RT) for non-small-cell lung cancer (NSCLC) could be used as an objective means of quantifying RP. Patients and Methods: We analyzed potential correlations between DLCO and RP in 140 patients who received definitive RT ({>=}60 Gy) with or without chemotherapy for primary NSCLC. All underwent DLCO analysis before and after RT. Post-RT DLCO values within 1 week of the RP diagnosis (Grade 0, 1, 2, or 3) were selected and compared with that individual's preradiation values. Percent reductions in DLCO and RP grade were compared by point biserial correlation in the entire patient group and in subgroups stratified according to various clinical factors. Results: Patients experiencing Grade 0, 1, 2, or 3 RP had median percentage changes in DLCO after RT of 10.7%, 13%, 22.1%, or 35.2%. Percent reduction in DLCO correlated with RP Grade {<=}1 vs. {>=}2 (p = 0.0004). This association held for the following subgroups: age {>=}65 years, advanced stage, smokers, use of chemotherapy, volume of normal lung receiving at least 20 Gy {>=}30%, and baseline DLCO or forced expiratory volume in 1 second {>=}60%. Conclusions: By correlating percent change in DLCO from pretreatment values at the time of diagnosis of RP with RP grade, we were able to identify categories of RP based on the change in DLCO. These criteria provide a basis for an objective scoring system for RP based on change in DLCO.

Lopez Guerra, Jose Luis [Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX (United States) [Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX (United States); Department of Radiation Oncology, Hospitales Universitarios Virgen del Rocio, Seville (Spain); Gomez, Daniel, E-mail: dgomez@mdanderson.org [Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX (United States)] [Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX (United States); Zhuang Yan; Levy, Lawrence B. [Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX (United States)] [Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX (United States); Eapen, George [Department of Pulmonary Medicine, University of Texas MD Anderson Cancer Center, Houston, TX (United States)] [Department of Pulmonary Medicine, University of Texas MD Anderson Cancer Center, Houston, TX (United States); Liu Hongmei; Mohan, Radhe; Komaki, Ritsuko; Cox, James D.; Liao Zhongxing [Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX (United States)] [Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX (United States)

2012-08-01

234

Radiation Protection Basics  

MedlinePLUS

... Basic Concepts of Radiation Protection time distance shielding Time The amount of radiation exposure increases and decreases ... exposure. How does EPA use the concept of time in radiation protection? When we set a radiation ...

235

Radiation Oncology Treatment Team  

MedlinePLUS

... Prostate Skin Upper GI Latest Research Find a Radiation Oncologist Last Name: Facility: City: State: Zip Code: ... who specializes in using radiation to treat cancer . Radiation Oncologists Radiation oncologists are the doctors who will ...

236

Radiation Therapy for Osteosarcoma  

MedlinePLUS

... for osteosarcoma Next Topic Clinical trials for osteosarcoma Radiation therapy for osteosarcoma Radiation therapy uses high-energy ... back or surgery is not possible. External beam radiation therapy This is the type of radiation therapy ...

237

Radiation Protection  

NSDL National Science Digital Library

Chemotherapy and radiation can be powerful weapons against cancer. But they harm healthy cells as well. Cells of the immune system and G.I. tract are especially vulnerable: instead of repairing the damage, they respond by committing cellular suicide. In contrast, tumor cells have mutations that make them resistant to cell death. Roswell Park Cancer Institute researcher Andrei Gudkov and his colleagues recently harnessed this property to create a new drug.

Science Update (AAAS;)

2008-05-01

238

Acquisition of reproducible transmission near-infrared (NIR) spectra of solid samples with inconsistent shapes by irradiation with isotropically diffused radiation using polytetrafluoroethylene (PTFE) beads.  

PubMed

A bead-incorporated transmission scheme (BITS) has been demonstrated for collecting reproducible transmission near-infrared (NIR) spectra of samples with inconsistent shapes. Isotropically diffused NIR radiation was applied around a sample and the surrounding radiation was allowed to interact homogeneously with the sample for transmission measurement. Samples were packed in 1.40 mm polytetrafluoroethylene (PTFE) beads, ideal diffusers without NIR absorption, and then transmission spectra were collected by illuminating the sample-containing beads using NIR radiation. When collimated radiation was directly applied, a small portion of the non-fully diffused radiation (NFDR) propagated through the void space of the packing and eventually degraded the reproducibility. Pre-diffused radiation was introduced by placing an additional PTFE disk in front of the packing to diminish NFDR, which produced more reproducible spectral features. The proposed scheme was evaluated by analyzing two different solid samples: density determination for individual polyethylene (PE) pellets and identification of mining locality for tourmalines. Because spectral collection was reproducible, the use of the spectrum acquired from one PE pellet was sufficient to accurately determine the density of nine other pellets with different shapes. The differentiation of tourmalines, which are even more dissimilar in appearance, according to their mining locality was also feasible with the help of the scheme. PMID:24818217

Lee, Jinah; Duy, Pham Khac; Yoon, Jihye; Chung, Hoeil

2014-05-19

239

A Monte Carlo Synthetic-Acceleration Method for Solving the Thermal Radiation Diffusion Equation  

SciTech Connect

We present a novel synthetic-acceleration based Monte Carlo method for solving the equilibrium thermal radiation diusion equation in three dimensions. The algorithm performance is compared against traditional solution techniques using a Marshak benchmark problem and a more complex multiple material problem. Our results show that not only can our Monte Carlo method be an eective solver for sparse matrix systems, but also that it performs competitively with deterministic methods including preconditioned Conjugate Gradient while producing numerically identical results. We also discuss various aspects of preconditioning the method and its general applicability to broader classes of problems.

Evans, Thomas M [ORNL] [ORNL; Mosher, Scott W [ORNL] [ORNL; Slattery, Stuart [University of Wisconsin, Madison] [University of Wisconsin, Madison

2014-01-01

240

Three-dimensional diffusion of non-sorbing species in porous sandstone: computer simulation based on X-ray microtomography using synchrotron radiation  

Microsoft Academic Search

The diffusion pathways of porous sandstone were examined by a three-dimensional (3-D) imaging technique based on X-ray computed tomography (CT) using the SPring-8 (Super Photon ring-8 GeV, Hyogo, Japan) synchrotron radiation facility. The analysis was undertaken to develop better understanding of the diffusion pathways in natural rock as a key factor in clarifying the detailed mechanism of the diffusion of

Yoshito Nakashima; Tsukasa Nakano; Koichi Nakamura; Kentaro Uesugi; Akira Tsuchiyama; Susumu Ikeda

2004-01-01

241

ANOMALOUS DIFFUSE INTERSTELLAR BANDS IN THE SPECTRUM OF HERSCHEL 36. II. ANALYSIS OF RADIATIVELY EXCITED CH{sup +}, CH, AND DIFFUSE INTERSTELLAR BANDS  

SciTech Connect

Absorption spectra toward Herschel 36 (Her 36) for the A-bar{sup 1}{Pi} Leftwards-Open-Headed-Arrow X-tilde{sup 1}{Sigma} transitions of CH{sup +} in the J = 1 excited rotational level and for the A-bar{sup 2}{Delta} Leftwards-Open-Headed-Arrow X-tilde{sup 2}{Pi} transitions of CH in the J = 3/2 excited fine structure level have been analyzed. These excited levels are above their ground levels by 40.1 K and {approx}25.7 K and indicate high radiative temperatures of the environment of 14.6 K and 6.7 K, respectively. The effect of the high radiative temperature is more spectacular in some diffuse interstellar bands (DIBs) observed toward Her 36; remarkable extended tails toward red (ETRs) were observed. We interpret these ETRs as being due to a small decrease of the rotational constants upon excitation of the excited electronic states. Along with radiative pumping of a great many high-J rotational levels, this causes the ETRs. In order to study this effect quantitatively, we have developed a model calculation in which the effects of collisions and radiation are treated simultaneously. The simplest case of linear molecules is considered. It has been found that the ETR is reproduced if the fraction of the variation of the rotational constant, {beta} {identical_to} (B' - B)/B, is sufficiently high (3%-5%) and the radiative temperature is high (T{sub r} > 50 K). Although modeling for general molecules is beyond the scope of this paper, the results indicate that the prototypical DIBs {lambda}5780.5, {lambda}5797.1, and {lambda}6613.6 which show the pronounced ETRs are due to polar molecules that are sensitive to the radiative excitation. The requirement of high {beta} favors relatively small molecules with three to six heavy atoms. DIBs {lambda}5849.8, {lambda}6196.0, and {lambda}6379.3 that do not show the pronounced ETRs are likely due to non-polar molecules or large polar molecules with small {beta}.

Oka, Takeshi; Welty, Daniel E.; Johnson, Sean; York, Donald G.; Hobbs, L. M. [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Dahlstrom, Julie, E-mail: t-oka@uchicago.edu [Department of Physics and Astronomy, Carthage College, 2001 Alford Park Drive, Kenosha, WI 53140 (United States)

2013-08-10

242

A Radiation Chemistry Code Based on the Green's Function of the Diffusion Equation  

NASA Technical Reports Server (NTRS)

Stochastic radiation track structure codes are of great interest for space radiation studies and hadron therapy in medicine. These codes are used for a many purposes, notably for microdosimetry and DNA damage studies. In the last two decades, they were also used with the Independent Reaction Times (IRT) method in the simulation of chemical reactions, to calculate the yield of various radiolytic species produced during the radiolysis of water and in chemical dosimeters. Recently, we have developed a Green's function based code to simulate reversible chemical reactions with an intermediate state, which yielded results in excellent agreement with those obtained by using the IRT method. This code was also used to simulate and the interaction of particles with membrane receptors. We are in the process of including this program for use with the Monte-Carlo track structure code Relativistic Ion Tracks (RITRACKS). This recent addition should greatly expand the capabilities of RITRACKS, notably to simulate DNA damage by both the direct and indirect effect.

Plante, Ianik; Wu, Honglu

2014-01-01

243

A Multigroup diffusion solver using pseudo transient continuation for a radiation-hydrodynamic code with patch-based AMR  

SciTech Connect

We present a scheme to solve the nonlinear multigroup radiation diffusion (MGD) equations. The method is incorporated into a massively parallel, multidimensional, Eulerian radiation-hydrodynamic code with adaptive mesh refinement (AMR). The patch-based AMR algorithm refines in both space and time creating a hierarchy of levels, coarsest to finest. The physics modules are time-advanced using operator splitting. On each level, separate 'level-solve' packages advance the modules. Our multigroup level-solve adapts an implicit procedure which leads to a two-step iterative scheme that alternates between elliptic solves for each group with intra-cell group coupling. For robustness, we introduce pseudo transient continuation ({Psi}tc). We analyze the magnitude of the {Psi}tc parameter to ensure positivity of the resulting linear system, diagonal dominance and convergence of the two-step scheme. For AMR, a level defines a subdomain for refinement. For diffusive processes such as MGD, the refined level uses Dirichet boundary data at the coarse-fine interface and the data is derived from the coarse level solution. After advancing on the fine level, an additional procedure, the sync-solve (SS), is required in order to enforce conservation. The MGD SS reduces to an elliptic solve on a combined grid for a system of G equations, where G is the number of groups. We adapt the 'partial temperature' scheme for the SS; hence, we reuse the infrastructure developed for scalar equations. Results are presented. We consider a multigroup test problem with a known analytic solution. We demonstrate utility of {Psi}tc by running with increasingly larger timesteps. Lastly, we simulate the sudden release of energy Y inside an Al sphere (r = 15 cm) suspended in air at STP. For Y = 11 kT, we find that gray radiation diffusion and MGD produce similar results. However, if Y = 1 MT, the two packages yield different results. Our large Y simulation contradicts a long-standing theory and demonstrates the inadequacy of gray diffusion.

Shestakov, A I; Offner, S R

2006-09-21

244

A multigroup diffusion solver using pseudo transient continuation for a radiation-hydrodynamic code with patch-based AMR  

SciTech Connect

We present a scheme to solve the nonlinear multigroup radiation diffusion (MGD) equations. The method is incorporated into a massively parallel, multidimensional, Eulerian radiation-hydrodynamic code with Adaptive Mesh Refinement (AMR). The patch-based AMR algorithm refines in both space and time creating a hierarchy of levels, coarsest to finest. The physics modules are time-advanced using operator splitting. On each level, separate 'level-solve' packages advance the modules. Our multigroup level-solve adapts an implicit procedure which leads to a two-step iterative scheme that alternates between elliptic solves for each group with intra-cell group coupling. For robustness, we introduce pseudo transient continuation ({psi}tc). We analyze the magnitude of the {psi}tc parameter to ensure positivity of the resulting linear system, diagonal dominance and convergence of the two-step scheme. For AMR, a level defines a subdomain for refinement. For diffusive processes such as MGD, the refined level uses Dirichlet boundary data at the coarse-fine interface and the data is derived from the coarse level solution. After advancing on the fine level, an additional procedure, the sync-solve (SS), is required in order to enforce conservation. The MGD SS reduces to an elliptic solve on a combined grid for a system of G equations, where G is the number of groups. We adapt the 'partial temperature' scheme for the SS; hence, we reuse the infrastructure developed for scalar equations. Results are presented. We consider a multigroup test problem with a known analytic solution. We demonstrate utility of {psi}tc by running with increasingly larger timesteps. Lastly, we simulate the sudden release of energy Y inside an Al sphere (r = 15 cm) suspended in air at STP. For Y = 11 kT, we find that gray radiation diffusion and MGD produce similar results. However, if Y = 1 MT, the two packages yield different results. Our large Y simulation contradicts a long-standing theory and demonstrates the inadequacy of gray diffusion.

Shestakov, Aleksei I. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore CA 94550 (United States)], E-mail: shestakov@llnl.gov; Offner, Stella S.R. [Physics Department, University of California, Berkeley CA 94720 (United States)], E-mail: soffner@berkely.edu

2008-01-10

245

Diffusion Tensor Imaging of Normal-Appearing White Matter as Biomarker for Radiation-Induced Late Delayed Cognitive Decline  

SciTech Connect

Purpose: To determine whether early assessment of cerebral white matter degradation can predict late delayed cognitive decline after radiotherapy (RT). Methods and Materials: Ten patients undergoing conformal fractionated brain RT participated in a prospective diffusion tensor magnetic resonance imaging study. Magnetic resonance imaging studies were acquired before RT, at 3 and 6 weeks during RT, and 10, 30, and 78 weeks after starting RT. The diffusivity variables in the parahippocampal cingulum bundle and temporal lobe white matter were computed. A quality-of-life survey and neurocognitive function tests were administered before and after RT at the magnetic resonance imaging follow-up visits. Results: In both structures, longitudinal diffusivity ({lambda}{sub Double-Vertical-Line }) decreased and perpendicular diffusivity ({lambda}{sub Up-Tack }) increased after RT, with early changes correlating to later changes (p < .05). The radiation dose correlated with an increase in cingulum {lambda}{sub Up-Tack} at 3 weeks, and patients with >50% of cingula volume receiving >12 Gy had a greater increase in {lambda}{sub Up-Tack} at 3 and 6 weeks (p < .05). The post-RT changes in verbal recall scores correlated linearly with the late changes in cingulum {lambda}{sub Double-Vertical-Line} (30 weeks, p < .02). Using receiver operating characteristic curves, early cingulum {lambda}{sub Double-Vertical-Line} changes predicted for post-RT changes in verbal recall scores (3 and 6 weeks, p < .05). The neurocognitive test scores correlated significantly with the quality-of-life survey results. Conclusions: The correlation between early diffusivity changes in the parahippocampal cingulum and the late decline in verbal recall suggests that diffusion tensor imaging might be useful as a biomarker for predicting late delayed cognitive decline.

Chapman, Christopher H., E-mail: chchap@umich.edu [Department of Radiation Oncology, University of Michigan Medical School, Ann Arbor, MI (United States); Nagesh, Vijaya [Department of Radiation Oncology, University of Michigan Medical School, Ann Arbor, MI (United States); Sundgren, Pia C. [Department of Radiology, University of Michigan Medical School, Ann Arbor, MI (United States); Department of Radiology, Skane University Hospital, Lund (Sweden); Buchtel, Henry [Department of Psychiatry, University of Michigan Medical School, Ann Arbor, MI (United States); Veterans Affairs Ann Arbor Healthcare System, Ann Arbor, MI (United States); Chenevert, Thomas L. [Department of Radiology, University of Michigan Medical School, Ann Arbor, MI (United States); Junck, Larry [Department of Neurology, University of Michigan Medical School, Ann Arbor, MI (United States); Lawrence, Theodore S.; Tsien, Christina I. [Department of Radiation Oncology, University of Michigan Medical School, Ann Arbor, MI (United States); Cao, Yue [Department of Radiation Oncology, University of Michigan Medical School, Ann Arbor, MI (United States); Department of Radiology, University of Michigan Medical School, Ann Arbor, MI (United States)

2012-04-01

246

Shortwave Radiation  

NASA Technical Reports Server (NTRS)

Accurate shortwave radiation data is critical to evapotranspiration (ET) models used for developing irrigation schedules to optimize crop production while saving water, minimizing fertilizer, herbicide, and pesticide applications, reducing soil erosion, and protecting surface and ground water quality. Low cost silicon cell pyranometers have proven to be sufficiently accurate and robust for widespread use in agricultural applications under unobstructed daylight conditions. More expensive thermopile pyranometers are required for use as calibration standards and measurements under light with unique spectral properties (electric lights, under vegetation, in greenhouses and growth chambers). Routine cleaning, leveling, and annual calibration checks will help to ensure the integrity of long-term data.

Klassen, Steve; Bugbee, Bruce

2005-01-01

247

Radiative heat transfer in isothermal spherical media  

Microsoft Academic Search

Radiative heat transfer in emitting, absorbing, and scattering spherical media is analyzed. The medium is assumed to be gray, isothermal, and linear-anisotropically scattering. The medium is confined in the space between two gray concentric spheres, which diffusely emit, and specularly and diffusely reflect radiation. Approximate solutions of the equation of radiative transfer are obtained using the spherical harmonics method. Results

W. Li; T. W. Tong

1990-01-01

248

The implications of the COBE diffuse microwave radiation results for cosmic strings  

NASA Technical Reports Server (NTRS)

We compare the anisotropies in the cosmic microwave background radiation measured by the COBE experiment to those predicted by cosmic string theories. We use an analytic model for the Delta T/T power spectrum that is based on our previous numerical simulations of strings, under the assumption that cosmic strings are the sole source of the measured anisotropy. This implies a value for the string mass per unit length of 1.5 +/- 0.5 x 10 exp -6 C-squared/G. This is within the range of values required for cosmic strings to successfully seed the formation of large-scale structures in the universe. These results clearly encourage further studies of Delta T/T and large-scale structure in the cosmic string model.

Bennett, David P.; Stebbins, Albert; Bouchet, Francois R.

1992-01-01

249

Non-diffusive resonant acceleration of electrons in the radiation belts  

SciTech Connect

We describe a mechanism of resonant electron acceleration by oblique high-amplitude whistler waves under conditions typical for the Earth radiation belts. We use statistics of spacecraft observations of whistlers in the Earth radiation belts to obtain the dependence of the angle {theta} between the wave-normal and the background magnetic field on magnetic latitude {lambda}. According to this statistics, the angle {theta} already approaches the resonance cone at {lambda}{approx}15 Degree-Sign and remains close to it up to {lambda}{approx}30 Degree-Sign -40 Degree-Sign on the dayside. The parallel component of the electrostatic field of whistler waves often increases around {lambda}{approx}15 Degree-Sign up to one hundred of mV/m. We show that due to this increase of the electric field, the whistler waves can trap electrons into the potential well via wave particle resonant interaction corresponding to Landau resonance. Trapped electrons then move with the wave to higher latitudes where they escape from the resonance. Strong acceleration is favored by adiabatic invariance along the increasing magnetic field, which continuously transfers the parallel energy gained to perpendicular energy, allowing resonance to be reached and maintained. The concomitant increase of the wave phase velocity allows for even stronger relative acceleration at low energy <50keV. Each trapping-escape event of electrons of {approx}10keV to 100 keV results in an energy gain of up to 100 keV in the inhomogeneous magnetic field of the Earth dipole. For electrons with initial energy below 100 keV, such rapid acceleration should hasten their drop into the loss-cone and their precipitation into the atmosphere. We discuss the role of the considered mechanism in the eventual formation of a trapped distribution of relativistic electrons for initial energies larger than 100 keV and in microbursts precipitations of lower energy particles.

Artemyev, A. V.; Krasnoselskikh, V. V.; Agapitov, O. V. [LPC2E/CNRS, University of Orleans, Orleans (France); Mourenas, D. [CEA, DAM, DIF, F-91297 Arpajon (France); Rolland, G. [CNES, Toulouse (France)

2012-12-15

250

Dependence of diffusive radiative transfer on grain-size, temperature, and Fe-content: Implications for mantle processes  

NASA Astrophysics Data System (ADS)

Locally diffusive, radiative heat transport inside the earth is represented by an effective thermal conductivity ( krad,dif), calculated from spectra. Previous geophysical models assumed that emissivity ( ?) equals unity, which violates local radiative equilibrium in an internally heated, grainy medium. Our new formulation accounts for ? depending on frequency, physical scattering depending on grain-size ( d), and for light lost through back-reflections at interfaces. Mantle values of krad,dif are estimated from recent visible spectra of olivine combined with new IR data. The following trends hold for krad,dif calculated from olivine spectra, and should be equally valid for pyroxene and spinel: (1) pressure is unimportant, (2) radiative thermal conductivity depends non-linearly on d, temperature ( T), and Fe 2+ content ( X), (3) maxima occur in krad,dif( d) when the grains are large enough to emit substantially, but not so large that light is strongly attenuated within a single-grain, (4) the dependence of krad,dif on Fe 2+ content parallels that with d because absorption is controlled by the product dX (Beer's law), and (5) a local minimum occurs in krad,dif near 2000 K for d > 2 mm because at that temperature the peak position of the blackbody curve coincides with that of the strongly absorbing Fe 2+ peak in the visible. Larger krad,dif exists at lower and higher temperatures because mean free paths are long in the transmitting near-IR and UV spectral regions. As integration smooths over spectral details, the above representation based on olivine becomes increasingly accurate for other phases as grain-size decreases. For conditions expected in the transition zone, ? krad,dif/? T is negative, which is destabilizing [Dubuffet, F., Yuen, D.A., Rainey, E.S.G., 2002. Controlling thermal chaos in the mantle by positive feedback from radiative thermal conductivity. Nonlinear Proc. Geophys. 9, 1-13]. In the lower mantle, photon transport dominates phonon, promoting stable, weak convection. That radiative transfer is linked to chemical composition and grain-size suggests that this process impacts planetary evolution through the non-linear feedback with rheology.

Hofmeister, A. M.

2005-08-01

251

Radiation dosimeters  

DOEpatents

Radiation dosimeters and dosimeter badges. The dosimeter badges include first and second parts which are connected to join using a securement to produce a sealed area in which at least one dosimeter is held and protected. The badge parts are separated to expose the dosimeters to a stimulating laser beam used to read dose exposure information therefrom. The badge is constructed to allow automated disassembly and reassembly in a uniquely fitting relationship. An electronic memory is included to provide calibration and identification information used during reading of the dosimeter. Dosimeter mounts which reduce thermal heating requirements are shown. Dosimeter constructions and production methods using thin substrates and phosphor binder-layers applied thereto are also taught.

Hoelsher, James W. (Pullman, WA); Hegland, Joel E. (Pullman, WA); Braunlich, Peter F. (Pullman, WA); Tetzlaff, Wolfgang (Pullman, WA)

1992-01-01

252

A method for determining the diffusion coefficient in Fe(II/III) radiation dosimetry gels using finite elements  

NASA Astrophysics Data System (ADS)

Magnetic resonance imaging (MRI) may be used to image three-dimensional dose distributions of ionizing radiation in tissue equivalent gels infused with ferrous sulphate solutions, commonly known as Fricke gels. In this technique, ferrous ions are oxidized to ferric ions by free radicals produced by ionizing radiation. A limitation on this technique is the diffussion of ferric ions in the gel. A method is presented for evaluating the diffusion coefficient in Fricke gels. Finite elements are used to model variations of the concentration in space, coupled with an analytical scheme to integrate the resulting system of equations through time. This method may be used for problems with one, two or three space dimensions and with arbitrary initial and boundary conditions. Results are presented for one- and two-dimensional data.

Harris, P. J.; Piercy, A.; Baldock, C.

1996-09-01

253

Radiation induces diffusible feeder cell factor(s) that cooperate with ROCK inhibitor to conditionally reprogram and immortalize epithelial cells.  

PubMed

Both feeder cells and Rho kinase inhibition are required for the conditional reprogramming and immortalization of human epithelial cells. In the present study, we demonstrated that the Rho kinase inhibitor Y-27632, significantly suppresses keratinocyte differentiation and extends life span in serum-containing medium but does not lead to immortalization in the absence of feeder cells. Using Transwell culture plates, we further demonstrated that physical contact between the feeder cells and keratinocytes is not required for inducing immortalization and, more importantly, that irradiation of the feeder cells is required for this induction. Consistent with these experiments, conditioned medium was shown to induce and maintain conditionally immortalized cells, which was accompanied by increased telomerase expression. The activity of conditioned medium directly correlated with radiation-induced apoptosis of the feeder cells. Thus, the induction of conditionally reprogrammed cells is mediated by a combination of Y-27632 and a diffusible factor (or factors) released by apoptotic feeder cells. PMID:24096078

Palechor-Ceron, Nancy; Suprynowicz, Frank A; Upadhyay, Geeta; Dakic, Aleksandra; Minas, Tsion; Simic, Vera; Johnson, Michael; Albanese, Christopher; Schlegel, Richard; Liu, Xuefeng

2013-12-01

254

A Search for Radiative Neutrino Decay and its Potential Contribution to the Cosmic Diffuse Gamma-Ray Flux.  

NASA Astrophysics Data System (ADS)

We have performed a sensitive search for a massive neutrino species. The premise of the search is the existence of an unstable massive neutrino that decays radiatively. Because of its electromagnetic daughter product, a radiative decay may be the only mode that can be observed directly. Using core collapse supernovae--known to be copious producers of neutrinos--as a cosmic neutrino laboratory, a detailed model has been developed to predict the decay-produced photon energy spectrum as a function of neutrino mass mnu and lifetime taunu. Using the COMPTEL instrument aboard the Compton Gamma-Ray Observatory, observations of two recent nearby type-II supernovae (SN1987A, SN1993J) were made to search for the characteristic photon emission in the MeV energy range. This search was sensitive to neutrino masses mnu > 100 eV, lifetimes ~10^5 <= taunu <= 1015 seconds, and radiative branching ratios B_ ? >= 10^ {-5}. We have found no evidence for a radiative decay mode and thus exclude a new region of mnu/tau nu/B_?-parameter space. In the context of the neutrino decay hypothesis, the gamma -ray observation of SN1987A made with the Gamma -Ray Spectrometer aboard the Solar Maximum Mission satellite has been re-analyzed. A complimentary analysis was made to determine the potential contribution an isotropic sea of radiatively decaying neutrinos might make to the cosmic diffuse gamma-ray flux, specifically to the so-called MeV-bump. Two possible sources were considered here: the sea of neutrinos produced by the continuous generation of supernovae in the Universe, and the flux of relic neutrinos created in the Big Bang. A predictive model was developed for both cases. In the supernova scenario, the neutrino decay emission was parameterized as a function of supernova rate and the epoch of galaxy formation; while in the case of relic neutrinos the photon flux was parameterized as a function of the relic neutrino abundance. Cosmological factors were included in both models. The predicted emission (spectral shape and flux level) from neutrino decay was compared to the measurements of the cosmic flux of gamma-rays, for a wide range of neutrino mass and lifetime. The spectra from both the supernova and relic scenarios were inconsistent with the cosmic diffuse measurements in the range 0.1 to 30 MeV, leading to a conservative limit Bgamma <= 10^{-1}.. The predicted emission from relic neutrino decay was found to be consistent with the feature known as the MeV-bump--for a narrow range of m_? and tau_?. This range of parameter values, however, is excluded by mass density arguments and the assumption of an Omega = 1 Universe. This work represents a systematic search for massive neutrinos using an astrophysical source other than our Sun. Although negative results are obtained from this search, the observational results are used to constrain fundamental particle, astrophysical, and cosmological phenomena.

Miller, Richard Scott

1995-01-01

255

Dosimetry of space radiations  

NASA Technical Reports Server (NTRS)

Harmful effects of space radiation are discussed. Radiation dosimetry methods are given. Dosimetry monitoring is investigated. Methods for measuring space radiation by ionization, thermoluminescence, and nuclear photographic emulsions are described.

Arkhangelskiy, V. V.; Markelov, V. V.; Skvortsov, S. S.; Smirennyy, L. N.; Turkin, V. N.; Chernykh, I. V.

1973-01-01

256

Radiation Therapy for Cancer  

MedlinePLUS

... basic unit of light and other forms of electromagnetic radiation . It can be thought of as a ... radiation therapy in fewer sessions, using smaller radiation fields and higher doses than 3D-CRT in most ...

257

Radiation from Relativistic Jets  

NASA Technical Reports Server (NTRS)

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.

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

258

Spectroscopy of diffuse light in dust clouds. Scattered light and the solar neighbourhood radiation field  

NASA Astrophysics Data System (ADS)

Context. The optical surface brightness of dark nebulae is mainly due to scattering of integrated starlight by classical dust grains. It contains information on the impinging interstellar radiation field, cloud structure, and grain scattering properties. We have obtained spectra of the scattered light from 3500 to 9000 Å in two globules, the Thumbprint Nebula and DC 303.8-14.2. Aims. We use observations of the scattered light to study the impinging integrated starlight spectrum as well as the scattered H? and other line emissions from all over the sky. We search also for the presence of other than scattered light in the two globules. Methods. We obtained long-slit spectra encompassing the whole globule plus adjacent sky in a one-slit setting, thus enabling efficient elimination of airglow and other foreground sky components. We calculated synthetic integrated starlight spectra for the solar neighbourhood using HIPPARCOS-based stellar distributions and the spectral library of Pickles. Results. Spectra are presented separately for the bright rims and dark cores of the globules. The continuum spectral energy distributions and absorption line spectra can be well modelled with the synthetic integrated starlight spectra. Emission lines of H? +[N II], H?, and [S II] are detected and are interpreted in terms of scattered light plus an in situ warm ionized medium component behind the globules. We detected an excess of emission over the wavelength range 5200-8000 Å in DC 303.8-14.2 but the nature of this emission remains open. Based on observations collected at the European Southern Observatory, Chile, under programme ESO No. 073.C-0239(A). Appendix A is available in electronic form at http://www.aanda.org.

Lehtinen, K.; Mattila, K.

2013-01-01

259

Investigation of radiation enhanced diffusion of magnesium in substrates flown on the NASA genesis mission.  

SciTech Connect

The thermal diffusion of an Mg implant in Si has been measured with SIMS and compared to RIMS (resonant ionisation mass spectrometry) measurements of Mg implantation and diffusion in Si wafers exposed to solar wind irradiation in the NASA Genesis mission. The Genesis samples show much more surface segregation that the samples annealed in the laboratory, due to diffusion and segregation of the implanted Mg to the heavily damaged near surface regions of the Genesis wafers. This Mg transport has been modeled by solving a set of stiff differential equations and found to agree with RIMS measurements for a Mg interstitial migration energy of 0.7 eV.

King, B. V.; Pellin, M. J.; Burnett, D. S. (Materials Science Division); (Univ. of Newcastle); (California Inst. of Tech.)

2008-12-01

260

Solar radiation resource assessment  

SciTech Connect

The bulletin discusses the following: introduction; Why is solar radiation resource assessment important Understanding the basics; the solar radiation resource assessment project; and future activities.

Not Available

1990-11-01

261

Influence of clouds and diffuse radiation on ecosystem-atmosphere CO2 and CO18O exchanges  

NASA Astrophysics Data System (ADS)

This study evaluates the potential impact of clouds on ecosystem CO2 and CO2 isotope fluxes ("isofluxes") in two contrasting ecosystems (a broadleaf deciduous forest and a C4 grassland) in a region for which cloud cover, meteorological, and isotope data are available for driving the isotope-enabled land surface model (ISOLSM). Our model results indicate a large impact of clouds on ecosystem CO2 fluxes and isofluxes. Despite lower irradiance on partly cloudy and cloudy days, predicted forest canopy photosynthesis was substantially higher than on clear, sunny days, and the highest carbon uptake was achieved on the cloudiest day. This effect was driven by a large increase in light-limited shade leaf photosynthesis following an increase in the diffuse fraction of irradiance. Photosynthetic isofluxes, by contrast, were largest on partly cloudy days, as leaf water isotopic composition was only slightly depleted and photosynthesis was enhanced, as compared to adjacent clear-sky days. On the cloudiest day, the forest exhibited intermediate isofluxes: although photosynthesis was highest on this day, leaf-to-atmosphere isofluxes were reduced from a feedback of transpiration on canopy relative humidity and leaf water. Photosynthesis and isofluxes were both reduced in the C4 grass canopy with increasing cloud cover and diffuse fraction as a result of near-constant light limitation of photosynthesis. These results suggest that some of the unexplained variation in global mean ?18O of CO2 may be driven by large-scale changes in clouds and aerosols and their impacts on diffuse radiation, photosynthesis, and relative humidity.

Still, C. J.; Riley, W. J.; Biraud, S. C.; Noone, D. C.; Buenning, N. H.; Randerson, J. T.; Torn, M. S.; Welker, J.; White, J. W. C.; Vachon, R.; Farquhar, G. D.; Berry, J. A.

2009-03-01

262

Simulation of Infrared Laser Heating of Silica Using Heat Conduction and Multifrequency Radiation Diffusion Equations Adapted for Homogeneous Refractive Lossy Media  

SciTech Connect

Localized, transient heating of materials using micro-scale, highly absorbing laser light has been used in many industries to anneal, melt and ablate material with high precision. Accurate modeling of the relative contributions of conductive, convective and radiative losses as a function of laser parameters is essential to optimizing micro-scale laser processing of materials. In bulk semi-transparent materials such as silicate glass melts, radiation transport is known to play a significantly larger role as the temperature increases. Conventionally, radiation is treated in the frequency-averaged diffusive limit (Rosseland approximation). However, the role and proper treatment of radiative processes under rapidly heated, high thermal gradient conditions, often created through laser-matter interactions, is at present not clear. Starting from the radiation transport equation for homogeneous, refractive lossy media, they derive the corresponding time-dependent multi-frequency diffusion equations. Zeroth and first moments of the transport equation couple the energy density, flux and pressure tensor. The system is closed by neglecting the temporal derivative of the flux and replacing the pressure tensor by its diagonal analogue. The radiation equations are coupled to a diffusion equation for the matter temperature. They are interested in modeling infrared laser heating of silica over sub-millimeter length scales, and at possibly rapid rates. Hence, in contrast to related work, they retain the temporal derivative of the radiation field. They derive boundary conditions at a planar air-silica interface taking account of reflectivities obtained from the Fresnel relations that include absorption. The effect of a temperature-dependent absorption index is explored through construction of a multi-phonon dielectric function that includes mode dispersion. The spectral dimension is discretized into a finite number of intervals yielding a system of multigroup diffusion equations. Simulations are presented. To demonstrate the bulk heat loss due to radiation and the effect of the radiation's temporal derivative, they model cooling of a silica slab, initially at 2500 K, for 10 s. Retaining the derivative enables correctly modeling the loss of photons initially present in the slab. Other simulations model irradiating silica discs (of approximately 5 mm radii and thickness) with a CO2 laser: {lambda} = 10.59 and 4.6 um, Gaussian profile, r{sub 0} = 0.5 mm for 1/e decay. By surrounding the disks in room-temperature air, they make use of the boundary conditions described above.

Shestakov, A I; Matthews, M J; Vignes, R M; Stolken, J S

2010-10-28

263

Radiative transfer via spherical harmonics  

Microsoft Academic Search

It is shown that several approximate treatments of radiative transfer (classic diffusion; diffusion with temperature jump boundary conditions; differential approximation) have a common origin in the spherical harmonic expansion of the equation of transfer. Comparisons with exact results, computed numerically with a discrete ordinates computer code (ANISN), are made for several problems, with and without heat sources, for the standard

G. C. Pomraning

1979-01-01

264

Monolithic, radiation hard charge sensitive preamplifier using diffused N-channel junction field effect transistors  

Microsoft Academic Search

A monolithic preamplifier entirely based on epitaxial channel, diffused-gate N-JFET has been designed and thoroughly investigated by means of SPICE simulation and breadboard implementation. Performance, tolerances, and matching of the devices are remarkably good, and the excess noise can be reduced in future runs. A preamplifier has been wired using monolithic JFET and is working according to predictions. The preamplifier

V. Radeka; S. Rescia; P. F. Manfredi; V. Speziali

1991-01-01

265

The radiation stimulated diffusion role in high dose, low energy, high temperature ion implantation  

Microsoft Academic Search

A low energy, high dose and temperature ion implantation modeling method is presented. The diffusion equations for impurity and non-equilibrium vacancies are solved taking into account the source functions for impurity atoms and vacancies and the recession of surface due to sputtering. The source functions as well as the sputtering yields acid the surface moving velocity are determined from atom

F. G. Jurabekova; S. A. Lem; T. S. Pugacheva; S. H. Valiev; Y. Miyagawa

1997-01-01

266

The radiation stimulated diffusion role in high dose, low energy, high temperature ion implantation  

Microsoft Academic Search

A low energy, high dose and temperature ion implantation modeling method is presented. The diffusion equations for impurity and non-equilibrium vacancies are solved taking into account the source functions for impurity atoms and vacancies and the recession of surface due to sputtering. The source functions as well as the sputtering yields and the surface moving velocity are determined from atom

S. H. Valiev; T. S. Pugacheva; F. G. Jurabekova; S. A. Lem; Y. Miyagawa

1997-01-01

267

The statistical characteristics of diffuse multipath radiation and its effect on antenna performance  

Microsoft Academic Search

Diffuse multipath is a random phenomenon that arises out of the diffraction of waves from rough surfaces. This form of multipath can, in turn, affect the angle estimation performance of monopulse antenna systems. In order to evaluate its effect, it is necessary to obtain the channel spread function that results. This function is basically the wave number spectrum of the

T. P. McGarty

1975-01-01

268

Statistical Characteristics of Diffuse Multipath Radiation and Its Effect on Antenna Performance.  

National Technical Information Service (NTIS)

Diffuse multipath is a random phenomenon that arises out of the diffraction of waves from rough surfaces. This form of multipath can, in turn, affect the angle estimation performance of monopulse antenna systems. In order to evaluate its effect, it is nec...

T. P. McGarty

1975-01-01

269

Latitude Variation of the Diffuse Component of the Mean Energy gamma Radiation.  

National Technical Information Service (NTIS)

For determining the diffuse component of gamma ray in the 15 to 75 MeV range arriving from near the galactic center, a digitized spark chamber was launched aboard two balloons from Resende, Brazil on 19 November and 3 December 1975. In each flight the det...

C. M. Espirito Santo

1981-01-01

270

C II Radiative Cooling of the Diffuse Gas in the Milky Way  

NASA Astrophysics Data System (ADS)

The heating and cooling of the interstellar medium (ISM) allow the gas in the ISM to coexist at very different temperatures in thermal pressure equilibrium. The rate at which the gas cools or heats is therefore a fundamental ingredient for any theory of the ISM. The heating cannot be directly determined, but the cooling can be inferred from observations of .CII*, which is an important coolant in different environments. The amount of cooling can be measured through either the intensity of the 157.7 ?m [C II] emission line or the CII* absorption lines at 1037.018 and 1335.708 Å, observable with the Far Ultraviolet Spectroscopic Explorer and the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope, respectively. We present the results of a survey of these far-UV absorption lines in 43 objects situated at |b|>~30deg. Measured column densities of CII*, S II, P II, and Fe II are combined with H I 21 cm emission measurements to derive the cooling rates (per H atom using H I and per nucleon using S II) and to analyze the ionization structure, depletion, and metallicity content of the low-, intermediate-, and high-velocity clouds (LVCs, IVCs, and HVCs) along the different sight lines. Based on the depletion and the ionization structure, the LVCs, IVCs, and HVCs consist mostly of warm neutral and ionized clouds. For the LVCs, the mean cooling rate in ergs s-1 per H atom is -25.70+0.19-0.36 dex (1 ? dispersion). With a smaller sample and a bias toward high H I column density, the cooling rate per nucleon is similar. The corresponding total Galactic C II luminosity in the 157.7 ?m emission line is L~2.6×107 Lsolar. Combining N(CII*) with the intensity of H? emission, we derive that ~50% of the CII* radiative cooling comes from the warm ionized medium (WIM). The large dispersion in the cooling rates is certainly due to a combination of differences in the ionization fraction, in the dust-to-gas fraction, and physical conditions between sight lines. For the IVC Intermediate-Velocity (IV) Arch at z~1 kpc we find that on average the cooling is a factor of 2 lower than in the LVCs that probe gas at lower z. For an HVC (complex C, at z>6 kpc) we find the much lower rate of -26.99+0.21-0.53 dex, similar to the rates observed in a sample of damped Ly? absorber systems (DLAs). The fact that in the Milky Way a substantial fraction of the C II cooling comes from the WIM implies that this is probably also true in the DLAs. We also derive the electron density, assuming a typical temperature of the warm gas of 6000 K: for the LVCs, =0.08+/-0.04 cm-3, and for the IV Arch, =0.03+/-0.01 cm-3 (1 ? dispersion). Finally, we measured the column densities N(S II) and N(P II) in many sight lines and confirm that sulphur appears undepleted in the ISM. Phosphorus becomes progressively more deficient when logN(HI)>19.7 dex, which can mean that either P becomes more depleted into dust as more neutral gas is present or P is always depleted by about -0.3 dex, but the higher value of P II at lower H I column density indicates the need for an ionization correction.

Lehner, N.; Wakker, B. P.; Savage, B. D.

2004-11-01

271

Solar radiation modelling  

NASA Astrophysics Data System (ADS)

The Sun is the main energy source of the life on the Earth. Thus, solar radiation energy data and models are important for many areas of research and applications. Many parameters influence the amount of solar energy at a particular standing point of the Earth's surface; therefore, many solar radiation models were produced in the last few years. Solar radiation energy depends mostly on incidence angle, which is defined by astronomical and surface parameters. Our solar radiation model is based on defining incidence angle by computing normal-to-the-surface tangent plane and direction of the Sun. If a part of the surface is in the shadow, it receives lesser energy than sunny areas. That is why shadow determination is an important part of the model. The sky is usually not completely clear, so meteorological parameters had to be integrated into the model. Meteorological model distinguishes among direct and diffuse Sun radiation. The model was tested and implemented for the whole Slovenia and it was also compared with previous studies. Case study surface data were calculated from the DEM with a 25 m resolution. The astronomical data, which were required for virtual Sun motion simulation around the Earth, were derived from the astronomical almanac. Meteorological data were acquired from observed mean values on 24 meteorological stations between 1961 and 1990. All calculations were made for hours and decades and finally, the annual quasiglobal radiation energy, which is the energy received by inclined plane from the Sun in one year, was calculated from the sum of all the energies of all the decades.

Zakšek, Klemen; Podobnikar, Tomaž; Oštir, Krištof

2005-03-01

272

SAS-2 observations of the diffuse gamma radiation in the galactic latitude interval from 10 to 90 deg in both hemispheres  

NASA Technical Reports Server (NTRS)

An analysis of all the second Small Astronomy Satellite (SAS-2) gamma-ray data for galactic latitudes higher than 10 deg in both hemispheres has shown that the intensity varies with galactic latitude, being larger near 10 deg than 90 deg. For energies above 100 MeV the gamma-ray data are consistent with a latitude distribution of the form I(b) = C1 + C2/sin b, with the second term being dominant. This result suggests that the radiation above 100 MeV is coming largely from local regions of the galactic disk. Between 35 and 100 MeV, a similar equation is also a good representation of the data, but here the two terms are comparable. These results indicate that the diffuse radiation above 35 MeV consists of two parts, one with a relatively hard galactic component and the other an isotropic steep spectral component which extrapolates back well to the low-energy (less than 10 MeV) diffuse radiation. The steepness of the diffuse isotropic component places significant constraints on possible theoretical models of this radiation.

Fichtel, C. E.; Hartman, R. C.; Kniffen, D. A.; Thompson, D. J.; Ogelman, H. B.; Ozel, M. E.; Tumer, T.

1977-01-01

273

Hazard calculations of diffuse reflected laser radiation for the SELENE program  

NASA Technical Reports Server (NTRS)

The hazards from diffuse laser light reflections off water clouds, ice clouds, and fog and from possible specular reflections off ice clouds were assessed with the American National Standards (ANSI Z136.1-1986) for the free-electron-laser parameters under consideration for the Segmented Efficient Laser Emission for Non-Nuclear Electricity (SELENE) Program. Diffuse laser reflection hazards exist for water cloud surfaces less than 722 m in altitude and ice cloud surfaces less than 850 m in altitude. Specular reflections from ice crystals in cirrus clouds are not probable; however, any specular reflection is a hazard to ground observers. The hazard to the laser operators and any ground observers during heavy fog conditions is of such significant magnitude that the laser should not be operated in fog.

Miner, Gilda A.; Babb, Phillip D.

1993-01-01

274

CO-HP2-N2/Air Diffusion Flames: Thermal Radiation and Transient Effects  

NASA Astrophysics Data System (ADS)

Flames of CO/H2/N2 fuels have been investigated for various reasons. For instance, laminar, premixed flames were investigated experimentally by van Tiggelen and coworkers to determine the rate constant of the water-gas shift reaction [12.1] and the inhibition induced by CF3BR [12.2], [12.3], and numerically by Rogg and Williams [12.4] who derived a reduced kinetic mechanism for wet CO flames. Laminar, non-premixed flames were studied, for instance, by Drake and Blint [12.5], who investigated experimentally and numerically the structure of counterflow diffusion flames in the Tsuji geometry paying special attention to NO x formation. For the latter geometry, Chen et al [12.6] derived a reduced kinetic mechanism which they used in the numerical simulation of turbulent diffusion flames. For further information on work relevant to flames of CO/H2/N2 fuels the cited papers should be consulted.

Chen, J.-Y.; Liu, Y.; Rogg, B.

275

Relationships between diffuse reflectance and vegetation canopy variables based on the radiative transfer theory  

NASA Technical Reports Server (NTRS)

Out of the lengthy original expression of the diffuse reflectance formula, simple working equations were derived by employing characteristic parameters, which are independent of the canopy coverage and identifiable by field observations. The typical asymptotic nature of reflectance data that is usually observed in biomass studies was clearly explained. The usefulness of the simplified equations was demonstrated by the exceptionally close fit of the theoretical curves to two separately acquired data sets for alfalfa and shortgrass prairie canopies.

Park, J. K.; Deering, D. W.

1981-01-01

276

Handbook of radiation effects  

Microsoft Academic Search

This book emphasizes radiation effects on solid state devices from exposure to the types of radiation found outside the atmosphere (in space, or in the vicinity of an exploding nuclear device). It contains a basic study of radiation shielding of payload components for payloads in space and specifically covers radiation effects on minority and majority carriers, optical media and organic

A. Holmes-Siedle; L. Adams

1993-01-01

277

Radiation nose concept  

Microsoft Academic Search

The feasibility of a radiation nose concept is demonstrated. In radiation nose system an array of sensors is used to monitor various ranges and types of radiation, therefore increasing the working dose range and the sensitivity of the overall system. Ideally, each material in sensor array should be sensitive to only one type of radiation, which can be achieved via

K. Arshak; O. Korostynska; C. Cunniffe

2006-01-01

278

Radiation Critical Readiness Review  

NASA Technical Reports Server (NTRS)

This slide presentation reviews the radiation preparedness and radiation monitors on the International Space Station (ISS). It includes information on the Tissue Equivalent Proportional Counter (TEPC), Radiation Area Monitors, Extra-Vehicular Charged Particle Directional Spectrometer (EV-CPDS), and the space radiation analysis group.

Misek, William

2010-01-01

279

Advanced radiator concepts  

NASA Technical Reports Server (NTRS)

The liquid droplet radiator and the liquid belt radiator currently under study by the NASA LeRC are discussed. These advanced concepts offer benefits in reduced mass, compact stowage, and ease of deployment. Operation and components of the radiators are described, heat transfer characteristics are discussed, and critical technologies are identified. The impact of the radiators on large power systems is also assessed.

Diem-Kirsop, P. S.

1985-01-01

280

Radiation and Gut  

Microsoft Academic Search

Two books with very similar titles have been published recently: Radiation and the Gastrointestinal Tract (edited by A Dubois et al) and Radiation and Gut. Despite their rather similar titles, their content is very different. The former is concerned with acute radiation effects and their avoidance or control in the context of radiation therapy and the possible irradiation of military

John D Harrison

1997-01-01

281

Radiation and People  

ERIC Educational Resources Information Center

Describes the development of radiation as a tool of medicine. Includes topics on history of radiation, electromagnetic spectrum, X-ray tubes, high energy machines, radioactive sources, artificial radioactivity, radioactive scanning, units, present radiation background, and effect of radiation on living tissue. (DS)

Freilich, Florence G.

1970-01-01

282

Radiation detection and measurement  

Microsoft Academic Search

Introductory material covers radiation sources, radiation interactions, general properties of radiation detectors, and counting statistics and error prediction. This is followed by detailed sections on gas-filled detectors, scintillation counters, semiconductor detectors, neutron detectors and spectroscopy, detector electronics and pulse processing, and miscellaneous radiation detectors and applications.

Glenn F. Knoll

1979-01-01

283

Radiation Effects on Free Convection Flow past an Impulsively Started Infinite Vertical Plate with Ramped Wall Temperature and Constant Mass Diffusion  

NASA Astrophysics Data System (ADS)

The interaction of free convection with thermal radiation of a viscous incompressible unsteady flow past an impulsively started infinite vertical plate in the presence of chemical species concentration and a temperature boundary condition which follows a ramp function up until some specified time and then remains constant is analyzed. The fluid is assumed to be gray, emitting-absorbing but no-scattering medium and the optically thick radiation limit is considered. The Cogley-Vincenti-Gilles formulation is adopted to simulate the radiation component of heat transfer. The dimensionless governing equations are solved using Laplace transform technique. The velocity, the temperature and the concentration profiles are shown on graphs for different gasses. The variation of skin-friction is also shown in a table. The effects of different parameters like Radiation parameter ( F ), thermal Grashof number ( Gr ), Prandtl number (Pr), Schmidt number (Sc), mass to thermal buoyancy ratio parameter ( N ) for the three cases N = 0 (the buoyancy force is due to thermal diffusion only), N>0 (the mass buoyancy force acts in the same direction of thermal buoyancy force) and N<0 (the mass buoyancy force acts in the opposite direction of thermal buoyancy force) and time ( t ) are discussed. The interaction of free convection with thermal radiation near a ramped temperature plate has also been compared with the flow near a plate with constant temperature. It is observed that the velocity increases with decreasing radiation parameter.

Narahari, M.; Bég, O. Anwar

2010-06-01

284

Difference Between IR Radiation Spectra of Ethanol in Free Diffusion Combustion Regime and Regime Influenced by an Air Flow in Modeling of a Fire Tornado  

NASA Astrophysics Data System (ADS)

Results of experimental investigations of liquid fuel combustion in the regime of a twisted jet (model of a fire tornado) are presented. Flame radiation spectra were registered. In the chosen spectral range of registration (2.2-4.8 ?m), six spectral intervals were clearly traced in which the main portion of radiated energy was concentrated. Using the ratio of the sums of spectral intensities in the vicinities of the 6th and 3rd maxima, we successfully distinguished the regimes of modeled fire tornado and free diffusion fuel combustion.

Sherstobitov, M. V.; Tsvyk, R. Sh.

2013-06-01

285

Operational radiation safety - training  

SciTech Connect

This report was written to supplement NCRP Report No. 59, Operational Radiation Safety Program, which sets forth the basic elements of a radiation safety program. Effective radiation safety programs should include training for workers exposed to either radioactive material or other radiation sources and this report seeks to provide guidance for the development of training in organizations with employees who are exposed to radiation in the course of their work. The guidance provided is intended to cover the basic elements of needed training and thus should be useful to the entire range of radiation users from small single source operations to relatively complex radiation operations.

Not Available

1983-01-01

286

Measurement of diffuse solar radiation on a horizontal surface at Ilorin (8°32'N, 4°46'E) Nigeria: Preliminary results  

NASA Astrophysics Data System (ADS)

Using an Eppley `Black and White' pyranometer fitted with a shadow band and a digital recorder/printer, hourly diffuse solar irradiance Hd falling on a horizontal surface at Ilorin, Nigeria has been measured from February to July 1993. The diffuse radiation data, after necessary correction for shadow band effect, were analyzed to obtain the diurnal and monthly variations of Hd. The highest daily total of diffuse radiation (Hdd) of value 4473+/-60 Wm-2 day-1 was recorded on the dust-haze day and the lowest of value 2194+/-29 Wm-2 day-1 on a mostly overcast day. Similarly, the highest monthly average of daily total of diffuse radiation Hdm, of value 3237+/-43 Wm-2 day-1 was observed in April and the least of value 2872+/-34 Wm-2 day-1 in February. Also obtained are the diurnal and monthly variations of hourly values of Hd/H, where H is the corresponding hourly global irradiance measured separately by another instrument at the same location and time as Hd.

Iziomon, Moses G.; Aro, Theophilus O.

1995-01-01

287

Radial diffusion in the Uranian radiation belts: inferences from satellite absorption loss models  

SciTech Connect

Phase space density profiles for protons and electrons with first invariants {mu}{le}100 MeV/G (integral invariants {ital K}=0.3 and 0.6 G{sup 1/2} {ital R}{sub {ital U}}) previously derived from measurements by the low energy charged particle (LECP) detector on Voyager 2 during the 1986 Uranus encounter are analyzed using solutions of the time-averaged radial diffusion equation in a dipolar magnetic field. These profiles are selected for their consistency with an absence of local sources of particles. A loss model consisting of absorption by the major inner satellites Miranda, Ariel, and Umbriel is assumed and the corresponding form of the time-averaged radial diffusion coefficient {ital D}({ital L}) (taken to be of the form {ital D}({ital L})={ital D}{sub 0}{ital L}{sup {ital n}}, where {ital n} is an integer) is determined by a minimum-variance fit to the phase space density profiles. Satellite macrosignatures present in the experimentally derived profiles are approximately reproduced in several cases lending credence to the loss model and indicating that magnetospheric distributed losses are not as rapid as satellite absorption near the minimum satellite {ital L} shells for these particles. The latter inference implies an upper limit of approximately 10 cm{sup {minus}3} for the neutral hydrogen number density near the orbit of Ariel, based on a comparison of charge exchange lifetimes with the calculated satellite absorption lifetimes. The preferred forms for {ital D}({ital L}) are characterized by a low-order {ital L} dependence ({similar to}{ital L}{sup 3}{minus}{ital L4}) and an amplitude ({ital D}{sub 0}{congruent}10{sup {minus}11}--10{sup {minus}10} {ital R}{sup 2}{sub {ital U}} {sup {minus}1}). The inferred {ital L} dependence is least consistent with terrestrial-type diffusion mechanisms including magnetic impulses and electrostatic field fluctuations of purely magnetospheric origin.

Hood, L.L. (Lunar and Planetary Laboratory, University of Arizona, Tucson (US))

1989-11-01

288

Measurements of the anisotropy of the cosmic background radiation and diffuse galactic emission at millimeter and submillimeter wavelengths  

NASA Technical Reports Server (NTRS)

The results of a balloon-borne observing program to measure the large angular scale brightness distribution of the 2.7 K cosmic background radiation (CBR) at millimeter and submillimeter wavelengths are reported. A new determination of the dipole anisotropy of the CBR is found with 3.40 + or - 0.42 mK toward alpha = 12.1 + or - 0.24 hr, delta = - 23 + or - 5 deg in a 1.2 to 8/cm band and 4.7 + or - 1.4 mK toward alpha = 9.9 + 1.7 or - 1.1 hr, delta = - 38 + or - 21 deg between 5 and 18/cm, where the amplitudes are listed as thermodynamic temperatures. New estimates of the absolute temperature in these two bands of 2.86 + or - 0.26 K and 3.01 + or - 0.31 are obtained under the assumption that the CBR has a Planck spectrum. The diffuse Galactic emission is fitted by a secant distribution in Galactic latitude, and the resulting Galactic pole antenna temperatures are given. Maps of sky brightness, measurements of zodiacal emission, and measurements of fluctuations of the atmospheric emission which dominates the noise budget are also presented.

Halpern, Mark; Benford, Richard; Meyer, Stephan; Muehlner, Dirk; Weiss, Rainer

1988-01-01

289

Chemical Reaction Effects on MHD Flow Past a Linearly Accelerated Vertical Plate with Variable Temperature and Mass Diffusion in the Presence of Thermal Radiation  

NASA Astrophysics Data System (ADS)

An exact solution of first order chemical reaction effects on a radiative flow past a linearly accelerated infinite isothermal vertical plate with variable mass diffusion, under the action of a transversely applied magnetic field has been presented. The plate temperature is raised linearly with time and the concentration level near the plate is also raised to C'w linearly with time. The dimensionless governing equations are tackled using the Laplace-transform technique. The velocity, temperature and concentration fields are studied for different physical parameters such as the magnetic field parameter, radiation parameter, chemical reaction parameter, thermal Grashof number, mass Grashof number, Schmidt number, Prandtl number and time. It is observed that velocity increases with decreasing magnetic field parameter or radiation parameter. But the trend is just reversed with respect to the chemical reaction parameter

Muthucumaraswamy, R.; Geetha, E.

2013-08-01

290

Radiation protection guidelines for radiation emergencies  

SciTech Connect

The system of dose limitation and present guidance for emergency workers and guidance for intervention on behalf of the public are discussed. There are three elements for the system of dose limitation: justification, optimization and dose limits. The first element is basically a political process in this country. Justification is based on a risk-benefit analysis, and justification of the use of radioactive materials or radiation is generally not within the authority of radiation protection managers. Radiation protection managers typically assess detriments or harm caused by radiation exposure and have very little expertise in assessing the benefits of a particular practice involving nuclear material.

Lessard, E.T.; Meinhold, C.B.

1986-01-01

291

A new radiation stable plastic scintillator  

Microsoft Academic Search

The influence of various components of a plastic scintillator (high concentrations of primary dopant, secondary fluor, diffusion enhancer and stabilizer) on its radiation hardness has been experimentally determined. The diffusion enhancing technique was shown to be the most powerful tool for improving radiation hardness. A new polystyrene scintillator that decreases its light output by only 4% after 2.8 Mrad irradiation

V. G. Senchishin; F. Markley; V. N. Lebedev; V. E. Kovtun; V. S. Koba; A. V. Kuznichenko; V. D. Tizkaja; J. A. Budagov; G. Bellettini; V. P. Seminozhenko; I. I. Zalubovsky; I. E. Chirikov-Zorin

1995-01-01

292

Modeling of explosion thermal radiation  

NASA Astrophysics Data System (ADS)

The hydrodynamic and radiation processes accompanying explosions of chemical explosives and fuel-air mixtures have been considered. Computer modeling of the radiation from a fire ball of explosion and a flame of diffusion combustion of a hydrocarbon fuel has been performed. The dependences of the heat flux density from the region occupied by explosion and combustion products on its temperature and geometric characteristics have been determined. Thermal load distributions on targets of different orientations in the vicinity of the energy release zone have been obtained. A comparison of the thermal parameters on radiation detectors with the criteria of thermal affection of people and ignition of combustible materials has been made.

Stepanov, K. L.; Stanchits, L. K.; Stankevich, Yu. A.

2011-01-01

293

Low Dose Radiation Research  

NSDL National Science Digital Library

The US Department of Energy's Low Dose Radiation Research Program supports research that investigates the health risks from exposure to radiation at low levels. This Web site provides an overview of radiation biology, up-to-date information and archived results from program-related research, and other resources for the benefit of researchers and the general public alike. Some research projects include comparing low dose radiation to endogenous oxidative damage, determining thresholds for radiation exposure, determining genetics factors that make some individuals more susceptible to radiation-induced damage, and more.

294

Plutonium radiation surrogate  

DOEpatents

A self-contained source of gamma-ray and neutron radiation suitable for use as a radiation surrogate for weapons-grade plutonium is described. The source generates a radiation spectrum similar to that of weapons-grade plutonium at 5% energy resolution between 59 and 2614 keV, but contains no special nuclear material and emits little .alpha.-particle radiation. The weapons-grade plutonium radiation surrogate also emits neutrons having fluxes commensurate with the gamma-radiation intensities employed.

Frank, Michael I. (Dublin, CA)

2010-02-02

295

Radiation potentials generated by space radiation  

NASA Astrophysics Data System (ADS)

The mechanism for generating electric potentials and currents in conductors of electronic equipment on board spacecraft subjected to space radiation is examined. Radiation potentials and currents are calculated for a system that consists of two insulated conductors. Using the simplest model we obtain results which can be expanded to a more complex geometry of conductors.

Lyubomudrov, A. A.

2013-12-01

296

What Is Radiation Shielding?  

NASA Video Gallery

Kerry Lee, NASA Orion radiation system manager, explains how radiation shielding is used to block harmful particles coming into the spacecraft without producing secondary particles that can cause e...

297

Radiation from hard objects  

SciTech Connect

The inference of the diameter of hard objects is insensitive to radiation efficiency. Deductions of radiation efficiency from observations are very sensitive - possibly overly so. Inferences of the initial velocity and trajectory vary similarly, and hence are comparably sensitive.

Canavan, G.H.

1997-02-01

298

Prostaglandins and Radiation Enteritis.  

National Technical Information Service (NTIS)

A series of experiments was done to test the proposition that radiation to the intestine induces prostaglandin production which turn enhances the radiation injury. The results did not support the hypothesis, in that, pharmacologic blockade of prostaglandi...

J. P. Delaney

1987-01-01

299

Solar Radiation on Mars.  

National Technical Information Service (NTIS)

Detailed information on solar radiation characteristics on Mars are necessary for effective design of future planned solar energy systems operating on the surface of Mars. Presented here is a procedure and solar radiation related data from which the diurn...

J. Appelbaum D. J. Flood

1989-01-01

300

Radiation effects in space  

SciTech Connect

The paper discusses the radiation environment in space that astronauts are likely to be exposed to. Emphasis is on proton and HZE particle effects. Recommendations for radiation protection guidelines are presented. (ACR)

Fry, R.J.M.

1986-01-01

301

Radiation Protection Handbook  

NASA Technical Reports Server (NTRS)

A handbook which sets forth the Kennedy Space Center radiation protection policy is presented. The book also covers administrative direction and guidance on organizational and procedural requirements of the program. Only ionizing radiation is covered.

1972-01-01

302

Fluorescent radiation converter  

NASA Technical Reports Server (NTRS)

A fluorescence radiation converter is described which includes a substantially undoped optically transparent substrate and a waveshifter coating deposited on at least one portion of the substrate for absorption of radiation and conversion of fluorescent radiation. The coating is formed to substantially 1000 g/liter of a solvent, 70 to 200 g/liter of an organic polymer, and 0.2 to 25 g/liter of at least one organic fluorescent dye. The incoming incident radiation impinges on the coating. Radiation is absorbed by the fluorescent dye and is re-emitted as a longer wavelength radiation. Radiation is trapped within the substrate and is totally internally reflected by the boundary surface. Emitted radiation leaves the substrate ends to be detected.

Viehmann, W. (inventor)

1981-01-01

303

Prostate radiation - discharge  

MedlinePLUS

... these side effects: Skin problems during or after prostate radiation treatment is rare. Your skin over the ... keeping or getting an erection may occur after prostate radiation therapy but may not be noticed for ...

304

Acute Radiation Syndrome  

MedlinePLUS

... bromide Methyl isocyanate Nicotine Nitrogen mustard Opioids Organic solvents Osmium tetroxide Paraquat Phosgene Phosgene oxime Phosphine Phosphorus ... Radiation Disasters Public Health Planning for Radiological and Nuclear Terrorism Radiation Basics Made Simple Radiological Terrorism: Just ...

305

Synchrotron-radiation research  

SciTech Connect

The use of radiation from synchrotron sources has started a renaissance in materials, physics, chemistry, and biology. Synchrotron radiation has advantages over conventional x rays in that its source brightness is a thousand times greater throughout a continuous energy spectrum, and resonances are produced with specific electron energy levels. Two major synchrotron radiation sources are operated by DOE: the Stanford Synchrotron Radiation Laboratory at SLAC, and the National Synchrotron Light Source at Brookhaven. (DLC)

Cunningham, J.E.

1982-01-01

306

[Radiation induced side effects].  

PubMed

More than half of all people with cancer are treated with radiation therapy. Over the last decade the technical advances, both in therapy beam precision and imaging, have greatly improved the therapeutic ratio and accuracy of modern radiotherapy. However, damaging healthy tissues near the tumor leads to radiation induced injury that develops immediately and continue to progress long after exposure to radiation. Recently dramatic advances have been made in understanding the determinant of tissue response to radiation exposure. PMID:22641879

Henni, Mehdi; Ali, David

2012-04-01

307

Maintaining radiation protection records  

SciTech Connect

This Report is part of a series prepared under the auspices of Scientific Committee 46 on Operational Radiation Safety. It provides guidance on maintaining radiation protection records. Record keeping is an essential element of every radiation protection program. This Report describes the elements that should enter into the design of a program for the maintenance of operational radiation safety records. The problems of the length of time for retention of records for operational, regulatory, epidemiologic and legal uses are discussed in detail.

Not Available

1992-11-30

308

Operational radiation safety program  

SciTech Connect

For many years the National Council on Radiation Protection and Measurements and its predecessors have provided extensive recommendations dealing with the many aspects of radiation protection. The objective of this report is to describe the elements of an operational radiation safety program incorporating many of these recommendations. An effective radiation safety program can do much to reduce exposures to a level as low as practicable within the NCRP recommended dose limits and to minimize the potential for accidental exposures.

Not Available

1980-01-01

309

Dangers of Radiation Exposure  

NSDL National Science Digital Library

This is a lesson about radiation and the various sources of radiation that a spacecraft may encounter in its journey. Learners will calculate their annual exposure to high-energy radiation, identify sources of high-energy radiation, and explain why the near-Mercury environment is a concern for the Mercury MESSENGER mission. This is lesson 2 of 4 in the high school track of a module, titled Staying Cool. Note: the student guide starts on p. 17 of the PDF.

310

The Cosmological Background Radiation  

Microsoft Academic Search

This book provides an introduction to the physics, astrophysics and cosmology of the cosmic microwave background radiation. Adopting the Standard Big Bang model of the universe, the authors cover topics including the origin of the background, intrinsic fluctuations, and the universe and background radiation after recombination. Finally they present measurement of the radiation and its anisotropies, along with a review

Marc Lachièze-Rey; Edgard Gunzig

1999-01-01

311

MICROSPHERES FOR RADIATION THERAPY  

Microsoft Academic Search

The treatment of malignant tumors with ionizing radiation using ceramic ; microspheres that can be localized at selected sites for interstitial therapy is ; discussed. Thus, radiation damage in healthy tissues can be minimized by ; tailoring radioactivity to control dose, dose rate, and volume of tissue ; irradiated. The mean life, radiation energies, and beta-gamma dose can be ;

J. F. Perry; M. K. Loken; J. P. Ryan; L. D. MacLean

1962-01-01

312

Radiation Research Program (RRP)  

Cancer.gov

The RRP is responsible for NCI's clinically-related extramural radiation research program. The RRP establishes priorities, allocates resources, and evaluates the effectiveness of such radiation research being conducted by NCI grantees. RRP staff represent the program at NCI management and scientific meetings and provide scientific support to leadership on matters related to radiation research.

313

Geostationary earth radiation budget  

Microsoft Academic Search

The Earth Radiation Budget (ERB), the balance between the incoming solar radiation from the sun and the outgoing reflected and scattered solar radiation and the thermal infrared emission from the Earth, provides information on the fundamental energy source of the climate system. To fulfil global coverage and sampling requirements, the ERB measurements have to be made from space. Broad-band measurements

Ruzbeh Mossavati; Steve Kellock; Johannes Mueller; J. E. Harries; J. E. Murray; Eric C. Sawyer; Martin E. Caldwell; M. Oliver; J. Delderfield; Michael C. Sandford

1997-01-01

314

Radiation port dermatophytosis  

SciTech Connect

We report two cases in which dermatophytic infection developed almost entirely within a radiation field mimicking an acute radiation effect. Radiotherapists and dermatologists should be aware of this possibility and be able to differentiate it from radiation dermatitis. Topical antifungal agents are the recommended treatment after diagnosis is established.

Rosen, T.; Dupuy, J.; Maor, M.; Altman, A.

1988-12-01

315

Space Radiation Environment  

NASA Technical Reports Server (NTRS)

Coupled with the increasing concern over trapped radiation effects on microelectronics, the availability of new data, long term changes in the Earth's magentic field, and observed variations in the trapped radiation fluxes have generated the need for better, more comprehensive tools for modeling and predicting the Earth's trapped radiation environment and its effects on space systems.

Garrett, H.

1998-01-01

316

Solar radiation modelling  

Microsoft Academic Search

The Sun is the main energy source of the life on the Earth. Thus, solar radiation energy data and models are important for many areas of research and applications. Many parameters influence the amount of solar energy at a particular standing point of the Earth's surface; therefore, many solar radiation models were produced in the last few years. Solar radiation

Klemen Zaksek; Tomaz Podobnikar; Krištof Oštir

2005-01-01

317

JPL Radiation Effects Facilities  

NASA Technical Reports Server (NTRS)

Radiation Effects Group investigates the effects of space radiation on present and future microelectronic and optoelectronic technologies, evaluate the risk of using them in specific space missions, and recommend component and design techniques for JPL and NASA programs to reduce reliability risk from space radiation.

Thorbourn, Dennis

2013-01-01

318

Data assimilation of radiation belt electrons  

Microsoft Academic Search

We present results from a data-assimilation of radiation belt electrons and investigate the effect of the radial diffusion and the amplitude of the plasmashpheric hiss. In the data-assimilation, we use our 1-D radial diffusion model [Miyoshi et al., 2003, JGR] which includes various physical processes of the radiation belts such as radial diffusion, Coulomb collisions, and wave-particle interactions. We assimilate

Y. Miyoshi; G. Ueno; V. Jordanova; G. Reeves; T. Goka

2006-01-01

319

Stimulated diffuse-band radiation generated by hybrid and two-photon pumping in K2-K system  

Microsoft Academic Search

By hybrid and two-photon pumping covering a wide wavelength region of 685.0 - 718.0 nm in a K2-K system, yellow stimulated defuse-band radiation corresponding to the transition 2 3$PRDg yields a 3(summation)u+ of molecular potassium was generated. The excitation and collision energy-transfer mechanisms are discussed.

H. Y. Jin; Lijuan Qin; Shilan Deng; Y. F. Li; Zugeng Wang

1992-01-01

320

Radiation: Facts, Risks and Realities  

MedlinePLUS

... to natural radiation comes from other elements in Earth’s crust, such as thorium and potassium. The radiation ... area. Another natural source is cosmic (space) radiation. Earth is constantly exposed to radiation created by processes ...

321

Radiation Research: Chemistry and Physics.  

National Technical Information Service (NTIS)

Papers in this Proceedings are grouped under the following headings: (1) primary processes in radiation physics and chemistry; (2) radiation chemistry - general chemistry; (3) radiation chemistry - DNA and model systems; (4) radiation chemistry - other mo...

J. J. Broerse G. W. Barendsen H. B. Kal A. J. van der Kogel

1983-01-01

322

Radiation Therapy for Bone Cancer  

MedlinePLUS

... bone cancer Next Topic Chemotherapy for bone cancer Radiation therapy for bone cancer Radiation therapy uses high- ... control symptoms like pain and swelling. Intensity-modulated radiation therapy Intensity-modulated radiation therapy (IMRT) is an ...

323

Solar radiation in Iceland  

NASA Astrophysics Data System (ADS)

Short wave radiation has been observed at several locations in Iceland in recent years. The observations reveal that there is large spatial variability in the incoming radiation. There are indications of a coast-to-inland gradient and there is much greater radiation at central-inland locations than further west as well in the far east. The results are in line with Markús Á. Einarsson's reports where estimation of radiation was based on manned cloud observations shortly after the middle of the 20th century. Values of radiation retrieved from the operational simulations of the European Centre for Medium-range Weather Forecasts (ECMWF) compare in general well with the observations.

Ólafsson, Haraldur; Cataldi, Maxime; Zehouf, Hafsa; Pálmason, Bolli

2014-05-01

324

Handbook of radiation effects  

SciTech Connect

This book emphasizes radiation effects on solid state devices from exposure to the types of radiation found outside the atmosphere (in space, or in the vicinity of an exploding nuclear device). It contains a basic study of radiation shielding of payload components for payloads in space and specifically covers radiation effects on minority and majority carriers, optical media and organic materials. It also includes some basic information on radioactivity, monitoring equipment and different types of radiation fields. This book is not oriented toward health physics.

Holmes-Siedle, A.; Adams, L.

1993-12-31

325

Solar cell radiation handbook  

NASA Technical Reports Server (NTRS)

A method is presented for predicting the degradation of a solar array in a space radiation environment. Solar cell technology which emphasizes the cell parameters that degrade in a radiation environment, is discussed along with the experimental techniques used in the evaluation of radiation effects. Other topics discussed include: theoretical aspects of radiation damage, methods for developing relative damage coefficients, nature of the space radiation environment, method of calculating equivalent fluence from electron and proton energy spectrums and relative damage coefficients, and comparison of flight data with estimated degradation.

Carter, J. R., Jr.; Tada, H. Y.

1973-01-01

326

Solar radiation measurement project  

NASA Technical Reports Server (NTRS)

The Xavier solar radiation measurement project and station are described. Measurements of the total solar radiation on a horizontal surface from an Eppley pyranometer were collected into computer data files. Total radiation in watt hours was converted from ten minute intervals to hourly intervals. Graphs of this total radiation data are included. A computer program in Fortran was written to calculate the total extraterrestrial radiation on a horizontal surface for each day of the month. Educational and social benefits of the project are cited.

Ioup, J. W.

1981-01-01

327

Fluorescent radiation converter  

NASA Technical Reports Server (NTRS)

Fluorescent radiation converter used optically transparent substrate. One side of substrate is coated with plastic film containing fluorescent organic dyes that absorb optical radiation at one wavelength and emit it at longer one. Coating is formulated to respond to specific wavelengths. Emitted radiation is reflected internally inside substrate, amplifying intensity that reaches radiation detector. Converter can be made in several shapes and size; round and square bars coated all round their lengths are useful in converting relatively intense radiation and transmitting it through substrate over lengthy distances.

Viehmann, W.

1980-01-01

328

Dynamics of Radiation Belt Particles  

NASA Astrophysics Data System (ADS)

This paper reviews basic concepts of particle dynamics underlying theoretical aspect of radiation belt modeling and data analysis. We outline the theory of adiabatic invariants of quasiperiodic Hamiltonian systems and derive the invariants of particle motion trapped in the radiation belts. We discuss how the nonlinearity of resonant interaction of particles with small-amplitude plasma waves, ubiquitous across the inner magnetosphere, can make particle motion stochastic. Long-term evolution of a stochastic system can be described by the Fokker-Plank (diffusion) equation. We derive the kinetic equation of particle diffusion in the invariant space and discuss its limitations and associated challenges which need to be addressed in forthcoming radiation belt models and data analysis.

Ukhorskiy, A. Y.; Sitnov, M. I.

2013-11-01

329

Thermal radiation effect on mixed convection heat and mass transfer of a non-Newtonian fluid over a vertical surface embedded in a porous medium in the presence of thermal diffusion and diffusion-thermo effects  

NASA Astrophysics Data System (ADS)

Thermal radiation, thermal diffusion, and diffusion-thermo effects on heat and mass transfer by mixed convection of non-Newtonian power-law fluids over a vertical permeable surface embedded in a saturated porous medium are investigated. The governing equations describing the problem are non-dimensionalized and transformed into a non-similar form. The transformed equations are solved by using the local non-similarity method combined with the shooting technique. The effects of the physical parameters of the problem on the fluid temperature and concentration are illustrated graphically and analyzed. Also, the effects of the pertinent parameters on the local Nusselt number and the local Sherwood number are presented.

Mahmoud, M. A. A.; Megahed, A. M.

2013-01-01

330

Breaking all the invariants: Anomalous electron radiation belt diffusion by pitch angle scattering in the presence of split magnetic drift shells  

NASA Astrophysics Data System (ADS)

electron observations near geostationary orbit routinely show pitch angle distributions peaked away from 90 degrees. These "butterfly" distributions are consistent with magnetic drift shell splitting combined with a radial flux gradient. During magnetic storms, nature adds pitch angle scattering to split drift shells, breaking all three adiabatic invariants of the particle's motion. Therefore, some degree of anomalous radial diffusion is likely, and cross terms between the gyration and drift invariants and between the bounce and drift invariants arise. Using typical assumptions about the pitch angle scattering and the magnetic field topology, we calculate these anomalous diffusion coefficients near geostationary orbit. We show that the anomalous radial diffusion can exceed that due to more traditional drift-resonant wave-particle interactions. We also show that the neglected cross terms, particularly the bounce-drift cross term, can be significant. These results suggest necessary additions to some global electron radiation belt simulations.

O'Brien, T. P.

2014-01-01

331

On the numerical simulation of particle dynamics in the radiation belt: 2. Procedure based on the diagonalization of the diffusion tensor  

NASA Astrophysics Data System (ADS)

In this paper, we conclude the survey and comparison of different numerical methods used to solve the diffusion equation for particle dynamics in the Earth's radiation belt, initiated in Camporeale et al. (2013). Here we focus on the diagonalization procedure introduced by Albert and Young (2005) that, by performing a change of coordinates, solves the diffusion equation in a space where the mixed diffusion terms are null. We describe the diagonalization procedure and its numerical implementation, which is not as straightforward as the implementation of a traditional solver in a rectangular domain. We compare the computing times with and without the diagonalization procedure, and we conclude that this procedure is generally not advantageous from the point of view of computational efficiency.

Camporeale, E.; Delzanno, G. L.; Zaharia, S.; Koller, J.

2013-06-01

332

[The radiation accident].  

PubMed

The reactor accident of Chernobyl in April 1986 has shown us all the dangers which are inherent ever in the peaceful use of atomic energy. The effects of exposure to ionizing radiation are dependent on biological effectiveness, on dose, on duration of exposure and on the age of the exposed person (the younger the graver). Acute ionizing radiation of the whole body leads to radiation disease or radiation syndrome of different stages of severity according to dosage. If the patient survives other consequences of ionizing radiation may arise: non-stochastic effects such as cataracts, keloid formation, fibrosis of the lungs and infertility) and stochastic effects (oncogenesis and mutagenesis). The sensitivity to ionizing radiation is especially high in childhood because of the high velocity of cell metabolism and cell growth, the large body-surface area and because their repair mechanism following radiation damage is not yet. PMID:3188527

Stögmann, W

1988-08-26

333

Gas particle radiator  

NASA Technical Reports Server (NTRS)

The performance of a new space radiator concept, the gas particle radiator (GPR), is studied. The GPR uses a gas containing submicron particles as the radiating medium contained between the radiator's emitting surface and a transparent window. For a modest volume fraction of submicron particles and gas thickness, it is found that the emissivity is determined by the window transmittance. The window must have a high transmittance in the infrared and be structurally strong enough to contain the gas-particle mixture. When the GPR is compared to a proposed titanium wall, potassium heat pipe radiator, with both radiators operating at a power level of 1.01 MW at 775 K, it is found that the GPR mass is 31 percent lower than that of the heat pipe radiator.

Chubb, Donald L.

1987-01-01

334

Radiation-induced gliomas  

PubMed Central

Radiation-induced gliomas represent a relatively rare but well-characterized entity in the neuro-oncologic literature. Extensive retrospective cohort data in pediatric populations after therapeutic intracranial radiation show a clearly increased risk in glioma incidence that is both patient age- and radiation dose/volume-dependent. Data in adults are more limited but show heightened risk in certain groups exposed to radiation. In both populations, there is no evidence linking increased risk associated with routine exposure to diagnostic radiation. At the molecular level, recent studies have found distinct genetic differences between radiation-induced gliomas and their spontaneously-occurring counterparts. Clinically, there is understandable reluctance on the part of clinicians to re-treat patients due to concern for cumulative neurotoxicity. However, available data suggest that aggressive intervention can lead to improved outcomes in patients with radiation-induced gliomas.

Prasad, Gautam; Haas-Kogan, Daphne A.

2013-01-01

335

High-power radiating plasma  

NASA Technical Reports Server (NTRS)

The physical principles underlying the use of radiating plasmas for the optical pumping of lasers are described. Particular consideration is given to the properties of radiating plasmas; radiation selectivity; the dynamics, equilibrium, and stability of radiating plasmas; the radiative Reynolds number; and experimental results on radiating discharges.

Rozanov, V. B.; Rukhadze, A. A.

1984-01-01

336

Measurement of the ferric diffusion coefficient in agarose and gelatine gels by utilization of the evolution of a radiation induced edge as reflected in relaxation rate images  

NASA Astrophysics Data System (ADS)

A method has been developed to determine the diffusion coefficients of ferric ions in ferrous sulphate doped gels. A radiation induced edge was created in the gel, and two spin-echo sequences were used to acquire a pair of images of the gel at different points of time. For each of these image pairs, a longitudinal relaxation rate image was derived. From profiles through these images, the standard deviations of the Gaussian functions that characterize diffusion were determined. These data provided the basis for the determination of the ferric diffusion coefficients by two different methods. Simulations indicate that the use of single spin-echo images in this procedure may in some cases lead to a significant underestimation of the diffusion coefficient. The technique was applied to different agarose and gelatine gels that were prepared, irradiated and imaged simultaneously. The results indicate that the diffusion coefficient is lower in a gelatine gel than in an agarose gel. Addition of xylenol orange to a gelatine gel lowers the diffusion coefficient from 1.45 to , at the cost of significantly lower sensitivity. The addition of benzoic acid to the latter gel did not increase the sensitivity.

Pedersen, Torje V.; Olsen, Dag R.; Skretting, Arne

1997-08-01

337

The effects of the diffuse radiation fields due to multiple scattering and thermal reradiation by dust on the dynamics and thermodynamics of a dusty cometary atmosphere  

NASA Technical Reports Server (NTRS)

A self-consistent model of a dirty, clathrate cometary nucleus is extended to account for diffuse radiation fields caused by multiple scattering and thermal reradiation of the solar continuum by dust. The model is configured to fit conditions expected for the various spacecraft which will encounter Halley's comet at 0.89 AU. The atmosphere is assumed a chemically reactive dust-gas mixture in quasi-steady spherically symmetric expansion. The effect of electron-neutral ion collisions is accounted for, along with rate constants of the various species of clathrate ice particles and radiative transfer of the solar input in the UV, visible and near-IR intervals. The opacity of the circumnuclear dust is projected to be an order of magnitude greater than previous estimates, which severely impacts the potential visibility of the nucleus to the cameras of the flyby satellites.

Marconi, M. L.; Mendis, D. A.

1984-01-01

338

Involved Field Radiation After Autologous Stem Cell Transplant for Diffuse Large B-Cell Lymphoma in the Rituximab Era  

Microsoft Academic Search

Purpose: For patients with recurrent or refractory large B-cell non-Hodgkin's lymphoma, high-dose chemotherapy and autologous stem cell transplant (ASCT) is the treatment of choice. We evaluated the role of involved field radiation therapy (IFRT) post-ASCT for patients initially induced with cyclophosphamide, adriamycin, vincristine, and prednisone (CHOP) or, more recently, rituximab-CHOP (R-CHOP). Materials and Methods: Between May 1992 and April 2005,

Tithi Biswas; Sughosh Dhakal; Rui Chen; Ollivier Hyrien; Steven Bernstein; Jonathan W. Friedberg; Richard I. Fisher; Jane Liesveld; Gordon Phillips; Louis S. Constine

2010-01-01

339

Radiation physics, biophysics, and radiation biology  

SciTech Connect

Research at the Center for Radiological Research is a multidisciplenary blend of physics, chemistry and biology aimed at understanding the mechanisms involved in the health problems resulting from human exposure to ionizing radiations. The focus is increased on biochemistry and the application of the techniques of molecular biology to the problems of radiation biology. Research highlights of the program from the past year are described. A mathematical model describing the production of single-strand and double-strand breaks in DNA as a function radiation quality has been completed. For the first time Monte Carlo techniques have been used to obtain directly the spatial distribution of DNA moieties altered by radiation. This information was obtained by including the transport codes a realistic description of the electronic structure of DNA. We have investigated structure activity relationships for the potential oncogenicity of a new generation of bioreductive drugs that function as hypoxic cytotoxins. Experimental and theoretical investigation of the inverse dose rate effect, whereby medium LET radiations actually produce an c effect when the dose is protracted, is now at a point where the basic mechanisms are reasonably understood and the complex interplay between dose, dose rate and radiation quality which is necessary for the effect to be present can now be predicted at least in vitro. In terms of early radiobiological damage, a quantitative link has been established between basic energy deposition and locally multiply damaged sites, the radiochemical precursor of DNA double strand breaks; specifically, the spatial and energy deposition requirements necessary to form LMDs have been evaluated. For the first time, a mechanically understood biological fingerprint'' of high-LET radiation has been established. Specifically measurement of the ratio of inter-to intra-chromosomal aberrations produces a unique signature from alpha-particles or neutrons.

Hall, E.J.; Zaider, M.

1993-05-01

340

Earth Radiation Measurement Science  

NASA Technical Reports Server (NTRS)

This document is the final report for NASA Grant NAG1-1959, 'Earth Radiation Measurement Science'. The purpose of this grant was to perform research in this area for the needs of the Clouds and Earth Radiant Energy System (CERES) project and for the Earth Radiation Budget Experiment (ERBE), which are bing conducted by the Radiation and Aerosols Branch of the Atmospheric Sciences Division of Langley Research Center. Earth Radiation Measurement Science investigates the processes by which measurements are converted into data products. Under this grant, research was to be conducted for five tasks: (1) Point Response Function Measurements; (2) Temporal Sampling of Outgoing Longwave Radiation; (3) Spatial Averaging of Radiation Budget Data; (4) CERES Data Validation and Applications; and (5) ScaRaB Data Validation and Application.

Smith, G. Louis

2000-01-01

341

Atomistic modeling of intrinsic and radiation-enhanced fission gas (Xe) diffusion in UO2±x: Implications for nuclear fuel performance modeling  

NASA Astrophysics Data System (ADS)

Based on density functional theory (DFT) and empirical potential calculations, the diffusivity of fission gas atoms (Xe) in UO2 nuclear fuel has been calculated for a range of non-stoichiometry (i.e. UO2±x), under both out-of-pile (no irradiation) and in-pile (irradiation) conditions. This was achieved by first deriving expressions for the activation energy that account for the type of trap site that the fission gas atoms occupy, which includes the corresponding type of mobile cluster, the charge state of these defects and the chemistry acting as boundary condition. In the next step DFT calculations were used to estimate migration barriers and internal energy contributions to the thermodynamic properties and calculations based on empirical potentials were used to estimate defect formation and migration entropies (i.e. pre-exponentials). The diffusivities calculated for out-of-pile conditions as function of the UO2±x non-stoichiometry were used to validate the accuracy of the diffusion models and the DFT calculations against available experimental data. The Xe diffusivity is predicted to depend strongly on the UO2±x non-stoichiometry due to a combination of changes in the preferred Xe trap site and in the concentration of uranium vacancies enabling Xe diffusion, which is consistent with experiments. After establishing the validity of the modeling approach, it was used for studying Xe diffusion under in-pile conditions, for which experimental data is very scarce. The radiation-enhanced Xe diffusivity is compared to existing empirical models. Finally, the predicted fission gas diffusion rates were implemented in the BISON fuel performance code and fission gas release from a Risø fuel rod irradiation experiment was simulated.

Andersson, D. A.; Garcia, P.; Liu, X.-Y.; Pastore, G.; Tonks, M.; Millett, P.; Dorado, B.; Gaston, D. R.; Andrs, D.; Williamson, R. L.; Martineau, R. C.; Uberuaga, B. P.; Stanek, C. R.

2014-08-01

342

Environmental Radiation Protection  

NASA Astrophysics Data System (ADS)

The environmental distribution of radionuclides, released from nuclear facilities and other sources, and the principles of the emergency countermeasures for radiation protection of the public and workers are discussed in this chapter. The concentration levels of radionuclides in various aquatic and terrestrial environments and the exposure levels of the population due to the various sources of radiation (natural and artificial radionuclides, cosmic radiation, diagnostic medical examinations, atmospheric nuclear tests, etc.) are presented.

Maeda, Y.; Osaki, S.; Vincze, A.

343

RHOBOT: Radiation hardened robotics  

SciTech Connect

A survey of robotic applications in radioactive environments has been conducted, and analysis of robotic system components and their response to the varying types and strengths of radiation has been completed. Two specific robotic systems for accident recovery and nuclear fuel movement have been analyzed in detail for radiation hardness. Finally, a general design approach for radiation-hardened robotics systems has been developed and is presented. This report completes this project which was funded under the Laboratory Directed Research and Development program.

Bennett, P.C.; Posey, L.D. [Sandia National Labs., Albuquerque, NM (United States)

1997-10-01

344

Stereotactic Body Radiation Therapy  

Microsoft Academic Search

\\u000a Technological advancements in imaging and radiation planning and delivery have made it possible for cranial stereotactic radiosurgery\\u000a techniques to be applied to tumors outside of the brain. Although high-dose radiation therapy may be delivered in a single\\u000a fraction, referred to as extracranial stereotactic radiosurgery (SRS), more often, high-precision radiation is delivered in\\u000a more than one fraction, leading to the field

Laura A. Dawson

345

Rotating bubble membrane radiator  

DOEpatents

A heat radiator useful for expelling waste heat from a power generating system aboard a space vehicle is disclosed. Liquid to be cooled is passed to the interior of a rotating bubble membrane radiator, where it is sprayed into the interior of the bubble. Liquid impacting upon the interior surface of the bubble is cooled and the heat radiated from the outer surface of the membrane. Cooled liquid is collected by the action of centrifical force about the equator of the rotating membrane and returned to the power system. Details regarding a complete space power system employing the radiator are given.

Webb, Brent J. (West Richland, WA); Coomes, Edmund P. (West Richland, WA)

1988-12-06

346

Flexible radiator system  

NASA Technical Reports Server (NTRS)

The soft tube radiator subsystem is described including applicable system requirements, the design and limitations of the subsystem components, and the panel manufacturing method. The soft tube radiator subsystem is applicable to payloads requiring 1 to 12 kW of heat rejection for orbital lifetimes per mission of 30 days or less. The flexible radiator stowage volume required is about 60% and the system weight is about 40% of an equivalent heat rejection rigid panel. The cost should also be considerably less. The flexible radiator is particularly suited to shuttle orbiter sortie payloads and also whose mission lengths do not exceed the 30 day design life.

Oren, J. A.

1982-01-01

347

Charms of radiation research.  

SciTech Connect

Most of my professional efforts over nearly five decades have been devoted to radiation research, that is, studies of the physical, chemical, and biological actions of high-energy radiation on matter. (By the term 'high-energy radiation' I mean here x rays, .GAMMA. rays, neutrons, and charged particles of high enough energies to produce ionization in matter. I exclude visible light, infrared waves, microwaves, and sound waves.) Charms of radiation research lie in its interdisciplinary character; although my training was in basic physics, the scope of my interest has gradually increased to cover many other areas, to my deep satisfaction. High-energy radiation is an important component of the universe, and of our environment. It often provides an effective avenue for characterizing matter and understanding its behavior. Near Earth's surface this radiation is normally present in exceptionally low quantity, and yet it plays a significant role in some atmospheric phenomena such as auroras, and also in the evolution of life. The recent advent of various devices for producing high-energy radiation has opened up the possibility of many applications, including medical and industrial uses. I have worked on some aspects of those uses. At every opportunity to address a broad audience I try to convey a sense of intellectual fun, together with some of the elements of the basic science involved. A goal of radiation education might be to make the word 'radiation' as common and familiar as words such as 'fire' and 'electricity' through increased usage.

Inokuti, M.; Physics

2005-01-01

348

Radiation coloration resistant glass  

DOEpatents

A radiation coloration resistant glass is disclosed which is used in a radiation environment sufficient to cause coloration in most forms of glass. The coloration resistant glass includes higher proportions by weight of water and has been found to be extremely resistant to color change when exposed to such radiation levels. The coloration resistant glass is free of cerium oxide and has more than about 0.5% by weight water content. Even when exposed to gamma radiation of more than 10.sup.7 rad, the coloration resistant glass does not lose transparency.

Tomozawa, Minoru (Troy, NY); Watson, E. Bruce (Troy, NY); Acocella, John (Troy, NY)

1986-01-01

349

Solar and Infrared Radiation Station (SIRS) Handbook  

SciTech Connect

The Solar Infrared Radiation Station (SIRS) provides continuous measurements of broadband shortwave (solar) and longwave (atmospheric or infrared) irradiances for downwelling and upwelling components. The following six irradiance measurements are collected from a network of stations to help determine the total radiative flux exchange within the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) Climate Research Facility: • Direct normal shortwave (solar beam) • Diffuse horizontal shortwave (sky) • Global horizontal shortwave (total hemispheric) • Upwelling shortwave (reflected) • Downwelling longwave (atmospheric infrared) • Upwelling longwave (surface infrared)

Stoffel, T

2005-07-01

350

Radiation physics, biophysics, and radiation biology  

SciTech Connect

The following research programs from the Center for Radiological Research of Columbia University are described: Design and development of a new wall-less ultra miniature proportional counter for nanodosimetry; some recent measurements of ionization distributions for heavy ions at nanometer site sizes with a wall-less proportional counter; a calculation of exciton energies in periodic systems with helical symmetry: application to a hydrogen fluoride chain; electron energy-loss function in polynucleotide and the question of plasmon excitation; a non-parametric, microdosimetric-based approach to the evaluation of the biological effects of low doses of ionizing radiation; high-LET radiation risk assessment at medium doses; high-LET radiobiological effects: increased lesion severity or increased lesion proximity; photoneutrons generated by high energy medical linacs; the biological effectiveness of neutrons; implications for radiation protection; molecular characterization of oncogenes induced by neutrons; and the inverse dose-rate effect for oncogenic transformation by charged particles is LET dependent.

Hall, E.J.

1992-05-01

351

Spontaneous radiation of a brownian nanoparticle  

NASA Astrophysics Data System (ADS)

It is shown that a charged Brownian nanoparticle (or an electron) similar to a two-level atom can generate spontaneous and induced radiation upon switching on an external field. The diffusion mechanism of charging nanoparticles is examined. The radiation process is a macroscopic quantum phenomenon, which can be used in synthetic biology, medicine, and other fields of science and engineering.

Lasukov, V. V.; Dybov, A. R.

2011-09-01

352

Radiation biology: concepts for radiation protection.  

PubMed

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 pioneering work of Muller, Sax, and McClintock, and many others, has stood the test of time. The idea that x-rays could damage the genetic material and result in interactions that could lead to gene mutations and a range of chromosomal alterations is now interpretable in terms of induced DNA damage and errors of DNA repair. The expanded idea that such genetic alterations can be induced by DNA damage that is produced by one or two tracks of ionizing radiation remains the mainstay of radiation biology. The impact of the more recent molecular approaches to unraveling the mechanism behind this simple concept has confirmed this fundamental observation. The remarkable advances have allowed for a fairly complete understanding of the specific types of DNA damage induced by ionizing radiations and the pivotal role played by the errors of repair of double-strand breaks. Given our considerably enhanced knowledge of the details of the DNA repair processes involved, misrepair is a very unlikely event. The role of potential confounders of the concept of dose-response (e.g., bystander effects, genomic instability, and adaptive responses) is taking on a growing importance to the field. The evolving need is to begin to consider mechanistically-based dose-response models for cancer risk such that any potential impact of confounders on the response at low, environmental doses can be assessed. Thus, radiation biology research has always had a focus on how best to protect human health from radiation exposures and will continue to do so. PMID:15891452

Preston, R Julian

2005-06-01

353

Radiation biology: concepts for radiation protection.  

PubMed

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 pioneering work of Muller, Sax, and McClintock, and many others, has stood the test of time. The idea that x-rays could damage the genetic material and result in interactions that could lead to gene mutations and a range of chromosomal alterations is now interpretable in terms of induced DNA damage and errors of DNA repair. The expanded idea that such genetic alterations can be induced by DNA damage that is produced by one or two tracks of ionizing radiation remains the mainstay of radiation biology. The impact of the more recent molecular approaches to unraveling the mechanism behind this simple concept has confirmed this fundamental observation. The remarkable advances have allowed for a fairly complete understanding of the specific types of DNA damage induced by ionizing radiations and the pivotal role played by the errors of repair of double-strand breaks. Given our considerably enhanced knowledge of the details of the DNA repair processes involved, misrepair is a very unlikely event. The role of potential confounders of the concept of dose-response (e.g., bystander effects, genomic instability, and adaptive responses) is taking on a growing importance to the field. The evolving need is to begin to consider mechanistically-based dose-response models for cancer risk such that any potential impact of confounders on the response at low, environmental doses can be assessed. Thus, radiation biology research has always had a focus on how best to protect human health from radiation exposures and will continue to do so. PMID:15194918

Preston, R Julian

2004-07-01

354

Significance of tumor size and radiation dose to local control in Stage I–III diffuse large cell lymphoma treated with CHOP-Bleo and radiation  

Microsoft Academic Search

Purpose: The purpose of this study was ti evaluate the possible effect of adjunctive involve field (IF) radiotherapy on long-term local control for patients with Ann Arbor Stage I–III diffuse large cell lymphoma (DLCL) who achieved a complete remission on a combined modality program which included cyclophosphamide, doxorubicin, vincristine, prednisone, and Bleomycin (CHOP-Belo).Methods and Materials: One hundred and ninety patients

Lillian M. Fuller; Matthew J. Krasin; William S. Velasquez; Pamela K. Allen; Peter McLaughlin; M. Alma Rodriguez; Fredrick B. Hagemeister; Forrest Swan; Fernando Cabanillas; Judy L. Palmer; James D. Cox

1995-01-01

355

Radiation turbulence interactions in pulverized coal flames: Chaotic map models of soot fluctuations in turbulent diffusion flames. Quarterly report, October 1995--December 1995  

SciTech Connect

In this paper, we introduce a methodology to characterize soot volume fraction fluctuations in turbulent diffusion flames via chaotic maps. The approach is based on the hypothesis that the fluctuations of properties in turbulent flames is deterministic in nature, rather than statistical. Out objective is to develop models to mimic these fluctuations. The models will be used eventually in comprehensive algorithms to study the true physics of turbulent flames and the interaction of turbulence with radiation. To this extent, we measured the time series of soot scattering coefficient in an ethylene diffusion flame from light scattering experiments. Following this, corresponding power spectra and delay maps were calculated. It was shown that if the data were averaged, the characteristics of the fluctuations were almost completely washed out. The psds from experiments were successfully modeled using a series of logistic maps.

McDonough, J.M.; Menguc, M.P.; Mukerji, S.; Swabb, S.; Manickavasagam, S.; Ghosal, S.

1995-12-31

356

Diffusive and Radiative Transport in Fires (DARTFire): Opposed-Flow Flame Spread in Low-Velocity Flows  

NASA Technical Reports Server (NTRS)

For flames spreading into a low-velocity flow that can only be obtained in microgravity, we have observed behavior that is different from that which is obtained at higher velocities where radiative effects are unimportant and species transport is relatively fast. Unfortunately, lack of a large body of low-gravity flame spread experimental data inhibits progress in developing an understanding of the physics of low-velocity, opposed-flow flame spread phenomena. Recent DARTFire sounding rocket experimental studies though, coupled with developing theory and modelling, have allowed some strides in understanding to be made, on which we report here. Four launches to date have resulted in six experiments for opposed-flow flame spread over a thick PMMA sample. During the 6 min microgravity period, the PMMA samples were ignited, and steady flame spread was studied under varied flow velocity, oxidizer atmospheric conditions, and, because radiative heat transfer is so important in these slowly spreading flames, external radiant flux. These were the first attempts at such experimental control and measurement in microgravity. A recent reflight of the Solid Surface Combustion Experiment (SSCE) has demonstrated, as modelling predicts, that for the thick fuel of the DARTFire experiment, flame spread in a quiescent environment is a transient process evolving from ignition to extinction on the order of 600 s (Altenkirch et al., 1999). Further study then of the effects of radiation in the very low-velocity opposing flows is of interest in understanding the transition from steady, sustained spread to the unsteady evolution to extinction as the opposing flow is reduced further and eventually removed.

Altenkirch, R. A.; Olson, S. L.; Deering, J. L.; Tang, L.; Bhattacharjee, S.

1999-01-01

357

[Efficacy of CHOP+/-Rituximab-like therapy plus radiation therapy for patients with diffuse large B-cell lymphoma stage I].  

PubMed

Clinically, R-CHOP-like therapy plus radiation therapy is commonly performed for patients with limited stage diffuse large B-cell lymphoma. However, the efficacy and the safety of the management have not been evaluated properly. In particular, we have few definitive reports about patients with stage I DLBCL. This time we evaluated the effect of CHOP+/-R-like therapy plus radiation therapy, by analyzing 28 patients with stage I DLBCL, retrospectively. 15 patients were treated with the RCHOP-like therapy, and 13 received CHOP-like therapy combined with radiation therapy. A complete response was observed in all of the patients. With a median follow-up time of 14 months, 1-year progression-free survival (PFS) was 100%, and the 1-year overall survival (OS) was 100% for the patients receiving the R-CHOP-like therapy. With a median follow-up time of 68 months, 5-year PFS was 84. 6%, and 5-year OS was 100% for patients receiving the CHOP-like therapy. Since the followup time was not enough and the patient numbers were too few, the benefit of the addition of Rituximab to the CHOP therapy could not be clarified. We need to assess the safety and the efficacy of the combined modality therapy for patients with limited-stage DLBCL by a larger prospective study. PMID:20495315

Ueda, Kyoko; Yokoyama, Masahiro; Asai, Hiroaki; Koudaira, Makoto; Yamada, Syuhei; Katsube, Atsushi; Mishima, Yuko; Sakajiri, Sakura; Takeuchi, Kengo; Saotome, Takashi; Terui, Yasuhito; Takahashi, Syunji; Hatake, Kiyohiko

2010-05-01

358

Application of Computer Global Radiation for Areas of High Relief.  

National Technical Information Service (NTIS)

The variation over uneven terrain of the daily total of incident shortwave (global) radiation under cloudless conditions may be estimated by existing methods for calculating direct and diffuse solar radiation on a slope. A computer program for performing ...

J. T. Andrews L. D. Williams R. G. Barry

1971-01-01

359

Radiation Hydrodynamics in Classical Novae  

NASA Astrophysics Data System (ADS)

A new hydrodynamics code, designed for the purpose of modeling various radiation hydrodynamic processes in classical novae, is described. This code is based on an older code written by G. S. Kutter, W. M. Sparks, S. G. Starrfield, and J. W. Truran, but has been almost entirely rewritten with many additions and modifications. New input physics includes the following: (1) allowance for the decoupling of the gas and radiation temperatures under the assumption of diffusive energy transport, (2) effects of spectral lines on the radiative momentum balance in the outflowing material, and (3) the computation of the formal solution to the transfer equation, used to compute broad-band colors (presently U, B, and V) at various points in the model sequence. A few preliminary results are presented, along with an outline for future short-term and long-term work.

Hayes, J.

1992-12-01

360

Plastic plasticizer and radiation  

Microsoft Academic Search

Examination concerning the possibilities of decomposition of ; plasticizers such as phthalic acid esters and phosphoric acid esters or toxicity ; reduction thereof by the radiation has been made. (1) Radiation effects: Sham ; polluted solution having various kinds of concentrations of said ester was ; irradiated with ⁶°Co gamma -ray to 0.3 Mrad\\/hr. The results show that ; with

Sunada

1973-01-01

361

On the Jitter Radiation  

NASA Astrophysics Data System (ADS)

In a small-scale turbulent medium, when the nonrelativistic Larmor radius RL = mc 2/eB exceeds the correlation length ? of the magnetic field, the magnetic Bremsstrahlung radiation of charged relativistic particles unavoidably proceeds to the so-called jitter radiation regime. The cooling timescale of parent particles is identical to the synchrotron cooling time, thus this radiation regime can be produced with very high efficiency in different astrophysical sources characterized by high turbulence. The jitter radiation has distinct spectral features shifted toward high energies, compared to synchrotron radiation. This effect makes the jitter mechanism an attractive broad-band gamma-ray production channel, which, in highly magnetized and turbulent environments, can compete or even dominate over other high-energy radiation mechanisms. In this paper, we present a novel study of the spectral properties of the jitter radiation performed within the framework of perturbation theory. The derived general expression for the spectral power of radiation is presented in a compact and convenient form for numerical calculations.

Kelner, S. R.; Aharonian, F. A.; Khangulyan, D.

2013-09-01

362

Synchrotron Radiation II.  

ERIC Educational Resources Information Center

Synchrotron radiation is a unique form of radiation that spans the electro-magnetic spectrum from X-rays through the ultraviolet and visible into the infrared. Tunable monochromators enable scientists to select a narrow band of wavelengths at any point in the spectrum. (Author/BB)

MOSAIC, 1978

1978-01-01

363

ON THE JITTER RADIATION  

SciTech Connect

In a small-scale turbulent medium, when the nonrelativistic Larmor radius R{sub L} = mc {sup 2}/eB exceeds the correlation length {lambda} of the magnetic field, the magnetic Bremsstrahlung radiation of charged relativistic particles unavoidably proceeds to the so-called jitter radiation regime. The cooling timescale of parent particles is identical to the synchrotron cooling time, thus this radiation regime can be produced with very high efficiency in different astrophysical sources characterized by high turbulence. The jitter radiation has distinct spectral features shifted toward high energies, compared to synchrotron radiation. This effect makes the jitter mechanism an attractive broad-band gamma-ray production channel, which, in highly magnetized and turbulent environments, can compete or even dominate over other high-energy radiation mechanisms. In this paper, we present a novel study of the spectral properties of the jitter radiation performed within the framework of perturbation theory. The derived general expression for the spectral power of radiation is presented in a compact and convenient form for numerical calculations.

Kelner, S. R. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-6917 Heidelberg (Germany); Aharonian, F. A. [Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2 (Ireland); Khangulyan, D., E-mail: skelner@rambler.ru, E-mail: Felix.Aharonian@mpi-hd.mpg.de, E-mail: khangul@astro.isas.jaxa.jp [Institute of Space and Astronautical Science/JAXA, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)

2013-09-01

364

Treatment of Radiation Injury  

PubMed Central

Significance: Radiation exposure as a result of radiation treatment, accident, or terrorism may cause serious problems such as deficiency due to necrosis or loss of function, fibrosis, or intractable ulcers in the tissues and organs. When the skin, bone, oral mucous membrane, guts, or salivary glands are damaged by ionizing radiation, the management and treatment are very lengthy and difficult. Critical Issues: In severe and irreversible injuries, surgery remains the mainstay of treatment. Several surgical procedures, such as debridement, skin grafting, and local and free-vascularized flaps, are widely used. Recent Advances: In specific cases of major morbidity or in high-risk patients, a newly developed therapy using a patient's own stem cells is safe and effective. Adipose tissue, normally a rich source of mesenchymal stem cells, which are similar to those from the bone marrow, can be harvested, since the procedure is easy, and abundant tissue can be obtained with minimal invasiveness. Future Directions: Based on the molecular basis of radiation injuries, several prospective treatments are under development. Single-nucleotide polymorphisms focus on an individual's sensitivity to radiation in radiogenomics, and the pathology of radiation fibrosis or the effect of radiation on wound healing is being studied and will lead to new insight into the treatment of radiation injuries. Protectors and mitigators are being actively investigated in terms of the timing of administration or dose.

Akita, Sadanori

2014-01-01

365

PROTECTION AGAINST RADIATION INJURY  

Microsoft Academic Search

An account is given of the principles of protection against radiation ; injury and of the recommendations of Emergency Health Services, Department of ; National Health and Welfare, to those responsible for the protection of the ; health of persons at risk from nuclear weapon fallout radiations. Protection ; against injury is based on 2 concepts: procedures that result in

F. C. Pace; W. R. Waters

1961-01-01

366

Ultraviolet radiation changes  

NASA Technical Reports Server (NTRS)

A major consequence of ozone depletion is an increase in solar ultraviolet (UV) radiation received at the Earth's surface. This chapter discusses advances that were made since the previous assessment (World Meteorological Organization (WMO)) to our understanding of UV radiation. The impacts of these changes in UV on the biosphere are not included, because they are discussed in the effects assessment.

Mckenzie, Richard L.; Frederick, John E.; Ilyas, Mohammad; Filyushkin, V.; Wahner, Andreas; Stamnes, K.; Muthusubramanian, P.; Blumthaler, M.; Roy, Colin E.; Madronich, Sasha

1991-01-01

367

Radiation-induced pneumothorax  

SciTech Connect

Pneumothorax is an uncommon complication of radiation therapy to the chest. The proposed pathogenesis is radiation-induced fibrosis promoting subpleural bleb formation that ruptures resulting in pneumothorax. We report on two young patients with primary sarcomas without pulmonary metastases who developed spontaneous pneumothorax after irradiation. Neither patient had antecedent radiographic evidence of pulmonary fibrosis.

Epstein, D.M.; Littman, P.; Gefter, W.B.; Miller, W.T.; Raney, R.B. Jr.

1983-01-01

368

Radiation-induced enteropathy  

Microsoft Academic Search

The incidence of chronic radiation enteritis appears to have risen in recent years due to the increasing utilization of radiotherapy for abdominal and pelvic malignancies. The etiology, pathogenesis, and management of radiation enteritis are discussed. Two case reports exemplify the progressive nature of the disease. Case 1 demonstrates the classical picture of multiple exacerbations and remissions of partial small bowel

M. E. Sher; J. Bauer

1990-01-01

369

Solar radiation in Lebanon  

Microsoft Academic Search

Solar radiation data for two sites in Lebanon are analyzed and presented in a form suitable for their use by practicing engineers. Correlations of the Angstrom-Page type for daily and monthly data are developed. Probability density functions for daily values of global radiation for each month are compared with the results of Liu and Jordan. The atmospheric model developed by

A. A. Sfeir

1981-01-01

370

Radiation biology of mosquitoes  

Microsoft Academic Search

There is currently renewed interest in assessing the feasibility of the sterile insect technique (SIT) to control African malaria vectors in designated areas. The SIT relies on the sterilization of males before mass release, with sterilization currently being achieved through the use of ionizing radiation. This paper reviews previous work on radiation sterilization of Anopheles mosquitoes. In general, the pupal

Michelle EH Helinski; Andrew G Parker; Bart GJ Knols

2009-01-01

371

Radiation Exposure Compensation Program  

NSDL National Science Digital Library

This is the Justice Department's Radiation Exposure Compensation Program homepage. This site features information about the Radiation Exposure Compensation Act, including claimant categories, claim forms, and the Energy Employees Occupational Illness Compensation Program Act. This site also provides a table illustrating a summary of all claims received and compensation paid to date.

Program, U. S.

372

Earth Radiation Budget Satellite  

Microsoft Academic Search

A satellite to measure the earth's radiation budget is to be integrated, tested, and delivered ready for launch on the space shuttle by April 1984. Although there have been Earth radiation budget instruments in NASA's experimental NIMBUS 6 and 7 spacecraft, this will be the first time this factor can be measured on a global basis over a 24-hour day.

Peter M. Bell

1981-01-01

373

Earth Radiation Budget Experiment  

Microsoft Academic Search

During the past 4 years, instruments of the Earth Radiation Budget Experiment (ERBE) have been collecting data on two satellites. The first of these is the Earth Radiation Budget Satellite (ERBS). The second is the operational NOAA-9 satellite. In addition, ERBE has instruments on the operational NOAA-10. The NOAA-10 instruments have been collecting data for the last 2 years. The

Bruce R. Barkstrom; Edwin F. Harrison; Robert B. Lee III

1990-01-01

374

ARCTIC RADIATION BUDGET CHANGES  

Microsoft Academic Search

Scanning radiometers of the Earth Radiation Budget Experiment provided global measurements for 1985 through 1988 and Clouds and the Earth's Radiant Energy System (CERES) instruments have made measurements from 2000 to the present. These data have been used to study interannual and decadal variations for the Arctic region in July. The satellite record of Earth radiation budget demonstrates that the

G. Louis Smith; T. Dale Bess

375

Chitosan and radiation chemistry  

Microsoft Academic Search

Chitosan as a raw material with special properties has drawn attention of scientists working in the field of radiation processing and natural polymer products development, and also of specialists working in the field of radiation protection and oncologists. Especially the applications concern reduced molecular weight chitosan which still retain its chemical structure; such form of the compound is fostering biological,

Andrzej G. Chmielewski

2010-01-01

376

Microcircuit Radiation Effects Databank.  

National Technical Information Service (NTIS)

Radiation test data submitted by many testers is collated to serve as a reference for engineers who are concerned with and have some knowledge of the effects of the natural radiation environment on microcircuits. Total dose damage information and single e...

1983-01-01

377

Health and Environmental Radiation  

SciTech Connect

This paper discusses health benefits attributed to low-level radiation. Increased immune competence and radiogenic metabolism following low-dose irradiation elicits benefits in reproduction, cancer mortality, and average lifetime. Evidence is cited that suggests 200000 premature cancer deaths in this country would be prevented each year by radiation supplementation.

Luckey, T.D.

1999-06-06

378

Physics for Radiation Protection  

NASA Astrophysics Data System (ADS)

A practical guide to the basic physics that radiation protection professionals need A much-needed working resource for health physicists and other radiation protection professionals, this volume presents clear, thorough, up-to-date explanations of the basic physics necessary to address real-world problems in radiation protection. Designed for readers with limited as well as basic science backgrounds, Physics for Radiation Protection emphasizes applied concepts and carefully illustrates all topics through examples as well as practice problems. Physics for Radiation Protection draws substantially on current resource data available for health physics use, providing decay schemes and emission energies for approximately 100 of the most common radionuclides encountered by practitioners. Excerpts of the Chart of the Nuclides, activation cross sections, fission yields, fission-product chains, photon attenuation coefficients, and nuclear masses are also provided. Coverage includes: * The atom as an energy system * An overview of the major discoveries in radiation physics * Extensive discussion of radioactivity, including sources and materials * Nuclear interactions and processes of radiation dose * Calculational methods for radiation exposure, dose, and shielding * Nuclear fission and production of activation and fission products * Specialty topics ranging from nuclear criticality and applied statistics to X rays * Extensive and current resource data cross-referenced to standard compendiums * Extensive appendices and more than 400 figures

Martin, James E.

2000-06-01

379

Radiative forcing by contrails  

Microsoft Academic Search

A parametric study of the instantaneous radiative impact of contrails is presented using three diÄerent radiative transfer models for a series of model atmospheres and cloud parameters. Contrails are treat- ed as geometrically and optically thin plane parallel homogeneous cirrus layers in a static atmosphere. The ice water content is varied as a function of ambient temperature. The model atmospheres

R. Meerkotter; U. Schumann; D. R. Doelling; P. Minnis; T. Nakajima; Y. Tsushima

1999-01-01

380

Radiation of Massive Gravitation.  

National Technical Information Service (NTIS)

The radiation problem in massive and massless linear Einstein gravitation is analyzed for mass discontinuities in the limit of vanishing graviton mass m. It is found that in this limit the radiation into the massive helicity + or - 2 modes becomes equal t...

P. Vannieuwenhuizen

1972-01-01

381

Forecasting Radiation Fog  

NSDL National Science Digital Library

The goal of this training module is to help you increase your understanding of how radiation fog forms, grows, and dissipates. Such understanding, in turn, can help you more efficiently and accurately evaluate the ability of a given atmospheric environment to generate and/or maintain radiation fog.

Spangler, Tim

1999-04-08

382

RADIATION-CURABLE COATINGS  

EPA Science Inventory

The report gives results of an evaluation of radiation-curable coatings as a technology for reducing volatile organic compound (VOC) emissions from surface coating operations. urvey of the literature was conducted to assess the state of the technology and emissions from radiation...

383

Radiation and health*  

PubMed Central

Radiation has been a source of fascination and concern ever since Wilhelm Konrad Röntgen discovered X-rays on 8 November 1895. Over the years, health workers as well as the public have been concerned about medical uses of X-rays, the presence of radon in buildings, radioactive waste from nuclear power stations, fallout from nuclear test explosions, radioactive consumer products, microwave ovens, and many other sources of radiation. Most recently, the tragic accident at the Chernobyl nuclear power station in the USSR, and the subsequent contamination over most of Europe, has again wakened interest and concern and also reminded us about a number of misconceptions about radiation. This article describes the essentials about radiation (especially ionizing radiation) and its health effects.

Lindell, B.

1987-01-01

384

Deployable Heat Pipe Radiator  

NASA Technical Reports Server (NTRS)

A 1.2- by 1.8-m variable conductance heat pipe radiator was designed, built, and tested. The radiator has deployment capability and can passively control Freon-21 fluid loop temperatures under varying loads and environments. It consists of six grooved variable conductance heat pipes attached to a 0.032-in. aluminum panel. Heat is supplied to the radiator via a fluid header or a single-fluid flexible heat pipe header. The heat pipe header is an artery design that has a flexible section capable of bending up to 90 degrees. Radiator loads as high as 850 watts were successfully tested. Over a load variation of 200 watts, the outlet temperature of the Freon-21 fluid varied by 7 F. An alternate control system was also investigated which used a variable conductance heat pipe header attached to the heat pipe radiator panel.

Edelstein, F.

1975-01-01

385

Ultrasensitive Human Radiation Dosimetry  

NASA Technical Reports Server (NTRS)

The problem we are addressing concerns the astronauts, and their exposure to radiation during spaceflight. The amount of this radiation is a variable depending on solar events and orbital characteristics. Our goal is to measure the total integrated quantity of radiation damage to the cell nucleus in astronauts or other people exposed to radiation. In my lab, we are turning up the microscope from the level of the chromosome, about eight orders of magnitude, to the molecular level. It is well known that radiation causes DNA and chromosome damage. We are developing methods to measure a specific molecular lesion. The lesion that we have selected to measure is thymidine diol, which is created by hydroxyl radicals adding across the 5.6 double bond of thymidine in DNA.

Hammen, Richard

1985-01-01

386

Gravitational diffraction radiation  

SciTech Connect

We show that if the visible universe is a membrane embedded in a higher-dimensional space, particles in uniform motion radiate gravitational waves because of spacetime lumpiness. This phenomenon is analogous to the electromagnetic diffraction radiation of a charge moving near to a metallic grating. In the gravitational case, the role of the metallic grating is played by the inhomogeneities of the extra-dimensional space, such as a hidden brane. We derive a general formula for gravitational diffraction radiation and apply it to a higher-dimensional scenario with flat compact extra dimensions. Gravitational diffraction radiation may carry away a significant portion of the particle's initial energy. This allows to set stringent limits on the scale of brane perturbations. Physical effects of gravitational diffraction radiation are briefly discussed.

Cardoso, Vitor; Cavaglia, Marco; Pimenta, Mario [Department of Physics and Astronomy, University of Mississippi, University, Mississippi 38677-1848 (United States); Department of Physics and Astronomy, University of Mississippi, University, Mississippi 38677-1848 (United States); Departamento de Fisica, IST, Avenida Rovisco Pais, 1049-001 Lisbon (Portugal); LIP, Avenida Elias Garcia, 14-1, 1000-149 Lisbon (Portugal)

2006-10-15

387

Chitosan and radiation chemistry  

NASA Astrophysics Data System (ADS)

Chitosan as a raw material with special properties has drawn attention of scientists working in the field of radiation processing and natural polymer products development, and also of specialists working in the field of radiation protection and oncologists. Especially the applications concern reduced molecular weight chitosan which still retain its chemical structure; such form of the compound is fostering biological, physical and chemical reactivity of the product. Chitosan degrades into fragments under ?-ray or electron beam irradiation. Antibacterial properties of the product are applied in manufacturing hydrogel for wound dressing and additional healing properties can be achieved by incorporating in the hydrogel matrix chitosan bonded silver clusters. Another possible application of chitosan is in reducing radiation damage to the radiation workers or radiation cured patients. In the case of radioisotopes oral or respiratory chitosan-based materials can be applied as chelators. Applications of chitosan in oncology are also reported.

Chmielewski, Andrzej G.

2010-03-01

388

Fundamentals of Radiation Dosimetry  

SciTech Connect

The basic concepts of radiation dosimetry are reviewed on basis of ICRU reports and text books. The radiation field is described with, among others, the particle fluence. Cross sections for indirectly ionizing radiation are defined and indicated is how they are related to the mass energy transfer and mass energy absorption coefficients. Definitions of total and restricted mass stopping powers of directly ionizing radiation are given. The dosimetric quantities, kerma, absorbed dose and exposure together with the relations between them are discussed in depth. Finally it is indicated how the absorbed dose can be measured with a calorimeter by measuring the temperature increase and with an ionisation chamber measuring the charge produced by the ionizing radiation and making use of the Bragg-Gray relation.

Bos, Adrie J. J. [Delft University of Technology, Faculty of Applied Sciences, Mekelweg 15, 2629JB Delft (Netherlands)

2011-05-05

389

Coherent curvature radiation  

NASA Astrophysics Data System (ADS)

With regard to coherent curvature radiation (CCR), calculations of the exact nature of the coherence requirements and the properties of the resulting radiation are reexamined. It is found that the general theory of CCR from plasma waves, as developed by Buscauer and Benford (1976), is correct only in the limit in which the plasma particles are stationary in the wave frame. In addition, features of their calculations, namely radiated energy which exceeds the product of the square of the number of particles times single particle radiation, as well as the feature of radiation at frequencies higher than the cutoff frequency for single particle emission, can be understood as spurious contributions originating in the boundary conditions.

Kirk, J. G.

1980-02-01

390

Nuclear radiation actuated valve  

DOEpatents

A nuclear radiation actuated valve for a nuclear reactor. The valve has a valve first part (such as a valve rod with piston) and a valve second part (such as a valve tube surrounding the valve rod, with the valve tube having side slots surrounding the piston). Both valve parts have known nuclear radiation swelling characteristics. The valve's first part is positioned to receive nuclear radiation from the nuclear reactor's fuel region. The valve's second part is positioned so that its nuclear radiation induced swelling is different from that of the valve's first part. The valve's second part also is positioned so that the valve's first and second parts create a valve orifice which changes in size due to the different nuclear radiation caused swelling of the valve's first part compared to the valve's second part. The valve may be used in a nuclear reactor's core coolant system.

Christiansen, David W. (Kennewick, WA) [Kennewick, WA; Schively, Dixon P. (Richland, WA) [Richland, WA

1985-01-01

391

Underwater radiation detector  

DOEpatents

A detector apparatus for differentiating between gamma and neutron radiation is provided. The detector includes a pair of differentially shielded Geiger-Mueller tubes. The first tube is wrapped in silver foil and the second tube is wrapped in lead foil. Both the silver and lead foils allow the passage of gamma rays at a constant rate in a gamma ray only field. When neutrons are present, however, the silver activates and emits beta radiation that is also detected by the silver wrapped Geiger-Mueller tube while the radiation detected by the lead wrapped Geiger-Mueller tube remains constant. The amount of radiation impinging on the separate Geiger-Mueller tubes is then correlated in order to distinguish between the neutron and gamma radiations.

Kruse, Lyle W. (Albuquerque, NM); McKnight, Richard P. (Albuquerque, NM)

1986-01-01

392

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...

393

Solar radiation for Mars power systems  

NASA Technical Reports Server (NTRS)

Detailed information about the solar radiation characteristics on Mars are necessary for effective design of future planned solar energy systems operating on the surface of Mars. A procedure and solar radiation related data from which the diurnally and daily variation of the global, direct (or beam), and diffuse insolation on Mars are calculated, are presented. The radiation data are based on measured optical depth of the Martian atmosphere derived from images taken of the Sun with a special diode on the Viking Lander cameras; and computation based on multiple wavelength and multiple scattering of the solar radiation.

Appelbaum, Joseph; Landis, Geoffrey A.

1991-01-01

394

Genetic effects of ionizing radiation.  

National Technical Information Service (NTIS)

Ionizing radiation effects on the gem cells, which can result in genetic abnormalities, are described. The basic mechanisms of radiation interactions with chromosomes, or specifically DNA, which can result in radiation induced mutation are discussed. Meth...

P. A. H. Saunders

1991-01-01

395

Exact solution of the problem of the diffuse reflection of solar radiation in a semi-infinite planetary atmosphere for the case of a four-term scattering phase function  

Microsoft Academic Search

An exact analytical expression is obtained for the coefficient of reflection of solar radiation from a plane-parallel semi-infinite planetary atmosphere (e.g., the Venus atmosphere) for the case of a four-term phase function. This exact solution along with the similarity relation are used to develop an approximate method for determining the intensities of diffusely reflected radiation at the upper boundary of

O. I. Smoktii

1976-01-01

396

Solar radiation on Mars: Update 1991  

NASA Technical Reports Server (NTRS)

Detailed information on solar radiation characteristics on Mars are necessary for effective design of future planned solar energy systems operating on the surface of Mars. A procedure and solar radiation related data are presented from which the daily variation of the global, direct beam and diffuse insolation on Mars are calculated. Given the optical depth of the Mars atmosphere, the global radiation is calculated from the normalized net flux function based on multiple wavelength and multiple scattering of the solar radiation. The direct beam was derived from the optical depth using Beer's law, and the diffuse component was obtained from the difference of the global and the direct beam radiation. The optical depths of the Mars atmosphere were derived from images taken of the Sun with a special diode on the cameras used on the two Viking Landers.

Appelbaum, Joseph; Landis, Geoffrey A.

1991-01-01

397

Modifying Radiation Damage  

PubMed Central

Radiation leaves a fairly characteristic footprint in biological materials, but this is rapidly all but obliterated by the canonical biological responses to the radiation damage. The innate immune recognition systems that sense “danger” through direct radiation damage and through associated collateral damage set in motion a chain of events that, in a tissue compromised by radiation, often unwittingly result in oscillating waves of molecular and cellular responses as tissues attempt to heal. Understanding “nature’s whispers” that inform on these processes will lead to novel forms of intervention targeted more precisely towards modifying them in an appropriate and timely fashion so as to improve the healing process and prevent or mitigate the development of acute and late effects of normal tissue radiation damage, whether it be accidental, as a result of a terrorist incident, or of therapeutic treatment of cancer. Here we attempt to discuss some of the non-free radical scavenging mechanisms that modify radiation responses and comment on where we see them within a conceptual framework of an evolving radiation-induced lesion.

Kim, Kwanghee; McBride, William H.

2011-01-01

398

Beneficial uses of radiation  

SciTech Connect

An overall decline in technical literacy within the American public has come at a time when technological advances are accelerating in the United States and around the world. This had led to a large communication gulf between the general public and the technologists. Nowhere is this more evident then with the topic of radiation. Regrettably, too few people know about sources of radiation, the pervasiveness, amounts, and variabilities, and do not have a true understanding of the environment in which we live. Nor do many people know that radiation has been used in beneficial ways for decades around the world. While the general public does not know of the scientific applications to which radiation has been deployed, it nevertheless had benefited tremendously from these efforts. Thanks to the well know properties of radiation, scientific ingenuity has found many uses of radiation in chemical and agricultural research, biomedical research, in the diagnoses and treatment of hundreds of types of diseases, in industrial applications, food irradiation, and many others. This paper provides a sample of the types of uses to which radiation has been used to help advance the betterment of humankind.

Fox, M.R.

1991-10-01

399

Microenvironment and Radiation Therapy  

PubMed Central

Dependency on tumor oxygenation is one of the major features of radiation therapy and this has led many radiation biologists and oncologists to focus on tumor hypoxia. The first approach to overcome tumor hypoxia was to improve tumor oxygenation by increasing oxygen delivery and a subsequent approach was the use of radiosensitizers in combination with radiation therapy. Clinical use of some of these approaches was promising, but they are not widely used due to several limitations. Hypoxia-inducible factor 1 (HIF-1) is a transcription factor that is activated by hypoxia and induces the expression of various genes related to the adaptation of cellular metabolism to hypoxia, invasion and metastasis of cancer cells and angiogenesis, and so forth. HIF-1 is a potent target to enhance the therapeutic effects of radiation therapy. Another approach is antiangiogenic therapy. The combination with radiation therapy is promising, but several factors including surrogate markers, timing and duration, and so forth have to be optimized before introducing it into clinics. In this review, we examined how the tumor microenvironment influences the effects of radiation and how we can enhance the antitumor effects of radiation therapy by modifying the tumor microenvironment.

Yoshimura, Michio; Itasaka, Satoshi; Harada, Hiroshi; Hiraoka, Masahiro

2013-01-01

400

Stimulated coherent transition radiation  

SciTech Connect

Coherent radiation emitted from a relativistic electron bunch consists of wavelengths longer than or comparable to the bunch length. The intensity of this radiation out-numbers that of its incoherent counterpart, which extends to wavelengths shorter than the bunch length, by a factor equal to the number of electrons in the bunch. In typical accelerators, this factor is about 8 to 11 orders of magnitude. The spectrum of the coherent radiation is determined by the Fourier transform of the electron bunch distribution and, therefore, contains information of the bunch distribution. Coherent transition radiation emitted from subpicosecond electron bunches at the Stanford SUNSHINE facility is observed in the far-infrared regime through a room-temperature pyroelectric bolometer and characterized through the electron bunch-length study. To measure the bunch length, a new frequency-resolved subpicosecond bunch-length measuring system is developed. This system uses a far-infrared Michelson interferometer to measure the spectrum of coherent transition radiation through optical autocorrelation with resolution far better than existing time-resolved methods. Hence, the radiation spectrum and the bunch length are deduced from the autocorrelation measurement. To study the stimulation of coherent transition radiation, a special cavity named BRAICER is invented. Far-infrared light pulses of coherent transition radiation emitted from electron bunches are delayed and circulated in the cavity to coincide with subsequent incoming electron bunches. This coincidence of light pulses with electron bunches enables the light to do work on electrons, and thus stimulates more radiated energy. The possibilities of extending the bunch-length measuring system to measure the three-dimensional bunch distribution and making the BRAICER cavity a broadband, high-intensity, coherent, far-infrared light source are also discussed.

Hung-chi Lihn

1996-03-01

401

RADIATIVE TRANSFER IN ULTRARELATIVISTIC OUTFLOWS  

SciTech Connect

Analytical and numerical solutions are obtained for the equation of radiative transfer in ultrarelativistic opaque jets. The solution describes the initial trapping of radiation, its adiabatic cooling, and the transition to transparency. Two opposite regimes are examined. (1) Matter-dominated outflow. Surprisingly, radiation develops enormous anisotropy in the fluid frame before decoupling from the fluid. The radiation is strongly polarized. (2) Radiation-dominated outflow. The transfer occurs as if radiation propagated in vacuum, preserving the angular distribution and the blackbody shape of the spectrum. The escaping radiation has a blackbody spectrum if (and only if) the outflow energy is dominated by radiation up to the photospheric radius.

Beloborodov, Andrei M., E-mail: amb@phys.columbia.edu [Physics Department and Columbia Astrophysics Laboratory, Columbia University, 538 West 120th Street New York, NY 10027 (United States)

2011-08-20

402

Human radiation tolerance  

NASA Technical Reports Server (NTRS)

The acute radiation syndrome in man is clinically bounded by death at high dose levels and by the prodromal syndrome of untoward physiological effects at minimal levels of clinically effective exposure. As in lower animals, man experiences principally three acute modes of death from radiation exposure (Bond et al., 1965). These are known collectively as the lethal radiation syndromes: central nervous system death, gastrointestinal death, and hematopoietic death. The effect of multiple exposure on lethality, the effect of multiple exposure on hematopoietic recovery, and quantitative aspects of cell and tissue repair are discussed.

Lushbaugh, C. C.

1974-01-01

403

Radiation Damage Theory  

SciTech Connect

This chapter presents an overview of basic radiation damage theory, including older and more recent models, to provide framework, within which radiation effects, such as void swelling, can be rationalized. A complete review of the literature is not attempted, but sufficient references are given to provide a decent introduction to a quite large number of publications in the field. Many derivations are different from and, in our view, more elegant than in the original publications. The work is directed to both theoreticians and experimentalists, and, especially, to those passionate individuals who are going to take the radiation damage theory (RDT) to the future.

Golubov, Stanislav I [ORNL; Barashev, Aleksandr [University of Liverpool; Stoller, Roger E [ORNL

2012-01-01

404

Radiative forcing of climate  

NASA Technical Reports Server (NTRS)

An update of the scientific discussions presented in Chapter 2 of the Intergovernmental Panel on Climate Change (IPCC) report is presented. The update discusses the atmospheric radiative and chemical species of significance for climate change. There are two major objectives of the present update. The first is an extension of the discussion on the Global Warming Potentials (GWP's), including a reevaluation in view of the updates in the lifetimes of the radiatively active species. The second important objective is to underscore major developments in the radiative forcing of climate due to the observed stratospheric ozone losses occurring between 1979 and 1990.

Ramanswamy, V.; Shine, Keith; Leovy, Conway; Wang, Wei-Chyung; Rodhe, Henning; Wuebbles, Donald J.; Ding, M.; Lelieveld, Joseph; Edmonds, Jae A.; Mccormick, M. Patrick

1991-01-01

405

Palliative radiation therapy.  

PubMed

Animal owners may be reluctant to have pets with incurable cancer subjected to euthanasia. Palliative radiation therapy may provide significant relief of pain in such pets. Palliative irradiation is comprised of a few radiation treatments, frequently given over a short time and using larger than normal fractional doses. Animals tolerate palliative irradiation well, and recent reports attest to the usefulness of palliative radiation to relieve discomfort associated with both skeletal and extraskeletal tumors. Although there is more to learn regarding the response of canine and feline tumors to palliative irradiation, it is a proven modality for relief of pain in many incurable cancer patients. PMID:8532977

Thrall, D E; LaRue, S M

1995-08-01

406

Microcircuit radiation effects databank  

NASA Technical Reports Server (NTRS)

This databank is the collation of radiation test data submitted by many testers and serves as a reference for engineers who are concerned with and have some knowledge of the effects of the natural radiation environment on microcircuits. It contains radiation sensitivity results from ground tests and is divided into two sections. Section A lists total dose damage information, and section B lists single event upset cross sections, I.E., the probability of a soft error (bit flip) or of a hard error (latchup).

1983-01-01

407

Liquid sheet radiator  

NASA Technical Reports Server (NTRS)

A new external flow radiator concept, the liquid sheet radiator (LSR), is introduced. The LSR sheet flow is described and an expression for the length/width (l/w), ratio is presented. A linear dependence of l/w on velocity is predicted that agrees with experimental results. Specific power for the LSR is calculated and is found to be nearly the same as the specific power of a liquid droplet radiator, (LDR). Several sheet thicknesses and widths were experimentally investigated. In no case was the flow found to be unstable.

Chubb, Donald L.; White, K. Alan, III

1987-01-01

408

Composition for radiation shielding  

DOEpatents

A composition for use as a radiation shield. The shield has a depleted urum core for absorbing gamma rays and a bismuth coating for preventing chemical corrosion and absorbing gamma rays. Alternatively, a sheet of gadolinium may be positioned between the uranium core and the bismuth coating for absorbing neutrons. The composition is preferably in the form of a container for storing materials that emit radiation such as gamma rays and neutrons. The container is preferably formed by casting bismuth around a pre-formed uranium container having a gadolinium sheeting, and allowing the bismuth to cool. The resulting container is a structurally sound, corrosion-resistant, radiation-absorbing container.

Kronberg, James W. (Aiken, SC)

1994-01-01

409

Miniaturized radiation chirper  

DOEpatents

The disclosure relates to a miniaturized radiation chirper for use with a small battery supplying on the order of 5 volts. A poor quality CdTe crystal which is not necessarily suitable for high resolution gamma ray spectroscopy is incorporated with appropriate electronics so that the chirper emits an audible noise at a rate that is proportional to radiation exposure level. The chirper is intended to serve as a personnel radiation warning device that utilizes new and novel electronics with a novel detector, a CdTe crystal. The resultant device is much smaller and has much longer battery life than existing chirpers.

Umbarger, C. John (Los Alamos, NM); Wolf, Michael A. (Los Alamos, NM)

1980-01-01

410

Radiation physics, biophysics, and radiation biology  

NASA Astrophysics Data System (ADS)

This annual report contains a summary of our current research. Some highlights include: experimental microdosimetry, track structure, extension of the Dual Radiation Action model to be time dependent, experiments showing that the reverse dose-rate effect for onogenic transformation, first rated for neutrons, has also been observed for charged particles of intermediate LET, an analysis of low dose-rate, research in hyperthermia, studies in molecular cloning, low dose rate studies, experimental studies on high LET, and molecular studies on DNA.

Hall, E. J.; Zaider, M.

1990-05-01

411

Tin Can Radiation Detector.  

ERIC Educational Resources Information Center

Provides instructions for making tin can radiation detectors from empty aluminum cans, aluminum foil, clear plastic, copper wire, silica gel, and fine, unwaxed dental floss put together with tape or glue. Also provides suggestions for activities using the detectors. (JN)

Crull, John L.

1986-01-01

412

Radiation Technology, Issue 6.  

National Technical Information Service (NTIS)

The publication deals with theoretical and experimental works on the nuclear-physical basis of radiation technology, isotope thermoelectric generators, equipment irradiation, pulse proton generator, nuclear methods of analysis, gamma flaw detection, radio...

1971-01-01

413

Radiation Dose Uncertainty Code.  

National Technical Information Service (NTIS)

Systems, machine readable storage, and methods for solving a respiratory tract model of radiation dosage. Steps include selecting input parameters associated with a respiratory tract model, computing a probability density function for the input parameters...

E. Houston E. B. Farfan W. E. Bolch W. E. Bolch

2003-01-01

414

Ionizing radiation detector  

DOEpatents

An ionizing radiation detector is provided which is based on the principle of analog electronic integration of radiation sensor currents in the sub-pico to nano ampere range between fixed voltage switching thresholds with automatic voltage reversal each time the appropriate threshold is reached. The thresholds are provided by a first NAND gate Schmitt trigger which is coupled with a second NAND gate Schmitt trigger operating in an alternate switching state from the first gate to turn either a visible or audible indicating device on and off in response to the gate switching rate which is indicative of the level of radiation being sensed. The detector can be configured as a small, personal radiation dosimeter which is simple to operate and responsive over a dynamic range of at least 0.01 to 1000 R/hr.

Thacker, Louis H. (Knoxville, TN)

1990-01-01

415

External Radiation Therapy  

MedlinePLUS Videos and Cool Tools

Narrator: When the cancer is not completely contained in the prostate or when the patient is older the treatment that is frequently used ... There are different forms of radiation for prostate cancer. They really boil down to two different types. ...

416

Pregnancy and Radiation Exposure  

MedlinePLUS

... Study Released . PDS on Radiation Instruments . Update of Nuclear Power Environmental Standards Upcoming Events . NRC Meeting Webcasts - ... Exposure to the Embryo or Fetus from Diagnostic Nuclear Medicine Pregnant women may be administered radioactive materials ...

417

Cataracts and avionic radiations.  

PubMed Central

Nine cases of hertzian radiation cataracts are reported among personnel working in operational aviation environments, where they were irradiated repeatedly at subliminal non-thermal field intensities. The resultant ocular pathology evolved insidiously and slowly over a period of years in a similar way to other forms of radiational injury. By the time of consultation examination, all had progressed to a relatively late state, exhibiting not only capsular cataract but also vesiculation and opacification of the proximal subcapsular lens substance. In addition to the ocular dangers of chronic exposure to nonionising radiation reference is made to the nonthermal effect or the radiation effect per se, as this could relate to general health--for example, as a possible previously unsuspected aetiological or contributory factor in many other disease processes. Images

Zaret, M M; Snyder, W Z

1977-01-01

418

Radiation Therapy (For Parents)  

MedlinePLUS

... temporary, it can be permanent. Sore Mouth and Tooth Decay The tissues of the mouth may be sore ... and there may be an increased risk of tooth decay if a child received radiation therapy to the ...

419

[Genetic effects of radiation].  

PubMed

This paper is a short review of genetic effect of radiation. This includes methods and results of a large-scale genetic study on specific loci in mice and of various studies in the offspring of atomic-bomb survivors. As for the latter, there is no results obtained which suggest the effect of parental exposure to radiation. Further, in recent years, studies are conducted to the offspring born to parents who were survivors of childhood cancers. In several reports, the mean gonad dose is quite large whereas in most instances, the results do not indicate genetic effect following parental exposure to radiation. Possible reasons for the difficulties in detecting genetic effect of radiation are discussed. PMID:22514926

Nakamura, Nori

2012-03-01

420

Radiation Therapy. Guideline Series.  

National Technical Information Service (NTIS)

Guidelines adopted by the Health Systems Agency of Southwestern Pennsylvania to facilitate the development of a radiation therapy program are presented. Using the guidelines, subarea planning councils, in collaboration with health systems agency staff, ar...

1978-01-01

421

Space radiation studies  

NASA Technical Reports Server (NTRS)

Instrument design and data analysis expertise was provided in support of several space radiation monitoring programs. The Verification of Flight Instrumentation (VFI) program at NASA included both the Active Radiation Detector (ARD) and the Nuclear Radiation Monitor (NRM). Design, partial fabrication, calibration and partial data analysis capability to the ARD program was provided, as well as detector head design and fabrication, software development and partial data analysis capability to the NRM program. The ARD flew on Spacelab-1 in 1983, performed flawlessly and was returned to MSFC after flight with unchanged calibration factors. The NRM, flown on Spacelab-2 in 1985, also performed without fault, not only recording the ambient gamma ray background on the Spacelab, but also recording radiation events of astrophysical significance.

Gregory, J. C.

1986-01-01

422

Radiation-Induced Bioradicals  

NASA Astrophysics Data System (ADS)

This chapter represents the second part of a review in which the production and application of radiation-induced radicals in biological matter are discussed. In part one the general aspects of the four stages (physical, physicochemical, chemical and biological) of interaction of radiation with matter in general and biological matter in particular, were discussed. Here an overview is presented of modem technologies and theoretical methods available for studying these radiation effects. The relevance is highlighted of electron paramagnetic resonance spectroscopy and quantum chemical calculations with respect to obtaining structural information on bioradicals, and a survey is given of the research studies in this field. We also discuss some basic aspects of modem accelerator technologies which can be used for creating radicals and we conclude with an overview of applications of radiation processing in biology and related fields such as biomedical and environmental engineering, food technology, medicine and pharmacy.

Lahorte, Philippe; Mondelaers, Wim

423

Amorphous silicon radiation detectors  

DOEpatents

Hydrogenated amorphous silicon radiation detector devices having enhanced signal are disclosed. Specifically provided are transversely oriented electrode layers and layered detector configurations of amorphous silicon, the structure of which allow high electric fields upon application of a bias thereby beneficially resulting in a reduction in noise from contact injection and an increase in signal including avalanche multiplication and gain of the signal produced by incoming high energy radiation. These enhanced radiation sensitive devices can be used as measuring and detection means for visible light, low energy photons and high energy ionizing particles such as electrons, x-rays, alpha particles, beta particles and gamma radiation. Particular utility of the device is disclosed for precision powder crystallography and biological identification.

Street, Robert A. (Palo Alto, CA); Perez-Mendez, Victor (Berkeley, CA); Kaplan, Selig N. (El Cerrito, CA)

1992-01-01

424

Radiation myelopathy: a review  

SciTech Connect

Radiation myelopathy is a serious potential complication associated with radiation therapy to the spinal cord. Its exact cause is unknown. It represents a spectrum of syndromes, the most common of which are acute transient radiation myelopathy and chronic progressive radiation myelitis. A review of the literature indicates that cord damage is related to a number of controllable factors including dose fraction size, treatment time, total dose, length of cord irradiated, technical and clerical errors. Other less well understood factors that appear to contribute to the risk such as combined chemoradiotherapy effects and hyperthermia should also be recognized. A better awareness and understanding of these factors should ultimately lead to safer and more effective treatments. 56 references.

Goldwein, J.W.

1987-01-01

425

Monte Carlo radiative transfer  

NASA Astrophysics Data System (ADS)

I outline methods for calculating the solution of Monte Carlo Radiative Transfer (MCRT) in scattering, absorption and emission processes of dust and gas, including polarization. I provide a bibliography of relevant papers on methods with astrophysical applications.

Whitney, B. A.

2011-03-01

426

Monte Carlo radiative transfer  

NASA Astrophysics Data System (ADS)

I outline methods for calculating the solution of Monte Carlo Radiative Transfer (MCRT) in scattering, absorption and emission processes of dust and gas, including polarization. I provide a bibliography of relevant papers on methods with astrophysical applications.

Whitney, Barbara A.

2011-12-01

427

Gas particle radiator  

NASA Technical Reports Server (NTRS)

A gas particle radiator adapted to operate in a microgravity space environment having a transparent boundary which transmits energy in the infrared spectrum, and a gas particle mixture that yields high absorption and emittances are described.

Chubb, Donald L. (inventor)

1988-01-01

428

EM Radiation Program  

NSDL National Science Digital Library

The EM Radiation program displays the electric field vectors (in the x-y plane) and magnetic field contours (for the field in the z direction) calculated from the Lienard-Wiechert potentials for a charged particle. The default scenario shows the resulting radiation from a charged particle in simple harmonic motion. Additional particle trajectories can be specified using the Display | Switch GUI menu item. EM Radiation is an Open Source Physics program written for the teaching of electromagnetism. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the em_radiation.jar file will run the program if Java is installed. Other electromagnetism programs are also available. They can be found by searching ComPADRE for Open Source Physics, OSP, or electromagnetism.

Christian, Wolfgang

2008-05-20

429

Amorphous silicon radiation detectors  

DOEpatents

Hydrogenated amorphous silicon radiation detector devices having enhanced signal are disclosed. Specifically provided are transversely oriented electrode layers and layered detector configurations of amorphous silicon, the structure of which allow high electric fields upon application of a bias thereby beneficially resulting in a reduction in noise from contact injection and an increase in signal including avalanche multiplication and gain of the signal produced by incoming high energy radiation. These enhanced radiation sensitive devices can be used as measuring and detection means for visible light, low energy photons and high energy ionizing particles such as electrons, x-rays, alpha particles, beta particles and gamma radiation. Particular utility of the device is disclosed for precision powder crystallography and biological identification. 13 figs.

Street, R.A.; Perez-Mendez, V.; Kaplan, S.N.

1992-11-17

430

Environmental Radiation Exposures  

Cancer.gov

Atomic Bomb Survivors Semipalatinsk Nuclear Test Site, Kazakhstan Study of Radiation Doses and Cancer Risks Resulting from the 1945 "Trinity" Atomic Weapon Test Thyroid Disease in Young Persons Near Chernobyl Techa River Print This Page Environmental

431

Brookhaven Radiation Effects Facility.  

National Technical Information Service (NTIS)

The Neutral Particle Beam (NPB) Radiation Effects Facility (REF), funded by the Strategic Defense Initiative Office (SDIO) through the Defense Nuclear Agency (DNA) and the Air Force Weapons Laboratory (AFWL), has been constructed at Brookhaven National La...

C. L. Snead P. Grand T. Ward

1988-01-01

432

Method of enhancing radiation response of radiation detection materials  

DOEpatents

The present invention is a method of increasing radiation response of a radiation detection material for a given radiation signal by first pressurizing the radiation detection material. Pressurization may be accomplished by any means including mechanical and/or hydraulic. In this application, the term "pressure" includes fluid pressure and/or mechanical stress.

Miller, Steven D. (Richland, WA) [Richland, WA

1997-01-01

433

Auditing radiation sterilization facilities  

NASA Astrophysics Data System (ADS)

The diversity of radiation sterilization systems available today places renewed emphasis on the need for thorough Quality Assurance audits of these facilities. Evaluating compliance with Good Manufacturing Practices is an obvious requirement, but an effective audit must also evaluate installation and performance qualification programs (validation_, and process control and monitoring procedures in detail. The present paper describes general standards that radiation sterilization operations should meet in each of these key areas, and provides basic guidance for conducting QA audits of these facilities.

Beck, Jeffrey A.

434

Nanocomposites for radiation sensing  

NASA Astrophysics Data System (ADS)

The use of light emitting nanoparticles in polymer and glass matrices was studied for the detection of radiation. These nanocomposite scintillators were produced by various approaches including quantum dot/polymer, fluoride nanophosphor/epoxy and halide nanophosphor containing glass-ceramic composites. The synthesis and characterization of these nanoparticles as well as their incorporation into composites is discussed. Further, the application of these composites for radiation detection and spectroscopy is described.

Wagner, Brent K.; Kang, Zhitao; Nadler, Jason; Rosson, Robert; Kahn, Bernd

2012-05-01

435

Dynamic hohlraum radiation hydrodynamics  

Microsoft Academic Search

Z-pinch dynamic hohlraums are a promising indirect-drive inertial confinement fusion approach. Comparison of multiple experimental methods with integrated Z-pinch\\/hohlraum\\/capsule computer simulations builds understanding of the hohlraum interior conditions. Time-resolved x-ray images determine the motion of the radiating shock that heats the hohlraum as it propagates toward the hohlraum axis. The images also measure the radius of radiation-driven capsules as they

J. E. Bailey; G. A. Chandler; R. C. Mancini; S. A. Slutz; G. A. Rochau; M. Bump; T. J. Buris-Mog; G. Cooper; G. Dunham; I. Golovkin; J. D. Kilkenny; P. W. Lake; R. J. Leeper; R. Lemke; J. J. Macfarlane; T. A. Mehlhorn; T. C. Moore; T. J. Nash; A. Nikroo; D. S. Nielsen; K. L. Peterson; C. L. Ruiz; D. G. Schroen; D. Steinman; W. Varnum

2006-01-01

436

Radiation environment mapping  

NASA Technical Reports Server (NTRS)

An experimental set up to map the cosmic radiation field inside the Spacelab vehicle to determine the potential biological hazards present is described. In addition to the integral linear energy transfer (LET) spectrum for protons and HZE particles, the parameters to be determined include the total radiation dose; fluence of neutrons, protons, and high charge and energy (HZE) particles. These results are to be derived from measurements made in passive dosimeters.

Benton, E. Y.

1981-01-01

437

Radiation Color Plot  

NSDL National Science Digital Library

Energy from the sun reaches the Earth and some is absorbed by the air, land, and water. Some of the energy is reflected back into space, meaning it does not heat the land, air, or water. In this lesson students will read a color plot of Earth's absorption of the sun's radiation. They will evaluate causes for difference in absorption rates at different points around the world and draw conclusions about factors effecting absorption of sun's radiation.

438

The topographic variability of solar radiation  

NASA Astrophysics Data System (ADS)

This research explores the spatial and temporal variability of incoming and net solar radiation over different topographic regions and examines the atmospheric and terrain parameters that control this variability. A twostream radiative transfer algorithm is used with digital elevation data and atmospheric optical properties to model the detailed interaction of incoming direct and diffuse solar irradiance with a reflective topographic surface. The mean, variance, and spatial autocorrelation in incoming solar radiation are compared for different regions, including the Konza Prairie, home of the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE). A simplified radiation model is used to identify the physical factors controlling differences in radiation regimes among terrain. Topography does not significantly affect the regional mean calculated over 10 x 10 sq km areas, except for the most rugged terrain. Average spatial autocorrelation in incoming radiation varies from 200 to 1200 m depending on the terrain. The radiation model is also used with LANDSAT Thematic Mapper data and digital elevation data to estimate net solar radiation across the FIFE site. Model estimates are in excellent agreement with field pyranometer measurements. Topography is the most important factor controlling the spatial variability of net solar radiation for the site. Variability in reflectance is of secondary importance. If the effects of topography on satellite reflectance and incoming irradiance are ignored, the resulting map of apparent net solar radiation shows little spatial variability and poor correlation with field measurements.

Dubayah, Ralph O.

439

Radiation associated tumors following therapeutic cranial radiation  

PubMed Central

Background: A serious, albeit rare, sequel of therapeutic ionizing radiotherapy is delayed development of a new, histologically distinct neoplasm within the radiation field. Methods: We identified 27 cases, from a 10-year period, of intracranial tumors arising after cranial irradiation. The original lesions for which cranial radiation was used for treatment included: tinea capitis (1), acute lymphoblastic leukemia (ALL; 5), sarcoma (1), scalp hemangioma (1), cranial nerve schwannoma (1) and primary (13) and metastatic (1) brain tumors, pituitary tumor (1), germinoma (1), pinealoma (1), and unknown histology (1). Dose of cranial irradiation ranged from 1800 to 6500 cGy, with a mean of 4596 cGy. Age at cranial irradiation ranged from 1 month to 43 years, with a mean of 13.4 years. Results: Latency between radiotherapy and diagnosis of a radiation-induced neoplasm ranged from 4 to 47 years (mean 18.8 years). Radiation-induced tumors included: meningiomas (14), sarcomas (7), malignant astrocytomas (4), and medulloblastomas (2). Data were analyzed to evaluate possible correlations between gender, age at irradiation, dose of irradiation, latency, use of chemotherapy, and radiation-induced neoplasm histology. Significant correlations existed between age at cranial irradiation and development of either a benign neoplasm (mean age 8.5 years) versus a malignant neoplasm (mean age 20.3; P = 0.012), and development of either a meningioma (mean age 7.0 years) or a sarcoma (mean age 27.4 years; P = 0.0001). There was also a significant positive correlation between latency and development of either a meningioma (mean latency 21.8 years) or a sarcoma (mean latency 7.7 years; P = 0.001). The correlation between dose of cranial irradiation and development of either a meningioma (mean dose 4128 cGy) or a sarcoma (mean dose 5631 cGy) approached significance (P = 0.059). Conclusions: Our study is the first to show that younger patients had a longer latency period and were more likely to have lower-grade lesions (e.g. meningiomas) as a secondary neoplasm, while older patients had a shorter latency period and were more likely to have higher-grade lesions (e.g. sarcomas).

Chowdhary, Abhineet; Spence, Alex M.; Sales, Lindsay; Rostomily, Robert C.; Rockhill, Jason K.; Silbergeld, Daniel L.

2012-01-01

440

Test problems for radiation and radiation-hydrodynamics codes  

NASA Technical Reports Server (NTRS)

A number of test problems for radiation and radiation-hydrodynamics computer codes are described. These include evolution to radiative equilibrium, cooling from radiative equilibrium, subcritical and supercritical radiating shocks, and a radiating blast wave in a power-law density distribution. For each test problem, example input parameters and plots of the results are presented. Some test problems for pure hydrodynamics are also suggested. The radiation-hydrodynamics code used to perform the example test problems and the equations it solves are described in some detail.

Ensman, Lisa

1994-01-01

441

Handbook of radiation effects  

SciTech Connect

This handbook is intended to serve as a tool for designers of equipment and scientific instruments in cases where they are required to ensure the survival of the equipment in radiation environments. High-technology materials, especially semiconductors and optics, tend to degrade on exposure to radiation in many different ways. Intense high-energy radiation environments are found in nuclear reactors and accelerators, machines for radiation therapy, industrial sterilization, and space. Some engineers have to build equipment which will survive a nuclear explosion from a hostile source. Proper handling of a disaster with radioactive materials requires equipment which depends utterly on semiconductor microelectronics and imaging devices. Thus the technology of radiation-tolerant electronics is an instrument for good social spheres as diverse as disaster planning and the exploration of Mars. In order to design equipment for intense environments like those described above, then degradation from high-energy irradiation must be seen as a basic design parameter. The aim of this handbook is to assist the engineer or student in that thought; to make it possible to write intelligent specifications; to offer some understanding of the complex variety of effects which occur when high-technology components encounter high-energy radiation; and to go thoroughly into the balance of choices of how to alleviate the effects and hence achieve the design aims of the project. Separate abstracts were prepared for 15 chapters of this book.

Holmes-Siedle, A. (ed.) (Radiation Experiments and Monitors, Oxford (United Kingdom) Univ. of West London (United Kingdom)); Adams, L. (ed.) (European Space Agency-ESTEC, Noordwijk (Netherlands). Radiation Effects and Analysis Techniques Unit)

1993-01-01

442

Packet personal radiation monitor  

DOEpatents

A personal radiation monitor of the chirper type is provided for detecting ionizing radiation. A battery powered high voltage power supply is used to generate and apply a high voltage bias to a G-M tube radiation sensor. The high voltage is monitored by a low-loss sensing network which generates a feedback signal to control the high voltage power supply such that the high voltage bias is recharged to +500 VDC when the current pulses of the sensor, generated by the detection of ionizing radiation events, discharges the high voltage bias to +450 VDC. During the high voltage recharge period an audio transducer is activated to produce an audible "chirp". The rate of the "chirps" is controlled by the rate at which the high voltage bias is recharged, which is proportional to the radiation field intensity to which the sensor is exposed. The chirp rate sensitivity is set to be approximately 1.5 (chirps/min/MR/hr.). The G-M tube sensor is used in a current sensing mode so that the device does not paralyze in a high radiation field.

Phelps, James E. (Knoxville, TN)

1989-01-01

443

ISO radiation sterilization standards  

NASA Astrophysics Data System (ADS)

This presentation provides an overview of the current status of the ISO radiation sterilization standards. The ISO standards are voluntary standards which detail both the validation and routine control of the sterilization process. ISO 11137 was approved in 1994 and published in 1995. When reviewing the standard you will note that less than 20% of the standard is devoted to requirements and the remainder is guidance on how to comply with the requirements. Future standards developments in radiation sterilization are being focused on providing additional guidance. The guidance that is currently provided in informative annexes of ISO 11137 includes: device/packaging materials, dose setting methods, and dosimeters and dose measurement, currently, there are four Technical Reports being developed to provide additional guidance: 1. AAMI Draft TIR, "Radiation Sterilization Material Qualification" 2. ISO TR 13409-1996, "Sterilization of health care products — Radiation sterilization — Substantiation of 25 kGy as a sterilization dose for small or infrequent production batches" 3. ISO Draft TR, "Sterilization of health care products — Radiation sterilization Selection of a sterilization dose for a single production batch" li]4. ISO Draft TR, "Sterilization of health care products — Radiation sterilization-Product Families, Plans for Sampling and Frequency of Dose Audits."

Lambert, Byron J.; Hansen, Joyce M.

1998-06-01

444

[Radiation myelopathy and plexopathy].  

PubMed

Radiation myelopathy (RM) is a relatively rare disorder characterized by white matter lesions of the spinal cord resulting from irradiation. It is divided into two forms by the latent periods: transient RM and delayed RM. The delayed RM develops usually non-transverse myelopathy symptoms such as dissociated sensory disturbance, unilateral leg weakness, and gait disturbance with asymmetric steps. Spinal MRI shows initially cord swelling and long T1/T2 intramedullary lesion with enhancement, then exhibits cord atrophy. Histopathological findings of delayed RM are white matter necrosis, demyelination, venous wall thickening and hyalinization. Glial theory and vascular hypothesis have been proposed to explain its pathophysiology. Several therapies such as adrenocorticosteroid, anticoagulation and hyperbaric oxygen have been tried to this disease with variable benefits. Radiation plexopathy is classified into two major types by the location: radiation-induced brachial plexopathy (BP) and radiation-induced lumbosacral plexopathy (LSP). The BP initially emerges as arm and shoulder pain, whereas LSP as leg weakness. Myokymia and fasciculations are observed in both types. Electrophysiological study reveals findings of peripheral neuropathy. It is often difficult to distinguish the radiation plexopathy from cancer invasion to the plexus, but MRI is useful to differentiate between these diseases. Pathological findings are small vessel obstruction, thick fibrosis, axonal degeneration and demyelination. Its pathomechanism is presumed that radiation-induced fibrous tissue compresses the nerve root as well as microvascular obstruction of the nerve. Adrenocorticosteroid and anticoagulation are considered as the strategy for symptomatic relief. PMID:18306658

Shimazaki, Haruo; Nakano, Imaharu

2008-02-01

445

Acute radiation syndrome caused by accidental radiation exposure - therapeutic principles  

PubMed Central

Fortunately radiation accidents are infrequent occurrences, but since they have the potential of large scale events like the nuclear accidents of Chernobyl and Fukushima, preparatory planning of the medical management of radiation accident victims is very important. Radiation accidents can result in different types of radiation exposure for which the diagnostic and therapeutic measures, as well as the outcomes, differ. The clinical course of acute radiation syndrome depends on the absorbed radiation dose and its distribution. Multi-organ-involvement and multi-organ-failure need be taken into account. The most vulnerable organ system to radiation exposure is the hematopoietic system. In addition to hematopoietic syndrome, radiation induced damage to the skin plays an important role in diagnostics and the treatment of radiation accident victims. The most important therapeutic principles with special reference to hematopoietic syndrome and cutaneous radiation syndrome are reviewed.

2011-01-01

446

Diffuse Scattering of the Conduction Electrons of a Metallic Substrate by an Adsorbate: an Experimental Study Using Synchrotron Infrared Radiation  

SciTech Connect

Due to its intrinsic high brightness, high stability, and proportionality to the stored electron beam current, synchrotrons IR spectroscopy has revealed itself as an unique tool to experimentally test a physical phenomenon occurring at metallic interfaces, the theory for which was motivated by previous observations. Any adsorbate induces inelastic scattering of the conduction electrons, which causes a broadband IR reflectance change, and was predicted to induce a concomitant DC resistivity change. By choosing a well ordered single crystal thin film of Cu(111), we have checked that the DC resistivity change, and the asymptotic limit of the IR reflectance change are linearly dependent, but independent of the nature of the adsorbate. Coadsorption experiments which have been used to modify the induced density of states at the Fermi level, have further demonstrated that the friction coefficient, which is responsible for the elastic scattering phenomenon, is chemically specific. This article describes the use of synchrotron radiation as an absolute source and its application to the study of dynamics of adsorbates on surfaces.

Hein, M.; Otto, A.; Dumas, P.; Williams, G. P.

1999-07-19

447

Development of pulse radiation antennas  

Microsoft Academic Search

In this paper, the development of pulse radiation antennas is summarized. Loaded dipole antennas, TEM horn antennas and its variations, and reflector impulse radiating antennas are discussed as the main forms of antennas which can radiate pulse. The advantages and disadvantages concernin