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Eighteen days of MERLIN data and 42 hours of A-array VLA data at 1.4 GHz have been combined to image a 10-arcmin field centred on the Hubble Deep and Flanking Fields (HDF and HFF). A complete sample of 92 radio sources with 1.4-GHz flux densities above 40 microJy has been imaged using MERLIN+VLA. The images are amongst the most sensitive yet made at 1.4 GHz, with rms noise levels of 3.3 microJy/beam in the 0.2-arcsec images. Virtually all the sources are resolved, with angular sizes in the range 0.2 to 3 arcsec. No additional sources were detected down to 23 microJy in the central 3 arcmin, indicating that sources fainter than 40 microJy are heavily resolved with MERLIN and must have typical angular sizes greater than 0.5 arcsec. Compact radio sources were used to align the optical data to the ICRF, to

We present an innovative method for magnetic resonance force microscopy (MRFM) with ultra-low dissipation, by using the higher modes of the mechanical detector as radio frequency (rf) source. This method allows MRFM on samples without the need to be close to an rf source. Furthermore, since rf sources require currents that give dissipation, our method enables nuclear magnetic resonance experiments at ultra-low temperatures. Removing the need for an on-chip rf source is an important step towards a MRFM which can be widely used in condensed matter physics.

Radio synchrotron emission, its polarization and its Faraday rotation are powerful tools to study the strength and structure of interstellar magnetic fields. The total intensity traces the strength and distribution of total magnetic fields. Total fields in gas-rich spiral arms and bars of nearby galaxies have strengths of 20-30 $\mu$Gauss, due to the amplification of turbulent fields, and are dynamically important. In the Milky Way, the total field strength is about 6 $\mu$G near the Sun and several 100 $\mu$G in filaments near the Galactic Center. -- The polarized intensity measures ordered fields with a preferred orientation, which can be regular or anisotropic fields. Ordered fields with spiral structure exist in grand-design, barred, flocculent and even in irregular galaxies. The strongest ordered fields are found in interarm regions, sometimes forming "magnetic spiral arms" between the optical arms. Halo fields are X-shaped, probably due to outflows. -- The Faraday rotation of the polarization vectors traces coherent regular fields which have a preferred direction. In some galaxies Faraday rotation reveals large-scale patterns which are signatures of dynamo fields. However, in most galaxies the field has a complicated structure and interacts with local gas flows. In the Milky Way, diffuse polarized radio emission and Faraday rotation of the polarized emission from pulsars and background sources show many small-scale and large-scale magnetic features, but the overall field structure in our Galaxy is still under debate.

The detection of electromagnetic pulses from high energy showers is used as a means to search for Ultra-High Energy cosmic ray and neutrino interactions. An approximate formula has been obtained to numerically evaluate the radio pulse emitted by a charged particle that instantaneously accelerates, moves at constant speed along a straight track and halts again instantaneously. The approximate solution is applied to the particle track after dividing it in smaller subintervals. The resulting algorithm (often referred to as the ZHS algorithm) is also the basis for most of the simulations of the electric field produced in high energy showers in dense media. In this work, the electromagnetic pulses as predicted with the ZHS algorithm are compared to those obtained with an exact solution of the electric field produced by a charged particle track. The precise conditions that must apply for the algorithm to be valid are discussed and its accuracy is addressed. This comparison is also made for electromagnetic showers in dense media. The ZHS algorithm is shown to describe Cherenkov radiation and to be valid for most situations of interest concerning detectors searching for Ultra-High Energy neutrinos. The results of this work are also relevant for the simulation of pulses emitted from air showers.

Homan & Lister (2006) have recently published circular-polarization (CP) detections for 34 objects in the MOJAVE sample - a set of bright, compact AGN being monitored by the Very Long Baseline Array at 15 GHz. We report the detection of 15-GHz parsec-scale CP in two more AGN (3C345 and 2231+114), and confirm the MOJAVE detection of CP in 1633+382. It is generally believed that the most likely mechanism for the generation of this CP is Faraday conversion of linear polarization to CP. A helical jet magnetic-field (B-field) geometry can facilitate this process - linearly polarized emission from the far side of the jet is converted to CP as it passes through the magnetised plasma at the front side of the jet on its way toward the observer. In this case, the sign of the generated CP is essentially determined by the pitch angle and helicity of the helical B field. We have determined the pitch-angle regimes and helicities of the helical jet B fields in 8 AGN for which parsec-scale CP has been detected, and used them to predict the expected CP signs for these AGN if the CP is generated via conversion in these helical fields. We have obtained the intriguing result that our predictions agree with the observed signs in all eight cases, provided that the longitudinal B-field components in the jets correspond to South magnetic poles. This clearly non-random pattern demonstrates that the observed CP in AGN is directly associated with the presence of helical jet B fields. These results suggest that helical B fields are ubiquitous in AGN jets.

We observe a large fraction of circular polarization in radio emission from extensive air showers recorded during thunderstorms, much higher than in the emission from air showers measured during fair-weather circumstances. We show that the circular polarization of the air showers measured during thunderstorms can be explained by the change in the direction of the transverse current as a function of altitude induced by atmospheric electric fields. Thus by using the full set of Stokes parameters for these events, we obtain a good characterization of the electric fields in thunderclouds. We also measure a large horizontal component of the electric fields in the two events that we have analysed.

Theory of the superconductor-insulator-superconductor (S-I-S) multilayer structure in superconducting accelerating cavity application is reviewed. The theoretical field limit, optimum layer thicknesses and material combination, and surface resistance are discussed. Those for the S-S bilayer structure are also reviewed.

Radio observations explain certain kinds of stellar activity and reliable estimates of magnetic field strengths are derived for the radio emitting regions. Radio observation of flare stars shows rapidly varying bursts of radiation with frequencies of up to 5 GHz. The inferred brightness temperatures of these bursts (10 to the 10th power to 10 to the 14th power) imply that the radiation is coherent. Two mechanisms are proposed to generate such radiation: (1) plasma radiation, and (2) electron cyclotron masers. The high brightness temperatures of the bursts up to 10 to the 20th power K) makes the latter the most plausible. For bursts in the 5 GHz range, the magnetic field strength would be approximately 900 Gauss.

No Description

We present our very recent results on the sub-mJy radio source populations at 1.4 GHz based on the Extended Chandra Deep Field South VLA survey, which reaches ~ 30 {\mu}Jy, with details on their number counts, evolution, and luminosity functions. The sub-mJy radio sky turns out to be a complex mix of star-forming galaxies and radio-quiet AGN evolving at a similar, strong rate and declining radio-loud AGN. While the well-known flattening of the radio number counts below 1 mJy is mostly due to star-forming galaxies, these sources and AGN make up an approximately equal fraction of the sub-mJy sky. Our results shed also light on a fifty-year-old issue, namely radio emission from radio-quiet AGN, and suggest that it is closely related to star formation, at least at z ~ 1.5 - 2. The implications of our findings for future, deeper radio surveys, including those with the Square Kilometre Array, are also discussed. One of the main messages, especially to non-radio astronomers, is that radio surveys are reaching such faint limits that, while previously they were mainly useful for radio quasars and radio galaxies, they are now detecting mostly star-forming galaxies and radio-quiet AGN, i.e., the bulk of the extragalactic sources studied in the infrared, optical, and X-ray bands.

576 p. 24 cm

We report the results of a combined experimental and modeling study of the electrical breakdown of hydrogen and deuterium in static (DC) and radio-frequency (RF, 13.56 MHz) electric fields. For the simulations of the breakdown events, simplified models are used and only electrons are traced by Monte Carlo simulation. The experimental DC Paschen curve of hydrogen is used for the determination of the effective secondary electron emission coefficient. A very good agreement between the experimental and the calculated RF breakdown characteristics for hydrogen is found. For deuterium, on the other hand, presently available cross section sets do not allow a reproduction of RF breakdown characteristics.

We report the results of a combined experimental and modeling study of the electrical breakdown of hydrogen and deuterium in static (DC) and radio-frequency (RF, 13.56 MHz) electric fields. For the simulations of the breakdown events, simplified models are used and only electrons are traced by Monte Carlo simulation. The experimental DC Paschen curve of hydrogen is used for the determination of the effective secondary electron emission coefficient. A very good agreement between the experimental and the calculated RF breakdown characteristics for hydrogen is found. For deuterium, on the other hand, presently available cross section sets do not allow a reproduction of RF breakdown characteristics.

Stefan Tilkov talks with Jay Fields, author of the book Working Effectively with Unit Tests, about unit testing in practice. Topics include how to write good unit tests, what mistakes to avoid, and different categories of unit tests. Jay explains the value of unit tests and why you might want to delete them if you [...]

Bent-tailed (BT) radio sources have long been known to trace over densities in the Universe up to z ~ 1 and there is increasing evidence this association persists out to redshifts of 2. The morphology of the jets in BT galaxies is primarily a function of the environment that they have resided in and so BTs provide invaluable clues as to their local conditions. Thus, not only can samples of BT galaxies be used as signposts of large-scale structure, but are also valuable for obtaining a statistical measurement of properties of the intra-cluster medium including the presence of cluster accretion shocks & winds, and as historical anemometers, preserving the dynamical history of their surroundings in their jets. We discuss the use of BTs to unveil large-scale structure and provide an example in which a BT was used to unlock the dynamical history of its host cluster. In addition to their use as density and dynamical indicators, BTs are useful probes of the magnetic field on their environment on scales which are inaccessible to other methods. Here we discuss a novel way in which a particular sub-class of BTs, the so-called `corkscrew' galaxies might further elucidate the coherence lengths of the magnetic fields in their vicinity. Given that BTs are estimated to make up a large population in next generation surveys we posit that the use of jets in this way could provide a unique source of environmental information for clusters and groups up to z = 2.

We present evidence for observation of virtual electromagnetic fields in the radio domain from experiment T926 at the Fermilab Meson Test Beam Facility. Relativistic protons with 120 GeV energy traversed a sealed electromagnetic cavity and were observed in the radio regime of 200MHz-GHz. Closely related to ordinary Cherenkov radiation, which we also measured, the virtual fields require no acceleration for their existence. The experiment is also the first observation of fields from hadronic showers, an independent and new confirmation of coherent radio emission from ultra-relativistic particles. Conditions of very low signal to noise were overcome by a novel and unbiased filtering strategy that exploits exhaustive studies of correlations in the noise backgrounds. Linear scaling of the signal region with the number of beam particles provides evidence of coherence. Extrapolation to measurement of the field of a single relativistic proton charge is consistent within errors. Our study also illustrates new data processing methods that may be applied broadly in conditions of extremely low signal to noise.

Book Source: Digital Library of India Item 2015.13978 dc.contributor.author: Ramo Simon dc.contributor.author: Whinnery John R. dc.contributor.other: Cousins James H dc.date.accessioned: 2015-06-23T22:36:39Z dc.date.available: 2015-06-23T22:36:39Z dc.date.digitalpublicationdate: 2006-02-22 dc.date.citation: 1944 dc.identifier: Librarian, Bits-Pilani dc.identifier.barcode: 99999990149322 dc.identifier.origpath: /data1/upload/0004/419 dc.identifier.copyno: 1 dc.identifier.uri: http://www.new.dli.ernet.in/handle/2015/13978 dc.description.scanningcentre: C-DAC, Noida dc.description.main: 1 dc.description.tagged: 0 dc.description.totalpages: 526 dc.format.mimetype: application/pdf dc.language.iso: English dc.publisher.digitalrepublisher: Digital Library Of India dc.publisher: John Wiley And Sons, Inc. dc.rights: Copyright Permitted dc.source.library: Central Library, Bits- Pilani dc.subject.classification: Technology dc.subject.keywords: Voltage dc.subject.keywords: Circuit dc.title: Fields And Waves In Modern Radio

Book Source: Digital Library of India Item 2015.13978 dc.contributor.author: Ramo Simon dc.contributor.author: Whinnery John R. dc.contributor.other: Cousins James H dc.date.accessioned: 2015-06-23T22:36:39Z dc.date.available: 2015-06-23T22:36:39Z dc.date.digitalpublicationdate: 2006-02-22 dc.date.citation: 1944 dc.identifier: Librarian, Bits-Pilani dc.identifier.barcode: 99999990149322 dc.identifier.origpath: /data1/upload/0004/419 dc.identifier.copyno: 1 dc.identifier.uri: http://www.new.dli.ernet.in/handle/2015/13978 dc.description.scanningcentre: C-DAC, Noida dc.description.main: 1 dc.description.tagged: 0 dc.description.totalpages: 526 dc.format.mimetype: application/pdf dc.language.iso: English dc.publisher.digitalrepublisher: Digital Library Of India dc.publisher: John Wiley And Sons, Inc. dc.rights: Copyright Permitted dc.source.library: Central Library, Bits- Pilani dc.subject.classification: Technology dc.subject.keywords: Voltage dc.subject.keywords: Circuit dc.title: Fields And Waves In Modern Radio

This article is from PLoS ONE , volume 9 . Abstract The effects of weak magnetic fields on the biological production of reactive oxygen species (ROS) from intracellular superoxide (O2•−) and extracellular hydrogen peroxide (H2O2) were investigated in vitro with rat pulmonary arterial smooth muscle cells (rPASMC). A decrease in O2•− and an increase in H2O2 concentrations were observed in the presence of a 7 MHz radio frequency (RF) at 10 μTRMS and static 45 μT magnetic fields. We propose that O2•− and H2O2 production in some metabolic processes occur through singlet-triplet modulation of semiquinone flavin (FADH•) enzymes and O2•− spin-correlated radical pairs. Spin-radical pair products are modulated by the 7 MHz RF magnetic fields that presumably decouple flavin hyperfine interactions during spin coherence. RF flavin hyperfine decoupling results in an increase of H2O2 singlet state products, which creates cellular oxidative stress and acts as a secondary messenger that affects cellular proliferation. This study demonstrates the interplay between O2•− and H2O2 production when influenced by RF magnetic fields and underscores the subtle effects of low-frequency magnetic fields on oxidative metabolism, ROS signaling, and cellular growth.

JVonD Radio - E.A. Fields

We are engaged in a program of infrared imaging photometry of high redshift radio galaxies. The observations are being done using NICMOS2 and NICMOS3 arrays on the DuPont 100-inch telescope at Las Campanas Observatory. In addition, Persson and Matthews are measuring the spectral energy distributions of normal cluster galaxies in the redshift range 0 to 1. These measurements are being done with a 58 x 62 InSb array on the Palomar 5-m telescope. During the course of these observations we have imaged roughly 20 square arcminutes of sky to limiting magnitudes greater than 20 in the J, H, and K passbands (3 sigma in 3 square arcseconds). We have detected several relatively bright, extremely red, extended objects during the course of this work. Because the radio galaxy program requires Thuan-Gunn gri photometry, we are able to construct rough photometric energy distributions for many of the objects. A sample of the galaxy magnitudes within 4 arcseconds diameter is given. All the detections are real; either the objects show up at several wavelengths, or in subsets of the data. The reddest object in the table, 9ab'B' was found in a field of galaxies in a rich cluster at z = 0.4; 9ab'A' lies 8 arcseconds from it.

The atmospheric electric fields in thunderclouds have been shown to significantly modify the intensity and polarization patterns of the radio footprint of cosmic-ray-induced extensive air showers. Simulations indicated a very non-linear dependence of the signal strength in the frequency window of 30-80 MHz on the magnitude of the atmospheric electric field. In this work we present an explanation of this dependence based on Monte-Carlo simulations, supported by arguments based on electron dynamics in air showers and expressed in terms of a simplified model. We show that by extending the frequency window to lower frequencies additional sensitivity to the atmospheric electric field is obtained.

The atmospheric electric fields in thunderclouds have been shown to significantly modify the intensity and polarization patterns of the radio footprint of cosmic-ray-induced extensive air showers. Simulations indicated a very non-linear dependence of the signal strength in the frequency window of 30-80 MHz on the magnitude of the atmospheric electric field. In this work we present an explanation of this dependence based on Monte-Carlo simulations, supported by arguments based on electron dynamics in air showers and expressed in terms of a simplified model. We show that by extending the frequency window to lower frequencies additional sensitivity to the atmospheric electric field is obtained.

The dwarf M stars YZ Canis Minoris and AD Leonis exhibit narrow band, slowly varying (hours) microwave emission that cannot be explained by conventional thermal radiation mechanisms. The dwarf M stars AD Leonis and Wolf 424 emit rapid spikes whose high brightness temperatures similarly require a nonthermal radiation process which could result from coherent mechanisms such as an electron cyclotron maser or coherent plasma radiation. If the electron cyclotron maser emits at the second or third harmonic of the gyrofrequency, the coronal magnetic field strength H = 250 C or 167 G and constraints on the plasma frequency imply an electron density of N sub e = 6 x 10 to the 9th power/cc. Coherent plasma radiation requires similar values of electron density but much weaker magnetic fields. Radio spikes from AD Leonis and Wolf 424 have rise times tau sub R 5 ms, indicating a linear size of L 1.5 x 10 to the 8th power cm, or less than 0.005 of the stellar radius. Although Ap magnetic stars have strong dipole magnetic fields, they exhibit no detectable gyroresonant radiation, suggesting that these stars do not have hot, dense coronae. The binary RS CVn star UX Arietis exhibits variable emission at 6 cm wavelength on time scales ranging from 30 s to more than one hour. The shortest variation implies a linear size much less than that of the halo observed by VLBI techniques, and most probably sizes smaller than those of the component stars. The observed variations might be due to absorption by a thermal plasma located between the stars.

At very low frequencies, the new pan-European radio telescope LOFAR is opening the last unexplored window of the electromagnetic spectrum for astrophysical studies. The revolutionary APERTIF phased arrays that are about to be installed on the Westerbork radio telescope (WSRT) will dramatically increase the survey speed for the WSRT. Combined surveys with these two facilities will deeply chart the northern sky over almost two decades in radio frequency from \sim 15 up to 1400 MHz. Here we briefly describe some of the capabilities of these new facilities and what radio surveys are planned to study fundamental issues related the formation and evolution of galaxies and clusters of galaxies. In the second part we briefly review some recent observational results directly showing that diffuse radio emission in clusters traces shocks due to cluster mergers. As these diffuse radio sources are relatively bright at low frequencies, LOFAR should be able to detect thousands of such sources up to the epoch of cluster formation. This will allow addressing many question about the origin and evolution of shocks and magnetic fields in clusters. At the end we briefly review some of the first and very preliminary LOFAR results on clusters.

Tracklist: 1. The Skunk Trap 2. Children 3. Old Friends And Old Wine 4. Feathered Friends 5. Moths 6. The Snake Story (A Commercial) 7. The Temperance Lecture 8. Promotions Unlimited 9. The Swim To Catalina Island 10. The Pharmacist

Redbricks Radio 17th March - Part One - Spider Park and Birley Fields

David Bacon is Thorne Dreyer's guest today on Rag Radio. David's acclaimed new book -- totally bilingual -- is  In the Fields of the North: En los campos del norte . The book includes more than 300 photos and a series of personal narratives that bring a little known or understood universe to life.   Bacon is a California-based writer, documentary photographer, and longtime union organizer. The author of several books about migration, Bacon was a factory worker and union organizer for two decades with the United Farm Workers, the International Ladies Garment Workers, and other unions. Today, he documents the changing conditions in the workforce, the impact of the global economy, war and migration, and the struggle for human rights. David does not characterize himself as an objective journalist, but rather as an unabashed advocate for social change.  This is David Bacon's fourth visit to Rag Radio. Find the earlier shows here . About this book: "A new bilingual book by David Bacon offers both a dramatic antidote to the deplorable reality of racism and a majestic life-affirming view of these hidden women, men and children. In the Fields of the North is a landmark fusion of journalism and documentary photography. -- Paul Von Blum, Truthdig "David Bacon renews and updates the progressive documentary tradition with these extraordinary, carefully chosen portraits of farmworkers, their families and communities." -- Mike Davis, author of City of Quartz and Magical Urbanism    "In this landmark work of photo-journalism, activist and photographer David Bacon documents the experiences of some of the hardest-working and most disenfranchised laborers in the country: the farmworkers who are responsible for making California 'America's breadbasket.' Combining haunting photographs with the voices of migrant farmworkers, Bacon offers three-dimensional portraits of laborers living under tarps, in trailer camps, and between countries, following jobs that last only for the harvesting season. He uncovers the inherent abuse in the labor contractor work system, and drives home the almost feudal nature of laboring in America's fields." -- University of California Press Rag Radio is produced in the studios of KOOP 91.7-FM, an all-volunteer, cooperatively-run, solar-powered community radio station in Austin, Texas, in association with The Rag Blog and the New Journalism Project, a Texas 501(c)(3) nonprofit. The host and producer of Rag Radio, Thorne Dreyer, is a prominent Austin-based activist and writer who was a pioneer of the ’60s underground press movement. The show’s engineer and co-producer is Tracey Schulz and the staff photographer is Roger Baker. The syndicated show is broadcast (and streamed ) live Fridays, 2-3 p.m. (Central) on  KOOP, and is later  rebroadcast and streamed on WFTE-FM in Mt. Cobb and Scranton, PA., on Houston Pacifica's KPFT HD-3 90.1, and by KKRN, 88.5-FM  in Round Mountain, CA -- and as a featured podcast at Veterans Today Live . Running time: 54:19. Contact: [email protected].

David Bacon is Thorne Dreyer's guest today on Rag Radio. David's acclaimed new book -- totally bilingual -- is  In the Fields of the North: En los campos del norte . The book includes more than 300 photos and a series of personal narratives that bring a little known or understood universe to life.   Bacon is a California-based writer, documentary photographer, and longtime union organizer. The author of several books about migration, Bacon was a factory worker and union organizer for two decades with the United Farm Workers, the International Ladies Garment Workers, and other unions. Today, he documents the changing conditions in the workforce, the impact of the global economy, war and migration, and the struggle for human rights. David does not characterize himself as an objective journalist, but rather as an unabashed advocate for social change.  This is David Bacon's fourth visit to Rag Radio. Find the earlier shows here . About this book: "A new bilingual book by David Bacon offers both a dramatic antidote to the deplorable reality of racism and a majestic life-affirming view of these hidden women, men and children. In the Fields of the North is a landmark fusion of journalism and documentary photography. -- Paul Von Blum, Truthdig "David Bacon renews and updates the progressive documentary tradition with these extraordinary, carefully chosen portraits of farmworkers, their families and communities." -- Mike Davis, author of City of Quartz and Magical Urbanism    "In this landmark work of photo-journalism, activist and photographer David Bacon documents the experiences of some of the hardest-working and most disenfranchised laborers in the country: the farmworkers who are responsible for making California 'America's breadbasket.' Combining haunting photographs with the voices of migrant farmworkers, Bacon offers three-dimensional portraits of laborers living under tarps, in trailer camps, and between countries, following jobs that last only for the harvesting season. He uncovers the inherent abuse in the labor contractor work system, and drives home the almost feudal nature of laboring in America's fields." -- University of California Press Rag Radio is produced in the studios of KOOP 91.7-FM, an all-volunteer, cooperatively-run, solar-powered community radio station in Austin, Texas, in association with The Rag Blog and the New Journalism Project, a Texas 501(c)(3) nonprofit. The host and producer of Rag Radio, Thorne Dreyer, is a prominent Austin-based activist and writer who was a pioneer of the ’60s underground press movement. The show’s engineer and co-producer is Tracey Schulz and the staff photographer is Roger Baker. The syndicated show is broadcast (and streamed ) live Fridays, 2-3 p.m. (Central) on  KOOP, and is later  rebroadcast and streamed on WFTE-FM in Mt. Cobb and Scranton, PA., on Houston Pacifica's KPFT HD-3 90.1, and by KKRN, 88.5-FM  in Round Mountain, CA -- and as a featured podcast at Veterans Today Live . Running time: 54:19. Contact: [email protected].

David Bacon is Thorne Dreyer's guest today on Rag Radio. David's acclaimed new book -- totally bilingual -- is  In the Fields of the North: En los campos del norte . The book includes more than 300 photos and a series of personal narratives that bring a little known or understood universe to life.   Bacon is a California-based writer, documentary photographer, and longtime union organizer. The author of several books about migration, Bacon was a factory worker and union organizer for two decades with the United Farm Workers, the International Ladies Garment Workers, and other unions. Today, he documents the changing conditions in the workforce, the impact of the global economy, war and migration, and the struggle for human rights. David does not characterize himself as an objective journalist, but rather as an unabashed advocate for social change.  This is David Bacon's fourth visit to Rag Radio. Find the earlier shows here . About this book: "A new bilingual book by David Bacon offers both a dramatic antidote to the deplorable reality of racism and a majestic life-affirming view of these hidden women, men and children. In the Fields of the North is a landmark fusion of journalism and documentary photography. -- Paul Von Blum, Truthdig "David Bacon renews and updates the progressive documentary tradition with these extraordinary, carefully chosen portraits of farmworkers, their families and communities." -- Mike Davis, author of City of Quartz and Magical Urbanism    "In this landmark work of photo-journalism, activist and photographer David Bacon documents the experiences of some of the hardest-working and most disenfranchised laborers in the country: the farmworkers who are responsible for making California 'America's breadbasket.' Combining haunting photographs with the voices of migrant farmworkers, Bacon offers three-dimensional portraits of laborers living under tarps, in trailer camps, and between countries, following jobs that last only for the harvesting season. He uncovers the inherent abuse in the labor contractor work system, and drives home the almost feudal nature of laboring in America's fields." -- University of California Press Rag Radio is produced in the studios of KOOP 91.7-FM, an all-volunteer, cooperatively-run, solar-powered community radio station in Austin, Texas, in association with The Rag Blog and the New Journalism Project, a Texas 501(c)(3) nonprofit. The host and producer of Rag Radio, Thorne Dreyer, is a prominent Austin-based activist and writer who was a pioneer of the ’60s underground press movement. The show’s engineer and co-producer is Tracey Schulz and the staff photographer is Roger Baker. The syndicated show is broadcast (and streamed ) live Fridays, 2-3 p.m. (Central) on  KOOP, and is later  rebroadcast and streamed on WFTE-FM in Mt. Cobb and Scranton, PA., on Houston Pacifica's KPFT HD-3 90.1, and by KKRN, 88.5-FM  in Round Mountain, CA -- and as a featured podcast at Veterans Today Live . Running time: 54:19. Contact: [email protected].

We investigate the origin of the high Faraday rotation measures (RMs) found for polarized radio galaxies in clusters. The two most likely origins are, magnetic fields local to the source, or magnetic fields located in the foreground intra-cluster medium (ICM). The latter is identified as the null hypothesis. Rudnick & Blundell (2003) have recently suggested that the presence of magnetic fields local to the source may be revealed in correlations of the position angles (PAs) of the source intrinsic linear polarization and the RMs. We investigate the claim of Rudnick & Blundell to have found a relationship between the intrinsic PA0 of the radio source PKS 1246-410 and its RM, by testing the clustering strength of the PA0-RM scatter plot. We show that the claimed relationship is an artifact of an improperly performed null-experiment. We describe a gradient alignment statistic aimed at finding correlations between PA0 and RM maps. This statistic does not require any null-experiment since it gives a unique (zero) result in the case of uncorrelated maps. We apply it to a number of extended radio sources in galaxy clusters (PKS 1246-410, Cygnus A, Hydra A, and 3C465). In no case is a significant large-scale alignment of PA0 and RM maps detected. We find significant small-scale co-alignment in all cases, but we are able to fully identify this with map making artifacts through a suitable statistical test. We conclude that there is presently no existing evidence for Faraday rotation local to radio lobes. Given the existing independent pieces of evidence, we favor the null hypothesis that the observed Faraday screens are produced by intracluster magnetic fields.

Some galaxy clusters show diffuse radio emission in the form of peripheral relics (so far attributed to primary, shock-(re)accelerated electrons) or central halos. Analysing radio and X-ray data from the literature, we find new connections between halos and relics, such as a universal linear relation between their peak radio brightness and the gas column density. Our results indicate that halos, relics, and halo-relic bridges in a cluster, all arise from the same, homogeneous cosmic ray (CR) ion (CRI) distribution. We analytically derive the signature of synchrotron emission from secondary electrons and positrons (CREs) produced in hadronic CRI collisions, for an arbitrary magnetic field evolution. In our model, flat spectrum halos (both giant and minihalos) arise from steady-state magnetic fields, whereas relics and steep halos reflect recent or irregular magnetic growth. This naturally explains the properties of halos, relics, and the connections between them, without invoking particle (re)acceleration in weak shocks or turbulence. We find CRI energy densities in the range u_p~10^-[12.4,13.3]erg cm^-3, with a spectral index s_p=-2.20+-0.05, and identify a ~0.1 magnetic energy fraction in some halos and behind relics, as far as 2Mpc from the cluster's centre. The CRI homogeneity suggests strong CR diffusion, D(100GeV)>~10^32cm^2s^-1. The strong magnetisation imposes strict upper limits on >10GeV CRE (re)acceleration in weak shocks (efficiency

Tracklist: 1. Narrative Introduction - W.C. Fields Jr. 2. Original Radio Broadcast 3. Narrative Introduction - W.C. Fields Jr. 4. Original Radio Broadcast

We present results of three-dimensional, fully nonlinear MHD simulations of a large-scale magnetic field evolution in a barred galaxy. The model does not take into consideration the dynamo process. We find that the obtained magnetic field configurations are highly similar to the observed maps of the polarized intensity of barred galaxies, because the modeled vectors form coherent structures along the bar and spiral arms. Due to the dynamical influence of the bar the gas forms spiral waves which go radially outward. Each spiral arm forms the magnetic arm which stays much longer in the disk, than the gaseous spiral structure. Additionally the modeled total energy of magnetic field grows due to strong compression and shear of non-axisymmetrical bar flows and differential rotation, respectively.

We present results of three-dimensional, fully nonlinear MHD simulations of a large-scale magnetic field evolution in a barred galaxy. The model does not take into consideration the dynamo process. We find that the obtained magnetic field configurations are highly similar to the observed maps of the polarized intensity of barred galaxies, because the modeled vectors form coherent structures along the bar and spiral arms. Due to the dynamical influence of the bar the gas forms spiral waves which go radially outward. Each spiral arm forms the magnetic arm which stays much longer in the disk, than the gaseous spiral structure. Additionally the modeled total energy of magnetic field grows due to strong compression and shear of non-axisymmetrical bar flows and differential rotation, respectively.

We present results of three-dimensional, fully nonlinear MHD simulations of a large-scale magnetic field evolution in a barred galaxy. The model does not take into consideration the dynamo process. We find that the obtained magnetic field configurations are highly similar to the observed maps of the polarized intensity of barred galaxies, because the modeled vectors form coherent structures along the bar and spiral arms. Due to the dynamical influence of the bar the gas forms spiral waves which go radially outward. Each spiral arm forms the magnetic arm which stays much longer in the disk, than the gaseous spiral structure. Additionally the modeled total energy of magnetic field grows due to strong compression and shear of non-axisymmetrical bar flows and differential rotation, respectively.

JVonD Radio - E.A. Fields II

In the following interview the Anarchist Radio Berlin (aradio.blogsport.de) made with an UK-based organizer from the Reclaim the fields initiative, we talk about the planned international camp in North-Wales, the relationship of food sovereignty and the prison system, and the topic of prison abolition as such. Please send feedback and comments at: aradio-berlin/at/riseup(.)net

We examine the proposal that the dispersion measures (DMs) and Faraday rotation measures (RMs) of extragalactic linearly-polarized fast radio bursts (FRBs) can be used to probe the intergalactic magnetic field (IGMF) in filaments of galaxies. The DM through the cosmic web is dominated by contributions from the warm-hot intergalactic medium (WHIM) in filaments and from the gas in voids. On the other hand, RM is induced mostly by the hot medium in galaxy clusters, and only a fraction of it is produced in the WHIM. We show that if one excludes FRBs whose sightlines pass through galaxy clusters, the line-of-sight strength of the IGMF in filaments, $B_{||}$, is approximately $C(\langle 1+z \rangle/f_{DM})(RM/DM)$, where $C$ is a known constant. Here, the redshift of the FRB is not required to be known; $f_{DM}$ is the fraction of total DM due to the WHIM, while $\langle 1+z \rangle$ is the redshift of interevening gas weighted by the WHIM gas density, both of which can be evaluated for a given cosmology model solely from the DM of an FRB. Using data on structure formation simulations and a model IGMF, we show that $C(\langle 1+z \rangle/f_{DM})(RM/DM)$ closely reproduces the density-weighted line-of-sight strength of the IGMF in filaments of the large-scale structure.

http://uf.catalog.fcla.edu/uf.jsp?st=UF002388706&ix=nu&I=0&V=D&pm=1

We present our attempts to detect magnetic fields in filamentary large-scale structure (LSS) by observing polarized synchrotron emission emitted by structure formation shocks. Little is known about the strength and order of magnetic fields beyond the largest clusters of galaxies, and synchrotron emission holds enormous promise as a means of probing magnetic fields in these low density regions. We report on observations taken at the Green Bank Telescope which reveal a possible Mpc extension to the Coma cluster relic. We also highlight the major obstacle that diffuse galactic foreground emission poses for any search for large-scale, low surface-brightness extragalactic emission. Finally we explore cross-correlation of diffuse radio emission with optical tracers of LSS as a means to statistically detecting magnetic fields in the presence of this confounding foreground emission.

An analytical model of a class of RF intrusion sensor systems was constructed. The constituents of the model are: a slotted coaxial cable laid circularly on the ground, an electromagnetic scatterer intended to simulate a human frame target in the vicinity of the cable and an antenna near the center of the circular configuration. Using the concept of a general electromagnetic field as a superposition of plane-wave fields ('plane-wave spectral representation of fields'), calculations were made of: (a) the fields from the cable slots as if the cable were in free space; (b) the effect of ground reflections on the fields were from the slots; (c) the fields of the waves scattered from the human frame target directly toward the antenna in response to the incident wave fields ((a) plus (b); and (d) the effect of ground reflections on the scattered wave fields. These calculations were programmed for the VAX computer and some numerical results are presented for various orientations and positions of the human frame target. (Author)

This paper presents a practical method of computing radio fields in regions of strong focusing, using ray intercept data provided by a standard ray tracing program. The procedure extends the usefulness of the ray trace by allowing fields to be computed near caustics and cusps where ray density calculations fail. Using a plane wave decomposition of the field components, phase integrals are computed by curve fitting intercepts of ray traced through ionospheric or tropospheric media whose refractive indices vary arbitrarily with altitude. A numerical algorithm is described for performing the plane-wave angular spectral integrations. This procedure avoids the complications associated with higher order asymptotic techniques, allowing a much broader range of refractivity-index profiles to be analyzed by a single method. It is applied to two sample profiles, and the results agree very closely with higher order stationary-phase estimates in caustic regions. Moreover, the computer code runs efficiently, despite the presence of highly oscillatory integrands. The method is capable of including the effects of weak collisions, the spherical earth, and azimuthally dependent transmitter configurations. An extension of the angular spectral representations is given to include regions throughout the vicinity of a thin, overdense layer. (Author)

We present catalogues of faint 1.4-GHz radio sources from extremely-deep Very Large Array pointings in the Lockman Hole, the Hubble Deep Field North (HDF-N) and ELAIS N2. Our analysis of the HDF-N data has produced maps that are significantly deeper than those previously published and we have used these to search for counterparts to submm sources. For each of the fields we have derived normalised differential source counts and in the case of the HDF-N find no evidence for the previously-reported under-density of sources; our counts are entirely consistent with those found for the majority of other fields. The catalogues are available as an online supplement to this paper and the maps are also available for download.

We estimate minimum energy magnetic fields (B_min) for a sample of galaxies with measured gas surface densities, spanning from normal spirals to starbursts. We show that the ratio of the minimum energy magnetic pressure to the total pressure in the ISM decreases substantially with increasing surface density; for Arp 220 this ratio is ~10^-4. Therefore, if the minimum energy estimate is applicable, magnetic fields in starbursts are dynamically weak compared to gravity, in contrast to normal spiral galaxies. We argue, however, that rapid cooling of relativistic electrons in starbursts invalidates the minimum energy estimate. We critically assess a number of independent constraints on the magnetic field strength in starbursts. In particular, we argue that the existence of the FIR-radio correlation implies that the synchrotron cooling timescale for cosmic ray electrons is much shorter than their escape time from the galactic disk; this in turn implies that the true magnetic field in starbursts is significantly larger than B_min. The strongest argument against such large fields is that one might expect starbursts to have steep radio spectra indicative of strong synchrotron cooling, which is not observed. We show, however, that ionization and bremsstrahlung losses can flatten the nonthermal spectra of starburst galaxies even in the presence of rapid cooling, providing much better agreement with observed spectra. We further demonstrate that ionization and bremsstrahlung losses are likely to be important in shaping the radio spectra of most starbursts at GHz frequencies, thereby preserving the linearity of the FIR-radio correlation. We thus conclude that magnetic fields in starbursts are significantly larger than B_min. We highlight several observations that can test this conclusion.

We present a catalogue of MgII absorption systems obtained from high resolution UVES/VLT data of 77 QSOs in the redshift range 0.6 < z < 2.0, and down to an equivalent width W_0 > 0.1 \AA. The statistical properties of our sample are found to be in agreement with those from previous work in the literature. However, we point out that the previously observed increase with redshift of dN/dz for weak absorbers, pertains exclusively to very weak absorbers with W_0 < 0.1 \AA. Instead, dN/dz for absorbers with W_0 in the range 0.1-0.3 \AA actually decreases with redshift, similarly to the case of strong absorbers. We then use this catalogue to extend our earlier analysis of the links between the Faraday Rotation Measure of the quasars and the presence of intervening MgII absorbing systems in their spectra. In contrast to the case with strong MgII absorption systems W_0 > 0.3 \AA, the weaker systems do not contribute significantly to the observed Rotation Measure of the background quasars. This is possibly due to the higher impact parameters of the weak systems compared to strong ones, suggesting that the high column density magnetized material that is responsible for the Faraday Rotation is located within about 50 kpc of the galaxies. Finally, we show that this result also rules out the possibility that some unexpected secondary correlation between the quasar redshift and its intrinsic Rotation Measure is responsible for the association of high Rotation Measure and strong intervening MgII absorption that we have presented elsewhere, since this would have produced an equal effect for the weak absorption line systems, which exhibit a very similar distribution of quasar redshifts.

We exploit the vastly increased sensitivity of the Expanded Very Large Array (EVLA) to study the radio continuum and polarization properties of the post-starburst, dwarf irregular galaxy IC10 at 6 cm, at a linear resolution of ~50 pc. We find close agreement between radio continuum and Halpha emission, from the brightest HII regions to the weaker emission in the disk. A quantitative analysis shows a strictly linear correlation, where the thermal component contributes 50% to the total radio emission, the remainder being due to a non-thermal component with a surprisingly steep radio spectral index of between -0.7 and -1.0 suggesting substantial radiation losses of the cosmic-ray electrons. We confirm and clearly resolve polarized emission at the 10-20% level associated with a non-thermal superbubble, where the ordered magnetic field is possibly enhanced due to the compression of the expanding bubble. A fraction of the cosmic-ray electrons has likely escaped because the measured radio emission is a factor of 3 lower than what is suggested by the Halpha inferred SFR.

Theoretical limits to the performance of superconductors in high magnetic fields parallel to their surfaces are of key relevance to current and future accelerating cavities, especially those made of new higher-Tc materials such as Nb$_3$Sn, NbN, and MgB$_2$. Indeed, beyond the so-called superheating field $H_{\mathcal{sh}}$, flux will spontaneously penetrate even a perfect superconducting surface and ruin the performance. We present intuitive arguments and simple estimates for $H_{\mathcal{sh}}$, and combine them with our previous rigorous calculations, which we summarize. We briefly discuss experimental measurements of the superheating field, comparing to our estimates. We explore the effects of materials anisotropy and the danger of disorder in nucleating vortex entry. Will we need to control surface orientation in the layered compound MgB$_2$? Can we estimate theoretically whether dirt and defects make these new materials fundamentally more challenging to optimize than niobium? Finally, we discuss and analyze recent proposals to use thin superconducting layers or laminates to enhance the performance of superconducting cavities. Flux entering a laminate can lead to so-called pancake vortices; we consider the physics of the dislocation motion and potential re-annihilation or stabilization of these vortices after their entry.

The feasibility of computerized simulation of the physics of advanced microwave anti-icing systems, which preheat impinging supercooled water droplets prior to impact, was investigated. Theoretical and experimental work performed to create a physically realistic simulation is described. The behavior of the absorption cross section for melting ice particles was measured by a resonant cavity technique and found to agree with theoretical predictions. Values of the dielectric parameters of supercooled water were measured by a similar technique at lambda = 2.82 cm down to -17 C. The hydrodynamic behavior of accelerated water droplets was studied photograhically in a wind tunnel. Droplets were found to initially deform as oblate spheroids and to eventually become unstable and break up in Bessel function modes for large values of acceleration or droplet size. This confirms the theory as to the maximum stable droplet size in the atmosphere. A computer code which predicts droplet trajectories in an arbitrary flow field was written and confirmed experimentally. The results were consolidated into a simulation to study the heating by electromagnetic fields of droplets impinging onto an object such as an airfoil. It was determined that there is sufficient time to heat droplets prior to impact for typical parameter values. Design curves for such a system are presented.

Journal of Research of the National Bureau of Standards