Sample records for radiation fields encountered

  1. Frequency of encounter of aircraft in a random horizontal field

    NASA Technical Reports Server (NTRS)

    Bird, J. D.; Smith, K. A.

    1976-01-01

    Calculations were made of the frequency of encounter as a function of azimuth of encounter of a passing aircraft with the aircraft in a random planar horizontal field. All the field aircraft moved at a constant speed but in random directions. These calculations included the total frequency of encounter with the aircraft of the field and the frequency of encounter with those aircraft of the field which were encountered in the fore quadrant, in the lateral quadrants, and in the rear quadrant; the calculations were made for various speed ratios of the field aircraft and the passing aircraft.

  2. Police-citizen encounters and field citations : Do encounter characteristics influence ticketing?

    Microsoft Academic Search

    Robert A. Brown; James Frank

    2005-01-01

    Purpose – To provide an empirical analysis of what influences police use of field citations (tickets) against citizens in nontraffic and traffic encounters. Design\\/methodology\\/approach – The research was conducted using systematic social observations of police-citizen encounters in Cincinnati, Ohio, from April 1997 to 1998. Multiple logistic regression models were used to examine the effects of legal and extralegal factors on

  3. Sound radiation from an airfoil encountering an oblique gust in its plane of motion

    NASA Technical Reports Server (NTRS)

    Glegg, Stewart A. L.

    1989-01-01

    An evaluation is conducted of the acoustic field radiated when an airfoil encounters a gust in the plane of motion, with a view to the prediction of helicopter tail rotor noise. The analysis is based on the unsteady thickness noise theory of Glegg (1987). Sound radiation is shown to be dominated by the transient effect of the blade tip moving into the velocity deficit, so that the effects of blade rotation are not important.

  4. Titan's Magnetic Field Signature During the First Cassini Encounter

    Microsoft Academic Search

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

    2005-01-01

    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

  5. Jupiter radiation test levels and their expected impact on an encounter mission

    NASA Technical Reports Server (NTRS)

    Barengoltz, J. B.

    1972-01-01

    The upper limit, of electron and proton fluences for a thermoelectric outer planet spacecraft mission in a near-Jupiter environment, for use as radiation design restraints, were extracted from a model of the Jovian trapped radiation belts. Considerations of radiation effects in semiconductor devices were employed to construct simplified radiation test levels based on the design restraints. Corresponding levels, based on the nominal belt models, are one to three orders of magnitude smaller. In terms of expected radiation-induced degradation in semiconductor devices, an encounter with an environment as severe as the design restraints would require hardening the system in order to guarantee high reliability. On the other hand, the nominal levels would only necessitate care in the selection of components and the avoidance of certain semiconductor components.

  6. Astrophysical False Positives Encountered in Wide-Field Transit Searches

    Microsoft Academic Search

    David Charbonneau; Timothy M. Brown; Edward W. Dunham; David W. Latham; Dagny L. Looper; Georgi Mandushev

    2004-01-01

    Wide-field photometric transit surveys for Jupiter-sized planets are inundated by astrophysical false positives, namely systems that contain an eclipsing binary and mimic the desired photometric signature. We discuss several examples of such false alarms. These systems were initially identified as candidates by the PSST instrument at Lowell Observatory. For three of the examples, we present follow-up spectroscopy that demonstrates that

  7. Radiation Field on Superspace

    E-print Network

    P. F. Gonzalez-Diaz

    1994-03-18

    We study the dynamics of multiwormhole configurations within the framework of the Euclidean Polyakov approach to string theory, incorporating a modification to the Hamiltonian which makes it impossible to interpret the Coleman Alpha parameters of the effective interactions as a quantum field on superspace, reducible to an infinite tower of fields on space-time. We obtain a Planckian probability measure for the Alphas that allows $\\frac{1}{2}\\alpha^{2}$ to be interpreted as the energy of the quanta of a radiation field on superspace whose values may still fix the coupling constants.

  8. Measurement of routinely encountered neutron field doses using portable survey instruments and a Bonner multisphere system

    E-print Network

    Davis, Donald Reed

    1981-01-01

    for Position NSC-B . . 24 Figure 10. Neutron Spectrum Characteristics for Position CYC-A . . 25 Figure 11. Neutron Spectrum Characteristics for Position CYC-B . . 26 INTRODUCTION One of the most complex problems faced today by those in the radiation... protection field deals with the acquisition of meaningful data for personnel exposure to poorly defined fields of neutron radiation. As the neutron is an uncharged particle, subsequent interactions are based upon direct nuclear reactions with the absorbing...

  9. Gamma radiation field intensity meter

    DOEpatents

    Thacker, Louis H. (Knoxville, TN)

    1994-01-01

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

  10. Gamma radiation field intensity meter

    DOEpatents

    Thacker, L.H.

    1995-10-17

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

  11. Gamma radiation field intensity meter

    DOEpatents

    Thacker, Louis H. (Knoxville, TN)

    1995-01-01

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

  12. Gamma radiation field intensity meter

    DOEpatents

    Thacker, L.H.

    1994-08-16

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

  13. Use of a field model to analyze probable fire environments encountered within the complex geometries of nuclear power plants

    SciTech Connect

    Boccio, J.L.; Usher, J.L.; Singhal, A.K.; Tam, L.T.

    1985-08-01

    A fire in a nuclear power plant (NPP) can damage equipment needed to safely operate the plant and thereby either directly cause an accident or else reduce the plant's margin of safety. The development of a field-model fire code to analyze the probable fire environments encountered within NPP is discussed. A set of fire tests carried out under the aegis of the US Nuclear Regulatory Commission (NRC) is described. The results of these tests are then utilized to validate the field model.

  14. Gravitational radiative corrections from effective field theory

    SciTech Connect

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

    2010-06-15

    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.

  15. Field Experiences in Health: Making Them Successful Close Encounters of the Real Kind.

    ERIC Educational Resources Information Center

    Chen, Moon S.

    1981-01-01

    Four principles for arranging successful field experiences in health are: (1) Organize the experience as a partnership involving the student, faculty member, and health practitioner; (2) Require regular feedback from students; (3) Provide the student with input from the health practitioner; and (4) Observe and evaluate the students in the field

  16. Tracing Magnetic Fields by Atomic Alignment in Extended Radiation Fields

    NASA Astrophysics Data System (ADS)

    Zhang, Heshou; Yan, Huirong; Dong, Le

    2015-05-01

    Tracing magnetic field is crucial as magnetic field plays an important role in many astrophysical processes. Earlier studies have demonstrated that ground state alignment (GSA) is an effective way to detect a weak magnetic field (1G? B? {{10}-15} G) in a diffuse medium. We explore the atomic alignment in the presence of an extended radiation field for both absorption lines and emission lines. The alignment in the circumstellar medium, binary systems, disks, and the local interstellar medium are considered in order to study the alignment in the radiation field where the pumping source has a clear geometric structure. Furthermore, the multipole expansion method is adopted to study GSA induced in the radiation field with unidentified pumping sources. We study the alignment in the dominant radiation components of the general radiation field: the dipole and quadrupole radiation field. We discuss the approximation of GSA in a general radiation field by summing the contribution from the dipole and quadrupole radiation field. We conclude that GSA is a powerful tool for detecting weak magnetic fields in the diffuse medium in general radiation fields.

  17. Encounters with fierce dogs and itchy bedbugs: why my first field work failed.

    PubMed

    Svanberg, Ingvar

    2014-01-01

    This essay, which is the fifth in the series "Recollections, Reflections, and Revelations: Personal Experiences in Ethnobiology", is a personal reminiscence by the researcher on his first field experience in Turkey in the late 1970s, which was a failure from an ethnobiological point of view but a success for a social scientist pursuing Turkic studies. The author later returned to ethnobiology during subsequent fieldwork on the Faroes. PMID:24885471

  18. Encounters with fierce dogs and itchy bedbugs: why my first field work failed

    PubMed Central

    2014-01-01

    This essay, which is the fifth in the series “Recollections, Reflections, and Revelations: Personal Experiences in Ethnobiology”, is a personal reminiscence by the researcher on his first field experience in Turkey in the late 1970s, which was a failure from an ethnobiological point of view but a success for a social scientist pursuing Turkic studies. The author later returned to ethnobiology during subsequent fieldwork on the Faroes. PMID:24885471

  19. Near-field radiation in nanoscale gaps

    E-print Network

    Sambegoro, Poetro Lebdo

    2011-01-01

    The theoretical calculations for near-field radiation heat transfer based on a local dielectric constant approach indicate that the heat transfer will go to infinity as the gap becomes very small. To correct this anomaly, ...

  20. Focus on correlation effects in radiation fields

    NASA Astrophysics Data System (ADS)

    Bauer, D.; Brabec, T.; Fehske, H.; Lochbrunner, S.; Meiwes-Broer, K.-H.; Redmer, R.

    2013-06-01

    Many processes in nature are governed by the interaction of electro-magnetic radiation with matter. New tools such as femtosecond and free-electron lasers allow one to study the interaction in unprecedented detail with high temporal and spatial resolution. In addition, much work is devoted to the exploration of novel target systems that couple to radiation in an effective and controllable way or that could serve as efficient sources of energetic particles when being subjected to intense laser fields. The interaction between matter and radiation fields as well as their mutual modification via correlations constitutes a rich field of research that is impossible to cover exhaustively. The papers in this focus issue represent a selection that largely reflects the program of the international conference on ‘Correlation Effects in Radiation Fields’ held in 2011 in Rostock, Germany.

  1. Radiation field for Einstein vacuum equations

    E-print Network

    Wang, Fang, Ph. D. Massachusetts Institute of Technology

    2010-01-01

    The radiation field introduced by Friedlander provides a direct approach to the asymptotic expansion of solutions to the wave equation near null infinity. We use this concept to study the asymptotic behavior of solutions ...

  2. Scattering by an electromagnetic radiation field

    E-print Network

    Donato Bini; Andrea Geralico

    2014-08-21

    Motion of test particles in the gravitational field associated with an electromagnetic plane wave is investigated. The interaction with the radiation field is modeled by a force term {\\it \\`a la} Poynting-Robertson entering the equations of motion given by the 4-momentum density of radiation observed in the particle's rest frame with a multiplicative constant factor expressing the strength of the interaction itself. Explicit analytical solutions are obtained. Scattering of fields by the electromagnetic wave, i.e., scalar (spin 0), massless spin $\\frac12$ and electromagnetic (spin 1) fields, is studied too.

  3. Radiation Reaction in High-Intense Fields

    E-print Network

    Seto, Keita

    2015-01-01

    After the development of the radiating electron model by P. A. M. Dirac in 1938, many authors have tried to reformulate this model so-called radiation reaction. Recently, this effects has become important for ultra-intense laser-electron (plasma) interactions. In our recent research, we found a method for the stabilization of radiation reaction in quantum vacuum [PTEP 2014, 043A01 (2014), PTEP 2015, 023A01 (2015)]. In the other hand, the field modification by high-intense fields should be required under 10PW lasers, like ELI-NP facility. In this paper, I propose the combined method how to adopt the high-intense field correction with the stabilization by quantum vacuum as the extension from the model by Dirac.

  4. Radiation Entropy and Near-Field Thermophotovoltaics

    NASA Astrophysics Data System (ADS)

    Zhang, Zhuomin M.

    2008-08-01

    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.

  5. Voyager: Neptune Encounter Highlights

    NASA Technical Reports Server (NTRS)

    1989-01-01

    Voyager encounter data are presented in computer animation (CA) and real (R) animation. The highlights include a view of 2 full rotations of Neptune. It shows spacecraft trajectory 'diving' over Neptune and intercepting Triton's orbit, depicting radiation and occulation zones. Also shown are a renegade orbit of Triton and Voyager's encounter with Neptune's Magnetopause. A model of the spacecraft's complex maneuvers during close encounters of Neptune and Triton is presented. A view from Earth of Neptune's occulation experiment is is shown as well as a recreation of Voyager's final pass. There is detail of Voyager's Image Compensation technique which produces Voyager images. Eighteen images were produced on June 22 - 23, 1989, from 57 million miles away. A 68 day sequence which provides a stroboscopic view - colorization approximates what is seen by the human eye. Real time images recorded live from Voyager on 8/24/89 are presented. Photoclinometry produced the topography of Triton. Three images are used to create a sequence of Neptune's rings. The globe of Neptune and 2 views of the south pole are shown as well as Neptune rotating. The rotation of a scooter is frozen in images showing differential motion. There is a view of rotation of the Great Dark Spot about its own axis. Photoclinometry provides a 3-dimensional perspective using a color mosaic of Triton images. The globe is used to indicate the orientation of Neptune's crescent. The east and west plumes on Triton are shown.

  6. RADIATION FIELDS, SCATTERING AND INVERSE SCATTERING ...

    E-print Network

    2006-12-26

    We define the forward and backward radiation fields on an asymptotically ... hyperbolic manifold is determined up to invariants by the scattering matrix at all energies. ..... we will compactify the problem and obtain uniform estimates as s ? ??. ...... Note that since p = 0 is satisfied for the solutions to this system, and ? = ?0 = 0 ...

  7. Chiral-field microwave antennas (Chiral microwave near fields for far-field radiation)

    E-print Network

    Kamenetskii, E O; Shavit, R

    2015-01-01

    In a single-element structure we obtain a radiation pattern with a squint due to chiral microwave near fields originated from a magnetostatic-mode ferrite disk. At the magnetostatic resonances, one has strong subwavelength localization of energy of microwave radiation. Magnetostatic oscillations in a thin ferrite disk are characterized by unique topological properties: the Poynting-vector vortices and the field helicity. The chiral-topology near fields allow obtaining unique phase structure distribution for far-field microwave radiation.

  8. The Voyager 2 Neptune encounter

    SciTech Connect

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

    1989-10-01

    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.

  9. Polarized radiation diagnostics of stellar magnetic fields

    NASA Astrophysics Data System (ADS)

    Mathys, Gautier

    The main techniques used to diagnose magnetic fields in stars from polarimetric observations are presented. First, a summary of the physics of spectral line formation in the presence of a magnetic field is given. Departures from the simple case of linear Zeeman effect are briefly considered: partial Paschen-Back effect, contribution of hyperfine structure, and combined Stark and Zeeman effects. Important approximate solutions of the equation of transfer of polarized light in spectral lines are introduced. The procedure for disk-integration of emergent Stokes profiles, which is central to stellar magnetic field studies, is described, with special attention to the treatment of stellar rotation. This formalism is used to discuss the determination of the mean longitudinal magnetic field (through the photographic technique and through Balmer line photopolarimetry). This is done within the specific framework of Ap stars, which, with their unique large-scale organized magnetic fields, are an ideal laboratory for studies of stellar magnetism. Special attention is paid to those Ap stars whose magnetically split line components are resolved in high-dispersion Stokes I spectra, and to the determination of their mean magnetic field modulus. Various techniques of exploitation of the information contained in polarized spectral line profiles are reviewed: the moment technique (in particular, the determination of the crossover and of the mean quadratic field), Zeeman-Doppler imaging, and least-squares deconvolution. The prospects that these methods open for linear polarization studies are sketched. The way in which linear polarization diagnostics complement their Stokes I and V counterparts is emphasized by consideration of the results of broad band linear polarization measurements. Illustrations of the use of various diagnostics to derive properties of the magnetic fields of Ap stars are given. This is used to show the interest of deriving more physically realistic models of the geometric structure of these fields. How this can possibly be achieved is briefly discussed. An overview of the current status of polarimetric studies of magnetic fields in non-degenerate stars of other types is presented. The final section is devoted to magnetic fields of white dwarfs. Current knowledge of magnetic fields of isolated white dwarfs is briefly reviewed. Diagnostic techniques are discussed, with particular emphasis on the variety of physical processes to be considered for understanding of spectral line formation over the broad range of magnetic field strengths encountered in these stars.

  10. Radiation Effects on Current Field Programmable Technologies

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

    Manufacturers of field programmable gate arrays (FPGAS) take different technological and architectural approaches that directly affect radiation performance. Similar y 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.

  11. Plasma wake field XUV radiation source

    DOEpatents

    Prono, Daniel S. (Los Alamos, NM); Jones, Michael E. (Los Alamos, NM)

    1997-01-01

    A XUV radiation source uses an interaction of electron beam pulses with a gas to create a plasma radiator. A flowing gas system (10) defines a circulation loop (12) with a device (14), such as a high pressure pump or the like, for circulating the gas. A nozzle or jet (16) produces a sonic atmospheric pressure flow and increases the density of the gas for interacting with an electron beam. An electron beam is formed by a conventional radio frequency (rf) accelerator (26) and electron pulses are conventionally formed by a beam buncher (28). The rf energy is thus converted to electron beam energy, the beam energy is used to create and then thermalize an atmospheric density flowing gas to a fully ionized plasma by interaction of beam pulses with the plasma wake field, and the energetic plasma then loses energy by line radiation at XUV wavelengths Collection and focusing optics (18) are used to collect XUV radiation emitted as line radiation when the high energy density plasma loses energy that was transferred from the electron beam pulses to the plasma.

  12. Cellular response to modulated radiation fields

    NASA Astrophysics Data System (ADS)

    Claridge Mackonis, E.; Suchowerska, N.; Zhang, M.; Ebert, M.; McKenzie, D. R.; Jackson, M.

    2007-09-01

    Cell survival following exposure to spatially modulated beams, as created by intensity-modulated radiotherapy (IMRT), is investigated. In vitro experiments were performed using malignant melanoma cells (MM576) exposed to a therapeutic megavoltage photon beam. We compared cell survival in modulated fields with cell survival in uniform control fields. Three different spatial modulations of the field were used: a control 'uniform' field in which all cells in a flask were uniformly exposed; a 'quarter' field in which 25% of cells at one end of the flask were exposed and a 'striped' field in which 25% of cells were exposed in three parallel stripes. The cell survival in both the shielded and unshielded regions of the modulated fields, as determined by a clonogenic assay, were compared to the cell survival in the uniform field. We have distinguished three ways in which cell survival is influenced by the fate of neighbouring cells. The first of these (type I effect) is the previously reported classical Bystander effect, where cell survival is reduced when communicating with irradiated cells. We find two new types of Bystander effect. The type II effect is an observed increase in cell survival when nearby cells receive a lethal dose. The type III effect is an increase in the survival of cells receiving a high dose of radiation, when nearby cells receive a low dose. These observations of the Bystander effects emphasize the need for improved radiobiological models, which include communicated effects and account for the effects of modulated dose distribution.

  13. Radiation reaction in quantum field theory

    E-print Network

    Atsushi Higuchi

    2004-03-30

    We investigate radiation-reaction effects for a charged scalar particle accelerated by an external potential realized as a space-dependent mass term in quantum electrodynamics. In particular, we calculate the position shift of the final-state wave packet of the charged particle due to radiation at lowest order in the fine structure constant alpha and in the small h-bar approximation. We show that it disagrees with the result obtained using the Lorentz-Dirac formula for the radiation-reaction force, and that it agrees with the classical theory if one assumes that the particle loses its energy to radiation at each moment of time according to the Larmor formula in the static frame of the potential. However, the discrepancy is much smaller than the Compton wavelength of the particle. We also point out that the electromagnetic correction to the potential has no classical limit. (Correction. Surface terms were erroneously discarded to arrive at Eq. (59). By correcting this error we find that the position shift according to the Lorentz-Dirac theory obtained from Eq. (12) is reproduced by quantum field theory in the hbar -> 0 limit. We also find that the small V(z) approximation is unnecessary for this agreement. See Sec. VII.)

  14. Limited-field radiation for bifocal germinoma

    SciTech Connect

    Lafay-Cousin, Lucie [Pediatric Brain Tumor Program, Hospital for Sick Children, Toronto, Ontario (Canada)]. E-mail: lucie.lafay-cousin@sickkids.ca; Millar, Barbara-Ann [Department of Radiation Oncology, Princess Margaret Hospital, Toronto, Ontario (Canada); Mabbott, Donald [Pediatric Brain Tumor Program, Hospital for Sick Children, Toronto, Ontario (Canada); Department of Psychology, Hospital for Sick Children, Toronto, Ontario (Canada); Spiegler, Brenda [Department of Psychology, Hospital for Sick Children, Toronto, Ontario (Canada); Drake, Jim [Department of Neurosurgery, Hospital for Sick Children, Toronto, Ontario (Canada); Bartels, Ute [Pediatric Brain Tumor Program, Hospital for Sick Children, Toronto, Ontario (Canada); Huang, Annie [Pediatric Brain Tumor Program, Hospital for Sick Children, Toronto, Ontario (Canada); Bouffet, Eric [Pediatric Brain Tumor Program, Hospital for Sick Children, Toronto, Ontario (Canada)

    2006-06-01

    Purpose: To report the incidence, characteristics, treatment, and outcomes of bifocal germinomas treated with chemotherapy followed by focal radiation. Methods and Materials: This was a retrospective review. Inclusion criteria included radiologic diagnosis of bifocal germinoma involving the pineal and neurohypophyseal region, no evidence of dissemination on spinal MRI, negative results from cerebrospinal fluid cytologic evaluation, and negative tumor markers. Results: Between 1995 and 2004, 6 patients (5 male, 1 female; median age, 12.8 years) fulfilled the inclusion criteria. All had symptoms of diabetes insipidus at presentation. On MRI, 4 patients had a pineal and suprasellar mass, and 2 had a pineal mass associated with abnormal neurohypophyseal enhancement. All patients received chemotherapy followed by limited-field radiation and achieved complete remission after chemotherapy. The radiation field involved the whole ventricular system (range, 2,400-4,000 cGy) with or without a boost to the primary lesions. All patients remain in complete remission at a median follow-up of 48.1 months (range, 9-73.4 months). Conclusions: This experience suggests that bifocal germinoma can be considered a locoregional rather than a metastatic disease. Chemotherapy and focal radiotherapy might be sufficient to provide excellent outcomes. Staging refinement with new diagnostic tools will likely increase the incidence of the entity.

  15. This manual does not address chemical, physical and/or radiation hazards that are commonly encountered in a laboratory setting and is to be regarded as an addendum to the UNBC Chemical

    E-print Network

    Northern British Columbia, University of

    Manual This manual does not address chemical, physical and/or radiation hazards that are commonly encountered in a laboratory setting and is to be regarded as an addendum to the UNBC Chemical Laboratory, handling, waste disposal and emergency management of bio-hazardous materials for the University of Northern

  16. Virtual radiation fields for ALARA determination

    SciTech Connect

    Knight, T.W.

    1995-12-31

    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.

  17. Observations of the diffuse UV radiation field

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  18. Radiation reaction in strong field QED

    E-print Network

    Anton Ilderton; Greger Torgrimsson

    2013-07-31

    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 the electromagnetic coupling alpha. For the explicit example of scattering in a plane wave background, we compare QED with classical electrodynamics in the limit h-bar goes to zero, finding agreement with the Lorentz-Abraham-Dirac and Landau-Lifshitz equations, and with Larmor's formula. The first quantum corrections are also presented.

  19. Solar wind-magnetosphere interaction during the possible encounter of Comet Halley's tail in 1910 inferred from mid-latitude geomagnetic field disturbances

    NASA Astrophysics Data System (ADS)

    Iyemori, T.; Araki, T.

    Geomagnetic disturbances from the period April to June 1910 are analyzed to detect the possible effects of the Comet Halley on the solar wind-magnetosphere interaction. Data from six midlatitude geomagnetic observatories are used to calculate the longitudinally symmetric (i.e., Dst) and asymmetric fields. An application of a linear prediction filter to separate the solar wind dynamic pressure effect on the disturbances from that of the ring current, suggests that there exists a compressional variation in the Dst on May 18 which is around or slightly earlier than the time of estimated cometary tail encounter. The normal-run magnetogram from Agincourt on the dayside and that from Lu-Kia-Pang on the nightside, also indicate rather strong (i.e., 30-40 nT) compressional variation. The disturbances characteristic to the solar wind-magnetosphere interaction under the southward IMF condition and that of the ring current development are seen during the period. These results suggest that the earth's magnetosphere had been affected by a dense cometary plasma tail with high dynamic pressure, though the solar wind-magnetosphere interaction typically observed under the southward IMF condition had been taking place during the encounter.

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

    NASA Technical Reports Server (NTRS)

    Wilson, Lester A.

    2005-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Ahn, Kyungjin

    2015-02-01

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

  2. Radiation Entropy and Near-Field Thermophotovoltaics

    Microsoft Academic Search

    Zhuomin M. Zhang

    2008-01-01

    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

  3. Radiation effects on fluorinated field oxides and associated devices

    Microsoft Academic Search

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

    1990-01-01

    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

  4. Radiation Fields in the Vicinity of Compact Accelerator Neutron Generators

    SciTech Connect

    David L. Chichester; Brandon W. Blackburn; Augustine J. Caffrey

    2006-10-01

    Intense pulsed radiation fields emitted from sealed tube neutron generators provide a challenge for modern health physics survey instrumentation. The spectral sensitivity of these survey instruments requires calibration under realistic field conditions while the pulsed emission characteristics of neutron generators can vary from conditions of steady-state operation. As a general guide for assessing radiological conditions around neutron generators, experiments and modeling simulations have been performed to assess radiation fields near DD and DT neutron generators. The presence of other materials and material configurations can also have important effects on the radiation dose fields around compact accelerator neutron generators.

  5. Analysis and synthesis of cloud pattern for radiation field studies

    SciTech Connect

    Beyer, H.G.; Hammer, A.; Luther, J.; Poplawska, J.; Stolzenburg, K.; Wieting, P. (Car von Ossietzky Universitaet Oldenburg (Germany))

    1994-05-01

    A method for the analysis of small scale, short term characteristics of radiations fields under intermediate sky conditions (clouds of cumulus type) is described. It is based on the extraction of cloud field structures from sky photographs. The cloud structures are described as fractal objects. Based on this representation a procedure for the generation of synthetic cloud pattern and related radiation fields is given. Statistical characteristics of synthetic irradiance data sets are compared with empirical data from an array of ground sensors.

  6. Radiation field associated with Hiroshima and Nagasaki

    SciTech Connect

    Loewe, W.E.

    1984-08-01

    Accuracy of dosimetric estimates can determine the value of the atomic bomb survivor experience in establishing radiation risks. The status of a major revision of this dosimetry, initiated in 1980, is assessed. 3 references, 6 figures.

  7. VOYAGER OBSERVATIONS OF THE DIFFUSE FAR-ULTRAVIOLET RADIATION FIELD

    SciTech Connect

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

    2012-03-01

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

  8. Detection of alpha radiation in a beta radiation field

    DOEpatents

    Mohagheghi, Amir H. (Albuquerque, NM); Reese, Robert P. (Edgewood, NM)

    2001-01-01

    An apparatus and method for detecting alpha particles in the presence of high activities of beta particles utilizing an alpha spectrometer. The apparatus of the present invention utilizes a magnetic field applied around the sample in an alpha spectrometer to deflect the beta particles from the sample prior to reaching the detector, thus permitting detection of low concentrations of alpha particles. In the method of the invention, the strength of magnetic field required to adequately deflect the beta particles and permit alpha particle detection is given by an algorithm that controls the field strength as a function of sample beta energy and the distance of the sample to the detector.

  9. Understanding metropolitan patterns of daily encounters.

    PubMed

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

    2013-08-20

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

  10. Radiation tolerant silicon nitride insulated gate field effect transistors

    NASA Technical Reports Server (NTRS)

    Newman, P. A.

    1969-01-01

    Metal-Insulated-Semiconductor Field Effect Transistor /MISFET/ device uses a silicon nitride passivation layer over a thin silicon oxide layer to enhance the radiation tolerance. It is useful in electronic systems exposed to space radiation environment or the effects of nuclear weapons.

  11. Fiber optics in transient radiation fields

    SciTech Connect

    Lyons, P.B.

    1985-01-01

    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.

  12. Radiation-field mapping of insect irradiation canisters

    Microsoft Academic Search

    Marlon L. Walker; William L. McLaughlin; James M. Puhl; Patrick Gomes

    1997-01-01

    Dosimetry methods developed at NIST for mapping ionizing radiation fields were applied to canisters used in 137Cs dry-source irradiators designed for insect sterilization. The method of mapping the radiation fields inside of these canisters as they cycled through the gamma-ray irradiators involved the use of radiochromic films, which increase in optical density proportionately to the absorbed dose. A dosimeter film

  13. The Geomagnetic Field and Radiation in Near-Earth Orbits

    NASA Technical Reports Server (NTRS)

    Heirtzler, J. R.

    1999-01-01

    This report shows, in detail, how the geomagnetic field interacts with the particle flux of the radiation belts to create a hazard to spacecraft and humans in near-Earth orbit. It illustrates the geometry of the geomagnetic field lines, especially around the area where the field strength is anomalously low in the South Atlantic Ocean. It discusses how the field will probably change in the future and the consequences that may have on hazards in near space.

  14. The galileo venus encounter.

    PubMed

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

    1991-09-27

    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

  15. Radiative processes in strong magnetic fields

    Microsoft Academic Search

    A. K. Harding

    1991-01-01

    The behavior of electromagnetic processes in strong magnetic fields is currently of great interest in high-energy astrophysics. Strong magnetic fields affect the physics in several fundamental ways: energies perpendicular to the field are quantized, transverse momentum is not conserved and electron\\/positron spin is important. The relaxation of transverse momentum conservation allows first order processes and their inverses: one-photon pair production

  16. Radiation from Relativistic Shocks with Turbulent Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Nishkawa, K.; Medvedev, M.; Zhang, B.; Hardee, P.; Niemiec, J.; Mizuno, A.; Nordlund, A.; Frederiksen, J.; Sol, H.; Pohl, M.; Hartmann, D. H.; Oka, M.; Fishman, J.

    2009-01-01

    Recent PIC simulations of relativistic electron-positron (electron-ion) jets injected into a stationary medium show that particle acceleration occurs at shocked region. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the shock. The "jitter" radiation from deflected electrons in turbulent magnetic fields has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants. New recent calculation of spectra with various different Lorentz factors of jets (two electrons) and initial magnetic fields. New spectra based on small simulations will be presented.

  17. Radiation Signatures of Sub-Larmor Scale Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Medvedev, Mikhail V.; Frederiksen, Jacob Trier; Haugbølle, Troels; Nordlund, Åke

    2011-08-01

    Spontaneous rapid growth of strong magnetic fields is rather ubiquitous in high-energy density environments ranging from astrophysical sources (e.g., gamma-ray bursts and relativistic shocks), to reconnection, to laser-plasma interaction laboratory experiments, where they are produced by kinetic streaming instabilities of the Weibel type. Relativistic electrons propagating through these sub-Larmor-scale magnetic fields radiate in the jitter regime, in which the anisotropy of the magnetic fields and the particle distribution have a strong effect on the produced radiation. Here we develop the general theory of jitter radiation, which (1) includes anisotropic magnetic fields and electron velocity distributions, (2) accounts for the effects of trapped electrons, and (3) extends the description to large deflection angles of radiating particles thus establishing a cross-over between the classical jitter and synchrotron regimes. Our results are in remarkable agreement with the radiation spectra obtained from particle-in-cell simulations of the classical Weibel instability. Particularly interesting is the onset of the field growth, when the transient hard synchrotron-violating spectra are common as a result of the dominant role of the trapped population. This effect can serve as a distinct observational signature of the violent field growth in astrophysical sources and lab experiments. It is also interesting that a system with small-scale fields tends to evolve toward the small-angle jitter regime, which can, under certain conditions, dominate the overall emission of a source.

  18. Encounter (Resonances) Hayley Hung

    E-print Network

    Hung, Hayley

    lighting effects, "Encounter (Reso- nances)" offers a new approach to the presentation of a piece of work- ered painting technique by using reproductions of various color palettes and resolutions as metaphors of representation (global shape, micro and macro structure), in an effort to encourage a level of pro- longed

  19. Alien Visitations Close Encounters

    E-print Network

    Walter, Frederick M.

    Alien Visitations #12;#12;Close Encounters · I: Visual sighting of aerial object (UFO) · II are indeed unidentified. ·Most are Venus. ·Almost certainly none are alien spacecraft Picture from Robert do aliens think? #12;How to Serve Man #12;#12;

  20. Radiation fields of helical antenna in compressible electron plasma

    Microsoft Academic Search

    V. L. TALEKAR; K. R. SONI

    1974-01-01

    Expressions for the radiation fields in a compressible electron plasma medium are derived pertaining to the helical antenna of finite size immersed in it. The current distribution on the helical antenna is assumed to be an out-going travelling wave with an arbitrary phase propagation constant. From these general expressions fields of circular loop and linear antennas can be deduced as

  1. Electron trajectories in pulsed radiation fields

    SciTech Connect

    Einwohner, T.; Lippmann, B.A.

    1987-05-01

    The work reported here analyzes the dynamical behavior of an electron, initially at rest, when subjected to a radiation pulse of arbitrary, but integrable, shape. This is done by a general integration procedure that has been programmed in VAXIMA. Upon choosing a specific shape for the pulse, VAXIMA finds both the space-time trajectory and the four-momentum of the electron. These are obtained in analytic or numerical form - or both - at the choice of the user. Several examples of analytical and numerical solutions, for different pulse shapes, are given.

  2. Adaptive radiations: From field to genomic studies

    PubMed Central

    Hodges, Scott A.; Derieg, Nathan J.

    2009-01-01

    Adaptive radiations were central to Darwin's formation of his theory of natural selection, and today they are still the centerpiece for many studies of adaptation and speciation. Here, we review the advantages of adaptive radiations, especially recent ones, for detecting evolutionary trends and the genetic dissection of adaptive traits. We focus on Aquilegia as a primary example of these advantages and highlight progress in understanding the genetic basis of flower color. Phylogenetic analysis of Aquilegia indicates that flower color transitions proceed by changes in the types of anthocyanin pigments produced or their complete loss. Biochemical, crossing, and gene expression studies have provided a wealth of information about the genetic basis of these transitions in Aquilegia. To obtain both enzymatic and regulatory candidate genes for the entire flavonoid pathway, which produces anthocyanins, we used a combination of sequence searches of the Aquilegia Gene Index, phylogenetic analyses, and the isolation of novel sequences by using degenerate PCR and RACE. In total we identified 34 genes that are likely involved in the flavonoid pathway. A number of these genes appear to be single copy in Aquilegia and thus variation in their expression may have been key for floral color evolution. Future studies will be able to use these sequences along with next-generation sequencing technologies to follow expression and sequence variation at the population level. The genetic dissection of other adaptive traits in Aquilegia should also be possible soon as genomic resources such as whole-genome sequencing become available. PMID:19528644

  3. Ways of providing radiation resistance of magnetic field semiconductor sensors

    NASA Astrophysics Data System (ADS)

    Bolshakova, I. A.; Krukovskii, S.; Holyaka, R.; Matkovskii, A.; Moroz, A.

    2001-06-01

    Hall magnetic field sensors resistant to hard ionizing irradiation are being developed for operation under the radiation conditions of space and in charged particle accelerators. Radiation resistance of the sensors is first determined by the properties of semiconductor materials of sensitive elements; we have used microcrystals and thin layers of III-V semiconductors. Applying complex doping by rare-earth elements and isovalent impurities in certain proportions, we have obtained magnetic field sensors resistant to irradiation by fast neutrons and ?-quanta. Tests of their radiation resistance were carried out at IBR-2 at the Joint Institute for Nuclear Research (Dubna). When exposed to neutrons with E=0.1-13 MeV and intensity of 10 10 n cm -2 s -1, the main parameter of the sensors—their sensitivity to magnetic fields—changes by no more than 0.1% up to fluences of 10 14 n cm -2. Further improvement of radiation resistance of sensor materials is expected by means of a combination of metallurgical methods of complex doping with the technology of radiation modification, which includes an interchanging of nuclear doping and fast neutron irradiation with thermoprocessing cycles. A special magnetometric system is to be developed in which the main element is the functionally integrated magnetometric transducer consisting of a semiconductor Hall microgenerator and a copper microsolenoid, which forms the actuating field around the microgenerator. The application of such a magnetometric system with radiation resistant magnetic field sensors will provide magnetic field measurements with an accuracy of 0.1% under hard radiation conditions.

  4. Field Testing of a Portable Radiation Detector and Mapping System

    SciTech Connect

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

    1998-03-01

    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.

  5. Near-field radiative transfer: Thermal radiation, thermophotovoltaic power generation and optical characterization

    NASA Astrophysics Data System (ADS)

    Francoeur, Mathieu

    This dissertation focuses on near-field radiative transfer, which can be defined as the discipline concerned with energy transfer via electromagnetic waves at sub-wavelength distances. Three specific subjects related to this discipline are investigated, namely near-field thermal radiation, nanoscale-gap thermophotovoltaic (nano-TPV) power generation and optical characterization. An algorithm for the solution of near-field thermal radiation problems in one-dimensional layered media is developed, and several tests are performed showing the accuracy, consistency and versatility of the procedure. The possibility of tuning near-field radiative heat transfer via thin films supporting surface phonon-polaritons (SPhPs) in the infrared is afterwards investigated via the computation of the local density of electromagnetic states and the radiative heat flux between two films. Results reveal that due to SPhP coupling, fine tuning of near-field radiative heat transfer is possible by solely varying the structure of the system, the structure being the film thicknesses and their distance of separation. The coexistence of two regimes of near-field thermal radiation between two thin films of silicon carbide is demonstrated via numerical simulations and an asymptotic analysis of the radiative heat transfer coefficient. The impacts of thermal effects on the performances of nano-TPV power generators are investigated via the solution of the coupled near-field thermal radiation, charge and heat transport problem. The viability of nano-TPV devices proposed so far in the literature, based on a tungsten radiator at 2000 K and indium gallium antimonide cell, is questioned due to excessive heating of the junction converting thermal radiation into electricity. Using a convective thermal management system, a heat transfer coefficient as high as 105 Wm-2K-1 is required to maintain the junction at room temperature. The possibility of characterizing non-intrusively, and potentially in real-time, nanoparticles from 5 nm to 100 nm in size via scattered surface wave is explored. The feasibility of the characterization framework is theoretically demonstrated via a sensitivity analysis of the scattering matrix elements. Measurements of the scattering matrix elements for 200 nm and 50 nm gold spherical particles show the great sensitivity of the characterization tool, although an ultimate calibration is difficult with the current version of the experimental set-up. KEYWORDS: Near-field thermal radiation, Surface phonon-polariton, Nanoscale-gap thermophotoltaic power generation, Optical characterization of nanoparticles, Scattering (Mueller) matrix

  6. Synchrotron radiation with radiation reaction. [relativistic electron motion in strong astrophysical magnetic fields

    NASA Technical Reports Server (NTRS)

    Nelson, Robert W.; Wasserman, Ira

    1991-01-01

    A rigorous discussion is presented of the classical motion of a relativistic electron in a magnetic field and the resulting electromagnetic radiation when radiation reaction is important. In particular, for an electron injected with initial energy gamma(0), a systematic perturbative solution to the Lorentz-Dirac equation of motion is developed for field strengths satisfying gamma(0) B much less than 6 x 10 to the 15th G. A particularly accurate solution to the electron orbital motion in this regime is found and it is demonstrated how lowest-order corrections can be calculated. It is shown that the total energy-loss rate corresponds to what would be found using the exact Larmor power formula without including radiation reaction. Provided that the particle energy and field strength satisfy the same contraint, it is explicitly demonstrated that the intuitive prescription for calculating the time-integrated radiation spectrum described above is correct.

  7. Scientific results from the Pioneer Saturn encounter - Summary

    NASA Astrophysics Data System (ADS)

    Opp, A. G.

    1980-01-01

    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.

  8. Cosmological fluctuations of a random field and radiation fluid

    NASA Astrophysics Data System (ADS)

    Bastero-Gil, Mar; Berera, Arjun; Moss, Ian G.; Ramos, Rudnei O.

    2014-05-01

    A generalization of the random fluid hydrodynamic fluctuation theory due to Landau and Lifshitz is applied to describe cosmological fluctuations in systems with radiation and scalar fields. The viscous pressures, parametrized in terms of the bulk and shear viscosity coefficients, and the respective random fluctuations in the radiation fluid are combined with the stochastic and dissipative scalar evolution equation. This results in a complete set of equations describing the perturbations in both scalar and radiation fluids. These derived equations are then studied, as an example, in the context of warm inflation. Similar treatments can be done for other cosmological early universe scenarios involving thermal or statistical fluctuations.

  9. Modeling surface magnetic fields in stars with radiative envelopes

    NASA Astrophysics Data System (ADS)

    Kochukhov, Oleg

    2014-08-01

    Stars with radiative envelopes, specifically the upper main sequence chemically peculiar (Ap) stars, were among the first objects outside our solar system for which surface magnetic fields have been detected. Currently magnetic Ap stars remains the only class of stars for which high-resolution measurements of both linear and circular polarization in individual spectral lines are feasible. Consequently, these stars provide unique opportunities to study the physics of polarized radiative transfer in stellar atmospheres, to analyze in detail stellar magnetic field topologies and their relation to starspots, and to test different methodologies of stellar magnetic field mapping. Here I present an overview of different approaches to modeling the surface fields in magnetic A- and B-type stars. In particular, I summarize the ongoing efforts to interpret high-resolution full Stokes vector spectra of these stars using magnetic Doppler imaging. These studies reveal an unexpected complexity of the magnetic field geometries in some Ap stars.

  10. STABILITY OF THE TOROIDAL MAGNETIC FIELD IN STELLAR RADIATION ZONES

    SciTech Connect

    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

    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.

  11. Topological magnetoelectric effects in microwave far-field radiation

    E-print Network

    Berezin, M; Shavit, R

    2015-01-01

    Similar to electromagnetism, described by the Maxwell equations, the physics of magnetoelectric (ME) phenomena deals with the fundamental problem of the relationship between electric and magnetic fields. Despite a formal resemblance between the two notions, they concern effects of different natures. In general, ME coupling effects manifest in numerous macroscopic phenomena in solids with space and time symmetry breakings. Recently it was shown that the near fields in the proximity of a small ferrite particle with magnetic dipolar mode (MDM) oscillations have the space and time symmetry breakings and topological properties of these fields are different from topological properties of the free space electromagnetic (EM) fields. Such MDM originated fields, called magnetoelectric (ME) fields, carry both spin and orbital angular momentums. They are characterized by power flow vortices and non zero helicity. In this paper, we report on observation of the topological ME effects in far field microwave radiation based ...

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

    NASA Astrophysics Data System (ADS)

    Kalugin, M. A.

    2010-12-01

    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.

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

    SciTech Connect

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

    2010-12-15

    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.

  14. Voyager Encounter Highlights

    NASA Technical Reports Server (NTRS)

    1989-01-01

    The following are presented: computer animation of trajectories for both Voyagers 1 and 2; view of Jupiter during one orbit of Ganymede; computer animation of Voyager 2's encounter with Jupiter and its satellites; time lapse of the planet's rotation and its satellites; stroboscopic sequence of selected frames; cloud motion; Jupiter's Great Red Spot (4/25 - 5/24, 1979) through a violet filter; and the Great Red Spot through a blue filter by Voyager 1. The dynamics of Jupiter's clouds are shown - the whole planet is shown first, then two closer looks are repeated several times. Also included are pans of stills of Jupiter's satellites and a computer simulation tour of Saturn system from POV just behind Voyager, made of 116 images of Saturn through a green filter and of 516 images taken by Voyager 1 (9/12 - 9/14, 1980). Frames are enhanced to show the motion of features in Saturn's rings. Pans of stills of Saturn's satellites are shown. There is computer animation of the planet's system, rings, and Sigma Sagittari. Images on January 14, 1986 are through an orange filter. Uranus's satellites are shown as is computer animation of an August 1989 encounter.

  15. S-76 high intensity radiated fields, volume 3

    Microsoft Academic Search

    Jerry Blair

    1993-01-01

    The Federal Aviation Administration (FAA) Technical Center sponsored a series of High Intensity Radiated Fields (HIRF) tests on a Sikorsky S-76 rotorcraft. The project was conducted to evaluate the practically of performing aircraft level HIRF tests, determine the effects of HIRF on a specific rotorcraft with the potential to obtain information on rotorcraft in general, and evaluate the effects of

  16. S-76 high intensity radiated fields, volume 1

    Microsoft Academic Search

    Jerry Blair

    1993-01-01

    The Federal Aviation Administration (FAA) Technical Center sponsored a series of High Intensity Radiated Fields (HIRF) test on a Sikorsky S-76 rotorcraft. The project was conducted to evaluate the practicality of performing aircraft level HIRF tests, determine the effects of HIRF on a specific rotorcraft with the potential to obtain information on rotorcraft in general, and evaluate the effects of

  17. S-76 high intensity radiated fields, volume 2

    Microsoft Academic Search

    Jerry Blair

    1993-01-01

    The Federal Aviation Administration (FAA) Technical Center sponsored a series of High Intensity Radiated Fields (HIRF) test on a Sikorsky S-76 rotorcraft. The project was conducted to evaluate the practically of performing aircraft level HIRF tests, determine the effects of HIRF on a specific rotorcraft with the potential to obtain information on rotorcraft in general, and evaluate the effects of

  18. Out-of-Field Cell Survival Following Exposure to Intensity-Modulated Radiation Fields

    Microsoft Academic Search

    Karl T. Butterworth; Conor K. McGarry; Colman Trainor; Joe M. O’Sullivan; Alan R. Hounsell; Kevin M. Prise

    2011-01-01

    Purpose: To determine the in-field and out-of-field cell survival of cells irradiated with either primary field or scattered radiation in the presence and absence of intercellular communication. Methods and Materials: Cell survival was determined by clonogenic assay in human prostate cancer (DU145) and primary fibroblast (AGO1552) cells following exposure to different field configurations delivered using a 6-MV photon beam produced

  19. Nanodosimetric Characterization of Mixed Radiation Fields: Status and Perspectives

    NASA Astrophysics Data System (ADS)

    Schulte, Reinhard; Bashkirov, Vladimir; Casiraghi, Margherita

    The nanodosimetric characterization of mixed radiation fields containing variable fluences of charged particles, neutrons, and photons with stochastic quantities related to the number of ionizations in biological targets of nanometric size is an active area of research and development. Applications include measurements in low-dose radiation environments, including outer space, for radiation protection as well as characterization of mixed radiation therapy fields present in particle therapy with protons, light ions, or neutrons. Approaches for the nanodosimetric characterization of mixed radiation fields should consist of balance of theoretical Monte Carlo simulations and experimental studies that can inform each other. The former should be carefully benchmarked with the latter, usually employing detectors filled with low-pressure gas in which nanodosimetric studies are possible. Research in experimental nanodosimetry has exploited the principle of low-pressure-gas scaling of mean interaction distances between energy transfer points up to a million-fold, thus allowing to collect single charges (ions or electrons) generated in cylindrical volumes equivalent to a short segment of DNA. When combined with arrival-time selection, position resolution of down to 5 nm, has been achieved for experimental track structure studies. The results of these experimental studies and Monte Carlo simulations using the Monte Carlo codes will be summarized. More recently, we have studied a new principle of 2D low-energy ion detection by impact ionization in a hole-pattern detector in combination with a low-pressure time projection chamber. First proof-of-principle and performance studies with this track-imaging detector and corresponding Monte Carlo simulations will be presented. The full potential of nanometric quantities in characterizing radiation quality for dosimetry of ionizing radiation is yet to be explored. The most significant signature of radiation quality may be the size and frequency of clustered ionization events in nanometric scales. Radiobiological evidence points to the importance of these clustered events and the hypothesis that the frequency of large clusters leading to irreparable events in DNA correlate with secondary cancer risk and other late effects of mixed radiation fields should be tested in the future.

  20. Teacher Educators Using Encounter Stories

    ERIC Educational Resources Information Center

    Davis, Danné E.; Kellinger, Janna Jackson

    2014-01-01

    Many prospective teachers are unaware of the encounters that Black, heterosexual women or White lesbians face. Here, we present encounter stories--individual narratives of poignant encounters and interactions that we have experienced with people unlike us--to identify with and ultimately draw on their experiences. Subsequently, the narratives…

  1. A Direct Encounter with a VLF Saucer Source Region?

    NASA Astrophysics Data System (ADS)

    Kabirzadeh, R.; Knudsen, D. J.; Bounds, S. R.; Clemmons, J. H.; Pfaff, R. F.; Wallis, D. D.

    2009-12-01

    The GEODESIC sounding rocket encountered dozens of localized, VLF-wave-filled density depletions in an auroral return current region at altitudes between 900-1000 km. While these are similar to well-studied lower-hybrid “spikelets”, which are electrostatic, many of the GEODESIC events exhibited strong VLF magnetic field enhancements as well. In the present study we show that these magnetic field fluctuations can be interpreted as the result of B-aligned electron currents driven by fluctuating electric fields parallel to B. This observation suggests that the electromagnetic wave-filled cavities are signatures of unstable filaments of return current fluctuating at VLF frequencies. We argue that the cavities’ spatial dimensions, their location inside the return current region and their total radiated power are consistent with the properties of VLF saucer source regions inferred from earlier satellite observations [James, J. Geophys. Res., 81, 501, 1976; Ergun et al., Geophys. Res. Lett., 28, 3805, 2001] taken at higher altitudes.

  2. Circular polarization of synchrotron radiation in high magnetic fields

    NASA Astrophysics Data System (ADS)

    de Búrca, D.; Shearer, A.

    2015-06-01

    The general model for incoherent synchrotron radiation has long been known, with the first theory being published by Westfold in 1959 and continued by Westfold and Legg in 1968. When this model was first developed, it was applied to radiation from Jupiter, with a magnetic field of ?1G. Pulsars have a magnetic field of ?1012 G. The Westfold and Legg model predict a circular polarization which is proportional to the square root of the magnetic field, and consequently predicts greater than 100 per cent circular polarization at high magnetic fields. Here a new model is derived based upon a more detailed analysis of the pitch angle distribution. This model is concerned with the frequency range f_{B_0}/? ? flesssim f_{B_0}, noting that f_{B_0} = 2.7× 10^7B, which for a relatively high magnetic field (˜106-108 G) leaves emission in the optical range. This is much lower than the expected frequency peak for a mono-energetic particle of 0.293eB/4? m_e c? ^2. We predict the circular polarization peaks around 107G in the optical regime with the radiation almost 15 per cent circularly polarized. The linear polarization changes from about 60 to 80 per cent in the same regime. We examine implications of this for pulsar studies.

  3. Field dependent emission rates in radiation damaged GaAs

    SciTech Connect

    Fleming, R. M.; Myers, S. M.; Wampler, W. R.; Lang, D. V.; Seager, C. H.; Campbell, J. M. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1415 (United States)

    2014-07-07

    We have measured the temperature and field dependence of emission rates from five traps in electron damaged GaAs. Four of the traps have previously been identified as radiation defects. One of the traps, seen in higher doped diodes, has not been previously identified. We have fit the data to a multiphonon emission theory that allows recombination in GaAs to be characterized over a broad range of temperature and electric field. These results demonstrate an efficient method to calculate field-dependent emission rates in GaAs.

  4. Operation Sun Beam, Shots Little Feller II and Small Boy. Project Officer's report - Project 7. 16. Airborne E-field radiation measurements of electromagnetic-pulse phenomena

    SciTech Connect

    Butler, K.L.

    1985-09-01

    Airborne measurements of the absolute vertical electric field (E-field) of the radiated electromagnetic pulse were attempted for Shots Little Feller II and Small Boy. Instrumentation included calibrated vertical whip antennas, wideband magnetic tape recorders, and photographs of oscilloscope traces. One instrumented aircraft participated in Little Feller II (C-131F); two aircraft participated in Small Boy (a C-131F and an A-3A). No detectable signals were recorded for either event. It is concluded that the vertical E-field intensities encountered were below the calibrated levels of the instrumentation or the method of instrumentation and calibration was inadequate for nonrepetitive pulse signals.

  5. Near-field radiative heat transfer in mesoporous alumina

    NASA Astrophysics Data System (ADS)

    Jing, Li; Yan-Hui, Feng; Xin-Xin, Zhang; Cong-Liang, Huang; Ge, Wang

    2015-01-01

    The thermal conductivity of mesoporous material has aroused the great interest of scholars due to its wide applications such as insulation, catalyst, etc. Mesoporous alumina substrate consists of uniformly distributed, unconnected cylindrical pores. Near-field radiative heat transfer cannot be ignored, when the diameters of the pores are less than the characteristic wavelength of thermal radiation. In this paper, near-field radiation across a cylindrical pore is simulated by employing the fluctuation dissipation theorem and Green function. Such factors as the diameter of the pore, and the temperature of the material are further analyzed. The research results show that the radiative heat transfer on a mesoscale is 2˜4 orders higher than on a macroscale. The heat flux and equivalent thermal conductivity of radiation across a cylindrical pore decrease exponentially with pore diameter increasing, while increase with temperature increasing. The calculated equivalent thermal conductivity of radiation is further developed to modify the thermal conductivity of the mesoporous alumina. The combined thermal conductivity of the mesoporous alumina is obtained by using porosity weighted dilute medium and compared with the measurement. The combined thermal conductivity of mesoporous silica decreases gradually with pore diameter increasing, while increases smoothly with temperature increasing, which is in good agreement with the experimental data. The larger the porosity, the more significant the near-field effect is, which cannot be ignored. Project supported by the National Natural Science Foundation of China (Grant No. 51422601), the National Basic Research Program of China (Grant No. 2012CB720404), and the National Key Technology Research and Development Program of China (Grant No. 2013BAJ01B03).

  6. UV Radiation Fields Produced by Young Embedded Star Clusters

    E-print Network

    M. Fatuzzo; F. C. Adams

    2007-12-20

    A large fraction of stars form within young embedded clusters, and these environments produce a substantial ultraviolet (UV) background radiation field, which can provide feedback on the star formation process. To assess the possible effects of young stellar clusters on the formation of their constituent stars and planets, this paper constructs the expected radiation fields produced by these clusters. We include both the observed distribution of cluster sizes $N$ in the solar neighborhood and an extended distribution that includes clusters with larger $N$. The paper presents distributions of the FUV and EUV luminosities for clusters with given stellar membership $N$, distributions of FUV and EUV luminosity convolved over the expected distribution of cluster sizes $N$, and the corresponding distributions of FUV and EUV fluxes. These flux distributions are calculated both with and without the effects of extinction. Finally, we consider the effects of variations in the stellar initial mass function on these radiation fields. Taken together, these results specify the distributions of radiation environments that forming solar systems are expected to experience.

  7. Quantum driven dissipative parametric oscillator in a blackbody radiation field

    SciTech Connect

    Pachón, Leonardo A. [Grupo de Física Atómica y Molecular, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín (Colombia) [Grupo de Física Atómica y Molecular, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín (Colombia); Department of Chemistry and Center for Quantum Information and Quantum Control, Chemical Physics Theory Group, University of Toronto, Toronto, Ontario M5S 3H6 (Canada); Brumer, Paul [Department of Chemistry and Center for Quantum Information and Quantum Control, Chemical Physics Theory Group, University of Toronto, Toronto, Ontario M5S 3H6 (Canada)] [Department of Chemistry and Center for Quantum Information and Quantum Control, Chemical Physics Theory Group, University of Toronto, Toronto, Ontario M5S 3H6 (Canada)

    2014-01-15

    We consider the general open system problem of a charged quantum oscillator confined in a harmonic trap, whose frequency can be arbitrarily modulated in time, that interacts with both an incoherent quantized (blackbody) radiation field and with an arbitrary coherent laser field. We assume that the oscillator is initially in thermodynamic equilibrium with its environment, a non-factorized initial density matrix of the system and the environment, and that at t = 0 the modulation of the frequency, the coupling to the incoherent and the coherent radiation are switched on. The subsequent dynamics, induced by the presence of the blackbody radiation, the laser field, and the frequency modulation, is studied in the framework of the influence functional approach. This approach allows incorporating, in analytic closed formulae, the non-Markovian character of the oscillator-environment interaction at any temperature as well the non-Markovian character of the blackbody radiation and its zero-point fluctuations. Expressions for the time evolution of the covariance matrix elements of the quantum fluctuations and the reduced density-operator are obtained.

  8. Signatures of Radiation Reaction in Ultra-Intense Laser Fields

    E-print Network

    C. Harvey; T. Heinzl; M. Marklund

    2011-10-04

    We discuss radiation reaction effects on charges propagating in ultra-intense laser fields. Our analysis is based on an analytic solution of the Landau-Lifshitz equation. We suggest to measure radiation reaction in terms of a symmetry breaking parameter associated with the violation of null translation invariance in the direction opposite to the laser beam. As the Landau-Lifshitz equation is nonlinear the energy transfer within the pulse is rather sensitive to initial conditions. This is elucidated by comparing colliding and fixed target modes in electron laser collisions.

  9. Compliance with High-Intensity Radiated Fields Regulations - Emitter's Perspective

    NASA Technical Reports Server (NTRS)

    Statman, Joseph; Jamnejad, Vahraz; Nguyen, Lee

    2012-01-01

    NASA's Deep Space Network (DSN) uses high-power transmitters on its large antennas to communicate with spacecraft of NASA and its partner agencies. The prime reflectors of the DSN antennas are parabolic, at 34m and 70m in diameter. The DSN transmitters radiate Continuous Wave (CW) signals at 20 kW - 500 kW at X-band and S-band frequencies. The combination of antenna reflector size and high frequency results in a very narrow beam with extensive oscillating near-field pattern. Another unique feature of the DSN antennas is that they (and the radiated beam) move mostly at very slow sidereal rate, essentially identical in magnitude and at the opposite direction of Earth rotation.The DSN is in the process of revamping its documentation to provide analysis of the High Intensity Radiation Fields (HIRF) environment resulting from radio frequency radiation from DSN antennas for comparison to FAA regulations regarding certification of HIRF protection as outlined in the FAA regulations on HIRF protection for aircraft electrical and electronic systems (Title 14, Code of Federal Regulations (14 CFR) [section sign][section sign] 23.1308, 25.1317, 27.1317, and 29.1317).This paper presents work done at JPL, in consultation with the FAA. The work includes analysis of the radiated field structure created by the unique DSN emitters (combination of transmitters and antennas) and comparing it to the fields defined in the environments in the FAA regulations. The paper identifies areas that required special attention, including the implications of the very narrow beam of the DSN emitters and the sidereal rate motion. The paper derives the maximum emitter power allowed without mitigation and the mitigation zones, where required.Finally, the paper presents summary of the results of the analyses of the DSN emitters and the resulting DSN process documentation.

  10. Performance of radiation survey meters in X- and gamma-radiation fields.

    PubMed

    Ceklic, Sandra; Arandjic, Danijela; Zivanovic, Milos; Ciraj-Bjelac, Olivera; Lazarevic, Djordje

    2014-11-01

    The aim of this work was to investigate the different types of radiation detectors commonly used for radiation protection purposes as survey meters. The study was performed on survey meters that use different detectors as ionisation chamber, Geiger Mueller (GM) counter and scintillation detector. For each survey meter, energy dependence and angular response in X- and gamma-radiation fields was tested. The following commercially available survey meters were investigated: ionisation chambers Victoreen 451P, Babyline 31 and VA-J-15A, Geiger counter MRK-M87, 6150 AD6 and FAG FH 40F2 and scintillation counter 6150 ADB. As a source of gamma radiation, (137)Cs and (60)Co were used whereas X-ray radiation fields were generated using an X-ray unit. The radiation characteristics of the survey meters were mostly in compliance with references estimated by standard IEC 1017-2. However, some of them showed larger deviation at lower energies. GM counters exhibit strong energy dependence for low-energy photons. PMID:25063785

  11. Thermal heat radiation, near-field energy density and near-field radiative heat transfer of coated materials

    E-print Network

    Svend-Age Biehs

    2011-03-15

    We investigate the thermal radiation and thermal near-field energy density of a metal-coated semi-infinite body for different substrates. We show that the surface polariton coupling within the metal coating leads to an enhancement of the TM-mode part of the thermal near-field energy density when a polar substrate is used. In this case the result obtained for a free standing metal film is retrieved. In contrast, in the case of a metal substrate there is no enhancement in the TM-mode part, as can also be explained within the framework of surface plasmon coupling within the coating. Finally, we discuss the influence of the enhanced thermal energy density on the near-field radiative heat transfer between a simple semi-infinite and a coated semi-infinite body for different material combinations.

  12. THE RADIATIVE TRANSFER OF SYNCHROTRON RADIATION THROUGH A COMPRESSED RANDOM MAGNETIC FIELD

    SciTech Connect

    Cawthorne, T. V. [Jeremiah Horrocks Institute, University of Central Lancashire, Preston, Lancashire PR1 2HE (United Kingdom); Hughes, P. A. [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109-1042 (United States)

    2013-07-01

    This paper examines the radiative transfer of synchrotron radiation in the presence of a magnetic field configuration resulting from the compression of a highly disordered magnetic field. It is shown that, provided Faraday rotation and circular polarization can be neglected, the radiative transfer equations for synchrotron radiation separate for this configuration, and the intensities and polarization values for sources that are uniform on large scales can be found straightforwardly in the case where opacity is significant. Although the emission and absorption coefficients must, in general, be obtained numerically, the process is much simpler than a full numerical solution to the transfer equations. Some illustrative results are given and an interesting effect, whereby the polarization increases while the magnetic field distribution becomes less strongly confined to the plane of compression, is discussed. The results are of importance for the interpretation of polarization near the edges of lobes in radio galaxies and of bright features in the parsec-scale jets of active galactic nuclei, where such magnetic field configurations are believed to exist.

  13. Study on neutron radiation field of carbon ions therapy

    E-print Network

    Xu, Jun-Kui; Li, Wu-Yuan; Yan, Wei-Wei; Chen, Xi-Meng; Mao, Wang; Pang, Cheng-Guo

    2015-01-01

    Carbon ions offer significant advantages for deep-seated local tumors therapy due to their physical and biological properties. Secondary particles, especially neutrons caused by heavy ion reactions should be carefully considered in treatment process and radiation protection. For radiation protection purposes, the FLUKA Code was used in order to evaluate the radiation field at deep tumor therapy room of HIRFL in this paper. The neutron energy spectra, neutron dose and energy deposition of carbon ion and neutron in tissue-like media was studied for bombardment of solid water target by 430MeV/u C ions. It is found that the calculated neutron dose have a good agreement with the experimental date, and the secondary neutron dose may not exceed one in a thousand of the carbon ions dose at Bragg peak area in tissue-like media.

  14. Study on neutron radiation field of carbon ions therapy

    E-print Network

    Jun-Kui Xu; You-Wu Su; Wu-Yuan Li; Wei-Wei Yan; Xi-Meng Chen; Wang Mao; Cheng-Guo Pang

    2015-03-18

    Carbon ions offer significant advantages for deep-seated local tumors therapy due to their physical and biological properties. Secondary particles, especially neutrons caused by heavy ion reactions should be carefully considered in treatment process and radiation protection. For radiation protection purposes, the FLUKA Code was used in order to evaluate the radiation field at deep tumor therapy room of HIRFL in this paper. The neutron energy spectra, neutron dose and energy deposition of carbon ion and neutron in tissue-like media was studied for bombardment of solid water target by 430MeV/u C ions. It is found that the calculated neutron dose have a good agreement with the experimental date, and the secondary neutron dose may not exceed one in a thousand of the carbon ions dose at Bragg peak area in tissue-like media.

  15. Verification of light & radiation field coincidence quality assurance for radiation therapy by using a-Se based DR system

    NASA Astrophysics Data System (ADS)

    Kim, Jin-Young; Park, Eun-Tae; Choi, Yun-Seon; Cho, Heung-Lae; Ahn, Ki-Jung; Park, Sung-Kwang; Kim, Ji-Na; Suh, Tae-Suk; Kim, Jin-Seon; Hong, Ju-Yeon; Park, Jeong-Eun; Kim, Kyo-Tae; Oh, Kyung-Min; Kim, Hyunjung; Jo, Sun-Mi; Oh, Won-Yong; Jin, Seong-Jin; Cho, Woong

    2015-04-01

    Currently, the American Association of Physicists in Medicine (AAPM) recommends measuring the surface field size once a week by using an analog film in order to verify light and radiation field coincidence in the Quality Assurance (QA) of radiotherapy. However, the use of the film does not allow for a quantitative method of evaluation, and measuring the light field with radiation field detectors in a 2D array is difficult. Therefore, we used an amorphous-Se (a-Se) digital radiation detection system to measure the light and radiation fields simultaneously for a quantitative QA system, and the feasibility of using such a system was confirmed by ensuring the coincidence of the light and the radiation field measurements. The characteristics of the analog film and the a-Se digital radiation detection system were compared by delivering to each doses of 100, 10 monitor units(MU) of radiation at a rate of 400 MU/min to a radiation field 100 × 100 mm2 in size from a 100 cm source-surface distance (SSD). A 0.5 mm to 0.6 mm difference was measured in the X-axis, and a 0.3 mm difference was measured in the Y-axis. The difference in the measurements of the coincidence of light and the radiation field was less than 0.3 mm, which is relatively insignificant. These results indicate that the use of an a-Se digital radiation detection system is adequate for quality assurance of radiotherapy using light and radiation field coincidence. In addition, the experiment is considered to have provided valuable results in that the a-Se based digital radiation detection system enables simple and accurate QA for clinical radiation therapy by assessing the coincidence in the alignment of the light and the radiation fields.

  16. Analysis of the radiated information in spinning sound fields.

    PubMed

    Carley, Michael

    2010-10-01

    The information content of a spinning sound field is analyzed using a combination of exact and asymptotic results, in order to set limits on how accurately source identification can be carried out. Using a transformation of the circular source to an exactly equivalent set of line source modes, given by Chebyshev polynomials, it is found that the line source modes of order greater than the source wavenumber generate exponentially small fields. Asymptotic analysis shows that the remaining, lower order, modes radiate efficiently only into a region around the source plane, with this region shrinking as the mode order is increased. The results explain the ill-conditioning of source identification methods; the successful use of low order models in active noise control; and the low radiation efficiency of subsonic jets. PMID:20968340

  17. Potential theoretic methods for far field sound radiation calculations

    NASA Technical Reports Server (NTRS)

    Hariharan, S. I.; Stenger, Edward J.; Scott, J. R.

    1995-01-01

    In the area of computational acoustics, procedures which accurately predict the far-field sound radiation are much sought after. A systematic development of such procedures are found in a sequence of papers by Atassi. The method presented here is an alternate approach to predicting far field sound based on simple layer potential theoretic methods. The main advantages of this method are: it requires only a simple free space Green's function, it can accommodate arbitrary shapes of Kirchoff surfaces, and is readily extendable to three-dimensional problems. Moreover, the procedure presented here, though tested for unsteady lifting airfoil problems, can easily be adapted to other areas of interest, such as jet noise radiation problems. Results are presented for lifting airfoil problems and comparisons are made with the results reported by Atassi. Direct comparisons are also made for the flat plate case.

  18. Radiative Neutron Capture on Carbon-14 in Effective Field Theory

    E-print Network

    Gautam Rupak; Lakma Fernando; Akshay Vaghani

    2012-04-19

    The cross section for radiative capture of neutron on carbon-14 is calculated using the model-independent formalism of halo effective field theory. The dominant contribution from E1 transition is considered, and the cross section is expressed in terms of elastic scattering parameters of the effective range expansion. Contributions from both resonant and non-resonant interaction are calculated. Significant interference between these leads to a capture contribution that deviates from simple Breit-Wigner resonance form.

  19. Radiation from electrons in graphene in strong electric field

    E-print Network

    Yokomizo, N

    2014-01-01

    We study the interaction of electrons in graphene with the quantized electromagnetic field in the presence of an applied uniform electric field using the Dirac model of graphene. Electronic states are represented by exact solutions of the Dirac equation in the electric background, and amplitudes of first-order Feynman diagrams describing the interaction with the photon field are calculated for massive Dirac particles in both valleys. Photon emission probabilities from a single electron and from a many-electron system at the charge neutrality point are derived, including the angular and frequency dependence, and several limiting cases are analyzed. The pattern of photon emission at the Dirac point in a strong field is determined by an interplay between the nonperturbative creation of electron-hole pairs and spontaneous emission, allowing for the possibility of observing the Schwinger effect in measurements of the radiation emitted by pristine graphene under DC voltage.

  20. New Horizons encounters Jupiter

    Microsoft Academic Search

    Michael Carroll

    2007-01-01

    NASA's New Horizons spacecraft, en route to Pluto, flew within 2.3 million kilometers of Jupiter. The results have estounded and excited planetary scientists, with new data on its moons, red spots, rings and magnetic field.

  1. Plasma satellites in the presence of a non-coherent and unpolarized radiation field

    NASA Astrophysics Data System (ADS)

    Truong-Bach, Mr.; Drawin, H. W.

    1982-06-01

    Satellite lines produced by longitudinal electrostatic plasma waves in the presence of a noncoherent and unpolarized radiation field are investigated by perturbation theory expanded to fourth order. The results show that the Baranger and Mozer plasma satellites are shifted even in the zero radiation field limit, and that their strength can be enhanced by the radiation field.

  2. Electric field enhancement and far-field radiation pattern of the nanoantenna with concentric rings.

    PubMed

    Chen, Shih-Wen; Huang, Yi-Han; Chao, Bo-Kai; Hsueh, Chun-Hway; Li, Jia-Han

    2014-12-01

    The optical antennas have the potential in various applications because of their field enhancement and directivity control. The directivity of a dipole antenna can be improved by directivity-enhanced Raman scattering structure, which is a combination of a dipole antenna and a ring reflector layer on a ground plane. The concentric rings can collect the light into the center hole. Depending upon the geometry of the antenna inside the hole, different electric field enhancements can be achieved. In this paper, we propose to combine the concentric rings with the directivity-enhanced Raman scattering structure in order to study its electric field enhancement and the far-field radiation pattern by finite-difference time-domain simulations. Compared with the structure without the concentric rings over the ground plane, it is found that our proposed structure can obtain stronger electric field enhancements and narrower radiation beams because the gold rings can help to couple the light into the nanoantenna and they also scatter light into the far field and modify the far-field radiation pattern. The designed structures were fabricated and the chemical molecules of thiophenol were attached on the structures for surface-enhanced Raman scattering (SERS) measurements. The measured results show that the structure with concentric rings can have stronger SERS signals. The effects of the dielectric layer thickness in our proposed structure on the near-field enhancements and far-field radiation are also investigated. The proposed structure can be useful for several nanoantenna applications, such as sensing or detecting. PMID:26088981

  3. Electric field enhancement and far-field radiation pattern of the nanoantenna with concentric rings

    NASA Astrophysics Data System (ADS)

    Chen, Shih-Wen; Huang, Yi-Han; Chao, Bo-Kai; Hsueh, Chun-Hway; Li, Jia-Han

    2014-12-01

    The optical antennas have the potential in various applications because of their field enhancement and directivity control. The directivity of a dipole antenna can be improved by directivity-enhanced Raman scattering structure, which is a combination of a dipole antenna and a ring reflector layer on a ground plane. The concentric rings can collect the light into the center hole. Depending upon the geometry of the antenna inside the hole, different electric field enhancements can be achieved. In this paper, we propose to combine the concentric rings with the directivity-enhanced Raman scattering structure in order to study its electric field enhancement and the far-field radiation pattern by finite-difference time-domain simulations. Compared with the structure without the concentric rings over the ground plane, it is found that our proposed structure can obtain stronger electric field enhancements and narrower radiation beams because the gold rings can help to couple the light into the nanoantenna and they also scatter light into the far field and modify the far-field radiation pattern. The designed structures were fabricated and the chemical molecules of thiophenol were attached on the structures for surface-enhanced Raman scattering (SERS) measurements. The measured results show that the structure with concentric rings can have stronger SERS signals. The effects of the dielectric layer thickness in our proposed structure on the near-field enhancements and far-field radiation are also investigated. The proposed structure can be useful for several nanoantenna applications, such as sensing or detecting.

  4. Microwave background radiation anisotropy from scalar field gradients

    SciTech Connect

    Stebbins, A. (NASA/Fermilab Astrophysics Center, Fermilab MS209, Box 500, Batavia, Illinois 60510-0500 (United States)); Veeraraghavan, S. (Physics Astronomy Department, University of Massachusetts, Amherst, Massachusetts 01003 (United States) Steward Observatory, University of Arizona, Tucson, Arizona 85721 (United States))

    1993-09-15

    Analytic calculations of the cosmological density fluctuations and microwave background radiation anisotropies induced by gradients in a topologically trivial scalar field are presented. This anlaytic solution should provide a good test for numerical simulations of microwave anisotropy from scalar fields. To the extent that these results generalize to other scalar field models and configurations, they imply that (1) MBR measurements limit large-scale primordial variations greater than about 5[times]10[sup 16] GeV within our horizon, (2) the total scalar field variation is a fair predictor of the magnitude of the MBR anisotropy, but is only accurate to within a factor of about three, (3) scalar fields as well as other models of seeded perturbations produce a few times more anisotropy [Delta][ital T]/[ital T] for a given density fluctuation [delta][rho]/[rho] (on the same scale) than do primordial adiabatic perturbations, (4) models of scalar field seeds which produce a scale-invariant spectrum of perturbations seem to require galaxies to be more clustered than the mass on small scales, and (5) scalar fields do not tilt'' the Universe.

  5. Quantum signature in classical electrodynamics of the free radiation field

    E-print Network

    Michele Marrocco

    2015-05-20

    Quantum optics is a field of research based on the quantum theory of light. Here, we show that the classical theory of light can be equally effective in explaining a cornerstone of quantum optics: the quantization of the free radiation field. The quantization lies at the heart of quantum optics and has never been obtained classically. Instead, we find it by taking into account the degeneracy of the spherical harmonics that appear in multipole terms of the ordinary Maxwell theory of the free electromagnetic field. In this context, the number of energy quanta is determined by a finite countable set of spherical harmonics of higher order than the fundamental (monopole). This one plays, instead, the role of the electromagnetic vacuum that, contrary to the common view, has its place in the classical theory of light.

  6. Close encounters with DNA.

    PubMed

    Maffeo, C; Yoo, J; Comer, J; Wells, D B; Luan, B; Aksimentiev, A

    2014-10-15

    Over the past ten years, the all-atom molecular dynamics method has grown in the scale of both systems and processes amenable to it and in its ability to make quantitative predictions about the behavior of experimental systems. The field of computational DNA research is no exception, witnessing a dramatic increase in the size of systems simulated with atomic resolution, the duration of individual simulations and the realism of the simulation outcomes. In this topical review, we describe the hallmark physical properties of DNA from the perspective of all-atom simulations. We demonstrate the amazing ability of such simulations to reveal the microscopic physical origins of experimentally observed phenomena. We also discuss the frustrating limitations associated with imperfections of present atomic force fields and inadequate sampling. The review is focused on the following four physical properties of DNA: effective electric charge, response to an external mechanical force, interaction with other DNA molecules and behavior in an external electric field. PMID:25238560

  7. Photoionization and photodissociation rates in solar and blackbody radiation fields

    NASA Astrophysics Data System (ADS)

    Huebner, W. F.; Mukherjee, J.

    2015-02-01

    Rate coefficients for ionization and dissociation have been calculated for over 140 atomic, molecular, and ionic species in the radiation fields of (1) the quiet and the active Sun at 1 AU heliocentric distance and (2) blackbodies at four selected temperatures in the range from T=1000 K to 1,000,000 K without factors for radiation dilution with distance from the source. The rate coefficients in units of transitions per second (s-1) and associated excess energies of the photo products in eV are tabulated for about 265 ionization, dissociation, and dissociative ionization branches. Users can interactively access this information and plot and download cross sections and wavelength-binned results for various solar activities and blackbody temperatures on our website

  8. [Biological effects of nonionizing radiation: low frequency electromagnetic fields].

    PubMed

    Busljeta, I; Gomzi, M; Trosi?, I

    2000-03-01

    This article reviews various studies on effects of electric and magnetic fields of extremely low frequencies on human health and gives an overview of residential and occupational exposure to different sources, currently established exposure limitations, and protection measures. Throughout the evolution biological systems adapted to natural electric and magnetic fields. Only hundred years ago human exposure to radiation was limited to electric and magnetic fields arising either from extraterrestrial or terrestrial sources, yet both natural. For the past fifty years there has been large growth of artificial sources of electric and magnetic fields, especially with frequencies of 50 and 60 Hz (power generating and distribution systems). The concern about long-term exposure to artificial fields and possible adverse effects on human health has been entirely justified and led to numerous intensive epidemiological and laboratory studies. Results of several epidemiological studies confirm the connection between exposure to electric and magnetic fields of extremely low frequencies (up to 300 Hz) and increased risk of leukemia and brain tumor in children and adults. In addition, the risk of breast cancer in occupationally exposed population has increased. Laboratory studies on animal models, in vitro systems, and human volunteers did not confirm this connection. There is a growing interest in investigation of other possible adverse health effects such as neurodegenerative diseases (Alzheimer's disease and other forms of dementia, amyotrophic lateral sclerosis), cardiovascular disorders (arrhythmias and acute myocardial infarction), psychiatric disorders, and electrosensitivity. PMID:11059071

  9. Radiative corrections from heavy fast-roll fields during inflation

    NASA Astrophysics Data System (ADS)

    Jain, Rajeev Kumar; Sandora, McCullen; Sloth, Martin S.

    2015-06-01

    We investigate radiative corrections to the inflaton potential from heavy fields undergoing a fast-roll phase transition. We find that a logarithmic one-loop correction to the inflaton potential involving this field can induce a temporary running of the spectral index. The induced running can be a short burst of strong running, which may be related to the observed anomalies on large scales in the cosmic microwave spectrum, or extend over many e-folds, sustaining an effectively constant running to be searched for in the future. We implement this in a general class of models, where effects are mediated through a heavy messenger field sitting in its minimum. Interestingly, within the present framework it is a generic outcome that a large running implies a small field model with a vanishing tensor-to-scalar ratio, circumventing the normal expectation that small field models typically lead to an unobservably small running of the spectral index. An observable level of tensor modes can also be accommodated, but, surprisingly, this requires running to be induced by a curvaton. If upcoming observations are consistent with a small tensor-to-scalar ratio as predicted by small field models of inflation, then the present study serves as an explicit example contrary to the general expectation that the running will be unobservable.

  10. Intercomparison of radiation protection instrumentation in a pulsed neutron field

    NASA Astrophysics Data System (ADS)

    Caresana, M.; Denker, A.; Esposito, A.; Ferrarini, M.; Golnik, N.; Hohmann, E.; Leuschner, A.; Luszik-Bhadra, M.; Manessi, G.; Mayer, S.; Ott, K.; Röhrich, J.; Silari, M.; Trompier, F.; Volnhals, M.; Wielunski, M.

    2014-02-01

    In the framework of the EURADOS working group 11, an intercomparison of active neutron survey meters was performed in a pulsed neutron field (PNF). The aim of the exercise was to evaluate the performances of various neutron instruments, including commercially available rem-counters, personal dosemeters and instrument prototypes. The measurements took place at the cyclotron of the Helmholtz-Zentrum Berlin für Materialien und Energie GmbH. The cyclotron is routinely used for proton therapy of ocular tumours, but an experimental area is also available. For the therapy the machine accelerates protons to 68 MeV. The interaction of the proton beam with a thick tungsten target produces a neutron field with energy up to about 60 MeV. One interesting feature of the cyclotron is that the beam can be delivered in bursts, with the possibility to modify in a simple and flexible way the burst length and the ion current. Through this possibility one can obtain radiation bursts of variable duration and intensity. All instruments were placed in a reference position and irradiated with neutrons delivered in bursts of different intensity. The analysis of the instrument response as a function of the burst charge (the total electric charge of the protons in the burst shot onto the tungsten target) permitted to assess for each device the dose underestimation due to the time structure of the radiation field. The personal neutron dosemeters were exposed on a standard PMMA slab phantom and the response linearity was evaluated.

  11. Field Deployable Gamma Radiation Detectors for DHS Use

    SciTech Connect

    Sanjoy Mukhopadhyay

    2007-08-31

    Recently, the U.S. Department of Homeland Security (DHS) has integrated all nuclear detection research, development, testing, evaluation, acquisition, and operational support into a single office: the Domestic Nuclear Detection Office (DNDO). The DNDO has specific requirements set for all commercial and government off-the-shelf radiation detection equipment and data acquisition systems. This article would investigate several recent developments in field deployable gamma radiation detectors that are attempting to meet the DNDO specifications. Commercially available, transportable, handheld radio isotope identification devices (RIID) are inadequate for DHS’s requirements in terms of sensitivity, resolution, response time and reach back capability. The leading commercial vendor manufacturing handheld gamma spectrometer in the United States is Thermo Electron Corporation. Thermo Electron’s identiFINDER™, which primarily uses sodium iodide crystals (3.18-cm x 2.54-cm cylinders) as gamma detector, has a Full-Width-at-Half-Maximum energy resolution of 7 percent at 662 keV. Thermo Electron has just recently come up with a reach-back capability patented as RadReachBack™ that enables emergency personnel to obtain real-time technical analysis of radiation samples they find in the field. The current project has the goal to build a prototype handheld gamma spectrometer, equipped with a digital camera and an embedded cell phone to be used as an RIID with higher sensitivity (comparable to that of a 7.62-cm x 7.62-cm sodium iodide crystal at low gamma energy ranging from 30 keV to 3,000 keV), better resolution (< 3.0 percent at 662 keV), faster response time (able to detect the presence of gamma-emitting radio isotopes within 5 seconds of approach), which will make it useful as a field deployable tool. The handheld equipment continuously monitors the ambient gamma radiation and, if it comes across any radiation anomalies with higher than normal gamma gross counts, it sets an alarm condition. When a substantial alarm level is reached, the system auto triggers saving of relevant spectral data and software-triggers the digital camera to take a snapshot. The spectral data including in situ analysis and the imagery data will be packaged in a suitable format and sent to a command post using an imbedded cell phone.

  12. Intense THz-RADIATION Sources Using Semiconductors Irradiated with Femtosecond Laser Pulses in a Magnetic Field

    NASA Astrophysics Data System (ADS)

    Izumida, Shinji; Ono, Shingo; Liu, Zhenlin; Ohtake, Hideyuki; Sarukura, Nobuhiko

    We report significant enhancement of THz radiation from InAs under magnetic field irradiated with femtosecond pulses. The THz-radiation power is significantly enhanced and reaches sub-mW level in a 1.7-T magnetic field with 1.5-W excitation power. The THz-radiation power is related almost quadratically both to the magnetic field and excitation laser power. Furthermore, the radiation spectrum is found to be controlled by the excitation pulsewidth, chirp direction of the excitation pulse, and the magnetic field. Additionally, we have demonstrated a new method to generate THz radiation from a saturable Bragg reflector in a magnetic field.

  13. Localisation of atomic populations in the optical radiation field

    NASA Astrophysics Data System (ADS)

    Efremova, E. A.; Gordeev, M. Yu; Rozhdestvensky, Yu V.

    2014-10-01

    The possibility of two-dimensional spatial localisation of atomic populations under the influence of the travelling wave fields in the tripod-configuration of quantum states is studied for the first time. Three travelling waves propagating in the same plane at an angle of 120° to each other form a system of standing waves under the influence of which atomic populations are localised. The size of the region of spatial localisation of the populations, in principle, can be hundredths of a wavelength of optical radiation.

  14. Tail terms in gravitational radiation reaction via effective field theory

    E-print Network

    S. Foffa; R. Sturani

    2012-12-24

    Gravitational radiation reaction affects the dynamics of gravitationally bound binary systems. Here we focus on the leading "tail" term which modifies binary dynamics at fourth post-Newtonian order, as first computed by Blanchet and Damour. We re-produce this result using effective field theory techniques in the framework of the Lagrangian formalism suitably extended to include dissipation effects. We recover the known logarithmic tail term, consistently with the recent interpretation of the logarithmic tail term in the mass parameter as a renormalization group effect of the Bondi mass of the system.

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

    SciTech Connect

    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

    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.

  16. Thermoacoustic Monitoring of Radiation Field of Scanning Electron Beam

    NASA Astrophysics Data System (ADS)

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

    1997-05-01

    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.

  17. Encounter with Zoology

    E-print Network

    Macfarlane, Alan

    2014-12-12

    Introduction Cambridge is famous for its zoology and ethology, from Charles Darwin to David Attenborough. And within Cambridge my own College, King’s, was the home of much of their academic career of several important figures in this field in the second... ; became aware of the selective nature of consciousness and attention and the things you do attend to are apprehended in a self-conscious way; seemed to me that if you could understand how the different signals are treated in the nervous system...

  18. Encounter with Sociology

    E-print Network

    Macfarlane, Alan

    2014-12-12

    no anthropology’. I had never read any Fortes, Evans-Pritchard etc. So read Fortes and being a Marxist I could not buy it. I was a primitive Marxist and economic determinist. 0:41:09 That is how I wrote my critique of Meyer, which won the Curl Prize. I don... .D., because of the conditions of writing, a new baby and written in five months. My wife in the field and very stoical, worked with the people and always busy but not directly involved in my work. Awful climate in the monsoon. The living conditions...

  19. Novel properties of the q-analogue quantized radiation field

    NASA Technical Reports Server (NTRS)

    Nelson, Charles A.

    1993-01-01

    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 generalizations and their associated number-phase uncertainty relations are manifestly q-independent in the n greater than g number basis. However, in the q-coherent state z greater than q basis, the variance of the generic electric field, (delta(E))(sup 2) is found to be increased by a factor lambda(z) where lambda(z) greater than 1 if q not equal to 1. At large amplitudes, the amplitude itself would be quantized if the available resolution of unity for the q-analog coherent states is accepted in the formulation. These consequences are remarkable versus the conventional q = 1 limit.

  20. Analytical Problems Encountered with NIOSH Method 5521 for Total Isocyanates

    Microsoft Academic Search

    Rosa J. Key-Schwartz

    1995-01-01

    A recent analysis for total isocyanates in air using National Institute for Occupational Safety and Health Method 5521 presented difficulties in the identification of an oligomeric isocyanate species. Two problems were encountered during the analysis. A false negative response in the high performance liquid chromatography chromatogram was encountered in a majority of the field samples. An anomalous peak served to

  1. Temperature Dependent Behavior of Near Field Radiative Heat Transfer

    NASA Astrophysics Data System (ADS)

    Joachim, Robert

    2014-03-01

    We have designed and implemented an apparatus capable of measuring near field radiative heat transfer (NFRT) from room temperature down to cryogenic temperatures in vacuum. Utilizing a bimaterial cantilever with a 20 ?m glass sphere attached to the end in the pendulum geometry as a thermal detector and an optical fiber interferometer as a displacement detector we were able to measure the heat flux between a substrate and the glass sphere. The apparatus was sensitive enough to measure displacements of 1 nm and heat fluxes of 50 pW. NFRT was observed at temperatures ranging from 300K to 100K and at displacements down to 100nm. These measurements were performed for various combinations of Si, SiO2 and sapphire. The thermodynamic formulation of Lifshitz's theory for attraction between dielectrics predicts that NFRT will scale as T2 while far field radiative transfer will scale as T4 and that the crossover between these two regimes will occur at a distance given by (1/2 ?)(? c/kbT). Our data confirms these predictions. Supported by Air Force grant AFOSR FA9550-12-1-0065.

  2. Radiation from Secondary Planar Surfaces Sources in Quantum Field Theory

    NASA Astrophysics Data System (ADS)

    Maksuwan, A.; Viriyasrisuwattana, P.

    2015-06-01

    In quantum optics (optical coherence) theorem, many sources are employed in the laboratory are secondary planar sources. A source of this kind is usually an aperture in an opaque planar surface screen, illuminated either directly or via an optical system with primary sources. The expression following into the formulation of the radiation in radiant intensity which, analytical solution has not given the time evolution of amplitude. In this research, we consider this problem in quantum field theory (QFT) view point. By using the method of study based on a configuration space for explaining characteristic of the complete process, which begins and ends with the vacuum state so-called vacuum-to-vacuum transition amplitude between emitters and detectors. Propose in this research, we attend and explain the radiation for radiant intensity with time evolution process. To calculation amplitude transition of massive quantum particles propagator stimulated emission by secondary planar surface sources in space-time. Finally, we use the mathematical program for corresponding numerical evaluations between quantum optics and quantum field theory situation.

  3. Development of a Characterized Radiation Field for Evaluating Sensor Performance

    SciTech Connect

    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

    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)

  4. Characterization of the near-field and the far-field for a vertically radiating antenna over a ground plane.

    E-print Network

    Sarkar, Tapan K.

    Characterization of the near-field and the far-field for a vertically radiating antenna over, Kingsville, TX 78363 E-mail: ade@syr.edu Introduction The definition and application of Near-Field and Far-field is done for the evaluation of the far-field criterion in a wireless communication scenario. This paper

  5. The perturbation correction factor of ionisation chambers in beta -radiation fields

    Microsoft Academic Search

    J. Bohm

    1980-01-01

    In determining the absorbed dose in a solid medium by means of gas-filled ionisation chambers, the perturbation of the radiation field by the chamber needs to be taken into account. So far, an appropriate correction factor has neither been calculated nor measured for beta -radiation. This work describes its experimental determination for an extrapolation chamber and beta -radiation fields of

  6. Limits on the Applicability of Classical Electromagnetic Fields as Inferred from the Radiation Reaction

    E-print Network

    McDonald, Kirk

    field strength be arbitrarily large? If we require that the radiation­reaction force on a charged =mc 2 in Gaussian units. It seems less appreciated that the part of the classi­ cal radiation reactionLimits on the Applicability of Classical Electromagnetic Fields as Inferred from the Radiation

  7. Limits on the Applicability of Classical Electromagnetic Fields as Inferred from the Radiation Reaction

    E-print Network

    McDonald, Kirk

    field strength be arbitrarily large? If we require that the radiation-reaction force on a charged units. It seems less appreciated that the part of the classi- cal radiation reaction that is independentLimits on the Applicability of Classical Electromagnetic Fields as Inferred from the Radiation

  8. Further progress in the characterisation of complex radiation fields.

    PubMed

    Spurny, Frantisek; Silari, Marco

    2008-01-01

    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

  9. Voyager Saturn encounter press briefing

    NASA Technical Reports Server (NTRS)

    1980-01-01

    The briefing reviewed the mission planning of the Voyager project. The near encounter trajectories of both Voyager spacecraft were examined. The Saturn system is discussed with particular emphasis on Saturn's moons.

  10. Irradiators for measuring the biological effects of low dose-rate ionizing radiation fields

    E-print Network

    Davidson, Matthew Allen

    2011-01-01

    Biological response to ionizing radiation differs with radiation field. Particle type, energy spectrum, and dose-rate all affect biological response per unit dose. This thesis describes methods of spectral analysis, ...

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

    ERIC Educational Resources Information Center

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

    2011-01-01

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

  12. Observations of the diffuse near-UV radiation field

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    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.

  13. High-resolution optical telescope for ultraviolet /UV/ radiation field

    NASA Technical Reports Server (NTRS)

    Karayan, W. W.

    1979-01-01

    Design techniques are discussed for all-reflecting optics from first-order system considerations and applications currently utilized in the field of astronomical optics. The solution of the Dall-Karkham design problem is described, showing the advantage of inexpensive construction as compared with higher order surfaces. The design process reported here is a F/5 collecting system which quickly mates directly with the spectrometer; it is capable of achieving desired high resolution and sensitivity requirements. The theoretical limit of aberration tolerances is achieved with less than 1/8 of a wavelength at final focus (OPD). The design of spectrometer for ultra-violet (UV) radiation and its mechanism is included in this study.

  14. Two-photon coherent states of the radiation field

    NASA Technical Reports Server (NTRS)

    Yuen, H. P.

    1976-01-01

    The concept of a two-photon coherent state is introduced for applications in quantum optics. It is a simple generalization of the well-known minimum-uncertainty wave packets. The detailed properties of two-photon coherent states are developed and distinguished from ordinary coherent states. These two-photon coherent states are mathematically generated from coherent states through unitary operators associated with quadratic Hamiltonians. Physically they are the radiation states of ideal two-photon lasers operating far above threshold, according to the self-consistent-field approximation. The mean-square quantum noise behavior of these states, which is basically the same as those of minimum-uncertainty states, leads to applications not obtainable from coherent states or one-photon lasers. The essential behavior of two-photon coherent states is unchanged by small losses in the system. The counting rates or distributions these states generate in photocount experiments also reveal their difference from coherent states.

  15. Intercomparison of radiation protection instrumentation in a pulsed neutron field

    E-print Network

    Caresana, M; Esposito, A; Ferrarini, M; Golnik, N; Hohmann, E; Leuschner, A; Luszik-Bhadra, M; Manessi, G; Mayer, S; Ott, K; Röhrich, J; Silari, M; Trompier, F; Volnhals, M; Wielunski, M

    2014-01-01

    In the framework of the EURADOS working group 11, an intercomparison of active neutron survey meters was performed in a pulsed neutron field (PNF). The aim of the exercise was to evaluate the performances of various neutron instruments, including commercially available rem-counters, personal dosemeters and instrument prototypes. The measurements took place at the cyclotron of the Helmholtz-Zentrum Berlin für Materialien und Energie GmbH. The cyclotron is routinely used for proton therapy of ocular tumours, but an experimental area is also available. For the therapy the machine accelerates protons to 68 MeV. The interaction of the proton beam with a thick tungsten target produces a neutron field with energy up to about 60 MeV. One interesting feature of the cyclotron is that the beam can be delivered in bursts, with the possibility to modify in a simple and flexible way the burst length and the ion current. Through this possibility one can obtain radiation bursts of variable duration and intensity. All instru...

  16. Extractable proteins from field radiation vulcanized natural rubber latex

    NASA Astrophysics Data System (ADS)

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

    2005-07-01

    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.

  17. S-76 high intensity radiated fields, volume 3

    NASA Astrophysics Data System (ADS)

    Blair, Jerry

    1993-10-01

    The Federal Aviation Administration (FAA) Technical Center sponsored a series of High Intensity Radiated Fields (HIRF) tests on a Sikorsky S-76 rotorcraft. The project was conducted to evaluate the practically of performing aircraft level HIRF tests, determine the effects of HIRF on a specific rotorcraft with the potential to obtain information on rotorcraft in general, and evaluate the effects of exposure to 'real world' HIRF emitters. HIRF ground and flight tests were conducted to achieve the objective of the project. Site calibration (SCAL) measurements were made in the test area to determine the levels at which the S-76 would be irradiated when placed in the test area. Ground tests consisted of Low Level Swept Coupling (LLSC) and Low Level Swept Fields (LLSF) tests. The flight tests were flown directly into the main beam of a variety of pulsed and continuous wave (CW) transmitters including the Over the Horizon Back Scatter (OTHB), PAVE PAWS, ASR-9, FPS-65, and FPS-16 radars. Results of the S-76 tests added credibility to the existence of HIRF as a flight safety hazard. In the evaluation of the emitters, the flight tests showed repeatable instances where exposure resulted in instrumentation disruptions. It should however be noted that all the observed disruptions were of a non-critical nature.

  18. S-76 high intensity radiated fields, volume 1

    NASA Astrophysics Data System (ADS)

    Blair, Jerry

    1993-10-01

    The Federal Aviation Administration (FAA) Technical Center sponsored a series of High Intensity Radiated Fields (HIRF) test on a Sikorsky S-76 rotorcraft. The project was conducted to evaluate the practicality of performing aircraft level HIRF tests, determine the effects of HIRF on a specific rotorcraft with the potential to obtain information on rotorcraft in general, and evaluate the effects of exposure to real world HIRF emitters. HIRF ground and flight tests were conducted to achieve the objective of the project. Site calibration (SCAL) measurements were made in the test area to determine the levels at which the S-76 would be irradiated when placed in the test area. Ground tests consisted of Low Level Swept Coupling (LLSC) and Low Level Swept Fields (LLSF) tests. The flight tests were flown directly into the main beam of a variety of pulsed and continuous wave (CW) transmitters including the Over the Horizon Back Scatter (OTHB), PAVE PAWS, ASR-9, FPS-65, and FPS-16 radars. Results of the S-76 tests added credibility to the existence of HIRF as a flight safety hazard. In the evaluation of the emitters, the flight tests showed repeatable instances where exposure resulted in instrumentation disruptions. It should be noted that all the observed disruptions were of a non-critical nature.

  19. S-76 high intensity radiated fields, volume 2

    NASA Astrophysics Data System (ADS)

    Blair, Jerry

    1993-10-01

    The Federal Aviation Administration (FAA) Technical Center sponsored a series of High Intensity Radiated Fields (HIRF) test on a Sikorsky S-76 rotorcraft. The project was conducted to evaluate the practically of performing aircraft level HIRF tests, determine the effects of HIRF on a specific rotorcraft with the potential to obtain information on rotorcraft in general, and evaluate the effects of exposure to real world HIRF emitters. HIRF ground and flight tests were conducted to achieve the objective of the project. Site calibration (SCAL) measurements were made in the test area to determine the levels at which the S-76 would be irradiated when placed in the test area. Ground tests consisted of Low Level Swept Coupling (LLSC) and Low Level Swept Fields (LLSF) tests. The flight tests were flown directly into the main beam of a variety of pulsed and continuous wave (CW) transmitters including the Over the Horizon Back Scatter (OTHB), PAVE PAWS, ASR-9, FPS-65, and FPS-16 radars. Results of the S-76 tests added credibility to the existence of HIRF as a flight safety hazard. In the evaluation of the emitters, the flight tests showed repeatable instances where exposure resulted in instrumentation disruptions. It should be noted that all the observed disruptions were of a non-critical nature.

  20. Reverberation Chamber Uniformity Validation and Radiated Susceptibility Test Procedures for the NASA High Intensity Radiated Fields Laboratory

    NASA Technical Reports Server (NTRS)

    Koppen, Sandra V.; Nguyen, Truong X.; Mielnik, John J.

    2010-01-01

    The NASA Langley Research Center's High Intensity Radiated Fields Laboratory has developed a capability based on the RTCA/DO-160F Section 20 guidelines for radiated electromagnetic susceptibility testing in reverberation chambers. Phase 1 of the test procedure utilizes mode-tuned stirrer techniques and E-field probe measurements to validate chamber uniformity, determines chamber loading effects, and defines a radiated susceptibility test process. The test procedure is segmented into numbered operations that are largely software controlled. This document is intended as a laboratory test reference and includes diagrams of test setups, equipment lists, as well as test results and analysis. Phase 2 of development is discussed.

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

    PubMed Central

    Kerns, James R.; Anand, Aman

    2013-01-01

    Purpose: Photo-stimulable phosphor computed radiography (CR) has characteristics that allow the output to be manipulated by both radiation and optical light. The authors have developed a method that uses these characteristics to carry out radiation field and light field coincidence quality assurance on linear accelerators. Methods: CR detectors from Kodak were used outside their cassettes to measure both radiation and light field edges from a Varian linear accelerator. The CR detector was first exposed to a radiation field and then to a slightly smaller light field. The light impinged on the detector's latent image, removing to an extent the portion exposed to the light field. The detector was then digitally scanned. A MATLAB-based algorithm was developed to automatically analyze the images and determine the edges of the light and radiation fields, the vector between the field centers, and the crosshair center. Radiographic film was also used as a control to confirm the radiation field size. Results: Analysis showed a high degree of repeatability with the proposed method. Results between the proposed method and radiographic film showed excellent agreement of the radiation field. The effect of varying monitor units and light exposure time was tested and found to be very small. Radiation and light field sizes were determined with an uncertainty of less than 1 mm, and light and crosshair centers were determined within 0.1 mm. Conclusions: A new method was developed to digitally determine the radiation and light field size using CR photo-stimulable phosphor plates. The method is quick and reproducible, allowing for the streamlined and robust assessment of light and radiation field coincidence, with no observer interpretation needed. PMID:24320415

  2. In uence of UV Radiation Fields on Density Diagnostics with He-like Triplets

    E-print Network

    Ness, Jan-Uwe

    In uence of UV Radiation Fields on Density Diagnostics with He-like Triplets Jan-Uwe Ness 1 , Rolf;1 ) is due to a UV radiation #12;eld instead of the collisions in a high-density plasma. We illustrate this e and neglecting them. The sources of the UV radiation are assumed to be the respective stellar surfaces

  3. Influence of UV radiation fields on density diagnostics with He-like triplets

    E-print Network

    Ness, Jan-Uwe

    Influence of UV radiation fields on density diagnostics with He-like triplets Jan-Uwe Ness1, Rolf of the UV radiation are assumed to be the respective stellar surfaces, but in the case of Algol to density effects and how UV radiation can interfere with these effects. We will then show

  4. Acoustic radiation force in tissue-like solids due to modulated sound field

    E-print Network

    Guzina, Bojan

    Acoustic radiation force in tissue-like solids due to modulated sound field Egor V. Dontsov, Bojan April 2012 Available online 23 May 2012 Keywords: Acoustic radiation force Nonlinear acoustics Modulated-called acoustic radiation force) in homogeneous tissue-like solids generated by an elevated-intensity, focused

  5. Defect Mass in Gravitational Field and Red Shift of Atomic and Nuclear Radiation Spectra

    E-print Network

    Kh. M. Beshtoev

    2000-04-19

    It is shown, that radiation spectrum of atoms (or nuclei) in the gravitational field has a red shift since the effective mass of radiating electrons (or nucleons) changes in this field. This red shift is equal to the red shift of radiation spectrum in the gravitational field measured in existence experiments. The same shift must arise when the photon (or $ \\gamma $ quantum) is passing through the gravitational field if it participates in gravitational interactions (photon has no rest mass). The absence of the double effect in the experiments, probably, means that photons (or $ \\gamma $ quanta) are passing through the gravitational field without interactions.

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

    PubMed

    Fournier-Bidoz, Nathalie; Kirova, Youlia M; Campana, Francois; Dendale, Rémi; Fourquet, Alain

    2012-01-01

    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. PMID:21945169

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

    SciTech Connect

    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

    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.

  8. Non-thermal continuous and modulated electromagnetic radiation fields effects on sleep EEG of rats?

    PubMed Central

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

    2012-01-01

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

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

    PubMed

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

    2012-12-01

    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

  10. Modeling Magnetic Radiations of Electronic Circuits Using Near-Field Scanning Method

    Microsoft Academic Search

    Yolanda Vives-Gilabert; Christian Arcambal; Anne Louis; Francois de Daran; Philippe Eudeline; Blahcne Mazari

    2007-01-01

    In this paper, a simple method to obtain the equivalent radiation emitting sources of an electronic circuit using the near-field scanning method is presented. The model is based on a set of elemental dipoles that substitutes the electronic circuit and radiates the same magnetic field. Two different approaches are presented: a set of electric dipoles and a set of magnetic

  11. Shallow water inhomogeneous distribution of acoustic field in radiated noise measurement

    Microsoft Academic Search

    Hu Pengtao; Zhang Fusheng; Yang Desen

    2011-01-01

    Studies were conducted on inhomogeneous distribution of acoustic field in shallow water target radiated noise measurement. Acoustic vector processing theoretical model for this scenario was derived, and detailed examples showed that the inhomogeneous distribution of acoustic fields in testing sea is related to many factors, such as target sound source structure, radiation directivity, the bandwidth and frequency of the signals,

  12. Low-frequency electromagnetic radiation of a Schwarzschild black hole in a test nonuniform magnetic field

    Microsoft Academic Search

    I. I. Salukvadze

    1994-01-01

    The electromagnetic radiation process of a Schwarzschild black hole moving in the nonuniform magnetic field is investigated. The total flux of radiation was obtained. A theoretical calculation has been carried out under the test magnetic field assumption, i.e., energy-momentum tensor does not disturb Schwarzschild background metric. The technique of the Teukolsky equation has been used. The Greens function from the

  13. The radiated fields of the fundamental mode of photonic crystal fibers

    E-print Network

    The radiated fields of the fundamental mode of photonic crystal fibers Ali Dabirian,1 Mahmood of photonic crystal fibers has important manifestations in the radiated fields in terms of i) a focusing. A. Birks, P. S. J. Russell, and D. M. Atkin, "All-silica single-mode optical fiber with photonic

  14. Deformation field validation and inversion applied to adaptive radiation therapy

    NASA Astrophysics Data System (ADS)

    Vercauteren, Tom; De Gersem, Werner; Olteanu, Luiza A. M.; Madani, Indira; Duprez, Fréderic; Berwouts, Dieter; Speleers, Bruno; De Neve, Wilfried

    2013-08-01

    Development and implementation of chronological and anti-chronological adaptive dose accumulation strategies in adaptive intensity-modulated radiation therapy (IMRT) for head-and-neck cancer. An algorithm based on Newton iterations was implemented to efficiently compute inverse deformation fields (DFs). Four verification steps were performed to ensure a valid dose propagation: intra-cell folding detection finds zero or negative Jacobian determinants in the input DF; inter-cell folding detection is implemented on the resolution of the output DF; a region growing algorithm detects undefined values in the output DF; DF domains can be composed and displayed on the CT data. In 2011, one patient with nonmetastatic head and neck cancer selected from a three phase adaptive DPBN study was used to illustrate the algorithms implemented for adaptive chronological and anti-chronological dose accumulation. The patient received three 18F-FDG-PET/CTs prior to each treatment phase and one CT after finalizing treatment. Contour propagation and DF generation between two consecutive CTs was performed in Atlas-based autosegmentation (ABAS). Deformable image registration based dose accumulations were performed on CT1 and CT4. Dose propagation was done using combinations of DFs or their inversions. We have implemented a chronological and anti-chronological dose accumulation algorithm based on DF inversion. Algorithms were designed and implemented to detect cell folding.

  15. Comparative investigation of three dose rate meters for their viability in pulsed radiation fields.

    PubMed

    Gotz, M; Karsch, L; Pawelke, J

    2015-06-01

    Pulsed radiation fields, characterized by microsecond pulse duration and correspondingly high pulse dose rates, are increasingly used in therapeutic, diagnostic and research applications. Yet, dose rate meters which are used to monitor radiation protection areas or to inspect radiation shielding are mostly designed, characterized and tested for continuous fields and show severe deficiencies in highly pulsed fields. Despite general awareness of the problem, knowledge of the specific limitations of individual instruments is very limited, complicating reliable measurements. We present here the results of testing three commercial dose rate meters, the RamION ionization chamber, the LB 1236-H proportional counter and the 6150AD-b scintillation counter, for their response in pulsed radiation fields of varied pulse dose and duration. Of these three the RamION proved reliable, operating in a pulsed radiation field within its specifications, while the other two instruments were only able to measure very limited pulse doses and pulse dose rates reliably. PMID:25978117

  16. Magnetic-field control of near-field radiative heat transfer and the realization of highly tunable hyperbolic thermal emitters

    E-print Network

    Moncada-Villa, Edwin; Garcia-Vidal, Francisco J; Garcia-Martin, Antonio; Cuevas, Juan Carlos

    2015-01-01

    We present a comprehensive theoretical study of the magnetic field dependence of the near-field radiative heat transfer (NFRHT) between two parallel plates. We show that when the plates are made of doped semiconductors, the near-field thermal radiation can be severely affected by the application of a static magnetic field. We find that irrespective of its direction, the presence of a magnetic field reduces the radiative heat conductance, and dramatic reductions up to 700% can be found with fields of about 6 T at room temperature. We show that this striking behavior is due to the fact that the magnetic field radically changes the nature of the NFRHT. The field not only affects the electromagnetic surface waves (both plasmons and phonon polaritons) that normally dominate the near-field radiation in doped semiconductors, but it also induces hyperbolic modes that progressively dominate the heat transfer as the field increases. In particular, we show that when the field is perpendicular to the plates, the semicond...

  17. Far-field radiation of aft turbofan noise

    NASA Technical Reports Server (NTRS)

    Rice, E. J.; Saule, A. V.

    1980-01-01

    Approximate expressions were developed for the noise radiation from the aft duct. The results of approximate aft radiation equation compare favorably to more exact Wiener-Hopf radiation results. Refraction as well as convective effects in the multiple flow streams is considered. The peak in the radiation pattern, which occurs nearly at engine sideline, is composed of modes with relatively large cut-off ratios. This implies that aft fan radiation will be inherently more difficult to suppress that the fan inlet noise. The theoretical multimodal radiation pattern is compared to experimental data for the first two harmonics of blade passage frequency for three full scale fans at two speeds. The agreement between theory and experiment is quite good.

  18. 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...

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

    Microsoft Academic Search

    Schmotzer

    1982-01-01

    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

  20. Graphene Field Effect Transistors for Detection of Ionizing Radiation

    E-print Network

    Chen, Yong P.

    , Igor Jovanovic, and Yong P. Chen, Member, IEEE Abstract­A novel radiation detector based on a graphene study on the graphene-based radiation detector response to X-rays. We observed increasing resistance performance detectors for the use in detection of special nuclear material (SNM) has been a topic of interest

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

    Microsoft Academic Search

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

    2009-01-01

    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

  2. Computation of radiative fields in opposed-flow flame spread in a microgravity environment

    NASA Astrophysics Data System (ADS)

    Villaraza, Jeanie Ray P.

    The purpose of this thesis is to perform radiation computations in opposed-flow flame spread in a microgravity environment. In this work, the flame spread simulations consider a thermally thin, PMMA fuel in a quiescent, microgravity environment or facing low opposed-flow velocities at ambient conditions of 1 atm and 50-50 volumetric mixture of oxygen and nitrogen. The flame spread model, which is a Computational Fluid Dynamics (CFD) model, is used for numerical simulations in combination with a radiation model. The CFD code is written in FORTRAN language, and a Matlab code is developed for plotting results. The temperature and species fields from CFD computations are used as inputs into the radiation model. Radiative quantities are calculated by using a global balance method along with the total transmittance non-homogeneous model. Radiation effect on thermocouple temperature measurement is investigated. Although this topic is well known, performing radiation correction calculations usually considers surface radiation only and not gas radiation. The inclusion of gas radiation is utilized in predicting the gas temperature that a thermocouple would measure. A narrow bed radiation model is used to determine the average incident radiative flux at a specified location from which a thermocouple temperature measurement is predicted. This study focuses on the quiescent microgravity environment only. The effect of parameters such as thermocouple surface emissivity and bead diameter are also studied. For the main part of this thesis, the effect of gas radiation on the mechanism of flame spread over a thermally thin, solid fuel in microgravity is investigated computationally. Generated radiative fields including thermal and species fields are utilized to investigate the nature of the influence of gas radiation on flame structure as well as its role in the mechanism of opposed-flow flame spread. The opposed-flow configuration considers low flow velocities including a quiescent environment where radiation has been shown to be dominant. However, given the fact that gas radiation acts as a loss mechanism, and at the same time, it enhances forward heat transfer through radiation feedback to the fuel surface, there is no definitive work that establishes the role of gas radiation. This thesis explores the role played by gas radiation as a driving versus as a retarding mechanism. In this work, it is found that gas radiation is important in capturing flame images and spread rates. Gas radiation primarily acts as a loss mechanism through its effects on flame temperature which overwhelms the radiation feedback to the surface.

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

    SciTech Connect

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

    1997-02-01

    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.

  4. Calculations of Surface Radiation in Arid Regions--A Case Study

    Microsoft Academic Search

    Ming-Dah Chou; Guoliang Ji; Kuo-Nan Liou; Szu-Cheng S. Ou

    1992-01-01

    The difficulties encountered in the derivation of surface radiation budget in arid regions are studied using the surface and satellite data measured during the preliminary field experiment for the Land-Atmosphere Interactions Experiment conducted at the Heihe River basin in western China. The surface radiation is derived by coupling theoretical radiative calculations with satellite cloud retrievals. Comparisons with the surface measurements

  5. Evaluation of the impact of non-uniform neutron radiation fields on the dose received by glove box radiation workers

    NASA Astrophysics Data System (ADS)

    Crawford, Arthur Bryan

    The effort to estimate the radiation dose received by an occupationally exposed worker is a complex task. Regulatory guidance assumes that the stochastic risks from uniform and non-uniform whole-body irradiations are equal. An ideal uniform irradiation of the whole body would require a broad parallel radiation field of relatively high-energy radiation, which many occupationally exposed workers do not experience. In reality, workers are exposed to a non-uniform irradiation of the whole body such as a radiation field with one or more types of radiation, each with varying energies and/or fluence rates, incident on the worker. Most occupational radiation exposure at LANL is due to neutron radiation. Many of these exposures originate from activities performed in glove boxes with nuclear materials. A standard Los Alamos 2 x 2 x 2 glove box is modeled with the source material being clean weapons grade plutonium. Dosimeter tally planes were modeled to stimulate the various positions that a dosimeter can be worn. An anthropomorphic phantom was used to determine whole body dose. Various geometries of source position and phantom location were used to determine the effects of streaming on the radiation dose a worker may receive. Based on computational and experimental results, the effects of a non-uniform radiation field have on radiation dose received by a worker in a glove box environment are: (1) Dosimeter worn at chest level can overestimate the whole body dose between a factor of two to six depending on location of the phantom with the source material close to the front of the glove box, (2) Dosimeter should be worn at waist level instead of chest level to more accurately reflect the whole body dose received, (3) Dose can be significantly higher for specific locations of the worker relative to the position of the source, (4) On the average the testes contribute almost 44% of the whole body dose for a male, and (5) Appropriate design considerations such as more shielding on the bottom of the glove box and controls such as the use of internal or external shielding can reduce the effects on dose from these non-uniform fields.

  6. Determination of the electromagnetic fields radiated from the ARES EMP simulator

    Microsoft Academic Search

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

    1994-01-01

    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

  7. Quantum field theoretic treatment of pion production via proton synchrotron radiation in strong magnetic fields: Effects of Landau levels

    NASA Astrophysics Data System (ADS)

    Maruyama, Tomoyuki; Cheoun, Myung-Ki; Kajino, Toshitaka; Kwon, Youngshin; Mathews, Grant J.; Ryu, Chung-Yeol

    2015-06-01

    We study pion production from proton synchrotron radiation in the presence of strong magnetic fields by using the exact proton propagator in a strong magnetic field and explicitly including the anomalous magnetic moment. In this exact quantum field approach the magnitude of pion synchrotron emission turns out to be much smaller than that obtained in the semiclassical approach. However, we also find that the anomalous magnetic moment of the proton greatly enhances the production rate about by 2 orders of magnitude.

  8. Radiation reaction in strong fields from an alternative perspective

    E-print Network

    Yevgen Kravets

    2014-08-19

    Current classical theory of radiation reaction has several deficiencies such as "runaway solutions" and violation of causality. The Landau-Lifshitz approximation to the exact equation introduced by Lorentz, Abraham and Dirac is widely used, though questions remain regarding its domain of validity. This thesis explores an alternative treatment of the motion of a radiating electron, based on an equation first proposed by Ford and O'Connell. A general condition is found for solutions of this equation to deviate from those of Landau-Lifshitz. By exploring radiation reaction effects on a particle colliding with an ultra-intense laser pulse we show that the regime where there is a significant deviation of these two approaches can never be reached with existing or proposed laser facilities. The methods used to explore single particle interaction with an intense laser pulse are extended to describe the interaction of a particle bunch with various realistic laser pulses. We find that the interaction leads to a decrease in average momentum and relative momentum spread. However, the decrease appears to be independent of the length of the pulse and depends only on the energy in the pulse regardless of how it is distributed. Radiation reaction effects occuring during the scattering of an electron by a heavy, highly-charged nucleus are studied. Radiation reaction is seen to affect the particle's motion. We find noticeable differences between the predictions of the Ford-O'Connell and Landau-Lifshitz equations, albeit in regimes where quantum effects would be important.

  9. THE SCOTTISH ENCOUNTER WITH TROPICAL DISEASE

    E-print Network

    Schnaufer, Achim

    Timeline 4-5 David Livingstone 6-7 Patrick Manson 8-9 African Trypanosomiasis 10-11 The Scottish Encounter with African Trypanosomiasis 12-13 Leishmaniasis 14-15 The Scottish Encounter with Leishmaniasis 16

  10. Ultraviolet radiation and consumer effects on a field-grown intertidal macroalgal assemblage in Antarctica

    Microsoft Academic Search

    KA T HARINA; Z ACHER; A N G E L A W U L F Fw; CHRISTIAN W IENCKE

    2007-01-01

    Ultraviolet radiation (UVR) research on marine macroalgae has hithero focussed on physiological effects at the organism level, while little is known on the impact of UV radiation on macroalgal assemblages and even less on interactive effects with other community drivers, e.g. consumers. Field experiments on macrobenthos are scarce, particularly in the Antarctic region. Therefore, the effects of UVR and consumers

  11. Low-Cost Shielding to Minimize Radiation Errors of Temperature Sensors in the Field

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The importance of shielding temperature sensors from solar radiation is understood, but there is a lack of prescriptive advice for plant scientists to build inexpensive, effective shields for replicated field experiments. Using general physical principles that govern radiation shielding, a number of...

  12. Particle acceleration and radiation by direct electric fields in flaring complex solar active regions

    E-print Network

    Anastasiadis, Anastasios

    Particle acceleration and radiation by direct electric fields in flaring complex solar active-Meudon, 92195 Meudon Cedex, FRANCE Abstract The acceleration and radiation of solar energetic particles with the existing observations. 1 Introduction The approach used for particle acceleration models proposed for solar

  13. Investigating the Shortwave Radiative Effects of Cloud Field Geometry in the Tropical Western Pacific

    NASA Astrophysics Data System (ADS)

    Foster, M.; Veron, D.

    2007-12-01

    In the last decade numerous advances have been made in parameterizing cloud-radiation interactions. Recent improvements have involved statistical representations of the influence of three-dimensional cloud fields on the domain averaged radiation. A stand-alone comparison of traditional plane-parallel shortwave radiative transfer code against a statistical algorithm and observations is performed using four years of data from the Atmospheric Radiation Measurement Program's Tropical Western Pacific Clouds and Radiation Testbed Site. Statistical cloud properties are derived from observed cloud chord lengths and input into the stochastic model, removing the necessity of explicitly simulating individual cloud fields and allowing for extended model runs. The purpose of the comparison is to identify objectively meteorological situations where 3-dimensional cloud field geometries are radiatively significant such that a statistical approach to radiative transfer, such as the stochastic technique, is more appropriate than the traditional plane-parallel approach. Results suggest that the relationship between vertical extent of liquid cloud and liquid water path is one indicator of radiatively important cloud regimes, as is the relationship between solar zenith angle and cloud fraction. A simple-parameterization based on criteria developed from these results is applied to the plane-parallel model to represent the effect of complex cloud field geometry. The preliminary runs show improvement in the performance of the plane-parallel model when compared to observations.

  14. Reference panel anisotropy and diffuse radiation - some implications for field spectroscopy

    Microsoft Academic Search

    E. M. Rollin; E. J. Milton; D. R. Emery

    2000-01-01

    Field goniometer measurements were obtained to examine the angular variation in the reflectance of direct beam, diffuse and global radiation from two types of Spectralon panel. The results indicate that optical grade (99% reflective) and grey (20% reflective) SpectralonTM exhibit different non-Lambertian properties with respect to direct beam irradiance. The angular variation in the reflectance of diffuse radiation by the

  15. Radiation Characteristics of Guiding Radar System Based on H-Field Leaky Coaxial Cable

    Microsoft Academic Search

    N. Blaunstein; Z. Dank; M. Zilbershtein

    2002-01-01

    In this work we continue the analysis of a radiation pattern of the leaky coaxial cable (LCC). We concentrate on the influence of geometry of braided cable shields and the jacket material on redistribution of field pattern both across and along the LCC system. The main goal of that investigation is to predict the fraction of the power radiated in

  16. Correlated measurements of UHF radar signatures, RF radiation and electric field changes from lightning

    Microsoft Academic Search

    D. M. Levine; V. Mazur

    1983-01-01

    During Storm Hazards - 82, simultaneous measurements are made of radar echoes, fast and slow field changes and RF radiation from lightning. Radio frequency radiation and radar echoes are also obtained during periods when the research aircraft is struck by lightning. These data are presently used to better understand the electrical processes which occur during strikes to the aircraft. Preliminary

  17. Correlated measurements of UHF radar signatures, RF radiation, and electric field changes from lightning

    Microsoft Academic Search

    D. M. Levine; V. Mazur

    1983-01-01

    During Storm Hazards - 82, simultaneous measurements were made of radar echoes, fast and slow field changes and RF radiation from lightning near the Wallops Flight Facility. RF radiation and radar echoes were also obtained during periods when the NASA F106 research aircraft was struck by lightning. These data are presently being used to better understand the electrical processes which

  18. AIP/123-QED Experimental determination of radiated internal wave power without pressure field

    E-print Network

    Texas at Austin. University of

    AIP/123-QED Experimental determination of radiated internal wave power without pressure field data-dimensional internal gravity waves. Both J and P are determined from expressions involving only a scalar function of a stratified fluid past a knife edge. The results for the radiated internal wave power given by the stream

  19. LETTER TO THE EDITOR: Comments on 'Cellular response to modulated radiation fields'

    NASA Astrophysics Data System (ADS)

    Ross, C. K.; Klassen, N. V.

    2009-03-01

    The authors of a recent paper (Claridge Mackonis et al 2007 Phys. Med. Biol. 52 5469-82) measured cell survival in spatially modulated radiation fields. They claim to have identified two new types of radiation-induced bystander effect. We conclude that their claims are not supported by their data.

  20. The Electric Field and Waves Instruments on the Radiation Belt Storm Probes Mission

    E-print Network

    Wygant, J. R.

    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 ...

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

    PubMed

    Ahrens, Jens; Spors, Sascha

    2011-11-01

    An approach to the synthesis of moving virtual sound sources with complex radiation properties in wave field synthesis is presented. The approach exploits the fact that any stationary sound source of finite spatial extent radiates spherical waves at sufficient distance. The angular dependency of the radiation properties of the source under consideration is reflected by the amplitude and phase distribution on the spherical wave fronts. The sound field emitted by a uniformly moving monopole source is derived and the far-field radiation properties of the complex virtual source under consideration are incorporated in order to derive a closed-form expression for the loudspeaker driving signal. The results are illustrated via numerical simulations of the synthesis of the sound field of a sample moving complex virtual source. PMID:22087909

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

    SciTech Connect

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

    2006-04-19

    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.

  3. Cherenkov Radiation in Magnetic Field and its Application for Electron Beam Parameters Measurements

    Microsoft Academic Search

    Yu. A. Bashmakov; V. A. Karpov

    1997-01-01

    The spatial-angular distribution of radiation emitted by ultrarelativistic electron in air in presence of a magnetic field is investigated. The experiments were performed with electron beam extracted from synchrotron \\

  4. THz near-field imaging of biological tissues employing synchrotron radiation

    E-print Network

    Division Biomaterials and Bioengineering, Department of Preventive and Restorative Dental Sciences, University of the synchrotron radiation. The scanning microscope utilizes conical waveguides as near-field probes with apertures

  5. Evaluation of the trade-offs encountered in planning and treating locally advanced head and neck cancer: intensity-modulated radiation therapy vs dual-arc volumetric-modulated arc therapy

    PubMed Central

    Oliver, M; McConnell, D; Romani, M; McAllister, A; Pearce, A; Andronowski, A; Wang, X; Leszczynski, K

    2012-01-01

    Objective The primary purpose of this study was to assess the practical trade-offs between intensity-modulated radiation therapy (IMRT) and dual-arc volumetric-modulated arc therapy (DA-VMAT) for locally advanced head and neck cancer (HNC). Methods For 15 locally advanced HNC data sets, nine-field step-and-shoot IMRT plans and two full-rotation DA-VMAT treatment plans were created in the Pinnacle3 v. 9.0 (Philips Medical Systems, Fitchburg, WI) treatment planning environment and then delivered on a Clinac iX (Varian Medical Systems, Palo Alto, CA) to a cylindrical detector array. The treatment planning goals were organised into four groups based on their importance: (1) spinal cord, brainstem, optical structures; (2) planning target volumes; (3) parotids, mandible, larynx and brachial plexus; and (4) normal tissues. Results Compared with IMRT, DA-VMAT plans were of equal plan quality (p>0.05 for each group), able to be delivered in a shorter time (3.1 min vs 8.3 min, p<0.0001), delivered fewer monitor units (on average 28% fewer, p<0.0001) and produced similar delivery accuracy (p>0.05 at ?2%/2mm and ?3%/3mm). However, the VMAT plans took more planning time (28.9 min vs 7.7 min per cycle, p<0.0001) and required more data for a three-dimensional dose (20 times more, p<0.0001). Conclusions Nine-field step-and-shoot IMRT and DA-VMAT are both capable of meeting the majority of planning goals for locally advanced HNC. The main trade-offs between the techniques are shorter treatment time for DA-VMAT but longer planning time and the additional resources required for implementation of a new technology. Based on this study, our clinic has incorporated DA-VMAT for locally advanced HNC. Advances in knowledge DA-VMAT is a suitable alternative to IMRT for locally advanced HNC. PMID:22806619

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

    Microsoft Academic Search

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

    2011-01-01

    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

  7. Analysis of Radiated Fields for the Design of a RJ45 Connector Using FDTD Method

    Microsoft Academic Search

    Hsing-Yi Chen; Shu-Wei Shiu

    2008-01-01

    The finite-difference time-domain (FDTD) method is successfully used to calculate the electric fields radiated from a prototype of a RJ45 connector for Ethernet transmission. Simulation results of the electric fields radiated from the prototype of this RJ45 connector are validated by measurement data for vertical and horizontal polarizations in 300 ~ 1000 MHz frequency range. It is also found that

  8. Highly efficient generation of THz radiation in semiconductors under magnetic field

    Microsoft Academic Search

    N. Sarukura; H. Ohtake; Z. Liu; S. Izumida; S. Ono

    1999-01-01

    Previously, we have reported the significant enhancement of THz radiation power from InAs under a magnetic field when irradiated with femtosecond optical pulses. In this presentation, we report the spectrum control of this intense THz-radiation by the width of the excitation pulses and magnetic field. A Ti:sapphire laser delivered 100-fsec pulses for the excitation. The sample was non-doped bulk InAs

  9. Business Traveler Satisfaction with Hotel Service Encounters

    Microsoft Academic Search

    Evita Yung; Andrew Chan

    2002-01-01

    This study examines customer satisfaction with a series of hotel services. Five service encounters were examined in a sample of business travelers (n = 140) who had stayed in Hong Kong hotels. Overall satisfaction and repurchase intention were differentially impacted by the various service encounters. Business center encounters had the greatest effect on business traveler satisfaction, followed by check-out and

  10. Knot in Cen A: Stochastic Magnetic Field for Diffusive Synchrotron Radiation?

    E-print Network

    Jirong Mao; Jiancheng Wang

    2007-09-14

    The emission of relativistic electrons moving in the random and small-scale magnetic field is presented by diffusive synchrotron radiation (DSR). In this Letter, we revisit the perturbative treatment of DSR. We propose that random and small-scale magnetic field might be generated by the turbulence. As an example, multi-band radiation of the knot in Cen A comes from the electrons with energy $\\gamma_e\\sim 10^3-10^4$ in the magnetic field of $10^{-3}G$. The multi-band spectrum of DSR is well determined by the feature of stochastic magnetic field. These results put strong constraint to the models of particle acceleration.

  11. Strong-Field Perspective on High-Harmonic Radiation from Bulk Solids

    NASA Astrophysics Data System (ADS)

    Higuchi, Takuya; Stockman, Mark I.; Hommelhoff, Peter

    2014-11-01

    Mechanisms of high-harmonic generation from crystals are described by treating the electric field of a laser as a quasistatic strong field. Under the quasistatic electric field, electrons in periodic potentials form dressed states, known as Wannier-Stark states. The energy differences between the dressed states determine the frequencies of the radiation. The radiation yield is determined by the magnitudes of the interband and intraband current matrix elements between the dressed states. The generation of attosecond pulses from solids is predicted. Ramifications for strong-field physics are discussed.

  12. Effects of External Radiation Fields on Line Emission—Application to Star-forming Regions

    NASA Astrophysics Data System (ADS)

    Chatzikos, Marios; Ferland, G. J.; Williams, R. J. R.; Porter, Ryan; van Hoof, P. A. M.

    2013-12-01

    A variety of astronomical environments contain clouds irradiated by a combination of isotropic and beamed radiation fields. For example, molecular clouds may be irradiated by the isotropic cosmic microwave background, as well as by a nearby active galactic nucleus. These radiation fields excite atoms and molecules and produce emission in different ways. We revisit the escape probability theorem and derive a novel expression that accounts for the presence of external radiation fields. We show that when the field is isotropic the escape probability is reduced relative to that in the absence of external radiation. This is in agreement with previous results obtained under ad hoc assumptions or with the two-level system, but can be applied to complex many-level models of atoms or molecules. This treatment is in the development version of the spectral synthesis code CLOUDY. We examine the spectrum of a Spitzer cloud embedded in the local interstellar radiation field and show that about 60% of its emission lines are sensitive to background subtraction. We argue that this geometric approach could provide an additional tool toward understanding the complex radiation fields of starburst galaxies.

  13. Effects of external radiation fields on line emission—application to star-forming regions

    SciTech Connect

    Chatzikos, Marios; Ferland, G. J. [University of Kentucky, Lexington, KY 40506 (United States); Williams, R. J. R. [AWE plc, Aldermaston, Reading RG7 4PR (United Kingdom); Porter, Ryan [Department of Physics and Astronomy and Center for Simulational Physics, University of Georgia, Athens, GA 30602-2451 (United States); Van Hoof, P. A. M., E-mail: mchatzikos@gmail.com [Royal Observatory of Belgium, Avenue Circulaire 3, B-1180 Uccle (Belgium)

    2013-12-20

    A variety of astronomical environments contain clouds irradiated by a combination of isotropic and beamed radiation fields. For example, molecular clouds may be irradiated by the isotropic cosmic microwave background, as well as by a nearby active galactic nucleus. These radiation fields excite atoms and molecules and produce emission in different ways. We revisit the escape probability theorem and derive a novel expression that accounts for the presence of external radiation fields. We show that when the field is isotropic the escape probability is reduced relative to that in the absence of external radiation. This is in agreement with previous results obtained under ad hoc assumptions or with the two-level system, but can be applied to complex many-level models of atoms or molecules. This treatment is in the development version of the spectral synthesis code CLOUDY. We examine the spectrum of a Spitzer cloud embedded in the local interstellar radiation field and show that about 60% of its emission lines are sensitive to background subtraction. We argue that this geometric approach could provide an additional tool toward understanding the complex radiation fields of starburst galaxies.

  14. Radiation pressure and the linear momentum of the electromagnetic field

    E-print Network

    Mansuripur, Masud

    2013-01-01

    We derive the force of the electromagnetic radiation on material objects by a direct application of the Lorentz law of classical electro-dynamics. The derivation is straightforward in the case of solid metals and solid dielectrics, where the mass density and the optical constants of the media are assumed to remain unchanged under internal and external pressures, and where material flow and deformation can be ignored. For metallic mirrors, we separate the contribution to the radiation pressure of the electrical charge density from that of the current density of the conduction electrons. In the case of dielectric media, we examine the forces experienced by bound charges and currents, and determine the contribution of each to the radiation pressure. These analyses reveal the existence of a lateral radiation pressure inside the dielectric media, one that is exerted at and around the edges of a finite-diameter light beam. The lateral pressure turns out to be compressive for s-polarized light and expansive for p-po...

  15. Radiative Neutron beta-DECAY in Effective Field Theory

    Microsoft Academic Search

    S. Gardner

    2007-01-01

    I consider radiative beta-decay of the neutron in heavy baryon chiral perturbation theory. Nucleon-structure effects not encoded in the weak coupling constants gA and gV enter at the {O} (0.5%)-level, making a sensitive test of the Dirac structure of the weak currents possible.

  16. Optical measurement of acoustic radiation pressure of the near-field acoustic levitation through transparent object

    E-print Network

    Nakamura, Satoshi; Sasao, Yasuhiro; Katsura, Kogure; Naoki, Kondo

    2013-01-01

    It is known that macroscopic objects can be levitated for few to several hundred micrometers by near-field acoustic field and this phenomenon is called near-field acoustic levitation (NFAL). Although there are various experiments conducted to measure integrated acoustic pressure on the object surface, up to now there was no direct method to measure pressure distribution. In this study we measured the acoustic radiation pressure of the near-field acoustic levitation via pressure-sensitive paint.

  17. Basic theory for polarized, astrophysical maser radiation in a magnetic field

    NASA Technical Reports Server (NTRS)

    Watson, William D.

    1994-01-01

    Fundamental alterations in the theory and resulting behavior of polarized, astrophysical maser radiation in the presence of a magnetic field have been asserted based on a calculation of instabilities in the radiative transfer. I reconsider the radiative transfer and find that the relevant instabilities do not occur. Calculational errors in the previous investigation are identified. In addition, such instabilities would have appeared -- but did not -- in the numerous numerical solutions to the same radiative transfer equations that have been presented in the literature. As a result, all modifications that have been presented in a recent series of papers (Elitzur 1991, 1993) to the theory for polarized maser radiation in the presence of a magnetic field are invalid. The basic theory is thus clarified.

  18. LiF:Mg,Ti (MTT) TL Detectors optimised for high-LET radiation dosimetry

    Microsoft Academic Search

    P. Bilski; M. Budzanowski; P. Olko; E. Mandowska

    2004-01-01

    The properties of LiF:Mg,Ti (distributed as, e.g., TLD-100 or MTS-N), the most frequently used thermoluminescent detector, have been optimised for measurements of sparsely ionising radiation (gamma rays), typically encountered in radiation protection or clinical dosimetry. However, these detectors need also to be applied in conditions of mixed-field dosimetry with a high-LET component, such as those encountered in heavy ion beams

  19. Brief encounters: Assembling cosmetic surgery tourism.

    PubMed

    Holliday, Ruth; Bell, David; Cheung, Olive; Jones, Meredith; Probyn, Elspeth

    2015-01-01

    This paper reports findings from a large-scale, multi-disciplinary, mixed methods project which explores empirically and theoretically the rapidly growing but poorly understood (and barely regulated) phenomenon of cosmetic surgery tourism (CST). We explore CST by drawing on theories of flows, networks and assemblages, aiming to produce a fuller and more nuanced account of - and accounting for - CST. This enables us to conceptualise CST as an interplay of places, people, things, ideas and practices. Through specific instances of assembling cosmetic surgery that we encountered in the field, and that we illustrate with material from interviews with patients, facilitators and surgeons, our analysis advances understandings and theorisations of medical mobilities, globalisation and assemblage thinking. PMID:24985788

  20. Synchro-curvature radiation of charged particles in the strong curved magnetic fields

    SciTech Connect

    Kelner, S. R.; Prosekin, A. Yu.; Aharonian, F. A., E-mail: Stanislav.Kelner@mpi-hd.mpg.de, E-mail: Anton.Prosekin@mpi-hd.mpg.de, E-mail: Felix.Aharonian@mpi-hd.mpg.de [Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany)

    2015-01-01

    It is generally believed that the radiation of relativistic particles in a curved magnetic field proceeds in either the synchrotron or the curvature radiation modes. In this paper we show that in strong curved magnetic fields a significant fraction of the energy of relativistic electrons can be radiated away in the intermediate, the so-called synchro-curvature regime. Because of the persistent change of the trajectory curvature, the radiation varies with the frequency of particle gyration. While this effect can be ignored in the synchrotron and curvature regimes, the variability plays a key role in the formation of the synchro-curvature radiation. Using the Hamiltonian formalism, we find that the particle trajectory has the form of a helix wound around the drift trajectory. This allows us to calculate analytically the intensity and energy distribution of prompt radiation in the general case of magnetic bremsstrahlung in the curved magnetic field. We show that the transition to the limit of the synchrotron and curvature radiation regimes is determined by the relation between the drift velocity and the component of the particle velocity perpendicular to the drift trajectory. The detailed numerical calculations, which take into account the energy losses of particles, confirm the principal conclusions based on the simplified analytical treatment of the problem, and allow us to analyze quantitatively the transition between different radiation regimes for a broad range of initial pitch angles. These calculations demonstrate that even very small pitch angles may lead to significant deviations from the spectrum of the standard curvature radiation when it is formally assumed that a charged particle moves strictly along the magnetic line. We argue that in the case of realization of specific configurations of the electric and magnetic fields, the gamma-ray emission of the pulsar magnetospheres can be dominated by the component radiated in the synchro-curvature regime.

  1. The perturbation correction factor of ionisation chambers in beta-radiation fields.

    PubMed

    Böhm, J

    1980-01-01

    In determining the absorbed dose in a solid medium by means of gas-filled ionisation chambers, the perturbation of the radiation field by the chamber needs to be taken into account. So far, an appropriate correction factor has neither been calculated nor measured for beta-radiation. This work describes its experimental determination for an extrapolation chamber and beta-radiation fields of 147Pm, 204Tl, and 90Sr + 90Y. The results show that the correction factor may be assumed to be the product of a shield factor and a scatter factor the magnitudes of which depend on the chamber geometry and the radiation field. The change of the perturbation correction factor with phantom depth is important for the measurement of depth dose curves. This is demonstrated by an example. PMID:7360793

  2. Gamma heating measurements in a mixed radiation field

    SciTech Connect

    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

    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.

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

    SciTech Connect

    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

    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.

  4. Heat flux splitter for near-field thermal radiation

    E-print Network

    Ben-Abdallah, Philippe; Frechette, Luc; Biehs, Svend-Age

    2015-01-01

    We demonstrate the possibility to efficiently split the near-field heat flux exchanged between graphene nano-disks by tuning their doping. This result paves the way for the developement of an active control of propagation directions for heat fluxes exchanged in near-field throughout integrated nanostructures networks.

  5. Field size effect of radiation quality in carbon therapy using passive method.

    PubMed

    Nose, H; Kase, Y; Matsufuji, N; Kanai, T

    2009-03-01

    The authors have investigated the dependency of radiation quality and absorbed dose on radiation field size in therapeutic carbon beams. The field size of the broad beam, formed using the passive technique, was controlled from 20 to 100 mm per side with a multileaf collimator. The absorbed dose and radiation quality on the beam center were evaluated at several depths in a water phantom using microdosimetric technique in experiments and Monte Carlo simulations. With an increase in the field size, the radiation quality was reduced, although the absorbed dose grew at the center of the field. This indicates that the dose and radiation quality at the center of the broad beam are influenced by particles from the off-center region via large-angle scattering and that such particles have relatively low radiation quality and mainly consist of fragment particles. Because such a tendency appeared to be more remarkable in the deeper region of the water phantom, it is likely that fragment particles that are born in a water phantom have a marked role in determining the field size effect. PMID:19378747

  6. Inner-shell photoionization in weak and strong radiation fields

    Microsoft Academic Search

    S. H. Southworth; R. W. Dunford; D. L. Ederer; E. P. Kanter; B. Krässig; L. Young

    2004-01-01

    The X-ray beams presently produced at synchrotron-radiation facilities interact weakly with matter, and the observation of double photoionization is due to electron-electron interactions. The intensities of future X-ray free-electron lasers are expected to produce double photoionization by absorption of two photons. The example of double K-shell photoionization of neon is discussed in the one- and two-photon cases. We also describe

  7. Inner-shell photoionization in weak and strong radiation fields

    Microsoft Academic Search

    S. H. Southworth; R. W. Dunford; D. L. Ederer; E. P. Kanter; B. Krässig; L. Young

    2004-01-01

    The X-ray beams presently produced at synchrotron-radiation facilities interact weakly with matter, and the observation of double photoionization is due to electron–electron interactions. The intensities of future X-ray free-electron lasers are expected to produce double photoionization by absorption of two photons. The example of double K-shell photoionization of neon is discussed in the one- and two-photon cases. We also describe

  8. Radiative neutron beta-decay in effective field theory

    Microsoft Academic Search

    Véronique Bernard; Susan Gardner; Ulf-G. Meißner; Chi Zhang

    2004-01-01

    We consider radiative beta-decay of the neutron in heavy baryon chiral perturbation theory, with an extension including explicit Delta degrees of freedom. We compute the photon energy spectrum as well as the photon polarization; both observables are dominated by the electron bremsstrahlung contribution. Nucleon-structure effects not encoded in the weak coupling constants gA and gV are determined at next-to-leading order

  9. Large Current Radiators

    Microsoft Academic Search

    G. P. Pochanin

    2006-01-01

    The work is devoted to investigations aiming at developing special type of radiating antennas which are known as Harmuth's large current radiator. Physical and technical problems encountered when radiators designed and ways for their overcoming are discussed

  10. The radiation field characteristics of piezoelectric polymer membrane transducers when operating into air

    Microsoft Academic Search

    Gordon Hayward; Graham Benny; R. Banks; W. Galbraith

    2000-01-01

    This paper describes the evaluation of the radiation field characteristics of PVDF membrane transducers, whereby the active area is defined by an appropriate electrode pattern when operating into air. Measurement, including conventional scanning of the fields and laser vibrometry, is supplemented by finite element modeling over the frequency range 500 kHz to 1.1 MHz. Contrary to expectation, the surface displacements

  11. Effect of external magnetic fields and resonance radiofrequency radiation on radical reactions

    NASA Astrophysics Data System (ADS)

    Molin, Yu. N.; Anisimov, O. A.; Koptyug, A. V.; Saik, V. O.; Antzutkin, O. N.

    1990-06-01

    It is well known that an external magnetic field can affect the rate of singlet-triplet transitions in a radical pair and hence its recombination probability in liquid. Resonance radiofrequency (RF) radiation induces quantum beats in the kinetics of radical pair recombination. At high RF field amplitudes the singlet-triplet transitions in radical pairs can be efficiently suppressed.

  12. Sub-THz Beam-forming using Near-field Coupling of Distributed Active Radiator Arrays

    E-print Network

    Hajimiri, Ali

    Sub-THz Beam-forming using Near-field Coupling of Distributed Active Radiator Arrays Kaushik of beam-forming at sub-THz frequencies in CMOS. Near-field coupling is shown to be a scalable method and industrial safety. However, generation of high enough THz power in silicon has been a major bottleneck

  13. Developing Si(Li) nuclear radiation detectors by pulsed electric field treatment

    Microsoft Academic Search

    R. A. Muminov; S. A. Radzhapov; A. K. Saimbetov

    2009-01-01

    Fabrication of Si(Li) nuclear radiation detectors using lithium ion drift under the action of a pulsed electric field is considered. Optimum treatment regime parameters are determined, including the pulse amplitude, duration, and repetition rate. Experimental data are presented, which show that the ion drift in a pulsed electric field decreases the semiconductor bulk compensation time by a factor of two

  14. Measurement of temperature field in the region near to the radiator by using digital holography

    Microsoft Academic Search

    Yan Li; Dayong Wang; Guangjun Wang; Yizhuo Zhang; Changgeng Liu

    2009-01-01

    A simple method for measurement of temperature field in the region near to the metal plate of the radiator is demonstrated by using digital holography in the Lensless Fourier transform configuration (LFT). The temperature is measured within the boundary layer of the convective flow field. The deviation of the temperature produced by this method, from that obtained by the thermocouple

  15. Line Element for a Radiating Electron in a Generally Covariant Unified Field Theory

    Microsoft Academic Search

    Myron W. Evans

    A method is given to determine the four-dimensional line element for a radi- ating electron in a generally covariant unified field theory. The radiating elec- tron is described classically as an object of finite volume and mass, carrying the electron charge ?e. Starting from the most general line element in four dimensions and curvilinear coordinates, the Einstein Hilbert field equation

  16. Far-field analysis of fluctuating supermodes radiated from phase-locked array lasers

    Microsoft Academic Search

    Hiroyuki Yoshimura; Nobukatsu Takai; Toshimitsu Asakura

    1994-01-01

    The effects of fluctuations of the supermodes radiated from the phased-locked array lasers on the far field are theoretically analyzed on the basis of coherence theory. As a result, the far-field patterns are deformed, with increases in the parameters proportional to the integrated intensity fluctuations and the spatial correlation length of fluctuations of the supermodes. However, the effect of fluctuations

  17. Fan Noise Prediction System Development: Source/Radiation Field Coupling and Workstation Conversion for the Acoustic Radiation Code

    NASA Technical Reports Server (NTRS)

    Meyer, H. D.

    1993-01-01

    The Acoustic Radiation Code (ARC) is a finite element program used on the IBM mainframe to predict far-field acoustic radiation from a turbofan engine inlet. In this report, requirements for developers of internal aerodynamic codes regarding use of their program output an input for the ARC are discussed. More specifically, the particular input needed from the Bolt, Beranek and Newman/Pratt and Whitney (turbofan source noise generation) Code (BBN/PWC) is described. In a separate analysis, a method of coupling the source and radiation models, that recognizes waves crossing the interface in both directions, has been derived. A preliminary version of the coupled code has been developed and used for initial evaluation of coupling issues. Results thus far have shown that reflection from the inlet is sufficient to indicate that full coupling of the source and radiation fields is needed for accurate noise predictions ' Also, for this contract, the ARC has been modified for use on the Sun and Silicon Graphics Iris UNIX workstations. Changes and additions involved in this effort are described in an appendix.

  18. Scattering theory of multilevel atoms interacting with arbitrary radiation fields

    E-print Network

    Xuereb, André; Horak, Peter; Freegarde, Tim

    2009-01-01

    We present a generic transfer matrix approach for the description of the interaction of atoms possessing multiple ground state and excited state sublevels with light fields. This model allows us to treat multi-level atoms as classical scatterers in light fields modified by, in principle, arbitrarily complex optical components such as mirrors, resonators, dispersive or dichroic elements, or filters. We verify our formalism for two prototypical sub-Doppler cooling mechanisms and show that it agrees with the standard literature.

  19. Scattering theory of multilevel atoms interacting with arbitrary radiation fields

    E-print Network

    André Xuereb; Peter Domokos; Peter Horak; Tim Freegarde

    2009-10-05

    We present a generic transfer matrix approach for the description of the interaction of atoms possessing multiple ground state and excited state sublevels with light fields. This model allows us to treat multi-level atoms as classical scatterers in light fields modified by, in principle, arbitrarily complex optical components such as mirrors, resonators, dispersive or dichroic elements, or filters. We verify our formalism for two prototypical sub-Doppler cooling mechanisms and show that it agrees with the standard literature.

  20. Prediction of Radiated Emissions Using Near-Field Measurements

    Microsoft Academic Search

    Haixiao Weng; Daryl G. Beetner; Richard E. DuBroff

    2011-01-01

    A procedure is developed to predict electromagnetic interference from electronic products using near-field scan data. Measured near-field data are used to define equivalent electric and magnetic current sources characterizing the electromagnetic emis- sions from an electronic circuit. Reconciliation of the equivalent sources is performed to allow the sources to be accurately applied within full-wave numerical modeling tools like finite-difference time

  1. Simulation of Relativistic Shocks and Associated Radiation from Turbulent Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Mizuno, Y.; Niemiec, J.; Medvedev, M.; Zhang, B.; Hardee, P.; Frederiksen, J.; Sol, H.; Pohl, M.; Hartmann, D. H.; Fishman, G. J.

    2010-01-01

    Recent PIC simulations of relativistic electron-positron (electron-ion) jets injected into a stationary medium show that particle acceleration occurs at shocked regions. Simulations show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields and particle acceleration. These magnetic fields contribute to the electron's transverse deflection behind the shock. The jitter'' radiation from deflected electrons in turbulent magnetic fields has different properties than synchrotron radiation, which is calculated in a uniform magnetic field. This jitter radiation may be important for understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets in general, and supernova remnants. We will present detailed spectra for conditions relevant of various astrophysical sites of shock formation via the Weibel instability. In particular we will discuss the application to GRBs and SNRs

  2. Direct radiation from a strong dc electric field. [Related to solar millisecond radio bursts

    SciTech Connect

    Wentzel, D.G. (Maryland, University, College Park (USA))

    1991-05-01

    Simulations have shown that a strong dc electric field yields, after electrostatic transients, a beam of electrons that is nearly flat in velocity distribution yet emits strong electrostatic and electromagnetic waves. Electric energy is converted 'directly' into radiation. This radiation is derived analytically in order to learn how the radiation may depend on field strength and beam density in astronomical objects. Any wave with a significant electric component along the dc electric field grows exponentially in time, with the growth rate proportional to the number of electrons in the beam. The lower limits on the dc electric field and the beam density are set by competing plasma processes. The results are related to solar millisecond radio bursts. 7 refs.

  3. Radiative neutron beta-decay in effective field theory

    E-print Network

    V. Bernard; S. Gardner; U. -G. Meißner; C. Zhang

    2004-04-28

    We consider radiative \\beta--decay of the neutron in heavy baryon chiral perturbation theory, with an extension including explicit \\Delta degrees of freedom. We compute the photon energy spectrum as well as the photon polarization; both observables are dominated by the electron bremsstrahlung contribution. Nucleon-structure effects not encoded in the weak coupling constants g_A and g_V are determined at next-to-leading order in the chiral expansion, and enter at the {\\cal O}(0.5%)-level, making a sensitive test of the Dirac structure of the weak currents possible.

  4. Radiative neutron beta-decay in effective field theory

    Microsoft Academic Search

    Veronique Bernard; Susan Gardner; U.-G. Meißner; C. Zhang

    2004-01-01

    We consider radiative \\\\beta--decay of the neutron in heavy baryon chiral\\u000aperturbation theory, with an extension including explicit \\\\Delta degrees of\\u000afreedom. We compute the photon energy spectrum as well as the photon\\u000apolarization; both observables are dominated by the electron bremsstrahlung\\u000acontribution. Nucleon-structure effects not encoded in the weak coupling\\u000aconstants g_A and g_V are determined at next-to-leading order

  5. Traffic encounters and Hocman: Associating motorcycle ethnography with design

    Microsoft Academic Search

    Mattias Esbjörnsson; Oskar Juhlin; Mattias Östergren

    2004-01-01

    Brief encounters between acquainted and unacquainted motorcyclists are enjoyable moments. This truly mobile form of social interaction is difficult to study through traditional ethnographic fieldwork. However, the method is applicable when integrated in a design approach where the participants collaborate to integrate the field study, the design and the evaluation. This has made it possible to generate a novel mobile

  6. The thermalization process of an atom with the thermal radiation field

    NASA Astrophysics Data System (ADS)

    Flores-Hidalgo, G.

    2007-11-01

    We study the time evolution of an atom suddenly coupled to a thermal radiation field. As a simplified model of the atom-electromagnetic field system we use a system composed of a harmonic oscillator linearly coupled to a scalar field in the framework of the recently introduced dressed coordinates and dressed states. We show that the time evolution of the thermal expectation values for the occupation number operators depends exclusively on the probabilities associated with the emission and absorption of field quanta. In particular, the time evolution of the number operator associated with the atom is given in terms of the probability of remaining in the first excited state and the decay probabilities from this state by emission of field quanta of frequencies ?k. Also, it is shown that independent of the initial state of the atom, it thermalizes with the thermal radiation field in a time scale of the order of the inverse coupling constant.

  7. Radiation from relativistic jets in turbulent magnetic fields

    SciTech Connect

    Nishikawa, K.-I.; Mizuno, Y. [National Space Science and Technology Center, Huntsville, AL 35805 (United States); Medvedev, M. [Department of Physics and Astronomy, University of Kansas, KS 66045 (United States); Zhang, B. [Department of Physics, University of Nevada, Las Vegas, NV 89154 (United States); Hardee, P. [Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL 35487 (United States); Niemiec, J. [Institute of Nuclear Physics PAN, ul. Radzikowskiego 152, 31-342 Krakow (Poland); Nordlund, A.; Frederiksen, J. [Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Oe (Denmark); Sol, H. [LUTH, Observatore de Paris-Meudon, 5 place Jules Jansen, 92195 Meudon Cedex (France); Fishman, G. J. [NASA/MSFC, Huntsville, AL 35805 (United States)

    2009-05-25

    Using our new 3-D relativistic electromagnetic particle (REMP) code parallelized with MPI, we have investigated long-term particle acceleration associated with an relativistic electron-positron jet propagating in an unmagnetized ambient electron-positron plasma. The simulations have been performed using a much longer simulation system than our previous simulations in order to investigate the full nonlinear stage of the Weibel instability and its particle acceleration mechanism. Cold jet electrons are thermalized and ambient electrons are accelerated in the resulting shocks. The acceleration of ambient electrons leads to a maximum ambient electron density three times larger than the original value. Behind the bow shock in the jet shock strong electromagnetic fields are generated. These fields may lead to the afterglow emission. We have calculated the time evolution of the spectrum from two electrons propagating in a uniform parallel magnetic field to verify the technique.

  8. Radiation from Relativistic Jets in Turbulent Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Mizuno, Y.; Medvedev, M.; Zhang, B.; Hardee, P.; Niemiec, J.; Nordlund, A.; Frederiksen, J.; Mizuno, Y.; Sol, H.; Fishman, G. J.

    2008-01-01

    Using our new 3-D relativistic electromagnetic particle (REMP) code parallelized with MPI, we have investigated long-term particle acceleration associated with an relativistic electron-positron jet propagating in an unmagnetized ambient electron-positron plasma. The simulations have been performed using a much longer simulation system than our previous simulations in order to investigate the full nonlinear stage of the Weibel instability and its particle acceleration mechanism. Cold jet electrons are thermalized and ambient electrons are accelerated in the resulting shocks. The acceleration of ambient electrons leads to a maximum ambient electron density three times larger than the original value. Behind the bow shock in the jet shock strong electromagnetic fields are generated. These fields may lead to the afterglow emission. We have calculated the time evolution of the spectrum from two electrons propagating in a uniform parallel magnetic field to verify the technique.

  9. Cherenkov Radiation Induced by Cosmogenic Neutrinos in Near-Field

    NASA Astrophysics Data System (ADS)

    Hu, Chia-Yu; Chen, Chih-Ching; Chen, Pisin

    2013-12-01

    The radio technique of cosmogenic neutrino detection, which relies on the Cherenkov signals coherently emitted from the particle showers in dense medium, has now become a mature field. We present an alternative approach to calculate such Cherenkov pulse by a numerical code based on the finite difference time-domain (FDTD) method that does not rely on the far-field approximation. We show that for a shower elongated by the LPM (Landau-Pomeranchuk-Migdal) effect and thus with a multi-peak structure, the generated Cherenkov signal will always be a bipolar and asymmetric waveform in the near-field regime regardless of the specific variations of the multi-peak structure, which makes it a generic and distinctive feature. This should provide an important characteristic signature for the identification of ultra-high energy cosmogenic neutrinos.

  10. Atomic radiative corrections without QED: role of the zero-point field

    E-print Network

    Ana María Cetto; Luis de la Peña; Andrea Valdés-Hernández

    2013-01-26

    We derive the atomic radiative corrections predicted by QED using an alternative approach that offers the advantage of physical clarity and transparency. The element that gives rise to these corrections is the fluctuating zero-point radiation field (ZPF) of average energy (hbar \\omega)/2 per mode, which - in contrast with QED - is taken here as a primordial real entity in permanent interaction with matter and responsible for its quantization. After briefly recalling how quantum mechanics itself emerges as a result of the balance between the ZPF and radiation reaction, the most important higher-order effects of the radiative terms on the atom are studied. The nonrelativistic QED formulas for the lifetimes and the Lamb shift, as well as the corrections to the latter due to external factors that modify the vacuum field, are thus obtained in a self-consistent approach and without the need to resort to second quantization to the present order of approximation.

  11. Influence of Preoperative Radiation Field on Postoperative Leak Rates in Esophageal Cancer Patients after Trimodality Therapy

    PubMed Central

    Juloori, Aditya; Tucker, Susan L.; Komaki, Ritsuko; Liao, Zhongxing; Correa, Arlene M.; Swisher, Stephen G.; Hofstetter, Wayne L.; Lin, Steven H.

    2014-01-01

    Introduction Postoperative morbidities, such as anastomotic leaks, are common after trimodality therapy (chemoradiation followed by surgery) for esophageal cancer. We investigated for factors associated with an increased incidence of anastomotic leaks. Methods Data from 285 esophageal cancer patients treated from 2000–2011 with trimodality therapy was analyzed. Anastomotic location relative to preoperative radiation field was assessed using postoperative computed tomographic imaging. Logistic regression was used to evaluate for factors associated with any or clinically relevant (CR) (? grade 2) leaks. Results Overall anastomotic leak rate was 11% (31/285), and CR leak rate was 6% (17/285). Multivariable analysis identified body mass index (BMI) (OR 1.09, 95%CI 1.00–1.17; OR 1.11, 95%CI 1.01–1.22), three-field surgery (OR 10.01, 95%CI 3.83–26.21; OR 4.83, 95%CI 1.39–16.71), and within radiation field (“in-field”) anastomosis (OR 5.37, 95%CI 2.21–13.04; OR 8.63, 95%CI 2.90–25.65) as independent predictors of both all grade and CR leaks, respectively. While patients with distal esophageal tumors and Ivor-Lewis surgery had the lowest incidence of all grade (6.5%) and CR leaks (4.2%), most of the leaks were associated with the anastomosis constructed within the field of radiation (in-field: 39% and 30% versus out-of-field: 2.6% and 1.0%, respectively, for total and CR leaks, p<0.0001, Fisher’s Exact test). Conclusions Esophagogastric anastomosis placed within the preoperative radiation field was a very strong predictor for anastomotic leaks in esophageal cancer patients treated with trimodality therapy, among other factors. Surgical planning should include a critical evaluation of the preoperative radiation fields to ensure proper anastomotic placement after chemoradiation therapy. PMID:24736077

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

    SciTech Connect

    Kurkin, S. A.; Hramov, A. E.; Koronovskii, A. A. [Saratov State University, Astrakhanskaja 83, Saratov 410012 (Russian Federation) [Saratov State University, Astrakhanskaja 83, Saratov 410012 (Russian Federation); Saratov State Technical University, Politechnicheskaja 77, Saratov 410028 (Russian Federation)

    2013-07-22

    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.

  13. Personal Radiation Detector Field Test and Evaluation Campaign

    SciTech Connect

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

    2007-07-09

    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.

  14. Electromagnetic field measurement method to generate radiation map

    Microsoft Academic Search

    Cesar Camilo Rodriguez; Celso Andres Forero; Homero Ortega Boada

    2012-01-01

    An electromagnetic field monitoring method is proposed and tested during measurement campaigns at urban zone of Bucaramanga city, Colombia. Communication tools are used integrated with a Geographic Information System, an online server and the access to data base by means of web services. A set of measuring equipment is connected to the communication system in order to manage a great

  15. Accelerated Detector - Quantum Field Correlations: From Vacuum Fluctuations to Radiation Flux

    E-print Network

    Shih-Yuin Lin; B. L. Hu

    2006-06-21

    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.

  16. A supplemental ultraviolet-B radiation system for open-top field chambers

    Microsoft Academic Search

    F. L. Booker; E. L. Fiscus; R. B. Philbeck; A. S. Heagle; J. E. Miller; W. W. Heck

    2009-01-01

    To assess the combined effects on plants of increased UV-B radiation and chronic exposure to Oâ, a commonly used constant-addition supplemental UV-B radiation system was modified for use in open-top field chambers. Lamp banks containing 14 filtered UV-B-313 fluorescent lamps were suspended in 33 chambers to which either charcoal-filtered, nonfiltered, or nonfiltered air plus Oâ was added. Lamp banks provided

  17. Radiated Emissions and Magnetic Field Characterization of a 2kW Electrothermal Propulsion System

    Microsoft Academic Search

    Alexander L. Bogorad; Justin J. Likar; Matthew P. Deeter; Kevin A. August; Graham P. Doorley; Roman Herschitz

    2008-01-01

    Earth-orbiting spacecraft that include increasingly sensitive telecommunications, Earth-observing\\/sensing, and\\/or scientific instrument payloads often utilize electric propulsion systems. Such systems can generate high levels of radiated and conducted electromagnetic interference (EMI) making the accurate characterization of propulsion system EMI critical to spacecraft design. Radiated emissions and magnetic field measurements were performed on a 2-kW hydrazine arcjet electrothermal propulsion engine at the

  18. Exposure to extremely-low-frequency electromagnetic fields and radiofrequency radiation: cardiovascular effects in humans

    Microsoft Academic Search

    James R. Jauchem

    1997-01-01

    Cardiovascular changes in humans exposed to nonionizing radiation [including extremely-low-frequency electromagnetic fields\\u000a (ELF EMFs) and radiofrequency radiation (RFR)] are reviewed. Both acute and long-term effects have been investigated. In general,\\u000a if heating does not occur during exposure, current flow appears to be necessary for major cardiovascular effects to ensue,\\u000a such as those due to electric shock. Whereas most studies have

  19. Contribution of backscattering to radiation fields in the Source Projector Facility

    Microsoft Academic Search

    E. Marshall; K. Vaziri; F. Krueger; D. Cossairt

    1996-01-01

    The Radiation Physics Source Projection Facility at Fermilab employs three collimated ¹³⁷Cs sources for different calibration purposes. This facility is used to calibrate many of the instruments used at Fermilab to measure both prompt and residual radiation fields due to accelerator operations. A study was done using three air ion chambers (2.5 ml, 80 ml, and 1000 ml) to measure

  20. Near-field thermal radiation between doped silicon plates at nanoscale gaps

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    Radiative heat transfer can be significantly enhanced via photon tunneling through a nanometer-scale gap to the point that it exceeds the blackbody limit. Here we report quantitative measurements of the near-field thermal radiation between doped-Si plates (width=480 ? m and length=1.34 cm ). A novel MEMS-based platform enables us to maintain doped-Si plates at nanoscale gap distances that cannot be achieved by other methods. The measured radiative heat transfer coefficient was found to be 2.91 times greater than the blackbody limit at a 400-nm vacuum gap.

  1. Particle beams in ultrastrong laser fields: direct laser acceleration and radiation reaction effects

    NASA Astrophysics Data System (ADS)

    Salamin, Yousef I.; Li, Jian-Xing; Hatsagortsyan, Karen Z.; Tamburini, Matteo; Di Piazza, Antonino; Keitel, Christoph H.

    2015-03-01

    Several aspects of the interaction of particle beams with ultrastrong laser fields are discussed. Firstly, we consider regimes when radiation reaction is not essential and it is demonstrated that employing chirped laser pulses, significant improvement of the direct acceleration of particles can be achieved. Results from single- and many-particle calculations of the particle acceleration, in vacuum, by plane-wave fields, as well as in tightly-focused laser beams, show that the mean energies and their spreads qualify them for important applications. Secondly, we investigate the effect of radiation reaction in electron-laser-beam interactions. Signatures of the quantum radiation reaction during the interaction of an electron bunch with a focused superstrong ultrashort laser pulse can be observed in a characteristic behavior of the spectral bandwidth, and the angular spread of the nonlinear Compton radiation on the laser pulse duration. Furthermore, it is shown that the radiation reaction effects can be employed to control the electron dynamics via the nonlinear interplay between the Lorentz and radiation reaction forces. In particular, it is shown that an ultrarelativistic electron bunch colliding head- on with a strong bichromatic laser pulse can be deflected in a controllable way, by changing either the relative phase or the relative amplitude between the two frequency components of the bichromatic field.

  2. Radiation magnetohydrodynamic simulation of plasma formed on a surface by a megagauss field.

    PubMed

    Esaulov, A A; Bauer, B S; Makhin, V; Siemon, R E; Lindemuth, I R; Awe, T J; Reinovsky, R E; Struve, K W; Desjarlais, M P; Mehlhorn, T A

    2008-03-01

    Radiation magnetohydrodynamic modeling is used to study the plasma formed on the surface of a cylindrical metallic load, driven by megagauss magnetic field at the 1MA Zebra generator (University of Nevada, Reno). An ionized aluminum plasma is used to represent the "core-corona" behavior in which a heterogeneous Z-pinch consists of a hot low-density corona surrounding a dense low-temperature core. The radiation dynamics model included simultaneously a self-consistent treatment of both the opaque and transparent plasma regions in a corona. For the parameters of this experiment, the boundary of the opaque plasma region emits the major radiation power with Planckian black-body spectrum in the extreme ultraviolet corresponding to an equilibrium temperature of 16 eV. The radiation heat transport significantly exceeds the electron and ion kinetic heat transport in the outer layers of the opaque plasma. Electromagnetic field energy is partly radiated (13%) and partly deposited into inner corona and core regions (87%). Surface temperature estimates are sensitive to the radiation effects, but the surface motion in response to pressure and magnetic forces is not. The general results of the present investigation are applicable to the liner compression experiments at multi-MA long-pulse current accelerators such as Atlas and Shiva Star. Also the radiation magnetohydrodynamic model discussed in the paper may be useful for understanding key effects of wire array implosion dynamics. PMID:18517530

  3. Simulation studies of wide and medium field of view earth radiation data analysis

    NASA Technical Reports Server (NTRS)

    Green, R. N.

    1978-01-01

    A parameter estimation technique is presented to estimate the radiative flux distribution over the earth from radiometer measurements at satellite altitude. The technique analyzes measurements from a wide field of view (WFOV), horizon to horizon, nadir pointing sensor with a mathematical technique to derive the radiative flux estimates at the top of the atmosphere for resolution elements smaller than the sensor field of view. A computer simulation of the data analysis technique is presented for both earth-emitted and reflected radiation. Zonal resolutions are considered as well as the global integration of plane flux. An estimate of the equator-to-pole gradient is obtained from the zonal estimates. Sensitivity studies of the derived flux distribution to directional model errors are also presented. In addition to the WFOV results, medium field of view results are presented.

  4. Radiation of a nonrelativistic particle during its finite motion in a central field

    SciTech Connect

    Karnakov, B. M., E-mail: karnak@theor.mephi.ru; Korneev, Ph. A., E-mail: korneev@theor.mephi.ru; Popruzhenko, S. V. [Moscow Institute of Engineering Physics (State University) (Russian Federation)

    2008-04-15

    The spectrum and expressions for the intensity of dipole radiation lines are obtained for a classical nonrelativistic charged particle that executes a finite aperiodic motion in an arbitrary central field along a non-closed trajectory. It is shown that, in this case of a conditionally periodic motion, the radiaton spectrum consists of two series of equally spaced lines. It is pointed out that, according to the correspondence principle, the rise of two such series in the classical theory corresponds to the well-known selection rule |{delta}l = 1 for the dipole radiation in a central field in quantum theory, where l is the orbital angular momentum of the particle. The results obtained can be applied to the description of the radiation and the absorption of a classical collisionless electron plasma in nanoparticles irradiated by an intense laser field. As an example, the rate of collisionless absorption of electromagnetic wave energy in equilibrium isotropic nanoplasma is calculated.

  5. Radiation reaction and gravitational waves in the effective field theory approach

    E-print Network

    Chad R. Galley; Manuel Tiglio

    2009-03-05

    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.

  6. Gravitational radiation generated by cosmological phase transition magnetic fields

    SciTech Connect

    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

    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.

  7. Passive Lossless Huygens Metasurfaces for Conversion of Arbitrary Source Field to Directive Radiation

    E-print Network

    Epstein, Ariel

    2014-01-01

    We present a semi-analytical formulation of the interaction between a given source field and a scalar Huygens metasurface (HMS), a recently introduced promising concept for wavefront manipulation based on a sheet of orthogonal electric and magnetic dipoles. Utilizing the equivalent surface impedance representation of these metasurfaces, we establish that an arbitrary source field can be converted into directive radiation via a passive lossless HMS if two physical conditions are met: local power conservation and local impedance equalization. Expressing the fields via their plane-wave spectrum and harnessing the slowly-varying envelope approximation we obtain semi-analytical formulae for the scattered fields, and prescribe the surface reactance required for the metasurface implementation. The resultant design procedure indicates that the local impedance equalization induces a Fresnel-like reflection, while local power conservation forms a radiating virtual aperture which follows the total excitation field magni...

  8. On the magnetic field signal radiated by an atmospheric pressure room temperature plasma jet

    SciTech Connect

    Wu, S.; Huang, Q.; Wang, Z.; Lu, X. [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)

    2013-01-28

    In this paper, the magnetic field signal radiated from an atmospheric pressure room temperature plasma plume is measured. It's found that the magnetic field signal has similar waveform as the current carried by the plasma plume. By calibration of the magnetic field signal, the plasma plume current is obtained by measuring the magnetic field signal radiated by the plasma plume. In addition, it is found that, when gas flow modes changes from laminar regime to turbulence regime, the magnetic field signal waveforms appears different, it changes from a smooth curve to a curve with multiple spikes. Furthermore, it is confirmed that the plasma plume generated by a single electrode (without ground electrode) plasma jet device carries higher current than that with ground electrode.

  9. High-resolution optical telescope for ultraviolet \\/UV\\/ radiation field

    Microsoft Academic Search

    W. W. Karayan

    1979-01-01

    Design techniques are discussed for all-reflecting optics from first-order system considerations and applications currently utilized in the field of astronomical optics. The solution of the Dall-Karkham design problem is described, showing the advantage of inexpensive construction as compared with higher order surfaces. The design process reported here is a F\\/5 collecting system which quickly mates directly with the spectrometer; it

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

    NASA Astrophysics Data System (ADS)

    Wang, Chunsheng; Liu, Hui; Li, Xueai; Jiang, Binhao

    2015-06-01

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

  11. Magnetized Kelvin-Helmholtz instability in the presence of a radiation field

    NASA Astrophysics Data System (ADS)

    Shadmehri, Mohsen; Enayati, Zahra; Khajavi, Mahdi

    2012-10-01

    The purpose of this study is to analyze the dynamical role of a radiation field on the growth rate of the unstable Kelvin-Helmholtz (KH) perturbations. As a first step toward this purpose, the analyze is done in a general way, irrespective of applying the model to a specific astronomical system. The transition zone between the two layers of the fluid is ignored. Then, we perform a linear analysis and by imposing suitable boundary conditions and considering a radiation field, we obtain appropriate dispersion relation. Unstable modes are studied by solving the dispersion equation numerically, and then growth rates of them are obtained. By analyzing our dispersion relation, we show that for a wide range of the input parameters, the radiation field has a destabilizing effect on KH instability. In eruptions of the galaxies or supermassive stars, the radiation field is dynamically important and because of the enhanced KH growth rates in the presence of the radiation; these eruptions can inject more momentum and energy into their environment and excite more turbulent motions.

  12. Radiation drag in the field of a non-spherical source

    NASA Astrophysics Data System (ADS)

    Bini, D.; Geralico, A.; Passamonti, A.

    2015-01-01

    The motion of a test particle in the gravitational field of a non-spherical source endowed with both mass and mass quadrupole moment is investigated when a test radiation field is also present. The background is described by the Erez-Rosen solution, which is a static space-time belonging to the Weyl class of solutions to the vacuum Einstein's field equations, and reduces to the familiar Schwarzschild solution when the quadrupole parameter vanishes. The radiation flux has a fixed but arbitrary (non-zero) angular momentum. The interaction with the radiation field is assumed to be Thomson-like, i.e. the particles absorb and re-emit radiation, thus suffering for a friction-like drag force. Such an additional force is responsible for the Poynting-Robertson effect, which is well established in the framework of Newtonian gravity and has been recently extended to the general theory of relativity. The balance between gravitational attraction, centrifugal force and radiation drag leads to the occurrence of equilibrium circular orbits which are attractors for the surrounding matter for every fixed value of the interaction strength. The presence of the quadrupolar structure of the source introduces a further degree of freedom: there exists a whole family of equilibrium orbits parametrized by the quadrupole parameter, generalizing previous works. This scenario is expected to play a role in the context of accretion matter around compact objects.

  13. Field size dependent mapping of medical linear accelerator radiation leakage.

    PubMed

    Bezin, Jérémi V?; Veres, Attila; Lefkopoulos, Dimitri; Chavaudra, Jean; Deutsch, Eric; de Vathaire, Florent; Diallo, Ibrahima

    2015-03-01

    The purpose of this study was to investigate the suitability of a graphics library based model for the assessment of linear accelerator radiation leakage. Transmission through the shielding elements was evaluated using the build-up factor corrected exponential attenuation law and the contribution from the electron guide was estimated using the approximation of a linear isotropic radioactive source. Model parameters were estimated by a fitting series of thermoluminescent dosimeter leakage measurements, achieved up to 100 cm from the beam central axis along three directions. The distribution of leakage data at the patient plane reflected the architecture of the shielding elements. Thus, the maximum leakage dose was found under the collimator when only one jaw shielded the primary beam and was about 0.08% of the dose at isocentre. Overall, we observe that the main contributor to leakage dose according to our model was the electron beam guide. Concerning the discrepancies between the measurements used to calibrate the model and the calculations from the model, the average difference was about 7%. Finally, graphics library modelling is a readily and suitable way to estimate leakage dose distribution on a personal computer. Such data could be useful for dosimetric evaluations in late effect studies. PMID:25675153

  14. Field size dependent mapping of medical linear accelerator radiation leakage

    NASA Astrophysics Data System (ADS)

    V? Bezin, Jérémi; Veres, Attila; Lefkopoulos, Dimitri; Chavaudra, Jean; Deutsch, Eric; de Vathaire, Florent; Diallo, Ibrahima

    2015-03-01

    The purpose of this study was to investigate the suitability of a graphics library based model for the assessment of linear accelerator radiation leakage. Transmission through the shielding elements was evaluated using the build-up factor corrected exponential attenuation law and the contribution from the electron guide was estimated using the approximation of a linear isotropic radioactive source. Model parameters were estimated by a fitting series of thermoluminescent dosimeter leakage measurements, achieved up to 100?cm from the beam central axis along three directions. The distribution of leakage data at the patient plane reflected the architecture of the shielding elements. Thus, the maximum leakage dose was found under the collimator when only one jaw shielded the primary beam and was about 0.08% of the dose at isocentre. Overall, we observe that the main contributor to leakage dose according to our model was the electron beam guide. Concerning the discrepancies between the measurements used to calibrate the model and the calculations from the model, the average difference was about 7%. Finally, graphics library modelling is a readily and suitable way to estimate leakage dose distribution on a personal computer. Such data could be useful for dosimetric evaluations in late effect studies.

  15. Radiative multipole moments of integer-spin fields in curved spacetime

    NASA Astrophysics Data System (ADS)

    Leonard, Stephen W.; Poisson, Eric

    1997-10-01

    Radiative multipole moments of scalar, electromagnetic, and linearized gravitational fields in Schwarzschild spacetime are computed to third order in v in a weak-field, slow-motion approximation, where v is a characteristic velocity associated with the motion of the source. These moments are defined for all three types of radiation by relations of the form ?(t,x-->)=r-1?lmMlm(u)Ylm(?,?), where ? is the radiation field at infinity and Mlm are the radiative moments, functions of retarded time u=t-r-2Mln(r/2M-1); M is the mass parameter of the Schwarzschild spacetime and (t,x-->)=(t,r,?,?) are the usual Schwarzschild coordinates. For all three types of radiation the moments share the same mathematical structure: To zeroth order in v, the radiative moments are given by relations of the form Mlm(u)~(d/du)l??(u,x-->)rlY¯lm(?,?)dx-->, where ? is the source of the radiation. A radiative moment of order l is therefore given by the corresponding source moment differentiated l times with respect to retarded time. To second order in v, additional terms appear inside the spatial integrals, and the radiative moments become Mlm(u)~(d/du)l?[1+O(r2?2u)+O(M/r)]?rlY¯lm dx-->. The term involving r2?2u can be interpreted as a special-relativistic correction to the wave-generation problem. The term involving M/r comes from general relativity. These correction terms of order v2 are near-zone corrections which depend on the detailed behavior of the source. Furthermore, the radiative multipole moments are still local functions of u, as they depend on the state of the source at retarded time u only. To third order in v, the radiative moments become Mlm(u)-->Mlm(u)+2M?u-?[ln(u-u')+const]M ¨lm(u') du', where overdots indicate differentiation with respect to u'. This expression shows that the O(v3) correction terms occur outside the spatial integrals, so that they do not depend on the detailed behavior of the source. Furthermore, the radiative multipole moments now display a nonlocality in time, as they depend on the state of the source at all times prior to the retarded time u, with the factor ln(u-u') assigning most of the weight to the source's recent past. (The term involving the constant is actually local.) The correction terms of order v3 are wave-propagation corrections which are heuristically understood as arising from the scattering of the radiation by the spacetime curvature surrounding the source. The radiative multipole moments are computed explicitly for all three types of radiation by taking advantage of the symmetries of the Schwarzschild metric to separate the variables in the wave equations. Our calculations show that the truly nonlocal wave-propagation correction - the term involving ln(u-u') - takes a universal form which is independent of multipole order and field type. We also show that in general relativity, temporal and spatial curvatures contribute equally to the wave-propagation corrections. Finally, we produce an alternative derivation of the radiative moments of a scalar field based on the retarded Green's function of DeWitt and Brehme. This calculation shows that the tail part of the Green's function is entirely responsible for the wave-propagation corrections in the radiative moments.

  16. ROTATION AND STABILITY OF THE TOROIDAL MAGNETIC FIELD IN STELLAR RADIATION ZONES

    SciTech Connect

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

    2013-03-20

    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.

  17. Collapse of Low Mass Clouds in the Presence of UV Radiation Field

    E-print Network

    Hajime Susa; Tetsu Kitayama

    2000-04-21

    The collapse of marginally Jeans unstable primordial gas clouds in the presence of UV radiation field is discussed. Assuming that the dynamical collapse proceeds approximately in an isothermal self-similar fashion, we investigate the thermal evolution of collapsing central core until H$_2$ cooling dominates photoheating and the temperature drops to below $10^4$K. Consequently, the mass of the cooled core is evaluated as $M_{cool}=3.6\\times 10^6 M_\\odot(I_{21}/1)^{-0.32}$. This scale depends only on the incident UV intensity, and provides a lower limit to the mass of collapsed objects in the UV radiation field.

  18. Entanglement and nonclassicality for multimode radiation-field states

    SciTech Connect

    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

    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.

  19. Please report any Smalltooth Sawfish encounter!

    E-print Network

    Watson, Craig A.

    . The International Sawfish Encounter Database (ISED) was established as a sawfish tracking database to assist Carvalho Tel: (352) 392-2360 Cell: (352) 871-8230 International Sawfish Encounter Database Florida Program greatly help conservation efforts by providing the following information: · Your name, phone number, and e

  20. Modeling of Lorentz forces and radiated wave fields for bulk wave electromagnetic acoustic transducers

    NASA Astrophysics Data System (ADS)

    Zhai, Guofu; Wang, Kaican; Wang, Yakun; Su, Riliang; Kang, Lei

    2013-08-01

    Currently, the finite element method (FEM) and analytical calculation are widely employed for the modeling of electromagnetic acoustic transducers (EMATs). However, it takes long time for finite element calculation. Previous analytical models for bulk wave EMATs are generally considered separately and incompletely, and expressions of radiated wave fields contain infinite integrations and multiple singular points, which result in complex numerical computation. A complete model containing the Lorentz force and radiated wave field calculation for the EMAT with a spiral coil and a NdFeB permanent magnet is established. By introducing a current loop instead of the permanent magnet and adopting the truncated region eigenfunction expansion (TREE) method, the distributions of static and dynamic magnetic fields and their generated Lorentz forces are calculated. A series expansion method is proposed for the computation of radiated wave fields, which replaces the integration by series operation and avoids the solutions of singular points effectively. The Lorentz forces and radiated wave fields of a typical transducer are computed. The validity of the model is verified by FEM and experiments. Their good agreements verify the accuracy and validity of the model.

  1. On Whether Angular Momentum in Electric and Magnetic Fields Radiates to Infinity

    NASA Technical Reports Server (NTRS)

    Canning, Francis X.; Knudsen, Steven

    2006-01-01

    The Feynman Disk experiment and a related thought experiment with a static magnetic field and capacitor are studied. The mechanical torque integrated over time (angular impulse) is related to the angular momentum in the electric/magnetic field. This is not called an electromagnetic field since quasi-static as well as electromagnetic effects are included. The angular momentum in the electric/magnetic field is examined to determine its static and radiative components. This comparison was then examined to see if it clarified the Abraham-Minkowski paradox.

  2. Ultraviolet radiation penetrating vehicle glass: a field based comparative study

    NASA Astrophysics Data System (ADS)

    Kimlin, M. G.; Parisi, A. V.

    1999-04-01

    The solar UV transmitted through automobile glass was measured in the field in two cars using a spectroradiometer. The two cars were identical except that one of the cars had all of the windows (except the windshield) tinted. The measured spectral erythemal UV on a horizontal plane with the windows fully closed was reduced in the tinted car by a factor of 42 when compared with the erythemal UV measured in the untinted car. The ambient UVA irradiances at various locations within four different makes of car and a tractor were also measured with a broad band UVA hand-held meter. The average normalized daily UVA exposure (measured with a broad band UVA meter) was 1.3 times higher in a large family sedan when compared with that in a small hatchback and the UVA exposure in a car with tinted windows was 3.8 times less than in a similar untinted car.

  3. Ultraviolet radiation penetrating vehicle glass: a field based comparative study.

    PubMed

    Kimlin, M G; Parisi, A V

    1999-04-01

    The solar UV transmitted through automobile glass was measured in the field in two cars using a spectroradiometer. The two cars were identical except that one of the cars had all of the windows (except the windshield) tinted. The measured spectral erythemal UV on a horizontal plane with the windows fully closed was reduced in the tinted car by a factor of 42 when compared with the erythemal UV measured in the untinted car. The ambient UVA irradiances at various locations within four different makes of car and a tractor were also measured with a broad band UVA handheld meter. The average normalized daily UVA exposure (measured with a broad band UVA meter) was 1.3 times higher in a large family sedan when compared with that in a small hatchback and the UVA exposure in a car with tinted windows was 3.8 times less than in a similar untinted car. PMID:10232805

  4. Testing of Performance of Optical Fibers Under Irradiation in Intense Radiation Fields, When Subjected to Very High Temperatures

    SciTech Connect

    Blue, Thomas; Windl, Wolfgang; Dickerson, Bryan

    2013-01-03

    The primary objective of this project is to measure and model the performance of optical fibers in intense radiation fields when subjected to very high temperatures. This research will pave the way for fiber optic and optically based sensors under conditions expected in future high-temperature gas-cooled reactors. Sensor life and signal-to-noise ratios are susceptible to attenuation of the light signal due to scattering and absorbance in the fibers. This project will provide an experimental and theoretical study of the darkening of optical fibers in high-radiation and high-temperature environments. Although optical fibers have been studied for moderate radiation fluence and flux levels, the results of irradiation at very high temperatures have not been published for extended in-core exposures. Several previous multi-scale modeling efforts have studied irradiation effects on the mechanical properties of materials. However, model-based prediction of irradiation-induced changes in silica�s optical transport properties has only recently started to receive attention due to possible applications as optical transmission components in fusion reactors. Nearly all damage-modeling studies have been performed in the molecular-dynamics domain, limited to very short times and small systems. Extended-time modeling, however, is crucial to predicting the long-term effects of irradiation at high temperatures, since the experimental testing may not encompass the displacement rate that the fibers will encounter if they are deployed in the VHTR. The project team will pursue such extended-time modeling, including the effects of the ambient and recrystallization. The process will be based on kinetic MC modeling using the concept of amorphous material consisting of building blocks of defect-pairs or clusters, which has been successfully applied to kinetic modeling in amorphized and recrystallized silicon. Using this procedure, the team will model compensation for rate effects, and the interplay of rate effects with the effects of annealing, to accurately predict the fibers� reliability and expected lifetime

  5. Radiative widths and splitting of cyclotron lines in superstrong magnetic fields

    NASA Technical Reports Server (NTRS)

    Pavlov, G. G.; Bezchastnov, V. G.; Meszaros, P.; Alexander, S. G.

    1991-01-01

    The radiative line widths of the Landau levels in a superstrong magnetic field are calculated and simple analytic expressions and fits are given for these which are valid over a wide range of the principal quantum number and the magnetic field strength. If QED corrections are not taken into account, all levels but the first are doubly degenerate, corresponding to the two possible spin projections. However, the interaction with the QED vacuum removes this degeneracy, leading to an energy splitting of each level which exceeds the radiative linewidth for low Landau levels if the magnetic field is not too large (B is less than approximately 10 exp 13 G). Estimations are presented of the splitting in various limits as a function of field strength and Landau number. The possibility of observing this splitting in accreting X-ray pulsars and in gamma-ray bursters is discussed.

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

    SciTech Connect

    Lee, H. C.; Jiang, T. F. [Institute of Physics, National Chiao Tung University, Hsinchu 30010, Taiwan (China)

    2010-11-15

    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 (v{sub x0}) to the longitudinal velocity (v{sub z0}) 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 (v{sub x0}:v{sub z0}) 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 (v{sub x0}:v{sub z0}). The radiation from hard x-ray to gamma-ray regions can be generated with a broad radiation angle, thus available for applications.

  7. Accelerated local Monte Carlo estimate in calculation of laser radiation fields in tissue

    NASA Astrophysics Data System (ADS)

    Lappa, Alexander V.; Kamalov, Vladimir A.; Potapov, Alexey E.; Shipitsin, Ilia E.

    1999-03-01

    The Monte Carlo methods are widely used in biooptics to calculate different characteristics of the optical radiation fields. In the most cases the radiation characteristics including local ones (fluence, absorbed dose, etc.) are calculated with non-local Monte Carlo estimates, which give the values averaged over some region. These methods can lead to large systematical errors if the characteristics have fast space variation. At the same time there are local algorithms in the theory of the Monte Carlo methods. They are widely used in calculations of fields of ionizing radiation. In particular, the famous Kalos `local estimate' allows computations of radiation flux at a fixed point. This estimate solves the problem of the systematical error but because of infinite variance it has lower convergence and stability in comparison with non-local methods. Recently a method of acceleration of convergence of the Monte Carlo estimates possessing infinite variance was suggested. In the present work this accelerated Monte Carlo algorithm is applied to the Kalos estimate under typical conditions of biooptics (rat liver irradiated by 1.064 mkm laser). It is shown that the algorithm gives the gain in computational time up to 100 times. Obtained results allow us to recommend this algorithm for calculation of local characteristics of laser radiation fields in biological tissues.

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

    SciTech Connect

    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

    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.

  9. 11/5/2007 M. Holdridge 1 New Horizons Pluto EncounterNew Horizons Pluto Encounter

    E-print Network

    Young, Leslie A.

    11/5/2007 M. Holdridge 1 New Horizons Pluto EncounterNew Horizons Pluto Encounter Baseline Review not conclude the concept development phase of planning the Pluto encounter. Continued analysis and trades, we are finding the Pluto flyby is a very unique flyby in terms of geometry and goals

  10. Developing Si(Li) nuclear radiation detectors by pulsed electric field treatment

    Microsoft Academic Search

    R. A. Muminov; S. A. Radzhapov; A. K. Saimbetov

    2009-01-01

    Fabrication of Si(Li) nuclear radiation detectors using lithium ion drift under the action of a pulsed electric field is considered.\\u000a Optimum treatment regime parameters are determined, including the pulse amplitude, duration, and repetition rate. Experimental\\u000a data are presented, which show that the ion drift in a pulsed electric field decreases the semiconductor bulk compensation\\u000a time by a factor of two

  11. Measurement of temperature field in the region near to the radiator by using digital holography

    NASA Astrophysics Data System (ADS)

    Li, Yan; Wang, Dayong; Wang, Guangjun; Zhang, Yizhuo; Liu, Changgeng

    2009-07-01

    A simple method for measurement of temperature field in the region near to the metal plate of the radiator is demonstrated by using digital holography in the Lensless Fourier transform configuration (LFT). The temperature is measured within the boundary layer of the convective flow field. The deviation of the temperature produced by this method, from that obtained by the thermocouple is rather small. It has shown that the method is reasonable and efficient.

  12. Predictions of mixed non-Gaussian cosmological density fields for the cosmic microwave background radiation

    Microsoft Academic Search

    Ana Paula Andrade; Carlos Alexandre Wuensche; Andre Luiz B. Ribeiro

    2003-01-01

    We present simulations of the Cosmic Microwave Background Radiation (CMBR)\\u000apower spectrum for a class of mixed, non-Gaussian, primordial random fields. We\\u000aassume a skew positive mixed model with adiabatic inflation perturbations plus\\u000aadditional isocurvature perturbations possibly produced by topological defects.\\u000aThe joint probability distribution used in this context is a weighted\\u000acombination of Gaussian and non-Gaussian random fields, such

  13. Predictions of Mixed Non-Gaussian Cosmological Density Fields for the Cosmic Microwave Background Radiation

    Microsoft Academic Search

    A. P. A. Andrade; C. A. Wuensche; A. L. B. Ribeiro

    2004-01-01

    We present simulations of the cosmic microwave background radiation (CMBR) power spectrum for a class of mixed, non-Gaussian, primordial random fields. We assume a skew-positive mixed model with adiabatic inflation perturbations plus additional isocurvature perturbations possibly produced by topological defects. The joint probability distribution used in this context is a weighted combination of Gaussian and non-Gaussian random fields, such as

  14. Low Noise Junction Field Effect Transistors in a Silicon Radiation Detector Technology

    Microsoft Academic Search

    Gian-Franco Dalla Betta; Maurizio Boscardin; F. Fenotti; L. Pancheri; C. Piemonte; L. Ratti; N. Zorzi

    2006-01-01

    We report on n-channel Junction Field Effect Transistors fabricated on high resistivity silicon by means of a specially tailored radiation detector technology. This research activity is being carried out in the framework of a project aiming at the integration of read-out circuits in the same detector substrate. Possible applications are in the field of medical\\/industrial imaging, space and high energy

  15. On Consideration of Radiated Power in RF Field Simulations for MRI

    PubMed Central

    Liu, Wanzhan; Kao, Chien-ping; Collins, Christopher M.; Smith, Michael B.; Yang, Qing X.

    2012-01-01

    In numerical analyses of RF fields for MRI, RF power is often permitted to radiate out of the problem region. In reality, RF power will be confined by the magnet bore and RF screen enclosing the magnet room. We present numerical calculations at different frequencies for various surface and volume coils, with samples from simple spheres to the human body in environments from free space to a shielded RF room. Results for calculations within a limited problem region show radiated power increases with frequency. When the magnet room RF screen is included, nearly all the power is dissipated in the human subject. For limited problem regions, inclusion of a term for radiation loss results in an underestimation of transmit efficiency compared to results including the complete bore and RF screen. If the term for radiated power is not included, calculated coil efficiencies are slightly overestimated compared to the complete case. PMID:22473620

  16. Geodesic synchrotron radiation. [emission by freely falling particles in gravitational field

    NASA Technical Reports Server (NTRS)

    Breuer, R. A.; Chrzanowksi, P. L.; Hughes, H. G., III; Misner, C. W.

    1973-01-01

    This paper presents the results and methods of computing the high-frequency radiation emitted by freely falling particles moving in circular geodesic orbits in a spherically symmetric gravitational field. The high-frequency radiation, to which the methods of this paper apply, is the principal part of radiated energy only in the case of a particle moving in a highly relativistic, and therefore unstable, circular geodesic. The geodesic synchrotron radiation emitted in this case shows excitation of high-frequency harmonics and a narrow angular distribution. A Green's-function solution of the scalar wave equation is obtained using WKB methods. For application to relativistic circular orbits, a parabolic WKB approximation is required and yields solutions in terms of parabolic cylinder functions.

  17. Transient quantum coherent response to a partially coherent radiation field

    SciTech Connect

    Sadeq, Zaheen S.; Brumer, Paul, E-mail: pbrumer@chem.utoronto.ca [Department of Chemistry and Center for Quantum Information and Quantum Control, Chemical Physics Theory Group, University of Toronto, Toronto, Ontario M5S 3H6 (Canada)] [Department of Chemistry and Center for Quantum Information and Quantum Control, Chemical Physics Theory Group, University of Toronto, Toronto, Ontario M5S 3H6 (Canada)

    2014-02-21

    The response of an arbitrary closed quantum system to a partially coherent electric field is investigated, with a focus on the transient coherences in the system. As a model we examine, both perturbatively and numerically, the coherences induced in a three level V system. Both rapid turn-on and pulsed turn-on effects are investigated. The effect of a long and incoherent pulse is also considered, demonstrating that during the pulse the system shows a coherent response which reduces after the pulse is over. Both the pulsed scenario and the thermally broadened CW case approach a mixed state in the long time limit, with rates dictated by the adjacent level spacings and the coherence time of the light, and via a mechanism that is distinctly different from traditional decoherence. These two excitation scenarios are also explored for a minimal “toy” model of the electronic levels in pigment protein complex PC645 by both a collisionally broadened CW laser and by a noisy pulse, where unexpectedly long transient coherence times are observed and explained. The significance of environmentally induced decoherence is noted.

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

    SciTech Connect

    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

    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.

  19. Application of whole-body personal TL dosemeters in mixed field beta-gamma radiation.

    PubMed

    Ciupek, K; Aksamit, D; Wo?oszczuk, K

    2014-11-01

    Application of whole-body personal TL dosemeters based on a high-sensitivity LiF:Mg,Cu,P (MCP-N) in mixed field beta-gamma radiation has been characterised. The measurements were carried out with (90)Sr/(90)Y, (85)Kr and (137)Cs point sources to calculate the energy response and linearity of the TLD response in a dose range of 0.1-30 mSv. From the result, calibration curves were obtained, enabling the readout of individual dose equivalent Hp(10) from gamma radiation and Hp(0.07) from beta radiation in mixed field beta-gamma. Limitation of the methodology and its application are presented and discussed. PMID:25009188

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

    PubMed

    Norman H, Machado R; Maximiliano, Trujillo T; Javier E, García G; Diana C, Narvaez G; Paula A, Marín M; Róbinson A, Torres V

    2013-01-01

    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

  1. Response of alanine and radio-photo-luminescence dosemeters to mixed high-energy radiation fields.

    PubMed

    Vincke, H; Brunner, I; Floret, I; Forkel-Wirth, D; Fuerstner, M; Mayer, S; Theis, C

    2007-01-01

    Alanine and Radio-Photo-Luminescence (RPL) dosemeters are passive dosemeters used to monitor absorbed dose in all kind of radiation fields. However, up to now both dosemeter types are calibrated to photon sources only. In order to study the response of RPL and alanine dosemeters to mixed high-energy particle fields like those occurring at CERN's accelerators, an irradiation campaign at the CERN-EC High-Energy Reference field Facility (CERF-field) was performed. In this facility a copper target is irradiated by hadrons with a momentum of 120 GeV/c. Dosemeters were exposed to various mixed radiation fields by placing them at various positions on the surface of the target. In addition to the experiment FLUKA Monte Carlo simulations were carried out, which provide information concerning the energy deposition at the dosemeter locations. This paper compares the measurements with the simulation results and discusses the radiation field compositions present at the various dosemeter positions on the target. PMID:17369266

  2. Breast Cancer Regional Radiation Fields for Supraclavicular and Axillary Lymph Node Treatment: Is a Posterior Axillary Boost Field Technique Optimal?

    SciTech Connect

    Wang Xiaochun [Department of Radiation Physics, University of Texas, M. D. Anderson Cancer Center, Houston, TX (United States)], E-mail: xiaochunw@mdanderson.org; Yu, T.K. [Department of Radiation Oncology, University of Texas, M. D. Anderson Cancer Center, Houston, TX (United States); Salehpour, Mohammad; Zhang, Sean X.; Sun, T.L. [Department of Radiation Physics, University of Texas, M. D. Anderson Cancer Center, Houston, TX (United States); Buchholz, Thomas A. [Department of Radiation Oncology, University of Texas, M. D. Anderson Cancer Center, Houston, TX (United States)

    2009-05-01

    Purpose: To assess whether using an anterior oblique supraclavicular (SCV) field with a posterior axillary boost (PAB) field is an optimal technique for targeting axillary (AX) lymph nodes compared with two computed tomography (CT)-based techniques: (1) an SCV field with an anterior boost field and (2) intensity-modulated radiotherapy (IMRT). Methods and Materials: Ten patients with CT simulation data treated with postmastectomy radiation that included an SCV field were selected for the study. Supraclavicular nodes and AX Level I-III nodes within the SCV field were contoured and defined as the treatment target. Plans using the three techniques were generated and evaluated for each patient. Results: The anterior axillary boost field and IMRT resulted in superior dose coverage compared with PAB. Namely, treatment volumes that received 105%, 80%, and 30% of prescribed dose for IMRT plans were significantly less than those for the anterior axillary boost plans, which were significantly less than PAB. For PAB and anterior axillary boost plans, there was a linear correlation between treatment volume receiving 105% of prescribed dose and maximum target depth. Furthermore, the IMRT technique resulted in better lung sparing and dose conformity to the target than anterior axillary boost, which again was significantly better than PAB. The maximum cord dose for IMRT was small, but higher than for the other two techniques. More monitor units were required to deliver the IMRT plan than the PAB plan, which was more than the anterior axillary boost plan. Conclusions: The PAB technique is not optimal for treatment of AX lymph nodes in an SCV field. We conclude that CT treatment planning with dose optimization around delineated target volumes should become standard for radiation treatments of supraclavicular and AX lymph nodes.

  3. The Effects of Aerosol on Atmospheric UV Radiation: Measurements and Modeling from the MILAGRO Field Campaign

    Microsoft Academic Search

    S. Madronich; S. Hall; R. Shetter; J. Slusser; P. Arnott

    2007-01-01

    The MILAGRO field campaign took place in and near Mexico City 1-30 March 2006. A comprehensive data set was obtained on atmospheric chemical composition (gas and aerosol), aerosol microphysics, spectral radiation, and meteorology from surface-, aircraft-, and satellite-based instruments. For much of this time, the lower atmosphere was laden with large amounts of aerosols originating from urban and industrial sources,

  4. Radiative Corrections, Divergences, Regularization, Renormalization, Renormalization Group and All That in Examples in Quantum Field Theory

    Microsoft Academic Search

    D. I. Kazakov

    2009-01-01

    The present lectures are a practical guide to the calculation of radiative corrections to the Green functions in quantum field theory. The appearance of ultraviolet divergences is explained, their classification is given, the renormalization procedure which allows one to get the finite results is described, and the basis of the renormalization group in QFT is presented. Numerous examples of calculations

  5. Magnitude dependence of radiated energy spectra: Far-field expressions of slip pulses in earthquake models

    E-print Network

    Shaw, Bruce E.

    Magnitude dependence of radiated energy spectra: Far-field expressions of slip pulses in earthquake density and then averaging over events of a similar size to examine the magnitude dependence. Assuming dependence on event magnitude for the different frictional instabilities that we have examined, suggesting

  6. The effect of microscopic and global radiative heat exchange on the field predictions of compartment fires

    Microsoft Academic Search

    J. X. Wen; L. Y. Huang; J. Roberts

    2001-01-01

    This paper reports on some further results of the CFD simulations of large-scale compartment fires previously reported in Wen et al. (Proceedings of the Combustion Institute , vol. 27, 1998) and Wen and Huang (Fire Safety J 2000;34(1)). It focuses on the use of the laminar flamelet approach and highlights the effect of microscopic radiation on the field predictions of

  7. Concept of Double Peak electric field distribution in the development of radiation hard silicon detectors

    Microsoft Academic Search

    E. Verbitskaya; V. Eremin; Z. Li; J. Härkönen; M. Bruzzi

    2007-01-01

    The concept of Double Peak (DP) electric field distribution is considered for the analysis of operational characteristics of irradiated silicon detectors. The key point of the model is trapping of equilibrium carriers to the midgap energy levels of radiation-induced defects, which leads to a non-uniform distribution of space charge concentration with positively and negatively charged regions adjacent to the p+

  8. Far-field radiation pattern in Coherent Anti-stokes Raman Scattering (CARS) Microscopy.

    E-print Network

    Paris-Sud XI, Université de

    Far-field radiation pattern in Coherent Anti-stokes Raman Scattering (CARS) Microscopy. David is investigated in Coherent Anti-stokes Raman Scattering (CARS) microscopy both in the forward (F-CARS) and backward (E-CARS) directions. While we assume no refraction index mismatch between the sample

  9. Star Formation in the Galaxy and the Fluctuating UV Radiation Field

    NASA Technical Reports Server (NTRS)

    Hollenbach, David; Parravano, A.; McKee, C.; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    We examine the formation of massive stars in the Galaxy, the resultant fluctuating UV radiation field, and the effect of this Field on the star-forming interstellar medium. Following previous researchers such as Habing (1968), we calculate the average interstellar radiation field at the Solar Circle of the Galaxy. However, our new calculations follow more closely the time dependence of the field at any point. We show that there is a significant difference between the mean field and the median field, and that there are substantial fluctuations of the field (on timescales of order 100 million years) at a given point. Far Ultraviolet Radiation (FUV, photon energies of 6 eV - 13.6 eV) has been recognized as the main source of heating of the neutral interstellar gas. Given the pressure of the interstellar medium (ISM) the FUV field determines whether the thermal balance of the neutral gas results in cold (T approximately 50 - 100 K) clouds (CNM), warm (T about 10,000 K) (WNM), for a combination of the two (the two phase ISM) We present results for the time history of the FUV field for points in the local ISM of the Milky Way Galaxy. The presence of this fluctuating heating rate converts CNM to WNM and vice versa. We show how to calculate the average fractions of the gas in the CNM and WNM when the interstellar gas is subject to this fluctuating FUV field. The knowledge of how these fractions depend on the gas properties (i.e. mean density and composition) and on the FUV-sources (i.e. the star formation rate, or the IMF, or the size distribution of associations) is a basic step in building any detailed model of the large scale behavior of the ISM and the mutual relation between the ISM and the SFR.

  10. Do planetary encounters reset surfaces of near Earth asteroids?

    NASA Astrophysics Data System (ADS)

    Nesvorný, David; Bottke, William F.; Vokrouhlický, David; Chapman, Clark R.; Rafkin, Scot

    2010-10-01

    Processes such as the solar wind sputtering and micrometeorite impacts can modify optical properties of surfaces of airless bodies. This explains why spectra of the main belt asteroids, exposed to these 'space weathering' processes over eons, do not match the laboratory spectra of ordinary chondrite (OC) meteorites. In contrast, an important fraction of Near Earth Asteroids (NEAs), defined as Q-types in the asteroid taxonomy, display spectral attributes that are a good match to OCs. Here we study the possibility that the Q-type NEAs underwent recent encounters with the terrestrial planets and that the tidal gravity (or other effects) during these encounters exposed fresh OC material on the surface (thus giving it the Q-type spectral properties). We used numerical integrations to determine the statistics of encounters of NEAs to planets. The results were used to calculate the fraction and orbital distribution of Q-type asteroids expected in the model as a function of the space weathering timescale, tsw (see main text for definition), and maximum distance, r?, at which planetary encounters can reset the surface. We found that tsw ˜ 10 6 yr (at 1 AU) and r? ˜ 5 Rpl, where Rpl is the planetary radius, best fit the data. Values tsw < 10 5 yr would require that r? > 20 Rpl, which is probably implausible because these very distant encounters should be irrelevant. Also, the fraction of Q-type NEAs would be probably much larger than the one observed if tsw > 10 7 yr. We found that tsw ? q2, where q is the perihelion distance, expected if the solar wind sputtering controls tsw, provides a better match to the orbital distribution of Q-type NEAs than models with fixed tsw. We also discuss how the Earth magnetosphere and radiation effects such as YORP can influence the spectral properties of NEAs.

  11. [An encounter with extraterrestrial intelligence].

    PubMed

    Hisabayashi, Hisashi

    2003-12-01

    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

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

    SciTech Connect

    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

    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.

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

    NASA Astrophysics Data System (ADS)

    Nicholas, Joyce Shealy

    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.

  14. Field emitter type CdTe radiation detector for x-ray imager

    NASA Astrophysics Data System (ADS)

    Sakata, Takuya; Ikeda, Yoshiaki; Shiozawa, Kazufumi; Neo, Yoichiro; Morii, Hisashi; Aoki, Toru; Mimura, Hidenori

    2006-08-01

    We proposed a new addressing method that used a field emitter type electronic source for the radiation imaging detector. We enabled this device to operate room temperature by using Cadmium Telluride (CdTe) diode. In this addressing method, the energy of the electron from electronic source in each pixel was much uniformed and the electron beams can be focused within a micro meter diameter. Therefore, because this proposed device was lead out by field emitter, it was expected to achieve the super-high resolution X-ray imager. In this paper, we used the carbon nanoneedle field emitter, and the proposed device operation was confirmed by verifying principle about one pixel.

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

    SciTech Connect

    Katayama, I. [Interdisciplinary Research Center, Yokohama National University, Yokohama 240-8501 (Japan); Shimosato, H.; Bito, M.; Furusawa, K. [Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531 (Japan); Adachi, M.; Zen, H.; Kimura, S.; Katoh, M. [UVSOR, Institute of Molecular Science, Okazaki 444-8585 (Japan); School of Physical Sciences, Graduate Universities for Advanced Studies (SOKENDAI), Okazaki 444-8585 (Japan); Shimada, M. [High Energy Accelerator Research Organization, KEK, Tsukuba 305-0801 (Japan); Yamamoto, N.; Hosaka, M. [Graduate School of Engineering, Nagoya University, Nagoya 464-8603 (Japan); Ashida, M. [Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531 (Japan); PRESTO, JST (Japan)

    2012-03-12

    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.

  16. Polarization-dependent heating of the cosmic microwave background radiation by a magnetic field

    E-print Network

    Bialynicka-Birula, Zofia

    2014-01-01

    The changes in the cosmic microwave background (CMB) spectrum seen as an increase of temperature due to a strong magnetic field are determined and their influence on the polarization of the radiation is exhibited. The effect is due to the coupling of the CMB photons to the magnetic field in the QED vacuum via the interaction with virtual pairs. In spite of the fact that the distortion of the CMB spectrum for magnetic fields that exist in the vicinity of magnetars is quite large, this effect is very difficult to detect at present because the required angular resolutions is not yet available.

  17. Polarization-dependent heating of the cosmic microwave background radiation by a magnetic field

    NASA Astrophysics Data System (ADS)

    Bialynicka-Birula, Zofia; Bialynicki-Birula, Iwo

    2014-12-01

    The changes in the cosmic microwave background (CMB) spectrum seen as an increase of temperature due to a strong magnetic field are determined and their influence on the polarization of the radiation is exhibited. The effect is due to the coupling of the CMB photons to the magnetic field in the QED vacuum via the interaction with virtual pairs. In spite of the fact that the distortion of the CMB spectrum for magnetic fields that exist in the vicinity of magnetars is quite large, this effect is very difficult to detect at present because the required angular resolutions is not yet available.

  18. Generation of Magnetic Fields and Jitter Radiation in GRBs. I. Kinetic Theory

    E-print Network

    Mikhail V. Medvedev

    2001-02-23

    We present a theory of generation of strong (sub-equipartition) magnetic fields in relativistic collisionless GRB shocks. These fields produced by the kinetic two-stream instability are tangled on very small spatial scales. This has a clear signature in the otherwise synchrotron(-self-Compton) $\\gamma$-ray spectrum. Second, we present an analytical theory of jitter radiation, which is emitted when the correlation length of the magnetic field is smaller then the gyration (Larmor) radius of the accelerated electrons. We demonstrate that the spectral power $P(\

  19. Comparison of curricula in radiation technology in the field of radiotherapy in selected European Union countries

    PubMed Central

    Janaszczyk, Agnieszka; Bogusz-Czerniewicz, Marta

    2011-01-01

    Background Radiation technology is a discipline of medical science which deals with diagnostics, imaging and radiotherapy, that is treatment by ionizing radiation. Aim To present and compare the existing curricula of radiation technology in selected EU countries. Materials and methods The research work done for the purpose of the comparative analysis was based on the methods of diagnostic test and document analysis. Results The comparison of curricula in selected countries, namely Austria, France, the Netherlands and Poland, showed that admission criteria to radiation technology courses are varied and depend on regulations of respective Ministries of Health. The most restrictive conditions, including written tests in biology, chemistry and physics, and psychometric test, are those in France. Contents of basic and specialist subject groups are very similar in all the countries. The difference is in the number of ECT points assigned to particular subjects and the number of course hours offered. The longest practical training is provided in the Netherlands and the shortest one in Poland. The duration of studies in the Netherlands is 4 years, while in Poland it is 3 years. Austria is the only country to offer extra practical training in quality management. Conclusion Graduates in the compared EU countries have similar level of qualifications in the fields of operation of radiological equipment, radiotherapy, nuclear medicine, foreign language and specialist terminology in the field of medical and physical sciences, general knowledge of medical and physical sciences, and detailed knowledge of radiation technology. PMID:24376979

  20. Quantum statistical properties of the radiation field in a cavity with a movable mirror

    E-print Network

    C. Brif; A. Mann

    1999-05-11

    A quantum system composed of a cavity radiation field interacting with a movable mirror is considered and quantum statistical properties of the field are studied. Such a system can serve in principle as an idealized meter for detection of a weak classical force coupled to the mirror which is modelled by a quantum harmonic oscillator. It is shown that the standard quantum limit on the measurement of the mirror position arises naturally from the properties of the system during its dynamical evolution. However, the force detection sensitivity of the system falls short of the corresponding standard quantum limit. We also study the effect of the nonlinear interaction between the moving mirror and the radiation pressure on the quadrature fluctuations of the initially coherent cavity field.

  1. Cosmic ray pressure driven magnetic field amplification: dimensional, radiative and field orientation effects

    NASA Astrophysics Data System (ADS)

    Downes, T. P.; Drury, L. O'C.

    2014-10-01

    Observations of non-thermal emission from several supernova remnants suggest that magnetic fields close to the blastwave are much stronger than would be naively expected from simple shock compression of the field permeating the interstellar medium (ISM). We investigate in some detail a simple model based on turbulence generation by cosmic ray pressure gradients. Previously, this model was investigated using 2D magnetohydrodynamic simulations. Motivated by the well-known qualitative differences between 2D and 3D turbulence, we further our investigations of this model using both 2D and 3D simulations to study the influence of the dimensionality of the simulations on the field amplification achieved. Further, since the model implies the formation of shocks which can, in principle, be efficiently cooled by collisional cooling, we include such cooling in our simulations to ascertain whether it could increase the field amplification achieved. Finally, we examine the influence of different orientations of the magnetic field with respect to the normal of the blastwave. We find that dimensionality has a slight influence on the overall amplification achieved, but a significant impact on the morphology of the amplified field. Collisional cooling has surprisingly little impact, primarily due to the short time which any element of the ISM resides in the precursor region for supernova blastwaves. Even allowing for a wide range of orientations of the magnetic field, we find that the magnetic field can be expected to be amplified by, on average, at least an order of magnitude in the precursors of supernova blastwaves.

  2. Bull. Astr. Soc. India (2004) 32, 151158 A model of the stellar radiation field in the UV

    E-print Network

    2004-01-01

    Bull. Astr. Soc. India (2004) 32, 151­158 A model of the stellar radiation field in the UV N components of the UV (912 °A - 3000 °A) radiation field over the entire sky. We have developed a model to predict the ISRF in the UV within a few hundred parsecs of the Sun using the Hipparcos star catalog. We

  3. Voyager 1 encounter with the Saturnian system

    NASA Technical Reports Server (NTRS)

    Stone, E. C.; Miner, E. D.

    1981-01-01

    The Voyager 1 Saturn flyby mission of March 1979 is reviewed, with brief discussions of its flight, trajectory, science plan formulation and telemetered data. Analytical results of such data with respect to Saturn's atmosphere, rings, icy satellites, Titan satellite atmosphere and the Saturn magnetosphere, are summarized. The Voyager science investigations comprise imaging science (ISS), infrared radiation (IRIS), photopolarimetry (PPS), ultraviolet spectroscopy (UVS), radio science (RSS), magnetic fields (MAG), plasma particles (PLS), plasma waves (PWS), planetary radio astronomy (PRA), low energy charged particles (LECP), and cosmic-ray particles (CRS).

  4. Characterisation of radiation field for irradiation of biological samples at nuclear reactor-comparison of twin detector and recombination methods.

    PubMed

    Golnik, N; Gryzi?ski, M A; Kowalska, M; Meronka, K; Tulik, P

    2014-10-01

    Central Laboratory for Radiological Protection is involved in achieving scientific project on biological dosimetry. The project includes irradiation of blood samples in radiation fields of nuclear reactor. A simple facility for irradiation of biological samples has been prepared at horizontal channel of the nuclear reactor MARIA in NCBJ in Poland. The radiation field, composed mainly of gamma radiation and thermal neutrons, has been characterised in terms of tissue kerma using twin-detector technique and recombination chambers. PMID:24366246

  5. Intercomparison of radiation protection devices in a high-energy stray neutron field, Part II: Bonner sphere spectrometry

    Microsoft Academic Search

    B. Wiegel; S. Agosteo; R. Bedogni; M. Caresana; A. Esposito; G. Fehrenbacher; M. Ferrarini; E. Hohmann; C. Hranitzky; A. Kasper; S. Khurana; V. Mares; M. Reginatto; S. Rollet; W. Rühm; D. Schardt; M. Silari; G. Simmer; E. Weitzenegger

    2009-01-01

    The European Commission has funded within its 6th Framework Programme a three-year project (2005–2007) called CONRAD, COordinated Network for RAdiation Dosimetry. A major task of the CONRAD Work Package “complex mixed radiation fields at workplaces” was to organise a benchmark exercise in a workplace field at a high-energy particle accelerator where neutrons are the dominant radiation component. The CONRAD benchmark

  6. Response of dosemeters in the radiation field generated by a TW-class laser system.

    PubMed

    Olšovcová, V; Klír, D; Krása, J; Kr?s, M; Velyhan, A; Zelenka, Z; Rus, B

    2014-10-01

    State-of-the-art laser systems are able to generate ionising radiation of significantly high energies by focusing ultra-short and intense pulses onto targets. Thus, measures ensuring the radiation protection of both working personnel and the general public are required. However, commercially available dosemeters are primarily designed for measurement in continuous fields. Therefore, it is important to explore their response to very short pulses. In this study, the responses of dosemeters in a radiation field generated by iodine high-power and Ti:Sapphire laser systems are examined in proton and electron acceleration experiments. Within these experiments, electron bunches of femtosecond pulse duration and 100-MeV energy and proton bunches with sub-nanosecond pulse duration and energy of several megaelectronvolts were generated in single-shot regimes. Responses of typical detectors (TLD, films and electronic personal dosemeter) were analysed and compared. Further, a first attempt was carried out to characterise the radiation field generated by TW-class laser systems. PMID:24563524

  7. Estimation of the radiation field homogeneity in 60Co blood irradiator

    NASA Astrophysics Data System (ADS)

    Urban, Tomas

    2014-11-01

    The aim of this work is to estimate the homogeneity of the radiation field in various configurations and relative activities of the “disposed” but still relatively highly active (approximately thousands of Curies, i.e. tens of TBq) sources for their potential use in irradiation of blood (or blood derivatives). Small dose rate, which is already unusable/inappropriate for the teletherapy, may be still utilized by simultaneous use of multiple sources or reducing the distance to the irradiated object (blood unit). To estimate the homogeneity of the radiation field a modeling approach has been chosen in which Monte Carlo code MCNP has been employed. (In-) homogeneity of the radiation field has been estimated on the basis of isodoses in the water phantom and for various configurations and relative activities of the 60Co sources. The results of simulations are also discussed with regard to further optimization (homogeneity of the sample irradiation, costs, radiation protection of service staff, availability of a sufficient number of resources, etc.).

  8. Influence of external magnetic and laser radiation fields on Feshbach resonances in collision of atoms

    E-print Network

    Gazazyan, E A; Chaltykyan, V O

    2012-01-01

    We study collision of two atoms with formation of Feshbach resonance at combined interaction with the external magnetic field and laser radiation. 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. In addition, in case of one-photon resonance the lower vibrational molecular state is coupled by laser radiation with the continuum of the elastic channel and forms laser-induced Feshbach resonance via both Autler-Townes effect and LICS mechanism. We study the combined process of formation of Feshbach resonances; this enables the control of Feshbach resonance by varying the magnetic field and intensity and frequency of laser radiation. We obtain the cross-sections of elastic and inelastic scattering and show that quenching of resonance occurs at the energy equal to that of the systems ground state. Dependence of the cross-se...

  9. Evaluating a radiation monitor for mixed-field environments based on SRAM technology

    NASA Astrophysics Data System (ADS)

    Tsiligiannis, G.; Dilillo, L.; Bosio, A.; Girard, P.; Pravossoudovitch, S.; Todri, A.; Virazel, A.; Mekki, J.; Brugger, M.; Wrobel, F.; Saigne, F.

    2014-05-01

    Instruments operating in particle accelerators and colliders are exposed to radiations that are composed of particles of different types and energies. Several of these instruments often embed devices that are not hardened against radiation effects. Thus, there is a strong need for monitoring the levels of radiation inside the mixed-field radiation areas, throughout different positions. Different metrics exist for measuring the radiation damage induced to electronic devices, such as the Total Ionizing Dose (TID), the Displacement Damage (DD) and of course the fluence of particles for estimating the error rates of the electronic devices among other applications. In this paper, we propose an SRAM based monitor, that is used to define the fluence of High Energy Hadrons (HEH) by detecting Single Event Upsets in the memory array. We evaluated the device by testing it inside the H4IRRAD area of CERN, a test area that reproduces the radiation conditions inside the Large Hadron Collider (LHC) tunnel and its shielded areas. By using stability estimation methods and presenting experimental data, we prove that this device is proper to be used for such a purpose.

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

    SciTech Connect

    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

    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.

  11. Predicting the Earth encounters of (99942) Apophis

    Microsoft Academic Search

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

    2008-01-01

    Arecibo delay-Doppler measurements of (99942) Apophis in 2005 and 2006 resulted in a five standard-deviation trajectory correction to the optically predicted close approach distance to Earth in 2029. The radar measurements reduced the volume of the statistical uncertainty region entering the encounter to 7.3% of the pre-radar solution, but increased the trajectory uncertainty growth rate across the encounter by 800%

  12. Predicting the Earth encounters of (99942) Apophis

    Microsoft Academic Search

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

    2008-01-01

    Arecibo delay Doppler measurements of (99942) Apophis in 2005 and 2006 resulted in a five standard-deviation trajectory correction to the optically predicted close approach distance to Earth in 2029. The radar measurements reduced the volume of the statistical uncertainty region entering the encounter to 7.3% of the pre-radar solution, but increased the trajectory uncertainty growth rate across the encounter by

  13. Predicting the Earth encounters of (99942) Apophis

    Microsoft Academic Search

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

    2008-01-01

    Arecibo delay–Doppler measurements of (99942) Apophis in 2005 and 2006 resulted in a five standard-deviation trajectory correction to the optically predicted close approach distance to Earth in 2029. The radar measurements reduced the volume of the statistical uncertainty region entering the encounter to 7.3% of the pre-radar solution, but increased the trajectory uncertainty growth rate across the encounter by 800%

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

    PubMed

    Ganeev, R A

    2013-01-01

    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

  15. Development of a proposed international standard for certification of aircraft to High Intensity Radiated Fields (HIRF)

    NASA Technical Reports Server (NTRS)

    Sargent, Noel B.

    1993-01-01

    Avionic systems performing critical functions in modern aircraft are potentially susceptible to the hazards of electromagnetic radiation from ground and airborne transmitters. The Federal Aviation Administration (FAA) requested that the Society of Automotive Engineers (SAE) coordinate the development of procedures and guidance material which can be used during the aircraft certification process to ensure adequate protection against high intensity radiated fields (HIRF). This paper addresses both the technical challenge of drafting a certification procedure and guidance standard as well as the management process used by the SAE subcommittee AE4R to converge a diverse range of opinions by its international membership in the shortest possible time.

  16. High-field half-cycle terahertz radiation from relativistic laser interaction with thin solid targets

    SciTech Connect

    Ding, W. J.; Koh, W. S. [A-STAR Institute of High Performance Computing, Singapore 138632 (Singapore)] [A-STAR Institute of High Performance Computing, Singapore 138632 (Singapore); Sheng, Z. M. [Key Laboratory for Laser Plasmas (MoE) and Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China) [Key Laboratory for Laser Plasmas (MoE) and Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); SUPA, Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom)

    2013-11-11

    It is found that half-cycle terahertz (THz) pulses with the peak field over 100 MV/cm can be produced in ultrashort intense laser interactions with thin solid targets. These THz pulses are shown to emit from both the front and rear sides of the solid target and are attributed to the coherent transition radiation by laser-produced ultrashort fast electron bunches. After the primary THz pulses, subsequent secondary half-cycle pulses are generated while some refluxing electrons cross the vacuum-target interfaces. Since such strong THz radiation is well synchronized with the driving lasers, it is particularly suitable for applications in various pump-probe experiments.

  17. VizieR Online Data Catalog: Radiation fields in star-forming galaxies (Popescu+, 2013)

    NASA Astrophysics Data System (ADS)

    Popescu, C. C.; Tuffs, R. J.

    2013-09-01

    Radiative transfer model calculations of energy density of radiation fields (RFs) are presented on a cylindrical grid (r,z). The radiation fields are given for different values of central face-on dust opacity in the B-band {tau}Bf, which is the only parameter of the model shaping the spatial variation of the RFs. Since the energy densities of the radiation fields are additive quantities, they scale with the spatially integrated luminosity density at a given wavelength. Therefore RFs are only calculated for a fixed reference luminosity density (see Section 3 of journal paper). The radiation fields are separately calculated for the disk, thin disk and bulge. For the bulge different values of the Sersic index are considered. In total calculations are for seven values of the central face-on dust opacity, taufB=0.1,0.3,0.5,1.0,2.0,4.0,8.0. Solutions for other values of taufB can be found by interpolation. Four values for the Sersic index of the bulge are considered, n=1,2,4,8. In total we have 7 (for taufB) x 6 (wavelengths) x 1 (disk) + 7 (for taufB) x 15 (wavelengths) x 1 ( thin disk) + 7 (for taufB) x 6 (wavelengths) x 4 (for Sersic indices of bulge) = 315 combinations. In our model we consider the wavelength range from 912 Angstroem to 5 micron, as listed in Table E.2 of Popescu et al. (2011, Cat. J/A+A/527/109). Thus, the library contains a total of 315 files with two-dimensional spatial grids of energy densities of the RFs, in files.tar file. (2 data files).

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

    SciTech Connect

    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

    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.

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

    SciTech Connect

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

    2010-10-26

    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.

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

    SciTech Connect

    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

    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.

  1. The electric field changes and UHF radiations caused by the triggered lightning in Japan

    NASA Technical Reports Server (NTRS)

    Kawasaki, Zen-Ichiro; Kanao, Tadashi; Matsuura, Kenji; Nakano, Minoru; Horii, Kenji; Nakamura, Koichi

    1991-01-01

    In the rocket triggered lightning experiment of fiscal 1989, researchers observed electromagnetic field changes and UHF electromagnetic radiation accompanying rocket triggered lightning. It was found that no rapid changes corresponding to the return stroke of natural lightning were observed in the electric field changes accompanying rocket triggered lightning. However, continuous currents were present. In the case of rocket triggered lightning to the tower, electromagnetic field changes corresponding to the initiation of triggered lightning showed a bipolar pulse of a relatively large amplitude. In contrast, the rocket triggered lightning to the ground did not have such a bipolar pulse. The UHF radiation accompanying the rocket triggered lightning preceded the waveform portions corresponding to the first changes in electromagnetic fields. The number of isolated pulses in the UHF radiation showed a correlation with the time duration from rocket launching up to triggered lightning. The time interval between consecutive isolated pulses tended to get shorter with the passage of time, just like the stepped leaders of natural lightning.

  2. Particle Acceleration and Radiation associated with Magnetic Field Generation from Relativistic Collisionless Shocks

    E-print Network

    K. -I. Nishikawa; P. Hardee; G. Richardson; R. Preece; H. Sol; G. J. Fishman

    2003-12-03

    Shock acceleration is an ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic jet front propagating through an ambient plasma with and without initial magnetic fields. We find only small differences in the results between no ambient and weak ambient magnetic fields. Simulations show that the Weibel instability created in the collisionless shock front accelerates particles perpendicular and parallel to the jet propagation direction. The simulation results show that this instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields, which contribute to the electron's transverse deflection behind the jet head. The ``jitter'' radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

  3. Simulation of Relativistic Shocks and Associated Radiation from Turbulent Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Niemiec, J.; Medvedev, M.; Zhang, B.; Hardee, P.; Mizuno, Y.; Nordlund, A.; Frederiksen, J.; Sol, H.; Pohl, M.; Hartmann, D. H.; Fishman, J. F.

    2009-01-01

    Plasma instabilities excited in collisionless shocks are responsible for particle acceleration. We have investigated the particle acceleration and shock structure associated with an unmagnetized relativistic electron-positron jet propagating into an unmagnetized electron-positron plasma. Cold jet electrons are thermalized and slowed while the ambient electrons are swept up to create a partially developed hydrodynamic-like shock structure. In the leading shock, electron density increases by a factor of about 3.5 in the simulation frame. Strong electromagnetic fields are generated in the trailing shock and provide an emission site. These magnetic fields contribute to the electron's transverse deflection behind the shock. The jitter'' radiation from deflected electrons in turbulent magnetic fields has different properties than synchrotron radiation, which is calculated in a uniform magnetic field. This jitter radiation may be important for understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets in general, and supernova remnants. New spectra based on simulations will be presented.

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

    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.

  5. Influence of external magnetic and laser radiation fields on Feshbach resonances in collision of atoms

    E-print Network

    E. A. Gazazyan; A. D. Gazazyan; V. O. Chaltykyan

    2012-09-21

    We study collision of two atoms with formation of Feshbach resonance at combined interaction with the external magnetic field and laser radiation. 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. In addition, in case of one-photon resonance the lower vibrational molecular state is coupled by laser radiation with the continuum of the elastic channel and forms laser-induced Feshbach resonance via both Autler-Townes effect and LICS mechanism. We study the combined process of formation of Feshbach resonances; this enables the control of Feshbach resonance by varying the magnetic field and intensity and frequency of laser radiation. We obtain the cross-sections of elastic and inelastic scattering and show that quenching of resonance occurs at the energy equal to that of the systems ground state. Dependence of the cross-sections on the magnetic field and laser intensity is examined in detail. In all considered cases, the scattering length is obtained depending on the magnetic and laser fields are studied. In the absence of magnetic interaction if the hyperfine substates of the quasibound state in the closed channel and those of individual colliding atoms in the open channel are the same, Feshbach resonances may arise via weak interaction between nuclear and electronic motions, which leads to transitions between electronic states. The obtained results can be employed in new studies of collisions of cold atoms, e.g., of alkali metal atoms and for interpretation of new experiments in BECs.

  6. Photon statistics of radiation scattered by relativistic electrons in an interfering electromagnetic field

    NASA Astrophysics Data System (ADS)

    Bertolotti, M.; Sibilia, C.; Perina, J.; Perinova, V.

    1984-09-01

    The statistical properties of backscattered radiation in the electron rest frame are studied when the radiation system is coupled to a 'reservoir' (electron beam). Anticorrelation effects are found to occur between scattered modes; super-Poissonian statistics also occurs in each emitted mode when the short-time approximation is adopted. In the radiation field, two incident modes at nearly the same frequency and two backscattered modes at nearly equal frequency are considered. The coherent state technique and the q-c number correspondence are employed, working in the Schroedinger picture with the generalized Fokker-Plack equation for the antinormal quasi-distribution function. The factorial moments are derived from the solution of that equation.

  7. Performance analysis of a filtered wide field-of-view radiometer for earth radiation budget measurements

    NASA Technical Reports Server (NTRS)

    Cooper, J. E.; Luther, M. R.

    1978-01-01

    The proposed Earth Radiation Budget Satellite System (ERBSS) of the 1980's will include a wide field-of-view (WFOV) fixed axes earth radiator discriminator consisting of a shortwave channel and a total (unfiltered) channel. The broadband spectral isolation required for the shortwave channel is achieved by use of a hemispherical fused silica (Suprasil W) dome filter placed in front of a wire wound thermopile radiation detector. A description is presented of the thermal response of the single-fused silica dome filter in the ERBSS WFOV shortwave channel conceptual design and the impact of that response on the channel measurement. Results from design definition and performance analysis studies are included. Problems associated with achieving the desired levels of confidence in a high accuracy filtered, WFOV radiometer are discussed. Design approaches, ground calibration, and data reduction techniques which minimize measurement uncertainties are explained.

  8. Simulation of relativistic shocks and associated radiation from turbulent magnetic fields

    NASA Astrophysics Data System (ADS)

    Nishikawa, K.-I.; Niemiec, J.; Medvedev, M.; Zhang, B.; Hardee, P.; Nordlund, A.?.; Frederiksen, J.; Mizuno, Y.; Sol, H.; Pohl, M.; Hartmann, D. H.; Fishman, G. J.

    2011-08-01

    Using our new 3-D relativistic particle-in-cell (PIC) code, we investigated long-term particle acceleration associated with a relativistic electron-positron jet propagating in an unmagnetized ambient electron-positron plasma. The simulations were performed using a much longer simulation system than our previous simulations in order to investigate the full nonlinear stage of the Weibel instability and its particle acceleration mechanism. Cold jet electrons are thermalized and ambient electrons are accelerated in the resulting shocks. Acceleration of ambient electrons leads to a maximum ambient electron density three times larger than the original value as predicted by hydrodynamic compression. Behind the bow shock, in the jet shock, strong electromagnetic fields are generated. These fields may lead to time dependent afterglow emission. In order to go beyond the standard synchrotron model used in astrophysical objects we have used PIC simulations and calculated radiation based on first principles. We calculated radiation from electrons propagating in a uniform parallel magnetic field to verify the technique. We also used the technique to calculate emission from electrons based on simulations with a small system. We obtain spectra which are consistent with those generated from electrons propagating in turbulent magnetic fields. This turbulent magnetic field is similar to the magnetic field generated at an early nonlinear stage of the Weibel instability. A fully developed shock within a larger system may generate a jitter/synchrotron spectrum.

  9. Simulation of Relativistic Shocks and Associated Radiation from Turbulent Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Nishikawa, K.-I.; Niemiec, J.; Medvedev, M.; Zhang, B.; Hardee, P.; Mizuno, Y.; Nordlund, A.; Frederiksen, J.; Sol, H.; Pohl, M.; Hartmann, D. H.; Fishman, G. J.

    2011-10-01

    Using our new 3-D relativistic particle-in-cell (PIC) code, we investigated long-term particle acceleration associated with a relativistic electron-positron jet propagating in an unmagnetized ambient electron-positron plasma. The simulations were performed using a much longer simulation system than our previous simulations in order to investigate the full nonlinear stage of the Weibel instability and its particle acceleration mechanism. Cold jet electrons are thermalized and ambient electrons are accelerated in the resulting shocks. Acceleration of ambient electrons leads to a maximum ambient electron density three times larger than the original value as predicted by the hydrodynamic compression. Behind the bow shock, in the jet shock, strong electromagnetic fields are generated. These fields may lead to time dependent afterglow emission. In order to go beyond the standard synchrotron model used in astrophysical objects we have used PIC simulations and calculated radiation based on the first principles. We calculated radiation from electrons propagating in a uniform parallel magnetic field to verify the technique. We also used the technique to calculate emission from electrons based on simulations with a small system. We obtained spectra which are consistent with those generated from electrons propagating in turbulent magnetic fields. This turbulent magnetic field is similar to the magnetic field generated at an early nonlinear stage of the Weibel instability. A fully developed shock within a larger system may generate a jitter/synchrotron spectrum.

  10. Simulation of Relativistic Shocks and Associated Radiation from Turbulent Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Niemiec, J.; Medvedev, M.; Zhang, B.; Hardee, P.; Nordlund, A.; Frederiksen, J.; Mizuno, Y.; Sol, H.; Pohl, M.; Hartmann, D. H.; Fishman, G. J.

    2011-01-01

    Using our new 3-D relativistic particle-in-cell (PIC) code, we investigated long-term particle acceleration associated with a relativistic electron-positron jet propagating in an unmagnetized ambient electron-positron plasma. The simulations were performed using a much longer simulation system than our previous simulations in order to investigate the full nonlinear stage of the Weibel instability and its particle acceleration mechanism. Cold jet electrons are thermalized and ambient electrons are accelerated in the resulting shocks. Acceleration of ambient electrons leads to a maximum ambient electron density three times larger than the original value as predicted by hydrodynamic compression. Behind the bow shock, in the jet shock, strong electromagnetic fields are generated. These fields may lead to time dependent afterglow emission. In order to go beyond the standard synchrotron model used in astrophysical objects we have used PIC simulations and calculated radiation based on first principles. We calculated radiation from electrons propagating in a uniform parallel magnetic field to verify the technique. We also used the technique to calculate emission from electrons based on simulations with a small system. We obtain spectra which are consistent with those generated from electrons propagating in turbulent magnetic fields. This turbulent magnetic field is similar to the magnetic field generated at an early nonlinear stage of the Weibel instability. A fully developed shock within a larger system may generate a jitter/synchrotron spectrum.

  11. Unified Classical and Quantum Radiation Mechanism for Ultra-Relativistic Electrons in Curved and Inhomogeneous Magnetic Fields

    E-print Network

    T. Harko; K. S. Cheng

    2002-04-10

    We analyze the general radiation emission mechanism from a charged particle moving in a curved inhomogeneous magnetic field. The consideration of the gradient makes the curved vacuum magnetic field compatible with the Maxwell equations and adds a non-trivial term to the transverse drift velocity and, consequently, to the general radiation spectrum. To obtain the radiation spectrum in the classical domain a general expression for the spectral distribution and characteristic frequency of an electron in arbitrary motion is derived by using Schwinger's method. The radiation patterns of the ultrarelativistic electron are represented in terms of the acceleration of the particle. The same results can be obtained by considering that the motion of the electron can be formally described as an evolution due to magnetic and electric forces. By defining an effective electromagnetic field, which combines the magnetic field with the fictitious electric field associated to the curvature and drift motion, one can obtain all the physical characteristics of the radiation by replacing the constant magnetic field with the effective field. The power, angular distribution and spectral distribution of all three components (synchrotron, curvature and gradient) of the radiation are considered in both classical and quantum domain in the framework of this unified formalism. In the quantum domain the proposed approach allows the study of the effects of the inhomogeneities and curvature of the magnetic field on the radiative transitions rates of electrons between low-lying Landau levels and the ground state.

  12. A CLOSER ENCOUNTER WITH MARS

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Taking advantage of Mars's closest approach to Earth in eight years, astronomers using NASA's Hubble Space Telescope have taken the space-based observatory's sharpest views yet of the Red Planet. NASA is releasing these images to commemorate the second anniversary of the Mars Pathfinder landing. The lander and its rover, Sojourner, touched down on the Red Planet's rolling hills on July 4, 1997, embarking on an historic three-month mission to gather information on the planet's atmosphere, climate, and geology. The telescope's Wide Field and Planetary Camera 2 snapped these images between April 27 and May 6, when Mars was 54 million miles (87 million kilometers) from Earth. From this distance the telescope could see Martian features as small as 12 miles (19 kilometers) wide. The telescope obtained four images, which, together, show the entire planet. Each view depicts the planet as it completes one quarter of its daily rotation. In these views the north polar cap is tilted toward the Earth and is visible prominently at the top of each picture. The images were taken in the middle of the Martian northern summer, when the polar cap had shrunk to its smallest size. During this season the Sun shines continuously on the polar cap. Previous telescopic and spacecraft observations have shown that this summertime 'residual' polar cap is composed of water ice, just like Earth's polar caps. These Hubble telescope snapshots reveal that substantial changes in the bright and dark markings on Mars have occurred in the 20 years since the NASA Viking spacecraft missions first mapped the planet. The Martian surface is dynamic and ever changing. Some regions that were dark 20 years ago are now bright red; some areas that were bright red are now dark. Winds move sand and dust from region to region, often in spectacular dust storms. Over long timescales many of the larger bright and dark markings remain stable, but smaller details come and go as they are covered and then uncovered by sand and dust. The upper-left image is centered near the location of the Pathfinder landing site. Dark sand dunes that surround the polar cap merge into a large, dark region called Acidalia. This area, as shown by images from the Hubble telescope and other spacecraft, is composed of dark, sand-sized grains of pulverized volcanic rock. Below and to the left of Acidalia are the massive Martian canyon systems of Valles Marineris, some of which form long linear markings that were once thought by some to be canals. Early morning clouds can be seen along the left limb of the planet, and a large cyclonic storm composed of water ice is churning near the polar cap. The upper-right image is centered on the region of the planet known as Tharsis, home of the largest volcanoes in the solar system. The bright, ring-like feature just to the left of center is the volcano Olympus Mons, which is more than 340 miles (550 kilometers) across and 17 miles (27 kilometers) high. Thick deposits of fine-grained, windblown dust cover most of this hemisphere. The colors indicate that the dust is heavily oxidized ('rusted'), and millions (or perhaps billions) of years of dust storms have homogenized its composition. Prominent late afternoon clouds along the right limb of the planet can be seen. The lower-left image is centered near another volcanic region known as Elysium. This area shows many small, dark markings that have been observed by the Hubble telescope and other spacecraft to change as a result of the movement of sand and dust across the Martian surface. In the upper left of this image, at high northern latitudes, a large chevron-shaped area of water ice clouds mark a storm front. Along the right limb, a large cloud system has formed around the Olympus Mons volcano. The lower-right image is centered on the dark feature known as Syrtis Major, first seen telescopically by the astronomer Christiaan Huygens in the 17th century. Many small, dark, circular impact craters can be seen in this region, attesting to the Hubble telescope's ability to reveal fine detail on the planet's surface. To

  13. NEAs' Satellites Under Close Encounters with Earth

    NASA Astrophysics Data System (ADS)

    Araujo, Rosana; Winter, O. C.

    2012-10-01

    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.

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

    SciTech Connect

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

    1993-10-01

    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.

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

    SciTech Connect

    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

    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.

  16. A method to detect ultra high energy electrons using earth's magnetic field as a radiator

    NASA Technical Reports Server (NTRS)

    Stephens, S. A.; Balasubrahmanyan, V. K.

    1983-01-01

    It is pointed out that the detection of electrons with energies exceeding a few TeV, which lose energy rapidly through synchrotron and inverse Compton processes, would provide valuable information on the distribution of sources and on the propagation of cosmic rays in the solar neighborhood. However, it would not be possible to measure the energy spectrum beyond a few TeV with any of the existing experimental techniques. The present investigation is, therefore concerned with the possibility of detecting electrons with energies exceeding a few TeV on the basis of the photons emitted through synchrotron radiation in the earth's magnetic field. Attention is given to the synchrotron radiation of electrons in the earth's magnetic field, detector response and energy estimation, and the characteristics of an ideal detector, capable of detecting photons with energies equal to or greater than 20 keV.

  17. Electron-beam dynamics in a strong laser field including quantum radiation reaction

    E-print Network

    Norman Neitz; Antonino Di Piazza

    2014-08-06

    The evolution of an electron beam colliding head-on with a strong plane-wave field is investigated in the framework of strong-field QED including radiation-reaction effects due to photon emission. Employing a kinetic approach to describe the electron and the photon distribution it is shown that at a given total laser fluence the final electron distribution depends on the shape of the laser envelope and on the pulse duration, in contrast to the classical predictions of radiation reaction based on the Landau-Lifshitz equation. Finally, it is investigated how the pair-creation process leads to a nonlinear coupled evolution of the electrons in the beam, of the produced charged particles, and of the emitted photons.

  18. EM Modeling of Far-Field Radiation Patterns for Antennas on the GMA-TT UAV

    NASA Technical Reports Server (NTRS)

    Mackenzie, Anne I.

    2015-01-01

    To optimize communication with the Generic Modular Aircraft T-Tail (GMA-TT) unmanned aerial vehicle (UAV), electromagnetic (EM) simulations have been performed to predict the performance of two antenna types on the aircraft. Simulated far-field radiation patterns tell the amount of power radiated by the antennas and the aircraft together, taking into account blockage by the aircraft as well as radiation by conducting and dielectric portions of the aircraft. With a knowledge of the polarization and distance of the two communicating antennas, e.g. one on the UAV and one on the ground, and the transmitted signal strength, a calculation may be performed to find the strength of the signal travelling from one antenna to the other and to check that the transmitted signal meets the receiver system requirements for the designated range. In order to do this, the antenna frequency and polarization must be known for each antenna, in addition to its design and location. The permittivity, permeability, and geometry of the UAV components must also be known. The full-wave method of moments solution produces the appropriate dBi radiation pattern in which the received signal strength is calculated relative to that of an isotropic radiator.

  19. Durability and shielding performance of borated Ceramicrete coatings in beta and gamma radiation fields

    NASA Astrophysics Data System (ADS)

    Wagh, Arun S.; Sayenko, S. Yu.; Dovbnya, A. N.; Shkuropatenko, V. A.; Tarasov, R. V.; Rybka, A. V.; Zakharchenko, A. A.

    2015-07-01

    Ceramicrete™, a chemically bonded phosphate ceramic, was developed for nuclear waste immobilization and nuclear radiation shielding. Ceramicrete products are fabricated by an acid-base reaction between magnesium oxide and mono potassium phosphate. Fillers are used to impart desired properties to the product. Ceramicrete's tailored compositions have resulted in several commercial structural products, including corrosion- and fire-protection coatings. Their borated version, called Borobond™, has been studied for its neutron shielding capabilities and is being used in structures built for storage of nuclear materials. This investigation assesses the durability and shielding performance of borated Ceramicrete coatings when exposed to gamma and beta radiations to predict the composition needed for optimal shielding performance in a realistic nuclear radiation field. Investigations were conducted using experimental data coupled with predictive Monte Carlo computer model. The results show that it is possible to produce products for simultaneous shielding of all three types of nuclear radiations, viz., neutrons, gamma-, and beta-rays. Additionally, because sprayable Ceramicrete coatings exhibit excellent corrosion- and fire-protection characteristics on steel, this research also establishes an opportunity to produce thick coatings to enhance the shielding performance of corrosion and fire protection coatings for use in high radiation environment in nuclear industry.

  20. Plasma wave detection of terahertz radiation by silicon field effects transistors: Responsivity and noise equivalent power

    Microsoft Academic Search

    R. Tauk; F. Teppe; S. Boubanga; D. Coquillat; W. Knap; Y. M. Meziani; C. Gallon; F. Boeuf; T. Skotnicki; C. Fenouillet-Beranger; D. K. Maude; S. Rumyantsev; M. S. Shur

    2006-01-01

    Si metal oxide semiconductor field effect transistors (MOSFETs) with the gate lengths of 120-300 nm have been studied as room temperature plasma wave detectors of 0.7 THz electromagnetic radiation. In agreement with the plasma wave detection theory, the response was found to depend on the gate length and the gate bias. The obtained values of responsivity (=10-10 W\\/Hz0.5) demonstrate the

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

    Microsoft Academic Search

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

    1998-01-01

    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)

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

    Microsoft Academic Search

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

    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

  3. On The Relativistic Classical Motion of a Radiating Spinning Particle in a Magnetic Field

    E-print Network

    Arnab Kar; S. G. Rajeev

    2010-10-01

    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.

  4. High-resolution ultraviolet radiation fields of classical T Tauri stars

    SciTech Connect

    France, Kevin [Center for Astrophysics and Space Astronomy, University of Colorado, 389 UCB, Boulder, CO 80309 (United States); Schindhelm, Eric [Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder, CO 80302 (United States); Bergin, Edwin A. [Department of Astronomy, University of Michigan, 830 Dennison Building, 500 Church Street, Ann Arbor, MI 48109 (United States); Roueff, Evelyne; Abgrall, Hervé, E-mail: kevin.france@colorado.edu [LERMA and UMR 8112 du CNRS, Observatoire de Paris, Section de Meudon, Place J. Janssen, F-92195 Meudon (France)

    2014-04-01

    The far-ultraviolet (FUV; 912-1700 Å) radiation field from accreting central stars in classical T Tauri systems influences the disk chemistry during the period of giant planet formation. The FUV field may also play a critical role in determining the evolution of the inner disk (r < 10 AU), from a gas- and dust-rich primordial disk to a transitional system where the optically thick warm dust distribution has been depleted. Previous efforts to measure the true stellar+accretion-generated FUV luminosity (both hot gas emission lines and continua) have been complicated by a combination of low-sensitivity and/or low-spectral resolution and did not include the contribution from the bright Ly? emission line. In this work, we present a high-resolution spectroscopic study of the FUV radiation fields of 16 T Tauri stars whose dust disks display a range of evolutionary states. We include reconstructed Ly? line profiles and remove atomic and molecular disk emission (from H{sub 2} and CO fluorescence) to provide robust measurements of both the FUV continuum and hot gas lines (e.g., Ly?, N V, C IV, He II) for an appreciable sample of T Tauri stars for the first time. We find that the flux of the typical classical T Tauri star FUV radiation field at 1 AU from the central star is ?10{sup 7} times the average interstellar radiation field. The Ly? emission line contributes an average of 88% of the total FUV flux, with the FUV continuum accounting for an average of 8%. Both the FUV continuum and Ly? flux are strongly correlated with C IV flux, suggesting that accretion processes dominate the production of both of these components. On average, only ?0.5% of the total FUV flux is emitted between the Lyman limit (912 Å) and the H{sub 2} (0-0) absorption band at 1110 Å. The total and component-level high-resolution radiation fields are made publicly available in machine-readable format.

  5. Scalar fields in the Lense-Thirring background with a cosmic string and Hawking radiation

    NASA Astrophysics Data System (ADS)

    Vieira, H. S.; Bezerra, V. B.; Costa, André A.

    2015-03-01

    We analyze the influence of the gravitational field produced by a slowly rotating black hole with a cosmic string along the axis of symmetry on a massive scalar field. Exact solutions of both angular and radial parts of the Klein-Gordon equation in this spacetime are obtained, and are given in terms of the confluent Heun functions. We emphasize the role of the presence of the cosmic string in these solutions. We also investigate the solutions in regions near and far from the event horizon. From the radial solution, we obtain the exact wave solutions near the exterior horizon of the black hole, and discuss the Hawking radiation of massive scalar particles.

  6. Near-field thermal radiation between hyperbolic metamaterials: Graphite and carbon nanotubes

    SciTech Connect

    Liu, X. L.; Zhang, R. Z.; Zhang, Z. M., E-mail: zhuomin.zhang@me.gatech.edu [G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

    2013-11-18

    The near-field radiative heat transfer for two hyperbolic metamaterials, namely, graphite and vertically aligned carbon nanotubes (CNTs), is investigated. Graphite is a naturally existing uniaxial medium, while CNT arrays can be modeled as an effective anisotropic medium. Different hyperbolic modes can be separately supported by these materials in certain infrared regions, resulting in a strong enhancement in near-field heat transfer. It is predicted that the heat flux between two CNT arrays can exceed that between SiC plates at any vacuum gap distance and is about 10 times higher with a 10?nm gap.

  7. Radiative accretion shocks along nonuniform stellar magnetic fields in classical T Tauri stars

    NASA Astrophysics Data System (ADS)

    Orlando, S.; Bonito, R.; Argiroffi, C.; Reale, F.; Peres, G.; Miceli, M.; Matsakos, T.; Stehlé, C.; Ibgui, L.; de Sa, L.; Chièze, J. P.; Lanz, T.

    2013-11-01

    Context. According to the magnetospheric accretion model, hot spots form on the surface of classical T Tauri stars (CTTSs) in regions where accreting disk material impacts the stellar surface at supersonic velocity, generating a shock. Aims: We investigate the dynamics and stability of postshock plasma that streams along nonuniform stellar magnetic fields at the impact region of accretion columns. We study how the magnetic field configuration and strength determine the structure, geometry, and location of the shock-heated plasma. Methods: We model the impact of an accretion stream onto the chromosphere of a CTTS by 2D axisymmetric magnetohydrodynamic simulations. Our model considers the gravity, the radiative cooling, and the magnetic-field-oriented thermal conduction (including the effects of heat flux saturation). We explore different configurations and strengths of the magnetic field. Results: The structure, stability, and location of the shocked plasma strongly depend on the configuration and strength of the magnetic field. In the case of weak magnetic fields (plasma ? ? 1 in the postshock region), a large component of B may develop perpendicular to the stream at the base of the accretion column, which limits the sinking of the shocked plasma into the chromosphere and perturbs the overstable shock oscillations induced by radiative cooling. An envelope of dense and cold chromospheric material may also develop around the shocked column. For strong magnetic fields (? < 1 in the postshock region close to the chromosphere), the field configuration determines the position of the shock and its stand-off height. If the field is strongly tapered close to the chromosphere, an oblique shock may form well above the stellar surface at the height where the plasma ? ? 1. In general, we find that a nonuniform magnetic field makes the distribution of emission measure vs. temperature of the postshock plasma at T > 106 K lower than when there is uniform magnetic field. Conclusions: The initial magnetic field strength and configuration in the region of impact of the stream are expected to influence the chromospheric absorption and, therefore, the observability of the shock-heated plasma in the X-ray band. In addition, the field strength and configuration also influence the energy balance of the shocked plasma with its emission measure at T > 106 K, which is lower than expected for a uniform field. The above effects contribute to underestimating the mass accretion rates derived in the X-ray band. Movies are available in electronic form at http://www.aanda.org

  8. Star Formation In the Galaxy and the Fluctuating UV Radiation Field

    NASA Technical Reports Server (NTRS)

    Hollenbach, David; Parravano, Antonio; McKee, Christopher H.; DeVincenzi, D. (Technical Monitor)

    2002-01-01

    We examine the formation of massive stars in the Galaxy, the resultant fluctuating UV (ultraviolet) radiation field, and the effect of this field on the star-forming interstellar medium. There are substantial fluctuations of the UV radiation field in space (scales of 100's of parsecs) and time (time-scales of order 100 million years). The FUV (far ultraviolet) (6 eV less than hv less than 13.6 eV) field and the pressure determines whether the thermal balance of the neutral gas results in cold clouds or warm (T approx. 10(exp 4) K) neutral medium. We show how to calculate the average fractions of the gas in the cold and warm phases when the interstellar gas is subject to this fluctuating FUV field. The knowledge of how these fractions depend on the gas properties and on the FUV sources is a basic step in building a model of the large scale behavior of the ISM (interstellar medium) and the mutual relation between the ISM and the star formation rate.

  9. Star Formation in the Galaxy and the Fluctuating UV Radiation Field

    NASA Technical Reports Server (NTRS)

    Hollenbach, David; Parravano, Antonio; McKee, Christopher H.; Fonda, Mark (Technical Monitor)

    2001-01-01

    We examine the formation of massive stars in the Galaxy, the resultant fluctuating UV radiation field, and the effect of this field on the star-forming interstellar medium (ISM). There are substantial fluctuations of the UV radiation field in space (scales of 100's of parsecs) and time (time-scales of order 100 million years) at the solar circle. The Far Ultraviolet (FUV) (6 eV< hv < 13.6 eV) field and the pressure determines whether the thermal balance of the neutral gas results in cold clouds or warm (T - 10(exp 4) neutral medium. We show how to calculate the average fractions of the gas in the cold and warm phases when the interstellar gas is subject to this fluctuating FUV field. The knowledge of how these fractions depend on the gas properties and on the FUV sources is a basic step in building a model of the large scale behavior of the ISM and the mutual relation between the ISM and the star formation rate. Application is made to observations of spiral galaxies which correlate the star formation rate per unit area with the surface density of the gas. We acknowledge support from the NASA Astrophysical Theory program.

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

    NASA Technical Reports Server (NTRS)

    Torres-Pomales, Wilfredo

    2012-01-01

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

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

    SciTech Connect

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

    2009-11-30

    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.

  12. Lightning-channel morphology by return-stroke radiation field waveforms

    NASA Technical Reports Server (NTRS)

    Willett, J. C.; Le Vine, D. M.; Idone, V. P.

    1995-01-01

    Simultaneous video and wideband electric field recordings of 32 cloud-to-ground lightning flashes in Florida were analyzed to show the formation of new channels to ground can be detected by examination of the return-stroke radiation fields alone. The return-stroke E and dE/dt waveforms were subjectively classified according to their fine structure. Then the video images were examined field by field to identify each waveform with a visible channel to ground. Fifty-five correlated waveforms and channel images were obtained. Of these, all 34 first-stroke waveforms (multiple jagged E peaks, noisy dE/dt), 8 of which were not radiated by the chronologically first stroke in the flash, came from new channels to ground (not previously seen on video). All 18 subsequent-stroke waveforms (smoothly rounded E and quiet dE/dt after initial peak) were radiated by old channels (illuminated by a previous stroke). Two double-ground waveforms (two distinct first-return-stroke pulses separated by tens of microseconds or less) coincided with video fields showing two new channels. One `anomalous-stroke' waveform (beginning like a first stroke and ending like a subsequent) was produced by a new channel segment to ground branching off an old channel. This waveform classification depends on the presence or absence of high-frequency fine structure. Fourier analysis shows that first-stroke waveforms contain about 18 dB more spectral power in the frequency interval from 500 kHz to at least 7 MHz than subsequent-stroke waveforms for at least 13 microseconds after the main peak.

  13. Effect of organ size and position on out-of-field dose distributions during radiation therapy

    PubMed Central

    Scarboro, Sarah B; Stovall, Marilyn; White, Allen; Smith, Susan A; Yaldo, Derek; Kry, Stephen F; Howell, Rebecca M

    2011-01-01

    Mantle field irradiation has historically been the standard radiation treatment for Hodgkin lymphoma. It involves treating large regions of the chest and neck with high doses of radiation (up to 30 Gy). Previous epidemiological studies on the incidence of second malignancies following radiation therapy for Hodgkin lymphoma have revealed an increased incidence of second tumors in various organs, including lung, breast, thyroid and digestive tract. Multiple other studies, including the Surveillance, Epidemiology and End Results, indicated an increased incidence in digestive tract including stomach cancers following mantle field radiotherapy. Assessment of stomach dose is challenging because the stomach is outside the treatment field but very near the treatment border where there are steep dose gradients. In addition, the stomach can vary greatly in size and position. We sought to evaluate the dosimetric impact of the size and variable position of the stomach relative to the field border for a typical Hodgkin lymphoma mantle field irradiation. The mean stomach dose was measured using thermoluminescent dosimetry for nine variations in stomach size and position. The mean doses to the nine stomach variations ranged from 0.43 to 0.83 Gy when 30 Gy was delivered to the treatment isocenter. Statistical analyses indicated that there were no significant differences in the mean stomach dose when the stomach was symmetrically expanded up to 3 cm or shifted laterally (medial, anterior or posterior shifts) by up to 3 cm. There was, however, a significant (P > 0.01) difference in the mean dose when the stomach was shifted superiorly or inferiorly by ? 2.5 cm. PMID:21076195

  14. Effect of organ size and position on out-of-field dose distributions during radiation therapy

    NASA Astrophysics Data System (ADS)

    Scarboro, Sarah B.; Stovall, Marilyn; White, Allen; Smith, Susan A.; Yaldo, Derek; Kry, Stephen F.; Howell, Rebecca M.

    2010-12-01

    Mantle field irradiation has historically been the standard radiation treatment for Hodgkin lymphoma. It involves treating large regions of the chest and neck with high doses of radiation (up to 30 Gy). Previous epidemiological studies on the incidence of second malignancies following radiation therapy for Hodgkin lymphoma have revealed an increased incidence of second tumors in various organs, including lung, breast, thyroid and digestive tract. Multiple other studies, including the Surveillance, Epidemiology and End Results, indicated an increased incidence in digestive tract including stomach cancers following mantle field radiotherapy. Assessment of stomach dose is challenging because the stomach is outside the treatment field but very near the treatment border where there are steep dose gradients. In addition, the stomach can vary greatly in size and position. We sought to evaluate the dosimetric impact of the size and variable position of the stomach relative to the field border for a typical Hodgkin lymphoma mantle field irradiation. The mean stomach dose was measured using thermoluminescent dosimetry for nine variations in stomach size and position. The mean doses to the nine stomach variations ranged from 0.43 to 0.83 Gy when 30 Gy was delivered to the treatment isocenter. Statistical analyses indicated that there were no significant differences in the mean stomach dose when the stomach was symmetrically expanded up to 3 cm or shifted laterally (medial, anterior or posterior shifts) by up to 3 cm. There was, however, a significant (P > 0.01) difference in the mean dose when the stomach was shifted superiorly or inferiorly by >=2.5 cm.

  15. Falling Man: encounters with catastrophic change.

    PubMed

    Charles, Marilyn

    2011-08-01

    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

  16. SU-E-T-368: Effect of a Strong Magnetic Field On Select Radiation Dosimeters

    SciTech Connect

    Mathis, M; Wen, Z; Tailor, R; Sawakuchi, G; Flint, D; Beddar, S; Ibbott, G [The University of Texas MD Anderson Cancer Center, Houston, TX (United States)

    2014-06-01

    Purpose: To determine the effect of a strong magnetic field on TLD-100, OSLD (Al{sub 2}O{sub 2}:C), and PRESAGE dosimetry devices. This study will help to determine which types of dosimeters can be used for quality assurance and in-vivo dosimetry measurements in a magnetic resonance imaginglinear accelerator (MRI-linac) system. Methods: The dosimeters were separated into two categories which were either exposed or not exposed to a strong magnetic field. In each category a set of dosimeters was irradiated with 0, 2, or 6 Gy. To expose the dosimeters to a magnetic field the samples in that category were place in a Bruker small animal magnetic resonance scanner at a field strength slightly greater than 2.5 T for at least 1 hour preirradiation and at least 1 hour post-irradiation. Irradiations were performed with a 6 MV x-ray beam from a Varian TrueBeam linac with 10×10 cm{sup 2} field at a 600 MU/min dose rate. The samples that received no radiation dose were used as control detectors. Results: The readouts of the dosimeters which were not exposed to a strong magnetic field were compared with the measurements of the dosimetry devices which were exposed to a magnetic field. No significant differences (less than 2% difference) in the performance of TLD, OSLD, or PRESAGE dosimeters due to exposure to a strong magnetic field were observed. Conclusion: Exposure to a strong magnetic field before and after irradiation does not appear to change the dosimetric properties of TLD, OSLD, or PRESAGE which indicates that these dosimeters have potential for use in quality assurance and in-vivo dosimetry in a MRI-linac. We plan to further test the effect of magnetic fields on these devices by irradiating them in the presence of a magnetic fields similar to those produced by a MRI-linac system. Elekta-MD Anderson Cancer Center Research Agreement.

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

    Microsoft Academic Search

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

    2007-01-01

    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

  18. Magnetic field effect on tunnel ionization of deep impurities by terahertz radiation S.D. Ganichev1

    E-print Network

    Ganichev, Sergey

    Magnetic field effect on tunnel ionization of deep impurities by terahertz radiation S.D. Ganichev1-Technical Institute, St. Petersburg, Russia Abstract: A suppression of tunnelling ionization of deep impurities magnetic fields. Overview Tunneling ionization of deep centers in the terahertz field of high-intensity far

  19. Chemical Composition of Tropospheric Air Mass Encountered During High Altitude Flight (>11.5km) over Antarctica at Latitude 86S During the 2009 Fall Operation Ice Bridge Field Campaign

    NASA Astrophysics Data System (ADS)

    Yang, M. M.; Blake, D. R.; Meinardi, S.; Vay, S. A.; Choi, Y.; Rana, M.; Slate, T.; Sachse, G. W.; Diskin, G. S.

    2010-12-01

    As part of the Operation Ice Bridge (OIB) campaign in 2009, the NASA DC-8 aircraft was used to fill the data-time gap in laser observation of the changes in ice sheets, glaciers and sea ice between the end of ICESat-I in 2009 and the launch of ICESat-II in 2015. In addition to the cryospheric instruments, four in situ atmospheric sampling instruments participated in this campaign, measuring CO2, CO, water vapor and various VOCs. During a high altitude research flight on October 25th 2009 (figure 1) strong enhancements of CO, CH4, N2O, CH3Cl, ethane, acetylene and methanol were observed in an air mass that was encountered at Latitude 86S. Other significant VOC enhancements observed included OCS, CFC-12, CFC-11, propane, ethanol, acetaldehyde, acetone and butanone. The presence of these hydrocarbons in the air mass and their correlation coefficients with CO suggests that the source of the plume is biomass burning. Hysplit forward and backward trajectories indicate that the possible origin of the plume could be the active fires burning in South America at the time. Due to the long lifetimes of both CFC-12 and CFC-11, their enhancements observed over Antarctica are consistent with transport from the Northern hemisphere. Unfortunately, the Southern hemisphere is heavily under-sampled during the austral spring, with few if any high-resolution airborne observations of atmospheric gases ever made over Antarctica. This leaves us without the basis for comparison with other data products. However, the data presented here shows evidence that tropospheric pollution (biomass burning emissions) is transported from lower latitudes toward the South pole, which may not have been observed in the past. Figure 1: October 25th, 2009: NASA DC-8 flight path from Punta Arenas, Chile, to Antarctica and return with the purpose of conducting a parallel survey from W 120° to E 10° along 86°S. Nearly the entire flight was flown at high altitude (>10.5 km) for a total duration of 11.5 hours.

  20. Analysis of near-field radiation transfer within nano-gaps using FDTD method

    NASA Astrophysics Data System (ADS)

    Didari, Azadeh; Mengüç, M. Pinar

    2014-10-01

    Enhancement of near-field radiative emission via coupling of surface plasmons in nano-gaps formed between thin films is important for understanding and implementation of energy harvesting using nano-thermophotovoltaic cells. Design and construction of such cells need to be carried out along with detailed modeling studies, necessitating accurate calculation of near-field emission within thin films. The objective of this paper is to provide a methodology based on finite difference time domain analysis for the calculation of the near-field thermal radiation emission based on local density of electromagnetic states. Near-field thermal emission is investigated within the nano-gap formed between thin silicon carbide layers where both support surface phonon polaritons. Modeling of this problem with the FDTD method is not trivial particularly for establishing the Drude-Lorentz permittivity model and the selection of the right boundary conditions. We present an effective boundary condition, for calculation of Local Density Of electromagnetic States (LDOS) via Finite Difference Time Domain Method (FDTD) for applications to nano-scale geometries. We conclude that Convolutional Perfectly Matched Layer (CPML) is the optimum boundary condition that gives the most accurate results compared against the other methodologies for parallel plates separated by nano-gaps. This boundary condition allows more streamlined simulations to be carried out when working with sub-wavelength structures. The challenges and the possible solutions to overcome these difficulties are discussed in detail.

  1. Influence of induced axial magnetic field on plasma dynamics and radiative characteristics of Z pinches.

    PubMed

    Kantsyrev, V L; Esaulov, A A; Safronova, A S; Velikovich, A L; Rudakov, L I; Osborne, G C; Shrestha, I; Weller, M E; Williamson, K M; Stafford, A; Shlyaptseva, V V

    2011-10-01

    The influence of an induced axial magnetic field on plasma dynamics and radiative characteristics of Z pinches is investigated. An axial magnetic field was induced in a novel Z-pinch load: a double planar wire array with skewed wires (DPWAsk), which represents a planar wire array in an open magnetic configuration. The induced axial magnetic field suppressed magneto-Rayleigh-Taylor (MRT) instabilities (with m = 0 and m = 1 instability modes) in the Z-pinch plasma. The influence of the initial axial magnetic field on the structure of the plasma column at stagnation was manifested through the formation of a more uniform plasma column compared to a standard double planar wire array (DPWA) load [V. L. Kantsyrev et al., Phys. Plasmas 15, 030704 (2008)]. The DPWAsk load is characterized by suppression of MRT instabilities and by the formation of the sub-keV radiation pulse that occurs before the main x-ray peak. Gradients in plasma parameters along the cathode-anode gap were observed and analyzed for DPWAsk loads made from low atomic number Z (Al) and mid-Z (brass) wires. PMID:22181284

  2. On the low order approximation of radiation fields generated by some hollow-cylindrical ion beams accelerated to produce exoergic nuclear reactions

    Microsoft Academic Search

    D. M. Timus; D. A. Bradley; B. D. Timus; S. L. Kalla; H. M. Srivastava; E. G. Finantu; E. N. Mateescu

    2000-01-01

    Increasing interest is being shown in obtaining accurate predictions concerning radiation fields produced by hollow-cylindrical ion beams impinging on homogeneous plane targets, the net effect of this process being exoergic nuclear reactions. Previous theoretical studies by the authors have focused on radiation fields generated by homogeneous plane ring-shaped sources, based on a unified treatment of the radiation field distribution developed

  3. Cosmological consequences of classical flavor-space locked gauge field radiation

    NASA Astrophysics Data System (ADS)

    Bielefeld, Jannis; Caldwell, Robert R.

    2015-06-01

    We propose a classical SU(2) gauge field in a flavor-space locked configuration as a species of radiation in the early Universe and show that it would have a significant imprint on a primordial stochastic gravitational wave spectrum. In the flavor-space locked configuration, the electric and magnetic fields of each flavor are parallel and mutually orthogonal to other flavors, with isotropic and homogeneous stress energy. Due to the non-Abelian coupling, the gauge field breaks the symmetry between left- and right-circularly polarized gravitational waves. This broken chiral symmetry results in a unique signal: nonzero cross-correlation of the cosmic microwave background temperature and polarization, T B and E B , both of which should be zero in the standard, chiral symmetric case. We forecast the ability of current and future cosmic microwave background experiments to constrain this model. Furthermore, a wide range of behavior is shown to emerge, depending on the gauge field coupling, abundance, and allocation into electric and magnetic field energy density. The fluctuation power of primordial gravitational waves oscillates back and forth into fluctuations of the gauge field. In certain cases, the gravitational wave spectrum is shown to be suppressed or amplified by up to an order of magnitude depending on the initial conditions of the gauge field.

  4. Cosmological consequences of classical flavor-space locked gauge field radiation

    E-print Network

    Jannis Bielefeld; Robert R. Caldwell

    2015-05-28

    We propose a classical SU(2) gauge field in a flavor-space locked configuration as a species of radiation in the early universe, and show that it would have a significant imprint on a primordial stochastic gravitational wave spectrum. In the flavor-space locked configuration, the electric and magnetic fields of each flavor are parallel and mutually orthogonal to other flavors, with isotropic and homogeneous stress-energy. Due to the non-Abelian coupling, the gauge field breaks the symmetry between left- and right-circularly polarized gravitational waves. This broken chiral symmetry results in a unique signal: non-zero cross correlation of the cosmic microwave background temperature and polarization, $TB$ and $EB$, both of which should be zero in the standard, chiral symmetric case. We forecast the ability of current and future CMB experiments to constrain this model. Furthermore, a wide range of behavior is shown to emerge, depending on the gauge field coupling, abundance, and allocation into electric and magnetic field energy density. The fluctuation power of primordial gravitational waves oscillates back and forth into fluctuations of the gauge field. In certain cases, the gravitational wave spectrum is shown to be suppressed or amplified by up to an order of magnitude depending on the initial conditions of the gauge field.

  5. Comptonization in Ultra-Strong Magnetic Fields: Numerical Solution to the Radiative Transfer Problem

    NASA Technical Reports Server (NTRS)

    Ceccobello, C.; Farinelli, R.; Titarchuk, L.

    2014-01-01

    We consider the radiative transfer problem in a plane-parallel slab of thermal electrons in the presence of an ultra-strong magnetic field (B approximately greater than B(sub c) approx. = 4.4 x 10(exp 13) G). Under these conditions, the magnetic field behaves like a birefringent medium for the propagating photons, and the electromagnetic radiation is split into two polarization modes, ordinary and extraordinary, that have different cross-sections. When the optical depth of the slab is large, the ordinary-mode photons are strongly Comptonized and the photon field is dominated by an isotropic component. Aims. The radiative transfer problem in strong magnetic fields presents many mathematical issues and analytical or numerical solutions can be obtained only under some given approximations. We investigate this problem both from the analytical and numerical point of view, provide a test of the previous analytical estimates, and extend these results with numerical techniques. Methods. We consider here the case of low temperature black-body photons propagating in a sub-relativistic temperature plasma, which allows us to deal with a semi-Fokker-Planck approximation of the radiative transfer equation. The problem can then be treated with the variable separation method, and we use a numerical technique to find solutions to the eigenvalue problem in the case of a singular kernel of the space operator. The singularity of the space kernel is the result of the strong angular dependence of the electron cross-section in the presence of a strong magnetic field. Results. We provide the numerical solution obtained for eigenvalues and eigenfunctions of the space operator, and the emerging Comptonization spectrum of the ordinary-mode photons for any eigenvalue of the space equation and for energies significantly lesser than the cyclotron energy, which is on the order of MeV for the intensity of the magnetic field here considered. Conclusions. We derived the specific intensity of the ordinary photons, under the approximation of large angle and large optical depth. These assumptions allow the equation to be treated using a diffusion-like approximation.

  6. Intercomparison of radiation protection devices in a high-energy stray neutron field. Part III: Instrument response

    Microsoft Academic Search

    M. Silari; S. Agosteo; P. Beck; R. Bedogni; E. Cale; M. Caresana; C. Domingo; L. Donadille; N. Dubourg; A. Esposito; G. Fehrenbacher; F. Fernández; M. Ferrarini; A. Fiechtner; A. Fuchs; M. J. García; N. Golnik; F. Gutermuth; S. Khurana; Th. Klages; M. Latocha; V. Mares; S. Mayer; T. Radon; H. Reithmeier; S. Rollet; H. Roos; W. Rühm; S. Sandri; D. Schardt; G. Simmer; F. Spurný; F. Trompier; C. Villa-Grasa; E. Weitzenegger; B. Wiegel; M. Wielunski; F. Wissmann; A. Zechner; M. Zielczy?ski

    2009-01-01

    The European Commission has funded within its 6th Framework Programme a three-year project (2005–2007) called CONRAD, COordinated Network for RAdiation Dosimetry. The organizational framework for this project was provided by the European radiation Dosimetry Group EURADOS. Work Package 6 of CONRAD dealt with “complex mixed radiation fields at workplaces” and in this context it organised a benchmark exercise, which included

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

    SciTech Connect

    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

    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.

  8. Convergence of vector spherical wave expansion method applied to near-field radiative transfer.

    PubMed

    Sasihithlu, Karthik; Narayanaswamy, Arvind

    2011-07-01

    Near-field radiative transfer between two objects can be computed using Rytov's theory of fluctuational electrodynamics in which the strength of electromagnetic sources is related to temperature through the fluctuation-dissipation theorem, and the resultant energy transfer is described using the dyadic Green's function of the vector Helmholtz equation. When the two objects are spheres, the dyadic Green's function can be expanded in a series of vector spherical waves. Based on comparison with the convergence criterion for the case of radiative transfer between two parallel surfaces, we derive a relation for the number of vector spherical waves required for convergence in the case of radiative transfer between two spheres. We show that when electromagnetic surface waves are active at a frequency the number of vector spherical waves required for convergence is proportional to Rmax/d when d/Rmax ? 0, where Rmax is the radius of the larger sphere, and d is the smallest gap between the two spheres. This criterion for convergence applies equally well to other near-field electromagnetic scattering problems. PMID:21747546

  9. Microdosimetric measurements in the secondary radiation field produced in (12)C-therapy irradiations.

    PubMed

    Wissmann, F; Giesen, U; Klages, T; Schardt, D; Martino, G; Sunil, C

    2010-08-01

    The ambient dose equivalent from the secondary radiation produced during irradiation of a cylindrical water phantom with 200 MeV/u (12)C-ions was investigated at the biophysics cave at GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. Pencil-like ion beams were delivered by the heavy-ion synchrotron SIS18 using the slow extraction mode. Since the secondary radiation field outside the phantom is complex in its particle composition and particle energy distribution, microdosimetric methods developed for the dosimetry of the cosmic radiation field at flight altitudes, which is similar in terms of complexity, were applied. Lineal energy distributions and the ambient dose equivalent were measured with a tissue-equivalent proportional counter at different particle emission angles. An additional veto counter allowed the identification of the different contributions of charged and neutral particles. A significant increase in the mean quality factor was observed at large emission angles which could be attributed to the decreasing contributions of charged particles compared to the (relative) contributions from neutrons. PMID:20340029

  10. Experimental determination of radiated internal wave power without pressure field data

    SciTech Connect

    Lee, Frank M.; Morrison, P. J. [Physics Department and Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712–1192 (United States)] [Physics Department and Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712–1192 (United States); Paoletti, M. S.; Swinney, Harry L. [Physics Department, The University of Texas at Austin, Austin, Texas 78712–1192 (United States)] [Physics Department, The University of Texas at Austin, Austin, Texas 78712–1192 (United States)

    2014-04-15

    We present a method to determine, using only velocity field data, the time-averaged energy flux (J) and total radiated power P for two-dimensional internal gravity waves. Both (J) and P are determined from expressions involving only a scalar function, the stream function ?. We test the method using data from a direct numerical simulation for tidal flow of a stratified fluid past a knife edge. The results for the radiated internal wave power given by the stream function method agree to within 0.5% with results obtained using pressure and velocity data from the numerical simulation. The results for the radiated power computed from the stream function agree well with power computed from the velocity and pressure if the starting point for the stream function computation is on a solid boundary, but if a boundary point is not available, care must be taken to choose an appropriate starting point. We also test the stream function method by applying it to laboratory data for tidal flow past a knife edge, and the results are found to agree with the direct numerical simulation. The supplementary material includes a Matlab code with a graphical user interface that can be used to compute the energy flux and power from two-dimensional velocity field data.

  11. Uniformly Accelerated Charge in a Quantum Field: From Radiation Reaction to Unruh Effect

    E-print Network

    Philip R. Johnson; B. L. Hu

    2005-01-10

    We present a stochastic theory for the nonequilibrium dynamics of charges moving in a quantum scalar field based on the worldline influence functional and the close-time-path (CTP or in-in) coarse-grained effective action method. We summarize (1) the steps leading to a derivation of a modified Abraham-Lorentz-Dirac equation whose solutions describe a causal semiclassical theory free of runaway solutions and without pre-acceleration patholigies, and (2) the transformation to a stochastic effective action which generates Abraham-Lorentz-Dirac-Langevin equations depicting the fluctuations of a particle's worldline around its semiclassical trajectory. We point out the misconceptions in trying to directly relate radiation reaction to vacuum fluctuations, and discuss how, in the framework that we have developed, an array of phenomena, from classical radiation and radiation reaction to the Unruh effect, are interrelated to each other as manifestations at the classical, stochastic and quantum levels. Using this method we give a derivation of the Unruh effect for the spacetime worldline coordinates of an accelerating charge. Our stochastic particle-field model, which was inspired by earlier work in cosmological backreaction, can be used as an analog to the black hole backreaction problem describing the stochastic dynamics of a black hole event horizon.

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

    NASA Astrophysics Data System (ADS)

    Nauenberg, Michael

    2007-11-01

    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.

  13. Israeli Adolescents and Military Service: Encounters.

    ERIC Educational Resources Information Center

    Levy, Amihay; And Others

    1987-01-01

    Asserts that inadequate attention has been paid to the problems of the young soldier entering army life in Israel. Delineates some areas of friction and vulnerability between the worlds of the youth and the military. Describes the systematization of these encounters into groups, creating the "Binary Model," which helps in locating and treating…

  14. Entering a Crack: An Encounter with Gossip

    ERIC Educational Resources Information Center

    Henderson, Linda

    2014-01-01

    In this paper, I enter a crack to think otherwise about the concept "gossip". Drawing on previous scholarship engaging with Deleuzian concepts to inform research methodologies, this paper builds on this body of work. Following Deleuze and Guattari, the paper undertakes a mapping of gossip, subsequent to an encounter with a crack.…

  15. The Basic Encounter Group: An Alternative View.

    ERIC Educational Resources Information Center

    Bozarth, Jerold D.

    1986-01-01

    Considers the fundamental premises of the person-centered basic encounter group. Groups are considered unusual insofar as the focus is on the individuals in the groups, each becoming empowered to allow inner potential to develop and to move in a constructive direction. The counselor facilitates such growth: client-centered therapy is a way of…

  16. Mixed encounters, limited perception and optimal foraging.

    PubMed

    Berec, L

    2000-09-01

    This article demonstrates how perceptual constraints of predators and the possibility that predators encounter prey both sequentially (one prey type at a time) and simultaneously (two or more prey types at a time) may influence the predator attack decisions, diet composition and functional response of a behavioural predator-prey system. Individuals of a predator species are assumed to forage optimally on two prey types and to have exact knowledge of prey population numbers (or densities) only in a neighbourhood of their actual spatial location. The system characteristics are inspected by means of a discrete-time, discrete-space, individual-based model of the one-predator-two-prey interaction. Model predictions are compared with ones that have been obtained by assuming only sequential encounters of predators with prey and/or omniscient predators aware of prey population densities in the whole environment. It is shown that the zero-one prey choice rule, optimal for sequential encounters and omniscient predators, shifts to abruptly changing partial preferences for both prey types in the case of omniscient predators faced with both types of prey encounters. The latter, in turn, become gradually changing partial preferences when predator omniscience is considered only local. PMID:11016087

  17. Encounter: A Picture Book for Any Classroom.

    ERIC Educational Resources Information Center

    Hazler, Kitty Y.

    2002-01-01

    Describes the content of the picture book, "Encounter," written by Jane Yolen and illustrated by David Shannon. States that it focuses on the arrival of Christopher Columbus to San Salvador (El Salvador) from a boy's perspective. Includes questions for use when discussing the messages and content of the book. (CMK)

  18. Problems Encountered by Novice Pair Programmers

    ERIC Educational Resources Information Center

    Hanks, Brian

    2008-01-01

    In a study of the types of problems encountered by students that led them to seek assistance, Robins et al. [2006] found that the most common problems were related to trivial mechanics. The students in this study worked by themselves on their programming exercises. This article discusses a replication of the Robins et al. study in which the…

  19. PLANT PROTECTIVE RESPONSE TO ENHANCED UV-B RADIATION UNDER FIELD CONDITIONS: LEAF OPTICAL PROPERTIES AND PHOTOSYNTHESIS

    EPA Science Inventory

    Plants of Vicia faba were grown in the field during early to midsummer while receiving two levels of supplemental UV-B radiation. Light-saturated photosynthesis and stomatal diffusive conductance of intact leaves did not show any indications of UV-radiation damage. Supplemental U...

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

    Microsoft Academic Search

    Sergei Zimin

    1992-01-01

    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

  1. Close encounters of the stellar kind

    NASA Astrophysics Data System (ADS)

    Bailer-Jones, C. A. L.

    2015-03-01

    Stars which pass close to the Sun can perturb the Oort cloud, injecting comets into the inner solar system where they may collide with the Earth. Using van Leeuwen's re-reduction of the Hipparcos data complemented by the original Hipparcos and Tycho-2 catalogues, along with recent radial velocity surveys, I integrate the orbits of over 50 000 stars through the Galaxy to look for close encounters. The search uses a Monte Carlo sampling of the covariance of the data in order to properly characterize the uncertainties in the times, distances, and speeds of the encounters. I show that modelling stellar encounters by assuming instead a linear relative motion produces, for many encounters, inaccurate and biased results. I find 42, 14, and 4 stars which have encounter distances below 2, 1, and 0.5 pc respectively, although some of these stars have questionable data. Of the 14 stars coming within 1 pc, 5 were found by at least one of three previous studies (which found a total of 7 coming within 1 pc). The closest encounter appears to be Hip 85605, a K or M star, which has a 90% probability of coming between 0.04 and 0.20 pc between 240 and 470 kyr from now (90% Bayesian confidence interval). However, its astrometry may be incorrect, in which case the closest encounter found is the K7 dwarf GL 710, which has a 90% probability of coming within 0.10-0.44 pc in about 1.3 Myr. A larger perturbation may have been caused by gamma Microscopii, a G6 giant with a mass of about 2.5 M?, which came within 0.35-1.34 pc (90% confidence interval) around 3.8 Myr ago. Full Table 3 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/575/A35

  2. Distribution of ³²P in laboratory colonies of Solenopsis invicta (Hymenoptera: Formicidae) after feeding on labeled Heliothis zeal (Lepidoptera: Noctuidae) eggs: an explanation of discrepancies encountered in field predation experiments

    Microsoft Academic Search

    G. S. Nuessly; W. L. Sterling

    1986-01-01

    Factors responsible for low recovery rates of radioactive Solenopsis invicta Buren following placement of ³²P-labeled Heliothis zea (Boddie) eggs on cotton in field predation tests were investigated using laboratory colonies of the ants. S. invicta workers became radioactive while handling labeled eggs by rupturing the egg chorion or by picking up labeled substances present on the surface of eggs. Foragers

  3. A Multirate Störmer Algorithm for Close Encounters

    NASA Astrophysics Data System (ADS)

    Grazier, K. R.; Newman, W. I.; Sharp, P. W.

    2013-04-01

    We present, analyze, and test a multirate Störmer-based algorithm for integrating close encounters when performing N-body simulations of the Sun, planets, and a large number of test particles. The algorithm is intended primarily for accurate simulations of the outer solar system. The algorithm uses stepsizes H and hi , i = 1, ..., Np , where hi Lt H and Np is the number of planets. The stepsize H is used for the integration of the orbital motion of the Sun and planets at all times. H is also used as the stepsize for the integration of the orbital motion of test particles when they are not undergoing a close encounter. The stepsize hi is used to integrate the orbital motion of test particles during a close encounter with the ith planet. The position of the Sun and planets during a close encounter is calculated using Hermite interpolation. We tested the algorithm on two contrasting problems, and compared its performance with the existing method which uses the same stepsize for all bodies (this stepsize must be significantly smaller than H to ensure the close encounters are integrated accurately). Our tests show that the integration error for the new and existing methods are comparable when the stepsizes are chosen to minimize the error, and that for this choice of stepsizes the new method requires considerably less CPU time than the existing method. This work has been conducted in part at the Jet Propulsion Laboratory, California Institute of Technology under a contract with the National Aeronautics and Space Administration. Government sponsorship acknowledged.

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

    SciTech Connect

    Vladimir Pascalutsa; Marc Vanderhaeghen

    2007-10-12

    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.

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

    SciTech Connect

    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

    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.

  6. Pulsed currents carried by whistlers. IV. Electric fields and radiation excited by an electrode

    SciTech Connect

    Stenzel, R.L.; Urrutia, J.M.; Rousculp, C.L. [Department of Physics, University of California, Los Angeles, California 90024-1547 (United States)] [Department of Physics, University of California, Los Angeles, California 90024-1547 (United States)

    1995-04-01

    Electromagnetic properties of current pulses carried by whistler wave packets are obtained from a basic laboratory experiment. While the magnetic field and current density are described in the preceding companion paper (Part III), the present analysis starts with the electric field. The inductive and space charge electric field contributions are separately calculated in Fourier space from the measured magnetic field and Ohm`s law along B{sub 0}. Inverse Fourier transformation yields the total electric field in space and time, separated into rotational and divergent contributions. The space-charge density in whistler wave packets is obtained. The cross-field tensor conductivity is determined. The frozen-in condition is nearly satisfied, {bold E}+{bold v}{sub {ital e}}{times}{bold B}{congruent}0. The dissipation is obtained from Poynting`s theorem. The waves are collisionally damped; Landau damping is negligible. A radiation resistance for the electrode is determined. Analogous to Poynting`s theorem, the transport of helicity is analyzed. Current helicity is generated by a flow of helicity between pulses traveling in opposite directions which carry opposite signs of helicity. Helicity is dissipated by collisions. These observations complete a detailed description of whistler/current pulses which can occur in various laboratory and space plasmas. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  7. Designing and Dosimetry of a Shield for Photon Fields of Radiation Therapy in Oral Cavity Cancer.

    PubMed

    Jabbari, Keyvan; Senobari, Somayeh; Roayaei, Mahnaz; Rostampour, Masoumeh

    2015-01-01

    The cancer of oral cavity is related to lesions of mucous membrane of tongue and gum that can be treated with radiation therapy. A lateral photon field can be used to treat this kind of tumor, which has a side-effect on normal tissue in the opposite side of the oral cavity. In this study the dosimetric effect of the various shields in oral cavity is evaluated. In this study, a special phantom similar to the structure of oral cavity with capability of film dosimetry was designed and constructed. The various shield slabs were made of five materials: Lead, Plexiglas, Acrylic resin, Silicon and Plaster. For irradiation, Cobalt 60 (60Co) and 6 MV photon beams were used. The film dosimetry before and after the shield was performed using GAFCHROMIC EBT2 films. The film before the shield measures the magnitude of backscattering radiation from the shield. The prescribed dose was 150 cGy. Results showed that 3 cm of the lead in both energies had the maximum absorption of radiation. The absorbed dose to opposite side of shield for 6 MV photon beams and 60Co were 21 and 32 cGy, respectively. The minimum attenuation on radiation was observed in silicon shield for which the dose of opposite side were 116 and 147 cGy for 6 MV and 60Co respectively. The maximum backscattered dose was measured 177 cGy and 219 cGy using 3 cm thickness of lead, which was quite considerable. The minimum backscattering where for acrylic resin 101 and 118 cGy for 6 MV and cobalt. In this study, it was concluded that the amount of backscattering for 3 cm Lead shield is quite considerable and increases the dose significantly. A composite layer of shield with 1-2 cm lead and 1 cm acrylic resin can have the protective effect and low backscattering radiation at the same time. PMID:26120570

  8. Designing and Dosimetry of a Shield for Photon Fields of Radiation Therapy in Oral Cavity Cancer

    PubMed Central

    Jabbari, Keyvan; Senobari, Somayeh; Roayaei, Mahnaz; Rostampour, Masoumeh

    2015-01-01

    The cancer of oral cavity is related to lesions of mucous membrane of tongue and gum that can be treated with radiation therapy. A lateral photon field can be used to treat this kind of tumor, which has a side-effect on normal tissue in the opposite side of the oral cavity. In this study the dosimetric effect of the various shields in oral cavity is evaluated. In this study, a special phantom similar to the structure of oral cavity with capability of film dosimetry was designed and constructed. The various shield slabs were made of five materials: Lead, Plexiglas, Acrylic resin, Silicon and Plaster. For irradiation, Cobalt 60 (60Co) and 6 MV photon beams were used. The film dosimetry before and after the shield was performed using GAFCHROMIC EBT2 films. The film before the shield measures the magnitude of backscattering radiation from the shield. The prescribed dose was 150 cGy. Results showed that 3 cm of the lead in both energies had the maximum absorption of radiation. The absorbed dose to opposite side of shield for 6 MV photon beams and 60Co were 21 and 32 cGy, respectively. The minimum attenuation on radiation was observed in silicon shield for which the dose of opposite side were 116 and 147 cGy for 6 MV and 60Co respectively. The maximum backscattered dose was measured 177 cGy and 219 cGy using 3 cm thickness of lead, which was quite considerable. The minimum backscattering where for acrylic resin 101 and 118 cGy for 6 MV and cobalt. In this study, it was concluded that the amount of backscattering for 3 cm Lead shield is quite considerable and increases the dose significantly. A composite layer of shield with 1–2 cm lead and 1 cm acrylic resin can have the protective effect and low backscattering radiation at the same time. PMID:26120570

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

    SciTech Connect

    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

    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.

  10. Minimizing Total Variation for Field Splitting with Feathering in Intensity-Modulated Radiation Therapy

    NASA Astrophysics Data System (ADS)

    Liu, Yunlong; Wu, Xiaodong

    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 multileaf collimator (MLC) with a maximum leaf spread constraint is used to deliver the prescribed radiation intensity maps (IMs). However, the maximum leaf spread of an MLC may require to split a large IM into several overlapping sub-IMs with each being delivered separately. We develop an efficient algorithm for solving the field splitting problem while minimizing the total variation of the resulting sub-IMs, thus improving the treatment delivery efficiency. Our basic idea is to formulate the field splitting problem as computing a shortest path in a directed acyclic graph, which expresses a special "layered" structure. The edge weights in the graph can be computed by solving an optimal vector decomposition problem using local searching and the proximity scaling technique as we can prove the L^natural-convexity and totally unimodularity of the problem. Moreover, the edge weights of the graph satisfy the Monge property, which enables us to solve this shortest path problem by examining only a small portion of the graph, yielding a time-efficient algorithm.

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

    PubMed

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

    2002-12-01

    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

  12. Theoretical Study of Field Intensity of THz Radiation from GaAs Large-Aperture Photoconductive Antennas

    NASA Astrophysics Data System (ADS)

    Shi, Wei; Hou, Lei

    2006-10-01

    We simulate the THz radiation's time domain waveforms of both the near field and the far field of a GaAs large aperture photoconductive antenna based on the current surge model. Because the micro-kinetic factors, such as transient state changes of current carrier's mobility and lifetime of current carriers, are taken into account in the calculation, we find out the influences of these factors on the THz radiation intensity by changing the above parameters. The results are of guiding significance to design of high-power photoconductive THz radiation antenna materials.

  13. Photoinduced processes in solid polymer solutions of dyes in an interference field of laser radiation

    SciTech Connect

    Sizykh, A G; Tarakanova, E A [Quantum Electronics Division, Krasnoyarsk State University, Krasnoyarsk (Russian Federation)

    1998-12-31

    An investigation was made of the relationships governing the photochemical mechanism of formation of light-induced gratings in solid polymer solutions of a dye with a high quantum yield of the triplet states. The combined analysis of the results of real and numerical experiments was made for a solution of eosin K in gelatin. The protonation rate constant of the dye was measured and the dependence of the diffraction efficiency on the duration of irradiation was explained taking diffusion of the dye into account. A method was proposed for determination of the duffusion coefficient in a spatially modified interference field of the laser radiation. The diffusion coefficients were found. (nonlinear optical phenomena)

  14. Photodissociation rates of OH, OD, and CN by the interstellar radiation field

    NASA Technical Reports Server (NTRS)

    Nee, J. B.; Lee, L. C.

    1985-01-01

    The photoabsorption cross sections for OH, OD, and CN in the vacuum ultraviolet region are measured. The cross sections for the hydroxyl radicals are of the order of 10 to the -17th sq cm, but the photoabsorption for CN is so low that only an upper limit of 2 x 10 to the -18th sq cm is obtained. The molecular photodissociative processes are discussed. The photodissociation cross sections are inferred from the photoabsorption cross sections. On the basis of the measured data, the photodissociation rates by the interstellar radiation field are computed and discussed.

  15. Photodissociation rates of OH, OD, and CN by the interstellar radiation field

    SciTech Connect

    Nee, J.B.; Lee, L.C.

    1985-04-01

    The photoabsorption cross sections for OH, OD, and CN in the vacuum ultraviolet region are measured. The cross sections for the hydroxyl radicals are of the order of 10/sup -17/ cm/sup -2/, but the photoabsorption for CN is so low that only an upper limit of 2 x 10/sup -18/ is obtained. The molecular photodissociative processes are discussed. The photodissociation cross sections are inferred from the photoabsorption cross sections. On the basis of the measured data, the photodissociation rates by the interstellar radiation field are computed and discussed.

  16. Fields and radiation of 'true' and current magnetic dipoles in a medium

    NASA Astrophysics Data System (ADS)

    Ginzburg, V. L.

    'True' and current magnetic dipoles in a medium with permittivity and magnetic permeability are compared in terms of the fields and radiation generated by them. 'True' dipoles are those formed by two magnetic poles (monopoles) of different sign, while current dipoles are those with the form of a miniature ring (solenoid) with current or with the form of a small permanent magnet. As an example, an analysis is made of the energy of Vavilov-Cerenkov emission for point magnetic dipoles of both types as well as for electric dipoles.

  17. Investigating Undergraduate Students’ Conceptions of Radiation

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  18. Distribution of /sup 32/P in laboratory colonies of Solenopsis invicta (Hymenoptera: Formicidae) after feeding on labeled Heliothis zeal (Lepidoptera: Noctuidae) eggs: an explanation of discrepancies encountered in field predation experiments

    SciTech Connect

    Nuessly, G.S.; Sterling, W.L.

    1986-12-01

    Factors responsible for low recovery rates of radioactive Solenopsis invicta Buren following placement of /sup 32/P-labeled Heliothis zea (Boddie) eggs on cotton in field predation tests were investigated using laboratory colonies of the ants. S. invicta workers became radioactive while handling labeled eggs by rupturing the egg chorion or by picking up labeled substances present on the surface of eggs. Foragers that removed the eggs from the plants picked up significantly more of the label than did workers that were sampled from the colonies between 12 and 72 h after egg introduction. Percentage of workers that became labeled over time was much lower with the solid live food than in other studies that used powdered food sources. Problems in finding labeled ants in the field may have been associated with low mean levels of /sup 32/P per ant, together with difficulty in locating and isolating labeled ants from the population. Results indicate that egg predation rates estimated from counts per minute per predator have high variability, and suggest fairly large errors in estimates of eggs consumed per ant. Use of recovery rates of labeled predators to improve estimation of predation rates is discussed.

  19. Stellar encounters in the context of outburst phenomena

    NASA Astrophysics Data System (ADS)

    Forgan, Duncan; Rice, Ken

    2010-02-01

    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.

  20. Near-field radiative heat transfer across a pore and its effects on thermal conductivity of mesoporous silica

    NASA Astrophysics Data System (ADS)

    Li, Jing; Feng, Yanhui; Zhang, Xinxin; Huang, Congliang; Wang, Ge

    2015-01-01

    Mesoporous silica substrate consists of uniformly distributed, unconnected cylindrical or spherical pores. Since the diameters of the pores are less than the wavelength, near-field radiative heat transfer across a cylindrical or spherical pore was simulated by employing the fluctuation dissipation theorem and Green function. Such factors as the diameter of the pore, and the temperature of the material were analyzed. It turned out that when the diameter is greater than 1 nm and less than 50 nm, the radiative heat flux at the mesoscale is 2-6 orders higher than the value at the macroscale, and decreases exponentially with the pore radius increasing for both cylindrical and spherical pore. The thermal conductivity of the mesoporous silica was modified with consideration of near-field radiation. It was concluded that the combined thermal conductivities of mesoporous silica which considering near-field radiation can agree with the experimental results more properly than non-considering near-field radiation. The smaller the pore diameter, the more significant the near-field radiation effect. The combined thermal conductivities of mesoporous silica decrease gradually with the pore diameter increasing, while increase smoothly with the temperature increasing.

  1. White phosphorus poisoning--explosive encounter.

    PubMed

    Pande, T K; Pandey, S

    2004-03-01

    Poisoning by white or yellow phosphorus is reported in various forms and also in ages varying from infants to adults, but spontaneous combustion and explosion during its management has never been described. This incidence occurred while attempting to pass a Ryle's tube. Its free end first exhibited a yellow flame and this later on led to an explosive encounter. Role of static electricity generated while handling plastic materials leading to ignition and explosion cannot be overlooked. PMID:15636320

  2. Effective field theory calculation of two-deuteron radiative capture reaction at astrophysical energies

    NASA Astrophysics Data System (ADS)

    Sadeghi, H.; Khalili, H.

    2014-08-01

    Two-deuteron radiative capture reaction is one of the deuterium-burning processes that the cross section is not well known at very low-energies. We develop the formalism based on pionless Effective Field Theory (EFT) for deuteron-deuteron ( dd) scattering to derive the cross section of two-deuteron radiative capture. Within this formalism the two- and three-body forces, should also be included in the capture cross section calculations. The aim of the present work is to calculate the observables of the low-energy dd photonuclear reactions. The cross section and the astrophysical S-factor for the 2H( d, ?)4He reaction have been calculated. The 4He is studied as four-body bound states in the pionless EFT. The theoretical uncertainties for observables are estimated based on the variation of the cutoffs. The astrophysical S-factor is accurately determined to be 6.9×10-6 keV b (6.1×10-6 keV b) for two-body (two- and three-body) at zero energy. A satisfactory agreement between theory and experiment for dd radiative capture observables up to order of calculation has been found by insertion of three-body force.

  3. Sub-THz radiation room temperature sensitivity of long-channel silicon field effect transistors

    NASA Astrophysics Data System (ADS)

    Sizov, F.; Golenkov, A.; But, D.; Sakhno, M.; Reva, V.

    2012-06-01

    Room temperature operating n-MOSFETs (n-type metal-oxide silicon field effect transistors) used for registration of sub-THz (sub-terahertz) radiation in the frequency range ? = 53-145 GHz are considered. n-MOSFETs were manufactured by 1-?m Si CMOS technology applied to epitaxial Si-layers (d ?15 ?m) deposited on thick Si substrates (d = 640 ?m). It was shown that for transistors with the channel width to length ratio W/L = 20/3 ?m without any special antennas used for radiation input, the noise equivalent power (NEP) for radiation frequency ? ?76 GHz can reach NEP ˜6×10-10 W/Hz1/2. With estimated frequency dependent antenna effective area Sest for contact wires considered as antennas, the estimated possible noise equivalent power NEPpos for n-MOSFET structures themselves can be from ˜15 to ˜103 times better in the specral range of ? ˜55-78 GHz reaching NEPpos ?10-12 W/Hz1/2.

  4. Experimental determination of radiated internal wave power without pressure field data

    E-print Network

    Lee, Frank M; Swinney, Harry L; Morrison, P J

    2014-01-01

    We present a method to determine, using only velocity field data, the time-averaged energy flux $\\left$ and total radiated power $P$ for two-dimensional internal gravity waves. Both $\\left$ and $P$ are determined from expressions involving only a scalar function, the stream function $\\psi$. We test the method using data from a direct numerical simulation for tidal flow of a stratified fluid past a knife edge. The results for the radiated internal wave power given by the stream function method agree to within 0.5% with results obtained using pressure and velocity data from the numerical simulation. The results for the radiated power computed from the stream function agree well with power computed from the velocity and pressure if the starting point for the stream function computation is on a solid boundary, but if a boundary point is not available, care must be taken to choose an appropriate starting point. We also test the stream function method by applying it to laboratory data for tidal flow past a knife ed...

  5. Radiative Corrections, Divergences, Regularization, Renormalization, Renormalization Group and All That in Examples in Quantum Field Theory

    E-print Network

    D. I. Kazakov

    2009-01-15

    The present lectures are a practical guide to the calculation of radiative corrections to the Green functions in quantum field theory. The appearance of ultraviolet divergences is explained, their classification is given, the renormalization procedure which allows one to get the finite results is described, and the basis of the renormalization group in QFT is presented. Numerous examples of calculations in scalar and gauge theories are given. Quantum anomalies are discussed. In conclusion the procedure which allows one to get rid of infrared divergences in S-matrix elements is described. The lectures are based on the standard quantum field theory textbooks, the list of which is given at the end of the text. These lectures were given to the 4-th year students of the Department of General and Applied Physics of the Moscow Institute of Physics and Technology (Technical University).

  6. Magnetic tunnel structures: Transport properties controlled by bias, magnetic field, and microwave and optical radiation

    NASA Astrophysics Data System (ADS)

    Volkov, N. V.; Eremin, E. V.; Tarasov, A. S.; Rautskii, M. V.; Varnakov, S. N.; Ovchinnikov, S. G.; Patrin, G. S.

    2012-10-01

    Different phenomena that give rise to a spin-polarized current in some systems with magnetic tunnel junctions are considered. In a manganite-based magnetic tunnel structure in CIP geometry, the effect of current-channel switching was observed, which causes bias-driven magnetoresistance, rf rectification, and the photoelectric effect. The second system under study, ferromagnetic/insulator/semiconductor, exhibits the features of the transport properties in CIP geometry that are also related to the current-channel switching effect. The described properties can be controlled by a bias, a magnetic field, and optical radiation. At last, the third system under consideration is a cooperative assembly of magnetic tunnel junctions. This system exhibits tunnel magnetoresistance and the magnetic-field-driven microwave detection effect.

  7. A novel coaxial Ku-band transit radiation oscillator without external guiding magnetic field

    SciTech Connect

    Ling, Junpu, E-mail: lingjunpu@163.com; Zhang, Jiande; He, Juntao; Jiang, Tao [College of Photoelectric Science and Engineering, National University of Defense Technology, Changsha 410073 (China)] [College of Photoelectric Science and Engineering, National University of Defense Technology, Changsha 410073 (China)

    2014-02-15

    A novel coaxial transit radiation oscillator without external guiding magnetic field is designed to generate high power microwave at Ku-band. By using a coaxial structure, the space-charge potential energy is suppressed significantly, that is good for enhancing efficient beam-wave interaction. In order to improve the transmission stability of the unmagnetized intense relativistic electron beam, a Pierce-like cathode is employed in the novel device. By contrast with conventional relativistic microwave generators, this kind of device has the advantages of high stability, non-guiding magnetic field, and high efficiency. Moreover, with the coaxial design, it is possible to improve the power-handing capacity by increasing the radial dimension of the Ku-band device. With a 550?keV and 7.5?kA electron beam, a 1.25?GW microwave pulse at 12.08?GHz has been obtained in the simulation. The power conversion efficiency is about 30%.

  8. Near-field radiative heat transfer between metamaterials coated with silicon carbide thin films

    NASA Astrophysics Data System (ADS)

    Basu, Soumyadipta; Yang, Yue; Wang, Liping

    2015-01-01

    In this letter, we study the near-field radiative heat transfer between two metamaterial substrates coated with silicon carbide (SiC) thin films. It is known that metamaterials can enhance the near-field heat transfer over ordinary materials due to excitation of magnetic plasmons associated with s polarization, while strong surface phonon polariton exists for SiC. By careful tuning of the optical properties of metamaterial, it is possible to excite electrical and magnetic resonances for the metamaterial and surface phonon polaritons for SiC at different spectral regions, resulting in the enhanced heat transfer. The effect of the SiC film thickness at different vacuum gaps is investigated. Results obtained from this study will be beneficial for application of thin film coatings for energy harvesting.

  9. Near-Field Radiative Heat Transfer between Metamaterials coated with Silicon Carbide Film

    E-print Network

    Basu, Soumyadipta; Wang, Liping

    2014-01-01

    In this letter, we study the near-field radiative heat transfer between two metamaterial substrates coated with silicon carbide (SiC) thin films. It is known that metamaterials can enhance the near-field heat transfer over ordinary materials due to excitation of magnetic plasmons associated with s polarization, while strong surface phonon polariton exists for SiC.By careful tuning of the optical properties of metamaterial it is possible to excite electrical and magnetic resonance for the metamaterial and surface phonon polaritons for SiC at different spectral regions, resulting in the enhanced heat transfer. The effect of the SiC film thickness at different vacuum gaps is investigated. Results obtained from this study will be beneficial for application of thin film coatings for energy harvesting.

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

    NASA Astrophysics Data System (ADS)

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

    2005-02-01

    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 Gy of 6 MV therapeutic x-rays. The sensitivity of SWNT-FET devices to x-ray irradiation is elucidated by real-time dose monitoring experiments and accumulated dose reading based on threshold voltage shift. SWNT-FET devices exhibit sensitivities to x-rays that are at least comparable to or orders of magnitude higher than commercial MOSFET (metal-oxide semiconductor field effect transistor) dosimeters and could find applications as miniature dosimeters for microbeam profiling and implantation.

  11. Radiators

    Microsoft Academic Search

    1985-01-01

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

  12. Radiation 

    E-print Network

    Unknown

    2011-08-17

    State. s. ABSTRACT This study is an attempt to find a tentative atmospheric index of human comfort and to show its applications for the area of College Station~ Texas. Temperature, relative humidity~ air move- ment, and global short-wave radiation... (direct plus diffuse) were combined into a single numerical expression for outdoor human comfort. The contribution of global short-wave radiation to the heat load on man also is evaluated in a single numerical expression, and expressed as an equivalent...

  13. A prototype scintillation dosimeter customized for small and dynamic megavoltage radiation fields.

    PubMed

    Lambert, Jamil; Yin, Yongbai; McKenzie, David R; Law, Susan H; Ralston, Anna; Suchowerska, Natalka

    2010-02-21

    A prototype plastic scintillation dosimeter has been developed with a small sensitive volume, rapid response and good dosimetric performance. The novelty of this design is the use of an air core light guide to transport the scintillation signal out of the primary radiation field. The significance of this innovation is that it eliminates the Cerenkov background signal that is generated in conventional optical fibres. The dosimeter performance was compared to existing commercial dosimeters in 6 MV and 18 MV photon beams and 6 MeV and 20 MeV electron beams, in both static and dynamic fields. The dosimeter was tested in small static fields and in dynamically delivered fields where the detector volume is shielded, while the stem is irradiated. The depth dose measurements for the photon beams agreed with ionization chamber measurements to within 1.6%, except in the build-up region due to positional uncertainty. For the 6 MeV and 20 MeV electron beams, the percentage depth dose measurements agreed with the ionization chamber measurements to within 3.6% and 4.5%, respectively. For field sizes of 1 cm x 1 cm and greater, the air core dosimeter readings agreed with diamond detector readings to within 1.2%. The air core dosimeter was accurate in dynamically delivered fields and had no measurable stem effect. The air core dosimeter was accurate over a range of field sizes, energies and dose rates, confirming that it is a sensitive and accurate dosimeter with high spatial resolution suitable for use in megavoltage photon and electron beams. PMID:20107251

  14. Investigation of the behavior of protection elements against field radiated line coupled UWB-pulses

    NASA Astrophysics Data System (ADS)

    Krzikalla, R.; Ter Haseborg, J. L.

    2006-09-01

    To protect electronic systems against electromagnetic interferences in general nonlinear protection circuits are used. These protection circuits are optimized mostly against special transient interferences such as lightning electromagnetic pulses (LEMP) or electromagnetic pulses caused by nuclear explosions (NEMP). Previous investigations have shown that these protection elements could be undermined by so-called ultra wideband (UWB) pulses. Thereby a direct charge of the UWB-pulse to the elements has been assumed. This assumption was a worst case approximation because in practice UWB-pulses only get into systems by coupling effects. In this investigation the behavior of typical nonlinear protection elements has been tested with field radiated line coupled UWB-pulses. For that line coupled UWB-pulses have been defined depending on the coupling behavior of typical electronic systems and a possibility of generation of this kind of pulses is presented. After it typical nonlinear protection elements such as spark gaps, varistors and protection diodes have been tested with the previously defined test pulses. Finally the measured behavior of the elements has been compared with the behavior by direct charged UWB-pulses and the protection effect of the elements against field radiated line coupled UWB-pulses is re-evaluated.

  15. Hot accretion disks with pairs: Effects of magnetic field and thermal cyclocsynchrotron radiation

    NASA Astrophysics Data System (ADS)

    Kusunose, Masaaki; Zdziarski, Andrzej A.

    1994-02-01

    We show the effects of thermal cyclosynchrotron radiation and magnetic viscosity on the structure of hot, two-temperature accretion disks. Magnetic field, B, is assumed to be randomly oriented and the ratio of magnetic pressure to either gas pressure, alpha = Pmag/Pgas, or the sum of the gas and radiation pressures, alpha = (Pmag/Pgas + Prad), is fixed. We find those effects do not change the qualitative properties of the disks, i.e., there are still two critical accretion rates related to production of e+/- pairs, (M dot)(Ucr) and (M dot)(Lcr), that affect the number of local and global disk solutions, as recently found by Bjoernsson and Svensson for the case with B = 0. However, a critical value of the alpha-viscosity parameter above which those critical accretion rates disappear becomes smaller than alphacr = 1 found in the case of B = 0, for Pmag = alpha(Pgas + Prad). If Pmag = alpha Pgas, on the other hand, alphacr is still about unity. Moreover, when Comptonized cyclosynchrotron radiation dominates Comptonized bremsstrahlung, radiation from the disk obeys a power law with the energy spectral index of approximately 0.5, in a qualitative agreement with X-ray observations of active galactic nuclei (AGNS) and Galactic black hole candidates. We also extend the hot disk solutions for Pmag = alpha(Pgas + Prad) to the effectively optically thick region, where they merge with the standard cold disk solutions. We find that the mapping method by Bjoernsson and Svensson gives a good approximation to the disk structure in the hot region and show where it breaks in the transition region. Finally, we find a region in the disk parameter space with no solutions due to the inability of Coulomb heating to supply enough energy to electrons.

  16. Dependence of absorbed dose along the radiation beam axis on depth and on radiation field for photons produced in linac Saturne II plus.

    PubMed

    Lobodziec, W

    1987-05-01

    The paper discusses the dependence of percentage depth dose and tissue phantom ratio on depth and on radiation field size for photons produced in a linac Saturne II plus. The results expressed by the simple formulas have been presented in tables and on graphs. PMID:3589960

  17. Analytical Model for Calculating the Radiation Field of Microstrip Antennas With Artificial Magnetic Superstrates: Theory and Experiment

    Microsoft Academic Search

    Hussein Attia; Leila Yousefi; Omar M. Ramahi

    2011-01-01

    A fast analytical solution for the radiation field of a microstrip antenna loaded with a generalized superstrate is proposed using the cavity model of microstrip antennas in con- junction with the reciprocity theorem and the transmission line analogy. The proposed analytical formulation for the antenna's far-field is much faster when compared to full-wave numerical methods. It only needs 2% of

  18. Study of electric field radiated by WiFi sources inside an aircraft - 3D computations and real tests

    Microsoft Academic Search

    Emmanuel Perrin; Fabrice Tristant; Stéphane Gouverneur; René Fayat; Christophe Guiffaut; Alain Reineix; Jean-Patrick Moreau

    2008-01-01

    In this paper, the electric field radiated by WiFi sources inside an aircraft is studied. 3D modeling using the FDTD method allows calculation of electric field near punctual locations and on the entire aircraft's surface. The influence of the furniture inside the cabin is also discussed. Measurements in the aircraft (a Dassault Aviation Falcon) are presented. The comparison with real

  19. A comparison of RF field uniformity in a compact semi-anechoic room and OATS

    Microsoft Academic Search

    J. E. Teune; S. W. Mee

    2001-01-01

    To provide a uniform RF field for immunity testing, a basic understanding of the antenna beamwidth radiation pattern is required. Ground floor and wall reflections and resonance contribute to the field nonuniformity. During the process of developing an automotive RF immunity test requirement, obstacles to meeting this requirement were encountered due to the absence of an absorber lined ground plane

  20. Cosmological Consequences of Classical Flavor-Space Locked Gauge Field Radiation

    E-print Network

    Bielefeld, Jannis

    2015-01-01

    We propose a classical SU(2) gauge field in a flavor-space locked configuration as a species of radiation in the early universe, and show that it would have a significant imprint on a primordial stochastic gravitational wave spectrum. In the flavor-space locked configuration, the electric and magnetic fields of each flavor are parallel and mutually orthogonal to other flavors, with isotropic and homogeneous stress-energy. Due to the non-Abelian coupling, the gauge field breaks the symmetry between left- and right-circularly polarized gravitational waves. This broken chiral symmetry results in a unique signal: non-zero cross correlation of the cosmic microwave background temperature and polarization, $TB$ and $EB$, both of which should be zero in the standard, chiral symmetric case. We forecast the ability of current and future CMB experiments to constrain this model. Furthermore, a wide range of behavior is shown to emerge, depending on the gauge field coupling, abundance, and allocation into electric and mag...

  1. Near-Field Radiation Between Graphene-Covered Carbon Nanotube Arrays

    NASA Astrophysics Data System (ADS)

    Zhang, Richard; Liu, Xianglei; Zhang, Zhuomin; Nanoscale Thermal Radiation Laboratory Team

    2015-03-01

    It has been shown that at nanometer gap distances, or the near-field, thermal radiation is enhanced over blackbody between hyperbolic metamaterials. It was shown that vertically aligned carbon nanotube (VACNT) arrays in the near-field demonstrate exceptional enhancement. In this study, graphene is covered on the surfaces of two semi-infinite VACNT arrays separated by a sub-micron vacuum gap. Doped graphene (? >= 0.3 eV) is found to improve photon tunneling in a broad hyperbolic frequency range, due to the interaction with graphene-graphene surface plasmons. Increasing doping that shifts the peak spectral heat flux toward higher frequencies attests to the tunable bandgap of graphene. Although graphene covering of VACNT does not offer many magnitudes of near-field heat flux enhancement over uncovered VACNT, this study identifies conditions (i.e. gap distance and doping) that best augments heat transfer to that of VACNT arrays. In addition, this study demonstrates the near-field Poynting vector to determine the energy absorption due to graphene. It is found that graphene, in low frequencies and high chemical potentials, attenuates large penetration depths of hyperbolic modes, thereby increasing the contribution of graphene-graphene surface plasmons. This study has an impact toward designing carbon-based emitters and thermal junctions.

  2. The effect of cumulus cloud field anisotropy on solar radiative fluxes and atmospheric heating rates

    NASA Astrophysics Data System (ADS)

    Hinkelman, Laura M.

    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.

  3. Near-field effects of Cherenkov radiation induced by ultra high energy cosmic neutrinos

    NASA Astrophysics Data System (ADS)

    Hu, Chia-Yu; Chen, Chih-Ching; Chen, Pisin

    2012-02-01

    The radio approach based on the Askaryan effect for detecting the ultra-high energy cosmic neutrinos has become a mature experimental technique. So far the existing calculations of the Cherenkov radiation associated with the Askaryan effect has been mostly based on the far-field approximation, whose validity maybe challenged when the detector is close to the event. In this paper we present an alternative approach to calculate the Cherenkov pulse by a numerical code based on the finite difference time-domain (FDTD) method. This approach has the advantage of providing the solution everywhere in space, contrary to other methods that rely on the far-field approximation. We also present a one-dimensional theoretical model for the shower with analytical solution, which helps to elucidate our nonzero-width simulation results. We show that for a shower with symmetric longitudinal development, the resulting near-field waveform would be asymmetric in time. In addition, we demonstrate that for a shower elongated by the LPM (Landau-Pomeranchuk-Migdal) effect and thus with a multi-peak structure, a bipolar, asymmetric waveform is still preserved in the near-field regime irrespective of the specific variations of the multi-peak structure, which makes it a generic, distinctive feature. This should provide an important characteristic signature for the identification of ultra-high energy cosmogenic neutrinos.

  4. Exposures involving perturbations of the EM field have non-linear effects on radiation response and can alter the expression of radiation induced bystander effects

    NASA Astrophysics Data System (ADS)

    Mothersill, Carmel; Seymour, Colin

    2012-07-01

    Our recent data suggest there is a physical component to the bystander signal induced by radiation exposure and that alternative medicine techniques such as Reiki and acupuncture or exposures to weak EM fields alter the response of cells to direct irradiation and either altered bystander signal production or altered the response of cells receiving bystander signals. Our proposed mechanism to explain these findings is that perturbation of electromagnetic (EM) fields is central to the induction of low radiation dose responses especially non-targeted bystander effects. In this presentation we review the alternative medicine data and other data sets from our laboratory which test our hypothesis that perturbation of bio-fields will modulate radiation response in the low dose region. The other data sets include exposure to MRI, shielding using lead and or Faraday cages, the use of physical barriers to bystander signal transmission and the use of membrane channel blockers. The data taken together strongly suggest that EM field perturbation can modulate low dose response and that in fact the EM field rather than the targeted deposition of ionizing energy in the DNA may be the key determinant of dose response in a cell or organism The results also lead us to suspect that at least when chemical transmission is blocked, bystander signals can be transmitted by other means. Our recent experiments suggest light signals and volatiles are not likely. We conclude that alternative medicine and other techniques involving electromagnetic perturbations can modify the response of cells to low doses of ionizing radiation and can induce bystander effects similar to those seen in medium transfer experiments. In addition to the obvious implications for mechanistic studies of low dose effects, this could perhaps provide a novel target to exploit in space radiation protection and in optimizing therapeutic gain during radiotherapy.

  5. Comparison of target coverage and dose to organs at risk between simultaneous integrated-boost whole-field intensity-modulated radiation therapy and junctioned intensity-modulated radiation therapy with a conventional radiotherapy field in treatment of nasopharyngeal carcinoma

    Microsoft Academic Search

    Jin-Beom Chung; Jeong-Woo Lee; Jae-Sung Kim; In-Ah Kim; Doo-Hyun Lee; Yon-Lae Kim; Kyoung-Sik Choi; Bo-Young Choe; Tae-Suk Suh

    We have retrospectively investigated 15 nasopharyngeal carcinoma patients treated at our institution between March 2007 and\\u000a August 2009. We used simultaneous integrated-boost whole field intensity-modulated radiation therapy (SIB WF-IMRT) to treat\\u000a the entire planning target volume in the head and neck cancer. All of the SIB WF-IMRT plans were replanned by use of the junctioned\\u000a intensity modulated radiation therapy (J-IMRT)

  6. Acoustic radiation force in tissue-like solids due to modulated sound field

    NASA Astrophysics Data System (ADS)

    Dontsov, Egor V.; Guzina, Bojan B.

    2012-10-01

    The focus of this study is the sustained body force (the so-called acoustic radiation force) in homogeneous tissue-like solids generated by an elevated-intensity, focused ultrasound field (Mach number=O(10-3)) in situations when the latter is modulated by a low-frequency signal. This intermediate-asymptotics problem, which bears relevance to a number of emerging biomedical applications, is characterized by a number of small (but non-vanishing) parameters including the Mach number, the ratio between the modulation and ultrasound frequency, the ratio of the shear to bulk modulus, and the dimensionless attenuation coefficient. On approximating the response of soft tissues as that of a nonlinear viscoelastic solid with heat conduction, the featured second-order problem is tackled via a scaling paradigm wherein the transverse coordinates are scaled by the width of the focal region, while the axial and temporal coordinate are each split into a "fast" and "slow" component with the twin aim of: (i) canceling the linear terms from the field equations governing the propagation of elevated-intensity ultrasound, and (ii) accounting for the effect of ultrasound modulation. In the context of the focused ultrasound analyses, the key feature of the proposed study revolves around the dual-time-scale treatment of the temporal variable, which allows one to parse out the contribution of ultrasound and its modulation in the nonlinear solution. In this way the acoustic radiation force (ARF), giving rise to the mean tissue motion, is exacted by computing the "fast" time average of the germane field equations. A comparison with the existing theory reveals a number of key features that are brought to light by the new formulation, including the contributions to the ARF of ultrasound modulation and thermal expansion, as well as the precise role of constitutive nonlinearities in generating the sustained body force in tissue-like solids by a focused ultrasound beam.

  7. Emission of terahertz radiation from GaN/AlGaN heterostructure under electron heating in lateral electric field

    SciTech Connect

    Shalygin, V. A.; Vorobjev, L. E.; Firsov, D. A.; Sofronov, A. N.; Melentyev, G. A. [St. Petersburg State Polytechnic University, 195251 St. Petersburg (Russian Federation); Lundin, W. V.; Sakharov, A. V.; Tsatsulnikov, A. F. [Ioffe Physical-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation)

    2013-12-04

    Spontaneous emission of terahertz radiation from modulation-doped AlGaN/GaN heterostructure under conditions of heating of a two-dimensional electron gas in the lateral electric field has been studied. The experimental data on the field dependence of the integral intensity of THz emission is compared with the theoretical simulation of blackbody-like emission from hot 2D electrons. Complementary transport measurements have been carried out to determine the dependence of effective electron temperature on electric field.

  8. THE UNIVERSITY OF UTAH RADIATION PROTECTION PROGRAM

    E-print Network

    Tipple, Brett

    : 45 Medical US: 53 Industrial US: FUNDAMENTALS OF RADIATION by which energy is emitted or propagated through space as particles or waves. Ionizing radiations are those molecular bonds. The radiations most commonly encountered are free electrons and photons of electromagnetic

  9. Experimental verification of isotropic radiation from a coherent dipole source via electric-field-driven LC resonator metamaterials.

    PubMed

    Tichit, Paul-Henri; Burokur, Shah Nawaz; Qiu, Cheng-Wei; de Lustrac, André

    2013-09-27

    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

  10. First spacecraft encounter with an asteroid approaches

    NASA Technical Reports Server (NTRS)

    Tholen, David J.

    1991-01-01

    During the course of the Galileo spacecraft's journey to Jupiter it will make two excursions through the steroid belt situated between Mars and Jupiter. The first excursion involves an encounter with the asteroid 951 Gaspra, which will take place on October 29, 1991. Gaspra is a small (about 15 km diameter) asteroid near the outer edge of the main asteroid belt. It's spectral classification is S, suggesting a composition similar to those of stony-iron meteorites. A figure is given showing the brightness of this asteroid as a function of time.

  11. BWR radiation assessment and control program: assessment and control of BWR radiation fields. Volume 2. Final report

    Microsoft Academic Search

    Marble

    1983-01-01

    This report covers work on the BWR Radiation Assessment and Control (BRAC) Program from 1978 to 1982. The major activities during this report period were assessment of the radiation-level trends in BWRs, evaluation of the effects of forward-pumped heater drains on BWR water quality, installation and operation of a corrosion-product deposition loop in an operating BWR, and analyzation of fuel

  12. BWR Radiation Assessment and Control Program: assessment and control of BWR radiation fields. Volume 1. Executive summary

    Microsoft Academic Search

    Anstine

    1983-01-01

    This report covers work on the BWR Radiation Assessment and Control (BRAC) Program from 1978 to 1982. The major activities during this report period were assessment of the radiation-level trends in BWRs, evaluation of the effects of forward-pumped heater drains on BWR water quality, installation and operation of a corrosion-product deposition loop in an operating BWR, and analyzation of fuel-deposit

  13. Radiation Field of Packages Carrying Spent Co-60 Radioactive Sources - 12437

    SciTech Connect

    Marzo, Giuseppe A.; Giorgiantoni, Giorgio; Sepielli, Massimo [ENEA, C. R. Casaccia, Roma (Italy)

    2012-07-01

    Among the diverse radioactive sources commonly exploited in medical and industrial applications, Co- 60 is increasingly used as strong gamma emitter. Over time, source manufacturers favored Co-60 as opposed to other gamma emitters because its relatively short half-life (5.27 year) that minimizes issues related to the management of disused sources. Disused Co-60 sources can retain a significant amount of radioactivity (from hundreds of MBq to several GBq) that still poses safety concerns on their handling and transportation. In this context a detailed knowledge of their radiation field would provide the necessary information for taking actions in preventing unnecessary doses to the workers and the population by optimizing transportation procedures and handling operations. We modeled the geometry and the materials constituting a transportation packaging of a spent Co-60 source which had an original maximum activity of a few GBq and was enclosed in a small lead irradiator. Then we applied a Monte Carlo transport code (MCNP5) for tracking down the gamma photons emitted by the source, including the secondary photons resulting by the interaction of the source photons with the surrounding materials. This allowed for the evaluation of the radiation field inside and outside the packaging, and the corresponding equivalent dose useful for checking the compliance with the regulations and the health risk of possible radiation exposure. We found that a typical 60-liters drum carrying a spent Co-60 source, enclosed in its original irradiator, with a residual activity of 300 MBq could already overcome an equivalent dose of 0.2 mSv/h on the drum external surface, which is the maximum equivalent dose at any point of the surface for this packaging as prescribed by local regulations. This condition is even more apparent when the source is slightly displaced with respect to the rotation axis of the drum, an easily occurring condition for sources not properly packaged, generating non-compliant hot-spots on the drum surface. As an example, a displacement of 5 cm translates in an increase of 80% in the dose level on the nearest side of the drum. We also found that the equivalent dose is significantly influenced by the scattered source photons and the secondary photons, whose contribution to the radiation field is mainly determined by the package geometry. The developed model resulted in an important tool for exploring the detail of the radiation field of a spent Co-60 source packaged for transportation allowing to check for compliance with the regulations and to evaluate risks to the workers and the population. It is worth to point out that this modeling approach is completely general and can be applied to a variety of different problems not limited to the transportation of radioactive material. In the example illustrated in this work, a small Co-60 source inside its irradiator and properly packaged in a drum for transport, presents a hot-spot on the drum surface if the irradiator is displaced of just few centimeters with respect to the rotation axis of the drum. A Monte Carlo simulation provided a complete description of the radiation field in the volume surrounding the packaging as a function of photon energy showing that a significant contribution comes from source photons scattered by the package itself. As an example, the Transport Index (TI) of this packaging was calculated, resulting in a value of 0.5. This value is low when compared to the regulations, however suggests that an individual just 1 meter afar from the packaging receives, in a few hours, a dose comparable to that received with a radiograph. This might be the case of the driver of a truck transporting the packaging, in particular when a number of packages are transported at the same time. It is important to notice that the results presented in this work are general, and can be appropriately scaled to represent the radiation field of similar geometries with gamma sources of different activity. However, this quick application of a Monte Carlo simulation provides useful insights

  14. Intercomparison of radiation protection devices in a high-energy stray neutron field, Part I: Monte Carlo simulations

    Microsoft Academic Search

    S. Rollet; S. Agosteo; G. Fehrenbacher; C. Hranitzky; T. Radon; M. Wind

    2009-01-01

    An intercomparison of radiation protection devices in a high-energy stray neutron field was held in the framework of the COordinated Network for Radiation Dosimetry [CONRAD, http:\\/\\/www.eurados.org\\/conrad\\/conrad_overview.htm], financed by the European Commission. An irradiation hall of the GSI (Gesellschaft für Schwerionenforschung, Darmstadt, Germany) was the facility selected for this benchmark experiment. The measurements were carried out outside the shielding barriers of

  15. Effects of Photoperiod, Temperature and Radiation on the Rate of Leaf Appearance in Quinoa ( Chenopodium quinoa Willd.) under Field Conditions

    Microsoft Academic Search

    H. Daniel Bertero

    2001-01-01

    Effects of radiation on the phyllochron of nine quinoa (Chenopodium quinoa Willd.) cultivars growing under field conditions were quantified. Rate of change of photoperiod had no effect on phyllochron. Radiation responses differed markedly between cultivars, ranging from insensitive in the most tropical cultivars (Nariño and Ecu-621) to 0.55°Cdmol PPFDm?2d?1in the Peruvian cultivar Amarilla de Marangan??. Cultivars reported as having the

  16. Effects of enhanced ultraviolet-B radiation on plant nutrients and decomposition of spring wheat under field conditions

    Microsoft Academic Search

    Ming Yue; Yuan Li; Xunling Wang

    1998-01-01

    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

  17. Intraspecific responses in grain quality of 10 wheat cultivars to enhanced UV-B radiation under field conditions

    Microsoft Academic Search

    Yanqun Zu; Yuan Li; Jianjun Chen; Haiyan Chen

    2004-01-01

    Field studies were conducted to determine the potential for intraspecific responses in grain quality of 10 wheat (Triticum aestivum) cultivars to enhanced ultraviolet-B (UV-B, 280–315 nm) radiation. The plants were exposed to 5 kJm?2 supplemental UV-B radiation, simulating a depletion of 20% stratospheric ozone. In wheat cultivars tested, intraspecific responses in 16 amino acid contents and total amino acid contents

  18. Intraspecific differences in physiological response of 20 soybean cultivars to enhanced ultraviolet-B radiation under field conditions

    Microsoft Academic Search

    Zu Yanqun; Li Yuan; Chen Haiyan; Chen Jianjun

    2003-01-01

    Field studies were conducted to determine the potential for alterations in physiology and the intraspecific variation in physiological sensitivity of 20 soybean cultivars to enhanced ultraviolet-B (UV-B, 280–315 nm) radiation. The supplemental UV-B radiation was 5 kJ m?2, simulating a depletion of 20% stratospheric ozone. Out of 20 soybean cultivars (from South China, North China) tested, twelve showed significant decreases

  19. Intraspecific differences in physiological response of 20 wheat cultivars to enhanced ultraviolet-B radiation under field conditions

    Microsoft Academic Search

    Li Yuan; Zu Yanqun; Chen Jianjun; Chen Haiyan; Yang Jilong; Hu Zhide

    2000-01-01

    Field studies were conducted to determine the potential for alterations in physiology and the intraspecific variation in sensitivity of 20 wheat (Triticum aestivum) cultivars to enhanced ultraviolet-B (UV-B, 280–315 nm) radiation. The supplemental UV-B radiation was 5 kJ m?2, simulating a depletion of 20% stratospheric ozone. Out of 20 wheat cultivars (from South China, North China and Mexico) tested, 13

  20. Near-field radiative thermal transfer between a nanostructured periodic material and a planar substrate

    NASA Astrophysics Data System (ADS)

    Chalabi, Hamidreza; Hasman, Erez; Brongersma, Mark L.

    2015-01-01

    This paper provides a method based on rigorous coupled wave analysis for the calculation of the radiative thermal conductance between a layer that is patterned with arbitrary, periodically repeating features and a planar substrate. This method is applied to study the transfer from an array of beams with a rectangular cross section. The impact of the structure size and spacing on the thermal conductance are investigated. These calculations are compared to an effective medium theory, which becomes increasingly accurate as the structure sizes fall well below the relevant resonance wavelengths of materials and structures. Moreover, comparisons are made with a modified proximity approximation and the far-field approximation, which become valid for small and large spacings, respectively. Results show that new levels of control over the magnitude and spectral contributions to thermal conductance can be achieved with corrugated structures relative to planar ones. Specifically, we show for SiC arrays with rectangular cross sections and with the same filling fraction, that the use of a smaller periodicity leads to a lowered far-field thermal transfer and an increased near-field thermal transfer.

  1. Simulation of Relativistic Shocks and Associated Radiation from Turbulent Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.; Niemiec, J.; Medvedev, M.; Zhang, B.; Hardee, P.; Mizuno, Y.; Nordlund, A.; Frederiksen, J.; Sol, H.; Pohl, M.; Oka, M.; Hartmann, D. H.; Fishman, J. F.

    2009-01-01

    Plasma instabilities (e.g., Buneman, Weibel and other two-stream instabilities) excited in collisionless shocks are responsible for particle (electron, positron, and ion) acceleration. Using a new 3-D relativistic particle-in-cell code, we have investigated the particle acceleration and shock structure associated with an unmagnetized relativistic electron-positron jet propagating into an unmagnetized electron-positron plasma. The simulation has been performed using a long simulation system in order to study the nonlinear stages of the Weibel instability, the particle acceleration mechanism, and the shock structure. Cold jet electrons are thermalized and slowed while the ambient electrons are swept up to create a partially developed hydrodynamic (HD) like shock structure. In the leading shock, electron density increases by a factor of <_ 3.5 in the simulation frame. Strong electromagnetic fields are generated in the trailing shock and provide an emission site. We discuss the possible implication of our simulation results within the AGN and GRB context. We have calculated the time evolution of the spectrum from two electrons propagating in a uniform parallel magnetic field to verify the technique. The same technique will be used to calculate radiation from accelerated electrons (positrons) in turbulent magnetic fields generated by Weibel instability.

  2. Comet Hyakutake's close encounter with the Sun

    NASA Astrophysics Data System (ADS)

    1996-05-01

    LASCO is a joint project between NRL (USA), the Max Planck Institut für Aeronomie (Germany), the Laboratoire d'Astronomie Spatiale (France), and the School of Physics and Space Research at the University of Birmingham (UK). "Such observations require a special instrument in space to suppress the glare of the Sun and reveal the comet and its tails", said Dr. Guenter Brueckner, NRL's principal investigator for LASCO. Scattering of sunlight in the Earth's atmosphere prevented good views from the ground during the comet's "perihelion passage" when it was closest to the Sun. The orbital period of Comet Hyakutake has been estimated to be 10,000 years. Hyakutake is called a "new" comet because it was not seen when, and if, it last visited the solar system. As Hyakutake approaches the Sun, it is being heated enormously. If this is the first visit of the comet, it could be broken into pieces, according to scientists. Images captured by the LASCO instrument have shown that this did not happen when the comet was in LASCO's field of view, which is approximately the size of the constellation Orion. "Comet Hyakutake could have passed through the solar system many times before", said Dr. Brueckner, who is also head of the NRL's Solar Physics Branch. "How many times remains a mystery". Hyakutake's orbit carries it back into the so-called "Oort Cloud" a vast collection of billions of comets that is located 1.4 light years away from the solar system. These comets are presumably the remnants of the cloud from which the solar system were formed billions of years ago. When the comet enters the outer atmosphere of the Sun, it begins to react with the Sun's environment and can be used as a "probe" of the solar corona. LASCO images show the head of the comet, and clearly visible are three separate tails that behave differently as Hyakutake swings around the Sun. These tails are made of different materials ; dust of different sizes, perhaps chunks of ice and atomic particles, each of which reacts differently with their environment. The heavy particles follow the comet in its orbit without being redirected by an outside force while the light dust particles are lining up away from the Sun and are driven by the Sun's intensive radiation. Finally, the atomic particles are repelled from the comet by the solar wind and presumably line up with the magnetic field of the solar corona. As the comet speeds through the corona at 37 miles per second, these forces have direct influence on its tails, which could clearly be seen changing their relative direction over the seven-day observation period. Coronal mass ejections were also observed by LASCO, in which hot gases were expelled and accelerated by the corona's magnetic field to travel through the interplanetary medium. A strong reaction between such a solar high-speed cloud and the portion of the comet's tails made of atomic particles is expected when Hyakutake crosses the equatorial plane of the Sun. The comet was out of LASCO's field of view during this crossing, but the scientists will have another opportunity when Hyakutake reappears from behind the Sun and can be seen later in the southern hemisphere's night sky with ordinary telescopes. Researchers expect to learn more about the tails of the comet and the surrounding solar corona with more detailed analysis. SOHO is a project of international cooperation between ESA and NASA. More information can be found on the LASCO Comet Hyakutake page on the World Wide Web http://lasco-www.nrl.navy.mil/b2-1996.html and on the SOHO home page http://sohowww.nascom.nasa.gov.

  3. STELLAR ENCOUNTER RATE IN GALACTIC GLOBULAR CLUSTERS

    SciTech Connect

    Bahramian, Arash; Heinke, Craig O.; Sivakoff, Gregory R.; Gladstone, Jeanette C., E-mail: bahramia@ualberta.ca [Department of Physics, University of Alberta, CCIS 4-183, Edmonton, AB, T5K 1V4 (Canada)

    2013-04-01

    The high stellar densities in the cores of globular clusters cause significant stellar interactions. These stellar interactions can produce close binary mass-transferring systems involving compact objects and their progeny, such as X-ray binaries and radio millisecond pulsars. Comparing the numbers of these systems and interaction rates in different clusters drives our understanding of how cluster parameters affect the production of close binaries. In this paper we estimate stellar encounter rates ({Gamma}) for 124 Galactic globular clusters based on observational data as opposed to the methods previously employed, which assumed 'King-model' profiles for all clusters. By deprojecting cluster surface brightness profiles to estimate luminosity density profiles, we treat 'King-model' and 'core-collapsed' clusters in the same way. In addition, we use Monte Carlo simulations to investigate the effects of uncertainties in various observational parameters (distance, reddening, surface brightness) on {Gamma}, producing the first catalog of globular cluster stellar encounter rates with estimated errors. Comparing our results with published observations of likely products of stellar interactions (numbers of X-ray binaries, numbers of radio millisecond pulsars, and {gamma}-ray luminosity) we find both clear correlations and some differences with published results.

  4. Spectroscopic diagnosis of long-scale-length exploding-foil plasma in the presence of an intense radiation field

    SciTech Connect

    Shepard, T.D.; Keane, C.J.; Suter, L.J. (Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)); Abdallah, J. Jr. (Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States))

    1992-10-01

    An effective technique for measuring the local electron temperature and density of a laser-produced plasma involves analysis of the emission and/or absorption spectrum from an impurity dopant. However, when an intense high-energy radiation field is present the ionization balance, level population, and resulting spectrum produced by the impurity may be significantly perturbed. We are currently using several computer models to study the effects of such a radiation field for experimental conditions that could be obtained using the Nova laser facility, and are concentrating on the behavior of line intensity ratios that are typically used for density and temperature diagnosis. The goal of this work is to determine the feasibility of spectroscopic diagnosis when an intense high-energy radiation field is present.

  5. Shielding of radiation fields generated by {sup 252}Cf in a concrete maze. Part 1: Experiment

    SciTech Connect

    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

    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.

  6. Multiphoton Ionization of Hydrogen Atoms in a Circularly Polarized Strong Radiation Field

    NASA Astrophysics Data System (ADS)

    Titi, A. S.; Drake, G. W. F.

    2007-06-01

    The scattering matrix for the multiphoton ionization of a hydrogen atom in a circularly polarized strong radiation field, where the Coulomb potential is also included, is calculated. This leads to a divergent scattering matrix. By carrying out a unitary transformation to a frame in which the electron sees an oscillating nucleus, the singularity can be isolated and removed. The expression for the resulting nonsingular scattering matrix is written in terms of Bessel functions (representing direct single scattering) and Anger functions (representing rescattering). Both contributions interfere quantum mechanically. Intuitively, this provides a direct link to a path integral formulation of the problem. Finally, to compare our calculations with other calculations and to experimental results, the angular distribution of the ejected electrons is computed.

  7. Nuclear Radiation Fields on the Mars Surface: Risk Analysis for Long-term Living Environment

    NASA Technical Reports Server (NTRS)

    Anderson, Brooke M.; Clowdsley, Martha S.; Qualls, Garry D.; Nealy, John E.

    2005-01-01

    Mars, our nearest planet outward from the sun, has been targeted for several decades as a prospective site for expanded human habitation. Background space radiation exposures on Mars are expected to be orders of magnitude higher than on Earth. Recent risk analysis procedures based on detailed dosimetric techniques applicable to sensitive human organs have been developed along with experimental data regarding cell mutation rates resulting from exposures to a broad range of particle types and energy spectra. In this context, simulated exposure and subsequent risk for humans in residence on Mars are examined. A conceptual habitat structure, CAD-modeled with duly considered inherent shielding properties, has been implemented. Body self-shielding is evaluated using NASA standard computerized male and female models. The background environment is taken to consist not only of exposure from incident cosmic ray ions and their secondaries, but also include the contribution from secondary neutron fields produced in the tenuous atmosphere and the underlying regolith.

  8. The high energy gamma-ray background and the interstellar radiation field

    NASA Astrophysics Data System (ADS)

    Chary, Ranga-Ram

    This thesis provides an independent estimate of the high latitude (! b! > 20°) contribution to the E > 30 MeV gamma-ray background from Galactic nucleon-nucleon, electron bremsstrahlung and inverse Compton processes. In particular, the inverse Compton contribution has been estimated for different cosmic ray electron distributions and after factoring in the anisotropy in the interstellar radiation field and the anisotropic Klein-Nishina scattering cross section. A model for the interstellar radiation field from 0.1 ?m to 1000 ?m is also presented to fit the intensities observed by recent satellite experiments, especially the DIRBE and FIRAS instruments on COBE. I find that the emission from the inverse Compton process when the anisotropy in the radiation field is included can be higher by up to 50% when compared to estimates that adopt an isotropic radiation field. Simulated inverse Compton maps with a cosmic ray electron distribution represented by a ``pill box'' extending up to a distance of 5 kpc above the Galactic plane provide better fits to the EGRET intensity maps suggesting that the cosmic ray halo may be larger than previously thought. With this distribution, I find that the net contribution from the IC process to the gamma-ray background can be as high as 20% at high Galactic latitudes. Fitting for the Galactic components of gamma-ray emission confirms the existence of an isotropic component with an intensity that can be represented by the form 27.7 × E(MeV)-2.16 photons m-2 s-1 sr -1 MeV-1, in excellent agreement with previous estimates. The spectrum of the isotropic component further argues strongly in favor of unresolved gamma-ray blazars being the source of this emission. Introduction of an anisotropic component improves the quality of the fits. However, this component, which could potentially arise from the dark matter in the Galactic halo, is not well characterized by a single power law which might be associated with any single dark matter candidate. It has an intensity of about a third of the isotropic background above E > 100 MeV-1, at the level of 3 × 10-2 photons m-2 s-1 sr-1 . The best fit power law spectrum to this component has a photon index of -1.7. Based on the intensity and spectrum of the anisotropic component I derive upper limits of 109Msolar for the mass of cold, baryonic gas within the solar circle and a primordial black hole number density limit of 7 × 107 pc -3 which is more than an order of magnitude smaller than previous limits. If the spectrum of the anisotropic component is indeed confirmed to have an index of -1.7, it appears more likely that the signal arises in unresolved Galactic sources such as pulsars.

  9. New Results from Space and Field Observations on the Aerosol Direct and Indirect Radiative Forcing

    NASA Technical Reports Server (NTRS)

    Kaufman, Yoram J.; Remer, Lorraine; Tanre, Didier; Boucher, Olivier; Chin, Mian; Dubovik, Oleg; Holben, Brent

    2002-01-01

    New space observations from the MODIS instrument on board the Terra satellite and analysis of POLDER data flown on the ADEOS satellite, show in great details the spatial and seasonal variability of the global aerosol system. These spaceborne instruments distinguish fine aerosol from man-made regional pollution and biomass burning from mostly natural coarse dust and sea salt aerosol. E.g. fine regional pollution in and around the Indian sub-continent, Europe and North America; smoke from biomass burning in Southern Africa and Southern America; coarse dust from West Africa and mixed dust pollution and smoke from West and central Africa and East Asia. These regions were also studied extensively in focused field experiments and by the distributed AERONET network. The results generate the first climatologies of the aerosol system, are used to derive the aerosol radiative effects and to estimate the anthropogenic component. The measurements are also used to evaluate each other and constrain aerosol transport models.

  10. Linearly polarized radiation from astrophysical masers due to magnetic fields of intermediate strength

    NASA Technical Reports Server (NTRS)

    Nedoluha, Gerald E.; Watson, William D.

    1990-01-01

    Previous solutions for polarization of astrophysical maser radiation due to closed-shell molecules in a magnetic field have potentially serious limitations. These solutions are mostly based on the approximation that the Zeeman frequency g-Omega is much greater than the rate for stimulated emission R and the rate for decay Gamma of the molecular state. Others are asymptotic solutions obtained for an angular momentum J = 1-0 transition. It has been unclear whether the polarizations due to plausible Zeeman splittings are adequately represented by the solutions obtained for g-Omega/Gamma much greater than 1 and g-Omega/R much greater than 1. Actual masing transitions tend to involve molecular states with angular momenta that are higher than J = 1 and 0. Numerical solutions for the linear polarization are presented here which do not have the foregoing restrictions on the g-Omega and which are not limited to a J = 1-0 transition.

  11. Sampling and Analysis of Impact Crater Residues Found on the Wide Field Planetary Camera-2 Radiator

    NASA Technical Reports Server (NTRS)

    Kearsley, A. T.; Grime, G. W.; Colaux, J. L.; Jeynes, C.; Palitsin, V. V.; Webb, R, P.; Griffin, T. J.; Reed, B. B.; Anz-Meador, P. D.; Kou, J.-C.; Robinson, G. A.; Opiela, J. N.; Gerlach, L.

    2013-01-01

    After nearly 16 years in low Earth orbit (LEO), the Wide Field Planetary Camera-2 (WFPC2) was recovered from the Hubble Space Telescope (HST) in May 2009, during the 12 day shuttle mission designated STS-125. The WFPC-2 radiator had been struck by approximately 700 impactors producing crater features 300 microns and larger in size. Following optical inspection in 2009, agreement was reached for joint NASA-ESA study of crater residues, in 2011. Over 480 impact features were extracted at NASA Johnson Space Center's (JSC) Space Exposed Hardware clean-room and curation facility during 2012, and were shared between NASA and ESA. We describe analyses conducted using scanning electron microscopy (SEM) - energy dispersive X-ray spectrometry (EDX): by NASA at JSC's Astromaterials Research and Exploration Science (ARES) Division; and for ESA at the Natural History Museum (NHM), with Ion beam analysis (IBA) using a scanned proton microbeam at the University of Surrey Ion Beam Centre (IBC).

  12. Photon-dominated regions around cool stars: The effects of the color temperature of the radiation field

    NASA Technical Reports Server (NTRS)

    Spaans, Marco; Tielens, A. G. G. M.; Dishoeck, Ewine F. Van; Bakes, E. L. O.

    1994-01-01

    We have investigated the influence of the color temperature of the illuminating radiation field on the chemical and thermal structure of photon-dominated regions (PDRs). We present the results of a study of the photoelectric efficiency of heating by large molecules such as polycyclic aromatic hydrocarbons (PAHs) and very small grains for radiation fields characterized by different effective temperatures. We show that the efficiency for cooler (T(sub eff) approximately = 6000-10,000 K) stars is at most an order of magnitude smaller than that for hotter (T(sub eff) approximately = 20,000-30,000 K) stars. While cooler radiation fields result in less ultraviolet photons capable of heating, the efficiency per absorbed photon is higher, because the grains become less positively charged. We also present detailed calculations of the chemistry and thermal balance for generic PDRs (n(sub 0) approximately = 10(exp 3), G(sub 0) approximately = 10(exp 3)). For cooler radiation fields, the H/H2 and C(+)/C/CO transition layers shift toward the surface of the PDR, because fewer photons are available to photodissociate H2 and CO and to ionize C. The dominant cooling lines are the (C II) 158 micron and the (O I) 63 micron lines for the hotter radiation fields, but cooling by CO becomes dominant for a color temperature of 6000 K or lower. The (C II)/CO and (O I)/CO ratios are found to be very good diagnostics for the color temperature of the radiation field.

  13. Hot accretion disks with pairs: Effects of magnetic field and thermal cyclocsynchrotron radiation

    NASA Technical Reports Server (NTRS)

    Kusunose, Masaaki; Zdziarski, Andrzej A.

    1994-01-01

    We show the effects of thermal cyclosynchrotron radiation and magnetic viscosity on the structure of hot, two-temperature accretion disks. Magnetic field, B, is assumed to be randomly oriented and the ratio of magnetic pressure to either gas pressure, alpha = P(sub mag)/P(sub gas), or the sum of the gas and radiation pressures, alpha = (P(sub mag)/P(sub gas) + P(sub rad)), is fixed. We find those effects do not change the qualitative properties of the disks, i.e., there are still two critical accretion rates related to production of e(sup +/-) pairs, (M dot)((sup U)(sub cr)) and (M dot)((sup L)(sub cr)), that affect the number of local and global disk solutions, as recently found by Bjoernsson and Svensson for the case with B = 0. However, a critical value of the alpha-viscosity parameter above which those critical accretion rates disappear becomes smaller than alpha(sub cr) = 1 found in the case of B = 0, for P(sub mag) = alpha(P(sub gas) + P(sub rad)). If P(sub mag) = alpha P(sub gas), on the other hand, alpha(sub cr) is still about unity. Moreover, when Comptonized cyclosynchrotron radiation dominates Comptonized bremsstrahlung, radiation from the disk obeys a power law with the energy spectral index of approximately 0.5, in a qualitative agreement with X-ray observations of active galactic nuclei (AGNS) and Galactic black hole candidates. We also extend the hot disk solutions for P(sub mag) = alpha(P(sub gas) + P(sub rad)) to the effectively optically thick region, where they merge with the standard cold disk solutions. We find that the mapping method by Bjoernsson and Svensson gives a good approximation to the disk structure in the hot region and show where it breaks in the transition region. Finally, we find a region in the disk parameter space with no solutions due to the inability of Coulomb heating to supply enough energy to electrons.

  14. An Almost Linear Time Algorithm for Field Splitting in Radiation Therapy.

    PubMed

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

    2013-08-01

    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) with a maximum leaf spread constraint is used to deliver the prescribed intensity maps (IMs). However, the maximum leaf spread of an MLC may require to split a large intensity map into several overlapping sub-IMs with each being delivered separately. We develop a close-to-linear time algorithm for solving the field splitting problem while minimizing the total complexity of the resulting sub-IMs, thus improving the treatment delivery efficiency. Meanwhile, our algorithm strives to minimize the maximum beam-on time of those sub-IMs. Our basic idea is to formulate the field splitting problem as computing a shortest path in a directed acyclic graph, which expresses a special "layered" structure. The edge weights of the graph satisfy the Monge property, which enables us to solve this shortest path problem by examining only a small portion of the graph, yielding a close-to-linear time algorithm. To minimize the maximum beam-on time of the resulting sub-IMs, we consider an interesting min-max slope path problem in a monotone polygon which is solvable in linear time. The min-max slope path problem may be of interest in its own right. Experimental results based on real medical data and computer generated IMs showed that our new algorithm runs fast and produces high quality field splitting results. PMID:24999294

  15. VISCOUS EVOLUTION AND PHOTOEVAPORATION OF CIRCUMSTELLAR DISKS DUE TO EXTERNAL FAR ULTRAVIOLET RADIATION FIELDS

    SciTech Connect

    Anderson, Kassandra R.; Adams, Fred C. [Physics Department, University of Michigan, Ann Arbor, MI 48109 (United States); Calvet, Nuria [Astronomy Department, University of Michigan, Ann Arbor, MI 48109 (United States)

    2013-09-01

    This paper explores the effects of FUV radiation fields from external stars on circumstellar disk evolution. Disks residing in young clusters can be exposed to extreme levels of FUV flux from nearby OB stars, and observations show that disks in such environments are being actively photoevaporated. Typical FUV flux levels can be factors of {approx}10{sup 2}-10{sup 4} higher than the interstellar value. These fields are effective in driving mass loss from circumstellar disks because they act at large radial distance from the host star, i.e., where most of the disk mass is located, and where the gravitational potential well is shallow. We combine viscous evolution (an {alpha}-disk model) with an existing FUV photoevaporation model to derive constraints on disk lifetimes, and to determine disk properties as functions of time, including mass-loss rates, disk masses, and radii. We also consider the effects of X-ray photoevaporation from the host star using an existing model, and show that for disks around solar-mass stars, externally generated FUV fields are often the dominant mechanism in depleting disk material. For sufficiently large viscosities, FUV fields can efficiently photoevaporate disks over the entire range of parameter space. Disks with viscosity parameter {alpha} = 10{sup -3} are effectively dispersed within 1-3 Myr; for higher viscosities ({alpha} = 10{sup -2}) disks are dispersed within {approx}0.25-0.5 Myr. Furthermore, disk radii are truncated to less than {approx}100 AU, which can possibly affect the formation of planets. Our model predictions are consistent with the range of observed masses and radii of proplyds in the Orion Nebula Cluster.

  16. Radiation effects on junction field-effect transistors (JFETS), MOSFETs, and bipolar transistors, as related to SSC circuit design

    SciTech Connect

    Kennedy, E.J. (Tennessee Univ., Knoxville, TN (USA) Oak Ridge National Lab., TN (USA)); Alley, G.T.; Britton, C.L. Jr. (Oak Ridge National Lab., TN (USA)); Skubic, P.L. (Oklahoma Univ., Norman, OK (USA)); Gray, B.; Wu, A. (Tennessee Univ., Knoxville, TN (USA))

    1990-01-01

    Some results of radiation effects on selected junction field-effect transistors, MOS field-effect transistors, and bipolar junction transistors are presented. The evaluations include dc parameters, as well as capacitive variations and noise evaluations. The tests are made at the low current and voltage levels (in particular, at currents {le}1 mA) that are essential for the low-power regimes required by SSC circuitry. Detailed noise data are presented both before and after 5-Mrad (gamma) total-dose exposure. SPICE radiation models for three high-frequency bipolar processes are compared for a typical charge-sensitive preamplifier.

  17. Voyager program. Voyager 1 encounter at Jupiter, 5 March 1979

    NASA Technical Reports Server (NTRS)

    1979-01-01

    Highlights of Voyager 1 activity during the observatory and far-encounter phases are summarized. Daily sequence of events for the spacecraft during the period of greatest encounter activity (Feb. 26 through Mar. 7) the near-encounter phase is given. Times shown designate the time of signal reception at Deep Space Network stations. Events listed emphasize activities pertaining to the four remote sensing instruments on the scan platforms. However, the other 7 experiments will continuously collect data throughout the encounter period.

  18. Radiation

    Microsoft Academic Search

    Erik Seedhouse

    \\u000a It is more than forty years since astronauts ventured beyond Earth’s protective magnetic shield and travelled to the Moon.\\u000a Although the Apollo missions subjected astronauts to space radiation, the short duration minimized the risk, but an ECM will\\u000a subject astronauts to much longer exposure. In fact, astronauts will be in deep space for so long, they will run the risk

  19. Africa on My Mind: Encounters in the Field

    E-print Network

    Burgess, Elaine

    1990-01-01

    Crossroads areas were the hidden camp-like townships, the crude migrant single-sex barracks, and the pathetic, yet vibrant squatter communities. Clearly, as a contrivance in social engineering, apartheid has been an unholy success, compartmentalizing... Administration had managed to alienate the 95 Mid-American Review of Sociology right, the left, and the middle.5 I was asked what I was going to do about sanctions and about U. S. meddling. Some thought I should be boycotting the Republic's academic community. I...

  20. B cell follicles and antigen encounters of the third kind

    Microsoft Academic Search

    Jason G Cyster

    2010-01-01

    Defining where and in what form lymphocytes encounter antigen is fundamental to understanding how immune responses occur. Although knowledge of the recognition of antigen by CD4+ and CD8+ T cells has advanced greatly, understanding of the dynamics of B cell–antigen encounters has lagged. With the application of advanced imaging approaches, encounters of this third kind are now being brought into

  1. Customer complaining behaviour in technology-based service encounters

    Microsoft Academic Search

    Kaisa Snellman; Tiina Vihtkari

    2003-01-01

    Compares complaining behaviour in traditional and technology-based service encounters. Drawing on 160 negative critical incidents within Finnish retail banking, shows that, contradictory to common predictions, there are no significant differences in the complaining rates between the two types of service encounters. Attributes this finding to the high reliance of traditional complaining methods in both types of service encounters. Finds, however,

  2. Far-field sound radiation of a submerged cylindrical shell at finite depth from the free surface.

    PubMed

    Li, T Y; Miao, Y Y; Ye, W B; Zhu, X; Zhu, X M

    2014-09-01

    The far-field sound radiation behavior of a circular cylindrical shell submerged at finite depth from the free surface is studied. Based on the Flügge shell theory and the Helmholtz equation, the structure-acoustic coupling equation is established. An image method is applied so that the sound boundary condition of the free surface can be satisfied. Analytical expression of the far-field sound pressure is obtained using the stationary phase method and the Graf's addition theorem. In order to evaluate the effect of the submerged depth on sound radiation, the results of the submerged cylindrical shell at finite depth from the free surface are compared with those of the submerged cylindrical shell in the infinite fluid. The characteristics of the far-field sound pressure with the change of the depth are investigated. It is found that the submerged depth has a significant influence on the far-field sound pressure radiated from the submerged cylindrical shell due to the free surface effects. The work provides more understanding on the sound radiation properties of the submerged circular cylindrical shell without assuming infinite fluid field, which was commonly used in previous studies. PMID:25190381

  3. Dynamics of a stressful encounter: Cognitive appraisal, coping, and encounter outcomes

    Microsoft Academic Search

    Susan Folkman; Richard S. Lazarus; Christine Dunkel-Schetter; Anita DeLongis; Rand J. Gruen

    1986-01-01

    Despite the importance that is attributed to coping as a factor in psychological and somatic health outcomes, little is known about actual coping processes, the variables that influence them, and their relation to the outcomes of the stressful encounters people experience in their day-to-day lives. This study uses an intraindividu al analysis of the interrelations among primary appraisal (what was

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

    Microsoft Academic Search

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

    2006-01-01

    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

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

    Microsoft Academic Search

    A S Beddar; T M Briere; M Ouzidane

    2006-01-01

    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

  6. Binary-Pulsar Tests of Strong-Field Gravity and Gravitational Radiation Damping

    NASA Astrophysics Data System (ADS)

    Esposito-Farese, Gilles

    2006-02-01

    This talk reviews the constraints imposed by binary-pulsar data on gravity theories, focusing on "tensor-scalar" ones which are the best motivated alternatives to general relativity. We recall that binary-pulsar tests are qualitatively different from solar-system experiments, because of nonperturbative strong-field effects which can occur in compact objects like neutron stars, and because one can observe the effect of gravitational radiation damping. Some theories which are strictly indistinguishable from general relativity in the solar system are ruled out by binary-pulsar observations. During the last months, several impressive new experimental data have been published. Today, the most constraining binary pulsar is no longer the celebrated (Hulse-Taylor) PSR B1913+16, but the neutron star-white dwarf system PSR J1141-6545. In particular, in a region of the "theory space", solar-system tests were known to give the tightest constraints; PSR J1141-6545 is now almost as powerful. We also comment on the possible scalar-field effects for the detection of gravitational waves with future interferometers. The presence of a scalar partner to the graviton might be detectable with the LISA space experiment, but we already know that it would have a negligible effect for LIGO and VIRGO, so that the general relativistic wave templates can be used securely for these ground interferometers.

  7. Design and testing of indigenous cost effective three dimensional radiation field analyser (3D RFA).

    PubMed

    Ganesh, K M; Pichandi, A; Nehru, R M; Ravikumar, M

    2014-06-01

    The aim of the study is to design and validate an indigenous three dimensional Radiation Field Analyser (3D RFA). The feed system made for X, Y and Z axis movements is of lead screw with deep ball bearing mechanism made up of stain less steel driven by stepper motors with accuracy less than 0.5 mm. The telescopic column lifting unit was designed using linear actuation technology for lifting the water phantom. The acrylic phantom with dimensions of 800 x 750 x 570 mm was made with thickness of 15 mm. The software was developed in visual basic programming language, classified into two types, viz. beam analyzer software and beam acquisition software. The premeasurement checks were performed as per TG 106 recommendations. The physical parameters of photon PDDs such as Dmax, D10, D20 and Quality Index (QI), and the electron PDDs such as R50, Rp, E0, Epo and X-ray contamination values can be obtained instantaneously by using the developed RFA system. Also the results for profile data such as field size, central axis deviation, penumbra, flatness and symmetry calculated according to various protocols can be obtained for both photon and electron beams. The result of PDDs for photon beams were compared with BJR25 supplement values and the profile data were compared with TG 40 recommendation. The results were in agreement with standard protocols. PMID:23919396

  8. Transport and mixing in the radiation zones of rotating stars II. Axisymmetric magnetic field

    E-print Network

    S. Mathis; J. -P. Zahn

    2005-06-06

    The purpose of this paper is to improve the modeling of the mixing of chemical elements that occurs in stellar radiation zones. In addition to the classical rotational mixing considered in our previous paper, which results of the combined action of the thermally-driven meridional circulation and of the turbulence generated by the shear of differential rotation, we include here the effect of an axisymmetric magnetic field in a self-consistent way. We treat the advection of the field by the meridional circulation, its Ohmic diffusion, and the production of its toroidal component through the shear of differential rotation. The Lorentz force is assumed not to exceed the centrifugal force; it acts on the baroclinic balance and therefore on the meridional flow, and it has a strong impact on the transport of angular momentum. All variables and governing equations are expanded in spherical or spherical vectorial functions, to arbitrary order: this yields a system of partial differential equations in time and in the radial coordinate, which is ready to be implemented in a stellar structure code.

  9. Study of electric field distribution and low frequency noise of CdZnTe radiation detectors

    NASA Astrophysics Data System (ADS)

    Sik, O.; Grmela, L.; Elhadidy, H.; Dedic, V.; Sikula, J.; Grmela, P.; Franc, J.; Skarvada, P.; Holcman, V.

    2013-06-01

    Polarization phenomena in a metal-semiconductor-metal (M-S-M) structure of metallic Schottky contacts deposited on CdZnTe radiation detectors were studied. We evaluate the distribution of the electric field along the biased M-S-M structure by Pockels measurements. The results show that almost all the electric field is developed across the depletion layer of the reverse-biased contact. The noise measurements of the CdZnTe detectors studied show that the dominant noise is 1/fm noise. The 1/fm noise, with the parameter m close to one, is present at frequencies below 100 Hz and its bandwidth decreases in the course of the polarization process. At higher frequencies, we observed an increase of the m parameter to 2, which indicates a strengthened effect of the generation-recombination processes. In the frequency band of dominating 1/fm = 1 noise, the increase of magnitude of the noise spectral density was proportional to the power of 6, in relation to the current through the detector. This high value is explained as a result of a screening effect of the space charge buildup during the polarization.

  10. Angular distribution of binary encounter electrons

    SciTech Connect

    Liao, C.; Richard, P.; Grabbe, S. [Kansas State Univ., Manhattan, KS (United States)] [and others

    1993-05-01

    The double differential cross section, DDCS, of the binary encounter electrons (BEe) in 1 MeV/u F{sup q+} + H{sub 2} (q = 4, 6, 8, 9) is measured from 0 to 70 degrees with respect to the beam direction. At 0{degrees} the data confirm the decrease of the cross section with increasing projectile charge state. At larger observation angles, the data are in fair agreement with the prediction proposed by Shingal et al. where the ratio of the DDCS for 6+ ions to bare ions is less than 1 for {theta}{sub lab} > 30{degrees} and greater than 1 for {theta}{sub lab} < 30{degrees} as recently observed for C{sup q+}. We also observed that the energies of the BEe peak are charge state, q, independent at 0{degrees} observation angle, but q dependent at larger observation angles.

  11. Analysis of vortex wake encounter upsets

    NASA Technical Reports Server (NTRS)

    Johnson, W. A.; Teper, G. L.

    1974-01-01

    The problem of an airplane being upset by encountering the vortex wake of a large transport on takeoff or landing is currently receiving considerable attention. This report describes the technique and results of a study to assess the effectiveness of automatic control systems in alleviating vortex wake upsets. A six-degree-of-freedom nonlinear digital simulation was used for this purpose. The analysis included establishing the disturbance input due to penetrating a vortex wake from an arbitrary position and angle. Simulations were computed for both a general aviation airplane and a commercial jet transport. Dynamic responses were obtained for the penetrating aircraft with no augmentation, and with various command augmentation systems, as well as with human pilot control. The results of this preliminary study indicate that attitude command augmentation systems can provide significant alleviation of vortex wake upsets; and can do it better than a human pilot.

  12. Angle-dependent radiative grain alignment. Confirmation of a magnetic field - radiation anisotropy angle dependence on the efficiency of interstellar grain alignment

    NASA Astrophysics Data System (ADS)

    Andersson, B.-G.; Pintado, O.; Potter, S. B.; Straižys, V.; Charcos-Llorens, M.

    2011-10-01

    Context. Interstellar grain alignment studies are currently experiencing a renaissance due to the development of a new quantitative theory based on radiative alignment torques (RAT). One of the distinguishing predictions of this theory is a dependence of the grain alignment efficiency on the relative angle (?) between the magnetic field and the anisotropy direction of the radiation field. In an earlier study we found observational evidence for such an effect from observations of the polarization around the star HD 97300 in the Chamaeleon I cloud. However, due to the large uncertainties in the measured visual extinctions, the result was uncertain. Aims: By acquiring explicit spectral classification of the polarization targets, we have sought to perform a more precise reanalysis of the existing polarimetry data. Methods: We have obtained new spectral types for the stars in our for our polarization sample, which we combine with photometric data from the literature to derive accurate visual extinctions for our sample of background field stars. This allows a high accuracy test of the grain alignment efficiency as a function of ?. Results: We confirm and improve the measured accuracy of the variability of the grain alignment efficiency with ?, seen in the earlier study. We note that the grain temperature (heating) also shows a dependence on ? which we interpret as a natural effect of the projection of the grain surface to the illuminating radiation source. This dependence also allows us to derive an estimate of the fraction of aligned grains in the cloud.

  13. CLOSE STELLAR ENCOUNTERS IN YOUNG, SUBSTRUCTURED, DISSOLVING STAR CLUSTERS: STATISTICS AND EFFECTS ON PLANETARY SYSTEMS

    SciTech Connect

    Craig, Jonathan; Krumholz, Mark R., E-mail: krumholz@ucolick.org [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)

    2013-06-01

    Both simulations and observations indicate that stars form in filamentary, hierarchically clustered associations, most of which disperse into their galactic field once feedback destroys their parent clouds. However, during their early evolution in these substructured environments, stars can undergo close encounters with one another that might have significant impacts on their protoplanetary disks or young planetary systems. We perform N-body simulations of the early evolution of dissolving, substructured clusters with a wide range of properties, with the aim of quantifying the expected number and orbital element distributions of encounters as a function of cluster properties. We show that the presence of substructure both boosts the encounter rate and modifies the distribution of encounter velocities compared to what would be expected for a dynamically relaxed cluster. However, the boost only lasts for a dynamical time, and as a result the overall number of encounters expected remains low enough that gravitational stripping is unlikely to be a significant effect for the vast majority of star-forming environments in the Galaxy. We briefly discuss the implications of this result for models of the origin of the solar system, and of free-floating planets. We also provide tabulated encounter rates and orbital element distributions suitable for inclusion in population synthesis models of planet formation in a clustered environment.

  14. Toroidal magnetic fields for protecting astronauts from ionizing radiation in long duration deep space missions

    NASA Astrophysics Data System (ADS)

    Papini, Paolo; Spillantini, Piero

    2014-11-01

    Among the configurations of superconducting magnet structures proposed for protecting manned spaceships or manned deep space bases from ionizing radiation, toroidal ones are the most appealing for the efficient use of the magnetic field, being most of the incoming particle directions perpendicular to the induction lines of the field. The parameters of the toroid configuration essentially depend from the shape and volume of the habitat to be protected and the level of protection to be guaranteed. Two options are considered: (1) the magnetic system forming with the habitat a unique complex (compact toroid) to be launched as one piece; (2) the magnetic system to be launched separately from the habitat and assembled around it in space (large toroid). In first option the system habitat+toroid is assumed to have a cylindrical shape, with the toroid surrounding a cylindrical habitat, and launched with its axis on the axis of the launching system. The outer diameter is limited by the diameter of the shroud, which for present and foreseeable launching systems cannot be more than 9 m. The habitat is assumed to be 10 m long and have a 4 m diameter, leaving about 2 m all around for the protecting magnetic field. The volume of the habitat results about 100 m3, barely sufficient to a somewhat small crew (4-5 members) for a long duration (?2 years) mission. Technological problems and the huge magnetic pressure exerted on the inner cylindrical conductor of the toroid limit to not more than 4 T the maximum intensity of the magnetic field. With these parameters the mitigation of the dose inside the habitat due to the galactic cosmic rays (GCRs) is about 70% at minimum solar activity, while also most intense solar events cannot significantly contribute to the dose. The toroidal magnetic field can be produced by a large number of windings of the superconducting cable, arranged in cylindrical symmetry around the habitat to form continuous inner and outer cylindrical surfaces ('continuous' winding). In the option of separated launches for the habitat and the magnetic system, the volume of the habitat can be much larger, up to ?300 m3, i.e. a volume to be considered for a permanently manned space basis rather than for a spaceship. The toroidal field can occupy a larger volume around it, and indeed be less intense (B<3 T) for obtaining the same mitigation of the radiation dose inside the habitat. Also for the separate launches option several structural arrangements can be foreseen, depending from the considered number of windings. The limit of only two huge windings is the most attractive, as it minimizes the material and could be mechanically more stable, but it could be the most difficult to be assembled in space. Main parameters for the different configurations are reported, and the plan for the development of solutions and techniques is presented.

  15. Acoustic Radiation Force on a Finite-Sized Particle due to an Acoustic Field in a Viscous Compressible Fluid

    NASA Astrophysics Data System (ADS)

    Annamalai, Subramanian; Parmar, Manoj; Balachandar, S.

    2013-11-01

    Particles when subjected to acoustic waves experience a time-averaged second-order force known as the acoustic radiation force, which is of prime importance in the fields of microfluidics and acoustic levitation. Here, the acoustic radiation force on a rigid spherical particle in a viscous compressible medium due to progressive and standing waves is considered. The relevant length scales include: particle radius (a), acoustic wavelength (?) and viscous penetration depth (?). While a / ? and a / ? are arbitrary, ? << ? . A farfield derivation approach has been used in determining the radiated force. Expressing the flow-field as a sum of the incident and scattered fields, an analytical expression for the force is obtained as a summation over infinite series (monopole, dipole and higher sources). These results indicate that the contributions from monopole, dipole and their cross-interaction are sufficient to describe the acoustic radiation force. Subsequently, the monopole and dipole strengths are represented in terms of the particle surface and volume averages of the incoming velocity. This generalization allows one to evaluate the radiation force for an incoming wave of any functional form. However acoustic streaming effects are neglected.

  16. Final Report: Radiation-magnetohydrodynamic evolution and instability of conductors driven by megagauss magnetic fields

    SciTech Connect

    Bauer, Bruno, S.; Siemon, Richard, E.

    2008-10-22

    We are pleased to report important progress in experimentally characterizing and numerically modeling the transformation into plasma of walls subjected to pulsed megagauss magnetic fields. Understanding this is important to Magnetized Target Fusion (MTF) because an important limitation to the metal liner approach to MTF comes from the strong eddy current heating on the surface of the metal liner. This has intriguing non-linear aspects when the magnetic field is in the megagauss regime as needed for MTF, and may limit the magnetic field in an MTF implosion. Many faculty, students, and staff have contributed to this work, and, implicitly or explicitly, to this report. Contributors include, in addition to the PIs, Andrey Esaulov, Stephan Fuelling, Irvin Lindemuth, Volodymyr Makhin, Ioana Paraschiv, Milena Angelova, Tom Awe, Tasha Goodrich, Arunkumar Prasadam, Andrew Oxner, Bruno Le Galloudec, Radu Presura, and Vladimir Ivanov. Highlights of the progress made during the grant include: • 12 articles published, and 44 conference and workshop presentations made, on a broad range of issues related to this project; • An ongoing experiment that uses the 1 MA, 100-ns Zebra z-pinch at UNR to apply 2 5 megagauss to a variety of metal surfaces, examining plasma formation and evolution; • Numerical simulation studies of the 1-MA Zebra, and potential Shiva Star and Atlas experiments that include realistic equations of state and radiation effects, using a variety of tables. • Collaboration with other groups doing simulations of this experiment at LANL, VNIIEF, SNL, and NumerEx leading to a successful international workshop at UNR in the spring of 2008.

  17. NONTHERMAL RADIATION FROM SUPERNOVA REMNANTS: EFFECTS OF MAGNETIC FIELD AMPLIFICATION AND PARTICLE ESCAPE

    SciTech Connect

    Kang, Hyesung [Department of Earth Sciences, Pusan National University, Pusan 609-735 (Korea, Republic of); Jones, T. W. [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States); Edmon, Paul P., E-mail: kang@uju.es.pusan.ac.kr, E-mail: twj@msi.umn.edu, E-mail: pedmon@cfa.harvard.edu [Research Computing, Harvard University, Cambridge, MA 02138 (United States)

    2013-11-01

    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 {sup –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.

  18. Stirring of a planetesimal swarm - The role of distant encounters

    NASA Technical Reports Server (NTRS)

    Weidenschilling, Stuart J.

    1989-01-01

    The viscous stirring algorithm developed by Stewart and Wetherill (1988) to treat the random velocities induced in planetesimals by their mutual gravitational perturbations encompasses only the scattering of bodies in crossing orbits by close encounters. Expressions are presently derived for the stirring rate due to distant encounters on the basis of three-body formalism, using a stirring rate that has the same mass-dependence as that for close encounters. The relative importance of both the close encounter and distant encounter mechanisms depends on the Safronov number. Perturbations by a planetary embryo in scenarios that involve explosive growth are found capable of affecting planetesimal evolution in noncrossing orbits.

  19. The influence of longitudinal magnetic field on recombination radiation of low-pressure glow discharge in hydrogen and helium

    Microsoft Academic Search

    I. M. Ulanov; A. Yu. Litvintsev; V. A. Pinaev

    2011-01-01

    We study the influence of longitudinal magnetic field on the radiation of low-pressure glow discharges in hydrogen and helium.\\u000a We conducted experiments under a pressure in a discharge chamber of 10–20 Pa and a discharge current of 10–20 mA. A 0–1600\\u000a G magnetic field influenced only the cathode parts of the discharge, negative glow, and the dark Faraday space. The

  20. Sound radiation and wing mechanics in stridulating field crickets (Orthoptera: Gryllidae).

    PubMed

    Montealegre-Z, Fernando; Jonsson, Thorin; Robert, Daniel

    2011-06-15

    Male field crickets emit pure-tone mating calls by rubbing their wings together. Acoustic radiation is produced by rapid oscillations of the wings, as the right wing (RW), bearing a file, is swept across the plectrum borne on the left wing (LW). Earlier work found the natural resonant frequency (f(o)) of individual wings to be different, but there is no consensus on the origin of these differences. Previous studies suggested that the frequency along the song pulse is controlled independently by each wing. It has also been argued that the stridulatory file has a variable f(o) and that the frequency modulation observed in most species is associated with this variability. To test these two hypotheses, a method was developed for the non-contact measurement of wing vibrations during singing in actively stridulating Gryllus bimaculatus. Using focal microinjection of the neuroactivator eserine into the cricket's brain to elicit stridulation and micro-scanning laser Doppler vibrometry, we monitored wing vibration in actively singing insects. The results show significantly lower f(o) in LWs compared with RWs, with the LW f(o) being identical to the sound carrier frequency (N=44). But during stridulation, the two wings resonate at one identical frequency, the song carrier frequency, with the LW dominating in amplitude response. These measurements also demonstrate that the stridulatory file is a constant resonator, as no variation was observed in f(o) along the file during sound radiation. Our findings show that, as they engage in stridulation, cricket wings work as coupled oscillators that together control the mechanical oscillations generating the remarkably pure species-specific song. PMID:21613528

  1. Field-aligned chorus wave spectral power in Earth's outer radiation belt

    NASA Astrophysics Data System (ADS)

    Breuillard, H.; Agapitov, O.; Artemyev, A.; Kronberg, E. A.; Haaland, S. E.; Daly, P. W.; Krasnoselskikh, V. V.; Boscher, D.; Bourdarie, S.; Zaliznyak, Y.; Rolland, G.

    2015-05-01

    Chorus-type whistler waves are one of the most intense electromagnetic waves generated naturally in the magnetosphere. These waves have a substantial impact on the radiation belt dynamics as they are thought to contribute to electron acceleration and losses into the ionosphere through resonant wave-particle interaction. Our study is devoted to the determination of chorus wave power distribution on frequency in a wide range of magnetic latitudes, from 0 to 40°. We use 10 years of magnetic and electric field wave power measured by STAFF-SA onboard Cluster spacecraft to model the initial (equatorial) chorus wave spectral power, as well as PEACE and RAPID measurements to model the properties of energetic electrons (~ 0.1-100 keV) in the outer radiation belt. The dependence of this distribution upon latitude obtained from Cluster STAFF-SA is then consistently reproduced along a certain L-shell range (4 ? L ? 6.5), employing WHAMP-based ray tracing simulations in hot plasma within a realistic inner magnetospheric model. We show here that, as latitude increases, the chorus peak frequency is globally shifted towards lower frequencies. Making use of our simulations, the peak frequency variations can be explained mostly in terms of wave damping and amplification, but also cross-L propagation. These results are in good agreement with previous studies of chorus wave spectral extent using data from different spacecraft (Cluster, POLAR and THEMIS). The chorus peak frequency variations are then employed to calculate the pitch angle and energy diffusion rates, resulting in more effective pitch angle electron scattering (electron lifetime is halved) but less effective acceleration. These peak frequency parameters can thus be used to improve the accuracy of diffusion coefficient calculations.

  2. The voyager 2 encounter with the neptunian system.

    PubMed

    Stone, E C; Miner, E D

    1989-12-15

    An overview of the Voyager 2 encounter with Neptune is presented, including a brief discussion of the trajectory, the planned observations, and highlights of the results described in the 11 companion papers. Neptune's blue atmosphere has storm systems reminiscent of those in Jupiter's atmosphere. An optically thin methane ice cloud exists near the 1.5-bar pressure level, and an optically thick cloud exists below 3 bars. Neptune's magnetic field is highly tilted and offset from the planet's center; it rotates with a period of 16.11 hours. Two narrow and two broad rings circle the planet; the outermost of these rings has three optically thicker arc segments. Six new moons were discovered in circular prograde orbits, all well inside Triton's retrograde orbit. Triton has a highly reflective and geologically young surface, a thin nitrogen atmosphere, and at least two active geyser-like plumes. PMID:17755996

  3. The Voyager 2 encounter with the Neptunian system

    SciTech Connect

    Stone, E.C.; Miner, E.D. (California Institute of Technology, Pasadena (USA))

    1989-12-15

    An overview of the Voyager 2 encounter with Neptune is presented, including a brief discussion of the trajectory, the planned observations, and highlights of the results described in the 11 companion papers. Neptune's blue atmosphere has storm systems reminiscent of those in Jupiter's atmosphere. An optically thin methane ice cloud exists near the 1.5-bar pressure level, and an optically thick cloud exists below 3 bars. Neptune's magnetic field is highly tilted and offset from the planet's center; it rotates with a period of 16.11 hours. Two narrow and two broad rings circle the planet; the outermost of these rings has three optically thicker arc segments. Six moons were discovered in circular prograde orbits, all well inside Triton's retrograde orbit. Triton has a highly reflective and geologically young surface, a thin nitrogen atmosphere, and at least two active geyser-like plumes.

  4. Effects of UV-B radiation on soybean yield and seed quality: A six-year field study

    Microsoft Academic Search

    Alan H. Teramura; Joe H. Sullivan; John Lydon

    1990-01-01

    Two soybean, (Glycine max (L.) Merr.) cultivars, Essex and Williams, were grown in the field for 6 consecutive seasons under ambient and supplemental levels of ultraviolet-B radiation to determine the potential for alterations in yield or seed quality with a reduction in the stratospheric ozone column. The supplemental UV-B fluences simulated a 16 or 25% ozone depletion. The data presented

  5. Efficiency of high-order optical harmonic generation and of many-quantum processes in a multimode radiation field

    Microsoft Academic Search

    I. V. Tomov; Anatolii S. Chirkin

    1971-01-01

    An analysis is made of the generation of harmonics and of many-quantum processes (more than three quanta) in a specified field of laser radiation. Different statistics of the mode phases are considered and the absence of saturation effects is assumed. General relationships are derived for the calculation of the efficiency etak of a nonlinear k-th order process in the case

  6. EFFECTS OF ENHANCED ULTRAVIOLET-B RADIATION ON YIELD, AND DISEASE INCIDENCE AND SEVERITY FOR WHEAT UNDER FIELD CONDITIONS

    EPA Science Inventory

    The influence of enhanced UV-B radiation (280-320 nm) on wheat (Triticum aestivum cv. 'Florida 301') yield, and disease incidence and severity was investigated for two growing seasons under field conditions. Three levels of UV-B enhancement, simulating 8,12 and 16% stratospheric ...

  7. EFFECTS OF SUPPLEMENTAL ULTRAVIOLET-B RADIATION ON THE GROWTH AND PHYSIOLOGY OF FIELD-GROWN SOYBEAN

    EPA Science Inventory

    Soybeans were grown outdoors in field plots during 1983 and 1984 under ambient and 2 supplemental levels of biologically effective ultraviolet-B (UV-B) radiation (daily supplemental dose: 3.0 or 5.1 effective. These correspond to a 16 and 25% ozone reduction during clear sky cond...

  8. Electric currents and fields induced in cells in the human brain by radiation from hand-held cellular telephones

    NASA Astrophysics Data System (ADS)

    King, Ronold W. P.

    2000-01-01

    After a review of recent work on the interaction of electromagnetic fields from cellular telephones with the human head, the structural and radiating properties of two common types of transceivers are determined. These include the impedance and current amplitude distribution of the antennas. The tangential electric field maintained by the antennas on the adjacent surface of the head is next determined. From this, the electric field propagating through the skull into the brain is analyzed and, from it, the electric field in spherical and long cylindrical cells is determined. It ranges from 27 to 13.5 V/m in the first 3 cm inside the skull. Of interest is the fact that the induced field in the interior of all cells, regardless of their shape, is the same as the incident field in the brain. It is hoped that biomedical scientists will review these results and determine possible biological effects.

  9. Characterisation of bubble detectors for aircrew and space radiation exposure.

    PubMed

    Green, A R; Bennett, L G I; Lewis, B J; Tume, P; Andrews, H R; Noulty, R A; Ing, H

    2006-01-01

    The Earth's atmosphere acts as a natural radiation shield which protects terrestrial dwellers from the radiation environment encountered in space. In general, the intensity of this radiation field increases with distance from the ground owing to a decrease in the amount of atmospheric shielding. Neutrons form an important component of the radiation field to which the aircrew and spacecrew are exposed. In light of this, the neutron-sensitive bubble detector may be ideal as a portable personal dosemeter at jet altitudes and in space. This paper describes the ground-based characterisation of the bubble detector and the application of the bubble detector for the measurement of aircrew and spacecrew radiation exposure. PMID:16987919

  10. Fluence field modulated CT on a clinical TomoTherapy radiation therapy machine

    NASA Astrophysics Data System (ADS)

    Szczykutowicz, Timothy P.; Hermus, James

    2015-03-01

    Purpose: The multi-leaf collimator (MLC) assembly present on TomoTherapy (Accuray, Madison WI) radiation therapy (RT) and mega voltage CT machines is well suited to perform fluence field modulated CT (FFMCT). In addition, there is a demand in the RT environment for FFMCT imaging techniques, specifically volume of interest (VOI) imaging. Methods: A clinical TomoTherapy machine was programmed to deliver 30% imaging dose outside predefined VOIs. Four different size ROIs were placed at varying distances from isocenter. Projections intersecting the VOI received "full dose" while those not intersecting the VOI received 30% of the dose (i.e. the incident fluence for non VOI projections was 30% of the incident fluence for projections intersecting the VOI). Additional scans without fluence field modulation were acquired at "full" and 30% dose. The noise (pixel standard deviation) was measured inside the VOI region and compared between the three scans. Results: The VOI-FFMCT technique produced an image noise 1.09, 1.05, 1.05, and 1.21 times higher than the "full dose" scan for ROI sizes of 10 cm, 13 cm, 10 cm, and 6 cm respectively within the VOI region. Conclusions: Noise levels can be almost unchanged within clinically relevant VOIs sizes for RT applications while the integral imaging dose to the patient can be decreased, and/or the image quality in RT can be dramatically increased with no change in dose relative to non-FFMCT RT imaging. The ability to shift dose away from regions unimportant for clinical evaluation in order to improve image quality or reduce imaging dose has been demonstrated. This paper demonstrates that FFMCT can be performed using the MLC on a clinical TomoTherapy machine for the first time.

  11. Measuring the wobble of radiation field centers during gantry rotation and collimator movement on a linear accelerator

    SciTech Connect

    Du, Weiliang; Gao, Song [Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, Texas, 77030 (United States)

    2011-08-15

    Purpose: The isocenter accuracy of a linear accelerator is often assessed with star-shot films. This approach is limited in its ability to quantify three dimensional wobble of radiation field centers (RFCs). The authors report a Winston-Lutz based method to measure the 3D wobble of RFCs during gantry rotation, collimator rotation, and collimator field size change. Methods: A stationary ball-bearing phantom was imaged using multileaf collimator-shaped radiation fields at various gantry angles, collimator angles, and field sizes. The center of the ball-bearing served as a reference point, to which all RFCs were localized using a computer algorithm with subpixel accuracy. Then, the gantry rotation isocenter and the collimator rotation axis were derived from the coordinates of these RFCs. Finally, the deviation or wobble of the individual RFC from the derived isocenter or rotation axis was quantified. Results: The results showed that the RFCs were stable as the field size of the multileaf collimator was varied. The wobble of RFCs depended on the gantry angle and the collimator angle and was reproducible, indicating that the mechanical imperfections of the linac were mostly systematic and quantifiable. It was found that the 3D wobble of RFCs during gantry rotation was reduced after compensating for a constant misalignment of the multileaf collimator. Conclusions: The 3D wobble of RFCs can be measured with submillimeter precision using the proposed method. This method provides a useful tool for checking and adjusting the radiation isocenter tightness of a linac.

  12. Radiation, Gas and Magnetic Fields: Understanding Accretion Disks with Real Physics

    NASA Astrophysics Data System (ADS)

    Tao, Ted

    2011-01-01

    This dissertation studies some of the fundamental physics ingredients that underlie the theory of astrophysical accretion disks. We begin by focusing on local radiation magnetohydrodynamic instabilities in static, optically thick, vertically stratified media with constant flux mean opacity. Our analysis includes the effects of vertical gradients in a horizontal background magnetic field. Assuming rapid radiative diffusion, we use the zero gas pressure limit as an entry point for investigating the coupling between the photon bubble instability and the Parker instability. We find that the two instabilities transition smoothly into each other at a characteristic wavelength that is approximately equal to the magnetic pressure scale height times the ratio of radiation to magnetic pressure gradient forces. The Parker instability exists for longer wavelengths, while photon bubbles exist for wavelengths shorter than the transition wavelength. We also consider the effects of finite gas pressure on the coupled instabilities. Finite gas pressure introduces an additional short wavelength limit to the Parker-like behavior, and also limits the growth rate of the photon bubble instability to a constant value at high wave numbers. Finally, our analytic infinite wavenumber perturbation calculation strongly suggest that magnetic pressure gradients do not modify the photon bubble growth rate in the asymptotic regime. Our results may explain why photon bubbles have not yet been observed in recent stratified shearing box accretion disk simulations. Photon bubbles may physically exist in simulations with high radiation to gas pressure ratios, but higher spatial resolution will be needed to resolve the asymptotically growing unstable wavelengths. Next, we turn to the effects of local dissipation physics on the spectra and vertical structure of high luminosity stellar mass black hole X-ray binary accretion disks. More specifically, we present spectral calculations of non-LTE accretion disk models. We first use a dissipation profile based on scaling the results of shearing box simulations to a range of annuli parameters. We simultaneously scale the effective temperature, orbital frequency and surface density of a disk annulus according to the standard Shakura & Sunyaev model in order to bring increased dissipation to the disk surface layers (around the photosphere). We find that annuli spectrum transitions directly from that of a modified black body to one characteristic of saturated Compton scattering without first going through an intermediate power law regime as we increased the effective temperature and orbital frequency while decreasing mid-plane surface density. Next, we construct annuli models based on the parameters of a 0.8 Eddington disk orbiting a 6.62 solar mass black hole (with accretion efficiency approximately 0.083) using two modified dissipation profiles that explicitly put more dissipation per unit mass near the disk surface. The new dissipation profiles are qualitatively similar to the one found by Hirose et al. (2009) and produce strong and distinct non-thermal spectral tails. Our models also include physically motivated magnetic acceleration support based once again on scaling the Hirose et al. (2009) results. We present three full-disk spectra each based on one of the dissipation prescriptions. Our most aggressive dissipation profile results in a disk spectrum that is in approximate quantitative agreement with certain observations of the steep power law (SPL) spectral state from some black hole X-ray binaries.

  13. The effect of random field errors on the radiation spectra of selected APS (Advanced Photon Source) undulators

    SciTech Connect

    Alp, E.E.; Viccaro, P.J.

    1987-08-01

    The effect of random magnetic field errors are introduced into the calculations of spectral characteristics of tunable undulators for the proposed 7 GeV Advanced Photon Source (APS). Single electron calculations are made for an undulator with a first harmonic radiation tunable between 3.5 and 13 keV. Using the universal curves developed by Kincaid, the effect of randomly distributed field errors on the first and third harmonics of two proposed typical undulators are calculated. It is found that the lower limit of 0.5% in field errors is more than sufficient for the successful operation of the undulators planned for the APS.

  14. Optimal aircraft performance during microburst encounter

    NASA Technical Reports Server (NTRS)

    Psiaki, Mark L.; Stengel, Robert F.

    1991-01-01

    The effects of microburst characteristics on the optimal penetration performance of jet transport and general aviation aircraft are presented. The purpose is to determine the best possible performance that can be achieved in a broad range of microbursts. A secondary goal is to illustrate good strategies for dealing with a range of microbursts during takeoff and landing. Over 1100 optimal trajectories were computed for two aircraft types flying through idealized microbursts using a Successive Quadratic Programs trajectory optimization algorithm. Contours of safety metrics are plotted as functions of the length scales, magnitudes, and locations of horizontal wind shears and vertical downdrafts. These performance contours show three length-scale regimes for optimal microburst penetration. At short length scales, hazards usually associated with gustiness predominate (e.g., high normal load factor, rotational upset). At intermediate length scales, a degraded ability to maintain flight path and/or vertical velocity poses the most serious threat. At very long microburst length scales, excessive touchdown velocities may result. The ability to transit a microburst successfully also varies strongly with microburst location. The results show that both aircraft types could penetrate some very severe microbursts if optimal control histories were followed. Nevertheless, these control strategies assume perfect prior knowledge of the wind, and practical limits to successful encounter with real-time control capabilities would be lower. The optimally controlled jet transport can successfully penetrate higher intensity microbursts than can the general aviation aircraft.

  15. Vacuum Channeling Radiation by Relativistic Electrons in a Transverse Field of a Laser-Based Bessel Beam

    NASA Astrophysics Data System (ADS)

    Schächter, L.; Kimura, W. D.

    2015-05-01

    Relativistic electrons counterpropagating through the center of a radially polarized J1 optical Bessel beam in vacuum will emit radiation in a manner analogous to the channeling radiation that occurs when charged particles traverse through a crystal lattice. However, since this interaction occurs in vacuum, problems with scattering of the electrons by the lattice atoms are eliminated. Contrary to inverse Compton scattering, the emitted frequency is also determined by the amplitude of the laser field, rather than only by its frequency. Adjusting the value of the laser field permits the tuning of the emitted frequency over orders of magnitude, from terahertz to soft X rays. High flux intensities are predicted (˜100 MW /cm2 ). Extended interaction lengths are feasible due to the diffraction-free properties of the Bessel beam and its radial field, which confines the electron trajectory within the center of the Bessel beam.

  16. The influence of the type of filling gas on the response of ionisation chambers to a mixed high-energy radiation field.

    PubMed

    Mayer, S; Forkel-Wirth, D; Fuerstner, M; Roesler, S; Theis, C; Vincke, H

    2007-01-01

    Radiation protection dosimetry in radiation fields behind the shielding of high-energy accelerators such as CERN is a challenging task and the quantitative understanding of the detector response used for dosimetry is essential. Measurements with ionisation chambers are a standard method to determine absorbed dose (in the detector material). For applications in mixed radiation fields, ionisation chambers are often also calibrated in terms of ambient dose equivalent at conventional reference radiation fields. The response of a given ionisation chamber to the various particle types of a complex high-energy radiation field in terms of ambient dose equivalent depends of course on the materials used for the construction and the chamber gas used. This paper will present results of computational studies simulating the exposure of high-pressure ionisation chambers filled with different types of gases to the radiation field at CERN's CERN-EU high-energy reference field facility. At this facility complex high-energy radiation fields, similar to those produced by cosmic rays at flight altitudes, are produced. The particle fluence and spectra calculated with FLUKA Monte Carlo simulations have been benchmarked in several measurements. The results can be used to optimise the response of ionisation chambers for the measurement of ambient dose equivalent in high-energy mixed radiation fields. PMID:17575292

  17. PAH Strength and the Interstellar Radiation Field around the Massive Young Cluster NGC3603

    E-print Network

    V. Lebouteiller; B. Brandl; J. Bernard-Salas; D. Devost; J. R. Houck

    2007-04-18

    We present spatial distribution of polycyclic aromatic hydrocarbons and ionized gas within the Galactic giant HII region NGC3603. Using the IRS instrument on board the Spitzer Space Telescope, we study in particular the PAH emission features at ~5.7, 6.2, 7.7, 8.6, and 11.3um, and the [ArII] 6.99um, [NeII] 12.81um, [ArIII] 8.99um, and [SIV] 10.51um forbidden emission lines. The observations probe both ionized regions and photodissociation regions. Silicate emission is detected close to the central cluster while silicate absorption is seen further away. We find no significant variation of the PAH ionization fraction across the whole region. The emission of very small grains lies closer to the central stellar cluster than emission of PAHs. The PAH/VSG ratio anticorrelates with the hardness of the interstellar radiation field suggesting a destruction mechanism of the molecules within the ionized gas, as shown for low-metallicity galaxies by Madden et al. (2006).

  18. Flow-radiated noise. Study of the propagative spectral range of the wall pressure field

    NASA Astrophysics Data System (ADS)

    Benarrous, E.

    The complete model of the wall pressure field developed here incorporates many experimentally observed and proven partial similarities, as well as hypotheses to offset experimental gaps in certain frequency ranges and wave numbers. Initial comparisons show good agreement with experimental results across a wide range of frequencies and wave numbers. The main advantages of the model are: non-dependent adjustment constants; the explicit dependence of local, boundary layer scales; the explicit formulation of physical scales that control the similarity of frequencies and levels; incorporation of the whole range of frequencies and wave numbers; complete determination of the spectrum and interspectrum; and calculation of the root mean square. The study's acoustical range model explains the asymptotic behavior of the low-frequency spectrum, by separating incompressible and acoustic factors. This can be used to calculate the share of wall pressure fluctuations migrating in the form of a sound wave, thus providing an essential element in the problem of antenna or SONAR dome set noise and radiated noise.

  19. Atlas of wide-field-of-view outgoing longwave radiation derived from Nimbus 6 Earth radiation budget data set, July 1975 to June 1978

    NASA Technical Reports Server (NTRS)

    Bess, T. Dale; Smith, G. Louis

    1987-01-01

    An atlas of monthly mean outgoing longwave radiation global contour maps and associated spherical harmonic coefficients is presented. The atlas contains 36 months of continuous data from July 1975 to June 1978. The data were derived from the first Earth radiation budget experiment, which was flown on the Nimbus-6 Sun-synchronous satellite in 1975. Only the wide-field-of-view longwave measurements are cataloged in this atlas. The contour maps along with the associated sets of spherical harmonic coefficients form a valuable data set for studying different aspects of our changing climate over monthly, annual, and interannual scales in the time domain, and over regional, zonal, and global scales in the spatial domain.

  20. Single-cycle Terahertz Pulses with >0.2 V/A Field Amplitudes via Coherent Transition Radiation

    SciTech Connect

    Daranciang, Dan; /Stanford U., Chem. Dept.; Goodfellow, John; /Stanford U. Materials Sci. Dept.; Fuchs, Matthias; /SIMES, Stanford /SLAC, PULSE; Wen, Haidan; /ANL, APS; Ghimire, Shambhu; /SLAC, PULSE; Reis, David A.; /SIMES, Sanford /SLAC, PULSE /Stanford U., Appl. Phys. Dept.; Loos, Henrik; Fisher, Alan S.; /SLAC, LCLS; Lindenberg, Aaron M.; /Stanford U. Materials Sci. Dept. /SIMES, Stanford /SLAC, PULSE

    2012-02-15

    We demonstrate terahertz pulses with field amplitudes exceeding 0.2 V/{angstrom} generated by coherent transition radiation. Femtosecond, relativistic electron bunches generated at the Linac Coherent Light Source are passed through a beryllium foil, and the emitted radiation is characterized as a function of the bunch duration and charge. Broadband pulses centered at a frequency of 10 THz with energies of 140 {mu}J are measured. These far-below-bandgap pulses drive a nonlinear optical response in a silicon photodiode, with which we perform nonlinear autocorrelations that yield information regarding the terahertz temporal profile. Simulations of the spatiotemporal profile agree well with experimental results.