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1

Titan's Magnetic Field Signature During the First Cassini Encounter  

Microsoft Academic Search

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

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

2005-01-01

2

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

NASA Technical Reports Server (NTRS)

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

Barengoltz, J. B.

1972-01-01

3

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

4

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

5

Gamma radiation field intensity meter  

DOEpatents

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

Thacker, L.H.

1995-10-17

6

Field of a Radiation Distributuion  

E-print Network

General relativistic spherically symmetric matter field with a vanishing stress energy scalar is analyzed. Procedure for generating exact solutions of the field equations for such matter distributions is given. It is further pointed out that all such type I spherically symmetric fields with distinct eignvalues in the radial two space can be treated as a mixture of isotropic and directed radiations. Various classes of exact solutions are given. Junction conditions for such a matter field to the possible exterior solutions are also discussed.

I. H. Dwivedi

1997-10-12

7

Radiation Fields on Schwarzschild Spacetime  

NASA Astrophysics Data System (ADS)

In this paper we define the radiation field for the wave equation on the Schwarzschild black hole spacetime. In this context it has two components: the rescaled restriction of the time derivative of a solution to null infinity and to the event horizon. In the process, we establish some regularity properties of solutions of the wave equation on the spacetime. In particular, we prove that the regularity of the solution across the event horizon and across null infinity is determined by the regularity and decay rate of the initial data at the event horizon and at infinity. We also show that the radiation field is unitary with respect to the conserved energy and prove support theorems for each piece of the radiation field.

Baskin, Dean; Wang, Fang

2014-10-01

8

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

E-print Network

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

Emanuele Berti; Vitor Cardoso; Tanja Hinderer; Madalena Lemos; Frans Pretorius; Ulrich Sperhake; Nicolas Yunes

2010-03-03

9

Solution of an integral equation encountered in studies on radiative transfer in completely absorbing leaf canopies  

NASA Technical Reports Server (NTRS)

The leaf normal distribution function is related to the extinction coefficient of direct solar radiation by a Fredholm integral equation of the first kind. The integral equation is solved by the method of constrained least squares. The solutions are stable and correct only in extreme cases and, in general, it is not possible to recover an arbitrary leaf normal distribution function.

Myneni, Ranga B.; Kanemasu, Edward T.; Asrar, Ghassem

1988-01-01

10

GSM 900 MHz radiation inhibits ants' association between food sites and encountered cues.  

PubMed

The kinetics of the acquisition and loss of the use of olfactory and visual cues were previously obtained in six experimental colonies of the ant Myrmica sabuleti meinert 1861, under normal conditions. In the present work, the same experiments were conducted on six other naive identical colonies of M. sabuleti, under electromagnetic radiation similar to those surrounding GSM and communication masts. In this situation, no association between food and either olfactory or visual cues occurred. After a recovery period, the ants were able to make such an association but never reached the expected score. Such ants having acquired a weaker olfactory or visual score and still undergoing olfactory or visual training were again submitted to electromagnetic waves. Not only did they lose all that they had memorized, but also they lost it in a few hours instead of in a few days (as under normal conditions when no longer trained). They kept no visual memory at all (instead of keeping 10% of it as they normally do). The impact of GSM 900 MHz radiation was greater on the visual memory than on the olfactory one. These communication waves may have such a disastrous impact on a wide range of insects using olfactory and/or visual memory, i.e., on bees. PMID:22268919

Cammaerts, Marie-Claire; De Doncker, Philippe; Patris, Xavier; Bellens, François; Rachidi, Zoheir; Cammaerts, David

2012-06-01

11

Quantization of the Radiation Field  

Microsoft Academic Search

Quantum theory was born on December 14th, 1900, when Max Planck proposed the quantum hypothesis. In order to explain the frequency\\u000a distribution of electromagnetic radiation from a cavity surrounded by walls of temperature T, Planck postulated that the exchange of energy between the walls and the field takes place as the absorption and emission\\u000a of electromagnetic energy with a discrete

Eiichi Hanamura; Yutaka Kawabe; Akio Yamanaka

12

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.

13

Electrifying Encounters  

NSDL National Science Digital Library

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

Ebbers, Margaretha; Cross, Sandy

1999-09-01

14

221B Lecture Notes Quantum Field Theory III (Radiation Field)  

E-print Network

221B Lecture Notes Quantum Field Theory III (Radiation Field) 1 Quantization of Radiation Field Early development of quantum mechanics was led by the fact that electro- magnetic radiation is the convenient choice, while for highly rel- ativistic systems such as in high-energy physics. We use Coulomb

Murayama, Hitoshi

15

221B Lecture Notes Quantum Field Theory IV (Radiation Field)  

E-print Network

221B Lecture Notes Quantum Field Theory IV (Radiation Field) 1 Quantization of Radiation Field Early development of quantum mechanics was led by the fact that electro- magnetic radiation is the convenient choice, while for highly rel- ativistic systems such as in high-energy physics. We use Coulomb

Murayama, Hitoshi

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

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

18

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

19

Gravitational radiative corrections from effective field theory  

SciTech Connect

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

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

2010-06-15

20

Planetary encounters  

Microsoft Academic Search

This book provides a nontechnical account of plans and possibilities for planetary encounters by unmanned space probes. Early ideas about space travel are reviewed along with the development of rocket technology and early satellite and unmanned-probe launches. Detailed attention is given to the Mariner, Viking, Pioneer Jupiter, Pioneer Venus multiprobe, and Voyager spacecraft, as well as to test vehicles, launch

R. M. Powers

1978-01-01

21

Tracing Magnetic Fields by Atomic Alignment in Extended Radiation Fields  

E-print Network

Tracing magnetic fields is crucial as magnetic fields play an important role in many astrophysical processes. Earlier studies have demonstrated that Ground State Alignment (GSA) is a unique way to detect weak magnetic fields (1G> B> 1exp(-15)G) in diffuse media, they consider the situation when the pumping source is a point source, which applies when the star is very far away from the diffuse media. In this paper, we explore the GSA in the presence of extended radiation fields. For the radiation fields with a clear geometric structure, we consider the alignment in circumstellar medium, binary systems, disc, and Local Interstellar Medium (LISM). For the radiation fields with unidentified pumping sources, we apply the method of multipole expansion and discuss the GSA induced by each component. We demonstrate that for general radiation fields, it is adequate to consider the contribution from dipole and quadrupole radiation components. We find that in general polarization of absorption arizing from GSA coincides ...

Zhang, Heshou; Dong, Le

2014-01-01

22

Chance encounters.  

PubMed

How can physician executives change their thinking and expand their understanding? Chance encounters offer a way to draw on others' unique experiences and patterns of thought unknown to us and have our usual way of thinking challenged and sometimes shattered--one of life's most powerful experiences. After reflecting on three optimal personal learning experiences from a recent conference, the author determines that the only common thread is the interdisciplinary thoughts expressed by a passionately involved individual whose approach to the problem is completely different from his own. These conferences offer the inquisitive physician entrepreneur the opportunity to hear how venture capitalists, population geneticists, business development experts, biotech CEOs, and big pharma scientists view the potential of the sequencing of the human genome to change medicine. Being able to see the world in a new way, the author concludes, is tied to the essence of entrepreneurship and the essence of joyful living. PMID:11387898

Bottles, K

2001-01-01

23

Measurement of ESD-gun radiated fields  

Microsoft Academic Search

Transient radiated fields from an ESD-gun are measured. Experimental results show that very strong transient electromagnetic fields exist nearby the ESD-gun. In the system level ESD test (IEC 61000-4-2) applied to devices, this transient field is directly coupled to printed circuit assembly traces and associated signal\\/power cables through space, which produce less accurate data.

Masamitsu Honda

2007-01-01

24

Radiation effects on current field programmable technologies  

Microsoft Academic Search

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

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

1997-01-01

25

Chemical Processes in Astrophysical Radiation Fields  

SciTech Connect

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

Stancil, P.C.; Dalgarno, A.

1997-12-31

26

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.

Bini, Donato

2014-01-01

27

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

28

Effects of impurity radiation on reversed-field pinch evolution  

SciTech Connect

The effects of impurity radiation on the evolution of a reversed-field pinch plasma are studied by means of a one-dimensional MHD simulation code that includes both plasma transport and impurity effects, and follows the plasma through a series of equilibrium states. The equations are split into two sets, one that contains plasma transport and another that contains atomic physics effects. Two codes were developed and linked together to solve the full problem. Results are presented for the ZT-S, ZT-40, and RFX experiments with a fixed set of parameters, typical or envisioned, and various concentrations of impurities. Radiation barriers are encountered, and limits are found on the acceptable level of low Z impurities that may be present in these devices. It is shown that the temperatures currently observed in the ZT-S experiment are radiation limited. Next, a criterion for radiation barrier burn-through is derived in terms of appropriate nondimensional parameters and calibrated by comparison to the numerical simulations for the case of oxygen.

Caramana, E.J.; Perkins, F.W.

1980-01-01

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

Symmetries of Type D 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 D 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 introduced and the conditions under which PR type D 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 D pure radiation fields admit Maxwell collineation along the propagation vector l.

Ahsan, Zafar; Ali, Musavvir

2012-07-01

31

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

Microsoft Academic Search

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

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

2009-01-01

32

RADIATION FIELDS, SCATTERING AND INVERSE SCATTERING ...  

E-print Network

problems of mathematics and physics, which goes back to the work of Fadeev and Pavlov [8], .... satisfy (2.4) corresponding to two different conformal representatives. ...... See for example exercise 6.2 on page 52 of [51]. ..... This paper is dedicated to the memory of F.G. Friedlander, who started the study of radiation fields.

2006-12-26

33

Neptune encounter highlights  

NASA Astrophysics Data System (ADS)

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

1989-11-01

34

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

PubMed

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

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

2009-04-01

35

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

36

Automatic field shaping for conformal radiation therapy.  

PubMed

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

Ayyangar, K

1994-04-01

37

Cellular response to modulated radiation fields  

NASA Astrophysics Data System (ADS)

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

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

2007-09-01

38

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

39

RADIATION FIELDS, SCATTERING AND INVERSE SCATTERING ON ASYMPTOTICALLY HYPERBOLIC MANIFOLDS  

E-print Network

RADIATION FIELDS, SCATTERING AND INVERSE SCATTERING ON ASYMPTOTICALLY HYPERBOLIC MANIFOLDS ANT ^ONIO S´A BARRETO Abstract. We define the forward and backward radiation fields on an asymptotically to the one defined by stationary methods. Furthermore, we prove a support theorem for the radiation fields

Sá Barreto, Antônio

40

Reading the Other: Ethics of Encounter  

ERIC Educational Resources Information Center

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

Allen, Sarah

2008-01-01

41

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

NASA Astrophysics Data System (ADS)

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

Iyemori, T.; Araki, T.

42

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

43

Near-Field Radiative Cooling of Nanostructures Biswajeet Guha,  

E-print Network

Near-Field Radiative Cooling of Nanostructures Biswajeet Guha, Clayton Otey, Carl B. Poitras 14853, United States *S Supporting Information ABSTRACT: We measure near-field radiative cooling cooling capabilities. We show that the measured trend of radiative cooling agrees well theoretical

Lipson, Michal

44

Radiation field characterization and shielding studies  

NASA Astrophysics Data System (ADS)

The ELI-Beamlines facility in the Czech Republic will offer to users versatile radiation sources in an unprecedented energy range. Laser-driven proton beams are expected to range between 50 MeV and 3 GeV. The number of particles delivered per laser shot is estimated to be 1010-1012. Starting from analytical calculations, as well as from dedicated simulations, the main proton fields produced in the laser-matter interaction have been described and used to characterize the "source terms" in full simulations with the Monte Carlo code FLUKA in order to assess a proper shielding. We present the results of this study and the proposed solutions together with a cross-check analysis performed with the Monte Carlo code GEANT4.

Ferrari, A.; Amato, E.; Margarone, D.

2013-07-01

45

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

46

Voyager 1: Encounter with Saturn  

Microsoft Academic Search

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,

N. Panagakos

1980-01-01

47

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.

Bini, Donato; Haney, Maria; Jantzen, Robert T

2014-01-01

48

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

49

Internal Pulse Amplification in High Field, Silicon Radiation Detection Junctions  

Microsoft Academic Search

Significant internal pulse amplification has been observed in silicon p-n junction radiation detectors operated in the very high field (but prebreakdown) region. Such internal electric field values (peak fields of 60 - 250 kilovolts cm-1) are attainable over distances of up to 250 microns through the use of geometrical control of the field existing at the surface of the junction.

Gerald C. Huth; James B. Trice; James A. Shannon; Russell A. McKinney

1965-01-01

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

Radiation and photoelectron dynamics in ultrastrong laser fields  

Microsoft Academic Search

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

Isaac Ghebregziabher

2008-01-01

52

Angry Birds Space Encounter  

NASA Video Gallery

At NASA's Kennedy Space Center Visitor Complex in Florida, a grand opening celebration was held for the new Angry Birds Space Encounter, March 22. Finland-based Rovio Entertainment, the creator of ...

53

Curiosity: Sunglasses Encounter  

Microsoft Academic Search

Curiosity: Sunglasses Encounter, taken by Amy Aschenbrenner on the Linfield College Semester Abroad program in San Ramón, Costa Rica. 3rd place, Linfield Students Abroad division, in the 2012 Linfield College Study Abroad Photo Contest.

Amy Aschenbrenner

2011-01-01

54

Galileo: The Earth encounter  

NASA Technical Reports Server (NTRS)

The following subject areas are covered: Galileo Veega trajectory to Jupiter; lunar science objectives; Earth science objectives; Santa 2 data flow; Galileo - the U.S./Canada connections and European connections; UV spectrometer observations during close encounter periods; phase angle and cone angle of the Earth during the Earth encounters; Lunar orbit traverse at EGA1; Moon imaging - EGA1; Galileo imaging Earth after EGA1; and Earth 1 flyby geometry.

Clarke, Theodore C.

1991-01-01

55

Stretched exponential survival statistics for microorganisms in radiation field  

NASA Astrophysics Data System (ADS)

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

56

The amplification of magnetic fields during the radiation ERA  

Microsoft Academic Search

During the radiation era the relative motion of the proton fluid and the electron-photon fluid generates a small magnetic field. Cosmic turbulence can amplify that seed field, but the extent of the amplification has not been certain. This paper addresses the amplification issue afresh. Spectral techniques are used to solve an evolutionary equation for a linear combination of magnetic field

R. Baierlein

1978-01-01

57

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

58

Radiated and nonradiated electromagnetic fields in an FEL amplifier  

Microsoft Academic Search

For a free-electron laser (FEL) amplifier model, which incorporates not only potential but also rotational nonradiated electromagnetic fields, we study the repercussions of account for those fields on the beam–microwave interaction. Equations of excitation for the radiated and nonradiated parts of the driven electromagnetic field are derived. A new analytical technique of approximate integration of the nonradiated part along the

V. A. Goryashko; K. Ilyenko; A. N. Opanasenko

2010-01-01

59

Radiated and nonradiated electromagnetic fields in an FEL amplifier  

Microsoft Academic Search

For a free-electron laser (FEL) amplifier model, which incorporates not only potential but also rotational nonradiated electromagnetic fields, we study the repercussions of account for those fields on the beam-microwave interaction. Equations of excitation for the radiated and nonradiated parts of the driven electromagnetic field are derived. A new analytical technique of approximate integration of the nonradiated part along the

V. A. Goryashko; K. Ilyenko; A. N. Opanasenko

2010-01-01

60

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

61

Radiation-Reaction Trapping of Electrons in Extreme Laser Fields  

E-print Network

A radiation-reaction trapping (RRT) of electrons is revealed in the near-QED regime of laser-plasma interaction. Electrons quivering in laser pulse experience radiation reaction (RR) recoil force by radiating photons. When the laser field reaches the threshold, the RR force becomes significant enough to compensate for the expelling laser ponderomotive force. Then electrons are trapped inside the laser pulse instead of being scattered off transversely and form a dense plasma bunch. The mechanism is demonstrated

Ji, L L; Kostyukov, I Yu; Shen, B F; Akli, K

2014-01-01

62

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

63

Hawking radiation of a vector field and gravitational anomalies  

NASA Astrophysics Data System (ADS)

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

Murata, Keiju; Miyamoto, Umpei

2007-10-01

64

ELECTRIC FIELDS, ELECTRON PRECIPITATION, AND VLF RADIATION  

Microsoft Academic Search

A balloon payload instrumented with thunderstorm dynamics (see Herman and Goldberg, a double-probe electric field detector and an X 1978; Markson, 1978; and references therein). ray scintillation counter was launched from This paper presents electric field, conducti- Roberval, Quebec, Canada (L = 4.1) at 0828 UT vity, and bremsstrahlung X ray data from a (0328 LT) on July 9, 1975.

E. A. Bering; T. J. Rosenberg; J. R. Benbrook; D. Detrick; D. L. Matthews; M. J. Rycroft; M. A. Saunders; W. R. Sheldon

1980-01-01

65

Radiation from Relativistic Shocks with Turbulent Magnetic Fields  

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

66

Alien Visitations Close Encounters  

E-print Network

Alien Visitations #12;#12;Close Encounters · I: Visual sighting of aerial object (UFO) · II damage · III: Direct observation of extraterrestrials · IV: Abduction #12;UFOs What is a UFO? ·All Sheaffer: http://www.debunker.com/ufo.html #12;#12;#12;Extraordinary Claims Require Extraordinary Evidence

Walter, Frederick M.

67

Gravitational radiation from preheating with many fields  

SciTech Connect

Parametric resonances provide a mechanism by which particles can be created just after inflation. Thus far, attention has focused on a single or many inflaton fields coupled to a single scalar field. However, generically we expect the inflaton to couple to many other relativistic degrees of freedom present in the early universe. Using simulations in an expanding Friedmann-Lemaître-Robertson-Walker spacetime, in this paper we show how preheating is affected by the addition of multiple fields coupled to the inflaton. We focus our attention on gravitational wave production — an important potential observational signature of the preheating stage. We find that preheating and its gravitational wave signature is robust to the coupling of the inflaton to more matter fields.

Jr, John T. Giblin [Department of Physics, Kenyon College, 201 North College Road, Gambier, OH 43022 (United States); Price, Larry R.; Siemens, Xavier, E-mail: giblinj@kenyon.edu, E-mail: larry@gravity.phys.uwm.edu, E-mail: siemens@gravity.phys.uwm.edu [Center for Gravitation and Cosmology, Department of Physics, University of Wisconsin — Milwaukee, P.O. Box 413, Milwaukee, WI 53201 (United States)

2010-08-01

68

Field distribution in a generalized geometric radiation state  

NASA Astrophysics Data System (ADS)

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

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

1995-03-01

69

Relativistic electron moving in a multimode quantized radiation field  

Microsoft Academic Search

We derive a set of exact solutions of the Dirac equation for a single electron moving in a multimode quantized radiation field. All the modes in this field are propagating in the same direction. Our method entails the application of the Lie-algebra procedure. We discuss the physical meaning and possible applications of these solutions.

Dong-Sheng Guo; Ju Gao; Amy Hwia-May Chu

1996-01-01

70

Visual verification of linac light and radiation fields coincidence  

SciTech Connect

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

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

2003-06-30

71

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

72

Spontaneous Radiation Emission from Short, High Field Strength Insertion Devices  

SciTech Connect

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

Geoffrey Krafft

2005-09-15

73

Radiation from sub-Larmor scale magnetic fields  

Microsoft Academic Search

Spontaneous rapid growth of strong magnetic fields is ubiquitous in high-energy density environments ranging from astrophysical sources and relativistic shocks, to reconnection, to laser-plasma interaction laboratory experiments, where they are produced by kinetic streaming instabilities of the Weibel type. Relativistic electrons propagating through these sub-Larmor-scale magnetic fields radiate in the jitter regime, in which the anisotropy of the magnetic fields

M. V. Medvedev; J. T. Frederiksen; T. Haugbølle; Å. Nordlund

2010-01-01

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

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

76

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

77

IAEA programme in the field of radiation technology  

NASA Astrophysics Data System (ADS)

Radiation technologies applying gamma sources and electron accelerators for material modification are well-established processes. There are over 160 gamma industrial irradiators and 1300 electron industrial accelerators in operation worldwide. A new advancement in the field of radiation sources engineering is the development of high power direct e-/X conversion sources based on electron accelerators. Technologies to be developed beside environmental applications could be nanomaterials, structure engineered materials (sorbents, composites, ordered polymers, etc.) and natural polymers' processing. New products based on radiation-processed polysaccharides have already been commercialised in many countries of the East Asia and Pacific Region, especially in those being rich in natural polymers. Very important and promising applications concern environmental protection-radiation technology, being a clean and environment friendly process, helps to curb pollutants' emission as well. Industrial plants for flue gas treatment have been constructed in Poland and China. The pilot plant in Bulgaria using this technology has just started its operation. The Polish plant is equipped with accelerators of over 1 MW power, a breakthrough in radiation technology application. The industrial plant for wastewater treatment is under development in Korea and a pilot plant for sewage sludge irradiation has been in operation in India for many years. Due to recent developments, the Agency has restructured its programme and organized a Technical Meeting (TM) on "Emerging Applications of Radiation Technology for the 21st Century" at its Headquarters in Vienna, Austria, in April 2003, to review the present situation and possible developments of radiation technology to contribute to a sustainable development. This meeting provided the basic input to launch others in the most important fields of radiation technology applications: "Advances in Radiation Chemistry of Polymers" (Notre Dame, USA, September 2003), "Status of Industrial Scale Radiation Treatment of Wastewater" (Taejon, Republic of Korea, October 2003), "Radiation Processing of Polysaccharides" (Takasaki, Japan, November 2003), "Emerging Applications of Radiation in Nanotechnology" (Bologna, Italy, March 2004) and "Radiation Processing of Gaseous and Liquid Effluents" (Sofia, Bulgaria, September 2004). The Agency is presently supervising three Coordinated Research Projects on radiation wastewater treatment, radiation synthesis stimuli-responsive hydrogels for separation purposes and degradation effects of polymers. The role of this technology for a sustainable development is well illustrated by the fact that over 30 technical cooperation projects (including three regional ones) were accomplished in the years 2003-2004 and several new projects are being expected for the new cycle 2005-2006. Detailed analyses of the results of both, regular and TC programmes, laid the foundation for formulation of the new programme for the years 2006-2007. The emphasis will be put on nanotechnology, natural polymers, environment and health protection, including combat with hazardous bioagents.

Chmielewski, Andrzej G.; Haji-Saeid, Mohammad

2005-07-01

78

Voyager Encounter Highlights  

NASA Technical Reports Server (NTRS)

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

1989-01-01

79

Light scattering by radiation fields: the optical medium analogy  

E-print Network

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

Donato Bini; Pierluigi Fortini; Andrea Geralico; Maria Haney; Antonello Ortolan

2014-08-23

80

Black Hole Evaporation and Nonequilibrium Thermodynamics for a Radiation Field  

E-print Network

When a black hole is put in an "empty" space (zero temperature space) on which there is no matter except the matter of the Hawking radiation (Hawking field), then an outgoing energy flow from the black hole into the empty space exists. By the way, an equilibrium between two arbitrary systems can not allow the existence of an energy (heat) flow from one system to another. Consequently, in the case of a black hole evaporation in the empty space, the Hawking field should be in a nonequilibrium state. Hence the total behaviour of the evaporation, for example the time evolution of the total entropy, should be analysed with a nonequilibrium thermodynamics for the Hawking field. This manuscript explains briefly the way of constructing a nonequilibrium thermodynamic theory for a radiation field, and apply it to a simplified model of a black hole evaporation to calculate the time evolution of the total entropy.

Hiromi Saida

2005-05-18

81

Radiation Signatures of Sub-Larmor Scale Magnetic Fields  

Microsoft Academic Search

Spontaneous rapid growth of strong magnetic fields is rather ubiquitous in high-energy density environments ranging from astrophysical sources (e.g., gamma-ray bursts and relativistic shocks), to reconnection, to laser-plasma interaction laboratory experiments, where they are produced by kinetic streaming instabilities of the Weibel type. Relativistic electrons propagating through these sub-Larmor-scale magnetic fields radiate in the jitter regime, in which the anisotropy

Mikhail V. Medvedev; Jacob Trier Frederiksen; Troels Haugboelle; Åke Nordlund

2011-01-01

82

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

83

Radiation-Reaction Trapping of Electrons in Extreme Laser Fields  

NASA Astrophysics Data System (ADS)

A radiation-reaction trapping (RRT) of electrons is revealed in the near-QED regime of laser-plasma interaction. Electrons quivering in laser pulse experience radiation reaction (RR) recoil force by radiating photons. When the laser field reaches the threshold, the RR force becomes significant enough to compensate for the expelling laser ponderomotive force. Then electrons are trapped inside the laser pulse instead of being scattered off transversely and form a dense plasma bunch. The mechanism is demonstrated both by full three-dimensional particle-in-cell simulations using the QED photonic approach and numerical test-particle modeling based on the classical Landau-Lifshitz formula of RR force. Furthermore, the proposed analysis shows that the threshold of laser field amplitude for RRT is approximately the cubic root of laser wavelength over classical electron radius. Because of the pinching effect of the trapped electron bunch, the required laser intensity for RRT can be further reduced.

Ji, L. L.; Pukhov, A.; Kostyukov, I. Yu.; Shen, B. F.; Akli, K.

2014-04-01

84

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

2005-09-13

85

Real-Time Display of Radiation Field Intensity Distribution.  

National Technical Information Service (NTIS)

A real-time display system has been designed and tested for use with a radiation field monitor. The system uses only pulse and wave-form generators, a multiplexer and an oscilloscope. The display consits of either a three-dimensional representation of the...

P. A. Berardo, J. A. Willis

1973-01-01

86

Nanodosimetric Characterization of Mixed Radiation Fields: Status and Perspectives  

NASA Astrophysics Data System (ADS)

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

Schulte, Reinhard; Bashkirov, Vladimir; Casiraghi, Margherita

87

Stochastic theory of radiative transfer through generalized cloud fields  

NASA Astrophysics Data System (ADS)

We present a coherent treatment, based on linear kinetic theory, of stochastic radiative transfer in an atmosphere containing clouds. A brief summary of statistical cloud radiation models is included. We explore the sensitivities inherent in the stochastic approach by using a well-known plane-parallel model developed by Fouquart and Bonnel together with our own stochastic model which generalizes earlier work of F. Malvagi, R. N. Byrne, G. C. Pomraning, and R. C. J. Somerville. In overcast conditions, in comparison to the plane parallel model, the stochastic model underestimates transmittance at small optical depths (<7) and overestimates transmittance at large optical depths. The stochastic model is strongly sensitive to cloud optical properties, including cloud water content and cloud droplet effective radius. The extension of the stochastic approach to an atmospheric general circulation model parameterization appears to be most appropriate for cloud fraction ranging from 25 to 70%. We conclude that stochastic theory holds substantial promise as a modeling approach for calculating shortwave radiative transfer through partially cloudy fields. Unlike cloud-resolving models and Monte Carlo cloud models, stochastic cloud models do not depend on specific realizations of the cloud field. Instead, they calculate the transfer of radiation through a cloudy atmosphere whose properties are known statistically in the form of probability density functions characterizing cloud geometry and cloud optical properties. The advantage of the stochastic approach is its theoretical generality and its potential for representing a complex cloud field realistically at modest computational cost.

Lane-Veron, Dana E.; Somerville, Richard C. J.

2004-09-01

88

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

89

Anomalous Radiative Trapping in Laser Fields of Extreme Intensity  

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

90

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

91

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

NASA Astrophysics Data System (ADS)

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

Reynolds, Sarah J.

92

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

2012-04-25

93

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

94

Importance of radiation field screening in XPS and XAFS spectra  

NASA Astrophysics Data System (ADS)

In this work the importance of radiation field screening is stressed in Keldysh's Green's function theory to study X-ray photoelectron spectroscopy (XPS) spectra and X-ray absorption fine structure (XAFS). So far these terms have been supposed to be small, however, we have found that these effects play a crucial role to analyze resonance effects. In particular the importance of these vertex correction is important in the analyses of multiatom resonant photoemission (MARPE) spectra and the resonance effects in XAFS. We also investigate the contribution from polarized part Wp of the screened Coulomb interaction W to the resonance effects. We find that W? v is quite a good approximation. Off the resonance these radiation field screening diagrams are not important. They have no contribution to loss processes even though they include W> and W<.

Fujikawa, Takashi; Arai, Hiroko

2003-01-01

95

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

96

Field-deployable gamma-radiation detectors for DHS use  

Microsoft Academic Search

Recently, the 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 off-the-shelf and government off-the-shelf radiation detection equipment and data acquisition systems. This article would investigate several recent developments in field deployable

Sanjoy Mukhopadhyay

2007-01-01

97

SCATTERED GAMMA RADIATION MEASUREMENTS FROM A LANTHANUM140 CONTAMINATED FIELD  

Microsoft Academic Search

A 90 deg sector of a circle of approximately 500-foot radius was ; contaminated with-a La¹⁴° aqueous solution to an approximate level of 0.65 ; millicuries per square foot as a means of simulating an area approaching an ; infinite contaminated field. Radiation measurements were made in an open hole ; with a PDR-27A radiac instrument to determine the percentage

C. L. Schlemm; A. A. Jr. Anthony

1959-01-01

98

Cosmological perturbations for an inflaton field coupled to radiation  

E-print Network

Within the framework of the interacting fluid formalism, we provide the numerical solution to the Boltzmann equation describing the evolution of an inflaton field coupled to radiation. We study the behavior of the system during the slow-roll regime, in the case in which an additional stochastic source term is included in the set of equations, and we recover the expression for the cosmological perturbations previously obtained in the Warm inflation scenarios.

Visinelli, Luca

2014-01-01

99

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

100

Radiation from sub-Larmor scale magnetic fields  

Microsoft Academic Search

Spontaneous rapid growth of strong magnetic fields is rather ubiquitous in\\u000ahigh-energy density environments ranging from astrophysical sources (e.g.,\\u000agamma-ray bursts and relativistic shocks), to reconnection, to laser-plasma\\u000ainteraction laboratory experiments, where they are produced by kinetic\\u000astreaming instabilities of the Weibel type. Relativistic electrons propagating\\u000athrough these sub-Larmor-scale magnetic fields radiate in the jitter regime, in\\u000awhich the anisotropy

Mikhail V. Medvedev; Jacob Trier Frederiksen; Troels Haugboelle; Aake Nordlund

2010-01-01

101

Radiation from electrons in graphene in strong electric field  

NASA Astrophysics Data System (ADS)

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.

Yokomizo, N.

2014-12-01

102

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.

Yokomizo, N

2014-01-01

103

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

104

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

105

Close encounters with DNA.  

PubMed

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

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

2014-10-15

106

Close encounters with DNA  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

107

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

108

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

109

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

110

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

111

Tactics for promoting sexual encounters  

Microsoft Academic Search

Through empirical studies we explored the perceived effectiveness and reported usage of tactics to promote sexual encounters. In the first study (N = 58) we identified 122 acts and 34 tactics for promoting sexual encounters. In the second study (N = 50) we examined the perceived effectiveness of each tactic when used by a man and when used by a

Arlette E. Greer; David M. Buss

1994-01-01

112

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

113

Cyclotron Line Features from Near-Critical Fields II: on the Effect of Anisotropic Radiation Fields  

E-print Network

We assess the impact of radiation anisotropy on the line shapes that result from relativistic magnetic Compton scattering in the low-density/high-field regime. A Monte Carlo implementation of radiation transport allows for spatial diffusion of photons in arbitrary geometries and accounts for relativistic angular redistribution. The cross section includes natural line widths and photon "spawning" from up to fourth harmonic photons. In our first paper we noted that even if the photon injection is isotropic a strongly anisotropic radiation field rapidly ensues. We now investigate the angular distribution of cyclotron spectra emerging from an internally irradiated magnetized plasma with a prescribed global geometry (either cylindrical or plane parallel) and the effects of anisotropic photon injection on the line shapes. Varying the input angular distribution permits a better understanding of the line formation process in more realistic scenarios where the radiative mechanisms are influenced by the intrinsic anisotropy of the field and by moderate relativistic beaming. In general, the line features are most pronounced along the directions of the anisotropic continuum injection and tend to be weakened in other directions, relative to the line features resulting from an isotropic continuum injection. We find that the enhancements at the line wings of the fundamental, which appear prominantly in the case of isotropic continuum injection, are strongly suppressed along the direction of anisotropy in the case of beamed continuum injection, regardless of geometry or beaming pattern.

Rafael A. Araya-Gochez; Alice K. Harding

2000-07-13

114

Cosmic Radiation Fields: Sources in the early Universe  

NASA Astrophysics Data System (ADS)

The workshop "Cosmic Radiation Fields - Sources in the Early Universe" (CRF 2010) focuses on the connection between the extragalactic infrared background and sources in the early universe, in particular stars powered by dark matter burning (Dark Stars; DS). The workshop covers the following topics: the cosmic infrared background, formation of early stars, dark stars, effect of dark matter in the early universe, dark matter halos, primordial star formation rate, and reionization. Further information can be found on the conference webpage: http://www.desy.de/crf2010/. Organizing committee: Tanja Kneiske, Martin Raue, Dominik Elsaesser, Alexander Gewering-Peine, Peter Hausschildt, Dieter Horns, and Andreas Maurer.

Raue, Martin; Kneiske, Tanja; Horns, Dieter; Elsaesser, Dominik; Hauschildt, Peter

115

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

2003-07-22

116

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

117

Concurrent field enhancement and high transmission of THz radiation in nanoslit arrays  

NASA Astrophysics Data System (ADS)

We experimentally and numerically investigate the transmission of THz radiation through uniform nanoslit arrays. These structures are capable of inducing plasmon-mediated field enhancement while concurrently providing high field transmission. Combined with intense THz radiation, estimated field strengths as high as 26 MV/cm are obtained in the near-field regime which will facilitate nonlinear THz experiments.

Shalaby, Mostafa; Merbold, Hannes; Peccianti, Marco; Razzari, Luca; Sharma, Gargi; Ozaki, Tsuneyuki; Morandotti, Roberto; Feurer, Thomas; Weber, Anja; Heyderman, Laura; Patterson, Bruce; Sigg, Hans

2011-07-01

118

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

119

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

120

Voyager encounters Saturn: Scientific highlights  

NASA Technical Reports Server (NTRS)

Observations generated by Voyager 1's encounter with Saturn are disclosed. Atmospheric conditions, the rings, new moons and the five inner moons are described. Titan, Hyperion and Iapetus are discussed in detail, as is Saturn's magnetosphere.

1980-01-01

121

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

SciTech Connect

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

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

2010-05-15

122

Classical calculation of radiative lifetimes of atomic hydrogen in a homogeneous magnetic field  

SciTech Connect

Radiative lifetimes of hydrogenic atoms in a homogeneous magnetic field of moderate strength are calculated on the basis of classical radiation. The modifications of the Keplerian orbits due to the magnetic field are incorporated by classical perturbation theory. The model is complemented by a classical radiative decay calculation using the radiated Larmor power. A recently derived highly accurate formula for the transition rate of a field-free hydrogenic state is averaged over the angular momentum oscillations caused by the magnetic field. The resulting radiative lifetimes for diamagnetic eigenstates classified by n,m and the diamagnetic energy shift C compare well with quantum results.

Horbatsch, M.W.; Hessels, E.A.; Horbatsch, M. [Department of Physics and Astronomy, York University, 4700 Keele Street, Toronto, Ontario, M3J 1P3 (Canada)

2005-09-15

123

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.,

124

Transition radiation from an ultrarelativistic particle in an external field at grazing emission angles  

SciTech Connect

The effect of an external field on the transition radiation from an ultrarelativistic particle is considered at grazing emission angles. The angular and frequency distribution of transition radiation is found. It is shown that the external field substantially increases the angular asymmetry of transition radiation at grazing emission angles.

Ivliev, S. V.; Ryazanov, M. I.; Strikhanov, M. N. [Moscow Engineering Physics Institute (State University) (Russian Federation)

2006-05-15

125

Space radiation dosimetry in low-Earth orbit and beyond  

Microsoft Academic Search

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

E. R. Benton; E. V. Benton

2001-01-01

126

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

2011-05-24

127

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

128

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

129

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

130

Field test of a post-closure radiation monitor  

SciTech Connect

The DOE is conducting remedial actions at many sites contaminated with radioactive materials. After closure of these sites, long-term subsurface monitoring is typically required by law. This monitoring is generally labor intensive and expensive using conventional sampling and analysis techniques. The U.S. Department of Energy`s Morgantown Energy Technology Center (METC) has contracted with Babcock and Wilcox to develop a Long-Term Post-Closure Radiation Monitoring System (LPRMS) to reduce these monitoring costs. A prototype LPRMS probe was built, and B&W and FERMCO field tested this monitoring probe at the Fernald Environmental Management Project in the fall of 1994 with funding from the DOE`s Office of Technology Development (EM-50) through METC. The system was used to measure soil and water with known uranium contamination levels, both in drums and in situ at depths up to 3 meters. For comparison purposes, measurements were also performed using a more conventional survey probe with a sodium iodide scintillator directly butt-coupled to detection electronics. This paper presents a description and the results of the field tests. The results were used to characterize the lower detection limits, precision and bias of the system, which allowed the DOE to judge the monitoring system`s ability to meet its long-term post-closure radiation monitoring needs. Based on the test results, the monitoring system has been redesigned for fabrication and testing in a potential Phase III of this program. If the DOE feels that this system can meet its needs and chooses to continue into Phase III of this program, this redesigned full scale prototype system will be built and tested for a period of approximately a year. Such a system can be used at a variety of radioactively contaminated sites.

Reed, S. [Babcock & Wilcox, Alliance, OH (United States); Christy, C.E. [Morgantown Energy Technology Center, WV (United States); Heath, R.E. [FERMCO, Cincinnati, OH (United States)

1995-12-01

131

Voyager flight engineering preparations for Neptune encounter  

NASA Technical Reports Server (NTRS)

Voyager 2 will make the first close observations of the planet Neptune, during the period from June 1 to October 1,1989. A number of flight engineering activities are being conducted in preparation for the encounter. This paper discusses the most significant of these activities: new image motion compensation techniques, attitude control system changes, new exposure capabilities, new data handling capabilities, radiation protection measures, and new navigation methods. In addition, the process of performing late sequence updates is discussed. An overview of the Neptune mission is also presented.

Miller, L. J.; Savary, K. E.

1988-01-01

132

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

133

Simulation of Van Allen Probes plasmapause encounters  

NASA Astrophysics Data System (ADS)

We use an E × B-driven plasmapause test particle (PTP) simulation to provide global contextual information for in situ measurements by the Van Allen Probes (Radiation Belt Storm Probes (RBSP)) during 15-20 January 2013. During 120 h of simulation time beginning on 15 January, geomagnetic activity produced three plumes. The third and largest simulated plume formed during enhanced convection on 17 January, and survived as a rotating, wrapped, residual plume for tens of hours. To validate the simulation, we compare its output with RBSP data. Virtual RBSP satellites recorded 28 virtual plasmapause encounters during 15-19 January. For 26 of 28 (92%) virtual crossings, there were corresponding actual RBSP encounters with plasmapause density gradients. The mean difference in encounter time between model and data is 36 min. The mean model-data difference in radial location is 0.40 ± 0.05 RE. The model-data agreement is better for strong convection than for quiet or weakly disturbed conditions. On 18 January, both RBSP spacecraft crossed a tenuous, detached plasma feature at approximately the same time and nightside location as a wrapped residual plume, predicted by the model to have formed 32 h earlier on 17 January. The agreement between simulation and data indicates that the model-provided global information is adequate to correctly interpret the RBSP density observations.

Goldstein, J.; Pascuale, S. De; Kletzing, C.; Kurth, W.; Genestreti, K. J.; Skoug, R. M.; Larsen, B. A.; Kistler, L. M.; Mouikis, C.; Spence, H.

2014-09-01

134

The Voyager encounters with Saturn  

NASA Astrophysics Data System (ADS)

In 1972, the Voyager Program was undertaken by NASA as a major step in the exploration of the outer solar system. Recently the objectives of this program have been extended to include an investigation of Uranus and possibly Neptune. In connection with the present investigation, a brief description of the Voyager spacecraft is presented and an overview of the scientific results from the Saturn encounters is provided. Two essentially identical Voyager spacecraft were launched in 1977 toward encounters with the Jovian and Saturnian planetary systems. The Voyager 1 trajectory at Saturn was chosen to provide a close encounter with Titan, a planet-sized satellite with an atmosphere, and to provide an optimum geometry for dual-frequency radio occultation studies of Saturn's rings. The Voyager 2 trajectory provided improved viewing of the rings.

Stone, E. C.

1984-04-01

135

Microdosimetry of pulsed radiation fields employing the variance method.  

PubMed

The relationship between dose mean lineal energy and relative variance has been exploited previously to derive yD from the calculated variance in current measurements in steady and uniform radiation fields. Recently Kellerer and Rossi made the observation that utilization of two detectors can make the variance technique practicable in time-varying fields. We report here the first measurements of yD for 10 MeV X rays and 9 and 18 MeV electrons from a pulsed linear accelerator using the variance method. Two independent analog-to-digital converters were used to obtain data from two spherical proportional counters in synchrony with the beam pulse. The method is described in detail and results are reported for site diameters of 1/2, 1, and 2 microns. Data for an accurate determination of yD can be obtained with this technique in less than 1 min, making possible an essentially "on line" determination of yD or zD in a clinical situation. PMID:3081938

Kliauga, P; Amols, H; Lindborg, L

1986-02-01

136

Extractable proteins from field radiation vulcanized natural rubber latex  

NASA Astrophysics Data System (ADS)

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

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

2005-07-01

137

Inferring Magnetic Fields in Low-Velocity Radiative Shocks  

NASA Astrophysics Data System (ADS)

Shock waves with velocities less than about 100 km/s occur in many types of astrophysical objects, including jets from young stars and planetary nebulae. Radial velocities and flux ratios of the emission lines in the cooling zones behind these shocks provide a great deal of information both about the flow dynamics and the physical conditions such as electron temperature, density, and ionization fraction. However, a key piece of the puzzle, magnetic field strength, has been difficult to infer because most shocked gas shows no discernible Zeeman splitting or polarization, and the line ratios are degenerate with respect to the field strength. In this work we show that adding the additional constraint of a spatially-resolved cooling-zone size breaks the degeneracy of the line ratio information and makes it possible to estimate Alfvenic Mach numbers of radiative shock waves stellar jets using only quantities that are readily observable. We discuss how the method works, quantify its intrinsic scatter, and apply it to well-known systems that have been studied with HST.

Wright, Anna; Hartigan, Patrick

2014-01-01

138

The wave properties of matter and the zeropoint radiation field  

NASA Astrophysics Data System (ADS)

The origin of the wave properties of matter is discussed from the point of view of stochastic electrodynamics. A nonrelativistic model of a charged particle with an effective structure embedded in the random zeropoint radiation field reveals that the field induces a high-frequency vibration on the particle; internal consistency of the theory fixes the frequency of this jittering at mc2/?. The particle is therefore assumed to interact intensely with stationary zeropoint waves of this frequency as seen from its proper frame of reference; such waves, identified here as de Broglie's phase waves, give rise to a modulated wave in the laboratory frame, with de Broglie's wavelength and phase velocity equal to the particle velocity. The time-independent equation that describes this modulated wave is shown to be the stationary Schrödinger equation (or the Klein-Gordon equation in the relativistic version). In a heuristic analysis appled to simple periodic cases, the quantization rules are recovered from the assumption that for a particle in a stationary state there must correspond a stationary modulation. Along an independent and complementary line of reasoning, an equation for the probability amplitude in configuration space for a particle under a general potential V(x) is constructed, and it is shown that under conditions derived from stochastic electrodynamics it reduces to Schrödinger's equation. This equation reflects therefore the dual nature of the quantum particles, by describing simultaneously the corresponding modulated wave and the ensemble of particles.

de La Peña, L.; Cetto, A. M.

1994-05-01

139

Linac head scatter factor for asymmetric radiation field  

NASA Astrophysics Data System (ADS)

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

Soubra, Mazen Ahmed

1997-11-01

140

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

141

Voyager 1 encounters new region of space  

NASA Astrophysics Data System (ADS)

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

Zielinski, Sarah

2006-10-01

142

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

Microsoft Academic Search

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

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

2005-01-01

143

Mathilde Encounter: June 27, 1997  

NSDL National Science Digital Library

This site presents a brief account of the Near Earth Asteroid Rendezvous (NEAR) flyby of the asteroid 253 Mathilde. Materials include descriptions of the NEAR mission, pre-encounter optical navigation, science objectives, images, and animations. Links to related topics are included.

144

Difficulties Japanese Gay Youth Encounter  

ERIC Educational Resources Information Center

This feature is a collection of brief essays recently written by Japanese and Chinese gay youth, followed by commentary from several leading educators and scholars. Akihiko Komiya's "Difficulties Japanese Gay Youth Encounter" provides excerpts from the stories of six gay youth and their everyday lives, based on their letters in "Buddy", a magazine…

Komiya, Akihiko; Ofuji, Keiko

2003-01-01

145

Normal tissue toxicity after small field hypofractionated stereotactic body radiation  

Microsoft Academic Search

Stereotactic body radiation (SBRT) is an emerging tool in radiation oncology in which the targeting accuracy is improved via the detection and processing of a three-dimensional coordinate system that is aligned to the target. With improved targeting accuracy, SBRT allows for the minimization of normal tissue volume exposed to high radiation dose as well as the escalation of fractional dose

Michael T Milano; Louis S Constine; Paul Okunieff

2008-01-01

146

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

147

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

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

148

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

149

Deformation field validation and inversion applied to adaptive radiation therapy  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

150

Near-field radiative heat transfer between a sphere and a substrate  

NASA Astrophysics Data System (ADS)

Near-field force and energy exchange between two objects due to quantum electrodynamic fluctuations give rise to interesting phenomena such as Casimir and van der Waals forces and thermal radiative transfer exceeding Planck’s theory of blackbody radiation. Although significant progress has been made in the past on the precise measurement of Casimir force related to zero-point energy, experimental demonstration of near-field enhancement of radiative heat transfer is difficult. In this work, we present a sensitive technique of measuring near-field radiative transfer between a microsphere and a substrate using a bimaterial atomic force microscope cantilever, resulting in “heat transfer-distance” curves. Measurements of radiative transfer between a sphere and a flat substrate show the presence of strong near-field effects resulting in enhancement of heat transfer over the predictions of the Planck blackbody radiation theory.

Narayanaswamy, Arvind; Shen, Sheng; Chen, Gang

2008-09-01

151

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, using only velocity field data, the time-averaged energy flux J and total radiated power P for two, the stream function . We test the method using data from a direct nu- merical simulation for tidal flow

Texas at Austin. University of

152

Higher-order spin effects in the dynamics of compact binaries II. Radiation field  

E-print Network

Higher-order spin effects in the dynamics of compact binaries II. Radiation field Luc Blancheta by binary black holes, we investigate the gravitational radiation field of point particles with spins within of rapidly rotating Kerr-type black-hole binaries with the ground- based detectors LIGO, Virgo, GEO 600

153

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

154

CHARACTERISTICS OF FAR FIELD AND ENERGY FLOW DUE TO A MOVING RADIATING SOURCE IN VARIOUS MEDIA  

E-print Network

CHARACTERISTICS OF FAR FIELD AND ENERGY FLOW DUE TO A MOVING RADIATING SOURCE IN VARIOUS MEDIA FIELD AND ENERGV FLOW DUE TO A MOVING RADIATING SOURCE IN VARIOUS MEDIA CONTENTS Acknowledgement. Abst.1 Definit.ion and physical meaning 3.2 Examples of DWS's 3.2.1 vacuum 3.2.2 isot.ropic non-dispersive media

Ng, Chung-Sang

155

Assessment of the ECMWF Model Cloudiness and Surface Radiation Fields at the ARM SGP Site  

Microsoft Academic Search

The cloud and radiation fields produced by the operational European Centre for Medium-Range Weather Forecasts (ECMWF) forecasts are assessed using observations from the Atmospheric Radiation Measurement (ARM) Program Southern Great Plains (SGP) site over the April through May 1999 period. Over the first 36 hours of the forecasts, most of the model fields, taken over a 24-hour time window (either

J.-J. Morcrette

2001-01-01

156

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

157

Radiation dose optimized lateral expansion of the field of view in synchrotron radiation X-ray tomographic microscopy  

PubMed Central

Volumetric data at micrometer level resolution can be acquired within a few minutes using synchrotron-radiation-based tomographic microscopy. The field of view along the rotation axis of the sample can easily be increased by stacking several tomograms, allowing the investigation of long and thin objects at high resolution. On the contrary, an extension of the field of view in the perpendicular direction is non-trivial. This paper presents an acquisition protocol which increases the field of view of the tomographic dataset perpendicular to its rotation axis. The acquisition protocol can be tuned as a function of the reconstruction quality and scanning time. Since the scanning time is proportional to the radiation dose imparted to the sample, this method can be used to increase the field of view of tomographic microscopy instruments while optimizing the radiation dose for radiation-sensitive samples and keeping the quality of the tomographic dataset on the required level. This approach, dubbed wide-field synchrotron radiation tomographic microscopy, can increase the lateral field of view up to five times. The method has been successfully applied for the three-dimensional imaging of entire rat lung acini with a diameter of 4.1?mm at a voxel size of 1.48?µm. PMID:20724780

Haberthur, David; Hintermuller, Christoph; Marone, Federica; Schittny, Johannes C.; Stampanoni, Marco

2010-01-01

158

THz near-field imaging of biological tissues employing synchrotron radiation  

E-print Network

THz near-field imaging of biological tissues employing synchrotron radiation Ulrich Schadea scanning near-field infrared microscopy (SNIM) below 1 THz is demonstrated. The near-field tech- nique (0.06 THz) is derived from the transmittance spectra of the near-field probes. The potential

159

Stand-off detection of mixed radiation fields  

NASA Astrophysics Data System (ADS)

The goal of this study is to present unconventional detection and imaging principles which may lead to novel detection and characterization methodologies for standoff detection of radiation. While there currently are a number of effective technologies and methodologies for nuclear detection based on direct and indirect-ionization detector architectures operating on radiation counting techniques, the problem of detecting nuclear radiation at significant standoff distances remains one of the most difficult and most important challenges. The phenomenology of alternative signatures, a physical algorithm aimed to assess remotely biological hazards of nuclear radiation, and the design of efficient standoff detection architectures are presented.

Giakos, G. C.

2008-03-01

160

Development of a Characterized Radiation Field for Evaluating Sensor Performance  

Microsoft Academic Search

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

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

2008-01-01

161

Aspects of electromagnetic radiation reaction in strong fields  

E-print Network

With the recent advances in laser technology, experimental investigation of radiation reaction phenomena is at last becoming a realistic prospect. A pedagogical introduction to electromagnetic radiation reaction is given with the emphasis on matter driven by ultra-intense lasers. Single-particle, multi-particle, classical and quantum aspects are all addressed.

Burton, D A

2014-01-01

162

Radiation of charges in a strong undulator electromagnetic field  

Microsoft Academic Search

The asymptotic expressions for the spectral-angular distribution of radiation are found in the limit alphagamma >> 1, where gamma is the relativistic parameter and alpha is the maximal angular deviation of the electron velocity. The radiation distribution is obtained in an associated coordinate system moving with the average charge velocity and is then transformed to the laboratory coordinate system.

M. M. Nikitin; V. Yu. Muravyatkin; V. Ya. Epp

1991-01-01

163

Shielding distribution for anisotropic radiation in low earth orbit  

Microsoft Academic Search

The highly directional nature of radiation encountered in low earth orbit (LEO) can be a basis for distributing mass for spacecraft radiation shielding. Trapped (Van Allen) radiation at low altitudes is concentrated within a plane perpendicular to the local geometric field lines. Trapped high-energy protons (which penetrate the relatively thin shielding required for electrons) have a pronounced east-west asymmetry at

M. W. Henley

1986-01-01

164

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...

165

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

NASA Astrophysics Data System (ADS)

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

Popescu, Cristina C.; Tuffs, Richard J.

2013-12-01

166

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

NASA Astrophysics Data System (ADS)

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

Villaraza, Jeanie Ray P.

167

Normal tissue toxicity after small field hypofractionated stereotactic body radiation  

PubMed Central

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

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

2008-01-01

168

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

SciTech Connect

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

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

1997-02-01

169

Directional States of Symmetric-Top Molecules Produced by Combined Static and Radiative Electric Fields  

E-print Network

We show that combined electrostatic and radiative fields can greatly amplify the directional properties, such as axis orientation and alignment, of symmetric top molecules. In our computational study, we consider all four symmetry combinations of the prolate and oblate inertia and polarizability tensors, as well as the collinear and perpendicular (or tilted) geometries of the two fields. In, respectively, the collinear or perpendicular fields, the oblate or prolate polarizability interaction due to the radiative field forces the permanent dipole into alignment with the static field. Two mechanisms are found to be responsible for the amplification of the molecules' orientation, which ensues once the static field is turned on: (a) permanent-dipole coupling of the opposite-parity tunneling doublets created by the oblate polarizability interaction in collinear static and radiative fields; (b) hybridization of the opposite parity states via the polarizability interaction and their coupling by the permanent dipole ...

Härtelt, Marko

2008-01-01

170

Numerical Simulation of a Convective Turbulence Encounter  

NASA Technical Reports Server (NTRS)

A numerical simulation of a convective turbulence event is investigated and compared with observational data. The numerical results show severe turbulence of similar scale and intensity to that encountered during the test flight. This turbulence is associated with buoyant plumes that penetrate the upper-level thunderstorm outflow. The simulated radar reflectivity compares well with that obtained from the aircraft's onboard radar. Resolved scales of motion as small as 50 m are needed in order to accurately diagnose aircraft normal load accelerations. Given this requirement, realistic turbulence fields may be created by merging subgrid-scales of turbulence to a convective-cloud simulation. A hazard algorithm for use with model data sets is demonstrated. The algorithm diagnoses the RMS normal loads from second moments of the vertical velocity field and is independent of aircraft motion.

Proctor, Fred H.; Hamilton, David W.; Bowles, Roland L.

2002-01-01

171

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

172

Increasing Radiation Tolerance of Field-Programmable-Gate-Array-Based Computers Through Redundancy  

E-print Network

Increasing Radiation Tolerance of Field-Programmable- Gate-Array-Based Computers Through Redundancy-access-memory-based field-programmable gate arrays. Such computer systems allow the in-flight reconfiguration of hardware a computer architecture for static random-access-memory-based field-programmable gate arrays that resists

LaMeres, Brock J.

173

Threshold shifts in strong radiation fields: The connection between dc and ac effects  

Microsoft Academic Search

We have studied near-threshold single-photon detachment of a model negative ion, in the presence of a second, intense radiation field. We find a simple, continuous connection between detachment in strong static fields (dc limit) and the increased energy needed to detach an electron into an intense optical field (ac limit). Below this shifted threshold energy, net detachment is suppressed because

L. A. Bloomfield

1989-01-01

174

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

175

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

176

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

177

Very high energy gamma-ray absorption via localized diffuse radiation fields  

NASA Astrophysics Data System (ADS)

When Very High Energy (VHE) gamma-rays (E>100 GeV) transverse low energy photon fields, the production of electron-positron pairs leads to the attenuation of the intrinsic gamma-ray flux. This phenomena is well know for VHE radiation from extragalactic sources, like e.g. blazars, interacting with the cosmic infrared background. In this contribution the absorption of VHE gamma-rays due to the interaction with localized low energy radiation fields, e.g. the Milky Way diffuse radiation field, cluster radiation fields and radiation fields in voids and filaments is discussed. While the photon field densities of these inhomogeneous radiation fields can be several orders of magnitude higher compared to the homogeneous background, the distances are in general shorter leading to an overall smaller effect. On the other hand, the detection of such an attenuation could be used to study the IR emission on different scales, measure the distance of galactic sources, or investigate particle physics phenomena beyond the standard model. It is investigated how forthcoming imaging air Cherenkov telescopes, like CTA, and wide angle Cherenkov arrays, like HiSCORE, with their improved sensitivities up to several hundred TeV will measure this absorption feature.

Maurer, Andreas; Becerra-Gonzalez, Josefa; Raue, Martin; Horns, Dieter

2012-12-01

178

Radiation of a neutral polarizable particle moving uniformly through a thermal radiation field  

NASA Astrophysics Data System (ADS)

We discuss the properties of thermal electromagnetic radiation produced by a neutral polarizable nanoparticle moving with an arbitrary relativistic velocity in a heated vacuum background with a fixed temperature. We show that the particle in its own rest frame acquires the radiation temperature of a vacuum multiplied by a velocity-dependent factor, and then it emits thermal photons predominantly in a forward direction. The intensity of the radiation for a moving particle proves to be much higher than that for a particle at rest. For metal particles with high energy, the ratio of emitted and absorbed radiation power is proportional to the Lorentz factor squared.

Dedkov, G. V.; Kyasov, A. A.

2014-10-01

179

Radiational self-polarization of electrons moving in the electromagnetic plane-wave field  

Microsoft Academic Search

Summary  The radiational self-polarization effect induced by spontaneous radiation is shown to be possible for an electron moving in\\u000a the electromagnetic plane-wave field. It is quite similar to the well-known Sokolov-Ternov effect, as regards the synchrotron\\u000a radiation. The physical analysis of the self-polarization process is given and qualitative estimates for experimental observation\\u000a of the predicted effect are discussed.

V. G. Bagrov; N. I. Fedosov; G. F. Kopytov; S. S. Oxsyzyan; V. B. Tlyachev

1989-01-01

180

Close encounters and a black hole in the globular clusters  

NASA Astrophysics Data System (ADS)

It is known that the presence of a black hole in the globular cluster (GC) affects the stellar density profile and the central stellar dynamics. In this paper a problem of the dynamical evolution under close encounters in the GC where a black hole is present is considered. Since the evolution temp depends on the rate of the stellar encounters an exact expression for the probability of encounters with given changes of energy integral and angular momentum per unit mass is determined assuming an anisotropic field star distribution function. It is used as a core of the collisional term of the Boltzman's equation. A behaviour of the probability density in a globular cluster with and without a black hole has been studied for Plummer and King-Michie models in the isotropic and anisotropic cases. Because of this method takes weak as well as close encounters into account it is more general method than Fokker-Planck one.

Ashurov, Abdikul

2005-01-01

181

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

NASA Technical Reports Server (NTRS)

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

Wen, Guo-Yong; Marshak, Alexander; Cahalan, Robert F.

2004-01-01

182

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

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

183

A unified presentation of certain families of elliptic-type integrals related to radiation field problems  

Microsoft Academic Search

Motivated by their importance or potential for applications in certain problems in radiation physics, several interesting families of elliptic-type integrals were recently studied by many authors. The object of this paper is to present a systematic account of these families in a unified and generalized form which itself is potentially useful in various radiation field problems. Some relevant connections of

H. M. Srivastava; R. N. Siddiqi

1995-01-01

184

Polarization of atomic radiation in stochastic plasma fields V. I. Savchenko and N. J. Fisch  

E-print Network

Polarization of atomic radiation in stochastic plasma fields V. I. Savchenko and N. J. Fisch Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (May 12, 1997) When of the radiation emitted by the atoms exhibits differently polarized line core and line wings. This unusual effect

185

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

186

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 wherein the transverse coordinates are scaled by the width of the focal region, while the axial plate, the radiation force of sound is a phenomenon that has been intensely studied for over a century

Guzina, Bojan

187

Radiation spectra of electrons moving in a spiral in magnetic fields  

Microsoft Academic Search

Analytical and numerical investigations of the radiation spectra of electrons moving in magnetic fields in transparent isotropic medium are performed. The results showed that the Doppler effect influence on the peculiarities of the radiation power spectral distribution of the electrons were essential near the Cherenkov threshold.

A. V. Konstantinovich; S. V. Melnychuk; I. A. Konstantinovich

2003-01-01

188

Peculiarities of the radiation spectra of electrons moving in a spiral in magnetic fields  

Microsoft Academic Search

Peculiarities of the radiation spectra of two electrons moving one by one in a spiral in vacuum can be investigated combining analytical and numerical methods. Investigations of the radiation spectra of the charged particles moving in magnetic fields in transparent isotropic medium and in vacuum offer practical applications in electronics, astrophysics, plasma physics, and physics of storage rings.

A. V. Konstantinovich; S. V. Melnychuk; L. A. Konstantinovich

2004-01-01

189

RHrFPGA Radiation-Hardened Re-programmable Field-Programmable Gate Array  

NASA Technical Reports Server (NTRS)

Viewgraphs on the development of the Radiation-Hardened Re-programmable Field-Programmable Gate Array (RHrFPGA) are presented. The topics include: 1) Radiation Test Suite; 2) Testing Interface; 3) Test Configuration; 4) Facilities; 5) Test Programs; 6) Test Procedure; and 7) Test Results. A summary of heavy ion and proton testing is also included.

Sanders, A. B.; LaBel, K. A.; McCabe, J. F.; Gardner, G. A.; Lintz, J.; Ross, C.; Golke, K.; Burns, B.; Carts, M. A.; Kim, H. S.

2004-01-01

190

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.

191

Preliminary science results of Voyager 1 Saturn encounter  

NASA Technical Reports Server (NTRS)

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

Bane, D.

1981-01-01

192

Modulation of the earth's electric field by cosmic radiation  

Microsoft Academic Search

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

Ralph Markson

1981-01-01

193

Field Distribution and Radiation Resistance of a Straight Vertical Unloaded Antenna Radiating at One of Its Harmonics  

Microsoft Academic Search

The operation at the harmonics of the grounded antenna and of an ungrounded antenna at any distance above ground has been considered as far as current, voltage and power distribution, electromagnetic field and radiation resistance are concerned. The antenna is always assumed to be a straight vertical wire and unloaded. The ground is supposed to be a perfect conductor.

S. A. Levin; C. J. Young

1926-01-01

194

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

195

Effect of Grating Fabrication on Radiation Sensitivity of Fiber Bragg Gratings in Gamma Radiation Field  

Microsoft Academic Search

The influence of grating fabrication on radiation sensitivity of the FBGs has been investigated experimentally. The FBGs were fabricated in different process and concen- trations. Pre-irradiation and -loading were applied to change the radiation sensitivity of the FBGs. The FBGs were fabricated in photosensitive fiber and coupling single mode fiber with a concentration in a range from 0.33 to 23

Song Lin; Ningfang Song; Jing Jin; Xueqin Wang; Gongliu Yang

2011-01-01

196

Directional states of symmetric-top molecules produced by combined static and radiative electric fields.  

PubMed

We show that combined electrostatic and radiative fields can greatly amplify the directional properties, such as axis orientation and alignment, of symmetric top molecules. In our computational study, we consider all four symmetry combinations of the prolate and oblate inertia and polarizability tensors, as well as the collinear and perpendicular (or tilted) geometries of the two fields. In, respectively, the collinear or perpendicular fields, the oblate or prolate polarizability interaction due to the radiative field forces the permanent dipole into alignment with the static field. Two mechanisms are found to be responsible for the amplification of the molecules' orientation, which ensues once the static field is turned on: (a) permanent-dipole coupling of the opposite-parity tunneling doublets created by the oblate polarizability interaction in collinear static and radiative fields and (b) hybridization of the opposite parity states via the polarizability interaction and their coupling by the permanent dipole interaction to the collinear or perpendicular static field. In perpendicular fields, the oblate polarizability interaction, along with the loss of cylindrical symmetry, is found to preclude the wrong-way orientation, causing all states to become high-field seeking with respect to the static field. The adiabatic labels of the states in the tilted fields depend on the adiabatic path taken through the parameter space comprised of the permanent and induced-dipole interaction parameters and the tilt angle between the two field vectors. PMID:18554019

Härtelt, Marko; Friedrich, Bretislav

2008-06-14

197

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

E-print Network

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

Higuchi, Takuya; Hommelhoff, Peter

2014-01-01

198

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

199

Local field effects and stimulated multimode scattering of resonance radiation in a two-level medium  

Microsoft Academic Search

Scattering of resonance radiation in a dense two-level medium is considered with allowance for the local field effects. The\\u000a system is studied in the framework of the mean-field approximation for a modified hierarchy of the Bogoliubov-Born-Green-Kirkwood-Yvon\\u000a equations for reduced density matrices of an ensemble of atoms and modes of a quantized electromagnetic field. The local field\\u000a correction is consistently derived

M. G. Gladush; A. A. Panteleev; Vl. C. Roerich

2006-01-01

200

Position sensitive detection of neutrons in high radiation background field  

NASA Astrophysics Data System (ADS)

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 ?m2) spectroscopic Timepix detector adapted for neutron detection utilizing very thin 10B 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.

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

2014-01-01

201

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

2013-12-04

202

Polarization of atomic radiation in stochastic plasma fields  

SciTech Connect

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

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

1997-05-12

203

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

204

Optimal Background Attenuation for Fielded Radiation Detection Systems  

SciTech Connect

Radiation detectors are often placed in positions difficult to shield from the effects of terrestrial background. This is particularly true in the case of Radiation Portal Monitor (RPM) systems, as their wide viewing angle and outdoor installations make them susceptible to terrestrial background from the surrounding area. A low background is desired in most cases, especially when the background noise is of comparable strength to the signal of interest. The problem of shielding a generalized RPM from terrestrial background is considered. Various detector and shielding scenarios are modeled with the Monte-Carlo N Particle (MCNP) computer code. Amounts of nominal-density shielding needed to attenuate the terrestrial background to varying degrees are given, along with optimal shielding geometry to be used in areas where natural shielding is limited, and where radiation detection must occur in the presence of natural background. Common shielding solutions such as steel plating are evaluated based on the signal to noise ratio and the benefits are weighed against the incremental cost.

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

2006-10-29

205

On the parameterization of the biological effect in a mixed radiation field.  

PubMed

The exposure of astronauts and electronics to the cosmic radiation especially to the particle component pose a major risk to all space flights. Up to now it is not possible to quantify this risk within acceptable limits of accuracy. This uncertainty is not only caused by difficulties in the more or less exact prediction of the incidence of the cosmic radiation but depends also on the problem of the quantification of the radiation field and the correlation of the biological effect. Usually the biological action of a mixed radiation field is estimated as product of the measured dose with an average quality factor, the relative biological efficiency. Because of the large variation in energy and atomic number of the cosmic particles, average values of the quality factor are not precise for risk estimation. A more appropriate way to treat the biological effects of mixed radiation is the concept of particle fluence and action cross section. PMID:11540044

Kraft, G; Scholz, M

1994-10-01

206

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

SciTech Connect

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

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

2012-01-01

207

On the Probability of Stellar Encounters in Globular Clusters  

NASA Astrophysics Data System (ADS)

The number of stellar encounters in a globular cluster per unit time, with given changes in energy and direction of motion relative to the cluster center, has been determined assuming an anisotropic field star distribution function. An exact expression for the integrated probability of such encounters is derived for the case of equal-mass stars, and ranges of physical variables are analyzed. The distributions of the probability and number of encounters in a globular cluster with and without a black hole in the Plummer and King models are also studied. It is shown that the influence of the black hole on the probability distribution almost vanishes at the distance r0~1.55rc, where rc is the core radius of the cluster. Moreover, in the area of radius (2-3)r0 strong encounters are significant and the Fokker-Planck approximation cannot be used for modeling the dynamical evolution of globular clusters. The method is developed for determining the probability of distant (weak), as well as close, encounters and for studying the dynamical evolution of globular clusters in the space of the energy integral (E) and angular momentum per unit mass (J) under close encounters.

Ashurov, A. E.

2004-04-01

208

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

209

Radiative widths and splitting of cyclotron lines in superstrong magnetic fields  

Microsoft Academic Search

The radiative line widths of the Landau levels in a superstrong magnetic field are calculated and simple analytic expressions and fits are given for these which are valid over a wide range of the principal quantum number and the magnetic field strength. If QED corrections are not taken into account, all levels but the first are doubly degenerate, corresponding to

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

1991-01-01

210

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

E-print Network

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

Hajimiri, Ali

211

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

212

The Radiation from an Electron Moving in a Uniform Magnetic Field  

Microsoft Academic Search

The radiation from an electron moving in a uniform magnetic field is investigated quantum mechanically. Reasons are given for expecting deviations from the classical calculations at electron energies of about 100 Mev in the presence of a magnetic field of 104 gauss. The quantum-mechanical calculation is carried through and is compared with the classical calculation. Although the deviations are considerable,

G. Parzen

1951-01-01

213

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

214

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

215

Transformation Properties of External Radiation Fields, Energy-Loss Rates and Scattered Spectra, and a Model for Blazar Variability  

E-print Network

We treat transformation properties of external radiation fields in the proper frame of a plasma moving with constant speed. The specific spectral energy densities of external isotropic and accretion-disk radiation fields are derived in the comoving frame of relativistic outflows, such as those thought to be found near black-hole jet and gamma-ray burst sources. Nonthermal electrons and positrons Compton-scatter this radiation field, and high-energy protons and ions interact with this field through photomeson and photopair production. We revisit the problem of the Compton-scattered spectrum associated with an external accretion-disk radiation field, and clarify a past treatment by the authors. Simple expressions for energy-loss rates and Thomson-scattered spectra are given for ambient soft photon fields consisting either of a surrounding external isotropic monochromatic radiation field, or of an azimuthally symmetric, geometrically thin accretion-disk radiation field. A simplified model for blazar emission, wh...

Dermer, C D

2002-01-01

216

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

217

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

218

Simulation of Relativistic Shocks and Associated Radiation from Turbulent Magnetic Fields  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

219

Spectral evolution of non-thermal electron distributions in intense radiation fields  

E-print Network

(abridged) Models of many astrophysical gamma-ray sources assume they contain a homogeneous distribution of electrons that are injected as a power-law in energy and evolve by interacting with radiation fields, magnetic fields and particles in the source and by escaping. This problem is particularly complicated if the radiation fields have higher energy density than the magnetic field and are sufficiently energetic that inverse Compton scattering is not limited to the Thomson regime. We present a simple, time-dependent, semi-analytical solution of the electron kinetic equation that treats both continuous and impulsive injection, cooling via synchrotron and inverse Compton radiation, (taking into account Klein-Nishina effects) and energy dependent particle escape. The kinetic equation for an arbitrary, time-dependent source function is solved by the method of Laplace transformations. Using an approximate expression for the energy loss rate that takes into account synchrotron and inverse Compton losses including...

Manolakou, K; Kirk, J G

2007-01-01

220

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

221

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

222

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

223

Reflecting on death: The emotionality of the research encounter  

Microsoft Academic Search

This paper considers some of the issues encountered when researching a particular space in which death is engaged: a cemetery landscape. Building on literature available on research and reflexivity, the paper addresses some of the challenges the author dealt with when both in and away from the cemetery field site. At the core of the paper is the recognition that

Kate Woodthorpe

2009-01-01

224

Collaborative Partnering with Districts: Problems Encountered, Lessons Learned.  

ERIC Educational Resources Information Center

This paper examines the accomplishments of the Mid-Continent Research for Education and Learning (McREL) district research partners. Informed by 2 years of collaborative experience, the report documents the process McREL used in selecting partner sites and guides future field-based research partnerships by discussing problems encountered and…

Goodwin, Bryan R.; Gaddy, Barbara B.; Cicchinelli, Louis F.

225

Two-temperature steady-state thermodynamics for a radiation field  

NASA Astrophysics Data System (ADS)

A candidate for a consistent steady-state thermodynamics is constructed for a radiation field in vacuum sandwiched by two black bodies of different temperatures. Because of the collisionless nature of photons, a steady state of a radiation field is completely determined by the temperatures of the two black bodies. Then the zeroth, first, second and third laws can be extended to steady states, where the idea of local steady states plays an important role in the system whose geometrical shape is anisotropic and inhomogeneous. The thermodynamic formalism presented in this paper does not include an energy flux as a state variable. This is consistent with the notable conclusion by [C. Essex, Adv. Thermodyn. 3 (1990) 435; Planet. Space. Sci. 32 (1984) 1035] that, contrary to the success in the irreversible thermodynamics for dissipative systems, a nonequilibrium radiation field does not obey the bilinear formalism of the entropy production rate using an energy flux and its conjugate force. Although the formalism given in this paper may be unique to a radiation field, a nonequilibrium order parameter of steady states of a radiation field is explicitly defined. This order parameter denotes that the geometrical shape of the system determines how a steady state is far from an equilibrium. The higher the geometrical symmetry, the more distant the steady state.

Saida, Hiromi

2005-10-01

226

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

PubMed

Intraoperative radiation therapy (IORT) consists of delivering a large, single-fraction dose of radiation to a surgically exposed tumour or tumour bed at the time of surgery. With the availability of a mobile linear accelerator in the OR, IORT procedures have become more feasible for medical centres and more accessible to cancer patients. Often the area requiring irradiation is larger than what the treatment applicators will allow, and therefore, two or more adjoining fields are used. Unfortunately, the divergence and scattering of the electron beams may cause significant dose variations in the region of the field junction. Furthermore, because IORT treatments are delivered in a large single fraction, the effects of underdosing or overdosing could be more critical when compared to fractionated external beam therapy. Proper matching of the fields is therefore an important technical aspect of treatment delivery. We have studied the matching region using the largest flat applicator available for three different possibilities: abutting the fields, leaving a small gap or creating an overlap. Measurements were done using film dosimetry for the available energies of 4, 6, 9 and 12 MeV. Our results show the presence of clinically significant cold spots for the low-energy beams when the fields are either gapped or abutted, suggesting that the fields should be overlapped. No fields should be gapped. The results suggest that an optimal dose distribution may be obtained by overlapping the fields at 4 and 6 MeV and simply abutting the fields at 9 and 12 MeV. However, due to uncertainties in the placement of lead shields during treatment delivery, one may wish to consider overlapping the higher energy fields as well. PMID:16953035

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

2006-09-21

227

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

NASA Astrophysics Data System (ADS)

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

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

2006-09-01

228

A Numerical Treatment of Anisotropic Radiation Fields Coupled with Relativistic Resistive Magnetofluids  

NASA Astrophysics Data System (ADS)

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 × 4 matrices (for the gas-radiation interaction) and 3 × 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.; Ohsuga, Ken

2013-08-01

229

Determination of ¹N gamma radiation fields at BWR nuclear power stations  

Microsoft Academic Search

Measurements of environmental gamma radiation fields produced by ¹N in components above the floor in the turbine buildings of two large BWR power plants were carried out in April 1975, using pressurized argon ionization chambers and NaI(Tl) and Ge(Li) spectrometers. Both turbine buildings are heavily side-shielded, so that the bulk of the radiation outside the buildings is skyshine. The shapes

W. M. Lowder; P. D. Raft; G. deP Burke

1976-01-01

230

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

E-print Network

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 $TdS=dE+PdV$.

Papnoi, Uma; Ghosh, Sushant G

2014-01-01

231

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

E-print Network

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 $TdS=dE+PdV$.

Uma Papnoi; Megan Govender; Sushant G Ghosh

2014-11-10

232

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

233

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

2005-07-13

234

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

SciTech Connect

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

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

2006-06-15

235

Miniature scintillating detector for small field radiation therapy.  

PubMed

In planning stereotactic radiosurgery treatments, depth dose curves, profiles, and dose rate of treatment beams are difficult to obtain with conventional detectors because of loss of lateral electronic equilibrium and volume averaging. A scintillating detector with high spatial resolution and good reliability has been developed to overcome this problem. The miniature dosimeter consists of two identical radiation-resistant 10 m long silica optical fibers, each connected to an independent silicon photodiode. A small cylindrical polystyrene scintillator (3.9 mm3) is optically glued to the detection fiber. The light seen by the photodiode connected to this fiber arises from fluorescence of the scintillator and from the Cerenkov effect produced in silica. The reference signal produced by the fiber without scintillator is used to subtract the Cerenkov light contribution from the raw detector response. The sensitive volume of the scintillating detector is nearly water-equivalent and thus minimizes dose distribution perturbation in water. The miniature dosimeter has a spatial resolution comparable to the film-densitometer system. Profiles of 1 cm diam, 6 MV photon beam measured with both systems show very similar shapes. Furthermore, the use of photodiodes instead of photomultiplier tubes gives a better stability response and offers the possibility to perform absolute dosimetry. PMID:10619239

Létourneau, D; Pouliot, J; Roy, R

1999-12-01

236

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

237

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

NASA Technical Reports Server (NTRS)

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 made, and the governing differential equations and boundary conditions are satisfied. The solution has the additional attribute of being specified in closed form in terms of elementary functions. This solution is discussed from the point of view of deducing lightning current wave forms from measurements of the electromagnetic fields and understanding the effects of channel tortuosity on the radiated fields. In addition, it is compared with two approximate solutions, the traditional moment approximation and the Fraunhofer approximation, and a set of criteria describing their applicability are presented and interpreted.

Le Vine, D. M.; Meneghini, R.

1978-01-01

238

Radiation effects and radiation back reaction in strong and QED-strong pulsed laser fields  

NASA Astrophysics Data System (ADS)

A particle counter-propagating in strong laser field may experience QED strong field, as long as the energy associated with its motion is sufficiently high. An electric field may be considered to be QED-strong if it exceeds the Schwinger limit: E>m^2c^3/eh. Counter-propagating electrons can be generated in the course of strong laser pulse interaction with a solid target, so that QED effects become both macroscopic and significant, at high laser intensities. A correlated example exists in close proximity to a pulsar, where a QED-strong electric field may be exerted by relativistic charged particles, gyrating in the strong magnetic field of a neutron star, as the result of the Lorentz transformation of the electromagnetic field. We offer a model which is based on a numerical procedure to solve the Lorentz-Abraham-Dirac equation, with the self-force, in a classical limit, with QED corrections derived from the solution of the Dirac equation, for QED-strong fields. The QED effects are included into a kinetic physical and PIC numerical model via the effective interaction integral, quantitatively accounting for the electron and positron interactions with virtual photons.

Sokolov, Igor; Bulanov, Stepan; Naumova, Natalia; Nees, John; Yanovsky, Victor

2008-04-01

239

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 ...

Bini, Donato; Passamonti, Andrea

2014-01-01

240

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

PubMed

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

Kimlin, M G; Parisi, A V

1999-04-01

241

Ultraviolet radiation penetrating vehicle glass: a field based comparative study  

NASA Astrophysics Data System (ADS)

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

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

1999-04-01

242

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

SciTech Connect

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

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

2013-03-20

243

Global precipitation estimates from satellite - Using difference fields of outgoing long-wave radiation  

NASA Technical Reports Server (NTRS)

Global precipitation estimates using satellite data are derived using difference fields of outgoing long-wave radiation (OLR). The difference fields consist of clear OLR minus cloudy OLR, which is a measure of long-wave cloud radiative forcing at the top of the earth-atmosphere system; and clear daytime OLR minus clear night-time OLR, which is a measure of the diurnal variation of surface heating. All geophysical parameters used to compute OLR are derived from an analysis of the HIRS2/MSU sounding data. The derived global precipitation estimates show good agreement with collocated raingage data over land.

Wu, Man-Li

1991-01-01

244

Urban encounters: the game of real life  

Microsoft Academic Search

In this paper we describe our ongoing work on modelling urban encounters by extending Conway's Game of Life. We develop our model based on empirical data collected using a Tamagotchi-like mobile game that recorded people's encounters by sensing nearby devices using Bluetooth. Our findings include the identification of useful ways to capture and analyse data to derive a model of

Vassilis Kostakos; Eamonn O'Neill

2008-01-01

245

Please report any Smalltooth Sawfish encounter!  

E-print Network

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

Watson, Craig A.

246

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

247

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

248

Transient quantum coherent response to a partially coherent radiation field.  

PubMed

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. PMID:24559335

Sadeq, Zaheen S; Brumer, Paul

2014-02-21

249

Transient quantum coherent response to a partially coherent radiation field  

NASA Astrophysics Data System (ADS)

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

2014-02-01

250

Transient Quantum Coherent Response to a Partially Coherent Radiation Field  

E-print Network

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 difference 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.

Z. S. Sadeq; Paul Brumer

2013-12-10

251

A field study of pollutant deposition in radiation fog  

SciTech Connect

Deposition during fog episodes can make a significant contribution to the overall flux of pollutants in certain ecosystems. Furthermore, when atmospheric stagnation prevents normal ventilation in a region, fog deposition may become the main route of pollutant removal. Fogs can consequently exert dominant control over pollutant levels in certain atmospheres. The southern San Joaquin Valley (SJV) of California is a region prone to wintertime episodes of atmospheric stagnation. These lead to elevated pollutant concentrations and/or dense, widespread fogs. Major oil-recovery operations plus widespread agricultural and livestock feeding activities are important sources of SO/sub 2/, NO/sub X/ and NH/sub 3/ in the valley. A multifaceted program of field monitoring was conducted in the SJV during the winter 1984-1985, focusing on aspects of pollutant scavenging and removal in the fog-laden atmosphere. Concentrations of major species were measured in gas, dry aerosol and fogwater phases. In addition, depositional fluxes were monitored by surrogate-surface methods. These measurements were employed to directly assess the magnitude of removal enhancement by fog.

Waldman, J.M.; Jacob, D.J.; Munger, J.W.; Hoffman, M.R.

1986-04-01

252

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

253

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

254

Radiative widths and splitting of cyclotron lines in superstrong magnetic fields  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

255

Local field effects and stimulated multimode scattering of resonance radiation in a two-level medium  

SciTech Connect

Scattering of resonance radiation in a dense two-level medium is considered with allowance for the local field effects. The system is studied in the framework of the mean-field approximation for a modified hierarchy of the Bogoliubov-Born-Green-Kirkwood-Yvon equations for reduced density matrices of an ensemble of atoms and modes of a quantized electromagnetic field. The local field correction is consistently derived from the initial Hamiltonian of the system. The problem of scattering of a short rectangular pulse from a quasi-point sample is considered numerically and theoretically. The possibility of a multimode spectrum of scattered radiation with frequencies multiple of the Rabi frequency and with other intermediate frequencies is demonstrated. The relative intensities of spectral lines are determined.

Gladush, M. G., E-mail: mglad@triniti.ru; Panteleev, A. A.; Roerich, Vl. C. [Russian Federation State Research Center TRINITI (Russian Federation)

2006-08-15

256

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

NASA Astrophysics Data System (ADS)

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

Novokhatski, A.

2011-06-01

257

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

E-print Network

Gravitational waves 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. Linearised equations for the electromagnetic field on perturbed Minkowski space are derived and solved analytically. The inverse Gertsenshtein conversion of gravitational waves in a static electromagnetic field is rederived, and the resultant electromagnetic radiation is shown to be significant for highly magnetised 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 gravitational wave strength increase...

Chua, Alvin J K; Gair, Jonathan R

2014-01-01

258

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

259

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

E-print Network

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 MHD 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 resp...

Downes, T P

2014-01-01

260

Flame driving of axial acoustic fields - Comparison between flame radiation and acoustic intensity measurements  

Microsoft Academic Search

The paper describes results of an ongoing investigation of the mechanisms responsible for the driving of axial instabilities in solid-propellant rocket motors. Specifically, the results of two experimental methods for measuring the driving of axial acoustic fields by sidewall-stabilized diffusion flames are compared. Driving of acoustic fields by diffusion flames was investigated using LDV and C-H flame-radiation measurements. These studies

T. Y. Chen; U. G. Hegde; B. R. Daniel; B. T. Zinn

1990-01-01

261

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

262

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

NASA Astrophysics Data System (ADS)

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

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

2009-07-01

263

Transformation Properties of External Radiation Fields, Energy-Loss Rates and Scattered Spectra, and a Model for Blazar Variability  

E-print Network

We treat transformation properties of external radiation fields in the proper frame of a plasma moving with constant speed. The specific spectral energy densities of external isotropic and accretion-disk radiation fields are derived in the comoving frame of relativistic outflows, such as those thought to be found near black-hole jet and gamma-ray burst sources. Nonthermal electrons and positrons Compton-scatter this radiation field, and high-energy protons and ions interact with this field through photomeson and photopair production. We revisit the problem of the Compton-scattered spectrum associated with an external accretion-disk radiation field, and clarify a past treatment by the authors. Simple expressions for energy-loss rates and Thomson-scattered spectra are given for ambient soft photon fields consisting either of a surrounding external isotropic monochromatic radiation field, or of an azimuthally symmetric, geometrically thin accretion-disk radiation field. A model for blazar emission is presented that displays a characteristic spectral and variability behavior due to the presence of a direct accretion-disk component. The disk component and distinct flaring behavior can be bright enough to be detected from flat spectrum radio quasars with {\\it GLAST}. Spectral states of blazars are characterized by the relative importance of the accretion-disk and scattered radiation fields and, in the extended jet, by the accretion disk, inner jet, and cosmic microwave background radiation fields.

C. D. Dermer; R. Schlickeiser

2002-02-14

264

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

E-print Network

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

Young, Leslie A.

265

Near-field radiative transfer between two unequal sized spheres with large size disparities.  

PubMed

We compute near-field radiative transfer between two spheres of unequal radii R1 and R2 such that R2 ? 40R1. For R2 = 40R1, the smallest gap to which we have been able to compute radiative transfer is d = 0.016R1. To accomplish these computations, we have had to modify existing methods for computing near-field radiative transfer between two spheres in the following ways: (1) exact calculations of coefficients of vector translation theorem are replaced by approximations valid for the limit d ? R1, and (2) recursion relations for a normalized form of translation coefficients are derived which enable us to replace computations of spherical Bessel and Hankel functions by computations of ratios of spherical Bessel or spherical Hankel functions. The results are then compared with the predictions of the modified proximity approximation. PMID:24977544

Sasihithlu, Karthik; Narayanaswamy, Arvind

2014-06-16

266

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

267

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

268

The NOAA-9 Earth Radiation Budget Experiment Wide Field-of-View Data Set  

NASA Technical Reports Server (NTRS)

The Earth Radiation Budget Experiment (ERBE) consisted of wide field-of-view (WFOV) radiometers and scanning radiometers for measuring outgoing longwave radiation and solar radiation reflected from the Earth. These instruments were carried by the dedicated Earth Radiation Budget Satellite (ERBS) and by the NOAA-9 and -10 operational spacecraft. The WFOV radiometers provided data from which instantaneous fluxes at the top of the atmosphere (TOA) are computed by use of a numerical filter algorithm. Monthly mean fluxes over a 5-degree equal angle grid are computed from the instantaneous TOA fluxes. The WFOV radiometers aboard the NOAA-9 spacecraft operated from February 1985 through December 1992, at which time a failure of the shortwave radiometer ended the usable data after nearly 8 years. This paper examines the monthly mean products from that data set.

Bush, Kathryn A.; Smith, G. Louis; Young, David F.

1999-01-01

269

Measurement of neutron dose equivalent to proton therapy patients outside of the proton radiation field  

Microsoft Academic Search

Measurements of neutron dose equivalent values and neutron spectral fluences close to but outside of the therapeutic proton radiation field are presented. The neutron spectral fluences were determined at five locations with Bonner sphere measurements and established by unfolding techniques. More than 50 additional neutron dose equivalent values were measured with LiI and BF3 thermal neutron detectors surrounded by a

X Yan; U Titt; A. M Koehler; W. D Newhauser

2002-01-01

270

SCATTERED GAMMA RADIATION MEASUREMENTS FROM A Co⁶° CONTAMINATED FIELD  

Microsoft Academic Search

A 90 deg sector of a circle of 604-foot radius was contamirated with ; cobalt-60 point sources to an approximate level of 1.72 millicuries per square ; foot, as a means of simulating an area approaching an infinite contaminated field. ; Radiation measurements were made in an open hole with a PDR-27A radiac instrument ; and Dupont 553 film to

C. L. Schlemm; A. E. Jr. Anthony; Z. G. Burson

1959-01-01

271

P. ZEEMAN. 2014 Measurements concerning Radiation Phenomena in the magnetic Field (Mesures relatives au phnomne Zeeman). -  

E-print Network

382 P. ZEEMAN. 2014 Measurements concerning Radiation Phenomena in the magnetic Field (Mesures relatives au phénomène Zeeman). - P. 197. La source de lumière est une étincelle donnée par une bobine d indécises. E. PERREAU. H.-P. CADY.- The electrolysis and electrolytic conductivity of certain substances

Paris-Sud XI, Université de

272

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.

273

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

2013-05-15

274

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

275

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

E-print Network

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

Paris-Sud XI, Université de

276

Radiation Reaction in Relativistic Motion of a Particle in a Wave Field  

Microsoft Academic Search

An approximate solution of the equations of motion of Dirac's classical theory f pointlike particles is obtained for a particle in the field of a plane wave, under the assumption that the radiation reaction terms in these equations can be considered as small. The appearance of runaway terms in this solution is avoided by letting the interaction set in gradually.

E. Gora

1951-01-01

277

Radiation and Magnetic Field Effects on New Semiconductor Power Devices for Hl-Lhc Experiments  

NASA Astrophysics Data System (ADS)

The radiation hardness of commercial Silicon Carbide and Gallium Nitride power MOSFETs is presented in this paper, for Total Ionizing Dose effects and Single Event Effects, under ?, neutrons, protons and heavy ions. Similar tests are discussed for commercial DC-DC converters, also tested in operation under magnetic field.

Fiore, S.; Abbate, C.; Baccaro, S.; Busatto, G.; Citterio, M.; Iannuzzo, F.; Lanza, A.; Latorre, S.; Lazzaroni, M.; Sanseverino, A.; Velardi, F.

2014-06-01

278

Encounters between binary and single stars and their effect on the dynamical evolution of stellar systems  

Microsoft Academic Search

More than 1.4times10⁴ computer-simulated encounters between ; binaries and field stars have been run for various preencounter relative ; velocities V\\/subf\\/ and impact parameters p. At low values of V\\/subf\\/, the ; encounter causes the binary orbit to shrink and become more tightly bound with ; the two more massive of the three stars involved in the encounter remaining in

J. G. Hills

1975-01-01

279

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

Thomas Blue; Wolfgang Windl; Bryan Dickerson

2013-01-03

280

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

SciTech Connect

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

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

2008-04-01

281

Radiation Belt Data-Assimilation Using Self-Consistent Storm-Time Magnetic Fields  

NASA Astrophysics Data System (ADS)

The lack of suitably realistic magnetic field models for use in radiation belt data assimilation remains a critical unresolved problem in space weather specification and prediction. Although the high-energy radiation belt particles themselves do not significantly alter the magnetic fields in which they drift, the lower-energy ring current populations do. And the deviation (especially during storms) of the real magnetic field from that computed even with the best of the presently available empirical models can be very large. To overcome this problem, the LANL DREAM code has been modified to use magnetic fields that are self-consistently maintained in force balance with the plasma. We compare second and third adiabatic invariants computed from the self-consistent fields to those obtained with empirical B-field models, and we utilize a phase-space density matching technique in order to test the various field models. Finally, the PSD at constant mu and K in a data-assimilation model obtained with the self-consistent and non-self-consistent magnetic field models will be compared.

Henderson, M. G.; Koller, J.; Chen, Y.; Zaharia, S.; Jordanova, V.; Reeves, G. D.

2008-12-01

282

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

283

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

284

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

285

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

286

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

PubMed Central

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

Janaszczyk, Agnieszka; Bogusz-Czerniewicz, Marta

2011-01-01

287

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

288

Satellite ephemerides for the Voyager Neptune encounter  

Microsoft Academic Search

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

Robert A. Jacobson

1988-01-01

289

Pioneer to encounter Saturn on September 1  

NASA Technical Reports Server (NTRS)

The encounter of the Pioneer 11 Spacecraft with Saturn, designed to provide information on the evolution of the Sun and its planets, is described. Photographs and measurements of Saturn, its rings, and several of its 10 satellites, including Titan, to be taken by Pioneer instruments, are emphasized. The encounter sequence and spacecraft trajectory are discussed. A description of Saturn and its atmosphere is included. Onboard instruments and experiments are also described.

1979-01-01

290

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

291

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

292

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

NASA Astrophysics Data System (ADS)

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

Trujillo Bueno, J.

2012-12-01

293

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

Microsoft Academic Search

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

Anderson D. E. Jr; Steven A. Lloyd

1990-01-01

294

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

PubMed

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

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

2014-10-01

295

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

296

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

Microsoft Academic Search

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

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

2008-01-01

297

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

298

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

299

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

300

Radiation hardening of MOS devices by boron. [for stabilizing gate threshold potential of field effect device  

NASA Technical Reports Server (NTRS)

A technique is described for radiation hardening of MOS devices and specifically for stabilizing the gate threshold potential at room temperature of a radiation subjected MOS field-effect device with a semiconductor substrate, an insulating layer of oxide on the substrate, and a gate electrode disposed on the insulating layer. The boron is introduced within a layer of the oxide of about 100 A-300 A thickness immediately adjacent the semiconductor-insulator interface. The concentration of boron in the oxide layer is preferably maintained on the order of 10 to the 18th power atoms/cu cm. The technique serves to reduce and substantially annihilate radiation induced positive gate charge accumulations.

Danchenko, V. (inventor)

1974-01-01

301

Near-field radiative heat transfer between doped silicon nanowire arrays  

NASA Astrophysics Data System (ADS)

In this letter, we investigate the near-field radiative heat transfer between two doped silicon nanowire arrays separated by a vacuum gap. Using effective medium theory and fluctuational electrodynamics, the radiative heat transfer is calculated for the silicon nanowire arrays with different filling fractions at different vacuum gaps. The energy transfer increases as the nanowire array becomes less dense due to enhancement in channels available for heat transfer. To further understand the impact of filling fraction to the total heat transfer, the dispersion relation of coupled surface plasmon polaritons is calculated inside the vacuum gap by considering temperature-dependent dielectric functions for the doped silicon nanowires. When the filling fraction is 0.5, the radiative heat transfer at a vacuum gap of 20 nm between the nanowire arrays is almost three times of that between two doped silicon plates. Results from this study will facilitate the application of doped silicon nanowires for energy harvesting and thermal management.

Basu, Soumyadipta; Wang, Liping

2013-02-01

302

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

303

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

304

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

305

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

306

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

307

Synchro-Curvature Self-Compton Radiation of Electrons in Curved Magnetic Fields  

E-print Network

In this paper we present the spectrum of synchro-curvature self-Compton (SCSC) radiation of relativistic electrons with a power-law distribution of Lorentz factors. We find that the resulting spectrum is significantly different from that of either synchrotron self-Compton or curvature self-Compton radiation if both the curvature radius of the magnetic field and the cyclotron radius of the electrons are within some proper ranges. The effects of electrons' cooling and drifting, the low-energy self absorption in seed spectra, and the Klein-Nishina cutoff are also discussed, in order to get an accurate picture. We take gamma-ray bursts (GRBs) as our example environment for discussions. The results would be considered as a universal approach of the self-Compton emission of relativistic electrons moving in curved magnetic fields, and thus could be applied to many astrophysical phenomena, including GRBs, active galactic nuclei (AGNs), and pulsars.

Zhang, Bo

2010-01-01

308

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

2014-03-11

309

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

310

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

311

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

312

Near-field measurement of radiation levels of extended spatially uncorrelated sound sources  

NASA Astrophysics Data System (ADS)

A method is considered for measuring the radiation levels of extended spatially uncorrelated sound sources in the near field in the case of their imprecise positioning with respect to the measurement system—a linear antenna array. An algorithm is proposed for synthesizing the vector of weight coefficients ensuring the given value of methodological measurement error under maximum suppression of external noise. Examples are given of numerical modeling and experimental testing of the method in natural conditions.

Orlov, D. A.; Turchin, V. I.; Fiks, G. E.; Fiks, I. Sh.

2012-05-01

313

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

314

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

315

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

NASA Astrophysics Data System (ADS)

The MILAGRO field campaign took place in and near Mexico City 1-30 March 2006. A comprehensive data set was obtained on atmospheric chemical composition (gas and aerosol), aerosol microphysics, spectral radiation, and meteorology from surface-, aircraft-, and satellite-based instruments. For much of this time, the lower atmosphere was laden with large amounts of aerosols originating from urban and industrial sources, biomass fires, and wind-blown dust. Spectral radiation measurements are available from filter radiometers and spectroradiometers, and span ultraviolet (UV) wavelengths important to surface biota and tropospheric photochemistry. By combining the spectral radiation measurements, aerosol composition, optical, and microphysical measurements, and modeling, an assessment is now possible on how aerosols affect surface UV radiation (e.g. DNA damage, erythema, vitamin-D production) and vertical profiles of photolysis frequencies (e.g. JNO2, JO3(O1D), JCH2O, JHONO). Interactions between aerosol-scattered radiation and absorption by gaseous pollutants (esp. O3, SO2, and NO2) can also be evaluated. Implications for human health and photochemical oxidant formation will be discussed.

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

2007-05-01

316

Magnetic Field Generation through Angular Momentum Exchange between Circularly Polarized Radiation and Charged Particles  

SciTech Connect

The interaction between circularly polarized (CP) radiation and charged particles can lead to generation of magnetic field through an inverse Faraday effect. The spin of the circularly polarized electromagnetic wave can be converted into the angular momentum of the charged particles so long as there is dissipation. We demonstrate this by considering two mechanisms of angular momentum absorption relevant for laser-plasma interactions: electron-ion collisions and ionization. The precise dissipative mechanism, however, plays a role in determining the efficiency of the magnetic field generation.

G. Shvets; N.J. Fisch; J.-M. Rax

2002-01-18

317

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

318

Over-response of synthetic microDiamond detectors in small radiation fields  

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

319

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

SciTech Connect

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

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

2011-11-01

320

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

321

Star Formation In the Galaxy and the Fluctuating UV Radiation Field  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

322

Effects of Lightning Return Stroke Parameters on Radiated Fields, on the Ground and in the Ionosphere  

NASA Astrophysics Data System (ADS)

We present numerical simulations of lightning return stroke currents and the fields radiated in the Earth-ionosphere waveguide and into the lower ionosphere. Where previous lightning-ionosphere interaction models approximate the return stroke current as constant over the altitude range of the return stroke, we implement a modified transmission line model of the return stroke, with either linear (MTLL) or exponential (MTLE) current decay with altitude. Using this model we investigate the effects of the return stroke rise time ?r, fall time ?f, propagation speed vrs, and terminal altitude h on both the electrostatic and radiated fields. These parameters affect the field amplitudes and waveforms both as measured along the ground and in the lower ionosphere, the latter having implications for sprite initiation, D-region ionization and elve luminosity. In addition, these parameters affect the interpretation of temporal signatures of elves. We present results that demonstrate the effects of each of the four parameters on fields, ionization, and elve luminosity and temporal signature. We further investigate the effects of these parameters on the relationship between peak current Ik and E100, the electric field measured at 100 km range on the ground.

Marshall, R. A.

2012-12-01

323

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

2007-05-03

324

Spectral evolution of non-thermal electron distributions in intense radiation fields  

E-print Network

(abridged) Models of many astrophysical gamma-ray sources assume they contain a homogeneous distribution of electrons that are injected as a power-law in energy and evolve by interacting with radiation fields, magnetic fields and particles in the source and by escaping. This problem is particularly complicated if the radiation fields have higher energy density than the magnetic field and are sufficiently energetic that inverse Compton scattering is not limited to the Thomson regime. We present a simple, time-dependent, semi-analytical solution of the electron kinetic equation that treats both continuous and impulsive injection, cooling via synchrotron and inverse Compton radiation, (taking into account Klein-Nishina effects) and energy dependent particle escape. The kinetic equation for an arbitrary, time-dependent source function is solved by the method of Laplace transformations. Using an approximate expression for the energy loss rate that takes into account synchrotron and inverse Compton losses including Klein-Nishina effects for scattering off an isotropic photon field with either a power-law or black-body distribution, we find explicit expressions for the cooling time and escape probability of individual electrons. This enables the full, time-dependent solution to be reduced to a single quadrature. From the electron distribution, we then construct the time-dependent, multi-wavelength emission spectrum. We compare our solutions with several limiting cases and discuss the general appearance and temporal behaviour of spectral features (i.e., cooling breaks, bumps etc.). As a specific example, we model the broad-band energy spectrum of the open stellar association Westerlund-2 at different times of its evolution, and compare it with observations.

K. Manolakou; D. Horns; J. G. Kirk

2007-08-13

325

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

326

Homeless women's experiences of service provider encounters.  

PubMed

Service providers are gatekeepers to health-sustaining services and resources, although little is known about service encounters from the perspective of homeless women. We conducted in-depth semistructured interviews with 15 homeless women to better understand their experiences of service encounters. Using a phenomenological method, 160 significant statements were extracted from participant transcripts; more positive than negative interactions were reported. The 10 themes that emerged fall along a dehumanizing/humanizing continuum primarily separated by the power participants experienced in the interaction and the trust they felt in the service provider. Implications for nursing practice and research are offered. PMID:24528122

Biederman, Donna J; Nichols, Tracy R

2014-01-01

327

The Voyager 2 encounter with Uranus  

NASA Astrophysics Data System (ADS)

The instruments and science investigations of the Voyager 2 payload are listed in tables and illustrated with a drawing, and a general overview of the encounter with Uranus in January 1986 is given. The spacecraft approached to within 107,100 km of the center of Uranus, and to within 29,000 km of the Uranian satellite Miranda before continuing on for an encounter with Neptune in 1989; the trajectory also permitted radio occultation studies of the Uranian rings and radio and UV occultation studies of the planet's atmosphere. Diagrams of the trajectory are provided.

Stone, E. C.

1987-12-01

328

The Voyager 2 encounter with Uranus  

NASA Technical Reports Server (NTRS)

The instruments and science investigations of the Voyager 2 payload are listed in tables and illustrated with a drawing, and a general overview of the encounter with Uranus in January 1986 is given. The spacecraft approached to within 107,100 km of the center of Uranus, and to within 29,000 km of the Uranian satellite Miranda before continuing on for an encounter with Neptune in 1989; the trajectory also permitted radio occultation studies of the Uranian rings and radio and UV occultation studies of the planet's atmosphere. Diagrams of the trajectory are provided.

Stone, E. C.

1987-01-01

329

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

330

Inhibition of the production of reactive oxygen species in mouse peritoneal neutrophils by millimeter wave radiation in the near and far field zones of the radiator  

Microsoft Academic Search

Using the luminol-dependent chemiluminescence technique effects of a low-intensity electromagnetic field (EMF) of extremely high frequency of the production of reactive oxygen species (ROS) by mouse peritoneal neutrophils was studied. The neutrophils were activated by opsonized zymosan. It was found that the EMF inhibits the ROS production by the neutrophils. However, in the near field zone of the channel radiator

A. B. Gapeyev; V. G. Safronova; N. K. Chemeris; E. E. Fesenko

1997-01-01

331

Field tests of a portable tissue equivalent survey meter for monitoring mixed beta/gamma radiation fields  

SciTech Connect

A portable radiation survey meter that provides a tissue equivalent response to photons and beta particles has been designed and field tested. The detector is a very thin plastic scintillator that closely simulates the actual geometry and scattering properties of the relevant skin tissues. The meter reads out the D(0.07) dose rate directly, and indicates the tissue dose rates at other depths with the use of tissue equivalent filters of appropriate thicknesses. Data are presented which compare the D(0.07) and D(10) dose rates recorded by the Tissue Equivalent (TE) survey meter with dose rates recorded by two commercial ion chamber meters for a number of laboratory and field sources. Most commercial ion chamber meters fail to respond adequately to the extreme off-axis beta particles from extended beta sources, and hence require the application of large beta correction factors to change the instrument reading to the true D(0.07) dose rate. The tissue equivalent survey meter exhibits an angular response to beta particles that is very similar to the angular response of an extrapolation chamber. Consequently, there is close agreement between the TE meter and extrapolation chamber readings for a wide variety of beta and mixed beta-gamma rdiation fields. D(0.07), D(3), and D(10) dose rates, measured with the INEL TE meter at a number of typical work stations, are presented.

Martz, D.E.; Rich, B.L.; Johnson, L.O.; Daniel, S.H. III

1986-05-01

332

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

333

Radiation field characterization and shielding studies for the ELI Beamlines facility  

NASA Astrophysics Data System (ADS)

The ELI (Extreme Light Infrastructure) Beamlines facility in the Czech Republic, which is planned to complete the installation in 2015, is one of the four pillars of the ELI European project. Several laser beamlines with ultrahigh intensities and ultrashort pulses are foreseen, offering versatile radiation sources in an unprecedented energy range: laser-driven particle beams are expected to range between 1 and 50 GeV for electrons and from 100 MeV up to 3 GeV for protons. The number of particles delivered per laser shot is estimated to be 109-1010 for the electron beams and 1010-1012 for the proton beams. The high energy and current values of the produced particles, together with the potentiality to operate at 10 Hz laser repetition rate, require an accurate study of the primary and secondary radiation fields to optimize appropriate shielding solutions: this is a key issue to minimize prompt and residual doses in order to protect the personnel, reduce the radiation damage of electronic devices and avoid strong limitations in the operational time. A general shielding study for the 10 PW (0.016 Hz) and 2 PW (10 Hz) laser beamlines is presented here. Starting from analytical calculations, as well as from dedicated simulations, the main electron and proton fields produced in the laser-matter interaction have been described and used to characterize the "source terms" in full simulations with the Monte Carlo code FLUKA. The secondary radiation fields have been then analyzed to assess a proper shielding. The results of this study and the proposed solutions for the beam dumps of the high energy beamlines, together with a cross-check analysis performed with the Monte Carlo code GEANT4, are presented.

Ferrari, A.; Amato, E.; Margarone, D.; Cowan, T.; Korn, G.

2013-05-01

334

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

SciTech Connect

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

Kantsyrev, V. L.; Esaulov, A. A.; Safronova, A. S.; Osborne, G. C.; Shrestha, I.; Weller, M. E.; Stafford, A.; Shlyaptseva, V. V. [Physics Department, University of Nevada, Reno, Nevada 89557 (United States); Velikovich, A. L. [Plasma Physics Division, Naval Research Laboratory, Washington, D.C. 20375 (United States); Rudakov, L. I. [Icarus Research Inc., Bethesda, Maryland 20824 (United States); Williamson, K. M. [Physics Department, University of Nevada, Reno, Nevada 89557 (United States); Plasma Engineering Research Laboratory, Texas A and M University, Corpus Christi, TX 78412 (United States)

2011-10-15

335

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

SciTech Connect

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

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

2006-01-07

336

Comptonization in Ultra-Strong Magnetic Field: A Numerical Solution of the Radiative Transfer Problem  

NASA Astrophysics Data System (ADS)

We consider the radiative transfer problem in a plane-parallel slab of thermal electrons in presence of an ultra-strong magnetic field (B>~4.4×1013 G). Under such conditions, the magnetic field behaves as a birefringent medium for the propagating photons, and the electromagnetic radiation is splitted into two polarization modes, ordinary and extraordinary, having different cross-sections. When the optical depth of the slab is large, the ordinary-mode photons are significantly more Comptonized and the photon field is dominated by the isotropic component. For sub-relativistic electron temperatures, it is possible to treat the full kinetic Boltzmann equation for such photons using the Fokker-Planck approximation. The full solution is then obtained by the method of variable separation. We report the numerical solution obtained for eigenvalues and eigenfunctions of the space operator, and consider the emerging Comptonization spectrum of the ordinary-mode photons for energies significantly less than the cyclotron energy, which is of the order of MeV for the intensity of the magnetic field here considered.

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

2011-08-01

337

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

338

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

339

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

Microsoft Academic Search

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

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

2007-01-01

340

Superkicks in ultrarelativistic encounters of spinning black holes  

E-print Network

We study ultrarelativistic encounters of two spinning, equal-mass black holes through simulations in full numerical relativity. Two initial data sequences are studied in detail: one that leads to scattering and one that leads to a grazing collision and merger. In all cases, the initial black hole spins lie in the orbital plane, a configuration that leads to the so-called "superkicks". In astrophysical, quasicircular inspirals, such kicks can be as large as ~3,000 km/s; here, we find configurations that exceed ~15,000 km/s. We find that the maximum recoil is to a good approximation proportional to the total amount of energy radiated in gravitational waves, but largely independent of whether a merger occurs or not. This shows that the mechanism predominantly responsible for the superkick is not related to merger dynamics. Rather, a consistent explanation is that the "bobbing" motion of the orbit causes an asymmetric beaming of the radiation produced by the in-plane orbital motion of the binary, and the net asymmetry is balanced by a recoil. We use our results to formulate some conjectures on the ultimate kick achievable in any black hole encounter.

Ulrich Sperhake; Emanuele Berti; Vitor Cardoso; Frans Pretorius; Nicolas Yunes

2010-11-15

341

Participants in urban Mexican male homosexual encounters  

Microsoft Academic Search

Preliminary data are presented on 53 urban Mexican males interviewed during 1970–1971 in a study of homosexual encounters in a large Mexican city. These data are compared with data from recent studies in the United States and England of male homosexual behavior. Although preliminary and limited, the Mexican data indicate that cultural factors are important determinants of life styles and

J. M. Carrier

1971-01-01

342

Consumerism, reflexivity and the medical encounter  

Microsoft Academic Search

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

Deborah Lupton

1997-01-01

343

Earth imaging results from Galileo's second encounter  

Microsoft Academic Search

The recent flyby of the Galileo spacecraft en route to Jupiter contributes a unique perspective to our view of our home planet. Imaging activities conducted during the second Earth encounter provide an important opportunity to assess new methods and approaches on familiar territory. These include unique multispectral observations, low light-level imaging (searches for aurorae, lightning and artificial lights on the

R. Greenberg; M. Belton; E. Dejong; A. Ingersoll; K. Klaasen; P. Geissler; J. Moersch; W. R. Thompson

1993-01-01

344

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

345

Exploring power in multicultural counselling encounters  

Microsoft Academic Search

Power is a central dynamic in multicultural encounters. Yet many people, especially counsellors, are reluctant to discuss their experiences with power and what it means to them. As a result, power remains an often unspoken, disturbing issue in multicultural counselling and counsellor education. This article addresses this silence by: a) clarifying the relationship between power and cultural racism; b) discussing

Marylou Ramsey

1996-01-01

346

Rural encounters: cultural translations through video  

Microsoft Academic Search

Requirements gathering for design in rural and remote areas needs to be considered within the prevailing cultural context. We explain our use of video as a technological site for cultural encounters during the preparatory elicitation of cultural influences and determinants. We outline the factors leading to the development of a co-generative approach arising from our understanding of the role played

David Browning; Nicola J. Bidwell; Dianna Hardy; Peta-marie Standley

2008-01-01

347

The Voyager 2 encounter with Uranus  

Microsoft Academic Search

The instruments and science investigations of the Voyager 2 payload are listed in tables and illustrated with a drawing, and a general overview of the encounter with Uranus in January 1986 is given. The spacecraft approached to within 107,100 km of the center of Uranus, and to within 29,000 km of the Uranian satellite Miranda before continuing on for an

E. C. Stone

1987-01-01

348

THE SCOTTISH ENCOUNTER WITH TROPICAL DISEASE  

E-print Network

Scots. These pioneers preceded Dr David Livingstone (1813-1873) whose success as an explorer in Africa Timeline 4-5 David Livingstone 6-7 Patrick Manson 8-9 African Trypanosomiasis 10-11 The Scottish Encounter aims to celebrate these discoveries. Why were so many discoveries in Parasitology made by Scots

Schnaufer, Achim

349

VLA feedhorn for Voyager encounter of Neptune  

NASA Technical Reports Server (NTRS)

A high gain, low noise corrugated feedhorn was designed and developed by JPL for use in Very Large Array (VLA) antennas, near Soccoro, New Mexico. The new feedhorn will enable the VLA to support the Voyager encounter of Neptune in August of 1989. This will significantly enhance the receiving capability of the United States for that historic event.

Manshadi, F.; Bathker, D. A.; Marlin, H. W.

1986-01-01

350

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

351

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.

352

Students Encountering Obstacles Using a CAS.  

ERIC Educational Resources Information Center

Describes a pilot study on the use of computer algebra at the upper secondary level. A symbolic calculator was introduced in a pre-examination class studying for advanced pre-university mathematics. Focuses on the identification of obstacles that students encounter while using computer algebra with the theoretical framework of Realistic…

Drijvers, Paul

2000-01-01

353

Pattern-function quantum tomography: a tool for experimentally investigating the real state of radiation fields  

NASA Astrophysics Data System (ADS)

We have exploited pattern function quantum homodyne tomography (QHT) to enlight deviations from the Gaussian state for a squeezed vacuum field generated by a type-I below threshold OPO. This tomographic method allows to fully characterize the state without any a--priori assumption on its statistics. Applying pattern function QHT to the radiation outing a type-I below threshold OPO, we have measured photon number distributions different from those expected for a Gaussian field. Being the Wigner function and the quadrature marginal distribution Gaussian for a Gaussian field, the actual state has been analysed by looking at data variance and Kurtosis (0 for a Gaussian distribution) as a function of the quadrature angle ?. A clear deviation of the Kurtosis from zero has been found for different OPO cavities. This deviation increases as the threshold is approached.

Porzio, Alberto; D'Auria, Virginia; Solimeno, Salvatore; Paris, Matteo G.

2005-08-01

354

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

SciTech Connect

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

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

1991-01-01

355

Electro-optic techniques for temporal profile characterisation of relativistic Coulomb fields and coherent synchrotron radiation  

NASA Astrophysics Data System (ADS)

Electro-optic (EO) detection of relativistic Coulomb fields offers a method for non-destructive longitudinal profile measurements of ultrashort bunches. Techniques for single-shot EO characterisation of Coulomb fields which have been developed or demonstrated at the FELIX free electron laser (FEL) facility are discussed. In addition, recent FELIX experiments have used single-shot electro-optic detection to measure the temporal profile of the far-infrared electric field pulse of coherent synchrotron radiation (CSR), initial results of which are reported here. Such time-resolved CSR measurements have the potential for a completely non-invasive bunch longitudinal profile determination, without the ambiguity in profile that is present in CSR spectral measurements.

Jamison, S. P.; Berden, G.; MacLeod, A. M.; Jaroszynski, D. A.; Redlich, B.; van der Meer, A. F. G.; Gillespie, W. A.

2006-02-01

356

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

357

Radiation spectrum of an electron moving in a spiral in magnetic field in transparent media and in vacuum  

Microsoft Academic Search

Using the exact integral relationship for the spectral distribution of radiation power of an electron moving along a spiral\\u000a in vacuum, the fine structure of synchrotron radiation spectrum at the first harmonics was investigated. The variation of\\u000a the power spectral distribution of synchrotron-Cherenkov radiation for an electron moving in magnetic field in a transparent\\u000a medium is studied.

A. V. Konstantinovich; S. V. Melnychuk; I. A. Konstantinovich

2006-01-01

358

A study on quantitative analysis of field size and dose by using gating system in 4D conformal radiation treatment  

Microsoft Academic Search

This study evaluated the gating-based 4-D conformal radiation therapy (4D-CT) treatment planning by a comparison with the common 3-D conformal radiation therapy (3D-CT) treatment planning and examined the change in treatment field size and dose to the tumors and adjacent normal tissues because an unnecessary dose is also included in the 3-D treatment planning for the radiation treatment of tumors

Youn-Sang Ji; Kyung-Rae Dong; Chang-Bok Kim; Woon-Kwan Chung; Jae-Hwan Cho; Hae-Kag Lee

2012-01-01

359

Influences of cosmic radiation, artificial radioactivity and aerosol concentration upon the fair-weather atmospheric electric field in Lisbon (1955 1991)  

Microsoft Academic Search

The atmospheric electric field is influenced by cosmic radiation, radioactivity and aerosols. In this work we investigate the existence of: (i) correlations between relative anomalies of annual values of atmospheric electric field and cosmic radiation intensity, artificial radioactivity and aerosol concentration; (ii) seasonal correlations between relative anomalies of the atmospheric electric field and cosmic radiation intensity. We used data of

Cláudia Serrano; A. Heitor Reis; Rui Rosa; Paulo S. Lucio

2006-01-01

360

Influences of cosmic radiation, artificial radioactivity and aerosol concentration upon the fair-weather atmospheric electric field in Lisbon (1955–1991)  

Microsoft Academic Search

The atmospheric electric field is influenced by cosmic radiation, radioactivity and aerosols. In this work we investigate the existence of: (i) correlations between relative anomalies of annual values of atmospheric electric field and cosmic radiation intensity, artificial radioactivity and aerosol concentration; (ii) seasonal correlations between relative anomalies of the atmospheric electric field and cosmic radiation intensity. We used data of

Cláudia Serrano; A. Heitor Reis; Rui Rosa; Paulo S. Lucio

2006-01-01

361

Non-thermal vasodilatation by radio frequency burst-type electromagnetic field radiation in the frog.  

PubMed Central

1. When the web of the anaesthetized Xenopus laevis was perfused with Ringer solution maintained at 20 degrees C, radio frequency (RF) burst-type electromagnetic (EM) field radiation not only dilated arterioles of the web which had been preconstricted with noradrenaline, but also dilated arterioles under non-stimulated conditions. The EM field-induced vasodilatation increased slowly and reached a plateau 60 min after the onset of radiation. After the cessation of radiation, vasodilatation remained for 10-20 min, then slowly subsided. 2. When a 10 MHz, 1 V (peak to peak) generator voltage induced a 7.3 milliGauss, 2.19 V cm-1 EM field, the vasodilatory effect was optimum when bursts were applied 50% of the total time at 10 kHz burst rate. 3. The vasodilatory effect was not secondary to dielectric heat in the web, because the EM field was too weak to have produced enough heat to dilate the arterioles and heat would have been constantly conducted away by the perfusion solution. 4. During perfusion with Ringer solution warmed to 30 degrees C, no vasodilatation was found, but perfusion with Ringer solution warmed to 35 degrees C induced only 11% vasodilatation. Perfusion with Ringer solution warmed to 37 degrees C induced irreversible vasoconstriction. The pattern of vasodilatation induced by warm Ringer solution was different from the vasodilatory effect of weak EM field radiation. 5. The extent of the vasodilatory effect was influenced by Ca2+ concentration of the perfusion medium. Under normal Ca2+ conditions arterioles dilated to 126% of the control diameter, while under Ca(2+)-free conditions arterioles dilated to 131% of the control value and under high-Ca2+ conditions (twice the normal level) arterioles dilated to 111% of the control value. This suggests that the vasodilatory effect may be caused by facilitation of Ca2+ outflow, and the extent of this flow may settle down to the equilibrium level of countercurrent flux between Ca2+ influx and outflow. 6. The vasodilatory effect was not inhibited under perfusion with Na(+)-free Ringer solution, suggesting that Na(+)-Ca2+ exchange system may not be involved in the vasodilatory effect. The vasodilatory effect was inhibited by vanadate, an inhibitor of Ca(2+)-ATPase, and was abolished by Methylene Blue, an inhibitor of guanylate cyclase. The evidence suggests that the mechanism of the vasodilatory effect may depend on an increase in Ca2+ outflow through the plasma membrane of the smooth muscle and/or an increase in Ca2+ influx into the sarcoplasmic reticulum.(ABSTRACT TRUNCATED AT 400 WORDS) Images Fig. 2 PMID:1770439

Miura, M; Okada, J

1991-01-01

362

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

363

An optimal numerical filter for wide-field-of-view measurements of earth-emitted radiation  

NASA Technical Reports Server (NTRS)

A technique is described in which all data points along an arc of the orbit may be used in an optimal numerical filter for wide-field-of-view measurements of earth emitted radiation. The statistical filter design is derived whereby the filter is required to give a minimum variance estimate of the radiative exitance at discrete points along the ground track of the satellite. An equation for the optimal numerical filter is given by minimizing the estimate error variance equation with respect to the filter weights, resulting in a discrete form of the Wiener-Hopf equation. Finally, variances of the errors in the radiant exitance can be computed along the ground track and in the cross track directions.

Smith, G. L.; House, F. B.

1981-01-01

364

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

SciTech Connect

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

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

2010-12-07

365

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

NASA Astrophysics Data System (ADS)

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

Behrens, R.

2013-02-01

366

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

367

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

NASA Astrophysics Data System (ADS)

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

Massillon-JL, G.

2010-12-01

368

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

369

Cloud-Radiation Field Changes due to the Direct Effect of Smoke Aerosols in Southeast Mexico  

NASA Astrophysics Data System (ADS)

In general, aerosols affect climate mainly by directly absorbing and scattering input solar radiation and indirectly through their rule as cloud condensation nuclei. Smoke aerosols from biomass burning are considered to be the second most important source of anthropogenic particles (sulfate aerosols being the first) that are influencing the climate. Numerical simulations are carried on MM5 (using the CCM2 radiative scheme) by introducing the smoke aerosol spectral optical properties in the southeastern Mexican region. The neighborhood of this region is the most important source of biomass burning aerosols in Central America during the dry season (February-June). The particles are considered to be homogeneous in composition and the optical properties are calculated using Mie theory and the Remer et al. (1998) smoke model. Simulations are performed for March 17-20 and April 18-20, 2003. These two periods resulted to be a relative maximum in the number of fires detected in the studied region according to different algorithms based on satellite imagery. GDAS data are used to initialize the MM5 model. The goal is to study the changes in the cloud-radiation field due to the aerosol direct effect varying the smoke aerosol optical properties, especially the optical depth. Preliminary results support the argument that not only the aerosol effect is important but also the cloud changes due to the radiative differences caused by the aerosol direct effect itself. These cloud effects followed very different ways sometimes depending on atmospheric conditions of course, but also on other characteristics such as orography or land surface features. The simulations indicate a wide range on the surface radiative forcing varying from -40 W/m2 for smoke particles with an optical depth of 0.2 (at 670 nm), to -140 W/m2 for particles with an optical depth of 0.8.

Montero-Martinez, M. J.

2003-12-01

370

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.

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

2012-01-01

371

Induced Radioactivity of Materials by Stray Radiation Fields at an Electron Accelerator  

SciTech Connect

Samples of soil, water, aluminum, copper and iron were irradiated in the stray radiation field generated by the interaction of a 28.5 GeV electron beam in a copper-dump in the Beam Dump East facility at SLAC. The specific activity induced in the samples was measured by gamma spectroscopy and other techniques. In addition, the isotope production in the samples was calculated with detailed Monte Carlo simulations using the FLUKA code. The calculated activities are compared to the experimental values and differences are discussed.

Roesler, Stefan

2001-07-16

372

Photodissociation rates of OH, OD, and CN by the interstellar radiation field  

NASA Technical Reports Server (NTRS)

The photoabsorption cross sections for OH, OD, and CN in the vacuum ultraviolet region are measured. The cross sections for the hydroxyl radicals are of the order of 10 to the -17th sq cm, but the photoabsorption for CN is so low that only an upper limit of 2 x 10 to the -18th sq cm is obtained. The molecular photodissociative processes are discussed. The photodissociation cross sections are inferred from the photoabsorption cross sections. On the basis of the measured data, the photodissociation rates by the interstellar radiation field are computed and discussed.

Nee, J. B.; Lee, L. C.

1985-01-01

373

Dynamic characteristics of far-field radiation of current modulated phase-locked diode laser arrays  

NASA Technical Reports Server (NTRS)

A versatile and powerful streak camera/frame grabber system for studying the evolution of the near and far field radiation patterns of diode lasers was assembled and tested. Software needed to analyze and display the data acquired with the steak camera/frame grabber system was written and the total package used to record and perform preliminary analyses on the behavior of two types of laser, a ten emitter gain guided array and a flared waveguide Y-coupled array. Examples of the information which can be gathered with this system are presented.

Elliott, R. A.; Hartnett, K.

1987-01-01

374

Freud and film: encounters in the Weltgeist.  

PubMed

Freud's antipathy toward film is striking, since film and dreams are formed by similar mechanisms. Nevertheless, Freud occasionally and unavoidably encountered film. This paper details some of these encounters. Ten years after viewing time-lapse photography, a fore-runner of moving pictures, at the Salpêtrière, he was conceptualizing a model of the mind and of the formation of dreams that in some ways parallels the film apparatus invented by the Lumière brothers in December 1895. On his visit to America in 1905, Freud saw movies in New York City. In 1925, he refused a lucrative offer to consult on a film, and he discouraged Karl Abraham and Hanns Sachs from consulting on the first psychoanalytic film, Pabst's Secrets of a Soul (1926). He was, however, once sighted viewing an American double feature in Vienna. The paper closes with a critique of his acting in home movies. PMID:10650559

Sklarew, B

1999-01-01

375

Numerical Study of a Convective Turbulence Encounter  

NASA Technical Reports Server (NTRS)

A numerical simulation of a convective turbulence event is investigated and compared with observational data. The specific case was encountered during one of NASA's flight tests and was characterized by severe turbulence. The event was associated with overshooting convective turrets that contained low to moderate radar reflectivity. Model comparisons with observations are quite favorable. Turbulence hazard metrics are proposed and applied to the numerical data set. Issues such as adequate grid size are examined.

Proctor, Fred H.; Hamilton, David W.; Bowles, Roland L.

2002-01-01

376

Introduction to the Ulysses encounter with Jupiter  

NASA Technical Reports Server (NTRS)

The Ulysses spacecraft encountered Jupiter in February 1992, passing within 6.31 radii of the planet. For approximately 8 days it was inside the Jovian magnetosphere, and for several days before and after that, Ulysses was in the interaction regions formed by the solar wind (the magnetosheath and boundary layer). The inbound trajectory was at an approximately 1000 LT and the outbound trajectory was at 1800 LT, that is, dusk, a unique feature of the flight path. Three regions interior to the magnetosphere were identified as on previous missions both inbound and outbound. In addition, the spacecraft twice penetrated a cusplike region at high latitude in the inner magnetosphere. Following closest approach, Ulysses traversed the Io plasma torus in basically a north-south direction. Although Ulysses is a heliospheric mission, the experiments were suited to an investigation of Jupiter's magnetosphere and have returned much new information. This introduction to the accompanying articles by the Ulysses investigators provides basic information on the experiments, the spacecraft, and the trajectory. In addition, the scientific context of the encounter is reviewed on the basis of the preliminary analyses of the Ulysses observations and a rudimentary comparison with the earlier Pioneer and Voyager results. Some important scientific questions raised by the encounter, along with some tentative answers, are presented.

Smith, Edward J.; Wenzel, Klaus-Peter

1993-01-01

377

Multiphoton processes in scattering and ionization in an intense linearly-polarized radiation field  

SciTech Connect

We have employed the Gavrila-Kaminski formulation for the conversion of the time-dependent Schrodinger equation to a set of coupled differential equations that describe the interaction of an electron with a proton in the presence of an intense linearly-polarized radiation field in the Kramers-Henneberger gauge. The differential equations are solved numerically by a linear algebraic prescription effectively applied to electron-molecule collisions. We studied both electron-proton collisions assisted by the laser field and multiphoton ionization of H. In the former, we observed the capture-escape resonances while in the latter, we found evidence of the stabilization mechanism as the intensity reaches 10{sup 18} W/cm{sup 2}.

Collins, L.A. (Los Alamos National Lab., NM (United States)); Csanak, G. (Tsukuba Univ., Ibaraki (Japan))

1992-01-01

378

Multiphoton processes in scattering and ionization in an intense linearly-polarized radiation field  

SciTech Connect

We have employed the Gavrila-Kaminski formulation for the conversion of the time-dependent Schrodinger equation to a set of coupled differential equations that describe the interaction of an electron with a proton in the presence of an intense linearly-polarized radiation field in the Kramers-Henneberger gauge. The differential equations are solved numerically by a linear algebraic prescription effectively applied to electron-molecule collisions. We studied both electron-proton collisions assisted by the laser field and multiphoton ionization of H. In the former, we observed the capture-escape resonances while in the latter, we found evidence of the stabilization mechanism as the intensity reaches 10{sup 18} W/cm{sup 2}.

Collins, L.A. [Los Alamos National Lab., NM (United States); Csanak, G. [Tsukuba Univ., Ibaraki (Japan)

1992-06-01

379

Propagation of Light in the Field of Stationary and Radiative Gravitational Multipoles  

E-print Network

Extremely high precision of near-future radio/optical interferometric observatories like SKA, Gaia, SIM and the unparalleled sensitivity of LIGO/LISA gravitational-wave detectors demands more deep theoretical treatment of relativistic effects in the propagation of electromagnetic signals through variable gravitational fields of the solar system, oscillating and precessing neutron stars, coalescing binary systems, exploding supernova, and colliding galaxies. Especially important for future gravitational-wave observatories is the problem of propagation of light rays in the field of multipolar gravitational waves emitted by a localized source of gravitational radiation. Present paper suggests physically-adequate and consistent mathematical solution of this problem in the first post-Minkowskian approximation of General Relativity which accounts for all time-dependent multipole moments of an isolated astronomical system.

Sergei Kopeikin; Pavel Korobkov; Alexander Polnarev

2006-03-15

380

Galileo early cruise, including Venus, first Earth, and Gaspra encounters  

NASA Technical Reports Server (NTRS)

This article documents Deep Space Network (DSN) support for the Galileo cruise to Jupiter. The unique trajectory affords multiple encounters during this cruise phase. Each encounter had or will have unique requirements for data acquisition and DSN support configurations. An overview of the cruise and encounters through the asteroid Gaspra encounter is provided.

Beyer, P. E.; Oconnor, R. C.; Mudgway, D. J.

1992-01-01

381

Galileo early cruise, including Venus, First Earth, and Gaspra encounters  

NASA Technical Reports Server (NTRS)

This article documents DSN support for the Galileo cruise to Jupiter. The mission's unique trajectory affords multiple encounters during this cruise phase. Each encounter had or will have unique requirements for data acquisition and DSN support configurations. An overview of the cruise and its encounters, up through the asteroid Gaspra encounter, is provided.

Beyer, P. E.; Oconnor, R. C.; Mudgway, D. J.

1992-01-01

382

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

383

Experimental determination of radiated internal wave power without pressure field data  

E-print Network

We present a method to determine, using only velocity field data, the time-averaged energy flux $\\left$ and total radiated power $P$ for two-dimensional internal gravity waves. Both $\\left$ and $P$ are determined from expressions involving only a scalar function, the stream function $\\psi$. We test the method using data from a direct numerical simulation for tidal flow of a stratified fluid past a knife edge. The results for the radiated internal wave power given by the stream function method agree to within 0.5% with results obtained using pressure and velocity data from the numerical simulation. The results for the radiated power computed from the stream function agree well with power computed from the velocity and pressure if the starting point for the stream function computation is on a solid boundary, but if a boundary point is not available, care must be taken to choose an appropriate starting point. We also test the stream function method by applying it to laboratory data for tidal flow past a knife ed...

Lee, Frank M; Swinney, Harry L; Morrison, P J

2014-01-01

384

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

385

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

386

Analgesic effect of simultaneous exposure to infrared laser radiation and ?T magnetic field in rats  

NASA Astrophysics Data System (ADS)

The aim of the experiment was to estimate the effect of repeated simultaneous exposures to infrared laser radiation and ?T variable magnetic field used in magnetostimulation on pain perception in rats, as well as the involvement of endogenous opioid system in the mechanism of this effect. In experimental group clean-shaven scull of male Wistar rats placed individually in a specially designed plastic chamber were simultaneously exposed to infrared laser radiation (wavelength - 855 nm, mean power - 4,1 mW, energy density - 30 J/cm2) and variable magnetic field of saw-like shape of impulse, at a frequency of basic impulse 180-195 Hz and mean induction value of 120 ?T generated by magneto-laser applicator of device for magnetostimulation Viofor JPS (Med & Life, Poland) 12 minutes daily for 2 periods of 5 consecutive days, with 2 days-lasting break between them, while control animals were sham-exposed. The pain perception was determined by means of "hot plate" test on the basis of calculated analgesic index. As a result of repeated exposures a significant increase in analgesic index persisting also till 14 th day after the end of a cycle of exposures was observed. This analgesic effect was inhibited by prior i.p. injection of opioid antagonist - Naloxone.

Cieslar, Grzegorz; Mrowiec, Janina; Kasperczyk, Slawomir; Sieron-Stoltny, Karolina; Sieron, Aleksander

2008-03-01

387

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

388

Stellar encounters in the context of outburst phenomena  

NASA Astrophysics Data System (ADS)

Young stellar systems are known to undergo outbursts, where the star experiences an increased accretion rate, and the system's luminosity increases accordingly. The archetype is the FU Orionis (FU Ori) outburst, where the accretion rate can increase by three orders of magnitude (and the brightness of the system by five magnitudes). The cause appears to be instability in the circumstellar disc, but there is currently some debate as to the nature of this instability (e.g. thermal, gravitational, magneto-rotational). This paper details high-resolution smoothed particle hydrodynamics (SPH) simulations that were carried out to investigate the influence of stellar encounters on disc dynamics. Star-star encounters (where the primary has a self-gravitating, marginally stable protostellar disc) were simulated with various orbital parameters to investigate the resulting disc structure and dynamics. Crucially, the simulations include the effects of radiative transfer to realistically model the resulting thermodynamics. Our results show that the accretion history and luminosity of the system during the encounter display many of the features of outburst phenomena. In particular, the magnitudes and decay times seen are comparable to those of FU Ori. There are two caveats to this assertion: the first is that these events are not expected to occur frequently enough to explain all FU Ori or EX Lupi; the second is that the inner discs of these simulations are subject to numerical viscosity, which will act to reduce the accretion rate (although it has less of an effect on the total mass accreted). In short, these results cannot rule out binary interactions as a potential source of some FU Ori-esque outbursts.

Forgan, Duncan; Rice, Ken

2010-02-01

389

Radiation damage of amorphous silicon, thin-film, field-effect transistors.  

PubMed

The effect of 60Co radiation on the noise and drain-source current characteristics of hydrogenated amorphous silicon (alpha-Si:H) field-effect transistors (FETs) was examined as a function of dose to cumulative doses as high as approximately 2 x 10(4) Gy. Following these measurements, room-temperature and elevated-temperature annealing of induced radiation damage was examined. The FETs examined are representative of those incorporated in alpha-Si:H arrays under development for various x-ray medical imaging applications. No significant effect upon the noise characteristics of the FETs was observed as a result of the radiation. The predominant drain-source current effect with increasing dose was a shift of the transfer characteristic toward negative gate voltage and/or a decrease of the transfer characteristic subthreshold slope. This resulted in large increases in leakage current for gate voltages where the FETs were initially highly nonconducting. This leakage current increase was less pronounced for more negative gate voltages and was further diminished by maintaining the FETs at a more negative gate voltage during the irradiation. Following the radiation measurements, room-temperature annealing resulted in a 10% to 50% reduction in the leakage current in the first day followed by a logarithmic decrease thereafter. Elevated-temperature annealing for 2 h at 200 degrees C restored FET leakage current and threshold voltage properties to their preirradiation values. The irradiation effects are small for cumulative doses less than approximately 100 Gy, which is larger than the clinical lifetime dose for an imaging detector for chest radiography or for fluoroscopy (with infrequent exposure to the direct beam). For significantly higher dose applications such as mammography, fluoroscopy (with frequent direct beam exposure), and radiotherapy imaging, the results suggest that periodic elevated-temperature annealing or operation of the arrays at more negative gate voltages may be necessary. PMID:8724748

Boudry, J M; Antonuk, L E

1996-05-01

390

The effect of an external electric field on radiation transmission and Compton scattering in plexiglass  

NASA Astrophysics Data System (ADS)

The effect of an external electric field on radiation transmission of a plexiglass sample has been studied by using an extremely narrow-collimated-beam transmission method. Also, the photon scattering properties of the charge centers have been determined by changing the charge density distributions of the plexiglass sample with an external electric field having an intensity in the range 0-1000 V/cm. The plexiglass sample was bombarded by 59.5 keV gamma rays emitted from an Am-241 point source. The transmitted and Compton scattered photons were detected by a Si(Li) detector. Appreciable variations were observed in the transmission factors of the plexiglass sample as a function of applied field. The results show that the electrical properties of the plexiglass sample changes with the applied electric field and the gamma ray irradiations although it is a dielectric material. Furthermore, the negatively charged scattering centers are slightly more effective than the positively charged scattering centers in the Compton scattering of gamma rays from an insulator sample, similar to result found for conductor and semiconductors.

Demir, D.

2008-04-01

391

The effect of cumulus cloud field anisotropy on solar radiative fluxes and atmospheric heating rates  

NASA Astrophysics Data System (ADS)

The effect of fair-weather cumulus cloud field anisotropy on domain average surface fluxes and atmospheric heating profiles was studied. Causes of anisotropy were investigated using a large-eddy simulation (LES) model. Cloud formation under a variety of environmental conditions was simulated and the degree of anisotropy in the output fields was calculated. Wind shear was found to be the single greatest factor in the development of both vertically tilted and horizontally stretched cloud structures. A stochastic field generation algorithm was used to produce twenty three-dimensional liquid water content fields based on the statistical properties of the LES cloud scenes. Progressively greater degrees of tilt and stretching were imposed on each of these scenes, so that an ensemble of scenes were produced for each level of distortion. The resulting scenes were used as input to a three-dimensional Monte Carlo model. Domain-average transmission, reflection, and absorption of broadband solar radiation were computed for each scene along with the average heating rate profile. Both tilt and horizontal stretching were found to significantly affect calculated fluxes, with the amount and sign of flux differences depending strongly on sun position relative to cloud distortion geometry. For nearly all solar geometries, domain-averaged fluxes and atmospheric heating rate profiles calculated using the Independent Pixel Approximation differed substantially from the corresponding three-dimensional Monte Carlo results.

Hinkelman, Laura M.

392

Generalized Reference Fields and Source Interpolation for the Difference Formulation of Radiation Transport  

SciTech Connect

In the difference formulation for the transport of thermally emitted photons, the photon intensity is defined relative to a reference field, the black body at the local material temperature. This choice of reference field combines the separate emission and absorption terms that nearly cancel, removing the dominant cause of noise in the Monte Carlo solution of thick systems, but introduces time and space derivative source terms that can not be determined until the end of the time step. The space derivative source term can also lead to noise induced crashes under certain conditions where the real physical photon intensity differs strongly from a black body at the local material temperature. In this paper, we consider a difference formulation relative to the material temperature at the beginning of the time step, or in cases where an alternative temperature better describes the radiation field, that temperature. The result is a method where iterative solution of the material energy equation is efficient and noise induced crashes are avoided. We couple our generalized reference field scheme with an ad hoc interpolation of the space derivative source, resulting in an algorithm that produces the correct flux between zones as the physical system approaches the thick limit.

Luu, T C; Brooks, E D; Szoke, A

2009-02-05

393

Astrophysical False Positives Encountered in Wide-Field Transit Searches  

E-print Network

in tight orbits about their parent stars [for a review, see 1, 2]. Several of these projects are small these requirements. Rather, the current challenge is that of efficiently rejecting astro- physical false positives, i

394

Africa on My Mind: Encounters in the Field  

E-print Network

Journal ofSociology 3 (Spring) .76-89. __. 1981. "Athletics and Higher .Education: A Conflict Perspective." Paper pre~entedat the annual meetings of the North American Society for the Soclolo~ of Sport, Dallas (November). . __. 1984. Conflict Theory... and the Sociology of Sport." Arena Review 8 (November):45-54. __.1988. "Conflict Theory and Deviance in Sport." International Review for . the Sociology ofSport 23:193-204. EItzen, D. Stanley and Maxine Baca Zinn. 1989. "The De-Athleticization of Wo~en: The Naming...

Burgess, Elaine

1990-01-01

395

Ionizing radiation  

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

396

Field effects of cadmium contamination in the radiation characteristics of maize  

NASA Astrophysics Data System (ADS)

Cadmium is one of the most common toxic heavy metals in our environment. Cadmium is a particularly dangerous element, because it dissolves readily, making it easily available to plants. It is thus able to accumulate in various links in the food chain, finally reaching humans, at the end of the chain. Adverse effects on human body was reported in 1858 at first. If it enters the body, damage to health, cause changes and can also cause cancer. Our study was designated to simulate the effects of cadmium on maize in field conditions, during the 2011 growing season. The impact of cadmium on maize was investigated at the Agro-meteorological Research Station in Keszthely. A Swiss-bred maize hybrid, Sperlona (FAO 340), with a short vegetation period, was sown in the experiments at the plant density (70,000 plants per hectare) widely used under Hungarian climatic conditions for growing grain maize. Effects of cadmium on corn life were studied under two water supplies. Evapotranspirometers of the Thornthwaite type were used for the "ad libitum" treatment and the the rainfed variant was sown in field plots. 0,5 M concentration of cadmium was used, which was sprayed weekly. The aim of the investigation was to simulate impact of atmospheric pollution of traffic origin (low and frequent doses in the field). Plant height was registered weekly similarly to leaf area index (LAI). Albedo was measured by pyranometers of the CMA-11 type (Kipp & Zonen, Vaisala). From this the most important radiative properties were calculated, so the net radiation balance, latent heat, sensible heat and the Bowen ratio. The values of LAI for the cadmium contaminated maize were significantly lower compared to the control maize. The net radiation balance was about the same in both treatments. Cadmium causes the latent heat decreased, while the sensible heat increased compared to the control treatment. The Bowen ratio in the polluted crops was higher, than the cadmium-untreated area. The yield of maize declined as a result of cadmium pollution. The number of distorted cobs increased on a very high extent. It means that both the quantity and quality of yield deteriorated in cadmium polluted fields. This article was made under the project TÁMOP-4.2.1/B-09/1/KONV-2010-0003 and TÁMOP-4.2.2/B-10/1-2010-0025. These projects are supported by the European Union and co-financed by the European Social Fund.

Illes, B.; Anda, A.

2012-04-01

397

Matter and radiation in the strong magnetic fields of neutron stars  

NASA Astrophysics Data System (ADS)

Recent observations of the radiation from highly magnetized neutron stars have provided a wealth of information on these objects, but they have also raised many new questions. We study various aspects of the surfaces and magnetospheres of neutron stars, including the cohesive properties and condensation of the stellar surface, formation of magnetosphere acceleration zones, and the initiation and propagation of electron-positron cascades through the magnetosphere. We present calculations of the electronic structure of matter in strong magnetic fields ranging from B = 10^12 G to 2 × 10^15 G, appropriate for observed magnetic neutron stars. Our calculations are based on the density functional theory. We find that condensed matter surfaces composed of hydrogen, helium, and carbon are all bound relative to individual atoms for B = 10^12 G or higher. Condensed iron surfaces, however, are only significantly bound for B [Special characters omitted.] 10^14 G. We also present Hartree-Fock calculations of the polarization-dependent photoionization cross sections of the He atom in strong magnetic fields ranging from 10^12 G to 10^14 G. We investigate several important astrophysical implications of our calculations of the cohesive property of magnetic condensed matter. We find that for sufficiently strong magnetic fields and/or low temperatures, the neutron star surface may be in a condensed state with little gas or plasma above it; such surface condensation may lead to the formation of a charge-depleted acceleration zone ("vacuum gap") in the magnetosphere above the stellar polar cap. We quantitatively determine the conditions for surface condensation and vacuum gap formation in magnetic neutron stars. We find that condensation can occur if the thermal energy kT of the neutron star surface is less than about 8% of its cohesive energy Q s , and that a vacuum gap can form if kT is less than about 4% of Qs . We study the conditions for the onset of pair cascades in the magnetospheres of neutron stars and the related pulsar death line/boundary. We also present Monte Carlo simulations of the full pair cascade from onset to completion. Our calculations generalize previous works to the superstrong field regime. We find that curvature radiation is a viable mechanism for the initiation of pair cascades, but that resonant and nonresonant inverse Compton scatterings are not. Additionally, we obtain the final photon spectra and pair energy distribution functions of the cascade and find significant differences between their nature in high-field neutron stars and in moderate-field neutron stars.

Medin, Zachary James

398

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,

399

Intermolecular interactions in a radiation field via the method of induced moments  

SciTech Connect

Molecular quantum electrodynamics is employed to calculate a generalized formula for the energy shift between a pair of molecules that have electric polarizability of arbitrary multipole order and are in the presence of an intense electromagnetic field. In contrast to a previous calculation of the dipole-dipole contribution, which required fourth-order time-dependent perturbation theory for its evaluation, the present approach involves calculating the interaction between the multipole moments induced at each center by the incident beam and the resonant multipole-multipole coupling tensor together with the average value of the spatial correlation function of the displacement field for an N-photon state. The theory developed applies to the situation where the molecular pair is held fixed relative to the direction of propagation of the radiation field or is allowed to be completely randomly oriented. Explicit results are obtained for dipole-quadrupole and quadrupole-quadrupole polarizable molecules. For oriented systems the energy shift for linear and circular polarizations is examined for incident radiation propagating in directions parallel and perpendicular to the intermolecular join, and the asymptotic behavior is obtained at the limits of short and large separation distance. After performing a pair orientation average, the energy shift in the near zone is found to exhibit an R{sup -1} power-law behavior with separation distance, while the far zone has a modulated R{sup -2} dependence in all of the cases considered. None of the energy shifts obtained display discriminatory characteristics, with respect to either the handedness of the incident beam or the individual species.

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

2006-01-15

400

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

NASA Astrophysics Data System (ADS)

The Electric Fields and Waves (EFW) Instruments on the two Radiation Belt Storm Probe (RBSP) spacecraft (recently renamed the Van Allen Probes) are designed to measure three dimensional quasi-static and low frequency electric fields and waves associated with the major mechanisms responsible for the acceleration of energetic charged particles in the inner magnetosphere of the Earth. For this measurement, the instrument uses two pairs of spherical double probe sensors at the ends of orthogonal centripetally deployed booms in the spin plane with tip-to-tip separations of 100 meters. The third component of the electric field is measured by two spherical sensors separated by ˜15 m, deployed at the ends of two stacer booms oppositely directed along the spin axis of the spacecraft. The instrument provides a continuous stream of measurements over the entire orbit of the low frequency electric field vector at 32 samples/s in a survey mode. This survey mode also includes measurements of spacecraft potential to provide information on thermal electron plasma variations and structure. Survey mode spectral information allows the continuous evaluation of the peak value and spectral power in electric, magnetic and density fluctuations from several Hz to 6.5 kHz. On-board cross-spectral data allows the calculation of field-aligned wave Poynting flux along the magnetic field. For higher frequency waveform information, two different programmable burst memories are used with nominal sampling rates of 512 samples/s and 16 k samples/s. The EFW burst modes provide targeted measurements over brief time intervals of 3-d electric fields, 3-d wave magnetic fields (from the EMFISIS magnetic search coil sensors), and spacecraft potential. In the burst modes all six sensor-spacecraft potential measurements are telemetered enabling interferometric timing of small-scale plasma structures. In the first burst mode, the instrument stores all or a substantial fraction of the high frequency measurements in a 32 gigabyte burst memory. The sub-intervals to be downloaded are uplinked by ground command after inspection of instrument survey data and other information available on the ground. The second burst mode involves autonomous storing and playback of data controlled by flight software algorithms, which assess the "highest quality" events on the basis of instrument measurements and information from other instruments available on orbit. The EFW instrument provides 3-d wave electric field signals with a frequency response up to 400 kHz to the EMFISIS instrument for analysis and telemetry (Kletzing et al. Space Sci. Rev. 2013).

Wygant, J. R.; Bonnell, J. W.; Goetz, K.; Ergun, R. E.; Mozer, F. S.; Bale, S. D.; Ludlam, M.; Turin, P.; Harvey, P. R.; Hochmann, R.; Harps, K.; Dalton, G.; McCauley, J.; Rachelson, W.; Gordon, D.; Donakowski, B.; Shultz, C.; Smith, C.; Diaz-Aguado, M.; Fischer, J.; Heavner, S.; Berg, P.; Malsapina, D. M.; Bolton, M. K.; Hudson, M.; Strangeway, R. J.; Baker, D. N.; Li, X.; Albert, J.; Foster, J. C.; Chaston, C. C.; Mann, I.; Donovan, E.; Cully, C. M.; Cattell, C. A.; Krasnoselskikh, V.; Kersten, K.; Brenneman, A.; Tao, J. B.

2013-11-01

401

Gynogenesis in carp, Cyprinus Carpio L. and tench, Tinca Tinca L. induced by 60Co radiation in highly homogeneous radiating field  

NASA Astrophysics Data System (ADS)

The paper deals with a method of fertility inactivation of fish spermatozoa by gamma radiation. Spermatozoa motility remained unchanged after irradiation. Irradiated sperm has been utilized to induced gynogenesis by means of retention of the second polar body and of mitotic gynogenesis, realized in carp for the first time. Homogeneity of gamma-rays field was + - 1 %.

Pipota, J.; Linhart, O.

402

Earth imaging results from Galileo's second encounter  

NASA Technical Reports Server (NTRS)

The recent flyby of the Galileo spacecraft en route to Jupiter contributes a unique perspective to our view of our home planet. Imaging activities conducted during the second Earth encounter provide an important opportunity to assess new methods and approaches on familiar territory. These include unique multispectral observations, low light-level imaging (searches for aurorae, lightning and artificial lights on the nightside) and experiments with multiple exposure times to extend the effective radiometric resolution and dynamic range of the camera system. Galileo imaging data has the potential to make important contributions to terrestrial remote sensing. This is because the particular set of filters included in the Solid State Imaging system are not presently incorporated in any currently operating Earth-orbiting sensor system. The visible/near-infrared bandpasses of the SSI filters are well suited to remote sensing of geological, glaciological, botanical, and meteorological phenomena. Data from this and the previous Earth encounter may provide an extremely valuable reference point in time for comparison with similar data expected from EOS or other systems in the future, contributing directly to our knowledge of global change. The highest resolution imaging (0.2 km/pixel) during the December, 1992 encounter occurred over the central Andes; a five filter mosaic of visible and near infrared bands displays the remarkable spectral heterogeneity of this geologically diverse region. As Galileo departed the Earth, cooperative imaging with the Near Infrared Mapping Spectrometer (NIMS) instrument targeted Antarctica, Australia, and Indonesia at 1.0 to 2.5 km/pixel resolutions in the early morning local times near the terminator. The Antarctic data are of particular interest, potentially allowing ice grain size mapping using the 889 and 968 nm filters and providing an important means of calibrating the technique for application to the Galilean satellites. As the spacecraft receded further, regional scale imaging provided data which, along with data from the previous encounter, will enable the production of global multispectral mosaics of Earth in each of the SSI filters.

Greenberg, R.; Belton, M.; Dejong, E.; Ingersoll, A.; Klaasen, K.; Geissler, P.; Moersch, J.; Thompson, W. R.

1993-01-01

403

NGC 2442: Tidal Encounters and the Evolution of Spiral Galaxies  

E-print Network

Using imaging Fabry-Perot data, we study the star-forming properties and kinematics of the nearby barred spiral galaxy NGC 2442. The Halpha emission is very localized along the strong spiral arms of the galaxy, and shows a marked asymmetry between the sharp, well-defined northern tidal arm and the weaker southern arm. The velocity field appears highly distorted, with a rapidly rotating nuclear component. We find evidence for strong non-circular motions along the northern arm, coincident with the pronounced dust lane and regions of intense star formation. The strong asymmetries, disturbed velocity field, and presence of a perturbed companion suggest that we are witnessing a strong kinematic response to a close interaction, which has redistributed the star formation activity throughout the disk of NGC 2442. Dynamical modeling supports this hypothesis, and suggests that the regions of strongest star formation are coincident with strong shocks occurring along the perturbed northern arm. Despite this redistribution of gas on small scales, this galaxy does not show a significant departure from the Tully-Fisher relation, nor does it appear to be experiencing any strong starburst. Moreover, our models predict that in a few x 10^8 years, NGC 2442 will have recovered from this encounter and will experience another passage -- and ultimately a merger -- in a few Gyr. Given the environment of many disk galaxies, this tidal encounter cycle seems likely to be a normal phase of disk galaxy evolution.

Chris Mihos; Greg Bothun

1997-01-06

404

Are encounters between negative and positive streamers likely to produce X-rays?  

NASA Astrophysics Data System (ADS)

The underlying processes responsible for the production of high-energy radiation (X- and gamma rays) recently discovered in thunderstorms are not fully understood [e.g., Dwyer et al., Space Sci. Rev., 2012]. In particular, it has been shown that stepped leaders produce X-ray bursts synchronized with the occurrence of new steps [Dwyer et al., GRL, 32, L01803, 2005]. However, as the physical processes responsible for the mechanism of stepping are also unknown, the complete causal chain between leader propagation and X-ray production is not established yet. Laboratory studies of spark and leader discharges and their associated X-ray production are performed precisely to address this point. A consensus exists that in the case of production by leaders, X-rays are due to bremsstrahlung emission from thermal runaway electrons. Thermal runaway electrons are produced through the acceleration of thermal electrons by extreme electric fields (E>250 kV/cm at ground pressure). These electric fields could be produced over short durations at the tips of streamer discharges [Moss et al., JGR, 111, A02307, 2006; Celestin and Pasko, JGR, 116, A03315, 2011]. Some authors have recently suggested that encounters between negative and positive streamers could strongly enhance the electric field, and hence would be responsible for X-ray production [Cooray et al., JASTP, 71,1890, 2009; Kochkin et al., J. Phys. D: Appl. Phys., 45, 425202, 2012]. Moreover, encounters of streamers with different polarities are very common. Indeed, during the formation of a new leader step, the negative streamer zone around the tip of a negative leader and the positive streamers initiated from the positive part of a bidirectional space leader strongly interact. In laboratory sparks, when positive streamers are approaching a sharp cathode, negative streamers are initiated from the cathode and collide with the positive streamers. Given that positive and negative streamers carry positive and negative charges at their fronts, respectively, it is reasonable to consider that the electric field between a negative and a positive streamer would increase as the two streamers are getting closer. However, this problem is more complex than it seems because an increase of the electric field above the breakdown threshold will increase the charge density at this location, which in turn, will tend to screen out the electric field. One clearly sees that this is in fact a complex non-linear problem that depends on the dynamics of both streamers. In this work, we will simulate numerically encounters between negative and positive streamers in order to examine the behavior of the maximum electric field that can be reached. We will determine if such collisions are likely to increase the electric field up to magnitudes sufficient to produce thermal runaway electrons and the associated X-rays.

Celestin, Sebastien; Tholin, Fabien; Bonaventura, Zdenek; Bourdon, Anne

2013-04-01

405

Exposures involving perturbations of the EM field have non-linear effects on radiation response and can alter the expression of radiation induced bystander effects  

NASA Astrophysics Data System (ADS)

Our recent data suggest there is a physical component to the bystander signal induced by radiation exposure and that alternative medicine techniques such as Reiki and acupuncture or exposures to weak EM fields alter the response of cells to direct irradiation and either altered bystander signal production or altered the response of cells receiving bystander signals. Our proposed mechanism to explain these findings is that perturbation of electromagnetic (EM) fields is central to the induction of low radiation dose responses especially non-targeted bystander effects. In this presentation we review the alternative medicine data and other data sets from our laboratory which test our hypothesis that perturbation of bio-fields will modulate radiation response in the low dose region. The other data sets include exposure to MRI, shielding using lead and or Faraday cages, the use of physical barriers to bystander signal transmission and the use of membrane channel blockers. The data taken together strongly suggest that EM field perturbation can modulate low dose response and that in fact the EM field rather than the targeted deposition of ionizing energy in the DNA may be the key determinant of dose response in a cell or organism The results also lead us to suspect that at least when chemical transmission is blocked, bystander signals can be transmitted by other means. Our recent experiments suggest light signals and volatiles are not likely. We conclude that alternative medicine and other techniques involving electromagnetic perturbations can modify the response of cells to low doses of ionizing radiation and can induce bystander effects similar to those seen in medium transfer experiments. In addition to the obvious implications for mechanistic studies of low dose effects, this could perhaps provide a novel target to exploit in space radiation protection and in optimizing therapeutic gain during radiotherapy.

Mothersill, Carmel; Seymour, Colin

2012-07-01

406

Application of different TL detectors for the photon dosimetry in mixed radiation fields used for BNCT.  

PubMed

Different approaches for the measurement of a relatively small gamma dose in strong fields of thermal and epithermal neutrons as used for Boron Neutron Capture Therapy (BNCT) have been studied with various thermoluminescence detectors (TLDs). CaF(2):Tm detectors are insensitive to thermal neutrons but not tissue-equivalent. A disadvantage of applying tissue-equivalent (7)LiF detectors is a strong neutron signal resulting from the unavoidable presence of (6)Li traces. To overcome this problem it is usual to apply pairs of LiF detectors with different (6)Li content. The experimental determination of the thermal neutron response ratio of such a pair at the Geesthacht Neutron Facility (GeNF) operated by PTB enables measurement of the photon dose. In the experimental mixed field of thermal neutrons and photons of the TRIGA reactor at Mainz the photon dose measured with different types of (7)LiF/(nat)LiF TLD pairs agree within a standard uncertainty of 6% whereas the CaF(2):Tm detectors exhibit a photon dose by more than a factor of 2 higher. It is proposed to determine suitable photon energy correction factors for CaF(2):Tm detectors with the help of the (7)LiF/(nat)LiF TLD pairs in the radiation field of interest. PMID:16644976

Burgkhardt, B; Bilski, P; Budzanowski, M; Böttger, R; Eberhardt, K; Hampel, G; Olko, P; Straubing, A

2006-01-01

407

Simulation of Relativistic Shocks and Associated Radiation from Turbulent Magnetic Fields  

NASA Technical Reports Server (NTRS)

Plasma instabilities (e.g., Buneman, Weibel and other two-stream instabilities) excited in collisionless shocks are responsible for particle (electron, positron, and ion) acceleration. Using a new 3-D relativistic particle-in-cell code, we have investigated the particle acceleration and shock structure associated with an unmagnetized relativistic electron-positron jet propagating into an unmagnetized electron-positron plasma. The simulation has been performed using a long simulation system in order to study the nonlinear stages of the Weibel instability, the particle acceleration mechanism, and the shock structure. Cold jet electrons are thermalized and slowed while the ambient electrons are swept up to create a partially developed hydrodynamic (HD) like shock structure. In the leading shock, electron density increases by a factor of <_ 3.5 in the simulation frame. Strong electromagnetic fields are generated in the trailing shock and provide an emission site. We discuss the possible implication of our simulation results within the AGN and GRB context. We have calculated the time evolution of the spectrum from two electrons propagating in a uniform parallel magnetic field to verify the technique. The same technique will be used to calculate radiation from accelerated electrons (positrons) in turbulent magnetic fields generated by Weibel instability.

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

2009-01-01

408

A Topological Structure in the Set of Classical Free Radiation Electromagnetic Fields  

E-print Network

The aim of this work is to proceed with the development of a model of topological electromagnetism in empty space, proposed by one of us some time ago and based on the existence of a topological structure associated with the radiation fields in standard Maxwell's theory. This structure consists in pairs of complex scalar fields, say $\\phi$ and $\\theta$, that can be interpreted as maps $\\phi,\\theta: S^3\\mapsto S^2$, the level lines of which are orthogonal to one another, where $S^3$ is the compactified physical 3-space $R^3$, with only one point at infinity, and $S^2$ is the 2-sphere identified with the complete complex plane. These maps were discovered and studied in 1931 by the German mathematician H. Hopf, who showed that the set of all of them can be ordered in homotopy classes, labeled by the so called Hopf index, equal to $\\gamma=\\pm 1,\\,\\pm 2,\\,\\cdots ,\\, \\pm k,...$ but without $\\gamma=0$. In the model presented here and at the level of the scalars $\\phi$ and $\\theta$, the equations of motion are highly nonlinear; however there is a transformation of variables that converts exactly these equations (not by truncation!) into the linear Maxwell's ones for the magnetic and electric fields $\\B$ and $\\E$.

A. F. Ranada; A. Tiemblo

2014-07-29

409

On momentum and energy of a non-radiating electromagnetic field  

E-print Network

This paper inspects more closely the problem of the momentum and energy of a bound (non-radiating) electromagnetic (EM) field. It has been shown that for an isolated system of non-relativistic mechanically free charged particles a transformation of mechanical to EM momentum and vice versa occurs in accordance with the requirement PG=const, where PG is the canonical momentum. If such a system contains bound charges, fixed on insulators then, according to the assumption of a number of authors, a so-called "hidden" momentum can contribute into the total momentum of the system. The problem of "hidden momentum" (pro and contra) is also examined in the paper, as well as the law of conservation of total energy for different static configurations of the system "magnetic dipole plus charged particle". Analyzing two expressions for electromagnetic momentum of a bound EM field, qA and the Poynting expression, we emphasize that they coincide with each other for quasi-static configurations, but give a discrepancy for rapid dynamical processes. We conclude that neither the first, nor the second expressions provide a continuous implementation of the momentum conservation law. Finally, we consider the energy flux in a bound EM field, using the Umov vector. It has been shown that Umov vector can be directly derived from Maxwell equations. A new form of the momentum-energy tensor, which explicitly unites the mechanical and EM masses, has been proposed.

Alexander L. Kholmetskii

2005-01-28

410

STELLAR ENCOUNTER RATE IN GALACTIC GLOBULAR CLUSTERS  

SciTech Connect

The high stellar densities in the cores of globular clusters cause significant stellar interactions. These stellar interactions can produce close binary mass-transferring systems involving compact objects and their progeny, such as X-ray binaries and radio millisecond pulsars. Comparing the numbers of these systems and interaction rates in different clusters drives our understanding of how cluster parameters affect the production of close binaries. In this paper we estimate stellar encounter rates ({Gamma}) for 124 Galactic globular clusters based on observational data as opposed to the methods previously employed, which assumed 'King-model' profiles for all clusters. By deprojecting cluster surface brightness profiles to estimate luminosity density profiles, we treat 'King-model' and 'core-collapsed' clusters in the same way. In addition, we use Monte Carlo simulations to investigate the effects of uncertainties in various observational parameters (distance, reddening, surface brightness) on {Gamma}, producing the first catalog of globular cluster stellar encounter rates with estimated errors. Comparing our results with published observations of likely products of stellar interactions (numbers of X-ray binaries, numbers of radio millisecond pulsars, and {gamma}-ray luminosity) we find both clear correlations and some differences with published results.

Bahramian, Arash; Heinke, Craig O.; Sivakoff, Gregory R.; Gladstone, Jeanette C., E-mail: bahramia@ualberta.ca [Department of Physics, University of Alberta, CCIS 4-183, Edmonton, AB, T5K 1V4 (Canada)

2013-04-01

411

Envisioning invertebrates and other aquatic encounters  

NASA Astrophysics Data System (ADS)

To "envision" animals is to visualize, to experience, to figure, to image, kinds of species, discourses, representations, institutions, histories, epistemologies; and, to "imagine possible" a set of material and ethical relationships between species. This dissertation explores the "envisioning of animals" that takes place through/across/between the interfaces of seawater/visuality/experience/biology/technology/phyla---as illustrated in the documentary works of Jean Painleve (scientist and filmmaker), Genevieve Hamon (filmmaker and set-designer), Leni Riefenstahl (filmmaker and photographer), and David Powell (scientist and aquarist). In each case, aesthetic conceptions of beauty and/or ambiguity coupled with biological epistemology and phenomenology of the organisms themselves compete over "what gets to count as culture and nature," and in doing so, construct a host of hybridized and enmeshed "encounters." In the process the following questions are raised: What is the role of the ocean---it's ecosystems and semiotics---in the production of "envisioning"? How are animals used---and in turn shape and reshape the users---to construct tropes of encounter? What theories can be used to understand the phenomenological, semiotic, material, and rhetorical use/miss-use of animals in the articulation of history, economy, biology, narrativity, and representation? How does this motley crew of documentarians answer differently "the animal question," and challenge and/or reinforce anthropocentrism? Divided into two parts, the dissertation first develops a set of methodological questions derived from critical appraisal of "envisioning," encountering, and embodying through science studies, as well as an account of the use and misuse of animals as only "stand ins" for human intentionality; secondly, the dissertation analyses the work of the documentarians in question. Jean Painleve and Genevieve Hamon are shown to critique traditions of representation in nature/science films, particularly through challenging anthropocentrism with a "toolkit" of surrealist strategies and a biological knowledge of octopuses. Soft and hard corals (anthrozoans) are shown to enact a "biosemiotics" or "zoosemiotics" that "presses against" Leni Riefenstahl's "fascist (and humanist) aesthetic," which desires to memorialize "beautiful and unpolluted" coral communities. "The Drifter's Gallery," the primary designer being David Powell, at the Monterey Bay Aquarium, is shown to install a promise of immediate and luminous experience of "jellyfish otherness," but delivers an account of jellyfish as historically situated "actors" with in biocapitalism. The work of these documentarians is particularly prescient, considering the growing international concern about coral bleaching, anthropogenic pollution, over-harvesting, and commercialization of the oceans' resources. As a form of "situated knowledge," this dissertation expands the boundaries of "who/what gets to count?" to encompass an ethical concern about systems of power that constitutively produce animal and human actors. If we are to be committed to understanding the encounters and formations of encounters between non-human animals and human animals, then projects that bridge---rather than divide---disciplines are necessary endeavors for more inhabitable futures; this project attempts such a bridge.

Hayward, Eva

412

Ethogram of selected behaviors initiated by free-ranging short-finned pilot whales ( Globicephala macrorhynchus ) and directed to human swimmers during open water encounters  

Microsoft Academic Search

In order to establish an ethogram of interactive behaviors initiated by free- ranging short-finned pilot whales (Globice phala macrorhynchus) and directed to human swimmers, we initiated encounters with non-habituated pilot whale groups during open water encounters southwest of Tenerife, Canary Islands, over two field seasons (1996 and 2001). Human swim- mers followed a precautionary set of rules during approaches. Encounters

Michael Scheer; Bianka Hofmann; Itay P. Behr

2004-01-01

413

Effect of the ionizing radiation on the rain-time atmospheric electric field  

NASA Astrophysics Data System (ADS)

The atmospheric electric field, or potential gradient (PG) at Kakioka, 150 southwest of the Fukushima Nuclear Power Plant (NPP) shows peculiar behaviors after the accident, March 2012 due to the conductivity enhancement in the air by the ionizing radiation. This means that the PG provides significant information on the dynamics of the radioactive materials. During last EGU assembly 2012, we showed that the fine-weather PG decreased by one-two orders of magnitudes at the arrival of the radioactive plume, and that the PG recovered in various way depending on various types of re-suspension processes in addition to the physical decay of the deposited radioactive materials. We extended this work to the rain-time PG, which is very simple because of high variability of the PG depending on the cloud types and distribution. We yet found a statistical difference between rain-time PGs before and after the Fukushima NPP Accident: one-hour averaged rain-time PG during the first 45 days after the accident is not as much scattered to the negative side as those during the same period of different years or during 40 days before accident. Further examination of one-minute averaged data (1 Hz sampling) during the second half March for 2006-2012 revealed that this difference comes from short time-spans of negative peaks rather than the peak value after the accident compared to those before the accident. On the other hand, characteristics of positive peaks (cloud without rain) are unchanged. The results suggest either (1) the effect on the local charges in the rain cloud is narrowed under high dose of ionized radiation, making positive charges in the cloud less shielded by the negative charges, or (2) negative charge of ionized aerosol decays much faster under higher dose of ionized radiation due to the shortened time constant of the ionized aerosol (? 1-?, where ? is the atmospheric electric conductivity).

Yamauchi, Masatoshi; Takeda, Masahiko; Makino, Masahiko; Owada, Takeshi

2013-04-01

414

3D hybrid modeling of the plasma environment near Titan for T5 encounter  

NASA Astrophysics Data System (ADS)

Wave-particle interactions play a very important role in the plasma dynamics near Titan: mass loading, excitation of low-frequency waves and formation of the particle velocity distribution function (e.g. ring/shelllike distributions, etc.) The kinetic approach is important for estimating collision processes; e.g., charge exchange. In this report we discuss results of 3D hybrid modeling of the interaction between Saturn's magnetosphere and Titan's atmosphere/ionosphere for T5 encounter. T5 flyby is the only encounter when the 2 main ionizating sources of Titan atmosphere, solar radiation and corotating plasma, align quasi-antiparallel. The modeling is based on recent analysis of the Cassini Plasma Spectrometer (CAPS) and the Cassini Ion, and Neutral Mass Spectrometer (INMS) measurements during the T5 flyby through Titan's ram-side and polar ionosphere [1, 2]. Magnetic field data was used from the MAG instrument [3]. In our model the background ions (O+, H+), all pickup ions, and ionospheric ions are considered as a particles, whereas the electrons are described as a fluid (see e.g. [4]). Inhomogeneous photoionization (in the dayside ionosphere), electron-impact ionization, and charge exchange are included in our model. The temperature of the background electrons and pickup electrons was also incorporated into the generalized Ohm's law. We also take into account collisions between ions and neutrals. In our hybrid simulations we use Chamberlain profiles for the exosphere's components. The moon is considered as a weakly conducting body. The first results of our hybridmodeling show a strong asymmetry in the background (H+, O+) and pickup (H+2 , N+2 ,CH+4 ) ion density profiles. Such strong asymmetry cannot be explained by a single-fluid multi-species 3D MHD model [5], which included complex chemistry but does not produce finite gyroradius and kinetic effects.

Lipatov, A. S.; Sittler, E. C., Jr.; Hartle, R. E.; Cooper, J. F.; Sarantos, M.

2012-09-01

415

Near field of terahertz radiation transmitted through a lateral non-centrosymmetric grating  

NASA Astrophysics Data System (ADS)

The transmission of a terahertz (THz) wave through a grating of metallic strips deposited on a flat surface of a dielectric medium has been considered. It has been assumed that the unit cell of the lateral grating does not have a spatial inversion center and the grating period is small compared to the radiation wavelength. The found amplitudes and phases of the spatial harmonics of the transmitted wave in the near field have been used to calculate the components of the tensor of asymmetry parameters responsible for the generation of photocurrents in a doped quantum well embedded in the non-centrosymmetric system under consideration. It has been found that, at a strip height greater than the skin depth, the parameters of the transmitted spatial harmonics are nearly independent of the height. It has been shown that the metallic grating exhibits strong birefringence, and the radiation polarized either circularly or linearly at an angle of 45° with respect to the principal axes of the lateral grating induces superposition of photocurrents owing to the circular or linear electronic ratchet effects.

Ivchenko, E. L.; Petrov, M. I.

2014-09-01

416

Nuclear Radiation Fields on the Mars Surface: Risk Analysis for Long-term Living Environment  

NASA Technical Reports Server (NTRS)

Mars, our nearest planet outward from the sun, has been targeted for several decades as a prospective site for expanded human habitation. Background space radiation exposures on Mars are expected to be orders of magnitude higher than on Earth. Recent risk analysis procedures based on detailed dosimetric techniques applicable to sensitive human organs have been developed along with experimental data regarding cell mutation rates resulting from exposures to a broad range of particle types and energy spectra. In this context, simulated exposure and subsequent risk for humans in residence on Mars are examined. A conceptual habitat structure, CAD-modeled with duly considered inherent shielding properties, has been implemented. Body self-shielding is evaluated using NASA standard computerized male and female models. The background environment is taken to consist not only of exposure from incident cosmic ray ions and their secondaries, but also include the contribution from secondary neutron fields produced in the tenuous atmosphere and the underlying regolith.

Anderson, Brooke M.; Clowdsley, Martha S.; Qualls, Garry D.; Nealy, John E.

2005-01-01

417

The high energy gamma-ray background and the interstellar radiation field  

NASA Astrophysics Data System (ADS)

This thesis provides an independent estimate of the high latitude (! b! > 20°) contribution to the E > 30 MeV gamma-ray background from Galactic nucleon-nucleon, electron bremsstrahlung and inverse Compton processes. In particular, the inverse Compton contribution has been estimated for different cosmic ray electron distributions and after factoring in the anisotropy in the interstellar radiation field and the anisotropic Klein-Nishina scattering cross section. A model for the interstellar radiation field from 0.1 ?m to 1000 ?m is also presented to fit the intensities observed by recent satellite experiments, especially the DIRBE and FIRAS instruments on COBE. I find that the emission from the inverse Compton process when the anisotropy in the radiation field is included can be higher by up to 50% when compared to estimates that adopt an isotropic radiation field. Simulated inverse Compton maps with a cosmic ray electron distribution represented by a ``pill box'' extending up to a distance of 5 kpc above the Galactic plane provide better fits to the EGRET intensity maps suggesting that the cosmic ray halo may be larger than previously thought. With this distribution, I find that the net contribution from the IC process to the gamma-ray background can be as high as 20% at high Galactic latitudes. Fitting for the Galactic components of gamma-ray emission confirms the existence of an isotropic component with an intensity that can be represented by the form 27.7 × E(MeV)-2.16 photons m-2 s-1 sr -1 MeV-1, in excellent agreement with previous estimates. The spectrum of the isotropic component further argues strongly in favor of unresolved gamma-ray blazars being the source of this emission. Introduction of an anisotropic component improves the quality of the fits. However, this component, which could potentially arise from the dark matter in the Galactic halo, is not well characterized by a single power law which might be associated with any single dark matter candidate. It has an intensity of about a third of the isotropic background above E > 100 MeV-1, at the level of 3 × 10-2 photons m-2 s-1 sr-1 . The best fit power law spectrum to this component has a photon index of -1.7. Based on the intensity and spectrum of the anisotropic component I derive upper limits of 109Msolar for the mass of cold, baryonic gas within the solar circle and a primordial black hole number density limit of 7 × 107 pc -3 which is more than an order of magnitude smaller than previous limits. If the spectrum of the anisotropic component is indeed confirmed to have an index of -1.7, it appears more likely that the signal arises in unresolved Galactic sources such as pulsars.

Chary, Ranga-Ram

418

Sharp edges to neutral hydrogen disks in galaxies and the extragalactic radiation field  

NASA Technical Reports Server (NTRS)

It is shown that the very sharp truncation of the neutral hydrogen distribution seen in NGC 3198 (and probably M33) is well modeled as the result of ionization of the atomic gas by the extragalactic radiation field. Below a critical column density of about a few times 10 exp 19/sq cm the gas is dominantly ionized and undetectable in the 21-cm line. It is inferred from the photoionization models that the total disk gas distribution in NGC 3198 is actually fairly axisymmetric. The critical column density for ionization is not a strong function of galaxy mass or mass distribution; thus, all galaxies should show a cutoff at approximately the same column density. Specific models of 3198 suggest that the extragalactic ionizing photon flux is 5000-10,000 photons/sq cm s.

Maloney, Philip

1993-01-01

419

The attainment of large accelerating gradients using near field synchrotron radiation  

SciTech Connect

Lienard-Wiechert potentials are used to find the electromagnetic field everywhere in free space resulting from a point charge moving on a helical trajectory. The total power emitted as synchrotron radiation from a particle on a circular path is calculated. The point charge results are generalized to the case of a line charge, and formulae are presented which can easily be evaluated numerically. A useful gradient of 80 MeV/m per kA of peak driving beam current over a distance of 1 cm is calculated using two 5 MeV driving beams moving on 1 cm radius helical orbits with bunch length 1 mm. 11 refs., 5 figs.

Decker, G.

1989-01-01

420

Radiation pressure and the linear momentum of the electromagnetic field in magnetic media  

E-print Network

We examine the force of the electromagnetic radiation on linear, isotropic, homogeneous media specified in terms of their permittivity epsilon and permeability mu. A formula is proposed for the electromagnetic Lorentz force on the magnetization M, which is treated here as an Amperian current loop. Using the proposed formula, we demonstrate conservation of momentum in several cases that are amenable to rigorous analysis based on the classical Maxwell equations, the Lorentz law of force, and the constitutive relations. Our analysis yields precise expressions for the density of the electromagnetic and mechanical momenta inside the media that are specified by their (epsilon, mu) parameters. An interesting consequence of this analysis is the identification of an "intrinsic" mechanical momentum density, ExM/c^2, analogous to the electromagnetic (or Abraham) momentum density, ExH/c^2. (Here E and H are the magnitudes of the electric and magnetic fields, respectively, and c is the speed of light in vacuum.) This intr...

Mansuripur, Masud

2014-01-01

421

Stratification of the radiation field inside a photobioreactor during microalgae growth.  

PubMed

Light availability is a main issue in autotrophic growth of photosynthetic microorganisms. The change of the suspended cells concentration and that of their chlorophylls content during microalgal growth alters the optical properties of the aqueous suspension. This brings about changes in the properties of the radiation field inside the reactor. In this work, we have computed the evolution in time of the local volumetric rate of absorption of photons inside a photobioreactor by means of a Monte Carlo simulation algorithm previously developed. From this study, we have computed two operational variables that are useful tools for the analysis, performance comparison, optimization and scaling up of photobioreactors: the average rate of photon absorption and the volumetric distribution function of photons absorption rates. Based on these two variables, it is possible to systematically quantify the degree of stratification of the culture medium, which is a decisive aspect that hampers the reactor efficiency regarding the energy usage for biomass production. PMID:23692312

Heinrich, Josué M; Niizawa, Ignacio; Botta, Fausto A; Trombert, Alejandro R; Irazoqui, Horacio A

2013-01-01

422

Sampling and Analysis of Impact Crater Residues Found on the Wide Field Planetary Camera-2 Radiator  

NASA Technical Reports Server (NTRS)

After nearly 16 years in low Earth orbit (LEO), the Wide Field Planetary Camera-2 (WFPC2) was recovered from the Hubble Space Telescope (HST) in May 2009, during the 12 day shuttle mission designated STS-125. The WFPC-2 radiator had been struck by approximately 700 impactors producing crater features 300 microns and larger in size. Following optical inspection in 2009, agreement was reached for joint NASA-ESA study of crater residues, in 2011. Over 480 impact features were extracted at NASA Johnson Space Center's (JSC) Space Exposed Hardware clean-room and curation facility during 2012, and were shared between NASA and ESA. We describe analyses conducted using scanning electron microscopy (SEM) - energy dispersive X-ray spectrometry (EDX): by NASA at JSC's Astromaterials Research and Exploration Science (ARES) Division; and for ESA at the Natural History Museum (NHM), with Ion beam analysis (IBA) using a scanned proton microbeam at the University of Surrey Ion Beam Centre (IBC).

Kearsley, A. T.; Grime, G. W.; Colaux, J. L.; Jeynes, C.; Palitsin, V. V.; Webb, R, P.; Griffin, T. J.; Reed, B. B.; Anz-Meador, P. D.; Kou, J.-C.; Robinson, G. A.; Opiela, J. N.; Gerlach, L.

2013-01-01

423

New Results from Space and Field Observations on the Aerosol Direct and Indirect Radiative Forcing  

NASA Technical Reports Server (NTRS)

New space observations from the MODIS instrument on board the Terra satellite and analysis of POLDER data flown on the ADEOS satellite, show in great details the spatial and seasonal variability of the global aerosol system. These spaceborne instruments distinguish fine aerosol from man-made regional pollution and biomass burning from mostly natural coarse dust and sea salt aerosol. E.g. fine regional pollution in and around the Indian sub-continent, Europe and North America; smoke from biomass burning in Southern Africa and Southern America; coarse dust from West Africa and mixed dust pollution and smoke from West and central Africa and East Asia. These regions were also studied extensively in focused field experiments and by the distributed AERONET network. The results generate the first climatologies of the aerosol system, are used to derive the aerosol radiative effects and to estimate the anthropogenic component. The measurements are also used to evaluate each other and constrain aerosol transport models.

Kaufman, Yoram J.; Remer, Lorraine; Tanre, Didier; Boucher, Olivier; Chin, Mian; Dubovik, Oleg; Holben, Brent

2002-01-01

424

Energy streamlines in near-field radiative heat transfer between hyperbolic metamaterials.  

PubMed

Metallodielectric photonic crystals having hyperbolic dispersions are called indefinite materials because of their ability to guide modes with extremely large lateral wavevectors. While this is useful for enhancing near-field radiative heat transfer, it could also give rise to large lateral displacements of the energy pathways. The energy streamlines can be used to depict the flow of electromagnetic energy through a structure when wave propagation does not follow ray optics. We obtain the energy streamlines through two semi-infinite uniaxial anisotropic effective medium structures, separated by a small vacuum gap, using the Green functions and fluctuation-dissipation theorem. The lateral shifts are determined from the streamlines within two penetration depths. For hyperbolic modes, the predicted lateral shift can be several thousand times of the vacuum gap width. PMID:24978074

Bright, T J; Liu, X L; Zhang, Z M

2014-06-30

425

OBSERVATIONAL CONSTRAINTS ON THE STELLAR RADIATION FIELD IMPINGING ON TRANSITIONAL DISK ATMOSPHERES  

SciTech Connect

Mid-infrared atomic and ionic line ratios measured in spectra of pre-main-sequence stars are sensitive indicators of the hardness of the radiation field impinging on the disk surface. We present a low-resolution Spitzer IRS search for [Ar II] at 6.98 {mu}m, [Ne II] at 12.81 {mu}m, and [Ne III] 15.55 {mu}m lines in 56 transitional disks. These objects, characterized by reduced near-infrared but strong far-infrared excess emission, are ideal targets to set constraints on the stellar radiation field onto the disk, because their spectra are not contaminated by shock emission from jets/outflows or by molecular emission lines. After demonstrating that we can detect [Ne II] lines and recover their fluxes from the low-resolution spectra, here we report the first detections of [Ar II] lines toward protoplanetary disks. We did not detect [Ne III] emission in any of our sources. Our [Ne II]/[Ne III] line flux ratios combined with literature data suggest that a soft-EUV or X-ray spectrum produces these gas lines. Furthermore, the [Ar II]/[Ne II] line flux ratios point to a soft X-ray and/or soft-EUV stellar spectrum as the ionization source of the [Ar II] and [Ne II] emitting layer of the disk. If the soft X-ray component dominates over the EUV, then we would expect larger photoevaporation rates and, hence, a reduction of the time available to form planets.

Szulagyi, Judit [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Pascucci, Ilaria [Lunar and Planetary Laboratory, University of Arizona, 1629 East University Boulevard, Tucson, AZ 85721 (United States); Abraham, Peter; Moor, Attila [Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Konkoly Thege Miklos ut 15-17, H-1121 Budapest (Hungary); Apai, Daniel [Department of Astronomy, The University of Arizona, 933 N Cherry Avenue, Tucson, AZ 85721 (United States); Bouwman, Jeroen, E-mail: szulagyi@konkoly.hu [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany)

2012-11-01

426

Structure of the near zone electric field and the power radiated from a VLF antenna in the ionosphere  

NASA Astrophysics Data System (ADS)

In this paper we examine the electric field and radiated power produced in the near zone of a ring VLF antenna whose loop plane is aligned parallel to the external magnetic field. In this case there exist two resonance surfaces, one inside the other, which can be given in parametric form. The electric field singularity on the resonance surfaces is of a logarithmic type, but there are also curves and points (focuses) where the field displays a more severe singularity (branch pole type). The asymptotes of the field close to the resonance surfaces are given. Using the expression for the Fourier component of the antenna generated magnetic current, the radiated power and the percentage of the power that goes into the whistler mode are calculated for different values of the angle between the antenna loop and the external magnetic field. The results show that only a small portion of the radiated power is transferred to the whistler mode. Suggestions as to how to increase the portion of the radiated power that goes into whistler waves are discussed.

Sotnikov, V. I.; Solovyev, G. I.; Ashour-Abdalla, M.; Schriver, D.; Fiala, V.

1993-11-01

427

Böhm extrapolation chamber: Study of its behavior in beta radiation fields at the Calibration Laboratory of IPEN  

NASA Astrophysics Data System (ADS)

The Calibration Laboratory (LCI) at the Instituto de Pesquisas Energéticas e Nucleares (IPEN) is going to establish a Böhm extrapolation chamber as a primary standard system for the dosimetry and calibration of beta radiation sources and detectors. This chamber was already tested in beta radiation beams with an aluminized Mylar entrance window, and now, it was characterized with an original Hostaphan entrance window. A comparison between the results of the extrapolation chamber with the two entrance windows was performed. The results showed that this extrapolation chamber presents the same effectiveness in beta radiation fields as a primary standard system with both entrance windows, showing that any one of them may be utilized.

Antonio, Patrícia L.; Xavier, Marcos; Caldas, Linda V. E.

2014-11-01

428

Viscous Evolution and Photoevaporation of Circumstellar Disks Due to External Far Ultraviolet Radiation Fields  

NASA Astrophysics Data System (ADS)

This paper explores the effects of FUV radiation fields from external stars on circumstellar disk evolution. Disks residing in young clusters can be exposed to extreme levels of FUV flux from nearby OB stars, and observations show that disks in such environments are being actively photoevaporated. Typical FUV flux levels can be factors of ~102-104 higher than the interstellar value. These fields are effective in driving mass loss from circumstellar disks because they act at large radial distance from the host star, i.e., where most of the disk mass is located, and where the gravitational potential well is shallow. We combine viscous evolution (an ?-disk model) with an existing FUV photoevaporation model to derive constraints on disk lifetimes, and to determine disk properties as functions of time, including mass-loss rates, disk masses, and radii. We also consider the effects of X-ray photoevaporation from the host star using an existing model, and show that for disks around solar-mass stars, externally generated FUV fields are often the dominant mechanism in depleting disk material. For sufficiently large viscosities, FUV fields can efficiently photoevaporate disks over the entire range of parameter space. Disks with viscosity parameter ? = 10-3 are effectively dispersed within 1-3 Myr for higher viscosities (? = 10-2) disks are dispersed within ~0.25-0.5 Myr. Furthermore, disk radii are truncated to less than ~100 AU, which can possibly affect the formation of planets. Our model predictions are consistent with the range of observed masses and radii of proplyds in the Orion Nebula Cluster.

Anderson, Kassandra R.; Adams, Fred C.; Calvet, Nuria

2013-09-01

429

Acoustic field modeling for physiotherapy ultrasound applicators by using approximated functions of measured non-uniform radiation distributions.  

PubMed

The strongest therapeutic effects in ultrasonic physiotherapy are mainly produced at the first centimeters, i.e. close to the applicator surface and, in general, only in the near-field zone. The acoustic field produced in practice by this type of transducers differs from the classical models because the vibration distribution on the real transducer surfaces is non-uniform. However, neither models using uniform distribution, nor those using typical non-uniform distribution patterns for the source accurately represent the radiation of this kind of transducers. Although this therapy is widely used and many efforts have been made in experimentally studying the patterns of ultrasound radiation produced during physiotherapy applications (IEC-61689, 1998), additional modeling researches still would be needed in order to achieve improved models giving field patterns closer to the measured ultrasonic results. In this paper, acoustic patterns produced from two source radiation functions are proposed and evaluated for field modeling of physiotherapy applicators. Both the functions are approximations to the pressure distribution measured close to the emitting surface and they are based on the modulation of the classical simply-supported function using either sinusoidal or Bessel-type distributions. The simply-supported function is accounted for the radiator-fixing condition and the modulation function simulates the complex vibration distribution of this kind of transducer. The modulator Bessel function is based on reports about Bessel-type vibration distributions found in piezoelectric disk resonators. The use of a selected sinusoidal segment represents another analytical option for obtaining an approximated behavior of the measured data in a real applicator. Both the field models are implemented using the finite element method (FEM) to obtain the numerical solution of wave equation at each point in the radiated space. The solution is reached by considering axisymmetric radiation in attenuation-free media. The results indicate the viability of applying an adequate model for acoustic field calculation by simulating the radiating distribution on the emitting surface as either sinusoidal or Bessel-modulated functions. Models using both the functions describe reasonably real behaviors, but those based on Bessel functions are better correlated with the measurements. The results for three commercial applicators indicate the possibility of representing, with adequate verisimilitude, the acoustic field radiated by physiotherapy ultrasound transducers using linear combinations of Bessel profiles describing the radiation source. PMID:22405588

Gutiérrez, Mario Ibrahín; Calás, Héctor; Ramos, Antonio; Vera, Arturo; Leija, Lorenzo

2012-08-01

430

A reexamination of the local time asymmetry of lobe encounters at geosynchronous orbit: CRRES, ATS 5, and LANL observations  

Microsoft Academic Search

The local time of occurrence of a geosynchronous plasma flux dropout or lobe encounter is dependent on the longitude of the observing spacecraft. Satellites located on or west of the International Geomagnetic Reference Field (IGRF) model magnetic dip prime meridian (magnetic dip meridian) observe almost exclusively (77%) dawnside lobe encounters, while satellites located east of the magnetic dip meridian observe

Mark B. Moldwin; Mark I. Fernandez; Hamid K. Rassoul; Michelle F. Thomsen; Samuel J. Bame; David J. McComas; J. F. Fennell

1998-01-01

431

Voyager Briefing: Expectations of the Neptune Encounter  

NASA Technical Reports Server (NTRS)

This NASA KSC video release presents a news briefing held Aug. 4, 1989 at NASA Headquarters three weeks after Voyager 2's official "encounter" with Neptune began. The video is comprised of two slide presentations followed by a short question and answer period. The press conference is moderated by Charles Redmond, (NASA Public Affairs), includes an introduction by Dr. Geoffrey A Briggs (Dir., Solar System Exploration Div.), and features Norman R. Haynes (Voyager Project Manager, JPL) and Dr. Edward C. Stone (Voyager Project Scientist, Cal Tech). Mr. Haynes' presentation centers on Voyager's history, engineering changes, and spacecraft trajectories while Dr. Stone presents the scientific aspects of Voyager, including the 11 scientific investigations planned for the mission, instruments used, and imaging techniques.

1989-01-01

432

Radiation effects on JFETs (Junction Field-Effect Transistors), MOSFETs, and dipolar transistors, as related to SSC circuit design  

NASA Astrophysics Data System (ADS)

Some results of radiation effects on selected junction field-effect transistors, MOS field-effect transistors, and bipolar junction transistors are presented. The evaluations include dc parameters, as well as capacitive variations and noise evaluations. The tests are made at the low current and voltage levels (in particular, at currents less or equal to 1 mA) that are essential for the low-power regimes required by SSC circuitry. Detailed noise data are presented both before and after 5-Mrad (gamma) total-dose exposure. SPICE radiation models for three high-frequency bipolar processes are compared for a typical charge-sensitive preamplifier.

Kennedy, E. J.; Alley, G. T.; Britton, C. L., Jr.; Skubic, P. L.; Gray, B.; Wu, A.

1990-10-01

433

Humanitarian Encounters in Post-Conflict Aceh, Indonesia.  

E-print Network

?? Humanitarian Encounters in Post-Conflict Aceh, Indonesia In "Humanitarian Encounters in Post-Conflict Aceh, Indonesia," I examine the humanitarian involvement in Aceh, Indonesia following two momentous… (more)

Grayman, Jesse Hession

2013-01-01

434

Galileo post-Gaspra cruise and Earth-2 encounter  

NASA Technical Reports Server (NTRS)

This article documents DSN support for the Galileo cruise after the Oct. 1991 encounter with the asteroid Gaspra. This article also details the Earth-2 encounter and the special non-DSN support provided during the Earth-2 closest approach.

Beyer, P. E.; Andrews, M. M.

1993-01-01

435

Genetic effects of strong magnetic fields in Drosophila melanogaster. II. Lack of interaction between homogeneous fields and fission neutron-plus-gamma radiation  

SciTech Connect

Anticipated use of extremely large magnets in future, controlled thermonuclear reactors and occasional exposures in various occupational and research environments both require that biological effects of these fields be investigated. The genetic effects of high magnetic field intensities ranging from 13,000 to 37,000 G, using Drosophila melanogaster have been investigated. Results from these experiments provided no evidence of a statistically significant increase in the frequency of sex-linked, recessive, lethals in adult Drosophila males. However, since ionizing radiation - both gamma and neutron - also may be present in the vicinity of controlled thermonuclear reactors and high-energy accelerators, it is important to test for possible interaction (synergistic or antagonistic) between radiation and magnetic field effects. Such interaction was studied by Close and Beischer for mean life span and by Mittler for sex-linked recessive lethals, using low magnetic field intensities and short exposure periods in these experiments, much longer exposures, stronger fields, and a combination neutron and gamma radiation exposure are employed.

Kale, P.G.; Baum, J.W.

1980-01-01