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1

Titan's magnetic field signature during the first Cassini encounter.  

PubMed

The magnetic field signature obtained by Cassini during its first close encounter with Titan on 26 October 2004 is presented and explained in terms of an advanced model. Titan was inside the saturnian magnetosphere. A magnetic field minimum before closest approach marked Cassini's entry into the magnetic ionopause layer. Cassini then left the northern and entered the southern magnetic tail lobe. The magnetic field before and after the encounter was approximately constant for approximately 20 Titan radii, but the field orientation changed exactly at the location of Titan's orbit. No evidence of an internal magnetic field at Titan was detected. PMID:15890875

Backes, Heiko; Neubauer, Fritz M; Dougherty, Michele K; Achilleos, Nicholas; André, Nicolas; Arridge, Christopher S; Bertucci, Cesar; Jones, Geraint H; Khurana, Krishan K; Russell, Christopher T; Wennmacher, Alexandre

2005-05-13

2

Intensity of Cavitation Damage Encountered in Field Installations.  

National Technical Information Service (NTIS)

A nomogram called Cavitation Damage Intensity Estimator is presented for estimating cavitation damage intensities of field installations. This simple approach is based on an earlier definition of cavitation damage intensity as the power absorbed per unit ...

A. Thiruvengadam

1965-01-01

3

Radiation Hardened Field Oxide.  

National Technical Information Service (NTIS)

This paper describes the development of a radiation-tolerant field oxide compatible with both MOS and bipolar technologies. Data is presented which illustrates that nonguardbanded devices utilizing conventional field oxide structures cannot be expected to...

J. R. Adams W. R. Dawes T. J. Sanders

1977-01-01

4

REVIEW: Biological effects of electromagnetic fields and radiation  

Microsoft Academic Search

There is much debate and controversy surrounding the effects of low intensity electromagnetic fields and radiation. A few subtle biological effects have been observed in experiments using animals and volunteers, but there is no convincing evidence to suggest that exposure to the fields commonly encountered in the environment will cause any significant adverse health effect in humans.

Zenon Sienkiewicz

1998-01-01

5

Gamma radiation field intensity meter  

DOEpatents

A gamma radiation intensity meter measures dose rate of a radiation field. The gamma radiation intensity meter includes a tritium battery emitting beta rays generating a current which is essentially constant. Dose rate is correlated to an amount of movement of an electroscope element charged by the tritium battery. Ionizing radiation decreases the voltage at the element and causes movement. A bleed resistor is coupled between the electroscope support element or electrode and the ionization chamber wall electrode. 4 figs.

Thacker, L.H.

1995-10-17

6

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

NASA Astrophysics Data System (ADS)

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

Morgan, W. F.

7

Small fields: Nonequilibrium radiation dosimetry  

Microsoft Academic Search

Advances in radiation treatment with beamlet-based intensity modulation, image-guided radiation therapy, and stereotactic radiosurgery (including specialized equipments like CyberKnife, Gamma Knife, tomotherapy, and high-resolution multileaf collimating systems) have resulted in the use of reduced treatment fields to a subcentimeter scale. Compared to the traditional radiotherapy with fields {>=}4x4 cm², this can result in significant uncertainty in the accuracy of clinical

Indra J. Das; George X. Ding; Anders Ahnesjö

2008-01-01

8

Small fields: Nonequilibrium radiation dosimetry  

SciTech Connect

Advances in radiation treatment with beamlet-based intensity modulation, image-guided radiation therapy, and stereotactic radiosurgery (including specialized equipments like CyberKnife, Gamma Knife, tomotherapy, and high-resolution multileaf collimating systems) have resulted in the use of reduced treatment fields to a subcentimeter scale. Compared to the traditional radiotherapy with fields {>=}4x4 cm{sup 2}, this can result in significant uncertainty in the accuracy of clinical dosimetry. The dosimetry of small fields is challenging due to nonequilibrium conditions created as a consequence of the secondary electron track lengths and the source size projected through the collimating system that are comparable to the treatment field size. It is further complicated by the prolonged electron tracks in the presence of low-density inhomogeneities. Also, radiation detectors introduced into such fields usually perturb the level of disequilibrium. Hence, the dosimetric accuracy previously achieved for standard radiotherapy applications is at risk for both absolute and relative dose determination. This article summarizes the present knowledge and gives an insight into the future procedures to handle the nonequilibrium radiation dosimetry problems. It is anticipated that new miniature detectors with controlled perturbations and corrections will be available to meet the demand for accurate measurements. It is also expected that the Monte Carlo techniques will increasingly be used in assessing the accuracy, verification, and calculation of dose, and will aid perturbation calculations of detectors used in small and highly conformal radiation beams.

Das, Indra J.; Ding, George X.; Ahnesjoe, Anders [Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States); Department of Radiation Oncology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232 (United States); Department of Oncology, Radiology and Clinical Immunology, Section of Oncology, Uppsala University, S-751 85 Uppsala and Nucletron AB, S-751 47 Uppsala (Sweden)

2008-01-15

9

Semianalytical estimates of scattering thresholds and gravitational radiation in ultrarelativistic black hole encounters  

SciTech Connect

Ultrarelativistic collisions of black holes are ideal gedanken experiments to study the nonlinearities of general relativity. In this paper we use semianalytical tools to better understand the nature of these collisions and the emitted gravitational radiation. We explain many features of the energy spectra extracted from numerical relativity simulations using two complementary semianalytical calculations. In the first calculation we estimate the radiation by a 'zero-frequency limit' analysis of the collision of two point particles with finite impact parameter. In the second calculation we replace one of the black holes by a point particle plunging with arbitrary energy and impact parameter into a Schwarzschild black hole, and we explore the multipolar structure of the radiation paying particular attention to the near-critical regime. We also use a geodesic analogy to provide qualitative estimates of the dependence of the scattering threshold on the black hole spin and on the dimensionality of the spacetime.

Berti, Emanuele [Department of Physics and Astronomy, The University of Mississippi, University, Mississippi 38677 (United States); California Institute of Technology, Pasadena, California 91109 (United States); Cardoso, Vitor [Department of Physics and Astronomy, University of Mississippi, University, Mississippi 38677 (United States); CENTRA, Departamento de Fisica, Instituto Superior Tecnico, Avenida Rovisco Pais 1, 1049 Lisboa (Portugal); Hinderer, Tanja [California Institute of Technology, Pasadena, California 91109 (United States); Lemos, Madalena [CENTRA, Departamento de Fisica, Instituto Superior Tecnico, Avenida Rovisco Pais 1, 1049 Lisboa (Portugal); Pretorius, Frans; Yunes, Nicolas [Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States); Sperhake, Ulrich [Department of Physics and Astronomy, The University of Mississippi, University, Mississippi 38677 (United States); California Institute of Technology, Pasadena, California 91109 (United States); Institut de Ciencies de l'Espai (CSIC-IEEC), Facultat de Ciencies, Campus UAB, Torre C5 parells, Bellaterra, 08193 (Spain)

2010-05-15

10

Electrifying Encounters  

NSDL National Science Digital Library

In this "electrifying encounter," fifth-grade students teamed up with elementary education students for a celebration of science and technology learning. A problem-solving-through-technology approach was used to give the preservice teachers valuable exper

Ebbers, Margaretha; Cross, Sandy

1999-09-01

11

Behavior of Loads During Voltage Dips Encountered in Stability Studies Field and Laboratory Tests  

Microsoft Academic Search

The lack of knowledge of the behavior of loads during the voltage depressions caused by faults in HV grids has been emphasized on many occasions. Field and laboratory tests were advocated for more realistic representation of loads in transient stability studies.

F. Illicico; A. Ceyhan; G. Ruckstuhl

1972-01-01

12

Gravitational radiative corrections from effective field theory  

SciTech Connect

In this paper we construct an effective field theory (EFT) that describes long wavelength gravitational radiation from compact systems. To leading order, this EFT consists of the multipole expansion, which we describe in terms of a diffeomorphism invariant point particle Lagrangian. The EFT also systematically captures 'post-Minkowskian' corrections to the multipole expansion due to nonlinear terms in general relativity. Specifically, we compute long distance corrections from the coupling of the (mass) monopole moment to the quadrupole moment, including up to two mass insertions. Along the way, we encounter both logarithmic short distance (UV) and long wavelength (IR) divergences. We show that the UV divergences can be (1) absorbed into a renormalization of the multipole moments and (2) resummed via the renormalization group. The IR singularities are shown to cancel from properly defined physical observables. As a concrete example of the formalism, we use this EFT to reproduce a number of post-Newtonian corrections to the gravitational wave energy flux from nonrelativistic binaries, including long distance effects up to 3 post-Newtonian (v{sup 6}) order. Our results verify that the factorization of scales proposed in the NRGR framework of Goldberger and Rothstein is consistent up to order 3PN.

Goldberger, Walter D.; Ross, Andreas [Department of Physics, Yale University, New Haven, Connecticut 06520 (United States)

2010-06-15

13

Chemical Processes in Astrophysical Radiation Fields  

SciTech Connect

The effects of stimulated photon emission on chemical processes in a radiation field are considered and their influence on the chemistry of the early universe and other astrophysical environments is investigated. Spontaneous and stimulated radiative attachment rate coefficients for H(-), Li(-) and C(-) are presented.

Stancil, P.C.; Dalgarno, A.

1997-12-31

14

Transient fields radiated by TEM horns  

Microsoft Academic Search

A simple theoretical model is presented whereby the TEM horn is viewed as capturing a rectangular constant-solid-angle section of an expanding spherical wave. Neglecting edge diffraction effects, this translates to a radiating magnetic current in the aperture using classical aperture antenna methods. The radiated fields at various distances are formulated in the frequency domain, and the use of Fourier superposition

L. L. Tsai; W. T. Hudson; G. Brown

1975-01-01

15

Radiation effects on current field programmable technologies  

Microsoft Academic Search

Manufacturers of field programmable gate arrays (FPGAs) take different technological and architectural approaches that directly affect radiation performance. Similar technological and architectural features are used in related technologies such as programmable substrates and quick-turn application specific integrated circuits (ASICs). After analyzing current technologies and architectures and their radiation-effects implications, this paper includes extensive test data quantifying various devices' total dose

R. Katz; K. Label; J. J. Wang; B. Cronquist; R. Koga; S. Penzin; G. Swift

1997-01-01

16

Radiation field edge detection in portal images  

Microsoft Academic Search

In fractionated radiation therapy with high energy photon beams, patient set-up is verified by analysing the position of the radiation field relative to the patient anatomy. This analysis is performed in an X-ray film, which has been exposed at the beam exit side of the patient during irradiation. Electronic portal image detectors, such as fluorescent screens, scanning diode arrays, or

J. Bijhold; K. G. A. Gilhuijs; M. van Herk; H. Meertens

1991-01-01

17

High Intensity Radiated Fields (HIRF) project plan  

NASA Astrophysics Data System (ADS)

Addressed here is the Federal Aviation Administration's approach to High Intensity Radiated Fields (HIRF) affecting the aviation community. Near- and far-term tasks are described. Deliverables, program management, scheduling, and cost issues are discussed.

Glynn, Michael S.; Blair, Jerry T.; Hintze, M. Marx

1991-09-01

18

Electromagnetic radiation field of an electron avalanche  

NASA Astrophysics Data System (ADS)

Electron avalanches are the main constituent of electrical discharges in the atmosphere. However, the electromagnetic radiation field generated by a single electron avalanche growing in different field configurations has not yet been evaluated in the literature. In this paper, the electromagnetic radiation fields created by electron avalanches were evaluated for electric fields in pointed, co-axial and spherical geometries. The results show that the radiation field has a duration of approximately 1-2 ns, with a rise time in the range of 0.25 ns. The wave-shape takes the form of an initial peak followed by an overshoot in the opposite direction. The electromagnetic spectrum generated by the avalanches has a peak around 109 Hz.

Cooray, Vernon; Cooray, Gerald

2012-11-01

19

Radiated fields from an electromagnetic pulse simulator  

NASA Astrophysics Data System (ADS)

Simulators of electromagnetic pulses allow generation within a limited time of very high-intensity fields such as those produced in a nuclear explosion. These fields can be radiated out of the test zone at a lower but nevertheless significant level; if the intensity of these fields is sufficiently high, damage to humans and electronic equipment can result. An evaluation of the potential danger of these simulator emissions requires knowledge of the amplitude, duration, and the energy of the radiated impulses. A technique is presented for calculating the fields radiated by a parallel-plane electromagnetic pulse simulator. The same method can also be applied to a rhombic type simulator. Sample numerical results are presented along with the calculations of the energy and power density and a discussion of the formation of the field in the frequency domain.

Pelletier, M.; Delisle, G. Y.; Kashyap, S.

20

Radiative processes: Potentials or Fields?  

SciTech Connect

In this work we prove that the transition amplitudes of processes involving the emission of one or more real photons is gauge invariant through terms that are always proportional to the electromagnetic field tensor.

Moreno, Matias [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Mexico, D.F. 04510 (Mexico); Lopez Castro, Gabriel [Departamento de Fisica, Centro de Investigacion y Estudios Avanzados, Mexico, D.F. (Mexico)

2010-07-29

21

Fields radiated by electrostatic discharges  

Microsoft Academic Search

Electrostatic discharge (ESD) fields are examined both analytically and experimentally. Measurements indicate that the electric fields can be quite significant (⩾150 V\\/m at a distance at 1.5 m, for example) for short periods of time (a few nanoseconds), particularly for relatively low-voltage events (⩽6 kV). A relatively simple dipole model for an ESD spark is developed and used to predict

Perry F. Wilson; M. T. Ma

1991-01-01

22

Radiation Entropy and Near-Field Thermophotovoltaics  

NASA Astrophysics Data System (ADS)

Radiation entropy was key to the original derivation of Planck's law of blackbody radiation, in 1900. This discovery opened the door to quantum mechanical theory and Planck was awarded the Nobel Prize in Physics in 1918. Thermal radiation plays an important role in incandescent lamps, solar energy utilization, temperature measurements, materials processing, remote sensing for astronomy and space exploration, combustion and furnace design, food processing, cryogenic engineering, as well as numerous agricultural, health, and military applications. While Planck's law has been fruitfully applied to a large number of engineering problems for over 100 years, questions have been raised about its limitation in micro/nano systems, especially at subwavelength distances or in the near field. When two objects are located closer than the characteristic wavelength, wave interference and photon tunneling occurs that can result in significant enhancement of the radiative transfer. Recent studies have shown that the near-field effects can realize emerging technologies, such as superlens, sub-wavelength light source, polariton-assisted nanolithography, thermophotovoltaic (TPV) systems, scanning tunneling thermal microscopy, etc. The concept of entropy has also been applied to explain laser cooling of solids as well as the second law efficiency of devices that utilize thermal radiation to produce electricity. However, little is known as regards the nature of entropy in near-field radiation. Some history and recent advances are reviewed in this presentation with a call for research of radiation entropy in the near field, due to the important applications in the optimization of thermophotovoltaic converters and in the design of practical systems that can harvest photon energies efficiently.

Zhang, Zhuomin M.

2008-08-01

23

Studies about space radiation promote new fields in radiation biology.  

PubMed

Astronauts are constantly exposed to space radiation of various types of energy with a low dose-rate during long-term stays in space. Therefore, it is important to determine correctly the biological effects of space radiation on human health. Studies about biological the effects at a low dose and a low dose-rate include various aspects of microbeams, bystander effects, radioadaptive responses and hormesis which are important fields in radiation biology. In addition, space radiations contain high linear energy transfer (LET) particles. In particular, neutrons may cause reverse effectiveness at a low dose-rate in comparison to ionizing radiation. We are also interested in p53-centered signal transduction pathways involved in the cell cycle, DNA repair and apoptosis induced by space radiations. We must also study whether the relative biological effectiveness (RBE) of space radiation is affected by microgravity which is another typical component in space. To confirm this, we must prepare centrifuge systems in an International Space Station (ISS). In addition, we must prepare many types of equipment for space experiments in an ISS, because we cannot use conventional equipment from our laboratories. Furthermore, the research for space radiation might give us valuable information about the birth and evolution of life on the Earth. We can also realize the importance of preventing the ozone layer from depletion by the use of exposure equipment to sunlight in an ISS. For these reasons, we desire to educate space researchers of the next generation based on the consideration of the preservation of the Earth from research about space radiation. PMID:12793723

Ohnishi, Takeo; Takahashi, Akihisa; Ohnishi, Ken

2002-12-01

24

Monte Carlo Simulation of the Radiation Environment Encountered by a Biochip During a Space Mission to Mars  

Microsoft Academic Search

Simulations with a Monte Carlo tool kit have been performed to determine the radiation environment a specific device, called a biochip, would face if it were placed into a rover bound to explore Mars' surface. A biochip is a miniaturized device that can be used to detect organic molecules in situ. Its specific detection part is constituted of proteins whose

A. Le Postollec; S. Incerti; M. Dobrijevic; L. Desorgher; G. Santin; P. Moretto; O. Vandenabeele-Trambouze; G. Coussot; L. Dartnell; P. Nieminen

2009-01-01

25

RADIATION DAMPING IN A GRAVITATIONAL FIELD  

Microsoft Academic Search

The validity of the principle of equivalence is examined relative to a ; charged mass point moving in an externally given gravitational field. The ; precedure is a covariant generalization of Dirac's work on the classical ; radiating electron. Just as Dirac's calculation was kept Lorentz invariant ; throughout, the present calculation is maintained generally covariant throughout. ; With the

B. S. DeWitt; R. W. Brehme

1960-01-01

26

Monte Carlo simulation of the radiation environment encountered by a biochip during a space mission to Mars.  

PubMed

Simulations with a Monte Carlo tool kit have been performed to determine the radiation environment a specific device, called a biochip, would face if it were placed into a rover bound to explore Mars' surface. A biochip is a miniaturized device that can be used to detect organic molecules in situ. Its specific detection part is constituted of proteins whose behavior under cosmic radiation is completely unknown and must be investigated to ensure a good functioning of the device under space conditions. The aim of this study is to define particle species and energy ranges that could be relevant to investigate during experiments on irradiation beam facilities. Several primary particles have been considered for galactic cosmic ray (GCR) and solar energetic particle (SEP) contributions. Ionizing doses accumulated in the biochip and differential fluxes of protons, alphas, neutrons, gammas, and electrons have been established for both the Earth-Mars transit and the journey at Mars' surface. Neutrons and gammas appear as dominant species on martian soil, whereas protons dominate during the interplanetary travel. Depending on solar event occurrence during the mission, an ionizing dose of around a few Grays (1 Gy = 100 rad) is expected. PMID:19368517

Le Postollec, A; Incerti, S; Dobrijevic, M; Desorgher, L; Santin, G; Moretto, P; Vandenabeele-Trambouze, O; Coussot, G; Dartnell, L; Nieminen, P

2009-04-01

27

The Voyager 2 Neptune encounter  

SciTech Connect

The findings made by the Voyager 2 Neptune encounter are reviewed. Data on the bowshock, magnetic field, magnetosphere, rings, plasma sheet, aurora, moons, and dust of Neptune are discussed. Findings made concerning Triton are summarized.

Tsurutani, B.T. (JPL, Pasadena, CA (USA))

1989-10-01

28

Automatic field shaping for conformal radiation therapy.  

PubMed

A computer method has been developed to shape the radiation field to conform to the shape of the target as visualized through the beam's eye view (BEV) perspective for conformal radiation therapy. Initially, a series of 2D target contours to define the target size are input into the computer. These target contour data are mapped onto a 3D surface and thereafter projected onto a BEV plane. The projection's outer boundary of the target is auto-contoured. After auto-contouring, a margin is automatically added to define the radiation beam cross section. Since the BEV plane is arbitrarily oriented about the target, the beam orientation can be non-coplanar to the plane of the target contours. For a chosen beam orientation, the conformal treatment beam cross section can be generated automatically using this computer technique and output to either a laser printer, a plotter or stored on files for transfer to the linear accelerator computer system. PMID:7924269

Ayyangar, K

1994-04-01

29

Radiation effects on current field programmable technologies  

SciTech Connect

Manufacturers of field programmable gate arrays (FPGAs) take different technological and architectural approaches that directly affect radiation performance. Similar technological and architectural features are used in related technologies such as programmable substrates and quick-turn application specific integrated circuits (ASICs). After analyzing current technologies and architectures and their radiation-effects implications, this paper includes extensive test data quantifying various devices` total dose and single event susceptibilities, including performance degradation effects and temporary or permanent re-configuration faults. Test results will concentrate on recent technologies being used in space flight electronic systems and those being developed for use in the near term. This paper will provide the first extensive study of various configuration memories used in programmable devices. Radiation performance limits and their impacts will be discussed for each design. In addition, the interplay between device scaling, process, bias voltage, design, and architecture will be explored. Lastly, areas of ongoing research will be discussed.

Katz, R.; LaBel, K. [NASA, Greenbelt, MD (United States). Goddard Space Flight Center; Wang, J.J.; Cronquist, B. [Actel Corp., Sunnyvale, CA (United States); Koga, R.; Penzin, S. [Aerospace Corp., Los Angeles, CA (United States); Swift, G. [California Inst. of Tech., Pasadena, CA (United States). Jet Propulsion Lab.

1997-12-01

30

Haemopoietic cell renewal in radiation fields  

NASA Astrophysics Data System (ADS)

Space flight activities are inevitably associated with a chronic exposure of astronauts to a complex mixture of ionising radiation. Although no acute radiation consequences are to be expected as a rule, the possibility of Solar Particle Events (SPE) associated with relatively high doses of radiation (1 or more Gray) cannot be excluded. It is the responsibility of physicians in charge of the health of astronauts to evaluate before, during and after space flight activities the functional status of haemopoietic cell renewal. Chronic low level exposure of dogs indicate that daily gamma-exposure doses below about 2 cGy are tolerated for several years as far as blood cell concentrations are concerned. However, the stem cell pool may be severely affected. The maintenance of sufficient blood cell counts is possible only through increased cell production to compensate for the radiation inflicted excess cell loss. This behaviour of haemopoietic cell renewal during chronic low level exposure can be simulated by bioengineering models of granulocytopoiesis. It is possible to define a ``turbulence region'' for cell loss rates, below which an prolonged adaptation to increased radiation fields can be expected to be tolerated. On the basis of these experimental results, it is recommended to develop new biological indicators to monitor haemopoietic cell renewal at the level of the stem cell pool using blood stem cells in addition to the determination of cytokine concentrations in the serum (and other novel approaches). To prepare for unexpected haemopoietic effects during prolonged space missions, research should be increased to modify the radiation sensitivity of haemopoietic stem cells (for instance by the application of certain regulatory molecules). In addition, a ``blood stem cell bank'' might be established for the autologous storage of stem cells and for use in space activities keeping them in a radiation protected container.

Fliedner, T. M.; Nothdurft, W.; Tibken, B.; Hofer, E.; Weiss, M.; Kindler, H.

1994-10-01

31

Electromagnetic Sounding of Titan's Interior in Search of an Ocean Using Magnetic Field Measurements During Close Encounters  

Microsoft Academic Search

One important objective of observational studies of Titan's interior is the characterization of an ammonia water ocean. Whereas the strong deviations from axissymmetry of the Jovian magnetic field can be used to electromagnetically sound the interior of the Galilean satellites of Jupiter, this technique is not available at Titan. In Titan's case an inducing field is applied to Titan's interior

F. M. Neubauer; N. Schilling; H. Backes

2003-01-01

32

Radiative processes in external gravitational fields  

SciTech Connect

Kinematically forbidden processes may be allowed in the presence of external gravitational fields. These can be taken into account by introducing generalized particle momenta. The corresponding transition probabilities can then be calculated to all orders in the metric deviation from the field-free expressions by simply replacing the particle momenta with their generalized counterparts. The procedure applies to particles of any spin and to any gravitational fields. Transition probabilities, emission power, and spectra are, to leading order, linear in the metric deviation. It is also shown how a small dissipation term in the particle wave equations can trigger a strong backreaction that introduces resonances in the radiative process and deeply affects the resulting gravitational background.

Papini, Giorgio [Department of Physics, University of Regina, Regina, Sask, S4S 0A2 (Canada); Prairie Particle Physics Institute, University of Regina, Regina, Sask, S4S 0A2 (Canada); International Institute for Advanced Scientific Studies, 89019 Vietri sul Mare (Saudi Arabia) (Italy)

2010-07-15

33

Virtual radiation fields for ALARA determination  

SciTech Connect

As computing power has increased, so too has the ability to model and simulate complex systems and processes. In addition, virtual reality technology has made it possible to visualize and understand many complex scientific and engineering problems. For this reason, a virtual dosimetry program called Virtual Radiation Fields (VRF) is developed to model radiation dose rate and cumulative dose to a receptor operating in a virtual radiation environment. With the design and testing of many facilities and products taking place in the virtual world, this program facilitates the concurrent consideration of radiological concerns during the design process. Three-dimensional (3D) graphical presentation of the radiation environment is made possible through the use of IGRIP, a graphical modeling program developed by Deneb Robotics, Inc. The VRF simulation program was designed to model and display a virtual dosimeter. As a demonstration of the program`s capability, the Hanford tank, C-106, was modeled to predict radiation doses to robotic equipment used to remove radioactive waste from the tank. To validate VRF dose predictions, comparison was made with reported values for tank C-106, which showed agreement to within 0.5%. Graphical information is presented regarding the 3D dose rate variation inside the tank. Cumulative dose predictions were made for the cleanup operations of tank C-106. A four-dimensional dose rate map generated by VRF was used to model the dose rate not only in 3D space but also as a function of the amount of waste remaining in the tank. This allowed VRF to predict dose rate at any stage in the waste removal process for an accurate simulation of the radiological conditions throughout the tank cleanup procedure.

Knight, T.W.

1995-12-31

34

Radiation reaction in strong field QED  

NASA Astrophysics Data System (ADS)

We derive radiation reaction from QED in a strong background field. We identify, in general, the diagrams and processes contributing to recoil effects in the average momentum of a scattered electron, using perturbation theory in the Furry picture: we work to lowest nontrivial order in ?. For the explicit example of scattering in a plane wave background, we compare QED with classical electrodynamics in the limit ??0, finding agreement with the Lorentz-Abraham-Dirac and Landau-Lifshitz equations, and with Larmor's formula. The first quantum corrections are also presented.

Ilderton, Anton; Torgrimsson, Greger

2013-10-01

35

Radiation Damping Partitions and RF-Fields  

SciTech Connect

In his classical paper ''Radiation Effects in Circular Accelerators'' K.W. Robinson has shown that the damping partitions in a circular machine cannot be changed by a radio-frequency field. The proof given there is quite general and valid for any RF-field, provided it is not so strong that it changes the equilibrium orbit appreciably. However, the physical mechanisms which prevent the possibility to alter the damping partitions is not very transparent. As a consequence, so-called ''damping cavities'' are still proposed from time to time. Here we want to illustrate the underlying physical principles by going in detail through the beam dynamics for the simple case of a cavity operating in a dipole (deflecting) mode and which is located in a region of finite dispersion in a storage ring.

Cornacchia, Massimo

2003-06-11

36

Reading the Other: Ethics of Encounter  

ERIC Educational Resources Information Center

|Most scholarly fields, at least in the humanities, have been asking the same questions about the politics of encounter for hundreds of years: Should we try to find a way to encounter an other without appropriating it, without imposing ourselves on it? Is encountering-without-appropriating even possible? These questions are profuse and taken up…

Allen, Sarah

2008-01-01

37

Far-Field Radiation Patterns of Terahertz Wire Waveguides  

Microsoft Academic Search

A formula for describing far-field radiation properties of metal wire waveguides is derived based on the Fresnel-Huygens diffraction theory. According to the formula, we find that the far-field patterns are the same for waveguides with different metal materials, and the amplitude of the electric field is in inverse proportion to the radiation distance. Furthermore, the far-field radiation properties versus the

Huawei Liang; Shuangchen Ruan; Min Zhang; Hong Su

2009-01-01

38

Dosimetry in radiation fields around high-energy proton accelerators  

Microsoft Academic Search

Radiation dosimetry at high-energy proton accelerators is a difficult task because of the complexity of the stray radiation field. A good knowledge of this mixed radiation field is very important to be able to select the type of detectors (active and\\/or passive) to be employed for routine area monitoring and to choose the personal dosimeter legally required for estimating the

S. Agosteo; S. Rollet; M. Silari; C. Theis

2008-01-01

39

A method for characterizing photon radiation fields  

SciTech Connect

Uncertainty in dosimetric and exposure rate measurements can increase in areas where multi-directional and low-energy photons (< 100 keV) exist because of variations in energy and angular measurement response. Also, accurate measurement of external exposures in spatially non-uniform fields may require multiple dosimetry. Therefore, knowledge of the photon fields in the workplace is required for full understanding of the accuracy of dosimeters and instruments, and for determining the need for multiple dosimeters. This project was designed to develop methods to characterize photon radiation fields in the workplace, and to test the methods in a plutonium facility. The photon field at selected work locations was characterized using TLDs and a collimated NaI(Tl) detector from which spatial variations in photon energy distributions were calculated from measured spectra. Laboratory results showed the accuracy and utility of the method. Field measurement results combined with observed work patterns suggested the following: (1) workers are exposed from all directions, but not isotropically, (2) photon energy distributions were directionally dependent, (3) stuffing nearby gloves into the glovebox reduced exposure rates significantly, (4) dosimeter placement on the front of the chest provided for a reasonable estimate of the average dose equivalent to workers` torsos, (5) justifiable conclusions regarding the need for multiple dosimetry can be made using this quantitative method, and (6) measurements of the exposure rates with ionization chambers pointed with open beta windows toward the glovebox provided the highest measured rates, although absolute accuracy of the field measurements still needs to be assessed.

Whicker, J.J.; Hsu, H.H. [Los Alamos National Lab., NM (United States); Hsieh, F.H.; Borak, T.B. [Colorado State Univ., Fort Collins, CO (United States). Dept. of Radiological Health Sciences

1999-04-01

40

Corrosion of Metals and Alloys in High Radiation Fields  

SciTech Connect

This paper rationalizes the impact of high radiation fields on corrosion, hydrogen embrittlement and corrosion fatigue and relates that impact to radiation induced changes in chemical reactivity, hydrogen fugacity, and surface chemistry.

Sindelar, R.L.

1999-11-19

41

A Radiative Parameterization of Stratocumulus Cloud Fields.  

NASA Astrophysics Data System (ADS)

A parameterization scheme is presented which allows the calculation of radiative reflected fluxes from a stratocumulus cloud field. The scheme is based upon plane-parallel calculations, such as delta-Eddington, and a simple procedure is outlined by which the plane-parallel fluxes may be transformed to those of the broken cloud case. This parameterization scheme has been tested for optical thicknesses ranging from =3 to 49, solar zenith angles ranging from 0 = 0° to 72.5°, and all values of cloud cover. Plane-parallel calculations become increasingly more accurate as optical depth decreases. This suggests that calculations including broken cloudiness effects such as shadowing are probably unnecessary in thin cirrus or aerosol layers over water.

Welch, R. M.; Wielicki, B. A.

1985-12-01

42

Electromagnetic field radiation model for lightning strokes to tall structures  

Microsoft Academic Search

This paper describes observation and analysis of electromagnetic field radiation from lightning strokes to tall structures. Electromagnetic field waveforms and current waveforms of lightning strokes to the CN Tower have been simultaneously measured since 1991. A new calculation model of electromagnetic field radiation is proposed. The proposed model consists of the lightning current propagation and distribution model and the electromagnetic

H. Motoyama; W. Janischewskyj; A. M. Hussein; W. A. Chisholm; J. S. Chang; R. Rusan

1996-01-01

43

The measurement of transient electromagnetic field radiated by electrostatic discharge  

Microsoft Academic Search

With the rapid development of the electronics industry the threat of fields radiated by electrostatic discharge (ESD) to electronic equipment is becoming more and more dangerous. A custom short monopole antenna and test method to measure the ESD electric field is presented. A series of tests of the electric field radiated by real human body ESD have explicitly revealed how

Jiusheng Huang; Bei Yuan Da Yuan

1999-01-01

44

Non-radiating monochromatic sources and their fields  

Microsoft Academic Search

A new theorem is derived from which a number of previously known results relating to non-radiating monochromatic sources readily follow. Expressions are also obtained for the field within any non-radiating spherically symmetric source. As an example explicit expressions are found for the field within non-radiating homogeneous spherical sources and curves are presented which show the behavior of the field in

Kisik Kim; Emil Wolf

1986-01-01

45

Radiation and Scattering from Large Polygonal Cylinders, Transverse Electric Fields.  

National Technical Information Service (NTIS)

The report deals with the computation of radiation and scattering of electromagnetic fields by electrically large convex conducting cylinders. A general computer program is developed for the case of transverse electric fields using the geometrical theory ...

J. R. Mautz R. F. Harrington

1975-01-01

46

Transient Radiated Fields from Sources Located on a Planar Surface.  

National Technical Information Service (NTIS)

Expressions for the transient radiated electric fields of a planar array of sources are developed for elements having known field distribution, as well as time delay, located on an infinite, perfectly conducting, ground plane. The analysis of such arrays ...

C. E. Smith

1977-01-01

47

Examination of MARINER-10 Magnetic Field Data for Heavy Ion Signatures During the Mercury I and III Encounters by Mariner-10  

NASA Astrophysics Data System (ADS)

From the Mariner-10 flybs of Mercury in the mid 1970s it was discovered that Mercury had a small intrinsic magnetic field and as a result a small magnetosphere with a standoff distance of ~1.5 Mercury Radii. In the mid 1980s it was discovered telescopically that Mercury has a strong but highly variable heavy ion exosphere of Na, K and Ca, with Na being the dominant species of the heavy ions. Some of these heavy ions are ionized through photo-ionization, directly from ion sputtering, and through charge exchange with solar wind and magnetosphere protons and He+. The questions arises to what extent can these ions be retained by Mercury's small magnetosphere and can they play a role in the plasma physics of this system? What wave-particle interactions are necessary for their thermalization? How cold do the heavy ions have to be in order to be retained in Mercury's magnetosphere? To investigate these questions we will examine the Mariner 10 magnetic field data for heavy ion signatures or lack of during its two brief encounters with Mercury's magnetosheath/magnetosphere.

Boardsen, S. A.; Slavin, J. A.

2006-12-01

48

Radiation Entropy and Near-Field Thermophotovoltaics  

Microsoft Academic Search

Radiation entropy was key to the original derivation of Planck's law of blackbody radiation, in 1900. This discovery opened the door to quantum mechanical theory and Planck was awarded the Nobel Prize in Physics in 1918. Thermal radiation plays an important role in incandescent lamps, solar energy utilization, temperature measurements, materials processing, remote sensing for astronomy and space exploration, combustion

Zhuomin M. Zhang

2008-01-01

49

The Mariner 10 Venus encounter - A review  

Microsoft Academic Search

A brief description is given of the Mariner 10 spacecraft, its complement of scientific instruments, and its encounter with Venus. It is noted that the geometry of the Venus encounter was dictated entirely by the necessity to use Venus' gravitational field to deflect the flight path toward Mercury. Results discussed include observations of plasma and magnetic-field perturbations several hundreds of

J. A. Dunne

1975-01-01

50

Radiational polarization of electrons in inhomogeneous magnetic field  

Microsoft Academic Search

The process of polarization of electrons due to radiation in an inhomogeneous magnetic field has been considered by means of operator formulation of quasiclassical approximation. A general expression for the probability of a spin-flip radiational transition in an arbitrary magnetic field has been obtained.

V. N. Baier; V. M. Katkov

1967-01-01

51

Radiation effects on fluorinated field oxides and associated devices  

Microsoft Academic Search

Fluorine has been introduced into the LOCOS field oxide by high-energy (2-MeV) F implantation and subsequent annealing at 950°C for 60 min. Improved radiation hardness of the field oxide and its associated device parameters was observed. N-channel MOSFETs isolated by the fluorinated oxide exhibit a lower radiation-induced source-drain leakage current. This is attributed to the smaller density of radiation-induced positive

Yasushiro Nishioka; Toshiyuki Itoga; Kiyonori Ohyu; Masataka Kato; Tso-Ping Ma

1990-01-01

52

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

NASA Astrophysics Data System (ADS)

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

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

1990-08-01

53

Smart Weapons Encounter Model.  

National Technical Information Service (NTIS)

This report covers the Smart Weapon Encounter Model (SWEM) developed to support the Tank Extended Range Munition (TERM) science and technology objective (STO) III G.3. The report describes the model's algorithm, input, and Output. SWEM uses solid geometry...

R. J. Pearson K. K. Chien

2000-01-01

54

COHERENT AND INCOHERENT STATES OF THE RADIATION FIELD  

Microsoft Academic Search

Methods are developed for discussing the photon statistics of arbitrary ; radiation fields in fully quantummechanical terms. In order to keep the ; classical limit of quantum electrodynamics plainly in view, extensive use is made ; of the coherent states of the field. These states, which reduce the field ; correlation functions to factorized forms, are shown to offer a

Roy Glauber

1963-01-01

55

Stretched exponential survival statistics for microorganisms in radiation field  

NASA Astrophysics Data System (ADS)

The so-called concave or tailed survival curves are reported both for multi and single species bacterial populations. Taking as an example Bacillus pumilus, frequently encountered in decontamination studies, it is shown that the tailed survival curves are adequately described by stretched (0radiation sensivity distribution for single species population under the given experimental conditions.

Plonka, A.; Bogus, W.

1999-11-01

56

Wireless Phones Electromagnetic Field Radiation Exposure Assessment  

Microsoft Academic Search

Problem statement: Inadequate knowledge of electromagnetic field emit ted by mobile phones and increased usage at close proximity, crea ted a lot of skepticism and speculations among end users on its safety or otherwise. Approach: In this study, near field electromagnetic field ra diation measurements were conducted on different brand of mobile phones in active mode using a tri-axis isotropic

A. D. Usman; W. F. Wan Ahmad; Ab Kadir; M. Mokhtar

2009-01-01

57

The Electromagnetic Dipole Radiation Field through the Hamiltonian Approach  

ERIC Educational Resources Information Center

|The dipole radiation from an oscillating charge is treated using the Hamiltonian approach to electrodynamics where the concept of cavity modes plays a central role. We show that the calculation of the radiation field can be obtained in a closed form within this approach by emphasizing the role of coherence between the cavity modes, which is…

Likar, A.; Razpet, N.

2009-01-01

58

The Electromagnetic Dipole Radiation Field through the Hamiltonian Approach  

ERIC Educational Resources Information Center

The dipole radiation from an oscillating charge is treated using the Hamiltonian approach to electrodynamics where the concept of cavity modes plays a central role. We show that the calculation of the radiation field can be obtained in a closed form within this approach by emphasizing the role of coherence between the cavity modes, which is…

Likar, A.; Razpet, N.

2009-01-01

59

Device for remote viewing of objects in ionizing radiation fields  

Microsoft Academic Search

A device is described for remote viewing of objects in ionizing radiation fields, wherein a fibre-optics channel for transmitting the image of an object under observation beyond the biological shield against ionizing radiation comprises an entrance lens in whose immediate vicinity there is placed one of the ends of a bundle of optic fibres, the other end of the bundle

B. I. Ivanov; N. M. Ivanov; I. K. Malakhov; J. D. Motin; I. A. Reformatsky; P. R. Sinitsyn

1980-01-01

60

Radiative Coupled Nonequilibrium Flow Fields Associated with Aeroassisted Orbital Transfer.  

National Technical Information Service (NTIS)

Development of an algorithm which will allow nonequilibrium flow field codes to be coupled to radiative transfer codes (currently limited to equilibrium applications) was initiated. The algorithm consists of an equation for the prediction of electronic st...

T. E. Horton

1986-01-01

61

Novel Properties of the Q-Analogue Quantized Radiation Field.  

National Technical Information Service (NTIS)

The 'classical limit' of the q-analog quantized radiation field is studied paralleling conventional quantum optics analyses. The q-generalizations of the phase operator of Susskind and Glogower and that of Pegg and Barnett are constructed. Both generaliza...

C. A. Nelson

1993-01-01

62

Fiber optics in transient radiation fields  

SciTech Connect

Fiber optics have been utilized in a variety of sensor and data transmission roles, some of which are complicated by the presence of ionizing radiation. In this paper, transient radiation effects in fibers are reviewed. Both luminescence and absorption processes are discussed in this paper, with emphasis on the latter subject. Most discussions are on effects occurring below 100 ns, with limited data in the microsecond time regime. This paper is intended as a review paper and its scope is restricted to previously published work. Areas that will profit from further study are highlighted.

Lyons, P.B.

1985-01-01

63

Reconstruction of radiating sound fields using minimum energy method.  

PubMed

A method for reconstructing a pressure field at the surface of a radiating body or source is presented using recording data of a microphone array. The radiation is assumed to consist of many spherical radiators, as microphone positions are present in the array. These monopoles are weighted using a parameter alpha, which broadens or narrows the overall radiation directivity as an effective and highly intuitive parameter of the radiation characteristics. A radiation matrix is built out of these weighted monopole radiators, and for different assumed values of alpha, a linear equation solver reconstructs the pressure field at the body's surface. It appears that from these many arbitrary reconstructions, the correct one minimizes the reconstruction energy. The method is tested, localizing the radiation points of a Balinese suling flute, reconstructing complex radiation from a duff frame drum, and determining the radiation directivity for the first seven modes of an Usbek tambourine. Stability in terms of measurement noise is demonstrated for the plain method, and additional highly effective algorithm is added for a noise level up to 0 dB. The stability of alpha in terms of minimal reconstruction energy is shown over the whole range of possible values for alpha. Additionally, the treatment of unwanted room reflections is discussed, still leading to satisfactory results in many cases. PMID:20058977

Bader, Rolf

2010-01-01

64

The electromagnetic field of receding radiation sources  

Microsoft Academic Search

Contents Some of the radiation characteristics of a receding electric dipole and those of a receding magnetic dipole are analyzed-in particular the attendant effects of frequency variation and phase aberration. The basic results implied by the transformation properties of the Hertz and Fitzgerald tensors seem to facilitate the analysis and broaden insight into the kinematic as well as into the

D. Schieber

1995-01-01

65

Tracking and Radiation Field Measurement with Pixel Detectors  

NASA Astrophysics Data System (ADS)

Continuous advances in the miniaturization of semiconductor technology allow nowadays fabrication of devices with performance exceeding the photographic techniques (nuclear emulsion). Single particle counting pixellated detectors open up a whole new field of possibilities in real-time detection and visualization of radiation and understanding its interaction in matter. Pixel detectors allows to visualize directly the ionization paths of different types of radiation, with additional energy and time information, even at very low fluxes which can be used for reconstruction of the incident radiation field.

Vykydal, Zdenek; Granja, Carlos; Jakubek, Jan; Platkevic, Michal; Pospisil, Stanislav

2010-01-01

66

The galileo venus encounter.  

PubMed

The Galileo spacecraft passed Venus on its way to Jupiter on 10 February 1990, less than 4 months after launch from Earth aboard the shuttle Atlantis. Because Galileo's instruments were selected for broad-based planetary exploration, the spacecraft was able to obtain a wide range of measurements during the Venus encounter. Together with ground-based observations conducted during the encounter, these observations have yielded more accurate information about the planet's plasma environment, cloud patterns, and the possible existence of lightning. PMID:17784091

Johnson, T V; Yeates, C M; Young, R; Dunne, J

1991-09-27

67

Asymptotic Radiation Field of Asymmetric Planar Dielectric Waveguide  

Microsoft Academic Search

Abstract—This paper describes the steepest-descent evaluation of the radiation field for both TE and TM modes of an asymmetric planar open waveguide. The cover, film and substrate field will be formulated in the spectral domain. The steepest-descent path in the complex axial transform plane (?-plane) is identified as a direct method and that in the complex ?-plane (? = ?

J.-S. Lee; D. P. Nyquist

2003-01-01

68

Field distribution in a generalized geometric radiation state  

NASA Astrophysics Data System (ADS)

Both the Wigner function and the field distribution function in the generalized geometric state of the radiation field, which were recently introduced by us [A.-S. F. Obada, S. S. Hassan, R. R. Puri, and M. S. Abdalla, Phys. Rev. A 48, 3174 (1993)], are calculated exactly and examined in both the phase-averaged and the nonaveraged cases.

Batarfi, H. A.; Abdalla, M. Sebawe; Obada, A.-S. F.; Hassan, S. S.

1995-03-01

69

Electromagnetic Field Radiation of Mobile Phone Inside Metallic Enclosure  

Microsoft Academic Search

A numerical study on the electromagnetic (EM) Held radiation of mobile phone inside metallic enclosure, for human safety aspect, is presented in this paper. The study on the effects of number of human bodies and their positions inside the metallic enclosure on the induced E-field was carried out. Results have shown that the E-field induced on the human head of

C. K. Tang; L. C. Fung; S. W. Leung

2007-01-01

70

Visual verification of linac light and radiation fields coincidence  

SciTech Connect

X-ray and light field alignment evaluation is carried out during linac quality assurance programs. In this paper, we compare the size of the light field measured by a photodiode and by a more traditional visual observation with the size of the x-ray field. The comparison between actual light field size, measured with the photodiode, and light field size measured by human eye allow us to verify the reliability of human eye in the evaluation of this parameter. The visual field is always larger than real light field; however, it agrees better with the x-ray field. It matches the light field if we take into account the 25% ({+-} 1%) of the decrement line of the maximum central lightening; however, this method simulates better the actual field employed in radiation treatments.

Monti, Angelo F.; Frigerio, Milena; Frigerio, Giovanna

2003-06-30

71

Radiative transfer in very strong magnetic fields  

NASA Astrophysics Data System (ADS)

The study of the cooling of neutron stars has been undertaken by many researchers in the past twenty-five years, but this study has been made difficult by the inherent theoretical and observational uncertainties; most observations of their thermal X-ray flux have yielded only upper limits. More sensitive satellites such as ROSAT and AXAF may provide more positive flux information, and it is important to know how to interpret these data in terms of surface temperature. One of the most important factors in this interpretation is the effect of the surface magnetic field.Young neutron stars are believed to have extremely strong magnetic fields, on the order of 10(12)G. These fields dominate the physics of the atmosphere. In particular, atoms in the atmospheres of neutron stars have much greater binding energies than in the zero-field case, and they are constrained to move along the field lines. We use a multiconfigurational Hartree-Fock code, modified for very strong magnetic fields, to calculate wavefunctions, energies and oscillator strengths for several atoms in representative values of the magnetic field.We then use these simulations to construct model atmospheres for neutron stars. Because of the low mass necessary for optical depth unity in the soft X-rays (typically [...]) and because of the short time scale for gravitational separation (~ 1 - 100s), the photosphere is likely to consist of a pure element. Numerous processes could cause many elements to be important, so we investigate atmospheres consisting of pure hydrogen, helium, carbon, nitrogen and silicon in magnetic fields of 9.4 x 10(11)G, 2.35 x 10(12)G, and 4.7 x 10(12)G.We also use the high-field energies to investigate soft X-ray lines in gamma-ray bursts. Highly ionized elements could create absorption lines in the 1-15keV range, and the identification of such lines in conjunction with cyclotron lines would determine the magnetic field and gravitational redshift on the surface of the star, which would provide clues to the equation of state on the interior. We conclude with a discussion of the prospect of identifying these lines with future satellites.

Miller, Michael Coleman

72

Corrosion of metals and alloys in high radiation fields  

SciTech Connect

Degradation in the properties of structural materials in high-energy proton accelerators will occur as a result of the radiation environment during routine accelerator operations. The potential for such degradation must be included in design and service life assessments of the materials and components. Structural materials in the window, target/blanket, and reflector regions of high-energy proton accelerators will be exposed to a mixed proton-neutron flux that will change the material's exposure environment and cause displacement damage and implant spallation products in the exposed metal. The effects of implantation and displacement damage on materials behavior have been studied on a more or less continuous basis for decades, while radiation effects on corrosion and corrosion related degradation processes has received relatively little attention. The high radiation fields will accelerate corrosion, enhance hydrogen uptake and permeation, and promote corrosion fatigue through environmental changes induced by radiolysis and the deposition of spallation products. Aluminum alloys are particularly susceptible to radiation-induced acceleration of corrosion, and may experience a decreased resistance to fatigue damage. The irradiation fields and the (n, p) reactions associated with tritium production will enhance the uptake and permeation of tritium through austenitic stainless. These radiation-induced effects must be considered in any realistic assessment of material performance in the APT target/blanket region. This paper rationalizes the impact of high radiation fields on corrosion, hydrogen embrittlement, and corrosion fatigue, and relates that impact to radiation-induced changes in chemical reactivity, hydrogen fugacity, and surface chemistry.

Sindelar, R.L.; Lam, P.S.; Louthan, M.R. Jr.; Iyer, N.C.

1999-09-01

73

Spontaneous Radiation Emission from Short, High Field Strength Insertion Devices  

SciTech Connect

Since the earliest papers on undulaters were published, it has been known how to calculate the spontaneous emission spectrum from ''short'' undulaters when the magnetic field strength parameter is small compared to unity, or in ''single'' frequency sinusoidal undulaters where the magnetic field strength parameter is comparable to or larger than unity, but where the magnetic field amplitude is constant throughout the undulater. Fewer general results have been obtained in the case where the insertion device is both short, i.e., the magnetic field strength parameter changes appreciably throughout the insertion device, and the magnetic field strength is high enough that ponderomotive effects, radiation retardation, and harmonic generation are important physical phenomena. In this paper a general method is presented for calculating the radiation spectrum for short, high-field insertion devices. It is used to calculate the emission from some insertion device designs of recent interest.

Geoffrey Krafft

2005-09-15

74

Field Testing of a Portable Radiation Detector and Mapping System  

SciTech Connect

Researchers at the Savannah River Site (SRS) have developed a man- portable radiation detector and mapping system (RADMAPS) which integrates the accumulation of radiation information with precise ground locations. RADMAPS provides field personnel with the ability to detect, locate, and characterize nuclear material at a site or facility by analyzing the gamma or neutron spectra and correlating them with position. the man-portable field unit records gamma or neutron count rate information and its location, along with date and time, using an embedded Global Positioning System (GPS). RADMAPS is an advancement in data fusion, integrating several off-the-shelf technologies with new computer software resulting in a system that is simple to deploy and provides information useful to field personnel in an easily understandable form. Decisions on subsequent actions can be made in the field to efficiently use available field resources. The technologies employed in this system include: recording GPS, radiation detection (typically scintillation detectors), pulse height analysis, analog-to-digital converters, removable solid-state (Flash or SRAM) memory cards, Geographic Information System (GIS) software and personal computers with CD-ROM supporting digital base maps. RADMAPS includes several field deployable data acquisition systems designed to simultaneously record radiation and geographic positions. This paper summarizes the capabilities of RADMAPS and some of the results of field tests performed with the system.

Hofstetter, K.J. [Westinghouse Savannah River Company, AIKEN, SC (United States); Hayes, D.W.; Eakle, R.F.

1998-03-01

75

Encounters with Protostellar Disks  

NASA Astrophysics Data System (ADS)

A numerical study of encounters between stars with circumstellar disks has bee completed. Cross sections and rates for disk tilt, disk disruption, and binary formation are estimated using a large data base of encounter simulations. The consequences of these results for star-forming regions and our solar system are discussed. A numerical code is developed which is capable of evolving a mixture of stars and gas in three dimensions. The algorithm is based on the method of smoothed-particle hydrodynamics combined with the heirarchical tree method of computing gravitational forces. The code is tested by simulating the collision between two sheets of gas and the radial pulsations of a polytropic gas sphere. A protostellar-disk model is developed based on simple assumptions. Test encounters are performed to determine the sensitivity of measured quantities on algorithm parameters, such as the gravitational tolerance and viscosity. It is shown that the solar system could have had an encounter shortly after its formation of sufficient strength to generate the observed obliquity yet retain enough mass and radial extent to form the planetary system. For the Orion B clusters as a whole, it is estimated that during a one-million-year period of time a few percent of the stars will experience an enoucnter that results in a disk tilt of 7 degrees or greater. For the central regions of NGC 2024 and the Trapezium cluster values of 24% and 39% are obtained, respectively. Encounters between equal-mass stars with periastra of 0.5, 1.0, 1.5, and 2.0 disk radii will retain on average about 15%, 40%, 55%, and 75% of the disk mass, respectively. For encounters that do not penetrate the disk a minimum of 15% of the mass is retained. Even in dense environments the characteristic lifetime of a disk due to disruptive encounters can be many millions of years. On average, an encounter that penetrates the disk will dissipate an amount of orbital energy equal to approximately 50% of the initial binding energy of the disk. For the central region of NGC 2024 a star-disk capture rate is estimated at Gamma_c=0.03 and 0.07 Myr^-1 for disk masses of 0.1 and 0.5 solar mass, respectively. The equivalent disk-disk capture rates are >=0.05 and 0.08 Myr^-1. The most favorable rate implies that during a 1-Myr period of time 16% of the stars will be captured into a binary. These rates are lower limits because of factors such as higher stellar densities in the past due to cluster expansion, the presence of substructure, and the existence of binary and higher-order systems. In particular, encounters may be a natural outcome of the star-formation process, at a time when protostars are surrounded by large massive disks and extended envelopes of material. (SECTION: Dissertation Abstracts)

Heller, Clayton H.

1992-12-01

76

Fields radiated by a nanoemitter in a graphene sheet  

NASA Astrophysics Data System (ADS)

The extraordinary properties of graphene make it a very promising material for optoelectronics. However, basic attributes of the electromagnetic field in graphene are still unexplored. Here we report on the in-plane fields radiated by a nanoemitter lying on a graphene sheet in terahertz regime, which present a rich dependence on frequency, distance to the source, and orientation of the dipole moment. The field pattern is mainly composed of a core region, dominated by surface plasmons, where the electric field can be several orders of magnitude larger than in vacuum, and an outer region where the field is virtually the same as what it would be in vacuum.

Nikitin, A. Yu.; Guinea, F.; Garcia-Vidal, F. J.; Martin-Moreno, L.

2011-11-01

77

IAEA programme in the field of radiation technology  

Microsoft Academic Search

Radiation technologies applying gamma sources and electron accelerators for material modification are well-established processes. There are over 160 gamma industrial irradiators and 1300 electron industrial accelerators in operation worldwide. A new advancement in the field of radiation sources engineering is the development of high power direct e?\\/X conversion sources based on electron accelerators.Technologies to be developed beside environmental applications could

Andrzej G. Chmielewski; Mohammad Haji-Saeid

2005-01-01

78

Petrov type D pure radiation fields of Kundt's class  

NASA Astrophysics Data System (ADS)

We present all Petrov type D pure radiation space-times, with or without cosmological constant, with a shear-free, nondiverging geodesic principal null congruence. We thus completely solve the problem of aligned Petrov type D pure radiation fields: either these are Robinson-Trautman space-times and are all explicitly known or they belong to the Kundt family, for which so far only isolated examples existed in the literature.

de Groote, Liselotte; van den Bergh, Norbert; Wylleman, Lode

2010-10-01

79

Synchrotron radiation in strongly coupled conformal field theories  

SciTech Connect

Using gauge/gravity duality, we compute the energy density and angular distribution of the power radiated by a quark undergoing circular motion in strongly coupled N=4 supersymmetric Yang-Mills theory. We compare the strong coupling results to those at weak coupling, finding them to be very similar. In both regimes, the angular distribution of the radiated power is in fact similar to that of synchrotron radiation produced by an electron in circular motion in classical electrodynamics: the quark emits radiation in a narrow beam along its velocity vector with a characteristic opening angle {alpha}{approx}1/{gamma}. To an observer far away from the quark, the emitted radiation appears as a short periodic burst, just like the light from a lighthouse does to a ship at sea. Our strong coupling results are valid for any strongly coupled conformal field theory with a dual classical gravity description.

Athanasiou, Christiana; Chesler, Paul M.; Liu, Hong; Rajagopal, Krishna [Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Nickel, Dominik [Institute for Nuclear Theory, University of Washington, Seattle, Washington 98195 (United States)

2010-06-15

80

Synchrotron radiation in strongly coupled conformal field theories  

NASA Astrophysics Data System (ADS)

Using gauge/gravity duality, we compute the energy density and angular distribution of the power radiated by a quark undergoing circular motion in strongly coupled N=4 supersymmetric Yang-Mills theory. We compare the strong coupling results to those at weak coupling, finding them to be very similar. In both regimes, the angular distribution of the radiated power is in fact similar to that of synchrotron radiation produced by an electron in circular motion in classical electrodynamics: the quark emits radiation in a narrow beam along its velocity vector with a characteristic opening angle ?˜1/?. To an observer far away from the quark, the emitted radiation appears as a short periodic burst, just like the light from a lighthouse does to a ship at sea. Our strong coupling results are valid for any strongly coupled conformal field theory with a dual classical gravity description.

Athanasiou, Christiana; Chesler, Paul M.; Liu, Hong; Nickel, Dominik; Rajagopal, Krishna

2010-06-01

81

Stellar encounters: a stimulus for disc fragmentation?  

NASA Astrophysics Data System (ADS)

An interaction between a star-disc system and another star will perturb the disc, possibly resulting in a significant modification of the disc structure and its properties. It is still unclear if such an encounter can trigger fragmentation of the disc to form brown dwarfs or gas giant planets. This paper details high-resolution smoothed particle hydrodynamics (SPH) simulations investigating the influence of stellar encounters on disc dynamics. Star-star encounters (where the primary has a self-gravitating, marginally stable protostellar disc, and the secondary has no disc) were simulated with various orbital parameters to investigate the resulting disc structure and dynamics. This work is the first of its kind to incorporate realistic radiative transfer techniques to realistically model the resulting thermodynamics. The results suggest that the effect of stellar encounters is to prohibit fragmentation - compressive and shock heating stabilizes the disc, and the radiative cooling is insufficient to trigger gravitational instability. The encounter strips the outer regions of the disc (either through tidal tails or by capture of matter to form a disc around the secondary), which triggers a readjustment of the primary disc to a steeper surface density profile (and a flatter Toomre Q profile). The disc around the secondary plays a role in the potential capture of the secondary to form a binary. However, this applies only to orbits that are parabolic - hyperbolic encounters do not form a secondary disc, and are not captured.

Forgan, Duncan; Rice, Ken

2009-12-01

82

Radiation of Electron in the Field of Plane Light Wave  

SciTech Connect

Results of integration of a Lorentz equation for a relativistic electron moving in the field of running, plane, linear polarized electromagnetic wave are presented in the paper. It is shown that electron velocities in the field of the wave are almost periodic functions of time. For calculations of angular spectrum of electron radiation intensity expansion of the electromagnetic field in a wave zone into generalized Fourier series was used. Expressions for the radiation intensity spectrum are presented in the paper. Derived results are illustrated for electron and laser beam parameters of NSC KIPT X-ray generator NESTOR. It is shown that for low intensity of the interacting electromagnetic wave the results of energy and angular spectrum calculations in the frame of classical electrodynamics completely coincide with calculation results produced using quantum electrodynamics. Simultaneously, derived expressions give possibilities to investigate dependence of energy and angular Compton radiation spectrum on phase of interaction and the interacting wave intensity.

Zelinsky, A.; Drebot, I.V.; Grigorev, Yu.N.; Zvonareva, O.D.; /Kharkov, KIPT; Tatchyn, R.; /SLAC

2006-02-24

83

Stability of the Toroidal Magnetic Field in Stellar Radiation Zones  

NASA Astrophysics Data System (ADS)

The stability of the magnetic field in radiation zones is of crucial importance for mixing, angular momentum transport, etc. We consider the stability properties of a star containing a predominant toroidal field in spherical geometry by means of a linear stability in the Boussinesq approximation taking into account the effect of thermal conductivity. We calculate the growth rate of instability and analyze in detail the effects of stable stratification and heat transport. We argue that the stabilizing influence of gravity can never entirely suppress the instability caused by electric currents in radiation zones. However, the stable stratification can essentially decrease the growth rate of instability

Bonanno, Alfio; Urpin, Vadim

2012-03-01

84

STABILITY OF THE TOROIDAL MAGNETIC FIELD IN STELLAR RADIATION ZONES  

SciTech Connect

The stability of the magnetic field in radiation zones is of crucial importance for mixing, angular momentum transport, etc. We consider the stability properties of a star containing a predominant toroidal field in spherical geometry by means of a linear stability in the Boussinesq approximation taking into account the effect of thermal conductivity. We calculate the growth rate of instability and analyze in detail the effects of stable stratification and heat transport. We argue that the stabilizing influence of gravity can never entirely suppress the instability caused by electric currents in radiation zones. However, the stable stratification can essentially decrease the growth rate of instability.

Bonanno, Alfio [INAF, Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania (Italy); Urpin, Vadim, E-mail: alfio.bonanno@inaf.it, E-mail: vadim.urpin@uv.es [INFN, Sezione di Catania, Via S. Sofia 72, 95123 Catania (Italy)

2012-03-10

85

Characterization of a CT ionization chamber for radiation field mapping.  

PubMed

A pencil-type ionization chamber, developed at Instituto de Pesquisas Energéticas e Nucleares (IPEN), was characterized with the objective to verify the possibility of its application in radiation field mapping procedures. The characterization tests were evaluated, and the results were satisfactory. The results obtained for the X radiation field mapping with the homemade chamber were compared with those of a PTW Farmer-type chamber (TN 30011-1). The maximum difference observed in this comparison was only 1.25%, showing good agreement. PMID:22138024

Perini, Ana P; Neves, Lucio P; Vivolo, Vitor; Xavier, Marcos; Khoury, Helen J; Caldas, Linda V E

2011-11-30

86

Double photoionization of atomic ions in high frequency radiation fields  

NASA Astrophysics Data System (ADS)

In support of planned experiments involving the photoionization of atomic ions at LCLS/SLAC and FLASH/DESY using EBITs, we have derived time-dependent close-coupling equations for both the Schrodinger and Dirac equations which track the correlated three body breakup of a two-electron atomic ion in the presence of an attosecond high frequency radiation field. For the double photoionization of Ne+8 and U+90, we calculate the strengths of electric dipole and quadrupole radiation field effects on the energy and angular correlated motion of the two photoelectrons.

Pindzola, M. S.; Robicheaux, F.; Colgan, J.

2011-06-01

87

Light scattering by radiation fields: The optical medium analogy  

NASA Astrophysics Data System (ADS)

The optical medium analogy of a radiation field generated by either an exact gravitational plane wave or an exact electromagnetic wave in the framework of general relativity is developed. The equivalent medium of the associated background field is inhomogeneous and anisotropic in the former case, whereas it is inhomogeneous but isotropic in the latter. The features of light scattering are investigated by assuming the interaction region to be sandwiched between two flat spacetime regions, where light rays propagate along straight lines. Standard tools of ordinary wave optics are used to study the deflection of photon paths due to the interaction with the radiation fields, allowing for a comparison between the optical properties of the equivalent media associated with the different background fields.

Bini, D.; Fortini, P.; Geralico, A.; Haney, M.; Ortolan, A.

2013-04-01

88

Scientific results from the Pioneer Saturn encounter - Summary  

NASA Astrophysics Data System (ADS)

The scientific results of the Pioneer Saturn encounter with Saturn are summarized. The Pioneer mission was designed to image the planet, its satellites and rings, and measure its particulate environment and the magnetic field and photon and charged particle radiation by means of 11 operational scientific instruments and its 2.293-GHz telemetry carrier signal. Principle results of the mission include the discovery of an additional ring and a previously unidentified satellite, the further characterization of the physical properties of Saturn and its magnetic field, and the description of the planetary magnetosphere. The successful completion of the mission demonstrated the ability of spacecraft such as Voyager 1 and 2 to survive the particle environments of Saturn's rings and trapped radiation environments, and Pioneer Saturn is expected to continue transmitting information on the interplanetary medium and the solar wind interaction with the interstellar medium until the mid-1980's.

Opp, A. G.

1980-01-01

89

Maximal near-field radiative heat transfer between two plates  

NASA Astrophysics Data System (ADS)

Near-field radiative transfer is a promising way to significantly and simultaneously enhance both thermo-photovoltaic (TPV) devices power densities and efficiencies. A parametric study of Drude and Lorentz models performances in maximizing near-field radiative heat transfer between two semi-infinite planes separated by nanometric distances at room temperature is presented in this paper. Optimal parameters of these models that provide optical properties maximizing the radiative heat flux are reported and compared to real materials usually considered in similar studies, silicon carbide and heavily doped silicon in this case. Results are obtained by exact and approximate (in the extreme near-field regime and the electrostatic limit hypothesis) calculations. The two methods are compared in terms of accuracy and CPU resources consumption. Their differences are explained according to a mesoscopic description of nearfield radiative heat transfer. Finally, the frequently assumed hypothesis which states a maximal radiative heat transfer when the two semi-infinite planes are of identical materials is numerically confirmed. Its subsequent practical constraints are then discussed. Presented results enlighten relevant paths to follow in order to choose or design materials maximizing nano-TPV devices performances.

Nefzaoui, Elyes; Ezzahri, Younès; Drévillon, Jérémie; Joulain, Karl

2013-09-01

90

Far- and near-field approximation for diffraction radiation  

NASA Astrophysics Data System (ADS)

A new beam diagnostic technique based on the Optical Diffraction Radiation Interference (ODRI) has been recently proposed and experimentally investigated. The technique is based on the use of a two slits system. The far field approximation has shown rather accurate correspondence with experimental data when slits are centered with respect to the beam propagation line. Using formulas involving near field we point out in this work that a general treatment is needed with offset larger than 50 ?m.

Shpakov, V.; Dabagov, S. B.; Castellano, M.; Cianchi, A.; Honkavaara, K.; Kube, G.; Chiadroni, E.

2013-08-01

91

The radiation field of a hypersonic nozzle flow  

Microsoft Academic Search

This paper discusses features of the spectra observed looking axially towards the throat of a hypersonic nozzle in a shock tunnel assembly. At the throat, the gas is optically opaque, while at the nozzle exit the gas is optically thin. In principle, the radiation field may be controlled by varying the nozzle shape and it may therefore be used for

P. F. Logan; R. J. Stalker

1977-01-01

92

Anisotropy of the Reflected Radiation Field Over Melting Glacier Ice  

Microsoft Academic Search

In this article we analyze the anisotropy of the reflected radiation field over melting glacier ice using 118 ground-based radiance measurements in Landsat TM Bands 2 and 4. The measurements were carried out on the tongue of the Morteratschgletscher, Switzerland. On the basis of directional measurements several bidirectional reflectance distribution functions (BRDFs) were derived for dirty and clean glacier ice

Wouter H. Knap; Carleen H. Reijmer

1998-01-01

93

Intermolecular interactions in the presence of an intense radiation field  

Microsoft Academic Search

It is well known that the R-6 dependence of the dispersion interaction is modified to R-7 at large intermolecular separations where retardation effects play an important role. In this paper, the theory of intermolecular interactions between two non-polar molecules in the presence of an external radiation field is given and a general expression for the interaction energy is obtained. The

T. Thirunamachandran

1980-01-01

94

Elementary effects in humans exposed to electromagnetic fields and radiation  

Microsoft Academic Search

Exposure to electromagnetic fields and radiation causes physical and chemical changes in the body provided energy is absorbed. Guidelines to protect people are briefly reviewed and its shortcomings discussed. A health factor (HF) is proposed. Radio waves, even with high information content, are not likely to be a risk of cancer.

Walter Van Loock

2009-01-01

95

Problems of human exposure in electromagnetic fields and radiation  

Microsoft Academic Search

Recent technological applications with radio waves induced public fear about possible adverse effects. A brief and simple overview and classification of the effects when exposed to non ionizing electromagnetic fields and radiation is presented. Basics are given of the actual guidelines to protect people and some discrepancies are discussed. The introduction of safety factors (SF) and health factors (HF) is

V. L. Walter

2008-01-01

96

Focusing pulsed electromagnetic radiation in the near field  

Microsoft Academic Search

Intense, subnanosecond electric fields can be used either to stimulate bioelectric effects, such as calcium release in cells (which can lead to various secondary physiological effects), or to generate local hyperthermia. High power wideband antennas radiating electromagnetic waves in the subnanosecond range allows us to treat deep lesions non-invasively. Electromagnetic waves launched at the first focal point of the reflector

S. Xiao; M. Miglliaccio; J. T. Camp; C. E. Baum; K. H. Schoenbach

2009-01-01

97

Giotto encounters Comet Halley  

NASA Astrophysics Data System (ADS)

The passage of Giotto to within 600 km of the Halley nucleus on March 14, 1986 is described and illustrated with diagrams and sample images. The principal operational parameters of the spacecraft are given; plans to return it to within 20,000 km of the earth and send it to an encounter with Comet Grigg-Skjellerup in 1992 are outlined; and the results for Comet Halley are summarized. Findings reported include nucleus diameter 15 km, nucleus height 7-10 km, nucleus albedo 2-4 percent, total gas production rate at the time of encounter 6.9 x 10 to the 29th molecules/s (+ or - 50 percent), water content in the gas about 80 percent, gas radial velocity 900 m/s, and a relatively high concentration of C(+) near the nucleus. A total of 12,000 dust particles (with masses ranging from about 10 attogram to 140 microgram) were detected, beginning at a distance of about 290,000 km from the nucleus; preliminary analysis indicates the presence of H, C, N, O, Na, Mg, Si, K, Ca, and Fe.

van Nes, P.

1986-10-01

98

Simulation of the radiation fields from ionizing radiation sources inside the containment in an accident  

SciTech Connect

In the present work, a set of codes used for simulations of the radiation fields from ionizing radiation sources inside the containment in an accident is described. A method of evaluating the gamma dose rate from a space and energy distributed source is given. The dose rate is calculated by means of the design point kernel method and using buildup factors. The code MCU-REA with the ORIMCU module is used for the burnup calculations.

Kalugin, M. A., E-mail: kalugin@adis.vver.kiae.ru [Russian Research Center Kurchatov Institute (Russian Federation)

2010-12-15

99

Simulation of the radiation fields from ionizing radiation sources inside the containment in an accident  

NASA Astrophysics Data System (ADS)

In the present work, a set of codes used for simulations of the radiation fields from ionizing radiation sources inside the containment in an accident is described. A method of evaluating the gamma dose rate from a space and energy distributed source is given. The dose rate is calculated by means of the design point kernel method and using buildup factors. The code MCU-REA with the ORIMCU module is used for the burnup calculations.

Kalugin, M. A.

2010-12-01

100

Estimating Free Field, Far Field Radiated Noise Source Levels from Measurements Acquired in a Harbor Environment.  

National Technical Information Service (NTIS)

The radiated noise of ships or other underwater sources are typically characterized in terms of a far-field, plane-wave equivalent source level based on measurements assumed to have been acquired m a free field environment such as a deep water test range....

B. Fowler D. C. Barber

2012-01-01

101

Radiation from small-scale magnetic field turbulence: Implications for gamma-ray bursts and laboratory astrophysical plasmas  

NASA Astrophysics Data System (ADS)

Relativistic charged particles moving within regions of small-scale magnetic field turbulence radiate as they undergo transverse accelerations reflective of the magnetic field variation along the particle's path. For a particle of Lorentz factor gamma, relativistic beaming concentrates the bulk of the particle's emission within a small angle 1/gamma from the particle's forward direction. Synchrotron radiation is produced when large-scale magnetic fields cause the charged particles to gyrate, with the resulting radiation spectrum being primarily determined by the intermittent sweep of the relativistic beaming cone past the direction to the observer. In small-scale magnetic field turbulence, magnetic fields may be locally strong but varies over sufficiently small scales that the particle's emission is more consistently oriented towards a particular direction. Consequently, deflection effects cease to dominate the observed spectrum and the standard synchrotron model no longer applies. In this dissertation, we focus on the strong jitter radiation regime, in which the field varies over sufficiently short scales that the particle is never substantially deviated from a straight line path and an observer in the particle's forward direction receives consistently strong radiation over many correlation lengths of the magnetic field. We develop the general jitter radiation solutions for such a case and demonstrate that the resulting radiation spectrum differs notably from the synchtrotron spectrum and depends directly on the spectral distribution of the magnetic field encountered by the particle. The Weibel-like filamentation instability generates small-scale magnetic field turbulence through current filamentation in counterstreaming particle populations, such as may be found at or near propagating shock fronts, in outflow from regions of magnetic reconnection, or from a variety of other scenarios producing an anisotropic particle velocity distribution. The current filamentation produces an anisotropy in magnetic field distribution that causes the jitter radiation spectrum to be sensitive to the radiating particle's orientation with respect to the filamentation axis. Because the spectrum observed from any given direction will be dominated by emission from particle's moving along that particular line-of-sight, this results in a natural angular dependence of the jitter radiation spectrum. We explore the implications of jitter radiation's spectral sensitivity to the field anisotropy produced by the Weibel-like filamentation instability to relevant astrophysical and laboratory plasma scenarios. We calculate the jitter radiation spectra that may be produced in a high-energy density laboratory plasma by using quasi-monoenergetic electron beams to generate and then probe a region of current filamentation, and show that the jitter radiation may be used as a radiative diagnostic to determine features of the magnetic field distribution within this region. For gamma-ray bursts, this instability may play a significant role in generating magnetic field strength from relativistic collisionless shocks or other particle acceleration mechanisms. We show that the viewing angle dependence of the jitter radiation spectrum can result in a rapidly time-evolving spectrum whose hard-to-soft evolution, synchrotron-violating low-energy spectral indices, and correlation between low-energy spectral hardness and the flux at peak energy may explain trends noticed in time-resolved GRB spectral evolution. We generate the jitter radiation spectra as would be produced in the co-moving frame by a single, instantantaneously-illuminated shock front, which may then be relativistically transformed with appropriate geometry into a time-evolving spectrum and multiple such signals assembled to produce "synthetic" GRB for comparison with observations.

Reynolds, Sarah J.

102

Scenarios for future service encounters  

Microsoft Academic Search

This article develops research-based scenarios of future service encounters. Views from senior customer service directors in 14 major service companies regarding future service encounters and future roles and capabilities of customer service professionals were gathered. This was considered in the light of secondary data regarding technology and socio-economic projections. Short scenarios of future service encounters around key dimensions of technology,

Julia Kiely; Neal Beamish; Colin Armistead

2004-01-01

103

Thermoluminescent personnel dosimetry system design for mixed radiation fields  

SciTech Connect

A thermoluminescent badge system for personnel dosimetry is designed based on the dosimetric properties of CaSO{sub 4}:Dy TLD material. This material is characterized by an enhanced over-response to gamma radiation with energies below 200 KeV. Different filter combinations are used in four separate areas of the badge system to compensate for this energy over-response and to provide a measurement of radiation dose received during field exposure. The four badge areas house the open window, beta shield, bias filter and the deep dose areas. The response of the TLD material under these areas is used to measure two primary dosimetric quantities, the deep dose and the shallow dose equivalents delivered to tissue at the depths 1.0 cm and 0.007 cm respectively. The deep dose area of the badge (i.e. A4) is designed to give a direct measurement of the deep dose delivered during radiation exposure to photons with energies in the range 15 to 662 KeV. The badge is also designed to resolve mixed beta/gamma radiation fields by utilizing the response of the open window and the beta shield areas. The capability of the badge system to resolve mixed gamma radiation fields is examined in a theoretical situation where a low energy x-ray component is mixed with a Cs{sup 137} gamma component. The greatest sensitivity of the badge in such situations is when the low energy component has an effective photon energy lower than 40 KeV. This limit is set by the observed flat photon energy response of the difference ratios at energies higher than 40 KeV.

Rayes, I.M.

1988-01-01

104

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

105

New Algorithm for Field Splitting in Radiation Therapy  

Microsoft Academic Search

In this paper, we study an interesting geometric partition problem, called optimal field splitting, which arises in Intensity-Modulated Radiation Therapy (IMRT). In current clinical practice, a multi-leaf collimator (MLC) is used to deliver the prescribed intensity maps (IMs).\\u000a However, the maximum leaf spread of an MLC may require to split a large intensity map into several overlapping sub-IMs. We develop

Xiaodong Wu; Xin Dou; John E. Bayouth; John M. Buatti

2007-01-01

106

Modelling of radiation field around spent fuel container.  

PubMed

Operation of nuclear reactors leads to the production of spent nuclear fuel (SNF). There are two basic strategies of SNF management: ultimate disposal of SNF in geological formations and recycle or repeated utilisation of reprocessed SNF. In both options, there is an urgent necessity to study radiation properties of SNF. Information about SNF radiation properties is required at all stages of SNF management. In order to reach more effective utilisation of nuclear materials, new fuel cycles are under development based on uranium-plutonium, uranium-thorium and some other types of nuclear fuel. These promising types of nuclear fuel are characterised by quite different radiation properties at all the stages of nuclear fuel cycle (NFC) listed above. So, comparative analysis is required for radiation properties of different nuclear fuel types at different NFC stages. The results presented here were obtained from the numerical analysis of the radiation field around transport containers of different SNF types and in SNF storage. The calculations are carried out with the application of the computer code packages SCALE-4.3 and MCNP-4C. Comparison of the dose parameters obtained for different models of the transport container with experimental data allowed us to make certain conclusions about the errors of numerical results caused by the approximate geometrical description of the transport container. PMID:16604702

Kryuchkov, E F; Opalovsky, V A; Tikhomirov, G V

2005-01-01

107

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

Code of Federal Regulations, 2010 CFR

...Space 1 2010-01-01 2010-01-01 false High-intensity Radiated Fields (HIRF) Protection. 29.1317...CATEGORY ROTORCRAFT Equipment General § 29.1317 High-intensity Radiated Fields (HIRF) Protection....

2010-01-01

108

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

Code of Federal Regulations, 2010 CFR

...Space 1 2010-01-01 2010-01-01 false High-intensity Radiated Fields (HIRF) Protection. 27.1317...CATEGORY ROTORCRAFT Equipment General § 27.1317 High-intensity Radiated Fields (HIRF) Protection....

2010-01-01

109

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

Code of Federal Regulations, 2010 CFR

...Space 1 2009-01-01 2009-01-01 false High-intensity Radiated Fields (HIRF) Protection. 29.1317...CATEGORY ROTORCRAFT Equipment General § 29.1317 High-intensity Radiated Fields (HIRF) Protection....

2009-01-01

110

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

Code of Federal Regulations, 2010 CFR

...Space 1 2009-01-01 2009-01-01 false High-intensity Radiated Fields (HIRF) Protection. 27.1317...CATEGORY ROTORCRAFT Equipment General § 27.1317 High-intensity Radiated Fields (HIRF) Protection....

2009-01-01

111

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

Code of Federal Regulations, 2012 CFR

...false Measurements required: Field strength of spurious radiation. 2.1053 Section 2.1053 Telecommunication FEDERAL...1053 Measurements required: Field strength of spurious radiation. (a) Measurements shall be made to...

2012-10-01

112

Requirements on borehole radiators based on analytical estimation of radiated acoustic fields  

NASA Astrophysics Data System (ADS)

Acoustic action on a productive stratum is one method for intensification of hydrocarbon mining. The physical mechanisms of acoustic action can be divided into two main groups: force and energy. The effect of any mechanism is associated with the structure and characteristics of the acoustic fields created by the radiation sources in the borehole. Therefore, the force and energy characteristics of the acoustic fields in the vicinity of a borehole are of high importance. These characteristics make it possible to estimate the prospects of applying the acoustic action under different conditions. The analytical estimates of the force and energy characteristics of the acoustic fields in the vicinity of a borehole are presented, and the requirements imposed on new-generation of borehole radiators are formulated on this basis, the use of which would help to more effectively develop deposits of highly viscous oils and residual gas condensates.

Maksimov, G. A.

2013-05-01

113

Asymptotic Electromagnetic Fields in Models of Quantum-Mechanical Matter Interacting with the Quantized Radiation Field  

Microsoft Academic Search

In models of (non-relativistic and pseudo-relativistic) electrons interacting with static nuclei and with the (ultraviolet-cutoff) quantized radiation field, the existence of asymptotic electromagnetic fields is established. Our results yield some mathematically rigorous understanding of Rayleigh scattering and of the phenomenon of relaxation of isolated atoms to their ground states. Our proofs are based on propagation estimates for electrons inspired by

J. Froehlich; M. Griesemer; B. Schlein

2000-01-01

114

Asymptotic Electromagnetic Fields in Models of Quantum-Mechanical Matter Interacting with the Quantized Radiation Field  

Microsoft Academic Search

In models of (non-relativistic and pseudo-relativistic) electrons interacting with static nuclei and with the (ultraviolet-cutoff) quantized radiation field, the existence of asymptotic electromagnetic fields is established. Our results yield some mathematically rigorous understanding of Rayleigh scattering and of the phenomenon of relaxation of isolated atoms to their ground states. Our proofs are based on propagation estimates for electrons inspired by

J. Fröhlich; M. Griesemer; B. Schlein

2001-01-01

115

Universalist ethics in extraterrestrial encounter  

NASA Astrophysics Data System (ADS)

If humanity encounters an extraterrestrial civilization, or if two extraterrestrial civilizations encounter each other, then the outcome may depend not only on the civilizations' relative strength to destroy each other but also on what ethics are held by one or both civilizations. This paper explores outcomes of encounter scenarios in which one or both civilizations hold a universalist ethical framework. Several outcomes are possible in such scenarios, ranging from one civilization destroying the other to both civilizations racing to be the first to commit suicide. Thus, attention to the ethics of both humanity and extraterrestrials is warranted in human planning for such an encounter. Additionally, the possibility of such an encounter raises profound questions for contemporary human ethics, even if such an encounter never occurs.

Baum, Seth D.

2010-02-01

116

Generation of electromagnetic radiation based on nanotubes under a constant electric field and an electromagnetic wave field  

SciTech Connect

The possible generation of radiation in the millimeter range based on nanotubes by an alternating (rapidly oscillating) electric field under a constant (or nonstationary) electric field is studied. Radiation enhancement is based on a periodic dependence of the current in nanotubes in such electric fields. The results of a mathematical simulation are presented.

Sadykov, N. R., E-mail: sadykov@rambler.ru; Scorkin, N. A. [South Ural State University (Russian Federation)

2012-02-15

117

Examination of MARINER10 Magnetic Field Data for Heavy Ion Signatures During the Mercury I and III Encounters by Mariner10  

Microsoft Academic Search

From the Mariner-10 flybs of Mercury in the mid 1970s it was discovered that Mercury had a small intrinsic magnetic field and as a result a small magnetosphere with a standoff distance of ~1.5 Mercury Radii. In the mid 1980s it was discovered telescopically that Mercury has a strong but highly variable heavy ion exosphere of Na, K and Ca,

S. A. Boardsen; J. A. Slavin

2006-01-01

118

Covariant quantum mechanics and the symmetries of its radiation fields  

NASA Astrophysics Data System (ADS)

The requirement of gauge invariance for the Stückelberg equation for the relativistically covariant wave function of a system evolving according a universal world (or historical) time T implies the existence of a five dimensional pre-Maxwell field on the manifold of spacetime and r. The Maxwell theory is contained in this theory; integration of the field equations over r restores the Maxwell equations with the usual interpretation of the sources. The energy-momentum-mass tensor of this field has the form of a four dimensional invariant harmonic oscillator at each point in four-momentum space. The known solutions of the two body bound state problem indicate that the electromagnetic field strengths must lie in a restricted part of the spacelike region of Minkowski space in order for the spectrum and the wave functions to have the correct structure for the quantized radiation field. The wave functions form irreducible representations of O(2,1); the O(3,1) transformation properties of the field correspond to an induced representation.

Land, M. C.; Horwitz, L. P.

119

Frame-dragging fields and spin 1 gravitomagnetic radiation  

NASA Astrophysics Data System (ADS)

Experimental results published in 2004 (Ciufolini and Pavlis in Nature 431:958-960, 2004) and 2011 (Everitt et al. in Phys Rev Lett 106:221101, 1-5, 2011) have confirmed the frame-dragging phenomenon for a spinning earth predicted by Einstein's field equations. Since this is observed as a precession caused by the gravitomagnetic (GM) field of the rotating body, these experiments may be viewed as measurements of a GM field. The effect is encapsulated in the classic steady state solution for the vector potential field ? of a spinning sphere-a solution applying to a sphere with angular momentum J and describing a field filling space for all time (Weinberg in Gravitation and Cosmology, Wiley, New York, 1972). In a laboratory setting one may visualise the case of a sphere at rest (? =0, { t}<0), being spun up by an external torque at { t}=0 to the angular momentum J: the ? field of the textbook solution cannot establish itself instantaneously over all space at { t}=0, but must propagate with the velocity c, implying the existence of a travelling GM wave field yielding the textbook ? field for large enough t (Tolstoy in Int J Theor Phys 40(5):1021-1031, 2001). The linearized GM field equations of the post-Newtonian approximation being isomorphic with Maxwell's equations (Braginsky et al. in Phys Rev D 15(6):2047-2060, 1977), such GM waves are dipole waves of spin 1. It is well known that in purely gravitating systems conservation of angular momentum forbids the existence of dipole radiation (Misner et al. in Gravitation, Freeman & Co., New York, 1997); but this rule does not prohibit the insertion of angular momentum into the system from an external source-e.g., by applying a torque to our laboratory sphere.

Tolstoy, Ivan

2012-12-01

120

Method of calculating radiation fields at line frequencies  

NASA Astrophysics Data System (ADS)

An iterative method is proposed for calculating the radiation field at spectral line frequencies for plane-parallel moving atmospheres under the assumption of complete frequency redistribution. The method uses an approximate relationship between the total source function and the intensity to obtain the source function in the line. The time required for this calculation using this method is only three to five times greater than the time needed to obtain the formal solution of the equation, which is several times less than that required with the usually employed methods of Rybicki (1971) or Feautrier (1964). The basic equations, single-point quadrature formula, and algorithm for solving the equation of radiative transfer are presented and discussed, and the results of numerical experiments are reported.

Serbin, V. M.

1985-11-01

121

Radiation-hardened field coils for FMIT quadrupoles  

SciTech Connect

Modern accelerators of the Fusion Materials Irradiation Test (FMIT) class deliver enormous power onto their targets. The high beam currents of such machines produce highly activating radiation fields from beam/target interaction and normal beam losses. The 100-mA deuteron beam from the FMIT accelerator produces a backstreaming fast-neutron flux of 10/sup 11/ n/s-cm/sup 2/ near the target. In addition, the neutron contribution from distributed beam spill of 3 ..mu..A/m along the rest of the machine prevents the use of epoxy resin potting materials in all magnet field coils above 10-MeV beam energies. Two special techniques for radiation-hardened field coils have been developed at Los Alamos for use on the FMIT accelerator. One technique uses vitreous enamel coatings on the conductors and appears attractive for the drift-tube quadrupoles. Another method uses a thermally efficient two-layer coil design that has solid mineral-insulated (MI) conductors with indirect cooling coils, all bonded together in a lead matrix. Test results are discussed, along with applications of the quadrupoles in the FMIT facility that reduce gamma exposures during maintenance periods.

Grieggs, R.J.; Liska, D.J.; Harvey, A.

1983-01-01

122

Computation of High-Altitude Hypersonic Flow-Field Radiation.  

NASA Astrophysics Data System (ADS)

Accurate calculations of radiation on and from transatmospheric flight vehicles are currently a challenge to computational aerodynamicists. Due to combined effects of low density and hypersonic flight conditions, the gas in the shock-layer is in a state of thermal and chemical nonequilibrium. The present work aims at gathering existing ideas together about how such flows should be modeled and comparing them to recent, more accurate experiments that probe the separate energy modes of the different species of the gas in a more direct way than previously reported. Two recent Bow-Shock-Ultra-Violet flight experiments, and two recent shock-tube experiments are used to test the validity of the flow-field models implemented in the current state-of-the-art numerical codes. They involve highly non-equilibrium flow regimes in nitrogen and air with negligible ionization and provide detailed spectra emitted by the hot gas. A recent plasma torch experiment at Stanford, and the Cochise experiments at the Geophysics Directorate laboratories, have been the ideal experimental counterpart to test and improve the radiation calculation in the UV -visible spectral range and the IR region respectively. Each spectral region is used to probe several different aspects of the thermal and chemical nonequilibrium. A hierarchy of flow-field codes has been developed in conjunction with a greatly enhanced radiation code, termed NEQAIR2, to simulate these experiments. The flow -field codes involve axisymmetric Navier-Stokes and Burnett simulations around blunt-nose cones for the flight experiments and quasi-1D Euler simulations for the shock-tube experiments. They include between 5 and 8 chemical species and between 3 and 6 separate internal energy modes. The corresponding system of conservation equations are solved with finite volume, flux split algorithms. Gauss-Siedel line relaxation is used to increase efficiency of the fully-implicit method and exact numerical jacobians have been derived to increase the rate of convergence. The radiation code involves a collisional-radiative model based on a quasi-steady-state (QSS) approximation and a detailed line-by-line calculation for several atomic systems and molecular band systems. Comparisons of numerical spectra with the flight data show good agreement at the lower altitudes but the predictions are only within an order of magnitude at higher altitudes.

Moreau, Stephane

123

Synchrotron radiation from Neptune: Neptune's magnetic field and electron population  

SciTech Connect

On the basis of radio measurements of Neptune at 20 cm, one can infer the presence of {approximately} 0.4 mJy synchrotron radiation. By assuming a dipole-like magnetic field, with the energetic electrons confined to the magnetic equator, the authors estimate Neptune's magnetic dipole moment to be {approximately} 1 G R{sub N}{sup 3}. Its electron population should be between that in Uranus' and Jupiter's magnetospheres. If the electrons are injected by the solar wind, local acceleration processes in the magnetosphere are required to energize the particles, because adiabatic diffusion alone is not sufficient.

de Pater, I. (Univ. of California, Berkeley (USA)); Goertz, C.K. (Univ. of Iowa, Iowa City (USA))

1989-01-01

124

Synchrotron radiation from Neptune - Neptune's magnetic field and electron population  

NASA Astrophysics Data System (ADS)

On the basis of radio measurements of Neptune at 20 cm, one can infer the presence of about 0.4 mJy synchrotron radiation. By assuming a dipole-like magnetic field, with the energetic electrons confined to the magnetic equator, Neptune's magnetic dipole moment is estimated. Its electron population should be between that in Uranus' and Jupiter's magnetospheres. If the electrons are injected by the solar wind, local acceleration processes in the magnetosphere are required to energize the particles, because adiabatic diffusion alone is not sufficient.

de Pater, I.

1989-01-01

125

Helicity sensitive terahertz radiation detection by field effect transistors  

NASA Astrophysics Data System (ADS)

Terahertz light helicity sensitive photoresponse in GaAs/AlGaAs high electron mobility transistors. The helicity dependent detection mechanism is interpreted as an interference of plasma oscillations in the channel of the field-effect-transistors (generalized Dyakonov-Shur model). The observed helicity dependent photoresponse is by several orders of magnitude higher than any earlier reported one. Also, linear polarization sensitive photoresponse was registered by the same transistors. The results provide the basis for a new sensitive, all-electric, room-temperature, and fast (better than 1 ns) characterisation of all polarization parameters (Stokes parameters) of terahertz radiation. It paves the way towards terahertz ellipsometry and polarization sensitive imaging based on plasma effects in field-effect-transistors.

Drexler, C.; Dyakonova, N.; Olbrich, P.; Karch, J.; Schafberger, M.; Karpierz, K.; Mityagin, Yu.; Lifshits, M. B.; Teppe, F.; Klimenko, O.; Meziani, Y. M.; Knap, W.; Ganichev, S. D.

2012-06-01

126

Thermoacoustic Monitoring of Radiation Field of Scanning Electron Beam  

NASA Astrophysics Data System (ADS)

Thermoacoustic dosimeters on the base of thin rods and plates were used in control system of scanning electron beam in technological process of radiation--chemical modification of polymeric composites. They are characterized by low price, simplicity and reliability of construction. A system, incorporated the wire dosimeter with piezoelectric detector on its butt-end, electronic preamplifier, CAMAC crate and computer with corresponding software carried out continuous, nondistorting, and high-informative monitoring of extensive area under pulsed radiation. Dosimeter with ramifying body was displaced normally to initial direction of electron beam axis. Its body consisted of a few parallel titanic wire 140 cm long. Each of acoustic pulses, generated in dosimeter body by accelerator pulse sequence, carries the information about location and transverse distribution of corresponding electron pulse. A spatial profile of a radiation field, caused by any periodic shape of current in scanning magnet, was displayed immediately. It permitted fitting the profile to desirable that by varying the shape of magnet current.

Popov, G. F.; Kalinichenko, A. I.; Kresnin, Yu. A.; Stervoedov, N. G.

1997-05-01

127

Development of a Characterized Radiation Field for Evaluating Sensor Performance  

SciTech Connect

Numerous efforts are funded by US agencies (DOE, DoD, DHS) for development of novel radiation sensing and measurement systems. An effort has been undertaken to develop a flexible shielding system compatible with a variety of sources (beta, X-ray, gamma, and neutron) that can be highly characterized using conventional radiation detection and measurement systems. Sources available for use in this system include americium-beryllium (AmBe), plutonium-beryllium (PuBe), strontium-90 (Sr-90), californium-252 (Cf-252), krypton-85 (Kr-85), americium-241 (Am-241), and depleted uranium (DU). Shielding can be varied by utilization of materials that include lexan, water, oil, lead, and polyethylene. Arrangements and geometries of source(s) and shielding can produce symmetrical or asymmetrical radiation fields. The system has been developed to facilitate accurately repeatable configurations. Measurement positions are similarly capable of being accurately re-created. Stand-off measurement positions can be accurately re-established using differential global positioning system (GPS) navigation. Instruments used to characterize individual measurement locations include a variety of sodium iodide (NaI(Tl)) (3 x 3 inch, 4 x 4 x 16 inch, Fidler) and lithium iodide (LiI(Eu)) detectors (for use with multichannel analyzer software) and detectors for use with traditional hand held survey meters such as boron trifluoride (BF{sub 3}), helium-3 ({sup 3}He), and Geiger-Mueller (GM) tubes. Also available are Global Dosimetry thermoluminescent dosimeters (TLDs), CR39 neutron chips, and film badges. Data will be presented comparing measurement techniques with shielding/source configurations. The system is demonstrated to provide a highly functional process for comparison/characterization of various detector types relative to controllable radiation types and levels. Particular attention has been paid to use of neutron sources and measurements. (authors)

Rogers, D.M.; Coggins, T.L.; Marsh, J.; Mann, St.D.; Waggoner, Ch.A. [Institute for Clean Energy Technology (ICET) and Office of Regulatory Compliance, Mississippi State University, Starkville, MS (United States)

2008-07-01

128

Further progress in the characterisation of complex radiation fields.  

PubMed

One of the topics which forms part of CONRAD project addresses the problems related to the dosimetry of complex-mixed radiation fields at workplaces. This topic was included in work package (WP) 6. WP 6 was established to co-ordinate research activities in two areas:the development of new techniques and the improvement of current techniques for characterisation of complex workplace fields (including high-energy fields and pulsed fields): measurement and calculation of particle energy and direction distributions (Subgroup A); and model improvements for dose assessment of solar particle events (Subgroup B). In both cases in order to aid the research, WP 6 increases the efficiency of resource utilisation, and facilitates the technology transfer to practical application and for the development of standards. This contribution presents a general overview of activities of SG A; specific results related to the benchmark experiment at GSI Darmstadt are presented separately, and will be published in other way. As far as the results acquired in the frame of the SG B activities, these are presented in the meeting held as part of EURADOS AM 2008. PMID:18718960

Spurny, Frantisek; Silari, Marco

2008-08-21

129

A simple method to quantify the coincidence between portal image graticules and radiation field centers or radiation isocenter  

SciTech Connect

Purpose: The aim of this study was to develop a computerized method to quantify the coincidence between portal image graticules and radiation field centers or radiation isocenter. Three types of graticules were included in this study: Megavoltage (MV) mechanical graticule, MV electronic portal imaging device digital graticule, and kilovoltage (kV) on-board imaging digital graticule. Methods: A metal ball bearing (BB) was imaged with MV and kV x-ray beams in a procedure similar to a Winston-Lutz test. The radiation fields, graticules, and BB were localized in eight portal images using Hough transform-based computer algorithms. The center of the BB served as a static reference point in the 3D space so that the distances between the graticule centers and the radiation field centers were calculated. The radiation isocenter was determined from the radiation field centers at different gantry angles. Results: Misalignments of MV and kV portal imaging graticules varied with the gantry or x-ray source angle as a result of mechanical imperfections of the linear accelerator and its imaging system. While the three graticules in this study were aligned to the radiation field centers and the radiation isocenter within 2.0 mm, misalignments of 1.5-2.0 mm were found at certain gantry angles. These misalignments were highly reproducible with the gantry rotation. Conclusions: A simple method was developed to quantify the alignments of portal image graticules directly against the radiation field centers or the radiation isocenter. The advantage of this method is that it does not require the BB to be placed exactly at the radiation isocenter through a precalibrated surrogating device such as room lasers or light field crosshairs. The present method is useful for radiation therapy modalities that require high-precision portal imaging such as image-guided stereotactic radiotherapy.

Du Weiliang; Yang, James; Luo Dershan; Martel, Mary [Department of Radiation Physics, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030 (United States)

2010-05-15

130

The exact spectrum of scalar field perturbations in a radiation deformed closed de Sitter universe  

NASA Astrophysics Data System (ADS)

We observe that the equation of motion for a free scalar field in a closed universe with radiation and a positive cosmological constant is given by Lamé's equation. Computing the exact power spectrum of scalar field perturbations, the presence of both curvature and radiation produces a red tilt weakly dependent on the amount of radiation.

Sarangi, Sash; Schalm, Koenraad; Shiu, Gary; van der Schaar, Jan Pieter

2007-03-01

131

Measurement of the radiation field surrounding the Collider Detector at Fermilab  

SciTech Connect

We present here the first direct and detailed measurements of the spatial distribution of the ionizing radiation surrounding a hadron collider experiment. Using data from two different exposures we measure the effect of additional shielding on the radiation field around the Collider Detector at Fermilab (CDF). Employing a simple model we parameterize the ionizing radiation field surrounding the detector.

K. Kordas et al.

2004-01-28

132

A polygon matching algorithm and its applications to verification of radiation field placement in radiotherapy  

Microsoft Academic Search

An automated method for quantitative evaluation of geometric accuracy of radiation field placement during radiation therapy treatments has been developed and is presented in this article. The method is based on matching polygons representing the boundaries of the prescribed and treated radiation fields. An efficient algorithm for finding the intersection of two arbitrary simple polygons has been developed for that

Konrad Leszczynski; Stephen Loose

1995-01-01

133

Space radiation dosimetry in low-Earth orbit and beyond  

Microsoft Academic Search

Space radiation dosimetry presents one of the greatest challenges in the discipline of radiation protection. This is a result of both the highly complex nature of the radiation fields encountered in low-Earth orbit (LEO) and interplanetary space and of the constraints imposed by spaceflight on instrument design. This paper reviews the sources and composition of the space radiation environment in

E. R. Benton; E. V. Benton

2001-01-01

134

Stimulated radiative corrections in hydrogen in the presence of a strong laser field  

SciTech Connect

The stimulated radiative corrections (or ac-Stark shift, or light shift . . .) of the energy levels of a hydrogenic atom irradiated by an intense, nonresonant, monomode laser field, are evaluated within the framework of the time-dependent perturbation theory, up to and including fourth order. The calculation is performed by using a Sturmian representation of the Coulomb Green's function. Whenever it is possible, comparison is made with other results, and several limiting cases are considered. If the laser frequency ..omega -->..0, one recovers the results of the dc-Stark effect. If 2..omega.. becomes larger than the ionization energy of the atomic state considered, the fourth-order level shift acquires an imaginary part which may be connected, via an extension of the optical theorem, to the two-photon ionization cross section. We point out also the difficulties encountered, when trying to get sensible estimates from partial summation of the infinite sums entering the perturbative expression of the fourth-order amplitudes. Finally, the order of magnitude of these various corrections is discussed.

Arnous, E.; Bastian, J.; Maquet, A.

1983-02-01

135

Electromagnetic wave radiation by oscillating particles located in a constant electric field  

SciTech Connect

The electromagnetic waves radiated by charged and uncharged liquid particles oscillating in a constant electric field are studied theoretically. Expressions are obtained for the power radiated by such particles and the power produced by a single particle is evaluated.

Shishigin, S.A.; Kopytin, Yu.D.

1984-05-01

136

Inevitability of a magnetic field in the Sun's radiative interior  

NASA Astrophysics Data System (ADS)

The gas in the convective outer layers of the Sun rotates faster at the equator than in the polar regions, yet deeper inside (in the radiative zone) the gas rotates almost uniformly. There is a thin transition layer between these zones, called the tachocline. This structure has been measured seismologically, but no purely fluid-dynamical mechanism can explain its existence. Here we argue that a self-consistent model requires a large-scale magnetic field in the Sun's interior, as well as consideration of the Coriolis effects in the convection zone and in the tachocline. Turbulent stresses in the convection zone induce (through Coriolis effects) a meridional circulation, causing the gas from the convection zone to burrow downwards, thereby generating the horizontal and vertical shear that characterizes the tachocline. The interior magnetic field stops the burrowing, and confines the shear, as demanded by the observed structure of the tachocline. We outline a dynamical theory of the flow, from which we estimate a field strength of about 10-4 tesla just beneath the tachocline. An important test of this picture, after numerical refinement, will be quantitative consistency between the predicted and observed interior angular velocities.

Gough, D. O.; McIntyre, M. E.

1998-08-01

137

Observations of the diffuse near-UV radiation field  

NASA Astrophysics Data System (ADS)

The diffuse radiation field from 1650-3100 A has been observed by spectrometer aboard the Space Shuttle, and the contributions of the zodiacal light an the diffuse cosmic background to the signal have been derived. Colors ranging from 0.65 to 1.2 are found for the zodiacal light with an almost linear increase in the color with ecliptic latitude. This rise in color is due to UV brightness remaining almost constant while the visible brightnesses drop by almost a factor of two. This is interpreted as evidence that the grains responsible for the UV scattering have much more uniform distribution with distance from the ecliptic plane than do those grains responsible for the visible scattering. Intensities for the cosmic diffuse background ranging from 300 units to 900 units are found which are not consistent with either a correlation with N(H I) or with spatial isotropy.

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

1990-05-01

138

Radiative Capture Reactions in Lattice Effective Field Theory  

NASA Astrophysics Data System (ADS)

We outline a general method for computing nuclear capture reactions on the lattice. The method consists of two major parts. In this study we detail the second part which consists of calculating an effective two-body capture reaction on the lattice at finite volume. We solve this problem by calculating the two-point Green’s function using an infrared regulator and the capture amplitude to a two-body bound state. We demonstrate the details of this method by calculating on the lattice the leading M1 contribution to the radiative neutron capture on proton at low energies using pionless effective field theory. We find good agreement with exact continuum results. The approach we outline here can be used in a wide range of applications including few-body reactions in cold atomic systems and hadronic reactions in lattice quantum chromodynamics.

Rupak, Gautam; Lee, Dean

2013-07-01

139

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

ERIC Educational Resources Information Center

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

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

2011-01-01

140

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

ERIC Educational Resources Information Center

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

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

2011-01-01

141

Extractable proteins from field radiation vulcanized natural rubber latex  

NASA Astrophysics Data System (ADS)

The type I allergy associated with the use of natural rubber latex (NRL) products is caused by the NRL proteins leached by the sweat or other body fluids. Makuuchi's group proposed for the first time the proteins removal by the addition of water-soluble polymers (WSP) on radiation vulcanization of natural rubber latex (RVNRL) that is a promising process under development in many countries. In this study, Brazilian field natural rubber was irradiated with a 60Co gamma source to reduce the content of WSP in the final product. WSP was used as additive to improve the extraction of protein. After irradiation the RVNRL was centrifuged to extract the WSP and proteins. The analytical methodology for protein content was based on the modified Lowry method according to ASTM D5712. Protein determination was carried out in serum of latex and in the extracts of the gloves. The concentration of extractable water-soluble proteins in serum of irradiated field NRL (NRL1), not irradiated one (NRL2); of twice centrifuged sample with polymer additive NRL (NRL3) and of the glove manufactured (NRLG) are compared with commercial glove (CG). The irradiation process increases the extractable water-soluble proteins, EP, as reported in the literature. In this study the use of polymeric additive on the bi-centrifugation process to remove protein was successful and the EP of the glove obtained in NRL3 was at around 40% of the commercial glove.

Parra, Duclerc F.; Pinto Martins, Carlos Felipe; Collantes, Hugo D. C.; Lugao, Ademar B.

2005-07-01

142

BINARY ASTEROID ENCOUNTERS WITH TERRESTRIAL PLANETS: TIMESCALES AND EFFECTS  

SciTech Connect

Many asteroids that make close encounters with terrestrial planets are in a binary configuration. Here, we calculate the relevant encounter timescales and investigate the effects of encounters on a binary's mutual orbit. We use a combination of analytical and numerical approaches with a wide range of initial conditions. Our test cases include generic binaries with close, moderate, and wide separations, as well as seven well-characterized near-Earth binaries. We find that close approaches (<10 Earth radii) occur for almost all binaries on 1-10 million year timescales. At such distances, our results suggest substantial modifications to a binary's semimajor axis, eccentricity, and inclination, which we quantify. Encounters within 30 Earth radii typically occur on sub-million year timescales and significantly affect the wider binaries. Important processes in the lives of near-Earth binaries, such as tidal and radiative evolution, can be altered or stopped by planetary encounters.

Fang, Julia; Margot, Jean-Luc [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States)

2012-01-15

143

Linac head scatter factor for asymmetric radiation field  

NASA Astrophysics Data System (ADS)

The head scatter factor, Sh is an important dosimetric quantity used in radiation therapy dose calculation. It is empirically determined and its field size dependence reflects changes in photon scatter from components in the linac treatment head. In this work a detailed study of the physical factors influencing the determination of Sh was performed with particular attention given to asymmetric field geometries. Ionization measurements for 6 and 18 MV photon beams were made to examine the factors which determine Sh. These include: phantom size and material, collimator backscatter, non-lateral electronic equilibrium (LEE) conditions, electron contamination, collimator-exchange, photon energy, flattening filter and off-axis distance (OAD). Results indicated that LEE is not required for Sh measurements if electron contamination is minimized. Brass caps or polystyrene miniphantoms can both be used in Sh measurements provided the phantom thickness is large enough to stop contaminant electrons. Backscatter radiation effects into the monitor chamber were found to be negligible for the Siemens linac. It was found that the presence and shape of the flattening filter had a significant effect on the empirically determined value of Sh was also shown to be a function of OAD, particularly for small fields. For fields larger than 12×12 cm2/ Sh was independent of OAD. A flattening filter mass model was introduced to explain qualitatively the above results. A detailed Monte Carlo simulation of the Siemens KD2 linac head in 6 MV mode was performed to investigate the sources of head scatter which contribute to the measured Sh. The simulated head components include the flattening filter, the electron beam stopper, the primary collimator, the photon monitor chamber and the secondary collimators. The simulations showed that the scatter from the head of the Siemens linac is a complex function of the head components. On the central axis the flattening filter played the dominant role in the contributing to scatter. However this role was significantly reduced off- axis and other head components, such as the electron beam stopper and the primary collimator, became more important. The role of the mirror and ion chamber was relatively minor. Scatter from the secondary collimators was shown to be a function of the filed size and the position of the collimators in the treatment head. They were also found to play a dual role, both as a scatter source and as an attenuator for scatter produced upstream in the linac head. A closed form model, based on the work of Yu and Slobada, was developed to estimate head scatter factors for on- and off-axis asymmetric fields. The model requires three parameters to fit the measured data. The first, a constant c, has a physical significance and is independent of energy and off-axis distance. The second, g, shows a small variation with the energy and OAD while the third parameter, the primary-to-scatter ratio, is strongly dependent on energy and off-axis distance. Comparison of Sh, predicted by the model, to measurement for a large range of symmetric and asymmetric fields showed excellent agreement. A maximum of 0.7% discrepancy was observed at 12 cm OAD.

Soubra, Mazen Ahmed

1997-11-01

144

Simplified field-in-field technique for a large-scale implementation in breast radiation treatment  

SciTech Connect

We wanted to evaluate a simplified 'field-in-field' technique (SFF) that was implemented in our department of Radiation Oncology for breast treatment. This study evaluated 15 consecutive patients treated with a simplified field in field technique after breast-conserving surgery for early-stage breast cancer. Radiotherapy consisted of whole-breast irradiation to the total dose of 50 Gy in 25 fractions, and a boost of 16 Gy in 8 fractions to the tumor bed. We compared dosimetric outcomes of SFF to state-of-the-art electronic surface compensation (ESC) with dynamic leaves. An analysis of early skin toxicity of a population of 15 patients was performed. The median volume receiving at least 95% of the prescribed dose was 763 mL (range, 347-1472) for SFF vs. 779 mL (range, 349-1494) for ESC. The median residual 107% isodose was 0.1 mL (range, 0-63) for SFF and 1.9 mL (range, 0-57) for ESC. Monitor units were on average 25% higher in ESC plans compared with SFF. No patient treated with SFF had acute side effects superior to grade 1-NCI scale. SFF created homogenous 3D dose distributions equivalent to electronic surface compensation with dynamic leaves. It allowed the integration of a forward planned concomitant tumor bed boost as an additional multileaf collimator subfield of the tangential fields. Compared with electronic surface compensation with dynamic leaves, shorter treatment times allowed better radiation protection to the patient. Low-grade acute toxicity evaluated weekly during treatment and 2 months after treatment completion justified the pursuit of this technique for all breast patients in our department.

Fournier-Bidoz, Nathalie [Department of Medical Physics, Institut Curie, Paris (France); Department of Radiation Oncology, Institut Curie, Paris (France); Kirova, Youlia M., E-mail: youlia.kirova@curie.net [Department of Radiation Oncology, Institut Curie, Paris (France); Campana, Francois; Dendale, Remi; Fourquet, Alain [Department of Radiation Oncology, Institut Curie, Paris (France)

2012-07-01

145

Relationship between breakdown field and radiated electromagnetic field strength due to low voltage ESD below 1kV  

Microsoft Academic Search

Relationship between breakdown field strength and radiated electromagnetic field strength was examined in experimental study. In the first, transition duration of voltage and current rise time due to small gap discharge as the low voltage ESD investigated in time domain. The measurement system used the 12 GHz experimental system. And so, the sensing system was used an E-field sensor and

K. Kawamata; S. Minegishi; A. Haga; O. Fujiwara

2008-01-01

146

Electric-field correlation in quantum charged fluids coupled to the radiation field  

SciTech Connect

In a recent paper [S. El Boustani, P. R. Buenzli, and P. A. Martin, Phys. Rev. E 73, 036113 (2006)] about quantum charges in equilibrium with radiation, among other things the asymptotic form of the electric-field correlation has been obtained by a microscopic calculation. It has been found that this correlation has a long-range algebraic decay of the form 1/r{sup 3} (except in the classical limit). The macroscopic approach, in the Course of Theoretical Physics of Landau and Lifshitz, gives no such decay. In this Brief Report we revisit and complete the macroscopic approach of Landau and Lifshitz and suggest that, perhaps, the use of a classical electromagnetic field by El Boustani et al. was not justified.

Jancovici, B. [Laboratoire de Physique Theorique, Universite de Paris-Sud, 91405 Orsay Cedex (France)

2006-11-15

147

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

PubMed

The radiation exposure in space by cosmic radiation can be reduced through careful mission planning and constructive measures as example the provision of a radiation shelter, but it cannot be completely avoided. The reason for that are the extreme high energies of particles in this field and the herewith connected high penetration depth in matter. For missions outside the magnetosphere ionizing radiation is recognized as the key factor through its impact on crew health and performance. In absence of sporadic solar particle events the radiation exposure in Low Earth orbit (LEO) inside Spacecraft is determined by the galactic cosmic radiation (protons and heavier ions) and by the protons inside the South Atlantic Anomaly (SAA), an area where the radiation belt comes closer to the earth surface due to a displacement of the magnetic dipole axes from the Earth's center. In addition there is an albedo source of neutrons produced as interaction products of the primary galactic particles with the atoms of the earth atmosphere. Outside the spacecraft the dose is dominated by the electrons of the horns of the radiation belt located at about 60" latitude in Polar Regions. The radiation field has spatial and temporal variations in dependence of the Earth magnetic field and the solar cycle. The complexity of the radiation field inside a spacecraft is further increased through the interaction of the high energy components with the spacecraft shielding material and with the body of the astronauts. In interplanetary missions the radiation belt will be crossed in a couple of minutes and therefore its contribution to their radiation exposure is quite small, but subsequently the protection by the Earth magnetic field is lost, leaving only shielding measures as exposure reduction means. The report intends to describe the radiation field in space, the interaction of the particles with the magnetic field and shielding material and give some numbers on the radiation exposure in low earth orbits and in interplanetary missions. PMID:19205293

Reitz, Guenther

2008-01-01

148

Voyager 1 encounters new region of space  

NASA Astrophysics Data System (ADS)

Voyager 1, which left Earth in 1977 and is now about 10 billion miles away, has entered a region of space with strange anomalies, according to project scientist Ed Stone, former director of the Jet Propulsion Laboratory. The spacecraft has encountered magnetic potholes and bumps-areas where the magnetic field of the heliosheath either nearly vanishes or doubles, respectively. It also has encountered `anomalous cosmic rays' that are less energetic, and thus less dangerous, than galactic cosmic rays. In addition, the solar wind in the heliosheath has been slower than scientists had expected, only about 54,700 kilometers per hour compared with the predicted 322,000-483,000 kilometers per hour. Voyager 1 is expected to reach the edge of the heliosheath in about 10 years.

Zielinski, Sarah

2006-10-01

149

Correlation between the near magnetic field radiated by an EMI filter and its electric working  

Microsoft Academic Search

In this paper, the behavior in radiated mode of an EMI filter used in speed drives is analyzed. It was identified as one of the main sources of magnetic near field radiation. On one hand, the EMI filter is located upstream from the speed drive and is the victim of the other radiation sources of the speed drive. On the

Cecile Labarre; Francois Costa; Jacques Ecrabey

2010-01-01

150

Gamma-ray Burst Prompt Emission: Jitter Radiation in Stochastic Magnetic Field Revisited  

Microsoft Academic Search

We revisit the radiation mechanism of relativistic electrons in the stochastic magnetic field and apply it to the high-energy emissions of gamma-ray bursts (GRBs). We confirm that jitter radiation is a possible explanation for GRB prompt emission in the condition of a large electron deflection angle. In the turbulent scenario, the radiative spectral property of GRB prompt emission is decided

Jirong Mao; Jiancheng Wang

2011-01-01

151

Strong Enhancement of Terahertz Radiation from Laser Filaments in Air by a Static Electric Field  

Microsoft Academic Search

We observe a 3 order of magnitude enhancement of the terahertz energy radiated by a femtosecond pulse undergoing filamentation in air in the presence of a static electric field. Measurements of terahertz pulse duration, spectrum, polarization, and radiation pattern elucidate the physical processes responsible for this radiation. A theoretical model explains the results and predicts another 3 orders of magnitude

Aurélien Houard; Yi Liu; Bernard Prade; Vladimir T. Tikhonchuk; André Mysyrowicz

2008-01-01

152

Electromagnetic Fields Radiated by Fluorescent and Compact Fluorescent Lamps  

Microsoft Academic Search

In the scope of the monIT Project, it was found that fluorescent and compact fluorescent lamps are also important sources of radiation. More than increasing EMF levels in a particular environment, the radiation from ballasts may cause electronic interference with other devices. Two different lamps are analysed, in terms of both their radiated frequency spectrum and their compliance with European

Daniel Sebastião; Carla Oliveira; Gonçalo Carpinteiro; Diana Ladeira; Mónica Antunes; Luís M. Correia; Carlos Fernandes

153

Feasibility of EBT Gafchromic films for comparison exercises among standard beta radiation fields.  

PubMed

The feasibility of using radiochromic films to verify the metrological coherence among standard beta radiation fields was evaluated. Exercises were done between two Brazilian metrology laboratories in beta fields from (90)Sr/(90)Y, (85)Kr and (147)Pm radiation sources. Results showed that the radiochromic film was useful for field mapping aiming uniformity and alignment verification and it was not reliable for absorbed dose measurements only for (147)Pm beta field. PMID:22917942

Benavente, J A; Meira-Belo, L C; Reynaldo, S R; da Silva, T A

2012-07-27

154

Core collapse with strong encounters  

Microsoft Academic Search

This paper explores the possibility that close two-body encounters, though normally unimportant for the evolution of systems of point masses, may be important in the late stages of core collaspe when fewer than 100 particles remain in the core. An orbit-averaged integral equation in energy space is given for the time development of the system, on the assumption that all

J. Goodman

1983-01-01

155

An Encounter with Sex Discrimination  

ERIC Educational Resources Information Center

Phoned job inquiries by students for positions not traditionally held by persons of their sex were followed by calls from those for whom the jobs would have been traditionally appropriate. The results indicate that there is still much sex discrimination. The encounter is suggested as an effective teaching technique. (Author/DE)

Levinson, Richard M.

1976-01-01

156

Polarization dependence of radiation field on Tilted angle of tilted fiber Bragg gratings  

NASA Astrophysics Data System (ADS)

This paper numerically studied few-mode TFBG using Volume Current Method (VCM). Polarization dependent scattering (PDS) at some tilted angle were studied and the distribution of radiation field was numerically simulated. calculated Numerical results showed that when incident wavelengths near the resonant one, the power difference between radiation field of S and P polarization was much small for each mode.

Hong, Wei; Yang, Chun

2006-01-01

157

Apparatus for Scanning and Measuring the Near-Field Radiation of an Antenna.  

National Technical Information Service (NTIS)

Apparatus for measuring the near-field radiation of an antenna such that its far-field radiation characteristics can be determined. The invention utilizes the principle of the Foucault pendulum. It uses a bob attached to a long pendulum arm that is free t...

J. L. Poirier

1985-01-01

158

Analytical representation for 3D fields of antenna radiation in problems of georadar sounding  

Microsoft Academic Search

This paper describes algorithmization representations for field of radiation of the antennas applied in GPR scanning of subsurface structures, in stratiform and two-layer soils in three-dimensional approach. Results include asymptotic representations for fields on small distances from the antenna and analytical representation for a superficial wave. Asymptotic representations of field allow eliminating singularity in numerical modeling, to consider field influence

E. A. Rudenchik; L. B. Volkomirskaya; V. V. Varenkov; A. E. Reznikov; V. I. Sahterov

2008-01-01

159

The Solar and Thermal Radiation Field Below the Venus Clouds  

NASA Astrophysics Data System (ADS)

Even though the H2SO4 clouds that shroud Venus reflect ~80% of the incident sunlight and absorb more than half of the rest, entry probes show that the atmosphere is well illuminated between the cloud base ( ~47.5 km) and the surface. For example, the Pioneer Venus Large Probe entered near the dawn terminator (7:38 AM) and measured downward solar fluxes decreasing from ~200 W/m2 to ~20 W/m2 between the cloud base and surface (Tomasko et al., JGR, 85, 1980). The Venera spectrophotometers showed that the sunlight is most intense at 0.5 1 ? m, except in the near-IR spectral windows at 1.0, 1.1, 1.18, 1.27, 1.31, 1.74, and 2.3 ? m. The sub-cloud region is also illuminated by thermal emission from hot surface and lower atmosphere. This emission is most intense in these spectral windows, where it contributes 0.1 to 1 W/m2/sr/ ? m. A spectrum resolving multiple scattering model was used to study the spectral and angular distribution of this radiation to assess the feasibility of descent imaging from entry probes. The radiation field is azimuthally uniform everywhere below the clouds, even when the sun is on the horizon. At ? < 0.6 ? m, Rayleigh scattering optical depths between the cloud base and the surface are comparable to the optical depth of the main cloud deck (? R ~25 at 0.5 ? m). This scattering will dramatically reduce the contrast in high-altitude (>10 km) images of the surface at visible wavelengths. Fortunately, Rayleigh scattering decreases as 1/? 4, such that ? R<1 at 1.0? m. This spectral region is also relatively free of absorption by gases. It therefore may provide the best opportunity to image the surface from a falling probe. This work is supported by the NASA Planetary Atmospheres Program.

Crisp, D.

2000-10-01

160

A BCCD-based dosimeter for mixed radiation fields  

NASA Astrophysics Data System (ADS)

The development of a personal dosimeter based on a BCCD-detector for mixed neutron and gamma radiation in the energy range from thermal energy to 20 MeV for neutrons respectively 30 keV to a few MeV for gammas will be presented. The detector has to give information on the total radiation dose, D, and on the radiation quality. Both peaces of information are required to determine the directional dose equivalent. The basic radiation physics requirements for the detector as well as a concept of a buried channel CCD-matrix for radiation applications including the technology process will be described. A two dimensional device simulation package was used for both optimization of the charge storage nodes including free charge transfer and the basic electronic processes depending on radiation interaction with silicon.

Pierschel, M.; Ehwald, K.-E.; Heinemann, B.; Januschewski, F.; Schmitz, T.; Schröder, O.

1993-03-01

161

A genetic algorithm based method for source identification and far-field radiated emissions prediction from near-field measurements for PCB characterization  

Microsoft Academic Search

A new method for predicting the far-field radiated emissions and for finding the radiation sources of a device from near-field measurements is presented. It is based on the substitution of the original device by an equivalent set of elemental dipoles, placed over the main radiating sources, which radiate the same near-field (and therefore, far-field). This equivalent set of elemental dipoles

Joan-Ramon Regué; Miquel Ribó; Josep-Maria Garrell; Antonio Martín

2001-01-01

162

Radiative processes in a bichromatic laser field with multiple frequencies  

SciTech Connect

A review of experimental and theoretical studies on radiative processes induced by a bichromatic (two-frequency) laser radiation in atoms, molecules, and solids is presented. The optical excitation of matter is considered at transitions of different types: bound-bound, bound-free, and free-free. A special attention is devoted to the possibility of the coherent control of the basic characteristics of radiative phenomena by varying the relative phase of monochromatic components of radiation. It is shown that this method opens up new possibilities for controlling photoinduced processes. (review)

Astapenko, Valerii A [Moscow Institute of Physics and Technology (State University), Dolgoprudnyi, Moscow Region (Russian Federation)

2006-12-31

163

Edge detection of the radiation field in double exposure portal images using a curve propagation algorithm.  

PubMed

An accurate detection of the radiation field is crucial to 3D conformal radiotherapy (3D-CRT). Automated techniques to detect the field edges on double exposure portal images have previously focused on thresholding techniques. In this paper, we present a new approach based on a curve propagation technique (the Fast Marching method) which proves to be more effective at detecting the radiation field than its thresholding counterpart. The comparison of both techniques in terms of computational speed and effectiveness of the detection is presented using complex images with non-homogeneous intensity levels inside the radiation field, and gradual variations in intensity level at the field boundaries. Results show that our Fast Marching method is easier to automate, and converges faster to the boundaries of the segmented radiation field. The computation time of the Fast Marching technique is five times faster in typical portal images. PMID:19020476

Lasserre, Patricia; Cutt, Bryce; Moffat, James

2008-07-02

164

Comet Lovejoy Survives Close Encounter with Sun  

NASA Video Gallery

NOTE: This video loops 3 times. Comet Lovejoy survives its encounter with the sun. The comet is seen here exiting from behind the right side of the sun, after an hour of travel through its closest approach to the sun. By tracking how the comet interacts with the sun's atmosphere, the corona, and how material from the tail moves along the sun's magnetic field lines, solar scientists hope to learn more about the corona. This movie was filmed by the Solar Dynamics Observatory in 171 Angstrom wavelength, which is typically shown in yellow.

Holly Zell

2011-12-16

165

Effect of laser radiation and electric field on combustion of hydrocarbon-air mixtures  

Microsoft Academic Search

Publications on combustion of hydrocarbon-air mixtures under the action of a weak electric field and laser radiation are analyzed.\\u000a A specific feature of the authors’ experimental study is a pulsed-periodic action of an electric field and focused laser radiation,\\u000a which does not lead to electric discharge or optical breakdown. Numerous experiments reveal a noticeable effect of weak electric\\u000a fields on

P. K. Tretyakov; A. V. Tupikin; V. N. Zudov

2009-01-01

166

Development of a Characterized Radiation Field for Evaluating Sensor Performance  

Microsoft Academic Search

Numerous efforts are funded by US agencies (DOE, DoD, DHS) for development of novel radiation sensing and measurement systems. An effort has been undertaken to develop a flexible shielding system compatible with a variety of sources (beta, X-ray, gamma, and neutron) that can be highly characterized using conventional radiation detection and measurement systems. Sources available for use in this system

D. M. Rogers; T. L. Coggins; J. Marsh; St. D. Mann; Ch. A. Waggoner

2008-01-01

167

Optimal Background Attenuation for Fielded Radiation Detection Systems  

Microsoft Academic Search

Radiation detectors are often placed in positions difficult to shield from the effects of terrestrial background. This is particularly true in the case of Radiation Portal Monitor (RPM) systems, as their wide viewing angle and outdoor installations make them susceptible to terrestrial background from the surrounding area. A low background is desired in most cases, especially when the background noise

Sean M. Robinson; William R. Kaye; John E. Schweppe; Edward R. Siciliano

2006-01-01

168

Optimal Background Attenuation for Fielded Radiation Detection Systems  

Microsoft Academic Search

Radiation detectors are often placed in positions difficult to shield from the effects of terrestrial background. This is particularly true in the case of radiation portal monitor (RPM) systems, as their wide viewing angle and outdoor installations make them susceptible to terrestrial background from the surrounding area. A low background is desired in most cases, especially when attempting to extract

Sean M. Robinson; Willy R. Kaye; John E. Schweppe; Edward R. Siciliano

2007-01-01

169

Radiation fields in star-forming galaxies: the disc, thin disc and bulge  

NASA Astrophysics Data System (ADS)

We provide and describe a library of diffuse stellar radiation fields in spiral galaxies derived using calculations of the transfer of stellar radiation from the main morphological components - discs, thin discs and bulges - through the dusty interstellar medium. These radiation fields are self-consistent with the solutions for the integrated panchromatic spectral energy distributions (SEDs) previously presented using the same model. Because of this, observables calculated from the radiation fields, such as gamma-ray or radio emission, can be self-consistently combined with the solutions for the ultraviolet/optical/submillimetre SEDs, thus expanding the range of applicability of the radiation transfer model to a broader range of wavelengths and physical quantities. We also give analytic solutions for radiation fields in optically thin stellar discs, in stellar discs with one dust disc and in stellar discs with two dust discs. The analytic solutions for the direct light are exact and can be used as benchmarks. The analytic solutions with scattering are only approximate, becoming exact only in the extreme optically thick limit. We find strongly contrasting solutions for the spatial distribution of the radiation fields for discs, thin discs and bulges. For bulges, we find a strong dependence of the radiation fields on the Sérsic index.

Popescu, Cristina C.; Tuffs, Richard J.

2013-10-01

170

ESTIMATING SOLAR RADIATION EXPOSURE IN WETLANDS USING RADIATION MODELS, FIELD DATA, AND GEOGRAPHIC INFORMATION SYSTEMS  

EPA Science Inventory

This seminar will describe development of methods for the estimation of solar radiation doses in wetlands. The methodology presents a novel approach to incorporating aspects of solar radiation dosimetry that have historically received limited attention. These include effects of a...

171

METHODOLOGICAL NOTES: The nature of spontaneous radiation  

NASA Astrophysics Data System (ADS)

The nature of spontaneous radiation is discussed in its technical and historical aspects. The point of view encountered in the literature according to which spontaneous radiation is induced radiation produced by the zero-point (vacuum) oscillations of the electromagnetic field is criticized. Spontaneous radiation is not a purely quantum effect since it occurs also in the classical region (and in this case it is described by classical electrodynamics).

Ginzburg, Vitalii L.

1983-08-01

172

Virtual radiation fields -- A virtual environment tool for radiological analysis and simulation  

SciTech Connect

A virtual reality system was developed for computational and graphical modeling and simulation of radiation environments. This system, called Virtual Radiation Fields (VRF), demonstrates the usefulness of radiological analysis in simulation-based design for predicting radiation doses for robotic equipment and personnel working in a radiation environment. The system was developed for use in determining the radiation doses for robotic equipment to be used in tank-waste retrieval operations at the Hanford National Laboratory. As a reference case, specific application is made to simulate cleanup operations for Hanford tank C-106. A three-dimensional model representation of the tank and its predicted radiation levels are presented and analyzed. Tank cleanup operations were simulated to understand how radiation levels change during the cleanup phase and to predict cumulative radiation doses to robotic equipment to aid in the development of maintenance and replacement schedules.

Knight, T.W.; Dalton, G.R.; Tulenko, J.S. [Univ. of Florida, Gainesville, FL (United States). Dept. of Nuclear Engineering Sciences

1997-02-01

173

Personal Radiation Detector Field Test and Evaluation Campaign.  

National Technical Information Service (NTIS)

Following the success of the Anole test of portable detection system, the U.S. Department of Homeland Security (DHS) Domestic Nuclear Detection Office organized a test and evaluation campaign for personal radiation detectors (PRDs), also known as Pagers. ...

C. A. Hodge D. Yuan M. A. Krstich R. P. Keegan

2007-01-01

174

Normal tissue toxicity after small field hypofractionated stereotactic body radiation.  

PubMed

Stereotactic body radiation (SBRT) is an emerging tool in radiation oncology in which the targeting accuracy is improved via the detection and processing of a three-dimensional coordinate system that is aligned to the target. With improved targeting accuracy, SBRT allows for the minimization of normal tissue volume exposed to high radiation dose as well as the escalation of fractional dose delivery. The goal of SBRT is to minimize toxicity while maximizing tumor control. This review will discuss the basic principles of SBRT, the radiobiology of hypofractionated radiation and the outcome from published clinical trials of SBRT, with a focus on late toxicity after SBRT. While clinical data has shown SBRT to be safe in most circumstances, more data is needed to refine the ideal dose-volume metrics. PMID:18976463

Milano, Michael T; Constine, Louis S; Okunieff, Paul

2008-10-31

175

Determination of the electromagnetic fields radiated from the ARES EMP simulator  

Microsoft Academic Search

This paper describes a calculational model for evaluating the electromagnetic (EM) fields produced by the ARES simulator outside its normal working volume. The model employs transmission line theory to determine the simulator current distribution. Once this is determined, the radiated fields are computed approximately using the Norton surface-wave formalism. The transient electric and magnetic fields on the ground are calculated

Frederick M. Tesche; Charles Mo; R. William Shoup

1994-01-01

176

Increasing the focused response of impulse radiating antennas through polarization control of aperture fields  

Microsoft Academic Search

Wide-band, focused aperture antennas like impulse radiating antennas (IRAs) can see improved aperture efficiency through control of the aperture shape and aperture field distribution. The shape of the aperture fields is largely dictated by the transverse electromagnetic mode distribution on the nondispersive feed of the IRA. In this paper we consider reshaping the aperture field by controlling the polarization of

J. Scott Tyo; M. Dogan; J. H. Boddeker; C. J. Buchenauer

2006-01-01

177

Wake fields of a bunch on a general trajectory due to coherent synchrotron radiation  

Microsoft Academic Search

If short bunches travel along trajectories with small bending radii a simple geometrical condition permits strong longitudinal and radial wake fields to act: electromagnetic fields emitted by a particle can `overtake' on a shelter straight trajectory and interact with particles ahead. The bunch then starts to radiate coherently. The electromagnetic fields along the bunch have strong gradients and in general

Martin Dohlus; A. Kabel; T. Limberg

1997-01-01

178

WAKE FIELDS OF A BUNCH ON A GENERAL TRAJECTORY DUE TO COHERENT SYNCHROTRON RADIATION  

Microsoft Academic Search

If short bunches travel along trajectories with small bend- ing radii a simple geometrical condition permits strong lon- gitudinal and radial wake fields to act: electromagnetic fields emitted by a particle can 'overtake' on a shorter straight trajectory and interact with particles ahead. The bunch then starts to radiate coherently. The electromag- netic fields along the bunch have strong gradients

M. Dohlus; A. Kabel; T. Limberg

1998-01-01

179

The effects of table material on radiated field strength measurement reproducibility at open area test sites  

Microsoft Academic Search

Radiated field strength measurements at open area test sites (OATS) require a nonconductive table to support the equipment under test (EUT). Broadband field strength measurements were performed using tabletops of different materials and thicknesses to investigate the influence of the dielectric properties on the measured field strength. Differences of 10 dB were recorded between fibreglass and wood. Significant differences were

C. Zombolas

2001-01-01

180

Determination of the electromagnetic fields radiated from the ARES EMP simulator  

Microsoft Academic Search

This report describes a calculational model for evaluating the electromagnetic (EM) fields produced by the ARES simulator outside its normal working volume. The model employs transmission line theory to determine the simulator current distribution. Once this is determined, the radiated fields are computed approximately using the Norton surface-wave formalism. The transient electric and magnetic fields on the ground are calculated

Fred M. Tesche; Charles T. Mo

1993-01-01

181

Lesions of the optic radiations mimicking lateral geniculate nucleus visual field defects  

Microsoft Academic Search

Three patients were found to have visual field defects which involved homonymous horizontal sectors of the visual fields, thus mimicking field defects associated with lesions of the lateral geniculate nucleus. Computed tomography provided anatomical evidence that the responsible lesion involved the optic radiations rather than the lateral geniculate nucleus.

J E Carter; P OConnor; D Shacklett; M Rosenberg

1985-01-01

182

Frequency analysis of the induced effects due to the lightning stroke radiated electromagnetic field  

Microsoft Academic Search

The effects of a lightning stroke to the protection system of the control building of an industrial plant are investigated. The results of a frequency-analysis study of effects connected with point values of the electromagnetic field generated within the building or due to the presence of radiation fields, namely, fields whose harmonic components, characterized by small wavelengths compared to the

Condettina Buccella; Saverio Cristina; Antonio Orlandi

1992-01-01

183

Delineation of electric and magnetic field effects of extremely low frequency electromagnetic radiation on transcription  

Microsoft Academic Search

The relative effects of the electric and magnetic field components of extremely low frequency electromagnetic radiation (ELF) on transcription were examined in human leukemia HL-60 cells. Delineation of the individual field contributions was achieved by irradiating cells in separate concentric compartments of a culture dish within a solenoid chamber. This exposure system produced a homogeneous magnetic field with a coincident

James J. Greene; William J. Skowronski; J. Michael Mullins; Roland M. Nardone; Miguel Penafiel; Robert Meister

1991-01-01

184

Magnetic fields in extragalactic jets. II. Specific models and radiative processes  

Microsoft Academic Search

The authors previously calculated magnetic fields produced in axisymmetric charged particle beams (jets) in which electrons (electrons and positrons) have drift velocities with respect to protons. In the present paper numerical solutions are compared with Bessel function and helical magnetic field solutions. Magnetic fields are calculated within mildly relativistic, relativistic, and ultrarelativistic jets interacting with the 2.7 K background radiation.

William K. Rose

1989-01-01

185

Magnetic fields in extragalactic jets. II - Specific models and radiative processes  

Microsoft Academic Search

The authors previously calculated magnetic fields produced in axisymmetric charged particle beams (jets) in which electrons (electrons and positrons) have drift velocities with respect to protons. In the present paper numerical solutions are compared with Bessel function and helical magnetic field solutions. Magnetic fields are calculated within mildly relativistic, relativistic, and ultrarelativistic jets interacting with the 2.7 K background radiation.

William K. Rose

1989-01-01

186

Radiative Transitions for Molecular Collisions in an Intense Laser Field.  

National Technical Information Service (NTIS)

Quantum mechanical and semiclassical approaches are discussed for the study of molecular collisions in an intense laser field. Both a coherent state and Fock state representation of the photon field are investigated. The collision dynamics is described in...

T. P. George J. M. Yuan I. H. Zimmerman J. R. Laing

1976-01-01

187

Tuning Near Field Radiative Heat Flux through Surface Excitations with a Metal Insulator Transition  

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

188

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

PubMed

The control of heat flow is a formidable challenge due to lack of good thermal insulators. Promising new opportunities for heat flow control were recently theoretically discovered for radiative heat flow in near field, where large heat flow contrasts may be achieved by tuning electronic excitations on surfaces. Here we show experimentally that the phase transition of VO2 entails a change of surface polariton states that significantly affects radiative heat transfer in near field. In all cases the Derjaguin approximation correctly predicted radiative heat transfer in near field, but it underestimated the far field limit. Our results indicate that heat flow contrasts can be realized in near field that can be larger than those obtained in far field. PMID:23003960

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

2012-06-07

189

Absorption of radiation by electrons in intense magnetic fields  

Microsoft Academic Search

This paper presents a quantum-mechanical treatment of photon absorption by a homogeneous electron plasma in a uniform magnetic field, in the anisotropic limit for which the electron energies are concentrated in their motion parallel to the field. The results are intended to be appropriate especially for intense fields (in which quantization effects and highly anisotropic plasmas are to be expected).

J. K. Daugherty; J. Ventura

1978-01-01

190

Scalar Radiation Field of a Neutron-Source in Liquid Nitrogen.  

National Technical Information Service (NTIS)

A set of measured values was established for testing computational methods and computer programs for the calculation of the radiation transport from nuclear weapons. The scalar neutron and gamma radiation field from a 14 MeV neutron source in liquid nitro...

B. Broecker K. Clausen P. Johnsen P. Schneider-kuehnle M. Weinert

1974-01-01

191

FDTD method for three-dimensional numerical modeling of ESD radiation field  

Microsoft Academic Search

The Finite-difference frequency-domain (FDTD) method for electromagnetic scattering problems has been extensive applied, however, little has been reported toward using this method for electrostatic discharge (ESD) radiation. Here the FDTD method is used to model and predict the radiation field. A new mathematical descriptions of ESD current was selected after analyzing several typical mathematical descriptions of the ESD current according

Lei Xiaoyong; Li Guangqiang; Jia Mingjie; Wang Pengfei

2010-01-01

192

Determination of the temperature field of a heat-radiating cylinder  

Microsoft Academic Search

The paper examines the nonlinear boundary value problem pertaining to the steady-state temperature field of a heat-radiating cylinder with radiation from the ends of the cylinder governed by a Stefan-Boltzmann law. Application of the Green function together with the Hammerstein variational method enables reduction of the problem to a system of nonlinear algebraic equations.

E. V. Meinarovich

1977-01-01

193

Electromagnetic fields radiated from a lightning return stroke - Application of an exact solution to Maxwell's equations  

Microsoft Academic Search

A solution is presented for the electromagnetic fields radiated by an arbitrarily oriented current filament over a conducting ground plane in the case where the current propagates along the filament at the speed of light, and this solution is interpreted in terms of radiation from lightning return strokes. The solution is exact in the fullest sense; no mathematical approximations are

D. M. Le Vine; R. Meneghini

1978-01-01

194

Determination of Canine Dose Conversion Factors in Mixed Neutron and Gamma Radiation Fields.  

National Technical Information Service (NTIS)

The primary objective of mixed-field neutron/gamma radiation dosimetry in canine irradiation experiments conducted at the Armed Forces Radiobiology Research Institute (AFRRI) is to determine the absorbed midline tissue dose (MLT) at the region of interest...

B. A. Torres R. C. Bhatt J. C. Myska B. K. Holland

1996-01-01

195

Efficient use of radiation field in mass testing of hollow cylindrical parts. [Diesel engine crankshaft bushings  

Microsoft Academic Search

It is shown that the radiation fields used in radiographic testing of hollow cylindrical parts, such as crankshaft bushings, which are exposed in parts, can be more efficiently utilized. The concept of a so-called ''dense'' packing is introduced.

Levenberg

1976-01-01

196

Radiation Field in Air Due to Distributed Gamma-Ray Sources in the Ground.  

National Technical Information Service (NTIS)

A much more complete and detailed picture of the external environmental gamma-ray radiation field has been obtained through gamma-ray transport calculations of exposure rates, differential energy spectra, integral exposure rate spectra, and angular exposu...

H. Beck G. de Planque

1968-01-01

197

Radiation-thermal processing of high-viscous oil from Karazhanbas field  

NASA Astrophysics Data System (ADS)

Regularities of radiation-induced chemical conversion in high-viscous oil from Karazhanbas field (peninsula Buzachi, Kazakhstan) are discussed. Changes in hydrocarbon and fractional contents of liquid cracking products are analyzed.

Zaykina, R. F.; Zaykin, Y. A.; Mamonova, T. B.; Nadirov, N. K.

2001-02-01

198

Attenuation of VHE Gamma Rays by the Milky Way Interstellar Radiation Field  

SciTech Connect

The attenuation of very high energy gamma rays by pair production on the Galactic interstellar radiation field has long been thought of as negligible. However, a new calculation of the interstellar radiation field consistent with multi-wavelength observations by DIRBE and FIRAS indicates that the energy density of the Galactic interstellar radiation field is higher, particularly in the Galactic center, than previously thought. We have made a calculation of the attenuation of very high energy gamma rays in the Galaxy using this new interstellar radiation field which takes into account its nonuniform spatial and angular distributions. We find that the maximum attenuation occurs around 100 TeV at the level of about 25% for sources located at the Galactic center, and is important for both Galactic and extragalactic sources.

Moskalenko, Igor V.; /Stanford U., HEPL; Porter, Troy A.; /Louisiana State U.; Strong, Andrew W.; /Garching, Max Planck Inst., MPE

2006-04-19

199

Dose, dose-rate and field size effects on cell survival following exposure to non-uniform radiation fields  

NASA Astrophysics Data System (ADS)

For the delivery of intensity-modulated radiation therapy (IMRT), highly modulated fields are used to achieve dose conformity across a target tumour volume. Recent in vitro evidence has demonstrated significant alterations in cell survival occurring out-of-field which cannot be accounted for on the basis of scattered dose. The radiobiological effect of area, dose and dose-rate on out-of-field cell survival responses following exposure to intensity-modulated radiation fields is presented in this study. Cell survival was determined by clonogenic assay in human prostate cancer (DU-145) and primary fibroblast (AG0-1522) cells following exposure to different modulated field configurations delivered using a X-Rad 225 kVp x-ray source. Uniform survival responses were compared to in- and out-of-field responses in which 25-99% of the cell population was shielded. Dose delivered to the out-of-field region was varied from 1.6-37.2% of that delivered to the in-field region using different levels of brass shielding. Dose rate effects were determined for 0.2-4 Gy min-1 for uniform and modulated exposures with no effect seen in- or out-of-field. Survival responses showed little dependence on dose rate and area in- and out-of-field with a trend towards increased survival with decreased in-field area. Out-of-field survival responses were shown to scale in proportion to dose delivered to the in-field region and also local dose delivered out-of-field. Mathematical modelling of these findings has shown survival response to be highly dependent on dose delivered in- and out-of-field but not on area or dose rate. These data provide further insight into the radiobiological parameters impacting on cell survival following exposure to modulated irradiation fields highlighting the need for refinement of existing radiobiological models to incorporate non-targeted effects and modulated dose distributions.

Butterworth, Karl T.; McGarry, Conor K.; Trainor, Colman; McMahon, Stephen J.; O'Sullivan, Joe M.; Schettino, Giuseppe; Hounsell, Alan R.; Prise, Kevin M.

2012-05-01

200

Effect of ionizing radiation field on CsI aerosols formed by condensation of supersaturated vapor  

Microsoft Academic Search

The effect of the ionizing radiation field on the behavior of CsI aerosols formed by condensation of supersaturated vapor\\u000a was examined. Supersaturated CsI vapor was formed by evaporation from a metal surface ohmically heated to high temperatures.\\u000a A study of the size distribution function of CsI particles showed that, both in the field of 60Co ?-radiation and in a stationary

N. B. Mikheev; I. V. Melikhov; V. A. Lavrikov; A. N. Kamenskaya; V. V. Kulemin; S. A. Kulyukhin

2011-01-01

201

A simple ionizing radiation spectrometer/dosimeter based on radiation sensing field effect transistors (RadFETs)  

SciTech Connect

This paper reports on the processing steps in a silicon foundry leading to improved performance of the Radiation Sensing Field Effect Transistor (RadFET) and the use of multiple RadFETs in a handheld, battery operated, combination spectrometer/dosimeter.

Moreno, D.J.; Hughes, R.C.; Jenkins, M.W.; Drumm, C.R.

1997-05-01

202

3D Cloud Radiative Effects on Aerosol Optical Thickness Retrievals in Cumulus Cloud Fields in the Biomass Burning Region in Brazil  

NASA Astrophysics Data System (ADS)

Aerosol amount in clear regions of a cloudy atmosphere is a critical parameter in studying the interaction between aerosols and clouds. Since the global cloud cover is about 50%, cloudy scenes are often encountered in any satellite images. Aerosols are more or less transparent, while clouds are extremely reflective in the visible spectrum of solar radiation. The radiative transfer in clear-cloudy condition is highly three-dimensional (3D). This paper focuses on estimating the 3D effects on aerosol optical thickness retrievals using Monte Carlo simulations. An ASTER image of cumulus cloud fields in the biomass burning region in Brazil is simulated in this study. The MODIS products (i.e., cloud optical thickness, particle effective radius, cloud top pressure, surface reflectance, etc.) are used to construct the cloud property and surface reflectance fields. To estimate the cloud 3D effects, we assume a plane-parallel stratification of aerosol properties in the 60 km x 60 km ASTER image. The simulated solar radiation at the top of the atmosphere is compared with plane-parallel calculations. Furthermore, the 3D cloud radiative effects on aerosol optical thickness retrieval are estimated.

Wen, G.; Marshak, A.; Cahalan, R. F.

2004-12-01

203

Pyridinylidene-phenoxide in strong electric fields: controlling orientation, conical intersection, and radiation-less decay.  

PubMed

Strong electric fields open new routes for the control of radiation-less decay in molecules with conical intersections. Here, we present quantum chemical and quantum dynamical simulations which demonstrate that the radiation-less decay and related photoisomerization of pyridinylidene-phenoxide can be effectively manipulated with strong electric fields by shifting the conical intersection. Moreover, we show the effects of the electric field on the orientation of the molecules and on the photoexcitation and discuss the conditions for which the field induced coupling between rotational and vibronic states can be neglected. PMID:22867016

Belz, S; Zilberg, S; Berg, M; Grohmann, T; Leibscher, M

2012-08-20

204

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

SciTech Connect

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

Underwood, H.R. (Wheaton College, IL (United States)); Peterson, A.F. (Georgia Institute of Technology, Atlanta (United States)); Magin, R.L. (University of Illinois, Urbana (United States))

1992-02-01

205

Computation of High-Altitude Hypersonic Flow-Field Radiation  

Microsoft Academic Search

Accurate calculations of radiation on and from transatmospheric flight vehicles are currently a challenge to computational aerodynamicists. Due to combined effects of low density and hypersonic flight conditions, the gas in the shock-layer is in a state of thermal and chemical nonequilibrium. The present work aims at gathering existing ideas together about how such flows should be modeled and comparing

Stephane Moreau

1994-01-01

206

Comparison between GTEM and OATS radiated field emission measurements  

Microsoft Academic Search

Open area test site (OATS) is the standard test facility on radiated emission testing. The necessity of alternative methods to OATS that meet the requirements of CISPR or EN standards and the time, cost and space limitations of traditional alternative facilities (as semianechoic chambers) are impelling new methods; the problem using those new facilities is the acceptance of the measurements.

R. Guirado; R. del Rio; J. Carpio; F. Garnacho; A. Valladolid; M. Valcarcel

1995-01-01

207

A search for advanced fields in electro-magnetic radiation  

Microsoft Academic Search

An experiment to search for an advanced component of electromagnetic radiation, as suggested by the time symmetry of Maxwell's equations was conducted. A dipole transmitting antenna was driven periodically with 10.2 GHz microwave pulses of 12 ns duration and 4 watt instantaneous power. A receiving dipole antenna at a distance R = 10m away was instrumented to search for power

J. D. Schmidt

1980-01-01

208

ELECTRICAL FIELDS AND ELECTROMAGNETIC RADIATION FROM CHEMICAL EXPLOSIONS  

Microsoft Academic Search

3 7 3 \\/ d electromagnetic radiation generated by chemical ; detonations of charges ranging in size from 10g to roughly 25 kg were ; investigated over a frequency range extending from a few cycles per second to 500 ; megacycles per second. The electrical energy in all cases was found to cover a ; broad band of frequencies with

Keyes

1959-01-01

209

Modulation of the earth's electric field by cosmic radiation  

Microsoft Academic Search

Relationships between cosmic radiation levels and the ionospheric potential are investigated as a possible mechanism for solar effects on terrestrial meteorology not involving a heating process. Cosmic ray data obtained by the neutron monitor at Mount Washington, New Hampshire, and by the IMP 4 satellite were compared with measurements of ionospheric potential acquired by aircraft soundings in the Bahamas and

Ralph Markson

1981-01-01

210

Superkicks in hyperbolic encounters of binary black holes.  

PubMed

Generic inspirals and mergers of binary black holes produce beamed emission of gravitational radiation that can lead to a gravitational recoil or kick of the final black hole. The kick velocity depends on the mass ratio and spins of the binary as well as on the dynamics of the binary configuration. Studies have focused so far on the most astrophysically relevant configuration of quasicircular inspirals, for which kicks as large as approximately 3300 km s;(-1) have been found. We present the first study of gravitational recoil in hyperbolic encounters. Contrary to quasicircular configurations, in which the beamed radiation tends to average during the inspiral, radiation from hyperbolic encounters is plunge dominated, resulting in an enhancement of preferential beaming. As a consequence, it is possible in highly relativistic scatterings to achieve kick velocities as large as 10 000 km s;(-1). PMID:19257409

Healy, James; Herrmann, Frank; Hinder, Ian; Shoemaker, Deirdre M; Laguna, Pablo; Matzner, Richard A

2009-01-27

211

Origin of magnetic field enhancement in the generation of terahertz radiation from semiconductor surfaces.  

PubMed

We present a theory of the magnetic field enhancement of terahertz (THz) emission from photogenerated carriers in the surface depletion region of a semiconductor. A combination of the Drude-Lorentz model for the carrier dynamics with an appropriate solution of the radiation problem is sufficient to explain the strong B -field enhancement in THz radiation that has been observed experimentally. The effect arises primarily from the increased radiation efficiency of transient currents flowing in the plane of the surface. The model provides quantitative agreement with experiment for the pronounced angular dependence of the enhancement and predicts the correct trend for the enhancement in a variety of materials. PMID:18040471

Shan, J; Weiss, C; Wallenstein, R; Beigang, R; Heinz, T F

2001-06-01

212

Involved field radiation for Hodgkin's lymphoma: the actual dose to breasts in close proximity.  

PubMed

To decrease the risk of late toxicities in Hodgkin's lymphoma (HL) patients treated with radiation therapy (RT) (HL), involved field radiation therapy (IFRT) has largely replaced the extended fields. To determine the out-of-field dose delivered from a typical IFRT to surrounding critical structures, we measured the dose at various points in an anthropomorphic phantom. The phantom is divided into 1-inch-thick slices with the ability to insert TLDs at 3-cm intervals grid spacing. Two treatment fields were designed, and a total of 45 TLDs were placed (equally spaced) at the margin of the each of the 2 radiation fields. After performing a computed tomography simulation, 2 treatment plans targeting the mediastinum, a typical treatment field in patients with early stage HL, were generated. A total dose of 3060 cGy was delivered to the gross tumor volume for each field consecutively. The highest measured dose detected at 1 cm from the field edge in the planning target volume was 496 cGy, equivalent to 16% of the isocentric dose. The dose dropped significantly with increasing distance from the field edge. It ranged from 1.1-3.9% of the isocentric dose at a distance of 3.2-4 cm to <1.6% at a distance of >6 cm. Although the computer treatment planning system (CTPS) frequently underestimated the dose delivered, the difference in dose between measured and generated by CTPS was <2.5% in 90 positions measured. The collateral dose of radiation to breasts from IFRT is minimal. The out-of-field dose, although mildly underestimated by CTPS, becomes insignificant at >3 cm from the field edge of the radiation field. PMID:22513213

Dabaja, Bouthaina; Wang, Zhonglo; Stovall, Marilyn; Baker, Jamie S; Smith, Susan A; Khan, Meena; Ballas, Leslie; Salehpour, Mohammad R

2012-04-17

213

Involved field radiation for Hodgkin's lymphoma: The actual dose to breasts in close proximity  

SciTech Connect

To decrease the risk of late toxicities in Hodgkin's lymphoma (HL) patients treated with radiation therapy (RT) (HL), involved field radiation therapy (IFRT) has largely replaced the extended fields. To determine the out-of-field dose delivered from a typical IFRT to surrounding critical structures, we measured the dose at various points in an anthropomorphic phantom. The phantom is divided into 1-inch-thick slices with the ability to insert TLDs at 3-cm intervals grid spacing. Two treatment fields were designed, and a total of 45 TLDs were placed (equally spaced) at the margin of the each of the 2 radiation fields. After performing a computed tomography simulation, 2 treatment plans targeting the mediastinum, a typical treatment field in patients with early stage HL, were generated. A total dose of 3060 cGy was delivered to the gross tumor volume for each field consecutively. The highest measured dose detected at 1 cm from the field edge in the planning target volume was 496 cGy, equivalent to 16% of the isocentric dose. The dose dropped significantly with increasing distance from the field edge. It ranged from 1.1-3.9% of the isocentric dose at a distance of 3.2-4 cm to <1.6% at a distance of >6 cm. Although the computer treatment planning system (CTPS) frequently underestimated the dose delivered, the difference in dose between measured and generated by CTPS was <2.5% in 90 positions measured. The collateral dose of radiation to breasts from IFRT is minimal. The out-of-field dose, although mildly underestimated by CTPS, becomes insignificant at >3 cm from the field edge of the radiation field.

Dabaja, Bouthaina, E-mail: bdabaja@mdanderson.org [Departments of Radiation Oncology, Radiation Physics at University of Texas MD Anderson Cancer Center, Houston, TX (United States); Wang Zhonglo; Stovall, Marilyn; Baker, Jamie S.; Smith, Susan A.; Khan, Meena; Ballas, Leslie; Salehpour, Mohammad R. [Departments of Radiation Oncology, Radiation Physics at University of Texas MD Anderson Cancer Center, Houston, TX (United States)

2012-01-01

214

Gamma heating measurements in a mixed radiation field  

SciTech Connect

Gamma hearing measurements have been made in a low-Z assembly irradiated with 14-MeV neutrons and (n,n{prime}) gammas produced by a Texas Nuclear Model 9400 neutron generator. The assembly is composed of 144 magnesium sleeves (5cm {times} 5cm {times} 60cm {times} 3 mm thick) filled with graphite to simulate a fusion blanket test module. Heating measurements were made in the mid-line of the assembly using a proportional counter operating in the Continuously-varied Bias-voltage Acquisition (CBA) mode. The neutron induced atomic recoil signal was rejected by observing the signal rise-time differences inherent to radiations of different LET. The experiment was modelled using the one-dimensional radiation transport code ANISN/PC. The operating limits of this technique were identified by comparing measurements made at different positions in the assembly and then comparing these measurements to the calculated flux. 7 refs., 5 figs., 1 tab.

Chiu, H.K. (Illinois Univ., Urbana, IL (USA). Dept. of Nuclear Engineering); Bennett, E.F.; Micklich, B.J. (Argonne National Lab., IL (USA))

1990-09-01

215

Radiation-field control by single steam generator cooldowns. [PWR  

SciTech Connect

Steam generator radiation levels were compiled for several power reactor cooldowns executed using a single steam generator while the second generator's secondary side was isolated. These radiation levels were compared with normal cooldowns done using both steam generators. There are many fluctuations in the data, both up and down, but none which could be unambiguously attributed to single steam generator cooldowns. One cooldown, Oconee Unit 2 at the end of cycle 2 was studied in detail. Hourly primary system samples were analyzed for particulate and soluble radioactive corrosion products. The plant computer was used to monitor over 30 temperatures, pressures, and flows to compare the cooldown steam generator with the isolated steam generator. No major differences between the two, other than flow rates, were observed. A study of steam generator crud reduction by secondary side heating was also conducted. It was concluded that the technique has the potential for cleaning the tubes, but not the heads.

Schmotzer, J.K.

1982-12-01

216

Polarization of atomic radiation in stochastic plasma fields  

SciTech Connect

When a laser pulse of certain polarization or an electron beam excites atoms in a plasma, the atomic spectrum of the radiation emitted by the atoms exhibits differently polarized line core and line wings. This unusual effect, which is predicted to occur under a variety of conditions, can be accompanied by the appearance of the forbidden component in the spectrum, with polarization opposite to that of the exciting laser pulse.

Savchenko, V.I.; Fisch, N.J.

1997-05-12

217

Study of Zitterbewegung and the Radiated Fields in Graphene System  

NASA Astrophysics Data System (ADS)

We theoretically study Zitterbewegung behavior of electrons in graphene system when the external perpendicular magnetic field exists. The initial state is assumed as a wave packet shape which is the superposition of the positive and negative LLs. The evolution of the dipole moments and the excited electric fields are calculated for the localized and extended wave packets which exhibit different behavior. We further analyze their Fourier spectrum and study which factors affect the excited electric field as it can be directly detected in experiment. The results are analyzed and discussed.

Wang, Yi-Xiang; He, Yue-Juan; Xiong, Shi-Jie

2012-08-01

218

Calculation of the radiation force on a cylinder in a standing wave acoustic field  

Microsoft Academic Search

We present a new calculation of the radiation force on a cylinder in a standing wave acoustic field. We use the formula to calculate the force on a cylinder which is free to move in the field and one which is fixed in space.

David Haydock

2005-01-01

219

[The use of a detector of the extremely weak radiation as a variometer of gravitation field].  

PubMed

It was shown that the detector of extremely weak radiation with selectively increased sensitivity to the nonelectromagnetic, including the gravitational component of the spectrum of active physical fields can be used as the basis for constructing a variometer of gravitational field of a new type. PMID:11605376

Gorshkov, E S; Bondarenko, E G; Shapovalov, S N; Sokolovski?, V V; Troshichev, O A

220

FAR FIELD RADIATION FROM AN ARBITRARILY ORIENTED HERTZIAN DIPOLE IN AN UNBOUNDED ELECTRICALY GYROTROPIC MEDIUM  

Microsoft Academic Search

The solution to the problem of far field radiation from an arbitrarily oriented Hertzian dipole in an electrically gyrotropic medium is found with the application of dyadic Green's function (DGF) technique. The form of the DGF, which is expressed as the sum of two single dyads, simplifies the derivation of the far fields significantly in comparison to the existing methods.

Abdullah Eroglu; Jay K. Lee

2009-01-01

221

Electromagnetic field radiated from broadband signal transmission on power line carrier channels  

Microsoft Academic Search

A rigorous procedure is presented for the evaluation of the rectangular components of the electromagnetic field radiated by excited carrier channels on multiconductor overhead power lines above a lossy ground. The proposed full wave approach, based on the use of Hertz potentials, allows to carry out the high-frequency analysis of a spread spectrum transmission system. Field sources are the current

M. S. Sarto

1997-01-01

222

Lightning-Channel Morphology Revealed by Return-Stroke Radiation Field Waveforms.  

National Technical Information Service (NTIS)

Simultaneous video and wideband-electric-field recordings of 32 cloud- to-ground lightning flashes in Florida were analyzed to show that the formation of new channels to ground can be detected by examination of the return-stroke radiation fields alone. Th...

J. C. Willett D. M. LeVine V. P. Idone

1995-01-01

223

Cloud field identification for earth radiation budget studies. Part II: Cloud field classification for the ScaRaB radiometer  

SciTech Connect

The radiometer ScaRaB (scanner for radiation balance) has two narrowband channels (0.5-0.7 and 10.5-12.5 {mu}m) in addition to the two broadband channels (0.2-4 and 0.2-50 {mu}m) necessary for earth radiation budget (ERB) measurements in order to improve cloud detection. Most automatic cloud classifications were developed with measurements of very good spatial resolution (200 m to 5 km). Earth radiation budget experiments (ERBE), on the other hand, work at a spatial resolution of about 50 km (at nadir), and therefore a cloud field classification adapted to this scale must be investigated. For this study, ScaRaB measurements are simulated by collocated Advanced Very High Resolution Radiometer (AVHRR) ERBE data. The best-suited variables for a global cloud classification are chosen using as a reference cloud types determined by an operationally working threshold algorithm applied to AVHRR measurements at a reduced spatial resolution of 4 km over the North Atlantic. Cloud field types are then classified by an algorithm based on the dynamic clustering method. More recently, the authors have carried out a global cloud field identification using cloud parameters extracted by the 3I (improved initialization inversion) algorithm, from High-Resolution Infrared Sounder (HIRS) - Microwave Sounding Unit (MSU) data. This enables the authors first to determine mean values of the variables best suited for cloud field classification and then to use a maximum-likelihood method for the classification. The authors find that a classification of cloud fields is still possible at a spatial resolution of ERB measurements. Roughly, one can distinguish three cloud heights and two effective cloud amounts (combination of cloud emissivity and cloud cover). However, only by combining flux measurements (ERBE) with cloud field classifications from sounding instruments (HIRS/MSU) can differences in radiative behavior of specific cloud fields be evaluated accurately. 29 refs., 14 figs., 3 tabs.

Stubenrauch, C.J.; Seze, G.; Scott, N.A.; Chedin, A. [Laboratoire de Meteorologie Dynamique du CNRS, Palaiseau (France)] [and others

1996-03-01

224

Acetylcholinesterase: diffusional encounter rate constants for dumbbell models of ligand.  

PubMed Central

For some enzymes, virtually every substrate molecule that encounters the entrance to the active site proceeds to reaction, at low substrate concentrations. Such diffusion-limited enzymes display high apparent bimolecular rate constants ((kcat/KM)), which depend strongly upon solvent viscosity. Some experimental studies provide evidence that acetylcholinesterase falls into this category. Interestingly, the asymmetric charge distribution of acetylcholinesterase, apparent from the crystallographic structure, suggests that its electrostatic field accelerates the encounter of its cationic substrate, acetylcholine, with the entrance to the active site. Here we report simulations of the diffusion of substrate in the electrostatic field of acetylcholinesterase. We find that the field indeed guides the substrate to the mouth of the active site. The computed encounter rate constants depend upon the particular relative geometries of substrate and enzyme that are considered to represent successful encounters. With loose reaction criteria, the computed rates exceed those measured experimentally, but the rate constants vary appropriately with ionic strength. Although more restrictive reaction criteria lower the computed rates, they also lead to unrealistic variation of the rate constants with ionic strength. That these simulations do not agree well with experiment suggests that the simple diffusion model is incomplete. Structural fluctuations in the enzyme or events after the encounter may well contribute to rate limitation. Images FIGURE 1

Antosiewicz, J; Gilson, M K; Lee, I H; McCammon, J A

1995-01-01

225

Magnetic fields in extragalactic jets. II. Specific models and radiative processes  

SciTech Connect

The authors previously calculated magnetic fields produced in axisymmetric charged particle beams (jets) in which electrons (electrons and positrons) have drift velocities with respect to protons. In the present paper numerical solutions are compared with Bessel function and helical magnetic field solutions. Magnetic fields are calculated within mildly relativistic, relativistic, and ultrarelativistic jets interacting with the 2.7 K background radiation. A principal conclusion of these calculations is that large-scale magnetic fields with intensities comparable to those within radio galaxies can be generated by the interaction of mildly relativistic jets with the 2.7 K background radiation. Expressions for the radiation from electrons within jets are calculated, and mechanisms for electron accelerators are discussed. 6 references.

Rose, W.K.

1989-02-01

226

X-ray pixel beam array systems and methods for electronically shaping radiation fields and modulation radiation field intensity patterns for radiotherapy  

US Patent & Trademark Office Database

X-ray pixel beam array systems and methods for electronically shaping radiation fields and modulating radiation field intensity patterns for radiotherapy are disclosed. One exemplary pre-clinical system may include addressable electron field emitters (102, 104) that are operable to emit a plurality of electron pixel beams (106, 108, 110). Each electron pixel beam may correspond to an x-ray target (124) and x-ray pixel beam collimation aperture (136, 138) to convert a portion of energy associated with the electron pixel beam to a corresponding x-ray pixel beam (140, 142). Further, the x-ray pixel beam array collimator (130) forms a one-to-one correspondence between individual electron pixel beam and its corresponding x-ray pixel beam. One exemplary clinical system may include a high-energy electron source (1203), an n-stage scanning system (1210), x-ray pixel beam targets (1212), and an x-ray pixel beam array collimator (1214). A controller (1206) may sequentially direct electron beam pulses to predetermined x-ray pixel targets and produce an electronically controlled radiation field direction, pattern; and intensity pattern.

2012-11-06

227

A MEMS Device Capable of Measuring Near-Field Thermal Radiation between Membranes  

PubMed Central

For sensors constructed by freestanding membranes, when the gap between a freestanding membrane and the substrate or between membranes is at micron scale, the effects of near-field radiative heat transfer on the sensors' thermal performance should be considered during sensor design. The radiative heat flux is transferred from a membrane to a plane or from a membrane to a membrane. In the current study of the near-field thermal radiation, the scanning probe technology has difficulty in making a membrane separated at micron scale parallel to a plane or another membrane. A novel MEMS (micro electromechanical system) device was developed by sacrificial layer technique in this work to realize a double parallel freestanding membrane structure. Each freestanding membrane has a platinum thin-film resistor and the distance between the two membranes is 1 ?m. After evaluating the electrical and thermal characteristics of the lower freestanding membrane,experimental measurements of near-field radiative heat transfer between the lower membrane and the upper membrane were carried out by setting the lower membrane as a heat emitter and the upper membrane as a heat receiver. The near-field radiative heat transfer between the two membranes was validated by finding a larger-than-blackbody radiative heat transfer based on the experimental data.

Feng, Chong; Tang, Zhenan; Yu, Jun; Sun, Changyu

2013-01-01

228

Radiation of an Antenna in a Cold Plasma. Calculation of the Perturbation and Approximation Determination of the Radiation Field Rayonnement d'Une Antenne dans UN Plasma Froid. Calcul de la Perturbation et Determination Approchee du Champ.  

National Technical Information Service (NTIS)

The differential equation for calculation of the electric antenna radiation field of an antenna radiating in a cold plasma was drawn up. The electric field is isotropic and radiates near plasma resonance. Certain solutions are elaborated.

E. Argence

1974-01-01

229

Near-field imaging of radiated emission sources on printed-circuit boards  

Microsoft Academic Search

This paper presents a technique to assess the level of radiated emissions generated by printed-circuit board (PCB) structures based on equivalent magnetic currents. These currents are extracted from near-field measurements taken with a very high resolution (step size << ?) in comparison with near-field antenna applications. Near-field data allow the visualization and extraction of common-mode currents near transmission line discontinuities

Jean-Jacques Laurin; Z. Ouardhiri; J. Colinas

2001-01-01

230

Acoustic radiation torque on an irregularly shaped scatterer in an arbitrary sound field.  

PubMed

To eliminate the limitation of the conventional acoustic radiation torque theory, which is only applicable to a disklike scatterer in a plane sound field, a new theory is established to calculate the radiation torque on any irregularly shaped scatterer in any arbitrary sound field. First, with the aid of the conservation law of angular momentum, the acoustic radiation torque is expressed as the angular momentum flux through a spherical surface with the center at the scatterer's centroid. Second, the velocity potential of the scattered field is derived, taking into account the influences of the translational and rotational movements of the scatterer induced by the first order stress of the incident sound field. Finally, a general calculating formula of the acoustic radiation torque is achieved. For a disklike scatterer in a plane sound filed, results from the above formula are well identical with those conventional formulas. By studying the case of a semicircular cylinder scatterer in a standing-wave sound field, it is found that for an irregularly shaped scatterer its rotation velocity is normally nonzero and the radiation torque changes with the spatial attitude. PMID:19045760

Fan, Zongwei; Mei, Deqing; Yang, Keji; Chen, Zichen

2008-11-01

231

Evaporating very small grains as tracers of the UV radiation field in photo-dissociation regions  

NASA Astrophysics Data System (ADS)

Context. In photo-dissociation regions (PDRs), polycyclic aromatic hydrocarbons (PAHs) may be produced by evaporation of very small grains (VSGs) by the impinging UV radiation field from a nearby star. Aims: We quantitatively investigate the transition zone between evaporating VSGs (eVSGs) and PAHs in several PDRs. Methods: We studied the relative contribution of PAHs and eVSGs to the mid-IR emission in a wide range of excitation conditions. We fitted the observed mid-IR emission of PDRs by using a set of template band emission spectra of PAHs, eVSGs, and gas lines. The fitting tool PAHTAT (PAH Toulouse Astronomical Templates) is made available to the community as an IDL routine. From the results of the fit, we derived the fraction of carbon feVSG locked in eVSGs and compared it to the intensity of the local UV radiation field. Results: We show a clear decrease of feVSG with increasing intensity of the local UV radiation field, which supports the scenario of photo-destruction of eVSGs. Conversely, this dependence can be used to quantify the intensity of the UV radiation field for different PDRs, including unresolved ones. Conclusions: PAHTAT can be used to trace the intensity of the local UV radiation field in regions where eVSGs evaporate, which correspond to relatively dense (nH = [100,105] cm-3) and UV irradiated PDRs (G0 = [100,5 × 104] ) where H2 emits in rotational lines.

Pilleri, P.; Montillaud, J.; Berné, O.; Joblin, C.

2012-06-01

232

Microwave radiation power of relativistic electron beam with virtual cathode in the external magnetic field  

NASA Astrophysics Data System (ADS)

The study of the output power of the electromagnetic radiation of the relativistic electron beam (REB) with virtual cathode in the presence of external magnetic field has been found out. The typical dependencies of the output microwave power of the vircator versus external magnetic field have been analyzed by means of 3D electromagnetic simulation. It has been shown that the power of vircator demonstrates several maxima with external magnetic field growth. The characteristic features of the power behavior are determined by the conditions of the virtual cathode formation in the presence of the external transversal magnetic field and the REB self-magnetic fields.

Kurkin, S. A.; Hramov, A. E.; Koronovskii, A. A.

2013-07-01

233

Radiation Field Wave Forms Produced by Lightning Stepped Leaders  

Microsoft Academic Search

Broad band electric field data are presented which show stepped leader wave forms preceding records of distant lightning return strokes. The majority of leader pulses are characterized by a large initial peak with a small and slow opposite overshoot. Total pulse durations range from 15-40 us several milliseconds before the return stroke to 2-10 us immediately preceding the return stroke.

E. Philip Krider; George J. Radda

1975-01-01

234

Measurement of Two-Dimensional Photon Beam Distributions Using a Fiber-Optic Radiation Sensor for Small Field Radiation Therapy  

Microsoft Academic Search

In this study, we fabricated a fiber-optic radiation sensor with an organic scintillator to measure the high-energy photon beam from a clinical linear accelerator, and a two-dimensional fiber-optic sensor array to measure high-resolution and real-time dose distributions for small field radiotherapy dosimetry. The scintillating lights generated from each organic sensor probe embedded and arrayed in a water phantom are guided

Bongsoo Lee; Kyoung Won Jang; Dong Hyun Cho; Wook Jae Yoo; Sang Hun Shin; Hyung Sik Kim; Jeong Han Yi; Sin Kim; Hyosung Cho; Byung Gi Park; Joo Hyun Moon; Siyong Kim

2008-01-01

235

Coherent processes in atom in strong radiation fields  

NASA Astrophysics Data System (ADS)

During this grant period work proceeded to study alternative methods of integrating the higher dimensional time-dependent partial differential equations that arise in the study of atoms interacting with intense laser radiation. Present methods use, for example, Taylor series propagators applied to finite difference and basis set models. We have more recently developed modified propagators based on polynomial extrapolation and rational polynomial extrapolation (Buelisch-Stoer) and have prepared versions that can be effectively vectorized on Cray YMP computers, and in the case of polynomial extrapolation, parallelized on massively parallel computers. In addition, the stability and accuracy of the finite difference models have been compared to those based on interpolatory splines. The main effort in this grant was directed toward developing numerical integrators for the Schroedinger equation describing the interaction on atoms with circularly polarized light.

Clark, C. W.; McIlrath, T. J.

1993-09-01

236

Personal Radiation Detector Field Test and Evaluation Campaign  

SciTech Connect

Following the success of the Anole test of portable detection system, the U.S. Department of Homeland Security (DHS) Domestic Nuclear Detection Office organized a test and evaluation campaign for personal radiation detectors (PRDs), also known as 'Pagers'. This test, 'Bobcat', was conducted from July 17 to August 8, 2006, at the Nevada Test Site. The Bobcat test was designed to evaluate the performance of PRDs under various operational scenarios, such as pedestrian surveying, mobile surveying, cargo container screening, and pedestrian chokepoint monitoring. Under these testing scenarios, many operational characteristics of the PRDs, such as gamma and neutron sensitivities, positive detection and false alarm rates, response delay times, minimum detectable activities, and source localization errors, were analyzed. This paper will present the design, execution, and methodologies used to test this equipment for the DHS.

Chris A. Hodge, Ding Yuan, Raymond P. Keegan, Michael A. Krstich

2007-07-09

237

NOTE: Intraoperative radiation therapy using a mobile electron linear accelerator: field matching for large-field electron irradiation  

NASA Astrophysics Data System (ADS)

Intraoperative radiation therapy (IORT) consists of delivering a large, single-fraction dose of radiation to a surgically exposed tumour or tumour bed at the time of surgery. With the availability of a mobile linear accelerator in the OR, IORT procedures have become more feasible for medical centres and more accessible to cancer patients. Often the area requiring irradiation is larger than what the treatment applicators will allow, and therefore, two or more adjoining fields are used. Unfortunately, the divergence and scattering of the electron beams may cause significant dose variations in the region of the field junction. Furthermore, because IORT treatments are delivered in a large single fraction, the effects of underdosing or overdosing could be more critical when compared to fractionated external beam therapy. Proper matching of the fields is therefore an important technical aspect of treatment delivery. We have studied the matching region using the largest flat applicator available for three different possibilities: abutting the fields, leaving a small gap or creating an overlap. Measurements were done using film dosimetry for the available energies of 4, 6, 9 and 12 MeV. Our results show the presence of clinically significant cold spots for the low-energy beams when the fields are either gapped or abutted, suggesting that the fields should be overlapped. No fields should be gapped. The results suggest that an optimal dose distribution may be obtained by overlapping the fields at 4 and 6 MeV and simply abutting the fields at 9 and 12 MeV. However, due to uncertainties in the placement of lead shields during treatment delivery, one may wish to consider overlapping the higher energy fields as well.

Beddar, A. S.; Briere, T. M.; Ouzidane, M.

2006-09-01

238

Generation of Radiation from a Static Electric Field by a Relativistic Ionization Front  

Microsoft Academic Search

A new radiation source, in which the static electric field of an alternately biased capacitor array is directly converted into coherent radiation by a laser-produced ionization front (i.e., a moving gas\\/plasma boundary) is described. The process can be easily understood by a double Lorenz transformation to a frame moving with the ionization front and back to the laboratory frame. In

Patrick Muggli

1997-01-01

239

A systematic global mapping of the radiation field at aviation altitudes  

Microsoft Academic Search

This paper presents early results from aircraft measurements made by a Low-LET Radiation Spectrometer (LoLRS), as part of a long-range effort to study the complex dynamics of the atmospheric radiation field. For this purpose a comprehensive database is being generated to enable a multivariable global mapping (and eventually modeling) of doses and Linear-Energy-Transfer (LET) spectra at aviation altitudes. To accomplish

E. G. Stassinopoulos; C. A. Stauffer; G. J. Brucker

2003-01-01

240

Lightning electromagnetic radiation field spectra in the interval from 0. 2 to 20 MHz  

Microsoft Academic Search

Average energy spectral densities are presented for the fast transitions in most of the components that produce large radiation field impulses from cloud-to-ground lightning; first and subsequent return strokes; stepped, dart-stepped, and 'chaotic' leaders; and 'characteristic' cloud pulses. A disagreement in the previous literature about the spectral energy radiated by return strokes at high frequencies is noted and explained. The

J. C. Willett; J. C. Bailey; C. Leteinturier; E. P. Krider

1990-01-01

241

Modelling net radiation in a High Arctic environment using summer field camp data  

Microsoft Academic Search

A model is presented that uses easily obtained twice-daily field data (cloud-type, amount, temperature, wind speed at 2 m) to estimate net radiation for horizontal and slope sites in a High Arctic setting. Incoming shortwave radiation is estimated using a cloud-layer model, sensible and latent heat fluxes are determined using temperature and wind data, and the surface heat flux is

Kathy L. Young; Ming-Ko Woo

1997-01-01

242

Accelerated detector-quantum field correlations: From vacuum fluctuations to radiation flux  

SciTech Connect

In this paper we analyze the interaction of a uniformly accelerated detector with a quantum field in (3+1)D spacetime, aiming at the issue of how kinematics can render vacuum fluctuations the appearance of thermal radiance in the detector (Unruh effect) and how they engender flux of radiation for observers afar. Two basic questions are addressed in this study: (a) How are vacuum fluctuations related to the emitted radiation? (b) Is there emitted radiation with energy flux in the Unruh effect? We adopt a method which places the detector and the field on an equal footing and derive the two-point correlation functions of the detector and of the field separately with full account of their interplay. From the exact solutions, we are able to study the complete process from the initial transient to the final steady state, keeping track of all activities they engage in and the physical effects manifested. We derive a quantum radiation formula for a Minkowski observer. We find that there does exist a positive radiated power of quantum nature emitted by the detector, with a hint of certain features of the Unruh effect. We further verify that the total energy of the dressed detector and a part of the radiated energy from the detector is conserved. However, this part of the radiation ceases in steady state. So the hint of the Unruh effect in radiated power is actually not directly from the energy flux that the detector experiences in Unruh effect. Since all the relevant quantum and statistical information about the detector (atom) and the field can be obtained from the results presented here, they are expected to be useful, when appropriately generalized, for addressing issues of quantum information processing in atomic and optical systems, such as quantum decoherence, entanglement, and teleportation.

Lin, S.-Y.; Hu, B.L. [Center for Quantum and Gravitational Physics, Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan (China) and Department of Physics, University of Maryland, College Park, Maryland 20742-4111 (United States)

2006-06-15

243

Accelerated detector-quantum field correlations: From vacuum fluctuations to radiation flux  

NASA Astrophysics Data System (ADS)

In this paper we analyze the interaction of a uniformly accelerated detector with a quantum field in (3+1)D spacetime, aiming at the issue of how kinematics can render vacuum fluctuations the appearance of thermal radiance in the detector (Unruh effect) and how they engender flux of radiation for observers afar. Two basic questions are addressed in this study: (a) How are vacuum fluctuations related to the emitted radiation? (b) Is there emitted radiation with energy flux in the Unruh effect? We adopt a method which places the detector and the field on an equal footing and derive the two-point correlation functions of the detector and of the field separately with full account of their interplay. From the exact solutions, we are able to study the complete process from the initial transient to the final steady state, keeping track of all activities they engage in and the physical effects manifested. We derive a quantum radiation formula for a Minkowski observer. We find that there does exist a positive radiated power of quantum nature emitted by the detector, with a hint of certain features of the Unruh effect. We further verify that the total energy of the dressed detector and a part of the radiated energy from the detector is conserved. However, this part of the radiation ceases in steady state. So the hint of the Unruh effect in radiated power is actually not directly from the energy flux that the detector experiences in Unruh effect. Since all the relevant quantum and statistical information about the detector (atom) and the field can be obtained from the results presented here, they are expected to be useful, when appropriately generalized, for addressing issues of quantum information processing in atomic and optical systems, such as quantum decoherence, entanglement, and teleportation.

Lin, Shih-Yuin; Hu, B. L.

2006-06-01

244

Gravitational radiation generated by cosmological phase transition magnetic fields  

SciTech Connect

We study gravitational waves generated by the cosmological magnetic fields induced via bubble collisions during the electroweak (EW) and QCD phase transitions. The magnetic field generation mechanisms considered here are based on the use of the fundamental EW minimal supersymmetric and QCD Lagrangians. The gravitational waves spectrum is computed using a magnetohydrodynamic turbulence model. We find that the gravitational wave spectrum amplitude generated by the EW phase transition peaks at a frequency of approximately 1-2 mHz, and is of the order of 10{sup -20}-10{sup -21}; thus this signal is possibly detectable by the Laser Interferometer Space Antenna (LISA). The gravitational waves generated during the QCD phase transition, however, are outside the LISA sensitivity bands.

Kahniashvili, Tina [McWilliams Center for Cosmology and Department of Physics, Carnegie-Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Department of Physics, Laurentian University, Sudbury, Ontario P3E 2C6 (Canada); National Astrophysical Observatory, Ilia Chavchavadze State University, Tbilisi, GE-0160 (Georgia); Kisslinger, Leonard [McWilliams Center for Cosmology and Department of Physics, Carnegie-Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Stevens, Trevor [Department of Physics, West Virginia Wesleyan College, Buckhannon, West Virginia 26201 (United States)

2010-01-15

245

Entanglement and Teleportation of Gaussian States of the Radiation Field  

Microsoft Academic Search

We propose a reliable entanglement measure for a two-mode squeezed thermal state of the quantum electromagnetic field in terms of its Bures distance to the set of all separable states of the same kind. The requisite Uhlmann fidelity of a pair of two-mode squeezed thermal states is evaluated as the maximal transition probability between two four-mode purifications. By applying the

Paulina Marian; Tudor A. Marian; Horia Scutaru

2006-01-01

246

Retrieval of radiation fluxes from tilted wide field-of-view radiometer measurements  

NASA Astrophysics Data System (ADS)

The wide field-of-view radiometers aboard the Earth Radiation Budget Satellite operated for 15 years to provide a high quality radiation budget data set for climate research. Following a solar calibration, the radiometers did not return to Earth viewing position, but stopped short of nadir. Since that time, five years of measurements have been taken. Calibrations have been performed by use of special spacecraft maneuvers so that the measurements are well-calibrated. This paper presents the development of algorithms for retrieving the radiation fluxes at the "top of the atmosphere" taking into account the tilt of the WFOV radiometers from nadir.

Smith, G. Louis; Bush, Kathryn A.

2005-10-01

247

OPTICAL FIELD PARAMETERS: Estimate of the minimal coherence length of probe optical radiation in interferometry  

NASA Astrophysics Data System (ADS)

The minimal coherence length of probe optical radiation sufficient for formation of a homogeneous interference structure is estimated. The estimate is based on the analysis of the interference structure in the intensity distribution of the field scattered by rough surfaces and point objects and also formed in interferometers. Analysis was performed for the field intensity detected for the time T > 10?c (under the condition that the coherence time of the probe radiation is ?c > 3/?0, where ?0 is the central frequency of the emission spectrum). It is shown that the minimal coherence length Lc of the probe radiation, at which the homogeneous stratified interference structure of the scattered field can be still formed, is 8? (? is the central wavelength). The possibility of using this result for determining the maximal information content of the method of low-coherence optical tomography is analysed.

Bakut, P. A.; Mandrosov, V. I.

2007-01-01

248

Radiation reaction and gravitational waves in the effective field theory approach  

SciTech Connect

We compute the contribution to the Lagrangian from the leading order (2.5 post-Newtonian) radiation reaction and the quadrupolar gravitational waves emitted from a binary system using the effective field theory (EFT) approach of Goldberger and Rothstein. We use an initial value formulation of the underlying (quantum) framework to implement retarded boundary conditions and describe these real-time dissipative processes. We also demonstrate why the usual scattering formalism of quantum field theory inadequately accounts for these. The methods discussed here should be useful for deriving real-time quantities (including radiation reaction forces and gravitational wave emission) and hereditary terms in the post-Newtonian approximation (including memory, tail and other causal, history-dependent integrals) within the EFT approach. We also provide a consistent formulation of the radiation sector in the equivalent effective field theory approach of Kol and Smolkin.

Galley, Chad R.; Tiglio, Manuel [Center for Scientific Computation and Mathematical Modeling and Center for Fundamental Physics, Department of Physics, University of Maryland, College Park, Maryland, 20742 (United States)

2009-06-15

249

Design of the beam loss monitoring system in strong prompt radiation field  

NASA Astrophysics Data System (ADS)

It is inescapable that some electrons will be lost when they are accelerated or transported in the accelerator vacuum chamber. A beam loss monitoring (BLM) system, which works by the radiation measurement, has been successfully installed on the storage ring. Next on the schedule is design of the BLM system for LINAC and transport line. The radiation field around the LINAC and transport line consists of a strong prompt mixed (gamma, neutron) one. Its duty factor is only 10-6 at Hefei Light Source (HLS). A detector based on counting cannot be used here, while one based on integral charge may be suitable in such a field. The most effective detected objects for estimating beam loss by radiation measurement are shower electrons because they can indicate the beam loss position more clearly than ? rays. The detector also should have the ability to decrease stray radiation influence in strong prompt radiation field. For the requirements mentioned above, a new kind of photodiode detector is being developed. We analyzed the beam transportation process and calculated relevant parameters. Then the positions where the detectors should be fixed were determined. The CAN bus mode we use for the storage ring BLM system is out of date because of the rapid development in the communication field. TCP/IP communication is used for the new system.

Juexin, Li; Yuxiong, Li; Weimin, Li; Guanghua, Gong; Zhengguo, Zhao

2007-08-01

250

Stardust Dfmi Wild 2 Encounter Edr Data  

NASA Astrophysics Data System (ADS)

This data set contains raw data collected by the Dust Flux Monitor Instrument (DFMI) flown on board the STARDUST spacecraft during the Wild 2 comet encounter on January 2, 2004. The data in this archive are organized into one table in standard PDS format. This table records dust events which resulted from the encounter with the particles surrounding comet Wild 2. The data in the table spans a 33 minute period surrounding the encounter with Wild 2.

Semenov, B. V.; Tuzzolino, A. J.; McDonnell, J. A. M.; Taylor, H. W.; Acton, C. H.

2010-01-01

251

Output microwave radiation power of low-voltage vircator with external inhomogeneous magnetic field  

NASA Astrophysics Data System (ADS)

Dependence of the power of a broadband microwave radiation generated by a low-voltage oscillator with virtual cathode (vircator) on the parameters of an external inhomogeneous magnetic field has been studied by numerical simulations using a two-dimensional model. It is established that there are optimum parameters of the generator (configuration of the external magnetic field, electron beam current) for which the output radiation power is maximum. A relationship between the optimum conditions of virtual cathode formation in the electron beam and the microwave generation regime is established.

Kurkin, S. A.; Koronovskii, A. A.; Hramov, A. E.

2011-04-01

252

Rotation and Stability of the Toroidal Magnetic Field in Stellar Radiation Zones  

NASA Astrophysics Data System (ADS)

The stability of the magnetic field in radiation zones is of crucial importance for mixing and angular momentum transport in the stellar interior. We consider the stability properties of stars containing a predominant toroidal field in spherical geometry by means of a linear stability in the Boussinesq approximation taking into account the effect of thermal conductivity. We calculate the growth rate of instability and analyze in detail the effects of stable stratification and heat transport. We argue that the stabilizing influence of gravity can never entirely suppress the instability caused by electric currents in radiation zones. However, the stable stratification can essentially decrease the growth rate of instability.

Bonanno, Alfio; Urpin, Vadim

2013-03-01

253

Entanglement and nonclassicality for multimode radiation-field states  

SciTech Connect

Nonclassicality in the sense of quantum optics is a prerequisite for entanglement in multimode radiation states. In this work we bring out the possibilities of passing from the former to the latter, via action of classicality preserving systems like beam splitters, in a transparent manner. For single-mode states, a complete description of nonclassicality is available via the classical theory of moments, as a set of necessary and sufficient conditions on the photon number distribution. We show that when the mode is coupled to an ancilla in any coherent state, and the system is then acted upon by a beam splitter, these conditions turn exactly into signatures of negativity under partial transpose (NPT) entanglement of the output state. Since the classical moment problem does not generalize to two or more modes, we turn in these cases to other familiar sufficient but not necessary conditions for nonclassicality, namely the Mandel parameter criterion and its extensions. We generalize the Mandel matrix from one-mode states to the two-mode situation, leading to a natural classification of states with varying levels of nonclassicality. For two-mode states we present a single test that can, if successful, simultaneously show nonclassicality as well as NPT entanglement. We also develop a test for NPT entanglement after beam-splitter action on a nonclassical state, tracing carefully the way in which it goes beyond the Mandel nonclassicality test. The result of three-mode beam-splitter action after coupling to an ancilla in the ground state is treated in the same spirit. The concept of genuine tripartite entanglement, and scalar measures of nonclassicality at the Mandel level for two-mode systems, are discussed. Numerous examples illustrating all these concepts are presented.

Ivan, J. Solomon; Chaturvedi, S.; Ercolessi, E.; Marmo, G.; Morandi, G.; Mukunda, N.; Simon, R. [Raman Research Institute, C. V. Raman Avenue, Sadashivanagar, Bangalore 560 080 (India); School of Physics, University of Hyderabad, Hyderabad 500 046 (India); Physics Department, University of Bologna, CNISM and INFN, 46 v.Irnerio, I-40126 Bologna (Italy); Dipartimento di Scienze Fisiche, University of Napoli and INFN, v.Cinzia, I-80126 Naples (Italy); Physics Department, University of Bologna, CNISM and INFN, 6/2 v.le Berti Pichat, I-40127 Bologna (Italy); Centre for High Energy Physics, Indian Institute of Science, Bangalore 560 012 (India); The Institute of Mathematical Sciences, C.I.T Campus, Chennai 600 113 (India)

2011-03-15

254

Near- to far-field characteristics of acoustic radiation through plug flow jets.  

PubMed

This paper reports a theoretical study of the radiation of sound through jet exhausts. It focuses on the transition from near field to far field by considering the features of the near-field solution and how these features translate to the far field. The main focus of this work is the importance in some cases of lateral waves radiating from the jet. While the presence of lateral waves has long been recognized, there has been no systematic investigation of the practical consequences of these waves in the prediction of sound propagation through round jets. The physical mechanisms involved in the generation of these waves are presented as well as the conditions under which they become significant. Another issue is the possibility of "channeled waves" inside the jet associated with strong sound radiation in the forward arc. This paper also discusses the validity of the far-field approximation when lateral waves are present. It is shown that the standard far-field approximation can be improved by adding correction terms that account for the presence of the lateral waves and channeled waves. The challenge posed to computational aeroacoustics by these near-field effects is also discussed. PMID:19045763

Gabard, G

2008-11-01

255

Polar twilight UV-visible radiation field: Perturbations due to multiple scattering, ozone depletion, stratospheric clouds, and surface albedo  

SciTech Connect

The polar twilight atmosphere is different from that at mid-latitude in several ways which lead to significant changes in the wavelength-dependent radiation field. Ozone depletion in the stratosphere leads to increased scattering below 340 nm. Polar stratospheric clouds produce changes in the radiation field which depend on cloud height and thickness. A surface albedo near unity produces a large increase in scattering. Multiple scattering becomes a larger percentage of the radiation field as solar zenith angle increases. These perturbations on the radiation field lead to enhanced ozone destruction in the stratosphere, increased surface irradiance, and a significant wavelength-dependent increase in nadir radiance.

Anderson, D.E., Jr. (Naval Research Lab., Washington, DC (United States)); Lloyd, S.A. (Harvard Univ., Cambridge, MA (United States))

1990-05-20

256

Field maintenance of radiation-shielding windows at HFEF  

SciTech Connect

The achievement of excellent viewing through hot-cell shielding windows does not occur by chance. Instead, it requires a well planned and executed program of field maintenance. The lack of such a program is a major factor when a hot-cell facility has poor window viewing. At HFEF, all preventive maintenance is performed by one group of trained technical-support personnel under the immediate direction of a Systems Engineer, who has responsibility for the shielding windows. Window maintenance is prescheduled and recorded by being incorporated into the computerized Maintenance Data System (MDS). Measurements of window light transmission are scheduled annually to determine glass browning or oil cloudiness conditions within the window tank. The tank oil is sampled and chemically analyzed annually to determine the moisture content, the acidity, and the probable deterioration rate caused by irradiation.

Tobias, D.A.

1983-01-01

257

TOPICAL REVIEW: Strong field interaction of laser radiation  

NASA Astrophysics Data System (ADS)

The Review covers recent progress in laser-matter interaction at intensities above 1018 W cm-2. At these intensities electrons swing in the laser pulse with relativistic energies. The laser electric field is already much stronger than the atomic fields, and any material is instantaneously ionized, creating plasma. The physics of relativistic laser-plasma is highly non-linear and kinetic. The best numerical tools applicable here are particle-in-cell (PIC) codes, which provide the most fundamental plasma model as an ensemble of charged particles. The three-dimensional (3D) PIC code Virtual Laser-Plasma Laboratory runs on a massively parallel computer tracking trajectories of up to 109 particles simultaneously. This allows one to simulate real laser-plasma experiments for the first time. When the relativistically intense laser pulses propagate through plasma, a bunch of new physical effects appears. The laser pulses are subject to relativistic self-channelling and filamentation. The gigabar ponderomotive pressure of the laser pulse drives strong currents of plasma electrons in the laser propagation direction; these currents reach the Alfvén limit and generate 100 MG quasistatic magnetic fields. These magnetic fields, in turn, lead to the mutual filament attraction and super-channel formation. The electrons in the channels are accelerated up to gigaelectronvolt energies and the ions gain multi-MeV energies. We discuss different mechanisms of particle acceleration and compare numerical simulations with experimental data. One of the very important applications of the relativistically strong laser beams is the fast ignition (FI) concept for the inertial fusion energy (IFE). Petawatt-class lasers may provide enough energy to isochorically ignite a pre-compressed target consisting of thermonuclear fuel. The FI approach would ease dramatically the constraints on the implosion symmetry and improve the energy gain. However, there is a set of problems to solve before the FI will work. The laser pulse cannot reach the dense core of the target directly. The laser energy must be converted into fast particles first and then transported through the overdense plasma region. The energy spectra of the laser-generated particle beams, their emittance and transport problems are discussed here. The laser-particle interaction at relativistic intensities is highly non-linear and higher laser harmonics are generated. In plasma, the high-harmonic generation is a collective effect - it appears to be quite effective when an intense laser pulse is reflected from the overdense plasma layer. The plasma boundary is then driven by the laser ponderomotive force and works as a relativistically oscillating mirror. Another interesting application is the amplification of short-pulse laser in plasma by a counter-propagating pump pulse. 3D PIC simulations suggest that multi-terawatt pulses of sub-10 fs duration can be generated this way.

Pukhov, Alexander

2003-01-01

258

Quasinormal modes, scattering, and Hawking radiation of Kerr-Newman black holes in a magnetic field  

SciTech Connect

We perform a comprehensive analysis of the spectrum of proper oscillations (quasinormal modes), transmission/reflection coefficients, and Hawking radiation for a massive charged scalar field in the background of the Kerr-Newman black hole immersed in an asymptotically homogeneous magnetic field. There are two main effects: the Zeeman shift of the particle energy in the magnetic field and the difference of values of an electromagnetic potential between the horizon and infinity, i.e. the Faraday induction. We have shown that 'turning on' the magnetic field induces a stronger energy-emission rate and leads to 'recharging' of the black hole. Thus, a black hole immersed in a magnetic field evaporates much quicker, achieving thereby an extremal state in a shorter period of time. Quasinormal modes are moderately affected by the presence of a magnetic field which is assumed to be relatively small compared to the gravitational field of the black hole.

Kokkotas, K. D.; Konoplya, R. A.; Zhidenko, A. [Theoretical Astrophysics, Eberhard-Karls University of Tuebingen, Tuebingen 72076 (Germany); Centro de Matematica, Computacao e Cognicao, Universidade Federal do ABC, Rua Santa Adelia, 166, 09210-170, Santo Andre, Sao Paulo (Brazil)

2011-01-15

259

Field dynamics of coherent synchrotron radiation using a direct numerical solution of Maxwell's equations  

NASA Astrophysics Data System (ADS)

We present and discuss the properties of the coherent electromagnetic fields of a very short, ultrarelativistic bunch in a rectangular vacuum chamber inside a bending magnet. The analysis is based on the results of a direct numerical solution of Maxwell’s equations together with Newton’s equations. We use a new dispersion-free time-domain algorithm which employs a more efficient use of finite element mesh techniques and, hence, produces self-consistent and stable solutions for very short bunches. We investigate the fine structure of the coherent synchrotron radiation fields. We also discuss coherent edge radiation. We present a clear picture of the field using the electric field lines constructed from the numerical solutions. This method should be useful in the study of existing and future concepts of particle accelerators and ultrafast coherent light sources, where high peak currents and very short bunches are envisioned.

Novokhatski, A.

2011-06-01

260

Field Dynamics of Coherent Synchrotron Radiation Using a Direct Numerical Solution of Maxwell's Equations  

SciTech Connect

We present and discuss the properties of the coherent electromagnetic fields of a very short, ultrarelativistic bunch in a rectangular vacuum chamber inside a bending magnet. The analysis is based on the results of a direct numerical solution of Maxwell's equations together with Newton's equations. We use a new dispersion-free time-domain algorithm which employs a more efficient use of finite element mesh techniques and, hence, produces self-consistent and stable solutions for very short bunches. We investigate the fine structure of the coherent synchrotron radiation fields. We also discuss coherent edge radiation. We present a clear picture of the field using the electric field lines constructed from the numerical solutions. This method should be useful in the study of existing and future concepts of particle accelerators and ultrafast coherent light sources, where high peak currents and very short bunches are envisioned.

Novokhatski, A.; /SLAC

2011-08-17

261

Terahertz radiation from carbon nanorings in external collinear constant and varying electric fields  

NASA Astrophysics Data System (ADS)

We consider the response of a quasi-one-dimensional ballistic carbon ring to the field of an electromagnetic wave propagating along the normal to the ring plane in the presence of a constant electric field collinear to the field of the wave. The dipole moment and the radiation intensity of the ring are calculated for the ballistic motion of a conduction electron. The possibility of implementation of regular periodic and chaotic regimes of ring emission under the action of external fields is demonstrated. The radiation spectrum of the ring is analyzed, and the dependence of the scattering cross section for an electromagnetic wave incident on the ring on its frequency and amplitude is calculated.

Fedorov, E. G.; Yanyushkina, N. N.; Belonenko, M. B.

2013-04-01

262

Cloud Field Identification for Earth Radiation Budget Studies. Part II: Cloud Field Classification for the ScaRaB Radiometer.  

NASA Astrophysics Data System (ADS)

Gaining a better understanding of the influence of clouds on the earth's energy budget requires a cloud classification that takes into account cloud height, thickness, and cloud cover. The radiometer ScaRaB (scanner for radiation balance), which was launched in January 1994, has two narrowband channels (0.5 0.7 and 10.5 12.5 µm) in addition to the two broadband channels (0.2 4 and 0.2 50 µm) necessary for earth radiation budget (ERB) measurements in order to improve cloud detection. Most automatic cloud classifications were developed with measurements of very good spatial resolution (200 m to 5 km). Earth radiation budget experiments (ERBE), on the hand, work at a spatial resolution of about 50 km (at nadir), and therefore a cloud field classification adapted to this scale must be investigated. For this study, ScaRaB measurements are simulated by collocated Advanced Very High Resolution Radiometer (AVHRR) ERBE data. The best-suited variables for a global cloud classification are chosen using as a reference cloud types determined by an operationally working threshold algorithm applied to AVHRR measurements at a reduced spatial resolution of 4 km over the North Atlantic. Cloud field types are then classified by an algorithm based on the dynamic clustering method. More recently, the authors have carried out a global cloud field identification using cloud parameters extracted by the 3I (improved initialization inversion) algorithm, from High-Resolution Infrared Sounder (HIRS)-Microwave Sounding Unit (MSU) data. This enables the authors first to determine mean values of the variables best suited for cloud field classification and then to use a maximum-likelihood method for the classification. The authors find that a classification of cloud fields is still possible at a spatial resolution of ERB measurements. Roughly, one can distinguish three cloud heights and two effective cloud amounts (combination of cloud emissivity and cloud cover). However, only by combining flux measurements (ERBE) with cloud field classifications from sounding instruments (HIRS/MSU) can differences in radiative behavior of specific cloud fields be evaluated accurately.

Stubenrauch, C. J.; Seze, G.; Scott, N. A.; Chedin, A.; Desbois, M.; Kandel, R. S.

1996-03-01

263

Analytic theory for betatron radiation from relativistic electrons in ion plasma channels with magnetic field  

NASA Astrophysics Data System (ADS)

We analytically solve the relativistic equation of motion for an electron in ion plasma channels and calculate the corresponding trajectory as well as the synchrotron radiation. The relativistic effect on a trajectory is strong, i.e., many high-order harmonic terms in the trajectory, when the ratio of the initial transverse velocity (vx0) to the longitudinal velocity (vz0) of the electron injected to ion plasma channels is high. Interestingly, these high-order harmonic terms result in a quite broad and intense radiation spectrum, especially at an oblique angle, in contrast to an earlier understanding. As the initial velocity ratio (vx0:vz0) decreases, the relativistic effect becomes weak; only the first and second harmonic terms remain in the transverse and longitudinal trajectories, respectively, which coincides with the result of Esarey et al. [Phys. Rev. E 65, 056505 (2002)]. Our formalism also allows the description of electron's trajectory in the presence of an applied magnetic field. Critical magnetic fields for cyclotron motions are figured out and compared with semiclassical results. The cyclotron motion leads to more high-order harmonic terms than the trajectory without magnetic fields and causes an immensely broad spectrum with vastly large radiation amplitude for high initial velocity ratios (vx0:vz0). The radiation from hard x-ray to gamma-ray regions can be generated with a broad radiation angle, thus available for applications.

Lee, H. C.; Jiang, T. F.

2010-11-01

264

Development of a cryogenic radiation detector for mapping radio frequency superconducting cavity field emissions  

SciTech Connect

Field emissions in a super conducting helium cooled RF cavity and the production of radiation (mostly X-Rays) have been measured externally on cryomodules at Jefferson Lab since 1991. External measurements are limited to radiation energies above 100 keV due to shielding of the stainless steel cryogenic body. To measure the onset of and to map field emissions from a superconducting cavity requires the detecting instrument be inside the shield and within the liquid Helium. Two possible measurement systems are undergoing testing at JLab. A CsI detector array set on photodiodes and an X-Ray film camera with a fixed aperture. Several devices were tested in the cell with liquid Helium without success. The lone survivor, a CsI array, worked but saturated at high power levels due to backscatter. The array was encased in a lead shield with a slit opening set to measure the radiation emitted directly from the cell eliminating a large portion of the backscatter. This is a work in progress and te sting should be complete before the PAC 05. The second system being tested is passive. It is a shielded box with an aperture to expose radiation diagnostic film located inside to direct radiation from the cell. Developing a technique for mapping field emissions in cryogenic cells will assist scientists and engineers in pinpointing any surface imperfections for examination.

Danny Dotson; John Mammosser

2005-05-01

265

Complete linear polarization of Lyman-. cap alpha. radiation from metastable hydrogen atoms in external electric fields  

SciTech Connect

The linear Stark effect of hydrogen was investigated for the metastable H(2s) state measuring the degree of linear polarization of field-induced Lyman-..cap alpha.. radiation. For sufficiently large electric fields (few kV/cm) the measured degree of linear polarization P is almost complete (Papprox. =-100%). This result is in excellent agreement with theoretical predictions, if the fine structure of hydrogen is taken into account.

Harbich, W.; Hippler, R.; Kleinpoppen, H.; Lutz, H.O.

1989-04-01

266

Radiative transfer modeling of upwelling light field in coastal waters  

NASA Astrophysics Data System (ADS)

Numerical simulations of the radiance distribution in coastal waters are a complex problem, but playing a growingly important role in optical oceanography and remote sensing applications. The present study attempts to modify the Inherent Optical Properties (IOPs) to allow the phase function to vary with depth, and the bottom boundary to take into account a sloping/irregular surface and the effective reflectance of the bottom material. It then uses the Hydrolight numerical model to compute Apparent Optical Properties (AOPs) for modified IOPs and bottom boundary conditions compared to the default values available in the standard Hydrolight model. The comparison of the profiles of upwelling radiance simulated with depth-dependent IOPs as well as modified bottom boundary conditions for realistic cases of coastal waters off Point Calimere of southern India shows a good match between the simulated and measured upwelling radiance profile data, whereas there is a significant drift between the upwelling radiances simulated from the standard Hydrolight model (with default values) and measured data. Further comparison for different solar zenith conditions at a coastal station indicates that the upwelling radiances simulated with the depth-dependent IOPs and modified bottom boundary conditions are in good agreement with the measured radiance profile data. This simulation captures significant changes in the upwelling radiance field influenced by the bottom boundary layer as well. These results clearly emphasize the importance of using realistic depth-dependent IOPs as well as bottom boundary conditions as input to Hydrolight in order to obtain more accurate AOPs in coastal waters.

Sundarabalan, Balasubramanian; Shanmugam, Palanisamy; Manjusha, Sadasivan

2013-05-01

267

Hawking radiation for a Proca field in D dimensions  

NASA Astrophysics Data System (ADS)

We study the wave equation of a massive vector boson in the background of a D-dimensional Schwarzschild black hole. The mass term introduces a coupling between two physical degrees of freedom of the field, and we solve the resulting system of ordinary differential equations numerically, without decoupling. We show how to define decoupled transmission factors from an S matrix and compute them for various modes, masses, and space-time dimensions. The mass term lifts the degeneracy between transverse modes, in D=4, and excites the longitudinal modes, in particular, the s wave. Moreover, it increases the contribution of waves with larger ?, which can be dominant at intermediate energies. The transmission factors are then used to obtain the Hawking fluxes in this channel. Our results alert for the importance of modeling the longitudinal modes correctly, instead of treating them as decoupled scalars as they are in current black hole event generators; thus, they can be used to improve such generators for phenomenological studies of TeV gravity scenarios.

Herdeiro, Carlos; Sampaio, Marco O. P.; Wang, Mengjie

2012-01-01

268

[An encounter with extraterrestrial intelligence].  

PubMed

It is much easier to find extraterrestrial intelligence than to detect simple organisms living on other planets. However, it is hard to communicate with such intelligence without the mutual understanding of inter-stellar communication protocol. The radio SETI (The Search for Extra-Terrestrial Intelligence) was initiated with the pioneering work of F. Drake in 1960, one year after the historical SETI paper by Cocconi and Morrison. This talk explains that SETI evolves with two bases of science; the understanding of our universe and the development of technology. Since SETI has had strong connection with radio astronomy from its early beginning, the impacts of radio astronomical findings and technological breakthrough can be seen in many aspects of the SETI history. Topics of this talk include the detection of microwave 3 K background radiation in the universe. Interstellar atomic and molecular lines found in radio-wave spectra provide the evidence of pre-biotic chemical evolution in such region. Radio telescope imaging and spectral technique are closely associated with methodology of SETI. Topics of the talk extend to new Allen Telescope Array and projected Square Kilometer Array. Recent optical SETI and the discoveries of extra solar planets are also explained. In the end, the recent understanding of our universe is briefly introduced in terms of matter, dark matter and dark energy. Even our understanding of the universe has been evolutionarily revolved and accumulated after 1960, we must recognize that our universe is still poorly understood and that astronomy and SETI are required to proceed hand in hand. PMID:15136757

Hisabayashi, Hisashi

2003-12-01

269

Theoretical model for sound radiation from annular jet pipes: far- and near-field solutions  

NASA Astrophysics Data System (ADS)

An analytical model is presented for sound radiation from a semi-infinite unflanged annular duct. The duct carries a jet which issues into a uniform mean flow while an inner cylindrical centre body extends downstream from the duct exit. This geometrical arrangement forms an idealized representation of a turbofan exhaust where noise propagates along the annular bypass duct, refracts through the external bypass stream and radiates to the far field. The instability wave of the vortex sheet and its interaction with the acoustic field are accounted for in an exact way in the current solution. Efficient numerical procedures are presented for evaluating near-field and far-field solutions, and these are used as the basis for a parametric study to illustrate the effect of varying the hub tip ratio, and the ratio of jet velocity to external flow velocity. Since the ‘Kutta’ condition can be turned on and off in the current solution, this capability is used to assess the effect of vortex shedding on noise radiation. Far-field directivity patterns are presented for single modes and also for a multi-mode ‘broadband’ source model in which all cut-on modes are assumed to be present with equal modal power. Good agreement is found between analytical solutions and experimental data. Near-field pressure maps of the acoustic and instability portions of the solution are generated for selected tones.

Gabard, G.; Astley, R. J.

270

Encountering! The Arts Part of Basic Education.  

ERIC Educational Resources Information Center

|This publication contains an "Encountering Model" and model lessons for integrating arts experiences into the basic curriculum at the elementary and junior high school levels. The model uses a three-phase learning sequence in which each phase is labeled an "encounter." The first phase is "exploration," when students are provided with certain…

Oklahoma State Dept. of Education, Oklahoma City. Curriculum Div.

271

Communication in everyday interpersonal and intergroup encounters  

Microsoft Academic Search

Communication that occurs in everyday encounters influences the development and maintenance of relationships. Many theorists have called for paying greater attention to everyday communication behavior. To date, this call has not been addressed in research comparing interpersonal and intergroup communication. The purpose of this study was to compare communication in everyday interpersonal and intergroup encounters. Two sets of data were

William B. Gudykunst; Robin B. Shapiro

1996-01-01

272

Encounter-based worms: Analysis and Defense  

Microsoft Academic Search

An encounter-based network is a frequently disconnected wireless ad hoc network requir- ing immediate neighbors to store and forward aggregated data for information dissemina- tions. Using traditional approaches such as gateways or firewalls to deter worm propagation in encounter-based networks is inappropriate. We propose a worm interaction approach that relies upon automated beneficial worm generation to alleviate problems of worm

Sapon Tanachaiwiwat; Ahmed Helmy

2007-01-01

273

GAMMA-RAY BURST PROMPT EMISSION: JITTER RADIATION IN STOCHASTIC MAGNETIC FIELD REVISITED  

SciTech Connect

We revisit the radiation mechanism of relativistic electrons in the stochastic magnetic field and apply it to the high-energy emissions of gamma-ray bursts (GRBs). We confirm that jitter radiation is a possible explanation for GRB prompt emission in the condition of a large electron deflection angle. In the turbulent scenario, the radiative spectral property of GRB prompt emission is decided by the kinetic energy spectrum of turbulence. The intensity of the random and small-scale magnetic field is determined by the viscous scale of the turbulent eddy. The microphysical parameters {epsilon}{sub e} and {epsilon}{sub B} can be obtained. The acceleration and cooling timescales are estimated as well. Due to particle acceleration in magnetized filamentary turbulence, the maximum energy released from the relativistic electrons can reach a value of about 10{sup 14} eV. The GeV GRBs are possible sources of high-energy cosmic-ray.

Mao, Jirong [International Center for Astrophysics, Korea Astronomy and Space Science Institute, 776, Daedeokdae-ro, Yuseong-gu, Daejeon 305-348 (Korea, Republic of); Wang Jiancheng, E-mail: jirong.mao@brera.inaf.it [Yunnan Observatory, Chinese Academy of Sciences, Kunming, Yunnan Province 650011 (China)

2011-04-10

274

Design of organic scintillators for non-standard radiation field dosimetry: Experimental setup.  

PubMed

This paper describes an experimental setup designed for sensing the luminescent light coming from an organic plastic scintillator stimulated with ionizing radiation. This device is intended to be a part of a complete dosimeter system for characterization of small radiation fields which is the project of the doctoral thesis of the medical physicist at the Radiation Oncology facility of Hospital San Vicente Fundación in conjunction with the Universidad de Antioquia of Medellín Colombia. Some preliminary results predict a good performance of the unit, but further studies must be conducted in order to have a completed evaluation of the system. This is the first step in the development of an accuracy tool for measurement of non-standard fields in the Radiotherapy or Radiosurgery processes. PMID:24110369

Norman H, Machado R; Maximiliano, Trujillo T; Javier E, Garcia G; Diana C, Narvaez G; Paula A, Marin M; Robinson A, Torres V

2013-07-01

275

A quasi-classical method for deriving the equations of radiative transfer in a magnetic field  

NASA Astrophysics Data System (ADS)

A new derivation of the matrix equations of radiative transfer in a magnetic field is presented, which is based on the classical approach of M. Born and V.E. Stepanov. Convenient vector relations making it possible to formulate the radiative-transfer equations in an arbitrary coordinate system and choose a convenient system of Stokes parameters are presented. The cases of the solar atmosphere and a stellar atmosphere with a dipolar magnetic field are presented as examples. The use of the radiative-transfer equations written in terms of two main oscillation components (the method of V.E. Stepanov) can lead to crude errors when the complex nature of the absorption coefficients is taken into account.

Rachkovskii, D. N.

2013-10-01

276

Gamma-ray Burst Prompt Emission: Jitter Radiation in Stochastic Magnetic Field Revisited  

NASA Astrophysics Data System (ADS)

We revisit the radiation mechanism of relativistic electrons in the stochastic magnetic field and apply it to the high-energy emissions of gamma-ray bursts (GRBs). We confirm that jitter radiation is a possible explanation for GRB prompt emission in the condition of a large electron deflection angle. In the turbulent scenario, the radiative spectral property of GRB prompt emission is decided by the kinetic energy spectrum of turbulence. The intensity of the random and small-scale magnetic field is determined by the viscous scale of the turbulent eddy. The microphysical parameters epsilon e and epsilon B can be obtained. The acceleration and cooling timescales are estimated as well. Due to particle acceleration in magnetized filamentary turbulence, the maximum energy released from the relativistic electrons can reach a value of about 1014 eV. The GeV GRBs are possible sources of high-energy cosmic-ray.

Mao, Jirong; Wang, Jiancheng

2011-04-01

277

Near-field thermal radiation between graphene-covered doped silicon plates.  

PubMed

The present work describes a theoretical investigation of the near-field thermal radiation between doped Si plates coated with a mono-layer of graphene. It is found that the radiative heat flux between doped Si plates can be either enhanced or suppressed by introducing graphene layer, depending on the Si doping concentration and chemical potential of graphene. Graphene can enhance the heat flux if it matches resonance frequencies of surface plasmon at vacuum-source and vacuum-receiver interfaces. In particular, significant enhancement is achieved when graphene is coated on both surfaces that originally does not support the surface plasmon resonance. The results obtained in this study provide an important guideline into enhancing the near-field thermal radiation between doped Si plates by introducing graphene. PMID:24104109

Lim, Mikyung; Lee, Seung S; Lee, Bong Jae

2013-09-23

278

Coherent phase control of excitation of atoms by bichromatic laser radiation in an electric field  

SciTech Connect

A new method for coherent phase control of excitation of atoms in a discrete spectrum under the action of bichromatic laser radiation with the frequency ratio 1:2 is analysed. An important feature of this control method is the presence of a electrostatic field, which removes the parity selection rule for one of the control channels. It is shown that for the phase difference between the monochromatic radiation components, corresponding to the destructive interference between channels, there exists the electrostatic field strength at which the excited atomic transition is 'bleached'. It is proposed to use luminescence at the adjacent atomic transition for detecting the phase dependence of optical excitation. (interaction of laser radiation with matter. laser plasma)

Astapenko, Valerii A [Laser Center, Moscow Institute of Physics and Technology, Dolgoprudnyi, Moscow region (Russian Federation)

2005-06-30

279

Development of a Field Well-Head Safety System for Use with Radiation-Generating Devices  

SciTech Connect

This paper discusses the design, testing and application of a new interlock system for field use with neutron generating bore hole probes at the Idaho National Engineering and Environmental Laboratory. Such probes produce 14 MeV neutrons at a yield up to 3×108 neutrons/s, and present an ionizing radiation hazard to personnel particularly when operated in an unshielded configuration. This interlock system prevents personnel from being exposed to the relatively high radiation fields caused by an unsafe condition when an operating neutron generator probe is withdrawn from a well in the ground. An electromechanical interlock prototype system has been designed, built and tested, and has been found to be effective at preventing this event. The design is simple, is effective in mitigating the hazard, and can be installed in minutes. The system could be modified to interlock radiation-generating devices other than neutron generators that are used in similar environments.

Keegan, Raymond Patrick; Lopez, Juan Carlos; McGrath, Christopher Andrew

2003-12-01

280

The photoevaporation of a neutral structure by an EUV+FUV radiation field  

NASA Astrophysics Data System (ADS)

The EUV photoionizing radiation and FUV dissociating radiation from newly born stars photoevaporate their parental neutral cloud, leading to the formation of dense clumps that could eventually form additional stars. We study the effects of including a photodissociating FUV flux in models of the fragmentation of a photoevaporating, self-gravitating molecular cloud. We compute 3D simulations of the interaction of an inhomogeneous, neutral, self-gravitating cloud with external EUV and FUV radiation fields, and calculate the number of collapsing clumps and their mass. We find that the presence of an outer photodissociation region has an important effect on the formation of dense structures due to the expansion of an H II region. In particular, including a FUV field leads to the earlier formation of a larger number of dense clumps, which might lead to the formation of more stars.

Lora, V.; Vasconcelos, M. J.; Raga, A. C.; Esquivel, A.; Cerqueira, A. H.

2013-10-01

281

Consideration of the radiation dose delivered away from the treatment field to patients in radiotherapy  

PubMed Central

Radiation delivery to cancer patients for radiotherapy is invariably accompanied by unwanted radiation to other parts of the patient’s body. Traditionally, considerable effort has been made to calculate and measure the radiation dose to the target as well as to nearby critical structures. Only recently has attention been focused also on the relatively low doses that exist far from the primary radiation beams. In several clinical scenarios, such doses have been associated with cardiac toxicity as well as an increased risk of secondary cancer induction. Out-of-field dose is a result of leakage and scatter and generally difficult to predict accurately. The present review aims to present existing data, from measurements and calculations, and discuss its implications for radiotherapy.

Taylor, Michael L.; Kron, Tomas

2011-01-01

282

Estimating Attenuation of Ultraviolet Radiation in Streams: Field and Laboratory Methods  

Microsoft Academic Search

We adapted and tested a laboratory quantitative filter pad method and field-based microcosm method for estimating diffuse attenuation coefficients (Kd) of ultraviolet radiation (UVR) for a wide range of stream optical environments (Kd320 = 3-44 m )1 ). Logistical difficulties of direct measurements of UVR attenu- ation have inhibited widespread monitoring of this important parameter in streams. Suspended sediment concentrations

Patrick Belmont; Bruce R. Hargreaves; Donald P. Morris; Craig E. Williamson

2007-01-01

283

Evaluation of Breast Sentinel Lymph Node Coverage by Standard Radiation Therapy Fields  

Microsoft Academic Search

Background: Biopsy of the breast sentinel lymph node (SLN) is now a standard staging procedure for early-stage invasive breast cancer. The anatomic location of the breast SLN and its relationship to standard radiation fields has not been described. Methods and Materials: A retrospective review of radiotherapy treatment planning data sets was performed in patients with breast cancer who had undergone

Rachel Rabinovitch; Ari Ballonoff; Francis M. S. Newman; Christina Finlayson

2008-01-01

284

SAR Distribution in Visible Human Head Exposure to the Field Radiated by CRT Computer Monitors  

Microsoft Academic Search

Based on finite difference time domain method, the specific absorption rate in the visible human head model exposed to the field radiated by cathode ray tube of computer monitor has been simulated numerically. Computer monitor made by Cathode ray tube (CRT) used for information display is usually in closer proximity, therefore, it is important to consider the possible health hazards

Han Yu-nan; Lu Ying-hua; Liu Ning; He Peng-fei

2007-01-01

285

Far field radiation from an arbitrarily oriented Hertzian dipole in an unbounded electrically gyrotropic medium  

Microsoft Academic Search

The general solution to the problem of far field radiation from an arbitrarily oriented Hertzian dipole in an electrically gyrotropic medium such as magnetically biased cold plasma, is found using the dyadic Green's function for the gyrotropic medium which is expressed as a sum of two single dyads. The numerical results are given in different frequency bands using Clemmow-Mually-Allis (CMA)

Abdullah Eroglu; J. K. Lee

2005-01-01

286

Generating High-Intensity Electromagnetic Fields for Radiated-Susceptibility Test  

Microsoft Academic Search

This paper discusses a feasibility study covering the generation of high-intensity electromagnetic fields for radiated susceptibility or ordnance hazard tests. A new type of antenna using an elliptic-cylinder reflector is discussed. The results of laboratory measurements made with such an antenna are displayed graphically and discussed in the text of the paper. The advantages and limitations of this device are

Victor P. Musil

1968-01-01

287

Harmonic generation by a classical hydrogen atom in the presence of an intense radiation field  

SciTech Connect

We present the results of a calculation of high-order harmonic generation by a classical hydrogen atom, submitted to an intense, single-mode, radiation field. The spectra showing these harmonics associated with different kinds of trajectories as well as with an ensemble average of trajectories are discussed.

Bandarage, G.; Maquet, A.; Cooper, J. (Joint Institute for Laboratory Astrophysics, Boulder, CO (US) National Institute of Standards and Technology, Boulder, CO (US) University of Colorado, Boulder, Colorado 80309-0440 (US))

1990-02-01

288

Gamma scintillation probe for field use and measurements of radiation background in Puget Sound  

Microsoft Academic Search

A probe containing a 5 x 4-in. NaI( TI) crystal was built for field survey work with a small ship and portable counting equipment. The gamma radiation background was mcas- ured to a depth of 80 m at 3 locations in the lower part of Puget Sound. The count rate dccreascd very rapidly and nonlinearly in the first few meters

CHARLES M. PROCTOR; EMANUEL PAPADOPULOS; RALPH H. FIRMINHAC

1962-01-01

289

On the stability of cyclotron radiation emitted perpendicularly to a magnetic field  

Microsoft Academic Search

Conditions under which the resonant 'absorption' mechanism for electromagnetic radiation propagating perpendicular to a static magnetic field at harmonics of the cyclotron frequency can become unstable in a collisionless Vlasov plasma are examined. Specifically, the type of electron velocity distribution function for which the appropriate spectral absorptivity will change sign is investigated. The stability of both extraordinary and ordinary modes

K. Audenaerde

1977-01-01

290

Operational characterization of the radiation field of the high intensity operating mode of Hermes III  

SciTech Connect

A high-intensity mode for Hermes III gamma simulator at Sandia National Laboratories, providing an average dose rate of 2.5 {times} 10{sup l3} rads(Si)/s over a 2:1 uniformity area of 80 cm{sup 2}, has been reported previously. This source provides an average dose of 370 krad(Si) over the useful area in a radiation pulse with a rise time of 8 ns and a pulse width of 11 ns. Use of this source permits photon testing of radiation effects in a regime previously accessible only underground or using e-beam simulation. This work characterizes both the spatial and temporal variations of the radiation field produced by the high-intensity source. This radiation source depends on the transport of a converging electron beam in a gas cell to the converter, where the forward-directed character of the bremsstrahlung results in the formation of a radiation focus slightly downstream of the faceplate. Because the electron trajectories vary during the radiation pulse, the time history of the radiation is a function of position.

Harper-Slaboszewicz, V.J.; Mikkelson, K.A.; Westfall, R.L. [Sandia National Labs., Albuquerque, NM (United States); Neely, S.M. [Ktech Corp., Albuquerque, NM (United States)

1992-12-31

291

Permanent-Magnet Field Source for the Production of Circularly Polarized Radiation Via Helical Free-Electron Lasers.  

National Technical Information Service (NTIS)

A relativistic electron beam laser produces circularly polarized 15 GHz radiation by means of a transverse magnetic field of which the orientation rotates continuously in the phi direction with displacement along the z axis. A field strength of about 500 ...

H. A. Leupold A. B. Morcos

1985-01-01

292

REVIEWS OF TOPICAL PROBLEMS Gravitational radiation of systems and the role of their force field  

NASA Astrophysics Data System (ADS)

Gravitational radiation (GR) from compact relativistic systems with a known energy-momentum tensor (EMT) and GR from two masses elliptically orbiting their common center of inertia are considered. In the ultrarelativistic limit, the GR spectrum of a charge rotating in a uniform magnetic field, a Coulomb field, a magnetic moment field, and a combination of the last two fields differs by a factor 4?Gm2?2/e2 (? being of the order of the charge Lorentz factor) from its electromagnetic radiation (EMR) spectrum. This factor is independent of the radiation frequency but does depend on the wave vector direction and the way the field behaves outside of the orbit. For a plane wave external field, the proportionality between the gravitational and electromagnetic radiation spectra is exact, whatever the velocity of the charge. Qualitative estimates of ? are given for a charge moving ultrarelativistically in an arbitrary field, showing that it is of the order of the ratio of the nonlocal and local source contributions to the GR. The localization of external forces near the orbit violates the proportionality of the spectra and reduces GR by about the Lorentz factor squared. The GR spectrum of a rotating relativistic string with masses at the ends is given, and it is shown that the contributions by the masses and string are of the same order of magnitude. In the nonrelativistic limit, the harmonics of GR spectra behave universally for all the rotating systems considered. A trajectory method is developed for calculating the GR spectrum. In this method, the spatial (and hence polarization) components of the conserved EMT are calculated in the long wavelength approximation from the time component of the EMTs of the constituent masses of the system. Using this method, the GR spectrum of two masses moving in elliptic orbits about their common center of inertia is calculated, as are the relativistic corrections to it.

Nikishov, Anatolii I.; Ritus, Vladimir I.

2011-02-01

293

Evaluation of Breast Sentinel Lymph Node Coverage by Standard Radiation Therapy Fields  

SciTech Connect

Background: Biopsy of the breast sentinel lymph node (SLN) is now a standard staging procedure for early-stage invasive breast cancer. The anatomic location of the breast SLN and its relationship to standard radiation fields has not been described. Methods and Materials: A retrospective review of radiotherapy treatment planning data sets was performed in patients with breast cancer who had undergone SLN biopsy, and those with a surgical clip at the SLN biopsy site were identified. The location of the clip was evaluated relative to vertebral body level on an anterior-posterior digitally reconstructed radiograph, treated whole-breast tangential radiation fields, and standard axillary fields in 106 data sets meeting these criteria. Results: The breast SLN varied in vertebral body level position, ranging from T2 to T7 but most commonly opposite T4. The SLN clip was located below the base of the clavicle in 90%, and hence would be excluded from standard axillary radiotherapy fields where the inferior border is placed at this level. The clip was within the irradiated whole-breast tangent fields in 78%, beneath the superior-posterior corner multileaf collimators in 12%, and outside the tangent field borders in 10%. Conclusions: Standard axillary fields do not encompass the lymph nodes at highest risk of containing tumor in breast cancer patients. Elimination of the superior-posterior corner MLCs from the tangent field design would result in inclusion of the breast SLN in 90% of patients treated with standard whole-breast irradiation.

Rabinovitch, Rachel [Department of Radiation Oncology, University of Colorado Cancer Center, Aurora, CO (United States)], E-mail: Rachel.rabinovitch@uchsc.edu; Ballonoff, Ari; Newman, Francis M.S. [Department of Radiation Oncology, University of Colorado Cancer Center, Aurora, CO (United States); Finlayson, Christina [Department of GI, Tumor, and Endocrine Surgery, University of Colorado Cancer Center, Aurora, CO (United States)

2008-04-01

294

Spatially Flat Robertson-Walker Cosmology with Mixed Radiation and Thermalized Massless Scalar Field Content  

NASA Astrophysics Data System (ADS)

Basically, in this paper our interest has been focused on the following problem: how did the thermalization of the minimally coupled mass-less scalar field go in the early radiation dominated spatially flat Robertson-Walker Universe and what kind of cosmological consequences did it have by its back-reaction effect? Therefore, we have worked out explicitly the exact frequency modes, quantized the massless field on the (k = 0)-radiation dominated background and, finally, have estimated the many-particle expectation value of the conservative energy-momentum tensor, assuming a Bose-Einstein distribution (at the radiation equilibrium temperature) of the quanta. Unlike the Minkowskian case, when w = 3p for the massless scalar source, this time, we get equal supplementary contributions to the pressure and the energy-density of the thermalized field. They mainly come from the decaying amplitude of the exact frequency modes and principially, strongly influence the evolution of the mixed radiation and thernalized massless scalar field dominated (k = 0)-Robertson-Walker Universe by the back reaction effect. It arises a maximal, Planckian-like, critical tenperature and the mixed matter Universe smoothly goes from the phase of the coherent massless scalar field domination, when a ~t^(1/3) and the deceleration parameter q = 2, to the usual phase of radiation a ~t^(1/2) and q = 1. The exact solution of Einstein equations over the whole of this transition has been concretely estimated in closed form as well as the "luminosity-distance versus cosmological red-shift" relation that fully characterizes the model.

Dariescu, Ciprian; Hamamoto, Shinji

295

Electric field detection of coherent synchrotron radiation in a storage ring generated using laser bunch slicing  

NASA Astrophysics Data System (ADS)

The electric field of coherent synchrotron radiation (CSR) generated by laser bunch slicing in a storage ring has been detected by an electro-optic sampling method. The gate pulses for sampling are sent through a large-mode-area photonic-crystal fiber. The observed electric field profile of the CSR is in good agreement with the spectrum of the CSR observed using Fourier transform far-infrared spectrometry, indicating good phase stability in the CSR. The longitudinal density profiles of electrons modulated by laser pulses were evaluated from the electric field profile.

Katayama, I.; Shimosato, H.; Bito, M.; Furusawa, K.; Adachi, M.; Shimada, M.; Zen, H.; Kimura, S.; Yamamoto, N.; Hosaka, M.; Katoh, M.; Ashida, M.

2012-03-01

296

Cosmic radiation and magnetic fields: Exposure assessment and health outcomes among airline flight crews  

NASA Astrophysics Data System (ADS)

Airline flight crews are chronically exposed to cosmic radiation and to magnetic fields generated by the aircraft's electrical system. Potential disease risks have been identified in health studies among commercial flight crews outside of the United States and among military pilots within the United States. The objectives of this study were (1) to quantify exposure to both cosmic radiation and magnetic fields onboard aircraft, (2) to develop a methodology for estimating career cosmic radiation doses to individual crew members, and (3) to compare mortality among United States commercial pilots and navigators with that of all occupational groups. Cosmic radiation equivalent doses to bone marrow and skeletal tissue were calculated on a flight-by-flight basis. Flight-by-flight calculations were used to develop an estimation methodology for cumulative (career) cosmic radiation doses. Magnetic fields were measured directly onboard aircraft during flight. Health outcomes among United States commercial pilots and navigators were investigated using proportional mortality ratios, proportional cancer mortality ratios, and mortality odds ratios. Based on the sample used in this study, the cosmic radiation equivalent dose to bone marrow and skeletal tissue associated with air travel ranges from 30 to 570 microsieverts per 100 flight hours (not including ground time) depending on altitude, latitude, phase of solar cycle, and flight duration. Magnetic field exposure appears to be characterized by frequencies between 100 and 800 hertz and varies in strength depending on stages of flight, location within the aircraft, and aircraft type. Based on limited measurements, maximum field strengths may increase from 0.6 microtesla in economy class to 1.2 microtesla in first class, suggesting that cockpit exposures may be higher. Potential synergistic effects of cosmic radiation and magnetic fields may be associated with certain cancers found in excess among flight crews, in particular, breast cancer among female flight attendants. Mortality analyses indicate that United States pilots and navigators have experienced significantly increased mortality due to cancer of the kidney and renal pelvis, cancer of the prostate, cancer of the lip, buccal cavity and pharynx, motor neuron disease, external causes of death and accidents. The results of this study support the need for further evaluation of health outcomes experienced by flight crews and the relationship of these outcomes to occupational exposures.

Nicholas, Joyce Shealy

297

Deconvolution of wide field-of-view radiometer measurements of earth-emitted radiation. I - Theory  

NASA Astrophysics Data System (ADS)

The theory of deconvolution of wide field-of-view (WFOV) radiometer measurements of earth-emitted radiation provides a technique by which the resolution of such measurements can be enhanced to provide radiant exitance at the top of the atmosphere with a finer resolution than the field of view. An analytical solution for the earth-emitted radiant exitance in terms of WFOV radiometer measurements is derived for the nonaxisymmetric (or regional) case, in which the measurements and radiant exitance are considered to be functions of both latitude and longitude. This solution makes it possible to deconvolve a set of WFOV radiometer measurements of earth-emitted radiation and obtain information with a finer resolution than the instantaneous field of view of the instrument. It is shown that there are tradeoffs involved in the selection between WFOV and scanning radiometers.

Smith, G. L.; Green, R. N.

1981-03-01

298

Anisotropic scattering in an inhomogeneous atmosphere. II. The radiation field in deep layers of a semi-infinite medium  

SciTech Connect

The radiation field is analyzed for an infinite plane atmosphere in which the phase function and single scattering albedo are regarded as given functions of optical depth. The particular case of weak true absorption or nearly conservative scattering is considered. Equations are derived for the radiation field in the deep layers of a semi-infinite, inhomogeneous atmosphere illuminated by parallel rays.

Yanovitskii, E.G.

1978-07-01

299

Far field radiation from an arbitrarily oriented Hertzian dipole in the presence of a layered anisotropic medium  

Microsoft Academic Search

Far field radiation from an arbitrarily oriented Hertzian dipole for two-layered uniaxially anisotropic medium with a tilted optic axis is treated analytically by using the dyadic Green's function of the problem when the dipole is placed over or embedded in a two-layered uniaxially anisotropic medium. The radiation fields are evaluated using the steepest descent method. Parameter studies including anisotropy, layer

Abdullah Eroglu; Jay Kyoon Lee

2005-01-01

300

A Closed-Form Solution for ELF Radiated Fields of a Line-Current Antenna in Earth-Ionosphere Waveguide  

Microsoft Academic Search

The empirical formulas for extremely low frequency (ELF) radiated fields of a line-current antenna grounding at each end in the Earth-ionosphere waveguide have been given in some literatures. But the derivation of the radiated fields in spherical waveguide is mathematically not strict. In this paper, a scalar wave function is used in mode theory of wave propagation to closely solve

Liu Chao; Zheng Long-Gen; Li Yong-Pin

2009-01-01

301

A new multistack radiation boundary condition for FDTD based on self-teleportation of fields  

SciTech Connect

In [Electromagnetics 23 (2003) 187], a technique for injecting perfect plane waves into finite regions of space in FDTD was reported. The essence of the technique, called Field Teleportation, is to invoke the principle of equivalent sources using FDTDs discrete definition of the curl to copy any field propagating in one FDTD domain to a finite region of another domain. In this paper, we apply this technique of Field Teleportation to the original domain itself to create a transparent boundary across which any outward traveling FDTD field produces an exact negative copy of itself. When this copied field is teleported one cell ahead and one cell forward in time it causes significant self-cancelation of the original field. Illustrative experiments in two-dimensions show that a two-layer (10-cell thick) multi-stack Radiation Boundary Condition (RBC) with a simplest Huygens's termination readily yields reflection coefficients of the order of -80 dB up to grazing incidence for all the fields radiated by a harmonic point source ({lambda} = 30 cells) in free space located 20 cells away from the boundary. Similarly low levels of artificial reflection are demonstrated for a case in which the RBC cuts through five different magnetodielectric materials.

Diaz, Rodolfo E. [Material-Wave Interaction Laboratory, Electrical Engineering Department, Arizona State University, Tempe Center, 951 S. Mill Ave., Suite no. 199, Tempe, AZ 85287-9509 (United States); Scherbatko, Igor [Material-Wave Interaction Laboratory, Electrical Engineering Department, Arizona State University, Tempe Center, 951 S. Mill Ave., Suite no. 199, Tempe, AZ 85287-9509 (United States)]. E-mail: igor_s@asu.edu

2005-02-10

302

Electron-positron pair oscillation in spatially inhomogeneous electric fields and radiation  

NASA Astrophysics Data System (ADS)

It is known that strong electric fields produce electron and positron pairs from the vacuum, and due to the back-reaction these pairs oscillate back and forth coherently with the alternating electric fields in time. We study this phenomenon in spatially inhomogeneous and bound electric fields by integrating the equations of energy-momentum and particle-number conservations and Maxwell equations. The space and time evolutions of the pair-induced electric field, electric charge- and current-densities are calculated. The results show non-vanishing electric charge-density and the propagation of pair-induced electric fields, that are different from the case of homogeneous and unbound electric fields. The space and time variations of pair-induced electric charges and currents emit an electromagnetic radiation. We obtain the narrow spectrum and intensity of this radiation, whose peak ? locates in the region around 4 keV for electric field strength ˜E. We discuss their relevances to both the laboratory experiments for electron and positron pair-productions and the astrophysical observations of compact stars with an electromagnetic structure.

Han, Wen-Biao; Ruffini, Remo; Xue, She-Sheng

2010-07-01

303

Polarized Radiation Diagnostics for Measuring the Magnetic Field of the Outer Solar Atmosphere  

NASA Astrophysics Data System (ADS)

The basic idea of optical pumping, for which Alfred Kastler received the 1966 Nobel Prize in physics, is that the absorption and scattering of light that is near-resonant with an optical transition can produce large population imbalances among the magnetic sublevels of atomic ground states as well as in excited states. The degree of this radiatively-induced atomic level polarization, which is very sensitive to the presence of magnetic fields, can be determined by observing the polarization of the scattered or transmitted spectral line radiation. Probably, the most important point for solar physics is that the outer solar atmosphere is indeed an optically pumped vapor and that the polarization of the emergent spectral line radiation can be exploited for detecting magnetic fields that are too weak and/or too tangled so as to produce measurable Zeeman polarization signals. In this talk we review some recent radiative transfer simulations of the polarization produced by optical pumping in selected IR, FUV and EUV spectral lines, showing that their sensitivity to the Hanle effect is very suitable for magnetic field measurements in the outer solar atmosphere. We argue that solar magnetometry using the spectral lines of optically pumped atoms in the chromosphere, transition region and corona should be a high-priority goal for large aperture solar telescopes, such as ATST, EST and SOLAR-C.

Trujillo Bueno, J.

2012-12-01

304

EVOLUTION OF X-RAY AND FAR-ULTRAVIOLET DISK-DISPERSING RADIATION FIELDS  

SciTech Connect

We present new X-ray and far-ultraviolet (FUV) observations of T Tauri stars covering the age range 1-10 Myr. Our goals are to observationally constrain the intensity of radiation fields responsible for evaporating gas from the circumstellar disk and to assess the feasibility of current photoevaporation models, focusing on X-ray and UV radiation. We greatly increase the number of 7-10 Myr old T Tauri stars observed in X-rays by including observations of the well-populated 25 Ori aggregate in the Orion OB1a subassociation. With these new 7-10 Myr objects, we confirm that X-ray emission remains constant from 1 to 10 Myr. We also show, for the first time, observational evidence for the evolution of FUV radiation fields with a sample of 56 accreting and non-accreting young stars spanning 1 Myr to 1 Gyr. We find that the FUV emission decreases on timescales consistent with the decline of accretion in classical T Tauri stars until reaching the chromospheric level in weak T Tauri stars and debris disks. Overall, we find that the observed strength of high-energy radiation is consistent with that required by photoevaporation models to dissipate the disks in timescales of approximately 10 Myr. Finally, we find that the high-energy fields that affect gas evolution are not similarly affecting dust evolution; in particular, we find that disks with inner clearings, transitional disks, have similar levels of FUV emission as full disks.

Ingleby, Laura; Calvet, Nuria; Miller, Jon; Bergin, Edwin; Hartmann, Lee [Department of Astronomy, University of Michigan, 830 Dennison Building, 500 Church Street, Ann Arbor, MI 48109 (United States); Hernandez, Jesus; Briceno, Cesar [Centro de Investigaciones de Astronomia (CIDA), Merida, 5101-A (Venezuela, Bolivarian Republic of); Espaillat, Catherine, E-mail: lingleby@umich.edu, E-mail: ncalvet@umich.edu, E-mail: jonmm@umich.edu, E-mail: ebergin@umich.edu, E-mail: lhartm@umich.edu, E-mail: jesush@cida.ve, E-mail: briceno@cida.ve, E-mail: cespaillat@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-78, Cambridge, MA 02138 (United States)

2011-04-15

305

Analysis of the radiation from the violin f-holes using patch near field acoustical holography  

NASA Astrophysics Data System (ADS)

Although differential pressure measurements offer a direct means to understand the energy flow from the f-holes of the violin they have been performed only at discrete frequencies over relatively limited portions of the acoustic field, and none have ever covered an entire f-hole over a broad frequency region. Application of recently developed near field acoustical holography (NAH) patch processing techniques to 108-node planar rectangular grid microphone data provides a powerful tool to understand the flow of acoustic energy from the f-holes up to 4 kHz. The grid covered each f-hole as well as a small portion of the violin top-plate and provided the necessary spatial resolution to allow isolation of only f-hole aperture radiation in the NAH processing. The projected radiativity in the far field at 1.2 m from just the f-holes was compared with prior microphone measurements in an anechoic chamber over an entire sphere around the violin. As expected the lowest cavity mode A0 was the major radiator at the frequencies below all the corpus modes. Surprisingly the first corpus bending modes appear to radiate strongly through the f-holes also. [Work supported by ONR and NSF.

Williams, Earl G.; Bissinger, George

2003-04-01

306

Would Larger Radiation Fields Lead to a Faster Onset of Pain Relief in the Palliation of Bone Metastases?  

SciTech Connect

Purpose: Hemibody irradiation has been shown to relieve bony metastatic pain within 24-48 hours of treatment, whereas for local external beam radiation, onset of pain relief is 1-4 weeks after radiation. The primary objective of this study is to examine whether there is a relationship between the areas of radiation treatment and onset of pain relief. Methods and Materials: From Jan 1999 to Jan 2002, a total of 653 patients with symptomatic bone metastases were treated with external beam radiation. Pain scores and analgesic consumption were recorded at baseline and Weeks 1, 2, 4, 8, and 12. The areas of radiation treatment for all patients were calculated, then correlated with the response and analyzed in various ways. We first compared pain score alone with mean radiation field size. Second, we combined pain score and analgesic consumption. Last, we implemented the International Consensus end points for pain score and analgesic intake. Results: Assessment of 653 patients showed no significant correlation comparing pain scores alone with radiation field area, with the exception of Week 4 for partial responders. Again, no significant correlation was found when combining both analgesic intake and pain score against radiation field size. Even when implementing the International Consensus end point definitions for radiation response, the only significant correlation between radiation field size and response was observed in Week 2 for partial response. Conclusion: There was no statistical significance between mean areas of radiation treatment with the onset of pain relief.

Chow, Edward [Rapid Response Radiotherapy Program, Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto (Canada)], E-mail: edward.chow@sunnybrook.ca; Makhani, Leila; Culleton, Shaelyn; Makhani, Nadiya; Davis, Lori; Campos, Sarah; Sinclair, Emily [Rapid Response Radiotherapy Program, Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto (Canada)

2009-08-01

307

Optical radiation and ionization of hydrogen atoms in heterogeneous exothermal reactions proceeding in an electric field  

NASA Astrophysics Data System (ADS)

Optical radiation related to the Balmer series (H?, H?, H?) of hydrogen atoms is discovered when studying the isothermal reaction of trimeric acetone peroxide decomposition on the surface of oxidized tungsten in a static electric field with a strength of up to 4 × 106 V/cm at T = 300 K. The distance from the surface over which desorbing excited hydrogen atoms radiate is determined from the Stark splitting of the lines. Electronically excited atoms remaining on the surface ionize according to the surface ionization mechanism.

Blashenkov, N. M.; Lavrent'ev, G. Ya.

2009-09-01

308

Strong field-induced frequency conversion of laser radiation in plasma plumes: recent achievements.  

PubMed

New findings in plasma harmonics studies using strong laser fields are reviewed. We discuss recent achievements in the growth of the efficiency of coherent extreme ultraviolet (XUV) radiation sources based on frequency conversion of the ultrashort pulses in the laser-produced plasmas, which allowed for the spectral and structural studies of matter through the high-order harmonic generation (HHG) spectroscopy. These studies showed that plasma HHG can open new opportunities in many unexpected areas of laser-matter interaction. Besides being considered as an alternative method for generation of coherent XUV radiation, it can be used as a powerful tool for various spectroscopic and analytical applications. PMID:23864818

Ganeev, R A

2013-06-20

309

Polarization of Charged Particles due to Radiation of Slow Waves in the External Magnetic Field  

NASA Astrophysics Data System (ADS)

Results of investigation of the interaction of charged particles with spin 1/2 moving in the external uniform magnetic field with slow electromagnetic waves of the helix wave guide are presented. The transfer of particles along Landau levels due to emitting and absorbing of slow electromagnetic waves in the regions of anomalous (ADE) and normal (NDE) Doppler effects is studied. Processes involving spin flip are considered. It is demonstrated that under spontaneous radiation in the region of ADE polarization of particles is possible. Complex Doppler effect (involving quantum kick) is studied. It is demonstrated that polarization of charged particles due to induced radiation is possible in this case.

Buts, V. A.; Buts, A. V.; Ivanov, B. I.; Manuilenko, O. V.

1997-05-01

310

Impact of magnetic field inhomogeneity on electron cyclotron radiative loss in tokamak reactors  

SciTech Connect

The potential importance of electron cyclotron (EC) emission in the local electron power balance in the steady-state regimes of ITER operation with high temperatures, as well as in the DEMO reactor, requires accurate calculation of the one-dimensional (over magnetic surfaces) distribution of the net radiated power density, P{sub EC}({rho}). When the central electron temperature increases to {approx}30 keV, the local EC radiative loss comprises a substantial fraction of the heating power from fusion alphas and is close to the total auxiliary NBI heating power, P{sub EC}(0) Asymptotically-Equal-To 0.3P{sub {alpha}}(0) Asymptotically-Equal-To P{sub aux}(0). In the present paper, the model of EC radiative transport in an axisymmetric toroidal plasma is extended to the case of an inhomogeneous magnetic field B(R, Z). The impact of such inhomogeneity on local and total power losses is analyzed in the framework of this model by using the CYNEQ code. It is shown that, for the magnetic field B, temperature T{sub e}, density n{sub e}, and wall reflection coefficient R{sub w} expected in ITER and DEMO, accurate simulations of the EC radiative loss require self-consistent 1.5D transport analysis (i.e., one-dimensional simulations of plasma transport and two-dimensional simulations of plasma equilibrium). It is shown that EC radiative transport can be described with good accuracy in the 1D approximation with the surface-averaged magnetic field, B({rho}) = Left-Pointing-Angle-Bracket B(R, Z) Right-Pointing-Angle-Bracket {sub ms}. This makes it possible to substantially reduce the computational time required for time-dependent self-consistent 1.5D transport analysis. Benchmarking of the CYNEQ results with available results of the RAYTEC, EXACTEC, and CYTRAN codes is performed for various approximations of the magnetic field.

Kukushkin, A. B.; Minashin, P. V. [National Research Centre Kurchatov Institute, Tokamak Physics Institute (Russian Federation); Polevoi, A. R. [Route de Vinon sur Verdon, ITER Organization (France)

2012-03-15

311

The Electric and Magnetic Field Instrument Suite with Integrated Science (EMFISIS) on the Radiation Belt Storm Probes  

Microsoft Academic Search

The physics of the creation and loss of radiation belt particles is intimately connected to the electric and magnetic fields which mediate these processes. A large range of field dynamics and time scales are involved in this physics from ring current magnetic fields to microscopic kinetic interactions such as whistler-mode chorus waves with energetic electrons. To measure these key field

C. A. Kletzing; W. Kurth; M. Acuna; R. Torbert; R. Thorne; V. Jordanova; S. Bounds; C. Smith; O. Santolik; R. Pfaff; D. Rowland; G. Hospodarsky; W. Baumjohann; R. Nakamura; P. Puhl-Quinn

2006-01-01

312

Wave Science with the Electric and Magnetic Field Instrument Suite with Integrated Science (EMFISIS) on the Radiation Belt Storm Probes  

Microsoft Academic Search

The physics of the creation and loss of radiation belt particles is intimately connected to the electric and magnetic fields of waves which mediate these processes. A large range of field regimes are involved in this physics from ring current magnetic fields to microscopic kinetic interactions such as whistler-mode chorus waves with energetic electrons. To measure these key field interactions,

S. R. Bounds; C. A. Kletzing; W. S. Kurth; M. H. Acuna; R. B. Torbert; R. Thorne; V. Jordanova; C. Smith; O. Santolik; R. Pfaff; D. Rpwlamd; G. Hospodarsky; W. Baumjohann; R. Nakamura; P. Puhl-Quinn

2008-01-01

313

The Electric and Magnetic Field Instrument Suite with Integrated Science (EMFISIS) on the Radiation Belt Storm Probes  

Microsoft Academic Search

The physics of the creation and loss of radiation belt particles is intimately connected to the electric and magnetic fields which mediate these processes. A large range of field regimes are involved in this physics from ring current magnetic fields to microscopic kinetic interactions such as whistler-mode chorus waves with energetic electrons. To measure these key field interactions, NASA has

Craig Kletzing

2008-01-01

314

Internal Electric Field Behavior of Cadmium Zinc Telluride Radiation Detectors Under High Carrier Injection  

SciTech Connect

The behavior of the internal electric-field of nuclear-radiation detectors substantially affects the detector's performance. We investigated the distribution of the internal field in cadmium zinc telluride (CZT) detectors under high carrier injection. We noted the build-up of a space charge region near the cathode that produces a built-in field opposing the applied field. Its presence entails the collapse of the electric field in the rest of detector, other than the portion near the cathode. Such a space-charge region originates from serious hole-trapping in CZT. The device's operating temperature greatly affects the width of the space-charge region. With increasing temperature from 5 C to 35 C, its width expanded from about 1/6 to 1/2 of the total depth of the detector.

Yang, G.; Bolotnikov, A.E.; Camarda, G.S.; Cui, Y.; Hossain, A.; Kim, K.H.; Gul, R.; and James, R.B.

2010-10-26

315

A study of the biological effects of modulated 6 MV radiation fields  

NASA Astrophysics Data System (ADS)

The delivery of spatially modulated radiation fields has been shown to impact on in vitro cell survival responses. To study the effect of modulated fields on cell survival, dose response curves were determined for human DU-145 prostate, T98G glioma tumour cells and normal primary AGO-1552 fibroblast cells exposed to modulated and non-modulated field configurations delivered using a 6 MV Linac with multi-leaf collimator. When exposed to uniform fields delivered as a non-modulated or modulated configuration, no significant differences in survival were observed with the exception of DU-145 cells at a dose of 8 Gy (p = 0.024). Survival responses were determined for exposure to non-uniform-modulated beams in DU-145 and T98G and showed no deviation from the survival response observed following uniform non-modulated exposures. The results of these experiments indicate no major deviation in response to modulated fields compared to uniform exposures.

Butterworth, Karl T.; McGarry, Conor K.; O'Sullivan, Joe M.; Hounsell, Alan R.; Prise, Kevin M.

2010-03-01

316

Matching Intensity-Modulated Radiation Therapy to an Anterior Low Neck Field  

SciTech Connect

When using intensity-modulated radiation therapy (IMRT) to treat head and neck cancer with the primary site above the level of the larynx, there are two basic options for the low neck lymphatics: to treat the entire neck with IMRT, or to match the IMRT plan to a conventional anterior 'low neck' field. In view of the potential advantages of using a conventional low neck field, it is important to look for ways to minimize or manage the problems of matching IMRT to a conventional radiotherapy field. Treating the low neck with a single anterior field and the standard larynx block decreases the dose to the larynx and often results in a superior IMRT plan at the primary site. The purpose of this article is to review the most applicable studies and to discuss our experience with implementing a technique that involves moving the position of the superior border of the low neck field several times during a single treatment fraction.

Amdur, Robert J. [Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, FL (United States)], E-mail: amdurrj@shands.ufl.edu; Liu, Chihray; Li, Jonathan; Mendenhall, William; Hinerman, Russell [Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, FL (United States)

2007-10-01

317

Exploring Digital Encounters in the Public Arena  

NASA Astrophysics Data System (ADS)

In this chapter, we explore the types of encounters that technology enables. We consider the differences between digital and nondigital encounters through two pilot studies carried out in the city of Bath, United Kingdom. We investigate how technology can be appropriated for shared interactions that support conscious (or unconscious) social encounters, and highlight the importance of space and the role of place in providing temporal and spatial mechanisms facilitating different types of shared encounters. Here, we apply a method based on intervention through "sensing and projecting" Bluetooth names and digital identity in the public arena, and describe initial observations about people's reaction toward the projection of their Bluetooth names in public. In particular, we note the significance of constructing socially meaningful relations between people mediated by these technologies. We discuss initial results and outline issues raised in detail before finally describing the ongoing work.

Schieck, Ava Fatah Gen.; Kostakos, Vassilis; Penn, Alan

318

Calculation of harmonic radiation and nuclear coupling arising from atoms in strong laser fields  

SciTech Connect

A numerical, time-dependent quantum mechanical model is used to describe the interaction of an isolated ion with an intense applied laser field, including both electron and nuclear degrees of freedom. Calculated results are presented. We find that the model ion radiates in low odd harmonics of the laser frequency, in qualitative agreement with experimental observations. In addition, it radiates strongly in the x-ray region, at frequencies comparable with the electron Rydberg frequency. Such radiation should be possible to observe in future experiments. If it exists, it could provide a basis for a reasonably coherent x-ray source. We find that the probability of induced nuclear excitation is small for higher electric multipoles, although observable probabilities are obtained under appropriate circumstances for L = 1. 2 refs., 12 figs.

Rinker, G.A.; Solem, J.C.; Biedenharn, L.C.

1988-01-01

319

Assessment of radiation-induced second cancer risks in proton therapy and IMRT for organs inside the primary radiation field.  

PubMed

There is clinical evidence that second malignancies in radiation therapy occur mainly within the beam path, i.e. in the medium or high-dose region. The purpose of this study was to assess the risk for developing a radiation-induced tumor within the treated volume and to compare this risk for proton therapy and intensity-modulated photon therapy (IMRT). Instead of using data for specific patients we have created a representative scenario. Fully contoured age- and gender-specific whole body phantoms (4 year and 14 year old) were uploaded into a treatment planning system and tumor volumes were contoured based on patients treated for optic glioma and vertebral body Ewing's sarcoma. Treatment plans for IMRT and proton therapy treatments were generated. Lifetime attributable risks (LARs) for developing a second malignancy were calculated using a risk model considering cell kill, mutation, repopulation, as well as inhomogeneous organ doses. For standard fractionation schemes, the LAR for developing a second malignancy from radiation therapy alone was found to be up to 2.7% for a 4 year old optic glioma patient treated with IMRT considering a soft-tissue carcinoma risk model only. Sarcoma risks were found to be below 1% in all cases. For a 14 year old, risks were found to be about a factor of 2 lower. For Ewing's sarcoma cases the risks based on a sarcoma model were typically higher than the carcinoma risks, i.e. LAR up to 1.3% for soft-tissue sarcoma. In all cases, the risk from proton therapy turned out to be lower by at least a factor of 2 and up to a factor of 10. This is mainly due to lower total energy deposited in the patient when using proton beams. However, the comparison of a three-field and four-field proton plan also shows that the distribution of the dose, i.e. the particular treatment plan, plays a role. When using different fractionation schemes, the estimated risks roughly scale with the total dose difference in%. In conclusion, proton therapy can significantly reduce the risk for developing an in-field second malignancy. The risk depends on treatment planning parameters, i.e. an analysis based on our formalism could be applied within treatment planning programs to guide treatment plans for pediatric patients. PMID:22968191

Paganetti, Harald; Athar, Basit S; Moteabbed, Maryam; A Adams, Judith; Schneider, Uwe; Yock, Torunn I

2012-09-12

320

Brief chemotherapy, involved field radiation therapy, and central nervous system prophylaxis for paranasal sinus lymphoma.  

PubMed

Lymphoma of the paranasal sinus is a rare tumor characterized by bulky local disease, early systemic dissemination, and a propensity for central nervous system (CNS) spread. Treatment with radiation alone generally has been disappointing. Based on previous encouraging reports of initial brief chemotherapy followed by involved field radiation therapy (IFRT) for localized large cell lymphoma, four consecutive patients with paranasal sinus lymphoma were treated with 6 weeks of chemotherapy followed by IFRT and CNS prophylaxis. All patients had bulky localized disease and diffuse large cell lymphoma. Complete response was seen in all patients, and none have had a relapse (minimum follow-up, 25 months; range, 25 to 32 months). Chemotherapy and radiation therapy were well tolerated. One patient developed an osteogenic sarcoma in the radiation field 32 months after completion of therapy. Administration of early frequent chemotherapy followed by IFRT and CNS prophylaxis appears to be an effective treatment strategy for patients with localized large cell lymphoma of the paranasal sinuses. PMID:1375527

Cooper, D L; Ginsberg, S S

1992-06-15

321

Occupational radiation exposure history of Idaho Field Office Operations at the INEL  

SciTech Connect

An extensive review has been made of the occupational radiation exposure records of workers at the Idaho National Engineering Laboratory (INEL) over the period of 1951 through 1990. The focus has been on workers employed by contractors and employees of the Idaho Field Operations Office (ID) of the United States Department of Energy (USDOE) and does not include the Naval Reactors Facility (NRF), the Argonne National Laboratory (ANL), or other operations field offices at the INEL. The radiation protection guides have decreased from 15 rem/year to 5 rem/year in 1990 for whole body penetrating radiation exposure. During these 40 years of nuclear operations (in excess of 200,000 man-years of work), a total of twelve individuals involved in four accidents exceeded the annual guidelines for exposure; nine of these exposures were received during life saving efforts on January 3, 1961 following the SL-1 reactor accident which killed three military personnel. These exposures ranged from 8 to 27 rem. Only one individual has exceeded the annual whole body penetrating radiation protection guidelines in the last 29 years.

Horan, J.R.; Braun, J.B.

1993-10-01

322

On the relativistic classical motion of a radiating spinning particle in a magnetic field  

SciTech Connect

Research Highlights: > We propose classical equations of motion for a charged particle with magnetic moment. > We account for radiation reaction as well. > Unlike previous proposals we do not have runaway solutions. > We find that the particle loses energy even in a constant magnetic field for a particular spin-polarized state. - Abstract: We propose classical equations of motion for a charged particle with magnetic moment, taking radiation reaction into account. This generalizes the Landau-Lifshitz equations for the spinless case. In the special case of spin-polarized motion in a constant magnetic field (synchrotron motion) we verify that the particle does lose energy. Previous proposals did not predict dissipation of energy and also suffered from runaway solutions analogous to those of the Lorentz-Dirac equations of motion.

Kar, Arnab, E-mail: arnabkar@pas.rochester.edu [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States); Rajeev, S.G. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States)

2011-04-15

323

Strong Near-Field Enhancement of Radiative Heat Transfer between Metallic Surfaces  

NASA Astrophysics Data System (ADS)

Near-field heat transfer across a gap between plane-parallel tungsten layers in vacuo was studied experimentally with the temperature of the cold sample near 5 K and the temperature of the hot sample in the range 10-40 K as a function of the gap size d. At gaps smaller than one-third of the peak wavelength ?m given by Wien’s displacement law, the near-field effect was observed. In comparison with blackbody radiation, hundred times higher values of heat flux were achieved at d?1?m. Heat flux normalized to the radiative power transferred between black surfaces showed scaling (?m/d)n, where n?2.6. This Letter describes the results of experiment and a comparison with present theory over 4 orders of magnitude of heat flux.

Kralik, Tomas; Hanzelka, Pavel; Zobac, Martin; Musilova, Vera; Fort, Tomas; Horak, Michal

2012-11-01

324

Strong near-field enhancement of radiative heat transfer between metallic surfaces.  

PubMed

Near-field heat transfer across a gap between plane-parallel tungsten layers in vacuo was studied experimentally with the temperature of the cold sample near 5 K and the temperature of the hot sample in the range 10-40 K as a function of the gap size d. At gaps smaller than one-third of the peak wavelength ?(m) given by Wien's displacement law, the near-field effect was observed. In comparison with blackbody radiation, hundred times higher values of heat flux were achieved at d?1 ?m. Heat flux normalized to the radiative power transferred between black surfaces showed scaling (?(m)/d)(n), where n?2.6. This Letter describes the results of experiment and a comparison with present theory over 4 orders of magnitude of heat flux. PMID:23368126

Kralik, Tomas; Hanzelka, Pavel; Zobac, Martin; Musilova, Vera; Fort, Tomas; Horak, Michal

2012-11-27

325

Partitioned and Linearly Approximated Impulse Responses for Rapid Calculation of Radiated Sound Fields from Rectangular Transducers  

NASA Astrophysics Data System (ADS)

A rapid calculation method for the radiated sound field from a rectangular transducer is proposed. The radiated field is calculated using the convolution integral between the driving signal of the transducer and the time derivative of the spatial impulse response. The proposed method partitions the integral interval with the driving signal of the transducer and approximates the spatial impulse response as a straight line. The time derivative of the response takes constant values. These constant values are separately multiplied by integrated values of the driving signal prepared in advance. The convolution integral is expressed in a very brief form using several basic mathematical operations. Therefore, the time required for the entire calculation is markedly reduced. It becomes at least about 1/40 of that in which the convolution is directly calculated using the conventional method.

Masuyama, Hiroyuki; Nagai, Keinosuke; Mizutani, Koichi

2002-05-01

326

A comparison of collimator geometries for imaging mixed radiation fields with fast liquid organic scintillators  

SciTech Connect

As a result of recent advances in digital pulse-shape discrimination methods it has become possible to image mixed fields (radiation environments compromising both neutrons and gamma rays) relatively quickly with a single, organic liquid 'fast' scintillator within a heavy metal collimator. The use of a liquid scintillator has significant benefits over other techniques for imaging radiation environments as the acquired data can be analysed to provide separate information about the gamma and neutron emissions from a source (or sources) in a single scan. The imaging resolution achieved is fundamentally related to the detector efficiency and to the collimator geometry. In this paper the impact of using two different geometries of tungsten collimator are compared experimentally and three different materials considered in the Monte Carlo simulation, in order to determine the optimum set-up for mixed-field imaging. The measurements were performed in the low-scatter facility of the National Physical Laboratory, Teddington. (authors)

Gamage, K. A. A.; Joyce, M. J. [Engineering Dept., Lancaster Univ., Lancaster, Lancashire, LA1 4YR (United Kingdom); Taylor, G. C. [Neutron Metrology Group, National Physical Laboratory, Teddington, Middlesex, TW11 0LW (United Kingdom)

2011-07-01

327

Approximate method of solving problems of radiation transfer in a cold plasma with strong magnetic field  

NASA Astrophysics Data System (ADS)

Two approximate methods of solution for problems of radiative transfer in a plasma with a magnetic field are proposed; only the approximation of a cold plasma is considered. One method involves the coupled diffusion of normal waves with generalized Marshak boundary conditions, while the other is based on selecting the constants in the diffusion solution by means of the integral form of the transfer equations obtained for arbitrary anisotropy of the transfer coefficients, and they differ by the method of extending the diffusion solution from the depth of the medium to the emitting boundary. The methods lead to comparatively simple analytic expressions convenient not only for calculations but also for qualitative investigation of the spectral, angular, and polarization characteristics of the emerging radiation for arbitrary direction of the magnetic field.

Kaminker, A. D.; Pavlov, G. G.; Silantev, N. A.; Shibanov, Iu. A.

1982-04-01

328

Very massive runaway stars from three-body encounters  

NASA Astrophysics Data System (ADS)

Very massive stars preferentially reside in the cores of their parent clusters and form binary or multiple systems. We study the role of tight very massive binaries in the origin of the field population of very massive stars. We performed numerical simulations of dynamical encounters between single (massive) stars and a very massive binary with parameters similar to those of the most massive known Galactic binaries, WR 20a and NGC 3603-A1. We found that these three-body encounters could be responsible for the origin of high peculiar velocities (?70 km s-1) observed for some very massive (?60-70 M?) runaway stars in the Milky Way and the Large Magellanic Cloud (e.g. ? Cep, BD+43°3654, Sk -67°22, BI 237, 30 Dor 016), which can hardly be explained within the framework of the binary-supernova scenario. The production of high-velocity massive stars via three-body encounters is accompanied by the recoil of the binary in the opposite direction to the ejected star. We show that the relative position of the very massive binary R145 and the runaway early B-type star Sk-69°206 on the sky is consistent with the possibility that both objects were ejected from the central cluster, R136, of the star-forming region 30 Doradus via the same dynamical event - a three-body encounter.

Gvaramadze, Vasilii V.; Gualandris, Alessia

2011-01-01

329

The Effect of the Static Magnetic Field on the Response of Radiation Survey Instruments  

Microsoft Academic Search

The effects on the response of eight radiation survey instruments in static magnetic fields up to 0.03 T (300 G) have been investigated. The instruments studied are the Xetex 303B Pacer, the Bicron Micro Rem survey meter, the Victoreen 450~ survey meter, the Victoreen 440 survey meter, the SLAC orange meter, the Keithley 36150 survey meter, the Andersson-Braun neutron remmeter,

James C. Liu; Stan Mao; R. C. McCall; R. Donahue

1993-01-01

330

Equilibrium Statistical Mechanics of Matter Interacting with the Quantized Radiation Field  

Microsoft Academic Search

The thermodynamic properties of several systems of multilevel atoms interacting with a quantized radiation field are investigated. We allow a quantum-mechanical treatment of the translational degrees of freedom and do not require the rotating-wave approximation. In the finite-photon-mode case one can calculate the free energy per atom in the thermodynamic limit exactly and rigorously. In the infinite-mode case we only

Klaus Hepp; Elliott H. Lieb

1973-01-01

331

Methodology For Establishment Of The Radiation Control System At The Karachaganak Oil Gas-Condensate Field  

Microsoft Academic Search

\\u000a At the present time radiological contamination by natural radionuclides of industrial platforms of oil-fields is well-known,\\u000a but far from being resolved problem for many countries. Problem as a whole has gained an environmental-technological value.\\u000a The solution of the problem given requires an introduction at the oil-and-gas production facilities of the complex measures\\u000a on normalization of radiation - ecological conditions, decrease

S. V. Reznikov; K. K. Kadyrzhanov; A. Zh. Tuleushev; Zh. N. Marabaev; S. N. Lukashenko; V. P. Solodukhin; I. V. Kazachevskiy; T. I. Ageyeva

332

Intraoperative radiation therapy for advanced neuroblastoma: the problem of securing the IORT field  

Microsoft Academic Search

The purpose of this study is to evaluate the efficacy of intraoperative radiation therapy (IORT) and the problem of securing\\u000a the IORT field in advanced pediatric neuroblastoma. Between 1996 and 2005, 12 children received IORT for advanced pediatric\\u000a neuroblastoma patients. Electron beam energies ranged from 10 to 12 MeV and median dose was 10 Gy (8–12 Gy). All of them had\\u000a surgery with

Kiminobu Sugito; Takeshi Kusafuka; Mayumi Hoshino; Mikiya Inoue; Hiroshi Goto; Taro Ikeda; Noritsugu Hagiwara; Tsugumichi Koshinaga; Masahiro Fukuzawa; Masanori Nakamura; Hiroyuki Shichino; Motoaki Chin; Hideo Mugishima; Tsutomu Saito; Yoshiaki Tanaka

2007-01-01

333

Cell phone electromagnetic field radiations affect rhizogenesis through impairment of biochemical processes  

Microsoft Academic Search

Indiscriminate adoption and use of cell phone technology has tremendously increased the levels of electromagnetic field radiations\\u000a (EMFr) in the natural environment. It has raised the concerns among the scientists regarding the possible risks of EMFr to\\u000a living organisms. However, not much has been done to assess the damage caused to plants that are continuously exposed to EMFr\\u000a present in

Harminder Pal Singh; Ved Parkash Sharma; Daizy Rani Batish; Ravinder Kumar Kohli

334

Silicon PIN radiation detectors with on-chip front-end junction field effect transistors  

Microsoft Academic Search

We report on the latest results obtained from the development of a fabrication technology for PIN radiation detectors with on-chip front-end junction field effect transistors (JFETs) integrated on high-resistivity, FZ silicon. P-doped polysilicon back-side gettering prevented carrier lifetime degradation in spite of the relatively high thermal budget characterizing the fabrication process, allowing very low leakage currents (?1nA\\/cm2 at full depletion)

G. F. Dalla Betta; G. Verzellesi; M. Boscardin; L. Bosisio; G. U. Pignatel; L. Ferrario; M. Zen; G. Soncini

1998-01-01

335

The Radiation Field Wave Forms Produced by Intracloud Lightning Discharge Processes  

Microsoft Academic Search

The large-amplitude radiation field pulses produced by intracloud lightning discharge processes have been recorded with submicrosecond time resolution. The wave forms are distinctly different from those produced by return strokes in cloud-to-ground lightning, yet they are surprisingly alike within a discharge and in different discharges. The shapes tend to be bipolar, with two or three narrow, fast-rising pulses superimposed on

Charles D. Weidman; E. Philip Krider

1979-01-01

336

Field measurement of the transmission of visible and infrared radiation through the atmosphere  

Microsoft Academic Search

The paper deals with instruments and system for making field measurements of the transmission of visible and infrared radiation through the atmosphere. The historical development and design philosophy of the instrumentation are reviewed. The atmospheric transmissometer models discussed and compared include the 14-708 model, the 14-708VRL model, and the 14-709, 14710, and 14-711 models. The operating range and special features

F. M. Zweibaum; J. R. Moulton

1976-01-01

337

Noninversive partial velocity amplification of radiation by ions due to their rotation in a magnetic field  

Microsoft Academic Search

It is shown that upon the application of an external magnetic field, a gas of ionized particles may experience noninversive\\u000a partial velocity amplification of radiation by ions due to their Larmor rotation. In this case, virtually all ions may be\\u000a in the ground state. It may happen that approximately half the number of ions in the medium amplify the incident

A. I. Parkhomenko

2002-01-01

338

NOTE: Measurement of ionizing radiation using carbon nanotube field effect transistor  

Microsoft Academic Search

Single-walled carbon nanotubes (SWNTs) are a new class of highly promising nanomaterials for future nano-electronics. Here, we present an initial investigation of the feasibility of using SWNT field effect transistors (SWNT-FETs) formed on silicon-oxide substrates and suspended FETs for radiation dosimetry applications. Electrical measurements and atomic force microscopy (AFM) revealed the intactness of SWNT-FET devices after exposure to over 1

Xiao-Wu Tang; Yong Yang; Woong Kim; Qian Wang; Pengfei Qi; Hongjie Dai; Lei Xing

2005-01-01

339

Initial Field Measurements with the Multisensor Airborne Radiation Survey (MARS) High Purity Germanium (HPGe) Detector Array  

SciTech Connect

Abstract: The Multi-sensor Airborne Radiation Survey (MARS) project has developed a new single cryostat detector array design for high purity germanium (HPGe) gamma ray spectrometers that achieves the high detection efficiency required for stand-off detection and actionable characterization of radiological threats. This approach is necessary since a high efficiency HPGe detector can only be built as an array due to limitations in growing large germanium crystals. The system is ruggedized and shock mounted for use in a variety of field applications. This paper reports on results from initial field measurements conducted in a truck and on two different boats.

Fast, James E.; Bonebrake, Christopher A.; Dorow, Kevin E.; Glasgow, Brian D.; Jensen, Jeffrey L.; Morris, Scott J.; Orrell, John L.; Pitts, W. Karl; Rohrer, John S.; Todd, Lindsay C.

2010-06-29

340

Near-field thermal radiation transfer controlled by plasmons in graphene  

NASA Astrophysics Data System (ADS)

It is shown that thermally excited plasmon-polariton modes can strongly mediate, enhance, and tune the near-field radiation transfer between two closely separated graphene sheets. The dependence of near-field heat exchange on doping and electron relaxation time is analyzed in the near infrared within the framework of fluctuational electrodynamics. The dominant contribution to heat transfer can be controlled to arise from either interband or intraband processes. We predict maximum transfer at low doping and for plasmons in two graphene sheets in resonance, with orders-of-magnitude enhancement (e.g., 102 to 103 for separations between 0.1 ?m and 10 nm) over the Stefan-Boltzmann law, known as the far-field limit. Strong, tunable, near-field transfer offers the promise of an externally controllable thermal switch as well as a novel hybrid graphene-graphene thermoelectric/thermophotovoltaic energy conversion platform.

Ilic, Ognjen; Jablan, Marinko; Joannopoulos, John D.; Celanovic, Ivan; Buljan, Hrvoje; Solja?i?, Marin

2012-04-01

341

Lyman-{alpha} radiation of a metastable hydrogen beam to measure electric fields  

SciTech Connect

The interaction between a metastable H(2s) atomic hydrogen beam and an external electric field leads to the emission of the Lyman-{alpha} line. It originates in the Stark mixing of the near-degenerate 2s{sub 1/2} and 2p{sub 1/2} levels separated by the Lamb shift. The quenched radiation proportional to the square of the electric field amplitude is recovered in vacuum by using such an atomic probe beam. We observe the strong enhancement of the signal when the field is oscillating at the Lamb shift frequency. This technique is applied in a plasma, offering an alternative way to measure weak electric fields by direct and non-intrusive means.

Lejeune, A.; Cherigier-Kovacic, L.; Doveil, F.

2011-10-31

342

Generation of Seed Magnetic Field Around First Stars: Effects of Radiation Force  

NASA Astrophysics Data System (ADS)

We investigate seed magnetic field generation in the early universe by the radiation force of first stars. In a previous study with the steady assumption, large amplitudes (~10-15 G for first stars, ~10-11 G for QSOs) are predicted. In this study, we formulate this issue in an unsteady framework. Then, we consider a specific model of magnetic field generation around a very massive first star. Consequently, we (1) find that the steady assumption is not valid in realistic situations and (2) obtain a much smaller magnetic field strength than that predicted by Langer et al. In addition, we find that the momentum transfer process during photoionization is more important than Thomson scattering. The resultant magnetic flux density around the first star is lsim10-19 G. This seed magnetic field will not affect subsequent star formation in the neighborhood of first stars.

Ando, Masashi; Doi, Kentaro; Susa, Hajime

2010-06-01

343

NEAs' Satellites Under Close Encounters with Earth  

NASA Astrophysics Data System (ADS)

In the present work we took into account the gravitational effects experienced by a NEA (Near-Earth Asteroid), during a close encounter with Earth, in order to estimate the stability regions of NEAs' satellites as a function of the encounter conditions and for different primary-satellite mass ratio values. Initially, the methodology consisted on numerically simulating a system composed by the Sun, the planets of the Solar System, and samples of NEAs belonging to the groups Apollo, Atens and Amor, for a period of 10 Myr. All encounters with Earth closer than 100 Earth's radius were registered. The next step consisted on simulating all those registered close encounters considering the Earth, the asteroid that perform the close encounter, and a cloud of satellites around the asteroid. We considered no-interacting satellites with circular orbits, random values for the inclination, longitude of the ascending node and true anomaly, and with radial distribution going from 0.024 to 0.4 Hill's radius of the asteroid. The largest radial distance for which all the satellites survive (no collision or ejection) is defined as the critical radius. We present a statistical analysis of the registered encounters and the critical radius found, defining the stable regions as a function of the impact parameter - d, and of the relative velocity - V. For the case of massless satellites, we found that all satellites survived for encounters with d>0.3 Earth Hill's radius. For impact parameter d<0.13 Earth Hill's radius, we found that particles with radial distance greater than 0.24 Hill's radius of the asteroid, are unstable, for any relative velocity. The results for the other considered cases will be presented and discussed. We also discuss the implications of the regions found, specially in the NEAs-binary scenarios.

Araujo, Rosana; Winter, O. C.

2012-10-01

344

Study of magnetic field expansion using a plasma generator for space radiation active protection  

NASA Astrophysics Data System (ADS)

There are many active protecting methods including Electrostatic Fields, Confined Magnetic Field, Unconfined Magnetic Field and Plasma Shielding etc. for defending the high-energy solar particle events (SPE) and Galactic Cosmic Rays (GCR) in deep space exploration. The concept of using cold plasma to expand a magnetic field is the best one of all possible methods so far. The magnetic field expansion caused by plasma can improve its protective efficiency of space particles. One kind of plasma generator has been developed and installed into the cylindrical permanent magnet in the eccentric. A plasma stream is produced using a helical-shaped antenna driven by a radio-frequency (RF) power supply of 13.56 MHz, which exits from both sides of the magnet and makes the magnetic field expand on one side. The discharging belts phenomenon is similar to the Earth's radiation belt, but the mechanism has yet to be understood. A magnetic probe is used to measure the magnetic field expansion distributions, and the results indicate that the magnetic field intensity increases under higher increments of the discharge power.

Jia, Xiang-Hong; Jia, Shao-Xia; Xu, Feng; Bai, Yan-Qiang; Wan, Jun; Liu, Hong-Tao; Jiang, Rui; Ma, Hong-Bo; Wang, Shou-Guo

2013-09-01

345

COMPLEX SCATTERED RADIATION FIELDS AND MULTIPLE MAGNETIC FIELDS IN THE PROTOSTELLAR CLUSTER IN NGC 2264  

SciTech Connect

Near-infrared imaging polarimetry in the J, H, and K{sub s} bands has been carried out for the protostellar cluster region around NGC 2264 IRS 2 in the Monoceros OB1 molecular cloud. Various infrared reflection nebula clusters (IRNCs) associated with NGC 2264 IRS 2 and the IRAS 12 S1 core, as well as local infrared reflection nebulae (IRNe), were detected. The illuminating sources of the IRNe were identified with known or new near- and mid-infrared sources. In addition, 314 point-like sources were detected in all three bands and their aperture polarimetry was studied. Using a color-color diagram, reddened field stars and diskless pre-main-sequence stars were selected to trace the magnetic field (MF) structure of the molecular cloud. The mean polarization position angle of the point-like sources is 81 Degree-Sign {+-} 29 Degree-Sign in the cluster core, and 58 Degree-Sign {+-} 24 Degree-Sign in the perimeter of the cluster core, which is interpreted as the projected direction on the sky of the MF in the observed region of the cloud. The Chandrasekhar-Fermi method gives a rough estimate of the MF strength to be about 100 {mu}G. A comparison with recent numerical simulations of the cluster formation implies that the cloud dynamics is controlled by the relatively strong MF. The local MF direction is well associated with that of CO outflow for IRAS 12 S1 and consistent with that inferred from submillimeter polarimetry. In contrast, the local MF direction runs roughly perpendicular to the Galactic MF direction.

Kwon, Jungmi; Tamura, Motohide; Kandori, Ryo; Kusakabe, Nobuhiko; Hashimoto, Jun; Nakajima, Yasushi; Nakamura, Fumitaka [National Astronomical Observatory of Japan, Tokyo 181-8588 (Japan); Nagayama, Takahiro [Department of Astrophysics, Nagoya University, Nagoya 464-8602 (Japan); Nagata, Tetsuya [Department of Astronomy, Kyoto University, Kyoto 606-8502 (Japan); Hough, James H. [Centre for Astrophysics Research, University of Hertfordshire, Hatfield, Herts AL10 9AB (United Kingdom); Werner, Michael W. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Teixeira, Paula S., E-mail: jungmi.kwon@nao.ac.jp [European Southern Observatory, D-85748 Garching bei Muenchen (Germany)

2011-11-01

346

Determination of High-Frequency Current Distribution Using EMTP-Based Transmission Line Models with Resulting Radiated Electromagnetic Fields  

SciTech Connect

Application of BPL technologies to existing overhead high-voltage power lines would benefit greatly from improved simulation tools capable of predicting performance - such as the electromagnetic fields radiated from such lines. Existing EMTP-based frequency-dependent line models are attractive since their parameters are derived from physical design dimensions which are easily obtained. However, to calculate the radiated electromagnetic fields, detailed current distributions need to be determined. This paper presents a method of using EMTP line models to determine the current distribution on the lines, as well as a technique for using these current distributions to determine the radiated electromagnetic fields.

Mork, B; Nelson, R; Kirkendall, B; Stenvig, N

2009-11-30

347

Evolution of ring current and radiation belt particles under the influence of storm-time electric fields  

Microsoft Academic Search

Electric field and potential distributions in the inner magnetosphere during geomagnetic storms have been investigated using the Akebono\\/EFD data. Using this electric field, we study injection of ring current particles and acceleration of radiation belt electrons by single-particle calculations. During the main phase, the dawn-dusk electric field is intensified especially in a range of 2 < L < 5 with

Y. Nishimura; A. Shinbori; T. Ono; M. Iizima; A. Kumamoto

2007-01-01

348

On the effect of a radiation field in modifying the intermolecular interaction between two chiral molecules  

SciTech Connect

The change in the mutual energy of interaction between a pair of chiral molecules coupled via the exchange of a single virtual photon and in the presence of an electromagnetic field is calculated using nonrelativistic quantum electrodynamics. The particular viewpoint adopted is one that has an intuitive physical appeal and resembles a classical treatment. It involves the coupling of electric and magnetic dipole moments induced at each center by the incident radiation field to the resonant dipole-dipole interaction tensor. The energy shift is evaluated for fixed as well as random orientations of the molecular pair with respect to the direction of propagation of the field. A complete polarization analysis is carried out for the former situation by examining the effect of incident radiation that is linearly or circularly polarized and traveling in a direction that is parallel or perpendicular to the intermolecular distance vector. After tumble averaging, all polarization dependence of the energy shift vanishes. In both cases the interaction energy is directly proportional to the irradiance of the applied field, and is discriminatory, changing sign when one optically active species is replaced by its enantiomer. The asymptotic behavior of the energy shift at the limits of large and small separations is also studied.

Salam, A. [Department of Chemistry, Wake Forest University, Winston-Salem, North Carolina 27109-7486 (United States)

2006-01-07

349

Falling Man: encounters with catastrophic change.  

PubMed

The assault on the twin towers thrust Americans into an encounter with catastrophic change. Previously protected by the illusion of security fed by our relative imperviousness to others' points of view, we are harshly awakened to our defensive blindness. This rupture helps us see the particular beyond the seeming universality, locating culture as a variable frame defining meanings through the narratives that hold complexities of human experience in conceptual space. Don DeLillo's Falling Man offers a reading of catastrophe as a forced encounter with fallibility, breaking apart illusions of sameness and difference, towards integration of what trauma excludes from awareness. PMID:21864142

Charles, Marilyn

2011-08-01

350

Field Comparisons of Direct and Component Measurements of Net Radiation under Clear Skies.  

NASA Astrophysics Data System (ADS)

Accurate measurements of net radiation are basic to all studies of the surface energy budget. In preparation for an energy budget experiment significant differences were found between direct and component measurement of net radiation, which prompted this investigation of their cause. The instruments involved were an all-black single-dome Fritschen-type net pyrradiometer, two Eppley model 8 48 pyranometers, and an Eppley model PIR pyrgeometer. Each had recently been calibrated. The accuracy of the component instruments was considered first. Comparisons of about one hour on each of three nights between the pyrgeometer and five empirical formulas showed that the average departure over all formulas from the pyrgeometer average was 1%. Other comparisons between the pyrgeometer and an infrared thermometer viewing the surface yielded similar results. Alternate shading and unshading of the pyrgeometer looking upward during daytime resulted in a formula that was used to correct the downward longwave radiation under clear skies. The correction is dependent on wind speed, in contrast to a recent paper showing negligible dependence, but is in accord with earlier findings. Based on the manufacturer's specifications, the pyranometer calibrations were considered to be within 2% of the World Radiation Reference.Thus a series of experiments was carried out using what were believed to be reasonably accurate component measurements of net radiation and measurements from the net pyrradiometer. The results showed that the sensitivity of the latter was less in the longwave band than in the shortwave band in agreement with findings of others. Speculating on possible further dependence of sensitivity to the upward and downward streams of radiation, a method was developed to determine the magnitude of the individual net pyrmdiometer components. A reflective double-shell hemispherical cup was affixed to the upward or downward face of the net pyrradiometer such that linear regression could be applied to simultaneous measurements from the net pyrradiometer, pyranometer, pyrgeometer, and the inner cup temperature, assumed to he at air temperature, to estimate the individual components. Although a substantial difference in shartwave sensitivity was computed using this method, the result was not definitive because of the limited number and the narrow range of longwave observations. Nevertheless, the method can be employed in the field to verify uniform sensitivity of a net pyrradiometer's sensing surfaces to shortwave and longwave radiation. The method may have particular application to Fritschen-type net pyrradiometers of recently improved design after extended field use.

Duchon, Claude E.; Wilk, Gregory E.

1994-02-01

351

The effect of the static magnetic field on the response of radiation survey instruments.  

PubMed

The effects on the response of eight radiation survey instruments in static magnetic fields up to 0.03 T (300 G) have been investigated. The instruments studied are the Xetex 303B Pacer, the Bicron Micro Rem survey meter, the Victoreen 450p survey meter, the Victoreen 440 survey meter, the SLAC orange meter, the Keithley 36150 survey meter, the Anderson-Braun neutron remmeter, and the Victoreen 488 neutron survey meter. The results show that the effect may depend on several factors such as instrument design, alignment of the instrument axis with the magnetic flux lines, whether the instrument is stationary or moving relative to the magnetic field, the direction of the movement relative to the magnetic flux lines, and the magnetic field intensity. Also presented are results of work to enhance magnetic shielding of some of the instruments. PMID:8416216

Liu, J C; Mao, S; McCall, R C; Donahue, R

1993-01-01

352

The statistical properties of electromagnetic fields with application to radiation and scattering  

SciTech Connect

Determining the relationships between different average values is an important step in any physics-based statistical theory. If these relationships exist and exhibit certain properties, then probability densities or distributions can be assigned to the field variables and the transition from an average-value theory'' to a statistical theory'' is complete. For electromagnetics, no such average-value relationships have been demonstrated to exist. The derivation of these relationships and their range of validity are the subject of consideration here. For purposes of this discussion, we limit our attention to the fields inside a complex cavity, but with the ultimate goal of deriving the statistics of the far radiated and scattered fields of complex envelopes.

Lehman, T.H. (Lehman (T.H.), Albuquerque, NM (USA)); Miller, E.K. (Los Alamos National Lab., NM (USA))

1991-01-01

353

Inverse method predicting spinning modes radiated by a ducted fan from free-field measurements.  

PubMed

In the study the inverse problem of deducing the modal structure of the acoustic field generated by a ducted turbofan is addressed using conventional farfield directivity measurements. The final objective is to make input data available for predicting noise radiation in other configurations that would not have been tested. The present paper is devoted to the analytical part of that study. The proposed method is based on the equations governing ducted sound propagation and free-field radiation. It leads to fast computations checked on Rolls-Royce tests made in the framework of previous European projects. Results seem to be reliable although the system of equations to be solved is generally underdetermined (more propagating modes than acoustic measurements). A limited number of modes are thus selected according to any a priori knowledge of the sources. A first guess of the source amplitudes is obtained by adjusting the calculated maximum of radiation of each mode to the measured sound pressure level at the same angle. A least squares fitting gives the final solution. A simple correction can be made to take account of the mean flow velocity inside the nacelle which shifts the directivity patterns. It consists of modifying the actual frequency to keep the cut-off ratios unchanged. PMID:15759694

Lewy, Serge

2005-02-01

354

Theoretical calculation of the modulated acoustic radiation force on spheres and cylinders in a standing plane wave-field  

Microsoft Academic Search

The acoustic radiation force on objects is the result of nonlinear properties of wave propagation in continuous media. The acoustic radiation force is known to be static for a continuous wave and is used for many applications. This force can also be dynamic (oscillatory) if the incident sound wave-field is modulated (slow time-variations). The purpose of the present paper is

F. G. Mitri

2005-01-01

355

Enhanced UV-B radiation, flower attributes and pollinator behaviour in Cistus creticus: a Mediterranean field study  

Microsoft Academic Search

The aim of this investigation was to examine the reasons for the higher pollination success in Cistus creticus under enhanced UV-B radiation (Stephanou & Manetas 1998). Thus, a selected array of floral attributes as well as the frequency and duration of insect visits were studied in the field under ambient or ambient plus supplemental UV-B radiation, simulating a 15% ozone

M. Stephanou; Y. Petropoulou; O. Georgiou; Y. Manetas

2000-01-01

356

A study on radiation shielding analysis for toroidal field coils of a tokamak-type fusion reactor  

Microsoft Academic Search

A study on the radiation shield for toroidal field (TF) coils of a tokamak type fusion device is reported. The study was performed to provide the design data base for the radiation shielding analysis for TF coils which can be commonly used for other systems, and to produce some universal recommendation about the neutron flux attenuation in the shield of

Sergei Zimin

1992-01-01

357

Measurements of the four-point coherence function of a laser radiation field in a turbulent atmosphere  

Microsoft Academic Search

The results of an experimental investigation of the four-point coherence function of a complex field of laser radiation in a turbulent atmosphere are presented. The measurements were conducted in a region of random focusings of radiation intensity at large values of the wave parameter. The results of the measurements are compared with the results of analogous measurements but at small

A. S. Gurvich; V. Kan

1979-01-01

358

Power relations in intergroup encounters: a case study of Jewish–Arab encounters in Israel  

Microsoft Academic Search

The purpose of this study is to examine processes and patterns of power relations between majority and minority groups, as manifested in a case study of intergroup encounters between Jews and Arabs in Israel. The research method was qualitative, relying mostly on ethnographic data assembled during the last 4 years of an educational encounter project aimed at reducing hostility and

Ifat Maoz

2000-01-01

359

Chiral effective-field theory in the Delta(1232) region : II. radiative pion photoproduction  

SciTech Connect

We present a theoretical study of the radiative pion photoproduction on the nucleon ($\\gamma N \\rightarrow \\pi N \\gamma'$) in the $\\De$-resonance region, with the aim to determine the magnetic dipole moment (MDM) of the $\\Delta^+(1232)$. The study is done within the framework of chiral effective-field theory where the expansion is performed (to next-to-leading order) in the $\\delta$ power-counting scheme which is an extension of chiral perturbation theory to the $\\Delta$-resonance energy region. We present in detail the results for the absorptive part of the $\\Delta$ MDM, as well as a sensitivity study for the radiative pion photoproduction observables on the real part of the $\\Delta$ MDM. We find that an asymmetry for circular polarization of the photon beam may provide a model-independent way to measure the $\\Delta$ MDM.

Vladimir Pascalutsa; Marc Vanderhaeghen

2007-10-12

360

Silicon field-effect transistors as radiation detectors for the Sub-THz range  

SciTech Connect

The nonresonance response of silicon metal-oxide-semiconductor field-effect transistors (Si-MOSFETs) with a long channel (1-20 {mu}m) to radiation in the frequency range 43-135 GHz is studied. The transistors are fabricated by the standard CMOS technology with 1-{mu}m design rules. The volt-watt sensitivity and the noise equivalent power (NEP) for such detectors are estimated with the calculated effective area of the detecting element taken into account. It is shown that such transistors can operate at room temperature as broadband direct detectors of sub-THz radiation. In the 4-5 mm range of wavelengths, the volt-watt sensitivity can be as high as tens of kV/W and the NEP can amount to 10{sup -11} - 10{sup -12}W/{radical}Hz . The parameters of detectors under study can be improved by the optimization of planar antennas.

But, D. B., E-mail: but.dmitry@gmail.com; Golenkov, O. G.; Sakhno, N. V.; Sizov, F. F.; Korinets, S. V.; Gumenjuk-Sichevska, J. V.; Reva, V. P.; Bunchuk, S. G. [National Academy of Sciences of Ukraine, Lashkaryov Institute of Semiconductor Physics (Ukraine)

2012-05-15

361

Simulation of the radiation fields of the Beta Secondary Standard BSS 2  

NASA Astrophysics Data System (ADS)

Since several years, the irradiation facility for beta radiation, the Beta Secondary Standard BSS 2 developed at PTB, is in worldwide use to irradiate devices with calibrated beta sources. In this work the electron and photon particle spectra of the BSS 2 radiation fields are made available as data files, in addition angular distributions and the depth dose profiles are given. The spectra were determined using the Monte Carlo particle transport code BEAMnrc and are provided as electronic files. In order to verify the simulations, from the same simulations the depth dose curves in a phantom were deduced and compared with corresponding measurements — the agreement is quite good — proving the correctness of the particle spectra.

Behrens, R.

2013-02-01

362

Dosimetry in steep dose-rate gradient radiation fields: A challenge in clinical applications  

SciTech Connect

The fundamental goal of radiotherapy is to reduce the damage to normal tissue and optimize the dose to the tumor with an associated high probability of cure. Because of this, an accurate and precise knowledge of the radiation dose distribution delivered around the tumor volume during radiotherapy treatments such as stereotactic radiosurgery, intensity modulated radiotherapy or brachytherapy with low-energy X-ray and beta particle sources is of great importance. However, in each of these radiation fields, there exists a steep dose-rate gradient which makes it very difficult to perform accurate dose measurements. In this work, the physics phenomena involved in the energy absorption for each of these situations are discussed, and a brief revision of what the Medical Physics community is doing is presented.

Massillon-JL, G. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, A.P. 20-364, 01000 DF (Mexico)

2010-12-07

363

Dosimetry in steep dose-rate gradient radiation fields: A challenge in clinical applications  

NASA Astrophysics Data System (ADS)

The fundamental goal of radiotherapy is to reduce the damage to normal tissue and optimize the dose to the tumor with an associated high probability of cure. Because of this, an accurate and precise knowledge of the radiation dose distribution delivered around the tumor volume during radiotherapy treatments such as stereotactic radiosurgery, intensity modulated radiotherapy or brachytherapy with low-energy X-ray and beta particle sources is of great importance. However, in each of these radiation fields, there exists a steep dose-rate gradient which makes it very difficult to perform accurate dose measurements. In this work, the physics phenomena involved in the energy absorption for each of these situations are discussed, and a brief revision of what the Medical Physics community is doing is presented.

Massillon-Jl, G.

2010-12-01

364

A macromodel-based algorithm for the calculation of lightning radiated electromagnetic fields and induced voltages in transmission lines  

Microsoft Academic Search

In this paper, we propose a fast and efficient algorithm for the calculation of lightning radiated electromagnetic (EM) fields in the space. These macromodel-based calculations will be done using a mixed timefrequency domain method. Vector Fitting algorithm is employed to trace the poles\\/residues position of the channel-base current-radiated electromagnetic fields system transfer function in different points of the space. The

Sina Mashayekhi; Behzad Kordi

2011-01-01

365

Transport equation for 2D electron liquid under microwave radiation plus magnetic field and the Zero Resistance State  

Microsoft Academic Search

A general transport equation for the center of mass motion is constructed to\\u000astudy transports of electronic system under uniform magnetic field and\\u000amicrowave radiation. The equation is applied to study 2D electron system in the\\u000alimit of weak disorder where negative resistance instability is observed when\\u000athe radiation field is strong enough. A solution of the transport equation with

Tai-Kai Ng; Lixin Dai

2005-01-01

366

Critique of ``Quantum Enigma: Physics Encounters Consciousness''  

NASA Astrophysics Data System (ADS)

The central claim that understanding quantum mechanics requires a conscious observer, which is made by B. Rosenblum and F. Kuttner in their book “Quantum Enigma: Physics encounters consciousness”, is shown to be based on various misunderstandings and distortions of the foundations of quantum mechanics.

Nauenberg, Michael

2007-11-01

367

Real World Evaluation of Encounter Gossip.  

National Technical Information Service (NTIS)

Encounter Gossip is a family of message propagation protocols for mobile ad-hoc networks. The coverage of propagation (the fraction of nodes that receive the message) can be made arbitrarily close to 1 at the cost of increased bandwidth overhead. This pap...

D. E. Cooper I. Mitrani P. Ezhilchelvan

2008-01-01

368

Identification of commonly encountered Pratylenchus in Oregon  

Technology Transfer Automated Retrieval System (TEKTRAN)

Pratylenchus species are commonly encountered in soil samples collected from a diversity of economically important crops in Oregon, including potato and small fruits. Proper identification is critical to the selection of an appropriate management strategy since, in many cases, populations are an as...

369

Retail sales explanations: resolving unsatisfactory sales encounters  

Microsoft Academic Search

The general proposition that a salesperson's explanation adequacy plays a critical role in the resolution of unsatisfactory sales encounters for consumers is investigated in a cross-sectional context. The findings indicate that explanation adequacy is influenced by both the style and content of the explanation, and the timeliness of an organization's reaction, whereas explanation adequacy only indirectly affects the final perceptions

Jarrad Dunning; Aron OCass; Anthony Pecotich

2004-01-01

370

Consumerism, reflexivity and the medical encounter  

Microsoft Academic Search

Much emphasis has been placed recently in sociological, policy and popular discourses on changes in lay people's attitudes towards the medical profession that have been labelled by some as a move towards the embracing of “consumerism”. Notions of consumerism tend to assume that lay people act as “rational” actors in the context of the medical encounter. They align with broader

Deborah Lupton

1997-01-01

371

Experimental observation of further frequency upshift from dc to ac radiation converter with perpendicular dc magnetic field  

PubMed

A frequency upshift of a short microwave pulse is generated by the interaction between a relativistic underdense ionization front and a periodic electrostatic field with a perpendicular dc magnetic field. When the dc magnetic field is applied, further frequency upshift of 3 GHz is observed with respect to an unmagnetized case which has typically a GHz range. The radiation frequency depends on both the plasma density and the strength of the dc magnetic field, i.e., the plasma frequency and the cyclotron frequency. The frequency of the emitted radiation is in reasonable agreement with the theoretical values. PMID:11082591

Higashiguchi; Yugami; Gao; Niiyama; Sasaki; Takahashi; Ito; Nishida

2000-11-20

372

Deconvolution of Wide-Field-of-View Measurements of Reflected Solar Radiation.  

NASA Astrophysics Data System (ADS)

Wide-field-of-view (WFOV) radiometers have been flown as part of the Earth Radiation Budget instrument on the Nimbus 6 and 7 spacecraft and as part of the Earth Radiation Budget Experiment (ERBE) instruments aboard the ERBE spacecraft and also the NOAA 9 and 10 operational spacecraft. The measurement is the integral of the reflected solar flux distribution at the top of the earth-atmosphere system over the field-of-view of the radiometer. This paper develops the solution to this two-dimensional integral equation for the albedo distribution in terms of the measurements.The assumption is made that the bidirectional function is known and is invariant with longitude. The resulting axial symmetry of the integral operator permits the separation of the two-dimensional integral equation into a set of uncoupled one-dimensional integral equations for the latitudinal functions. This permits a better understanding of the problem while also considerably reducing the computer resources required for the solution. The one-dimensional integral equations are each approximated by a matrix equation. The matrices are each ill-conditioned, due to the resolution of WFOV data. The solution is expressed in terms of observable and unobservable components. In order to produce acceptable albedo fields from WFOV measurements, it is necessary to use ancillary data for these unobservable components. The limits of resolution are also indicated.

Smith, G. Louis; Rutan, David

1990-02-01

373

Radiation Therapy Field Extent for Adjuvant Treatment of Axillary Metastases From Malignant Melanoma  

SciTech Connect

Purpose: To compare treatment-related outcomes and toxicity for patients with axillary lymph node metastases from malignant melanoma treated with postoperative radiation therapy (RT) to either the axilla only or both the axilla and supraclavicular fossa (extended field [EF]). Methods and Materials: The medical records of 200 consecutive patients treated with postoperative RT for axillary lymph node metastases from malignant melanoma were retrospectively reviewed. All patients received postoperative hypofractionated RT for high-risk features; 95 patients (48%) received RT to the axilla only and 105 patients (52%) to the EF. Results: At a median follow-up of 59 months, 111 patients (56%) had sustained relapse, and 99 patients (50%) had died. The 5-year overall survival, disease-free survival, and distant metastasis-free survival rates were 51%, 43%, and 46%, respectively. The 5-year axillary control rate was 88%. There was no difference in axillary control rates on the basis of the treated field (89% for axilla only vs. 86% for EF; p = 0.4). Forty-seven patients (24%) developed treatment-related complications. On both univariate and multivariate analyses, only treatment with EF irradiation was significantly associated with increased treatment-related complications. Conclusions: Adjuvant hypofractionated RT to the axilla only for metastatic malignant melanoma with high-risk features is an effective method to control axillary disease. Limiting the radiation field to the axilla only produced equivalent axillary control rates to EF and resulted in lower treatment-related complication rates.

Beadle, Beth M. [Department of Radiation Oncology, University of Texas M. D. Anderson Cancer Center, Houston, TX (United States); Guadagnolo, B. Ashleigh [Department of Radiation Oncology, University of Texas M. D. Anderson Cancer Center, Houston, TX (United States)], E-mail: aguadagn@mdanderson.org; Ballo, Matthew T. [Department of Radiation Oncology, University of Texas M. D. Anderson Cancer Center, Houston, TX (United States); Lee, Jeffrey E.; Gershenwald, Jeffrey E.; Cormier, Janice N.; Mansfield, Paul F.; Ross, Merrick I. [Department of Surgical Oncology, University of Texas M. D. Anderson Cancer Center, Houston, TX (United States); Zagars, Gunar K. [Department of Radiation Oncology, University of Texas M. D. Anderson Cancer Center, Houston, TX (United States)

2009-04-01

374

The test of electromagnetic field radiated by electrostatic discharge (ESD) from the real charged human body in the office  

Microsoft Academic Search

A customised ultra-wide band E-field probe and H-field probe with wide band oscilloscope were used to test the electromagnetic field radiated from electrostatic discharge (ESD). Many tests were carried out by real charged human body discharge to the ground. The results show that the electric field in 10 cm by a human holding a metal pen with a potential of

Huang Jiu-Sheng; Deng Qi-Bin; Liu Fang; Fu Peng-Cheng; Liu Pei-Zhu

2000-01-01

375

Newton’s second law, radiation reaction and type II Einstein-Maxwell fields  

NASA Astrophysics Data System (ADS)

Considering perturbations of the Reissner-Nordström metric while keeping the perturbations in the class of type II Einstein-Maxwell metrics, we perform a spherical harmonic expansion of all the variables up to the quadrupole term. This leads to rather surprising results. Referring to the source of the metric as a type II particle (analogous to referring to a Schwarzschild-Reissner-Nordström or Kerr-Newman particle), we see immediately that the Bondi momentum of the particle takes the classical form of mass times velocity plus an electromagnetic radiation reaction term, while the Bondi mass loss equation becomes the classical gravitational and electromagnetic (electric and magnetic) dipole and quadrupole radiation. The Bondi momentum loss equation turns into Newton’s second law of motion containing the Abraham-Lorentz-Dirac radiation reaction force plus a momentum recoil (rocket) force, while the reality condition on the Bondi mass aspect yields the conservation of angular momentum. Two things must be pointed out: (1) these results, (equations of motion, etc) take place, not in the spacetime of the type II metric but in an auxiliary space referred to as {H}-space, whose physical meaning is rather obscure and (2) this analysis of the type II field equations is a very special case of a similar analysis of the general asymptotically flat Einstein-Maxwell equations. Although the final results are similar (though not the same), the analysis uses different equations (specifically, the type II field equations) and is vastly simpler than the general case. Without a great deal of the technical structures needed in the general case, one can see rather easily where the basic results reside in the type II field equations.

Newman, Ezra T.

2011-12-01

376

Modeling the response of thermoluminescence detectors exposed to low- and high-LET radiation fields.  

PubMed

Lithium fluoride thermoluminescence (TL) detectors, with different Li composition (Li-6 and Li-7) and various activators (LiF:Mg,Ti, LiF:Mg,Cu,P), are widely used for dosimetry in space. The primary radiation field in space is composed of fast electrons, protons and heavy charged particles (HCP). By its interaction with the structures of the spacecraft, this field may be modified inside the crew cabin. Therefore, calibration of TL detectors against a dose of gamma-rays is not sufficient for relating the TL readout to absorbed dose or to quantities relevant in radiation protection, without suitable correction. We introduce and calculate the detection efficiency, eta, relative to gamma-ray dose, of lithium fluoride detectors after proton and heavy charged particle (HCP) irradiation. We calculate eta for MCP-N (LiF:Mg,Cu,P) and for MTS-N (LiF:Mg,Ti) using microdosimetric models. The microdosimetric distributions used in these models (for HCP of charges between Z=1 to Z=8 and in the energy range between 0.3 MeV/amu and 20 MeV/amu) are calculated using an analytical model, based on the results of Monte Carlo simulated charged particle tracks using the MOCA-14 code. The ratio etaMCP-N/etaMTS-N for protons of stopping power (in water) below 10 keV/microm lies in the range between 0.65 and 1.0 and for HCP with Z>1--between 0.3 and 0.6. The stopping power of the particle is found not to be a unique parameter to scale the response of TL detectors. The combination of response of LiF:Mg,Cu,P and LiF:Mg,Cu,P detectors can be more suitable for a dose correction in space radiation fields. PMID:12793731

Olko, Pawel; Bilski, Pawel; Budzanowski, Maciej; Waligórski, Michael Patrick Russell; Reitz, Guenther

2002-12-01

377

Determination of canine dose conversion factors in mixed neutron and gamma radiation fields. Technical report  

SciTech Connect

The primary objective of mixed-field neutron/gamma radiation dosimetry in canine irradiation experiments conducted at the Armed Forces Radiobiology Research Institute (AFRRI) is to determine the absorbed midline tissue dose (MLT) at the region of interest in the canine. A dose conversion factor (DCF) can be applied to free-in-air (FIA) dose measurements to estimate the MLT doses to canines. This report is a summary of the measured DCFs that were used to determine the MLT doses in canines at AFRRI from 1979 to 1992.

Torres, B.A.; Bhatt, R.C.; Myska, J.C.; Holland, B.K.

1996-07-01

378

Deconvolution of wide-field-of-view satellite radiometer measurements of reflected solar radiation  

NASA Astrophysics Data System (ADS)

An approach is presented by which the deconvolution of wide-field-of-view (WFOV) measurements of solar radiation reflected from earth is reduced from the solution of a two-dimensional integral equation to the solution of a set of one-dimensional integral equations. This reduces the storage needed for the required matrices by an order of magnitude and the computations by two orders of magnitude. Also, the theoretical and operational difficulties associated with the solution of ill-posed problems are greatly simplified by working with one-dimensional integral equations rather than with a two-dimensional integral equation.

Smith, G. L.

1981-06-01

379

The Use of Molecular Imaging to Evaluate Radiation Fields in the Adjuvant Setting of Breast Cancer  

Microsoft Academic Search

\\u000a Purpose:  To evaluate standard radiation fields in locally advanced breast cancer using the information of a preoperative FDG-PET showing\\u000a lymph node involvement.\\u000a \\u000a \\u000a \\u000a Patients and Methods:  In 15 consecutive patients, referred for postoperative radiotherapy, a standard simulation was performed. Planning CT was\\u000a fused semiautomatically with preoperative FDG-PET, and thoracic wall\\/breast (clinical target volume [CTV]), lungs, and location(s)\\u000a of axillary nodal involvement on FDG-PET

Samuel Bral; Vincent Vinh-Hung; Hendrik Everaert; Peter De Coninck; Guy Storme

2008-01-01

380

The limitations of using vertical cutoff rigidities determined from the IGRF magnetic field models for computing aircraft radiation dose.  

PubMed

Vertical cutoff rigidities derived from the International Geomagnetic Reference Fields (IGRF) are normally used to compute the radiation dose at a specific location and to organize the radiation dose measurements acquired at aircraft altitudes. This paper presents some of the usually ignored limits on the accuracy of the vertical cutoff rigidity models and describes some of the computational artifacts present in these models. It is noted that recent aircraft surveys of the radiation dose experienced along specific flight paths is sufficiently precise that the secular variation of the geomagnetic field is observable. PMID:14727668

Smart, D F; Shea, M A

2003-01-01

381

Measurement of Radiated Electromagnetic Field due to Low Voltage ESD with Spherical Electrode in 1-3GHz Frequency Bandwidth  

NASA Astrophysics Data System (ADS)

The micro-gap discharge as the low voltage ESD shows very fast transition-duration of about 32 ps or less. Furthermore, the breakdown field strength in the gap was very high of about 80 MV/m in low voltage discharging of below 400V. The relationship between the breakdown field strength in the gap and the amplitude of radiated electromagnetic field was examined in experimental study. The amplitude of radiated electromagnetic field was proportion to the breakdown field strength at the gap in the resonance experimental system using the discharge electrode with dipole configuration. In this time, we present an improved experimental system to measure the amplitude of radiated electromagnetic filed in more wideband region using spherical electrodes and a horn antenna. As a result, the amplitude of radiated electromagnetic field is proportion to the discharge voltage from 300V to 620V, and the amplitude of radiated electromagnetic field was according to the diameter of spherical electrode in 1-3GHz frequency bandwidth.

Kawamata, Ken; Minegishi, Shigeki; Fujiwara, Osamu

382

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Coherent phase control of excitation of atoms by bichromatic laser radiation in an electric field  

NASA Astrophysics Data System (ADS)

A new method for coherent phase control of excitation of atoms in a discrete spectrum under the action of bichromatic laser radiation with the frequency ratio 1:2 is analysed. An important feature of this control method is the presence of a electrostatic field, which removes the parity selection rule for one of the control channels. It is shown that for the phase difference between the monochromatic radiation components, corresponding to the destructive interference between channels, there exists the electrostatic field strength at which the excited atomic transition is 'bleached'. It is proposed to use luminescence at the adjacent atomic transition for detecting the phase dependence of optical excitation.

Astapenko, Valerii A.

2005-06-01

383

Experimental Verification of Isotropic Radiation from a Coherent Dipole Source via Electric-Field-Driven LC Resonator Metamaterials  

NASA Astrophysics Data System (ADS)

It has long been conjectured that isotropic radiation by a simple coherent source is impossible due to changes in polarization. Though hypothetical, the isotropic source is usually taken as the reference for determining a radiator’s gain and directivity. Here, we demonstrate both theoretically and experimentally that an isotropic radiator can be made of a simple and finite source surrounded by electric-field-driven LC resonator metamaterials designed by space manipulation. As a proof-of-concept demonstration, we show the first isotropic source with omnidirectional radiation from a dipole source (applicable to all distributed sources), which can open up several possibilities in axion electrodynamics, optical illusion, novel transformation-optic devices, wireless communication, and antenna engineering. Owing to the electric- field-driven LC resonator realization scheme, this principle can be readily applied to higher frequency regimes where magnetism is usually not present.

Tichit, Paul-Henri; Burokur, Shah Nawaz; Qiu, Cheng-Wei; de Lustrac, André

2013-09-01

384

Pitch angle scattering and synchrotron radiation of relativistic runaway electrons in tokamak stochastic magnetic fields  

SciTech Connect

In a recent work [J. R. Martin-Solis and R. Sanchez, Phys. Plasmas 13, 012508 (2006)], the increase that the presence of stochastic magnetic fields causes on the synchrotron radiation losses of relativistic runaway electrons was quantified using a guiding-center approximation. Here, we complete those studies by considering instead the mechanism which dominates the interaction at the gyromotion level. It is shown that, under typical tokamak conditions, the resonant cyclotron interaction with high enough parallel (to the magnetic field) wave numbers (k{parallel}) modes can create, even for moderate magnetic fluctuation levels, an upper bound on the runaway energy. Implications for disruption-generated runaway electrons will be also discussed.

Martin-Solis, Jose Ramon [Universidad Carlos III, Madrid, Spain; Sanchez, Raul [ORNL

2008-01-01

385

Multiphoton processes in scattering and ionization in an intense linearly-polarized radiation field  

SciTech Connect

We have employed the Gavrila-Kaminski formulation for the conversion of the time-dependent Schrodinger equation to a set of coupled differential equations that describe the interaction of an electron with a proton in the presence of an intense linearly-polarized radiation field in the Kramers-Henneberger gauge. The differential equations are solved numerically by a linear algebraic prescription effectively applied to electron-molecule collisions. We studied both electron-proton collisions assisted by the laser field and multiphoton ionization of H. In the former, we observed the capture-escape resonances while in the latter, we found evidence of the stabilization mechanism as the intensity reaches 10{sup 18} W/cm{sup 2}.

Collins, L.A. (Los Alamos National Lab., NM (United States)); Csanak, G. (Tsukuba Univ., Ibaraki (Japan))

1992-01-01

386

Multiphoton processes in scattering and ionization in an intense linearly-polarized radiation field  

SciTech Connect

We have employed the Gavrila-Kaminski formulation for the conversion of the time-dependent Schrodinger equation to a set of coupled differential equations that describe the interaction of an electron with a proton in the presence of an intense linearly-polarized radiation field in the Kramers-Henneberger gauge. The differential equations are solved numerically by a linear algebraic prescription effectively applied to electron-molecule collisions. We studied both electron-proton collisions assisted by the laser field and multiphoton ionization of H. In the former, we observed the capture-escape resonances while in the latter, we found evidence of the stabilization mechanism as the intensity reaches 10{sup 18} W/cm{sup 2}.

Collins, L.A. [Los Alamos National Lab., NM (United States); Csanak, G. [Tsukuba Univ., Ibaraki (Japan)

1992-06-01

387

Mirror effect induced by the dilaton field on the Hawking radiation  

SciTech Connect

A ''stringy particle'' action is naturally derived from Kaluza-Klein compactification of a test string action coupled to the dilaton field in a conformally invariant manner. According to the standard procedure, we perform the second quantization of the stringy particle. As an interesting application, we consider evaporation of a near-extremal dilatonic black hole by Hawking radiation via the stringy particles. We show that a mirror surface which reflects them is induced by the dilaton field outside the the horizon when the size of the black hole is comparable to the Planck scale. As a result, the energy flux does not propagate across the surface, and hence the evaporation of the dilatonic black hole stops just before the naked singularity at the extremal state appears even though the surface gravity is non-zero in the extremal limit.

Maeda, Kengo [Department of General Education, Kobe City College of Technology, Kobe 651-2194 (Japan); Okamura, Takashi [Department of Physics, Kwansei Gakuin University, Sanda 669-1337 (Japan)

2006-11-03

388

Performance of neutron and gamma personnel dosimetry in mixed radiation fields  

SciTech Connect

From 1974 to 1980, six personnel dosimetry intercomparison studies (PDIS) were conducted at the Oak Ridge National Laboratory (ORNL) to evaluate the performance of personnel dosimeters in a variety of neutron and gamma fields produced by operating the Health Physics Research Reactor (HPRR) in the steady state mode with and without spectral modifying shields. A total of 58 different organizations participated in these studies which produced approximately 2000 measurements of neutron and gamma dose equivalents on anthropomorphic phantoms for five different reactor spectra. Based on these data, the relative performance of three basic types of neutron dosimeters (nuclear emulsion film, thermoluminescent (TLD), and track-etch) and two basic types of gamma dosimeters (film and TLD) in mixed radiation fields was assessed.

Swaja, R.E.; Sims, C.S.

1981-01-01

389

Factors affecting the gamma response of TLD-700 chips in mixed-radiation fields  

SciTech Connect

To determine the causes of gamma dose equivalent overestimates observed during mixed-radiation field personnel dosimetry intercomparisons at Oak Ridge National Laboratory, a study was performed to evaluate the effects of phosphor neutron sensitivity, badge materials, and phantoms on the response of TLD-700 chips. The results of the study presented in this paper indicate that even if a phosphor with relatively low neutron sensitivity is used, significant gamma overestimates can occur in mixed fields due to the interaction of the phosphor and badge materials with neutrons. Low energy photons can also contribute to gamma dose equivalent overestimates due to the increased sensitivity of the TLD-700 phosphor to photons with energies below about 100 keV.

Swaja, R.E. (Health and Safety Research Div., Oak Ridge National Lab., Oak Ridge, TN (US)); Scofield, P.A. (Radiological and Occupational Health Dept., Univ. of Michigan, Ann Arbor, MI (US))

1986-10-01

390

The signal from an emitting source moving in a Schwarzschild spacetime under the influence of a radiation field  

NASA Astrophysics Data System (ADS)

The motion of matter immersed in a radiation field is affected by a radiation drag, as a result of scattering or absorption and re-emission. The resulting friction-like drag, also known as the Poynting-Robertson effect, has been recently studied in the general relativistic background of the Schwarzschild and Kerr metric, under the assumption that all photons in the radiation field possess the same angular momentum. We calculate here the signal produced by an emitting point-like specific source moving in a Schwarzschild spacetime under the influence of such a radiation field. We derive the flux, redshift factor and solid angle of the hot spot as a function of (coordinate) time, as well as the time-integrated image of the hot spot as seen by an observer at infinity. The results are then compared with those for a spot moving on a circular geodesic in a Schwarzschild metric.

Bini, Donato; Falanga, Maurizio; Geralico, Andrea; Stella, Luigi

2012-03-01

391

Predicting age of ovarian failure after radiation to a field that includes the ovaries  

SciTech Connect

Purpose: To predict the age at which ovarian failure is likely to develop after radiation to a field that includes the ovary in women treated for cancer. Methods and Materials: Modern computed tomography radiotherapy planning allows determination of the effective dose of radiation received by the ovaries. Together with our recent assessment of the radiosensitivity of the human oocyte, the effective surviving fraction of primordial oocytes can be determined and the age of ovarian failure, with 95% confidence limits, predicted for any given dose of radiotherapy. Results: The effective sterilizing dose (ESD: dose of fractionated radiotherapy [Gy] at which premature ovarian failure occurs immediately after treatment in 97.5% of patients) decreases with increasing age at treatment. ESD at birth is 20.3 Gy; at 10 years 18.4 Gy, at 20 years 16.5 Gy, and at 30 years 14.3 Gy. We have calculated 95% confidence limits for age at premature ovarian failure for estimated radiation doses to the ovary from 1 Gy to the ESD from birth to 50 years. Conclusions: We report the first model to reliably predict the age of ovarian failure after treatment with a known dose of radiotherapy. Clinical application of this model will enable physicians to counsel women on their reproductive potential following successful treatment.

Wallace, W. Hamish B. [Section of Child Life and Health, Department of Reproductive and Developmental Sciences, University of Edinburgh, Edinburgh, Scotland (United Kingdom)]. E-mail: Hamish.Wallace@ed.ac.uk; Thomson, Angela B. [Royal Hospital for Sick Children, Yorkhill, Glasgow, Scotland (United Kingdom); Saran, Frank [Royal Marsden NHS Trust Foundation, Sutton (United Kingdom); Kelsey, Tom W. [School of Computer Science, University of St. Andrews, St. Andrews, Scotland (United Kingdom)

2005-07-01

392

Adjuvant paclitaxel and carboplatin chemotherapy with involved field radiation in advanced endometrial cancer: A sequential approach  

SciTech Connect

Purpose: To determine the feasibility of adjuvant paclitaxel and carboplatin chemotherapy interposed with involved field radiotherapy for women with advanced endometrial cancer. Methods and Materials: This was a prospective cohort study of women with Stage III and IV endometrial cancer. Adjuvant therapy consisted of 4 cycles of paclitaxel (175 mg/m{sup 2}) and carboplatin (350 mg/m{sup 2}) every 3 weeks, followed sequentially by external beam radiotherapy (RT) to the pelvis (45 Gy), followed by an additional two cycles of chemotherapy. Para-aortic RT and/or HDR vault brachytherapy (BT) were added at the discretion of the treating physician. Results: Thirty-three patients (median age, 63 years) received treatment between April 2002 and June 2005. Median follow-up was 21 months. Stage distribution was as follows: IIIA (21%), IIIC (70%), IVB (9%). Combination chemotherapy was successfully administered to 30 patients (91%) and 25 patients (76%), before and after RT respectively. Nine patients (27%) experienced acute Grade 3 or 4 chemotherapy toxicities. All patients completed pelvic RT; 19 (58%) received standard 4-field RT and 14 (42%) received intensity-modulated radiotherapy. Ten (30%) received extended field radiation. Four patients (12%) experienced acute Grade 3 or 4 RT toxicities. Six (18%) patients developed chronic RT toxicity. There were no treatment-related deaths. Two-year disease-free and overall survival rates were both 55%. There was only one pelvic relapse (3%). Conclusions: Adjuvant treatment with combination chemotherapy interposed with involved field radiation in advanced endometrial cancer was well tolerated. This protocol may be suitable for further evaluation in a clinical trial.

Lupe, Krystine [Department of Radiation Oncology, University of Western Ontario and London Health Sciences Centre, London, Ontario (Canada); Kwon, Janice [Division of Gynecologic Oncology, University of Western Ontario and London Health Sciences Centre, London, Ontario (Canada)]. E-mail: Janice.kwon@lhsc.on.ca; D'Souza, David [Department of Radiation Oncology, University of Western Ontario and London Health Sciences Centre, London, Ontario (Canada); Gawlik, Christine [Department of Pharmacy, University of Western Ontario and London Health Sciences Centre, London, Ontario (Canada); Stitt, Larry [Department of Biostatistics and Epidemiology, University of Western Ontario and London Health Sciences Centre, London, Ontario (Canada); Whiston, Frances [Clinical Cancer Research Program, University of Western Ontario and London Health Sciences Centre, London, Ontario (Canada); Nascu, Patricia [Department of Obstetrics and Gynecology, University of Western Ontario and London Health Sciences Centre, London, Ontario (Canada); Wong, Eugene [Department of Radiation Oncology, University of Western Ontario and London Health Sciences Centre, London, Ontario (Canada); Carey, Mark S. [Division of Gynecologic Oncology, University of Western Ontario and London Health Sciences Centre, London, Ontario (Canada)

2007-01-01

393

Freud and film: encounters in the Weltgeist.  

PubMed

Freud's antipathy toward film is striking, since film and dreams are formed by similar mechanisms. Nevertheless, Freud occasionally and unavoidably encountered film. This paper details some of these encounters. Ten years after viewing time-lapse photography, a fore-runner of moving pictures, at the Salpêtrière, he was conceptualizing a model of the mind and of the formation of dreams that in some ways parallels the film apparatus invented by the Lumière brothers in December 1895. On his visit to America in 1905, Freud saw movies in New York City. In 1925, he refused a lucrative offer to consult on a film, and he discouraged Karl Abraham and Hanns Sachs from consulting on the first psychoanalytic film, Pabst's Secrets of a Soul (1926). He was, however, once sighted viewing an American double feature in Vienna. The paper closes with a critique of his acting in home movies. PMID:10650559

Sklarew, B

1999-01-01

394

Encounters: Chamber Piece for Eight Players  

Microsoft Academic Search

Encounters: Chamber Piece for Eight Players is a three-movement composition that was conceived as a dance piece. Though it features only eight instrumentalists, the wide range of timbres present in the ensemble creates a dramatic and theatrical effect suitable for a dance setting. The piece also functions effectively without dance.\\u000aEach of the three movements’ subtitles – Entrance, Apparition, and

Michael Stephen Hegedus

2005-01-01

395

Modelling close encounters with Öpik's theory  

Microsoft Academic Search

The results obtained by numerical integration of the equations of motion of fictitious comets, in the restricted circular three-dimensional three-body problem, are compared with those obtained with Öpik's theory of close encounters, for an experimental set-up similar to that used by Froeschlé and Rickman (1980, 1981) to model both the infeed of comets from the trans-jovian region into the Jupiter

G. B. Valsecchi; Cl. Froeschlé; R. Gonczi

1997-01-01

396

Multiple emotional contagions in service encounters  

Microsoft Academic Search

This paper investigates the dynamic impact of multiple sequential emotional displays by employees on customers’ negative emotions.\\u000a Using video-based stimuli to manipulate emotional displays by employees, this study shows the sequential occurrences of negative\\u000a and positive emotional contagions in service failure and recovery encounters. The results suggest that higher levels of employees’\\u000a negative emotional displays lead to a greater increase

Jiangang Du; Xiucheng Fan; Tianjun Feng

2011-01-01

397

Background X-ray Radiation Fields Produced by Young Embedded Star Clusters  

NASA Astrophysics Data System (ADS)

Most star formation in our galaxy occurs within embedded clusters, and these background environments can affect the star and planet formation processes occurring within them. In turn, young stellar members can shape the background environment and thereby provide a feedback mechanism. This work explores one aspect of stellar feedback by quantifying the background X-ray radiation fields produced by young stellar objects. Specifically, the distributions of X-ray luminosities and X-ray fluxes produced by cluster environments are constructed as a function of cluster membership size N. Composite flux distributions, for given distributions of cluster sizes N, are also constructed. The resulting distributions are wide and the X-ray radiation fields are moderately intense, with the expected flux levels exceeding the cosmic and galactic X-ray backgrounds by factors of ˜10-1000 (for energies 0.2--15 keV). For circumstellar disks that are geometrically thin and optically thick, the X-ray flux from the background cluster dominates that provided by a typical central star in the outer disk where r ? 9-14 AU. In addition, the expectation value of the ionization rate provided by the cluster X-ray background is ?X ˜ 8 × 10-17 s-1, about 4-8 times larger than the canonical value of the ionization rate from cosmic rays. These elevated flux levels in clusters indicate that X-rays can affect ionization, chemistry, and heating in circumstellar disks and in the material between young stellar objects.

Adams, Fred C.; Fatuzzo, Marco; Holden, Lisa

2012-09-01

398

Radiation-based near-field thermal rectification with phase transition materials  

NASA Astrophysics Data System (ADS)

The capability of manipulating heat flow has promising applications in thermal management and thermal circuits. In this Letter, we report strong thermal rectification effect based on the near-field thermal radiation between silicon dioxide (SiO2) and a phase transition material, vanadium dioxide (VO2), separated by nanometer vacuum gaps under the framework of fluctuational electrodynamics. Strong coupling of surface phonon polaritons between SiO2 and insulating VO2 leads to enhanced near-field radiative transfer, which on the other hand is suppressed when VO2 becomes metallic, resulting in thermal rectification. The rectification factor is close to 1 when vacuum gap is at 1 ?m and it increases to almost 2 at sub-20-nm gaps when emitter and receiver temperatures are set to 400 and 300 K, respectively. Replacing bulk SiO2 with a thin film of several nanometers, rectification factor of 3 can be achieved when the vacuum gap is around 100 nm.

Yang, Yue; Basu, Soumyadipta; Wang, Liping

2013-10-01

399

Far-field radiated from a vertical magnetic dipole in the sea with a rough upper surface  

Microsoft Academic Search

The problem of communication in the sea has been considered as propagation of radio waves in a three-layered medium (air, sea, and ground). With the aid of the perturbation calculus, this paper analyzes the influence exerted onto the electromagnetic field of arrangements radiating a pure transverse electric field in the sea. The sea height varies continuously with the distance from

Osama M. Abo-Seida; Samira Tadros Bishay; Khaled Mohamed El-Morabie

2006-01-01

400

Lightning return stroke current radiation in presence of a conducting ground: 1. Theory and numerical evaluation of the electromagnetic fields  

Microsoft Academic Search

The general theory describing the electromagnetic field radiated by a lightning stroke over a conducting ground is presented in this paper. The derivation of the Green functions necessary to solve the problem is discussed in detail, and the determination of the expressions for the electromagnetic field components is carried out in a form that minimizes the final computational costs. A

Federico Delfino; Renato Procopio; Mansueto Rossi

2008-01-01

401

A Radiative transfer Model for Soil Media with Considering the volume Effects of Soil Particles: field observation and Numerical Simulation  

Microsoft Academic Search

This paper presents the development of an improved soil radiative transfer model (RTM) which considering the volume scattering effect of soil particles, an unexplored part of traditional RTMs, through field experiments and numerical simulations. The field observations were conducted by using the ground based passive microwave radiometer (GBMR) to measure the brightness temperature of dry sand layer over background materials,

Hui Lu; Toshio KOIKE; Hiroyuki TSUTSUI; Tobias GRAF; David Ndegwa KURIA; Hideyuki FUJII; M. Mourita

2006-01-01

402

ROLE FOR THE MAGNETIC FIELD IN THE RADIATION-INDUCED EFFLUX OF CALCIUM IONS FROM BRAIN TISSUE 'IN VITRO'  

EPA Science Inventory

Two independent laboratories have demonstrated that specific frequencies of electromagnetic radiation can cause a change in the efflux of calcium ions from brain tissue in vitro. Under a static magnetic field intensity of 38 microTesla (microT) due to the earth's magnetic field, ...

403

The development of low level coastal flow fields when solar radiation is blocked by smoke  

SciTech Connect

Thick layers of smoke, injected into the atmosphere by fires ignited by a nuclear exchange, would block the incident solar radiation and allow continental regions to cool while oceanic areas remain at constant temperature. It has been suggested that the resultant horizontal temperature gradient could initiate precipitation along the coastline that would rapidly scavenge the smoke. This hypothesis is being investigated using an enhanced version of the Colorado State University mesoscale model to simulate the flow field in the vicinity of continental coastlines. The model has been modified to include cloud formation and the effects of these clouds on the transfer of infrared radiation as well as improving the basic long wave radiation parameterization. For moderate westerly winds over the east coast (offshore flow), a layer of fog forms just above the ground that, after about 2 days, evolves into a stratus cloud. Over the ocean a similar stratus cloud forms because of upward mixing of water vapor and radiative cooling. Once these similar cloud layers form, the cooling rates over land and sea become nearly the same eliminating the proposed mechanism for development of convective precipitation and scavenging of mid- or high-level smoke. For the same westerly winds on the west coast (onshore flow), the sequence is similar but evolves more quickly because more moisture is present in the upwind maritime air. In both cases, the formation of ground fog prevents the air temperature in the surface layer from falling below the temperature at which saturation occurs. Before the temperature decreases further, moisture must be removed from the layer.

Molenkamp, C.R.

1987-08-01

404

Generalized Reference Fields and Source Interpolation for the Difference Formulation of Radiation Transport  

SciTech Connect

In the difference formulation for the transport of thermally emitted photons, the photon intensity is defined relative to a reference field, the black body at the local material temperature. This choice of reference field combines the separate emission and absorption terms that nearly cancel, removing the dominant cause of noise in the Monte Carlo solution of thick systems, but introduces time and space derivative source terms that can not be determined until the end of the time step. The space derivative source term can also lead to noise induced crashes under certain conditions where the real physical photon intensity differs strongly from a black body at the local material temperature. In this paper, we consider a difference formulation relative to the material temperature at the beginning of the time step, or in cases where an alternative temperature better describes the radiation field, that temperature. The result is a method where iterative solution of the material energy equation is efficient and noise induced crashes are avoided. We couple our generalized reference field scheme with an ad hoc interpolation of the space derivative source, resulting in an algorithm that produces the correct flux between zones as the physical system approaches the thick limit.

Luu, T C; Brooks, E D; Szoke, A

2009-02-05

405

Generalized reference fields and source interpolation for the difference formulation of radiation transport  

SciTech Connect

In the difference formulation for the transport of thermally emitted photons the photon intensity is defined relative to a reference field, the black body at the local material temperature. This choice of reference field combines the separate emission and absorption terms that nearly cancel, thereby removing the dominant cause of noise in the Monte Carlo solution of thick systems, but introduces time and space derivative source terms that cannot be determined until the end of the time step. The space derivative source term can also lead to noise induced crashes under certain conditions where the real physical photon intensity differs strongly from a black body at the local material temperature. In this paper, we consider a difference formulation relative to the material temperature at the beginning of the time step, or in cases where an alternative temperature better describes the radiation field, that temperature. The result is a method where iterative solution of the material energy equation is efficient and noise induced crashes are avoided. We couple our generalized reference field scheme with an ad hoc interpolation of the space derivative source, resulting in an algorithm that produces the correct flux between zones as the physical system approaches the thick limit.

Luu, Thomas [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94550 (United States); Brooks, Eugene D. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94550 (United States)], E-mail: brooks3@llnl.gov; Szoke, Abraham [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94550 (United States)

2010-03-01

406

The effect of cumulus cloud field anisotropy on solar radiative fluxes and atmospheric heating rates  

NASA Astrophysics Data System (ADS)

The effect of fair-weather cumulus cloud field anisotropy on domain average surface fluxes and atmospheric heating profiles was studied. Causes of anisotropy were investigated using a large-eddy simulation (LES) model. Cloud formation under a variety of environmental conditions was simulated and the degree of anisotropy in the output fields was calculated. Wind shear was found to be the single greatest factor in the development of both vertically tilted and horizontally stretched cloud structures. A stochastic field generation algorithm was used to produce twenty three-dimensional liquid water content fields based on the statistical properties of the LES cloud scenes. Progressively greater degrees of tilt and stretching were imposed on each of these scenes, so that an ensemble of scenes were produced for each level of distortion. The resulting scenes were used as input to a three-dimensional Monte Carlo model. Domain-average transmission, reflection, and absorption of broadband solar radiation were computed for each scene along with the average heating rate profile. Both tilt and horizontal stretching were found to significantly affect calculated fluxes, with the amount and sign of flux differences depending strongly on sun position relative to cloud distortion geometry. For nearly all solar geometries, domain-averaged fluxes and atmospheric heating rate profiles calculated using the Independent Pixel Approximation differed substantially from the corresponding three-dimensional Monte Carlo results.

Hinkelman, Laura M.

407

Interaction of carbon dioxide laser radiation with a nanotube array in the presence of a constant electric field  

SciTech Connect

The dependence of the current density on the leading edge width of the alternating (high-frequency) field amplitude is studied at various constant (or unsteady) fields. The dependence of amplified microwaves in the two-millimeter range on a longitudinal coordinate is determined. The problem of submillimeter radiation generation in a system of parallel carbon nanotubes exposed to two-frequency carbon dioxide (CO{sub 2} laser) laser radiation in the presence of a constant (or unsteady) field is studied. The possibility of using freely oriented carbon nanotubes parallel to each other is shown.

Sadykov, N. R., E-mail: n.r.sadykov@rambler.ru [Branch of South Ural State University (Russian Federation); Scorkin, N. A. [Snezhinsk Physics and Technology Institute of the National Research Nuclear University 'MEPhI' (Russian Federation)

2012-06-15

408

Exposure of arctic field scientists to ultraviolet radiation evaluated using personal dosimeters.  

PubMed

During July 2000 we used an electronic personal dosimeter (X-2000) and a biological dosimeter (Deutsches Zentrum für Luft- und Raumfahrt: Biofilm) to characterize the UV radiation exposure of arctic field scientists involved in biological and geological fieldwork. These personnel were working at the Haughton impact structure on Devon Island (75 degrees N) in the Canadian High Arctic under a 24 h photoperiod. During a typical day of field activities under a clear sky, the total daily erythemally weighted exposure, as measured by electronic dosimetry, was up to 5.8 standard erythemal dose (SED). Overcast skies (typically 7-8 okta of stratus) reduced exposures by a mean of 54%. We estimate that during a month of field activity in July a typical field scientist at this latitude could potentially receive approximately 80 SED to the face. Because of body movements the upper body was exposed to a UV regimen that often changed on second-to-second time-scales as assessed by electronic dosimetry. Over a typical 10 min period on vehicle traverse, we found that erythemal exposure could vary to up to 87% of the mean exposure. Time-integrated exposures showed that the type of outdoor field activities in the treeless expanse of the polar desert had little effect on the exposure received. Although absolute exposure changed in accordance with the time of day, the exposure ratio (dose received over horizontal dose) did not vary much over the day. Under clear skies the mean exposure ratio was 0.35 +/- 0.12 for individual activities at different times of the day assessed using electronic dosimetry. Biological dosimetry showed that the occupation was important in determining daily exposures. In our study, scientists in the field received an approximately two-fold higher dose than individuals, such as medics and computer scientists, who spent the majority of their time in tents. PMID:11683037

Cockell, C S; Scherer, K; Horneck, G; Rettberg, P; Facius, R; Gugg-Helminger, A; Driscoll, C; Lee, P

2001-10-01

409

Stellar encounters in the context of outburst phenomena  

NASA Astrophysics Data System (ADS)

Young stellar systems are known to undergo outbursts, where the star experiences an increased accretion rate, and the system's luminosity increases accordingly. The archetype is the FU Orionis (FU Ori) outburst, where the accretion rate can increase by three orders of magnitude (and the brightness of the system by five magnitudes). The cause appears to be instability in the circumstellar disc, but there is currently some debate as to the nature of this instability (e.g. thermal, gravitational, magneto-rotational). This paper details high-resolution smoothed particle hydrodynamics (SPH) simulations that were carried out to investigate the influence of stellar encounters on disc dynamics. Star-star encounters (where the primary has a self-gravitating, marginally stable protostellar disc) were simulated with various orbital parameters to investigate the resulting disc structure and dynamics. Crucially, the simulations include the effects of radiative transfer to realistically model the resulting thermodynamics. Our results show that the accretion history and luminosity of the system during the encounter display many of the features of outburst phenomena. In particular, the magnitudes and decay times seen are comparable to those of FU Ori. There are two caveats to this assertion: the first is that these events are not expected to occur frequently enough to explain all FU Ori or EX Lupi; the second is that the inner discs of these simulations are subject to numerical viscosity, which will act to reduce the accretion rate (although it has less of an effect on the total mass accreted). In short, these results cannot rule out binary interactions as a potential source of some FU Ori-esque outbursts.

Forgan, Duncan; Rice, Ken

2010-02-01

410

The Electric Field and Waves Instruments on the Radiation Belt Storm Probes Mission  

NASA Astrophysics Data System (ADS)

The Electric Fields and Waves (EFW) Instruments on the two Radiation Belt Storm Probe (RBSP) spacecraft (recently renamed the Van Allen Probes) are designed to measure three dimensional quasi-static and low frequency electric fields and waves associated with the major mechanisms responsible for the acceleration of energetic charged particles in the inner magnetosphere of the Earth. For this measurement, the instrument uses two pairs of spherical double probe sensors at the ends of orthogonal centripetally deployed booms in the spin plane with tip-to-tip separations of 100 meters. The third component of the electric field is measured by two spherical sensors separated by ˜15 m, deployed at the ends of two stacer booms oppositely directed along the spin axis of the spacecraft. The instrument provides a continuous stream of measurements over the entire orbit of the low frequency electric field vector at 32 samples/s in a survey mode. This survey mode also includes measurements of spacecraft potential to provide information on thermal electron plasma variations and structure. Survey mode spectral information allows the continuous evaluation of the peak value and spectral power in electric, magnetic and density fluctuations from several Hz to 6.5 kHz. On-board cross-spectral data allows the calculation of field-aligned wave Poynting flux along the magnetic field. For higher frequency waveform information, two different programmable burst memories are used with nominal sampling rates of 512 samples/s and 16 k samples/s. The EFW burst modes provide targeted measurements over brief time intervals of 3-d electric fields, 3-d wave magnetic fields (from the EMFISIS magnetic search coil sensors), and spacecraft potential. In the burst modes all six sensor-spacecraft potential measurements are telemetered enabling interferometric timing of small-scale plasma structures. In the first burst mode, the instrument stores all or a substantial fraction of the high frequency measurements in a 32 gigabyte burst memory. The sub-intervals to be downloaded are uplinked by ground command after inspection of instrument survey data and other information available on the ground. The second burst mode involves autonomous storing and playback of data controlled by flight software algorithms, which assess the "highest quality" events on the basis of instrument measurements and information from other instruments available on orbit. The EFW instrument provides 3-d wave electric field signals with a frequency response up to 400 kHz to the EMFISIS instrument for analysis and telemetry (Kletzing et al. Space Sci. Rev. 2013).

Wygant, J. R.; Bonnell, J. W.; Goetz, K.; Ergun, R. E.; Mozer, F. S.; Bale, S. D.; Ludlam, M.; Turin, P.; Harvey, P. R.; Hochmann, R.; Harps, K.; Dalton, G.; McCauley, J.; Rachelson, W.; Gordon, D.; Donakowski, B.; Shultz, C.; Smith, C.; Diaz-Aguado, M.; Fischer, J.; Heavner, S.; Berg, P.; Malsapina, D. M.; Bolton, M. K.; Hudson, M.; Strangeway, R. J.; Baker, D. N.; Li, X.; Albert, J.; Foster, J. C.; Chaston, C. C.; Mann, I.; Donovan, E.; Cully, C. M.; Cattell, C. A.; Krasnoselskikh, V.; Kersten, K.; Brenneman, A.; Tao, J. B.

2013-10-01

411

Wave Science with the Electric and Magnetic Field Instrument Suite with Integrated Science (EMFISIS) on the Radiation Belt Storm Probes  

NASA Astrophysics Data System (ADS)

The physics of the creation and loss of radiation belt particles is intimately connected to the electric and magnetic fields of waves which mediate these processes. A large range of field regimes are involved in this physics from ring current magnetic fields to microscopic kinetic interactions such as whistler-mode chorus waves with energetic electrons. To measure these key field interactions, NASA has selected the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) on the Radiation Belt Storm Probes (RBSP). EMFISIS is an integrated set of instruments consisting of a tri-axial fluxgate magnetometer (MAG) and a Waves instrument which includes a tri-axial search coil magnetometer and measures AC electric and magnetic fields from 10 Hz to 400 kHz. The broad frequency range of the Waves instrument enables the identification of resonances and cutoffs from Waves to achieve high cadence, accurate plasma density measurements that are essential to RBSP theory and modeling efforts. In combination with the selected double probe electric field and particle investigations on RBSP, EMFISIS will provide the essential measurements necessary to open the frontier of predictive capability for the Earth's highly variable radiation belts. We discuss of the key scientific goals of the EMFISIS investigation with particular attention to the wave physics of the radiation belts.

Bounds, S. R.; Kletzing, C. A.; Kurth, W. S.; Acuna, M. H.; Torbert, R. B.; Thorne, R.; Jordanova, V.; Smith, C.; Santolik, O.; Pfaff, R.; Rpwlamd, D.; Hospodarsky, G.; Baumjohann, W.; Nakamura, R.; Puhl-Quinn, P.

2008-12-01

412

Relative output factor and beam profile measurements of small radiation fields with an L-alanine\\/K-Band EPR minidosimeter  

Microsoft Academic Search

The performance of an L-alanine dosimeter with millimeter dimensions was evaluated for dosimetry in small radiation fields. Relative output factor (ROF) measurements were made for 0.5x0.5, 1x1, 3x3, 5x5, 10x10 cm² square fields and for 5-, 10-, 20-, 40-mm-diam circular fields. In beam profile (BP) measurements, only 1x1, 3x3, 5x5 cm² square fields and 10-, 20-, 40-mm-diam circular fields were

Oswaldo Baffa; Carlos Eduardo de Almeida; Adelaide de Almeida; Carmen Sandra Guzman Calcina; Felipe Chen Abrego

2007-01-01

413

Experimental Verification of Isotropic Radiation from a Coherent Dipole Source via Electric-Field-Driven LC Resonator Metamaterials.  

PubMed

It has long been conjectured that isotropic radiation by a simple coherent source is impossible due to changes in polarization. Though hypothetical, the isotropic source is usually taken as the reference for determining a radiator's gain and directivity. Here, we demonstrate both theoretically and experimentally that an isotropic radiator can be made of a simple and finite source surrounded by electric-field-driven LC resonator metamaterials designed by space manipulation. As a proof-of-concept demonstration, we show the first isotropic source with omnidirectional radiation from a dipole source (applicable to all distributed sources), which can open up several possibilities in axion electrodynamics, optical illusion, novel transformation-optic devices, wireless communication, and antenna engineering. Owing to the electric- field-driven LC resonator realization scheme, this principle can be readily applied to higher frequency regimes where magnetism is usually not present. PMID:24116780

Tichit, Paul-Henri; Burokur, Shah Nawaz; Qiu, Cheng-Wei; de Lustrac, André

2013-09-24

414

A Potential-Theoretic Method for Far-Field Sound Radiation Calculations  

NASA Astrophysics Data System (ADS)

The far-field acoustic radiation due to the interaction of upstream, unsteady vortical disturbances with an airfoil in subsonic, compressible flow is calculated using potential theory. A Kirchhoff surface is placed in the near field surrounding the airfoil and the pressure on this surface is calculated from the unsteady flow field, obtained using a second-order finite-difference code. The governing equation is reduced to the Helmholtz equation in the frequency domain and the solution is written in terms of an integral over the Kirchhoff surface involving the free-space Green's function and an unknown single-layer density function. The single-layer density is then determined from the boundary condition on the Kirchhoff surface. This method is presented as an alternative to classical Kirchhoff methods. It has the advantage of being able to accommodate arbitrarily shaped Kirchhoff surfaces and is also readily extendable to three-dimensional problems. Numerical results are presented for thin, symmetric, and loaded airfoils. Thin-airfoil results are compared to the analytical solution, and thick-airfoil results are checked for numerical convergence and compared to results obtained from a time-domain Euler solver.

Hariharan, S. I.; Scott, J. R.; Kreider, K. L.

2000-10-01

415

The Influence of Resonance Helical Field on the Z eff and Impurity Radiation in IR-T1 Tokamak  

Microsoft Academic Search

The influence of resonant helical field, RHF, on effective ion charge, Z\\u000a eff, and impurity radiations on IR-T1 tokamak discharges was studied. The theoretical calculation of Z\\u000a eff with RHF indicated that the Z\\u000a eff decreased. To observe the effects of reduced Z\\u000a eff on impurity radiation, two important parts of plasma were investigated, equilibrium region of plasma and disruptive

M. Mahmoodi Darian; A. Hojabri; M. K. Salem; M. Ghoranneviss

2006-01-01

416

Effects of enhanced ultraviolet-B radiation on plant nutrients and decomposition of spring wheat under field conditions  

Microsoft Academic Search

Spring wheat (Triticum aestivum) was grown in the field under ambient and supplemental levels of ultraviolet-B (UV-B, 280–315 nm) radiation to determine the potential for alteration in plant nutrients, decomposition, leaf quality and dry matter yield. Supplemental UV-B radiation simulating a 12, 20 and 25% stratospheric ozone depletion significantly decreased dry matter yield, but had no significant impact on harvest

Ming Yue; Yuan Li; Xunling Wang

1998-01-01

417

Effect of the ionizing radiation on the rain-time atmospheric electric field  

NASA Astrophysics Data System (ADS)

The atmospheric electric field, or potential gradient (PG) at Kakioka, 150 southwest of the Fukushima Nuclear Power Plant (NPP) shows peculiar behaviors after the accident, March 2012 due to the conductivity enhancement in the air by the ionizing radiation. This means that the PG provides significant information on the dynamics of the radioactive materials. During last EGU assembly 2012, we showed that the fine-weather PG decreased by one-two orders of magnitudes at the arrival of the radioactive plume, and that the PG recovered in various way depending on various types of re-suspension processes in addition to the physical decay of the deposited radioactive materials. We extended this work to the rain-time PG, which is very simple because of high variability of the PG depending on the cloud types and distribution. We yet found a statistical difference between rain-time PGs before and after the Fukushima NPP Accident: one-hour averaged rain-time PG during the first 45 days after the accident is not as much scattered to the negative side as those during the same period of different years or during 40 days before accident. Further examination of one-minute averaged data (1 Hz sampling) during the second half March for 2006-2012 revealed that this difference comes from short time-spans of negative peaks rather than the peak value after the accident compared to those before the accident. On the other hand, characteristics of positive peaks (cloud without rain) are unchanged. The results suggest either (1) the effect on the local charges in the rain cloud is narrowed under high dose of ionized radiation, making positive charges in the cloud less shielded by the negative charges, or (2) negative charge of ionized aerosol decays much faster under higher dose of ionized radiation due to the shortened time constant of the ionized aerosol (? 1-?, where ? is the atmospheric electric conductivity).

Yamauchi, Masatoshi; Takeda, Masahiko; Makino, Masahiko; Owada, Takeshi

2013-04-01

418

Are encounters between negative and positive streamers likely to produce X-rays?  

NASA Astrophysics Data System (ADS)

The underlying processes responsible for the production of high-energy radiation (X- and gamma rays) recently discovered in thunderstorms are not fully understood [e.g., Dwyer et al., Space Sci. Rev., 2012]. In particular, it has been shown that stepped leaders produce X-ray bursts synchronized with the occurrence of new steps [Dwyer et al., GRL, 32, L01803, 2005]. However, as the physical processes responsible for the mechanism of stepping are also unknown, the complete causal chain between leader propagation and X-ray production is not established yet. Laboratory studies of spark and leader discharges and their associated X-ray production are performed precisely to address this point. A consensus exists that in the case of production by leaders, X-rays are due to bremsstrahlung emission from thermal runaway electrons. Thermal runaway electrons are produced through the acceleration of thermal electrons by extreme electric fields (E>250 kV/cm at ground pressure). These electric fields could be produced over short durations at the tips of streamer discharges [Moss et al., JGR, 111, A02307, 2006; Celestin and Pasko, JGR, 116, A03315, 2011]. Some authors have recently suggested that encounters between negative and positive streamers could strongly enhance the electric field, and hence would be responsible for X-ray production [Cooray et al., JASTP, 71,1890, 2009; Kochkin et al., J. Phys. D: Appl. Phys., 45, 425202, 2012]. Moreover, encounters of streamers with different polarities are very common. Indeed, during the formation of a new leader step, the negative streamer zone around the tip of a negative leader and the positive streamers initiated from the positive part of a bidirectional space leader strongly interact. In laboratory sparks, when positive streamers are approaching a sharp cathode, negative streamers are initiated from the cathode and collide with the positive streamers. Given that positive and negative streamers carry positive and negative charges at their fronts, respectively, it is reasonable to consider that the electric field between a negative and a positive streamer would increase as the two streamers are getting closer. However, this problem is more complex than it seems because an increase of the electric field above the breakdown threshold will increase the charge density at this location, which in turn, will tend to screen out the electric field. One clearly sees that this is in fact a complex non-linear problem that depends on the dynamics of both streamers. In this work, we will simulate numerically encounters between negative and positive streamers in order to examine the behavior of the maximum electric field that can be reached. We will determine if such collisions are likely to increase the electric field up to magnitudes sufficient to produce thermal runaway electrons and the associated X-rays.

Celestin, Sebastien; Tholin, Fabien; Bonaventura, Zdenek; Bourdon, Anne

2013-04-01

419

Muir-Torre syndrome-associated pleomorphic liposarcoma arising in a previous radiation field.  

PubMed

Muir-Torre syndrome is a variant of Lynch syndrome, characterised by sebaceous neoplasia and/or keratoacanthomas associated with visceral malignancies. Muir-Torre syndrome is caused by germline mutations of one of the mismatch repair genes, frequently MSH2 and less frequently MLH1 and MSH6. Visceral malignancies associated with Muir-Torre syndrome and Lynch syndrome include colorectal, endometrial and other gastrointestinal, urological and gynaecological malignancies. Small numbers of Lynch syndrome-associated soft tissue sarcomas have been reported, but there are no reported cases of soft tissue sarcomas in Muir-Torre syndrome. In this study, we report a 74-year-old man with known Muir-Torre syndrome with confirmed MSH2 germline mutation, diagnosed with pleomorphic liposarcoma of the right buttock in a previous radiation field. The tumour showed loss of expression of MSH2 and MSH6 on immunohistochemistry. Immunohistochemistry on another pleomorphic liposarcoma in a different patient with no previous history of Muir-Torre syndrome or Lynch syndrome showed no loss of expression of mismatch repair proteins. This is the first report of Muir-Torre syndrome-associated sarcoma and the first case of post-radiation sarcoma in Lynch syndrome. PMID:23299928

Yozu, Masato; Symmans, Pennie; Dray, Michael; Griffin, Jennifer; Han, Catherine; Ng, Daniel; Parry, Susan; Wong, Kp

2013-01-09

420

The attainment of large accelerating gradients using near field synchrotron radiation  

SciTech Connect

Lienard-Wiechert potentials are used to find the electromagnetic field everywhere in free space resulting from a point charge moving on a helical trajectory. The total power emitted as synchrotron radiation from a particle on a circular path is calculated. The point charge results are generalized to the case of a line charge, and formulae are presented which can easily be evaluated numerically. A useful gradient of 80 MeV/m per kA of peak driving beam current over a distance of 1 cm is calculated using two 5 MeV driving beams moving on 1 cm radius helical orbits with bunch length 1 mm. 11 refs., 5 figs.

Decker, G.

1989-01-01

421

Alanine blends for ESR measurements of thermal neutron fluence in a mixed radiation field.  

PubMed

In this paper, the results of a study on the electron spin resonance (ESR) dosimetry to measure thermal neutron fluence in a mixed radiation field (neutron and photons) are presented. The ESR responses of alanine dosemeters with different additives are compared. In particular, the (10)B-acid boric and the Gd-oxide were chosen to enhance the sensitivity of alanine dosemeters to thermal neutrons. Irradiations were carried out inside the thermal column of the TAPIRO reactor of the ENEA center, Casaccia Rome. The main results are a greater neutron sensitivity and a smaller lowest detectable fluence for the dosemeters with gadolinium than for dosemeters of alanine with (10)B, which is well known to be much more sensitive to thermal neutrons than simple alanine. PMID:17517673

Marrale, M; Brai, M; Gennaro, G; Triolo, A; Bartolotta, A; D'Oca, M C; Rosi, G

2007-05-21

422

Shielding of radiation fields generated by {sup 252}Cf in a concrete maze. Part 1: Experiment  

SciTech Connect

A concrete room with a single-legged maze was constructed in order to simulate a medical accelerator room. Gamma and neutron measurements were performed along the maze with (a) a {sup 252}Cf source and (b) a tungsten-moderated {sup 252}Cf source placed inside the room. The measurements were repeated after placing an inner borated polyethylene door of varying thickness (2.54--10.16 cm) at 2 different locations. Measurements were also performed after lining the inside of the maze with different neutron moderating materials. The following results are reported: (1) the variation and contributions of individual components of the radiation fields as a function of distance along the maze, (2) the attenuation of neutron dose equivalent and reduction of capture gamma rays as a function of borated polyethylene (BPE) inner door thickness and location of the inner door; and (3) the effect of lining the maze corner with different neutron moderating materials.

Ipe, N.E. [Stanford Univ., CA (US). Stanford Linear Accelerator Center; McCall, R.C. [McCall Associates, Woodside, CA (US); Jenkins, T.M. [Jenkins (T.M.), Palo Alto, CA (US); Benson, E. [ICF Kaiser, Richland, WA (US)

1998-02-01

423

Exposure to extremely-low-frequency electromagnetic fields and radiofrequency radiation: cardiovascular effects in humans.  

PubMed

Cardiovascular changes in humans exposed to nonionizing radiation [including extremely-low-frequency electromagnetic fields (ELF EMFs) and radiofrequency radiation (RFR)] are reviewed. Both acute and long-term effects have been investigated. In general, if heating does not occur during exposure, current flow appears to be necessary for major cardiovascular effects to ensue, such as those due to electric shock. Whereas most studies have revealed no acute effect of static or time-varying ELF EMFs on the blood pressure, heart rate, or electrocardiogram waveform, others have reported subtle effects on the heart rate. The possible health consequences of these results are unknown. Regarding long-term effects of ELF EMFs, reports from the former Soviet Union in the early 1960s indicated arrhythmias and tachycardia in high-voltage-switchyard workers. Subsequent studies in Western countries, however, did not confirm these findings. These studies are limited by uncertainties regarding exposure durations and appropriate control groups. Investigations of acute cardiovascular changes in humans purposely exposed to RFR have been limited to studies of magnetic resonance imaging (which, in addition to RFR, involves static and time-varying magnetic fields). It has been concluded that such exposures, as presently performed, are not likely to cause adverse cardiovascular effects. Reports of hypertension in workers potentially exposed to high levels of RFR during accidents are considered to be incidental (due to anxiety and posttraumatic stress). Soviet investigators have also indicated that long-term RFR exposure may result in hypotension and bradycardia or tachycardia. Other researchers, however, have been incapable of replicating these results, and some scientists have attributed the effects to chance variations and mishandling of data. In summary, studies have not yielded any obvious cardiovascular-related hazards of acute or long-term exposures to ELF EMFs or RFR at levels below current exposure standards. PMID:9258703

Jauchem, J R

1997-01-01

424

Inverse Compton Emission from Galactic Supernova Remnants: Effect of the Interstellar Radiation Field  

SciTech Connect

The evidence for particle acceleration in supernova shells comes from electrons whose synchrotron emission is observed in radio and X-rays. Recent observations by the HESS instrument reveal that supernova remnants also emit TeV {gamma}-rays; long awaited experimental evidence that supernova remnants can accelerate cosmic rays up to the ''knee'' energies. Still, uncertainty exists whether these {gamma}-rays are produced by electrons via inverse Compton scattering or by protons via {pi}{sup 0}-decay. The multi-wavelength spectra of supernova remnants can be fitted with both mechanisms, although a preference is often given to {pi}{sup 0}-decay due to the spectral shape at very high energies. A recent study of the interstellar radiation field indicates that its energy density, especially in the inner Galaxy, is higher than previously thought. In this paper we evaluate the effect of the interstellar radiation field on the inverse Compton emission of electrons accelerated in a supernova remnant located at different distances from the Galactic Centre. We show that contribution of optical and infra-red photons to the inverse Compton emission may exceed the contribution of cosmic microwave background and in some cases broaden the resulted {gamma}-ray spectrum. Additionally, we show that if a supernova remnant is located close to the Galactic Centre its {gamma}-ray spectrum will exhibit a ''universal'' cutoff at very high energies due to the Klein-Nishina effect and not due to the cut-off of the electron spectrum. As an example, we apply our calculations to the supernova remnants RX J1713.7-3946 and G0.9+0.1 recently observed by HESS.

Porter, Troy A.; /UC, Santa Cruz; Moskalenko, Igor V.; /Stanford U., HEPL; Strong, Andrew W.; /Garching, Max Planck Inst., MPE

2006-08-01

425

Selected Radiation Physical Studies in the Field of Radiotherapy with Fast Electrons and Co-60 gamma Radiation.  

National Technical Information Service (NTIS)

The application of thermoluminescent dosimetry for the development of new irradiation procedures is reported. Of particular interest are some subjects as betatron dosimetry, surface radiation loading in the case of electron irradiation, x-ray contaminatio...

K. Wuerthner

1983-01-01

426

Metamaterials with hyperbolic dispersion relations and their near-field and radiated-wave applications  

NASA Astrophysics Data System (ADS)

We present theoretical and numerical studies of near- and far-field scattering properties of planar and cylindrical uniaxially anisotropic metamaterials having hyperbolic dispersion relations. The imaging properties of single-layer and bilayer lenses consisting, respectively, of one and two anisotropic layers are studied with a view to fabrication. In order to facilitate understanding of the influence of material parameters on near-field imaging properties, a Green's function analysis for a uniaxially anisotropic slab is derived. We introduce a multiplexer that can be demonstrated by illuminating a slab composed of a metal-insulator multi-layer stack through a small aperture, and use this example to evaluate the performance of the analytic model. The theory for inductive and capacitive elements realized from anisotropic slabs is furthermore developed. These elements are shown to have low sensitivity to angle of incidence and non-dispersive performance. Low-pass filtering and anti-reflection examples are given. We present an optical leaky waveguide, which can support both forward and backward leaky waves. The radiation behavior is analyzed with a transverse resonance approach, and supported by finite element simulation results. The backward leaky nature can be exploited to develop a sub-diffraction limit imaging system. Finally, we extend our focus to the field behavior inside cylindrically anisotropic materials, and derive a Green's function and resulting formation for resonance cones, which provides a basis for two optical devices, an optical multiplexer based on the dispersive properties of a metal-insulator stack, and a far-field bilayer subwavelength imaging system.

Liu, Huikan

427

3D hybrid modeling of the plasma environment near Titan for T5 encounter  

NASA Astrophysics Data System (ADS)

Wave-particle interactions play a very important role in the plasma dynamics near Titan: mass loading, excitation of low-frequency waves and formation of the particle velocity distribution function (e.g. ring/shelllike distributions, etc.) The kinetic approach is important for estimating collision processes; e.g., charge exchange. In this report we discuss results of 3D hybrid modeling of the interaction between Saturn's magnetosphere and Titan's atmosphere/ionosphere for T5 encounter. T5 flyby is the only encounter when the 2 main ionizating sources of Titan atmosphere, solar radiation and corotating plasma, align quasi-antiparallel. The modeling is based on recent analysis of the Cassini Plasma Spectrometer (CAPS) and the Cassini Ion, and Neutral Mass Spectrometer (INMS) measurements during the T5 flyby through Titan's ram-side and polar ionosphere [1, 2]. Magnetic field data was used from the MAG instrument [3]. In our model the background ions (O+, H+), all pickup ions, and ionospheric ions are considered as a particles, whereas the electrons are described as a fluid (see e.g. [4]). Inhomogeneous photoionization (in the dayside ionosphere), electron-impact ionization, and charge exchange are included in our model. The temperature of the background electrons and pickup electrons was also incorporated into the generalized Ohm's law. We also take into account collisions between ions and neutrals. In our hybrid simulations we use Chamberlain profiles for the exosphere's components. The moon is considered as a weakly conducting body. The first results of our hybridmodeling show a strong asymmetry in the background (H+, O+) and pickup (H+2 , N+2 ,CH+4 ) ion density profiles. Such strong asymmetry cannot be explained by a single-fluid multi-species 3D MHD model [5], which included complex chemistry but does not produce finite gyroradius and kinetic effects.

Lipatov, A. S.; Sittler, E. C., Jr.; Hartle, R. E.; Cooper, J. F.; Sarantos, M.

2012-09-01

428

The Interaction of Upper-Tropospheric Water Vapor and the Earth's Infrared Radiation Field.  

NASA Astrophysics Data System (ADS)

A fundamental problem in predicting the response of the climate to anthropogenic perturbations to the atmospheric radiation field is understanding the role of water vapor. Water can provide a positive feedback to a temperature perturbation that is easily understood since a warmer atmosphere can contain more water and be more opaque. This feedback almost certainly occurs in the lower troposphere where shallow convection quickly transports water vapor into the boundary layer from the sea surface and maintains constant high relative humidity. The upper troposphere, however, is isolated from the underlying sea surface over large regions of the globe that are characterized by persistent sinking motion. Given the lack of a comprehensive long-term record of global upper-tropospheric water vapor, its role in climate processes is an unesolved question and is the underlying motivation for the work in this dissertation. The first two chapters present introductory material. In Chapter Three, the ability to measure moisture and to model the radiation field in the upper-troposphere is examined. Radiances observed by the GOES-VAS 6.7 ?m channel are compared to computations from simultaneous aircraft soundings of temperature and moisture. This comparison shows that all three models overestimate the observed brightness temperatures but reproduce the full range in observed brightness temperatures. Possible sources for this bias are investigated, and it is concluded that no one mechanism can alone account for the observed discrepancies. In Chapter Four, regional and seasonal characteristics of upper tropospheric moisture and the ability of a circulation model to capture them is examined. Large-scale variability of moisture in the upper troposphere in 1989 is examined using ECMWF model analyses and TOVS satellite radiances. Radiances computed from the ECMWF analyses reproduce the general locations and seasonal cycle of the TOVS-observed moisture features, but lack the moisture gradients and seasonal contrasts than indicated by the TOVS observations. Dynamically, the TOVS-observed regions of significant subtropical dryness are correlated with persistent subsidence indicated by ECMWF 300mb vertical velocity analyses. In Chapter Five, the impact of infra-red radiative heating on the evolution of observed atmospheric profiles and the vertical distribution of water vapor is considered. Gravity wave motions are explored as a mechanism to produce vertical layering of moisture and infra-red cooling is shown to slightly amplify the gravity wave. The static and dynamic stability of moist layers is explored.

Salathe, Eric Paul, Jr.

429

Theoretical Prediction of the Acoustical Nonlinear Field Radiated from a Concave Focusing Source with a Wide Aperture Angle  

NASA Astrophysics Data System (ADS)

We propose a time-domain theoretical approach to predict the acoustic nonlinear field radiated from a concave focusing spherical source with a wide aperture angle. The nonlinear sound propagation is theoretically described by an accurate mathematical model including the continuity and momentum equations. Numerical calculation is implemented by using the finite difference time domain algorithm in the oblate spheroidal coordinate system. To examine the validity of the theoretical model, we calculate the sound fields radiated from concave spherical focusing transducers with aperture angles 30° and 40° and the results are compared with those obtained by the SBE solution.

Sun, Min; Zhang, Dong; Gong, Xiu-Fen

2006-03-01

430

Submicrosecond intercomparison of radiation fields and currents in triggered lightning return strokes based on the transmission-line model  

NASA Astrophysics Data System (ADS)

The transmission line model of return stroke radiation (Ulman and McLain, 1970) is tested using rocket-triggered lightning. The electric radiation field, current at the channel base, and stroke-propagation velocity were measured simultaneously. Good agreement is found between the model and the measurements for the first few microseconds. However, the correlation between optical and transmission line model velocity on a stroke-by-stroke basis is poor. The possible explanations for this poor correlation are examined. Also, a formula is presented for estimating peak currents in subsequent return strokes from remotely measured, truncated peak electric fields at a given range.

Willett, J. C.; Bailey, J. C.; Idone, V. P.; Eybert-Berard, E.; Barret, L.

1989-09-01

431

Wouthuysen-Field coupling strength and application to high-redshift 21-cm radiation  

NASA Astrophysics Data System (ADS)

The first ultraviolet sources in the universe are expected to have coupled the HI spin temperature to the gas kinetic temperature via scattering in the Ly? resonance (the `Wouthuysen-Field effect'). By establishing an HI spin temperature different from the temperature of the cosmic microwave background, the Wouthuysen-Field effect should allow observations of HI during the reionization epoch in the redshifted 21-cm hyperfine line. This paper investigates four mechanisms that can affect the strength of the Wouthuysen-Field effect that were not previously considered. (1) Photons redshifting into the HI Lyman resonances may excite an H atom and result in a radiative cascade terminating in two-photon 2s1/2-> 1s1/2 emission, rather than always degrading to Ly? as usually assumed. (2) The fine structure of the Ly? resonance alters the photon frequency distribution and leads to a suppression of the scattering rate. (3) The spin-flip scatterings change the frequency of the photon and cause the photon spectrum to relax not to the kinetic temperature of the gas but to a temperature between the kinetic and spin temperatures, effectively reducing the strength of the Wouthuysen-Field coupling. (4) Near line centre, a photon can change its frequency by several times the line width in a single scattering event, thus potentially invalidating the usual calculation of the Ly? spectral distortion based on the diffusion approximation. It is shown that (1) suppresses the Wouthuysen-Field coupling strength by a factor of up to ~2, while (2) and (3) are important only at low kinetic temperatures. Effect (4) has a <=3 per cent effect for kinetic temperatures Tk>= 2K. In particular, if the pre-reionization intergalactic medium was efficiently heated by X-rays, only effect (1) is important. Fitting formulae for the Wouthuysen-Field coupling strength are provided for the range of Tk>= 2K and Gunn-Peterson optical depth 105 < ?GP < 107 so that all of these effects can be easily incorporated into 21-cm codes.

Hirata, Christopher M.

2006-03-01

432

Collision of two atoms in laser radiation field with formation of Feshbach resonances  

NASA Astrophysics Data System (ADS)

Based on the simplest two-channel model we theoretically consider laser induced elastic and inelastic collision of two atoms with formation of Feshbach resonance. In cases of one- and two-photon resonances of laser radiation with two discrete vibrational molecular levels, we show that Feshbach resonances appear at interaction of external magnetic field with dressed states formed via Autler-Townes effect. We also study the laser-induced inelastic collision and its influence on the considered processes. In case of two-photon resonance between discrete vibrational molecular states the Feshbach resonances arise under action of magnetic field via Autler-Townes effect, while the laser-induced transition into the elastic-channel continuum is in this case absent. We obtain the cross-sections of elastic and inelastic scattering and show that quenching of resonance occurs under certain conditions. The obtained results can be employed in new studies of collisions of atoms, e.g., of alkali metal atoms, and for interpretation of new experiments in BECs.

Gazazyan, Emil A.; Gazazyan, Alfred D.; Chaltykyan, Vigen O.

2013-09-01

433

Radiative transfer in ocean turbulence and its effect on underwater light field  

NASA Astrophysics Data System (ADS)

Turbulence in the upper ocean generates fluctuations in temperature and salinity, which result in variations in inherent optical properties (IOPs) and further change the underwater light field. A simulation-based study is performed for the radiative transfer (RT) of natural light in the turbulent flows in the upper ocean. For a canonical problem of turbulent shear flow interacting with the sea surface with and without surface waves, large-eddy simulations are performed for fluid motions and the transport of temperature and salinity. Based on the resolved turbulence temperature and salinity fields, IOP variations are quantified, and the inhomogeneous RT equation is then simulated using a Monte Carlo method. Through the simulations of a variety of cases with different flow, temperature, and salinity conditions, the statistics of downwelling irradiance are quantified and analyzed. It is found that the vertical profile of the mean downwelling irradiance is mainly determined by the vertical structure of the mean values of the IOPs; and turbulence effect is manifested in the horizontal variations of the downwelling irradiance. The magnitude of the irradiance variation is governed by the differences in the temperature and salinity between their values at the surface and in the deep region. In the presence of surface waves, the irradiance variation is enhanced due to the surface deformation, which is also largely affected by wave-turbulence interaction. The LES and inhomogeneous RT simulation may provide a useful tool for the characterization of upper-ocean turbulence processes based on underwater RT measurements.

Xu, Zao; Guo, Xin; Shen, Lian; Yue, Dick K. P.

2012-07-01

434

The Voyager 2 Encounter with the Uranian System.  

ERIC Educational Resources Information Center

|A series of 12 reports on the Voyager Two experiments in the Uranian system. Reports are included on: (1) imaging science; (2) photometry; (3) infrared; (4) ultraviolet; (5) radio science; (6) magnetic fields; (7) plasma; (8) charged particles; (9) magnetosphere (hot plasma and radiation); (10) radion observations; and (11) plasma waves. An…

Stone, E. C.; Miner, E. D.

1986-01-01

435

The Field and Radiation Impedance of Mechanical Radiators on the Free Surface of a Semi-Infinite Isotropic Solid  

Microsoft Academic Search

Definite integral representations are obtained for the field at an arbitrary point in a semiinfinite solid, due to stresses on the free surface which vary sinusoidally with time. From these integrals, asymptotic expressions have been obtained for the field at infinity in the solid, and polar diagrams showing the variation of field strength with direction are given. Integrals are also

G. F. Miller; H. Pursey

1954-01-01

436

Three-dimensional dosimetry of small megavoltage radiation fields using radiochromic gels and optical CT scanning  

NASA Astrophysics Data System (ADS)

The dosimetry of small fields as used in stereotactic radiotherapy, radiosurgery and intensity-modulated radiation therapy can be challenging and inaccurate due to partial volume averaging effects and possible disruption of charged particle equilibrium. Consequently, there exists a need for an integrating, tissue equivalent dosimeter with high spatial resolution to avoid perturbing the radiation beam and artificially broadening the measured beam penumbra. In this work, radiochromic ferrous xylenol-orange (FX) and leuco crystal violet (LCV) micelle gels were used to measure relative dose factors (RDFs), percent depth dose profiles and relative lateral beam profiles of 6 MV x-ray pencil beams of diameter 28.1, 9.8 and 4.9 mm. The pencil beams were produced via stereotactic collimators mounted on a Varian 2100 EX linear accelerator. The gels were read using optical computed tomography (CT). Data sets were compared quantitatively with dosimetric measurements made with radiographic (Kodak EDR2) and radiochromic (GAFChromic® EBT) film, respectively. Using a fast cone-beam optical CT scanner (Vista™), corrections for diffusion in the FX gel data yielded RDFs that were comparable to those obtained by minimally diffusing LCV gels. Considering EBT film-measured RDF data as reference, cone-beam CT-scanned LCV gel data, corrected for scattered stray light, were found to be in agreement within 0.5% and -0.6% for the 9.8 and 4.9 mm diameter fields, respectively. The validity of the scattered stray light correction was confirmed by general agreement with RDF data obtained from the same LCV gel read out with a laser CT scanner that is less prone to the acceptance of scattered stray light. Percent depth dose profiles and lateral beam profiles were found to agree within experimental error for the FX gel (corrected for diffusion), LCV gel (corrected for scattered stray light), and EBT and EDR2 films. The results from this study reveal that a three-dimensional dosimetry method utilizing optical CT-scanned radiochromic gels allows for the acquisition of a self-consistent volumetric data set in a single exposure, with sufficient spatial resolution to accurately characterize small fields.

Babic, Steven; McNiven, Andrea; Battista, Jerry; Jordan, Kevin

2009-04-01

437

Combined effect of X-ray radiation and static magnetic fields on reactive oxygen species in rat lymphocytes in vitro.  

PubMed

The aim of this study was to investigate the effect of static magnetic fields (SMF) on reactive oxygen species induced by X-ray radiation. The experiments were performed on lymphocytes from male albino Wistar rats. After exposure to 3?Gy X-ray radiation (with a dose rate of 560?mGy/min) the measurement of intracellular reactive oxygen species in lymphocytes, using a fluorescent probe, was done before exposure to the SMF, and after 15?min, 1 and 2?h of exposure to the SMF or a corresponding incubation time. For SMF exposure, 0?mT (50?µT magnetic field induction opposite to the geomagnetic field) and 5?mT fields were chosen. The trend of SMF effects for 0?mT was always opposite that of 5?mT. The first one decreased the rate of fluorescence change, while the latter one increased it. PMID:23184469

Polita?ski, Piotr; Rajkowska, El?bieta; Brodecki, Marcin; Bednarek, Andrzej; Zmy?lony, Marek

2012-11-26

438

Nonthermal Radiation from Supernova Remnants: Effects of Magnetic Field Amplification and Particle Escape  

NASA Astrophysics Data System (ADS)

We explore nonlinear effects of wave-particle interactions on the diffusive shock acceleration (DSA) process in Type Ia-like supernova remnant (SNR) blast waves by implementing phenomenological models for magnetic field amplification (MFA), Alfvénic drift, and particle escape in time-dependent numerical simulations of nonlinear DSA. For typical SNR parameters, the cosmic-ray (CR) protons can be accelerated to PeV energies only if the region of amplified field ahead of the shock is extensive enough to contain the diffusion lengths of the particles of interest. Even with the help of Alfvénic drift, it remains somewhat challenging to construct a nonlinear DSA model for SNRs in which of the order of 10% of the supernova explosion energy is converted into CR energy and the magnetic field is amplified by a factor of 10 or so in the shock precursor, while, at the same time, the energy spectrum of PeV protons is steeper than E –2. To explore the influence of these physical effects on observed SNR emission, we also compute the resulting radio-to-gamma-ray spectra. Nonthermal emission spectra, especially in X-ray and gamma-ray bands, depend on the time-dependent evolution of the CR injection process, MFA, and particle escape, as well as the shock dynamic evolution. This result comes from the fact that the high-energy end of the CR spectrum is composed of particles that are injected in the very early stages of the blast wave evolution. Thus, it is crucial to better understand the plasma wave-particle interactions associated with collisionless shocks in detailed modeling of nonthermal radiation from SNRs.

Kang, Hyesung; Jones, T. W.; Edmon, Paul P.

2013-11-01

439

Simulation and measurements of the response of an air ionisation chamber exposed to a mixed high-energy radiation field.  

PubMed

CERN's radiation protection group operates a network of simple and robust ionisation chambers that are installed inside CERN's accelerator tunnels. These ionisation chambers are used for the remote reading of ambient dose rate equivalents inside the machines during beam-off periods. This Radiation Protection Monitor for dose rates due to Induced Radioactivity ('PMI', trade name: PTW, Type 34031) is a non-confined air ionisation plastic chamber which is operated under atmospheric pressure. Besides its current field of operation it is planned to extend the use of this detector in the Large Hadron Collider to measure radiation under beam operation conditions to obtain an indication of the machine performance. Until now, studies of the PMI detector have been limited to the response to photons. In order to evaluate its response to other radiation components, this chamber type was tested at CERF, the high-energy reference field facility at CERN. Six PMI detectors were installed around a copper target being irradiated by a mixed hadron beam with a momentum of 120 GeV c(-1). Each of the chosen detector positions was defined by a different radiation field, varying in type and energy of the incident particles. For all positions, detailed measurements and FLUKA simulations of the detector response were performed. This paper presents the promising comparison between the measurements and simulations and analyses the influence of the different particle types on the resulting detector response. PMID:16604664

Vincke, Helmut; Forkel-Wirth, Doris; Perrin, Daniel; Theis, Chris

2005-01-01

440

Reanalysis of relativistic radiation belt electron phase space density using multisatellite observations: Sensitivity to empirical magnetic field models  

Microsoft Academic Search

Using empirical external magnetic field models (T89, T96, T01s, and T04s) and simultaneous observations from four satellites (CRRES, Akebono, and two GEO satellites) during a 7-day period from 1 to 7 August 1991, we performed a combined reanalysis of radiation belt electron phase space density (PSD). While precise L* locations of the satellites are sensitive to the adopted magnetic field

Binbin Ni; Yuri Shprits; Richard Thorne; Reiner Friedel; Tsugunobu Nagai

2009-01-01

441

Circuit analysis of electromagnetic radiation and field coupling effects for networks with embedded full-wave modules  

Microsoft Academic Search

With continually increasing operating frequencies, the analysis of electromagnetic interference (EMI)-related effects is becoming an important issue for high-speed designs. An algorithm is presented for fast analysis of radiation and incident field coupling effects in high-speed circuits. The proposed technique provides an efficient means for combining the solutions from full-wave field solvers such as the finite-difference time-domain (FDTD) method with

Ihsan Erdin; Michel S. Nakhla; Ramachandra Achar

2000-01-01

442

Reproductive Encounters: Negev Bedouin Women's Lay Encounters at Childbirth in an Israeli Hospital  

Microsoft Academic Search

Though hospital studies have often focused on the vertical relationships between patients and medical staff, the interactions between patients have received much less attention. Whereas interaction with staff members is episodic, patients often spend long hours sharing intimate space and daily routines. Such encounters are particularly important when hospitals cater to social groups embedded in socio-political tensions. This paper examines

Shifra Kisch

2009-01-01

443

Reproductive encounters: Negev bedouin women’s lay encounters at childbirth in an Israeli hospital  

Microsoft Academic Search

Though hospital studies have often focused on the vertical relationships between patients and medical staff, the interactions between patients have received much less attention. Whereas interaction with staff members is episodic, patients often spend long hours sharing intimate space and daily routines. Such encounters are particularly important when hospitals cater to social groups embedded in socio-political tensions. This paper examines

Shifra Kisch

2009-01-01

444