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1

Encounters  

Microsoft Academic Search

The Tarkunde Committee confirmed that the police and the government of Andhra Pradesh were involved in the cruel practice of committing planned murders and covering it up as encounter. It recommended that the central government institute an independent commission of inquiry to verify facts about encounters. Clearly, what was being labeled by the government as encounters was a planned strategy

Peoples Union for Democratic Rights PUDR

2011-01-01

2

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

PubMed

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

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

2005-05-13

3

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

E-print Network

MEASUREMENT OF ROUTINELY ENCOUNTERED NEUTRON FIELD DOSES USING PORTABLE SURVEY INSTRUMENTS AND A BONNER MULTISPHERE SYSTEM A Thesis By Donald Reed Davis Submitted to the Graduate College of Texas ASM University in partial fulfillment... of the requirement for the degree of MASTER OF SCIENCE (May 1981) Major subject: Nuclear Engineering (Health Physics) MEASUREMENT OF ROUTINELY ENCOUNTERED NEUTRON FIELD DOSES USING PORTABLE SURVEY INSTRUMENTS AND A BONNER MULTISPHERE SYSTEM A Thesis By DONALD...

Davis, Donald Reed

1981-01-01

4

Africa on My Mind: Encounters in the Field  

E-print Network

~). While grappling with the project focus, I was, s~ultane~~l'y faced .~th dissonance over personal demographics. It wasn t Just. the initial suspicion social scientists' commonly face, or the natural apprehension of people in an authoritarian society... on the field. But I also had to come to grips with the way in which the field was intruding on the project and me. I have yet to find a reference to the ways in which social scientists should react to, or behave in, an authoritarian environment, or how...

Burgess, Elaine

1990-01-01

5

Energy fields nursing: a brief encounter of a unitary kind.  

PubMed

This paper explores the practical application of Martha Rogers' Science of Unitary Human Beings using a brief case study to illustrate the central concept of energy fields. Pattern manifestation appraisal and deliberative mutual patterning gave guidance for the care of a patient who had recently had a bilateral mastectomy. It is suggested that far from being a complicated and esoteric framework, the Science of Unitary Human Beings will have considerable impact on future nursing practice. PMID:8288421

Biley, F C

1993-12-01

6

Estimates of trapped radiation encountered on low-thrust trajectories through the Van Allen belts  

NASA Technical Reports Server (NTRS)

Estimates were made of the number of trapped protons and electrons encountered by vehicles on low-thrust trajectories through the Van Allen belts. The estimates serve as a first step in assessing whether these radiations present a problem to on-board sensitive components and payload. The integrated proton spectra and electron spectra are presented for the case of a trajectory described by a vehicle with a constant-thrust acceleration A sub c equal to 0.001 meter/sq sec. This value of acceleration corresponds to a trip time of about 54 days from low earth orbit to synchronous orbit. It is shown that the time spent in the belts and hence the radiation encountered vary nearly inversely with the value of thrust acceleration. Thus, the integrated spectral values presented for the case of A sub c = 0.001 meter/sq sec can be generalized for any other value of thrust acceleration by multiplying them by the factor 0.001/A sub c.

Karp, I. M.

1973-01-01

7

Radiation Field on Superspace  

E-print Network

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.

P. F. Gonzalez-Diaz

1994-03-18

8

Gamma radiation field intensity meter  

DOEpatents

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

Thacker, Louis H. (Knoxville, TN)

1995-01-01

9

Gamma radiation field intensity meter  

DOEpatents

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

Thacker, L.H.

1995-10-17

10

Gamma radiation field intensity meter  

DOEpatents

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

Thacker, Louis H. (Knoxville, TN)

1994-01-01

11

Gamma radiation field intensity meter  

DOEpatents

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

Thacker, L.H.

1994-08-16

12

Pioneer 10 and 11 Jovian encounters: radiation dose and biological lethality.  

PubMed

In their recent Jupiter flybys Pioneer 10 and Pioneer 11 passed through a belt of intense particulate radiation. For Pioneer 10 the radiation dose on the craft's outer surface was at least 5 x 10(5) rads from electrons plus 1.0 x 10(6) rads from protons; the radiation dose inside the craft (0.3 cm aluminum) was approximately 4.5 x 10(5) rads. For Pioneer 11 the surface dose was at least 1.3 x 10(5) rads from electrons plus 3 x 10(5) rads from protons; the interior radiation dose was approximately 1.2 x 10(5) rads. Significant survival of microbial spores would be possible at these calculated doses; however, even the interior dose of Pioneer 11 would be lethal to man and most multicellular biological organisms. PMID:12678105

Miller, M W; Kaufman, G E; Maillie, H D

1976-01-01

13

Semi-relativistic approximation to gravitational radiation from encounters with nonspinning black holes  

E-print Network

The capture of compact bodies by black holes in galactic nuclei is an important prospective source for low frequency gravitational wave detectors, such as the planned Laser Interferometer Space Antenna. This paper calculates, using a semirelativistic approximation, the total energy and angular momentum lost to gravitational radiation by compact bodies on very high eccentricity orbits passing close to a supermassive, nonspinning black hole; these quantities determine the characteristics of the orbital evolution necessary to estimate the capture rate. The semirelativistic approximation improves upon treatments which use orbits at Newtonian-order and quadrupolar radiation emission, and matches well onto accurate Teukolsky simulations for low eccentricity orbits. Formulae are presented for the semirelativistic energy and angular momentum fluxes as a function of general orbital parameters.

Jonathan R Gair; Daniel J Kennefick; Shane L Larson

2007-01-04

14

Field calibration studies for ionisation chambers in mixed high-energy radiation fields.  

PubMed

The monitoring of ambient doses at work places around high-energy accelerators is a challenging task due the complexity of the mixed stray radiation fields encountered. At CERN, mainly Centronics IG5 high-pressure ionisation chambers are used to monitor radiation exposure in mixed fields. The monitors are calibrated in the operational quantity ambient dose equivalent H*(10) using standard, source-generated photon- and neutron fields. However, the relationship between ionisation chamber reading and ambient dose equivalent in a mixed high-energy radiation field can only be assessed if the spectral response to every component and the field composition is known. Therefore, comprehensive studies were performed at the CERN-EU high-energy reference field facility where the spectral fluence for each particle type has been assessed with Monte Carlo simulations. Moreover, studies have been performed in an accessible controlled radiation area in the vicinity of a beam loss point of CERN's proton synchrotron. The comparison of measurements and calculations has shown reasonable agreement for most exposure conditions. The results indicate that conventionally calibrated ionisation chambers can give satisfactory response in terms of ambient dose equivalent in stray radiation fields at high-energy accelerators in many cases. These studies are one step towards establishing a method of 'field calibration' of radiation protection instruments in which Monte Carlo simulations will be used to establish a correct correlation between the response of specific detectors to a given high-energy radiation field. PMID:17522038

Theis, C; Forkel-Wirth, D; Fuerstner, M; Mayer, S; Otto, Th; Roesler, S; Vincke, H

2007-01-01

15

Relativistic theory for radiative forward electron emission in heavy ion-atom encounters  

NASA Astrophysics Data System (ADS)

The forward electron emission with simultaneous photon production during the scattering of relativistic, highly stripped projectiles from light target atoms is calculated within the Dirac theory. The method of calculation is a simplification of the impulse approximation and is based on the relation of the cross section for radiative capture to continuum of loosely bound electrons to the frame-transformed electron bremsstrahlung cross section. It is demonstrated that such an approximation is well justified in a large region of energies and photon emission angles, with the exception of the extreme forward and backward emission and the soft-photon energy limit. The cusp spectrum and the corresponding angular distribution are compared to recent experimental data for the collision system 90.38 MeV/amu U88+ + N2.

Jakubaßa-Amundsen, Doris; Müller, Robert; Surzhykov, Andrey; Yerokhin, Vladimir

2014-12-01

16

High Energy Astrophysics: Radiation Field G.V. Bicknell Description of the Radiation Field  

E-print Network

High Energy Astrophysics: Radiation Field © G.V. Bicknell Description of the Radiation Field Based on: Chapter 1 of Rybicki & Lightman, Radiative Processes in Astrophysics, and Chapter 12 of Shu, Radiation. #12;High Energy Astrophysics: Radiation Field 2/112 1 Introduction We see astrophysical objects

Bicknell, Geoff

17

Quasi light fields: Extending the light field to coherent radiation  

E-print Network

Imaging technologies such as dynamic viewpoint generation are engineered for incoherent radiation using the traditional light field, and for coherent radiation using electromagnetic field theory. We present a model of ...

Accardi, Anthony J.

18

Electrifying Encounters  

NSDL National Science Digital Library

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

Margaretha Ebbers

1999-09-01

19

The response of survey meters to pulsed radiation fields  

SciTech Connect

The response of most survey meters to steady radiation fields is fairly well known and documented. However, hardly any data is available in the literature regarding the response of these instruments to pulsed radiation. Pulsed radiation fields are encountered, e.g., in the vicinity of linear electron accelerators or klystrons. An instrument that ordinarily responds well to the average dose rate spread out evenly in time may not be able to cope with such a high dose rate. Instruments which have long dead times such as Geiger Mueller and proportional counters tend to become saturated in such fields and only count repetition rate. Ionization chambers are less influenced, however, they must be operated with adequate voltage to overcome recombination losses. Scintillation survey meters may become non-linear at higher dose rates for pulsed radiation because the photomultiplier cannot handle the instantaneous currents that are required. Because of the need to test the response of different radiation detection instruments to pulsed fields, a pulsed x-ray facility has been built (I/sub p/87). A brief description of this facility is given along with tests of several different instruments. 5 refs., 4 figs., 1 tab.

McCall, R.C.; Ipe, N.E.

1987-11-01

20

In situ observations of reconnection Hall magnetic fields at Mars: Evidence for ion diffusion region encounters  

Microsoft Academic Search

We present Mars Global Surveyor measurements of bipolar out-of-plane magnetic fields at current sheets in Mars' magnetosphere. These signatures match predictions from simulations and terrestrial observations of collisionless magnetic reconnection, and could similarly indicate differential ion and electron motion and the resulting Hall current systems near magnetic X lines. Thus, these observations may represent passages through or very near reconnection

J. S. Halekas; J. P. Eastwood; D. A. Brain; T. D. Phan; M. Øieroset; R. P. Lin

2009-01-01

21

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

PubMed

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

Svanberg, Ingvar

2014-01-01

22

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

PubMed Central

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

2014-01-01

23

Tuning near field radiation by doped silicon  

NASA Astrophysics Data System (ADS)

In this letter, we demonstrate theoretically and experimentally that bulk silicon can be employed to overcome the challenge of tuning near field radiation. Theoretical calculation shows that the nanoscale radiation between bulk silicon and silicon dioxide can be tuned by changing the carrier concentration of silicon. Near field radiation measurements are carried out on multiple bulk silicon samples with different doping concentrations. The measured near field conductance agrees well with theoretical predictions, which demonstrates a tuning range from 2 nW/K to 6 nW/K at a gap of ˜60 nm.

Shi, Jiawei; Li, Pengfei; Liu, Baoan; Shen, Sheng

2013-05-01

24

Harmonic undulator radiations with constant magnetic field  

NASA Astrophysics Data System (ADS)

Harmonic undulators has been analysed in the presence of constant magnetic field along the direction of main undulator field. The spectrum modifications in harmonic undulator radiations and intensity degradation as a function of constant magnetic field magnitude at fundamental and third harmonics have been evaluated with a numerical integration method and generalised Bessel function. The role of harmonic field to overcome the intensity reduction due to constant magnetic field and energy spread in electron beam has also been demonstrated.

Jeevakhan, Hussain; Mishra, G.

2015-01-01

25

SOI microdosemetry for mixed field radiation protection  

Microsoft Academic Search

Radiation protection in mixed neutron\\/gamma fields produced by radiation sources is relevant in many industrial applications such as bore hole logging and prompt gamma neutron activation analysis, security applications and neutron radiography. Online monitoring of the dose equivalent received from a neutron\\/gamma source would permit real time dosemetry in industrial and medical applications. A silicon on insulator (SOI) microdosemeter has

D. A. Prokopovich; M. I. Reinhard; I. M. Cornelius; A. B. Rosenfeld

2008-01-01

26

Radiation field for Einstein vacuum equations  

E-print Network

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 ...

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

2010-01-01

27

Near-field radiation in nanoscale gaps  

E-print Network

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, ...

Sambegoro, Poetro Lebdo

2011-01-01

28

Scattering by an electromagnetic radiation field  

E-print Network

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.

Donato Bini; Andrea Geralico

2014-08-21

29

Symmetries of Type N Pure Radiation Fields  

NASA Astrophysics Data System (ADS)

The geometrical symmetries corresponding to the continuous groups of collineations and motions generated by a null vector l are considered. These symmetries have been translated into the language of Newman-Penrose formalism for pure radiation (PR) type N fields. It is seen that for such fields, conformal, special conformal and homothetic motions degenerate to motion. The concept of free curvature, matter curvature and matter affine collineations have been discussed and the conditions under which PR type N fields admit such collineations have been obtained. Moreover, it is shown that the projective collineation degenerate to matter affine, special projective, conformal, special conformal, null geodesic and special null geodesic collineations. It is also seen that type N pure radiation fields admit Maxwell collineation along the propagation vector l.

Ahsan, Zafar; Ali, Musavvir

2014-10-01

30

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

E-print Network

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.

Kamenetskii, E O; Shavit, R

2015-01-01

31

Radiation reaction fields for an accelerated dipole for scalar and electromagnetic radiation  

Microsoft Academic Search

The radiation reaction fields are calculated for an accelerated changing dipole in scalar and electromagnetic (em) radiation fields. The radiation reaction is shown to alter the damping fields of a time varying dipole in the em case, but not the scalar case. In both cases the radiation reaction field can exert a force on an accelerated monopole and also on

W. G. Unruh

1999-01-01

32

Radiation Effects on Current Field Programmable Technologies  

NASA Technical Reports Server (NTRS)

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.

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

1997-01-01

33

Haemopoietic cell renewal in radiation fields  

NASA Astrophysics Data System (ADS)

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

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

1994-10-01

34

Plasma wake field XUV radiation source  

DOEpatents

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.

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

1997-01-01

35

Childhood's Chance Encounters.  

ERIC Educational Resources Information Center

Discusses various encounters children may have that leave lasting impressions, including encounters with animals or natural elements in general, those with people that evolve into friendship or tension, and fantasy encounters. Examples are given from films and literature, and sample creative activities involving encounters are suggested for…

Zingher, Gary

1996-01-01

36

Limited-field radiation for bifocal germinoma  

SciTech Connect

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.

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

37

Virtual radiation fields for ALARA determination  

SciTech Connect

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

Knight, T.W.

1995-12-31

38

Observations of the diffuse UV radiation field  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

39

Scatter radiation influences in nuclide calibration fields  

NASA Astrophysics Data System (ADS)

The goal of this study is to characterize the 137Cs and 60Co nuclide calibration fields of the reference irradiation facility with collimated beam geometry as part of the Dosimetry Laboratory Seibersdorf. Air kerma along the main beam axis with source-detector distances up to 19 m and additionally lateral field profiles are investigated by comparing mainly ionization chamber measurements with MCNP Monte Carlo computer simulations. The scatter radiation contributions from various facility components including simulations with and without air environment are studied by detailed modeling of the facility. Relative differences between measured and simulated results are currently within about 1-2%, i.e., roughly two to three times of the total measurement uncertainties, but reasons due to scattering influences and further improvements in the model are discussed.

Hranitzky, C.; Stadtmann, H.

2007-09-01

40

Electromagnetic radiation by quark-gluon plasma in magnetic field  

E-print Network

The electromagnetic radiation by quark-gluon plasma in strong magnetic field is calculated. The contributing processes are synchrotron radiation and one--photon annihilation. It is shown that in relativistic heavy--ion collisions at RHIC and LHC synchrotron radiation dominates over the annihilation. Moreover, it constitutes a significant part of all photons produced by the plasma at low transverse momenta; its magnitude depends on the plasma temperature and the magnetic field strength. Electromagnetic radiation in magnetic field is probably the missing piece that resolves a discrepancy between the theoretical models and the experimental data. It is argued that electromagnetic radiation increases with the magnetic field strength and plasma temperature.

Kirill Tuchin

2012-06-03

41

AfricaArray International Geophysics Field School: Applications of Near Surface Geophysics to challenges encountered in mine planning  

NASA Astrophysics Data System (ADS)

Hard rock exploration and mining presents many opportunities for the effective use of near surface geophysics. For over 10 years the AfricaArray international geophysics field school has been hosted at a variety of mines in South Africa. While the main objective of the field school is practical training for the next generation of geophysicists, being hosted at a mine has allowed us to investigate applications of near surface geophysics in the early stages of mine planning and development as geophysics is often cheaper and faster than drilling. Several applications include: detailed delineation of dykes and stringer dykes, physical property measurements on drill core for modeling and marker horizons, determination of overburden thickness, locations of water and faults. Dolerite dykes are usually magnetic and are associated with loss of ground (i.e. where the dyke replaces the ore and thus reduces the amount of ore available) and safety/stability concerns. Thus the accurate mapping of dykes and narrow stringers that are associated with them are crucial to the safe planning of a mine. We have acquired several case studies where ground magnetic surveys have greatly improved on the resolution and detail of airborne magnetic surveys in regions of complicated dyke swarms. In many cases, thin stringer dykes of less than 5 cm have been detected. Physical property measurements of these dykes can be used to distinguish between different ages of dykes. It is important to accurately determine overburden thickness when planning an open pit mine as this directly affects the cost of development. Depending on the nature of the overburden, both refraction seismic and or DC resistivity can provide continuous profiling in the area of interest that fills in gaps between boreholes. DC resistivity is also effective for determining water associated with dykes and structures that may affect mine planning. The field school mainly addresses the training of a variety of students. The core students are the geophysics Honours students (~4th year undergraduates). In addition, up to 8 students from all over Africa are included in the program to help address practical training in Africa. The final cohort are minority students from the USA. Participants spend a week planning and costing out surveys, a week in the field collecting data using different methods including: gravity, DGPS, magnetics, resistivity, refraction seismic, EM methods, core logging and physical property measurements. The final week is spent interpreting and integrating their results. Graduate students are given the opportunity to instruct on the field school and manage the logistics for a particular method. The field school is unique in Africa and satisfies a need for practical training with limited resources, with a rare blend of cultural interactions!

Webb, S. J.; Jones, M. Q.; Durrheim, R. J.; Nyblade, A.; Snyman, Q.

2012-12-01

42

Electromagnetic field radiation model for lightning strokes to tall structures  

Microsoft Academic Search

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

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

1996-01-01

43

Electromagnetic field radiation model for lightning strokes to tall structures  

SciTech Connect

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

Motoyama, H. [CRIEPI, Tokyo (Japan)] [CRIEPI, Tokyo (Japan); Janischewskyj, W.; Hussein, A.M. [Univ. of Toronto, Ontario (Canada)] [Univ. of Toronto, Ontario (Canada); Chisholm, W.A. [Ontario Hydro Technologies, Toronto, Ontario (Canada)] [Ontario Hydro Technologies, Toronto, Ontario (Canada); Chang, J.S. [McMaster Univ., Hamilton, Ontario (Canada)] [McMaster Univ., Hamilton, Ontario (Canada); Rusan, R.

1996-07-01

44

Scattering of particles by radiation fields: a comparative analysis  

E-print Network

The features of the scattering of massive neutral particles propagating in the field of a gravitational plane wave are compared with those characterizing their interaction with an electromagnetic radiation field. The motion is geodesic in the former case, whereas in the case of an electromagnetic pulse it is accelerated by the radiation field filling the associated spacetime region. The interaction with the radiation field is modeled by a force term entering the equations of motion proportional to the 4-momentum density of radiation observed in the particle's rest frame. The corresponding classical scattering cross sections are evaluated too.

Donato Bini; Andrea Geralico; Maria Haney; Robert T. Jantzen

2014-08-22

45

Radiation burst from a single {gamma}-photon field  

SciTech Connect

The radiation burst from a single {gamma}-photon field interacting with a dense resonant absorber is studied theoretically and experimentally. This effect was discovered for the fist time by P. Helisto et al.[Phys. Rev. Lett. 66, 2037 (1991)] and it was named the ''gamma echo''. The echo is generated by a 180 Degree-Sign phase shift of the incident radiation field, attained by an abrupt change of the position of the absorber with respect to the radiation source during the coherence time of the photon wave packet. Three distinguishing cases of the gamma echo are considered; i.e., the photon is in exact resonance with the absorber, close to resonance (on the slope of the absorption line), and far from resonance (on the far wings of the resonance line). In resonance the amplitude of the radiation burst is two times larger than the amplitude of the input radiation field just before its phase shift. This burst was explained by Helisto et al. as a result of constructive interference of the coherently scattered field with the phase-shifted input field, both having almost the same amplitude. We found that out of resonance the scattered radiation field acquires an additional component with almost the same amplitude as the amplitude of the incident radiation field. The phase of the additional field depends on the optical thickness of the absorber and resonant detuning. Far from resonance this field interferes destructively with the phase-shifted incident radiation field and radiation quenching is observed. Close to resonance the three fields interfere constructively and the amplitude of the radiation burst is three times larger than the amplitude of the input radiation field.

Shakhmuratov, R. N. [Kazan Physical-Technical Institute, Russian Academy of Sciences, 10/7 Sibirsky Trakt, Kazan 420029 (Russian Federation); Department of Physics and Institute for Quantum Studies, TAMU, College Station, Texas 77843-4242 (United States); Vagizov, F. [Kazan Federal University, 18 Kremlyovskaya Street, Kazan 420008 (Russian Federation); Department of Physics and Institute for Quantum Studies, TAMU, College Station, Texas 77843-4242 (United States); Kocharovskaya, O. [Department of Physics and Institute for Quantum Studies, TAMU, College Station, Texas 77843-4242 (United States)

2011-10-15

46

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)

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.

Wilson, Lester A.

2005-01-01

47

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

E-print Network

We present a novel method to implement time-delayed propagation of radiation fields in cosmological 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 transfer 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.

Ahn, Kyungjin

2015-01-01

48

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

NASA Astrophysics Data System (ADS)

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.

Ahn, Kyungjin

2015-02-01

49

Haemopoietic cell renewal in radiation fields  

Microsoft Academic Search

Space flight activities are inevitably associated with a chronic exposure of astronauts to a complex mixture of ionising radiation. Although no acute radiation consequences are to be expected as a rule, the possibility of Solar Particle Events (SPE) associated with relatively high doses of radiation (1 or more Gray) cannot be excluded. It is the responsibility of physicians in charge

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

1994-01-01

50

Negative radiation pressure in case of two interacting fields  

E-print Network

We study a simple toy model, which although probably does not have any direct physical applications, can serve as a nice pedagogical example for explanation strange phenomenon of negative radiation pressure and can also give some insight for understanding the interaction between radiation and a vortex. The model discussed is a classical field theory of two interacting scalar fields in 1+1 d. Without coupling one of the fields is governed by the ordinary $\\phi^4$ equation and the second one obeys the Klein-Gordon equation. The possibility of existence of the {\\it negative radiation pressure} with a respect to the mass ratio of those two fields is discussed.

Tomasz Romanczukiewicz

2008-07-15

51

Scattering of Particles by Radiation Fields: a Comparative Analysis  

NASA Astrophysics Data System (ADS)

The features of the scattering of massive neutral particles propagating in the field of a gravitational plane wave are compared with those characterizing their interaction with an electromagnetic radiation field. The comparative analysis shows that the scattering process is strongly influenced by the nature of the interaction between particles and radiation field, in principle leading to detectable observational consequences. A much more detailed examination of this problem can be found in our paper published in Phys. Rev. D 86, 064016 (2012).

Haney, M.; Bini, D.; Geralico, A.; Jantzen, R. T.

2015-01-01

52

Stretched exponential survival statistics for microorganisms in radiation field  

NASA Astrophysics Data System (ADS)

The so-called concave or tailed survival curves are reported both for multi and single species bacterial populations. Taking as an example Bacillus pumilus, frequently encountered in decontamination studies, it is shown that the tailed survival curves are adequately described by stretched (0< ?<1) exponential SF=exp[-( D/ D0) ?], where SF denotes the fraction of species surviving the irradiation dose D, D0 is the effective dose, and ? is the dispersion parameter interpreted phenomenologically in terms of radiation sensivity distribution for single species population under the given experimental conditions.

Plonka, Andrzej; Bogus, Wlodzimierz

1999-11-01

53

Theoretical investigation of non-equilibrium chemistry and optical radiation in hypersonic flow fields  

NASA Technical Reports Server (NTRS)

Future space vehicles returning from distant missions or high earth orbits may enter the upper regions of the atmosphere and use aerodynamic drag to reduce their velocity before they skip out of the atmosphere and enter low earth orbit. The Aeroassist Flight Experiment (AFE) is designed to explore the special problems encountered in such entries. A computer code was developed to calculate the radiative transport along line-or-sight in the general 3-D flow field about an arbitrary entry vehicle, if the temperatures and species concentrations along the line-of-sight are known. The radiative heating calculation at the stagnation point of the AFE vehicle along the entry trajectory was performed, including a detailed line-by-line accounting of the radiative transport in the vacuum ultraviolet (below 200 nm) by the atomic N and O lines. A method was developed for making measurements of the haze particles in the Titan atmosphere above 200 km altitude. Several other tasks of a continuing nature, to improve the technical ability to calculate the nonequilibrium gas dynamic flow field and radiative heating of entry vehicles, were completed or advanced.

Whiting, Ellis E.

1990-01-01

54

Near field transient radiation patterns for circular pistons  

Microsoft Academic Search

The exact impulse response of field parameters for any field point on or off axis for the case where a circular disc radiator face is subjected to a displacement step corresponding to a velocity impulse is reviewed. By convolution, the transient field pattern for any arbitrary motion of the disc can be obtained. The exact response for a half-sine monopulse

D. Robinson; S. Lees; L. Bess

1974-01-01

55

COHERENT AND INCOHERENT STATES OF THE RADIATION FIELD  

Microsoft Academic Search

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

Roy Glauber

1963-01-01

56

Detection of alpha radiation in a beta radiation field  

DOEpatents

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.

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

2001-01-01

57

Mariner 10 venus encounter.  

PubMed

The Mariner 10 spacecraft encountered Venus at 1701 G.M.T. on 5 February 1974. The preplanned encounter science sequence was executed satisfactorily, accomplishing all objectives despite a number of spacecraft problems that had occurred in the early phases of the flight. Seven experiments were conducted, including observations of the solar wind interaction region, extreme ultraviolet and infrared emissions, radio occultation, and imaging. PMID:17791368

Dunne, J A

1974-03-29

58

VOYAGER OBSERVATIONS OF THE DIFFUSE FAR-ULTRAVIOLET RADIATION FIELD  

SciTech Connect

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

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

2012-03-01

59

Voyager 1: Encounter with Saturn  

NASA Technical Reports Server (NTRS)

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

Panagakos, N.

1980-01-01

60

The Electromagnetic Dipole Radiation Field through the Hamiltonian Approach  

ERIC Educational Resources Information Center

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

Likar, A.; Razpet, N.

2009-01-01

61

Radiation tolerant silicon nitride insulated gate field effect transistors  

NASA Technical Reports Server (NTRS)

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.

Newman, P. A.

1969-01-01

62

Understanding metropolitan patterns of daily encounters.  

PubMed

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

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

2013-08-20

63

The Geomagnetic Field and Radiation in Near-Earth Orbits  

NASA Technical Reports Server (NTRS)

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.

Heirtzler, J. R.

1999-01-01

64

Encounter Group Effects of Soccer Team Performance.  

ERIC Educational Resources Information Center

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

Magen, Zipora

1980-01-01

65

Multimodal far-field acoustic radiation pattern: An approximate equation  

NASA Technical Reports Server (NTRS)

The far-field sound radiation theory for a circular duct was studied for both single mode and multimodal inputs. The investigation was intended to develop a method to determine the acoustic power produced by turbofans as a function of mode cut-off ratio. With reasonable simplifying assumptions the single mode radiation pattern was shown to be reducible to a function of mode cut-off ratio only. With modal cut-off ratio as the dominant variable, multimodal radiation patterns can be reduced to a simple explicit expression. This approximate expression provides excellent agreement with an exact calculation of the sound radiation pattern using equal acoustic power per mode.

Rice, E. J.

1977-01-01

66

The clinical encounter revisited.  

PubMed

The patient-physician encounter is the pivotal starting point of any healthcare delivery, but it is subject to multiple process breakdowns and prevalent suboptimal performance. An overview of the techniques and components of a successful encounter valid for every setting and readily applicable is presented, stressing 7 rules: (1) ensuring optimal environment, tools, and teamwork; (2) viewing each encounter not only as a cognitive/biomedical challenge, but also as a personal one, and a learning opportunity; (3) adopting an attitude of curiosity, concentration, compassion, and commitment, and maintaining a systematic, orderly approach; (4) "simple is beautiful"-making the most of the basic clinical data and their many unique advantages; (5) minding "the silent dimension"-being attentive to the patient's identity and emotions; (6) following the "Holy Trinity" of gathering all information, consulting databases/colleagues, and tailoring gained knowledge to the individual patient; and (7) using the encounter as a "window of opportunity" to further the patient's health-not just the major problem, by addressing screening and prevention; promoting health literacy and shared decision-making; and establishing proper follow-up. Barriers to implementation identified can be overcome by continuous educational interventions. A high-quality encounter sets a virtuous cycle of patient-provider interaction and results in increasing satisfaction, adherence, and improved health outcomes. PMID:24333201

Schattner, Ami

2014-04-01

67

Evaluating near-field radiation patterns of commercial antennas  

Microsoft Academic Search

A source reconstruction technique from the measured near fields is proposed to obtain a set of equivalent currents that will characterize the forward and backward radiation patterns of an antenna. Once the equivalent sources are determined, the electromagnetic field at any aspect angle and distance from the antenna can be calculated. In this paper, the method is applied to the

Fernando Las-Heras; Marcos Rodríguez Pino; Susana Loredo; Yuri Alvarez; Tapan K. Sarkar

2006-01-01

68

Primordial magnetic field and spectral distortion of cosmic background radiation  

E-print Network

The role played by a primordial magnetic field during the pre-recombination epoch is analysed through the cyclotron radiation (due to the free electrons) it might produce in the primordial plasma. We discuss the constraint implied by the measurement or lack thereof COBE on this primordial field.

Denis Puy; Patrick Peter

1998-02-26

69

Formation of neutron fields for radiation technologies  

NASA Astrophysics Data System (ADS)

The article considers the problem of forming a neutron field in the experimental channels of the water-cooled research reactors. Using the software package MCU5 we calculated a neutron field in different moderators which the experimental channel passes through. It is shown that the most appropriate moderator for neutron transmutation doping is the beryllium. The optimal location of the channel in the moderator was determined.

Varlachev, V. A.; Emets, E. G.; Kuznetsov, S. I.; Bogdan, A. M.; Varlacheva, N. V.

2014-11-01

70

Electron trajectories in pulsed radiation fields  

SciTech Connect

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.

Einwohner, T.; Lippmann, B.A.

1987-05-01

71

Alien Visitations Close Encounters  

E-print Network

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;

Walter, Frederick M.

72

A Lakatosian Encounter  

ERIC Educational Resources Information Center

There is much to be learned and pondered by reading "Proofs and Refutations," by Imre Lakatos. It highlights the importance of mathematical definitions, and how definitions evolve to capture the essence of the object they are defining. It also provides an exhilarating encounter with the ups and downs of the mathematical reasoning process, where…

Chick, Helen

2010-01-01

73

Adaptive radiations: From field to genomic studies  

PubMed Central

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

Hodges, Scott A.; Derieg, Nathan J.

2009-01-01

74

Field Testing of a Portable Radiation Detector and Mapping System  

SciTech Connect

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

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

1998-03-01

75

An evaluation of RAMS radiation schemes by field measurements  

SciTech Connect

At present, two radiation schemes are used in RAMS: the Mahrer and Pielke (M-P) scheme and the Chen and Cotton (C-C) scheme. The M-P scheme requires little computational expense, but does not include the radiative effects of liquid water or ice; the C-C scheme accounts for the radiative effects of liquid water and ice but is fairly expensive computationally. For simulations with clouds, the C-C scheme is obviously a better choice, but for clear sky conditions, RAMS users face a decision regarding which radiation scheme to use. It has been noted that the choice of radiation scheme may result in significantly different results for the same case. To examine the differences in the radiative fluxes and the boundary-layer structure corresponding to the two radiation schemes in RAMS we have carried out a study where Rams was used to simulate the same case with two different radiation schemes. The modeled radiative fluxes by the two schemes were then compared with the field measurements. A description of the observations and the case study, a comparison and discussion of the results, and a summary and conclusions follow.

Zhong, S; Doran, J C

1994-02-01

76

Relativistic ponderomotive forces in the field of intense laser radiation  

NASA Astrophysics Data System (ADS)

The motion of a relativistic charged particle in the presence of the field of high-power laser radiation represented in the form of a Gaussian beam of arbitrary mode is analyzed. The vector potential of the radiation field is expanded in terms of a small parameter (the ratio of the wavelength to the Gaussian beam waist). A specific feature of averaging with respect to the phases of the high-mode Gaussian beams is demonstrated. The averaged equations for the motion of particle and a general expression for the ponderomotive relativistic force for the circularly polarized radiation are derived. It is demonstrated that relativistic effects suppress the averaged action of high-power laser radiation on the particle.

Castillo, A. J.; Milant'ev, V. P.

2014-09-01

77

Synchrotron radiation in strongly coupled conformal field theories  

E-print Network

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

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

2011-09-16

78

Synchrotron radiation in strongly coupled conformal field theories  

SciTech Connect

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

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

2010-06-15

79

Synchrotron radiation in strongly coupled conformal field theories  

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

80

BPS Dyon in a Weak Electromagnetic Field: Equations of Motion and Radiation Fields  

E-print Network

Dynamics of a BPS dyon in a weak, constant, electromagnetic field is studied through a perturbative analysis of appropriate non-linear field equations. The full Lorentz force law for a BPS dyon is established. Also derived are the radiation fields accompanying the motion.

Dongsu Bak; Choonkyu Lee

1994-02-09

81

Measuring the radiation field and radiation hard detectors at JET: Recent developments  

NASA Astrophysics Data System (ADS)

Since in ITER the radiation field will be much more demanding than that of present day devices, research programmes at JET are aimed at developing radiation hard diagnostics and related components. Initially, significant efforts are devoted to determining the radiation field of both the plasma and in the immediate environment with better accuracy. New developments in MCNP calculations and dedicated measurements provide useful information about the radiation field in the Torus Hall, even during non-operational periods. The effect of using Beryllium in the near future for JET first wall, is being assessed. New materials for activation samples are under consideration and will be tested to improve the calibration accuracy of JET neutron diagnostics. The long-term goal of this work is to obtain spectrometric information from an appropriate combination of different materials. Several studies are under way to modify the radiation field at the detectors by using LiH or pure water as neutron filters, to alleviate the problem of the background in ?-ray measurements. A suite of radiation hard detectors for neutrons, magnetic field and charged particles are being developed. Super-heated fluid neutron detectors, used for yield and imaging, are being upgraded, in order to provide a broad-band spectrometric capability. Chemical vapour deposited diamond diodes are being qualified as counters and as spectrometers. Prototypes of Hall probes made of InSb have been installed on the machine and have provided some preliminary results. Si-on-insulator detectors are under development for use in neutral particle analysers and are currently being bench-tested. Some attention is being devoted to optical components, fibres and mirrors, and to investigating radiation hard electronics using reconfigurable Field Programmable Gate Arrays.

Murari, A.; Edlington, T.; Angelone, M.; Bertalot, L.; Bolshakova, I.; Bonheure, G.; Brzozowski, J.; Coccorese, V.; Holyaka, R.; Kiptily, V.; Lengar, I.; Morgan, P.; Pillon, M.; Popovichev, S.; Prior, P.; Prokopowicz, R.; Quercia, A.; Rubel, M.; Santala, M.; Shevelev, A.; Syme, B.; Vagliasindi, G.; Villari, R.; Zoita, V. L.; JET-EFDA Contributors

2008-08-01

82

Graphene field effect transistors for applications in radiation detection  

NASA Astrophysics Data System (ADS)

This thesis describes the development of a radiation detector which incorporates graphene into the device architecture through the use of FEM simulations and experiments with X-ray radiation. The device relies on sensing the changes in the local electric field arising from radiation interactions in a macroscopic absorber coupled to a graphene field effect transistor (GFET). Following an ionizing event in the electrically biased undoped semiconducting absorber, the generated charge carriers alter the local electric field which modulates the resistance of the GFET. FEM simulations were used to gain an understanding of the detector's potential performance for devices fabricated on an intrinsic silicon absorber to coincide with the experiments. In addition, experimental results of the device's response to X-ray irradiation at cryogenic temperatures, down to 4.3 K, are discussed. The X-ray source utilized during the experiments generated a continuous spectrum up to 40 keV, with a flux of 106 counts per second at 40 cm through a 1 mm diameter source collimator, when operated at 40 kV at 100 muA. A resistance change of more than 50% was observed in the GFETs between the high flux, 40 kV at 80 muA, and no flux conditions with a range of device response for intermediate flux settings. There was no radiation response from the devices which were not electrically gated. These initial results suggest that a GFET is sensitive to the amount of incident X-ray radiation.

Lopez, Gabriel A.

83

Electromagnetic Fields Radiated by a Circular Loop with Arbitrary Current  

E-print Network

We present a rigorous approach to compute the electromagnetic fields radiated by a thin circular loop with arbitrary current. We employ a polar transmission representation along with a Kontorovich-Lebedev transform to derive integral representations of the field in the interior and exterior regions of a sphere circumscribing the loop. The convergence of the obtained expressions is discussed and comparison with full-wave simulation and other methods are shown.

Salem, Mohamed A

2014-01-01

84

Electromagnetic Fields Radiated by a Circular Loop With Arbitrary Current  

NASA Astrophysics Data System (ADS)

We present a rigorous approach to compute the electromagnetic fields radiated by a thin circular loop with arbitrary current. We employ a polar transmission representation along with a Kontorovich-Lebedev transform to derive integral representations of the field in the interior and exterior regions of a sphere circumscribing the loop. The convergence of the obtained expressions is discussed and comparisons with full-wave simulation and other methods are shown.

Salem, Mohamed A.; Caloz, Christophe

2015-01-01

85

Far-field radiation from a cleaved cylindrical dielectric waveguide  

SciTech Connect

Angular spread in the far-field radiation pattern of a cleaved dielectric waveguide is determined from the modal structure at the surface of the waveguide using the Smythe vector integral formulation. Essential features: First, a mode exists in the fiber that has no wavelength cutoff--the so-called HE{sub 11} mode. This mode arises when non-azimuthal angular dependence of the incoming radiation is present. Second, the energy flow from this hybrid mode fills the fiber face and is not annularly shaped as opposed to the symmetric TE and TM modes. Third, the HE{sub 11} mode is not polarization dependent in contrast to the TE and TM modes. Fourth, for small differences in the refractive indices between the core and cladding regions, only the HE{sub 11} mode will be supported until the next modes appear around 3.33{lambda}. At this point, three new modes can propagate and the model structure of the radiation becomes more complicated. Fifth, the far-field radiation pattern will have negligibly small angular dependence in the phases of the vector fields when only the lowest mode is present; the amplitude has an overall angular dependent form factor. Furthermore, when other modes are present (above 3.33{lambda}), the phase of the vector fields will acquire an angular dependence.

Cerjan, C. [Advanced Microtechnology Program, Lawrence Livermore National Laboratory, CA (United States)

1996-07-09

86

Miniature scintillating detector for small field radiation therapy D. Letourneaua)  

E-print Network

Miniature scintillating detector for small field radiation therapy D. Le´tourneaua) Centre curves, profiles, and dose rate of treatment beams are difficult to obtain with conventional detectors because of loss of lateral elec- tronic equilibrium and volume averaging. A scintillating detector

Pouliot, Jean

87

Radiative neutrino decay in a strong magnetic field  

SciTech Connect

The radiative decay of neutrinos in a strong magnetic field that have relatively high energies, E ? m{sub e}, is studied with allowance for positronium contribution to the photon polarization operator in the vicinity of the cyclotron resonance. It is shown that the probability for the process ? ? ?? increases substantially upon taking into account the positronium contribution.

Anikin, R. A., E-mail: anik-roman@mail.ru; Mikheev, N. V., E-mail: mikheev@uniyar.ac.ru [Yaroslavl State University (Russian Federation)

2013-12-15

88

Radiation of the blackbody in the external field  

E-print Network

The blackbody is considered in the external general field. The additional coefficients of stimulated emission and absorption are introduced into the Einstein mechanism. Then, the generalized Planck formula is derived. The Einstein and Debye formula for the specific heat is possible to generalize. The application of the theory to the sonoluminescence, the relic radiation and solar spectrum is discussed.

Miroslav Pardy

2006-03-06

89

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

NASA Astrophysics Data System (ADS)

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

Kalugin, M. A.

2010-12-01

90

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

SciTech Connect

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

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

2010-12-15

91

Field dependent emission rates in radiation damaged GaAs  

SciTech Connect

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.

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

92

High field CdS detector for infrared radiation  

NASA Technical Reports Server (NTRS)

An infrared radiation detector including a cadmium sulfide platelet having a cathode formed on one of its ends and an anode formed on its other end is presented. The platelet is suitably doped such that stationary high-field domains are formed adjacent the cathode when based in the negative differential conductivity region. A negative potential is applied to the cathode such that a high-field domain is formed adjacent to the cathode. A potential measuring probe is located between the cathode and the anode at the edge of the high-field domain and means are provided for measuring the potential at the probe whereby this measurement is indicative of the infrared radiation striking the platelet.

Tyagi, R. C.; Robertson, J. B.; Boer, K. W.; Hadley, H. C., Jr. (inventors)

1974-01-01

93

Near-field radiative heat transfer in mesoporous alumina  

NASA Astrophysics Data System (ADS)

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).

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

2015-01-01

94

Quantum driven dissipative parametric oscillator in a blackbody radiation field  

SciTech Connect

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.

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

95

Anomalous radiative trapping in laser fields of extreme intensity.  

PubMed

We demonstrate that charged particles in a sufficiently intense standing wave are compressed toward, and oscillate synchronously at, the antinodes of the electric field. We call this unusual behavior anomalous radiative trapping (ART). We show using dipole pulses, which offer a path to increased laser intensity, that ART opens up new possibilities for the generation of radiation and particle beams, both of which are high energy, directed, and collimated. ART also provides a mechanism for particle control in high-intensity quantum-electrodynamics experiments. PMID:25032929

Gonoskov, A; Bashinov, A; Gonoskov, I; Harvey, C; Ilderton, A; Kim, A; Marklund, M; Mourou, G; Sergeev, A

2014-07-01

96

Radiative transfer model validations during the First ISLSCP Field Experiment  

NASA Technical Reports Server (NTRS)

Two simple radiative transfer models, the 5S model based on Tanre et al. (1985, 1986) and the wide-band model of Morcrette (1984) are validated by comparing their outputs with results obtained during the First ISLSCP Field Experiment on concomitant radiosonde, aerosol turbidity, and radiation measurements and sky photographs. Results showed that the 5S model overestimates the short-wave irradiance by 13.2 W/sq m, whereas the Morcrette model underestimated the long-wave irradiance by 7.4 W/sq m.

Frouin, Robert; Breon, Francois-Marie; Gautier, Catherine

1990-01-01

97

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

NASA Technical Reports Server (NTRS)

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.

Statman, Joseph; Jamnejad, Vahraz; Nguyen, Lee

2012-01-01

98

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

PubMed

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

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

2014-11-01

99

Modern Classical Electrodynamics and Electromagnetic Radiation - Vacuum Field Theory Aspects  

E-print Network

The work is devoted to studying some new classical electrodynamics models of interacting charged point particles and related with them physical aspects. Based on the vacuum field theory no-geometry approach, developed in \\cite{BPT,BPT1}, the Lagrangian and Hamiltonian reformulations of some alternative classical electrodynamics models are devised. A problem closely related to the radiation reaction force is analyzed aiming to explain the Wheeler and Feynman reaction radiation mechanism, well known as the absorption radiation theory, and strongly dependent on the Mach type interaction of a charged point particle in an ambient vacuum electromagnetic medium. There are discussed some relationships between this problem and the one derived within the context of the vacuum field theory approach. The R. \\ Feynman's \\textquotedblleft heretical\\textquotedblright\\ approach \\cite{Dy1,Dy2} to deriving the Lorentz force based Maxwell electromagnetic equations is also revisited, its complete legacy is argued both by means of the geometric considerations and its deep relation with the vacuum field theory approach devised before in \\cite{BPT0,BPT1}. \\ Being completely classical, we reanalyze the Feynman's derivation from the classical Lagrangian and Hamiltonian points of view \\ and construct its nontrivial \\ relativistic generalization compatible with the mentioned above vacuum field theory approach.

N. N. Bogolubov; A. K. Prykarpatsky

2013-02-16

100

High field magnetic resonance imaging-based gel dosimetry for small radiation fields  

NASA Astrophysics Data System (ADS)

Small megavoltage photon radiation fields (< 3cm diameter) are used in advanced radiation therapy techniques, such as intensity modulated radiotherapy, and stereotactic radiosurgery, as well as for cellular and preclinical radiobiology studies (very small fields, <1 mm diameter). Radiation dose characteristics for these small fields are difficult to determine in multiple dimensions because of steep dose gradients (30--40% per mm) and conditions of electronic disequilibrium. Conventional radiation dosimetry techniques have limitations for small fields because detector size may be large compared to radiation field size and/or dose acquisition may be restricted to one or two dimensions. Polymer gel dosimetry, is a three-dimensional (3D) dosimeter based on radiation-induced polymerization of tissue equivalent gelatin. Polymer gel dosimeters can be read using magnetic resonance imaging (MRI), which detects changes in relaxivity due to gel polymerization. Spatial resolution for dose readout is limited to 0.25--0.5mm pixel size because of available the magnetic field strengths (1.5T and 3T) and the stability of polymer gelatin at room temperature. A reliable glucose-based MAGIC (methacrylic and ascorbic acid in gelatine initiated by copper) gel dosimeter was formulated and evaluated for small field 3D dosimetry using 3T and 7T high field MRI for dose readout. The melting point of the original recipe MAGIC gel was increased by 4°C by adding 10% glucose to improve gel stability. Excellent spatial resolution of 79um (1.5 hr scan) and 39um (12 hr scan) was achieved using 7T MRI, proving gel stability for long scan times and high resolution 3D dosimetry.

Ding, Xuanfeng

101

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

E-print Network

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.

Svend-Age Biehs

2011-03-15

102

Study on neutron radiation field of carbon ions therapy  

E-print Network

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.

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

2015-01-01

103

Study on neutron radiation field of carbon ions therapy  

E-print Network

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.

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

2015-03-18

104

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

SciTech Connect

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.

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

105

A Computational Model of Cellular Response to Modulated Radiation Fields  

SciTech Connect

Purpose: To develop a model to describe the response of cell populations to spatially modulated radiation exposures of relevance to advanced radiotherapies. Materials and Methods: A Monte Carlo model of cellular radiation response was developed. This model incorporated damage from both direct radiation and intercellular communication including bystander signaling. The predictions of this model were compared to previously measured survival curves for a normal human fibroblast line (AGO1522) and prostate tumor cells (DU145) exposed to spatially modulated fields. Results: The model was found to be able to accurately reproduce cell survival both in populations which were directly exposed to radiation and those which were outside the primary treatment field. The model predicts that the bystander effect makes a significant contribution to cell killing even in uniformly irradiated cells. The bystander effect contribution varies strongly with dose, falling from a high of 80% at low doses to 25% and 50% at 4 Gy for AGO1522 and DU145 cells, respectively. This was verified using the inducible nitric oxide synthase inhibitor aminoguanidine to inhibit the bystander effect in cells exposed to different doses, which showed significantly larger reductions in cell killing at lower doses. Conclusions: The model presented in this work accurately reproduces cell survival following modulated radiation exposures, both in and out of the primary treatment field, by incorporating a bystander component. In addition, the model suggests that the bystander effect is responsible for a significant portion of cell killing in uniformly irradiated cells, 50% and 70% at doses of 2 Gy in AGO1522 and DU145 cells, respectively. This description is a significant departure from accepted radiobiological models and may have a significant impact on optimization of treatment planning approaches if proven to be applicable in vivo.

McMahon, Stephen J., E-mail: stephen.mcmahon@qub.ac.uk [Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland (United Kingdom); Butterworth, Karl T. [Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland (United Kingdom)] [Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland (United Kingdom); McGarry, Conor K. [Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland (United Kingdom) [Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland (United Kingdom); Radiotherapy Physics, Northern Ireland Cancer Centre, Belfast Health and Social Care Trust, Northern Ireland (United Kingdom); Trainor, Colman [Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland (United Kingdom)] [Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland (United Kingdom); O'Sullivan, Joe M. [Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland (United Kingdom) [Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland (United Kingdom); Clinical Oncology, Northern Ireland Cancer Centre, Belfast Health and Social Care Trust, Belfast, Northern Ireland (United Kingdom); Hounsell, Alan R. [Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland (United Kingdom) [Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland (United Kingdom); Radiotherapy Physics, Northern Ireland Cancer Centre, Belfast Health and Social Care Trust, Northern Ireland (United Kingdom); Prise, Kevin M. [Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland (United Kingdom)] [Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland (United Kingdom)

2012-09-01

106

Electrically-gated near-field radiative thermal transistor  

E-print Network

In this work, we propose a near-field radiative thermal transistor made of two graphene-covered silicon carbide (SiC) plates separated by a nanometer vacuum gap. Thick SiC plates serve as the thermal "source" and "drain", while graphene sheets function as the "gate" to modulate the near-field photon tunneling by tuning chemical potential with applied voltage biases symmetrically or asymmetrically. The radiative heat flux calculated from fluctuational electrodynamics significantly varies with graphene chemical potentials, which can tune the coupling between graphene plasmon across the vacuum gap. Thermal modulation, switching, and amplification, which are the key features required for a thermal transistor, are theoretically realized and analyzed. This work will pave the way to active thermal management, thermal circuits, and thermal computing.

Yang, Yue

2015-01-01

107

Local field and radiative relaxation rate in a dielectric medium  

SciTech Connect

The effect of macroscopic parameters of a substance on the optical characteristics of impurity particles is investigated. A generalized control equation is derived for two-level emitters forming an ensemble of optical centers in a transparent dielectric medium. In this equation, the effective values of the acting pump field and the radiative relaxation rate of an optical center are taken into account. The formalism developed here is a completely microscopic approach based on the chain of the Bogoliubov-Born-Green-Kirkwood-Yvon equations for reduced density matrices and correlation operators for material particles and modes of a quantized radiation field. The method used here makes it possible to take into account the effects of individual and collective behavior of emitters, which are associated with the presence of an intermediate medium, consistently without using phenomenological procedures. It is shown that the resultant analytic expression for the effective lifetime of the excited state of an optical center conforms with experimental data.

Kuznetsov, D. V., E-mail: dkusnet@yandex.ru; Roerich, Vl. K. [Troitsk Institute for Innovation and Fusion Research (SRC RF TRINITI), State Research Center of Russian Federation (Russian Federation); Gladush, M. G., E-mail: mglad@isan.troitsk.ru [Vladimir State University (Russian Federation)

2011-10-15

108

Modelling of radiation field around spent fuel container.  

PubMed

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

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

2005-01-01

109

Near-field radiative heat transfer and noncontact friction  

Microsoft Academic Search

All material bodies are surrounded by a fluctuating electromagnetic field because of the thermal and quantum fluctuations of the current density inside them. Close to the surface of planar sources (when the distance d≪lambdaT=cℏ\\/kBT ), thermal radiation can be spatially and temporally coherent if the surface can support surface modes like surface plasmon polaritons, surface phonon polaritons, or adsorbate vibrational

A. I. Volokitin; B. N. J. Persson

2007-01-01

110

Radiative Neutron Capture on Carbon-14 in Effective Field Theory  

E-print Network

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.

Gautam Rupak; Lakma Fernando; Akshay Vaghani

2012-04-19

111

Radiative Neutron Capture on Carbon-14 in Effective Field Theory  

E-print Network

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.

Rupak, Gautam; Vaghani, Akshay

2012-01-01

112

Absorption probability of neutrino fields and Hawking radiation  

E-print Network

We analyse the scattering of neutrino fields from Kerr black holes. Adopting the notation of Teukolsky and Press, we derive the connection relation between the normalizations of ingoing and outgoing waves at the horizon and at infinity. It turns out that the connection relation for neutrino waves neither depends on the frequency $\\omega$ and angular momentum quantum numbers $l,m$ of the wave, nor on the black hole parameters $M,a$. As a result of that the absorption probability of neutrino fields $\\Gamma_{lm}(\\omega)$ which determines the average number of neutrinos emitted in the mode $(\\omega,l,m)$ in Hawking radiation, does not explicitly depend on the frequency $\\omega$ and angular momentum quantum numbers $l,m$. The form of $\\Gamma$ only in terms of Teukolsky's normalizations at infinity and at the horizon is derived. This is another aspect in which neutrino fields are essentially different than bosonic fields.

Koray Düzta?

2015-03-17

113

Radiation from electrons in graphene in strong electric field  

E-print Network

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.

N. Yokomizo

2014-05-05

114

Absorption probability of neutrino fields and Hawking radiation  

E-print Network

We analyse the scattering of neutrino fields from Kerr black holes. Adopting the notation of Teukolsky and Press, we derive the connection relation between the normalizations of ingoing and outgoing waves at the horizon and at infinity. It turns out that the connection relation for neutrino waves neither depends on the frequency $\\omega$ and angular momentum quantum numbers $l,m$ of the wave, nor on the black hole parameters $M,a$. As a result of that the absorption probability of neutrino fields $\\Gamma_{lm}(\\omega)$ which determines the average number of neutrinos emitted in the mode $(\\omega,l,m)$ in Hawking radiation, does not explicitly depend on the frequency $\\omega$ and angular momentum quantum numbers $l,m$. The form of $\\Gamma$ only in terms of Teukolsky's normalizations at infinity and at the horizon is derived. This is another aspect in which neutrino fields are essentially different than bosonic fields.

Düzta?, Koray

2015-01-01

115

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

Code of Federal Regulations, 2013 CFR

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

2013-10-01

116

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

Code of Federal Regulations, 2014 CFR

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

2014-10-01

117

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

Code of Federal Regulations, 2012 CFR

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

2012-10-01

118

Radiation and photoelectron dynamics in ultrastrong laser fields  

NASA Astrophysics Data System (ADS)

We investigate photoelectron and radiation products from the interaction of ultra-strong (>1 x 1017W/cm 2) laser radiation with atoms. In the strong field regime (1 x 1013W/cm2 to 1 x 10 16W/cm2) the interaction is understood in the frame work of Schrodinger equation under the dipole approximation. In ultra-strong laser fields the dipole approximation breaks down. The magnetic field of the laser field, implicitly ignored in the dipole approximation, starts to play a crucial role on the dynamics of photoelectrons in the continuum. We measured ion yields of Ar and Kr as high as Ar9+ and Kr9+ charge states in ultra-strong laser field. The ion yield measurements were compared against a 3D relativistic, rescattering model. The model which uses a tunneling ionization rate from Ammosov, Delone and Krainov (ADK) to calculate the sequential ionization is in qualitative and quantitative agreement with the experiment in the sequential ionization region. The use of a non-relativistic, quasi-classical (WKB approximation) tunneling ionization which proved to be useful for strong field ionization is validated to describe ionization in ultra-strong fields throughout this dissertation. Photoelectron continuum dynamics in a laser field with peak intensity beyond 1 x 1018W/cm2 is highly non-linear and relativistic. We measured photoelectron products, with a dynamic range of four orders of magnitude, from the single atom photoionization of argon and xenon exposed to relativistic laser intensity, 1 x 10 19W/cm2. The highest detected photoelectron energies from atomic photoionization in a circularly polarized laser field are 1.2MeV and 1.3MeV for Ar and Xe atoms respectively. The measurements show different photoelectron energy spectra for Ar and Xe. The spectrum for Ar drops rapidly by three orders of magnitude over the energy range from 0 to 250keV. Beyond this range, the spectrum exhibits a broad local maximum at about 550keV and extends out to 1.2MeV. The spectrum for Xe doesn't show local maximum, instead the spectrum drops by only three orders of magnitude over the entire range from 0 to 1.3MeV. The highly non-linear and relativistic continuum photoelectrons in ultrastrong laser focus results in radiation of high energy photons from non-linear Thomson scattering. We identify three regimes for the interaction as a function of the single cycle quiver amplitude of the photoelectron to the laser focus waist. Adopting a one-dimensional or plane wave approximation when the laser driven excursion of the photoelectron exceeds the focus waist overestimates the total radiated energy by a factor as much as an order of magnitude. Despite this, the spectral amplitude of the radiated high-energy photons from ionization in a laser focus is comparable to the plane wave case for excursions up to the beam waist since the laser focus imparts an extra boost of speed for electrons exiting the focus. Full spatial and temporal integration that includes the ionization of charge states before the peak of the pulse do not alter significantly from results that include only the radiation from ionization of the charge state at the peak of the laser field. The effect of quantum versus classical treatment of the relativistic photoelectron on radiation is quantified using a Monte-Carlo classical and semiclassical tunneling probability current models of ionization for intensities in the range of 1 x 1016W/cm 2 to 1 x 1020W/cm 2. For nonrelativistic intensities, whether the radiation from the photoionization is treated coherently or incoherently, classically or semiclassically, leads to a negligible effect on radiation. For relativistic intensities, coherently summing across the tunneling ionization probability current decreases the radiation by an order of magnitude when compared to classical ionization or incoherent summation of the radiation from the tunneling ionization probability current. The interference effect is most pronounced for high-energy photons since ionization and the electron quiver may be 1mum and extends over multiple radiation wavelengths. (Abst

Ghebregziabher, Isaac

2008-10-01

119

RADIATION FIELDS FOR SEMILINEAR WAVE EQUATIONS DEAN BASKIN AND ANT^ONIO SA BARRETO  

E-print Network

RADIATION FIELDS FOR SEMILINEAR WAVE EQUATIONS DEAN BASKIN AND ANT^ONIO S´A BARRETO Abstract. We define the radiation fields of solutions to critical semilinear wave equations in R3 and use them to define the scattering operator. We also prove a support theorem for the radiation fields with radial

Sá Barreto, Antônio

120

Universalist ethics in extraterrestrial encounter  

NASA Astrophysics Data System (ADS)

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

Baum, Seth D.

2010-02-01

121

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

PubMed

The Institute for Radiological Protection and Nuclear Safety owns two facilities producing realistic mixed neutron-photon radiation fields, CANEL, an accelerator driven moderator modular device, and SIGMA, a graphite moderated americium-beryllium assembly. These fields are representative of some of those encountered at nuclear workplaces, and the corresponding facilities are designed and used for calibration of various instruments, such as survey meters, personal dosimeters or spectrometric devices. In the framework of the European project EVIDOS, irradiations of personal dosimeters were performed at CANEL and SIGMA. Monte Carlo calculations were performed to estimate the reference values of the personal dose equivalent at both facilities. The Hp(10) values were calculated for three different angular positions, 0 degrees, 45 degrees and 75 degrees, of an ICRU phantom located at the position of irradiation. PMID:17578872

Lacoste, V; Gressier, V

2007-01-01

122

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

E-print Network

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

J. Froehlich; M. Griesemer; B. Schlein

2000-09-27

123

Photoionization and photodissociation rates in solar and blackbody radiation fields  

NASA Astrophysics Data System (ADS)

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

Huebner, W. F.; Mukherjee, J.

2015-02-01

124

Frame-dragging fields and spin 1 gravitomagnetic radiation  

NASA Astrophysics Data System (ADS)

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

Tolstoy, Ivan

2012-12-01

125

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

SciTech Connect

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

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

2012-02-15

126

Intercomparison of radiation protection instrumentation in a pulsed neutron field  

NASA Astrophysics Data System (ADS)

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.

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

127

Field Deployable Gamma Radiation Detectors for DHS Use  

SciTech Connect

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.

Sanjoy Mukhopadhyay

2007-08-31

128

Computation of High-Altitude Hypersonic Flow-Field Radiation.  

NASA Astrophysics Data System (ADS)

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

Moreau, Stephane

129

Localisation of atomic populations in the optical radiation field  

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

130

Radiative Corrections from Heavy Fast-Roll Fields during Inflation  

E-print Network

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 unobservable small running of the spectral index. An observable level of tensor modes can also be accommodated, but, sur...

Jain, Rajeev Kumar; Sloth, Martin S

2015-01-01

131

Interaction of Electromagnetic Radiation with Supercritical Magnetic Field  

E-print Network

It is pointed, that effects of refraction of electromagnetic radiation in the medium, formed by the magnetized vacuum, become essential already for relatively soft photons, not hard enough to create an electron-positron pair, including those belonging to soft gamma-, X-ray, optic and radio- range, if the magnetic field B exceeds the critical value of Bcr=m^2/e=4.4 10^13 Gauss. Three leading terms in the asymptotic expansion of the one-loop polarization operator in a constant magnetic field are found for B>>Bcr, and the corresponding refraction index is shown to depend only on the propagation direction of the photon relative to the external field. It is established, that the refraction index for one of polarization modes unlimitedly grows with the field, while the other is saturated at a moderate level. The photon capture effect is extended to soft photons. The results may be essential in studying reflection, refraction and splitting of X-rays, light and radio waves by magnetic fields of magnetars, as well as in considering emission of such waves by charged particles .

A. E. Shabad

2004-01-12

132

Pioneer 11 Encounter. [with Jupiter  

NASA Technical Reports Server (NTRS)

Pioneer 11's encounter with Jupiter is discussed in detail. The scientific experiments carried out on the probe are described along with the instruments used. Tables are included which provide data on the times of experiments, encounters, and the distances from Jupiter. Educational study projects are also given.

1975-01-01

133

Successful I.D. Encounters.  

ERIC Educational Resources Information Center

Instructional Development (I.D.) encounters are dependent for success on such variables as power, politics, promotion, and organizational placement. I.D. consultants must be aware of power bases or orientation of other personnel and clients, e.g., these four "power personalities" which affect their efforts in managing I.D. encounters: the gate…

Poorman, Margaret J.

134

Novel properties of the q-analogue quantized radiation field  

NASA Technical Reports Server (NTRS)

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.

Nelson, Charles A.

1993-01-01

135

Thermoacoustic Monitoring of Radiation Field of Scanning Electron Beam  

NASA Astrophysics Data System (ADS)

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

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

1997-05-01

136

Encounter with Zoology  

E-print Network

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... ’s, is Barry Keverne, who gives the concluding interview. 6 The zoology museum in Cambridge, with the whale. Many of Darwin’s objects are here. Alan Macfarlane explains the connections to Robert Malthus, another Cambridge figure...

Macfarlane, Alan

2014-12-12

137

Development of a Characterized Radiation Field for Evaluating Sensor Performance  

SciTech Connect

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

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

2008-07-01

138

Two encounters with the flank low-latitude boundary layer - Further evidence for closed field topology and investigation of the internal structure  

NASA Technical Reports Server (NTRS)

The structure of the flank low-latitude boundary layer (LLBL) is examined through differential energy spectra and particle angular anisotropies for traversals of the dawn flank (December 19, 1977) and dusk flank (July 7, 1978) during periods of predominantly northward magnetosheath field orientation. Spectra are presented that were obtained from combined ISEE 1 low-energy-proton and electron-differential-energy-analyzer and medium-energy-particle-instrument data extending over the 200-eV/q to 2-MeV energy range for the plasma sheet, stagnation region, outer LLBL, and magnetosheath regions. The stagnation region and the outer LLBL are each a mixture of plasma-sheet and magnetosheath populations, but the stagnation region contains a relatively higher fraction of plasma sheet particles, consistent with its placement earthward of the outer LLBL. Evidence for energization of thermal electrons appears during the dusk flank crossing. Bidirectional field-aligned ion distributions are observed with typically 5-to-1 enhancement of the flux along the magnetic field during certain portions of the dusk flank crossing.

Traver, D. P.; Mitchell, D. G.; Williams, D. J.; Frank, L. A.; Huang, C. Y.

1991-01-01

139

Role of fluctuational electrodynamics in near-field radiative heat transfer  

Microsoft Academic Search

The objective of this paper is to discuss the role of fluctuational electrodynamics in the context of a generalized radiative heat transfer problem. Near-field effects, including the interference phenomenon and radiation tunneling, are important for applications to nanostructures. The classical theory of radiative transfer cannot be readily applied as the feature size approaches the dominant wavelength of radiative emission. At

Mathieu Francoeur; M. Pinar Mengüç

2008-01-01

140

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

Microsoft Academic Search

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

J. Bohm

1980-01-01

141

Experimental determination of radiated internal wave power without pressure field Frank M. Lee,1  

E-print Network

for tidal flow of a stratified fluid past a knife edge. The results for the radiated internal wave powerExperimental determination of radiated internal wave power without pressure field data Frank M. Lee to determine, using only velocity field data, the time-averaged energy flux J and total radiated power P

Morrison, Philip J.,

142

Demonstration of Strong Near-Field Radiative Heat Transfer between Integrated Nanostructures  

E-print Network

silicon dioxide (SiO2) for its surface phonon polariton resonances, at 495 and 1160 cm-1 , shown to allowDemonstration of Strong Near-Field Radiative Heat Transfer between Integrated Nanostructures transport, thermal radiation, near-field radiation, microelectromechanical systems (MEMS), surface phonon

Lipson, Michal

143

Electromagnetic radiation from a synchrotron beam in a field of short magnets  

NASA Astrophysics Data System (ADS)

Dipole elctromagnetic radiation from a synchrotron beam in a sharply azimuthally nonuniform magnetic field is examined. The spectum-angle characteristics of the radiation are determined by an analytical calculation of the magnetic field of short plane rectangular magnets. It is shown that the spectral density of the radiation increases exponentially as the gap between the magnetic poles decreases.

Smoliakov, N. V.

1988-03-01

144

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

Microsoft Academic Search

In a recent paper [S. El Boustani, P. R. Buenzli, and P. A. Martin, Phys. Rev. E 73, 036113 (2006)] about quantum charges in equilibrium with radiation, among other things the asymptotic form of the electric-field correlation has been obtained by a microscopic calculation. It has been found that this correlation has a long-range algebraic decay of the form 1\\/r3

B. Jancovici

2006-01-01

145

Laser Plasma Interaction and Non-classical Properties of Radiation Field  

E-print Network

We show by explicit calculations that non-classical states of the radiation field can be produced by allowing short term interaction between a coherent state of the radiation field with plasma. Whereas, long term interaction, which thermalizes the radiation field, can produce non-classical states of the radiation field only at sufficiently small temperatures. A measure of k-th order squeezing, stricter than the one proposed by Zhang et al, is used to check the emergence of squeezing. It is also shown that photons in the considered thermalized field would follow super-Poissonian statistics.

Aabhaas Vineet Mallik; Pratyay Ghosh; Ananda Dasgupta

2011-06-14

146

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

E-print Network

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, ...

Davidson, Matthew Allen

2011-01-01

147

Voyager Saturn encounter press briefing  

NASA Technical Reports Server (NTRS)

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.

1980-01-01

148

BINARY ASTEROID ENCOUNTERS WITH TERRESTRIAL PLANETS: TIMESCALES AND EFFECTS  

SciTech Connect

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

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

2012-01-15

149

Mixed radiation field dosimetry utilizing Nuclear Quadrupole Resonance  

SciTech Connect

This project has proposed to develop a novel dosimetry system that is capable of directly evaluating the chemical/biological damage caused by neutrons, photons, or both in a single measurement. The dosimeter itself will consist of a small volume of biological equivalent material that is probed for radiation damage with Nuclear Quadrupole Resonance (NQR) techniques. NQR has previously been utilized as a sensitive probe of structural and chemical changes at the molecular level for a variety of organic compounds. The biological equivalent materials used in this study will not only have a density similar to tissue (tissue equivalent) but will have the same atomic components as tissue. This is a significant requirement if the important neutron interactions that occur in tissue are to occur in the dosimeter as well. The overall objective of this study is to investigate a methodology to perform accurate mixed-field (neutron and photon) dosimetry for biological systems.

Hintenlang, D.

1991-01-01

150

Chemical Abundances and the Metagalactic Radiation Field at High Redshift  

E-print Network

We have carried out model calculations of the photoionized intergalactic medium (IGM) to determine the effects on the predicted ionic column densities due to uncertainties in the published dielectronic recombination (DR) rate coefficients. Based on our previous experimental work and a comparison of published theoretical DR rates, we estimate there is in general a factor of 2 uncertainty in existing DR rates used for modeling the IGM. We demonstrate that this uncertainty results in factors of ~1.9 uncertainty in the predicted N V and Si IV column densities, ~1.6 for O VI, and ~1.7 for C IV. We show that these systematic uncertainties translate into a systematic uncertainty of up to a factor of ~3.1 in the Si/C abundance ratio inferred from observations. The inferred IGM abundance ratio could thus be less than the solar Si/C ratio or greater than 3 times the solar ratio. If the latter is true, then it suggests the metagalactic radiation field is not due purely to active galactic nuclei, but includes a significant stellar component. Lastly, column density ratios of Si IV to C IV versus C II to C IV are often used to constrain the decrement in the metagalactic radiation field at the He II absorption edge. We show that the variation in the predicted Si IV to C IV ratio due to a factor of 2 uncertainty in the DR rates is almost as large as that due to a factor of 10 change in the decrement. Laboratory measurements of the relevant DR resonance strengths and energies are the only unambiguous method to remove the effects of these atomic physics uncertainties from models of the IGM.

Daniel Wolf Savin

1999-11-01

151

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

SciTech Connect

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 with a Varian linear accelerator. Results: Nonuniform dose distributions were delivered using a multileaf collimator (MLC) in which half of the cell population was shielded. Clonogenic survival in the shielded region was significantly lower than that predicted from the linear quadratic model. In both cell lines, the out-of-field responses appeared to saturate at 40%-50% survival at a scattered dose of 0.70 Gy in DU-145 cells and 0.24 Gy in AGO1522 cells. There was an approximately eightfold difference in the initial slopes of the out-of-field response compared with the {alpha}-component of the uniform field response. In contrast, cells in the exposed part of the field showed increased survival. These observations were abrogated by direct physical inhibition of cellular communication and by the addition of the inducible nitric oxide synthase inhibitor aminoguanidine known to inhibit intercellular bystander effects. Additional studies showed the proportion of cells irradiated and dose delivered to the shielded and exposed regions of the field to impact on response. Conclusions: These data demonstrate out-of-field effects as important determinants of cell survival following exposure to modulated irradiation fields with cellular communication between differentially irradiated cell populations playing an important role. Validation of these observations in additional cell models may facilitate the refinement of existing radiobiological models and the observations considered important determinants of cell survival.

Butterworth, Karl T., E-mail: k.butterworth@qub.ac.u [Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland (United Kingdom); McGarry, Conor K. [Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland (United Kingdom); Radiotherapy Physics, Northern Ireland Cancer Centre, Belfast Health and Social Care Trust, Northern Ireland (United Kingdom); Trainor, Colman [Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland (United Kingdom); O'Sullivan, Joe M. [Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland (United Kingdom); Clinical Oncology, Northern Ireland Cancer Centre, Belfast Health and Social Care Trust, Belfast, Northern Ireland (United Kingdom); Hounsell, Alan R. [Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland (United Kingdom); Radiotherapy Physics, Northern Ireland Cancer Centre, Belfast Health and Social Care Trust, Northern Ireland (United Kingdom); Prise, Kevin M. [Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland (United Kingdom)

2011-04-01

152

Magnetic field and radiative transfer modelling of a quiescent prominence  

NASA Astrophysics Data System (ADS)

Aims: The aim of this work is to analyse the multi-instrument observations of the June 22, 2010 prominence to study its structure in detail, including the prominence-corona transition region and the dark bubble located below the prominence body. Methods: We combined results of the 3D magnetic field modelling with 2D prominence fine structure radiative transfer models to fully exploit the available observations. Results: The 3D linear force-free field model with the unsheared bipole reproduces the morphology of the analysed prominence reasonably well, thus providing useful information about its magnetic field configuration and the location of the magnetic dips. The 2D models of the prominence fine structures provide a good representation of the local plasma configuration in the region dominated by the quasi-vertical threads. However, the low observed Lyman-? central intensities and the morphology of the analysed prominence suggest that its upper central part is not directly illuminated from the solar surface. Conclusions: This multi-disciplinary prominence study allows us to argue that a large part of the prominence-corona transition region plasma can be located inside the magnetic dips in small-scale features that surround the cool prominence material located in the dip centre. We also argue that the dark prominence bubbles can be formed because of perturbations of the prominence magnetic field by parasitic bipoles, causing them to be devoid of the magnetic dips. Magnetic dips, however, form thin layers that surround these bubbles, which might explain the occurrence of the cool prominence material in the lines of sight intersecting the prominence bubbles. Movie and Appendix A are available in electronic form at http://www.aanda.org

Gunár, S.; Schwartz, P.; Dudík, J.; Schmieder, B.; Heinzel, P.; Jur?ák, J.

2014-07-01

153

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

ERIC Educational Resources Information Center

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

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

2011-01-01

154

Predicting the Earth encounters of (99942) Apophis  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

155

On the divergence difficulty of quantized field theories and the rigorous treatment of radiation reaction : with related additional papers   

E-print Network

By an orthodox application of the perturbation theory to the general case of a quantized field, it is shown that the divergence difficulty hitherto encountered arises from a faulty application of the expansion method. The ...

Peng, Hwan-Wu

156

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

SciTech Connect

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

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

2012-07-01

157

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

SciTech Connect

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.

Kerns, James R. [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 and Graduate School of Biomedical Sciences, The University of Texas Health Science Center Houston, Houston, Texas 77030 (United States)] [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 and Graduate School of Biomedical Sciences, The University of Texas Health Science Center Houston, Houston, Texas 77030 (United States); Anand, Aman [Department of Radiation Oncology, Mayo Clinic, Scottsdale, Arizona 85259 (United States)] [Department of Radiation Oncology, Mayo Clinic, Scottsdale, Arizona 85259 (United States)

2013-11-15

158

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

PubMed Central

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

Kerns, James R.; Anand, Aman

2013-01-01

159

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

PubMed

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

Reitz, Guenther

2008-01-01

160

Near-field thermal radiation transfer controlled by plasmons in graphene  

E-print Network

It is shown that thermally excited plasmon-polariton modes can strongly mediate, enhance, and tune the near-field radiation transfer between two closely separated graphene sheets. The dependence of near-field heat exchange ...

Ilic, Ognjen

161

Radiation fields for nanoscale systems Ming Liang Zhang* and D. A. Drabold**  

E-print Network

Radiation fields for nanoscale systems Ming Liang Zhang* and D. A. Drabold** Department of Physics-classical radiation theory, temporal coarse graining * Corresponding author: e-mail zhangm@ohio.edu, Phone: (01) 740 semi-classical radiation theory (SCRT) with these sources, the microscopic Maxwell equations can

Drabold, David

162

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

E-print Network

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

Guzina, Bojan

163

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

Microsoft Academic Search

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

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

2008-01-01

164

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

E-print Network

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.

Kh. M. Beshtoev

2000-04-19

165

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

PubMed Central

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

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

2012-01-01

166

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

PubMed

In a recent paper [S. El Boustani, P. R. Buenzli, and P. A. Martin, Phys. Rev. E 73, 036113 (2006)] about quantum charges in equilibrium with radiation, among other things the asymptotic form of the electric-field correlation has been obtained by a microscopic calculation. It has been found that this correlation has a long-range algebraic decay of the form 1/r3 (except in the classical limit). The macroscopic approach, in the Course of Theoretical Physics of Landau and Lifshitz, gives no such decay. In this Brief Report we revisit and complete the macroscopic approach of Landau and Lifshitz and suggest that, perhaps, the use of a classical electromagnetic field by El Boustani was not justified. PMID:17279955

Jancovici, B

2006-11-01

167

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

E-print Network

In a recent paper [S.El Boustani, P.R.Buenzli, and Ph.A.Martin, Phys.Rev. E 73, 036113 (2006) cond-mat/0511537], about quantum charges in equilibrium with radiation, among other things the asymptotic form of the electric-field correlation has been obtained by a microscopic calculation. It has been found that this correlation has a long-range algebraic decay (except in the classical limit). The macroscopic approach, in the Course of Theoretical Physics of Landau and Lifshitz, gives no such long-range algebraic decay. In this Brief Report, we revisit and complete the macroscopic approach of Landau and Lifshitz, we confirm their result, and suggest that, perhaps, the use of a classical electromagnetic field by El Boustani et al. was not justified.

B. Jancovici

2006-11-23

168

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

SciTech Connect

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

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

2006-11-15

169

Practical method for evaluating the sound field radiated from a waveguide.  

PubMed

This letter presents a simple and practical method for evaluating the sound field radiated from a waveguide. By using the proposed method, detailed information about the radiated sound field can be obtained by measuring the sound field in the mouth of the baffled waveguide. To examine this method's effectiveness, the radiated sound pressure distribution in space was first evaluated by using the proposed method, and then it was measured directly for comparison. Experiments using two different waveguides showed good agreement between the evaluated and the measured radiated sound pressure distributions. PMID:25618097

Feng, Xuelei; Shen, Yong; Chen, Simiao; Zhao, Ye

2015-01-01

170

Far-field multimodal acoustic radiation directivity. [from ducted bodies  

NASA Technical Reports Server (NTRS)

Approximate equations for the far field acoustic radiation patterns in the forward quadrant from a flanged circular duct were compared with exact equations for both single and multimodal excitations. The single mode comparison showed good agreement between the exact and approximate equations for the principal lobes of higher radial order modes. For lower and especially for zero radial order modes, there was some error in the angular location and decibel level of principal lobe peak pressure obtained from the approximate equation. Some agreement of sidelobes was also observed although the approximate equation was not intended to simulate the sidelobes. The multimodal approximate summation equations consisting only of a simple function of directivity angle and an acoustic power biasing function were checked against the exact equations for several distributions of modal power and showed excellent agreement with exact equations for all cases. Although many modes contribute to the final level and shape of the directivity curve, the major contributions appear to come from the higher radial order modes.

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

1977-01-01

171

A Lakatosian Encounter with Probability  

ERIC Educational Resources Information Center

There is much to be learned and pondered by reading "Proofs and Refutations" by Imre Lakatos (Lakatos, 1976). It highlights the importance of mathematical definitions, and how definitions evolve to capture the essence of the object they are defining. It also provides an exhilarating encounter with the ups and downs of the mathematical reasoning…

Chick, Helen

2010-01-01

172

Enhancement or Suppression of the Near-Field Radiative Heat Transfer Between Two Materials  

Microsoft Academic Search

Control of near-field radiative heat transfer is significant due to its practical applications. We propose an approach to control near-field thermal radiation between two closely spaced bodies by inserting a suspended thin film. Numerical simulations are carried out for different material combinations of doped silicon and aluminum (Al). Investigation showed that the heat flux between the two bodies can be

Z. H. Zheng; Y. M. Xuan

2011-01-01

173

Gamma Ray Bursts from Interaction of Relativistic Flows with Radiation Fields  

E-print Network

Relativistic flows resulting from sudden explosive events upscatter ambient interstellar photons of local radiation fields. For Lorentz factor $ > 100$ and dense optical - UV radiation fields the emergent signal is a typical gamma ray burst. Presumably the explosions occur in dense globular clusters or in galactic nuclei, at cosmological distances.

Amotz Shemi

1994-04-20

174

A uniformly moving polarizable particle in a thermal radiation field with arbitrary spin direction  

E-print Network

We have generalized our recent results (Arm. J. Phys., 2014) relating to the dynamics, heating and radiation of a small rotating polarizable particle moving in a thermal radiation field in the case of arbitrary spin orientation. General expressions for the tangential force, heating rate and intensity of thermal and nonthermal radiation are given. It is shown that the intensity of nonthermal radiation does not depend on the linear velocity and spin direction of the particle.

A. A. Kyasov; G. V. Dedkov

2014-12-16

175

The Solar and Thermal Radiation Field Below the Venus Clouds  

NASA Astrophysics Data System (ADS)

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

Crisp, D.

2000-10-01

176

Far-field radiation of aft turbofan noise  

NASA Technical Reports Server (NTRS)

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.

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

1980-01-01

177

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...

178

Graphene Field Effect Transistors for Detection of Ionizing Radiation  

E-print Network

, 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

Chen, Yong P.

179

Estimating the Reliability of Electronic Parts in High Radiation Fields  

NASA Technical Reports Server (NTRS)

Radiation effects on materials and electronic parts constrain the lifetime of flight systems visiting Europa. Understanding mission lifetime limits is critical to the design and planning of such a mission. Therefore, the operational aspects of radiation dose are a mission success issue. To predict and manage mission lifetime in a high radiation environment, system engineers need capable tools to trade radiation design choices against system design and reliability, and science achievements. Conventional tools and approaches provided past missions with conservative designs without the ability to predict their lifetime beyond the baseline mission.This paper describes a more systematic approach to understanding spacecraft design margin, allowing better prediction of spacecraft lifetime. This is possible because of newly available electronic parts radiation effects statistics and an enhanced spacecraft system reliability methodology. This new approach can be used in conjunction with traditional approaches for mission design. This paper describes the fundamentals of the new methodology.

Everline, Chester; Clark, Karla; Man, Guy; Rasmussen, Robert; Johnston, Allan; Kohlhase, Charles; Paulos, Todd

2008-01-01

180

Graphene-assisted near-field radiative heat transfer between corrugated polar materials  

SciTech Connect

Graphene has attracted great attention in nanoelectronics, optics, and energy harvesting. Here, the near-field radiative heat transfer between graphene-covered corrugated silica is investigated based on the exact scattering theory. It is found that graphene can improve the radiative heat flux between silica gratings by more than one order of magnitude and alleviate the performance sensitivity to lateral shift. The underlying mechanism is mainly attributed to the improved photon tunneling of modes away from phonon resonances. Besides, coating with graphene leads to nonlocal radiative transfer that breaks Derjaguin's proximity approximation and enables corrugated silica to outperform bulk silica in near-field radiation.

Liu, X. L.; 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)

2014-06-23

181

Radiated electric field measurements in U.S. Army helicopters  

Microsoft Academic Search

Aircraft systems and medical devices generate electromagnetic fields. EMI can cause faulty operation of aircraft systems or medical devices and endanger patients or aircraft crewmembers. A ground and inflight study was conducted to describe the electromagnetic fields in typical operations. Broadband isotropic field sensors measured electric fields from 5 kHz to 3 MHz, 3 to 500 MHz, and 0.5 MHz

James E. Bruckart

1992-01-01

182

Reduction of the Background Magnetic Field Inhibits Ability of Drosophila melanogaster to Survive Ionizing Radiation  

PubMed Central

The effects of exposure to an environment where the background magnetic field has been reduced were studied on wild-type Drosophila melanogaster by measuring its ability to survive a single exposure to ionizing radiation during its larval stage. The experimental design presented shows a timeframe, ionizing radiation dose and background magnetic field parameters that will cause a significant and reproducible reduction of survival on this insect model. These results suggest that background magnetic fields may play a fundamental role in the recovery or harm of a biological system that is exposed to single doses of ionizing radiation. PMID:22532126

Portelli, Lucas; Madapatha, Dinu; Martino, Carlos; Hernandez, Mark; Barnes, Frank

2012-01-01

183

Analysis of the failures and corrective actions for the LHC cryogenics radiation tolerant electronics and its field instruments  

SciTech Connect

The LHC cryogenic system radiation tolerant electronics and their associated field instruments have been in nominal conditions since before the commissioning of the first LHC beams in September 2008. This system is made of about 15’000 field instruments (thermometers, pressure sensors, liquid helium level gauges, electrical heaters and position switches), 7’500 electronic cards and 853 electronic crates. Since mid-2008 a software tool has been deployed, this allows an operator to report a problem and then lists the corrective actions. The tool is a great help in detecting recurrent problems that may be tackled by a hardware or software consolidation. The corrective actions range from simple resets, exchange of defective equipment, repair of electrical connectors, etc. However a recurrent problem that heals by itself is present on some channels. This type of fault is extremely difficult to diagnose and it appears as a temporary opening of an electrical circuit; its duration can range from a few minutes to several months. This paper presents the main type of problems encountered during the last four years, their evolution over time, the various hardware or software consolidations that have resulted and whether they have had an impact in the availability of the LHC beam.

Balle, Christoph; Casas, Juan; Vauthier, Nicolas [CERN, TE Department, 1211 Geneva (Switzerland)

2014-01-29

184

Analysis of the failures and corrective actions for the LHC cryogenics radiation tolerant electronics and its field instruments  

NASA Astrophysics Data System (ADS)

The LHC cryogenic system radiation tolerant electronics and their associated field instruments have been in nominal conditions since before the commissioning of the first LHC beams in September 2008. This system is made of about 15'000 field instruments (thermometers, pressure sensors, liquid helium level gauges, electrical heaters and position switches), 7'500 electronic cards and 853 electronic crates. Since mid-2008 a software tool has been deployed, this allows an operator to report a problem and then lists the corrective actions. The tool is a great help in detecting recurrent problems that may be tackled by a hardware or software consolidation. The corrective actions range from simple resets, exchange of defective equipment, repair of electrical connectors, etc. However a recurrent problem that heals by itself is present on some channels. This type of fault is extremely difficult to diagnose and it appears as a temporary opening of an electrical circuit; its duration can range from a few minutes to several months. This paper presents the main type of problems encountered during the last four years, their evolution over time, the various hardware or software consolidations that have resulted and whether they have had an impact in the availability of the LHC beam.

Balle, Christoph; Casas, Juan; Vauthier, Nicolas

2014-01-01

185

The radiated fields of focussing air-coupled ultrasonic phased arrays  

Microsoft Academic Search

This paper presents an investigation into the fields radiated into air by ultrasonic phased arrays under transient excitation. In particular, it includes a theoretical prediction of spatial variations in amplitude throughout the both the near-field and far-field of such arrays. The approach has been used to predict the result of phasing to produce a focus in air, which can be

A. Neild; D. A. Hutchins; T. J. Robertson; L. A. J. Davis; D. R. Billson

2005-01-01

186

Near field radiation characteristics of implantable square spiral chip inductor antennas for bio-sensors  

Microsoft Academic Search

This work presents the experimental characterization of implantable square spiral chip inductor antennas (SSCIA) in free space. Results indicate that the measured near field relative signal strength of the SSCIA agrees with simulated results and confirm that in the near field region the radiation field is fairly uniform in all directions. The results show the applicability of SSCIA for the

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

2007-01-01

187

The electromagnetic fields and the radiation of a spatio-temporally varying electric current loop  

E-print Network

The electric and magnetic fields of a spatio-temporally varying electric current loop are calculated using the Jefimenko equations. The radiation and the nonradiation parts of the electromagnetic fields are derived in the framework of Maxwell's theory of electromagnetic fields. In this way, a new, exact, analytical solution of the Maxwell equation is found.

Markus Lazar

2013-04-12

188

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

Microsoft Academic Search

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

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

1991-01-01

189

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

NASA Astrophysics Data System (ADS)

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.

Crawford, Arthur Bryan

190

Measurement of visible radiation transfer in water under laboratory and field conditions  

NASA Astrophysics Data System (ADS)

Solar radiation transfer in a body of water strongly influences thermal conditions and the growth of photosynthetic organisms. The development of methods for accurately predicting this transfer is investigated. The optical properties of natural waters and the distribution of radiation of water samples under laboratory conditions were measured. The results were compared with predictions. The distribution of radiation under field conditions were also measured. A complete set of optical property measurements were obtained from samples of water from the Wabash River.

Incropera, F. P.

1981-09-01

191

Scatter radiation intensities around full-field digital mammography units.  

PubMed

The aim of this study was to investigate the scatter radiation intensity around digital mammography systems and apply these data to standard shielding calculations to reveal whether shielding design of existing breast screening rooms is adequate for the use of digital mammography systems. Three digital mammography systems from GE Healthcare, Hologic and Philips were employed in the study. A breast-equivalent phantom was imaged under clinical workload conditions and scatter radiation intensities around the digital mammography systems were measured for a range of angles in three planes using an ionisation chamber. The results were compared with those from previous studies of film-screen systems. It may be deduced from the results that scattering in the backward direction is significant for all three systems, while scattering in the forward direction can be significant for some planes around the GE and Hologic systems. Measurements at typical clinical settings on each system revealed the Philips system to have markedly lower scatter radiation intensities than the other systems. Substituting the measured scattered radiation intensity into shielding calculations yielded barrier requirements similar to those already in place at the screening centres operating these systems. Current radiation protection requirements based on film-screen technology remain sufficient when applied to rooms with digital mammography installations and no alteration is required to the structural shielding. PMID:23239693

Judge, M A; Keavey, E; Phelan, N

2013-01-01

192

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

SciTech Connect

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

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

1997-05-01

193

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

PubMed

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

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

2012-06-01

194

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

E-print Network

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

Texas at Austin. University of

195

Plasma wave resonant detection of femtosecond pulsed terahertz radiation by a nanometer field-effect transistor  

E-print Network

Plasma wave resonant detection of femtosecond pulsed terahertz radiation by a nanometer field detection of femtosecond pulsed terahertz radiation obtained by optical rectification in a ZnTe crystal show that physical mechanism of the detection is related to the plasma waves excited in the transistor

Levelut, Claire

196

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...

197

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

Microsoft Academic Search

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

D. M. Le Vine; R. Meneghini

1978-01-01

198

Acoustic radiation potential on a sphere in plane, cylindrical, and spherical standing wave fields  

Microsoft Academic Search

The method of Gor'kov is applied for deriving the acoustic radiation potential on a sphere in an arbitrary sound field. Generalized potential and force expressions are derived for arbitrary standing wave modes in rectangular, cylindrical, and spherical geometries for the case where the sphere radius is much smaller than the wavelength. Criteria for determining radiation-potential minima are derived and examples

M. Barmatz; P. Collas

1985-01-01

199

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

E-print Network

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 ...

Wygant, J. R.

200

Radiation Damage of Myoglobin Crystals in Weak Stationary Electric and Magnetic Fields  

NASA Astrophysics Data System (ADS)

Radiation damage is one of the bottlenecks in the field of structural biology. Cryo-cooling of protein crystals provided a breakthrough in the 1980s and resulted in significant reductions in radiation damage. Other factors positively influencing the progression of damage include the application of radical scavengers and reductions in the experimental beam size. Here we study the impact on radiation damage of applying static magnetic and electric fields during protein diffraction experiments, ultimately probing the Lorenz force effect on primary photoelectrons and secondary Auger electrons, which both contribute to the damage process. The design of a special mounting pin using graphene for applying electric fields on a crystalline sample is described. Analyses of myoglobin protein crystals exposed to the fields of ~40 mT and -300 V show a slower global radiation damage rate and also changes in the progression of specific damage process on the molecular level, in particular at doses extending beyond the Garman limit of 30 MGy.

Trame, C. B.; Dragovic, M.; Chiu, H.-J.

2014-03-01

201

Near-field radiative heat transfer between closely spaced graphene and amorphous SiO2  

Microsoft Academic Search

We study the near-field radiative energy transfer between graphene and an amorphous SiO2 substrate. In comparison with the existing theories of near-field radiative heat transfer our theory takes into account that the free carriers in graphene are moving relative to the substrate with a drift velocity v. In this case the heat flux is determined by both thermal and quantum

A. I. Volokitin; B. N. J. Persson

2011-01-01

202

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

PubMed

A rectangular microstrip antenna radiator is investigated for its near-zone radiation characteristics in water. Calculations of a cavity model theory are compared with the electric-field measurements of a miniature nonperturbing diode-dipole E-field probe whose 3 mm tip was positioned by an automatic three-axis scanning system. These comparisons have implications for the use of microstrip antennas in a multielement microwave hyperthermia applicator. Half-wavelength rectangular microstrip patches were designed to radiate in water at 915 MHz. Both low (epsilon r = 10) and high (epsilon r = 85) dielectric constant substrates were tested. Normal and tangential components of the near-zone radiated electric field were discriminated by appropriate orientation of the E-field probe. Low normal to transverse electric-field ratios at 3.0 cm depth indicate that the radiators may be useful for hyperthermia heating with an intervening water bolus. Electric-field pattern addition from a three-element linear array of these elements in water indicates that phase and amplitude adjustment can achieve some limited control over the distribution of radiated power. PMID:1612617

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

1992-02-01

203

Angular momentum loss of primordial gas in Ly? radiation field  

NASA Astrophysics Data System (ADS)

We present results on the radiation drag exerted by an isotropic and homogeneous background of Ly? photons on neutral gas clouds orbiting within H II regions around Population III stars of different masses. The Doppler shift causes a frequency difference between photons moving in the direction of the cloud and opposite to it resulting in a net momentum loss of the cloud in the direction of motion. We find that half of the angular momentum of gas with v? ? 20 km s-1 near (r ? 3 kpc) a Population III star of 120 M? at z = 20 is lost within ˜106 yr. The radiation drag is a strong function of cloud velocity that peaks at v ˜ 20 km s-1 reflecting the frequency dependence of the photon cross-section. Clouds moving with velocities larger than ˜100 km s-1 lose their angular momentum on time-scales of ˜108 yr. At lower redshifts radiation drag becomes inefficient as the Ly? photon density in H II regions decreases by a factor (1 + z)3 and angular momentum is lost on time-scales ? 108 yr even for low-velocity clouds. Our results suggest that a sweet spot exists for the loss of angular momentum by radiation drag for gas clouds at z > 10 and with v ˜ 20 km s-1. Comparison to dynamical friction forces acting on typical gas clouds suggest that radiation drag is the dominant effect impacting the orbit. We propose that this effect can suppress the formation of extended gas discs in the first galaxies and help gas accretion near galactic centres and central black holes.

Yajima, Hidenobu; Khochfar, Sadegh

2014-06-01

204

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

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

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

2012-01-01

205

Lightning-channel morphology revealed by return-stroke radiation field waveforms  

Microsoft Academic Search

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

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

1995-01-01

206

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

E-print Network

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.

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

2013-01-01

207

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

208

Absorption cross section and Hawking radiation of the electromagnetic field with Weyl corrections  

E-print Network

We have investigated the absorption cross section and the Hawking radiation of electromagnetic field with Weyl correction in the background of a four-dimensional Schwarzschild black hole spacetime. Our results show that the properties of the absorption cross section and the Hawking radiation depend not only on the Weyl correction parameter, but also on the parity of the electromagnetic field, which is quite different from those of the usual electromagnetic field without Weyl correction in the four-dimensional spacetime. With increase of Weyl correction parameter, the absorption probability, the absorption cross section, the power emission spectra and the luminosity of Hawking radiation decreases with Weyl correction parameter for the odd-parity electromagnetic field and increases with the event-parity electromagnetic field.

Hao Liao; Songbai Chen; Jiliang Jing

2013-12-19

209

Encounters with Spectral Theory Copenhagen University  

E-print Network

Encounters with Spectral Theory Gerd Grubb Copenhagen University November 2, 2012 Gerd Grubb Grubb Copenhagen University Encounters with Spectral Theory #12;What is spectral theory? In mathematics decomposition of A. Gerd Grubb Copenhagen University Encounters with Spectral Theory #12;Example: The vibrating

Grubb, Gerd

210

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

NASA Technical Reports Server (NTRS)

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.

Watson, William D.

1994-01-01

211

COMET ENCOUNTERS AND CARBON 14  

SciTech Connect

The {sup 14}C production of shock-accelerated particles is calculated in terms of the total energy released in energetic particles. The recently reported 1.2% jump in the {sup 14}C content of the atmosphere in the year C.E. 775, it is found, would require {approx}> 10{sup 34} erg in energetic particles, less than first estimates but far more than any known solar flare on record. It is noted that the superflare from a large comet (comparable to C/Hale-Bopp) colliding with the sun could produce shock-accelerated GeV cosmic rays in the solar corona and/or solar wind, and possibly account for the C.E. 775 event. Several additional predictions of cometary encounters with the sun and other stars may be observable in the future.

Eichler, David; Mordecai, David, E-mail: eichler.david@gmail.com [Physics Department, Ben-Gurion University, Be'er-Sheva 84105 (Israel)

2012-12-20

212

Gamma heating measurements in a mixed radiation field  

SciTech Connect

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

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

1990-09-01

213

Position sensitive detection of neutrons in high radiation background field.  

PubMed

We present the development of a high-resolution position sensitive device for detection of slow neutrons in the environment of extremely high ? and e(-) radiation background. We make use of a planar silicon pixelated (pixel size: 55 × 55 ?m(2)) spectroscopic Timepix detector adapted for neutron detection utilizing very thin (10)B converter placed onto detector surface. We demonstrate that electromagnetic radiation background can be discriminated from the neutron signal utilizing the fact that each particle type produces characteristic ionization tracks in the pixelated detector. Particular tracks can be distinguished by their 2D shape (in the detector plane) and spectroscopic response using single event analysis. A Cd sheet served as thermal neutron stopper as well as intensive source of gamma rays and energetic electrons. Highly efficient discrimination was successful even at very low neutron to electromagnetic background ratio about 10(-4). PMID:24517756

Vavrik, D; Jakubek, J; Pospisil, S; Vacik, J

2014-01-01

214

Position sensitive detection of neutrons in high radiation background field  

SciTech Connect

We present the development of a high-resolution position sensitive device for detection of slow neutrons in the environment of extremely high ? and e{sup ?} radiation background. We make use of a planar silicon pixelated (pixel size: 55 × 55 ?m{sup 2}) spectroscopic Timepix detector adapted for neutron detection utilizing very thin {sup 10}B converter placed onto detector surface. We demonstrate that electromagnetic radiation background can be discriminated from the neutron signal utilizing the fact that each particle type produces characteristic ionization tracks in the pixelated detector. Particular tracks can be distinguished by their 2D shape (in the detector plane) and spectroscopic response using single event analysis. A Cd sheet served as thermal neutron stopper as well as intensive source of gamma rays and energetic electrons. Highly efficient discrimination was successful even at very low neutron to electromagnetic background ratio about 10{sup ?4}.

Vavrik, D., E-mail: vavrik@itam.cas.cz [Institute of Experimental and Applied Physics, Czech Technical University in Prague, Horska 3a/22, Prague (Czech Republic); Institute of Theoretical and Applied Mechanics, Academy of Sciences of the Czech Republic, Prosecka 76, 190 00 Prague 9 (Czech Republic); Jakubek, J.; Pospisil, S. [Institute of Theoretical and Applied Mechanics, Academy of Sciences of the Czech Republic, Prosecka 76, 190 00 Prague 9 (Czech Republic)] [Institute of Theoretical and Applied Mechanics, Academy of Sciences of the Czech Republic, Prosecka 76, 190 00 Prague 9 (Czech Republic); Vacik, J. [Nuclear Physics Institute, Academy of Sciences of the Czech Republic, Rez, 250 68 Prague, Czech Republic (Czech Republic)] [Nuclear Physics Institute, Academy of Sciences of the Czech Republic, Rez, 250 68 Prague, Czech Republic (Czech Republic)

2014-01-15

215

Strong far field coherent scattering of ultraviolet radiation by holococcolithophores  

E-print Network

By considering the structure of holococcoliths (calcite plates that cover holococcolithophores, a haploid phase of the coccolithophore life cycle) as a photonic structure, we apply a discrete dipolar approximation to study the light backscattering properties of these algae. We show that some holococcolith structures have the ability to scatter the ultraviolet (UV) radiation. This property may represent an advantage for holococcolithophores possessing it, by allowing them to live higher in the water column than other coccolithophores.

Quintero-Torres, R; Torres, M; Estrada, M; Cros, L

2007-01-01

216

Synchro-Curvature Radiation of Charged Particles in the Strong Curved Magnetic Fields  

NASA Astrophysics Data System (ADS)

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.

Kelner, S. R.; Prosekin, A. Yu.; Aharonian, F. A.

2015-01-01

217

Radiation Isotope Identification Device (RIIDs) Field Test and Evaluation Campaign  

SciTech Connect

Handheld, backpack, and mobile sensors are elements of the Global Nuclear Detection System for the interdiction and control of illicit radiological and nuclear materials. They are used by the U.S. Department of Homeland Security (DHS) and other government agencies and organizations in various roles for border protection, law enforcement, and nonproliferation monitoring. In order to systematically document the operational performance of the common commercial off-the-shelf portable radiation detection systems, the DHS Domestic Nuclear Detection Office conducted a test and evaluation campaign conducted at the Nevada Test Site from January 18 to February 27, 2006. Named 'Anole', it was the first test of its kind in terms of technical design and test complexities. The Anole test results offer users information for selecting appropriate mission-specific portable radiation detection systems. The campaign also offered manufacturers the opportunity to submit their equipment for independent operationally relevant testing to subsequently improve their detector performance. This paper will present the design, execution, and methodologies of the DHS Anole portable radiation detection system test campaign.

Christopher Hodge, Raymond Keegan

2007-08-01

218

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

PubMed

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

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

2012-01-01

219

Numerical Treatment of Anisotropic Radiation Field Coupling with the Relativistic Resistive Magnetofluids  

E-print Network

We develop a numerical scheme for solving a fully special relativistic resistive radiation magnetohydrodynamics. Our code guarantees conservations of total mass, momentum and energy. Radiation energy density and radiation flux are consistently updated using the M-1 closure method, which can resolve an anisotropic radiation fields in contrast to the Eddington approximation as well as the flux-limited diffusion approximation. For the resistive part, we adopt a simple form of the Ohm's law. The advection terms are explicitly solved with an approximate Riemann solver, mainly HLL scheme, and HLLC and HLLD schemes for some tests. The source terms, which describe the gas-radiation interaction and the magnetic energy dissipation, are implicitly integrated, relaxing the Courant-Friedrichs-Lewy condition even in optically thick regime or a large magnetic Reynolds number regime. Although we need to invert $4\\times 4$ (for gas-radiation interaction) and $3\\times 3$ (for magnetic energy dissipation) matrices at each grid ...

Takahashi, Hiroyuki R

2013-01-01

220

Scattering of Polarized Radiation by Atoms in Magnetic and Electric Fields  

E-print Network

The polarization of radiation by scattering on an atom embedded in combined external quadrupole electric and uniform magnetic fields is studied theoretically. Analytic formulae are derived for the scattering phase matrix. Limiting cases of scattering under Zeeman effect, and Hanle effect in weak magnetic fields are discussed.

Yee Yee Oo; K. N. Nagendra; Sharath Ananthamurthy; G. Ramachandran

2005-09-26

221

Commutation Rules and Eigenvalues of Spin and Orbital Angular Momentum of Radiation Fields  

Microsoft Academic Search

We investigate the separation of the total angular momentum J of the electromagnetic field into a ‘spin’ part S and an ‘orbital’ part L. We show that both ‘spin’ and ‘orbital’ angular momentum are observables. However, the transversality of the radiation field affects the commutation relations for the associated quantum operators. This implies that neither S nor L are angular

S. J. van Enk; G. Nienhuis

1994-01-01

222

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

Microsoft Academic Search

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

M. S. Sarto

1997-01-01

223

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

Microsoft Academic Search

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

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

2009-01-01

224

Cyclotron Maser Cooling of Particle Beams and Quantum Field Action Effect on Radiation Cooling  

NASA Astrophysics Data System (ADS)

A new particle beam cooling scheme “cyclotron maser cooling” (CMC) was examined. Under a stimulating rf field below the critical value prescribed by an action time of the field, a beam of gyrating electrons obeyed the Liouville's theorem. However, when the field reached the critical value, the beam abruptly jumped to a critical point of the radiative system undergoing CMC, where all electrons accumulated at one discrete energy within about 30 ns. On the other hand, when the field exceeded the critical value by less than 1 dB, a coherent energy modulation took place in gyrations. As a possible mechanism of this remarkable phenomena, a phase transition or a macroscopic quantum jump induced by the “quantum field action effect” on radiation cooling was presented. Under a stimulating ratiation field below the quantum field action any oscillator system remains non-radiative. However, under the stimulating quantum field action, a macroscopic quantum jump to the radiative system takes place leading to its cooling to a stable state irrespective of photon emission mode.

Ikegami, Hidetsugu

1997-08-01

225

Brief encounters: Assembling cosmetic surgery tourism.  

PubMed

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

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

2015-01-01

226

Generation of attosecond pulses of recombination radiation in two-colour laser fields  

SciTech Connect

The possibility of generation of attosecond pulses of recombination radiation upon the above-threshold tunnel ionisation of atoms (ions) in two-colour laser fields is studied. The method of classical photoelectron trajectories in the continuum is used to determine the laser field parameters minimising the duration of recombination radiation. It is shown that pulses of duration of several tens of attoseconds can be generated in such fields. The principal possibility of generation of coherent electromagnetic pulses of duration {tau}{sub g{approx}}<1 as is also shown. (nonlinear optical phenomena)

Taranukhin, Vladimir D; Jiangang, Zheng [Department of Physics, M.V. Lomonosov Moscow State University, Moscow (Russian Federation)

2005-01-31

227

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

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

228

Electromagnetic signatures of far-field gravitational radiation in the 1 + 3 approach  

NASA Astrophysics Data System (ADS)

Gravitational waves (GWs) from astrophysical sources can interact with background electromagnetic fields, giving rise to distinctive and potentially detectable electromagnetic signatures. In this paper, we study such interactions for far-field gravitational radiation using the 1 + 3 approach to relativity. Linearized equations for the electromagnetic field on perturbed Minkowski space are derived and solved analytically. The inverse Gertsenshte?n conversion of GWs in a static electromagnetic field is rederived, and the resultant electromagnetic radiation is shown to be significant for highly magnetized pulsars in compact binary systems. We also obtain a variety of nonlinear interference effects for interacting gravitational and electromagnetic waves, although wave-wave resonances previously described in the literature are absent when the electric-magnetic self-interaction is taken into account. The fluctuation and amplification of electromagnetic energy flux as the GW strength increases towards the gravitational-electromagnetic frequency ratio is a possible signature of gravitational radiation from extended astrophysical sources.

Chua, Alvin J. K.; Cañizares, Priscilla; Gair, Jonathan R.

2015-01-01

229

[Influence of enhanced UV-B radiation and straw application on soil respiration in soybean field].  

PubMed

Field experiment was carried out in 2008 in order to investigate the effects of enhanced UV-B radiation and straw application on soil respiration in soybean field. LI-8100 automated soil CO2 flux system was used to measure soil respiration under 20% enhanced UV-B radiation, straw application, 20% enhanced UV-B radiation + straw application and control. Environmental factors such as air temperature, soil temperature and moisture were also measured. Results indicated that supplemental UV-B radiation reduced soil respiration rate by 30.31%, straw application increased soil respiration rate by 14.51%, while enhanced UV-B radiation + straw application combined treatment had no significant effect on soil respiration. Enhanced UV-B radiation enhanced the carbon conversion rate of straw. Significant relationship were found between soil respiration rate and soil temperature under the control, enhanced UV-B, straw application, and enhanced UV-B + straw application, the fitting equation determined coefficients R2 were 0.434, 0.563, 0.451 and 0.513. The Q10 (temperature sensitivity coefficients) for soil respiration were 1.55, 1.91, 1.80 and 1.71, respectively. It was reflected that enhanced UV-B radiation, straw application and enhanced UV-B radiation + straw returning increased the Q10 for soil respiration. PMID:20825038

Hu, Zheng-hua; Li, Han-mao; Yang, Yan-ping; Chen, Shu-tao; Li, Cen-zi; Shen, Shuang-he

2010-07-01

230

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

PubMed Central

For sensors constructed by freestanding membranes, when the gap between a freestanding membrane and the substrate or between membranes is at micron scale, the effects of near-field radiative heat transfer on the sensors' thermal performance should be considered during sensor design. The radiative heat flux is transferred from a membrane to a plane or from a membrane to a membrane. In the current study of the near-field thermal radiation, the scanning probe technology has difficulty in making a membrane separated at micron scale parallel to a plane or another membrane. A novel MEMS (micro electromechanical system) device was developed by sacrificial layer technique in this work to realize a double parallel freestanding membrane structure. Each freestanding membrane has a platinum thin-film resistor and the distance between the two membranes is 1 ?m. After evaluating the electrical and thermal characteristics of the lower freestanding membrane,experimental measurements of near-field radiative heat transfer between the lower membrane and the upper membrane were carried out by setting the lower membrane as a heat emitter and the upper membrane as a heat receiver. The near-field radiative heat transfer between the two membranes was validated by finding a larger-than-blackbody radiative heat transfer based on the experimental data. PMID:23385413

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

2013-01-01

231

Radiation from relativistic jets in turbulent magnetic fields  

SciTech Connect

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.

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

232

Collective modes in free plasmas subjected to a radiation field  

NASA Astrophysics Data System (ADS)

In this study we report the effects of an electromagnetic field on the physical properties of free plasmas3.The calculations are carried out in the semi-classical approximation, i.e., the electromagnetic field is treated classically and the electrons from a quantum mechanical viewpoint. The results show that the collective modes are damped away more smoothly and in a smaller frequency range than those reported by previous studies. An exponential-like decay of the frequencies is readily observable from the plot of the plasmon frequency as a function of the external field amplitude. We successfully recreate the results of previous studies. We also obtain that the single photon processes has a pronounced effect on the decrease of the frequency range of modulation.

Ribeiro, B. V.; Santos, D. D. A.; Amato, M. A.; Fonseca, A. L. A.

2014-05-01

233

Radiation from Relativistic Jets in Turbulent Magnetic Fields  

NASA Technical Reports Server (NTRS)

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.

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

234

Pioneer Saturn Encounter. [Pioneer 11 space probe  

NASA Technical Reports Server (NTRS)

The Pioneer Saturn Spacecraft, which began its journey as Pioneer 11, provided the first close view of the rings of Saturn as well as its system of moons. Its payload of 11 operating instruments obtained or confirmed data about the mass, temperature, composition, radiation belts, and atmosphere of the planet and its larger satellite, Titan. It made photometric and polarization measurements of lapetus, Rhea, Dione, and Tethys, as well as discovered additional rings. Scientific highlights of the mission are summarized. Color imagery provided by the photopolarimeter is included along with illustrations of the planet's magnetic field and radiation belts.

1979-01-01

235

The Gravitational Field of a Radiating Electromagnetic Dipole  

E-print Network

We begin with the time-dependent electric and magnetic dipole solution of Maxwell's equations in Minkowski space. This Maxwell field is then used to determine the behavior of the gravitational field (the Weyl tensor) as a second-order perturbation off of the Minkowski background. From the Weyl tensor we go on and find the spin-coefficients and the full metric in this approximation. The physical meaning of many of the relations is discussed. In particular we can identify the conservation law of angular momentum that contains an angular momentum flux term.

Tim Adamo; Ezra T Newman

2008-07-22

236

Icing Encounter Duration Sensitivity Study  

NASA Technical Reports Server (NTRS)

This paper describes a study performed to investigate how aerodynamic performance degradation progresses with time throughout an exposure to icing conditions. It is one of the first documented studies of the effects of ice contamination on aerodynamic performance at various points in time throughout an icing encounter. Both a 1.5 and 6 ft chord, two-dimensional, NACA-23012 airfoils were subjected to icing conditions in the NASA Icing Research Tunnel for varying lengths of time. At the end of each run, lift, drag, and pitching moment measurements were made. Measurements with the 1.5 ft chord model showed that maximum lift and pitching moment degraded more rapidly early in the exposure and degraded more slowly as time progressed. Drag for the 1.5 ft chord model degraded more linearly with time, although drag for very short exposure durations was slightly higher than expected. Only drag measurements were made with the 6 ft chord airfoil. Here, drag for the long exposures was higher than expected. Novel comparison of drag measurements versus an icing scaling parameter, accumulation parameter times collection efficiency was used to compare the data from the two different size model. The comparisons provided a means of assessing the level of fidelity needed for accurate icing simulation.

Addy, Harold E., Jr.; Lee, Sam

2011-01-01

237

Quantum Field Theoretic Treatment of Pion Production via Proton Synchrotron Radiation in Strong Magnetic Fields: Effects of Landau Levels  

E-print Network

We study pion production from proton synchrotron radiation in the presence of strong magnetic fields. We derive the exact proton propagator from the Dirac equation in a strong magnetic field by 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 semi-classical approach. However, we also find that the anomalous magnetic moment of the proton greatly enhances the production rate about by two order magnitude.

Maruyama, Tomoyuki; Kajino, Toshitaka; Kwon, Yongshin; Mathews, Grant J; Ryu, Chung-Yeol

2015-01-01

238

A NUMERICAL TREATMENT OF ANISOTROPIC RADIATION FIELDS COUPLED WITH RELATIVISTIC RESISTIVE MAGNETOFLUIDS  

SciTech Connect

We develop a numerical scheme for solving fully special relativistic, resistive radiation magnetohydrodynamics. Our code guarantees conservation of total mass, momentum, and energy. The radiation energy density and the radiation flux are consistently updated using the M-1 closure method, which can resolve an anisotropic radiation field, in contrast to the Eddington approximation, as well as the flux-limited diffusion approximation. For the resistive part, we adopt a simple form of Ohm's law. The advection terms are explicitly solved with an approximate Riemann solver, mainly the Harten-Lax-van Leer scheme; the HLLC and HLLD schemes are also solved for some tests. The source terms, which describe the gas-radiation interaction and the magnetic energy dissipation, are implicitly integrated, relaxing the Courant-Friedrichs-Lewy condition even in an optically thick regime or a large magnetic Reynolds number regime. Although we need to invert 4 Multiplication-Sign 4 matrices (for the gas-radiation interaction) and 3 Multiplication-Sign 3 matrices (for the magnetic energy dissipation) at each grid point for implicit integration, they are obtained analytically without preventing massive parallel computing. We show that our code gives reasonable outcomes in numerical tests for ideal magnetohydrodynamics, propagating radiation, and radiation hydrodynamics. We also applied our resistive code to the relativistic Petschek-type magnetic reconnection, revealing the reduction of the reconnection rate via radiation drag.

Takahashi, Hiroyuki R. [Center for Computational Astrophysics, National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Ohsuga, Ken [Division of Theoretical Astronomy, National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan)

2013-08-01

239

Radiation Field Wave Forms Produced by Lightning Stepped Leaders  

Microsoft Academic Search

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

E. Philip Krider; George J. Radda

1975-01-01

240

Personal Radiation Detector Field Test and Evaluation Campaign  

SciTech Connect

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

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

2007-07-09

241

BOBCAT Personal Radiation Detector Field Test and Evaluation Campaign  

SciTech Connect

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

Chris Hodge

2008-03-01

242

The magneto-Coulomb radiation of ultrarelativistic electrons in a strong magnetic field  

NASA Astrophysics Data System (ADS)

The propagation of ultrarelativistic (TeV or higher) electrons along the lines of an intense (TG) magnetic field and the resulting generation of hard gamma radiation by the Joint action of matter and the magnetic field (the magneto-Coulomb mechanism, MCM, proposed by Kel'ner and Kotov, 1985) are investigated analytically. In the MCM, the particles undergo Coulomb collisions with the target matter and are raised to excited Landau states, and gamma photons are generated as they undergo radiative transition to lower levels. The MCM cross sections for the case of a fully ionized plasma target are calculated, and the spectrum, angular distribution, and polarization of the MCM radiation are determined. It is shown that the electron energy loss due to MCM radiation is dominant for conditions consistent with the two-level approximation employed. The implications of the MCM for the gamma emission of neutron stars are considered.

Kotov, Y. D.; Kelner, S. R.

1985-12-01

243

Spectra of Radiation Emitted from Open-Ended and Closed Carbon Nanotubes Exposed to Microwave Fields  

NASA Astrophysics Data System (ADS)

We performed experiments in which both open-ended and closed carbon nanotubes were exposed to 2.46 GHz microwaves over the course of several irradiation and cooling cycles at a pressure of 10-6 torr. The spectra of the radiation emitted from the nanotubes indicate that the intensity of the emitted radiation with wavelengths of 650-1000 nm increased during the irradiation cycles. However, the intensity of the radiation emitted from untreated nanotubes increased substantially more than the intensity of the radiation emitted from nanotubes that had been chemically treated in order to open nanotube ends. As open-ended nanotubes have a lower work function than closed nanotubes, and as nanotube ends are known to open as they are heated, our results suggest that the mechanism responsible for the emission of infrared, visible and ultraviolet radiation from carbon nanotubes exposed to microwaves is field emission-induced luminescence.

Cavness, B.; McGara, N.; Williams, S.

2013-08-01

244

Double Gas Puff Z-Pinch with Axial Magnetic Field for K-Shell Radiation Production  

Microsoft Academic Search

A double gas puff with a solid fill inner shell and an annular outer shell with axial magnetic field is proposed as a possible load configuration for a plasma radiation source for K-shell radiation production of high-Z materials. This load configuration is investigated in the experiments with neon gas puffs on the IMRI-5 generator (400 kA, 430 ns) and with

Alexander V. Shishlov; Rina B. Baksht; Stanislav A. Chaikovsky; Aleksey Yu. Labetsky; Vladimir I. Oreshkin; Alexander G. Rousskikh; Anatoly V. Fedunin

2002-01-01

245

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

Microsoft Academic Search

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

James R. Jauchem

1997-01-01

246

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

Microsoft Academic Search

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

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

1990-01-01

247

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

E-print Network

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.

Shih-Yuin Lin; B. L. Hu

2006-06-21

248

Plasma wave instability and amplification of terahertz radiation in field-effect-transistor arrays.  

PubMed

We show that the strong amplification of terahertz radiation takes place in an array of field-effect transistors at small DC drain currents due to hydrodynamic plasmon instability of the collective plasmon mode. Planar designs compatible with standard integrated circuit fabrication processes and strong coupling of terahertz radiation to plasmon modes in FET arrays make such arrays very attractive for potential applications in solid-state terahertz amplifiers and emitters. PMID:21693816

Popov, V V; Tsymbalov, G M; Shur, M S

2008-09-24

249

Thermodynamic structure of field equations near apparent horizon for radiating black holes  

NASA Astrophysics Data System (ADS)

We study the intriguing analogy between gravitational dynamics of the horizon and thermodynamics for the case of nonstationary radiating spherically symmetric black holes both in four dimensions and higher dimensions. By defining all kinematical parameters of nonstationary radiating black holes in terms of null vectors, we demonstrate that it is possible to interpret the Einstein field equations near the apparent horizon in the form of a thermodynamical identity T dS = dE+P dV.

Papnoi, Uma; Govender, Megan; Ghosh, Sushant G.

2014-10-01

250

Polarized Atomic Radiative Emission in the Presence of Electric and Magnetic Fields  

Microsoft Academic Search

A reduced-density-matrix approach provides a very general framework for the theoretical description of polarized radiative\\u000a emission during single-photon transitions from bound and autoionizing states of atomic systems in the presence of a general\\u000a arrangement of static (or quasistatic) electric and magnetic fields. Polarized radiative emission from partially ionized atomic\\u000a systems in plasmas can occur as a result of the excitation

V. L. Jacobs

251

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

Microsoft Academic Search

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

Kathy L. Young; Ming-Ko Woo

1997-01-01

252

Transient radiation field of a circular loop antenna  

Microsoft Academic Search

For a circular loop antenna excited by a frequency-hand-limited rectangular voltage pulse, the time variation of the electric field at remote points in various directions has been computed. The computations are for a loop of radiusbmade from wire of radiusa, for which the thickness parameterOmega = 2 ln (2pi b\\/a) = 15. The moment method was used in obtaining the

A. Abo-Zena; R. Beam

1972-01-01

253

Radiation field of a gas-discharge superluminescent laser  

Microsoft Academic Search

This study investigates single-mode superluminescence (SL) excited by longitudinal discharge in neon (λ=614 nm). It is demonstrated that the single-mode SL field can be represented with a good approximation as a coherent superposition of a few modes from an open cavity with different polarization states. The contribution of the higher-order modes determining the transformation of the SL beam during propagation

N. A. Domnina; V. V. Lebedeva; A. I. Odintsov; R. I. Sokolovskii

1989-01-01

254

Modulation and amplification of radiative far field heat transfer : towards a simple radiative thermal transistor  

E-print Network

We show in this article that phase change materials (PCM) exhibiting a phase transition between a dielectric state and a metallic state are good candidates to perform modulation as well as amplification of radiative thermal flux. We propose a simple situation in plane parallel geometry where a so-called radiative thermal transistor could be achieved. In this configuration, we put a PCM between two blackbodies at different temperatures. We show that the transistor effect can be achieved easily when this material has its critical temperature between the two blackbody temperatures. We also see, that the more the material is reflective in the metallic state, the more switching effect is realized whereas the more PCM transition is stiff in temperature, the more thermal amplification is high. We finally take the example of VO2 that exhibits an insulator-metallic transition at 68{\\textdegree}C. We show that a demonstrator of a radiative transistor could easily be achieved in view of the heat flux levels predicted. F...

Joulain, Karl; Drevillon, Jeremie; Ben-Abdallah, Philippe

2015-01-01

255

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

E-print Network

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...

Epstein, Ariel

2014-01-01

256

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

SciTech Connect

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.

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

257

Field size dependent mapping of medical linear accelerator radiation leakage  

NASA Astrophysics Data System (ADS)

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.

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

2015-03-01

258

Field size dependent mapping of medical linear accelerator radiation leakage.  

PubMed

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

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

2015-03-01

259

Radiation drag in the field of a non-spherical source  

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

260

Radiation drag in the field of a non-spherical source  

E-print Network

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 spacetime 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.

Donato Bini; Andrea Geralico; Andrea Passamonti

2014-10-12

261

Edge diffracted caustic fields. [spacecraft antenna radiation patterns  

NASA Technical Reports Server (NTRS)

The fields near a caustic created by an edge diffraction process are computed using the equivalent current concept. These fields are shown to have the property commonly associated with ray optical analysis or the Geometrical Theory of Diffraction (GTD), e.g., a 90 deg phase shift as the ray passes through the caustic. The present effort is directed toward consideration of the caustic created by an edge diffraction process. Particular attention is focused on electromagnetic excitation. The acoustic excitation for the hard boundary condition is outlined in an appendix. In addition, goal is to establish the extent of the caustic region. This is of particular importance when a ray optical solution involves multiply-diffracted terms in that the minimum size of the body that can be analyzed may be restricted by the extent of the caustic, i.e., the 90 deg phase shift used in ray optical analysis may be introduced only if the caustic is contained on the surface being studied.

Burnside, W. D.; Peters, L., Jr.

1974-01-01

262

Voyager 2 Saturn encounter attitude and articulation control experience  

NASA Technical Reports Server (NTRS)

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

Hill, M.

1982-01-01

263

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

NASA Astrophysics Data System (ADS)

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.

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

2013-08-01

264

TOPICAL REVIEW: Strong field interaction of laser radiation  

NASA Astrophysics Data System (ADS)

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

Pukhov, Alexander

2003-01-01

265

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

SciTech Connect

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

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

1990-05-20

266

The Amplitude Nth-Power Squeezing of Radiation Fields in the Degenerate Raman Process  

NASA Technical Reports Server (NTRS)

In this paper we study the amplitude Nth-power squeezing of radiation fields in the degenerate Raman process by using the modified effective Hamiltonian approach recently suggested by us. We found that if the field is initially in a coherent state it will not get squeezing for any Nth-power; if the field is initially in a squeezed vacuum, it may get Nth-power squeezing. The time evolution of the field fluctuation was discussed. Its dependences on power-order N, mean photon number bar-n, and squeezing angle xi are analyzed.

Zhang, Zhi-Ming; Pan, Jin-Fang; Xu, Lei

1996-01-01

267

The Outflows Accelerated by the Magnetic Fields and Radiation Force of Accretion Disks  

NASA Astrophysics Data System (ADS)

The inner region of a luminous accretion disk is radiation-pressure-dominated. We estimate the surface temperature of a radiation-pressure-dominated accretion disk, \\Theta =c_s^2/r^2\\Omega _K^2\\ll (H/r)^2, which is significantly lower than that of a gas-pressure-dominated disk, ? ~ (H/r)2. This means that the outflow can be launched magnetically from the photosphere of the radiation-pressure-dominated disk only if the effective potential barrier along the magnetic field line is extremely shallow or no potential barrier is present. For the latter case, the slow sonic point in the outflow will probably be in the disk, which leads to a slow circular dense flow above the disk. This implies that hot gas (probably in the corona) is necessary for launching an outflow from the radiation-pressure-dominated disk, which provides a natural explanation for the observational evidence that the relativistic jets are related to hot plasma in some X-ray binaries and active galactic nuclei. We investigate the outflows accelerated from the hot corona above the disk by the magnetic field and radiation force of the accretion disk. We find that with the help of the radiation force, the mass loss rate in the outflow is high, which leads to a slow outflow. This may be why the jets in radio-loud narrow-line Seyfert galaxies are in general mildly relativistic compared with those in blazars.

Cao, Xinwu

2014-03-01

268

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

SciTech Connect

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

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

2011-01-15

269

Coupled radiative, flow and temperature-field analysis of a free-burning arc  

NASA Astrophysics Data System (ADS)

A computer simulation of a thermal plasma that utilizes a detailed line-by-line radiative analysis coupled to a flow and temperature-field analysis has been written. The radiative transport portion of the model uses the S-N discrete ordinates method and the required spectral radiative properties are calculated from basic atomic data. The flow and temperature-field portion of the calculation is handled using the finite-volume method. The thermal plasma configuration studied using this coupled model is a two-dimensional, axisymmetric, 200 A, 1 cm long, free-burning arc located in a one-atmosphere argon environment. Results from this analysis are compared with those from an uncoupled, line-by-line radiative analysis of this same arc and from a flow and temperature-field analysis that utilizes net emission coefficients to model the radiative source term. As thought, noticeable differences are found between results from the coupled and uncoupled analyses. This work proves that it is feasible to conduct two-dimensional, coupled, line-by-line calculations in a thermal plasma, but the computational times are large.

Menart, J.; Malik, S.; Lin, L.

2000-02-01

270

Transient quantum coherent response to a partially coherent radiation field  

SciTech Connect

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.

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

271

Spectral Analysis for Systems of Atoms and Molecules Coupled to the Quantized Radiation Field  

Microsoft Academic Search

:  We consider systems of static nuclei and electrons – atoms and molecules – coupled to the quantized radiation field. The interactions\\u000a between electrons and the soft modes of the quantized electromagnetic field are described by minimal coupling, p?p?e\\u000a \\u000a A (x), where A(x) is the electromagnetic vector potential with an ultraviolet cutoff. If the interactions between the electrons and the quantized

Volker Bach; Jürg Fröhlich; Israel Michael Sigal

1999-01-01

272

Investigation of voltages and electric fields in silicon radiation detectors using a scanning electron microscope  

NASA Astrophysics Data System (ADS)

The paper describes qualitative and quantitative methods to measure voltages and electric fields in a biased silicon p +/n -/n + radiation detector with a scanning electron microscope using voltage-contrast phenomenon. The contrast is converted to voltage mathematically using simple equations. After splitting the detector, voltages and electric fields inside the detector can be imaged and measured. The results are compared with capacitance-voltage measurements and 2D electrical simulations.

Leinonen, Kari

2005-12-01

273

Radiative transfer equations in broad-band, time-varying fields  

NASA Technical Reports Server (NTRS)

A derivation of the equation of transfer is obtained by starting with Maxwell's equations in the 'slowly varying envelope' form. Particular attention is paid to characterizing the intensity that is 'seen' by the atom (which is found to be related to a Wigner distribution of the electric field). The equation of transfer is found to be valid for 'broad-band' slowly varying radiation fields.

Cooper, J.; Zoller, P.

1984-01-01

274

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

Microsoft Academic Search

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

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

2009-01-01

275

Accelerated expansion in the effective field theory of a radiation dominated universe  

E-print Network

We construct the effective field theory of a perfect fluid in the early universe. Focusing on the case where the fluid has the equation of state of radiation, we show that it may lead to corrections to the background dynamics that can dominate over those of an effective field theory of gravity alone. We describe the periods of accelerated expansion, in the form of inflationary and bounce solutions, that arise in the background dynamics and discuss their regime of validity within EFT.

Bruno Balthazar; Pedro G. Ferreira

2015-02-12

276

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

Microsoft Academic Search

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

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

2004-01-01

277

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

Microsoft Academic Search

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

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

2003-01-01

278

Encounter with Jupiter. [Pioneer 10 space probe  

NASA Technical Reports Server (NTRS)

Pioneer 10 space probe's encounter with the Jupiter is discussed in detail. Tables are presented which include data on the distances during the encounter, times of crossing satellite orbits, important events in the flight near Jupiter, and time of experiments. Educational study projects are also included.

1975-01-01

279

THE SCOTTISH ENCOUNTER WITH TROPICAL DISEASE  

E-print Network

and his former Glasgow University pupil James Watt (1736-1819) invented the steam engine. Scottish-17 The Filariases 18-19 The Scottish Encounter with Filariases 20-21 Parasitic Flukes 22-23 The Scottish Encounter elsewhere. Two of the most influential early European explorers of Africa were James Bruce (1730-1794), who

Schnaufer, Achim

280

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

SciTech Connect

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

Blue, Thomas; Windl, Wolfgang; Dickerson, Bryan

2013-01-03

281

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

PubMed Central

Radiation delivery to cancer patients for radiotherapy is invariably accompanied by unwanted radiation to other parts of the patient’s body. Traditionally, considerable effort has been made to calculate and measure the radiation dose to the target as well as to nearby critical structures. Only recently has attention been focused also on the relatively low doses that exist far from the primary radiation beams. In several clinical scenarios, such doses have been associated with cardiac toxicity as well as an increased risk of secondary cancer induction. Out-of-field dose is a result of leakage and scatter and generally difficult to predict accurately. The present review aims to present existing data, from measurements and calculations, and discuss its implications for radiotherapy. PMID:21731221

Taylor, Michael L.; Kron, Tomas

2011-01-01

282

On Consideration of Radiated Power in RF Field Simulations for MRI  

PubMed Central

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

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

2012-01-01

283

A Study of an N Molecule Quantized-Radiation-Field Hamiltonian  

E-print Network

In this dissertation a simple Hamiltonian for a system of inter-acting molecules and radiation field is developed from a model of N Two-Level Molecules interacting, via a dipole approximation, with a single mode, quantized radiation field. The exact eigenvalues and eigenvectors of this Hamiltonian are compared with analytical results obtained from several different approximation schemes applied to the simple model. The consequence of this comparison is the development of validity criteria for the utilization of these approximation schemes to more difficult problems. For example, an analysis done here indicates that using an independent molecule approximation in an explanation of the "build up" of coherent radiation in a gas laser (maser) may be inappropriate.

Michael Thomas Tavis

2012-06-01

284

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

285

On the electromagnetic fields, Poynting vector, and peak power radiated by lightning return strokes  

NASA Technical Reports Server (NTRS)

The initial radiation fields, Poynting vector, and total electromagnetic power that a vertical return stroke radiates into the upper half space have been computed when the speed of the stroke, nu, is a significant fraction of the speed of light, c, assuming that at large distances and early times the source is an infinitesimal dipole. The initial current is also assumed to satisfy the transmission-line model with a constant nu and to be perpendicular to an infinite, perfectly conducting ground. The effect of a large nu is to increase the radiation fields by a factor of (1-beta-sq cos-sq theta) exp -1, where beta = nu/c and theta is measured from the vertical, and the Poynting vector by a factor of (1-beta-sq cos-sq theta) exp -2.

Krider, E. P.

1992-01-01

286

A new approach to calculate the field radiated from arbitrarily structured transducer arrays  

Microsoft Academic Search

A efficient time-domain algorithm, based on the spatial pulse response approach, is proposed for the determination of the acoustic fields radiated by means of acoustical sources. The computations are performed by the discrete representation array modelling (DREAM) procedure, specially adapted to study the planar and arbitrarily structured multielement transducer arrays. DREAM, based on the discrete representation computational concept, acts as

Bogdan Piwakowski; Khalid Sbai

1999-01-01

287

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

Microsoft Academic Search

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

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

2007-01-01

288

Maker fringes in the Terahertz radiation produced by a 2-color laser field in air  

E-print Network

, A. Baltuska, E. Goulielmakis, M. Lezius, and F. Krausz, "Gouy phase shift for a few-cycle laserMaker fringes in the Terahertz radiation produced by a 2-color laser field in air Y. Liu, A. Houard, M. Durand, B. Prade, A. Mysyrowicz* Laboratoire d'Optique Appliquée, ENSTA, Ecole Polytechnique

Paris-Sud XI, Université de

289

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

E-print Network

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

Shaw, Bruce E.

290

Hawking radiation for a scalar field conformally coupled to an AdS black hole  

E-print Network

The decomposition in normal modes of a scalar field conformally coupled to an AdS black hole leads to a Heun equation with simple coefficients thanks to conformal invariance. By applying the Damour-Ruffini method we can relate the critical exponent of the radial part at the horizon surface to the Hawking radiation of scalar particles.

P. Valtancoli

2015-02-05

291

Terahertz radiation from oscillating electrons in laser-induced wake fields  

SciTech Connect

Strong terahertz (1 THz=10{sup 12} Hz) radiation can be generated by the electron oscillation in fs-laser-induced wake fields. The interaction of a fs-laser pulse with a low-density plasma layer is studied in detail using numerical simulations. The spatial distribution and temporal evolution of terahertz electron current developed in a low-density plasma layer are presented, which enables us to calculate the intensity distribution of THz radiation. It is shown that laser and plasma parameters, such as laser intensity, pulse width, and background plasma density, are of key importance to the process. The optimum condition for wake-field excitation and terahertz emission is discussed upon the simulation results. Radiation peaked at 6.4 THz, with 900 fs duration and 9% bandwidth, can be generated in a plasma of density 5x10{sup 17} cm{sup -3}. It turns out that the maximum radiation intensity scales as n{sub 0}{sup 3}a{sub 0}{sup 4} when wake field is resonantly excited, where n{sub 0} and a{sub 0} are, respectively, the plasma density and the normalized field amplitude of the laser pulse.

Cao Lihua; Zheng Chunyang; Liu Zhanjun; Li Bin [Institute of Applied Physics and Computational Mathematics, P.O. Box 8009, Beijing 100088 (China); Yu Wei; Xu Han [Shanghai Institute of Optics and Fine Mechanics, Shanghai 201800 (China); Bogaerts, A. [Department of Chemistry, University of Antwerp, B-2610 Wilrijk-Antwerp (Belgium)

2004-10-01

292

Anisotropic radiation field and trapped photons around the Kerr black hole  

Microsoft Academic Search

Aims: In order to understand the anisotropic properties of local radiation field in the curved spacetime around a rotating black hole, we investigate the appearance of a black hole seen by an observer located near the black hole. When the black hole is in front of a source of illumination the black hole casts shadow in the illumination. Accordingly, the

Rohta Takahashi; Masaaki Takahashi

2010-01-01

293

Would be the photon a composed particle? quantization of field fluxes in electromagnetic radiation  

E-print Network

[En] Here it is made a comparative analysis between the classical and the quantum expressions for the energy of electromagnetic radiation (ER). The comparison points to the possibility of the quantization of the magnetic and the electric field fluxes in the ER.

Celso de Araujo Duarte

2013-12-02

294

Generating High-Intensity Electromagnetic Fields for Radiated-Susceptibility Test  

Microsoft Academic Search

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

Victor P. Musil

1968-01-01

295

Cloud inhomogeneity effects on radiative transfer simulations for clouds measured in the BBC field campaign  

Microsoft Academic Search

Clouds are known to play the leading role on the energy exchange between the Earth and the atmosphere. Even though, the complexity of cloud's wavelength dependent optical properties and geometrical form make the realistic treatment of cloud fields in the radiative transfer modelling one of the biggest challenges of the atmospherical sciences. The 4DCLOUDS project was conceived with the aim

S. Gimeno García; J. Meywerk; T. Trautmann

2003-01-01

296

EFFECTS OF UV-B RADIATION ON SOYBEAN YIELD AND SEED QUALITY: A 6-YEAR FIELD  

EPA Science Inventory

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 stra...

297

On the sound field radiated by a tuning fork Daniel A. Russell  

E-print Network

On the sound field radiated by a tuning fork Daniel A. Russell Science and Mathematics Department, Kettering University, Flint, Michigan 48504 Received 14 June 1999; accepted 25 April 2000 When a sounding. © 2000 American Association of Physics Teachers. I. INTRODUCTION If one rotates a sounding tuning fork

Russell, Daniel A.

298

Modeling electromagnetic field radiated by Lightning coupling to overhead transmission lines  

Microsoft Academic Search

The major aim of our investigations is the computation of the voltages induced by an external transient electromagnetic excitation, especially due to the lightning discharge coupling to overhead transmission line networks. In this paper we propose a hybrid method for evaluating the electromagnetic field radiated by lightning The Agrawal et al. model coupling model will be used in order to

N. M'ziou; L. Mokhnache; A. Boubakeur

2008-01-01

299

Radiation from Small-Scale Magnetic Field Turbulence: Implications for Gamma-Ray Bursts and Laboratory Astrophysical Plasmas  

E-print Network

Relativistic charged particles moving within regions of small-scale magnetic field turbulence radiate as they undergo transverse accelerations reflective of the magnetic field variation along the particle's path. For a particle of Lorentz factor...

Reynolds, Sarah J

2012-05-31

300

Assessment of the ultraviolet radiation field in ocean waters from space-based measurements and full radiative-transfer calculations.  

PubMed

Quantitative assessment of the UV effects on aquatic ecosystems requires an estimate of the in-water radiation field. Actual ocean UV reflectances are needed for improving the total ozone retrievals from the total ozone mapping spectrometer (TOMS) and the ozone monitoring instrument (OMI) flown on NASA's Aura satellite. The estimate of underwater UV radiation can be done on the basis of measurements from the TOMS/OMI and full models of radiative transfer (RT) in the atmosphere-ocean system. The Hydrolight code, modified for extension to the UV, is used for the generation of look-up tables for in-water irradiances. A look-up table for surface radiances generated with a full RT code is input for the Hydrolight simulations. A model of seawater inherent optical properties (IOPs) is an extension of the Case 1 water model to the UV. A new element of the IOP model is parameterization of particulate matter absorption based on recent in situ data. A chlorophyll product from ocean color sensors is input for the IOP model. Verification of the in-water computational scheme shows that the calculated diffuse attenuation coefficient Kd is in good agreement with the measured Kd. PMID:15943340

Vasilkov, Alexander P; Herman, Jay R; Ahmad, Ziauddin; Kahru, Mati; Mitchell, B Greg

2005-05-10

301

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

NASA Astrophysics Data System (ADS)

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

Nikishov, Anatolii I.; Ritus, Vladimir I.

2011-02-01

302

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

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

303

Numerical Prediction and Measurement of ESD Radiated Fields by Free-Space Field Sensors  

Microsoft Academic Search

This paper describes the evaluation of electric and magnetic fields due to electrostatic discharges (ESDs) using an efficient numerical prediction model and measurements obtained with simple field sensors. The numerical prediction model is implemented using software based on the finite integration technique (FIT). The ESD generator is efficiently modeled, and the contact-mode discharge current is well reproduced taking into account

Spartaco Caniggia; Francescaromana Maradei

2007-01-01

304

Thermal electron acceleration by localized bursts of electric field in the radiation belts  

NASA Astrophysics Data System (ADS)

In this paper we investigate the resonant interaction of thermal ˜10-100 eV electrons with a burst of electrostatic field that results in electron acceleration to kilovolt energies. This single burst contains a large parallel electric field of one sign and a much smaller, longer-lasting parallel field of the opposite sign. The Van Allen Probe spacecraft often observes clusters of spatially localized bursts in the Earth's outer radiation belts. These structures propagate mostly away from the geomagnetic equator and share properties of soliton-like nonlinear electron acoustic waves: a velocity of propagation is about the thermal velocity of cold electrons (˜3000-10,000 km/s), and a spatial scale of electric field localization along the field lines is about the Debye radius of hot electrons (˜5-30 km). We model the nonlinear resonant interaction of these electric field structures and cold background electrons.

Artemyev, A. V.; Agapitov, O. V.; Mozer, F.; Krasnoselskikh, V.

2014-08-01

305

[An encounter with extraterrestrial intelligence].  

PubMed

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

Hisabayashi, Hisashi

2003-12-01

306

Role of phase difference between superposing lasers and magnetic field for efficient terahertz radiation generation by tunnel ionization  

NASA Astrophysics Data System (ADS)

The generation of terahertz (THz) radiation is an active field of research due to its applications in THz spectroscopy, material characterization, imaging, topography, etc. Since plasma can sustain high field and it is a nonlinear medium, the plasma based schemes are very attractive techniques for the THz radiation generation. In the present work, we make use of tunnel ionization, where quick ionization is achieved with the help of two femtosecond lasers having a phase difference. Then the generated plasma cylinder is caused to oscillate and radiate at the frequency in the THz range. An application of DC magnetic field on the plasma cylinder helps getting a directional THz radiation emission. The role of phase difference and the magnetic field for efficient THz radiation generation and a control on the emission of radiation are discussed. The conversion efficiency of the present scheme is ˜10-3 and it supersedes several other schemes.

Malik, Anil Kumar; Malik, Hitendra K.

2011-11-01

307

Accelerated expansion in the effective field theory of a radiation dominated universe  

NASA Astrophysics Data System (ADS)

We construct the effective field theory of a perfect fluid in the early Universe. Focusing on the case where the fluid has the equation of state of radiation, we show that it may lead to corrections to the background dynamics that can dominate over those of an effective field theory of gravity alone. We describe the periods of accelerated expansion, in the form of inflationary and bounce solutions, that arise in the background dynamics and discuss their regime of validity within effective field theory.

Balthazar, Bruno; Ferreira, Pedro G.

2015-03-01

308

Surface Electromagnetic Field Radiated by a Subwavelength Hole in a Metal Film  

NASA Astrophysics Data System (ADS)

We present an analytical expression for the electromagnetic field at the surface radiated by a hole in a metal film. This expression is valid for any metal, from the optical range to longer wavelengths, and for distances to the hole larger than a few tens of nanometers. The field pattern presents a rich behavior, showing three regions (a complex short distance, an intermediate range dominated by surface plasmon polaritons, and a long-distance one dominated by Norton waves). The crossover distances between these regimes depend strongly on both the wavelength and the angle with respect to the incident field.

Nikitin, A. Yu.; García-Vidal, F. J.; Martín-Moreno, L.

2010-08-01

309

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

SciTech Connect

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

Katayama, I. [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

310

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

NASA Astrophysics Data System (ADS)

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.

Bialynicka-Birula, Zofia; Bialynicki-Birula, Iwo

2014-12-01

311

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

E-print Network

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.

Bialynicka-Birula, Zofia

2014-01-01

312

Terahertz radiation induced chaotic electron transport in semiconductor superlattices with a tilted magnetic field  

NASA Astrophysics Data System (ADS)

Chaotic electron transport in semiconductor superlattice induced by terahertz electric field that is superimposed on a dc electric field along the superlattice axis are studied using the semiclassical motion equations including the effect of dissipation. A magnetic field that is tilted relative to the superlattice axis is also applied to the system. Numerical simulation shows that electrons in superlattice miniband exhibit complicate nonlinear oscillating modes with the influence of terahertz radiation. Transitions between frequency-locking and chaos via pattern forming bifurcations are observed with the varying of terahertz amplitude. It is found that the chaotic regions gradually contract as the dissipation increases. We attribute the appearance of complicate nonlinear oscillation in superlattice to the interaction between terahertz radiation and internal cooperative oscillating mode relative to Bloch oscillation and cyclotron oscillation.

Wang, C.; Wang, F.; Cao, J. C.

2014-09-01

313

Terahertz radiation induced chaotic electron transport in semiconductor superlattices with a tilted magnetic field.  

PubMed

Chaotic electron transport in semiconductor superlattice induced by terahertz electric field that is superimposed on a dc electric field along the superlattice axis are studied using the semiclassical motion equations including the effect of dissipation. A magnetic field that is tilted relative to the superlattice axis is also applied to the system. Numerical simulation shows that electrons in superlattice miniband exhibit complicate nonlinear oscillating modes with the influence of terahertz radiation. Transitions between frequency-locking and chaos via pattern forming bifurcations are observed with the varying of terahertz amplitude. It is found that the chaotic regions gradually contract as the dissipation increases. We attribute the appearance of complicate nonlinear oscillation in superlattice to the interaction between terahertz radiation and internal cooperative oscillating mode relative to Bloch oscillation and cyclotron oscillation. PMID:25273189

Wang, C; Wang, F; Cao, J C

2014-09-01

314

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

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

315

Enhancement of near-field radiative heat transfer using polar dielectric thin films  

NASA Astrophysics Data System (ADS)

Thermal radiative emission from a hot surface to a cold surface plays an important role in many applications, including energy conversion, thermal management, lithography, data storage and thermal microscopy. Recent studies on bulk materials have confirmed long-standing theoretical predictions indicating that when the gap between the surfaces is reduced to tens of nanometres, well below the peak wavelength of the blackbody emission spectrum, the radiative heat flux increases by orders of magnitude. However, despite recent attempts, whether such enhancements can be obtained in nanoscale dielectric films thinner than the penetration depth of thermal radiation, as suggested by theory, remains experimentally unknown. Here, using an experimental platform that comprises a heat-flow calorimeter with a resolution of about 100?pW (ref. 7), we experimentally demonstrate a dramatic increase in near-field radiative heat transfer, comparable to that obtained between bulk materials, even for very thin dielectric films (50–100?nm) when the spatial separation between the hot and cold surfaces is comparable to the film thickness. We explain these results by analysing the spectral characteristics and mode shapes of surface phonon polaritons, which dominate near-field radiative heat transport in polar dielectric thin films.

Song, Bai; Ganjeh, Yashar; Sadat, Seid; Thompson, Dakotah; Fiorino, Anthony; Fernández-Hurtado, Víctor; Feist, Johannes; Garcia-Vidal, Francisco J.; Cuevas, Juan Carlos; Reddy, Pramod; Meyhofer, Edgar

2015-03-01

316

Enhancement of near-field radiative heat transfer using polar dielectric thin films.  

PubMed

Thermal radiative emission from a hot surface to a cold surface plays an important role in many applications, including energy conversion, thermal management, lithography, data storage and thermal microscopy. Recent studies on bulk materials have confirmed long-standing theoretical predictions indicating that when the gap between the surfaces is reduced to tens of nanometres, well below the peak wavelength of the blackbody emission spectrum, the radiative heat flux increases by orders of magnitude. However, despite recent attempts, whether such enhancements can be obtained in nanoscale dielectric films thinner than the penetration depth of thermal radiation, as suggested by theory, remains experimentally unknown. Here, using an experimental platform that comprises a heat-flow calorimeter with a resolution of about 100?pW (ref. 7), we experimentally demonstrate a dramatic increase in near-field radiative heat transfer, comparable to that obtained between bulk materials, even for very thin dielectric films (50-100?nm) when the spatial separation between the hot and cold surfaces is comparable to the film thickness. We explain these results by analysing the spectral characteristics and mode shapes of surface phonon polaritons, which dominate near-field radiative heat transport in polar dielectric thin films. PMID:25705866

Song, Bai; Ganjeh, Yashar; Sadat, Seid; Thompson, Dakotah; Fiorino, Anthony; Fernández-Hurtado, Víctor; Feist, Johannes; Garcia-Vidal, Francisco J; Cuevas, Juan Carlos; Reddy, Pramod; Meyhofer, Edgar

2015-03-01

317

Three-Body Encounters of Black Holes in Globular Clusters  

E-print Network

Evidence has been mounting for the existence of black holes with masses from 10^2 to 10^4 M_Solar associated with stellar clusters. Such intermediate-mass black holes (IMBHs) will encounter other black holes in the dense cores of these clusters. The binaries produced in these interactions will be perturbed by other objects as well thus changing the orbital characteristics of the binaries. These binaries and their subsequent mergers due to gravitational radiation are important sources of gravitational waves. We present the results of numerical simulations of high mass ratio encounters, which help clarify the interactions of intermediate-mass black holes in globular clusters and help determine what types of detectable gravitational wave signatures are likely.

Kayhan Gultekin; M. Coleman Miller; Douglas P. Hamilton

2003-07-01

318

Estimation of the radiation field homogeneity in 60Co blood irradiator  

NASA Astrophysics Data System (ADS)

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.).

Urban, Tomas

2014-11-01

319

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

PubMed

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

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

2014-10-01

320

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

SciTech Connect

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

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

2011-04-15

321

A parametric study of the effect of inlet lip shape upon the radiated sound field  

NASA Technical Reports Server (NTRS)

Far field sound radiation predictions for four different axisymmetric inlet lips excited by different tangential acoustic modes at several cut-off ratios are presented. These results were obtained by numerical integration of a special cylindrically symmetric integral representation of the external solutions of the Helmholtz equation which yields unique solutions at all wave numbers. The paper presents plots which detail the dependence of the relative SPL (dB) in the field upon the engine inlet lip shape, the modal input, and the cut-off ratio. Examination of these data indicate that: (1) as the inlet lip becomes larger the predominant acoustic radiation peak in the field becomes narrower and moves towards the centerline of the inlet; (2) as the order of the tangential acoustic mode of the driver increases the radiated sound peak again becomes narrower but moves away from the inlet centerline; and (3) as the cut-off ratio is increased for a specific tangential acoustic mode the predominant radiation peak becomes narrower and moves towards the centerline of the inlet.

Meyer, W. L.; Zinn, B. T.

1984-01-01

322

Molecular connectivity: intermolecular accessibility and encounter simulation.  

PubMed

The simple molecular connectivity indices are interpreted as summations of bond accessibilities to bimolecular encounters with another, identical molecule. To transcend this model, a molecule is treated as disjecta membra with each bond modeled as a discrete cell in a dynamic simulation of many molecules. Each bond accessibility is transformed into a cellular automata rule. The dynamics are run for each of 38 alkanes, recording the average number of cell encounters, beta. The beta values show a high correlation with the boiling points. The significance of the bond accessibilities and the concept of intermolecular encounters explaining the molecular connectivity indices is supported by these findings. PMID:11760005

Kier, L B; Hall, L H

2001-01-01

323

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

NASA Astrophysics Data System (ADS)

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.

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

324

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

SciTech Connect

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

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

2009-08-01

325

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

NASA Technical Reports Server (NTRS)

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 occur during strikes to the aircraft. Preliminary conclusions based on data obtained in 1982 verify that the events recorded aboard the aircraft occurred during lightning but also indicate that they occur with surprising frequency very early in the flash.

Levine, D. M.; Mazur, V.

1983-01-01

326

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

NASA Technical Reports Server (NTRS)

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 conclusions verify that the events recorded aboard the aircraft occurred during lightning but also indicate that they occur with surprising frequency very early in the flash.

Levine, D. M.; Mazur, V.

1983-01-01

327

Symmetry breaking from radiation reaction in ultra-intense laser fields  

NASA Astrophysics Data System (ADS)

We discuss radiation reaction effects on charges propagating in ultraintense laser fields. Our analysis is based on an analytic solution of the Landau-Lifshitz equation. We suggest quantifying 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.

Harvey, Chris; Heinzl, Thomas; Marklund, Mattias

2011-12-01

328

Circularly polarized localized near-field radiation at the nanoscale  

Microsoft Academic Search

Diffraction-limited circularly polarized electromagnetic radiation has been widely used in the literature for various applications\\u000a at both optical and microwave frequencies. With advances in nanotechnology, emerging plasmonic nano-optical applications,\\u000a such as all-optical magnetic recording, require circularly polarized electromagnetic radiation beyond the diffraction limit.\\u000a In this study, a plasmonic cross-dipole nano-antenna is investigated to obtain a circularly polarized near-field optical spot

E. Ögüt; G. Kiziltas; K. ?endur

2010-01-01

329

Strong Field-Induced Frequency Conversion of Laser Radiation in Plasma Plumes: Recent Achievements  

PubMed Central

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

Ganeev, R. A.

2013-01-01

330

Limitations of scanned human copresence encounters for modelling proximity-borne malware  

E-print Network

by scanners. We show that the statistical properties of scanned encounters differ from actual device. In addition to helping us understand the limitations of encounter data gathered by scanners in the field, our for advertisements and crime prevention [3], increasing the risk of such malware threats. In the case

Voelker, Geoffrey M.

331

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

SciTech Connect

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

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

2010-10-26

332

Radiated Electric Field from a Solar Cell Module Set on the Ground Plane  

NASA Astrophysics Data System (ADS)

Radiated electric field from a solar cell module set on the ground plane has been studied experimentally and theoretically in order to clarify the antenna effect of the solar cell module. In experimental examination, the radiated electric field characteristics of the thin-film Si solar cell module were measured by using the semi-anechoic chamber including the ground plane. In theoretical examination, the solar cell was assumed as a conducting wire, which has limited electric conductivity. And the radiated electric field of a solar cell was analyzed by using the method of moment. In both examinations, the maximum value of electric field strength for every frequency was measured or calculated when the solar cell module was rotated by 360 degree. Consequently the calculation value agreed with the measurement one within 3dB at the whole frequency region from 30MHz to 300MHz. As the results, we confirmed the availability and the validity of the calculation method by assuming the solar cell module as the conducting wire in the semi-anechoic chamber with the ground plane.

Hasegawa, Ryosuke; Tomisawa, Mariko; Tokuda, Masamitsu

333

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

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

334

Simulation of Relativistic Shocks and Associated Radiation from Turbulent Magnetic Fields  

NASA Technical Reports Server (NTRS)

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.

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

335

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

NASA Technical Reports Server (NTRS)

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. While some Fermi acceleration may occur at the jet front, the majority of electron acceleration takes place behind the jet front and cannot be characterized as Fermi acceleration. 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.

Nishikawa, K.; Hardee, P. E.; Richardson, G. A.; Preece, R. D.; Sol, H.; Fishman, G. J.

2003-01-01

336

First-Year Principal Encounters Homophobia  

ERIC Educational Resources Information Center

A 1st-year principal encounters homonegativity and an ethical dilemma when she attempts to terminate a teacher because of the teacher's inadequate and ineffective teaching. The teacher responds by threatening to "out" Ms. L. to the parents.

Retelle, Ellen

2011-01-01

337

Exploring Digital Encounters in the Public Arena  

NASA Astrophysics Data System (ADS)

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

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

338

The Writing of "Encounter": The Editor's Perspective.  

ERIC Educational Resources Information Center

Discusses the reasons for publishing the picture book "Encounters," which tells of the fateful first meeting of Christopher Columbus and the Native Americans from the point of view of a boy raised in the Tanio culture. (RS)

Ingber, Bonnie Verburg

1992-01-01

339

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

NASA Astrophysics Data System (ADS)

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.

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

2012-10-01

340

Simulation of Relativistic Shocks and Associated Radiation from Turbulent Magnetic Fields  

NASA Technical Reports Server (NTRS)

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.

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

341

Study of high speed complex number algorithms. [for determining antenna for field radiation patterns  

NASA Technical Reports Server (NTRS)

A method of evaluating the radiation integral on the curved surface of a reflecting antenna is presented. A three dimensional Fourier transform approach is used to generate a two dimensional radiation cross-section along a planer cut at any angle phi through the far field pattern. Salient to the method is an algorithm for evaluating a subset of the total three dimensional discrete Fourier transform results. The subset elements are selectively evaluated to yield data along a geometric plane of constant. The algorithm is extremely efficient so that computation of the induced surface currents via the physical optics approximation dominates the computer time required to compute a radiation pattern. Application to paraboloid reflectors with off-focus feeds in presented, but the method is easily extended to offset antenna systems and reflectors of arbitrary shapes. Numerical results were computed for both gain and phase and are compared with other published work.

Heisler, R.

1981-01-01

342

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

NASA Technical Reports Server (NTRS)

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.

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

1978-01-01

343

Acoustic radiation potential on a sphere in plane, cylindrical, and spherical standing wave fields  

NASA Technical Reports Server (NTRS)

The method of Gor'kov is applied for deriving the acoustic radiation potential on a sphere in an arbitrary sound field. Generalized potential and force expressions are derived for arbitrary standing wave modes in rectangular, cylindrical, and spherical geometries for the case where the sphere radius is much smaller than the wavelength. Criteria for determining radiation-potential minima are derived and examples of characteristic spatial radiation-potential profiles are presented. Single modes that can sustain stable positioning are discussed for each geometry. The localizing force strengths for representative standing wave modes in the three geometries are also compared. The positioning of samples due to acoustic forces only are considered. However, the method developed is general and is extended to include gravity or other external forces.

Barmatz, M.; Collas, P.

1985-01-01

344

Very massive runaway stars from three-body encounters  

NASA Astrophysics Data System (ADS)

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

Gvaramadze, Vasilii V.; Gualandris, Alessia

2011-01-01

345

GLOBAL ELECTROMAGNETIC RADIATION POLLUTION: RISK ASSESSMENT FROM FIELD MEASUREMENTS AND ANIMAL EXPERIMENTS  

NASA Astrophysics Data System (ADS)

The extended use of wireless technology throughout the globe in almost all developed and non-developed countries has forced a large number of scientists to get involved in the investigation of the effects. The major issue is that unlike other forms of radiation exposure, this “non-ionizing electromagnetic radiation” was not present throughout the evolution of life in earth and therefore there are no adaptive mechanisms evolved. All organisms are vulnerable to the possible effects of radiation depending on the actual exposure level. “Safety limits” on the power density have been proposed but ongoing research has shown that these limits are not really safe for humans, not mentioning the entire population of living creatures on earth. The so called “Electrosmog Pollution” originating from the numerous radio and TV stations, communication satellite emission, but most importantly from mobile phone mast antennas, are of major concern, because it is gradually increasing at exponential rate. Therefore the key question is, do living organisms react upon their exposure to fields of non ionizing electromagnetic radiation? To have this question answered extensive research is being performed in various laboratories. One approach of our research includes field measurements within houses and classrooms, since a considerable proportion of the population in each country is exposed to the radiation coming from the nearby mast stations, in order to make a risk assessment. The measurements showed that in many cases the actual radiation present was potentially harmful. In other words, although the measured values were below the national safety levels, nevertheless they were above the levels of other countries. Therefore it has been suggested that a new cellular network should be constructed in order to minimize radiation levels in living areas and schools. Our experimental work is focusing on the elucidation of the effects of non-ionizing EMFs on mice exposed to mobile phone and wireless DECT phone radiation and especially on the brain tissues. The brain is the major organ of the body that if affected by environmentally derived radiation, several cognitive - related functions shall be altered, such as memory and learning. We have approached this issue by means of behavioural tests (i.e. Morris water maze) and also by proteomics analysis (very precise separation and identification of the brain proteins by sophisticated techniques). Both ways of approaches have shown important deficits, suggesting that the normal use of the mobile and wireless phone next to the brain should be avoided and that new safety guidelines must be established.

Fragkopoulou, A. F.; Margaritis, L. H.

2009-12-01

346

Tidal Disruptions of White Dwarfs from Ultra-Close Encounters with Intermediate Mass Spinning Black Holes  

E-print Network

We present numerical relativity results of tidal disruptions of white dwarfs from ultra-close encounters with a spinning, intermediate mass black hole. These encounters require a full general relativistic treatment of gravity. We show that the disruption process and prompt accretion of the debris strongly depend on the magnitude and orientation of the black hole spin. However, the late-time accretion onto the black hole follows the same decay, $\\dot{M}$ ~ t^{-5/3}, estimated from Newtonian gravity disruption studies. We compute the spectrum of the disk formed from the fallback material using a slim disk model. The disk spectrum peaks in the soft X-rays and sustains Eddington luminosity for 1-3 yrs after the disruption. For arbitrary black hole spin orientations, the disrupted material is scattered away from the orbital plane by relativistic frame dragging, which often leads to obscuration of the inner fallback disk by the outflowing debris. The disruption events also yield bursts of gravitational radiation with characteristic frequencies of ~3.2 Hz and strain amplitudes of ~10^{-18} for galactic intermediate mass black holes. The optimistic rate of considered ultra-close disruptions is consistent with no sources found in ROSAT all-sky survey. The future missions like Wide-Field X-ray Telescope (WFXT) could observe dozens of events.

Roland Haas; Roman V. Shcherbakov; Tanja Bode; Pablo Laguna

2012-01-20

347

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

SciTech Connect

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

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

1993-10-01

348

DOE Task Force meeting on Electrical Breakdown of Insulating Ceramics in a High Radiation Field  

SciTech Connect

This volume contains the abstracts and presentation material from the Research Assistance Task Force Meeting Electrical Breakdown of Insulating Ceramics in a High-Radiation Field.'' The meeting was jointly sponsored by the Office of Basic Energy Sciences and the Office of Fusion Energy of the US Department of Energy in Vail, Colorado, May 28--June 1, 1991. The 26 participants represented expertise in fusion, radiation damage, electrical breakdown, ceramics, and semiconductor and electronic structures. These participants came from universities, industries, national laboratories, and government. The attendees represented eight nations. The Task Force meeting was organized in response to the recent discovery that a combination of temperature, electric field, and radiation for an extended period of time has an unexplained adverse effect in ceramics, termed radiation-enhanced electrical degradation (REED). REED occurs after an incubation period and continues to accelerate with irradiation until the ceramics can no longer be regarded as insulators. It appears that REED is irreversible and the ceramic insulators cannot be readily annealed or otherwise repaired for future services. This effect poses a serious threat for fusion reactors, which require electrical insulators in diagnostic devices, in radio frequency and neutral beam systems, and in magnetic assemblies. The problem of selecting suitable electrical insulating materials in thus far more serious than previously anticipated.

Green, P.H. (comp.) [comp.

1991-08-01

349

Nonbaryonic dark matter and scalar field coupled with a transversal interaction plus decoupled radiation  

NASA Astrophysics Data System (ADS)

We analyze a universe filled with interacting dark matter, a scalar field accommodated as dark radiation along with dark energy plus a decoupled radiation term within the framework of the spatially flat Friedmann-Robertson-Walker (FRW) spacetime. We work in a three-dimensional internal space spanned by the interaction vector and use a transversal interaction Q t for solving the source equation in order to find all the interacting component energy densities. We asymptotically reconstruct the scalar field and potential from an early radiation era to the late dominate dark energy one, passing through an intermediate epoch dominated by dark matter. We apply the ? 2 method to the updated observational Hubble data for constraining the cosmic parameters, contrast with the Union 2 sample of supernovae, and analyze the amount of dark energy in the radiation era. It turns out that our model fulfills the severe bound of ? ? ( z?1100)<0.018 at 2 ? level, is consistent with the recent analysis that includes cosmic microwave background anisotropy measurements from the Atacama Cosmology Telescope and the South Pole Telescope along with the future constraints achievable by Planck and CMBPol experiments, and satisfies the stringent bound ? ? ( z?1010)<0.04 at 2 ? level in the big-bang nucleosynthesis epoch.

Chimento, Luis P.; Richarte, Martín G.

2013-07-01

350

The Lambda CDM-model in quantum field theory on curved spacetime and Dark Radiation  

E-print Network

In the standard model of cosmology, the universe is described by a Robertson-Walker spacetime, while its matter/energy content is modeled by a perfect fluid with three components corresponding to matter/dust, radiation and a cosmological constant. On the other hand, in particle physics matter and radiation are described in terms of quantum field theory on Minkowski spacetime. We unify these seemingly different theoretical frameworks by analysing the standard model of cosmology from first principles within quantum field theory on curved spacetime: assuming that the universe is homogeneous and isotropic on large scales, we specify a class of quantum states whose expectation value of the energy density is qualitatively and quantitatively of the standard perfect fluid form up to potential corrections. Qualitatively, these corrections depend on new parameters not present in the standard Lambda CDM-model and can account for e.g. the phenomenon of Dark Radiation (N_eff>3.046), having a characteristic signature which clearly deviates from other potential Dark Radiation sources such as e.g. sterile neutrinos. Quantitatively, we find that our more fundamental model can be perfectly matched to observational data, such that we arrive at a natural and fundamental extension of the Lambda CDM-model.

Thomas-Paul Hack

2013-06-13

351

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

NASA Technical Reports Server (NTRS)

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.

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

1983-01-01

352

Massive charged scalar field in the Kerr-Newman background: Hawking radiation  

NASA Astrophysics Data System (ADS)

We perform accurate calculations of the energy-, momentum-, and charge-emission rates of a charged scalar field in the background of the Kerr-Newman black hole at the range of parameters for which the effect is not negligibly small and, at the same time, the semiclassical regime is, at least marginally, valid. For black holes with charge below or not much higher than the charge accretion limit Q˜?M/e (where e and ? are the electron's mass and charge), the time between the consequent emitting of two charged particles is very large. For primordial black holes the transition between the increasing and decreasing of the ratio Q/M occurs around the charge accretion limit. The rotation increases the intensity of radiation up to three orders, while the effect of the field's mass strongly suppresses the radiation.

Konoplya, R. A.; Zhidenko, A.

2014-04-01

353

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

E-print Network

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.

Norman Neitz; Antonino Di Piazza

2014-08-06

354

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

E-print Network

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.

Neitz, Norman

2014-01-01

355

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

NASA Astrophysics Data System (ADS)

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.

Neitz, N.; Di Piazza, A.

2014-08-01

356

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

SciTech Connect

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

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

2011-04-15

357

Spectrally enhancing near-field radiative heat transfer by exciting magnetic polariton in SiC gratings  

E-print Network

In the present work, we theoretically demonstrate, for the first time, that near field radiative transport between 1D periodic grating microstructures separated by subwavelength vacuum gaps can be significantly enhanced by exciting magnetic resonance or polariton. Fluctuational electrodynamics that incorporates scattering matrix theory with rigorous coupled wave analysis is employed to exactly calculate the near field radiative heat flux between two SiC gratings. Besides the well known coupled surface phonon polaritons (SPhP), an additional spectral radiative heat flux peak, which is due to magnetic polariton, is found within the phonon absorption band of SiC. The mechanisms, behaviors and interplays between magnetic polariton, coupled SPhP, single interface SPhP, and Wood's anomaly in the near field radiative transport are elucidated in detail. The findings will open up a new way to control near field radiative heat transfer by magnetic resonance with micro or nanostructured metamaterials.

Yang, Yue

2015-01-01

358

A space weather index for the radiation field at aviation altitudes  

NASA Astrophysics Data System (ADS)

The additional dose contribution to the radiation exposure at aviation altitudes during Solar Particle Events (SPEs) has been a matter of concern for many years. After the Halloween storms in 2003 several airlines began to implement mitigation measures such as rerouting and lowering flight altitudes in response to alerts on the NOAA S-scale regarding solar radiation storms. These alerts are based on the integral proton flux above 10 MeV measured aboard the corresponding GOES-satellite which is operated outside the Earth's atmosphere in a geosynchronous orbit. This integral proton flux has, however, been proved to be an insufficient parameter to apply to the radiation field at aviation altitudes without an accompanying analysis of the shape of the energy spectrum. Consequently, false alarms and corresponding disproportionate reactions ensued. Since mitigating measures can be quite cost-intensive, there has been a demand for appropriate space weather information among responsible airline managers for about a decade. Against this background, we propose the introduction of a new Space Weather index D, based on dose rates at aviation altitudes produced by solar protons during solar radiation storms, as the relevant parameter for the assessment of corresponding radiation exposure. The Space Weather index D is a natural number given by a graduated table of ranges of dose rates in ascending order which is derived by an equation depending on the dose rate of solar protons.

Meier, Matthias M.; Matthiä, Daniel

2014-04-01

359

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

Microsoft Academic Search

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

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

360

Effect of Spatial Organization on Solar Radiative Transfer in Three-Dimensional Idealized Stratocumulus Cloud Fields  

Microsoft Academic Search

To relate the error associated with 1D radiative calculations to the geometrical scales of cloud organization and\\/or in-cloud optical inhomogeneities, a new idealized methodology, based on a Fourier statistical technique, has been developed. Three-dimensional cloud fields with variability over a selected range of horizontal spatial scales and consistent vertical structure can be obtained and controlled by a small number of

F. Di Giuseppe; A. M. Tompkins

2003-01-01

361

Application of granulated activated carbon packed-bed reactor in microwave radiation field to treat BTX  

Microsoft Academic Search

A process applying granulated activated carbon (GAC) to adsorb benzene, toluene and xylene (BTX) and using microwave (MW) energy to treat the BTX adsorbed by GAC was developed. Benzene at 20.0 mg\\/L, toluene at 30.0 mg\\/L, xylene at 24.6 mg\\/L and BTX at 13.4 mg\\/L (adsorbed by GAC) could be treated to a non-detectable level in a microwave radiation field.

Chih-Ju G. Jon; H. S. Tai

1998-01-01

362

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

Microsoft Academic Search

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

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

1998-01-01

363

The Radiation Field Wave Forms Produced by Intracloud Lightning Discharge Processes  

Microsoft Academic Search

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

Charles D. Weidman; E. Philip Krider

1979-01-01

364

Radiative properties of diamagnetic levels in atoms: Dependence of transition probability on magnetic field strength  

Microsoft Academic Search

We study the effect of diamagnetic interaction on the probability of radiative transitions of an atom from states split by\\u000a a field. We write the analytic expressions for the diamagnetic corrections to the matrix elements of transitions belonging\\u000a to the Lyman and Balmer series and of transitions between arbitrary nondegenerate states in hydrogen. We also discuss the\\u000a perturbation theory for

V. D. Ovsyannikov; V. V. Chernushin

1999-01-01

365

Sterilization of liquid foods by pulsed electric fields  

Microsoft Academic Search

Recent advances in the field of high-voltage pulse power technology have provided scope for the development of nonthermal sterilization methods free from the disadvantages commonly encountered with existing physical, chemical, or radiation sterilization. The flexibility allowed in the application of electrical energy can make high-field sterilization economical, compact, energy efficient, and environmentally acceptable. The main thrust of present research in

Shesha H. Jayaram

2000-01-01

366

Electromagnetic field and radiation for a charge moving along a helical trajectory inside a waveguide with dielectric filling  

E-print Network

We investigate the electromagnetic field generated by a point charge moving along a helical trajectory inside a circular waveguide with conducting walls filled by homogeneous dielectric. The parts corresponding to the radiation field are separated and the formulae for the radiation intensity are derived for both TE and TM waves. It is shown that the main part of the radiated quanta is emitted in the form of the TE waves. Various limiting cases are considered. The results of the numerical calculations show that the insertion of the waveguide provides an additional mechanism for tuning the characteristics of the emitted radiation by choosing the parameters of the waveguide and filling medium.

A. S. Kotanjyan; A. A. Saharian

2007-08-27

367

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

SciTech Connect

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

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

2010-06-29

368

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

SciTech Connect

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.

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

369

High-resolution Ultraviolet Radiation Fields of Classical T Tauri Stars  

NASA Astrophysics Data System (ADS)

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 H2 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 ~107 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 H2 (0-0) absorption band at 1110 Å. The total and component-level high-resolution radiation fields are made publicly available in machine-readable format. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555.

France, Kevin; Schindhelm, Eric; Bergin, Edwin A.; Roueff, Evelyne; Abgrall, Hervé

2014-04-01

370

Over-response of synthetic microDiamond detectors in small radiation fields.  

PubMed

The recently commercialized PTW microDiamond detector (T60019) has been designed for use in small radiation fields. Here we report on the measurement of relative output ratios for small fields using five microDiamond detectors. All of the microDiamond detectors over-responded in fields smaller than 20?mm, by up to 9.3% for a 4?mm field. The over-response was independent of accelerator type and choice of collimation. The over-response was slightly larger than that observed in silicon diodes. Since all five microDiamond detectors showed the same over-response the corrections presented here should be transferable to other examples of the microDiamond detector, provided that the detector meets the manufacturing specifications and the beam characteristics are comparable. PMID:25211368

Ralston, Anna; Tyler, Madelaine; Liu, Paul; McKenzie, David; Suchowerska, Natalka

2014-10-01

371

THz near-field imaging of biological tissues employing synchrotron radiation (Invited Paper)  

NASA Astrophysics Data System (ADS)

Terahertz scanning near-field infrared microscopy (SNIM) below 1 THz is demonstrated. The near-field technique benefits from the broadband and highly brilliant coherent synchrotron radiation (CSR) from an electron storage ring and from a detection method based on locking on to the intrinsic time structure of the synchrotron radiation. The scanning microscope utilizes conical waveguides as near-field probes with apertures smaller than the wavelength. Different cone approaches have been investigated to obtain maximum transmittance. Together with a Martin-Puplett spectrometer the set-up enables spectroscopic mapping of the transmittance of samples well below the diffraction limit. Spatial resolution down to about ?/40 at 2 wavenumbers (0.06 THz) is derived from the transmittance spectra of the near-field probes. The potential of the technique is exemplified by imaging biological samples. Strongly absorbing living leaves have been imaged in transmittance with a spatial resolution of 130 ?m at about 12 wavenumbers (0.36 THz). The THz near-field images reveal distinct structural differences of leaves from different plants investigated. The technique presented also allows spectral imaging of bulky organic tissues. Human teeth samples of various thicknesses have been imaged between 2 and 20 wavenumbers (between 0.06 and 0.6 THz). Regions of enamel and dentin within tooth samples are spatially and spectrally resolved, and buried caries lesions are imaged through both the outer enamel and into the underlying dentin.

Schade, Ulrich; Holldack, Karsten; Martin, Michael C.; Fried, Daniel

2005-04-01

372

Influence of Electric Field Distribution on High-Power Array Antenna Radiation Pattern with Rectangular Aperture  

NASA Astrophysics Data System (ADS)

The antenna element with rectangular aperture is one of the main forms of the array antenna. The electric field amplitude distribution of the rectangular aperture, as well as the phase distribution is the most important parameter that affects the radiation gain and beam direction of the array antenna. In this work, a theoretical study is carried out on array antennae for high-power microwave (HPM) applications. An electric integration method is applied to obtain the far-field radiation pattern with different kinds of electric field distributions. Moreover, the influence of the electric field amplitude and phase on the performance of the array antenna is analyzed. For one antenna element, uniform electric field distribution is not the best choice. However, the uniform distribution has specific advantages for an array antenna consisting of combined antenna elements. The phase deviation has more significant influence on the performance of the array antenna than the amplitude deviation. It indicates that a good working phase shifter with high-power capacity and time-adjusting capability is very important.

Yang, Yi-Ming; Yuan, Cheng-Wei; Qian, Bao-Liang

2014-06-01

373

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

NASA Technical Reports Server (NTRS)

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.

Torres-Pomales, Wilfredo

2012-01-01

374

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

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

375

Lightning-channel morphology by return-stroke radiation field waveforms  

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

376

Encounters, endings and temporality in psychiatric nursing.  

PubMed

This paper is derived from data obtained from a study in progress. The study is a phenomenological research project grounded in the work of Martin Heidegger and Hans-George Gadamer. Psychiatric nurses were interviewed about their experience of the nurse-patient encounter. During the course of the study it became apparent that the significance of encounters did not 'end' with the termination of the relationship. 'Endings' went further than notions of relationship 'termination' familiar in the psychiatric nursing literature. The ending of the encounter seemed to encapsulate much of the significance of the encounter for the nurse. It also became apparent that, for these nurses, time was not experienced in a linear way. Viewed in this non-linear way, the past is no less meaningful for being past. The past is with us and influences the present, that is, our actions now. The future is no less meaningful for having not yet been. The future engages us in possibilities. So, unlike the narrow concept of termination, the lived experience of endings captures the totality of the relationship and the encounter and therefore lives on in the present. In the lived experience of endings the past and the future are both significant and have meaning. PMID:9080274

Walsh, K

1997-03-01

377

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

SciTech Connect

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

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

2009-11-30

378

Radiation  

Cancer.gov

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

379

The radiation fields around a proton therapy facility: A comparison of Monte Carlo simulations  

NASA Astrophysics Data System (ADS)

A proton therapy test facility with a beam current lower than 10 nA in average, and an energy up to 150 MeV, is planned to be sited at the Frascati ENEA Research Center, in Italy. The accelerator is composed of a sequence of linear sections. The first one is a commercial 7 MeV proton linac, from which the beam is injected in a SCDTL (Side Coupled Drift Tube Linac) structure reaching the energy of 52 MeV. Then a conventional CCL (coupled Cavity Linac) with side coupling cavities completes the accelerator. The linear structure has the important advantage that the main radiation losses during the acceleration process occur to protons with energy below 20 MeV, with a consequent low production of neutrons and secondary radiation. From the radiation protection point of view the source of radiation for this facility is then almost completely located at the final target. Physical and geometrical models of the device have been developed and implemented into radiation transport computer codes based on the Monte Carlo method. The scope is the assessment of the radiation field around the main source for supporting the safety analysis. For the assessment independent researchers used two different Monte Carlo computer codes named FLUKA (FLUktuierende KAskade) and MCNPX (Monte Carlo N-Particle eXtended) respectively. Both are general purpose tools for calculations of particle transport and interactions with matter, covering an extended range of applications including proton beam analysis. Nevertheless each one utilizes its own nuclear cross section libraries and uses specific physics models for particle types and energies. The models implemented into the codes are described and the results are presented. The differences between the two calculations are reported and discussed pointing out disadvantages and advantages of each code in the specific application.

Ottaviano, G.; Picardi, L.; Pillon, M.; Ronsivalle, C.; Sandri, S.

2014-02-01

380

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

NASA Astrophysics Data System (ADS)

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 , Phys. PlasmasPHPAEN1070-664X10.1063/1.2896577 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.

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

381

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

NASA Astrophysics Data System (ADS)

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.

Didari, Azadeh; Mengüç, M. Pinar

2014-10-01

382

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)

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.

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

383

Galileo Orbit Determination for the Ida Encounter  

E-print Network

This paper summarizes orbit determination activities leading Up its encounter with asteroid 243-Ida on August 28, 1993. In addition to the nominal 2-way S-band range and Doppler radio metric data obtained from the Deep Space Network several navigational aids were brought together make this encounter successful. These include a comprehensive ground-based observation campaign of the asteroid during rhe four years prior to the flyby to improve Ida's ephemeris significantly, and the Optical Navigation picture campaign which helped decrease considerably the uncertainties of Galileo's position relative to Ida. Details in the modeling of Galileo's orbit and in the navigational tools described above will be explained, and the results of several key orbit solutions will be given. the encounter, reconstructions of Galileo's orbit with respect to Ida were performed using several SS1 science images of the asteroid that were returned to Earth from September 1993 through late April 1994. The final d...

Nicho Ls On' P. G. Antreasian; F. T. Nicholson; P. H. Kdlemeyn; S. Bhiiskaran; R. J. Hawl; P. Htdamek

384

Magnetic field effects on the energy deposition spectra of MV photon radiation.  

PubMed

Several groups worldwide have proposed various concepts for improving megavoltage (MV) radiotherapy that involve irradiating patients in the presence of a magnetic field-either for image guidance in the case of hybrid radiotherapy-MRI machines or for purposes of introducing tighter control over dose distributions. The presence of a magnetic field alters the trajectory of charged particles between interactions with the medium and thus has the potential to alter energy deposition patterns within a sub-cellular target volume. In this work, we use the MC radiation transport code PENELOPE with appropriate algorithms invoked to incorporate magnetic field deflections to investigate electron energy fluence in the presence of a uniform magnetic field and the energy deposition spectra within a 10 microm water sphere as a function of magnetic field strength. The simulations suggest only very minor changes to the electron fluence even for extremely strong magnetic fields. Further, calculations of the dose-averaged lineal energy indicate that a magnetic field strength of at least 70 T is required before beam quality will change by more than 2%. PMID:19088391

Kirkby, C; Stanescu, T; Fallone, B G

2009-01-21

385

The K-shell radiation of a double gas puff z-pinch with an axial magnetic field  

Microsoft Academic Search

A double shell z-pinch with an axial magnetic field is considered as a K-shell plasma radiation source. One-dimensional radiation-hydrodynamics calculations performed suggest that this scheme holds promise for the production of the K-shell radiation of krypton (h[nu] [approximate] 12 17 keV). As a first step in verifying the advantages of this scheme, experiments have been performed to optimize a neon

S. A. Chaikovsky; A. Yu. Labetsky; V. I. Oreshkin; A. V. Shishlov; R. B. Baksht; A. V. Fedunin; A. G. Rousskikh

2003-01-01

386

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

SciTech Connect

Average energy spectral densities are presented for the fast transitions in most of the components that produce large radiation field impulses from cloud-to-ground lightning; first and subsequent return strokes; stepped, dart-stepped, and 'chaotic' leaders; and 'characteristic' cloud pulses. A disagreement in the previous literature about the spectral energy radiated by return strokes at high frequencies is noted and explained. The authors show that the spectral amplitudes are not seriously distorted by propagation over less than 35 km of seawater, although as much as 45 km of such propagation does appear to produce significant attenuation above about 10 MHz. First and subsequent return strokes produce identical spectra between 0.2 and 20 MHz. The spectra of stepped and dart-stepped leader steps are nearly identical and are very similar to that of characteristic pulses. The spectra of leader steps also match return stroke spectra above 2-3 MHz after the former are increased by about 7 dB. The shapes of individual spectra do not depend on their amplitude, so the shapes of the average spectra are probably not distorted by the trigger thresholds used in the data acquisition. Return strokes are the strongest sources of radiation from cloud-to-ground lightning in the 0.2- to 20-MHz frequency range, although certain intracloud processes are stronger radiators above 8 MHz.

Willett, J.C. (Air Force Geophysics Lab., Hanscom AFB, MA (USA)); Bailey, J.C. (Univ. of Alabama, Huntsville (USA)); Leteinturier, C. (Inst. de Physique et Chimie des Materiaux (France)); Krider, E.P. (Univ. of Arizona, Tucson (USA))

1990-11-20

387

Satellite ephemerides for the Voyager Neptune encounter  

NASA Technical Reports Server (NTRS)

This paper presents the results of the latest fits of both analytical theory and numerically integrated Neptunian satellite orbits to Earth-based astrometric observations. Ephemerides based on the integrated orbits will be used by the Voyager project for pre-encounter planning and analysis until late 1988 when the final pre-encounter ephemerides will be produced. As a by-product of the orbit fits, new estimates of the Neptune mass, the second zonal harmonic of Neptune, and the pole orientation of Neptune are obtained. The theory and integrated orbits are compared with each other and with orbits obtained by previous investigators.

Jacobson, Robert A.

1988-01-01

388

Satellite ephemerides for the Voyager Neptune encounter  

NASA Astrophysics Data System (ADS)

This paper presents the results of the latest fits of both analytical theory and numerically integrated Neptunian satellite orbits to Earth-based astrometric observations. Ephemerides based on the integrated orbits will be used by the Voyager project for pre-encounter planning and analysis until late 1988 when the final pre-encounter ephemerides will be produced. As a by-product of the orbit fits, new estimates of the Neptune mass, the second zonal harmonic of Neptune, and the pole orientation of Neptune are obtained. The theory and integrated orbits are compared with each other and with orbits obtained by previous investigators.

Jacobson, Robert A.

389

Sequencing Voyager II for the Uranus encounter  

NASA Technical Reports Server (NTRS)

The process of developing the programmed sequence of events necessary for the Voyager 2 spacecraft to return desired data from its Uranus encounter is discussed. The major steps in the sequence process are reviewed, and the elements of the Mission Sequence Software are described. The design phase and the implementation phase of the sequence process are discussed, and the Computer Command Subsystem architecture is examined in detail. The software's role in constructing the sequences and converting them into onboard programs is elucidated, and the problems unique to the Uranus encounter sequences are considered.

Morris, R. B.

1986-01-01

390

Experimental determination of radiated internal wave power without pressure field data  

SciTech Connect

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.

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

391

Experimental determination of radiated internal wave power without pressure field data  

NASA Astrophysics Data System (ADS)

We present a method to determine, using only velocity field data, the time-averaged energy flux left<{J}right> and total radiated power P for two-dimensional internal gravity waves. Both left<{J}right> 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.

Lee, Frank M.; Paoletti, M. S.; Swinney, Harry L.; Morrison, P. J.

2014-04-01

392

Relating the radiated piano sound field to the vibrational modes of the soundboard  

NASA Astrophysics Data System (ADS)

The sound field near a piano sound board is determined by moving a microphone over a grid of points above and below the sound board as well as in a plane in front of the piano using the experimental techniques of modal analysis with soundboard excitation at a bridge point by a swept sine signal. Since the standard modal analysis signal processing technique relies on tracking phase relations between excitation and response, it is possible to relate the sound field in terms of the vibrating structure which radiated it. Animations of sound board motion and sound field pressure variations are shown for the lowest four modes. It is noted that in all modes the locations of maximal excursion correlate with the sound pressure maxima or minima, respectively.

Hansen, Uwe J.; Bork, Ingolf; Rossing, Thomas D.

2003-10-01

393

The effective mass of atom-radiation field system and the cavity-field Wigner distribution in the presence of a homogeneous gravitational field in the Jaynes-Cummings model  

E-print Network

The effective mass that approximately describes the effect of a classical homogeneous gravitational field on an interacting atom-radiation field system is determined within the framework of the Jaynes-Cummings model. By taking into account both the atomic motion and gravitational field, a full quantum treatment of the internal and external dynamics of the atom is presented. By solving exactly the Schrodinger equation in the interaction picture, the evolving state of the system is found. Influence of a classical homogeneous gravitational field on the energy eigenvalues, the effective mass of atom-radiation field system and the Wigner distribution of the radiation field are studied, when initially the radiation field is prepared in a coherent state and the two-level atom is in a coherent superposition of the excited and ground states.

M. Mohammadi

2009-02-01

394

Fractionated Wide-Field Radiation Therapy Followed by Fractionated Local-Field Irradiation for Treating Widespread Painful Bone Metastasis  

SciTech Connect

Purpose: Wide-field radiation therapy (WFRT) is an effective treatment for widespread bone metastasis. We evaluated local-field irradiation (LFI) after fractionated WFRT (f-WFRT) for treating the patients with multiple painful bone lesions. Methods and Materials: From 1998 to 2007, 32 patients with multiple bone metastases were treated with fractionated LFI (f-LFI) after f-WFRT. All patients initially received 15 Gy in 5 fractions to a wide field, followed by LFI (9-15 Gy in 3 Gy fractions). Response was assessed by evaluating the degree of pain relief using a visual analog scale before radiotherapy, after f-WFRT, and after f-LFI. Results: Fractionated LFI following f-WFRT yielded an overall relief rate of 93.8% and a complete relief rate of 43.8%. The rate of the appearance of new disease was 6.3% for the patients with complete relief, 20.5% for the patients with a partial relief, and 50% for the patients with no relief. Conclusion: Fractionated LFI after f-WFRT is a well-tolerated and effective treatment for multiple metastatic bone disease.

Ki, Yongkan [Department of Radiation Oncology, Medical Research Institute, Pusan National University Hospital, Pusan National University School of Medicine, Busan (Korea, Republic of); Kim, Wontaek, E-mail: rokwt@hanmail.ne [Department of Radiation Oncology, Medical Research Institute, Pusan National University Hospital, Pusan National University School of Medicine, Busan (Korea, Republic of); Nam, Jiho; Kim, Donghyun; Jeon, Hosang; Park, Dahl; Kim, Dongwon [Department of Radiation Oncology, Medical Research Institute, Pusan National University Hospital, Pusan National University School of Medicine, Busan (Korea, Republic of)

2011-01-01

395

Al toxicity effects on radiation interception and radiation use efficiency of Al-tolerant and Al-sensitive wheat cultivars under field conditions  

Microsoft Academic Search

Soil acidity and Al toxicity are highly extended in agricultural lands of Chile, especially where wheat is widely sown. To evaluate quantitatively the response of wheat biomass and its physiological determinants (intercepted radiation and radiation use efficiency) to Al toxicity, two field experiments were conducted in an Andisol in Valdivia (39°47?S, 73°14?W), Chile, during the 2005–2006 and 2006–2007 growing seasons.

Susana R. Valle; Dante Pinochet; Daniel F. Calderini

2009-01-01

396

Terahertz radiation and second-harmonic generation from InAs: Bulk versus surface electric-field-induced contributions  

E-print Network

Terahertz radiation and second-harmonic generation from InAs: Bulk versus surface electric-harmonic generation and terahertz radiation emission indicates that the observed dominant surface electric-field-induced contributions Matthew Reid, Igor V. Cravetchi, and Robert Fedosejevs Department of Electrical and Computer

Reid, Matthew

397

Method of moments analysis of EM fields in a multilayered spheroid radiated by a thin circular loop antenna  

Microsoft Academic Search

This paper presents derivation and computation of electromagnetic (EM) fields inside a dielectric prolate spheroid radiated by a loop antenna. The dielectric spheroid is considered to be multilayered, and a thin circular loop antenna that is loaded by a voltage source radiates on the top of the prolate spheroid. The multiple interaction of transmitted and reflected waves with the spheroid

Le-Wei Li; Mui-Seng Yeo; Mook-Seng Leong

2004-01-01

398

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...

399

Inverse bremsstrahlung absorption in large radiation fields during binary collisions-classical theory. II. Integrated rate coefficients for Coulomb collisions  

Microsoft Academic Search

For pt.I see ibid., vol.5, p.508 (1972). Integrated rate coefficients for the absorption of electromagnetic radiation in plasma when the plasma frequency is less than the radiation frequency are calculated from classical expressions derived earlier. The resulting formula is applicable over the complete range of field strengths. Numerical calculations are used to give useful interpolation formulae for the complete range

G J Pert

1976-01-01

400

Local field effects on the radiative lifetimes of Ce$^{3+}$ in different hosts  

E-print Network

For emitters embedded in media of various refractive indices, different theoretical models predicted substantially different dependencies of the spontaneous emission lifetime on refractive index. It has been claimed that various measurements on $4f\\to 4f$ radiative transition of Eu$^{3+}$ in hosts with variable refractive index appear to favor the real-cavity model [J. Fluoresc. 13, 201 (2003) and references therein, Phys. Rev. Lett. 91, 203903 (2003)]. We notice that $5d\\to 4f$ radiative transition of rare-earth ions, dominated by allowed electric-dipole transitions with line strengths less perturbed by the ligands, serves as a better test of different models. We analyze the lifetimes of $5d\\to 4f$ transition of Ce$^{3+}$ in hosts of refractive indices varying from 1.4 to 2.2. The results favor the macroscopic virtual-cavity model based on Lorentz local field [J. Fluoresc. 13, 201 (2003)].

Chang-Kui Duan; Michael F. Reid

2005-05-24

401

Shortwave surface radiation budget network for observing small-scale cloud inhomogeneity fields  

NASA Astrophysics Data System (ADS)

As part of the High Definition Clouds and Precipitation for advancing Climate Prediction Observational Prototype Experiment (HOPE), a high spatial density network of 99 silicon photodiode pyranometers was set up around Jülich (10 km x 12 km area) from April to July 2013, to capture the variability in the radiation field at the surface induced by small-scale cloud inhomogeneity. Each of these autonomously operated pyranometer stations was equipped with weather sensors for simultaneous measurements of ambient air temperature and relative humidity. In this paper, we provide the details of this unique setup of the pyranometer network and the data analysis with initial quality screening procedure we adopted. We also present some exemplary cases consisting of the days with clear, broken cloudy and overcast skies to assess our spatio-temporal observations from the network, and validate their consistency with other collocated radiation measurements available during the HOPE period.

Madhavan, B. L.; Kalisch, J.; Macke, A.

2015-03-01

402

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

SciTech Connect

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

Vladimir Pascalutsa; Marc Vanderhaeghen

2007-10-12

403

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

SciTech Connect

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

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

2012-05-15

404

Three-dimensional evolution of magnetic fields in a differentially rotating stellar radiative zone  

NASA Astrophysics Data System (ADS)

Context. The question of the origin and evolution of magnetic fields in stars possessing a radiative envelope, like the A-type stars, is still regarded as a challenge for stellar physics. Those zones are likely to be differentially rotating, which suggests that strong interactions between differential rotation and magnetic fields could be at play in such regions. Aims: We would like to analyse in detail the evolution of magnetic fields in a differentially rotating stellar radiative zone and the possible presence of magnetic instabilities. Methods: We numerically compute the joint evolution of the magnetic and velocity fields in a 3D spherical shell starting from an initial profile for the poloidal magnetic field and differential rotation. In order to characterise the nature of the magnetic instabilities that may be expected, we use the predictions of a local linear analysis. Results: The poloidal magnetic field is initially wound up by the differential rotation to produce a toroidal field which becomes unstable. We find that different types of instabilities may occur, depending on the balance between the shear strength and the magnetic field intensity. In the particular setup studied here where the differential rotation is dominant, the instability is not of the Tayler-type but is the magneto-rotational instability. The growth rate of the instability depends mainly on the initial rotation rate, while the background state typically oscillates over a poloidal Alfvén time. We thus find that the axisymmetric magnetic configuration is strongly modified by the instability only if the ratio between the poloidal Alfvén frequency and the rotation rate is sufficiently small. An enhanced transport of angular momentum is found in the most unstable cases: the typical time to flatten the rotation profile is then much faster than the decay time associated with the phase-mixing mechanism, which also occurs in the stable cases. When the instability saturates before reaching a significant amplitude, the magnetic configuration relaxes into a stable axisymmetric equilibrium formed by several twisted tori. Conclusions: We conclude that the magneto-rotational instability is always favoured (over the Tayler instability) in unstratified spherical shells when an initial poloidal field is sheared by a sufficiently strong cylindrical differential rotation. A possible application to the magnetic desert observed among A stars is given. We argue that the dichotomy between stars exhibiting strong axisymmetric fields (Ap stars) and those harbouring a sub-Gauss magnetism could be linked to the threshold for the instability.

Jouve, L.; Gastine, T.; Lignières, F.

2015-03-01

405

Inadequacies in the conventional treatment of the radiation field of moving sources  

E-print Network

There is a fundamental difference between the classical expression for the retarded electromagnetic potential and the corresponding retarded solution of the wave equation that governs the electromagnetic field. While the boundary contribution to the retarded solution for the {\\em potential} can always be rendered equal to zero by means of a gauge transformation that preserves the Lorenz condition, the boundary contribution to the retarded solution of the wave equation governing the {\\em field} may be neglected only if it diminishes with distance faster than the contribution of the source density in the far zone. In the case of a source whose distribution pattern both rotates and travels faster than light {\\em in vacuo}, as realized in recent experiments, the boundary term in the retarded solution governing the field is by a factor of the order of $R^{1/2}$ {\\em larger} than the source term of this solution in the limit that the distance $R$ of the boundary from the source tends to infinity. This result is consistent with the prediction of the retarded potential that part of the radiation field generated by a rotating superluminal source decays as $R^{-1/2}$, instead of $R^{-1}$, a prediction that is confirmed experimentally. More importantly, it pinpoints the reason why an argument based on a solution of the wave equation governing the field in which the boundary term is neglected (such as appears in the published literature) misses the nonspherical decay of the field.

Houshang Ardavan; Arzhang Ardavan; John Singleton; Joseph Fasel; Andrea Schmidt

2009-08-10

406

Three-dimensional solar radiative transfer in small tropical cumulus fields derived from high-resolution imagery  

Microsoft Academic Search

Since three-dimensional (3-D) radiative transfer in cloudy atmospheres is too expensive for large-scale atmospheric models, approximate radiative transfer methods are used. The accuracy of these approximations for a large sample of realistic cloud fields has not been determined. This study examines 150 fields of small marine tropical cumulus to assess the magnitude of 3-D effects on domain average solar fluxes

Timothy C. Benner; K. Franklin Evans

2001-01-01

407

The effect of a strong external radiation field on protostellar envelopes in Orion  

E-print Network

We discuss the effects of an enhanced interstellar radiation field (ISRF) on the observables of protostellar cores in the Orion cloud region. Dust radiative transfer is used to constrain the envelope physical structure by reproducing SCUBA 850 micron emission. Previously reported 13CO, C17O and H2CO line observations are reproduced through detailed Monte Carlo line radiative transfer models. It is found that the 13CO line emission is marginally optically thick and sensitive to the physical conditions in the outer envelope. An increased temperature in this region is needed in order to reproduce the 13CO line strengths and it is suggested to be caused by a strong heating from the exterior, corresponding to an ISRF in Orion 10^3 times stronger than the "standard" ISRF. The typical temperatures in the outer envelope are higher than the desorption temperature for CO. The C17O emission is less sensitive to this increased temperature but rather traces the bulk envelope material. The data are only fit by a model where CO is depleted, except in the inner and outermost regions where the temperature increases above 30-40 K. The fact that the temperatures do not drop below approximately 25 K in any of the envelopes whereas a significant fraction of CO is frozen-out suggest that the interstellar radiation field has changed through the evolution of the cores. The H2CO lines are successfully reproduced in the model of an increased ISRF with constant abundances of 3-5x10^{-10}.

Jes K. Jorgensen; Doug Johnstone; Ewine F. van Dishoeck; Steven D. Doty

2005-12-12

408

Identification of commonly encountered Pratylenchus in Oregon  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

409

Entering a Crack: An Encounter with Gossip  

ERIC Educational Resources Information Center

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.…

Henderson, Linda

2014-01-01

410

Meaningful encounters Explorative studies about designers  

E-print Network

, or look for books that explain these children's behaviour. However, the way that children with autismMeaningful encounters Explorative studies about designers learning from children with autism of this book may be reproduced or transmitted in any form or by any means, electronical or mechanical

Epema, Dick H.J.

411

The Pioneer 8 Earth-Moon encounter  

NASA Astrophysics Data System (ADS)

In the May 7, 1991, Eos, F. M. Neubauer and K.-H. Glassmeier took up the cause of “historical correctness” in a comment on the conarticle by F. Fanale (Eos, November 20, 1990, p. 1803) about the Galileo encounter with the Earth-Moon system in December 1990. The 1991 article pointed out that Fanale was incorrect in claiming that Galileo was to perform the first “encounter by a spacecraft from deep space with the Earth-Moon system,” since Giotto encountered the Earth in July 1990.While this event certainly invalidates the claim of primacy for the Galileo spacecraft, it does not award it to Giotto. The October 1987 Journal of Geophysical Research contains a paper by the late Fredrick L. Scarf describing results from the Pioneer 8 encounter with the geomagnetic tail in April and May 1985. At that time, the Pioneer 8 solar arrays' long exposure to space had so degraded the power levels of the spacecraft that Scarfs plasma wave instrument was the only one that could be operated.

Moses, Stewart L.

412

The Pioneer 8 Earth-Moon encounter  

Microsoft Academic Search

In the May 7, 1991, Eos, F. M. Neubauer and K.-H. Glassmeier took up the cause of ``historical correctness'' in a comment on the conarticle by F. Fanale (Eos, November 20, 1990, p. 1803) about the Galileo encounter with the Earth-Moon system in December 1990. The 1991 article pointed out that Fanale was incorrect in claiming that Galileo was to

Stewart L. Moses

1991-01-01

413

Sixth Graders Speak Out: Troublesome Intercultural Encounters.  

ERIC Educational Resources Information Center

Researchers have pointed to cultural diversity as a major source of conflict in our nation's schools, noting that these conflicts have the potential to escalate into violence. This study seeks to identify the types of intercultural encounters that young people themselves find troublesome. Participants were 906 sixth graders in 12 elementary…

Jaasma, Marjorie A.

414

Measuring Customer Satisfaction in Tourist Service Encounters  

Microsoft Academic Search

This paper sets out to model quality and satisfaction judgements of college students within four distinct tourist encounters. A novel approach is used where respondents rated an entire service setting by proxy when evaluating a picture in which certain quality variables had been manipulated. Each picture contained separate ôobjectsö of the service that we claim would be evaluated on a

Doren Chadee; Jan Mattsson

1996-01-01

415

Reliability of the internal service encounter  

Microsoft Academic Search

Purpose – Service quality has been an active area of research during the last two decades. In this research, typically, service quality is considered from the viewpoint of the customer who is the recipient of the service, i.e. the “external customer”, and the research efforts have focused on identifying the dimensions of quality in this “external service encounter”. In the

Gamini Gunawardane

2011-01-01

416

Encounter: A Picture Book for Any Classroom.  

ERIC Educational Resources Information Center

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)

Hazler, Kitty Y.

2002-01-01

417

EPOXI COMET ENCOUNTER Nov. 2, 2010  

E-print Network

1 EPOXI COMET ENCOUNTER FACT SHEET Nov. 2, 2010 Quick Facts Flyby Spacecraft Dimensions: 3.3 meters storage via small, 16-amp- hourrechargeable nickel hydrogen battery Comet Hartley 2 Nucleus shape.m. EDT July 4, 2005) Earth-comet distance at time of impact: 133.6 million kilometers (83 million miles

Gruner, Daniel S.

418

Initial Encounters of an FE Kind  

ERIC Educational Resources Information Center

The discussion of students' initial encounters in this paper is based upon data from a research project funded by the ESRC as part of the Teaching and Learning Research Programme (TLRP) extension to Wales programme. The research investigated the experiences of "Learning and Working in Further Education Colleges in Wales" and followed the learning…

Salisbury, Jane; Jephcote, Martin

2008-01-01

419

Stardust Comet Wild 2 Encounter (Artist's Concept)  

NASA Technical Reports Server (NTRS)

Artist's rendering of the Stardust spacecraft. The spacecraft was launched on February 7, 1999, from Cape Canaveral Air Station, Florida, aboard a Delta II rocket. The primary goal of Stardust is to collect dust and carbon-based samples during its closest encounter with Comet Wild 2 -- pronounced 'Vilt 2' after the name of its Swiss discoverer.

2005-01-01

420

Encountering Pedagogy through Relational Art Practices  

ERIC Educational Resources Information Center

Two artists involved in "socially engaged art" practice were invited to work with art education teacher candidates and instructors in an effort to rethink notions of teaching, learning and art. We initiated this residency, which we called "The Summerhill Residency", to examine how learning encounters might create environments for meaningful…

Irwin, Rita L.; O'Donoghue, Donal

2012-01-01

421

Nonlinear polarization response of a gaseous medium in the regime of atom stabilization in a strong radiation field  

SciTech Connect

The nonlinear polarization response of a quantum system modeling a silver atom in the field of high-intensity radiation in the IR and UV spectral ranges has been studied by direct numerical integration of a nonstationary Schroedinger equation. The domains of applicability of perturbation theory and polarization expansion in powers of the field intensity are determined. The contribution of excited atoms and electrons in a continuum to the atomic polarization response at the field frequency, which arises due to the radiation-induced excitation and photoionization processes, is analyzed. Features of the nonlinear response to an external field under conditions of atom stabilization are considered.

Volkova, E. A.; Popov, A. M., E-mail: alexander.m.popov@gmail.com; Tikhonova, O. V. [Moscow State University, Skobeltsyn Institute of Nuclear Physics (Russian Federation)] [Moscow State University, Skobeltsyn Institute of Nuclear Physics (Russian Federation)

2013-03-15

422

The analysis of complex mixed-radiation fields using near real-time imaging.  

PubMed

A new mixed-field imaging system has been constructed at Lancaster University using the principles of collimation and back projection to passively locate and assess sources of neutron and gamma-ray radiation. The system was set up at the University of Manchester where three radiation sources: (252)Cf, a lead-shielded (241)Am/Be and a (22)Na source were imaged. Real-time discrimination was used to find the respective components of the neutron and gamma-ray fields detected by a single EJ-301 liquid scintillator, allowing separate images of neutron and gamma-ray emitters to be formed. (252)Cf and (22)Na were successfully observed and located in the gamma-ray image; however, the (241)Am/Be was not seen owing to surrounding lead shielding. The (252)Cf and (241)Am/Be neutron sources were seen clearly in the neutron image, demonstrating the advantage of this mixed-field technique over a gamma-ray-only image where the (241)Am/Be source would have gone undetected. PMID:24782559

Beaumont, Jonathan; Mellor, Matthew P; Joyce, Malcolm J

2014-10-01

423

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

SciTech Connect

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

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

2009-04-01

424

Pediatric radiation oncology  

SciTech Connect

This text covers all aspects of radiation therapy for treatment of pediatric cancer. The book describes the proper use of irradiation in each of the malignancies of childhood, including tumors that are rarely encountered in adult practice. These include acute leukemia; supratentorial brain tumors; tumors of the posterior fossa of the brain and spinal canal; retinoblastoma and optic nerve glioma; neuroblastoma; Hodgkin's disease; malignant lymphoma; Ewing's sarcoma; osteosarcoma; rhabdomyosarcoma; Desmoid tumor; Wilms' tumor; liver and biliary tumors; germ cell and stromal cell tumors of the gonads; endocrine, aerodigestive tract, and breast tumors; Langerhans' cell histiocytosis; and skin cancer and hemangiomas. For each type of malignancy, the authors describe the epidemiology, common presenting signs and symptoms, staging, and proper diagnostic workup. Particular attention is given to the indications for radiation therapy and the planning of a course of radiotherapy, including the optimal radiation dose, field size, and technique.

Halperin, E.C.; Kun, L.E.; Constine, L.S.; Tarbell, N.J.

1989-01-01

425

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

NASA Astrophysics Data System (ADS)

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

Newman, Ezra T.

2011-12-01

426

Mode Content Determination of Terahertz Corrugated Waveguides Using Experimentally Measured Radiated Field Patterns  

PubMed Central

This work focuses on the accuracy of the mode content measurements in an overmoded corrugated waveguide using measured radiated field patterns. Experimental results were obtained at 250 GHz using a vector network analyzer with over 70 dB of dynamic range. The intensity and phase profiles of the fields radiated from the end of the 19 mm diameter helically tapped brass waveguide were measured on planes at 7, 10, and 13 cm from the waveguide end. The measured fields were back propagated to the waveguide aperture to provide three independent estimates of the field at the waveguide exit aperture. Projecting that field onto the modes of the guide determined the waveguide mode content. The three independent mode content estimates were found to agree with one another to an accuracy of better than ±0.3%. These direct determinations of the mode content were compared with indirect measurements using the experimentally measured amplitude in three planes, with the phase determined by a phase retrieval algorithm. The phase retrieval technique using the planes at 7, 10, and 13 cm yielded a mode content estimate in excellent agreement, within 0.3%, of the direct measurements. Phase retrieval results using planes at 10, 20, and 30 cm were less accurate due to truncation of the measurement in the transverse plane. The reported measurements benefited greatly from a precise mechanical alignment of the scanner with respect to the waveguide axis. These results will help to understand the accuracy of mode content measurements made directly in cold test and indirectly in hot test using the phase retrieval technique. PMID:25264391

Jawla, Sudheer K.; Nanni, Emilio A.; Shapiro, Michael A.; Woskov, Paul P.; Temkin, Richard J.

2012-01-01

427

Polarization phase matrices for radiation scattering on atoms in external magnetic fields: The case of forbidden transitions in astrophysics  

E-print Network

Using a quantum electrodynamical approach, we derive the scattering phase matrices for polarized radiation involving forbidden line transitions and in the presence of an external magnetic field. The case of (J=0->2->0) scattering is considered as an example. The non-magnetic Rayleigh scattering phase matrix is also presented. The Stokes profiles in a single scattering event are computed for the strong field (Zeeman) and weak field (Hanle) limits, covering also the regime of intermediate field strengths (Hanle- Zeeman).

Oo, Yee Yee; Sampoorna, M; Nagendra, K N; Ramachandran, G

2008-01-01

428

Polarization phase matrices for radiation scattering on atoms in external magnetic fields: The case of forbidden transitions in astrophysics  

E-print Network

Using a quantum electrodynamical approach, we derive the scattering phase matrices for polarized radiation involving forbidden line transitions and in the presence of an external magnetic field. The case of (J=0->2->0) scattering is considered as an example. The non-magnetic Rayleigh scattering phase matrix is also presented. The Stokes profiles in a single scattering event are computed for the strong field (Zeeman) and weak field (Hanle) limits, covering also the regime of intermediate field strengths (Hanle- Zeeman).

Yee Yee Oo; Phyu Phyu San; M. Sampoorna; K. N. Nagendra; G. Ramachandran

2008-05-26

429

Photoinduced processes in solid polymer solutions of dyes in an interference field of laser radiation  

SciTech Connect

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)

Sizykh, A G; Tarakanova, E A [Quantum Electronics Division, Krasnoyarsk State University, Krasnoyarsk (Russian Federation)

1998-12-31

430

?-ray generation enhancement by the charge separation field in laser-target interaction in the radiation dominated regime  

NASA Astrophysics Data System (ADS)

A new source of radiation can be created with a laser pulse of intensity ?1023 W/cm2 interacting with a slightly overdense plasma. Collective effects driven by the electrostatic field significantly enhance the synchrotron radiation. They impact on the laser energy repartition leading to a specific emission but also constitute a crucial element for the intense radiation production. They allow electrons to be accelerated over a length up to 10 laser wavelengths favoring emission of an intense radiation. It is shown that charge separation field depends on the ion mass and target thickness but also on laser polarization. These phenomena are studied with an one dimensional relativistic particle-in-cell code accounting for the classical radiation reaction force.

Capdessus, R.; Lobet, M.; d'Humières, E.; Tikhonchuk, V. T.

2014-12-01

431

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

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.

Nuessly, G.S.; Sterling, W.L.

1986-12-01

432

The signal from an emitting source moving in a Schwarzschild spacetime under the influence of a radiation field  

E-print Network

The motion of matter immersed in a radiation field is affected by radiation drag, as a result of scattering or absorption and re-emission. The resulting friction-like drag, also known as Poynting-Robertson effect, has been recently studied in the general relativistic background of the Schwarzschild and Kerr metric, under the assumption that all photons in the radiation field possess the same angular momentum. We calculate here the signal produced by an emitting point-like specific source moving in a Schwarzschild spacetime under the influence of such a radiation field. We derive the flux, redshift factor and solid angle of the hot spot as a function of (coordinate) time, as well as the time-integrated image of the hot spot as seen by an observer at infinity. The results are then compared with those for a spot moving on a circular geodesic in a Schwarzschild metric.

Donato Bini; Maurizio Falanga; Andrea Geralico; Luigi Stella

2014-08-22

433

Near-field radiative heat transfer between metamaterials coated with silicon carbide thin films  

NASA Astrophysics Data System (ADS)

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.

Basu, Soumyadipta; Yang, Yue; Wang, Liping

2015-01-01

434

A novel coaxial Ku-band transit radiation oscillator without external guiding magnetic field  

SciTech Connect

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%.

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

435

Performance of neutron and gamma personnel dosimetry in mixed radiation fields  

SciTech Connect

From 1974 to 1980, six personnel dosimetry intercomparison studies (PDIS) were conducted at the Oak Ridge National Laboratory (ORNL) to evaluate the performance of personnel dosimeters in a variety of neutron and gamma fields produced by operating the Health Physics Research Reactor (HPRR) in the steady state mode with and without spectral modifying shields. A total of 58 different organizations participated in these studies which produced approximately 2000 measurements of neutron and gamma dose equivalents on anthropomorphic phantoms for five different reactor spectra. Based on these data, the relative performance of three basic types of neutron dosimeters (nuclear emulsion film, thermoluminescent (TLD), and track-etch) and two basic types of gamma dosimeters (film and TLD) in mixed radiation fields was assessed.

Swaja, R.E.; Sims, C.S.

1981-01-01

436

Thermal radiation fields in time-dependent linear media at finite temperature  

NASA Astrophysics Data System (ADS)

The properties of thermal radiation fields in linear media which have time-dependent parameters are investigated on the basis of the invariant operator method. For quantum mechanical description of the electromagnetic waves whose amplitude and/or frequency vary with time, we introduce a quadratic invariant operator that is constructed according to its exact definition. The density operator of the system, being considered signal plus noise, is obtained via maximization of the entropy. The expectation values of the energy operator, the Hamiltonian, and the invariant operator are obtained in the thermal state and their thermal behaviours are illustrated in detail. It is shown that the fluctuations of the electric and the magnetic fields do not depend on signal plus noise and dissipate with time due to the conductivity in media. Our theory of wave propagation in time-varying media is applied to describe the biophoton signal in order to promote the understanding of our developments.

Ryeol Choi, Jeong

2013-10-01

437

Ultrasonic field of a flat transducer with a nonuniform pressure amplitude distribution on its radiating surface  

NASA Astrophysics Data System (ADS)

The influence of a noneven pressure amplitude distribution over the surface of a flat transducer on the generated ultrasonic field is investigated. Expressions for directivity and distribution functions are derived for the field along the radiative axis. Methods are analyzed for creating a given pressure amplitude distribution on a piezoelectric plate surface, and calculations are made for a liquid medium. Results show that the ultrasonic beam formed by the inspection zone can be narrowed considerably, and the spreading can be diminished by creating a nonuniform pressure amplitude distribution on the transducer surface. Flat transducers with annular electrodes are found to yield improved results over transducers with depoled piezoelectric elements. Theoretical and experimental results are also compared, and demonstrate good consistency.

Kondratev, Iu. A.

1981-09-01

438

Magnetic tunnel structures: Transport properties controlled by bias, magnetic field, and microwave and optical radiation  

NASA Astrophysics Data System (ADS)

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.

Volkov, N. V.; Eremin, E. V.; Tarasov, A. S.; Rautskii, M. V.; Varnakov, S. N.; Ovchinnikov, S. G.; Patrin, G. S.

2012-10-01

439

Polarized radiance fields under a dynamic ocean surface: a three-dimensional radiative transfer solution  

SciTech Connect

The hybrid matrix operator, Monte Carlo (HMOMC) method previously reported [Appl. Opt.47, 1063-1071 (2008)APOPAI0003-693510.1364/AO.47.001063] is improved by neglecting higher-order terms in the coupling of the matrix operators and by introducing a dual grid scheme. The computational efficiency for solving the vector radiative transfer equation in a full 3D coupled atmosphere-surface-ocean system is substantially improved, and, thus, large-scale simulations of the radiance distribution become feasible. The improved method is applied to the computation of the polarized radiance field under realistic surface waves simulated by the power spectral density method. To the authors' best knowledge, this is the first time that the polarized radiance field under a dynamic ocean surface and the underwater image of an object above such an ocean surface have been reported.

You Yu; Zhai Pengwang; Kattawar, George W.; Yang Ping

2009-06-01

440

Predicting age of ovarian failure after radiation to a field that includes the ovaries  

SciTech Connect

Purpose: To predict the age at which ovarian failure is likely to develop after radiation to a field that includes the ovary in women treated for cancer. Methods and Materials: Modern computed tomography radiotherapy planning allows determination of the effective dose of radiation received by the ovaries. Together with our recent assessment of the radiosensitivity of the human oocyte, the effective surviving fraction of primordial oocytes can be determined and the age of ovarian failure, with 95% confidence limits, predicted for any given dose of radiotherapy. Results: The effective sterilizing dose (ESD: dose of fractionated radiotherapy [Gy] at which premature ovarian failure occurs immediately after treatment in 97.5% of patients) decreases with increasing age at treatment. ESD at birth is 20.3 Gy; at 10 years 18.4 Gy, at 20 years 16.5 Gy, and at 30 years 14.3 Gy. We have calculated 95% confidence limits for age at premature ovarian failure for estimated radiation doses to the ovary from 1 Gy to the ESD from birth to 50 years. Conclusions: We report the first model to reliably predict the age of ovarian failure after treatment with a known dose of radiotherapy. Clinical application of this model will enable physicians to counsel women on their reproductive potential following successful treatment.

Wallace, W. Hamish B. [Section of Child Life and Health, Department of Reproductive and Developmental Sciences, University of Edinburgh, Edinburgh, Scotland (United Kingdom)]. E-mail: Hamish.Wallace@ed.ac.uk; Thomson, Angela B. [Royal Hospital for Sick Children, Yorkhill, Glasgow, Scotland (United Kingdom); Saran, Frank [Royal Marsden NHS Trust Foundation, Sutton (United Kingdom); Kelsey, Tom W. [School of Computer Science, University of St. Andrews, St. Andrews, Scotland (United Kingdom)

2005-07-01

441

Radiation induced precursor flow field ahead of a Jovian entry body  

NASA Technical Reports Server (NTRS)

The change in flow properties ahead of the bow shock of a Jovian entry body, resulting from absorption of radiation from the shock layer, is investigated. Ultraviolet radiation is absorbed by the free stream gases, causing dissociation, ionization, and an increase in enthalpy of flow ahead of the shock wave. As a result of increased fluid enthalpy, the entire flow field in the precursor region is perturbed. The variation in flow properties is determined by employing the small perturbation technique of classical aerodynamics as well as the thin layer approximation for the preheating zone. By employing physically realistic models of radiative transfer, solutions are obtained for velocity, pressure, density, temperature, and enthalpy variations. The results indicate that the precursor flow effects, in general, are greater at higher altitudes. Just ahead of the shock, however, the effects are larger at lower altitudes. Pre-heating of the gas significantly increases the static pressure and temperature ahead of the shock for velocities exceeding 36 km/sec.

Tiwari, S.; Szema, K. Y.

1977-01-01

442

Near-field radiative heat transfer across a pore and its effects on thermal conductivity of mesoporous silica  

NASA Astrophysics Data System (ADS)

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.

Li, Jing; Feng, Yanhui; Zhang, Xinxin; Huang, Congliang; Wang, Ge

2015-01-01

443

Adjuvant paclitaxel and carboplatin chemotherapy with involved field radiation in advanced endometrial cancer: A sequential approach  

SciTech Connect

Purpose: To determine the feasibility of adjuvant paclitaxel and carboplatin chemotherapy interposed with involved field radiotherapy for women with advanced endometrial cancer. Methods and Materials: This was a prospective cohort study of women with Stage III and IV endometrial cancer. Adjuvant therapy consisted of 4 cycles of paclitaxel (175 mg/m{sup 2}) and carboplatin (350 mg/m{sup 2}) every 3 weeks, followed sequentially by external beam radiotherapy (RT) to the pelvis (45 Gy), followed by an additional two cycles of chemotherapy. Para-aortic RT and/or HDR vault brachytherapy (BT) were added at the discretion of the treating physician. Results: Thirty-three patients (median age, 63 years) received treatment between April 2002 and June 2005. Median follow-up was 21 months. Stage distribution was as follows: IIIA (21%), IIIC (70%), IVB (9%). Combination chemotherapy was successfully administered to 30 patients (91%) and 25 patients (76%), before and after RT respectively. Nine patients (27%) experienced acute Grade 3 or 4 chemotherapy toxicities. All patients completed pelvic RT; 19 (58%) received standard 4-field RT and 14 (42%) received intensity-modulated radiotherapy. Ten (30%) received extended field radiation. Four patients (12%) experienced acute Grade 3 or 4 RT toxicities. Six (18%) patients developed chronic RT toxicity. There were no treatment-related deaths. Two-year disease-free and overall survival rates were both 55%. There was only one pelvic relapse (3%). Conclusions: Adjuvant treatment with combination chemotherapy interposed with involved field radiation in advanced endometrial cancer was well tolerated. This protocol may be suitable for further evaluation in a clinical trial.

Lupe, Krystine [Department of Radiation Oncology, University of Western Ontario and London Health Sciences Centre, London, Ontario (Canada); Kwon, Janice [Division of Gynecologic Oncology, University of Western Ontario and London Health Sciences Centre, London, Ontario (Canada)]. E-mail: Janice.kwon@lhsc.on.ca; D'Souza, David [Department of Radiation Oncology, University of Western Ontario and London Health Sciences Centre, London, Ontario (Canada); Gawlik, Christine [Department of Pharmacy, University of Western Ontario and London Health Sciences Centre, London, Ontario (Canada); Stitt, Larry [Department of Biostatistics and Epidemiology, University of Western Ontario and London Health Sciences Centre, London, Ontario (Canada); Whiston, Frances [Clinical Cancer Research Program, University of Western Ontario and London Health Sciences Centre, London, Ontario (Canada); Nascu, Patricia [Department of Obstetrics and Gynecology, University of Western Ontario and London Health Sciences Centre, London, Ontario (Canada); Wong, Eugene [Department of Radiation Oncology, University of Western Ontario and London Health Sciences Centre, London, Ontario (Canada); Carey, Mark S. [Division of Gynecologic Oncology, University of Western Ontario and London Health Sciences Centre, London, Ontario (Canada)

2007-01-01

444

A prototype scintillation dosimeter customized for small and dynamic megavoltage radiation fields  

NASA Astrophysics Data System (ADS)

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 × 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.

Lambert, Jamil; Yin, Yongbai; McKenzie, David R.; Law, Susan H.; Ralston, Anna; Suchowerska, Natalka

2010-02-01

445

Background X-ray Radiation Fields Produced by Young Embedded Star Clusters  

NASA Astrophysics Data System (ADS)

Most star formation in our galaxy occurs within embedded clusters, and these background environments can affect the star and planet formation processes occurring within them. In turn, young stellar members can shape the background environment and thereby provide a feedback mechanism. This work explores one aspect of stellar feedback by quantifying the background X-ray radiation fields produced by young stellar objects. Specifically, the distributions of X-ray luminosities and X-ray fluxes produced by cluster environments are constructed as a function of cluster membership size N. Composite flux distributions, for given distributions of cluster sizes N, are also constructed. The resulting distributions are wide and the X-ray radiation fields are moderately intense, with the expected flux levels exceeding the cosmic and galactic X-ray backgrounds by factors of ˜10-1000 (for energies 0.2--15 keV). For circumstellar disks that are geometrically thin and optically thick, the X-ray flux from the background cluster dominates that provided by a typical central star in the outer disk where r ? 9-14 AU. In addition, the expectation value of the ionization rate provided by the cluster X-ray background is ?X ˜ 8 × 10-17 s-1, about 4-8 times larger than the canonical value of the ionization rate from cosmic rays. These elevated flux levels in clusters indicate that X-rays can affect ionization, chemistry, and heating in circumstellar disks and in the material between young stellar objects.

Adams, Fred C.; Fatuzzo, Marco; Holden, Lisa

2012-09-01

446

Inner Magnetosphere Modeling at the CCMC: Ring Current, Radiation Belt and Magnetic Field Mapping  

NASA Astrophysics Data System (ADS)

Modeling of the inner magnetosphere has entered center stage with the launch of the Van Allen Probes (RBSP) in 2012. The Community Coordinated Modeling Center (CCMC) has drastically improved its offerings of inner magnetosphere models that cover energetic particles in the Earth's ring current and radiation belts. Models added to the CCMC include the stand-alone Comprehensive Inner Magnetosphere-Ionosphere (CIMI) model by M.C. Fok, the Rice Convection Model (RCM) by R. Wolf and S. Sazykin and numerous versions of the Tsyganenko magnetic field model (T89, T96, T01quiet, TS05). These models join the LANL* model by Y. Yu hat was offered for instant run earlier in the year. In addition to these stand-alone models, the Comprehensive Ring Current Model (CRCM) by M.C. Fok and N. Buzulukova joined as a component of the Space Weather Modeling Framework (SWMF) in the magnetosphere model run-on-request category. We present modeling results of the ring current and radiation belt models and demonstrate tracking of satellites such as RBSP. Calculations using the magnetic field models include mappings to the magnetic equator or to minimum-B positions and the determination of foot points in the ionosphere.

Rastaetter, L.; Mendoza, A. M.; Chulaki, A.; Kuznetsova, M. M.; Zheng, Y.

2013-12-01

447

A field methodology to study effects of UV radiation on fish larvae.  

PubMed

There is a considerable lack of in situ specific information about the effects of UV-B radiation on limnic animals studied in the field. We exposed larval pike (Esox lucius L.) in two types of cuvettes (glass and quartz) placed at different depths (5 or 15 cm) to natural solar UV or to artificially enhanced UV-B (lamps on 3 h per day), simulating the scenarios for coming decades. Dose realism and comparability with earlier laboratory experiments was the main purpose, and therefore UV-B irradiances to the surface as well as underwater irradiances were directly measured. Result showed that UV-B dose rates in natural waters are low even though DOC concentration was low (4.8 mg/l) in our study lake. A slight increase in ambient UV-B dose rates was enough to cause neurobehavioral symptoms in pike larvae. However, the dose rates applied were inadequate to affect superoxide dismutase (SOD) or HSP70. While assessing the suggested risks due to increased UV, conclusions emphasize the importance of conducting field UV studies as supplements to laboratory experiments. We also recommend direct measurements of UV-radiation at sites where the target organisms are actually exposed. PMID:15223283